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32,629,238 | https://en.wikipedia.org/wiki/Ford%209-inch%20axle | The Ford 9-inch is an automobile axle manufactured by Ford Motor Company. It is known as one of the most popular axles in automotive history. It was introduced in 1957 model year cars and ended production in 1986, having been phased out in favor of the Ford 8.8 inch axle. However, aftermarket companies still produce the 9-inch design. It is a semi-floating drop-out axle and had a GAWR up to .
One of the features which distinguishes this axle from other high-performance or heavy-duty domestic solid axles is that unlike other axle designs, access to the differential gears is not through the rear center cover; rather, in the Ford 9 inch, the rear cover is welded to the axle housing, and access to internals is obtained by removing the center cover on the pinion (front) side of the axle through which the driveshaft yoke connects, with the differential assembly coming out of the axle as a unit attached to the cover. Although this requires disconnecting the driveshaft to access the internal gearset, it offers the advantage of being able to disassemble and reassemble the differential gears and adjust clearances conveniently on the benchtop, rather than with the restricted access of working within the axle housing under the car.
General specifications
Ring gear measures
Factory nodular center sections are usually marked with an "N".
Factory center section's biggest flaw is the pinion bearing pilot support, which are prone to cracking due to the nature of the pinion gear/crown gear relationship.
Factory center sections carry two (2) different bearing dimensions ().
Factory axle shaft and differential spline count is 28 and 31, although aftermarket axles with 35 and 40 spline count are readily available from reputable manufacturers.
Wide variety of axle bearing flanges were fabricated.
Although most factory assemblies carried drum brakes, there were units which were fitted with disc brakes (Thunderbird, etc.).
Factory axle (wheel) bearings are retained via a press-on collar, and not an internal c-clip inside the differential.
Axles are straight, and not tapered (which can be cut and resplined, if so needed).
Common applications
1957-1986 Ford F-100 & F-150
1958-1960 Edsel (All series including Wagons)
1976-1980 Ford Granada
1976-1979 Lincoln Versailles
1957-1970 Ford Fairlane
1957-1971 Ford Thunderbird
1964 1/2-1973 Ford Mustang
1966-1983 Ford Bronco
1967-1984 Ford Falcon (Australia)
1968-1976 Ford Torino
1969-1970 1/2 Ford Falcon (North America)
1957-1959 Ranchero and Wagon
1967-1973 Ranchero
Note:
See also
10.5" Corporate 14 Bolt Differential
Dana 60
Notes
References
Automotive engineering
Automobile axles | Ford 9-inch axle | Engineering | 568 |
653,778 | https://en.wikipedia.org/wiki/Dystonia | Dystonia is a neurological hyperkinetic movement disorder in which sustained or repetitive muscle contractions occur involuntarily, resulting in twisting and repetitive movements or abnormal fixed postures. The movements may resemble a tremor. Dystonia is often intensified or exacerbated by physical activity, and symptoms may progress into adjacent muscles.
The disorder may be hereditary or caused by other factors such as birth-related or other physical trauma, infection, poisoning (e.g., lead poisoning) or reaction to pharmaceutical drugs, particularly neuroleptics, or stress. Treatment must be highly customized to the needs of the individual and may include oral medications, chemodenervation botulinum neurotoxin injections, physical therapy, or other supportive therapies, and surgical procedures such as deep brain stimulation.
Classification
There are multiple types of dystonia, and many diseases and conditions may cause dystonia.
Dystonia is classified by:
Clinical characteristics such as age of onset, body distribution, nature of the symptoms, and associated features such as additional movement disorders or neurological symptoms, and
Cause (which includes changes or damage to the nervous system and inheritance).
Physicians use these classifications to guide diagnosis and treatment.
Types
Generalized
Focal
Psychogenic
Acute dystonic reaction
Vegetative-vascular
Generalized dystonias
For example, dystonia musculorum deformans (Oppenheim, Flatau-Sterling syndrome):
Normal birth history and milestones
Autosomal dominant
Childhood onset
Starts in lower limbs and spreads upwards
Also known as torsion dystonia or idiopathic torsion dystonia (old terminology "dystonia musculorum deformans").
Focal dystonias
These most common dystonias are typically classified as follows:
The combination of blepharospasmodic contractions and oromandibular dystonia is called cranial dystonia or Meige's syndrome.
Genetic/primary
There is a group called myoclonic dystonia where some cases are hereditary and have been associated with a missense mutation in the dopamine-D2 receptor. Some of these cases have responded well to alcohol.
Other genes that have been associated with dystonia include CIZ1, GNAL, ATP1A3, and PRRT2. Another report has linked THAP1 and SLC20A2 to dystonia.
Signs and symptoms
Symptoms vary according to the kind of dystonia involved. In most cases, dystonia tends to lead to abnormal posturing, in particular on movement. Many individuals with the condition have continuous pain, cramping, and relentless muscle spasms due to involuntary muscle movements. Other motor symptoms are possible including lip smacking.
An accurate diagnosis may be difficult because of the way the disorder manifests itself. Affected individuals may be diagnosed as having similar and perhaps related disorders including Parkinson's disease, essential tremor, carpal tunnel syndrome, temporomandibular joint disorder, Tourette's syndrome, conversion disorder or other neuromuscular movement disorders. It has been found that the prevalence of dystonia is high in individuals with Huntington's disease, where the most common clinical presentations are internal shoulder rotation, sustained fist clenching, knee flexion, and foot inversion. Risk factors for increased dystonia in patients with Huntington's disease include long disease duration and use of antidopaminergic medication.
Causes
Primary dystonia is suspected when the dystonia is the only sign and there is no identifiable cause or structural abnormality in the central nervous system. Researchers suspect it is caused by a pathology of the central nervous system, likely originating in those parts of the brain concerned with motor function—such as the basal ganglia and the GABA (gamma-aminobutyric acid) producing Purkinje neurons. The precise cause of primary dystonia is unknown. In many cases it may involve some genetic predisposition towards the disorder combined with environmental conditions.
Meningitis and encephalitis caused by viral, bacterial, and fungal infections of the brain have been associated with dystonia. The main mechanism is inflammation of the blood vessels, causing restriction of blood flow to the basal ganglia. Other mechanisms include direct nerve injury by the organism or a toxin, or autoimmune mechanisms.
Malfunction of the sodium-potassium pump may be a factor in some dystonias. The - pump has been shown to control and set the intrinsic activity mode of cerebellar Purkinje neurons. This suggests that the pump might not simply be a homeostatic, "housekeeping" molecule for ionic gradients; but could be a computational element in the cerebellum and the brain. Indeed, an ouabain block of - pumps in the cerebellum of a live mouse results in it displaying ataxia and dystonia. Ataxia is observed for lower ouabain concentrations, dystonia is observed at higher ouabain concentrations. A mutation in the - pump (ATP1A3 gene) can cause rapid onset dystonia parkinsonism. The parkinsonism aspect of this disease may be attributable to malfunctioning - pumps in the basal ganglia; the dystonia aspect may be attributable to malfunctioning - pumps in the cerebellum (that act to corrupt its input to the basal ganglia) possibly in Purkinje neurons.
Cerebellum issues causing dystonia is described by Filip et al. 2013: "Although dystonia has traditionally been regarded as a basal ganglia dysfunction, recent provocative evidence has emerged of cerebellar involvement in the pathophysiology of this enigmatic disease. It has been suggested that the cerebellum plays an important role in dystonia etiology, from neuroanatomical research of complex networks showing that the cerebellum is connected to a wide range of other central nervous system structures involved in movement control to animal models indicating that signs of dystonia are due to cerebellum dysfunction and completely disappear after cerebellectomy, and finally to clinical observations in secondary dystonia patients with various types of cerebellar lesions. It is proposed that dystonia is a large-scale dysfunction, involving not only cortico-basal ganglia-thalamo-cortical pathways, but the cortico-ponto-cerebello-thalamo-cortical loop as well. Even in the absence of traditional "cerebellar signs" in most dystonia patients, there are more subtle indications of cerebellar dysfunction. It is clear that as long as the cerebellum's role in dystonia genesis remains unexamined, it will be difficult to significantly improve the current standards of dystonia treatment or to provide curative treatment."
Treatment
Various treatments focus on sedating brain functions or blocking nerve communications with the muscles via drugs, neuro-suppression, or selective denervation surgery. Almost all treatments have negative side-effects and risks. A geste antagoniste is a physical gesture or position (such as touching one's chin) that temporarily interrupts dystonia, it is also known as a sensory trick. Patients may be aware of the presence of a geste antagoniste that provides some relief. Therapy for dystonia can involve prosthetics that passively simulate the stimulation.
Physical intervention
While research in the area of effectiveness of physical therapy intervention for dystonia remains weak, there is reason to believe that rehabilitation can benefit dystonia patients. Physical therapy can be utilized to manage changes in balance, mobility and overall function that occur as a result of the disorder. A variety of treatment strategies can be employed to address the unique needs of each individual. Potential treatment interventions include splinting, therapeutic exercise, manual stretching, soft tissue and joint mobilization, postural training and bracing, neuromuscular electrical stimulation, constraint-induced movement therapy, activity and environmental modification, and gait training.
Recent research has investigated further into the role of physiotherapy in the treatment of dystonia. A recent study showed that reducing psychological stress, in conjunction with exercise, is beneficial for reducing truncal dystonia in patients with Parkinson's disease. Another study emphasized progressive relaxation, isometric muscle endurance, dynamic strength, coordination, balance, and body perception, seeing significant improvements to patients' quality of life after 4 weeks.
Since the root of the problem is neurological, doctors have explored sensorimotor retraining activities to enable the brain to "rewire" itself and eliminate dystonic movements. The work of several doctors such as Nancy Byl and Joaquin Farias has shown that sensorimotor retraining activities and proprioceptive stimulation can induce neuroplasticity, making it possible for patients to recover substantial function that was lost due to Cervical Dystonia, hand dystonia, blepharospasm, oromandibular dystonia, dysphonia and musicians' dystonia.
Due to the rare and variable nature of dystonia, research investigating the effectiveness of these treatments is limited. There is no gold standard for physiotherapy rehabilitation. To date, focal cervical dystonia has received the most research attention; however, study designs are poorly controlled and limited to small sample sizes.
Baclofen
A baclofen pump has been used to treat patients of all ages exhibiting muscle spasticity along with dystonia. The pump delivers baclofen via a catheter to the thecal space surrounding the spinal cord. The pump itself is placed in the abdomen. It can be refilled periodically by access through the skin. Baclofen can also be taken in tablet form
Botulinum toxin injection
Botulinum toxin injections into affected muscles have proved quite successful in providing some relief for around 3–6 months, depending on the kind of dystonia. Botox or Dysport injections have the advantage of ready availability (the same form is used for cosmetic surgery) and the effects are not permanent. There is a risk of temporary paralysis of the muscles being injected or the leaking of the toxin into adjacent muscle groups, causing weakness or paralysis in them. The injections must be repeated, as the effects wear off and around 15% of recipients develop immunity to the toxin. There is a Type A and a Type B toxin approved for treatment of dystonia; often, those that develop resistance to Type A may be able to use Type B.
Muscle relaxants
Clonazepam, a benzodiazepine, is also sometimes prescribed. However, for most, their effects are limited and side-effects like mental confusion, sedation, mood swings, and short-term memory loss occur.
Ketogenic diet
One complex case study found that a ketogenic type diet may have been helpful in reducing symptoms associated with alternating hemiplegia of childhood (AHC) of a young child. However, as the researchers noted, their results could have been corollary in nature and not due to the diet itself, though future research is warranted.
Surgery
Surgery, such as the denervation of selected muscles, may also provide some relief; however, the destruction of nerves in the limbs or brain is not reversible and should be considered only in the most extreme cases. Recently, the procedure of deep brain stimulation (DBS) has proven successful in a number of cases of severe generalised dystonia. DBS as treatment for medication-refractory dystonia, on the other hand, may increase the risk of suicide in patients. However, reference data of patients without DBS therapy are lacking.
History
The Italian Bernardino Ramazzini provided one of the first descriptions of task-specific dystonia in 1713 in a book of occupational diseases, The Morbis Artificum.
In chapter II of this book's Supplementum, Ramazzini noted that "Scribes and Notaries" may develop "incessant movement of the hand, always in the same direction … the continuous and almost tonic strain on the muscles... that results in failure of power in the right hand". A report from the British Civil Service also contained an early description of writer's cramp. In 1864, Solly coined the term "scrivener's palsy" for this condition. These historical reports usually attributed the etiology of the motor abnormalities to overuse. Then, dystonia was reported in detail in 1911, when Hermann Oppenheim, Edward Flatau and Wladyslaw Sterling described some Jewish children affected by a syndrome that was retrospectively considered to represent familial cases of DYT1 dystonia. Some decades later, in 1975, the first international conference on dystonia was held in New York. It was then recognized that, in addition to severe generalized forms, the dystonia phenotype also encompasses poorly-progressive focal and segmental cases with onset in adulthood, such as blepharospasm, torticollis and writer's cramp.
These forms were previously considered independent disorders and were mainly classified among neuroses. A modern definition of dystonia was worded some years later, in 1984. During the following years it became evident that dystonia syndromes are numerous and diversified, new terminological descriptors (e.g., dystonia plus, heredodegenerative dystonias, etc.) and additional classification schemes were introduced. The clinical complexity of dystonia was then fully recognized.
See also
Extrapyramidal symptoms
Hypertonia
Sydenham's chorea
Ulegyria (brain condition with dystonia symptoms)
References
External links
A Boston Marathon record is about to be set – by a man with a movement disorder in The Washington Post
GeneReview/NIH/UW entry on Dystonia Overview
GeneReviews/NCBI/NIH/UW entry on Early-Onset Primary Dystonia
Film on Dystonia from Public Broadcasting Service
A story of one woman's struggle with dystonia at MSNBC.com
Extrapyramidal and movement disorders
Adverse effects of psychoactive drugs
Articles containing video clips | Dystonia | Chemistry | 2,943 |
56,556,388 | https://en.wikipedia.org/wiki/Basic%20Principles%20for%20the%20Treatment%20of%20Prisoners | The Basic Principles for the Treatment of Prisoners were adopted and proclaimed by the General Assembly of the United Nations by resolution 45/111 on 14 December 1990.
Article 1 protects human dignity. Article 2 bans discrimination.
References
United Nations General Assembly resolutions
Human rights
Prisoners and detainees
Discrimination
1990 in law | Basic Principles for the Treatment of Prisoners | Biology | 59 |
11,798,314 | https://en.wikipedia.org/wiki/Control%20of%20International%20Trade%20in%20Endangered%20Species | Control of International Trade in Endangered Species also known as COTES is an organisation (1996) which complies with CITES.
COTES is used in the United Kingdom to convict wildlife crimes involving protected and endangered species.
References
Endangered species
Conservation in the United Kingdom | Control of International Trade in Endangered Species | Biology | 53 |
8,969,039 | https://en.wikipedia.org/wiki/Electrochromic%20device | An electrochromic device (ECD) controls optical properties such as optical transmission, absorption, reflectance and/or emittance in a continual but reversible manner on application of voltage (electrochromism). This property enables an ECD to be used for applications like smart glass, electrochromic mirrors, and electrochromic display devices.
History
The history of electro-coloration goes back to 1704 when Diesbach discovered Prussian blue (hexacyanoferrate), which changes color from transparent to blue under oxidation of iron. In the 1930s, Kobosew and Nekrassow first noted electrochemical coloration in bulk tungsten oxide. While working at Balzers in Lichtenstein, T. Kraus provided a detailed description of the electrochemical coloration in a thin film of tungsten trioxide (WO3) on 30 July 1953. In 1969, S. K. Deb demonstrated electrochromic coloration in WO3 thin films. Deb observed electrochromic color by applying an electric field on the order of 104 Vcm−1 across WO3 thin film. In fact, the real birth of the EC technology is usually attributed to S. K. Deb’s seminal paper of 1973, wherein he described the coloration mechanism in WO3. The electrochromism occurs due to the electrochemical redox reactions that take place in electrochromic materials. Various types of materials and structures can be used to construct electrochromic devices, depending on the specific applications.
Device structure
Electrochromic (sometimes called electrochromatic) devices are one kind of electrochromic cells. The basic structure of ECD consists of two EC layers separated by an electrolytic layer. The ECD works on an external voltage, for which the conducting electrodes are used on the either side of both EC layers. Electrochromic devices can be categorized in two types depending upon the kind of electrolyte used viz. Laminated ECD are the one in which liquid gel is used while in solid electrolyte EC devices solid inorganic or organic material is used. The basic structure of electrochromic device embodies five superimposed layers on one substrate or positioned between two substrates in a laminated configuration. In this structure there are three principally different kinds of layered materials in the ECD: The EC layer and ion-storage layer conduct ions and electrons and belong to the class of mixed conductors. The electrolyte is a pure ion conductor and separates the two EC layers. The transparent conductors are pure electron conductors. Optical absorption occurs when electrons move into the EC layers from the transparent conductors along with charge balancing ions entering from the electrolyte.
Solid-state devices
In solid-state electrochromic devices, a solid inorganic or organic material is used as the electrolyte. Ta2O5 and ZrO2 are the most extensively studied inorganic solid electrolytes.
Laminated devices
Laminated electrochromic devices contain a liquid gel which is used as the electrolyte.
Mode of operation
Typically, ECD are of two types depending on the modes of device operation, namely the transmission mode and reflectance mode. In the transmission mode, the conducting electrodes are transparent and control the light intensity passing through them; this mode is used in smart-window applications. In the reflectance mode, one of the transparent conducting electrodes (TCE) is replaced with a reflective surface like aluminum, gold or silver, which controls the reflective light intensity; this mode is useful in rear-view mirrors of cars and EC display devices.
Applications
Smart windows
Windows have both direct and indirect impacts on building energy consumption. Electrochromic windows, or the application of electrochromic switchable glazes deposited on to windows, also known as smart windows, are a technology for energy efficiency used in buildings by controlling the amount of sunlight passing through.
The solar-optical properties of electrochromic coatings vary over a wide range in response to an applied electrical signal that can be applied via execution of laboratory processes, such as Cyclic Voltammetry (CV). Specifically, these smart windows are made of Tungsten Oxide (WO3). Tungsten Oxide is known to be a standard material used for electrochromic devices because of its wide optical window, ranging from 400-630 nm, and prolonged cyclic stability on the order of thousands of cycles. To enhance the electrochromic performance of Tungsten Oxide coatings, electro chromic coatings are prepared by introducing a small amount of dopamine (DA) into a peroxo tungstic acid (PTA) precursor sol to form tungsten complexes on the surface of nanoparticles. This processing method shows promising cyclic stability as it will last up to thirty five thousand cycles which is greater than that of regular WO3 since new ligand formation promotes plasmonic tuning in nanoparticle electrochemistry. They can also produce less glare than fritted glass. The efficiency of electrochromic windows is dependent on the intrinsic properties of the coating, the placement of the coating within a window system, and parameters related to the building they are used for. In addition to this, electrochromic coating efficiency is directly dependent on the growth kinetics of such thin-film layers since thinner films, and non-even coatings, have a lower optical signal compared to the thicker films with more uniformity having more control and experience a greater optical signal.
These windows usually contain layers for tinting in response to increases in incoming sunlight and to protect from UV radiation. For example the glass developed by Gesimat, has a tungsten oxide layer, a polyvinyl butyral layer and a Prussian Blue layer sandwiched by two dual layers of glass and fluorine-doped glass coated with tin oxide. The tungsten oxide and Prussian Blue layers form the positive and negative ends of a battery using the incoming light energy. The polyvinyl butyral (PVB) forms the central layer and serves as a polymer electrolyte. This allows for the flow of ions which, in turn, generates a current.
Mirrors
Electrochromic mirrors use a combination of optoelectronic sensors and complex electronics that monitor both ambient light and the intensity of the light shining on the surface. As soon as glare makes contact with the surface, these mirrors automatically dim reflections of flashing light from following vehicles at night so that a driver can see them without discomfort. These mirrors, however, only dim relative to the amount of light that shines on them.
Other displays
Electrochromic displays can operate in one of two modes: reflecting light mode, where light or other radiation strikes a surface and is redirected, or transmitting light mode, which is transmitted through a substrate; the majority of displays operates in a reflective mode.
Even though electrochromic devices are considered to be more “passive” since they do not emit light and need external illumination to function, electrochromic coatings on devices have been proposed for flat panel displays and visual-display units (VDUs). For example, an electrochromic coating was featured on an iPod in the early 2000s, and the Nanochromic screen surpassed that of the original iPod in terms of its fidelity in display quality and screen brightness. Electrochromics have been used for other display applications as well; however, the technology is still somewhat nascent and competes with Liquid-crystal displays (LCDs) and their presence in the market.
Electrochromic devices do have advantages over materials synthesized to produce LCD based optoelectronics, such as consuming little to no power in producing images and the same amount of power is needed to keep present displays, and there is no restriction to the size of such a device since it is dependent on manufacturing capability and number of electrodes. But they are not regularly used because of their quick response times, 𝜏, estimated by the equation l=(Dt)0.5. For type I-electrochromics (solution-phase) species, the diffusion coefficient is on the order of 10–7 cm2/s. In comparison, for type III-electrochromic species, the diffusion coefficient is on the order of 10–12 cm2/s, which allows for a longer response time on the order of ten seconds compared to almost a millisecond when using type I devices. Such electrochromic displays, to be used commercially, need to be optimized at the materials processing and synthesis level to compete with LCDs in advanced display technologies beyond the iPod.
Other applications include dynamically tinting goggles and motorcycle helmet visors, and special paper for drawing on with a stylus.
Gallery
References
Optical devices | Electrochromic device | Materials_science,Engineering | 1,788 |
13,693,851 | https://en.wikipedia.org/wiki/Specified%20minimum%20yield%20strength | Specified Minimum Yield Strength (SMYS) means the specified minimum yield strength for steel pipe manufactured in accordance with a listed specification1. This is a common term used in the oil and gas industry for steel pipe used under the jurisdiction of the United States Department of Transportation. It is an indication of the minimum stress a pipe may experience that will cause plastic (permanent) deformation.
The SMYS is required to determine the maximum allowable operating pressure (MAOP) of a pipeline, as determined by Barlow's Formula which is P = (2 * S * T)/(OD * SF), where P is pressure, OD is the pipe’s outside diameter, S is the SMYS, T is its wall thickness, and SF is a [Safety Factor].
See also
History of the petroleum industry in the United States
References
ASME B31G-2012 "Manual for Determining the Remaining Strength of Corroded Pipelines pg. 2
Mechanical standards
Petroleum in the United States
Plasticity (physics) | Specified minimum yield strength | Materials_science,Engineering | 206 |
9,354,293 | https://en.wikipedia.org/wiki/Pasteur%20effect | The Pasteur effect describes how available oxygen inhibits ethanol fermentation, driving yeast to switch toward aerobic respiration for increased generation of the energy carrier adenosine triphosphate (ATP). More generally, in the medical literature, the Pasteur effect refers to how the cellular presence of oxygen causes in cells a decrease in the rate of glycolysis and also a suppression of lactate accumulation. The effect occurs in animal tissues, as well as in microorganisms belonging to the fungal kingdom.
Discovery
The effect was described by Louis Pasteur in 1857 in experiments showing that aeration of yeasted broth causes cell growth to increase while the fermentation rate decreases, based on lowered ethanol production.
Explanation
Yeast fungi, being facultative anaerobes, can either produce energy through ethanol fermentation or aerobic respiration. When the O2 concentration is low, the two pyruvate molecules formed through glycolysis are each fermented into ethanol and carbon dioxide. While only 2 ATP are produced per glucose, this method is utilized under anaerobic conditions because it oxidizes the electron shuttle NADH into NAD+ for another round of glycolysis and ethanol fermentation.
If the concentration of oxygen increases, pyruvate is instead converted to acetyl CoA, used in the citric acid cycle, and undergoes oxidative phosphorylation. Per glucose, 10 NADH and 2 FADH2 are produced in cellular respiration for a significant amount of proton pumping to produce a proton gradient utilized by ATP Synthase. While the exact ATP output ranges based on considerations like the overall electrochemical gradient, aerobic respiration produces far more ATP than the anaerobic process of ethanol fermentation. The increased ATP and citrate from aerobic respiration allosterically inhibit the glycolysis enzyme phosphofructokinase 1 because less pyruvate is needed to produce the same amount of ATP.
Despite this energetic incentive, Rosario Lagunas has shown that yeast continue to partially ferment available glucose into ethanol for many reasons. First, glucose metabolism is faster through ethanol fermentation because it involves fewer enzymes and limits all reactions to the cytoplasm. Second, ethanol has bactericidal activity by causing damage to the cell membrane and protein denaturing, allowing yeast fungus to outcompete environmental bacteria for resources. Third, partial fermentation may be a defense mechanism against environmental competitors depleting all oxygen faster than the yeast's regulatory systems could fully switch from aerobic respiration to ethanol fermentation.
Practical implications
The fermentation processes used in alcohol production is commonly maintained in low oxygen conditions, under a blanket of carbon dioxide, while growing yeast for biomass involves aerating the broth for maximized energy production. Despite the bactericidal effects of ethanol, acidifying effects of fermentation, and low oxygen conditions of industrial alcohol production, bacteria that undergo lactic acid fermentation can contaminate such facilities because lactic acid has a low pKa of 3.86 to avoid decoupling the pH membrane gradient that supports regulated transport.
See also
Ethanol fermentation
Fermentation (biochemistry)
Facultative anaerobic organism
Allosteric regulation
References
Further reading
Fermentation
Metabolism | Pasteur effect | Chemistry,Biology | 683 |
60,482,408 | https://en.wikipedia.org/wiki/Sascha%20Braunig | Sascha Braunig (born 1983) is a Canadian painter. She is best known for her hyperrealist and surrealist paintings of lay figures.
Life and education
Braunig was born in Qualicum Beach, British Columbia and lives and works in Portland, Maine.
In 2005, Braunig received a BFA in painting and photography from The Cooper Union. She went on to graduate with her MFA in painting from Yale School of Art in 2008.
Work
While at Yale School of Art, Braunig began experimenting with video. She frequently uses lighting effects and simple materials such as clay or styrofoam to create three-dimensional models or masks, on which she bases the figures in her paintings.
Braunig has received two MacDowell fellowships, in 2013 and 2023, where she worked in Peterborough, New Hampshire.
In 2015 she took part in the New Museum triennial exhibition titled Surround Audience. She has had solo exhibitions at MoMA PS1, New York and at Norway's Kunsthall Stavanger. Her work is included in the collection of the National Gallery of Victoria, Melbourne, Australia, among others.
Her inspirations range from contemporary film directors like David Cronenberg to the Flemish painters of the Northern Renaissance, such as Jan van Eyck.
Braunig was included in the 2014 Thames and Hudson book 100 Painters of Tomorrow.
References
1983 births
21st-century Canadian women artists
21st-century Canadian painters
Artists from British Columbia
People from the Regional District of Nanaimo
Artists from Portland, Oregon
Living people
Cooper Union alumni
Yale School of Art alumni
MacDowell Colony fellows
Multimedia artists | Sascha Braunig | Technology | 322 |
14,627 | https://en.wikipedia.org/wiki/Isaac%20Newton | Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English polymath active as a mathematician, physicist, astronomer, alchemist, theologian, and author who was described in his time as a natural philosopher. Newton was a key figure in the Scientific Revolution and the Enlightenment that followed. Newton's book (Mathematical Principles of Natural Philosophy), first published in 1687, achieved the first great unification in physics and established classical mechanics. Newton also made seminal contributions to optics, and shares credit with German mathematician Gottfried Wilhelm Leibniz for formulating infinitesimal calculus, though he developed calculus years before Leibniz. He contributed to and refined the scientific method, and his work is considered the most influential in bringing forth modern science.
In the , Newton formulated the laws of motion and universal gravitation that formed the dominant scientific viewpoint for centuries until it was superseded by the theory of relativity. He used his mathematical description of gravity to derive Kepler's laws of planetary motion, account for tides, the trajectories of comets, the precession of the equinoxes and other phenomena, eradicating doubt about the Solar System's heliocentricity. Newton solved the two-body problem, and introduced the three-body problem. He demonstrated that the motion of objects on Earth and celestial bodies could be accounted for by the same principles. Newton's inference that the Earth is an oblate spheroid was later confirmed by the geodetic measurements of Maupertuis, La Condamine, and others, thereby convincing most European scientists of the superiority of Newtonian mechanics over earlier systems.
Newton built the first reflecting telescope and developed a sophisticated theory of colour based on the observation that a prism separates white light into the colours of the visible spectrum. His work on light was collected in his influential book Opticks, published in 1704. He formulated an empirical law of cooling, which was the first heat transfer formulation and serves as the formal basis of convective heat transfer, made the first theoretical calculation of the speed of sound, and introduced the notions of a Newtonian fluid and a black body. Furthermore, he made early investigations into electricity, with an idea from his book Opticks arguably the beginning of the field theory of the electric force. In addition to his creation of calculus, as a mathematician, he generalized the binomial theorem to any real number, contributed to the study of power series, developed a method for approximating the roots of a function, classified most of the cubic plane curves, and also originated the Newton-Cotes formulas for numerical integration. He further devised an early form of regression analysis.
Newton was a fellow of Trinity College and the second Lucasian Professor of Mathematics at the University of Cambridge; he was appointed at the age of 26. He was a devout but unorthodox Christian who privately rejected the doctrine of the Trinity. He refused to take holy orders in the Church of England, unlike most members of the Cambridge faculty of the day. Beyond his work on the mathematical sciences, Newton dedicated much of his time to the study of alchemy and biblical chronology, but most of his work in those areas remained unpublished until long after his death. Politically and personally tied to the Whig party, Newton served two brief terms as Member of Parliament for the University of Cambridge, in 1689–1690 and 1701–1702. He was knighted by Queen Anne in 1705 and spent the last three decades of his life in London, serving as Warden (1696–1699) and Master (1699–1727) of the Royal Mint, in which he increased the accuracy and security of British coinage, as well as president of the Royal Society (1703–1727).
Early life
Isaac Newton was born (according to the Julian calendar in use in England at the time) on Christmas Day, 25 December 1642 (NS 4 January 1643) at Woolsthorpe Manor in Woolsthorpe-by-Colsterworth, a hamlet in the county of Lincolnshire. His father, also named Isaac Newton, had died three months before. Born prematurely, Newton was a small child; his mother Hannah Ayscough reportedly said that he could have fit inside a quart mug. When Newton was three, his mother remarried and went to live with her new husband, the Reverend Barnabas Smith, leaving her son in the care of his maternal grandmother, Margery Ayscough (née Blythe). Newton disliked his stepfather and maintained some enmity towards his mother for marrying him, as revealed by this entry in a list of sins committed up to the age of 19: "Threatening my father and mother Smith to burn them and the house over them." Newton's mother had three children (Mary, Benjamin, and Hannah) from her second marriage.
The King's School
From the age of about twelve until he was seventeen, Newton was educated at The King's School in Grantham, which taught Latin and Ancient Greek and probably imparted a significant foundation of mathematics. He was removed from school by his mother and returned to Woolsthorpe-by-Colsterworth by October 1659. His mother, widowed for the second time, attempted to make him a farmer, an occupation he hated. Henry Stokes, master at The King's School, persuaded his mother to send him back to school. Motivated partly by a desire for revenge against a schoolyard bully, he became the top-ranked student, distinguishing himself mainly by building sundials and models of windmills.
University of Cambridge
In June 1661, Newton was admitted to Trinity College at the University of Cambridge. His uncle the Reverend William Ayscough, who had studied at Cambridge, recommended him to the university. At Cambridge, Newton started as a subsizar, paying his way by performing valet duties until he was awarded a scholarship in 1664, which covered his university costs for four more years until the completion of his MA. At the time, Cambridge's teachings were based on those of Aristotle, whom Newton read along with then more modern philosophers, including Descartes and astronomers such as Galileo Galilei and Thomas Street. He set down in his notebook a series of "Quaestiones" about mechanical philosophy as he found it. In 1665, he discovered the generalised binomial theorem and began to develop a mathematical theory that later became calculus. Soon after Newton obtained his BA degree at Cambridge in August 1665, the university temporarily closed as a precaution against the Great Plague.
Although he had been undistinguished as a Cambridge student, his private studies and the years following his bachelor's degree have been described as "the richest and most productive ever experienced by a scientist". The next two years alone saw the development of theories on calculus, optics, and the law of gravitation, at his home in Woolsthorpe.
Newton has been described as an "exceptionally organized" person when it came to note-taking and his work, further dog-earing pages he saw as important. Furthermore, Newton's "indexes look like present-day indexes: They are alphabetical, by topic." His books showed his interests to be wide-ranging, with Newton himself described as a "Janusian thinker, someone who could mix and combine seemingly disparate fields to stimulate creative breakthroughs."
In April 1667, Newton returned to the University of Cambridge, and in October he was elected as a fellow of Trinity. Fellows were required to take holy orders and be ordained as Anglican priests, although this was not enforced in the Restoration years, and an assertion of conformity to the Church of England was sufficient. He made the commitment that "I will either set Theology as the object of my studies and will take holy orders when the time prescribed by these statutes [7 years] arrives, or I will resign from the college." Up until this point he had not thought much about religion and had twice signed his agreement to the Thirty-nine Articles, the basis of Church of England doctrine. By 1675 the issue could not be avoided, and by then his unconventional views stood in the way.
His academic work impressed the Lucasian professor Isaac Barrow, who was anxious to develop his own religious and administrative potential (he became master of Trinity College two years later); in 1669, Newton succeeded him, only one year after receiving his MA. Newton argued that this should exempt him from the ordination requirement, and King Charles II, whose permission was needed, accepted this argument; thus, a conflict between Newton's religious views and Anglican orthodoxy was averted. He was appointed at the age of 26.
The Lucasian Professor of Mathematics at Cambridge position included the responsibility of instructing geography. In 1672, and again in 1681, Newton published a revised, corrected, and amended edition of the Geographia Generalis, a geography textbook first published in 1650 by the then-deceased Bernhardus Varenius. In the Geographia Generalis, Varenius attempted to create a theoretical foundation linking scientific principles to classical concepts in geography, and considered geography to be a mix between science and pure mathematics applied to quantifying features of the Earth. While it is unclear if Newton ever lectured in geography, the 1733 Dugdale and Shaw English translation of the book stated Newton published the book to be read by students while he lectured on the subject. The Geographia Generalis is viewed by some as the dividing line between ancient and modern traditions in the history of geography, and Newton's involvement in the subsequent editions is thought to be a large part of the reason for this enduring legacy.
Newton was elected a Fellow of the Royal Society (FRS) in 1672.
Mid-life
Calculus
Newton's work has been said "to distinctly advance every branch of mathematics then studied". His work on the subject, usually referred to as fluxions or calculus, seen in a manuscript of October 1666, is now published among Newton's mathematical papers. His work De analysi per aequationes numero terminorum infinitas, sent by Isaac Barrow to John Collins in June 1669, was identified by Barrow in a letter sent to Collins that August as the work "of an extraordinary genius and proficiency in these things". Newton later became involved in a dispute with Leibniz over priority in the development of calculus. Both are now credited with independently developing calculus, though with very different mathematical notations. However, it is established that Newton came to develop calculus much earlier than Leibniz. Leibniz's notation is recognized as the more convenient notation, being adopted by continental European mathematicians, and after 1820, by British mathematicians.
Historian of science A. Rupert Hall notes that while Leibniz deserves credit for his independent formulation of calculus, Newton was undoubtedly the first to develop it, stating:Hall further notes that in Principia, Newton was able to "formulate and resolve problems by the integration of differential equations" and "in fact, he anticipated in his book many results that later exponents of the calculus regarded as their own novel achievements."
It has been noted that despite the convenience of Leibniz's notation, Newton's notation could still have been used to develop multivariate techniques, with his dot notation still widely used in physics. Some academics have noted the richness and depth of Newton's work, such as physicist Roger Penrose, stating "in most cases Newton’s geometrical methods are not only more concise and elegant, they reveal deeper principles than would become evident by the use of those formal methods of calculus that nowadays would seem more direct." Mathematician Vladimir Arnold states "Comparing the texts of Newton with the comments of his successors, it is striking how Newton’s original presentation is more modern, more understandable and richer in ideas than the translation due to commentators of his geometrical ideas into the formal language of the calculus of Leibniz."
His work extensively uses calculus in geometric form based on limiting values of the ratios of vanishingly small quantities: in the Principia itself, Newton gave demonstration of this under the name of "the method of first and last ratios" and explained why he put his expositions in this form, remarking also that "hereby the same thing is performed as by the method of indivisibles." Because of this, the Principia has been called "a book dense with the theory and application of the infinitesimal calculus" in modern times and in Newton's time "nearly all of it is of this calculus." His use of methods involving "one or more orders of the infinitesimally small" is present in his De motu corporum in gyrum of 1684 and in his papers on motion "during the two decades preceding 1684".
Newton had been reluctant to publish his calculus because he feared controversy and criticism. He was close to the Swiss mathematician Nicolas Fatio de Duillier. In 1691, Duillier started to write a new version of Newton's Principia, and corresponded with Leibniz. In 1693, the relationship between Duillier and Newton deteriorated and the book was never completed. Starting in 1699, Duillier accused Leibniz of plagiarism. Mathematician John Keill accused Leibniz of plagiarism in 1708 in the Royal Society journal, thereby deteriorating the situation even more. The dispute then broke out in full force in 1711 when the Royal Society proclaimed in a study that it was Newton who was the true discoverer and labelled Leibniz a fraud; it was later found that Newton wrote the study's concluding remarks on Leibniz. Thus began the bitter controversy which marred the lives of both men until Leibniz's death in 1716.
Newton is credited with the generalised binomial theorem, valid for any exponent. He discovered Newton's identities, Newton's method, classified cubic plane curves (polynomials of degree three in two variables), made substantial contributions to the theory of finite differences, with Newton regarded as "the single most significant contributor to finite difference interpolation", with many formulas created by Newton. He was the first to state Bézout's theorem, and was also the first to use fractional indices and to employ coordinate geometry to derive solutions to Diophantine equations. He approximated partial sums of the harmonic series by logarithms (a precursor to Euler's summation formula) and was the first to use power series with confidence and to revert power series. His work on infinite series was inspired by Simon Stevin's decimals.
Optics
In 1666, Newton observed that the spectrum of colours exiting a prism in the position of minimum deviation is oblong, even when the light ray entering the prism is circular, which is to say, the prism refracts different colours by different angles. This led him to conclude that colour is a property intrinsic to light – a point which had, until then, been a matter of debate.
From 1670 to 1672, Newton lectured on optics. During this period he investigated the refraction of light, demonstrating that the multicoloured image produced by a prism, which he named a spectrum, could be recomposed into white light by a lens and a second prism. Modern scholarship has revealed that Newton's analysis and resynthesis of white light owes a debt to corpuscular alchemy.
In his work on Newton's rings in 1671, he used a method that was unprecedented in the 17th century, as "he averaged all of the differences, and he then calculated the difference between the average and the value for the first ring", in effect introducing a now standard method for reducing noise in measurements, and which does not appear elsewhere at the time. He extended his "error-slaying method" to studies of equinoxes in 1700, which was described as an "altogether unprecedented method" but differed in that here "Newton required good values for each of the original equinoctial times, and so he devised a method that allowed them to, as it were, self-correct." Newton is credited with introducing "an embryonic linear regression analysis. Not only did he perform the averaging of a set of data, 50 years before Tobias Mayer, but summing the residuals to zero he forced the regression line to pass through the average point". Newton also "distinguished between two inhomogeneous sets of data and might have thought of an optimal solution in terms of bias, though not in terms of effectiveness".
He showed that coloured light does not change its properties by separating out a coloured beam and shining it on various objects, and that regardless of whether reflected, scattered, or transmitted, the light remains the same colour. Thus, he observed that colour is the result of objects interacting with already-coloured light rather than objects generating the colour themselves. This is known as Newton's theory of colour.
From this work, he concluded that the lens of any refracting telescope would suffer from the dispersion of light into colours (chromatic aberration). As a proof of the concept, he constructed a telescope using reflective mirrors instead of lenses as the objective to bypass that problem. Building the design, the first known functional reflecting telescope, today known as a Newtonian telescope, involved solving the problem of a suitable mirror material and shaping technique. He grounded his own mirrors out of a custom composition of highly reflective speculum metal, using Newton's rings to judge the quality of the optics for his telescopes. In late 1668, he was able to produce this first reflecting telescope. It was about eight inches long and it gave a clearer and larger image. In 1671, he was asked for a demonstration of his reflecting telescope by the Royal Society. Their interest encouraged him to publish his notes, Of Colours, which he later expanded into the work Opticks. When Robert Hooke criticised some of Newton's ideas, Newton was so offended that he withdrew from public debate. Newton and Hooke had brief exchanges in 1679–80, when Hooke, appointed to manage the Royal Society's correspondence, opened up a correspondence intended to elicit contributions from Newton to Royal Society transactions, which had the effect of stimulating Newton to work out a proof that the elliptical form of planetary orbits would result from a centripetal force inversely proportional to the square of the radius vector. The two men remained generally on poor terms until Hooke's death.
Newton argued that light is composed of particles or corpuscles, which were refracted by accelerating into a denser medium. He verged on soundlike waves to explain the repeated pattern of reflection and transmission by thin films (Opticks Bk. II, Props. 12), but still retained his theory of 'fits' that disposed corpuscles to be reflected or transmitted (Props.13). Physicists later favoured a purely wavelike explanation of light to account for the interference patterns and the general phenomenon of diffraction. Despite his known preference of a particle theory, Newton in fact noted that light had both particle-like and wave-like properties in Opticks, and was the first to attempt to reconcile the two theories, thereby anticipating later developments of wave-particle duality, which is the modern understanding of light.
In his Hypothesis of Light of 1675, Newton posited the existence of the ether to transmit forces between particles. The contact with the Cambridge Platonist philosopher Henry More revived his interest in alchemy. He replaced the ether with occult forces based on Hermetic ideas of attraction and repulsion between particles. His contributions to science cannot be isolated from his interest in alchemy. This was at a time when there was no clear distinction between alchemy and science.
In 1704, Newton published Opticks, in which he expounded his corpuscular theory of light, and included a set of queries at the end. In line with his corpuscle theory, he thought that ordinary matter was made of grosser corpuscles and speculated that through a kind of alchemical transmutation "Are not gross Bodies and Light convertible into one another, ... and may not Bodies receive much of their Activity from the Particles of Light which enter their Composition?" He also constructed a primitive form of a frictional electrostatic generator, using a glass globe.
In Opticks, he was the first to show a diagram using a prism as a beam expander, and also the use of multiple-prism arrays. Some 278 years after Newton's discussion, multiple-prism beam expanders became central to the development of narrow-linewidth tunable lasers. Also, the use of these prismatic beam expanders led to the multiple-prism dispersion theory.
Subsequent to Newton, much has been amended. Thomas Young and Augustin-Jean Fresnel discarded Newton's particle theory in favour of Huygens' wave theory to show that colour is the visible manifestation of light's wavelength. Science also slowly came to realise the difference between perception of colour and mathematisable optics. The German poet and scientist, Goethe, could not shake the Newtonian foundation but "one hole Goethe did find in Newton's armour, ... Newton had committed himself to the doctrine that refraction without colour was impossible. He, therefore, thought that the object-glasses of telescopes must forever remain imperfect, achromatism and refraction being incompatible. This inference was proved by Dollond to be wrong."
Gravity
Newton had been developing his theory of gravitation as far back as 1665. In 1679, Newton returned to his work on celestial mechanics by considering gravitation and its effect on the orbits of planets with reference to Kepler's laws of planetary motion. This followed stimulation by a brief exchange of letters in 1679–80 with Hooke, who had been appointed Secretary of the Royal Society, and who opened a correspondence intended to elicit contributions from Newton to Royal Society transactions. Newton's reawakening interest in astronomical matters received further stimulus by the appearance of a comet in the winter of 1680–1681, on which he corresponded with John Flamsteed. After the exchanges with Hooke, Newton worked out a proof that the elliptical form of planetary orbits would result from a centripetal force inversely proportional to the square of the radius vector. Newton communicated his results to Edmond Halley and to the Royal Society in , a tract written on about nine sheets which was copied into the Royal Society's Register Book in December 1684. This tract contained the nucleus that Newton developed and expanded to form the Principia.
The was published on 5 July 1687 with encouragement and financial help from Halley. In this work, Newton stated the three universal laws of motion. Together, these laws describe the relationship between any object, the forces acting upon it and the resulting motion, laying the foundation for classical mechanics. They contributed to many advances during the Industrial Revolution which soon followed and were not improved upon for more than 200 years. Many of these advances continue to be the underpinnings of non-relativistic technologies in the modern world. He used the Latin word gravitas (weight) for the effect that would become known as gravity, and defined the law of universal gravitation.
In the same work, Newton presented a calculus-like method of geometrical analysis using 'first and last ratios', gave the first analytical determination (based on Boyle's law) of the speed of sound in air, inferred the oblateness of Earth's spheroidal figure, accounted for the precession of the equinoxes as a result of the Moon's gravitational attraction on the Earth's oblateness, initiated the gravitational study of the irregularities in the motion of the Moon, provided a theory for the determination of the orbits of comets, and much more. Newton's biographer David Brewster reported that the complexity of applying his theory of gravity to the motion of the moon was so great it affected Newton's health: "[H]e was deprived of his appetite and sleep" during his work on the problem in 1692–93, and told the astronomer John Machin that "his head never ached but when he was studying the subject". According to Brewster, Edmund Halley also told John Conduitt that when pressed to complete his analysis Newton "always replied that it made his head ache, and kept him awake so often, that he would think of it no more". [Emphasis in original]
Newton made clear his heliocentric view of the Solar System—developed in a somewhat modern way because already in the mid-1680s he recognised the "deviation of the Sun" from the centre of gravity of the Solar System. For Newton, it was not precisely the centre of the Sun or any other body that could be considered at rest, but rather "the common centre of gravity of the Earth, the Sun and all the Planets is to be esteem'd the Centre of the World", and this centre of gravity "either is at rest or moves uniformly forward in a right line". (Newton adopted the "at rest" alternative in view of common consent that the centre, wherever it was, was at rest.)
Newton was criticised for introducing "occult agencies" into science because of his postulate of an invisible force able to act over vast distances. Later, in the second edition of the Principia (1713), Newton firmly rejected such criticisms in a concluding General Scholium, writing that it was enough that the phenomena implied a gravitational attraction, as they did; but they did not so far indicate its cause, and it was both unnecessary and improper to frame hypotheses of things that were not implied by the phenomena. (Here Newton used what became his famous expression .)
With the , Newton became internationally recognised. He acquired a circle of admirers, including the Swiss-born mathematician Nicolas Fatio de Duillier.
In 1710, Newton found 72 of the 78 "species" of cubic curves and categorised them into four types. In 1717, and probably with Newton's help, James Stirling proved that every cubic was one of these four types. Newton also claimed that the four types could be obtained by plane projection from one of them, and this was proved in 1731, four years after his death.
Philosophy of Science
Starting with the second edition of his Principia, Newton included a final section on science philosophy or method. It was here that he wrote his famous line, in Latin, "hypotheses non fingo", which can be translated as "I don't make hypotheses," (the direct translation of "fingo" is "frame", but in context he was advocating against the use of hypotheses in science). He went on to posit that if there is no data to explain a finding, one should simply wait for that data, rather than guessing at an explanation. The full quote as translated is, "Hitherto I have not been able to discover the cause of those properties of gravity from phenomena, and I frame no hypotheses, for whatever is not deduced from the phenomena is to be called an hypothesis; and hypotheses, whether metaphysical or physical, whether of occult qualities or mechanical, have no place in experimental philosophy. In this philosophy particular propositions are inferred from the phenomena, and afterwards rendered general by induction. Thus it was that the impenetrability, the mobility, and the impulsive force of bodies, and the laws of motion and of gravitation, were discovered. And to us it is enough that gravity does really exist, and act according to the laws which we have explained, and abundantly serves to account for all the motions of the celestial bodies, and of our sea."
This idea that Newton became anti-hypothesis has been disputed, since earlier editions of the Principia were in fact divided in sections headed by hypotheses. However, he seems to have gone away from that, as evidenced from his famous line in his "Opticks", where he wrote, in English, "Hypotheses have no place in experimental science."
Later life
Royal Mint
In the 1690s, Newton wrote a number of religious tracts dealing with the literal and symbolic interpretation of the Bible. A manuscript Newton sent to John Locke in which he disputed the fidelity of 1 John 5:7—the Johannine Comma—and its fidelity to the original manuscripts of the New Testament, remained unpublished until 1785.
Newton was also a member of the Parliament of England for Cambridge University in 1689 and 1701, but according to some accounts his only comments were to complain about a cold draught in the chamber and request that the window be closed. He was, however, noted by Cambridge diarist Abraham de la Pryme to have rebuked students who were frightening locals by claiming that a house was haunted.
Newton moved to London to take up the post of warden of the Royal Mint during the reign of King William III in 1696, a position that he had obtained through the patronage of Charles Montagu, 1st Earl of Halifax, then Chancellor of the Exchequer. He took charge of England's great recoining, trod on the toes of Lord Lucas, Governor of the Tower, and secured the job of deputy comptroller of the temporary Chester branch for Edmond Halley. Newton became perhaps the best-known Master of the Mint upon the death of Thomas Neale in 1699, a position he held for the last 30 years of his life. These appointments were intended as sinecures, but Newton took them seriously. He retired from his Cambridge duties in 1701, and exercised his authority to reform the currency and punish clippers and counterfeiters.
As Warden, and afterwards as Master, of the Royal Mint, Newton estimated that 20 percent of the coins taken in during the Great Recoinage of 1696 were counterfeit. Counterfeiting was high treason, punishable by the felon being hanged, drawn and quartered. Despite this, convicting even the most flagrant criminals could be extremely difficult, but Newton proved equal to the task.
Disguised as a habitué of bars and taverns, he gathered much of that evidence himself. For all the barriers placed to prosecution, and separating the branches of government, English law still had ancient and formidable customs of authority. Newton had himself made a justice of the peace in all the home counties. A draft letter regarding the matter is included in Newton's personal first edition of Philosophiæ Naturalis Principia Mathematica, which he must have been amending at the time. Then he conducted more than 100 cross-examinations of witnesses, informers, and suspects between June 1698 and Christmas 1699. He successfully prosecuted 28 coiners, including serial counterfeiter William Chaloner, who was subsequently hanged.
Newton was made president of the Royal Society in 1703 and an associate of the French Académie des Sciences. In his position at the Royal Society, Newton made an enemy of John Flamsteed, the Astronomer Royal, by prematurely publishing Flamsteed's Historia Coelestis Britannica, which Newton had used in his studies.
Knighthood
In April 1705, Queen Anne knighted Newton during a royal visit to Trinity College, Cambridge. The knighthood is likely to have been motivated by political considerations connected with the parliamentary election in May 1705, rather than any recognition of Newton's scientific work or services as Master of the Mint. Newton was the second scientist to be knighted, after Francis Bacon.
As a result of a report written by Newton on 21 September 1717 to the Lords Commissioners of His Majesty's Treasury, the bimetallic relationship between gold coins and silver coins was changed by royal proclamation on 22 December 1717, forbidding the exchange of gold guineas for more than 21 silver shillings. This inadvertently resulted in a silver shortage as silver coins were used to pay for imports, while exports were paid for in gold, effectively moving Britain from the silver standard to its first gold standard. It is a matter of debate as to whether he intended to do this or not. It has been argued that Newton conceived of his work at the Mint as a continuation of his alchemical work.
Newton was invested in the South Sea Company and lost some £20,000 (£4.4 million in 2020) when it collapsed in around 1720.
Toward the end of his life, Newton took up residence at Cranbury Park, near Winchester, with his niece and her husband, until his death. His half-niece, Catherine Barton, served as his hostess in social affairs at his house on Jermyn Street in London; he was her "very loving Uncle", according to his letter to her when she was recovering from smallpox.
Death
Newton died in his sleep in London on 20 March 1727 (OS 20 March 1726; NS 31 March 1727). He was given a ceremonial funeral, attended by nobles, scientists, and philosophers, and was buried in Westminster Abbey among kings and queens. He was the first scientist to be buried in the abbey. Voltaire may have been present at his funeral. A bachelor, he had divested much of his estate to relatives during his last years, and died intestate. His papers went to John Conduitt and Catherine Barton.
Shortly after his death, a plaster death mask was moulded of Newton. It was used by Flemish sculptor John Michael Rysbrack in making a sculpture of Newton. It is now held by the Royal Society, who created a 3D scan of it in 2012.
Newton's hair was posthumously examined and found to contain mercury, probably resulting from his alchemical pursuits. Mercury poisoning could explain Newton's eccentricity in late life.
Personality
Although it was claimed that he was once engaged, Newton never married. The French writer and philosopher Voltaire, who was in London at the time of Newton's funeral, said that he "was never sensible to any passion, was not subject to the common frailties of mankind, nor had any commerce with women—a circumstance which was assured me by the physician and surgeon who attended him in his last moments.” There exists a widespread belief that Newton died a virgin, and writers as diverse as mathematician Charles Hutton, economist John Maynard Keynes, and physicist Carl Sagan have commented on it.
Newton had a close friendship with the Swiss mathematician Nicolas Fatio de Duillier, whom he met in London around 1689; some of their correspondence has survived. Their relationship came to an abrupt and unexplained end in 1693, and at the same time Newton suffered a nervous breakdown, which included sending wild accusatory letters to his friends Samuel Pepys and John Locke. His note to the latter included the charge that Locke had endeavoured to "embroil" him with "woemen & by other means".
Newton appeared to be relatively modest about his achievements, writing in a later memoir, "I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me." Nonetheless, he could be fiercely competitive and did on occasion hold grudges against his intellectual rivals, not abstaining from personal attacks when it suited him—a common trait found in many of his contemporaries. In a letter to Robert Hooke in February 1676, for instance, he confessed "If I have seen further it is by standing on the shoulders of giants." Some historians argued that this, written at a time when Newton and Hooke were disputing over optical discoveries, was an oblique attack on Hooke who was presumably short and hunchbacked, rather than (or in addition to) a statement of modesty. On the other hand, the widely known proverb about standing on the shoulders of giants, found in 17th century poet George Herbert's (1651) among others, had as its main point that "a dwarf on a giant's shoulders sees farther of the two", and so in effect place Newton himself rather than Hooke as the 'dwarf' who saw farther.
Theology
Religious views
Although born into an Anglican family, by his thirties Newton held a Christian faith that, had it been made public, would not have been considered orthodox by mainstream Christianity, with historian Stephen Snobelen labelling him a heretic.
By 1672, he had started to record his theological researches in notebooks which he showed to no one and which have only been available for public examination since 1972. Over half of what Newton wrote concerned theology and alchemy, and most has never been printed. His writings demonstrate an extensive knowledge of early Church writings and show that in the conflict between Athanasius and Arius which defined the Creed, he took the side of Arius, the loser, who rejected the conventional view of the Trinity. Newton "recognized Christ as a divine mediator between God and man, who was subordinate to the Father who created him." He was especially interested in prophecy, but for him, "the great apostasy was trinitarianism."
Newton tried unsuccessfully to obtain one of the two fellowships that exempted the holder from the ordination requirement. At the last moment in 1675 he received a dispensation from the government that excused him and all future holders of the Lucasian chair.
Worshipping Jesus Christ as God was, in Newton's eyes, idolatry, an act he believed to be the fundamental sin. In 1999, Snobelen wrote, "Isaac Newton was a heretic. But ... he never made a public declaration of his private faith—which the orthodox would have deemed extremely radical. He hid his faith so well that scholars are still unraveling his personal beliefs." Snobelen concludes that Newton was at least a Socinian sympathiser (he owned and had thoroughly read at least eight Socinian books), possibly an Arian and almost certainly an anti-trinitarian.
Although the laws of motion and universal gravitation became Newton's best-known discoveries, he warned against using them to view the Universe as a mere machine, as if akin to a great clock. He said, "So then gravity may put the planets into motion, but without the Divine Power it could never put them into such a circulating motion, as they have about the sun".
Along with his scientific fame, Newton's studies of the Bible and of the early Church Fathers were also noteworthy. Newton wrote works on textual criticism, most notably An Historical Account of Two Notable Corruptions of Scripture and Observations upon the Prophecies of Daniel, and the Apocalypse of St. John. He placed the crucifixion of Jesus Christ at 3 April, AD 33, which agrees with one traditionally accepted date.
He believed in a rationally immanent world, but he rejected the hylozoism implicit in Leibniz and Baruch Spinoza. The ordered and dynamically informed Universe could be understood, and must be understood, by an active reason. In his correspondence, Newton claimed that in writing the Principia "I had an eye upon such Principles as might work with considering men for the belief of a Deity". He saw evidence of design in the system of the world: "Such a wonderful uniformity in the planetary system must be allowed the effect of choice". But Newton insisted that divine intervention would eventually be required to reform the system, due to the slow growth of instabilities. For this, Leibniz lampooned him: "God Almighty wants to wind up his watch from time to time: otherwise it would cease to move. He had not, it seems, sufficient foresight to make it a perpetual motion."
Newton's position was vigorously defended by his follower Samuel Clarke in a famous correspondence. A century later, Pierre-Simon Laplace's work Celestial Mechanics had a natural explanation for why the planet orbits do not require periodic divine intervention. The contrast between Laplace's mechanistic worldview and Newton's one is the most strident considering the famous answer which the French scientist gave Napoleon, who had criticised him for the absence of the Creator in the Mécanique céleste: "Sire, j'ai pu me passer de cette hypothèse" ("Sir, I didn't need this hypothesis").
Scholars long debated whether Newton disputed the doctrine of the Trinity. His first biographer, David Brewster, who compiled his manuscripts, interpreted Newton as questioning the veracity of some passages used to support the Trinity, but never denying the doctrine of the Trinity as such. In the twentieth century, encrypted manuscripts written by Newton and bought by John Maynard Keynes (among others) were deciphered and it became known that Newton did indeed reject Trinitarianism.
Religious thought
Newton and Robert Boyle's approach to the mechanical philosophy was promoted by rationalist pamphleteers as a viable alternative to the pantheists and enthusiasts, and was accepted hesitantly by orthodox preachers as well as dissident preachers like the latitudinarians. The clarity and simplicity of science was seen as a way to combat the emotional and metaphysical superlatives of both superstitious enthusiasm and the threat of atheism, and at the same time, the second wave of English deists used Newton's discoveries to demonstrate the possibility of a "Natural Religion".
The attacks made against pre-Enlightenment "magical thinking", and the mystical elements of Christianity, were given their foundation with Boyle's mechanical conception of the universe. Newton gave Boyle's ideas their completion through mathematical proofs and, perhaps more importantly, was very successful in popularising them.
Alchemy
Of an estimated ten million words of writing in Newton's papers, about one million deal with alchemy. Many of Newton's writings on alchemy are copies of other manuscripts, with his own annotations. Alchemical texts mix artisanal knowledge with philosophical speculation, often hidden behind layers of wordplay, allegory, and imagery to protect craft secrets. Some of the content contained in Newton's papers could have been considered heretical by the church.
In 1888, after spending sixteen years cataloguing Newton's papers, Cambridge University kept a small number and returned the rest to the Earl of Portsmouth. In 1936, a descendant offered the papers for sale at Sotheby's. The collection was broken up and sold for a total of about £9,000. John Maynard Keynes was one of about three dozen bidders who obtained part of the collection at auction. Keynes went on to reassemble an estimated half of Newton's collection of papers on alchemy before donating his collection to Cambridge University in 1946.
