id int64 580 79M | url stringlengths 31 175 | text stringlengths 9 245k | source stringlengths 1 109 | categories stringclasses 160
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13,081,591 | https://en.wikipedia.org/wiki/Socket%20F%2B | Socket F+ (also Socket Fr2 internally ) is a CPU Socket for AMD server processors starting from the 45 nm generation of the K10 CPU family. It is the successor to Socket F. The main difference between the two sockets is the supported HyperTransport version, while Socket F supports HyperTransport 2.0 at 1.0 GHz speed, Socket F+ supports HyperTransport 3.0 at up to 2.6 GHz speed and is backwards compatible with version 1.0 and 2.0.
See also
List of AMD microprocessors
References
AMD server sockets | Socket F+ | Technology | 125 |
58,685,207 | https://en.wikipedia.org/wiki/Kron%20reduction | In power engineering, Kron reduction is a method used to reduce or eliminate the desired node without need of repeating the steps like in Gaussian elimination.
It is named after American electrical engineer Gabriel Kron.
Description
Kron reduction is a useful tool to eliminate unused nodes in a Y-parameter matrix. For example, three linear elements linked in series with a port at each end may be easily modeled as a 4X4 nodal admittance matrix of Y-parameters, but only the two port nodes normally need to be considered for modeling and simulation. Kron reduction may be used to eliminate the internal nodes, and thereby reducing the 4th order Y-parameter matrix to a 2nd order Y-parameter matrix. The 2nd order Y-parameter matrix is then more easily converted to a Z-parameter matrix or S-parameter matrix when needed.
Matrix operations
Consider a general Y-parameter matrix that may be created from a combination of linear elements constructed such that two internal nodes exist.
While it is possible to use the 4X4 matrix in simulations or to construct a 4X4 S-parameter matrix, is may be simpler to reduce the Y-parameter matrix to a 2X2 by eliminating the two internal nodes through Kron Reduction, and then simulating with a 2X2 matrix and/or converting to a 2X2 S-parameter or Z-Parameter matrix.
The process for executing a Kron reduction is as follows:
Select the Kth row/column used to model the undesired internal nodes to be eliminated. Apply the below formula to all other matrix entries that do not reside on the Kth row and column. Then simply remove the Kth row and column of the matrix, which reduces the size of the matrix by one.
Kron Reduction for the Kth row/column of an NxN matrix:
Linear elements that are also passive always form a symmetric Y-parameter matrix, that is, in all cases. The number of computations of a Kron reduction may be reduced by taking advantage of this symmetry, as shown ion the equation below.
Kron Reduction for symmetric NxN matrices:
Once all the matrix entries have been modified by the Kron Reduction equation, the Kth row/column me be eliminated, and the matrix order is reduced by one. Repeat for all internal nodes desired to be eliminated
Simplified theory and derivation
The concept behind Kron reduction is quite simple. Y-parameters are measured using nodes shorted to ground, but unused nodes, that is nodes without ports, are not necessarily grounded, and their state is not directly known to the outside. Therefore, the Y-parameter matrix of the full network does not adequately describe the Y-parameter of the network being modeled, and contains extraneous entries if some nodes do not have ports.
Consider the case of two lumped elements of equal value in series, two resistors of equal resistance for example. If both resistors have an admittance of , and the series network has an admittance of . The full admittance matrix that accounts for all three nodes in the network would look like below, using standard Y-parameter matrix construction techniques:
However, it is easily observed that the two resistors in series, each with an assigned admittance of Y, has a net admittance of , and since resistors do not leak current to ground, that the network Y12 is equal and opposite to YR11, that is YR12 = -YR11. The 2 port network without the middle node can be created by inspection and is shown below:
Since row and column 2 of the matrix is to be eliminated, we can rewrite without row 2 and column 2. We will call this rewritten matrix .
Now we have a basis to create the translation equation by finding an equation that translates each entry in to the corresponding entry in :
For each of the four entries, it can be observed that subtracting from the left-of-arrow value successfully makes the translation. Since is identical to , each case of meets the condition shown in the general translation equations.
The same process may be used for elements of arbitrary admittance ( etc.) and networks of arbitrary size, but the algebra becomes more complex. The trick is to deduce and/or calculate an expression that translates the original matrix entries to the reduced matrix entries.
See also
Schur complement
Power-flow study
References
Power engineering
Electric power | Kron reduction | Physics,Engineering | 889 |
26,658,547 | https://en.wikipedia.org/wiki/BTB/POZ%20domain | The BTB/POZ domain (BTB for BR-C, ttk and bab or POZ for Pox virus and Zinc finger) is a structural domain found in proteins across the domain Eukarya. Given its prevalence in eukaryotes and its absence in Archaea and bacteria, it likely arose after the origin of eukaryotes. While primarily a protein-protein interaction domain, some BTB domains have additional functionality in transcriptional regulation, cytoskeletal mobility, protein ubiquitination and degradation, and ion channel formation and operation. BTB domains have traditionally been classified by the other structural features present in the protein.
Discovery
The BTB/POZ domain was first described by two independent research groups in 1994. Researchers at UCLA found a conserved 115 amino acid motif in nine Drosophila proteins, including Broad complex, tramtrack, and bric-a-brac, and labelled the conserved region the BTB domain. At the same time, a group at Imperial Cancer Research Fund Laboratories in London discovered the same 120 amino acid motif in a set of otherwise unrelated zinc finger proteins and a set of pox-virus proteins, and thus named the region the POZ domain.
Structure
The motif is approximately 120 amino acids long, with a core fold of 95 amino acids that form five alpha helices and three beta sheets. The alpha helices form two hairpin structures, A1/A2 and A4/A5, out of the first and second and the fourth and fifth alpha helices respectively. The remaining alpha helix, A3, bridges the two. The three beta sheets cap the A1/A2 hairpin. Additional secondary structures can surround this core fold. For example, BTB domains in Kelch proteins, C2H2 zinc finger proteins, and HTH-containing proteins frequently include an additional alpha helix and beta sheet at the N-terminus of the domain.
Function
The BTB domain is primarily a protein-protein interaction domain. In zinc-finger proteins, it commonly forms homodimers with other BTB domains, mediates heteromeric dimerization, and recruits transcriptional corepressors.
References
Protein domains | BTB/POZ domain | Biology | 442 |
415,914 | https://en.wikipedia.org/wiki/Bisbee%20Blue | Bisbee Blue or Bisbee turquoise refers to the turquoise that comes from copper mines located in the vicinity of Bisbee, Arizona. Bisbee turquoise can be found in many different shades of color and quality, from soft, low quality pale blue, to the quality hard brilliant blue turquoise and almost every shade of blue in between. The highest grade of Bisbee Blue turquoise is almost lapis lazuli blue and has a brownish-red spiderweb matrix. Green turquoise is also found in Bisbee.
History
Discovery
Though small amounts of turquoise were found in the Campbell shaft mine, as well as in stream beds in the Mule Mountains, the vast majority of Bisbee turquoise surfaced when the Phelps Dodge Corporation started open pit mining operations at the location now known as the Lavender Pit, especially the eastern side of the pit. Large amounts of a conglomerate rock bed needed to be removed before the copper ore located more deeply could be reached. This sedimentary conglomerate "waste" rock was the host for most of the turquoise, in both vein and nugget form.
Recovery
During the time that the largest quantities of turquoise were being extracted from the mine, the company made no organized effort to recover it. It simply got loaded into large dump trucks and hauled off to the "dumps". During this time (primarily from the late 1950s to the late 1960s), some of the recovered turquoise was obtained by company employees taking it home in their lunch boxes, etc. Though this activity was prohibited, the prohibition was rarely enforced. For several years (mostly the early to late 1970s), these individuals, locally known as "dumpers", were the only source for this fine turquoise aside from those who were granted exclusive access to collect turquoise existing in the mine dumps during a set day annually for a marginal fee.
During this time, Phelps Dodge leased out the dumps to Bob Matthews. Matthews and associates were the only legal miners of the Bisbee turquoise and other copper minerals in history besides the annual dig pass holders. Matthews sold large lots to the famous artists the Zacharys from Albuquerque, New Mexico, the owners of the Turquoise Museum in Albuquerque, John Hartman in Durango, Colorado, and many other famous artists and traders. Some of Matthews' turquoise was sent to Durango to be made into jewelry by his brother-in-law Cecil Mickelson's jewelry company. The company made Bisbee Blue and Villa Grove inlay turquoise jewelry up until the 1980s. In the early 2000s the Durango Silver Company, bought what was thought to be left of the Bob Matthews/Cecil Mickelson Collection of Bisbee turquoise. This collection amounted to approximately of rough Bisbee turquoise. Still, numerous reputable artists and suppliers continue to sell what remains of the exquisite and highly collectible turquoise from Bisbee.
References
Bisbee Turquoise
Durango Silver Company
Phosphate minerals
Gemstones
Bisbee, Arizona | Bisbee Blue | Physics | 578 |
41,579,775 | https://en.wikipedia.org/wiki/Actinoquinol | Actinoquinol is a chemical compound that absorbs UVB light.
References
Quinolines
Sulfonic acids | Actinoquinol | Chemistry | 25 |
32,073,497 | https://en.wikipedia.org/wiki/Glutamate%20permease | The sodium/glutamate symporter, also known as glutamate permease, is a transmembrane protein family found in bacteria and archaea. These proteins are symporters that are responsible for the sodium-dependent uptake of extracellular glutamate into the cell. They are integral membrane proteins located in the bacterial inner membrane. The best-studied member of the family is GltS from Escherichia coli. GltS contains ten transmembrane helices arranged in two antiparallel 5-helix domains and functions as a homodimer. Substrates for GltS include L- and D-glutamate, as well as toxic analogs α-methylglutamate, and homocysteate. In studies of E. coli growth, bacteria without GltS were unable to grow in a medium where glutamate is the only source of carbon.
The family is evolutionarily distant from other glutamate transporters. Phylogenetic analyses of GltS genes suggest that their presence in cyanobacteria can be attributed to at least two horizontal gene transfer events.
References
Protein families | Glutamate permease | Biology | 239 |
58,945,004 | https://en.wikipedia.org/wiki/Rajadurai%20Foundation | Rajadurai Foundation was established in 2009 by Sivanandi Rajadurai, the mission of which is to build human potential through advancement of professional aspiration, academic scholarship, protection of environment and societies and gift real hope through all-inclusive partnership and spirituality.
Activities
Rajadurai Foundation conducts mentorship programs by delivering scientific and motivational lectures to students, academicians and educators. It promotes the idea of emission control.
Rajadurai as a Corporate Executive has been involved with various Research Institutes to close the gap between Innovative Inventions and Industrialization since 1990. He continues to dedicate his engagements on Industry University Interaction to bring forth best possible solutions for industrial problems. He is a Chairman of Industry Institute Interaction Cell (IIIC) in 2011 and Member of Governing Council since 2012, Annai Vailankanni College of Engineering. He is a Member of Research Advisory Board (National) & Board of Research in 2018, Hindustan Institute of Technology & Science. He is a Board of Studies Member in 2018 & Member of Advisory Committee in 2019 Bannari Amman Institute of Technology. He is a Member of Internal Quality Assurance Cell (IQAC) & Institution Innovation Council (IIC) in 2019, Academy of Maritime Education and Training (AMET) University. Rajadurai Foundation established a merit award in Loyola college for the best student of M.Sc. chemistry in the name of Rev. Fr. Sebastian Kalarickal S.J, to recognize his dedicated services to students from the year 2006. He instituted Gurusmrithi Award in 2006 in Mar Ivanios College to be given to the Best Student of M.Sc. Chemistry every year.
Rajadurai Foundation provides awareness education programs in order to develop clean and green environment and to achieve carbon neutral earth. He Initiated and inaugurated Green Technology Centre in James Engineering College to motivate professors and students for a global approach to protect the environment from challenges such as acid rain, global warming, ozone depletion, rainforest deterioration, river contamination, sea level rise, accumulation of hazardous wastes, air pollution and over population, assisted SRM Institute of Science and Technology to develop SAE BAJA Formula Race with CO2 reduction, also achieved Near Zero Emission and received National Award.
Rajadurai Foundation actively involves in conducting and supporting sports & cultural activities by Sponsored Anna University Volleyball Match Sports Day Volleyball League in 2018, presented Sponsor for Kanyakumari District Kabaddi team, who participated in Tamil Nadu State Level Kabbadi Tournament – 2019, sponsored RF cricket team participated in S.S.V. Boys 4th year Tennis Ball Cricket Tournament-2020 to develop identified talent and boost the morale & confidence of the young and dynamic players.
References
Educational foundations
Environmental education
Social welfare charities
Foundations based in India | Rajadurai Foundation | Environmental_science | 552 |
77,310,445 | https://en.wikipedia.org/wiki/Deep%20backward%20stochastic%20differential%20equation%20method | Deep backward stochastic differential equation method is a numerical method that combines deep learning with Backward stochastic differential equation (BSDE). This method is particularly useful for solving high-dimensional problems in financial derivatives pricing and risk management. By leveraging the powerful function approximation capabilities of deep neural networks, deep BSDE addresses the computational challenges faced by traditional numerical methods in high-dimensional settings.
History
Backwards stochastic differential equations
BSDEs were first introduced by Pardoux and Peng in 1990 and have since become essential tools in stochastic control and financial mathematics. In the 1990s, Étienne Pardoux and Shige Peng established the existence and uniqueness theory for BSDE solutions, applying BSDEs to financial mathematics and control theory. For instance, BSDEs have been widely used in option pricing, risk measurement, and dynamic hedging.
Deep learning
Deep Learning is a machine learning method based on multilayer neural networks. Its core concept can be traced back to the neural computing models of the 1940s. In the 1980s, the proposal of the backpropagation algorithm made the training of multilayer neural networks possible. In 2006, the Deep Belief Networks proposed by Geoffrey Hinton and others rekindled interest in deep learning. Since then, deep learning has made groundbreaking advancements in image processing, speech recognition, natural language processing, and other fields.
Limitations of traditional numerical methods
Traditional numerical methods for solving stochastic differential equations include the Euler–Maruyama method, Milstein method, Runge–Kutta method (SDE) and methods based on different representations of iterated stochastic integrals.
But as financial problems become more complex, traditional numerical methods for BSDEs (such as the Monte Carlo method, finite difference method, etc.) have shown limitations such as high computational complexity and the curse of dimensionality.
In high-dimensional scenarios, the Monte Carlo method requires numerous simulation paths to ensure accuracy, resulting in lengthy computation times. In particular, for nonlinear BSDEs, the convergence rate is slow, making it challenging to handle complex financial derivative pricing problems.
The finite difference method, on the other hand, experiences exponential growth in the number of computation grids with increasing dimensions, leading to significant computational and storage demands. This method is generally suitable for simple boundary conditions and low-dimensional BSDEs, but it is less effective in complex situations.
Deep BSDE method
The combination of deep learning with BSDEs, known as deep BSDE, was proposed by Han, Jentzen, and E in 2018 as a solution to the high-dimensional challenges faced by traditional numerical methods. The Deep BSDE approach leverages the powerful nonlinear fitting capabilities of deep learning, approximating the solution of BSDEs by constructing neural networks. The specific idea is to represent the solution of a BSDE as the output of a neural network and train the network to approximate the solution.
Model
Mathematical method
Backward Stochastic Differential Equations (BSDEs) represent a powerful mathematical tool extensively applied in fields such as stochastic control, financial mathematics, and beyond. Unlike traditional Stochastic differential equations (SDEs), which are solved forward in time, BSDEs are solved backward, starting from a future time and moving backwards to the present. This unique characteristic makes BSDEs particularly suitable for problems involving terminal conditions and uncertainties.
A backward stochastic differential equation (BSDE) can be formulated as:
In this equation:
is the terminal condition specified at time .
is called the generator of the BSDE
is the solution consists of stochastic processes and which are adapted to the filtration
is a standard Brownian motion.
The goal is to find adapted processes and that satisfy this equation. Traditional numerical methods struggle with BSDEs due to the curse of dimensionality, which makes computations in high-dimensional spaces extremely challenging.
Methodology overview
Source:
1. Semilinear parabolic PDEs
We consider a general class of PDEs represented by
In this equation:
is the terminal condition specified at time .
and represent the time and -dimensional space variable, respectively.
is a known vector-valued function, denotes the transpose associated to , and denotes the Hessian of function with respect to .
is a known vector-valued function, and is a known nonlinear function.
2. Stochastic process representation
Let be a -dimensional Brownian motion and be a -dimensional stochastic process which satisfies
3. Backward stochastic differential equation (BSDE)
Then the solution of the PDE satisfies the following BSDE:
4. Temporal discretization
Discretize the time interval into steps :
where and .
5. Neural network approximation
Use a multilayer feedforward neural network to approximate:
for , where are parameters of the neural network approximating at .
6. Training the neural network
Stack all sub-networks in the approximation step to form a deep neural network. Train the network using paths and as input data, minimizing the loss function:
where is the approximation of .
Neural network architecture
Source:
Deep learning encompass a class of machine learning techniques that have transformed numerous fields by enabling the modeling and interpretation of intricate data structures. These methods, often referred to as deep learning, are distinguished by their hierarchical architecture comprising multiple layers of interconnected nodes, or neurons. This architecture allows deep neural networks to autonomously learn abstract representations of data, making them particularly effective in tasks such as image recognition, natural language processing, and financial modeling. The core of this method lies in designing an appropriate neural network structure (such as fully connected networks or recurrent neural networks) and selecting effective optimization algorithms.
The choice of deep BSDE network architecture, the number of layers, and the number of neurons per layer are crucial hyperparameters that significantly impact the performance of the deep BSDE method. The deep BSDE method constructs neural networks to approximate the solutions for and , and utilizes stochastic gradient descent and other optimization algorithms for training.
The fig illustrates the network architecture for the deep BSDE method. Note that denotes the variable approximated directly by subnetworks, and denotes the variable computed iteratively in the network. There are three types of connections in this network:
i) is the multilayer feedforward neural network approximating the spatial gradients at time . The weights of this subnetwork are the parameters optimized.
ii) is the forward iteration providing the final output of the network as an approximation of , characterized by Eqs. 5 and 6. There are no parameters optimized in this type of connection.
iii) is the shortcut connecting blocks at different times, characterized by Eqs. 4 and 6. There are also no parameters optimized in this type of connection.
Algorithms
Adam optimizer
This function implements the Adam algorithm for minimizing the target function .
Function: ADAM(, , , , , ) is
// Initialize the first moment vector
// Initialize the second moment vector
// Initialize timestep
// Step 1: Initialize parameters
// Step 2: Optimization loop
while has not converged do
// Compute gradient of at timestep
// Update biased first moment estimate
// Update biased second raw moment estimate
// Compute bias-corrected first moment estimate
// Compute bias-corrected second moment estimate
// Update parameters
return
With the ADAM algorithm described above, we now present the pseudocode corresponding to a multilayer feedforward neural network:
Backpropagation algorithm
This function implements the backpropagation algorithm for training a multi-layer feedforward neural network.
Function: BackPropagation(set ) is
// Step 1: Random initialization
// Step 2: Optimization loop
repeat until termination condition is met:
for each :
// Compute output
// Compute gradients
for each output neuron :
// Gradient of output neuron
for each hidden neuron :
// Gradient of hidden neuron
// Update weights
for each weight :
// Update rule for weight
for each weight :
// Update rule for weight
// Update parameters
for each parameter :
// Update rule for parameter
for each parameter :
// Update rule for parameter
// Step 3: Construct the trained multi-layer feedforward neural network
return trained neural network
Combining the ADAM algorithm and a multilayer feedforward neural network, we provide the following pseudocode for solving the optimal investment portfolio:
Numerical solution for optimal investment portfolio
Source:
This function calculates the optimal investment portfolio using the specified parameters and stochastic processes.
function OptimalInvestment(, , ) is
// Step 1: Initialization
for to maxstep do
, // Parameter initialization
for to do
// Update feedforward neural network unit
// Step 2: Compute loss function
// Step 3: Update parameters using ADAM optimization
// Step 4: Return terminal state
return
Application
Deep BSDE is widely used in the fields of financial derivatives pricing, risk management, and asset allocation. It is particularly suitable for:
High-Dimensional Option Pricing: Pricing complex derivatives like basket options and Asian options, which involve multiple underlying assets. Traditional methods such as finite difference methods and Monte Carlo simulations struggle with these high-dimensional problems due to the curse of dimensionality, where the computational cost increases exponentially with the number of dimensions. Deep BSDE methods utilize the function approximation capabilities of deep neural networks to manage this complexity and provide accurate pricing solutions. The deep BSDE approach is particularly beneficial in scenarios where traditional numerical methods fall short. For instance, in high-dimensional option pricing, methods like finite difference or Monte Carlo simulations face significant challenges due to the exponential increase in computational requirements with the number of dimensions. Deep BSDE methods overcome this by leveraging deep learning to approximate solutions to high-dimensional PDEs efficiently.
Risk Measurement: Calculating risk measures such as Conditional Value-at-Risk (CVaR) and Expected shortfall (ES). These risk measures are crucial for financial institutions to assess potential losses in their portfolios. Deep BSDE methods enable efficient computation of these risk metrics even in high-dimensional settings, thereby improving the accuracy and robustness of risk assessments. In risk management, deep BSDE methods enhance the computation of advanced risk measures like CVaR and ES, which are essential for capturing tail risk in portfolios. These measures provide a more comprehensive understanding of potential losses compared to simpler metrics like Value-at-Risk (VaR). The use of deep neural networks enables these computations to be feasible even in high-dimensional contexts, ensuring accurate and reliable risk assessments.
Dynamic Asset Allocation: Determining optimal strategies for asset allocation over time in a stochastic environment. This involves creating investment strategies that adapt to changing market conditions and asset price dynamics. By modeling the stochastic behavior of asset returns and incorporating it into the allocation decisions, deep BSDE methods allow investors to dynamically adjust their portfolios, maximizing expected returns while managing risk effectively. For dynamic asset allocation, deep BSDE methods offer significant advantages by optimizing investment strategies in response to market changes. This dynamic approach is critical for managing portfolios in a stochastic financial environment, where asset prices are subject to random fluctuations. Deep BSDE methods provide a framework for developing and executing strategies that adapt to these fluctuations, leading to more resilient and effective asset management.
Advantages and disadvantages
Advantages
Sources:
High-dimensional capability: Compared to traditional numerical methods, deep BSDE performs exceptionally well in high-dimensional problems.
Flexibility: The incorporation of deep neural networks allows this method to adapt to various types of BSDEs and financial models.
Parallel computing: Deep learning frameworks support GPU acceleration, significantly improving computational efficiency.
Disadvantages
Sources:
Training time: Training deep neural networks typically requires substantial data and computational resources.
Parameter sensitivity: The choice of neural network architecture and hyperparameters greatly impacts the results, often requiring experience and trial-and-error.
See also
Bellman equation
Dynamic programming
Applications of artificial intelligence
List of artificial intelligence projects
Backward stochastic differential equation
Stochastic process
Stochastic volatility
Stochastic partial differential equations
Diffusion process
Stochastic difference equation
References
Further reading
Evans, Lawrence C (2013). An Introduction to Stochastic Differential Equations American Mathematical Society.
Desmond Higham and Peter Kloeden: "An Introduction to the Numerical Simulation of Stochastic Differential Equations", SIAM, (2021).
Stochastic simulation
Numerical analysis | Deep backward stochastic differential equation method | Mathematics | 2,505 |
46,796,038 | https://en.wikipedia.org/wiki/BioSentinel | BioSentinel is a lowcost CubeSat spacecraft on a astrobiology mission that will use budding yeast to detect, measure, and compare the impact of deep space radiation on DNA repair over long time beyond low Earth orbit.
Selected in 2013 for a 2022 launch, the spacecraft will operate in the deep space radiation environment throughout its 18-month mission. This will help scientists understand the health threat from cosmic rays and deep space environment on living organisms and reduce the risk associated with long-term human exploration, as NASA plans to send humans farther into space than ever before. The spacecraft was launched on 16 November 2022 as part of the Artemis 1 mission. In August 2023, NASA extended BioSentinel's mission into November 2024.
The mission was developed by NASA Ames Research Center.
Background
BioSentinel is one of ten low-cost CubeSat missions that flew as secondary payloads aboard Artemis 1, the first test flight of NASA's Space Launch System. The spacecraft was deployed in cis-lunar space as NASA's first mission to send living organisms beyond low Earth orbit since Apollo 17 in 1972.
Objective
The primary objective of BioSentinel is to develop a biosensor using a simple model organism (yeast) to detect, measure, and correlate the impact of space radiation to living organisms over long durations beyond low Earth orbit (LEO) and into heliocentric orbit. While progress has been made with simulations, no terrestrial laboratory can duplicate the unique space radiation environment.
Biological science
The BioSentinel biosensor uses the budding yeast Saccharomyces cerevisiae to detect and measure DNA damage response after exposure to the deep space radiation environment. Two yeast strains were selected for this mission: a wild type strain proficient in DNA repair, and a strain defective in the repair of DNA double strand breaks (DSBs), deleterious lesions generated by ionizing radiation. Budding yeast was selected not only because of its flight heritage, but also because of its similarities with human cells, especially its DSB repair mechanisms. The biosensor consists of specifically engineered yeast strains and growth medium containing a metabolic indicator dye. Therefore, culture growth and metabolic activity of yeast cells directly indicate successful repair of DNA damage.
After completing the Moon flyby and spacecraft checkout, the science mission phase will begin with the wetting of the first set of yeast-containing wells with specialized media. Multiple sets of wells will be activated at different time points over the 18-month mission. One reserve set of wells will be activated in the occurrence of a solar particle event (SPE). Approximately, a 4 to 5 krad total ionizing dose is anticipated. Payload science data and spacecraft telemetry will be stored on board and then downloaded to the ground.
Biological measurements will be compared to data provided by onboard radiation sensors and dosimeters.
Additionally, two identical BioSentinel payloads have been developed: one for the International Space Station (ISS), which is in similar microgravity conditions but a comparatively low-radiation environment, and one for use as a delayed-synchronous ground control at Earth gravity and, due to Earth's magnetic field, at Earth-surface-level radiation. The payload on the ISS has been warmed up and rehydrated in January 2022, the one on Earth surface, weeks later. They will help calibrate the biological effects of radiation in deep space to analogous measurements conducted on Earth and on the ISS.
Spacecraft
The Biosentinel spacecraft will consist of a 6U CubeSat bus format, with external dimensions of 10 cm × 20 cm × 30 cm and a mass of about . At launch, BioSentinel resides within the second stage on the launch vehicle from which it is deployed to a lunar flyby trajectory and into an Earth-trailing heliocentric orbit.
Of the total 6 Units volume, 4 Units will hold the science payload, including a radiation dosimeter and a dedicated 3-color spectrometer for each well; 0.5U will house the ADCS (Attitude Determination and Control Subsystem), 0.5U will house the EPS (Electrical Power System) and C&DH (Command and Data Handling) avionics, and 1U will house the attitude control thruster assembly, which will be 3D printed all in one piece: cold gas (DuPont R236fa) propellant tanks, lines and seven nozzles. The use of 3D printing also allows the optimization of space for increased propellant storage (165 grams ). The thrust of each nozzle is 50 mN, and a specific impulse of 31 seconds. The attitude control system is being developed and fabricated by the Georgia Institute of Technology.
Electric power will be generated by deployable solar panels rated at 30 watts, and telecommunications will rely on the Iris transponder at X-band.
The spacecraft is being developed by NASA Ames Research Center (AMR), in collaboration with NASA Jet Propulsion Laboratory (JPL), NASA Johnson Space Center (JSC), NASA Marshall Space Flight Center (MSFC), and NASA Headquarters.
See also
The 10 CubeSats flying in the Artemis 1 mission
Near-Earth Asteroid Scout by NASA was a solar sail spacecraft that was planned to encounter a near-Earth asteroid (mission failure)
BioSentinel is an astrobiology mission
LunIR by Lockheed Martin Space
Lunar IceCube, by the Morehead State University
CubeSat for Solar Particles (CuSP)
Lunar Polar Hydrogen Mapper (LunaH-Map), designed by the Arizona State University
EQUULEUS, submitted by JAXA and the University of Tokyo
OMOTENASHI, submitted by JAXA, was a lunar lander (mission failure)
ArgoMoon, designed by Argotec and coordinated by Italian Space Agency (ASI)
Team Miles, by Fluid and Reason LLC, Tampa, Florida
The 3 CubeSat missions removed from Artemis 1
Lunar Flashlight will map exposed water ice on the Moon
Cislunar Explorers, Cornell University, Ithaca, New York
Earth Escape Explorer (CU-E3), University of Colorado Boulder
Astrobiology missions
Bion
BIOPAN
Biosatellite program
List of microorganisms tested in outer space
O/OREOS
OREOcube
Tanpopo
References
External links
Fact Sheet of BioSentinel, at NASA
CubeSats
DNA repair
Space exposure experiments
Space-flown life
2022 in the United States
Spacecraft launched in 2022
NASA space probes
Astrobiology space missions
Secondary payloads | BioSentinel | Biology | 1,325 |
639,778 | https://en.wikipedia.org/wiki/Hilbert%27s%20sixth%20problem | Hilbert's sixth problem is to axiomatize those branches of physics in which mathematics is prevalent. It occurs on the widely cited list of Hilbert's problems in mathematics that he presented in the year 1900. In its common English translation, the explicit statement reads:
6. Mathematical Treatment of the Axioms of Physics. The investigations on the foundations of geometry suggest the problem: To treat in the same manner, by means of axioms, those physical sciences in which already today mathematics plays an important part; in the first rank are the theory of probabilities and mechanics.
Hilbert gave the further explanation of this problem and its possible specific forms:
"As to the axioms of the theory of probabilities, it seems to me desirable that their logical investigation should be accompanied by a rigorous and satisfactory development of the method of mean values in mathematical physics, and in particular in the kinetic theory of gases. ... Boltzmann's work on the principles of mechanics suggests the problem of developing mathematically the limiting processes, there merely indicated, which lead from the atomistic view to the laws of motion of continua."
History
David Hilbert himself devoted much of his research to the sixth problem; in particular, he worked in those fields of physics that arose after he stated the problem.
In the 1910s, celestial mechanics evolved into general relativity. Hilbert and Emmy Noether corresponded extensively with Albert Einstein on the formulation of the theory.
In the 1920s, mechanics of microscopic systems evolved into quantum mechanics. Hilbert, with the assistance of John von Neumann, L. Nordheim, and E. P. Wigner, worked on the axiomatic basis of quantum mechanics (see Hilbert space). At the same time, but independently, Dirac formulated quantum mechanics in a way that is close to an axiomatic system, as did Hermann Weyl with the assistance of Erwin Schrödinger.
In the 1930s, probability theory was put on an axiomatic basis by Andrey Kolmogorov, using measure theory.
Since the 1960s, following the work of Arthur Wightman and Rudolf Haag, modern quantum field theory can also be considered close to an axiomatic description.
In the 1990s-2000s the problem of "the limiting processes, there merely indicated, which lead from the atomistic view to the laws of motion of continua" was approached by many groups of mathematicians. Main recent results are summarized by Laure Saint-Raymond, Marshall Slemrod, Alexander N. Gorban and Ilya Karlin.
Status
Hilbert’s sixth problem was a proposal to expand the axiomatic method outside the existing mathematical disciplines, to physics and beyond. This expansion requires development of semantics of physics with formal analysis of the notion of physical reality that should be done. Two fundamental theories capture the majority of the fundamental phenomena of physics:
Quantum field theory, which provides the mathematical framework for the Standard Model;
General relativity, which describes space-time and gravity at macroscopic scale.
Hilbert considered general relativity as an essential part of the foundation of physics. However, quantum field theory is not logically consistent with general relativity, indicating the need for a still-unknown theory of quantum gravity, where the semantics of physics is expected to play a central role. Hilbert's sixth problem thus remains open. Nevertheless, in recent years it has fostered research regarding the foundations of physics with a particular emphasis on the role of logic and precision of language, leading to some interesting results viz. a direct realization of uncertainty principle from Cauchy's definition of `derivative' and the unravelling of a semantic obstacle in the path of any theory of quantum gravity from the axiomatic perspective, unravelling of a logical tautology in the quantum tests of equivalence principle and formal unprovability of the first Maxwell's equation.
See also
Wightman axioms
Constructive quantum field theory
Notes
References
External links
David Hilbert, Mathematical Problems, Problem 6, in English translation.
06
Unsolved problems in physics | Hilbert's sixth problem | Physics,Mathematics | 808 |
48,607,529 | https://en.wikipedia.org/wiki/Wildlife%20of%20Yemen | The wildlife of Yemen is substantial and varied. Yemen is a large country in the southern half of the Arabian Peninsula with several geographic regions, each with a diversity of plants and animals adapted to their own particular habitats. As well as high mountains and deserts, there is a coastal plain and long coastline. The country has links with Europe and Asia, and the continent of Africa is close at hand. The flora and fauna have influences from all these regions and the country also serves as a staging post for migratory birds.
Geography
Yemen is in the southern half of the Arabian Peninsula, bordering the Red Sea, the Gulf of Aden and the Arabian Sea. The country is divided into four geographical regions: the Tihamah or coastal plains to the west, the western highlands, the central highlands, and the Rub' al Khali, or "Empty Quarter", in the east, the largest sand desert in the world. The Tihamah forms an arid flat plain alongside the Red Sea coast. There are many lagoons here and considerable biodiversity; streams from the western highlands sink and evaporate before reaching the coast.
The Sarawat Mountains (or Sarat Mountains) in Saudi Arabia extend southwards into Yemen, where they divide into two ranges. The western highlands run parallel with the Red Sea coast and to the east of them, the land slopes gently towards the Persian Gulf. These mountains receive up to of rain in places and are the wettest part of the country. Rainfall comes from southwestern monsoons and from thunderstorms in summer. For over two thousand years the steep slopes of these mountains have been terraced and intensively cropped, and little of the indigenous vegetation remains.
The central highlands rise up to over and contain the highest peaks of the Arabian Peninsula. They are in the rain shadow of the western highlands but receive enough rainfall for the cultivation of irrigated wheat and barley. The Rub' al Khali desert region receives almost no rainfall. Both this range and the western highlands feature many wadis, dry watercourses which have been carved out by floods when the occasional torrential downpour occurs. These often support more vascular plants than other arid areas.
Flora
At high altitudes, the native flora of the western highlands is dominated by African juniper. This juniper woodland is similar to woodland in East Africa. Vachellia origena is a common leguminous tree growing in patches of woodland, in hedgerows and as individual trees on cultivated terraces in the western highlands. Shrubs such as Euryops arabicus grow here, and on southern slopes there are succulent plants such as aloes and euphorbias. At lower elevations there is a shrubby forest with species including the Abyssinian rose and the camphor bush. Lower still, below about , Acacia and myrrh are the dominant woody plants.
In the Hadhramaut region of southern Yemen, wheat and millet is grown and both coconut palms and date palms are cultivated, and frankincence also grows here. The western coastal Tihama plains are irrigated for the production of citrus, bananas and dates. Figs, coffee, khat, wheat, barley and sorghum are grown on the slopes above. On the Red Sea coast there are extensive stands of white mangrove over a coastal stretch of about , with sporadic clumps elsewhere.
The sandy Rub' al Khali has very little plant diversity, about 37 species of flowering plant have been recorded here, 17 of which are only found around the periphery. There are no trees here, Typical xeric plants include the dwarf shrubs Calligonum crinitum and saltbush, and several species of sedge.
Fauna
About 464 species of bird have been recorded in Yemen, ten of which are endemic to the country including the Socotra buzzard, the Socotra scops owl, the Socotra cisticola, the Socotra warbler, the Socotra starling, the Socotra sunbird, the Arabian accentor, the Socotra bunting, the Socotra sparrow, and the Abd al-Kuri sparrow. The cliff faces of the western highlands provide habitat for the griffon vulture, the Verreaux's eagle, and the small Barbary falcon. The juniper woodlands in the west are home to the Yemen linnet, Yemen thrush, Yemen warbler, and the African paradise flycatcher, and many migratory birds pass through this area twice a year.
The hamadryas baboon is present in parts of the country, and there are believed to be about seventy wild Arabian leopards remaining here. A captive breeding programme is being undertaken at Taiz Zoo in the Yemeni highlands. Other mammals found in Yemen include the mountain gazelle, gray wolf, Blanford's fox, Rüppell's fox, caracal, sand cat, wildcat, common genet, striped hyena, golden jackal, honey badger, bushy-tailed mongoose, rock hyrax, desert hedgehog, Arabian shrew, golden spiny mouse, lesser Egyptian jerboa, several species of gerbils, king jird, Yemeni mouse and a number of species of bat.
Snakes found in Yemen include the Arabian cobra, the horned viper, and the puff adder, as well as several species of sea snakes. There is the endemic Yemen monitor, numerous species of lizard, several geckos, and the veiled chameleon. The African helmeted turtle and tortoise are found on land, and several species of sea turtle breed on the beaches.
Yemen has coastlines on the Red Sea and the Indian Ocean. These mostly have shallow fringing reefs where corals proliferate and a diverse invertebrate fauna. These reefs provide a spawning ground and a protective environment for the young of many species of fish. Marine mammals including whales and dolphins are found here, as are sharks and many species of fish. Sea birds proliferate along the coastline. The island of Socotra and its archipelago are also part of Yemen, about east of the Horn of Africa and south of the Arabian Peninsula. These islands have a unique flora and are fringed by coral reefs. Some seven hundred species of plant and animal are endemic to the Socotra island group.
References
Yemen
Fauna of Yemen | Wildlife of Yemen | Biology | 1,291 |
47,507,934 | https://en.wikipedia.org/wiki/International%20Ground%20Source%20Heat%20Pump%20Association | Established in 1987, the International Ground Source Heat Pump Association (IGSHPA) is a nonprofit, membership-based organization that promotes geothermal heat pump technology. It was a outreach unit of the College of Engineering, Architecture and Technology (CEAT) at Oklahoma State University until 2020. In June 2020, the OSU Board of Regents voted to approve a transfer of IGSHPA, its intellectual property, and assets to the control of the Geothermal Exchange Organization (GEO).
Primary Efforts
IGSHPA is the main organization for establishing standards of practice and standards of design for Geothermal Heat Pump (GHP) systems in the US. Related organizations have been formed in other countries on four continents, including Australia, Canada, China, India, South Korea, and Sweden.
Conferences
Each year the association hosts an annual conference for people such as manufacturers, contractors, distributors, and drillers.
Standards
IGSHPA sets and revises standards for Geothermal Heat Pump (GHP) system installs based on ongoing research and field application results.
See also
Association of Energy Engineers
Geothermal heat pump (GHP)
Thermal battery
Renewable thermal energy
External links
International Ground Source Heat Pump Association
References
Heat pumps
Heating, ventilation, and air conditioning
Engineering organizations
Trade associations based in the United States
Energy business associations | International Ground Source Heat Pump Association | Engineering | 263 |
27,861,937 | https://en.wikipedia.org/wiki/Pivalonitrile | Pivalonitrile is a nitrile with the semi-structural formula (CH3)3CCN, abbreviated t-BuCN. This aliphatic organic compound is a clear, colourless liquid that is used as a solvent and as a labile ligand in coordination chemistry. Pivalonitrile is isomeric with tert-butyl isocyanide but the two compounds do not exist in chemical equilibrium, unlike its silicon analog trimethylsilyl cyanide.
References
5
Tert-butyl compounds | Pivalonitrile | Chemistry | 112 |
24,384,363 | https://en.wikipedia.org/wiki/List%20of%20Blu-ray%20player%20manufacturers | This aims to be a complete list of Blu-ray manufacturers.
This list is not necessarily complete or up to date - if you see a manufacturer that should be here but is not (or one that should not be here but is), please update the page accordingly.
A
American Recordable Media
Ayankaran International
Acu-disc
C
Cambridge Audio
CMC Magnetics
D
Denon
F
Fukuda
I
Imation
Insignia
J
JVC
L
LaCie
LG
M
Maxell
Microsoft
Moser Baer
O
OPPO Digital
P
Panasonic
Philips
Pioneer Corporation
R
Ritek
River Pro Audio
S
Sony
Samsung
Sharp
V
Verbatim Corporation
Y
Yamaha Corporation
References
See also
Blu-ray Disc authoring
Blu-ray Disc
Blu-ray Disc Association
Blu-ray Disc recordable
Blu-ray Region Code
CBHD Based on HD DVD format.
Comparison of high definition optical disc formats
Digital rights management
HD DVD
HD NVD
High definition optical disc format war
Optical disc
PlayStation 3
PlayStation 4
Xbox One
Audio storage
Blu-ray Disc
Computer storage media
Consumer electronics
DVD manufacturing
High-definition television
Java platform
Lists of consumer electronics manufacturers | List of Blu-ray player manufacturers | Technology | 223 |
2,674,010 | https://en.wikipedia.org/wiki/Salt%20metathesis%20reaction | A salt metathesis reaction is a chemical process involving the exchange of bonds between two reacting chemical species which results in the creation of products with similar or identical bonding affiliations. This reaction is represented by the general scheme:
AB + CD -> AD + CB
Typical examples are the reactions between oxysalts and binary compounds such as salts, hydrohalic acids and metal hydroxides:
\mathit{ab}A_\mathit{x}(BO_\mathit{y})_\mathit{z}{} + \mathit{xz}C_\mathit{a}D_\mathit{b}{} -> \mathit{bx}A_\mathit{a}D_\mathit{z}{} + \mathit{az}C_\mathit{x}(BO_\mathit{y})_\mathit{b}{}
Another classical example are the reactions between oxysalts in solution:
\mathit{ab}A_\mathit{x}(BO_\mathit{p})_\mathit{y}{} + \mathit{xy}C_\mathit{a}(DO_\mathit{q})_\mathit{b}{} -> \mathit{bx}A_\mathit{a}(DO_\mathit{q})_\mathit{y}{} + \mathit{ay}C_\mathit{x}(BO_\mathit{p})_\mathit{b}{}
The bond between the reacting species can be either ionic or covalent. Classically, these reactions result in the precipitation of one product.
In older literature, the term double decomposition is common. The term double decomposition is more specifically used when at least one of the substances does not dissolve in the solvent, as the ligand or ion exchange takes place in the solid state of the reactant. For example:
AX(aq) + BY(s) → AY(aq) + BX(s).
Types of reactions
Counterion exchange
Salt metathesis is a common technique for exchanging counterions. The choice of reactants is guided by a solubility chart or lattice energy. HSAB theory can also be used to predict the products of a metathesis reaction.
Salt metathesis is often employed to obtain salts that are soluble in organic solvents. Illustrative is the conversion of sodium perrhenate to the tetrabutylammonium salt:
NaReO4 + N(C4H9)4Cl → N(C4H9)4[ReO4] + NaCl
The tetrabutylammonium salt precipitates from the aqueous solution. It is soluble in dichloromethane.
Salt metathesis can be conducted in nonaqueous solution, illustrated by the conversion of ferrocenium tetrafluoroborate to a more lipophilic salt containing the tetrakis(pentafluorophenyl)borate anion:
[Fe(C5H5)2]BF4 + NaB(C6F5)4 → [Fe(C5H5)2]B(C6F5)4 + NaBF4
When the reaction is conducted in dichloromethane, the salt NaBF4 precipitates and the B(C6F5)4- salt remains in solution.
Metathesis reactions can occur between two inorganic salts when one product is insoluble in water. For example, the precipitation of silver chloride from a mixture of silver nitrate and cobalt hexammine chloride delivers the nitrate salt of the cobalt complex:
3 + [Co(NH3)6]Cl3 → 3 AgCl + [Co(NH3)6](NO3)3
The reactants need not be highly soluble for metathesis reactions to take place. For example barium thiocyanate forms when boiling a slurry of copper(I) thiocyanate and barium hydroxide in water:
+ 2 → + 2CuOH
Alkylation
Metal complexes are alkylated via salt metathesis reactions. Illustrative is the methylation of titanocene dichloride to give the Petasis reagent:
(C5H5)2TiCl2 + 2 ClMgCH3 → (C5H5)2Ti(CH3)2 + 2 MgCl2
The salt product typically precipitates from the reaction solvent.
Neutralization reaction
A neutralization reaction is a type of double replacement reaction. A neutralization reaction occurs when an acid reacts with an equal amount of a base. This reaction usually produces a salt. One example, hydrochloric acid reacts with disodium iron tetracarbonyl to produce the iron dihydride:
Reaction between an acid and a carbonate or bicarbonate salt yields carbonic acid, which spontaneously decomposes into carbon dioxide and water. The release of carbon dioxide gas from the reaction mixture drives the reaction to completion. For example, a common, science-fair "volcano" reaction involves the reaction of hydrochloric acid with sodium carbonate:
Salt-free metathesis reaction
In contrast to salt metathesis reactions, which are driven by the precipitation of solid salts, are salt-free reductions, which are driven by formation of silyl halides, Salt-free metathesis reactions proceed homogeneously.
See also
Single displacement reaction
References
Chemical reactions
Inorganic reactions | Salt metathesis reaction | Chemistry | 1,170 |
23,977,916 | https://en.wikipedia.org/wiki/Trichotomine | Trichotomine is a bright blue pigment found in the berries of the plant Clerodendrum trichotomum, which is native to China and Japan. It has a novel chromophore structure which differs from previously studied plant pigments.
References
Biological pigments | Trichotomine | Biology | 57 |
2,063,365 | https://en.wikipedia.org/wiki/Fish%20reproduction | Fish reproductive organs include testes and ovaries. In most species, gonads are paired organs of similar size, which can be partially or totally fused. There may also be a range of secondary organs that increase reproductive fitness. The genital papilla is a small, fleshy tube behind the anus in some fishes, from which the sperm or eggs are released; the sex of a fish can often be determined by the shape of its papilla.
Anatomy
Testes
Most male fish have two testes of similar size. In the case of sharks, the testes on the right side is usually larger. The primitive jawless fish have only a single testis, located in the midline of the body, although even this forms from the fusion of paired structures in the embryo.
Under a tough membranous shell, the tunica albuginea, the testis of some teleost fish, contains very fine coiled tubes called seminiferous tubules. The tubules are lined with a layer of cells (germ cells) that from puberty into old age, develop into sperm cells (also known as spermatozoa or male gametes). The developing sperm travel through the seminiferous tubules to the rete testis located in the mediastinum testis, to the efferent ducts, and then to the epididymis where newly created sperm cells mature (see spermatogenesis). The sperm move into the vas deferens, and are eventually expelled through the urethra and out of the urethral orifice through muscular contractions.
However, most fish do not possess seminiferous tubules. Instead, the sperm are produced in spherical structures called sperm ampullae. These are seasonal structures, releasing their contents during the breeding season, and then being reabsorbed by the body. Before the next breeding season, new sperm ampullae begin to form and ripen. The ampullae are otherwise essentially identical to the seminiferous tubules in higher vertebrates, including the same range of cell types.
In terms of spermatogonia distribution, the structure of teleosts testes has two types: in the most common, spermatogonia occur all along the seminiferous tubules, while in Atherinomorph fish they are confined to the distal portion of these structures. Fish can present cystic or semi-cystic spermatogenesis in relation to the release phase of germ cells in cysts to the seminiferous tubules lumen.
Ovaries
Many of the features found in ovaries are common to all vertebrates, including the presence of follicular cells and tunica albuginea There may be hundreds or even millions of fertile eggs present in the ovary of a fish at any given time. Fresh eggs may be developing from the germinal epithelium throughout life. Corpora lutea are found only in mammals, and in some elasmobranch fish; in other species, the remnants of the follicle are quickly resorbed by the ovary. The ovary of teleosts is often contains a hollow, lymph-filled space which opens into the oviduct, and into which the eggs are shed. Most normal female fish have two ovaries. In some elasmobranchs, only the right ovary develops fully. In the primitive jawless fish, and some teleosts, there is only one ovary, formed by the fusion of the paired organs in the embryo.
Fish ovaries may be of three types: gymnovarian, secondary gymnovarian or cystovarian. In the first type, the oocytes are released directly into the coelomic cavity and then enter the ostium, then through the oviduct and are eliminated. Secondary gymnovarian ovaries shed ova into the coelom from which they go directly into the oviduct. In the third type, the oocytes are conveyed to the exterior through the oviduct. Gymnovaries are the primitive condition found in lungfish, sturgeon, and bowfin. Cystovaries characterize most teleosts, where the ovary lumen has continuity with the oviduct. Secondary gymnovaries are found in salmonids and a few other teleosts.
Eggs
The eggs of fish and amphibians are jellylike. Cartilagenous fish (sharks, skates, rays, chimaeras) eggs are fertilized internally and exhibit a wide variety of both internal and external embryonic development. Most fish species spawn eggs that are fertilized externally, typically with the male inseminating the eggs after the female lays them. These eggs do not have a shell and would dry out in the air. Even air-breathing amphibians lay their eggs in water, or in protective foam as with the Coast foam-nest treefrog, Chiromantis xerampelina.
Intromittent organs
Male cartilaginous fishes (sharks and rays), as well as the males of some live-bearing ray finned fishes, have fins that have been modified to function as intromittent organs, reproductive appendages which allow internal fertilization. In ray finned fish they are called gonopodiums or andropodiums, and in cartilaginous fish they are called claspers.
Gonopodia are found on the males of some species in the Anablepidae and Poeciliidae families. They are anal fins that have been modified to function as movable intromittent organs and are used to impregnate females with milt during mating. The third, fourth and fifth rays of the male's anal fin are formed into a tube-like structure in which the sperm of the fish is ejected. When ready for mating, the gonopodium becomes erect and points forward towards the female. The male shortly inserts the organ into the sex opening of the female, with hook-like adaptations that allow the fish to grip onto the female to ensure impregnation. If a female remains stationary and her partner contacts her vent with his gonopodium, she is fertilized. The sperm is preserved in the female's oviduct. This allows females to fertilize themselves at any time without further assistance from males. In some species, the gonopodium may be half the total body length. Occasionally the fin is too long to be used, as in the "lyretail" breeds of Xiphophorus helleri. Hormone treated females may develop gonopodia. These are useless for breeding.
Similar organs with similar characteristics are found in other fishes, for example the andropodium in the Hemirhamphodon or in the Goodeidae.
Claspers are found on the males of cartilaginous fishes. They are the posterior part of the pelvic fins that have also been modified to function as intromittent organs, and are used to channel semen into the female's cloaca during copulation. The act of mating in sharks usually includes raising one of the claspers to allow water into a siphon through a specific orifice. The clasper is then inserted into the cloaca, where it opens like an umbrella to anchor its position. The siphon then begins to contract expelling water and sperm.
