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3,365,329 | https://en.wikipedia.org/wiki/Design%20for%20logistics | Design for logistics is a series of concepts in the field of supply chain management involving product and design approaches that help to control logistics costs and increase customer service level. These concepts were introduced by Professor Hau Lee of Stanford University, and have the three key components: Economic packaging and transportation, Concurrent and parallel processing, and Standardization.
Economic packaging and transportation
There are three levels, moving from operational, to tactical and finally strategic.
Common sense: Product and packaging must be designed so it is easy to ship and shelf (for instance, Rubbermaid design that fits Walmart's 14x14 shelving). Making a product much stronger and more rugged than necessary for its normal function typically increases parts cost, but sometimes it lowers the net cost by reducing the cost of padding and protection for shipping.
Facilitate logistic function: Must be easy to pack and repack, and easy to track.
Enables efficient design of supply chain and business model: For instance, IKEA's supply chain and business model (flat packages etc.)
Concurrent and parallel processing
Modify the manufacturing process so that steps that were previously performed in a sequence can be completed at the same time. This will help reduce manufacturing lead time, lower inventory costs through improved forecasting, and reduce safety stock requirements, among other benefits.
Standardization
The idea of standardization is to exploit economies of scale, and doing things once that can be applied many times. Standardization can be done through:
Parts: Where common parts are used in many different products
Process: Standardize manufacturing and product processes so that decisions about which specific product to manufacture can be delayed. This is in fact delayed differentiation.
Product: Also known as downward substitution. For instance, car rental companies frequently fill reservations with higher-end vehicles when the lower-end vehicles are not available.
Procurement: Standardize processing equipment and approaches that can be used for several products (for instance, one machine for both high and low end products).
References
Supply chain management
Design for X | Design for logistics | Engineering | 397 |
5,119,641 | https://en.wikipedia.org/wiki/HD%20125823 | HD 125823, also known as V761 Centauri or a Centauri, is a variable star in the constellation Centaurus. It is a blue-white star that is visible to the naked eye with a mean apparent visual magnitude of +4.41. The distance to this star is approximately 460 light years based on parallax measurements. It is a member of the Upper Centaurus–Lupus subgroup of the Scorpius–Centaurus association.
In 1965, W. P. Bidelman discovered that the intensities of the star's neutral helium lines had varied on photographic plates taken over the period 1908 to 1911. This variation was confirmed by A. D. Thackeray in 1966. The star ranges from a helium-strong B2 class to a helium-weak B8 with a period of 8.82 days. Radial velocity measurements during the 1970s showed differing velocity variations for helium and other elements. The magnetic field strength peaks at a negative maximum in phase with the maximum helium line strength. Weak emission has been detected in the singly-ionized lines of silicon, magnesium, and iron, but not in the neutral lines of hydrogen and helium.
This is a magnetic peculiar Bp star that shows periodic variation in the strength of its neutral helium lines. It is classified as an SX Arietis type variable star and its brightness varies from magnitude +4.38 to +4.43 with a period of 8.82 days. The star displays very different helium abundances between the two hemispheres, and, unusually, helium-3 has been detected in the weaker southern hemisphere. Latitudinal abundance concentrations have been found for iron, nitrogen, and oxygen. The variation in helium concentration effects the density scale height of the atmosphere, causing helium rich regions to have a lower luminosity in the visual band but emitting stronger levels of far ultraviolet.
References
Ap stars
SX Arietis variables
Centaurus
Centauri, a
Durchmusterung objects
125823
070300
5378
Centauri, V761
B-type main-sequence stars | HD 125823 | Astronomy | 434 |
30,270,129 | https://en.wikipedia.org/wiki/Tube%20domain | In mathematics, a tube domain is a generalization of the notion of a vertical strip (or half-plane) in the complex plane to several complex variables. A strip can be thought of as the collection of complex numbers whose real part lie in a given subset of the real line and whose imaginary part is unconstrained; likewise, a tube is the set of complex vectors whose real part is in some given collection of real vectors, and whose imaginary part is unconstrained.
Tube domains are domains of the Laplace transform of a function of several real variables (see multidimensional Laplace transform). Hardy spaces on tubes can be defined in a manner in which a version of the Paley–Wiener theorem from one variable continues to hold, and characterizes the elements of Hardy spaces as the Laplace transforms of functions with appropriate integrability properties. Tubes over convex sets are domains of holomorphy. The Hardy spaces on tubes over convex cones have an especially rich structure, so that precise results are known concerning the boundary values of Hp functions. In mathematical physics, the future tube is the tube domain associated to the interior of the past null cone in Minkowski space, and has applications in relativity theory and quantum gravity. Certain tubes over cones support a Bergman metric in terms of which they become bounded symmetric domains. One of these is the Siegel half-space which is fundamental in arithmetic.
Definition
Let Rn denote real coordinate space of dimension n and Cn denote complex coordinate space. Then any element of Cn can be decomposed into real and imaginary parts:
Let A be an open subset of Rn. The tube over A, denoted TA, is the subset of Cn consisting of all elements whose real parts lie in A:
Tubes as domains of holomorphy
Suppose that A is a connected open set. Then any complex-valued function that is holomorphic in a tube TA can be extended uniquely to a holomorphic function on the convex hull of the tube , which is also a tube, and in fact
Since any convex open set is a domain of holomorphy (holomorphically convex), a convex tube is also a domain of holomorphy. So the holomorphic envelope of any tube is equal to its convex hull.
Hardy spaces
Let A be an open set in Rn. The Hardy space H p(TA) is the set of all holomorphic functions F in TA such that
for all x in A.
In the special case of p = 2, functions in H2(TA) can be characterized as follows. Let ƒ be a complex-valued function on Rn satisfying
The Fourier–Laplace transform of ƒ is defined by
Then F is well-defined and belongs to H2(TA). Conversely, every element of H2(TA) has this form.
A corollary of this characterization is that H2(TA) contains a nonzero function if and only if A contains no straight line.
Tubes over cones
Let A be an open convex cone in Rn. This means that A is an open convex set such that, whenever x lies in A, so does the entire ray from the origin to x. Symbolically,
If A is a cone, then the elements of H2(TA) have L2 boundary limits in the sense that
exists in L2(B). There is an analogous result for Hp(TA), but it requires additional regularity of the cone (specifically, the dual cone A* needs to have nonempty interior).
See also
Reinhardt domain
Siegel domain
Notes
Citations
Sources
.
.
.
.
.
Fourier analysis
Harmonic analysis
Several complex variables | Tube domain | Mathematics | 744 |
271,195 | https://en.wikipedia.org/wiki/Radio%20propagation | Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for amateur radio communications, international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems.
Several different types of propagation are used in practical radio transmission systems. Line-of-sight propagation means radio waves which travel in a straight line from the transmitting antenna to the receiving antenna. Line of sight transmission is used for medium-distance radio transmission, such as cell phones, cordless phones, walkie-talkies, wireless networks, FM radio, television broadcasting, radar, and satellite communication (such as satellite television). Line-of-sight transmission on the surface of the Earth is limited to the distance to the visual horizon, which depends on the height of transmitting and receiving antennas. It is the only propagation method possible at microwave frequencies and above.
At lower frequencies in the MF, LF, and VLF bands, diffraction allows radio waves to bend over hills and other obstacles, and travel beyond the horizon, following the contour of the Earth. These are called surface waves or ground wave propagation. AM broadcast and amateur radio stations use ground waves to cover their listening areas. As the frequency gets lower, the attenuation with distance decreases, so very low frequency (VLF) to extremely low frequency (ELF) ground waves can be used to communicate worldwide. VLF to ELF waves can penetrate significant distances through water and earth, and these frequencies are used for mine communication and military communication with submerged submarines.
At medium wave and shortwave frequencies (MF and HF bands), radio waves can refract from the ionosphere, a layer of charged particles (ions) high in the atmosphere. This means that medium and short radio waves transmitted at an angle into the sky can be refracted back to Earth at great distances beyond the horizon – even transcontinental distances. This is called skywave propagation. It is used by amateur radio operators to communicate with operators in distant countries, and by shortwave broadcast stations to transmit internationally.
In addition, there are several less common radio propagation mechanisms, such as tropospheric scattering (troposcatter), tropospheric ducting (ducting) at VHF frequencies and near vertical incidence skywave (NVIS) which are used when HF communications are desired within a few hundred miles.
Frequency dependence
At different frequencies, radio waves travel through the atmosphere by different mechanisms or modes:
Free space propagation
In free space, all electromagnetic waves (radio, light, X-rays, etc.) obey the inverse-square law which states that the power density of an electromagnetic wave is proportional to the inverse of the square of the distance from a point source or:
At typical communication distances from a transmitter, the transmitting antenna usually can be approximated by a point source. Doubling the distance of a receiver from a transmitter means that the power density of the radiated wave at that new location is reduced to one-quarter of its previous value.
The power density per surface unit is proportional to the product of the electric and magnetic field strengths. Thus, doubling the propagation path distance from the transmitter reduces each of these received field strengths over a free-space path by one-half.
Radio waves in vacuum travel at the speed of light. The Earth's atmosphere is thin enough that radio waves in the atmosphere travel very close to the speed of light, but variations in density and temperature can cause some slight refraction (bending) of waves over distances.
Direct modes (line-of-sight)
Line-of-sight refers to radio waves which travel directly in a line from the transmitting antenna to the receiving antenna, often also called direct-wave. It does not necessarily require a cleared sight path; at lower frequencies radio waves can pass through buildings, foliage and other obstructions. This is the most common propagation mode at VHF and above, and the only possible mode at microwave frequencies and above. On the surface of the Earth, line of sight propagation is limited by the visual horizon to about . This is the method used by cell phones, cordless phones, walkie-talkies, wireless networks, point-to-point microwave radio relay links, FM and television broadcasting and radar. Satellite communication uses longer line-of-sight paths; for example home satellite dishes receive signals from communication satellites above the Earth, and ground stations can communicate with spacecraft billions of miles from Earth.
Ground plane reflection effects are an important factor in VHF line-of-sight propagation. The interference between the direct beam line-of-sight and the ground reflected beam often leads to an effective inverse-fourth-power law for ground-plane limited radiation.
Surface modes (groundwave)
Lower frequency (between 30 and 3,000 kHz) vertically polarized radio waves can travel as surface waves following the contour of the Earth; this is called ground wave propagation.
In this mode the radio wave propagates by interacting with the conductive surface of the Earth. The wave "clings" to the surface and thus follows the curvature of the Earth, so ground waves can travel over mountains and beyond the horizon. Ground waves propagate in vertical polarization so vertical antennas (monopoles) are required. Since the ground is not a perfect electrical conductor, ground waves are attenuated as they follow the Earth's surface. Attenuation is proportional to frequency, so ground waves are the main mode of propagation at lower frequencies, in the MF, LF and VLF bands. Ground waves are used by radio broadcasting stations in the MF and LF bands, and for time signals and radio navigation systems.
At even lower frequencies, in the VLF to ELF bands, an Earth-ionosphere waveguide mechanism allows even longer range transmission. These frequencies are used for secure military communications. They can also penetrate to a significant depth into seawater, and so are used for one-way military communication to submerged submarines.
Early long-distance radio communication (wireless telegraphy) before the mid-1920s used low frequencies in the longwave bands and relied exclusively on ground-wave propagation. Frequencies above 3 MHz were regarded as useless and were given to hobbyists (radio amateurs). The discovery around 1920 of the ionospheric reflection or skywave mechanism made the medium wave and short wave frequencies useful for long-distance communication and they were allocated to commercial and military users.
Non-line-of-sight modes
Measuring HF propagation
HF propagation conditions can be simulated using radio propagation models, such as the Voice of America Coverage Analysis Program, and realtime measurements can be done using chirp transmitters. For radio amateurs the WSPR mode provides maps with real time propagation conditions between a network of transmitters and receivers. Even without special beacons the realtime propagation conditions can be measured: A worldwide network of receivers decodes morse code signals on amateur radio frequencies in realtime and provides sophisticated search functions and propagation maps for every station received.
Practical effects
The average person can notice the effects of changes in radio propagation in several ways.
In AM broadcasting, the dramatic ionospheric changes that occur overnight in the mediumwave band drive a unique broadcast license scheme in the United States, with entirely different transmitter power output levels and directional antenna patterns to cope with skywave propagation at night. Very few stations are allowed to run without modifications during dark hours, typically only those on clear channels in North America. Many stations have no authorization to run at all outside of daylight hours.
For FM broadcasting (and the few remaining low-band TV stations), weather is the primary cause for changes in VHF propagation, along with some diurnal changes when the sky is mostly without cloud cover. These changes are most obvious during temperature inversions, such as in the late-night and early-morning hours when it is clear, allowing the ground and the air near it to cool more rapidly. This not only causes dew, frost, or fog, but also causes a slight "drag" on the bottom of the radio waves, bending the signals down such that they can follow the Earth's curvature over the normal radio horizon. The result is typically several stations being heard from another media market – usually a neighboring one, but sometimes ones from a few hundred kilometers (miles) away. Ice storms are also the result of inversions, but these normally cause more scattered omnidirection propagation, resulting mainly in interference, often among weather radio stations. In late spring and early summer, a combination of other atmospheric factors can occasionally cause skips that duct high-power signals to places well over 1000 km (600 miles) away.
Non-broadcast signals are also affected. Mobile phone signals are in the UHF band, ranging from 700 to over 2600 MHz, a range which makes them even more prone to weather-induced propagation changes. In urban (and to some extent suburban) areas with a high population density, this is partly offset by the use of smaller cells, which use lower effective radiated power and beam tilt to reduce interference, and therefore increase frequency reuse and user capacity. However, since this would not be very cost-effective in more rural areas, these cells are larger and so more likely to cause interference over longer distances when propagation conditions allow.
While this is generally transparent to the user thanks to the way that cellular networks handle cell-to-cell handoffs, when cross-border signals are involved, unexpected charges for international roaming may occur despite not having left the country at all. This often occurs between southern San Diego and northern Tijuana at the western end of the U.S./Mexico border, and between eastern Detroit and western Windsor along the U.S./Canada border. Since signals can travel unobstructed over a body of water far larger than the Detroit River, and cool water temperatures also cause inversions in surface air, this "fringe roaming" sometimes occurs across the Great Lakes, and between islands in the Caribbean. Signals can skip from the Dominican Republic to a mountainside in Puerto Rico and vice versa, or between the U.S. and British Virgin Islands, among others. While unintended cross-border roaming is often automatically removed by mobile phone company billing systems, inter-island roaming is typically not.
Empirical models
A radio propagation model, also known as the radio wave propagation model or the radio frequency propagation model, is an empirical mathematical formulation for the characterization of radio wave propagation as a function of frequency, distance and other conditions. A single model is usually developed to predict the behavior of propagation for all similar links under similar constraints. Created with the goal of formalizing the way radio waves are propagated from one place to another, such models typically predict the path loss along a link or the effective coverage area of a transmitter.
The inventor of radio communication, Guglielmo Marconi, before 1900 formulated the first crude empirical rule of radio propagation: the maximum transmission distance varied as the square of the height of the antenna.
As the path loss encountered along any radio link serves as the dominant factor for characterization of propagation for the link, radio propagation models typically focus on realization of the path loss with the auxiliary task of predicting the area of coverage for a transmitter or modeling the distribution of signals over different regions.
Because each individual telecommunication link has to encounter different terrain, path, obstructions, atmospheric conditions and other phenomena, it is intractable to formulate the exact loss for all telecommunication systems in a single mathematical equation. As a result, different models exist for different types of radio links under different conditions. The models rely on computing the median path loss for a link under a certain probability that the considered conditions will occur.
Radio propagation models are empirical in nature, which means, they are developed based on large collections of data collected for the specific scenario. For any model, the collection of data has to be sufficiently large to provide enough likeliness (or enough scope) to all kind of situations that can happen in that specific scenario. Like all empirical models, radio propagation models do not point out the exact behavior of a link, rather, they predict the most likely behavior the link may exhibit under the specified conditions.
Different models have been developed to meet the needs of realizing the propagation behavior in different conditions. Types of models for radio propagation include:
Models for free space attenuation
Free-space path loss
Dipole field strength in free space
Friis transmission equation
Models for outdoor attenuation
Terrain models
ITU terrain model
Egli model
Longley–Rice irregular terrain model (ITM)
Two-ray ground-reflection model
City models
Okumura model
Hata model
COST Hata model
Models for indoor attenuation
ITU model for indoor attenuation
Log-distance path loss model
See also
Anomalous propagation
Channel model
Computation of radiowave attenuation in the atmosphere
Critical frequency
Diversity scheme
Earth bulge
Earth-ionosphere waveguide
Effective Earth radius
Electromagnetic radiation
F2 propagation
Fading
Free space
Fresnel zone
Inversion (meteorology)
Kennelly–Heaviside layer
Link budget
Mobility model
Nakagami fading
Near and far field
Propagation graph
Radio atmospherics
Radio frequency
Radio horizon
Radio resource management
Ray tracing (physics)
Rayleigh fading
Schumann resonance
Skip (radio)
Skip zone
Skywave
Traffic generation model
Tropospheric propagation
TV and FM DX
Upfade
Vertical and horizontal (radio propagation)
VOACAP – Free professional HF propagation prediction software
Footnotes
References
Further reading
External links
Solar widget Propagation widget based on NOAA data. Also available as WordPress plugin.
ARRL Propagation Page The American Radio Relay League page on radio propagation.
HF Radio and Ionospheric Prediction Service - Australia
NASA Space Weather Action Center
Online Propagation Tools, HF Solar Data, and HF Propagation Tutorials
HF ionospheric propagation several pages | Radio propagation | Physics | 2,864 |
59,537,838 | https://en.wikipedia.org/wiki/Chip%20on%20board | Chip on board (COB) is a method of circuit board manufacturing in which integrated circuits (e.g. microprocessors) are attached (wired, bonded directly) to a printed circuit board, and covered by a blob of epoxy. Chip on board eliminates the packaging of individual semiconductor devices, which allows a completed product to be less costly, lighter, and more compact. In some cases, COB construction improves the operation of radio frequency systems by reducing the inductance and capacitance of integrated circuit leads.
COB effectively merges two levels of electronic packaging: level 1 (components) and level 2 (wiring boards), and may be referred to as "level 1.5".
Construction
A finished semiconductor wafer is cut into dies. Each die is then physically bonded to the PCB.
Three different methods are used to connect the terminal pads of the integrated circuit (or other semiconductor device) with the conductive traces of the printed circuit board.
Flip chip
In "flip chip on board", the device is inverted, with the top layer of metallization facing the circuit board. Small balls of solder are placed on the circuit board traces where connections to the chip are required. The chip and board are passed through a reflow soldering process to make the electrical connections.
Wire bonding
In "wire bonding", the chip is attached to the board with an adhesive. Each pad on the device is connected with a fine wire lead that is welded to the pad and to the circuit board. This is similar to the way that an integrated circuit is connected to its lead frame, but instead the chip is wire-bonded directly to the circuit board.
Glob-top
Flexible circuit board
In "tape-automated bonding", thin flat metal tape leads are attached to the semiconductor device pads, then welded to the printed circuit board.
In all cases, the chip and connections are covered with an encapsulant to reduce entry of moisture or corrosive gases to the chip, to protect the wire bonds or tape leads from physical damage, and to help dissipate heat.
The printed circuit board substrate may be assembled into the final product, for example, as in a pocket calculator, or, in the case of a multi-chip module, the module may be inserted in a socket or otherwise attached to yet another circuit board. The substrate wiring board may include heat-dissipating layers where the mounted devices handle significant power, such as in LED lighting or power semiconductors. Or, the substrate may have low-loss properties required at microwave radio frequencies.
COB LED modules
COBs containing arrays of light-emitting diodes have made LED lighting more efficient.
LED COBs include a layer of silicone containing yellow Ce:YAG phosphor that encapsulates the LEDs and turns the blue light of the LEDs into white light. The COB is usually built on an aluminum PCB that provides good thermal conductivity to a heatsink. COB LEDs could be compared with multi chip modules or hybrid integrated circuits since all three can incorporate multiple dies into a single unit.
COB variants are also used in newer LED bulbs as in this case the substrate can be either glass, sapphire or sometimes regular phenolic.
With a transparent substrate the LED chips may be installed "upside down" shining through for higher outcoupling. Typically they are glued to the substrate with UV setting glue, interconnects attached, and the encapsulant and phosphor applied in a single step with a back reflective coating applied to channel light out of the device.
References
Electronics manufacturing
Printed circuit board manufacturing | Chip on board | Engineering | 751 |
33,703,023 | https://en.wikipedia.org/wiki/List%20of%20largest%20infrared%20telescopes | The largest infrared telescopes for infrared astronomy are listed in terms of diameter of primary mirror. The infrared spectrum with its longer wavelength than visible light has a number of challenges, especially for ground-based observatories but also in space. Notably infrared radiation is emitted by all physical objects above Absolute Zero temperature so telescopes are subject to local interference.
Overall
Infrared observations from Earth's surface are possible in a limited way but can be very dependent on location and atmospheric conditions. Water vapour in the Earth's atmosphere blocks much of the infrared band, although some limited observations are possible and there is a number of infrared observatories.
Sometimes other optical telescopes can make infrared observations if they are equipped with the right detectors, even if they are not dedicated infrared observatories. For ground-based observatories, the location can make a big difference in how much observation is possible.
Space telescopes only
See also
Lists of telescopes
Infrared telescope
List of largest optical reflecting telescopes
Space Flyer Unit
Diffuse Infrared Background Experiment (all-sky infrared observation on COBE, launched 1989)
References
Lists of telescopes
Telescopes | List of largest infrared telescopes | Astronomy | 222 |
31,116,908 | https://en.wikipedia.org/wiki/Fig4 | Polyphosphoinositide phosphatase also known as phosphatidylinositol 3,5-bisphosphate 5-phosphatase or SAC domain-containing protein 3 (Sac3) is an enzyme that in humans is encoded by the FIG4 gene. Fig4 is an abbreviation for Factor-Induced Gene.
Function
Sac3 protein belongs to a family of human phosphoinositide phosphatases containing a Sac1-homology domain. The Sac1 phosphatase domain encompasses approximately 400 amino acids and consists of seven conserved motifs. It harbors the signature CX5R (T/S) catalytic sequence also found in other lipid and protein tyrosine phosphatases. The founding protein, containing this evolutionarily-conserved domain, has been the first gene product isolated in a screen for Suppressors of yeast ACtin mutations and therefore named Sac1. There are 5 human genes containing a Sac1 domain. Three of these genes (gene symbols SACM1L, INPP5F and FIG4), harbor a single Sac1 domain. In the other two genes, synaptojanin 1 and 2, the Sac1 domain coexists with another phosphoinositide phosphatase domain, with both domains supporting phosphate hydrolysis. In humans, the FIG4 gene localizes on chromosome 6 and encodes a Sac3 protein of 907 amino acids.
Sac3 is characterized as a widespread 97-kDa protein that, in in vitro assays, displays phosphatase activity towards a range of 5’-phosphorylated phosphoinositides. Sac3 forms a hetero-oligomer with ArPIKfyve (gene symbol, VAC14) and this binary complex associates with the phosphoinositide kinase PIKFYVE in a ternary PAS complex (from the first letters of PIKfyve-ArPIKfyve-Sac3), which is required to maintain proper endosomal membrane dynamics. This unique physical association of two enzymes with opposing functions leads to activation of the phosphoinositide kinase PIKfyve and increases of PIKfyve-catalized PtdIns(3,5)P2 and PtdIns5P production. Sac3 is active as a phosphatase in the triple complex and is responsible for turning over PtdIns(3,5)P2 to PtdIns3P. The PAS complex function is critical for life, because the knockout of each of the 3 genes encoding the PIKfyve, ArPIKfyve or Sac3 protein causes early embryonic, perinatal, or early juvenile lethality in mice.
Ectopically expressed Sac3 protein has a very short half-life of only ~18 min due to fast degradation in the proteasome. Co-expression of ArPIKfyve markedly prolongs Sac3 half-life, whereas siRNA-mediated ArPIKfyve knockdown profoundly reduces Sac3 levels. Thus, the Sac3 cellular levels are critically dependent on Sac3 physical interaction with ArPIKfyve. The C-terminal part of Sac3 is essential for this interaction. Insulin treatment of 3T3L1 adipocytes inhibits the Sac3 phosphatase activity as measured in vitro. Small interfering RNA-mediated knockdown of endogenous Sac3 by ~60%, resulting in a slight but significant elevation of PtdIns(3,5)P2 in 3T3L1 adipocytes, increases GLUT4 translocation and glucose uptake in response to insulin. In contrast, ectopic expression of Sac3, but not that of a phosphatase-deficient point-mutant, decreases GLUT4 plasma membrane abundance in response to insulin. Thus, Sac3 is an insulin-sensitive lipid phosphatase whose down-regulation improves insulin responsiveness.
Medical significance
Mutations in the FIG4 gene cause a rare autosomal recessive Charcot-Marie-Tooth peripheral neuropathy type 4J (CMT4J). Most CMT4J patients (15 out of the reported 16) are compound heterozygotes, i.e., the one FIG4 allele is null whereas the other encodes a mutant protein with threonine for isoleucine substitution at position 41. The Sac3I41T point mutation abrogates the protective action of ArPIKfyve on Sac3 half-life. As a result mutant Sac3 is rapidly degraded in the proteasome. Consequently, the Sac3I41T protein level in patient fibroblasts is from very low to undetectable. Clinically, the onset and severity of CMT4J symptoms vary markedly, suggesting an important role of genetic background in the individual course of disease. In two siblings, with severe peripheral motor deficits and moderate sensory symptoms, the disease had relatively little impact on the central nervous system. Phosphoinositide profiling in fibroblasts derived from the largest CMT4J cohort reported in USA thus far reveals decreased steady-state levels of both PtdIns(3,5)P2 and PtdIns5P. This unexpected direction of the changes is a result of impaired activation of the PIKFYVE kinase under the condition of Sac3 protein deficiency and a failure of the PAS complex assembly. The reduction in PtdIns(3,5)P2 and PtdIns5P levels is reportedly unrelated to gender or the disease onset, suggesting that the pathological decline in levels of the two lipids might precede the disease symptoms. FIG4 mutations are also found (without proven causation) in patients with amyotrophic lateral sclerosis (ALS) as well as in other spectrum of phenotypes such as Yunis-Varon syndrome, cortical malformation with seizures and psychiatric co-morbidities, and cerebral hypomyelination.
Mouse models
Spontaneous FIG4 knockout leads to mutant mice with smaller size, selectively reduced PtdIns(3,5)P2 levels in isolated fibroblasts, diluted pigmentation, central and peripheral neurodegeneration, hydrocephalus, abnormal tremor and gait, and eventually juvenile lethality, hence the name pale tremor mouse (plt). Neuronal autophagy has been suggested as an important consequence of the knockout, however, its primary relevance is disputed. The plt mice show distinct morphological defects in motor and central neurons on the one hand, and sensory neurons - on the other. Transgenic mice with one spontaneously null allele and another encoding several copies of mouse Sac3I41T mutant (i.e., the genotypic equivalent of human CMT4J), are dose-dependently rescued from the lethality, neurodegeneration, and brain apoptosis observed in the plt mice. However, the hydrocephalus and diluted pigmentation seen in plt mice are not corrected.
Evolutionary biology
Genes encoding orthologs of human Sac3 are found in all eukaryotes. The most studied is the S. cerevisiae gene, discovered in a screen for yeast pheromone (Factor)-Induced Genes, hence the name Fig, with the number 4 reflecting the serendipity of isolation. Yeast Fig4p is a specific PtdIns(3,5)P2 5’-phosphatase, which physically interacts with Vac14p (the ortholog of human ArPIKfyve), and the PtdIns(3,5)P2-producing enzyme Fab1p (the ortholog of PIKfyve). The yeast Fab1p-Vac14p-Fig4p complex also involves Vac7p and potentially Atg18p. Deletion of Fig4p in budding yeast has relatively little effect on growth, basal PtdIns(3,5)P2 levels and the vacuolar size in comparison with the deletions of Vac14p or Fab1p. In brief, in evolution Sac3/Fig4 retained the Sac1 domain, phosphoinositide phosphatase activity, and the protein interactions from yeast. In mice, the protein is essential in early postnatal development. In humans, its I41T point mutation in combination with a null allele causes a neurodegenerative disorder.
References
Further reading
External links
GeneReviews/NCBI/NIH/UW entry on Charcot-Marie-Tooth Neuropathy Type 4
Proteins | Fig4 | Chemistry | 1,820 |
68,064,150 | https://en.wikipedia.org/wiki/NGC%204643 | NGC 4643 is a lenticular galaxy located in the constellation Virgo. It is a member of the NGC 4753 Group of galaxies, which is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster.
References
External links
Virgo (constellation)
4643
Barred lenticular galaxies
042797 | NGC 4643 | Astronomy | 81 |
18,527,533 | https://en.wikipedia.org/wiki/Canadian%20Nuclear%20Society | The Canadian Nuclear Society (CNS) is a not-for-profit organization representing individuals contributing to, or otherwise supporting, nuclear science and engineering in Canada. Since 2017, the group has invested in the development of small modular reactor technology.
The CNS is a member of the International Nuclear Societies Council (INSC).
History and mandate
The Canadian Nuclear Society was established in 1979 as "the technical society of the Canadian Nuclear Association (CNA)". Although legally a division of the CNA, the CNS operated independently from the start, with its own volunteer Council (Board of Directors), its own mandate, its own activities, and its own budget. In 1998 the CNS incorporated independently as a federal, not-for-profit corporation, following an overwhelming vote from members. Since then the legal name of the CNS is "Canadian Nuclear Society/Société Nucléaire Canadienne, Inc.".
The CNS is dedicated to the exchange of information, both within the nuclear professional and academic community, and with the public, in the field of applied nuclear science and technology. This encompasses all aspects of nuclear energy, uranium, fission and other nuclear technologies such as occupational and environmental protection, medical diagnosis and treatment, the use of radioisotopes, and food preservation.
Governance
The CNS is governed by a council, acting as its board of directors, consisting of an executive committee and nine - sixteen members-at-large. The 2017–2018 executive committee consists of: Daniel Gammage (president), Peter Ozemoyah (past president), John Luxat (1st vice-president and president-elect), Keith Stratton (2nd vice-president), Mohamed Younis (treasurer), Colin Hunt (secretary), Ken Smith (financial administrator), Ben Rouben (executive director), Peter Easton (communications director), and John Roberts (chair of the Education and Communications Committee).
Membership
The CNS membership includes about 1200 individuals, mostly from within Canada.
The primary category of CNS membership is that of an individual directly involved in the use or development of a nuclear technology in any of the above areas or an individual who is simply interested in nuclear technology.
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Operational structure and activities
The CNS is structured along five main technical Divisions (Design & Materials, Fuel Technologies, Nuclear Operations & Maintenance, Nuclear Science & Engineering, and Environment & Waste Management), whose main activities are to organize and conduct workshops, courses, symposia, or conferences within their respective technical areas.
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The CNS holds an annual conference each June, which includes technical sessions covering all fields, as well as plenary sessions that address topics of broad interest.
At the local level across the country, the CNS includes fourteen branches (nine in Ontario, one in each of Alberta, Saskatchewan, Manitoba, Quebec, and New Brunswick)
Affiliations
The CNS is affiliated with several "sister" nuclear societies around the world, and is also an organizational member of the Engineering Institute of Canada (EIC). The president of the CNS is an ex officio voting member of the board of directors of the Canadian Nuclear Association.
References
External links
Canadian Nuclear Society website
1979 establishments in Canada
Scientific organizations based in Canada
Nuclear organizations
Engineering societies based in Canada | Canadian Nuclear Society | Engineering | 754 |
18,783,051 | https://en.wikipedia.org/wiki/Late%20Pleistocene%20extinctions | The Late Pleistocene to the beginning of the Holocene saw the extinction of the majority of the world's megafauna (typically defined as animal species having body masses over ), which resulted in a collapse in faunal density and diversity across the globe. The extinctions during the Late Pleistocene are differentiated from previous extinctions by its extreme size bias towards large animals (with small animals being largely unaffected), and widespread absence of ecological succession to replace these extinct megafaunal species, and the regime shift of previously established faunal relationships and habitats as a consequence. The timing and severity of the extinctions varied by region and are thought to have been driven by varying combinations of human and climatic factors. Human impact on megafauna populations is thought to have been driven by hunting ("overkill"), as well as possibly environmental alteration. The relative importance of human vs climatic factors in the extinctions has been the subject of long-running controversy.
Major extinctions occurred in Australia-New Guinea (Sahul) beginning approximately 50,000 years ago and in the Americas about 13,000 years ago, coinciding in time with the early human migrations into these regions. Extinctions in northern Eurasia were staggered over tens of thousands of years between 50,000 and 10,000 years ago, while extinctions in the Americas were virtually simultaneous, spanning only 3000 years at most. Overall, during the Late Pleistocene about 65% of all megafaunal species worldwide became extinct, rising to 72% in North America, 83% in South America and 88% in Australia, with all mammals over becoming extinct in Australia and the Americas, and around 80% globally. Africa, South Asia and Southeast Asia experienced more moderate extinctions than other regions.
Extinctions by biogeographic realm
Summary
Introduction
The Late Pleistocene saw the extinction of many mammals weighing more than , including around 80% of mammals over 1 tonne. The proportion of megafauna extinctions is progressively larger the further the human migratory distance from Africa, with the highest extinction rates in Australia, and North and South America.
The increased extent of extinction mirrors the migration pattern of modern humans: the further away from Africa, the more recently humans inhabited the area, the less time those environments (including its megafauna) had to become accustomed to humans (and vice versa).
There are two main hypotheses to explain this extinction:
Climate change associated with the advance and retreat of major ice caps or ice sheets causing reduction in favorable habitat.
Human hunting causing attrition of megafauna populations, commonly known as "overkill".
There are some inconsistencies between the current available data and the prehistoric overkill hypothesis. For instance, there are ambiguities around the timing of Australian megafauna extinctions. Evidence supporting the prehistoric overkill hypothesis includes the persistence of megafauna on some islands for millennia past the disappearance of their continental cousins. For instance, ground sloths survived on the Antilles long after North and South American ground sloths were extinct, woolly mammoths died out on remote Wrangel Island 6,000 years after their extinction on the mainland, and Steller's sea cows persisted off the isolated and uninhabited Commander Islands for thousands of years after they had vanished from the continental shores of the north Pacific. The later disappearance of these island species correlates with the later colonization of these islands by humans.
Still, there are some arguments that species responded differently to environmental changes, and no one factor by itself explains the large variety of extinctions. The causes may involve the interplay of climate change, competition between species, unstable population dynamics, and hunting as well as competition by humans.
The original debates as to whether human arrival times or climate change constituted the primary cause of megafaunal extinctions necessarily were based on paleontological evidence coupled with geological dating techniques. Recently, genetic analyses of surviving megafaunal populations have contributed new evidence, leading to the conclusion: "The inability of climate to predict the observed population decline of megafauna, especially during the past 75,000 years, implies that human impact became the main driver of megafauna dynamics around this date."
Africa
Although Africa was one of the least affected regions, the region still suffered extinctions, particularly around the Late Pleistocene-Holocene transition. These extinctions were likely predominantly climatically driven by changes to grassland habitats.
Ungulates
Even-Toed Ungulates
Suidae (swine)
Metridiochoerus (ssp.)
Kolpochoerus (ssp.)
Bovidae (bovines, antelope)
Giant buffalo (Syncerus antiquus)
Megalotragus
Rusingoryx
Southern springbok (Antidorcas australis)
Bond's springbok (Antidorcas bondi)
Damaliscus hypsodon
Damaliscus niro
Atlantic gazelle (Gazella atlantica)
Gazella tingitana
Caprinae
Makapania?
Cervidae (deer)
Megaceroides algericus (North Africa)
Odd-toed Ungulates
Rhinoceros (Rhinocerotidae).
Narrow-nosed rhinoceros (Stephanorhinus hemitoechus, North Africa)
Ceratotherium mauritanicum
Wild Equus spp.
Caballine horses
Equus algericus (North Africa)
Subgenus Asinus (asses)
Equus melkiensis (North Africa)
Zebras
Giant zebra (Equus capensis)
Saharan zebra (Equus mauritanicus)
Proboscidea
Elephantidae (elephants)
Palaeoloxodon iolensis? (other authors suggest that this taxon went extinct at the end of the Middle Pleistocene)
Rodentia
Paraethomys filfilae?
South Asia and Southeast Asia
The timing of extinctions on the Indian subcontinent is uncertain due to a lack of reliable dating. Similar issues have been reported for Chinese sites, though there is no evidence for any of the megafaunal taxa having survived into the Holocene in that region. Extinctions in Southeast Asia and South China have been proposed to be the result of environmental shift from open to closed forested habitats.
Ungulates
Even-Toed Ungulates
Several Bovidae spp.
Bos palaesondaicus (ancestor to the banteng)
Cebu tamaraw (Bubalus cebuensis)
Bubalus grovesi
Short-horned water buffalo (Bubalus mephistopheles)
Bubalus palaeokerabau
Hippopotamidae
Hexaprotodon (Indian subcontinent and Southeast Asia)
Odd-toed Ungulates
Equus spp.
Equus namadicus (Indian subcontinent)
Yunnan horse (Equus yunanensis)
Giant tapir (Tapirus augustus, Southeast Asia and Southern China)
Taprus sinensis
Pholidota
Giant Asian pangolin (Manis palaeojavanica)
Carnivora
Caniformia
Arctoidea
Bears
Ailuropoda baconi (ancestor to the giant panda)
Afrotheria
Afroinsectiphilia
Orycteropodidae/Tubulidentata
Aardvark (Orycteropus afer; extirpated in South Asia circa 13,000 BCE)
Paenungulata
Tethytheria
Proboscideans
Stegodontidae
Stegodon spp. (including Stegodon florensis on Flores, Stegodon orientalis in East and Southeast Asia, and Stegodon sp. in the Indian subcontinent)
Elephantidae
Palaeoloxodon spp.
Palaeoloxodon namadicus (Indian subcontinent, possibly also Southeast Asia)
Birds
Japanese flightless duck (Shiriyanetta hasegawai)
Leptoptilos robustus
Ostriches (Struthio) (Indian subcontinent)
Reptiles
Crocodilia
Alligator munensis?
Testudines (turtles and tortoises)
Manouria oyamai
Primates
Several simian (Simiiformes) spp.
Pongo (orangutans)
Pongo weidenreichi (South China)
Various Homo spp. (archaic humans)
Homo erectus soloensis (Java)
Homo floresiensis (Flores)
Homo luzonensis (Luzon, Philippines)
Denisovans (Homo sp.)
Europe, Northern and East Asia
The Palearctic realm spans the entirety of the European continent and stretches into northern Asia, through the Caucasus and central Asia to northern China, Siberia and Beringia. Extinctions were more severe in Northern Eurasia than in Africa or South and Southeast Asia. These extinctions were staggered over tens of thousands of years, spanning from around 50,000 years Before Present (BP) to around 10,000 years BP, with temperate adapted species like the straight-tusked elephant and the narrow-nosed rhinoceros generally going extinct earlier than cold adapted species like the woolly mammoth and woolly rhinoceros. Climate change has been considered a probable major factor in the extinctions, possibly in combination with human hunting.
Ungulates
Even-Toed Hoofed Mammals
Various Bovidae spp.
Steppe bison (Bison priscus)
Baikal yak (Bos baikalensis)
European water buffalo (Bubalus murrensis)
Bubalus wansijocki (extinct buffalo native to North China)
Bubalus teilhardi
European tahr (Hemitragus cedrensis)
Giant muskox (Praeovibos priscus)
Northern saiga antelope (Saiga borealis)
Twisted-horned antelope (Spirocerus kiakhtensis)
Goat-horned antelope (Parabubalis capricornis)
Various deer (Cervidae) spp.
Giant deer/Irish elk (Megaloceros giganteus)
Cretan deer (Candiacervus spp.)
Haploidoceros mediterraneus
Sinomegaceros spp. (including Sinomegaceros yabei in Japan, and Sinomegaceros ordosianus and possibly Sinomegaceros pachyosteus in China).
Dwarf Ryuku deer (Cervus astylodon)
All native Hippopotamus spp.
Hippopotamus amphibius (European range, still extant in Africa)
Maltese dwarf hippopotamus (Hippopotamus melitensis)
Cyprus dwarf hippopotamus (Hippopotamus minor)
Sicilian dwarf hippopotamus (Hippopotamus pentlandi)
Camelus knoblochi and other Camelus spp.
Odd-Toed Hoofed Mammals
Various Equus spp. e.g.
Various wild horse subspecies (e.g. Equus c. gallicus, Equus c. latipes, Equus c. uralensis)
Equus dalianensis (wild horse species known from North China)
European wild ass (Equus hydruntinus) (survived in refugia in Anatolia until late Holocene)
Equus ovodovi (survived in refugia in North China until late Holocene)
All native Rhinoceros (Rhinocerotidae) spp.
Elasmotherium
Woolly rhinoceros (Coelodonta antiquitatis)
Stephanorhinus spp.
Merck's rhinoceros (Stephanorhinus kirchbergensis)
Narrow-nosed rhinoceros (Stephanorhinus hemiotoechus)
Carnivora
Caniformia
Canidae
Caninae
Wolves
Cave wolf (Canis lupus spelaeus)
Dire wolf (Aenocyon dirus)
Dholes
European dhole (Cuon alpinus europaeus)
Sardinian dhole (Cynotherium sardous)
Arctoidea
Various Ursus spp.
Steppe brown bear (Ursus arctos "priscus")
Gamssulzen cave bear (Ursus ingressus)
Pleistocene small cave bear (Ursus rossicus)
Cave bear (Ursus spelaeus)
Giant polar bear (Ursus maritimus tyrannus)
Musteloidea
Mustelidae
Several otter (Lutrinae) spp.
Robust Pleistocene European otter (Cyrnaonyx)
Algarolutra
Sardinian giant otter (Megalenhydris barbaricina)
Sardinian dwarf otter (Sardolutra)
Cretan otter (Lutrogale cretensis)
Feliformia
Various Felidae (cats) spp.
Homotherium latidens (sometimes called the scimitar-toothed cat)
Cave lynx (Lynx pardinus spelaeus)
Issoire lynx (Lynx issiodorensis)
Panthera spp.
Cave lion (Panthera spelaea)
European ice age leopard (Panthera pardus spelaea)
Hyaenidae (hyenas)
Cave hyena (Crocuta crocuta spelaea and Crocuta crocuta ultima)
"Hyaena" prisca
All native Elephant (Elephantidae) spp.
Mammoths
Woolly mammoth (Mammuthus primigenius)
Dwarf Sardinian mammoth (Mammuthus lamarmorai)
Straight-tusked elephant (Palaeoloxodon antiquus) (Europe)
Palaeoloxodon naumanni (Japan, possibly also Korea and northern China)
Palaeoloxodon huaihoensis (China)
Dwarf elephant
Palaeoloxodon creutzburgi (Crete)
Cyprus dwarf elephant (Palaeoloxodon cypriotes)
Palaeoloxodon mnaidriensis (Sicily)
Rodents
Allocricetus bursae
Cricetus major (alternatively Cricetus cricetus major)
Dicrostonyx gulielmi (ancestor to the Arctic lemming)
Giant Eurasian porcupine (Hystrix refossa)
Leithia spp. (Maltese and Sicilian giant dormouse)
Marmota paleocaucasica
Microtus grafi
Mimomys spp.
M. pyrenaicus
M. chandolensis
Pliomys lenki
Spermophilus citelloides
Spermophilus severskensis
Spermophilus superciliosus
Trogontherium cuvieri (large beaver)
Lagomorpha
Lepus tanaiticus (alternatively Lepus timidus tanaiticus)
Pika (Ochotona) spp. e.g.
Giant pika (Ochotona whartoni)
Tonomochota spp.
T. khasanensis
T. sikhotana
T. major
Birds
Yakutian goose (Anser djuktaiensis)
East Asian Ostrich (Struthio anderssoni)
Various European crane spp. (Genus Grus)
Grus primigenia
Grus melitensis
Cretan owl (Athene cretensis)
Primates
Homo
Denisovans (Homo sp.)
Neanderthals (Homo (sapiens) neanderthalensis; survived until about 40,000 years ago on the Iberian peninsula)
Reptiles
Solitudo sicula; survived in Sicily until about 12,500 years ago.
Lacerta siculimelitensis; from Malta.
Extinctions in North America were concentrated at the end of the Late Pleistocene, around 13,800–11,400 years Before Present, which were coincident with the onset of the Younger Dryas cooling period, as well as the emergence of the hunter-gatherer Clovis culture. The relative importance of human and climactic factors in the North American extinctions has been the subject of significant controversy. Extinctions totalled around 35 genera. The radiocarbon record for North America south of the Alaska-Yukon region has been described as "inadequate" to construct a reliable chronology.
North American extinctions (noted as herbivores (H) or carnivores (C)) included:
Ungulates
Even-Toed Hoofed Mammals
Various Bovidae spp.
Most forms of Pleistocene bison (only Bison bison in North America, and Bison bonasus in Eurasia, survived)
Ancient bison (Bison antiquus) (H)
Long-horned/Giant bison (Bison latifrons) (H)
Steppe bison (Bison priscus) (H)
Bison occidentalis (H)
Several members of Caprinae (the muskox survived)
Giant muskox (Praeovibos priscus) (H)
Shrub-ox (Euceratherium collinum) (H)
Harlan's muskox (Bootherium bombifrons) (H)
Soergel's ox (Soergelia mayfieldi) (H)
Harrington's mountain goat (Oreamnos harringtoni; smaller and more southern distribution than its surviving relative) (H)
Saiga antelope (Saiga tatarica; extirpated) (H)
Deer
Stag-moose (Cervalces scotti) (H)
American mountain deer (Odocoileus lucasi) (H)
Torontoceros hypnogeos (H)
Various Antilocapridae genera (pronghorns survived)
Capromeryx (H)
Stockoceros (H)
Tetrameryx (H)
Pacific pronghorn (Antilocapra pacifica) (H)
Several peccary (Tayassuidae) spp.
Flat-headed peccary (Platygonus) (H)
Long-nosed peccary (Mylohyus) (H)
Collared peccary (Dicotyles tajacu; extirpated, range semi-recolonised) (H) (Muknalia minimus is a junior synonym)
Various members of Camelidae
Western camel (Camelops hesternus) (H)
Stilt legged llamas (Hemiauchenia ssp.) (H)
Stout legged llamas (Palaeolama ssp.) (H)
Odd-Toed Hoofed Mammals
All native forms of Equidae
Caballine true horses (Equus cf. ferus) from the Late Pleistocene of North America have historically been assigned to many different species, including Equus fraternus, Equus scotti and Equus lambei, but the taxonomy of these horses is unclear, and many of these species may be synonymous with each other, perhaps only representing a single species.
Stilt-legged horse (Haringtonhippus francisci / Equus francisci; (H)
Tapirs (Tapirus; three species)
California tapir (Tapirus californicus) (H)
Merriam's tapir (Tapirus merriami) (H)
Vero tapir (Tapirus veroensis) (H)
Order Notoungulata
Mixotoxodon (H)
Carnivora
Feliformia
Several Felidae spp.
Sabertooths (Machairodontinae)
Smilodon fatalis (sabertooth cat) (C)
Homotherium serum scimitar-toothed cat (C)
American cheetah (Miracinonyx trumani; not true cheetah)
Cougar (Puma concolor; megafaunal ecomorph extirpated from North America, South American populations recolonised former range) (C)
Jaguarundi (Herpailurus yagouaroundi; extirpated, range semi-recolonised) (C)
Margay (Leopardus weidii; extirpated) (C)
Ocelot (Leopardus pardalis; extirpated, range marginally recolonised) (C)
Jaguars
Pleistocene North American jaguar (Panthera onca augusta; range semi-recolonised by other subspecies) (C)
North America Jaguar
Panthera balamoides (dubious, suggested to be a junior synonym of the short faced bear Arctotherium)
Lions
American lion (Panthera atrox) (C)
Cave lion (Panthera spelaea; present only in Alaska and Yukon) (C)
Caniformia
Canidae
Dire wolf (Aenocyon dirus) (C)
Pleistocene coyote (Canis latrans orcutti) (C)
Megafaunal wolf e.g.
Beringian wolf (Canis lupus ssp.) (C)
Dhole (Cuon alpinus; extirpated) (C)
Protocyon troglodytes (C)
Arctoidea
Musteloidea
Mephitidae
Short-faced skunk (Brachyprotoma obtusata) (C)
Mustelidae
Steppe polecat (Mustela eversmanii; extirpated) (C)
Various bear (Ursidae) spp.
Arctodus simus (C)
Florida spectacled bear (Tremarctos floridanus) (C)
South American short-faced bear (Arctotherium wingei) (C)
Giant polar bear (Ursus maritimus tyrannus; a possible inhabitant) (C)
Afrotheria
Paenungulata
Tethytheria
All native spp. of Proboscidea
Mastodons
American mastodon (Mammut americanum) (H)
Pacific mastodon (Mammut pacificus) (H) (validity uncertain)
Gomphotheriidae spp.
Cuvieronius (H)
Mammoth (Mammuthus) spp.
Columbian mammoth (Mammuthus columbi) (H)
Pygmy mammoth (Mammuthus exilis) (H)
Woolly mammoth (Mammuthus primigenius) (H)
Sirenia
Dugongidae
Steller's sea cow (Hydrodamalis gigas; extirpated from North America, survived in Beringia into 18th century) (H)
Euarchontoglires
Bats
Stock's vampire bat (Desmodus stocki) (C)
Pristine mustached bat (Pteronotus (Phyllodia) pristinus) (C)
Rodents
Giant beaver (Castoroides) spp.
Castoroides ohioensis (H)
Castoroides leiseyorum (H)
Klein's porcupine (Erethizon kleini) (H)
Giant island deer mouse (Peromyscus nesodytes) (C)
Neochoerus spp. e.g.
Pinckney's capybara (Neochoerus pinckneyi) (H)
Neochoerus aesopi (H)
Neotoma findleyi
Neotoma pygmaea
Synaptomys australis
All giant hutia (Heptaxodontidae) spp.
Blunt-toothed giant hutia (Amblyrhiza inundata; could grow as large as an American black bear) (H)
Plate-toothed giant hutia (Elasmodontomys obliquus) (H)
Twisted-toothed mouse (Quemisia gravis) (H)
Osborn's key mouse (Clidomys osborn's) (H)
Xaymaca fulvopulvis (H)
Lagomorphs
Aztlan rabbit (Aztlanolagus sp.) (H)
Giant pika (Ochotona whartoni) (H)
Eulipotyphla
Notiosorex dalquesti
Notiosorex harrisi
Xenarthra
Pilosa
Giant anteater (Myrmecophaga tridactyla; extirpated, range partially recolonised) (C)
All remaining ground sloth spp.
Eremotherium (megatheriid giant ground sloth) (H)
Nothrotheriops (nothrotheriid ground sloth) (H)
Megalonychid ground sloth spp.
Megalonyx (H)
Nohochichak (H)
Xibalbaonyx (H)
Meizonyx
Mylodontid ground sloth spp.
Paramylodon (H)
Cingulata
All members of Glyptodontinae
Glyptotherium (H)
Beautiful armadillo (Dasypus bellus) (H)
Pachyarmatherium
All Pampatheriidae spp.
Holmesina (H)
Pampatherium (H)
Birds
Water Fowl
Ducks
Bermuda flightless duck (Anas pachyscelus) (H)
Californian flightless sea duck (Chendytes lawi) (C)
Mexican stiff-tailed duck (Oxyura zapatima) (H)
Neochen barbadiana (H)
Turkey (Meleagris) spp.
Californian turkey (Meleagris californica) (H)
Meleagris crassipes (H)
Various Gruiformes spp.
All cave rail (Nesotrochis) spp. e.g.
Antillean cave rail (Nesotrochis debooyi) (C)
Barbados rail (Incertae sedis) (C)
Cuban flightless crane (Antigone cubensis) (H)
La Brea crane (Grus pagei) (H)
Various flamingo (Phoenicopteridae) spp.
Minute flamingo (Phoenicopterus minutus) (C)
Cope's flamingo (Phoenicopterus copei) (C)
Dow's puffin (Fratercula dowi) (C)
Pleistocene Mexican diver spp.
Plyolimbus baryosteus (C)
Podiceps spp.
Podiceps parvus (C)
Storks
La Brea/Asphalt stork (Ciconia maltha) (C)
Wetmore's stork (Mycteria wetmorei) (C)
Pleistocene Mexican cormorants spp. (genus Phalacrocorax)
Phalacrocorax goletensis (C)
Phalacrocorax chapalensis (C)
All remaining teratorn (Teratornithidae) spp.
Aiolornis incredibilis (C)
Cathartornis gracilis (C)
Oscaravis olsoni (C)
Teratornis merriami (C)
Teratornis woodburnensis (C)
Several New World vultures (Cathartidae) spp.
Pleistocene black vulture (Coragyps occidentalis ssp.) (C)
Megafaunal Californian condor (Gymnogyps amplus) (C)
Clark's condor (Breagyps clarki) (C)
Cuban condor (Gymnogyps varonai) (C)
Several Accipitridae spp.
American neophrone vulture (Neophrontops americanus) (C)
Woodward's eagle (Amplibuteo woodwardi) (C)
Cuban great hawk (Buteogallus borrasi) (C)
Daggett's eagle (Buteogallus daggetti) (C)
Fragile eagle (Buteogallus fragilis) (C)
Cuban giant hawk (Gigantohierax suarezi) (C)
Errant eagle (Neogyps errans) (C)
Grinnell's crested eagle (Spizaetus grinnelli) (C)
Willett's hawk-eagle (Spizaetus willetti) (C)
Caribbean titan hawk (Titanohierax) (C)
Several owl (Strigiformes) spp.
Brea miniature owl (Asphaltoglaux) (C)
Kurochkin's pygmy owl (Glaucidium kurochkini) (C)
Brea owl (Oraristix brea) (C)
Cuban giant owl (Ornimegalonyx) (C)
Bermuda flicker (Colaptes oceanicus) (C)
Several caracara (Caracarinae) spp.
Bahaman terrestrial caracara (Caracara sp.) (C)
Puerto Rican terrestrial caracara (Caracara sp.) (C)
Jamaican caracara (Carcara tellustris) (C)
Cuban caracara (Milvago sp.) (C)
Hispaniolan caracara (Milvago sp.) (C)
Psittacopasserae
Psittaciformes
Mexican thick-billed parrot (Rhynchopsitta phillipsi) (H)
Several giant tortoise spp.
Hesperotestudo (H)
Gopherus spp.
Gopherus donlaloi (H)
Chelonoidis spp.
Chelonoidis marcanoi (H)
Chelonoidis alburyorum (H)
The survivors are in some ways as significant as the losses: bison (H), grey wolf (C), lynx (C), grizzly bear (C), American black bear (C), deer (e.g. caribou, moose, wapiti (elk), Odocoileus spp.) (H), pronghorn (H), white-lipped peccary (H), muskox (H), bighorn sheep (H), and mountain goat (H); the list of survivors also include species which were extirpated during the Quaternary extinction event, but recolonised at least part of their ranges during the mid-Holocene from South American relict populations, such as the cougar (C), jaguar (C), giant anteater (C), collared peccary (H), ocelot (C) and jaguarundi (C). All save the pronghorns and giant anteaters were descended from Asian ancestors that had evolved with human predators. Pronghorns are the second-fastest land mammal (after the cheetah), which may have helped them elude hunters. More difficult to explain in the context of overkill is the survival of bison, since these animals first appeared in North America less than 240,000 years ago and so were geographically removed from human predators for a sizeable period of time. Because ancient bison evolved into living bison, there was no continent-wide extinction of bison at the end of the Pleistocene (although the genus was regionally extirpated in many areas). The survival of bison into the Holocene and recent times is therefore inconsistent with the overkill scenario. By the end of the Pleistocene, when humans first entered North America, these large animals had been geographically separated from intensive human hunting for more than 200,000 years. Given this enormous span of geologic time, bison would almost certainly have been very nearly as naive as native North American large mammals.
The culture that has been connected with the wave of extinctions in North America is the paleo-American culture associated with the Clovis people (q.v.), who were thought to use spear throwers to kill large animals. The chief criticism of the "prehistoric overkill hypothesis" has been that the human population at the time was too small and/or not sufficiently widespread geographically to have been capable of such ecologically significant impacts. This criticism does not mean that climate change scenarios explaining the extinction are automatically to be preferred by default, however, any more than weaknesses in climate change arguments can be taken as supporting overkill. Some form of a combination of both factors could be plausible, and overkill would be a lot easier to achieve large-scale extinction with an already stressed population due to climate change.
South America
South America suffered among the worst losses of the continents, with around 83% of its megafauna going extinct. These extinctions postdate the arrival of modern humans in South America around 15,000 years ago. Both human and climatic factors have been attributed as factors in the extinctions by various authors. Although some megafauna has been historically suggested to have survived into the early Holocene based on radiocarbon dates this may be the result of dating errors due to contamination. The extinctions are coincident with the end of the Antarctic Cold Reversal (a cooling period earlier and less severe than the Northern Hemisphere Younger Dryas) and the emergence of Fishtail projectile points, which became widespread across South America. Fishtail projectile points are thought to have been used in big game hunting, though direct evidence of exploitation of extinct megafauna by humans is rare, though megafauna exploitation has been documented at a number of sites. Fishtail points rapidly disappeared after the extinction of the megafauna, and were replaced by other styles more suited to hunting smaller prey. Some authors have proposed the "Broken Zig-Zag" model, where human hunting and climate change causing a reduction in open habitats preferred by megafauna were synergistic factors in megafauna extinction in South America.
Ungulates
Even-Toed Hoofed Mammals
Several Cervidae (deer) spp.
Morenelaphus
Antifer
Agalmaceros blicki (potentially synonym of modern white-tailed deer)
Odocoileus salinae
Various Camelidae spp.
Eulamaops
Stilt legged llama Hemiauchenia
Stout legged llama Palaeolama
Odd-Toed Hoofed Mammals
Several species of tapirs (Tapiridae)
Tapirus cristatellus
All Pleistocene wild horse genera (Equidae)
Equus neogeus
Hippidion
Hippidion devillei
Hippidion principale
Hippidion saldiasi
All remaining Meridiungulata genera
Order Litopterna
Macraucheniidae
Macrauchenia
Macraucheniopsis
Xenorhinotherium
Proterotheriidae
Neolicaphrium recens
Order Notoungulata
Toxodontidae
Piauhytherium (Some authors regard this taxon as synonym of Trigodonops)
Mixotoxodon
Toxodon
Trigodonops
Primates
Platyrrhini (New World monkeys)
Atelidae
Protopithecus
Caipora
Cartelles
Alouatta mauroi
Carnivora
Feliformia
Several Felidae spp.
Saber-toothed cat (Smilodon) spp.
Smilodon fatalis (northwestern South America)
Smilodon populator (eastern and southern South America)
Patagonian jaguar (Panthera onca mesembrina) (some authors have suggested that these remains actually belong to the American lion instead)
Caniformia
Canidae
Dire wolf (Aenocyon dirus)
Nehring's wolf (Canis nehringi)
Protocyon
Pleistocene bush dog (Speothos pacivorus)
Ursidae (bears)
South American short-faced bear (Arctotherium spp.)
Arctotherium bonairense
Arctotherium tarijense
Arctotherium wingei
Rodents
Neochoerus
Bats
Giant vampire bat (Desmodus draculae)
Proboscidea (elephants and relatives)
Gomphotheridae
Cuvieronius
Notiomastodon
Xenarthrans
All remaining ground sloth genera
Megatheriidae spp.
Eremotherium
Megatherium
Nothrotheriidae spp.
Nothropus
Nothrotherium
Megalonychidae spp.
Ahytherium
Australonyx
Diabolotherium
Megistonyx
Mylodontidae spp. (including Scelidotheriinae)
Catonyx
Glossotherium
Lestodon
Mylodon
Scelidotherium
Scelidodon
Mylodonopsis
Ocnotherium
Valgipes
All remaining Glyptodontinae spp.
Doedicurus
Glyptodon/Chlamydotherium
Heteroglyptodon
Hoplophorus
Lomaphorus
Neosclerocalyptus
Neuryurus
Panochthus
Parapanochthus
Plaxhaplous
Sclerocalyptus
Several Dasypodidae spp.
Beautiful armadillo (Dasypus bellus)
Eutatus
Pachyarmatherium
Propaopus
All Pampatheriidae spp.
Holmesina (et Chlamytherium occidentale)
Pampatherium
Tonnicinctus
Birds
Various Caracarinae spp.
Venezuelan caracara (Caracara major)
Seymour's caracara (Caracara seymouri)
Peruvian caracara (Milvago brodkorbi)
Various Cathartidae spp.
Pampagyps imperator
Geronogyps reliquus
Wingegyps cartellei
Pleistovultur nevesi
Various Tadorninae spp.
Neochen debilis
Neochen pugil
Psilopterus (small terror bird remains dated to the Late Pleistocene, but these are disputed)
Reptiles
Crocs & Gators
Caiman venezuelensis
Testudines
Chelonoidis lutzae (Argentina)
Peltocephalus maturin
Sahul (Australia-New Guinea) and the Pacific
A scarcity of reliably dated megafaunal bone deposits has made it difficult to construct timelines for megafaunal extinctions in certain areas, leading to a divide among researches about when and how megafaunal species went extinct.
There are at least three hypotheses regarding the extinction of the Australian megafauna:
that they went extinct with the arrival of the Aboriginal Australians on the continent,
that they went extinct due to natural climate change.
This theory is based on evidence of megafauna surviving until 40,000 years ago, a full 30,000 years after homo sapiens first landed in Australia, and thus that the two groups coexisted for a long time. Evidence of these animals existing at that time come from fossil records and ocean sediment. To begin with, sediment core drilled in the Indian Ocean off the SW coast of Australia indicate the existence of a fungus called Sporormiella, which survived off the dung of plant-eating mammals. The abundance of these spores in the sediment prior to 45,000 years ago indicates that many large mammals existed in the southwest Australian landscape until that point. The sediment data also indicates that the megafauna population collapsed within a few thousand years, around the 45,000 years ago, suggesting a rapid extinction event. In addition, fossils found at South Walker Creek, which is the youngest megafauna site in northern Australia, indicate that at least 16 species of megafauna survived there until 40,000 years ago. Furthermore, there is no firm evidence of homo sapiens living at South Walker Creek 40,000 years ago, therefore no human cause can be attributed to the extinction of these megafauna. However, there is evidence of major environmental deterioration of South Water Creek 40,000 years ago, which may have caused the extinct event. These changes include increased fire, reduction in grasslands, and the loss of fresh water. The same environmental deterioration is seen across Australia at the time, further strengthening the climate change argument. Australia's climate at the time could best be described as an overall drying of the landscape due to lower precipitation, resulting in less fresh water availability and more drought conditions. Overall, this led to changes in vegetation, increased fires, overall reduction in grasslands, and a greater competition for already scarce fresh water. These environmental changes proved to be too much for the Australian megafauna to cope with, causing the extinction of 90% of megafauna species.
The third hypothesis shared by some scientists is that human impacts and natural climate changes led to the extinction of Australian megafauna. About 75% of Australia is semi-arid or arid, so it makes sense that megafauna species used the same fresh water resources as humans. This competition could have led to more hunting of megafauna. Furthermore, Homo sapiens used fire agriculture to burn impassable land. This further diminished the already disappearing grassland which contained plants that were a key dietary component of herbivorous megafauna. While there is no scientific consensus on this, it is plausible that homo sapiens and natural climate change had a combined impact. Overall, there is a great deal of evidence for humans being the culprit, but by ruling out climate change completely as a cause of the Australian megafauna extinction we are not getting the whole picture. The climate change in Australia 45,000 years ago destabilized the ecosystem, making it particularly vulnerable to hunting and fire agriculture by humans; this is probably what led to the extinction of the Australian megafauna.
Several studies provide evidence that climate change caused megafaunal extinction during the Pleistocene in Australia. One group of researchers analyzed fossilized teeth found at Cuddie Springs in southeastern Australia. By analyzing oxygen isotopes, they measured aridity, and by analyzing carbon isotopes and dental microwear texture analysis, they assessed megafaunal diets and vegetation. During the middle Pleistocene, southeastern Australia was dominated by browsers, including fauna that consumed C4 plants. By the late Pleistocene, the C4 plant dietary component had decreased considerably. This shift may have been caused by increasingly arid conditions, which may have caused dietary restrictions. Other isotopic analyses of eggshells and wombat teeth also point to a decline of C4 vegetation after 45 Ka. This decline in C4 vegetation is coincident with increasing aridity. Increasingly arid conditions in southeastern Australia during the late Pleistocene may have stressed megafauna, and contributed to their decline.
In Sahul (a former continent composed of Australia and New Guinea), the sudden and extensive spate of extinctions occurred earlier than in the rest of the world. Most evidence points to a 20,000 year period after human arrival circa 63,000 BCE, but scientific argument continues as to the exact date range. In the rest of the Pacific (other Australasian islands such as New Caledonia, and Oceania) although in some respects far later, endemic fauna also usually perished quickly upon the arrival of humans in the late Pleistocene and early Holocene.
Marsupials
Various members of Diprotodontidae
Diprotodon (largest known marsupial)
Hulitherium tomasetti
Maokopia ronaldi
Zygomaturus
Palorchestes ("marsupial tapir")
Various members of Vombatidae
Lasiorhinus angustidens (giant wombat)
Phascolonus (giant wombat)
Ramasayia magna (giant wombat)
Vombatus hacketti (Hackett's wombat)
Warendja wakefieldi (dwarf wombat)
Sedophascolomys (giant wombat)
Phascolarctos stirtoni (giant koala)
Marsupial lion (Thylacoleo carnifex)
Borungaboodie (giant potoroo)
Various members of Macropodidae (kangaroos, wallabies, etc.)
Procoptodon (short-faced kangaroos) e.g.
Procoptodon goliah
Sthenurus (giant kangaroo)
Simosthenurus (giant kangaroo)
Various Macropus (giant kangaroo) spp. e.g.
Macropus ferragus
Macropus titan
Macropus pearsoni
Protemnodon spp. (giant wallaby)
Troposodon (wallaby)
Bohra (giant tree kangaroo)
Propleopus oscillans (omnivorous, giant musky rat-kangaroo)
Nombe
Congruus
Various forms of Sarcophilus (Tasmanian devil)
Sarcophilus laniarius (25% larger than modern species, unclear if it is actually a distinct species from living Tasmanian devil)
Sarcophilus moornaensis
Monotremes: egg-laying mammals.