All of Newton's known writings on alchemy are currently being put online in a project undertaken by Indiana University: "The Chymistry of Isaac Newton" and summarised in a book.
In June 2020, two unpublished pages of Newton's notes on Jan Baptist van Helmont's book on plague, De Peste, were being auctioned online by Bonhams. Newton's analysis of this book, which he made in Cambridge while protecting himself from London's 1665–1666 infection, is the most substantial written statement he is known to have made about the plague, according to Bonhams. As far as the therapy is concerned, Newton writes that "the best is a toad suspended by the legs in a chimney for three days, which at last vomited up earth with various insects in it, on to a dish of yellow wax, and shortly after died. Combining powdered toad with the excretions and serum made into lozenges and worn about the affected area drove away the contagion and drew out the poison".
Legacy
Recognition
The mathematician and astronomer Joseph-Louis Lagrange frequently asserted that Newton was the greatest genius who ever lived, and once added that Newton was also "the most fortunate, for we cannot find more than once a system of the world to establish." English poet Alexander Pope wrote the famous epitaph:
But this was not allowed to be inscribed in Newton's monument at Westminster. The epitaph added is as follows:
which can be translated as follows:
Newton has been called "the most influential figure in the history of Western science", and has been regarded as "the central figure in the history of science", who "more than anyone else is the source of our great confidence in the power of science." New Scientist called Newton "the supreme genius and most enigmatic character in the history of science". The philosopher and historian David Hume also declared that Newton was "the greatest and rarest genius that ever arose for the ornament and instruction of the species". In his home of Monticello, Thomas Jefferson, a Founding Father and President of the United States, kept portraits of John Locke, Sir Francis Bacon, and Newton, whom he described as "the three greatest men that have ever lived, without any exception", and who he credited with laying "the foundation of those superstructures which have been raised in the Physical and Moral sciences".
Newton has further been called "the towering figure of the Scientific Revolution" and that "In a period rich with outstanding thinkers, Newton was simply the most outstanding." The polymath Johann Wolfgang von Goethe labeled Newton's birth as the "Christmas of the modern age". In the Italian polymath Vilfredo Pareto's estimation, Newton was the greatest human being who ever lived. On the bicentennial of Newton's death in 1927, astronomer James Jeans stated that he "was certainly the greatest man of science, and perhaps the greatest intellect, the human race has seen". Newton ultimately conceived four revolutions—in optics, mathematics, mechanics, and gravity—but also foresaw a fifth in electricity, though he lacked the time and energy in old age to fully accomplish it.
The physicist Ludwig Boltzmann called Newton's Principia "the first and greatest work ever written about theoretical physics". Physicist Stephen Hawking similarly called Principia "probably the most important single work ever published in the physical sciences".
Physicist Edward Andrade stated that Newton "was capable of greater sustained mental effort than any man, before or since", and noted earlier the place of Isaac Newton in history, stating:The French physicist and mathematician Jean-Baptiste Biot praised Newton's genius, stating that:
Despite his rivalry with Gottfried Wilhem Leibniz, Leibniz still praised the work of Newton, with him responding to a question at a dinner in 1701 from Sophia Charlotte, the Queen of Prussia, about his view of Newton with:
Mathematician E.T. Bell ranked Newton alongside Carl Friedrich Gauss and Archimedes as the three greatest mathematicians of all time. In The Cambridge Companion to Isaac Newton (2016), he is described as being "from a very young age, an extraordinary problem-solver, as good, it would appear, as humanity has ever produced". He is ultimately ranked among the top two or three greatest theoretical scientists ever, alongside James Clerk Maxwell and Albert Einstein, the greatest mathematician ever alongside Carl F. Gauss, and among the best experimentalists ever, thereby "putting Newton in a class by himself among empirical scientists, for one has trouble in thinking of any other candidate who was in the first rank of even two of these categories." Also noted is "At least in comparison to subsequent scientists, Newton was also exceptional in his ability to put his scientific effort in much wider perspective". Gauss himself had Archimedes and Newton as his heroes, and used terms such as clarissimus or magnus to describe other intellectuals such as great mathematicians and philosophers, but reserved summus for Newton only, and once remarked that "Newton remains forever the master of all masters!"
Albert Einstein kept a picture of Newton on his study wall alongside ones of Michael Faraday and of James Clerk Maxwell. Einstein stated that Newton's creation of calculus in relation to his laws of motion was "perhaps the greatest advance in thought that a single individual was ever privileged to make." He also noted the influence of Newton, stating that:In 1999, an opinion poll of 100 of the day's leading physicists voted Einstein the "greatest physicist ever," with Newton the runner-up, while a parallel survey of rank-and-file physicists ranked Newton as the greatest. In 2005, a dual survey of both the public and of members of Britain's Royal Society (formerly headed by Newton) asking who had the greater effect on both the history of science and on the history of mankind, Newton or Einstein, both the public and the Royal Society deemed Newton to have made the greater overall contributions for both.
In 1999, Time named Newton the Person of the Century for the 17th century. Newton placed sixth in the 100 Greatest Britons poll conducted by BBC in 2002. However, in 2003, he was voted as the greatest Briton in a poll conducted by BBC World, with Winston Churchill second. He was voted as the greatest Cantabrigian by University of Cambridge students in 2009.
Physicist Lev Landau ranked physicists on a logarithmic scale of productivity and genius ranging from 0 to 5. The highest ranking, 0, was assigned to Newton. Einstein was ranked 0.5. A rank of 1 was awarded to the fathers of quantum mechanics, such as Werner Heisenberg and Paul Dirac. Landau, a Nobel prize winner and the discoverer of superfluidity, ranked himself as 2.
The SI derived unit of force is named the Newton in his honour.
Apple incident
Newton himself often told the story that he was inspired to formulate his theory of gravitation by watching the fall of an apple from a tree. The story is believed to have passed into popular knowledge after being related by Catherine Barton, Newton's niece, to Voltaire. Voltaire then wrote in his Essay on Epic Poetry (1727), "Sir Isaac Newton walking in his gardens, had the first thought of his system of gravitation, upon seeing an apple falling from a tree."
Although it has been said that the apple story is a myth and that he did not arrive at his theory of gravity at any single moment, acquaintances of Newton (such as William Stukeley, whose manuscript account of 1752 has been made available by the Royal Society) do in fact confirm the incident, though not the apocryphal version that the apple actually hit Newton's head. Stukeley recorded in his Memoirs of Sir Isaac Newton's Life a conversation with Newton in Kensington on 15 April 1726:
John Conduitt, Newton's assistant at the Royal Mint and husband of Newton's niece, also described the event when he wrote about Newton's life:
It is known from his notebooks that Newton was grappling in the late 1660s with the idea that terrestrial gravity extends, in an inverse-square proportion, to the Moon; however, it took him two decades to develop the full-fledged theory. The question was not whether gravity existed, but whether it extended so far from Earth that it could also be the force holding the Moon to its orbit. Newton showed that if the force decreased as the inverse square of the distance, one could indeed calculate the Moon's orbital period, and get good agreement. He guessed the same force was responsible for other orbital motions, and hence named it "universal gravitation".
Various trees are claimed to be "the" apple tree which Newton describes. The King's School, Grantham claims that the tree was purchased by the school, uprooted and transported to the headmaster's garden some years later. The staff of the (now) National Trust-owned Woolsthorpe Manor dispute this, and claim that a tree present in their gardens is the one described by Newton. A descendant of the original tree can be seen growing outside the main gate of Trinity College, Cambridge, below the room Newton lived in when he studied there. The National Fruit Collection at Brogdale in Kent can supply grafts from their tree, which appears identical to Flower of Kent, a coarse-fleshed cooking variety.
Commemorations
Newton's monument (1731) can be seen in Westminster Abbey, at the north of the entrance to the choir against the choir screen, near his tomb. It was executed by the sculptor Michael Rysbrack (1694–1770) in white and grey marble with design by the architect William Kent. The monument features a figure of Newton reclining on top of a sarcophagus, his right elbow resting on several of his great books and his left hand pointing to a scroll with a mathematical design. Above him is a pyramid and a celestial globe showing the signs of the Zodiac and the path of the comet of 1680. A relief panel depicts putti using instruments such as a telescope and prism.
From 1978 until 1988, an image of Newton designed by Harry Ecclestone appeared on Series D £1 banknotes issued by the Bank of England (the last £1 notes to be issued by the Bank of England). Newton was shown on the reverse of the notes holding a book and accompanied by a telescope, a prism and a map of the Solar System.
A statue of Isaac Newton, looking at an apple at his feet, can be seen at the Oxford University Museum of Natural History. A large bronze statue, Newton, after William Blake, by Eduardo Paolozzi, dated 1995 and inspired by Blake's etching, dominates the piazza of the British Library in London. A bronze statue of Newton was erected in 1858 in the centre of Grantham where he went to school, prominently standing in front of Grantham Guildhall.
The still-surviving farmhouse at Woolsthorpe By Colsterworth is a Grade I listed building by Historic England through being his birthplace and "where he discovered gravity and developed his theories regarding the refraction of light".
The Enlightenment
Enlightenment philosophers chose a short history of scientific predecessors—Galileo, Boyle, and Newton principally—as the guides and guarantors of their applications of the singular concept of nature and natural law to every physical and social field of the day. In this respect, the lessons of history and the social structures built upon it could be discarded.
It is held by European philosophers of the Enlightenment and by historians of the Enlightenment that Newton's publication of the Principia was a turning point in the Scientific Revolution and started the Enlightenment. It was Newton's conception of the universe based upon natural and rationally understandable laws that became one of the seeds for Enlightenment ideology. Locke and Voltaire applied concepts of natural law to political systems advocating intrinsic rights; the physiocrats and Adam Smith applied natural conceptions of psychology and self-interest to economic systems; and sociologists criticised the current social order for trying to fit history into natural models of progress. Monboddo and Samuel Clarke resisted elements of Newton's work, but eventually rationalised it to conform with their strong religious views of nature.
Works
Published in his lifetime
De analysi per aequationes numero terminorum infinitas (1669, published 1711)
Of Natures Obvious Laws & Processes in Vegetation (unpublished, –75)
De motu corporum in gyrum (1684)
Philosophiæ Naturalis Principia Mathematica (1687)
Scala graduum Caloris. Calorum Descriptiones & signa (1701)
Opticks (1704)
Reports as Master of the Mint (1701–1725)
Arithmetica Universalis (1707)
Published posthumously
De mundi systemate (The System of the World) (1728)
Optical Lectures (1728)
The Chronology of Ancient Kingdoms Amended (1728)
Observations on Daniel and The Apocalypse of St. John (1733)
Method of Fluxions (1671, published 1736)
An Historical Account of Two Notable Corruptions of Scripture (1754)
See also
Elements of the Philosophy of Newton, a book by Voltaire
List of multiple discoveries: seventeenth century
List of things named after Isaac Newton
List of presidents of the Royal Society
References
Notes
Citations
Bibliography
Further reading
Primary
Newton, Isaac. The Principia: Mathematical Principles of Natural Philosophy. University of California Press, (1999)
Brackenridge, J. Bruce. The Key to Newton's Dynamics: The Kepler Problem and the Principia: Containing an English Translation of Sections 1, 2, and 3 of Book One from the First (1687) Edition of Newton's Mathematical Principles of Natural Philosophy, University of California Press (1996)
Newton, Isaac. The Optical Papers of Isaac Newton. Vol. 1: The Optical Lectures, 1670–1672, Cambridge University Press (1984)
Newton, Isaac. Opticks (4th ed. 1730) online edition
Newton, I. (1952). Opticks, or A Treatise of the Reflections, Refractions, Inflections & Colours of Light. New York: Dover Publications.
Newton, I. Sir Isaac Newton's Mathematical Principles of Natural Philosophy and His System of the World, tr. A. Motte, rev. Florian Cajori. Berkeley: University of California Press (1934)
– 8 volumes.
Newton, Isaac. The correspondence of Isaac Newton, ed. H.W. Turnbull and others, 7 vols (1959–77)
Newton's Philosophy of Nature: Selections from His Writings edited by H.S. Thayer (1953; online edition)
Isaac Newton, Sir; J Edleston; Roger Cotes, Correspondence of Sir Isaac Newton and Professor Cotes, including letters of other eminent men, London, John W. Parker, West Strand; Cambridge, John Deighton (1850, Google Books)
Maclaurin, C. (1748). An Account of Sir Isaac Newton's Philosophical Discoveries, in Four Books. London: A. Millar and J. Nourse
Newton, I. (1958). Isaac Newton's Papers and Letters on Natural Philosophy and Related Documents, eds. I.B. Cohen and R.E. Schofield. Cambridge: Harvard University Press
Newton, I. (1962). The Unpublished Scientific Papers of Isaac Newton: A Selection from the Portsmouth Collection in the University Library, Cambridge, ed. A.R. Hall and M.B. Hall. Cambridge: Cambridge University Press
Newton, I. (1975). Isaac Newton's 'Theory of the Moon's Motion''' (1702). London: Dawson
Alchemy
– Preface by Albert Einstein. Reprinted by Johnson Reprint Corporation, New York (1972)
Keynes took a close interest in Newton and owned many of Newton's private papers.
(edited by A.H. White; originally published in 1752)
Trabue, J. "Ann and Arthur Storer of Calvert County, Maryland, Friends of Sir Isaac Newton," The American Genealogist 79 (2004): 13–27.
Religion
Dobbs, Betty Jo Tetter. The Janus Faces of Genius: The Role of Alchemy in Newton's Thought. (1991), links the alchemy to Arianism
Force, James E., and Richard H. Popkin, eds. Newton and Religion: Context, Nature, and Influence. (1999), pp. xvii, 325.; 13 papers by scholars using newly opened manuscripts
Science
Berlinski, David. Newton's Gift: How Sir Isaac Newton Unlocked the System of the World. (2000);
Cohen, I. Bernard and Smith, George E., ed. The Cambridge Companion to Newton. (2002). Focuses on philosophical issues only; excerpt and text search; complete edition online
This well documented work provides, in particular, valuable information regarding Newton's knowledge of Patristics
Hawking, Stephen, ed. On the Shoulders of Giants. Places selections from Newton's Principia in the context of selected writings by Copernicus, Kepler, Galileo and Einstein
Newton, Isaac. Papers and Letters in Natural Philosophy'', edited by I. Bernard Cohen. Harvard University Press, 1958, 1978; .
External links
Enlightening Science digital project : Texts of his papers, "Popularisations" and podcasts at the Newton Project
Writings by Newton
Newton's works – full texts, at the Newton Project
Newton's papers in the Royal Society's archives
The Newton Manuscripts at the National Library of Israel – the collection of all his religious writings
"Newton Papers" – Cambridge Digital Library
1642 births
1727 deaths
17th-century alchemists
17th-century apocalypticists
17th-century English astronomers
17th-century English mathematicians
17th-century English male writers
17th-century English writers
17th-century writers in Latin
18th-century alchemists
18th-century apocalypticists
18th-century English astronomers
18th-century British scientists
18th-century English mathematicians
18th-century English male writers
18th-century English writers
18th-century writers in Latin
Alumni of Trinity College, Cambridge
Antitrinitarians
Ballistics experts
English scientific instrument makers
British writers in Latin
Burials at Westminster Abbey
Color scientists
Copernican Revolution
Creators of temperature scales
British critics of atheism
English alchemists
English Anglicans
English Christians
English inventors
English justices of the peace
English knights
English mathematicians
English MPs 1689–1690
English MPs 1701–1702
English physicists
Enlightenment scientists
Experimental physicists
Fellows of the Royal Society
Fellows of Trinity College, Cambridge
Fluid dynamicists
British geometers
Linear algebraists
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History of calculus
Knights Bachelor
Lucasian Professors of Mathematics
Masters of the Mint
Members of the pre-1707 Parliament of England for the University of Cambridge
Natural philosophers
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People educated at The King's School, Grantham
People from South Kesteven District
Philosophers of science
Post-Reformation Arian Christians
Presidents of the Royal Society
Theoretical physicists
Writers about religion and science | Isaac Newton | Physics,Chemistry,Astronomy,Mathematics | 12,655 |
13,371,175 | https://en.wikipedia.org/wiki/Phenomorphan | Phenomorphan is an opioid analgesic. It is not currently used in medicine, but has similar side-effects to other opiates, which include itching, nausea and respiratory depression.
Phenomorphan is a highly potent drug due to the N-phenethyl group, which boosts affinity to the μ-opioid receptor, and so phenomorphan is around 10x more potent than levorphanol, which is itself 6-8x the potency of morphine. Other analogues where the N-(2-phenylethyl) group has been replaced by other aromatic rings are even more potent, with the N-(2-(2-furyl)ethyl) and the N-(2-(2-thienyl)ethyl) analogues being 60x and 45x stronger than levorphanol, respectively.
See also
14-Cinnamoyloxycodeinone
14-Phenylpropoxymetopon
7-PET
N-Phenethylnormorphine
N-Phenethylnordesomorphine
N-Phenethyl-14-ethoxymetopon
RAM-378
Ro4-1539
References
Synthetic opioids
Morphinans
Hydroxyarenes
Mu-opioid receptor agonists | Phenomorphan | Chemistry | 288 |
29,843,595 | https://en.wikipedia.org/wiki/DexNet | Dex-net is a robotic. It uses a Grasp Quality Convolutional Neural Network to learn how to grasp unusually shaped objects.
History
Dex-net was developed by University of California, Berkeley professor Ken Goldberg and graduate student Jeff Mahler.
Design
Dex-net includes a high-resolution 3-D sensor and two arms, each controlled by a different neural network. One arm is equipped with a conventional robot gripper and another with a suction system. The robot’s software scans an object and then asks both neural networks to decide, on the fly, whether to grab or suck a particular object. It runs on an off-the-shelf industrial machine made by Swiss robotics company ABB.
The software learns by attempting to pick up objects in a virtual environment. Dex-Net can generalize from an object it has seen before to a new one. The robot can "nudge" such virtual objects to examine it if it is unsure how to grasp it. The trial data set was 6.7 million point clouds, grasps and analytic grasp metrics generated from thousands of 3D models. Grasps are defined as a gripper's planar position, angle and depth relative to an RGB-D sensor.
Mean picks per hour
A metric called mean picks per hour (MPPH) is calculated by multiplying the average time per pick and the average probability of success for a specific set of objects. The new metric allows labs working on picking robots to compare their results.
Humans are capable of between 400 and 600 MPPH. In a contest organized by Amazon recently, the best robots were capable of between 70 and 95. Dex-net has achieved 200 to 300.
References
Artificial neural networks
Robotics | DexNet | Engineering | 347 |
75,631,986 | https://en.wikipedia.org/wiki/Mathini%20Sellathurai | Mathini Sellathurai is an electrical engineer whose research topics include wireless communications, radar, cognitive radio, and multiple-input and multiple-output radio communications. Educated in Sri Lanka, Sweden and Canada, she has worked in Canada, the US, and Scotland, where she is professor in signal processing and dean of science and engineering at Heriot-Watt University.
Education and career
Sellathurai has a bachelor's degree in engineering from the University of Peradeniya in Sri Lanka. She earned a licenciate in signal processing and communications in 1997 from the KTH Royal Institute of Technology in Stockholm, Sweden, and completed a Ph.D. in 2001 from McMaster University in Hamilton, Ontario. Her doctoral dissertation was supervised by Simon Haykin and concerned the Bell Laboratories Layered Space-Time architecture for exploiting multi-path wireless communications; it won the 2002 Natural Sciences and Engineering Council Doctoral Prize. As a doctoral student, she also worked as a visiting researcher at Bell Labs in the US.
After postdoctoral research at the Communications Research Centre Canada from 2001 to 2004, she joined Heriot-Watt University in 2004.
Recognition
Sellathurai was named an IEEE Fellow, in the 2024 class of fellows, "for contributions to multi-user, multi-functional and multi-antenna wireless communications".
References
External links
Year of birth missing (living people)
Living people
Electrical engineers
Women electrical engineers
KTH Royal Institute of Technology alumni
McMaster University alumni
Academics of Heriot-Watt University
Fellows of the IEEE | Mathini Sellathurai | Engineering | 306 |
8,084,851 | https://en.wikipedia.org/wiki/Place%20syntax | Within geographic information systems, Place syntax is a term in spatial analysis. There is potential in combining geographically oriented accessibility research and geometrically oriented research in architecture, such as space syntax, as stated by for example, Ståhle et al.
References
External links
Place Syntax: Geographic accessibility with axial lines in GIS
Geographic information systems | Place syntax | Technology | 67 |
3,332,850 | https://en.wikipedia.org/wiki/Lutidine | Lutidine is the trivial name used to describe the chemical compounds which are dimethyl derivatives of pyridine. They were discovered in Dippel's oil and named (as an anagram of toluidine, with which they share their empirical formula) by Thomas Anderson in 1851. Their chemical properties resemble those of pyridine, although the presence of the methyl groups may prohibit some of the more straightforward reactions. Lutidine comes in several isomers:
2,3-Lutidine (2,3-dimethylpyridine)
2,4-Lutidine (2,4-dimethylpyridine)
2,5-Lutidine (2,5-dimethylpyridine)
2,6-Lutidine (2,6-dimethylpyridine)
3,4-Lutidine (3,4-dimethylpyridine)
3,5-Lutidine (3,5-dimethylpyridine)
All isomers share the molecular weight 107,16 g/mol and the chemical formula C7H9N.
Pyridines
Amines
Amine solvents | Lutidine | Chemistry | 247 |
66,261,967 | https://en.wikipedia.org/wiki/List%20of%20plant%20genera%20named%20for%20people%20%28K%E2%80%93P%29 | Since the first printing of Carl Linnaeus's Species Plantarum in 1753, plants have been assigned one epithet or name for their species and one name for their genus, a grouping of related species. Thousands of plants have been named for people, including botanists and their colleagues, plant collectors, horticulturists, explorers, rulers, politicians, clerics, doctors, philosophers and scientists. Even before Linnaeus, botanists such as Joseph Pitton de Tournefort, Charles Plumier and Pier Antonio Micheli were naming plants for people, sometimes in gratitude for the financial support of their patrons.
Early works researching the naming of plant genera include an 1810 glossary by and an etymological dictionary in two editions (1853 and 1856) by Georg Christian Wittstein. Modern works include The Gardener's Botanical by Ross Bayton, Index of Eponymic Plant Names and Encyclopedia of Eponymic Plant Names by Lotte Burkhardt, Plants of the World by Maarten J. M. Christenhusz (lead author), Michael F. Fay and Mark W. Chase, The A to Z of Plant Names by Allan J. Coombes, the four-volume CRC World Dictionary of Plant Names by Umberto Quattrocchi, and Stearn's Dictionary of Plant Names for Gardeners by William T. Stearn; these supply the seed-bearing genera listed in the first column below. Excluded from this list are genus names not accepted (as of January 2021) at Plants of the World Online, which includes updates to Plants of the World (2017).
Key
Ba = listed in Bayton's The Gardener's Botanical
Bt = listed in Burkhardt's Encyclopedia of Eponymic Plant Names
Bu = listed in Burkhardt's Index of Eponymic Plant Names
Ch = listed in Christenhusz's Plants of the World
Co = listed in Coombes's The A to Z of Plant Names
Qu = listed in Quattrocchi's CRC World Dictionary of Plant Names
St = listed in Stearn's Dictionary of Plant Names for Gardeners
In addition, Burkhardt's Index is used as a reference for every row in the table, except as noted.
Genera
See also
List of plant genus names with etymologies: A–C, D–K, L–P, Q–Z
List of plant family names with etymologies
Notes
Citations
References
See http://creativecommons.org/licenses/by/4.0/ for license.
See http://creativecommons.org/licenses/by/4.0/ for license.
See http://www.plantsoftheworldonline.org/terms-and-conditions for license.
Further reading
Systematic
Systematic
Taxonomy (biology)
Glossaries of biology
Gardening lists
Genera named for people (K-P)
Named for people (K-P)
Wikipedia glossaries using tables
Lists of eponyms | List of plant genera named for people (K–P) | Biology | 611 |
5,143,567 | https://en.wikipedia.org/wiki/Imago%20therapy | Imago Relationship Therapy (IRT) is a form of therapy that focuses on relationship counseling.
IRT was developed by Harville Hendrix and Helen LaKelly Hunt. The word imago is Latin for "image"; in this sense, it refers to the "unconscious image of similar love", according to one therapist.
A 2017 study of the method's effectiveness found that couples participating in IRT increased marital satisfaction during treatment (and to a lesser extent at a follow-up) but that the improvements were not clinically significant.
References
Interpersonal relationships
Relationship counseling | Imago therapy | Biology | 117 |
17,001,425 | https://en.wikipedia.org/wiki/Minor%20planet | According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term minor planet, but that year's meeting reclassified minor planets and comets into dwarf planets and small Solar System bodies (SSSBs). In contrast to the eight official planets of the Solar System, all minor planets fail to clear their orbital neighborhood.
Minor planets include asteroids (near-Earth objects, Earth trojans, Mars trojans, Mars-crossers, main-belt asteroids and Jupiter trojans), as well as distant minor planets (Uranus trojans, Neptune trojans, centaurs and trans-Neptunian objects), most of which reside in the Kuiper belt and the scattered disc. , there are known objects, divided into 740,000 numbered, with only one of them recognized as a dwarf planet (secured discoveries) and 652,085 unnumbered minor planets, with only five of those officially recognized as a dwarf planet.
The first minor planet to be discovered was Ceres in 1801, though it was called a 'planet' at the time and an 'asteroid' soon after; the term minor planet was not introduced until 1841, and was considered a subcategory of 'planet' until 1932. The term planetoid has also been used, especially for larger, planetary objects such as those the IAU has called dwarf planets since 2006. Historically, the terms asteroid, minor planet, and planetoid have been more or less synonymous. This terminology has become more complicated by the discovery of numerous minor planets beyond the orbit of Jupiter, especially trans-Neptunian objects that are generally not considered asteroids. A minor planet seen releasing gas may be dually classified as a comet.
Objects are called dwarf planets if their own gravity is sufficient to achieve hydrostatic equilibrium and form an ellipsoidal shape. All other minor planets and comets are called small Solar System bodies. The IAU stated that the term minor planet may still be used, but the term small Solar System body will be preferred. However, for purposes of numbering and naming, the traditional distinction between minor planet and comet is still used.
Populations
Hundreds of thousands of minor planets have been discovered within the Solar System and thousands more are discovered each month. The Minor Planet Center has documented over 213 million observations and 794,832 minor planets, of which 541,128 have orbits known well enough to be assigned permanent official numbers. Of these, 21,922 have official names. , the lowest-numbered unnamed minor planet is , and the highest-numbered named minor planet is 594913 ꞌAylóꞌchaxnim.
There are various broad minor-planet populations:
Asteroids; traditionally, most have been bodies in the inner Solar System.
Near-Earth asteroids, those whose orbits take them inside the orbit of Mars. Further subclassification of these, based on orbital distance, is used:
Apohele asteroids orbit inside of Earth's perihelion distance and thus are contained entirely within the orbit of Earth.
Aten asteroids, those that have a semimajor axis of less than Earth's and an aphelion (furthest distance from the Sun) greater than 0.983 AU.
Apollo asteroids are those asteroids with a semimajor axis greater than Earth's while having a perihelion distance of 1.017 AU or less. Like Aten asteroids, Apollo asteroids are Earth-crossers.
Amor asteroids are those near-Earth asteroids that approach the orbit of Earth from beyond but do not cross it. Amor asteroids are further subdivided into four subgroups, depending on where their semimajor axis falls between Earth's orbit and the asteroid belt.
Earth trojans, asteroids sharing Earth's orbit and gravitationally locked to it. As of 2022, two Earth trojans are known: 2010 TK7 and 2020 XL5.
Mars trojans, asteroids sharing Mars's orbit and gravitationally locked to it. As of 2007, eight such asteroids are known.
Asteroid belt, whose members follow roughly circular orbits between Mars and Jupiter. These are the original and best-known group of asteroids.
Jupiter trojans, asteroids sharing Jupiter's orbit and gravitationally locked to it. Numerically they are estimated to equal the main-belt asteroids.
Distant minor planets, an umbrella term for minor planets in the outer Solar System.
Centaurs, bodies in the outer Solar System between Jupiter and Neptune. They have unstable orbits due to the gravitational influence of the giant planets, and therefore must have come from elsewhere, probably outside Neptune.
Neptune trojans, bodies sharing Neptune's orbit and gravitationally locked to it. Although only a handful are known, there is evidence that Neptune trojans are more numerous than either the asteroids in the asteroid belt or the Jupiter trojans.
Trans-Neptunian objects, bodies at or beyond the orbit of Neptune, the outermost planet.
The Kuiper belt, objects inside an apparent population drop-off approximately 55 AU from the Sun.
Classical Kuiper belt objects like Makemake, also known as cubewanos, are in primordial, relatively circular orbits that are not in resonance with Neptune.
Resonant Kuiper belt objects.
Plutinos, bodies like that are in a 2:3 resonance with Neptune.
Scattered disc objects like Eris, with aphelia outside the Kuiper belt. These are thought to have been scattered by Neptune.
Resonant scattered disc objects.
Detached objects such as Sedna, with both an aphelion and a perihelion outside the Kuiper belt.
Sednoids, detached objects with a perihelion greater than 75 AU (Sedna, , and Leleākūhonua).
The Oort cloud, a hypothetical population thought to be the source of long-period comets and that may extend to 50,000 AU from the Sun.
Naming conventions
All astronomical bodies in the Solar System need a distinct designation. The naming of minor planets runs through a three-step process. First, a provisional designation is given upon discovery—because the object still may turn out to be a false positive or become lost later on—called a provisionally designated minor planet. After the observation arc is accurate enough to predict its future location, a minor planet is formally designated and receives a number. It is then a numbered minor planet. Finally, in the third step, it may be named by its discoverers. However, only a small fraction of all minor planets have been named. The vast majority are either numbered or have still only a provisional designation. Example of the naming process:
– provisional designation upon discovery on 24 April 1932
– formal designation, receives an official number
1862 Apollo – named minor planet, receives a name, the alphanumeric code is dropped
Provisional designation
A newly discovered minor planet is given a provisional designation. For example, the provisional designation consists of the year of discovery (2002) and an alphanumeric code indicating the half-month of discovery and the sequence within that half-month. Once an asteroid's orbit has been confirmed, it is given a number, and later may also be given a name (e.g. 433 Eros). The formal naming convention uses parentheses around the number, but dropping the parentheses is quite common. Informally, it is common to drop the number altogether or to drop it after the first mention when a name is repeated in running text.
Minor planets that have been given a number but not a name keep their provisional designation, e.g. (29075) 1950 DA. Because modern discovery techniques are finding vast numbers of new asteroids, they are increasingly being left unnamed. The earliest discovered to be left unnamed was for a long time (3360) 1981 VA, now 3360 Syrinx. In November 2006 its position as the lowest-numbered unnamed asteroid passed to (now 3708 Socus), and in May 2021 to . On rare occasions, a small object's provisional designation may become used as a name in itself: the then-unnamed gave its "name" to a group of objects that became known as classical Kuiper belt objects ("cubewanos") before it was finally named 15760 Albion in January 2018.
A few objects are cross-listed as both comets and asteroids, such as 4015 Wilson–Harrington, which is also listed as 107P/Wilson–Harrington.
Numbering
Minor planets are awarded an official number once their orbits are confirmed. With the increasing rapidity of discovery, these are now six-figure numbers. The switch from five figures to six figures arrived with the publication of the Minor Planet Circular (MPC) of October 19, 2005, which saw the highest-numbered minor planet jump from 99947 to 118161.
Naming
The first few asteroids were named after figures from Greek and Roman mythology, but as such names started to dwindle the names of famous people, literary characters, discoverers' spouses, children, colleagues, and even television characters were used.
Gender
The first asteroid to be given a non-mythological name was 20 Massalia, named after the Greek name for the city of Marseille. The first to be given an entirely non-Classical name was 45 Eugenia, named after Empress Eugénie de Montijo, the wife of Napoleon III. For some time only female (or feminized) names were used; Alexander von Humboldt was the first man to have an asteroid named after him, but his name was feminized to 54 Alexandra. This unspoken tradition lasted until 334 Chicago was named; even then, female names showed up in the list for years after.
Eccentric
As the number of asteroids began to run into the hundreds, and eventually, in the thousands, discoverers began to give them increasingly frivolous names. The first hints of this were 482 Petrina and 483 Seppina, named after the discoverer's pet dogs. However, there was little controversy about this until 1971, upon the naming of 2309 Mr. Spock (the name of the discoverer's cat). Although the IAU subsequently discouraged the use of pet names as sources, eccentric asteroid names are still being proposed and accepted, such as 4321 Zero, 6042 Cheshirecat, 9007 James Bond, 13579 Allodd and 24680 Alleven, and 26858 Misterrogers.
Discoverer's name
A well-established rule is that, unlike comets, minor planets may not be named after their discoverer(s). One way to circumvent this rule has been for astronomers to exchange the courtesy of naming their discoveries after each other. Rare exceptions to this rule are 1927 Suvanto and 96747 Crespodasilva. 1927 Suvanto was named after its discoverer, Rafael Suvanto, posthumously by the Minor Planet Center. He died four years after the discovery in the last days of the Finnish winter war of 1939-40. 96747 Crespodasilva was named after its discoverer, Lucy d'Escoffier Crespo da Silva, because she died shortly after the discovery, at age 22.
Languages
Names were adapted to various languages from the beginning. 1 Ceres, Ceres being its Anglo-Latin name, was actually named Cerere, the Italian form of the name. German, French, Arabic, and Hindi use forms similar to the English, whereas Russian uses a form, Tserera, similar to the Italian. In Greek, the name was translated to Δήμητρα (Demeter), the Greek equivalent of the Roman goddess Ceres. In the early years, before it started causing conflicts, asteroids named after Roman figures were generally translated in Greek; other examples are Ἥρα (Hera) for 3 Juno, Ἑστία (Hestia) for 4 Vesta, Χλωρίς (Chloris) for 8 Flora, and Πίστη (Pistis) for 37 Fides. In Chinese, the names are not given the Chinese forms of the deities they are named after, but rather typically have a syllable or two for the character of the deity or person, followed by 神 'god(dess)' or 女 'woman' if just one syllable, plus 星 'star/planet', so that most asteroid names are written with three Chinese characters. Thus Ceres is 穀神星 'grain goddess planet', Pallas is 智神星 'wisdom goddess planet', etc.
Physical properties of comets and minor planets
Commission 15 of the International Astronomical Union is dedicated to the Physical Study of Comets & Minor Planets.
Archival data on the physical properties of comets and minor planets are found in the PDS Asteroid/Dust Archive. This includes standard asteroid physical characteristics such as the properties of binary systems, occultation timings and diameters, masses, densities, rotation periods, surface temperatures, albedoes, spin vectors, taxonomy, and absolute magnitudes and slopes. In addition, European Asteroid Research Node (E.A.R.N.), an association of asteroid research groups, maintains a Data Base of Physical and Dynamical Properties of Near Earth Asteroids.
Environmental properties
Environmental characteristics have three aspects: space environment, surface environment and internal environment, including geological, optical, thermal and radiological environmental properties, etc., which are the basis for understanding the basic properties of minor planets, carrying out scientific research, and are also an important reference basis for designing the payload of exploration missions
Radiation environment
Without the protection of an atmosphere and its own strong magnetic field, the minor planet's surface is directly exposed to the surrounding radiation environment. In the cosmic space where minor planets are located, the radiation on the surface of the planets can be divided into two categories according to their sources: one comes from the sun, including electromagnetic radiation from the sun, and ionizing radiation from the solar wind and solar energy particles; the other comes from the sun outside the solar system, that is, galactic cosmic rays, etc.
Optical environment
Usually during one rotation period of a minor planet, the albedo of a minor planet will change slightly due to its irregular shape and uneven distribution of material composition. This small change will be reflected in the periodic change of the planet's light curve, which can be observed by ground-based equipment, so as to obtain the planet's magnitude, rotation period, rotation axis orientation, shape, albedo distribution, and scattering properties. Generally speaking, the albedo of minor planets is usually low, and the overall statistical distribution is bimodal, corresponding to C-type (average 0.035) and S-type (average 0.15) minor planets. In the minor planet exploration mission, measuring the albedo and color changes of the planet surface is also the most basic method to directly know the difference in the material composition of the planet surface.
Geological environment
The geological environment on the surface of minor planets is similar to that of other unprotected celestial bodies, with the most widespread geomorphological feature present being impact craters: however, the fact that most minor planets are rubble pile structures, which are loose and porous, gives the impact action on the surface of minor planets its unique characteristics. On highly porous minor planets, small impact events produce spatter blankets similar to common impact events: whereas large impact events are dominated by compaction and spatter blankets are difficult to form, and the longer the planets receive such large impacts, the greater the overall density. In addition, statistical analysis of impact craters is an important means of obtaining information on the age of a planet surface. Although the Crater Size-Frequency Distribution (CSFD) method of dating commonly used on minor planet surfaces does not allow absolute ages to be obtained, it can be used to determine the relative ages of different geological bodies for comparison. In addition to impact, there are a variety of other rich geological effects on the surface of minor planets, such as mass wasting on slopes and impact crater walls, large-scale linear features associated with graben, and electrostatic transport of dust. By analysing the various geological processes on the surface of minor planets, it is possible to learn about the possible internal activity at this stage and some of the key evolutionary information about the long-term interaction with the external environment, which may lead to some indication of the nature of the parent body's origin. Many of the larger planets are often covered by a layer of soil (regolith) of unknown thickness. Compared to other atmosphere-free bodies in the solar system (e.g. the Moon), minor planets have weaker gravity fields and are less capable of retaining fine-grained material, resulting in a somewhat larger surface soil layer size. Soil layers are inevitably subject to intense space weathering that alters their physical and chemical properties due to direct exposure to the surrounding space environment. In silicate-rich soils, the outer layers of Fe are reduced to nano-phase Fe (np-Fe), which is the main product of space weathering. For some small planets, their surfaces are more exposed as boulders of varying sizes, up to 100 metres in diameter, due to their weaker gravitational pull. These boulders are of high scientific interest, as they may be either deeply buried material excavated by impact action or fragments of the planet's parent body that have survived. The rocks provide more direct and primitive information about the material inside the minor planet and the nature of its parent body than the soil layer, and the different colours and forms of the rocks indicate different sources of material on the surface of the minor planet or different evolutionary processes.
Magnetic environment
Usually in the interior of the planet, the convection of the conductive fluid will generate a large and strong magnetic field. However, the size of a minor planet is generally small and most of the minor planets have a "crushed stone pile" structure, and there is basically no "dynamo" structure inside, so it will not generate a self-generated dipole magnetic field like the Earth. But some minor planets do have magnetic fields—on the one hand, some minor planets have remanent magnetism: if the parent body had a magnetic field or if the nearby planetary body has a strong magnetic field, the rocks on the parent body will be magnetised during the cooling process and the planet formed by the fission of the parent body will still retain remanence, which can also be detected in extraterrestrial meteorites from the minor planets; on the other hand, if the minor planets are composed of electrically conductive material and their internal conductivity is similar to that of carbon- or iron-bearing meteorites, the interaction between the minor planets and the solar wind is likely to be unipolar induction, resulting in an external magnetic field for the minor planet. In addition, the magnetic fields of minor planets are not static; impact events, weathering in space and changes in the thermal environment can alter the existing magnetic fields of minor planets. At present, there are not many direct observations of minor planet magnetic fields, and the few existing planets detection projects generally carry magnetometers, with some targets such as Gaspra and Braille measured to have strong magnetic fields nearby, while others such as Lutetia have no magnetic field.
See also
Groups of minor planets
List of minor planets
Dwarf planet
Quasi-satellite
Small Solar System body
List of minor planets and comets visited by spacecraft
Notes
References
External links
Minor Planet Center
Logarithmic graph of asteroid discoveries from 1801-2015
Solar System | Minor planet | Astronomy | 3,993 |
67,967,062 | https://en.wikipedia.org/wiki/Archiv%20der%20Pharmazie | The Archiv der Pharmazie (German pronunciation: [ˈ arˈçiːf ˈdeːɐ̯ farmaˈtsiː], English: Archive of Pharmacy) is a monthly peer-reviewed scientific journal covering all aspects of chemistry in the life sciences. The journal was established in 1822 and is published by Wiley-VCH on behalf of the Deutsche Pharmazeutische Gesellschaft; it is the oldest German pharmaceutical journal still in publication. Until 2019, the editor-in-chief was Holger Stark (Heinrich Heine University Düsseldorf). He was succeeded in 2020 by Andreas Link (University of Greifswald).
History
The first edition appeared in 1822 under the name Archiv des Apothekervereins im nördlichen Teutschland für die Pharmacie und ihre Huelfswissenschaften (English: Archive of the Pharmacists' Association in Northern Germany for Pharmacy and its Auxiliary Sciences). In 1832, the journal was merged with Liebigs Annalen (then known as Annalen der Pharmacie), but would split from it following editorial disputes between the editors Justus von Liebig and Rudolph Brandes. From 1924 (volume 242) the journal was called Archiv der Pharmazie und Berichte der Deutschen Pharmazeutischen Gesellschaft (English: Archive of Pharmacy and Reports from the German Pharmaceutical Society), before obtaining its current name in 1971.
In 1995 the publication language changed from German to English.
Abstracting and indexing
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2022 impact factor of 5.1.
References
External links
Monthly journals
Wiley-VCH academic journals
Medicinal chemistry journals
Publications established in 1822
Hybrid open access journals
English-language journals | Archiv der Pharmazie | Chemistry | 373 |
1,675,601 | https://en.wikipedia.org/wiki/Manifold%20vacuum | Manifold vacuum, or engine vacuum in a petrol engine is the difference in air pressure between the engine's intake manifold and Earth's atmosphere.
Manifold vacuum is an effect of a piston's movement on the induction stroke and the airflow through a throttle in the intervening carburetor or throttle body leading to the intake manifold. It is a result of the amount of restriction of airflow through the engine. In some engines, the manifold vacuum is also used as an auxiliary power source to drive engine accessories and for the crankcase ventilation system.
Manifold vacuums should not be confused with venturi vacuums, which are an effect exploited in carburetors to establish a pressure difference roughly proportional to mass airflow and to maintain a somewhat constant air/fuel ratio.
It is also used in light airplanes to provide airflow for pneumatic gyroscopic instruments.
Overview
The rate of airflow through an internal combustion engine is an important factor determining the amount of power the engine generates. Most gasoline engines are controlled by limiting that flow with a throttle that restricts intake airflow, while a diesel engine is controlled by the amount of fuel supplied to the cylinder, and so has no "throttle" as such. Manifold vacuum is present in all naturally aspirated engines that use throttles (including carbureted and fuel injected gasoline engines using the Otto cycle or the two-stroke cycle; diesel engines do not have throttle plates).
The mass flow through the engine is the product of the rotation rate of the engine, the displacement of the engine, and the density of the intake stream in the intake manifold. In most applications the rotation rate is set by the application (engine speed in a vehicle or machinery speed in other applications). The displacement is dependent on the engine geometry, which is generally not adjustable while the engine is in use (although a handful of models do have this feature, see variable displacement). Restricting the input flow reduces the density (and hence pressure) in the intake manifold, reducing the amount of power produced. It is also a major source of engine drag (see engine braking), as the low-pressure air in the intake manifold provides less pressure on the piston during the induction stroke.
When the throttle is opened (in a car, the accelerator pedal is depressed), ambient air is free to fill the intake manifold, increasing the pressure (filling the vacuum). A carburetor or fuel injection system adds fuel to the airflow in the correct proportion, providing energy to the engine. When the throttle is opened all the way, the engine's air induction system is exposed to full atmospheric pressure, and maximum airflow through the engine is achieved. In a naturally aspirated engine, output power is limited by the ambient barometric pressure. Superchargers and turbochargers boost manifold pressure above atmospheric pressure.
Modern developments
Modern engines use a manifold absolute pressure (abbreviated as MAP) sensor to measure air pressure in the intake manifold. Manifold absolute pressure is one of a multitude of parameters used by the engine control unit (ECU) to optimize engine operation. It is important to differentiate between absolute and gauge pressure when dealing with certain applications, particularly those that experience changes in elevation during normal operation.
Motivated by government regulations mandating reduction of fuel consumption (in the USA) or reduction of carbon dioxide emissions (in Europe), passenger cars and light trucks have been fitted with a variety of technologies (downsized engines; lockup, multi-ratio and overdrive transmissions; variable valve timing, forced induction, diesel engines, et al.) which render manifold vacuum inadequate or unavailable. Electric vacuum pumps are now commonly used for powering pneumatic accessories.
Manifold vacuum vs. venturi vacuum
Manifold vacuum is caused by a different phenomenon than venturi vacuum, which is present inside carburetors. Venturi vacuum is caused by the venturi effect which, for fixed ambient conditions (air density and temperature), depends on the total mass flow through the carburetor. In engines that use carburetors, the venturi vacuum is approximately proportional to the total mass flow through the engine (and hence the total power output). As ambient pressure (altitude, weather) or temperature change, the carburetor may need to be adjusted to maintain this relationship.
Manifold pressure may also be "ported". Porting is selecting a location for the pressure tap within the throttle plate's range of motion. Depending on throttle position, a ported pressure tap may be either upstream or downstream of the throttle. As the throttle position changes, a "ported" pressure tap is selectively connected to either manifold pressure or ambient pressure. Older (pre-OBD II) engines often used ported manifold pressure taps for ignition distributors and emission-control components.
Manifold vacuum in cars
Most automobiles use four-stroke Otto cycle engines with multiple cylinders attached to a single inlet manifold. During the intake stroke, the piston descends in the cylinder and the intake valve is open. As the piston descends it effectively increases the volume in the cylinder above it, setting up low pressure. Atmospheric pressure pushes air through the manifold and carburetor or fuel injection system, where it is mixed with fuel. Because multiple cylinders operate at different times in the engine cycle, there is almost constant pressure difference through the inlet manifold from carburetor to engine.
To control the amount of fuel/air mix entering the engine, a simple butterfly valve (throttle plate) is generally fitted at the start of the intake manifold (just below the carburetor in carbureted engines). The butterfly valve is simply a circular disc fitted on a spindle, fitting inside the pipe work. It is connected to the accelerator pedal of the car, and is set to be fully open when the pedal is fully pressed and fully closed when the pedal is released. The butterfly valve often contains a small "idle cutout", a hole that allows small amounts of fuel/air mixture into the engine even when the valve is fully closed, or the carburetor has a separate air bypass with its own idle jet.
If the engine is operating under light or no load and low or closed throttle, there is high manifold vacuum. As the throttle is opened, the engine speed increases rapidly. The engine speed is limited only by the amount of fuel/air mixture that is available in the manifold. Under full throttle and light load, other effects (such as valve float, turbulence in the cylinders, or ignition timing) limit engine speed so that the manifold pressure can increase—but in practice, parasitic drag on the internal walls of the manifold, plus the restrictive nature of the venturi at the heart of the carburetor, means that a low pressure will always be set up as the engine's internal volume exceeds the amount of the air the manifold is capable of delivering.
If the engine is operating under heavy load at wide throttle openings (such as accelerating from a stop or pulling the car up a hill) then engine speed is limited by the load and minimal vacuum will be created. Engine speed is low but the butterfly valve is fully open. Since the pistons are descending more slowly than under no load, the pressure differences are less marked and parasitic drag in the induction system is negligible. The engine pulls air into the cylinders at the full ambient pressure.
More vacuum is created in some situations. On deceleration or when descending a hill, the throttle will be closed and a low gear selected to control speed. The engine will be rotating fast because the road wheels and transmission are moving quickly, but the butterfly valve will be fully closed. The flow of air through the engine is strongly restricted by the throttle, producing a strong vacuum on the engine side of the butterfly valve which will tend to limit the speed of the engine. This phenomenon, known as engine braking, is used to prevent acceleration or even to slow down with minimal or no brake usage (as when descending a long or steep hill). This vacuum braking should not be confused with compression braking (aka a "Jake brake"), or with exhaust braking, which are often used on large diesel trucks. Such devices are necessary for engine braking with a diesel as they lack a throttle to restrict the air flow enough to create sufficient vacuum to brake a vehicle.
Uses of manifold vacuum
This low (or negative) pressure can be put to use. A pressure gauge measuring the manifold pressure can be fitted to give the driver an indication of how hard the engine is working and it can be used to achieve maximum momentary fuel efficiency by adjusting driving habits: minimizing manifold vacuum increases momentary efficiency. A weak manifold vacuum under closed-throttle conditions shows that the butterfly valve or internal components of the engine (valves or piston rings) are worn, preventing good pumping action by the engine and reducing overall efficiency.
Vacuum used to be a common way to drive auxiliary systems on the vehicle. Vacuum systems tend to be unreliable with age as the vacuum tubing becomes brittle and susceptible to leaks.
Before 1960
Windshield wiper motors - Prior to the introduction of Federal Motor Vehicle Safety Standards in the USA by the National Traffic and Motor Vehicle Safety Act of 1966, it was common to use manifold vacuum to drive windscreen wipers with a pneumatic motor. This system is cheap and simple but resulted in wipers whose speed is inversely proportional to how hard the engine is working.
Power door lock motors.
"Autovac" fuel lifter, which uses vacuum to raise fuel from the main tank to a small auxiliary tank, from which it flows by gravity to the carburetor. This eliminated the fuel pump which, in early cars, was an unreliable item.
1960–1990
Automotive vacuum systems reached their height of use between the 1960s and 1980s. During this time a huge variety of vacuum switches, delay valves and accessory devices were created. As an example, a 1967 Ford Thunderbird used vacuum for:
Vacuum-assist brake servos (power brakes) use atmospheric pressure pressing against the engine manifold vacuum to increase pressure on the brakes. Since braking is nearly always accompanied by the closing of the throttle and associated high manifold vacuum, this system is simple and almost foolproof. Vacuum tanks were installed on trailers to control their integrated braking systems.
Transmission shift control
Doors for the hidden headlamps
Remote trunk latch release
Power door locks
HVAC air routing - Vehicle HVAC systems used manifold vacuum to drive actuators controlling airflow and temperature.
Control of the heater core valve
Rear cabin vent control
Tilt-away steering wheel release
Other items that can be powered by vacuum include:
Exhaust gas recirculation solenoid
Power steering pump
Fuel pressure regulator
Modern usage
Modern cars have a minimal amount of accessories that use vacuum. Many accessories previously driven by vacuum have been replaced by electronic accessories. Some modern accessories that sometimes use vacuum include:
Vacuum-assist brake servos
Positive crankcase ventilation valve
Charcoal canister
Manifold vacuum in diesel engines
Many diesel engines do not have butterfly valve throttles. The manifold is connected directly to the air intake and the only suction created is that caused by the descending piston with no venturi to increase it, and the engine power is controlled by varying the amount of fuel that is injected into the cylinder by a fuel injection system. This assists in making diesels much more efficient than petrol engines.
If vacuum is required (vehicles that can be fitted with both petrol and diesel engines often have systems requiring it), a butterfly valve connected to the throttle can be fitted to the manifold. This reduces efficiency and is still not as effective as it is not connected to a venturi. Since low-pressure is only created on the overrun (such as when descending hills with a closed throttle), not over a wide range of situations as in a petrol engine, a vacuum tank is fitted.
Most diesel engines now have a separate vacuum pump ("exhauster") fitted to provide vacuum at all times, at all engine speeds.
Many new BMW petrol engines do not use a throttle in normal running, but instead use "Valvetronic" variable-lift intake valves to control the amount of air entering the engine. Like a diesel engine, manifold vacuum is practically non-existent in these engines and a different source must be utilised to power the brake servo.
See also
Vacuum delay valve
References
Internal combustion engine
Engine technology
Vacuum | Manifold vacuum | Physics,Technology,Engineering | 2,487 |
32,848,710 | https://en.wikipedia.org/wiki/Q-Meixner%20polynomials | In mathematics, the q-Meixner polynomials are a family of basic hypergeometric orthogonal polynomials in the basic Askey scheme. give a detailed list of their properties.
Definition
The polynomials are given in terms of basic hypergeometric functions by
References
Orthogonal polynomials
Q-analogs
Special hypergeometric functions | Q-Meixner polynomials | Mathematics | 63 |
24,979 | https://en.wikipedia.org/wiki/4-polytope | In geometry, a 4-polytope (sometimes also called a polychoron, polycell, or polyhedroid) is a four-dimensional polytope. It is a connected and closed figure, composed of lower-dimensional polytopal elements: vertices, edges, faces (polygons), and cells (polyhedra). Each face is shared by exactly two cells. The 4-polytopes were discovered by the Swiss mathematician Ludwig Schläfli before 1853.
The two-dimensional analogue of a 4-polytope is a polygon, and the three-dimensional analogue is a polyhedron.
Topologically 4-polytopes are closely related to the uniform honeycombs, such as the cubic honeycomb, which tessellate 3-space; similarly the 3D cube is related to the infinite 2D square tiling. Convex 4-polytopes can be cut and unfolded as nets in 3-space.
Definition
A 4-polytope is a closed four-dimensional figure. It comprises vertices (corner points), edges, faces and cells. A cell is the three-dimensional analogue of a face, and is therefore a polyhedron. Each face must join exactly two cells, analogous to the way in which each edge of a polyhedron joins just two faces. Like any polytope, the elements of a 4-polytope cannot be subdivided into two or more sets which are also 4-polytopes, i.e. it is not a compound.
Geometry
The convex regular 4-polytopes are the four-dimensional analogues of the Platonic solids. The most familiar 4-polytope is the tesseract or hypercube, the 4D analogue of the cube.
The convex regular 4-polytopes can be ordered by size as a measure of 4-dimensional content (hypervolume) for the same radius. Each greater polytope in the sequence is rounder than its predecessor, enclosing more content within the same radius. The 4-simplex (5-cell) is the limit smallest case, and the 120-cell is the largest. Complexity (as measured by comparing configuration matrices or simply the number of vertices) follows the same ordering.
Visualisation
4-polytopes cannot be seen in three-dimensional space due to their extra dimension. Several techniques are used to help visualise them.
Orthogonal projection
Orthogonal projections can be used to show various symmetry orientations of a 4-polytope. They can be drawn in 2D as vertex-edge graphs, and can be shown in 3D with solid faces as visible projective envelopes.
Perspective projection
Just as a 3D shape can be projected onto a flat sheet, so a 4-D shape can be projected onto 3-space or even onto a flat sheet. One common projection is a Schlegel diagram which uses stereographic projection of points on the surface of a 3-sphere into three dimensions, connected by straight edges, faces, and cells drawn in 3-space.
Sectioning
Just as a slice through a polyhedron reveals a cut surface, so a slice through a 4-polytope reveals a cut "hypersurface" in three dimensions. A sequence of such sections can be used to build up an understanding of the overall shape. The extra dimension can be equated with time to produce a smooth animation of these cross sections.
Nets
A net of a 4-polytope is composed of polyhedral cells that are connected by their faces and all occupy the same three-dimensional space, just as the polygon faces of a net of a polyhedron are connected by their edges and all occupy the same plane.
Topological characteristics
The topology of any given 4-polytope is defined by its Betti numbers and torsion coefficients.
The value of the Euler characteristic used to characterise polyhedra does not generalize usefully to higher dimensions, and is zero for all 4-polytopes, whatever their underlying topology. This inadequacy of the Euler characteristic to reliably distinguish between different topologies in higher dimensions led to the discovery of the more sophisticated Betti numbers.
Similarly, the notion of orientability of a polyhedron is insufficient to characterise the surface twistings of toroidal 4-polytopes, and this led to the use of torsion coefficients.
Classification
Criteria
Like all polytopes, 4-polytopes may be classified based on properties like "convexity" and "symmetry".
A 4-polytope is convex if its boundary (including its cells, faces and edges) does not intersect itself and the line segment joining any two points of the 4-polytope is contained in the 4-polytope or its interior; otherwise, it is non-convex. Self-intersecting 4-polytopes are also known as star 4-polytopes, from analogy with the star-like shapes of the non-convex star polygons and Kepler–Poinsot polyhedra.
A 4-polytope is regular if it is transitive on its flags. This means that its cells are all congruent regular polyhedra, and similarly its vertex figures are congruent and of another kind of regular polyhedron.
A convex 4-polytope is semi-regular if it has a symmetry group under which all vertices are equivalent (vertex-transitive) and its cells are regular polyhedra. The cells may be of two or more kinds, provided that they have the same kind of face. There are only 3 cases identified by Thorold Gosset in 1900: the rectified 5-cell, rectified 600-cell, and snub 24-cell.
A 4-polytope is uniform if it has a symmetry group under which all vertices are equivalent, and its cells are uniform polyhedra. The faces of a uniform 4-polytope must be regular.
A 4-polytope is scaliform if it is vertex-transitive, and has all equal length edges. This allows cells which are not uniform, such as the regular-faced convex Johnson solids.
A regular 4-polytope which is also convex is said to be a convex regular 4-polytope.
A 4-polytope is prismatic if it is the Cartesian product of two or more lower-dimensional polytopes. A prismatic 4-polytope is uniform if its factors are uniform. The hypercube is prismatic (product of two squares, or of a cube and line segment), but is considered separately because it has symmetries other than those inherited from its factors.
A tiling or honeycomb of 3-space is the division of three-dimensional Euclidean space into a repetitive grid of polyhedral cells. Such tilings or tessellations are infinite and do not bound a "4D" volume, and are examples of infinite 4-polytopes. A uniform tiling of 3-space is one whose vertices are congruent and related by a space group and whose cells are uniform polyhedra.
Classes
The following lists the various categories of 4-polytopes classified according to the criteria above:
Uniform 4-polytope (vertex-transitive):
Convex uniform 4-polytopes (64, plus two infinite families)
47 non-prismatic convex uniform 4-polytope including:
6 Convex regular 4-polytope
Prismatic uniform 4-polytopes:
{} × {p,q} : 18 polyhedral hyperprisms (including cubic hyperprism, the regular hypercube)
Prisms built on antiprisms (infinite family)
{p} × {q} : duoprisms (infinite family)
Non-convex uniform 4-polytopes (10 + unknown)
10 (regular) Schläfli-Hess polytopes
57 hyperprisms built on nonconvex uniform polyhedra
Unknown total number of nonconvex uniform 4-polytopes: Norman Johnson and other collaborators have identified 2191 forms (convex and star, excluding the infinite families), all constructed by vertex figures by Stella4D software.
Other convex 4-polytopes:
Polyhedral pyramid
Polyhedral bipyramid
Polyhedral prism
Infinite uniform 4-polytopes of Euclidean 3-space (uniform tessellations of convex uniform cells)
28 convex uniform honeycombs: uniform convex polyhedral tessellations, including:
1 regular tessellation, cubic honeycomb: {4,3,4}
Infinite uniform 4-polytopes of hyperbolic 3-space (uniform tessellations of convex uniform cells)
76 Wythoffian convex uniform honeycombs in hyperbolic space, including:
4 regular tessellation of compact hyperbolic 3-space: {3,5,3}, {4,3,5}, {5,3,4}, {5,3,5}
Dual uniform 4-polytope (cell-transitive):
41 unique dual convex uniform 4-polytopes
17 unique dual convex uniform polyhedral prisms
infinite family of dual convex uniform duoprisms (irregular tetrahedral cells)
27 unique convex dual uniform honeycombs, including:
Rhombic dodecahedral honeycomb
Disphenoid tetrahedral honeycomb
Others:
Weaire–Phelan structure periodic space-filling honeycomb with irregular cells
Abstract regular 4-polytopes:
11-cell
57-cell
These categories include only the 4-polytopes that exhibit a high degree of symmetry. Many other 4-polytopes are possible, but they have not been studied as extensively as the ones included in these categories.