Physiology
Oogonia development in teleosts fish varies according to the group, and the determination of oogenesis dynamics allows the understanding of maturation and fertilisation processes. Changes in the nucleus, ooplasm, and the surrounding layers characterize the oocyte maturation process.
Postovulatory follicles are structures formed after oocyte release; they do not have endocrine function, present a wide irregular lumen, and are rapidly reabsorbed in a process involving the apoptosis of follicular cells. A degenerative process called follicular atresia reabsorbs vitellogenic oocytes not spawned. This process can also occur, but less frequently, in oocytes in other development stages.
Some fish are hermaphrodites, having both testes and ovaries either at different phases in their life cycle or, as in hamlets, have them simultaneously.
Reproductive strategies
In fish, fertilisation of eggs can be either external or internal. In many species of fish, fins have been modified to allow internal fertilisation. Similarly, development of the embryo can be external or internal, although some species show a change between the two at various stages of embryo development. Thierry Lodé described reproductive strategies in terms of the development of the zygote and the interrelationship with the parents; there are five classifications – ovuliparity, oviparity, ovo-viviparity, histotrophic viviparity and hemotrophic viviparity.
Ovuliparity
Ovuliparity means the female lays unfertilised eggs (ova), which must then be externally fertilised. Examples of ovuliparous fish include salmon, goldfish, cichlids, tuna and eels. In the majority of these species, fertilisation takes place outside the mother's body, with the male and female fish shedding their gametes into the surrounding water.
Oviparity
Oviparity is where fertilisation occurs internally and so the female sheds zygotes (or newly developing embryos) into the water, often with important outer tissues added. Over 97% of all known fish are oviparous (needs confirmation, since the ovuliparity is a new term which may be confused with oviparity. If ovuliparity is used, most of the fishes have ovuliparity breeding strategy). In oviparous fish, internal fertilisation requires the male to use some sort of intromittent organ to deliver sperm into the genital opening of the female. Examples include the oviparous sharks, such as the horn shark, and oviparous rays, such as skates. In these cases, the male is equipped with a pair of modified pelvic fins known as claspers.
Marine fish can produce high numbers of eggs which are often released into the open water column. The eggs have an average diameter of . The eggs are generally surrounded by the extraembryonic membranes but do not develop a shell, hard or soft, around these membranes. Some fish have thick, leathery coats, especially if they must withstand physical force or desiccation. These type of eggs can also be very small and fragile.
The newly hatched young of oviparous fish are called larvae. They are usually poorly formed, carry a large yolk sac (for nourishment) and are very different in appearance from juvenile and adult specimens. The larval period in oviparous fish is relatively short (usually only several weeks), and larvae rapidly grow and change appearance and structure (a process termed metamorphosis) to become juveniles. During this transition larvae must switch from their yolk sac to feeding on zooplankton prey, a process which depends on typically inadequate zooplankton density, starving many larvae.
Ovoviviparity
In ovoviviparous fish the eggs develop inside the mother's body after internal fertilisation but receive little or no nourishment directly from the mother, depending instead on a food reserve inside the egg, the yolk. Each embryo develops in its own egg. Familiar examples of ovoviviparous fish include guppies, angel sharks, and coelacanths.
Viviparity
There are two types of viviparity, differentiated by how the offspring gain their nutrients.
Histotrophic (tissue eating) viviparity means embryos develop in the female's oviducts but obtain nutrients by consuming other tissues, such as ova (oophagy) or zygotes. This has been observed primarily among sharks such as the shortfin mako and porbeagle, but is known for a few bony fish as well such as the halfbeak Nomorhamphus ebrardtii. An unusual mode of vivipary is adelphophagy or intrauterine cannibalism, in which the largest embryos eat weaker, smaller unborn siblings. This is most commonly found among sharks such as the grey nurse shark, but has also been reported for Nomorhamphus ebrardtii.
Hemotrophic (blood eating) viviparity means embryos develop in the female's (or male's) oviduct and nutrients are provided directly by the parent, typically via a structure similar to, or analogous to the placenta seen in mammals. Examples of hemotrophic fish include the surfperches, splitfins, lemon shark, seahorses and pipefish.
Aquarists commonly refer to ovoviviparous and viviparous fish as livebearers.
Hermaphroditism
Hermaphroditism occurs when a given individual in a species possesses both male and female reproductive organs, or can alternate between possessing first one, and then the other. Hermaphroditism is common in invertebrates but rare in vertebrates. It can be contrasted with gonochorism, where each individual in a species is either male or female, and remains that way throughout their lives. Most fish are gonochorists, but hermaphroditism is known to occur in 14 families of teleost fishes.
Usually hermaphrodites are sequential, meaning they can switch sex, usually from female to male (protogyny). This can happen if a dominant male is removed from a group of females. The largest female in the harem can switch sex over a few days and replace the dominant male. This is found amongst coral reef fishes such as groupers, parrotfishes and wrasses. It is less common for a male to switch to a female (protandry). As an example, most wrasses are protogynous hermaphrodites within a haremic mating system. Hermaphroditism allows for complex mating systems. Wrasses exhibit three different mating systems: polygynous, lek-like, and promiscuous mating systems. Group spawning and pair spawning occur within mating systems. The type of spawning that occurs depends on male body size. Labroids typically exhibit broadcast spawning, releasing high amounts of planktonic eggs, which are broadcast by tidal currents; adult wrasses have no interaction with offspring. Wrasse of a particular subgroup of the family Labridae, Labrini, do not exhibit broadcast spawning.
Less commonly hermaphrodites can be synchronous, meaning they simultaneously possess both ovaries and testicles and can function as either sex at any one time. Black hamlets "take turns releasing sperm and eggs during spawning. Because such egg trading is advantageous to both individuals, hamlets are typically monogamous for short periods of time–an unusual situation in fishes." The sex of many fishes is not fixed, but can change with physical and social changes to the environment where the fish lives.
Particularly among fishes, hermaphroditism can pay off in situations where one sex is more likely to survive and reproduce, perhaps because it is larger. Anemone fishes are sequential hermaphrodites which are born as males, and become females only when they are mature. Anemone fishes live together monogamously in an anemone, protected by the anemone stings. The males do not have to compete with other males, and female anemone fish are typically larger. When a female dies a juvenile (male) anemone fish moves in, and "the resident male then turns into a female and reproductive advantages of the large female–small male combination continue". In other fishes sex changes are reversible. For example, if some gobies are grouped by sex (male or female), some will switch sex.
The mangrove rivulus Kryptolebias marmoratus produces both eggs and sperm by meiosis and routinely reproduces by self-fertilization. Each individual hermaphrodite normally fertilizes itself when an egg and sperm that it has produced by an internal organ unite inside the fish's body. In nature, this mode of reproduction can yield highly homozygous lines composed of individuals so genetically uniform as to be, in effect, identical to one another. The capacity for selfing in these fishes has apparently persisted for at least several hundred thousand years.
Although inbreeding, especially in the extreme form of self-fertilization, is ordinarily regarded as detrimental because it leads to expression of deleterious recessive alleles, self-fertilization does provide the benefit of fertilization assurance (reproductive assurance) at each generation.
Sexual parasitism
Sexual parasitism is a mode of sexual reproduction, unique to anglerfish, in which the males of a species are much smaller than the females, and rely on the females for food and protection from predators. The males give nothing back except the sperm which the females need in order to produce the next generation.
Some anglerfish, like those of the deep sea ceratioid group, employ this unusual mating method. Because individuals are very thinly distributed, encounters are also very rare. Therefore, finding a mate is problematic. When scientists first started capturing ceratioid anglerfish, they noticed that all the specimens were female. These individuals were a few centimetres in size and almost all of them had what appeared to be parasites attached to them. It turned out that these "parasites" were highly reduced male ceratioid anglerfish. This indicates the anglerfish use a polyandrous mating system.
The methods by which the anglerfish locate mates are variable. Some species have minute eyes unfit for identifying females, while others have underdeveloped nostrils, making it unlikely that they effectively find females using olfaction. When a male finds a female, he bites into her skin, and releases an enzyme that digests the skin of his mouth and her body, fusing the pair down to the blood-vessel level. The male becomes dependent on the female host for survival by receiving nutrients via their now-shared circulatory system, and provides sperm to the female in return. After fusing, males increase in volume and become much larger relative to free-living males of the species. They live and remain reproductively functional as long as the female stays alive, and can take part in multiple spawnings. This extreme sexual dimorphism ensures that when the female is ready to spawn she has a mate immediately available. Multiple males can be incorporated into a single individual female with up to eight males in some species, though some taxa appear to have a one male per female rule. In addition to the physiological adaptations, the immune system is altered to allow the conjoining.
Another form of sexual parasitism is hybridogenesis, where the reproductive effort of another species is exploited. One such example is a species in the genus Poeciliopsis. This fish consist only of females that mates with males from a closely related species. All the paternal chromosomes are discarded during the production of eggs. The females get to pass their maternal genome to the next generation, unlike the males of the other species.
One explanation for the evolution of sexual parasitism is that the relative low density of females in deep-sea environments leaves little opportunity for mate choice among anglerfish. Females remain large to accommodate fecundity, as is evidenced by their large ovaries and eggs. Males would be expected to shrink to reduce metabolic costs in resource-poor environments and would develop highly specialized female-finding abilities. If a male manages to find a female parasitic attachment, then it is ultimately more likely to improve lifetime fitness relative to free living, particularly when the prospect of finding future mates is poor. An additional advantage to parasitism is that the male's sperm can be used in multiple fertilizations, as he stays always available to the female for mating. Higher densities of male-female encounters might correlate with species that demonstrate facultative parasitism or simply use a more traditional temporary contact mating.
Parthenogenesis
Parthenogenesis is a form of asexual reproduction in which growth and development of embryos occur without fertilization. In animals, parthenogenesis means development of an embryo from an unfertilized egg cell. The first all-female (unisexual) reproduction in vertebrates was described in the Amazon molly in 1932. Since then at least 50 species of unisexual vertebrate have been described, including at least 20 fish, 25 lizards, a single snake species, frogs, and salamanders. As with all types of asexual reproduction, there are both costs (low genetic diversity and therefore susceptibility to adverse mutations that might occur) and benefits (reproduction without the need for a male) associated with parthenogenesis.
Parthenogenesis in sharks has been confirmed in the bonnethead and zebra shark. Other, usually sexual species, may occasionally reproduce parthenogenetically, and the hammerhead and blacktip sharks are recent additions to the known list of facultative parthenogenetic vertebrates.
A special case of parthenogenesis is gynogenesis. In this type of reproduction, offspring are produced by the same mechanism as in parthenogenesis, however, the egg is stimulated to develop simply by the presence of sperm - the sperm cells do not contribute any genetic material to the offspring. Because gynogenetic species are all female, activation of their eggs requires mating with males of a closely related species for the needed stimulus. The Amazon molly, (pictured), reproduces by gynogenesis.
Others
The elkhorn sculpin (Alcichthys elongatus) is a marine teleost with a unique reproductive mode called “internal gametic association”. Sperm are introduced into the ovary by copulation and then enter the micropylar canal of ovulated eggs in the ovarian cavity. However, actual sperm-egg fusion does not occur until the eggs have been released into sea water.
Inbreeding
Inbreeding depression
The effect of inbreeding on reproductive behavior was studied in the poeciliid fish Heterandria formosa. One generation of full-sib mating was found to decrease reproductive performance and likely reproductive success of male progeny. Other traits that displayed inbreeding depression were offspring viability and maturation time of both males and females.
Exposure of zebra fish to a chemical environmental agent, analogous to that caused by anthropogenic pollution, amplified the effects of inbreeding on key reproductive traits. Embryo viability was significantly reduced in inbred exposed fish and there was a tendency for inbred males to sire fewer offspring.
The behaviors of juvenile Coho salmon with either low or medium inbreeding were compared in paired contests. Fish with low inbreeding showed almost twice the aggressive pursuit in defending territory than fish with medium inbreeding, and furthermore had a higher specific growth rate. A significant effect of inbreeding depression on juvenile survival was also found, but only in high-density competitive environments, suggesting that intra-specific competition can magnify the deleterious effects of inbreeding.
Inbreeding avoidance
Inbreeding ordinarily has negative fitness consequences (inbreeding depression), and as a result species have evolved mechanisms to avoid inbreeding. Numerous inbreeding avoidance mechanisms operating prior to mating have been described. However, inbreeding avoidance mechanisms that operate subsequent to copulation are less well known. In guppies, a post-copulatory mechanism of inbreeding avoidance occurs based on competition between sperm of rival males for achieving fertilisation. In competitions between sperm from an unrelated male and from a full sibling male, a significant bias in paternity towards the unrelated male was observed.
Inbreeding depression is considered to be due largely to the expression of homozygous deleterious recessive mutations. Outcrossing between unrelated individuals results in the beneficial masking of deleterious recessive mutations in progeny.
Sexual strategies
Spawning strategies
Spawning grounds
Examples
Goldfish
Goldfish, like all cyprinids, are egg-layers. They usually start breeding after a significant temperature change, often in spring. Males chase females, prompting them to release their eggs by bumping and nudging them. As the female goldfish spawns her eggs, the male goldfish stays close behind fertilizing them. Their eggs are adhesive and attach to aquatic vegetation. The eggs hatch within 48 to 72 hours. Within a week or so, the fry begins to assume its final shape, although a year may pass before they develop a mature goldfish colour; until then they are a metallic brown like their wild ancestors. In their first weeks of life, the fry grow quickly—an adaptation born of the high risk of getting devoured by the adult goldfish.
Carp
A member of the Cyprinidae, carp spawn in times between April and August, largely dependent upon the climate and conditions they live in. Oxygen levels of the water, availability of food, size of each fish, age, number of times the fish has spawned before and water temperature are all factors known to effect when and how many eggs each carp will spawn at any one time.
Siamese fighting fish
Prior to spawning, male Siamese fighting fish build bubble nests at the surface of the water. When a male becomes interested in a female, he will flare his gills, twist his body, and spread his fins. The female darkens in colour and curves her body back and forth. The act of spawning takes place in a "nuptial embrace" where the male wraps his body around the female, each embrace resulting in the release of 10-40 eggs until the female is exhausted of eggs. The male, from his side, releases milt into the water and fertilization takes place externally. During and after spawning, the male uses his mouth to retrieve sinking eggs and deposit them in the bubble nest. Once the female has released all of her eggs, she is chased away from the male's territory, as it is likely that she'll eat the eggs due to hunger. The eggs remain in the male's care. He keeps them in the bubble nest, making sure none fall to the bottom and repairing the nest as needed. Incubation lasts for 24–36 hours, and the newly hatched larvae remain in the nest for the next 2–3 days, until their yolk sacs are fully absorbed. Afterwards the fry leave the nest and the free-swimming stage begins.
See also
Evolution of sexual reproduction
References
Further references
Agarwal NK (2008) Fish Reproduction APH Publishing. .
Babin PJ, Cerdà J and Lubzens E (Eds) (2007) The Fish Oocyte: From Basic Studies to Biotechnological Applications Springer. .
Bone Q and Moore R (2008) Biology of Fishes Chapter 8: Reproduction and Life Histories, pp. 217–255. Taylor & Francis. .
Cabrita E, Robles V and Paz Herraez P (Eds) (2008) Methods in Reproductive Aquaculture: Marine and Freshwater Species CRC Press. .
Cole, Kathleen Sabina (Ed) (2010) Reproduction and Sexuality in Marine Fishes: Patterns and Processes University of California Press. .
Hoar WS, Randall DJ and Donaldson EM (Eds) (1983) Fish Physiology: Volume 9: Reproduction Part A: Endocrine tissues and hormones. Academic Press. .
Hoar WS, Randall DJ and Donaldson EM (Eds) (1983) Fish Physiology: Volume 9: Reproduction Part B: Behavior and fertility control. Academic Press. .
Jakobsen T, Fogarty MJ, Megrey BA and Moksness E (Eds) (2009) Fish Reproductive Biology: Implications for Assessment and Management John Wiley & Sons. .
Melamed P and Sherwood N (Eds) (2005) Hormones and Their Receptors in Fish Reproduction World Scientific. .
Potts GW, Wootton RJ and Wootton RJ (Eds) (1984) Fish reproduction: strategies and tactics Academic Press. .
Rocha MJ, Arukwe A and Kapoor BG (Eds) (2008) Fish Reproduction CRC Press. .
External links
Aquatic ecology
Biological oceanography
Ichthyology | Fish reproduction | Biology | 5,959 |
2,268,024 | https://en.wikipedia.org/wiki/Smart%20message | Smart message is a communications protocol designed by Intel and Nokia by which various software upgrades—including ringtones—can be made "over the air", through the wireless connection.
Smart Messaging is basically a special type of short message, with its own prefixes and codes, that makes it possible for the phone to recognize the message as, instead of a text message to the attention of the user, a "functional" message that should be treated as: a ringtone, a screen logo, in some cases even a business card or group graphics that can be used to identify who is calling.
Mobile telecommunication services | Smart message | Technology | 123 |
59,186,680 | https://en.wikipedia.org/wiki/NGC%207606 | NGC 7606 is a spiral galaxy located in the constellation Aquarius. It is located at a distance of circa 100 million light years from Earth, which, given its apparent dimensions, means that NGC 7606 is about 165,000 light years across. It was discovered by William Herschel on September 28, 1785. The galaxy is included in the Herschel 400 Catalogue. It lies 45 arcminutes northeast from psi2 Aquarii. It can be seen with a 4 inch telescope but its visibility is greatly affected by light pollution.
Characteristics
NGC 7606 is a spiral galaxy seen on inclination. It has a bright nucleus surrounded by a prominent bulge, which is seen elliptical due to the inclination. No bar has been observed. A ring with an apparent diameter of 0.85 arcminutes has been detected at the central part of the galaxy. The galaxy features two main arms, that can be traced for nearly 360°, and several arm fragments. The arms are smooth and rather tight, although not as tightly wound as the ones of NGC 488. Few bright spots have been observed in the arms. The galaxy is found to host a supermassive black hole, whose mass based on bulge velocity dispersion σ is estimated to be 15-22 million . NGC 7606 is an isolated galaxy.
Supernovae
Two supernovae have been observed in NGC 7606:
SN 1965M (type unknown, mag. 16) was discovered by Paul Wild on 4 October 1965.
SN 1987N (type Ia, mag. 13.8) was discovered by Robert Evans on 14 December 1987.
Gallery
References
External links
Unbarred spiral galaxies
Aquarius (constellation)
7606
71047
Astronomical objects discovered in 1785
Discoveries by William Herschel | NGC 7606 | Astronomy | 354 |
84,553 | https://en.wikipedia.org/wiki/Lotus%20Symphony%20%28MS-DOS%29 | Lotus Symphony was an integrated software package for creating and editing text, spreadsheets, charts and other documents on the MS-DOS operating systems. It was released by Lotus Development as a follow-on to its popular spreadsheet program, Lotus 1-2-3, and was produced from 1984 to 1992. Lotus Jazz on the Apple Macintosh was a sibling product.
IBM revived the name Lotus Symphony in 2007 for a new office suite based on OpenOffice.org, but the two programs are otherwise unrelated.
History
Lotus 1-2-3 had originally been billed as an integrated product with spreadsheet, database and graphing functions (hence the name "1-2-3"). Other products described as "integrated", such as Ashton-Tate's Framework and AppleWorks, from Apple Computer, normally included word processor functionality. Symphony was Lotus' response.
Overview
Symphony for MS-DOS is a program that loads entirely into memory on startup, and can run as an MS-DOS task on versions of Microsoft Windows (3.x/95/98/ME). Using the Command Prompt, and a .pif file, Symphony can also be used on Windows XP and its successors.
Using ALT+F10 the user can alternate among the five "environments" of the program, each a rendering of the same underlying data. The environments are:
SHEET, a spreadsheet program very similar to 1-2-3
DOC, a word processor
GRAPH, a graphical charting program
FORM, a table-based database management system
COMM, a communications program
Several "add-in applications" can be "attached" and activated, extending Symphony's capabilities, including a powerful macro manager, a document outliner, a spell-checker, statistics, various communications configurations, and a tutorial, which demonstrates Symphony usage by running macros. The program allows the screen to be split into panes and distinct Windows, showing different views of the underlying data simultaneously, each of which can display any of the five environments. The user is then able to see that changes made in one environment are reflected in others simultaneously, perhaps the package's most interesting feature.
All the data that Symphony handles is kept in spreadsheet-like cells. The other environments—word processing, database, communications, graphics—in essence only change the display format and focus of that data (including available menus, special keys, and functionality), which can be saved and retrieved as .WR1 files.
Symphony was designed to work completely in the standard 640k of conventional memory, supplemented by any expanded memory. Similar and competitive packages included SmartWare, Microsoft Works, Context MBA, Framework, Enable and Ability Office.
Symphony's spreadsheet engine was similar to, but not the same as the one used in Lotus 1-2-3, once the most popular of its kind. Additional enhancements included:
The ability to create unique application looking spreadsheets using customizable macro driven menus and display Windows, the result being menu driven applications that, to the user, resembled little of their original spreadsheet heritage.
A rearranged worksheet menu, placing COPY as the first menu item, then the other most frequently used items after that.
Additional @ formula functions building on 1-2-3's spreadsheet only formulas.
Multiple menu systems, retaining 1-2-3's uniquely identified first-character menu items.
The addition of the TAB key to anchor ranges, instead of just using the period key.
The ability to copy "to a location" and end up at that location, instead of at the copy "from location."
Symphony put the power of the spreadsheet at the user's fingertips and used all of the available keys on IBM's 84-key PC keyboard. In this way, the user could use both hands to select menu functions, navigate menus and spreadsheets, as well as, all other Symphony functions by touch. The introduction of the US IBM PC 104-key keyboard and later ergonomic keyboards diluted this advantage.
Compared to other word processors of the day such as Micropro WordStar 3.3, WordPerfect 4.2, and Microsoft Word 2.0, Symphony's word processing environment was simple, but effective and uncomplicated.
Compared to other database programs of the day—Ashton-Tate's dBase III, MDBS Knowledgeman, Borland Paradox 2.0 and Borland Reflex 1.0—Symphony's FORM environment was not as robust, lacking the analytical abilities of Reflex and the pseudo relational power of dBase III. However, it was integrated directly into the spreadsheet and included the ability to "generate" a FORM from spreadsheet fields. The generator would automatically create the database input form, all the underlying spreadsheet architecture, with range names and query fields, turning a simple spreadsheet into an instant database in seconds. 3.0-Symphony extended earlier enhancements with additional add-ons, most notably:
WYSIWYG (what-you-see-is-what-you-get) GUI (graphical user interface) and the addition of mouse support
BASE, the ability to integrate with any dBase IV file, no matter its size.
ExtraK add-on, extending memory capabilities for spreadsheet larger than 4MB.
Like its predecessor Lotus 1-2-3, Symphony contained a reasonably powerful programming language referred to as its "Symphony Command Language (or SCL) ", which could be saved either within a spreadsheet or separately in "libraries" in the form of macros: lists of menu operations, data, and other macro keywords. (One is "menucall," which allows users to call their own menus, embedded into spreadsheets, which behave just like Symphony's own.) Symphony's "learn" mode for macro recording automated this process, helping the end-user to quickly write macros to duplicate repetitive tasks or to go beyond that, without the need to understand computer programming. One of the most significant features of Symphony was the integration of the various modules using this command language. In its day, it was one of the few programs that would be able to log onto a stock market source, select data using dynamic or pre-assigned criteria, place that data into a spreadsheet, perform calculations, then chart the data and print out the results. All of this could take place unattended on a preset schedule.
See also
Lotus Multi-Byte Character Set (LMBCS)
References
External links
Dinosaur Sightings: Lotus Symphony 3.0 (for DOS) by Greg Shultz, TechRepublic
1984 software
DOS software
Symphony
Office suites
Spreadsheet software | Lotus Symphony (MS-DOS) | Mathematics | 1,380 |
251,434 | https://en.wikipedia.org/wiki/Pie%20rule | The pie rule, sometimes referred to as the swap rule, is a rule used to balance abstract strategy games where a first-move advantage has been demonstrated. After the first move is made in a game that uses the pie rule, the second player must select one of two options:
Letting the move stand. The second player remains the second player and moves immediately.
Switching places. The second player becomes the first-moving player with the move already done by the opponent, and the opponent plays the first move of their new color.
Depending on the game, there may be two ways to implement switching places.
Switching colors means that the players exchange pieces. The player who made the first move becomes the second player and makes the second move on the board. This is demonstrated in the chess diagrams shown here.
Switching the first piece can occur in games where the board starts empty and the first move consists of placing one piece. Suppose the colors are white versus black, and black places the first piece. This piece is replaced by a white piece in the corresponding location for white, and the black piece is returned to black's supply. In a game such as Hex or TwixT, the corresponding location is at a cell "reflected" across the nearest (or either) diagonal. In games such as Y, where the board is not directional, the white stone replaces the black stone in the same cell. Players keep their respective color pieces, and play continues with black making the next move. This is effectively the same as switching colors.
The use of pie rule was first reported in 1909 for a game in the Mancala family. Among modern games, Hex uses this rule. TwixT in tournament play uses a swap rule. In Meridians, the first player places 2 stones on the board before the second player chooses the color. The rule can be applied to other games which are otherwise solved for one player, such as Gomoku or Tablut.
The rule gets its name from the divide and choose method of ensuring fairness in when dividing a pie between two people: one person cuts the pie in half, then the other person chooses which half to eat. The person cutting the pie, knowing that the other person will choose the larger piece, will make as equal a division as possible.
This rule acts as a normalization factor in games where there may be a first-move advantage. In games that cannot end in a draw, such as Hex, the pie rule theoretically gives the second player a win (since one of the players must have a winning strategy after the first move, and the second player can choose to be this player), but the practical result is that the first player will choose a move neither too strong nor too weak, and the second player will have to decide whether switching places is worth the first-move advantage.
Use for determining komi in Go
In Go, one player can choose the amount of komi. (These are the points given to the second player as compensation for not going first.) The other player then decides whether to accept that or switch colors with the other player. This leads players to choose fair komi amounts because if they choose a komi that is too advantageous, the other player can just choose to play White and take advantage of that high komi.
References
Board game terminology
Rules of thumb
Fair division | Pie rule | Mathematics | 677 |
3,720,055 | https://en.wikipedia.org/wiki/Road%20junction | A junction is where two or more roads meet.
History
Roads began as a means of linking locations of interest: towns, forts and geographic features such as river fords. Where roads met outside of an existing settlement, these junctions often led to a new settlement. Scotch Corner is an example of such a location.
In the United Kingdom and other countries, the practice of giving names to junctions emerged, to help travellers find their way. Junctions took the name of a prominent nearby business or a point of interest.
As of the road networks increased in density and traffic flows followed suit, managing the flow of traffic across the junction became of increasing importance, to minimize delays and improve safety. The first innovation was to add traffic control devices, such as stop signs and traffic lights that regulated traffic flow. Next came lane controls that limited what each lane of traffic was allowed to do while crossing. Turns across oncoming traffic might be prohibited, or allowed only when oncoming and crossing traffic was stopped.
This was followed by specialized junction designs that incorporated information about traffic volumes, speeds, driver intent and many other factors.
Types
The most basic distinction among junction types is whether or not the roads cross at the same or different elevations. More expensive, grade-separated interchanges generally offer higher throughput at higher cost. Single-grade intersections are lower cost and lower throughput. Each main type comes in many variants.
Interchange
At interchanges, roads pass above or below each other, using grade separation and slip roads. The terms motorway junction and highway interchange typically refer to this layout. They can be further subdivided into those with and without signal controls.
Signalized (traffic-light controlled) interchanges include such "diamond" designs as the diverging diamond, Michigan urban diamond, three-level diamond, and tight diamond. Others include center-turn overpass, contraflow left, single loop, and single-point urban overpass.
Non-signalized designs include the cloverleaf, contraflow left, dogbone (restricted dumbbell), double crossover merging, dumbbell (grade-separated bowtie), echelon, free-flow interchange, partial cloverleaf, raindrop, single and double roundabouts (grade-separated roundabout), single-point urban, stack, and windmill.
(literally "autobahn cross"), short form , and abbreviated as AK, is a four-way interchange on the German autobahn network. (literally "autobahn triangle"), short form , and abbreviated as AD, is a three-way interchange on the German autobahn network.
Intersection
At intersections, roads cross at-grade. They also can be further subdivided into those with and without signal controls.
Signalized designs include advanced stop line, bowtie, box junction, continuous-flow intersection, continuous Green-T, double-wide, hook turn, jughandle, median u-turn, Michigan left, paired, quadrant, seagulls, slip lane, split, staggered, superstreet, Texas T, Texas U-turn and turnarounds.
Non-signalized designs include unsignalized variations on continuous-flow 3 and 4-leg, median u-turn and superstreet, along with Maryland T/J, roundabout and traffic circle.
Safety
In the EU it is estimated that around 5,000 out of 26,100 people who are killed in car crashes are killed in a junction collision, in 2015, while it was around 8,000 in 2006. During the 2006–2015 decade, this means around 20% of road fatalities occur at junctions.
By kind of users junctions fatalities are car users, 34%; pedestrians, 23%; motorcycle, 21%; pedal-cycle 12%; and other road users, the remaining.
Causes of fatalities
It has been considered that several causes might lead to fatalities; for instance:
Observation missed – the largest category, encompassing all factors that cause a driver or rider to not notice something:
Physical factors:
Temporary obstruction to view
Permanent obstruction to view
Permanent sight obstruction
Human factors:
Faulty diagnosis – a misunderstanding of another road user's actions or the road conditions
Distraction
Inadequate plan – the details of the situation, as interpreted by the road user, are lacking in quantity and/or quality (including their correspondence to reality)
Inattention
Faulty diagnosis (not leading to observation missed)
Information failure – the road user judged the situation incorrectly and made a decision based upon the incorrect judgement (e.g. thinking that another vehicle is moving when it is not, and thus colliding with it)
Communication failure – a miscommunication between road users
Inadequate plan (not leading to observation missed)
Insufficient knowledge
Protected intersections
Bicycles
A number of features make this protected intersection much safer. A corner refuge island, a setback crossing of the pedestrians and cyclists, generally between 1.5–7 metres of setback, a forward stop bar, which allows cyclists to stop for a traffic light well ahead of motor traffic who must stop behind the crosswalk. Separate signal staging or at least an advance green for cyclists and pedestrians is used to give cyclists and pedestrians no conflicts or a head start over traffic. The design makes a right turn on red, and sometimes left on red depending on the geometry of the intersection in question, possible in many cases, often without stopping.
Cyclists ideally have a protected bike lane on the approach to the intersection, separated by a concrete median with splay kerbs if possible, and have a protected bike lane width of at least 2 metres if possible (one way). In the Netherlands, most one way cycle paths are at least 2.5 metres wide.
Bicycle traffic can be accommodated with the low grade bike lanes in the roadway or higher grade and much safer protected bicycle paths that are physically separated from the roadway.
In Manchester, UK, traffic engineers have designed a protected junction known as the Cycle-Optimised Signal (CYCLOPS) Junction. This design places a circulatory cycle track around the edge of the junction, with pedestrian crossing on the inside. This design allows for an all-red pedestrian / cyclist phase with reduced conflicts. Traffic signals are timed to allow cyclists to make a right turn (across oncoming traffic) in one turn). It also allows for diagonal crossings (pedestrian scramble) and reduces crossing distances for pedestrians.
Pedestrians
Intersections generally must manage pedestrian as well as vehicle traffic. Pedestrian aids include crosswalks, pedestrian-directed traffic signals ("walk light") and over/underpasses. Walk lights may be accompanied by audio signals to aid the visually impaired. Medians can offer pedestrian islands, allowing pedestrians to divide their crossings into a separate segment for each traffic direction, possibly with a separate signal for each.
See also
List of road junctions in the United Kingdom
Junction (traffic)
References
Transport infrastructure | Road junction | Physics | 1,372 |
71,384,016 | https://en.wikipedia.org/wiki/Leucocoprinus%20elaeidis | Leucocoprinus elaeidis (or elaidis) is a species of mushroom-producing fungus in the family Agaricaceae. In the local language, it is commonly known as elela.
Taxonomy
It was first described in 1927 by the Belgian mycologist Maurice Beeli who classified it as Lepiota elaeidis (or elaidis), whilst illustrations of the mushrooms were produced by Mme M. Goossens-Fontana.
In 1977 it was reclassified by the Belgian mycologist Paul Heinemann who classified it as Leucocoprinus elaeidis.
Description
Leucocoprinus elaeidis is a dapperling mushroom with thin white flesh and stem flesh that may stain yellow.
Cap: 7-12cm wide with thin 2mm thick flesh. The cap is a fluffy white and coated in white flakes or scales whilst the umbo or centre disc is sometimes tinged brown or yellowish. It starts bulbous and cylindrical before expanding to campanulate (bell shaped) and flattening further with age making the umbo more pronounced. There are slight striations at the cap edges. Gills: Free with a collar, crowded and white but yellowing when damaged. Stem: 7-9cm long and 8-12mm thick, expanding at the base to 15-20mm. The stem is hollow and easily detaches from the cap. White and smooth above the stem ring and scaly or flaky white below but staining yellow when touched or damaged. The movable stem ring is white and fluffy at the edges and is located towards the top of the cap (superior or apical). Spore print: White. Spores: Amygdaliform. 8.5-11 x 5.3-7.4 μm. Smell: Pleasant. Taste: Pleasant. When dry the mushroom develops an ochre colour whilst the gills discolour yellowish.
Habitat and distribution
L. elaeidis is scarcely recorded and little known. It grows on the ground and in grass near elaeis, coffee and eucalyptus trees and is sometimes found on rotten wood or compost.
The specimens studied by Beeli were found in groups in the grass at the foot of Elaeis oil palms in the Eala region of the Zaïre (now the Democratic Republic of the Congo). They were also found near lake Edward and lake Kivu to the North East of the country and have been observed in Mali and Senegal.
Similar species
The description and illustrations of L. elaeidis suggest that the species is similar to Leucocoprinus cretaceous which can present with a yellow coloured stem when the white coating is brushed off or Leucocoprinus cepistipes, which can bruise yellow when handled. The illustration and spore size more closely match L. cretaceus so this species may be synonymous with it.
References
Leucocoprinus
Taxa named by Paul Heinemann
Fungi described in 1927
Fungi of Africa
Taxa named by Maurice Beeli
Fungus species | Leucocoprinus elaeidis | Biology | 621 |
44,532,941 | https://en.wikipedia.org/wiki/Ringed%20topos | In mathematics, a ringed topos is a generalization of a ringed space; that is, the notion is obtained by replacing a "topological space" by a "topos". The notion of a ringed topos has applications to deformation theory in algebraic geometry (cf. cotangent complex) and the mathematical foundation of quantum mechanics. In the latter subject, a Bohr topos is a ringed topos that plays the role of a quantum phase space.
The definition of a topos-version of a "locally ringed space" is not straightforward, as the meaning of "local" in this context is not obvious. One can introduce the notion of a locally ringed topos by introducing a sort of geometric conditions of local rings (see SGA4, Exposé IV, Exercise 13.9), which is equivalent to saying that all the stalks of the structure ring object are local rings when there are enough points.
Morphisms
A morphism of ringed topoi is a pair consisting of a topos morphism and a ring homomorphism .
If one replaces a "topos" by an ∞-topos, then one gets the notion of a ringed ∞-topos.
Examples
Ringed topos of a topological space
One of the key motivating examples of a ringed topos comes from topology. Consider the site of a topological space , and the sheaf of continuous functionssending an object , an open subset of , to the ring of continuous functions on . Then, the pair forms a ringed topos. Note this can be generalized to any ringed space whereso the pair is a ringed topos.
Ringed topos of a scheme
Another key example is the ringed topos associated to a scheme , which is again the ringed topos associated to the underlying locally ringed space.
Relation with functor of points
Recall that the functor of points view of scheme theory defines a scheme as a functor which satisfies a sheaf condition and gluing condition. That is, for any open cover of affine schemes, there is the following exact sequenceAlso, there must exist open affine subfunctorscovering , meaning for any , there is a . Then, there is a topos associated to whose underlying site is the site of open subfunctors. This site is isomorphic to the site associated to the underlying topological space of the ringed space corresponding to the scheme. Then, topos theory gives a way to construct scheme theory without having to use locally ringed spaces using the associated locally ringed topos.
Ringed topos of sets
The category of sets is equivalent to the category of sheaves on the category with one object and only the identity morphism, so . Then, given any ring , there is an associated sheaf . This can be used to find toy examples of morphisms of ringed topoi.
Notes
References
The standard reference is the fourth volume of the Séminaire de Géométrie Algébrique du Bois Marie.
Francis, J. Derived Algebraic Geometry Over -Rings
Grothendieck Duality for Derived Stacks
Sheaf theory | Ringed topos | Mathematics | 650 |
27,837,391 | https://en.wikipedia.org/wiki/SyncEvolution | SyncEvolution synchronizes Evolution's contact, calendar and task items via SyncML. The items are exchanged in the vCard 2.1 or 3.0 format and iCalendar 2.0 format via the Synthesis C++ client API library, which should make SyncEvolution compatible with the majority of SyncML servers. Full, one-way and incremental synchronization of items are supported.
SyncEvolution synchronizes personal information management (PIM) data such as contacts, appointments, tasks and memos using the Synthesis sync engine, which provides support for the SyncML synchronization protocol.
SyncEvolution synchronizes with SyncML servers over HTTP and with SyncML capable phones locally over Bluetooth/OBEX. Plugins provide access to the data which is to be synchronized. Binaries are available for Linux desktops (synchronizing data in GNOME Evolution, with KDE supported indirectly already and Akonadi support in development), for MeeGo and for Maemo 5/Nokia N900. The source code can be compiled for Unix-like systems and provides a framework to build custom SyncML clients or servers.
External links
https://lwn.net/Articles/392295/
Free software programmed in C++
SyncML
Software using the GNU Lesser General Public License | SyncEvolution | Technology | 284 |
4,778,188 | https://en.wikipedia.org/wiki/List%20of%20platform-independent%20GUI%20libraries | This is a list of notable library packages implementing a graphical user interface (GUI) platform-independent GUI library (PIGUI). These can be used to develop software that can be ported to multiple computing platforms with no change to its source code.
In C, C++
In other languages
No longer available or supported
See also
List of widget toolkits
List of rich web application frameworks
Further reading
Richard Chimera, Evaluation of Platform Independent User Interface Builders, March 1993, Human-Computer Interaction Laboratory University of Maryland
References
Computer libraries
Cross-platform software | List of platform-independent GUI libraries | Technology | 114 |
68,008,035 | https://en.wikipedia.org/wiki/Yuri%20Mikhailovich%20Smirnov | Yuri Mikhailovich Smirnov (Юрий Михайлович Смирнов, September 19, 1921, Kaluga – September 3, 2007, Moscow) was a Soviet and Russian mathematician, specializing in topology.
Biography
Yuri M. Smirnov was born in a family of clerical employees. His mother was imprisoned in 1937 for anti-Soviet activity and, as later revealed, was executed by gun shot. While studying at school, Yuri M. Smirnov was interested in mathematics and astronomy and after completing undergraduate study in 1939 entered the astronomy department of the Faculty of Mechanics and Mathematics of Moscow State University. However, soon under the influence of A. N. Kolmogorov, he transferred to the mathematical department of the same Faculty.
After his second year of undergraduate study, Smirnov went in autumn 1941 to the front and served as a radio operator in the Northern Fleet until the end of WW II. After demobilization in 1945, he continued his studies at the Faculty of Mechanics and Mathematics of Moscow State University and began to participate in the seminars of the famous topologist P. S. Alexandrov. In 1948 Smirnov graduated from the Faculty of Mechanics and Mathematics and entered the graduate school of the same faculty, at the same time starting to work as a junior researcher at the Steklov Institute of Mathematics. In 1951 he defended his Ph.D. (Russian Candidate of Sciences) thesis О топологических пространствах, компактных в данном отрезке мощностей (On topological spaces, compact in a given interval of cardinalities), which was supervised by P. S. Alexandrov. In 1957 Smirnov received his Russian Doctor of Sciences degree with thesis Исследование по общей и равномерной топологии методом покрытий (Investigation of general and uniform topology by the covering method).
From 1945 until the end of his life he worked at the Department of Higher Geometry and Topology of the Faculty of Mechanics and Mathematics of Moscow State University, from 1953 as an associate professor, and from 1958 as a full professor. He taught courses on analytical geometry, linear algebra and topology, linear algebra and geometry, differential geometry and topology, and the theories of retracts, shapes, and equivariant compactifications.
Smirnov published over a hundred scientific papers, most of which are related to general topology. He is the author of fundamental results on the problem of metrization of topological spaces and in equivariant topology, as well as in dimension theory and in the theories of shapes, retracts, and proximity spaces. His name is associated with the famous Nagata-Smirnov metrization theorem (proved independently by the Japanese mathematician Jun-iti Nagata). The theorem gives necessary and sufficient conditions for the existence of a metric generating the original topology.
Smirnov gave lectures not only in Russia, but also in Germany, Poland, Bulgaria, Georgia, Armenia, Uzbekistan, and Tajikistan. He supervised 12 Russian Doctor of Sciences (habilitation) degrees and more than 35 Candidate of Sciences degrees (PhDs).
He was awarded the Order of the Patriotic War for his WW II service. In 1962 he was an Invited Speaker with talk Некоторые вопросы равномерной топологии (Some questions of uniform topology) at the International Congress of Mathematicians in Stockholm. He was awarded honorary titles: Honored Professor of Moscow State University (1996), Honored Scientist of the USSR (1981), and Honored Scientist of the Russian Federation (2002). In 1995 he received the Wacław Sierpiński Medal jointly from the Polish Academy of Sciences and the University of Warsaw.
References
External links
Летопись Московского университета (Annals of Moscow University)
Страница Ю. М. Смирнова на сайте кафедры высшей геометрии и топологии (Smirnov's page on the website of the Department of Higher Geometry and Topology)
Smirnov, Yurii Mikhailovich, Math-Net.Ru
Интервью в сборнике «Мехматяне вспоминают» (Interview in the collection "Mechanicians Remember")
1921 births
2007 deaths
20th-century Russian mathematicians
21st-century Russian mathematicians
Soviet mathematicians
Topologists
People from Kaluga
Moscow State University alumni
Academic staff of Moscow State University | Yuri Mikhailovich Smirnov | Mathematics | 1,062 |
40,837 | https://en.wikipedia.org/wiki/Call-second | In telecommunications, a call-second is a unit used to measure communications traffic density, equivalent to one call with a duration of one second.
Traffic is measured independent of users. For example, one user making two 75-second calls is equivalent to two users each making one 75-second call, as each case produces 150 call-seconds of traffic.
A CCS (centacall-second) is often used to describe 100 call-seconds, so 3600 call-seconds = 36 CCS = 1 call-hour.
In a communication network, a trunk (link) can carry numerous concurrent calls by means of multiplexing. Hence a particular number of call-seconds can be carried in infinitely many ways as calls are established and cleared over time. For example, one call-hour could be one call for an hour or two (possibly concurrent) calls for half an hour each. Call-seconds give a measure of the average number of concurrent calls.
Offered load is defined as the traffic density per unit time, measured in erlangs. An erlang is defined as one call-hour per hour, or 3,600 call-seconds per hour.
Hence, if one CCS is measured over a one-hour period, the offered load is 1/36 erlangs.
References
Units of measurement
Telecommunications | Call-second | Mathematics,Technology | 266 |
51,630,337 | https://en.wikipedia.org/wiki/NGC%20233 | NGC 233 is an elliptical galaxy located in the constellation Andromeda. It was discovered on September 11, 1784 by William Herschel.
One supernova has been observed in NGC 233: SN2021abzd (typeIa-91bg-like, mag. 17.3).
See also
List of NGC objects (1–1000)
References
External links
0233
Elliptical galaxies
Andromeda (constellation)
002604
00464
+05-02-041
17840911
Discoveries by William Herschel | NGC 233 | Astronomy | 109 |
10,218,627 | https://en.wikipedia.org/wiki/Texas%20statistical%20areas | The U.S. currently has 80 statistical areas that have been delineated by the Office of Management and Budget (OMB). On July 21, 2023, the OMB delineated 13 combined statistical areas, 26 metropolitan statistical areas, and 41 micropolitan statistical areas in Texas. As of 2023, the largest of these is the Dallas-Fort Worth, TX-OK CSA, encompassing the area around the twin cities of Dallas and Fort Worth in the northern part of the state.
Owing to its large area and population - the second-highest amongst the 50 states in both respects - Texas contains the most statistical areas of any state.
Table
Primary statistical areas
Primary statistical areas (PSAs) include all combined statistical areas and any core-based statistical area that is not a constituent of a combined statistical area. Of the 80 statistical areas of Texas, 42 are PSAs comprising 13 combined statistical areas, 11 metropolitan statistical areas, and 18 micropolitan statistical areas.
See also
Geography of Texas
Demographics of Texas
Notes
References
External links
Office of Management and Budget
United States Census Bureau
United States statistical areas
Statistical Areas Of Texas
Statistical Areas Of Texas | Texas statistical areas | Mathematics | 232 |
10,111,265 | https://en.wikipedia.org/wiki/Tributyltin%20hydride | Tributyltin hydride is an organotin compound with the formula (C4H9)3SnH. It is a colorless liquid that is soluble in organic solvents. The compound is used as a source of hydrogen atoms in organic synthesis.
Synthesis and characterization
The compound is produced by reduction of tributyltin oxide with polymethylhydrosiloxane:
2 "[MeSi(H)O]n" + (Bu3Sn)2O → "[MeSi(OH)O]n" + 2 Bu3SnH
It can also be synthesized by a reduction of tributyltin chloride with lithium aluminium hydride.
The hydride is a distillable liquid that is mildly sensitive to air, decomposing to (Bu3Sn)2O. Its IR spectrum exhibits a strong band at 1814 cm−1 for νSn−H.
Applications
It is a specialized reagent in organic synthesis. Combined with azobisisobutyronitrile (AIBN) or by irradiation with light, tributyltin hydride converts organic halides (and related groups) to the corresponding hydrocarbon. This process occurs via a radical chain mechanism involving the radical Bu3Sn•. The radical abstracts a H• from another equivalent of tributyltin hydride, propagating the chain. Tributyltin hydride's utility as a H• donor can be attributed to its relatively weak bond strength (78 kcal/mol).
It is the reagent of choice for hydrostannylation reactions:
RC2R′ + HSnBu3 → RC(H)=C(SnBu3)R′
See also
Tributyltin
Trimethylsilyl
References
Further reading
Hayashi, K.; Iyoda, J.; Shiihara, I. "Reaction of organotin oxides, alkoxides and acyloxides with organosilicon hydrides. New preparative method of organotin hydrides " J. Organomet. Chem. 1967, 10, 81.
Organotin compounds
Radical initiators
Metal hydrides
Tin(IV) compounds
Butyl compounds | Tributyltin hydride | Chemistry,Materials_science | 479 |
52,740,225 | https://en.wikipedia.org/wiki/Phosphorus%20trifluorodichloride | Phosphorus trifluorodichloride is a chemical compound with the chemical formula PF3Cl2. The covalent molecule trigonal bipyramidal molecular geometry. The central phosphorus atom has sp3d hybridization, and the molecule has an asymmetric charge distribution. It appears as a colorless gas with a disagreeable odor, and it turns into a liquid at -8 °C.
Phosphorus trifluorodichloride is formed by mixing phosphorus trifluoride with chlorine PF3 + Cl2 → PF3Cl2
The P-F bond length is 1.546 Å for equatorial position and 1.593 for the axial position and the P-Cl bond length is 2.004 Å. The chlorine atoms are in equatorial positions in the molecule.
References
Phosphorus(V) compounds
Fluorine compounds
Chlorine(−I) compounds
Gases | Phosphorus trifluorodichloride | Physics,Chemistry | 185 |
47,872,424 | https://en.wikipedia.org/wiki/Pleometrosis | Pleometrosis is a behavior observed in social insects where colony formation is initiated by multiple queens primarily by the same species of insect. This type of behavior has been mainly studied in ants but also occurs in wasps, bees, and termites. This behavior is of significant interest to scientists particularly in ants and termites because nest formation often happens between queens that are unrelated, ruling out the argument of inclusive fitness as the driving force of pleometrosis. Whereas in other species such as wasps and bees co-founding queens are often related. The majority of species that engage in pleometrosis after the initial stages of colony formation will reduce their colonies number of queens down to one dominant queen and either kill or push out the supernumerary queens. However there are some cases where pleometrosis-formed colonies keep multiple queens for longer than the early stages of colony growth. Multiple queens can help to speed a colony through the early stages of colony growth by producing a larger worker ant population faster which helps to out-compete other colonies in colony-dense areas. However forming colonies with multiple queens can also cause intra-colony competition between the queens possibly lowering the likelihood of survival of a queen in a pleometrotic colony.
Selection pressures causing pleometrosis in ants
The driving selection pressure that causes ant species to form colonies through pleometrosis appears to be inter-colony competition in areas with high colony density. When a queen enters an area in which she wants to form a colony, there may be a finite amount of resources to fuel the colony thus necessitating intense competition and territoriality for resources between ant colonies. If the queen forms a colony on her own then she has a low probability of surviving because other colonies may be able to produce workers faster than her or may already be past the early stages of colony formation. Forming the colony on her own could also cause her to have to forage for food to out-compete other colonies through number of offspring. This foraging behavior puts her at risk of predators. However, if she and multiple queens form a colony through pleometrosis they can produce a larger worker force of ants faster and get to a mature reproductive stage of colony growth faster, thus decreasing the chances of death due to inter-colony competition. It has been observed that ants which form pleometrotic colonies engage in less foraging behavior, thus lowering their chance of predation. Having multiple queens cuts down on foraging behavior because each queen uses her own stored energy reserves to feed the brood. By founding the colony pleometrotically ants can form new colonies in high colony density areas and take control of resources in the surrounding area faster. Some genera of ants such as Azteca use the additional worker ants early in the colonies formation to monopolize and take control of resources in close proximity of the colony thus stopping other con-specific colonies from acquiring those resources. This strategy allows the pleometrotic colonies to monopolize the area and starve out competing colonies. The additional worker force in pleometrotic colonies also allows for bigger and more effective brood raids on con-specific colonies which additionally helps to out-compete colonies. A key aspect of founding a colony in a high density colony area is being able to produce a worker force quickly and efficiently so as to not be starved out or robbed of brood from other colonies causing starvation. By engaging in pleometrosis queens increase their chance of survival past the early stages of colony formation due to the increased worker force produced by multiple reproductive individuals. The colony can better control its surrounding resources and effectively compete with other colonies.