Echidna
Murrayglossus hacketti (giant echidna)
Megalibgwilia ramsayi
Birds
Pygmy Cassowary (Casuarius lydekkeri)
Genyornis (a dromornithid
Giant malleefowl (Progura gallinacea)
Cryptogyps lacertosus
Dynatoaetus gaffae
Several Phoenicopteridae spp.
Xenorhynchopsis spp. (Australian flamingo)
Xenorhynchopsis minor
Xenorhynchopsis tibialis
Reptiles
Crocs & Gators
Ikanogavialis (the last fully marine crocodilian)
Paludirex (Australian freshwater mekosuchine crocodiian)
Quinkana (Australian terrestrial mekosuchine crocodilian, apex predator)
Volia (a two-to-three meter long mekosuchine crocodylian, apex predator of Pleistocene Fiji)
Mekosuchus
Mekosuchus inexpectatus (New Caledonian land crocodile)
Mekosuchus kalpokasi (Vanuatu land crocodile)
Varanus sp. (Pleistocene and Holocene New Caledonia)
Megalania (Varanus pricus) (a giant predatory monitor lizard comparable or larger than the Komodo dragon)
Snakes
Wonambi (a five-to-six-metre-long Australian constrictor snake)
Several spp. of Meiolaniidae (giant armoured turtles)
Meiolania
Ninjemys
Causes
History of research
The megafaunal extinctions were already recognized as a distinct phenomenon by some scientists in the 19th century:
Several decades later in his 1911 book The World of Life (published 2 years before his death), Wallace revisited the issue of the Pleistocene megafauna extinctions, concluding that the extinctons were at least in part the result of human agency in combination with other factors. Discussion of the topic became more widespread during the 20th century, particularly following the proposal of the "overkill hypothesis" by Paul Schultz Martin during the 1960s. By the end of the 20th century, two "camps" of researchers had emerged on the topic, one supporting climate change, the other supporting human hunting as the primary cause of the extinctions.
Hunting
The hunting hypothesis suggests that humans hunted megaherbivores to extinction, which in turn caused the extinction of carnivores and scavengers which had preyed upon those animals. This hypothesis holds Pleistocene humans responsible for the megafaunal extinction. One variant, known as blitzkrieg, portrays this process as relatively quick. Some of the direct evidence for this includes: fossils of some megafauna found in conjunction with human remains, embedded arrows and tool cut marks found in megafaunal bones, and European cave paintings that depict such hunting. Biogeographical evidence is also suggestive: the areas of the world where humans evolved currently have more of their Pleistocene megafaunal diversity (the elephants and rhinos of Asia and Africa) compared to other areas such as Australia, the Americas, Madagascar and New Zealand without the earliest humans. The overkill hypothesis, a variant of the hunting hypothesis, was proposed in 1966 by Paul S. Martin, Professor of Geosciences Emeritus at the Desert Laboratory of the University of Arizona.
Circumstantially, the close correlation in time between the appearance of humans in an area and extinction there provides weight for this scenario. Radiocarbon dating has supported the plausibility of this correlation being reflective of causation. The megafaunal extinctions covered a vast period of time and highly variable climatic situations. The earliest extinctions in Australia were complete approximately 50,000 BP, well before the Last Glacial Maximum and before rises in temperature. The most recent extinction in New Zealand was complete no earlier than 500 BP and during a period of cooling. In between these extremes megafaunal extinctions have occurred progressively in such places as North America, South America and Madagascar with no climatic commonality. The only common factor that can be ascertained is the arrival of humans. This phenomenon appears even within regions. The mammal extinction wave in Australia about 50,000 years ago coincides not with known climatic changes, but with the arrival of humans. In addition, large mammal species like the giant kangaroo Protemnodon appear to have succumbed sooner on the Australian mainland than on Tasmania, which was colonised by humans a few thousand years later. A study published in 2015 supported the hypothesis further by running several thousand scenarios that correlated the time windows in which each species is known to have become extinct with the arrival of humans on different continents or islands. This was compared against climate reconstructions for the last 90,000 years. The researchers found correlations of human spread and species extinction indicating that the human impact was the main cause of the extinction, while climate change exacerbated the frequency of extinctions. The study, however, found an apparently low extinction rate in the fossil record of mainland Asia. A 2020 study published in Science Advances found that human population size and/or specific human activities, not climate change, caused rapidly rising global mammal extinction rates during the past 126,000 years. Around 96% of all mammalian extinctions over this time period are attributable to human impacts. According to Tobias Andermann, lead author of the study, "these extinctions did not happen continuously and at constant pace. Instead, bursts of extinctions are detected across different continents at times when humans first reached them. More recently, the magnitude of human driven extinctions has picked up the pace again, this time on a global scale." On a related note, the population declines of still extant megafauna during the Pleistocene have also been shown to correlate with human expansion rather than climate change.
The extinction's extreme bias towards larger animals further supports a relationship with human activity rather than climate change. There is evidence that the average size of mammalian fauna declined over the course of the Quaternary, a phenomenon that was likely linked to disproportionate hunting of large animals by humans.
Extinction through human hunting has been supported by archaeological finds of mammoths with projectile points embedded in their skeletons, by observations of modern naive animals allowing hunters to approach easily and by computer models by Mosimann and Martin, and Whittington and Dyke, and most recently by Alroy.
In 2024 a paper was published in Science Advances that added additional support to the overkill hypothesis in North America when the skull of an 18 month old child, dated to 12,800 years ago, was analyzed for chemical signatures attributable to both maternal milk and solid food. Specific isotopes of carbon and nitrogen most closely matched those that would have been found in the mammoth genus and secondarily elk or bison.
A number of objections have been raised regarding the hunting hypothesis. Notable among them is the sparsity of evidence of human hunting of megafauna. There is no archeological evidence that in North America megafauna other than mammoths, mastodons, gomphotheres and bison were hunted, despite the fact that, for example, camels and horses are very frequently reported in fossil history. Overkill proponents, however, say this is due to the fast extinction process in North America and the low probability of animals with signs of butchery to be preserved. The majority of North American taxa have too sparse a fossil record to accurately assess the frequency of human hunting of them. A study by Surovell and Grund concluded "archaeological sites dating to the time of the coexistence of humans and extinct fauna are rare. Those that preserve bone are considerably more rare, and of those, only a very few show unambiguous evidence of human hunting of any type of prey whatsoever." Eugene S. Hunn suggests that the birthrate in hunter-gatherer societies is generally too low, that too much effort is involved in the bringing down of a large animal by a hunting party, and that in order for hunter-gatherers to have brought about the extinction of megafauna simply by hunting them to death, an extraordinary amount of meat would have had to have been wasted. Proponents of hunting as a cause of the extinctions argue that statistical modelling validates that relatively low-level hunting can have significant effect on megafauna populations due to their slow life cycles, and that hunting can cause top-down forcing trophic cascade events that destabilize ecosystems.
Second-order predation
The Second-Order Predation Hypothesis says that as humans entered the New World they continued their policy of killing predators, which had been successful in the Old World but because they were more efficient and because the fauna, both herbivores and carnivores, were more naive, they killed off enough carnivores to upset the ecological balance of the continent, causing overpopulation, environmental exhaustion, and environmental collapse. The hypothesis accounts for changes in animal, plant, and human populations.
The scenario is as follows:
After the arrival of H. sapiens in the New World, existing predators must share the prey populations with this new predator. Because of this competition, populations of original, or first-order, predators cannot find enough food; they are in direct competition with humans.
Second-order predation begins as humans begin to kill predators.
Prey populations are no longer well controlled by predation. Killing of nonhuman predators by H. sapiens reduces their numbers to a point where these predators no longer regulate the size of the prey populations.
Lack of regulation by first-order predators triggers boom-and-bust cycles in prey populations. Prey populations expand and consequently overgraze and over-browse the land. Soon the environment is no longer able to support them. As a result, many herbivores starve. Species that rely on the slowest recruiting food become extinct, followed by species that cannot extract the maximum benefit from every bit of their food.
Boom-bust cycles in herbivore populations change the nature of the vegetative environment, with consequent climatic impacts on relative humidity and continentality. Through overgrazing and overbrowsing, mixed parkland becomes grassland, and climatic continentality increases.
The second-order predation hypothesis has been supported by a computer model, the Pleistocene extinction model (PEM), which, using the same assumptions and values for all variables (herbivore population, herbivore recruitment rates, food needed per human, herbivore hunting rates, etc.) other than those for hunting of predators. It compares the overkill hypothesis (predator hunting = 0) with second-order predation (predator hunting varied between 0.01 and 0.05 for different runs). The findings are that second-order predation is more consistent with extinction than is overkill (results graph at left). The Pleistocene extinction model is the only test of multiple hypotheses and is the only model to specifically test combination hypotheses by artificially introducing sufficient climate change to cause extinction. When overkill and climate change are combined they balance each other out. Climate change reduces the number of plants, overkill removes animals, therefore fewer plants are eaten. Second-order predation combined with climate change exacerbates the effect of climate change. (results graph at right). The second-order predation hypothesis is further supported by the observation above that there was a massive increase in bison populations.
However, this hypothesis has been criticised on the grounds that the multispecies model produces a mass extinction through indirect competition between herbivore species: small species with high reproductive rates subsidize predation on large species with low reproductive rates. All prey species are lumped in the Pleistocene extinction model. Also, the control of population sizes by predators is not fully supported by observations of modern ecosystems. The hypothesis further assumes decreases in vegetation due to climate change, but deglaciation doubled the habitable area of North America. Any vegetational changes that did occur failed to cause almost any extinctions of small vertebrates, and they are more narrowly distributed on average, which detractors cite as evidence against the hypothesis.
Competition for water
In southeastern Australia, the scarcity of water during the interval in which humans arrived in Australia suggests that human competition with megafauna for precious water sources may have played a role in the extinction of the latter.
Landscape alteration
One consequence of the colonisation by humans of lands previously uninhabited by them may have been the introduction of new fire regimes because of extensive fire use by humans. There is evidence that anthropogenic fire use had major impacts on the local environments in both Australia and North America.
Climate change
At the end of the 19th and beginning of the 20th centuries, when scientists first realized that there had been glacial and interglacial ages, and that they were somehow associated with the prevalence or disappearance of certain animals, they surmised that the termination of the Pleistocene ice age might be an explanation for the extinctions.
The most obvious change associated with the termination of an ice age is the increase in temperature. Between 15,000 BP and 10,000 BP, a 6 °C increase in global mean annual temperatures occurred. This was generally thought to be the cause of the extinctions. According to this hypothesis, a temperature increase sufficient to melt the Wisconsin ice sheet could have placed enough thermal stress on cold-adapted mammals to cause them to die. Their heavy fur, which helps conserve body heat in the glacial cold, might have prevented the dumping of excess heat, causing the mammals to die of heat exhaustion. Large mammals, with their reduced surface area-to-volume ratio, would have fared worse than small mammals. A study covering the past 56,000 years indicates that rapid warming events with temperature changes of up to had an important impact on the extinction of megafauna. Ancient DNA and radiocarbon data indicates that local genetic populations were replaced by others within the same species or by others within the same genus. Survival of populations was dependent on the existence of refugia and long distance dispersals, which may have been disrupted by human hunters.
Other scientists have proposed that increasingly extreme weather—hotter summers and colder winters—referred to as "continentality", or related changes in rainfall caused the extinctions. It has been shown that vegetation changed from mixed woodland-parkland to separate prairie and woodland. This may have affected the kinds of food available. Shorter growing seasons may have caused the extinction of large herbivores and the dwarfing of many others. In this case, as observed, bison and other large ruminants would have fared better than horses, elephants and other monogastrics, because ruminants are able to extract more nutrition from limited quantities of high-fiber food and better able to deal with anti-herbivory toxins. So, in general, when vegetation becomes more specialized, herbivores with less diet flexibility may be less able to find the mix of vegetation they need to sustain life and reproduce, within a given area. Increased continentality resulted in reduced and less predictable rainfall limiting the availability of plants necessary for energy and nutrition. It has been suggested that this change in rainfall restricted the amount of time favorable for reproduction. This could disproportionately harm large animals, since they have longer, more inflexible mating periods, and so may have produced young at unfavorable seasons (i.e., when sufficient food, water, or shelter was unavailable because of shifts in the growing season). In contrast, small mammals, with their shorter life cycles, shorter reproductive cycles, and shorter gestation periods, could have adjusted to the increased unpredictability of the climate, both as individuals and as species which allowed them to synchronize their reproductive efforts with conditions favorable for offspring survival. If so, smaller mammals would have lost fewer offspring and would have been better able to repeat the reproductive effort when circumstances once more favored offspring survival. A study looking at the environmental conditions across Europe, Siberia and the Americas from 25,000 to 10,000 YBP found that prolonged warming events leading to deglaciation and maximum rainfall occurred just prior to the transformation of the rangelands that supported megaherbivores into widespread wetlands that supported herbivore-resistant plants. The study proposes that moisture-driven environmental change led to the megafaunal extinctions and that Africa's trans-equatorial position allowed rangeland to continue to exist between the deserts and the central forests, therefore fewer megafauna species became extinct there.
Evidence in Southeast Asia, in contrast to Europe, Australia, and the Americas, suggests that climate change and an increasing sea level were significant factors in the extinction of several herbivorous species. Alterations in vegetation growth and new access routes for early humans and mammals to previously isolated, localized ecosystems were detrimental to select groups of fauna.
Some evidence from Europe also suggests climatic changes were responsible for extinctions there, as the individuals extinctions tended to occur during times of environmental change and did not correlate particularly well with human migrations.
In Australia, some studies have suggested that extinctions of megafauna began before the peopling of the continent, favouring climate change as the driver.
In Beringia, megafauna may have gone extinct because of particularly intense paludification and because the land connection between Eurasia and North America flooded before the Cordilleran Ice Sheet retreated far enough to reopen the corridor between Beringia and the remainder of North America. Woolly mammoths became extirpated from Beringia because of climatic factors, although human activity also played a synergistic role in their decline. In North America, a Radiocarbon-dated Event-Count (REC) modelling study found that megafaunal declines in North America correlated with climatic changes instead of human population expansion.
In the North American Great Lakes region, the population declines of mastodons and mammoths have been found to correlate with climatic fluctuations during the Younger Dryas rather than human activity.
In the Argentine Pampas, the flooding of vast swathes of the once much larger Pampas grasslands may have played a role in the extinctions of its megafaunal assemblages.
Critics object that since there were multiple glacial advances and withdrawals in the evolutionary history of many of the megafauna, it is rather implausible that only after the last glacial maximum would there be such extinctions. Proponents of climate change as the extinction event's cause like David J. Meltzer suggest that the last deglaciation may have been markedly different from previous ones. Also, one study suggests that the Pleistocene megafaunal composition may have differed markedly from that of earlier interglacials, making the Pleistocene populations particularly vulnerable to changes in their environment.
Studies propose that the annual mean temperature of the current interglacial that we have seen for the last 10,000 years is no higher than that of previous interglacials, yet most of the same large mammals survived similar temperature increases. In addition, numerous species such as mammoths on Wrangel Island and St. Paul Island survived in human-free refugia despite changes in climate. This would not be expected if climate change were responsible (unless their maritime climates offered some protection against climate change not afforded to coastal populations on the mainland). Under normal ecological assumptions island populations should be more vulnerable to extinction due to climate change because of small populations and an inability to migrate to more favorable climes.
Critics have also identified a number of problems with the continentality hypotheses. Megaherbivores have prospered at other times of continental climate. For example, megaherbivores thrived in Pleistocene Siberia, which had and has a more continental climate than Pleistocene or modern (post-Pleistocene, interglacial) North America. The animals that became extinct actually should have prospered during the shift from mixed woodland-parkland to prairie, because their primary food source, grass, was increasing rather than decreasing. Although the vegetation did become more spatially specialized, the amount of prairie and grass available increased, which would have been good for horses and for mammoths, and yet they became extinct. This criticism ignores the increased abundance and broad geographic extent of Pleistocene bison at the end of the Pleistocene, which would have increased competition for these resources in a manner not seen in any earlier interglacials. Although horses became extinct in the New World, they were successfully reintroduced by the Spanish in the 16th century—into a modern post-Pleistocene, interglacial climate. Today there are feral horses still living in those same environments. They find a sufficient mix of food to avoid toxins, they extract enough nutrition from forage to reproduce effectively and the timing of their gestation is not an issue. This criticism ignores the fact that present-day horses are not competing for resources with ground sloths, mammoths, mastodons, camels, llamas, and bison. Similarly, mammoths survived the Pleistocene Holocene transition on isolated, uninhabited islands in the Mediterranean Sea until 4,000 to 7,000 years ago, as well as on Wrangel Island in the Siberian Arctic. Additionally, large mammals should have been able to migrate, permanently or seasonally, if they found the temperature too extreme, the breeding season too short, or the rainfall too sparse or unpredictable. Seasons vary geographically. By migrating away from the equator, herbivores could have found areas with growing seasons more favorable for finding food and breeding successfully. Modern-day African elephants migrate during periods of drought to places where there is apt to be water. Large animals also store more fat in their bodies than do medium-sized animals and this should have allowed them to compensate for extreme seasonal fluctuations in food availability.
Some evidence weighs against climate change as a valid hypothesis as applied to Australia. It has been shown that the prevailing climate at the time of extinction (40,000–50,000 BP) was similar to that of today, and that the extinct animals were strongly adapted to an arid climate. The evidence indicates that all of the extinctions took place in the same short time period, which was the time when humans entered the landscape. The main mechanism for extinction was probably fire (started by humans) in a then much less fire-adapted landscape. Isotopic evidence shows sudden changes in the diet of surviving species, which could correspond to the stress they experienced before extinction.
Some evidence obtained from analysis of the tusks of mastodons from the American Great Lakes region appears inconsistent with the climate change hypothesis. Over a span of several thousand years prior to their extinction in the area, the mastodons show a trend of declining age at maturation. This is the opposite of what one would expect if they were experiencing stresses from deteriorating environmental conditions, but is consistent with a reduction in intraspecific competition that would result from a population being reduced by human hunting.
It may be observed that neither the overkill nor the climate change hypotheses can fully explain events: browsers, mixed feeders and non-ruminant grazer species suffered most, while relatively more ruminant grazers survived. However, a broader variation of the overkill hypothesis may predict this, because changes in vegetation wrought by either Second Order Predation (see below) or anthropogenic fire preferentially selects against browse species.
Disease
The hyperdisease hypothesis, as advanced by Ross D. E. MacFee and Preston A. Marx, attributes the extinction of large mammals during the late Pleistocene to indirect effects of the newly arrived aboriginal humans. In more recent times, disease has driven many vulnerable species to extinction; the introduction of avian malaria and avipoxvirus, for example, has greatly decreased the populations of the endemic birds of Hawaii, with some going extinct. The hyperdisease hypothesis proposes that humans or animals traveling with them (e.g., chickens or domestic dogs) introduced one or more highly virulent diseases into vulnerable populations of native mammals, eventually causing extinctions. The extinction was biased toward larger-sized species because smaller species have greater resilience because of their life history traits (e.g., shorter gestation time, greater population sizes, etc.). Humans are thought to be the cause because other earlier immigrations of mammals into North America from Eurasia did not cause extinctions. A similar suggestion is that pathogens were transmitted by the expanding humans via the domesticated dogs they brought with them. A related theory proposes that a highly contagious prion disease similar to chronic wasting disease or scrapie that was capable of infecting a large number of species was the culprit. Animals weakened by this "superprion" would also have easily become reservoirs of viral and bacterial diseases as they succumbed to neurological degeneration from the prion, causing a cascade of different diseases to spread among various mammal species. This theory could potentially explain the prevalence of heterozygosity at codon 129 of the prion protein gene in humans, which has been speculated to be the result of natural selection against homozygous genotypes that were more susceptible to prion disease and thus potentially a tell-tale of a major prion pandemic that affected humans of or younger than reproductive age far in the past and disproportionately killed before they could reproduce those with homozygous genotypes at codon 129.
If a disease was indeed responsible for the end-Pleistocene extinctions, then there are several criteria it must satisfy (see Table 7.3 in MacPhee & Marx 1997). First, the pathogen must have a stable carrier state in a reservoir species. That is, it must be able to sustain itself in the environment when there are no susceptible hosts available to infect. Second, the pathogen must have a high infection rate, such that it is able to infect virtually all individuals of all ages and sexes encountered. Third, it must be extremely lethal, with a mortality rate of c. 50–75%. Finally, it must have the ability to infect multiple host species without posing a serious threat to humans. Humans may be infected, but the disease must not be highly lethal or able to cause an epidemic.
As with other hypotheses, a number of counterarguments to the hyperdisease hypothesis have been put forth. Generally speaking, disease has to be very virulent to kill off all the individuals in a genus or species. Even such a virulent disease as West Nile fever is unlikely to have caused extinction. The disease would need to be implausibly selective while being simultaneously implausibly broad. Such a disease needs to be capable of killing off wolves such as Canis dirus or goats such as Oreamnos harringtoni while leaving other very similar species (Canis lupus and Oreamnos americanus, respectively) unaffected. It would need to be capable of killing off flightless birds while leaving closely related flighted species unaffected. Yet while remaining sufficiently selective to afflict only individual species within genera it must be capable of fatally infecting across such clades as birds, marsupials, placentals, testudines, and crocodilians. No disease with such a broad scope of fatal infectivity is known, much less one that remains simultaneously incapable of infecting numerous closely related species within those disparate clades. On the other hand, this objection does not account for the possibility of a variety of different diseases being introduced around the same era. Numerous species including wolves, mammoths, camelids, and horses had emigrated continually between Asia and North America over the past 100,000 years. For the disease hypothesis to be applicable there it would require that the population remain immunologically naive despite this constant transmission of genetic and pathogenic material. The dog-specific hypothesis in particular cannot account for several major extinction events, notably the Americas (for reasons already covered) and Australia. Dogs did not arrive in Australia until approximately 35,000 years after the first humans arrived there, and approximately 30,000 years after the Australian megafaunal extinction was complete.
Extraterrestrial impact
An extraterrestrial impact, which has occasionally been proposed as a cause of the Younger Dryas, has been suggested by some authors as a potential cause of the extinction of North America's megafauna due to the temporal proximity between a proposed date for such an impact and the following megafaunal extinctions. However, the Younger Dryas impact hypothesis lacks widespread support among scholars due to various inconsistencies in the hypothesis, and another group of researchers has published a review contesting the arguments for it point by point.
Geomagnetic field weakening
Around 41,500 years ago, the Earth's magnetic field weakened in an event known as the Laschamp event. This weakening may have caused increased flux of UV-B radiation and has been suggested by a few authors as a cause of megafaunal extinctions in the Late Quaternary. The full effects of such events on the biosphere are poorly understood, however these explanations have been criticized as they do not account for the population bottlenecks seen in many megafaunal species and nor is there evidence for extreme radio-isotopic changes during the event. Considering these factors, causation is unlikely.
Effects
The extinction of the megafauna has been argued by some authors to be disappearance of the mammoth steppe rather than the other way around. Alaska now has low nutrient soil unable to support bison, mammoths, and horses. R. Dale Guthrie has claimed this as a cause of the extinction of the megafauna there; however, he may be interpreting it backwards. The loss of large herbivores to break up the permafrost allows the cold soils that are unable to support large herbivores today. Today, in the arctic, where trucks have broken the permafrost grasses and diverse flora and fauna can be supported. In addition, Chapin (Chapin 1980) showed that simply adding fertilizer to the soil in Alaska could make grasses grow again like they did in the era of the mammoth steppe. Possibly, the extinction of the megafauna and the corresponding loss of dung is what led to low nutrient levels in modern-day soil and therefore is why the landscape can no longer support megafauna.
However, more recent authors have viewed it as more likely that the collapse of the mammoth steppe was driven by climatic warming, which in turn impacted the megafauna, rather than the other way around.
Megafauna play a significant role in the lateral transport of mineral nutrients in an ecosystem, tending to translocate them from areas of high to those of lower abundance. They do so by their movement between the time they consume the nutrient and the time they release it through elimination (or, to a much lesser extent, through decomposition after death). In South America's Amazon Basin, it is estimated that such lateral diffusion was reduced over 98% following the megafaunal extinctions that occurred roughly 12,500 years ago. Given that phosphorus availability is thought to limit productivity in much of the region, the decrease in its transport from the western part of the basin and from floodplains (both of which derive their supply from the uplift of the Andes) to other areas is thought to have significantly impacted the region's ecology, and the effects may not yet have reached their limits. The extinction of the mammoths allowed grasslands they had maintained through grazing habits to become birch forests. The new forest and the resulting forest fires may have induced climate change. Such disappearances might be the result of the proliferation of modern humans.
Large populations of megaherbivores have the potential to contribute greatly to the atmospheric concentration of methane, which is an important greenhouse gas. Modern ruminant herbivores produce methane as a byproduct of foregut fermentation in digestion, and release it through belching or flatulence. Today, around 20% of annual methane emissions come from livestock methane release. In the Mesozoic, it has been estimated that sauropods could have emitted 520 million tons of methane to the atmosphere annually, contributing to the warmer climate of the time (up to 10 °C warmer than at present). This large emission follows from the enormous estimated biomass of sauropods, and because methane production of individual herbivores is believed to be almost proportional to their mass.
Recent studies have indicated that the extinction of megafaunal herbivores may have caused a reduction in atmospheric methane. One study examined the methane emissions from the bison that occupied the Great Plains of North America before contact with European settlers. The study estimated that the removal of the bison caused a decrease of as much as 2.2 million tons per year. Another study examined the change in the methane concentration in the atmosphere at the end of the Pleistocene epoch after the extinction of megafauna in the Americas. After early humans migrated to the Americas about 13,000 BP, their hunting and other associated ecological impacts led to the extinction of many megafaunal species there. Calculations suggest that this extinction decreased methane production by about 9.6 million tons per year. This suggests that the absence of megafaunal methane emissions may have contributed to the abrupt climatic cooling at the onset of the Younger Dryas. The decrease in atmospheric methane that occurred at that time, as recorded in ice cores, was 2–4 times more rapid than any other decrease in the last half million years, suggesting that an unusual mechanism was at work.
The extermination of megafauna left many niches vacant, which has been cited as an explanation for the vulnerability and fragility of many ecosystems to destruction in the later Holocene extinction. The comparative lack of megafauna in modern ecosystems has reduced high-order interactions among surviving species, reducing ecological complexity. This depauperate, post-megafaunal ecological state has been associated with diminished ecological resilience to stressors. Many extant species of plants have adaptations that were advantageous in the presence of megafauna but are now useless in their absence. The demise of megafaunal ecosystem engineers in the Arctic that maintained open grassland environments has been highly detrimental to shorebirds of the genus Numenius.
Relationship to later extinctions
There is no general agreement on where the Quaternary extinction event ends, and the Holocene, or anthropogenic, extinction begins, or if they should be considered separate events at all. Some authors have argued that the activities of earlier archaic humans have also resulted in extinctions, though the evidence for this is equivocal.
This hypothesis is supported by rapid megafaunal extinction following recent human colonisation in Australia, New Zealand and Madagascar, in a similar way that any large, adaptable predator moving into a new ecosystem would. In many cases, it is suggested even minimal hunting pressure was enough to wipe out large fauna, particularly on geographically isolated islands. Only during the most recent parts of the extinction have plants also suffered large losses.
See also
List of Ice Age species preserved as permafrost mummies
References
External links
Hyperdisease hypothesis
Second-order predation
Other links
Extinction events
Pleistocene
Events that forced the climate
Younger Dryas impact hypothesis
Megafauna | Late Pleistocene extinctions | Biology | 16,165 |
42,600,851 | https://en.wikipedia.org/wiki/Intercalation%20%28biochemistry%29 | In biochemistry, intercalation is the insertion of molecules between the planar bases of deoxyribonucleic acid (DNA). This process is used as a method for analyzing DNA and it is also the basis of certain kinds of poisoning.
There are several ways molecules (in this case, also known as ligands) can interact with DNA. Ligands may interact with DNA by covalently binding, electrostatically binding, or intercalating. Intercalation occurs when ligands of an appropriate size and chemical nature fit themselves in between base pairs of DNA. These ligands are mostly polycyclic, aromatic, and planar, and therefore often make good nucleic acid stains. Intensively studied DNA intercalators include berberine, ethidium bromide, proflavine, daunomycin, doxorubicin, and thalidomide. DNA intercalators are used in chemotherapeutic treatment to inhibit DNA replication in rapidly growing cancer cells. Examples include doxorubicin (adriamycin) and daunorubicin (both of which are used in treatment of Hodgkin's lymphoma), and dactinomycin (used in Wilm's tumour, Ewing's Sarcoma, rhabdomyosarcoma).
Metallointercalators are complexes of a metal cation with polycyclic aromatic ligands. The most commonly used metal ion is ruthenium(II), because its complexes are very slow to decompose in the biological environment. Other metallic cations that have been used include rhodium(III) and iridium(III). Typical ligands attached to the metal ion are dipyridine and terpyridine whose planar structure is ideal for intercalation.
In order for an intercalator to fit between base pairs, the DNA must dynamically open a space between its base pairs by unwinding. The degree of unwinding varies depending on the intercalator; for example, ethidium cation (the ionic form of ethidium bromide found in aqueous solution) unwinds DNA by about 26°, whereas proflavine unwinds it by about 17°. This unwinding causes the base pairs to separate, or "rise", creating an opening of about 0.34 nm (3.4 Å). This unwinding induces local structural changes to the DNA strand, such as lengthening of the DNA strand or twisting of the base pairs. These structural modifications can lead to functional changes, often to the inhibition of transcription and replication and DNA repair processes, which makes intercalators potent mutagens. For this reason, DNA intercalators are often carcinogenic, such as the exo (but not the endo) 8,9 epoxide of aflatoxin B1 and acridines such as proflavine or quinacrine.
Intercalation as a mechanism of interaction between cationic, planar, polycyclic aromatic systems of the correct size (on the order of a base pair) was first proposed by Leonard Lerman in 1961. One proposed mechanism of intercalation is as follows: In aqueous isotonic solution, the cationic intercalator is attracted electrostatically to the surface of the polyanionic DNA. The ligand displaces a sodium and/or magnesium cation present in the "condensation cloud" of such cations that surrounds DNA (to partially balance the sum of the negative charges carried by each phosphate oxygen), thus forming a weak electrostatic association with the outer surface of DNA. From this position, the ligand diffuses along the surface of the DNA and may slide into the hydrophobic environment found between two base pairs that may transiently "open" to form an intercalation site, allowing the ethidium to move away from the hydrophilic (aqueous) environment surrounding the DNA and into the intercalation site. The base pairs transiently form such openings due to energy absorbed during collisions with solvent molecules.
See also
Anthracycline
Intercalation (chemistry)
Molecular tweezers
Twisted intercalating nucleic acid
References
Supramolecular chemistry | Intercalation (biochemistry) | Chemistry,Materials_science | 886 |
12,840,831 | https://en.wikipedia.org/wiki/Electronic%20Case%20Filing%20System | Electronic Case Filing System (ECFS) is an automated system developed in Tarrant County, Texas that enables law enforcement agencies, criminal district attorneys, county criminal courts, criminal district courts, and the defense bar to process and exchange information about criminal offenses. ECFS software does not work on the Mac.
History
ECFS was conceived in November 2002 in Tarrant County, Texas. Initially, the purpose of the system was to enable law enforcement agencies to submit offense reports to the criminal district attorney's office for possible prosecution. In July 2003, the Criminal District Attorney accepted the first electronic case filing via ECFS. Since that time, more than 100,000 cases have been filed in ECFS by the 47 Law Enforcement Agencies located in Tarrant County, Texas. ECFS was expanded in June 2004 to incorporate the Grand Jury function which is able to return indictments to the Criminal District Courts on the same day that a True Bill is decided.
In January 2005, ECFS was extended to enable judges and their court staff to effectively manage the docket (caseload) for each of the nine (9) Criminal District Courts. Since the implementation of ECFS, Tarrant County has been able to control the jail population, despite a significant increase in the number of cases being filed. In August 2005, ECFS was extended to enable members of the Tarrant County Criminal Defense Lawyers Association to browse and view defendants, offenses, and evidence via ECFS. Through this process, defense attorneys are no longer required to visit the Criminal District Attorney's Office to view and copy files.
Since January 2006, the Criminal District Attorney's Office has been completely paperless and all Offense Reports are submitted via ECFS and made available to Law Enforcement Agencies, County and District Courts, and Defense Attorneys. In July 2006, ECFS was extended to allow criminal defendants to be magistrated electronically. This process also allows the Office of Attorney appointments to be notified that the defendant has requested that defense counsel be appointed which triggers a business process that captures financial information, facilitates a determination of indigency, and when appropriate appoints defense counsel.
In 2005, the Tarrant County Criminal Defense Lawyer's Association, a non-profit charitable association, implemented its own software design to enable all attorneys, whether members of TCCDLA or not, to access the ECFS system. The software only works on PCs and will not work on Apple's Mac platform. The process enables an attorney to access his or her case files from any computer on the World Wide Web and is secure and reliable. TCCDLA has continuously revised its software process to enable access 24-7, with little downtime. TCCDLA also installed computers in the Tarrant County Justice Center that allow subscribers to access files while in the courthouse. Storm's Edge Technologies is the computer software company that exclusively provides support and design of the TCCDLA ECFS access system.
Project contributors
Criminal District Attorney's Office:
Honorable Tim Curry, Tarrant County Criminal District Attorney
Alan Levy, Tarrant County Assistant Criminal District Attorney
David Montague, Tarrant County Assistant Criminal District Attorney
Betty Arvin, Tarrant County Assistant Criminal District Attorney
Kurt Stallings, Tarrant County Assistant Criminal District Attorney
Richard Alpert, Tarrant County Assistant Criminal District Attorney
Mark Thielman, Tarrant County Assistant Criminal District Attorney
Miles Brissette, Tarrant County Assistant Criminal District Attorney
Tracey Kapsidelis, Tarrant County Assistant Criminal District Attorney
John Cramer, Tarrant County Assistant Criminal District Attorney
Information technology:
Steve Smith, Tarrant County Chief Information Officer
Mark O'Neal, Tarrant County Enterprise Architect
Scott Hill, Tarrant County Customer Service and Support Manager
Keith Hughes, Tarrant County Quality Assurance Manager
Steve Harrelson, Tarrant County Application Development
Jan Debee, Tarrant County Application Development
Martin McCreary, Tarrant County Application Development
Phil Blankenship, Tarrant County Application Development
Divya Gupta, Tarrant County Quality Assurance
Bing Chen, Tarrant County Quality Assurance
Dick Renn, Tarrant County Application Support
Mozelle Duckett, Tarrant County Application Support
Tarrant County Criminal Defense Lawyer's Association:
William H. "Bill" Ray, President 2008, overseer of Defense Lawyer application to ECFS
Storm's Edge Technologies:
Dan Fitzgerald, President Storm's Edge Technologies, chief software designer and website designer for TCCDLA
Pilot Agency:
Forest Hill Police Department - Lt. Chris Hebert and Sgt. Dan Dennis
External links
Tarrant County Criminal Defense Lawyers Association
References
Business software
Information systems
Management systems
Tarrant County, Texas | Electronic Case Filing System | Technology | 922 |
75,288,841 | https://en.wikipedia.org/wiki/Ruzinurad | Ruzinurad (SHR4640) is a selective urate transporter 1 (URAT1) inhibitor in development for hyperuricaemia and gout. It is developed by Jiangsu Hengrui.
References
Quinolines
Carboxylic acids
Antigout agents
Cyclobutanes
Thioethers
Bromoarenes
Drugs developed by Jiangsu Hengrui | Ruzinurad | Chemistry | 79 |
72,436,244 | https://en.wikipedia.org/wiki/Motus%20%28wildlife%20tracking%20network%29 | Motus (Latin for movement) is a network of radio receivers for tracking signals from transmitters attached to wild animals. Motus uses radio telemetry for real-time tracking. It was launched by Birds Canada in 2014 in the US and Canada.
, more than 1,500 receiver stations had been installed in 34 countries. Most receivers are concentrated in the United States and Canada, where the network began. The network has spread rapidly because it provides important key data useful to researchers and conservationists, both nationally and internationally.
The Motus transmitter's great advantage is its small size and weight. Transmitters weigh , and can therefore be attached to all animals, even insects such as a bee or butterfly.
Once a researcher or organization receives state and federal permits, they only need to acquire the appropriate transmitters and attach them to their study objects. Current transmitters' range (depending on size) is up to 12 miles (20 kilometers).
The long-used geolocators and GPS loggers are light and small but only store the desired data; they cannot wirelessly transmit the data. This means that researchers must recapture the transmitter-equipped animal to read the stored information, which can take a long time, and many times is unsuccessful.
The transmitter is attached in a suitable way, depending on the animal to be tracked, either with a thread or an adhesive. After a certain time the glue and thread dissolve and the transmitter falls off, in the meantime having transmitted all the data to the receivers it passed.
References
External links
Schematic view of the Motus system.
Picture of a swallow fitted with a motus transmitter.
Radio technology
Zoology
Animal migration
Geopositioning | Motus (wildlife tracking network) | Technology,Engineering,Biology | 336 |
5,365,784 | https://en.wikipedia.org/wiki/Smalley%20%28excavator%29 | A smalley is a type of small excavator with two wheels on a single axle. It had no drive to the wheels, moving instead by pulling itself along using the excavator or 'backhoe' arm. Once in location the machine worked as any other 360° excavator, with two fixed-adjustable front legs, and two rear legs which could be mechanically height-adjusted from within the cab. For larger distances the machine could be towed on the road at moderate speeds using a suitable vehicle such as a Land Rover or large van.
Smalley evolved over the years and produced the Smalley 425 which has two drive wheels and two steering wheels. It uses a Lister Diesel engine, ST1. Single Cylinder, 6.5HP . 360 Degree turn, no electrics and manual start. Later models, which are still made today, use a different engine and have an alternator to power an electric starter motor. The 1977 needed the side support or else it would be too easy to tip over. (Note: The photo is missing the cab)
Richard Smalley is credited with being the inventor of the world’s first mini excavator in 1959, although now superseded by tracked derivations of the compact excavator at the concept was highly successful in allowing a compact and cost effective machine, with these 'walking' or 'tow-behind' excavators having been sold into more than forty countries throughout the world (including over 100 machines to Japan before 1968).
The manufacturer, Richard Smalley (Engineering) Ltd. was based in Osbournby near Sleaford in Lincolnshire, England.
References
External links
Richard Smalley Technical Services
Image of a Smalley in use
Oily Hands - Smalley Towable Diggers
Engineering vehicles | Smalley (excavator) | Engineering | 362 |
5,375,984 | https://en.wikipedia.org/wiki/Commentariolus | The Commentariolus (Little Commentary) is Nicolaus Copernicus's brief outline of an early version of his revolutionary heliocentric theory of the universe. After further long development of his theory, Copernicus published the mature version in 1543 in his landmark work, De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres).
Copernicus wrote the Commentariolus in Latin by 1514 and circulated copies to his friends and colleagues. It thus became known among Copernicus's contemporaries, though it was never printed during his lifetime. In 1533, Johann Albrecht Widmannstetter delivered a series of lectures in Rome outlining Copernicus' theory. Pope Clement VII and several Catholic cardinals heard the lectures and were interested in the theory. On 1 November 1536, Nikolaus von Schönberg, Archbishop of Capua and since the preceding year a cardinal, wrote to Copernicus from Rome and asked him for a copy of his writings "at the earliest possible moment".
Although copies of the Commentariolus circulated for a time after Copernicus's death, it subsequently lapsed into obscurity, and its previous existence remained known only indirectly, until a surviving manuscript copy was discovered and published in the second half of the nineteenth century.
Summary
The Commentariolus is subdivided into eight sections (or chapters), of which all but the first bear brief descriptive titles. After a brief introduction, the first section states seven postulates from which Copernicus proposes to show that the apparent motion of the planets can be explained systematically.
The seven postulates
Celestial bodies do not all revolve around a single point.
The centre of the Earth is the centre of the lunar sphere—the orbit of the Moon around the Earth.
All the spheres rotate around the Sun, which is near the centre of the Universe.
The distance between the Earth and the Sun is an insignificant fraction of the distance from the Earth and the Sun to the stars, so parallax is not observed in the stars.
The stars are immovable; their apparent daily motion is caused by the daily rotation of the Earth.
The Earth is moved in a sphere around the Sun, causing the apparent annual migration of the Sun; the Earth has more than one motion.
The Earth’s orbital motion around the Sun causes the seeming reverse in direction of the motions of the planets.
The remaining seven sections are titled, in order, De ordine orbium ("The order of the spheres"), De motibus qui circa solem apparent ("The apparent motions of the Sun"), Quod aequalitas motum non ad aequinoctia sed ad stellas fixas referatur ("Equal motion should be measured not by the equinoxes but by the fixed stars"), De Luna ("The Moon"), De tribus superioribus: Saturno, Jove et Marte ("The outer planets: Saturn, Jupiter and Mars"), De Venere ("Venus") and De Mercurio ("Mercury").
The order of the spheres
In this section, the heavenly spheres are given in order from outermost to innermost.
The outermost sphere is that of the fixed stars, which remains perfectly stationary. Then follow those of Saturn, Jupiter, Mars, Earth, Venus and Mercury, which each revolve about the Sun from west to east with successively shorter periods of revolution, Saturn's being between 29 and 30 years, Jupiter's between 11 and 12, Mars's between 2 and 3, Earth's exactly one, Venus's between 8 and 9 months, and Mercury's between 2 and 3 months. The Moon's sphere, however, revolves around the Earth in a period of one month, and moves with it around the Sun like an epicycle.
The apparent motion of the Sun
This section explains how the apparent motion of the Sun could arise from three separate motions of the Earth. The first motion is a uniform revolution, with a period of one year, from west to east along a circular orbit whose centre is offset from the Sun by 1/25 of the orbit's radius.
The second motion is the daily rotation about an axis which passes through the Earth's centre and is inclined at an angle of about 23° to the perpendicular to the plane of its orbit.
The third motion is a precession of the Earth's axis of rotation about an axis perpendicular to the plane of its orbit. Copernicus specified the rate of this precession with respect to the radial line from the Earth to the centre of its orbit as being slightly less than a year, with an implied direction as being from west to east. With respect to the fixed stars, this precession is very slow, and in the opposite direction—from east to west—and explains the phenomenon of the precession of the equinoxes.
Equal motion should be measured not by the equinoxes but by the fixed stars
Here Copernicus asserts that the motion of the equinoxes and celestial poles has not been uniform, and argues that consequently they should not be used to define the reference frame with respect to which the motions of the planets are measured, and that the periods of the various planetary motions are more accurately determinable if those motions are measured with respect to the fixed stars. He maintains that he had found the length of the sidereal year to have always been 365 days 6 hours and 10 minutes.
The Moon
Including the annual revolution around the Sun, which the Moon shares with the Earth in his system,
Copernicus explains the Moon's motion as composed of five independent motions. Its motion around the Earth lies in a plane which is inclined at an angle of 5° to the plane of the Earth's orbit, and which precesses from east to west around an axis perpendicular to that plane, with a period of between 18 and 19 years with respect to the fixed stars. The remaining three motions, which take place within this orbital plane, are depicted in the diagram to the right. The first of these is that of the first, and larger, of two epicycles, whose center (represented by the point e1 in the diagram) moves uniformly from west to east around the circumference of a deferent centred on the Earth (represented by point T in the diagram), with a period of one draconitic month. The centre of the second, smaller epicycle (represented by the point e2 in the diagram) moves uniformly from east to west around the circumference of the first so that the period of the angle β in the diagram is one anomalistic month.
The Moon itself, represented by the point M in the diagram, moves uniformly from west to east around the circumference of the second epicycle so that the period of the angle γ is half a synodic month. Copernicus states that whenever the point e1 lies on the line joining the Earth to the centre of its orbit (represented by the dotted line OTC in the diagram, of which only the point T here lies in the Moon's orbital plane), the Moon M will lie precisely between e1 and e2. However, this can occur only once every 19 years, when this line coincides with the line of nodes WTE. At other times it does not lie in the moon's orbital plane and the point e1 cannot therefore pass through it. In general, then, while the Moon will be close to conjunction or opposition to the Sun whenever it lies precisely between e1 and e2, these events will not be precisely simultaneous.
The ratio which Copernicus took as that for the relative lengths of the small epicycle, large epicycle and deferent is 4:19:180.
The outer planets, Saturn, Jupiter and Mars
The theories Copernicus gives in the Commentariolus for the motions of the outer planets all have the same general structure, and only differ in the values of the various parameters needed to specify their motions completely. Their orbits are not coplanar with that of the Earth, but do share its centre as their own common centre, and lie in planes that are only slightly inclined to the Earth's orbital plane. Unlike the Moon's orbital plane, those of the superior planets do not precess. Their inclinations to the Earth's orbital plane do oscillate, however, between the limits 0°10′ and 1°50′ for Mars, 1°15′ and 1°40′ for Jupiter, and 2°15′ and 2°40′ for Saturn. Although Copernicus supposes these oscillations to take place around the orbits' lines of nodes that he assumes to remain fixed, the mechanism he uses to model them does cause tiny oscillations in the lines of nodes as well. As Kepler later pointed out, the necessity for assuming oscillations in the inclinations of the outer planets' orbital planes is an artefact of Copernicus's having taken them as passing through the centre of the Earth's orbit. If he had taken them as passing through the Sun, he would not have needed to introduce these oscillations.
Like the Moon's motion, that of the outer planets, represented in the diagram to the right, is produced by a combination of a deferent and two epicycles. The centre of the first, and larger of the two epicycles, represented by the point e1 in the diagram, revolves uniformly from west to east around the circumference of a deferent whose centre is the centre of the Earth's orbit, represented by the point S in the diagram, with a period relative to the fixed stars as given in the section The order of the spheres above.
The centre of the second epicycle, represented by the point e2 in the diagram, revolves uniformly from east to west around the circumference of the first, with the same period relative to the radial line joining S to e1. As a consequence, the direction of the radial line joining e1 to e2 remains fixed relative to the fixed stars, parallel to the planet's line of apses EW, and the point e2 describes an eccentric circle whose radius is equal to that of the deferent, and whose centre, represented by the point O in the diagram, is offset from that of the deferent by the radius of the first epicycle. In his later work, De revolutionibus orbium coelestium, Copernicus uses this eccentric circle directly, rather than representing it as a combination of a deferent and an epicycle.
The planet itself, represented by the point P in the diagram, revolves uniformly from west to east around the circumference of the second epicycle, whose radius is exactly one third of that of the first, at twice the rate of revolution of e1 about S. This device enabled Copernicus to dispense with the equant, a much-criticised feature of Claudius Ptolemy's theories for the motions of the outer planets. In a heliocentric version of Ptolemy's models, his equant would lie at the point Q in the diagram, offset along the line of apses EW from the point S by a distance one and a third times the radius of Copernicus's first epicycle. The centre of the planet's deferent, with the same radius as Copernicus's, would lie at the point C, mid-way between S and Q. The planet itself would lie at the point of intersection of this deferent with the line QP. While this point only coincides exactly with P whenever they are both at an apsis, the difference between their positions is always negligible in comparison with the inaccuracies inherent to both theories.
For the ratios of the radii of the outer planets' deferents to radius of the Earth, the Commentariolus gives 1 for Mars, 5 for Jupiter, and 9 for Saturn. For the ratios of the radii of their deferents to the radii of the larger of their epicycles, it gives 6 for Mars, 12 for Jupiter, and 11 for Saturn.
Venus
In the last two sections Copernicus talks about Venus and Mercury. The first has a system of circles and takes 9 months to complete a revolution.
Mercury
Mercury's orbit is harder than any of the other planets' to study because it is visible for only a few days a year. Mercury, just like Venus, has two epicycles, one greater than another. It takes almost three months to complete a revolution.
Notes
References
Bibliography
Bardi, A. (2024). Copernicus and Axiomatics. In: Sriraman, B. (eds) Handbook of the History and Philosophy of Mathematical Practice. Springer, Cham. https://doi.org/10.1007/978-3-031-40846-5_110
External links
http://www.fh-augsburg.de/%7Eharsch/Chronologia/Lspost16/Copernicus/kop_c00.html Complete Latin text online at Bibliotheca Augustana.
Edward Rosen's English translation (2004, pp.57–65))
https://web.archive.org/web/20090803215559/http://www.geocities.com/soho/gallery/8084/copernicus.htm
16th-century books
Astronomy books
Texts in Latin
Works by Nicolaus Copernicus
Manuscripts of the Austrian National Library | Commentariolus | Astronomy | 2,835 |
44,639,771 | https://en.wikipedia.org/wiki/Flory%E2%80%93Stockmayer%20theory | Flory–Stockmayer theory is a theory governing the cross-linking and gelation of step-growth polymers. The Flory–Stockmayer theory represents an advancement from the Carothers equation, allowing for the identification of the gel point for polymer synthesis not at stoichiometric balance. The theory was initially conceptualized by Paul Flory in 1941 and then was further developed by Walter Stockmayer in 1944 to include cross-linking with an arbitrary initial size distribution.
The Flory–Stockmayer theory was the first theory investigating percolation processes. Flory–Stockmayer theory is a special case of random graph theory of gelation.
History
Gelation occurs when a polymer forms large interconnected polymer molecules through cross-linking. In other words, polymer chains are cross-linked with other polymer chains to form an infinitely large molecule, interspersed with smaller complex molecules, shifting the polymer from a liquid to a network solid or gel phase. The Carothers equation is an effective method for calculating the degree of polymerization for stoichiometrically balanced reactions. However, the Carothers equation is limited to branched systems, describing the degree of polymerization only at the onset of cross-linking. The Flory–Stockmayer Theory allows for the prediction of when gelation occurs using percent conversion of initial monomer and is not confined to cases of stoichiometric balance. Additionally, the Flory–Stockmayer Theory can be used to predict whether gelation is possible through analyzing the limiting reagent of the step-growth polymerization.
Flory’s assumptions
In creating the Flory–Stockmayer Theory, Flory made three assumptions that affect the accuracy of this model. These assumptions were:
All functional groups on a branch unit are equally reactive
All reactions occur between A and B
There are no intramolecular reactions
As a result of these assumptions, a conversion slightly higher than that predicted by the Flory–Stockmayer Theory is commonly needed to actually create a polymer gel. Since steric hindrance effects prevent each functional group from being equally reactive and intramolecular reactions do occur, the gel forms at slightly higher conversion.
Flory postulated that his treatment can also be applied to chain-growth polymerization mechanisms, as the three criteria stated above are satisfied under the assumptions that (1) the probability of chain termination is independent of chain length, and (2) multifunctional co-monomers react randomly with growing polymer chains.
General case
The Flory–Stockmayer Theory predicts the gel point for the system consisting of three types of monomer units
linear units with two A-groups (concentration ),
linear units with two B groups (concentration ),
branched A units (concentration ).
The following definitions are used to formally define the system
is the number of reactive functional groups on the branch unit (i.e. the functionality of that branch unit)
is the probability that A has reacted (conversion of A groups)
is the probability that B has reacted (conversion of B groups)
is the ratio of number of A groups in the branch unit to the total number of A groups
is the ratio between total number of A and B groups. So that
The theory states that the gelation occurs only if , where
is the critical value for cross-linking and is presented as a function of ,
or, alternatively, as a function of ,
.
One may now substitute expressions for into definition of and obtain
the critical values of that admit gelation. Thus gelation occurs if
alternatively, the same condition for reads,
The both inequalities are equivalent and one may use the one that is more convenient. For instance, depending on which conversion or is resolved analytically.
Trifunctional A monomer with difunctional B monomer
Since all the A functional groups are from the trifunctional monomer, ρ = 1 and
Therefore, gelation occurs when
or when,
Similarly, gelation occurs when
References
Polymer chemistry | Flory–Stockmayer theory | Chemistry,Materials_science,Engineering | 808 |
19,132,161 | https://en.wikipedia.org/wiki/Ordered%20semigroup | In mathematics, an ordered semigroup is a semigroup (S,•) together with a partial order ≤ that is compatible with the semigroup operation, meaning that x ≤ y implies z•x ≤ z•y and x•z ≤ y•z for all x, y, z in S.
An ordered monoid and an ordered group are, respectively, a monoid or a group that are endowed with a partial order that makes them ordered semigroups. The terms posemigroup, pogroup and pomonoid are sometimes used, where "po" is an abbreviation for "partially ordered".
The positive integers, the nonnegative integers and the integers form respectively a posemigroup, a pomonoid, and a pogroup under addition and the natural ordering.
Every semigroup can be considered as a posemigroup endowed with the trivial (discrete) partial order "=".
A morphism or homomorphism of posemigroups is a semigroup homomorphism that preserves the order (equivalently, that is monotonically increasing).
Category-theoretic interpretation
A pomonoid can be considered as a monoidal category that is both skeletal and thin, with an object of for each element of , a unique morphism from to if and only if , the tensor product being given by , and the unit by .
References
T.S. Blyth, Lattices and Ordered Algebraic Structures, Springer, 2005, , chap. 11.
Ordered algebraic structures
Semigroup theory | Ordered semigroup | Mathematics | 309 |
24,000,751 | https://en.wikipedia.org/wiki/Bachelor%20of%20Electrical%20Engineering | Bachelor of Electrical Engineering (B.E.E. or BEE) is an undergraduate academic degree offered to a student who completes three to five years of study in electrical engineering at a university or college.
There are many institutes offering Bachelor of Science in Electrical Engineering (B.S.E.E. or B.Sc.E.E.) or Bachelor of Engineering in Electrical Engineering (B.E.E.E.).
Duration
Program duration varies throughout the world depending upon the education curriculum. For example, in the US, this course requires four years to complete. On the other hand, in the UK, it takes three years to complete.
In some countries, it takes five years to complete. Study topics normally covered in this course include Direct Current, Alternating Current, Electrical Machines, AC & DC Motors, Transformers, Generators, Rotating Devices, Power Engineering, Power Transmission and Power Distribution.
References
External links
PDH Courses For Engineers
Engineering education
Electrical engineering
Electrical Engineering | Bachelor of Electrical Engineering | Engineering | 197 |
40,690,393 | https://en.wikipedia.org/wiki/Sparassol | Sparassol is an antibiotic and antifungal isolated from Sparassis crispa.
External links
Antibiotics
Antifungals | Sparassol | Chemistry,Biology | 29 |
10,010,996 | https://en.wikipedia.org/wiki/Naval%20Network%20Warfare%20Command | The Naval Network Warfare Command (NAVNETWARCOM) is the United States Navy's information operations, intelligence, networks, and space unit. Naval Network Warfare Command's mission is to execute, under Commander TENTH Fleet Operational Control, tactical-level command and control of Navy Networks and to leverage Joint Space Capabilities for Navy and Joint Operations.
History
In 2002, some 23 organizations from several commands, including the former Naval Space Command, Naval Computer and Telecommunications Command, Fleet Information Warfare Center, and Navy Component Task Force - Computer Network Defense were brought together to form Naval Network Warfare Command, emphasizing the organization's focus on the operation and defense of the Navy's networks.
In 2005, with the disestablishment of Naval Security Group (NAVSECGRU), NETWARCOM brought the former Naval Security Group Activities (NSGAs) under its umbrella, designating them Naval Information Operation Center(s) (NIOC) and Naval Information Operation Detachment(s) (NIOD). The mission of the command fundamentally changed, making it the Navy's lead for Information Operations, as well as Networks and Space.
The assumption, alignment, and integration of Fleet Intelligence Type Commander duties, responsibilities and functions at NETWARCOM in 2008 began a measured and evolutionary process to improve integrated Fleet Intelligence and ISR readiness. This alignment provides a single Fleet champion for ISR and positions Fleet Intelligence for better and timelier support to fleet operations.
In 2009, the Secretary of Defense directed the establishment of U.S. Cyber Command. Each of the services was also directed to establish a supporting command to U.S. Cyber Command; as a result, the Naval Information Operations Centers (NIOC) were moved to the reestablished Tenth Fleet to help form U.S. Fleet Cyber Command. Naval Network Warfare Command was reorganized and its mission revised to "operate and defend the Navy's portion of the Global Information Grid and deliver reliable and secure Net-centric and space war-fighting capabilities in support of strategic, operational and tactical missions across the Navy".
The headquarters is at Navy Cyber Forces in Norfolk, Virginia.
Organization
Naval Network Warfare Command acts as Combined Task Force 1010 (network operations & defense) for Tenth Fleet
CTF 1010 - Naval Network Warfare Command
CTG 1010.3 - NCTAMS PAC
CTG 1010.4 - NCTAMS LANT
See also
United States Tenth Fleet
U.S. Navy Information Dominance Corps
Naval Computer and Telecommunications Command
Navy Information Operations Command, Hawaii
References
External links
History of NAVNETWARCON Archived
Commands of the United States Navy
Military globalization
Military units and formations established in 2002
Cyberinfrastructure
Net-centric
Military units and formations in Virginia
Military communications units and formations of the United States | Naval Network Warfare Command | Technology | 558 |
45,438,065 | https://en.wikipedia.org/wiki/Penicillium%20discolor | Penicillium discolor is a species of the genus of Penicillium which occurs in nuts, vegetables and cheese and produces chaetoglobosins (chaetoglobosin A - J), palitantin, cyclopenin, cyclopenol, cyclopeptin, dehydrocyclopeptin, viridicatin and viridicatol.
See also
List of Penicillium species
References
discolor
Fungi described in 1997
Fungus species | Penicillium discolor | Biology | 105 |
191,395 | https://en.wikipedia.org/wiki/Jade | Jade is an umbrella term for two different types of decorative rocks used for jewelry or ornaments. Jade is often referred to by either of two different silicate mineral names: nephrite (a silicate of calcium and magnesium in the amphibole group of minerals), or jadeite (a silicate of sodium and aluminum in the pyroxene group of minerals). Nephrite is typically green, although may be yellow, white or black. Jadeite varies from white or near-colorless, through various shades of green (including an emerald green, termed 'imperial'), to lavender, yellow, orange, brown and black. Rarely it may be blue.
Both of these names refer to their use as gemstones, and each has a mineralogically more specific name. Both the amphibole jade (nephrite) and pyroxene jade are mineral aggregates (rocks) rather than mineral species. Nephrite was deprecated by the International Mineralogical Association as a mineral species name in 1978 (replaced by tremolite). The name "nephrite" is mineralogically correct for referring to the rock. Jadeite, is a legitimate mineral species, differing from the pyroxene jade rock. In China, the name jadeite has been replaced with fei cui, the traditional Chinese name for this gem that was in use long before Damour created the name in 1863.
Jade is well known for its ornamental use in East Asian, South Asian, and Southeast Asian art. It is commonly used in Latin America, such as Mexico and Guatemala. The use of jade in Mesoamerica for symbolic and ideological ritual was influenced by its rarity and value among pre-Columbian Mesoamerican cultures, such as the Olmecs, the Maya, and other ancient civilizations of the Valley of Mexico.
Jade is classified into three main types: Type A, Type B, and Type C. Type A jade refers to natural, untreated jadeite jade, prized for its purity and vibrant colors. It is the most valuable and sought-after type, often characterized by its vivid green hues and high translucency. Type A jade is revered for its symbolism of purity, harmony, and protection in various cultures, especially in East Asia where it holds significant cultural and spiritual importance. Types B and C have been enhanced with resin and colourant respectively.
Etymology
The English word jade is derived (via French and Latin 'flanks, kidney area') from the Spanish term (first recorded in 1565) or 'loin stone', from its reputed efficacy in curing ailments of the loins and kidneys. Nephrite is derived from , a Latin translation of the Spanish .
History
East Asia
Prehistoric and historic China
During Neolithic times, the key known sources of nephrite jade in China for utilitarian and ceremonial jade items were the now-depleted deposits in the Ningshao area in the Yangtze River Delta (Liangzhu culture 3400–2250 BC) and in an area of the Liaoning province and Inner Mongolia (Hongshan culture 4700–2200 BC). Dushan Jade (a rock composed largely of anorthite feldspar and zoisite) was being mined as early as 6000 BC. In the Yin Ruins of the Shang Dynasty (1600 to 1050 BC) in Anyang, Dushan Jade ornaments were unearthed in the tomb of the Shang kings.
Jade was considered to be the "imperial gem" and was used to create many utilitarian and ceremonial objects, from indoor decorative items to jade burial suits. From the earliest Chinese dynasties to the present, the jade deposits most used were not only those of Khotan in the Western Chinese province of Xinjiang but other parts of China as well, such as Lantian, Shaanxi. There, white and greenish nephrite jade is found in small quarries and as pebbles and boulders in the rivers flowing from the Kuen-Lun mountain range eastward into the Takla-Makan desert area. The river jade collection is concentrated in the Yarkand, the White Jade (Yurungkash) and Black Jade (Karakash) Rivers. From the Kingdom of Khotan, on the southern leg of the Silk Road, yearly tribute payments consisting of the most precious white jade were made to the Chinese Imperial court and there worked into objets d'art by skilled artisans as jade had a status-value exceeding that of gold or silver. Jade became a favourite material for the crafting of Chinese scholars' objects, such as rests for calligraphy brushes, as well as the mouthpieces of some opium pipes, due to the belief that breathing through jade would bestow longevity upon smokers who used such a pipe.
Jadeite, with its bright emerald-green, lavender, pink, orange, yellow, red, black, white, near-colorless and brown colors was imported from Burma to China in quantity only after about 1800. The vivid white to green variety became known as fei cui (翡翠) or kingfisher jade, due to its resemblance to the feathers of the kingfisher bird. That definition was later expanded to include all other colors that the rock is found in. It quickly became almost as popular as nephrite and a favorite of Qing Dynasty's aristocracy, while scholars still had strong attachment to nephrite (white jade, or Hetian jade), which they deemed to be the symbol of a nobleman.
In the history of the art of the Chinese empire, jade has had a special significance, comparable with that of gold and diamonds in the West. Jade was used for the finest objects and cult figures, and for grave furnishings for high-ranking members of the imperial family. Due to that significance and the rising middle class in China, in 2010 the finest jade when found in nuggets of "mutton fat" jade – so-named for its marbled white consistency – could sell for $3,000 an ounce, a tenfold increase from a decade previously.
The Chinese character 玉 (yù) is used to denote the several types of stone known in English as "jade" (e.g. 玉器, jadewares), such as jadeite (硬玉, 'hard jade', another name for 翡翠) and nephrite (軟玉, 'soft jade'). While still in use, the terms "hard jade" and "soft jade" resulted from a mistranslation by a Japanese geologist, and should be avoided.
But because of the value added culturally to jades throughout Chinese history, the word has also come to refer more generally to precious or ornamental stones, and is very common in more symbolic usage as in phrases like 拋磚引玉/抛砖引玉 (lit. "casting a brick (i.e. the speaker's own words) to draw a jade (i.e. pearls of wisdom from the other party)"), 玉容 (a beautiful face; "jade countenance"), and 玉立 (slim and graceful; "jade standing upright"). The character has a similar range of meanings when appearing as a radical as parts of other characters.
Prehistoric and historic Japan
Jade in Japan was used for jade bracelets. It was a symbol of wealth and power. Leaders also used jade in rituals. It is the national stone of Japan.
Examples of use in Japan can be traced back to the early Jomon period about 7,000 years ago. XRF analysis results have revealed that all jade used in Japan since the Jomon period is from Itoigawa.
The jade culture that blossomed in ancient Japan respected green ones, and jade of other colors was not used. There is a theory that the reason why the meaning is that it was believed that the color of green enables the reproduction of fertility, the life, and the soul of the earth.
Prehistoric and historic Korea
The use of jade and other greenstone was a long-term tradition in Korea ( – AD 668). Jade is found in small numbers of pit-houses and burials. The craft production of small comma-shaped and tubular "jades" using materials such as jade, microcline, jasper, etc., in southern Korea originates from the Middle Mumun Pottery Period (–550 BC). Comma-shaped jades are found on some of the gold crowns of Silla royalty (/400–668 AD) and sumptuous elite burials of the Korean Three Kingdoms. After the state of Silla united the Korean Peninsula in 668, the widespread popularisation of death rituals related to Buddhism resulted in the decline of the use of jade in burials as prestige mortuary goods.
South Asia
India
The Jain temple of Kolanpak in the Nalgonda district, Telangana, India is home to a high sculpture of Mahavira that is carved entirely out of jade. India is also noted for its craftsman tradition of using large amounts of green serpentine or false jade obtained primarily from Afghanistan in order to fashion jewellery and ornamental items such as sword hilts and dagger handles.
The Salar Jung Museum in Hyderabad has a wide range of jade hilted daggers, mostly owned by the former Sultans of Hyderabad.
Southeast Asia
Myanmar
Today, it is estimated that Myanmar is the origin of upwards of 70% of the world's supply of high-quality jadeite. Most of the jadeite mined in Myanmar is not cut for use in Myanmar, instead being transported to other nations, primarily in Asia, for use in jewelry and other products. The jadeite deposits found in Kachinland, in Myanmar's northern regions is the highest quality jadeite in the world, considered precious by sources in China going as far back as the 10th century.
Jadeite in Myanmar is primarily found in the "Jade Tract" located in Lonkin Township in Kachin State in northern Myanmar which encompasses the alluvial region of the Uyu River between the 25th and 26th parallels. Present-day extraction of jade in this region occurs at the Phakant-gyi, Maw Sisa, Tin Tin, and Khansee mines. Khansee is also the only mine that produces maw sit sit, a kosmochlor-rich jade rock. Mines at Tawmaw and Hweka are mostly exhausted. From 1964 to 1981, mining was exclusively an enterprise of the Myanmar government. In 1981, 1985, and 1995, the Gemstone laws were modified to allow increasing private enterprise. In addition to this region, there are also notable mines in the neighboring Sagaing District, near the towns of Nasibon and Natmaw and Hkamti. Sagaing is a district in Myanmar proper, not a part of the ethic Kachin State.
Southeast Asia
Carved nephrite jade was the main commodity trade of an extensive prehistoric trading network connecting multiple areas in Southeast Asia. The nephrite jade was mined in eastern Taiwan by the animist Taiwanese indigenous peoples and processed mostly in the Philippines by the animist indigenous Filipinos. Some were also processed in Vietnam, while the peoples of Brunei, Cambodia, Indonesia, Malaysia, Singapore, and Thailand also participated in the massive animist-led nephrite jade trading network, where other commodities were also traded. Participants in the network at the time had a majority animist population. The maritime road is one of the most extensive sea-based trade networks of a single geological material in the prehistoric world. It was in existence for at least 3,000 years, where its peak production was from 2000 BCE to 500 CE, older than the Silk Road in mainland Eurasia. It began to wane during its final centuries from 500 CE until 1000 CE. The entire period of the network was a golden age for the diverse animist societies of the region.