See also
Regular 4-polytope
3-sphere – analogue of a sphere in 4-dimensional space. This is not a 4-polytope, since it is not bounded by polyhedral cells.
The duocylinder is a figure in 4-dimensional space related to the duoprisms. It is also not a 4-polytope because its bounding volumes are not polyhedral.
References
Notes
Bibliography
H.S.M. Coxeter:
H.S.M. Coxeter, M.S. Longuet-Higgins and J.C.P. Miller: Uniform Polyhedra, Philosophical Transactions of the Royal Society of London, Londne, 1954
Kaleidoscopes: Selected Writings of H.S.M. Coxeter, edited by F. Arthur Sherk, Peter McMullen, Anthony C. Thompson, Asia Ivic Weiss, Wiley-Interscience Publication, 1995,
(Paper 22) H.S.M. Coxeter, Regular and Semi Regular Polytopes I, [Math. Zeit. 46 (1940) 380–407, MR 2,10]
(Paper 23) H.S.M. Coxeter, Regular and Semi-Regular Polytopes II, [Math. Zeit. 188 (1985) 559–591]
(Paper 24) H.S.M. Coxeter, Regular and Semi-Regular Polytopes III, [Math. Zeit. 200 (1988) 3–45]
J.H. Conway and M.J.T. Guy: Four-Dimensional Archimedean Polytopes, Proceedings of the Colloquium on Convexity at Copenhagen, page 38 und 39, 1965
N.W. Johnson: The Theory of Uniform Polytopes and Honeycombs, Ph.D. Dissertation, University of Toronto, 1966
Four-dimensional Archimedean Polytopes (German), Marco Möller, 2004 PhD dissertation
External links
Uniform Polychora, Jonathan Bowers
Uniform polychoron Viewer - Java3D Applet with sources
R. Klitzing, polychora
Four-dimensional geometry
Algebraic topology | 4-polytope | Mathematics | 2,425 |
43,819,148 | https://en.wikipedia.org/wiki/Maya%20astronomy | Maya astronomy is the study of the Moon, planets, Milky Way, Sun, and astronomical phenomena by the Precolumbian Maya civilization of Mesoamerica.
The Classic Maya in particular developed some of the most accurate pre-telescope astronomy in the world, aided by their fully developed writing system and their positional numeral system, both of which are fully indigenous to Mesoamerica. The Classic Maya understood many astronomical phenomena: for example, their estimate of the length of the synodic month was more accurate than Ptolemy's, and their calculation of the length of the tropical solar year was more accurate than that of the Spanish when the latter first arrived. Many temples from the Maya architecture have features oriented to celestial events.
European and Maya calendars
European calendar
In 46 BC Julius Caesar decreed that the year would be made up of twelve months of approximately 30 days each to make a year of 365 days and a leap year of 366 days. The civil year had 365.25 days. This is the Julian calendar. The solar year has 365.2422 days and by 1582 there was an appreciable discrepancy between the winter solstice and Christmas and the vernal equinox and Easter. Pope Gregory XIII, with the help of Italian astronomer Aloysius Lilius (Luigi Lilio), reformed this system by abolishing the days October 5 through October 14, 1582. This brought the civil and tropical years back into line. He also missed three days every four centuries by decreeing that centuries are only leap years if they are evenly divisible by 400. So for example 1700, 1800, and 1900 are not leap years but 1600 and 2000 are. This is the Gregorian calendar. Astronomers use the Julian/Gregorian calendar. Dates before 46 BC are converted to the Julian calendar. This is the proleptic Julian calendar. Astronomical calculations return a year zero and years before that are negative numbers. This is astronomical dating. There is no year zero in historical dating. In historical dating the year 1 BC is followed by the year 1 so for example, the year −3113 (astronomical dating) is the same as 3114 BC (historical dating).
Many mayanists convert Maya calendar dates into the proleptic Gregorian calendar. In this calendar, Julian calendar dates are revised as if the Gregorian calendar had been in use before October 15, 1582. These dates must be converted to astronomical dates before they can be used to study Maya astronomy because astronomers use the Julian/Gregorian calendar. Proleptic Gregorian dates vary substantially from astronomical dates. For example, the mythical creation date in the Maya calendar is August 11, 3114 BC in the proleptic Gregorian calendar and September 6, −3113 astronomical.
Julian days
Astronomers describe time as a number of days and a fraction of a day since noon January 1, −4712 Greenwich Mean Time. The Julian day starts at noon because they are interested in things that are visible at night. The number of days and fraction of a day elapsed since this time is a Julian day. The whole number of days elapsed since this time is a Julian day number.
Maya calendars
There are three main Maya calendars:
The Long Count is a count of days. There are examples of Long Counts with many places but most of them give five places since the mythical creation date – 13.0.0.0.0.
The Tzolkʼin is a 260-day calendar made up of a day from one to 13 and 20 day names. By pairing the numbers with the 20 names, that leaves 260 unique days with every combination of numbers/names happening once. This calendar was of the most sacred to the Maya, and was used as an almanac to determine farming cycles, and for religious practices to specify dates for ceremonies. These 260 days were each considered individual gods and goddesses that were not persuaded by a higher power. Unlike the 365 day year, this 260 day year was used less for counting/calculations, and more to arrange tasks, celebrations, ceremonies, etc. In some present day Maya communities, this 260 day almanac is still used, mostly for religious practices.
The Haab' is a 365-day year made up of a day of zero to 19 and 18 months with five unlucky days at the end of the year.
When the Tzolkʼin and Haabʼ are both given, the date is called a calendar round. The same calendar round repeats every 18,980 days – approximately 52 years. The calendar round on the mythical starting date of this creation was 4 Ahau 8 Kumk'u. When this date occurs again it is called a calendar round completion.
A Year Bearer is a Tzolkʼin day name that occurs on the first day of the Haab'. A number of different year bearer systems were in use in Mesoamerica.
Correlating the Maya and European calendar
The Maya and European calendars are correlated by using the Julian day number of the starting date of the current creation — 13.0.0.0.0, 4 Ajaw, 8 Kumk'u. The Julian day number of noon on this day was 584,283. This is the GMT correlation.
Sources of astronomical inscriptions
Maya codices
At the time of the Spanish conquest the Maya had many books. These were painted on folding bark cloth. The Spanish conquistadors and Catholic priests destroyed them whenever they found them. The most infamous example of this was the burning of a large number of these in Maní, Yucatán by Bishop Diego de Landa in July 1562. Only four of these codices exist today. These are the Dresden, Madrid, Paris and Grolier codices. The Dresden Codex is an astronomical Almanac. The Madrid Codex mainly consists of almanacs and horoscopes that were used to help Maya priests in the performance of their ceremonies and divinatory rituals. It also contains astronomical tables, although less than are found in the other three surviving Maya codices. The Paris Codex contains prophecies for tuns and katuns (see Mesoamerican Long Count calendar), and a Maya zodiac. The Grolier Codex is a Venus almanac.
Ernst Förstemann, a librarian at the Royal Public Library of Dresden, recognized that the Dresden Codex is an astronomical almanac and was able to decipher much of it in the early 20th century.
Maya monuments
Maya stelae
The Maya erected a large number of stelae. These had a Long Count date. They also included a supplementary series. The supplementary series included lunar data – the number of days elapsed in the current lunation, the length of the lunation and the number of the lunation in a series of six. Some of them included an 819-day count which may be a count of the days in a cycle associated with Jupiter. See Jupiter and Saturn below. Some other astronomical events were recorded, for example the eclipse warning on Quirigua Stela E – 9.17.0.0.0. A partial solar eclipse was visible in Mesoamerica two days later on 9.17.0.0.2 – Friday January 18, 771.
Santa Elena Poco Uinic Stela 3 records a total solar eclipse that crossed directly over the site, this eclipse is dated on 9.17.19.13.16 5 K'ib' 14 Ch'en - July 16, 790, the inscription mentions the date along a Maya glyph for solar eclipse.
Calendric inscriptions
Many Mayan temples were inscribed with hieroglyphic texts. These contain both calendric and astronomical content.
Methods of astronomical observation
Maya astronomy was naked-eye astronomy based on the observations of the azimuths of the rising and setting of heavenly bodies. City planning and alignment was often arranged in line with astronomical paths and events. The Maya also believed that the will and actions of gods could be interpreted in the alignment of the planets and stars.
Many wells located in Mayan ruins were also observatories of the zenithal passage of the sun.
One of the most studied sites for the topic of Mayan astronomy is the El Caracol at Chichen Itza. The Caracol is an observatory aligned to follow the path of Venus through the year. The grand staircase leading to the once cylindrical structure deviates 27.5 degrees from the alignment of the surrounding buildings to align with the northern extreme of Venus; the northeast-southwest diagonal of the site aligns with the sunrise of the summer solstice and the sunset of the winter solstice.
Astronomical observations
Solar
The Maya were aware of the solstices and equinoxes. This is demonstrated in building alignments. More important to them were zenithal passage days. In the tropics the Sun passes directly overhead twice each year. Many known structures in Mayan temples were built to observe this. An example of such temples is the observatory at Xochicalco. The observatory is an underground chamber with a hole in the ceiling. Two days of the year on May 15 and July 29, the sun would directly illuminate an illustration of the sun on the floor. Munro S. Edmonson studied 60 mesoamerican calendars and found remarkable consistency in the calendars, except for a number of different year bearer systems. He thought that these different year bearers were based on the solar years in which they were initiated. The sun was very important in the Mayan culture. The Mayan sun god was Kinich Ahau, one of the Mayan creator gods. Kinich Ahau would shine in the sky all day before being believed to transform himself into a jaguar at night to pass through Xibalba, the Mayan underworld.
The Maya were aware of the fact that the 365-day Haab' differs from the Tropical year by about 0.25 days per year. A number of different intervals are given on Maya monuments that can be used to approximate the tropical year. The most accurate of these is that the tropical year exceeds the length of the 365 day Haab' by one day every 1,508 days. The occurrence of a particular solstice on a given date in the Haab' will repeat after the passage of 1,508 365-day Haab' years. The Haab' will lose one day every 1,508 days and it will take 1,508 Haab' years to lose one Haab' year. So 365 x 1,508 = 365.2422 x 1,507 or 1,508 Haab' years = 1,507 Tropical years of 365.2422 days.
The Tropical Year in the Maya codices
The solstices and equinoxes are described in many almanacs and tables in the Maya codices. There are three seasonal tables and four related almanacs in the Dresden Codex. There are five solar almanacs in the Madrid Codex and possibly an almanac in the Paris codex. Many of these can be dated to the second half of the ninth and first half of the tenth centuries.
The Dresden Codex
The upper and lower seasonal tables (pages 61–69) unify the Haab', the solstices and equinoxes, the eclipse cycle and the year bearer (0 Pop). The table refers to the middle of the tenth century but includes more than a dozen other base dates from the fourth to the eleventh centuries.
The rainmaking almanac (pages 29b to 30b) refers to the Haab' and the tropical year. During the year in question the summer solstice preceded the Half Year by a few days. This confirms that the year was either 857 or 899. It also describes a four-part rain-making ceremony similar to Yucatecan ceremonies known from modern ethnography.
The Spliced Table (pages 31.a to 39.a) is the combination of two separate tables. It includes rituals including those of the Uayab', the Half Year, agricultural and meteorological matters. It contains a reference to the Half Year, skybands, two of which contain Venus glyphs. The table has four base dates; two in the fourth century, one in the ninth and one in the tenth century. Three of these are also base dates in the seasonal table
The Burner Almanac (pages 33c to 39c) contains the stations of the Burner cycle, a system for dividing the Tzolkʼin that is known from the colonial history of Yucatán. The almanac also refers to eclipse seasons and stations of the tropical year. This almanac refers to a few years before and just after 1520, when the codex may have already been in the hands of the Spanish.
The Conjugal Almanac (pages 22c to 23c) is one of a series of almanacs dealing with conjugal relationships between pairs of deities. It may contain a reference to the vernal equinox.
In addition to the astronomical tables preserved in the Dresden codex, there are illustrations of different deities and their relation to the positions of the planets.
The Madrid Codex
Pages 10b,c – 11b, c of the Madrid Codex contain two almanacs similar to the seasonal tables of the Dresden Codex. In the lower almanac the Half Year of the Haab' occurred on the same day as the summer solstice, dating this event to the year 925.
The long almanac (pages 12b to 18b) includes iconography of the Haab, abundant rain and astronomy. The almanac contains several eclipse glyphs, spaced at correct eclipse intervals. The eclipse and calendar dates allow one to date the almanac to the year 924. The combination of this almanac and the seasonal almanacs in this codex are the functional equivalent of the two seasonal almanacs in the Dresden Codex.
Pages 58.c to 62.c are a tropical-year almanac. It is an 1820-day almanac made up of 20 rows of 91 days each. One of the captions associates an equinox with a glyph for Venus. This dates the almanac to a date between 890 and 962.
The Bird Almanac (pages 26c to 27c) has an unusual structure (5 x 156 = 780 days). One of its pictures is probably a reference to the vernal equinox. This almanac can't be dated.
The Paris Codex
The God C almanacs (pages 15a, b to 18a, b) are very incomplete and partially effaced. It is impossible to ascertain their lengths or dates. Two known Haab' rituals can be recognized. It's possible that the God C almanacs are equivalent to the seasonal tables in the Dresden Codex and the God C almanacs in the Paris Codex
The Books of Chilam Balam
The Book of Chilam Balam specifically refers to the Half Year, the solstices and equinoxes.
Building alignments
Anthony Aveni and Horst Hartung published an extensive study of building alignments in the Maya area. They found that most orientations occur in a zone 8°-18° east of north with many at 14° and 25° east of north. He believes that the 25° south of east orientations are oriented to the position on the horizon of sunrise on the winter solstice and that the 25° north of west orientations are aligned with sunset on the summer solstice. Further systematic research has led to the recognition of several orientation groups, most of which refer to agriculturally significant sunrise and sunset dates.
Two diagonal alignments across the platform of the base Caracol at Chichén Itzá, are aligned with the azimuth of the sunrise on the summer solstice and an alignment perpendicular to the base of the lower platform corresponds to the azimuth of the sunset on the summer solstice. One of the windows in the round tower provides a narrow slit for viewing the sunset on the equinoxes. The Caracol was also used to observe the zenithal passage of the Sun. An alignment perpendicular to the base of the upper platform and one from the center of a doorway above the symbolate monument are aligned with the azimuth of the sunset on zenith passage days.
Other solar observatories are at Uaxactun, Oxkintok and Yaxchilan.
Lunar
Many inscriptions include data on the number of days elapsed in the current lunation, the number of days in the current lunation and the position of the lunation in a cycle of six lunations.
Modern astronomers consider conjunction of Sun and Moon (when the Sun and Moon have the same ecliptic longitude) to be the New Moon. The Maya counted the zero day of the lunar cycle as either the first day when one could no longer see the waning crescent Moon or the first day when one could see the thin crescent waxing Moon (the Palenque system). Using this system, the zero date of the lunar count is about two days after astronomical new Moon. Aveni and Fuls analysed a large number of these inscription and found strong evidence for the Palenque system. However Fuls found "... at least two different methods and formulas were used to calculate the moon's age and position in the six-month cycle..."
Building alignments
A number of orientations to lunar extremes (standstill positions on the horizon) have been identified. Most of them are concentrated on the Northeast Coast of the Yucatan peninsula, where the cult of goddess Ixchel, associated with the Moon, is known to have been important.
Mercury
Pages 30c-33c of the Dresden codex are a Venus-Mercury almanac. The 2340-day length of the Venus-Mercury almanac is a close approximation of the synodic periods of Venus (4 x 585) and Mercury (20 x 117). The Almanac also refers to the summer solstice and the Haab' uayeb ceremonies for the tenth century AD.
Venus
Venus was extremely important to the people of Mesoamerica. Its cycles were carefully tracked by the Maya. The Maya associated the planet Venus with war, and battles would be arranged to align with the movements of Venus. The Maya would also sacrifice captured enemies according to Venus' position in the sky.
Because Venus is closer to the Sun than the Earth, it passes the Earth during its orbit. When it passes behind the Sun at superior conjunction and between the Earth and the Sun at inferior conjunction it is invisible. Particularly dramatic is the disappearance as evening star and its reappearance as the morning star approximately eight days later, after inferior conjunction. The cycle of Venus is 583.92 days long but it varies between 576.6 and 588.1 days. Astronomers calculate heliacal phenomena (first and last visibility of rising or setting bodies) using the arcus visionis – the difference in altitude between the body and the center of the Sun at the time of geometric rising or setting of the body, not including the 34 arc minutes of refraction that allows one to see a body before its geometric rise or the 0.266,563,88... degree semidiameter of the sun. Atmospheric phenomena like extinction are not considered. The required arcus visionis varies with the brightness of the body. Because Venus varies in size and has phases, a different arcus visionus is used for the four different rising and settings.
Dresden Codex
The Dresden Codex pages 24 and 46 to 50 are a Venus almanac. Bricker and Bricker write:
"The Venus table tracks the synodic cycle of Venus by listing the formal or canonical dates of planet's first and last appearances as 'morning star' and 'evening star'. The emphasis, both iconographic and textual, is on first appearance as morning star (heliacal rise), the dates of which are given quite accurately, This first appearance was regarded as a time of danger and the major purpose of the Venus table was to provide warnings of such dangerous days. The table lists the tzolkin days for the four appearance/disappearance events during each of the 65 consecutive Venus cycles, a period of approximately 104 years. The table was used at least four times with different starting dates, from the tenth through the fourteenth centuries AD."
Because the Maya canonical period was 584 days and the synodic period is 583.92 days, an error accumulated in the table over time. Possible correction schemes from the codex are discussed by Aveni and Bricker and Bricker.
The Dresden Codex pages 8–59 is a planetary table that commensurates the synodic cycles of Mars and Venus. There are four possible base dates, two in the seventh and two in the eighth centuries.
Pages 30c-33c of the Dresden codex are a Venus-Mercury almanac. The 2340-day length of the Venus-Mercury almanac is a close approximation of the synodic periods of Venus (4 x 585) and Mercury (20 x 117). The Almanac also refers to the summer solstice and the Haab' uayeb ceremonies for the tenth century AD.
The Grolier Codex
The Grolier Codex lists Tzolkʼin dates for the appearance/disappearances of Venus for half of the Venus cycles in the Dresden codex. These are the same dates listed in Dresden.
Building alignments
The Caracol at Chichen Itza contains the remains of windows through which the extreme elongations of the planet can be seen. Four of the main orientations of the lower platform mark the points of the maximum horizontal displacement of the planet during the year. Two alignments of the surviving windows in the upper tower align with the extreme positions of the planet at its greatest north and south declinations.
Building 22 at Copán is called the Venus temple because Venus symbols are inscribed on it. It has a narrow window that can be used to observe Venus on certain dates.
The Governors Palace at Uxmal differs 30° from the northeast alignment of the other buildings. The door faces southeast. About 4.5 km from the door is a pyramidal hill, from where Venus northerly extremes could be observed over the Governor's Palace. The cornices of the building have hundreds of masks of Chaac with Venus symbols under the eyelids.
Inscriptions
De Meis has a table of 14 Long Count inscriptions that record heliacal phenomena of Venus.
De Meis has a table of 11 Long Counts that record the greatest elongation of Venus.
The Bonampak murals depict the victory of king Chaan Muan with his enemies lying down, pleading for their lives on a date which was the heliacal rising of Venus and a zenith passage of the Sun.
Mars
The Dresden Codex
The Dresden Codex contains three Mars tables and there is a partial Mars almanac in the Madrid codex.
Pages 43b to 45b of the Dresden codex are a table of the 780-day synodic cycle of Mars. The retrograde period of its path, when it is brightest and visible for the longest time, is emphasized. The table is dated to the retrograde period of 818 AD. The text refers to an eclipse season (when the moon is near its ascending or descending node) that coincided with the retrograde motion of mars.
The upper and lower water tables on pages 69–74 share the same pages in the Dresden Codex but are different from each other.
The upper table has 13 groups of 54 days – 702 days. This is the time needed for Mars to return to the same celestial longitude, if the celestial period included a retrograde period. The table was revised for reuse; it has seven base dates from the seventh to the eleventh centuries.
The lower water table has 28 groups of 65 days – 1820 days. This table has only one picture – a scene of torrential rain on page 74. This has been erroneously interpreted as a depiction of the end of the world. The purpose of the table is to track several cultural and natural cycles. These are planting and harvesting, drought, rain and hurricane season, the eclipse season and the relationship of the Milky Way to the horizon. The table was periodically revised by giving it five base dates from the fourth to the twelfth centuries.
The Dresden Codex pages 8–59 is a planetary table that commensurates the synodic cycles of Mars and Venus. There are four possible base dates, two in the seventh and two in the eighth centuries.
The Madrid Codex
Page 2a of the Madrid codex is an almanac of the synodic cycle of Mars. This heavily damaged page is probably a fragment of a longer table. The 78-day periods and iconography are similar to the table in the Dresden Codex.
Jupiter and Saturn
Saturn and particularly Jupiter are two of the brightest celestial objects. As the Earth passes superior planets in its orbit closer to the Sun they appear to stop moving in the direction of travel of their orbits and back up for a period before resuming their path through the sky. This is apparent retrograde motion. When they start or end retrograde motion their daily motion is stationary before going in another direction.
Inscriptions
Lounsbury found that the dates of several inscriptions commemorating dynastic rituals at Palenque by Kʼinich Kan Bahlam II coincide with the departure of Jupiter from its secondary stationary point. He also showed that close conjunctions of Jupiter, Saturn and/or Mars were probably celebrated, particularly the "2 Cib 14 Mol" event on about July 21, 690 (Proleptic Gregorian calendar date) – July 18 astronomical.
The Dumbarton Oaks Relief Panel 1 came from El Cayo, Chiapas – a site 12 kilometers up the Usumacinta River from Piedras Negras. Fox and Juteson (1978) found that two of these dates are separated by 378 days – close to the mean synodic period of Saturn – 378.1 days. Each date also falls a few days before Saturn reached its second stationary point, before ending its retrograde motion. The Brickers identified two additional dates that are part of the same series.
Susan Milbrath has extended Lounsbury's work concerning Jupiter to other classic and post-classic sites. Central to her work is her identification of God K (K'awil) as Jupiter. Another component of her work is the tying together of the synodic cycles of Jupiter and Saturn with the katun cycles of the Long Count. She finds a clear link between God K images and dates coinciding with its stationary points in retrograde. She believes that K'awil is the god of the retrograde cycles of Jupiter and Saturn. The Brickers question this interpretation.
Maya Codices
No clear Jupiter or Saturn almanac can be found in the codices.
Eclipses
The Dresden Codex
The Dresden Codex pages 51 and 58 are an eclipse table. The table contains a warning of all solar and most lunar eclipses. It does not specify which ones will be visible in the Maya area. The length of the table is 405 synodic lunations (439.5 draconic months, about 33 years). It was meant to be recycled and has a periodic correction scheme. The starting date is in the eighth century and has corrections allowing it to be used up to the eighteenth century. The table also relates eclipses and lunar phenomena to the cycles of Venus, possibly Mercury and other celestial and seasonal phenomena.
An eclipse can occur when the Moon's orbit crosses the ecliptic. This happens twice a year and is referred to as the ascending or descending node. An eclipse can occur during a period 18 days before or after an ascending or descending node. This is an Eclipse season. Three entry dates in the Dresden Codex eclipse table give the eclipse season for November – December 755.
The Madrid Codex
Pages 10a – 13a of the Madrid Codex are an eclipse almanac similar to the one in the Dresden Codex. The table is concerned with rain, drought, the agricultural cycle and how these correspond with eclipses. These eclipses probably correspond to the eclipses in the Dresden Codex (the eighth or ninth century).
The Paris Codex
The Katun Pages (pages 2–11) in the Paris Codex are concerned with the rituals to be performed at Katun completions. They also contain references to historical astronomical events during the fifth to the eighth centuries. These include eclipses, references to Venus and the relationship of Venus to named constellations.
Inscriptions
Santa Elena Poco Uinic Stela 3 has the Mesoamerican long count date of 9.17.19.13.16 5 K'ib' 14 Ch'en inscribed with a Maya glyph of a total solar eclipse, a unique record in the Maya region.
Lord Kan II of Caracol had altar 21 installed in the center of a ball court. It has inscriptions that mark important dates of the accomplishments of his ancestor Lord Water and himself. Lord Kan II used the dates of important astronomical phenomena for these. For example:
9.5.19.1.2 9 Ik 5 Uo – April 14, 553, total lunar eclipse – Accession of Lord Water, grandfather of Kan II
9.6.8.4.2 7 Ik 0 Zip – April 27, 562, annular solar eclipse 8 days ago and penumbral lunar eclipse in 7 days – Star war to Tikal
9.7.19.10.0 1 Ahau 3 Pop – March 13, 593, partial solar eclipse five days ago – Ball game
The stars
The Maya identified 13 constellations along the ecliptic. These are the content of an almanac in the Paris Codex. Each of these was associated with an animal. These animal representations are pictured in two almanacs in the Madrid Codex where they are related to other astronomical phenomena – eclipses and Venus – and Haab rituals.
Paris Codex
Pages 21–24 of the Paris Codex are a zodiacal almanac. It is made up of five rows of 364 days each. Each row is divided into 13 subdivisions of 28 days each. Its iconography consists of animals, including a scorpion suspended from a skyband and eclipse glyphs. It dates from the eighth century.
Madrid Codex
The longest almanac in the Madrid codex (pages 65–72,73b) is a compendium of information about agriculture, ceremonies, rituals and other matters. Astronomical information includes references to eclipses, the synodic cycles of Venus and zodiacal constellations. The almanac dates to the middle of the fifteenth century.
The Milky Way
The Milky Way appears as a hazy band of faint stars. It is the disc of our own galaxy, viewed edge-on from within it. It appears as a 10°-wide band of diffuse light passing all the way around the sky. It crosses the ecliptic at a high angle. Its most prominent feature is a large dust cloud that forms a dark rift in its southern and western part.
There is no almanac in the codices that refers specifically to the Milky Way but there are references to it in almanacs concerned with other phenomena.
Precession of the equinoxes
The equinoxes move westward along the ecliptic relative to the fixed stars, opposite to the yearly motion of the Sun along the ecliptic, returning to the same position approximately every 26,000 years.
The "Serpent Numbers" in the Dresden Codex pp. 61–69 is a table of dates written in the coils of undulating serpents. Beyer was the first to notice that the Serpent Series is based on an unusually long distance number of 1.18.1.8.0.16 (5,482,096 days – more than 15,000 years). Grofe believes that this interval is quite close to a whole multiple of the sidereal year, returning the sun to precisely the same position against the background of stars. He proposes that this is an observation of the precession of the equinoxes and that the serpent series shows how the Maya calculated this by observing the sidereal position of total lunar eclipses at fixed points within the tropical year. Bricker and Bricker think that he based this on misinterpretation of the epigraphy and give their reasons in Astronomy in the Maya Codices.
Notes
References
Bibliography
Astronomy
Ancient astronomy | Maya astronomy | Astronomy | 6,618 |
33,753,674 | https://en.wikipedia.org/wiki/Tylopilus%20alboater | Tylopilus alboater, called the black velvet bolete, by some, is a bolete fungus in the family Boletaceae. The species is found in North America east of the Rocky Mountains, and in eastern Asia, including China, Japan, Taiwan, and Thailand. A mycorrhizal species, it grows solitarily, scattered, or in groups on the ground usually under deciduous trees, particularly oak, although it has been recorded from deciduous, coniferous, and mixed forests.
The fruit bodies have a black to grayish-brown cap that measures up to in diameter. The caps of young specimens have a velvety texture and are covered with a whitish to gray powdery coating; this texture and coating is gradually lost as the mushroom matures, and the cap often develops cracks. The pores on the underside of the cap are small and pinkish. The stem is bluish purple to black, and measures up to long by thick. Both the pore surface and the whitish cap flesh will stain pink to reddish gray, and eventually turn black after being cut or injured. The mushroom is edible, and generally considered one of the best edible Tylopilus species.
Taxonomy and naming
The species was first described in 1822 as Boletus alboater by Lewis David de Schweinitz from specimens he collected in North Carolina. Elias Magnus Fries sanctioned this name in his 1821 Systema Mycologicum. The species was one of several Boletus species that Otto Kuntze transferred to Suillus in his 1898 Revisio Generum Plantarum. American mycologist William Alphonso Murrill transferred it to the genus Tylopilus in 1909. In 1931, French mycologist Jean-Edouard Gilbert transferred the species to his newly created genus Porphyrellus, but this name has since been subsumed into Tylopilus.
In 1875, Charles Horton Peck described Boletus nigrellus from specimens he collected in Sand Lake, New York. Murrill reduced this name to synonymy with T. alboater in 1916, and noted that Peck's description was made from young material obtained "before the white tubes had been colored by mature spores". Several later authorities have treated Peck's species as a synonym of Tylopilus alboater; this synonymy, however, is not indicated by either of the taxonomic authorities Index Fungorum or MycoBank.
The specific epithet alboater means "white and black". It is commonly known as the "black velvet bolete"; Murrill called it the "blackish bolete".
Description
The shape of the cap is initially convex before later becoming broadly convex to eventually flattened in maturity; the diameter of the cap is typically between . The cap surface is dry, with a velvet-like texture, although in age it can become rimose (developing a network of cracks and small crevices). The cap color is initially black to dark grayish brown; young specimens can have a whitish bloom (resembling a dusting of fine powder) on the surface. Fruit bodies, especially young specimens, tend to be free of maggots and other insect larvae. As the mushroom matures, the bloom disappears and the color fades to become grayish to grayish brown. The cap flesh is whitish, but after it is cut or injured, it will stain pink to reddish gray, and eventually turn black.
Spores are produced in basidia that are arranged in a vertically arranged layer of minute tubes on the underside of the cap that create a surface of pores. This surface is whitish when young before turning dull pink or flesh-colored in maturity. When bruised, the pore surface initially stains reddish and slowly turns black. The shape of the pores is angular to irregular, and they are small, with roughly two pores per millimeter. The tubes are deep, and usually sunken around the area of attachment to the stem. The stem is long by thick, and is equal in width throughout its length, slightly thicker towards the base, or somewhat thicker in the middle. It is the same color as the cap, or paler. The surface texture of the stem is usually smooth, although some specimens may be slightly reticulated near the top. The spore print can range from pinkish to a deep flesh color.
The spores are oval to ellipsoid in shape, smooth, hyaline (translucent), and measure 7–11 by 3.5–5 μm. The basidia are club-shaped, four-spored, and measure 15–24 by 6–7.5 μm. Pleurocystidia (cystidia found on the tube faces) are irregularly club-shaped, with dimensions of 20–36 by 7–10 μm, while cheilocystidia (found on the tube edge) are club-shaped, rare, occur singly, and measure 18–32 by 7–9 μm. Although rare, there are also caulocystidia (occurring on the stem) that are arranged in groups, and which measure individually 24–30 by 6–9 μm. Clamp connections are absent from the hyphae of T. alboater.
Tylopilus alboater is an edible mushroom with a pleasant odor and a mild taste. It is considered one of the best of the edible Tylopilus—a genus that is usually associated with bitter-tasting, unpalatable species. Frying slices of the mushroom brings out a "delicate, earthy, nutty flavor"; longer frying times make the cap "pleasantly crisp". The mushrooms can be used in mushroom dying.
Similar species
Some Tylopilus species have a superficial resemblance to T. alboater and might be confused with it, including T. atronicotianus, T. atratus, and T. griseocarneus. T. atratus produces smaller fruit bodies with caps up to in diameter, and its whitish flesh directly stains black without any intermediate reddish phase when injured. It is known from only from western New York state. The "false black velvet bolete", T. atronicotianus, has a brownish cap that lacks the velvety texture of T. alboater, and has stems that are minutely velvety and almost black near the base. T. griseocarneus, found in the Atlantic and Gulf Coastal Plains of North America, is readily distinguished from T. alboater by the strong orange to red discoloration that results when cutting or damaging the flesh of a fresh specimen. Furthermore, T. griseocarneus lacks the whitish bloom present on young caps of T. alboater, and typically has a more prominently reticulated stem. Specimens of T. alboater that are paler than usual can be confused with T. ferrugineus, but the latter has yellow cystidia when mounted in KOH, while the cystidia of the former are brownish yellow under similar conditions.
Distribution and habitat
Tylopilus alboater is a mycorrhizal species, and its fruit bodies grow on the ground solitarily, scattered, or in groups under deciduous trees, particularly oak. Fruiting occurs in deciduous, coniferous, and mixed forests. Its dark color makes it difficult to notice in the field.
In North America, the mushroom is widely distributed east of the Rocky Mountains. The distribution ranges from Quebec in Canada, south to the New England states down to Florida, extending west to Missouri, Michigan, and Texas. It is also found in Mexico. In Asia, it has been recorded from China (Anhui, Fujian, Guangdong, Guangxi, and Sichuan), Japan, Taiwan, and Thailand.
See also
List of North American boletes
References
Cited text
External links
Wax mushroom model at the New York State Museum
alboater
Edible fungi
Fungi described in 1822
Fungi of Asia
Fungi of North America
Fungus species | Tylopilus alboater | Biology | 1,634 |
70,426,129 | https://en.wikipedia.org/wiki/Aetokthonotoxin | Aetokthonotoxin (AETX), colloquially known as eagle toxin, is a chemical compound that was identified in 2021 as the cyanobacterial neurotoxin causing vacuolar myelinopathy (VM) in eagles in North America. As the biosynthesis of aetokthonotoxin depends on the availability of bromide ions in freshwater systems and requires an interplay between the toxin-producing cyanobacterium Aetokthonos hydrillicola and the host plant it requires to live (Hydrilla verticillata), it took more than 25 years to identify aetokthonotoxin as the VM-inducing toxin after the disease has first been diagnosed in bald eagles in 1994. The toxin cascades through the food-chain: Among other animals, it builds up in fish and waterfowl such as coots or ducks which feed on hydrilla colonized with the cyanobacterium. Aetokthonotoxin is transmitted to raptors, such as the bald eagle, as they prey on AETX poisoned animals. The total synthesis of AETX was achieved in 2021, the enzymatic functions of the 5 enzymes involved in AETX biosynthesis were described in 2022.
Biosynthesis
The biosynthesis of AETX and the functions of the enzymes AetA, AetB, AetD, AetE, and AetF were described in 2022. AetF, a FAD-dependent halogenase, brominates L-tryptophan at the 5 position. The 5-bromo-L-tryptophan can then undergo two separate reactions. One route involves a second bromination by AetF at position 7 to yield 5,7-dibromo-L-tryptophan. This molecule then goes on to react with AetD, an iron-dependent nitrile synthase, to form an indole-3-carbonitrile derivative. The second route taken by the 5-bromo-L-tryptophan starting material involves the tryptophanase AetE, which cleaves 5-bromo-L-tryptophan into 5-bromoindole, pyruvic acid and ammonia. 5-bromoindole can then go on to react with a different FAD-dependent halogenase called AetA to form 2,3,5-tribromoindole. the 2,3,5-tribromoindole and the dibrominated-indole-3-carbonitrile then undergo biaryl coupling facilitated by the cytochrome P450 enzyme AetB to form AETX.
See also
Cyanotoxin
Harmful algal bloom
Persistent organic pollutant
References
Neurotoxins
Cyanotoxins
Bacterial alkaloids
Halogen-containing natural products
Nitriles
Bromoarenes
Indoles
Bromine-containing natural products
Indole alkaloids
Halogen-containing alkaloids | Aetokthonotoxin | Chemistry | 637 |
78,863,667 | https://en.wikipedia.org/wiki/C/1936%20K1%20%28Peltier%29 | Peltier's Comet, formal designation C/1936 K1, is a non-periodic comet that became visible to the naked eye between July and August 1936. It is the fifth of 10 comets discovered by American astronomer, Leslie C. Peltier.
References
External links
Non-periodic comets
Near-Earth comets | C/1936 K1 (Peltier) | Astronomy | 66 |
21,809,607 | https://en.wikipedia.org/wiki/NC-SI | NC-SI, abbreviated from network controller sideband interface, is an electrical interface and protocol defined by the Distributed Management Task Force (DMTF). The NC-SI enables the connection of a baseboard management controller (BMC) to one or more network interface controllers (NICs) in a server computer system for the purpose of enabling out-of-band system management. This allows the BMC to use the network connections of the NIC ports for the management traffic, in addition to the regular host traffic.
The NC-SI defines a control communication protocol between the BMC and NICs. The NC-SI is supported over several transports and physical interfaces.
Hardware interface
The RMII-based transport (RBT) interface defined by NC-SI is based on the RMII specification with some modifications that allow connection of multiple network controllers to a single BMC. The NC-SI can also operate over a variety of other electrical interfaces, including SMBus and PCI Express when used over the Management Component Transport Protocol (MCTP).
The table below sums up the signals comprising the RBT interface.
Traffic types
The NC-SI defines two fundamental types of traffic, pass-through and control traffic. Pass-through traffic consists of data exchanged between the BMC and the network via the NC-SI interface. Control traffic is used to inventory and configure aspects of NIC operation and control the NC-SI interface.
Control traffic is broken down into three sub-types:
Commands, sent from the BMC to one of the NICs
Responses, sent by the NICs as results of the commands
Asynchronous event notifications (AENs), sent asynchronously by the NICs and equivalently to interrupts, upon the occurrence of the specified event
When the NC-SI is used over RBT, standard Ethernet framing is used for all traffic types. Control traffic is identified by using an EtherType of 0x88F8. When the NC-SI is used in conjunction with MCTP, MCTP provides the packetization methodology and traffic type identification.
See also
Management Component Transport Protocol (MCTP)
Platform Management Components Intercommunication (PMCI)
References
External links
DMTF Homepage
NC-SI Specification rev 1.1.0
NC-SI over MCTP Binding Specification rev 1.2.2
DMTF standards
Out-of-band management | NC-SI | Technology | 489 |
50,586,295 | https://en.wikipedia.org/wiki/Back%20action%20%28quantum%29 |
Introduction (error in measurement)
Back Action in quantum mechanics is the phenomenon in which the act of measuring a property of a particle directly influences the state of the particle. In all scientific measurement, there exists a degree of error due to a variety of factors. This could include unaccounted-for variables, imperfect procedure execution, or imperfect measurement devices. In classical mechanics, it is assumed that the error of any experiment could theoretically be zero if all relevant aspects of the configuration are known and the measurement devices are perfect. However, quantum mechanical theory supports that the act of measuring a quantity, regardless of the degree of precision, carries inherent uncertainty as the measurement influences the quantity itself. This behavior is known as back action. This is due to the fact that quantum uncertainty carries minimum fluctuations as a probability. For example, even objects at absolute zero still carry ‘motion’ due to such fluctuations.
Simultaneous measurement & uncertainty
Simultaneous measurement is not possible in quantum mechanics for observables that do not commute (the commutator of the observables is not equal to zero). Since observable quantities are treated as operators, their values do not necessarily follow classical algebraic properties. For this reason, there always remains a minimum uncertainty in regard to the uncertainty principle. This relationship sets a minimum uncertainty when measuring position and momentum. However, it can be extended to any incompatible observables.
Effect of measurement on system
Each observable operator has a set of eigenstates, each with an eigenvalue. The full initial state of a system is a linear combination of the full set of its eigenstates. Upon measurement, the state then collapses to an eigenstate with a given probability and will proceed to evolve over time after measurement. Thus, measuring a system affects its future behavior and will thus affect further measurements of non-commuting observables.
Using bra-ket notation, consider a given system that begins in a state , and an observable operator with the set of eigenstates each with a corresponding eigenvalue . A measurement of is made, and the probability of getting is as follows:
The particle's state has now collapsed to the state . Now, consider another observable with the set of eigenstates each with a corresponding eigenvalue . If a subsequent measurement of on the system is made, the possible outcomes are now , each with the following probability:
Had not been measured first, the probability of each outcome would have remained as:
Thus, unless and share and identical set of eigenstates (that is to say, ), the initial measurement fundamentally influences the system to affect future measurements. This statement is identical to stating that if the commutator of the two observables is non-zero, repeated observations of the observables will present altered results. Observables will share the set of eigenstates if
Back action is an area of active research. Recent experiments with nanomechanical systems have attempted to evade back action while making measurements.
References
Quantum mechanics | Back action (quantum) | Physics | 629 |
92,962 | https://en.wikipedia.org/wiki/Lemierre%27s%20syndrome | Lemierre's syndrome is infectious thrombophlebitis of the internal jugular vein. It most often develops as a complication of a bacterial sore throat infection in young, otherwise healthy adults. The thrombophlebitis is a serious condition and may lead to further systemic complications such as bacteria in the blood or septic emboli.
Lemierre's syndrome occurs most often when a bacterial (e.g., Fusobacterium necrophorum) throat infection progresses to the formation of a peritonsillar abscess. Deep in the abscess, anaerobic bacteria can flourish. When the abscess wall ruptures internally, the drainage carrying bacteria seeps through the soft tissue and infects the nearby structures. Spread of infection to the nearby internal jugular vein provides a gateway for the spread of bacteria through the bloodstream. The inflammation surrounding the vein and compression of the vein may lead to blood clot formation. Pieces of the potentially infected clot can break off and travel through the right heart into the lungs as emboli, blocking branches of the pulmonary artery that carry deoxygenated blood from the right side of the heart to the lungs.
Sepsis following a throat infection was first described by Hugo Schottmüller in 1918. In 1936, André Lemierre published a series of 20 cases where throat infections were followed by identified anaerobic sepsis, of whom 18 died.
Signs and symptoms
The signs and symptoms of Lemierre's syndrome vary, but usually start with a sore throat, fever, and general body weakness. These are followed by extreme lethargy, spiked fevers, rigors, swollen cervical lymph nodes, and a swollen, tender or painful neck. Often there is abdominal pain, diarrhea, nausea and vomiting during this phase. These signs and symptoms usually occur several days to two weeks after the initial symptoms.
Symptoms of pulmonary involvement can be shortness of breath, cough and painful breathing (pleuritic chest pain). Rarely, blood is coughed up. Painful or inflamed joints can occur when the joints are involved.
Septic shock can also arise. This presents with low blood pressure, increased heart rate, decreased urine output and an increased rate of breathing. Some cases will also present with meningitis, which will typically manifest as neck stiffness, headache and sensitivity of the eyes to light. Liver enlargement and spleen enlargement can be found, but are not always associated with liver or spleen abscesses. Other signs and symptoms that may occur:
Headache (unrelated to meningitis)
Memory loss
Muscle pain
Jaundice
Decreased ability to open the jaw
Crepitations are sometimes heard over the lungs
Pericardial friction rubs as a sign of pericarditis (rare)
Cranial nerve paralysis and Horner's syndrome (both rare)
Cause
The bacteria causing the thrombophlebitis are anaerobic bacteria that are typically normal components of the microorganisms that inhabit the mouth and throat. Species of Fusobacterium, specifically Fusobacterium necrophorum, are most commonly the causative bacteria, but various bacteria have been implicated. One 1989 study found that 81% of Lemierres's syndrome had been infected with Fusobacterium necrophorum, while 11% were caused by other Fusobacterium species. MRSA might also be an issue in Lemierre infections. Rarely Lemierre's syndrome is caused by other (usually Gram-negative) bacteria, which include Bacteroides fragilis and Bacteroides melaninogenicus, Peptostreptococcus spp., Streptococcus microaerophile, Staphylococcus aureus, Streptococcus pyogenes, and Eikenella corrodens.
Pathophysiology
Lemierre's syndrome begins with an infection of the head and neck region, with most primary sources of infection in the palatine tonsils and peritonsillar tissue. Usually this infection is a pharyngitis (which occurred in 87.1% of patients as reported by a literature review), and can be preceded by infectious mononucleosis as reported in several cases. It can also be initiated by infections of the ear, mastoid bone, sinuses, or saliva glands.
During the primary infection, F. necrophorum colonizes the infection site and the infection spreads to the parapharyngeal space. The bacteria then invade the peritonsillar blood vessels where they can spread to the internal jugular vein. In this vein, the bacteria cause the formation of a thrombus containing these bacteria. Furthermore, the internal jugular vein becomes inflamed. This septic thrombophlebitis can give rise to septic microemboli that disseminate to other parts of the body where they can form abscesses and septic infarctions. The first capillaries that the emboli encounter where they can nestle themselves are the pulmonary capillaries. As a consequence, the most frequently involved site of septic metastases are the lungs, followed by the joints (knee, hip, sternoclavicular joint, shoulder and elbow). In the lungs, the bacteria cause abscesses, nodulary and cavitary lesions. Pleural effusion is often present. Other sites involved in septic metastasis and abscess formation are the muscles and soft tissues, liver, spleen, kidneys and nervous system (intracranial abscesses, meningitis).
Production of bacterial toxins such as lipopolysaccharide leads to secretion of cytokines by white blood cells which then both lead to symptoms of sepsis. F. necrophorum produces hemagglutinin which causes platelet aggregation that can lead to diffuse intravascular coagulation and thrombocytopenia.
Diagnosis
Diagnosis and the imaging (and laboratory) studies to be ordered largely depend on the patient history, signs and symptoms. If a persistent sore throat with signs of sepsis are found, physicians are cautioned to screen for Lemierre's syndrome.
Laboratory investigations reveal signs of a bacterial infection with elevated C-reactive protein, erythrocyte sedimentation rate and white blood cells (notably neutrophils). Platelet count can be low or high. Liver and kidney function tests are often abnormal.
Thrombosis of the internal jugular vein can be displayed with sonography. Thrombi that have developed recently have low echogenicity or echogenicity similar to the flowing blood, and in such cases pressure with the ultrasound probe show a non-compressible jugular vein - a sure sign of thrombosis. Also color or power Doppler ultrasound identify a low echogenicity blood clot. A CT scan or an MRI scan is more sensitive in displaying the thrombus of the intra-thoracic retrosternal veins, but are rarely needed.
Chest X-ray and chest CT may show pleural effusion, nodules, infiltrates, abscesses and cavitations.
Bacterial cultures taken from the blood, joint aspirates or other sites can identify the causative agent of the disease.
Other illnesses that can be included in the differential diagnosis are:
Q fever
Tuberculosis
Pneumonia
Treatment
Lemierre's syndrome is primarily treated with antibiotics given intravenously. Fusobacterium necrophorum is generally highly susceptible to beta-lactam antibiotics, metronidazole, clindamycin and third generation cephalosporins while the other fusobacteria have varying degrees of resistance to beta-lactams and clindamycin. Additionally, there may exist a co-infection by another bacterium. For these reasons is often advised not to use monotherapy in treating Lemierre's syndrome. Penicillin and penicillin-derived antibiotics can thus be combined with a beta-lactamase inhibitor such as clavulanic acid or with metronidazole. Clindamycin can be given as monotherapy.
If antibiotic therapy is unsuccessful, additional treatments include draining of any abscesses and ligation of the internal jugular vein where the antibiotic cannot penetrate.
There is no evidence to opt for or against the use of anticoagulation therapy. The low incidence of Lemierre's syndrome has not made it possible to set up clinical trials to study the disease.
Prognosis
The mortality rate was 90% prior to antibiotic therapy. In the contemporary era, a mortality of 4% has been estimated. Since this disease is not well known and often remains undiagnosed, mortality might be much higher. Approximately 10% of those with the condition experience clinical sequelae, including cranial nerve palsy and orthopaedic limitations.
Epidemiology
Lemierre's syndrome is currently rare, but was more common in the early 20th century before the discovery of penicillin. The reduced use of antibiotics for sore throats may have increased the risk of this disease, with 19 cases in 1997 and 34 cases in 1999 reported in the UK. The estimated incidence rate is 0.8 to 3.6 cases per million in the general population, but is higher in healthy young adults. The number of cases reported is increasing; however, because of its rarity, physicians may be unaware of its existence, possibly leading to underdiagnosis.
History
Sepsis following from a throat infection was described by Hugo Schottmüller in 1918. In 1936, André Lemierre published a series of 20 cases where throat infections were followed by identified anaerobic sepsis, of whom 18 patients died.
References
Bacterial diseases
Syndromes caused by microbes
Rare infectious diseases | Lemierre's syndrome | Biology | 2,048 |
38,488,397 | https://en.wikipedia.org/wiki/Ramaria%20caulifloriformis | Ramaria caulifloriformis is a species of coral fungus in the family Gomphaceae. It was first described in 1956 as Clavaria caulifloriformis by Chester Leathers from collections made near Topinabee, Michigan. It was transferred into the genus Ramara in 1970 by E.J.H. Corner. The creamy-brown fruit bodies measure tall by wide, and have a cauliflower head-like appearance (for which the species is named). Spores are ellipsoid, verrucose (covered with warts or wartlike projections), and measure 8–10 by 4–5 μm.
References
External links
Fungi described in 1956
Fungi of the United States
Gomphaceae
Fungi without expected TNC conservation status
Fungus species | Ramaria caulifloriformis | Biology | 163 |
25,271,400 | https://en.wikipedia.org/wiki/List%20of%20Kosmos%20satellites%20%28751%E2%80%931000%29 | The designation Kosmos ( meaning Cosmos) is a generic name given to a large number of Soviet, and subsequently Russian, satellites, the first of which was launched in 1962. Satellites given Kosmos designations include military spacecraft, failed probes to the Moon and the planets, prototypes for crewed spacecraft, and scientific spacecraft. This is a list of satellites with Kosmos designations between 751 and 1000.
* — satellite was destroyed in orbit rather than decaying and burning up in the Earth's atmosphere
See also
List of USA satellites
References
0751
Spacecraft that broke apart in space | List of Kosmos satellites (751–1000) | Technology | 120 |
65,933,492 | https://en.wikipedia.org/wiki/Tracklib | Tracklib is a music service that allows producers to sample original music and clear the samples for official use. The platform was founded with the aim to solve legal and ethical issues surrounding sampling and music clearances. The platform has been previously used to sample and clear tracks for commercial releases by J. Cole, Lil Wayne, DJ Khaled, Mary J Blige, Brockhampton, A-Reece among others.
History
Tracklib is based in Stockholm, Sweden and was originally founded in 2014. After an invite-only beta version in 2017, the music service officially launched to the public in April 2018. In May 2020, Tracklib changed their service to a subscription model.
Services
The catalog of Tracklib consists of original master recordings and stems. Each track is part of one out of three tiers (Category A, B, or C) which each its purchase and clearance costs. Users can browse and hear all music before downloading it in WAV-format to use in a digital audio workstation (DAW) such as Ableton, Reason, or FL Studio. In 2019, Tracklib developed and launched a technology for users to select and preview loops. Tracklib functions as an intermediary between record labels, publishers, copyright owners, and artists. This allows users to clear all music and purchase a license for official usage of the selected recording(s). The difference with other music services such as Splice and Loopmasters, is that Tracklib only includes original master recordings and stems. All music is previously released and no royalty-free sounds or sample packs are available on Tracklib.
Catalog
Original master recordings on Tracklib include music from artists such as Bob James, Louis Armstrong, Billie Holiday, Sly and Robbie, Ray Charles, across genres such as jazz, R&B/soul, reggae, classical music, rock music, and hip hop. The catalog also includes previously unreleased recordings by Isaac Hayes.
Releases
J. Cole - "Middle Child" (6× platinum)
¥$ (Kanye West & Ty Dolla $ign) - “Burn”
DJ Khaled - "Holy Mountain"
Brockhampton - "Dearly Departed"
Lil Wayne - "Harden"
Fred Again - "Leavemealone"
Nas - "WTF SMH"
Drake - "Stories About My Brother"
Nicki Minaj - "Super Freaky Girl"
Mary J. Blige - "Know"
Phantogram - Ceremony
Vic Mensa - "Let U Know"
Other notable artists with songs containing Tracklib samples are Firebeatz, A-Trak, Young M.A, $NOT & Statik Selektah.
Advisory board
Tracklib's advisory board consists of producers Prince Paul, Erick Sermon, and Drumma Boy, later joined by producer Zaytoven in 2018 and Scott Storch in 2020. Former Spotify executives Petra Hansson and Niklas Ivarsson joined the advisory board in 2019.
See also
Loopmasters
Splice (platform)
Grooveshark
AccuRadio
References
Computing websites
Cross-platform software
Internet properties established in 2012
Project management software
Project hosting websites
Sampling (music)
Version control | Tracklib | Technology,Engineering | 635 |
214,121 | https://en.wikipedia.org/wiki/List%20of%20largest%20optical%20reflecting%20telescopes | This list of the largest optical reflecting telescopes with objective diameters of or greater is sorted by aperture, which is a measure of the light-gathering power and resolution of a reflecting telescope. The mirrors themselves can be larger than the aperture, and some telescopes may use aperture synthesis through interferometry. Telescopes designed to be used as optical astronomical interferometers such as the Keck I and II used together as the Keck Interferometer (up to 85 m) can reach higher resolutions, although at a narrower range of observations. When the two mirrors are on one mount, the combined mirror spacing of the Large Binocular Telescope (22.8 m) allows fuller use of the aperture synthesis.
Largest does not always equate to being the best telescopes, and overall light gathering power of the optical system can be a poor measure of a telescope's performance. Space-based telescopes, such as the Hubble Space Telescope, take advantage of being above the Earth's atmosphere to reach higher resolution and greater light gathering through longer exposure times. Location in the northern or southern hemisphere of the Earth can also limit what part of the sky can be observed, and climate conditions at the observatory site affect how often the telescope can be used each year.
The combination of large mirrors, locations selected for stable atmosphere and favorable climate conditions, and active optics and adaptive optics to correct for much of atmospheric turbulence allow the largest Earth based telescopes to reach higher resolution than the Hubble Space Telescope. Another advantage of Earth based telescopes is the comparatively low cost of upgrading and replacing instruments.
Table of reflecting telescopes
This list is ordered by optical aperture, which has historically been a useful gauge of limiting resolution, optical area, physical size, and cost. Multiple mirror telescopes that are on the same mount and can form a single combined image are ranked by their equivalent aperture. Fixed altitude telescopes (e.g. HET) are also ranked by their equivalent aperture. All telescopes with an effective aperture of at least at visible or near-infrared wavelengths are included.
There are only a few sites capable of polishing the mirrors for these telescopes. SAGEM in France polished the four VLT mirrors, the two Gemini mirrors, and the 36 segments for GTC. The Steward Observatory Mirror Lab cast and polished the two LBT mirrors, the two Magellan mirrors, the MMT replacement mirror, and the LSST primary/tertiary mirror. It is currently making the mirrors for the Giant Magellan Telescope. The Keck segments were made by Schott AG. The SALT and LAMOST segments were cast and polished by LZOS. The mirror for Subaru was cast by Corning and polished at Contraves Brashear Systems in Pennsylvania, USA.
This table does not include all the largest mirrors manufactured. The Steward Observatory Mirror Lab produced the 6.5 metre f/1.25 collimator used in the Large Optical Test and Integration Site of Lockheed Martin, used for vacuum optical testing of other telescopes.
Segmented mirrors are also referred to as mosaic mirrors. Single mirrors are also referred to monolithic mirrors, and can be sub-categorized in types, such as solid or honeycomb.
Chronological list of largest telescopes
These telescopes were the largest in the world at the time of their construction, by the same aperture criterion as above.
Future telescopes
Under construction
These telescopes are under construction and will meet the list inclusion criteria once completed:
Extremely Large Telescope, Chile – . Construction began in 2018, first light planned in 2028.
Thirty Meter Telescope, Hawaii, USA – . Construction began in 2014 but halted in 2015; it has not resumed.
Giant Magellan Telescope, Chile – seven 8.4 m mirrors on a single mount. This provides an effective aperture equivalent to a 21.4 m mirror and the resolving power equivalent to a 24.5 m mirror. First light planned in 2029.
Vera C. Rubin Observatory, Chile – . First light planned in 2025.
San Pedro Martir Telescope, Baja California, Mexico – . First light planned in 2023.
Magdalena Ridge Observatory Interferometer, New Mexico, USA – An optical interferometer array with ten telescopes. The light gathering power is equivalent to a single aperture. The first telescope was installed in 2016; construction was paused in 2019 due to insufficient funding and has not resumed.
Timau National Observatory, Indonesia – . Construction expected to be completed by early 2025.
Proposed
Selected large telescopes which are in detailed design or pre-construction phases:
Large UV Optical Infrared Surveyor (LUVOIR), a proposed space telescope for launch in the mid 2030s.
MUltiplexed Survey Telescope (MUST), a 6.5 m spectroscopic survey telescope.
Chinese Giant Solar Telescope (CGST), an infrared and optical solar telescope, with light-gathering power equivalent to a 5 m diameter aperture.
Advanced Liquid-mirror Probe of Astrophysics, Cosmology and Asteroids (ALPACA), a proposed Earth-based 8 metre telescope, by Arlin Crotts of Columbia University.
See also
List of largest infrared telescopes
List of telescope types
Lists of telescopes
References
Further reading
External links
List of large reflecting telescopes
The World's Largest Optical Telescopes
Largest optical telescopes of the world
Selected largest telescopes
Sidereal Messenger Large refracting telescopes (date 1884)
Optical telescopes
Largest optical telescopes
Telescope | List of largest optical reflecting telescopes | Astronomy | 1,070 |
7,463,734 | https://en.wikipedia.org/wiki/Glomeraceae | The Glomeraceae are a family of arbuscular mycorrhizal (AM) fungi that form symbiotic relationships (mycorrhizas) with plant roots. The family was circumscribed in 1989.
References
Fungus families
Glomerales | Glomeraceae | Biology | 60 |
9,730,285 | https://en.wikipedia.org/wiki/Spherical%20design | A spherical design, part of combinatorial design theory in mathematics, is a finite set of N points on the d-dimensional unit d-sphere Sd such that the average value of any polynomial f of degree t or less on the set equals the average value of f on the whole sphere (that is, the integral of f over Sd divided by the area or measure of Sd). Such a set is often called a spherical t-design to indicate the value of t, which is a fundamental parameter. The concept of a spherical design is due to Delsarte, Goethals, and Seidel, although these objects were understood as particular examples of cubature formulas earlier.
Spherical designs can be of value in approximation theory, in statistics for experimental design, in combinatorics, and in geometry. The main problem is to find examples, given d and t, that are not too large; however, such examples may be hard to come by.
Spherical t-designs have also recently been appropriated in quantum mechanics in the form of quantum t-designs with various applications to quantum information theory and quantum computing.
Existence of spherical designs
The existence and structure of spherical designs on the circle were studied in depth by Hong. Shortly thereafter, Seymour and Zaslavsky proved that such designs exist of all sufficiently large sizes; that is, given positive integers d and t, there is a number N(d,t) such that for every N ≥ N(d,t) there exists a spherical t-design of N points in dimension d. However, their proof gave no idea of how big N(d,t) is.
Mimura constructively found conditions in terms of the number of points and the dimension which characterize exactly when spherical 2-designs exist. Maximally sized collections of equiangular lines (up to identification of lines as antipodal points on the sphere) are examples of minimal sized spherical 5-designs. There are many sporadic small spherical designs; many of them are related to finite group actions on the sphere.
In 2013, Bondarenko, Radchenko, and Viazovska obtained the asymptotic upper bound
for all positive integers d and t. This asymptotically matches the lower bound given originally by Delsarte, Goethals, and Seidel. The value of Cd is currently unknown, while exact values of are known in relatively few cases.
See also
Thomson problem
External links
Spherical t-designs for different values of N and t can be found precomputed at Neil Sloane's website and Robert Womersley's website.