Costs and benefits of pleometrosis
Pleometrosis is necessary to survive inter-colony competition in high-density and resource-limited areas but the majority of pleometrotic colonies cut back to one queen before the reproductive stages of colony growth. So this suggests that a queen has a better chance of surviving and reproducing offspring if she forms a colony with other queens even though eventually she may be pushed out or killed by intra-colony competition. The risk of being out-competed by a con-specific queen within one's own colony must be less than the risk of dying out due to other insect colonies. So in high density colony areas or resource-limited areas where inter-colony competition is high, selection for pleometrosis is higher because the chance of survival in a pleometrotic colony is greater. As the number of queens in a pleometrotic colony increases, the chances of each queen becoming the dominant queen in the colony lowers, but still selection pressures choose pleometrosis over haplometrosis. Depending on the species of ant and the selection pressures of the colony there are multiple ways a queen can become the one dominant queen in the colony and gain the full benefit of a pleometrotic colony. The queens that normally come out as dominant in pleometrotic colonies lay more eggs, have well-developed ovaries, and do not engage in foraging behavior. Worker ants even play a role in deciding whether a queen will become the dominant individual in some species by feeding the queen who is the most fertile more than other queens in the nest. Queens will also engage in dominance actions to assert dominance over the nest such as brood cannibalism of other queens' brood. When the most fertile queen in the nest decides to directly challenge another queen, it is usually the initiating queen that wins and takes control of the colony, turning it into a one queen colony. The benefits of pleometrosis is certain situations outweigh the costs for queens, regardless of the intra-colony competition it causes. Thus it has evolved to occur in high density areas of inter-colony competition.
Colony foundation by pleometrosis in Azteca ants
Azteca ants form colonies in the internodes of Cecropia trees which are native to Mexico and South America. The tree provides the ants with food and shelter and the ants protect the tree from other insects thus engaging in a mutualistic relationship. Queens form colonies by burrowing into the inter node of the tree and then sealing off the entrance hole with parenchyma cells, after which they begin to lay eggs to produce the first brood. Any queens which decide to engage in pleometrosis can easily see the filled in hole and will chew through it quickly and join the fellow queen in the inter node. Colonies that are formed in these trees try to out-compete other colonies by monopolizing the resources of a tree first. By forming a pleometrotic colony in a Cecropia tree the queens can produce workers faster and take control of the resources in the tree first thus out-competing other colonies. However, the social interactions between queens in a pleometrotic colony differ depending on the species of Azteca. In Azteca xanthochroa which are more aggressive, pleometrotic colonies work together to produce a greater number of workers at the start of colony formation but once the colony breaks out of the inter node of the tree the interactions between the queens change. Once this step occurs queens will try to kill each other to become the dominant queen in the colony and switch the colony to a single queen colony. However in species of A. constructor which are less aggressive, once the worker ants leave the inter node to take control of the tree's resources, multiple queens remain cooperative with each other for up to a year. Hypothesizes as to why A. constructor colonies engage in cooperative breeding with multiple queens could be due to similarities in A. constructor queens fighting abilities or the inclusive fitness benefits in some colonies of A. constructor. In contrast pleometrotic colonies of A. xanthochroa form and change to one queen colonies after the early stages of colony formation. There are also examples of pleometrotic colonies forming with multiple species of Azteca, however, when these form the more aggressive species will out-compete and kill off the other queens in the colony once the early stages of formation have passed. Mixed species pleometrosis is rare but helps to support the fact that the majority of social insects who form pleometrotic colonies do not do so for kin selection-related benefits, but to be able to out-compete other colonies in the early stages of development.
References
Myrmecology
Insect behavior
Sociobiology
Superorganisms | Pleometrosis | Biology | 1,716 |
17,699,115 | https://en.wikipedia.org/wiki/Newton%E2%80%93Pepys%20problem | The Newton–Pepys problem is a probability problem concerning the probability of throwing sixes from a certain number of dice.
In 1693 Samuel Pepys and Isaac Newton corresponded over a problem posed to Pepys by a school teacher named John Smith. The problem was:
Pepys initially thought that outcome C had the highest probability, but Newton correctly concluded that outcome A actually has the highest probability.
Solution
The probabilities of outcomes A, B and C are:
These results may be obtained by applying the binomial distribution (although Newton obtained them from first principles). In general, if P(n) is the probability of throwing at least n sixes with 6n dice, then:
As n grows, P(n) decreases monotonically towards an asymptotic limit of 1/2.
Example in R
The solution outlined above can be implemented in R as follows:
for (s in 1:3) { # looking for s = 1, 2 or 3 sixes
n = 6*s # ... in n = 6, 12 or 18 dice
q = pbinom(s-1, n, 1/6) # q = Prob( <s sixes in n dice )
cat("Probability of at least", s, "six in", n, "fair dice:", 1-q, "\n")
}
Newton's explanation
Although Newton correctly calculated the odds of each bet, he provided a separate intuitive explanation to Pepys. He imagined that B and C toss their dice in groups of six, and said that A was most favorable because it required a 6 in only one toss, while B and C required a 6 in each of their tosses. This explanation assumes that a group does not produce more than one 6, so it does not actually correspond to the original problem.
Generalizations
A natural generalization of the problem is to consider n non-necessarily fair dice, with p the probability that each die will select the 6 face when thrown (notice that actually the number of faces of the dice and which face should be selected are irrelevant). If r is the total number of dice selecting the 6 face, then is the probability of having at least k correct selections when throwing exactly n dice. Then the original Newton–Pepys problem can be generalized as follows:
Let be natural positive numbers s.t. . Is then not smaller than for all n, p, k?
Notice that, with this notation, the original Newton–Pepys problem reads as: is ?
As noticed in Rubin and Evans (1961), there are no uniform answers to the generalized Newton–Pepys problem since answers depend on k, n and p. There are nonetheless some variations of the previous questions that admit uniform answers:
(from Chaundy and Bullard (1960)):
If are positive natural numbers, and , then .
If are positive natural numbers, and , then .
(from Varagnolo, Pillonetto and Schenato (2013)):
If are positive natural numbers, and then .
References
Factorial and binomial topics
Probability problems
Isaac Newton
Mathematical problems | Newton–Pepys problem | Mathematics | 639 |
7,085,802 | https://en.wikipedia.org/wiki/Free-floating%20barrel | A free-floating barrel is a firearm design used in precision rifles, particularly match grade benchrest rifles, to accurize the weapon system.
With conventional rifles, the gun barrel rests in contact with the fore-end of the gunstock, sometimes along the whole length. If the stock is wooden, environmental conditions or operational use may warp the wood, which may also cause the barrel to shift its alignment slightly over time, altering the projectile's external ballistics and thus the point of impact. Contact between the barrel and the stock affects the natural frequency of the barrel, which can reduce accuracy especially when the barrel gets hot with repeated firing. The effect of the stock on the barrel can cause the barrel to vibrate inconsistently from shot to shot, depending on the external forces acting upon the stock at the time of the shot. Such vibrations affect the bullet's trajectory, changing the point of impact.
A free-floating barrel is one where the barrel and stock do not touch at any point along the barrel's length. The barrel is attached to its receiver, which is attached to the stock, but the barrel does not touch any other gun parts except perhaps the front sight, which is often mounted on the barrel. This minimizes possible variance in mechanical pressure distortions of the barrel alignment, and allows vibration to occur at the natural frequency of the barrel consistently and uniformly.
Alternatives include using a stock made from composite materials which do not deform as much under temperature or humidity changes, or a wooden stock with a fiberglass contact area ("glass bedding"). Stocks which contact the barrel are still popular for many utility weapons, though most precision rifle designs have adopted free-floating barrels.
References
RifleShooter Mag
Firearm components | Free-floating barrel | Technology | 352 |
43,349,009 | https://en.wikipedia.org/wiki/Fosetyl-Al | Fosetyl-Al is an organophosphorus compound that is used as a fungicide. With the formula [C2H5OP(H)O2]3Al. It is derived from ethylphosphite.
References
Fungicides
Phosphites
Aluminium compounds | Fosetyl-Al | Biology | 62 |
43,386,313 | https://en.wikipedia.org/wiki/Creative%20industry%20in%20Brazil | The creative industry in Brazil refers to various economic sectors of Brazil that depend on the talents and creativity to develop. In other words, these economic sectors generate wealth for the region through knowledge, culture and creativity, and contribute to sustainable development (environmental, economic and social). The term 'creative industries' was coined by the United Kingdom in 1990 and, in 2001, was augmented by two important additions: by researcher John Howkins, who applied an entrepreneurial vision when focusing on the transformation of creativity in product; and professor Richard Florida, whose research focused on the professionals involved in the creative processes of production, and addressed the social aspects and the "potential contribution to the development" of the "creative class".
The first international study emerged in 2008, conducted by the United Nations Conference on Trade and Development (UNCTAD). In the same year, another study by FIRJAN was published, this time concentrating on the economic impact of creativity on Brazil. The creative economy in Latin America has since been referred to as the “Orange Economy” in a publication released by the Inter-American Development Bank (IDB). This 2013 study claimed that Brazil's Orange Economy could be valued at US$66.87 billion providing 5,280,000 jobs. At the time and to provide a comparative value, Venezuelan oil exports amounted to US$62 billion. Brazil's Orange Economy was responsible for US$9,414 million in exports, a figure that is higher than the US$8,016 million value of coffee exports over the same period.
A 2021 study on Intellectual Property Intensive Sectors in the Brazilian Economy was undertaken as part of the National Strategy on Intellectual Property 2021–2030 and the creation of the Intellectual Property website.
Creative professions
The Classificação Brasileira de Ocupações - CBO (read "Brazilian Classification of Occupations") from the Ministry of Labour and Employment lists of all professions in the country and has mapped the creative work market in Brazil. The study isolated fourteen creative professions in which knowledge is a transforming input of production:
Architecture and Engineering
Art
Performing Arts
Biotechnology
Design
Cultural expressions
Film & Video
Editorial Market
Fashion
Music
Research and development
Advertising
Software, Computer & Telecom
Television & Radio.
History
The first initiative to map the creative industries from any country was from the United Kingdom at the end of 1990. The goal was to prove that these sectors have an important role to the culture and the potential to generate jobs and wealth to the country. Then, these creative industries were mapped, and all others who maintained relations with them as well. Thus, it was built a view of the weight of the creative chains in the production process.
Three years after this pioneering work, specifically in 2001, two others arose from:
Researcher John Howkins, who built his study according to a corporate vision (based on marketing concepts of intellectual property); and
Teacher Richard Florida, who showed off the so-called "creative class" (professionals who work with creative processes).
It did not take long for the United Nations Conference on Trade and Development (UNCTAD, 2008) to launch another study on the subject, only this time with an international scope. According to the survey, the exports of the creative industries in the world exceeded 500 billion dollars.
Given the importance of the issue to the world and specifically to Brazil, the study A Cadeia da Indústria Criativa no Brasil (read "The Chain of Creative Industry in Brazil"), was undertaken. It was updated in 2011 and published in 2012. This tool to map the creative industry in the country is able to list information about each of these professions, such as the number of jobs and the amount of wages and the education level required. Thus, it unites information from both the Classificação Nacional de Atividades Econômicas (i.e. "National Classification of Economic Activities") and the "Brazilian Classification of Occupations".
In general, the creative industries encompass "economic activity directly related to the art world - especially the visual arts, performing arts, literature and publishing, photography, crafts, libraries, museums, galleries, archives, spots designated by the National Historic Landmark and festivals of arts (...) electronic media and other recent media (...) design-related activities.
The theme is sometimes confused with the term "cultural industry". However, "the scope of the creative economy is determined by the extent of the creative industries." In other words, cultural products and services would be part of a larger category of creative products and services.
Chain
For the United Nations Conference on Trade and Development (UNCTAD), the chain of creative industry comprises the "cycles of creation, production and distribution of goods and services that use creativity and intellectual capital as primary inputs." Thus, it can be divided into three major areas:
creative core (the creative economic activities)
related activities (provide goods and services directly to the core), and
support (provide goods and services indirectly to the core).
The United Kingdom's Department for Culture, Media and Sport considers as creative industries activities "that have their origin in creativity, skill and individual talent and which have a potential for creating wealth and jobs through the generation and exploitation of intellectual property."
Based on this concept, it can be said that Brazil is very important when it comes to creative industry. After all, it is one of the largest producers in the world of creativity. Analyzing the remuneration of the Brazilian people, it was found that the wages of those working in the creative industry in Brazil are almost three times higher than the national average wage (comparison value: R$4,693 and R$1,733, respectively). And among creative professionals, those from Rio de Janeiro, São Paulo and the Federal District receive the best salaries. These are data from the "Creative Industries Mapping", which was based on information from 2011. The study addresses issues such as jobs, wages, average wage per state, number of employees by segment and even from the GDP creative country.
In 2015 the World Intellectual Property Organization (WIPO) assisted in the preparation of over 50 national studies to measure the size of copyright industries around the world.
Federal Government and the Creative Industries
In May 2012, the Brazilian president Dilma Rousseff decreed the creation of the Secretaria da Economia Criativa ("Creative Economy Secretariat"). The goal of SEC is to create, implement and monitor public policy that have the culture as a strategic axis, "prioritizing support and encouragement to professionals and to the micro and small Brazilian creative endeavors."
According to a report from the United Nations, Brazil was not among the top twenty producers in the industry yet, but the initiative of creating the SEC indicated the government's desire to reposition the "culture as development axis of the Brazilian state." To the President of the National Bank for Economic and Social Development (BNDES), Luciano Coutinho, this is a recognition that creative activities are important for the country "in a long-term perspective, having as a goal a more inclusive and sustainable development.
Globally, the countries that have excelled in the industry are China, in the first place, followed by the United States and Germany. But Brazil has contributed greatly in the fields of architecture, fashion and design, revealing its creative potential worldwide.
In December, 2021, the National Intellectual Property Strategy was enacted through Decree 10.886/2021. Among the macro objectives of the national strategy is to map the Brazilian creative industry and the action to approximate innovation clusters of the creative industry to intellectual property. Concomitantly, the Brazilian Federal Government also created the portal on intellectual property.
Brazilian x-ray
In 2014, the Creative Economy Secretary of the Ministry of Culture, Cláudia Leitão, claimed that the country was learning to grow in this area, to transform "Brazilian creativity into innovation and innovation into wealth." The creative industry in Brazil gathers, generally, "young, educated and well-paid professionals" that earn 42% above the average wage in the country.
It is difficult to know how much an idea or innovation costs, as they are intangible assets. One way of measuring their impact is to create metrics and to use qualitative and quantitative research. A first study in 2013 identified the general economic data related to the Creative Industry in Brazil, such as:
Share of GDP: R$110 billion
Enterprises: 243 thousand
Professionals: 810 thousand, of which the most numerous are:
Architects and engineers: 229 877 employees formal;
Programmers information systems: 50,440;
Business analysts: 45,324;
Research and market analyst: 25,141;
Marketing manager: 20,382;
Advertising agents: 14,032;
Graphic Designer: 17,806;
Biologist: 15,182;
Manager of research and development: 13,414;
Designer of bespoke shoes: 13,068.
Wages: the best paid creative activities are:
Geologists and geophysicals: R$11,385;
Directors of TV shows: R$10,753;
Actors: R$10,348;
Biotechnologists: R$8,701;
News room directors: R$7,774;
Magazine editors: R$7,594;
Architects and engineers: R$7,524;
Electrical Engineers, electronics engineers and Computer engineers: R$7,431;
Screenwriters: R$7,347;
Researchers in general: R$7,102.
In 2019, the Federation of industries of Rio Janeiro (FIRJAN) updated its previous 2017 research and published a national study that mapped the Brazilian creative industries indicating that in 2017 there were 837,200 employees, a decrease of 3,9 in comparison to 2015. It also concluded that the overall remuneration in the creative industries was higher than the Brazilian average.
A 2021 study on Intellectual Property Intensive Sectors in the Brazilian Economy was undertaken as part of the National Strategy on Intellectual Property 2021–2030 and the creation of the Intellectual Property website. The main findings of the study were:
out of 673 economic classes, 450 were classified as IP-intensive sectors,
the IP-intensive sectors employed 19,3 million people, and
the share of GDP between 2014 and 2016 amounted to R$2,1 trillion Reais or 44,2 % of GDP.
Notes
References
External links
Creative Industry
Department for culture, media & Sport
Annual Report of Social Information (RAIS)
"Creative Industries Mapping Documents"
CBO listing (PDF 1,2 KB)
Industry in Brazil
Creativity
Economics of the arts and literature | Creative industry in Brazil | Biology | 2,150 |
9,859,641 | https://en.wikipedia.org/wiki/Heidelberg-K%C3%B6nigstuhl%20State%20Observatory | Heidelberg-Königstuhl State Observatory () is a historic astronomical observatory located near the summit of the Königstuhl hill in the city of Heidelberg in Germany. The predecessor of the current observatory was originally opened in 1774 in the nearby city of Mannheim but degradation of observational conditions there resulted in a relocation to the Königstuhl in 1898.
The observatory forms part of the Center of Astronomy of the University of Heidelberg. The Max Planck Institute for Astronomy opened on an adjacent site in 1967. Prof. Dr. Andreas Quirrenbach is the observatory's director since 2005.
History
The instrumentation of the observatory originated from the Mannheim Observatory, founded in 1774. In 1880, the observatory was provisionally moved to Karlsruhe because the astronomical/atmospherical seeing conditions worsened. In subsequent years, three other locations were considered, with Heidelberg-Königstuhl finally being chosen.
On 20 June 1898, the "Großherzogliche Bergsternwarte" was ceremonially inaugurated by Frederick I, Grand Duke of Baden. The astronomical institute comprised two complementary departments, the astrophysical, led by Max Wolf, and the astrometrical led by Karl Wilhelm Valentiner. Valentiner was director of the Mannheim observatory and initiated the move to Karlsruhe. After Valentiner's retirement in 1909, both departments were placed under the administration of Max Wolf.
While the new observatory complex was still under construction Max Wolf obtained a grant of $10,000 from the American philanthropist Catherine Wolfe Bruce for the acquisition of a powerful new dual refractor telescope, the Bruce double astrograph. For many years this telescope was the observatory's main research instrument. He later obtained a grant to build the observatory's a reflector telescope, the observatory's first.
The main field of activity of the observatory was the investigation of nebulae and the search for asteroids. Wolf, his staff and his successors discovered over 800 asteroids, including the first trojan asteroid Achilles in 1906.
The observatory ceased to be run by the German federal government in 2005 when it was joined with the Institute of Theoretical Astrophysics and Astronomical Calculation Institute to make up the Center of Astronomy of the University of Heidelberg.
Between 1912 and 1957, Karl Wilhelm Reinmuth discovered almost 400 asteroids from the Heidelberg-Königstuhl State Observatory.
See also
List of astronomical observatories
References
External links
Official observatory website (German/English)
Astronomical observatories in Germany
Heidelberg University
Astronomy institutes and departments
Buildings and structures in Heidelberg | Heidelberg-Königstuhl State Observatory | Astronomy | 505 |
4,336,844 | https://en.wikipedia.org/wiki/DEMOS | DEMOS (Dialogovaya Edinaya Mobilnaya Operatsionnaya Sistema: ) is a Unix-like operating system developed in the Soviet Union. It is derived from Berkeley Software Distribution (BSD) Unix.
Development
DEMOS's development was initiated in the Kurchatov Institute of Atomic Energy in Moscow in 1982, and development continued in cooperation from other institutes, and commercialized by DEMOS Co-operative which employed most key contributors to DEMOS and to its earlier alternative, MNOS (a clone of Version 6 Unix). MNOS and DEMOS version 1.x were gradually merged from 1986 until 1990, leaving the joint OS, DEMOS version 2.x, with support for different Cyrillic script character encoding (charsets) (KOI-8 and U-code, used in DEMOS 1 and MNOS, respectively).
Initially it was developed for SM-4 (a PDP-11/40 clone) and SM-1600. Later it was ported to Elektronika-1082, BESM, ES EVM, clones of VAX-11 (SM-1700), and several other platforms, including PC/XT, Elektronika-85 (a clone of DEC Professional), and several Motorola 68020-based microcomputers.
The development of DEMOS effectively ceased in 1991, when the second project of the DEMOS team, RELCOM, took priority.
See also
MOS (operating system)
References
Mapping Russian Cyberspace — Rafal Rohozinski, United Nations Research Institute for Social Development, 1999
https://astr0baby.wordpress.com/2016/10/17/soviet-unix-clone-demos/
https://www.opendemocracy.net/en/odr/usenet-coup/
Computing in the Soviet Union
Soviet inventions
Berkeley Software Distribution | DEMOS | Technology | 385 |
18,444 | https://en.wikipedia.org/wiki/Loch | Loch ( ) is a word meaning "lake" or "sea inlet" in Scottish and Irish Gaelic, subsequently borrowed into English. In Irish contexts, it often appears in the anglicized form "lough". A small loch is called a lochan.
Lochs which connect to the sea may be called "sea lochs" or "sea loughs". Some such bodies of water could also be called firths, fjords, estuaries, straits or bays.
Background
This name for a body of water is Insular Celtic in origin and is applied to most lakes in
Scotland and to many sea inlets in the west and north of Scotland. The word comes from Proto-Indo-European (), and is related to the Latin (), English lay () and French , as well as the Italian, Portuguese and Spanish word for a lake, lago.
Lowland Scots orthography, like Scottish Gaelic, Welsh and Irish, represents with , so the word was borrowed with identical spelling.
English borrowed the word separately from a number of loughs in the previous Cumbric language areas of Northumbria and Cumbria. Earlier forms of English included the sound as (compare Scots with English bright). However, by the time Scotland and England joined under a single parliament, English had lost the sound. This form was therefore used when the English settled Ireland. The Scots convention of using remained, hence the modern Scottish English loch.
In Welsh, what corresponds to lo is in Old Welsh and in Middle Welsh (such as in today's Welsh placenames Llanllwchaiarn, Llwchwr, Llyn Cwm Llwch, Amlwch, Maesllwch), the Goidelic lo being taken into Scottish Gaelic by the gradual replacement of much Brittonic orthography with Goidelic orthography in Scotland.
Many of the loughs in Northern England have also previously been called "meres" (a Northern English-dialect word for "lake", and an archaic Standard English word meaning "a lake that is broad in relation to its depth"), similar to the Dutch , such as the Black Lough in Northumberland. However, reference to the latter as loughs (lower case initial), rather than as lakes, inlets and so on, is unusual.
Some lochs in Southern Scotland have a Brythonic, rather than Goidelic, etymology, such as Loch Ryan, where the Gaelic has replaced a Cumbric equivalent of Welsh . The same is, perhaps, the case for bodies of water in Northern England named with 'Low' or 'Lough', or else represents a borrowing of the Brythonic word into the Northumbrian dialect of Old English.
Although there is no strict size definition, a smaller loch is often known as a lochan (spelled the same also in Scottish Gaelic; in Irish, it is spelled ).
Perhaps the most famous Scottish loch is Loch Ness, although there are other famous ones, such as Loch Awe, Loch Lomond and Loch Tay.
Examples of sea lochs in Scotland include Loch Long, Loch Fyne, Loch Linnhe, and Loch Eriboll. Elsewhere in Britain, places like the Afon Dyfi can be considered sea lochs.
Uses of lochs
Some new reservoirs for hydroelectric schemes have been given names faithful to the names for natural bodies of water. For example, the Loch Sloy scheme and Lochs Laggan and Treig (which form part of the Lochaber hydroelectric scheme near Fort William). Other expanses are simply called reservoirs, e.g. Blackwater Reservoir above Kinlochleven.
Scottish lakes
Scotland has very few bodies of water called lakes. The Lake of Menteith, an Anglicisation of the Scots Laich o Menteith meaning a "low-lying bit of land in Menteith", is applied to the loch there because of the similarity of the sounds of the words laich and lake. Until the 19th century the body of water was known as the Loch of Menteith. The Lake of the Hirsel, Pressmennan Lake, Lake Louise and Raith Lake are man-made bodies of water in Scotland, referred to as lakes.
Lochs outside Scotland and Ireland
As "loch" is a common Gaelic word, it is found as the root of several Manx place names.
The United States naval port of Pearl Harbor, on the south coast of the main Hawaiian island of Oʻahu, is one of a complex of sea inlets. It contains three subareas called 'lochs' named East, Middle, and West or Kaihuopala‘ai, Wai‘awa, and Komoawa.
Loch Raven Reservoir is a reservoir in Baltimore County, Maryland.
Brenton Loch in the Falkland Islands is a sea loch, near Lafonia, East Falkland.
In the Scottish settlement of Glengarry County in present-day Eastern Ontario, there is a lake called Loch Garry. Loch Garry was named by those who settled in the area, Clan MacDonell of Glengarry, after the well-known loch their clan is from, Loch Garry in Scotland. Similarly, lakes named Loch Broom, Big Loch, Greendale Loch, and Loch Lomond can be found in Nova Scotia, along with Loch Leven in Newfoundland, and Loch Leven in Saskatchewan.
Loch Fyne is a fjord in Greenland named by Douglas Clavering in 1823.
See also
List of lochs of Scotland
List of loughs of Ireland
List of loughs of England
Ria
Lake-burst
References
Highlands and Islands of Scotland
Scottish coast and countryside
Hydronymy
Shibboleths
Lakes of Northern Ireland | Loch | Environmental_science | 1,162 |
373,974 | https://en.wikipedia.org/wiki/Ergine | Ergine, also known as lysergic acid amide and lysergamide, is an ergoline alkaloid that occurs in Clavicipitaceous fungi, which includes Convolvulaceae vines (Morning Glory), which have a permanent bond with these fungi. The most common source of ergine for consumers is the seeds of Ipomoea tricolor, Ipomoea corymbosa, and Argyreia nervosa; isoergine and lysergic acid propanolamide have also been shown to contribute to their psychoactivity.
Occurrence in nature
Ergine is not a biosynthetic endpoint itself, but rather a hydrolysis product of lysergic acid hydroxyethylamide (LAH), lysergic acid hydroxymethylethylamide (ergonovine), and ergopeptines or their ergopeptam precursors.
Lysergic acid hydroxyethylamide is very vulnerable to this hydrolysis, and many analyses of ergoline-containing fungi show little to no LAH and substantial amounts of ergine.
An ergine analog, 8-hydroxyergine, has also been found in natural products in two studies. Methylergonovine and methylmethylergonovine (methysergide) have also been found in a natural product in only one study; these are documented as semisynthetic chemicals, so the findings need to be repeated for certainty. The aforementioned chemicals are the only natural ergoamides.
LAH & ergine are predominant in Claviceps paspali, but are only found in trace amounts in the more well-known Claviceps purpurea (both are ergot-spreading fungi). The major products of C. purpurea are ergopeptines, but C. paspali does not generate ergopeptines. Ergonovine is the only ergoamide in C. purpurea in a substantial amount.
LAH & ergine are also found in the related fungi, Periglandula, which are permanently connected with Ipomoea tricolor, Ipomoea corymbosa, Argyreia nervosa ("morning glory", coaxihuitl, Hawaiian baby woodrose), and an estimated over 440 other Convolvulaceae (ergolines have been identified in 42 of these plants and not all of them contain ergine). Ergonovine is present in Ipomoea tricolor in one-tenth to one-third of the amount of ergine. This variable may account for the varying reports about the psychedelic effect of these seeds.
Other fungi that have been found to contain LAH and/or ergine:
Unidentified Acremonium species that infects sleepy grass (C. purpurea also infects sleepy grass).
Unidentified Acremonium species that infects drunken horse grass
Acremonium coenophialum (infects Festuca arundinacea)
Epichloë gansuensis var. inebriens (infects drunken horse grass)
Metarhizium brunneum
Metarhizium acridum
Metarhizium anisopliae
Metarhizium flavoviride
Metarhizium robertsii
Aspergillus leporis
Aspergillus homomorphus
Aspergillus hancockii
All of these fungi are related to Claviceps fungi. Aspergillus is considered to be a more distant relative of Claviceps.
Other fungi that possibly contain ergine (i.e. they have been found to contain ergonovine and/or ergopeptines):
Claviceps hirtella
Neotyphodium lolii
Unidentified Epichlöe and Neotyphodium (asexual forms of Epichlöe) species
Aspergillus fumigata
Aspergillus flavus
Botritis fabae
Curvularia lunata
Geotrichum candidum
Balansia cyperi
Balansia claviceps
Balansia epichloë
Epichloë amarillans
Epichloë cabralii (H)
Epichloë canadensis (H)
Epichloë coenophiala (H)
Epichloë festucae
Epichloë festucae var. lolii
Epichloë festucae var. lolii x E. typhina (H)
Epichloë inebriens
Epichloë glyceriae
Epichloë mollis
Epichloë typhina
Epichloë typhina ssp. poae
Epichloë typhina ssp. clarkii
Epichloë sp. AroTG-2(H)
Epichloë sp. FaTG-2(H)
Epichloë sp. FaTG-4(H)
Hypomyces aurantius
Sepedonium sp.
Cunnigbamella blakesleana
Mucor biemalis
Rhizopus nigricans
Psychedelic effects
Ergine has only been given a minuscule amount of attention. Albert Hofmann and his colleagues self-administered ergine, and it was adminstered in two clinical trials. Synthetic ergine was used in all cases. Albert Hofmann stated that ergine induces a "psychotomimetic" effect with "a marked narcotic component": "Tired, dreamy, incapable of clear thoughts. Very sensitive to noises which give an unpleasant sensation." There are parallels between Hofmann's comments and the ones in the two trials:
Heim 1968 also noted "paraesthesia", "synesthesia" and an "overestimation of the time that had passed" (isoergine), but also concluded, "our experiments with ᴅ-lysergic acid amide also confirm the results that Sᴏʟᴍꜱ had made with this substance, namely a predominantly sedative intoxication." Hofmann emphasized this sedative effect:
"Furthermore there is not only a quantitative difference between the principles of Ipomoea [tricolor] and Turbina corymbosa and LSD; there is likewise a qualitative one, LSD being a very specific hallucinogen, whereas the psychic effects of lysergic acid amide and the total alkaloids of these two plants are characterized by a pronounced narcotic component (Hofmann, 1968)."
"A substance very closely related to LSD, the monoethylamide of lysergic acid (LAE-32), in which an ethyl group is replaced by a hydrogen atom on the diethylamide residue of LSD, proved to be some ten times less psychoactive than LSD. The hallucinogenic effect is also qualitatively different: it is characterized by a narcotic component. This narcotic effect is yet more pronounced in lysergic acid amide (LA-111), in which both ethyl groups of LSD are displaced by hydrogen atoms. These effects, which I established in comparative self-experiments with LA-111 and LAE-32, were corroborated by subsequent clinical investigations."
"The experience had some strong narcotic effect, but at the same time there was a very strange sense of voidness. In this [void], everything loses its meaning. It is a very mystical experience."
Pharmacology
Pharmacodynamics
Ergine interacts with serotonin, dopamine, and adrenergic receptors similarly to but with lower affinity than lysergic acid diethylamide (LSD). The psychedelic effects of ergine can be attributed to activation of serotonin 5-HT2A receptors.
Chemistry
History
Ergine was first obtained by Sidney Smith and Geoffrey Willward Timmis in 1932.
Albert Hofmann was first to identify ergine as a natural constituent of Turbina corymbosa seeds.
Biosynthesis
The biosynthetic pathway to ergine starts like most other ergoline alkaloid- with the formation of the ergoline scaffold. This synthesis starts with the prenylation of L-tryptophan in an SN1 fashion with dimethylallyl diphosphate (DMAPP) as the prenyl donor and catalyzed by prenyltransferase 4-dimethylallyltryptophan synthase (DMATS), to form 4-L-dimethylallyltryptophan (4-L-DMAT). The DMAPP is derived from mevalonic acid. A three strep mechanism is proposed to form 4-L-DMAT: the formation of an allylic carbocation, a nucleophilic attack of the indole nucleus to the cation, followed by deprotonation to restore aromaticity and to generate 4-L-DMAT. 4-Dimethylallyltyptophan N-methyltransferase (EasF) catalyzes the N-methylation of 4-L-DMAT at the amino of the tryptophan backbone, using S-Adenosyl methionine (SAM) as the methyl source, to form 4-dimethylallyl-L-abrine (4-DMA-L-abrine). The conversion of 4-DMA-L-abrine to chanoclavine-I is thought to occur through a decarboxylation and two oxidation steps, catalyzed by the FAD dependent oxidoreductase, EasE, and the catalase, EasC. The chanoclavine intermediate is then oxidized to chanoclavine-l-aldehyde, catalyzed by the short-chain dehydrogenase/reductase (SDR), EasD.
From here, the biosynthesis diverges and the products formed are plant and fungus-specific. The biosynthesis of ergine in Claviceps purpurea will be exemplified, in which agroclavine is produced following the formation of chanoclavine-l-aldehyde, catalyzed by EasA through a keto-enol tautomerization to facilitate rotation about the C-C bond, followed by tautomerization back to the aldehyde and condensation with the proximal secondary amine to form an iminium species, which is subsequently reduced to the tertiary amine and yielding argoclavine. Cytochrome P450 monooxygenases (CYP450) are then thought to catalyze the formation of elymoclavine from argoclavine via a 2 electron oxidation. This is further converted to paspalic acid via a 4 electron oxidation, catalyzed by cloA, a CYP450 monooxygenase. Paspalic acid then undergoes isomerization of the C-C double bond in conjugation with the acid to form D-lysergic acid. While the specifics of the formation of ergine from D-lysergic acid are not known, it is proposed to occur through a nonribosomal peptide synthase (NRPS) with two enzymes primarily involve: D-lysergyl peptide synthase (LPS) 1 and 2.
Use of Morning Glory seeds as a drug
History
Albert Hofmann describes ergine as "the main constituent of ololiuhqui". Ololiuhqui was used by South American healers in shamanic healing ceremonies. Similarly, ingestion of morning glory seeds by Mazatec tribes to "commune with their gods" was reported by Richard Schultes in 1941 and is still practiced today.
According to the ethnobotanist R. Gordon Wasson, Thomas MacDougall and Francisco Ortega ("Chico"), a Zapotec guide and trader, should be credited for the discovery of the ceremonial use of Ipomoea tricolor seeds in Zapotec towns and villages in the uplands of southern Oaxaca. The seeds of both Ipomoea tricolor and Rivea corymbosa, another species which has a similar chemical profile, are used in some Zapotec towns.
The Central Intelligence Agency conducted research on the psychedelic properties of Rivea corymbosa seeds for MKULTRA.
Physiological effects
While its physiological effects vary from person to person, the following symptoms have been attributed to the consumption of ergine or ergine containing seeds:
Sedation
Visual and auditory hallucinations
Euphoria
Loss of motor control
Nausea
Vasoconstriction
Delusion
Anxiety
Paranoia
Irregular heartbeat
One study found that 2 of 4 human subjects experienced cardiovascular dysregulation and the study had to be halted, concluding that the ingestion of seeds containing ergine was less safe than commonly believed. Importantly this may have been a product of other substances within the seeds. The same study also observed that reactions were highly differing in type and intensity between different subjects.
Like other psychedelics, ergine is not considered to be addictive. Additionally, there are no known deaths directly associated with pharmacological effects of ergine consumption. All associated deaths are due to indirect causes, such as self-harm, impaired judgement, and adverse drug interactions. One known case involved a suicide that was reported in 1964 after ingestion of morning glory seeds. Another instance is a death due to falling off of a building after ingestion of Hawaiian baby woodrose seeds and alcohol. A study gave mice 3000 mg/kg with no lethal effects.
Adverse effects
A 2016 study showed that penniclavine was the predomiant alkaloid in Ipomoea tricolor seeds. Ergoclavines are known to cause convulsive ergotism, the milder form of ergotism. Gangrenous ergotism is caused by ergopeptines: the complex peptide moiety forces persistance at the receptor sites. Ergopeptines are rare in Convolvulaceae, being found in 10 species, not including the three that are commonly ingested, although Paulke 2014 says analytical evidence suggests that A. nervosa contains ergopeptines. Many people desire purified seed extracts, but the efficacy of this is questionable, as even pure ergine and ergonovine have shown toxic effects.
Ergine:
"The expression and behavior of the test subjects changed just 45 minutes after taking the substance: the test subjects appeared to be suffering, their facial expressions were deteriorating as if they had suffered a serious illness, and their movements were noticeably slower."
"In the self-reports of both test subjects, complaints about vegetative symptoms predominated: unpleasant, flu-like feeling of illness, nausea, sudden onset of nausea, with vomiting that could be stopped with 2 cm3 of Cyclicinum hydrochloricum. In addition, sensations of heat, sweating, dizziness, a feeling of heaviness and general tiredness were observed."
Heim 1968
Ergonovine:
"Walking in this dreamy state was difficult due to leg cramps and slight incoordination. There was always a great desire to lie supine."
"One of us (J.B.) felt the cramping in the legs as painful and debilitating."
"We all had a slight hangover the following morning."
"The mild entheogenic effects of ergonovine are similar to those of LSD. However, in dramatic contrast to LSD, the somatic effects of ergonovine greatly overshadow its psychic effects, so much so that we had no wish to ingest more than 10.0 mg,"
Bigwood 1979
Chemical coatings on seeds
Garden seeds, in general, may be coated with fungicides et. al. (e.g. neonicotinoids, Thiram, and ApronMaxx). It is rumored that this is the cause of the severe adverse effects that have been observed, but the seeds, themselves, contain toxins, specifically glycoresins and ergoclavines. Some people even believe that an emetic chemical is purposely added to the seeds to prevent people from ingesting them, but that has never been proven. One 1964 article states that reported adverse effects must come from the seeds, as the stated insecticide is too "inocuous" to humans to be responsible.
A related rumor is that the seeds contain cyanogenic glycosides. The UseNet post on which this is based contains two references, but neither of them support that claim, and Eckart Eich says that they probably don't occur in many Convolvulaceae. There is a similar claim in a publication from 1973, warning about "a strychnine-like alkaloid", but that is probably just a misapplication of the claim that peyote contains strychnine, which, itself, is a rumor.
Legal status
The legality of consuming, cultivating, and possessing ergine varies depending on the country.
There are no laws against possession of ergine-containing seeds in the United States. However, possession of the pure compound without a prescription or a DEA license would be prosecuted, as ergine, under the name "lysergic acid amide", is listed under Schedule III of the Controlled Substances Act. Similarly, ergine is considered a Class A substance in the United Kingdom, categorized as a precursor to LSD.
In most Australian states, the consumption of ergine containing materials is prohibited under state legislation.
In Canada, ergine is not illegal to possess as it is not listed under Canada's Controlled Drugs and Substances Act, though it is likely illegal to sell for human consumption.
In New Zealand, ergine is a controlled drug, however the plants and seeds of the morning glory species are legal to possess, cultivate, buy, and distribute.
See also
Argyreia nervosa
List of entheogenic/hallucinogenic species
List of psychoactive plants
Tlitliltzin (Ipomoea tricolor)
References
Further reading
External links
Hofmann, A. Teonanácatl and Ololiuqui, two ancient magic drugs of Mexico Bulletin on Narcotics 1971 1 3
TiHKAL (A & A Shulgin) #26
LSA Vault – Erowid
Alkaloids found in fungi
Lysergamides
Plant toxins
Quinoline alkaloids
Serotonin receptor agonists
Tryptamine alkaloids
Vasoconstrictors | Ergine | Chemistry | 3,910 |
51,328,770 | https://en.wikipedia.org/wiki/Mouse%20bungee | A mouse bungee is a device that secures the cable of a computer mouse, preventing the cable from tangling and providing full freedom of movement. It can be made out of plastic, metal, and silicon fabricated tools. In 1994 they were mostly used in offices, but their popularity rose within the gaming industry, and they are now mostly marketed to esports players.
Functionality
The mouse bungee consists of a wide, stable base plate with non-slip bottom and a crane-like, oblique, sprung clamp for the cable, which rises about 10 cm high. In plastic frames a stabilisation weight is incorporated, which ensures the necessary weight. Ideally, it is in front of the Mouse and the cable length is manually set so that the entire mouse pad can be easily reached with the mouse, but does not create unnecessary loops in the cable. The back of the cable remains still on the table without causing an annoyance. Some of the models also feature a USB hub, which asks for adding an additional input cable from the computer, but offers several output options, like USB 2.0 and USB 3.0.
History
Although DIY cord holders were popular since the introduction of corded computer mice, the first dedicated product came from the company Mouse Bungee, represented by the CEO Ed Larkin. Back in 1994, he introduced a simple solution which offered a mouse cord holder and a mouse pad. Since the idea didn't flourish within the business world, the company sold the project to Razer Inc back in 2010. Later that year Razer introduced a revised version without a mouse pad, and the product ended up as the current market leader within the field of Gaming Mouse Bungees. At that point the trend was created and other companies started following it. Soon enough all the major manufacturers of computer peripherals joined the market with their solution, and today there are over 20 different products on the market.
References
, press.razer.com.
The inventor of mouse bungees wasn’t actually a gamer, but it doesn’t matter, gdgtpreview.com.
See also
Computer accessibility
Computer Mouse
Computer
Computer peripherals | Mouse bungee | Technology | 433 |
1,167,036 | https://en.wikipedia.org/wiki/Robot%20locomotion | Robot locomotion is the collective name for the various methods that robots use to transport themselves from place to place.
Wheeled robots are typically quite energy efficient and simple to control. However, other forms of locomotion may be more appropriate for a number of reasons, for example traversing rough terrain, as well as moving and interacting in human environments. Furthermore, studying bipedal and insect-like robots may beneficially impact on biomechanics.
A major goal in this field is in developing capabilities for robots to autonomously decide how, when, and where to move. However, coordinating numerous robot joints for even simple matters, like negotiating stairs, is difficult. Autonomous robot locomotion is a major technological obstacle for many areas of robotics, such as humanoids (like Honda's Asimo).
Types of locomotion
Walking
See Passive dynamics
See Zero Moment Point
See Leg mechanism
See Hexapod (robotics)
Walking robots simulate human or animal gait, as a replacement for wheeled motion. Legged motion makes it possible to negotiate uneven surfaces, steps, and other areas that would be difficult for a wheeled robot to reach, as well as causes less damage to environmental terrain as wheeled robots, which would erode it.
Hexapod robots are based on insect locomotion, most popularly the cockroach and stick insect, whose neurological and sensory output is less complex than other animals. Multiple legs allow several different gaits, even if a leg is damaged, making their movements more useful in robots transporting objects.
Examples of advanced running robots include ASIMO, BigDog, HUBO 2, RunBot, and Toyota Partner Robot.
Rolling
In terms of energy efficiency on hard, flat surfaces, wheeled robots are the most efficient. This is because an ideal, non-deformable rolling (but not slipping) wheel loses no energy. This is in contrast to legged robots which suffer an impact with the ground at heel strike and lose energy as a result.
For simplicity, most mobile robots have four wheels or a number of continuous tracks. Some researchers have tried to create more complex wheeled robots with only one or two wheels. These can have certain advantages such as greater efficiency and reduced parts, as well as allowing a robot to navigate in confined places that a four-wheeled robot would not be able to.
Examples:
Boe-Bot,
Cosmobot,
Elmer,
Elsie,
Enon,
HERO,
IRobot Create,
iRobot's Roomba,
Johns Hopkins Beast,
Land Walker,
Modulus robot,
Musa,
Omnibot,
PaPeRo,
Phobot,
Pocketdelta robot,
Push the Talking Trash Can,
RB5X,
Rovio,
Seropi,
Shakey the robot,
Sony Rolly,
Spykee,
TiLR,
Topo,
TR Araña, and
Wakamaru.
Hopping
Several robots, built in the 1980s by Marc Raibert at the MIT Leg Laboratory, successfully demonstrated very dynamic walking. Initially, a robot with only one leg, and a very small foot, could stay upright simply by hopping. The movement is the same as that of a person on a pogo stick. As the robot falls to one side, it would jump slightly in that direction, in order to catch itself. Soon, the algorithm was generalised to two and four legs. A bipedal robot was demonstrated running and even performing somersaults. A quadruped was also demonstrated which could trot, run, pace, and bound.
Examples:
The MIT cheetah cub is an electrically powered quadruped robot with passive compliant legs capable of self-stabilizing in large range of speeds.
The Tekken II is a small quadruped designed to walk on irregular terrains adaptively.
Metachronal motion
Coordinated, sequential mechanical action having the appearance of a traveling wave is called a metachronal rhythm or wave, and is employed in nature by ciliates for transport, and by worms and arthropods for locomotion.
Slithering
Several snake robots have been successfully developed. Mimicking the way real snakes move, these robots can navigate very confined spaces, meaning they may one day be used to search for people trapped in collapsed buildings. The Japanese ACM-R5 snake robot can even navigate both on land and in water.
Examples:
Snake-arm robot,
Roboboa, and
Snakebot.
Swimming
See Autonomous underwater vehicles
Brachiating
Brachiation allows robots to travel by swinging, using energy only to grab and release surfaces. This motion is similar to an ape swinging from tree to tree. The two types of brachiation can be compared to bipedal walking motions (continuous contact) or running (ricochetal). Continuous contact is when a hand/grasping mechanism is always attached to the surface being crossed; ricochetal employs a phase of aerial "flight" from one surface/limb to the next.
Hybrid
Robots can also be designed to perform locomotion in multiple modes. For example, the Reconfigurable Bipedal Snake Robot can both slither like a snake and walk like a biped robot.
Biologically inspired locomotion
The desire to create robots with dynamic locomotive abilities has driven scientists to look to nature for solutions. Several robots capable of basic locomotion in a single mode have been invented but are found to lack several capabilities, hence limiting their functions and applications. Highly intelligent robots are needed in several areas such as search and rescue missions, battlefields, and landscape investigation. Thus robots of this nature need to be small, light, quick, and possess the ability to move in multiple locomotive modes. As it turns out, multiple animals have provided inspiration for the design of several robots. Some such animals are:
Pteromyini (flying squirrels)
Pteromyini (a tribe made up of flying squirrels) exhibit great mobility while on land by making use of their quadruped walking ability with high-degrees of freedom (DoF) legs. In air, flying squirrels glide through by utilizing lift forces from the membrane between their legs. They possess a highly flexible membrane that allows for unrestrained movement of the legs. They use their highly elastic membrane to glide while in air and demonstrate lithe movement on the ground. In addition, Pteromyini are able to exhibit multi-modal locomotion due to the membrane that connects the fore and hind legs which also enhances their gliding ability. It has been proven that a flexible membrane possesses a higher lift coefficient than rigid plates and delays the angle of attack at which stall occurs. The flying squirrel also possesses thick bundles on the edges of its membrane, wingtips and tail which helps to minimize fluctuations and unnecessary energy loss.
Pteromyini are able to boost their gliding ability due to the numerous physical attributes they possess.
The flexible muscle structure serves multiple purposes. For one, the plagiopatagium, which serves as the primary generator of lift for the flying squirrel, is able to effectively function due to its thin and flexible muscles. The plagiopatagium is able to control tension on the membrane due to contraction and expansion. Tension control can ultimately help in energy savings due to minimized fluttering of the membrane. Once the squirrel lands, it contracts its membrane to ensure that the membrane does not sag when it is walking.
The propatagium and uropatagium serve to provide extra lift for Pteromyini. While the propatagium is situated between the head and forelimbs of the flying squirrel, the uropatagium is located at the tail and hind limbs and these serve to provide the flying squirrel with increased agility and drag for landing.
Additionally, the flying squirrel possesses thick rope-like muscle structures on the edges of its membrane to maintain the shape of the membranes. These muscular structures called platysma, tibiocarpalis, and semitendinosus, are located on the propatagium, plagiopatagium and uropatagium respectively. These thick muscle structures serve to guard against unnecessary fluttering due to strong wind pressures during gliding hence minimizing energy loss.
The wingtips are situated at the forelimb wrists and serve to form an airfoil which minimizes the effect of induced drag due to the formation of wingtip vortices. The wingtips dampen the effects of the vortices and obstruct the induced drag from affecting the whole wing. Flying squirrels are able to unfold and fold their wingtips while gliding by using their thumbs. This serves to prevent undesired sagging of the wingtips.
The tail of the flying squirrel allows for improved gliding abilities as it plays a critical role. As opposed to other vertebrates, Pteromyini possess a tail that is flattened to gain more aerodynamic surface as they glide. This also allows the flying squirrel to maintain pitch angle stability of its tail. This is particularly useful during landing as the flying squirrel is able to widen its pitch angle and induce more drag so as to decelerate and land safely.
Furthermore, the legs and tail of Pteromyini serve to control their gliding direction. Due to the flexibility of the membranes around the legs, the chord angle and dihedral angle between the membrane and coronal plane of the body is controlled. This allows the animal to create rolling, pitching, and yawing movements which in turn control the speed and direction of the gliding. During landing, the animal is able to rapidly reduce its speed by increasing drag and changing its pitch angle using its membranes and further increasing air resistance by loosening the tension between the membranes of its legs.
Desmodus Rotundus (vampire bat)
The common vampire bats are known to possess powerful modes of terrestrial locomotion, such as jumping, and aerial locomotion such as gliding. Several studies have demonstrated that the morphology of the bat enables it to easily and effectively alternate between both locomotive modes. The anatomy that aids in this is essentially built around the largest muscle in the body of the bat, pectoralis profundus (posterior division). Between the two modes of locomotion, there are three bones that are shared. These three main bones are integral parts of the arm structure, namely the humerus, ulna, and radius. Since there already exists a sharing of components for both modes, no additional muscles are needed when transitioning from jumping to gliding.
A detailed study of the morphology of the shoulder of the bat shows that the bones of the arm are slightly sturdier and the ulna and the radius have been fused so as to accommodate heavy reaction forces from the ground
Schistocerca gregaria (desert locust)
The desert locust is known for its ability to jump and fly over long distances as well as crawl on land. A detailed study of the anatomy of this organism provides some detail about the mechanisms for locomotion. The hind legs of the locust are developed for jumping. They possess a semi-lunar process which consists of the large extensor tibiae muscle, small flexor tibiae muscle, and banana-shaped thickened cuticle. When the tibiae muscle flexes, the mechanical advantage of the muscles and the vertical thrust component of the leg extension are increased. These desert locusts utilize a catapult mechanism wherein the energy is first stored in the hind legs and then released to extend the legs.