Others
Māori
Nephrite jade in New Zealand is known as pounamu in the Māori language (often called "greenstone" in New Zealand English), and plays an important role in Māori culture. It is considered a taonga, or treasure, and therefore protected under the Treaty of Waitangi, and the exploitation of it is restricted and closely monitored. It is found only in the South Island of New Zealand, known as Te Wai Pounamu in Māori—"The [land of] Greenstone Water", or Te Wahi Pounamu—"The Place of Greenstone".
Pounamu taonga increase in mana (prestige) as they pass from one generation to another. The most prized taonga are those with known histories going back many generations. These are believed to have their own mana and were often given as gifts to seal important agreements.
Tools, weapons and ornaments were made of it; in particular adzes, the 'mere' (short club), and the hei-tiki (neck pendant). Nephrite jewellery of Maori design is widely popular with locals and tourists, although some of the jade used for these is now imported from British Columbia and elsewhere.
Pounamu taonga include tools such as toki (adzes), whao (chisels), whao whakakōka (gouges), ripi pounamu (knives), scrapers, awls, hammer stones, and drill points. Hunting tools include matau (fishing hooks) and lures, spear points, and kākā poria (leg rings for fastening captive birds); weapons such as mere (short handled clubs); and ornaments such as pendants (hei-tiki, hei matau and pekapeka), ear pendants (kuru and kapeu), and cloak pins.
Functional pounamu tools were widely worn for both practical and ornamental reasons, and continued to be worn as purely ornamental pendants (hei kakï) even after they were no longer used as tools.
Mesoamerica
Jade was a rare and valued material in pre-Columbian Mesoamerica. The only source from which the various indigenous cultures, such as the Olmec and Maya, could obtain jade was located in the Motagua River valley in Guatemala. Jade was largely an elite good, and was usually carved in various ways, whether serving as a medium upon which hieroglyphs were inscribed, or shaped into symbolic figurines. Generally, the material was highly symbolic, and it was often employed in the performance of ideological practices and rituals.
Canada
Jade was first identified in Canada by Chinese settlers in 1886 in British Columbia. At this time jade was considered worthless because the settlers were searching for gold. Jade was not commercialized in Canada until the 1970s. The mining business Loex James Ltd., which was started by two Californians, began commercial mining of Canadian jade in 1972.
Mining is done from large boulders that contain bountiful deposits of jade. Jade is exposed using diamond-tipped core drills in order to extract samples. This is done to ensure that the jade meets requirements. Hydraulic spreaders are then inserted into cleavage points in the rock so that the jade can be broken away. Once the boulders are removed and the jade is accessible, it is broken down into more manageable 10-tonne pieces using water-cooled diamond saws. The jade is then loaded onto trucks and transported to the proper storage facilities.
Russia
Russia imported jade from China for a long time, but in the 1860s its own jade deposits were found in Siberia. Today, the main deposits of jade are located in Eastern Siberia, but jade is also extracted in the Polar Urals and in the Krasnoyarsk territory (Kantegirskoye and Kurtushibinskoye deposits). Russian raw jade reserves are estimated at 336 tons.
Russian jade culture is closely connected with such jewellery production as Fabergé, whose workshops combined the green stone with gold, diamonds, emeralds, and rubies.
Siberia
In the 1950s and 1960s, there was a strong belief among many Siberians, which stemmed from tradition, that jade was part of a class of sacred objects that had life.
Mongolia
In the 1950s and 1960s, there was a strong belief among many Mongolians, which came from ancient tradition, that jade was part of a class of sacred objects that had life.
Gallery
The mineral
Nephrite and jadeite
It was not until 1863 that French mineralogist Alexis Damour determined that what was referred to as "jade" could in fact be one of two different minerals, either nephrite or jadeite.
Nephrite consists of a microcrystalline interlocking fibrous matrix of the calcium, magnesium-iron rich amphibole mineral series tremolite (calcium-magnesium)-ferroactinolite (calcium-magnesium-iron). The middle member of this series with an intermediate composition is called actinolite (the silky fibrous mineral form is one form of asbestos). The higher the iron content, the greener the colour. Tremolite occurs in metamorphosed dolomitic limestones, and actinolite in metamorphic greenschists/glaucophane schists.
Jadeite is a sodium- and aluminium-rich pyroxene. The more precious kind of jade, this is a microcrystalline interlocking growth of crystals (not a fibrous matrix as nephrite is.) It only occurs in metamorphic rocks.
Both nephrite and jadeite were used from prehistoric periods for hardstone carving. Jadeite has about the same hardness (between 6.0 and 7.0 Mohs hardness) as quartz, while nephrite is slightly softer (6.0 to 6.5) and so can be worked with quartz or garnet sand, and polished with bamboo or even ground jade. However nephrite is tougher and more resistant to breakage. Among the earliest known jade artifacts excavated from prehistoric sites are simple ornaments with bead, button, and tubular shapes. Additionally, jade was used for adze heads, knives, and other weapons, which can be delicately shaped.
As metal-working technologies became available, the beauty of jade made it valuable for ornaments and decorative objects.
Unusual varieties
The name Nephrite derives from the Greek word meaning "kidney". This is because in ancient times it was believed that wearing this kind of jade around the waist could cure kidney disease.
Nephrite can be found in a creamy white form (known in China as "mutton fat" jade) as well as in a variety of light green colours, whereas jadeite shows more colour variations, including blue, brown, red, black, dark green, lavender and white. Of the two, jadeite is rarer, documented in fewer than 12 places worldwide. Translucent emerald-green jadeite is the most prized variety, both historically and today. As "quetzal" jade, bright green jadeite from Guatemala was treasured by Mesoamerican cultures, and as "kingfisher" jade, vivid green rocks from Burma became the preferred stone of post-1800 Chinese imperial scholars and rulers. Burma (Myanmar) and Guatemala are the principal sources of modern gem jadeite. In the area of Mogaung in the Myitkyina District of Upper Burma, jadeite formed a layer in the dark-green serpentine, and has been quarried and exported for well over a hundred years. Canada provides the major share of modern lapidary nephrite.
Enhancement
Jade may be enhanced (sometimes called "stabilized"). Some merchants will refer to these as grades, but degree of enhancement is different from colour and texture quality. In other words, Type A jadeite is not enhanced but can have poor colour and texture. There are three main methods of enhancement, sometimes referred to as the ABC Treatment System:
Type A jadeite has not been treated in any way except surface waxing.
Type B treatment involves exposing a promising but stained piece of jadeite to chemical bleaches and/or acids and impregnating it with a clear polymer resin. This results in a significant improvement of transparency and colour of the material. Currently, infrared spectroscopy is the most accurate test for the detection of polymer in jadeite.
Type C jade has been artificially stained or dyed. The effects are somewhat uncontrollable and may result in a dull brown. In any case, translucency is usually lost.
B+C jade is a combination of B and C: it has been both impregnated and artificially stained.
Type D jade refers to a composite stone such as a doublet comprising a jade top with a plastic backing.
Industry
Myanmar
See also
Cheonmachong – Tumulus of the Silla kingdom in Korea, containing jade artifacts
Mumun pottery period – Time in Korea when jade ornament production began
Pounamu – Type of hard stone found in New Zealand, some of which are nephrite
Serpentine subgroup – Group of minerals, some of which are known as false jade
References
Further reading
Rémusat, Abel, 1820. Histoire de la ville de Khotan: tirée des annales de la chine et traduite du chinois; Suivie de Recherches sur la substance minérale appelée par les Chinois Pierre de Iu, et sur le Jaspe des anciens. Abel Rémusat. Paris. L'imprimerie de doublet. 1820. 239 pp. Downloadable from:
Laufer, Berthold, 1912, Jade: A Study in Chinese Archeology & Religion, Reprint: Dover Publications, New York. 1974.
Rawson, Jessica, 1975, Chinese Jade Throughout the Ages, London: Albert Saifer,
Jadeite sources in Mesoamerica (PDF). .
Between hell and the Stone of Heaven: Observer article on Jade Mining in Burma
Old Chinese Jades: Real or Fake?
Types of jade: 100 stone images with accompanying information. .
Hughes, R.W., ed. (2022) Jade A Gemologist’s Guide. Bangkok: Lotus Publishing, 534 pp.
External links
The British Museum – 7,000 years of Chinese jade
Gravity Measurement For Testing Jade (2008 archived version)
mindat.org (Mineralogical data about Jade)
Jade in Canada
"Jade in British Columbia table", BC Govt MINFILE summary of jade showings and producers
Canadian Rockhound magazine feature on jade
Chinese sculpture
Gemstones
Hardstone carving
Inosilicates
Provincial symbols of British Columbia
Shades of green
Symbols of Alaska | Jade | Physics | 4,608 |
509,628 | https://en.wikipedia.org/wiki/SMART%20Information%20Retrieval%20System | The SMART (System for the Mechanical Analysis and Retrieval of Text) Information Retrieval System is an information retrieval system developed at Cornell University in the 1960s. Many important concepts in information retrieval were developed as part of research on the SMART system, including the vector space model, relevance feedback, and Rocchio classification.
Gerard Salton led the group that developed SMART. Other contributors included Mike Lesk.
The SMART system also provides a set of corpora, queries and reference rankings, taken from different subjects, notably
ADI: publications from information science reviews
Computer science
Cranfield collection: publications from aeronautic reviews
Forensic science: library science
MEDLARS collection: publications from medical reviews
Time magazine collection: archives of the generalist review Time in 1963
To the legacy of the SMART system belongs the so-called SMART triple notation, a mnemonic scheme for denoting tf-idf weighting variants in the vector space model. The mnemonic for representing a combination of weights takes the form ddd.qqq, where the first three letters represents the term weighting of the collection document vector and the second three letters represents the term weighting for the query document vector. For example, ltc.lnn represents the ltc weighting applied to a collection document and the lnn weighting applied to a query document.
The following tables establish the SMART notation:
The gray letters in the first, fifth, and ninth columns are the scheme used by Salton and Buckley in their 1988 paper. The bold letters in the second, sixth, and tenth columns are the scheme used in experiments reported thereafter.
References
External links
Software and test collections (FTP at Cornell University)
Interactive SMART tutorial
Discontinued software
Search engine software | SMART Information Retrieval System | Engineering | 345 |
2,645,647 | https://en.wikipedia.org/wiki/List%20of%20numerical-analysis%20software | Listed here are notable end-user computer applications intended for use with numerical or data analysis:
Numerical-software packages
General-purpose computer algebra systems
Interface-oriented
Language-oriented
Historically significant
Expensive Desk Calculator written for the TX-0 and PDP-1 in the late 1950s or early 1960s.
S is an (array-based) programming language with strong numerical support. R is an implementation of the S language.
See also
References
Lists of software
Mathematics-related lists
Software | List of numerical-analysis software | Mathematics,Technology | 97 |
25,287,284 | https://en.wikipedia.org/wiki/Hessenberg%20variety | In geometry, Hessenberg varieties, first studied by Filippo De Mari, Claudio Procesi, and Mark A. Shayman, are a family of subvarieties of the full flag variety which are defined by a Hessenberg function h and a linear transformation X. The study of Hessenberg varieties was first motivated by questions in numerical analysis in relation to algorithms for computing eigenvalues and eigenspaces of the linear operator X. Later work by T. A. Springer, Dale Peterson, Bertram Kostant, among others, found connections with combinatorics, representation theory and cohomology.
Definitions
A Hessenberg function is a map
such that
for each i. For example, the function that sends the numbers 1 to 5 (in order) to 2, 3, 3, 4, and 5 is a Hessenberg function.
For any Hessenberg function h and a linear transformation
the Hessenberg variety is the set of all flags such that
for all i.
Examples
Some examples of Hessenberg varieties (with their function) include:
The Full Flag variety: h(i) = n for all i
The Peterson variety: for
The Springer variety: for all .
References
Bertram Kostant, Flag manifold quantum cohomology, the Toda lattice, and the representation with highest weight , Selecta Mathematica (N.S.) 2, 1996, 43–91.
Julianna Tymoczko, Linear conditions imposed on flag varieties, American Journal of Mathematics 128 (2006), 1587–1604.
Algebraic geometry
Algebraic combinatorics | Hessenberg variety | Mathematics | 316 |
59,615,541 | https://en.wikipedia.org/wiki/Institute%20of%20Acoustics%2C%20Chinese%20Academy%20of%20Sciences | The Institute of Acoustics (IOA, ) of the Chinese Academy of Sciences (CAS) was established in 1964 by the Chinese government in the context of China's national defense needs for acoustic research, under the auspices of Marshall Nie Rongzhen.
By the end of 2017, the IOA counts more than 700 researchers focusing on the study of basic and applied acoustics, in the following fields:
Underwater acoustics and underwater acoustical detection;
Environmental acoustics and noise control technologies;
Ultrasonics and acoustical micro-electromechanical system technologies;
Communication acoustics, language/speech information processing; Integration of acoustics with digital systems, and network new media technologies.
Seven academicians of the Chinese Academy of Sciences have been elected from the IOA, they were/are: Wang Dezhao, Ma Dayou, Ying Chongfu, , Hou Chaohuan, Li Qihu, Wang Chenghao.
IOA is the de facto sponsor of Acoustical Society of China (ASC), a nongovernmental organization officially affiliated to China Association for Science and Technology.
In 2012, the ASC co-hosted with the Acoustical Society of America a joint meeting in Hong Kong. In 2014, the IOA hosted the International Congress on Sound and Vibration in Beijing. In 2015, the IOA co-hosted with The French Acoustics Society The 9th International Conference Auditorium Acoustics in Paris. And according to the IOA official web site, it will co-host with the ASC an International Congress on Ultrasonics in 2021.
The IOA publishes 7 academic journals, among others, Acta Acustica (incl. English version) and Applied Acoustics.
References
Research institutes of the Chinese Academy of Sciences
Acoustics
1964 establishments in China
Physics research institutes | Institute of Acoustics, Chinese Academy of Sciences | Physics | 366 |
60,460,210 | https://en.wikipedia.org/wiki/HD%20102956%20b | HD 102956 b or Isagel is an extrasolar planet discovered in 2010 by a team of American astronomers led by John Johnson using Doppler spectroscopy and the Keck Observatory in Hawaii. HD 102956 b is in the orbit of host star HD 102956. The planet is at most the mass of Jupiter, orbiting every 6.5 days at a distance of 12 million km. HD 202956 b has a very circular orbit. The system is roughly 399 light years from us.
Discovery and nomenclature
The name HD 102956 derives directly from the fact that the star is the 102,956th star catalogued in the Henry Draper catalog. The designation of b is given to the first planet orbiting a given star.
The star is one of the 2.5 million brightest stars in the sky and is part of the Tycho-2 Catalogue. It is not visible to the naked eye with an apparent magnitude of 8.
NameExoWorlds
In 2019 this planet was announced as part of the IAU NameExoWorlds project where it was designated as the planet that will be named by Sweden. The winning proposal was Isagel, from Nobel laureate Harry Martinson's space poem Aniara.
Host star
HD 102956 (Aniara) is an orange subgiant with a mass and radius of 1.68 and 4.4 , respectively. The surface temperature is about . The star is 11.6 times brighter than the Sun. The star's age is estimated at 2.3 billion years.
References
Exoplanets discovered in 2010
Giant planets
Ursa Major
Exoplanets detected by radial velocity
Exoplanets with proper names | HD 102956 b | Astronomy | 345 |
36,490,792 | https://en.wikipedia.org/wiki/Marine%20Environmental%20Data%20and%20Information%20Network | The Marine Environmental Data and Information Network (MEDIN) is a United Kingdom organization created to curate marine environmental data. It is overseen by the UK government's Marine Science Co-ordination Committee.
References
Oceanography
Scientific organisations based in the United Kingdom | Marine Environmental Data and Information Network | Physics,Environmental_science | 51 |
2,695,546 | https://en.wikipedia.org/wiki/Rho%20Telescopii | Rho Telescopii (ρ Tel, ρ Telescopii) is the Bayer designation for an astrometric binary star system in the southern constellation of Telescopium. It is visible to the naked eye, with an apparent visual magnitude of +5.17. Based upon an annual parallax shift of 17.63 mas as measured from Earth, it is located approximately 185 light years from the Sun.
This appears to be a single-lined spectroscopic binary as it displays radial velocity variation with a period of 1.7 days. The visible component is an F-type main sequence star with a stellar classification of F6 V. It has about double the mass of the Sun and is radiating 25.6 times the solar luminosity from its photosphere at an effective temperature of 6,303 K. The star is a bright X-ray source with a luminosity of .
Relative to neighboring stars, Rho Telescopii has a peculiar velocity of . It may be a member of the Tucana-Horologium association.
References
F-type main-sequence stars
Astrometric binaries
Telescopii, Rho
Telescopium
Durchmusterung objects
177171
093815
7213 | Rho Telescopii | Astronomy | 262 |
31,332,116 | https://en.wikipedia.org/wiki/Reentry%20Breakup%20Recorder | A Reentry Breakup Recorder (REBR) is a device that is designed to be placed aboard a spacecraft to record pertinent data when the spacecraft (intentionally) breaks up as it re-enters Earth's atmosphere.
The device records data regarding the thermal, acceleration, rotational and other stresses the vehicle is subject to. In the final stages it transmits the data back to a laboratory before it is destroyed when it hits the surface.
History
Two REBRs were launched in January 2011 on the Japanese Kounotori 2 transfer vehicle. One recorded the subsequent re-entry of that vehicle, and the other was placed aboard the Johannes Kepler ATV, which reentered Earth's atmosphere on 21 June 2011.
The Kounotori 2 vehicle re-entered on 30 March 2011. Its REBR successfully collected and returned its data; it survived the impact with the ocean and while floating continued to transmit. It took between 6 and 8 weeks to analyze the data.
The second unit was intended to collect data during the reentry of the Johannes Kepler ATV (ATV-2); however the device failed to make contact after reentry and consequently no data was retrieved.
Two other units were used successfully for Kounotori 3 for its reentry on September 14, 2012, and Edoardo Amaldi ATV (ATV-3) on October 3, 2012.
Predecessor technology: image documentation of reentry and breakup
Earlier data collection from reentry and breakup was mostly visual and spectrographic. A particularly well-documented case is seen in a reentry and breakup over the South Pacific—recorded by a large team of NASA and ESA space agency personnel with extensive photographic image and video data collection, at multiple spectrographic wavelengths—occurred in September 2008, following the first mission of the ESA cargo spacecraft—the Automated Transfer Vehicle Jules Verne—to the International Space Station (ISS) in March 2008.
On 5 September 2008, Jules Verne undocked from the ISS and maneuvered to an orbital position below the ISS. It remained in that orbit until the night of 29 September.
At 10:00:27 UTC, Jules Verne started its first de-orbit burn of 6 minutes, followed by a second burn of 15 minutes at 12:58:18 UTC. At 13:31 GMT, Jules Verne re-entered the atmosphere at an altitude of , and then completed its destructive re-entry as planned over the following 12 minutes,
depositing debris in the South Pacific Ocean southwest of Tahiti.
This was recorded with video and still photography at night by two aircraft flying over the South Pacific for purposes of data gathering.
The NASA documentary of the project is in the gallery, below.
Gallery
References
External links
Photo and diagram of the first REBRs, April 2011.
Atmospheric entry
Spacecraft communication
Spacecraft instruments
Articles containing video clips | Reentry Breakup Recorder | Engineering | 576 |
22,128,220 | https://en.wikipedia.org/wiki/Baffle%20%28heat%20transfer%29 | Baffles are flow-directing or obstructing vanes or panels used to direct a flow of liquid or gas. It is used in some household stoves and in some industrial process vessels (tanks), such as shell and tube heat exchangers, chemical reactors, and static mixers.
Baffles are an integral part of the shell and tube heat exchanger design. A baffle is designed to support tube bundles and direct the flow of fluids for maximum efficiency. Baffle design and tolerances for heat exchangers are discussed in the standards of the Tubular Exchanger Manufacturers Association (TEMA).
Use of baffles
The main roles of a baffle in a shell and tube heat exchanger are to:
Hold tubes in position (preventing sagging), both in production and operation
Prevent the effects of steam starvation, which is increased with both fluid velocity and the length of the exchanger
Direct shell-side fluid flow along the tube field. This increases fluid velocity and the effective heat transfer co-efficient of the exchanger
In a static mixer, baffles are used to minimize the tangential component of velocity which causes vortex formation, and thus promotes mixing.
In a chemical reactor, baffles are often attached to the interior walls to promote mixing and thus increase heat transfer and possibly chemical reaction rates.
In a household stoves like Handölkassetten and similar stoves a baffle is used to prevent the gas from going directly up in the chimney and possibly causing a chimney fire and direct the gas towards the front of the oven before it continues upwards into the chimney. In this case the baffle helps increase the efficiency of the stove as more heat leaves the gas before it exits.
The baffles prevent the rotational flow without affecting radial or longitudinal flow. The tank is provided with baffles which prevent swirling and vortex formation. Except in very large tanks, four(4) baffles are placed.
Types of baffles
Implementation of baffles is decided on the basis of size, cost and their ability to lend support to the tube bundles and direct flow:
Longitudinal Flow Baffles (used in a two-pass shell)
Impingement Baffles (used for protecting bundle when entrance velocity is high)
Orifice Baffles
Single segmental
Double segmental
Support/Blanking baffles
Deresonating (detuning) baffles used to reduce tube vibration(Anish Apw)
Installation of baffles
As mentioned, baffles deal with the concern of support and fluid direction in heat exchangers. In this way it is vital that they are spaced correctly at installation. The minimum baffle spacing is the greater of 50.8 mm or one fifth of the inner shell diameter. The maximum baffle spacing is dependent on material and size of tubes. The Tubular Exchanger Manufacturers Association sets out guidelines. There are also segments with a "no tubes in window" design that affects the acceptable spacing within the design. An important design consideration is that no recirculation zones or dead spots form – both of which are counterproductive to effective heat transfer.
References
(Editors) Perry, R.H. and Green, D.W. (Oct, 2007) Perry's Chemical Engineers' Handbook (8th ed.) McGraw-Hill
Wolverine Tube Inc, (2008) Heat Transfer Data Book Available
Professor J. Kavanagh (2009) Heat Transfer Lectures 4&5 Usyd Chemical Engineering Department
Heat exchangers | Baffle (heat transfer) | Chemistry,Engineering | 708 |
26,946,790 | https://en.wikipedia.org/wiki/Termite-leu%20RNA%20motif | The Termite-leu RNA motif is a conserved RNA structure discovered by bioinformatics. It is found only in DNA sequences extracted from uncultivated bacteria living in termite hindguts, and has not yet been detected in any known cultivated organism. In many cases, Termite-leu RNAs are found in the likely 5′ untranslated regions of multive genes related to the synthesis of the amino acid leucine. However, in several cases it is not found in this type of location. Therefore, it was considered ambiguous as to whether Termite-leu RNAs constitute cis-regulatory elements.
References
External links
Cis-regulatory RNA elements
Non-coding RNA | Termite-leu RNA motif | Chemistry | 144 |
2,667,603 | https://en.wikipedia.org/wiki/Controversy%20over%20Cantor%27s%20theory | In mathematical logic, the theory of infinite sets was first developed by Georg Cantor. Although this work has become a thoroughly standard fixture of classical set theory, it has been criticized in several areas by mathematicians and philosophers.
Cantor's theorem implies that there are sets having cardinality greater than the infinite cardinality of the set of natural numbers. Cantor's argument for this theorem is presented with one small change. This argument can be improved by using a definition he gave later. The resulting argument uses only five axioms of set theory.
Cantor's set theory was controversial at the start, but later became largely accepted. Most modern mathematics textbooks implicitly use Cantor's views on mathematical infinity. For example, a line is generally presented as the infinite set of its points, and it is commonly taught that there are more real numbers than rational numbers (see cardinality of the continuum).
Cantor's argument
Cantor's first proof that infinite sets can have different cardinalities was published in 1874. This proof demonstrates that the set of natural numbers and the set of real numbers have different cardinalities. It uses the theorem that a bounded increasing sequence of real numbers has a limit, which can be proved by using Cantor's or Richard Dedekind's construction of the irrational numbers. Because Leopold Kronecker did not accept these constructions, Cantor was motivated to develop a new proof.
In 1891, he published "a much simpler proof ... which does not depend on considering the irrational numbers." His new proof uses his diagonal argument to prove that there exists an infinite set with a larger number of elements (or greater cardinality) than the set of natural numbers N = {1, 2, 3, ...}. This larger set consists of the elements (x1, x2, x3, ...), where each xn is either m or w. Each of these elements corresponds to a subset of N—namely, the element (x1, x2, x3, ...) corresponds to {n ∈ N: xn = w}. So Cantor's argument implies that the set of all subsets of N has greater cardinality than N. The set of all subsets of N is denoted by P(N), the power set of N.
Cantor generalized his argument to an arbitrary set A and the set consisting of all functions from A to {0, 1}. Each of these functions corresponds to a subset of A, so his generalized argument implies the theorem: The power set P(A) has greater cardinality than A. This is known as Cantor's theorem.
The argument below is a modern version of Cantor's argument that uses power sets (for his original argument, see Cantor's diagonal argument). By presenting a modern argument, it is possible to see which assumptions of axiomatic set theory are used. The first part of the argument proves that N and P(N) have different cardinalities:
There exists at least one infinite set. This assumption (not formally specified by Cantor) is captured in formal set theory by the axiom of infinity. This axiom implies that N, the set of all natural numbers, exists.
P(N), the set of all subsets of N, exists. In formal set theory, this is implied by the power set axiom, which says that for every set there is a set of all of its subsets.
The concept of "having the same number" or "having the same cardinality" can be captured by the idea of one-to-one correspondence. This (purely definitional) assumption is sometimes known as Hume's principle. As Frege said, "If a waiter wishes to be certain of laying exactly as many knives on a table as plates, he has no need to count either of them; all he has to do is to lay immediately to the right of every plate a knife, taking care that every knife on the table lies immediately to the right of a plate. Plates and knives are thus correlated one to one." Sets in such a correlation are called equinumerous, and the correlation is called a one-to-one correspondence.
A set cannot be put into one-to-one correspondence with its power set. This implies that N and P(N) have different cardinalities. It depends on very few assumptions of set theory, and, as John P. Mayberry puts it, is a "simple and beautiful argument" that is "pregnant with consequences". Here is the argument:
Let be a set and be its power set. The following theorem will be proved: If is a function from to then it is not onto. This theorem implies that there is no one-to-one correspondence between and since such a correspondence must be onto. Proof of theorem: Define the diagonal subset Since proving that for all will imply that is not onto. Let Then which implies So if then and if then Since one of these sets contains and the other does not, Therefore, is not in the image of , so is not onto.
Next Cantor shows that is equinumerous with a subset of . From this and the fact that and have different cardinalities, he concludes that has greater cardinality than . This conclusion uses his 1878 definition: If A and B have different cardinalities, then either B is equinumerous with a subset of A (in this case, B has less cardinality than A) or A is equinumerous with a subset of B (in this case, B has greater cardinality than A). This definition leaves out the case where A and B are equinumerous with a subset of the other set—that is, A is equinumerous with a subset of B and B is equinumerous with a subset of A. Because Cantor implicitly assumed that cardinalities are linearly ordered, this case cannot occur. After using his 1878 definition, Cantor stated that in an 1883 article he proved that cardinalities are well-ordered, which implies they are linearly ordered. This proof used his well-ordering principle "every set can be well-ordered", which he called a "law of thought". The well-ordering principle is equivalent to the axiom of choice.
Around 1895, Cantor began to regard the well-ordering principle as a theorem and attempted to prove it. In 1895, Cantor also gave a new definition of "greater than" that correctly defines this concept without the aid of his well-ordering principle. By using Cantor's new definition, the modern argument that P(N) has greater cardinality than N can be completed using weaker assumptions than his original argument:
The concept of "having greater cardinality" can be captured by Cantor's 1895 definition: B has greater cardinality than A if (1) A is equinumerous with a subset of B, and (2) B is not equinumerous with a subset of A. Clause (1) says B is at least as large as A, which is consistent with our definition of "having the same cardinality". Clause (2) implies that the case where A and B are equinumerous with a subset of the other set is false. Since clause (2) says that A is not at least as large as B, the two clauses together say that B is larger (has greater cardinality) than A.
The power set has greater cardinality than which implies that P(N) has greater cardinality than N. Here is the proof:
Define the subset Define which maps onto Since implies is a one-to-one correspondence from to Therefore, is equinumerous with a subset of
Using proof by contradiction, assume that a subset of is equinumerous with . Then there is a one-to-one correspondence from to Define from to if then if then Since maps onto maps onto contradicting the theorem above stating that a function from to is not onto. Therefore, is not equinumerous with a subset of
Besides the axioms of infinity and power set, the axioms of separation, extensionality, and pairing were used in the modern argument. For example, the axiom of separation was used to define the diagonal subset the axiom of extensionality was used to prove and the axiom of pairing was used in the definition of the subset
Reception of the argument
Initially, Cantor's theory was controversial among mathematicians and (later) philosophers. As Leopold Kronecker claimed: "I don't know what predominates in Cantor's theory – philosophy or theology, but I am sure that there is no mathematics there." Many mathematicians agreed with Kronecker that the completed infinite may be part of philosophy or theology, but that it has no proper place in mathematics. Logician has commented on the energy devoted to refuting this "harmless little argument" (i.e. Cantor's diagonal argument) asking, "what had it done to anyone to make them angry with it?" Mathematician Solomon Feferman has referred to Cantor's theories as “simply not relevant to everyday mathematics.”
Before Cantor, the notion of infinity was often taken as a useful abstraction which helped mathematicians reason about the finite world; for example the use of infinite limit cases in calculus. The infinite was deemed to have at most a potential existence, rather than an actual existence. "Actual infinity does not exist. What we call infinite is only the endless possibility of creating new objects no matter how many exist already". Carl Friedrich Gauss's views on the subject can be paraphrased as: "Infinity is nothing more than a figure of speech which helps us talk about limits. The notion of a completed infinity doesn't belong in mathematics." In other words, the only access we have to the infinite is through the notion of limits, and hence, we must not treat infinite sets as if they have an existence exactly comparable to the existence of finite sets.
Cantor's ideas ultimately were largely accepted, strongly supported by David Hilbert, amongst others. Hilbert predicted: "No one will drive us from the paradise which Cantor created for us." To which Wittgenstein replied "if one person can see it as a paradise of mathematicians, why should not another see it as a joke?" The rejection of Cantor's infinitary ideas influenced the development of schools of mathematics such as constructivism and intuitionism.
Wittgenstein did not object to mathematical formalism wholesale, but had a finitist view on what Cantor's proof meant. The philosopher maintained that belief in infinities arises from confusing the intensional nature of mathematical laws with the extensional nature of sets, sequences, symbols etc. A series of symbols is finite in his view: In Wittgenstein's words: "...A curve is not composed of points, it is a law that points
obey, or again, a law according to which points can be constructed."
He also described the diagonal argument as "hocus pocus" and not proving what it purports to do.
Objection to the axiom of infinity
A common objection to Cantor's theory of infinite number involves the axiom of infinity (which is, indeed, an axiom and not a logical truth). Mayberry has noted that "... the set-theoretical axioms that sustain modern mathematics are self-evident in differing degrees. One of them—indeed, the most important of them, namely Cantor's Axiom, the so-called Axiom of Infinity—has scarcely any claim to self-evidence at all …"
Another objection is that the use of infinite sets is not adequately justified by analogy to finite sets. Hermann Weyl wrote:
The difficulty with finitism is to develop foundations of mathematics using finitist assumptions, that incorporates what everyone would reasonably regard as mathematics (for example, that includes real analysis).
See also
Preintuitionism
Notes
References
"Aus dem Paradies, das Cantor uns geschaffen, soll uns niemand vertreiben können."
Translated in
(address to the Fourth International Congress of Mathematicians)
External links
Doron Zeilberger's 68th Opinion
Philosopher Hartley Slater's argument against the idea of "number" that underpins Cantor's set theory
Wolfgang Mueckenheim: Transfinity - A Source Book
Hodges "An editor recalls some hopeless papers"
Discovery and invention controversies
History of mathematics
Philosophy of mathematics
Set theory
Georg Cantor | Controversy over Cantor's theory | Mathematics | 2,554 |
915,558 | https://en.wikipedia.org/wiki/Property%20B | In mathematics, Property B is a certain set theoretic property. Formally, given a finite set X, a collection C of subsets of X has Property B if we can partition X into two disjoint subsets Y and Z such that every set in C meets both Y and Z.
The property gets its name from mathematician Felix Bernstein, who first introduced the property in 1908.
Property B is equivalent to 2-coloring the hypergraph described by the collection C. A hypergraph with property B is also called 2-colorable. Sometimes it is also called bipartite, by analogy to the bipartite graphs.
Property B is often studied for uniform hypergraphs (set systems in which all subsets of the system have the same cardinality) but it has also been considered in the non-uniform case.
The problem of checking whether a collection C has Property B is called the set splitting problem.
Smallest set-families without property B
The smallest number of sets in a collection of sets of size n such that C does not have Property B is denoted by m(n).
Known values of m(n)
It is known that m(1) = 1, m(2) = 3, and m(3) = 7 (as can by seen by the following examples); the value of m(4) = 23 (Östergård), although finding this result was the result of an exhaustive search. An upper bound of 23 (Seymour, Toft) and a lower bound of 21 (Manning) have been proven. At the time of this writing (March 2017), there is no OEIS entry for the sequence m(n) yet, due to the lack of terms known.
m(1)
For n = 1, set X = {1}, and C = {{1}}. Then C does not have Property B.
m(2)
For n = 2, set X = {1, 2, 3} and C = {{1, 2}, {1, 3}, {2, 3}} (a triangle). Then C does not have Property B, so m(2) <= 3. However, C' = {{1, 2}, {1, 3}} does (set Y = {1} and Z = {2, 3}), so m(2) >= 3.
m(3)
For n = 3, set X = {1, 2, 3, 4, 5, 6, 7}, and C = {{1, 2, 4}, {2, 3, 5}, {3, 4, 6}, {4, 5, 7}, {5, 6, 1}, {6, 7, 2}, {7, 1, 3}} (the Steiner triple system S7); C does not have Property B (so m(3) <= 7), but if any element of C is omitted, then that element can be taken as Y, and the set of remaining elements C' will have Property B (so for this particular case, m(3) >= 7). One may check all other collections of 6 3-sets to see that all have Property B.
m(4)
Östergård (2014) through an exhaustive search found m(4) = 23. Seymour (1974) constructed a hypergraph on 11 vertices with 23 edges without Property B, which shows that m(4) <= 23. Manning (1995) narrowed the floor such that m(4) >= 21.
Asymptotics of m(n)
Erdős (1963) proved that for any collection of fewer than sets of size n, there exists a 2-coloring in which all set are bichromatic. The proof is simple: Consider a random coloring. The probability that an arbitrary set is monochromatic is . By a union bound, the probability that there exist a monochromatic set is less than . Therefore, there exists a good coloring.
Erdős (1964) showed the existence of an n-uniform hypergraph with hyperedges which does not have property B (i.e., does not have a 2-coloring in which all hyperedges are bichromatic), establishing an upper bound.
Schmidt (1963) proved that every collection of at most sets of size n has property B. Erdős and Lovász conjectured that . Beck in 1978 improved the lower bound to , where is an arbitrary small positive number. In 2000, Radhakrishnan and Srinivasan improved the lower bound to . They used a clever probabilistic algorithm.
See also
Set splitting problem
References
Further reading
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Families of sets
Hypergraphs | Property B | Mathematics | 981 |
9,758,445 | https://en.wikipedia.org/wiki/Maximal%20semilattice%20quotient | In abstract algebra, a branch of mathematics, a maximal semilattice quotient is a commutative monoid derived from another commutative monoid by making certain elements equivalent to each other.
Every commutative monoid can be endowed with its algebraic preordering ≤ . By definition, x≤ y holds, if there exists z such that x+z=y. Further, for x, y in M, let hold, if there exists a positive integer n such that x≤ ny, and let hold, if and . The binary relation is a monoid congruence of M, and the quotient monoid is the maximal semilattice quotient of M.
This terminology can be explained by the fact that the canonical projection p from M onto is universal among all monoid homomorphisms from M to a (∨,0)-semilattice, that is, for any (∨,0)-semilattice S and any monoid homomorphism f: M→ S, there exists a unique (∨,0)-homomorphism such that f=gp.
If M is a refinement monoid, then is a distributive semilattice.
References
A.H. Clifford and G.B. Preston, The Algebraic Theory of Semigroups. Vol. I. Mathematical Surveys, No. 7, American Mathematical Society, Providence, R.I. 1961. xv+224 p.
Lattice theory | Maximal semilattice quotient | Mathematics | 306 |
52,332,253 | https://en.wikipedia.org/wiki/Octagon%20Computer%20Superstore | Octagon Computer Superstore is a computer retail store in the Philippines. It has 150 branches nationwide along with their subsidiary, Micro Valley Computer Center with headquarters at 747 Romualdez Street, corner Zobel Street, Ermita, Manila. The store offers information technology products, mainly computers and components, laptops, smartphones and tablets and the like.
History
Octagon Computer Superstore started in 1982 as an IT products retailer. They mainly sell computer sets, accessories and components. It then grew from a being an IT products retailer with a lone store in Manila to a chain of computer retail stores with branches nationwide.
From 1990s to 2010, Octagon became a reselling partner to various computer component manufacturers such as Acer, Hewlett-Packard, Logitech, and Seagate. With high sales, the company was given citations such as the Acer's Excellent Major Account Development Award in 1995 and Cisco's Retail Store of the Year in 2009.
Upon attaining nationwide reach, Octagon opened their subsidiary store, Micro Valley Computer Center, with several branches in Cabanatuan, Davao, Dumaguete and Manila. Micro Valley are focused more on computer parts and accessories, and also offers extended computer repair service. Meanwhile, from IT products, Octagon expanded their product range to computer accessories, gadgets, Android phones and tablets, and digital printers.
In 2012, Octagon became the official Philippine retail partner of Antec, an American computer component manufacturer.
Octagon Computer Superstore remains to be the predominant computer retailer company in the Philippines with 151 branches versus its rivals Silicon Valley Computer Group Philippines with 51 branches and Gaisano Interpace Computer Systems with 20 branches.
Branches
Octagon now has 150 branches nationwide with around 1,000 employees. Across the country, they are commonly seen in major malls like SM Malls, KCC Malls, Robinson's Malls, and Gaisano Malls. Octagon Computer Superstore and Micro Valley Computer Center has stand-alone branches in Manila, Zamboanga, Dumaguete, Vigan, Batangas, Butuan, Cagayan de Oro, Dipolog and Davao.
See also
CD-R King
Silicon Valley
References
External links
Octagon Website
Retail companies of the Philippines
Philippine brands
Electronic component distributors
Retail companies established in 1982
Computer hardware companies
Consumer electronics retailers
Home computer hardware companies
Companies based in Manila
Privately held companies of the Philippines | Octagon Computer Superstore | Technology | 501 |
28,557,445 | https://en.wikipedia.org/wiki/Blackbird%20%28wind-powered%20vehicle%29 | Blackbird is an experimental wind-powered vehicle, built in 2010 to demonstrate that it is possible for such a vehicle to go directly downwind faster than the wind (sometimes abbreviated as DDWFTTW). Blackbird employs a rotor connected to the wheels and does not have a motor, battery, or flywheel. It was constructed by Rick Cavallaro and John Borton of Sportvision, sponsored by Google and Joby Energy in association with the San Jose State University aeronautics department.
In a test supervised and recognized by the North American Land Sailing Association in July 2010, Cavallaro achieved a speed of sailing directly downwind in winds: almost three times the speed of the wind. In 2012, Blackbird also demonstrated sailing directly upwind with twice the speed of the wind.
Theory
Rotor-powered vehicles are wind-powered vehicles that use rotors—instead of sails—which may have a shroud around them (ducted fan) or constitute an unducted propeller, and which may adjust orientation to face the apparent wind. The rotor may be connected via a drive train to wheels or to a generator that provides electrical power to electric motors that drive the wheels.
A vehicle with a bladed rotor mechanically connected to the wheels can be designed to go at a speed faster than that of the wind, both directly into the wind and directly downwind. Upwind, the rotor works as a wind turbine driving the wheels. Downwind, it works as a propeller, driven by the wheels. In both cases, power comes from the difference in velocity between the air mass and the ground, as received by the vehicle's rotor or wheels.
Relative to the vehicle, both the air and the ground are passing backwards. However, travelling upwind, the air is coming at the vehicle faster than the ground, whereas travelling downwind faster than the wind speed, the air is coming at the vehicle more slowly than the ground. The vehicle draws power from the faster of the two media in each case and imparts it to the slower of the two: upwind, drawing power from the wind and imparting it to the wheels and, downwind, drawing power from the wheels and imparting it to the rotor: in each case in proportion to the velocity of the medium, relative to the vehicle.
In summary:
Upwind: the rotor harvests power from the oncoming air and drives the wheels, as would a wind turbine.
Downwind: when the vehicle is traveling faster than the windspeed, the ground is the fastest-moving medium relative to the vehicle, so the wheels harvest the power and impart it to the rotor, which propels the vehicle.
How fast a given wind speed can propel a vehicle in either direction is limited only by the efficiency of the turbine blades, losses in the drive train, and the vehicle's aerodynamic drag, apart from the drag of the turbine.
History
In 2006, following a viral internet debate started by Rick Cavallaro as a brain teaser, a wind-powered, propeller-driven vehicle was built and filmed, demonstrating that it is possible to sail 'dead' downwind faster than the wind by the power of the available wind only.
In 2009, professor Drela of MIT worked out the equations for such a device and concluded that one could be built "without too much difficulty". Other researchers arrived at similar conclusions.
The same year, team members Rick Cavallaro and John Borton of Sportvision, sponsored by Google and in association with the San Jose State University aeronautics department, built a test vehicle nicknamed Blackbird. A year later, in 2010, Cavallaro successfully tested the vehicle, achieving more than twice the speed of wind, definitively demonstrating that it is possible to build a vehicle which can achieve the claim. A second test with an improved vehicle in 2011 reached close to three times the speed of wind.
After proposing the vehicle's design, and presenting the analysis to demonstrate its viability, the Blackbird team learned that others had previously conceived and built similar designs: most notably, aerodynamics engineer Andrew B. Bauer, later with the Douglas Aircraft Company, built and demonstrated such a vehicle in 1969, based on an analysis presented in a student's paper from some twenty years earlier.
Bauer reported "a rearward deflection of a foot-long tuft located about 12 feet forward of the propeller plane," indicating that his vehicle went faster than the true wind (the strand would have streamed forward, if the apparent wind was from behind). Several sources of engineering and scientific articles explain the theory and physics of such a device. Besides still photography, a film has been found showing it in operation.
Achievements
On 7 and 8 March 2010, the team reported testing their vehicle on a motor-driven moving belt (treadmill), showing that it would advance against the belt, which means that it can progress dead downwind faster than the wind.
On 24 March 2010, the team ran the vehicle on the Ivanpah dry lake bed south of Las Vegas, Nevada, showing that it could accelerate dead downwind from a standstill and reach velocities well in excess of wind speed. That is, the vehicle was progressing dead downwind faster than the wind. Officials of the North American Land Sailing Association (NALSA) were in attendance and one NALSA Board of Directors member (Bob Dill) was there for every run and collected his own rough wind and GPS data.
On July 2, 2010, Blackbird set the world's first certified record for going directly downwind, faster than the wind, using only power from the available wind during its run on El Mirage Dry Lake. The yacht achieved a dead downwind speed of about 2.8 times the speed of the wind.
On June 16, 2012, Blackbird set the world's first certified record for going directly upwind, without tacking, using only power from the wind. The yacht achieved a dead upwind speed of about 2.1 times the speed of the wind.
Controversy
In 2021, University of California, Los Angeles physics professor Alexander Kusenko disputed the claim citing the role of possible wind gusts and other factors in the apparent accomplishment, having seen a YouTube video on the Veritasium channel by Derek Muller. Kusenko and Muller entered into a $10,000 bet that required Muller to prove the validity of the claim, which was witnessed by noted scientists, Neil deGrasse Tyson and Bill Nye. Muller won the bet to Kusenko's satisfaction with a series of model experiments, investigation of the original supporting data of the Blackbird run, and exploration of the supporting equations.
Although Kusenko conceded the bet on a technicality, he stated that he saw no evidence that Blackbird exceeded the speed of the wind, following the given constraints of the experiment.
Current status
In July 2013, Cavallaro sold Blackbird in an eBay auction. It was purchased by Neil Cutcliffe. In May 2023, Cutcliffe donated it to the Castle Air Museum in Atwater, California. Museum curators plan to restore and preserve it as a static display.
See also
Greenbird – wind-powered vehicle that set 126.1 mph (202.9 km/h) land speed record on March 26, 2009 (not directly downwind)
List of motorized trikes
External links
Archived Blackbird project website, with pictures and speed graph
North American Land Sailing Association
Video of Blackbird on YouTube
Downwind Noir (article by Kimball Livingstone)
Video proving the validity of the Blackbird record run with a $10,000 bet against a physics professor
Counterintuitive Performance of Land and Sea Yachts
References
Marine propulsion
Tricycles | Blackbird (wind-powered vehicle) | Engineering | 1,565 |
4,556,843 | https://en.wikipedia.org/wiki/Santa%20suit | A Santa suit is a suit worn by a person portraying the legendary figure Santa Claus. The modern American version of the suit can be attributed to the work of Thomas Nast for Harper's Weekly magazine, although it is often thought that Haddon Sundblom designed the suit in his advertising work for The Coca-Cola Company. Sundblom's work did standardize the western image of Santa, and popularized the image of the red suit with white fur trim. This has become the image of the American Santa, while in some European countries where Saint Nicholas remains popular, the outfit worn is closer to religious clothing, including a Bishop's mitre.
History
The first appearance of a modern Santa Claus, complete with what we consider to be the Santa suit was in drawings by Thomas Nast. Nast's original drawings were of a small Santa who could slide down chimneys, but his later works made him full size. He was also the first to draw Santa wearing a red suit, a fur-lined stocking cap, and a wide belt with a large buckle.
Prior to Nast's work, Santa's outfit was tan in color, and it was he that changed it to red, although he also drew Santa in a green suit. This change is often attributed to the work of Haddon Sundblom, who drew images of Santa in advertising for the Coca-Cola Company since 1931. Although Sundblom's work certainly changed the perception of Santa Claus, the red suit was shown on the covers of Harper's Weekly at least forty years before his work for the soda company was published. The Coca-Cola Company itself has attributed the red color of the suit to Nast's earlier work. Prior to the Coca-Cola advertising, the image of Santa was in a state of flux. He was portrayed in a variety of forms, including both the modern forms and in some cases as a gnome. It was Sundblom's work which standardised the form of Santa to the earlier Nast work, including the red suit outfit.
Design
There are regional differences in the type of suit that Santa Claus wears. Typically in the United States and United Kingdom, he wears a white fur trimmed red jacket and pants with a broad buckled belt, a matching hat, and black boots. In Continental European countries such as the Low Countries or Austria, with Saint Nicholas still remaining popular, the outfit is closer to that of the saint, being a long robe and a Bishop's mitre.
References
External links
Costume design
Suits (clothing)
Santa Claus | Santa suit | Engineering | 519 |
35,740,250 | https://en.wikipedia.org/wiki/Capped%20square%20antiprismatic%20molecular%20geometry | In chemistry, the capped square antiprismatic molecular geometry describes the shape of compounds where nine atoms, groups of atoms, or ligands are arranged around a central atom, defining the vertices of a gyroelongated square pyramid. The symmetry group of the resulting object is C4v
The gyroelongated square pyramid is a square pyramid with a square antiprism connected to the square base. In this respect, it can be seen as a "capped" square antiprism (a square antiprism with a pyramid erected on one of the square faces).
It is very similar to the tricapped trigonal prismatic molecular geometry, and there is some dispute over the specific geometry exhibited by certain molecules.
Examples:
[SiCo9(CO)21]2-, defined by the Co9 framework, which encapsulates the Si atom
[Pb(phen)4(OClO3)]+, defined by the N8O framework, which encapsulates the Pb2+ ion
[Ge9]4-, a zintl ion
Th(troopolonate)4(H2O), defined by the O9 framework, which encapsulates the Th4+ ion
is sometimes described as having a capped square antiprismatic geometry, although its geometry is most often described as tricapped trigonal prismatic.
, a lanthanum(III) complex with a La–La bond.
Bicapped square antiprismatic molecular geometry
Square antiprisms can be capped on both square faces, giving bicapped square antiprismatic molecular geometry. The bicapped square antiprismatic atoms surrounding a central atom define the vertices of a gyroelongated square bipyramid. The symmetry group of this object is D4d.
Examples:
B10H12, defined by the B10 framework
[AsRh10(CO)22]3− and [SRh10(CO)22]2−, defined by the Rh10 framework, which encapsulates the main group atoms As and S
[TlSn8]3−, a zintl ion
References
Stereochemistry
Molecular geometry | Capped square antiprismatic molecular geometry | Physics,Chemistry | 455 |
9,628,780 | https://en.wikipedia.org/wiki/Animal%20migration | Animal migration is the relatively long-distance movement of individual animals, usually on a seasonal basis. It is the most common form of migration in ecology. It is found in all major animal groups, including birds, mammals, fish, reptiles, amphibians, insects, and crustaceans. The cause of migration may be local climate, local availability of food, the season of the year or for mating.
To be counted as a true migration, and not just a local dispersal or irruption, the movement of the animals should be an annual or seasonal occurrence, or a major habitat change as part of their life. An annual event could include Northern Hemisphere birds migrating south for the winter, or wildebeest migrating annually for seasonal grazing. A major habitat change could include young Atlantic salmon or sea lamprey leaving the river of their birth when they have reached a few inches in size. Some traditional forms of human migration fit this pattern.
Migrations can be studied using traditional identification tags such as bird rings, or tracked directly with electronic tracking devices.
Before animal migration was understood, folklore explanations were formulated for the appearance and disappearance of some species, such as that barnacle geese grew from goose barnacles.
Overview
Concepts
Migration can take very different forms in different species, and has a variety of causes.
As such, there is no simple accepted definition of migration. One of the most commonly used definitions, proposed by the zoologist J. S. Kennedy is
Migration encompasses four related concepts: persistent straight movement; relocation of an individual on a greater scale (in both space and time) than its normal daily activities; seasonal to-and-fro movement of a population between two areas; and movement leading to the redistribution of individuals within a population. Migration can be either obligate, meaning individuals must migrate, or facultative, meaning individuals can "choose" to migrate or not. Within a migratory species or even within a single population, often not all individuals migrate. Complete migration is when all individuals migrate, partial migration is when some individuals migrate while others do not, and differential migration is when the difference between migratory and non-migratory individuals is based on discernible characteristics like age or sex. Irregular (non-cyclical) migrations such as irruptions can occur under pressure of famine, overpopulation of a locality, or some more obscure influence.
Seasonal
Seasonal migration is the movement of various species from one habitat to another during the year. Resource availability changes depending on seasonal fluctuations, which influence migration patterns. Some species such as Pacific salmon migrate to reproduce; every year, they swim upstream to mate and then return to the ocean. Temperature is a driving factor of migration that is dependent on the time of year. Many species, especially birds, migrate to warmer locations during the winter to escape poor environmental conditions.
Circadian
Circadian migration is where birds utilise circadian rhythm (CR) to regulate migration in both fall and spring. In circadian migration, clocks of both circadian (daily) and circannual (annual) patterns are used to determine the birds' orientation in both time and space as they migrate from one destination to the next. This type of migration is advantageous in birds that, during the winter, remain close to the equator, and also allows the monitoring of the auditory and spatial memory of the bird's brain to remember an optimal site of migration. These birds also have timing mechanisms that provide them with the distance to their destination.
Tidal
Tidal migration is the use of tides by organisms to move periodically from one habitat to another. This type of migration is often used in order to find food or mates. Tides can carry organisms horizontally and vertically for as little as a few nanometres to even thousands of kilometres. The most common form of tidal migration is to and from the intertidal zone during daily tidal cycles. These zones are often populated by many different species and are rich in nutrients. Organisms like crabs, nematodes, and small fish move in and out of these areas as the tides rise and fall, typically about every twelve hours. The cycle movements are associated with foraging of marine and bird species. Typically, during low tide, smaller or younger species will emerge to forage because they can survive in the shallower water and have less chance of being preyed upon. During high tide, larger species can be found due to the deeper water and nutrient upwelling from the tidal movements. Tidal migration is often facilitated by ocean currents.
Diel
While most migratory movements occur on an annual cycle, some daily movements are also described as migration. Many aquatic animals make a diel vertical migration, travelling a few hundred metres up and down the water column, while some jellyfish make daily horizontal migrations of a few hundred metres.
In specific groups
Different kinds of animals migrate in different ways.
In birds
Approximately 1,800 of the world's 10,000 bird species migrate long distances each year in response to the seasons. Many of these migrations are north-south, with species feeding and breeding in high northern latitudes in the summer and moving some hundreds of kilometres south for the winter. Some species extend this strategy to migrate annually between the Northern and Southern Hemispheres. The Arctic tern has the longest migration journey of any bird: it flies from its Arctic breeding grounds to the Antarctic and back again each year, a distance of at least , giving it two summers every year.
Bird migration is controlled primarily by day length, signalled by hormonal changes in the bird's body. On migration, birds navigate using multiple senses. Many birds use a sun compass, requiring them to compensate for the sun's changing position with time of day. Navigation involves the ability to detect magnetic fields.
In fish
Most fish species are relatively limited in their movements, remaining in a single geographical area and making short migrations to overwinter, to spawn, or to feed. A few hundred species migrate long distances, in some cases of thousands of kilometres. About 120 species of fish, including several species of salmon, migrate between saltwater and freshwater (they are 'diadromous').
Forage fish such as herring and capelin migrate around substantial parts of the North Atlantic ocean. The capelin, for example, spawn around the southern and western coasts of Iceland; their larvae drift clockwise around Iceland, while the fish swim northwards towards Jan Mayen island to feed and return to Iceland parallel with Greenland's east coast.
In the 'sardine run', billions of Southern African pilchard Sardinops sagax spawn in the cold waters of the Agulhas Bank and move northward along the east coast of South Africa between May and July.
In insects
Some winged insects such as locusts and certain butterflies and dragonflies with strong flight migrate long distances. Among the dragonflies, species of Libellula and Sympetrum are known for mass migration, while Pantala flavescens, known as the globe skimmer or wandering glider dragonfly, makes the longest ocean crossing of any insect: between India and Africa. Exceptionally, swarms of the desert locust, Schistocerca gregaria, flew westwards across the Atlantic Ocean for during October 1988, using air currents in the Inter-Tropical Convergence Zone.
In some migratory butterflies, such as the monarch butterfly and the painted lady, no individual completes the whole migration. Instead, the butterflies mate and reproduce on the journey, and successive generations continue the migration.
In mammals
Some mammals undertake exceptional migrations; reindeer have one of the longest terrestrial migrations on the planet, reaching as much as per year in North America. However, over the course of a year, grey wolves move the most. One grey wolf covered a total cumulative annual distance of .
Mass migration occurs in mammals such as the Serengeti 'great migration', an annual circular pattern of movement with some 1.7 million wildebeest and hundreds of thousands of other large game animals, including gazelles and zebra. More than 20 such species engage, or used to engage, in mass migrations. Of these migrations, those of the springbok, black wildebeest, blesbok, scimitar-horned oryx, and kulan have ceased. Long-distance migrations occur in some batsnotably the mass migration of the Mexican free-tailed bat between Oregon and southern Mexico. Migration is important in cetaceans, including whales, dolphins and porpoises; some species travel long distances between their feeding and their breeding areas.
Humans are mammals, but human migration, as commonly defined, is when individuals often permanently change where they live, which does not fit the patterns described here. An exception is some traditional migratory patterns such as transhumance, in which herders and their animals move seasonally between mountains and valleys, and the seasonal movements of nomads.
In other animals
Among the reptiles, adult sea turtles migrate long distances to breed, as do some amphibians. Hatchling sea turtles, too, emerge from underground nests, crawl down to the water, and swim offshore to reach the open sea. Juvenile green sea turtles make use of Earth's magnetic field to navigate.
Some crustaceans migrate, such as the largely-terrestrial Christmas Island red crab, which moves en masse each year by the millions. Like other crabs, they breathe using gills, which must remain wet, so they avoid direct sunlight, digging burrows to shelter from the sun. They mate on land near their burrows. The females incubate their eggs in their abdominal brood pouches for two weeks. Then they return to the sea to release their eggs at high tide in the moon's last quarter. The larvae spend a few weeks at sea and then return to land.
Tracking Migration
Scientists gather observations of animal migration by tracking their movements. Animals were traditionally tracked with identification tags such as bird rings for later recovery. However, no information was obtained about the actual route followed between release and recovery, and only a fraction of tagged individuals were recovered. More convenient, therefore, are electronic devices such as radio-tracking collars that can be followed by radio, whether handheld, in a vehicle or aircraft, or by satellite. GPS animal tracking enables accurate positions to be broadcast at regular intervals, but the devices are inevitably heavier and more expensive than those without GPS. An alternative is the Argos Doppler tag, also called a 'Platform Transmitter Terminal' (PTT), which sends regularly to the polar-orbiting Argos satellites; using Doppler shift, the animal's location can be estimated, relatively roughly compared to GPS, but at a lower cost and weight. A technology suitable for small birds which cannot carry the heavier devices is the geolocator which logs the light level as the bird flies, for analysis on recapture. There is scope for further development of systems able to track small animals globally.
Radio-tracking tags can be fitted to insects, including dragonflies and bees.
In culture
Before animal migration was understood, various folklore and erroneous explanations were formulated to account for the disappearance or sudden arrival of birds in an area. In Ancient Greece, Aristotle proposed that robins turned into redstarts when summer arrived. The barnacle goose was explained in European Medieval bestiaries and manuscripts as either growing like fruit on trees, or developing from goose barnacles on pieces of driftwood. Another example is the swallow, which was once thought, even by naturalists such as Gilbert White, to hibernate either underwater, buried in muddy riverbanks, or in hollow trees.
See also
Great American Interchange
References
Further reading
General
Baker, R. R. (1978) The Evolutionary Ecology of Animal Migration. Holmes & Meier. .
Dingle, H. (1996) Migration: The Biology of Life on the Move. Oxford University Press. .
Gauthreaux, S. A. (1980) Animal Migration, Orientation, and Navigation. Academic Press. .
Milner-Gulland, E. J., Fryxell, J. M., and Sinclair, A. R. E. (2011) Animal Migration: A Synthesis. Oxford University Press. .
Rankin, M. (1985) Migration: Mechanisms and Adaptive Significance: Contributions in Marine Science. Marine Science Institute. .
Riede, K. (2002) Global Register of Migratory Species. With database and GIS maps on CD. .
By group
Drake, V. A. and Gatehouse, A. G. (1995) Insect migration: tracking resources through space and time. Cambridge University Press.
Elphick, J. (1995) The atlas of bird migration: tracing the great journeys of the world's birds. Random House.
Greenberg, R. and Marra, P. P. (2005) Birds of Two Worlds: The Ecology and Evolution of Migration. Johns Hopkins University Press.
Lucas, M. C. and Baras, E. (2001) Migration of freshwater fishes. Blackwell Science.
MacKeown, B. A. (1984) Fish migration. Timber Press.
Sonnenschein, E; Berthold, P. (2003) Avian migration. Springer.
For children
Gans, R. and Mirocha, P. How do Birds Find their Way? HarperCollins. (Stage 2)
Marsh, L. (2010) Amazing Animal Journeys. National Geographic Society. (Level 3)
External links
Migration Basics from U.S. National Park Service
Witnessing the Great Migration in Serengeti and Masai Mara
Global Register of Migratory Species – identifies, maps and features 4,300 migratory vertebrate species
Animal migration on PubMed MeSH term F01.145.113.083
Ethology | Animal migration | Biology | 2,775 |
46,635,388 | https://en.wikipedia.org/wiki/CD%20Crucis | CD Crucis, also known as HD 311884, is an eclipsing binary star system in the constellation Crux. It is around 14,000 light years away near the faint open cluster Hogg 15. The binary contains a Wolf–Rayet star and is also known as WR 47.
System
CD Cru is composed of two massive and highly luminous stars aligned so that they eclipse each other as they orbit every 6 days and 6 hours. One is a hot blue O-type main sequence star of spectral type O5V that is 57 times as massive as the Sun, while the other is an even hotter Wolf–Rayet star of spectral type WN6 that is 48 times as massive as the Sun. The WR star dominates the spectrum but is less bright, so which star is considered the primary varies. For clarity the components are referred to as WR and O
Hogg 15
Hogg 15 is a small faint open cluster that has been calculated to lie about 4.2 kpc away. CD Cru is considered a likely member of the cluster, in which case it would be the brightest member by over a magnitude. It lies outside the central two arc-minute condensation of the cluster, but well within the outer bounds discovered for the member stars. The cluster is calculated to be only eight million years old.
The brighter and closer cluster NGC 4609 lies 10 arc-minutes away, and both clusters are near the centre of the dark Coalsack Nebula. Both clusters are actually more distant than the Coalsack so are seen through it rather than against it. It suffers 3.5 magnitudes of interstellar extinction. Between the two clusters lies the 5th magnitude BZ Crucis, a much closer foreground object.
Properties
The WR component is five times the radius of the sun, but its high temperature means it is over 100,000 times more luminous. Its mass is determined from the orbital motion to be .
The O star is larger at , more luminous at , and more massive at . Although the stars are only separated by around , they are well separated because of their small size.
References
Crux
Crucis, CD
311884
O-type main-sequence stars
Wolf–Rayet stars
J12435102-6305148
062115
Eclipsing binaries | CD Crucis | Astronomy | 471 |
15,476 | https://en.wikipedia.org/wiki/Internet%20protocol%20suite | The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and the Internet Protocol (IP). Early versions of this networking model were known as the Department of Defense (DoD) model because the research and development were funded by the United States Department of Defense through DARPA.
The Internet protocol suite provides end-to-end data communication specifying how data should be packetized, addressed, transmitted, routed, and received. This functionality is organized into four abstraction layers, which classify all related protocols according to each protocol's scope of networking. An implementation of the layers for a particular application forms a protocol stack. From lowest to highest, the layers are the link layer, containing communication methods for data that remains within a single network segment (link); the internet layer, providing internetworking between independent networks; the transport layer, handling host-to-host communication; and the application layer, providing process-to-process data exchange for applications.
The technical standards underlying the Internet protocol suite and its constituent protocols are maintained by the Internet Engineering Task Force (IETF). The Internet protocol suite predates the OSI model, a more comprehensive reference framework for general networking systems.
History
Early research
Initially referred to as the DOD Internet Architecture Model, the Internet protocol suite has its roots in research and development sponsored by the Defense Advanced Research Projects Agency (DARPA) in the late 1960s. After DARPA initiated the pioneering ARPANET in 1969, Steve Crocker established a "Networking Working Group" which developed a host-host protocol, the Network Control Program (NCP). In the early 1970s, DARPA started work on several other data transmission technologies, including mobile packet radio, packet satellite service, local area networks, and other data networks in the public and private domains. In 1972, Bob Kahn joined the DARPA Information Processing Technology Office, where he worked on both satellite packet networks and ground-based radio packet networks, and recognized the value of being able to communicate across both. In the spring of 1973, Vinton Cerf joined Kahn with the goal of designing the next protocol generation for the ARPANET to enable internetworking. They drew on the experience from the ARPANET research community, the International Network Working Group, which Cerf chaired, and researchers at Xerox PARC.
By the summer of 1973, Kahn and Cerf had worked out a fundamental reformulation, in which the differences between local network protocols were hidden by using a common internetwork protocol, and, instead of the network being responsible for reliability, as in the existing ARPANET protocols, this function was delegated to the hosts. Cerf credits Louis Pouzin and Hubert Zimmermann, designers of the CYCLADES network, with important influences on this design. The new protocol was implemented as the Transmission Control Program in 1974 by Cerf, Yogen Dalal and Carl Sunshine.
Initially, the Transmission Control Program (the Internet Protocol did not then exist as a separate protocol) provided only a reliable byte stream service to its users, not datagrams. Several versions were developed through the Internet Experiment Note series. As experience with the protocol grew, collaborators recommended division of functionality into layers of distinct protocols, allowing users direct access to datagram service. Advocates included Bob Metcalfe and Yogen Dalal at Xerox PARC; Danny Cohen, who needed it for his packet voice work; and Jonathan Postel of the University of Southern California's Information Sciences Institute, who edited the Request for Comments (RFCs), the technical and strategic document series that has both documented and catalyzed Internet development. Postel stated, "We are screwing up in our design of Internet protocols by violating the principle of layering." Encapsulation of different mechanisms was intended to create an environment where the upper layers could access only what was needed from the lower layers. A monolithic design would be inflexible and lead to scalability issues. In version 4, written in 1978, Postel split the Transmission Control Program into two distinct protocols, the Internet Protocol as connectionless layer and the Transmission Control Protocol as a reliable connection-oriented service.
The design of the network included the recognition that it should provide only the functions of efficiently transmitting and routing traffic between end nodes and that all other intelligence should be located at the edge of the network, in the end nodes. This end-to-end principle was pioneered by Louis Pouzin in the CYCLADES network, based on the ideas of Donald Davies. Using this design, it became possible to connect other networks to the ARPANET that used the same principle, irrespective of other local characteristics, thereby solving Kahn's initial internetworking problem. A popular expression is that TCP/IP, the eventual product of Cerf and Kahn's work, can run over "two tin cans and a string." Years later, as a joke in 1999, the IP over Avian Carriers formal protocol specification was created and successfully tested two years later. 10 years later still, it was adapted for IPv6.
DARPA contracted with BBN Technologies, Stanford University, and the University College London to develop operational versions of the protocol on several hardware platforms. During development of the protocol the version number of the packet routing layer progressed from version 1 to version 4, the latter of which was installed in the ARPANET in 1983. It became known as Internet Protocol version 4 (IPv4) as the protocol that is still in use in the Internet, alongside its current successor, Internet Protocol version 6 (IPv6).
