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51,518,781 | https://en.wikipedia.org/wiki/Directory-based%20cache%20coherence | In computer engineering, directory-based cache coherence is a type of cache coherence mechanism, where directories are used to manage caches in place of bus snooping. Bus snooping methods scale poorly due to the use of broadcasting. These methods can be used to target both performance and scalability of directory systems.
Full bit vector format
In the full bit vector format, for each possible cache line in memory, a bit is used to track whether every individual processor has that line stored in its cache. The full bit vector format is the simplest structure to implement, but the least scalable. The SGI Origin 2000 uses a combination of full bit vector and coarse bit vector depending on the number of processors.
Each directory entry must have 1 bit stored per processor per cache line, along with bits for tracking the state of the directory. This leads to the total size required being (number of processors)×number of cache lines, having a storage overhead ratio of (number of processors)/(cache block size×8).
It can be observed that directory overhead scales linearly with the number of processors. While this may be fine for a small number of processors, when implemented in large systems the size requirements for the directory becomes excessive. For example, with a block size of 32 bytes and 1024 processors, the storage overhead ratio becomes 1024/(32×8) = 400%.
Coarse bit vector format
The coarse bit vector format has a similar structure to the full bit vector format, though rather than tracking one bit per processor for every cache line, the directory groups several processors into nodes, storing whether a cache line is stored in a node rather than a processor. This improves size requirements at the expense of bus traffic saving (processors per node - 1)×(total lines) bits of space. Thus the ratio overhead is the same, just replacing number of processors with number of processor groups. When a bus request is made for a cache line that one processor in the group has, the directory broadcasts the signal into every processor in the node rather than just the caches that contain it, leading to unnecessary traffic to nodes that do not have the data cached.
In this case the directory entry uses 1 bit for a group of processors for each cache line. For the same example as Full Bit Vector format if we consider 1 bit for 8 processors as a group, then the storage overhead will be 128/(32×8)=50%. This is a significant improvement over the Full Bit Vector format.
Sparse directory format
A cache only stores a small subset of blocks in main memory at a particular time. Hence most of the entries in the directory will belong to uncached blocks. In the sparse directory format the wastage is reduced by storing only the cached blocks in the directory. Consider a processor with a cache size of 64KB with a block size of 32 bytes and the main memory size to be 4MB. The maximum number of entries that the directory can have in the sparse directory format is 2048. If the directory has an entry for all the blocks in the memory the number of entries in the directory will be 131072. Thus it is evident that the storage improvement provided by sparse directory format is very significant.
Number-balanced binary tree format
In this format the directory is decentralised and distributed among the caches that share a memory block. Different caches that share a memory block are arranged in the form of a binary tree. The cache that accesses a memory block first is the root node. Each memory block has the root node information (HEAD) and Sharing counter field (SC). The SC field has the number of caches that share the block. Each cache entry has pointers to the next sharing caches known as L-CHD and R-CHD. A condition for this directory is that the binary tree should be number balanced, i.e the number of nodes in the left sub tree must be equal to or one greater than the number of nodes in the right subtree. All the subtrees should also be number balanced.
Chained directory format
In this format the memory holds the directory pointer to the latest cache that accessed the block and each cache has the pointer to the previous cache that accessed the block. So when a processor sends a write request to a block in memory, the processor sends invalidations down the chain of pointers. In this directory when a cache block is replaced we need to traverse the list in order to change the directory which increases latency. In order to prevent this doubly linked lists are widely used now in which each cached copy has pointers to previous and the next cache that accesses the block.
Limited pointer format
The limited pointer format uses a set number of pointers to track the processors that are caching the data. When a new processor caches a block, a free pointer is chosen from a pool to point to that processor. There are a few options for handling cases when the number of sharers exceeds the number of free pointers. One method is to invalidate one of the sharers, using its pointer for the new requestor, though this can be costly in cases where a block has a large number of readers, such as a lock. Another method is to have a separate pool of free pointers available to all the blocks. This method is usually effective as the number of blocks shared by a large number of processors is not normally very large.
References
Computer architecture | Directory-based cache coherence | [
"Technology",
"Engineering"
] | 1,109 | [
"Computers",
"Computer engineering",
"Computer architecture"
] |
51,518,803 | https://en.wikipedia.org/wiki/Steered-response%20power | Steered-response power (SRP) is a family of acoustic source localization algorithms that can be interpreted as a beamforming-based approach that searches for the candidate position or direction that maximizes the output of a steered delay-and-sum beamformer.
Steered-response power with phase transform (SRP-PHAT) is a variant using a "phase transform" to make it more robust in adverse acoustic environments.
Algorithm
Steered-response power
Consider a system of microphones, where each microphone is denoted by a subindex . The discrete-time output signal from a microphone is . The (unweighted) steered-response power (SRP) at a spatial point can be expressed as
where denotes the set of integer numbers and would be the time-lag due to the propagation from a source located at to the -th microphone.
The (weighted) SRP can be rewritten as
where denotes complex conjugation, represents the discrete-time Fourier transform of and is a weighting function in the frequency domain (later discussed). The term is the discrete time-difference of arrival (TDOA) of a signal emitted at position to microphones and , given by
where is the sampling frequency of the system, is the sound propagation speed, is the position of the -th microphone, is the 2-norm and denotes the rounding operator.
Generalized cross-correlation
The above SRP objective function can be expressed as a sum of generalized cross-correlations (GCCs) for the different microphone pairs at the time-lag corresponding to their TDOA
where the GCC for a microphone pair is defined as
The phase transform (PHAT) is an effective GCC weighting for time delay estimation in reverberant environments, that forces the GCC to consider only the phase information of the involved signals:
Estimation of source location
The SRP-PHAT algorithm consists in a grid-search procedure that evaluates the objective function on a grid of candidate source locations to estimate the spatial location of the sound source, , as the point of the grid that provides the maximum SRP:
Modified SRP-PHAT
Modifications of the classical SRP-PHAT algorithm have been proposed to reduce the computational cost of the grid-search step of the algorithm and to increase the robustness of the method. In the classical SRP-PHAT, for each microphone pair and for each point of the grid, a unique integer TDOA value is selected to be the acoustic delay corresponding to that grid point. This procedure does not guarantee that all TDOAs are associated to points on the grid, nor that the spatial grid is consistent, since some of the points may not correspond to an intersection of hyperboloids. This issue becomes more problematic with coarse grids since, when the number of points is reduced, part of the TDOA information gets lost because most delays are not anymore associated to any point in the grid.
The modified SRP-PHAT collects and uses the TDOA information related to the volume surrounding each spatial point of the search grid by considering a modified objective function:
where and are the lower and upper accumulation limits of GCC delays, which depend on the spatial location .
Accumulation limits
The accumulation limits can be calculated beforehand in an exact way by exploring the boundaries separating the regions corresponding to the points of the grid. Alternatively, they can be selected by considering the spatial gradient of the TDOA , where each component of the gradient is:
For a rectangular grid where neighboring points are separated a distance , the lower and upper accumulation limits are given by:
where and the gradient direction angles are given by
See also
Acoustic source localization
Multilateration
Audio signal processing
References
Acoustics
Signal processing
Digital signal processing | Steered-response power | [
"Physics",
"Technology",
"Engineering"
] | 751 | [
"Telecommunications engineering",
"Computer engineering",
"Signal processing",
"Classical mechanics",
"Acoustics"
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51,519,180 | https://en.wikipedia.org/wiki/Angular%20Correlation%20of%20Electron%20Positron%20Annihilation%20Radiation | Angular Correlation of Electron Positron Annihilation Radiation (ACAR or ACPAR) is a technique of solid state physics to investigate the electronic structure of metals. It uses positrons which are implanted into a sample and annihilate with the electrons. In the majority of annihilation events, two gamma quanta are created that are, in the reference frame of the electron-positron pair, emitted in exactly opposite directions. In the laboratory frame, there is a small angular deviation from collinearity, which is caused by the momentum of the electron. Hence, measuring the angular correlation of the annihilation radiation yields information about the momentum distribution of the electrons in the solid.
Investigation of the electronic structure
All the macroscopic electronic and magnetic properties of a solid result from its microscopic electronic structure.
In the simple free electron model, the electrons do not interact with each other nor with the atomic cores. The relation between energy and momentum is given by
with the electron mass . Hence, there is an unambiguous connection between electron energy and momentum. Because of the Pauli exclusion principle the electrons fill all the states up to a maximum energy, the so-called Fermi energy. By the momentum-energy relation, this corresponds to the Fermi momentum . The border between occupied and unoccupied momentum states, the Fermi surface, is arguably the most significant feature of the electronic structure and has a strong influence on the solid's properties. In the free electron model, the Fermi surface is a sphere.
With ACAR it is possible to measure the momentum distribution of the electrons. A measurement on a free electron gas for example would give a positive intensity for momenta and zero intensity for . The Fermi surface itself can easily be identified from such a measurement by the discontinuity at .
In reality, there is interaction between the electrons with each other and the atomic cores of the crystal. This has several consequences: For example, the unambiguous relation between energy and momentum of an electronic state is broken and an electronic band structure is formed. Measuring the momentum of one electronic state gives a distribution of momenta which are all separated by reciprocal lattice vectors. Hence, an ACAR measurement on a solid with completely filled bands (i.e. on an insulator) gives a continuous distribution. An ACAR measurement on a metal has discontinuities where bands cross the Fermi level in all Brillouin zones in reciprocal space. This discontinuous distribution is superimposed by a continuous distribution from the entirely filled bands. From the discontinuities the Fermi surface can be extracted.
Since positrons that are created by beta decay possess a longitudinal spin polarization it is possible to investigate the spin-resolved electronic structure of magnetic materials. In this way, contributions from the majority and minority spin channel can be separated and the Fermi surface in the respective spin channels can be measured.
ACAR has several advantages and disadvantages compared to other, more well known techniques for the investigation of the electronic structure like ARPES and quantum oscillation: ACAR requires neither low temperatures, high magnetic fields or UHV conditions. Furthermore, it is possible to probe the electronic structure at the surface and in the bulk ( deep). However, ACAR is reliant on defect free samples as vacancy concentrations of up to per atom can efficiently trap positrons and distort the measurement.
Theory
In an ACAR measurement the angular deviation of many pairs of annihilation radiation is measured. Therefore, the underlying physical observable is often called 'two photon momentum density' (TPMD) or . Quantum mechanically, can be expressed as the squared absolute value of the Fourier transform of the multi-particle wave function of all the electron and the positron in the solid:
As it is not possible to imagine or compute the multi-particle wave function , it is often written as the sum of the single particle wave functions of the electron in the th state in the th band and the positron wave function :
The enhancement factor accounts for the electron-positron correlation. There exist sophisticated enhancement models to describe the electron-positron correlations, but in the following it will be assumed that . This approximation is called the independent particle model (IPM).
A very illustrative form of the TPMD can be obtained by the use of the Fourier coefficients for the wave function product :
These Fourier coefficients are distributed over all reciprocal vectors . If one assumes that the overlap of the electron and the positron wave function is constant for the same band , summing over all reciprocal lattice vectors gives a very instructive result:
The function is the Heaviside step function and the constant . This means, if is folded back into the first Brillouin zone, the resulting density is flat except at the Fermi momentum. Therefore, the Fermi surface can be easily identified by looking for this discontinuities in .
Experimental details
When a positron is implanted into a solid it will quickly lose all its kinetic energy and annihilate with an electron. By this process two gamma quanta with each are created which are in the reference frame of the electron positron pair emitted in exactly anti-parallel directions. In the laboratory frame, however, there is a Doppler shift from and an angular deviation from collinearity. Although the full momentum information about the momentum of the electron is encoded in the annihilation radiation, due to technical limitations it cannot be fully recovered. Either one measures the Doppler broadening of the annihilation radiation (DBAR) or the angular correlation of the annihilation radiation (ACAR).
For DBAR a detector with a high energy resolution like a high purity germanium detector is needed. Such detectors typically do not resolve the position of absorbed photons. Hence only the longitudinal component of the electron momentum can be measured. The resulting measurement is a 1D projection of .
In ACAR position sensitive detectors, gamma cameras or multi wire proportional chambers, are used. Such detectors have a position resolution of typically but an energy resolution which is just good enough to sort out scattered photons or background radiation. As is discarded, a 2D projection of is measured. In order to get a high angular resolution of and better, the detectors have to be set up at distances between from each other. Although it is possible to get even better angular resolutions by placing the detectors further apart, this comes at cost of the counting rate. Already with moderate detector distances, the measurement of one projection of typically takes weeks.
As ACAR measures projections of the TPMD it is necessary to reconstruct in order to recover the Fermi surface. For such a reconstruction similar techniques as for X-ray computed tomography are used. In contrast to a human body, a crystal has many symmetries which can be included into the reconstruction. This makes the procedure more complex but increases the quality of the reconstruction. Another way to evaluate ACAR spectra is by a quantitative comparison with ab initio calculations.
History
In the early years, ACAR was mainly used to investigate the physics of the electron-positron annihilation process. In the 1930s several annihilation mechanism were discussed. Otto Klemperer could show with his angular correlation setup that the electron-positron pairs annihilate mainly into two gamma quanta which are emitted anti-parallel. In the 1950s, it was realized that by measuring the deviation from collinearity of the annihilation radiation information about the electronic structure of a solid can be obtained.
During this time mainly setups with 'long slit geometry' were used. They consisted of a positron source and a sample in the center, one fixed detector on one side and a second movable detector on the other side of the sample. Each detector was collimated in such a way that the active area was much smaller in one than in the other dimension (thus 'long slit'). A measurement with a long slit setup yields a 1D projection of the electron momentum density . Hence, this technique is called 1D-ACAR.
The development of two-dimensional gamma cameras and multi wire proportional chambers in the 1970s and early 1980s led to the setting up of the first 2D-ACAR spectrometer. This was an improvement to 1D-ACAR in two ways: i) The detection efficiency could be improved and ii) the informational content was greatly increased as the measurement gave a 2D projection of . An important early example of the use of spin-polarized 2D-ACAR is the proof of half metallicity in the half-Heusler alloy NiMnSb.
References
Notes
Further reading
Laboratory techniques in condensed matter physics | Angular Correlation of Electron Positron Annihilation Radiation | [
"Physics",
"Chemistry",
"Materials_science"
] | 1,782 | [
"Condensed matter physics",
"Laboratory techniques in condensed matter physics"
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51,520,196 | https://en.wikipedia.org/wiki/EPIC%20204278916 | EPIC 204278916 is a pre-main-sequence star, about five million years old with a spectral type of M1, implying a red dwarf. It is part of the Upper Scorpius sub-group of the Scorpius–Centaurus association, and is in the constellation Scorpius. The star is approximately the size of the Sun at , but is only half its mass () and a fraction of its luminosity ().
This stellar object was first characterized by the 2nd USNO CCD Astrograph Catalog and the Two Micron All-Sky Survey, and was further studied during the Kepler space telescope's extended K2 mission Campaign 2 between 23 August and 13 November 2014.
Luminosity
In August 2016, a team of astronomers, led by Simone Scaringi of the Max Planck Institute for Extraterrestrial Physics in Germany, reported that this red dwarf star has a resolved circumstellar disc. Further, the research team observed unusual luminosity dimmings of up to 65% for 25 consecutive days (out of 79 total observation days). The variability in luminosity was highly periodic and attributed to stellar rotation. The researchers hypothesized that the irregular dimmings were caused by either a warped inner-disk edge or transiting cometary-like objects in either circular or eccentric orbits.
See also
Disrupted planet
List of stars that have unusual dimming periods
References
External links
EPIC Catalog at MAST
Astronomical objects discovered in 2016
Scorpius
M-type main-sequence stars
Pre-main-sequence stars
J16020757-2257467
Upper Scorpius | EPIC 204278916 | [
"Astronomy"
] | 339 | [
"Scorpius",
"Constellations"
] |
51,521,334 | https://en.wikipedia.org/wiki/DOPIPE | DOPIPE parallelism is a method to perform loop-level parallelism by pipelining the statements in a loop. Pipelined parallelism may exist at different levels of abstraction like loops, functions and algorithmic stages. The extent of parallelism depends upon the programmers' ability to make best use of this concept. It also depends upon factors like identifying and separating the independent tasks and executing them parallelly.
Background
The main purpose of employing loop-level parallelism is to search and split sequential tasks of a program and convert them into parallel tasks without any prior information about the algorithm. Parts of data that are recurring and consume significant amount of execution time are good candidates for loop-level parallelism. Some common applications of loop-level parallelism are found in mathematical analysis that uses multiple-dimension matrices which are iterated in nested loops.
There are different kind of parallelization techniques which are used on the basis of data storage overhead, degree of parallelization and data dependencies. Some of the known techniques are: DOALL, DOACROSS and DOPIPE.
DOALL: This technique is used where we can parallelize each iteration of the loop without any interaction between the iterations. Hence, the overall run-time gets reduced from N * T (for a serial processor, where T is the execution time for each iteration) to only T (since all the N iterations are executed in parallel).
DOACROSS: This technique is used wherever there is a possibility for data dependencies. Hence, we parallelize tasks in such a manner that all the data independent tasks are executed in parallel, but the dependent ones are executed sequentially. There is a degree of synchronization used to sync the dependent tasks across parallel processors.
Description
DOPIPE is a pipelined parallelization technique that is used in programs where each element produced during each iteration is consumed in the later iteration. The following example shows how to implement the DOPIPE technique to reduce the total execution time by breaking the tasks inside the loop and executing them in a pipelined manner. The breaking into tasks takes place in such a way that all the dependencies within the loop are unidirectional, i.e. the following iteration does not depend on the previous iteration.
Example
The program below shows a pseudocode for DOPIPE parallelization.
In this code, we see that there are three tasks (F0, F1 and F2) inside a loop iterating over j for 1 to N. Following is a list of dependencies in the code:
F1[j] → T F1[j+1], implies that statement F1 in iteration j+1 must be executed after statement F1 in iteration j. This is also known as true dependency.
F1[j] → T F2[j], implies that statement F2 in iteration j must be executed after statement F1 in iteration j.for (j=1; j<=N; j++) {
F0: o[j] = x[j] - a[j];
F1: z[j] = z[j-1] * 5;
F2: y[j] = z[j] * w[j];
}If this code would have been executed sequentially, then the total time consumed would be equal to N * (TF0 + TF1 + TF2), where TF0, TF1 and TF2 denote execution time for functions F0, F1 and F2 respectively per iteration.
Now, if we parallelize the loop by pipelining the statements inside the loop in the following manner:for (j=1; j<=N; j++) {
F0: o[j] = x[j] - a[j]; // DOALL parallelism
}
for (j=1; j<=N; j++) {
F1: z[j] = z[j-1] * 5; // DOPIPE parallelism
post(j); // The result of F1 is posted and available for use
}
for (j=1; j<=N; j++) {
wait(j); // It waits till the F1 completes and produces the value z[j] to be used by F2
F2: y[j] = z[j] * w[j];
}Since, F0 is an independent function, i.e. it does not have any loop-carried dependency (no dependence on j+1 or j-1 iterations). Neither it has any dependency across other statements in the loop. Hence, we can completely separate out this function and run it parallelly using DOALL parallelism. On the other hand, Statements F1 and F2 are dependent (explained above), therefore we split them into two different loops and execute them in a pipelined fashion. We use post(j) and wait(j) to synchronize between F1 and F2 loops.
Starting from the first iteration of j, statement F1 gets executed in TF1 time. Meanwhile, F2 is not getting executed since it is waiting for the value z[j] to be produced by F1. When F1 completes its execution for iteration j, it posts the value using post(j). After waiting for F1's execution, using wait(j), F2 starts its execution since it has the value z[j] available for use. Also, since F1's execution is not restricted by F2, hence F1 executes j+1 simultaneously. The figure below shows the execution timeline of all the statements.
From the figure, we see that the total time to execute F0 is TF0, since all the iterations of F0 are executed in parallel. While for F1 and F2, the total execution time is equal to N * TF1 + TF2 (considering negligible synchronization time).
This is considerably less than the time obtained during sequential execution.
Comparison with other models
DOALL parallelism mainly works on principle of divide and conquer. Here all the tasks run in different iterations that use unique set of data. So the problem with this implementation is that when large amount of data works is computed together, a large cache space is needed to work for different threads. Since there is no dependencies in the threads, there is no overhead for the inter - thread communication.
While in DOPIPE, there is a synchronization overhead between the threads. But, due to its pipelined structure, it requires less cache space because the data produced is immediately consumed by the consumer.
See also
Parallel computing
Loop level parallelism
Task parallelism
Data dependency
OpenMP
Automatic parallelization
Thread (computing)
Cache (computing)
References
Computer architecture
Parallel computing | DOPIPE | [
"Technology",
"Engineering"
] | 1,384 | [
"Computers",
"Computer engineering",
"Computer architecture"
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51,521,751 | https://en.wikipedia.org/wiki/Erle%20Ellis | Erle Christopher Ellis (born 11 March 1963 in Washington, DC) is an American environmental scientist. Ellis's work investigates the causes and consequences of long-term ecological changes caused by humans at local to global scales, including those related to the Anthropocene. As of 2015 he is a professor of Geography and Environmental Systems at the University of Maryland, Baltimore County where he directs the Laboratory for Anthroecology.
Education and career
Ellis received an A.B. in Biology in 1986 and a Ph.D. in Plant Biology from Cornell University in 1990 with Roger Spanswick. After receiving his Ph.D., Ellis taught English at Nanjing Agricultural University in 1990/1991, and returned to China to study nitrogen cycling in China's village landscapes from 1993-1996. From 1996 to 2000, he worked with Stephen Gliessman at the University of California, Santa Cruz.
In 2000 he was hired as an assistant professor in the department of Geography and Environmental Systems of the University of Maryland, Baltimore County; he was promoted to professor in 2015.
He is a fellow of the Global Land Programme (Scientific Steering Committee 2012-2017) of Future Earth, a former member of the Anthropocene Working Group of the International Commission on Stratigraphy, a Senior Fellow at the Breakthrough Institute (and coauthor of the Ecomodernist Manifesto), and an advisor to the Nature Needs Half movement. He has taught ecology as a visiting professor at the Harvard Graduate School of Design (2013-2015) and was a visiting professor at the Carnegie Institution's Department of Global Ecology (2006/2007).
Work
Ellis' research has explored long-term ecological changes in China's villages, and in 2008, he produced the first global map of anthropogenic biomes (and coined the term "anthrome") together with Navin Ramankutty. In 2019, he helped to lead a massive collaboration of archaeologists to map land use changes around the world over the past 10,000 years.
Ellis has published more than 100 scientific articles relating to global and local ecological changes caused by humans, and is a Global Highly Cited Researcher (Cross-Field, 2018, 2019, 2020). He has also written a number of articles and opinions communicating his work and other matters relating to humans as agents of ecological change, at Science, Nature, New Scientist, The New York Times, Breakthrough Journal, and other venues. His first book, Anthropocene: A Very Short Introduction, was published in 2018.
Awards
2021-2024 Presidential Research Professor, UMBC.
2019 Innovation in Sustainability Science Award, Ecological Society of America.
References
External links
Anthropocene: A Very Short Introduction
Discover: Human Influence on Ecology Mapped
Department Website
Profile at the Laboratory for Anthroecology
Anthropocene Working Group of the International Commission on Stratigraphy
20th-century American scientists
21st-century American scientists
American environmentalists
American ecologists
Environmental studies scholars
Environmentalism in China
Harvard Graduate School of Design faculty
Human impact on the environment
Landscape architecture
1963 births
Living people
Scientists from Washington, D.C. | Erle Ellis | [
"Engineering"
] | 627 | [
"Landscape architecture",
"Architecture"
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51,522,091 | https://en.wikipedia.org/wiki/TGK%20PG | TGK PG () is an automated cargo spacecraft project to replace Progress-MS as the Russian logistic vehicle to the ISS. It was requested for development to take advantage of the increased lift capacity of the Soyuz-2.1b. The initial development contract was awarded to RSC Energia by Roscosmos on December 11, 2015. The spacecraft is not expected to fly before 2020.
Spacecraft description
Born out of the need to reduce the flights to the ISS from 2018 onward, it was designed as a radical departure from the Progress design. It would incorporate concepts and technologies developed from the Orel and Progress-MS projects. One critical characteristic would be a 370 days on-orbit design life, compared to the 210 days of the Progress and Soyuz. This would allow less ships to be launched per year while maintaining a full complement on the station.
It would consist of a service module on the aft, an unpressurized propellant cluster of six tanks on the center, a pressurized module with docking adapter on the fore and a truss structure connecting all the parts. It would use the reaction control system of the Progress-MS and an orbital manoeuvring rocket engine already developed for another spacecraft. The new design would have a single deposit of propellant that could be used by the spacecraft or to refuel the space station.
See also
Comparison of space station cargo vehicles
Progress spacecraft – an expendable cargo vehicle currently in use by the Russian Federal Space Agency
Automated Transfer Vehicle – a retired expendable cargo vehicle used by the ESA
Cygnus spacecraft – an expendable cargo vehicle developed by Orbital Sciences Corporation under American CRS program, currently in use.
H-II Transfer Vehicle – a retired expendable cargo vehicle used by JAXA
Dragon 2 cargo spacecraft - a reusable cargo vehicle developed by SpaceX, under American CRS program, currently in use.
Dream Chaser Cargo System - a cargo variant of the reusable SNC's spaceplane
References
External links
RussianSpaceWeb TGK PG
Proposed spacecraft
Cargo spacecraft
Space program of Russia | TGK PG | [
"Astronomy"
] | 422 | [
"Astronomy stubs",
"Spacecraft stubs"
] |
51,522,936 | https://en.wikipedia.org/wiki/%CE%93-Decalactone | γ-Decalactone is a lactone and aroma compound with the chemical formula C10H18O2. It has an intense peach flavour, naturally present in many fruits and fermentations. It is particularly important in the formulation of peach, apricot, and strawberry flavourants for drinks, food, personal care products, pharmaceutical drugs, and household goods.
See also
δ-Decalactone
References
Gamma-lactones | Γ-Decalactone | [
"Chemistry"
] | 91 | [
"Organic compounds",
"Organic compound stubs",
"Organic chemistry stubs"
] |
51,523,111 | https://en.wikipedia.org/wiki/Jasmine%20lactone | Jasmine lactone is a lactone and aroma compound with a powerful fatty-fruity peach and apricot flavor. Its chemical formula is C10H16O2. It occurs naturally in jasmine oil, tuberose, gardenia, mimosa, honeysuckle, lily, tea, peach, and ginger. It is used as a food spice and is mainly used for the preparation of apricot, peach, dairy products, and as a tropical fruit flavor.
References
Delta-lactones
Heterocyclic compounds with 1 ring | Jasmine lactone | [
"Chemistry"
] | 112 | [
"Organic compounds",
"Organic compound stubs",
"Organic chemistry stubs"
] |
51,523,246 | https://en.wikipedia.org/wiki/K2-33 | K2-33 is an extremely young pre-main-sequence star located about away from the Earth in the constellation of Scorpius. It is known to host one planet, a super-Neptune, named K2-33b. It is also notable for its young age.
Nomenclature and history
K2-33 also has the 2MASS catalogue number J16101473-1919095 and EPIC designation 205117205.
Planetary candidates were detected around the star by NASA's Kepler Mission on its K2 mission, a mission tasked with discovering planets in transit around their stars. The transit method that Kepler uses involves detecting dips in brightness in stars. These dips in brightness can be interpreted as planets whose orbits pass in front of their stars from the perspective of Earth, although other phenomenon can also be responsible which is why the term planetary candidate is used.
Following the acceptance of the discovery paper, the Kepler team provided an additional moniker for the system of "K2-33". The discoverers referred to the star as K2-33, which is the normal procedure for naming the exoplanets discovered by the spacecraft. Hence, this is the name used by the public to refer to the star and its planet.
Candidate planets that are associated with stars studied by the Kepler Mission are assigned the designations ".01" etc. after the star's name, in the order of discovery. If planet candidates are detected simultaneously, then the ordering follows the order of orbital periods from shortest to longest. Following these rules, there was only one candidate planet were detected, with an orbital period of 5.424865 days.
The designation of b is given to the first planet orbiting a given star, followed by the other letters of the alphabet. In the case of K2-33, there was only one planet, so only the letter b are used. The name K2-33 derives directly from the fact that the star is the catalogued 33rd star discovered by K2 to have confirmed planets.
Stellar characteristics
This star was identified as a young pre-main-sequence object that belongs to the Upper Scorpius subgroup of the Scorpius–Centaurus association in a 2001 article, based on its high lithium content and position in the HR diagram. This is the nearest OB association and recent massive star formation region, with the Upper Scorpius subgroup having a mean distance of 140 parsecs (470 light-years). Direct parallax measurements, by the Gaia spacecraft, indicate that K2-33 is at a distance of 139 ± 0.5 pc, consistent with association to Upper Scorpius. The age of this subgroup is estimated at 11 ± 2 million years, while evolutionary models estimate to K2-33 an independent age of 9.3 million years.
K2-33's spectrum is best modelled with a spectral type of M3.3 and a visual extinction of 0.75 magnitudes, so the star can be considered to be a red dwarf. Its effective temperature has been measured at 3,540 K, which together with the apparent brightness of the star indicates a luminosity of 0.15 times the solar luminosity and a radius of 1.05 times the solar radius. This large size is typical of young stars and indicates that the star is still in the process of contracting towards the main sequence. The mass of this star is not known accurately, and has been estimated at 0.56 or 0.31 times the solar mass. The metallicity of K2-33 is consistent with being equal to the solar value ([Fe/H] = 0).
As a young star, K2-33 has a fast rotation, with a projected rotational velocity of 8.2 km/s. The rotation period of the star, 6.3 days, is known from the light curve obtained by the Kepler spacecraft, causing periodic variations of about 2% in the brightness of the star as star spots appear and disappear from Earth's line of sight. This stellar variability was removed for the analysis of the transit signal of the planet K2-33b.
K2-33 is almost certainly not a binary star. Radial velocity data obtained by the HIRES spectrograph, in the Keck I Telescope, do not show an acceleration larger than 2.6 km/s/yr, which excludes objects more massive than 0.14 solar masses at 3 AU or closer. Adaptive optics infrared observations by the NIRC2 imager, in the Keck II Telescope, can exclude companions more massive than 19 Jupiter masses at 3 AU or further, and 11-12 Jupiter masses at 6-23 AU. The combination of both observational limits only allows for the existence of brown dwarfs or very low mass stars at separations of 1-3 AU.
Planetary system
The only known planet transits the star; this means that the planet's orbit appear to cross in front of their star as viewed from the Earth's perspective. Its inclination relative to Earth's line of sight, or how far above or below the plane of sight it is, vary by less than one degree. This allows direct measurements of the planet's periods and relative diameters (compared to the host star) by monitoring the planet's transit of the star.
K2-33b is known remarkably for its extremely young age, only one other planet is younger (V830 Tau b), with an age of around 2 million years, while K2-33b is only 9.3 million years old. Nonetheless, it is quite a discovery in the search of exoplanets.
Infrared measurements by the Spitzer Space Telescope show that there is still a disk of planetary debris, indicating that planet formation may not be finished yet.
References
J16101473-1919095
Planetary transit variables
Planetary systems with one confirmed planet
Pre-main-sequence stars
Scorpius
Upper Scorpius | K2-33 | [
"Astronomy"
] | 1,215 | [
"Scorpius",
"Constellations"
] |
51,523,353 | https://en.wikipedia.org/wiki/Khajidsuren%20Bolormaa | Khajidsuren Bolormaa, or Khajidsurengiin Bolormaa, (; born January 18, 1965) is a Mongolian mineralogical engineer, as well as a healthcare and children's rights advocate, who served as the First Lady of Mongolia from 2009 to 2017. Bolormaa is the wife of former President Tsakhiagiin Elbegdorj. In 2006, Bolormaa founded the Bolor Foundation, which cares for orphans in Mongolia.
Biography
Bolormaa was born on January 18, 1965, in Ulaanbaatar, Mongolia. She graduated high school in Mongolia. She then enrolled at Lviv State University in Lviv, Ukrainian S.S.R. (present-day Ukraine), from 1983 to 1988 to study geochemistry. Bolormaa met her future husband, Tsakhiagiin Elbegdorj, while both were students living in Lviv. The couple married and had their first son, who was born in Lviv. They returned to Mongolia in 1988.
Khajidsurengiin Bolormaa worked as a mineralogical engineer for the government-run Central Geological Laboratory of Mongolia. She then established and opened Ankh-Erdene, a private research laboratory focusing on mineralogy and the Mongolia's mining industry.
Tsakhiagiin Elbegdorj was elected president in 2009, making Bolormaa the First Lady of Mongolia. Elbegdorj was re-elected in 2013.
In March 2010, First Lady Bolormaa established the Hope Cancer-free Mongolia National Foundation to improve cancer treatment services in the country. She called for increased cooperation between 38 Asian First Ladies to fight cancer on the continent, especially among women. The foundation retrained Mongolian doctors, nurses and other staff at both domestic and international medical facilities between 2010 and 2013.
References
Living people
1965 births
First ladies of Mongolia
Mongolian engineers
Mining engineers
Mongolian health activists
Children's rights activists
People from Ulaanbaatar
20th-century Mongolian women
20th-century Mongolian people
21st-century Mongolian women
21st-century Mongolian people | Khajidsuren Bolormaa | [
"Engineering"
] | 438 | [
"Mining engineering",
"Mining engineers"
] |
51,523,453 | https://en.wikipedia.org/wiki/Moto%20Z%20Play | Moto Z Play is an Android smartphone developed by Motorola Mobility. Unveiled in August 2016 at IFA Berlin, it is a mid-range version of the Moto Z, distinguished primarily by its larger battery (thus making it a de facto successor to the Moto X Play, a similarly-positioned counterpart to the company's 2015 flagship, the Moto X Style). As with the Moto Z, the Z Play is compatible with "MotoMods" accessories that can be magnetically attached to the device to provide additional functionality.