In order for a perfect jump to occur, the locust must push its legs on the ground with a strong enough force so as to initiate a fast takeoff. The force must be adequate enough in order to attain a quick takeoff and decent jump height. The force must also be generated quickly. In order to effectively transition from the jumping mode to the flying mode, the insect must adjust the time during the wing opening to maximize the distance and height of the jump. When it is at the zenith of its jump, the flight mode becomes actuated.
Multi-modal robot locomotion based on bio-inspiration
Modeling of a multi-modal walking and gliding robot after Pteromyini (flying squirrels)
Following the discovery of the requisite model to mimic, researchers sought to design a legged robot that was capable of achieving effective motion in aerial and terrestrial environments by the use of a flexible membrane. Thus, to achieve this goal, the following design considerations had to be taken into account:
1. The shape and area of the membrane had to be consciously selected so that the intended aerodynamic capabilities of this membrane could be achieved. Additionally, the design of the membrane would affect the design of the legs since the membrane is attached to the legs.
2. The membrane had to be flexible enough to allow for unrestricted movement of the legs during gliding and walking. However, the amount of flexibility had to be controlled due to the fact that excessive flexibility could lead to a significant loss of energy caused by the oscillations at regions of the membrane where strong pressure occur.
3. The leg of the robot had to be designed to allow for appropriate torques for walking as well as gliding.
In order to incorporate these factors, close attention had to be paid to the characteristics of the flying squirrel. The aerodynamic features of the robot were modeled using dynamic modeling and simulation. By imitating the thick muscle bundles of the membrane of the flying squirrel, the designers were able to minimize the fluctuations and oscillations on the membrane edges of the robot, thus reducing needless energy loss. Furthermore, the amount of drag on the wing of the robot was reduced by the use of retractable wingtips thereby allowing for improved gliding abilities. Moreover, the leg of the robot was designed to incorporate sufficient torque after mimicking the anatomy of Pteryomini's leg using virtual work analysis.
Following the design of the leg and membrane of the robot, its average gliding ratio (GR) was determined to be 1.88. The robot functioned effectively, walking in several gait patterns and crawling with its high DoF legs. The robot was also able to land safely. These performances demonstrated the gliding and walking capabilities of the robot and its multi-modal locomotion
Modeling of a multi-modal jumping and gliding robot after the Desmodus Rotundus (vampire bat)
The design of the robot called Multi-Mo Bat involved the establishment of four primary phases of operation: energy storage phase, jumping phase, coasting phase, and gliding phase. The energy storing phase essentially involves the reservation of energy for the jumping energy. This energy is stored in the main power springs. This process additionally creates a torque around the joint of the shoulders which in turn configures the legs for jumping. Once the stored energy is released, the jump phase can be initiated. When the jump phase is initiated and the robot takes off from the ground, it transitions to the coast phase which occurs until the acme is reached and it begins to descend. As the robot descends, drag helps to reduce the speed at which it descends as the wing is reconfigured due to increased drag on the bottom of the airfoils. At this stage, the robot glides down.
The anatomy of the arm of the vampire bat plays a key role in the design of the leg of the robot. In order to minimize the number of Degrees of Freedom (DoFs), the two components of the arm are mirrored over the xz plane. This then creates the four-bar design of the leg structure of the robot which results in only two independent DoFs.
Modeling of a multi-modal jumping and flying robot after the Schistocerca gregaria (desert locust)
The robot designed was powered by a single DC motor which integrated the performances of jumping and flapping. It was designed as an incorporation of the inverted slider-crank mechanism for the construction of the legs, a dog-clutch system to serve as the mechanism for winching, and a rack-pinion mechanism used for the flapping-wing system. This design incorporated a very efficient energy storage and release mechanism and an integrated wing flapping mechanism.
A robot with features similar to the locust was developed. The primary feature of the robot's design was a gear system powered by a single motor which allowed the robot to perform its jumping and flapping motions. Just like the motion of the locust, the motion of the robot is initiated by the flexing of the legs to the position of maximum energy storage after which the energy is released immediately to generate the force necessary to attain flight.
The robot was tested for performance and the results demonstrated that the robot was able to jump to an approximate height of 0.9m while weighing 23g and flapping its wings at a frequency of about 19 Hz. The robot tested without flapping wings performed less impressively, showing about 30% decrease in jumping performance as compared to the robot with the wings. These results are quite impressive as it is expected that the reverse be the case since the weight of the wings should have impacted the jumping.
Approaches
Product optimization
Motion planning
Motion capture may be performed on humans, insects and other organisms.
Machine learning, typically with reinforcement learning.
Notable researchers in the field
Rodney Brooks
Marc Raibert
Jessica Hodgins
Red Whittaker
Shuuji Kajita, who introduced preview control to realize the anticipatory nature of walking in humanoid robots of the Humanoid Robotics Project.
See also
Microswimmer
References
External links
Robot Locomotion
Robot control | Robot locomotion | Physics,Engineering | 3,535 |
5,578,523 | https://en.wikipedia.org/wiki/Witt%20group | In mathematics, a Witt group of a field, named after Ernst Witt, is an abelian group whose elements are represented by symmetric bilinear forms over the field.
Definition
Fix a field k of characteristic not equal to 2. All vector spaces will be assumed to be finite-dimensional. Two spaces equipped with symmetric bilinear forms are equivalent if one can be obtained from the other by adding a metabolic quadratic space, that is, zero or more copies of a hyperbolic plane, the non-degenerate two-dimensional symmetric bilinear form with a norm 0 vector. Each class is represented by the core form of a Witt decomposition.
The Witt group of k is the abelian group W(k) of equivalence classes of non-degenerate symmetric bilinear forms, with the group operation corresponding to the orthogonal direct sum of forms. It is additively generated by the classes of one-dimensional forms. Although classes may contain spaces of different dimension, the parity of the dimension is constant across a class and so rk: W(k) → Z/2Z is a homomorphism.
The elements of finite order in the Witt group have order a power of 2; the torsion subgroup is the kernel of the functorial map from W(k) to W(kpy), where kpy is the Pythagorean closure of k; it is generated by the Pfister forms with a non-zero sum of squares. If k is not formally real, then the Witt group is torsion, with exponent a power of 2. The height of the field k is the exponent of the torsion in the Witt group, if this is finite, or ∞ otherwise.
Ring structure
The Witt group of k can be given a commutative ring structure, by using the tensor product of quadratic forms to define the ring product. This is sometimes called the Witt ring W(k), though the term "Witt ring" is often also used for a completely different ring of Witt vectors.
To discuss the structure of this ring one assumes that k is of characteristic not equal to 2, so that one may identify symmetric bilinear forms and quadratic forms.
The kernel of the rank mod 2 homomorphism is a prime ideal, I, of the Witt ring termed the fundamental ideal. The ring homomorphisms from W(k) to Z correspond to the field orderings of k, by taking signature with respective to the ordering. The Witt ring is a Jacobson ring. It is a Noetherian ring if and only if there are finitely many square classes; that is, if the squares in k form a subgroup of finite index in the multiplicative group of k.
If k is not formally real, the fundamental ideal is the only prime ideal of W and consists precisely of the nilpotent elements; W is a local ring and has Krull dimension 0.
If k is real, then the nilpotent elements are precisely those of finite additive order, and these in turn are the forms all of whose signatures are 0; W has Krull dimension 1.
If k is a real Pythagorean field then the zero-divisors of W are the elements for which some signature is 0; otherwise, the zero-divisors are exactly the fundamental ideal.
If k is an ordered field with positive cone P then Sylvester's law of inertia holds for quadratic forms over k and the signature defines a ring homomorphism from W(k) to Z, with kernel a prime ideal KP. These prime ideals are in bijection with the orderings Xk of k and constitute the minimal prime ideal spectrum MinSpec W(k) of W(k). The bijection is a homeomorphism between MinSpec W(k) with the Zariski topology and the set of orderings Xk with the Harrison topology.
The n-th power of the fundamental ideal is additively generated by the n-fold Pfister forms.
Examples
The Witt ring of C, and indeed any algebraically closed field or quadratically closed field, is Z/2Z.
The Witt ring of R is Z.
The Witt ring of a finite field Fq with q odd is Z/4Z if q ≡ 3 mod 4 and isomorphic to the group ring (Z/2Z)[F*/F*2] if q ≡ 1 mod 4.
The Witt ring of a local field with maximal ideal of norm congruent to 1 modulo 4 is isomorphic to the group ring (Z/2Z)[V] where V is the Klein 4-group.
The Witt ring of a local field with maximal ideal of norm congruent to 3 modulo 4 is (Z/4Z)[C2] where C2 is a cyclic group of order 2.
The Witt ring of Q2 is of order 32 and is given by
.
Invariants
Certain invariants of a quadratic form can be regarded as functions on Witt classes. Dimension mod 2 is a function on classes: the discriminant is also well-defined. The Hasse invariant of a quadratic form is again, a well-defined function on Witt classes with values in the Brauer group of the field of definition.
Rank and discriminant
A ring is defined over K, Q(K), as a set of pairs (d, e) with d in K*/K*2 and e in Z/2Z. Addition and multiplication are defined by:
.
Then there is a surjective ring homomorphism from W(K) to this obtained by mapping a class to discriminant and rank mod 2. The kernel is I2. The elements of Q may be regarded as classifying graded quadratic extensions of K.
Brauer–Wall group
The triple of discriminant, rank mod 2 and Hasse invariant defines a map from W(K) to the Brauer–Wall group BW(K).
Witt ring of a local field
Let K be a complete local field with valuation v, uniformiser π and residue field k of characteristic not equal to 2. There is an injection W(k) → W(K) which lifts the diagonal form ⟨a1,...an⟩ to ⟨u1,...un⟩ where ui is a unit of K with image ai in k. This yields
identifying W(k) with its image in W(K).
Witt ring of a number field
Let K be a number field. For quadratic forms over K, there is a Hasse invariant ±1 for every finite place corresponding to the Hilbert symbols. The invariants of a form over a number field are precisely the dimension, discriminant, all local Hasse invariants and the signatures coming from real embeddings.
The symbol ring is defined over K, Sym(K), as a set of triples (d, e, f ) with d in K*/K*2, e in Z/2 and f a sequence of elements ±1 indexed by the places of K, subject to the condition that all but finitely many terms of f are +1, that the value on acomplex places is +1 and that the product of all the terms in f is +1. Let [a, b] be the sequence of Hilbert symbols: it satisfies the conditions on f just stated.
Addition and multiplication is defined as follows:
.
Then there is a surjective ring homomorphism from W(K) to Sym(K) obtained by mapping a class to discriminant, rank mod 2, and the sequence of Hasse invariants. The kernel is I3.
The symbol ring is a realisation of the Brauer-Wall group.
Witt ring of the rationals
The Hasse–Minkowski theorem implies that there is an injection
.
One can make this concrete and compute the image by using the "second residue homomorphism" W(Qp) → W(Fp). Composed with the map W(Q) → W(Qp), one obtains a group homomorphism ∂p: W(Q) → W(Fp) (for p = 2, ∂2 is defined to be the 2-adic valuation of the discriminant, taken mod 2).
One will then have a split exact sequence
which can be written as an isomorphism
where the first component is the signature.
Witt ring and Milnor's K-theory
Let k be a field of characteristic not equal to 2. The powers of the ideal I of forms of even dimension ("fundamental ideal") in form a descending filtration and one may consider the associated graded ring, that is the direct sum of quotients . Let be the quadratic form considered as an element of the Witt ring. Then is an element of I and correspondingly a product of the form
is an element of . John Milnor in a 1970 paper proved that the mapping from to that sends to is multilinear and maps Steinberg elements (elements such that for some and such that one has ) to 0. This means that this mapping defines a homomorphism from the Milnor ring of k to the graded Witt ring. Milnor showed also that this homomorphism sends elements divisible by 2 to 0 and that it is surjective. In the same paper, he made a conjecture that this homomorphism is an isomorphism for all fields k (of characteristic different from 2). This became known as the Milnor conjecture on quadratic forms.
The conjecture was proved by Dmitry Orlov, Alexander Vishik, and Vladimir Voevodsky in 1996 (published in 2007) for the case , leading to increased understanding of the structure of quadratic forms over arbitrary fields.
Grothendieck-Witt ring
The Grothendieck-Witt ring GW is a related construction generated by isometry classes of nonsingular quadratic spaces with addition given by orthogonal sum and multiplication given by tensor product. Since two spaces that differ by a hyperbolic plane are not identified in GW, the inverse for the addition needs to be introduced formally through the construction that was discovered by Grothendieck (see Grothendieck group). There is a natural homomorphism GW → Z given by dimension: a field is quadratically closed if and only if this is an isomorphism. The hyperbolic spaces generate an ideal in GW and the Witt ring W is the quotient. The exterior power gives the Grothendieck-Witt ring the additional structure of a λ-ring.
Examples
The Grothendieck-Witt ring of C, and indeed any algebraically closed field or quadratically closed field, is Z.
The Grothendieck-Witt ring of R is isomorphic to the group ring Z[C2], where C2 is a cyclic group of order 2.
The Grothendieck-Witt ring of any finite field of odd characteristic is Z ⊕ Z/2Z with trivial multiplication in the second component. The element (1, 0) corresponds to the quadratic form ⟨a⟩ where a is not a square in the finite field.
The Grothendieck-Witt ring of a local field with maximal ideal of norm congruent to 1 modulo 4 is isomorphic to Z ⊕ (Z/2Z)3.
The Grothendieck-Witt ring of a local field with maximal ideal of norm congruent to 3 modulo 4 it is Z' ⊕ Z/4Z ⊕ Z/2Z.
Grothendieck-Witt ring and motivic stable homotopy groups of spheres
Fabien Morel showed that the Grothendieck-Witt ring of a perfect field is isomorphic to the motivic stable homotopy group of spheres π0,0(S0,0) (see "A¹ homotopy theory").
Witt equivalence
Two fields are said to be Witt equivalent if their Witt rings are isomorphic.
For global fields there is a local-to-global principle: two global fields are Witt equivalent if and only if there is a bijection between their places such that the corresponding local fields are Witt equivalent. In particular, two number fields K and L are Witt equivalent if and only if there is a bijection T between the places of K and the places of L and a group isomorphism t between their square-class groups, preserving degree 2 Hilbert symbols. In this case the pair (T, t) is called a reciprocity equivalence or a degree 2 Hilbert symbol equivalence. Some variations and extensions of this condition, such as "tame degree l Hilbert symbol equivalence", have also been studied.
Generalizations
Witt groups can also be defined in the same way for skew-symmetric forms, and for quadratic forms, and more generally ε-quadratic forms, over any *-ring R.
The resulting groups (and generalizations thereof) are known as the even-dimensional symmetric L-groups L2k(R) and even-dimensional quadratic L-groups L2k(R). The quadratic L-groups are 4-periodic, with L0(R) being the Witt group of (1)-quadratic forms (symmetric), and L2(R) being the Witt group of (−1)-quadratic forms (skew-symmetric); symmetric L-groups are not 4-periodic for all rings, hence they provide a less exact generalization.
L-groups are central objects in surgery theory, forming one of the three terms of the surgery exact sequence.
See also
Reduced height of a field
Notes
References
Further reading
External links
Witt rings in the Springer encyclopedia of mathematics
Quadratic forms | Witt group | Mathematics | 2,887 |
68,119,217 | https://en.wikipedia.org/wiki/Boletus%20pseudopinophilus | Boletus pseudopinophilus is a species of porcini-like fungus native to eastern North America, where it grows under Pinus elliottii and Pinus palustris. Previously regarded as Boletus pinophilus it was found to have diverged significantly from the latter species.
References
pseudopinophilus
Fungi of North America
Edible fungi
Fungi described in 2019
Fungus species | Boletus pseudopinophilus | Biology | 81 |
72,731,277 | https://en.wikipedia.org/wiki/Hygronarius | Hygronarius is a genus of fungi in the family Cortinariaceae.
Taxonomy
The genus was created in 2022 when the family Cortinariaceae, which previously contained only the one genus of Cortinarius was reclassified based on genomic data and split into the genera of Cortinarius, Aureonarius, Austrocortinarius, Calonarius, Cystinarius, Hygronarius, Mystinarius, Phlegmacium, Thaxterogaster and Volvanarius.
The genus is further divided with subgenus and section classifications:
Hygronarius subgenus Hygronarius includes the section: Hygronarius.
Hygronarius subgenus Viscincisi includes the sections: Austroduracini and Viscincisi.
Etymology
The name Hygronarius derives from the word hygrophanous and Cortinarius. This is in reference to the hygrophanous caps of the species within this genera which display colour variations depending on moisture content.
Species
, Species Fungorum accepted 5 species of Hygronarius.
Hygronarius austroduracinus (M.M. Moser) Liimat. & Niskanen (2022)
Hygronarius parahumilis (Garnica) Liimat. & Niskanen (2022)
Hygronarius renidens (Fr.) Niskanen & Liimat. (2022)
Hygronarius viridibasalis (M.M. Moser) Liimat. & Niskanen (2022)
Hygronarius viscincisus (Soop) Niskanen & Liimat. (2022)
References
Agaricales genera
Cortinariaceae | Hygronarius | Biology | 379 |
1,586,724 | https://en.wikipedia.org/wiki/Triangulum%20Minus | Triangulum Minus (Latin for the Smaller Triangle) was a constellation created by Johannes Hevelius. Its name is sometimes wrongly written as Triangulum Minor. It was formed from the southern parts of his Triangula (plural form of Triangulum), alongside Triangulum Majus, but is no longer in use. The triangle was defined by the fifth-magnitude stars ι Trianguli (6 Tri), 10 Trianguli, and 12 Trianguli.
Also known as TZ Trianguli, 6 Trianguli is a multiple star system with a combined magnitude of 4.7, whose main component is a yellow giant of spectral type G5III.
References
External links
Ian Ridpath's Star Tales
Triangulum Minor Shane Horvatin
Former constellations
Constellations listed by Johannes Hevelius | Triangulum Minus | Astronomy | 170 |
67,801,265 | https://en.wikipedia.org/wiki/Guilded | Guilded is a VoIP, instant messaging, and digital distribution platform designed by Guilded Inc. and was bought by Roblox Corporation on August 16, 2021 for $90M. Guilded is based in San Francisco. Users communicate with voice calls, video calls, text messaging, media and files in private chats or as part of communities called "servers". Guilded was founded by Eli Brown, a former Facebook and Xbox employee. Guilded is available on Windows, Linux, macOS, Android, and iOS.
Guilded is a main competitor of Discord and primarily focuses on video game communities, such as those focused on competitive gaming and esports. It provides features intended for video gaming clans, such as scheduling tools and integrated calendars. Guilded is developed by Guilded, Inc. which has been an independent product group of the Roblox Corporation since August 16, 2021.
On May 31, 2024, Roblox Corporation announced that all current accounts must have a Roblox account linked before July 15, 2024 to continue using their Guilded account, while new users will only have the option to sign up with Roblox.
On October 12, 2024, Guilded restricted access to users from Russia due to Guilded having the fear that it would be blocked in the country.
References
2017 software
Android (operating system) software
Freeware
IOS software
Instant messaging clients for Linux
Instant messaging clients
Internet properties established in 2017
MacOS instant messaging clients
Proprietary cross-platform software
Proprietary freeware for Linux
Voice over IP clients for Linux
Windows instant messaging clients | Guilded | Technology | 320 |
3,145,455 | https://en.wikipedia.org/wiki/Otto%20Struve%20Telescope | The Otto Struve Telescope was the first major telescope to be built at McDonald Observatory. Located in the Davis Mountains in West Texas, the Otto Struve Telescope was designed by Warner & Swasey Company and constructed between 1933 and 1939 by the Paterson-Leitch Company. Its mirror was the second largest in the world at the time. It was named after the Ukrainian-American astronomer of Baltic German origin Otto Struve in 1966, three years after his death; Struve had been the director of McDonald Observatory from 1932–1950.
The Davis Mountains is an excellent location for astronomical research because of the clear dry air and moderately high elevation. The remote nature of the facility proved to be a significant challenge in transporting such a large mirror. It was a very precarious journey for the Otto Struve Telescope's mirror to this remote part of Texas and up to the top of Mount Locke. The mirror was transported from the local town of Fort Davis up the mountain by Carleton D. Wilson, owner of a local trucking company, while locals cheered as they looked on.
The Otto Struve telescope is still in use today. It is updated with modern imaging detectors allowing astronomers to conduct many types of research.
Noted applications and Discoveries
The telescope was one of two used to set up and define the Johnson-Morgan UBV photometric system.
In 1949, G. Kuiper of Yerkes Observatory discovered a new moon of planet Neptune, named Nereid. The moon was discovered on photographic plates taken in a search for moons of Neptune.
Contemporaries on commissioning
The Otto Struve telescope saw first light in 1939, behind the 100-inch Hooker telescope and ahead of two large British Commonwealth telescopes, both in Canada. Many competing projects were delayed due to the war in the early 1940s.
Four largest telescopes in 1939:
See also
List of largest optical telescopes in the 20th century
List of largest optical reflecting telescopes
List of the largest optical telescopes in the contiguous United States
Notes
References
External links
"Pour Three Ton Telescope Mirror." Popular Science, April 1934, p. 41.
Science: The 82-Inch McDonald Telescope (1939), industrial film capturing the construction and design of the Otto Struve Telescope, Texas Archive of the Moving Image.
Telescopes
University of Texas at Austin | Otto Struve Telescope | Astronomy | 462 |
36,718,435 | https://en.wikipedia.org/wiki/Netgear%20Switch%20Discovery%20Protocol | Netgear Switch Discovery Protocol (NSDP) is a management protocol for several network device families, designed by Netgear.
Message structure
Common message header
Message body record structure
Message body records are type–length–value (TLV) structures. Type field may be one of following values in the table(list in incomplete):
Protocol flow examples
Network devices discovery (MAC-address an device model discovery):
Host with MAC=XX:XX:XX:XX:XX:XX from UDP-port 63321 or 63323 sending packet to broadcast IP-address 255.255.255.255 and UDP-port 63322 or 63324
Header @0x00000000 0x01 0x01 0x000000000000 0xXXXXXXXXXXXX 0x000000000000 0x0000 0x0001 0x4E534450 0x00000000
Body @0x00000020 0x0001 0x0000 0x0004 0x0000
Marker @0x00000028 0xFFFF0000
EACH Device responds with message like
Header @0x00000000 0x01 0x02 0x000000000000 0xXXXXXXXXXXXX 0xYYYYYYYYYYYY 0x0000 0x0001 0x4E534450 0x00000000
Body @0x00000020 0x0001 0x0028 0x47 0x53 0x31 0x30 0x35 0x45 0x20*0x22 0x0004 0x0006 0xYYYYYYYYYYYY
Marker @0x00000058 0xFFFF0000
Device support for protocol
GS105E ProSAFE Plus
GS108E ProSAFE Plus
GS724T
GS748T
FS116E (IP-network description and Firmware version TLVs are not supported)
FS726TP (uses 63323 and 63324 UDP-ports for interconnection)
Devices firmware update
Device firmware update is made with TFTP protocol, but you need to send NSDP request to turn on TFTP-server first.
See also
IP
UDP
MAC
Netgear
References
External links
NETGEAR official site
openSource Perl-written cross-platform toolkit for NSDP managed devices project site (in russian)
LinNetx openSource C-written utility for ProsafePlus switches management via NSDP, not operational
ngadmin C-written admin utility; GPLv2 license
ProSafeLinux Remark: sparse information; FreeBSD license
NSDP Protocol Wireshark dissector Remark: GPL license
Nsdtool – a toolset of scripts to detect NETGEAR switches in local networks
NETGEAR firmware update
NSDP
Network management
Device discovery protocols | Netgear Switch Discovery Protocol | Technology,Engineering | 631 |
40,651,042 | https://en.wikipedia.org/wiki/Lycoctonine | Lycoctonine is a plant alkaloid and a precursor to the ABC ring system of taxoids. Distinguish from lycaconitine, which is the N-succinimido-benzoic-ester.
External links
Pyrrolidine alkaloids
Taxanes | Lycoctonine | Chemistry | 63 |
24,548,944 | https://en.wikipedia.org/wiki/Rare%20Earths%20Facility | The Rare Earths Facility was a production plant for various chemicals and metals including thorium, uranium, and radium. It was located in West Chicago, Illinois, USA.
History
The site was opened in 1931 by the Lindsay Light and Chemical Company. It processed ores like monazite to produce elements, including thorium and uranium. It also made gaslight mantles, and during World War II, hydrofluoric acid.
In 1958, it became owned by American Potash and Chemical Company (AMPOT), which at one point had a 'Lindsay Chemical Division.'
In 1967, AMPOT, and thus the facility, were bought by Kerr-McGee. The Rare Earths Facility were closed by Kerr-McGee in 1973.
In 2005, KMCC was spun off from Kerr-McGee as Tronox, shortly before Kerr-McGee was acquired by Anadarko Petroleum. Tronox inherited responsibility for the Rare Earths Facility and other sites. Tronox went bankrupt in 2009 and shareholders sued Anadarko Petroleum, partly for having misled investors in Tronox about its environmental debts.
Pollution
In the early years, people from the surrounding community used the mill tailings as fill dirt in various properties, such as their yards and gardens. A woman who played in such a yard as a child later sued Kerr-McGee over her Hodgkin's disease and settled out of court in 1988.
Radioactive waste from the plant was put in a local landfill that later became a public park called Reed-Keppler Park.
Kress Creek and West Branch Dupage River (including sediments, banks, and floodplains) were contaminated by years of rainwater runoff from REF going into a storm sewer and then into the creek. The floodplain includes people's yards.
The West Chicago Sewage Treatment Plant was contaminated when mill tailings from REF were used as fill dirt there. This also resulted in pollution of the West Branch Dupage River from runoff and erosion.
In 1991, the Illinois Department of Public Health found elevated cancer rates in the community.
See also
EnergySolutions
References
1931 establishments in Illinois
1973 disestablishments in Illinois
Metallurgical facilities
Metal companies based in Illinois
Chemical companies of the United States | Rare Earths Facility | Chemistry,Materials_science | 457 |
37,663,509 | https://en.wikipedia.org/wiki/ArduPilot | ArduPilot is an open source, uncrewed vehicle Autopilot Software Suite, capable of controlling:
Multirotor drones
Fixed-wing and VTOL aircraft
Helicopters
ROVs
Ground rovers
Boats
Submarines
Uncrewed Surface Vessels (USVs)
Antenna trackers
Blimps
ArduPilot was originally developed by hobbyists to control model aircraft and rovers and has evolved into a full-featured and reliable autopilot used by industry, research organisations and amateurs.
Software and Hardware
Software suite
The ArduPilot software suite consists of navigation software (typically referred to as firmware when it is compiled to binary form for microcontroller hardware targets) running on the vehicle (either Copter, Plane, Rover, AntennaTracker, or Sub), along with ground station controlling software including Mission Planner, APM Planner, QGroundControl, MavProxy, Tower and others.
ArduPilot source code is stored and managed on GitHub, with over 800 contributors.
The software suite is automatically built nightly, with continuous integration and unit testing provided by Travis CI, and a build and compiling environment including the GNU cross-platform compiler and Waf. Pre-compiled binaries running on various hardware platforms are available for user download from ArduPilot's sub-websites.
Supported hardware
Copter, Plane, Rover, AntennaTracker, or Sub software runs on a wide variety of embedded hardware (including full blown Linux computers), typically consisting of one or more microcontroller or microprocessor connected to peripheral sensors used for navigation. These sensors include MEMS gyroscopes and accelerometers at a minimum, necessary for multirotor flight and plane stabilization. Sensors usually include, in addition, one or more compass, altimeter (barometric) and GPS, along with optional additional sensors such as optical flow sensors, airspeed indicators, laser or sonar altimeters or rangefinders, monocular, stereoscopic or RGB-D cameras. Sensors may be on the same electronic board, or external.
Ground Station software, used for programming or monitoring vehicle operation, is available for Windows, Linux, macOS, iOS, and Android.
ArduPilot runs on a wide variety of hardware platforms, including the following, listed in alphabetical order:
Intel Aero (Linux or STM32 Base)
APM 2.X (Atmel Mega Microcontroller Arduino base), designed by Jordi Munoz in 2010. APM, for ArduPilotMega, only runs on older versions of ArduPilot.
BeagleBone Blue and PXF Mini (BeagleBone Black cape).
The Cube, formerly called Pixhawk 2, (ARM Cortex microcontroller base), designed by ProfiCNC in 2015.
Edge , drone controller with video streaming system, designed by Emlid.
Erle-Brain , (Linux base) designed by Erle Robotics.
Intel Minnowboard (Linux Base).
Navigator Flight Controller by Blue Robotics
Navio2 and Navio+ (Raspberry Pi Linux based), designed by Emlid.
Parrot Bebop, and Parrot C.H.U.C.K., designed by Parrot, S.A.
Pixhawk, (ARM Cortex microcontroller base), originally designed by Lorenz Meier and ETH Zurich, improved and launched in 2013 by PX4, 3DRobotics, and the ArduPilot development team.
PixRacer, (ARM Cortex microcontroller base) designed by AUAV.
Qualcomm SnapDragon (Linux base).
Virtual Robotics VRBrain (ARM Cortex microcontroller base).
Xilinx SoC Zynq processor (Linux base, ARM and FPGA processor).
In addition to the above base navigation platforms, ArduPilot supports integration and communication with on-vehicle companion, or auxiliary computers for advanced navigation requiring more powerful processing. These include NVidia TX1 and TX2 ( Nvidia Jetson architecture), Intel Edison and Intel Joule, HardKernel ODROID, and Raspberry Pi computers.
Features
Common to all vehicles
ArduPilot provides a large set of features, including the following common for all vehicles:
Fully autonomous, semi-autonomous and fully manual flight modes, programmable missions with 3D waypoints, optional geofencing.
Stabilization options to negate the need for a third party co-pilot.
Simulation with a variety of simulators, including ArduPilot Software in the Loop (SITL) Simulator.
Large number of navigation sensors supported, including several models of RTK GPSs, traditional L1 GPSs, barometers, magnetometers, laser and sonar rangefinders, optical flow, ADS-B transponder, infrared, airspeed, sensors, and computer vision/motion capture devices.
Sensor communication via SPI, I²C, CAN Bus, Serial communication, SMBus.
Failsafes for loss of radio contact, GPS and breaching a predefined boundary, minimum battery power level.
Support for navigation in GPS denied environments, with vision-based positioning, optical flow, SLAM, Ultra Wide Band positioning.
Support for actuators such as parachutes and magnetic grippers.
Support for brushless and brushed motors.
Photographic and video gimbal support and integration.
Integration and communication with powerful secondary, or "companion", computers
Rich documentation through ArduPilot wiki.
Support and discussion through ArduPilot discourse forum, Gitter chat channels, GitHub, Facebook.
Copter-specific
Flight modes: Stabilize, Alt Hold, Loiter, RTL (Return-to-Launch), Auto, Acro, AutoTune, Brake, Circle, Drift, Guided, (and Guided_NoGPS), Land, PosHold, Sport, Throw, Follow Me, Simple, Super Simple, Avoid_ADSB.
Auto-tuning
Wide variety of frame types supported, including tricopters, quadcopters, hexacopters, flat and co-axial octocopters, and custom motor configurations
Support for traditional electric and gas helicopters, mono copters, tandem helicopters.
Plane-specific
Fly By Wire modes, loiter, auto, acrobatic modes.
Take-off options: Hand launch, bungee, catapult, vertical transition (for VTOL planes).
Landing options: Adjustable glide slope, helical, reverse thrust, net, vertical transition (for VTOL planes).
Auto-tuning, simulation with JSBSIM, X-Plane and RealFlight simulators.
Support for a large variety of VTOL architectures: Quadplanes, Tilt wings, tilt rotors, tail sitters, ornithopters.
Optimization of 3 or 4 channel airplanes.
Rover-specific
Manual, Learning, Auto, Steering, Hold and Guided operational modes.
Support for wheeled and track architectures.
Submarine-specific
Depth hold: Using pressure-based depth sensors, submarines can maintain depth within a few centimeters.
Light Control: Control of subsea lighting through the controller.
ArduPilot is fully documented within its wiki, totaling the equivalent of about 700 printed pages and divided in six top sections: The Copter, Plane, Rover, and Submarine vehicle related subsections are aimed at users. A "developer" subsection for advanced uses is aimed primarily at software and hardware engineers, and a "common" section regrouping information common to all vehicle types is shared within the first four sections.
ArduPilot use cases
Hobbyists and amateurs
Drone racing
Building and operation of radio control models for recreation
Professional
Aerial photogrammetry
Aerial photography and filmmaking.
Remote sensing
Search and rescue
Robotic applications
Academic research
Package delivery
History
Early years, 2007–2012
The ArduPilot project earliest roots date back to late 2007 when Jordi Munoz, who later co-founded 3DRobotics with Chris Anderson, wrote an Arduino program (which he called "ArduCopter") to stabilize an RC Helicopter. In 2009 Munoz and Anderson released Ardupilot 1.0 (flight controller software) along with a hardware board it could run on. That same year Munoz, who had built a traditional RC helicopter UAV able to fly autonomously, won the first Sparkfun AVC competition. The project grew further thanks to many members of the DIY Drones community, including Chris Anderson who championed the project and had founded the forum based community earlier in 2007.
The first ArduPilot version supported only fixed-wing aircraft and was based on a thermopile sensor, which relies on determining the location of the horizon relative to the aircraft by measuring the difference in temperature between the sky and the ground. Later, the system was improved to replace thermopiles with an Inertial Measurement Unit (IMU) using a combination of accelerometers, gyroscopes and magnetometers. Vehicle support was later expanded to other vehicle types which led to the Copter, Plane, Rover, and Submarine subprojects.
The years 2011 and 2012 witnessed an explosive growth in the autopilot functionality and codebase size, thanks in large part to new participation from Andrew "Tridge" Tridgell and HAL author Pat Hickey. Tridge's contributions included automatic testing and simulation capabilities for Ardupilot, along with PyMavlink and Mavproxy. Hickey was instrumental in bringing the AP_ HAL library to the code base: HAL (Hardware Abstraction Layer) greatly simplified and modularized the code base by introducing and confining low-level hardware implementation specifics to a separate hardware library. The year 2012 also saw Randy Mackay taking the role of lead maintainer of Copter, after a request from former maintainer Jason Short, and Tridge taking over the role of lead Plane maintainer, after Doug Weibel who went on to earn a Ph.D. in Aerospace Engineering. Both Randy and Tridge are current lead maintainers to date.
The free software approach to ArduPilot code development is similar to that of the Linux Operating system and the GNU Project, and the PX4/Pixhawk and Paparazzi Project, where low cost and availability enabled hobbyists to build autonomous small remotely piloted aircraft, such as micro air vehicles and miniature UAVs. The drone industry, similarly, progressively leveraged ArduPilot code to build professional, high-end autonomous vehicles.
Maturity, 2013–2016
While early versions of ArduPilot used the APM flight controller, an AVR CPU running the Arduino open-source programming language (which explains the "Ardu" part of the project name), later years witnessed a significant re-write of the code base in C++ with many supporting utilities written in Python.
Between 2013 and 2014 ArduPilot evolved to run on a range of hardware platforms and operating system beyond the original Arduino Atmel based microcontroller architecture, first with the commercial introduction of the Pixhawk hardware flight controller, a collaborative effort between PX4, 3DRobotics and the ArduPilot development team, and later to the Parrot's Bebop2 and the Linux-based flight controllers like Raspberry Pi based NAVIO2 and BeagleBone based ErleBrain. A key event within this time period included the first flight of a plane under Linux in mid 2014.
Late 2014 saw the formation of DroneCode, formed to bring together the leading open source UAV software projects, and most notably to solidify the relationship and collaboration of the ArduPilot and the PX4 projects. ArduPilot's involvement with DroneCode ended in September 2016. 2015 was also a banner year for 3DRobotics, a heavy sponsor of ArduPilot development, with its introduction of the Solo quadcopter, an off the shelf quadcopter running ArduPilot. Solo's commercial success, however, was not to be.
Fall of 2015 again saw a key event in the history of the autopilot, with a swarm of 50 planes running ArduPilot simultaneously flown at the Advanced Robotic Systems Engineering Laboratory (ARSENL) team at the Naval Postgraduate School.
Within this time period, ArduPilot's code base was significantly refactored, to the point where it ceased to bear any similarity to its early Arduino years.
Current, 2018–present
ArduPilot code evolution continues with support for integrating and communicating with powerful companion computers for autonomous navigation, plane support for additional VTOL architectures, integration with ROS, support for gliders, and tighter integration for submarines. The project evolves under the umbrella of ArduPilot.org, a project within the Software in the Public Interest (spi-inc.org) not-for-profit organisation. ArduPilot is sponsored in part by a growing list of corporate partners.
UAV Outback Challenge
In 2012, the Canberra UAV Team successfully took first place in the prestigious UAV Outback Challenge. The CanberraUAV Team included ArduPlane Developers and the airplane flown was controlled by an APM 2 Autopilot. In 2014 the CanberraUAV Team and ArduPilot took first place again, by successfully delivering a bottle to the "lost" hiker. In 2016 ArduPilot placed first in the technically more challenging competition, ahead of strong competition from international teams.
Community
ArduPilot is jointly managed by a group of volunteers located around the world, using the Internet (discourse based forum, gitter channel) to communicate, plan, develop and support it. The development team meets weekly in a chat meeting, open to all, using Mumble. In addition, hundreds of users contribute ideas, code and documentation to the project. ArduPilot is licensed under the GPL Version 3 and is free to download and use.
Customizability
The flexibility of ArduPilot makes it very popular in the DIY field but it has also gained popularity with professional users and companies. 3DRobotics' Solo quadcopter, for instance, uses ArduPilot, as have a large number of professional aerospace companies such as Boeing. The flexibility allows for support of a wide variety of frame types and sizes, different sensors, camera gimbals and RC transmitters depending on the operator's preferences.
ArduPilot has been successfully integrated into many airplanes such as the Bixler 2.0. The customizability and ease of installation have allowed the ArduPilot platform to be integrated for a variety of missions. The Mission Planner (Windows) ground control station allows the user to easily configure, program, use, or simulate an ArduPilot board for purposes such as mapping, search and rescue, and surveying areas.
See also
Open-source robotics
Other projects for autonomous aircraft control:
PX4 autopilot
Paparazzi Project
Slugs
Other projects for ground vehicles & cars driven:
OpenPilot
Tesla Autopilot
References
Unmanned aerial vehicles
Unmanned underwater vehicles
Robots
Unmanned ground vehicles
Software using the GNU General Public License
Free software programmed in C++
Free software programmed in Python
Cross-platform free software | ArduPilot | Physics,Technology | 3,127 |
33,701,720 | https://en.wikipedia.org/wiki/2-sec-Butyl-4%2C5-dihydrothiazole | 2-sec-Butyl-4,5-dihydrothiazole (also known as SBT) is a thiazoline compound with the molecular formula C7H13NS. A volatile pheromone found in rodents such as mice and rats, SBT is excreted in the urine and promotes aggression amongst males while inducing synchronized estrus in females.
Binding to MUP
Mouse major urinary proteins (MUPs) are responsible for binding to hydrophobic ligands such as the pheromone SBT. SBT binds within MUP-I's barrel-shaped active site, forming a hydrogen bond with a water molecule within the active site, which in turn is stabilized by forming hydrogen bonds with residue Phe56 and another water molecule; this second water molecule also forms hydrogen bonds to residues in the active site, namely Leu58 and Thr39. SBT also forms van der Waals forces with several of MUP-I's residues, including Ala121, Leu123, Leu134, Leu72, Val100, and Phe108.
When bound, MUP safely carries SBT through the aqueous environment; once the protein-ligand complex is excreted in the urine, MUP helps prevent SBT decomposition and controls the slow release of SBT over a prolonged period of time, resulting in the physiological and behavioral responses of animals who come into contact with the pheromone.
Synthesis
SBT can be produced from 3-(2-aminoethanethio)-4-methylhex-2-enenitrile; however, it is also possible to synthesize SBT from ethanolamine and 2-methylbutanoic acid, using Lawesson's reagent and microwave irradiation.
References
Mammalian pheromones
Thiazolines
Sec-Butyl compounds | 2-sec-Butyl-4,5-dihydrothiazole | Chemistry | 392 |
9,880,208 | https://en.wikipedia.org/wiki/Cyclin-dependent%20kinase%204 | Cyclin-dependent kinase 4 (CDK4), also known as cell division protein kinase 4, is an enzyme that is encoded by the CDK4 gene in humans. CDK4 is a member of the cyclin-dependent kinase family, a group of serine/threonine kinases which regulate the cell cycle. CDK4 regulates the G1/S transition by contributing to the phosphorylation of retinoblastoma (RB) protein, which leads to the release of protein factors like E2F1 that promote S-phase progression. It is regulated by cyclins like cyclin D proteins, regulatory kinases, and cyclin kinase inhibitors (CKIs). Dysregulation of the CDK4 pathway is common in many cancers, and CDK4 is a new therapeutic target in cancer treatment.
Structure
The CDK4 gene is located on chromosome 12 in humans. The gene is composed of 4,583 base pairs which together code for the 303 amino acid protein with a molecular mass of 33,730 Da. All CDK proteins, including CDK4, have two lobes: the smaller N-terminal lobe (which contains an inhibitory G-loop), and the C terminal lobe (which contains an activation domain and a T-loop). Between these two lobes is the serine/threonine kinase domain where ATP binds. In its completely inactive form, CDK4's T-loop blocks the ATP binding site, and the surrounding amino acid side chains prevent ATP binding. The kinase's activity increases when it dimerizes with the corresponding cyclin, cyclin D, which causes a conformational change at the ATP binding site. CDK activating kinase (CAK) then phosphorylates the T172 site (located on the T-loop). These two actions move the T-loop out of the active ATP-binding site and make ATP binding more favorable.
Notably, CDK6 is very related to CDK4 in both structure and function. They share 71% of their amino acids and both regulate the G1/S transition by phosphorylating Rb. CDK4 and 6 differ in their cellular localization and other off-pathway roles, however are commonly referred together as CDK4/6.
The CDK4 protein is similar to the fungi gene products of S. cerevisiae cdc28 and S. pombe cdc2.
Function
CDK4 is the catalytic subunit of the protein-kinase complex CDK4-cyclin D, which plays a role in G1/S cell cycle progression. During G1 phase, the cell grows and prepares for the DNA replication that occurs in the S phase. There is a G1/S checkpoint which acts as a committed step to enter S-phase. This checkpoint ensures that cells moving toward mitosis are large enough and do not have DNA damage that could be passed on to daughter cells.
There are two models of CDK4 cell cycle regulation. The older model proposes that the kinase is responsible for the phosphorylation of retinoblastoma gene product (Rb). The Ser/Thr-kinase component of cyclin D-CDK4 (DC) forms complexes that phosphorylate and inhibit members of the retinoblastoma (RB) protein family including RB1 and regulate the cell-cycle during G1/S transition. Phosphorylation of RB1 allows dissociation of the transcription factor E2F from the RB/E2F complexes and the subsequent transcription of E2F target genes which are responsible for the progression through the G1 phase. In this model, CDK4 inhibits Rb, which inhibits E2F, which promotes progression into S phase.
The newer model, as proposed in a 2014 paper by Narasimha et al., The CDK4-cyclin D complex phosphorylates the retinoblastoma tumor suppressor protein (Rb) and its related proteins p107 and p130, which go on to inhibit cell cycle progression. As a kinase, the CDK4 serine/threonine active site converts ATP to ADP and transfers the removed phosphate group to Rb. Rb is mono-phosphorylated in early G1 by the CDK4-cyclin D complex. When mono-phosphorylated, Rb exists as one of the 14 isoforms, which bind to protein factors like E1a, and proteins in the E2F family.
The new model of CDK4 regulation posits that at the G1/S checkpoint, if a cell seems healthy, CDK2 (a different cyclin dependent kinase) inactivates Rb, and these protein factors are released back into the cell. E2F proteins then activate the transcription of genes that cause S-phase progression. However, if at the G1/S checkpoint a cell detects DNA damage, it will response by activating the CDK4-cyclin D complex to mono-phosphorylate, and activate Rb. This prevents Rb from dissociating from E2F protins, which prevents them from activating the transcription of the S-phase progression genes.
While CDK4 primarily regulates the cell cycle through phosphorylation of Rb, there is evidence of a secondary, more direct role independent of Rb. CDK4 may be able to directly phosphorylate transcription factors and co-regulators like Smad3, MYC, FOXM1, and MEP50 to regulate the cell cycle, survival and senescence.
Interestingly, CDK4-null mutant mice are viable, and in-vitro experiments show that cell proliferation is not significantly affected, likely due to compensatory roles played by other CDKs. However, CDK plays a significant role in cancer development.
Mechanisms of regulation
CDK4 is only active during the G1-S phase, which controlled by cyclin D and CDK inhibitors. CDK activity is negatively regulated by cyclin kinase inhibitors (CKIs), which belong to one of two families. The INK4 family of CKIs are inhibitors which bind and inhibit CDK4/6, also preventing subsequent binding to cyclin D. The Cip/Kip family inhibitors are not specific to CDK4/6, and instead bind and inhibit the cyclin-CDK complex.
CDK4 activity is positively regulated by cyclin D, which creates a conformational change in CDK4 that opens the active site for kinase activity. Cyclins are proteins that change concentration periodically during the cell cycle. They are extremely specific and diverse, which serves to regulate the cell cycle with precision. Cyclin D levels oscillate during the G1 phase, first increasing and accumulating, then rapidly decreasing during the transition to the S phase. Cyclin D levels are stimulated by growth factors, without which cyclin D levels would stay low regardless of cell cycle stage. After its role in G1 is complete, cyclin D is translocated from the nucleus to the cytoplasm in S phase, modulating the nuclear cyclin D levels, and therefore modulating the activity of CDK4 to promote the S phase transition.
Clinical significance
Cancer
Cancer, or uncontrolled cell proliferation, is believed to result from disturbances to mechanisms that usually control cell proliferation (tumor suppressors) and mechanisms that normally encourage cell proliferation (proto-oncogenes). Cell cycle regulation mechanisms called checkpoints, like G1/S, are in place to prevent this uncontrolled division.
Mutations in the CDK4 gene as well as in its related proteins including D-type cyclins, p16(INK4a), CDKN2A and Rb were all found to be associated with tumorigenesis of a variety of cancers, including sarcomas, gliomas, lymphomas and tumors of the mammary gland. One specific point mutation of CDK4 (R24C) was first identified in melanoma patients. This mutation was introduced also in animal models and its role as a cancer driver oncogene was studied thoroughly. Nowadays, deregulated CDK4 is considered to be a potential therapeutic target in some cancer types and various CDK4 inhibitors are being tested for cancer treatment in clinical trials. Multiple polyadenylation sites of this gene have been reported.
Cyclin D and CDK4/6 activities are observed to be up-regulated in certain cancers, sparking interest in the development of small-molecule inhibitors of CDK4/6. Ribociclib are US FDA approved CDK4 and CDK6 inhibitors for the treatment of estrogen receptor positive/ HER2 negative advanced breast cancer.
HIV
There is some evidence that CDK4 plays a role in the HIV-1 restriction pathway in primary microphages. Cell cycle control plays a major role in determining susceptibility to HIV-1 infection. Active CDKs phosphorylate SAMHD1, deactivating the enzyme which usually can restrict HIV-1 replication. A complex formed by cyclin D2-CDK4-p21 lowers the amount of active CDK in the cell, allowing SAMHD1 to exist in its active, dephosphorylated form that restricts HIV-1 replication.
Interactions
Cyclin-dependent kinase 4 has been shown to interact with:
CDC37,
CDKN1B,
CDKN2B,
CDKN2C,
CEBPA,
CCND1,
CCND3,
DBNL,
MyoD,
P16,
PCNA, and
SERTAD1.
References
Further reading
External links
Cell cycle regulators
Protein kinases
EC 2.7.11
Oncogenes | Cyclin-dependent kinase 4 | Chemistry | 2,054 |
63,922,480 | https://en.wikipedia.org/wiki/Mining%20Research%20and%20Development%20Establishment | The Mining Research and Development Establishment (MRDE) was a division of the National Coal Board. Its site in Bretby, Derbyshire is now a commercial business park.
History
MRDE's function was research into and testing of mining equipment and procedures.
It was created in 1969 with a merger between the Central Engineering Establishment (CEE) and the Mining Research Establishment (MRE). MRE was set up in 1951 to work on projects in conjunction with National Coal Board (NCB) headquarters divisions such as the Production Department and Scientific Department. It was based at Isleworth in West London. CEE was created in 1954 to work on research and development projects in conjunction with other departments, and was based at Bretby. In 1985 the MRDE merged with the Mining Department.
Awards
It won the Queens Award for Technological Achievement in 1991 for its extraction drum for dust and frictional ignition control.
Structure
The site was on the south side of the A511 in the south of Derbyshire.
See also
National Coal Board
References
Coal mining in the United Kingdom
Engineering research institutes
Mining engineering
Mining organizations
Science and technology in Derbyshire
South Derbyshire District | Mining Research and Development Establishment | Engineering | 227 |
2,952,350 | https://en.wikipedia.org/wiki/Cotton%20effect | The Cotton effect in physics, is the characteristic change in optical rotatory dispersion and/or circular dichroism in the vicinity of an absorption band of a substance.
In a wavelength region where the light is absorbed, the absolute magnitude of the optical rotation at first varies rapidly with wavelength, crosses zero at absorption maxima and then again varies rapidly with wavelength but in the opposite direction. This phenomenon was discovered in 1895 by the French physicist Aimé Cotton (1869–1951).
The Cotton effect is called positive if the optical rotation first increases as the wavelength decreases (as first observed by Cotton), and negative if the rotation first decreases.
A protein structure such as a beta sheet shows a negative Cotton effect.
See also
Cotton–Mouton effect
References
Polarization (waves)
Atomic, molecular, and optical physics | Cotton effect | Physics,Chemistry | 167 |
72,500,325 | https://en.wikipedia.org/wiki/EDIM%20technology | Epitope Detection in Monocytes (EDIM) is a technology that uses the innate immune system's mechanisms to detect biomarkers or antigens in immune cells. It is a non-invasive form of liquid biopsy, i.e. biopsy from blood, which analyzes activated macrophages (CD14+/CD16+) for disease-specific epitopes, such as tumor cell components.
Macrophages are part of the human immune system. They are involved in the detection, phagocytosis and destruction of organisms which are deemed harmful.
In case of cancerous tumors, macrophages ingest tumor cells and dissolve them with the help of enzymes, storing tumor proteins intracellularly, even when little tumor mass is present. With the help of EDIM technologie, activated macrophages containing intracellular tumor epitopes can be detected using CD14 and CD16 specific antibodies.