Early implementation
In 1975, a two-network IP communications test was performed between Stanford and University College London. In November 1977, a three-network IP test was conducted between sites in the US, the UK, and Norway. Several other IP prototypes were developed at multiple research centers between 1978 and 1983.
A computer called a router is provided with an interface to each network. It forwards network packets back and forth between them. Originally a router was called gateway, but the term was changed to avoid confusion with other types of gateways.
Adoption
In March 1982, the US Department of Defense declared TCP/IP as the standard for all military computer networking. In the same year, NORSAR/NDRE and Peter Kirstein's research group at University College London adopted the protocol. The migration of the ARPANET from NCP to TCP/IP was officially completed on flag day January 1, 1983, when the new protocols were permanently activated.
In 1985, the Internet Advisory Board (later Internet Architecture Board) held a three-day TCP/IP workshop for the computer industry, attended by 250 vendor representatives, promoting the protocol and leading to its increasing commercial use. In 1985, the first Interop conference focused on network interoperability by broader adoption of TCP/IP. The conference was founded by Dan Lynch, an early Internet activist. From the beginning, large corporations, such as IBM and DEC, attended the meeting.
IBM, AT&T and DEC were the first major corporations to adopt TCP/IP, this despite having competing proprietary protocols. In IBM, from 1984, Barry Appelman's group did TCP/IP development. They navigated the corporate politics to get a stream of TCP/IP products for various IBM systems, including MVS, VM, and OS/2. At the same time, several smaller companies, such as FTP Software and the Wollongong Group, began offering TCP/IP stacks for DOS and Microsoft Windows. The first VM/CMS TCP/IP stack came from the University of Wisconsin.
Some of the early TCP/IP stacks were written single-handedly by a few programmers. Jay Elinsky and Oleg Vishnepolsky of IBM Research wrote TCP/IP stacks for VM/CMS and OS/2, respectively. In 1984 Donald Gillies at MIT wrote a ntcp multi-connection TCP which runs atop the IP/PacketDriver layer maintained by John Romkey at MIT in 1983–84. Romkey leveraged this TCP in 1986 when FTP Software was founded. Starting in 1985, Phil Karn created a multi-connection TCP application for ham radio systems (KA9Q TCP).
The spread of TCP/IP was fueled further in June 1989, when the University of California, Berkeley agreed to place the TCP/IP code developed for BSD UNIX into the public domain. Various corporate vendors, including IBM, included this code in commercial TCP/IP software releases. For Windows 3.1, the dominant PC operating system among consumers in the first half of the 1990s, Peter Tattam's release of the Trumpet Winsock TCP/IP stack was key to bringing the Internet to home users. Trumpet Winsock allowed TCP/IP operations over a serial connection (SLIP or PPP). The typical home PC of the time had an external Hayes-compatible modem connected via an RS-232 port with an 8250 or 16550 UART which required this type of stack. Later, Microsoft would release their own TCP/IP add-on stack for Windows for Workgroups 3.11 and a native stack in Windows 95. These events helped cement TCP/IP's dominance over other protocols on Microsoft-based networks, which included IBM's Systems Network Architecture (SNA), and on other platforms such as Digital Equipment Corporation's DECnet, Open Systems Interconnection (OSI), and Xerox Network Systems (XNS).
Nonetheless, for a period in the late 1980s and early 1990s, engineers, organizations and nations were polarized over the issue of which standard, the OSI model or the Internet protocol suite, would result in the best and most robust computer networks.
Formal specification and standards
The technical standards underlying the Internet protocol suite and its constituent protocols have been delegated to the Internet Engineering Task Force (IETF).
The characteristic architecture of the Internet protocol suite is its broad division into operating scopes for the protocols that constitute its core functionality. The defining specifications of the suite are RFC 1122 and 1123, which broadly outlines four abstraction layers (as well as related protocols); the link layer, IP layer, transport layer, and application layer, along with support protocols. These have stood the test of time, as the IETF has never modified this structure. As such a model of networking, the Internet protocol suite predates the OSI model, a more comprehensive reference framework for general networking systems.
Key architectural principles
The end-to-end principle has evolved over time. Its original expression put the maintenance of state and overall intelligence at the edges, and assumed the Internet that connected the edges retained no state and concentrated on speed and simplicity. Real-world needs for firewalls, network address translators, web content caches and the like have forced changes in this principle.
The robustness principle states: "In general, an implementation must be conservative in its sending behavior, and liberal in its receiving behavior. That is, it must be careful to send well-formed datagrams, but must accept any datagram that it can interpret (e.g., not object to technical errors where the meaning is still clear)." "The second part of the principle is almost as important: software on other hosts may contain deficiencies that make it unwise to exploit legal but obscure protocol features."
Encapsulation is used to provide abstraction of protocols and services. Encapsulation is usually aligned with the division of the protocol suite into layers of general functionality. In general, an application (the highest level of the model) uses a set of protocols to send its data down the layers. The data is further encapsulated at each level.
An early pair of architectural documents, and , titled Requirements for Internet Hosts, emphasizes architectural principles over layering. RFC 1122/23 are structured in sections referring to layers, but the documents refer to many other architectural principles, and do not emphasize layering. They loosely defines a four-layer model, with the layers having names, not numbers, as follows:
The application layer is the scope within which applications, or processes, create user data and communicate this data to other applications on another or the same host. The applications make use of the services provided by the underlying lower layers, especially the transport layer which provides reliable or unreliable pipes to other processes. The communications partners are characterized by the application architecture, such as the client–server model and peer-to-peer networking. This is the layer in which all application protocols, such as SMTP, FTP, SSH, HTTP, operate. Processes are addressed via ports which essentially represent services.
The transport layer performs host-to-host communications on either the local network or remote networks separated by routers. It provides a channel for the communication needs of applications. UDP is the basic transport layer protocol, providing an unreliable connectionless datagram service. The Transmission Control Protocol provides flow-control, connection establishment, and reliable transmission of data.
The internet layer exchanges datagrams across network boundaries. It provides a uniform networking interface that hides the actual topology (layout) of the underlying network connections. It is therefore also the layer that establishes internetworking. Indeed, it defines and establishes the Internet. This layer defines the addressing and routing structures used for the TCP/IP protocol suite. The primary protocol in this scope is the Internet Protocol, which defines IP addresses. Its function in routing is to transport datagrams to the next host, functioning as an IP router, that has the connectivity to a network closer to the final data destination.
The link layer defines the networking methods within the scope of the local network link on which hosts communicate without intervening routers. This layer includes the protocols used to describe the local network topology and the interfaces needed to effect the transmission of internet layer datagrams to next-neighbor hosts.
Link layer
The protocols of the link layer operate within the scope of the local network connection to which a host is attached. This regime is called the link in TCP/IP parlance and is the lowest component layer of the suite. The link includes all hosts accessible without traversing a router. The size of the link is therefore determined by the networking hardware design. In principle, TCP/IP is designed to be hardware independent and may be implemented on top of virtually any link-layer technology. This includes not only hardware implementations but also virtual link layers such as virtual private networks and networking tunnels.
The link layer is used to move packets between the internet layer interfaces of two different hosts on the same link. The processes of transmitting and receiving packets on the link can be controlled in the device driver for the network card, as well as in firmware or by specialized chipsets. These perform functions, such as framing, to prepare the internet layer packets for transmission, and finally transmit the frames to the physical layer and over a transmission medium. The TCP/IP model includes specifications for translating the network addressing methods used in the Internet Protocol to link-layer addresses, such as media access control (MAC) addresses. All other aspects below that level, however, are implicitly assumed to exist and are not explicitly defined in the TCP/IP model.
The link layer in the TCP/IP model has corresponding functions in Layer 2 of the OSI model.
Internet layer
Internetworking requires sending data from the source network to the destination network. This process is called routing and is supported by host addressing and identification using the hierarchical IP addressing system. The internet layer provides an unreliable datagram transmission facility between hosts located on potentially different IP networks by forwarding datagrams to an appropriate next-hop router for further relaying to its destination. The internet layer has the responsibility of sending packets across potentially multiple networks. With this functionality, the internet layer makes possible internetworking, the interworking of different IP networks, and it essentially establishes the Internet.
The internet layer does not distinguish between the various transport layer protocols. IP carries data for a variety of different upper layer protocols. These protocols are each identified by a unique protocol number: for example, Internet Control Message Protocol (ICMP) and Internet Group Management Protocol (IGMP) are protocols 1 and 2, respectively.
The Internet Protocol is the principal component of the internet layer, and it defines two addressing systems to identify network hosts and to locate them on the network. The original address system of the ARPANET and its successor, the Internet, is Internet Protocol version 4 (IPv4). It uses a 32-bit IP address and is therefore capable of identifying approximately four billion hosts. This limitation was eliminated in 1998 by the standardization of Internet Protocol version 6 (IPv6) which uses 128-bit addresses. IPv6 production implementations emerged in approximately 2006.
Transport layer
The transport layer establishes basic data channels that applications use for task-specific data exchange. The layer establishes host-to-host connectivity in the form of end-to-end message transfer services that are independent of the underlying network and independent of the structure of user data and the logistics of exchanging information. Connectivity at the transport layer can be categorized as either connection-oriented, implemented in TCP, or connectionless, implemented in UDP. The protocols in this layer may provide error control, segmentation, flow control, congestion control, and application addressing (port numbers).
For the purpose of providing process-specific transmission channels for applications, the layer establishes the concept of the network port. This is a numbered logical construct allocated specifically for each of the communication channels an application needs. For many types of services, these port numbers have been standardized so that client computers may address specific services of a server computer without the involvement of service discovery or directory services.
Because IP provides only a best-effort delivery, some transport-layer protocols offer reliability.
TCP is a connection-oriented protocol that addresses numerous reliability issues in providing a reliable byte stream:
data arrives in-order
data has minimal error (i.e., correctness)
duplicate data is discarded
lost or discarded packets are resent
includes traffic congestion control
The newer Stream Control Transmission Protocol (SCTP) is also a reliable, connection-oriented transport mechanism. It is message-stream-oriented, not byte-stream-oriented like TCP, and provides multiple streams multiplexed over a single connection. It also provides multihoming support, in which a connection end can be represented by multiple IP addresses (representing multiple physical interfaces), such that if one fails, the connection is not interrupted. It was developed initially for telephony applications (to transport SS7 over IP).
Reliability can also be achieved by running IP over a reliable data-link protocol such as the High-Level Data Link Control (HDLC).
The User Datagram Protocol (UDP) is a connectionless datagram protocol. Like IP, it is a best-effort, unreliable protocol. Reliability is addressed through error detection using a checksum algorithm. UDP is typically used for applications such as streaming media (audio, video, Voice over IP, etc.) where on-time arrival is more important than reliability, or for simple query/response applications like DNS lookups, where the overhead of setting up a reliable connection is disproportionately large. Real-time Transport Protocol (RTP) is a datagram protocol that is used over UDP and is designed for real-time data such as streaming media.
The applications at any given network address are distinguished by their TCP or UDP port. By convention, certain well-known ports are associated with specific applications.
The TCP/IP model's transport or host-to-host layer corresponds roughly to the fourth layer in the OSI model, also called the transport layer.
QUIC is rapidly emerging as an alternative transport protocol. Whilst it is technically carried via UDP packets it seeks to offer enhanced transport connectivity relative to TCP. HTTP/3 works exclusively via QUIC.
Application layer
The application layer includes the protocols used by most applications for providing user services or exchanging application data over the network connections established by the lower-level protocols. This may include some basic network support services such as routing protocols and host configuration. Examples of application layer protocols include the Hypertext Transfer Protocol (HTTP), the File Transfer Protocol (FTP), the Simple Mail Transfer Protocol (SMTP), and the Dynamic Host Configuration Protocol (DHCP). Data coded according to application layer protocols are encapsulated into transport layer protocol units (such as TCP streams or UDP datagrams), which in turn use lower layer protocols to effect actual data transfer.
The TCP/IP model does not consider the specifics of formatting and presenting data and does not define additional layers between the application and transport layers as in the OSI model (presentation and session layers). According to the TCP/IP model, such functions are the realm of libraries and application programming interfaces. The application layer in the TCP/IP model is often compared to a combination of the fifth (session), sixth (presentation), and seventh (application) layers of the OSI model.
Application layer protocols are often associated with particular client–server applications, and common services have well-known port numbers reserved by the Internet Assigned Numbers Authority (IANA). For example, the HyperText Transfer Protocol uses server port 80 and Telnet uses server port 23. Clients connecting to a service usually use ephemeral ports, i.e., port numbers assigned only for the duration of the transaction at random or from a specific range configured in the application.
At the application layer, the TCP/IP model distinguishes between user protocols and support protocols. Support protocols provide services to a system of network infrastructure. User protocols are used for actual user applications. For example, FTP is a user protocol and DNS is a support protocol.
Although the applications are usually aware of key qualities of the transport layer connection such as the endpoint IP addresses and port numbers, application layer protocols generally treat the transport layer (and lower) protocols as black boxes which provide a stable network connection across which to communicate. The transport layer and lower-level layers are unconcerned with the specifics of application layer protocols. Routers and switches do not typically examine the encapsulated traffic, rather they just provide a conduit for it. However, some firewall and bandwidth throttling applications use deep packet inspection to interpret application data. An example is the Resource Reservation Protocol (RSVP). It is also sometimes necessary for Applications affected by NAT to consider the application payload.
Layering evolution and representations in the literature
The Internet protocol suite evolved through research and development funded over a period of time. In this process, the specifics of protocol components and their layering changed. In addition, parallel research and commercial interests from industry associations competed with design features. In particular, efforts in the International Organization for Standardization led to a similar goal, but with a wider scope of networking in general. Efforts to consolidate the two principal schools of layering, which were superficially similar, but diverged sharply in detail, led independent textbook authors to formulate abridging teaching tools.
The following table shows various such networking models. The number of layers varies between three and seven.
Some of the networking models are from textbooks, which are secondary sources that may conflict with the intent of RFC 1122 and other IETF primary sources.
Comparison of TCP/IP and OSI layering
The three top layers in the OSI model, i.e. the application layer, the presentation layer and the session layer, are not distinguished separately in the TCP/IP model which only has an application layer above the transport layer. While some pure OSI protocol applications, such as X.400, also combined them, there is no requirement that a TCP/IP protocol stack must impose monolithic architecture above the transport layer. For example, the NFS application protocol runs over the External Data Representation (XDR) presentation protocol, which, in turn, runs over a protocol called Remote Procedure Call (RPC). RPC provides reliable record transmission, so it can safely use the best-effort UDP transport.
Different authors have interpreted the TCP/IP model differently, and disagree whether the link layer, or any aspect of the TCP/IP model, covers OSI layer 1 (physical layer) issues, or whether TCP/IP assumes a hardware layer exists below the link layer. Several authors have attempted to incorporate the OSI model's layers 1 and 2 into the TCP/IP model since these are commonly referred to in modern standards (for example, by IEEE and ITU). This often results in a model with five layers, where the link layer or network access layer is split into the OSI model's layers 1 and 2.
The IETF protocol development effort is not concerned with strict layering. Some of its protocols may not fit cleanly into the OSI model, although RFCs sometimes refer to it and often use the old OSI layer numbers. The IETF has repeatedly stated that Internet Protocol and architecture development is not intended to be OSI-compliant. RFC 3439, referring to the internet architecture, contains a section entitled: "Layering Considered Harmful".
For example, the session and presentation layers of the OSI suite are considered to be included in the application layer of the TCP/IP suite. The functionality of the session layer can be found in protocols like HTTP and SMTP and is more evident in protocols like Telnet and the Session Initiation Protocol (SIP). Session-layer functionality is also realized with the port numbering of the TCP and UDP protocols, which are included in the transport layer of the TCP/IP suite. Functions of the presentation layer are realized in the TCP/IP applications with the MIME standard in data exchange.
Another difference is in the treatment of routing protocols. The OSI routing protocol IS-IS belongs to the network layer, and does not depend on CLNS for delivering packets from one router to another, but defines its own layer-3 encapsulation. In contrast, OSPF, RIP, BGP and other routing protocols defined by the IETF are transported over IP, and, for the purpose of sending and receiving routing protocol packets, routers act as hosts. As a consequence, routing protocols are included in the application layer. Some authors, such as Tanenbaum in Computer Networks, describe routing protocols in the same layer as IP, reasoning that routing protocols inform decisions made by the forwarding process of routers.
IETF protocols can be encapsulated recursively, as demonstrated by tunnelling protocols such as Generic Routing Encapsulation (GRE). GRE uses the same mechanism that OSI uses for tunnelling at the network layer.
Implementations
The Internet protocol suite does not presume any specific hardware or software environment. It only requires that hardware and a software layer exists that is capable of sending and receiving packets on a computer network. As a result, the suite has been implemented on essentially every computing platform. A minimal implementation of TCP/IP includes the following: Internet Protocol (IP), Address Resolution Protocol (ARP), Internet Control Message Protocol (ICMP), Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and Internet Group Management Protocol (IGMP). In addition to IP, ICMP, TCP, UDP, Internet Protocol version 6 requires Neighbor Discovery Protocol (NDP), ICMPv6, and Multicast Listener Discovery (MLD) and is often accompanied by an integrated IPSec security layer.
See also
BBN Report 1822, an early layered network model
Fast Local Internet Protocol
List of automation protocols
List of information technology initialisms
List of IP protocol numbers
Lists of network protocols
List of TCP and UDP port numbers
Notes
References
Bibliography
External links
Internet History – Pages on Robert Kahn, Vinton Cerf, and TCP/IP (reviewed by Cerf and Kahn).
The Ultimate Guide to TCP/IP
The TCP/IP Guide – A comprehensive look at the protocols and the procedure and processes involved
History of the Internet
Network architecture
Reference models | Internet protocol suite | Engineering | 5,809 |
1,548,014 | https://en.wikipedia.org/wiki/Mister%20Hyde%20%28Marvel%20Comics%29 | Mister Hyde (Calvin Zabo) is a supervillain appearing in American comic books published by Marvel Comics. Created by writer Stan Lee and artist Don Heck, the character first appeared in Journey into Mystery #99 (December 1963). Calvin Zabo is a supervillain known under the codename of Mister Hyde. He is the father of the superhero Daisy Johnson. The character has also been a member of the Masters of Evil.
Calvin Zabo appeared in the second season of the television series Agents of S.H.I.E.L.D., portrayed by Kyle MacLachlan.
Development
Concept and creation
Calvin Zabo / Mister Hyde is inspired by Dr. Jekyll and Mr. Hyde from the 1886 Gothic novella Strange Case of Dr Jekyll and Mr Hyde written by Robert Louis Stevenson.
Publication history
Calvin Zabo debuted in Journey into Mystery #99 (December 1963), created by Stan Lee and Don Heck. He has appeared as a regular character in Thunderbolts since issue #157, and remained with the team after the title transitioned into Dark Avengers beginning with issue #176.
Fictional character biography
Calvin Zabo was born in Trenton, New Jersey and becomes a morally abject but brilliant biochemist who discovered the effects of hormones on human physiology. His favorite storybook was Stevenson's 1886 classic, Strange Case of Dr Jekyll and Mr Hyde. He convinced himself that the experiment Dr. Jekyll performed in the story could actually be accomplished and became obsessed with the idea of unleashing his full bestial nature in a superhuman form.
However, he needed money to do this, so he robbed his various employers systematically. Though too intelligent to be caught, the medical community became suspicious, due to his tendency of always getting employed by organizations which were subsequently robbed. Zabo eventually sought work as a surgeon in the hospital where Donald Blake worked as a directing physician, yet Blake would not allow him that job due to his history. Zabo became so enraged that Blake would not give him the position, even though he did indeed intend to rob the organization, and swore revenge.
He eventually became successful in creating his formula and turned himself into a massive, Hulk-like creature he called Mister Hyde, named after the character in the story. In this new form, Hyde found out he had immense strength allowing him to crush cars and tear through steel as though it were made of cardboard. With his new superhuman powers he sought out Blake, whom he tried to kill by throwing him from a window, but Blake transformed into Thor by striking his cane on the wall and survived, with Thor claiming that he have saved Blake. Hyde, hearing of this on the radio, decided to eliminate Thor. He tried framing him for a bank robbery by using his vast strength to rip open a bank vault while disguised as Thor. While Blake and Jane Foster were out, Hyde met and kidnapped them at gunpoint. As Blake, he got tied up next to a bomb that would explode in 24 hours unless Hyde defused it. However, when attempting to steal a Polaris submarine to roam the seas like a pirate, After Thor defeated Hyde, the authorities saw his brute strength and realized he must have impersonated Thor, but Thor forced himself to let him escape, as Jane thought Blake is still in danger.
Hyde went into business as a full-time professional supervillain and teamed up with the Cobra to get revenge upon Thor, but they were both defeated, despite getting Thor's hammer from him briefly. With the Cobra, he was bailed out and employed by Loki to kidnap Jane Foster and they battled Thor again. Loki doubled their powers to try to help them. Loki showed Thor where Jane was being held. The house had many traps set up for Thor, and Jane was almost killed in an explosion. Thor was able to defeat both villains, and Hyde was caught by a ray which paralyzed him. Both Hyde and the Cobra were jailed and Jane's life was saved by an Asgardian formula Balder sent to Thor. Hyde and the Cobra escaped prison, but were eventually recaptured by Daredevil. They teamed with the Jester to get revenge, but were defeated again. With the Scorpion, Hyde then battled Captain America and the Falcon. Teaming with the Cobra again, Hyde attempted to acquire Cagliostro's serum. While serving in prison following this failed attempt, Hyde was ensnared by the mind-control power of the Purple Man, and forced to battle Daredevil in an arena alongside the Cobra, the Jester and the Gladiator.
Tiring of their repeated failures, the Cobra elected to sever their partnership when he escaped from Ryker's Island, taking the time to taunt Hyde before leaving. For a long time, Hyde never forgave him for the slight. With Batroc the Leaper, Hyde later blackmailed New York City with a hijacked supertanker and attempted to destroy the entire city to kill the Cobra. Eventually, he was defeated by Captain America with Batroc's aid. Hyde again stalked the Cobra seeking revenge, and this time battled Spider-Man. He was imprisoned again, but escaped Ryker's Island and battled Spider-Man and the Black Cat during another attempt on the Cobra's life. Hyde later battled Daredevil again.
Hyde later became a member of Baron Helmut Zemo's incarnation of the Masters of Evil and invaded Avengers Mansion along with them, torturing the Black Knight and Edwin Jarvis. With Goliath and the Wrecking Crew, he nearly killed Hercules, but was defeated by the Avengers. Hyde later attempted an escape from the Vault alongside Titania, Vibro, the Griffin, and the Armadillo, but was defeated and recaptured by the Captain. He eventually escaped from the Vault alongside the Wizard and others. Hyde was later defeated in single combat by the Cobra, who earned Hyde's respect as a result.
Hyde later fought with The Professor and received head trauma that limited his ability to transform. He was subsequently caught by the police when he coincidentally checked into the same hotel as the one where the Daily Bugle staff were attending Robbie Robertson's retirement party, allowing Peter Parker to defeat him using an improvised costume. Shortly after, Hyde had several run-ins with the Ghost Rider in which he was defeated with the Penance Stare.
Hyde briefly helped the symbiote-bonded Toxin track the Cobra after a prison escape by providing a piece of skin for the symbiote to track with.
Zabo was being held in the Raft (the Ryker's Island Prison complex) 6 months after the events of "Avengers Disassembled." When a prison break was caused by Electro, Zabo emerged in his Hyde persona, fought with Daredevil, and was knocked unconscious by Luke Cage.
At one point, Zabo was discovered by the Young Avengers to be selling a derivative of his Hyde formula on the street as one of the various illegal substances known as Mutant Growth Hormone.
Zabo grafts abilities similar to the powers of Spider-Man to homeless teenagers. After Spider-Man revealed his identity during the "Civil War" storyline, Zabo sought to recreate the circumstances of Spider-Man's "birth", by taking in orphans off the street, imbuing them with spider-powers, and seeing whether or not the teenagers would give in to their darker impulses. During the ensuing battle with Spider-Man, Hyde pulled webbing off his face, taking his eyelids with it, and was hit in the face with hydrochloric acid, courtesy of one of his own Guinea pigs. It is stated by Spider-Man that he has been left blinded and had his face ruined as a result. Dr. Curt Connors was later seen aiding Spider-Man in a cure for Zabo, one of Zabo's test subjects.
Hyde's daughter is Daisy Johnson, who is a member of S.H.I.E.L.D.; her mother was apparently a sex worker whose services Calvin Zabo frequented and the girl was put up for adoption after birth. Daisy subsequently manifested superpowers inherited from Zabo's mutated genetic code.
The Hood hired him as part of his criminal organization to take advantage of the split in the superhero community caused by the Superhuman Registration Act.
Later, he was seen with Cobra (who was now operating as King Cobra), Firebrand and the Mauler, who attacked Yellowjacket, the Constrictor and other Initiative staff and trainees.
Hyde worked with Boomerang, Tiger Shark, and Whirlwind to manipulate Venom III into procuring Norman Osborn's fortunes. This was thwarted by Venom and Green Goblin as Osborn threw a bomb into Hyde's mouth, causing him to spit out blood. Osborn then warned Hyde and the other villains that if they ever cross him again, he will kill everyone that they ever loved before they are tortured to death.
Hyde joins the Grim Reaper's new Lethal Legion, claiming embarrassment over Norman Osborn blowing a bomb up in his mouth.
Hyde appears as a member of the Hood's crime syndicate during an attack on the New Avengers.
Hyde was selected to be a part of the "beta team" of the Thunderbolts, alongside Boomerang, the Shocker, Gunna and Centurius.
Later, Hyde began a drug operation in California where he came into conflict with Robbie Reyes after his car had some of Hyde's pills inside. Hyde's mercenaries chase Robbie down during the race to retrieve the car and the pills. Robbie is gunned down by the mercenaries when he mistakes them for police and they torch the scene. Robbie is revived as a demonic being called the Ghost Rider and defeats Zabo, becoming something of a local hero and urban legend. Having regrouped and refined his Hyde formula into new blue pills, Calvin Zabo gradually takes over the L.A. criminal underground with his "Blue Hyde Brigade", which includes Guero and his gang, longtime enemies of Robbie, calling themselves the "Blue Krüe."
During the "Avengers: Standoff!" storyline, Hyde was an inmate of Pleasant Hill, a gated community established by S.H.I.E.L.D. Mister Hyde was knocked out by Warwolf.
During the "Opening Salvo" part of the Secret Empire storyline, Hyde is recruited by Baron Helmut Zemo to join the Army of Evil. During HYDRA's takeover of the United States, Hyde is one of a few Army of Evil members not in a stasis pod and is shown leading a group of HYDRA soldiers to invade New Attilan and capture the Inhumans. He, alongside HYDRA's Avengers, catch his daughter Daisy and her team, the Secret Warriors. During interrogation, Daisy uses her powers to destroy the Helicarrier they are in, forcing Hyde to retreat.
Following the "Gang War" storyline, Mister Hyde is seen as an inmate at Ravencroft. When nurse Shay Marken is feeding the detained inmates, Mister Hyde claims that he is in his Calvin Zabo form which does not fool Nurse Marken. Then Mister Hyde vows to rip Nurse Marken apart as she states that now she is addressing Mister Hyde.
In Immortal Thor, Hyde allies with Grey Gargoyle, King Cobra, and Radioactive Man. After Grey Gargoyle petrified Thor, Mister Hyde shattered his body. However, Thor regenerates with Enchantress' help. With help from Enchantress, Sif, and Magni of Earth-3515. Thor defeats the villains who are taken to Daedalus LLC, a subsidiary of Roxxon.
Powers and abilities
The process that transforms Calvin Zabo into his Mister Hyde persona are growth hormones caused by ingestion of a chemical formula. As his body adjusted to its new form, Hyde's strength, stamina, durability, and healing were all boosted to uncommon levels. Hyde's powers are so sufficient that he can stand up and face Joe Fixit in a fight. He was shown tearing apart an armored car door with ease. Through further experimental procedures over the years, his abilities have been increased beyond their original limits. Zabo must consume his special serum periodically for him to remain as one identity from another. However, mental stress or pain could impair this transformation into Hyde. He employs a wristwatch-like device supplied with the formula that injects itself directly into his bloodstream, thus enabling to transform himself by button pushing.
Due to the nature of these transformations, Hyde's skin is warped. This gives his face a distorted look reminiscent of Lon Chaney's make-up used in The Phantom of the Opera.
Zabo is also an intelligent research scientist with a Ph.D. in medicine and biochemistry. When assuming his Hyde form, he loses those skills.
Reception
Marc Buxton of Den of Geek ranked Mister Hyde 15th in their "Marvel’s 31 Best Monsters" list and called him a "monstrous force worthy of his classic monster namesake."
Other versions
Age of Apocalypse
In the timeline of the Age of Apocalypse storyline, Mister Hyde (as well as the Cobra) is a near-feral and cannibal "scavenger". He is known to prowl graveyards and attack anyone entering his territory.
Elseworlds
Mister Hyde appeared in the Elseworlds crossover comic book Daredevil/Batman: Eye for an Eye. Two-Face partnered with Hyde for a series of technological robberies. In truth, Two-Face had implanted Hyde's brain with the material needed to "grow" an experimental "organic" computer chip and fed Hyde pills to keep him enraged. Once grown, the chip would kill Hyde, its current growth also weakening Hyde's strength as his energy is diverted to support the chip (Batman noting during the fight that Hyde should normally have a punch that could knock Superman into orbit). Hyde berates Two-Face, proud he has abandoned his past as Zabo and insults Two-Face for hanging onto his Harvey Dent side, as well as using a coin to decide between right and wrong. Two-Face is glad the process will kill Hyde. In the end, Daredevil uses his past friendship with Dent to talk Two-Face into supplying the antidote for the chip, which saves Hyde's life.
House of M
Mister Hyde appears as a member of the Hood's Masters of Evil. Before the Red Guard attacks Santo Rico, Hyde leaves the team alongside the Cobra, Crossbones, and Thunderball. Hyde was later seen as an Army scientist.
Marvel Zombies
A zombified Mister Hyde appears in Marvel Zombies 4. He is seen attacking the new Midnight Sons, trying to bite one of them, but he is quickly killed by the Man-Thing when he rips the zombie Hyde apart and then, holding a huge boulder, drops it down on him, crushing the zombie Hyde to death instantly.
Thor: The Mighty Avenger
Mister Hyde is the antagonist of the first two issues of this alternate universe retelling of Thor's origin. Thor, confused and partially amnesiac, stops Hyde from hassling an innocent woman. This drives Hyde into an obsession with Thor's new friend, a museum employee named Jane Foster.
In other media
Television
Calvin Zabo / Mister Hyde appears in "The Mighty Thor" segment of The Marvel Super Heroes, voiced by Henry Comor.
Calvin Johnson appears in the second season of Agents of S.H.I.E.L.D., portrayed by Kyle MacLachlan. This version, initially known as the "Doctor", uses a formula described as being primarily composed of "anabolic-androgenic steroids, a liver enzyme blocker, various metabolic enhancers, methamphetamines, gorilla testosterone, and a drop of peppermint", with a minimum of one milligram of adrenaline being required to achieve its full effect. Additionally, he is the husband of an Inhuman named Jiaying. Throughout his appearances, he joins forces with Jiaying to seek revenge on Daniel Whitehall for dissecting her and S.H.I.E.L.D. for denying him his revenge until he eventually realizes the error of his ways and saves Daisy Johnson from Jiaying by killing the latter for her. Following this, Phil Coulson alters his memory, which allows him to start over with a new identity and take up work as a veterinarian named "Winslow". As of the fourth season, Glenn Talbot successfully tasked scientists with recreating Zabo's formula and empowering Jeffrey Mace as part of "Project: Patriot".
Video games
Calvin Zabo / Mister Hyde appears as a boss in Iron Man and X-O Manowar in Heavy Metal, voiced by Tim Jones.
Calvin Zabo / Mister Hyde appears as a boss and playable character in Marvel Avengers Alliance 2.
Calvin Zabo / Mister Hyde appears as a boss in Marvel Heroes. The Lizard breaks him out of prison to keep his human side dormant. In exchange, Zabo injects the Lizard with his Hyde formula to make him stronger and so they can combine their respective formulas and poison the Bronx Zoo's water supply to create reptilian-animal hybrids, only to be defeated by the players.
Cal Johnson / Mister Hyde appears as a playable character in Lego Marvel's Avengers via the "Agents of S.H.I.E.L.D." DLC.
References
External links
Mister Hyde at Marvel.com
Characters created by Don Heck
Characters created by Stan Lee
Comics characters introduced in 1963
Fictional biochemists
Fictional biologists
Fictional characters from New Jersey
Fictional mad scientists
Fictional medical specialists
Marvel Comics characters with accelerated healing
Marvel Comics characters with superhuman durability or invulnerability
Marvel Comics characters with superhuman senses
Marvel Comics characters with superhuman strength
Marvel Comics male supervillains
Marvel Comics mutates
Marvel Comics scientists
Marvel Comics supervillains
Marvel Comics television characters
Works based on Strange Case of Dr Jekyll and Mr Hyde | Mister Hyde (Marvel Comics) | Chemistry | 3,678 |
9,672,320 | https://en.wikipedia.org/wiki/Contextual%20Query%20Language | Contextual Query Language (CQL), previously known as Common Query Language, is a formal language for representing queries to information retrieval systems such as search engines, bibliographic catalogs and museum collection information. Based on the semantics of Z39.50, its design objective is that queries be human readable and writable, and that the language be intuitive while maintaining the expressiveness of more complex query languages. It is being developed and maintained by the Z39.50 Maintenance Agency, part of the Library of Congress.
Examples of query syntax
Simple queries:
dinosaur
"complete dinosaur"
title = "complete dinosaur"
title exact "the complete dinosaur"
dinosaur or bird
Palomar assignment and "ice age"
dinosaur not reptile
dinosaur and bird or dinobird
(bird or dinosaur) and (feathers or scales)
"feathered dinosaur" and (yixian or jehol)
Queries accessing publication indexes:
publicationYear < 1980
lengthOfFemur > 2.4
bioMass >= 100
Queries based on the proximity of words to each other in a document:
ribs prox/distance<=5 chevrons
ribs prox/unit=sentence chevrons
ribs prox/distance>0/unit=paragraph chevrons
Queries across multiple dimensions:
date within "2002 2005"
dateRange encloses 2003
Queries based on relevance:
subject any/relevant "fish frog"
subject any/rel.lr "fish frog"
The latter example specifies using a specific algorithm for logistic regression.
References
External links
Z39.50 Maintenance Agency at the Library of Congress
A Gentle Introduction to CQL
Information retrieval systems
Library science
Library of Congress
Query languages
Knowledge representation languages | Contextual Query Language | Technology | 349 |
840,350 | https://en.wikipedia.org/wiki/Kimbell%20Art%20Museum | The Kimbell Art Museum in Fort Worth, Texas, hosts an art collection as well as traveling art exhibitions, educational programs and an extensive research library. Its initial artwork came from the private collection of Kay and Velma Kimbell, who also provided funds for a new building to house it.
The building was designed by architect Louis I. Kahn and is widely recognized as one of the most significant works of architecture of recent times. It is especially noted for the wash of silvery natural light across its vaulted gallery ceilings.
History
Kay Kimbell was a wealthy Fort Worth businessman who built an empire of over 70 companies in a variety of industries. He married Velma Fuller, who kindled his interest in art collecting by taking him to an art show in Fort Worth in 1931, where he bought a British painting. They set up the Kimbell Art Foundation in 1935 to establish an art institute, and by the time of his death in 1964, the couple had amassed what was considered to be the best selection of old masters in the Southwest. Kay left much of his estate to the Kimbell Art Foundation, and Velma bequeathed her share of the estate to the foundation as well, with the key directive to "build a museum of the first class."
The foundation's board of trustees hired Richard Fargo Brown, then director of the Los Angeles County Museum of Art, as the founding director of the museum with the task of constructing a building to house the Kimbell's art collection. Upon accepting the post, Brown declared that the new building should itself be a work of art, "as much a gem as one of the Rembrandts or Van Dycks housed within it." The proposed museum was given space in a 9.5 acre (3.8 hectare) site in Fort Worth's Cultural District, which was already home to three other museums, including the Fort Worth Art Museum-Center (now the Modern Art Museum of Fort Worth) and the Amon Carter Museum, specializing in art of the American West.
Brown discussed the goals of the institution and its new building with the trustees and summarized them in a four-page "Policy Statement" and a nineteen-page "Pre-Architectural Program" in June 1966. After interviewing a number of prominent architects, the museum hired Louis I. Kahn in October 1966. Kahn's previous works included such acclaimed structures as the Salk Institute in California, and he had recently been honored by being chosen to design the National Assembly Building for what would become the capital of the new nation of Bangladesh. Construction for the Kimbell Art Museum began in the summer of 1969. The new building opened in October 1972 and quickly achieved an international reputation for architectural excellence.
Brown also expanded the Kimbell collection by acquiring several works of significant quality by artists like Duccio, El Greco, Rubens, and Rembrandt.
After Richard Fargo Brown's death in 1979, Edmund "Ted" Pillsbury was appointed director of the museum. Previously he had been the director of the newly opened Yale Center for British Art, which, coincidentally, was also designed by Louis Kahn. He had also been a curator at the Yale Art Gallery, Kahn's first art museum. Pillsbury continued the art acquisition program in an aggressive but disciplined fashion. Richard Brettell, director of the Dallas Museum of Art, said, "He was, in some ways, single-handedly responsible for turning the Kimbell from an institution with a great building into one whose collection matched its architecture in quality".
In 1989, Pillsbury announced plans to expand the museum's building to accommodate its enlarged collection, but the plan was dropped because of strong opposition to any major alteration of the original Louis Kahn structure. In 2007, the Kimbell solved that problem by announcing plans to construct an additional, separate building across the street from the original building. While this did not alter the Kahn structure, it did significantly alter Kahn's work. Kahn had designed the building to be approach from the lawn, and the new structire significantly altered that plan. Designed by Renzo Piano, and relocated to the west lawn, the new structure opened to the public in November 2013.
The museum is part of the Monuments Men and Women Museum Network, launched in 2021 by the Monuments Men Foundation for the Preservation of Art.
The collection
In 1966, before the museum even had a building, founding director Brown included this directive in his Policy Statement: "The goal shall be definitive excellence, not size of collection." Accordingly, the museum's collection today consists of only about 350 works of art, but they are of notably high quality.
The European collection is the most extensive in the museum and includes Michelangelo's first known painting, The Torment of Saint Anthony, the only painting by Michelangelo on exhibit in the Americas. It also includes works by Duccio, Fra Angelico, Mantegna, El Greco, Carracci, Caravaggio, Rubens, Guercino, La Tour, Poussin, Velázquez, Rembrandt, Boucher, Gainsborough, Vigée-Lebrun, Friedrich (the first painting by the artist acquired by a public collection outside of Europe), Cézanne, Monet, Caillebotte, Matisse, Bonnard, Mondrian, Braque, Miró and Picasso. Works from the classical period include antiquities from Ancient Egypt, Assyria, Greece and Rome. The Asian collection comprises sculptures, paintings, bronzes, ceramics, and works of decorative art from China, Korea, Japan, India, Nepal, Tibet, Cambodia, and Thailand. Precolumbian art is represented by Maya works in ceramic, stone, shell, and jade, Olmec, Zapotec, and Aztec sculpture, as well as pieces from the Conte and Huari cultures. The African collection consists primarily of bronze, wood, and terracotta sculpture from West and Central Africa, including examples from Nigeria, Angola, and the Democratic Republic of the Congo, and Oceanic art is represented by a Maori figure.
The museum owns only a few pieces created after the mid-20th century (believing that era to be the province of its neighbor, the Modern Art Museum of Fort Worth) and no American art (believing that to be the province of its other neighbor, the Amon Carter Museum).
The museum also houses a substantial library with over 59,000 books, periodicals and auction catalogs that are available as a resource to art historians and to faculty and graduate students from surrounding universities.
The building
Preparation
Brown's "Policy Statement" set a clear architectural direction by calling for the new building to be "a work of art", It was augmented by his "Pre-Architectural Program", which specified that "natural light should play a vital part" in the design and that "the form of the building should be so complete in its beauty that additions would spoil that form." Brown called for a building of modest scale that would not overwhelm either the artwork or the viewer.
After an extensive search that included interviews with such noted architects as Marcel Breuer, Mies van der Rohe, Pier Luigi Nervi, Gordon Bunshaft and Edward Larrabee Barnes, the commission was awarded to Louis Kahn in October 1966. From Kahn's point of view, Brown was an ideal client. Brown had been an admirer of Kahn's work for some time, and the approach he specified for the building was very much in line with Kahn's, particularly its emphasis on natural light.
Because Kahn had a reputation for significant time and cost overruns, a local engineering and architectural firm owned by Preston M. Geren was made associate architect, a practice followed in Fort Worth for out-of-state architects. Frank Sherwood served as their project coordinator. The Geren organization had a solid reputation for bringing in projects on time and within budget, but by their own admission they were not especially innovative. The contract called for control over construction to be turned over to Geren when Kahn had finished the design, a provision that eventually led to conflict because Kahn felt that a design was never finished until the building was constructed. Kahn once said, "the building gives you answers as it grows and becomes itself." The museum trustees settled the issue by deciding that Geren would report directly to them instead of to Kahn, but that Kahn would have final say over the design, except that any changes would have to be approved by Brown.
The new museum was to be built on a gentle slope below the Amon Carter Museum, whose entrance and terrace faced the Fort Worth skyline. Kahn was asked to build the Kimbell museum no more than 40 feet (12 m) high so it would not interfere with the view from the Carter Museum. Kahn initially proposed a low but very spacious building 450 feet (137 m) square, but Brown rejected that proposal and insisted that Kahn design a much smaller structure, a decision that would have repercussions several years later when a proposal to expand the building created a storm of controversy.
Architecture
The museum is composed of 16 parallel vaults that are each 100 feet (30.6 m) long, 20 feet (6 m) high and 20 feet (6 m) wide (internal measurements). Intervening low channels separate the vaults. The vaults are grouped into three wings. The north and south wings each have six vaults, with the western one open as a portico. The central space has four vaults, with the western one open as an entry porch facing a courtyard partially enclosed by the two outside wings.
With one exception, the art galleries are located on the upper floor of the museum to allow access to natural light. Service and curatorial spaces as well as an additional gallery occupy the ground floor. Each interior vault has a slot along its apex to allow natural light into the galleries. Air ducts and other mechanical services are located in the flat channels between the vaults.
Kahn used several techniques to give the galleries an inviting atmosphere. The ends of the vaults, which are made of concrete block, are faced with travertine inside and out. The steel handrails were "blasted" with ground pecan shells to create a matte surface texture. The museum has three glass-walled courtyards that bring natural light to the gallery spaces. One of them penetrates the gallery floor to bring natural light to the conservation studio on the ground floor.
The landscape has been described as "Kahn's most elegant built example of landscape planning" by Philadelphia landscape architect George Patton. Approaching the main entrance past a lawn edged by pools with running water, the visitor enters a courtyard through a grove of Yaupon Holly trees. The sound of footsteps on the gravel walkway echoes from the walls on either side of the courtyard and is magnified under the curved ceiling of the entry porch. After that subtle preparation, the visitor enters the hushed museum with silvery light spread across its ceiling. Harriet Pattison played the lead role in the landscape design and is also the person who suggested that open porches flanking the entrance would create a good transition from the lawn and courtyard to the galleries inside. Pattison, who had also worked with Kahn on other projects, was an employee of Patton. She is the mother of film director Nathaniel Kahn, Louis Kahn's son who made the film "My Architect" about his father.
Vaults
Kahn's first design for the galleries called for angular vaults of folded concrete plates with light slots at the top. Brown liked the light slots but rejected this particular design because it had the ceilings 30 feet (9 m) high, too high for the museum he envisioned. Further research by Marshall Meyers, Kahn's project architect for the Kimbell museum, revealed that using a cycloid curve for the gallery vaults would reduce the ceiling height and provide other benefits as well. The relatively flat cycloid curve would produce elegant galleries that were wide in proportion to their height, allowing the ceiling to be lowered to 20 feet (6 m). More importantly, that curve could also be used to produce a beautiful distribution of natural light from a slot in the top of the gallery across the entire gallery ceiling.
Kahn was pleased with this development because it allowed him to design the museum with galleries that resembled the ancient Roman vaults he had always admired. The thin, curved shells needed for the roof were challenging to build, however, so Kahn called in a leading authority on concrete construction, August Komendant, with whom he had worked before (and who, like Kahn, was born in Estonia). Kahn generally referred to the museum's roof form as a vault, but Komendant explained that it was actually a shell playing the role of a beam. More precisely, as professor Steven Fleming points out, the shells that form the gallery roofs are "post-tensioned curved concrete beams, spanning an incredible 100 feet" (30.5 m), which "happened to have been the maximum distance that concrete walls or vaults could be produced without requiring expansion control joints." Both terms, vault and shell, are used in professional literature describing the museum.
True vaults, such as the Roman vaults that Kahn admired, will collapse if not supported along the entire lengths of each side. Not fully understanding the capabilities of modern concrete shells, Kahn initially planned to include many more support columns than were necessary for the gallery roofs. Komendant was able to use post-tensioned concrete that was only five inches thick to create gallery "vaults" that need support columns only at their four corners.
The Geren firm, which had been asked to look for ways to keep costs low, objected that the cycloid vaults would be too expensive and urged a flat roof instead. Kahn, however, insisted on a vaulted roof, which would enable him to create galleries with a comforting, room-like atmosphere yet with minimal need for columns or other internal structures that would reduce the museum's flexibility. Eventually a deal was struck whereby Geren would be responsible for the foundation and basement while Komendant would be responsible for the upper floors and cycloid shells. Kahn placed one of these shells at the front of each of the three wings as a porch or portico to illustrate how the building was constructed. The effect was, in his words, "like a piece of sculpture outside the building."
Thos. S. Byrne, Ltd. was the contractor for the project, with A. T. Seymour as project manager. Virgil Earp and L. G. Shaw, Byrne's project superintendents, designed forms with a cycloid shape that were made from hinged plywood and lined with an oily coating so they could be reused to pour concrete for multiple sections of the vaults, helping to ensure consistency. The long, straight channels at the bottoms of the shells were cast first so they could be used as platforms to support the workmen pouring concrete for the cycloid curves. After all the concrete had been poured and strengthened with internal post-tensioning cables, however, the curved parts of the shells carried the weight of their lower straight edges instead of the other way around.
To prevent the shells from collapsing at the long light slots at their apexes, concrete struts were inserted at 10-foot (3 m) intervals. A relatively thick concrete arch was added to each end of the shells to stiffen them further. To make it clear that the curved shells are supported only at their four corners and not by the walls at the ends of the vaults, thin arcs of transparent material were inserted between the curve of the shells and the end walls. Because the stiffening arches of the shells are thicker at the top, the transparent strips are tapered, thinner at the top than at the bottom. In addition, a linear transparent strip was placed between the straight bottoms of the shells and the long exterior walls to show that the shells aren't supported by those walls either. In addition to revealing the building's structure, these features bring additional natural light into the galleries in a way that is safe for the paintings.
The vault roofs, which are visible to approaching visitors, were covered with lead sheathing inspired by the lead covering of the complexly curved roofs of the Doge's Palace and St. Mark's Basilica in Venice, Italy.
Skylights
David Brownlee and David DeLong, authors of Louis I. Kahn: In The Realm of Architecture, declare that "in Fort Worth, Kahn created a skylight system without peer in the history of architecture." Robert McCarter, author of Louis I. Kahn, says the entry gallery is "one of the most beautiful spaces ever built", with its "astonishing, ethereal, silver-colored light." Carter Wiseman, author of Louis I. Kahn: Beyond Time and Style, said that "the light in the Kimbell gallery assumed an almost ethereal quality, and has been the distinguishing factor in its fame ever since."
Creating a natural lighting system that has evoked such acclaim was challenging, and Kahn's office and the lighting designer Richard Kelly investigated over 100 approaches in their search for the proper skylight system. The goal was to illuminate the galleries with indirect natural light while excluding all direct sunlight, which would damage the artwork. Richard Kelly, lighting consultant, determined that a reflecting screen made of perforated anodized aluminum with a specific curve could be used to distribute natural light evenly across the cycloid curve of the ceiling. He hired a computer expert to determine the exact shape of the reflector's curve, making it one of the first architectural elements to be designed with computer technology.
In areas without art, such as the lobby, cafeteria and library, the entire reflector is perforated, making it possible for people standing beneath to glimpse passing clouds. In the gallery spaces, the central part of the reflector, which is directly beneath the sun, is solid, while the remainder is perforated. The concrete surfaces of the ceiling were given a high finish to further assist the reflection of the light. The result is that the strong Texas sun enters a narrow slot at the top of each vault and is evenly reflected from a curved screen across the entire arc of the polished concrete ceiling, ensuring a beautiful distribution of natural light that had never before been achieved.
Expansion
In 1989, director Ted Pillsbury, Brown's successor, announced plans to add two wings to the north and south ends of the building and chose architect Romaldo Giurgola to design them. A firestorm of protest erupted. Critics pointed out that founding director Brown's "Pre-Architectural Program" had specified that "the form of the building should be so complete in its beauty that additions would spoil that form," and that Kahn had achieved that goal extraordinarily well.
A group of prominent architects signed a letter acknowledging the need for additional space but arguing that the proposed addition would compromise the proportions of the original. They noted that when Kahn himself was questioned about the possibility of a future expansion, he said that it should "occur as a new building and be situated away from the present structure across the lawn". Esther Kahn, Louis Kahn's widow, published a letter voicing similar sentiments, noting that "there is room on the site for a separate building, which could be connected to the present museum." The project was cancelled a few months later.
Renzo Piano Pavilion
In 2006, the idea of an expansion surfaced once again at a dinner in Fort Worth attended by Timothy Potts, the museum's director at the time (Eric M. Lee has been the director since March 2009); Kay Fortson, president of the Kimbell Art Foundation and a key figure in the creation of the original building; Ben Fortson, a trustee; and Sue Ann Kahn, Louis Kahn's daughter and a vocal opponent of the original plan for expansion. The new proposal was exactly in line with Louis Kahn's own thoughts for expansion: a separate building. At that time, the new structure was to be sited on land to the back of the Kahn building.
In April 2007, the museum announced that Renzo Piano had been chosen to design the new building. Piano was an obvious choice because he had worked in Louis Kahn's office as a young man and had later established a reputation as one of the world's leading museum architects. Piano had been particularly active in Texas, designing the Menil Collection in Houston, a commission in Louis Kahn's studio at the time of Kahn's death, and the Nasher Sculpture Center in Dallas. He also designed the expansion for the Art Institute of Chicago and was co-designer of the Pompidou Centre in Paris.
The schematic designs for the new Kimbell building were made public in November 2008, and the plans were released in May 2010. The 85,000 square foot (7,900 m2) structure would complement the original building but not mimic it. Unlike the original, its lines would be rectilinear, not curvilinear. Like the original, however, it would have three bays with the middle bay stepped back from the other two. The new building expansion, named the Renzo Piano Pavilion, was officially inaugurated to the public on November 27, 2013.
The new building should also resolve a parking issue at the museum. Kahn was deeply troubled by the negative impact of the automobile on city life; he once spoke of "the destruction of the city by the motor car." Fundamentally opposed to the idea of orienting buildings to the automobile, Kahn placed the main parking lot in the back of the building, intending for visitors to walk around the building and enter through carefully planned landscaping. Most visitors, however, entered through the back door on the ground floor, missing the entry experience that Kahn had designed. The new building will solve the problem with an underground parking garage. After visitors ascend to the gallery level of the new building, they can exit it and walk across the lawn and the courtyard to enter the original building as Kahn had intended.
Recognition
In 1998, the American Institute of Architects gave the museum their prestigious Twenty-five Year Award, which is awarded to no more than one building per year.
Robert Campbell, architectural critic for the Boston Globe and winner of the Pulitzer Prize for Criticism, declared it to be "the greatest American building of the second half of the 20th century."
Robert McCarter, author of Louis I. Kahn, said that the Kimbell Art Museum "is rightly considered Kahn's greatest built work" and "has been the subject of more scholarly studies than all his other works combined."
Carter Wiseman, author of Louis I. Kahn: Beyond Time and Style, said, "With the Kimbell, Kahn had achieved something unique in the history of modern architecture, a building that engages an element of nature—sunlight—with unprecedented skill and combined it with a contemporary program in a structure that also called upon the most advanced engineering while invoking the monuments of the past."
Thos. S. Byrne, Ltd., the construction contractor, won the first Build America Award from the Associated General Contractors of America in 1972 for the "innovative construction techniques" used on the museum.
European collection highlights
Asian collection highlights
Management
The Kimbell Art Museum derives around 65% of its $12 million budget from its unrestricted endowment of more than $400 million. The endowment fell from $466 million to $398 million during the 2007–2008 financial crisis. The museum has no special funds for acquisitions. Museum membership is at 15,000. In 2019, the museum appointed Guillaume Kientz as the curator of European art; he had previously worked in the Louvre.
See also
Amon Carter Museum
Modern Art Museum of Fort Worth
References
External links
QTVR walk-through of the museum
Kimbell Art Museum – Google Arts & Culture
1972 establishments in Texas
Art museums and galleries established in 1972
Art museums and galleries in Texas
Asian art museums in the United States
Buildings and structures completed in 1972
Concrete shell structures
Former private collections in the United States
Louis Kahn buildings
Mesoamerican art museums in the United States
Modernist architecture in Texas
Museums in Fort Worth, Texas
Renzo Piano buildings
Thin-shell structures | Kimbell Art Museum | Technology | 4,893 |
17,887,653 | https://en.wikipedia.org/wiki/Orthogonal%20array | In mathematics, an orthogonal array (more specifically, a fixed-level orthogonal array) is a "table" (array) whose entries come from a fixed finite set of symbols (for example, {1,2,...,v}), arranged in such a way that there is an integer t so that for every selection of t columns of the table, all ordered t-tuples of the symbols, formed by taking the entries in each row restricted to these columns, appear the same number of times. The number t is called the strength of the orthogonal array. Here are two examples:
The example at left is that of an orthogonal array with symbol set {1,2} and strength 2. Notice that the four ordered pairs (2-tuples) formed by the rows restricted to the first and third columns, namely (1,1), (2,1), (1,2) and (2,2), are all the possible ordered pairs of the two element set and each appears exactly once. The second and third columns would give, (1,1), (2,1), (2,2) and (1,2); again, all possible ordered pairs each appearing once. The same statement would hold had the first and second columns been used. This is thus an orthogonal array of strength two.
In the example on the right, the rows restricted to the first three columns contain the 8 possible ordered triples consisting of 0's and 1's, each appearing once. The same holds for any other choice of three columns. Thus this is an orthogonal array of strength 3.
A mixed-level orthogonal array is one in which each column may have a different number of symbols. An example is given below.
Orthogonal arrays generalize, in a tabular form, the idea of mutually orthogonal Latin squares. These arrays have many connections to other combinatorial designs and have applications in the statistical design of experiments, coding theory, cryptography and various types of software testing.
Definition
For t ≤ k, an orthogonal array of type (N, k, v, t) – an OA(N, k, v, t) for short – is an N × k array whose entries are chosen from a set X with v points (a v-set) such that in every subset of t columns of the array, every t-tuple of points of X is repeated the same number of times. The number of repeats is usually denoted λ.
In many applications these parameters are given the following names:
N is the number of experimental runs,
k is the number of factors,
v is the number of levels,
t is the strength, and
λ is the index.
The definition of strength leads to the parameter relation
N = λvt.
An orthogonal array is simple if it does not contain any repeated rows. (Subarrays of t columns may have repeated rows, as in the OA(18, 7, 3, 2) example pictured in this section.)
An orthogonal array is linear if X is a finite field Fq of order q (q a prime power) and the rows of the array form a subspace of the vector space (Fq)k. The right-hand example in the introduction is linear over the field F2. Every linear orthogonal array is simple.
In a mixed-level orthogonal array, the symbols in the columns may be chosen from different sets having different numbers of points, as in the following example:
{| class="wikitable"
|-
| 0 || 0 || 0 || 0 || 0
|-
| 1 || 1 || 1 || 1 || 0
|-
| 0 || 0 || 1 || 1 || 1
|-
| 1 || 1 || 0 || 0 || 1
|-
| 0 || 1 || 0 || 1 || 2
|-
| 1 || 0 || 1 || 0 || 2
|-
| 0 || 1 || 1 || 0 || 3
|-
| 1 || 0 || 0 || 1 || 3
|}
This array has strength 2:
Any pair of the first four columns contains each of the ordered pairs (0, 0), (0, 1), (1, 0) and (1, 1) two times.
Columns 4 and 5 – or column 5 with any one of the other columns – contains each ordered pair (i, j) once, where i = 0 or 1 and j = 0, 1, 2, or 3.
It may thus be denoted may be denoted OA(8, 5, 2441, 2), as is discussed below. The expression 2441 indicates that four factors have 2 levels and one has 4 levels.
As in this example, there is no single ``index" or repetition number λ in a mixed-level orthogonal array of strength t: Each subarray of t columns can have a different λ.
Terminology and notation
The terms symmetric and asymmetric are sometimes used for fixed-level and mixed-level. Here symmetry refers to the property that all factors have the same number of levels, not to the "shape" of the array: a symmetric orthogonal array is almost never a symmetric matrix.
The notation OA(N, k, v, t) is sometimes contracted so that one may, for example, write simply OA(k, v), as long as the text makes clear the unstated parameter values. In the other direction, it may be expanded for mixed-level arrays. Here one would write OA(N, k, v1···vk, t), where column i has vi levels. This notation is usually shortened when values v are repeated, so that one writes OA(8, 5, 2441, 2) for the example at the end of the last section, rather than OA(8, 5, 2·2·2·2·4, 2). In similar fashion, one may shorten OA(N, k, v, t) to OA(N, vk, t) for fixed-level arrays.
This OA notation does not explicitly include the index λ, but λ can be recovered from the other parameters via the relation N = λvt. This is effective when the parameters all have specific numerical values, but less so when a class of orthogonal arrays is intended. For example, when indicating the class of arrays having strength t = 2 and index λ=1, the notation OA(N, k, v, 2) is insufficient to determine λ by itself. This is typically remedied by writing OA(v2, k, v, 2) instead. While notations that explicitly include the parameter λ do not have this problem, they cannot easily be extended to denote mixed-level arrays.
Some authors define an OA(N, k, v, t) as being k × N rather than N × k. In such cases the strength of the array is defined in terms of a subset of t rows rather than columns.
Except for the prefix OA, the notation OA(N, k, v, t) is the same as that introduced by Rao. While this notation is very common, it not universal. Hedayat, Sloane and Stufken recommend it as standard, but list eight alternatives found in the literature, and there are others.
Examples
An example of an OA(16, 5, 4, 2); a strength 2, 4-level design of index 1 with 16 runs:
An example of an OA(27, 5, 3, 2) (written as its transpose for ease of viewing):
This example has index λ = 3.
Trivial examples
An array consisting of all k-tuples of a v-set, arranged so that the k-tuples are rows, automatically ("trivially") has strength k, and so is an OA(vk, k, v, k).
Any OA(N, k, v, k) would be considered trivial since such arrays are easily constructed by simply listing all the k-tuples of the v-set λ times.
Mutually orthogonal Latin squares
An OA(n2, 3, n, 2) is equivalent to a Latin square of order n. For k ≤ n+1, an OA(n2, k, n, 2) is equivalent to a set of k − 2 mutually orthogonal Latin squares of order n. Such index one, strength 2 orthogonal arrays are also known as Hyper-Graeco-Latin square designs in the statistical literature.
Let A be a strength 2, index 1 orthogonal array on an n-set of elements, identified with the set of natural numbers {1,...,n}. Choose and fix, in order, two columns of A, called the indexing columns. Because the strength is 2 and the index is 1, all ordered pairs (i, j) with 1 ≤ i, j ≤ n appear exactly once in the rows of the indexing columns. Here i and j will in turn index the rows and columns of a n×n square. Take any other column of A and fill the (i, j) cell of this square with the entry that is in this column of A and in the row of A whose indexing columns contain (i, j). The resulting square is a Latin square of order n. For example, consider this OA(9, 4, 3, 2):
By choosing columns 3 and 4 (in that order) as the indexing columns, the first column produces the Latin square
while the second column produces the Latin square
These two squares, moreover, are mutually orthogonal. In general, the Latin squares produced in this way from an orthogonal array will be orthogonal Latin squares, so the k − 2 columns other than the indexing columns will produce a set of k − 2 mutually orthogonal Latin squares.
This construction is completely reversible and so strength 2, index 1 orthogonal arrays can be constructed from sets of mutually orthogonal Latin squares.
Latin squares, Latin cubes and Latin hypercubes
Orthogonal arrays provide a uniform way to describe these diverse objects which are of interest in the statistical design of experiments.
Latin squares
As mentioned in the previous section, a Latin square of order n can be thought of as an OA(n2, 3, n, 2). Actually, the orthogonal array can lead to six Latin squares since any ordered pair of distinct columns can be used as the indexing columns. However, these are all isotopic and are considered equivalent. For concreteness we shall always assume that the first two columns in their natural order are used as the indexing columns.
Latin cubes
In the statistics literature, a Latin cube is a three-dimensional n × n × n matrix consisting of n layers, each having n rows and n columns such that the n distinct elements which appear are repeated n2 times and arranged so that in each layer parallel to each of the three pairs of opposite faces of the cube all the n distinct elements appear and each is repeated exactly n times in that layer.
Note that with this definition a layer of a Latin cube need not be a Latin square. In fact, no row, column or file (the cells of a particular position in the different layers) need be a permutation of the n symbols.
A Latin cube of order n is equivalent to an OA(n3, 4 ,n, 2).
Two Latin cubes of order n are orthogonal if, among the n3 pairs of elements chosen from corresponding cells of the two cubes, each distinct ordered pair of the elements occurs exactly n times. A set of k − 3 mutually orthogonal Latin cubes of order n is equivalent to an OA(n3, k, n, 2). An example of a pair of mutually orthogonal Latin cubes of order three was given as the OA(27, 5, 3, 2) in the Examples section above.
Unlike the case with Latin squares, in which there are no constraints, the indexing columns of the orthogonal array representation of a Latin cube must be selected so as to form an OA(n3, 3, n, 3).
Latin hypercubes
An m-dimensional Latin hypercube of order n of the rth class is an n × n × ... ×n m-dimensional matrix having nr distinct elements, each repeated nm − r times, and such that each element occurs exactly n m − r − 1 times in each of its m sets of n parallel (m − 1)-dimensional linear subspaces (or "layers"). Two such Latin hypercubes of the same order n and class r with the property that, when one is superimposed on the other, every element of the one occurs exactly nm − 2r times with every element of the other, are said to be orthogonal.
A set of k − m mutually orthogonal m-dimensional Latin hypercubes of order n is equivalent to an OA(nm, k, n, 2), where the indexing columns form an OA(nm, m, n, m).
History
The concepts of Latin squares and mutually orthogonal Latin squares were generalized to Latin cubes and hypercubes, and orthogonal Latin cubes and hypercubes by . generalized these results to arrays of strength t. The present notion of orthogonal array as a generalization of these ideas, due to legendary scientist C. R. Rao, appears in , with his generalization to mixed-level arrays appearing in 1973.
Rao initially used the term "array" with no modifier, and defined it to mean simply a subset of all treatment combinations – a simple array. The possibility of non-simple arrays arose naturally when making treatment combinations the rows of a matrix. Hedayat, Sloane and Stufken credit K. Bush with the term "orthogonal array".
Other constructions
Hadamard matrices
There exists an OA(4λ, 4λ − 1, 2, 2) if and only if there exists a Hadamard matrix of order 4λ. To proceed in one direction, let H be a Hadamard matrix of order 4m in standardized form (first row and column entries are all +1). Delete the first row and take the transpose to obtain the desired orthogonal array. The following example illustrates this. (The reverse construction is similar.)
The order 8 standardized Hadamard matrix below (±1 entries indicated only by sign),
produces the OA(8, 7, 2, 2):
Using columns 1, 2 and 4 as indexing columns, the remaining columns produce four mutually orthogonal Latin cubes of order 2.
Codes
Let C ⊆ (Fq)n, be a linear code of dimension m with minimum distance d. Then C⊥ (the orthogonal complement of the vector subspace C) is a (linear) OA(qn-m, n, q, d − 1)
where λ = qn − m − d + 1.
Applications
Threshold schemes
Secret sharing (also called secret splitting) consists of methods for distributing a secret amongst a group of participants, each of whom is allocated a share of the secret. The secret can be reconstructed only when a sufficient number of shares, of possibly different types, are combined; individual shares are of no use on their own. A secret sharing scheme is perfect if every collection of participants that does not meet the criteria for obtaining the secret, has no additional knowledge of what the secret is than does an individual with no share.
In one type of secret sharing scheme there is one dealer and n players. The dealer gives shares of a secret to the players, but only when specific conditions are fulfilled will the players be able to reconstruct the secret. The dealer accomplishes this by giving each player a share in such a way that any group of t (for threshold) or more players can together reconstruct the secret but no group of fewer than t players can. Such a system is called a (t, n)-threshold scheme.
An OA(vt, n+1, v, t) may be used to construct a perfect (t, n)-threshold scheme.
Let A be the orthogonal array. The first n columns will be used to provide shares to the players, while the last column represents the secret to be shared. If the dealer wishes to share a secret S, only the rows of A whose last entry is S are used in the scheme. The dealer randomly selects one of these rows, and hands out to player i the entry in this row in column i as shares.
Factorial designs
A factorial experiment is a statistically structured experiment in which several factors (watering levels, antibiotics, fertilizers, etc.) are applied to each experimental unit at finitely many levels, which may be quantitative or qualitative. In a full factorial experiment all combinations of levels of the factors need to be tested. In a fractional factorial design only a subset of treatment combinations are used.
An orthogonal array can be used to design a fractional factorial experiment. The columns represent the various factors and the entries are the levels at which the factors are observed. An experimental run is a row of the orthogonal array, that is, a specific combination of factor levels. The strength of the array determines the resolution of the fractional design. When using one of these designs, the treatment units and trial order should be randomized as much as the design allows. For example, one recommendation is that an appropriately sized orthogonal array be randomly selected from those available, and that the run order then be randomized.
Mixed-level designs occur naturally in the statistical setting.