Specifications
The Moto Z Play's chassis utilizes a metal frame and body; it is thicker than the flagship Moto Z model, at , and includes a USB-C connector and a 3.5 mm headphone jack. The rear of the device contains pogo pin connectors used to communicate with "MotoMod" accessories. The Moto Z Play includes a 1080p display, an octa-core Qualcomm Snapdragon 625 system-on-chip, and 3GB of RAM. The Moto Z Play includes 32GB of internal storage, expandable via MicroSDXC card, a 16-megapixel rear-facing camera, a 5-megapixel front-facing camera, and a fingerprint scanner.
Reception
CNET noted that the Z Play had advantages over the more expensive Moto Z, including a bigger battery and a headphone jack, although the Z Play was thicker and heavier, and the fingerprint sensor was once again criticized for looking too much like a home button. The camera was considered to be "altogether satisfactory for quick, casual shots", with fewer white balance issues than the Moto Z, but grainy low-light shots. In a test of "mild" real-world use, the device's battery lasted four days on a single charge. While judged as being slower in tests than the competing Alcatel Idol 4S and OnePlus 3, it was felt that the Moto Z's performance was "enough to satisfy your common phone needs", and was not sluggish in launching apps and performing common tasks. In conclusion, it was felt that the Moto Z Play was "an affordable phone with an impressively enduring battery life."
References
Android (operating system) devices
Motorola smartphones
Mobile phones introduced in 2016
Modular smartphones
Discontinued smartphones | Moto Z Play | [
"Engineering"
] | 487 | [
"Modular design",
"Modular smartphones"
] |
51,525,633 | https://en.wikipedia.org/wiki/Size-asymmetric%20competition | Size-asymmetric competition refers to situations in which larger individuals exploit disproportionately greater amounts of resources when competing with smaller individuals. This type of competition is common among plants but also exists among animals. Size-asymmetric competition usually results from large individuals monopolizing the resource by "pre-emption"—i.e., exploiting the resource before smaller individuals are able to obtain it. Size-asymmetric competition has major effects on population structure and diversity within ecological communities.
Definition of size asymmetry
Resource competition can vary from completely symmetric (all individuals receive the same amount of resources, irrespective of their size, known also as scramble competition) to perfectly size-symmetric (all individuals exploit the same amount of resource per unit biomass) to absolutely size-asymmetric (the largest individuals exploit all the available resource). The degree of size asymmetry can be described by the parameter θ in the following equation focusing on the partition of the resource r among n individuals of sizes Bj.
where ri refers to the amount of resources consumed by individuals in the neighbourhood of j. When θ = 1, competition is perfectly size-symmetric—e.g., if a large individual is twice the size of its smaller competitor, the large individual will acquire twice the amount of that resource (i.e. both individuals will exploit the same amount of resource per biomass unit). When θ > 1, competition is size-asymmetric—e.g., if a large individual is twice the size of its smaller competitor and θ = 2, the large individual will acquire four times the amount of that resource (i.e., the large individual will exploit twice the amount of resource per biomass unit). As θ increases, competition becomes more size-asymmetric, and larger plants get larger amounts of resources per unit of biomass compared with smaller plants.
Differences in size asymmetry among resources in plant communities
Competition among plants for light is size-asymmetric because of the directionality of its supply. Higher leaves shade lower leaves but not vice versa. Competition for nutrients appears to be relatively size-symmetric, although it has been hypothesized that a patchy distribution of nutrients in the soil may lead to size asymmetry in competition among roots. Nothing is known about the size asymmetry of competition for water.
Implication for plant communities
Various ecological processes and patterns have been shown to be affected by the degree of size asymmetry—e.g., succession, biomass distribution, grazing response, population growth, ecosystem functioning, coexistence and species richness. A large body of evidence shows that species loss following nutrient enrichment (eutrophication) is related to light competition. However, there is still a debate whether this phenomenon is related to the size asymmetry of light competition or to other factors.
Contrasting assumptions about size asymmetry characterise the two leading and competing theories in plant ecology, the R* theory and the CSR theory. The R* theory assumes that competition is size-symmetric and therefore predicts that competitive ability in nature results from the ability to withstand low level of resources (known as the R* rule). In contrast the CSR theory assumes that competition is size-asymmetric and therefore predicts that competitive ability in nature results from the ability to grow fast and attain a large size.
Size-asymmetric competition affects also several evolutionary processes in relation to trait selection. Evolution of plant height is highly affected by asymmetric light competition. Theory predicts that only under asymmetric light competition, plants will grow upward and invest in wood production at the expense of investment in leaves, or in reproductive organs (flowers and fruits). Consistent with this, there is evidence that plant height increases as water availability increases, presumably due to increase in the relative importance of size-asymmetric competition for light. Similarly, investment in the size of seeds at the expense of their number may be more effective under size-asymmetric resource competition, since larger seeds tend to produce larger seedlings that are better competitors.
Size-asymmetric competition can be exploited in managing plant communities, such as the suppression of weed in crop fields. Weeds are a greater problem for farmer in dry than in moist environments, in large part because crops can suppress weeds much more effectively under size-asymmetric competition for light than under more size-symmetric competition below ground.
See also
Competition (biology)
Asymmetric competition
Resource (biology)
Resource partitioning
Plant ecology
Jacob Weiner
References
Ecology
Biological interactions
Competition | Size-asymmetric competition | [
"Biology"
] | 932 | [
"Behavior",
"Biological interactions",
"Ecology",
"nan",
"Ethology"
] |
51,525,870 | https://en.wikipedia.org/wiki/Dianethole | Dianethole is a naturally occurring organic compound that is found in anise and fennel. It is a dimeric polymer of anethole. It has estrogenic activity, and along with anethole and photoanethole, may be responsible for the estrogenic effects of anise and fennel. These compounds bear resemblance to the estrogens stilbene and diethylstilbestrol, which may explain their estrogenic activity. In fact, it is said that diethylstilbestrol and related drugs were originally modeled after dianethole and photoanethole.
See also
Anol
Hexestrol
References
Phytoestrogens | Dianethole | [
"Chemistry"
] | 139 | [
"Organic compounds",
"Organic compound stubs",
"Organic chemistry stubs"
] |
51,526,024 | https://en.wikipedia.org/wiki/Ratio%20meter%20systems | A Ratiometer type temperature indicating system consists of a sensing element and a moving-coil indicator, which unlike the conventional type has two coils moving together in a permanent-magnet field of non-uniform strength. The coil arrangements and the methods of obtaining the non-uniform field depends on the manufacturer's design. The main application behind in this ratiometer system is to find the unknown resistance, namely Rx. This plays a major role in the aircraft industry, in finding cylinder head temperatures exposed to turbine exhaust gases. It can also be used to measure temperatures of systems such as engine oil and carburetor air.
Methods of obtaining non-uniform magnetic coil
Parallel coil
Parallel coil is a method of obtaining non-uniform coil in ratiometer systems in which the hairsprings are wounded parallelly in order to allow the signal to pass through it.
Cross coil
The coil is wound from 99.99% pure copper on a wood which was treated with many oxidizers and chemicals.
The benefits from using foil inductors comes in the form of less distortion and higher dynamic headroom, when used on crossovers for modern high performance speakers.
In these methods two parallel resistance arms are formed; one containing the coil and a fixed calibrating resistance R1, and the other containing a coil in series with a calibrating resistance R2 and the temperature-sensing element Rx. Both arms are supplied with direct current from the aircraft's main power source, but the coils are so wound that current flows through them in opposite directions.
As in any moving-coil indicator, rotation of the measuring element is produced by forces which are proportional to product of the current and field strength, and the direction of rotation depends on the direction of current relative to the magnetic field. In a ratio meter, therefore, it follows that the force produced by one coil will always tend to rotate the measuring element in the opposite direction to the force produced by the second coil, and further more, as the magnetic field is of non-uniform strength, the coil carrying the greater current will always move towards the area of weaker field, and vice versa.
When the temperature at the sensing element Rx increases, then in accordance with the temperature/resistance relationship of the material used for the element, its resistance will increase and so cause a decrease in the force created by it.
When the measuring elements at the mid-position of its rotation, the currents in both windings can be in the same field strength simultaneously.
A ratiometer systems, however, do not require hair springs for exerting a controlling torque, this being provided solely by the appropriate coil winding and non-uniform field arrangements. Should variations occur in the power supply they will affect both coils equally so that the ratio of current flowing in the coils remains the same and tendencies for them to move to positions of differing field strength are counterbalanced.
References
Measuring instruments | Ratio meter systems | [
"Technology",
"Engineering"
] | 587 | [
"Measuring instruments"
] |
51,526,185 | https://en.wikipedia.org/wiki/Desulfomonile | Desulfomonile is a Gram negative, strict anaerobe and non-motile bacterial genus from the family of Syntrophaceae. Desulfomonile bacteria can reduce sulfur oxyanions to H2S.
See also
List of bacterial orders
List of bacteria genera
References
Further reading
Bacteria genera
Thermodesulfobacteriota | Desulfomonile | [
"Biology"
] | 72 | [
"Bacteria stubs",
"Bacteria"
] |
51,527,865 | https://en.wikipedia.org/wiki/Triparanol | Triparanol (, ; brand name and development code MER/29, as well as many other brand names) was the first synthetic cholesterol-lowering drug. It was patented in 1959 and introduced in the United States in 1960. The developmental code name of triparanol, MER/29, became so well known that it became the registered trade name of the drug. It was withdrawn in 1962 due to severe adverse effects such as nausea and vomiting, vision loss due to irreversible cataracts, alopecia, skin disorders (e.g., dryness, itching, peeling, and "fish-scale" texture), and accelerated atherosclerosis. It is now considered to be obsolete.
The drug acts by inhibiting 24-dehydrocholesterol reductase, which catalyzes the final step of cholesterol biosynthesis, the conversion of desmosterol into cholesterol. Although effective in reducing cholesterol levels, this results in tissue accumulation of desmosterol, which in turn is responsible for the side effects of triparanol. Unlike statins, triparanol does not inhibit HMG-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis, and in contrast to triparanol, statins can lower cholesterol levels without resulting in accumulation of intermediates like desmosterol.
Estrogen is known to lower cholesterol levels, but produces side effects like gynecomastia and decreased libido in men. It was hoped that a drug could be developed that lacked overt estrogenic effects but still lowered cholesterol levels. Triparanol is a triphenylethanol and was derived from chlorotrianisene (TACE), a nonsteroidal triphenylethylene estrogen. The nonsteroidal triphenylethanol antiestrogen ethamoxytriphetol (MER-25) is a derivative of triparanol. The selective estrogen receptor modulator clomifene is also structurally related to triparanol. The developers of triparanol jokingly referred to it as a "non-estrogenic estrogen" due to its lipid-lowering effects without other estrogenic effects.
See also
Azacosterol
Desmosterolosis
X-linked ichthyosis
Clomestrone
Mytatrienediol
References
24-Dehydrocholesterol reductase inhibitors
Tertiary alcohols
Diethylamino compounds
Hypolipidemic agents
Organochlorides
Phenol ethers
Withdrawn drugs
Ethanolamines | Triparanol | [
"Chemistry"
] | 542 | [
"Drug safety",
"Withdrawn drugs"
] |
51,527,976 | https://en.wikipedia.org/wiki/Pawe%C5%82%20Urban | Paweł Urban (also spelled as Pawel L. Urban (Chinese name: 鄂本帕偉)) is a chemist and is a professor of Chemistry in the National Tsing Hua University (Hsinchu, Taiwan). He received his Ph.D. in Chemistry from the University of York (United Kingdom). Urban's research interests include mass spectrometry and biochemical analysis.
Academic activity
Urban is an inventor of the hydrogel micropatch sampling method, fizzy extraction, systems for imaging chemical reactions, and micro-arrays for mass spectrometry (MAMS). He co-authored a book on time-resolved mass spectrometry, and over 100 papers. Urban is editorial board member of Scientific Reports, HardwareX, PeerJ, and acted as a guest editor in Philosophical Transactions of the Royal Society A. His h-index is 34. He received the Ta-You Wu Memorial Award.
References
Living people
Alumni of the University of York
Taiwanese chemists
Academic staff of the National Tsing Hua University
Mass spectrometrists
Year of birth missing (living people) | Paweł Urban | [
"Physics",
"Chemistry"
] | 228 | [
"Biochemists",
"Mass spectrometry",
"Spectrum (physical sciences)",
"Mass spectrometrists"
] |
51,528,233 | https://en.wikipedia.org/wiki/Connectivity%20%28media%29 | Connectivity refers broadly to social connections forged through mediated communications systems. That is, "since the arrival of the World Wide Web and the spread of mobile communications, mediated connectivity has been quietly normalized as central to a consolidating 'global imaginary'". One aspect of this is the ability of the social media to accumulate economic capital from the users' connections and activities on social media platforms by using certain mechanisms in their architecture. According to several scholars (van Dijck and Poell) "it is a key element of social media logic, having a material and metaphorical importance in social media culture". This concept originates from the technological term of "connectivity" but its application to the media field has acquired additional social and cultural implications. The increasing role of social media in everyday life serves as the basis of such connectivity in the 21st century. It shows the interrelations between the users activities on social media and at the same time the empowerment of the social media platforms with the data that was produced by the users and given to those services for granted.
Notion of connectivity
Connectivity developed with the rise of the Internet, first with the introduction Web 1.0 and later Web 2.0. New improvements in equipment, software, the advancement of speed and access have increased the level and quality of connectivity. Along with these improvements, new media such as social networking systems (e.g. Facebook, Twitter, Google+), websites that provide access to user-generated content (e.g. Youtube, Myspace, Flickr), trading and marketing sites (e.g. Amazon, eBay, Groupon) and also game sites (e.g. FarmVille, The Sims Social) have become an essential part of everyday life of an average user: "Just as electricity in the 19th and 20th centuries transformed societies by penetrating every fibre of people's personal and professional lives, network connectivity is probably the most powerful transformative force in early 21st-century cultures". This made a shift in the understanding of the nature of connectivity and moved the initial focus just from a technical side of the notion to its increasingly acquired techno-socio-cultural character.
As mentioned before, connectivity is built on the principles of Web 2.0. that promote an openness, create the vision of empowerment of the user in the generation of a new content and coordination of the information flow on the Internet. These mechanisms encourage staying in touch with each other despite distances and share as much data as possible. According to Youngs, the development of the Internet has resulted in the deeper permeation of ICTs into public and private spheres of peoples' life, their relationships and spheres of identity. Hence, connectivity becomes a resource of maintaining these activities. However, van Dijck notices that this connectivity is not just a neutral feature of new media, but is manufactured by the combination of human and technological resources, where the role of technologies is intransparent. Algorithms and protocols that are part of such platforms prompt users activities and online experiences on social media platforms. One of the most prominent activities on social media includes sharing and as Kennedy argues, "sharing rhetoric draws on a cultural image of connectivity. Social media platforms are not the only actors to use such imagining, mobile-based platforms do the same. Network providers, handset manufacturers, and social media platforms each promote social activities of togetherness enabled by their products which evidences a sustained cultural norm of sharing through teletechnologies for the purpose of affective connectivity". Therefore, such architecture creates even bigger demand in connectivity that is continuously exploited by the online market.
Example of the application of connectivity
Facebook can serve as a good example how connectivity is being produced and exploited by social media. Van Dijck mentions three concepts implemented in the technological side of connectivity which result in the connective structure of the platform and in the creation of its additional social and cultural dimensions. These are platform, protocol and interface.
Several scholars (van Dijck, Gillespie) mention in their works the ambiguity of the term "platform" that promises to bring openness, access, to be neutral and help people build social connections and participate in online activities, but in fact implies a more complicated structure of the media, most of the time created for the profit purposes and as the enhancement of control under the users. As for the protocols and interfaces, the algorithms behind the platform are intransparent and presented to the user as intermediaries for "staying in touch", being connected, encouraging to make those connections, but at the same time the platform itself "facilitates the cultivation of 'weak ties' as well as the fabrication of 'strong ties'". Therefore, connectivity becomes a new type of social capital gained from the platform's working principles.
See also
Web 2.0
Participatory culture
Sharing economy
Network economics
The Wealth of Networks
References
Social media
Media studies
Information Age
Information economy
Hyperreality | Connectivity (media) | [
"Technology"
] | 992 | [
"Information Age",
"Science and technology studies",
"Computing and society",
"Hyperreality",
"Social media"
] |
51,528,309 | https://en.wikipedia.org/wiki/Stance%20%28vehicle%29 | The stance of a vehicle is determined by its suspension height and the fitment of the wheels in the fender arches. It may refer to any vehicle, including sports cars, pickup trucks and off-road vehicles, however it is mostly associated with lowered sports cars, sedans, hatchbacks, vans and other body styles of passenger cars. The term stance is most commonly associated with the stanced car subculture, a style of modifying cars which emphasizes lowering cars, typically with either coilovers or air suspension, and often adding negative camber to the wheels to achieve the "stanced" look. The main parameters of the vehicle's stance are suspension height and position of the wheels. Suspension height usually depends on the suspension components while wheel position usually depends on the rim size and offset. Tire fitment also plays a big role from both visual and functional perspective.
Customization style
The term "stance" or "stanced" is often used to describe a car customization style. The term "stance" is often used in conjunction with "slammed" or "lowered". Key elements of the stance style are: lowered suspension (lowering springs, coilovers or air suspension), stretched tires and negative camber. Oftentimes, the main purpose of a stanced car project is to achieve an improved visual appeal rather than improved performance characteristics or handling, however some cars combine both. Stance is related to other modification styles such as JDM (Japanese Domestic Market), Euro style and VIP style.
A popular lowered stance customization that first emerged in the 1940s was the taildragger car, described by Motor Trend as follows:
Negative camber
Camber is a measurement from the centerline of the wheel/tire relative to the road's surface. Negative camber is when the top of the wheel/tire angles inward toward the center of the vehicle. When done sparingly, negative camber greatly improves the handling characteristics of a vehicle. It does this by keeping the center of the tire perpendicular to the road when the car is turning. Therefore, allowing the optimum amount of tire tread to contact the road.
Conversely, negative camber will decrease tire grip in straight line acceleration and braking. This is due to the same reasoning, when the vehicle is not turning less tread will be in contact with the road or track, resulting in less grip and lost performance. Many drift cars, however, use negative camber on their front wheels for better handling characteristics as the negative camber keeps the contact patch of the tire perpendicular to the road when going through turns with much steering angle.
While most normal vehicles maintain about 0.5° - 1° of camber, in the stance community, some owners run up to 45° of negative camber to achieve the stance they are looking for.
Origin
Some sources credit the origin of the "stance" style to motorsport, stating that enthusiasts started seeking to modify their cars to replicate the low to the ground look of race cars, as typically, most racecars designed for race tracks feature low and stiff suspension along with light and wide sport wheels for better handling and cornering on the race tracks.
If the original approach was based on the functional standpoint, modern modification style is often based on the visual standpoint. Extremely lowered cars tend to be show cars and typically do not play the role of daily driver or race car. Extreme body work, suspension and wheel setups often make them less comfortable to drive on public roads and sometimes unsafe.
Culture and events
The origin of many of the key elements of modern "stance" style is typically credited to Japan, however, other countries previously have also had similar subcultures of car modification that developed largely independently of Japan, and as such, the true origins of "stance" is hard to pinpoint as the style has spread to many countries. Stance centric car shows are hosted around the world on most continents. Events happen yearly that host many stanced cars, such as Stancenation, Wörthersee Treffen, FittedUK, Wekfest, Ultrace and H2Oi. There is also a significant stanced car presence at larger events such as SEMA, Tokyo Auto Salon and Osaka Auto Messe.
References
Vehicle design | Stance (vehicle) | [
"Engineering"
] | 848 | [
"Vehicle design",
"Design"
] |
51,528,560 | https://en.wikipedia.org/wiki/Meizu%20PRO%205%20Ubuntu%20Edition | The Meizu PRO 5 Ubuntu Edition is a smartphone designed and produced by the Chinese manufacturer Meizu, which runs on Ubuntu Touch. It is an alternative version of the Meizu PRO 5. It was unveiled on February 17, 2016.
History
Rumors about an Ubuntu-powered edition of the Meizu PRO 5 appeared after photos of a Meizu PRO 5 running Ubuntu Touch 15.04 had been leaked. It was reported that this device would be showcased at the Mobile World Congress in April 2016.
Release
The Meizu PRO 5 Ubuntu was officially released on February 17, 2016. International pre-orders began on February 22, 2016, through online retailer JD.com.
Features
Ubuntu Touch
The PRO 5 Ubuntu Edition is running Ubuntu Touch, which is a mobile operating system based on the Ubuntu linux distribution developed by Canonical. Its goal is to provide a free and open-source mobile operating system and deliver a different approach to user experience by focusing on so-called “scopes” instead of traditional apps.
Hardware and design
The technical specifications and outer appearance of the PRO 5 Ubuntu Edition is identical with the Meizu PRO 5. The Meizu PRO 5 features a Samsung Exynos 7420 Octa with an array of eight ARM Cortex CPU cores, an ARM Mali-T760 MP8 GPU and 3 GB of RAM. Meizu Global Brand Manager Ard Boudeling explained in November 2015 that Meizu decided to use the Samsung Exynos SoC because it is “currently [..] the only option if you want to build a genuine premium device”.
The Meizu PRO 5 Ubuntu Edition has a full-metal body, which measures x x and weighs . It has a slate form factor, being rectangular with rounded corners and has only one central physical button at the front.
The PRO 5 Ubuntu Edition is only available in with 32 GB of internal storage and with a champagne gold body.
The PRO 5 Ubuntu Edition features a 5.7-inch AMOLED multi-touch capacitive touchscreen display with a (FHD resolution of 1080 by 1920 pixels. The pixel density of the display is 387 ppi.
In addition to the touchscreen input and the front key, the device has a volume/zoom control and the power/lock button on the right side and a 3.5mm TRS audio jack, which is powered by a dedicated Hi-Fi amplifier supporting 32-bit audio with a frequency range of up to 192 kHz.
The PRO 5 Ubuntu Edition uses a USB-C connector for both data connectivity and charging.
The Meizu PRO 5 Ubuntu Edition has two cameras. The rear camera has a resolution of 21.16 MP, a ƒ/2.2 aperture and a 6-element lens. Furthermore, the phase-detection autofocus of the rear camera is laser-supported. The front camera has a resolution of 5 MP, a ƒ/2.0 aperture and a 5-element lens.
Reception
While the device itself had been praised for its specifications and build quality, critics have criticized the Ubuntu Touch operating system.
GSMArena stated that "overall, all the bits and pieces that made the Meizu Pro 5 great are still present, but even on paper, we can already see quite a lot of compromises brought about by the new OS in the Ubuntu Edition at hand".
Softpedia gave the device a rating of 4 out of 5 stars, concluding that they "would recommend [the] Meizu PRO 5 Ubuntu Edition to those who like smartphones with big screens, Ubuntu Phone fans [..], as well as very curious people who get bored easily and always enjoy trying something new".
See also
Meizu
Meizu PRO 5
Comparison of smartphones
List of open-source mobile phones
References
External links
Official product page Meizu
Ubuntu Touch devices
Mobile phones introduced in 2015
Meizu smartphones
Discontinued flagship smartphones | Meizu PRO 5 Ubuntu Edition | [
"Technology"
] | 840 | [
"Discontinued flagship smartphones",
"Flagship smartphones"
] |
51,528,677 | https://en.wikipedia.org/wiki/Meizu%20M3%20Max | The Meizu M3 Max is a smartphone designed and produced by the Chinese manufacturer Meizu, which runs on Flyme OS, Meizu's modified Android operating system. It is a current phablet model of the M series. It was unveiled on September 5, 2016, in Beijing.
History
In August, rumors about a new phablet Meizu device appeared after the company released some teasers for a new device mentioning that it will be a device containing “Max” in the product name. At the same point, invitations containing a Nokia device for a Meizu launch event on September 5, 2016, had been sent out.
On August 26, 2016, several leaked photos of the upcoming phablet device had been released.
Release
As announced, the M3 Max was released in Beijing on August 10, 2016.
Pre-orders for the M3 Max began after the launch event on August 10, 2016.
Features
Flyme
The Meizu M3 Max was released with an updated version of Flyme OS, a modified operating system based on Android Marshmallow. It features an alternative, flat design and improved one-handed usability.
Hardware and design
The Meizu M3 Max features a MediaTek Helio P10 system-on-a-chip with an array of eight ARM Cortex-A53 CPU cores, an ARM Mali-T860 MP2 GPU and 3 GB of RAM.
The M3 Max is available in four different colors (grey, silver, champagne gold and rose gold) and comes with 3 GB of RAM and 32 GB of internal storage.
The Meizu M3 Max has a full-metal body, which measures x x and weighs . It has a slate form factor, being rectangular with rounded corners and has only one central physical button at the front. Unlike most other Android smartphones, the M3 Max doesn't have capacitive buttons nor on-screen buttons. The functionality of these keys is implemented using a technology called mBack, which makes use of gestures with the physical button. The M3 Max further extends this button by a fingerprint sensor called mTouch.
The M3 Max features a fully laminated 6-inch IPS multi-touch capacitive touchscreen display with a FHD resolution of 1080 by 1920 pixels. The pixel density of the display is 296 ppi.
In addition to the touchscreen input and the front key, the device has volume/zoom control buttons and the power/lock button on the right side, a 3.5mm TRS audio jack on the top and a microUSB (Micro-B type) port on the bottom for charging and connectivity.
The Meizu M3 Max has two cameras. The rear camera has a resolution of 13 MP, a ƒ/2.2 aperture, a 5-element lens, phase-detection autofocus and an LED flash. The front camera has a resolution of 5 MP, a ƒ/2.0 aperture and a 4-element lens.
See also
Comparison of smartphones
References
External links
Official product page Meizu
Phablets
Android (operating system) devices
Mobile phones introduced in 2016
M3 Max
Discontinued smartphones | Meizu M3 Max | [
"Technology"
] | 633 | [
"Crossover devices",
"Phablets"
] |
51,528,709 | https://en.wikipedia.org/wiki/Five%20Great%20Kilns | The Five Great Kilns (), also known as Five Famous Kilns, is a generic term for ceramic kilns or wares (in Chinese 窯 yáo can mean either) which produced Chinese ceramics during the Song dynasty (960–1279) that were later held in particularly high esteem. The group were only so called by much later writers, and of the five, only two (Ru and Guan) seem to have produced wares directly ordered by the Imperial court, though all can be of very high quality. All were imitated later, often with considerable success.
All except Ding ware used celadon glazes, and in Western terms the celadon kilns are stoneware, as opposed to the Ding early porcelain. The celadons placed great emphasis on elegant forms and their ceramic glazes, and were otherwise lightly decorated, with no painting.
The five kilns produced respectively:
Ru ware (汝)
Jun ware (钧)
Guan ware (官)
Ding ware (定)
Ge ware (哥)
History of the term
Although the group and name is generally said in books to have been a coinage by Chinese writers from the Ming or Qing dynasties, a recent paper analysing the main Chinese scholars suggests the modern number and selection of "great kilns", as given here, in fact only dates back to the mid-20th century, with various numbers and other kilns often found in previous writings. In particular, the semi-mythical Chai ware, and Longquan celadon often feature in earlier groupings, and Jun ware is often omitted.
Notes
References
Rawson, Jessica (ed). The British Museum Book of Chinese Art, 2007 (2nd edn), British Museum Press,
Chinese pottery
China-related lists of superlatives
Kilns
Song dynasty | Five Great Kilns | [
"Chemistry",
"Engineering"
] | 376 | [
"Chemical equipment",
"Kilns"
] |
51,528,799 | https://en.wikipedia.org/wiki/Bisdehydrodoisynolic%20acid | Bisdehydrodoisynolic acid (BDDA), as the (Z)-isomer ((Z)-BDDA), is a synthetic, nonsteroidal estrogen related to doisynolic acid that was never marketed. It is one of the most potent estrogens known, although it has more recently been characterized as a selective estrogen receptor modulator (SERM). BDDA and other doisynolic acid derivatives display relatively low affinity accompanied by disproportionately high estrogenic potency in vivo, which was eventually determined to be due to transformation into metabolites with greater estrogenic activity. The drug was discovered in 1947 as a degradation product of the reaction of equilenin or dihydroequilenin with potassium hydroxide. It is the seco-analogue of equilenin, while doisynolic acid is the seco-analogue of estrone. These compounds, along with diethylstilbestrol, can be considered to be open-ring analogues of estradiol. The methyl ether of BDDA, doisynoestrol, is also an estrogen, and in contrast to BDDA, has been marketed.
See also
Allenolic acid
Carbestrol
Fenestrel
Methallenestril
Stilbestrol
Triphenylethylene
References
Carboxylic acids
Phenanthrenes
Synthetic estrogens
Hydroxyarenes | Bisdehydrodoisynolic acid | [
"Chemistry"
] | 299 | [
"Carboxylic acids",
"Functional groups"
] |
51,529,056 | https://en.wikipedia.org/wiki/Coalesse | Coalesse is a United States–based furniture company founded in 2008. It is a division of Steelcase and creates products with the goal of encouraging collaboration. Coalesse is headquartered in Grand Rapids, Michigan, with their design headquarters in San Francisco and their main showroom located in the Merchandise Mart in Chicago.
Company overview
Coalesse launched in June 2008 at the NeoCon World's Trade Fair in Chicago. It is a combination of Steelcase's Brayton, Metro, and Vecta brands, but also includes pieces made by Carl Hansen & Son, Walter Knoll AG & Co., Viccarbe, and PP Mobler. Their original brand focus was on designing office and home furniture that appeals to what the company called “live/work lifestyles, but later shifted their focus away from creating home-oriented pieces toward creating more work-oriented pieces.”
In 2012, it was announced that Coalesse was planning to expand their business operations into Europe.
References
Furniture companies of the United States
Manufacturing companies based in Michigan
Companies based in Grand Rapids, Michigan
Industrial design | Coalesse | [
"Engineering"
] | 220 | [
"Industrial design",
"Design engineering",
"Design"
] |
51,529,492 | https://en.wikipedia.org/wiki/Acquired%20neuroprotection | Acquired neuroprotection is a synaptic-activity-dependent form of adaptation in the nervous system that renders neurons more resistant to harmful conditions. The term was coined by Hilmar Bading. This use-dependent enhancement of cellular survival activity requires changes in gene expression triggered by neuronal activity and nuclear calcium signaling. In rodents, components of the neuroprotective gene program can reduce brain damage caused by seizure-like activity or by a stroke. In acute and chronic neurodegenerative diseases, gene regulatory events important for acquired neuroprotection are antagonized by extrasynaptic NMDA receptor signaling leading to increased vulnerability, loss of structural integrity, and bioenergetics dysfunction.
References
Neuroscience
Neurophysiology | Acquired neuroprotection | [
"Biology"
] | 157 | [
"Neuroscience"
] |
51,529,881 | https://en.wikipedia.org/wiki/Nuclear%20calcium | The concentration of calcium in the cell nucleus can increase in response to signals from the environment. Nuclear calcium is an evolutionary conserved potent regulator of gene expression that allows cells to undergo long-lasting adaptive responses. The 'Nuclear Calcium Hypothesis’ by Hilmar Bading describes nuclear calcium in neurons as an important signaling end-point in synapse-to-nucleus communication that activates gene expression programs needed for persistent adaptations. In the nervous system, nuclear calcium is required for long-term memory formation, acquired neuroprotection, and the development of chronic inflammatory pain. In the heart, nuclear calcium is important for the development of cardiac hypertrophy. In the immune system, nuclear calcium is required for human T cell activation. Plants use nuclear calcium to control symbiosis signaling.
References
Neuroscience
Gene expression
Calcium | Nuclear calcium | [
"Chemistry",
"Biology"
] | 166 | [
"Neuroscience",
"Gene expression",
"Molecular genetics",
"Cellular processes",
"Molecular biology",
"Biochemistry"
] |
51,529,934 | https://en.wikipedia.org/wiki/Q%20Cygni | Q Cygni (Q Cyg), is a star located in the constellation Cygnus. It is also known as Nova Cygni 1876, and has the designation NGC 7114, and HR 8296. Nova Cygni is located in the northwestern portion of Cygnus along the border with Lacerta.
One of the earliest novae recorded, Q Cygni was discovered by astronomer Johann Friedrich Julius Schmidt on November 24, 1876. The star had undergone a nova, brightening to about 3rd magnitude and remaining as bright for four days.
The system is termed a cataclysmic variable, composed of a white dwarf in close orbit with another star that orbit each other every 10 hours. The white dwarf is surrounded by an accretion disc, which blazes much brighter than the star it circles. The system has been estimated to be 740 ± 11 parsecs distant. The secondary star has been estimated to be around 0.6 times as massive as the Sun, making it an orange dwarf of spectral type K5. Also known as a donor star, the secondary supplies mass to the white dwarf via its accretion disc.
A small nebulous disc was reported around the nova and this led to it being listed in the New General Catalogue as a possible planetary nebula. No nebulosity is visible in modern observations and the Revised New General Catalogue lists this as a "non-existent" object.
References
External links
Stars of Cygnus
Cygnus (constellation)
Novae
8296
J21414393+4250290
Durchmusterung objects
NGC objects
Cygni, Q | Q Cygni | [
"Astronomy"
] | 331 | [
"Novae",
"Cygnus (constellation)",
"Astronomical events",
"Constellations"
] |
51,530,038 | https://en.wikipedia.org/wiki/Witt%20vector%20cohomology | In mathematics, Witt vector cohomology was an early p-adic cohomology theory for algebraic varieties introduced by . Serre constructed it by defining a sheaf of truncated Witt rings Wn over a variety V and then taking the inverse limit of the sheaf cohomology groups Hi(V, Wn) of these sheaves. Serre observed that though it gives cohomology groups over a field of characteristic 0, it cannot be a Weil cohomology theory because the cohomology groups vanish when i > dim(V). For Abelian varieties, showed that one could obtain a reasonable first cohomology group by taking the direct sum of the Witt vector cohomology and the Tate module of the Picard variety.