Areas of Application
Currently, EDIM technology is used for the blood test PanTum Detect. Here, the method is applied to examine which individuals would benefit from further cancer detection examinations with imaging procedures (MRI, PET/CT) to clarify a possible tumor disease. The two biomarkers used for PanTum Detect are TKTL1 and DNaseX.
The PanTum Detect blood test exploits the EDIM technology utilizing the fact that activated monocytes/macrophages phagocytose tumor cells and contain tumor proteins intracellularly.
References
Blood tests
Biomarkers
Biotechnology
Endocrine function tests
Cancer screening | EDIM technology | Chemistry,Biology | 311 |
437,891 | https://en.wikipedia.org/wiki/Henry%20Fairfield%20Osborn | Henry Fairfield Osborn, Sr. (August 8, 1857 – November 6, 1935) was an American paleontologist, geologist and eugenics advocate. He was the president of the American Museum of Natural History for 25 years and a cofounder of the American Eugenics Society.
Early life and education
Family
Henry Fairfield Osborn was born in Fairfield, Connecticut on August 8, 1857, in a family of distinction. He was the eldest son of shipping magnate and railroad tycoon William Henry Osborn and Virginia Reed (née Sturges) Osborn.
His maternal grandparents were Jonathan Sturges, a prominent New York businessman and arts patron who was a direct descendant of Jonathan Sturges, a U.S. Representative from Connecticut, and Mary Pemberton Cady, a direct descendant of prominent educator Ebenezer Pemberton. His maternal aunt, Amelia Sturges, was the first wife of J. P. Morgan, but died of tuberculosis soon after their wedding.
His younger brother was William Church Osborn, who served as president of the Metropolitan Museum of Art, and married philanthropist and social reformer Alice Clinton Hoadley Dodge, a daughter of William E. Dodge Jr.
Education
From 1873 to 1877, Osborn studied at Princeton University, obtaining a B.A. in geology and archaeology, where he was mentored by paleontologist Edward Drinker Cope. Two years later, Osborn took a special course of study in anatomy in the College of Physicians and Surgeons and Bellevue Medical School of New York under Dr. William H. Welch, and subsequently studied embryology and comparative anatomy under Thomas Huxley at London, as well as Francis Maitland Balfour at Cambridge University, England.
In 1880, Osborn obtained a doctorate in paleontology from Princeton, becoming a lecturer in biology and professor of comparative anatomy from the same university between 1883 and 1890.
Career
In 1891, Osborn was hired by Columbia University as a professor of zoology; simultaneously, he accepted a position at the American Museum of Natural History, New York, where he served as the curator of a newly formed Department of Vertebrate Paleontology.
Fossil hunting
As a curator, he assembled a remarkable team of fossil hunters and preparators, including William King Gregory, Roy Chapman Andrews, Barnum Brown, and Charles R. Knight.
Long a member of the US Geological Survey, Osborn became its senior vertebrate paleontologist in 1924. He led many fossil-hunting expeditions into the American Southwest, starting with his first to Colorado and Wyoming in 1877. Osborn conducted research on Tyrannosaurus brains by cutting open fossilized braincases with a diamond saw. (Modern researchers use computed tomography scans and 3D reconstruction software to visualize the interior of dinosaur endocrania without damaging valuable specimens.)
On November 23, 1897, he was elected member of the Boone and Crockett Club, a wildlife conservation organization founded by Theodore Roosevelt and George Bird Grinnell. Thanks to his considerable family wealth and personal connections, he succeeded Morris K. Jesup as the president of the AMNH's Board of Trustees in 1908, serving until 1933, during which time he accumulated one of the finest fossil collections in the world.
Additionally, Osborn served as president of the New York Zoological Society from 1909 to 1925.
He was elected as a member to the American Philosophical Society in 1886. He accumulated a number of prizes for his work in paleontology. In 1901, Osborn was elected a Fellow of the American Academy of Arts and Sciences. He described and named Ornitholestes in 1903, Tyrannosaurus rex and Albertosaurus in 1905, Pentaceratops in 1923, and Velociraptor in 1924.
In 1929 Osborn was awarded the Daniel Giraud Elliot Medal from the National Academy of Sciences.
American Museum of Natural History
His legacy at the American Museum has proved more enduring than his scientific reputation. Edward J. Larson described Osborn as "a first-rate science administrator and a third-rate scientist." Indeed, Osborn's greatest contributions to science ultimately lay in his efforts to popularize it through visual means. At his urging, staff members at the American Museum of Natural History invested new energy in display, and the museum became one of the pre-eminent sites for exhibition in the early twentieth century as a result. The murals, habitat dioramas, and dinosaur mounts executed during his tenure at the museum attracted millions of visitors, and inspired other museums to imitate his innovations. But his decision to invest heavily in exhibition also alienated certain members of the scientific community and angered curators hoping to spend more time on their own research. Additionally, his efforts to imbue the museum's exhibits and educational programs with his own racist and eugenist beliefs disturbed many of his contemporaries and have marred his legacy.
Theories
Dawn Man Theory
Osborn developed his own evolutionary theory of human origins called the "Dawn Man Theory". His theory was founded on the discovery of Piltdown Man (Eoanthropus) which was dated to the Late (Upper) Pliocene. Writing before Piltdown was exposed as a hoax, the Eoanthropus or "Dawn Man" Osborn maintained sprang from a common ancestor with the ape during the Oligocene period which he believed developed entirely separately during the Miocene (16 million years ago). Therefore, Osborn argued that all apes (Simia, following the pre-Darwinian classification of Linnaeus) had evolved entirely parallel to the ancestors of man (homo). Osborn himself wrote:
While believing in common ancestry between man and ape, Osborn denied that this ancestor was ape-like. The common ancestor between man and ape Osborn always maintained was more human than ape. Writing to Arthur Keith in 1927, he remarked "when our Oligocene ancestor is found it will not be an ape, but it will be surprisingly pro-human". His student William K. Gregory called Osborn's idiosyncratic view on man's origins as a form of "Parallel Evolution", but many creationists misinterpreted Osborn, greatly frustrating him, and believed he was asserting humankind had never evolved from a lower life form.
Evolutionary views
Osborn was originally a supporter of Edward Drinker Cope's neo-Lamarckism, however he later abandoned this view. Osborn became a proponent of organic selection, also known as the Baldwin effect.
Osborn was a believer in orthogenesis; he coined the term aristogenesis for his theory. His aristogenesis was based on a "physicochemical approach" to evolution. He believed that aristogenes operate as biomechanisms in the geneplasm of the organism. He also held the view that mutations and natural selection play no creative role in evolution and that aristogenesis was the origin of new novelty. Osborn equated this struggle for evolutionary advancement with the striving for spiritual salvation, thereby combining his biological and spiritual viewpoints.
Eugenics
Osborn, who cofounded the American Eugenics Society in 1922, advocated that heredity is superior to influences from the environment. As an extension of this, he accepted that distinct races existed with fixed hereditary traits, and held the Nordic or Anglo-Saxon "race" to be highest. Osborn therefore supported eugenics to preserve "good" racial stock. Due to this, he endorsed Madison Grant's The Passing of the Great Race, writing both the second and fourth prefaces of the book, which argued for such views. The book was praised by Adolf Hitler who called the book 'his bible' for it advocated a rigid system of selection through the elimination of those who, according to the writer's opinion, are to be seen as 'weak' or 'unfit'.
Personal life
In June 1881, Osborn was married to writer Lucretia Thatcher Perry (1858–1930) at the military chapel on Governors Island. She was the daughter of Brigadier General Alexander James Perry and Josephine (Adams) Perry, and a descendant of Justice Christopher Raymond Perry). Lucretia's sister, Josephine Adams Perry, was the wife of banker Junius Spencer Morgan II. Thatcher Perry had five children with Osborn, including Henry Fairfield Osborn Jr., the naturalist and conservationist.
After his father's death in 1894, Osborn inherited his Rhenish style home, Castle Rock, in Garrison, New York in the Hudson Highlands, which his father had purchased in 1859, and where he concentrated on his philanthropy after his 1882 retirement. After his mother's death in 1902, the remainder of his parents' estate was equally divided between Henry and his brother William.
Following an "illness of nearly a year", his wife died at their country home in August 1930. Osborn died suddenly on November 6, 1935, in his study at Castle Rock, overlooking the Hudson River.
Eponyms
The dinosaur Saurolophus osborni was named after Osborn by Barnum Brown in 1912.
An African dwarf crocodile, Osteolaemus osborni, was named in his honor by Karl Patterson Schmidt in 1919.
Also named in his honor is the early canid genus Osbornodon.
Published books
From the Greeks to Darwin: An Outline of the Development of the Evolution Idea (1894)
Present Problems in Evolution and Heredity (1892)
Evolution of Mammalian Molar Teeth: To and From the Triangular Type (1907)
Men of the Old Stone Age: Their Environment, Life and Art (1915)
The Origin and Evolution of Life (1916)
Men of the Old Stone Age (1916)
The Age of Mammals in Europe, Asia and North America (1921)
Evolution and Religion (1923)
Evolution And Religion In Education (1926)
Man Rises to Parnassus: Critical Epochs in the Pre-History of Man (1927)
Aristogenesis, the Creative Principle in the Origin of Species (1934)
See also
"The New Museum Idea"
References
Works cited
Larsson, H.C.E., 2001. Endocranial Anatomy of Carcharodontosaurus saharicus. In D.H. Tanke & K. Carpenter (eds.), Mesozoic Vertebrate Life: pp. 19–33.
Further reading
Robertson, Thomas, "Total War and the Total Environment: Fairfield Osborn, William Vogt, and the Birth of Global Ecology," Environmental History, 17 (April 2012), 336–64.
(Madison Grant was a friend and collaborator of Osborn)
National Academy of Sciences: Biographical Memoir of Henry Fairfield Osborn (1857–1935), by William K. Gregory, 1937
External links
Bibliography of the published writings of Henry Fairfield Osborn for the years 1877-1915
Brief essay on Osborn's racial theories
brief biographical sketch
1857 births
1935 deaths
20th-century American scientists
American conservationists
American eugenicists
American paleontologists
American white supremacists
Columbia University faculty
Fellows of the American Academy of Arts and Sciences
Foreign members of the Royal Society
Members of the United States National Academy of Sciences
Orthogenesis
People associated with the American Museum of Natural History
People from Fairfield, Connecticut
Recipients of the Cullum Geographical Medal
United States Geological Survey personnel
Wildlife Conservation Society people
Wollaston Medal winners
Members of the American Philosophical Society
Sturges family
Proponents of scientific racism
American founders | Henry Fairfield Osborn | Biology | 2,264 |
44,632,306 | https://en.wikipedia.org/wiki/Psilocybe%20oaxacana | Psilocybe oaxacana is a species of psychedelic mushroom in the family Hymenogastraceae native to Oaxaca, Mexico. It is in the Psilocybe fagicola complex with Psilocybe fagicola, Psilocybe banderillensis, Psilocybe columbiana, Psilocybe herrerae, Psilocybe keralensis, Psilocybe neoxalapensis, and Psilocybe teofiloi.
See also
List of Psilocybe species
List of Psilocybin mushrooms
Psilocybe
References
External links
The taxonomy of Psilocybe fagicola-complex
Entheogens
Psychoactive fungi
oaxacana
Psychedelic tryptamine carriers
Fungi described in 2004
Fungi of North America
Taxa named by Gastón Guzmán
Fungus species | Psilocybe oaxacana | Biology | 165 |
144,615 | https://en.wikipedia.org/wiki/Psychological%20warfare | Psychological warfare (PSYWAR), or the basic aspects of modern psychological operations (PsyOp), has been known by many other names or terms, including Military Information Support Operations (MISO), Psy Ops, political warfare, "Hearts and Minds", and propaganda. The term is used "to denote any action which is practiced mainly by psychological methods with the aim of evoking a planned psychological reaction in other people".
Various techniques are used, and are aimed at influencing a target audience's value system, belief system, emotions, motives, reasoning, or behavior. It is used to induce confessions or reinforce attitudes and behaviors favorable to the originator's objectives, and are sometimes combined with black operations or false flag tactics. It is also used to destroy the morale of enemies through tactics that aim to depress troops' psychological states.
Target audiences can be governments, organizations, groups, and individuals, and is not just limited to soldiers. Civilians of foreign territories can also be targeted by technology and media so as to cause an effect on the government of their country.
Stories are foundational to the art and practice of psyops. Mass communication such as radio allows for direct communication with an enemy populace, and therefore has been used in many efforts. Social media channels and the internet allow for campaigns of disinformation and misinformation performed by agents anywhere in the world.
History
Early
Since prehistoric times, warlords and chiefs have recognized the importance of weakening the morale of their opponents. According to Polyaenus, in the Battle of Pelusium (525 BC) between the Persian Empire and ancient Egypt, the Persian forces used cats and other animals as a psychological tactic against the Egyptians, who avoided harming cats due to religious belief and superstitions.
Currying favor with supporters was the other side of psychological warfare, and an early practitioner of this was Alexander the Great, who successfully conquered large parts of Europe and the Middle East and held on to his territorial gains by co-opting local elites into the Greek administration and culture. Alexander left some of his men behind in each conquered city to introduce Greek culture and oppress dissident views. His soldiers were paid dowries to marry locals in an effort to encourage assimilation.
Genghis Khan, leader of the Mongolian Empire in the 13th century AD employed less subtle techniques. Defeating the will of the enemy before having to attack and reaching a consented settlement was preferable to facing his wrath. The Mongol generals demanded submission to the Khan and threatened the initially captured villages with complete destruction if they refused to surrender. If they had to fight to take the settlement, the Mongol generals fulfilled their threats and massacred the survivors. Tales of the encroaching horde spread to the next villages and created an aura of insecurity that undermined the possibility of future resistance.
Genghis Khan also employed tactics that made his numbers seem greater than they actually were. During night operations he ordered each soldier to light three torches at dusk to give the illusion of an overwhelming army and deceive and intimidate enemy scouts. He also sometimes had objects tied to the tails of his horses, so that riding on open and dry fields raised a cloud of dust that gave the enemy the impression of great numbers. His soldiers used arrows specially notched to whistle as they flew through the air, creating a terrifying noise.
Another tactic favored by the Mongols was catapulting severed human heads over city walls to frighten the inhabitants and spread disease in the besieged city's closed confines. This was especially used by the later Turko-Mongol chieftain.
The Muslim caliph Omar, in his battles against the Byzantine Empire, sent small reinforcements in the form of a continuous stream, giving the impression that a large force would accumulate eventually if not swiftly dealt with.
During the early Qin dynasty and late Eastern Zhou dynasty in 1st century AD China, the Empty Fort Strategy was used to trick the enemy into believing that an empty location was an ambush, in order to prevent them from attacking it using reverse psychology. This tactic also relied on luck, should the enemy believe that the location is a threat to them.
In the 6th century BCE Greek Bias of Priene successfully resisted the Lydian king Alyattes by fattening up a pair of mules and driving them out of the besieged city. When Alyattes' envoy was then sent to Priene, Bias had piles of sand covered with wheat to give the impression of plentiful resources.
This ruse appears to have been well known in medieval Europe: defenders in castles or towns under siege would throw food from the walls to show besiegers that provisions were plentiful. A famous example occurs in the 8th-century legend of Lady Carcas, who supposedly persuaded the Franks to abandon a five-year siege by this means and gave her name to Carcassonne as a result.
During the Granada War, Spanish captain Hernán Pérez del Pulgar routinely employed psychological tactics as part of his guerrilla actions against the Emirate of Granada. In 1490, infiltrating the city by night with a small retinue of soldiers, he nailed a letter of challenge on the main mosque and set fire to the alcaicería before withdrawing.
In 1574, having been informed about the pirate attacks previous to the Battle of Manila, Spanish captain Juan de Salcedo had his relief force return to the city by night while playing marching music and carrying torches in loose formations, so they would appear to be a much larger army to any nearby enemy. They reached the city unopposed.
Modern Era
Because psyops shape public opinion and public memory, the rise of the printing press and mass communication greatly increased the use of psyops for military advantage. During the Indian Wars of the 17th through 19th centuries, politicians, newspaper reports and fictional novels about Native Americans all conveyed the belief that tribes in the Northeast had "died out," and leaders of New England communities even gave speeches about the "last Indians" in New England, even as Native Americans continued to reside in these communities. There was significant military value in these narratives, as they enabled the justification of "manifest destiny," a policy used by the U.S. to expand into western territories.
During the Attack on Marstrand in 1719, Peter Tordenskjold carried out military deception against the Swedes. Although probably apocryphal, he apparently succeeded in making his small force appear larger and feed disinformation to his opponents, similar to the Operations Fortitude and Titanic in World War II.
World War I
The start of modern psychological operations in war is generally dated to World War I. By that point, Western societies were increasingly educated and urbanized, and mass media was available in the form of large circulation newspapers and posters. It was also possible to transmit propaganda to the enemy via the use of airborne leaflets or through explosive delivery systems like modified artillery or mortar rounds.
At the start of the war, the belligerents, especially the British and Germans, began distributing propaganda, both domestically and on the Western front. The British had several advantages that allowed them to succeed in the battle for world opinion; they had one of the world's most reputable news systems, with much experience in international and cross-cultural communication, and they controlled much of the undersea communications cable system then in operation. These capabilities were easily transitioned to the task of warfare.
The British also had a diplomatic service that maintained good relations with many nations around the world, in contrast to the reputation of the German services. While German attempts to foment revolution in parts of the British Empire, such as Ireland and India, were ineffective, extensive experience in the Middle East allowed the British to successfully induce the Arabs to revolt against the Ottoman Empire.
In August 1914, David Lloyd George appointed a Member of Parliament (MP), Charles Masterman, to head a Propaganda Agency at Wellington House. A distinguished body of literary talent was enlisted for the task, with its members including Arthur Conan Doyle, Ford Madox Ford, G. K. Chesterton, Thomas Hardy, Rudyard Kipling and H. G. Wells. Over 1,160 pamphlets were published during the war and distributed to neutral countries, and eventually, to Germany. One of the first significant publications, the Report on Alleged German Outrages of 1915, had a great effect on general opinion across the world. The pamphlet documented atrocities, both actual and alleged, committed by the German army against Belgian civilians. A Dutch illustrator, Louis Raemaekers, provided the highly emotional drawings which appeared in the pamphlet.
In 1917, the bureau was subsumed into the new Department of Information and branched out into telegraph communications, radio, newspapers, magazines and the cinema. In 1918, Viscount Northcliffe was appointed Director of Propaganda in Enemy Countries. The department was split between propaganda against Germany organized by H.G Wells, and propaganda against the Austro-Hungarian Empire supervised by Wickham Steed and Robert William Seton-Watson; the attempts of the latter focused on the lack of ethnic cohesion in the Empire and stoked the grievances of minorities such as the Croats and Slovenes. It had a significant effect on the final collapse of the Austro-Hungarian Army at the Battle of Vittorio Veneto.
Aerial leaflets were dropped over German trenches containing postcards from prisoners of war detailing their humane conditions, surrender notices and general propaganda against the Kaiser and the German generals. By the end of the war, MI7b had distributed almost 26 million leaflets. The Germans began shooting the leaflet-dropping pilots, prompting the British to develop unmanned leaflet balloons that drifted across no-man's land. At least one in seven of these leaflets were not handed in by the soldiers to their superiors, despite severe penalties for that offence. Even General Hindenburg admitted that "Unsuspectingly, many thousands consumed the poison", and POWs admitted to being disillusioned by the propaganda leaflets that depicted the use of German troops as mere cannon fodder. In 1915, the British began airdropping a regular leaflet newspaper Le Courrier de l'Air for civilians in German-occupied France and Belgium.
At the start of the war, the French government took control of the media to suppress negative coverage. Only in 1916, with the establishment of the Maison de la Presse, did they begin to use similar tactics for the purpose of psychological warfare. One of its sections was the "Service de la Propagande aérienne" (Aerial Propaganda Service), headed by Professor Tonnelat and Jean-Jacques Waltz, an Alsatian artist code-named "Hansi". The French tended to distribute leaflets of images only, although the full publication of US President Woodrow Wilson's Fourteen Points, which had been heavily edited in the German newspapers, was distributed via airborne leaflets by the French.
The Central Powers were slow to use these techniques; however, at the start of the war the Germans succeeded in inducing the Sultan of the Ottoman Empire to declare 'holy war', or Jihad, against the Western infidels. They also attempted to foment rebellion against the British Empire in places as far afield as Ireland, Afghanistan, and India. The Germans' greatest success was in giving the Russian revolutionary, Lenin, free transit on a sealed train from Switzerland to Finland after the overthrow of the Tsar. This soon paid off when the Bolshevik Revolution took Russia out of the war.
World War II
Adolf Hitler was greatly influenced by the psychological warfare tactics the Allies employed during World War I, and attributed Germany's defeat in the conflict to the effects this tactics had on German troops. He became committed to the use of mass propaganda to influence the minds of the German population in the decades to come. By calling his movement The Third Reich, he was able to convince many civilians that his cause was not just a fad, but the way of their future. Joseph Goebbels was appointed as Propaganda Minister when Hitler came to power in 1933, and he portrayed Hitler as a messianic figure for the redemption of Germany. Hitler also coupled this with the resonating projections of his orations for effect.
Germany's Fall Grün plan of invasion of Czechoslovakia had a large part dealing with psychological warfare aimed both at the Czechoslovak civilians and government as well as, crucially, at Czechoslovakia's allies. It became successful to the point that Germany gained the acquiescence of the British and French governments to the German occupation of Czechoslovakia without having to fight an all-out war, sustaining only minimum losses in covert war before the Munich Agreement.
After the outbreak of World War II in 1939, the British set up the Political Warfare Executive to produce and distribute propaganda. Through the use of powerful transmitters, broadcasts could be made across Europe. Sefton Delmer managed a successful black propaganda campaign through several radio stations which were designed to be popular with German troops while at the same time introducing news material that would weaken their morale under a veneer of authenticity. British Prime Minister Winston Churchill made use of radio broadcasts for propaganda against the Germans. Churchill favoured deception; he said "In wartime, truth is so precious that she should always be attended by a bodyguard of lies.".
During World War II, the British made extensive use of deception – developing many new techniques and theories. The main protagonists at this time were 'A' Force, set up in 1940 under Dudley Clarke, and the London Controlling Section, chartered in 1942 under the control of John Bevan. Clarke pioneered many of the strategies of military deception. His ideas for combining fictional orders of battle, visual deception and double agents helped define Allied deception strategy during the war, for which he has been referred to as "the greatest British deceiver of WW2".
During the lead-up to the Allied invasion of Normandy, many new tactics in psychological warfare were devised. The plan for Operation Bodyguard set out a general strategy to mislead German high command as to the date and location of the invasion, which was obviously going to happen. Planning began in 1943 under the auspices of the London Controlling Section (LCS). A draft strategy, referred to as Plan Jael, was presented to Allied high command at the Tehran Conference. Operation Fortitude was intended to convince the Germans of a greater Allied military strength than was the case, through fictional field armies, faked operations to prepare the ground for invasion and "leaked" misinformation about the Allied order of battle and war plans.
Elaborate naval deceptions (Operations Glimmer, Taxable and Big Drum) were undertaken in the English Channel. Small ships and aircraft simulated invasion fleets lying off Pas de Calais, Cap d'Antifer and the western flank of the real invasion force. At the same time Operation Titanic involved the RAF dropping fake paratroopers to the east and west of the Normandy landings.
The deceptions were implemented with the use of double agents, radio traffic and visual deception. The British "Double Cross" anti-espionage operation had proven very successful from the outset of the war, and the LCS was able to use double agents to send back misleading information about Allied invasion plans. The use of visual deception, including mock tanks and other military hardware had been developed during the North Africa campaign. Mock hardware was created for Bodyguard; in particular, dummy landing craft were stockpiled to give the impression that the invasion would take place near Calais.
The Operation was a strategic success and the Normandy landings caught German defences unaware. Continuing deception, portraying the landings as a diversion from a forthcoming main invasion in the Calais region, led Hitler into delaying transferring forces from Calais to the real battleground for nearly seven weeks.
Vietnam War
The United States ran an extensive program of psychological warfare during the Vietnam War. The Phoenix Program had the dual aim of assassinating National Liberation Front of South Vietnam (NLF or Viet Cong) personnel and terrorizing any potential sympathizers or passive supporters. During the Phoenix Program, over 19,000 NLF supporters were killed. In Operation Wandering Soul, the United States also used tapes of distorted human sounds and played them during the night making the Vietnamese soldiers think that the dead were back for revenge.
The Vietcong and their forces also used a program of psychological warfare during this war. Trịnh Thị Ngọ, also known as Thu Hương and Hanoi Hannah, was a Vietnamese radio personality. She made English-language broadcasts for North Vietnam directed at United States troops. During the Vietnam War, Ngọ became famous among US soldiers for her propaganda broadcasts on Radio Hanoi. Her scripts were written by the North Vietnamese Army and were intended to frighten and shame the soldiers into leaving their posts. She made three broadcasts a day, reading a list of newly killed or imprisoned Americans, and playing popular US anti-war songs in an effort to incite feelings of nostalgia and homesickness, attempting to persuade US GIs that the US involvement in the Vietnam War was unjust and immoral. A typical broadcast began as follows:
How are you, GI Joe? It seems to me that most of you are poorly informed about the going of the war, to say nothing about a correct explanation of your presence over here. Nothing is more confused than to be ordered into a war to die or to be maimed for life without the faintest idea of what's going on.
21st century
The CIA made extensive use of Contra soldiers to destabilize the Sandinista government in Nicaragua. The CIA used psychological warfare techniques against the Panamanians by delivering unlicensed TV broadcasts. The United States government has used propaganda broadcasts against the Cuban government through TV Marti, based in Miami, Florida. However, the Cuban government has been successful at jamming the signal of TV Marti.
In the Iraq War, the United States used the shock and awe campaign to psychologically maim and break the will of the Iraqi Army to fight.
In cyberspace, social media has enabled the use of disinformation on a wide scale. Analysts have found evidence of doctored or misleading photographs spread by social media in the Syrian Civil War and 2014 Russian military intervention in Ukraine, possibly with state involvement. Military and governments have engaged in psychological operations (PSYOP) and informational warfare (IW) on social networking platforms to regulate foreign propaganda, which includes countries like the US, Russia, and China.
In 2022, Meta and the Stanford Internet Observatory found that over five years people associated with the U.S. military, who tried to conceal their identities, created fake accounts on social media systems including Balatarin, Facebook, Instagram, Odnoklassniki, Telegram, Twitter, VKontakte and YouTube in an influence operation in Central Asia and the Middle East. Their posts, primarily in Arabic, Farsi and Russian, criticized Iran, China and Russia and gave pro-Western narratives. Data suggested the activity was a series of covert campaigns rather than a single operation.
In operations in the South and East China Seas, both the United States and China have been engaged in "cognitive warfare", which involves displays of force, staged photographs and sharing disinformation. The start of the public use of "cognitive warfare" as a clear movement occurred in 2013 with China's political rhetoric.
Methods
Most modern uses of the term psychological warfare refer to the following military methods:
Demoralization:
Distributing pamphlets that encourage desertion or supply instructions on how to surrender.
Shock and awe military strategy.
Projecting repetitive and disturbing noises and music for long periods at high volume towards groups under siege like during Operation Nifty Package.
Propaganda radio stations, such as Lord Haw-Haw in World War II on the "Germany calling" station.
False flag events.
Terrorism
The threat of Chemical weapons.
Information warfare.
Most of these techniques were developed during World War II or earlier, and have been used to some degree in every conflict since. Daniel Lerner was in the OSS (the predecessor to the American CIA) and in his book, attempts to analyze how effective the various strategies were. He concludes that there is little evidence that any of them were dramatically successful, except perhaps surrender instructions over loudspeakers when victory was imminent. Measuring the success or failure of psychological warfare is very hard, as the conditions are very far from being a controlled experiment.
Lerner also divides psychological warfare operations into three categories:
White propaganda (omissions and emphasis): Truthful and not strongly biased, where the source of information is acknowledged.
Grey propaganda (omissions, emphasis and racial/ethnic/religious bias): Largely truthful, containing no information that can be proven wrong; the source is not identified.
Black propaganda (commissions of falsification): Inherently deceitful, information given in the product is attributed to a source that was not responsible for its creation.
Lerner says grey and black operations ultimately have a heavy cost, in that the target population sooner or later recognizes them as propaganda and discredits the source. He writes, "This is one of the few dogmas advanced by Sykewarriors that is likely to endure as an axiom of propaganda: Credibility is a condition of persuasion. Before you can make a man do as you say, you must make him believe what you say." Consistent with this idea, the Allied strategy in World War II was predominantly one of truth (with certain exceptions).
In Propaganda: The Formation of Men's Attitudes, Jacques Ellul discusses psychological warfare as a common peace policy practice between nations as a form of indirect aggression. This type of propaganda drains the public opinion of an opposing regime by stripping away its power on public opinion. This form of aggression is hard to defend against because no international court of justice is capable of protecting against psychological aggression since it cannot be legally adjudicated. "Here the propagandists is [sic] dealing with a foreign adversary whose morale he seeks to destroy by psychological means so that the opponent begins to doubt the validity of his beliefs and actions."
Terrorism
According to Boaz Ganor, terrorism weakens the sense of security and disturbs daily life, damaging the target country's capability to function. Terrorism is a strategy that aims to influence public opinion into pressuring leaders to give in to the terrorists' demands, and the population becomes a tool to advance the political agenda.
By country
China
According to U.S. military analysts, attacking the enemy's mind is an important element of the People's Republic of China's military strategy. This type of warfare is rooted in the Chinese Stratagems outlined by Sun Tzu in The Art of War and Thirty-Six Stratagems. In its dealings with its rivals, China is expected to utilize Marxism to mobilize communist loyalists, as well as flex its economic and military muscle to persuade other nations to act in the Chinese government's interests. The Chinese government also tries to control the media to keep a tight hold on propaganda efforts for its people. The Chinese government also utilizes cognitive warfare against Taiwan.
France
The Centre interarmées des actions sur l'environnement is an organization made up of 300 soldiers whose mission is to assure to the four service arm of the French Armed Forces psychological warfare capacities. Deployed in particular to Mali and Afghanistan, its missions "consist in better explaining and accepting the action of French forces in operation with local actors and thus gaining their trust: direct aid to the populations, management of reconstruction sites, actions of communication of influence with the population, elites and local elected officials". The center has capacities for analysis, influence, expertise and instruction.
Germany
In the German , the Zentrum Operative Kommunikation is responsible for PSYOP efforts. The center is subordinate to the Cyber and Information Domain Service branch alongside multiple IT and Electronic Warfare battalions and consists of around 1000 soldiers. One project of the German PSYOP forces is the radio station Stimme der Freiheit (Sada-e Azadi, Voice of Freedom), heard by thousands of Afghans. Another is the publication of various newspapers and magazines in Kosovo and Afghanistan, where German soldiers serve with NATO.
Iran
The Iranian government had an operation program to use the 2022 FIFA World Cup as a psyop against concurrent people's protests.
Israel
The Israeli government and its military make use of psychological warfare. In 2021, Israeli newspaper Haaretz revealed that "Abu Ali Express", a popular news page on Telegram and Twitter purportedly dedicated to "Arab affairs", was actually run by a Jewish Israeli paid consultant to the Israel Defense Forces (IDF). The IDF's psyops account had been the source of a number of noteworthy reports that were afterwards cited by the Israeli and international media.
Russia
Soviet Union
United Kingdom
The British were one of the first major military powers to use psychological warfare in the First and Second World Wars. In the current British Armed Forces, PsyOps are handled by the tri-service 15 Psychological Operations Group. (See also MI5 and Secret Intelligence Service). The Psychological Operations Group comprises over 150 personnel, approximately 75 from the regular Armed Services and 75 from the Reserves. The Group supports deployed commanders in the provision of psychological operations in operational and tactical environments.
The Group was established immediately after the 1991 Gulf War, has since grown significantly in size to meet operational requirements, and since 2015 has been one of the sub-units of the 77th Brigade, formerly called the Security Assistance Group.
In June 2015, NSA files published by Glenn Greenwald revealed details of the JTRIG group at British intelligence agency GCHQ covertly manipulating online communities. This is in line with JTRIG's goal: to "destroy, deny, degrade [and] disrupt" enemies by "discrediting" them, planting misinformation and shutting down their communications.
In March 2019, it emerged that the Defence Science and Technology Laboratory (DSTL) of the UK's Ministry of Defence (MoD) is tendering to arms companies and universities for £70M worth of assistance under a project to develop new methods of psychological warfare. The project is known as the human and social sciences research capability (HSSRC).
United States
The term psychological warfare is believed to have migrated from Germany to the United States in 1941. During World War II, the United States Joint Chiefs of Staff defined psychological warfare broadly, stating "Psychological warfare employs any weapon to influence the mind of the enemy. The weapons are psychological only in the effect they produce and not because of the weapons themselves." The U.S. Department of Defense (DoD) currently defines psychological warfare as:
"The planned use of propaganda and other psychological actions having the primary purpose of influencing the opinions, emotions, attitudes, and behavior of hostile foreign groups in such a way as to support the achievement of national objectives."
This definition indicates that a critical element of the U.S. psychological operations capabilities includes propaganda and by extension counterpropaganda. Joint Publication 3–53 establishes specific policy to use public affairs mediums to counter propaganda from foreign origins.
The purpose of United States psychological operations is to induce or reinforce attitudes and behaviors favorable to US objectives. The Special Activities Center (SAC) is a division of the Central Intelligence Agency's Directorate of Operations, responsible for Covert Action and "Special Activities". These special activities include covert political influence (which includes psychological operations) and paramilitary operations. SAC's political influence group is the only US unit allowed to conduct these operations covertly and is considered the primary unit in this area.
Dedicated psychological operations units exist in the United States Army and United States Marine Corps. The United States Navy and the 193rd Special Operations Wing of the United States Air Force also plans and executes limited PSYOP missions. United States PSYOP units and soldiers of all branches of the military are prohibited by law from targeting U.S. citizens with PSYOP within the borders of the United States (Executive Order S-1233, DOD Directive S-3321.1, and National Security Decision Directive 130). While United States Army PSYOP units may offer non-PSYOP support to domestic military missions, they can only target foreign audiences.
A U.S. Army field manual released in January 2013 states that "Inform and Influence Activities" are critical for describing, directing, and leading military operations. Several Army Division leadership staff are assigned to “planning, integration and synchronization of designated information-related capabilities."
Journalist and fiction writer P.W. Singer, author of Wired for War, teaches military leaders about how to incorporate "useful fiction" stories and narrative structure into military psyops.
In September 2022, the DoD launched an audit of covert information warfare after social media companies identified a suspected U.S. military operation.
See also
Active measures
Brainwashing
Character assassination
Charles Douglas Jackson
Cognitive dissonance
Cordwainer Smith
Demonizing the enemy
Directed-energy weapon
Fear mongering
Information warfare
Lawfare
Media manipulation
Military psychology
Mind games
Minor sabotage
Moral panic
Noisy investigation
Orwellian
Psychological manipulation
Special Operations
Strategy of tension
Taliban propaganda
The Shock Doctrine
Unconventional Warfare
Peter Watson (intellectual historian)
Zersetzung
NATO
Able Archer 83
UK
Briggs Plan
Information Research Department
US specific:
Information Operations Roadmap
NLF and PAVN battle tactics
Zarqawi PSYOP program
World War II:
Psychological Warfare Division
USSR
Active measures
Related:
Asymmetric warfare
Fourth generation warfare
References
Bibliography
Abner, Alan K. Psywarriors : psychological warfare during the Korean War (1951) online
Cohen, Fred. Frauds, Spies, and Lies – and How to Defeat Them. (2006). ASP Press.
Cohen, Fred. World War 3 ... Information Warfare Basics. (2006). ASP Press.
Holzmann, Ashley F. "Artists of War: A History of United States Propaganda, Psychological Warfare, Psychological Operations and a Proposal for Its Ever-Changing Future." US Army Command and General Staff College, 2020) online
Linebarger, Paul M. A. Psychological Warfare: International Propaganda and Communications. (1948). Revised second edition, Duell, Sloan and Pearce (1954).
Pease, Stephen E. Psywar : psychological warfare in Korea, 1950-1953 (1992) online
Roberts III, Mervyn Edwin. The Psychological War for Vietnam, 1960–1968 (2018)
Roetter, Charles. The art of psychological warfare, 1914-1945 (1974) online
Simpson, Christopher. Science of Coercion: Communication Research & Psychological Warfare, 1945–1960 (1994) online
Song, Tae Eun. "Information/Psychological Warfare in the Russia-Ukraine War: Overview and Implications." IFANS FOCUS 2022.9 (May 2022): 1-4. online
Voloshin, Nikolay, and Leyla Garaybeli. "Putin's Psychological Warfare in Ukraine and Syria" Insights of Pakistan, Iran and the Caucasus Studies 2.3 (2023): 50-54. online
External links
Movie: Psywar: The Real Battlefield is the Mind by Metanoia films
The history of psychological warfare
IWS Psychological Operations (PsyOps) / Influence Operations
"Pentagon psychological warfare operation", USA Today, 15 December 2005
"U.S. Adapts Cold-War Idea to Fight Terrorists", New York Times, 18 March 2008
US Army PSYOPS Info – Detailed information about the US Army Psychological Operation Soldiers
IWS — The Information Warfare Site
U.S. — PSYOP producing mid-eastern kids comic book
The Institute of Heraldry — Psychological Operations
Psychological warfare
The Nature of Psychological Warfare (CIA 1958) Original
Aggression
Crowd psychology
Information operations and warfare
Mind control
Propaganda techniques
Psychological warfare techniques
Warfare by type
Warfare of the late modern period | Psychological warfare | Biology | 6,444 |
38,682,159 | https://en.wikipedia.org/wiki/Trichoglossum%20hirsutum | Trichoglossum hirsutum is a species of fungus in the family Geoglossaceae. In the UK, it has been given the recommended English name of hairy earthtongue. In North America it is known variously as velvety black earth tongue, velvety earth tongue, shaggy earth tongue, or black earth tongue. DNA evidence suggests the hairy earthtongue may be a species complex.
Taxonomy
The species was first described by mycologist Christian Hendrik Persoon in 1794 as Geoglossum hirsutum. In 1907 Jean Louis Émile Boudier transferred the species to his new genus Trichoglossum, of which it is the type. Initial molecular research, based on cladistic analysis of DNA sequences, indicates that Trichoglossum hirsutum sensu lato comprises at least three separate taxa in Europe and North America, though these may not be morphologically distinguishable. At least one of these cryptic species occurs in both continents.
Description
Ascocarps are club-shaped, up to tall, black to dark brown, with a swollen, spore-bearing head, up to a quarter or half the ascocarp height, and a finely hirsute, cylindrical stipe (stem) up to wide. Microscopically, dark, thick-walled, acute setae are present. The asci are 8-spored, the ascospores 110–160 × 5–7 μm, becoming 15-septate at maturity.
The epithet hirsutum (Latin: 'hairy') refers to the fine hairs (setae) that cover the ascocarp.
Similar species
Many Trichoglossum species appear similar in the field and can only be identified by microscopic examination. Superficially similar species of Geoglossum lack setae and are not finely hirsute under a hand lens. Thuemenidium atropurpureum is usually more robust and can be slightly purplish. Microglossum species have non-black hues. Tolypocladium ophioglossoides can appear similar in age.
Conservation
In Europe the short-spored earthtongue is typical of waxcap grasslands, a declining habitat due to changing agricultural practices.
Gallery
References
External links
Trichoglossum hirsutum at mushroomobserver.org
Trichoglossum hirsutum at California Fungi
Key to Club Fungi in the Pacific Northwest
Geoglossaceae
Fungi of North America
Fungi of Europe
Fungi described in 1794
Fungi of Macaronesia
Taxa named by Christiaan Hendrik Persoon
Fungus species | Trichoglossum hirsutum | Biology | 535 |
15,378,722 | https://en.wikipedia.org/wiki/DASB | DASB, also known as 3-amino-4-(2-dimethylaminomethylphenylsulfanyl)-benzonitrile, is a compound that binds to the serotonin transporter.
Labeled with carbon-11 — a radioactive isotope — it has been used as a radioligand in neuroimaging with positron emission tomography (PET) since around year 2000.
In this context it is regarded as one of the superior radioligands for PET study of the serotonin transporter in the brain,
since it has high selectivity for the serotonin transporter.
The DASB image from a human PET scan shows high binding in the midbrain, thalamus and striatum, moderate binding in the medial temporal lobe and anterior cingulate, and low binding in neocortex.
The cerebellum is often regarded as a region with no specific serotonin transporter binding and the brain region is used as a reference in some studies.
Since the serotonin transporter is the target of SSRIs used in the treatment of major depression it has been natural to examine DASB binding in depressed patients.
Several such research studies have been performed.
There are a number of alternative PET radioligands for imaging the serotonin transporter: [11C]ADAM, [11C]MADAM, [11C]AFM, [11C]DAPA, [11C]McN5652, and [11C]-NS 4194.
A related molecule to DASB, that can be labeled with fluorine-18, has also been suggested as a PET radioligand.
With single-photon emission computed tomography (SPECT) using the radioisotope iodine-123 there are further radioligands available: [123I]ODAM, [123I]IDAM, [123I]ADAM, and [123I]β-CIT.
A few studies have examined the difference in binding between the radioligands in nonhuman primates,
as well as in pigs.
Other compounds that can be labeled to work as PET radioligands for the study of the serotonin system are, e.g., altanserin and WAY-100635.
Methodological issues
The binding potential of DASB can be estimated with kinetic modeling on a series of brain scans.
A test-retest reproducibility PET study indicates that [11C]DASB can be used to measure the serotonin transporter parameters with high reliability in receptor-rich brain regions.
When the DASB neuroimages are analyzed the kinetic models suggested by Ichise and coworkers can be employed to estimate the binding potential.
A test-retest reproducibility experiment has been performed to evaluate this approach.
Studies
Besides the studies listed below a few occupancy studies have been reported.
References
Treatment of bipolar disorder
Nitriles
Thioethers
PET radiotracers | DASB | Chemistry | 617 |
34,623,478 | https://en.wikipedia.org/wiki/List%20of%20enterprise%20portal%20vendors | This is a list of notable vendors of enterprise portals. An enterprise portal is a framework for integrating information, people and processes across organizational boundaries.
enterprise portal vendors | List of enterprise portal vendors | Technology | 33 |
50,425 | https://en.wikipedia.org/wiki/Quantum%20Hall%20effect | The quantum Hall effect (or integer quantum Hall effect) is a quantized version of the Hall effect which is observed in two-dimensional electron systems subjected to low temperatures and strong magnetic fields, in which the Hall resistance exhibits steps that take on the quantized values
where is the Hall voltage, is the channel current, is the elementary charge and is the Planck constant. The divisor can take on either integer () or fractional () values. Here, is roughly but not exactly equal to the filling factor of Landau levels. The quantum Hall effect is referred to as the integer or fractional quantum Hall effect depending on whether is an integer or fraction, respectively.
The striking feature of the integer quantum Hall effect is the persistence of the quantization (i.e. the Hall plateau) as the electron density is varied. Since the electron density remains constant when the Fermi level is in a clean spectral gap, this situation corresponds to one where the Fermi level is an energy with a finite density of states, though these states are localized (see Anderson localization).
The fractional quantum Hall effect is more complicated and still considered an open research problem. Its existence relies fundamentally on electron–electron interactions. In 1988, it was proposed that there was a quantum Hall effect without Landau levels. This quantum Hall effect is referred to as the quantum anomalous Hall (QAH) effect. There is also a new concept of the quantum spin Hall effect which is an analogue of the quantum Hall effect, where spin currents flow instead of charge currents.
Applications
Electrical resistance standards
The quantization of the Hall conductance () has the important property of being exceedingly precise. Actual measurements of the Hall conductance have been found to be integer or fractional multiples of to better than one part in a billion. It has allowed for the definition of a new practical standard for electrical resistance, based on the resistance quantum given by the von Klitzing constant . This is named after Klaus von Klitzing, the discoverer of exact quantization. The quantum Hall effect also provides an extremely precise independent determination of the fine-structure constant, a quantity of fundamental importance in quantum electrodynamics.
In 1990, a fixed conventional value was defined for use in resistance calibrations worldwide. On 16 November 2018, the 26th meeting of the General Conference on Weights and Measures decided to fix exact values of (the Planck constant) and (the elementary charge), superseding the 1990 conventional value with an exact permanent value (intrinsic standard) .
Research status
The fractional quantum Hall effect is considered part of exact quantization. Exact quantization in full generality is not completely understood but it has been explained as a very subtle manifestation of the combination of the principle of gauge invariance together with another symmetry (see Anomalies). The integer quantum Hall effect instead is considered a solved research problem and understood in the scope of TKNN formula and Chern–Simons Lagrangians.
The fractional quantum Hall effect is still considered an open research problem. The fractional quantum Hall effect can be also understood as an integer quantum Hall effect, although not of electrons but of charge–flux composites known as composite fermions. Other models to explain the fractional quantum Hall effect also exists.
Currently it is considered an open research problem because no single, confirmed and agreed list of fractional quantum numbers exists, neither a single agreed model to explain all of them, although there are such claims in the scope of composite fermions and Non Abelian Chern–Simons Lagrangians.
History
In 1957, Carl Frosch and Lincoln Derick were able to manufacture the first silicon dioxide field effect transistors at Bell Labs, the first transistors in which drain and source were adjacent at the surface. Subsequently, a team demonstrated a working MOSFET at Bell Labs 1960. This enabled physicists to study electron behavior in a nearly ideal two-dimensional gas.
In a MOSFET, conduction electrons travel in a thin surface layer, and a "gate" voltage controls the number of charge carriers in this layer. This allows researchers to explore quantum effects by operating high-purity MOSFETs at liquid helium temperatures.
The integer quantization of the Hall conductance was originally predicted by University of Tokyo researchers Tsuneya Ando, Yukio Matsumoto and Yasutada Uemura in 1975, on the basis of an approximate calculation which they themselves did not believe to be true. In 1978, the Gakushuin University researchers Jun-ichi Wakabayashi and Shinji Kawaji subsequently observed the effect in experiments carried out on the inversion layer of MOSFETs.
In 1980, Klaus von Klitzing, working at the high magnetic field laboratory in Grenoble with silicon-based MOSFET samples developed by Michael Pepper and Gerhard Dorda, made the unexpected discovery that the Hall resistance was exactly quantized. For this finding, von Klitzing was awarded the 1985 Nobel Prize in Physics. A link between exact quantization and gauge invariance was subsequently proposed by Robert Laughlin, who connected the quantized conductivity to the quantized charge transport in a Thouless charge pump. Most integer quantum Hall experiments are now performed on gallium arsenide heterostructures, although many other semiconductor materials can be used. In 2007, the integer quantum Hall effect was reported in graphene at temperatures as high as room temperature, and in the magnesium zinc oxide ZnO–MgxZn1−xO.
Integer quantum Hall effect
Landau levels
In two dimensions, when classical electrons are subjected to a magnetic field they follow circular cyclotron orbits. When the system is treated quantum mechanically, these orbits are quantized. To determine the values of the energy levels the Schrödinger equation must be solved.
Since the system is subjected to a magnetic field, it has to be introduced as an electromagnetic vector potential in the Schrödinger equation. The system considered is an electron gas that is free to move in the x and y directions, but is tightly confined in the z direction. Then, a magnetic field is applied in the z direction and according to the Landau gauge the electromagnetic vector potential is and the scalar potential is . Thus the Schrödinger equation for a particle of charge and effective mass in this system is:
where is the canonical momentum, which is replaced by the operator and is the total energy.
To solve this equation it is possible to separate it into two equations since the magnetic field just affects the movement along x and y axes. The total energy becomes then, the sum of two contributions . The corresponding equations in z axis is:
To simplify things, the solution is considered as an infinite well. Thus the solutions for the z direction are the energies , and the wavefunctions are sinusoidal. For the and directions, the solution of the Schrödinger equation can be chosen to be the product of a plane wave in -direction with some unknown function of , i.e., . This is because the vector potential does not depend on and the momentum operator therefore commutes with the Hamiltonian. By substituting this Ansatz into the Schrödinger equation one gets the one-dimensional harmonic oscillator equation centered at .
where is defined as the cyclotron frequency and the magnetic length. The energies are:
,
And the wavefunctions for the motion in the plane are given by the product of a plane wave in and Hermite polynomials attenuated by the gaussian function in , which are the wavefunctions of a harmonic oscillator.
From the expression for the Landau levels one notices that the energy depends only on , not on . States with the same but different are degenerate.
Density of states
At zero field, the density of states per unit surface for the two-dimensional electron gas taking into account degeneration due to spin is independent of the energy
.
As the field is turned on, the density of states collapses from the constant to a Dirac comb, a series of Dirac functions, corresponding to the Landau levels separated . At finite temperature, however, the Landau levels acquire a width being the time between scattering events. Commonly it is assumed that the precise shape of Landau levels is a Gaussian or Lorentzian profile.
Another feature is that the wave functions form parallel strips in the -direction spaced equally along the -axis, along the lines of . Since there is nothing special about any direction in the -plane if the vector potential was differently chosen one should find circular symmetry.
Given a sample of dimensions and applying the periodic boundary conditions in the -direction being an integer, one gets that each parabolic potential is placed at a value .
The number of states for each Landau Level and can be calculated from the ratio between the total magnetic flux that passes through the sample and the magnetic flux corresponding to a state.
Thus the density of states per unit surface is
.
Note the dependency of the density of states with the magnetic field. The larger the magnetic field is, the more states are in each Landau level. As a consequence, there is more confinement in the system since fewer energy levels are occupied.
Rewriting the last expression as it is clear that each Landau level contains as many states as in a 2DEG in a .
Given the fact that electrons are fermions, for each state available in the Landau levels it corresponds to two electrons, one electron with each value for the spin . However, if a large magnetic field is applied, the energies split into two levels due to the magnetic moment associated with the alignment of the spin with the magnetic field. The difference in the energies is being a factor which depends on the material ( for free electrons) and the Bohr magneton. The sign is taken when the spin is parallel to the field and when it is antiparallel. This fact called spin splitting implies that the density of states for each level is reduced by a half. Note that is proportional to the magnetic field so, the larger the magnetic field is, the more relevant is the split.
In order to get the number of occupied Landau levels, one defines the so-called filling factor as the ratio between the density of states in a 2DEG and the density of states in the Landau levels.