Quality control
Orthogonal arrays played a central role in the development of Taguchi methods by Genichi Taguchi, which took place during his visit to Indian Statistical Institute in the early 1950s. His methods were successfully applied and adopted by Japanese and Indian industries and subsequently were also embraced by US industry albeit with some reservations. Taguchi's catalog contains both fixed- and mixed-level arrays.
Testing
Orthogonal array testing is a black box testing technique which is a systematic, statistical way of software testing. It is used when the number of inputs to the system is relatively small, but too large to allow for exhaustive testing of every possible input to the systems. It is particularly effective in finding errors associated with faulty logic within computer software systems. Orthogonal arrays can be applied in user interface testing, system testing, regression testing and performance testing.
The permutations of factor levels comprising a single treatment are so chosen that their responses are uncorrelated and hence each treatment gives a unique piece of information. The net effect of organizing the experiment in such treatments is that the same piece of information is gathered in the minimum number of experiments.
See also
Combinatorial design
Latin hypercube sampling
Graeco-Latin squares
Notes
References
External links
Hyper-Graeco-Latin square designs
A SAS example using PROC FACTEX
Kuhfeld, Warren F. "Orthogonal Arrays". SAS Institute Inc. SAS provides a catalog of over 117,000 orthogonal arrays.
Combinatorics
Design of experiments
Latin squares
Combinatorial design | Orthogonal array | Mathematics | 3,947 |
44,054,999 | https://en.wikipedia.org/wiki/Eric%20Betzig | Robert Eric Betzig (born January 13, 1960) is an American physicist who works as a professor of physics and professor of molecular and cell biology at the University of California, Berkeley. He is also a senior fellow at the Janelia Farm Research Campus in Ashburn, Virginia.
Betzig has worked to develop the field of fluorescence microscopy and photoactivated localization microscopy. He was awarded the 2014 Nobel Prize in Chemistry for "the development of super-resolved fluorescence microscopy" along with Stefan Hell and fellow Cornell alumnus William E. Moerner.
Early life and education
Betzig was born in Ann Arbor, Michigan, in 1960, the son of Helen Betzig and engineer Robert Betzig. Aspiring to work in the aerospace industry, Betzig studied physics at the California Institute of Technology and graduated with a BS degree in 1983. He then went on to study at Cornell University where Michael Isaacson was his supervisor, and he also worked with Aaron Lewis. There he obtained an MS degree and a PhD degree in applied physics and engineering physics in 1985 and 1988, respectively. For his PhD he focused on developing high-resolution optical microscopes that could see past the theoretical limit of 0.2 micrometers.
Career
Bell Laboratories
After receiving his doctorate, Betzig was hired by AT&T Bell Laboratories in the Semiconductor Physics Research Department in 1989. That year Betzig's colleague, William E. Moerner, developed the first optical microscope that could see past the .2 micrometer limit, known as the Abbe limit, but it could only function at temperatures near absolute zero. Inspired by Moerner's research, Betzig became the first person to image individual fluorescent molecules at room temperature while determining their positions within less than .2 micrometers in 1993. For this he received the William O. Baker Award for Initiatives in Research (previously known as the National Academy of Sciences Award for Initiatives in Research). Betzig was also awarded the William L. McMillan Award in 1992.
Ann Arbor Machine Company
In 1994, Betzig became frustrated with the academic community and the uncertainty of the corporate structure of Bell Laboratories, prompting him to leave both. He spent some years as a stay-at-home dad before reentering the workforce in 1996, when he took up the position of vice president of research and development at Ann Arbor Machine Company, which was partially owned by the Betzig family. Here he developed Flexible Adaptive Servohydraulic Technology (FAST), but after spending millions of dollars on development he only sold two devices.
Return to academia
In 2002, Betzig returned to the field of microscopy and founded New Millennium Research in Okemos, Michigan. Inspired by Mike Davidson's work with fluorescent proteins, he developed photoactivated localization microscopy (PALM), a method of controlling fluorescent proteins that used pulses of light to create images of a higher resolution than were previously thought possible. In the living room of his old Bell Labs collaborator Harald Hess, Betzig and Hess developed the first optical microscope based on this technology. They built their first prototype in under two months, earning them widespread attention. In October of that year, the Howard Hughes Medical Institute's Janelia Farm Research Campus hired him, but his lab was still under construction at the time.
In early 2006, he formally joined Janelia as a group leader to work on developing super high-resolution fluorescence microscopy techniques. He used this technique to study the division of cells in human embryos. In 2010, he was offered the Max Delbruck Prize, but he declined it and Xiaowei Zhuang received the award. In 2014, Betzig was jointly awarded the Nobel Prize in Chemistry along with Stefan Hell and William E. Moerner.
On May 31, 2016 he was appointed an Academician of the Pontifical Academy of Sciences by Pope Francis.
In the summer of 2017, Betzig joined the Berkeley faculty with a joint appointment at Lawrence Berkeley National Laboratory.
Selected research papers
1993: Single molecules observed by near-field scanning optical microscopy, E Betzig, RJ Chichester – Science
1992: Near-field optics: microscopy, spectroscopy, and surface modification beyond the diffraction limit, E Betzig, JK Trautman – Science
2006: Imaging intracellular fluorescent proteins at nanometer resolution, E Betzig, GH Patterson, R Sougrat.
2014: Lattice light-sheet microscopy: imaging molecules to embryos at high spatiotemporal resolution, G Seydoux, US Tulu, DP Kiehart, E Betzig
Personal life
Betzig has married twice. His first wife was condensed matter physicist , with whom he has a two sons, Cayden and Ravi. His second wife is biophysicist Na Ji, with whom he has three children, Max, Mia and Zoe.
References
External links
Eric Betzig talk: Developing PALM Microscopy
Eric Betzig, SPIE Photonics West plenary presentation: Single molecules, cells, and super-resolution optics
Eric Betzig, Beyond the Nobel Prize – New approaches to microscopy
1960 births
Living people
California Institute of Technology alumni
Cornell University College of Engineering alumni
21st-century American physicists
American Nobel laureates
Nobel laureates in Chemistry
Scientists from Ann Arbor, Michigan
Howard Hughes Medical Investigators
Microscopists
University of California, Berkeley College of Letters and Science faculty | Eric Betzig | Chemistry | 1,095 |
2,745,805 | https://en.wikipedia.org/wiki/Buyer%27s%20remorse | Buyer's remorse is the sense of regret after having made a purchase. It is frequently associated with the purchase of an expensive item such as a vehicle or real estate.
Buyer's remorse is thought to stem from cognitive dissonance, specifically post-decision dissonance, that arises when a person must make a difficult decision, such as a heavily invested purchase between two similarly appealing alternatives. Factors that affect buyer's remorse may include the resources invested, the involvement of the purchaser, whether the purchase is compatible with the purchaser's goals, and feelings encountered post-purchase that include regret.
Causes
The remorse may be caused by various factors, such as: the person purchased a product now rather than waiting, the item was purchased in an ethically unsound way, the property was purchased on borrowed money, the purchased object was something that would not be acceptable to others, or the purchased object was something that the buyer later questions the value and need of.
In the phase before purchasing, a prospective buyer often feels positive emotions associated with a purchase (desire, a sense of heightened possibilities, and an anticipation of the enjoyment that will accompany using the product, for example); afterwards, having made the purchase, they are more fully able to experience the negative aspects: all the opportunity costs of the purchase, and a reduction in purchasing power.
Also, before the purchase, the buyer has a full array of options, including not purchasing; afterwards, their options have been reduced to:
continuing with the purchase, surrendering all alternatives
renouncing the purchase
Buyer's remorse can also be caused or increased by worrying that other people may later question the purchase or claim to know better alternatives.
The remorse associated with some extreme shopping activity may be, again, a sign of some deeper disquiet. However, normal "buyer's remorse" should not be confused with the complex emotional dynamics of "shopaholic" behavior, just as a binge on a special occasion should not be confused with a serious eating disorder such as bulimia.
Cognitive dissonance
The phenomenon of buyer's remorse has been generally associated with the psychological theory of cognitive dissonance, a state of psychological discomfort when at least two elements of cognition are in opposition, and which motivates the person to appease it by changing how they think about the situation. Buyer's remorse is an example of post-decision dissonance, where a person is stressed by a made decision and seeks to decrease their discomfort. The buyer may change their behavior, their feelings, their knowledge about the world (what they thought the purchased item would be like), or even their knowledge of themselves. The more resources such as money, time, and cognitive resources that are invested into making a purchase, the more likely the buyer will experience buyer's remorse or psychological discomfort.
Psychologists have focused on three main elements that are related to cognitive dissonance and buyer's remorse. They are: effort, responsibility, and commitment. Effort is the resources invested in a purchase (material, intellectual, psychological, and others) and effort is directly related to the importance of the purchase. Purchases that require high amounts of effort but do not bear high rewards are likely to lead to buyer's remorse. Responsibility refers to the fact that the purchase is done out of free will. Buyers that have no choice on the purchase will be less likely to feel dissonance because it was not of their own volition. Commitment refers to the continuing of an action. The purchase of an automobile has high commitment because the car must usually be driven for a long duration. Purchases with higher commitment will lead to more buyer's remorse. Low rewards matched with these three conditions will most likely result in buyer's remorse via cognitive dissonance. The buyer feels anxiety and psychological discomfort because their behavior (the purchase of the item) does not match their attitude (their expectation of the purchased item).
The following scale was developed by Sweeney, Hausknecht, and Soutar in a study to investigate three elements (one emotional, two cognitive) of buyer's remorse.
There may be a duality of attitudes that explain how a person may be satisfied with their purchase but have the intention to never repeat the purchase. For example, a husband who takes his wife to the most expensive restaurant in town for their anniversary only to find that the food and service does not meet his expectations might still be satisfied with his decision to go to the restaurant but have the intention to never return. In this extension of cognitive dissonance, the duality of satisfaction and intention are separate phenomena within buyer's remorse.
Involvement
In social psychology, "involvement" describes the effort, investment, and commitment in purchases. Involvement is often coupled with cognitive dissonance to explain buyer's remorse. In most cases, buyer's remorse resulting from a purchase that demands high involvement and results in cognitive dissonance is, all else (most notably nominal purchase price) being equal, harder to overcome than is buyer's remorse resulting from a purchase that demands low involvement and results in cognitive dissonance. This phenomenon is a result of the brain's instinctive (and rational) treatment of the transaction costs involved in acquiring a product as part of the purchase price of that product: The more involvement that a purchase requires or the purchaser puts in, the more dissonance or psychological discomfort the buyer will experience if dissatisfied with the purchase, just as if the purchaser had spent more "on paper" (i.e., paid a higher nominal price) for the product.
Studies investigating the link between cognitive dissonance and impulse buying have shown that impulse buyers experience less cognitive dissonance when they are disappointed with their purchase. The main explanation for this is that impulse buyers go into the purchase already without high expectations. Another possible explanation, at least among more sophisticated buyers, is that persons who are dissatisfied with a purchase that they made on impulse may blame that dissatisfaction at least in part on their own failure to thoroughly consider whether the product will satisfy their prior expectations even if it performs as advertised, thus blaming any discrepancy at least in part on themselves (via their own impulsivity) rather than on the purchased product (via any sort of difference between its promised and its actual attributes and/or performance).
Paradox of choice
The paradox of choice is a theory by American psychologist Barry Schwartz claiming that, after a certain threshold is reached, an increase in the number of choices will cause a significant amount of psychological distress. This distress, according to Professor Schwartz, can manifest itself in many ways. One way is through buyer's remorse. The theory states that buyer's remorse is created through increasing opportunity costs associated with increased choices. Opportunity costs associated with alternative choices compound and create strong feelings of dissonance and remorse.
As the number of choices increase, it is easier to imagine a different choice that may have been better than the one selected. The constant comparison to one's expectations induces regret, which reduces the satisfaction of any decision, even if it fills the individual's needs. When there are many alternatives to consider, it is easy to imagine the attractive features of rejected choices and there is a decrease in overall satisfaction.
Consider the number of choices in a simple supermarket. There are likely to be many different options for a single type of product. With so many to choose from, the customer might expect that one of the available options must be perfect for their needs and will have no drawbacks. This leads to expectations rarely being met, a significant psychological issue. In the example of a supermarket, buying the wrong product may not be a significant mistake. For more involved decisions, the consequences of a wrong decision are significant.
Reducing
Choice-supportive bias leads to an increased liking of one's choices, including purchases. This seems to contradict the concept of buyer's remorse. However, this choice enhancement can collapse when presented with even minor indication that the wrong choice was made. While initial positivity towards a decision is greater for more difficult decisions, this positivity also has greater vulnerability to evidence of an incorrect choice. This effect is larger when the purchaser is more involved in the decision. However, buyer's remorse can be reduced by post-purchase confirmation, though post-purchase communication may aggravate a buyer's discomfort if the purchase did not meet the buyer's predominant goals. Indeed, if the purchase meets an individual's goals there will be less post-purchase dissonance which means there will be less remorse and greater decision satisfaction.
Marketing implications
Buyer's remorse is a powerful experience for consumers. For years, marketers have been attempting to reduce buyer's remorse through many different methods. One specific technique employed by marketers is the inclusion of a coupon towards a future purchase at the point of sale. This has many benefits for both the consumer and retailer. First, the consumer is more likely to return to the store with the coupon, which will result in a higher percentage of repeat customers. Each successive time a purchase is made and is deemed satisfactory, buyer's remorse is less likely to be experienced. Customers can justify their purchases with product performance.
Another technique used is the money back guarantee, a guarantee from the retailer that the product will meet the customer's needs or the customer is entitled to a full refund. This technique is highly successful at lessening buyer's remorse because it immediately makes the decision a changeable one. The unchangeability of an "all-sales-final" purchase can lead to a larger amount of psychological discomfort at the point of the decision. This makes the stakes higher, and poor choices will cause significant buyer's remorse.
In addition, legislation exists in various parts of the world enforcing the right to a cooling-off period, during which contracts may be cancelled and goods returned for any reason, for a full refund.
See also
Analysis paralysis
Caveat emptor
Friendly fraud
Marketing
Overchoice
Post-purchase rationalization
Regret (decision theory)
Winner's curse
References
Consumer behaviour | Buyer's remorse | Biology | 2,048 |
54,936,329 | https://en.wikipedia.org/wiki/2017%20Barcelona%20attacks | On the afternoon of 17 August 2017, 22-year-old Younes Abouyaaqoub drove a van into pedestrians on La Rambla street in Barcelona, Catalonia, Spain killing 13 people and injuring at least 130 others, one of whom died 10 days later on 27 August. Abouyaaqoub fled the attack on foot, then killed another person in order to steal the victim's car to make his escape.
Nine hours after the Barcelona attack, five men thought to be members of the same terrorist cell drove into pedestrians in nearby Cambrils, killing one woman and injuring six others. All five of those attackers were shot and killed by police.
The night before the Barcelona attack, an explosion occurred in a house in the Catalan town of Alcanar, destroying the building and killing two members of the terrorist cell, including the 40-year-old imam thought to be the mastermind. The home had more than 120 gas canisters inside which police believe the cell was attempting to make into one large bomb (or three smaller bombs to be placed in three vans that they had rented) but which they accidentally detonated.
The Prime Minister of Spain, Mariano Rajoy, called the attack in Barcelona a jihadist attack. Amaq News Agency attributed indirect responsibility for the attack to the Islamic State. The attacks were the deadliest in Spain since the March 2004 Madrid train bombings and the deadliest in Barcelona since the 1987 Hipercor bombing. Younes Abouyaaqoub, the driver of the van in the Barcelona attack, was killed by police in Subirats, a town west of Barcelona on 21 August.
A 2022 statement by former Spanish police commissioner José Manuel Villarejo appeared to suggest in the Spanish High Court that the Spanish National Intelligence Service was aware of the attacks. Others have dismissed this statement as a conspiracy theory.
Attacks
Van attack on pedestrians in La Rambla
At 16:56 CEST (UTC+2) on 17 August 2017, Younes Abouyaaqoub drove a white Fiat Talento van onto the pavement of Barcelona's La Rambla, crashing into pedestrians for about between Plaça de Catalunya and Liceu before stopping on the Joan Miró mosaic. Witnesses said the vehicle zigzagged at high speed down the street, ramming pedestrians and cyclists.
The numerous impacts the van had received caused the airbag to inflate and the driver protection system to automatically shut down the electrical system of the van, causing it to halt. In the confusion, Abouyaaqoub was able to get away. He fled on foot and made his way to the university district before hijacking a car and stabbing the driver to death.
The van used in the La Rambla attack was rented in the neighbouring area of Santa Perpètua de Mogoda, along with a similar van, considered to be a getaway vehicle, and found by 19:00 in Vic. Younes Abouyaaqoub's credit card was used to pay for the van rental.
In a police press conference at 19:00 local time, a spokesperson confirmed the terrorist nature of the event.
Ramming of a police barricade on Avinguda Diagonal
About two hours after the attack on La Rambla, a white Ford Focus rammed a police barricade in Avinguda Diagonal, leaving an officer injured. The vehicle fled to a neighboring area, Sant Just Desvern, and the driver abandoned the car near the building known as Walden 7. The police found a man stabbed to death in the rear seat who, they believe, was murdered by the Ramblas driver who had escaped by hijacking the car.
Related events
Alcanar explosions
First explosion
On August 16, the day before the Barcelona attacks, an explosion destroyed a house in Alcanar. Abdelbaki Es Satty and another man, Youssef Aallaa, died in the Alcanar explosion.
Police initially thought it was an accidental gas explosion, but hours later believed the explosion was caused by stockpiled explosives accidentally going off. A Moroccan man was injured in the explosion and taken to the hospital. The explosive TATP and 120 canisters of butane and propane were found inside the house. Catalan bomb squads carried out a controlled explosion at the property where the gas canisters were stored. There was speculation that the terrorists intended to take trucks loaded with explosives and combustible gas to attack the Sagrada Família.
Police said they were working under the hypothesis that the terrorists shot in Cambrils were connected to the Barcelona attack and Alcanar explosions. Police chief Josep Lluís Trapero believed terrorists were in the process of manipulating the gas canisters when they exploded, after which they decided to continue their plans by conducting more rudimentary vehicle ramming attacks.
Second explosion
A second explosion occurred at the same location during excavation, possibly caused by a spark from a backhoe igniting a gas canister among the debris. At least nine people were injured, with one police officer in critical condition.
Cambrils attack
At about 21:30 on 17 August, Houssaine Abouyaaqoub, Omar Hichamy, Mohamed Hichamy, Moussa Oukabir, and Said Aalla were seen on a security camera at a local shop purchasing four knives and one axe.
At around 1:00 am on 18 August in Cambrils, the five men drove an Audi A3 automobile into a crowd of pedestrians before it rolled over at the intersection of Passeig Miramar, Passeig Marítim, and Rambla de Jaume I streets. The five individuals inside were wearing fake suicide vests and attacked bystanders with knives. They stabbed a 63-year-old Spanish woman to death and injured six other people in the attack, including a Cuban tourist and a police officer.
A police officer shot and killed four of the assailants, while a fifth died of his injuries hours later. Bystanders filmed one of the assailants being shot by police as he ran towards them. The men were linked to the Barcelona attack according to the police.
Subirats
On 21 August, police shot and killed Younes Abouyaaqoub in an area of vineyards near the train tracks, thanks to the call of a neighbor of the town warning that there was a stranger in the vicinity of the town who could be the terrorist from Las Ramblas.
Casualties
Aside from eight attackers, 16 people of nine nationalities were killed: 14 who were struck by the van in La Rambla, including one who died from injuries ten days after the attack, one stabbed in Barcelona by the La Rambla attacker when the attacker stole his car, and one who was struck by the car in Cambrils. Eleven of the victims were foreign nationals, ten of them tourists. More than 130 people from over 34 nations were injured, many critically.
Suspects
The imam Abdelbaki Es Satty died in the Alcanar gas explosion on 16 August, as did Youssef Aalla, brother of Said Aallaa. Five suspected members were shot dead by police on 18 August after the Cambrils attack: Moussa Oukabir, Omar Hychami, El Houssaine Abouyaaqoub, Said Aallaa and Mohamed Hychami. Younes Abouyaaqoub, the man believed to have been the van driver, was killed by police on 21 August. Four additional suspects were detained by police.
Younes Abouyaaqoub
Younes Abouyaaqoub, aged 22, was born on 1 January 1995 in M'rirt, Morocco, and had lived in Ripoll, Spain since he was four years old. He was the driver of the van that killed 13 people on La Rambla. He initially fled the scene of the attack on La Rambla through the Mercat de la Boqueria, then hijacked a car near the Zona Universitària station, stabbing the driver, Pau Pérez, to death. On 21 August, police caught up with him in Subirats, a village near Barcelona. He was wearing a fake suicide vest and shouted "Allahu Akbar" before police shot and killed him.
According to police sources, his identity documents were found in the second van, which was intercepted by Catalan police in Vic. His mother told the press that her son had been brainwashed by the imam Abdelbaki Es Satty.
Houssaine Abouyaaqoub
Houssaine Abouyaaqoub, aged 19, was the brother of Younes Abouyaaqoub and one of the attackers killed in Cambrils in the early hours of 18 August. He was a deliveryman for a kebab restaurant in Ripoll. Both Abouyaaqoub brothers were first cousins of Mohamed and Omar Hychami.
Moussa Oukabir
Moussa Oukabir was 17 at the time of the attack. He was shot and killed by police after the Cambrils attack.
The Fiat Talento van used in the La Rambla attack had been rented using the ID of Oukabir's brother who told police that Moussa Oukabir had stolen his ID.
Moussa Oukabir had been living legally in Spain since 2005. In 2014 and 2015, he played futsal (a form of indoor football) for the local Ripoll youth team. In 2015, when asked on the social media website Kiwi what he would do in his first day as king of the world, he responded, "Kill the infidels and only spare Muslims who follow the religion." Moussa's brother has told the judge that Moussa had increased his prayer frequency, chided him for not spending time with Muslims only, and had told him that Muslims have to do "jihad, which implies war".
Said Aallaa
Said Aallaa, 19, was born in Naour, Morocco. He had been living in Ribes de Freser, Spain, a village near Ripoll.
He was shot and killed by police after the Cambrils attack. La Vanguardia reported that Aallaa's social media contained photographs of firearms and that his religiosity was evidenced by his membership in Islamic study groups. Said had left a note in his room apologising for the harm he was about to cause.
Youssef Aallaa
Aalla's death in the explosion at Alcanar was later confirmed by police from DNA at the explosion site. Like all the other suspects, Youssef was born in Morocco. Youssef was a brother of Said Aallaa. Their father said Youssef attended the mosque.
Mohamed Hychami
Mohamed Hychami, aged 24 was born in Mrirt, Morocco. He was the cousin of Younes Abouyaaqoub, the driver of the van in the La Rambla attack. He was in the Audi used in the Cambrils attack and was shot and killed by police there. Hychami's mother told the media that Mohamed had said he was leaving on vacation and would return in a week.
Omar Hychami
Omar Hychami was 21, and was born in Mrirt, Morocco. He was the brother of fellow attacker Mohamed Hychami, and the cousin of the Rambla van driver Younes Abouyaaqoub. He worked for an agricultural construction sector.
Abdelbaki Es Satty
Abdelbaki Es Satty was a 44-year-old imam in Ripoll who was born in Morocco in 1973 and arrived in Spain in 2002. He was convicted of drug smuggling in 2014 and was to be deported from Spain, but Es Satty claimed deportation violated his human rights and he remained in Spain. A successful asylum application in November 2014 facilitated him moving freely in the 26 EU countries of the Schengen area. On 21 August, he was confirmed to have died in the accidental explosion in Alcanar on 16 August. As the imam thought to have been important in radicalising the other terrorists, he has been considered the "mastermind" of the planned attacks.
Es Satty had been renting a room in the house for four months. Es Satty, who had been employed as imam at the Ripoll mosque since 2015, quit "abruptly" in June. He had also stayed in Belgium for approximately three months in 2016, where he had been searching for work, including in Vilvoorde. Investigators believe the imam might be aligned with the Salafist movement, but this might not be unusual, as one in three Islamic prayer centers in Catalonia is.
He has been described as "unfailingly courteous and studiously discreet", betraying no radicalism in his appearance and interactions with those who did not know him, and training those in his terrorist cell to also lead double lives.
Arrests
Police arrested four men in connection with the attacks. Three of the men were arrested in Ripoll: the owner of the car used in the Cambrils attack, the brother of Moussa Oukabir, and a third man. In Alcanar, 20-year-old Mohamed Houli Chemlal, who survived the Alcanar explosion, was also arrested. Mohamed Houli Chemlal and Driss Oukabir have been charged with membership of a terror organisation and murder, with Mohamed also being charged with possession of explosives. Both were found to be guilty by the Audiencia Nacional in 2021, although being acquitted of terrorist homicide charges. By 24 August 2017, two of the suspects, Salh El Karib and Mohamed Aalla, had been released on certain conditions, including that they hand over their passports.
ISIL inspiration
The ISIL-linked Amaq News Agency claimed the attack was carried out in response to the call for targeting states in the anti-ISIL coalition, of which Spain is a member, contributing about 400 soldiers training Iraqi Armed Forces and Iraqi Police forces.
The Economist portrayed the motivation for this 2017 attack in Spain as rather 'less obvious', Spain being 'a minor player in the campaign against ISIS and other groups', though admittedly Spain contributed 150 soldiers to Operation Serval fighting Islamic militants in Mali, and in online propaganda linked to ISIL the Sagrada Família basilica was suggested as a possible target and ISIL was suggested to have boasted about recovering the Islamic lands of Al-Andalus.
Reactions
Domestic
Mossos d'Esquadra, the police force of Catalonia, launched Operation Cage to locate the perpetrators. All public events in Barcelona were cancelled, and both Carles Puigdemont, the President of the Generalitat of Catalonia, and Ada Colau, the Mayor of Barcelona, cancelled their holidays to return to the city and take part in crisis management. Likewise, Prime Minister of Spain Mariano Rajoy cancelled his holidays and travelled to Barcelona with the Spanish Deputy Prime Minister, Soraya Sáenz de Santamaría, and Juan Ignacio Zoido, the Spanish Minister of the Interior. Spain declared three days of mourning.
The day after the attacks, a minute's silence led by King Felipe VI, Catalan president Carles Puigdemont, and Barcelona mayor Ada Colau was observed at Plaça de Catalunya, which ended with applause and chants of "No tinc por" ("I am not afraid"). During the following days candles and flowers were left at the Joan Miró mosaic at La Rambla, in memory of the victims. The King and Queen also left a wreath in the name of the Crown.
On 26 August 2017, a large crowd marched down the Passeig de Gràcia in Barcelona in a protest against the terror attacks. The march was called by the city council and Catalan government. Some people booed the King of Spain and displayed signs blaming the Head of State for the Spanish arms sales. Other demonstrators displayed Spanish and Catalan flags.
On 10 September 2017, the security and emergency services were awarded the Medal of Honour of the Catalan Parliament (Medalla d'Honor del Parlament de Catalunya). With this medal the Catalan Parliament recognises the dedication, effort, and courage of the Mossos d'Esquadra, Guàrdia Urbana de Barcelona, Local Police of Cambrils, and the Emergency Services. The Major of the Catalan Police, Josep Lluís Trapero Álvarez, collected the award and made a speech mourning the victims.
International
Many world leaders reacted to the events, condemning the attacks and expressing shock and solidarity with Spain, as well as offering support.
News sources asked whether the attack would affect the vote in the 2017 Catalan independence referendum.
Aftermath
Several days after the attack, islamophobic incidents occurred in Sevilla, Logroño and Granada.
The Interior Ministry and the Cuerpo Nacional de Policía recommended the installation of bollards, but the Generalitat chose to increase the presence of police officers instead.
Threat to Spain and Gibraltar
On the night of 23 August 2017, the Islamic State of Iraq and the Levant uploaded a video praising the perpetrators of the attack and warning of more violence if the military actions against them in Syria and Iraq did not end, and threatening Gibraltar with an atomic bomb. The language used was Spanish. They also threatened to recreate al-Andalus as a caliphate and take revenge for the Muslims who died at the hands of the Spanish Inquisition.
The first author of the video was identified as Abu Lais Al Qurtubí (el Cordobés in Spanish) or Abu Laiz al Qurtubi, named Muhammad Yasin Ahram Pérez, Tomasa Pérez's oldest son, who converted to Islam after her marriage to the Moroccan Abdelah Ahram. He said "If you can’t make the hegira (journey) to the Islamic State, carry out jihad where you are; jihad doesn’t have borders. Allah willing, Al Andalus will become again what it was, part of the caliphate. Spanish Christians, don’t forget the Muslim blood spilt during the Spanish inquisition. We will take revenge for your massacre, the one you are carrying out now against Islamic State". The hooded author has been identified as Abu Salman Al-Andalus or Abu Salman al-Andalusí (el andaluz). Pérez stated: "We hope that Allah accepts the sacrifice of our brothers in Barcelona. Our war with you will continue until the world ends."
The threatening video to Gibraltar was published by Abu Albara Bin Malik and spread by Al Wafa. The threatening video was produced in Wilayat Jair, Deir Ezzor, Syria. According to Sahrawi journalist Bachir Mohamed Lahsen, terrorists only publish threats for propagandistic use and they should not be taken seriously.
As a response, Twitter users created an Internet meme based on the message by Pérez.
Verdict
In May 2021, the National Audience court sentenced three members of the jihadist organization which committed the attacks in 2017. Two of the accused, Mohamed Houli Chemlal and Driss Oukabir, were sentenced to an upwards of 53 and 46 years in prison respectively, the third, Said Ben Iazza, to 8 years in prison for the crime of collaboration. They were also banned from approaching the town of Alcanar, where they prepared the attacks.
2022 statements by José Manuel Villarejo
In January 2022, former police commissioner José Manuel Villarejo, appeared to suggest that the Spanish authorities knew of Younes Abouyaaquob's plans ahead of time and used it to hamstring the Catalonian Independence movement, prompting Catalan president Pere Aragonès to call for an investigation. Many have dismissed the allegations as a conspiracy theory.
In popular media
In 2020, Catalan journalist Anna Teixidor published a book about the attacks titled Sense por de morir: Els silencis del 17-A. The book was published in Spanish and Catalan.
A three-part docuseries 800 Meters about the attacks and the police investigation was released on Netflix on 25 March 2022. The series was directed by Elías León.
See also
2017 in Spain
List of terrorist incidents in August 2017
Timeline of Barcelona
1987 Hipercor bombing
2008 Barcelona terror plot
Notes
References
External links
2010s in Barcelona
2017 in Catalonia
2017 murders in Spain
2017 road incidents in Europe
August 2017 crimes in Europe
August 2017 events in Spain
Baix Camp
Crime in Barcelona
Terrorist incidents involving knife attacks in Europe
Improvised explosive device bombings in 2017
Improvised explosive device bombings in Spain
Islamic terrorist incidents in 2017
La Rambla, Barcelona
Mass murder in 2017
21st-century mass murder in Spain
Road incidents in Spain
Knife attacks in Spain
2017 disasters in Spain
Terrorist incidents in Europe in 2017
Terrorist incidents in Spain in the 2010s
Terrorist incidents involving vehicular attacks in Europe
ISIL terrorist incidents in Spain
Vehicular rampage in Europe
Gas explosions | 2017 Barcelona attacks | Chemistry | 4,268 |
29,385,825 | https://en.wikipedia.org/wiki/Oslo%20Astrological%20Clock | The Oslo Astrological Clock is located at Karl Johans gate 3 in Oslo, the capital city of Norway. The astrological clock was donated by Christian Ringnes and features artwork designed by artists Elena Engelsen and Per Ung. Ringnes explained during his unveiling speech, "we aim to actively contribute in making Oslo a beautiful and pleasant city."
Clock Structure
The clock is in diameter; with the clock face at . Astrological signs are cast in bronze and are painted. The rings are made of copper and are also painted. The tiles in the dial are coated with 22-carat gold leaf and the total weight of the clock is approx. .
Artwork
It was designed by artists Elena Engelsen and Per Ung, who spent over a year collaborating on the project. Engelsen created the exotic animal characters star, while Ung designed the human characters in the zodiac. This was the couple’s second joint artwork venture.
Unveiling
The unveiling of the clock took place on October 20, 2010 at a ceremony hosted by Mayor Fabian Stang at Karl Johans gate 3 in central Oslo. He has been quoted as saying, “We are incredibly proud that Oslo now has an astrological clock, especially as it was designed by Elena Engelsen and Per Ung, two of Norway’s most renowned artists. The clock is clearly visible and will set a solid mark on the cityscape."
As a representation of the 12 Zodiac signs, 12 of the foremost astrologers in Norway were among the invited guests at the ceremony.
See also
Prague Astronomical Clock
References
2010 works
Individual clocks
Time in Norway
Astrology | Oslo Astrological Clock | Astronomy | 334 |
38,814,216 | https://en.wikipedia.org/wiki/SAKO%20%28programming%20language%29 | SAKO (PL: System Automatycznego KOdowania - EN: An Automatic Coding System) is a Polish language-based programming language written in years 1959-1960 by a team from ZAM division of Polish Academy of Sciences. Originally developed for the computers XYZ and ZAM-2,
in later years also for ZAM-21, ZAM-41 and Mińsk-22.
General features of the SAKO language:
commands similar to sentences used in natural language
shortened the time of learning the principles of programming
easy to use, reduced coding time
transparent program code, low probability of making a mistake
It had a static address allocation. It was possible to insert code in SAS macro assembler. The compilation proceeded in two stages:
From SAKO to simplified SAS macro assembler (SAS-W).
From SAS-W to machine language.
The most characteristic feature of SAKO are Polish commands, e.g. CZYTAJ, SKOCZ DO. Designed primarily for programming numerical calculations.
"Hello, world" example
TEKST:
HELLO, WORLD
LINIA
STOP NASTEPNY
KONIEC
References
Prace Zakładu Aparatów Matematycznych PAN, "System Automatycznego Kodowania SAKO. Cz. 1, Opis języka", PAN – Warszawa 1961
Leon Łukaszewicz, Antoni Mazurkiewicz "System automatycznego kodowania SAKO" Zakład Narodowy im. Ossolińskich, Polish Academy of Sciences Publishing House, Wrocław-Warszawa-Kraków 1966
Antoni Mazurkiewicz "Arithmetic Formulae and the Use of Subroutines in SAKO" Annual Review in Automatic Programming, Vol. 2
Leon Łukaszewicz "SAKO — An Automatic Coding System" Annual Review in Automatic Programming, Vol. 2
Władysław Turski "Some Results of Research on Automatic Programming in Eastern Europe" Advances in Computers, Vol. 5
"Algorytmy" Vol. 1 No. 1, Institute of Mathematical Machines, Polish Academy of Sciences, Warsaw
CIA-RDP80T00246A011500230001-8
Citations
Non-English-based programming languages
Science and technology in Poland | SAKO (programming language) | Technology | 477 |
75,419,268 | https://en.wikipedia.org/wiki/Second-order%20Jahn-Teller%20distortion%20in%20main-group%20element%20compounds | Second-order Jahn-Teller distortion (commonly known as pseudo Jahn-Teller distortion) is a singular, general, and powerful approach rigorously based in first-principle vibronic coupling interactions. It enables prediction and explication of molecular geometries that are not necessarily satisfactorily or even correctly explained by semi-empirical theories such as Walsh diagrams, atomic state hybridization, valence shell electron pair repulsion (VSEPR), softness-hardness-based models, aromaticity and antiaromaticity, hyperconjugation, etc.
The application to main-group element compounds utilizes principles of group theory and symmetry. A molecule will distort in order to maximize symmetry-allowed interactions between the highest occupied molecular orbitals and lowest unoccupied molecular orbitals, and thereby stabilize the HOMOs and destabilize the LUMOs (resulting in the overall stabilization of the molecule). The extent of second-order Jahn-Teller distortion is inversely proportional to the energy difference between orbitals. Direct products are used to determine the allowedness of a given interaction: the interaction is allowed if the product of the symmetry of the first molecular orbital, the symmetry of the vibration, and the symmetry of the second molecular orbital contains the totally symmetric irreducible representation of the molecule’s point group. For heavier main-group compounds, molecular orbital interactions are larger due to the decreasing bond strength resulting in a smaller energy difference between the interacting orbitals.
Geometries of heavier group 13 and 14 analogues of multiply bound species
Group 14 analogues of alkenes and alkynes have previously been prepared. Moving down the group, the compounds experience increasing geometric distortion, becoming increasingly trans-bent from the original linear geometry and displaying increasingly limited shortening of the multiple bond. These patterns are also observed in group 13 multiply-bonded compounds. These geometry trends are rationalized below.
Semiempirical approaches
Hybridization
This trend can be rationalized with hybridization – moving down a group, the gap between the ns and np orbitals widens and there is an increasing mismatch between valence orbital sizes. The mismatch leads to lower hybridization – that is, increased nonbonding character on each of the heavier group 13 or 14 atoms involved in multiple bonding, which manifests as increased deviation from the typically expected linear and planar geometries. This rationalization is not especially cohesive with the typical approach to multiple bonds in organic chemistry – that is, a single σ-bond and one or two π-bonds.
Double donor-acceptor bonding
This rationalization is simple and preserves the double-bond nature of the group 13 or 14 atom interaction. The multiple bond is not exactly a typical σ+π interaction; rather the two halves of the alkyne analogue are treated as singlet bent monomers and the multiple bond is treated as an aggregation between them, with the spxpy-hybridized filled orbital on one group 13 or 14 atom donating to the vacant pz of the other.
Valence bond resonating lone pair
This rationalization is consistent with valence bond theory and suggests a weakened E-E multiple bond. The electron pair is described as resonating between the two group 13 or 14 atoms, and the resonance is favored by occupation of the empty (but not mandatorily vacant) orbital.
Second-order Jahn-Teller distortion approach
Second-order Jahn-Teller distortion provides a rigorous and first-principles approach to the distortion problem. The interactions between the HOMOs and LUMOs to afford a new set of molecular orbitals is an example of second-order Jahn-Teller distortion.
Cis- and trans-pyramidalization of alkene analogues
The trans-pyramidalization distortion is taken as an example. The frontier molecular orbitals of the undistorted alkene possessing D2h symmetry have symmetries ag (HOMO-1), b2u (HOMO), b1g (LUMO), and b3u (LUMO+1). The symmetry of the trans-pyramidalization vibration is b1g. A triple product of ground state, vibrational mode, and excited state that can be taken is b2u (HOMO) x b1g (trans-pyramidalizing vibrational mode) x b3u (LUMO+1) = a1g. Since a1g is the totally symmetric representation, the b2u and b3u molecular orbitals participate in an allowed interaction through the trans-pyramidalizing vibrational mode. The molecule will distort in a trans-pyramidal fashion (into C2h symmetry) in order to enable this interaction, which produces a more stabilized HOMO and more destabilized LUMO.
This treatment can be repeated for all other combinations of HOMO-1, HOMO and LUMO, LUMO+1. Notably, it is found that the HOMO and LUMO are symmetry-disallowed to mix.
Cis- and trans-bending of alkyne analogues
This distortion can be treated in the same fashion, using the triple product to determine whether or not the distortion from the undistorted linear D∞h symmetry will produce a symmetry-allowed interaction (and therefore, whether or not the distortion will occur).
Pyramidalization and inversion of trivalent group 15 compounds and group 14 radicals
The pyramidalization and energies of inversion of group 15 :MR3 (M = N, P, As, Sb, Bi) and group 14 •MR3 molecules can also be predicted and rationalized using a second-order Jahn-Teller distortion treatment. The “parent” planar molecule possessing D3h symmetry has frontier orbitals of a2” (HOMO) and a1’ (LUMO) symmetries. The pyramidalizing vibration mode has symmetry a2”. The triple product yields the totally symmetric representation a1’, indicating that the molecule will indeed pyramidalize into C3v symmetry.
The energies of inversion can also be predicted and compared. Due to lower energy overlap between the 3p and 1s orbitals in PH3 (versus between 2p and 1s in NH3), the HOMO-LUMO energy gap in PH3 will be smaller than that of NH3. This allows for a stronger interaction between the HOMO and LUMO in second-order Jahn-Teller fashion. The distortion stabilizes the HOMO and destabilizes the LUMO, resulting in a larger barrier to inversion in PH3.
Tetrahedral geometry of tetravalent second- and third-row main-group-element hydrides
Tetravalent main-group-element hydrides of form APH4 (AP = B−, C, N+, O2+, Al−, Si, P+, and S2+, where AP is a tetravalent atom or ion) are known to distort from the square planar to tetrahedral geometry. For all APH4 systems in D4h symmetry, the ground state is a1g. The exact electronic configuration, however, is dependent on the electronegativity of the main group element. The distortion to tetrahedral geometry has b2u symmetry. For these APH4 systems, the a2u→b1g* and eu→eg* one-electron charge-transfer transitions are most active in the b2u mode.
References
Condensed matter physics
Solid-state chemistry | Second-order Jahn-Teller distortion in main-group element compounds | Physics,Chemistry,Materials_science,Engineering | 1,522 |
74,204,240 | https://en.wikipedia.org/wiki/Reactances%20of%20synchronous%20machines | The reactances of synchronous machines comprise a set of characteristic constants used in the theory of synchronous machines. Technically, these constants are specified in units of the electrical reactance (ohms), although they are typically expressed in the per-unit system and thus dimensionless. Since for practically all (except for the tiniest) machines the resistance of the coils is negligibly small in comparison to the reactance, the latter can be used instead of (complex) electrical impedance, simplifying the calculations.
Two reactions theory
The air gap of the machines with a salient pole rotor is quite different along the pole axis (so called direct axis) and in the orthogonal direction (so called quadrature axis). Andre Blondel in 1899 proposed in his paper "Empirical Theory of Synchronous Generators" the two reactions theory that divided the armature magnetomotive force (MMF) into two components: the direct axis component and the quadrature axis component. The direct axis component is aligned with the magnetic axis of the rotor, while the quadrature (or transverse) axis component is perpendicular to the direct axis. The relative strengths of these two components depend on the design of the machine and the operating conditions. Since the equations naturally split into direct and quadrature components, many reactances come in pairs, one for the direct axis (with the index d), one for the quadrature axis (with the index q). This is often using direct-quadrature-zero transformation.
In machines with a cylindrical rotor the air gap is uniform, the reactances along the d and q axes are equal, and d/q indices are frequently dropped.
States of the generator
The flux linkages of the generator vary with its state. Usually applied for transients after a short circuit current. Three states are considered:
the steady-state is the normal operating condition with the armature magnetic flux going through the rotor;
the sub-transient state () is the one the generator enters immediately after the fault (short circuit). In this state the armature flux is pushed completely out of the rotor. The state is very brief, as the current in the damper winding quickly decays allowing the armature flux to enter the rotor poles only. The generator goes into transient state;
in the transient state () the flux is still out of the field winding of the rotor. The transient state decays to steady-state in few cycles.
The sub-transient () and transient () states are cheracterized by significantly smaller reactances.
Leakage reactances
The nature of magnetic flux makes it inevitable that part of the flux deviates from the intended "useful" path. In most designs, the productive flux links the rotor and stator; the flux that links just the stator (or the rotor) to itself is useless for energy conversion and thus is considered to be wasted leakage flux (stray flux). The corresponding inductance is called leakage inductance. Due to the presence of air gap, the role of the leakage flux is more important in a synchronous machine in comparison to a transformer.
Synchronous reactances
The synchronous reactances are exhibited by the armature in the steady-state operation of the machine. The three-phase system is viewed as a superposition of two: the direct one, where the maximum of the phase current is reached when the pole is oriented towards the winding and the quadrature one, that is 90° offset.
The per-phase reactance can be determined in a mental experiment where the rotor poles are perfectly aligned with a specific angle of the phase field in the armature (0° for , 90° for the ). In this case, the reactance will be related with the flux linkage and the phase current as , where is the circular frequency. The conditions for this mental experiment are hard to recreate in practice, but:
when the armature is short-circuited, the flowing current is practically all reactive (as the coil resistance is negligible), thus under the short-circuit condition the poles of the rotor are aligned with the armature magnetomotive force;
when the armature is left open-circuit, the voltage on the terminals is also aligned with the same phase and is equal to . If saturation is neglected, the flux linkage is the same.
Therefore, the direct synchronous reactance can be determined as a ratio of the voltage in open condition to short-circuit current : . These current and voltage values can be obtained from the open-circuit saturation curve and the synchronous impedance curve.
The synchronous reactance is a sum of the leakage reactance and the reactance of the armature itself (): .
Sequence network reactances
When analyzing unbalanced three-phase systems it is common to describe a system of symmetrical components. This models the machine by three components, each with a positive sequence reactance , a negative sequence reactance and a
zero sequence reactance .
List of reactances
Das identifies the following reactances:
leakage reactance . Potier reactance is an estimate of the armature leakage reactance;
synchronous reactance (also );
transient reactance ;
subtransient reactance ;
quadrature axis reactances , , , counterparts to , , ;
negative sequence reactance ;
zero sequence reactance .
References
Sources
Electrical engineering
Electrical generators | Reactances of synchronous machines | Physics,Technology,Engineering | 1,137 |
78,536,622 | https://en.wikipedia.org/wiki/Washington%20Hood | Washington Hood (February 2, 1808 – July 17, 1840) was an American surveyor with the U.S. Army Corps of Topographical Engineers. A 1827 West Point graduate, he worked with fellow officer Robert E. Lee to determine the boundary line between the state of Ohio and Michigan Territory in 1835.
Biography
Hood was born on February 2, 1808, in Philadelphia. He was the eldest of twelve children born to Eliza Forebaugh and John McClellan Hood, an Irish immigrant and wholesale grocery and wine merchant. John Hood constructed Hood Mansion, a country estate in Limerick, Pennsylvania, in 1834. The site of a family mausoleum where Hood and his parents are interred, the estate has been abandoned since 2008.
A 1827 graduate of the United States Military Academy, Hood worked as a surveyor and topographical engineer. He is best known for working with fellow officer Robert E. Lee to map the border between the state of Ohio and Michigan Territory in 1835, when he earned a promotion to first lieutenant. He resigned in 1836 to work as a private-sector civil engineer in Cuba before rejoining the Army Corps of Topographical Engineers as a captain. He mapped the Oregon Territory in 1838 but reproduced errors found in earlier maps.
In 1839, President Martin Van Buren dispatched an expedition led by Hood to survey parts of Indian Territory bordering the states of Missouri and Arkansas (present-day northeastern Oklahoma). Hood contracted a disease, probably yellow fever, while on the expedition. He died in Bedford Springs, Pennsylvania, on July 17, 1840, at the age of 32.
Hood's journals, letters, drawings, maps, architectural plans, and other papers are held in the collections of the Winterthur Library and the Beinecke Rare Book and Manuscript Library at Yale University.
References
External links
Washington Hood drawings in the collection of the Winterthur Library
1808 births
1840 deaths
19th-century American explorers
American surveyors
American topographers
Engineers from Philadelphia
Military personnel from Philadelphia
United States Army Corps of Topographical Engineers
United States Army officers
United States Military Academy alumni | Washington Hood | Engineering | 410 |
34,112,437 | https://en.wikipedia.org/wiki/4-AcO-MET | 4-acetoxy-MET (4-acetoxy-N-methyl-N-ethyltryptamine), also known as 4-AcO-MET or metacetin, is a hallucinogenic tryptamine. It is the acetate ester of 4-HO-MET, and a homologue of 4-AcO-DMT. It is a novel compound with very little history of human use. It is sometimes sold as a research chemical by online retailers.
Due to its similarity to the psilocin prodrug 4-AcO-DMT, which is deacetylated to form psilocin in vivo, it is expected that 4-AcO-MET is also quickly hydrolyzed into 4-HO-MET by serum esterases, but human studies concerning the metabolic fate of this drug are lacking.
Legality
In the United States, 4-Acetoxy-MET is not scheduled. It may be considered an analogue of psilocin, a Schedule I drug under the Controlled Substances Act. As such, the sale for human consumption or the use for illicit non-medical purposes could be considered a crime under the Federal Analogue Act.
In Switzerland, 4-Acetoxy-MET is a controlled substance under Verzeichnis E.
In the United Kingdom, 4-Acetoxy-MET is a Class A drug in the UK because it is an ester of the drug 4-HO-MET, which is a Class A drug under the tryptamine catch-all clause.
References
Psychedelic tryptamines
Designer drugs
Acetate esters
pl:4-Acetoksy-N,N-dietylotryptamina
sv:4-acetoxy-DET | 4-AcO-MET | Chemistry | 359 |
18,178,856 | https://en.wikipedia.org/wiki/Ranimustine | Ranimustine (INN, marketed under the tradename Cymerin; also known as MCNU) is a nitrosourea alkylating agent approved in Japan for the treatment of chronic myelogenous leukemia and polycythemia vera.
It has never been filed for FDA evaluation in the United States, where it is not marketed.
Synthesis
Ranimustine is made by reacting the primary amine of a pyranose sugar (2) with o-nitrophenyl N-(2-chloroethyl)-N-nitrosocarbamate (1) to form the nitrosourea group.
References
External links
Cymerin サイメリン (PDF) Mitsubishi Tanabe Pharma. October 2007.
Alkylating antineoplastic agents
Nitrosamines
Nitrosoureas
Ureas
Chloroethyl compounds | Ranimustine | Chemistry | 186 |
72,095,612 | https://en.wikipedia.org/wiki/Death%20of%20Cindy%20James | Cynthia Elizabeth James (née Hack; June 12, 1944 June 2—June 8, 1989) was a Canadian nurse who disappeared from Richmond, British Columbia, on May 25, 1989. She was found deceased approximately two weeks later in the yard of an abandoned house, hogtied and with a nylon stocking wrapped around her throat. An autopsy indicated that she had died of an overdose of morphine, diazepam, and flurazepam. James's death was notable as she had made numerous reports to authorities dating back to 1982, alleging that she had been a victim of various acts of stalking, harassment, vandalism, home invasions, and physical attacks perpetrated by an unknown assailant.
James's death and prior allegations were subject of great dispute, as the Royal Canadian Mounted Police (RCMP) were unable to find any evidence suggesting she had been an actual victim of a stalker. Furthermore, she had a documented medical history of depression and suicidal thoughts, leading authorities to suspect that she may have been fabricating the various attacks and other incidents herself, orchestrating them to appear as legitimate, culminating in an eventual staged suicide. Over the nearly seven-year period James reported the incidents, the RCMP allocated an estimated $1–1.5 million in funds to investigate her claims, marking one of the longest and most costly police investigations in British Columbia history.
Despite skepticism from authorities, James's family members publicly insisted that she had in fact been preyed upon, and eventually murdered. A coroner's inquest was held in the spring of 1990 which included testimony from more than 80 witnesses. The inquest ultimately resulted in the conclusion that James had died of an "unknown event."
James's death received international media coverage and was the subject of an Unsolved Mysteries segment in 1991. Furthermore, two different books were published in 1991 chronicling her life and death: Who Killed Cindy James by British journalist Ian Mulgrew, and The Deaths of Cindy James by Neal Hall, a Canadian crime reporter who had extensively covered James's case for the Vancouver Sun. In 2021, a podcast on James, Death by Unknown Event, narrated by Pamela Adlon, was released by Audible.
Background
Cynthia Elizabeth Hack was born in Oliver, British Columbia, Canada, on June 12, 1944, to Matilda "Tilley", a homemaker, and Otto Hack, an English teacher and former colonel in the Royal Canadian Air Force. Both of her parents were of Russian descent. She was one of six children, with three older brothers and two younger sisters. Cindy spent part of her teenage years in Ottawa due to her father's involvement in the air force, and attended high school there. She recorded in her private diaries that her childhood had been marked by her father's strictness, which included corporal punishment.
In adulthood, Cindy pursued a nursing career in Vancouver, and enrolled in nursing school in 1962. During this period, her father had reenlisted with the air force and relocated the family to France, where she visited them during holidays. During this time, in letters to her family, Cindy occasionally referred to an unnamed intern she had met during her studies. She claimed that the two had at one point been engaged, and that, after finding he had terminal cancer, the man committed suicide while the couple were on a skiing trip. None of her parents or siblings, however, ever met the man, and Cindy did not name him.
In the summer of 1965, Cindy met Roy Makepeace, a South African psychiatrist 18 years her senior. The two married on December 9, 1966, the same year she graduated from nursing school with a BSN. Cindy's parents were skeptical of the marriage due to the couple's age difference, and her father felt that Makepeace had taken advantage of Cindy's "naiveté and gullibility." Her family testified that the couple's marriage was troubled and that the two were at times emotionally distant. Though Cindy later made accusations of spousal abuse, Makepeace asserted he "only slapped her twice" over the course of their marriage. Though licensed as a psychiatrist in his home country of South Africa, Makepeace failed twice to obtain his medical license in Canada and instead accepted a job as an Assistant Professor in the Faculty of Medicine at the University of British Columbia.
Cindy worked as a pediatric nurse at Vancouver General Hospital—where her husband had also one time been employed—from 1966 to 1975. In 1973, Makepeace took a job as director of health services at BC Hydro. In April 1975, Cindy was hired as a team coordinater at Vancouver's Blenheim House, a facility caring for children with behavioral disorders. She worked at Blenheim House for approximately 12 years, and was noted by her colleagues for her competence and professionalism.
Allegations of harassment
Spanning a nearly seven year-period between 1982 and 1989, Cindy reported approximately 90 incidents of criminal activity to the Royal Canadian Mounted Police (RCMP). Her claims included alleged acts of stalking, vandalism, arson, harassment, intimidation, home invasions, and physical assaults perpetrated by an unknown person or persons.
1982
The incidents began in September 1982, four months after Cindy separated from Makepeace. In late September, she told friends and family members she suspected that a prowler had been lurking around her home. A series of obscene phone calls soon followed, the first of which was received on October 7, 1982. Cindy's mother relayed that, though she was reluctant to discuss her experiences, she indicated that the phone calls consisted of an individual speaking in different voices, and that, on some occasions, there was mere silence on the other end of the line. Cindy described some of the calls as sexual and violent in nature.
On October 11, Cindy received a phone call consisting of loud breathing noises, and the following day, received another call in a menacing whisper, which said: "I'll get you one night, Cindy." She reported the obscene calls to the RCMP, who visited her home and suggested she keep a list of each call and its contents, as well as get an unlisted number. Shortly after the officer left, Cindy received a call in which an apparent male voice said: "You fucking bitch. I'll get you." The next day, on the afternoon of October 13, the caller threatened her: "So you think calling the police will keep you safe? You wait. I've got my zipper open, I'm talking to my throbbing..." before she abruptly ended the call.
Two days later, Cindy reported to the RCMP that she had heard someone lurking outside her home and awoken in the morning to find her porch lights smashed. On October 15, she reported to police that someone had thrown a rock through one of her windows and entered her house, though nothing else had been disturbed. Four days later, on October 19, she reported that someone had entered her home and slashed a pillow on her bed.
Patrick McBride, a constable with the Vancouver RCMP, suspected the culprit was her estranged husband, Makepeace, who denied involvement. Cindy herself made conflicting statements regarding Makepeace, telling authorities she did not think he was capable of tormenting her, but also divulged to friends and coworkers that he was violently abusive during their marriage. On October 20, two tenants who rented the basement of Cindy's home reported to police that they heard strange noises upstairs on the main floor after she had left for work. A next-door neighbor informed McBride that she had witnessed a man standing outside the house on at least three different occasions, and one time entering the gate of the front yard. The neighbor insisted the man did not resemble Makepeace.
Cindy concurrently began a relationship with McBride, which lasted approximately one year. McBride, who had recently separated from his wife, moved into Cindy's house on October 31, 1982. She told friends that McBride had offered to stay for approximately two weeks, helping surveil in the event that the perpetrator arrived at her home. Several days after McBride moved in, he found Makepeace sitting in his parked car in an alley behind the house. When questioned, Makepeace claimed he was trying to catch Cindy's alleged intruder "in the act," and subsequently left after McBride informed him he had moved in.
In mid-November, McBride stated that he himself received a mysterious phone call at the home while Cindy was present, and that the caller spoke no words. McBride initially suspected the call may have been made from an airport terminal, as he could hear a woman's voice in the background over a public-address system, though it was eventually traced to an exchange in the Vancouver suburb of Richmond. Later in November, Cindy found a note pinned to her car windshield which featured a picture of a corpse lying under a medical sheet. On November 28, McBride observed that the phone lines outside the house had been cut in five different places. Cindy, who remained cordial and friendly with Makepeace despite their breakup, at times invited him to her home with McBride present, as both men had in common a shared fascination with finding her alleged harasser, and would often discuss the case together. McBride moved out of Cindy's home on December 1, though the two continued to casually date, frequently having dinners together in Vancouver and Bellingham, Washington, United States. The week of Christmas 1982, Cindy found a note outside her house reading "Merry Christmas," with a photo of a woman with her throat slashed, stained with red ink.
1983–1984
On the night of January 27, 1983, Agnes Woodcock, a friend and coworker from Blenheim House, visited Cindy's house and found her lying unconscious in her backyard, with a nylon stocking wrapped around her neck. Upon regaining consciousness, Cindy told Woodcock that she had been attacked from behind by an assailant while walking to her exterior garage, and that the individual brought her into the garage, where another male subject waited, and the two strangled her. She alleged that the men inserted a knife into her vagina and threatened to kill her younger sister, Melanie, if she reported the attack to authorities. Doctors who examined Cindy after the alleged attack found no concrete evidence of sexual assault, though Det. David Boywer-Smith remained ambivalent about her claim. At police request, Cindy was asked to see a psychiatrist but declined, as she feared doing so would stigmatize her; instead, she agreed to visit a general practitioner with experience in counseling.
Cindy relocated from her residence to a house in West Vancouver on February 1, 1983. Less than a week later, she received a threatening letter reading: "Run Rabbit Run, I'll show you how fucking good I am. Soon, bang, bang, you're dead." After a rash of further obscene calls, Cindy relocated again to another house in April 1983. Makepeace, who had made continued attempts to reconcile with his wife, showered her with several lavish gifts in the summer of 1983 and paid her airfare to Indonesia so she could visit her brother, Roger, who was stationed there. Several weeks after returning from the trip, Cindy found another note on August 22, which read: "Welcome back—death, blood, hate, etc."
Cindy painted her car a different color in an attempt to conceal her identity, and hired a private investigator, Ozzie Kaban, to help investigate her alleged stalker. She continued to pay for Kaban's services over the following six years. Kaban noted that Cindy went to extensive lengths to protect herself, such as wearing a portable panic button and keeping oil and pepper spray with her at all times. Between October and November 1983, Cindy discovered the remains of three strangled cats in her garden, each bound with rope. In her private diary, she accused Makepeace of destroying the garden in her backyard. She continued to receive numerous phone calls at home and at work, some of which were answered by her coworkers at Blenheim House, who told authorities the caller did not speak.
On January 30, 1984, Kaban overheard strange noises on a two-way radio he had given Cindy, prompting him to visit her home. Upon arrival, he found her lying unconscious on her living room floor with a paring knife stabbed through her hand, and a note pinned through with the knife. The note, which was crafted with letters cut-and-pasted from a magazine, read: "NOW YOU MUST DIE, CUNT." Cindy was taken to a local hospital, and in an interview with Kaban stated the last thing she remembered before being found was witnessing a man coming through the gate to her property before he assaulted her and bludgeoned her over the head with a blunt object. She stated that, once incapacitated, she recalled her attacker inserting a hypodermic needle into her arm. Doctors located a needle mark in her right arm, but found no traces of any drugs in her system. Cindy took a polygraph test after the incident, which purportedly showed no deception; however, the officer who conducted the test later stated that the results, by his estimation, proved "inconclusive." Constable Kiyo Ikoma, who reported to Cindy's residence the night of the alleged attack, stated that he observed blood smeared in circular patterns on the kitchen floor, as though someone had attempted to clean evidence.
In February 1984, detectives began increasingly questioning Makepeace, as Cindy had confided that she felt he was the one tormenting her. In interviews, Makepeace theorized that Cindy's attackers were part of the mafia and connected to her employment at Blenheim House, which often treated children who were wards of the court. In March 1984, Cindy's father Otto met with Makepeace at a doughnut shop in Vancouver wearing a police wiretap, and told Makepeace to cease contact with his daughter. After the meeting, Makepeace wrote and sent a six-page letter to Otto outlining his theory that he believed the mafia was after Cindy, and urged Otto to pressure police to investigate this angle.
Over the summer of 1984, Cindy's reported incidents of harassment reached a "crescendo" in intensity. On June 18, she phoned Kaban in a panic, and he rushed to her home to find her cowering in the garden, claiming someone had infiltrated the house. Kaban discovered her dog, Heidi, cowering in the basement, along with a note reading "Happy Birthday" alongside sexually-explicit photos. Heidi had been physically abused, and Kaban noted that the rope bound around her appeared to be the same discovered on the dead cats Cindy had found the previous autumn. On a windowsill in the basement, a cigarette butt was discovered which did not match the brand Cindy was known to smoke. Based on the physical abuse Heidi had endured, Kaban concluded that Cindy could not have been the perpetrator, stating: "She'd never have done that if she was the Cindy I knew." Over the following several weeks, further calls were received, one of which Kaban answered at Cindy's home while she was at work, and a dead cat was found lying in the stairwell of her house. On July 1, Cindy told Kaban two men had arrived at her front door posing as police officers, but fled when she radioed Kaban. Cindy subsequently reported a series of further obscene calls, one of which consisted of the caller saying: "You're dead, bitch. It's gonna feel good." A coworker of Cindy at Blenheim House also received a call which said: "Get rid of the big pig."
On July 9, 1984, Cindy's mother Tilley spent the night at her home. In the middle of the night, Tilley awoke to Heidi barking, and found Cindy checking windows and doors on the main floor of the house. Moments later, they both heard the doorbell ring, and discovered a window near the front porch cracked in several areas. Two weeks later, on July 23, Cindy claimed she was attacked by an assailant in nearby Dunbar Park while walking her dog at approximate 8:30 p.m. By her recollection, she was assailed by a bearded man driving a green van, with a female passenger. Several hours later, at around midnight, she was found in a dazed state attempting to enter the home of a neighbor, and had a dark-grey nylon stocking around her neck. Her dog Heidi was found by Kaban wandering in the area of the park. She was taken to the nearby University of British Columbia Health and Sciences Centre, where doctors observed two puncture marks in her right arm. While Cindy was being treated, a hospital receptionist told authorities a man with an accent had called the front desk inquiring about the hospital's security policies; when police played audio of Makepeace's voice, the receptionist felt there was a "strong possibility" it was the same person. In October 1984, while under the care of a hypnotherapist, Cindy recounted a repressed memory of witnessing a double murder but did not divulge further details.
1985–1986
Following the July 1984 attack, Cindy continued to receive anonymous phone calls, but none were long enough to be adequately traced by police, and police surveillance of her home proved unfruitful. In January 1985, while under hypnosis, Cindy told police she had witnessed her ex-husband murder a man and woman, then dismember their bodies with an axe while the couple were vacationing at a cabin on Thormanby Island, near Sechelt, in July 1981. According to Cindy, Makepeace smeared blood from one of the victims' severed limbs across her face during the dismemberment. It was later discovered that Cindy's sister, Melanie, was with her on this vacation, and had no recollection of anything sinister occurring.
In late June 1985, Cindy was involuntarily committed to the psychiatric unit at Vancouver's Lions Gate Hospital after having attempted suicide by overdosing on prescription drugs, though she later said she had not intended to kill herself. On July 2, she agreed to allow police to wiretap a phone conversation with Makepeace, during which she accused him of being the source of her problems, and confronted him about the memory she recounted under hypnosis of him murdering two people. During the conversation, Makepeace denied the incidents, deeming Cindy "insane" and involved in an "enormous" revenge fantasy. Following this recorded call, the RCMP employed officers to maintain 24-hour surveillance of Cindy, Makepeace, and two other unnamed suspects over a weeklong period. The surveillance was ultimately terminated after nothing unusual was observed. Authorities further investigated Cindy's claims regarding the alleged dismemberments committed by Makepeace and found no evidence of any murders or missing person cases in the Gulf Islands at the time. Makepeace's attorney stated that the accusation led authorities on a "wild goose chase" searching for the cabin location of the alleged murders, which they were unable to find.
Cindy received a package at her home in early July containing a charcoal-colored nylon stocking, along with a note reading: "Blood flowing freely." Several weeks later, on July 27, she found a cosmetics container on her front porch containing putrefied raw meat from a small animal. On August 5, Cindy called into the police station reporting a fire in her home. Authorities found what appeared to be pieces of burnt newspaper scattered in the room; another fire was reported by Cindy the following day.
On August 21, a third fire broke out in the basement bathroom of Cindy's home at approximately 4:45 a.m. When firefighters and police arrived at the residence, they observed Cindy in a "heated" discussion with private investigator Kaban, explaining that she had taken her dog out for a walk at approximately 3:15 am and returned home to discover the blaze. The window of the bathroom was found partly ajar by authorities, but the soot and dust on the windowsill showed no markings that an intruder had entered or exited through it. Charred remnants of a newspaper were discovered in the bathroom. A detective who investigated the fire later testified that he believed Cindy had started the blaze herself.
In the fall of 1985, Dr. Anthony Marcus, a psychologist, was requested by Carol Halliday of the RCMP to conduct interviews with Cindy and examine the various case files. Halliday, who had become involved with the case after reporting with a colleague at the August 21 fire incident, felt Cindy was lying and orchestrating her attacks, and that the various male officers who investigated them for her had been "conned by the histrionics of a pretty woman." Based on his interviews and analysis of police records, Marcus offered his professional opinion that Cindy may have been suffering from dissociative identity disorder stemming from a traumatic childhood incident, though he did not question Cindy about her early life during their interviews.
On December 1, Cindy relocated to a new house in Richmond. Ten days later, on December 11, at approximately 6:00 p.m., she was found by motorists semiconscious in a ditch approximately from her home, near the University of British Columbia campus. She was wearing men's work boots and a single glove, and again, a nylon stocking was tightly tied around her neck. Due to frigid temperatures, Cindy was suffering from hypothermia and was rushed to a local hospital, where it was suspected she had been injected with some sort of tranquilizer. She also exhibited bruising and various cuts on her body. When interviewed in the hospital, Cindy claimed to have no memory of what occurred, or how she had gotten to the location where she had been found; her last memory was going to have lunch during her workday, after which she stopped at a local pharmacy. Disconsolate over the feeling that police did not believe her, she flew to visit her brother Roger in West Germany for Christmas.