References
Algebraic geometry
Cohomology theories | Witt vector cohomology | [
"Mathematics"
] | 164 | [
"Fields of abstract algebra",
"Algebraic geometry"
] |
51,530,438 | https://en.wikipedia.org/wiki/Psi%20Leonis | ψ Leonis (Latinised as Psi Leonis, abbreviated to ψ Leo or psi Leo), is a solitary star located in the zodiac constellation of Leo, to the east-northeast of Regulus. It is faintly visible to the naked eye with an apparent visual magnitude of 5.38. Based upon stellar parallax measurements, it is located around 610 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an absorption factor of 0.3 due to interstellar dust.
Psi Leonis is an evolved red giant star with a stellar classification of M2 IIIab. It shines with a luminosity over 900 times that of the Sun from a relatively cool outer atmosphere that has an effective temperature of 3,756 K. It is a suspected variable star with a measured brightness variation of 0m.018. Psi Leonis has a magnitude 11.63 visual companion at an angular separation of 281.60 arcseconds along a position angle of 139°, as of 2000.
References
M-type giants
Suspected variables
Leo (constellation)
Leonis, Psi
3866
084194
047723
Leonis, 16
Durchmusterung objects | Psi Leonis | [
"Astronomy"
] | 245 | [
"Leo (constellation)",
"Constellations"
] |
70,124,884 | https://en.wikipedia.org/wiki/Bernoulli%20umbra | In Umbral calculus, the Bernoulli umbra is an umbra, a formal symbol, defined by the relation , where is the index-lowering operator, also known as evaluation operator and are Bernoulli numbers, called moments of the umbra. A similar umbra, defined as , where is also often used and sometimes called Bernoulli umbra as well. They are related by equality . Along with the Euler umbra, Bernoulli umbra is one of the most important umbras.
In Levi-Civita field, Bernoulli umbras can be represented by elements with power series and , with lowering index operator corresponding to taking the coefficient of of the power series. The numerators of the terms are given in OEIS A118050 and the denominators are in OEIS A118051. Since the coefficients of are non-zero, the both are infinitely large numbers, being infinitely close (but not equal, a bit smaller) to and being infinitely close (a bit smaller) to .
In Hardy fields (which are generalizations of Levi-Civita field) umbra corresponds to the germ at infinity of the function while corresponds to the germ at infinity of , where is inverse digamma function.
Exponentiation
Since Bernoulli polynomials is a generalization of Bernoulli numbers, exponentiation of Bernoulli umbra can be expressed via Bernoulli polynomials:
where is a real or complex number.
This can be further generalized using Hurwitz Zeta function:
From the Riemann functional equation for Zeta function it follows that
Derivative rule
Since and are the only two members of the sequences and that differ, the following rule follows for any analytic function :
Elementary functions of Bernoulli umbra
As a general rule, the following formula holds for any analytic function :
This allows to derive expressions for elementary functions of Bernoulli umbra.
Particularly,
Particularly,
,
,
Relations between exponential and logarithmic functions
Bernoulli umbra allows to establish relations between exponential, trigonometric and hyperbolic functions on one side and logarithms, inverse trigonometric and inverse hyperbolic functions on the other side in closed form:
References
Polynomials
Finite differences
Combinatorics
Factorial and binomial topics | Bernoulli umbra | [
"Mathematics"
] | 466 | [
"Mathematical analysis",
"Discrete mathematics",
"Factorial and binomial topics",
"Polynomials",
"Finite differences",
"Combinatorics",
"Algebra"
] |
70,125,038 | https://en.wikipedia.org/wiki/NGC%204324 | NGC 4324 is a lenticular galaxy located about 85 million light-years away in the constellation Virgo. It was discovered by astronomer Heinrich d'Arrest on March 4, 1862. NGC 4324 has a stellar mass of 5.62 × 1010 M☉, and a baryonic mass of 5.88 × 1010 M☉. The galaxy's total mass is around 5.25 × 1011 M☉. NGC 4324 is notable for having a ring of star formation surrounding its nucleus. It was considered a member of the Virgo II Groups until 1999, when its distance was recalculated and it was placed in the Virgo W Group.
Physical characteristics
First discovered in 1957 by Russian astronomer Kirill Ogorodnikov and described by Ogorodnikov as "a system of planet-like concentrations similar to beads" and as "equally-spaced bead-like concentrations of equal size and brightness similar to the annular nebula of Kant-Lapace nebular hypothesis.", NGC 4324 features an inner ring that surrounds the nucleus. The ring appears complete but broken on opposite sides of its diameter which led to Burstein et al. suggesting that the ring is not a ring at all but instead tightly wound spiral arms and that NGC 4324 is a misclassified spiral or lenticular galaxy. Despite this, the ring is considered to be a true ring. The ring hosts most of the molecular gas observed in NGC 4324 with roughly 1.7 × 109 M☉ of HI (neutral hydrogen) and 9 × 107 M☉ of HII (singly-ionised hydrogen). Despite this, HI was detected by Duprie et al. in 1996 that extends roughly 2 optical diameters suggesting that atomic hydrogen is not only concentrated in the ring.
In Ultraviolet light, the ring is bright, due to the presence of star formation that is occurring at an estimated rate of roughly 0.052 ± 0.021 M☉ per year, with star formation being segregated in the ring. In between the ring and the bulge of NGC 4324, there are tightly wound spiral arms that are defined mostly by dust.
The gas in the ring in NGC 4324 may have been accredited from filaments of galaxies or minor merging with gas-rich satellite galaxies.
Stellar populations
In the center of NGC 4324, the stellar population has a mean age of about 8 billion years, with an abundance ratio that is close to the sun, at [Mg/Fe]
0, and a metallicity that is slightly supersolar, at [Z/H] ~ +0.1. This suggests continuous effective star formation in the nucleus of NGC 4324. In the bulge of NGC 4324, the mean age of the stellar population is around 13 billion years, with abundance ratio of [Mg/Fe] = +0.15, and a metallicity of [Z/H] = −0.2 L −0.3. In the inner part of the disk of NGC 4324, the stellar population is old, with an abundance ratio of [Mg/Fe] = +0.2, and a metallicity of [Z/H] < −0.33. Such characteristics imply a brief single starburst took place more than 10 billion ago and formed the stellar disk of NGC 4324. In the ring-dominated area of the disk, the dominant stellar population is also old, despite being slightly younger than in the inner disk, and has chemical properties similar to the stars of the inner disk.
Activity
NGC 4324 is classified as a Seyfert Galaxy and as a LINER galaxy. Despite being classified as a Seyfert galaxy, NGC 4324 has no delectable nuclear radio continuum emission lines, suggesting that the emission lines that led to its classification as a Seyfert come from stellar processes such as photoionization driven by supernova remnants and/or planetary nebulae which can mimic the high-ionization nebular emission characteristic of the nuclei of other observed Seyfert Galaxies. This is despite the fact that NGC 4324 is host to a supermassive black hole with an estimated mass of 2.187 × 106 M☉.
Group membership
NGC 4324 is listed as member of the Virgo S Cloud, which is also known as the Virgo Southern Extension or the Virgo II Groups. It was placed in the NGC 4303 Group by P. Fouque et al. and A. M. Garcia et al. in 1992 and 1993 respectively, which is centered on the galaxy NGC 4303, which considered part of the Virgo Southern Extension. However, later distance measurements made with the Tully-Fisher method showed that NGC 4324 was not part of the NGC 4303 Group but was instead a member of the Virgo W Group, which lies at twice the distance of the Virgo Cluster and is centered on the elliptical galaxy NGC 4261.
See also
List of NGC objects (4001–5000)
NGC 7217
NGC 7742
External links
References
4324
040179
Virgo (constellation)
Astronomical objects discovered in 1862
Lenticular galaxies
07451
Seyfert galaxies
LINER galaxies
Ring galaxies | NGC 4324 | [
"Astronomy"
] | 1,052 | [
"Virgo (constellation)",
"Constellations"
] |
70,125,309 | https://en.wikipedia.org/wiki/Lemnis%20Gate | Lemnis Gate was a first-person arena shooter video game developed by Ratloop Games Canada and published by Frontier Foundry. It was released on September 28, 2021 for the PlayStation 4, PlayStation 5, Windows, Xbox One, and Xbox Series X/S. It was also published to Xbox Game Pass on its first day of release as well.
The game featured players taking turns in competitive multiplayer matches to complete 25 second runs with characters as they attempt to complete objectives. Each player's turn stacked on top of previous rounds, causing players to think critically over the best strategy to take in a given situation to win as previous loops continue.
Reception to the game was generally favorable, with critics praising its interesting take on first-person shooter mechanics and the injection of a new layer of strategy into the genre. The game's multiplayer servers were shut down on July 11, 2023, with reporters noting the game's low player count and that it is shut down during a wave of similar live service game failures.
Gameplay
Lemnis Gate was a turn-based first-person shooter with time loop and hero shooter elements. Games were either 1v1 or 2v2. The standard game mode, "Seek and Destroy", involved having one side defend five specific objectives from being destroyed at different points on the map while the other side attacked them. Whichever team either destroyed more objectives or defended them at the end of all the rounds would win the match.
Time loop mechanic
Central to Lemnis Gate was its time loop gameplay mechanic. Each player lead a team of six operatives with different abilities and took turns attempting to complete objectives in 25-second loops. Players would continue in alternating order until all of the operatives had completed a loop. Previously used operatives automatically carried out the actions that the player inputted for them in previous loops, and later operatives could disrupt the actions that they took in order to stop them from completing objectives.
One reviewer gave an example of how the loops affected gameplay: their operative was able to damage an opponent's character enough from an earlier loop that it caused a cascading effect, allowing them to eliminate all of the previously looped operatives and get a draw from a match because of the butterfly effect. Games could quickly devolve into puzzle-solving sessions, as players strategize over the best operative to choose and the best strategy to take in a given situation to score the most points. The game included a tutorial area which allows players to try out the different skillsets of the operatives before playing, but the game quickly pushes players into online matches.
Development
The development of Lemnis Gate was inspired by conversations that started in 2015, and development began in earnest in the middle of 2017. Game Director James Anderson explained their choice of using novel time mechanics, saying, "... there’s a lot of competition in the first person shooter genre, so we had to come up with a really unique hook and way to play the game." The developers felt that there was a large amount of competition in the first-person shooter space and wanted to create something with a unique take to attract players.
The game originally had a larger tutorial, but after Ratloop tested it with players, found that people were not interested in going through a lengthy intro before getting to play the game. The title of the game refers to the lemniscate, a mathematical curve that loops in on itself like a figure-eight. The game was delayed by a month to allow for more polish, and was also released on Xbox Game Pass simultaneously as its general release.
Reception
Reception to the game was generally favorable according to Metacritic, with critics praising its unique take on the hero shooter genre while sometimes criticizing its complexity. PC Gamer's Robert Zak felt that the game made familiar concepts from other first-person shooters interesting and fresh again, noting that the game "could prove an ever-swirling timesink for shooter fans with a cerebral side." Rock Paper Shotguns Matt Cox felt differently, saying that the game's often ended up being very evenly matched and that the last person to go would often win. In a mixed review, NMEs Jim Trinca felt that though the game's concept is interesting and that its ideas are brilliant, the first-person shooter mechanics that underpinned it were "underwhelming." IGN Italy'''s Di Angelo Bianco echoed Trinca's thoughts, noting that the game's underlying concept made up for some of the lack of personality its setting and characters exhibited. The game was on a GameSpot list which highlighted the highest-ranked first-person shooters on Metacritic from 2021.
Server shutdown
After failing to meet player count and sales expectations, Ratloop announced that the game would be delisted from all digital storefronts on April 11, 2023, with multiplayer servers shutting down on July 11. Console players can play a very limited form of the game via local multiplayer and the game's training modes, while gamers who purchased the game on PC are unable to play the title at all after its July shutdown. PC players asked the developers in the comments of the shutdown announcement to enable local multiplayer, which would allow the game to be played offline, but the developers did not respond. Reporters observed the game maintained a low number of concurrent players and speculated this contributed to the decision for the shutdown. Gameindustry.biz's James Batchelor and Push Square's Stephen Tailby noted that the title's failure is among a wave of several online and live service game shutdowns in 2023, continuing a market trend. Game Developer'''s Justin Carter said that the game was joining "2023's multiplayer graveyard."
References
External links
2021 video games
Asymmetrical multiplayer video games
Competitive games
Cooperative games
First-person shooter multiplayer online games
First-person shooters
Frontier Developments games
Hero shooters
Multiplayer online games
PlayStation 4 games
PlayStation 5 games
Ratloop games
Video games developed in Canada
Windows games
Xbox One games
Xbox Series X and Series S games | Lemnis Gate | [
"Physics",
"Mathematics"
] | 1,233 | [
"Cooperative games",
"Game theory",
"Asymmetry",
"Asymmetrical multiplayer video games",
"Symmetry"
] |
70,125,767 | https://en.wikipedia.org/wiki/Huallaga%20River%20Boats%20Collision%20%282021%29 | The Huallaga river boats collision was a fatal boat collision that killed 21 in Peru. It occurred on August 29, 2021, in the Alto Amazonas Province, west of the Department of Loreto. An additional unknown number of people were described as missing.
Description
The event occurred in the early morning of August 29 in the Alto Amazonas Province, when a motorized ferry collided with a river boat. The boat had approximately 80 people on board. Intense morning fog made it difficult to see.
Petroperú reported that the 80-person boat was called Ayachi, and the motor boat Nauta. Ayachi picked up its passengers at 1:00 a.m. in Santa María to transfer them to Yurimaguas, while Nauta headed for Iquitos. Ayachi's passengers belonged to an evangelical congregation called Nueva Jesuralén.
Rescue
At the time of the accident, smaller boats of locals came to rescue the survivors. A passenger from Ayachi relates:
"Some grabbed us from behind, desperate. We were under the boat. We have managed to get out. My colleagues don't. I have lost my wife and seven-year-old son."
Rescuers from the Peruvian National Police and the Peruvian Navy went to the scene, where they managed to rescue 50 people alive. At the beginning, 16 were reported missing.
The number of survivors rose to 60, and the number of deceased increased to 23 on August 31. One family was reported to have 14 deaths in the accident.
References
2021 in Peru
Collision
2021 disasters in Peru | Huallaga River Boats Collision (2021) | [
"Physics"
] | 321 | [
"Collision",
"Mechanics"
] |
70,126,157 | https://en.wikipedia.org/wiki/Calibrated%20automated%20thrombogram | The calibrated automated thrombogram (CAT or CT) is a thrombin generation assay (TGA) and global coagulation assay (GCA) which can be used as a coagulation test to assess thrombotic risk. It is the most widely used TGA. The CAT is a semi-automated test performed in a 96-well plate and requires specialized technologists to be performed. As a result, it has seen low implementation in routine laboratories and has been more limited to research settings. Lack of standardization with the CAT has also led to difficulties in study-to-study comparisons in research. However, efforts have recently been made towards standardization of the assay. An example of a specific commercial CAT is the Thrombinoscope by Thrombinoscope BV (now owned by Diagnostica Stago).
The CAT can be used to measure thrombogram parameters such as the endogenous thrombin potential (ETP) and to assess activated protein C resistance (APCR). The CAT ETP-based APC resistance test is especially sensitive to estrogen-induced procoagulation, such as with combined oral contraceptives.
In 2018, a commercial fully-automated TGA system and alternative to the CAT called the ST Genesia debuted. It has been said that this system should allow for more widespread adoption of TGAs in clinical laboratories. The ST Genesia system also shows improved reproducibility compared to the CAT.
References
Blood tests
Coagulation system
Medical signs | Calibrated automated thrombogram | [
"Chemistry"
] | 315 | [
"Blood tests",
"Chemical pathology"
] |
70,126,230 | https://en.wikipedia.org/wiki/Thrombin%20generation%20assay | A thrombin generation assay (TGA) or thrombin generation test (TGT) is a global coagulation assay (GCA) and type of coagulation test which can be used to assess coagulation and thrombotic risk. It is based on the potential of a plasma to generate thrombin over time, following activation of coagulation via addition of phospholipids, tissue factor, and calcium. The results of the TGA can be output as a thrombogram or thrombin generation curve using computer software with calculation of thrombogram parameters.
TGAs can be performed with methods like the semi-automated calibrated automated thrombogram (CAT) (2003) or the fully-automated ST Genesia system (2018). TGAs were first used as manual assays in the 1950s and have since become increasingly automated.
Parameters
Thrombogram parameters for the TGA include:
Lag time (minutes; time until thrombin first generated/thrombin concentration first increased)
Time to peak or ttPeak (minutes; time to maximum concentration of thrombin generated)
Start tail (minutes; time at which thrombin generation ends and all generated thrombin has been inhibited)
Peak height or peak thrombin (molar concentration (e.g., nM) of thrombin; peak or maximum concentration of thrombin generated)
Velocity index (slope of thrombin generation between lag time/first thrombin generation and time to peak; corresponds to first derivative of this part of curve)
Endogenous thrombin potential (ETP; area under the curve of the thrombin generation curve)
ETP-based APC resistance test
The addition of activated protein C (APC) to a TGA results in an inhibition of thrombin generation as measured by reduction of the endogenous thrombin potential (ETP; area under the thrombin generation curve). This can be used to assess APC resistance and is termed the ETP-based APC resistance test. Results may be expressed as normalized APC sensitivity ratio (nAPCsr), which corresponds to the ratio of the ETP measured in the presence and absence of APC divided by the same ratio in reference plasma. The higher the nAPCsr value, the greater the APC resistance of the person. The ETP-based APC resistance test was developed in 1997.
References
Blood tests
Coagulation system
Medical signs | Thrombin generation assay | [
"Chemistry"
] | 521 | [
"Blood tests",
"Chemical pathology"
] |
70,126,407 | https://en.wikipedia.org/wiki/Space%20ethics | Space ethics, astroethics or astrobioethics is a discipline of applied ethics that discusses the moral and ethical implications arising from astrobiological research, space exploration and space flight. It deals with practical contemporary issues like the protection of the space environment and hypothetical future issues pertaining to our interaction with extraterrestrial life forms.
Specific issues of space ethics include space debris mitigation, the militarization of space and the ethics of SETI and METI, but also more theoretical topics like space colonization, terraforming, directed panspermia and space mining. The field also concerns itself with more fundamental moral questions, such as the value of abiotic environments in space, the intrinsic value of extraterrestrial life, and how humans should treat extraterrestrial non-intelligent life (like microbes) and extraterrestrial intelligent life (and whether this distinction should be made in the first place).
Astroethical issues are often discussed as elements of broader issues such as general environmental protection and imperialism. Astroethics have been described as an emerging discipline gaining in attention, a "necessity for astrobiology" and a "true issue for the future of astrobiology".
Ethical guidelines for space exploration
Planetary Protection
A guiding principle in astroethics is that of Planetary Protection (PP), which seeks to prevent the introduction of lifeforms from Earth to other celestial bodies (forward contamination) and vice versa (back contamination), and thereby possible adverse consequences on existing ecospheres resulting from such contamination. This principle is anchored in the UN Outer Space Treaty, which was established in 1967 and has since been signed and ratified by all space-faring nations.
Precautionary Principle
The precautionary principle was defined in the 1998 Wingspread Conference on the Precautionary Principle. This approach is supposed to guide decisions in the face of a lack of scientific knowledge or consensus on a matter. In a 2010 COSPAR workshop at Princeton University, 26 experts embraced the precautionary principle and concluded that "further investigations before interference that is likely to be harmful to Earth and other extraterrestrial bodies, including extraterrestrial life and the contamination and disturbance of celestial environments", are to be conducted.
Other Astroethical Principles for SETI
SETI astrobiologist Margaret Race and Methodist theologian Richard Randolph have outlined 4 principles for the search for extra-terrestrial life within our solar system:
Cause no harm to Earth, its life, or its diverse ecosystems.
Respect the ecosystem on the surveyed celestial body, do not irreparably alter it or its evolutionary trajectory.
Follow proper scientific procedures with honesty and integrity during all phases of exploration.
Ensure international participation by all interested parties.
Issues
A wide range of concrete issues is discussed in astroethics. Some of them are herein elaborated.
Sterlility
Assumptions about outer space, particularly regarding space colonization, have characterized outer space as sterile and therefore a terra nullius. This assumption does not hold true, particularly considering that Earth is part of it.
Space debris
Millions of pieces of space debris, defunct artificial objects in space, are orbiting Earth. On average, one cataloged piece of space debris falls back onto the planet every day, potentially posing a risk to organisms and property. In total, an estimated 80 tons of space debris re-enter Earth's atmosphere every year. Due to the high friction with the atmospheric gases, the debris burns up, causing the release of its chemical components, which may contribute to atmospheric pollution and ozone depletion. Additionally, space debris orbits the Earth at extremely high velocity. In Low Earth Orbit, where all crewed space stations and many satellites are located, debris typically reaches speeds of around 8 km/s (approximately 18,000 mph or 29,000 km/h). As a result, even tiny pieces of debris can severely damage or destroy satellites and spacecraft in the event of a collision. This could pose a threat to the lives of astronauts on crewed missions and lead to the phenomenon of Kessler syndrome, where a collision of objects in space produces new fragments of space debris that could set off a chain reaction of more collisions. This could render the space around Earth untraversable for space missions and unsuitable for the use of satellites.
As of March 2022, there are no legally binding international laws about who is responsible for the extraction of space debris, or mandating a reduction of new space debris brought into Earth's orbit. However, space agencies of several countries have implemented their own standards and policies to reduce introduction of new space debris, and the Inter-Agency Space Debris Coordination Committee (IADC) has been founded to address issues regarding orbital debris. Additionally, JAXA is researching an electromagnetic tether that could be used to pull debris down into the atmosphere.
The moral problem is that those in power (space agencies) can launch material into the Earth's orbit for their own gains without being held accountable for it, while the general public has to bear the consequences (such as atmospheric pollution or the risk of being hit by space debris).
Satellite surveillance
Reconnaissance satellites are used for a variety of military and intelligence purposes, such as optical imaging and signals intelligence. It has been noted that such data could infringe on people's privacy and thereby lead to ethical and legal issues. It could also turn into a source of national security threats if such information got into malevolent hands. In order to ensure ethically correct obtainment and use of satellite data, leading researchers in law, meteorology and atmospheric science have called for new policy which would lead to more transparency and security.
Weaponizing space
In 1967, the Outer Space Treaty was signed, spurred by the development of intercontinental ballistic missiles, the Soviet Union's launch of Sputnik, the first artificial satellite, and the following arms race with the United States. The treaty outlaws all kinds of military action (including weapon tests) in space, limits the use of space to peaceful purposes only and ensures that all nations on Earth are free to explore space.
This treaty has since been called into question multiple times, especially by former President of the United States Donald Trump. On June 18, 2018, Trump announced plans to establish a space force, which would constitute a new, sixth branch of the United States military. He expressed that "When it comes to defending America, it is not enough to merely have an American presence in space. We must have American dominance in space". On December 20, 2019, the United States Space Force Act was signed into law with votes from both Democratic and Republican senators and House members. As a result, the United States Space Force was founded.
This was seen by some as an American contestation of the Outer Space Treaty. Viktor Bondarev, chair of the Federation Council Committee on Defense and Security, responded by saying that if the US were to go further and withdraw from the 1967 treaty, there would be "a tough response aimed at ensuring world security." This is despite Russia itself having a space force branch in their military.
Private spaceflight and space tourism
The emergence of space tourism gives rise to a number of ethical concerns. Future frequent and large-scale landings on celestial bodies like the moon may damage or pollute landing sites and the areas around them. While scientific activity in space is benign, this cannot be guaranteed for actions by private people. If, how, by what criteria and by whom laws should be made to ensure that space tourism doesn't negatively impact other celestial bodies is a question of astroethics.
Terraforming other celestial bodies
Terraforming is a controversial astroethical matter. Proponents of terraforming, like Robert Zubrin, argue that humans, being the only technologically advanced and intelligent species on Earth, have a moral obligation to make other celestial bodies habitable for Earth's lifeforms to ensure their survival after the inevitable destruction of our planet. The other, ecocentrist and biocentrist side of the debate criticizes this position as anthropocentrism and argues that other celestial bodies may already contain life which always has intrinsic value, no matter how advanced it may be. They oppose the interplanetary contamination and changes to the other world that would stem from terraforming, as they could endanger the indigenous life and alter its evolutionary trajectory.
Ethicality of SETI and METI
SETI and especially METI (Active SETI) are not uncontroversial and come with their own ethical implications. METI has been criticized as incompatible with the precautionary principle because it could reveal the location of our planet to potentially malevolent alien species. It therefore also potentially puts all of humanity at risk without the need for their individual prior consent, which violates the basic scientific rule of informed consent that all other science must abide by. Reflecting on human history, some authors even fear the enslavement of humanity, should we be discovered by a more advanced species. Similarly, Stephen Hawking, one of the most prominent METI critics, warned of the potential consequences of a meeting with such a species, citing the near-extinction of Aboriginal Tasmanians as an equivalent case from human history.
Concerns regarding the ethicality of METI might be a solution to the Fermi paradox. It is proposed that extraterrestrial life forms may abstain from attempting interstellar communication due to the potential danger it may pose to them, in line with the precautionary principle.
Other astroethical considerations regarding METI are the lack of legally enforceable protocols about the steps that should be taken once extraterrestrial life is discovered, the unpredictability of cultural consequences of that discovery (potential paradigm changes in policy, nations, religions, etc.), who will get to speak for humanity in case contact is made, how and by whom that person or group of people should be selected, and what the contents of the messages should be.
Value of extraterrestrial life
A further point of contention in the field is whether extraterrestrial life has intrinsic value and therefore if humans have a moral obligation to protect it. This becomes even more difficult when considering the wide span of possible extraterrestrial life forms and whether our treatment of them should differ based on criteria such as their advancement and intelligence. As former NASA chief historian Steven J. Dick put it, "Does Mars belong to the Martians, even if the Martians are only microbes?" Dick argues that the first step in deciding how we should interact with life forms is to assess their moral status, which is complicated by our ambiguous relations with animals on earth, sheltering some species as pets while eating and exterminating others. The principle of planetary protection provides that all life on other celestial bodies is worthy of protection from harm (also in the form of contamination) and therefore confers rights even on hypothetical extraterrestrial microbes, a situation that contrasts with our treatment of microbes and even most higher-developed organisms on Earth. This difference in treatment is hardly justifiable. Therefore, according to Dick, astroethical considerations will broaden our current ethical horizon: they will unveil such inconsistencies and double standards and move humanity from an anthropocentric ethic (ascribing intrinsic value only to rationing beings) to a cosmocentric or biocentric one that values all living things. In fact, Dick says that the finding of extraterrestrial life would "necessitate" a transition away from the anthropocentric approach because it would no longer be consistently applicable to a cosmos that harbors life beyond Earth.
Space burial
The decision to include several grams of human cremains onboard Peregrine Lunar Lander flight 01 was criticized by the Navajo Nation, whose president, Buu Nygren, argued that the Moon is sacred to the Navajo and other American Indian nations, saying "As stewards of our culture and traditions, it is our responsibility to voice our grievances when actions are taken that could desecrate sacred spaces and disregard deeply held cultural beliefs". Celestis CEO Charles Chafer responded that "[the company] reject[s] the whole premise that this is somehow desecration" and that "nobody owns the Moon". The launch was not successful in reaching the Moon.
References
See also
Environmental ethics
Ethics of technology
Astrobiology
Ethics of science and technology
Space applications
Space | Space ethics | [
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"Astronomy",
"Mathematics",
"Technology",
"Biology"
] | 2,511 | [
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"Outer space",
"Speculative evolution",
"Astrobiology",
"Space applications",
"Space",
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"Ethics of science and technology",
"Biological hypotheses",
"Spacetime",
"Astronomical sub-disciplines"
] |
70,127,972 | https://en.wikipedia.org/wiki/Magnetic%20field%20of%20Mars | The magnetic field of Mars is the magnetic field generated from Mars's interior. Today, Mars does not have a global magnetic field. However, Mars did power an early dynamo that produced a strong magnetic field 4 billion years ago, comparable to Earth's present surface field. After the early dynamo ceased, a weak late dynamo was reactivated (or persisted up to) ~3.8 billion years ago. The distribution of Martian crustal magnetism is similar to the Martian dichotomy. Whereas the Martian northern lowlands are largely unmagnetized, the southern hemisphere possesses strong remanent magnetization, showing alternating stripes. Scientific understanding of the evolution of the magnetic field of Mars is based on the combination of satellite measurements and Martian ground-based magnetic data.
Crustal magnetism
Satellite data
The reconstruction of the Martian global crustal magnetism is mainly based on magnetic field measurements from the Mars Global Surveyor (MGS) magnetic field experiment/electron reflectometer (MAG/ER) and Mars Atmosphere and Volatile Evolution (MAVEN) magnetic-field data. However, these satellites are located at altitudes of 90–6000 km and have spatial resolutions of ≥160 km, so the measured magnetization cannot observe crustal magnetic fields at shorter length scales.
Mars currently does not sustain an active dynamo based on the Mars Global Surveyor (MGS) and Mars Atmosphere and Volatile Evolution (MAVEN) magnetic field measurements. The satellite data show that the older (~4.2–4.3 billion years, ) southern-hemisphere crust records strong remanent magnetization (~22 nT), but the younger northern lowlands have a much weaker or zero remanent magnetization. The large basins formed during the Late Heavy Bombardment (LHB) (~ 4.1–3.9 Ga) (e.g., Argyre, Hellas, and Isidis) and volcanic provinces (e.g., Elysium, Olympus Mons, Tharsis Montes, and Alba Patera) lack magnetic signatures, but the younger Noachian and Hesperian volcanoes (e.g., Tyrrhenus Mons and Syrtis Major) have crustal remanence.
Mars lander observation
The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission measured the crustal field at the Insight landing site located in Elysium Planitia to be ~2 μT. This detailed ground-level data is an order of magnitude higher than satellite-based estimates of ~200 nT at the InSight landing site. The source of this high magnetization is suggested to be Noachian basement (~3.9 Ga) beneath the Early Amazonian and Hesperian flows (~3.6 and 1.5 Ga).
Paleomagnetism
Paleomagnetic evidence
Martian meteorites enable estimates of Mars's paleofield based on the thermal remanent magnetization (or TRM) (i.e., the remanent magnetization acquired when the meteorite cooled below the Curie temperature in the presence of the ambient magnetic field). The thermal remanent magnetization of carbonates in meteorite ALH84001 revealed that the early (4.1–3.9 Ga) Martian magnetic field was ~50 μT, much higher than the modern field, suggesting that a Martian dynamo was present until at least this time. Younger (~1.4 Ga) Martian Nakhlite meteorite Miller Range (MIL) 03346 recorded a paleofield of only ~5 μT. However, given the possible source locations of the Nakhlite meteorite, this paleointensity still suggests that the surface magnetization is stronger than the magnetic fields estimated from satellite measurements. The ~5 μT paleofield of this meteorite can be explained either by a late active dynamo or the field generated from lava flows emplaced in the absence of a late Martian dynamo.
Martian meteorites as paleomagnetic recorders
Martian meteorites contain a wide range of magnetic minerals that can record ancient remanent magnetism, including magnetite, titano-magnetite, pyrrhotite, and hematite. The magnetic mineralogy includes single domain (SD), pseudo single domain (PSD)-like, multi-domain (MD) states. However, only limited Martian meteorites are available to reconstruct the Martian paleofield due to aqueous, thermal, and shock overprints that make many Martian meteorites unsuitable for these studies. Paleomagnetic studies of Martian meteorites are listed in the table below:
Martian dynamo
Timeline of Martian dynamo
The exact timing and duration of the Martian dynamo remain unknown, but there are several constraints from satellite observations and paleomagnetic studies. The strong crustal magnetization in the southern hemisphere and the paleomagnetic evidence of ALH84001 indicate that Mars sustained a strong magnetic field between ~4.2–4.3 Ga. The absence of crustal magnetic signatures in the upper lowlands and large impact basins implies dynamo termination prior to the formation of these basins (~4.0–3.9 Ga). Magnetic anomalies from two young volcanoes (e.g., Tyrrhenus Mons, Syrtis Major) may reflect the presence of a Martian magnetic field with possible magnetic reversals during the late Noachian and Hesperian period.
Hemispheric magnetic dichotomy
One unresolved question is why the Martian crustal hemispheric dichotomy correlates to the magnetic dichotomy (and whether the origin of this dichotomy is an exogenic or endogenic process). One exogenic explanation is that the Borealis impact event resulted in thermal demagnetization of an initially magnetized northern hemisphere, but the proposed age of this event (~4.5 Ga) is long before the Martian dynamo termination (~4.0–4.1 Ga). An alternate model suggests that degree-1 mantle convection (i.e., a convective structure in which mantle upwelling dominates in one hemisphere but downwelling takes in the other hemisphere) can produce a single-hemisphere dynamo.
Alternating stripes
One striking feature in Martian crustal magnetism is the long E–W trending alternating stripes on the southern hemisphere (Terra Cimmeria and Terra Sirenum). It has been proposed that these bands are formed by plate tectonic activity similar to the alternating magnetic polarity caused by seafloor crust spreading on Earth or the results of repeated dike intrusions. However, careful selection of the data analysis method is required to interpret these alternating stripes. Using sparse solutions (e.g., L1 regularization) of crustal-field measurements instead of smoothing solutions (e.g., L2 regularization) shows highly magnetized local patches (with the rest of the crust unmagnetized) instead of stripes. These patches might be formed by localized events such as volcanism or heating by impact events, which may not require continuous fields (e.g., intermittent dynamo).
Dynamo mechanisms
The dynamo mechanism of Mars is poorly understood but expected to be similar to the Earth's dynamo mechanism. Thermal convection due to the high thermal gradients in the hot, initial core was likely the primary mechanism for driving a dynamo early in Mars's history. As the mantle and core cooled over time, inner-core crystallization (which would provide latent heat) and chemical convection may have played a major role in driving the dynamo. Following inner-core formation, light elements migrated from the inner-core boundary into the liquid outer core and drove convection by buoyancy. However, even InSight lander data could not confirm the presence of Mars's solid inner core, and we cannot exclude the possibility that there was no core crystallization (only thermal convection without chemical convection). Also, the possibility that magnetic fields may have been generated by a magma ocean cannot be ruled out.