Notes
References
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Design of experiments
Combinatorial design | Spherical design | Mathematics | 546 |
619,795 | https://en.wikipedia.org/wiki/History%20of%20the%20periodic%20table | The periodic table is an arrangement of the chemical elements, structured by their atomic number, electron configuration and recurring chemical properties. In the basic form, elements are presented in order of increasing atomic number, in the reading sequence. Then, rows and columns are created by starting new rows and inserting blank cells, so that rows (periods) and columns (groups) show elements with recurring properties (called periodicity). For example, all elements in group (column) 18 are noble gases that are largely—though not completely—unreactive.
The history of the periodic table reflects over two centuries of growth in the understanding of the chemical and physical properties of the elements, with major contributions made by Antoine-Laurent de Lavoisier, Johann Wolfgang Döbereiner, John Newlands, Julius Lothar Meyer, Dmitri Mendeleev, Glenn T. Seaborg, and others.
Early history
Around 330 BCE, the Greek philosopher Aristotle proposed that everything is made up of a mixture of one or more roots, an idea originally suggested by the Sicilian philosopher Empedocles. The four roots, which the Athenian philosopher Plato called elements, were earth, water, air and fire. Similar ideas existed in other ancient traditions, such as Indian philosophy with five elements: Earth, water, fire, air and aether collectively called 'pañca bhūta'.
Of the chemical elements shown on the periodic table, nine – carbon, sulfur, iron, copper, silver, tin, gold, mercury, and lead – have been known since antiquity, as they are found in their native form and are relatively simple to mine with primitive tools. Five more elements were known in the age of alchemy: zinc, arsenic, antimony, and bismuth. Platinum was known to pre-Columbian South Americans, but knowledge of it did not reach Europe until the 16th century.
First classification
The history of the periodic table is also a history of the discovery of the chemical elements. The first person in recorded history to discover a new element was Hennig Brand, a bankrupt German merchant. Brand tried to discover the philosopher's stone—a mythical object that was supposed to turn inexpensive base metals into gold. In 1669, or later, his experiments with distilled human urine resulted in the production of a glowing white substance, which he called "cold fire" (kaltes Feuer). He kept his discovery secret until 1680, when Anglo-Irish chemist Robert Boyle rediscovered phosphorus and published his findings. The discovery of phosphorus helped to raise the question of what it meant for a substance (any given variety of matter) to be an element, in a world where versions of atomic theory were only speculative and later understandings of the nature of substances were only beginning to become possible.
In 1661, Boyle defined elements as "those primitive and simple Bodies of which the mixt ones are said to be composed, and into which they are ultimately resolved."
In 1718, Étienne François Geoffroy's Affinity Table made use of several aspects — (1) tabular grouping and (2) correlation with chemical affinity — that would later be reprised.
In 1789, French chemist Antoine Lavoisier wrote Traité Élémentaire de Chimie (Elementary Treatise of Chemistry), which is considered to be the first modern textbook about chemistry. Lavoisier defined an element as a substance whose smallest units cannot be broken down into a simpler substance. Lavoisier's book contained a list of "simple substances" that Lavoisier believed could not be broken down further, which included oxygen, nitrogen, hydrogen, phosphorus, mercury, zinc and sulfur, which formed the basis for the modern list of elements. Lavoisier's list also included "light" and "caloric", which at the time were believed to be material substances. He classified these substances into metals and nonmetals. While many leading chemists refused to believe Lavoisier's new revelations, the Elementary Treatise was written well enough to convince the younger generation. However, Lavoisier's descriptions of his elements lack completeness, as he only classified them as metals and non-metals.
In 1808–10, British natural philosopher John Dalton published a method by which to arrive at provisional atomic weights for the elements known in his day, from stoichiometric measurements and reasonable inferences. Dalton's atomic theory was adopted by many chemists during the 1810s and 1820s.
In 1815, British physician and chemist William Prout noticed that atomic weights seemed to be multiples of that of hydrogen.
In 1817, German physicist Johann Wolfgang Döbereiner began to formulate one of the earliest attempts to classify the elements. In 1829, he found that he could form some of the elements into groups of three, with the members of each group having related properties. He termed these groups triads.
Definition of Triad law
"Chemically analogous elements arranged in increasing order of their atomic weights formed well marked groups of three called Triads in which the atomic weight of the middle element was found to be generally the arithmetic mean of the atomic weight of the other two elements in the triad.
chlorine, bromine, and iodine
calcium, strontium, and barium
sulfur, selenium, and tellurium
lithium, sodium, and potassium"
All those attempts to sort elements by atomic weights were inhibited by the inaccurate determination of weights, and not just slightly: carbon, oxygen and many other elements were believed to be half their actual masses (cf. the illustration by Dalton above), because only monatomic gases were believed to exist. Even though Amedeo Avogadro and, independently of him, André-Marie Ampère, proposed the solution in the form of diatomic molecules and Avogadro's law already in the 1810s, it was not until after Stanislao Cannizzaro's publications in late 1850s when the theory began to be widely considered.
In 1860, the modern scientific consensus emerged at the first international chemical conference, the Karlsruhe Congress, and a revised list of elements and atomic masses was adopted. It helped spur creation of more extensive systems. The first such system emerged in two years.
Comprehensive formalizations
French geologist Alexandre-Émile Béguyer de Chancourtois noticed that the elements, when ordered by their atomic weights, displayed similar properties at regular intervals. In 1862, he devised a three-dimensional chart, named the "telluric helix", after the element tellurium, which fell near the center of his diagram. With the elements arranged in a spiral on a cylinder by order of increasing atomic weight, de Chancourtois saw that elements with similar properties lined up vertically. The original paper from Chancourtois in Comptes rendus de l'Académie des Sciences did not include a chart and used geological rather than chemical terms. In 1863, he extended his work by including a chart and adding ions and compounds.
The next attempt was made in 1864. British chemist John Newlands presented in Chemical News a classification of the 62 known elements. Newlands noticed recurring trends in physical properties of the elements at recurring intervals of multiples of eight in order of mass number; based on this observation, he produced a classification of these elements into eight groups. Each group displayed a similar progression; Newlands likened these progressions to the progression of notes within a musical scale. Newlands's table left no gaps for possible future elements, and in some cases had two elements at the same position in the same octave. Newlands's table was ignored or ridiculed by some of his contemporaries. The Chemical Society refused to publish his work. The president of the Society, William Odling, defended the Society's decision by saying that such "theoretical" topics might be controversial; there was even harsher opposition from within the Society, suggesting the elements could have been just as well listed alphabetically. Later that year, Odling suggested a table of his own but failed to get recognition following his role in opposing Newlands's table.
German chemist Lothar Meyer also noted the sequences of similar chemical and physical properties repeated at periodic intervals. According to him, if the atomic weights were plotted as ordinates (i.e. vertically) and the atomic volumes as abscissas (i.e. horizontally)—the curve obtained is a series of maximums and minimums—the most electropositive elements would appear at the peaks of the curve in the order of their atomic weights. In 1864, a book of his was published; it contained an early version of the periodic table containing 28 elements, and classified elements into six families by their valence—for the first time, elements had been grouped according to their valence. Works on organizing the elements by atomic weight had until then been stymied by inaccurate measurements of the atomic weights. In 1868, he revised his table, but this revision was published as a draft only after his death. In a paper dated December 1869 which appeared early in 1870, Meyer published a new periodic table of 55 elements, in which the series of periods are ended by an element of the alkaline earth metal group. The paper also included a line chart of relative atomic volumes, which illustrated periodic relationships of physical characteristics of the elements, and which assisted Meyer in deciding where elements should appear in his periodic table. By this time he had already seen the publication of Mendeleev's first periodic table, but his work appears to have been largely independent.
In 1869, Russian chemist Dmitri Mendeleev arranged 63 elements by increasing atomic weight in several columns, noting recurring chemical properties across them. It is sometimes said that he played "chemical solitaire" on long train journeys, using cards containing the symbols, atomic weights, and chemical properties of the known elements. Another possibility is that he was inspired in part by the periodicity of the Sanskrit alphabet, which was pointed out to him by his friend and linguist Otto von Böhtlingk. Mendeleev used the trends he saw to suggest that atomic weights of some elements were incorrect, and accordingly changed their placements: for instance, he figured there was no place for a trivalent beryllium with the atomic weight of 14 in his work, and he cut both the atomic weight and valency of beryllium by a third, suggesting it was a divalent element with the atomic weight of 9.4. Mendeleev widely distributed printed broadsheets of the table to various chemists in Russia and abroad. Mendeleev argued in 1869 there were seven types of highest oxides. Mendeleev continued to improve his ordering; in 1870, it gained a tabular shape, and each column was given its own highest oxide, and in 1871, he further developed it and formulated what he termed the "law of periodicity". Some changes also occurred with new revisions, with some elements changing positions.
Priority dispute and recognition
Mendeleev's predictions and inability to incorporate the rare-earth metals
Even as Mendeleev corrected positions of some elements, he thought that some relationships that he could find in his grand scheme of periodicity could not be found because some elements were still undiscovered, and that the properties of such undiscovered elements could be deduced from their expected relationships with other elements. In 1870, he first tried to characterize the yet undiscovered elements, and he gave detailed predictions for three elements, which he termed eka-boron, eka-aluminium, and eka-silicium; he also more briefly noted a few other expectations. It has been proposed that the prefixes eka, dvi, and tri, Sanskrit for one, two, and three, respectively, are a tribute to Pāṇini and other ancient Sanskrit grammarians for their invention of a periodic alphabet. In 1871, Mendeleev expanded his predictions further.
Compared to the rest of the work, Mendeleev's 1869 list misplaces seven then known elements: indium, thorium, and five rare-earth metals: yttrium, cerium, lanthanum, erbium, and didymium. The last two were later found to be mixtures of two different elements; ignoring those would allow him to restore the logic of increasing atomic weight. These elements (all thought to be divalent at the time) puzzled Mendeleev as they did not show a regular increase in valency despite their seemingly consequential atomic weights. Mendeleev grouped them together, thinking of them as of a particular kind of series. In early 1870, he decided that the weights for these elements must be wrong and that the rare-earth metals should be trivalent (which accordingly increased their predicted atomic weights by half). He measured the heat capacity of indium, uranium, and cerium to demonstrate their higher assumed valency (which was soon confirmed by Prussian chemist Robert Bunsen). Mendeleev treated the change by assessing each element to an individual place in his system of the elements rather than continuing to treat them as a series.
Mendeleev noticed that there was a significant difference in atomic mass between cerium and tantalum with no element between them; his consideration was that between them, there was a row of yet undiscovered elements, which would display similar properties to those elements which were to be found above and below them: for instance, an eka-molybdenum would behave as a heavier homolog of molybdenum and a lighter homolog of wolfram (the name under which Mendeleev knew tungsten). This row would begin with a trivalent lanthanum, a tetravalent cerium, and a pentavalent didymium. However, the higher valency for didymium had not been established, and Mendeleev tried to do so himself. Having had no success in that, he abandoned his attempts to incorporate the rare-earth metals in late 1871 and embarked on his grand idea of luminiferous ether. His idea was carried on by Austrian-Hungarian chemist Bohuslav Brauner, who sought to find a place in the periodic table for the rare-earth metals; Mendeleev later referred to him as to "one of the true consolidators of the periodic law".
In addition to the predictions of scandium, gallium, and germanium that were quickly realized, Mendeleev's 1871 table left many more spaces for undiscovered elements, though he did not provide detailed predictions of their properties. In total, he predicted eighteen elements, though only half corresponded to elements that were later discovered.
Priority of discovery
None of the proposals were accepted immediately, and many contemporary chemists found it too abstract to have any meaningful value. Of those chemists that proposed their categorizations, Mendeleev strove to back his work and promote his vision of periodicity, Meyer did not promote his work very actively, and Newlands did not make a single attempt to gain recognition abroad.
Both Mendeleev and Meyer created their respective tables for their pedagogical needs; the difference between their tables is well explained by the fact that the two chemists sought to use a formalized system to solve different problems. Mendeleev's intent was to aid composition of his textbook, Foundations of Chemistry, whereas Meyer was rather concerned with presentation of theories. Mendeleev's predictions emerged outside of the pedagogical scope in the realm of journal science, while Meyer made no predictions at all and explicitly stated his table and his textbook it was contained in, Modern Theories, should not be used for prediction in order to make the point to his students to not make too many purely theoretically constructed projections.
Mendeleev and Meyer differed in temperament, at least when it came to promotion of their respective works. Boldness of Mendeleev's predictions was noted by some contemporary chemists, however skeptical they may have been. Meyer referred to Mendeleev's "boldness" in an edition of Modern Theories, whereas Mendeleev mocked Meyer's indecisiveness to predict in an edition of Foundations of Chemistry.
Recognition of Mendeleev's table
Eventually, the periodic table was appreciated for its descriptive power and for finally systematizing the relationship between the elements, although such appreciation was not universal. In 1881, Mendeleev and Meyer had an argument via an exchange of articles in British journal Chemical News over priority of the periodic table, which included an article from Mendeleev, one from Meyer, one of critique of the notion of periodicity, and many more. In 1882, the Royal Society in London awarded the Davy Medal to both Mendeleev and Meyer for their work to classify the elements; although two of Mendeleev's predicted elements had been discovered by then, Mendeleev's predictions were not at all mentioned in the prize rationale.
Mendeleev's eka-aluminium was discovered in 1875 and became known as gallium; eka-boron and eka-silicium were discovered in 1879 and 1886, respectively, and were named scandium and germanium. Mendeleev was even able to correct some initial measurements with his predictions, including the first prediction of gallium, which matched eka-aluminium fairly closely but had a different density. Mendeleev advised the discoverer, French chemist Paul-Émile Lecoq de Boisbaudran, to measure the density again; de Boisbaudran was initially skeptical (not least because he thought Mendeleev was trying to take credit from him) but eventually admitted the correctness of the prediction. Mendeleev contacted all three discoverers; all three noted the close similarity of their discovered elements with Mendeleev's predictions, with the last of them, German chemist Clemens Winkler, admitting this suggestion was not first made by Mendeleev or himself after the correspondence with him, but by a different person, German chemist Hieronymous Theodor Richter. Some contemporary chemists were not convinced by these discoveries, noting the dissimilarities between the new elements and the predictions or claiming those similarities that did exist were coincidental. However, success of Mendeleev's predictions helped spread the word about his periodic table. Later, chemists used the successes of these Mendeleev's predictions to justify his table.
By 1890, Mendeleev's periodic table had been universally recognized as a piece of basic chemical knowledge. Apart from his own correct predictions, a number of aspects may have contributed to this, such as the correct accommodation of many elements whose atomic weights were thought to have wrong values but were later corrected. The debate on the position of the rare-earth metals helped spur the discussion about the table as well. In 1889, Mendeleev noted at the Faraday Lecture to the Royal Institution in London that he had not expected to live long enough "to mention their discovery to the Chemical Society of Great Britain as a confirmation of the exactitude and generality of the periodic law".
Inert gases and ether
Inert gases
British chemist Henry Cavendish, the discoverer of hydrogen in 1766, discovered that air is composed of more gases than nitrogen and oxygen. He recorded these findings in 1784 and 1785; among them, he found a then-unidentified gas less reactive than nitrogen. Helium was first reported in 1868; the report was based on the new technique of spectroscopy; some spectral lines in light emitted by the Sun did not match those of any of the known elements. Mendeleev was not convinced by this finding since variance of temperature led to change of intensity of spectral lines and their location on the spectrum. This opinion was held by some other scientists of the day, some of whom believed the spectral lines were due to a particular state of hydrogen existing in the Sun's atmosphere. Others believed the spectral lines could belong to an element that occurred on the Sun but not on Earth; some believed it was yet to be found on Earth.
In 1894, British chemist William Ramsay and British physicist Lord Rayleigh isolated argon from air and determined that it was a new element. Argon, however, did not engage in any chemical reactions and was—highly unusually for a gas—monatomic; it did not fit into the periodic law and thus challenged the very notion of it. Not all scientists immediately accepted this report; Mendeleev's original response was that argon was a triatomic form of nitrogen rather than an element of its own. While the notion of a possibility of a group between that of halogens and that of alkali metals had existed (some scientists believed that several atomic weight values between halogens and alkali metals were missing, especially since places in this half of group VIII remained vacant), argon did not easily match the position between chlorine and potassium because its atomic weight exceeded those of both chlorine and potassium. Other explanations were proposed; for example, Ramsay supposed argon could be a mixture of different gases. For a while, Ramsay believed argon could be a mixture of three gases of similar atomic weights; this triad would resemble the triad of iron, cobalt, and nickel, and be similarly placed in group VIII. Certain that shorter periods contain triads of gases at their ends, Ramsay suggested in 1898 the existence of a gas between helium and argon with an atomic weight of 20; after its discovery later that year (it was named neon), Ramsay continued to interpret it as a member of a horizontal triad at the end of that period.
In 1896, Ramsay tested a report of American chemist William Francis Hillebrand, who found a stream of an unreactive gas from a sample of uraninite. Wishing to prove it was nitrogen, Ramsay analyzed a different uranium mineral, cleveite, and found a new element, which he named krypton. This finding was corrected by British chemist William Crookes, who matched its spectrum to that of the Sun's helium. Following this discovery, Ramsay, using fractional distillation to separate the components air, discovered several more such gases in 1898: metargon, krypton, neon, and xenon; detailed spectroscopic analysis of the first of these demonstrated it was argon contaminated by a carbon-based impurity. Ramsay was initially skeptical about the existence of gases heavier than argon, and the discovery of krypton and xenon came as a surprise to him; however, Ramsay accepted his own discovery, and the five newly discovered inert gases (now noble gases) were placed in a single column in the periodic table. Although Mendeleev's table predicted several undiscovered elements, it did not predict the existence of such inert gases, and Mendeleev originally rejected those findings as well.
Changes to the periodic table
Although the sequence of atomic weights suggested that inert gases should be located between halogens and alkali metals, and there were suggestions to put them into group VIII coming from as early as 1895, such placement contradicted one of Mendeleev's basic considerations, that of the highest oxides. Inert gases did not form any oxides, and no other compounds at all, and as such, their placement in a group where elements should form tetroxides was seen as merely auxiliary and not natural; Mendeleev doubted inclusion of those elements in group VIII. Later developments, particularly by British scientists, focused on correspondence of inert gases with halogens to their left and alkali metals to their right. In 1898, when only helium, argon, and krypton were definitively known, Crookes suggested these elements be placed in a single column between the hydrogen group and the fluorine group. In 1900, at the Prussian Academy of Sciences, Ramsay and Mendeleev discussed the new inert gases and their location in the periodic table; Ramsay proposed that these elements be put in a new group between halogens and alkali metals, to which Mendeleev agreed. Ramsay published an article after his discussions with Mendeleev; the tables in it featured halogens to the left of inert gases and alkali metals to the right. Two weeks before that discussion, Belgian botanist Léo Errera had proposed to the Royal Academy of Science, Letters and Fine Arts of Belgium to put those elements in a new group 0. In 1902, Mendeleev wrote that those elements should be put in a new group 0; he said this idea was consistent with what Ramsay suggested to him and referred to Errera as to the first person to suggest the idea. Mendeleev himself added these elements to the table as group 0 in 1902, without disturbing the basic concept of the periodic table.
In 1905, Swiss chemist Alfred Werner resolved the dead zone of Mendeleev's table. He determined that the rare-earth elements (lanthanides), 13 of which were known, lay within that gap. Although Mendeleev knew of lanthanum, cerium, and erbium, they were previously unaccounted for in the table because their total number and exact order were not known; Mendeleev still could not fit them in his table by 1901. This was in part a consequence of their similar chemistry and the imprecise determination of their atomic masses. Combined with the lack of a known group of similar elements, this rendered the placement of the lanthanides in the periodic table difficult. This discovery led to a restructuring of the table and the first appearance of the 32-column form.
Ether
By 1904, Mendeleev's table rearranged several elements, and included the noble gases along with most other newly discovered elements. It still had the dead zone, and a row zero was added above hydrogen and helium to include coronium and the ether, which were widely believed to be elements at the time. Although the Michelson–Morley experiment in 1887 cast doubt on the possibility of a luminiferous ether as a space-filling medium, physicists set constraints for its properties. Mendeleev believed it to be a very light gas, with an atomic weight several orders of magnitude smaller than that of hydrogen. He also postulated that it would rarely interact with other elements, similar to the noble gases of his group zero, and instead permeate substances at a velocity of per second.
Mendeleev was not satisfied with the lack of understanding of the nature of this periodicity; this would only be possible through the understanding of the composition of the atom. However, Mendeleev firmly believed that future would only develop the notion rather than challenge it and reaffirmed his belief in writing in 1902.
Atomic theory and isotopes
Radioactivity and isotopes
In 1907 it was discovered that thorium and radiothorium, products of radioactive decay, were physically different but chemically identical; this led Frederick Soddy to propose in 1910 that they were the same element but with different atomic weights. Soddy later proposed to call these elements with complete chemical identity "isotopes".
The problem of placing isotopes in the periodic table had arisen beginning in 1900 when four radioactive elements were known: radium, actinium, thorium, and uranium. These radioactive elements (termed "radioelements") were accordingly placed at the bottom of the periodic table, as they were known to have greater atomic weights than stable elements, although their exact order was not known. Researchers believed there were still more radioactive elements yet to be discovered, and during the next decade, the decay chains of thorium and uranium were extensively studied. Many new radioactive substances were found, including the noble gas radon, and their chemical properties were investigated. By 1912, almost 50 different radioactive substances had been found in the decay chains of thorium and uranium. American chemist Bertram Boltwood proposed several decay chains linking these radioelements between uranium and lead. These were thought at the time to be new chemical elements, substantially increasing the number of known "elements" and leading to speculations that their discoveries would undermine the concept of the periodic table which had long been established to obey the octet rule. For example, there was not enough room between lead and uranium to accommodate these discoveries, even assuming that some discoveries were duplicates or incorrect identifications. It was also believed that radioactive decay violated one of the central principles of the periodic table, namely that chemical elements could not undergo transmutations and always had unique identities.
Soddy and Kazimierz Fajans, who had been following these developments, published in 1913 that although these substances emitted different radiation, many of these substances were identical in their chemical characteristics, so shared the same place in the periodic table. They became known as isotopes, from the Greek ("same place"). Austrian chemist Friedrich Paneth cited a difference between "real elements" (elements) and "simple substances" (isotopes), also determining that the existence of different isotopes was mostly irrelevant in determining chemical properties.
Following British physicist Charles Glover Barkla's discovery of characteristic X-rays emitted from metals in 1906, British physicist Henry Moseley considered a possible correlation between X-ray emissions and physical properties of elements. Moseley, along with Charles Galton Darwin, Niels Bohr, and George de Hevesy, proposed that the nuclear charge (Z) might be mathematically related to physical properties. The significance of these atomic properties was determined in the Geiger–Marsden experiments, in which the atomic nucleus and its charge were discovered, conducted between 1908 and 1913.
Rutherford model and atomic number
In 1913, amateur Dutch physicist Antonius van den Broek was the first to propose that the atomic number (nuclear charge) determined the placement of elements in the periodic table. He correctly determined the atomic number of all elements up to atomic number 50 (tin), though he made several errors with heavier elements. However, Van den Broek did not have any method to experimentally verify the atomic numbers of elements; thus, they were still believed to be a consequence of atomic weight, which remained in use in ordering elements.
Moseley was determined to test Van den Broek's hypothesis. After a year of investigation of the Fraunhofer lines of various elements, he found a relationship between the X-ray wavelength of an element and its atomic number. With this, Moseley obtained the first accurate measurements of atomic numbers and determined an absolute sequence to the elements, allowing him to restructure the periodic table. Moseley's research immediately resolved discrepancies between atomic weight and chemical properties, where sequencing strictly by atomic weight would result in groups with inconsistent chemical properties. For example, his measurements of X-ray wavelengths enabled him to correctly place argon (Z = 18) before potassium (Z = 19), cobalt (Z = 27) before nickel (Z = 28), as well as tellurium (Z = 52) before iodine (Z = 53), in line with periodic trends. The determination of atomic numbers also clarified the order of chemically similar rare-earth elements; it was also used to confirm that Georges Urbain's claimed discovery of a new rare-earth element (celtium) was invalid, earning Moseley acclamation for this technique.
Swedish physicist Karl Siegbahn continued Moseley's work for elements heavier than gold (Z = 79), and found that the heaviest known element at the time, uranium, had atomic number 92. In determining the largest identified atomic number, gaps in the atomic number sequence were conclusively determined where an atomic number had no known corresponding element; the gaps occurred at atomic numbers 43 (technetium), 61 (promethium), 72 (hafnium), 75 (rhenium), 85 (astatine), and 87 (francium).
Electron shell and quantum mechanics
In 1888, Swedish physicist Johannes Rydberg working from the 1885 Balmer formula noticed that the atomic numbers of the noble gases was equal to doubled sums of squares of simple numbers: 2 = 2·12, 10 = 2(12 + 22), 18 = 2(12 + 22 + 22), 36 = 2(12 + 22 + 22 + 32), 54 = 2(12 + 22 + 22 + 32 + 32), 86 = 2(12 + 22 + 22 + 32 + 32 + 42). This finding was accepted as an explanation of the fixed lengths of periods and led to repositioning of the noble gases from the left edge of the table, in group 0, to the right, in group VIII. Unwillingness of the noble gases to engage in chemical reaction was explained in the alluded stability of closed noble gas electron configurations; from this notion emerged the octet rule originally referred to as Abegg's Rule of 1904. Among the notable works that established the importance of the periodicity of eight were the valence bond theory, published in 1916 by American chemist Gilbert N. Lewis and the octet theory of chemical bonding, published in 1919 by American chemist Irving Langmuir. The chemists' approach during the period of the Old Quantum Theory (1913 to 1925) was incorporated into the understanding of the electron shells and orbitals under current quantum mechanics. A real pioneer who gave us the foundation for our current model of electrons is Irving Langmuir. In his 1919 paper, he postulated the existence of "cells", which we now call orbitals, which could each only contain two electrons, and these were arranged in "equidistant layers" which we now call shells. He made an exception for the first shell to only contain two electrons. These postulates were introduced on the basis of Rydberg's rule which Niels Bohr had used not in chemistry, but in physics, to apply to the orbits of electrons around the nucleus. In the Langmuir paper, he introduced the rule as 2N2 where N was a positive integer.
The chemist Charles Rugeley Bury made the next major step toward our modern theory in 1921, by suggesting that eight and eighteen electrons in a shell form stable configurations. Bury's scheme was built upon that of earlier chemists and was a chemical model. Bury proposed that the electron configurations in transitional elements depended upon the valency electrons in their outer shell. In some early papers, the model was called the "Bohr-Bury Atom". He introduced the word transition to describe the elements now known as transition metals or transition elements.
In the 1910s and 1920s, pioneering research into quantum mechanics led to new developments in atomic theory and small changes to the periodic table. In the 19th century, Mendeleev had already asserted that there was a fixed periodicity of eight, and expected a mathematical correlation between atomic number and chemical properties. The Bohr model was developed beginning 1913, and championed the idea of electron configurations that determine chemical properties. Bohr proposed that elements in the same group behaved similarly because they have similar electron configurations, and that noble gases had filled valence shells; this forms the basis of the modern octet rule. Bohr's study of spectroscopy and chemistry was not usual among theoretical atomic physicists. Even Rutherford told Bohr that he was struggling "to form an idea of how you arrive at your conclusions". This is because none of the quantum mechanical equations describe the number of electrons per shell and orbital. Bohr acknowledged that he was influenced by the work of Walther Kossel, who in 1916 was the first to establish an important connection between the quantum atom and the periodic table. He noticed that the difference between the atomic numbers 2, 10, 18 of the first three noble gases, helium, neon, argon, was 8, and argued that the electrons in such atoms orbited in "closed shells". The first contained only 2 electrons, the second and third, 8 each. Bohr's research then led Austrian physicist Wolfgang Pauli to investigate the length of periods in the periodic table in 1924. Pauli demonstrated that this was not the case. Instead, the Pauli exclusion principle was developed, not upon a mathematical basis, but upon the previous developments in alignment with chemistry. This rule states that no electrons can coexist in the same quantum state, and showed, in conjunction with empirical observations, the existence of four quantum numbers and the consequence on the order of shell filling. This determines the order in which electron shells are filled and explains the periodicity of the periodic table.
British chemist Charles Bury is credited with the first use of the term transition metal in 1921 to refer to elements between the main-group elements of groups II and III. He explained the chemical properties of transition elements as a consequence of the filling of an inner subshell rather than the valence shell. This proposition, based upon the work of American chemist Gilbert N. Lewis, suggested the appearance of the d subshell in period 4 and the f subshell in period 6, lengthening the periods from 8 to 18 and then 18 to 32 elements, thus explaining the position of the lanthanides in the periodic table.
Proton and neutron
The discovery of proton and neutron demonstrated that an atom was divisible; this rendered Lavoisier's definition of a chemical element obsolete. A chemical element is defined today as a species of atoms with a consistent number of protons and that number is now known to be precisely the atomic number of an element. The discovery also explained the mechanism of several types of radioactive decay, such as alpha decay.
Eventually, it was proposed that protons and neutrons were made of even smaller particles called quarks; their discovery explained the transmutation of neutrons into protons in beta decay.
From short form into long form (into -A and -B groups)
Circa 1925, the periodic table changed by shifting some Reihen (series) to the right, into an extra set of columns (groups). The original groups I–VII were repeated, distinguished by adding "A" and "B". Group VIII (with three columns) remained sole.
Thus, Reihen 4 and 5 were shifted, and together formed new period 4 with groups IA–VIIA, VIII, IB–VIIB.
Later expansions and the end of the periodic table
Actinides
As early as 1913, Bohr's research on electronic structure led physicists such as Johannes Rydberg to extrapolate the properties of undiscovered elements heavier than uranium. Many agreed that the next noble gas after radon would most likely have the atomic number 118, from which it followed that the transition series in the seventh period should resemble those in the sixth. Although it was thought that these transition series would include a series analogous to the rare-earth elements, characterized by filling of the 5f shell, it was unknown where this series began. Predictions ranged from atomic number 90 (thorium) to 99, many of which proposed a beginning beyond the known elements (at or beyond atomic number 93). The elements from actinium to uranium were instead believed to form part of a fourth series of transition metals because of their high oxidation states; accordingly, they were placed in groups 3 through 6.
In 1940, neptunium and plutonium were the first transuranic elements to be discovered; they were placed in sequence beneath rhenium and osmium, respectively. However, preliminary investigations of their chemistry suggested a greater similarity to uranium than to lighter transition metals, challenging their placement in the periodic table. During his Manhattan Project research in 1943, American chemist Glenn T. Seaborg experienced unexpected difficulties in isolating the elements americium and curium, as they were believed to be part of a fourth series of transition metals. Seaborg wondered if these elements belonged to a different series, which would explain why their chemical properties, in particular the instability of higher oxidation states, were different from predictions. In 1945, against the advice of colleagues, he proposed a significant change to Mendeleev's table: the actinide series.
Seaborg's actinide concept of heavy element electronic structure proposed that the actinides form an inner transition series analogous to the rare-earth series of lanthanide elements—they would comprise the second row of the f-block (the 5f series), in which the lanthanides formed the 4f series. This facilitated chemical identification of americium and curium, and further experiments corroborated Seaborg's hypothesis; a spectroscopic study at the Los Alamos National Laboratory by a group led by American physicist Edwin McMillan indicated that 5f orbitals, rather than 6d orbitals, were indeed being filled. However, these studies could not unambiguously determine the first element with 5f electrons and therefore the first element in the actinide series; it was thus also referred to as the "thoride" or "uranide" series until it was later found that the series began with actinium.
In light of these observations and an apparent explanation for the chemistry of transuranic elements, and despite fear among his colleagues that it was a radical idea that would ruin his reputation, Seaborg nevertheless submitted it to Chemical & Engineering News and it gained widespread acceptance; new periodic tables thus placed the actinides below the lanthanides. Following its acceptance, the actinide concept proved pivotal in the groundwork for discoveries of heavier elements, such as berkelium in 1949. It also supported experimental results for a trend towards +3 oxidation states in the elements beyond americium—a trend observed in the analogous 4f series.
Relativistic effects and expansions beyond period 7
Seaborg's subsequent elaborations of the actinide concept theorized a series of superheavy elements in a transactinide series comprising elements from 104 to 121 and a superactinide series of elements from 122 to 153. He proposed an extended periodic table with an additional period of 50 elements (thus reaching element 168); this eighth period was derived from an extrapolation of the Aufbau principle and placed elements 121 to 138 in a g-block, in which a new g subshell would be filled. Seaborg's model, however, did not take into account relativistic effects resulting from high atomic number and electron orbital speed. Burkhard Fricke in 1971 and Pekka Pyykkö in 2010 used computer modeling to calculate the positions of elements up to Z = 172, and found that the positions of several elements were different from those predicted by Seaborg. Although models from Pyykkö and Fricke generally place element 172 as the next noble gas, there is no clear consensus on the electron configurations of elements beyond 120 and thus their placement in an extended periodic table. It is now thought that because of relativistic effects, such an extension will feature elements that break the periodicity in known elements, thus posing another hurdle to future periodic table constructs.
The discovery of tennessine in 2010 filled the last remaining gap in the seventh period. Any newly discovered elements will thus be placed in an eighth period.
Despite the completion of the seventh period, experimental chemistry of some transactinides has been shown to be inconsistent with the periodic law. In the 1990s, Ken Czerwinski at University of California, Berkeley observed similarities between rutherfordium and plutonium and between dubnium and protactinium, rather than a clear continuation of periodicity in groups 4 and 5. More recent experiments on copernicium and flerovium have yielded inconsistent results, some of which suggest that these elements behave more like the noble gas radon rather than mercury and lead, their respective congeners. As such, the chemistry of many superheavy elements has yet to be well characterized, and it remains unclear whether the periodic law can still be used to extrapolate the properties of undiscovered elements.
See also
History of chemistry
Periodic systems of small molecules
The Mystery of Matter: Search for the Elements (PBS film)
Discovery of chemical elements
Types of periodic tables
Notes
References
Sources
. Republished from
. Republished from
Further reading
. Republished from
External links
Development of the periodic table (part of a collection of pages that explores the periodic table and the elements) by the Royal Society of Chemistry
Dr. Eric Scerri's web page, which contains interviews, lectures and articles on various aspects of the periodic system, including the history of the periodic table.
The Internet Database of Periodic Tables – a large collection of periodic tables and periodic system formulations.
History of Mendeleev periodic table of elements as a data visualization at Stack Exchange
History of chemistry
Periodic table
Periodic table | History of the periodic table | Chemistry | 9,135 |
11,077,605 | https://en.wikipedia.org/wiki/Submillimeter%20Wave%20Astronomy%20Satellite | Submillimeter Wave Astronomy Satellite (SWAS, also Explorer 74 and SMEX-3) is a NASA submillimetre astronomy satellite, and is the fourth spacecraft in the Small Explorer program (SMEX). It was launched on 6 December 1998, at 00:57:54 UTC, from Vandenberg Air Force Base aboard a Pegasus XL launch vehicle. The telescope was designed by the Smithsonian Astrophysical Observatory (SAO) and integrated by Ball Aerospace, while the spacecraft was built by NASA's Goddard Space Flight Center (GSFC). The mission's principal investigator is Gary J. Melnick.
History
The Submillimeter Wave Astronomy Satellite mission was approved on 1 April 1989. The project began with the Mission Definition Phase, officially starting on 29 September 1989, and running through 31 January 1992. During this time, the mission underwent a conceptual design review on 8 June 1990, and a demonstration of the Schottky receivers and acousto-optical spectrometer concept was performed on 8 November 1991.
Development
The mission's Development Phase ran from February 1992, through May 1996. The Submillimeter Wave Telescope underwent a preliminary design review on 13 May 1992, and a critical design review (CDR) on 23 February 1993. Ball Aerospace was responsible for the construction of and integration of components into the telescope. The University of Cologne delivered the acousto-optical spectrometer to Ball for integration into the telescope on 2 December 1993, while Millitech Corporation delivered the Schottky receivers to Ball on 20 June 1994. Ball delivered the finished telescope to Goddard Space Flight Center on 20 December 1994. GSFC, which was responsible for construction of the spacecraft bus, conducted integration of spacecraft and instruments from January through March 1995. Spacecraft qualification and testing took place between 1 April 1995, and 15 December 1995. After this, SWAS was placed into storage until 1 September 1998, when launch preparation was begun.
Mission
SWAS was designed to study the chemical composition, energy balance and structure of interstellar clouds, both galactic and extragalactic, and investigate the processes of stellar and planetary formation. Its sole instrument is a telescope operating in the submillimeter wavelengths of far infrared and microwave radiation. The telescope is composed of three main components: a elliptical off-axis Cassegrain reflector with a beam width of 4 arcminutes at operating frequencies, two Schottky diode receivers, and an acousto-optical spectrometer. The system is sensitive to frequencies between 487–557 GHz (538–616 μm), which allows it to focus on the spectral lines of molecular oxygen (O2) at 487.249 GHz; neutral carbon () at 492.161 GHz; isotopic water (H218O) at 548.676 GHz; isotopic carbon monoxide (13CO) at 550.927 GHz; and water (H2O) at 556.936 GHz. Detailed 1° x 1° maps of giant molecular and dark cloud cores are generated from a grid of measurements taken at 3.7 arcminutes spacings. SWAS's submillimeter radiometers are a pair of passively cooled subharmonic Schottky diode receivers, with receiver noise figures of 2500-3000 K. An acousto-optical spectrometer (AOS) was provided by the University of Cologne, in Germany. Outputs of the two SWAS receivers are combined to form a final intermediate frequency, which extends from 1.4 to 2.8 GHz and is dispersed into 1400 1-MHz channels by the AOS. SWAS is designed to make pointed observations stabilized on three axes, with a position accuracy of about 38 arcseconds, and jitter of about 24 arcseconds. Attitude information is obtained from gyroscopes whose drift is corrected via a star tracker. Momentum wheels are used to maneuver the spacecraft.
Experiment
Submillimeter Wave Telescope
The SWAS instrument is a submillimeter-wave telescope that incorporates dual heterodyne radiometers and an acousto-optical spectrometer. SWAS will measure water, molecular oxygen, atomic carbon, and isotopic carbon monoxide spectral line emissions from galactic interstellar clouds in the wavelength range 540-616 micrometres. Such submillimetre wave radiation cannot be detected from the ground because of atmospheric attenuation. The SWAS measurements will provide new information about the physical conditions (density and temperature) and chemistry in star-forming molecular clouds.
Launch
The spacecraft was delivered to Orbital Sciences Corporation at Vandenberg Air Force Base on 2 November 1998, for integration onto their Pegasus XL launch vehicle. Launch occurred on 6 December 1998, at 00:57:54 UTC, from Orbital Sciences' Stargazer L-1011 TriStar mothership. Its initial orbit was a near-circular with an inclination of 69.90°.
SWAS was originally scheduled to launch in June 1995 but was delayed due to back-to-back launch failures of the Pegasus XL launch vehicle in June 1994 and June 1995. A launch opportunity in January 1997 was again canceled due to a Pegasus XL launch failure in November 1996.
The commissioning phase of the mission lasted until 19 December 1998, when the telescope began producing useful science data. The SWAS mission had a planned duration of two years and a cost estimate of US$60 million, but mission extensions allowed for five and a half years of continuous science operations. During this time, data was taken on more than 200 astronomical objects. The decision was made to end science and spacecraft operations on 21 July 2004, at which time the spacecraft was placed into hibernation.
Deep Impact mission
To support the Deep Impact mission at comet 9P/Tempel, SWAS was brought out of hibernation on 1 June 2005. Vehicle check-out was completed on 5 June 2005 with no discernible degradation of equipment found. SWAS observations of the comet focused on isotopic water output both before and after the Deep Impact impactor struck the comet's nucleus on 4 July 2005. While water output was found to naturally vary by more than a factor of three during the observation campaign, SWAS data showed that there was no excessive release of water due to the impact event. After three months of observation, SWAS was once again placed into hibernation on 1 September 2005.
, SWAS remains in Earth orbit on stand-by.
See also
Explorer program
References
Further reading
External links
SWAS website by the Center for Astrophysics Harvard & Smithsonian
SWAS data archive by NASA's Legacy Archive for Microwave Background Data Analysis
SWAS data archive by the NASA/IPAC Infrared Science Archive
SWAS website (archive) by NASA's Goddard Space Flight Center
Satellites orbiting Earth
Explorers Program
Space telescopes
Spacecraft launched in 1998
Submillimetre telescopes
Spacecraft launched by Pegasus rockets | Submillimeter Wave Astronomy Satellite | Astronomy | 1,405 |
53,231,843 | https://en.wikipedia.org/wiki/Brownout%20%28software%20engineering%29 | Brownout in software engineering is a technique that involves disabling certain features of an application.
Description
Brownout is used to increase the robustness of an application to computing capacity shortage. If too many users are simultaneously accessing an application hosted online, the underlying computing infrastructure may become overloaded, rendering the application unresponsive. Users are likely to abandon the application and switch to competing alternatives, hence incurring long-term revenue loss. To better deal with such a situation, the application can be given brownout capabilities: The application will disable certain features – e.g., an online shop will no longer display recommendations of related products – to avoid overload. Although reducing features generally has a negative impact on the short-term revenue of the application owner, long-term revenue loss can be avoided.
The technique is inspired by brownouts in power grids, which consists in reducing the power grid's voltage in case electricity demand exceeds production. Some consumers, such as incandescent light bulbs, will dim – hence originating the term – and draw less power, thus helping match demand with production. Similarly, a brownout application helps match its computing capacity requirements to what is available on the target infrastructure.
Brownout complements elasticity. The former can help the application withstand short-term capacity shortage, but does so without changing the capacity available to the application. In contrast, elasticity consists of adding (or removing) capacity to the application, preferably in advance, so as to avoid capacity shortage altogether. The two techniques can be combined; e.g., brownout is triggered when the number of users increases unexpectedly until elasticity can be triggered, the latter usually requiring minutes to show an effect.
Brownout is relatively non-intrusive for the developer, for example, it can be implemented as an advice in aspect-oriented programming. However, surrounding components, such as load-balancers, need to be made brownout-aware to distinguish between cases where an application is running normally and cases where the application maintains a low response time by triggering brownout.
References
Software engineering
Cloud computing | Brownout (software engineering) | Technology,Engineering | 429 |
39,316,385 | https://en.wikipedia.org/wiki/Impact%20survival | Impact survival is a theory that life, usually in the form of microbial bacteria, can survive under the extreme conditions of a major impact event, such as a meteorite striking the surface of a planet. This step is necessary for the possibility of panspermia. Microbial life must be able to survive both the escape out of a planetary atmosphere - likely due to a major impact - as well as the re-entry through the atmosphere, of and collision with, a second planetary body.
Dangers to life
For small organisms to leave a planet's orbit, escape velocity must be reached, the magnitude of which depends upon the mass of the planet. To reach these velocities, both the surviving organisms and the pieces of debris that they live on must withstand large amounts of acceleration and jerk. One calculation has determined that for possible organisms to be launched out of an orbit of a planet the size of Mars, jerk would be nearly 6x109 m/s3. In addition to this, the velocity of incoming meteorites are projected to be in the range of 20 to 25 km/s. Thus, any organisms that could survive a major impact event and be sent to outer space must be very small, light, and able to withstand large amounts of acceleration and jerk. While concerns over the heat of ejected rocks and the possible sterilizing effects it would have on the microbial life attached, it has been theorized that for rocks even less than 2 kilograms such as ALH84001, internal parts may never reach temperatures greater than 40 °C.
Possible organisms on Earth
Recent experiments have found organisms that can survive both the acceleration and jerk involved in reaching escape velocity. A major impact event was simulated using an air cannon to propel both ice and agar projectiles covered with chosen microorganisms to extreme speeds and then crashing the projectiles into a solid surface. Two species of bacteria were tested - R. erythropolis and B. subtilis - and while survival rates were low, at 100 GPa of peak pressure there was still a survival rate of 3.9x10−5 in the B. subtilis. These findings have been replicated with other bacteria as well - D. radiodurans as well as when shot into liquid water - with similar low, but not zero, survival rates. Also, experimental methods have been varied, and survival rates have also been found when bacteria are subjected to acceleration at an extended time, through the use of a centrifuge as well as when shot into liquid water. While very small, these non-zero results show that some lifeforms could survive the impact from a major impact event.
See also
Asteroid impact
Panspermia
Astrobiology
List of microorganisms tested in outer space
References
External links
Meteorites, Impacts, and Mass Extinction
Jupiter: friend or foe? An answer
Why Resilient Humans Would Survive Giant Asteroid Impact
Panspermia | Impact survival | Biology | 593 |
8,328,182 | https://en.wikipedia.org/wiki/3%2C5-Xylidine | 3,5-Xylidine is the organic compound with the formula C6H3(CH3)2NH2. It is one of several isomeric xylidines. It is a colorless viscous liquid. It is used in the production of the dye Pigment Red 149.
Production
3,5-Xylidine is produced industrially by amination of the xylenol using ammonia and alumina catalyst.
References
Anilines | 3,5-Xylidine | Chemistry | 97 |
84,726 | https://en.wikipedia.org/wiki/Sulfate | The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many are prepared from that acid.
Spelling
"Sulfate" is the spelling recommended by IUPAC, but "sulphate" was traditionally used in British English.
Structure
The sulfate anion consists of a central sulfur atom surrounded by four equivalent oxygen atoms in a tetrahedral arrangement. The symmetry of the isolated anion is the same as that of methane. The sulfur atom is in the +6 oxidation state while the four oxygen atoms are each in the −2 state. The sulfate ion carries an overall charge of −2 and it is the conjugate base of the bisulfate (or hydrogensulfate) ion, , which is in turn the conjugate base of , sulfuric acid. Organic sulfate esters, such as dimethyl sulfate, are covalent compounds and esters of sulfuric acid. The tetrahedral molecular geometry of the sulfate ion is as predicted by VSEPR theory.
Bonding
The first description of the bonding in modern terms was by Gilbert Lewis in his groundbreaking paper of 1916 where he described the bonding in terms of electron octets around each atom, that is no double bonds and a formal charge of +2 on the sulfur atom and -1 on each oxygen atom.
Later, Linus Pauling used valence bond theory to propose that the most significant resonance canonicals had two pi bonds involving d orbitals. His reasoning was that the charge on sulfur was thus reduced, in accordance with his principle of electroneutrality. The S−O bond length of 149 pm is shorter than the bond lengths in sulfuric acid of 157 pm for S−OH. The double bonding was taken by Pauling to account for the shortness of the S−O bond.
Pauling's use of d orbitals provoked a debate on the relative importance of pi bonding and bond polarity (electrostatic attraction) in causing the shortening of the S−O bond. The outcome was a broad consensus that d orbitals play a role, but are not as significant as Pauling had believed.
A widely accepted description involving pπ – dπ bonding was initially proposed by Durward William John Cruickshank. In this model, fully occupied p orbitals on oxygen overlap with empty sulfur d orbitals (principally the dz2 and dx2–y2). However, in this description, despite there being some π character to the S−O bonds, the bond has significant ionic character. For sulfuric acid, computational analysis (with natural bond orbitals) confirms a clear positive charge on sulfur (theoretically +2.45) and a low 3d occupancy. Therefore, the representation with four single bonds is the optimal Lewis structure rather than the one with two double bonds (thus the Lewis model, not the Pauling model).
In this model, the structure obeys the octet rule and the charge distribution is in agreement with the electronegativity of the atoms. The discrepancy between the S−O bond length in the sulfate ion and the S−OH bond length in sulfuric acid is explained by donation of p-orbital electrons from the terminal S=O bonds in sulfuric acid into the antibonding S−OH orbitals, weakening them resulting in the longer bond length of the latter.
However, Pauling's representation for sulfate and other main group compounds with oxygen is still a common way of representing the bonding in many textbooks. The apparent contradiction can be clarified if one realizes that the covalent double bonds in the Lewis structure actually represent bonds that are strongly polarized by more than 90% towards the oxygen atom. On the other hand, in the structure with a dipolar bond, the charge is localized as a lone pair on the oxygen.
Preparation
Typically metal sulfates are prepared by treating metal oxides, metal carbonates, or the metal itself with sulfuric acid:
Although written with simple anhydrous formulas, these conversions generally are conducted in the presence of water. Consequently the product sulfates are hydrated, corresponding to zinc sulfate , copper(II) sulfate , and cadmium sulfate .
Some metal sulfides can be oxidized to give metal sulfates.
Properties
There are numerous examples of ionic sulfates, many of which are highly soluble in water. Exceptions include calcium sulfate, strontium sulfate, lead(II) sulfate, barium sulfate, silver sulfate, and mercury sulfate, which are poorly soluble. Radium sulfate is the most insoluble sulfate known. The barium derivative is useful in the gravimetric analysis of sulfate: if one adds a solution of most barium salts, for instance barium chloride, to a solution containing sulfate ions, barium sulfate will precipitate out of solution as a whitish powder. This is a common laboratory test to determine if sulfate anions are present.
The sulfate ion can act as a ligand attaching either by one oxygen (monodentate) or by two oxygens as either a chelate or a bridge. An example is the complex or the neutral metal complex where the sulfate ion is acting as a bidentate ligand. The metal–oxygen bonds in sulfate complexes can have significant covalent character.
Uses and occurrence
Commercial applications
Sulfates are widely used industrially. Major compounds include:
Gypsum, the natural mineral form of hydrated calcium sulfate, is used to produce plaster. About 100 million tonnes per year are used by the construction industry.
Copper sulfate, a common algaecide, the more stable form () is used for galvanic cells as electrolyte
Iron(II) sulfate, a common form of iron in mineral supplements for humans, animals, and soil for plants
Magnesium sulfate (commonly known as Epsom salts), used in therapeutic baths
Lead(II) sulfate, produced on both plates during the discharge of a lead–acid battery
Sodium laureth sulfate, or SLES, a common detergent in shampoo formulations
Polyhalite, , used as fertiliser.
Occurrence in nature
Sulfate-reducing bacteria, some anaerobic microorganisms, such as those living in sediment or near deep sea thermal vents, use the reduction of sulfates coupled with the oxidation of organic compounds or hydrogen as an energy source for chemosynthesis.
History
Some sulfates were known to alchemists. The vitriol salts, from the Latin vitreolum, glassy, were so-called because they were some of the first transparent crystals known. Green vitriol is iron(II) sulfate heptahydrate, ; blue vitriol is copper(II) sulfate pentahydrate, and white vitriol is zinc sulfate heptahydrate, . Alum, a double sulfate of potassium and aluminium with the formula , figured in the development of the chemical industry.
Environmental effects
Sulfates occur as microscopic particles (aerosols) resulting from fossil fuel and biomass combustion. They increase the acidity of the atmosphere and form acid rain. The anaerobic sulfate-reducing bacteria Desulfovibrio desulfuricans and D. vulgaris can remove the black sulfate crust that often tarnishes buildings.
Main effects on climate
Reversal and accelerated warming
Hydrological cycle
Solar geoengineering
Hydrogensulfate (bisulfate)
The hydrogensulfate ion (), also called the bisulfate ion, is the conjugate base of sulfuric acid (). Sulfuric acid is classified as a strong acid; in aqueous solutions it ionizes completely to form hydronium () and hydrogensulfate () ions. In other words, the sulfuric acid behaves as a Brønsted–Lowry acid and is deprotonated to form hydrogensulfate ion. Hydrogensulfate has a valency of 1. An example of a salt containing the ion is sodium bisulfate, . In dilute solutions the hydrogensulfate ions also dissociate, forming more hydronium ions and sulfate ions ().
Other sulfur oxyanions
See also
Sulfonate
Sulfation and desulfation of lead–acid batteries
Sulfate-reducing microorganism
Notes
References
External links
Current global map of aerosol optical thickness
Particulates
Sulfur oxyanions | Sulfate | Chemistry | 1,727 |
16,880,172 | https://en.wikipedia.org/wiki/Finger%20tip%20unit | In medicine, a finger tip unit (FTU) is defined as the amount of ointment, cream or other semi-solid dosage form expressed from a tube with a 5 mm diameter nozzle, applied from the distal skin-crease to the tip of the index finger of an adult. The "distal skin-crease" is the skin crease over the joint nearest the end of the finger. One FTU is enough to treat an area of skin twice the size of the flat of an adult's hand with the fingers together, i.e. a "handprint". Two FTUs are approximately equivalent to 1 g of topical steroid.
One handprint is 0.8% (i.e. approximately 1%) of the total body surface area, and one FTU covers approximately two handprints. As two FTUs are approximately equivalent to 1g of topical application, the "Rule of Hand" states that "4 hand areas = 2 FTU = 1 g".
In the original study in the UK, one FTU weighed 0.49 g in men and 0.43 g in women. The area covered by one FTU was 312 cm2 in men and 257 cm2 in women. Very similar results were found in a Mexico study. The weight of an FTU has been recalculated in Japan, relating to the use of 5 g tubes of ointment with a much smaller nozzle diameter. The weight of ointment is less if the nozzle diameter is smaller than the standard 5 mm.
When a topical drug was used as a foam, the weight of an FTU was 52.5 μg: the area covered by one foam FTU was less than that of an FTU of cream.
Clinical use of FTU in patients
The FTU is particularly useful when counseling patients with regards to the amount of topical steroid cream they should be applying in order to minimize the side-effects which are associated with their use. The FTU can also be used in children.
The FTU concept has been used as a central part of an education programme for parents of children with atopic eczema.
The use of the FTU has been advocated to reduce the variation in usage of topical steroids and to encourage adherence to therapy. The FTU can also be used to guide the use of topical sunscreens.
Guidelines recommending use of FTU
Dermatology Working Groups in the UK and in Poland have recommended that guidance for use of topical corticosteroids in patient information leaflets should include clear FTU instructions, preferably with images of a FTU and a chart to show the number of units required for specific areas of the body. USA guidelines of care for the management of psoriasis with topical therapies include guidance of amount to be used based on the FTU.
European Guidelines for the treatment of atopic eczema recommend that application amount of topical anti-inflammatory therapy should follow the FTU rule. In the USA it has been recommended that the FTU should be used as part of the treatment plan and communication with patients and caregivers of children with atopic eczema.
Use of FTU in research
The FTU has been used to standardize the amount of cream being applied in clinical research studies in the UK, Belgium, Turkey, India, Iran, Pakistan, Malaysia, and the USA.
References
See also
Finger (unit)
Digit (unit)
Dermatologic terminology
Human-based units of measurement
Units of volume | Finger tip unit | Mathematics | 717 |
78,633,817 | https://en.wikipedia.org/wiki/Peronospora%20violacea | Peronospora violacea is a floricolous downy mildew which infects plants in the Caprifoliaceae. It has been reported from hosts in the genera Dipsacus, Knautia, Lomelosia, Scabiosa, and Succisa.
It produces conidiophores on the petals and styles of the host, oospores inside the petal and style tissue, and suppresses the development of the anthers. Infection is systemic, with hyphae produced in the xylem of the host rhizomes and stems.
In infected plants of Succisa pratensis the flowers have longer, pinker petals on which the conidophores are produced. However, other authors report that on the same host it causes the host corollas to be brownish and dead-looking.
Gallery
References
Peronosporales
Plant pathogens and diseases | Peronospora violacea | Biology | 188 |
169,250 | https://en.wikipedia.org/wiki/Lipid-anchored%20protein | Lipid-anchored proteins (also known as lipid-linked proteins) are proteins located on the surface of the cell membrane that are covalently attached to lipids embedded within the cell membrane. These proteins insert and assume a place in the bilayer structure of the membrane alongside the similar fatty acid tails. The lipid-anchored protein can be located on either side of the cell membrane. Thus, the lipid serves to anchor the protein to the cell membrane. They are a type of proteolipids.
The lipid groups play a role in protein interaction and can contribute to the function of the protein to which it is attached. Furthermore, the lipid serves as a mediator of membrane associations or as a determinant for specific protein-protein interactions. For example, lipid groups can play an important role in increasing molecular hydrophobicity. This allows for the interaction of proteins with cellular membranes and protein domains. In a dynamic role, lipidation can sequester a protein away from its substrate to inactivate the protein and then activate it by substrate presentation.
Overall, there are three main types of lipid-anchored proteins which include prenylated proteins, fatty acylated proteins and glycosylphosphatidylinositol-linked proteins (GPI). A protein can have multiple lipid groups covalently attached to it, but the site where the lipids bind to the protein depends both on the lipid group and protein.
Prenylated proteins
Prenylated proteins are proteins with covalently attached hydrophobic isoprene polymers (i.e. branched five-carbon hydrocarbon) at cysteine residues of the protein. More specifically, these isoprenoid groups, usually farnesyl (15-carbon) and geranylgeranyl (20-carbon) are attached to the protein via thioether linkages at cysteine residues near the C terminal of the protein. This prenylation of lipid chains to proteins facilitate their interaction with the cell membrane.
The prenylation motif “CaaX box” is the most common prenylation site in proteins, that is, the site where farnesyl or geranylgeranyl covalently attach. In the CaaX box sequence, the C represents the cysteine that is prenylated, the A represents any aliphatic amino acid and the X determines the type of prenylation that will occur. If the X is an Ala, Met, Ser or Gln the protein will be farnesylated via the farnesyltransferase enzyme and if the X is a Leu then the protein will be geranylgeranylated via the geranylgeranyltransferase I enzyme. Both of these enzymes are similar with each containing two subunits.
Roles and function
Prenylated proteins are particularly important for eukaryotic cell growth, differentiation and morphology. Furthermore, protein prenylation is a reversible post-translational modification to the cell membrane. This dynamic interaction of prenylated proteins with the cell membrane is important for their signalling functions and is often deregulated in disease processes such as cancer. More specifically, Ras is the protein that undergoes prenylation via farnesyltransferase and when it is switched on it can turn on genes involved in cell growth and differentiation. Thus overactiving Ras signalling can lead to cancer. An understanding of these prenylated proteins and their mechanisms have been important for the drug development efforts in combating cancer. Other prenylated proteins include members of the Rab and Rho families as well as lamins.
Some important prenylation chains that are involved in the HMG-CoA reductase metabolic pathway are geranylgeraniol, farnesol and dolichol. These isoprene polymers (e.g. geranyl pyrophosphate and farnesyl pyrophosphate) are involved in the condensations via enzymes such as prenyltransferase that eventually cyclizes to form cholesterol.
Fatty acylated proteins
Fatty acylated proteins are proteins that have been post-translationally modified to include the covalent attachment of fatty acids at certain amino acid residues. The most common fatty acids that are covalently attached to the protein are the saturated myristic (14-carbon) acid and palmitic acid (16-carbon). Proteins can be modified to contain either one or both of these fatty acids.
N-myristoylation
N-myristoylation (i.e. attachment of myristic acid) is generally an irreversible protein modification that typically occurs during protein synthesis in which the myrisitc acid is attached to the α-amino group of an N-terminal glycine residue through an amide linkage. This reaction is facilitated by N-myristoyltransferase . These proteins usually begin with a - sequence and with either a serine or threonine at position 5. Proteins that have been myristoylated are involved in signal transduction cascade, protein-protein interactions and in mechanisms that regulate protein targeting and function. An example in which the myristoylation of a protein is important is in apoptosis, programmed cell death. After the protein BH3 interacting-domain death agonist (Bid) has been myristoylated, it targets the protein to move to the mitochondrial membrane to release cytochrome c, which then ultimately leads to cell death. Other proteins that are myristoylated and involved in the regulation of apoptosis are actin and gelsolin.