In early 1986, Cindy formally changed her last name from Makepeace, the surname of her ex-husband, to James, hoping to further conceal her identity. To help assuage her fears, her friend Agnes Woodcock, and her husband, Tom, sometimes spent nights at Cindy's home. On April 16, the couple were awoken by Cindy, who stated she heard a commotion in the house. Upon investigating, they found another fire had been started in the basement. When they attempted to phone the fire department, they found the phone was dead. Tom fled across the street to a neighbor's residence to call police, and when exiting the house, claimed to have witnessed a man standing on the street outside the residence; when Tom approached him, the subject fled on foot.
Cindy stayed with the Woodcocks for several days following the fire, where they noted that she refused to eat and made comments that her life was no longer worth living. Allan Connolly, a psychiatrist who had been treating Cindy since January 1983, met with her and stated that, though he had long believed her allegations of harassment, he feared she was suicidal. Connolly had her committed to the psychiatric ward of St. Paul's Hospital for two weeks, where it was observed that she was suffering from anorexia and depression. She was subsequently transferred to Riverview Hospital, where a comprehensive psychological examination was conducted. The report noted:
After a ten-week hospital stay, Cindy was released. According to her father, she told him she had been "withholding information" regarding her alleged attacks, stating that she knew the identity of the assailant but refused to name him.
1987–1989
In August 1987, Cindy began working as a nurse at Richmond General Hospital. On August 28, her home alarm was triggered after a back window was broken, and three days later, on August 31, she reported to police that her front porch lightbulbs had been loosened. The following week, she reported that someone had used a glass cutter to create a hole in the basement door window. In February 1988, Cindy indicated that someone had shattered a window to her home after securing it with electrical tape.
On October 11, 1988, Makepeace received two strange voice messages on his home answering machine. One of the messages contained a hoarse voice speaking the phrase: "Cindy, dead meat soon," while the other stated: "More smack, more downers, another grand after we waste the cunt. No more deal." He gave the answering machine tapes to his attorney, as he distrusted the Vancouver police, whom he felt might target him as a suspect. Fifteen days later, Cindy was found unconscious in her garage. She had been hogtied, was nude from the waist down, and again had a black nylon stocking tied around her neck. Around this time, the RCMP hired mountain climber and knot expert Robert Chisnall to analyze the knots on the nylon stockings she had frequently been found bound with. At the time, Chisnall concluded that it was "highly unlikely" that Cindy would have been able to secure such knots herself.
In January 1989, Richard Johnston, a life insurance salesman from whom Cindy had purchased a policy, moved into the basement unit of her residence; she offered him the rental on the basis that she would feel more safe with someone else living with her. On April 8, a security guard at Richmond General Hospital, where Cindy was employed, discovered a note on the premises crafted with cut-and-pasted letters, which read: "SOON, CINDY". The phrase "sleep well" was also found written in the dew on her windshield. Following a reported attempted break-in at her home on April 29, the RCMP used scent hounds in an attempt to track the alleged intruder, but the dogs found no trail. On May 10, 1989, scent hounds were utilized again following another alleged break-in, and were able to track the scent of an unknown individual that led over the backyard fence of Cindy's home.
RCMP conclusions
Over the course of the nearly seven years that Cindy had reported the various incidents, the RCMP spent an estimated CA$1–1.5 million of resources investigating her claims, but no evidence could be located to corroborate them. Because of this, authorities suspected that Cindy was inventing the incidents herself, and staging them to appear as though she were the victim of a violent stalker. Cindy expressed frustration with the police department, aside from one detective, Jerry Anderson. In a complaint she filed against the RCMP for her perceived dismissal by several officers, she positively singled out Anderson "for his patience, unfailing professional conduct and his exemplary investigation of this case... He is the only member of the RCMP I feel I can trust and be comfortable with."
Disappearance
At approximately 4 p.m. on May 25, 1989, Cindy picked up her paycheck from Richmond General Hospital. There, she spoke with a coworker, who reported that she seemed to be in good spirits, and said Cindy informed her she had not experienced any suspicious activity at her home for at least two weeks. Cindy was last seen several hours later purchasing groceries at a Safeway supermarket and visiting a Bank of Montreal at the Blundell Shopping Centre. A bank patron told police they had stood in line behind Cindy at the bank's ATM, where she deposited her paycheck at approximately 7:59 pm.
That same day, Cindy had scheduled to have an infrared detection system installed in her home for security purposes, and had planned for her friends Agnes and Tom Woodcock to play bridge and spend the night. After not hearing from Cindy, the Woodcocks visited her home at approximately 10:00 pm, and found the house locked and Cindy's Chevrolet Citation absent. They briefly spoke with Johnston, who informed them she had mentioned earlier that she was going to do some shopping. The Woodcocks drove past the Blundell Shopping Centre which they knew Cindy to frequent and found her car abandoned in the lot. They proceeded to drive to the Richmond RCMP station to report Cindy as a missing person. Though she had only been missing for several hours, a patrol car was sent to investigate based on her extensive history with the police department.
Upon examination of the vehicle, blood was located inside the car on the driver's side door as well as groceries and a wrapped birthday gift for her friend's young son; contents from Cindy's wallet were found lying underneath the vehicle. A subsequent inspection of her home that night showed nothing had been disturbed: police observed that the house was orderly and clean, and filled with numerous "well-tended" houseplants. The Canadian Coast Guard deployed searches of rivers in the area, as well as the Gulf of Georgia, in an attempt to locate the missing woman.
Several days after Cindy was reported missing, her tenant, Johnston informed police he had received a call at his office from a man claiming to be her father, inquiring about her life insurance policy. Johnston's secretary informed the caller that he would need to visit the office, as private insurance matters could not be relayed over the phone. When authorities questioned Cindy's father, he denied ever making the phone call.
Death
On June 8, 1989, Gordon Starchuck, a municipal paving worker, discovered Cindy's body in the backyard of an abandoned house at 8111 Blundell Road, Richmond. Her body was hogtied with rope in a fetal position, and a black nylon stocking was bound tightly around her neck. Cindy's right leg lay beneath a bramble of blackberry bushes, and her coat was found lying near her body. The property where her remains were found was situated along a busy street near an intersection, which had frequent foot traffic from pedestrians. On the residence's exterior fuel tank, police found a graffito in orange spray paint reading: "Some bitch died here." A line, spray-painted along the ground with the same orange paint, ran from the fuel tank to the spot where her body lay, encircling it. Inside the abandoned home, another spray-painted graffito reading "Devil" was found.
Sheila Carlyle, a pathologist who examined Cindy's body at the scene, noted that her hands had been bound so tightly that one finger had scratched another down to the bone. A pinprick consistent with a hypodermic needle was located on the inner-right elbow of the body. Based on insect and larvae activity on the remains, forensic entomologist Gail Anderson concluded that the body had begun the decomposition process at the site where it was found as early as June 2, 1989.
An autopsy determined that Cindy had died of multiple drug intoxication from substantial amounts of morphine, diazepam, and flurazepam. Her blood toxicology report showed that she had ten times the lethal dose of morphine in her bloodstream. Based on an examination of her stomach contents, toxicologist Heather Dinn reported that Cindy had orally ingested approximately twenty 30-milligram tablets of flurazepam (or up to eighty tablets of a higher dose), in addition to numerous tablets of diazepam, a combination that itself was lethal. The method by which the morphine had been administered could not be determined, "baffling" the pharmacologist who analyzed the toxicology report. Traces of morphine were found in Cindy's stomach, though Dr. John McNeill stated that the amount could have resulted from intravenous injection of the drug. By McNeill's analysis, if Cindy had received the morphine via intravenous injection, she would have been rendered unconscious within mere minutes, and would have died within several hours. It was ultimately concluded by authorities that the overdose had been "so large that there was no reliable estimate of how long Cindy could have remained functional."
The RCMP suspected Cindy's cause of death was likely a suicide or accident, based on the assumption that she had fabricated her numerous prior claims of assaults and stalking, and this was quickly reported by several local tabloid news outlets. Her personal private investigator, Kaban, visited the morgue to examine her body on June 10 and observed that her remains exhibited lividity—the settling of blood postmortem, visible on the skin—on the left side of her body. Because her body had been found lying on its right side, Kaban felt that she may have died elsewhere, and that her body was relocated to the site where it was ultimately discovered.
A memorial service was held for Cindy on June 14, 1989, two days after what would have been her forty-fifth birthday. Police surveilled the memorial service using hidden cameras, capturing the faces and license plates of all who attended. Her ex-husband, Makepeace, was not in attendance. In the summer of 1989, the abandoned house where Cindy's body was discovered was demolished.
Coroner's inquest
An extensive inquest into Cindy's death was undertaken in the spring of 1990 in Burnaby, which consisted of five jurors and featured testimony from over eighty witnesses. The inquest was originally scheduled to run three weeks, but upon it "progressing much slower than expected," an additional twenty-one days were added. The inquest, which totaled forty days, was the longest and most expensive in British Columbia at that time.
Among the evidence presented were the two recorded phone messages Makepeace had received on his answering machine. During his testimony on the stand, Makepeace made various accusations against Cindy's family, alleging that her father had physically abused her throughout her childhood and that one of her brothers had molested her. He also accused the police of attempting to frame him. It was also revealed that, shortly after her death, Cindy's parents uncovered a hoard of various medications in her home (including sedatives and antipsychotic drugs) prescribed by her psychiatrists, which they disposed of by flushing down the toilet. Her younger sister, Melanie, also found a glass cutter in Cindy's purse along with a medical syringe kit, a urinary catheter, and saline solution in her bedroom.
Jurors were presented with graphic footage of Cindy's decomposing corpse as it was discovered at the scene, as well as numerous accounts detailing her mental state leading up to her death. Testimony was provided from several psychiatrists and psychologists, including those who had personally treated Cindy over the years. Dr. Paul Termansen testified that he believed she suffered from hysterical personality disorder, while Dr. Wesley Friesen—a longtime psychiatrist of Cindy's—stated he suspected she had borderline personality disorder with elements of post-traumatic stress disorder. By Friesen's account, Cindy possessed a "tremendous amount of rage" toward her father and, based on their numerous sessions, Friesen believed there was a "strong likelihood" that her father sexually abused her when she was a child, though she never indicated this to be the case.
Attempts to discern whether or not Cindy could have bound herself in the state she was discovered were also focused on during the inquest: using the same length of nylon found binding her body, knot expert Robert Chisnall demonstrated in court how she could have bound herself within a three-minute timeframe, before the effects of the narcotics in her system would have taken effect.
The inquest concluded on May 25, 1990, exactly one year after Cindy had disappeared. After deliberations, the jury was unable to determine whether her manner of death was suicide, homicide, or accidental. It was ultimately ruled that Cindy had died of an "unknown event," and the case was formally closed.
Media representation
Cindy's disappearance was profiled on the American series A Current Affair prior to her discovery, and her case was later profiled in a February 1991 episode of the NBC series Unsolved Mysteries. A docuseries was released the same month in Canada via BCTV. Two books chronicling her life, stalking allegations, and death were also published in 1991: The Deaths of Cindy James by Canadian journalist Neal Hall, and Who Killed Cindy James? by British journalist Ian Mulgrew. In September 2021, an Audible-produced podcast on James' death, entitled Death by Unknown Event, was released, featuring narration by actress and writer Pamela Adlon.
See also
List of solved missing person cases
List of unsolved deaths
Notes
References
Sources
1980s missing person cases
Deaths by person in Canada
Drug-related deaths in Canada
Formerly missing people
June 1989 events in Canada
May 1989 events in Canada
Missing person cases in Canada
Stalking
Unsolved deaths in Canada
Violence against women in British Columbia | Death of Cindy James | Biology | 7,548 |
213,454 | https://en.wikipedia.org/wiki/Corvus%20%28constellation%29 | Corvus is a small constellation in the Southern Celestial Hemisphere. Its name means "crow" in Latin. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it depicts a raven, a bird associated with stories about the god Apollo, perched on the back of Hydra the water snake. The four brightest stars, Gamma, Delta, Epsilon, and Beta Corvi, form a distinctive quadrilateral or cross-shape in the night sky.
With an apparent magnitude of 2.59, Gamma Corvi—also known as Gienah—is the brightest star in the constellation. It is an aging blue giant around four times as massive as the Sun. The young star Eta Corvi has been found to have two debris disks. Three star systems have exoplanets, and a fourth planetary system is unconfirmed. TV Corvi is a dwarf nova—a white dwarf and brown dwarf in very close orbit.
History and mythology
In the Babylonian star catalogues dating from at least 1100 BCE, what later became known as Corvus was called the Raven (MUL.UGA.MUSHEN). As with more familiar Classical astronomy, it was placed sitting on the tail of the Serpent (Greek Hydra). The Babylonian constellation was sacred to Adad, the god of rain and storm; in the second Millennium BCE it would have risen just before the autumnal rainy season. John H. Rogers observed that Hydra signified Ningishzida, the god of the underworld in the Babylonian compendium MUL.APIN. He proposed that Corvus and Crater (along with Hydra) were death symbols and marked the gate to the underworld. These two constellations, along with the eagle Aquila and the fish Piscis Austrinus, were introduced to the Greeks around 500 BCE; they marked the winter and summer solstices respectively. Furthermore, Hydra had been a landmark as it had straddled the celestial equator in antiquity. Corvus and Crater also featured in the iconography of Mithraism, which is thought to have been of middle-eastern origin before spreading into Ancient Greece and Rome.
Corvus is associated with the myth of Apollo and his lover Coronis the Lapith. Coronis had been unfaithful to Apollo; when he learned this information from a pure white crow (or raven in some versions), he turned its feathers black in a fit of rage. Another legend associated with Corvus is that a crow stopped on his way to fetch water for Apollo, to eat figs. Instead of telling the truth to Apollo, he lied and said that a snake, Hydra, kept him from the water, while holding a snake in his talons as proof. Apollo, realizing this was a lie, flung the crow (Corvus), cup (Crater), and snake (Hydra) into the sky. He further punished the wayward bird by ensuring it would forever be thirsty, both in real life and in the heavens, where the Cup is just out of reach.
In other cultures
In Chinese astronomy, the stars of Corvus are located within the Vermilion Bird of the South (南方朱雀, Nán Fāng Zhū Què). The four main stars depict a chariot, Zhen, which is the 28th and final lunar mansion; Alpha and Eta mark the linchpins for the wheels, and Zeta is Changsha, a coffin. In Indian astronomy, the five main stars of Corvus represent a hand or fist corresponding to the Hasta, the 13th nakshatra or lunar mansion.
Corvus was recognized as a constellation by several Polynesian cultures and used as a guide for ocean navigation.
In the Marquesas Islands, it was called Mee; in Pukapuka, it was called Te Manu, and in the Society Islands, it was called Metua-ai-papa. To Torres Strait Islanders, Corvus was the right hand (holding kupa fruit) of the huge constellation Tagai, a man fishing.
The Bororo people of Mato Grosso in central Brazil regarded the constellation as a land tortoise Geriguigui, while the Tucano people of the northwestern Amazon region saw it as an egret. To the Tupi people of São Luís Island in Brazil, Corvus might have been seen as a grill or barbecue—seychouioura, on which fish were grilled. The depiction could have also referred to the Great Square of Pegasus.
Characteristics
Covering 184 square degrees and hence 0.446% of the sky, Corvus ranks 70th of the 88 constellations in area. It is bordered by Virgo to the north and east, Hydra to the south, and Crater to the west. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "Crv". The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of six segments (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between and , while the declination coordinates are between −11.68° and −25.20°. Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 65°N.
Features
Stars
The German cartographer Johann Bayer used the Greek letters Alpha through Eta to label the most prominent stars in the constellation. John Flamsteed gave nine stars Flamsteed designations, while one star he designated in the neighbouring constellation Crater—31 Crateris—lay within Corvus once the constellation boundaries were established in 1930. Within the constellation's borders, there are 29 stars brighter than or equal to apparent magnitude 6.5.
Four principal stars, Delta, Gamma, Epsilon, and Beta Corvi, form a quadrilateral asterism known as "the "Spica's Spanker" or "the Sail". Although none of the stars are particularly bright, they lie in a dim area of the sky, rendering the asterism easy to distinguish in the night sky. Gamma and Delta serve as pointers toward Spica.
Also called Gienah, Gamma is the brightest star in Corvus at magnitude 2.59. Its traditional name means "wing", the star marking the left wing in Bayer's Uranometria. 154±1 light-years from Earth, it is a blue-white hued giant star of spectral type B8III that is times as massive, and 355 times as luminous as the Sun. Around million years old, it has largely exhausted its core hydrogen and begun expanding and cooling as it moves away from the main sequence. A binary star, it has a companion orange or red dwarf star of spectral type K5V to M5V that is about 0.8 times as massive as the Sun. Around 50 astronomical units distant from Gamma Corvi A, it is estimated to complete an orbit in 158 years.
Delta Corvi, traditionally called Algorab, is a double star divisible in small amateur telescopes. The primary is a blue-white star of magnitude 2.9, around 87 light-years from Earth. An enigmatic star around 2.7 times as massive as the Sun, it is more luminous (65–70 times that of the Sun) than its should be for its surface temperature of 10,400 K, and hence is either a 3.2 million year-old very young pre-main sequence star that has not settled down to a stable main sequence life stage, or a 260-million-year-old star that has begun to exhaust its core hydrogen and expand, cool and shine more brightly as it moves away from the main sequence. Its spectral type is given as A0IV, corresponding with the latter scenario. Warm circumstellar dust—by definition part of its inner stellar system—has been detected around Delta Corvi A. Delta Corvi B is an orange dwarf star of magnitude 8.51 and spectral class K, also surrounded by circumstellar dust. A post T-tauri star, it is at least 650 AU distant from its brighter companion and takes at least 9400 years to complete an orbit. Delta Corvi's common name means "the raven". It is one of two stars marking the right wing. Located 4.5 degrees northeast of Delta Corvi is Struve 1669, a binary star that is divisible into two stars 5.4" apart by small amateur telescopes, 280 light-years from Earth. The pair, both white stars, are visible to the naked eye at magnitude 5.2; the primary is of magnitude 5.9 and the secondary is of magnitude 6.0.
The raven's breast is marked by Beta Corvi (the proper name is Kraz), a star of magnitude 2.7 located 146 ± 1 light-years from Earth. Roughly 206 million years old and 3.7 ± 1 times as massive as the Sun, it has exhausted its core hydrogen and expanded and cooled to a surface temperature of around 5,100 K and is now a yellow bright giant star of spectral type G5II. It likely spent most of its existence as a blue-white main sequence star of spectral type B7V. Bearing the proper name of Minkar and marking the raven's nostril is Epsilon Corvi, located some 318 ± 5 light-years from Earth. It is a red giant of spectral type K2III that is around 54 times the Sun's radius and 930 times its luminosity. Around 4 times as massive as the Sun, it spent much of its life as a main-sequence star of spectral type B5V. Lying to the south of the quadrilateral between Beta and Epsilon Corvi is the orange-hued 6 Corvi, an ageing giant star of spectral type K1III that is around 70 times as luminous as the Sun. It is 331 ± 10 light-years away from Earth.
Named Alchiba, Alpha Corvi is a white-hued star of spectral type F1V and magnitude 4.0, 48.7 ± 0.1 light-years from Earth. It exhibits periodic changes in its spectrum over a three-day period, which suggests it is either a spectroscopic binary or (more likely) a pulsating Gamma Doradus-type variable. If the latter is the case, it is estimated to be 1.39 times as massive as the Sun. According to Bayer's atlas, it lies above the bird's beak.
Marking the raven's right wing is Eta Corvi, a yellow-white main-sequence star of type F2V that is 1.52 times as massive and 4.87 times as luminous as the Sun. It is 59 light-years distant from our Solar System. Two debris disks have been detected orbiting this star, one warm within 3.5 astronomical units and another out at ~150 astronomical units distant. Zeta Corvi marks the raven's neck. It is of apparent magnitude 5.21, separated by 7 arcseconds from the star HR 4691. Located 420 ± 10 light-years distant, it is a blue-white Be star of spectral type B8V, the presence of hydrogen emission lines in its spectrum indicating it has a circumstellar disc. These stars may be an optical double or a true multiple star system, with a separation of at least 50,000 astronomical units and the stars taking 3.5 million years to orbit each other. HR 4691 is itself double, composed of an ageing yellow-orange giant whose spectral type has been calculated at K0 or G3, and an F-type main-sequence star.
31 Crateris (which was originally placed in Crater by Flamsteed) is a 5.26 magnitude star which was once mistaken for a moon of Mercury. On 27 March 1974, the Mariner 10 mission detected emissions in the far ultraviolet from the planet (suggesting a satellite), but they were found to emanate from the star. It is in reality a remote binary star system with a hot blue-white star of spectral type B1.5V and a companion about which little is known. The two stars orbit each other every 2.9631 days. The primary is possibly a blue straggler of the Hyades group. The primary is around 15.5 times as massive as the Sun and 52262 times as luminous.
VV Corvi is a close spectroscopic binary, its two component stars orbiting each other with a period of 1.46 days. Both are yellow-white main-sequence stars of spectral type F5V, though the primary has begun expanding and cooling as it nears the end of its time on the main sequence. The mass ratio of the two stars is 0.775 ± 0.024. A tertiary companion was discovered during the Two Micron All-Sky Survey. W Corvi is an eclipsing binary that varies in brightness from apparent magnitude 11.16 to 12.5 over 9 hours. Its period has increased by 1/4 second over a century. It is an unusual system in that its two stars are very close to each other yet have different surface temperatures, and hence thermal transfer is not taking place as expected. SX Corvi is an eclipsing binary that is also a contact binary known as a W Ursae Majoris variable. The two component stars orbit closely enough to each other for mass to have been transferred between them—in this case the secondary having transferred a large amount of mass to the primary. RV Corvi is another eclipsing binary. Its brightness varies from apparent magnitude 8.6 to 9.16 over 18 hours. The system is composed of stars of spectral types F0 and G0, which orbit each other every 0.7473 days.
Close to Gamma Corvi and visible in the same binocular field is R Corvi, a long period (Mira) variable star. It ranges in brightness from a magnitude of 6.7 to 14.4 with a period of approximately 317 days. TT Corvi is a semiregular variable red giant of spectral type M3III and apparent magnitude 6.48 around 923 light years distant. It is around 993 times as luminous as the Sun. TU Corvi is a Delta Scuti variable—a class of short period (six hours at most) pulsating stars that have been used as standard candles and as subjects to study astroseismology. It varies by 0.025 of a magnitude around apparent magnitude 6.53 over 59 minutes.
Three star systems have confirmed planets. HD 103774 is a young yellow-white main-sequence star of apparent magnitude 7.12 that is 181 ± 5 light-years distant from Earth. It is 1.335 ± 0.03 times as massive and 3.5 ± 0.3 as luminous as the Sun. Variations in its radial velocity showed it was being orbited by a Neptune-sized planet every 5.9 days in 2013. HD 104067 is an orange dwarf of spectral type K2V of apparent magnitude 7.93 that is 69 ± 1 light-years distant from Earth. Around 80% as massive as the Sun, it is orbited by a planet 3.6 times the mass of Neptune every 55.8 days. WASP-83 has a planet around as massive as Saturn that orbits it every 5 days. It was discovered by its transit across the star in 2015. A fourth star system has an unconfirmed planet. HD 111031 is a sunlike star of spectral type G5V located 101 ± 2 light-years distant from Earth.
Ross 695 is a red dwarf star located a mere 28.9 ± 0.6 light-years distant from Earth. At apparent magnitude 11.27, it is much too faint to be seen with the unaided eye. A small star, it has around 23% the mass and radius of the Sun, but only 0.7% its luminosity. VHS J1256–1257 is a triple system of young brown dwarfs located light-years distant from Earth. The system consists of a central, equal-mass binary system of late-M spectral type dwarfs and an outer, planetary-mass brown dwarf companion that is widely separated at 102 ± 9 AU. DENIS-P J1228.2-1547 is a system composed of two brown dwarfs orbiting each other located 73 ± 3 light-years away from Earth. TV Corvi is a dwarf nova composed of a white dwarf and brown dwarf that orbit each other every 90 minutes. The system has a baseline magnitude of 17 that brightens periodically to magnitude 12, discovered by Clyde Tombaugh in 1931 and David Levy in 1990 and 2005.
Deep-sky objects
Corvus contains no Messier objects. It has several galaxies and a planetary nebula observable with amateur telescopes. The center of Corvus is home to a planetary nebula, NGC 4361. The nebula itself resembles a small elliptical galaxy and has a magnitude of 10.3, but the magnitude 13 star at its centre gives away its true nature. Corvus also contains the Stargate (asterism).
The NGC 4038 Group is a group of galaxies across Corvus and Crater. The group may contain between 13 and 27 galaxies. The best-known member is the Antennae peculiar galaxy, located 0.25 north of 31 Crateris. It consists of two interacting galaxies—NGC 4038 and 4039—that appear to have a heart shape as seen from Earth. The name originates from the huge tidal tails that come off the ends of the two galaxies, formed because of the spiral galaxies' original rotation. Both original galaxies were spiral galaxies and are now experiencing extensive star formation due to the interaction of gas clouds. The galaxies are 45 million light-years from Earth and each has multiple ultraluminous X-ray sources, the source of which is unknown. Astronomers theorize that they may be a rare type of x-ray emitting binary stars or intermediate-mass black holes. The Antennae Galaxies appear in a telescope at the 10th magnitude. SN 2004gt was a type Ic supernova that erupted on December 12, 2004. The progenitor was not identified from older images of the galaxy, and is either a type WC Wolf–Rayet star with a mass over 40 times that of the Sun, or a star 20 to 40 times as massive as the Sun in a binary star system. SN 2007sr was a Type Ia supernova event that peaked in brightness on December 14, 2007. The galaxy has been identified as a good place to take detailed images in case of further supernovae.
NGC 4027 is another member of the NGC 4038 group, notable for its extended spiral arm. Known as the Ringtail Galaxy, it lies close to 31 Crateris. A barred spiral galaxy, its distorted shape is probably due to a past collision, possibly with the nearby NGC 4027A. NGC 4782 and NGC 4783 are a pair of merging elliptical galaxies in the northeastern part of the constellation, around 200 million light-years distant.
Meteor showers
Two established meteor showers originate from within Corvus' boundaries. German astronomer Cuno Hoffmeister discovered and named the Corvids in 1937, after observing them between June 25 and July 2. They have not been seen since, nor was there evidence of a shower when previous records were examined. Hoffmeister noted the trajectory of the shower was similar to that of the comet 11P/Tempel–Swift–LINEAR, though this was not confirmed by Zhukov and colleagues in 2011. The shower has been tentatively linked with 4015 Wilson–Harrington. In January 2013, the MO Video Meteor Network published the discovery of the Eta Corvids, assigning some 300 meteors seen between January 20 and 26. Their existence was confirmed by data analysis later that year.
Popular culture
In 1624, German astronomer Jakob Bartsch equated the constellation Argo Navis with Noah's Ark, linking Corvus and Columba to the crow and dove that feature in the story in Genesis.
In Action Comics #14 (January 2013), which was published 7 November 2012, astrophysicist Neil deGrasse Tyson appears in the story, in which he determines that Superman's home planet, Krypton, orbited the red dwarf LHS 2520 in the constellation Corvus, 27.1 light-years from Earth. Tyson assisted DC Comics in selecting a real-life star that would be an appropriate parent star to Krypton, and picked the star in Corvus, the mascot of Superman's high school, the Smallville Crows.
See also
Corvus (Chinese astronomy)
Notes
References
Sources
External links
The Deep Photographic Guide to the Constellations: Corvus
The clickable Corvus
Warburg Institute Iconographic Database (medieval and early modern images of Corvus)
Constellations
Constellations listed by Ptolemy
Southern constellations | Corvus (constellation) | Astronomy | 4,350 |
2,488,073 | https://en.wikipedia.org/wiki/Polyhedron%20model | A polyhedron model is a physical construction of a polyhedron, constructed from cardboard, plastic board, wood board or other panel material, or, less commonly, solid material.
Since there are 75 uniform polyhedra, including the five regular convex polyhedra, five polyhedral compounds, four Kepler-Poinsot polyhedra, and thirteen Archimedean solids, constructing or collecting polyhedron models has become a common mathematical recreation. Polyhedron models are found in mathematics classrooms much as globes in geography classrooms.
Polyhedron models are notable as three-dimensional proof-of-concepts of geometric theories. Some polyhedra also make great centerpieces, tree toppers, Holiday decorations, or symbols. The Merkaba religious symbol, for example, is a stellated octahedron. Constructing large models offer challenges in engineering structural design.
Construction
Construction begins by choosing a size of the model, either the length of its edges or the height of the model. The size will dictate the material, the adhesive for edges, the construction time and the method of construction.
The second decision involves colours. A single-colour cardboard model is easiest to construct — and some models can be made by folding a pattern, called a net, from a single sheet of cardboard. Choosing colours requires geometric understanding of the polyhedron. One way is to colour each face differently. A second way is to colour all square faces the same, all pentagonal faces the same, and so forth. A third way is to colour opposite faces the same. Many polyhedra are also coloured such that no same-coloured faces touch each other along an edge or at a vertex.
For example, a 20-face icosahedron can use twenty colours, one colour, ten colours, or five colours, respectively.
An alternative way for polyhedral compound models is to use a different colour for each polyhedron component.
Net templates are then made. One way is to copy templates from a polyhedron-making book, such as Magnus Wenninger's Polyhedron Models, 1974 (). A second way is drawing faces on paper or with computer-aided design software and then drawing on them the polyhedron's edges. The exposed nets of the faces are then traced or printed on template material. A third way is using the software named Stella to print nets.
A model, particularly a large one, may require another polyhedron as its inner structure or as a construction mold. A suitable inner structure prevents the model from collapsing from age or stress.
The net templates are then replicated onto the material, matching carefully the chosen colours. Cardboard nets are usually cut with tabs on each edge, so the next step for cardboard nets is to score each fold with a knife. Panelboard nets, on the other hand, require molds and cement adhesives.
Assembling multi-colour models is easier with a model of a simpler related polyhedron used as a colour guide. Complex models, such as stellations, can have hundreds of polygons in their nets.
Interactive computer models
Recent computer graphics technologies allow people to rotate 3D polyhedron models on a computer video screen in all three dimensions. Recent technologies even provide shadows and textures for a more realistic effect.
See also
Polyhedron
List of Wenninger polyhedron models
External links
Stella: Polyhedron Navigator: Software to explore virtual polyhedra and print their nets to enable physical construction
Interactive 3D polyhedra in Java
Wooden Polyhedra Models
George Hart's extensive encyclopedia of polyhedra
George Hart's Pavilion of Polyhedreality
Online rotatable polyhedron models
WOODEN POLYHEDRA 30
Recreational mathematics
Model | Polyhedron model | Mathematics | 743 |
3,905,832 | https://en.wikipedia.org/wiki/Hermann%E2%80%93Mauguin%20notation | In geometry, Hermann–Mauguin notation is used to represent the symmetry elements in point groups, plane groups and space groups. It is named after the German crystallographer Carl Hermann (who introduced it in 1928) and the French mineralogist Charles-Victor Mauguin (who modified it in 1931). This notation is sometimes called international notation, because it was adopted as standard by the International Tables For Crystallography since their first edition in 1935.
The Hermann–Mauguin notation, compared with the Schoenflies notation, is preferred in crystallography because it can easily be used to include translational symmetry elements, and it specifies the directions of the symmetry axes.
Point groups
Rotation axes are denoted by a number n – 1, 2, 3, 4, 5, 6, 7, 8, ... (angle of rotation ). For improper rotations, Hermann–Mauguin symbols show rotoinversion axes, unlike Schoenflies and Shubnikov notations, that shows rotation-reflection axes. The rotoinversion axes are represented by the corresponding number with a macron, – , , , , , , , , ... . is equivalent to a mirror plane and usually notated as m. The direction of the mirror plane is defined as the direction perpendicular to it (the direction of the axis).
Hermann–Mauguin symbols show non-equivalent axes and planes in a symmetrical fashion. The direction of a symmetry element corresponds to its position in the Hermann–Mauguin symbol. If a rotation axis n and a mirror plane m have the same direction, then they are denoted as a fraction or n/m.
If two or more axes have the same direction, the axis with higher symmetry is shown. Higher symmetry means that the axis generates a pattern with more points. For example, rotation axes 3, 4, 5, 6, 7, 8 generate 3-, 4-, 5-, 6-, 7-, 8-point patterns, respectively. Improper rotation axes , , , , , generate 6-, 4-, 10-, 6-, 14-, 8-point patterns, respectively. If a rotation and a rotoinversion axis generate the same number of points, the rotation axis should be chosen. For example, the combination is equivalent to . Since generates 6 points, and 3 generates only 3, should be written instead of (not , because already contains the mirror plane m). Analogously, in the case when both 3 and axes are present, should be written. However we write , not , because both 4 and generate four points. In the case of the combination, where 2, 3, 6, , and axes are present, axes , , and 6 all generate 6-point patterns, as we can see on the figure in the right, but the latter should be used because it is a rotation axis – the symbol will be
Finally, the Hermann–Mauguin symbol depends on the type of the group.
Groups without higher-order axes (axes of order three or more)
These groups may contain only two-fold axes, mirror planes, and/or an inversion center. These are the crystallographic point groups 1 and (triclinic crystal system), 2, m, and (monoclinic), and 222, , and mm2 (orthorhombic). (The short form of is mmm.) If the symbol contains three positions, then they denote symmetry elements in the x, y, z direction, respectively.
Groups with one higher-order axis
First position – primary direction – z direction, assigned to the higher-order axis.
Second position – symmetrically equivalent secondary directions, which are perpendicular to the z-axis. These can be 2, m, or
Third position – symmetrically equivalent tertiary directions, passing between secondary directions. These can be 2, m, or
These are the crystallographic groups 3, 32, 3m, , and (trigonal crystal system), 4, 422, 4mm, , 2m, , and (tetragonal), and 6, 622, 6mm, , m2, , and (hexagonal). Analogously, symbols of non-crystallographic groups (with axes of order 5, 7, 8, 9, ...) can be constructed. These groups can be arranged in the following table
It can be noticed that in groups with odd-order axes n and the third position in symbol is always absent, because all n directions, perpendicular to higher-order axis, are symmetrically equivalent. For example, in the picture of a triangle all three mirror planes (S0, S1, S2) are equivalent – all of them pass through one vertex and the center of the opposite side.
For even-order axes n and there are secondary directions and tertiary directions. For example, in the picture of a regular hexagon one can distinguish two sets of mirror planes – three planes go through two opposite vertexes, and three other planes go through the centers of opposite sides. In this case any of two sets can be chosen as secondary directions, the rest set will be tertiary directions. Hence groups 2m, 2m, 2m, ... can be written as m2, m2, m2, ... . For symbols of point groups this order usually doesn't matter; however, it will be important for Hermann–Mauguin symbols of corresponding space groups, where secondary directions are directions of symmetry elements along unit cell translations b and c, while the tertiary directions correspond to the direction between unit cell translations b and c. For example, symbols Pm2 and P2m denote two different space groups. This also applies to symbols of space groups with odd-order axes 3 and . The perpendicular symmetry elements can go along unit cell translations b and c or between them. Space groups P321 and P312 are examples of the former and the latter cases, respectively.
The symbol of point group may be confusing; the corresponding Schoenflies symbol is D3d, which means that the group consists of 3-fold axis, three perpendicular 2-fold axes, and 3 vertical diagonal planes passing between these 2-fold axes, so it seems that the group can be denoted as 32m or 3m2. However, one should remember that, unlike Schoenflies notation, the direction of a plane in a Hermann–Mauguin symbol is defined as the direction perpendicular to the plane, and in the D3d group all mirror planes are perpendicular to 2-fold axes, so they should be written in the same position as . Second, these complexes generate an inversion center, which combining with the 3-fold rotation axis generates a rotoinversion axis.
Groups with n = ∞ are called limit groups or Curie groups.
Groups with several higher-order axes
These are the crystallographic groups of a cubic crystal system: 23, 432, , 3m, and . All of them contain four diagonal 3-fold axes. These axes are arranged as 3-fold axes in a cube, directed along its four space diagonals (the cube has symmetry). These symbols are constructed the following way:
First position – symmetrically equivalent directions of the coordinate axes x, y, and z. They are equivalent due to the presence of diagonal 3-fold axes.
Second position – diagonal 3 or axes.
Third position – diagonal directions between any two of the three coordinate axes x, y, and z. These can be 2, m, or .
All Hermann–Mauguin symbols presented above are called full symbols. For many groups they can be simplified by omitting n-fold rotation axes in positions. This can be done if the rotation axis can be unambiguously obtained from the combination of symmetry elements presented in the symbol. For example, the short symbol for is mmm, for is mm, and for is mm. In groups containing one higher-order axis, this higher-order axis cannot be omitted. For example, symbols and can be simplified to 4/mmm (or mm) and 6/mmm (or mm), but not to mmm; the short symbol for is m. The full and short symbols for all 32 crystallographic point groups are given in crystallographic point groups page.
Besides five cubic groups, there are two more non-crystallographic icosahedral groups (I and Ih in Schoenflies notation) and two limit groups (K and Kh in Schoenflies notation). The Hermann–Mauguin symbols were not designed for non-crystallographic groups, so their symbols are rather nominal and based on similarity to symbols of the crystallographic groups of a cubic crystal system. Group I can be denoted as 235, 25, 532, 53. The possible short symbols for Ih are m, m, mm, m. The possible symbols for limit group K are ∞∞ or 2∞, and for Kh are ∞ or m or ∞∞m.
Plane groups
Plane groups can be depicted using the Hermann–Mauguin system. The first letter is either lowercase p or c to represent primitive or centered unit cells. The next number is the rotational symmetry, as given above. The presence of mirror planes are denoted m, while glide reflections are only denoted g. Screw axes do not exist in two-dimensional spaces.
Space groups
The symbol of a space group is defined by combining the uppercase letter describing the lattice type with symbols specifying the symmetry elements. The symmetry elements are ordered the same way as in the symbol of corresponding point group (the group that is obtained if one removes all translational components from the space group). The symbols for symmetry elements are more diverse, because in addition to rotations axes and mirror planes, space group may contain more complex symmetry elements – screw axes (combination of rotation and translation) and glide planes (combination of mirror reflection and translation). As a result, many different space groups can correspond to the same point group. For example, choosing different lattice types and glide planes one can generate 28 different space groups from point group mmm, e.g. Pmmm, Pnnn, Pccm, Pban, Cmcm, Ibam, Fmmm, Fddd, and so on. In some cases, a space group is generated when translations are simply added to a point group. In other cases there is no point around which the point group applies. The notation is somewhat ambiguous, without a table giving more information. For example, space groups I23 and I23 (nos. 197 and 199) both contain two-fold rotational axes as well as two-fold screw axes. In the first, the two-fold axes intersect the three-fold axes, whereas in the second they do not.
Lattice types
These are the Bravais lattice types in three dimensions:
P – Primitive
I – Body centered (from the German "Innenzentriert")
F – Face centered (from the German "Flächenzentriert")
A – Base centered on A faces only
B – Base centered on B faces only
C – Base centered on C faces only
R – Rhombohedral
Screw axes
The screw axis is noted by a number, n, where the angle of rotation is . The degree of translation is then added as a subscript showing how far along the axis the translation is, as a portion of the parallel lattice vector. For example, 21 is a 180° (twofold) rotation followed by a translation of of the lattice vector. 31 is a 120° (threefold) rotation followed by a translation of of the lattice vector.
The possible screw axes are: 21, 31, 32, 41, 42, 43, 61, 62, 63, 64, and 65.
There are 4 enantiomorphic pairs of axes: (31 – 32), (41 – 43), (61 – 65), and (62 – 64). This enantiomorphism results in 11 pairs of enantiomorphic space groups, namely
Glide planes
The orientation of a glide plane is given by the position of the symbol in the Hermann–Mauguin designation, just as with mirror planes.
They are noted by a, b, or c depending on which axis (direction) the glide is along. There is also the n glide, which is a glide along the half of a diagonal of a face, and the d glide, which is along a quarter of either a face or space diagonal of the unit cell. The d glide is often called the diamond glide plane as it features in the diamond structure. In cases where there are two possibilities among a, b, and c (such as a or b), the letter e is used. (In these cases, centering entails that both glides occur.) To summarize:
a, b, or c glide translation along half the lattice vector of this face.
n glide translation along half a face diagonal.
d glide planes with translation along a quarter of a face diagonal or of a space diagonal.
e two glides with the same glide plane and translation along two (different) half-lattice vectors.
References
External links
Decoding the Hermann-Maguin Notation – An introduction into the Hermann-Maguin notation for beginners.
Crystallography
Chemical nomenclature | Hermann–Mauguin notation | Physics,Chemistry,Materials_science,Engineering | 2,721 |
11,905,171 | https://en.wikipedia.org/wiki/Tonelli%27s%20theorem%20%28functional%20analysis%29 | In mathematics, Tonelli's theorem in functional analysis is a fundamental result on the weak lower semicontinuity of nonlinear functionals on Lp spaces. As such, it has major implications for functional analysis and the calculus of variations. Roughly, it shows that weak lower semicontinuity for integral functionals is equivalent to convexity of the integral kernel. The result is attributed to the Italian mathematician Leonida Tonelli.
Statement of the theorem
Let be a bounded domain in -dimensional Euclidean space and let be a continuous extended real-valued function. Define a nonlinear functional on functions by
Then is sequentially weakly lower semicontinuous on the space for and weakly-∗ lower semicontinuous on if and only if is convex.
See also
References
(Theorem 10.16)
Calculus of variations
Convex analysis
Function spaces
Measure theory
Theorems in functional analysis
Variational analysis | Tonelli's theorem (functional analysis) | Mathematics | 176 |
40,030,297 | https://en.wikipedia.org/wiki/2003%20Etobicoke%20gas%20explosion | The 2003 Etobicoke gas explosion was a disaster which occurred on April 24, 2003, after a backhoe operated by Enbridge contractor Precision Utility breached a pipeline on Bloor Street in the Etobicoke district of Toronto, Ontario. The resulting explosion destroyed a two-story mixed commercial and residential building, killing seven people and injuring another four. Enbridge and several other companies were fined for the disaster in 2011. A memorial garden was dedicated at the site of the explosion in 2008.
Cause
On April 24, 2003, road work was being conducted to fix flooding concerns. Enbridge contracted Precision Utility to locate natural gas pipelines along Bloor Street, west of Kipling Avenue. A pipeline leading into a plaza was not identified and an employee struck the pipeline with a backhoe, causing natural gas to leak into the basement of a two-story strip mall with businesses and residential housing. The workers immediately noticed the error and went to their vehicles to obtain tools to fix the leak.
Explosion
At around 1:30pm, the gas leaking out from the pipeline ignited, destroying the strip mall and damaging nearby buildings. The explosion also caused a fire which also damaged an adjacent house. 100 people and 25 fire trucks were used to extinguish the fire. Windows in stores across the street were blown out, windshields were damaged on cars and one vehicle was destroyed.
Seven people were killed in the explosion. Robert Fairley was a resident of the building while Adele Brown, Elizabeth Roy and Lillian Guglietti were clients at a salon in the strip mall. Dora Carambelas, Tina Kirkimtzis, and Irene Miyama were also in the building when it exploded. Four people were also injured by falling debris.
After Hurricane Hazel, this explosion was the second-highest loss of life for a single event in Etobicoke. This is also the highest loss of life for an incident involving a pipeline in Canadian history.
Outcome
In April 2004, charges were laid concerning this incident but were dismissed in 2007. The dismissal was appealed and the case was reconsidered in 2011.
Warren Bitulithic Limited pled guilty to one charge under the Technical Standards and Safety Act in 2006. The charge was for damaging a natural gas pipeline without permission. The company was fined $225 000.
Enbridge pled guilty to one charge under the Ontario Occupational Health and Safety Act and fined $350 000. They also pled guilty to another charge under the Technical Standards and Safety Act, requiring Enbridge to pay another $350 000 fine. The charges were for not evacuating gas services and not locating and marking the gas services before excavation. Four additional charges placed against Enbridge were withdrawn. Precision Utility pled guilty and was fined $200 000 for not properly supervising an employee while they were locating the natural gas lines. An investigation by the Ministry of Labour found that the Precision employee did not use locate the pipelines by using available information and did not act when they should have noticed the presence of natural gas. Each fine included a victim surcharge where an additional 25% of their fines would be paid to help the victims of this incident.
By 2011 townhouses had been built on the site of the explosion. Milano’s Pizza, one of the businesses in the strip-mall, reopened across the street.
Peter Roy, the son of Elizabeth Roy, campaigned for gas companies to regularly install excess flow valves on pipelines to protect against runaway gas and high flow rates. He reported that Enbridge has begun doing this on their projects. Volunteers also established a scholarship for a student attending Humber College who is going to have a job in the gas sector.
Five years after the explosion, a memorial plaque, garden and two benches were placed at the site of the explosion during a memorial service. The service was organised by then-Toronto City Councillor Peter Milczyn.
See also
List of pipeline accidents
References
Etobicoke gas explosion
Disasters in Ontario
Explosions in Canada
Etobicoke gas explosion
Etobicoke
Gas explosions
Etobicoke gas explosion
Etobicoke gas explosion
Energy accidents and incidents in Canada | 2003 Etobicoke gas explosion | Chemistry | 830 |
8,380,557 | https://en.wikipedia.org/wiki/Reagent%20testing | Reagent testing is one of the processes used to identify substances contained within a pill, usually illicit substances.
With the increased prevalence of drugs being available in their pure forms, the terms "drug checking" or "pill testing" may also be used, although these terms usually refer to testing with a wider variety of techniques covered by drug checking.
Reagent testing notes
A test is done by taking a small scraping from a pill and placing it in the reagent testing liquid or dropping the reagent onto the scraping. The liquid will change colour when reacting with different chemicals to indicate the presence of certain substances.
Testing with a reagent kit does not indicate the pill is safe. While the testing process does show some particular substances are present, it may not show a harmful substance that is also present and unaccounted for by the testing process. Some substances that cause strong colour changes can also mask the presence of other substances that cause weaker colour changes. Thin layer chromatography is used with reagent testing to separate substances before testing and prevent this "masking" effect.
Ehrlich reagent can only detect drugs with an indole moiety, but this is useful because drugs from the NBOMe class do not have an indole and are often sold as LSD which does. The Ehrlich reagent has an additional benefit over other reagents in that it does not react with the paper on which LSD is often distributed.
Reagent tests are often limited to target specific chemicals, and when these substances are mis-sold it is usually by substitution of a different substance in the same chemical family, rendering the test unuseful for consumers. However, reagent tests for chemicals families also exist.
Lacing agents are often used to cut the weight of substances. Some of the most available and non-suspicious cutting agents are reducing sugars: The common dietary monosaccharides galactose, glucose and fructose are all reducing sugars. Sugar is the generic name for sucrose, a disaccharide composed of glucose and fructose.
Availability
As reagent testing has become more popular, vendors have begun to offer a greater range of tests. This increases the likelihood that a substance might have a unique profile of results, making the tests more useful.
Other reagents are discussed in scientific literature, but limited applications mean they may not be sold for consumer testing.
The National Institute of Justice provides information about "Color Test Reagents/Kits for Preliminary Identification
of Drugs of Abuse" in NIJ Standard–0604.01.
Several products are in early phases of development that are intended to allow their users to covertly detect (without using droppers, etc.) date-rape drugs, for instance reusable straws with components that change color in the presence of GHB, Rohypnol, or ketamine – see .
Reliability
Results will vary depending on sample adulteration, quantity, temperature, lighting, exposure to air, storage, as well as reagent quality and degradation. Colorimetric techniques have been developed.
If more than one bottle are open at the same time and the cap are put on the wrong reagent bottle, this may cross-contaminate the reagents and ruin them.
According to a 2003 research published in Pharmacotherapy, neither the Marquis, Mecke, nor Simon's reagents should be used by the public for harm reduction purposes. These agents do not help identify pure MDMA tablets. The research team suggests using gas chromatography-mass spectrometry as the most sensitive and specific testing method for identifying MDMA and its contaminants but this is out of reach for users in most countries and reagent tests remain popular, often distributed by harm-reduction organisations due to their low cost and high utility when multiple test reagents are used.
Legality
USA
Illinois
Home pill testing equipment is illegal in the US state of Illinois where the (720 ILCS 600/) Drug Paraphernalia Control Act specifically outlaws "testing equipment intended to be used unlawfully in a private home for identifying or in analyzing the strength, effectiveness or purity of cannabis or controlled substances;"
Tennessee
Rapid fentanyl test strips are decriminalized in Tennessee. Representative William Lamberth, R-Portland, introduced HB2177 in the Tennessee General Assembly on January 31, 2022, followed by the introduction of SB2427 by Senator Jack Johnson, R-Franklin, the following day. The bill was eventually passed by Governor Bill Lee on March 31. Fentanyl test strips were previously considered drug paraphernalia by Tennessee Code Annotated §39-17-402, which defines terms such as controlled substance and drug paraphernalia in Tennessee state law. Per TCA §39-17-425, possession of fentanyl test strips was previously a Class A misdemeanor, punishable by up to 11 months, 29 days in jail and fines of up to $2,500; distributing them was previously a Class E felony, punishable by prison sentences of one to six years and fines of up to $3,000.
Acid–base reaction
Bases (e.g. sodium bicarbonate) or acids (e.g. citric acid) are sometimes used as cutting agents. An individual base solution and acid solution can help determine if the substance contains an acid or base respectively, if an acid–base reaction will occur.
Alternative consumer solutions
Common cutting agents:
Sugar: Brix refractometers are used to determine sugar content. Traditional handheld refractometers are cheap and can be used to measure whole percentages. Digital handheld refractometers are used to determine percentages in decimal values.
Media
2014 documentary What's In My Baggie? deals with adulterants and additives in recreational drugs.
Largest public accessible database with reagent test results and their sources
See also
Counterfeit medications
Drug checking
Harm reduction
References
Adulteration
Analytical reagents
Chemical tests
Drug culture
Drug safety
Drug testing reagents
Harm reduction | Reagent testing | Chemistry | 1,253 |
34,577,664 | https://en.wikipedia.org/wiki/Phosphoryl%20fluoride | Phosphoryl fluoride (commonly called phosphorus oxyfluoride) is a compound with the chemical formula . It is a colorless gas that hydrolyzes rapidly. It has a critical temperature of 73 °C and a
critical pressure of 4.25 bars.
Synthesis and reactions
Phosphorus oxyfluoride is prepared by partial hydrolysis of phosphorus pentafluoride.
Phosphorus oxyfluoride is the progenitor of the simple fluorophosphoric acids by hydrolysis. The sequence starts with difluorophosphoric acid:
The next steps give monofluorophosphoric acid and phosphoric acid:
Phosphoryl fluoride combines with dimethylamine to produce dimethylaminophosphoryl difluoride and difluorophosphate and hexafluorophosphate ions.
References
Oxyfluorides
Phosphorus oxohalides
Phosphorus(V) compounds | Phosphoryl fluoride | Chemistry | 201 |
3,502,474 | https://en.wikipedia.org/wiki/Miracle%20of%20the%20Sun | The Miracle of the Sun (), also known as the Miracle of Fátima, is a series of events reported to have occurred miraculously on 13 October 1917, attended by a large crowd who had gathered in Fátima, Portugal, in response to a prophecy made by three shepherd children, Lúcia Santos and Francisco and Jacinta Marto. The prophecy was that the Virgin Mary (referred to as Our Lady of Fátima), would appear and perform miracles on that date. Newspapers published testimony from witnesses who said that they had seen extraordinary solar activity, such as the Sun appearing to "dance" or zig-zag in the sky, advance towards the Earth, or emit multicolored light and radiant colors. According to these reports, the event lasted approximately ten minutes.
The local bishop opened a canonical investigation of the event in November 1917, to review witness accounts and assess whether the alleged private revelations from Mary were compatible with Catholic theology. The local priest conducting the investigation was particularly convinced by the concurring testimony of extraordinary solar phenomena from secular reporters, government officials, and other skeptics in attendance. Bishop José da Silva declared the miracle "worthy of belief" on 13 October 1930, permitting "officially the cult of Our Lady of Fatima" within the Catholic Church.
At a gathering on 13 October 1951 at Fátima, the papal legate, Cardinal Federico Tedeschini, told the million people attending that on 30 October, 31 October, 1 November, and 8 November 1950, Pope Pius XII himself witnessed the miracle of the Sun from the Vatican gardens. The early and enduring interest in the miracle and related prophecies has had a significant impact on the devotional practices of many Catholics.
There has been much analysis of the event from critical sociological and scientific perspectives. According to critics, the eyewitness testimony was actually a collection of inconsistent and contradictory accounts. Proposed alternative explanations include witnesses being deceived by their senses due to prolonged staring at the Sun and then seeing something unusual as expected.
Background
In the spring of 1916, three Catholic shepherd children near Fátima reported visions of an angel. Beginning in May 1917, they also experienced apparitions of the Virgin Mary, whom they called the Lady of the Rosary. The children claimed the Lady prophesied that prayer would bring an end to the Great War, and that on 13 October that year, she would reveal her identity and perform a miracle "so that all may believe." Newspapers reported the prophecies, and many pilgrims began visiting the area. The children's accounts were deeply controversial, drawing intense criticism from both local secular and religious authorities. A provisional administrator briefly took the children into custody, believing the prophecies were politically motivated in opposition to the officially secular First Portuguese Republic established in 1910.
The event
Various claims have been made regarding the events that transpired. Many witnesses reported that after a period of rain, the dark clouds parted, revealing the Sun as an opaque, spinning disc in the sky. It was described as being significantly duller than usual, casting multicolored lights across the landscape, the people, and the surrounding clouds. The Sun was then reported to have careered towards the Earth before zig-zagging back to its normal position. Witnesses reported that their previously wet clothes became "suddenly and completely dry, as well as the wet and muddy ground that had been previously soaked because of the rain that had been falling". Not all witnesses reported seeing the Sun "dance". Some people only saw the radiant colors. A number of people (thousands according to some sources) saw nothing.
Skeptic Brian Dunning commented on an image commonly mistaken for a photograph of the Sun taken at Fatima: "An old black and white photograph of the actual sun miracle event shows a lot of dark rain clouds behind some trees and the sun poking through. There is certainly nothing in the photograph that looks unusual, but of course a photograph is static. Whatever the crowd saw was not interesting enough to be noticeable in a photograph". The photograph, originally published in 1951 by was subsequently determined to have been taken approximately eight years later in a different Portugal town of a different solar phenomenon. The misattributed image, however, continues to circulate on the internet.
The three children (Lúcia dos Santos and her cousins Jacinta and Francisco Marto) who originally claimed to have seen Our Lady of Fátima also reported seeing a panorama of visions, including those of Jesus, Our Lady of Sorrows, Our Lady of Mount Carmel, and Saint Joseph blessing the people. In the fourth edition of her memoirs, written in 1941, Lúcia said that on the occasion of their third visit to the Cova da Iria, on 13 July 1917, she asked the Lady to tell them who she was, and to perform a miracle so that everyone would believe. The Lady told her that they should continue to come to the Cova each month until October, when the requested miracle would occur.
De Marchi accounts
Descriptions of the events reported at Fátima were collected by Father John De Marchi, an Italian Catholic priest and researcher. De Marchi spent seven years in Fátima, from 1943 to 1950, conducting research and interviewing the principals at length. In The Immaculate Heart (1952), De Marchi reported that, "[t]heir ranks (those present on 13 October) included believers and non-believers, pious old ladies and scoffing young men. Hundreds, from these mixed categories, have given formal testimony. Reports do vary; impressions are in minor details confused, but none to our knowledge has directly denied the visible prodigy of the sun."
De Marchi authored several books on the subject, such as The True Story of Fátima. They include a number of witness descriptions:
"The sun, at one moment surrounded with scarlet flame, at another aureoled in yellow and deep purple, seemed to be in an exceedingly swift and whirling movement, at times appearing to be loosened from the sky and to be approaching the earth, strongly radiating heat." — Domingos Pinto Coelho, writing for the Catholic newspaper Ordem.
"The silver sun, enveloped in the same gauzy grey light, was seen to whirl and turn in the circle of broken clouds[.. The light turned a beautiful blue, as if it had come through the stained-glass windows of a cathedral, and spread itself over the people who knelt with outstretched hands[...] people wept and prayed with uncovered heads, in the presence of a miracle they had awaited. The seconds seemed like hours, so vivid were they." — Reporter for the Lisbon newspaper .
"The sun's disc did not remain immobile. This was not the sparkling of a heavenly body, for it spun round on itself in a mad whirl when suddenly a clamor was heard from all the people. The sun, whirling, seemed to loosen itself from the firmament and advance threateningly upon the earth as if to crush us with its huge fiery weight. The sensation during those moments was terrible." — De Marchi attributes this description to Almeida Garrett, Professor of Natural Sciences at Coimbra University. Theologian Father Stanley L. Jaki wrote that it was actually given by José Almeida Garrett, a young lawyer, and is often mistakenly attributed to his father, a professor of natural sciences at the University of Coimbra, named Gonçalo de Almeida Garrett.
"As if like a bolt from the blue, the clouds were wrenched apart, and the sun at its zenith appeared in all its splendor. It began to revolve vertiginously on its axis, like the most magnificent firewheel that could be imagined, taking on all the colors of the rainbow and sending forth multicolored flashes of light, producing the most astounding effect. This sublime and incomparable spectacle, which was repeated three distinct times, lasted for about ten minutes. The immense multitude, overcome by the evidence of such a tremendous prodigy, threw themselves on their knees." — Manuel Formigão, a professor at the seminary at Santarém, and a priest.
"I feel incapable of describing what I saw. I looked fixedly at the sun, which seemed pale and did not hurt my eyes. Looking like a ball of snow, revolving on itself, it suddenly seemed to come down in a zig-zag, menacing the earth. Terrified, I ran and hid myself among the people, who were weeping and expecting the end of the world at any moment." — Rev. Joaquim Lourenço, describing his boyhood experience in Alburitel, from Fátima.
"On that day of October 13, 1917, without remembering the predictions of the children, I was enchanted by a remarkable spectacle in the sky of a kind I had never seen before. I saw it from this veranda" — Portuguese poet Afonso Lopes Vieira.
De Marchi also drew on the newspaper account written by Avelino de Almeida, a journalist sent by the newspaper , who described in detail the reactions of the crowd.
Catholic Church recognition
The event was declared of "supernatural character" by the Catholic Church in 1930. A shrine was built near the site in Fátima, which has been attended by thousands of faithful.
Pope Pius XII approved the "Fatima apparitions" in 1940. Four times during the week that he declared the dogma of the Assumption of Mary (33 years after the actual event said to have occurred in Fátima), Pope Pius XII claimed to have witnessed the same "Miracle of the Sun". At 4:00p.m. on 30 October 1950, during a walk in the Vatican gardens, he arrived at the statue of Our Lady of Lourdes and began to see the miracle. He described himself in handwritten notes as "awestruck." He saw the same miracle on 31 October, again on 1 November (the date of the definition of the dogma) and then again on 8 November. He wrote that on other days at about the same time he tried to see if he could observe the Miracle of the Sun, but was unable to. He confided this information to a number of Vatican cardinals, to Sr. Pascalina Lehnert (the nun in charge of the papal apartments and his secretary) and finally to handwritten notes (discovered in 2008) that were later placed on display at the Vatican.
In 2017, Pope Francis approved the recognition of a miracle involving two of the children involved in the Fátima event, Francisco and Jacinta Marto, which paved the way for their canonization.
Believers' explanations
Within Catholicism, the event is seen as the fulfillment of a promise by Mary, mother of Jesus, to the shepherd children who said she appeared to them several times before 13 October 1917. According to the children's accounts, Mary, referred to as the "Lady of Fátima", promised them she would perform a miracle to show people they were telling the truth, and so caused the crowds to see the Sun make "incredible" movements in the sky. Catholics have regarded Mary as a powerful "miracle worker" for centuries, and this view has continued into the present. Various theologians and apologetic scientists have discussed the limits of scientific explanations for the event and proposed possible mechanisms through which divine intervention caused the solar phenomenon.
Fr Andrew Pinsent, research director of the Ian Ramsey Centre for Science and Religion at Oxford University, states that "a scientific perspective does not rule out miracles, and the event at Fatima is, in the view of many, particularly credible." He states that a usual prejudice involves a lack of understanding of the scope of scientific laws, which merely describe how natural systems behave isolated from free agents. Concluding that the event is "a public miracle of the most extraordinary kind and credibility", he sees the year of the event, as connected to significant historical milestones that call for Fátima's message of repentance: Protestantism in 1517, Freemasonry in 1717 and atheistic Communism in 1917.
Theologian, physicist, and priest Stanley L. Jaki, concurs, concluding that by divine intervention, a coordinated interplay of natural meteorological events, an enhancement of air lens with ice crystals, was made to occur at the exact time predicted, and this is the essence of the miracle.
Jaki described the phenomenon:
According to Jaki, the faithful should believe that a miracle occurred at Fátima, and "those who stake their purpose in life on Christ as the greatest and incomparably miraculous fact of history", need to pay attention to facts that support miracles.
De Marchi believed related miraculous phenomena, such as the Sun's effect on standing water from heavy rains that immediately preceded the event, to be genuine. According to De Marchi, "...engineers that have studied the case reckoned that an incredible amount of energy would have been necessary to dry up those pools of water that had formed on the field in a few minutes as it was reported by witnesses." De Marchi wrote that the prediction of an unspecified "miracle", the abrupt beginning and end of the event, the varied religious backgrounds of the observers, the sheer numbers of people present, reports of sightings by people up to away, and the lack of any known scientific causative factor make a mass hallucination or mass hysteria unlikely. De Marchi concludes that "given the indubitable reference to God, and the general context of the story, it seems that we must attribute to Him alone the most obvious and colossal miracle of history."
Leo Madigan, a former psychiatric nurse and local journalist at Fátima in the late 20th century, also dismisses suggestions from critics of mass hypnosis, and believes that astonishment, fear, exaltation and the spiritual nature of the phenomenon explain any inconsistency of witnesses descriptions. Madigan wrote that what people saw was "the reflection of the Lady's own light projected on the Sun itself".
Philippe Dalleur, a priest and faculty philosophy at the Pontificial University of the Holy Cross in Rome, studied photographs of the crowd taken by "O Século" photographer Judah Ruah. In his analysis of shadows, Dalleur states there are two light sources, one being the "silver sun" described by witnesses – but at the wrong elevation to be the Sun. He states that testimonies of witnesses who observed the phenomenon from a distance place the "silver sun" neither at the azimuth of the real Sun, nor at any fixed azimuth – but invariably at the direction of Fatima, concluding that the "silver sun" was a real luminous object over Fatima.
Skeptical explanations
Theologians, scientists and skeptics have responded to claims that conflict with established scientific knowledge regarding the behavior of the Sun. Science writer Benjamin Radford points out that "The sun did not really dance in the sky. We know this because, of course, everyone on Earth is under the same sun, and if the closest lying star to us suddenly began doing celestial gymnastics a few billion other people would surely have reported it". Radford wrote that psychological factors such as the power of suggestion and pareidolia can better explain the reported events. According to Radford, "No one suggests that those who reported seeing the Miracle of the Sun—or any other miracles at Fátima or elsewhere—are lying or hoaxing. Instead, they very likely experienced what they claimed to, though that experience took place mostly in their minds." Regarding claims of miraculous drying up of rain water, Radford wrote "it's not clear precisely what the weather was at the time of the miracle", and photography from the time of the event does not show that it had been raining as much or as long as was reported.
In The Evidence for Visions of the Virgin Mary (1983), former editor of the ASSAP's journal, Kevin McClure, whose intention in the book was to approach Marian apparition events in a sufficiently objective format for the reader "to make an independent decision as to what the visions may mean, and whence they may have come," wrote that "these events remain confusing and mystifying," and that the phenomenon is unique when compared to other abnormal events such as UFO sightings. He wrote that one is "not to say that a miraculous, stupendous, incomprehensible event did not occur" while looking for possible explanations. In reference to the accounts of the Miracle of the Sun phenomena, McClure writes that "the accounts of the miracle, of the dance of the sun', are simply not consistent”. McClure remarks that perception and memory becoming uncertain during an incomprehensible event is not surprising, but that the contradictions in the accounts must raise some doubts towards the objective nature of what was seen. While McClure is often misquoted in purportedly stating that he had never seen such a collection of contradictory accounts of a case in any of the research that he had done in the previous ten years, he was specifically referring to accounts of the alleged Marian apparitions that the three children witnessed, not the accounts of the Miracle of the Sun phenomena itself, when making such a claim.
According to professor of religion Lisa J. Schwebel, claims of the miracle present a number of difficulties. Schwebel states, "Not only did all those present not see the phenomenon, but also there are considerable inconsistencies among witnesses as to what they did see". Schwebel also observes that there is no authentic photo of the solar phenomena claimed, "despite the presence of hundreds of reporters and photographers at the field", and one photo often presented as authentic is actually "a solar eclipse in another part of the world taken sometime before 1917". There is some evidence to the effect that the miracle was expected by witnesses. The witness Joaquim Gregório Tavares, who was present at Fátima on 13 October, states, "We must declare that, although we admit the possibility of some miraculous fact, we were there while having in mind conversations we had earlier with cool-headed persons who were anticipating some changes of colour in the Sun". The villagers in Alburitel were preparing for a Sun miracle too. According to Maria do Carmo, "It was anticipated that the miracle would involve the stars". This is likely because in the months of July, August and September people at Fátima claimed the Sun's light dimmed and the sky became dark enough for stars to become visible. This was denied too by many witnesses from the previous months. She also states that on the morning of October 13, "the people of Alburitel were darkening bits of glass by exposing them to candle-smoke so that they might watch the Sun, with no harm to their eyes."