It is also unclear when and by what mechanism the Martian dynamo shut down. Perhaps a change in the cooling rate of the mantle may have caused the cessation of the Martian dynamo. One theory is giant impacts during the early and mid-Noachian periods stopped the dynamo by decreasing global heat flow at the core-mantle boundary.
The seismic measurements from the InSight lander revealed that the Martian outer core is in a liquid state and larger than expected. In one model, a partially crystallized Martian core explains the current state of Mars (i.e., lack of magnetic field despite liquid outer core), and this model predicts that the magnetic field has the potential to be reactivated in the future.
See also
Geology of Mars
Mars carbonate catastrophe
References
Mars
Magnetospheres
Planetary science | Magnetic field of Mars | [
"Astronomy"
] | 1,795 | [
"Magnetism in astronomy",
"Planetary science",
"Magnetospheres",
"Astronomical sub-disciplines"
] |
70,128,104 | https://en.wikipedia.org/wiki/Cerasicoccus%20arenae | Cerasicoccus arenae is a Gram-negative, obligately aerobic and non-spore-forming bacterium from the genus of Cerasicoccus which has been isolated from marine sand from Kamaishi. Cerasicoccus arenae can produce carotenoid.
References
Verrucomicrobiota
Bacteria described in 2007 | Cerasicoccus arenae | [
"Biology"
] | 73 | [
"Bacteria stubs",
"Bacteria"
] |
70,128,178 | https://en.wikipedia.org/wiki/Cerasicoccus | Cerasicoccus is a Gram-negative, non-motile, obligately aerobic and chemoheterotrophic bacterial genus from the family Puniceicoccaceae.
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Bacteria genera
Taxa described in 2007 | Cerasicoccus | [
"Biology"
] | 65 | [
"Bacteria stubs",
"Bacteria"
] |
70,128,218 | https://en.wikipedia.org/wiki/Cerasicoccus%20frondis | Cerasicoccus frondis is a Gram-negative, chemoheterotrophic bacterium from the genus of Cerasicoccus which has been isolated from seawater.
References
Verrucomicrobiota
Bacteria described in 2010 | Cerasicoccus frondis | [
"Biology"
] | 50 | [
"Bacteria stubs",
"Bacteria"
] |
70,128,315 | https://en.wikipedia.org/wiki/Coraliomargarita | Coraliomargarita is a Gram-negative, obligately aerobic and non-motile bacterial genus from the family of Puniceicoccaceae.
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Bacteria genera
Taxa described in 2007 | Coraliomargarita | [
"Biology"
] | 60 | [
"Bacteria stubs",
"Bacteria"
] |
70,128,343 | https://en.wikipedia.org/wiki/Coraliomargarita%20akajimensis | Coraliomargarita akajimensis is a Gram-negative, obligately aerobic, non-spore-forming and non-motile bacterium from the genus of Coraliomargarita which has been isolated from seawater from Japan.
References
Verrucomicrobiota
Bacteria described in 2007 | Coraliomargarita akajimensis | [
"Biology"
] | 67 | [
"Bacteria stubs",
"Bacteria"
] |
70,128,376 | https://en.wikipedia.org/wiki/Coraliomargarita%20sinensis | Coraliomargarita sinensis is a Gram-negative and obligately aerobic bacterium from the genus of Coraliomargarita which has been isolated from a marine solar saltern from the coast of Weihai.
References
Verrucomicrobiota
Bacteria described in 2019 | Coraliomargarita sinensis | [
"Biology"
] | 60 | [
"Bacteria stubs",
"Bacteria"
] |
70,128,500 | https://en.wikipedia.org/wiki/Terrimicrobium | Terrimicrobium is a Gram-negative, mesophilic, non-spore-forming, strictly anaerobic and non-motile genus of bacteria from the family of Terrimicrobiaceae with one known species (Terrimicrobium sacchariphilum). Terrimicrobium sacchariphilum has been isolated from a rice paddy field.
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Monotypic bacteria genera
Bacteria genera
Taxa described in 2014 | Terrimicrobium | [
"Biology"
] | 110 | [
"Bacteria stubs",
"Bacteria"
] |
70,128,724 | https://en.wikipedia.org/wiki/Fucophilus | Fucophilus is a fucoidan-utilizing genus of bacteria from the phylum Verrucomicrobiota with one known species (Fucophilus fucoidanolyticus). Fucophilus fucoidanolyticus has been isolated from the gut contend of a sea cucumber (Stichopus japonicus).
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Monotypic bacteria genera
Bacteria genera
Enigmatic bacteria taxa
Taxa described in 2003 | Fucophilus | [
"Biology"
] | 110 | [
"Bacteria stubs",
"Bacteria"
] |
70,128,871 | https://en.wikipedia.org/wiki/Pelagicoccus | Pelagicoccus is a Gram-negative genus of bacteria from the family of Puniceicoccaceae.
Phylogeny
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI)
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Bacteria genera
Taxa described in 2007 | Pelagicoccus | [
"Biology"
] | 86 | [
"Bacteria stubs",
"Bacteria"
] |
70,128,912 | https://en.wikipedia.org/wiki/Pelagicoccus%20mobilis | Pelagicoccus mobilis is a Gram-negative and chemoheterotrophic bacterium from the genus of Prosthecobacter which has been isolated from seawater from Japan.
References
Verrucomicrobiota
Bacteria described in 2007 | Pelagicoccus mobilis | [
"Biology"
] | 53 | [
"Bacteria stubs",
"Bacteria"
] |
70,129,230 | https://en.wikipedia.org/wiki/Opitutales | The Opitutales is an order in the phylum Verrucomicrobiota.
Phylogeny
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI)
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Bacteria orders | Opitutales | [
"Biology"
] | 81 | [
"Bacteria stubs",
"Bacteria"
] |
70,129,683 | https://en.wikipedia.org/wiki/NGC%207767 | NGC 7767 is a 14th-magnitude lenticular galaxy located within the constellation Pegasus. It was discovered in 1872 by Ralph Copeland using Lord Rosse's 72-inch telescope. It is an S0a type galaxy with a redshift of 0.026829.
References
7767
Pegasus (constellation)
IC objects
12805
Lenticular galaxies
Astronomical objects discovered in 1872
Discoveries by Ralph Copeland | NGC 7767 | [
"Astronomy"
] | 85 | [
"Pegasus (constellation)",
"Constellations"
] |
70,129,963 | https://en.wikipedia.org/wiki/Sidi%20Boulbra | Sidi Boulbra is a site that the Moroccan government has been considering building a nuclear plant since 1983. The site is located near the town of Sidi Ishaq, between Safi and Essaouira in the Essaouira province of Morocco.
History
The Moroccan government has planned to build a nuclear plant in Sidi Boulbra since 1983 with assistance from the French Company for Nuclear Studies and Achievements. Agreements have also been concluded with the Atomic Energy Commission. The Moroccan nuclear program initially provides for the construction of 6,600 MW, then it will be reduced to a single reactor with a capacity of 900 MW by 2005–2007. From this perspective, the Mamoura Center for Nuclear Studies was equipped with an American research reactor in the early 2000s.
The site was approved by the International Atomic Energy Agency (IAEA) in December 2005. However, on May 29, 2006, Energy Minister Mohamed Boutaleb confirmed that "Morocco does not have a nuclear program and does not intend to build thermonuclear power plants to obtain its electricity needs." In March 2007 the Russian group Atomstroyexport asserted in a press release that "Moscow is entering international competition, which sees many multinational companies providing Rabat with the technology to build a nuclear complex."
In 2015, an IAEA delegation made an eight-day visit to assess Morocco's ability to operate its nuclear power plants. In 2016, Morocco considered incorporating nuclear energy into its energy mix by 2030, in order to reduce its dependence on energy. According to the Moroccan newspaper Akhbar Al-Youm, construction work began on the Boulbra site in June 2016.
References
Energy in Morocco
Nuclear technology | Sidi Boulbra | [
"Physics"
] | 345 | [
"Nuclear technology",
"Nuclear physics"
] |
70,131,321 | https://en.wikipedia.org/wiki/Deposit%20gauge | A deposit gauge is a large, funnel-like scientific instrument used for capturing and measuring atmospheric particulates, notably soot, carried in air pollution and deposited back down to ground.
Design and construction
Deposit gauges are similar to rain gauges. They have a large circular funnel on top, made of stone so as not to be corroded by acid rain and mounted on a simple wooden or metal stand, which drains down into a collection bottle beneath. Typically the funnel has a wire-mesh screen around its perimeter to deter perching birds. Most are made to a standardized design, known as a standard deposit gauge, introduced in 1916 and formalized in a British Standard in 1951, which means the pollution collected in different places can be systematically studied and compared. The bottle is removed after a month and the contents taken away for analysis of water (such as rain, fog, and snow), insoluble matter (such as soot), and soluble matter.
Early history
The first gauges of this type were developed in the early 20th century by W.J. Russell of St Bartholomew's Hospital and the Coal Smoke Abatement Society. Between 1910 and 1916, the design was refined and standardized by the Committee for the Investigation of Atmospheric Pollution, a group of expert, volunteer scientists studying air pollution of which Sir Napier Shaw, first director of the Met Office, was chair. The first scientific paper featuring deposit gauge measurements was titled "The Sootfall of London: Its Amount, Quality, and Effects" and published in The Lancet in January 1912. Thanks to the introduction of the deposit gauge, air quality in Britain was monitored systematically from 1914 onward and this played an important role in determining the effectiveness of efforts to control pollution. By 1927, some deposit gauges were already showing 50 percent reductions in "deposited matter", although air pollution remained a major problem.
Over the next few decades, deposit gauges were deployed in many British towns and cities, allowing rough comparisons to be made of pollution in different parts of the country. According to pollution historian Stephen Mosley, by 1949, some 177 gauges had been deployed across Britain, so creating the world's first large-scale pollution monitoring network, but the number increased dramatically after the Great London Smog of 1952, reaching 615 in 1954 and 1066 in 1966.
Modern use
Although deposit gauges were inaccurate and their limitations were well known from the start, their widespread introduction still represented a considerable advance in the study and comparison of pollution at different times of the year and in different places. In his book State, Science and the Skies: Governmentalities of the British Atmosphere, Mark Whitehead, a geography lecturer at Aberystywth University, has described the deposit gauge as "perhaps the most important technological device in the history of Britain's air pollution monitoring". Even so, from the mid-20th century, it was gradually superseded by more accurate instruments and better methods of data collection and analysis.
Today, although air pollution is more likely to be measured with automated electronic sensors, deposit gauges are still occasionally used. Modern variants of the standard deposit gauge include the so-called "frisbee" gauge, in which the deposit collector is shaped like an inverted frisbee. Other variants include the directional deposit gauge, which has four tall, removable bottles to collect deposits arriving from different directions.
See also
Rain gauge
Air pollution measurement
References
Further reading
Air pollution
Atmospheric chemistry
Measuring instruments
Scientific instruments | Deposit gauge | [
"Chemistry",
"Technology",
"Engineering"
] | 699 | [
"Scientific instruments",
"nan",
"Measuring instruments"
] |
70,131,364 | https://en.wikipedia.org/wiki/Karl%20George%20Emel%C3%A9us | Karl George Emeléus (4 August 1901 in London–18 June 1989 in Belfast) was an English experimental physicist who spent half a century on the staff at Queen's University Belfast. His early research in detection of nuclear radiation led on to a lifetime of research into the conduction of electricity through gases.
Biography
Emeléus was the son of Karl Henry Emeléus and Ellen Briggs, the brother of inorganic chemist Harry Julius Emeléus and the father of petrologist Henry Emeleus. In 1928 he married Florence Mary Chambers, daughter of one of the founders of Chambers Motors, and they had four children – three sons and one daughter. As a direct consequence of the marriage Florence was forced to give up her job as Junior Lecturer in physics at Queen's University Belfast. He was known professionally as K. G. Emeléus or simply KGE, and by family and friends as George.
Education
Emeléus was educated at Hastings Grammar School and at St John's College, Cambridge and was awarded BA in 1922. Upon graduation, he joined the Cavendish Laboratory where he worked as a research student under Ernest Rutherford, James Chadwick and Edward Appleton,though Rutherford's involvement was very limited. Working with Chadwick he built a large Wilson cloud chamber this led to his lifelong interest in gaseous electronics.
Working with Appleton and another PhD student Miles Barnett, Emeléus investigated the maximum count rate of the Geiger counter. He followed Appleton to King's College London at the beginning of 1925 to take up a role as a demonstrator in physics and completed his thesis on "Methods for detecting single ionizing particles", for which Cambridge awarded him a PhD in1926.
Career
In 1927 he joined Queen's University Belfast (QUB) as a lecturer in Physics and later became Professor of Physics (1933–66).
Early in his career he wrote the book The Conduction of Electricity Through Gases. Electronics grew out of this sort of work in the early 20th century. During his long tenure at QUB he researched extensively into the conduction of electricity through gases, publishing more than 170 papers, with his last paper being submitted less than three weeks before his death. After the Second World War he advised local government in Northern Ireland on nuclear policy, both with respect to the possibility of a nuclear attack on the province and the possibility of a nuclear power station.
Books
The Conduction of Electricity Through Gases (Methuen, 1929, second edition 1936, third edition 1951)
Discharges in Electronegative Gases,Taylor & Francis Ltd (Jan 01, 1970),
Awards
He was awarded the title Commander of the British Empire in 1965 and was a member of the Royal Irish Academy. The Karl George Emeléus physics prize was established in 1984 by former students and friends for physics students at QUB.
References
External links
People educated at Hastings Grammar School
Alumni of King's College London
Alumni of St John's College, Cambridge
20th-century British physicists
English physicists
Experimental physicists
Plasma physicists
Academics of Queen's University Belfast
1901 births
1989 deaths | Karl George Emeléus | [
"Physics"
] | 621 | [
"Plasma physicists",
"Plasma physics"
] |
70,131,789 | https://en.wikipedia.org/wiki/HD%2033875 | HD 33875 (HR 1700) is a solitary star in the southern circumpolar constellation Mensa. With an apparent magnitude of 6.26, it is barely visible to the naked eye under ideal conditions. The star is located at a distance of 421 light years but is receding at a rate of .
HD 33875 is an ordinary A-type main-sequence star with a stellar classification of either A1 V or A0 V depending on the source. At present it has 2.38 times the mass of the Sun and 2.84 times the radius of the Sun. It shines at 49.2 times the Sun's luminosity from its photosphere at an effective temperature of 9,392 K, which gives it a white glow. HD 33875 is a fast rotator, spinning rapidly with a projected rotational velocity of .
References
Mensa (constellation)
A-type main-sequence stars
Mensae, 20
Durchmusterung objects
033875
023737
1700 | HD 33875 | [
"Astronomy"
] | 206 | [
"Mensa (constellation)",
"Constellations"
] |
70,133,207 | https://en.wikipedia.org/wiki/Cellulariella | Cellulariella is a genus of fungi belonging to the family Polyporaceae. It was first documented in 2014 by Ivan V. Zmitrovich and Vera F. Malysheva. It is made up of two species: Cellulariella acuta and Cellulariella warnieri.
References
Polyporaceae
Polyporales genera | Cellulariella | [
"Biology"
] | 69 | [
"Fungus stubs",
"Fungi"
] |
70,133,336 | https://en.wikipedia.org/wiki/Perenniporiopsis | Perenniporiopsis is a genus of fungi belonging to the Polyporaceae family. It was documented in 2017 by Chang Lin Zhao. It contains the single species: Perenniporiopsis minutissima.
References
Taxa described in 2017
Polyporaceae
Agaricomycetes genera | Perenniporiopsis | [
"Biology"
] | 60 | [
"Fungus stubs",
"Fungi"
] |
70,133,537 | https://en.wikipedia.org/wiki/Gamma3%20Octantis | {{DISPLAYTITLE:Gamma3 Octantis}}
Gamma3 Octantis, Latinized from γ3 Octantis, is a solitary star located in the southern circumpolar constellation Octans. It is faintly visible to the naked eye as an orange-hued star with an apparent magnitude of 5.28. The object is located relatively close at a distance of 264 light years but is receding with a heliocentric radial velocity of . At its current distance, Gamma3 Octantis' brightness is diminished by two tenths of a magnitude due to interstellar dust and Eggen (1993) lists it as a member of the old disk population. It has an absolute magnitude of +0.83.
Gamma3 Octantis has a stellar classification of K1/2 III, indicating that it is an evolved K-type star with the characteristics of a K1 and K2 giant star. It is a red clump star that is currently on the horizontal branch, fusing helium at its core. At present it has 2.23 times the mass of the Sun but has expanded to almost 10 times its girth. It radiates 50.5 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,879 K, which gives it a yellowish-orange glow. Gamma3 Octantis is metal enriched with an iron abundance 1.55 times that of the Sun and common for giant stars, spins slowly with a projected rotational velocity less than .
Gap between stars sharing Gamma designation
The very similar brightness and potentially close stars of Gamma2, 3 have been examined by the Gaia space telescope/observatory. Gamma2 is much more distant than the other two whose margins of error overlap when parallaxes are considered — they may thus be close enough to be in loose mutual orbital. These distances from our star system per Gaia's second Data Release (DR2) are, respectively, around 319 ± 5 ly and 259 ± 3 ly. The observation refines Gamma1 as being 262 ± 4 ly away.
References
Octans
K-type giants
Horizontal-branch stars
Octantis, Gamma3
000636
000814
0030
PD-82 00004
Octantis, 1 | Gamma3 Octantis | [
"Astronomy"
] | 464 | [
"Octans",
"Constellations"
] |
70,133,813 | https://en.wikipedia.org/wiki/Iodate%20nitrate | Iodate nitrates are mixed anion compounds that contain both iodate and nitrate anions.
Giant birefringence
Iodate nitrates can have high birefringence. The scandium salt has a giant birefringence of 0.348 at 546 nm. When discovered in 2021 it was a record high birefringence for oxyanion compounds, but it was exceeded by CeF2(SO4) just a month later with a value of 0.361 and sodium hydrogen squarate hydrate, NaHC4O4·H2O with a value of 0.52 at 1064 nm. All of these are beaten by hexagonal boron nitride (h-BN) with birefringence of 0.7 in visible light.
List
References
Iodates
Nitrates | Iodate nitrate | [
"Chemistry"
] | 175 | [
"Nitrates",
"Iodates",
"Oxidizing agents",
"Salts"
] |
70,133,895 | https://en.wikipedia.org/wiki/Kiln%20furniture | Kiln furniture are devices and implements inside furnaces used during the heating of manufactured individual pieces, such as pottery or other ceramic or metal components. Kiln furniture is made of refractory materials, i.e., materials that withstand high temperatures without deformation. Kiln furniture can account for up to 80% of the mass of a kiln charge.
Materials
Commonly used materials are cordierite (up to 1275 °C), mullite (up to 1750 °C), silicon carbide (up to 1500 °C), alumina (up to 1750 °C), zirconia (up to 1650 °C). The choice depends on cost, weight, and physical properties.
Functions and effects
Functions of kiln furniture include carrying the kiln/furnace load and protecting the load from various kind of damage: open file, smoke, debris, from deforming or sticking the components to each other. In addition to various carriers and plates, capsules with heating material may be used.
Kiln furniture influences the heat distribution in the furnace and the interaction of the load with the atmosphere in the furnace. Since the furniture is being heated along with the load, this increases energy consumption hence the operating costs increase. An additional increase of costs comes from wear of the furniture due to thermomechanical and chemical stresses. To decrease heat capacity porous materials or thinner furniture components may be used. However this calls for a trade-off with load-bearing capacity and stress resistance.
Types of kiln furniture
A saggar (also misspelled as sagger or segger) is a ceramic boxlike container used in the firing of pottery to enclose or protect ware being fired inside a kiln. Saggars have been used to protect, or safeguard, ware from open flame, smoke, gases and kiln debris. Traditionally, saggars were made primarily from fireclay. Modern saggars are made of alumina ceramic, cordierite ceramic, mullite ceramic silicon carbide and in special cases from zirconia.
A pernette or stilt is a prop to support pottery in a kiln so that pottery does not touch each other or kiln's floor. In archaeology, they may be upside-down fired clay tripods, leaving characteristic marks at the bottoms of the pottery/porcelain. They expose the bottom of the fired piece to the full heat.
Other types of furniture and furniture systems include kiln cars, kiln shelves, batts, tiles, and plates; tubes and beams; props and fittings, profile setters, rollers, stools; T-cranks, Y-cranks, pin cranks. The design of kiln furniture system depends on the wares manufactured: structural clay products, dinnerware, tiles, electronics ceramics, sanitaryware, electrical porcelain, etc.
References
Pottery
Kilns
Firing techniques | Kiln furniture | [
"Chemistry",
"Engineering"
] | 593 | [
"Chemical equipment",
"Kilns"
] |
70,135,057 | https://en.wikipedia.org/wiki/Twosday | Twosday is the name given to Tuesday, February 22, 2022, and an unofficial one-time secular observance held on that day, characterized as a fad. The name is a portmanteau of two and Tuesday, deriving from the fact that the digits of the date form a numeral palindrome marked by exclusivity or prevalence of the digit 2—when written in different numerical date formats, such as: , 22/2/22 and 2/22/22. It is also an ambigram. According to University of Portland professor Aziz Inan, the palindrome is one of the "ubiquitous palindromes", as it retains its defining characteristics globally, despite the differences in national date formats. In countries that apply the ISO 8601 international standard for the calendar, there is an additional congruence inasmuch as Tuesday is the second day of the week under this scheme.
Anticipation
The attraction to the date is due to apophenia. Twosday was cited as an example of humans being conditioned under societal institutions to notice only some while ignoring other coincidences that surround them. Attraction to numerology was cited as a reason as well.
In 2016, the website 22-2-22.com was created to count down to the date. Snopes wrote about Twosday in 2018, in one of its articles debunking false rumors about special dates—the claim about Twosday was rated as "True", but the concept was questioned as follows: "2/22/2022 certainly features a number of 2s, but isn’t it fudging things to use the 22nd day of a year [sic] that includes a number other than two?"
Events
The interest surrounding the date was noted as a social media phenomenon, with the hashtag #22222 receiving 58 million views on TikTok. Google marked the date with an Easter egg.
Twosday was marked by festivities in several cities:
In Sacramento, California, 222 couples were married, in a collective wedding at the California State Capitol.
In Las Vegas, Nevada, weddings were performed at the Harry Reid International Airport. It was suggested that the number of weddings may have broken the record for the most weddings in a single day in Clark County, Nevada.
In Singapore, 500 couples were scheduled to be wedded, nine times more than the usual.
An American food holiday "National Margarita Day" coincided with Twosday, and various thematic activities relating to Twosday took place, mostly in the form of sales promotions (such as 22% discounts). Various businesses engaged in other Twosday-specific sales promotions.
In Prague, a parodical party was organized on the tram line 22 at 22:22 (10:22 pm).
The Korean girl group NMIXX made its debut on 2022/02/22.
In Dubai, United Arab Emirates, the Museum of the Future was officially opened to commemorate the palindrome date.
Kanye West released Donda 2, his tenth studio album exclusively in Ye's Stem Player
In schools around the United States, children buried time capsules, and did other activities themed on the number two.
2:22 AM/PM births
Babies being born at 2:22 AM or 2:22 PM on this date created some media interest, with multiple news outlets running stories about such occurrences; for example:
Bodhi James Turner was born in the St John of God Murdoch Hospital in Perth, Australia at 2:22:22 AM.
Judah Grace was born in room no. 2 of the Alamance Regional Medical Center at Burlington, North Carolina on Twosday, at 2:22 AM. Her mother Aberli had earlier been diagnosed with Hodgkin's lymphoma, and was told by doctors that she could not have children. She named her daughter Judah "because it means praise — just praising God for giving us our heart’s desires".
Coleson was born in the North Alabama Medical Center in Florence, Alabama at 2:22 AM.
Landon was born in the Timpanogos Regional Hospital in Orem, Utah, at 2:22 AM. His parents had expected him to be born on 20 February.
Nevaeh Warren was born in the Mercy Hospital in the New York metropolitan area at 2:22 AM. Her twin sister, Renee Warren, was born at 2:20 AM.
Logan Jowill Coreas Vasquez was born in the Mercy Hospital in the New York metropolitan area at 2:22 PM. He is the son of Wendy Campos-Vasquez and Mercedes Manual Coreas.
Simon Thomas was born at the Good Samaritan Hospital in Cincinnati, Ohio at 2:22 PM, in room no. 2.
Other Twosdays
The subsequent Twosday in the United States date notation (i.e. another 2/22/22 that falls on a Tuesday) is February 22, 2422. In a year that ends with 22 (which could be 2122, 2222, etc.), that is the first subsequent occurrence of February 22 being on a Tuesday, per the 400-year Gregorian calendar cycle.
In popular culture
Late-night talk show hosts Stephen Colbert, Jimmy Kimmel, and Jimmy Fallon made references to Twosday in their programmes. Jimmy Kimmel Live! featured a Twosday-themed introductory sing-and-dance segment (calling the show "your second favorite show"), while Colbert conversed with a 2-shaped puppet.
See also
11/11/11, another common name for the Great Blue Norther of November 11, 1911 (natural disaster)
Doomsday method, and its mnemonic weekday names, which include "Twosday", as an earlier instance of this portmanteau
Framing (social sciences)
Notes
References
Unofficial observances
2020s fads and trends
Palindromes
Numerology
February 2022 | Twosday | [
"Physics",
"Mathematics"
] | 1,216 | [
"Mathematical objects",
"Numerology",
"Palindromes",
"Numbers",
"Symmetry"
] |
70,135,336 | https://en.wikipedia.org/wiki/Alterococcus | Alterococcus is a genus of bacteria from the family of Opitutaceae with one species Alterococcus agarolyticus.
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Bacteria genera
Monotypic bacteria genera
Taxa described in 1999 | Alterococcus | [
"Biology"
] | 57 | [
"Bacteria stubs",
"Bacteria"
] |
70,135,377 | https://en.wikipedia.org/wiki/Opitutaceae | The Opitutaceae are a Gram-negative and chemoheterotrophic order of the domain Bacteria. Opitutaceae bacteria were isolated from soil and coastal marine springs.
Phylogeny
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI)
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Bacteria families | Opitutaceae | [
"Biology"
] | 97 | [
"Bacteria stubs",
"Bacteria"
] |
70,135,602 | https://en.wikipedia.org/wiki/NGC%204326 | NGC 4326 is a barred spiral galaxy with a ring located about 330 million light-years away in the constellation Virgo. It was discovered by astronomer William Herschel on April 13, 1784, who described it as "vF, S, R, bM, 1st of 3". It is a large galaxy, with a diameter of around making it nearly twice the size of the Milky Way. NGC 4326 is also classified as a LINER galaxy. Despite being listed in the Virgo Cluster catalog as VCC 623, it is not a member of the Virgo Cluster but instead a background galaxy.
NGC 4326 is host to a supermassive black hole with and estimated mass of 3.7×108 solar masses.
Nearby Galaxies
NGC 4326 forms a pair with the galaxy NGC 4333, known as [T2015] nest 102514, in which NGC 4326 is the birghtest member of the pair. Both galaxies are part of the CfA2 Great Wall.
See also
List of NGC objects (4001–5000)
External links
References
4326
040192
Virgo (constellation)
Astronomical objects discovered in 1784
Barred spiral galaxies
LINER galaxies
Ring galaxies
07454
Great Wall filament | NGC 4326 | [
"Astronomy"
] | 250 | [
"Virgo (constellation)",
"Constellations"
] |
70,136,850 | https://en.wikipedia.org/wiki/Ereboglobus | Ereboglobus is a genus of bacteria from the family of Opitutaceae with one known species Ereboglobus luteus. Ereboglobus luteus has been isolated from guts of cockroach species.
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Bacteria genera
Monotypic bacteria genera
Taxa described in 2018 | Ereboglobus | [
"Biology"
] | 80 | [
"Bacteria stubs",
"Bacteria"
] |
70,136,927 | https://en.wikipedia.org/wiki/Geminisphaera | Geminisphaera is a genus of bacteria from the family of Opitutaceae with one known species Geminisphaera colitermitum.
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Bacteria genera
Monotypic bacteria genera
Taxa described in 2018 | Geminisphaera | [
"Biology"
] | 60 | [
"Bacteria stubs",
"Bacteria"
] |
70,137,025 | https://en.wikipedia.org/wiki/Lacunisphaera | Lacunisphaera is a Gram-negative, aerobic and motile genus of bacteria from the family of Opitutaceae.
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Bacteria genera
Taxa described in 2017 | Lacunisphaera | [
"Biology"
] | 54 | [
"Bacteria stubs",
"Bacteria"
] |
70,137,086 | https://en.wikipedia.org/wiki/Lacunisphaera%20parvula | Lacunisphaera parvula is a Gram-negative and aerobic bacterium from the genus of Lacunisphaera which has been isolated from a freshwater lake.
References
Verrucomicrobiota
Bacteria described in 2017 | Lacunisphaera parvula | [
"Biology"
] | 49 | [
"Bacteria stubs",
"Bacteria"
] |
70,137,126 | https://en.wikipedia.org/wiki/Nibricoccus | Nibricoccus is a Gram-negative, strictly aerobic and non-motile genus of bacteria from the family of Opitutaceae with one known species (Nibricoccus aquaticus). Nibricoccus aquaticus has been isolated from hyporheic freshwater from Korea.
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Bacteria genera
Monotypic bacteria genera
Taxa described in 2019 | Nibricoccus | [
"Biology"
] | 91 | [
"Bacteria stubs",
"Bacteria"
] |
70,137,186 | https://en.wikipedia.org/wiki/Oleiharenicola | Oleiharenicola is a genus of bacteria from the family of Opitutaceae.
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Bacteria genera
Taxa described in 2018 | Oleiharenicola | [
"Biology"
] | 45 | [
"Bacteria stubs",
"Bacteria"
] |
70,137,221 | https://en.wikipedia.org/wiki/Oleiharenicola%20alkalitolerans | Oleiharenicola alkalitolerans is a Gram-negative, strictly aerobic, neutrophilic and non-motile bacterium from the genus of Oleiharenicola which has been isolated from an oil sand tailings pond in Canada.
References
Verrucomicrobiota
Bacteria described in 2018 | Oleiharenicola alkalitolerans | [
"Biology"
] | 68 | [
"Bacteria stubs",
"Bacteria"
] |
70,137,433 | https://en.wikipedia.org/wiki/Oleiharenicola%20lentus | Oleiharenicola lentus is a Gram-negative, aerobic and motile bacterium from the genus of Oleiharenicola which has been isolated from irrigation water from Taiwan.
References
Verrucomicrobiota
Bacteria described in 2020 | Oleiharenicola lentus | [
"Biology"
] | 52 | [
"Bacteria stubs",
"Bacteria"
] |
70,137,465 | https://en.wikipedia.org/wiki/Opitutus | Opitutus is a genus of bacteria from the family of Opitutaceae with one known species (Opitutus terrae).
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Bacteria genera
Monotypic bacteria genera
Taxa described in 2001 | Opitutus | [
"Biology"
] | 58 | [
"Bacteria stubs",
"Bacteria"
] |
70,137,519 | https://en.wikipedia.org/wiki/Rariglobus | Rariglobus is a genus of bacteria from the family of Opitutaceae with one known species Rariglobus hedericola. Rariglobus hederico has been isolated from a freshwater ditch in Eugendorf.
See also
List of bacterial orders
List of bacteria genera
References
Verrucomicrobiota
Bacteria genera
Monotypic bacteria genera
Taxa described in 2020 | Rariglobus | [
"Biology"
] | 81 | [
"Bacteria stubs",
"Bacteria"
] |
70,137,625 | https://en.wikipedia.org/wiki/Activated%20protein%20C%20resistance%20test | The activated protein C resistance (APCR) test is a coagulation test used in the evaluation and diagnosis of activated protein C (APC) resistance, a form of hypercoagulability. Hereditary APC resistance is usually caused by the factor V Leiden mutation, whereas acquired APC resistance has been linked to antiphospholipid antibodies, pregnancy, and estrogen therapy. APC resistance can be measured using either an activated partial thromboplastin time (aPTT)-based test or an endogenous thrombin potential (ETP)-based test.
Methodology
The aPTT-based APC resistance test involves a modified aPTT test performed in the presence and absence of activated protein C (APC). The ratio of these aPTT values is calculated and is called the APC sensitivity ratio (APCsr) or simply APC ratio (APCr). This ratio is inversely related to the degree of APC resistance. The ETP-based APC resistance test involves the addition of APC to a thrombin generation assay (TGA). This results in an inhibition of thrombin generation as measured by reduction of the endogenous thrombin potential (ETP; area under the thrombin generation curve). The result is expressed as a normalized APC sensitivity ratio (nAPCsr), which corresponds to the ratio of the ETP measured in the presence and absence of APC divided by the same ratio in reference plasma. nAPCsr values range from 0 to 10. Opposite to the case of the APCsr with the aPTT-based APC resistance test, higher nAPCsr values indicate greater APC resistance. This is the result of the fact that APC prolongs the aPTT but inhibits thrombin generation.
Whereas the aPTT-based APC resistance test only measures the initiation phase of coagulation, the ETP-based test is a global assay and measures the initiation, propagation, and termination phases of coagulation. The initiation phase accounts for less than 5% of total thrombin generation, making aPTT-based tests poorly indicative of hypercoagulability in general. The aPTT-based assay is more sensitive to levels of prothrombin and factor VIII, whereas the ETP-based test is more sensitive to levels of tissue factor pathway inhibitor (TFPI) and protein S. The ETP-based test has traditionally been performed using methods such as the calibrated automated thrombogram (CAT) and has been limitedly available due to its technical difficulty. Recently however, a fully automated commercial test system called the ST Genesia has been introduced, and it has been said that this should allow for adoption of TGAs and ETP-based APC resistance tests in routine clinical settings.