S-palmitoylation
S-palmitoylation (i.e. attachment of palmitic acid) is a reversible protein modification in which a palmitic acid is attached to a specific cysteine residue via thioester linkage. The term S-acylation can also be used when other medium and long fatty acids chains are also attached to palmitoylated proteins. No consensus sequence for protein palmitoylation has been identified. Palmitoylated proteins are mainly found on the cytoplasmic side of the plasma membrane where they play a role in transmembrane signaling. The palmitoyl group can be removed by palmitoyl thioesterases. It is believed that this reverse palmitoylation may regulate the interaction of the protein with the membrane and thus have a role in signaling processes. Furthermore, this allows for the regulation of protein subcellular localization, stability and trafficking. An example in which palmitoylation of a protein plays a role in cell signaling pathways is in the clustering of proteins in the synapse. When the postsynaptic density protein 95 (PSD-95) is palmitoylated, it is restricted to the membrane and allows it to bind to and cluster ion channels in the postsynaptic membrane. Thus, palmitoylation can play a role in the regulation of neurotransmitter release.
Palmitoylation mediates the affinity of a protein for lipid rafts and facilitates the clustering of proteins. The clustering can increase the proximity of two molecules. Alternatively, clustering can sequester a protein away from a substrate. For example, palmitoylation of phospholipase D (PLD) sequesters the enzyme away from its substrate phosphatidylcholine. When cholesterol levels decrease or PIP2 levels increase the palmitate mediated localization is disrupted, the enzyme trafficks to PIP2 where it encounters its substrate and is active by substrate presentation.
GPI proteins
Glycosylphosphatidylinositol-anchored proteins (GPI-anchored proteins) are attached to a GPI complex molecular group via an amide linkage to the protein's C-terminal carboxyl group. This GPI complex consists of several main components that are all interconnected: a phosphoethanolamine, a linear tetrasaccharide (composed of three mannose and a glucosaminyl) and a phosphatidylinositol. The phosphatidylinositol group is glycosidically linked to the non-N-acetylated glucosamine of the tetrasaccharide. A phosphodiester bond is then formed between the mannose at the nonreducing end (of the tetrasaccaride) and the phosphoethanolamine. The phosphoethanolamine is then amide linked to the C-terminal of the carboxyl group of the respective protein. The GPI attachment occurs through the action of GPI-transamidase complex. The fatty acid chains of the phosphatidylinositol are inserted into the membrane and thus are what anchor the protein to the membrane. These proteins are only located on the exterior surface of the plasma membrane.
Roles and function
The sugar residues in the tetrasaccaride and the fatty acid residues in the phosphatidylinositol group vary depending on the protein. This great diversity is what allows the GPI proteins to have a wide range of functions including acting as hydrolytic enzymes, adhesion molecule, receptors, protease inhibitor and complement regulatory proteins. Furthermore, GPI proteins play an important in embryogenesis, development, neurogenesis, the immune system and fertilization. More specifically, the GPI protein IZUMO1R (also named JUNO after the Roman goddess of fertility) on the egg plasma has an essential role in sperm-egg fusion. Releasing the IZUMO1R (JUNO) GPI protein from the egg plasma membrane does not allow for sperm to fuse with the egg and it is suggested that this mechanism may contribute to the polyspermy block at the plasma membrane in eggs. Other roles that GPI modification allows for is in the association with membrane microdomains, transient homodimerization or in apical sorting in polarized cells.
References
External links
Membrane biology
Membrane proteins
Lipoproteins
Post-translational modification | Lipid-anchored protein | Chemistry,Biology | 2,097 |
34,787,877 | https://en.wikipedia.org/wiki/United%20States%20v.%20Ancheta | United States of America v. Ancheta (U.S. vs. Ancheta, 06-051 (C.D. Cal.)) is the name of a lawsuit against Jeanson James Ancheta of Downey, California by the U.S. Government and was handled by the United States District Court for the Central District of California. This is the first botnet related prosecution in U.S history.
Case summary
Ancheta violated the prohibited acts of accessing and transmitting malware with the intent and consequence of disrupting interstate and foreign commerce. The case was the first prosecution in the United States of America where an individual was sentenced to prison for profiting from the use of botnets that were used maliciously to launch destructive denial of service attacks and sending of large quantities of spam across the internet. The 57-month prison sentence for Ancheta was the longest in history for a defendant who has spread malware.
Ancheta pleaded guilty to conspiring to violate to the Computer Fraud and Abuse Act causing damage to computers used by the federal government of the United States in national defence and accessing a protected computer without authorization for the purpose of commit various types of fraud. Between the dates of June 25, 2004 and September 15, 2004 in Los Angeles county Ancheta and others knowingly conspired to violate , and of US Code. This refers to knowingly causing the transmission of a program, information, code or command and as a result of such conduct cause damage without authorization to a computer used in interstate and foreign commerce and communication and cause loss during a one-year period aggregating at least $5000 in value. Secondly Acheta and others conspired to violate , , and of US Code. This refers to access without authorization a computer used in interstate and foreign commerce and communication, and intentionally intimate the transmission from and through that computer multiple commercial electronic email messages that affect interstate and foreign commerce. Finally Ancheta was charged for laundering of monetary instruments under and faced criminal forfeiture under and .
Case technical details
Internet bots and botnets
Jeanson James Ancheta at the time of this crime was a 20-year-old high school drop-out. He found the rxbot software online and decided that he was going to use it to create a botnet army. Once established, he set up a website where he would rent his computer zombies to hackers so that they could employ them to fulfill whatever malicious job they had planned. Ancheta used at least one computer system at his place of residence and accessed the Internet from a dial up telephone line to configure and command the botnet and conduct any business communication. A co-conspirator residing in Boca Raton, Florida referred to as SoBE was also involved, as he had previous experience launching computer attacks.
An internet bot is a program that infects a computer and enables remote control of that computer. A security vulnerability in the computer system is exploited by the hacker in order to install and run the malware; in this case a worm. The program installs itself and is set up to run as a background process or daemon which remains undetectable to the computer user. The infected computer is often referred to as a zombie computer and was what Ancheta depended on as the building block of his botnet army. Ancheta engaged these computers to function in unison in a network formation; this is referred to as a botnet and the controller is called the bot herder. Ancheta's primary purpose of engaging large numbers of computers was to amplify the attack and reduce the time taken to execute it. Their greatest value is they provide a relatively high level of anonymity.
In 2005, the Federal Trade Commission in conjunction with 35 government agencies organized an initiative to encourage Internet service providers to actively monitor, identify and quarantine customers whose computers appeared to have been compromised, transformed into zombies, or appear to be under the remote control of hackers. One of the largest botnet implementations around that time (2005) was found by Dutch Police where a botnet of over 1.5 million computers was under a crime ring's control. These zombie computers were often employed as a response to anti-spam laws and spam filtering. Spammers started hiring virus writers and hackers to help them architect armies of zombie computers to send spam email from unsuspecting users' computers around the world. In February 2012, the Federal Communications Commission unveiled yet another plan that calls on Internet service providers to take specific steps to combat online threats from botnets.
IRC setup and worm development
In July 2004 Ancheta obtained access to a server from an internet hosting company, set it up as an IRC Server utilizing the IRCd program, and created a channel on IRC which he controlled remotely. Ancheta developed a computer worm which when installed and executed would report back to the IRC channel he controlled, scan for other computers with similar vulnerabilities, and leave itself open itself up for future unauthorized control. Ancheta initially developed this worm by modifying an existing Trojan called rxbot. While DDOS attacks were one use case for these botnets, another major purpose was to use them as a proxy server for email spam propagation. In 2004 it was reported that unsolicited email had doubled from late 2003, rising from 310 billion message to 700 billion messages. Worms like Conficker originally found in 2008 still remain a threat and is significantly more sophisticated, disallowing updates and communicated through encrypted channels.
Profiting
Ancheta advertised the sale of bots for the purpose of launching distributed denial-of-service (DDoS) attacks or to send spam. He sold access to the bots in clusters, usually up to 10,000 at a time. Ancheta acted as a consultant and advised the buyer on the exact number of bots they would need to successfully accomplish the designated attack. He would offer separate channels for an additional cost to assist in the control and direction of the bots, providing temporary control over the channel to the buyer. Around the time of this crime, it was estimated that an average botnet was 20,000 computers in size. He also profited from sale of the developed worm which he would configure for best propagation. Buyers also had the option of using their own malware to launch the attack and not use the worm he was offering. Ancheta accepted all payments through PayPal, where he would misleadingly describe the nature of the transaction as hosting, web hosting, or dedicated box services.
Case legal details
In total there were 17 different counts in this case.
Conspiracy to commit an offense or defraud a US agency
Count 1 was in violation of . This refers to the conspiracy between Ancheta and others to commit an offense or to defraud a US agency. This violated , and of US Code.
Fraud and related activity in connection with computers
Counts 2 through 11 were in violation of , and
Counts 2, 3 and 4 involved intentionally causing damage while accessing an unauthorized computer belonging to King Pao Electronic Co and Sanyo Electric Software which if completed would have caused damage exceeding $5000 and launching a distributed denial of service (DDOS) attack to a company (whose name remains confidential) which if completed would have caused damage exceeding $5000. In furtherance of the conspiracy Ancheta committed various overt acts, including payments to accomplices, directing numerous computers to adware servers controlled by Ancheta himself. These servers were where unsuspecting users would be redirected to download the malware. Counts 5 and 6 included knowingly causing the transmission of malicious code to protected computers belonging to the Naval Air Weapons Station China Lake and the US Defense Information Systems Agency; both used for justice, national defence, and national security. NAWS China Lake is a major Navy research, testing and evaluation facility and DISA provides IT and communication support the President and other top executive staff of the US Government.
Count 7 through 11 were in violation of and . Ancheta knowingly accessed without authorization, computers involved in interstate and foreign commerce by installing adware without notice, or consent with the sole intent to defraud. Between 8,744 and 53,321 computers (different for each count) were accessed without authorization and monetary amounts between $1306.52 and 7966.10 (different for each count) accepted as payment for services.
Laundering of monetary instruments
Counts 12 through 16 were in violation of . Knowing that property involved in a financial transaction represents the proceeds of some unlawful activity, Ancheta conducted financial transactions that involved the proceeds of specified unlawful activity and those proceeds were further used with the intent to promote more unlawful activity. Proceeds from selling worms and the rental of the botnet were being passed as legitimate online transactions such as payments for web hosting or dedicated box services. Anchta was also transferring the same payments to internet hosting companies for additional access to the servers used to commit further fraud. From November 2004 to May 2005 varying amounts of funds were transferred from Wells Fargo Bank to FDCServers and Sago Networks.
Criminal forfeiture
Count 17 was in violation of and . Ancheta was required to forfeit all property involved in the offence. This included $2998.81 generated from the sale of internet bots and proxies and deposited into a Wells Fargo account, approximately $58,357.86 in proceeds generated from the surreptitious install of adware on protected computers linked to a PayPal account owned by Ancheta, a 1993 BMW 325 IS, and all property used to commit or facilitate the commission of the above violations including desktop computers, laptops and hard drives.
Summary of laws applied
: Conspiracy to commit offense or to defraud United States
: Criminal Forfeiture
: Criminal Forfeiture
: Fraud and related activity in connection with email
: Fraud and related activity in connection with email
: Fraud and related activity in connection with email
: Computer trespassing in a government computer
: Committing fraud with a protected computer
: Damaging a protected computer (including viruses, worms)
: Damaging a protected computer (including viruses, worms)
: Conspiracy to violate (a)
: Laundering of monetary instruments
See also
Computer crime
Computer worm
Computer Fraud and Abuse Act
References
External links
Text of the decision
US Department of Justice - Ancheta Case
Wired.com How-to: Build your own botnet with open source software
United States federal criminal case law
Botnets
2006 in United States case law
United States District Court for the Central District of California cases
Hacking (computer security)
Denial-of-service attacks
2006 in computing | United States v. Ancheta | Technology | 2,173 |
43,201,908 | https://en.wikipedia.org/wiki/Valamon%20Viiniherman | Valamon Viiniherman Oy () is a distillery located in Finland that produces whisky and church wine. The company, founded in 1997, is owned by the Valamo Monastery.
History
The company was founded by the Valamo Monastery and a winery called Hermannin viinitila ("Hermann's Wine Estate") from Ilomantsi. The latter is the oldest wine estate in Finland, having been founded in 1989.
Valamon Viiniherman Oy was created by Father Andreas of the monastery.
In 2014, Valamon Viiniherman Oy launched the production of whisky, investing 1,2 million euros in the new venture destined to become the company's main stream of revenue. The first batch were planned for 2018. The distillery needed in the project forms a company of its own, and the majority of the shares is owned by the monastery. The person responsible for the production of alcoholic beverages in the monastery is Timo Kettunen.
In 2018, the winery lost its licence to sell its Church wine. Valamon provided 30% of the country's Church wine and had dropped the alcohol content of its wine below 15% for cheaper tax purposes. After losing its licence, the winery could not sell to parishes directly anymore, having to go through Alko for all sales, even when Valamon wanted to buy its own wine.
By 2019, the monastery was producing almost 50,000 liters of whisky and selling The Valamon Monastry Peated Single Malt in Alko stores.
Activities
The company produces wines, liqueurs and whisky. Valamon owns half of Valamon Viiniherman Oy. It made €60 000 in profits in 2012. The whisky is sometimes aged in barrels used for Church wine, giving the liquid a distinct darker tone.
References
External links
Distilleries
Drink companies of Finland
Food and drink companies established in 1997 | Valamon Viiniherman | Chemistry | 393 |
54,377,322 | https://en.wikipedia.org/wiki/1%2C5-Diaza-3%2C7-diphosphacyclooctanes | 1,5-Diaza-3,7-diphosphacyclooctanes are organophosphorus compounds with the formula [R'NCHP(R)CH], often abbreviated PN. They are air-sensitive white solids that are soluble in organic solvents. The ligands exist as meso and d,l-diastereomers, but only the meso forms function as bidentate ligands.
Some metal-PN complexes catalyze the hydrogen evolution reaction as well as the oxidation of hydrogen (H). The catalytic mechanism involves the interaction of substrate with the amines in the second coordination sphere.
Synthesis and reactions
The ligands are prepared by the condensation of a primary phosphine, formaldehyde, and a primary amine:
Diazadiphosphacyclooctanes function as chelating diphosphine ligands. Typical nickel complexes contain two such ligands are give the formula [Ni(PN)].
Cationic complexes of these and related ligands often exhibit enhanced reactivity toward H2. These complexes serve as electrocatalysts for H2 evolution.
Related ligands
Azadiphosphacycloheptanes are a related family of diphosphines, but containing only one amine. They are prepared by condensation of 1,2-bis(phenylphosphino)ethane, formaldehyde, and a primary amine. From the meso-isomer, typical nickel complexes contain two such ligands, i.e. [Ni(PNR')]. When bound to metals, these ligands adopt a conformation similar to that of 1,4-diazacycloheptanes. Acyclic phosphine-amine ligands have the formula (RPCH)NR'.
References
Chelating agents
Diphosphines
Phosphorus heterocycles | 1,5-Diaza-3,7-diphosphacyclooctanes | Chemistry | 397 |
15,637,117 | https://en.wikipedia.org/wiki/ChemMedChem | ChemMedChem is a biweekly peer-reviewed scientific journal covering medicinal chemistry. It is published by Wiley-VCH on behalf of Chemistry Europe. In addition to original research in the form of full papers and shorter communications, the journal contains review-type articles (reviews, minireviews, patent reviews, essays, highlights) as well as occasional book reviews and conference reports.
Topics covered include drug design, development and delivery, molecular modeling, combinatorial chemistry, drug target validation, lead generation, ADMET studies, and, as of 2017, nanomedicine (including targeted drug delivery, theranostics, and nanodrugs).
The first volume was published at the beginning of 2006 under the two founding chemical societies, the German Chemical Society and the Italian Chemical Society.
According to the Journal Citation Reports, the journal has a 2021 impact factor of 3.540.
References
External links
Chemistry Europe academic journals
Medicinal chemistry journals
Academic journals established in 2006
Wiley-VCH academic journals | ChemMedChem | Chemistry | 205 |
2,907,387 | https://en.wikipedia.org/wiki/Signed%20zero | Signed zero is zero with an associated sign. In ordinary arithmetic, the number 0 does not have a sign, so that −0, +0 and 0 are equivalent. However, in computing, some number representations allow for the existence of two zeros, often denoted by −0 (negative zero) and +0 (positive zero), regarded as equal by the numerical comparison operations but with possible different behaviors in particular operations. This occurs in the sign-magnitude and ones' complement signed number representations for integers, and in most floating-point number representations. The number 0 is usually encoded as +0, but can still be represented by +0, −0, or 0.
The IEEE 754 standard for floating-point arithmetic (presently used by most computers and programming languages that support floating-point numbers) requires both +0 and −0. Real arithmetic with signed zeros can be considered a variant of the extended real number line such that 1/−0 = −∞ and 1/+0 = +∞; division is undefined only for ±0/±0 and ±∞/±∞.
Negatively signed zero echoes the mathematical analysis concept of approaching 0 from below as a one-sided limit, which may be denoted by x → 0−, x → 0−, or x → ↑0. The notation "−0" may be used informally to denote a negative number that has been rounded to zero. The concept of negative zero also has some theoretical applications in statistical mechanics and other disciplines.
It is claimed that the inclusion of signed zero in IEEE 754 makes it much easier to achieve numerical accuracy in some critical problems, in particular when computing with complex elementary functions. On the other hand, the concept of signed zero runs contrary to the usual assumption made in mathematics that negative zero is the same value as zero. Representations that allow negative zero can be a source of errors in programs, if software developers do not take into account that while the two zero representations behave as equal under numeric comparisons, they yield different results in some operations.
Representations
Binary integer formats can use various encodings. In the widely used two's complement encoding, zero is unsigned. In a 1+7-bit sign-and-magnitude representation for integers, negative zero is represented by the bit string . In an 8-bit ones' complement representation, negative zero is represented by the bit string . In all these three encodings, positive or unsigned zero is represented by . However, the latter two encodings (with a signed zero) are uncommon for integer formats. The most common formats with a signed zero are floating-point formats (IEEE 754 formats or similar), described below.
In IEEE 754 binary floating-point formats, zero values are represented by the biased exponent and significand both being zero. Negative zero has the sign bit set to one. One may obtain negative zero as the result of certain computations, for instance as the result of arithmetic underflow on a negative number (other results may also be possible), or −1.0×0.0, or simply as −0.0.
In IEEE 754 decimal floating-point formats, a negative zero is represented by an exponent being any valid exponent in the range for the format, the true significand being zero, and the sign bit being one.
Properties and handling
The IEEE 754 floating-point standard specifies the behavior of positive zero and negative zero under various operations. The outcome may depend on the current IEEE rounding mode settings.
Notation
In systems that include both signed and unsigned zeros, the notation and is sometimes used for signed zeros.
Arithmetic
Addition and multiplication are commutative, but there are some special rules that have to be followed, which mean the usual mathematical rules for algebraic simplification may not apply. The sign below shows the obtained floating-point results (it is not the usual equality operator).
The usual rule for signs is always followed when multiplying or dividing:
(for different from ±∞)
(for different from 0)
There are special rules for adding or subtracting signed zero:
(for different from 0)
(for any finite , −0 when rounding toward negative)
Because of negative zero (and also when the rounding mode is upward or downward), the expressions and , for floating-point variables x and y, cannot be replaced by . However can be replaced by x with rounding to nearest (except when x can be a signaling NaN).
Some other special rules:
(follows the sign rule for division)
(for non-zero , follows the sign rule for division)
(Not a Number or interrupt for indeterminate form)
Division of a non-zero number by zero sets the divide by zero flag, and an operation producing a NaN sets the invalid operation flag. An exception handler is called if enabled for the corresponding flag.
Comparisons
According to the IEEE 754 standard, negative zero and positive zero should compare as equal with the usual (numerical) comparison operators, like the == operators of C and Java. In those languages, special programming tricks may be needed to distinguish the two values:
Type punning the number to an integer type, so as to look at the sign bit in the bit pattern;
using the ISO C copysign() function (IEEE 754 copySign operation) to copy the sign of the zero to some non-zero number;
using the ISO C signbit() macro (IEEE 754 isSignMinus operation) that returns whether the sign bit of a number is set;
taking the reciprocal of the zero to obtain either 1/(+0) = +∞ or 1/(−0) = −∞ (if the division by zero exception is not trapped).
Note: Casting to integral type will not always work, especially on two's complement systems.
However, some programming languages may provide alternative comparison operators that do distinguish the two zeros. This is the case, for example, of the method in Java's Double wrapper class.
In rounded values such as temperatures
Informally, one may use the notation "−0" for a negative value that was rounded to zero. This notation may be useful when a negative sign is significant; for example, when tabulating Celsius temperatures, where a negative sign means below freezing.
In statistical mechanics
In statistical mechanics, one sometimes uses negative temperatures to describe systems with population inversion, which can be considered to have a temperature greater than positive infinity, because the coefficient of energy in the population distribution function is −1/Temperature. In this context, a temperature of −0 is a (theoretical) temperature larger than any other negative temperature, corresponding to the (theoretical) maximum conceivable extent of population inversion, the opposite extreme to +0.
See also
Line with two origins
Extended real number line
References
a decimal floating-point specification that includes negative zero
Further reading
the changes in the Fortran SIGN function in Fortran 95 to accommodate negative zero
JScript's floating-point type with negative zero by definition
representation of negative zero in the Java virtual machine
how to handle negative zero when comparing floating-point numbers
one's complement numbers on the UNIVAC 1100 family computers
Computer arithmetic
0 (number) | Signed zero | Mathematics | 1,463 |
32,711,954 | https://en.wikipedia.org/wiki/School%20of%20Mining%20Engineering%20of%20Madrid | The School of Mining Engineering of Madrid (Spanish: Escuela Técnica Superior de Ingenieros de Minas y Energia) is located in calle Ríos Rosas, Madrid, Spain. It is one of the engineering schools of the Technical University of Madrid which was founded in 1971 through the integration of the Higher Technical Schools.
History
The mining school is older than the nineteenth-century building in which it is housed. It was founded in 1777 as the Academia de Minería y Geografía Subterránea de Almadén, located at Almadén, site of an important mercury mine, approximately 300 km south of Madrid. The curriculum was influenced by the Freiberg University of Mining and Technology.
Mercury became very valuable in the Americas in the mid 16th century due to the introduction of amalgamation, a process that uses mercury to extract the metals from gold and silver ore. Mercury was exported to the Americas, although there was also a source of mercury in Peru.
As Spain was impacted by the loss of its South American colonies, and the increasing economic importance of coal, Almadén became less appropriate for the site of a national mining school. It was relocated to Madrid in the 1830s.
Building
It was designed by Ricardo Velázquez Bosco. Like some other buildings by this architect, it features ceramic decorations by Daniel Zuloaga.
It was declared Bien de Interés Cultural in 1985.
See also
Exposición Nacional de Minería (1883)
Geological and Mining Institute of Spain
Palacio de Minería (Mexico)
References
External links
Website
Buildings and structures in Ríos Rosas neighborhood, Madrid
Bien de Interés Cultural landmarks in Madrid
Schools of mines | School of Mining Engineering of Madrid | Engineering | 333 |
2,407,249 | https://en.wikipedia.org/wiki/Geitonogamy | Geitonogamy (from Greek geiton (γείτων) = neighbor + gamein (γαμεῖν) = to marry) is a type of self-pollination. Geitonogamous pollination is sometimes distinguished from the fertilizations that can result from it, geitonogamy. If a plant is self-incompatible, geitonogamy can reduce seed production.
Geitonogamy is when pollen is exported using a vector (pollinator or wind) out of one flower but only to another flower on the same plant. It is a form of self-fertilization.
In flowering plants, pollen is transferred from a flower to another flower on the same plant, and in animal pollinated systems this is accomplished by a pollinator visiting multiple flowers on the same plant. Geitonogamy is also possible within species that are wind-pollinated, and may actually be a quite common source of self-fertilized seeds in self-compatible species. It also occurs in monoecious gymnosperms. Although geitonogamy is functionally cross-pollination involving a pollinating agent, genetically it is similar to autogamy since the pollen grains come from the same plant.
Monoecious plants like maize show geitonogamy. Geitonogamy is not possible for strictly dioecious plants, namely those with separate male and female flowers on different plants.
See also
Plant reproductive morphology
Self-fertilization
Autogamy Depression
References
Pollination
Plant reproduction | Geitonogamy | Biology | 322 |
1,281,160 | https://en.wikipedia.org/wiki/Resistance%20thermometer | Resistance thermometers, also called resistance temperature detectors (RTDs), are sensors used to measure temperature. Many RTD elements consist of a length of fine wire wrapped around a heat-resistant ceramic or glass core but other constructions are also used. The RTD wire is a pure material, typically platinum (Pt), nickel (Ni), or copper (Cu). The material has an accurate resistance/temperature relationship which is used to provide an indication of temperature. As RTD elements are fragile, they are often housed in protective probes.
RTDs, which have higher accuracy and repeatability, are slowly replacing thermocouples in industrial applications below 600 °C.
Resistance/temperature relationship of metals
Common RTD sensing elements for biomedical application constructed of platinum (Pt), nickel (Ni), or copper (Cu) have a repeatable, resistance versus temperature relationship (R vs T) and operating temperature range. The R vs T relationship is defined as the amount of resistance change of the sensor per degree of temperature change. The relative change in resistance (temperature coefficient of resistance) varies only slightly over the useful range of the sensor.
Platinum was proposed by Sir William Siemens as an element for a resistance temperature detector at the Bakerian lecture in 1871: it is a noble metal and has the most stable resistance–temperature relationship over the largest temperature range. Nickel elements have a limited temperature range because the temperature coefficient of resistance changes at temperatures over 300 °C (572 °F). Copper has a very linear resistance–temperature relationship; however, copper oxidizes at moderate temperatures and cannot be used over 150 °C (302 °F).
The significant characteristic of metals used as resistive elements is the linear approximation of the resistance versus temperature relationship between 0 and 100 °C. This temperature coefficient of resistance is denoted by α and is usually given in units of Ω/(Ω·°C):
where
is the resistance of the sensor at 0 °C,
is the resistance of the sensor at 100 °C.
Pure platinum has α = 0.003925 Ω/(Ω·°C) in the 0 to 100 °C range and is used in the construction of laboratory-grade RTDs. Conversely, two widely recognized standards for industrial RTDs IEC 60751 and ASTM E-1137 specify α = 0.00385 Ω/(Ω·°C). Before these standards were widely adopted, several different α values were used. It is still possible to find older probes that are made with platinum that have α = 0.003916 Ω/(Ω·°C) and 0.003902 Ω/(Ω·°C).
These different α values for platinum are achieved by doping – carefully introducing impurities, which become embedded in the lattice structure of the platinum and result in a different R vs. T curve and hence α value.
Calibration
To characterize the R vs T relationship of any RTD over a temperature range that represents the planned range of use, calibration must be performed at temperatures other than 0 °C and 100 °C. This is necessary to meet calibration requirements. Although RTDs are considered to be linear in operation, it must be proven that they are accurate with regard to the temperatures with which they will actually be used (see details in Comparison calibration option). Two common calibration methods are the fixed-point method and the comparison method.
Fixed-point calibration is used for the highest-accuracy calibrations by national metrology laboratories. It uses the triple point, freezing point or melting point of pure substances such as water, zinc, tin, and argon to generate a known and repeatable temperature. These cells allow the user to reproduce actual conditions of the ITS-90 temperature scale. Fixed-point calibrations provide extremely accurate calibrations (within ±0.001 °C). A common fixed-point calibration method for industrial-grade probes is the ice bath. The equipment is inexpensive, easy to use, and can accommodate several sensors at once. The ice point is designated as a secondary standard because its accuracy is ±0.005 °C (±0.009 °F), compared to ±0.001 °C (±0.0018 °F) for primary fixed points.
Comparison calibrations is commonly used with secondary standard platinum resistance thermometers and industrial RTDs. The thermometers being calibrated are compared to calibrated thermometers by means of a bath whose temperature is uniformly stable. Unlike fixed-point calibrations, comparisons can be made at any temperature between −100 °C and 500 °C (−148 °F to 932 °F). This method might be more cost-effective, since several sensors can be calibrated simultaneously with automated equipment. These electrically heated and well-stirred baths use silicone oils and molten salts as the medium for the various calibration temperatures.
Element types
The three main categories of RTD sensors are thin-film, wire-wound, and coiled elements. While these types are the ones most widely used in industry, other more exotic shapes are used; for example, carbon resistors are used at ultra-low temperatures (−273 °C to −173 °C).
Carbon resistor elements are cheap and widely used. They have very reproducible results at low temperatures. They are the most reliable over extremely wide range of temperatures. They generally do not suffer from significant hysteresis or strain gauge effects.
Strain-free elements use a wire coil minimally supported within a sealed housing filled with an inert gas. These sensors work up to and are used in the SPRTs that define ITS-90. They consist of platinum wire loosely coiled over a support structure, so the element is free to expand and contract with temperature. They are very susceptible to shock and vibration, as the loops of platinum can sway back and forth, causing deformation.
Thin-film elements have a sensing element that is formed by depositing a very thin layer of resistive material, normally platinum, on a ceramic substrate (plating). This layer is usually just 10 to 100 ångströms (1 to 10 nanometers) thick. This film is then coated with an epoxy or glass that helps protect the deposited film and also acts as a strain relief for the external lead wires. Disadvantages of this type are that they are not as stable as their wire-wound or coiled counterparts. They also can only be used over a limited temperature range due to the different expansion rates of the substrate and resistive deposited giving a "strain gauge" effect that can be seen in the resistive temperature coefficient. These elements work with temperatures to without further packaging, but can operate up to when suitably encapsulated in glass or ceramic. Special high-temperature RTD elements can be used up to with the right encapsulation.
Wire-wound elements can have greater accuracy, especially for wide temperature ranges. The coil diameter provides a compromise between mechanical stability and allowing expansion of the wire to minimize strain and consequential drift. The sensing wire is wrapped around an insulating mandrel or core. The winding core can be round or flat, but must be an electrical insulator. The coefficient of thermal expansion of the winding core material is matched to the sensing wire to minimize any mechanical strain. This strain on the element wire will result in a thermal measurement error. The sensing wire is connected to a larger wire, usually referred to as the element lead or wire. This wire is selected to be compatible with the sensing wire, so that the combination does not generate an emf that would distort the thermal measurement. These elements work with temperatures to 660 °C.
Coiled elements have largely replaced wire-wound elements in industry. This design has a wire coil that can expand freely over temperature, held in place by some mechanical support, which lets the coil keep its shape. This “strain free” design allows the sensing wire to expand and contract free of influence from other materials; in this respect it is similar to the SPRT, the primary standard upon which ITS-90 is based, while providing the durability necessary for industrial use. The basis of the sensing element is a small coil of platinum sensing wire. This coil resembles a filament in an incandescent light bulb. The housing or mandrel is a hard fired ceramic oxide tube with equally spaced bores that run transverse to the axes. The coil is inserted in the bores of the mandrel and then packed with a very finely ground ceramic powder. = This permits the sensing wire to move, while still remaining in good thermal contact with the process. These elements work with temperatures to 850 °C.
The current international standard that specifies tolerance and the temperature-to-electrical resistance relationship for platinum resistance thermometers (PRTs) is IEC 60751:2008; ASTM E1137 is also used in the United States. By far the most common devices used in industry have a nominal resistance of 100 ohms at 0 °C and are called Pt100 sensors ("Pt" is the symbol for platinum, "100" for the resistance in ohms at 0 °C). It is also possible to get Pt1000 sensors, where 1000 is for the resistance in ohms at 0 °C. The sensitivity of a standard 100 Ω sensor is a nominal 0.385 Ω/°C. RTDs with a sensitivity of 0.375 and 0.392 Ω/°C, as well as a variety of others, are also available.
Function
Resistance thermometers are constructed in a number of forms and offer greater stability, accuracy and repeatability in some cases than thermocouples. While thermocouples use the Seebeck effect to generate a voltage, resistance thermometers use electrical resistance and require a power source to operate. The resistance ideally varies nearly linearly with temperature per the Callendar–Van Dusen equation.
The platinum detecting wire needs to be kept free of contamination to remain stable. A platinum wire or film is supported on a former in such a way that it gets minimal differential expansion or other strains from its former, yet is reasonably resistant to vibration. RTD assemblies made from iron or copper are also used in some applications. Commercial platinum grades exhibit a temperature coefficient of resistance 0.00385/°C (0.385%/°C) (European Fundamental Interval). The sensor is usually made to have a resistance of 100 Ω at 0 °C. This is defined in BS EN 60751:1996 (taken from IEC 60751:1995). The American Fundamental Interval is 0.00392/°C, based on using a purer grade of platinum than the European standard. The American standard is from the Scientific Apparatus Manufacturers Association (SAMA), who are no longer in this standards field. As a result, the "American standard" is hardly the standard even in the US.
Lead-wire resistance can also be a factor; adopting three- and four-wire, instead of two-wire, connections can eliminate connection-lead resistance effects from measurements (see below); three-wire connection is sufficient for most purposes and is an almost universal industrial practice. Four-wire connections are used for the most precise applications.
Advantages and limitations
The advantages of platinum resistance thermometers include:
High accuracy
Low drift
Wide operating range
Suitability for precision applications.
Limitations:
RTDs in industrial applications are rarely used above 660 °C. At temperatures above 660 °C it becomes increasingly difficult to prevent the platinum from becoming contaminated by impurities from the metal sheath of the thermometer. This is why laboratory standard thermometers replace the metal sheath with a glass construction. At very low temperatures, say below −270 °C (3 K), because there are very few phonons, the resistance of an RTD is mainly determined by impurities and boundary scattering and thus basically independent of temperature. As a result, the sensitivity of the RTD is essentially zero and therefore not useful.
Compared to thermistors, platinum RTDs are less sensitive to small temperature changes and have a slower response time. However, thermistors have a smaller temperature range and stability.
RTDs vs thermocouples
The two most common ways of measuring temperatures for industrial applications are with resistance temperature detectors (RTDs) and thermocouples. The choice between them is typically determined by four factors.
Temperature If process temperatures are between , an industrial RTD is the preferred option. Thermocouples have a range of , so for temperatures above it is the contact temperature measurement device commonly found in physics laboratories.
Response time If the process requires a very fast response to temperature changes (fractions of a second as opposed to seconds), then a thermocouple is the best choice. Time response is measured by immersing the sensor in water moving at with a 63.2% step change.
Size A standard RTD sheath is in diameter; sheath diameters for thermocouples can be less than .
Accuracy and stability requirements If a tolerance of 2 °C is acceptable and the highest level of repeatability is not required, a thermocouple will serve. RTDs are capable of higher accuracy and can maintain stability for many years, while thermocouples can drift within the first few hours of use.
Construction
These elements nearly always require insulated leads attached. PVC, silicone rubber or PTFE insulators are used at temperatures below about 250 °C. Above this, glass fibre or ceramic are used. The measuring point, and usually most of the leads, require a housing or protective sleeve, often made of a metal alloy that is chemically inert to the process being monitored. Selecting and designing protection sheaths can require more care than the actual sensor, as the sheath must withstand chemical or physical attack and provide convenient attachment points.
The RTD construction design may be enhanced to handle shock and vibration by including compacted magnesium oxide (MgO) powder inside the sheath. MgO is used to isolate the conductors from the external sheath and from each other. MgO is used due to its dielectric constant, rounded grain structure, high-temperature capability, and its chemical inertness.
Wiring configurations
Two-wire configuration
The simplest resistance-thermometer configuration uses two wires. It is only used when high accuracy is not required, as the resistance of the connecting wires is added to that of the sensor, leading to errors of measurement. This configuration allows use of 100 meters of cable. This applies equally to balanced bridge and fixed bridge system.
For a balanced bridge usual setting is with R2 = R1, and R3 around the middle of the range of the RTD. So for example, if we are going to measure between , RTD resistance will range from 100 Ω to 138.5 Ω. We would choose R3 = 120 Ω. In that way we get a small measured voltage in the bridge.
Three-wire configuration
In order to minimize the effects of the lead resistances, a three-wire configuration can be used. The suggested setting for the configuration shown, is with R1 = R2, and R3 around the middle of the range of the RTD. Looking at the Wheatstone bridge circuit shown, the voltage drop on the lower left hand side is V_rtd + V_lead, and on the lower righthand side is V_R3 + V_lead, therefore the bridge voltage (V_b) is the difference, V_rtd − V_R3. The voltage drop due to the lead resistance has been cancelled out. This always applies if R1=R2, and R1, R2 >> RTD, R3. R1 and R2 can serve the use of limiting the current through the RTD, for example for a Pt100, limiting to 1 mA, and 5 V, would suggest a limiting resistance of approximately R1 = R2 = 5/0.001 = 5,000 Ohms.
Four-wire configuration
The four-wire resistance configuration increases the accuracy of measurement of resistance. Four-terminal sensing eliminates voltage drop in the measuring leads as a contribution to error. To increase accuracy further, any residual thermoelectric voltages generated by different wire types or screwed connections are eliminated by reversal of the direction of the 1 mA current and the leads to the DVM (digital voltmeter). The thermoelectric voltages will be produced in one direction only. By averaging the reversed measurements, the thermoelectric error voltages are cancelled out.
Classifications of RTDs
The highest-accuracy of all PRTs are the Ultra Precise Platinum Resistance Thermometers (UPRTs). This accuracy is achieved at the expense of durability and cost. The UPRT elements are wound from reference-grade platinum wire. Internal lead wires are usually made from platinum, while internal supports are made from quartz or fused silica. The sheaths are usually made from quartz or sometimes Inconel, depending on temperature range. Larger-diameter platinum wire is used, which drives up the cost and results in a lower resistance for the probe (typically 25.5 Ω). UPRTs have a wide temperature range (−200 °C to 1000 °C) and are approximately accurate to ±0.001 °C over the temperature range. UPRTs are only appropriate for laboratory use.
Another classification of laboratory PRTs is Standard Platinum Resistance Thermometers (Standard SPRTs). They are constructed like the UPRT, but the materials are more cost-effective. SPRTs commonly use reference-grade, high-purity smaller-diameter platinum wire, metal sheaths and ceramic type insulators. Internal lead wires are usually a nickel-based alloy. Standard PRTs are more limited in temperature range (−200 °C to 500 °C) and are approximately accurate to ±0.03 °C over the temperature range.
Industrial PRTs are designed to withstand industrial environments. They can be almost as durable as a thermocouple. Depending on the application, industrial PRTs can use thin-film or coil-wound elements. The internal lead wires can range from PTFE-insulated stranded nickel-plated copper to silver wire, depending on the sensor size and application. Sheath material is typically stainless steel; higher-temperature applications may demand Inconel. Other materials are used for specialized applications.
History
Contemporary to the Seebeck effect, the discovery that resistivity in metals is dependent on the temperature was announced in 1821 by Sir Humphry Davy.
The practical application of the tendency of electrical conductors to increase their electrical resistance with rising temperature was first described by Sir William Siemens at the Bakerian Lecture of 1871 before the Royal Society of Great Britain, suggesting platinum as a suitable element. The necessary methods of construction were established by Callendar, Griffiths, Holborn and Wein between 1885 and 1900.
In 1871 Carl Wilhelm Siemens invented the Platinum Resistance Temperature Detector and presented a three-term interpolation formula. Siemens’ RTD rapidly fell out of favour due to the instability of the temperature reading. Hugh Longbourne Callendar developed the first commercially successful platinum RTD in 1885.
A 1971 paper by Eriksson, Keuther, and Glatzel identified six noble metal alloys (63Pt37Rh, 37Pd63Rh, 26Pt74Ir, 10Pd90Ir, 34Pt66Au, 14Pd86Au) with approximately linear resistance temperature characteristics. The alloy 63Pt37Rh is similar to the readily available 70Pt30Rh alloy wire used in thermocouples.
The Space Shuttle made extensive use of platinum resistance thermometers. The only in-flight shutdown of a Space Shuttle Main Engine – mission STS-51F – was caused by multiple failures of RTDs which had become brittle and unreliable due to multiple heat-and-cool cycles. (The failures of the sensors falsely suggested that a fuel pump was critically overheating, and the engine was automatically shut down.) Following the engine failure incident, the RTDs were replaced with thermocouples.
Standard resistance thermometer data
Temperature sensors are usually supplied with thin-film elements. The resistance elements are rated in accordance with BS EN 60751:2008 as:
Resistance-thermometer elements functioning up to 1000 °C can be supplied. The relation between temperature and resistance is given by the Callendar–Van Dusen equation:
Here is the resistance at temperature T, is the resistance at 0 °C, and the constants (for an α = 0.00385 platinum RTD) are:
Since the B and C coefficients are relatively small, the resistance changes almost linearly with the temperature.
For positive temperature, solution of the quadratic equation yields the following relationship between temperature and resistance:
Then for a four-wire configuration with a 1 mA precision current source the relationship between temperature and measured voltage is
Temperature-dependent resistances for various popular resistance thermometers
Copied from German version, please do not remove
See also
Thermowell
Thermistor
Thermostat
Thermocouple
Notes
References
Sensors
Resistive components
Thermometers | Resistance thermometer | Physics,Technology,Engineering | 4,319 |
14,627,569 | https://en.wikipedia.org/wiki/Magnolia%20%C3%97%20soulangeana | Magnolia × soulangeana (Magnolia denudata × Magnolia liliiflora), the saucer magnolia or sometimes the tulip tree, is a hybrid flowering plant in the genus Magnolia and family Magnoliaceae. It is a deciduous tree with large, early-blooming flowers in various shades of white, pink, and purple. It is one of the most commonly used magnolias in horticulture, being widely planted in the British Isles, especially in the south of England; and in the United States, especially the east and west coasts.
Description
Growing as a multistemmed large shrub or small tree, Magnolia × soulangeana has alternate, simple, shiny, dark green oval-shaped leaves on stout stems. Its flowers emerge dramatically on a bare tree in early spring, with the deciduous leaves expanding shortly thereafter, lasting through summer until autumn.
Magnolia × soulangeana flowers are large, commonly 10–20 cm (4–8 in) across, and colored various shades of white, pink, and maroon. An American variety, 'Grace McDade' from Alabama, is reported to bear the largest flowers, with a 35 cm (14 in) diameter, white tinged with pinkish-purple. Another variety, Magnolia × soulangeana 'Jurmag1', is supposed to have the darkest and tightest flowers. The exact timing and length of flowering varies between named varieties, as does the shape of the flower. Some are globular, others a cup-and-saucer shape.
Hybrid origin
Magnolia × soulangeana was initially bred by French plantsman Étienne Soulange-Bodin (1774–1846), a retired cavalry officer in Napoleon's army, at his château de Fromont near Paris. He crossed Magnolia denudata with M. liliiflora in 1820, and was impressed with the resulting progeny's first precocious flowering in 1826.
Many times, Soulange-Bodin is cited as the author of this hybrid name, rarely with a reference to a publication however. If a source is given, it is often an English translation of a French title (see for example Callaway, D.J. (1994), World of Magnolias: 204). Soulange-Bodin certainly did not name the hybrid after himself. The name was proposed by members of the Société Linnéenne de Paris and published by Arsène Thiébaud de Berneaud, the secretary of the society, in Relation de la cinquième fête champêtre célébré le 24 mai 1826 in: Comte-Rendu des Travaux de la Société Linnéenne de Paris 1826: 269.
Cultivation
From France, the hybrid quickly entered cultivation in England and other parts of Europe, and also North America. Since then, plant breeders in many countries have continued to develop this plant, and over a hundred named horticultural varieties (cultivars) are now known.
Magnolia × soulangeana is notable for its ease of cultivation, and its relative tolerance to wind and alkaline soils (two vulnerabilities of many other magnolias).
The cultivar 'Brozzonii' has gained the Royal Horticultural Society's Award of Garden Merit.
Gallery
Notes
References
External links
Magnolia x soulangeana images at the Arnold Arboretum of Harvard University Plant Image Database
soulangeana
Hybrid plants
Garden plants of Asia
Garden plants of Europe
Ornamental trees | Magnolia × soulangeana | Biology | 692 |
2,982,822 | https://en.wikipedia.org/wiki/Blanket%20fort | A blanket fort is a construction commonly made using blankets, bed sheets, pillows, and sofa cushions. It is also known as a couch fort, pillow fort, sheet fort or den.
Parenting books frequently suggest building blanket forts as an activity for parents to participate in play with their children. A blanket fort is made by grabbing blankets around the house and setting them up in a room-like manner. Furniture such as a dining table, a bunk bed, chairs, or an overturned couch can form the foundation for a blanket fort. Clothespins, binder clips, and safety pins may be used to connect blankets and sheets.
In popular culture
As a staple of early childhood entertainment, blanket forts are commonly referenced in children's books, such as Corduroy's Sleepover, If You Give a Pig a Party, and Bob Odenkirk's Zilot & Other Important Rhymes.
In the third season of the television series Community, the episodes "Digital Exploration of Interior Design" and "Pillows and Blankets" focus on the idea of building the biggest blanket fort.
World record
According to Guinness World Records, the largest blanket fort ever was and was built by Cub Scouts Pack 502, Scouts BSA Troop 502B, and Scouts BSA Troop 502G in May 2023 in Mount Pleasant, South Carolina. The record was attempted "to empower the scouts towards meaningful service and to engage, raise awareness, and respond to needs within their community."
See also
Pillow fight
Tree house
References
Children's games
Bedding
Blankets
Pillows
Play (activity) | Blanket fort | Biology | 317 |
3,386,142 | https://en.wikipedia.org/wiki/Order%20operator | In quantum field theory, an order operator or an order field is a quantum field version of Landau's order parameter whose expectation value characterizes phase transitions. There exists a dual version of it, the disorder operator or disorder field, whose expectation value characterizes a phase transition by indicating the prolific presence of defect or vortex lines in an ordered phase.
The disorder operator is an operator that creates a discontinuity of the ordinary order operators or a monodromy for their values. For example, a 't Hooft operator is a disorder operator. So is the Jordan–Wigner transformation. The concept of a disorder observable was first introduced in the context of 2D Ising spin lattices, where a phase transition between spin-aligned (magnetized) and disordered phases happens at some temperature.
See also
Operator (physics)
Books
Kleinert, Hagen, Gauge Fields in Condensed Matter, Vol. I, " SUPERFLOW AND VORTEX LINES", pp. 1–742, Vol. II, "STRESSES AND DEFECTS", pp. 743–1456, World Scientific (Singapore, 1989); Paperback (also available online: Vol. I and Vol. II)
References
Quantum field theory
Statistical mechanics
Phase transitions | Order operator | Physics,Chemistry | 249 |
9,679,559 | https://en.wikipedia.org/wiki/HD%2012661%20b | HD 12661 b is a giant exoplanet two and a half times the mass of Jupiter orbiting around the star HD 12661.
References
Aries (constellation)
Giant planets
Exoplanets discovered in 2001
Exoplanets detected by radial velocity | HD 12661 b | Astronomy | 55 |
10,897,091 | https://en.wikipedia.org/wiki/Healer%20%28video%20games%29 | A healer is a type of character class in video gaming. When a game includes a health game mechanic and multiple classes, often one of the classes will be designed around the restoration of allies' health, known as healing, in order to delay or prevent their defeat. Such a class can be referred to as a healer. In addition to healing, healer classes are sometimes associated with buffs to assist allies in other ways, and nukes to contribute to the offense when healing is unnecessary.
When both healer and tank classes exist, a common grouping strategy is for the healer to focus healing on an allied tank, while the tank prevents other allies, including the healer, from losing health.
Healers are often represented as a fantasy spell-caster (such as a cleric, druid or shaman), a realistic combat specialist (such as a medic or paladin), a science-fiction technician (such as a repairman or engineer), or the like. Often, female gamers are associated with or stereotyped as always playing healer-class characters, with such characters being noted as often female as well.
History
NetHack, a single-player roguelike video game, first released in 1987 includes a description of healers in its accompanying guidebook. It states:
Other early examples of video games with healers in them include Chrono Trigger (1995) and Final Fantasy VII (1997). The former includes the character Marle, who is portrayed as a water mage and performs healing functions. Final Fantasy VII featured the magic-based character Aerith Gainsborough, who was able to restore chunks of health to the player's party. She would go on to become one of the more iconic healing characters in gaming. Unreal Tournament (1999) included healing in multiplayer gameplay. Healers were a markedly important facet of gameplay in the 2004 massively multiplayer online role-playing game (MMORPG) World of Warcraft. America's Army: Rise of a Soldier (2005) rewarded players for healing teammates.
Healers are often incorporated within the broader Support-class subset of characters in a game's playable roster. As such, healers and support characters are commonly associated with each other. Valve's Team Fortress 2 (2007), a first-person shooter (FPS) incorporated healers into gameplay. The game featured three support characters in general, with one being dedicated to solely healing. Team Fortress 2 featured competitive multiplayer, in which healer characters have been noted as vital in gameplay. In such competitive multiplayer, healer-class players have been noted as an underappreciated. Massively multiplayer online role-playing games (or MMORPGs) have been noted by PC Gamer to have a "usual problem of there being too few healers or tanks because most people want to be able to level and solo efficiently." Some players have been documented to prefer selecting healer-class characters in competitive multiplayer modes, who have cited a desire to help teammates and a relative accessibility as reasons why. Edwin Evans-Thirlwell of The Face wrote that "healer roles [in shooter games] stand out because they don't depend on hand-eye coordination, making them attractive both to players who find 'twitch-shooting' a turn-off and people with disabilities that affect their accuracy and reflexes." In the 2010s, a community sprung up around the concept of "healslutting", which sees some players submit to others while role-playing a healer character.
Roles and abilities
Multiplayer games featuring healing are not limited by genre, as the class is present in a variety of genres including role-playing games (RPG), first-person shooters (FPS), and multiplayer online battle arenas (MOBA).
A healer is generally tasked with restoring health, removing poison-like effects, and reviving fallen party members. Different games may include different mechanics, such as the ability to deal damage or to enhance the attributes of their allies. Healers require a degree of situational awareness, as well as resource management in regards to their kit. In shooters, healing abilities, such as throwable health packs typically aim themselves. However, there are examples of healer characters that do require shooting finesse, such as Ana of Overwatch, who is equipped with a hypodermic rifle.
In parties that include both a tank and a healer, it is customary for the latter to heal any damage taken by the former. In small groups, they may also be tasked to heal the group as well, but in large scale group-play there are typically specific healers assigned to party-wide damage (typically taken indirectly, via lesser minions, spells or environment/habitat of the boss).
Specifications
Targeting specifics
Healers fall into two major categories when it comes to targeting options: Single-Target and Multi-Target.
Single-Target healers often have much more potent spells than their Multi-Targeting counterparts, such as those that fully restore a target's Health or resurrect an ally that had previously lost all their Health.
Multi-Target healers tend to lack potency, but heal multiple allies (often the entire Party) with abilities. In Tactical RPGs or open-world games, their spells may utilize an Area of Effect (AoE) mechanic. Healers that fall into this sub-type often do not possess resurrection spells.
Healers often do not utilise only one targeting system. Targeting options tend to depend on the skill rather than the character.
Sub-jobs
Healers have a small number of roles that they can be delegated towards. Often, a healer will fill one or more of these roles. Alternatively, a healer may fill one of these roles in addition to some other job, such as damage dealing (Battle Cleric, Druid), inflicting negative statuses on enemies (Witch/Warlock), or even drawing in damage (Paladin).
Restoration: Restoring Health to allies. This tends to be the job most associated with healer classes.
Curation: Removing harmful or otherwise negative statuses from allies.
Support: Used in the context of healers, this typically refers to applying regenerative buffs or shields to allies.
Resurrection: The rarest healer archetype, focused on not preventing death, but overcoming it.
Necromancers are a blurry line against the grain of Resurrection healers. They're often more classified as a summoner, summoning skeleton or zombie themed minions to deal damage or draw enemy attacks.
In sexual roleplay
Choosing to play as a healer may sometimes be done as part of a dominant–submissive roleplaying dynamic. In "healslutting" (a combination of the words "heal" and "slut"), players engage with one another both in-game and through external avenues as one player assumes the healer role, submitting to the player who has selected an offensive- or tank-class character. The term gained widespread popularity through the 2016 first-person hero shooter Overwatch, in which the character Mercy is a dedicated healer commonly used by female players who largely wish to avoid direct combat. Aside from "healsluts", healer-class players may also conversely identify as "healdoms", in which they assume the dominant role in the dynamic as they can "control whether their partner lives or dies."
See also
Tank (video games), a common character class focused on drawing enemy damage.
References
Further reading
Character classes
Fictional healers
Video game terminology | Healer (video games) | Technology | 1,526 |
12,207,392 | https://en.wikipedia.org/wiki/Compact%20complement%20topology | In mathematics, the compact complement topology is a topology defined on the set of real numbers, defined by declaring a subset open if and only if it is either empty or its complement is compact in the standard Euclidean topology on .
References
Topology | Compact complement topology | Physics,Mathematics | 48 |
54,812,230 | https://en.wikipedia.org/wiki/Laser%2050 | The Laser 50 is an educational portable computer sold by Vtech that ran the BASIC programming language. It was released in 1984.
Specifications
The Laser 50 used a Zilog Z80 central processing unit running at 3.5 MHz, 2 kB to 18 kB of RAM, a 12 kB ROM, and a 80x7 dots LCD screen.
Microcomputers
Computer-related introductions in 1984 | Laser 50 | Technology | 80 |
48,729,126 | https://en.wikipedia.org/wiki/Authority%20distribution | The solution concept authority distribution was formulated by Lloyd Shapley and his student X. Hu in 2003 to measure the authority power of players in a well-contracted organization. The index generates the Shapley-Shubik power index and can be used in ranking, planning and organizational choice.
Definition
The organization contracts each individual by boss and approval relation with others. So each individual has its own authority structure, called command game. The Shapley-Shubik power index for these command games are
collectively denoted by a power transit matrix Ρ.
The authority distribution π is defined as the solution to the counterbalance equation π=πΡ. The basic idea for the counterbalance equation is that a person's power comes from his critical roles in others' command game; on the other hand, his power could also be redistributed to those who sit in his command game as vital players.
For a simple legislative body, π is simply the Shapley-Shubik power index, based on a probabilistic argument ().
Applications
Example 1. College ranking by applicants’ acceptance
Suppose that there are large numbers of college applicants to apply the colleges
Each applicant files multiple applications. Each college then offers some
of its applicants admissions and rejects all others. Now some applicants may get no offer
from any college; the other then get one offer or multiple offers. An applicant with multiple
offers will decide which college to go to and reject all other colleges which make offers
to him. Of all applicants who apply to and receive offers from College i, we let P(i,j) be
the proportion of those applicants who decide to go to college j. Such applicants of
course apply to and receive offers from College j as well.
To rank the colleges by the acceptance rates of the applicants to whom offers were
made, we can apply the authority distribution associated with the matrix P. The so-called “authority distribution” can be regarded as the measure of relative
attractiveness of the colleges from the applicants’ point of view.
Example 2. Journal rankings by citations
Assume there are n journals in a scientific field. For any Journal i, each issue
contains many papers, and each paper has its list of references or citations. A paper in journal j
can be cited in another paper in Journal i as a reference. Of all papers cited by Journal i (repetition
counted), we let P(i,j) be the proportion of those papers which are published on Journal j. So P
measures the direct impact between any two journals and P(i, i) is the self-citation rate
for Journal i . The authority distribution for π = πP would quantify the long-term influence of
each journal in the group of journals and can be used to rank these journals.
Example 3. Planning of a freeway system
A few small towns believe that building a freeway system would be to their common
benefit. Say, they plan to build freeways F1, F2, ..., Fn−1. We let Fn be the existing traffic
channels of car, truck and bus. We assume that all the potential freeways have the same
length. Otherwise we can make up the assumption by dividing long freeways into smaller
segments and rename them all. The freeways with higher traffic intensity should be built
with more driving lanes and so receive more investments. Of all the traffic flow on Fi, we
let P(i,j) be the (estimated) proportion of the traffic flowing into Fj. Then the authority
distribution π satisfying π = πP will measure the relative traffic intensity on each Fi and
can be used in the investment allocation.
A similar issue can be found in designing an Internet or Intranet system.
Example 4. Real Effective Exchange Rates Weights
Assume there are n countries. Let P(i,j) be country j's weights of consumption of country's total production.
The associated π measures the weights in the trading system of n countries.
Example 5. Sort Big Data Objects by Revealed Preference
When ranking big data observations, diverse consumers reveal heterogeneous preferences; but any revealed preference is a ranking between two observations, derived from a consumer’s rational consideration of many factors. Previous researchers have applied exogenous weighting and multivariate regression approaches, and spatial, network, or multidimensional analyses to sort complicated objects, ignoring the variety and variability of the objects. By recognizing the diversity and heterogeneity among both the observations and the consumers, Hu (2000) instead applies endogenous weighting to these contradictory revealed preferences. The outcome is a consistent steady-state solution to the counterbalance equilibrium within these contradictions. The solution takes into consideration the spillover effects of multiple-step interactions among the observations. When information from data is efficiently revealed in preferences, the revealed preferences greatly reduce the volume of the required data in the sorting process.
See also
Shapley value
Shapley-Shubik power index
Banzhaf power index
References
External links
Online Power Index Calculator (by Tomomi Matsui)
Computer Algorithms for Voting Power Analysis Web-based algorithms for voting power analysis
Power Index Calculator Computes various indices for (multiple) weighted voting games online. Includes some examples.
Systematic investment plan calculator Calculate your project potential returns on your mutual fund investments across various timeframes
Pretty Scale Calculate your attractiveness with pretty scale.
Game theory
Cooperative games
Electoral systems | Authority distribution | Mathematics | 1,095 |
2,756,880 | https://en.wikipedia.org/wiki/T.51/ISO/IEC%206937 | T.51 / ISO/IEC 6937:2001, Information technology — Coded graphic character set for text communication — Latin alphabet, is a multibyte extension of ASCII, or more precisely ISO/IEC 646-IRV. It was developed in common with ITU-T (then CCITT) for telematic services under the name of T.51, and first became an ISO standard in 1983. Certain byte codes are used as lead bytes for letters with diacritics. The value of the lead byte often indicates which diacritic that the letter has, and the follow byte then has the ASCII-value for the letter that the diacritic is on.
ISO/IEC 6937's architects were Hugh McGregor Ross, Peter Fenwick, Bernard Marti and Loek Zeckendorf.
ISO6937/2 defines 327 characters found in modern European languages using the Latin alphabet. Non-Latin European characters, such as Cyrillic and Greek, are not included in the standard. Also, some diacritics used with the Latin alphabet like the Romanian comma are not included, using cedilla instead as no distinction between cedilla and comma below was made at the time.
IANA has registered the charset names ISO_6937-2-25 and ISO_6937-2-add for two (older) versions of this standard (plus control codes). But in practice this character encoding is unused on the Internet.
Single byte characters
The primary set (first half) originally followed ISO 646-IRV before the ISO/IEC 646:1991 revision, that is, mostly following ASCII but with character 0x24 still denoted as an "international currency sign" (¤) instead of the dollar sign ($). The 1992 edition of ITU T.51 permits existing CCITT services to continue to interpret 0x24 as the international currency sign, but stipulates that new telecommunication applications should use it for the dollar sign (i.e. following the current ISO 646-IRV), and instead represent the international currency sign using the supplementary set.
The supplementary set (second half) contains a selection of spacing and non-spacing graphic characters, additional symbols and some locations reserved for future standardisation.
Both of these are ISO/IEC 2022 graphical character sets, with the primary set being a 94-code set and the secondary set being a 96-code set. In contexts where ISO 2022 code extension techniques are not in use, the primary set is designated as the G0 set and invoked over GL (0x20..0x7F), whereas the supplementary set is designated as the G2 set and invoked over GR (0xA0..0xFF) in an 8-bit environment, or by using the control code 0x19 as a single-shift in a 7-bit environment. This encoding of the Single Shift Two code matches its location in ISO-IR-106.