Supernatural explanations, such as those by Father Pio Scatizzi, who argues that observers in Fátima could not be collectively deceived, or that the effect was not seen by observatories in distant places because of divine intervention have been dismissed by critics who say those taking part in the event could certainly be deceived by their senses, or they could have experienced a localized, natural phenomenon. According to Benjamin Radford, "It is of course dangerous to stare directly at the sun, and to avoid permanently damaging their eyesight, those at Fátima that day were looking up in the sky around the sun, which, if you do it long enough, can give the illusion of the sun moving as the eye muscles tire." Others, such as professor of physics Auguste Meessen, suggest that optical effects created by the human eye can account for the reported phenomenon. Meessen presented his analysis of apparitions and "Miracles of the Sun" at the International Symposium "Science, Religion and Conscience" in 2003. While Meessen felt those who claim to have experienced miracles were "honestly experiencing what they report", he stated Sun miracles cannot be taken at face value and that the reported observations were optical effects caused by prolonged staring at the Sun. Meessen contends that retinal after-images produced after brief periods of Sun gazing are a likely cause of the observed dancing effects. Similarly, Meessen concluded that the color changes witnessed were most likely caused by the bleaching of photosensitive retinal cells. Shortly after the miracle, the Catholic lawyer named Coelho said in his article that a few days later, he saw the exact same motions and colour changes in the Sun as he did on 13 October. He says, "One doubt remained with us however. Was what we saw in the Sun an exceptional thing? Or could it be reproduced in analogous circumstances? Now it was precisely this analogy of circumstances that presented itself to us yesterday. We could see the Sun half overcast as on Saturday. And sincerely, we saw on that day the same succession of colors, the same rotary movement, etc."
Meessen observes that Sun Miracles have been witnessed in many places where religiously charged pilgrims have been encouraged to stare at the Sun. He cites the apparitions at Heroldsbach, Germany (1949) as an example, where many people within a crowd of over 10,000 testified to witnessing similar observations as at Fátima. Meessen also cites a British Journal of Ophthalmology article that discusses some modern examples of Sun Miracles. Prof. Stöckl, a meteorologist from Regensburg, also proposed a similar theory and made similar observations.
Critics also suggest that a combination of clouds, atmospheric effects and natural sunlight could have created the reported visual phenomena. Steuart Campbell, writing for the edition of Journal of Meteorology in 1989, postulated that a cloud of stratospheric dust changed the appearance of the Sun on 13 October, making it easy to look at, and causing it to to be yellow, blue, and violet, and to spin. In support of his hypothesis, Campbell reported that a blue and reddened Sun was reported in China as documented in 1983. Paul Simons, in an article entitled "Weather Secrets of Miracle at Fátima", stated that it is possible that some of the optical effects at Fátima may have been caused by a cloud of dust from the Sahara.
Skeptical investigator Joe Nickell wrote that the "dancing sun" effects reported at Fátima were "a combination of factors, including optical effects and meteorological phenomena, such as the sun being seen through thin clouds, causing it to appear as a silver disc. Other possibilities include an alteration in the density of the passing clouds, causing the sun's image to alternately brighten and dim and so seem to advance and recede, and dust or moisture droplets in the atmosphere refracting the sunlight and thus imparting a variety of colors". Nickell also suggests that unusual visual effects could have resulted from temporary retinal distortion caused by staring at the intense light of the Sun, or have been caused by a sundog, a relatively common atmospheric optical phenomenon. Nickell also highlights the psychological suggestibility of the witnesses, noting that devout spectators often come to locations where Marian apparitions have been reported "fully expecting some miraculous event", such as the 1988 Lubbock apparition of Mary in Texas, the Mother Cabrini Shrine near Denver, Colorado, in 1992, and Conyers, Georgia, in the early to mid-1990s.
See also
Marian apparition
The Miracle of Our Lady of Fatima, 1952 film
Fatima, 2020 film
References
Bibliography
(Online Text)
External links
Newspaper article in Portuguese that came out shortly after the alleged miracle.
Picture of the Sun during the alleged miracle. (archive)
Phil Plait "When self-fulfilling prophecies Knock"
BBC News article on Sun miracles at Knock
Fátima in Sister Lucia's own words – Free online version of the memoir book written by Lucia dos Santos, OCD
The True Story of Fatima – Free online version of the book written by Father John de Marchi, IMC
The Fatima Message books and documents
Christian miracles
Our Lady of Fátima
1917 in Portugal
Solar phenomena
20th-century Catholicism
1917 in Christianity
October 1917
Saint Joseph (husband of Mary)
Catholicism-related controversies
Wikipedia articles containing unlinked shortened footnotes | Miracle of the Sun | Physics | 4,923 |
2,649,255 | https://en.wikipedia.org/wiki/Xi1%20Sagittarii | {{DISPLAYTITLE:Xi1 Sagittarii}}
Xi1 Sagittarii (ξ1 Sagittarii) is a solitary, blue-white hued star in the zodiac constellation of Sagittarius. It is visible to the naked eye with an apparent visual magnitude of +5.06. Based upon a small annual parallax shift of 1.58 mas as seen from Earth, this system is located roughly 2,100 light years from the Sun.
This is a massive supergiant star with a stellar classification of B9/A0 Ib. With an estimated 7.8 times the mass of the Sun and an age of about 40 million years it has depleted the hydrogen at its core, causing it to expand to about 15 times the Sun's radius. It is radiating 2,753 times the Sun's luminosity from its photosphere at an effective temperature of about 9,400 K.
References
B-type supergiants
Sagittarii, Xi
Sagittarius (constellation)
Durchmusterung objects
Sagittarii, 36
175687
093057
7145 | Xi1 Sagittarii | Astronomy | 235 |
38,442,004 | https://en.wikipedia.org/wiki/Shuttle%20train | A shuttle train is a train that runs back and forth between two points, especially if it offers a frequent service over a short route. Shuttle trains are used in various ways, in various parts of the world. They commonly operate as a fixed consist, and run non-stop between their termini. They can be used to carry passengers, freight, or both.
Examples
Airport shuttle trains
An airport shuttle train may run between an airport and some other location, or connect two or more terminals. The second is usually in the form of a driverless people mover.
Italy
A shuttle train connects Galileo Galilei Airport in Pisa with Pisa Central railway station. It operates daily and takes five minutes.
United Kingdom
The Gatwick Airport Shuttle Transit is a people mover used to transfer passengers between the North and South Terminals at London Gatwick Airport. It runs every few minutes 24 hours a day, and the journey takes two minutes.
Car shuttle trains
A car shuttle train is used to transport accompanied automobiles, and usually also other types of road vehicles, for a relatively short distance. Car shuttle trains usually operate on lines passing through a rail tunnel and connecting two places not easily accessible to each other by road. On car shuttle train services, the occupants of the road vehicles being carried on the train usually stay with their vehicle throughout the rail journey.
Commuter shuttle trains
A shuttle train may be used to carry commuters, especially if at least one of the shuttle train's termini is an interchange station.
Japan
During the morning rush hour, the Aichi Loop Line shuttle train runs over the Aichi Loop Line between Mikawa-Toyota Station and Shin-Toyota Station in Toyota, Aichi Prefecture, Japan.
The northeastern end of the Tokyo Metro Chiyoda Line is single-tracked although the depot line runs in parallel. Trains serving the terminus are shuttles to the penultimate stop, Ayase.
The first section of the Fukutoshin Line of the Tokyo Metro was named the 'New Line', with shuttle trains running express in parallel with the Yurakucho Line, between the Ikebukuro and Kotake-mukaihara stations.
New Zealand
A diesel shuttle train runs between Papakura and Pukekohe on the Southern Line in Auckland, New Zealand as this section of the line has not yet been electrified. Battery powered EMUs have been ordered and will replace the ADL/ADC class DMU shuttle in 2019.
United States
There are three shuttle services in the New York City Subway, as well as several other non-shuttle services cut back to shuttle portions during overnights. However, of these services, only the 42nd Street Shuttle is a true shuttle that stops only at two locations. Five shuttle services were formerly run in the subway.
The Yellow Line on the Chicago "L" originally ran as a nonstop shuttle from Dempster Street in Skokie to Howard Street in Chicago, offering connections to the Red and Purple Lines. In 2012, an infill station opened on Oakton Street, no longer making the Yellow Line a true shuttle.
NJ Transit's Princeton Branch, or "dinky", is a shuttle line.
Unit trains that are dedicated to move on a regular basis between origin and destination are known as shuttle trains by the Union Pacific Railroad and the BNSF Railway
Others
Austria
The National Intermodal Network Austria, operated by Rail Cargo Austria, uses a hub-and-spoke system of shuttle trains to provide overnight links between the highest volume intermodal freight terminals in Austria. The hub of the network is located at Wels.
Bangladesh
The Chattogram University shuttle train is operated by Bangladesh Railway eastern division and monitored by university authority. Trains leave Chattogram railway station and Sholoshohor railway station, and city-bound trains leave Chattogram University railway station.
Hong Kong
The MTR Disneyland Resort line is a themed shuttle line linking the Hong Kong Disneyland Resort with the rest of the network. Another shuttle train runs between the Tseung Kwan O and LOHAS Park stations, on a spur serving a new residential development.
Spain
The R line, part of the Madrid subway, is a shuttle line connecting Ópera station (lines 2 and 5) with Príncipe Pío station (lines 6 and 10), which is also connected to Renfe commuter rail lines.
Switzerland
The Zermatt shuttle connects the mountaineering and ski resort of Zermatt (which has no road access) with nearby Täsch, where people travelling to and from Zermatt by motor vehicles are required to park their cars. For the better part of most days, the service operates every 20 min and takes 12 min.
United Kingdom
The Waterloo and City Line on the London Underground runs between Waterloo and Bank in the city.
The Slough to Windsor & Eton Line runs between and .
The Butetown Branch Line runs between Cardiff Queen Street and Cardiff Bay.
The Stourbridge Town Branch Line runs between Stourbridge Junction and Stourbridge Town
China
The Line 6 of the Suzhou Rail Transit running a shuttle service between Nanxiebu to Sangtiandao.
See also
Express train
High-speed rail
Luxury train
Shuttle bus
References
Trains
Rail transport articles in need of updating | Shuttle train | Technology | 1,050 |
30,984,143 | https://en.wikipedia.org/wiki/Attack%20Surface%20Analyzer | Attack Surface Analyzer was a tool created for the analysis of changes made to the attack surface of the operating systems since Windows Vista and beyond. It was a tool recommended by Microsoft in its SDL guidelines in the verification stage of the development.
History
According to the Microsoft SDL Team, they did not have an all in one tool for checking the changes made to the attack surface of Windows Operating System before Attack Surface Analyzer was developed. It was a problem to check and verify the effects of various software installations on the system way back since Windows Server 2003 was being developed. Back then they had to use multiple tools for every type of change made to the attack surface. It was a painful process when they had to check for everything again and again and using multiple tools.
It was this problem that made Microsoft create an application with which developers could analyze the changes made to the Windows Attack Surface. It has at first been used by the developers at Microsoft. Later, on January 18, 2011, a beta version (version 5.1.3.0) of a tool named Attack Surface Analyzer was released in public for the testers and IT administrators. Attack Surface Analyzer can compare two scan data of a system called the baseline scan and product scan. Both 32-bit and 64-bit versions of software are available for Windows Vista and Windows 7 (and respective Server editions). There is no news about a Windows XP version being released.
Features
Analysis of Different Threat Categories
Attack Surface Analyzer is all in one tool for analysis of changes made to the various parts of the attack surface of Windows 6 series Operating System (includes Windows Vista and Windows 7). Using this one tool, you can analyze the changes made to the Registry, File permissions, Windows IIS Server, GAC assemblies and a lot more can be done. According to Microsoft, it is the same tool in use by the engineers of the security team at Microsoft to analyze the effects of software installation on the Windows Operating System.
It would not have been possible when there was no all in one tool. You would have had to use different software for all the different parts of Windows and then combine the effects logically by yourself. The tool enlists the various elements it enumerates while running a system scan. The elements are:
files
registry keys
memory information
windows
Windows firewall
GAC Assemblies
network shares
Logon sessions
ports
named pipes
autorun tasks
RPC endpoints
processes
threads
desktops
handles
Microsoft Internet Information Services Server
The above list is a comprehensive set of elements that are both possible as well as important elements that can be changed when new software is installed on the system. While some software might change only a few elements in the list, some other can change a few more and different elements on the system. Attack Surface Analyzer combines all of them so that it is easier to analyze all parts.
Enlisting Threats
While Attack Surface Analyzer can tell you the changes for sure, in some cases, it will also be able to tell you that a particular change in the configuration is causing a threat. As of now, the tool does not enlist the threats in all the categories (or parts of the Operating System) it scans but only a few, the most noticeable of which are the issues in services configurations, File system ACLs and issues related to the processes running on the system.
Determining Threat Severity
Getting the list of threats to the system is a great thing when you have it from software released by Microsoft itself. After all, no one knows Windows better than Microsoft. With the improved concerns over security shown by Microsoft, it is important that the severity of a threat is also known to the IT team of an enterprise. The Attack Surface Analyzer also shows the severity of the threats that it finds. However, it seems not to report the severity of each and every threat. Instead it shows the severity of the threat by its category. For example, the severity of threat caused by “Executables With Weak ACLs” (threat severity of level 1) is less than that caused by “Processes With Impersonation Tokens” (threat severity of level 2). It is surely a desirable feature to enlist the level of severity caused by each threat rather by the category to which it belongs. There however, is no news about when that might be available.
Built in Help
Every organization has its experts on various domains of security. There may be a case when a network security expert in an organization is not aware of the details and terminology of some other domain (say Windows Services). However, the two issues may be connected to each other. While it is not possible (and in some case not important) for the experts of two security expert teams to know everything about the terms in use by each other, it might be required in a few cases. A brief description (along with a link to technet library describing the term in detail) of all threats and changes to the attack surface are enlisted in the report generated by the Attack Surface Analyzer. While the brief description is usually enough for the experts, it might be needed in other cases. Microsoft has made it easy to find the right resource for the term rather than relying upon the web search engines.
Organization of Changes made to the Attack Surface
Attack Surface of Windows Operating System concerns various parts of the Operating System. It would have been difficult for anyone to understand the report if all of the changes were listed in serial order. Attack Surface Analyzer makes it easy for the user to browse through the report by listing the threats in categories and providing a Table of contents in an HTML page.
Report Generation
Attack Surface Analyzer can compare two scan data (generated by itself on two different scans) and generate a report, which can then be viewed in the HTML format. It is also possible to run the scans on one system and then generate on another system using the same tool. This is good for Windows Vista Clients because it is not possible to generate report using the current version of Attack Surface Analyzer on Windows Vista. In such a case, Attack Surface Analyzer can be used to run scans on the Windows Vista Client, transfer the scan result files to a computer running Windows 7 and then generate and browse the report on the Windows 7 based computer.
System Requirements
Attack Surface Analyzer works on the Windows 6.X series of Operating Systems but report generation can only be done on 6.1 version Operating Systems. Following are the system requirements of Attack Surface Analyzer (from the official download page):
Installable on: Windows Vista, Windows 7, Windows Server 2008 and Windows Server 2008 R2
Collection of Attack Surface Data: Windows Vista, Windows 7, Windows Server 2008 and Windows Server 2008 R2
Analysis of Attack Surface data and report generation: Windows 7 or Windows Server 2008 R2 with Microsoft .Net 3.5 SP1
Microsoft has not enlisted any hardware requirements separately. The tool should be able to perform its job on any machine meeting the hardware requirements of the installed Operating System. Note, however, that the running time for generation of scan data and report depends on the hardware capabilities (better hardware would get the work done faster).
Scans
Attack Surface Analyzer list two types of scans namely baseline scan and product scan. In strict technical terms both the scans are same. The difference between them is logical, not technical.
Baseline Scan
This is the scan run that the user will run to generate the data on the initial system. This data is then compared with the product scan. After running the baseline scan, the product whose effect on the attack surface of the Operating System is to be checked is installed. The installation changes the system configuration (possibly) by installing services, changing firewall rules, installing new .NET assemblies and so on. Baseline scan is a logical scan run by the user using Attack Surface Analyzer that generates the file containing the configuration of the system before this software is installed.
Product Scan
Product scan signifies the state of the system after the ‘product’ was installed. In this context, the product is the software whose effects on the system upon installation are to be checked. To generate a report, two scans are required in minimum. The product scan would capture the changes made to the system by the installation of the software product under testing. The scan data generated in this scan is compared with the baseline scan data to find the changes made to the system configurations on different points. It is worth a note that more than one system state can be captured using Attack Surface Analyzer and any combination of them can be used for the report generation. However the ‘Baseline Scan’ should be the one that was taken before the other. The other can automatically be called as the product scan.
See also
Attack Surface
Security Development Lifecycle
Software Verification
External links
Download Attack Surface Analyzer
Attack Surface Analyzer Unofficial FAQ
Microsoft's Attack Surface Analyzer sheds light on software vulnerabilities
How to analyze attack surface using Attack Surface Analyzer?
Attack Surface Analyzer for Windows 7
Software giant introduces technology and consulting for application security
Vulnerabilities and Attack Surface
The Trustworthy Computing Security Development Lifecycle (MSDN Article)
References
Computer security software
Microsoft software
Year of introduction missing | Attack Surface Analyzer | Engineering | 1,843 |
2,099,428 | https://en.wikipedia.org/wiki/Saprobiont | Saprobionts are organisms that digest their food externally and then absorb the products. This process is called saprotrophic nutrition. Fungi are examples of saprobiontic organisms, which are a type of decomposer.
Saprobiontic organisms feed off dead and/or decaying biological materials. Digestion is accomplished by excretion of digestive enzymes which break down cell tissues, allowing saprobionts to extract the nutrients they need while leaving the indigestible waste. This is called extracellular digestion. This is very important in ecosystems, for the nutrient cycle.
Saprobionts should not be confused with detritivores, another class of decomposers which digest internally.
These organisms can be good sources of extracellular enzymes for industrial processes such as the production of fruit juice. For instance, the fungus Aspergillus niger is used to produce pectinase, an enzyme which is used to break down pectin in juice concentrates, making the juice appear more translucent.
References
Ecology
Dead wood | Saprobiont | Biology | 217 |
7,048,926 | https://en.wikipedia.org/wiki/Negative-bias%20temperature%20instability | Negative-bias temperature instability (NBTI) is a key reliability issue in MOSFETs, a type of transistor aging. NBTI manifests as an increase in the threshold voltage and consequent decrease in drain current and transconductance of a MOSFET. The degradation is often approximated by a power-law dependence on time. It is of immediate concern in p-channel MOS devices (pMOS), since they almost always operate with negative gate-to-source voltage; however, the very same mechanism also affects nMOS transistors when biased in the accumulation regime, i.e. with a negative bias applied to the gate.
More specifically, over time positive charges become trapped at the oxide-semiconductor boundary underneath the gate of a MOSFET. These positive charges partially cancel the negative gate voltage without contributing to conduction through the channel as electron holes in the semiconductor are supposed to. When the gate voltage is removed, the trapped charges dissipate over a time scale of milliseconds to hours. The problem has become more acute as transistors have shrunk, as there is less averaging of the effect over a large gate area. Thus, different transistors experience different amounts of NBTI, defeating standard circuit design techniques for tolerating manufacturing variability which depend on the close matching of adjacent transistors.
NBTI has become significant for portable electronics because it interacts badly with two common power-saving techniques: reduced operating voltages and clock gating. With lower operating voltages, the NBTI-induced threshold voltage change is a larger fraction of the logic voltage and disrupts operations. When a clock is gated off, transistors stop switching and NBTI effects accumulate much more rapidly. When the clock is re-enabled, the transistor thresholds have changed and the circuit may not operate. Some low-power designs switch to a low-frequency clock rather than stopping completely in order to mitigate NBTI effects.
Physics
The details of the mechanisms of NBTI have been debated, but two effects are believed to contribute: trapping of positively charged holes, and generation of interface states.
preexisting traps located in the bulk of the dielectric are filled with holes coming from the channel of pMOS. Those traps can be emptied when the stress voltage is removed, so that the Vth degradation can be recovered over time.
interface traps are generated, and these interface states become positively charged when the pMOS device is biased in the "on" state, i.e. with negative gate voltage. Some interface states may become deactivated when the stress is removed, so that the Vth degradation can be recovered over time.
The existence of two coexisting mechanisms has resulted in scientific controversy over the relative importance of each component, and over the mechanism of generation and recovery of interface states.
In sub-micrometer devices nitrogen is incorporated into the silicon gate oxide to reduce the gate leakage current density and prevent boron penetration. It is known that incorporating nitrogen enhances NBTI. For new technologies (45 nm and shorter nominal channel lengths), high-κ metal gate stacks are used as an alternative to improve the gate current density for a given equivalent oxide thickness (EOT). Even with the introduction of new materials like hafnium oxide in the gate stack, NBTI remains and is often exacerbated by additional charge trapping in the high-κ layer.
With the introduction of high κ metal gates, a new degradation mechanism has become more important, referred to as PBTI (for positive bias temperature instabilities), which affects nMOS transistor when positively biased. In this case, no interface states are generated and 100% of the Vth degradation may be recovered.
See also
Hot carrier injection
Electromigration
References
J.H. Stathis, S. Mahapatra, and T. Grasser, “Controversial issues in negative bias temperature instability”, Microelectronics Reliability, vol 81, pp. 244–251, Feb. 2018.
T. Grasser et al., “The paradigm shift in understanding the bias temperature instability: From reaction–diffusion to switching oxide traps”, IEEE Transactions on Electron Devices 58 (11), pp. 3652–3666, Nov. 2011.
D.K. Schroder, “Negative bias temperature instability: What do we understand?”, Microelectronics Reliability, vol. 47, no. 6, pp. 841–852, June 2007.
JH Stathis and S Zafar, “The negative bias temperature instability in MOS devices: A review”, Microelectronics Reliability, vol 46, no. 2, pp. 278–286, Feb. 2006.
M. Alam and S. Mahapatra, “A comprehensive model of PMOS NBTI degradation”, Microelectronics Reliability, vol. 45, no. 1, pp. 71–81, Jan. 2005.
Semiconductor device defects
Semiconductor device fabrication
Electronic engineering
Hardware testing | Negative-bias temperature instability | Materials_science,Technology,Engineering | 1,041 |
2,782,732 | https://en.wikipedia.org/wiki/Phosphoryl%20chloride%20%28data%20page%29 | This page provides supplementary chemical data on phosphoryl chloride.
Material Safety Data Sheets
Aldrich MSDS
Fisher MSDS
Thermodynamic properties
Spectral data
Structure and properties data
References
Chemical data pages
Chemical data pages cleanup | Phosphoryl chloride (data page) | Chemistry | 47 |
3,962,658 | https://en.wikipedia.org/wiki/Salmonella%20virus%20Epsilon15 | Epsilon 15 (or ε15) is a virus, specifically a bacteriophage, known to infect species of Salmonella bacteria including Salmonella anatum. The virus is a short, tailed phage with a double-stranded DNA genome of 39,671 base pairs and 49 open reading frames.
References
Podoviridae | Salmonella virus Epsilon15 | Biology | 70 |
48,707,171 | https://en.wikipedia.org/wiki/Oxy-Cope%20rearrangement | In organic chemistry, the oxy-Cope rearrangement is a chemical reaction. It involves reorganization of the skeleton of certain unsaturated alcohols. It is a variation of the Cope rearrangement in which 1,5-dien-3-ols are converted to unsaturated carbonyl compounds by a mechanism typical for such a [3,3]-sigmatropic rearrangement.
The reaction is highly general: a wide variety of precursors undergo the reorganization predictably and with ease, rendering it a highly useful synthetic tool. Further, production of the required starting material is often straightforward. The modification was first proposed in 1964 by Berson and Jones, who coined the term. The driving force is the formation of a carbonyl via spontaneous keto-enol tautomerization.
Base accelerates the reaction by 1010-1017, the anionic oxy-Cope rearrangement.
The formation of an enolate renders the reaction irreversible in most cases.
History
Sigmatropic rearrangements are useful organic synthesis. In an effort to demonstrate the versatility of the Cope rearrangement by demonstrating its tolerance of an alcohol situated at C-3 of a 1,5-diene, Berson and Jones heated a bicyclic diene alcohol in the gas phase to give cis-∆5,6-octalone in fair yield.
The modification is immensely appealing as a result of the two new disparately placed functional groups that lend themselves well to a variety of previously unavailable synthetic manipulations.
The next development occurred in 1975, when Evans and Golob reported the tremendous rate enhancements by base. Their use of potassium hydride in the cation's corresponding crown ether became the default approach for most applications. Indeed, in some cases, anionic assistance is intentionally forgone to accommodate for the production of overly sensitive enolate product. For example, in the following reaction only tar was obtained, a result that the authors attributed to the product's ostensible intolerance to base. The original oxy-Cope modification thus to this day occupies a relevant niche in synthetic chemistry.
Mechanism
Both the neutral and anionic variants of the oxy-Cope rearrangement may occur via either concerted or stepwise radical pathways, although the former mode is generally favored. The preferred intermediate is characterized by a chair-like conformation. Chirality transfer is effected by a highly ordered transition state. The positioning of the double bonds in the most readily accessible transition state determines the stereochemical course of the reaction A boat transition state is disfavored, but rearrangements occur via this path to an appreciable extent as well, resulting in the production of diastereomeric mixtures.
Steric effects can be significant.
Rearrangements for which a chair transition state is geometrically impossible nonetheless occur. In fact, enolate formation provides enough of a driving force to overcome the energetic barrier associated with both dearomatization and the boat conformer.
The concerted, synchronous pathways presented above generally predominate; it was calculated for anionic oxy-Cope processes that a divide of 17-34 kcal/mol favors heterolysis over homolysis. Several factors may bridge this energetic gap.
The large degree of strain and the presence of a methyl group's bulk favored the (Z)- instead of the expected (E)-cyclooctenone isomer, suggesting that the intermediate is not formed synchronously. Only with fragmentation and subsequent isomerization steps could the observed product be rationalized.
A study on the anionic oxy-Cope rearrangement carried out entirely in the gaseous phase reported that the rate enhancement stems not from solvent interactions, but from those within the structure itself.
Rate enhancement
In general, decreasing the stability of the oxy-Cope or anionic oxy-Cope substrate relative to that of the product results in increased rate of reaction by the principle of ground state destabilization. This desirable outcome is readily achieved in a variety of ways. Ionic interactions between metal and alkoxide are important: dissociative character causes rate acceleration. Use of 15-crown-5 in conjunction with sodium hydride afforded a 1.27-fold rate enhancement over the course of a bicyclic diene alkoxide's sigmatropic conversion to enolate product, while the same reaction with HMPT in 15-crown-5's place did not appreciably affect the rate. The use of potassium hydride in conjunction with 18-crown-6 to achieve the same end afforded a 180-fold maximum rate acceleration. From the above results it was concluded that rate increases as counterions more poorly approximate point charges—and with the addition of counterion-sequestering species.
The inclusion of more polar solvents and catalytic quantities of phase transfer salts has also been demonstrated to exert the same rate-enhancing effect.
Finally, the relief of ring strain over the course of a rearrangement will drive a reaction more forcibly to completion, thereby increasing its rate.
Scope
Because there exist multiple classes of natural products containing eight-membered rings, the syntheses of which having proved difficult, the anionic oxy-Cope rearrangement has been highlighted as a suitable alternative pathway. Its application here offers great stereochemical control, and its use is far more general than the relatively unsuccessful routes that had been employed before its development.
In spite of possible geometrical constraints, the required unsaturated substrates may contain triple bonds in place of either of the double bonds. Such an alkynol was effectively manipulated in the elegant synthesis of both poitediol and dactylol. These interesting sigmatropic rearrangements can occur either with anionic assistance or under thermal conditions.
Of particular interest is the application of the oxy-Cope to situations in which the immediate product reacts further in a predictable manner to furnish a desired final product. This goal was achieved in the synthesis of the cis-hydroazulenone below, in which the oxy-Cope intermediate was characterized by a stereoelectronic configuration amenable to remote SN displacement.
Further considerations
Potassium hydride, a frequently utilized reagent for the anionic oxy-Cope rearrangement, is occasionally contaminated with trace impurities that have been suggested to destroy the dienolate intermediate, resulting in putative polymerization. Macdonald et al., who documented the occurrence, prescribed pre-treatment with iodine to eliminate any potassium superoxide that may persist within a purchased batch of the material. This simple preparatory step, as they describe in their paper, effects dramatic improvement in both yield and reproducibility of results.
Important side reactions include heterolytic cleavage, in which the homoallylic alcohol decomposes into a carbonyl and an allylic system.
Suppression of this phenomenon is readily achievable by decreasing the ionic nature of the metal-alkoxide bond. Specifically, the use of more electronegative alkali metals or solvents less amenable to cation solvation generates the desired effect. In keeping with the above discussion, the rate of reaction may be diminished but should not approach an unsatisfactory level.
References
Rearrangement reactions
Name reactions | Oxy-Cope rearrangement | Chemistry | 1,514 |
61,690,798 | https://en.wikipedia.org/wiki/Terphenylquinones | Terphenylquinones are fungal dyes from the group of phenyl-substituted p-benzoquinones having the following general structure.
General chemical structure of terphenylquinones
Also derivatives with a central o-benzoquinone structure are known.
Biosynthesis
The biosynthesis of terphenylquinones is carried out by dimerization of substituted oxophenylpropanoic acids (phenylpyruvic acids).
Occurrence
Terphenylquinones are typical constituents of the Boletales.
Examples
{|class="wikitable sortable"
!Name||Structure|| CAS-Nr.||Origin
|-
|Polyporic acid||||548-59-4||Polypore of the order Aphyllophorales, lichen Yarrumia coronata
|-
|Atromentin||||519-67-5||Paxillus atrotomentosus (Basidiomycota)
|-
|Aurantiacin||||548-32-3||Hydnellum aurantiacum (Basidiomycota)
|-
|Phlebiarubron||||7204-23-1|| Cultures of Phlebia strigosozonata and Punctularia atropurpurascens (Basidiomycota)
|-
|Spiromentin B||||121254-56-6||Tapinella atrotomentosa (Basidiomycota) and cultures of Tapinella panuoides
|}
See also
Thelephoric acid
References
Quinones
Aromatic compounds | Terphenylquinones | Chemistry | 358 |
19,254,435 | https://en.wikipedia.org/wiki/Index%20of%20urban%20sociology%20articles | Urban sociology is the sociological study of social life and human interaction in metropolitan areas. It is a normative discipline of sociology seeking to study the structures, processes, changes and problems of an urban area and by doing so providing inputs for planning and policy making.
A
abandonment — accessibility — Active Living — activity centre — adaptive reuse — Administration for Children and Families — Acid Rain Program(EPA) — achievement gap in the United States — affirmative action — African American — Aid to Families with Dependent Children(AFDC) — air quality(indoor) — Air Pollution Index — air quality index — alienation — amalgamation — annexation — anomie — arcology — arson — asset-based community development — Asian American — Athens Charter — automobile — automobile dependency — autonomy
B
bureaucracy — birth rate — block grant — budget — bus — business cycle — business park
C
capitalism — capital improvement plan — carpool — carsharing — central business district — central place theory — charter school — City Beautiful movement — City of Light Development — city rhythm — civil rights — class stratification — clean air act — communal garden — Communities Directory — community development — community land trust — community of place — Community Reinvestment Act — commuting — complete streets — concentric zone model — conservation easement — Context Sensitive Solutions — context theory — Copenhagenization (bicycling) — core frame model — corporation — cost of living(U.S.) — counter urbanization — crime — criminal justice — cultural bias — culture of poverty
-The Coons Effect
D
de facto segregation — de jure segregation — death rate — decentralization — devolution — disability — disinvestment — division of labour
E
economic development — economic growth — elitism — emission standard — employment — empowerment zone — enterprise zone — entertainment center — entrepôt — ethnic enclave
F
Federal Housing Administration — FHA loan — fragmentation
G
gang — gentrification — globalization — government — Great Depression — gridlock — growth management
H
habitability — highway — Hispanic Americans — historic preservation — Home Mortgage Disclosure Act — homelessness — homeowners' association — Housing Act of 1937 — Housing Act of 1949 — Housing and Economic Recovery Act of 2008 — HOPE VI — human ecology — Department of Housing and Urban Development(H.U.D.) — hyperghettoization
I
immigration — inclusionary zoning — income — indoor air pollution in developing nations — industrial ecology — industrialization — inequality — infrastructure — interest group
J
K
kinship
L
land use — landfill — leapfrogging
M
magnet school — methanol — middle class — migration — modernization — Moving to Opportunity — multiple nuclei model
N
National Ambient Air Quality Standards — neighborhood — Neo-Marxism — nuclear family
O
organized crime — overcrowding
P
parochialism — Personal Responsibility and Work Opportunity Act — Phase I Environmental Site Assessment — polarization — police brutality — pollution — poverty — poverty line — privatization — public transport — psychological stress — public housing — public school — public transport
Q
R
racial discrimination — racial integration — racism — rail system — recycling — regime theory — revenue sharing — rural
S
savings and loan crisis — scholarship — segregation — single parent — smart growth — social complexity — social disorganization theory — social housing — social solidarity — social work — social welfare provision — Socialism — solidarity — Soviet Union — steam engine — streetcar — street children — suburbanization — suburb — sun belt
T
taxes — technology — Times Square Red, Times Square Blue —TANF — third world
U
underemployment — underground economy — unemployment — Uniform Crime Report — unionization — urban decay — Urban Mass Transportation Act of 1964 — urban renewal — urban sprawl — urbanization
V
Vice Lords — violence — volunteer — voting bloc
W
Wage — war on poverty — waste disposal — water supply — welfare — welfare reform — white flight — white collar crime — workfare
X
xenophobia
Y
Z
zoning
Urban-Related Lists
List of United States cities by population
See also
List of U.S. metropolitan areas with large African-American populations
List of air-filtering plants
Further reading
Flanagan, William G. (2001). Urban Sociology : Images and Structure, Prentice Hall,
Keiser, R. Lincoln. (1969). The Vice Lords: Warriors of the Streets, Holt, Rinehart and Winston,
Shannon, Thomas R. (2001). Urban Problems in Sociological Perspective, Waveland Press Inc,
Spradley, James P. (1999). You Owe Yourself a Drunk: An Ethnography of Urban Nomad, Waveland Press Inc,
Vargas, Joao H. Costa. (2006). Catching Hell in the City of Angels: Life And Meanings of Blackness in South Central Los Angeles, University of Minnesota Press,
Williams, Terry. (1992). Crackhouse: Notes from the End of the Line, Penguin Group(USA),
Urban sociology
Urban planning | Index of urban sociology articles | Engineering | 982 |
52,846,697 | https://en.wikipedia.org/wiki/T%C3%B8nne%20%28unit%29 | A tønne (plural tønner) is an old Norwegian unit of volume equivalent to a barrel. There was a dry tønne and a liquid tønne. The volume of a tønne has varied over time in Norway, including many local variations.
The dry tønne was standardized in 1824 as equivalent to . A tønne of potatoes weighed about . A dry tønne was divided into four fjerdinger, equivalent to each. The liquid tønne was equivalent to .
In addition, the term tønne (a "barrel of land") was used as a measurement of area equivalent to . This corresponded to the amount of land that could be sown with one tønne of seed.
References
External links
Norsk historisk leksikon: Kornmål. (lokalhistorikwiki.no).
Units of volume
Obsolete units of measurement | Tønne (unit) | Mathematics | 189 |
14,650,395 | https://en.wikipedia.org/wiki/Monadic%20second-order%20logic | In mathematical logic, monadic second-order logic (MSO) is the fragment of second-order logic where the second-order quantification is limited to quantification over sets. It is particularly important in the logic of graphs, because of Courcelle's theorem, which provides algorithms for evaluating monadic second-order formulas over graphs of bounded treewidth. It is also of fundamental importance in automata theory, where the Büchi–Elgot–Trakhtenbrot theorem gives a logical characterization of the regular languages.
Second-order logic allows quantification over predicates. However, MSO is the fragment in which second-order quantification is limited to monadic predicates (predicates having a single argument). This is often described as quantification over "sets" because monadic predicates are equivalent in expressive power to sets (the set of elements for which the predicate is true).
Variants
Monadic second-order logic comes in two variants. In the variant considered over structures such as graphs and in Courcelle's theorem, the formula may involve non-monadic predicates (in this case the binary edge predicate ), but quantification is restricted to be over monadic predicates only. In the variant considered in automata theory and the Büchi–Elgot–Trakhtenbrot theorem, all predicates, including those in the formula itself, must be monadic, with the exceptions of equality () and ordering () relations.
Computational complexity of evaluation
Existential monadic second-order logic (EMSO) is the fragment of MSO in which all quantifiers over sets must be existential quantifiers, outside of any other part of the formula. The first-order quantifiers are not restricted. By analogy to Fagin's theorem, according to which existential (non-monadic) second-order logic captures precisely the descriptive complexity of the complexity class NP, the class of problems that may be expressed in existential monadic second-order logic has been called monadic NP. The restriction to monadic logic makes it possible to prove separations in this logic that remain unproven for non-monadic second-order logic. For instance, in the logic of graphs, testing whether a graph is disconnected belongs to monadic NP, as the test can be represented by a formula that describes the existence of a proper subset of vertices with no edges connecting them to the rest of the graph; however, the complementary problem, testing whether a graph is connected, does not belong to monadic NP. The existence of an analogous pair of complementary problems, only one of which has an existential second-order formula (without the restriction to monadic formulas) is equivalent to the inequality of NP and coNP, an open question in computational complexity.
By contrast, when we wish to check whether a Boolean MSO formula is satisfied by an input finite tree, this problem can be solved in linear time in the tree, by translating the Boolean MSO formula to a tree automaton and evaluating the automaton on the tree. In terms of the query, however, the complexity of this process is generally nonelementary. Thanks to Courcelle's theorem, we can also evaluate a Boolean MSO formula in linear time on an input graph if the treewidth of the graph is bounded by a constant.
For MSO formulas that have free variables, when the input data is a tree or has bounded treewidth, there are efficient enumeration algorithms to produce the set of all solutions, ensuring that the input data is preprocessed in linear time and that each solution is then produced in a delay linear in the size of each solution, i.e., constant-delay in the common case where all free variables of the query are first-order variables (i.e., they do not represent sets). There are also efficient algorithms for counting the number of solutions of the MSO formula in that case.
Decidability and complexity of satisfiability
The satisfiability problem for monadic second-order logic is undecidable in general because this logic subsumes first-order logic.
The monadic second-order theory of the infinite complete binary tree, called S2S, is decidable. As a consequence of this result, the following theories are decidable:
The monadic second-order theory of trees.
The monadic second-order theory of under successor (S1S).
WS2S and WS1S, which restrict quantification to finite subsets (weak monadic second-order logic). Note that for binary numbers (represented by subsets), addition is definable even in WS1S.
For each of these theories (S2S, S1S, WS2S, WS1S), the complexity of the decision problem is nonelementary.
Use of satisfiability of MSO on trees in verification
Monadic second-order logic of trees has applications in formal verification. Decision procedures for MSO satisfiability have been used to prove properties of programs manipulating linked data structures, as a form of shape analysis, and for symbolic reasoning in hardware verification.
See also
Descriptive complexity theory
Monadic predicate calculus
Second-order logic
References
Mathematical logic | Monadic second-order logic | Mathematics | 1,122 |
74,267,976 | https://en.wikipedia.org/wiki/Ilaria%20Testa | Ilaria Testa is an Italian-born scientist who is a Professor at the Department of Applied Physics at the School of Engineering Science at the KTH Royal Institute of Technology. She has made major contributions to advanced microscopy, particularly superresolution microscopy (RESOLFT, STED).
Education
Testa studied physics at University of Genoa in Italy and graduated with a M.Sc. in 2005. In 2009, she earned her Ph.D. in Biotechnology. During her Ph.D., she worked on quantitative methods in single-molecule biophysics and studied transitional states in fluorescent proteins. After completing her thesis, supervised by Alberto Diaspro, she joined Stefan Hell's research group at the Max Planck Institute for Multidisciplinary Sciences in Göttingen, Germany as a postdoctoral researcher where she had already spent part of her doctoral studies.
Career and research
At the Max Planck Institute for Multidisciplinary Sciences in Göttingen, Testa played a central role in establishing the superresolution technique RESOLFT, showing that superresolution microscopy can be realized with lower levels of light in living cells and tissues making it more attractive for its usage in the life sciences.
From 2015 to 2024, Testa was appointed as a Fellow at the SciLifeLab in Stockholm and served as both an assistant professor and an associate professor at the KTH Royal Institute of Technology. At the SciLifeLab, she set up the Laboratory for Advanced Optical BioImaging.
In November 2024, she was appointed professor at the KTH Royal Institute of Technology.
Testa and her team continue to develop further and use superresolution techniques such as STED and RESOLFT microscopy to understand the fundamental biological processes for health and diseases.
Testa is a well-known microscopist who is an established member of the advanced microscopy community and is frequently invited on panels and as a keynote speaker at key conferences in the field.
Awards and honors
2015, ERC Starting Grant "MoNaLISA"
2017, ESP Young Investigator Award
2020, ERC Consolidator Grant "InSpIRe"
2025, RMS Award for Light Microscopy
References
External links
Can Microscopes Make Decisions? | Ilaria Testa | TEDxKTH
The Microscopists interviews Ilaria Testa
Living people
Women in optics
Year of birth missing (living people)
Microscopists
Optical physicists
European Research Council grantees
University of Genoa alumni
21st-century women physicists | Ilaria Testa | Chemistry | 497 |
18,480,401 | https://en.wikipedia.org/wiki/OSA-UCS | In colorimetry the OSA-UCS (Optical Society of America Uniform Color Scales) is a color space first published in 1947 and developed by the Optical Society of America’s Committee on Uniform Color Scales. Previously created color order systems, such as the Munsell color system, failed to represent perceptual uniformity in all directions. The committee decided that, in order to accurately represent uniform color differences in each direction, a new shape of three dimensional Cartesian geometry would need to be used.
History and development
The development of the OSA-UCS took place during many years, from 1947 to 1977. Not long after the first mathematical color model was developed by the CIE, David MacAdam showed that when selecting a color on the CIE chromaticity diagram, it could not be guaranteed that colors of the same perceived color difference around this color were at the same color distance with respect to the reference color. More simply, the Euclidean distance between any two colors on the chromaticity diagram could not be used as a uniform measure of perceived color difference. Immediately following this discovery, work began to create a space that would behave uniformly in all directions of color difference.
Starting with a sample of 59 colored tiles of non-uniform color differences, the OSA asked 72 observers to judge color differences between the different sample tiles. From the data collected, formulas were developed and parameters were defined to create the new uniform color space. They chose the reference 10 degree observer and Illuminant D65 to characterize the uniform space and a neutral gray background of 30% reflectance. In the end, 558 color samples were produced424 full step and 54 half stepand distributed by the OSA.
Design
Geometry
The ideal color solid with points all at an equal distance from a center point is a spherehowever, a collection of spheres can not be packed to form a larger solid without gaps. The geometry that the OSA finally chose is a rhombohedral lattice based on a cuboctahedron. Each of the twelve vertices of this solid are equal distance from the center, as well as from each of their neighbors. The last step to completing this geometry was in a rescaling of the vertical L axis, in order to achieve integer coordinate locations for color description. The color distance uniformity is maintained, as only the axis dimensions are scaled, and the scaling is accounted for in the color distance formula.
Coordinate values
The three perpendicular dimensions of the OSA-UCS are the lightness dimension L, the jaune dimension j (a yellow/blue opponent dimension) and the green dimension g (a green/red opponent dimension).
Lightness (L)
The lightness scale of the OSA-UCS color solid varies vertically from about -10 to 8. UCS lightness of 0 corresponds to the 30% reflective neutral background gray selected for their samples, while lighter shades have positive values and darker shades have negative values.
Jaune (j)
The jaune dimension of the OSA-UCS color solid runs horizontally and perpendicular to the L dimension. This is a yellow-blue chromatic dimension, varying from positive values appearing more yellowish to negative values appearing more blueish. A j value of 0 lies along the neutral axis.
Green (g)
The green dimension of the OSA-UCS runs horizontally perpendicular to both the L and j dimensions. This green-red chromatic axis varies from more greenish positive values to more pinkish negative values. Again, a g value of 0 lies along the neutral (L) axis.
Color groupings
The cuboctahedron structure of the OSA-UCS color solid can be geometrically divided into 9 planes, known as cleavage planes. These 9 cleavage planes are defined as:
L - A plane of constant L (lightness) that runs perpendicular to the L axis, where j and g can take on any values.
j - A plane of constant j (yellow-blueness) that runs perpendicular to the j axis, where L and g can take on any values.
g - A plane of constant g (red-greenness) that runs perpendicular to the g axis, where L and j can take on any values.
L+j - A plane of constant L+j that runs parallel to the g axis, at 35° from the L axis and 55° from the j axis.
L−j - A plane of constant L-j that runs parallel to the g axis, at 35° from the L axis and 55° from the j axis.
L+g - A plane of constant L+g that runs parallel to the j axis, at 35° from the L axis and 55° from the g axis.
L−g - A plane of constant L-g that runs parallel to the g axis, at 35° from the L axis and 55° from the g axis.
j+g - A plane of constant j+g that runs parallel to the L axis, at 45° from the j and g axes.
j−g - A plane of constant j-g that runs parallel to the L axis, at 45° from the j and g axes.
Color difference
OSA-UCS color difference is defined by the simple Euclidean distance between two colors in the color space, that takes into account the scaling done to the L axis. The formula used to calculate color difference between color 1 and 2 is:
Due to the design of the system, the color difference between two neighbors in the OSA-UCS color space is always 2. Small color differences can be accurately calculated using this formula. Larger color differences, however, require a non-linear correction for accuracy.
Color transformations
CIEXYZ to OSA-UCS
To perform an analytical conversion from a CIEXYZ value to OSA-UCS, the following steps should be followed. First, a factor representing the Helmholtz-Kohlrausch effect must be calculated from the x and y chromaticity coordinates:
Next determine the modified luminous reflectance:
Then calculate the lightness and chroma modification factor:
(given as in the original paper)
Convert the XYZ values to RGB using the linear matrix transformation:
Last, calculate a and b:
and multiply them by C to obtain OSA-UCS g and j:
OSA-UCS to CIEXYZ
Although no closed-form conversion from OSA-UCS to CIEXYZ exists, numerical solvers have been written, including one based on the Newton–Raphson method and another based on an artificial neural network.
See also
Color model
The Optical Society
CIEXYZ
CIELAB
CIELUV
David MacAdam
References
Color space | OSA-UCS | Mathematics | 1,365 |
14,573,037 | https://en.wikipedia.org/wiki/Monge%27s%20theorem | In geometry, Monge's theorem, named after Gaspard Monge, states that for any three circles in a plane, none of which is completely inside one of the others, the intersection points of each of the three pairs of external tangent lines are collinear.
For any two circles in a plane, an external tangent is a line that is tangent to both circles but does not pass between them. There are two such external tangent lines for any two circles. Each such pair has a unique intersection point in the extended Euclidean plane. Monge's theorem states that the three such points given by the three pairs of circles always lie in a straight line. In the case of two of the circles being of equal size, the two external tangent lines are parallel. In this case Monge's theorem asserts that the other two intersection points must lie on a line parallel to those two external tangents. In other words, if the two external tangents are considered to intersect at the point at infinity, then the other two intersection points must be on a line passing through the same point at infinity, so the line between them takes the same angle as the external tangent.
Proofs
The simplest proof employs a three-dimensional analogy. Let the three circles correspond to three spheres of different radii; the circles correspond to the equators that result from a plane passing through the centers of the spheres. The three spheres can be sandwiched uniquely between two planes. Each pair of spheres defines a cone that is externally tangent to both spheres, and the apex of this cone corresponds to the intersection point of the two external tangents, i.e., the external homothetic center (center of similarity). Since one line of the cone lies in each plane, the apex of each cone must lie in both planes, and hence somewhere on the line of intersection of the two planes. Therefore, the three external homothetic centers are collinear.
This proof is somewhat flawed, however, as it cannot account for cases where the smallest circle is located between the other two, nor any case where one circle is fully contained by another. It can be made fully general by using cones of equal apex angle rather than spheres, creating three similar cones. Any pair of similar three dimensional objects has a center of similarity, about which you could scale either object to coincide with the other; these lines of similarity replace the external tangents of the previous proof. Further, the line connecting any two apex points must also intersect their center of similarity. The three apex points always define a plane in three dimensions, and all three centers of similarity must lie in the plane containing the circular bases. Hence, the three centers must lie on the intersection of the two planes, which must be a line in three dimensions.
Monge's theorem can also be proved by using Desargues' theorem.
Another easy proof uses Menelaus' theorem, since the ratios can be calculated with the diameters of each circle, which will be eliminated by cyclic forms when using Menelaus' theorem.
Desargues' theorem also asserts that 3 points lie on a line, and has a similar proof using the same idea of considering it in 3 rather than 2 dimensions and writing the line as an intersection of 2 planes.
See also
Homothetic centers of circles
Problem of Apollonius
References
Bibliography
External links
Monge's Circle Theorem at MathWorld
Monge's theorem at cut-the-knot
Three Circles and Common Tangents at cut-the-knot
Euclidean plane geometry
Articles containing proofs
Theorems about circles | Monge's theorem | Mathematics | 719 |
36,213,191 | https://en.wikipedia.org/wiki/Dodecanal | Dodecanal, also known as lauraldehyde or dodecyl aldehyde, is an organic compound with the chemical formula CH3(CH2)10CHO. This colourless liquid is a component of many fragrances. It occurs naturally in citrus oils, but commercial samples are usually produced from dodecanol by dehydrogenation.
References
Fatty aldehydes
Alkanals | Dodecanal | Chemistry | 84 |
5,445,513 | https://en.wikipedia.org/wiki/Tellurium%20tetrabromide | Tellurium tetrabromide (TeBr4) is an inorganic chemical compound. It has a similar tetrameric structure to TeCl4. It can be made by reacting bromine and tellurium. In the vapour TeBr4 dissociates:
TeBr4 → TeBr2 + Br2
It is a conductor when molten, dissociating into the ions TeBr3+ and Br−. When dissolved in benzene and toluene, TeBr4 is present as the unionized tetramer Te4Br16. In solvents with donor properties such as acetonitrile, CH3CN ionic complexes are formed which make the solution conducting:
TeBr4 + 2CH3CN → (CH3CN)2TeBr3+ + Br−
References
Bromides
Tellurium halides
Tellurium(IV) compounds
Chalcohalides | Tellurium tetrabromide | Chemistry | 189 |
64,574,512 | https://en.wikipedia.org/wiki/Rita%20Casadio | Rita Casadio is an Adjunct Professor of Biochemistry/Biophysics in the Department of Pharmacy and Biotechnology at the University of Bologna.
Career
She earned her degree in physics at the University of Bologna, Italy. In 1987, she began her academic career as an assistant professor of biophysics at the University of Bologna, later becoming a full professor of biochemistry/biophysics in 2001. Her research primarily focuses on membrane and protein biophysics, as well as computer modeling of biological processes, including protein folding, stability and interactions.
She has authored more than 500 scientific papers and held key roles in various editorial and organizational positions within the field of bioinformatics.
Her work in machine learning has been used for protein structure prediction and methods from her group have been highly ranked in international competitions, such as the Critical Assessment of protein Structure Prediction (CASP) and the Critical Assessment of Function Annotation (CAFA).
Awards and honours
She was elected a Fellow of the International Society for Computational Biology (ISCB) in 2020 for outstanding contributions to the fields of computational biology and bioinformatics.
See also
ELIXIR
References
External links
Living people
Italian bioinformaticians
Academic staff of the University of Bologna
Year of birth missing (living people)
21st-century women scientists
Women biochemists
Computational biologists
Women computational biologists | Rita Casadio | Chemistry | 266 |
24,219,424 | https://en.wikipedia.org/wiki/Magnolia%20%C3%97%20wieseneri | Magnolia × wieseneri is a hybrid plant in the genus Magnolia and family Magnoliaceae. A small tree or large shrub with white highly fragrant blooms, it is the progeny of Magnolia sieboldii and Magnolia obovata.
Hybrid
The origins of Magnolia × wieseneri are obscure, but it is thought to have been a result of deliberate cross-breeding between the parent species some time in the 19th century or earlier in Japan, where it is known as Gyo Kusui or Ukesaki Oyama-renage. It entered European horticulture at the 1889 Paris Exposition, where it was on display at the Japanese Court stand. From here, it was collected for Kew Gardens, and named Magnolia × watsonii by Joseph Hooker in 1891. However, Élie-Abel Carrière had named a specimen six months earlier in 1890 after a Mr Wiesener, who had purchased a plant from a Japanese horticulturist at the Trocadéro at the same time as the Exposition, and hence the French botanist's name was preserved under International Code of Botanical Nomenclature naming rules.
Description
Magnolia × wieseneri is a multistemmed large shrub or small tree which may reach 6 m (20 ft) in height; it has leathery obovate green leaves that reach 20 cm (8 in) long by 10.5 cm (4 in) wide. Its most notable feature is the remarkable fragrance of the ivory-coloured flowers, which has been likened to pineapples and seen adjectives such as "ethereal", "spicy" and "aromatic" used. The flowers are cup-shaped at first, with a diameter of 10-12.5 cm (4–5 in), before flattening out to a diameter of 15–20 cm (6–8 in) after a few days.
Cultivation
A chance seedling, from the garden of Sir Peter Smithers at Vico Morcote in Switzerland, with more vigorous growth and larger flowers has been described as Magnolia "William Watson". The garden owner Smithers observed that there were specimens of M. obovata flowering nearby and that the cultivar is possibly a backcross with obovata.
References
wieseneri
Hybrid plants
Garden plants of Europe
Garden plants of North America
Ornamental trees | Magnolia × wieseneri | Biology | 472 |
1,962,912 | https://en.wikipedia.org/wiki/Hiyama%20coupling | The Hiyama coupling is a palladium-catalyzed cross-coupling reaction of organosilanes with organic halides used in organic chemistry to form carbon–carbon bonds (C-C bonds). This reaction was discovered in 1988 by Tamejiro Hiyama and Yasuo Hatanaka as a method to form carbon-carbon bonds synthetically with chemo- and regioselectivity. The Hiyama coupling has been applied to the synthesis of various natural products.
R: aryl, alkenyl or alkynyl
R': aryl, alkenyl, alkynyl or alkyl
R'': Cl, F or alkyl
X: Cl, Br, I or OTf
Reaction history
The Hiyama coupling was developed to combat the issues associated with other organometallic reagents. The initial reactivity of organosilicon was not actually first reported by Hiyama, as Kumada reported a coupling reaction using organofluorosilicates shown below. Organosilanes were then discovered, by Hiyama, to have reactivity when activated by a fluoride source. This reactivity, when combined with a palladium salt, creates a carbon-carbon bond with an electrophillic carbon, like an organic halide. Compared to the inherent issues of well-used organometalics reagents, such as organomagnesium (Grignard reagents) and organocopper reagents, which are very reactive and are known to have low chemoselectivity, enough to destroy functional groups on both coupling partners, organosilicon compounds are inactive. Other organometallic reagents using metals such as zinc, tin, and boron, reduce the reactivity issue, but have other problems associated with each reagent. Organozinc reagents are moisture sensitive, organotin compounds are toxic, and organoboron reagents are not readily available, are expensive, and aren't often stable. Organosilanes are readily available compounds that, upon activation (much like organotin or organoboron compounds) from fluoride or a base, can react with organohalides to form C-C bonds in a chemo- and regioselective manner. The reaction first reported was used to couple easily made (and activated) organosilicon nucleophiles and organohalides (electrophiles) in the presence of a palladium catalyst. Since this discovery, work has been done by various groups to expand the scope of this reaction and to "fix" the issues with this first coupling, such as the need for fluoride activation of the organosilane.
Mechanism
The organosilane is activated with fluoride (as some sort of salt such as TBAF or TASF) or a base to form a pentavalent silicon center which is labile enough to allow for the breaking of a C-Si bond during the transmetalation step. The general scheme to form this key intermediate is shown below. This step occurs in situ or at the same time as the catalytic cycle in the reaction.
The mechanism for the Hiyama coupling follows a catalytic cycle, including an A) oxidative addition step, in which the organic halide adds to the palladium oxidizing the metal from palladium(0) to palladium(II); a B) transmetalation step, in which the C-Si bond is broken and the second carbon fragment is bound to the palladium center; and finally C) a reductive elimination step, in which the C-C bond is formed and the palladium returns to its zero-valent state to start the cycle over again. The catalytic cycle is shown below.
Scope and limitations
Scope
The Hiyama coupling can be applied to the formation of Csp2-Csp2 (e.g. aryl–aryl) bonds as well as Csp2-Csp3 (e.g. aryl–alkyl) bonds. Good synthetic yields are obtained with couplings of aryl halides, vinyl halides, and allylic halides and organoiodides afford the best yields.
The scope of this reaction was expanded to include closure of medium-sized rings by Scott E. Denmark.
The coupling of alkyl halides with organohalosilanes as alternative organosilanes has also been performed. Organochlorosilanes allow couplings with aryl chlorides, which are abundant and generally more economical than aryl iodides. A nickel catalyst allows for access to new reactivity of organotrifluorosilanes as reported by GC Fu et al. Secondary alkyl halides are coupled with aryl silanes with good yields using this reaction.
Limitations
The Hiyama coupling is limited by the need for fluoride in order to activate the organosilicon reagent. Addition of fluoride cleaves any silicon protecting groups (e.g. silyl ethers), which are frequently employed in organic synthesis. The fluoride ion is also basic, so base sensitive protecting groups, acidic protons, and functional groups may be affected by the addition of this activator. Most of the active research concerning this reaction involves circumventing this problem. To overcome this issue, many groups have looked to the use of other basic additives for activation, or use of a different organosilane reagent all together, leading to the multiple variations of the original Hiyama coupling.
Variations
One modification of the Hiyama coupling utilizes a silacyclobutane ring and a fluoride source that is hydrated as shown below. This mimics the use of an alkoxysilane/organosilanol rather than the use of alkylsilane. The mechanism of this reaction, using a fluoride source, allowed for the design of future reactions that can avoid the use of the fluoride source.
Fluoride-free Hiyama couplings
Many modifications to the Hiyama coupling have been developed that avoid the use of a fluoride activator/base. Using organochlorosilanes, Hiyama found a coupling scheme utilizing NaOH as the basic activator. Modifications using alkoxysilanes have been reported with the use of milder bases like NaOH and even water. Study of these mechanisms have led to the development of the Hiyama–Denmark coupling which utilize organosilanols as coupling partners.
Another class of fluoride-free Hiyama couplings include the use of a Lewis acid additive, which allows for bases such as K3PO4 to be utilized, or for the reaction to proceed without a basic additive. The addition of a copper co-catalyst has also been reported to allow for the use of a milder activating agent and has even been shown to get turnover in which both the palladium(II) and copper(I) turnover in the catalytic cycle rather than addition of stoichiometric Lewis acid (e.g. silver(I), copper(I)).
Hiyama–Denmark coupling
The Hiyama–Denmark coupling is the modification of the Hiyama coupling that does not require a fluoride additive to utilize organosilanols and organic halides as coupling partners. The general reaction scheme is shown below, showcasing the utilization of a Brønsted base as the activating agent as opposed to fluoride, phosphine ligands are also used on the metal center.
A specific example of this reaction is shown with reagents. If fluoride had been used, as in the original Hiyama protocol, the tert-butyldimethylsilyl (TBS) ether would have likely been destroyed.
Hiyama–Denmark coupling mechanism
Examination of this reaction's mechanism suggests that the formation of the silonate is all that is needed to activate addition of the organosilane to the palladium center. The presence of a pentavalent silicon is not needed and kinetic analysis has shown that this reaction has first order dependence on silonate concentration. This is due to the key bond being formed, the Pd-O bond during the transmetalation step, that then allows for transfer of the carbon fragment onto the palladium center. Based on this observation, it seems that the rate limiting step in this catalytic cycle is the Pd-O bond formation, in which increased silonate concentrations increase the rate of this reaction (indicative of faster reactions).
See also
Heck reaction
Kumada coupling
Negishi coupling
Sonogashira coupling
Stille reaction
Suzuki reaction
Palladium-catalyzed coupling reactions
External links
Information about Hiyama couplings
Information about Hiyama–Denmark couplings
References
Organometallic chemistry
Carbon-carbon bond forming reactions
Palladium
Name reactions | Hiyama coupling | Chemistry | 1,839 |
35,146,189 | https://en.wikipedia.org/wiki/Quantum%20oscillations | In condensed matter physics, quantum oscillations describes a series of related experimental techniques used to map the Fermi surface of a metal in the presence of a strong magnetic field. These techniques are based on the principle of Landau quantization of Fermions moving in a magnetic field. For a gas of free fermions in a strong magnetic field, the energy levels are quantized into bands, called the Landau levels, whose separation is proportional to the strength of the magnetic field. In a quantum oscillation experiment, the external magnetic field is varied, which causes the Landau levels to pass over the Fermi surface, which in turn results in oscillations of the electronic density of states at the Fermi level; this produces oscillations in the many material properties which depend on this, including resistance (the Shubnikov–de Haas effect), Hall resistance, and magnetic susceptibility (the de Haas–van Alphen effect). Observation of quantum oscillations in a material is considered a signature of Fermi liquid behaviour.
Quantum oscillations have been used to study high temperature superconducting materials such as cuprates and pnictides. Studies using these experiments have shown that the ground state of underdoped cuprates behave similar to a Fermi liquid, and display characteristics such as Landau quasiparticles.
In 2021 this technique has been used to observe a predicted state called "electron–phonon fluid", a similar particle-quasiparticle state already known is the exciton–polariton fluid.
Experiment
When a magnetic field is applied to a system of free charged fermions, their energy states are quantized into the so-called Landau levels, given by
for integer-valued , where is the external magnetic field and are the fermion charge and effective mass respectively.
When the external magnetic field is increased in an isolated system, the Landau levels expand, and eventually "fall off" the Fermi surface. This leads to oscillations in the observed energy of the highest occupied level, and hence in many physical properties (including Hall conductivity, resistivity, and susceptibility). The periodicity of these oscillations can be measured, and in turn can be used to determine the cross-sectional area of the Fermi surface. If the axis of the magnetic field is varied at constant magnitude, similar oscillations are observed. The oscillations occur whenever the Landau orbits touch the Fermi surface. In this way, the complete geometry of the Fermi sphere can be mapped.
Underdoped cuprates
Studies of underdoped cuprate compounds such as YBa2Cu3O6+x through probes such as ARPES have indicated that these phases show characteristics of non-Fermi liquids, and in particular, the absence of well-defined Landau quasiparticles. However, quantum oscillations have been observed in these materials at low temperatures, if their superconductivity is suppressed by a sufficiently high magnetic field, which is evidence for the presence of well-defined quasiparticles with fermionic statistics. These experimental results thus disagree with those from ARPES and other probes.
See also
de Haas–van Alphen effect
Shubnikov–de Haas effect
Landau levels
References
Condensed matter physics
Experimental physics
Magnetism | Quantum oscillations | Physics,Chemistry,Materials_science,Engineering | 691 |
948,915 | https://en.wikipedia.org/wiki/Samuel%20Alexander | Samuel Alexander (6 January 1859 – 13 September 1938) was an Australian-born British philosopher. He was the first Jewish fellow of an Oxbridge college. He is now best known as an advocate of emergentism in biology.
Early life
He was born into a Jewish family at 436 George Street, Sydney, Australia, the third son of Samuel Alexander, a prosperous saddler, and Eliza née Sloman. His father died around the time he was born, of tuberculosis. Eliza moved the family to St Kilda, Victoria in 1863 or 1864, and Alexander was tutored, and placed at a private school. In 1871, he was sent to Wesley College, Melbourne, then under the headmastership of Martin Howy Irving.
Alexander matriculated at the University of Melbourne on 22 March 1875. He completed the first two years with distinction, but then left without taking a degree.
Academic career
In May 1877, Alexander sailed for England in an attempt to win a scholarship at Oxford or Cambridge. He was successful at Balliol College, Oxford, and matriculated there on 28 January 1878. He graduated B.A. in 1881, was elected a Fellow of Lincoln College in 1882, and graduated M.A. in 1884. He remained as philosophy tutor at Lincoln College to 1893. It was during this period that he developed his interest in psychology, then a neglected subject. He travelled on the continent of Europe, and in the winter of 1890–91 was in Germany working on experimental psychology at the laboratory of Hugo Münsterberg at Freiburg.
Alexander for much of his life was deaf, which acted as a handicap. For some time, he wanted to obtain a professorship. He made three unsuccessful attempts before he was appointed at Owens College, Manchester in 1893. Among his colleagues there was the educational theorist Catherine Isabella Dodd, whom he admired. Another educationalist he found impressive was Esther Lawrence, a cousin.
Robert Mackintosh (1858–1933) owed his appointment as lecturer in 1904 to the new Manchester theological faculty in 1904 to Alexander, he believed. Alexander introduced experimental psychology at Manchester in 1907, in unorthodox fashion, with the appointment of Tom Pear (1886–1972), later a professor. Pear was recruited while still an undergraduate, but was backed by Charles Sherrington, who had brought William George Smith as a lecturer to the University of Liverpool in 1905. He invited John Macmurray to be a lecturer in the philosophy department in 1919.
Alexander was president of the Aristotelian Society from 1908 to 1911, and again from 1936 to 1937. In 1913, he was made a Fellow of the British Academy. R. G. Collingwood met Alexander in 1917, when both were working for the United Kingdom, and they kept in touch on philosophy for the rest of Alexander's life. Collingwood later contended that Alexander had "philosophical genius of very high order". Alexander influenced A. N. Whitehead, and mentored others who went on to become major figures in 20th-century British philosophy. One such was John Anderson.
In 1924 Alexander retired from his chair, and was succeeded by John Leofric Stocks.
Awards and honours
He was given the Hon. LLD of St Andrews in 1905, and in later years he received Hon. Litt. D. degrees from Durham, Liverpool, Oxford and Cambridge.
In 1924, Alexander sat for the sculptor Jacob Epstein, who made two copies of a bust. One copy went to the Ben Uri Gallery & Museum, and the other to the University of Manchester. He was Herbert Spencer lecturer at Oxford in 1927, and in 1930 the Order of Merit was conferred on him, the first to a native of Australia.
Death and legacy
Alexander died on 13 September 1938. He was unmarried and his ashes lie in Manchester Southern cemetery (British Jewish Reform Congregation section). He left money to the University of Jerusalem and the University of Manchester. John Laird, his literary executor, edited Philosophical and Literary Pieces (1939). His papers were left to the John Rylands Library.
The building formerly known as Humanities Lime Grove at the University of Manchester was renamed the Samuel Alexander Building, in 2007. A theatre at Monash University, Melbourne, and a conference room at Wesley College, Melbourne are also named for him.