In general the filling factor is not an integer. It happens to be an integer when there is an exact number of filled Landau levels. Instead, it becomes a non-integer when the top level is not fully occupied. In actual experiments, one varies the magnetic field and fixes electron density (and not the Fermi energy!) or varies the electron density and fixes the magnetic field. Both cases correspond to a continuous variation of the filling factor and one cannot expect to be an integer. Since , by increasing the magnetic field, the Landau levels move up in energy and the number of states in each level grow, so fewer electrons occupy the top level until it becomes empty. If the magnetic field keeps increasing, eventually, all electrons will be in the lowest Landau level () and this is called the magnetic quantum limit.
Longitudinal resistivity
It is possible to relate the filling factor to the resistivity and hence, to the conductivity of the system. When is an integer, the Fermi energy lies in between Landau levels where there are no states available for carriers, so the conductivity becomes zero (it is considered that the magnetic field is big enough so that there is no overlap between Landau levels, otherwise there would be few electrons and the conductivity would be approximately ). Consequently, the resistivity becomes zero too (At very high magnetic fields it is proven that longitudinal conductivity and resistivity are proportional).
With the conductivity one finds
If the longitudinal resistivity is zero and transversal is finite, then . Thus both the longitudinal conductivity and resistivity become zero.
Instead, when is a half-integer, the Fermi energy is located at the peak of the density distribution of some Landau Level. This means that the conductivity will have a maximum .
This distribution of minimums and maximums corresponds to ¨quantum oscillations¨ called Shubnikov–de Haas oscillations which become more relevant as the magnetic field increases. Obviously, the height of the peaks are larger as the magnetic field increases since the density of states increases with the field, so there are more carriers which contribute to the resistivity. It is interesting to notice that if the magnetic field is very small, the longitudinal resistivity is a constant which means that the classical result is reached.
Transverse resistivity
From the classical relation of the transverse resistivity and substituting one finds out the quantization of the transverse resistivity and conductivity:
One concludes then, that the transverse resistivity is a multiple of the inverse of the so-called conductance quantum if the filling factor is an integer. In experiments, however, plateaus are observed for whole plateaus of filling values , which indicates that there are in fact electron states between the Landau levels. These states are localized in, for example, impurities of the material where they are trapped in orbits so they can not contribute to the conductivity. That is why the resistivity remains constant in between Landau levels. Again if the magnetic field decreases, one gets the classical result in which the resistivity is proportional to the magnetic field.
Photonic quantum Hall effect
The quantum Hall effect, in addition to being observed in two-dimensional electron systems, can be observed in photons. Photons do not possess inherent electric charge, but through the manipulation of discrete optical resonators and coupling phases or on-site phases, an artificial magnetic field can be created. This process can be expressed through a metaphor of photons bouncing between multiple mirrors. By shooting the light across multiple mirrors, the photons are routed and gain additional phase proportional to their angular momentum. This creates an effect like they are in a magnetic field.
Topological classification
The integers that appear in the Hall effect are examples of topological quantum numbers. They are known in mathematics as the first Chern numbers and are closely related to Berry's phase. A striking model of much interest in this context is the Azbel–Harper–Hofstadter model whose quantum phase diagram is the Hofstadter butterfly shown in the figure. The vertical axis is the strength of the magnetic field and the horizontal axis is the chemical potential, which fixes the electron density. The colors represent the integer Hall conductances. Warm colors represent positive integers and cold colors negative integers. Note, however, that the density of states in these regions of quantized Hall conductance is zero; hence, they cannot produce the plateaus observed in the experiments. The phase diagram is fractal and has structure on all scales. In the figure there is an obvious self-similarity. In the presence of disorder, which is the source of the plateaus seen in the experiments, this diagram is very different and the fractal structure is mostly washed away. Also, the experiments control the filling factor and not the Fermi energy. If this diagram is plotted as a function of filling factor, all the features are completely washed away, hence, it has very little to do with the actual Hall physics.
Concerning physical mechanisms, impurities and/or particular states (e.g., edge currents) are important for both the 'integer' and 'fractional' effects. In addition, Coulomb interaction is also essential in the fractional quantum Hall effect. The observed strong similarity between integer and fractional quantum Hall effects is explained by the tendency of electrons to form bound states with an even number of magnetic flux quanta, called composite fermions.
Bohr atom interpretation of the von Klitzing constant
The value of the von Klitzing constant may be obtained already on the level of a single atom within the Bohr model while looking at it as a single-electron Hall effect. While during the cyclotron motion on a circular orbit the centrifugal force is balanced by the Lorentz force responsible for the transverse induced voltage and the Hall effect, one may look at the Coulomb potential difference in the Bohr atom as the induced single atom Hall voltage and the periodic electron motion on a circle as a Hall current. Defining the single atom Hall current as a rate a single electron charge is making Kepler revolutions with angular frequency
and the induced Hall voltage as a difference between the hydrogen nucleus Coulomb potential at the electron orbital point and at infinity:
One obtains the quantization of the defined Bohr orbit Hall resistance in steps of the von Klitzing constant as
which for the Bohr atom is linear but not inverse in the integer n.
Relativistic analogs
Relativistic examples of the integer quantum Hall effect and quantum spin Hall effect arise in the context of lattice gauge theory.
See also
Quantum Hall transitions
Fractional quantum Hall effect
Quantum anomalous Hall effect
Quantum cellular automata
Composite fermions
Conductance Quantum
Hall effect
Hall probe
Graphene
Quantum spin Hall effect
Coulomb potential between two current loops embedded in a magnetic field
References
Further reading
25 years of Quantum Hall Effect, K. von Klitzing, Poincaré Seminar (Paris-2004). Postscript. Pdf.
Magnet Lab Press Release Quantum Hall Effect Observed at Room Temperature
Zyun F. Ezawa: Quantum Hall Effects - Field Theoretical Approach and Related Topics. World Scientific, Singapore 2008,
Sankar D. Sarma, Aron Pinczuk: Perspectives in Quantum Hall Effects. Wiley-VCH, Weinheim 2004,
E. I. Rashba and V. B. Timofeev, Quantum Hall Effect, Sov. Phys. – Semiconductors v. 20, pp. 617–647 (1986).
Hall effect
Condensed matter physics
Quantum electronics
Spintronics
Quantum phases
Mesoscopic physics
Articles containing video clips
1980 in science | Quantum Hall effect | Physics,Chemistry,Materials_science,Engineering | 3,646 |
207,547 | https://en.wikipedia.org/wiki/Th%C4%81bit%20ibn%20Qurra | Thābit ibn Qurra (full name: , , ; 826 or 836 – February 19, 901), was a polymath known for his work in mathematics, medicine, astronomy, and translation. He lived in Baghdad in the second half of the ninth century during the time of the Abbasid Caliphate.
Thābit ibn Qurra made important discoveries in algebra, geometry, and astronomy. In astronomy, Thābit is considered one of the first reformers of the Ptolemaic system, and in mechanics he was a founder of statics. Thābit also wrote extensively on medicine and produced philosophical treatises.
Biography
Thābit was born in Harran in Upper Mesopotamia, which at the time was part of the Diyar Mudar subdivision of the al-Jazira region of the Abbasid Caliphate. Thābit belonged to the Sabians of Harran, a Hellenized Semitic polytheistic astral religion that still existed in ninth-century Harran.
As a youth, Thābit worked as money changer in a marketplace in Harran until meeting Muḥammad ibn Mūsā, the oldest of three mathematicians and astronomers known as the Banū Mūsā. Thābit displayed such exceptional linguistic skills that ibn Mūsā chose him to come to Baghdad to be trained in mathematics, astronomy, and philosophy under the tutelage of the Banū Mūsā. Here, Thābit was introduced to not only a community of scholars but also to those who had significant power and influence in Baghdad.
Thābit and his pupils lived in the midst of the most intellectually vibrant, and probably the largest, city of the time, Baghdad. Thābit came to Baghdad in the first place to work for the Banū Mūsā becoming a part of their circle and helping them translate Greek mathematical texts. What is unknown is how Banū Mūsā and Thābit occupied himself with mathematics, astronomy, astrology, magic, mechanics, medicine, and philosophy. Later in his life, Thābit's patron was the Abbasid Caliph al-Mu'tadid (reigned 892–902), whom he became a court astronomer for. Thābit became the Caliph's personal friend and courtier. Thābit died in Baghdad in 901. His son, Sinan ibn Thabit and grandson, Ibrahim ibn Sinan would also make contributions to the medicine and science. By the end of his life, Thābit had managed to write 150 works on mathematics, astronomy, and medicine. With all the work done by Thābit, most of his work has not lasted time. There are less than a dozen works by him that have survived.
Translation
Thābit's native language was Syriac, which was the Middle Aramaic variety from Edessa, and he was fluent in both Medieval Greek and Arabic. He was the author to multiple treaties. Due to him being trilingual, Thābit was able to have a major role during the Graeco-Arabic translation movement. He would also make a school of translation in Baghdad.
Thābit translated from Greek into Arabic works by Apollonius of Perga, Archimedes, Euclid and Ptolemy. He revised the translation of Euclid's Elements of Hunayn ibn Ishaq. He also rewrote Ishaq ibn Hunayn's translation of Ptolemy's Almagest and translated Ptolemy's Geography.Thābit's translation of a work by Archimedes which gave a construction of a regular heptagon was discovered in the 20th century, the original having been lost.
Astronomy
Thābit is believed to have been an astronomer of Caliph al-Mu'tadid. Thābit was able to use his mathematical work on the examination of Ptolemaic astronomy. The medieval astronomical theory of the trepidation of the equinoxes is often attributed to Thābit. But it had already been described by Theon of Alexandria in his comments of the Handy Tables of Ptolemy. According to Copernicus, Thābit determined the length of the sidereal year as 365 days, 6 hours, 9 minutes and 12 seconds (an error of 2 seconds). Copernicus based his claim on the Latin text attributed to Thābit. Thābit published his observations of the Sun. In regards to Ptolemy's Planetary Hypotheses, Thābit examined the problems of the motion of the Sun and Moon, and the theory of sundials. When looking at Ptolemy's Hypotheses, Thābit ibn Qurra found the Sidereal year which is when looking at the Earth and measuring it against the background of fixed stars, it will have a constant value.
Thābit was also an author and wrote De Anno Solis. This book contained and recorded facts about the evolution in astronomy in the ninth century. Thābit mentioned in the book that Ptolemy and Hipparchus believed that the movement of stars is consistent with the movement commonly found in planets. What Thābit believed is that this idea can be broadened to include the Sun and Moon. With that in mind, he also thought that the solar year should be calculated by looking at the Sun's return to a given star.
Mathematics
In mathematics, Thābit derived an equation for determining amicable numbers. His proof of this rule is presented in the Treatise on the Derivation of the Amicable Numbers in an Easy Way. This was done while writing on the theory of numbers, extending their use to describe the ratios between geometrical quantities, a step which the Greeks did not take. Thābit's work on amicable numbers and number theory helped him to invest more heavily into the Geometrical relations of numbers establishing his Transversal (geometry) theorem.
Thābit described a generalized proof of the Pythagorean theorem. He provided a strengthened extension of Pythagoras' proof which included the knowledge of Euclid's fifth postulate. This postulate states that the intersection between two straight line segments combine to create two interior angles which are less than 180 degrees. The method of reduction and composition used by Thābit resulted in a combination and extension of contemporary and ancient knowledge on this famous proof. Thābit believed that geometry was tied with the equality and differences of magnitudes of lines and angles, as well as that ideas of motion (and ideas taken from physics more widely) should be integrated in geometry.
The continued work done on geometric relations and the resulting exponential series allowed Thābit to calculate multiple solutions to chessboard problems. This problem was less to do with the game itself, and more to do with the number of solutions or the nature of solutions possible. In Thābit's case, he worked with combinatorics to work on the permutations needed to win a game of chess.
In addition to Thābit's work on Euclidean geometry there is evidence that he was familiar with the geometry of Archimedes as well. His work with conic sections and the calculation of a paraboloid shape (cupola) show his proficiency as an Archimedean geometer. This is further embossed by Thābit's use of the Archimedean property in order to produce a rudimentary approximation of the volume of a paraboloid. The use of uneven sections, while relatively simple, does show a critical understanding of both Euclidean and Archimedean geometry. Thābit was also responsible for a commentary on Archimedes' .
Physics
In physics, Thābit rejected the Peripatetic and Aristotelian notions of a "natural place" for each element. He instead proposed a theory of motion in which both the upward and downward motions are caused by weight, and that the order of the universe is a result of two competing attractions (jadhb): one of these being "between the sublunar and celestial elements", and the other being "between all parts of each element separately". and in mechanics he was a founder of statics. In addition, Thābit's Liber Karatonis contained proof of the law of the lever. This work was the result of combining Aristotelian and Archimedean ideas of dynamics and mechanics.
One of Qurra's most important pieces of text is his work with the Kitab fi 'l-qarastun. This text consists of Arabic mechanical tradition. Another piece of important text is Kitab fi sifat alwazn, which discussed concepts of equal-armed balance. Qurra was reportedly one of the first to write about the concept of equal-armed balance or at least to systematize the treatment.
Qurra sought to establish a relationship between forces of motion and the distance traveled by the mobile.
Medicine
Thābit was well known as a physician and produced a substantial number of medical treatises and commentaries. His works included general reference books such as al-Dhakhira fī ilm al-tibb ("A Treasury of Medicine"), Kitāb al-Rawda fi l–tibb ("Book of the Garden of Medicine"), and al-Kunnash ("Collection"). He also produced specific works on topics such as gallstones; the treatment of diseases such as smallpox, measles, and conditions of the eye; and discussed veterinary medicine and the anatomy of birds. Thābit wrote commentaries on the works of Galen and others, including such works as On Plants (attributed to Aristotle but likely written by the first-century BC philosopher Nicolaus of Damascus).
One account of Thābit's work as a physician is given in Ibn al-Qiftī's Ta’rikh al-hukamā, where Thābit is credited with healing a butcher who was presumed to be certain to die.
Works
Only a few of Thābit's works are preserved in their original form.
On the Sector-Figure which deals with Menelaus' theorem.
On the Composition of Ratios
Kitab fi 'l-qarastun (Book of the Steelyard)
Kitab fi sifat alwazn (Book on the Description of Weight) - Short text on equal-armed balance
Additional works by Thābit include:
Kitāb al-Mafrūdāt (Book of Data)
Maqāla fīistikhrāj al-a‘dād al-mutahābba bi–suhūlat al-maslak ilā dhālika (Book on the Determination of Amicable Numbers)
Kitāb fi Misāhat qat‘ almakhrūt alladhī yusammaā al-mukāfi’ (Book on the Measurement of the Conic Section Called Parabolic)
Kitāb fī Sanat al-shams (Book on the Solar Year)
Qawl fi’l–Sabab alladhī ju‘ilat lahu miyāh al-bahr māliha (Discourse on the Reason Why Seawater Is Salted)
al-Dhakhira fī ilm al-tibb (A Treasury of Medicine)
Kitāb fi ‘ilm al-‘ayn . . . (Book on the Science of the Eye…)
Kitāb fi’l–jadarī wa’l–hasbā (Book on Smallpox and Measles)
Masā’il su’ila ’anhā Thābit ibn Qurra al-Harrānī (Questions Posed to Thābit. . .)
In his epitome of al-Qifṭī's Kitāb ikhbār al-'ulamā' bi akhbār al-ḥukamā, al-Zawzanī lists seven religious works in Syriac by Thābit and says that he also wrote in Syriac on music and geometry. According to Bar Hebraeus, the 13th-century Syriac historian, Thābit wrote some 150 works in Arabic and 16 in Syriac. He claims to have seen most of the Syriac works himself and lists them. The list of Bar Hebraeus is consistent with that of al-Zawzanī. Most of the works concern pagan religion, but there is a work on music and two on geometry as well as a "book of the chronicle of the ancient Syrian kings, who are Chaldeans" and a "book on the renown of his race and his forefathers, from whom they descend".
Eponyms
Thabit number
Thebit (crater)
See also
al-Battani, a contemporary Sabian astronomer and mathematician
References
Sources used
Further reading
Francis J. Carmody: The astronomical works of Thābit b. Qurra. 262 pp. Berkeley and Los Angeles: University of California Press, 1960.
Reviews: Seyyed Hossein Nasr (1998) in Isis 89 (1) pp. 112-113; Charles Burnett (1998) in Bulletin of the School of Oriental and African Studies, University of London 61 (2) p. 406.
Churton, Tobias. The Golden Builders: Alchemists, Rosicrucians, and the First Freemasons. Barnes and Noble Publishing, 2006.
Hakim S Ayub Ali. Zakhira-i Thābit ibn Qurra (preface by Hakim Syed Zillur Rahman), Aligarh, India, 1987.
External links
(PDF version)
Thabit ibn Qurra on Astrology & Magic
9th-century births
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Astronomers from the Abbasid Caliphate
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Syriac writers | Thābit ibn Qurra | Mathematics | 2,761 |
147,853 | https://en.wikipedia.org/wiki/Speed%20of%20sound | The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. More simply, the speed of sound is how fast vibrations travel. At , the speed of sound in air, is about , or in or one mile in . It depends strongly on temperature as well as the medium through which a sound wave is propagating.
At , the speed of sound in dry air (sea level 14.7 psi) is about .
The speed of sound in an ideal gas depends only on its temperature and composition. The speed has a weak dependence on frequency and pressure in dry air, deviating slightly from ideal behavior.
In colloquial speech, speed of sound refers to the speed of sound waves in air. However, the speed of sound varies from substance to substance: typically, sound travels most slowly in gases, faster in liquids, and fastest in solids.
For example, while sound travels at in air, it travels at in water (almost 4.3 times as fast) and at in iron (almost 15 times as fast). In an exceptionally stiff material such as diamond, sound travels at 12,000 m/s (39,370 ft/s), about 35 times its speed in air and about the fastest it can travel under normal conditions.
In theory, the speed of sound is actually the speed of vibrations. Sound waves in solids are composed of compression waves (just as in gases and liquids) and a different type of sound wave called a shear wave, which occurs only in solids. Shear waves in solids usually travel at different speeds than compression waves, as exhibited in seismology. The speed of compression waves in solids is determined by the medium's compressibility, shear modulus, and density. The speed of shear waves is determined only by the solid material's shear modulus and density.
In fluid dynamics, the speed of sound in a fluid medium (gas or liquid) is used as a relative measure for the speed of an object moving through the medium. The ratio of the speed of an object to the speed of sound (in the same medium) is called the object's Mach number. Objects moving at speeds greater than the speed of sound () are said to be traveling at supersonic speeds.
Earth
In Earth's atmosphere, the speed of sound varies greatly from about at high altitudes to about at high temperatures.
History
Sir Isaac Newton's 1687 Principia includes a computation of the speed of sound in air as . This is too low by about 15%. The discrepancy is due primarily to neglecting the (then unknown) effect of rapidly fluctuating temperature in a sound wave (in modern terms, sound wave compression and expansion of air is an adiabatic process, not an isothermal process). This error was later rectified by Laplace.
During the 17th century there were several attempts to measure the speed of sound accurately, including attempts by Marin Mersenne in 1630 (1,380 Parisian feet per second), Pierre Gassendi in 1635 (1,473 Parisian feet per second) and Robert Boyle (1,125 Parisian feet per second). In 1709, the Reverend William Derham, Rector of Upminster, published a more accurate measure of the speed of sound, at 1,072 Parisian feet per second. (The Parisian foot was . This is longer than the standard "international foot" in common use today, which was officially defined in 1959 as , making the speed of sound at 1,055 Parisian feet per second).
Derham used a telescope from the tower of the church of St. Laurence, Upminster to observe the flash of a distant shotgun being fired, and then measured the time until he heard the gunshot with a half-second pendulum. Measurements were made of gunshots from a number of local landmarks, including North Ockendon church. The distance was known by triangulation, and thus the speed that the sound had travelled was calculated.
Basic concepts
The transmission of sound can be illustrated by using a model consisting of an array of spherical objects interconnected by springs.
In real material terms, the spheres represent the material's molecules and the springs represent the bonds between them. Sound passes through the system by compressing and expanding the springs, transmitting the acoustic energy to neighboring spheres. This helps transmit the energy in-turn to the neighboring sphere's springs (bonds), and so on.
The speed of sound through the model depends on the stiffness/rigidity of the springs, and the mass of the spheres. As long as the spacing of the spheres remains constant, stiffer springs/bonds transmit energy more quickly, while more massive spheres transmit energy more slowly.
In a real material, the stiffness of the springs is known as the "elastic modulus", and the mass corresponds to the material density. Sound will travel more slowly in spongy materials and faster in stiffer ones. Effects like dispersion and reflection can also be understood using this model.
Some textbooks mistakenly state that the speed of sound increases with density. This notion is illustrated by presenting data for three materials, such as air, water, and steel and noting that the speed of sound is higher in the denser materials. But the example fails to take into account that the materials have vastly different compressibility, which more than makes up for the differences in density, which would slow wave speeds in the denser materials. An illustrative example of the two effects is that sound travels only 4.3 times faster in water than air, despite enormous differences in compressibility of the two media. The reason is that the greater density of water, which works to slow sound in water relative to the air, nearly makes up for the compressibility differences in the two media.
For instance, sound will travel 1.59 times faster in nickel than in bronze, due to the greater stiffness of nickel at about the same density. Similarly, sound travels about 1.41 times faster in light hydrogen (protium) gas than in heavy hydrogen (deuterium) gas, since deuterium has similar properties but twice the density. At the same time, "compression-type" sound will travel faster in solids than in liquids, and faster in liquids than in gases, because the solids are more difficult to compress than liquids, while liquids, in turn, are more difficult to compress than gases.
A practical example can be observed in Edinburgh when the "One o'Clock Gun" is fired at the eastern end of Edinburgh Castle. Standing at the base of the western end of the Castle Rock, the sound of the Gun can be heard through the rock, slightly before it arrives by the air route, partly delayed by the slightly longer route. It is particularly effective if a multi-gun salute such as for "The Queen's Birthday" is being fired.
Compression and shear waves
In a gas or liquid, sound consists of compression waves. In solids, waves propagate as two different types. A longitudinal wave is associated with compression and decompression in the direction of travel, and is the same process in gases and liquids, with an analogous compression-type wave in solids. Only compression waves are supported in gases and liquids. An additional type of wave, the transverse wave, also called a shear wave, occurs only in solids because only solids support elastic deformations. It is due to elastic deformation of the medium perpendicular to the direction of wave travel; the direction of shear-deformation is called the "polarization" of this type of wave. In general, transverse waves occur as a pair of orthogonal polarizations.
These different waves (compression waves and the different polarizations of shear waves) may have different speeds at the same frequency. Therefore, they arrive at an observer at different times, an extreme example being an earthquake, where sharp compression waves arrive first and rocking transverse waves seconds later.
The speed of a compression wave in a fluid is determined by the medium's compressibility and density. In solids, the compression waves are analogous to those in fluids, depending on compressibility and density, but with the additional factor of shear modulus which affects compression waves due to off-axis elastic energies which are able to influence effective tension and relaxation in a compression. The speed of shear waves, which can occur only in solids, is determined simply by the solid material's shear modulus and density.
Equations
The speed of sound in mathematical notation is conventionally represented by c, from the Latin celeritas meaning "swiftness".
For fluids in general, the speed of sound c is given by the Newton–Laplace equation:
where
is a coefficient of stiffness, the isentropic bulk modulus (or the modulus of bulk elasticity for gases);
is the density.
, where is the pressure and the derivative is taken isentropically, that is, at constant entropy s. This is because a sound wave travels so fast that its propagation can be approximated as an adiabatic process, meaning that there isn't enough time, during a pressure cycle of the sound, for significant heat conduction and radiation to occur.
Thus, the speed of sound increases with the stiffness (the resistance of an elastic body to deformation by an applied force) of the material and decreases with an increase in density. For ideal gases, the bulk modulus K is simply the gas pressure multiplied by the dimensionless adiabatic index, which is about 1.4 for air under normal conditions of pressure and temperature.
For general equations of state, if classical mechanics is used, the speed of sound c can be derived as follows:
Consider the sound wave propagating at speed through a pipe aligned with the axis and with a cross-sectional area of . In time interval it moves length . In steady state, the mass flow rate must be the same at the two ends of the tube, therefore the mass flux is constant and . Per Newton's second law, the pressure-gradient force provides the acceleration:
And therefore:
If relativistic effects are important, the speed of sound is calculated from the relativistic Euler equations.
In a non-dispersive medium, the speed of sound is independent of sound frequency, so the speeds of energy transport and sound propagation are the same for all frequencies. Air, a mixture of oxygen and nitrogen, constitutes a non-dispersive medium. However, air does contain a small amount of CO2 which is a dispersive medium, and causes dispersion to air at ultrasonic frequencies (greater than ).
In a dispersive medium, the speed of sound is a function of sound frequency, through the dispersion relation. Each frequency component propagates at its own speed, called the phase velocity, while the energy of the disturbance propagates at the group velocity. The same phenomenon occurs with light waves; see optical dispersion for a description.
Dependence on the properties of the medium
The speed of sound is variable and depends on the properties of the substance through which the wave is travelling. In solids, the speed of transverse (or shear) waves depends on the shear deformation under shear stress (called the shear modulus), and the density of the medium. Longitudinal (or compression) waves in solids depend on the same two factors with the addition of a dependence on compressibility.
In fluids, only the medium's compressibility and density are the important factors, since fluids do not transmit shear stresses. In heterogeneous fluids, such as a liquid filled with gas bubbles, the density of the liquid and the compressibility of the gas affect the speed of sound in an additive manner, as demonstrated in the hot chocolate effect.
In gases, adiabatic compressibility is directly related to pressure through the heat capacity ratio (adiabatic index), while pressure and density are inversely related to the temperature and molecular weight, thus making only the completely independent properties of temperature and molecular structure important (heat capacity ratio may be determined by temperature and molecular structure, but simple molecular weight is not sufficient to determine it).
Sound propagates faster in low molecular weight gases such as helium than it does in heavier gases such as xenon. For monatomic gases, the speed of sound is about 75% of the mean speed that the atoms move in that gas.
For a given ideal gas the molecular composition is fixed, and thus the speed of sound depends only on its temperature. At a constant temperature, the gas pressure has no effect on the speed of sound, since the density will increase, and since pressure and density (also proportional to pressure) have equal but opposite effects on the speed of sound, and the two contributions cancel out exactly. In a similar way, compression waves in solids depend both on compressibility and density—just as in liquids—but in gases the density contributes to the compressibility in such a way that some part of each attribute factors out, leaving only a dependence on temperature, molecular weight, and heat capacity ratio which can be independently derived from temperature and molecular composition (see derivations below). Thus, for a single given gas (assuming the molecular weight does not change) and over a small temperature range (for which the heat capacity is relatively constant), the speed of sound becomes dependent on only the temperature of the gas.
In non-ideal gas behavior regimen, for which the Van der Waals gas equation would be used, the proportionality is not exact, and there is a slight dependence of sound velocity on the gas pressure.
Humidity has a small but measurable effect on the speed of sound (causing it to increase by about 0.1%–0.6%), because oxygen and nitrogen molecules of the air are replaced by lighter molecules of water. This is a simple mixing effect.
Altitude variation and implications for atmospheric acoustics
In the Earth's atmosphere, the chief factor affecting the speed of sound is the temperature. For a given ideal gas with constant heat capacity and composition, the speed of sound is dependent solely upon temperature; see below. In such an ideal case, the effects of decreased density and decreased pressure of altitude cancel each other out, save for the residual effect of temperature.
Since temperature (and thus the speed of sound) decreases with increasing altitude up to , sound is refracted upward, away from listeners on the ground, creating an acoustic shadow at some distance from the source. The decrease of the speed of sound with height is referred to as a negative sound speed gradient.
However, there are variations in this trend above . In particular, in the stratosphere above about , the speed of sound increases with height, due to an increase in temperature from heating within the ozone layer. This produces a positive speed of sound gradient in this region. Still another region of positive gradient occurs at very high altitudes, in the thermosphere above .
Details
Speed of sound in ideal gases and air
For an ideal gas, K (the bulk modulus in equations above, equivalent to C, the coefficient of stiffness in solids) is given by
Thus, from the Newton–Laplace equation above, the speed of sound in an ideal gas is given by
where
γ is the adiabatic index also known as the isentropic expansion factor. It is the ratio of the specific heat of a gas at constant pressure to that of a gas at constant volume () and arises because a classical sound wave induces an adiabatic compression, in which the heat of the compression does not have enough time to escape the pressure pulse, and thus contributes to the pressure induced by the compression;
p is the pressure;
ρ is the density.
Using the ideal gas law to replace p with nRT/V, and replacing ρ with nM/V, the equation for an ideal gas becomes
where
cideal is the speed of sound in an ideal gas;
R is the molar gas constant;
k is the Boltzmann constant;
γ (gamma) is the adiabatic index. At room temperature, where thermal energy is fully partitioned into rotation (rotations are fully excited) but quantum effects prevent excitation of vibrational modes, the value is for diatomic gases (such as oxygen and nitrogen), according to kinetic theory. Gamma is actually experimentally measured over a range from 1.3991 to 1.403 at , for air. Gamma is exactly for monatomic gases (such as argon) and it is for triatomic molecule gases that, like , are not co-linear (a co-linear triatomic gas such as is equivalent to a diatomic gas for our purposes here);
T is the absolute temperature;
M is the molar mass of the gas. The mean molar mass for dry air is about ;
n is the number of moles;
m is the mass of a single molecule.
This equation applies only when the sound wave is a small perturbation on the ambient condition, and the certain other noted conditions are fulfilled, as noted below. Calculated values for cair have been found to vary slightly from experimentally determined values.
Newton famously considered the speed of sound before most of the development of thermodynamics and so incorrectly used isothermal calculations instead of adiabatic. His result was missing the factor of γ but was otherwise correct.
Numerical substitution of the above values gives the ideal gas approximation of sound velocity for gases, which is accurate at relatively low gas pressures and densities (for air, this includes standard Earth sea-level conditions). Also, for diatomic gases the use of requires that the gas exists in a temperature range high enough that rotational heat capacity is fully excited (i.e., molecular rotation is fully used as a heat energy "partition" or reservoir); but at the same time the temperature must be low enough that molecular vibrational modes contribute no heat capacity (i.e., insignificant heat goes into vibration, as all vibrational quantum modes above the minimum-energy-mode have energies that are too high to be populated by a significant number of molecules at this temperature). For air, these conditions are fulfilled at room temperature, and also temperatures considerably below room temperature (see tables below). See the section on gases in specific heat capacity for a more complete discussion of this phenomenon.
For air, we introduce the shorthand
In addition, we switch to the Celsius temperature , which is useful to calculate air speed in the region near (). Then, for dry air,
Substituting numerical values
and using the ideal diatomic gas value of , we have
Finally, Taylor expansion of the remaining square root in yields
A graph comparing results of the two equations is to the right, using the slightly more accurate value of for the speed of sound at .
Effects due to wind shear
The speed of sound varies with temperature. Since temperature and sound velocity normally decrease with increasing altitude, sound is refracted upward, away from listeners on the ground, creating an acoustic shadow at some distance from the source. Wind shear of 4 m/(s · km) can produce refraction equal to a typical temperature lapse rate of . Higher values of wind gradient will refract sound downward toward the surface in the downwind direction, eliminating the acoustic shadow on the downwind side. This will increase the audibility of sounds downwind. This downwind refraction effect occurs because there is a wind gradient; the fact that sound is carried along by the wind is not important.
For sound propagation, the exponential variation of wind speed with height can be defined as follows:
where
U(h) is the speed of the wind at height h;
ζ is the exponential coefficient based on ground surface roughness, typically between 0.08 and 0.52;
dU/dH(h) is the expected wind gradient at height h.
In the 1862 American Civil War Battle of Iuka, an acoustic shadow, believed to have been enhanced by a northeast wind, kept two divisions of Union soldiers out of the battle, because they could not hear the sounds of battle only (six miles) downwind.
Tables
In the standard atmosphere:
T0 is (= = ), giving a theoretical value of (= = = = ). Values ranging from 331.3 to may be found in reference literature, however;
T20 is (= = ), giving a value of (= = = = );
T25 is (= = ), giving a value of (= = = = ).
In fact, assuming an ideal gas, the speed of sound c depends on temperature and composition only, not on the pressure or density (since these change in lockstep for a given temperature and cancel out). Air is almost an ideal gas. The temperature of the air varies with altitude, giving the following variations in the speed of sound using the standard atmosphere—actual conditions may vary.
Given normal atmospheric conditions, the temperature, and thus speed of sound, varies with altitude:
Effect of frequency and gas composition
General physical considerations
The medium in which a sound wave is travelling does not always respond adiabatically, and as a result, the speed of sound can vary with frequency.
The limitations of the concept of speed of sound due to extreme attenuation are also of concern. The attenuation which exists at sea level for high frequencies applies to successively lower frequencies as atmospheric pressure decreases, or as the mean free path increases. For this reason, the concept of speed of sound (except for frequencies approaching zero) progressively loses its range of applicability at high altitudes. The standard equations for the speed of sound apply with reasonable accuracy only to situations in which the wavelength of the sound wave is considerably longer than the mean free path of molecules in a gas.
The molecular composition of the gas contributes both as the mass (M) of the molecules, and their heat capacities, and so both have an influence on speed of sound. In general, at the same molecular mass, monatomic gases have slightly higher speed of sound (over 9% higher) because they have a higher γ (...) than diatomics do (). Thus, at the same molecular mass, the speed of sound of a monatomic gas goes up by a factor of
This gives the 9% difference, and would be a typical ratio for speeds of sound at room temperature in helium vs. deuterium, each with a molecular weight of 4. Sound travels faster in helium than deuterium because adiabatic compression heats helium more since the helium molecules can store heat energy from compression only in translation, but not rotation. Thus helium molecules (monatomic molecules) travel faster in a sound wave and transmit sound faster. (Sound travels at about 70% of the mean molecular speed in gases; the figure is 75% in monatomic gases and 68% in diatomic gases).
In this example we have assumed that temperature is low enough that heat capacities are not influenced by molecular vibration (see heat capacity). However, vibrational modes simply cause gammas which decrease toward 1, since vibration modes in a polyatomic gas give the gas additional ways to store heat which do not affect temperature, and thus do not affect molecular velocity and sound velocity. Thus, the effect of higher temperatures and vibrational heat capacity acts to increase the difference between the speed of sound in monatomic vs. polyatomic molecules, with the speed remaining greater in monatomics.
Practical application to air
By far, the most important factor influencing the speed of sound in air is temperature. The speed is proportional to the square root of the absolute temperature, giving an increase of about per degree Celsius. For this reason, the pitch of a musical wind instrument increases as its temperature increases.
The speed of sound is raised by humidity. The difference between 0% and 100% humidity is about at standard pressure and temperature, but the size of the humidity effect increases dramatically with temperature.
The dependence on frequency and pressure are normally insignificant in practical applications. In dry air, the speed of sound increases by about as the frequency rises from to . For audible frequencies above it is relatively constant. Standard values of the speed of sound are quoted in the limit of low frequencies, where the wavelength is large compared to the mean free path.
As shown above, the approximate value 1000/3 = 333.33... m/s is exact a little below and is a good approximation for all "usual" outside temperatures (in temperate climates, at least), hence the usual rule of thumb to determine how far lightning has struck: count the seconds from the start of the lightning flash to the start of the corresponding roll of thunder and divide by 3: the result is the distance in kilometers to the nearest point of the lightning bolt. Or divide the number of seconds by 5 for an approximate distance in miles.
Mach number
Mach number, a useful quantity in aerodynamics, is the ratio of air speed to the local speed of sound. At altitude, for reasons explained, Mach number is a function of temperature.
Aircraft flight instruments, however, operate using pressure differential to compute Mach number, not temperature. The assumption is that a particular pressure represents a particular altitude and, therefore, a standard temperature. Aircraft flight instruments need to operate this way because the stagnation pressure sensed by a Pitot tube is dependent on altitude as well as speed.
Experimental methods
A range of different methods exist for the measurement of the speed of sound in air.
The earliest reasonably accurate estimate of the speed of sound in air was made by William Derham and acknowledged by Isaac Newton. Derham had a telescope at the top of the tower of the Church of St Laurence in Upminster, England. On a calm day, a synchronized pocket watch would be given to an assistant who would fire a shotgun at a pre-determined time from a conspicuous point some miles away, across the countryside. This could be confirmed by telescope. He then measured the interval between seeing gunsmoke and arrival of the sound using a half-second pendulum. The distance from where the gun was fired was found by triangulation, and simple division (distance/time) provided velocity. Lastly, by making many observations, using a range of different distances, the inaccuracy of the half-second pendulum could be averaged out, giving his final estimate of the speed of sound. Modern stopwatches enable this method to be used today over distances as short as 200–400 metres, and not needing something as loud as a shotgun.
Single-shot timing methods
The simplest concept is the measurement made using two microphones and a fast recording device such as a digital storage scope. This method uses the following idea.
If a sound source and two microphones are arranged in a straight line, with the sound source at one end, then the following can be measured:
The distance between the microphones (), called microphone basis.
The time of arrival between the signals (delay) reaching the different microphones ().
Then .
Other methods
In these methods, the time measurement has been replaced by a measurement of the inverse of time (frequency).
Kundt's tube is an example of an experiment which can be used to measure the speed of sound in a small volume. It has the advantage of being able to measure the speed of sound in any gas. This method uses a powder to make the nodes and antinodes visible to the human eye. This is an example of a compact experimental setup.
A tuning fork can be held near the mouth of a long pipe which is dipping into a barrel of water. In this system it is the case that the pipe can be brought to resonance if the length of the air column in the pipe is equal to where n is an integer. As the antinodal point for the pipe at the open end is slightly outside the mouth of the pipe it is best to find two or more points of resonance and then measure half a wavelength between these.
Here it is the case that v = fλ.
High-precision measurements in air
The effect of impurities can be significant when making high-precision measurements. Chemical desiccants can be used to dry the air, but will, in turn, contaminate the sample. The air can be dried cryogenically, but this has the effect of removing the carbon dioxide as well; therefore many high-precision measurements are performed with air free of carbon dioxide rather than with natural air. A 2002 review found that a 1963 measurement by Smith and Harlow using a cylindrical resonator gave "the most probable value of the standard speed of sound to date." The experiment was done with air from which the carbon dioxide had been removed, but the result was then corrected for this effect so as to be applicable to real air. The experiments were done at but corrected for temperature in order to report them at . The result was for dry air at STP, for frequencies from to .
Non-gaseous media
Speed of sound in solids
Three-dimensional solids
In a solid, there is a non-zero stiffness both for volumetric deformations and shear deformations. Hence, it is possible to generate sound waves with different velocities dependent
on the deformation mode. Sound waves generating volumetric deformations (compression) and shear deformations (shearing) are called pressure waves (longitudinal waves) and shear waves (transverse waves), respectively. In earthquakes, the corresponding seismic waves are called P-waves (primary waves) and S-waves (secondary waves), respectively. The sound velocities of these two types of waves propagating in a homogeneous 3-dimensional solid are respectively given by
where
K is the bulk modulus of the elastic materials;
G is the shear modulus of the elastic materials;
E is the Young's modulus;
ρ is the density;
ν is Poisson's ratio.
The last quantity is not an independent one, as . The speed of pressure waves depends both on the pressure and shear resistance properties of the material, while the speed of shear waves depends on the shear properties only.
Typically, pressure waves travel faster in materials than do shear waves, and in earthquakes this is the reason that the onset of an earthquake is often preceded by a quick upward-downward shock, before arrival of waves that produce a side-to-side motion. For example, for a typical steel alloy, , and , yielding a compressional speed csolid,p of . This is in reasonable agreement with csolid,p measured experimentally at for a (possibly different) type of steel. The shear speed csolid,s is estimated at using the same numbers.
Speed of sound in semiconductor solids can be very sensitive to the amount of electronic dopant in them.
One-dimensional solids
The speed of sound for pressure waves in stiff materials such as metals is sometimes given for "long rods" of the material in question, in which the speed is easier to measure. In rods where their diameter is shorter than a wavelength, the speed of pure pressure waves may be simplified and is given by:
where is Young's modulus. This is similar to the expression for shear waves, save that Young's modulus replaces the shear modulus. This speed of sound for pressure waves in long rods will always be slightly less than the same speed in homogeneous 3-dimensional solids, and the ratio of the speeds in the two different types of objects depends on Poisson's ratio for the material.
Speed of sound in liquids
In a fluid, the only non-zero stiffness is to volumetric deformation (a fluid does not sustain shear forces).
Hence the speed of sound in a fluid is given by
where is the bulk modulus of the fluid.
Water
In fresh water, sound travels at about at (see the External Links section below for online calculators). Applications of underwater sound can be found in sonar, acoustic communication and acoustical oceanography.
Seawater
In salt water that is free of air bubbles or suspended sediment, sound travels at about ( at , and 3% salinity by one method). The speed of sound in seawater depends on pressure (hence depth), temperature (a change of ~ ), and salinity (a change of 1‰ ~ ), and empirical equations have been derived to accurately calculate the speed of sound from these variables. Other factors affecting the speed of sound are minor. Since in most ocean regions temperature decreases with depth, the profile of the speed of sound with depth decreases to a minimum at a depth of several hundred metres. Below the minimum, sound speed increases again, as the effect of increasing pressure overcomes the effect of decreasing temperature (right). For more information see Dushaw et al.
An empirical equation for the speed of sound in sea water is provided by Mackenzie:
where
T is the temperature in degrees Celsius;
S is the salinity in parts per thousand;
z is the depth in metres.
The constants a1, a2, ..., a9 are
with check value for , , . This equation has a standard error of for salinity between 25 and 40 ppt. See for an online calculator.
(The Sound Speed vs. Depth graph does not correlate directly to the MacKenzie formula.
This is due to the fact that the temperature and salinity varies at different depths.
When T and S are held constant, the formula itself is always increasing with depth.)
Other equations for the speed of sound in sea water are accurate over a wide range of conditions, but are far more complicated, e.g., that by V. A. Del Grosso and the Chen-Millero-Li Equation.
Speed of sound in plasma
The speed of sound in a plasma for the common case that the electrons are hotter than the ions (but not too much hotter) is given by the formula (see here)
where
mi is the ion mass;
μ is the ratio of ion mass to proton mass ;
Te is the electron temperature;
Z is the charge state;
k is Boltzmann constant;
γ is the adiabatic index.
In contrast to a gas, the pressure and the density are provided by separate species: the pressure by the electrons and the density by the ions. The two are coupled through a fluctuating electric field.
Mars
The speed of sound on Mars varies as a function of frequency. Higher frequencies travel faster than lower frequencies. Higher frequency sound from lasers travels at , while low frequency sound travels at .
Gradients
When sound spreads out evenly in all directions in three dimensions, the intensity drops in proportion to the inverse square of the distance. However, in the ocean, there is a layer called the 'deep sound channel' or SOFAR channel which can confine sound waves at a particular depth.
In the SOFAR channel, the speed of sound is lower than that in the layers above and below. Just as light waves will refract towards a region of higher refractive index, sound waves will refract towards a region where their speed is reduced. The result is that sound gets confined in the layer, much the way light can be confined to a sheet of glass or optical fiber. Thus, the sound is confined in essentially two dimensions. In two dimensions the intensity drops in proportion to only the inverse of the distance. This allows waves to travel much further before being undetectably faint.
A similar effect occurs in the atmosphere. Project Mogul successfully used this effect to detect a nuclear explosion at a considerable distance.
See also
Acoustoelastic effect
Elastic wave
Second sound
Sonic boom
Sound barrier
Speeds of sound of the elements
Underwater acoustics
Vibrations
Bell X-1
References
External links
Speed of Sound Calculator
Calculation: Speed of Sound in Air and the Temperature
Speed of sound: Temperature Matters, Not Air Pressure
Properties of the U.S. Standard Atmosphere 1976
The Speed of Sound
How to Measure the Speed of Sound in a Laboratory
Did Sound Once Travel at Light Speed?
Acoustic Properties of Various Materials Including the Speed of Sound
Discovery of Sound in the Sea (uses of sound by humans and other animals)
Fluid dynamics
Aerodynamics
Acoustics
Sound
Sound measurements
Physical quantities
Chemical properties
Sound
Temporal rates | Speed of sound | Physics,Chemistry,Mathematics,Engineering | 7,353 |
73,637,313 | https://en.wikipedia.org/wiki/Biphytane | Biphytane (or bisphytane) is a C40 isoprenoid produced from glycerol dialkyl glycerol tetraether (GDGT) degradation. As a common lipid membrane component, biphytane is widely used as a biomarker for archaea. In particular, given its association with sites of active anaerobic oxidation of methane (AOM), it is considered a biomarker of methanotrophic archaea. It has been found in both marine and terrestrial environments.
Chemical structure
Glycerol dialkyl glycerol tetraethers (GDGT) are major membrane lipids synthesized by archaea and some bacteria. In particular, isoprenoid GDGTs are characterized by isoprenoid carbon chains connected to the glycerol molecules by ether bonds. Biphytane is produced by the chemical cleavage of the ether bonds within isoprenoid GDGT (GDGT-0). It is composed of isoprene units bound by ether bonds with six isoprene units (or two phytanes) linked together by a head-to-head linkage.
Biphytane can be found in cyclic forms containing one to three pentacyclic rings when derived from isoprenoid GDGTs with such biosynthetically cyclized isoprenoid carbon skeletons. In most analyzed samples from the environment, the acyclic form with biphytane as the isoprenoid carbon chain is typically the most abundant form. Hence, in this article, biphytane is used to refer to the acyclic form unless stated otherwise.
Biological origin
As it occurs within GDGT, biphytane has been detected in the water column, marine sediments, hydrothermally-influenced sediments, cold seep sediments dominated by anaerobic oxidation of methane activity, and limestone. Though it had been primarily studied in aquatic settings, recent studies have also started investigating terrestrial environments, such as peat bogs where the source of biphytane was identified as methanogenic peat archaea. Studies have reported the detection of biphytane in petroleum as well.
While early studies had considered GDGTs (and hence biphytane) to be biomarkers of extremophilic archaea, both indirect and direct evidence of GDGT originating from archaea of mesophilic marine environments or lacustrine environments with non-extreme pH and salinity have been available since the late 1970s. Because biphytane in particular has been widely detected in sties of active AOM activity, it is considered a biomarker of methanotrophic archaea.
Analogous to sterols in eukaryotic membranes, GDGT plays a similar role in improving the rigidity of archaeal cell membranes. Supporting this, it has been reported that thermophiles increase the degree of cyclization with increasing growth temperatures to further improve membrane fluidity.
Measurement techniques
Typically, biphytane measurement is performed as an indirect analysis of GDGT. When chemically deriving biphytane from such ether lipids, the ether bonds are first cleaved using hydrogen iodide (HI), boron trichloride (BCl3), or boron tribromide (BBr3) that produces alkyl halides. Then, the alkyl halides are either reduced to saturated hydrocarbons using HI/NaSCH3 or LiAlH4 or converted to methylthioesthers with NaSCH3. The obtained saturated or derivatized hydrocarbons can subsequently be separated and measured using standard gas chromatography-mass spectrometry (GC-MS) procedures.
Alternatively, direct analysis of GDGT can be done with liquid chromatography but, when further structural characterization is required, MS fragments characteristic of biphytane can be obtained via high-performance liquid chromatography linked to tandem mass spectrometry (HPLC-MS/MS).
The diagnostic mass spectral fragment ions for biphytane are m/z 197, 259, 267, 323, 383, 393, and 463. Because the cyclic biphytanes yield different mass spectral fragment ions, the modified forms of biphytane present in a sample can be differentiated.
Application as a biomarker
Biphytane is considered to have a relatively high stability given its detection in high abundance within both recent and ancient sediments and petroleum, suggesting its ability to persist thermal maturation. Whether biphytane degrades to shorter isoprenoids over time remains unclear.
Biphytane is a well-established biomarker of archaea since it is found exclusively in archaea and all major groups except for halophilic Archaea. When combined with other analyses, it could be used to gain further insight into the analyzed sample. For instance, the abundance ratio of the biphytane (both acyclic and cyclic) to phytane has been used to distinguish between different groups of anaerobic methanotrophic archaea (ANME) from marine sediments given its higher abundance in ANME-1 than -2.
Alternatively, δ13C measurements could be combined to further confirm the origin. Because methanotrophs utilize isotopically light carbon sources, they are characterized by very negative carbon isotope values (i.e. depleted in 13C). For example, by comparing δ13C values of biphytanic diacids and GDGT-derived biphytane from the same seep limestones, a study inferred that, despite the chemical similarity of the compounds, they likely were derived from different sources; while the biphytanic diacids were mostly derived from methane-oxidizing euryarchea, the biphytanes were from mixed sources.
Case study: Late Archean sediments
In 2006, Ventura et al. measured solvent-extractable hydrocarbons with GC-MS from metasedimentary rocks sampled from the Tisdale and Porcupine Assemblage (2,707 to 2685 Ma) near Timmins, ON, Canada. From the extracted samples, the authors measured biphytane, cyclic biphytanes, and derivatives of biphytanes. Because post-Archaean deposition of the compounds could be ruled out given the reduced adsorptive capacity and restricted porosity of the sediments, the authors were able to conclude that the presence of biphytane, along with other molecular fossils, suggests the existence of archaea in the Late Archean sedimentary environments and in subsurface hydrothermal settings.
References
Terpenes and terpenoids | Biphytane | Chemistry | 1,413 |
2,397,350 | https://en.wikipedia.org/wiki/Double%20hull | A double hull is a ship hull design and construction method where the bottom and sides of the ship have two complete layers of watertight hull surface: one outer layer forming the normal hull of the ship, and a second inner hull which is some distance inboard, typically by a few feet, which forms a redundant barrier to seawater in case the outer hull is damaged and leaks.
The space between the two hulls is sometimes used for storage of ballast water.
Double hulls are a more extensive safety measure than double bottoms, which have two hull layers only in the bottom of the ship but not the sides. In low-energy collisions, double hulls can prevent flooding beyond the penetrated compartment. In high-energy collisions, however, the distance to the inner hull is not sufficient and the inner compartment is penetrated as well.
Double hulls or double bottoms have been required in all passenger ships for decades as part of the Safety Of Life At Sea or SOLAS Convention.
Uses
Double hulls are significantly safer than double bottoms, which in turn are safer than single bottoms. In case of grounding or other underwater damage, most of the time the damage is limited to flooding the bottom compartment, and the main occupied areas of the ship remain intact.