The ISO/IEC 2022 escape sequence to designate the supplementary set of ISO/IEC 6937 as the G2 set is ESC . R (hex 1B 2E 52). The older ISO 6937/2:1983 supplementary set is registered as a 94-code set, and designated to G2 with ESC * l (hex 1B 2A 6C).
Two byte characters
Accented letters which are not allocated single codes in the primary or supplementary set are coded using two bytes. The first byte, the "non spacing diacritical mark", is followed by a letter from the base set e.g.:
small e with acute accent (é) = [Acute]+e
The ITU T.51 standard allocates column 4 of the supplementary set (i.e. 0xC0–CF when used in 8-bit format) to non-spacing diacritic characters. However, ISO/IEC 6937 defines a fully specified character repertoire, mapping a list of composition sequences to ISO/IEC 10646 character names which match those defined in Unicode. The isolated nonspacing bytes are not included in this repertoire, although spacing variants of the diacritics not otherwise present in ASCII are included, with the ASCII space being the trail byte. Hence, only certain combinations of lead byte and follow byte conform to the ISO/IEC standard.
This repertoire is also affixed to the ITU version of the specification as Annex A, although the ITU version does not reference it from the main text. It is described as a "unified superset" of the Latin-script character repertoires. It corresponds to the repertoire of ISO/IEC 10367 when the ASCII, Latin-1 (or Latin-5), Latin-2 and supplementary Latin sets are used.
This system also differs from the Unicode combining character system in that the diacritic code precedes the letter (as opposed to following it), making it more similar to ANSEL.
A little anomaly is that Latin Small Letter G with Cedilla is coded as if it were with an acute accent, that is, with a 0xC2 lead byte, since due to its descender interfering with a cedilla, the lowercase letter is usually with turned comma above: .
In total 13 diacritical marks can be followed by the selected characters from the primary set:
Codepage layout
The reference to combining characters in the U+0300—U+036F range for the codes in the range 0xC1—0xCF below is subject to the caveats mentioned above; they cannot simply be mapped to the codepoints listed. Also, Unicode distinguishes 0xE2 into uppercase D with stroke and uppercase Eth, which usually look different for the lowercase letters (0xF2 and 0xF3).
The older 1988 edition of ITU T.51 defined two versions of the supplementary set, with the first version lacking the non-breaking space, soft hyphen, not sign (¬) and broken bar (¦) present in the second version. The first version was defined as an extension of the T.61 supplementary set, and the second version as an extension of the first version. The current (1992) edition only includes the second version, deprecates certain characters, and updates the primary set to the current ISO-646-IRV (ASCII), although existing telematic services are permitted to retain the older behaviour.
Videotex version
The versions of the supplementary set used by the ITU T.101 standard for Videotex are based on the first supplementary set of the 1988 edition of T.51.
The default G2 set for Data Syntax 2 adds a ΅ at 0xC0, for combination with codes from a Greek primary set.
The supplementary set for Data Syntax 3 adds non-spacing marks for a "vector overbar" and solidus and several semigraphic characters.
ETS 300 706 version
The ETS 300 706 standard for World System Teletext bases its G2 set on ISO 6937. It is a superset of the supplementary set of T.61, and a superset of the first supplementary set of the 1988 edition of T.51, but collides with the current edition of T.51 in certain positions. Diacritic codes in the ETS version are specified as being "for association with" characters from the G0 set in use, such as US-ASCII or BS_viewdata. This version is shown in the chart below.
See also
ITU T.50
ITU T.61, a closely related character encoding for Teletex use
Footnotes
References
External links
ITU Recommendation T.51
ISO pages: ISO 6937-1:1983, ISO 6937-2:1983, ISO 6937-2:1983/Add 1:1989, ISO/IEC 6937:1994, ISO/IEC 6937:2001
WD 6937, Coded graphic character set for text communication - Latin alphabet (Revision of ISO/IEC 6937:1994) (ISO/IEC 6937:1994 draft)
ISO-IR-156 (ISO-IR registration of right-hand part)
T.51
T.51
Character encoding
Character sets
Computer-related introductions in 1983 | T.51/ISO/IEC 6937 | Technology | 1,714 |
43,942 | https://en.wikipedia.org/wiki/Petri%20dish | A Petri dish (alternatively known as a Petri plate or cell-culture dish) is a shallow transparent lidded dish that biologists use to hold growth medium in which cells can be cultured, originally, cells of bacteria, fungi and small mosses. The container is named after its inventor, German bacteriologist Julius Richard Petri. It is the most common type of culture plate. The Petri dish is one of the most common items in biology laboratories and has entered popular culture. The term is sometimes written in lower case, especially in non-technical literature.
What was later called Petri dish was originally developed by German physician Robert Koch in his private laboratory in 1881, as a precursor method. Petri, as assistant to Koch, at Berlin University made the final modifications in 1887 as used today.
Penicillin, the first antibiotic, was discovered in 1929 when Alexander Fleming noticed that penicillium mold contaminating a bacterial culture in a Petri dish had killed the bacteria around it.
History
The Petri dish was developed by German physician Julius Richard Petri (after whom the name is given) while working as an assistant to Robert Koch at Berlin University. Petri did not invent the culture dish himself; rather, it was a modified version of Koch's invention which used an agar medium that was developed by Walther Hesse. Koch had published a precursor dish in a booklet in 1881 titled "" (Methods for the Study of Pathogenic Organisms), which has been known as the "Bible of Bacteriology". He described a new bacterial culture method that used a glass slide with agar and a container (basically a Petri dish, a circular glass dish of 20 × 5 cm with matching lid) which he called ("moist chamber"). A bacterial culture was spread on the glass slide, then placed in the moist chamber with a small wet paper. Bacterial growth was easily visible.
Koch publicly demonstrated his plating method at the Seventh International Medical Congress in London in August 1881. There, Louis Pasteur exclaimed, "" ("What a great progress, Sir!") It was using this method that Koch discovered important pathogens of tuberculosis (Mycobacterium tuberculosis), anthrax (Bacillus anthracis), and cholera (Vibrio cholerae). For his research on tuberculosis, he was awarded the Nobel Prize in Physiology or Medicine in 1905. His students also made important discoveries. Friedrich Loeffler discovered the bacteria of glanders (Burkholderia mallei) in 1882 and diphtheria (Corynebacterium diphtheriae) in 1884; and Georg Theodor August Gaffky, the bacterium of typhoid (Salmonella enterica) in 1884.
Petri made changes in how the circular dish was used. It is often asserted that Petri developed a new culture plate, but this is incorrect. Instead of using a separate glass slide or plate on which culture media were placed, Petri directly placed media into the glass dish, eliminating unnecessary steps such as transferring the culture media, using the wet paper, and reducing the chance of contamination. He published the improved method in 1887 as "" ("A minor modification of the plating technique of Koch"). Although it could have been named "Koch dish", the final method was given an eponymous name Petri dish.
Features and variants
Petri dishes are usually cylindrical, mostly with diameters ranging from , and a height to diameter ratio ranging from 1:10 to 1:4. Squarish versions are also available.
Petri dishes were traditionally reusable and made of glass; often of heat-resistant borosilicate glass for proper sterilization at 120–160 °C.
Since the 1960s, plastic dishes, usually disposable, are also common.
The dishes are often covered with a shallow transparent lid, resembling a slightly wider version of the dish itself. The lids of glass dishes are usually loose-fitting. Plastic dishes may have close-fitting covers that delay the drying of the contents. Alternatively, some glass or plastic versions may have small holes around the rim, or ribs on the underside of the cover, to allow for air flow over the culture and prevent water condensation.
Some Petri dishes, especially plastic ones, usually feature rings and/or slots on their lids and bases so that they are less prone to sliding off one another when stacked or sticking to a smooth surface by suction.
Small dishes may have a protruding base that can be secured on a microscope stage for direct examination.
Some versions may have grids printed on the bottom to help in measuring the density of cultures.
A microplate is a single container with an array of flat-bottomed cavities, each being essentially a small Petri dish. It makes it possible to inoculate and grow dozens or hundreds of independent cultures of dozens of samples at the same time. Besides being much cheaper and convenient than separate dishes, the microplate is also more amenable to automated handling and inspection.
Some plates are separated into different mediums known as biplates, triplates, and quadplates.
Uses
Petri dishes are widely used in biology to cultivate microorganisms such as bacteria, yeasts, and molds. It is most suited for organisms that thrive on a solid or semisolid surface. The culture medium is often an agar plate, a layer a few mm thick of agar or agarose gel containing whatever nutrients the organism requires (such as blood, salts, carbohydrates, amino acids) and other desired ingredients (such as dyes, indicators, and medicinal drugs). The agar and other ingredients are dissolved in warm water and poured into the dish and left to cool down. Once the medium solidifies, a sample of the organism is inoculated ("plated"). The dishes are then left undisturbed for hours or days while the organism grows, possibly in an incubator. They are usually covered, or placed upside-down, to lessen the risk of contamination from airborne spores. Virus or phage cultures require that a population of bacteria be grown in the dish first, which then becomes the culture medium for the viral inoculum.
While Petri dishes are widespread in microbiological research, smaller dishes tend to be used for large-scale studies in which growing cells in Petri dishes can be relatively expensive and labor-intensive.
Petri dishes can be used to visualize the location of contamination on surfaces, such as kitchen counters and utensils, clothing, food preparation equipment, or animal and human skin. For this application, the Petri dishes may be filled so that the culture medium protrudes slightly above the edges of the dish to make it easier to take samples on hard objects. Shallow Petri dishes prepared in this way are called Replicate Organism Detection And Counting (RODAC) plates and are available commercially.
Petri dishes are also used for cell cultivation of isolated cells from eukaryotic organisms, such as in immunodiffusion studies, on solid agar or in a liquid medium.
Petri dishes may be used to observe the early stages of plant germination, and to grow plants asexually from isolated cells.
Petri dishes may be convenient enclosures to study the behavior of insects and other small animals.
Due to their large open surface, Petri dishes are effective containers to evaporate solvents and dry out precipitates, either at room temperature or in ovens and desiccators.
Petri dishes also make convenient temporary storage for samples, especially liquid, granular, or powdered ones, and small objects such as insects or seeds. Their transparency and flat profile allows the contents to be inspected with the naked eye, magnifying glass, or low-power microscope without removing the lid.
In popular culture
The Petri dish is one of a small number of laboratory equipment items whose name entered popular culture. It is often used metaphorically, e.g. for a contained community that is being studied as if they were microorganisms in a biology experiment, or an environment where original ideas and enterprises may flourish.
Unicode has a Petri dish emoji, "🧫", which has the code point U+1F9EB (HTML entity "🧫" or "🧫", UTF-8 "0xF0 0x9F 0xA7 0xAB").
See also
References
External links
Laboratory glassware
Microbiology equipment
German inventions
1887 in science
1887 in Germany | Petri dish | Biology | 1,764 |
12,937 | https://en.wikipedia.org/wiki/Gram-negative%20bacteria | Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists of a thin peptidoglycan cell wall sandwiched between an inner (cytoplasmic) membrane and an outer membrane. These bacteria are found in all environments that support life on Earth.
Within this category, notable species include the model organism Escherichia coli, along with various pathogenic bacteria, such as Pseudomonas aeruginosa, Chlamydia trachomatis, and Yersinia pestis. They pose significant challenges in the medical field due to their outer membrane, which acts as a protective barrier against numerous antibiotics (including penicillin), detergents that would normally damage the inner cell membrane, and the antimicrobial enzyme lysozyme produced by animals as part of their innate immune system. Furthermore, the outer leaflet of this membrane contains a complex lipopolysaccharide (LPS) whose lipid A component can trigger a toxic reaction when the bacteria are lysed by immune cells. This reaction may lead to septic shock, resulting in low blood pressure, respiratory failure, reduced oxygen delivery, and lactic acidosis.
Several classes of antibiotics have been developed to target gram-negative bacteria, including aminopenicillins, ureidopenicillins, cephalosporins, beta-lactam-betalactamase inhibitor combinations (such as piperacillin-tazobactam), folate antagonists, quinolones, and carbapenems. Many of these antibiotics also cover gram-positive bacteria. The antibiotics that specifically target gram-negative organisms include aminoglycosides, monobactams (such as aztreonam), and ciprofloxacin.
Characteristics
Conventional gram-negative (LPS-diderm) bacteria display :
An inner cell membrane is present (cytoplasmic)
A thin peptidoglycan layer is present (this is much thicker in gram-positive bacteria)
Has outer membrane containing lipopolysaccharides (LPS, which consists of lipid A, core polysaccharide, and O antigen) in its outer leaflet and phospholipids in the inner leaflet
Porins exist in the outer membrane, which act like pores for particular molecules
Between the outer membrane and the cytoplasmic membrane there is a space filled with a concentrated gel-like substance called periplasm
The S-layer is directly attached to the outer membrane rather than to the peptidoglycan
If present, flagella have four supporting rings instead of two
Teichoic acids or lipoteichoic acids are absent
Lipoproteins are attached to the polysaccharide backbone
Some contain Braun's lipoprotein, which serves as a link between the outer membrane and the peptidoglycan chain by a covalent bond
Most, with few exceptions, do not form spores
Classification
Along with cell shape, Gram staining is a rapid diagnostic tool and once was used to group species at the subdivision of Bacteria.
Historically, the kingdom Monera was divided into four divisions based on Gram staining: Firmicutes (+), Gracillicutes (−), Mollicutes (0) and Mendocutes (var.).
Since 1987, the monophyly of the gram-negative bacteria has been disproven with molecular studies. However some authors, such as Cavalier-Smith still treat them as a monophyletic taxon (though not a clade; his definition of monophyly requires a single common ancestor but does not require holophyly, the property that all descendants be encompassed by the taxon) and refer to the group as a subkingdom "Negibacteria".
Taxonomy
Bacteria are traditionally classified based on their Gram-staining response into the gram-positive and gram-negative bacteria. Having just one membrane, the gram-positive bacteria are also known as monoderm bacteria, while gram-negative bacteria, having two membranes, are also known as diderm bacteria. It was traditionally thought that the groups represent lineages, i.e., the extra membrane only evolved once, such that gram-negative bacteria are more closely related to one another than to any gram-positive bacteria. While this is often true, the classification system breaks down in some cases, with lineage groupings not matching the staining result. Thus, Gram staining cannot be reliably used to assess familial relationships of bacteria. Nevertheless, staining often gives reliable information about the composition of the cell membrane, distinguishing between the presence or absence of an outer lipid membrane.
Of these two structurally distinct groups of prokaryotic organisms, monoderm prokaryotes are thought to be ancestral. Based upon a number of different observations, including that the gram-positive bacteria are the most sensitive to antibiotics and that the gram-negative bacteria are, in general, resistant to antibiotics, it has been proposed that the outer cell membrane in gram-negative bacteria (diderms) evolved as a protective mechanism against antibiotic selection pressure. Some bacteria such as Deinococcus, which stain gram-positive due to the presence of a thick peptidoglycan layer, but also possess an outer cell membrane are suggested as intermediates in the transition between monoderm (gram-positive) and diderm (gram-negative) bacteria. The diderm bacteria can also be further differentiated between simple diderms lacking lipopolysaccharide (LPS); the archetypical diderm bacteria, in which the outer cell membrane contains lipopolysaccharide; and the diderm bacteria in which the outer cell membrane is made up of mycolic acid (e. g. Mycobacterium).
The conventional LPS-diderm group of gram-negative bacteria (e.g., Pseudomonadota, Aquificota, Chlamydiota, Bacteroidota, Chlorobiota, "Cyanobacteria", Fibrobacterota, Verrucomicrobiota, Planctomycetota, Spirochaetota, Acidobacteriota; "Hydrobacteria") are uniquely identified by a few conserved signature indel (CSI) in the HSP60 (GroEL) protein. In addition, a number of bacterial taxa (including Negativicutes, Fusobacteriota, Synergistota, and Elusimicrobiota) that are either part of the phylum Bacillota (a monoderm group) or branches in its proximity are also found to possess a diderm cell structure. They lack the GroEL signature. The presence of this CSI in all sequenced species of conventional lipopolysaccharide-containing gram-negative bacterial phyla provides evidence that these phyla of bacteria form a monophyletic clade and that no loss of the outer membrane from any species from this group has occurred.
Example species
The proteobacteria are a major superphylum of gram-negative bacteria, including E. coli, Salmonella, Shigella, and other Enterobacteriaceae, Pseudomonas, Moraxella, Helicobacter, Stenotrophomonas, Bdellovibrio, acetic acid bacteria, Legionella etc. Other notable groups of gram-negative bacteria include the cyanobacteria, spirochaetes, green sulfur, and green non-sulfur bacteria.
Medically-relevant gram-negative diplococci include the four types that cause a sexually transmitted disease (Neisseria gonorrhoeae), a meningitis (Neisseria meningitidis), and respiratory symptoms (Moraxella catarrhalis, A coccobacillus Haemophilus influenzae is another medically relevant coccal type.
Medically relevant gram-negative bacilli include a multitude of species. Some of them cause primarily respiratory problems (Klebsiella pneumoniae, Legionella pneumophila, Pseudomonas aeruginosa), primarily urinary problems (Escherichia coli, Proteus mirabilis, Enterobacter cloacae, Serratia marcescens), and primarily gastrointestinal problems (Helicobacter pylori, Salmonella enteritidis, Salmonella typhi).
Gram-negative bacteria associated with hospital-acquired infections include Acinetobacter baumannii, which cause bacteremia, secondary meningitis, and ventilator-associated pneumonia in hospital intensive-care units.
Bacterial transformation
Transformation is one of three processes for horizontal gene transfer, in which exogenous genetic material passes from one bacterium to another, the other two being conjugation (transfer of genetic material between two bacterial cells in direct contact) and transduction (injection of foreign DNA by a bacteriophage virus into the host bacterium). In transformation, the genetic material passes through the intervening medium, and uptake is completely dependent on the recipient bacterium.
As of 2014 about 80 species of bacteria were known to be capable of transformation, about evenly divided between gram-positive and gram-negative bacteria; the number might be an overestimate since several of the reports are supported by single papers. Transformation has been studied in medically important gram-negative bacteria species such as Helicobacter pylori, Legionella pneumophila, Neisseria meningitidis, Neisseria gonorrhoeae, Haemophilus influenzae and Vibrio cholerae. It has also been studied in gram-negative species found in soil such as Pseudomonas stutzeri, Acinetobacter baylyi, and gram-negative plant pathogens such as Ralstonia solanacearum and Xylella fastidiosa.
Role in disease
One of the several unique characteristics of gram-negative bacteria is the structure of the bacterial outer membrane. The outer leaflet of this membrane contains lipopolysaccharide (LPS), whose lipid A portion acts as an endotoxin. If gram-negative bacteria enter the circulatory system, LPS can trigger an innate immune response, activating the immune system and producing cytokines (hormonal regulators). This leads to inflammation and can cause a toxic reaction, resulting in fever, an increased respiratory rate, and low blood pressure. That is why some infections with gram-negative bacteria can lead to life-threatening septic shock.
The outer membrane protects the bacteria from several antibiotics, dyes, and detergents that would normally damage either the inner membrane or the cell wall (made of peptidoglycan). The outer membrane provides these bacteria with resistance to lysozyme and penicillin. The periplasmic space (space between the two cell membranes) also contains enzymes which break down or modify antibiotics. Drugs commonly used to treat gram negative infections include amino, carboxy and ureido penicillins (ampicillin, amoxicillin, pipercillin, ticarcillin). These drugs may be combined with beta-lactamase inhibitors to combat the presence of enzymes that can digest these drugs (known as beta-lactamases) in the peri-plasmic space. Other classes of drugs that have gram negative spectrum include cephalosporins, monobactams (aztreonam), aminoglycosides, quinolones, macrolides, chloramphenicol, folate antagonists, and carbapenems.
Orthographic note
The adjectives gram-positive and gram-negative derive from the surname of Hans Christian Gram, a Danish bacteriologist; as eponymous adjectives, their initial letter can be either capital G or lower-case g, depending on which style guide (e.g., that of the CDC), if any, governs the document being written. This is further explained at Gram staining § Orthographic note.
See also
Autochaperone
Gram-variable and gram-indeterminate bacteria
OMPdb (2011)
Outer membrane receptor
References
Notes
External links
3D structures of proteins from inner membranes of Ellie Wyithe's gram-negative bacteria
Staining
Bacteriology | Gram-negative bacteria | Chemistry,Biology | 2,608 |
50,820,388 | https://en.wikipedia.org/wiki/Maxim%20DL | MaxIm DL is a software package developed by Cyanogen Imaging for acquisition, processing, and analysis of astronomical imaging. It contains tools to process and analyze data from imaging array detectors such as CCDs.
It is available for Windows 7 and later. Installation on alternative operating systems is possible but not officially supported by the developer.
References
Science software
Astronomy software | Maxim DL | Astronomy | 71 |
76,624,748 | https://en.wikipedia.org/wiki/NGC%20716 | NGC 716 is a large barred spiral galaxy located in the constellation Aries, about 200 million light-years away from the Milky Way. The luminosity class of NGC 716 is I and has a large HI line. It also contains regions of ionized hydrogen. Many non-redshift measurements provide a distance of 54,023±8,169 Mpc (~176 million light years), which is within the distances calculated using the redshift value.
History
NGC 716 was discovered in 1886 by American astronomer Lewis Swift using a 40.64 cm (16 inch) optical telescope that used a mirror as a light-gathering element. It was also observed by the French astronomer Guillaume Bigourdan on 1 January 1892 and was added to the Index Catalog with the code IC 1743.
References
See also
List of NGC objects (1–1000)
Lists of galaxies
External links
NGC 716 at SEDS.org
NGC 716 at Theskylive.com
Barred spiral galaxies
Aries (constellation)
716
IC objects
Galaxies discovered in 1886
Discoveries by Lewis Swift | NGC 716 | Astronomy | 219 |
77,663,120 | https://en.wikipedia.org/wiki/Galerina%20semilanceata | Galerina semilanceata is a species of mushroom in the genus Galerina native to Washington state and California.
Description
This species is identified by its heavily veined, light colored cap, and small white V shaped powderings that go up the stem. The mushrooms are usually about 3 cm all around.
Conservation status
This species is not of concern and is quite common.
References
Hymenogastraceae
Fungi described in 1896
Fungus species | Galerina semilanceata | Biology | 88 |
72,615,273 | https://en.wikipedia.org/wiki/Weather%20of%202023 | The following is a list of weather events that occurred on Earth in the year 2023. The year saw a transition from La Niña to El Niño, with record high global average surface temperatures. There were several natural disasters around the world from various types of weather, including blizzards, cold waves, droughts, heat waves, wildfires, floods, tornadoes, and tropical cyclones. The deadliest weather event of the year was Storm Daniel, which killed over 5,900 people, with most of the fatalities coming from Libya. The costliest weather event of the year was Typhoon Doksuri, which caused $28.5 billion in damages in China, the Philippines and Taiwan. Another significant weather event was Cyclone Freddy, which became the longest lasting tropical cyclone on record, beating the previous mark of Hurricane John in 1994. The storm caused 1,434 fatalities, with most of the deaths coming from Malawi.
Deadliest events
Worst events
This is a list of weather events considered to be the most significant during 2023, in which reliable sources, surveys or academic assessments consider criteria such as, but not limited to: how impactful the event was, how deadly the event was, the impact on science, or other specific criteria. These events may be referred to as most important, most iconic, most signficiant, or the worst—but they are all considered key events in meteorology during the year.
Types
The following listed different types of special weather conditions worldwide.
Cold snaps and winter storms
In January, a cold snap in Afghanistan killed at least 166 people and more than 80,000 livestock. A national low temperature was set in Mohe City, China at , on January 23. Two days later, snow fell in Algeria for the first time in ten years.
Heat waves and droughts
Starting in April 2023, a record-breaking heat wave in Asia has affected multiple countries, including India, China, Laos and Thailand.
Tornadoes
An early-season tornado outbreak in the Southern United States was responsible for eight deaths and 53 injuries. On January 24, an EF3 tornado struck Deer Park, Texas, causing a tornado emergency. A storm complex in late February caused several tornadoes including a tornado that hit Cheyenne, Oklahoma, that killed one. A rare tornado near Taif, Saudi Arabia killed one person and injured one more. Two separate tornado outbreaks between March 24–March 27 and March 31–April 1 caused 58 deaths and two EF4 tornadoes in the US.
Tropical and subtropical cyclones
The first named tropical cyclone of the year was Cyclone Hale, which caused minimal damage and one death in New Zealand as an extratropical cyclone. Later in January, Cyclone Cheneso killed at least 33 people in Madagascar and left 20 missing. In addition, it damaged over 13,000 houses and 18 medical centers.
In February, Cyclone Freddy formed on February 4 and lasted until March 14, making it the longest lived tropical cyclone on record, surpassing Hurricane John of 1994, tracking across the entire Indian Ocean, the first to do so since Hudah and Leon-Eline in 2000. In addition, Freddy also recorded the highest accumulated cyclone energy of any tropical cyclone worldwide, at 87.01, surpassing the previous record of 85.26 by Hurricane Ioke in 2006. Freddy killed at least 1,434 people, and left 19 missing. In May, Cyclone Mocha formed and made landfall in Myanmar, killing 438 people and more than 101 missing. In June, Cyclone Biparjoy formed over the Arabian Sea and intensified into an extremely severe tropical cyclone, and made landfall in India, leaving at least 12 people dead.
Extratropical cyclones and European windstorms
Cyclone Helios which formed in early February brought recorded rain and humidity to Malta from 80 years. Luqa recorded rain with a total of 140.4 millimeters. meteo.it defined it as a Mediterranean tropical-like cyclone as it dissipated on February 11. Storm Otto, also known as Storm Ulf, brought high winds to the United Kingdom, Norway, and Germany. The highest wind gust was recorded in Cairngorms, UK, at 193 km/h (120 mph).
Wildfires
Over 100 wildfires have been confirmed in Alberta, Canada, and 13,000 people have been evacuated. The 2023 Hawaii wildfires killed over 110 people in the town on Lahaina, Hawaii.
Timeline
This is a timeline of weather events during 2023.
January
In January 2023, the National Oceanic and Atmospheric Administration documented 30 weather-related fatalities and 162 weather-related injuries in the United States and Territories of the United States.
November 2022–January 2023 – The rainy season in Malawi resulted in 42 fatalities from various severe weather incidents.
December 26–January 25 — 2022–2023 California floods: A series of atmospheric rivers impacts California, killing 22 people and causing at least 200,000 power outages in the state.
January 1 – A weather station in Abed, Denmark, measured the hottest temperature ever nationwide in the month of January, measuring , breaking the previous record of from January 10, 2005.
December 18, 2022 – February 5, 2023 — A shear line system caused flooding and landslides across the Philippines, killing 97 people with 25 more missing.
January 4 — Heavy rains caused a house to collapse in Matala, Angola, with two people being killed.
January 4–5 — Flooding and landslides in Buvaku, Democratic Republic of the Congo kills five people.
January 6–8 — Flooding and landslides in Indonesia kills five people.
January 10 — Flooding and landslides in Minas Gerais, Brazil kill six people.
January 10–17 — A cold snap in Afghanistan kills at least 166 people and more than 80,000 livestock. The coldest temperature recorded was in the province of Ghor.
January 12 — An early season tornado outbreak causes at least nine deaths in the Southern United States and several tornado emergencies.
January 12 — A lightning strike in HaOgen, Israel kills a person walking their dog.
January 13–16 — Heavy rains in Tijuana, Mexico, cause extreme flooding and a mudslide which killed two people.
January 14 — A flash flood in Medellín, Colombia killed two people and injured 25 others.
January 15 — Fatehpur, Rajasthan records a temperature of from a cold wave.
January 16 – Two EF1 tornadoes touch down in Iowa, the first tornadoes in the state in January since 1967.
January 16 — A landslide in Locroja District, Peru kills three people and leaves three others injured.
January 17 — An avalanche strikes Nyingchi, Tibet, killing 28.
January 18–19 — Flooding and landslides in Brazil kill 3 and leave 2 missing.
January 20 — Cyclone Cheneso leaves 33 dead and 20 missing in Madagascar.
January 27–February 6 — Heavy amounts of rain struck Auckland and the upper North Island in New Zealand causing massive flooding resulting in 4 deaths and 3 injuries
January 31 – Denmark had its wettest January on record, with a measurement of through the month, which beat the in January 2007 that previously held the record.
January 31–February 2 — An ice storm kills 10 people and causes 500,000 power outages across the Southern United States.
February
February 1 – of snow falls in New York City, becoming the latest date for first measurable snow there. Despite the minimal snow, a ground stop was still issued at LaGuardia Airport.
February 2 – Avalanche has buried a tourist near Mały Kościelec in Tatra Mountains, Poland. After a few days the men died.
February 3–4 – A cold wave briefly hit New England and Canada. The wind chill on Mount Washington, New Hampshire, drops to , marking the coldest wind chill ever recorded in the United States. The next day, the temperature of in Boston became the coldest day in the city since 1957.
February 5–7 – In the Mariano Nicolás Valcárcel District, 15 died from landslides that occurred after heavy rains.
February 4 – March 14 – Cyclone Freddy forms in the eastern Indian Ocean and makes landfall in Madagascar and Mozambique, becoming only the fourth storm to cross the entire Indian Ocean. Additionally, it was the longest lasting tropical cyclone on record with a duration of 5 weeks and 3 days, and holds the record for the highest accumulated cyclone energy (ACE) of any tropical cyclone of 87.01. 238 people die in Madagascar and Mozambique and over 1,200 people were killed in Malawi from extreme flooding and mudslides.
February 10 – Widespread record highs were broken across the Eastern United States, ranging from in Saint Johnsbury, Vermont, to in portions of North Carolina.
February 11–15 – Cyclone Gabrielle struck New Zealand particularly in the Gisborne and Hawkes Bay areas leaving 11 people dead while +3 are currently missing. Making it the most destructive cyclone in New Zealand since 1988.
February 16 – Record warm temperatures occur in the Eastern United States. Islip, New York, Bridgeport, Connecticut, Bedford, Massachusetts, and Newport, Rhode Island, all set record highs for the month of February. The record in Newport was broken by 6 °F (4 °C). At LaGuardia Airport, the low of tied for the warmest low on record, while Central Park observed a low of , the second warmest February low on record.
February 18–23 – Floods and mudslides kill at least 65 people across the state of São Paulo in Brazil.
February 21–28 – A major storm complex caused almost a million power outages throughout the United States, with Michigan being the most affected, with an ice storm that left at least one dead in Michigan when a power line fell on a volunteer firefighter.
March
March 1–3 – A storm complex containing both severe thunderstorms and heavy snowfall killed at least 13 people across the United States, including five in Kentucky, three in Alabama, two in Tennessee, one in Arkansas, and one in Mississippi.
March 6 – A landslide in Natuna Regency, Indonesia kills at least 50 people and four others remain missing.
March 7–20 – At least eight people were killed by Cyclone Yaku in Peru and Ecuador.
March 9–10 – Two people were killed and 9,400 were under evacuation orders as continuing atmospheric rivers brought heavy rains and flooding to parts of California.
March 15 – 16 deaths were reported as massive flash floods struck the Turkish provinces of Adiyaman and Sanliurfa, turning streets into rivers. These areas had been particularly hit hard by the past earthquakes.
March 21–22 – 5 died in California from high winds by a bomb cyclone that also caused two tornadoes, including one in Montebello.
March 22–25 – 14 died in the town Baardhere, Jubaland state, Somalia, when flash floods hit the area.
March 24–26 – 26 people were killed in a tornado outbreak in the Southern United States.
March 26 – 11 were killed and 67 were left missing by a landslide caused by heavy rains that occurred in Alausí, Ecuador.
March 31–April 1 – At least 26 people are killed in a tornado outbreak in the United States.
April
April 3 – Casper, Wyoming, saw its snowiest day on record, with of snow falling.
April 5 – An EF2 tornado hits the town of Glen Allen, Missouri, killing five people.
April 12–13 – Heavy rains affected Fort Lauderdale and South Florida, causing significant flooding.
April 14 – A temperature of at Windsor Locks, Connecticut, tied the state record for warmest April temperature. Additionally, a temperature of in Worcester, Massachusetts, became the earliest date for a ninety degree day.
April 19 – Tornadoes struck throughout the U.S. central plains, including a fatal EF3 tornado in Cole, Oklahoma. The outbreak lead to 3 fatalities.
April 21 – A significant tornado struck the Aung Myin Kone and Tadau villages near Myanmar's capital Naypyitaw, killing at least 8 people and injuring at least 128. At least 232 homes were also destroyed by the tornado.
April 22 - Gusty and strong winds in Pennsylvania lead to falling trees that killed 2 people.
April 27 — The hottest April temperature in Europe occurred, with the temperature in Córdoba, Spain at .
April 29 — A microburst in Texas caused “tens of millions of dollars” in damage.
May
May 3 – present — Floods in East Africa, especially in the DRC and Rwanda killed 440 and 129 respectively.
May 9 – Flooding caused a state of emergency in Auckland. 1 person was swept away by floodwaters in the Abbey Caves.
May 14–15 — Cyclone Mocha impacted Myanmar and Bangladesh, killing 438 people in total.
May 15 – Lightning kills one person and injured another in Texas.
May 16 – While in Cyclone Fabien, the Lu Peng Yuan Yu fishing vessel capsizes in the Indian Ocean. 16 of the 39 people on board have been confirmed dead.
May 16 – 17 — 17 people died and ten of thousands were left homeless in devastating floods in the Emilia-Romagna region of northern Italy.
May 18 –- Many daily record lows were set across the Northeastern United States, including Trenton, New Jersey, at , Montpelier, Vermont, at , Lebanon, New Hampshire, at , Bridgeport, Connecticut, at , Providence, Rhode Island, at , and Akron, Ohio, at . A temperature of became the coldest temperature so late in the year in Saranac Lake, New York, while Allentown, Pennsylvania, recorded their third latest freeze on record. This cold snap lead to several damaging frosts and freezes in Upstate New York.
May 19 – June 3 – Typhoon Mawar kills two people in Guam, one person in the Philippines, one person in Taiwan and two people in Japan.
May 23 – Two people were killed in a storm in Texas.
May 28 – A tourist boat sinks on Lake Maggiore in northern Italy, killing four.
May 29 – Shanghai records its hottest ever May temperature, at .
May 29 – Wildfires in Nova Scotia cause 16,000 to evacuate.
May 30 – A landslide in the southwestern Sichuan province, China, kills 19.
June
June 1–2 – Record heat affects portions of the Northeastern United States, with Burlington, Vermont, seeing a high of , the warmest temperature so early in the season there. The next day, daily records were set in Hartford and Philadelphia.
June 1 - Temperatures in Lapland, Finland reached , the coldest June temperature in the country.
June 2–4 – Floods in Haiti cause 51 deaths and injure 140 people. Additionally, over 13,500 homes were flooded and 820 were destroyed.
June 6–19 – Cyclone Biparjoy becomes the longest-lived cyclone in the Arabian Sea and kills 12 people in Gujarat.
June 8–9 – Windstorms and floods in Iran kill seven and leave 59 injured.
June 10 – Heavy rains in northeast Pakistan kills 25 and leaves 145 injured.
June 14–19 – A widespread tornado outbreak sequence leaves five dead and 120 injured
A low-end EF3 tornado damages or destroys nearly 200 homes in Perryton, Texas.
In Jasper County, Mississippi, over a dozen buildings were destroyed and one person was killed by an EF3 tornado.
June 17–18 – Floods and landslides in Nepal kill at least six and leave 28 missing.
June 20 – Two Texas cities broke all-time record high temperatures, with San Angelo reaching and Del Rio reaching . Air conditioning pushed ERCOT power demand to a record 81.2 GW.
June 20–26 – A second widespread tornado outbreak sequence across the United States leaves over 100 injured and eight dead.
An EF3 tornado in Matador, Texas, kills four people and destroys over ten buildings.
An EF2 tornado in Martin and Dubois County, Indiana, leaves one dead and another person injured.
At George Bush Intercontinental Airport, a record gust of was observed, surpassing the airport's previous highest gust of during Hurricane Ike.
June 22 – July 6 – Monsoon rains in Pakistan kill 55 people, including at least eight children.
June 25 – Ten people are killed from lightning strikes in Punjab province, Pakistan.
June 27 – Flash flood induced landslides in the Miansi and Weizhou townships in Sichuan province, China, result in four deaths and three missing people.
June 29 – Authorities in Mexico have said that within the past two weeks, over 100 people have died from heat related deaths as temperatures have came close to .
June 30 – Heavy rain and a tornado in KwaZulu-Natal, South Africa leaves at least seven people dead another seven missing.
July
July 1–7 – The World Meteorological Organization find that the first week of July was the hottest week recorded during an El Niño which was worsened by climate change. The record was broken twice and equaled once in that week.
{| class="wikitable"
! Date !! Average global temperature
|-
| align="right"|Monday, July 3 ||
|-
| align="right"|Tuesday, July 4 ||
|-
| align="right"|Wednesday, July 5 ||
|-
| align="right"|Thursday, July 6 ||
|}
July 3–present – Monsoon rains cause record-breaking and destructive floods in North India, killing over 100.
July 9 – The capital of India, New Delhi, receives its wettest July day in over 40 years, receiving of rain.
July 19 – A landslide in Raigad kills at least 16 people with another 100 feared dead under debris.
July 9–16 – Flash flooding in the Northeastern United States kills at least eight people and leaves two children missing.
July 10 – Torrential rain in southern Japan cause landslides that kill three people.
July 13–18 – Tropical Storm Talim leaves three dead across the Philippines and Southern China.
July 16 - Monsoon flooding in South Korea kill at least 41 people and 9 missing.
July 17 – Torrential rains cause a landslide in Quetame, Colombia leaves 14 dead.
July 18 – Phoenix recorded their warmest ever low temperature on record, at .
July 19 – A severe storm sweeps through the western Balkans, killing five people.
July 19–29 – Typhoon Doksuri causes at least 87 deaths and over $2 billion in damages.
July 27 – The MB Aya Express capsizes in the Philippines, killing 27.
July 27–29 – Record-breaking floods in China result in 30 deaths and $2 billion in damages.
July 22 – Another severe storms hits Serbia killing three.
July 24- Lightning in Upstate New York kills one person.
July 25 – A nighttime storm in Lombardy, Italy leaves four dead.
July 27 – August 11 – Typhoon Khanun kills at least two people in Okinawa.
July 30 – In Mari El, Russia, severe storms leave ten dead at a campsite.
August
August 3–23 – Floods in Carinthia and Slovenia kill seven people.
August 3 – 32 people are killed and one is left missing after a landslide in Shovi, Georgia.
August 4-8 - Severe storms, mainly in the Eastern United States kill two people and result in over a million power outages.
August 11 – Floods in Myanmar kills five.
August 12 – A landslide in Xi'an, China, kills 21 people and leaves six missing.
August 12 – Four people are killed by lightning strikes in separate incidents in Yemen.
August 16–22 – Hurricane Hilary kills two people in Mexico and becomes the first tropical cyclone to bring tropical storm force winds to California since 1997. Additionally, four states in the United States break tropical cyclone rainfall records.
August 20 – September 1 – Hurricane Franklin kills two people and leaves one missing in the Dominican Republic.
August 22 – September 3 – Typhoon Saola kills one person in the Philippines.
August 24–31 – Hurricane Idalia kills nine people in the Eastern United States after landfall in Florida.
August 27 – September 6 – Typhoon Haikui leaves two dead in Taiwan and China.
August 28–30 – Heavy rains in Tajikistan kills 21 people.
August 28 – Severe wind gusts strikes a thermal spa in Podhájska, Slovakia, injuring one person. Wooden booths at the spa were obliterated and swept away, trees were uprooted, and a camper was overturned. Tomas Pucik, a meteorologist and forecaster with the European Severe Storms Laboratory (ESSL) conducted a scientific study on the wind gusts. The study rated the damage caused IF1.5 on the International Fujita scale, with winds estimated between .
September
In September 2023, 20% of the earth's surface experienced new record high temperatures, the highest percentage of any month since the start of records in 1951.
September 2 - Flooding in the Southwestern United States kills one person at the Burning Man festival.
September 6 – A cyclone in Rio Grande do Sul causes floods that kill 21 people.
September 7–8 – The remnants of Typhoon Haikui combined with a low pressure trough cause widespread flooding in Hong Kong, killing four and injuring nearly 150.
September 4–11 – Storm Daniel causes catastrophic flooding across Libya and Southeast Europe, killing near 7,000 people and leaving 10,000 missing. Additionally, flooding in Greece is responsible for $2.14 billion in damages.
September 11 - September 2023 northeastern U.S. floods - The city of Leominster, Massachusetts, declares a state of emergency after rain up to brought unprecidented flash flooding.
September 19 – Three tornadoes, one rated as an EF3 tornado, hits Jiangsu in China. 10 people were killed.
September 21–22 – Flooding hits New Zealand South Island causing a state of emergency in Queenstown and Southland with Queenstown recording its wettest day in 24 years and Wānaka recording its wettest day in 17 years.
September 25 – Floods in Mexico and Guatemala kill 13 people and leave 22 missing.
September 24–25 — Floods in the Western Cape province of South Africa kill at least 11 and leave over 80,000 without electricity.
September 28–30 - New York City declares a state of emergency during major flooding in the city.
October
The month of October was the warmest October ever recorded.
October 4 – Monthly record highs were set in Burlington, Vermont, and Syracuse, New York, with temperatures of and .
October 4–5 – Heavy rains in Sikkim causes the South Lhonak Lake to outburst, killing at least 74 people in Sikkim and West Bengal.
October 6 – Six people are killed from rain-induced mudslides in Sri Lanka.
October 8 – Landslides in Yaoundé, Cameroon leaves 27 dead and left 50 injured.
October 8 – Bush fires in Darling Downs, Australia kills two people.
October 17–23 – Hurricane Norma kills three people in Sinaloa, Mexico.
October 19–27 – Cyclone Lola becomes the earliest Category 5 cyclone in the South Pacific region and kills two in Vanuatu.
October 22–25 – Hurricane Otis makes a devastating landfall near Acapulco, Mexico, as a Category 5, the strongest ever Pacific hurricane at landfall. At least 50 people are killed, with some estimates going up to 350, and $16 billion in damages are done.
October 28 – November 6 – Tropical Storm Pilar leaves two dead in El Salvador.
November
November 19 – Flooding in the Dominican Republic kills 21 people.
November 20 – Flooding in Turkey and Bulgaria kills nine people and leaves eleven crew members on the Kafkametler missing.
November 24-28 - A winter storm in the United States kills 4.
November 27 – A snowstorm in Ukraine and Moldova kills eight people and injures another 29.
December
December 2–18 – Cyclone Jasper becomes the wettest tropical cyclone in Australian history, with of rain falling in Northern Queensland.
December 3 – Flooding and landslides in Tanzania kills 47 people and injures another 85.
December 5 – An atmospheric river in the Pacific Northwest kills one person.
December 9-10 - A tornado outbreak kills 6 people in Tennessee.
December 14 – Over 500 people are injured in a subway collision in Beijing, partially due to slippery tracks in a winter storm.
December 16 – A severe thunderstorm in Bahía Blanca, Argentina kills 13 people.
December 18 – A storm in the Northeastern United States kills four people and causes over 600,000 power outages.
December 26 – 22 people are killed in floods in the Kasaï-Central provence of the Democratic Republic of the Congo.
December 27 – Thunderstorms in Eastern Australia kills 10 people.
December 29 – 20 people are killed in landslides in the South Kivu region of the Democratic Republic of the Congo.
December 30 - Flash flooding in KwaZulu-Natal, South Africa, kills 21.
December 31 - Tropical Storm Alvaro forms west of Madagascar, bringing heavy rain and strong winds to the island, then persisting into 2024.
Space weather
January 9 – An X1.9-class solar flare causes a widespread radio blackout across South and Central America. The active region that produced the solar flare also produced an X1.2-class solar flare on January 5.
December 14 – An X2.8-class solar flare, the largest since September 2017, causes an R2 radio blackout across South and Central America.
December 31 – An X5.0-class solar flare causes an R3 radio blackout over the Pacific.
Events in meteorology
January 9 – Perseverance provides the first ever detailed weather report on Mars.
See also
Weather of 2022
Weather of 2021
Notes
References
Weather by year
Weather-related lists
2023-related lists
2023 meteorology | Weather of 2023 | Physics | 5,171 |
20,000,238 | https://en.wikipedia.org/wiki/Cardboard%20modeling | Cardboard modeling or cardboard engineering is a form of modelling with paper, card stock, paperboard, and corrugated fiberboard. The term cardboard engineering is sometimes used to differentiate from the craft of making decorative cards. It is often referred to as paper modelling although in practice card is generally used.
History
Originally this was a form of modelling undertaken because of the low cost involved. Card, a means of cutting and glue are all that is needed. Some models are 100% card, while others use items of other materials to reinforce the model. After World War II cardboard models were promoted by a number of model companies. One company, ERG (Bournemouth) Ltd. produced a book "Cardboard Rolling Stock and How to Build It" and Superquick are still well known for their range of printed and pre-cut kits.
Books of printed models to cut out and make have been around a long time. Also, specially printed cards were available from which models could be made. In the UK Micromodels were well known for very small card models.
Models to cut out were also a feature of paperboard folding cartons. For many years, breakfast cereal makers had models to cut out on their packets.
The hobby has been revived through the use of ink-jet and laser colour printers, with the availability of inexpensive cutting plotters and laser engravers also reducing the time, effort, and tedium associated with cutting out the many parts. Using a vector graphics package, it is even possible for anyone to create their own models from scratch, though most use special software.
Models to cut out can also be downloaded from the internet.
See also
Net (polyhedron)
Paper model
Architectural model
References
External links
Scale modeling
Paper toys | Cardboard modeling | Physics,Engineering | 345 |
41,461,043 | https://en.wikipedia.org/wiki/Cinnamedrine | Cinnamedrine (, ), also known as N-cinnamylephedrine, is a sympathomimetic drug with similar effects relative to those of ephedrine. It also has some local anesthetic activity. Cinnamedrine was previously used, in combination with analgesics, as an antispasmodic to treat dysmenorrhea in the over-the-counter drug Midol in the 1980s. There is a case series of the drug being abused as a psychostimulant.
See also
Methylephedrine
Etafedrine
References
Abandoned drugs
Antispasmodics
Beta-Hydroxyamphetamines
Local anesthetics
Methamphetamines
Norepinephrine releasing agents
Sympathomimetics | Cinnamedrine | Chemistry | 165 |
30,423,565 | https://en.wikipedia.org/wiki/Nucleosome%20positioning%20region%20database | Nucleosome Positioning Region Database (NPRD) is a database of nucleosome formation sites (NFSs).
See also
References
External links
http://srs6.bionet.nsc.ru/srs6/.
Biological databases
Genetics databases | Nucleosome positioning region database | Biology | 59 |
3,846,760 | https://en.wikipedia.org/wiki/Tagish%20Lake%20%28meteorite%29 | The Tagish Lake meteorite fell at 16:43 UTC on 18 January 2000 in the Tagish Lake area in northwestern British Columbia, Canada.
History
Fragments of the Tagish Lake meteorite landed upon the Earth on January 18, 2000, at 16:43 UT (08:43 local time in Yukon) after a large meteoroid exploded in the upper atmosphere at altitudes of with an estimated total energy release of about 1.7 kilotons of TNT. Following the reported sighting of a fireball in southern Yukon and northern British Columbia, Canada, more than 500 fragments of the meteorite were collected from the lake's frozen surface. Post-event atmospheric photographs of the trail left by the associated fireball and U.S. Department of Defense satellite information yielded the meteor trajectory. Most of the stony, carbonaceous fragments landed on the Taku Arm of the lake, coming to rest on the lake's frozen surface. The passage of the fireball and the high-altitude explosion set off a wide array of satellite sensors as well as seismographs.
The local inhabitants described the smell in the air following the airburst as sulfurous and many first thought the blast was caused by a missile.
Meteoroid
The Tagish Lake meteoroid is estimated to have been 4 meters in diameter and 56 tonnes in weight before it entered the Earth's atmosphere. However, it is estimated that only 1.3 tonnes remained after ablation in the upper atmosphere and several fragmentation events, meaning that around 97% of the meteorite had vaporised, mainly becoming stratospheric dust that was seen as noctilucent clouds to the northwest of Edmonton at sunset, some 12 hours after the event. Of the 1.3 tonnes of fragmented rock, somewhat over (about 1%) was found and collected.
Specimens
Tagish Lake is classified as a carbonaceous chondrite, type C2 ungrouped. The pieces of the Tagish Lake meteorite are dark grey to almost black in color with small light-colored inclusions, and a maximum size of ~2.3 kg. Except for a greyish fusion crust, the meteorites have the visual appearance of a charcoal briquette. The fragments were transported in their frozen state to research facilities after they were collected by a local resident in late January, 2000. Initial studies of these fresh fragments were done in collaboration with researchers from NASA. Snowfall covered the remaining fragments until April 2000, when a search effort was mounted by researchers from the University of Calgary and University of Western Ontario. These later fragments were mostly found to have sunk into the ice by a few cm to more than 20 cm, and had to be collected out of meltwater holes, or cut in icy blocks from the frozen surface of Tagish Lake.
Fragments of the fresh, "pristine" Tagish Lake meteorite totaling more than 850 g are currently held in the collections at the Royal Ontario Museum and the University of Alberta. "Degraded" fragments from the April–May 2000 search are curated mainly at the University of Calgary and the University of Western Ontario.
Analysis and classification
Analyses have shown that Tagish Lake fragments are of a primitive type, containing unchanged stellar dust granules that may have been part of the cloud of material that created the Solar System and Sun. This meteorite shows some similarities to the two most primitive carbonaceous chondrite types, the CI and CM chondrites; it is nevertheless quite distinct from either of them. Tagish Lake has a much lower density than any other type of chondrite and is actually composed of two somewhat different rock types. The major difference between the two lithologies is in the abundance of carbonate minerals; one is poor in carbonates and the other is rich in them.
The meteorite contains an abundance of organic materials, including amino acids. The organics in the meteorite may have originally formed in the interstellar medium and/or the solar protoplanetary disk, but were subsequently modified in the meteorites' asteroidal parent bodies.
A portion of the carbon in the Tagish Lake meteorite is contained in what are called nanodiamonds—very tiny diamond grains at most only a few micrometers in size. In fact, Tagish Lake contains more of the nanodiamonds than any other meteorite.
As with many carbonaceous chondrites, and Type 2 specimens in particular, Tagish Lake contains water. The meteorite contains water-bearing serpentinite and saponite phyllosilicates; gypsum has been found, but may be weathering of meteoritic sulfides. The water is not Earthly contamination but isotopically different from terrestrial water.
The age of the meteorite is estimated to be about 4.55 billion years thus being a remainder of the period when the solar system was formed.
Origin
Based on eyewitness accounts of the fireball caused by the incoming meteor and on the calibrated photographs of the track which it had left behind and which was visible for about half an hour, scientists have managed to calculate the orbit it followed before it impacted with Earth. Although none of the photographs captured the fireball directly, the fireball path was reconstructed from two calibrated photos taken minutes after the event, giving the entry angle. Eyewitness accounts in the vicinity of Whitehorse, Yukon accurately constrained the ground track azimuth from either side. It was found that the Tagish Lake meteorite had a pre-entry Apollo type orbit that brought it from the outer reaches of the asteroid belt. Currently, there are only eleven meteorite falls with accurately determined pre-entry orbits, based on photographs or video recordings of the fireballs themselves taken from two or more different angles.
Further study of the reflectance spectrum of the meteorite indicate that it most likely originated from 773 Irmintraud, a D-type asteroid.
Comparisons
The double, and not the expected single, plume formation of debris, as seen in video and photographs of the 2013 Chelyabinsk meteor dust trail and believed by Peter Brown to have coincided near the primary airburst location, was also pictured following the Tagish Lake fireball, and according to Brown, likely indicates where rising air quickly flowed into the center of the trail, essentially in the same manner as a moving 3D version of a mushroom cloud.
See also
Glossary of meteoritics
773 Irmintraud, the asteroid that the Tagish Lake meteorite most likely came from.
References
Universe: The Definitive Visual Dictionary, Robert Dinwiddie, DK Adult Publishing, (2005), pg. 222.
Mittlefehldt, D.W., (2002), Geochemistry of the ungrouped carbonaceous chondrite Tagish Lake, the anomalous CM chondrite Bells, and comparison with CI and CM chondrites, Meteoritics and Planetary Science 37: 703–712. See summary of the article.
External links
Evidence of sodium rich alkaline water in the Tagish Lake parent body and implications for amino acid synthesis and racemization
Tagish Lake meteorite contains clues as to how life may have arisen on Earth
Tagish Lake meteorite may have held early forms of life, believe scientists
Ancient rock star finds a home at the University of Alberta
Researchers' website
The Geological Society; Article/Analysis
Brief Abstract
Tagish Lake meteorite specimen pictures
Meteorites found in Canada
Planetary science
Geography of British Columbia
Geography of Yukon
Natural history of British Columbia
Natural history of Yukon
2000 in British Columbia
2000 in science
Collection of the Royal Ontario Museum | Tagish Lake (meteorite) | Astronomy | 1,533 |
39,784,158 | https://en.wikipedia.org/wiki/Wood%20stabilization | Wood stabilization is a series of processes which use pressure and/or vacuum to impregnate wood cellular structure with certain monomers, acrylics, phenolics or other resins to improve dimensional stability, biological durability, hardness, and other material properties. When exposed to moisture through humidity absorption or direct immersion, most wood species will swell and change shape. When moisture comes into contact with wood, the water molecules penetrate the cell wall and become bound to cell wall components through hydrogen bonding. With addition of water to the cell wall, wood volume increases nearly proportionally to the volume of water added. Swelling increases until the fiber saturation point has been reached. Wood stabilization limits water absorption into the wood structure, thereby limiting the dimensional changes which arise from moisture exposure.
Wood stabilization is a subset of wood preservation processes specifically used by woodworking enthusiasts to alter the material properties of specific wood species for applications within their craft or trade. Examples of wood items which are commonly stabilized include knife handles, pistol grips, straight razors, game calls and jewelry. One of the most commonly used stabilizing methods utilizes a heat cured polymer known as methyl methacrylate (MMA).
Material properties
Material properties of stabilized wood varies by specific species and type of stabilization process used, however in softwoods and soft hardwoods, the improvement in strength, hardness and durability can be dramatic. For example, Poplar treated with MMA increased specimen density by 2.2 to 2.6 times with gains in hardness of approximately twofold (using the Janka Hardness Test).
References
Wood
Structural engineering
Woodworking techniques | Wood stabilization | Engineering | 327 |
554,661 | https://en.wikipedia.org/wiki/Finnish%20numerals | Numbers in Finnish are highly systematic, but can be irregular.
Cardinal numbers
The ordinary counting numbers (cardinals) from 0 to 10 are given in the table below. Cardinal numbers may be inflected and some of the inflected forms are irregular in form.
Note: in parentheses, alternative form for counting, and colloquial. The dialectic-colloquial forms may leave the d off and sometimes also the genitive ending n: ; ; ; ; ; . (Corresponding the formal and ordinary counting in Estonian.)
Teens and multiples of ten
To form teens, is added to the base number. is the partitive form of , meaning "second group of ten". Hyphens are written here to separate morphemes. In Finnish text, hyphens are not written.
, , …
one-second., two-second., … nine-second.
"one of the second, two of the second, … nine of the second"
11, 12, … 19
In older Finnish, all numbers were constructed like this. This usage is now considered archaic and the suffix is treated as a particle instead of meaning "of the second".
, , , …
two-ten., one-third., two-third., … nine-third.
"two tens, one of the third, two of the third, … nine of the third"
20, 21, 22, … 29
,
one-fourth., one-fifth.
"one of the fourth, one of the fifth"
31, 41
Even older forms included at the end, giving for example "one of the second decade" for 11 and "five of the third decade" for 25.
The numbers for tens (20, 30, up to 90) are constructed this way:
, , , …
two-ten., three-ten., four-ten., … nine-ten.
"two tens, three tens, four tens, … nine tens"
20, 30, 40, 90
In modern Finnish, the numbers 21–29, 31–39, and so on are constructed as in English:
, ,
two-ten. one, two-ten. two, two-ten. three
"two tens one, two tens two, two tens three"
21, 22, 23
Hundreds
100 is , 200 is and so on.
1000 is , 2000 is and so on.
So, 3721 is (actually written as one long word with no dashes in between).
Years
In older Finnish, years were expressed by counting centuries. Use of this convention is archaic. For instance, "1922", instead of the modern .
Long numbers (like 32534756) are separated in three-digit sections with spaces beginning from the end of the number (for example 32 534 756). Writing it with letters follows the same spacing, with one additional rule: in numbers over one million, "million" is written separately. The preceding example is written . (No dashes. They are only to make the number look clear.)
Inflection
Numbers can be inflected by case; all parts of the number except are inflected.
Nouns following a number in the nominative singular are usually in the singular partitive case, if the noun does not need to be in any other case and if the number is any number other than "one".
If the number is "one" and it is in the nominative singular then the noun and any adjectives following it will also be in the singular nominative.
But if the noun is in a case besides the nominative, the number and any adjectives following it will be in the same case. For example:
Sets
Numerals also have plural forms, which usually refer to things naturally occurring in pairs or other similarly well-defined sets, such as body parts and clothing items. Also names of celebrations are usually in the plural. The plural forms are inflected in cases in the same way as the corresponding nouns. For instance:
Etymology
Numbers from one to seven are apparently original in etymology. The words "eight" and "nine" have no confirmed etymology. The old theory is that they are compounds: * "10–2", or "eight" and * "10–1", or "nine", where the reconstructed word is similar to the Indo-European words for "ten" (*dek´m), but this is phonologically not plausible. Alternatively, they could be * and "itself, without two" and "without one", where is a form of "no" inflected with the Karelian reflexive conjugation ("itself, without two").
Ordinal numbers
These are the 'ordering' form of the numbers: "first, second, third", and so on. Ordinal numbers are generally formed by adding an -s ending, but first and second are completely different, and for the others the stems are not straightforward:
For teens, the first part of the word is changed; however, the words for "first" and "second" lose their irregularity in "eleven" and "twelve":
For twenty through ninety-nine, all parts of the number get the '-s' ending. 'First' and 'second' take the irregular form only at the end of a word. The regular forms are possible for them but they are less common.
100th is , 1000th is , 3721st is . Again, dashes only included here for clarity; the word is properly spelled without them.
Like cardinals, ordinal numbers can also be inflected:
The in the 'teens' is actually the partitive of , which is why gets no further inflection endings. (Literally || one-of-the-second'.)
Long ordinal numbers in Finnish are typed in almost the same way as the long cardinal numbers. 32534756 would be (in numbers over one million, "million" is written separately) . (Still, no dashes.)
Names of numbers
This is a feature of Finnish which does not have an exact counterpart in English (with the curious exceptions of calling a five-dollar bill a fiver and 9 niner in radio communication), but there is a counterpart in colloquial German, for example: 7er, 190er, 205er. These forms are used to refer to the actual number itself, rather than the quantity or order which the number represents. This should be clearer from the examples below, but first here is the list:
Also, refers to the shape of the number. Some examples of how these are used:
The 'number three tram' is the — when you are riding it, you are riding with
A magazine has the title 7 and is called
My car, a '93 model, is an when buying spare parts
If the car is a 190E Mercedes, it would be a .