Influences
Estrogens are well known to increase APC resistance, which has been described as acquired APC resistance. However, the aPTT-based APC resistance test is much less sensitive to the procoagulatory effects of estrogens than is the ETP-based test. Pregnancy and ethinylestradiol (EE)-containing combined birth control pills increase APC resistance as measured by either the aPTT- or ETP-based test. EE-containing birth control pills show different degrees of influence on the ETP-based test depending on the progestin, which may be due to varying degrees of androgenic antagonism of ethinylestradiol-mediated procoagulation. In contrast to EE-containing birth control pills, studies have not found increased APC resistance with menopausal hormone therapy or with estetrol- or estradiol-containing birth control pills using the aPTT-based test, though increased APC resistance has been shown with the ETP-based test. The increase in APC resistance is much greater with oral estrogens than with transdermal estradiol. Increased APC resistance with both the aPTT-based and ETP-based tests has been observed with feminizing hormone therapy in transgender women, which involves higher doses of estradiol than are used in other contexts. EE produces a much stronger increase in APC resistance than does estradiol. In relation to this, ethinylestradiol is associated with a higher risk of venous thromboembolism (VTE) than is estradiol.
History
The aPTT-based APC resistance test was developed in 1993, while the ETP-based test was developed in 1997. For many years, the ETP-based APC resistance test suffered from a lack of standardization which hampered study-to-study comparison. By 2020 however, a validated methodology was developed aiming to propose a standardized and harmonized scale for ETP-based APC resistance, the normalized activated protein C sensitivity ratio (nAPCsr).
References
Blood tests
Coagulation system
Medical signs | Activated protein C resistance test | [
"Chemistry"
] | 1,023 | [
"Blood tests",
"Chemical pathology"
] |
70,138,102 | https://en.wikipedia.org/wiki/Ostreopsis%20lenticularis | Ostreopsis lenticularis is a species of dinoflagellate in the family Ostreopsidaceae described in 1981 by Yasuwo Fukuyo. O. lenticularis is known to produce toxins, including ostreotoxin.
Distribution
O. lenticularis was first idientified on the Gambler and Society Islands of French Polynesia and New Caledonia in the Pacific Ocean.
References
Gonyaulacales
Dinoflagellate species
Protists described in 1981 | Ostreopsis lenticularis | [
"Biology"
] | 102 | [
"Algae stubs",
"Algae"
] |
70,138,119 | https://en.wikipedia.org/wiki/Mona%20Demaidi | Mona Nabil Demaidi () is an entrepreneur and women's rights advocate. She was born on December 14, 1988 in Nablus, Palestine. She obtained her Ph.D. in Advanced Software Engineering and Machine Learning and MSc with distinction in Software Engineering and Data Management from the University of Manchester, UK. Demaidi joined An-Najah National University in 2016, becoming the youngest female with a Ph.D. certificate at the Faculty of Engineering and Information Technology in Palestine. In 2014, she became a board member of Women in Engineering and Arab Women in Computing. In september 2024, Dr Demaidi became the dean for the Faculty of Digital Sciences and Director of International Relations at Arab American University (Palestine)
Biography
In 1993, Demaidi moved with her family to Dundee, UK, and went to primary school at Hawkhill School and Park Place School.
She finished high school in Palestine.
Mona Demaidi gained her Bachelor of Science (BSc) degree in Computer Engineering at An-Najah National University located in Nablus, Palestine. After getting her Master of Science degree in Advanced Software Engineering and Data Management in 2010/11 at the University of Manchester, she obtained her Ph.D. in Artificial Intelligence.
Experience
Mona Demaidi is the founder of STEMpire which is powered by PALMEC International. STEMpire empower future innovators through STEM education, bootcamps, and hackathons. In addition, Dr Mona is the chairwoman and advisory board member of Intersect Innovation Hub which is powered by Bank of Palestine. Moreover, she's a committee member for both ABET and Innovation and Entrepreneurship as well as being an assistant Professor at An-Najah National University. Also, Demaidi plays an important role in the IEEE Palestine Subsection as she's the chairwoman, Student Branch Counselor and a previous judge at the end of 2019. In addition to that, she was or currently is a judge in several foundations including the Hult Prize Foundation, flow accelerator and Code Your Future. Mona is also a co-founder for VTech Road and a Co-Managing Director for Girls in Tech, Inc. Demaidi is the Chairwoman of the Institute of Electrical and Electronics Engineers in Palestine and was the first woman to be granted an award from the Institute of Electrical and Electronics Engineers (senior membership). She also became the co-managing director for Girls in Tech in Palestine. Demaidi is also a researcher as she has issued six journal papers and a book Terminological Ontology Evaluator in eLearning on constructing online learning platforms using machine learning. Mona Demaidi developed the National Artificial Intelligence Strategy for Palestine in 2022.
Recognition
Since 2014, Demaidi has been a board member with Women in Engineering and Arab Women in computing. In 2017, “she became the first female chair for the Institute of Electrical and Electronics Engineers (IEEE) in Palestine.” Later she became the first woman to be awarded the senior membership from IEEE. In 2019, she became the Co-Managing Director for Girls in Tech in Palestine, which was “the first Girls in Tech chapter in the Middle East - North Africa (MENA) region.”
She was awarded for the Machine Learning project “Skin Cancer detection,” in World Summit on the Information Society Prizes 2020.
She was one of the representatives of the Palestinian team of An-Najah National University at the 6th Annual International Conferences for Arab Women in Computing in March 2019.
See also
Sanaa Alsarghali
Rula Hassanein
References
Palestinian women's rights activists
Palestinian women activists
Software engineers
Living people
1988 births
Women in computing | Mona Demaidi | [
"Engineering"
] | 736 | [
"Software engineering",
"Software engineers"
] |
70,140,085 | https://en.wikipedia.org/wiki/HS%20Hydrae | HS Hydrae is a triple star system in the equatorial constellation of Hydra. The inner pair were an eclipsing binary during the period 1920 until 2019, with HS Hya being the variable star designation. With a base apparent visual magnitude of 8.08, HS Hya is too dim to be viewed with the naked eye. During the primary eclipse, the magnitude dropped to 8.61; the secondary eclipse lowered the magnitude to 8.55. Based on parallax measurements, the system is located at a distance of approximately 335 light years from the Sun. It is drifting closer with a mean radial velocity of .
This star was determined to be an Algol variable as part of a survey of bright southern stars by W. Strohmeierand and associates in 1965, demonstrating it is a binary system with an orbital inclination close to the line of sight from the Earth. D. M. Popper found an eclipse periodicity of 1.568024 days for the pair with a combined estimated class of F3–F4. A longer-term analysis of the system's radial velocities in 1997 showed a third member of the system is likely orbiting the inner pair. This is probably a small red dwarf with about half the mass of the Sun and an orbital period of ~190 days.
In 1997, observations with the Hipparcos satellite showed the depth of both eclipses was lower than they were 20 years earlier. In 2012, P. Zasche and A. Paschke showed that the inclination of the orbital plane for the inner pair had changed by 15° since its discovery. The third member of the system is causing the orbit of the inner pair to precess, resulting in a change of inclination of 7.8° over the same period. By 2022, the eclipses have come to an end, with the final observed events captured by the TESS space telescope in 2019. Examination of earlier data showed that the eclipses had begun in the early 1920s, and the system is predicted to resume eclipses in 2195.
The combined stellar classification of this system is F5V, matching an F-type main-sequence star. The inner pair form a detached binary system that show ellipsoidal variation due to tidal interaction. The primary member, designated component A, has 1.31 times the mass and 1.28 times the radius of the Sun. The marginally smaller secondary, component B, has 1.27 times the mass with 1.22 times the radius of the Sun. The unseen third member, component C, has about 56% of the Sun's mass.
References
Further reading
F-type main-sequence stars
M-type main-sequence stars
Algol variables
Triple star systems
Hydra (constellation)
BD-18 2927
090242
050966
Hydrae, HS | HS Hydrae | [
"Astronomy"
] | 576 | [
"Hydra (constellation)",
"Constellations"
] |
70,140,127 | https://en.wikipedia.org/wiki/Potassium%20tetrafluoronickelate | Potassium tetrafluoronickelate is the inorganic compound with the formula K2NiF4. It features octahedral (high spin) Ni centers with Ni-F bond lengths of 2.006 Å. This green solid is a salt of tetrafluoronickelate. It is prepared by melting a mixture of nickel(II) fluoride, potassium fluoride, and potassium bifluoride. The compound adopts a perovskite-like structure consisting of layers of octahedral Ni centers interconnected by doubly bridging fluoride ligands. The layers are interconnected by potassium cations. It is one of the principal Ruddlesden-Popper phases. Early discoveries on cuprate superconductors focused on compounds with structures closely related to K2NiF4, e.g. lanthanum cuprate and derivative lanthanum barium copper oxide.
References
Nickel compounds
Fluorides
Metal halides
Crystal structure types | Potassium tetrafluoronickelate | [
"Chemistry",
"Materials_science"
] | 208 | [
"Inorganic compounds",
"Crystal structure types",
"Salts",
"Crystallography",
"Metal halides",
"Fluorides"
] |
53,072,448 | https://en.wikipedia.org/wiki/Voronoi%20formula | In mathematics, a Voronoi formula is an equality involving Fourier coefficients of automorphic forms, with the coefficients twisted by additive characters on either side. It can be regarded as a Poisson summation formula for non-abelian groups. The Voronoi (summation) formula for GL(2) has long been a standard tool for studying analytic properties of automorphic forms and their L-functions. There have been numerous results coming out the Voronoi formula on GL(2). The concept is named after Georgy Voronoy.
Classical application
To Voronoy and his contemporaries, the formula appeared tailor-made to evaluate certain finite sums. That seemed significant because several important questions in number theory involve finite sums of arithmetic quantities. In this connection, let us mention two classical examples, Dirichlet's divisor problem and the Gauss circle problem. The former estimates the size of d(n),
the number of positive divisors of an integer n. Dirichlet proved
where is Euler's constant ≈ 0.57721566. Gauss’ circle problem concerns the average size of
for which Gauss gave the estimate
Each problem has a geometric interpretation, with D(X) counting lattice
points in the region , and lattice points in the
disc . These two bounds are related, as we shall see, and come
from fairly elementary considerations.
In the series of papers Voronoy developed geometric and analytic methods to improve both Dirichlet’s and Gauss’ bound. Most importantly in
retrospect, he generalized the formula by allowing weighted sums, at the expense of introducing more general integral operations on f than the Fourier transform.
Modern formulation
Let ƒ be a Maass cusp form for the modular group PSL(2,Z) and a(n) its Fourier coefficients. Let a,c be integers with (a,c) = 1. Let ω be a well-behaved test function. The Voronoi formula for ƒ states
where is a multiplicative inverse of a modulo c and Ω is a certain integral Hankel transform of ω. (see )
References
Miller, S. D., & Schmid, W. (2006). Automorphic distributions, L-functions, and Voronoi summation for GL(3). Annals of mathematics, 423–488.
Voronoï, G. (1904). Sur une fonction transcendente et ses applications à la sommation de quelques séries. In Annales Scientifiques de l'École Normale Supérieure (Vol. 21, pp. 207–267).
Automorphic forms
Analytic number theory | Voronoi formula | [
"Mathematics"
] | 552 | [
"Analytic number theory",
"Number theory"
] |
53,072,781 | https://en.wikipedia.org/wiki/M5-brane | In theoretical physics, an M5-brane is a fundamental brane of M-theory. As such, it can be described explicitly as a black brane solution to eleven-dimensional supergravity, the low-energy limit of M-theory. In particular, it carries a magnetic charge under the 3-form gauge field of the 11-dimensional supergravity multiplet. The M5-brane is the electric-magnetic dual of the M2-brane.
Upon compactification, the M5-brane becomes either the D4-brane or the NS5-brane of type IIA supergravity, depending on whether the 11-dimensional theory is reduced along a direction parallel or orthogonal to the M5-brane, respectively.
The worldvolume theory on a stack of M5-branes at low energies is the six-dimensional N=(2,0) superconformal field theory (SCFT) with gauge algebra of the A-type. Other gauge algebras can be realised by placing the stack of branes on a singularity.
The PST model provides a Green-Schwarz description of the worldvolume physics of a single M5-brane. On the other hand, direct knowledge of the non-Abelian case, for instance via a Lagrangian description, is not presently available, due to various technical difficulties. Since superconformal symmetry is only available in 6 or lower spacetime dimensions, this maximally supersymmetric theory may be used to derive an infinite number of other theories. Furthermore, via the AdS/CFT correspondence, the M5-brane worldvolume theory can be used to study M-theory on asymptotically Anti-de Sitter (AdS) spacetimes.
Despite the lack of a Lagrangian formulation, brane constructions provide evidence that the M5-brane worldvolume theory can support four- and two-codimensional solitonic excitations, namely self-dual strings and three-branes.
References
String theory | M5-brane | [
"Astronomy"
] | 432 | [
"String theory",
"Astronomical hypotheses"
] |
53,072,876 | https://en.wikipedia.org/wiki/Taffrail | In naval architecture, a taffrail is the handrail around the open deck area toward the stern of a ship or boat. The rear deck of a ship is often called the afterdeck or poop deck. Not all ships have an afterdeck or poop deck. Sometimes taffrail refers to just the curved wooden top of the stern of a sailing man-of-war or East Indiaman ship. These wooden sailing ships usually had hand-carved wooden rails, often highly decorated. Sometimes taffrail refers to the complete deck area at the stern of a vessel.
A taffrail should not be confused with a pushpit, which is a common name for the tubular protection rail running around the stern of a small yacht.
A taffrail log is a mechanical speed logging device, used like a car odometer. The taffrail log was towed from the stern or taffrail of the ship by a long line. Taffrail logs were developed in the eighteenth century and became a practical device in the nineteenth century.
Gallery
See also
Common names for decks
Main deck
References
Sailing ship components
Shipbuilding
Nautical terminology | Taffrail | [
"Engineering"
] | 228 | [
"Shipbuilding",
"Marine engineering"
] |
53,072,995 | https://en.wikipedia.org/wiki/RNS%20formalism | In string theory, the Ramond–Neveu–Schwarz (RNS) formalism is an approach to formulating superstrings in which the worldsheet has explicit superconformal invariance but spacetime supersymmetry is hidden, in contrast to the Green–Schwarz formalism where the latter is explicit. It was originally developed by Pierre Ramond, André Neveu and John Schwarz in the RNS model in 1971, which gives rise to type II string theories and can also give type I string theory. Heterotic string theories can also be acquired through this formalism by using a different worldsheet action. There are various ways to quantize the string within this framework including light-cone quantization, old canonical quantization, and BRST quantization. A consistent string theory is only acquired if the spectrum of states is restricted through a procedure known as a GSO projection, with this projection being automatically present in the Green–Schwarz formalism.
History
The discovery of the Veneziano amplitude describing the scattering of four mesons in 1968 launched the study of dual resonance models which generalized these scattering amplitudes to the scattering with any number of mesons. While these are S-matrix theories rather than quantum field theories, Yoichiro Nambu, Holger Bech Nielsen, and Leonard Susskind gave them a string interpretation, whereby mesons behave as strings of finite length.
In 1970 Pierre Ramond was working at Yale trying to extend the dual resonance models to include fermionic degrees of freedom through a generalization of the Dirac equation. This led him to constructing the first superalgebra, the Ramond superalgebra. At the same time, Andre Neveu and John Schwarz were working at Princeton to extend existing dual resonance models by adding to them anticommutating creation and annihilation operators. This originally gave rise to a model containing only bosons. Shortly after their second paper on this topic, they realized that their model can be combined with Ramond's fermionic model, which they successfully did to give rise to the Ramond–Neveu–Schwarz (RNS) model, referred to at the time as the dual pion model.
This work was done with only hadronic physics in mind with no reference to strings, until 1974 when Stanley Mandelstam reinterpreted the RNS model as a model for spinning strings. Joël Scherk and John Schwartz were the first to suggest that it may describe elementary particles rather than just hadrons when they showed that the spin-2 particle of the model behaves as a graviton.
At the time, the main issue with the RNS model was that it contained a tachyon as the lowest energy state. It was only in 1976 with the introduction of GSO projection by Ferdinando Gliozzi, Joël Scherk, and David Olive that the first consistent tachyon-free string theories were constructed.
Overview
The RNS formalism is an approach to quantizing a string by working with the string worldsheet embedded in spacetime with both bosonic and fermionic fields on the worldsheet. There are a number of different approaches for quantizing the string in this formalism. The main ones are old covariant quantization, light-cone quantization, and BRST quantization via the path integral. The last approach starts from the Euclidean partition function
where is the worldsheet action with some gauge symmetry group that represents an overcounting of the physically distinct configurations of the fields that the action depends on. This overcounting is eliminated by dividing by the volume of the gauge group . BRST quantization proceeds by gauge fixing the path integral via the Fadeev–Popov procedure, which gives rise to a ghost action in addition to the now gauge fixed action.
The RNS model originates from using the supergravity action which upon gauge fixing gives the RNS action together with a ghost action describing holomorphic and antiholomorphic ghosts that are necessary to eliminate the unphysical temporal excitations of the fields. The physical states of this theory split up into a number of sectors depending on the periodicity condition of the fermionic fields. The full theory is inconsistent and contains an unphysical tachyon, however projecting out a number of these sectors can give rise to consistent tachyon-free theories. In particular, the RNS model gives rise to type IIA and type IIB string theory for closed strings, while combining the open string with a modified version of the IIB string gives rise to type I string theory. Starting instead from a supergravity action gives rise to heterotic string theories.
Constraint algebras
One way to classify all possible string theories that can be constructed using this formalism is by looking at the possible residual symmetry algebras that can arise. That is, gauge fixing does not always fully fix the entire gauge symmetry, but can instead leave behind some unfixed residual symmetry whose action keeps the gauge fixed action unchanged. The algebra corresponding to this residual symmetry is known as the constraint algebra. To give rise to a physical theory, this algebra must be imposed on the Hilbert space by projecting out unwanted states. Physical states are the ones that are annihilated by the action of this algebra on those states.
For example, in bosonic string theory the original diffeomorphismWeyl symmetry breaks down to a residual conformal symmetry, giving the conformal algebra whose generator is the stress-energy tensor . The physical states , are then those for which . Similarly, gauge fixing the supergravity action down to the RNS action leaves behind a residual superconformal algebra.
Physical conditions such as unitarity and a positive number of spatial dimensions limits the number of admissible constraint algebras. Besides the conformal algebra and the superconformal algebra, the other allowed algebras are the , and superconformal algebras. The first of these gives rise to heterotic string theories, while the other two give consistent but less physically interesting theories in low dimensions. Topological string theory is not found in this classification because for it the spin-statistics theorem does not hold in the conformal gauge which was required in the full argument.
RNS action
A string worldsheet is a two dimensional surface which can be parameterized by two coordinates where describes Euclidean time while parameterize the string at an instance in time. For closed strings while for open strings . Two other coordinate systems are often employed, these being complex coordinates defined by or the coordinates defined by . For the latter, a string at a given point in time is a circle around the origin in the complex plane, with smaller radii corresponding to earlier times.
The RNS model is formed using a superconformal field theory on the string worldsheet with an action of the form
where and are holomorphic and an antiholomorphic anticommutating fermionic fields and are bosonic fields. These bosonic fields have a physical interpretation as the coordinates of the string worldsheet embedded in spacetime, with running over the number of spacetime dimensions. For superstring theory in flat spacetime consistency of the theory requires exactly ten dimensions. The partial derivatives are derivatives in complex coordinates and .
Operators can be classified according to their behavior under rigid rescaling . If they transform as they are said to have weight . The weights of the two fermionic fields are and while that of the bosonic fields is . The holomorphic stress-energy tensor has weight and is given by
The presence of worldsheet supersymmetry gives rise to worldsheet supercurrents with the holomorphic supercurrent having weight and being given by
Any holomorphic operator with weight can be expanded out as a Laurent series
where are known as the modes and or depending on whether the operator is periodic or antiperiodic, respectively. The holomorphic stress-energy tensor and holomorphic supercurrent together form a closed algebra known as the super Virasoro algebra. Using a mode expansion where the stress tensor modes are given by and the supercurrent modes by , the algebra takes the form
where is the central charge. The algebra is sometimes referred to as the Ramond algebra when , are integers and the Neveu–Schwarz algebra when they are half-integers. For closed strings there are two copies of this algebra, one for the holomorphic and one for the antiholomorphic side, while for open strings there is only one copy.
Ramond and Neveu–Schwarz sectors
Closed strings are periodic in their spatial direction, a periodicity that must be respected by the fields living on the worldsheet. A Poincaré invariant theory must have periodic . For the fermionic fields, Lorentz invariance allows for two possible boundary condition; periodic or antiperiodic boundary conditions , with an analogous condition for the antiholomorphic fields. This can concisely be summarized as
where and are independent of each other and are either or . The periodic case () is known as the Ramond (R) boundary condition and the antiperiodic case () is known as the Neveu–Schwarz (NS) boundary condition. This gives four possible ways of putting fermions on the closed string, giving rise to four sectors in the Hilbert space, the NS–NS, NS–R, R–NS, and R–R sectors. The periodicity of the supercurrents is inherited from the periodicity of the fermions.
For open strings, the boundary condition requires that the surface term in the equations of motion vanishes which imposes the constraints
Thus, there are only two sectors for open strings, the R sector and the NS sector. It is often convenient to combine the two fields into a single field with an extended range defined according to
where now the R and NS sectors correspond to a periodicity or antiperiodicity condition on this extended field.
Spectra
The Hilbert space of the R sector and NS sector are determined by considering the modes and of the fermionic fields. Since in the R sector the powers are integers, this sector has a branch cut while the NS sector has half-integer and so no branch cut. The operator product expansion (OPE) of the fermionic theory translate to anticommutation relations for the modes given by
The states in the Hilbert space can then be built up by acting with these modes on the vacuum state. Since all annihilation modes for the NS sector have , it follows that its spectrum has a unique vacuum state that is annihilated by all the modes
The modes act as raising operators, and since they are anticommuting, each one can be acted on at most once, giving the NS sector spectrum.
The R sector has zero modes which map a vacuum state into another vacuum state. Under the rescaling , the anticommutating relation for these becomes the Dirac algebra, implying that the ground state of the R spectrum forms a representation of this algebra. In ten dimensions this is a Dirac spinor, a 32 dimensional representation which can be reduced down to two Weyl representations distinguished by their chirality. The R sector spectrum is formed by acting with modes at most once on these ground states.
Gauge fixing
The Lorentz covariant, diffeomorphism invariant action for the fermionic superstring is found by coupling the bosonic and fermionic fields to two-dimensional supergravity, giving the action
where is the two-dimensional vielbein and is the corresponding gravitino. This has the following symmetries:
Two-dimensional reparameterization invariance,
Two-dimensional Lorentz invariance,
Two-dimensional local supersymmetry,
Weyl symmetry,
Local S-symmetry; , where is a Majorana spinor,
Poincare symmetry.
The gauge symmetries of this action are diffeomorphism symmetry, Weyl symmetry, and local supersymmetry. To quantize the action, these symmetries must be gauge fixed, which is usually done through the superconformal gauge in which and , where and decouple from the action. Performing this gauge fixing through the Faddeev–Popov procedure leaves behind the RNS action and a BRST ghost action .
Ghosts
There are holomorphic and antiholomorphic ghosts in the gauge fixed superstring action. On the holomorphic side are a pair of anticommutating and fields with weight and , along with a pair of commutating fields and with weight and . These have an action of the form
with a similar action for the antiholomorphic ghosts. This action gives rise to additional ghost contributions to the overall stress energy tensor and supercurrents of the theory .
The ghost mode expansion is determined by their weights, with the anticommutating ghosts fields being periodic, while the commutating ghost fields being periodic in the R sector and antiperiodic in the NS sector. The modes satisfy the (anti)commutation relations and . The Ramond and the Neveu–Schwarz ground states are defined according to
Physical states
BRST quantization of the theory requires the construction of the BRST current
where and are the ghosts and are the matter and ghost stress tensors and supercurrents. The BRST charge is the corresponding charge associated with this current
The physical spectrum is the set of BRST cohomology classes. This is the set of states that are annihilated by the charge , with all states differing by a BRST exact state, also called a null state , being equivalent . There is the additional condition that , and for the R sector states . This condition truncates the ghost spectrum for kinematic reasons.
It is convenient to look at the lowest energy states of this theory. Introducing the fermion number operator allows for the NS and R sectors to be further subdivided into NS−, NS+, R−, and R+ sectors, where the sign denotes the sign of for the states.
NS−: This contains the NS ground state which is a tachyon of mass and four-momentum .
NS+: This contains the NS first excited state which corresponds to a massless vector boson with polarization satisfying and .
R−/R+: The R sector ground state is a massless Majorana–Weyl fermion with polarization , half of which belongs to the R+ sector and the other half to the R− sector.
These states are classified by what spin representation of the group they belong to, which is the rotation subgroup of the ten dimensional Lorentz group . In particular, the tachyonic NS− is a singlet while the NS+ state is a vector denoted by . The R+ sector Majorana–Weyl spinors belong to the representation while the R− belong to the representation.
For open strings, the NS+, NS−, R+, and R− form the possible massless and tachyonic states of the RNS string. For the closed strings, the physical states are the various combinations of these four sectors as left and right-moving sectors. The resulting string has a mass-shell condition of
where is the level, counting the creation operators used to create the state. The resulting states can again be classified according to the representation, with this being the direct product of the left-moving and right-moving representations, which decomposes into a sum over irreducible representations. There are no states where NS− is matched with NS+, R− or R+ since then the level matching condition is not meet, so the closed string theory has a single tachyon coming from the NS−NS− sector.
GSO projection
The naive RNS string Hilbert space does not give rise to a consistent string theory. There are three conditions that must be satisfied for the theory to be consistent. First, the vertex operators of the theory have to be mutually local, meaning that their OPEs have no branch cuts. Secondly, the OPEs must also closed. Lastly, the one-loop amplitudes must be modular invariant. The GSO projection is the projection of the Hilbert space onto the subset of sectors that are consistent under these three conditions. One set of consistent theories that results from the projection are type 0 string theories, although these are not tachyon-free. The other set of consistent theories are type II string theories which are tachyon-free, consisting of the sectors
IIA: (NS+,NS+), (R+,NS+), (NS+,R−), (R+,R−),
IIB: (NS+,NS+), (R+,NS+), (NS+,R+), (R+,R+).
A concise way to summarize these sectors is that type IIA theory only keeps sectors with and , while IIB theory only keeps sectors with .
Type I string theory can be constructed from type IIB theory that has gauged its worldsheet parity symmetry and has been combined with the GSO projected open RNS string. The open strings must also have Chan–Paton factors belonging to the gauge group. This last condition arises from a requirement to make the theory non-anomalous. Heterotic string theories can be constructed using this same formalism, except starting with an action different from the RNS action.
See also
GS formalism
GSO projection
Kalb–Ramond field
References
String theory | RNS formalism | [
"Astronomy"
] | 3,612 | [
"String theory",
"Astronomical hypotheses"
] |
53,073,359 | https://en.wikipedia.org/wiki/Quasitopos | In mathematics, specifically category theory, a quasitopos is a generalization of a topos. A topos has a subobject classifier classifying all subobjects, but in a quasitopos, only strong subobjects are classified. Quasitoposes are also required to be finitely cocomplete and locally cartesian closed. A solid quasitopos is one for which 0 is a strong subobject of 1.
References
External links
Topos theory | Quasitopos | [
"Mathematics"
] | 100 | [
"Topos theory",
"Mathematical structures",
"Category theory",
"Category theory stubs"
] |
53,073,378 | https://en.wikipedia.org/wiki/Girl%20Develop%20It | Girl Develop It (GDI) is a nonprofit organization devoted to getting women the materials they need to pursue careers in software development. Founded in 2010 in New York City, GDI provides affordable programs for adult women interested in learning web and software development in a judgment-free environment. GDI's mission is to give women of any income level, nationality, education level, and upbringing an environment in which to learn the skills to build websites and learn code to build programs with hands-on classes. Although at one time active in both the United States and Canada, GDI currently maintains active community chapters exclusively in the United States.
In 2018, responding to allegations of racism that had been leveled towards both staff and chapter leaders within the organization, the majority of active chapter leaders, volunteers, and organizers issued a letter to the board demanding a change in leadership and active transparency from the organization.
History
Girl Develop It was started in 2010 by Vanessa Hurst and Sara Chipps in New York City. GDI started with just one class that sold out in one day. In 2017, the organization reported chapters in 53 cities in 33 states and districts in the United States and one in Ottawa, Ontario Canada. In January 2019, following controversies surrounding transparency and efficacy of the GDI staff after allegations of racism, former chapter leaders estimated that only three chapters were actively organizing classes. As of July 2019 GDI lists 55,000 members in 60 chapters in the United States and none in other countries. However, only five of these chapters are actively organizing classes and events.
Founders
Vanessa Hurst
Hurst is a computer programmer, social entrepreneur, teacher, and lifetime girl scout, and a co-founder of Girl Develop It. In 2013 she launched the CodeMontage platform. She is also responsible for founding and running Developers For Good and also NYC-based Network of Technologists. She is currently based in Charlottesville. Hurst served on the board of GDI until the 2018 controversy, at which point she resigned her position on the board.
Controversies
On August 19, 2018, the leadership of a GDI chapter in Minneapolis were accused of discriminating against a woman of color via a Twitter post. In the post, a community member brought allegations to light that indicated two white GDI chapter leaders in Minneapolis had actively excluded another chapter leader in the Minneapolis chapter who is a woman of color. These actions resulted in her stepping down as a chapter leader. As a result of the lack of acknowledgement of this incident by the GDI Executive Director and board members, another chapter leader decided to step down from her position citing "race and feminism and the way organizations deal with being called out" as one of the reasons for leaving.
On December 3, 2018, further allegations of racism towards women of color came to light, this time from a former GDI HQ employee in an episode of the #causeascene podcast. In the episode, the former employee details many ways in which she experienced racism during her time working with GDI leadership, which ultimately led to her resigning from her position.
On December 7, 2018, various Chapter Leaders across the United States released an open letter to GDI HQ and board, demanding change in leadership due to racism allegations. By December 10, 2018, at least two chapters across the United States decided to go on hiatus in protest.
On December 12, 2018, GDI released an official statement of acknowledgement, outlining policy changes to address issues. Founder Vanessa Hurst stepped down from her position as board chair on December 11, 2018. Executive Director Corinne Warnshuis resigned in April 2019.
Former GDI chapter leaders, instructors, and volunteers created the hashtag #gdistrike to share updates and information about the controversy on Twitter. The organizers have also created a detailed timeline of events that is updated periodically with news about active chapters and leadership changes.
Staff
Katie Franco was selected as the organization's Executive Director in February 2020, ten months after Warnshuis' resignation.
Bindu Jallabah serves as the GDI Operations Director. Prior to joining GDI, Jallabah won awards for her work developing and executing the operational strategy for the Elwyn Baring Street Center. Bindu is also founder and Board Chair of Karanso Africa.
Board
As of July 2021, the GDI Executive Board includes the following individuals. (March 2020 board members.)
Brenda Jin
Janelle Jolley
Erynn Petersen
Kaya Thomas
Jeseekia Vaughn
Linnea Spampinato
Caity Campos
Rebecca Sadwick Shaddix
Erkeda DeRouen
Liliana Post
Ellen Beardsley
Activities
Chapters
There are five chapters of GDI, located in Chicago, IL, Washington D.C., Detroit, MI, New York, NY, and San Francisco, CA.
Curriculum
Girl Develop It (GDI) offers materials on their website that are licensed under a Creative Commons (CC BY-NC-SA 4.0) license and that provide visitors with tools and resources to develop online. The curriculum is hosted and constructed by the GDI community on the web-based version control repository GitHub and presented in a slide format, divided by topic. On the GitHub curriculum page, materials are broken up in a color coded format that shows whether they have been reviewed by other members of the community or if the topics meet the requirements or recommendations of the curriculum. These materials are used for in-person instruction.
As of July 2019 GDI shares ten course curricula through their GitHub repository. Four courses have been updated in 2019, two were last updated in 2018, one was last updated in 2017, and three were last updated in 2016.
Online Learning
In March 2020, amidst the COVID-19 pandemic, in an email newsletter, GDI announced that all classes would be moved to a virtual platform.
Hackathons
The organization and local chapters have hosted or participated in hackathons. During the Buffalo chapter's second event in 2016, developers competed to create websites for nonprofit woman- and minority-owned organizations. The organization has also hosted hackathons in Camden, in Wilmington, and in Seattle.
Supporters
GDI lists numerous companies and organizations on their website that have backed, partnered with, or supported them and their cause.
Named Partners
As of July 2021, GDI does not include any named partners on their website.
References
Educational charities based in the United States
Information technology charities
Youth charities
Organizations for women in science and technology
Computer science education | Girl Develop It | [
"Technology"
] | 1,299 | [
"Computer science education",
"Computer science",
"Organizations for women in science and technology",
"Women in science and technology"
] |
53,074,359 | https://en.wikipedia.org/wiki/Order-5%20truncated%20pentagonal%20hexecontahedron | The order-5 truncated pentagonal hexecontahedron is a convex polyhedron with 72 faces: 60 hexagons and 12 pentagons triangular, with 210 edges, and 140 vertices. Its dual is the pentakis snub dodecahedron.
It is Goldberg polyhedron {5+,3}2,1 in the icosahedral family, with chiral symmetry. The relationship between pentagons steps into 2 hexagons away, and then a turn with one more step.
It is a Fullerene C140.
Construction
It is explicitly called a pentatruncated pentagonal hexecontahedron since only the valence-5 vertices of the pentagonal hexecontahedron are truncated.