In low-energy collisions to the sides of the vessel, double hulls also prevent flooding beyond the penetrated compartment. In high-energy collisions, however, the distance to the inner hull is not sufficient and the inner compartment is penetrated as well.
A double bottom or hull also conveniently forms a stiff and strong girder or beam structure with the two hull plating layers as upper and lower plates for a composite beam. This greatly strengthens the hull in secondary hull bending and strength, and to some degree in primary hull bending and strength.
Double hulls can also:
be used as inboard tanks to carry oil, ballast water or fresh water (ventilated by a gooseneck)
help prevent pollution in case of liquid cargo (like oil in tankers)
help to maintain stability of ship; and
act as a platform for machinery and cargo.
Oil tankers
Double hulls' ability to prevent or reduce oil spills led to double hulls being standardized for other types of ships including oil tankers by the International Convention for the Prevention of Pollution from Ships or MARPOL Convention. A double hull does not protect against major, high-energy collisions or groundings which cause the majority of oil pollution, despite this being the reason that the double hull was mandated by United States legislation. After the Exxon Valdez oil spill disaster, when that ship grounded on Bligh Reef outside the port of Valdez, Alaska, the US Government required all new oil tankers built for use between US ports to be equipped with a full double hull.
Submarines
In submarine hulls, the double hull structure is significantly different, consisting of an outer light hull and inner pressure hull, with the outer hull intended more to provide a hydrodynamic shape for the submarine than the cylindrical inner pressure hull. It was introduced in the late 1890s by Maxime Laubeuf on French submarine Narval. In addition to tailoring the flow of water around the submarine (also known as hydrodynamic bypass), this outer skin serves as a mounting point for anechoic tiles, which are designed specifically to absorb sound rather than reflect it, helping to hide the vessel from sonar detection.
History
Leonardo da Vinci proposed the double-hulled ship design to protect against ramming and underwater damage from reefs or wreckage. Even if the outer hull was breached, the ship would remain afloat due to the second hull.
See also
Coulombi Egg Tanker
Naval architecture
Bulkhead
Submarine
Multihull
Whipple shield
References
Shipbuilding
Watercraft components | Double hull | Engineering | 755 |
26,174,425 | https://en.wikipedia.org/wiki/Minimal%20infective%20dose | The concept of a minimal infective dose (MID), also known as the infectious dose, has traditionally been used for infectious microorganisms that contaminate foods. MID was defined as the number of microorganisms ingested (the dose) from which a pathology is observed in the consumer. For example, to cause gastrointestinal disorders, the food must contain more than 100,000 Salmonella per gram or 1000 per gram for salmonellosis. however, some viruses like DHBV( duck hepatitis B virus) need as low as 9.5 x 10(9) virus per milliliters to cause liver infections.To know the dose ingested, it is also necessary to know the mass of the portion. This may be calculated using the following formula:
d\ =\ c \times m
where:
d = number of bacteria i.e. dose
c = concentration of bacteria
m = mass
This formulation has served as a basis for reasoning to establish the maximum concentrations permitted by the microbiological regulatory criteria intended to protect the health of consumers.
Dose-effect relationship and dose-response relationship
The concept of a dose-response relationship dates back to as 1493 but its modern usage reaches to the 20th century, as quantitative risk assessment matured as a discipline within the field of food safety.
An infectious bacterium in a food can cause various effects, such as diarrhea, vomiting, sepsis, meningitis, Guillain-Barré syndrome, and death. Most of the times, as the dose increases, the severity of the pathological effects increases, and a "dose-effect relationship" can often be established. For example, the higher the dose of Salmonella, the more diarrhea occurs soon after ingestion until it reaches to its maximum.
However, among people who have ingested the same dose, not all are affected. The proportion of people affected is called the response. The dose-response relationship for a given effect (e.g., diarrhea) is therefore the relationship between the dose and the likelihood of experiencing this effect. When the response is less than about 10%, it is observed that there is a strictly proportional relationship between dose and response:
P\ \propto r \times d
where:
P = probability of the effect considered
r = response
d = dosage
The dose-effect relationship and the dose-response relationship should not be confused.
Consequences
The existence of this relation has a first important consequence: the proportionality factor, symbolized by the letter r, corresponds precisely to the probability of the effect considered when the dose is equal to one bacterial cell. As a result, the minimum infective dose is exactly equal to one bacterial cell, deviating from the traditional notion of the MID. Proportionality has a second consequence: when the dose is divided by ten, the probability of observing the effect is also divided by ten.
Additionally, it is a relationship without threshold. In industrial practice, everything is done to reduce the probability that a serving contains the bacterium. There is therefore on the market food in which, for example, only one serving in a hundred is contaminated. The probability of the effect considered is then r / 100. If one in ten thousand is contaminated, the probability goes to r / 10,000, and so on. The line representing the relation can be extended towards zero: there is no threshold.
If the probability of not being infected when exposed to one bacterium is then the probability of not being infected by bacteria would be so the probability of being infected is
For readers familiar with the notion of D50 (the dose that causes the effect in 50% of consumers exposed to the hazard), in most cases the following relationship thus applies:
D50\ =\ -Ln(0.50)\ / \ r\ \approx 0.7\ / \ r
Comparisons
To compare the dose-response relationships for different effects caused by the same bacterium, or for the same effect caused by different bacteria, one can directly compare the values of r; also, it can be used to evaluate the efficacy of a drugs such as antibiotics. However, it may be easier to compare the doses causing the effect in 50% or 1% of consumers. These are values of D1 (dose causing the effect considered in 1% of consumers exposed to the hazard):
Escherichia coli (EHEC), haemolytic-uremic syndrome in children under 6 years: 8.4 bacterial cells;
Escherichia coli (EHEC), haemolytic-uraemic syndrome in children aged 6 to 14 years: 41.9 bacterial cells;
Listeria monocytogenes, severe listeriosis in the general population: 4.2x1011 bacterial cells;
Listeria monocytogenes, severe listeriosis in the susceptible population: 9.5x109 bacterial cells.
These examples highlight two important things:
D1 and r depend not only on the bacterium and the effect considered, but also on the belonging to categories of consumers susceptible to the disease; therefore, there are as many dose-response curves as there are pathogens, health effects and sensitivities of exposed individuals;
For the bacteria of the examples above, the orders of magnitude of the values of D1 are profoundly different. The hygiene practices and control measures that food chain businesses must implement against these bacteria are therefore not comparable.
Risk management
While consuming a low dose of pathogenic bacterium is associated with a low probability of disease, infection is still possible. This contributes to sporadic cases of food-borne illness in the population. There is no bacterial concentration in food below which a lack of epidemic is guaranteed.
Toxigenic bacteria
Some food-borne bacteria can cause disease by producing toxins, rather than infection like ETEC. Some synthesize a toxin only when their concentration in the food before ingestion exceeds a threshold, such as Staphylococcus aureus and Bacillus cereus. The concept of MID does not apply to them, but there is a concentration below which they do not constitute a danger to the health of the consumer.
See also
Viral load
Plaque forming unit
Virus quantification
References
Stella, P., Cerf, O., Koutsoumanis, KP, Nguyen-The, C., Sofos, JN, Valero, A. & Zwietering, MH (2013) Ranking the microbiological safety of foods: a new tool and its application to composite products. Trends in Food Science & Technology 33 (2): 124–138.
ANSES, the French Agency for Food, Environmental and Occupational Health and Safety, classifies in susceptible populations 'persons with a higher than average probability of developing, after exposure to the food hazard, symptoms of the disease, or serious forms of the disease'
Bacteria
Disease transmission | Minimal infective dose | Biology | 1,399 |
27,847,391 | https://en.wikipedia.org/wiki/Project%20Grab%20Bag | For environmental monitoring, Project Grab Bag was an air sampling program conducted in
the United States in the stratosphere of above-ground nuclear weapons testing in the Soviet Union.
The objective of the Grab Bag program was to develop an unmanned high-altitude balloon-borne system that would collect air samples at an altitude of typically and return them to earth for analyses. The air samples were analyzed for the presence of specific isotopes of krypton and xenon, unambiguous markers of fission reactions. These short-lived isotopes are created in the fission process and carried high into the atmosphere by the fireball, where they will remain for some days. The air sampling system was developed by the Balloons and Meteorological Systems group at General Mills, Inc. in Minneapolis, Minnesota, using large balloons fabricated of thin polyethylene film. The initial test of the sampling system collected an important air sample over the United States on August 14, 1953, at an altitude of . This sample contained debris from a nuclear weapon test in the USSR, designated Joe-4, that was conducted two days earlier, on August 12, 1953, at Semipalatinsk in Kazakhstan. This was the first test of a thermonuclear weapon by the USSR and was initiated by a 40-kiloton uranium-235 bomb and produced a total yield of 400 kilotons.
Background
The first nuclear detonation was an above-ground test, “Trinity”, conducted in New Mexico on July 16, 1945. It represented an important accomplishment of the Manhattan Project that had been initiated at Los Alamos National Laboratory in 1943. In less than two months following this test, nuclear weapons assembled at Los Alamos were used in the Pacific War against Japan. Hiroshima was devastated on August 6, 1945 with a uranium-235 gun device with a fission product yield of about 15 kilotons. Three days later, on August 9, 1945, a plutonium-239 implosion device with a yield of about 22 kilotons was detonated over Nagasaki. These events significantly influenced the conclusion of World War II as the incredibly destructive power of these new weapons became apparent. The Manhattan Project brought together scientists from the US and Britain to collaborate on this nuclear weapons development program. Los Alamos was the epicenter of this activity, and, in spite of high-level security, it was realized in 1948 that security of the program had been breached. Klaus Fuchs, a British theoretical physicist intimately involved in some of the most sensitive aspects of the program, had supplied the USSR with key information via outside contacts beginning in 1945. This information substantially advanced the Soviet effort in developing nuclear weapons. As the US became aware of the loss of key ideas and design concepts, it was important to reassess the state of the Soviet program in fission devices, and to monitor extensions of their program to fusion devices. One concern was the extent of progress made by the Soviets in producing fissionable material through reactor operations. Of even greater importance was the state of development of fission-fusion devices capable of orders of magnitude greater destructive power than the fission devices used against Japan.
The detection of reactor operations and above-ground nuclear weapon tests can be carried out in various ways. One approach used since the early 1950s has been the analyses of air samples collected at ground and low-level altitudes for the presence of particular radioactive nuclides. This technique is still in use, and there are a number of ground-based, radionuclide detectors for airborne debris in continuous operation in various parts of the world. An advantage of collecting air samples in the stratosphere is that powerful above-ground nuclear explosions carry bomb debris to elevated altitudes, where it is broadly distributed by winds aloft. The collection and analyses of this debris can therefore provide direct and timely information about a particular test. This article briefly describes the successful effort to develop and implement a program of gathering air samples using high-altitude balloon systems that were used from 1953 until late in 1956. The high-altitude balloon program that collected these samples was known as Project Grab Bag.
The Balloon and Meteorological Systems Group of General Mills, Inc. (GMI) had developed, along with other organizations, constant-level balloon systems capable of reliably carrying instruments and other equipment high into the stratosphere for sustained periods. These systems were ideal platforms on which to conduct experiments related to the observation of winds aloft, cosmic ray studies, and a variety of other investigations. Early in 1953 the eventual sponsors of the Grab Bag program conveyed to the GMI team under the direction of Harold E. Froehlich, principal engineer of the Balloons and Meteorological Systems Group, that high-altitude air samples containing debris from USSR above-ground nuclear weapon tests would be important in monitoring progress in their nuclear weapons program. The sponsors did not discuss specific kinds of debris or isotopes that were of interest. Sizable air samples obtained at high altitude, for example , were judged to be desirable, that is, samples of the order of at standard temperature and pressure conditions. This meant that samples of approximately would need to be collected at altitude. The sponsors also conveyed a sense of urgency in developing the capability to collect such samples. An important weapon test was expected to take place at the USSR test range in the latter part of the summer of 1953, in about six months. They also disclosed that two other US air sampling efforts were being developed and outlined those approaches using special high-altitude aircraft and sounding rockets. These approaches had limits in terms of the effective size of the air sample, and the balloon program offered the potential of being able to gather comparatively large air samples. The Grab Bag team began to develop the concept of suspending an uninflated envelope beneath a large helium-filled balloon, and carrying the envelope to high altitude and filling it with ambient air. An autopilot would then initiate the descent of the entire system. When the system had descended to about the air sample would be transferred from the envelope into an armored vessel that could withstand a variety of landing situations and protect the air sample from loss at the point of recovery. The balloon system would include an electronic controller and autopilot to carry out this sequence of events, and to return the entire system back to ground in a controlled descent. Simplified sketches of the grab bag system are illustrated in the three primary stages of flight in Figures 1-3: ascent of the system to the sampling altitude (Figure 1), collection of the air sample at high altitude (Figure 2), and recovery of the sample and descent of the system (Figure 3).
As shown schematically in Figure 1, a high-speed blower, the associated power supply and electronic control package was suspended from the base of the sample balloon, at the lowest point in the load train (#57). The base of the sample balloon was modified to take a cylindrical fitting (#40) that was fitted with the blower. The blower would operate at the ceiling altitude of for of the order of two hours to fill the sample balloon with about of air. The inflated sample balloon is illustrated in Figure 2 at the conclusion of the sampling cycle. At this point, an autopilot would release a predetermined amount of helium from the lifting balloon and initiate the descent of the entire system at a rate of about 400 feet per minute. As the system descended to about , an axial fan (#29) located at the top of the sample envelope would be activated to transfer the air sample into a flexible armored vessel (#27) located just above the sample balloon and below the lifting balloon and suspended parachute (#23). The transfer of the sample required a short period of time and then a valve at the base of the armored vessel (#29) was sealed. The system continued to descend and when the control unit contacted ground, explosive devices severed the connection between the lifting balloon and the parachute and this led to a collapse of the lifting balloon and conclusion of the flight. The Grab Bag concept resulted in a complex load train with electrical cables running along the entire length of the system, about in length. Launching of the system was a challenge to safely get this extended system off the ground, and to do so without damaging the lifting balloon, the sample envelope, electrical cables for the blowers, the autopilot and associated helium valve, antenna lines and other elements of the system.
The electronic control unit (#57) transmitted the altitude and key steps in the flight sequence, including:
The initiation of a high-altitude blower for a programmable period (typically 90 minutes) to fill the sample envelope with ambient air.
The initiation of the axial fan #25 (to transfer the air sample from the sample balloon into the armored vessel at an altitude of 10,000 feet).
The initiation of an autopilot function #116 (to valve helium from the lifting balloon).
The rate of descent of the system (typically 1000 to 2000 feet per minute).
The arming of the explosive cut down devices #57 (to rapidly deflate the lifting balloon when the lowest part of the system contacted the ground).
A non-rigid armored vessel (#27) was designed that would withstand the rigors of most landings and preserve the air sample of approximately . It consisted of three nested cylinders of flexible materials that, from the outside to the inside, were: a tough outer layer of plasticized nylon; an intermediate layer of woven nylon with very high tear strength, and; an innermost cylinder of polyethylene film that would serve as a gas barrier for the air sample. At takeoff the armored vessel hung in a deflated form around the steel cable (#27) and below an open parachute (#23) that would provide braking of the system descent if the rate exceeded about 2000 feet per minute. Launching of this complex balloon system required special handling techniques, and the entire process was referred to as a platform launch, a novel concept developed by Harold E. Froehlich, principal engineer of the Balloons and Meteorological System Group. In this form of launching the load train, nearly in length, was laid out on a ground cloth-covered runway with the lowest part of the load train in the upwind direction. The uppermost part of the system, the top of the lifting balloon, would be in the downwind direction. A heavy platform was positioned at a point toward the top of the lifting balloon, and the balloon material would pass over the platform and be securely held in place by a large horizontal padded roller about four feet in length. The helium inflation tube was located in the upper portion of the lifting balloon so that the helium source would inflate the section of the balloon beyond the platform. Since the system would be ascending to in altitude, only about 3% of the maximum balloon volume was filled with helium. The inflation took place by metering in an amount of helium lifting gas that would equal the gross weight of the system plus typically about 5% of ‘free lift’ to ensure that the system would ascend at an appropriate rate at the launching.
Launching was initiated by releasing the padded roller on the launch platform. The ascending balloon would then sequentially pick up the lower part of the lifting balloon, the deployed parachute and armored vessel, the uninflated envelope, and lastly the heavy insulated bag containing the controller, blower, instruments, telemetering equipment and power supply. There were variations of this procedure that evolved to facilitate the launching. For example, the heavy instrument bag and blower assembly was eventually mounted on the front of a vehicle that drove under the balloon system as it ascended during launching, and the bag was released from the vehicle using small explosive devices.
Grab Bag flights were typically launched early in the morning and recovered during daylight hours of that same day. The ascent time to was usually about three hours. As the balloon system approached the ceiling altitude, the excess lift (referred to as "free lift") that drove the system upward on launching filled out a duct system of the lifting balloon, and helium was automatically vented from the lifting balloon and slowed the ascent. As this process continued, the balloon system slowly ascended to the ceiling altitude and was in equilibrium, the lift of the helium balloon just balancing the total weight of the system. If this process took place as designed, about thirty minutes were needed to assure that the system was stable at the ceiling altitude of . If the system instruments indicated that the altitude was not changing, the blower attached to the sample envelope balloon at the base of the system was initiated by the controller. The effect of turning on the blower was almost immediately evident in the appearance of the sample balloon. Viewing the system through a tracking telescope clearly showed the sample envelope beginning to fill out. The sample gathering process typically required of the order of an hour or so to be completed, the appearance of the system then being of two balloons, one immediately on top of the other. The blower was then turned off by the controller and a valve closed that sealed the sample envelope from the outside. The autopilot was then activated by the controller, releasing helium from the lifting balloon (#116) and initiating a descent of the entire system. In practice, the descent of the system did not become apparent for of the order of an hour after the autopilot was activated. This was because the sample balloon, now containing a large volume of air, would generate lift with any descent due to adiabatic heating of the sample air in the isothermal stratosphere. It could require an hour or two to establish a nominal descent rate of the system. The descent to altitudes of the order of could take of the order of two to three hours. At this point the axial fan (#29) was automatically initiated to transfer air in the sample balloon into the armored vessel. This transfer was usually completed before the system reached an altitude of 4 or 5 thousand feet and a valve in the armored vessel valve just above the axial fan (#25) was sealed by the controller. As the system continued to descend and touched down, explosive cutters fired to release the lifting balloon from the lower part of the system and the armored vessel fell the short remaining distance, perhaps fifty feet, to the ground. Usually the recovery crew was at the landing site and immediately began the process of transferring the air sample from the armored vessel into high-pressure bottles for transfer to another laboratory for analyses.
A series of six test flights were carried out in the Grab Bag development program in which various system elements were examined. The seventh flight would be the first attempt to capture the first air sample at in the Minneapolis area in mid-August 1953. The six test flights carried out tests of various system components, and included: tests and further development of the launching procedure for this complex system; an evaluation of the system controller; adequacy of the power supply and the autopilot function; a study of the blower function at altitude to evaluate both its function and the volume of air delivered into the sample balloon as compared to the laboratory results; evaluation of the process in which the axial fan transferred the air sample from the sample balloon into the armored vessel and the vessel was sealed; and in each case, further development of logistics for system launching and recovery.
Fortunately, the first flight of the complete system occurred at a time that corresponded well with the above-ground test in the USSR. This first flight was successful and we were subsequently informed that the air sample provided information that was of vital interest to those assessing fission/fusion reactions and test activities around the world. We also learned that of the three approaches developed to capture air samples, the high-altitude balloon system was the only one to successfully accomplish this objective, and the sample was collected within the desired window of time. As before, there was no specific or definitive information. Photographs, films and notebooks further describing the development of the Grab Bag system and the platform launching process are contained in the archives of the International Balloon Museum, Albuquerque, New Mexico.
Some years later more information became available related to the fundamental observations that were being made of the air samples that were gathered in the Grab Bag program. This information was related to the presence and distribution of isotopes of inert gases, particularly isotopes of xenon and krypton. The fission of a nucleus produces two different nuclei, the mass of which nearly sums to the mass of the original nucleus. The fission of uranium or plutonium therefore produces a spectrum of different pairs of nuclei, generally in a bimodal mass distribution. The fission products will include isotopes of many elements and this includes the inert gases such as xenon and krypton. Some of the radioactive isotopes of these inert elements have half-lives or the order of days, and these isotopes have therefore decayed away and are not found in our solar system. However, a recent fission reaction such as in a reactor or in a nuclear explosion will produce small quantities of these radioactive isotopes. If they are detected in the atmosphere, their presence is evidence that a reactor has been operating, or that a recent nuclear detonation has taken place. This is the basis of the air sampling effort as a means for the detection and characterization of such activities.
As noted in the following table by Chien C. Lin, the isotopes of particular interest have short half-lives, so detection depends on sampling the atmosphere promptly following such operations. Note that the distribution and ratios of xenon isotopes can also be used to determine whether a particular detonation was of a uranium or plutonium device.
The explosion that was sampled by this first Grab Bag flight is known as Joe 4 and took place on August 12, 1953 at Semipalatinsk in Kazakhstan. It was a 40-kiloton uranium-235 bomb that ultimately produced a total yield of 400 kilotons. It was estimated that 15–20% of the energy was released by fusion (60–80 kilotons) and the rest was from fast fission.
The Grab Bag air sampling program was quickly expanded following the successful flight in August 1953, and there subsequently were more than two hundred Grab Bag flights launched during the subsequent two years. It was one of the largest programs that took place in the Balloon and Meteorological Systems organization at General Mills Inc. On February 19, 1963, U. S. Patent 3,077,779, for this high-altitude air sampling system was assigned to H. E. Froehlich, Roger A. Kizzek, Donald F. Melton, and Richard L. Schwoebel.
References
Nuclear weapons testing
Soviet Union–United States relations
Ballooning | Project Grab Bag | Technology | 3,775 |
56,669,979 | https://en.wikipedia.org/wiki/Rudin%27s%20conjecture | Rudin's conjecture is a mathematical conjecture in additive combinatorics and elementary number theory about an upper bound for the number of squares in finite arithmetic progressions. The conjecture, which has applications in the theory of trigonometric series, was first stated by Walter Rudin in his 1960 paper Trigonometric series with gaps.
For positive integers define the expression to be the number of perfect squares in the arithmetic progression , for , and define to be the maximum of the set . The conjecture asserts (in big O notation) that and in its stronger form that, if , .
References
Combinatorics
Conjectures | Rudin's conjecture | Mathematics | 124 |
65,745,795 | https://en.wikipedia.org/wiki/Jennifer%20Morse%20%28mathematician%29 | Jennifer Leigh Morse is a mathematician specializing in algebraic combinatorics. She is a professor of mathematics at the University of Virginia.
Research
Morse's interests in algebraic combinatorics include representation theory and applications to statistical physics, symmetric functions, Young tableaux, and -Schur functions, which are a generalization of Schur polynomials.
Education and career
Morse earned her Ph.D. in 1999 from the University of California, San Diego. Her dissertation, Explicit Expansions for Knop-Sahi and Macdonald Polynomials, was supervised by Adriano Garsia.
She has been a faculty member at the University of Pennsylvania, at the University of Miami, and at Drexel University before moving to the University of Virginia in 2017.
Book
Morse is one of six coauthors of the book -Schur Functions and Affine Schubert Calculus (Fields Institute Monographs 33, Springer, 2014).
Recognition
Morse was named a Simons Fellow in Mathematics in 2012 and again in 2021. She was elected as a Fellow of the American Mathematical Society in the 2021 class of fellows, "for contributions to algebraic combinatorics and representation theory and service to the mathematical community".
References
External links
Home page
Year of birth missing (living people)
Living people
20th-century American mathematicians
21st-century American mathematicians
Combinatorialists
University of California, San Diego alumni
University of Pennsylvania faculty
University of Miami faculty
Drexel University faculty
University of Virginia faculty
Fellows of the American Mathematical Society
20th-century American women mathematicians
21st-century American women mathematicians | Jennifer Morse (mathematician) | Mathematics | 307 |
4,230,269 | https://en.wikipedia.org/wiki/HD%2073526 | HD 73526 is a star in the southern constellation of Vela. With an apparent visual magnitude of +8.99, it is much too faint to be viewed with the naked eye. The star is located at a distance of approximately from the Sun based on parallax, and is drifting further away with a radial velocity of +26 km/s. It is a member of the thin disk population.
The stellar classification of HD 73526 is G6 V, indicating this is a G-type main-sequence star that, like the Sun, is generating energy through core hydrogen fusion. Based on its properties, it may be starting to evolve off the main sequence. This star has slightly more mass than the Sun and a 53% greater radius. The abundance of iron in its atmosphere suggests the star's metallicity – what astronomers term the abundance of elements with higher atomic number than helium – is 70% greater than in the Sun. It is a much older star with an estimated age of nearly ten billion years, and is spinning slowly with a projected rotational velocity of 1.7 km/s. The star is radiating more than double the luminosity of the Sun from its photosphere at an effective temperature of 5,564 K.
Planetary system
On June 13 2002, a 2.1 MJ planet HD 73526 b was announced orbiting HD 73526 in an orbit just a little smaller than that of Venus' orbit around the Sun. This planet receives an insolation 3.65 times that of Earth or 1.89 times that of Venus. This was a single planet system until 2006 when a 2.3 MJ second planet HD 73526 c was discovered. These planets forms a 2:1 orbital resonance with planet b. In fact, they seem to be in a very deep resonance with very long timescale stability due to an ACR (Apsidal Corotation Resonance) the planets seem to satisfy. Although these are minimum masses as the inclinations of these planets are unknown, orbital stability analysis indicates that the orbital inclinations of both planets are likely to be near 90°, making the minimum masses very close to the true masses of the planets.
See also
List of extrasolar planets
Gliese 876
References
External links
Extrasolar Planet Interactions by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona
G-type main-sequence stars
Planetary systems with two confirmed planets
Vela (constellation)
Durchmusterung objects
073526
042282 | HD 73526 | Astronomy | 513 |
8,359,069 | https://en.wikipedia.org/wiki/Rogue%20River%E2%80%93Siskiyou%20National%20Forest | The Rogue River–Siskiyou National Forest is a United States National Forest in the U.S. states of Oregon and California. The formerly separate Rogue River and Siskiyou National Forests were administratively combined in 2004. Now, the Rogue River–Siskiyou National Forest ranges from the crest of the Cascade Range west into the Siskiyou Mountains, covering almost . Forest headquarters are located in Medford, Oregon.
Geography
The former Rogue River portion of the Rogue River–Siskiyou National Forest is located in parts of five counties in southern Oregon and northern California. In descending order of land area they are Jackson, Klamath, Douglas, Siskiyou, and Josephine counties, with Siskiyou County being the only one in California. It has a land area of . There are local ranger district offices located in Ashland, Butte Falls, Grants Pass, Jacksonville, and Prospect.
The former Siskiyou portion of the Rogue River–Siskiyou National Forest is located in parts of four counties in southwestern Oregon and northwestern California. In descending order of land area they are Curry, Josephine, and Coos counties in Oregon and Del Norte County in California. It has a land area of . There are local ranger district offices located in Cave Junction, Gold Beach, and Powers.
Nearly all of the national forest is mountainous and includes parts of the Southern Oregon Coast Range, the Klamath Mountains, and the Cascade Range.
The largest river in the national forest is the Rogue River, which originates in the Cascade Range and flows through the Klamath Mountains and Coast Range. The Illinois River is a major tributary of the Rogue in the Klamath Mountains, while the Sixes, Elk, Pistol, Chetco, and Winchuck rivers drain the Coast Range directly to the Pacific Ocean.
Climate
History
The Siskiyou National Forest was established on October 5, 1906. On July 1, 1908, it absorbed Coquille National Forest and other lands. Rogue River National Forest traces its establishment back to the creation of the Ashland Forest Reserve on September 28, 1893, by the United States General Land Office. The lands were transferred to the Forest Service in 1906, and it became a National Forest on March 4, 1907. On July 1, 1908, Ashland was combined with other lands from Cascade, Klamath and Siskiyou National Forests to establish Crater National Forest. On July 18, 1915, part of Paulina National Forest was added, and on July 9, 1932, the name was changed to Rogue River.
World War II bombing
On September 9, 1942, an airplane dropped bombs on Mount Emily in the Siskiyou National Forest, turned around, and flew back over the Pacific Ocean. The bombs exploded and started a fire, which was put out by several forest service employees. Bomb fragments were said to have Japanese markings. Stewart Holbrook vividly described this event in his essay "First Bomb". It was later confirmed that the plane was indeed Japanese, and the incident became known as the Lookout Air Raids. It was the second bombing of the continental United States by an enemy aircraft, three months after the air attack by Japan on Dutch Harbor three months earlier on June 3–4.
Natural features
The national forest is home to some stands of old growth, including Port Orford cedar and Douglas fir in the Copper Salmon area. A 1993 Forest Service study estimated that the extent of old growth in the forest was some of which occurs in the Red Buttes Wilderness. Blue oak, Quercus douglasii, and Canyon live oak, Quercus chrysolepis occur in the Siskiyou National Forest. For the California endemic Blue Oak, the disjunctive stands are occurring near the northern limit of its range, which occur no farther north than Del Norte County. The world's tallest pine tree is a ponderosa and is located in the national forest.
In 2002, the massive Biscuit Fire burned nearly , including much of the Kalmiopsis Wilderness.
Protected areas
The Rogue River–Siskiyou National Forest contains all or part of eight separate wilderness areas, which together add up to :
Copper Salmon Wilderness -
Grassy Knob Wilderness -
Kalmiopsis Wilderness -
Red Buttes Wilderness -
Rogue–Umpqua Divide Wilderness -
Siskiyou Wilderness -
Sky Lakes Wilderness -
Wild Rogue Wilderness -
See also
High Cascades Complex Fires
List of U.S. National Forests
List of old growth forests
References
External links
Rogue River–Siskiyou National Forest
National forests of California
National forests of Oregon
Old-growth forests
Klamath Mountains
Rogue River (Oregon)
Cascade Range
Protected areas of Coos County, Oregon
Protected areas of Curry County, Oregon
Protected areas of Del Norte County, California
Protected areas of Siskiyou County, California
Protected areas of Jackson County, Oregon
Protected areas of Klamath County, Oregon
Protected areas of Douglas County, Oregon
Protected areas of Josephine County, Oregon
Protected areas established in 2004
2004 establishments in Oregon | Rogue River–Siskiyou National Forest | Biology | 993 |
73,262,087 | https://en.wikipedia.org/wiki/Leucocoprinus%20scissus | Leucocoprinus scissus is a species of mushroom producing fungus in the family Agaricaceae.
Taxonomy
It was described in 2021 by the mycologists Alfredo Justo, Angelini Claudio and Alberto Bizzi who classified it as Leucocoprinus scissus.
Description
Leucocoprinus scissus is a small dapperling mushroom with thin whitish flesh.
Cap: 1–4 cm wide starting conical-campanulate before expanding to conical to flat with a slight umbo. The surface is white with small, scattered brownish-ochre scales that surround the umbo and become sparser towards the cap margins. The margins are striated almost to the centre of the cap but are fragile and prone to splitting at maturity.
Gills: Free, white and moderately crowded, with a bulge in the middle (ventricose).
Stem: 2.5–6 cm wide and 2.5-4mm thick. It is cylindrical with a slight clavate taper up from the base which is up to 6mm thick. The surface is smooth and whitish above the stem ring and ochre-yellow below with the colour becoming more intense towards the base, where white threadlike (filiform) rhizomorphs may be present. The membranous stem ring is small and white but is easily removed and may sometimes be missing.
Spores: Ovoid to ellipsoid, without a germ pore. Dextrinoid and metachromatic. (5.5) 6-8 (8.5) x 4-6 (6.5) μm.
Smell: Indistinct.
Etymology
The specific epithet scissus is Latin for torn or split. This is in reference to the tendency for the edges of the cap to split at maturity.
Habitat and distribution
The species was discovered in the Dominican Republic where it was found growing gregariously on leaf litter in deciduous woodland in November.
References
scissus
Fungi described in 2021
Fungi of the Caribbean
Fungus species | Leucocoprinus scissus | Biology | 417 |
56,194,906 | https://en.wikipedia.org/wiki/Mental%20health%20informatics | Mental health informatics is a branch of health or clinical informatics focused on the use of information technology (IT) and information to improve mental health. Like health informatics, mental health informatics is a multidisciplinary field that promotes care delivery, research and education as well as the technology and methodologies required to implement it.
Metrics and coding
Terminology and coding systems such as the (DSM)
Specific mental health assessment and diagnostic systems
Data collection and storage systems
Systematic collection of information is fundamental to successful practices. Collecting data useful for mental illness diagnosis and treatment is challenging, as we lack quantitative biomarkers that might be used in standard health informatics, such as body temperature or blood pressure. Largely, current diagnosis and treatment is driven by clinical interviews between professionals and patients. Interviews are not only difficult to draw standardized data from because of diverse individual experience, condition, and accuracy of a patient's memory. Rapid advancements in computation and storage systems have the potential to transform this data collection process. For example, a 2014 study in Ireland explored the use of a smartphone application to record daily mood and thoughts. Such a collection process would provide plentiful standardized data less afflicted by patient recollection issues.
Integration of mental health function into electronic health record systems (EHRs) and larger organisational systems
Mobile and digital sensors
The ubiquity of smartphones and other mobile computing platforms is beginning to enable new types of data collection. Recent work has pioneered the use of passive data collection combined with analysis to provide highly relevant features such as: amount of time exposed to human speech, geospatial activity (total distance traveled throughout the day), physical activity, and sleep duration. Additionally, researchers are prototyping simple mobile applications that could replace portions of infrequent qualitative clinical interviews with more regular quantitative data.
Telehealth
Telehealth, telemedicine and telepsychiatry are new care delivery methods made possible by information technology. Specifically, there is a body of research investigating the use of mobile devices to deliver treatment suggestions or treatment reminders in the context of mental health.
Much of the telehealth literature is concerned with patient populations that are difficult to provide traditional medical care to, such as those in rural locations, soldiers, or veterans. These groups stand to benefit from telehealth practices. An inspector general review of US Veterans Affairs facilities in North Carolina and Virginia revealed that 36% of patients had to wait more than a month for appointments. Telehealth professionals are interested in decreasing these wait times by increasing aspects of appointment efficiency.
Patient perspectives
Of course, introducing significant use of new technology into medical practice is a large departure from conventional mental health treatment. Several studies investigate the effect of introducing technology into general medical interventions as well as mental health treatments specifically. A review of several studies found that patients were generally satisfied with the medical care received via Telehealth, however the effectiveness and efficiency of programs reported mixed results. In many studies it's challenging to determine if the outcomes were a result of the introduction of technology, as authors fail to describe why they are making such an intervention.
A study investigating the design of a passive mental health mobile application for use by teenagers and young adults indicated that teenagers would be most open to using technology to help with mental health issues if it was developed as a smartphone application. Additionally, teenagers would be more motivated in using such applications if there was a social or gamified component, however they expressed potential concern about negative perceptions about using the app. Research indicates that while older patients struggle to accept changes in care, technological resistance is generational, indicating that current and future generations would be open to using telehealth.
Technology to promote healthy practices
In addition to providing more accurate and reliable data for mental health care providers, smartphones have the ability to provide reminders for healthy practices and appointments. Jen Hyatt, the founder and CEO of Big White Wall, a UK behavioral health social enterprise, comments that existing mental healthcare focuses on diseases rather than health practices and behaviors. Particularly, research has showed that how much we travel and communicate with other people throughout the day is an important factor in our overall mental health. Future applications may leverage location systems in modern mobile phones to track a user's geospatial activity and suggest certain actions through notifications if dangerous patterns are detected.
Augmenting care delivery
In addition to new types of treatments and interactions, the introduction of technology and informatics has the ability to improve existing mental healthcare effectiveness and efficiency. A UK based study found that a simple digital intervention such as sending SMS (text message) reminders to patients a few days before a mental health appointment decreased missed clinical appointments by 25% to 28%, translating to a potential cost savings of more than £150 million.
Data analysis
Collection of enormous amounts of structured data on mental health patients introduces the possibility of improved mental health care, mental health policy, and overall perception of mental health. This analysis would be performed on a macro-scale, the study of the incidence of mental health in a public health and epidemiological context.
Need for mental health informatics
The need for and application of health informatics in primary and secondary health care has been well established in developed countries for 20 years or more. The application of informatics in mental health has not become as pervasive, in spite of professional recognition the domain appearing well suited to computerisation and the need for quantified outcome evidence. There also may be a professional reluctance to effect changes in established working patterns that the introduction of systems necessarily entails.
Concerns
Data and information in health informatics are inherently private and personal. Pervasive software systems designed to help diagnose and treat mental health symptoms expose a privacy vulnerability and will likely require regulatory standards and data protection compliance such as HIPAA to protect patients. A major impediment may be societal stigma associated with mental disorders as well as increased sensitivity about protecting the privacy and confidentiality of records in mental health care.
References
Health informatics
Mental health | Mental health informatics | Biology | 1,226 |
41,652,968 | https://en.wikipedia.org/wiki/Penicillium%20aethiopicum | Penicillium aethiopicum is a fungus species of the genus of Penicillium. Penicillium aethiopicum produces viridicatumtoxin and griseofulvin, two structurally interesting polyketides.
See also
List of Penicillium species
References
Further reading
Polyphasic Taxonomy of subgenus penicillium J.C. Frisvad & R. A. Samson
aethiopicum
Fungi described in 1989
Fungus species | Penicillium aethiopicum | Biology | 99 |
58,970,335 | https://en.wikipedia.org/wiki/EU%20Andromedae | EU Andromedae (often abbreviated to EU And) is a carbon star in the constellation Andromeda. Its apparent visual magnitude varies in an irregular manner between 10.7 and 11.8.
EU Andromedae was reported to be a carbon star by Oliver J. Lee et al. in 1947, based on objective prism observations undertaken as part of a Dearborn Observatory study of faint red stars. Years later, the variability of EU Andromedae was discovered by French amateur astronomer Roger Weber, who examined the star on photographic plates that he and Giuliano Romano had taken from May 1959 through October 1961. Weber announced the discovery in 1962 and noted that it was probably a long period variable, but he could not determine if it was a semi-regular or a Mira variable. It is number 149 in his catalog. There is some disagreement in the literature about what class of variable star EU Andromedae belongs to, with some researchers listing it as a slow irregular variable, and others listing it as a semi-regular variable.
Infrared observations of EU Andromedae show the presence of silicate grains, indicating the presence of an oxygen-rich circumstellar shell around the star, a combination known as a silicate star. Subsequently, a water maser was detected around this star (and for the first time around a carbon star), confirming the existence of the shell. The most recent observations suggest that the maser originated in a circumstellar disc, seen nearly edge-on, around an unseen companion with a minimum mass of 0.5 . Carbon dioxide has been detected for the first time in a silicate carbon star around EU Andromedae.
EU Andromedae is given as the standard star for the C-J5− spectral class. C-J spectral types are assigned to stars with strong isotopic bands of carbon molecules, defined as the ratio of to being less than four. A more complete spectral type includes the abundance indices C25 j3.5, which indicate the Swan band strength and the isotopic band ratio.
References
Andromeda (constellation)
Andromedae, EU
J23195888+4714345
Carbon stars
Slow irregular variables | EU Andromedae | Astronomy | 459 |
47,449,212 | https://en.wikipedia.org/wiki/Michigan%20Journal%20of%20Environmental%20and%20Administrative%20Law | The Michigan Journal of Environmental & Administrative Law is a student-run law review published at the University of Michigan School of Law. The journal publishes articles, notes, comments, and essays relating to administrative and environmental law.
History and overview
The journal was established in 2012 after "years of advocacy [by] environmental law students" at the University of Michigan School of Law. The journal's founding editors had the goal of "prompt[ing] new scholarship and the development of sound public policy approaches in both environmental law and administrative law." In 2016, Washington and Lee University's Law Journal Rankings placed the journal among the top three environmental, natural resources, and land use law journals with the highest impact factor.
Abstracting and indexing
The journal is abstracted or indexed in EBSCO databases, HeinOnline, LexisNexis, Westlaw, and the University of Washington's Current Index to Legal Periodicals. Tables of contents are also available through Infotrieve and Ingenta, and the journal posts past issues on its website.
See also
List of law journals
List of environmental law journals
References
External links
American law journals
Academic journals established in 2012
English-language journals
Environmental law journals
Law journals edited by students
University of Michigan
Journal
Biannual journals | Michigan Journal of Environmental and Administrative Law | Environmental_science | 256 |
899,452 | https://en.wikipedia.org/wiki/Lanchester%27s%20laws | Lanchester's laws are mathematical formulas for calculating the relative strengths of military forces. The Lanchester equations are differential equations describing the time dependence of two armies' strengths A and B as a function of time, with the function depending only on A and B.
In 1915 and 1916 during World War I, M. Osipov and Frederick Lanchester independently devised a series of differential equations to demonstrate the power relationships between opposing forces. Among these are what is known as Lanchester's linear law (for ancient combat) and Lanchester's square law (for modern combat with long-range weapons such as firearms).
As of 2017 modified variations of the Lanchester equations continue to form the basis of analysis in many of the US Army’s combat simulations, and in 2016 a RAND Corporation report examined by these laws the probable outcome in the event of a Russian invasion into the Baltic nations of Estonia, Latvia, and Lithuania.
Lanchester's linear law
For ancient combat, between phalanxes of soldiers with spears for example, one soldier could only ever fight exactly one other soldier at a time. If each soldier kills, and is killed by, exactly one other, then the number of soldiers remaining at the end of the battle is simply the difference between the larger army and the smaller, assuming identical weapons.
The linear law also applies to unaimed fire into an enemy-occupied area. The rate of attrition depends on the density of the available targets in the target area as well as the number of weapons shooting. If two forces, occupying the same land area and using the same weapons, shoot randomly into the same target area, they will both suffer the same rate and number of casualties, until the smaller force is eventually eliminated: the greater probability of any one shot hitting the larger force is balanced by the greater number of shots directed at the smaller force.
Lanchester's square law
Lanchester's square law is also known as the N-square law.
Description
With firearms engaging each other directly with aimed shooting from a distance, they can attack multiple targets and can receive fire from multiple directions. The rate of attrition now depends only on the number of weapons shooting. Lanchester determined that the power of such a force is proportional not to the number of units it has, but to the square of the number of units. This is known as Lanchester's square law.
More precisely, the law specifies the casualties a shooting force will inflict over a period of time, relative to those inflicted by the opposing force. In its basic form, the law is only useful to predict outcomes and casualties by attrition. It does not apply to whole armies, where tactical deployment means not all troops will be engaged all the time. It only works where each unit (soldier, ship, etc.) can kill only one equivalent unit at a time. For this reason, the law does not apply to machine guns, artillery with unguided munitions, or nuclear weapons. The law requires an assumption that casualties accumulate over time: it does not work in situations in which opposing troops kill each other instantly, either by shooting simultaneously or by one side getting off the first shot and inflicting multiple casualties.
Note that Lanchester's square law does not apply to technological force, only numerical force; so it requires an N-squared-fold increase in quality to compensate for an N-fold decrease in quantity.
Example equations
Suppose that two armies, Red and Blue, are engaging each other in combat. Red is shooting a continuous stream of bullets at Blue. Meanwhile, Blue is shooting a continuous stream of bullets at Red.
Let symbol A represent the number of soldiers in the Red force. Each one has offensive firepower α, which is the number of enemy soldiers it can incapacitate (e.g., kill or injure) per unit time. Likewise, Blue has B soldiers, each with offensive firepower β.
Lanchester's square law calculates the number of soldiers lost on each side using the following pair of equations. Here, dA/dt represents the rate at which the number of Red soldiers is changing at a particular instant. A negative value indicates the loss of soldiers. Similarly, dB/dt represents the rate of change of the number of Blue soldiers.
The solution to these equations shows that:
If α=β, i.e. the two sides have equal firepower, the side with more soldiers at the beginning of the battle will win;
If A=B, i.e. the two sides have equal numbers of soldiers, the side with greater firepower will win;
If A>B and α>β, then Red will win, while if A<B and α<β, Blue will win;
If A>B but α<β, or A<B but α>β, the winning side will depend on whether the ratio of β/α is greater or less than the square of the ratio of A/B. Thus, if numbers and firepower are unequal in opposite directions, a superiority in firepower equal to the square of the inferiority in numbers is required for victory; or, to put it another way, the effectiveness of the army rises proportionate to the square of the number of people in it, but only linearly with their fighting ability.
The first three of these conclusions are obvious. The final one is the origin of the name "square law".
Relation to the salvo combat model
Lanchester's equations are related to the more recent salvo combat model equations, with two main differences.
First, Lanchester's original equations form a continuous time model, whereas the basic salvo equations form a discrete time model. In a gun battle, bullets or shells are typically fired in large quantities. Each round has a relatively low chance of hitting its target, and does a relatively small amount of damage. Therefore, Lanchester's equations model gunfire as a stream of firepower that continuously weakens the enemy force over time.
By comparison, cruise missiles typically are fired in relatively small quantities. Each one has a high probability of hitting its target, and carries a relatively powerful warhead. Therefore, it makes more sense to model them as a discrete pulse (or salvo) of firepower in a discrete time model.
Second, Lanchester's equations include only offensive firepower, whereas the salvo equations also include defensive firepower. Given their small size and large number, it is not practical to intercept bullets and shells in a gun battle. By comparison, cruise missiles can be intercepted (shot down) by surface-to-air missiles and anti-aircraft guns. Therefore, missile combat models include those active defenses.
Lanchester's law in use
Lanchester's laws have been used to model historical battles for research purposes. Examples include Pickett's Charge of Confederate infantry against Union infantry during the 1863 Battle of Gettysburg, the 1940 Battle of Britain between the British and German air forces, and the Battle of Kursk.
In modern warfare, to take into account that to some extent both linear and the square apply often, an exponent of 1.5 is used. Lanchester's laws have also been used to model guerrilla warfare. The laws have also been applied to repeat battles with a range of inter-battle reinforcement strategies.
Attempts have been made to apply Lanchester's laws to conflicts between animal groups. Examples include tests with chimpanzees and ants. The chimpanzee application was relatively successful. A study of Australian meat ants and Argentine ants confirmed the square law, but a study of fire ants did not confirm the square law.
Helmbold Parameters
The Helmbold Parameters offer precise numerical indices, grounded in historical data, for quickly and accurately comparing battles in terms of bitterness and the degree of advantage held by each side. While their definition is modeled after a solution of the Lanchester Square Law's differential equations, their numerical values are based entirely on the initial and final strengths of the opponents and in no way depend upon the validity of Lanchester's Square Law as a model of attrition during the course of a battle.
The solution of Lanchester's Square Law used here can be written as:
Where:
is the time since the battle began
and are the surviving fractions of the attacker's and defender's forces at time
is the Helmbold intensity parameter
is the Helmbold defender's advantage parameter
is the duration of the battle
is the Helmbold bitterness parameter.
If the initial and final strengths of the two sides are known it is possible to solve for the parameters , , , and . If the battle duration is also known, then it is possible to solve for .
If, as is normally the case, is small enough that the hyperbolic functions can, without any significant error, be replaced by their series expansion up to terms in the first power of , and if abbreviations adopted for the casualty fractions are and , then the approximate relations that hold include and . That is a kind of "average" (specifically, the geometric mean) of the casualty fractions justifies using it as an index of the bitterness of the battle.
Statistical work prefers natural logarithms of the Helmbold Parameters. They are noted , , and .
Major findings
See Helmbold (2021):
The Helmbold parameters and are statistically independent, i.e., they measure distinct features of a battle.
The probability that the defender wins, , is related to the defender's advantage parameter via the logistic function, , with . This logistic function is almost exactly skew-symmetric about , rising from at , through at , to at . Because the probability of victory depends on the Helmbold advantage parameter rather than the force ratio, it is clear that force ratio is an inferior and untrustworthy predictor of victory in battle.
While the defender's advantage varies widely from one battle to the next, on average it has been practically constant since 1600 CE.
Most of the other battle parameters (specifically the initial force strengths, initial force ratios, casualty numbers, casualty exchange ratios, battle durations, and distances advanced by the attacker) have changed so slowly since 1600 CE that only the most acute observers would be likely to notice any change over their nominal 50-year military career.
Bitterness (), casualty fractions ( and in the above notation), and intensity () also changed slowly before 1939 CE. But since then they have followed a startlingly steeper declining curve.
Some observers have noticed a similar post-WWII decline in casualties at the level of wars instead of battles.
See also
Attrition warfare
Lotka–Volterra equations similar mathematical model for predator-prey dynamics
Maneuver warfare
Petrie multiplier similar mathematical model for sexism
Lewis Fry Richardson
Salvo combat model
References
Bibliography
Czarnecki, Joseph. N-Squared Law: An Examination of one of the Mathematical Theories behind the Dreadnought Battleship Naval Weapons of the World
Niall J. MacKay Lanchester combat models, Mathematics Today, 2006, Vol 42/5, pages 170–173.
External links
"Kicking Butt By the Numbers: Lanchester's Laws", a Designer's Notebook column by Ernest Adams in the Game Developer website
Differential equations
Predation
Combat modeling | Lanchester's laws | Mathematics | 2,279 |
56,968,762 | https://en.wikipedia.org/wiki/C28H40O4 | {{DISPLAYTITLE:C28H40O4}}
The molecular formula C28H40O4 (molar mass: 440.615 g/mol, exact mass: 440.2927 u) may refer to:
Megestrol caproate (MGC)
Pentagestrone acetate (PGA)
Molecular formulas | C28H40O4 | Physics,Chemistry | 73 |
16,934,252 | https://en.wikipedia.org/wiki/Data%20pack | A data pack (or fact pack) is a pre-made database that can be fed to a software, such as software agents, game, Internet bots or chatterbots, to teach information and facts, which it can later look up. In other words, a data pack can be used to feed minor updates into a system.
Introduction
Common data packs may include abbreviations, acronyms, dictionaries, lexicons and technical data, such as country codes, RFCs, filename extensions, TCP and UDP port numbers, country calling codes, and so on.
Data packs may come in formats of CSV and SQL that can easily be parsed or imported into a database management system.
The database may consist of a key-value pair, like an association list.
Data packs are commonly used within the video game industry to provide minor updates within their games. When a user downloads an update for a game they will be downloading loads of data packs which will contain updates for the game such as minor bug fixes or additional content. An example of a data pack used to update a game can be found on the references.