If a car has tires in size of 205, they would be called ( a set of-)"two hundred fives" or ( a number of-)"two hundred fives". Also ( a set of-)"two zero fives" or ( a number of-)"two zero fives".
The 106 bus is the
A 5€ bill may be called , a 10€ bill (in plural: /), a 20€ , a 100€ bill , etc.
Numbers in the spoken language
In spoken Finnish the final i in , as well as the final a in the numbers 11-19, is frequently dropped. Other short forms can be heard for the tens, where the element can be heard as "kyt": shortened words like (30), (40), (50), (60), (70), (80), (90) are not uncommon. When counting a list of items a kind of spoken shorthand can be heard. Thus, may become or even , but the forms can vary from person to person.
References
Fred Karlsson (2008), "Finnish: An Essential Grammar", Routledge, . Chapter 12, "Numerals".
Clemens Niemi (1945), "Finnish Grammar", third edition, Työmies Society, Superior, Wisconsin. Lessons XXVI "Cardinal Numbers" and XXVII "Ordinal Numbers". Reprinted with author given as "Niemla. M. Clemenns" , The Stewart Press, London (2008), .
Numerals
Numerals | Finnish numerals | Mathematics | 1,751 |
31,490,462 | https://en.wikipedia.org/wiki/Database%20of%20protein%20conformational%20diversity | The Database of protein conformational diversity (PCDB) is a database of diversity of protein tertiary structures within protein domains as determined by X-ray crystallography. Proteins are inherently flexible and this database collects information on this subject for use in molecular research. It uses the CATH database as a source of structures for each protein and reports the range of differences in the structures based on their superposition and reports a maximum RMSD. The interface for the database allows researchers to find proteins with a range of conformational flexibility allowing them to find highly flexible proteins for example. The database is run and maintained by a group of researchers based at the Universidad Nacional de Quilmes in Argentina.
See also
Crystallography
Protein structure
References
External links
Protein databases
Protein structure
Crystallographic databases | Database of protein conformational diversity | Chemistry,Materials_science | 158 |
3,480,657 | https://en.wikipedia.org/wiki/Design%20flow%20%28EDA%29 | Design flows are the explicit combination of electronic design automation tools to accomplish the design of an integrated circuit. Moore's law has driven the entire IC implementation RTL to GDSII design flows from one which uses primarily stand-alone synthesis, placement, and routing algorithms to an integrated construction and analysis flows for design closure. The challenges of rising interconnect delay led to a new way of thinking about and integrating design closure tools.
The RTL to GDSII flow underwent significant changes from 1980 through 2005. The continued scaling of CMOS technologies significantly changed the objectives of the various design steps. The lack of good predictors for delay has led to significant changes in recent design flows. New scaling challenges such as leakage power,
variability, and reliability will continue to require significant changes to the design closure process in the future. Many factors describe what drove the design flow from a set of separate design steps to a fully integrated approach, and what further changes are coming to address the latest challenges. In his keynote at the 40th Design Automation Conference entitled The Tides of EDA, Alberto Sangiovanni-Vincentelli distinguished three periods of EDA:
The Age of Invention: During the invention era, routing, placement, static timing analysis and logic synthesis were invented.
The Age of Implementation: In the age of implementation, these steps were drastically improved by designing sophisticated data structures and advanced algorithms. This allowed the tools in each of these design steps to keep pace with the rapidly increasing design sizes. However, due to the lack of good predictive cost functions, it became impossible to execute a design flow by a set of discrete steps, no matter how efficiently each of the steps was implemented.
The Age of Integration: This led to the age of integration where most of the design steps are performed in an integrated environment, driven by a set of incremental cost analyzers.
There are differences between the steps and methods of the design flow for analog and digital integrated circuits. Nonetheless, a typical VLSI design flow consists of various steps like design conceptualization, chip optimization, logical/physical implementation, and design validation and verification.
See also
Floorplan (microelectronics), creates the physical infrastructure into which the design is placed and routed
Placement (EDA), an essential step in Electronic Design Automation (EDA)
Routing (EDA), a crucial step in the design of integrated circuits
Power optimization (EDA), the use of EDA tools to optimize (reduce) the power consumption of a digital design, while preserving its functionality
Post-silicon validation, the final step in the EDA design flow
References
Electronic Design Automation For Integrated Circuits Handbook, by Lavagno, Martin, and Scheffer, – A survey of the field, from which this summary was derived, with permission.
Digital electronics
Electronic design automation
Electronics optimization | Design flow (EDA) | Engineering | 574 |
24,268,588 | https://en.wikipedia.org/wiki/KP-1461 | KP-161 is an experimental antiviral drug being studied for the treatment of HIV/AIDS. It belongs to the class of nucleoside reverse transcriptase inhibitors.
KP-1461 is a prodrug of the active antiviral agent KP-1212.
References
Reverse transcriptase inhibitors
Experimental drugs
Prodrugs | KP-1461 | Chemistry | 72 |
2,407,422 | https://en.wikipedia.org/wiki/Anta%20%28architecture%29 | An anta (pl. antæ, antae, or antas; Latin, possibly from ante, "before" or "in front of"), or sometimes parastas (pl. parastades), is a term in classical architecture describing the posts or pillars on either side of a doorway or entrance of a Greek temple – the slightly projecting piers which terminate the side walls (of the naos).
Antae are formed either by thickening the walls or by attaching a separate strip and can serve to reinforce brick walls, as in the Heraeum of Olympia (c. 600 BCE).
Antae differ from the pilaster, which is purely decorative, and does not have the structural support function of the anta.
Anta
In contrast to columns or pillars, antae are directly connected with the walls of a temple. They owe their origin to the vertical posts of timber employed in the early, more primitive palaces or temples of Greece, as at Tiryns and in the Temple of Hera at Olympia. They were used as load-bearing structures to carry the roof timbers, as no reliance could be placed on walls built with unburnt brick or in rubble masonry with clay mortar. Later, they became more decorative as the materials used for wall construction became sufficient to support the structure.
When there are columns between antae, as in a porch facade, rather than a solid wall, the columns are said to be in antis.
Anta capitals
The anta is generally crowned by a stone block designed to spread the load from superstructure (entablature) it supports, called an "anta capital" when it is structural, or sometimes "pilaster capital" if it is only decorative as often during the Roman period. In order not to protrude unduly from the wall, these anta capitals usually display a rather flat surface, so that the capital has more or less a brick-shaped structure overall. The anta capital can be more or less decorated depending on the artistic order it belongs to, with designs, at least in ancient Greek architecture, often quite different from the design of the column capitals it stands next to. This difference disappeared with Roman times, when anta or pilaster capitals have design very similar to those of the column capitals.
Distyle in antis
Early Greek temples, the "distyle temples", such as the 6th century BCE Siphnian Treasury had antae on both side of the porch, framing a set of columns (a disposition named "distyle in antis", meaning "two columns in between antae"). "Antae temple" is an alternative term.
See also
Distyle
Notes
References
Attribution:
Architectural elements
Ancient Greek architecture | Anta (architecture) | Technology,Engineering | 565 |
63,557,748 | https://en.wikipedia.org/wiki/NGC%203302 | NGC 3302 is an unbarred lenticular galaxy in the constellation Antlia. It was discovered by the astronomer John Herschel on January 28, 1835.
References
Antlia
3302
Unbarred lenticular galaxies
031391 | NGC 3302 | Astronomy | 49 |
8,203,685 | https://en.wikipedia.org/wiki/Bridge%20locus | In neuroscience the bridge locus for a particular sensory percept is a hypothetical set of neurons whose activity is the basis of that sensory percept. The term was introduced by D.N. Teller and E.Y. Pugh Jr. in 1983, and has been sparingly used. Activity in the bridge locus neurons is postulated to be necessary and sufficient for sensory perception: if the bridge locus neurons are not active, then the sensory perception does not occur, regardless of the actual sensory input. Conversely if the bridge locus neurons are active, then sensory perception occurs, regardless of the actual sensory input. It is the highest neural level of a sensory perception. So, for example, retinal neurons are not considered a bridge locus for visual perception because stimulating visual cortex can give rise to visual percepts.
Not all scholars believe in such a neural correlate of consciousness. Pessoa et al., for example, argue that there is no necessity for a bridge locus, basing their argument on the requirement of an isomorphism between neural states and conscious states. Thompson argues that there are good reasons to think that the notion of a bridge locus, which he calls a "localizationist approach", is misguided, questioning the premise that there has to be one particular neural stage whose activity forms the immediate substrate of perception. He argues, based upon work by Zeki & Shipp, DeYoe & Van Essen, and others, that brain regions are not independent stages or modules but have dense forward and backward projections that act reciprocally, and that visual processing is highly interactive and context-dependent. He also argues that cells in the visual cortex "are not mere 'feature detectors, and that neuroscience has revealed that the brain in fact employs distributed networks, rather than centralized representations. He equates the notion of a bridge locus to a Cartesian theatre and suggests that as a notion it should be abandoned.
References
Further reading
Cognitive neuroscience
Neuroscience
Cognition
Consciousness | Bridge locus | Biology | 400 |
39,682,392 | https://en.wikipedia.org/wiki/Material%20flow%20cost%20accounting | Material flow cost accounting (MFCA) is a management tool that assists organizations in better understanding the potential environmental and financial consequences of their material and energy practices and seeks to improve them via changes in those practices. It does so by assessing the physical material flows in a company or a supply chain and assign adequate associated costs to these flows.
History
The method was developed in Germany in the 1980s and is related to approaches such as eco balances, flow cost accounting and "Reststoffkostenrechnung".
The method became a huge success in Japan in the 2000s. By the year 2010 up to 300 companies had applied the MFCA approach, which was highly supported by the Japanese government.
In 2011 the International Organization for Standardization (ISO) published a norm on MFCA (i.e. EN ISO 14051:2011). In 2020 an analysis of 73 case studies was made about the experiences companies have made when applying MFCA including success factors and obstacles.
Objective and principles
The aim of MFCA is to enhance both environmental and economic performance through improved material and energy use. Since 2011 a general framework for MFCA has been provided by the ISO 14051 norm. In order to improve material and energy efficiency MFCA aims to:
Increasing transparency regarding material and energy flows and the respective costs
Supporting organizational decisions in areas such as process engineering, production planning, quality control, product design and supply chain management
Improving coordination and communication on material and energy use within organizations.
See also
Business process reengineering
Sustainable design
References
Environmental economics
ISO standards | Material flow cost accounting | Environmental_science | 317 |
57,052,173 | https://en.wikipedia.org/wiki/Radiation-induced%20lumbar%20plexopathy | Radiation-induced lumbar plexopathy (RILP) or radiation-induced lumbosacral plexopathy (RILSP) is nerve damage in the pelvis and lower spine area caused by therapeutic radiation treatments. RILP is a rare side effect of external beam radiation therapy and both interstitial and intracavity brachytherapy radiation implants. RILP is a Pelvic Radiation Disease symptom.
In general terms, such nerve damage may present in stages, earlier as demyelination and later as complications of chronic radiation fibrosis. RILP occurs as a result of radiation therapy administered to treat lymphoma or cancers within the abdomen or pelvic area such as cervical, ovarian, bladder, kidney, pancreatic, prostate, testicular, colorectal, colon, rectal or anal cancer. The lumbosacral plexus area is radiosensitive and radiation plexopathy can occur after exposure to mean or maximum radiation levels of 50-60 Gray with a significant rate difference noted within that range.
Signs and symptoms
Lumbosacral plexopathy is characterized by any of the following symptoms; usually bi-lateral and symmetrical, though unilateral is known.
Lower limb dysaesthesia, abnormal sensations of touch or feeling
Lower limb weakness
Lower limb numbness
Lower limb paresthesia, e.g., foot drop, muscle atrophy
Lower limb pain
Symptoms are typically a step-wise progression with periods of stability in between, weakness often appearing years later. Weakness frequently presents in the lower leg muscle groups. Symptoms are usually irreversible.
Initial onset of symptoms may occur as early as 2 to 3 months after radiotherapy. The median onset is approximately 5 years, but can be highly variable, 2-3 decades after radiation therapy. One case study recorded the initial onset occurring 36 years post treatment.
Cause
The treatment's ionizing radiation is an activation mechanism for apoptosis (cell death) within the targeted cancer, but it can also impact nearby healthy radiosensitive tissues, like the lumbosacral plexus. The occurrence and severity of RILP is related to the magnitude of ionizing radiation and the radiosensitivity of peripheral nerves may be further aggravated when combined with chemotherapy, like taxanes and platinum drugs, during treatment.
Pathophysiology
The pathophysiological process behind radiation's RILP nerve damage has been discussed since the 1960s and is still without a precise definition. Consensus does exist on a progression of RILP symptoms, with a stepping (a time delay) between two periods of plexopathy onset, the first from radiation injury and the later from fibrosis. Proposed mechanisms of the early nerve damage include microvascular damage (ischemia) supplying the myelin, radiation damage of the myelin, and oxygen free radical cell damage. The delayed nerve damage is attributed to compression neuropathy and a late fibro-atrophic ischemia from retractile fibrosis.
Diagnosis
The more common source of lumbar plexopathy is a direct or secondary tumor involvement of the plexus with MRI being the typical confirmation tool. Tumors typically present with enhancement of nerve roots and T2-weighted hyperintensity. The differential consideration of RILP requires taking a medical history and neurologic examination.
RILP's neurological symptoms can mimic other nerve disorders. People may present with pure lower motor neuron syndrome, a symptom of amyotrophic lateral sclerosis (ALS). RILP may also be misdiagnosed as leptomeningeal metastasis often showing nodular MRI enhancement of the cauda equina nerve roots or having increased CSF protein content.
Other differential diagnoses to consider are Chronic Inflammatory Demyelinating Polyradiculoneuropathy, neoplastic lumbosacral plexopathy, paraneoplastic neuronopathy, diabetic lumbosacral plexopathy, degenerative disk disease (osteoporosis of the spine), Osteoarthritis of the spine, Lumbar Spinal Stenosis, post-infectious plexopathy, carcinomatous meningitis (CM), mononeuritis multiplex, and chemotherapy-induced plexopathy.
The testing to resolve a RILP diagnosis involves blood serum analysis, X-rays, EMG, MRI and cerebrospinal fluid analysis.
Prevention
Since RILP's neurological changes are typically irreversible and a curative strategy has yet to be defined, prevention is the best approach. Treating the primary cancer remains an obvious requirement, but lower levels of lumbar plexus radiation dosing will minimize or eliminate RILP.
One method to reduce the lumbosacral plexus' dosing is to include it with other at-risk organs that get spared from radiation.
Key to prevention is resolving the lack of clinical evidence between radiation treatments and the onset of neurological problems. That relationship is hidden by RILP's low toxicity rate, the lack of a large monitored population size and the lack of data pooling across multiple institutions.
Management
Treatment of RILP is primarily supportive with mental, physiological and social aspects and consideration of any aggravating (synergistic) neurological factors.
To prevent compounding existing RILP symptoms and to minimize further progression
Remove co-morbidity factors
control diabetes and hypertension
avoid excessive alcohol use
avoiding any local trauma in the irradiated volume
controlling acute edema
control acute inflammation. Pharmaceuticals that may be effective are corticosteroids (Dexamethasone)
avoid stretching a plexus immobilized by fibrosis, e.g., carrying heavy loads or extensive movements, which may cause sudden neurological decompensation.
The effect on the person with the condition, depends upon the type of impairment. Handicaps may include physical challenges, bowel and/or bladder dysfunction and may occur in multiple settings of work and home. Physical and occupational therapy are important elements in maintaining mobility and use of the lower extremities, along with assistive aides such as Ankle-Foot-Orthotics (AFOs), cane, walkers, etc. Sensory reeducation techniques may be necessary for balance and lymphedema management may be required.
Pharmaceuticals that may be effective for RILP's neuropathic pain are
tricyclic antidepressants (TCAs) (amitriptyline)
Antiepileptics or anticonvulsants (gabapentin, pregabalin, carbamazepine, valproic acid)
Selective serotonin re-uptake inhibitors(SSRIs) (duloxetine) to preserve normal norepinephrine and serotonin levels
Analgesic drugs (pregabalin, methadone)
Opiates may used singularly or to potentate the concomitant use of TCAs.
Antiarrhythmics (mexilitine) for muscle stiffness
Non-pharmaceutical RILP considerations are
acupuncture for pain
massage for pain
transcutaneous electrical nerve stimulation (TENS) for pain
Benzodiazepines may be used for paraesthesia
quinine may be used for cramps
Functional impairment and residual pain can lead to social isolation. Cancer support groups are valuable resources to learn about the syndrome and therapeutic options, and are a means to voice emotions related to having cancer and surviving it.
Outcomes
With increasing cancer treatment survival rates, the quality of life for its survivors has become a public health priority. The effects of RILP can be debilitating. With no effective treatment to control radiation damage's progressive nature, limb dysfunction is the likely result.
Radiation damage's outcome is related to its initial onset time.
Acute symptoms, occurring in the first few days, have the most favorable outcomes, likely diminishing within a few weeks.
Early-delayed symptoms, occurring within the first months, typically include myelopathy. These issues frequently resolve without treatment.
Late-delayed symptoms, occurring several months or years after treatment, may also include myelopathy, but its severity level is more likely to worsen, resulting in permanent paralysis. Significant neurologic morbidity is typical, with a very slow neurologic recovery.
Epidemiology
An exact occurrence rate has not been established. Literature on the topic is sparse. Clinical occurrences of RILP are rare, affecting between 0.3 and 1.3% of those treated with abdominal or pelvic radiation. The incidence rate is variable, dependent upon the irradiated zone, dosage level and method of delivery. For example, when alternate dosing levels were compared, higher rates were observed, from 12 to 23%, the higher RILP rates occurring with higher dosages.
History
As of 1977 lumbosacral neuropathy arising from radiation therapy had been rarely reported. One of the earliest cases was in 1948.
The incidence rate of peripheral neuropathy has been demonstrated to decrease when lower therapeutic radiation dosing levels are used. A similar nerve injury, Radiation-induced Brachial Plexopathy (RIBP), may occur secondary to breast radiation therapy. Studies on RIBP have observed the brachial plexus' radiosensitivity. Injury was observed after dosages of 40 Gy in 20 fractions and RIBP significantly increased with doses greater than 2 Gy per fraction. RIBP is more common than lumbosacral radiculoplexopathy and has a clinical history with reduced dosing levels. RIBP occurrence rates were in the 60% range in the 1960s when 60 Gray treatments were applied in 5 Gray fractions; RIBP occurrences in the 2010s approach 1% with 50 Gray treatments applied in 3 Gy fractions.
RILP occurrence rates are estimated at 0.3% to 1.3%, though the actual rate is likely higher. The soft tissue damage leading to RILP is more commonly seen with exposure levels over 50 Gy, though has occurred with as little as 30 Gy. A major step toward reducing RILP occurrences is by limiting the lumbosacral plexus' dosing level when treating pelvic malignancies, limiting the mean dose to < 45 Gy. One approach to reduced levels, the plexus' mapping with other organs at risk, was clinically evaluated during the 2010s.
Clinical evidence of the cause-and-effect for prevention and the management of radiation induced polyneuropathy is limited.
In 2011 the Radiation Oncology Institute (ROI) announced the National Radiation Oncology Registry (NROR). ROI and Massachusetts General Hospital would initially focus the NROR on prostate cancer, collecting efficacy and side effect information (like radiation induced neuropathy, RILP) from people treated with radiotherapy. In 2013 the American Society for Radiation Oncology (ASTRO) joined the effort and the number of data collection sites increased to 30 for a 1-year pilot project. Pitfalls of medical data collection arose with only 14 sites being able to provide data and all those requiring significant manual entry efforts. The first NROR project conclusion was that future registries would need to cope with Big data analytics. In 2015 ASTRO, the National Cancer Institute and the American Association of Physicists in Medicine sponsored a Big Data Workshop at the National Institutes of Health.
Research
Experimental approaches for RILP treatment and management include:
Hyperbaric oxygen (HBO) has had mixed results restoring nerve function, some studies showing benefit, others without.
Anticoagulant therapy (warfin, heparin) has been tried for ischemia and capillary restoration, some without clear benefit, others with improved motor function.
PENTOCLO therapy- a combination of Pentoxifylline (PTX), vitamin E and clodronate, a bisphosphanate; the PTX for inflammation, vitamin E as a scavenger for oxygen free radicals that can lead to fibrosis and clodronate which may inhibit myelin nerve destruction.
Myofascial release may reduce compressive effects of fibrouses, freeing trapped nerves.
Mobilization of injured limbs via exoskeletal systems or hybrid assistive devices can provide the mobility lost to nerve damage, offering a workaround until new medical therapies e.g. tissue engineering can repair peripheral nerve injury.
See also
Radiation poisoning
Radiation therapy
ICD-10-CM World Health Organization's Code G62.82: Radiation-induced polyneuropathy
ICD-11-MMS (2018 version) World Health Organization's Code 8B92.0: Post radiation lumbosacral plexopathy
References
Peripheral nervous system disorders
Radiation health effects
Radiation therapy | Radiation-induced lumbar plexopathy | Chemistry,Materials_science | 2,638 |
1,216,778 | https://en.wikipedia.org/wiki/Ernest%20Nagel | Ernest Nagel (November 16, 1901 – September 20, 1985) was an American philosopher of science. Along with Rudolf Carnap, Hans Reichenbach, and Carl Hempel, he is sometimes seen as one of the major figures of the logical positivist movement. His 1961 book The Structure of Science is considered a foundational work in the logic of scientific explanation.
Life and career
Nagel was born in Nové Mesto nad Váhom (now in Slovakia, then Vágújhely and part of the Austro-Hungarian Empire) to Jewish parents. His mother, Frida Weiss, was from the nearby town of Vrbové (or Verbo).
He emigrated to the United States at the age of 10 and became a U.S. citizen in 1919. He received a BSc from the City College of New York in 1923, and earned his PhD from Columbia University in 1931, with a dissertation on the concept of measurement.
Through the award of a Guggeheim Fellowship he was able to spend a year in Europe (from August 1934 to July 1935) to learn about the new trends in philosophy on the continent.
Except for one year (1966-1967) at Rockefeller University, Nagel spent his entire academic career at Columbia. He became the first John Dewey Professor of Philosophy there in 1955. And then University Professor from 1967 until his retirement in 1970, after which he continued to teach. In 1977, he was one of the few philosophers elected to the National Academy of Sciences.
His work concerned the philosophy of mathematical fields such as geometry and probability, quantum mechanics, and the status of reductive and inductive theories of science. His book The Structure of Science (1961) practically inaugurated the field of analytic philosophy of science. He expounded the different kinds of explanation in different fields, and was sceptical about attempts to unify the nature of scientific laws or explanations. He was the first to propose that by positing analytic equivalencies (or "bridge laws") between the terms of different sciences, one could eliminate all ontological commitments except those required by the most basic science. He also upheld the view that social sciences are scientific, and should adopt the same standards as natural sciences.
Nagel wrote An Introduction to Logic and the Scientific Method with Morris Raphael Cohen, his CCNY teacher in 1934. In 1958, he published with James R. Newman Gödel's proof, a short book explicating Gödel's incompleteness theorems to those not well trained in mathematical logic. He edited the Journal of Philosophy (1939–1956) and the Journal of Symbolic Logic (1940-1946).
As a public intellectual, he supported a skeptical approach to claims of the paranormal, becoming one of the first sponsors and fellows of the Committee for Skeptical Inquiry in 1976, along with 24 other notable philosophers like W. V. Quine. The committee posthumously inducted him into their "Pantheon of Skeptics" in recognition of Nagel's contributions to the cause of scientific skepticism. Nagel was an atheist.
Nagel was an elected member of the American Philosophical Society (1962) and the American Academy of Arts and Sciences (1981).
He died in New York. He had two sons, Alexander Nagel (professor of mathematics at the University of Wisconsin) and Sidney Nagel (professor of physics at the University of Chicago).
Nagel's doctoral students include Morton White, Patrick Suppes, Henry Kyburg, Isaac Levi, and Kenneth Schaffner.
A festschrift, Philosophy, Science and Method: Essays in Honor of Ernest Nagel, was published in 1969.
Select works
On The Logic of Measurement (1930)
An Introduction to Logic and Scientific Method (with M. R. Cohen, 1934)
"The Formation of Modern Conceptions of Formal Logic in the Development of Geometry" (1939)
Principles of the Theory of Probability (1939)
"The Meaning of Reduction in the Natural Sciences" (1949)
Sovereign Reason (1954)
Logic without Metaphysics (1957)
The Structure of Science: Problems in the Logic of Scientific Explanation (1961, second ed. 1979)
Observation and Theory in Science (with others, 1971)
Teleology Revisited and Other Essays in the Philosophy and History of Science (1979)
References
Further reading
Suppes, P. (2006). Ernest Nagel.* In S. Sarkar & Pfeifer, J. (Eds.), The Philosophy of Science: An Encyclopedia (N-Z Indexed., Vol. 2, pp. 491–496). New York: Routledge. [Archived *author eprint]
External links
1901 births
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Members of the American Philosophical Society | Ernest Nagel | Mathematics | 1,118 |
678,158 | https://en.wikipedia.org/wiki/Endosperm | The endosperm is a tissue produced inside the seeds of most of the flowering plants following double fertilization. It is triploid (meaning three chromosome sets per nucleus) in most species, which may be auxin-driven. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein. This can make endosperm a source of nutrition in animal diet. For example, wheat endosperm is ground into flour for bread (the rest of the grain is included as well in whole wheat flour), while barley endosperm is the main source of sugars for beer production. Other examples of endosperm that forms the bulk of the edible portion are coconut "meat" and coconut "water", and corn. Some plants, such as certain orchids, lack endosperm in their seeds.
Ancestral flowering plants have seeds with small embryos and abundant endosperm. In some modern flowering plants the embryo occupies most of the seed and the endosperm is non-developed or consumed before the seed matures. In other flowering plant taxa, the Poaceae for example, the endosperm is greatly developed.
Double fertilization
An endosperm is formed after the two sperm nuclei inside a pollen grain reach the interior of a female gametophyte or megagametophyte, also called the embryonic sac. One sperm nucleus fertilizes the egg cell, forming a zygote, while the other sperm nucleus usually fuses with the binucleate central cell, forming a primary endosperm cell (its nucleus is often called the triple fusion nucleus). That cell created in the process of double fertilization develops into the endosperm. Because it is formed by a separate fertilization event, the endosperm is a separate entity from the developing embryo, and some consider it to be a separate organism.
About 70% of angiosperm species have endosperm cells that are polyploid. These are typically triploid (containing three sets of chromosomes), but can vary widely from diploid (2n) to 15n.
One flowering plant, Nuphar polysepala, has diploid endosperm, resulting from the fusion of a pollen nucleus with one, rather than two, maternal nuclei. The same is supposed for some other basal angiosperms. It is believed that early in the development of angiosperm lineages, there was a duplication in this mode of reproduction, producing seven-celled/eight-nucleate female gametophytes, and triploid endosperms with a 2:1 maternal to paternal genome ratio.
Double fertilisation is a characteristic feature of angiosperms.
Endosperm development
There are three types of endosperm development:
Nuclear endosperm development – where repeated free-nuclear divisions take place; if a cell wall is formed it will form after free-nuclear divisions. Commonly referred to as liquid endosperm. Coconut water is an example of this.
Cellular endosperm development – where a cell-wall formation is coincident with nuclear divisions. Coconut meat is cellular endosperm. Acoraceae has cellular endosperm development while other monocots are helobial.
Helobial endosperm development – where a cell wall is laid down between the first two nuclei, after which one half develops endosperm along the cellular pattern and the other half along the nuclear pattern.
Evolutionary origins
The evolutionary origins of double fertilization and endosperm are unclear, attracting researcher attention for over a century. There are the two major hypotheses:
The double fertilization initially used to produce two identical, independent embryos ("twins"). Later these embryos acquired different roles, one growing into the mature organism, and another merely supporting it. Thus, the early endosperm was probably diploid, like the embryo. Some gymnosperms, such as Ephedra, may produce twin embryos by double fertilization. Either of these two embryos is capable of filling in the seed, but normally only one develops further (the other eventually aborts). Also, most basal angiosperms still contain the four-cell embryo sac and produce diploid endosperms.
Endosperm is the evolutionary remnant of the actual gametophyte, similar to the complex multicellular gametophytes found in gymnosperms. In this case, acquisition of the additional nucleus from the sperm cell is a later evolutionary step. This nucleus may provide the parental (not only maternal) organism with some control over endosperm development. Becoming triploid or polyploid are later evolutionary steps of this "primary gametophyte". Nonflowering seed plants (conifers, cycads, Ginkgo, Ephedra) form a large homozygous female gametophyte to nourish the embryo within a seed.
The triploid transition - and the production of antipodal cells - may have occurred due to a shift in gametophyte development which produced a new interaction with an auxin-dependent mechanism originating in the earliest angiosperms.
Role in seed development
In some groups (e.g. grains of the family Poaceae), the endosperm persists to the mature seed stage as a storage tissue, in which case the seeds are called "albuminous" or "endospermous", and in others it is absorbed during embryo development (e.g., most members of the family Fabaceae, including the common bean, Phaseolus vulgaris), in which case the seeds are called "exalbuminous" or "cotyledonous" and the function of storage tissue is performed by enlarged cotyledons ("seed leaves"). In certain species (e.g. corn, Zea mays); the storage function is distributed between both endosperm and the embryo. Some mature endosperm tissue stores fats (e.g. castor bean, Ricinus communis) and others (including grains, such as wheat and corn) store mainly starches.
The dust-like seeds of orchids have no endosperm. Orchid seedlings are mycoheterotrophic in their early development. In some other species, such as coffee, the endosperm also does not develop. Instead, the nucellus produces a nutritive tissue termed "perisperm". The endosperm of some species is responsible for seed dormancy. Endosperm tissue also mediates the transfer of nutrients from the mother plant to the embryo, it acts as a location for gene imprinting, and is responsible for aborting seeds produced from genetically mismatched parents. In angiosperms, the endosperm contain hormones such as cytokinins, which regulate cellular differentiation and embryonic organ formation.
Cereal grains
Cereal crops are grown for their edible fruit (grains or caryopses), which are primarily endosperm. In the caryopsis, the thin fruit wall is fused to the seed coat. Therefore, the nutritious part of the grain is the seed and its endosperm. In some cases (e.g. wheat, rice) the endosperm is selectively retained in food processing (commonly called white flour), and the embryo (germ) and seed coat (bran) removed. The processed grain has a lower quality of nutrition. Endosperm thus has an important role within the human diet worldwide.
The aleurone is the outer layer of endosperm cells, present in all small grains and retained in many dicots with transient endosperm. The cereal aleurone functions for both storage and digestion. During germination, it secretes the amylase enzyme that breaks down endosperm starch into sugars to nourish the growing seedling.
See also
Ovule
References
External links
Endosperm: the pivot of the sexual conflict in flowering plants at Earthling Nature
Plant morphology
Plant physiology | Endosperm | Biology | 1,708 |
42,558,178 | https://en.wikipedia.org/wiki/Anion-exchange%20chromatography | Anion-exchange chromatography is a process that separates substances based on their charges using an ion-exchange resin containing positively charged groups, such as diethyl-aminoethyl groups (DEAE). In solution, the resin is coated with positively charged counter-ions (cations). Anion exchange resins will bind to negatively charged molecules, displacing the counter-ion. Anion exchange chromatography is commonly used to purify proteins, amino acids, sugars/carbohydrates and other acidic substances with a negative charge at higher pH levels. The tightness of the binding between the substance and the resin is based on the strength of the negative charge of the substance.
General technique for protein purification
A slurry of resin, such as DEAE-Sephadex is poured into the column. The matrix that is used is insoluble with charged groups that are covalently attached. These charged groups are referred to as exchangers like cation and anion exchangers. After it settles, the column is pre-equilibrated in buffer before the protein mixture is applied. DEAE-Sephadex is a positively-charged slurry that will have electrostatic interactions with the negatively charged atoms, making them elute later than the positively-charged molecules in the interested sample. This is a separation technique used widely to discover specific proteins, or enzymes in the body. Unbound proteins are collected in the flow-through and/or in subsequent buffer washes. Proteins that bind to the positively charged resin are retained and can be eluted in one of two ways. First, the salt concentration in the elution buffer is gradually increased. The negative ions in the salt solution (e.g. Cl−) compete with protein in binding to the resin. Second, the pH of the solution can be gradually decreased which results in a more positive charge on the protein, releasing it from the resin. Both of these techniques can displace the negatively charged protein which is then eluted into test tubes fractions with the buffer.
The separation of proteins will depend on the differences in total charge. Composition of ionizable side chain groups will determine the total charge of the protein at a particular pH. At the isoelectric point (pI), the total charge on the protein is 0 and it will not bind to the matrix. If the pH is above the pI, the protein will have a negative charge and bind to the matrix in an anion exchange column. The stability of the protein at values above or below the pI, will determine if an anion exchange column or cation exchange column should be used. If it is stable at pH values below the pI, the cation exchange column be used. If it is stable at pH values above the pI then the anion exchange column can be used.
References
Chromatography | Anion-exchange chromatography | Chemistry | 589 |
76,454,282 | https://en.wikipedia.org/wiki/Confocal%20endoscopy | Confocal endoscopy, or confocal laser endomicroscopy (CLE), is a modern imaging technique that allows the examination of real-time microscopic and histological features inside the body. In the word "endomicroscopy", endo- means "within" and -skopein means "to view or observe". CLE, also known as "optical biopsy", can analyse histology and cytology features of a tissue which otherwise is only possible by tissue biopsy.
Similar to confocal microscopy, the laser in CLE filtered by the pinhole excites the fluorescent dye through a beam splitter and objective lens. The fluorescent emission then follows similar paths into the detector. A pinhole is used to select emissions from the desired focal plane. Two categories of CLE exist, namely probe-based (pCLE) and the less common endoscopy-based endoscopy (eCLE).
CLE can be intubated to study the gastrointestinal (GI) tract and accessory digestive organs with a fluorescent dye. A variety of diseases, including inflammatory bowel disease (IBD) and Barrett's oesophagus, can be diagnosed by the magnified and in-depth view in combination with traditional endoscopy.
Significance
CLE can identify the lesions with a small depths of view under the tissue, in contrast to the surface level in conventional endoscopy. It also allows clinicians to discriminate benign or malignant lesions through real-time histological diagnosis by revealing the properties of the lamina at a cellular level.
An example is Whipple's disease. Conventional endoscopy presents a whitish-patterned duodenal mucosa. CLE, in comparison, generates two images –– the superficial images show capillary leak in duodenal mucosa while the deep images show cells of duodenal mucosa, including goblet cells and foamy macrophages in lamina propria. Compared to histological examination of the same duodenal site after periodic acid-Schiff staining, CLE identifies similar patterns of goblet cells and foamy macrophages.
Types
Two types of CLE have been invented, namely probe-based (pCLE) and endoscope-based CLE (eCLE).
Probe-based CLE
pCLE, developed by Mauna Kea Technologies, is a fibre bundle transit through the 2.8 mm working channel (the hollow hole) of the standard endoscope into the GI tract. With a fixed plane of imaging, each fibre acts as a pinhole to filter unwanted noise. The frame rate lies between 9 and 12 images/second.
Endoscope-based CLE
eCLE, developed by Pentax, is a confocal microscopy fixed at the end of the endoscopic tube. The integrated machine of eCLE is larger than the pCLE in diameter, making GI tract endoscopic intubation more difficult. eCLE has ceased commercially due to the camera's inflexibility.
Medical uses
Oesophagus
CLE is effective in detecting premalignant, including Barrett's oesophagus, and malignant (cancerous) lesions in the upper GI tract. The modifications of mucosa shown in histopathology as an index of malignancy can be identified under CLE, such as high-grade dysplasia. CLE can also be implemented to refer to the treatment of Barrett's oesophagus by measuring the lateral extent of neoplasia.
The Miami classification is the most popular system in oesophageal CLE diagnosis.
Stomach and duodenum
Similar to that of the oesophagus, CLE is able to detect early gastric cancer, as well as premalignant conditions, such as gastritis and intestinal metaplasia. CLE can detect and distinguish the stomach pit patterns to identify the disease in accordance with the Miami classification, which was refined in 2016 to include both pit patterns and the architecture of blood vessels. The refined classification allows clinicians to differentiate between neoplastic and non-neoplastic lesions.
The presence of Helicobacter pylori can also be identified using CLE by viewing the morphological changes in tissues.
Lower Gastrointestinal Tract
CLE reveals "soccer ball-like pattern" of narrower capillaries in malignant lymphomas; distorted architecture and fluorescein leakage from lumen in colonic adenocarcinoma; and blunt-shaped villi and crypts and increased intraepithelial lymphocytes in coeliac disease.
CLE can be utilized to identify adenoma and neoplasia in colorectal polyps and lesions. The Miami classification provides guidelines for clinicians to differentiate neoplastic and non-neoplastic lesions.
Inflammatory Bowel Disease (IBD)
CLE can be used for the identification of IBD and its subtypes (Crohn's disease and ulcerative colitis) based on the observation on morphological characteristics, such as architectural distortion, lowered crypt density, crypt irregularity and an abnormally high density of epithelial gaps. The prediction of IBD progression on non-inflamed epithelium is achievable, too, making way for a novel "treat-to-target" therapeutic approach.
Pancreas
Incorporating an EUS, CLE can accurately diagnose pancreatic cystic lesions, including mucinous and non-mucinous lesions. Special needles are used to collect fluid and cyst wall tissues for testing. Pancreatic ductal adenocarcinoma (PDAC) can also be viewed by CLE. Observing cystic lesions and PDAC, clinicians can identify early chronic pancreatitis and determine the malignancies of lesions.
Biliary duct
Biliary stricture can be viewed by CLE. The Miami and Paris classifications can be adapted to differentiate cancerous and inflammatory causes.
Others
The discrimination of inflammation and malignant tumor in lung and the urinary system may be done by using CLE and this is currently under research. Some usages such as oral and other head-and-neck cancer diagnosis have been proposed.
Molecular imaging
Antibodies of molecular targets are used to diagnose GI diseases by histology. CLE captures the fluorescence produced by specific antibodies binding to vascular endothelial growth factor (VEGF). Comparing the significant difference in fluorescent strength, clinicians can differentiate normal and neoplastic tissue. Molecular imaging with antibodies may be applied to CLE as a diagnostic benchmark due to high correlation with ex vivo microscopy.
The molecular imaging technique can be used in a similar manner in the examination of head and neck cancer using CLE, though the diagnostic targets may be different from those in the gastrointestinal tract.
Mechanism
Basic mechanism
The laser emitted by CLE through a pinhole is reflected by the beam splitter or a dichroic mirror and focused by an objective lens. The fluorescent dye in targeted tissue is excited and emits a specific wavelength. The emission from the focal plane of the tissue then is collected by the objective lens and the beam splitter. The laser is eventually filtered by a pinhole to reduce out-of-focus noise to enter the detector or photomultiplier tube.
Topical dyes
Cresyl violet and acriflavine can be used as topical dyes. Cresyl violet is a common stain in histology used for light microscopy sections, especially brain sections. In CLE, it can enhance the viewing of the cytoplasm, yet it limits tissue penetration and does not show anything about vasculature. Acriflavine is an antiseptic and dye. In CLE, it can stain the nuclei of GI surface epithelial cells. It is however subjected to cytotoxic and mutagenic properties, in addition to common side effects of irritation.
Intravenous dyes
Fluorescein is the most popular IV dye for CLE. Fluorescein is an FDA-cleared dye that is used in ophthalmology clinics in routine as it appears green under cobalt blue light. It is commonly applied topically to identify corneal diseases with slit lamp microscopes including corneal abrasion, ulcers, and infections; or intravenously to identify retinal diseases with angiography including macular degeneration and diabetic retinopathy. In CLE, it is usually administered intravenously immediately before the intubation of an endoscopic tube. The fluorescence is reported to be the most prominent from a few seconds to 8 minutes. Fluorescein is slowly eliminated; thus the fluorescence slowly decays up to a minimal detectable level after 1 hour, giving a time window for clinicians to investigate.
Recognition and optical flow algorithm
CLE's narrow field of vision makes it difficult for clinicians to identify the location and path of the probe, making it challenging to correspond the image obtained and the lesion location and direction. Research has proposed a crypt recognition algorithm, which predicts the pixel displacement by the moving angle and distance. By restoring the exploration path of CLE, clinicians can locate the sites of interest and improve diagnostic efficiency.
Image quality assessment
Research has proposed a new assessment method for filtering images yielded from CLE. As CLE often encounters image distortions, the degradation of image quality and loss of image information, eventually increase the difficulty of accurate diagnosis. A new image quality assessment (IQA) utilising Weber's Law and local descriptors assesses the quality and filters images with low diagnostic value.
Limitations
The variety of pathology conditions identifiable by CLE is limited. The histological diagnosis is limited to cancerous lesions and inflammation where the number of specific diseases identifiable is not numerous. Moreover, it requires specific training to operate CLE and correctly interpret CLE images, which are rarely used skills by experts in endoscopy. Owing to the narrow field of view, the applications of CLE might be restricted. Computer-aided diagnosis with AI technology may be beneficial in diagnosing CLE images.
Fluorescein is the only safe dye approved while cresyl violet and acriflavine are commonly used agents. The lack of choice of contrast agents may limit the application of CLE. For instance, patients allergic to fluorescein should never undergo CLE that involves the use of this intravenous dye.
The optical system consists of complex microscopic optical instruments, which are difficult to manufacture and assemble. Therefore, the tool is expensive.
CLE is mostly used in combination with other techniques instead of replacing conventional endoscopy with biopsy. CLE can only serve as a complementary to the traditional biopsy. By sharing the same working channel, conventional biopsy and CLE can be done alternatively by single intubation.
Adverse effects
The allergic properties of fluorescein, the common intravenous fluorescent dye for CLE, is the major culprit for the mild adverse events.
Intubation
CLE, similar to other diagnostic endoscopic techniques, may give rise to pancreatitis when used to examine the pancreas. The likelihood for pancreatitis is especially high in needle-based CLE. The incidence can be minimized by shortening the inspection time and avoiding excessive needle movement within the pancreatic cyst wall.
Fluorescein
Mild side effects, which are rare, include
Nausea
Vomiting with mild epigastric pain
Rash at injection site
Transient hypotension without shock
Diffuse erythema
These effects are manageable unless patients have prior experiences of them.
Cases of anaphylaxis are reported by ophthalmological uses of fluorescein. Prophylactic use of antihistamines can reduce the chances of allergic reactions or skin prick tests can identify the risk of allergic reactions.
Acriflavine
Acriflavine, another contrast agent for CLE, is potentially carcinogenic to humans due to its known mutagenic ability. The dye is therefore not approved by the FDA.
History
CLE is a modern, in vivo adaptation of confocal microscopy, the microscopic technique invented by Marvin Minsky in 1957.
Since 2004, CLE has been used for observing histopathological changes in gastrointestinal tissues.
See also
Confocal microscopy
Endoscopy
Contrast agent
References
Medicine | Confocal endoscopy | Biology | 2,587 |
12,570,324 | https://en.wikipedia.org/wiki/15%20Vulpeculae | 15 Vulpeculae is a variable star in the northern constellation of Vulpecula, located approximately 243 light years away based on parallax measurements. It has the variable star designation NT Vulpeculae; 15 Vulpeculae is the Flamsteed designation. It is visible to the naked eye as a faint, white-hued star with a typical apparent visual magnitude of 4.66. This object is moving closer to the Earth with a heliocentric radial velocity of .
The star is considered a marginal Am star with a stellar classification of A4 IIIm, matching an evolved A-type giant star. However, Gray & Garrison (1989) found a class of kA5hA7mA7 (IV–V), which matches a blend of subgiant and main sequence luminosity classes with the K-line (kA5) of an A5 star and the hydrogen (hA7) and metal (mA7) absorption lines of an A7 star. According to Çay &al. (2025) the star represents an evolutionary stage of a formerly typical Am star into a subgiant, which caused the star to lose most of the peculiar properties of an Am star but maintain some element abundance peculiarities. The star is 2.4 times more massive than the Sun and has expanded to four times the Sun's diameter. It is radiating 62 times the Sun's luminosity from its photosphere at an effective temperature of . It is an Alpha2 Canum Venaticorum-type variable with magnitude ranging from 4.62 down to 4.67 over a period of 14 days.
There is evidence that 15 Vulpeculae may have a companion star, given the high margins of error in the astrometric measurements taken by Gaia DR3, as well as its unusually slow projected rotational velocity, which could also be explained if the star is being viewed pole-on.
Notes
References
A-type giants
Am stars
Alpha2 Canum Venaticorum variables
Vulpecula
Durchmusterung objects
Vulpeculae, 15
189849
098543
7653
Vulpeculae, NT | 15 Vulpeculae | Astronomy | 446 |
63,295,596 | https://en.wikipedia.org/wiki/Janson%20inequality | In the mathematical theory of probability, Janson's inequality is a collection of related inequalities giving an exponential bound on the probability of many related events happening simultaneously by their pairwise dependence. Informally Janson's inequality involves taking a sample of many independent random binary variables, and a set of subsets of those variables and bounding the probability that the sample will contain any of those subsets by their pairwise correlation.
Statement
Let be our set of variables. We intend to sample these variables according to probabilities . Let be the random variable of the subset of that includes with probability . That is, independently, for every .
Let be a family of subsets of . We want to bound the probability that any is a subset of . We will bound it using the expectation of the number of such that , which we call , and a term from the pairwise probability of being in , which we call .
For , let be the random variable that is one if and zero otherwise. Let be the random variables of the number of sets in that are inside : . Then we define the following variables:
Then the Janson inequality is:
and
Tail bound
Janson later extended this result to give a tail bound on the probability of only a few sets being subsets. Let give the distance from the expected number of subsets. Let . Then we have
Uses
Janson's Inequality has been used in pseudorandomness for bounds on constant-depth circuits. Research leading to these inequalities were originally motivated by estimating chromatic numbers of random graphs.
References
Probabilistic inequalities | Janson inequality | Mathematics | 327 |
8,637,261 | https://en.wikipedia.org/wiki/Communications%2C%20Computers%2C%20and%20Networks | The Scientific American special issue on Communications, Computers, and Networks is a special issue of Scientific American dedicated to articles concerning impending changes to the Internet in the period prior to the expansion and mainstreaming of the World Wide Web via Mosaic and Netscape. This issue contained essays by a number of important computer science and internet pioneers. It bore the promotional cover title Scientific American presents the September 1991 Single Copy Issue: Communications, Computers, and Networks.
Reviews
University of California, Berkeley's September 1991 online journal, "Current Cites" commented: "Scientific American Special Issue on Communications, Computers and Networks 265(3) (September 1991): If you purchase a single issue of a magazine this year, this should be it. Filled with eleven articles by some of the biggest names in computer networking, this issue covers all bases and includes suggestions for further readings on the issues." In addition, a 4 September 1991 post to the University of Houston's "Computer System's Forum" also recommends the issue, stating: "These articles cover enough ground that I would recommend the issue to people getting ready to dive into the Internet or understand what is happening in networks these days." An additional post to this same forum on 21 August 1991 comments: "The authors are exceptional, including Mitch Kapor, Mark Weiser, Nicholas Negroponte, Alan Kay, Al Gore, and many others. An excellent issue."
Response
Of this issue, the Electronic Frontier Foundation stated in the article "Scientific American's September Issue to be Sent to All EFF Members" in its September 1991 newsletter:
This month's Scientific American ("Communications, Computers, and Networks") must surely represent the most complete collection of articles and commentary on all aspects of networking to date. As such we feel strongly that it should be made available to as many people as possible. Because of this, we have purchased a large number of copies of this issue that we will be using for various purposes over the coming year. The first use will be to deliver a free copy of to all our members. We are expecting the magazines to be delivered to us at the end of next week and they will go out to our members soon after. We realize that many of our members may already have a copy of their own, but if so we trust that they will use this extra copy to educate and enlighten someone else to the issues and potential of networking.
Table of contents
Gary Stix: "Profile: Information Theorist David A. Huffman"
Michael Dertouzos: "Communications, Computers and Networks"
Vint Cerf: "Networks"
Larry Tesler: "Networked Computing in the 1990s"
Mark Weiser: "The Computer for the 21st Century"
Nicholas Negroponte: "Products and Services for Computer Networks"
Lee Sproull and Sara Kiesler: "Computers, Networks and Work"
Thomas W. Malone and John F. Rockart: "Computers, Networks and the Corporation"
Alan Kay: "Computers, Networks and Education"
Computers, Networks and Public Policy
Al Gore: "Infrastructure for the Global Village"
Anne W. Branscomb: "Common Law for the Electronic Frontier"
Mitch Kapor: "Civil Liberties in Cyberspace"
See also
History of the Internet
Footnotes
References
Scientific American September 1991 (Special Issue: Communications, Computers, and Networks), Volume 265, Number 3.
External links
UC Berkeley, "Current_Cites", Library Technology Watch Program - Sept. 1991
University of Houston Computer Science Forum - Sept. 1991
Overview of the issue - Humanist Discussion Group, Sept. 1991
Texts related to the history of the Internet
Computer books
Scientific American | Communications, Computers, and Networks | Technology | 734 |
49,664,155 | https://en.wikipedia.org/wiki/Nullspace%20property | In compressed sensing, the nullspace property gives necessary and sufficient conditions on the reconstruction of sparse signals using the techniques of -relaxation. The term "nullspace property" originates from Cohen, Dahmen, and DeVore. The nullspace property is often difficult to check in practice, and the restricted isometry property is a more modern condition in the field of compressed sensing.
The technique of -relaxation
The non-convex -minimization problem,
subject to ,
is a standard problem in compressed sensing. However, -minimization is known to be NP-hard in general. As such, the technique of -relaxation is sometimes employed to circumvent the difficulties of signal reconstruction using the -norm. In -relaxation, the problem,
subject to ,
is solved in place of the problem. Note that this relaxation is convex and hence amenable to the standard techniques of linear programming - a computationally desirable feature. Naturally we wish to know when -relaxation will give the same answer as the problem. The nullspace property is one way to guarantee agreement.
Definition
An complex matrix has the nullspace property of order , if for all index sets with we have that: for all .
Recovery Condition
The following theorem gives necessary and sufficient condition on the recoverability of a given -sparse vector in . The proof of the theorem is a standard one, and the proof supplied here is summarized from Holger Rauhut.
Let be a complex matrix. Then every -sparse signal is the unique solution to the -relaxation problem with if and only if satisfies the nullspace property with order .
For the forwards direction notice that and are distinct vectors with by the linearity of , and hence by uniqueness we must have as desired. For the backwards direction, let be -sparse and another (not necessary -sparse) vector such that and . Define the (non-zero) vector and notice that it lies in the nullspace of . Call the support of , and then the result follows from an elementary application of the triangle inequality: , establishing the minimality of .
References
Linear algebra | Nullspace property | Mathematics | 421 |
33,969,294 | https://en.wikipedia.org/wiki/Tricholoma%20atrosquamosum | Tricholoma atrosquamosum, commonly known as dark-scaled knight, is an edible gilled mushroom native to Europe. The grey-capped fruit bodies are generally found singly or in small groups in deciduous woodland on chalk-based soils.
Taxonomy
Tricholoma atrosquamosum was described 1837 by French naturalist François Fulgis Chevallier as Agaricus atrosquamosus. It has also been classified as a subspecies of the related T. terreum by George Edward Massee. It lies within the section Terrea within the subgenus Tricholoma within the genus Tricholoma. Two varieties are recognised, var. atrosquamosum is generally a larger mushroom and squarrulosum smaller. Tricholoma atrosquamosum is commonly known as the dark-scaled knight.
Description
The cap is wide and covered with dark grey-brown scales. Young specimens have more conical caps which become convex to flat with maturity. It is generally darker than other grey-capped tricholomas. The stout stipe is high and wide and has no ring. It is grey with tiny blackish scales either all over or restricted to the apex. The base of the stipe can be tinged greenish or pinkish, and becomes reddish upon drying. The pale grey-brown gills are adnate or free (unattached to the stipe). The mushroom has a mealy smell and taste, though there can be a fruity, peppery or spicy edge to the former. The spore print is white.
Distribution and habitat
Tricholoma atrosquamosum is found in North America and Europe. It is generally rare in Europe, and in danger of extinction in the Netherlands. The fruit bodies appear under deciduous and coniferous trees, particularly beech and spruce on chalky (calcareous) soils. Variety squarrulosum is also rare (though more widely distributed in southern Europe), and associated with oak, pine and spruce on chalk soils, with its fruit bodies appearing September to November. Both subspecies are rare in the British Isles.
Edibility
Both subspecies are edible, and highly regarded by some. They can be confused with darker specimens of the poisonous T. pardinum, which is generally a larger mushroom and lacks the peppery aroma.
See also
List of North American Tricholoma
List of Tricholoma species
References
atrosquamosum
Edible fungi
Fungi of Europe
Fungi of North America
Fungi described in 1837
Taxa named by François Fulgis Chevallier
Fungus species | Tricholoma atrosquamosum | Biology | 520 |
47,633,996 | https://en.wikipedia.org/wiki/Invertebrate%20mitochondrial%20code | The invertebrate mitochondrial code (translation table 5) is a genetic code used by the mitochondrial genome of invertebrates. Mitochondria contain their own DNA and reproduce independently from their host cell. Variation in translation of the mitochondrial genetic code occurs when DNA codons result in non-standard amino acids has been identified in invertebrates, most notably arthropods. This variation has been helpful as a tool to improve upon the phylogenetic tree of invertebrates, like flatworms.
The code
AAs = FFLLSSSSYY**CCWWLLLLPPPPHHQQRRRRIIMMTTTTNNKKSSSSVVVVAAAADDEEGGGG
Starts = ---M----------------------------MMMM---------------M------------
Base1 = TTTTTTTTTTTTTTTTCCCCCCCCCCCCCCCCAAAAAAAAAAAAAAAAGGGGGGGGGGGGGGGG
Base2 = TTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGG
Base3 = TCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAG
Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).
Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), Valine (Val, V).
Differences from the standard code
Note: The codon AGG is absent in Drosophila.
Alternative initiation codons
ATA/AUA
ATT/AUU
ATC/AUC: Apis
GTG/GUG: Polyplacophora
TTG/UUG: Ascaris, Caenorhabditis.
Systematic range
Nematoda: Ascaris, Caenorhabditis;
Mollusca: Bivalvia); Polyplacophora;
Arthropoda/Crustacea: Artemia;
Arthropoda/Insecta: Drosophila [Locusta migratoria (migratory locust), Apis mellifera (honeybee)].
Other variations
Several arthropods translate the codon AGG as lysine instead of serine (as in the Pterobranchia Mitochondrial Code) or arginine (as in the standard genetic code).
GUG may possibly function as an initiator in Drosophila. AUU is not used as an initiator in Mytilus
"An exceptional mechanism must operate for initiation of translation of the cytochrome oxidase subunit I mRNA in both D. melanogaster and D. yakuba, since its only plausible initiation codon, AUA, is out of frame with the rest of the gene. Initiation appears to require the "reading" of an AUAA quadruplet, which would be equivalent to initiation at AUA followed immediately by a specific ribosomal frameshift. Another possible mechanism ... is that the mRNA is "edited" to bring the AUA initiation into frame."
See also
List of genetic codes
References
Molecular genetics
Gene expression
Protein biosynthesis | Invertebrate mitochondrial code | Chemistry,Biology | 900 |
65,249,555 | https://en.wikipedia.org/wiki/SB-228357 | SB-228357 is a drug which acts as a selective antagonist of the serotonin 5-HT2B and 5-HT2C receptors.
It has antidepressant and anxiolytic effects in animal models and inhibits 5-HT2B mediated proliferation of cardiac fibroblasts. It has also been found to reverse meta-chlorophenylpiperazine (mCPP)-induced hypolocomotion and to attenuate haloperidol-induced catalepsy.
The drug was under development by GlaxoSmithKline for the treatment of major depressive disorder and anxiety disorders. It reached the preclinical research phase of development. However, development of the drug was discontinued.
See also
RS-102221
SB-242084
SB-243213
References
5-HT2C antagonists
Abandoned drugs
Indoles
3-Pyridyl compounds
Ureas | SB-228357 | Chemistry | 200 |
55,691,349 | https://en.wikipedia.org/wiki/Razer%20Phone | The Razer Phone (code name: cheryl, stylized as RΛZΞR PHONE) is an Android-based phablet designed and developed by Razer Inc., released on November 15, 2017. While the device was designed mainly for mobile gamers, reviewers such as Engadget have noted that it is also good enough for everyday use.
History
As a result of Razer's acquisition of Nextbit in January 2017, Razer started developing its own phone. The Razer Phone, therefore, is very similar in design to the Nextbit Robin. Its fingerprint scanner and front camera's positioning is the same, and both phones have large bezels, although the Razer Phone is made of aluminum, unlike the plastic Robin.
In October 2018, Razer announced the Razer Phone 2 with numerous enhancements from the Razer Phone, such as improved screen and camera, wireless charging, and Razer Chroma lighting.
In February 2019, Razer confirmed that it had let 30 employees go and was shutting down several projects. It is assumed the Razer Phone 3 was among those projects canceled. Razer did confirm that it would continue to sell the Razer Phone 2 and that it remains committed to supporting the phone with the latest updates and features.
Specifications
Hardware
The Razer Phone's back is made of black aluminum with a chrome Razer logo. Special editions were released, one with a gold logo, and one with a green logo. The front glass is protected by Corning Gorilla Glass 3. The volume buttons are made of aluminum, and the power buttons are made of plastic.
It uses the Qualcomm Snapdragon 835 SoC, coupled with 8 GB LPDDR4X RAM and 64 GB internal storage. The internal storage is expandable by a microSD card.
The display is a 5.7" 1440p IPS LCD panel with a 16:9 aspect ratio. Its highlighted feature is an "UltraMotion" 120 Hz display with Qualcomm's Q-Sync variable refresh rate, similar to Apple's second-generation iPad Pro. The quick refresh rate allows for gamers to play with almost zero latency.
The phone comes with two 12 MP cameras on the back, one wide-angle and one telephoto. The wide-angle lens features an f/1.75 aperture, while the telephoto lens offers f/2.6 aperture.
It uses the USB-C charging port for its 4,000 mAh battery; capable of fast charging using Qualcomm Quick Charge 4+. It also has a 24W fast charger included in the box. The phone does not have a 3.5 mm headphone jack. The speakers are enhanced with Dolby Atmos, and the phone comes with a THX-certified USB-C to 3.5 mm headphone jack adapter.
Software
On release, the phone ran near-stock Android 7.1 Nougat. On April 16, 2018, the phone was upgraded to Android 8.1 Oreo. Its default launcher is Nova Launcher Prime. Razer CEO Min-Liang Tan confirmed to a user on Twitter that the Razer Phone would get Android Pie in 2019.
Accessories
Project Linda
At CES 2018, Razer previewed a prototype laptop codenamed "Project Linda" that uses the Razer Phone to power the computer. After the phone is placed into the touchpad area of the computer and a hardware button is pressed, a USB-C connector clicks into the phone, which also charges the phone when docked.
The laptop uses a custom operating system based on Android and has 200 GB of internal storage, a 13.3" 1440p display, two USB ports, a 720p webcam, a dual-array microphone, and a 3.5mm headphone jack, but lacks dedicated speakers and uses those built into the Razer Phone.