Its topology can be constructed in Conway polyhedron notation as t5gD and more simply wD as a whirled dodecahedron, reducing original pentagonal faces and adding 5 distorted hexagons around each, in clockwise or counter-clockwise forms. This picture shows its flat construction before the geometry is adjusted into a more spherical form. The snub can create a (5,3) geodesic polyhedron by k5k6.
Related polyhedra
The whirled dodecahedron creates more polyhedra by basic Conway polyhedron notation. The zip whirled dodecahedron makes a chamfered truncated icosahedron, and Goldberg (4,1). Whirl applied twice produces Goldberg (5,3), and applied twice with reverse orientations produces goldberg (7,0).
See also
Truncated pentagonal icositetrahedron t4gC
References
Fourth class of convex equilateral polyhedron with polyhedral symmetry related to fullerenes and viruses, Stan Schein and James Maurice Gaye, PNAS, Early Edition doi: 10.1073/pnas.1310939111
External links
VRML polyhedral generator Try "t5gI" (Conway polyhedron notation)
Goldberg polyhedra
Pentagonal tilings
Snub tilings
Fullerenes | Order-5 truncated pentagonal hexecontahedron | [
"Physics"
] | 421 | [
"Tessellation",
"Snub tilings",
"Symmetry"
] |
53,074,566 | https://en.wikipedia.org/wiki/Clarisse%20Iribagiza | Clarisse Iribagiza (born 28 January 1988) is a computer scientist in Rwanda. She is the CEO and co-founder of the mobile technology company HeHe Limited and she is one of the UNCTAD's seven "eTrade for Women Advocates from the developing world". She was previously the winner of the East African entrepreneur reality TV show Inspire Africa Season 1.
Biography
Iribagiza attended the University of Rwanda’s College of Science and Technology and she attended a short Massachusetts Institute of Technology (MIT) incubation program.
She founded her company whilst still an under graduate. Her company has grown to have two million customers. The company works with local suppliers and they get access to an on-line store for their goods, inventory maintenance and they receive digital payments from their end customers. HeHe Labs has partnered with GirlHub in an initiative that aims to inspire ambition in Rwandan girls. They teach them about not just ICT, but technology and design in general and in critical thinking.
Iribagiza was one of the "20 movers and shakers of Africa" named at the continent CEO Summit in 2012 and the following year Jeannette Kagame, the First Lady of Rwanda recognised her as one of the Imbuto Foundation's "Celebrating Young Rwandan Achievers".
In 2017 she was named as one of OkayAfrica's 100 Women. Irabagiza sits on the African Development Bank's Presidential Youth Advisory Group.
On 24 September 2019 the United Nations Conference on Trade and Development announced seven "eTrade for Women Advocates" from the developing world. Irabagiza was named and the others were Nina Angelovska, Nazanin Daneshvar, Xiaofei Yao, Patricia Zoundi Yao, Claudia de Heredia and Helianti Hilman. It was announced on the periphery of the United Nations General Assembly in New York but Irabagiza was one of two who did not attend the award ceremony.
Other awards
Forbes Africa's 30 Under 30 for 2015
An Italian think tank, LSDP (Lo Spazio della Politica) named Iribagiz among their top 100 global thinkers.
References
1988 births
Living people
21st-century scientists
21st-century women scientists
Computer scientists
21st-century Rwandan businesspeople
Rwandan scientists
University of Rwanda alumni
21st-century Rwandan businesswomen | Clarisse Iribagiza | [
"Technology"
] | 479 | [
"Computer science",
"Computer scientists"
] |
53,075,082 | https://en.wikipedia.org/wiki/NGC%20394 | NGC 394 is a lenticular galaxy located in the constellation Pisces. It was discovered on October 26, 1854 by R. J. Mitchell. It was described by Dreyer as "faint, small, 50 arcsec northeast of II 218.", with II 218 being NGC 392.
References
External links
0394
Lenticular galaxies
18541026
Pisces (constellation)
004049 | NGC 394 | [
"Astronomy"
] | 84 | [
"Pisces (constellation)",
"Constellations"
] |
53,075,124 | https://en.wikipedia.org/wiki/NGC%20395 | NGC 395 is an open cluster located in the constellation Tucana. It was discovered on August 1, 1826, by James Dunlop. It was described by Dreyer as "very faint, pretty large, round, gradually a little brighter middle."
See also
List of NGC objects (1–1000)
References
0395
18260801
Tucana
Open clusters
Discoveries by James Dunlop | NGC 395 | [
"Astronomy"
] | 78 | [
"Tucana",
"Constellations"
] |
53,075,730 | https://en.wikipedia.org/wiki/Michaelis%E2%80%93Menten%E2%80%93Monod%20kinetics | For Michaelis–Menten–Monod (MMM) kinetics it is intended the coupling of an enzyme-driven chemical reaction of the Michaelis–Menten type with the Monod growth of an organisms that performs the chemical reaction. The enzyme-driven reaction can be conceptualized as the binding of an enzyme E with the substrate S to form an intermediate complex C, which releases the reaction product P and the unchanged enzyme E. During the metabolic consumption of S, biomass B is produced, which synthesizes the enzyme, thus feeding back to the chemical reaction. The two processes can be expressed as
where and are the forward and backward equilibrium rate constants, is the reaction rate constant for product release, is the biomass yield coefficient, and is the enzyme yield coefficient.
Transient kinetics
The kinetic equations describing the reactions above can be derived from the GEBIK equations and are written as
where is the biomass mortality rate and is the enzyme degradation rate. These equations describe the full transient kinetics, but cannot be normally constrained to experiments because the complex C is difficult to measure and there is no clear consensus on whether it actually exists.
Quasi-steady-state kinetics
Equations 3 can be simplified by using the quasi-steady-state (QSS) approximation, that is, for ; under the QSS, the kinetic equations describing the MMM problem become
where is the Michaelis–Menten constant (also known as the half-saturation concentration and affinity).
Implicit analytic solution
If one hypothesizes that the enzyme is produced at a rate proportional to the biomass production and degrades at a rate proportional to the biomass mortality, then Eqs. 4 can be rewritten as
where , , , are explicit function of time . Note that Eq. (4b) and (4d) are linearly dependent on Eqs. (4a) and (4c), which are the two differential equations that can be used to solve the MMM problem. An implicit analytic solution can be obtained if is chosen as the independent variable and , , and ) are rewritten as functions of so to obtain
where has been substituted by as per mass balance , with the initial value when , and where has been substituted by as per the linear relation expressed by Eq. (4d). The analytic solution to Eq. (5b) is
with the initial biomass concentration when . To avoid the solution of a transcendental function, a polynomial Taylor expansion to the second-order in is used for in Eq. (6) as
Substituting Eq. (7) into Eq. (5a} and solving for with the initial value , one obtains the implicit solution for as
with the constants
For any chosen value of , the biomass concentration can be calculated with Eq. (7) at a time given by Eq. (8). The corresponding values of and can be determined using the mass balances introduced above.
See also
Enzyme kinetics
Michaelis–Menten kinetics
Monod
GEBIK equations
References
Enzyme kinetics | Michaelis–Menten–Monod kinetics | [
"Chemistry"
] | 622 | [
"Chemical kinetics",
"Enzyme kinetics"
] |
53,075,803 | https://en.wikipedia.org/wiki/Erythranthe | Erythranthe, the monkey-flowers and musk-flowers, is a diverse plant genus with more than 120 members (as of 2022) in the family Phrymaceae. Erythranthe was originally described as a separate genus, then generally regarded as a section within the genus Mimulus, and recently returned to generic rank. Mimulus sect. Diplacus was segregated from Mimulus as a separate genus at the same time. Mimulus remains as a small genus of eastern North America and the Southern Hemisphere. Molecular data show Erythranthe and Diplacus to be distinct evolutionary lines that are distinct from Mimulus as strictly defined, although this nomenclature is controversial.
Member species are usually annuals or herbaceous perennials. Flowers are red, pink, or yellow, often in various combinations. A large number of the Erythranthe species grow in moist to wet soils with some growing even in shallow water. They are not very drought resistant, but many of the species now classified as Diplacus are. Species are found at elevations from oceanside to high mountains as well as a wide variety of climates, though most prefer wet areas such as riverbanks.
The largest concentration of species is in western North America, but species are found elsewhere in the United States and Canada, as well as from Mexico to Chile and eastern Asia. Pollination is mostly by either bees or hummingbirds. Member species are widely cultivated and are subject to several pests and diseases. Several species are listed as threatened by the International Union for Conservation of Nature.
Description
Erythranthe is a highly diverse genus with the characteristics unifying the various species being axile placentation and long pedicels. Other characteristics of species can vary widely, especially between the sections, and even within some sections. Some species of Erythranthe are annuals and some are perennials. Flowers are red, pink, purple, or yellow, often in various combinations and shades of those colors. Some species produce copious amounts of aromatic compounds, giving them a musky odor (hence "musk-flowers"). Erythranthe is used as food by the larvae of some Lepidoptera species, such as the mouse moth (Amphipyra tragopoginis), as a main part of their diet.
Within the section Erythranthe, stems and leaves range from glabrous to hirsute, and are generally glandular. Leaves can be oblong, elliptical, or oval, with small tooths. Fruiting pedicels are longer than calyces. Calyces have sharp, definite angles and flat sides. Corollas are deciduous, relatively large (tube-throat long), and strongly red to purplish, magentarose, pink, or white, rarely yellow.
Erythranthe guttata is the most widespread of the genus Erythranthe and its characteristics are fairly representative of the genus. E. guttata is tall with disproportionately large long, tubular flowers. Leaves are opposite and oval, long. The species as strictly defined is perennial and spreads with stolons or rhizomes. The stem may be erect or recumbent. In the latter form, roots may develop at lower leaf nodes. Sometimes dwarfed, it may be hairless or have some hairs. Leaves are opposite, round to oval, usually coarsely and irregularly toothed or lobed. The bright yellow flowers are born on a raceme, most often with five or more flowers. The calyx has five lobes that are much shorter than the flower. Each flower has bilateral symmetry and has two lips. The upper lip usually has two lobes; the lower, three. The lower lip may have one large to many small red to reddish brown spots. The opening to the flower is hairy. The fruit is a two-valved capsule long, containing many seeds.
Erythranthe alsinoides is similar to several species found in the Pacific Northwest. It is an annual herb that blooms from April–June with a preference for shady and moist dense habitats. The plant is hairy to slightly hairy and grows from tall. The stems are often reddish. The leaves are opposite and have a few prominent upper veins. Blades are long. The petiole is about the same length. The flowers are yellow with reddish-brown spots, usually on the lower lip, and the upper and lower lips have fused, growing . Each flower is attached by a pedicel. The fruits are capsules.
Etymology and taxonomy
The derivation of Erythranthe is from Greek ἐρυθρός ("erythros"), red, with ἄνθος ("anthos"), flower. They are called monkey-flowers because some species have flowers shaped like a monkey's face. The widely used generic name, Latin mimus meaning "mimic actor", from the Greek mimos meaning "imitator" also alludes to the fancied monkey resemblance. The stem of Erythranthe can be either smooth or hairy, and this is known in a few species to be a trait determined by a simple allelic difference. At least E. lewisii is known to possess "flypaper-type" traps and is apparently protocarnivorous, supplementing its nutrients with small insects. Variations in color largely reflect concentrations of anthocyanins. The species that are subshrubs with woody stems were originally placed in the section Diplacus, and this was subsequently made a separate genus. Diplacus is clearly derived from within Mimulus, broadly defined, and was not usually considered to be a separate genus.
The French botanist Édouard Spach established Erythranthe as a separate genus with just the type species Erythranthe cardinalis. In 1885, American botanist Edward Lee Greene classified Erythranthe as a section of Mimulus while adding E. lewisii and E. parishii. In the 2012 restructuring of Mimulus by Barker et al., based largely upon DNA evidence, seven species were left in Mimulus as strictly defined; Erythranthe was greatly enlarged to include 111 species, based upon axile placentation and long pedicels, 46 placed into Diplacus (species with parietal placentation and sessile flowers), two placed in Uvedalia, and one each placed in Elacholoma, Mimetanthe, and Thyridia. All of the American genera are still referred to as "monkey-flowers".
Views on the evolutionary position of the monkey-flower species have changed. It was long considered to be in the family Scrophulariaceae, but is now placed in Phyrmaceae, primarily on the basis of DNA evidence. The genus Phryma (comprising only a single species), for which the family is named, is considerably different in morphology from all of the monkey-flowers.
Attempts at crossing species, whether from different sections or within the same section, of Erythranthe are not always successful. E. peregrina is an example of a successful naturally occurring hybrid that not only arose independently in two different locations, but is also a rare example of evolutionary recent allopolyploidization, complete chromosomal inheritance.
Charles Darwin's 1876 study of inbreeding depression and self-fertility in South American species was a progenitor for the study of Erythranthe biology. The genus has become a model system "for studies of evolutionary and ecological functional genomics ... [as it] ... contains a wide array of phenotypic, ecological and genomic diversity." Species under intense genomic study are mostly among the section Simiolus (E. guttata and relatives) and the section Erythranthe (including E. lewisii, E. cardinalis, E. parishii, and others). The genome sequence of E. guttata was released in late spring, 2007.
Many issues remain in Erythranthe taxonomy. E. guttata is highly complex, with many variations apparently reflecting differences in geographic environment and elevation. Molecular geneticists regard the species broadly as including both perennial and annual populations, but there is rationale for treating this complex as several distinct species (perennials are E. guttata, E. grandis, and E. corallina; annuals are E. microphylla and others). The perennials and annuals differ as groups from each other by an inversion sequence on chromosome 8. Evidence tentatively indicates that the perennials evolved from annual ancestors, although some evidence has been interpreted to indicate that E. nasuta evolved from E. guttata in central California between 500,000 and 200,000 years ago and since then become primarily a self-pollinator. Relationships among the apparently closely related E. tilingii, E. minor, and E. caespitosa are not clearly understood. Some currently recognized species may be just variants of other species: E. arenicola, E. brachystylis, E. regni. Chromosomal issues may affect the classification of some species: E. corallina, E. guttata, E. nasuta, E. tilingii, and E. utahensis.
Species
Species alphabetically
, Plants of the World Online accepted the following species and hybrids:
Erythranthe acutidens (Greene) G.L.Nesom
Erythranthe alsinoides (Douglas ex Benth.) G.L.Nesom & N.S.Fraga – chickweed monkey-flower (British Columbia to northern California)
Erythranthe ampliata (A.L.Grant) G.L.Nesom
Erythranthe androsacea (Curran ex Greene) N.S.Fraga – rockjasmine monkey-flower (California)
Erythranthe arenaria (A.L.Grant) G.L.Nesom
Erythranthe arenicola (Pennell) G.L.Nesom
Erythranthe arvensis (Greene) G.L.Nesom
Erythranthe austrolatidens G.L.Nesom
Erythranthe barbata (Greene) N.S.Fraga
Erythranthe bhutanica (Yamazaki) G.L.Nesom – (Asia)
Erythranthe bicolor (Hartw. ex Benth.) G.L.Nesom & N.S.Fraga – yellow and white monkey-flower (California)
Erythranthe bodinieri (Vaniot) G.L.Nesom – (Asia)
Erythranthe brachystylis (Edwin) G.L.Nesom
Erythranthe bracteosa (P.C.Tsoong) G.L.Nesom – (Asia)
Erythranthe breviflora (Piper) G.L.Nesom – (British Columbia to California to Wyoming)
Erythranthe brevinasuta G.L.Nesom
Erythranthe breweri (Greene) G.L.Nesom & N.S.Fraga – Brewer's monkey-flower (British Columbia to California to Colorado)
Erythranthe bridgesii (Benth.) G.L.Nesom – (South America)
Erythranthe caespitosa (Greene) G.L.Nesom
Erythranthe calcicola N.S.Fraga
Erythranthe calciphila (Gentry) G.L.Nesom
Erythranthe cardinalis (Douglas ex Benth.) Spach – scarlet monkey-flower (southwestern United States and Baja California)
Erythranthe carsonensis N.S.Fraga – Carson Valley monkey-flower (California and Nevada)
Erythranthe charlestonensis G.L.Nesom
Erythranthe chinatiensis G.L.Nesom
Erythranthe cinnabarina G.L.Nesom
Erythranthe corallina (Greene) G.L.Nesom
Erythranthe cordata (Greene) G.L.Nesom
Erythranthe cuprea (Dombrain) G.L.Nesom – Flor de cobre (Eng: copper flower) (central and southern Chile)
Erythranthe decora (A.L.Grant) G.L.Nesom
Erythranthe dentata (Nutt. ex Benth.) G.L.Nesom – toothleaf monkey-flower, coastal monkey-flower (British Columbia to northern California)
Erythranthe dentiloba (B.L.Rob. & Fernald) G.L.Nesom
Erythranthe depressa (Phil.) G.L.Nesom
Erythranthe diffusa (A.L.Grant) N.S.Fraga
Erythranthe diminuens G.L.Nesom – (Sonora, Mexico)
Erythranthe discolor (A.L.Grant) N.S.Fraga
Erythranthe eastwoodiae (Rydb.) G.L.Nesom & N.S.Fraga
Erythranthe erubescens G.L.Nesom
Erythranthe exigua (A.Gray) G.L.Nesom & N.S.Fraga – San Bernardino Mountains monkey-flower (southern California, Baja California)
Erythranthe filicaulis (S.Watson) G.L.Nesom & N.S.Fraga – slender-stemmed monkey-flower (California)
Erythranthe filicifolia (Sexton, K.G.Ferris & Schoenig) G.L.Nesom
Erythranthe flammea G.L.Nesom
Erythranthe floribunda (Douglas ex Lindl.) G.L.Nesom – manyflowered monkey-flower (western Canada, Pacific Coast, Rocky Mountains, northern Mexico)
Erythranthe gemmipara (W.A.Weber) G.L.Nesom & N.S.Fraga – Rocky Mountain monkey-flower (Colorado)
Erythranthe geniculata (Greene) G.L.Nesom
Erythranthe geyeri (Torr.) G.L.Nesom
Erythranthe glabrata (Kunth) G.L.Nesom – roundleaf monkey-flower (widespread in North America, Mesoamerica and South America)
Erythranthe glaucescens (Greene) G.L.Nesom – shieldbract monkey-flower (California)
Erythranthe gracilipes (B.L.Rob.) N.S.Fraga – slenderstalk monkey-flower (California)
Erythranthe grandis (Greene) G.L.Nesom
Erythranthe grayi (A.L.Grant) G.L.Nesom
Erythranthe guttata (Fisch. ex DC.) G.L.Nesom – common large monkey-flower, common monkey-flower, stream monkey-flower, seep monkey-flower (AK, AZ, CA, CO, CT, DE, ID, MI, MT, ND, NE, NM, NV, NY, OR, PA, SD, UT, WA, WY; Canada: BC, Yukon; Mexico to Guatemala; naturalized in Britain)
Erythranthe hallii (Greene) G.L.Nesom
Erythranthe hardhamiae N.S.Fraga
Erythranthe howaldiae G.L.Nesom
Erythranthe hymenophylla (Meinke) G.L.Nesom
Erythranthe inamoena (Greene) G.L.Nesom
Erythranthe inconspicua (A.Gray) G.L.Nesom – (syns. Mimulus acutidens and M. grayi)
Erythranthe inflata (Miq.) G.L.Nesom – (Asia)
Erythranthe inflatula (Suksd.) G.L.Nesom
Erythranthe jungermannioides (Suksd.) G.L.Nesom
Erythranthe karakormiana (Yamazaki) G.L.Nesom – (Asia)
Erythranthe laciniata (A.Gray) G.L.Nesom
Erythranthe lagunensis G.L.Nesom
Erythranthe latidens (Greene) G.L.Nesom – broadtooth monkey-flower (southern California, Baja California)
Erythranthe lewisii (Pursh) G.L.Nesom & N.S.Fraga – great purple monkey-flower, Lewis' monkey-flower (Alaska to California to Colorado)
Erythranthe linearifolia (A.L.Grant) G.L.Nesom & N.S.Fraga
Erythranthe lutea (L.) G.L.Nesom – yellow monkey-flower, monkey musk, blotched monkey-flower, and blood-drop-emlets (North and South America, naturalized in Britain)
Erythranthe madrensis (Seem.) G.L.Nesom
Erythranthe marmorata (Greene) G.L.Nesom
Erythranthe michiganensis (Pennell) G.L.Nesom – Michigan monkey-flower (Michigan)
Erythranthe microphylla (Benth.) G.L.Nesom
Erythranthe minima (C.Bohlen) J.M.Watson & A.R.Flores– (Michoacan, Mexico)
Erythranthe minor (A. Nelson) G.L.Nesom
Erythranthe montioides (A.Gray) N.S.Fraga – montia-like monkey-flower (California, Nevada)
Erythranthe moschata (Douglas ex Lindl.) G.L.Nesom – (North and South America, naturalized in Britain and Finland)
Erythranthe naiandina (J.M.Watson & C.Bohlen) G.L.Nesom
Erythranthe nasuta (Greene) G.L.Nesom
Erythranthe nelsonii (A.L.Grant) G.L.Nesom & N.S.Fraga – In 2014 Nesom lists as a synonym of Erythranthe verbenacea
Erythranthe nepalensis (Benth.) G.L.Nesom (Asia)
Erythranthe norrisii (Heckard & Shevock) G.L.Nesom
Erythranthe nudata (Curran ex Greene) G.L.Nesom
Erythranthe orizabae (Benth.) G.L.Nesom – (Mexico)
Erythranthe pallens (Greene) G.L.Nesom
Erythranthe palmeri (A.Gray) N.S.Fraga – Palmer's monkey-flower (central California south to Baja California)
Erythranthe pardalis (Pennell) G.L.Nesom
Erythranthe parishii (Greene) G.L.Nesom & N.S.Fraga – Parish's monkey-flower (southern California, western Nevada, Baja California)
Erythranthe parvula (Wooton & Standl.) G.L.Nesom
Erythranthe patula (Pennell) G.L.Nesom
Erythranthe pennellii (Gentry) G.L.Nesom
Erythranthe percaulis G.L.Nesom
Erythranthe platyphylla (Franch.) G.L.Nesom – (Asia)
Erythranthe plotocalyx G.L.Nesom
Erythranthe primuloides (Benth.) G.L.Nesom & N.S.Fraga – primrose monkey-flower (WA, OR, CA, ID, NV, UT, AZ, MT, NM)
Erythranthe procera (A.L.Grant) G.L.Nesom – (Asia)
Erythranthe ptilota G.L.Nesom
Erythranthe pulsiferae (A.Gray) G.L.Nesom – candelabrum monkey-flower (Washington to northern California)
Erythranthe purpurea (A.L.Grant) N.S.Fraga – little purple monkey-flower (southern California, Baja California)
Erythranthe regni G.L.Nesom
Erythranthe rhodopetra N.S.Fraga
Erythranthe rubella (A.Gray) N.S.Fraga – little redstem monkey-flower (CA, NV, UT, WY, CO, NM, TX)
Erythranthe rupestris (Greene) G.L.Nesom & N.S.Fraga
Erythranthe scouleri (Hook.) G.L.Nesom
Erythranthe serpentinicola D.J.Keil
Erythranthe sessilifolia (Maxim.) G.L.Nesom – (Asia)
Erythranthe shevockii (Heckard & Bacig.) N.S.Fraga – Kelso Creek monkey-flower (Kern County, California)
Erythranthe sierrae N.S.Fraga
Erythranthe sinoalba G.L.Nesom – (Asia)
Erythranthe sookensis B.G. Benedict – newly discovered 2012, originally named M. sookensis (British Columbia to northern California)
Erythranthe stolonifera (Novopokr.) G.L.Nesom – (Russia)
Erythranthe suksdorfii (A.Gray) N.S.Fraga – Suksdorf's monkey-flower and miniature monkey-flower (Washington, Oregon, California, Idaho, Montana, Wyoming, Colorado, Nevada, Utah, Arizona, New Mexico)
Erythranthe szechuanensis (Pai) G.L.Nesom – (Asia)
Erythranthe taylorii G.L.Nesom
Erythranthe tenella (Bunge) G.L.Nesom – (Asia)
Erythranthe thermalis (A. Nelson) G.L.Nesom – (Yellowstone National Park)
Erythranthe tibetica (P.C.Tsoong & H.P.Yang) G.L.Nesom – (Asia)
Erythranthe tilingii (Regel) G.L.Nesom – large mountain monkey-flower, Tiling's monkey-flower (Alaska to New Mexico)
Erythranthe trinitiensis G.L.Nesom
Erythranthe unimaculata (Pennell) G.L.Nesom
Erythranthe utahensis (Pennell) G.L.Nesom
Erythranthe verbenacea (Greene) G.L.Nesom & N.S.Fraga
Erythranthe veronicifolia (Greene) G.L.Nesom
Erythranthe visibilis G.L.Nesom
Erythranthe washingtonensis (Gand.) G.L.Nesom
Erythranthe willisii G.L.Nesom
Hybrids:
Erythranthe × burnetii (S.Arn.) Silverside
Erythranthe × hybrida (Voss) Silverside
Erythranthe × maculosa (T.Moore) Mabb.
Erythranthe × robertsii (Silverside) G.L.Nesom, syn. Erythranthe peregrina (M. Vallejo-Marin) G.L.Nesom – newly discovered 2012, originally named M. peregrinus (Scotland)
Species sectionally
In a 2014 paper, G. L. Nesom and N. S. Fraga placed Erythranthe members into the following 12 sections (unless listed below as "newly discovered"). Names accepted are from Plants of the World Online.
Erythranthe sect. Simiolus
Erythranthe arenicola (Pennell) G.L.Nesom
Erythranthe arvensis (Greene) G.L.Nesom
Erythranthe brachystylis (Edwin) G.L.Nesom
Erythranthe brevinasuta G.L.Nesom
Erythranthe caespitosa (Greene) G.L.Nesom
Erythranthe calciphila (Gentry) G.L.Nesom
Erythranthe charlestonensis G.L.Nesom
Erythranthe chinatiensis G.L.Nesom
Erythranthe corallina (Greene) G.L.Nesom
Erythranthe cordata (Greene) G.L.Nesom
Erythranthe decora (A.L.Grant) G.L.Nesom
Erythranthe diminuens G.L.Nesom – newly discovered in 2017 and added to this list (Sonora, Mexico)
Erythranthe dentiloba (B.L.Rob. & Fernald) G.L.Nesom
Erythranthe filicifolia (Sexton, K.G.Ferris & Schoenig) G.L.Nesom
Erythranthe geyeri (Torr.) G.L.Nesom
Erythranthe glabrata (Kunth) G.L.Nesom – roundleaf monkey-flower (widespread in North America, Mesoamerica and South America)
Erythranthe glaucescens (Greene) G.L.Nesom – shieldbract monkey-flower (California)
Erythranthe grandis (Greene) G.L.Nesom
Erythranthe guttata (Fisch. ex DC.) G.L.Nesom – common large monkey-flower, common monkey-flower, stream monkey-flower, seep monkey-flower (AK, AZ, CA, CO, CT, DE, ID, MI, MT, ND, NE, NM, NV, NY, OR, PA, SD, UT, WA, WY; Canada: BC, Yukon; Mexico to Guatemala; naturalized in Britain)
Erythranthe hallii (Greene) G.L.Nesom
Erythranthe inamoena (Greene) G.L.Nesom
Erythranthe laciniata (A.Gray) G.L.Nesom
Erythranthe lagunensis G.L.Nesom
Erythranthe madrensis (Seem.) G.L.Nesom
Erythranthe marmorata (Greene) G.L.Nesom
Erythranthe michiganensis (Pennell) G.L.Nesom – Michigan monkey-flower (Michigan)
Erythranthe microphylla (Benth.) G.L.Nesom
Erythranthe minima (C.Bohlen) J.M.Watson & A.R.Flores – (Michoacan, Mexico)
Erythranthe minor (A. Nelson) G.L.Nesom
Erythranthe nasuta (Greene) G.L.Nesom
Erythranthe nudata (Curran ex Greene) G.L.Nesom
Erythranthe pallens (Greene) G.L.Nesom
Erythranthe pardalis (Pennell) G.L.Nesom
Erythranthe parvula (Wooton & Standl.) G.L.Nesom
Erythranthe pennellii (Gentry) G.L.Nesom
Erythranthe percaulis G.L.Nesom
Erythranthe peregrina M. Vallejo-Marin, synonym of Erythranthe × robertsii – newly discovered 2012, originally named M. peregrinus (Scotland)
Erythranthe regni G.L.Nesom
Erythranthe scouleri (Hook.) G.L.Nesom
Erythranthe sookensis B.G. Benedict – originally named M. sookensis (British Columbia to northern California)
Erythranthe thermalis (A. Nelson) G.L.Nesom – (Yellowstone National Park)
Erythranthe tilingii (Regel) G.L.Nesom – large mountain monkey-flower, Tiling's monkey-flower (Alaska to New Mexico)
Erythranthe unimaculata (Pennell) G.L.Nesom
Erythranthe utahensis (Pennell) G.L.Nesom
Erythranthe visibilis G.L.Nesom
(South America)
Erythranthe acaulis (Phil.) G.L.Nesom, synonym of Erythranthe depressa var. depressa
Erythranthe andicola (Kunth) G.L.Nesom, synonym of Erythranthe glabrata
Erythranthe cuprea (Dombrain) G.L.Nesom – Flor de cobre (Eng: copper flower) (central and southern Chile)
Erythranthe depressa (Phil.) G.L.Nesom
Erythranthe lacerata (Pennell) G.L.Nesom, synonym of Erythranthe lutea var. lutea
Erythranthe lutea (L.) G.L.Nesom – yellow monkey-flower, monkey musk, blotched monkey-flower, and blood-drop-emlets (North and South America, naturalized in Britain)
Erythranthe naiandina (J.M.Watson & C.Bohlen) G.L.Nesom
Erythranthe parviflora (Lindl.) G.L.Nesom
Erythranthe pilosiuscula (Kunth) G.L.Nesom, synonym of Erythranthe glabrata
Erythranthe sect. Erythranthe
Erythranthe cardinalis (Douglas ex Benth.) Spach – scarlet monkey-flower (southwestern United States and Baja California)
Erythranthe cinnabarina G.L.Nesom
Erythranthe eastwoodiae (Rydb.) G.L.Nesom & N.S.Fraga
Erythranthe erubescens G.L.Nesom
Erythranthe flammea
Erythranthe lewisii (Pursh) G.L.Nesom & N.S.Fraga – great purple monkey-flower, Lewis' monkey-flower (Alaska to California to Colorado)
Erythranthe nelsonii (A.L.Grant) G.L.Nesom & N.S.Fraga – In 2014 Nesom lists as a synonym of Erythranthe verbenacea
Erythranthe parishii (Greene) G.L.Nesom & N.S.Fraga – Parish's monkey-flower (southern California, western Nevada, Baja California)
Erythranthe rupestris (Greene) G.L.Nesom & N.S.Fraga
Erythranthe verbenacea (Greene) G.L.Nesom & N.S.Fraga
Erythranthe sect. Mimulosma
Erythranthe ampliata (A.L.Grant) G.L.Nesom
Erythranthe arenaria (A.L.Grant) G.L.Nesom
Erythranthe austrolatidens G.L.Nesom
Erythranthe breviflora (Piper) G.L.Nesom – (British Columbia to California to Wyoming)
Erythranthe floribunda (Douglas ex Lindl.) G.L.Nesom – manyflowered monkey-flower (western Canada, Pacific Coast, Rocky Mountains, northern Mexico)
Erythranthe geniculata (Greene) G.L.Nesom
Erythranthe hymenophylla (Meinke) G.L.Nesom
Erythranthe inflatula (Suksd.) G.L.Nesom
Erythranthe inodora (Greene) G.L.Nesom, synonym of Erythranthe moschata
Erythranthe jungermannioides (Suksd.) G.L.Nesom
Erythranthe latidens (Greene) G.L.Nesom – broadtooth monkey-flower (southern California, Baja California)
Erythranthe moniliformis (Greene) G.L.Nesom, synonym of Erythranthe moschata
Erythranthe moschata (Douglas ex Lindl.) G.L.Nesom – (North and South America, naturalized in Britain and Finland)
Erythranthe norrisii (Heckard & Shevock) G.L.Nesom
Erythranthe patula (Pennell) G.L.Nesom
Erythranthe pulsiferae (A.Gray) G.L.Nesom – candelabrum monkey-flower (Washington to northern California)
Erythranthe taylorii G.L.Nesom
Erythranthe trinitiensis G.L.Nesom
Erythranthe washingtonensis (Gand.) G.L.Nesom
Erythranthe stolonifera (Novopokr.) G.L.Nesom – (Russia)
Erythranthe sect. Achlyopitheca
Erythranthe acutidens (Greene) G.L.Nesom
Erythranthe grayi (A.L.Grant) G.L.Nesom
Erythranthe inconspicua (A.Gray) G.L.Nesom – (syns. Mimulus acutidens and M. grayi)
Erythranthe sect. Paradantha
Erythranthe androsacea (Curran ex Greene) N.S.Fraga – rockjasmine monkey-flower (California)
Erythranthe barbata (Greene) N.S.Fraga
Erythranthe calcicola N.S.Fraga
Erythranthe carsonensis N.S.Fraga – Carson Valley monkey-flower (California and Nevada)
Erythranthe diffusa (A.L.Grant) N.S.Fraga
Erythranthe discolor (A.L.Grant) N.S.Fraga
Erythranthe gracilipes (B.L.Rob.) N.S.Fraga – slenderstalk monkey-flower (California)
Erythranthe hardhamiae N.S.Fraga
Erythranthe montioides (A.Gray) N.S.Fraga – montia-like monkey-flower (California, Nevada)
Erythranthe palmeri (A.Gray) N.S.Fraga – Palmer's monkey-flower (central California south to Baja California)
Erythranthe purpurea (A.L.Grant) N.S.Fraga – little purple monkey-flower (southern California, Baja California)
Erythranthe rhodopetra N.S.Fraga
Erythranthe rubella (A.Gray) N.S.Fraga – little redstem monkey-flower (CA, NV, UT, WY, CO, NM, TX)
Erythranthe shevockii (Heckard & Bacig.) N.S.Fraga – Kelso Creek monkey-flower (Kern County, California)
Erythranthe sierrae N.S.Fraga
Erythranthe suksdorfii (A.Gray) N.S.Fraga – Suksdorf's monkey-flower and miniature monkey-flower (Washington, Oregon, California, Idaho, Montana, Wyoming, Colorado, Nevada, Utah, Arizona, New Mexico)
Erythranthe sect. Monantha
Erythranthe linearifolia (A.L.Grant) G.L.Nesom & N.S.Fraga
Erythranthe primuloides (Benth.) G.L.Nesom & N.S.Fraga – primrose monkey-flower (WA, OR, CA, ID, NV, UT, AZ, MT, NM)
Erythranthe sect. Monimanthe
Erythranthe bicolor (Hartw. ex Benth.) G.L.Nesom & N.S.Fraga – yellow and white monkey-flower (California)
Erythranthe breweri (Greene) G.L.Nesom & N.S.Fraga – Brewer's monkey-flower (British Columbia to California to Colorado)
Erythranthe filicaulis (S.Watson) G.L.Nesom & N.S.Fraga – slender-stemmed monkey-flower (California)
Erythranthe sect. Alsinimimulus
Erythranthe alsinoides (Douglas ex Benth.) G.L.Nesom & N.S.Fraga – chickweed monkey-flower (British Columbia to northern California)
Erythranthe sect. Simigemma
Erythranthe gemmipara (W.A.Weber) G.L.Nesom & N.S.Fraga – Rocky Mountain monkey-flower (Colorado)
Erythranthe sect. Exigua
Erythranthe exigua (A.Gray) G.L.Nesom & N.S.Fraga – San Bernardino Mountains monkey-flower (southern California, Baja California)
Erythranthe sect. Sinopitheca
Erythranthe bracteosa (P.C.Tsoong) G.L.Nesom – (Asia)
Erythranthe bridgesii (Benth.) G.L.Nesom – (South America)
Erythranthe platyphylla (Franch.) G.L.Nesom – (Asia)
Erythranthe sessilifolia (Maxim.) G.L.Nesom – (Asia)
Erythranthe tibetica (P.C.Tsoong & H.P.Yang) G.L.Nesom – (Asia)
Erythranthe sect. Mimulasia
Erythranthe dentata (Nutt. ex Benth.) G.L.Nesom – toothleaf monkey-flower, coastal monkey-flower (British Columbia to northern California)
Erythranthe orizabae (Benth.) G.L.Nesom – (Mexico)
Erythranthe bhutanica (Yamazaki) G.L.Nesom – (Asia)
Erythranthe bodinieri (Vaniot) G.L.Nesom – (Asia)
Erythranthe inflata (Miq.) G.L.Nesom – (Asia)
Erythranthe karakormiana (Yamazaki) G.L.Nesom – (Asia)
Erythranthe nepalensis (Benth.) G.L.Nesom – (Asia)
Erythranthe procera (A.L.Grant) G.L.Nesom – (Asia)
Erythranthe sinoalba G.L.Nesom – (Asia)
Erythranthe szechuanensis (Pai) G.L.Nesom – (Asia)
Erythranthe tenella (Bunge) G.L.Nesom – (Asia)
Reproductive biology
Before recognition of E. cinnabarina as a species, E. lewisii was interpreted to be the sister of E. cardinalis. It is now clear that E. cinnabarina and E. cardinalis are sister species and that E. lewisii and E. erubescens are sister species. In the hypothesized phylogeny, the 'cinnabarina/cardinalis' pair is sister to the 'lewisii/erubescens' pair.