Works
Alexander contributed articles on philosophical subjects to Mind, the Proceedings of the Aristotelian Society, and the International Journal of Ethics. In 1887, he won the Green moral philosophy prize with an essay on the subject "In what direction does Moral Philosophy seem to you to admit or require advance?" It was the basis of his volume Moral Order and Progress, which was published in 1889 and went into its third edition in 1899. Alexander credited A. C. Bradley with introducing him to ethics, and his brother F. H. Bradley helped him with the book. He was influenced by T. H. Green, in whose memory the prize had been set up, but diverged from his views in pursuing evolutionary ethics.
Alexander was appointed Gifford lecturer at Glasgow in 1915, and delivered his lectures in the winters of 1917 and 1918. They drew on preliminary papers he had written from 1908 onwards. These materials he developed into his major work Space, Time, and Deity, published in two volumes in 1920. John Laird called it "the boldest adventure in detailed speculative metaphysics attempted in so grand a manner by any English writer between 1655 and 1920". His Arthur Davis Memorial Lecture on Spinoza and Time, in the nature of an annexe to Space, Time, and Deity, was published in 1921.
In 1933, Alexander published Beauty and Other Forms of Value, mainly an essay in aesthetics. It incorporated passages from papers that had appeared in the previous ten years. Compared to his systematic work, it was rather closer to the mainstream of British thought, and was praised highly by R. G. Collingwood.
Philosophical ideas
Two key concepts for Alexander are those of an "emergent quality" and the idea of emergent evolution:
His idea was to start with space and time, each of which he regarded as inconceivable without the other, in fact mutually equivalent. His thinking, as he said, originated in Instinct and Experience (1912) by C. Lloyd Morgan; who went on in 1922 to give an exposition of emergent properties. Pure spacetime emerges, through a process Alexander describes simply as "motion", the stuff and matter that make up our material world:
Alexander absolutizes spacetime, and even speaks of it as an "Entity|stuff" of which things are made. At the same time he also says that spacetime can be called "Motions" – not motion in the singular, but complexes of motions with kaleidoscopic changes within a continuum. In other words, for Alexander motion is primitive, and space and time are defined through relations between motions.
In Space, Time, and Deity Alexander held that an object may be before a consciousness, but is not in it; consciousness of an object is not the same as consciousness of one's consciousness of the object. For example, an object such as a chair may be apprehended by a consciousness, but the chair is not located within that consciousness; and, the contemplation of the chair is distinct from thinking about the act of contemplating the chair. Further, since the contemplation of an object is itself an action, in Alexander's view it cannot be "contemplated", but only subjectively experienced, or "enjoyed".
Alexander asked the question:
Alexander's views have been described as panentheistic.
Family
A change in Alexander's home life occurred in 1902 when the whole of his family—his mother, an aunt, two elder brothers and his sister—came from Australia to live with him. His sister became his hostess and on Wednesday evenings there were informal social gatherings.
Alexander was an "unofficial godfather" to writer Naomi Mitchison née Haldane, born in 1897. He took an interest in her studies, and wrote her long letters. Mitchison devoted a chapter in her autobiographical work You May Well Ask to Alexander, recounting affectionate anecdotes and quoting extensively from his letters.
Books
Moral Order and Progress (1889)
Locke (1908), a short study in the Philosophies Ancient and Modern Series.
Space, Time, and Deity (1920), Macmillan & Co., reprinted 1966 by Dover Publications, reprinted 2004 by Kessinger Publications: "volume one" : online version, "volume two" :
Spinoza and Time (1921)
Art and the Material (1925); Adamson Lecture for 1925
Beauty and Other Forms of Value (1933)
Philosophical and Literary Pieces (1939), (posthumous)
Notes
External links
Gifford Lectures biography
Samuel Alexander article by Emily Thomas in Internet Encyclopedia of Philosophy originally published 28 May 2012
John Slater's Introduction to the Collected Works of Samuel Alexander has some biographical details on Alexander's life.
Samuel Alexander papers at the University of Manchester Library
Article by recent occupier of Alexander's chair at the University of Manchester discussing the legacy of Whitehead and Alexander.
"Samuel Alexander and Zionism"
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804,964 | https://en.wikipedia.org/wiki/Dehumanization | Dehumanization is the denial of full humanity in others along with the cruelty and suffering that accompany it. A practical definition refers to it as the viewing and the treatment of other people as though they lack the mental capacities that are commonly attributed to humans. In this definition, every act or thought that regards a person as "less than" human is dehumanization.
Dehumanization is one form of incitement to genocide. It has also been used to justify war, judicial and extrajudicial killing, slavery, the confiscation of property, denial of suffrage and other rights, and to attack enemies or political opponents.
Conceptualizations
Behaviorally, dehumanization describes a disposition towards others that debases the others' individuality by either portraying it as an "individual" species or by portraying it as an "individual" object (e.g., someone who acts inhumanely towards humans). As a process, dehumanization may be understood as the opposite of personification, a figure of speech in which inanimate objects or abstractions are endowed with human qualities; dehumanization then is the disendowment of these same qualities or a reduction to abstraction.
In almost all contexts, dehumanization is used pejoratively along with a disruption of social norms, with the former applying to the actor(s) of behavioral dehumanization and the latter applying to the action(s) or processes of dehumanization. For instance, there is dehumanization for those who are perceived as lacking in culture or civility, which are concepts that are believed to distinguish humans from animals. Social norms define humane behavior and reflexively define what is outside of humane behavior or inhumane. Dehumanization differs from inhumane behaviors or processes in its breadth to propose competing social norms. It is an action of dehumanization as the old norms are depreciated to the competing new norms, which then redefine the action of dehumanization. If the new norms lose acceptance, then the action remains one of dehumanization. The definition of dehumanization remains in a reflexive state of a type-token ambiguity relative to both individual and societal scales.
In biological terms, dehumanization can be described as an introduced species marginalizing the human species, or an introduced person/process that debases other people inhumanely.
In political science and jurisprudence, the act of dehumanization is the inferential alienation of human rights or denaturalization of natural rights, a definition contingent upon presiding international law rather than social norms limited by human geography. In this context, a specialty within species does not need to constitute global citizenship or its inalienable rights; the human genome inherits both.
It is theorized that dehumanization takes on two forms: animalistic dehumanization, which is employed on a mostly intergroup basis; and mechanistic dehumanization, which is employed on a mostly interpersonal basis. Dehumanization can occur discursively (e.g., idiomatic language that likens individual human beings to non-human animals, verbal abuse, erasing one's voice from discourse), symbolically (e.g., imagery), or physically (e.g., chattel slavery, physical abuse, refusing eye contact). Dehumanization often ignores the target's individuality (i.e., the creative and exciting aspects of their personality) and can hinder one from feeling empathy or correctly understanding a stigmatized group.
Dehumanization may be carried out by a social institution (such as a state, school, or family), interpersonally, or even within oneself. Dehumanization can be unintentional, especially upon individuals, as with some types of de facto racism. State-organized dehumanization has historically been directed against perceived political, racial, ethnic, national, or religious minority groups. Other minoritized and marginalized individuals and groups (based on sexual orientation, gender, disability, class, or some other organizing principle) are also susceptible to various forms of dehumanization. The concept of dehumanization has received empirical attention in the psychological literature. It is conceptually related to infrahumanization, delegitimization, moral exclusion, and objectification. Dehumanization occurs across several domains; it is facilitated by status, power, and social connection; and results in behaviors like exclusion, violence, and support for violence against others.
"Dehumanisation is viewed as a central component to intergroup violence because it is frequently the most important precursor to moral exclusion, the process by which stigmatized groups are placed outside the boundary in which moral values, rules, and considerations of fairness apply."
David Livingstone Smith, director and founder of The Human Nature Project at the University of New England, argues that historically, human beings have been dehumanizing one another for thousands of years. In his work "The Paradoxes of Dehumanization", Smith proposes that dehumanization simultaneously regards people as human and subhuman. This paradox comes to light, as Smith identifies, because the reason people are dehumanized is so their human attributes can be taken advantage of.
Humanness
In Herbert Kelman's work on dehumanization, humanness has two features: "identity" (i.e., a perception of the person "as an individual, independent and distinguishable from others, capable of making choices") and "community" (i.e., a perception of the person as "part of an interconnected network of individuals who care for each other"). When a target's agency and embeddedness in a community are denied, they no longer elicit compassion or other moral responses and may suffer violence.
Objectification
Psychologist Barbara Fredrickson and Tomi-Ann Roberts argued that the sexual objectification of women extends beyond pornography (which emphasizes women's bodies over their uniquely human mental and emotional characteristics) to society generally. There is a normative emphasis on female appearance that causes women to take a third-person perspective on their bodies. The psychological distance women may feel from their bodies might cause them to dehumanize themselves. Some research has indicated that women and men exhibit a "sexual body part recognition bias", in which women's sexual body parts are better recognized when presented in isolation than in their entire bodies. In contrast, men's sexual body parts are better recognized in the context of their entire bodies than in isolation. Men who dehumanize women as either animals or objects are more liable to rape and sexually harass women and display more negative attitudes toward female rape victims.
Philosopher Martha Nussbaum identified seven components of sexual objectification: instrumentality, denial of autonomy, inertness, fungibility, violability, ownership, and denial of subjectivity.
In this context, instrumentality refers to when the objectified is used as an instrument to the objectifier's benefit. Denial of autonomy occurs in the form of the objectifier underestimating the objectified and denies their capabilities. In the case of inertness, the objectified is treated as if they are lazy and indolent. Fungibility brands the objectified to be easily replaceable. Volability is when the objectifier does not respect the objectified person's personal space or boundaries. Ownership is when the objectified is seen as another person's property. Lastly, the denial of subjectivity is a lack of sympathy for the objectified, or the dismissal of the notion that the objectified has feelings. These seven components cause the objectifier to view the objectified in a disrespectful way, therefore treating them so.
History
Native Americans
Native Americans were dehumanized as "merciless Indian savages" in the United States Declaration of Independence. Following the Wounded Knee massacre in December 1890, author L. Frank Baum wrote:The Pioneer has before declared that our only safety depends upon the total extermination [sic] of the Indians. Having wronged them for centuries we had better, in order to protect our civilization, follow it up by one more wrong and wipe these untamed and untamable creatures from the face of the earth. In this lies safety for our settlers and the soldiers who are under incompetent commands. Otherwise, we may expect future years to be as full of trouble with the redskins as those have been in the past. In Martin Luther King Jr.'s book on civil rights, Why We Can't Wait, he wrote:
Our nation was born in genocide when it embraced the doctrine that the original American, the Indian, was an inferior race. Even before there were large numbers of Negroes on our shores, the scar of racial hatred had already disfigured colonial society. From the sixteenth century forward, blood flowed in battles over racial supremacy. We are perhaps the only nation which tried as a matter of national policy to wipe out its indigenous population. Moreover, we elevated that tragic experience into a noble crusade. Indeed, even today we have not permitted ourselves to reject or to feel remorse for this shameful episode. Our literature, our films, our drama, our folklore all exalt it.
King was an active supporter of the Native American rights movement, which he drew parallels with his own leadership of the civil rights movement. Both movements aimed to overturn dehumanizing attitudes held by members of the public at large against them.
Israelis and Palestinians
Israel–Palestine relations have been historically hostile resulting in the ongoing Israeli–Palestinian conflict. During the 2014 Gaza War a survey using the Ascent of Man Scale found both sides on average when shown a version of the March of Progress image rated each other closer to an animal than a fully evolved human. On the scale with "0 corresponding to the left side of the image (i.e., quadrupedal human ancestor), and 100 corresponding to the right side of the image ('full' modern-day human)" Israelis on average rated Palestinians 39.81 points lower than their own group and Palestinians on average rated Israelis 37.03 points lower than their own group.
Dehumanizing zoomorphisms are found in both Israeli discourse and Palestinian discourse. During South Africa's submission to the International Court of Justice (ICJ) that Israel was committing genocide against the Palestinians, the president of the ICJ cited Yoav Gallant for using the phrase "human animals" in reference to Palestinians.
Causes and facilitating factors
Several lines of psychological research relate to the concept of dehumanization. Infrahumanization suggests that individuals think of and treat outgroup members as "less human" and more like animals; while Austrian ethnologist Irenäus Eibl-Eibesfeldt uses the term pseudo-speciation, a term that he borrowed from the psychoanalyst Erik Erikson, to imply that the dehumanized person or persons are regarded as not members of the human species. Specifically, individuals associate secondary emotions (which are seen as uniquely human) more with the ingroup than with the outgroup. Primary emotions (those experienced by all sentient beings, whether human or other animals) are found to be more associated with the outgroup. Dehumanization is intrinsically connected with violence. Often, one cannot do serious injury to another without first dehumanizing him or her in one's mind (as a form of rationalization). Military training is, among other things, systematic desensitization and dehumanization of the enemy, and military personnel may find it psychologically necessary to refer to the enemy as an animal or other non-human beings. Lt. Col. Dave Grossman has shown that without such desensitization it would be difficult, if not impossible, for one human to kill another human, even in combat or under threat to their own lives.
According to Daniel Bar-Tal, delegitimization is the "categorization of groups into extreme negative social categories which are excluded from human groups that are considered as acting within the limits of acceptable norms and values".
Moral exclusion occurs when outgroups are subject to a different set of moral values, rules, and fairness than are used in social relations with ingroup members. When individuals dehumanize others, they no longer experience distress when they treat them poorly. Moral exclusion is used to explain extreme behaviors like genocide, harsh immigration policies, and eugenics, but it can also happen on a more regular, everyday discriminatory level. In laboratory studies, people who are portrayed as lacking human qualities are treated in a particularly harsh and violent manner.
Dehumanized perception occurs when a subject experiences low frequencies of activation within their social cognition neural network. This includes areas of neural networking such as the superior temporal sulcus (STS) and the medial prefrontal cortex (mPFC). A 2001 study by psychologists Chris and Uta Frith suggests that the criticality of social interaction within a neural network has tendencies for subjects to dehumanize those seen as disgust-inducing, leading to social disengagement. Tasks involving social cognition typically activate the neural network responsible for subjective projections of disgust-inducing perceptions and patterns of dehumanization. "Besides manipulations of target persons, manipulations of social goals validate this prediction: Inferring preference, a mental-state inference, significantly increases mPFC and STS activity to these otherwise dehumanized targets." A 2007 study by Harris, McClure, van den Bos, Cohen, and Fiske suggests that a person's choice to dehumanize another person is due to decreased neural activity towards the projected target. This decreased neural activity is identified as low medial prefrontal cortex activation, which is associated with perceiving social information.
While social distance from the outgroup target is a necessary condition for dehumanization, some research suggests that this alone is insufficient. Psychological research has identified high status, power, and social connection as additional factors. Members of high-status groups more often associate humanity with the ingroup than the outgroup, while members of low-status groups exhibit no differences in associations with humanity. Thus, having a high status makes one more likely to dehumanize others. Low-status groups are more associated with human nature traits (e.g., warmth, emotionalism) than uniquely human characteristics, implying that they are closer to animals than humans because these traits are typical of humans but can be seen in other species. In addition, another line of work found that individuals in a position of power were more likely to objectify their subordinates, treating them as a means to one's end rather than focusing on their essentially human qualities. Finally, social connection—thinking about a close other or being in the actual presence of a close other—enables dehumanization by reducing the attribution of human mental states, increasing support for treating targets like animals, and increasing willingness to endorse harsh interrogation tactics. This is counterintuitive because social connection has documented personal health and well-being benefits but appears to impair intergroup relations.
Neuroimaging studies have discovered that the medial prefrontal cortex—a brain region distinctively involved in attributing mental states to others—shows diminished activation to extremely dehumanized targets (i.e., those rated, according to the stereotype content model, as low-warmth and low-competence, such as drug addicts or homeless people).
Race and ethnicity
Racist dehumanization entails that groups and individuals are understood as less than fully human by virtue of their race.
Dehumanization often occurs as a result of intergroup conflict. Ethnic and racial others are often represented as animals in popular culture and scholarship. There is evidence that this representation persists in the American context with African Americans implicitly associated with apes. To the extent that an individual has this dehumanizing implicit association, they are more likely to support violence against African Americans (e.g., jury decisions to execute defendants). Historically, dehumanization is frequently connected to genocidal conflicts in that ideologies before and during the conflict depict victims as subhuman (e.g., rodents). Immigrants may also be dehumanized in this manner.
In 1901, the six Australian colonies assented to federation, creating the modern nation state of Australia and its government. Section 51 (xxvi) excluded Aboriginals from the groups protected by special laws, and section 127 excluded Aboriginals from population counts. The Commonwealth Franchise Act 1902 categorically denied Aboriginals the right to vote. Indigenous Australians were not allowed the social security benefits (e.g., aged pensions and maternity allowances) which were provided to others. Aboriginals in rural areas were discriminated against and controlled as to where and how they could marry, work, live, and their movements.
In the U.S., African Americans were dehumanized by being classified as non-human primates. A California police officer who was also involved in the Rodney King beating described a dispute between an American Black couple as "something right out of Gorillas in the Mist". Franz Boas and Charles Darwin hypothesized that there might be an evolutionary process among primates. Monkeys and apes were least evolved, then savage and deformed anthropoids, which referred to people of African ancestry, to Caucasians as most developed.
Language
Language has been used as an essential tool in the process of dehumanizing others. Examples of dehumanizing language when referring to a person or group of people may include animal, cockroach, rat, vermin, monster, ape, snake, infestation, parasite, alien, savage, and subhuman. Other examples can include racist, sexist, and other derogatory forms of language. The use of dehumanizing language can influence others to view a targeted group as less human or less deserving of humane treatment.
In Unit 731, an imperial Japanese biological and chemical warfare research facility, brutal experiments were conducted on humans who the researchers referred to as 'maruta' (丸太) meaning logs. Yoshio Shinozuka, Japanese army medic who performed several vivisections in the facility said, "We called the victims 'logs.' We didn't want to think of them as people. We didn't want to admit that we were taking lives. So we convinced ourselves that what we were doing was like cutting down a tree."
Words such as migrant, immigrant, and expatriate are assigned to foreigners based on their social status and wealth, rather than ability, achievements, or political alignment. Expatriate is a word to describe the privileged, often light-skinned people newly residing in an area and has connotations that suggest ability, wealth, and trust. Meanwhile, the word immigrant is used to describe people coming to a new location to reside and infers a much less-desirable meaning.
The word "immigrant" is sometimes paired with "illegal", which harbors a profoundly derogatory connotation. Misuse of these terms—they are often used inaccurately—to describe the other, can alter the perception of a group as a whole in a negative way. Ryan Eller, the executive director of the immigrant advocacy group Define American, expressed the problem this way:
A series of language examinations found a direct relation between homophobic epithets and social cognitive distancing towards a group of homosexuals, a form of dehumanization. These epithets (e.g., faggot) were thought to function as dehumanizing labels because they tended to act as markers of deviance. One pair of studies found that subjects were more likely to associate malignant language with homosexuals, and that such language associations increased the physical distancing between the subject and the homosexual. This indicated that the malignant language could encourage dehumanization, cognitive and physical distancing in ways that other forms of malignant language do not. Another study involved a computational linguistic analysis of dehumanizing language regarding LGBTQ individuals and groups in the New York Times from 1986 to 2015. The study used previous psychological research on dehumanization to identify four language categories: (1) negative evaluations of a target group, (2) denial of agency, (3) moral disgust, and (4) likening members of the target group to non-human entities (e.g., machines, animals, vermin). The study revealed that LGBTQ people overall have been increasingly more humanized over time; however, they were found to be humanized less frequently than the New York Time's in-group identifier American.
Aliza Luft notes that the role of dehumanizing language and propaganda plays in violence and genocide is far less significant than other factors such as obedience to authority and peer pressure.
Property takeover
Property scholars define dehumanization as "the failure to recognize an individual's or group's humanity." Dehumanization often occurs alongside property confiscation. When a property takeover is coupled with dehumanization, the result is a dignity taking. There are several examples of dignity takings involving dehumanization.
From its founding, the United States repeatedly engaged in dignity takings from Native American populations, taking indigenous land in an "undeniably horrific, violent, and tragic record" of genocide and ethnocide. As recently as 2013, the degradation of a mountain sacred to the Hopi people—by spraying its peak pot with artificial snow made from wastewater—constituted another dignity taking by the U.S. Forest Service.
The 1921 Tulsa race massacre also constituted a dignity taking involving dehumanization. White rioters dehumanized African Americans by attacking, looting, and destroying homes and businesses in Greenwood, a predominantly Black neighborhood known as "Black Wall Street".
During the Holocaust, mass genocide—a severe form of dehumanization—accompanied the destruction and taking of Jewish property. This constituted a dignity taking.
Jewish settlers in the West Bank have been criticized for dehumanizing Palestinians and land grabbing on illegal settlements. These illegal settlement activities involve systemic settler violence against Palestinians, military orders, and state-sanctioned support. These actions force Palestinians to gradually give up their land and farming activities and gradually choke their sources of dignified income. Israeli soldiers sometimes actively participate in violence against civilians or look on from the sidelines.
Undocumented workers in the United States have also been subject to dehumanizing dignity takings when employers treat them as machines instead of people to justify dangerous working conditions. When harsh conditions lead to bodily injury or death, the property destroyed is the physical body.
Media-driven dehumanization
The propaganda model of Edward S. Herman and Noam Chomsky argues that corporate media are able to carry out large-scale, successful dehumanization campaigns when they promote the goals (profit-making) that the corporations are contractually obliged to maximize. State media are also capable of carrying out dehumanization campaigns, whether in democracies or dictatorships, which are pervasive enough that the population cannot avoid the dehumanizing memes.
War propaganda
National leaders use dehumanizing propaganda to sway public opinion in favor of the military elite's agenda or cause and to repel criticism and proper oversight. The Bush Jr administration used dehumanizing rhetoric to describe Arabs and Muslims collectively as backwards, violent fanatics who "hate us for our freedom" to justify his invasions of Afghanistan and Iraq and covert CIA operations in the Middle East and Africa. The media propaganda portrayed Arabs as a "monolithic evil" in the perception of the unwitting American public. They employed news, media, language, magazine stories, television, and popular culture to portray all Muslims as Arab and all Arabs as violent terrorists which much be feared, fought, and destroyed. Racism was also used by portraying all Arabs as dark-skinned and thus racially inferior and untrustworthy.
Non-state actors
Non-state actors—terrorists in particular—have also resorted to dehumanization to further their cause. The 1960s terrorist group Weather Underground had advocated violence against any authority figure and used the "police are pigs" meme to convince members that they were not harming human beings but merely killing wild animals. Likewise, rhetoric statements such as "terrorists are just scum", is an act of dehumanization.
In science, medicine, and technology
Relatively recent history has seen the relationship between dehumanization and science result in unethical scientific research. The Tuskegee syphilis experiment, Unit 731, and Nazi human experimentation on Jewish people are three such examples. In the former, African Americans with syphilis were recruited to participate in a study about the course of the disease. Even when treatment and a cure were eventually developed, they were withheld from the African-American participants so that researchers could continue their study. Similarly, Nazi scientists during the Holocaust conducted horrific experiments on Jewish people and Shiro Ishii's Unit 731 also did so to Chinese, Russian, Mongolian, American, and other nationalities held captive. Both were justified in the name of research and progress, which is indicative of the far-reaching effects that the culture of dehumanization had upon this society. When this research came to light, efforts were made to protect future research participants, and currently, institutional review boards exist to safeguard individuals from being exploited by scientists.
In a medical context, some dehumanizing practices have become more acceptable. While the dissection of human cadavers was seen as dehumanizing in the Dark Ages (see history of anatomy), the value of dissections as a training aid is such that they are now more widely accepted. Dehumanization has been associated with modern medicine generally and has explicitly been suggested as a coping mechanism for doctors who work with patients at the end of life. Researchers have identified six potential causes of dehumanization in medicine: deindividuating practices, impaired patient agency, dissimilarity (causes which do not facilitate the delivery of medical treatment), mechanization, empathy reduction, and moral disengagement (which could be argued to facilitate the delivery of medical treatment).
In some US states, legislation requires that a woman view ultrasound images of her fetus before having an abortion. Critics of the law argue that merely seeing an image of the fetus humanizes it and biases women against abortion. Similarly, a recent study showed that subtle humanization of medical patients appears to improve care for these patients. Radiologists evaluating X-rays reported more details to patients and expressed more empathy when a photo of the patient's face accompanied the X-rays. It appears that the inclusion of the photos counteracts the dehumanization of the medical process.
Dehumanization has applications outside traditional social contexts. Anthropomorphism (i.e., perceiving mental and physical capacities that reflect humans in nonhuman entities) is the inverse of dehumanization. Waytz, Epley, and Cacioppo suggest that the inverse of the factors that facilitate dehumanization (e.g., high status, power, and social connection) should promote anthropomorphism. That is, a low status, socially disconnected person without power should be more likely to attribute human qualities to pets or inanimate objects than a high-status, high-power, socially connected person.
Researchers have found that engaging in violent video game play diminishes perceptions of both one's own humanity and the humanity of the players who are targets of the game violence. While the players are dehumanized, the video game characters are often anthropomorphized.
Dehumanization has occurred historically under the pretense of "progress in the name of science". During the 1904 Louisiana Purchase Exposition, human zoos exhibited several natives from independent tribes worldwide, most notably a young Congolese man, Ota Benga. Benga's imprisonment was put on display as a public service showcasing "a degraded and degenerate race". After relocating to New York in 1906, public outcry led to the permanent ban and closure of human zoos in the United States.
In philosophy
Danish philosopher Søren Kierkegaard explained his stance of anti-dehumanization in his teachings and interpretations of Christian theology. He wrote in his book Works of Love his understanding to be that "to love one's neighbor means equality… your neighbor is every man… he is your neighbor on the basis of equality with you before God; but this equality absolutely every man has, and he has it absolutely."
In art
Spanish romanticism painter Francisco Goya often depicted subjectivity involving the atrocities of war and brutal violence conveying the process of dehumanization. In the romantic period of painting, martyrdom art was most often a means of deifying the oppressed and tormented, and it was common for Goya to depict evil personalities performing these acts; however, he broke convention by dehumanizing these martyr figures: "...one would not know whom the painting depicts, so determinedly has Goya reduced his subjects from martyrs to meat".
See also
References
External links
Abuse
Harassment and bullying
Incitement to genocide
Interpersonal relationships
Moral psychology
Prejudice and discrimination
Social psychology concepts
Social inequality
Terrorism tactics
Violence
Human rights abuses | Dehumanization | Biology | 6,082 |
648,513 | https://en.wikipedia.org/wiki/I/O%20bound | In computer science, I/O bound refers to a condition in which the time it takes to complete a computation is determined principally by the period spent waiting for input/output operations to be completed, which can be juxtaposed with being CPU bound. This circumstance arises when the rate at which data is requested is slower than the rate it is consumed or, in other words, more time is spent requesting data than processing it.
I/O bound as an inherent problem in computing
The I/O bound state has been identified as a problem in computing almost since its inception. The Von Neumann architecture, which is employed by many computing devices, this involves multiple possible solutions such as implementing a logically separate central processor unit which along with storing the instructions of the program also retrieves actual data usually from main memory and makes use of this more accessible data for working. When the process is terminated it writes back the results to the original storage (usually the main memory).
Since data must be moved between the CPU and memory along a bus which has a limited data transfer rate, there exists a condition that is known as the Von Neumann bottleneck. Put simply, this means that the data bandwidth between the CPU and memory tends to limit the overall speed of computation. In terms of the actual technology that makes up a computer, the Von Neumann Bottleneck predicts that it is easier to make the CPU perform calculations faster than it is to supply it with data at the necessary rate for this to be possible.
In recent history, the Von Neumann bottleneck has become more apparent. The design philosophy of modern computers is based upon a physically separate CPU and main memory. It is possible to make the CPU run at a high data transfer rate because data is moved between locations inside them across tiny distances. The physical separation between CPU and main memory, however, requires a data bus to move data across
comparatively long distances of centimetres or more. The problem of making this part of the system operate sufficiently fast to keep up with the CPU has been a great challenge to designers.
I/O bound as a practical problem
The I/O bound state is considered undesirable because it means that the CPU must stall its operation while waiting for data to be loaded or unloaded from main memory or secondary storage. With faster computation speed being the primary goal of new computer designs and components such as the CPU and memory being expensive, there is a strong imperative to avoid I/O bound states and eliminating them can yield a more economic improvement in performance than upgrading the CPU or memory.
As CPU gets faster, processes tend to get more I/O-bound
Or in simpler terms:
As CPU gets faster, processes tend to not increase in speed in proportion to CPU speed because they get more I/O-bound.
This means that I/O bound processes are slower than non-I/O bound processes, not faster. This is due to increases in the rate of data processing in the core, while the rate at which data is transferred from storage to the processor does not increase with it. As CPU clock speed increases, allowing more instructions to be executed in a given time window, the limiting factor of effective execution is the rate at which instructions can be delivered to the processor from storage, and sent from the processor to their destination. In short, programs naturally shift to being more and more I/O bound.
Comparison with CPU-bound
Assume we have one CPU-bound process and many I/O-bound processes. As the processes flow around the system, the following scenario may result. The CPU-bound process will get and hold the CPU. During this time, all the other processes will finish their I/O and will move into the ready queue, waiting for the CPU. While the processes wait in the ready queue, the I/O devices are idle. Eventually, the CPU-bound process finishes its CPU burst and moves to an I/O device. All the I/O-bound processes, which have short CPU bursts, execute quickly and move back to the I/O queues. At this point, the CPU sits idle. The CPU-bound process will then move back to the ready queue and be allocated the CPU. Again, all the I/O processes end up waiting in the ready queue until the CPU-bound process is done. There is a convoy effect as all the other processes wait for the one big process to get off the CPU. This effect results in lower CPU and device utilization than might be possible if the shorter processes were allowed to go first.
See also
CPU-bound
Memory-bound
References
Input/output
Computer performance | I/O bound | Technology | 929 |
38,120,561 | https://en.wikipedia.org/wiki/51%20Orionis | 51 Orionis is a single star in the equatorial constellation of Orion. It has the Bayer designation b Orionis, while 51 Orionis is the Flamsteed designation. This object is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.90. It is located approximately 299 light-years away from the Sun based on parallax, and is drifting further away with a radial velocity of +88 km/s.
This is an aging giant star with a stellar classification of K1III, having exhausted the supply of hydrogen at its core and expanded to 19 times the Sun's radius. It is four billion years old with 1.11 times the mass of the Sun. The star is radiating 132 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,458 K.
References
K-type giants
Orion (constellation)
Orionis, b
BD+01 1105
Orionis, 51
037984
026885
1963 | 51 Orionis | Astronomy | 213 |
6,879,764 | https://en.wikipedia.org/wiki/Antique%20Gas%20and%20Steam%20Engine%20Museum | The Antique Gas & Steam Engine Museum (AGSEM) is a living history museum founded in 1969. It is located on of county-owned land at 2040 N Santa Fe Ave. on the outskirts of Vista, California. The museum is a non-profit 501c(3) organization, run by several paid employees along with volunteer help.
The museum is open almost every day of the year and has two bi-annual shows, on the 3rd and 4th weekends of June and October. The museum also has other public and private events throughout the year.
Technology museum
Gas Engine Row has many large stationary gas engines from the early 1900s. On the row is an operational Fairbanks-Morse mine hoist winding engine, a pumphouse powered by a Fairbanks-Morse engine, a horsepower 1922 Fairbanks-Morse type YV engine connected to a large alternator, an enormous 1914 Chicago-Pneumatic hot-bulb air compressor, an Western engine, a Western engine, a Western engine and many other stationary engines. Almost all of the engines on Gas Engine Row can be seen running during the shows.
Steam Engine Row showcases many different types and sizes of stationary steam engines; from a monstrous Allis Chalmers Corliss engine with a flywheel, to a small J. Lefel & Sons portable engine. They are all powered by steam from two large boilers, nicknamed Pat and Rich, after two long-time museum volunteers who maintain and operate them.
Steam engines
There are six operational steam traction engines on the grounds, with a 1913 Buffalo-Pitts steamroller and a 1909 20 horsepower Case undergoing restoration. The operational steam tractors are an 1895 Russell & Co. 15-30 steam tractor, a 1902 Advance 16-30 steam tractor, a 1912 J.I. Case steam tractor, a 1920 Minneapolis steam tractor, and a 1916 15-30 Russell & Co. Most, if not all, of these tractors can be seen steaming around the grounds during the show days.
Tractors
The museum is also home to a large number of old tractors. Two D8 Caterpillars, a D9, a few large 1930s Caterpillars, some Best crawlers and many other examples of tracked tractors can be seen at the museum. The typical tractors such as Farmall, John Deere, Oliver, and Allis-Chalmers can be seen out at the museum, but there are more than a few rarer examples too. There is a 1924 Buffalo-Springfield road roller, a gigantic 1918 30-60 Aultman-Taylor gas tractor, a 1911 Fairbanks-Morse 15-25 kerosene tractor, a 1915 International Harvester Mogul 8-16, several Rumely Oil-Pulls, and many more.
Blacksmithing
There is an operational blacksmith shop with an operating line shaft setup powered by a 15-horsepower 1917 Mogul gasoline engine. During the show days, there are multiple forges lit, and multiple blacksmiths can be found working pieces of iron into many different things.
Model Railroad
Also located on museum grounds is the Short Track Model Railroad Club, featuring an NTrak model railroad with trains traveling through more than 40 modules, including a drive-in movie theater, a fairgrounds, farms, towns, and a coal mine and other scenes.
The Short Track, N-Scale, Model Railroad club is an educational organization that seeks to further the appreciation of railroad history in the United States. Many members are also National Model Railroad Association (NMRA) members and a few have earned the title of "Master Modeler." Their Donner Pass, N-scale, model railroad exhibit shows the Southern Pacific crossing of the Sierra Mountains between Colfax, CA and West Reno, NV.
There is also a small layout that can be operated by children (The Young & Victorious RR).
Textile museum
The Museum Weavers are housed in a barn, featuring more than 50 working looms for weaving. Members of this club meet weekly to learn and practice weaving, rug-making and rope-making.
Mill museum
The working gristmill grinds wheat and corn into flour, which is available for sale during the twice-yearly shows. During the summer months, the museum grows sorghum cane, which is made into molasses for the fall show.
Sawmill
The Sawmill is run by a D-3000 Cat diesel engine, Hawthorne Machinery in San Diego provided the cylinder liners. The Sawmill was re-assembled and improved following a donation from the Pederson Brothers who had operated it in the Big Bear area years ago. This is likely the only Sawmill that can be seen operating in San Diego County.
See also
Category: Museums in San Diego County
References
Official site
Big Blend Magazine article
Museums established in 1969
American West museums in California
Technology museums in California
Farm museums in California
Open-air museums in California
Textile museums in the United States
Mill museums in California
Transportation museums in California
Museums in San Diego County, California
Weaving
History of metallurgy
Schoolhouses in the United States
Steam museums in the United States
1969 establishments in California
Gas museums
Vista, California | Antique Gas and Steam Engine Museum | Chemistry,Materials_science | 1,016 |
22,579,001 | https://en.wikipedia.org/wiki/Gender%20differences%20in%20social%20network%20service%20use | Men and women use social network services (SNSs) differently and with different frequencies. In general, several researchers have found that women tend to use SNSs more than men and for different and more social purposes.
Historical connections
Technologies, including communications technologies, have a long history of shaping and being shaped by the gender of their users. Although technologies used to perform housework have an apparent historical connection to gender in many cultures, a more ready connection to SNSs may be drawn with telephones as a communications technology readily and widely available in the home. Telephone use has long had gendered connections ranging from the widespread assumption that women simply talk more than men, and the employment of women as telephone operators. In particular, young women have been closely associated with extensive and trivial use of the telephone for purely social purposes. Similarly, women's use of and influence on the development of computers has been trivialized while significant developments in computers have been masculinized.
There may be both real and perceived differences in how men and women use SNSs – and that those uses may shape the SNSs – has historical analogues. There is historical and contemporary evidence that current fears about young girls' online safety have historical antecedents such as telegraphs and telephones. Further, in many cases those historical reactions resulted in restrictions of girls' use of technology to protect them from predators, molesters, and other criminals threatening their innocence. Like current fears focused on computer use, particularly SNSs and other communication media, these fears are most intense when the medium enters the home. These fears have the potential to – at least temporarily – overwhelm the positive and empowering uses of these technologies. These historical fears are echoed in contemporary media accounts of youths' use of SNSs.
Finally, the histories of some SNSs themselves have ties with gender. For example, gay men were one of the earliest groups to join and use the early SNS Friendster.
Differences
Predilection for usage
Many studies have found that women are more likely to use either specific SNSs such as Facebook or MySpace or SNSs in general. In 2015, 73% of online men and 80% of online women used social networking sites. The gap in gender differences has become less apparent in LinkedIn. In 2015 about 26 percent of online men and 25% of online women used the business-and employee-oriented networking site.
Researchers who have examined the gender of users of multiple SNSs have found contradictory results. Hargittai's groundbreaking 2007 study examining race, gender, and other differences between undergraduate college student users of SNSs found that women were not only more likely to have used SNSes than men but that they were also more likely to have used many different services, including Facebook, MySpace, and Friendster; these differences persisted in several models and analyses. Although she only surveyed students at one institution – the University of Illinois at Chicago – Hargittai selected that institution intentionally as "an ideal location for studies of how different kinds of people use online sites and services." In contrast, data collected by the Pew Internet & American Life Project found that men were more likely to have multiple SNS profiles. Although the sample sizes of the two surveys are comparable – 1,650 Internet users in the Pew survey compared with 1,060 in Hargittai's survey – the data from the Pew survey are newer and arguably more representative of the entire adult United States population.
Pinterest, Facebook, and Instagram attract more females. Picture sharing sites overall are very popular among women. Pinterest alone attracts three times as many female users than male. However, use of Pinterest by men has increased from 5% in 2012. Facebook attracts about 77% of women online. Instagram is also more likely to attract women. Men are more likely to participate in online forums like Reddit, Digg or Slashdot. One in five men claim to be a part of an online forum.
Uses
In general, women seem to use SNSs more to explicitly foster social connections. A study conducted by Pew research centers found that women were more avid users of social media. In November 2010, the gap between men and women was as high as 15%. Female participants in a multi-stage study conducted in 2007 to discover the motivations of Facebook users scored higher on scales for social connection and posting of photographs. Studies have also been conducted on the differences between females and males with regards to blogging. The Pew Research Center found that younger females are more likely to blog than males their own age, even males that are older than them. Similarly, in a study of blogs maintained in MySpace, women were found to be more likely to not only write blogs but also write about family, romantic relationships, friendships, and health in those blogs. A study of Swedish SNS users found that women were more likely to have expressions of friendship, specifically in the areas of (a) publishing photos of their friends, (b) specifically naming their best friends, and (c) writing poems to and about their friends. Women were also more likely to have expressions related to family relationships and romantic relationships. One of the key findings of this research is that those men who do have expressions of romantic relationships in their profile had expressions just as strong as the women. However, the researcher speculated that this may be in part due to a desire to publicly express heterosexual behaviors and mannerisms instead of merely expressing romantic feelings.
A large-scale study of gender differences in MySpace found that both men and women tended to have a majority of female Friends, and both men and women tended to have a majority of female "Top" Friends in the site.
A later study found women to author disproportionately many (public) comments in MySpace,
but an investigation into the role of emotion in public MySpace comments found that women both give and receive stronger positive emotion.
It was hypothesised that women are simply more effective at using social networking sites because they are better able to harness positive emotion.
A study focused on the influence of gender and personality on individuals’ use of online social networking websites such as Facebook, reported that men use social networking sites with the intention of forming new relationships, whereas, women use them more for relationship maintenance. (Muscanell and Guadagno, 2012)
In addition to this, women are more likely to use Facebook or MySpace to compare themselves to others and also to search for information. Men, however, are more likely to look at other people's profiles with in the intention to find friends. (Haferkamp et al., 2012)
Privacy
Privacy has been the primary topic of many studies of SNS users, and many of these studies have found differences between male and female SNS users, although some studies have found results contradictory to those found in other studies.
Some researchers have found that women are more protective of their personal information and more likely to have private profiles. Other researchers have found that women are less likely to post some types of information. Acquisti and Gross found that women in their sample were less likely to reveal their sexual orientation, personal address, or cell phone number. This is similar to Pew Internet & American Life research of children users of SNSs that found that boys and girls presented different views of privacy and behaviors, with girls being more concerned about and restrictive of information such as city, town, last name, and cell phone number that could be used to locate them. At least one group of researchers has found that women are less likely to share information that "identifies them directly – last name, cell phone number, and address or home phone number," linking that resistance to women's greater concerns about "cyberstalking", "cyberbullying", and security problems.
Despite these concerns about privacy, researchers have found that women are more likely to maintain up-to-date photos of themselves. Further, Kolek and Saunders found in their sample of college student Facebook users that women were more likely to not only post a photograph of themselves in their profile but that they were more likely to have a publicly viewable Facebook account (a contradictory finding compared to many other studies), post photos, and post photo albums.
Women were more likely to have: (a) a publicly viewable Facebook account, (b) more photo albums, (c) more photos, (d) a photo of themselves as their profile picture, (e) positive references to alcohol, partying, or drugs, and (f) more positive references to or about the institution or institution-related activities. In general, women were more likely to disclose information about themselves in their Facebook profile, with the primary exception of sharing their telephone number. Similarly, female respondents to Strano's study were more likely to keep their profile photo recent and choose a photo that made them appear attractive, happy, and fun-loving. Citing several examples, Strano opined that there may also be a difference in how men and women Facebook users display and interpret profile photos depicting relationships.
Privacy has also been a concern for the SnapChat app, which allows you to send messages either text or photo or video which then disappear. One study has shown that security is not a major concern for the majority of users and that most do not use Snapchat to send sensitive content (although up to 25% may do so experimentally). As part of their research almost no statistically significant gender differences were found.
Cyberbullying
Past research carried out to investigate if there are any gender differences in cyber-bullying has found that boys commit more cyber verbal bullying, cyber forgery and more violence based on hidden identity or presenting themselves as other person. (Sincek 2014).
Mansplaining
A 2021 article found that mansplaining could be seen more prominent online rather than offline, saying that "More than 50% of our respondents in the United States and 30% in the UK heard of the term. We find a discrepancy between the percentage of women to whom mansplaining happened (54%) and men who were accused of mansplaining (24%)." The authors analyzed information and conducted experiments to find if mansplaining could cause potential silence of female voices because they were afraid they would have to face sexist remarks.
In online discussion
A 2021 article by Emily Van Duyn, Cynthia Peacock, and Natalie Jomini Stroud, suggests that women's voices are typically only heard in smaller matters.
Similarities
Although men and women users of SNSs exhibit different behavior and motivations, they share some similarities. For example, one study that examined the veracity of information shared on SNSs by college students found that men and women were as likely to "provide accurate and complete information about their birthday, schedule of classes, partner's name, AIM, or political views."
In contradiction to several of the studies described above that found that women are more likely to be SNS users, at least one very reputable study has found that men and women are equally likely to be SNS users. Data gathered in December 2008 by the Pew Internet & American Life Project showed that the SNS users in their sample were equally divided among men and women. As mentioned above, the data from the Pew survey are newer and arguably more representative of the entire adult United States population than the data in much of the previously described research.
Traditional gender roles
Some studies have found that traditional gender roles are present in SNSs, with men in this study conforming to traditional views of masculinity and the women to traditional views of femininity. Qualitative work with college student SNS users by Martínez Alemán and Wartman and Managgo et al. have found similar results for both Facebook and MySpace users. Moreover, the work by Managgo et al. discovered not only traditional gender roles and images but sexualisation of female users of MySpace. Similarly, research into the impact of comments in the profile of a Facebook users on that user's perceived attractiveness revealed a "sexual double standard", wherein negative statements resulted in male profile owners being judged more attractive and female profile owners less attractive. Finally, at least one study has found that men and women SNS users both left textual clues about their gender.
Other gender identities in social networking
In February 2014, Facebook announced the vast expansion of options for choosing gender identities to list on profiles, ranging to up to 56 gender identity choices. In August 2014, Facebook followed up with allowing gender-neutral relationship identities for identifying family members.
See also
Identity (social science)
Social aspects of television
Social networking service
References
Gender roles
Social media | Gender differences in social network service use | Technology | 2,575 |
32,424,889 | https://en.wikipedia.org/wiki/Psychiatric%20pharmacy | Psychiatric pharmacy, also known as mental health pharmacy, is the area of clinical pharmacy specializing in the treatment of people with psychiatric illnesses through the use of psychotropic medications. It is a branch of neuropsychiatric pharmacy, which includes neurologic pharmacy. Areas where psychiatric pharmacists are found most abundantly are in chemical dependency, developmental disabilities, long-term care facilities, adherence clinics, mental health clinics, and within the prison system. However, psychiatry and neurology are not the only areas where psychiatric pharmacists require comprehensive knowledge. They must also be proficient in clinical problem solving, interprofessionalism, and communication with understanding and empathy for the patient population they serve, as they are a sensitive group.
History
Psychiatric pharmacy was introduced in the late 1960s. The first time a psychiatric pharmacist was able to practice in a psychiatric unit was in 1971, as assigned by the US Public Health Service. This became the setting for the first published case where the role of a psychiatric pharmacist was elaborated upon. Psychiatric pharmacists were working not only in psychiatric inpatient and outpatient settings, but in methadone and disulfiram clinics, along with centers for mentally disabled people. During this time, the University of Tennessee created contracts which allowed for pharmacy dispensing and clinical services for local psychiatric facilities. This treatment paradigm involved some of the collaborative drug therapy management and medication therapy management (MTM) systems in which psychiatric pharmacists employ today.
The College of Psychiatric and Neurologic Pharmacists (CPNP) is a professional organization that represents psychiatric pharmacists within the United States. CPNP credits two key pharmacists with developing clinical psychiatric pharmacy as a specialty: Dr. Glen Stimmel, PharmD, BCPP and Dr. R. Lee Evans, PharmD, FASHP, BCPP. Dr. Stimmel would later become a founding member of CPNP, as well as serve as its president. Dr. Matthew Fuller PharmD, BCPP, FASHP, CPNP Foundation President 2006–2007, has recognized Dr. Stimmel as the "Father of Psychiatric Pharmacy." The specialty of psychiatric pharmacy was recognized by the Board of Pharmacy Specialties (BPS) in 1992.
Practitioners
In the United States
Psychiatric pharmacy is practiced by psychiatric (also called "neuropsychiatric") pharmacists. Psychiatric pharmacists tend to have a board certification in the specialty of psychiatric pharmacy, granting the title of Board Certified Psychiatric Pharmacist (BCPP) by the Board of Pharmacy Specialties (BPS), and attach the post-nominals after their professional degrees. Because the BPS does not have a separate certification for neurologic pharmacists, neurologic pharmacists may be classified as BCPP's as well (indeed, there is a significant amount of overlap between the two subspecialties). It is not uncommon for psychiatric pharmacists to be residency trained through a specialized residency (post-graduate year 2, abbreviated "PGY2") program in psychiatric pharmacy. The BCPP program validates that the pharmacist being certified has the progressive knowledge and experience to improve outcomes and recovery for patients with mental or neurological disabilities by designing, implementing, monitoring, and modifying treatment plans for patients as needed. It also ensures that the pharmacist being certified will educate patients, health care professionals, and other stakeholders.
Psychiatric pharmacists work in both the inpatient and outpatient settings.
Psychiatric pharmacists working for the Veterans Health Administration can have salaries between $112,268-145,955.
In the United Kingdom
Psychiatric pharmacy is practiced by specialist mental health pharmacists. Specialist mental health pharmacists tend to work in the inpatient setting, within mental health hospitals. Credentialing is performed through the College of Mental Health Pharmacy (CMHP), which assesses the experience and aptitude of pharmacists working in the field of mental health (psychiatric) pharmacy. Credentialed members are granted the title of Member of the College of Mental Health Pharmacy (MCMHP), and attach the post-nominals after their professional degrees. Notable psychiatric pharmacists include Professor David Taylor, foundation president of the college of mental health pharmacy.
Scope of practice
As experts in pharmacotherapy, psychiatric pharmacists are trained to assure that patients with mental illness are treated with the most appropriate medications for their conditions. They provide a variety of services aimed at making sure that patients are treated safely, that side effects are minimized (if not eliminated), and that pharmacologic treatments are efficacious at controlling or halting disease progression.
Comprehensive medication management
Psychiatric pharmacists provide a service called comprehensive medication management (CMM), which involves a thorough assessment of a patient's present and past medication history, laboratory work-up and exam findings, and treatment goals. During CMM, psychiatric pharmacists look for drug related problems (DRPs) related to their patients' pharmacotherapy and correct them in collaboration with psychiatrists, social workers, and other members of the interdisciplinary healthcare team, collaborating closely with the patient and their family.
Therapeutic drug monitoring
Psychiatric pharmacists provide therapeutic drug monitoring, which involves ordering laboratory tests that will measure the concentration of a medication in the blood. This is especially useful in the area of psychiatric pharmacy because a lot of drugs used to treat psychiatric illnesses (for example, lithium citrate and clozapine) have a narrow therapeutic window. There is a lot of potential for severe adverse reactions when using certain psychiatric medications, making therapeutic drug monitoring a useful tool for preventing harmful outcomes. The National Council for Behavioral Health, a collaborative that represents the interests of psychiatric professional organizations, offers recommendations for targeted, interdisciplinary interventions by psychiatric pharmacists, including pharmacist-lead clozapine clinics and providing long-acting injectable antipsychotic administration services.
Psychiatric pharmacists are sometimes involved in collaborative practice agreements which physicians, which allows pharmacists to add or remove medications from a patient's drug regimen, change the strengths/dose or frequencies of medications, the duration of treatment, and the route of administration. Combined with therapeutic drug monitoring, this allows psychiatric pharmacists to directly make changes to a patient's drug regimen based on the results from laboratory tests.
References
External links
"Explore Psychiatric Pharmacy Practice Settings", a video by CPNP interviewing psychiatric pharmacists about their clinical practice.
Psychiatry Toolkit, by Pharmacist's Letter
Pharmacy
Psychopharmacology | Psychiatric pharmacy | Chemistry | 1,378 |
25,213,120 | https://en.wikipedia.org/wiki/Analysis%20of%20water%20chemistry | Water chemistry analyses are carried out to identify and quantify the chemical components and properties of water samples. The type and sensitivity of the analysis depends on the purpose of the analysis and the anticipated use of the water. Chemical water analysis is carried out on water used in industrial processes, on waste-water stream, on rivers and stream, on rainfall and on the sea. In all cases the results of the analysis provides information that can be used to make decisions or to provide re-assurance that conditions are as expected.
The analytical parameters selected are chosen to be appropriate for the decision-making process or to establish acceptable normality. Water chemistry analysis is often the groundwork of studies of water quality, pollution, hydrology and geothermal waters.
Analytical methods routinely used can detect and measure all the natural elements and their inorganic compounds and a very wide range of organic chemical species using methods such as gas chromatography and mass spectrometry. In water treatment plants producing drinking water and in some industrial processes using products with distinctive taste and odors, specialized organoleptic methods may be used to detect smells at very low concentrations.
Types of water
Environmental water
Samples of water from the natural environment are routinely taken and analyzed as part of a pre-determined monitoring program by regulatory authorities to ensure that waters remain unpolluted, or if polluted, that the levels of pollution are not increasing or are falling in line with an agreed remediation plan. An example of such a scheme is the harmonized monitoring scheme operated on all the major river systems in the UK. The parameters analyzed will be highly dependent on nature of the local environment and/or the polluting sources in the area. In many cases the parameters will reflect the national and local water quality standards determined by law or other regulations. Typical parameters for ensuring that unpolluted surface waters remain within acceptable chemical standards include pH, major cations and anions including ammonia, nitrate, nitrite, phosphate, conductivity, phenol, chemical oxygen demand (COD) and biochemical oxygen demand (BOD).
Drinking water supplies
Surface or ground water abstracted for the supply of drinking water must be capable of meeting rigorous chemical standards following treatment. This requires a detailed knowledge of the water entering the treatment plant. In addition to the normal suite of environmental chemical parameters, other parameters such as hardness, phenol, oil and in some cases a real-time organic profile of the incoming water as in the River Dee regulation scheme.
Industrial process water
In industrial process, the control of the quality of process water can be critical to the quality of the end product. Water is often used as a carrier of reagents and the loss of reagent to product must be continuously monitored to ensure that correct replacement rate. Parameters measured relate specifically to the process in use and to any of the expected contaminants that may arise as by-products. This may include unwanted organic chemicals appearing in an inorganic chemical process through contamination with oils and greases from machinery. Monitoring the quality of the wastewater discharged from industrial premises is a key factor in controlling and minimizing pollution of the environment. In this application monitoring schemes Analyse for all possible contaminants arising within the process and in addition contaminants that may have particularly adverse impacts on the environment such as cyanide and many organic species such as pesticides. In the nuclear industry analysis focuses on specific isotopes or elements of interest. Where the nuclear industry makes wastewater discharges to rivers which have drinking water abstraction on them, radioisotopes which could potentially be harmful or those with long half-lives such as tritium will form part of the routine monitoring suite.
Methodology
To ensure consistency and repeatability, the methods use in the chemical analysis of water samples are often agreed and published at a national or state level. By convention these are often referred to as "Blue book".
Certain analyses are performed in-field (e.g. pH, specific conductance) while others involve sampling and laboratory testing.
The methods defined in the relevant standards can be broadly classified as:
Conventional wet chemistry including the Winkler method for dissolved oxygen, precipitation, filtration for solids, acidification, neutralization, titration etc. Colorimetric methods such as MBAS assay which indicates anionic surfactants in water and on site comparator methods to determine chlorine and chloramines. Nephelometers are used to measure solids concentrations as turbidity. These methods are generally robust and well tried and inexpensive, giving a reasonable degree of accuracy at modest sensitivity.
Electro chemistry including pH, conductivity and dissolved oxygen using oxygen electrode. These methods yield accurate and precise results using electronic equipment capable of feeding results directly into a laboratory data management system
Spectrophotometry is used particularly for metallic elements in solution producing results with very high sensitivity, but which may require some sample preparation prior to analysis and may also need specialized sampling methods to avoid sample deterioration in transit.
Chromatography is used for many organic species which are volatile, or which can yield a characteristic volatile component of after initial chemical processing.
Ion chromatography is a sensitive and stable technique that can measure lithium, ammonium NH4 and many other low molecular weight ions using ion exchange technology.
Gas chromatography can be used to determine methane, carbon dioxide, cyanide, oxygen, nitrogen and many other volatile components at reasonable sensitivities.
Mass spectrometry is used where very high sensitivity is required and is sometimes used as a back-end process after gas liquid chromatography for detecting trace organic chemicals.
Depending on the components, different methods are applied to determine the quantities or ratios of the components. While some methods can be performed with standard laboratory equipment, others require advanced devices, such as inductively coupled plasma mass spectrometry (ICP-MS).
Research
Many aspects of academic research and industrial research such as in pharmaceuticals, health products, and many others relies on accurate water analysis to identify substances of potential use, to refine those substances and to ensure that when they are manufactured for sale that the chemical composition remains consistent. The analytical methods used in this area can be very complex and may be specific to the process or area of research being conducted and may involve the use of bespoke analytical equipment.
Forensic analysis
In environmental management, water analysis is frequently deployed when pollution is suspected to identify the pollutant in order to take remedial action. The analysis can often enable the polluter to be identified. Such forensic work can examine the ratios of various components and can "type" samples of oils or other mixed organic contaminants to directly link the pollutant with the source.
In drinking water supplies the cause of unacceptable quality can similarly be determined by carefully targeted chemical analysis of samples taken throughout the distribution system.
In manufacturing, off-spec products may be directly tied back to unexpected changes in wet processing stages and analytical chemistry can identify which stages may be at fault and for what reason.
References
See also
Analytical chemistry
Drinking water quality standards
Analytical quality control
Analytical chemistry
Geochemistry
Analysis | Analysis of water chemistry | Chemistry | 1,442 |
2,261,176 | https://en.wikipedia.org/wiki/Hepatocyte%20nuclear%20factor%204 | HNF4 (Hepatocyte Nuclear Factor 4) is a nuclear receptor protein mostly expressed in the liver, gut, kidney, and pancreatic beta cells that is critical for liver development. In humans, there are two paralogs of HNF4, HNF4α and HNF4γ, encoded by two separate genes and respectively.
Ligands
HNF4 was originally classified as an orphan receptor that exhibits constitutive transactivation activity apparently by being continuously bound to a variety of fatty acids. The existence of a ligand for HNF4 has been somewhat controversial, but linoleic acid (LA) has been identified as the endogenous ligand of native HNF4 expressed in mouse liver; the binding of LA to HNF4 is reversible.
The ligand binding domain of HNF4, as with other nuclear receptors, adopts a canonical alpha helical sandwich fold and interacts with co-activator proteins.
HNF4 binds to the consensus sequence AGGTCAaAGGTCA in order to activate transcription.
Pathology
Mutations in the HNF4A gene have been linked to maturity onset diabetes of the young 1 (MODY1).
This seems to be caused by HNF4-a's role in the synthesis of SHBG, which is known to be severely diminished in patients with insulin-resistance.
See also
Hepatocyte nuclear factors
Hepatocyte nuclear factor 4A
References
External links
Intracellular receptors
Transcription factors | Hepatocyte nuclear factor 4 | Chemistry,Biology | 319 |
4,803,621 | https://en.wikipedia.org/wiki/Vesicular%20monoamine%20transporter%202 | The solute carrier family 18 member 2 (SLC18A2) also known as vesicular monoamine transporter 2 (VMAT2) is a protein that in humans is encoded by the SLC18A2 gene. SLC18A2 is an integral membrane protein that transports monoamines—particularly neurotransmitters such as dopamine, norepinephrine, serotonin, and histamine—from cellular cytosol into synaptic vesicles. In nigrostriatal pathway and mesolimbic pathway dopamine-releasing neurons, SLC18A2 function is also necessary for the vesicular release of the neurotransmitter GABA.
Binding sites and ligands
SLC18A2 is believed to possess at least two distinct binding sites, which are characterized by tetrabenazine (TBZ) and reserpine binding to the transporter. Amphetamine (TBZ site) and methamphetamine (reserpine site) bind at distinct sites on SLC18A2 to inhibit its function. SLC18A2 inhibitors like tetrabenazine and reserpine reduce the concentration of monoamine neurotransmitters in the synaptic cleft by inhibiting uptake through SLC18A2; the inhibition of SLC18A2 uptake by these drugs prevents the storage of neurotransmitters in synaptic vesicles and reduces the quantity of neurotransmitters that are released through exocytosis. Although many substituted amphetamines induce the release of neurotransmitters from vesicles through SLC18A2 while inhibiting uptake through SLC18A2, they may facilitate the release of monoamine neurotransmitters into the synaptic cleft by simultaneously reversing the direction of transport through the primary plasma membrane transport proteins for monoamines (i.e., the dopamine transporter, norepinephrine transporter, and serotonin transporter) in monoamine neurons. Other SLC18A2 inhibitors such as GZ-793A inhibit the reinforcing effects of methamphetamine, but without producing stimulant or reinforcing effects themselves.
Researchers have found that inhibiting the dopamine transporter (but not SLC18A2) will block the effects of amphetamine and cocaine; while, in another experiment, observing that disabling SLC18A2 (but not the dopamine transporter) prevents any notable action in test animals after amphetamine administration yet not cocaine administration. This suggests that amphetamine may be an atypical substrate with little to no ability to prevent dopamine reuptake via binding to the dopamine transporter but, instead, uses it to enter a neuron where it then interacts with SLC18A2 to induce efflux of dopamine from their vesicles into the cytoplasm whereupon dopamine transporters with amphetamine substrates attached move this recently liberated dopamine into the synaptic cleft.
Although most amphetamines and other monoamine releasing agents (MRA) act on VMAT2, several MRAs, including phentermine, phenmetrazine, and benzylpiperazine (BZP), are inactive at VMAT2. Others, including cathinones like mephedrone, methcathinone, and methylone, also show only weak VMAT2 activity (e.g., ~10-fold weaker than the corresponding amphetamines). MRAs acting on VMAT2 additionally continue to induce monoamine release in in-vitro systems in which VMAT2 is absent or inhibited.
List of VMAT2 Inhibitors
Lobelane
Quinlobelane
UKCP-110
CT-005404
GZ-11608
4-Benzyl-1-(3,4-dimethoxyphenethyl)piperidine [15565-25-0]
PC118857804
Valbenazine
JPC-141 (PC155541952)
arylpiperidinylquinazolines (APQs)
Inhibition
SLC18A2 is essential for enabling the release of neurotransmitters from the axon terminals of monoamine neurons into the synaptic cleft. If SLC18A2 function is inhibited or compromised, monoamine neurotransmitters such as dopamine cannot be released into the synapse via typical release mechanisms (i.e., exocytosis resulting from action potentials).
Cocaine users display a marked reduction in SLC18A2 immunoreactivity. Those with cocaine-induced mood disorders displayed a significant loss of SLC18A2 immunoreactivity; this might reflect damage to dopamine axon terminals in the striatum. These neuronal changes could play a role in causing disordered mood and motivational processes in more severely addicted users.
Induction
To date, no agent has been shown to directly interact with SLC18A2 in a way that promotes its activity. A VMAT2 positive allosteric modulator remains an elusive target in addiction and Parkinson's disease research. However, it has been observed that certain tricylcic and tetracylcic antidepressants (as well as a high-mesembrine Sceletium tortuosum extract) can upregulate the activity of VMAT2 in vitro, though whether this is due to a direct interaction is unknown.
In popular culture
Geneticist Dean Hamer has suggested that a particular allele of the SLC18A2 gene correlates with spirituality using data from a smoking survey, which included questions intended to measure "self-transcendence". Hamer performed the spirituality study on the side, independently of the National Cancer Institute smoking study. His findings were published in the mass-market book The God Gene: How Faith Is Hard-Wired into Our Genes. Hamer himself notes that SLC18A2 plays at most a minor role in influencing spirituality. Furthermore, Hamer's claim that the SLC18A2 gene contributes to spirituality is controversial. Hamer's study has not been published in a peer-reviewed journal and a reanalysis of the correlation demonstrates that it is not statistically significant.
References
Further reading
External links
Amphetamine
Biogenic amines
Molecular neuroscience
Neurotransmitter transporters
Receptors
Signal transduction
Solute carrier family
Articles containing video clips | Vesicular monoamine transporter 2 | Chemistry,Biology | 1,384 |
53,533,205 | https://en.wikipedia.org/wiki/Shanghai%20Astronomy%20Museum | Shanghai Astronomy Museum is a planetarium opened in 2021 in Lingang New City, Pudong New Area district, Shanghai. Its dome covers 38,000 square meters. It is the world's largest planetarium in terms of building scale. The planetarium, designed by New York City based Ennead Architects, serves as an educational and entertainment site for visitors. It is part of Shanghai Science and Technology Museum.
With no straight lines or right angles, the building was designed to reflect the shapes, movement and geometry of the universe. Ennead Architects design partner, Thomas J Wong, explained that the foundational design concept of the museum was to “abstractly embody within the architecture some of the fundamental laws of astrophysics, which are the rule in space.”
See also
List of planetariums
References
Astronomy
Planetaria in China
Buildings and structures in Shanghai
Tourist attractions in Shanghai
Museums established in 2021
2021 establishments in Shanghai | Shanghai Astronomy Museum | Astronomy | 187 |
31,682,956 | https://en.wikipedia.org/wiki/Taaffeite | Taaffeite (; BeMgAl4O8) is a mineral, named after its discoverer Richard Taaffe (1898–1967) who found the first sample, a cut and polished gem, in October 1945 in a jeweler's shop in Dublin, Ireland. As such, it is the only gemstone to have been initially identified from a faceted stone. Most pieces of the gem, prior to Taaffe, had been misidentified as spinel. For many years afterwards, it was known only in a few samples, and it is still one of the rarest gemstone minerals in the world.
Since 2002, the International Mineralogical Association-approved name for taaffeite as a mineral is magnesiotaaffeite-2N'2S.
Discovery
Taaffe bought a number of precious stones from a jeweller in October 1945. Upon noticing inconsistencies between the taaffeite and spinels, Taaffe sent some examples to B. W. Anderson of the Laboratory of the London Chamber of Commerce for identification on 1 November 1945. When Anderson replied on 5 November 1945, he told Taaffe that they were unsure of whether it was a spinel or something new; he also offered to write it up in Gemologist.
Properties
In 1951, chemical and X-ray analysis confirmed the principal constituents of taaffeite as beryllium, magnesium and aluminium, making taaffeite the first mineral to contain both beryllium and magnesium as essential components.
The confusion between spinel and taaffeite is understandable as certain structural features are identical in both. Anderson et al., classified taaffeite as an intermediate mineral between spinel and chrysoberyl. Unlike spinel, taaffeite displays the property of double refraction that allows distinction between these two minerals.
Usage
Because of its rarity, taaffeite is used only as a gemstone.
Formation and occurrence
Taaffeite occurs in carbonate rocks alongside fluorite, mica, spinel and tourmaline. This extremely rare mineral is increasingly found in alluvial deposits in Sri Lanka and southern Tanzania, as well as lower grade taaffeite in limestone sediments in China.
See also
List of minerals
Musgravite
References
Gemstones
Magnesium minerals
Aluminium minerals
Beryllium minerals
Hexagonal minerals | Taaffeite | Physics | 485 |
78,789,895 | https://en.wikipedia.org/wiki/2025%20in%20architecture | This article covers 2025 in architecture.
Events
January 7 to present - Several architecturally significant buildings were destroyed in the January 2025 Southern California wildfires.
Buildings and structures
Australia
Powerhouse Parramatta, expected in Sydney
Cambodia
Techno International Airport, expected in Phnom Penh
Japan
Naoshima New Museum of Art, expected in Naoshima
Tottori Prefectural Museum, in Tottori: expected to open on 30 March 2025
Netherlands
Fenix Museum, in Rotterdam: expected to open on 16 May 2025
United States
Doris Duke Theatre, in Becket, Massachusetts: expected to reopen after renovations on 9 July 2025
Universal Epic Universe, in Orlando, Florida: expected to open on 22 May 2025
Awards
AIA Gold Medal – Deborah Berke
Exhibitions
Deaths
January 3 - Hiroshi Hara, 88, Japanese architect (Kyōto Station, Umeda Sky Building, Sapporo Dome) (born 1936
References
See also
Timeline of architecture
:Category:Buildings and structures destroyed by the January 2025 Southern California wildfires
2025 architecture
2025-related lists
21st-century architecture | 2025 in architecture | Engineering | 217 |
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