References
External links
Android (operating system) devices
Mobile phones introduced in 2017
Mobile phones with multiple rear cameras
Mobile phones with 4K video recording
Discontinued flagship smartphones | Razer Phone | Technology | 834 |
671,262 | https://en.wikipedia.org/wiki/Abell%201835 | Abell 1835 is a galaxy cluster in the Abell catalogue. It is a cluster that also gravitational lenses more-distant background galaxies to make them visible to astronomers. The cluster has a red shift of around 75,900 km/s and spans 12.
In 2004, one of the galaxies lensed by this cluster was proposed to be the most distant galaxy known, Galaxy Abell 1835 IR1916.
See also
Abell 2218
List of Abell clusters
References
External links
Galaxy clusters
Virgo (constellation)
1835
Abell richness class 0 | Abell 1835 | Astronomy | 111 |
71,234,420 | https://en.wikipedia.org/wiki/List%20of%20blockchains | This is a list of blockchains - decentralized, cryptographic databases - and other distributed ledgers.
List
See also
Category:Blockchains
List of cryptocurrencies
References
General refs
https://arxiv.org/pdf/1708.05665.pdf
Blockchains
Blockchains | List of blockchains | Technology | 69 |
10,589,669 | https://en.wikipedia.org/wiki/Aspergillus%20terreus | Aspergillus terreus, also known as Aspergillus terrestris, is a fungus (mold) found worldwide in soil. Although thought to be strictly asexual until recently, A. terreus is now known to be capable of sexual reproduction. This saprotrophic fungus is prevalent in warmer climates such as tropical and subtropical regions. Aside from being located in soil, A. terreus has also been found in habitats such as decomposing vegetation and dust. A. terreus is commonly used in industry to produce important organic acids, such as itaconic acid and cis-aconitic acid, as well as enzymes, like xylanase. It was also the initial source for the drug mevinolin (lovastatin), a drug for lowering serum cholesterol.
Aspergillus terreus can cause opportunistic infection in people with deficient immune systems. It is relatively resistant to amphotericin B, a common antifungal drug. Aspergillus terreus also produces aspterric acid and 6-hydroxymellein, inhibitors of pollen development in Arabidopsis thaliana.
In 2023, Australian scientists discovered the ability of A. terreus to decompose polypropylene plastic completely in 140 days.
Appearance
Aspergillus terreus is brownish in colour and gets darker as it ages on culture media. On Czapek or malt extract agar (MEA) medium at , colonies have the conditions to grow rapidly and have smooth-like walls. In some cases, they are able to become floccose, achieving hair-like soft tufts. Colonies on malt extract agar grow faster and sporulate more densely than on many other media.
Aspergillus terreus has conidial heads that are compact, biseriate, and densely columnar, reaching 500 × 30–50 μm in diameter. Conidiophores of A. terreus are smooth and hyaline up to 100–250 × 4–6 μm in diameter. The conidia of A. terreus are small, about 2 μm in diameter, globose-shaped, smooth-walled, and can vary from light yellow to hyaline. Unique to this species is the production of aleurioconidia, asexual spores produced directly on the hyphae that are larger than the phialoconidia (e.g. 6–7 μm in diameter). This structure might be influential in the way A. terreus presents itself clinically as it can induce elevated inflammatory responses.
This fungus is readily distinguished from the other species of Aspergillus by its cinnamon-brown colony colouration and its production of aleurioconidia. A. terreus is a thermotolerant species since it has optimal growth in temperatures between , and maximum growth within .
Ecology
Aspergillus terreus, like other species of Aspergillus, produces spores that disperse efficiently in the air over a range of distances. The morphology of this fungus provides an accessible way for spores to disperse globally in air current. Elevation of the sporulating head atop a long stalk above the growing surface may facilitate spore dispersal through the air. Normally, spores in fungi are discharged into still air, but in A. terreus, it resolves this problem with a long stalk and it allows the spores to discharge into air currents like wind. In turn, A. terreus has a better chance to disperse its spores amongst a vast geography which subsequently explains for the worldwide prevalence of the fungus.
Despite A. terreus being found worldwide in warm, arable soil, it has been located in many different habitats such as compost and dust. Eventually, the dispersed fungal spores come into contact with either liquid or solid material and settle onto it, but only when the conditions are right do the spores germinate. One of the conditions important to the fungus is the level of moisture present in the material. The lowest water activity (Aw) capable of supporting growth of the fungus has been reported as 0.78. Tolerance of relatively low Aw conditions may explain, in part, the ubiquitous nature of this species given its ability to grow is a wide array of places. The soil of potted plants is one common habitat supporting the growth of A. terreus, and colonized soils may be important reservoirs of nosocomial infection. Other habitats include cotton, grains, and decomposing vegetation.
Genome
The Broad Fungal Genome Initiative funded by the National Institute of Allergy and Infectious Disease carried out the sequencing A. terreus in 2006. The result was 11.05 × genome sequence coverage. A. terreus contains 30-35 Mbp and roughly 10,000 protein-coding genes. Identification of virulence determinants within the genome of A. terreus may facilitate the development of new approaches to the treatment of A. terreus-related diseases. In addition, because A. terreus is resistant to the common antifungal drug amphotericin B, the mechanisms underlying its resistance may be better understood by genome-level investigation.
The polyketide synthase gene atX produces 6-Methylsalicylic acid in A. terreus.
Infection
Aspergillus terreus is not as common as other Aspergillus species to cause opportunistic infections in animals and humans. However, the incidence of A. terreus infection is increasing more rapidly than any other Aspergillus and for this reason it is considered an emerging agent of infection.
As an opportunistic pathogen, it is able to cause both systemic and superficial infections. Inhalation of fungal spores, which travel down along the respiratory tract, cause the typical respiratory infection. Other infections could also occur, such as onychomycosis and otomycosis. A. terreus has the ability to cause serious effects in immunocompromised patients who lack specific immune cells. Specifically, prolonged neutropenia predisposes humans and animals to this fungal disease.
Aspergillus terreus has no adaptation in terms of changing its physical structure when infecting a human or animal host. The fungus continues to grow as the characteristic hyphae filaments. Other pathogenic fungi usually switch over to a different growth stage, mycelia-to-yeast conversion, to best suit their new environment. This process does not occur in A. terreus.
Plants
For decades, A. terreus has been used in agriculture as a means to control pathogenic fungi from destroying crops. However, during the late 1980s, researchers described A. terreus as a fungal pathogen in plants. Crops such as wheat and ryegrass were shown to acquire disease following A. terreus infection. More recently, researchers have discovered the species can also cause foliar blight of potatoes. This was first described in India. A. terreus infection can have important implications because potatoes are considered the third-most important food crop in the world.
Aspergillus terreus has also been shown to disrupt the male sexual reproductive cycle in the plant model organism Arabidopsis thaliana. Its secondary metabolites, aspterric acid and 6-hydroxymellein, released from the fungus inhibit the production of pollen, the male gamete in plants. Since Arabidopsis thaliana cannot reproduce, it is sterile and cannot contribute offspring to the next generation. Ultimately, this has an effect on genetic diversity in the plant species.
Animals
Aspergillus terreus can cause infection in animals, but it is contained to a few species, such as dogs and cattle. Widely, A. terreus is found to cause mycotic abortion in cattle. In dogs, especially in the German Shepherd breed, this fungus is also responsible for sinusitis. It can further affect dogs through its dissemination. It can affect other parts of the body, including organs such as the spleen and kidneys. Also, the bone can be affected by A. terreus which could lead to spinal osteomyelitis.
Very few animal models exhibit A. terreus infections. Some successful animal models include the mouse and rabbit where A. terreus has formed pulmonary aspergillosis. These studies are important because it provides evidence that this fungal infection can cause disease.
Humans
In humans, A. terreus is less commonly encountered as a pathogen than other Aspergillus species, most notably A. fumigatus, A. flavus and A. niger. Although less frequently seen in clinical samples, A. terreus displays evidence of amphotericin B resistance which correlates to a high rate of dissemination and an overall poor prognosis.
Aspergillus terreus causes opportunistic infections mostly in immunocompromised people such as COPD patients who are taking corticosteroids, cancer patients receiving chemotherapy treatment, or HIV/AIDS patients. In an immunocompetent individual, the inhalation of spores initiates an immediate release of macrophages and neutrophils. In an immunosuppressed individual, this response is less vigorous. Most of these individuals suffer from neutropenia, which makes them less capable of defending themselves. In addition, A. terreus releases toxic metabolites that attack immune cells like neutrophils which provide the suitable conditions for the fungus to thrive.
Aspergillus terreus infection can lead to superficial infections in humans. These affect the outside layer of the body. It is commonly isolated from onychomycosis which is infection of human skin and nails. The incidence of onychomycosis as a result of A. terreus (not the common agent dermatophyte) is increasing. This happens to be the most frequently reported superficial infection in clinics and hospitals. Another common superficial infection caused by A. terreus includes otomycosis (ear infection), which is mostly isolated from patients who had recent surgical operations.
In addition, A. terreus infection can also result in four main systemic disease outcomes:
Allergic bronchopulmonary aspergillosis
Aspergillus bronchitis and invasive Aspergillus tracheobronchitis
Invasive (pulmonary) aspergillosis
Disseminated aspergillosis
Though all four disease outcomes can impose a great health risk to humans; invasive aspergillosis tends to result in the highest mortality and morbidity rates in humans. Epidemiology studies have shown the incidence of A. terreus in causing invasive aspergillosis has increased relative to other species in the genus. A. terreus infection causes 100% mortality rate in people who acquire invasive aspergillosis. Compared to 20 other Aspergillus species, A. terreus infection is associated with the poorest prognosis and high mortality. In fact, invasive aspergillosis has been named as the leading cause of death in leukemia and stem cell transplantation patients.
Treatment and prevention
Treatment of A. terreus is clinically challenging due to its nearly complete resistance to amphotericin B, the fallback drug for serious fungal infections. However, some newer drugs, such as voriconazole, posaconazole, and caspofungin, have shown promise in treating this agent.
The laboratory identification of A. terreus from clinical specimens can also be difficult. Currently, no rapid immunological tests are available for this species, and its correct identification remains dependent on culture. A. terreus strains have a tendency to mutate while in the animal host, resulting in a substantial reduction or loss of characteristic spore heads in primary culture. Such strains continue to produce small aleuroconidia similar in appearance to the aleurioconidia of Blastomyces dermatitidis.
In one study, nearly a third of A. terreus infections in hospitals were found to be associated with the presence of potted plants. Elimination of potted plants in the rooms of immunodeficient patients may have a role in prevention of illness. A. terreus has also been described in many studies as common to the hospital setting because of outside hospital construction and renovations. The amount of soil and debris reintroduced into the air is capable of travelling through the air and infecting immunosuppressed patients. A simple way to take preventive action is to provide good air filtration and ventilation throughout the hospital rooms. Elimination of inoculum is key to the prevention of nosocomial infection by A. terreus.
Industrial uses
Aspergillus terreus produces a number of secondary metabolites and mycotoxins, including territrem A, citreoviridin, citrinin, gliotoxin, patulin, terrein, terreic acid, asterric acid, and terretonin. The fungus also produces a secondary metabolite called lovastatin, a potent drug for lowering blood cholesterol levels in humans and animals. It is an inhibitor to one of the enzymes responsible in the catalyzing steps in cholesterol biosynthesis. Lovastatin is typically produced within fermentation conditions of the fungus. Fast growth of filamentous hyphae in the species A. terreus can result in low lovastatin production. To increase the production of this metabolite A. terreus requires important nutrients during fermentation. In this case, carbon and nitrogen are very important in fermentation productivity which in turn also increases the biomass of the metabolite lovastatin. A. terreus strains use glycerol and glucose as their best carbon sources for lovastatin production.
It is also used to produce the drug simvastatin that is chemically related to lovastatin.
References
Fungi described in 1918
terreus
Taxa named by Charles Thom
Fungus species | Aspergillus terreus | Biology | 2,857 |
14,468,598 | https://en.wikipedia.org/wiki/Content%20managed%20hosting | Content managed hosting is a service that couples website hosting with a content management system. Content management systems enable Web site owners or marketing departments to edit website content, share files, and hyperlink pages without needing to know markup or programming languages. It is an alternative to using an open-source content management system or purchasing an off-the-shelf system.
See also
Content Management Website
References
Website management | Content managed hosting | Technology | 81 |
37,506,594 | https://en.wikipedia.org/wiki/Snapchat | Snapchat is an American multimedia instant messaging app and service developed by Snap Inc., originally Snapchat Inc. One of the principal features of the multimedia Snapchat is that pictures and messages are usually available for only a short time before they become inaccessible to their recipients. The app has evolved from originally focusing on person-to-person photo sharing to presently featuring users' "Stories" of 24 hours of chronological content, along with "Discover", letting brands show ad-supported short-form content. It also allows users to store photos in a password-protected area called "My Eyes Only". It has also reportedly incorporated limited use of end-to-end encryption, with plans to broaden its use in the future.
Snapchat was created by Evan Spiegel, Bobby Murphy, and Reggie Brown, former students at Stanford University. It is known for representing a mobile-first direction for social media, and places significant emphasis on users interacting with virtual stickers and augmented reality objects. In 2023, Snapchat had over 300 million monthly active users. On average more than four billion Snaps were sent each day in 2020. Snapchat is popular among the younger generations, with most users being between 18 and 24. Snapchat is subject to privacy concerns with social networking services.
History
Prototype
According to documents and deposition statements, Reggie Brown brought the idea for a disappearing-pictures application to Evan Spiegel because Spiegel had prior business experience. Brown and Spiegel then pulled in Bobby Murphy, who had experience coding. The three worked closely together for several months and launched Snapchat as "Picaboo" on the iOS operating system on July 8, 2011. Reggie Brown was ousted from the company months after it was launched.
The app was relaunched as Snapchat in September 2011, and the team focused on usability and technical aspects, rather than branding efforts. One exception was the decision to keep a mascot designed by Brown, "Ghostface Chillah", named after Ghostface Killah of the hip-hop group Wu-Tang Clan.
On May 8, 2012, Reggie Brown sent an email to Evan Spiegel during their senior year at Stanford, in which he offered to re-negotiate his equitable share regarding ownership of the company. Lawyers for Snapchat claimed that Reggie Brown had made no contributions of value to the company, and was therefore entitled to nothing. In September 2014, Brown settled with Spiegel and Murphy for $157.5 million and was credited as one of the original authors of Snapchat.
In their first blog post, dated May 9, 2012, CEO Evan Spiegel described the company's mission: "Snapchat isn't about capturing the traditional Kodak moment. It's about communicating with the full range of human emotion—not just what appears to be pretty or perfect." He presented Snapchat as the solution to stresses caused by the longevity of personal information on social media, evidenced by "emergency detagging of Facebook photos before job interviews and photoshopping blemishes out of candid shots before they hit the internet.
Growth
As of May 2012, 25 Snapchat images were being sent per second and, as of November 2012, users had shared over one billion photos on the Snapchat iOS app, with 20 million photos being shared per day. That same month, Spiegel cited problems with user base scalability as the reason that Snapchat was experiencing some difficulties delivering its images, known as "snaps", in real time. Snapchat was released as an Android app on October 29, 2012.
In June 2013, Snapchat version 5.0, dubbed "Banquo", was released for iOS. The updated version introduced several speed and design enhancements, including swipe navigation, double-tap to reply, an improved friend finder, and in-app profiles. The name is a reference to a character from Shakespeare's Macbeth. Also in June 2013, Snapchat introduced Snapkidz for users under 13 years of age. Snapkidz was part of the original Snapchat application and was activated when the user provided a date of birth to verify his/her age. Snapkidz allowed children to take snaps and draw on them, but they could not send snaps to other users and could save snaps only locally on the device being used.
According to Snapchat's published statistics, as of May 2015, the app's users were viewing 2 billion videos per day, reaching 6 billion by November. By 2016, Snapchat had hit 10 billion daily video views. In May 2016, Snapchat raised $1.81 billion in equity offering, suggesting strong investor interest in the company. By May 31, 2016, the app had almost 10 million daily active users in the United Kingdom. In February 2017, Snapchat had 160 million daily active users, growing to 166 million in May.
Investel Capital Corp., a Canadian company, sued Snapchat for infringement on its geofiltering patent in 2016. They were seeking "monetary compensation and an order that would prohibit California-based Snapchat from infringing on its patent in the future."
In September 2016, Snapchat Inc. was renamed Snap Inc. to coincide with the introduction of the company's first hardware product, Spectacles—smartglasses with a built-in camera that can record 10 seconds of video at a time. On February 20, 2017, Spectacles became available for purchase online.
Snapchat announced a redesign in November 2017, which proved controversial with many of its followers. CNBC's Ingrid Angulo listed some of the reasons why many disliked the update, citing that sending a snap and re-watching stories was more complicated, stories and incoming snaps were now listed on the same page, and that the Discover page now included featured and sponsored content. A tweet sent by Kylie Jenner in February 2018, which criticized the redesign of the Snapchat app, reportedly caused Snap Inc. to lose more than $1.3 billion in market value. Over 1.2 million people signed a Change.org petition asking the company to remove the new app update.
In December 2019, App Annie announced Snapchat to be the 5th most downloaded mobile app of the decade. The data includes figures for iOS downloads starting from 2010 and Android downloads starting from 2012. Snapchat acquired AI Factory, a computer vision startup, in January 2020 to give a boost to its video capabilities.
In November 2020, Snapchat announced it would pay a total of $1 million a day to users who post viral videos. The company has not stated the criteria for a video to be considered viral or how many people the payout would be split between. The promotion, called Snapchat Spotlight, was initially intended to run until the end of the year. , the program continues to operate but its payout structure changed in 2021 as the company announced a shift from the $1 million per day model to a "millions per month" one.
In June 2022, Snapchat announced plans to launch Snapchat Plus, a paid subscription model. The subscription gives users early access to features, the ability to change the app icon and see which users rewatch their stories. In July 2022, the company reported that they had 347 million daily active users, an increase of 18% from the previous year. In August 2022, Snapchat announced that Snapchat Plus had more than 1 million subscribers and added four new features to the subscription including priority replies, post-view emoji, new Bitmoji content, and new app icons.
Features
Core functionality
Snapchat is primarily used for creating multimedia messages referred to as "snaps"; snaps can consist of a photo or a short video, and can be edited to include filters and effects, text captions, and drawings. Snaps can be directed privately to selected contacts, or to a semi-public "Story" or a public "Story" called "Our Story". The ability to send video snaps was added as a feature option in December 2012. By holding down on the photo button while inside the app, a video of up to ten seconds in length can be captured. Spiegel explained that this process allowed the video data to be compressed into the size of a photo. A later update allowed the ability to record up to 60 seconds, but are still segmented into 10 second intervals. After a single viewing, the video disappears by default. On May 1, 2014, the ability to communicate via video chat was added. Direct messaging features were also included in the update, allowing users to send ephemeral text messages to friends and family while saving any needed information by clicking on it. According to CIO, Snapchat uses real-time marketing concepts and temporality to make the app appealing to users. According to Marketing Pro, Snapchat attracts interest and potential customers by combining the AIDA (marketing) model with modern digital technology.
Private message photo snaps can be viewed for a user-specified length of time (1 to 10 seconds as determined by the sender) before they become inaccessible. Users were previously required to hold down on the screen in order to view a snap; this behavior was removed in July 2015 The requirement to hold on the screen was intended to frustrate the ability to take screenshots of snaps; the Snapchat app does not prevent screenshots from being taken but can notify the sender if it detects that it has been saved. However, these notifications can be bypassed through either unauthorized modifications to the app or by obtaining the image through external means. One snap per day can be replayed for free. In September 2015, Snapchat introduced the option to purchase additional replays through in-app purchases. The ability to purchase extra replays was removed in April 2016.
Friends can be added via usernames and phone contacts, using customizable "Snapcodes", or through the "Add Nearby" function, which scans for users near their location who are also in the Add Nearby menu. Spiegel explained that Snapchat is intended to counteract the trend of users being compelled to manage an idealized online identity of themselves, which he says has "taken all of the fun out of communicating."
In November 2014, Snapchat introduced "Snapcash", a feature that lets users send and receive money to each other through private messaging. The payments system is powered by Square.
In July 2016, Snapchat introduced a new, optional feature known as "Memories". Memories allow snaps and story posts to be saved into a private storage area, where they can be viewed alongside other photos stored on the device, as well as edited and published as snaps, story posts, or messages anytime. When shared with a user's current story, the memory would have a timestamp to indicate its age. Content in the Memories storage area can be searched by date or using a local object recognition system. Snaps accessible within Memories can additionally be placed into a "My Eyes Only" area that is locked with a Personal identification number (PIN). Snapchat has stated that the Memories feature was inspired by the practice of manually scrolling through photos on a phone to show them to others. In April 2017, the white border around old memories was removed. While originally intended to let viewers know the material was old, TechCrunch wrote that the indicator "ended up annoying users who didn't want their snaps altered, sometimes to the point where they would decide not to share the old content at all."
In May 2017, an update made it possible to send snaps with unlimited viewing time, dropping the previous ten-second maximum duration, with the content disappearing after being deliberately closed by the recipient. New creative tools, namely the ability to draw with an emoji, videos that play in a loop, and an eraser that lets users remove objects in a photo with the app filling in the space with the background, were also released.
In July 2017, Snapchat started allowing users to add links to snaps, enabling them to direct viewers to specific websites; the feature was only available for brands previously. Additionally, the update added more creative tools: A "Backdrop" feature lets users cut out a specific object from their photo and apply colorful patterns to it in order to bring greater emphasis to that object, and "Voice Filters" enable users to remix the sounds of their voices in the snap. Voice Filters was previously available as part of the feature enabling augmented reality lenses, with the new update adding a dedicated speaker icon to remix the audio in any snap.
In June 2020, Snap announced "minis", embeddable apps that live inside the parent Snap app.
In August 2022, Snap launched the "Family Center" feature which allows parents to monitor the activity of their children, ages 13–18, within the app.
In February 2023, Snapchat launched "My AI", a custom chatbot offering Snapchat+ users access to a mobile version of the AI chatbot ChatGPT. It followed up by announcing that its customizable My AI chatbot would be accessible to all users within the app in April 2023, a month after OpenAI allowed access to third parties, and would be available for group chats.
Filters, lenses, and stickers
Snaps can be personalized with various forms of visual effects and stickers. Geofilters are graphical overlays available if the user is within a certain geographical location, such as a city, event, or destination. Users can design and create their own geofilters for personal events at a fee of $10–15 USD per hour. They can also subscribe to an annual plan which ranges from $1,000 to $10,000 depending on the location, for a permanent filter. A similar feature known as Geostickers was launched in 10 major cities in 2016. Bitmoji are stickers featuring personalized cartoon avatars, which can be used in snaps and messaging. Bitmoji characters can also be used as World Lenses.
The "Lens" feature, introduced in September 2015, allows users to add real-time effects into their snaps by using face detection technology. This is activated by long-pressing on a face within the viewfinder. In April 2017, Snapchat extended this feature into "World Lenses", which use augmented reality technology to integrate 3D rendered elements (such as objects and animated characters) into scenes; these elements are placed and anchored in 3D space.
On October 26, 2018, at TwitchCon, Snap launched the Snap Camera desktop application for macOS and Windows PCs, which enables use of Snapchat lenses in videotelephony and live streaming services such as Skype, Twitch, YouTube, and Zoom. However, this was discontinued in January 2023. Snapchat also launched integration with Twitch, including an in-stream widget for Snapcodes, the ability to offer lenses to stream viewers and as an incentive to channel subscribers. Several video game-themed lenses were also launched at this time, including ones themed around League of Legends, Overwatch, and PlayerUnknown's Battlegrounds.
In August 2020, Snapchat collaborated with four TikTok influencers to launch Augmented Reality (AR) lenses to create a more interactive experience with users. The lenses now incorporate geo-locational mapping techniques to incorporate digital overlays onto real world surfaces. These lenses track 18 joints across the body to identify body movements, and generate effects around the body of the user. Advertising is now also utilizing AR lenses that make users a part of the advert. Coca-Cola, Pepsi and Taco Bell are just a select few of the brands now utilizing the tech on Snapchat. Consumers no longer scroll past these adverts, but become a part of them with AR lenses.
In March 2022, Snapchat launched the ability to share YouTube videos as stickers. The stickers function as clickable links that redirect users to a browser or the YouTube app.
Friend emojis
Friend emojis can be customized, however the default emojis are listed below.
The snapscore, which states the amount of snaps one has sent and received is recorded and is visible to one's friends. If users tap their own score it shows the ratio of sent and received snaps, the amount of snaps they have sent is on the right and the amount of snaps they have received is on the left, these numbers combined are their Snapchat score. There are multiple synonyms for Snapchat score such as Snapchat points, Snapscore, Snap points and Snap Number. YouTube has a similar rewards system called "Perks".
Stories and Discover
In October 2013, Snapchat introduced the "My Story" feature, which allows users to compile snaps into chronological storylines, accessible to all of their friends. By June 2014, photo and video snaps presented to friends in the Stories functionality had surpassed person-to-person private snaps as the most frequently used function of the service, with over one billion viewed per day—double the daily views tallied in April 2014.
In June 2014, the story feature was expanded to incorporate "Our Stories", which was then changed to "Live Stories" about a year later. The feature allows users on-location at specific events (such as music festivals or sporting events) to contribute snaps to a curated story advertised to all users, showcasing a single event from multiple perspectives and viewpoints. These curated snaps provided by the app's contributors and selected for the "Live" section could also be more localized, but Snapchat eventually scaled back the more personal imaging streams in order to emphasize public events.
An "Official Stories" designation was added in November 2015 to denote the public stories of notable figures and celebrities, similar to Twitter's "Verified account" program.
In January 2015, Snapchat introduced "Discover" an area containing channels of ad-supported short-form content from major publishers, including BuzzFeed, CNN, ESPN, Mashable, People, Vice and Snapchat itself among others. To address data usage concerns related to these functions, a "Travel Mode" option was added in August 2015. When activated, the feature prevents the automatic downloading of snaps until they are explicitly requested by the user.
In October 2016, the app was updated to replace its auto-advance functionality, which automatically moved users from one story to the next, with a "Story Playlist" feature, letting users select thumbnails of users in the list to play only selected stories.
In January 2017, Snapchat revamped its design, adding search functionality and a new global live "Our Story" feature, to which any user can contribute.
In May 2017, Snapchat introduced "Custom Stories", letting users collaboratively make stories combining their captures.
In June 2017, "Snap Map" was introduced, which allows users to optionally share their location with friends. A map display, accessible from the viewfinder, can be used to locate stories based on location data, supporting the use of Bitmoji as place markers. Entering a "Ghost Mode" hides the user from the map. The function is based on the app Zenly, which was acquired by Snap Inc. prior to its launch. The map data is supplied from OpenStreetMap and Mapbox, while satellite imagery comes from DigitalGlobe.
In February 2020, Snapchat released a Discover cartoon series called Bitmoji TV, which will star users' avatars.
Original video content
The Wall Street Journal reported in May 2017 that Snap Inc., the company developing Snapchat, had signed deals with NBCUniversal, A&E Networks, BBC, ABC, Metro-Goldwyn-Mayer and other content producers to develop original shows for viewing through Snapchat's "Stories" format. According to the report, Snap hoped to have several new shows available on a daily basis, with each show lasting between three and five minutes, and the company has sent out detailed reports to its partners on how to produce content for Snapchat. Over 2017 and 2018, Snap and partners launched several shows.
In, 2018 Snapchat and Vertical Networks (Snapchat Publisher Story) created a show called My Ex-BFF Court," which is a spoof of daytime-TV fare like the typical court shows we watch for example "Divorce Court" in which two ex-friends try to fix their problems. Who ever is guilty gets a funny sentence. Each episode is hosted by Judge Matteo Lane who is also known as Matthew Lane.
In 2018, Snapchat / Vertical Networks made a deal with Fox to make a television version of the dating and reality show Phone Swap.
In 2018, Snapchat got a new show called How Low Will You Go that was created by Above Average Productions and NBC.
In contrast to other messaging apps, Spiegel described Snapchat's messaging functions as being "conversational", rather than "transactional", as they sought to replicate the conversations he engaged in with friends. Spiegel stated that he did not experience conversational interactions while using the products of competitors like iMessage.
Rather than a traditional online notification, a blue pulsing "here" button is displayed within the sender's chat window if the recipient is currently viewing their own chat window. When this button is held down, a video chat function is immediately launched. By default, messages disappear after they are read, and a notification is sent to the recipient only when they start to type. Users can also use messages to reply to snaps that are part of a story. The video chat feature uses technology from AddLive—a real-time communications provider that Snapchat acquired prior to the feature's launch.
In regards to the "Here" indicator, Spiegel explained that "the accepted notion of an online indicator that every chat service has is really a negative indicator. It means 'my friend is available and doesn't want to talk to you,' versus this idea in Snapchat where 'my friend is here and is giving you their full attention.'" Spiegel further claimed that the Here video function prevents the awkwardness that can arise from apps that use typing indicators because, with text communication, conversations lose their fluidity as each user tries to avoid typing at the same time.
On March 29, 2016, Snapchat launched a major revision of the messaging functionality known as "Chat 2.0", adding stickers, easier access to audio and video conferencing, the ability to leave audio or video "notes", and the ability to share recent camera photos. The implementation of these features are meant to allow users to easily shift between text, audio, and video chat as needed while retaining an equal level of functionality. In June 2018, Snapchat added the feature of deleting a sent message (including; audio, video, and text) before it is read. A feature introduced in August 2018 allows users to send Musical GIFs, TuneMojis.
In August 2022, Snap Inc. announced it would discontinue all original scripted content with no plans to continue work in this direction.
In 2023, Snapchat had over 300 million monthly active users. In 2024, the countries with the most Snapchat users were India with 202.5 million users, followed by the United States with 106.5 million, Pakistan 31.9 million, France 27.5 million and the United Kingdom 23.1 million.
Encryption
In January 2018, Snapchat introduced the use of end-to-end encryption in the application but only for snaps (pictures and video), according to a Snapchat security engineer presenting at the January 2019 Real World Crypto Conference. As of the January 2019 conference Snapchat had plans to introduce end-to-end encryption for text messages and group chats in the future.
Business and multimedia
Demographics
Snapchat is popular among the younger generations, with most users being between 18 and 24 in 2023. On the app store, the age classification is 12+. In 2014, researchers from the University of Washington and Seattle Pacific University designed a user survey to help understand how and why the application was being used. The researchers originally hypothesized that due to the ephemeral nature of Snapchat messages, its use would be predominantly for privacy-sensitive content including the much talked about potential use for sexual content and sexting. However, it appears that Snapchat is used for a variety of creative purposes that are not necessarily privacy-related at all.
In the study, only 1.6% of respondents reported using Snapchat primarily for sexting, although 14.2% admitted to having sent sexual content via Snapchat at some point. These findings suggest that users do not seem to utilize Snapchat for sensitive content. Rather, the primary use for Snapchat was found to be for comedic content such as "stupid faces" with 59.8% of respondents reporting this use most commonly. The researchers also determined how Snapchat users do not use the application and what types of content they are not willing to send. They found that the majority of users are not willing to send content classified as sexting (74.8% of respondents), photos of documents (85.0% of respondents), messages containing legally questionable content (86.6% of respondents), or content considered mean or insulting (93.7% of respondents).
The study results also suggested that Snapchat's success is not due to its security properties, but because the users found the application to be fun. The researchers found that users seem to be well-aware (79.4% of respondents) that recovering snaps is possible and a majority of users (52.8% of respondents) report that this does not affect their behavior and use of Snapchat. Many users (52.8% of respondents) were found to use an arbitrary timeout length on snaps regardless of the content type or recipient. The remaining respondents were found to adjust their snaps' timeout depending on the content or the recipient. Reasons for adjusting the time length of snaps included the level of trust and relationship with the recipient, the time needed to comprehend the snap, and avoiding screenshots.
Communication
In the 2010s, Snapchat was seen as a messenger focused more on in-the-moment way sharing and less on the accumulation of permanent material.
Building on this distinction by launching as a mobile-first company, Snapchat, in the midst of the app revolution and the growing presence of cellular communication, did not have to make the transition to mobile in the way other competing social media networks had to do. Evan Spiegel himself described Snapchat as primarily a camera company. Spiegel also dismissed past comparisons to other social media networks such as Facebook and Twitter when he was asked if the 2016 presidential race was going to be remembered as the Snapchat election, although major candidates did occasionally use the app to reach voters. Nevertheless, the mobile app offered distinct publication, media, and news content within its Discover channel. Snapchat attempted to distinguish brand content and user-based messaging and sharing.
Monetization
Snapchat's developing features embody a deliberate strategy of monetization.
Snapchat announced its then-upcoming advertising efforts on October 17, 2014, when it acknowledged its need for a revenue stream. The company stated that it wanted to evaluate "if we can deliver an experience that's fun and informative, the way ads used to be, before they got creepy and targeted." Snapchat's first paid advertisement, in the form of a 20-second movie trailer for the horror film Ouija, was shown to users on October 19, 2014.
In January 2015, Snapchat began making a shift from focusing on growth to monetization. The company launched its "Discover" feature, which allowed for paid advertising by presenting short-form content from publishers. Its initial launch partners included CNN, Comedy Central, ESPN and Food Network, among others. In June 2015, Snapchat announced that it would allow advertisers to purchase sponsored geofilters for snaps; an early customer of the offering was McDonald's, who paid for a branded geofilter covering its restaurant locations in the United States. Snapchat made a push to earn ad revenue from its "Live Stories" feature in 2015, after initially launching the feature in 2014. Ad placements can be sold within a live story, or a story can be pitched by a sponsor. Live stories are estimated to reach an average of 20 million viewers in a 24-hour span.
Campaigns
In September 2015, the service entered into a partnership with the National Football League to present live stories from selected games (including a Sunday game, and marquee games such as Monday Night Football and Thursday Night Football), with both parties contributing content and handling ad sales. The 2015 Internet Trends Report by Mary Meeker highlighted the significant growth of vertical video viewing. Vertical video ads like Snapchat's are watched in their entirety nine times more than landscape video ads.
In 2016, Gatorade came out with an animated filter as part of the Super Bowl ads in 2016. The dunk lens of Gatorade received 165 million views on Snapchat.
In April 2016, NBC Olympics announced that it had reached a deal with Snapchat to allow stories from the 2016 Summer Olympics to be featured on Snapchat in the United States. The content would include a behind-the-scenes Discover channel curated by BuzzFeed (a company which NBCUniversal has funded), and stories featuring a combination of footage from NBC, athletes, and attendees. NBC sold advertising and entered into revenue sharing agreements. This marked the first time NBC allowed Olympics footage to be featured on third-party property.
In May 2016, as part of a campaign to promote X-Men: Apocalypse, 20th Century Fox paid for the entire array of lenses to be replaced by those based on characters from the X-Men series and films for a single day. In July 2016, it was reported that Snapchat had submitted a patent application for the process of using an object recognition system to deliver sponsored filters based on objects seen in a camera view. Later that year, in September 2016, Snapchat released its first hardware product, called the Spectacles. Evan Spiegel, CEO of Snap Inc., called it "a toy" but saw it as an upside to freeing his app from smartphone cameras.
In April 2017, Digiday reported that Snapchat would launch a self-service manager for advertising on the platform. The feature launched the following month, alongside news of a Snapchat Mobile Dashboard for tracking ad campaigns, which rolled out in June to select countries. Also in 2017, Snapchat introduced a "Snap to Store" advertising tool that lets companies using geostickers to track whether users buy their product or visit their store in a 7-day period after seeing the relevant geosticker. On November 13, 2018, Snapchat announced the launch of the Snap Store, where they sell Bitmoji merchandise personalized by avatars from users and their friends. Items for sale include shirts, mugs, shower curtains, and phone cases.
Development platform
In June 2018, Snapchat announced a new third-party development platform known as Snap Kit: a suite of components that allows partners to provide third-party integrations with aspects of the service. "Login Kit" is a social login platform that utilizes Snapchat accounts. It was promoted as being more privacy-conscious than competing equivalents, as services are only able to receive the user's display name (and, optionally, a Bitmoji avatar) and are subject to a 90-day inactivity timeout, preventing them from being able to collect any further personal information or social graphs through their authorization. "Creative Kit" allows apps to generate their own stickers to overlay into Snapchat posts. "Story Kit" can be used to embed and aggregate publicly posted stories (with for example, Bandsintown using Story Kit to aggregate stories posted by musicians), while "Bitmoji Kit" allows Bitmoji stickers to be integrated into third-party apps.
Snap Originals
In response to industry competition from streaming platforms such as Netflix, Snapchat announced in late 2018 that it would diversify its content by launching Snap Originals (episodic content including both scripted shows and documentaries).
In June 2020, Snapchat announced the creation of its first-ever "shoppable" original show called The Drop, which focused on "exclusive streetwear collage" from celebrities and designers. Each episode explored the relationship between the designer and celebrity collaborator. Viewers would learn about the item for sale and how it came together, as well as what time that day the item would go up for sale. Later that day, at the aforementioned time, the episode would be updated with more content that included a "swipe up to buy" action.
All projects related to original programming were ended in August 2022.
Premium accounts and sexual content
In 2014, Snapchat introduced a new feature called Snapcash which spurred its popularity among adult content creators.
Snapchat allows private premium accounts in which users can monetize their content. This feature is mostly used by models to monetize their adult content. Snapchat is increasingly becoming an integral part of the online porn industry.
Controversies
December 2013 hack
Snapchat was hacked on December 31, 2013. Gibson Security, an Australian security firm, had disclosed an API security vulnerability to the company on August 27, 2013, and then made public the source code for the exploit on December 25. On December 27, Snapchat announced that it had implemented mitigating features. Nonetheless, an anonymous group hacked them, saying that the mitigating features presented only "minor obstacles". The hackers revealed parts of approximately 4.6 million Snapchat usernames and phone numbers on a website named SnapchatDB.info and sent a statement to the popular technology blog TechCrunch saying that their objective had been to "raise public awareness... and... put public pressure on Snapchat" to fix the vulnerability. Snapchat apologized a week after the hack.
Federal Trade Commission
In 2014, Snapchat settled a complaint made by the US Federal Trade Commission (FTC). The government agency alleged that the company had exaggerated to the public the degree to which mobile app images and photos could actually be made to disappear. Under the terms of the agreement, Snapchat was not fined, but the app service agreed to have its claims and policies monitored by an independent party for a period of 20 years. The FTC concluded that Snapchat was prohibited from "misrepresenting the extent to which it maintains the privacy, security, or confidentiality of users' information."
Following the agreement, Snapchat updated its privacy page to state that the company "can't guarantee that messages will be deleted within a specific timeframe." Even after Snapchat deletes message data from their servers, that same data may remain in backup for a certain period of time. In a public blog post, the service warned that "If you've ever tried to recover lost data after accidentally deleting a drive or maybe watched an episode of CSI, you might know that with the right forensic tools, it's sometimes possible to retrieve data after it has been deleted."
In September 2024, the FTC released a report summarizing 9 company responses (including from Snapchat) to orders made by the agency pursuant to Section 6(b) of the Federal Trade Commission Act of 1914 to provide information about user and non-user data collection (including of children and teenagers) and data use by the companies that found that the companies' user and non-user data practices put individuals vulnerable to identity theft, stalking, unlawful discrimination, emotional distress and mental health issues, social stigma, and reputational harm.
Windows app
In November 2014, Snapchat announced a crackdown on third-party apps of its service and their users. Users of the Windows Phone platform were affected, as Snapchat did not have an official client for it, but numerous third-party apps existed, most popularly one called 6snap. In December, Microsoft was forced to remove 6snap and all other third-party apps of Snapchat from the Windows Phone Store; Snapchat however did not develop an official app for the platform, leaving its users on the platform behind. A petition from users requesting an official Snapchat app reached 43,000 signatures in 2015, but the company still refused to respond and to build an app for Windows Phone. Snapchat was criticized once again later in 2015 when it did not develop an app for Microsoft's Universal Windows Platform (UWP).
Lens incidents
In September 2015, an 18-year-old was using a Snapchat feature called "Lens" to record the speed she was driving her Mercedes-Benz C230 when she crashed into a Mitsubishi Outlander in Hampton, Georgia. The crash injured both drivers. The driver of the Outlander spent five weeks in intensive care while he was treated for severe traumatic brain injury. In April 2016, the Outlander driver sued both Snapchat and the user of Snapchat, alleging that Snapchat knew its application was being used in unlawful speed contests, yet did nothing to prevent such use so is negligent.
In October 2016, a similar collision occurred while a 22-year-old was driving at in Tampa, Florida, killing five people.
"Poor Country" remark
According to former Snapchat employee Anthony Pompliano in a lawsuit filed against Snap Inc., Spiegel made a statement in 2015 that Snapchat is "only for rich people" and that he does not "want to expand into poor countries like India and Spain". The incident sparked a Twitter trend called "#UninstallSnapchat", in which Indian users uninstalled the app, and caused backlash against the company, including a large number of low "one-star" ratings for the app in the Google Play Store and Apple's App Store. Snapchat's shares fell by 1.5%. In response to the allegation, Snapchat called Pompliano's claim "ridiculous", and elaborated that "Obviously Snapchat is for everyone. It's available worldwide to download for free."
Pompliano lawsuit
In January 2017, Pompliano filed a state lawsuit accusing Snapchat of doctoring growth metrics with the intention of deceiving investors. Pompliano said that Spiegel was dismissive of his concerns and that Pompliano was fired shortly thereafter. The judge dropped Pompliano's claims that Snapchat violated the Dodd-Frank and Consumer Protection Acts in retaliation against him, citing an arbitration clause in his contract. However, Snap Inc. faced blowback over a lack of disclosure regarding the contents of the lawsuit, resulting in plunging stock prices, several class-action lawsuits, and Federal investigations.
"Snap Map" privacy concerns
The June 2017 release of "Snap Map", a feature that broadcasts the user's location on a map, was met with concerns over privacy and safety. The feature, through an opt-in, delivers a message asking if the user would like to show their position on the map, but reportedly does not explain the ramifications of doing so, including that the app updates the user's position on the map each time the app is opened and not just when actively capturing snaps, potentially assisting stalkers. The map can be zoomed in to feature detailed geographical information, such as street addresses. The Daily Telegraph reported that police forces had issued child safety warnings, while other media publications wrote that safety concerns were also raised for teenagers and adults unaware of the feature's actual behavior. In a statement to The Verge, a Snapchat spokesperson said that "The safety of our community is very important to us and we want to make sure that all Snapchatters, parents, and educators have accurate information about how the Snap Map works".
Users have the ability to operate in "Ghost Mode", or select the friends that they wish to share their location with. Although there has been an increase in advertising on Snapchat, Snapchat has stated that they do not plan on running ads on Snap Map stories.
Rihanna controversy
In March 2018, an advertisement containing a poll about Rihanna was posted stating, "Would you rather punch Chris Brown or slap Rihanna?" Rihanna tweeted that Snapchat was "insensitive to domestic violence victims" and urged fans to delete Snapchat.
Body image concerns
The increased use of body and facial reshaping applications such as Snapchat and Facetune has been identified as a potential cause of body dysmorphic disorder. In August 2018, researchers from the Boston Medical Center wrote in a JAMA Facial Plastic Surgery essay that a phenomenon they called 'Snapchat dysmorphia' had been identified, where people request surgery to look like the edited version of themselves as they appear through Snapchat Filters.
Snapchat employees abused data access to spy on users
In May 2019, it was revealed that multiple Snapchat employees used an internal tool called SnapLion, originally designed to gather data in compliance with law enforcement requests, to spy on users.
Mozilla calls for public disclosures related to use of A.I.
Citing "vague, broad language" in Snapchat's privacy policy, Mozilla issued a September 2019 petition calling for public disclosures related to the app's use of facial emotion recognition technology. When reached for comment by Scientific American, representatives for Snapchat declined to share a public response.
Revenge porn
During the 2020 lockdown to inhibit the spread of COVID-19 in France, the app emerged as a hub for the dissemination of revenge porn of underage girls. Some users have also reported that perpetrators of revenge porn have utilized explicit images to seek sexual favors or powers over individuals.
In 2020, a woman in North Carolina sued Snapchat (as well as dating app Tinder and the five men named in the attack), claiming features of the app enabled her alleged rapist and his friends to hide evidence of the rape. In particular, the suit alleges that "because of the ways Snapchat is and has been designed, constructed, marketed, and maintained, [the woman's assailants] were able to send these nonconsensual, pornographic photographs and videos of [her] with little to no threat of law enforcement verifying that they did so." The woman told the court that parent company Snap Inc. "specifically and purposely designed, constructed, and maintained Snapchat to serve as a secretive and nefarious communications platform that encourages, solicits, and facilitates the creation and dissemination of illicit and non-consensual sexually explicit content...and allowed Snapchat to operate as a safe-haven from law enforcement."
Sale of fake pills
In December 2022, the National Crime Prevention Council wrote U.S. Attorney General Merrick Garland urging the Justice Department to examine Snaps business practices related to the sale of fake pills containing lethal amounts the synthetic opioid fentanyl. Less than a month later, it was widely reported that the Federal Bureau of Investigation launched a probe into the company and the sale of fake pills.
Illinois biometric data lawsuit
Snapchat was the subject of a class action lawsuit from the state of Illinois, alleging that the company violated the Biometric Information Privacy Act by collecting and storing biometric data on Illinois residents who used the app's filters and lenses without providing a written explanation on why the data was recorded and what its term of storage would be. The company opted to settle the lawsuit with a $35 million payout.
Grooming
In November 2024, British children's charity the NSPCC reported that according to statistics provided to them by the police, that the most popular app amongst online groomers was Snapchat. More than 7,000 Sexual Communication with a Child offences were recorded across the UK in the year to March 2024, the highest number since the offence was created. Snapchat made up nearly half of the 1,824 cases where the specific platform used for the grooming was recorded by the police.
Snapchat Speed Filter Crashes
In September 2015, Christal McGee was driving her Mercedes-Benz C230 in Georgia when she collided with a Mitsubishi Outlander at 107 mph. The high-speed crash severely injured the driver of the Mitsubishi, Wentworth Maynard, who required five weeks of intensive care and was left with a permanent brain injury. In April 2016, Maynard sued both McGee and Snapchat, claiming that McGee was using the Snapchat “speed filter” at the time of the crash. The lawsuit further alleged that Snapchat negligently allowed the feature despite knowing it encouraged dangerous speeding. In March 2022, the Georgia Supreme Court ruled that Snapchat must face claims that it defectively designed the “speed filter” application.
In May 2017, a group of teens in Wisconsin used Snapchat's "speed filter" to capture their car's speed as it reached 123 mph on a rural road. Moments later, the vehicle crashed into a tree, killing all three occupants. In May 2019, the families of two passengers, Hunter Morby and Landen Brown, filed a lawsuit against Snapchat, alleging that the company knew the filter encouraged reckless speeding among young users but failed to restrict its use. The case, Lemmon v. Snap, led to a landmark legal precedent. In May 2021, the 9th U.S. Circuit Court of Appeals ruled that Section 230 of the Communications Decency Act–which typically shields tech companies from liability for content created by users–did not bar the families' claims. The court distinguished between protecting platforms from liability for user-generated content and protecting them from liability for negligent product design, finding that the speed filter was a feature Snapchat itself had created. This decision allowed the case to proceed, marking a significant precedent for holding tech companies accountable for the design of their products. In 2021, Snap Inc. settled the lawsuit for an undisclosed amount.
In June 2021, a month after the 9th Circuit ruling, Snapchat removed the “speed filter”, citing its limited use for its removal. The decision came after mounting pressure from safety advocates, legal experts, and families affected by crashes allegedly linked to the feature. Critics had long argued that the filter incentivized reckless behavior, particularly among young and impressionable drivers, and called for stronger accountability from social media companies to prioritize user safety.
See also
Censorship of Snapchat
Comparison of cross-platform instant messaging clients
Instagram face
Picsart
Purikura, Japanese photo sticker booths which had earlier used Snapchat-like filters
Sobrr, another mobile application which deletes content after a specified time
Yahoo
Yo (app)
Yubo
Timeline of social media
References
Further reading
External links
2011 establishments in California
Android (operating system) software
Instant messaging
IOS software
Internet properties established in 2011
Internet television streaming services
Image-sharing websites
Proprietary cross-platform software
Privately held companies based in California
Streaming media systems
Technology companies based in Greater Los Angeles
Vertical video
Video on demand services
Mobile applications | Snapchat | Technology | 9,753 |
40,428,711 | https://en.wikipedia.org/wiki/Marcus%20Feldman | Marcus William Feldman (born 14 November 1942) is the Burnet C. and Mildred Finley Wohlford Professor of Biological Sciences, director of the Morrison Institute for Population and Resource Studies, and co-director of the Center for Computational, Evolutionary and Human Genomics (CEHG) at Stanford University. He is an Australian-born mathematician turned American theoretical biologist, best known for his mathematical evolutionary theory and computational studies in evolutionary biology, and for originating with L. L. Cavalli-Sforza the theory of cultural evolution.
Early life and education
Marcus Feldman was born and raised in Perth, Australia. His father Simon Feldman was an engineer, and this inspired him to take up mathematics. He studied at the University of Western Australia from where he matriculated in 1959, and graduated (with majors in mathematics and statistics) in 1964. In 1966 he obtained Master of Science degree in mathematics from Monash University. He went abroad to US to join a PhD programme at Stanford University. He earned his degree in 1969 under the supervision of Samuel Karlin in the Department of Mathematics. Karlin influenced him to pursue his research in population genetics using his computational know-how.
Professional career
After a brief work at Stanford as a research assistant for Karlin, and as acting assistant professor in the Department of Biology, Feldman returned to Australia to join at La Trobe University as a lecturer of mathematics. In 1971 he was appointed as assistant professor in the Department of Biological Sciences at Stanford, and went back to US. With L.L. Cavalli-Sforza in 1973, he originated the quantitative theory of cultural evolution, initiating a research program in cultural transmission and gene-culture coevolution. His own research into human molecular evolution such as in China led him to international recognition. He is the author of more than 625 scientific papers and several books on evolution, ecology, and mathematical biology.
In addition, he is the founding editor of Theoretical Population Biology (1971–2013) and an associate editor of Genetics, Human Genetics, Annals of Human Genetics, Annals of Human Biology, and Complexity. He was the editor of The American Naturalist from 1984 to 1990. He was a member of the board of trustees at the Santa Fe Institute from 1984 to 2006.
Award and honors
Guggenheim Fellowship in 1976–1977
Fellow of the Center for Advanced Study in the Behavioral Sciences, Stanford in 1983–84
Elected Fellow of the American Association for the Advancement of Science in 1986
Elected member of the American Society of Human Genetics
Fellow of the American Academy of Arts & Sciences in 1987
Fellow of the California Academy of Sciences in 1996
China Population Association Award in 1998
Honorary doctorate of philosophy from the Hebrew University of Jerusalem in 2005
Honorary doctorate of philosophy from the Tel Aviv University in 2010
Honorary professor at Beijing Normal University in 2002–2007
Honorary professor at Xi’an Jiaotong University in 2005
Paper of the Year 2003 award for biomedical science from The Lancet in 2003
Dan David Prize in 2011
Elected member of the American Philosophical Society in 2011
Elected member of the US National Academy of Sciences in 2013
Kimura Motoo award in human evolution in 2016
Alumni lifetime achievement award, University of Western Australia, in 2016
Honorary doctorate of philosophy from the University of St Andrews in 2022
Lifetime Achievement Award, Society for the Study of Evolution, in 2022
Lifetime Research Achievement Award, Society for Molecular Biology and Evolution, in 2024
References
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Center for Advanced Study in the Behavioral Sciences fellows | Marcus Feldman | Biology | 799 |
35,057,676 | https://en.wikipedia.org/wiki/Bacteriophage%20T12 | Bacteriophage T12 is a bacteriophage that infects Streptococcus pyogenes bacteria. It is a proposed species of the family Siphoviridae in the order Caudovirales also known as tailed viruses.
It converts a harmless strain of bacteria into a virulent strain. It carries the speA gene which codes for erythrogenic toxin A. speA is also known as streptococcal pyogenic exotoxin A, scarlet fever toxin A, or even scarlatinal toxin. Note that the name of the gene "speA" is italicized; the name of the toxin "speA" is not italicized. Erythrogenic toxin A converts a harmless, non-virulent strain of Streptococcus pyogenes to a virulent strain through lysogeny, a life cycle which is characterized by the ability of the genome to become a part of the host cell and be stably maintained there for generations. Phages with a lysogenic life cycle are also called temperate phages. Bacteriophage T12, proposed member of family Siphoviridae including related speA-carrying bacteriophages, is also a prototypic phage for all the speA-carrying phages of Streptococcus pyogenes, meaning that its genome is the prototype for the genomes of all such phages of S. pyogenes. It is the main suspect as the cause of scarlet fever, an infectious disease that affects small children.
Discovery and further research
The possibility of bacteriophage involvement in speA production was first introduced in 1926 when Cantacuzene and Boncieu reported that nonvirulent strains of S. pyogenes were transformed to virulent strains through some transferable element. Frobisher and Brown reported similar results in 1927, and in 1949, the reports were confirmed by Bingel Later, in 1964, Zabriskie reported that phage T12 could cause speA production by lysogeny in strains that it became a part of. In 1980, Johnson, Schlievert and Watson were able to confirm this and show that the gene for speA production was transferred from toxigenic strains of bacteria to non-toxigenic strains through lysogeny. In their experiment, every transformed, toxin-producing bacterial colony was lysogenic, i.e. contained the T12 gene. In addition, none of the colonies containing the T12 genome was negative for speA, and therefore, the conclusion was drawn that all lysogens produced the toxin.
However, McKane and Ferretti reported in 1981 that a spontaneous mutant of phage T12 induced speA production virulently. This mutant, the bacteriophage T12cp1, entered the lytic cycle, a life cycle in which the host cell is destroyed. In 1983, Johnson and Schlievert published a map of the T12 genome, revealing also that three rounds of packaging occur in the genome. The very next year, Johnson and Schlievert and Weeks and Ferreti also found, independently, that the bacteriophage T12 carries the structural gene for speA. In 1986, Johnson, Tomai and Schlievert mapped the attachment site (attP) for T12 adjacent to the speA gene, and established that all bacterial strains producing the toxin carry either phage T12 itself, or a closely related bacteriophage. And finally, in 1997, McShan and Ferretti published that they had found the second attachment site (attR) for T12, while also revealing in another publication, which was also credited to Tang, that bacteriophage T12 inserts into a gene that encodes a serine tRNA in the host.
Genome
The physical map of the T12 genome was found to be circular with a total length of 36.0kb. The phage genome is reported to carry the speA gene, which is a 1.7kb segment of the phage T12 genome flanked by SalI and HindIII sites.
The phage integrase gene (int) and the phage attachment site (attp) are located just upstream of the speA gene in the phage genome. The bacteriophage T12 integrates into S. pyogenes chromosome by site-specific recombination into the anticodon loop of a gene that codes for serine tRNA. The bacterial attachment site (attB) has a 96 base pair sequence homologous to the phage attachment site and is located at the 3’ end of the tRNA gene such that the coding sequence of the tRNA gene remains intact after integration of the prophage. Phage T12 is the first example of a phage from a gram-positive, low G-C content host that uses this kind of integration site.
Role in pathogenesis
Diseases like scarlet fever and Streptococcal toxic shock syndrome are caused by lysogenized streptococcal strains that produce speA. The diseases are systemic responses to the speA circulating within the body.
Scarlet fever
Scarlet fever, also known as scarletina, is so called because of the characteristic bright red rash it causes. It is most common in children between four and eight years of age.
Signs and symptoms
The first stage of scarlet fever is typically strep throat (streptococcal pharyngitis) characterized by sore throat, fever, headache and sometimes nausea and vomiting. In two to three days, this is followed by the appearance of a diffuse erythematous rash that has a sandpaper texture. The rash first appears on the neck, then spreads to the chest, back and body extremities. A yellowish white coating covers the tongue, and is later shed, leaving the tongue with a strawberry appearance and swollen papillae. The rash fades away after five to six days of the onset of the disease, and is followed by peeling of skin, particularly over the hands and feet.
Treatment
Penicillin, an antibiotic, is the drug of choice for the treatment of scarlet fever as for any other S. pyogenes infection. For those who are allergic to penicillin, the antibiotics erythromycin or clindamycin can be used. However, occasional resistance to these drugs has been reported.
Streptococcal toxic shock syndrome
In streptococcal toxic shock syndrome (StrepTSS), speA produced by infected streptococcal strains acts as a superantigen and interacts with human monocytes and T lymphocytes, inducing T-cell proliferation and production of monokines (e.g. tumor necrosis factor α, interleukin 1, interleukin 6), and lymphokines (e.g. tumor necrosis factor β, interleukin 2, and gamma-interferon). These cytokines(TNFα, TNFβ) seem to mediate the fever, shock and organ failure characteristic of the disease.
Signs and symptoms
Strep TSS is an acute, febrile illness that begins with a mild viral-like syndrome characterized by fever, chills, myalgia, diarrhea, vomiting and nausea and involves minor soft-tissue infection that may progress to shock, multi-organ failure, and death.
Treatment
While penicillin is an effective treatment of mild infection, it is less effective in a severe case. Emerging treatments for strep TSS include clindamycin and intravenous gamma-globulin.
Detection and elimination
The presence of lysogenic bacteriophage T12 can be tested through plaque assays if the indicator strain utilized is susceptible to the phage being tested. Plaque assays consist of pouring a soft agar solution with an indicator strain onto an agar plate. The indicator strain should be a strain of bacteria that can be infected by the phage that needs to be detected. After the soft agar is set the samples that are being tested for phage presence are then spread-plated onto the soft agar plates. The plates are then incubated overnight and checked for clearings (plaques) the next day. If the phage is present, indicator strains will become infected and go through the normal lysogenic cycle while the plates incubate, and then undergo lysis. The plaque that determines whether the phage is present or not is caused by the lysis of the indicator strains. Titers of plaques can be found by diluting the samples and counting plaque-forming units (PFUs).
Biochemical tests such as Southern blots can also be used to detect the speA that the phage produces from the speA gene. This was done in research by Johnson, Tomai and Schlievert in 1985 by isolating the DNA of Streptococcal strains and running a restriction digest using BglII. After the digest was complete, the DNA samples were run on gel to separate the DNA. The DNA from this gel was then transferred to nitrocellulose paper and incubated with probes specific for speA. An image of this Southern blot can be seen in this article.
Bacteriophages are very easily spread. At lower exposures, Ultraviolet light can enhance the production of both phage T12 and speA. Longer UV exposure times can kill the phage. UV light stresses lysogenic bacteria, leading the phages to propagate and burst the host bacterial cells. In the case of T12, exposure to UV light increases the propagation of bacteriophage T12 at 20 seconds of exposure. After 20 seconds of exposure the UV light starts to kill the bacteriophage by damaging its genome.
References
External links
UniProt taxonomy
Bacteriophages
Unaccepted virus taxa | Bacteriophage T12 | Biology | 2,081 |
15,076,371 | https://en.wikipedia.org/wiki/HIST1H3E | Histone H3.1 is a protein that in humans is encoded by the HIST1H3E gene.
Histones are basic nuclear proteins that are responsible for the nucleosome structure of the chromosomal fiber in eukaryotes. Two molecules of each of the four core histones (H2A, H2B, H3, and H4) form an octamer, around which approximately 146 bp of DNA is wrapped in repeating units, called nucleosomes. The linker histone, H1, interacts with linker DNA between nucleosomes and functions in the compaction of chromatin into higher order structures. This gene is intronless and encodes a member of the histone H3 family. Transcripts from this gene lack polyA tails but instead contain a palindromic termination element. This gene is found in the large histone gene cluster on chromosome 6.
References
Further reading | HIST1H3E | Chemistry | 197 |
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