Erythranthe lewisii is a model system for studying pollinator-based reproductive isolation. E. lewisii is pollinated by bees, primarily Bombus and Osmia, which feed on its nectar and transfer its pollen. Although it is fully interfertile with its sister species E. cardinalis, the two do not interbreed in the wild, a difference ascribed primarily to pollinator differences; E. cardinalis is pollinated by hummingbirds, especially Calypte anna and Selasphorus rufus. It was previously reported that evidence strongly linking pollination preference to color differences between the species, but this has been disproven. E. erubescens is mostly pollinated by Bombus balteatus, B. centralis, B. flavifrons, and B. vosnesenskii.
Erythranthe parishii is also closely related to E. lewisii, but it has evolved in a different direction as a self-pollinated species with small flowers.
E. eastwoodiae, E. nelsonii, E. rupestris, and E. verbenacea are also pollinated by hummingbirds. These four species as well as E. cardinalis and E. nelsonii produce bisexual flowers and are self-compatible. This approximate ratio of insect vs hummingbird pollination holds true for the rest of the genus. There have been two separate transformations to hummingbird pollination. Pollination changes are highly affected by changes in flower morphology. E. cardinalis and its sister species E. cinnabarina likely evolved via allopatric speciation.
Erythranthe guttata is pollinated by bees, such as Bombus impatiens. Inbreeding reduces flower quantity and size and pollen quality and quantity. E. guttata also displays a high degree of self-pollination. Erythranthe nasuta evolved from E. guttata in central California between 200,000 and 500,000 years ago and since then has become primarily a self-pollinator.
Distribution and habitat
Over 80% of Erythranthe species are found in western North America, especially California, Oregon, and Washington. Genus members are also found in Baja California, Alaska, British Columbia, Nevada, Utah, Idaho, Montana, Wyoming, Colorado, Arizona, New Mexico, and to a lesser extent the midwestern states, northeastern states, Canada, and Latin America. Members of this genus are found in eastern Asia; several species of which have a high degree of similarity with some of the species found in North and South America.
A large number of the species grow in moist to wet soils with some growing even in shallow water. They are not very drought resistant, but the species now classified as Diplacus are. Some species grow in dry areas, others in wet habitats, such as members of the section Simiolus, which are hydrophilic. Both overall plant size and corolla size vary greatly throughout the genus. A minimum of 25 of the species are listed as threatened by the International Union for Conservation of Nature. Species are found at elevations from oceanside to high mountains as well as a wide variety of climates, though most prefer wet areas such as riverbanks.
Pests and diseases
Diplacus, Erythranthe, and Mimulus are subject to a very similar set of pests and diseases. The pests these genera are susceptible to include: gall midges, golden mealybugs, thrips, and seed bugs. Diseases they are susceptible to include: crown gall, aster yellows phytoplasma, impatiens necrotic spot virus (INSV), leaf spots, powdery mildew — especially Erysiphe brunneopunctata and
Erysiphe cichoracearum, botrytis blight, pythium root rot, rusts, cucumber mosaic virus (CMV), as well as mineral and nutrient deficiencies.
Human culture
Horticulture
In horticulture, several species, cultivars and hybrids are used. Because of their wide range and many variations, the most important are those derived from E. gutatta and E. lutea. E. cuprea alone has at least 10 cultivars and hybrids.
Culinary uses
Erythranthe species tend to concentrate sodium chloride and other salts absorbed from the soils in which they grow in their leaves and stem tissues. Native Americans and early travelers in the American West used this plant as a salt substitute to season wild game. The entire plant is edible, but reported to be very salty and bitter unless well cooked. The juice from the leaves was used as a poultice for mild skin irritations and burns. Leaves can be used in salads and soups; flowers taste best before blooming. E. lutea has been used for cooking in Peru.
Alternative medical use
Erythranthe has been listed as one of the 38 plants that are used to prepare Bach flower remedies, a kind of alternative medicine promoted for its effect on health. However, according to Cancer Research UK, "there is no scientific evidence to prove that flower remedies can control, cure or prevent any type of disease, including cancer".
References
External links
Lamiales genera
Plant models | Erythranthe | [
"Biology"
] | 9,763 | [
"Model organisms",
"Plant models"
] |
53,076,456 | https://en.wikipedia.org/wiki/Ioliomics | Ioliomics (from a portmanteau of ions and liquids) is the study of ions in liquids (or liquid phases) and stipulated with fundamental differences of ionic interactions. Ioliomics covers a broad research area concerning structure, properties and applications of ions involved in various biological and chemical systems. The concept of this research discipline is related to other comprehensive research fields, such as genomics, proteomics, glycomics, petroleomics, etc., where the suffix -omics is used for describing the comprehensiveness of data.
Fundamental nature
The nature of chemical reactions and their description is one of the most fundamental problems in chemistry. The concepts of covalent and ionic bonds which emerged in the beginning of the 20th century specify the profound differences between their electronic structures. These differences, in turn, lead to dramatically different behavior of covalent and ionic compounds both in the solution and solid phase. In the solid phase, ionic compounds, e.g. salts, are prone to formation of crystal lattices; in polar solvents, they dissociate into ions surrounded by solvate shells, thus rendering the solution highly ionic conductive. In contrast to covalent bonds, ionic interactions demonstrate flexible, dynamic behavior, which allows tuning ionic compounds to obtain desired properties.
Importance
Ionic compounds interact strongly with the solvent medium; therefore, their impact on chemical and biochemical processes involving ions can be significant. Even in the case of simplest ions and solvents, the presence of the former can lead to rearrangement and restructuring of the latter. It is established that ionic reactions are involved in numerous phenomena at the scales of whole galaxies or single living cells. To name a few, in living cells, metal ions bind to metalloenzymes and other proteins therefore modulating their activity; ions are involved in the control of neuronal functioning during sleep – wakefulness cycles; anomalous activity of ion channels results in the development of various disorders, such as Parkinson's and Alzheimer's diseases, etc. Thus, despite the problems associated with the studies on properties and activities of ions in various chemical and biological systems, this research field is among the most urgent ones.
Ion-abundant liquid media
Of special interest are ion-abundant liquid media (such as ionic liquids, molten salts, liquid electrolytes, etc.), which represent “liquid ions” with excellent tunable properties for different applications. The systems are famous for their ability to solvent-solute self-organization phenomena and are often employed in chemistry, biochemistry and pharmaceutical research. One of the most important features of ion-abundant liquid media is their huge potential to be fine-tuned. Thus, one can design an ionic liquid with virtually any combination of physicochemical or biochemical properties.
Research in the area of “liquid ions” is a rapidly developing scientific field, and numerous data on their properties and activities have been accumulated so far. Currently, the concept finds applications in catalysis, electrochemistry, analytics, fuel production, biomass processing, biotechnology, biochemistry and pharmaceutics.
References
Biochemistry
Ions
Chemistry
Omics | Ioliomics | [
"Physics",
"Chemistry",
"Materials_science",
"Biology"
] | 628 | [
"Bioinformatics",
"Omics",
"Condensed matter physics",
"nan",
"Biochemistry",
"Chemical bonding"
] |
53,078,439 | https://en.wikipedia.org/wiki/IEC/IEEE%2061850-9-3 | IEC/IEEE 61850-9-3 (Power Utility Profile) or PUP is an international standard for precise time distribution and clock synchronization in electrical grids with an accuracy of 1 μs.
It supports precise time stamping of voltage and current measurement for differential protection, wide area monitoring and protection, busbar protection and event recording.
It can be used to ensure deterministic operation of critical functions in the automation system.
It belongs to the IEC 61850 standard suite for communication networks and systems for power utility automation.
IEC/IEEE 61850-9-3 is a profile (subset) of IEEE Std 1588 Precision Time Protocol (PTP) when clocks are singly attached.
IEC/IEEE 61850-9-3 provides seamless fault tolerance by attaching clocks to duplicated networks paths and by support of simultaneously active redundant master clocks.
For this case, the extensions to PTP defined in IEC 62439-3 Annex A apply.
Main features
IEC/IEEE 61850-9-3 uses the following IEEE Std 1588 options:
uses the PTP timescale based on TAI International Atomic Time, also delivers UTC Coordinated Universal Time
communicates on Layer 2 over Ethernet (IEEE 802.3) links, either in a Local Area Network or in a Wide Area Network (Metro-Ethernet)
measures the link delay by peer-to-peer (Pdelay) message exchange
transmits the clock correction indifferently in 1-step (preferred) or in 2-step
operates with the default best master clock algorithm, performed by master and by slave clocks
Performance
IEC/IEEE 61850-9-3 aims at an accuracy of better than 1 μs after crossing 15 bridges with transparent clocks.
It assumes that all network elements (bridges, routers, media converters, links) support PTP with a given performance:
Grandmaster (GC): 250 ns maximum inaccuracy
Transparent Clocks (TC): 50 ns maximum inaccuracy
Boundary Clocks (BC): 200 ns maximum inaccuracy
Media Converters: 50 ns maximum jitter and 25 ns maximum asymmetry
Link asymmetry: 25 ns maximum asymmetry
By relying on these guaranteed values, the network engineer can calculate the time inaccuracy at different nodes of the network and place the clocks, especially the grandmaster clocks suitably.
IEC TR 61850-90-4 (Network engineering guidelines) gives advice on the use of IEC/IEEE 61850-9-3.
IEEE 1588 settings
IEC/IEEE 61850-9-3 restricts the parameters of IEEE Std 1588 to the following values:
domainNumber: 0 (default), 93 (when conflict exist with another PTP time distribution)
Announce interval: 1 s (fixed)
Sync interval: 1 s (fixed)
Pdelay interval: 1 s (fixed)
Announce receipt time-out: 3 s (fixed)
priority1: 255 for slave-only
priority2: 255 for slave-only
transparent clock primary syntonization domain: 0 (default)
Additions to IEEE Std 1588
All clocks can be doubly attached using the IEC 62439-3 protocol (PRP "Parallel Redundancy Protocol" or HSR "High-availability Seamless Redundancy").
Several master clocks can be active at the same time; the slave selects the best master.
Time-outs ensure that the clocks can detect the loss of PTP messages also on the unused path.
Identification of the peer node to check the topology of the network and ensure that all elements support the protocol.
In network using store-and-forward media converters, the master appends a padding to Sync messages to ensure that Sync and Pdelay_Req/Pdelay_Resp messages have the same size (this will specified in IEEE 1588:2017)
Network management by SNMP according to IEC 62439-3 Annex E or by IEC 61850 consider the extension
Local time distribution
For applications that do not use the corresponding function in IEC 61850, the grandmaster may distribute local time (e.g. for human display) using the ALTERNATE_TIME_OFFSET_INDICATOR TLV as specified in IEEE Std 1588 §16.3.
Standard owners
This protocol has been developed 2012-2014 by the IEC SC65C WG15 in the framework of IEC 62439-3, which applies to all IEC industrial networks, as PTP profile L2P2P (Layer2, peer-to-peer).
To avoid parallel standards in IEC and IEEE in the field of grid automation, this work has been placed under the umbrella of the IEC&IEEE Joint Development 61850-9-3.
Technical responsibility rests with IEC SC65C WG15, which is committed to keep the IEC 62439-3 profile L2P2P and IEC/IEEE 61850-9-3 aligned.
References
External links
IEC 61588:2009 Precision clock synchronization protocol for networked measurement and control systems
IEC/IEEE 61850-9-3, Communication networks and systems for power utility automation – Part 9-3: Precision time protocol profile for power utility automation
IEC TR 61850-90-4:2013 Communication networks and systems for power utility automation - Part 90-4: Network engineering guidelines
Tutorial on HSR
Tutorial on Parallel Redundancy Protocol (PRP)
Tutorial on the fault-tolerant precision time protocol profiles in IEC 62439-3
IEC 62439-3 Tissues (Technical issues) database for IEC 62439-3
IEC 61850-9-3 Tissues (Technical issues) database for IEC/IEEE 61850-9-3
Networking standards
Network protocols | IEC/IEEE 61850-9-3 | [
"Technology",
"Engineering"
] | 1,186 | [
"Networking standards",
"Computer standards",
"Computer networks engineering"
] |
53,079,374 | https://en.wikipedia.org/wiki/Vibrio%20tubiashii | Vibrio tubiashii is a Gram-negative, rod-shaped (0.5 um-1.5 um) marine bacterium that uses a single polar flagellum for motility. It has been implicated in several diseases of marine organisms.
Discovery
Vibrio tubiashii was originally isolated from juvenile and larval bivalve mollusks suffering from bacillary necrosis, now called vibriosis. It was originally discovered by Tubiash et al. in 1965, hence the name, but not properly described until Hada et al. in 1984. Since its discovery and identification, V. tubiashii has been implicated in shellfish vibriosis across the globe, and more recently, coral diseases.
Pathogenicity
Like many Vibrio spp., V. tubiashii produces extracellular enzymes, specifically a zinc-metalloprotease and a cytolysin/hemolysin that are nearly identical to those produced by other pathogenic Vibrio strains. This being said, only the zinc-metalloprotease elicited disease symptoms in Crassostrea gigas consistent with vibriosis. In addition to shellfish disease, Vibrio-derived zinc-metalloprotease could be an integral virulence factor in diseases of scleractinian corals as it was shown to cause photoinactivation of the coral endosymbiont Symbiodinium, leading to tissue color loss and eventual tissue death.
The hemolytic activity of V. tubiashii cultures increases during early growth stages and progressively decreases throughout the stationary phase, while proteolytic activity shows a gradual increase starting in the early stationary phase, suggesting that pathogenesis in this organism requires higher cell density.
References
External links
Type strain of Vibrio tubiashii at BacDive - the Bacterial Diversity Metadatabase
Bacterial diseases
Vibrionales
Waterborne diseases
Marine microorganisms | Vibrio tubiashii | [
"Biology"
] | 403 | [
"Marine microorganisms",
"Microorganisms"
] |
53,079,421 | https://en.wikipedia.org/wiki/Dissimilatory%20nitrate%20reduction%20to%20ammonium | Dissimilatory nitrate reduction to ammonium (DNRA), also known as nitrate/nitrite ammonification, is the result of anaerobic respiration by chemoorganoheterotrophic microbes using nitrate (NO3−) as an electron acceptor for respiration. In anaerobic conditions microbes which undertake DNRA oxidise organic matter and use nitrate (rather than oxygen) as an electron acceptor, reducing it to nitrite, and then to ammonium (NO3− → NO2− → NH4+).
Dissimilatory nitrate reduction to ammonium is more common in prokaryotes but may also occur in eukaryotic microorganisms. DNRA is a component of the terrestrial and oceanic nitrogen cycle. Unlike denitrification, it acts to conserve bioavailable nitrogen in the system, producing soluble ammonium rather than unreactive nitrogen gas ().
Background and process
Cellular process
Dissimilatory nitrate reduction to ammonium is a two step process, reducing NO3− to NO2− then NO2− to NH4+, though the reaction may begin with NO2− directly. Each step is mediated by a different enzyme, the first step of dissimilatory nitrate reduction to ammonium is usually mediated by a periplasmic nitrate reductase. The second step (respiratory NO2− reduction to NH4+) is mediated by cytochrome c nitrite reductase, occurring at the periplasmic membrane surface. Despite DNRA not producing nitrous oxide (N2O) as an intermediate during nitrate reduction (as denitrification does), N2O may still be released as a byproduct, thus DNRA may also act as a sink of fixed, bioavailable nitrogen. DNRA's production of N2O may be enhanced at higher pH levels.
Denitrification
Dissimilatory nitrate reduction to ammonium is similar to the process of denitrification, though NO2− is reduced farther to NH4+ rather than to N2, transferring eight electrons. Both denitrifiers and nitrate ammonifiers are competing for NO3− in the environment. Despite the redox potential of dissimilatory nitrate reduction to ammonium being lower than denitrification and producing less Gibbs free energy, energy yield of denitrification may not be efficiently conserved in its series of enzymatic reactions and nitrate ammonifiers may achieve higher growth rates and outcompete denitrifiers. This is may be especially pronounced when NO3− is limiting compared to organic carbon, as organic carbon is oxidised more 'efficiently' per NO3− (as each molecule NO3− is reduced farther). The balance of denitrification and DNRA is important to the nitrogen cycle of an environment as both use NO3− but, unlike denitrification, which produces gaseous, non-bioavailable N2 (a sink of nitrogen), DNRA produces bioavailable, soluble NH4+.
Marine context
Marine microorganisms
As dissimilatory nitrate reduction to ammonium is an anaerobic respiration process, marine microorganisms capable of performing DNRA are most commonly found in environments low in O2, such as oxygen minimum zones (OMZs) in the water column, or sediments with steep O2 gradients.
DNRA has been documented in prokaryotes inhabiting the upper layer of marine sediments. For example, benthic sulfur bacteria in genera such as Beggiatoa and Thioploca inhabit anoxic sediments on continental shelves and obtain energy by oxidizing sulfide via DNRA. These bacteria are able to carry out DNRA using intracellular nitrate stored in vacuoles. The direct reduction of nitrate to ammonium via dissimilatory nitrate reduction, coupled with the direct conversion of ammonium to dinitrogen via Anammox, has been attributed to significant nitrogen loss in certain parts of the ocean; this DNRA-Anammox coupling by DNRA and Anammox bacteria can account for nitrate loss in areas with no detectable denitrification, such as in OMZs off the coast of Chile, Peru, and Namibia, as well as OMZs over the Omani Shelf in the Arabian Sea. While denitrification is more energetically favourable than DNRA, there is evidence that bacteria using DNRA conserve more energy than denitrifiers, allowing them to grow faster. Thus, via DNRA-Anammox coupling, bacteria using DNRA and Anammox may be stronger competitors for substrates than denitrifiers.
While dissimilatory nitrate reduction to ammonium is more commonly associated with prokaryotes, recent research has found increasing evidence of DNRA in various eukaryotic microorganisms. Of the known DNRA-capable fungal species, one is found in marine ecosystems; an isolate of ascomycete Aspergillus terreus from an OMZ of the Arabian Sea has been found to be capable of performing DNRA under anoxic conditions. Evidence of DNRA has also been found in marine foraminifers.
More recently, it has been discovered that using intracellular nitrate stores, diatoms can carry out dissimilatory nitrate reduction to ammonium, likely for short-term survival or for entering resting stages, thereby allowing them to persist in dark and anoxic conditions. However, their metabolism is probably not sustained by DNRA for long-term survival during resting stages, as these resting stages often can be much longer than their intracellular nitrate supply would last. The use of DNRA by diatoms is a possible explanation for how they can survive buried in dark, anoxic sediment layers on the ocean floor, without being able to carry out photosynthesis or aerobic respiration. Currently, DNRA is known to be carried out by the benthic diatom Amphora coffeaeformis, as well as the pelagic diatom Thalassiosira weissflogii. As diatoms are a significant source of oceanic primary production, the ability for diatoms to perform DNRA has major implications on their ecological role, as well as their role in the marine nitrogen cycle.
Ecological role
Unlike denitrification, which removes reactive nitrogen from the system under gaseous form (as N2 or N2O), dissimilatory nitrate reduction to ammonium conserves nitrogen as dissolved species within the system. Since DNRA takes nitrate and converts it into ammonium, it does not produce N2 or N2O gases. Consequently, DNRA recycles nitrogen rather than causing gaseous-N loss, which leads to more sustainable primary production and nitrification.
Within an ecosystem, denitrification and DNRA can occur simultaneously. Usually DNRA is about 15% of the total nitrate reduction rate, which includes both DNRA and denitrification. However, the relative importance of each process is influenced by environmental variables. For example, DNRA is found to be three to seven times higher in sediments under fish cages than nearby sediments due to the accumulation of organic carbon.
Conditions where dissimilatory nitrate reduction to ammonium is favoured over denitrification in marine coastal ecosystems include the following:
High carbon loads and high sulfate reduction rates (e.g. areas of coastal or river runoff)
Unvegetated subtidal sediment
Marshes with high temperatures and sulfate reduction rates (producing high levels of sulfides), e.g. mangroves
High organic matter deposition (e.g. aquacultures)
Ecosystems where organic matter has a high C/N ratio
High electron donor (organic carbon) to acceptor (nitrate) ratio
High summer temperatures and low NO3− concentrations
High sulfide concentration can inhibit the processes of nitrification and denitrification. Meanwhile, it can also enhance dissimilatory nitrate reduction to ammonium since high sulfide concentration provides more electron donors.
Ecosystems where DNRA is dominant have less nitrogen loss, resulting in higher levels of preserved nitrogen in the system. Within sediments, the total dissimilatory nitrate reduction to ammonium rate is higher in spring and summer compared to autumn. Prokaryotes are the major contributors for DNRA during summer, while eukaryotes and prokaryotes contribute similarly to DNRA during spring and autumn.
Potential benefits of using dissimilatory nitrate reduction to ammonium for individual organisms may include the following:
Detoxification of accumulated nitrite: if an enzyme uses nitrate as an electron acceptor and produces nitrite, it can result in high levels of intracellular nitrite concentrations that can be toxic to the cell. DNRA does not store nitrite within the cell, reducing the level of toxicity.
DNRA produces an electron sink that can be used for NADH re-oxidation into NAD+: the need for having an electron sink is more apparent when the environment is nitrate-limited.
Changes to f-ratio calculation
The balance of dissimilatory nitrate reduction to ammonium and denitrification alters the accuracy of f-ratio calculations. The f-ratio is used to quantify the efficiency of the biological pump, which reflects sequestering of carbon from the atmosphere to the deep sea. The f-ratio is calculated using estimates of 'new production' (primary productivity stimulated by nutrients entering the photic zone from outside the photic zone, for example from the deep ocean) and 'regenerated production' (primary productivity stimulated by nutrients already in the photic zone, released by remineralisation). Calculations of the f-ratio use the nitrogen species stimulating primary productivity as a proxy for the type of production occurring; productivity stimulated by NH4+ rather than NO3− is 'regenerated production'. DNRA also produces NH4+ (in addition to remineralisation) but from organic matter which has been exported from the photic zone; this may be subsequently reintroduced by mixing or upwelling of deeper water back to the surface, thereby, stimulating primary productivity; thus, in areas where high amounts of DNRA is occurring, f-ratio calculations will not be accurate.
References
Anaerobic digestion
Cellular respiration | Dissimilatory nitrate reduction to ammonium | [
"Chemistry",
"Engineering",
"Biology"
] | 2,177 | [
"Cellular respiration",
"Biochemistry",
"Anaerobic digestion",
"Environmental engineering",
"Water technology",
"Metabolism"
] |
53,080,832 | https://en.wikipedia.org/wiki/Institute%20for%20Genetic%20Engineering%20and%20Biotechnology | Institute for Genetic Engineering and Biotechnology (INGEB) is a Bosnian
public research institute, member of Sarajevo University (UNSA), and affiliate center of International Centre for Genetic Engineering and Biotechnology (ICGEB).
ICGEB was established as a special project of the United Nations Industrial Development Organization (UNIDO).
INGEB was founded under the name "Center for Genetic Engineering and Biotechnology", in 1988. INGEB's headquarters are located in Sarajevo.
One of INGEB's most prominent founders was Professor Rifat Hadžiselimović, with the support of the Government of Socialist Republic of Bosnia and Herzegovina, ANUBiH and the biggest B&H economic systems. After the establishment document, INGEB was entrusted with the functions maker, institutional creator and carrier of the overall scientific and professional work in the development of genetic engineering and biotechnology based molecular biology in B&H.
In 1993, by a legal act, the Assembly of Republic of Bosnia and Herzegovina, assumed the right of the founder of the institution, at the beginning of the Bosnian War, and later, in 1999, entitled founder of INGEB (as a "public institution that will operate within the University of Sarajevo") took over the Sarajevo Canton.
Structure and activities
In INGEB, there are following functional units:
Laboratory for forensic genetics;
Laboratory for human genetics;
Laboratory for GMO and food biosafety;
Laboratory for molecular genetics of natural resources;
Laboratory for bioinformatics and biostatistics, and
Laboratory for cytogenetics and genotoxicology.
Laboratory for Forensic Genetics
Laboratory for forensic genetics provides scientific approach to analysis of samples of different origin. In this laboratory DNA profiling is routinely done for skeletal remains, blood stains (on different materials), hair, semen, controversial traces on cigarette butts, controversial traces under fingernails, in urine etc.
Expert activities perform in laboratory for forensic genetics include:
paternity testing using samples of buccal swab (which reduces traumatic effect on children), blood, hair, bones and other baseline samples.
motherless paternity testing,
maternity testing without the presence of the father,
biological kinship testing,
forensic DNA analysis for police, prosecution, law offices, courts and private individual purposes.
In laboratory for forensic genetics scientific projects, supported by the respective ministries and foreign institutions, are implemented or are under realization. The focus of scientific research is directed towards genetic analysis of archaeological skeletal samples, forensic genetic parameters testing of Bosnian population, as well as towards a target oriented expansion of previously initiated population genetic research.
Laboratory for Human Genetics
This laboratory represents the organizational segment of the Institute which is dealing with genetic characterisation of DNA of human origin for the purpose of basic and applied research. We use molecular-genetics approach mainly PCR based in investigating the genetic structure.
Main activities of the laboratory comprise research directions:
detection of circulating DNA sequences as potential markers in molecular oncology,
gene expression profiling for characterization of therapeutical effects of novel and biological substances and individual genetic predisposition to complex traits (disorders).
Other important aspect is participation in higher education programs at University of Sarajevo as well as public engagement in developing molecular-genetics methods for support of medical diagnostics.
Laboratory for GMO and Food Biosafety
The laboratory scope includes wide array of activities mainly focused on the issues of food biosafety and plant biotechnology. It provides qualitative and quantitative analysis of specific DNA sequences in various food matrices, provides advice and correct interpretation of GMO related data to consumers and food safety authority and promotes science based approach to biosafety. In that respect the Laboratory has established communication with JRC-EURL-GMFF and follows the published guidelines. Also, the Laboratory develops new analytical methods, where appropriate, to bridge the gaps in the available methodology.
Research aspect of the Laboratory is mainly focused on endemic and endangered plant species with bioactive potential. Simultaneously with bioactive potential of a species, which is explored in in vitro and in vivo models, molecular markers are employed to evaluate its genetic diversity for the purpose of conservation.
Laboratory for Cytogenetics and Genotoxicology
Research activities of the Laboratory for Cytogenetics and Genotoxicology are based on:
Cytogenetic and genotoxicological analysis of bioactive potential of certain physical, chemical and biological agents, and
Cytogenetic and genotoxicological monitoring of human populations in Bosnia and Herzegovina.
Expert activity of the Laboratory for Cytogenetics and Genotoxicology mainly includes chromosome analysis and karyotyping of human samples. The most frequently used tests in research projects of this lab are based on cell culture and include: chromosome aberrations analysis, cytokinesis-block micronucleus cytome assay and sister chromatids exchange assay. Evaluation of cytotoxic and cytostatic potential of various chemical agents includes application of colorimetric method in different cell lines. Research capacities are significantly used for academic education and the realization of final thesis of Sarajevo University students.
Expertises:
Karyotype analysis;
Cytogenetic biodosimetry;
In vitro testing of genotoxic and cytotoxic potential of chemical substances and herbal extracts using:
Chromosome aberrations analysis;
Cytokinesis-block micronucleus cytome assay;
Sister-chromatid exchange assay;
Allium assay;
Alamar blue assay;
Trypan blue assay.
Primary cell lines establishment.
Projects:
Analysis of K2(B3O3F4OH) bioactive and medical potential; (ongoing project).
Analysis of natural bioactive compounds potential in the inhibition of genotoxic and cytotoxic effects in vitro; (2012-2013) Financed by Federal ministry of education and science.
Cytotoxicity and genotoxicity analysis of natural and synthetic food colorants in FB&H; (2011-2012) Financed by Federal ministry of education and science.
Evaluation of antitumor properties of halogenated boroxine; (2010-2011) Financed by Federal ministry of education and science.
Participation in international collaborative project: HUMNXL – Exfoliated cells micronucleus project; (2009-2011);
Analysis of the specific chromosomal markers of basal cell carcinoma; (2007-2009) Financed by the Ministry of Education and Science of Sarajevo Canton;
Cytogenetic markers in human populations of FB&H as possible bioindicators for Balcan syndrome; (2002-2003) Financed by Federal ministry of science, culture and sport.
References
External links
Institut za genetičko inženjerstvo i biotehnologiju u Sarajevu
Research institutes in Bosnia and Herzegovina
Genetic engineering
University of Sarajevo
Biological research institutes
Medical research institutes
Biochemistry research institutes
Research institutes established in 1988
Organizations based in Sarajevo | Institute for Genetic Engineering and Biotechnology | [
"Chemistry",
"Engineering",
"Biology"
] | 1,404 | [
"Biological engineering",
"Biochemistry organizations",
"Genetic engineering",
"Biochemistry research institutes",
"Molecular biology"
] |
53,081,264 | https://en.wikipedia.org/wiki/C2orf73 | Uncharacterized protein C2orf73 is a protein that in humans is encoded by the C2orf73 gene. The protein is predicted to be localized to the nucleus.
Gene
The full gene spans a total of 53,712 base pairs and contains nine exons. The gene's location in the Human genome is on chromosome 2 at position 2p16.2 and is flanked by the genes ACYP2 and SPTBN1. There are no aliases for this gene.
mRNA
The primary mRNA produced by the C2or73 gene is 1921 nucleotides long. There are six other mRNA isoforms produced by alternative splicing and variation in exon length.
Protein
The protein has a molecular mass of 32,142 daltons. There are four protein isoforms. The primary isoform (X1) is 287 amino acids long.
C2orf73 contains a short sequence motif, GDWWSH (This motif does not yet have any known function). The protein is lysine rich and leucine poor compared to the content of the average Human gene and has a predicted isoelectric point of 9.305.
Structure
A 3D structure for C2orf73 has not yet been determined experimentally. A computational prediction made by I-TASSER is presented to the right.
The PELE tool on Biology Workbench predicts three likely α-helices and one β-strand in the protein.
Post translational modifications
The GPS, NetPhos, MyHits and SUMOsp tools on ExPASy predict potential post-translational modifications for the protein. Six potential phosphorylation sites and one sumoylation site are predicted.
Subcellular localization
PSORT II predicts C2orf73 to be localized to the nucleus. This is supported by the predicted presence of a sumoylation site, which is involved in nuclear cytoplasmic transport.
Expression
GEO profiles from NCBI show that C2orf73 is weakly expressed in the following tissues in Humans: bone marrow, liver, heart, lung, brain, spinal cord, skeletal muscle, thymus, and epithelium.
Regulation of expression
The Genomatix El Dorado tool predicts many transcription factors to have a high binding affinity in the 1100 base pairs upstream of C2orf73. Many of the transcription factors normally regulate processes such as cell development and differentiation, cell death, and the cell cycle.
Interacting Proteins
Three proteins have been experimentally determined to interact with C2orf73 through Yeast Two-Hybrid experiments.
FCH and Double SH3 Domains 2 (FCHSD2) - Function has not yet been defined
Heat Shock Protein Family B Member 1 (HSPB1) - Aids cell's resistance to stress
SH3 Domain Binding Protein 4 (SH3BP4) - Involved in endocytosis of specific cell surface receptors
Function
The function of C2orf73 is currently not well understood by the scientific community or anyone else.
Homology
There are no paralogs of C2orf73 in the Human genome. Orthologs are found throughout, but are limited to, the phylum Chordata (with a few exceptions in other phyla of the kingdom Animalia, like the Octopus bimaculoides).
References
Uncharacterized proteins | C2orf73 | [
"Biology"
] | 677 | [
"Protein classification",
"Uncharacterized proteins"
] |
53,081,940 | https://en.wikipedia.org/wiki/GS%20formalism | Green–Schwarz (GS) formalism (named after Michael Green and John H. Schwarz) is an attempt to introduce fermions in string theory. The theory is equivalent to RNS formalism which has been GSO projected. This theory is very hard to quantize, being straightforward to quantize only in light cone gauge. A covariant quantization of spinning string, maintaining space-time supersymmetry manifest, is possible in a formalism inspired on the GS formalism, known as pure spinor formalism.
See also
Supersymmetry
RNS formalism
Notes
string theory | GS formalism | [
"Astronomy"
] | 127 | [
"String theory",
"Astronomical hypotheses"
] |
53,082,558 | https://en.wikipedia.org/wiki/Contaminants%20of%20emerging%20concern | Contaminants of emerging concern (CECs) is a term used by water quality professionals to describe pollutants that have been detected in environmental monitoring samples, that may cause ecological or human health impacts, and typically are not regulated under current environmental laws. Sources of these pollutants include agriculture, urban runoff and ordinary household products (such as soaps and disinfectants) and pharmaceuticals that are disposed to sewage treatment plants and subsequently discharged to surface waters.
CECs include different substances like pharmaceuticals, personal care products, industrial byproducts, and agricultural chemicals. These substances often bypass regular detection and treatment processes, leading to their unintended persistence in the environment. The complexity of CECs arises not only from their different chemical nature but also from the complex ways they interact with ecosystems and human health. As such, they are the focus of increasing examination by researchers, policymakers, and public health officials who want to understand their long-term effects and develop effective interventions. Global initiatives, like those from the World Health Organization (WHO) and the United States Environmental Protection Agency (US EPA), emphasize the need to create international standards and effective environmental policies to address the challenges posed by CECs. Public awareness and advocacy play crucial roles in driving the research agenda and policy development for CECs, highlighting the need for updated manufacturing practices and developing more remediation and detection methods.
History and background
The concept of CECs gained significant attention in the early 21st century as advances in analytical techniques allowed for the detection of these substances at trace levels in various environmental matrices. The increased awareness of CECs is partly due to their abundant presence in wastewater, surface water, groundwater, and drinking water, often because of urbanization, industrial activities, and the widespread use of pharmaceuticals and personal care products. The recognition of the potential risks posed by CECs has led to a growing body of research aimed at understanding their sources, fate, and effects in the environment, as well as the development of strategies for their management and removal.
Past events
In the 19th and early 20th centuries asbestos was used in many products and in building construction and was not considered a threat to human health or the environment. Deaths and lung problems caused by asbestos were first documented in the early 20th century. The first regulations of the asbestos industry were published in the UK in the 1930s. Regulation of asbestos in the US did not occur until the 1980s.
In the 1970s there was a serious issue with the water treatment infrastructure of some US states, notably in Southern California with water sourced from the Sacramento–San Joaquin River Delta. Water was being disinfected for domestic use through chlorine treatment, which was effective for killing microbial contaminants and bacteria, but in some cases, it reacted with runoff chemicals and organic matter to form trihalomethanes (THMs). Research done in the subsequent years began to suggest the carcinogenic and harmful nature of this category of compounds. EPA issued its first standard for THMs, applicable to public water systems, in 1979, and more stringent standards in 1998 and 2006.
Rapid industry changes also make the treatment and regulation of CECs particularly challenging. For instance, the replacing substance (GenX), for the recently regulated perfluorooctanoic acid (PFOA), a PFAS, had a more detrimental environmental impact, resulting in the subsequently banning of GenX as well. Hence, there is a pressing need for the treatment and management of CECs to keep up with global trends.
Classification
For a compound to be recognized as an emerging contaminant it has to meet at least two requirements:
Adverse human health effects have been associated with a compound.
There is an established relationship between the positive and negative effect(s) of the compound.
Emerging contaminants are those which have not previously been detected through water quality analysis, or have been found in small concentrations with uncertainty as to their effects. The risk they pose to human or environmental health is not fully understood.
Contaminant classes
Contaminants of emerging concern (CECs) can be broadly classed into several categories of chemicals such as pharmaceuticals and personal care products, cyanotoxins, nanoparticles, and flame retardants, among others. However, these classifications are constantly changing as new contaminants (or effects) are discovered and emerging contaminants from past years become less of a priority. These contaminants can generally be categorized as truly "new" contaminants that have only recently been discovered and researched, contaminants that were known about but their environmental effects were not fully understood, or "old" contaminants that have new information arising regarding their risks.
Pharmaceuticals
Pharmaceuticals are gaining more attention as CECs because of their continual introduction into the environment and their general lack of regulation. These compounds are often present at low concentrations in water bodies and little is currently known about their environmental and health effects from chronic exposure; pharmaceuticals are only now becoming a focus in toxicology due to improved analytical techniques that allow very low concentrations to be detected. There are several sources of pharmaceuticals in the environment, including most prominently effluent from sewage treatment plants, aquaculture and agricultural runoff.
Personal care products
Personal care products often contain a complex mixture of chemicals such as preservatives (e.g., parabens), UV filters (e.g., oxybenzone), plasticizers (e.g., phthalates), antimicrobials (e.g., triclosan), fragrances, and colorants. Many of these compounds are synthesized chemicals that are not typically found in nature. Chemicals from personal care products can enter the environment through various pathways. After use, they are often washed down the drain and can end up in the wastewater stream. These substances are not all completely removed by conventional wastewater treatment processes, leading to their release into natural water bodies. Some of these chemicals are persistent in the environment and can bioaccumulate in the tissues of organisms, potentially causing ecological disruptions. They can also have endocrine-disrupting properties that interfere with the hormonal systems of wildlife and humans.
Cyanotoxins
In recent years, there has been an increase of cyanobacterial blooms due to the eutrophication (or increase in nutrient levels) of surface waters around the world. Increases in certain nutrients, such as nitrogen and phosphorus, are linked to fertilizer runoff from agricultural fields, and are also found in certain products, such as detergents, in urban spaces. These blooms can release toxins that can decrease water quality and are a risk to human and wildlife health. Additionally, there are a lack of regulations regarding the maximum contaminant levels (MCL) allowed in drinking water sources. Cyanotoxins can have both acute and chronic toxic effects, and there are often many consequences for the health of the environment where these blooms occur.
Industrial chemicals
Industrial chemicals from various industries produce harmful chemicals that are known to cause harm to human health and the environment. Common industrial chemicals, like 1,4-Dioxanes, Perfluorooctane sulfonate (PFOS) and Perfluorooctanoic acid (PFOA), are commonly found in various water sources.
Nanomaterials
Nanomaterials include carbon-based materials, metal oxides, metals, and quantum dots. Nanomaterials can enter the environment during their manufacturing, consumer use, or disposal. Due to their small size, nanomaterials behave differently than larger particles. They have a high surface area to volume ratio, which can lead to increased reactivity and the potential to transport throughout the environment. Nanomaterials are challenging to detect and monitor due to their size and the absence of standardized methods for measuring their presence and concentration in various media.
Sources and pathways
Agricultural runoff
Agricultural runoff is a major pathway through which CECs enter the environment. Compounds like pesticides and pharmaceuticals from fertilizers are carried by water from farms into their surrounding areas soil and water bodies. Then runoff happens after rainfall or irrigation, which causes an influx of chemicals to leak out of the soil where they were dumped and into rivers, lakes, and groundwater. The runoff can contain a CEC’s which are not regulated or whose environmental impacts are not well understood, contributing to the pollution of aquatic ecosystems, and potentially affecting human water sources. A significant challenge is monitoring levels of CECs in bodies of water. A nationwide survey revealed that soil erosion, nutrient loss, and pesticide runoff from America's vast agricultural lands are leading causes of water quality pollution. Approximately 46% of rivers and streams in the United States have conditions which are harmful to aquatic life. Additionally, only about 28% of these water bodies are rated as 'healthy' based on their biological communities.
Industrial discharge
Industrial discharge is when waste products are released into the environment from manufacturing and chemical processing facilities. This waste can include a wide variety of CECs like heavy metals, solvents, and various organic compounds that are not regularly detected for or removed by standard treatment processes. These contaminants can accumulate in sediments and biota, posing risks to aquatic life and human health. The complexity and diversity of industrial discharge requires advanced treatment technologies and stricter regulatory frameworks to prevent CECs from contaminating the environment. Advanced oxidation processes and membrane technologies have been researched and shown to reduce CECs from industrial discharge, however there is an excessive cost to retrofit existing treatment facilities with this technology.
Urban runoff
Urban runoff is rainwater that runs through streets, gardens, and other urban surfaces, picking up various pollutants along the way. These pollutants can include CECs like microplastics from synthetic materials, polycyclic aromatic hydrocarbons (PAHs) from vehicle exhausts, and pharmaceuticals from improperly disposed medications. This untreated runoff can enter storm drains and eventually discharge into natural water bodies, often bypassing wastewater treatment facilities and leading to their accumulation in the environment, where they can cause harm to wildlife and potentially enter the human food chain. Permeable pavements and rain gardens are being implemented and tested in some urban areas to mitigate the effects of runoff, helping to filter pollutants before they reach the water system.
Wastewater treatment plants
Wastewater treatment plants (WWTPs) are designed to remove contaminants from domestic and industrial wastewater before it is released into the environment. However, some WWTPs, particularly older or under-resourced ones are not equipped to effectively remove all CECs, such as advanced pharmaceuticals, personal care product ingredients, and certain types of industrial chemicals. These substances can pass through the treatment process and enter aquatic ecosystems, which creates a challenge for water treatment technology and emphasizes the need for ongoing research and infrastructure improvement to address the removal of CECs from wastewater. Advances like tertiary treatment stages, which incorporate advanced filtration and chemical removal techniques, are being tested to address the presence of CECs in waste, though widespread implementation is yet to be seen due to novelty, cost, and logistical challenges.
Environmental and health impacts
Relation between compound and effects
There is an overlap of many anthropogenically sourced chemicals that humans are exposed to regularly. This makes it difficult to attribute negative health causality to a specific, isolated compound. EPA manages a Contaminant Candidate List to review substances that may need to be controlled in public water systems. EPA has also listed twelve contaminants of emerging concern at federal facilities, with ranging origins, health effects, and means of exposure. The twelve listed contaminants are as follows: Trichloropropane (TCP), Dioxane, Trinitrotoluene (TNT), Dinitrotoluene, Hexahydro-trinitro-triazane (RDX), N-nitroso-dimethylamine (NDMA), Perchlorate, Polybrominated biphenyls (PBBs), Tungsten, Polybrominated diphenyl ethers (PBDEs) and Nanomaterials.
Selected compounds listed as emerging contaminants
The NORMAN network enhances the exchange of information on emerging environmental substances. A Suspect List Exchange (SLE) has been created to allow sharing of the many potential contaminants of emerging concern. The list contains more than 100,000 chemicals.
Table 1 is a summary of emerging contaminants currently listed on one EPA website and a review article. Detailed use and health risk of commonly identified CECs are listed in the table below.
Aquatic life
The environmental impact of CECs on aquatic life is broad. For example, endocrine-disrupting chemicals (EDCs) have the potential to imitate natural hormones, which can lead to reproductive failures and eventually population declines or increases in fish and amphibians. EDCs are found in a variety of common contaminants, including pesticides and industrial chemicals, and they can also lead to altered growth and reproduction in aquatic life (US EPA) (USGS.gov). Microplastics are another concern, as they can lead to physical blockages in the digestive tracts of aquatic organisms and act as paths for other toxins, leading to bioaccumulation and increase in concentration as they move up each level of the food chain. These impacts not only threaten biodiversity but also the stability of aquatic ecosystems upon which many species depend. Ongoing monitoring and regulatory efforts are crucial for assessing the full scope of CECs' impacts and for the development of effective strategies to mitigate their presence in aquatic ecosystems (NOAA.gov).
Human health
When CECs bypass water filtration systems and contaminate drinking water or accumulate in the food chain, they can also cause risks to human health. Chronic exposure to low doses of CECs has been linked to various health issues. For example, certain pharmaceutical CECs and EDCs have been associated with hormonal imbalances, increased risks of certain cancers, and developmental problems. The antibiotics present in the environment can also contribute to the development of antibiotic-resistant bacteria, which poses a serious threat to human health by reducing the effectiveness of antibiotic treatments. Studies have shown that even at low concentrations, the presence of CECs in drinking water can correlate with neurological disorders and can decrease cognitive function over time. Certain perfluoroalkyl substances (PFAS), which are a type of CEC, have been linked to different adverse health outcomes like increased cholesterol levels, changes in liver enzymes, and reduced vaccine efficacy, which raises concerns about widespread exposure to these chemicals. The CDC also identifies exposure to high levels of CECs with negative effects on the immune system, by compromising the body’s ability to fight infections and increasing the risk of rheumatological diseases. Exposure to a combination of various CECs, which can occur through contaminated drinking water or food chains, may lead to cumulative on human health that are not yet fully understood.
Wildlife
Wildlife, particularly species reliant on aquatic environments, are exceptionally vulnerable to the disruptions caused by CECs. Terrestrial species can be exposed to CECs through contaminated food, water, and soil. These contaminants can cause pollution which can lead to mortality or can indirectly result in changes in behavior which affect essential activities like feeding and mating. Migratory species are especially at risk as they can spread the impact of CECs across various ecosystems. The health of wildlife populations is an important indicator of environmental quality, and the presence of CECs can signal broader ecological issues that require attention.
Detection and monitoring
Detection and monitoring of CECs is done through a variety of sophisticated analytical techniques. High-performance liquid chromatography (HPLC) paired with mass spectrometry (MS) can help identify organic CECs, due to their high sensitivity and selectivity EPA. For volatile and semi-volatile compounds, gas chromatography (GC) coupled with MS is commonly used FDA. Metals and metalloids are typically analyzed using techniques like inductively coupled plasma mass spectrometry (ICP-MS), which allows for the simultaneous analysis of multiple elements USGS. The complications with monitoring CECs go past just detection. Their pathways across different environmental also must be monitored. This can be done with passive sampling devices, which accumulate contaminants over time and give a comprehensive view of contaminant levels at different locations NOAA. Biosensors are also used and integrated to detect specific contaminants rapidly, which is important for on-site monitoring applications NIH. The use of remote sensing and geographic information systems (GIS) for spatial analysis is expanding, these tools facilitate the tracking of pollution spread NASA Earth Science. Recent advancements in nanotechnology have led to the development of nano-sensors which can detect trace amounts of CECs Nature Nanotechnology.
There are sites with waste that would take hundreds of years to clean up and prevent further seepage and contamination into the water table and surrounding biosphere. In the United States, the environmental regulatory agencies on the federal level are primarily responsible for determining standards and statutes which guide policy and control in the state to prevent citizens and the environment from being exposed to harmful compounds. Emerging contaminants are examples of instances in which regulation did not do what it was supposed to, and communities have been left vulnerable to adverse health effects. Many states have assessed what can be done about emerging contaminants and currently view it as a serious issue, but only eight states have specific risk management programs addressing emerging contaminants.
Regulations and management
These are tactics and methods that aim to remediate the effects of certain, or all, CECs by preventing movement throughout the environment, or limiting their concentrations in certain environmental systems. It is particularly important to ensure that water treatment approaches do not simply move contaminants from effluent to sludge given the potential for sludge to be spread to land providing an alternative route to entering the environment.
Advanced treatment plant technology
For some emerging contaminants, several advanced technologies—sonolysis, photocatalysis, Fenton-based oxidation and ozonation—have treated pollutants in laboratory experiments. Another technology is "enhanced coagulation" in which the treatment entity would work to optimize filtration by removing precursors to contamination through treatment. In the case of THMs, this meant lowering the pH, increasing the feed rate of coagulants, and encouraging domestic systems to operate with activated carbon filters and apparatuses that can perform reverse osmosis. Although these methods are effective, they are costly, and there have been many instances of treatment plants being resistant to pay for the removal of pollution, especially if it wasn't created in the water treatment process as many EC's occur from runoff, past pollution sources, and personal care products. It is also difficult to incentivize states to have their own policies surrounding contamination because it can be burdensome for states to pay for screening and prevention processes. There is also an element of environmental injustice, in that lower income communities with less purchasing and political power cannot buy their own system for filtration and are regularly exposed to harmful compounds in drinking water and food. However, recent treads for light-based systems shows great potential for such applications. With the decrease in cost of UV-LED systems and growing prevalence of solar powered systems, it shows great potential to remove CECs while keeping costs low.
Metal–organic framework-based nano-adsorbent remediation
Researchers have suggested that metal–organic frameworks (MOFs) and MOF-based nano-adsorbents (MOF-NAs) could be used in the removal of certain CECs, such as pharmaceuticals and personal care products, especially in wastewater treatment. Widespread use of MOF-based nano-adsorbents has yet to be implemented due to complications created by the vast physicochemical properties that CECs contain. The removal of CECs largely depends on the structure and porosity of the MOF-NAs and the physicochemical compatibility of both the CECs and the MOF-NAs. If a CEC is not compatible with the MOF-NA, then particular functional groups can be chemically added to increase compatibility between the two molecules. The addition of functional groups causes the reactions to rely on other chemical processes and mechanisms, such as hydrogen bonding, acid-base reactions, and complex electrostatic forces. MOF-based nano-adsorbent remediation heavily relies on water-qualities, such as pH, in order for the reaction to be executed efficiently. MOF-NA remediation can also be used to efficiently remove other heavy metals and organic compounds in wastewater treatment.
Membrane bioreactors
Another method of possible remediation for CECs is through the use of membrane bioreactors (MBRs) that act through mechanisms of sorption and biodegradation. Membrane bioreactors have shown results on being able to filter out certain solutes and chemicals from wastewater through methods of microfiltration, but due to the extremely small size of CECs, MBRs must rely on other mechanisms in order to ensure the removal of CECs. One mechanism that MBRs use to remove CECs from wastewater is sorption. Sorption of the CECs to sludge deposits in the MBR's system can allow the deposits to sit and be bombarded with water, causing the eventual biodegradation of CECs in the membrane. Sorption of a particular CEC can be even more efficient in the system if the CEC is hydrophobic, causing it to move from the wastewater to the sludge deposits more quickly.
Current events and advocacy
The management of CECs has gained increasing attention in recent years due to their potential impact on public health and the environment. In response to these concerns, various governmental and international organizations have initiated efforts to address CECs through research, regulation, and public outreach.
In January 2024, the White House Office of Science and Technology Policy announced a coordinated federal research initiative to address CECs in surface waters. The initiative aims to enhance understanding of the sources, occurrence, and effects of CECs, as well as to develop effective strategies for their removal and management.
Furthermore, the Organization for Economic Co-operation and Development (OECD) has been actively involved in addressing CECs. The OECD Workshop on Managing Contaminants of Emerging Concern in Surface Waters brought together experts from various countries to discuss challenges and solutions related to CECs, emphasizing the importance of international collaboration in tackling this global issue.
These recent developments underscore the growing recognition of the need for concerted efforts to address the challenges posed by CECs to protect public health and the environment.
Advocacy efforts for the regulation of CECs are important to push for legislation and regulatory action. Environmental advocacy groups raise awareness about the potential risks associated with CECs and urge for the advancement of environmental protection policies. These groups lobby for the enhancement of water quality standards, particularly the inclusion of CECs in the monitoring and treatment protocols of wastewater facilities, resulting in improved effluent quality NECRI. Additionally, they push for a comprehensive detection framework, and advocate for precautionary policies to prevent the release of harmful chemicals into the environment (Environmental Working Group).
References
Pollutants
Water pollution in the United States
Water pollution | Contaminants of emerging concern | [
"Chemistry",
"Environmental_science"
] | 4,795 | [
"Water pollution"
] |
53,082,933 | https://en.wikipedia.org/wiki/Abu%20al-Hasan%20al-Ahwazi | Abu al-Hasan al-Ahvazi () was a Persian mathematician and astronomer of the 4th AH/10th CE and 5th AH/11th CE centuries. His name suggests that he was originally from Ahvaz, now in modern Iran. The Iranian scholar Al-Biruni mentioned his name in his works, an indication that Ahvazi's works were considered to be important. Ahvazi mentioned the Iranian astronomer and mathematician Abū Ja'far al-Khāzin in one of his books. Since Al-Khazin died in 360 AH ( CE), it can be concluded that the final years of Ahvazi's life was contemporaneous to Biruni's childhood.
Ahvazi's book is extant.
, a work previously attributed to another author, was probably written by Abū l-Ḥasan al-Ahwazi (d. 428/1037) It contains eight chapters of original sayings that were intended to be understood as proverbs.
References
Sources
11th-century Iranian mathematicians
10th-century Iranian mathematicians
People from Ahvaz
10th-century Iranian astronomers
11th-century Iranian astronomers
Astronomers of the medieval Islamic world | Abu al-Hasan al-Ahwazi | [
"Astronomy"
] | 239 | [
"Astronomers",
"Astronomer stubs",
"Astronomy stubs"
] |
53,083,070 | https://en.wikipedia.org/wiki/Roll20 | Roll20 is a website consisting of a set of tools for playing tabletop role-playing games, also referred to as a virtual tabletop, which can be used as an aid to playing in person or remotely online. The site was launched in 2012 after a successful Kickstarter campaign. The platform's goal is to provide an authentic tabletop experience that does not try to turn the game into a video game, but instead aids the game master in providing immersive tools online. The blank slate nature of the platform makes integrating a multitude of tabletop role-playing games possible.
During quarantine as a result of the COVID-19 pandemic, it has allowed a variety of real life games to transition online, facilitating RPGs in an online space. In July 2022, it was announced that Roll20 would merge with OneBookShelf to become a new company. In June 2024, Roll20 purchased the digital tabletop role-playing toolset company Demiplane.
History
2012 – 2019
Roll20 was originally conceived as a personal project by three college roommates, Riley Dutton, Nolan Jones, and Richard Zayas, to help them continue to play Dungeons & Dragons after graduating and moving to different cities. After realizing that their personal app could help others as well, they started a Kickstarter campaign in the spring of 2012 with an initial goal of $5000; the campaign managed to raise almost $40,000. After a short beta testing period following the end of the Kickstarter campaign, Roll20 was released to the public in September 2012.
Roll20 reported reaching 1 million users in July 2015 and 2 million users in January 2017. Academic Evan Torner, in the book Watch Us Roll: Essays on Actual Play and Performance in Tabletop Role-Playing Games (2021), highlighted the impact of Roll20 on the actual play movement. Torner wrote, "Roll20 allows players to seamlessly control information in a shared 'tabletop' era and broadcast content of interest to both the group itself and the wider audience watching it play. Joined with Twitch and YouTube, it constitutes a powerful tool in the kit of industry up-and-comers" and that the "system would impact the play of millions at mass scale [...]. Roll20 would enable these players to document and broadcast their actual play experiences for others to consume".
In July 2016, Roll20 announced that they had acquired a license from Wizards of the Coast for official Dungeons & Dragons material. Along with the announcement, they released the first official module for Dungeons & Dragons 5th edition, Lost Mine of Phandelver, on the Roll20 Marketplace, which was followed by other releases. In February 2018, Paizo's Pathfinder and Starfinder games became officially supported on the platform.
In September 2018, one of the co-founders of Roll20, Nolan T. Jones, acting as head moderator of the Reddit Roll20 subreddit, banned Reddit user ApostleO, mistaking the account for another previously banned account whom Nolan believed to be circumventing the prior ban. After a failed attempt to get clarification and correction of the ban, ApostleO deleted his Roll20 account and posted a summary to Reddit of the hostile customer service. Many users criticized the ban, Jones' response, and the inclusion of Roll20 staff as moderators of the subreddit, leading Roll20 to apologize and turn over moderation of the subreddit to the community.
In February 2019, TechCrunch reported that Roll20's databases had been hacked along with those of 8 other companies, with the information of over 4 million users of the site posted for sale on a dark web marketplace.
2020 – present
When the COVID-19 pandemic began to prevent in-person gatherings in 2020, many groups who played in-person role-playing games turned to Roll20 to continue their games virtually. Liz Schuh, head of publishing and licensing for Dungeons & Dragons, stated that "virtual play rose 86%" in 2020 "aided by online platforms such as Roll20 and Fantasy Grounds". Erik Mona, for Paizo, commented that "tools like Roll20 and Discord played a huge role in keeping the Pathfinder and Starfinder communities together. They helped the annual PaizoCon, originally scheduled as an in-person event in Seattle, go fully digital in 2020".
In July 2021, Roll20 increased their subscription costs for the first time with the annual Plus tier increasing from $49.99 to $59.99 and the annual Pro tier increasing from $99.99 to $109.99; the monthly cost of these tiers also increased.
In February 2022, Ankit Lal, a Google veteran, become the company's CEO. Polygon reported that since March 2020 "the company has since tripled in size, growing from just 20 or 25 employees to nearly 60. Lal says that he now has two different groups of employees, one dedicated to users and another to publishers". Dicebreaker reported that per Roll20's PR team "the number of users on Roll20 has doubled in almost two years, going from five million users to more than 10 million". In June 2022, Roll20 announced a new partnership with OneBookShelf that would allow content creators on the Dungeon Masters Guild to sell modules and add-ons which are directly integrated with Roll20's virtual tabletop system.
In July 2022, Roll20 and OneBookShelf announced a merger between the two companies. This merger will combine the content libraries of both companies and make "OneBookShelf's PDF libraries accessible within Roll20". Lal will become the new company's CEO and Steve Wieck, CEO of OneBookShelf, will become president of the new company and join Roll20's board of directors. The combined company's name has not yet been announced. In 2023, the company had a temporary holding name of Wolves of Freeport, named after Wieck's EverQuest guild.
In June 2024, it was announced that Roll20 had acquired the digital tabletop role-playing toolset company Demiplane. Lal stated: "We want to make it as easy as possible for you to build your first character, to get into your first game, to try out playing TTRPGs. And we think the combination of the Roll20 VTT and the Demiplane character sheet ecosystem is going to do that". Christian Hoffer of ComicBook.com reported that this acquisition "won't have any immediate impact on users of either platform, but Demiplane CEO Peter Romenesko noted that the merged companies will look to close the difference between their two platforms very quickly". J. R. Zambrano, for Bell of Lost Souls, commented that "it seems that an era of consolidation is on the way as players like WotC and Roll20 move to consolidate their powerbases".
Features
Roll20 is a browser-based suite of tools that allows users to create and play tabletop role playing games. It is organized into individual game sessions, which users can create or join. These game sessions include various features of typical tabletop RPGs, including dynamic character sheets, automated dice rolling, shared maps with basic character and enemy tokens, and triggered sound effects, as well as a character creation tool for certain licensed game systems. The interface also includes integrated text chat, voice chat, and video chat, as well as Google Hangouts integration.
Roll20 also contains a separate marketplace, where art assets and complete game modules are sold, and a reference compendium for several game systems. Compendiums and game modules published through the marketplace are only available to use on the Roll20 platform, while some art assets and art packs can be transferred to other sites or downloaded and used for physical tabletop sessions. In addition to the free content, Roll20 also has extra features available for paying subscriber accounts, including dynamic lighting and fog of war for maps.
Besides the main browser version of Roll20, there are also iPad and Android versions. These mobile versions are more focused on the player experience, containing fewer features than the full browser site. Roll20 is available in English, with moderate support for 17 other languages through community-contributed translations using Crowdin.
Roll20 supports many tabletop systems, including the various editions of Dungeons & Dragons, Pathfinder, Shadowrun, Dungeon World, Gamma World, Traveller, Numenera, 13th Age, and others. For many less known tabletop systems, Roll20 has an open source repository where the community can contribute character sheet templates.
Following the purchase of Demiplane, Roll20 began to support cross-platform access so that content unlocked on one platform would be automatically unlocked on the other platform. , Paizo, Darrington Press, Kobold Press, and Renegade Game Studio have granted permission for cross-platform access to their products.
Other content
Roll20CON
Roll20 has held an online gaming convention named Roll20CON every year since 2016, consisting of an organized series of online games hosted on Roll20 and streamed on Twitch, along with other events. Roll20 has partnered with charitable organizations to run Roll20CON: The Cybersmile Foundation, an organization providing support for victims of cyberbullying, in 2016; and Take This, an organization focused on mental health in the gaming community, in 2019.
Burn Bryte
In July 2020, Roll20 released their own science fantasy role-playing game named Burn Bryte, with James Introcaso as lead designer. The game was first announced during Gen Con 2018, and was mentioned to be designed from the bottom up to be played on Roll20's virtual tabletop platform. Starting in August 2018, a playtest was launched for Roll20's Pro-subscribers, which was later expanded to their Plus-subscribers in November of the same year. With the games launch, multiple Actual Play campaigns were started on Twitch.
Reception
Jacob Brogan, in a review of Lost Mine of Phandelver on Roll20 for Slate in 2016, commented that "our experience wasn't always seamless at first" and that "all of this data also taxed my computer's resources, crashing my browser outright on at least one occasion. [...] In time, I overcame most of those hurdles, however, partly because Lost Mines has been so well implemented here. [...] Though working through it still requires care and preparation—much as its predigital version would—there's more than enough in the virtual package to while away hours with your fellow gamers, however far away they may be. More than any other virtual gaming system I've played with, Roll20's Lost Mines captured what it's like to delve into dungeons".
Ryan Hiller, for GeekDad in 2017, stated that "Roll20 is an industry leading web and tablet based virtual-tabletop application" and that "Roll20 is one of my must have digital tools for roleplaying". Hiller highlighted the fog-of-war and dynamic lighting features – "in a virtual game, each player would see only what they could see from where their specific character is standing and with the light they have available. This adds a whole new depth to the game as some players see encounters from entirely different perspectives, and areas of shadow become evident for use in concealment. Suddenly the rogue becomes much more interesting".
Tyler Wilde, for PC Gamer in 2017, compared using Roll20 and Tabletop Simulator to play Dungeons & Dragons. He wrote that Roll20 "is the cheaper, more practical solution for remote D&D: a clean mapping interface, easy access to official reference material, built-in video chat, and quick dice rolls. More serious players will probably prefer it". Leif Johnson, in a 2020 update on virtual tabletops for PC Gamer, wrote that Roll20 "allows a dizzying range of customization for maps, tokens, and more. Its menus are a bit drab, but they're intuitive almost to the point of genius, and the package is especially celebrated for its fantastic line-of-sight dynamic lighting system". However, the platform has some drawbacks such as "it's browser-based, which means your gameplay's subject to the vagaries of the server. It may cost nothing up front, but the free version restricts you to 100 MB for uploadable assets; to get 1GB, you'll need to fork over $4.99 a month or $49 per year. You also can't use the dynamic lighting functions unless you pay the sub, although you'll still have a fog of war option if you choose not to pay. But these are hardly deal killers. If you're relatively new to D&D and want a friendly place to hop in, Roll20's probably the best place to do it outside of a dining room table with friends".
Ari Szporn, for CBR in 2020, highlighted that Roll20 "provides integrated audio and video chat functions in an attempt to provide as comprehensive an experience as possible" and that the marketplace has third-party content creators who "can upload their own tokens, map tiles, pre-written adventures and more for members to purchase. Roll20 also has a 'Looking For Group' service to help players and DMs find new people to play with". Szporn also commented on Roll20's subscription service and stated that the free tier is "the best option for new players but is not recommended for DMs due to its limited access to Roll20's more advanced features". Luc Tran, in a separate review of various virtual tabletops for CBR, wrote that Roll20 has "a straightforward design tool for maps, dungeons and towns, as well as the ability to create and name multiple simple commands for actions like dice rolling [...]. While Roll20 is great, the fact that it is not licensed by Wizards of the Coast means it lacks a lot of official D&D material. Unless players choose to purchase specific game compendiums, D&D-specific characters, races, monsters and items will either have to be recreated in Roll20 or you'll have to find suitable replacements".
Academics Daniel Lawson and Justin Wigard, in the book Roleplaying Games in the Digital Age: Essays on Transmedia Storytelling, Tabletop RPGs and Fandom (2021), examined Roll20 as a digital space and the potential barriers to entry in play, such as the digital divide and various disabilities. They reviewed the levels of subscription and wrote that "Roll20 indelibly connects functionality to money. Thus, higher levels of subscription offer increased modes of accessibility in terms of available functionality within Roll20. In brief, money purchases remediative features—and thus rhetorical agency— in these game spaces. [...] Roll20 provides easy-to-use tools for integrating external assets, but incentivizes purchases assets which dramatically reduce accessibility barriers through ease of access".
Awards
Roll20 was named the Gold Winner in the "Best Software" category of the ENnie Awards in 2013, 2014, 2015, and 2016.
See also
Fantasy Grounds
Virtual tabletop (VTT)
References
External links
Browser-based game websites
ENnies winners
Internet properties established in 2012
Kickstarter projects
Mobile content
Role-playing game websites | Roll20 | [
"Technology"
] | 3,159 | [
"Mobile content"
] |
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