Example
SELECT capital FROM countries WHERE country='Sweden'
Data pack
A data pack DataPack Definition is similar to a data packet it contains loads of information (data) and stores it within a pack where the data can be compressed to reduce its file size. Only certain programs can read a data pack therefore when the data is packed it is vital to know whether the receiving program is able to unpack the data. An example of data packs which are able to deliver effective information can be found on the reference page.
Mobile data packs
When you refer to the word data pack it can come in many forms such as a mobile data pack. A mobile data pack refers to an add-on which can enable you to boost the amount of data which you can use on your mobile phone. The rate at which you use your data can also be monitored, so you know how much data you have left. Mobile data is a service which provides a similar service to Wi-Fi and allows you to connect to the Internet. So the purpose of a data pack is to increase the amount of data that your mobile has access to. An example of a mobile data pack can be found on the references.
See also
:Category:Lists
Data set
Semantic triple
External links
DarkBot @ SourceForge
A directory of fact packs
References
Artificial intelligence engineering
Databases | Data pack | Engineering | 496 |
17,208,397 | https://en.wikipedia.org/wiki/Farglitazar | Farglitazar is a peroxisome proliferator-activated receptor agonist which was formerly under development by GlaxoSmithKline, but has never been marketed. It progressed to phase II clinical trials for the treatment of hepatic fibrosis, but failed to show efficacy. After reaching phase III for type 2 diabetes, further development was discontinued.
References
Drugs developed by GSK plc
PPAR agonists
Oxazoles
Abandoned drugs | Farglitazar | Chemistry | 95 |
24,797,753 | https://en.wikipedia.org/wiki/Russula%20albidula | Russula albidula is a species of mushroom in the genus Russula. The species, known in the vernacular as the boring white russula or the whitish brittlegill, is nondescript, with a small or medium dirty white fruit body, and a highly acrid taste. It is found in eastern North America.
Taxonomy
The species was first described by the American mycologist Charles Horton Peck in 1898. Mycologist David Arora, describing the fruit bodies as "plain, unprepossessing, [and] profoundly forgettable", calls the species the "boring white Russula". Another common name is the "whitish brittlegill".
Description
The cap of the fruit body is convex to almost flat, broad, with a white surface that becomes yellowish when dry. The cap surface is viscid when moist, and have a cuticle that can be peeled off. The gills are white, equal, sometimes forking next to the stipe, and have an adnate or slightly decurrent attachment to the stem. The stipe is white, smooth, long and wide. The flesh, which is fragile and white, has a very bitter taste. Specimens found in the field are typically dirty and dingy.
In deposit, the spores are pale yellow. Viewed microscopically, they are roughly spherical, thin-walled, and have dimensions of 6–7.5 by 7.5–10 μm. The surface of the spores is marked by broken reticulations.
Edibility
The highly acrid taste of Russula albidula is a deterrent to consumption, although it is not considered poisonous.
Similar species
Other Russula species that bear a resemblance to R. albidula include R. albella, R. albida, R. anomala, and R. subalbidula. It may also be confused with white waxycaps (genus Hygrophorus) or Tricholoma species.
Habitat and distribution
The fruit bodies of Russula albidula can be found growing solitary or grouped together on the ground in woods (both mixed and coniferous) or the edges of woods; specimens are often found near oak trees. The species has a penchant for appearing in poor soil like that found on roadsides and along trails. Russula albidula is distributed in eastern North America.
See also
List of Russula species
References
External links
R. albidula at Index Fungorum
Mushroom Hobby Several photos, including spores
albida
Fungi of North America
Taxa named by Charles Horton Peck
Fungus species | Russula albidula | Biology | 523 |
65,471,441 | https://en.wikipedia.org/wiki/Froissart%20bound | In particle physics the Froissart bound, or Froissart limit, is a generic constraint that the total scattering cross section of two colliding high-energy particles cannot increase faster than , with c a normalization constant and s the square of the center-of-mass energy (s is one of the three Mandelstam variables).
See also
S-matrix theory
Regge theory
Further reading
The Froissart bound on scholarpedia, by M. Froissart
References
Scattering theory | Froissart bound | Physics,Chemistry | 107 |
22,535,079 | https://en.wikipedia.org/wiki/Penny%20battery | The penny battery is a voltaic pile which uses various coinage as the metal disks (pennies) of a traditional voltaic pile. The coins are stacked with pieces of electrolyte soaked paper in between (see diagram at right). The penny battery experiment is common during electrochemistry units in an educational setting.
Each cell in a penny battery can produce up to 0.8 volt, and many can be stacked together to produce higher voltages. Since the battery is a wet cell, the effectiveness will be reduced when the electrolyte evaporates.
Coinage selection
As the name implies, Canadian pennies from 1997 to 1999 may serve the zinc electrode and 1942-1996 pennies as the copper. Alternatively, American pennies from 1982–present may be used as the zinc electrodes and 1944-1982 pennies as the copper electrodes. A variety of other coins can also be used, with varying results.
Energy
Batteries convert the chemical energy of the two metals (electrodes) interacting with the acid on the matboard (electrolyte) into electrical energy. In this situation, the metal surface serves as the electrode and an electric current (movement of electrons from one metal to the other) is created when the wire connects both metal surfaces. In the first hour, a five cell penny battery is able to provide about watts. Each cell is defined as a stack of a zinc penny, matboard, and a copper penny. Each cell can provide about 0.6 volts. Indicating that to power an LED light, needing 1.7 volts, only three cells need to be used. As time goes on the amount of energy that the battery can provide decreases. A five cell penny battery can last up to hours providing minimal voltage. The stack of cells is also known as a voltaic pile.
Chemistry
A penny battery functions as a standard voltaic pile, and is powered by a redox reaction between zinc and acid. Electrons flow through the electrolyte solution from zinc toward copper because zinc has a higher activity than copper. The acid releases positively charged hydrogen ions that combine with these electrons to form hydrogen gas, which escapes to the atmosphere. The release of gas corresponds with a large increase in entropy, making the reaction irreversible.
The reaction can be written as two separate reactions in different regions of the cell, or as one overall reaction. The reactions shown here use acetic acid, but a variety of other acids can also be used.
Reaction at anodeZn(s) → (aq) + 2e−
Reaction in electrolyte solution(aq) + 2e− → (aq) + (g)
Overall reactionZn(s) + (aq) → (aq) + (aq) + (g)
Common misconceptions
Despite often being made of similar materials, this is not the same mechanism that powers a galvanic cell. Both types of cell can use acid as an electrolyte, copper as a cathode, and zinc as both an anode and as a substance to be oxidized. However they cause different substances to be reduced: voltaic piles reduce acid, and galvanic cells reduce copper. This is because galvanic cells contain dissolved copper ions, which can be reduced to form the more stable copper metal. Voltaic piles such as the penny battery start with all of their metal in solid form, so they don't contain any dissolved copper ions that can be reduced.
See also
List of battery types
References
Battery types
Chemistry experiments | Penny battery | Chemistry | 721 |
1,913,023 | https://en.wikipedia.org/wiki/Mamzer | In the Hebrew Bible and Jewish religious law, a mamzer (, , "estranged person"; plural mamzerim) is a person who is born as the result of certain forbidden relationships or incest (as it is defined by the Bible), or the descendant of such a person. Mamzer status () is not synonymous with the traditional western definition of illegitimacy, since it does not include children born to unmarried mothers.
Definition
Etymology
Some have explained the word mamzer as the masculine noun form derived from the root m-z-r, having a meaning of spoilt/corrupt.
According to Strong's Concordance: "from an unused root meaning 'to alienate'; a mongrel, i. e., born of a Jewish father and a heathen mother".
The Talmud explains the term homiletically as consisting of the words mum (defect) and zar (strange/alien), a euphemism for an illicit union in the person's lineage.
Hebrew Bible usage
The term occurs twice in the Hebrew Bible. The first time is (23:2 in non-Hebrew versions). The Septuagint translates the term mamzer as son "of a prostitute" (Greek: ), and the Latin Vulgate translates it as ("born of a prostitute"). In English, it is often translated as "bastard".
"shall not enter the congregation of the Lord" was explained by the Rabbis to mean that the bastard cannot marry a son or daughter of Israel. Alternatively, the "congregation of the Lord" could've referred to the legislature of ancient Israel.
The other occasion is in : "And a bastard (mamzer) shall dwell in Ashdod...".
Halakhic definitions
In the Talmud, the term mamzer is applied to the descendants of specific illicit unions. According to the Mishnah, a mamzer is the offspring of a biblically forbidden union for which his progenitors are liable to extirpation at the hands of heaven. An exception to this rule is when a Jewish man cohabits with a menstruant woman: Although he is liable thereby to extirpation, the child born from such union is not a mamzer. The practical bearing of this ruling is that it excludes from such defamation a child born outside of wedlock, and which child is often wrongly called "bastard" under common law. According to the Shulchan Aruch, a new line of mamzerim can only be produced by two Jews but the product of a non-Jew and a mamzeret (female mamzer) is a mamzer.
There are two categories of mamzerim. A child born of incest, as defined by the Bible, is a mamzer. Note, however, that an incestuous relationship between one or two non-Jews cannot produce a mamzer, and if the product of such a union were to convert, he or she would be the equal of any Jew.
A child born of a married Jewish woman's adultery is a mamzer. The child of a single woman and a man she could lawfully have married is not a mamzer. It is irrelevant if the man is married or not. If one of the parents is not Jewish, the child is not a mamzer. Any child born to a married woman, even if she is known to have been unfaithful, is presumed to be her husband's, unless she is so promiscuous that such a presumption becomes unsupportable, or if she enters a public relationship with another man.
A child born within 12 months of a woman's most recent meeting with her husband is presumed to be legitimate, since Jewish law believes that in rare cases, a pregnancy can last that long. However, if more than 9 months have elapsed, and she is known to have been unfaithful, then the presumption does not apply. Modern assisted reproductive technology has complicated the issue. Rabbi Moshe Feinstein ruled that if a married woman is inseminated by sperm from another man, the child is not a mamzer, since it did not result from an act of adultery; Rabbi Joel Teitelbaum (2005) disagreed, and ruled that, since the child is known to be that of a man other than her husband, it is a mamzer.
The status of an abandoned child (Hebrew: asufi) was determined by the state in which it was found. If there were indications that the foundling had been abandoned due to the parents being unable to support it, then, halakhically, the child would not be a mamzer. However, if the unknown parents could have supported the child, it was regarded as potentially being a mamzer. A child whose mother is known, but not the father, was known as "silent one" (Hebrew: shetuki), and fell into the same category as a foundling; this status, however, could be changed if the mother knew and revealed the identity of the father.
The mamzer status is hereditary – a child of a mamzer (whether mother or father) is also a mamzer. However, since these rules are regarded as applying only to Jews, and since traditional Rabbinical law regards Jewish status as only transmitted through the mother, the child of a male mamzer and a non-Jewish woman cannot be a mamzer. However, the child of a female mamzer and a non-Jewish man is a mamzer.
Marriage restrictions
The biblical rule against certain people becoming part of the "congregation of the Lord" was interpreted in the Talmud as a prohibition against ordinary Jews marrying such people. Although the biblical passage includes in this up to the tenth generation of the descendants of a mamzer, classical rabbis interpreted this as an idiom meaning "forever". Thus, in traditional Jewish law, a mamzer and his or her descendants are not allowed to marry an ordinary (non-mamzer) Jewish spouse.
The restriction does not prevent a mamzer from marrying another mamzer, nor from marrying a convert to Judaism, or a non-Jewish slave. However, foundlings suspected of being mamzerim were not so free; they were neither permitted to marry a mamzer, nor even to marry another foundling.
This interpretation is not universally shared, with Matthew Poole interpreting the "congregation of the Lord" as being the Israelite government.
Social status of mamzerim
Although in many historical societies, illegitimacy of birth was a quality which could make a person somewhat of an outcast, this was not the official attitude of Judaism; apart from the marriage restrictions, a mamzer is not officially considered a second-class citizen, and is supposed to be treated with as much respect as other Jews. For example, the Mishnah teaches that a learned mamzer should "take precedence" over an ignorant High Priest of Israel; the meaning of "take precedence" is not explicitly explained by the Mishnah, nor by the Talmud in general, although the preceding part of the Mishnah uses it to refer to the priority in which people should be rescued from danger, while other parts of the Mishnah use the phrase to refer to the priority in which people should receive aliyot.
Rabbis in the Talmud, and those in the Middle Ages, saw fit to spell out that, aside from in questions of marriage, a mamzer should be treated as an ordinary Jew. The Talmud insists that a mamzer should be considered as an ordinary relative for the purpose of inheritance, including levirate marriage. Maimonides and Joseph ben Ephraim Karo see fit to repeat this, and confirm that a mamzer can serve as a judge. Similarly, a tosafa insists that it is permissible for a mamzer to become a king.
The status of mamzerim could even be relinquished, either by the mamzer marrying a servant or the mamzer becoming a servant themselves, with their status being immediately relinquished upon their release.
Modern investigations into mamzer status
Orthodox Judaism
The principal approach in Orthodox Judaism is to require strict evidentiary standards for mamzer status, sufficiently strict that proof of the existence of mamzer status is hard to develop and generally does not arise. Typically, it is impossible to prove either that a prior marriage ever existed, or that a child was born of relations outside that marriage. Orthodox rabbis always allow the suspect child the benefit of the doubt in this matter. This usually leads to the conclusion that at the time of a person's birth, their parents were married, or that the person is the child of a man and woman who were married to each other when the child was conceived.
An example is a contemporary responsum by Rabbi Ovadia Yosef, establishing the impossibility to prove mamzer status in a case where the evidence might appear to be clear-cut. The case involved the daughter of an aguna who had been married by a Haredi rabbi to a husband who subsequently converted to Christianity and refused to participate in a Jewish divorce. The mother eventually divorced and remarried civilly, and had the daughter years later. The daughter had been raised as an Orthodox Jew and attended Beit Yaakov, a Haredi day school. The daughter brought up the question of her status herself prior to an impending marriage. Rabbi Yosef proceeded systematically to disqualify evidence that a prior marriage had ever taken place. The mother's evidence was immediately disqualified as an interested party. The ketubah (Jewish marriage contract/certificate) was never found. The rabbi who performed the marriage was contacted, but Rabbi Yosef wrote that his testimony could not be accepted without the ketubah, and in any event required corroboration by two witnesses. Attempts to contact the husband were abandoned after an adversarial conversation with his new, non-Jewish wife. Even if the husband could have been reached, he would only have been one witness, and his testimony could not have been accepted without a second witness. Thus, Rabbi Yosef concluded there was insufficient evidence that a valid prior marriage had ever taken place. Rabbi Yosef then proceeded to establish the possibility that the former husband might be the daughter's father. The mother testified that her former husband occasionally brought alimony payments and came for visitation in person, and hence, the two were sometimes at least momentarily alone together. Applying an ancient rule that when a husband and wife are known to be alone together behind a closed door, the law presumes sexual intercourse may well have taken place, Rabbi Yosef concluded that it was possible that the former husband was the daughter's father, and hence, Jewish law, which very strongly construes all evidence in favour of birth within marriage, had to presume that he was. Thus, Rabbi Yosef concluded that there was insufficient evidence of either a former marriage or that the new husband was the father, and hence, he concluded that there was insufficient evidence of mamzerut status. Rabbi Yosef said, "The ruling therefore must be that there is very great reason to permit this woman to marry and enter the congregation of God, and as it appears to me have I written."
Conservative rabbi Daniel S. Nevins, commenting on this case, noted that the box of traditional tools Rabbi Yosef used to discredit evidence of mamzer status may be sufficiently robust as to cover virtually all cases of inquiry in the types of situations a congregation rabbi would be likely to experience. Nonetheless, Orthodox rabbinical authorities hold that while contemporary rabbis have authority to refine procedural rules such as rules of evidence, they do not have the authority to abolish biblically mandated categories or procedures entirely.
Israeli law tries to prevent the conferring of mamzer status by refusing to allow men other than the husband or recent ex-husband from registering as a child's father without a court order. However, paternity tests have the potential to reveal mamzer status by removing the protection of the presumption of paternity on the part of a married woman's actual husband.
Conservative Judaism
The Committee on Jewish Law and Standards (CJLS) of the Rabbinical Assembly of Conservative Judaism has declared that Conservative Rabbis should not inquire into or accept evidence of mamzer status under any circumstances, rendering the category inoperative. In doing so, the CJLS distinguished the Conservative approach to Jewish law from the Orthodox approach, noting that Conservative Judaism regards Biblical law as only the beginning of a relationship rather than a final word, and that the Conservative movement regards it as its role and responsibility to revise Biblical law from time to time when such law conflicts with evolving concepts of morality.
Karaite Judaism
In Zechariah 9:6, "mamzer" is referenced similar to that of the nations of Ammon, Moab, Edom, Egypt, Tyre, Zidon, Ashkelon, Gaza, Philistia, etc. From such, Karaites have come to consider the most logical understanding of the Hebrew to actually refer to a nation of people. Karaites believe that such an understanding fits perfectly into the context of both Deuteronomy 23 and Zechariah 9, and several Medieval rabbinical Jewish sages felt it necessary to debate this topic with medieval Karaite Jewish sages.
In Israeli law
In the modern State of Israel, the law concerning matters of marriage, divorce, and personal status, is partially under the jurisdiction of religious courts. For example, there is no civil marriage in Israel. The Jewish religious regulations concerning mamzerim are thus also the national laws imposed on Jews living in Israel, including secular Jews. Because of the severe impediments to marriage which mamzer status accords in Jewish law, Israeli civil law has taken the position that the paternity of a child born within a marriage cannot legally be challenged in civil courts, in order to avoid creating a body of evidence that might be used to declare the child a mamzer, or create difficulties for a future marriage.
The existence of mamzer status as a category in Israeli family law has been criticized. An extensive review and opinion advocating the adoption of civil marriage in Israel, written by Prof. Pinhas Shifman and published in July 2001 by the Association for Civil Rights in Israel, mentions Mamzer among the categories of Israelis which, Professor Shifman believes, should have the right to marry spouses of their choice, and, he argues, current Israeli law interferes with, and denies, this right. Professor Shifman and ACRI advocate ending the religious monopoly over marriage in Israel, and cite the existence and difficulties of mamzer status as an argument against the use of religious law in marriage cases.
Israeli religious courts resolve mamzer status by generally ruling that the child was born within the marriage, despite the existence of evidence to the contrary. This convenient formula sometimes causes difficulties for lovers or subsequent spouses who wish to assert paternity over a child which may be biologically theirs. A 2006 case, in which a child born eight months and two weeks after a divorce, was declared the former husband's child, rather than the child of the wife's subsequent husband, and this was reported as causing a dilemma for the subsequent couple.
Nonetheless, the existence of the category of Mamzer, and the marital impediments inherent to it, is one of the arguments frequently used by Israeli secularists in calling for separation of religion and state, and for the institution of civil marriage. In 2014, the Center for Women's Justice announced it would petition the Israeli Supreme Court to bar secret blacklists of mamzerim by rabbinical courts, claiming they are an invasion of privacy.
Connection with French medieval nicknames
A persistent etymology of the surname Manser is connected to Hebrew mamzer. Supposedly Ebalus of Aquitaine (Count of Poitou and Duke of Aquitaine, c. 870 – 935) had the nickname "Manzer" or "Manser". As he is known to have been a bastard and reputed to have had a Jewish mother, this nickname is considered to be derived from mamzer. A similar explanation is offered also for the same nickname as used by another prince from Occitania: , a 10th-century count of Angoulême who also was a bastard. William the Conqueror may have been referred to as Bastardus and Mamzer.
References
Jewish marital law
Kinship and descent | Mamzer | Biology | 3,421 |
36,132,687 | https://en.wikipedia.org/wiki/Kosmos%201030 | Kosmos 1030 ( meaning Cosmos 1030) was a Soviet US-K missile early warning satellite which was launched in 1978 as part of the Soviet military's Oko programme. The satellite was designed to identify missile launches using optical telescopes and infrared sensors.
Launch
Kosmos 1030 was launched from Site 43/4 at Plesetsk Cosmodrome in the Russian SSR. A Molniya-M carrier rocket with a 2BL upper stage was used to perform the launch, which took place at 03:04 UTC on 6 September 1978.
Orbit
The launch successfully placed the satellite into a molniya orbit. It subsequently received its Kosmos designation, and the international designator 1978-083A. The United States Space Command assigned it the Satellite Catalog Number 11015.
The satellite self-destructed on October 10, 1978, breaking into 13 pieces of which several are still on orbit.
See also
1978 in spaceflight
List of Kosmos satellites (1001–1250)
List of Oko satellites
List of R-7 launches (1975-1979)
References
Kosmos satellites
Oko
1978 in spaceflight
Spacecraft launched in 1978
Spacecraft launched by Molniya-M rockets
Spacecraft which reentered in 2004
Spacecraft that broke apart in space | Kosmos 1030 | Technology | 259 |
883,885 | https://en.wikipedia.org/wiki/OCLC | OCLC, Inc., doing business as OCLC, is an American nonprofit cooperative organization "that provides shared technology services, original research, and community programs for its membership and the library community at large". It was founded in 1967 as the Ohio College Library Center, then became the Online Computer Library Center as it expanded. In 2017, the name was formally changed to OCLC, Inc. OCLC and thousands of its member libraries cooperatively produce and maintain WorldCat, the largest online public access catalog in the world. OCLC is funded mainly by the fees that libraries pay (around $217.8 million annually in total ) for the many different services it offers. OCLC also maintains the Dewey Decimal Classification system.
History
OCLC began in 1967, as the Ohio College Library Center, through a collaboration of university presidents, vice presidents, and library directors who wanted to create a cooperative, computerized network for libraries in the state of Ohio. The group first met on July 5, 1967, on the campus of Ohio State University to sign the articles of incorporation for the nonprofit organization and hired Frederick G. Kilgour, a former Yale University medical school librarian, as first executive director.
Kilgour and Ralph H. Parker, who was the head of libraries at the University of Missouri, had proposed the shared cataloging system in a 1965 report as consultants to the Committee of Librarians of the Ohio College Association. Kilgour and Parker wished to merge the latest information storage and retrieval system of the time, the computer, with the oldest, the library. They were inspired in part by the earlier Columbia–Harvard–Yale Medical Libraries Computerization Project, an attempt at shared automated printing of catalog cards. The plan was to merge the catalogs of Ohio libraries electronically through a computer network and database to streamline operations, control costs, and increase efficiency in library management, bringing libraries together cooperatively to best serve researchers and scholars. The first library to do online cataloging through OCLC was the Alden Library at Ohio University on August 26, 1971. This was the first online cataloging by any library worldwide.
Between 1967 and 1977, OCLC membership was limited to institutions in Ohio, but in 1978, a new governance structure was established that allowed institutions from other states to join. In 2002, the governance structure was again modified to accommodate participation from outside the United States.
As OCLC expanded services in the United States outside Ohio, it relied on establishing strategic partnerships with "networks", organizations that provided training, support and marketing services. By 2008, there were 15 independent United States regional service providers. OCLC networks played a key role in OCLC governance, with networks electing delegates to serve on the OCLC Members Council. During 2008, OCLC commissioned two studies to look at distribution channels; at the same time, the council approved governance changes that had been recommended by the Board of Trustees severing the tie between the networks and governance. In early 2009, OCLC negotiated new contracts with the former networks and opened a centralized support center.
In July 2010, the company was sued by SkyRiver, a rival startup, in an antitrust suit. Library automation company Innovative Interfaces joined SkyRiver in the suit. The suit was dropped in March 2013, however, following the acquisition of SkyRiver by Innovative Interfaces.
Innovative Interfaces was bought by ExLibris in 2020, therefore passing OCLC as the dominant supplier of ILS services in the US (over 70% market share for academic libraries and over 50% for public libraries for ExLibris, versus OCLC's 10% market share of both types of libraries in 2019).
In 2022, membership and governance expanded to include any institution with a subscription to one of many qualifying OCLC products (previously institutions qualified for membership by "contributing intellectual content or participating in global resource or reference sharing"), with the exception of for-profit organizations that are part of OCLC's partner program. This change reflected OCLC's expanding number of services due to its corporate acquisitions.
Presidents
The following people served successively as president of OCLC:
1967–1980: Frederick G. Kilgour
1980–1989: Rowland C. W. Brown
1989–1998: K. Wayne Smith
1998–2013: Jay Jordan
2013–present: Skip Prichard
Services
OCLC provides bibliographic, abstract and full-text information to anyone.
OCLC and its member libraries cooperatively produce and maintain WorldCat—the OCLC Online Union Catalog, the largest online public access catalog (OPAC) in the world. WorldCat has holding records from public and private libraries worldwide.
The Online Computer Library Center acquired the trademark and copyrights associated with the Dewey Decimal Classification System when it bought Forest Press in 1988. A browser for books with their Dewey Decimal Classifications was available until July 2013; it was replaced by the Classify Service.
Until August 2009, when it was sold to Backstage Library Works, OCLC owned a preservation microfilm and digitization operation called the OCLC Preservation Service Center, with its principal office in Bethlehem, Pennsylvania.
Starting in 1971, OCLC produced catalog cards for members alongside its shared online catalog; the company printed its last catalog cards on October 1, 2015.
, an around-the-clock reference service provided to users by a cooperative of participating global libraries, was acquired by Springshare from OCLC in 2019 and migrated to Springshare's LibAnswers platform.
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OCLC commercially sells software, such as:
CONTENTdm for managing digital collections
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WorldShare Management Services, an electronic resource management system
cloudLibrary, a cloud-based software system through which libraries manage and lend electronic books, digital magazines, newspapers, comics, and streaming media
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OCLC has been conducting research for the library community for more than 30 years. In accordance with its mission, OCLC makes its research outcomes known through various publications. These publications, including journal articles, reports, newsletters, and presentations, are available through the organization's website.
OCLC Publications – Research articles from various journals including The Code4Lib Journal, OCLC Research, Reference and User Services Quarterly, College & Research Libraries News, Art Libraries Journal, and National Education Association Newsletter. The most recent publications are displayed first, and all archived resources, starting in 1970, are also available.
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WebJunction, which provides training services to librarians, is a division of OCLC funded by grants from the Bill & Melinda Gates Foundation beginning in 2003.
OCLC partnered with search engine providers in 2003 to advocate for libraries and share information across the Internet landscape. Google, Yahoo!, and Ask.com all collaborated with OCLC to make WorldCat records searchable through those search engines.
OCLC's advocacy campaign "Geek the Library", started in 2009, highlights the role of public libraries. The campaign, funded by a grant from the Bill & Melinda Gates Foundation, uses a strategy based on the findings of the 2008 OCLC report, "From Awareness to Funding: A study of library support in America".
Other past advocacy campaigns have focused on sharing the knowledge gained from library and information research. Such projects have included communities such as the Society of American Archivists, the Open Archives Initiative, the Institute for Museum and Library Services, the International Organization for Standardization, the National Information Standards Organization, the World Wide Web Consortium, the Internet Engineering Task Force, and Internet2. One of the most successful contributions to this effort was the Dublin Core Metadata Initiative, "an open forum of libraries, archives, museums, technology organizations, and software companies who work together to develop interoperable online metadata standards that support a broad range of purposes and business models."
OCLC has collaborated with the Wikimedia Foundation and the Wikimedia volunteer community, through integrating library metadata with Wikimedia projects, hosting a Wikipedian in residence, and doing a national training program through WebJunction called "Wikipedia + Libraries: Better Together".
Online database: WorldCat
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Identifiers and linked data
OCLC assigns a unique control number (referred to as an "OCN" for "OCLC Control Number") to each new bibliographic record in WorldCat. Numbers are assigned serially, and in mid-2013 over a billion OCNs had been created. In September 2013, the OCLC declared these numbers to be in the public domain, removing a perceived barrier to widespread use of OCNs outside OCLC itself. The control numbers link WorldCat's records to local library system records by providing a common reference key for a record across libraries.
OCNs are particularly useful as identifiers for books and other bibliographic materials that do not have ISBNs (e.g., books published before 1970). OCNs are often used as identifiers for Wikipedia and Wikidata. In October 2013, it was reported that out of 29,673 instances of book infoboxes in Wikipedia, "there were 23,304 ISBNs and 15,226 OCNs", and regarding Wikidata: "of around 14 million Wikidata items, 28,741 were books. 5403 Wikidata items have an ISBN associated with them, and 12,262 have OCNs."
OCLC also runs the Virtual International Authority File (VIAF), an international name authority file, with oversight from the VIAF Council composed of representatives of institutions that contribute data to VIAF. VIAF numbers are broadly used as standard identifiers, including in Wikipedia.
Company acquisitions
OCLC acquired NetLibrary, a provider of electronic books and textbooks, in 2002 and sold it in 2010 to EBSCO Industries. OCLC owns 100% of the shares of OCLC PICA, a library automation systems and services company which has its headquarters in Leiden in the Netherlands and which was renamed "OCLC" at the end of 2007. In July 2006, the Research Libraries Group (RLG) merged with OCLC.
On January 11, 2008, OCLC announced that it had purchased EZproxy. It has also acquired OAIster. The process started in January 2009 and from October 31, 2009, OAIster records are freely available via WorldCat.org.
In 2013, OCLC acquired the Dutch library automation company HKA and its integrated library system Wise, which OCLC calls a "community engagement system" that "combines the power of customer relationship management, marketing, and analytics with ILS functions". OCLC began offering Wise to libraries in the United States in 2019.
In January 2015, OCLC acquired Sustainable Collection Services (SCS). SCS offered consulting services based on analyzing library print collection data to help libraries manage and share materials. In 2017, OCLC acquired Relais International, a library interlibrary loan service provider based in Ottawa, Canada.
A more complete list of mergers and acquisitions is available on the OCLC website.
Criticism
In May 2008, OCLC was criticized by Jeffrey Beall for monopolistic practices, among other faults. Library blogger Rick Mason responded that although he thought Beall had some "valid criticisms" of OCLC, he demurred from some of Beall's statements and warned readers to "beware the hyperbole and the personal nature of his criticism, for they strongly overshadow that which is worth stating".
In November 2008, the Board of Directors of OCLC unilaterally issued a new Policy for Use and Transfer of WorldCat Records that would have required member libraries to include an OCLC policy note on their bibliographic records; the policy caused an uproar among librarian bloggers. Among those who protested the policy was the non-librarian activist Aaron Swartz, who believed the policy would threaten projects such as the Open Library, Zotero, and Wikipedia, and who started a petition to "Stop the OCLC powergrab". Swartz's petition garnered 858 signatures, but the details of his proposed actions went largely unheeded. Within a few months, the library community had forced OCLC to retract its policy and to create a Review Board to consult with member libraries more transparently. In August 2012, OCLC recommended that member libraries adopt the Open Data Commons Attribution (ODC-BY) license when sharing library catalog data, although some member libraries have explicit agreements with OCLC that they can publish catalog data using the CC0 Public Domain Dedication.
See also
Dynix (software)
Public library advocacy
References
Further reading
See also: Information about licensing of WorldCat records and some other OCLC data.
External links
Hanging Together – the OCLC Research blog
OCLC Annual Reports collection at the OCLC Archives
1967 establishments in Ohio
Bibliographic database providers
Companies based in Dublin, Ohio
Cooperatives based in Ohio
Library automation
Library cataloging and classification
Library centers
Library-related organizations
Organizations established in 1967 | OCLC | Engineering | 2,881 |
1,350,243 | https://en.wikipedia.org/wiki/Sneaker%20wave | A sneaker wave, also known as a sleeper wave, or in Australia as a king wave, is a disproportionately large coastal wave that can sometimes appear in a wave train without warning.
Terminology
The term "sneaker wave" is popular rather than scientific, derived from the observation that such a wave can "sneak up" on an unwary beachgoer. There is no scientific coverage of the phenomenon as a distinct sort of wave with respect to height or predictability as there is on other extreme wave events such as tsunamis or rogue waves, and little or no scientific evidence has been gathered to identify, describe, or define sneaker waves. Although the term "rogue wave" — meaning an unusually tall or steep wave in mid-ocean — is sometimes used as a synonym for "sneaker wave," one American oceanographer distinguishes "rogue waves" as occurring on the ocean and "sneaker waves" as occurring at the shore, while the National Oceanic and Atmospheric Administration loosely defines rogue waves as offshore waves that are at least twice the height of surrounding waves and sneaker waves as waves near shore that are unexpectedly and significantly larger than other waves reaching shore at the time. Scientists do not yet understand what causes sneaker waves, and their relationship to rogue waves, if any, has not been established.
In a 2018 paper, Oregon State University researchers wrote that sneaker waves form in offshore storms that transfer wind energy to the ocean surface. The resulting waves then arrive along a coastline during periods of calm weather, and the greater amount of energy they contain compared to the regular waves that preceded them causes them to travel far higher up the shore than the other waves. As of 2021, the National Weather Service in the United States viewed ocean conditions along the United States West Coast as favorable for sneaker waves when an offshore storm generates waves with a particularly long period — perhaps longer than 15 seconds — between swells, allowing the swells to build considerable force before reaching shore, where they might appear either as conventional large waves or as sneaker waves.
Characteristics
Sneaker waves appear suddenly on a coastline and without warning; generally, it is not obvious that they are larger than other waves until they break and suddenly surge up a beach. A sneaker wave can occur following a period of 10 to 20 minutes of gentle, lapping waves. Upon arriving, a sneaker wave can surge more than beyond the foam line, rushing up a beach with great force. In addition to containing a large volume of rapidly surging water, a sneaker wave also tends to carry a large amount of sand and gravel with it. It can be strong enough to break over rocks and float or roll large, waterlogged logs lying on the beach weighing several hundred pounds, moving them up the beach during the landward surge and then back down toward the ocean as the wave retreats. Sneaker waves appear to be more common along steep coastlines than in areas with broader, more gently sloped beaches.
Hazards
The unpredictability of sneaker waves and their tendency to arrive suddenly after lengthy periods of gentle, lapping waves makes it easy for them to surprise unwary or inexperienced beachgoers; because they are much larger than preceding waves, sneaker waves can catch inattentive swimmers, waders, and other people on beaches and ocean jetties and wash them into the sea. The force of a sneaker wave's surge and the large volume of water rushing far up a beach is enough to suddenly submerge people thigh- or waist-deep, knock them off their feet, and drag them into the ocean or trap them against rocks. Many coastlines more prone to sneaker waves lie in colder parts of the world where beachgoers tend to wear heavier clothing; the amount of sand and gravel in a sneaker wave can quickly fill such clothing and footwear such as boots with sediment that weighs a person down as he or she is swept up a beach and then back into the sea, increasing the chances of drowning. Floating and rolling logs in a sneaker wave also pose a danger, as they can badly injure people as well as pin people down when they come to rest, and it can be difficult or impossible to move such a log before a person pinned by it drowns as later waves arrive and fill the person's lungs with water and sediment.
Geographic distribution
Sneaker waves are mainly referred to in warnings and reports of incidents for the coasts of Central and Northern California (including the San Francisco Bay Area's beaches, especially Ocean Beach, Baker Beach, and those that face the Pacific Ocean, e.g. from Big Sur to the California–Oregon border), Oregon, and Washington in the Western United States. Sneaker waves also occur on the coast of British Columbia in Western Canada, especially the province's southern coast, because they commonly occur on the west coast of Vancouver Island (including Tofino, Ucluelet, and Cape Scott Provincial Park). Sneaker waves are common on the southern coast of Iceland, and warning signs were erected at Reynisfjara and Kirkjufjara beaches, following three unrelated tourist deaths at those beaches over several years, the third of them in January 2017. In Australia, where they are known as "king waves," sneaker waves occur especially in Western Australia and Tasmania, where they can be a hazard for rock fishermen.
Along much of the United States West Coast, sneaker waves kill more people than all other weather hazards combined. In Oregon, 21 deaths were attributed to sneaker waves from 1990 through March 2021, most of the deaths occurring between October and April, although sneaker waves also occurred at other times of year.
A sneaker wave incident gained worldwide media attention when two large waves suddenly and unexpectedly struck a crowd watching the Mavericks surfing competition at Mavericks in Princeton-by-the-Sea, California, on February 13, 2010, breaking over a seawall onto a narrow beach and injuring at least 13 people. The incident was caught on film.
In March 2014, a massive wave struck Roi-Namur in Kwajalein Atoll in the Marshall Islands on an otherwise calm, sunny day, penetrating well inland, flooding parts of the island and swamping coastal roads.
On September 18, 2023, a sneaker wave smashed into a beachside restaurant at Marina Beach near Southbroom, South Africa, injuring seven people. One restaurant patron was swept out to sea but rescued by lifeguards. The wave was filmed.
Rio de Janeiro's Barra de Tijuca beach in Brazil experiences sneaker waves, known locally as ressaca waves. It also is a steep beach and a December 2023 news film shows the whole beach being cleared by a sneaker wave.
On 20 January 2024, one or more sneaker or rogue waves struck the United States Army′s Ronald Reagan Ballistic Missile Defense Test Site on Roi-Namur in Kwajalein Atoll in the Marshall Islands, breaking down the doors of a dining hall, knocking several people off their feet, moderately to severely damaging the dining hall, the Outrigger Bar and Grill, the chapel, and the Tradewinds Theater, and leaving parts of the island, including the automotive complex, underwater. The flooding of the dining hall was filmed. The wave or waves penetrated inland and probably were between tall amid a significant wave height of to .
Seventh wave
In many parts of the world, local folklore predicts that out of a certain number of waves, one will be much larger than the rest. "Every seventh wave" or "every ninth wave" are examples of such common beliefs that have wide circulation and have entered popular culture through music, literature, and art. These ideas have some scientific merit, due to the occurrence of wave groups at sea, but there is no explicit evidence for this specific phenomenon, or that these wave groups are related to sneaker waves. The saying is likely derived more from a cultural fascination with certain numbers, and it may also be designed to educate shore-dwellers about the necessity of remaining vigilant when near the ocean.
See also
Wind wave
Rogue wave
Tsunami
Megatsunami
Meteotsunami
References
External links
- Video of a sneaker wave off the Oregon coast
Water waves
Weather hazards | Sneaker wave | Physics,Chemistry | 1,670 |
55,704,468 | https://en.wikipedia.org/wiki/LTPP%20Data%20Analysis%20Contest | The LTPP International Data Analysis Contest or the LTPP Data Analysis Contest is an annual international data analysis contest held by the American Society of Civil Engineers and Federal Highway Administration. As the name suggests, the participants are supposed to use the LTPP data in their analysis. The winners of this data analysis contest are announced in early January during the Transportation Research Board annual meeting.
History
The LTPP database contains the data of more than 2,500 road sections across the US and Canada. The FHWA and ASCE launched a joint effort to encourage researchers around the world to use the LTPP data. The contest was first introduced in 1998 by the Transportation and Development Institute (T&DI) of the American Society of Civil Engineers and the LTPP of FHWA. The goal of the contest is to encourage consultants, academics and data scientists around the world to use the LTPP database for generating knowledge about the behaviour of pavements and roads.
Categories
The LTPP data analysis contest has four different categories:
Undergraduate Student Category
Graduate Category
Partnership Category
Challenge Category (Aramis Lopez Challenge)
The first two categories are limited to students. The participants of all categories are required to summarize their work within an article.
Winners
See also
List of engineering awards
List of mathematics awards
References
Federal Highway Administration
Awards of the American Society of Civil Engineers
Mathematics awards
Engineering awards | LTPP Data Analysis Contest | Technology | 268 |
2,108,845 | https://en.wikipedia.org/wiki/Alpha%20Capricorni | Alpha Capricorni (α Capricorni, abbreviated Alpha Cap, α Cap) is an optical double star in the constellation of Capricornus. The two physically unrelated components are designated:
α1 Capricorni
α2 Capricorni (also named Algedi).
They are separated by 0.11° on the sky, and resolvable with the naked eye, similar to Mizar and Alcor. α¹ Capricorni is fainter (apparent magnitude 4.27) than α² Capricorni (apparent magnitude 3.58).
Nomenclature
α Capricorni (Latinised to Alpha Capricorni) is the system's Bayer designation; α1 and α2 Capricorni, those of the two components.
Alpha Capricorni bore the traditional names Algedi, Algiedi, Al Giedi or Giedi, derived from the Arabic الجدي al-jady "the billy goat" or "kid". It also refers to the entire constellation of Capricornus. Giedi is sometimes also associated with Beta Capricorni. α1 and α2 Capricorni were also called Prima Giedi and Secunda Giedi, respectively. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Algedi for α2 Capricorni on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
Alpha Capricorni is known as 牛宿二 (the Second Star of the Ox) in Chinese astronomy.
References
Kaler, Jim. "Algedi". Retrieved December 5, 2016.
External links
Capricorni, Alpha
Capricornus
Double stars | Alpha Capricorni | Astronomy | 384 |
7,664,801 | https://en.wikipedia.org/wiki/3M | 3M Company (originally the Minnesota Mining and Manufacturing Company) is an American multinational conglomerate operating in the fields of industry, worker safety, and consumer goods. Based in the Saint Paul, Minnesota, suburb of Maplewood, the company produces over 60,000 products, including adhesives, abrasives, laminates, passive fire protection, personal protective equipment, window films, paint protection film, electrical, electronic connecting, insulating materials, car-care products, electronic circuits, and optical films. Among its best-known consumer brands are Scotch Tape, Scotchguard surface protectants, Post-it notes, and Nexcare adhesive bandages. 3M’s stock ticker symbol is MMM and is listed on the New York Stock Exchange, Inc. (NYSE), the Chicago Stock Exchange, Inc., and the SIX Swiss Exchange.
3M made $35.4 billion in total sales in 2021 and ranked number 102 in the Fortune 500 list of the largest United States corporations by total revenue. , the company had approximately 95,000 employees and operations in more than 70 countries. There are a few international subsidiaries, such as 3M India, 3M Japan, and 3M Canada.
In June 2023, 3M reached a settlement to pay more than $10 billion to US public water systems to resolve claims over the company's contamination of water with PFASs (so-called forever chemicals). It has been revealed that the company knew of the health harms of PFAS in the 1990s, yet concealed these harms and continues to sell contaminated products.
History
Five businessmen founded the Minnesota Mining and Manufacturing Company as a mining venture in Two Harbors, Minnesota, making their first sale on June 13, 1902. The goal was to mine corundum, a crystalline form of aluminium oxide, which failed because the mine's mineral holdings were anorthosite, a feldspar which had no commercial value. Co-founder John Dwan solicited funds in exchange for stock and Edgar Ober and Lucius Ordway took over the company in 1905. The company moved to Duluth and began researching and producing sandpaper products. William L. McKnight, later a key executive, joined the company in 1907, and A. G. Bush joined in 1909. 3M finally became financially stable in 1916 and was able to pay dividends.
The company moved to Saint Paul in 1910, where it remained for 52 years before outgrowing the campus and moving to its current headquarters at 3M Center in Maplewood, Minnesota, in 1962.
In 1947, 3M began producing perfluorooctanoic acid (PFOA), an industrial surfactant and chemical feedstock, by electrochemical fluorination. In 1951, DuPont purchased PFOA from then-Minnesota Mining and Manufacturing Company for use in the manufacturing of teflon, a product that brought DuPont a billion-dollar-a-year profit by the 1990s. DuPont referred to PFOA as C8. The original formula for Scotchgard, a water repellent applied to fabrics, was discovered accidentally in 1952 by 3M chemists Patsy Sherman and Samuel Smith. Sales began in 1956, and in 1973 the two chemists received a patent for the formula.
In the late 1950s, 3M produced the first asthma inhaler, but the company did not enter the pharmaceutical industry until the mid-1960s with the acquisition of Riker Laboratories, moving it from California to Minnesota. 3M retained the Riker Laboratories name for the subsidiary until at least 1985. In the mid-1990s, 3M Pharmaceuticals, as the division came to be called, produced the first CFC-free asthma inhaler in response to adoption of the Montreal Protocol by the United States. In the 1980s and 1990s, the company spent fifteen years developing a topical cream delivery technology which led in 1997 to health authority approval and marketing of a symptomatic treatment for genital warts, Aldara. 3M divested its pharmaceutical unit through three deals in 2006, netting more than . At the time, 3M Pharmaceuticals comprised about 20% of 3M's healthcare business and employed just over a thousand people.
By the 1970s, 3M developed a theatrical blood formula based on red colorfast microbeads suspended in a carrier liquid. This stage blood was sold as Nextel Simulated Blood and was used during the production of the 1978 film Dawn of the Dead. It has since been discontinued.
In the late 1970s, 3M Mincom was involved in some of the first digital audio recordings to see commercial release when a prototype machine was brought to the Sound 80 studios in Minneapolis. In 1979 3M introduced a digital audio recording system called "3M Digital Audio Mastering System".
3M launched "Press 'n Peel" a sticky bookmark page holder in stores in four cities in 1977, but the results were disappointing. A year later 3M instead issued free samples of it as a sticky note directly to consumers in Boise, Idaho, with 95% of those who tried them indicating they would buy the product. The product was sold as "Post-Its" in 1979 when the rollout introduction began, and was sold across the United States from April 6, 1980. The following year they were launched in Canada and Europe.
In 1980, the company acquired Comtal, a manufacturer of digital image processors.
21st century
On April 8, 2002, 3M's 100th anniversary, the company changed its legal name to "3M Company". On September 8, 2008, 3M announced an agreement to acquire Meguiar's, a car-care products company that was family-owned for over a century. In August 2010, 3M acquired Cogent Systems for $943 million, and on October 13, 2010, 3M completed acquisition of Arizant Inc. In December 2011, 3M completed the acquisition of the Winterthur Technology Group, a bonded abrasives company.
In 2011 by 3M created CloudLibrary as part of its library systems unit as a competitor to OverDrive, Inc.; in 2015 3M sold the North American part of that unit to Bibliotheca Group GmbH, a company founded in 2011 that was funded by One Equity Partners Capital Advisors, a division of JP Morgan Chase.
As of 2012, 3M was one of the 30 companies included in the Dow Jones Industrial Average, added on August 9, 1976, and was 97 on the 2011 Fortune 500 list. On January 3, 2012, it was announced that the Office and Consumer Products Division of Avery Dennison was being bought by 3M for $550 million. The transaction was canceled by 3M in September 2012 amid antitrust concerns.
In May 2013, 3M sold Scientific Anglers and Ross Reels to Orvis. Ross Reels had been acquired by 3M in 2010.
In March 2017, 3M purchased Johnson Controls International Plc's safety gear business, Scott Safety, for $2 billion.
In 2017, 3M had net sales for the year of $31.657 billion, up from $30.109 billion the year before. In 2018, it was reported that the company would pay $850 million to end the Minnesota water pollution case concerning perfluorochemicals.
On May 25, 2018, Michael F. Roman was appointed CEO by the board of directors. On December 19, 2018, 3M announced it had entered into a definitive agreement to acquire the technology business of M*Modal, for a total enterprise value of $1.0 billion.
In October 2019, 3M purchased Acelity and its KCI subsidiaries for $6.7 billion, including assumption of debt and other adjustments.
On May 1, 2020, 3M divested substantially all of its drug delivery business to an affiliate of Altaris Capital Partners, LLC. for approximately $650 million, including a 17% interest in the new operating company, Kindeva Drug Delivery.
In December 2021, 3M announced that it would merge its food-safety business with food testing and animal healthcare products maker Neogen. The deal, with an enterprise value of about $5.3 billion, closed in September 2022.
In July 2022, the company announced it would spin off its healthcare assets to form a new, independent firm, likely completing the transaction in 2023. 3M will retain an ownership stake of 19.9% in the new, publicly-traded health care company and gradually divest the holdings. The company will be known as Solventum Corporation.
In December 2022, the company announced plans to stop producing and using so-called forever chemicals (per and polyfluoroalkyl), which have been commonly used in items such as food packaging, cellphones, nonstick pans, firefighting foams, and clothing. These chemicals are well known for their water-resistant and nonstick properties, but they are also dangerous pollutants that are linked to serious health problems, including ulcerative colitis and cancer. The move comes as governments in the Netherlands and the United States consider actions against 3M.
In March 2024, 3M announced the appointment of William "Bill" Brown as chief executive officer to take effect on May 1, 2024. Michael Roman would remain in the role of executive chairman. Brown, 61, is the former chairman of the board and chief executive officer of L3Harris Technologies.
Products and patents
As of 2019, 3M produces approximately 60,000 products, and has four business groups focused on safety and industrial, transportation and electronics, health care, and consumer products. 3M obtained its first patent in 1924 and acquires approximately 3,000 new patents annually. The company surpassed the 100,000-patent threshold in 2014.
Environmental record
3M's Pollution Prevention Pays (3P) program was established in 1975. The program initially focused on pollution reduction at the plant level and was expanded to promote recycling and reduce waste across all divisions in 1989. By the early 1990s, approximately 2,500 3P projects decreased the company's total global pollutant generation by 50 percent and saved 3M $500–600 million by eliminating the production of waste requiring subsequent treatment.
In 1983, the Oakdale Dump in Oakdale, Minnesota, was listed as an EPA Superfund site after significant groundwater and soil contamination by VOCs and heavy metals was uncovered. The Oakdale Dump was a 3M dumping site utilized through the 1940s and 1950s.
During the 1990s and 2000s, 3M reduced releases of toxic pollutants by 99 percent and greenhouse gas emissions by 72 percent. As of 2012, the United States Environmental Protection Agency (EPA) had awarded 3M with the Energy Star Award each year that it has been presented.
"Forever chemicals" water pollution
In 1999, the EPA began investigating perfluorinated chemicals after receiving data on the global distribution and toxicity of perfluorooctanesulfonic acid (PFOS). These materials are part of a broad group of perfluoroalkyl and polyfluoroalkyl substances often referred to as PFAS, each of which has different chemical properties. 3M, the former primary producer of PFOS from the U.S., announced the phase-out of PFOS, perfluorooctanoic acid, and PFOS-related product production in May 2000. Perfluorinated compounds produced by 3M have been used in non-stick cookware, stain-resistant fabrics, and other products.
The Cottage Grove facility manufactured PFAS from the 1940s to 2002. In response to PFAS contamination of the Mississippi River and surrounding area, 3M stated the area will be "cleaned through a combination of groundwater pump-out wells and soil sediment excavation". The restoration plan was based on an analysis of the company property and surrounding lands. The on-site water treatment facility that handled the plant's post-production water was not capable of removing PFAS, which were released into the nearby Mississippi River. The clean-up cost estimate, which included a granular activated carbon system to remove PFAS from the ground water was $50 to $56 million, funded from a $147 million environmental reserve set aside in 2006.
In 2008, 3M created the Renewable Energy Division within 3M's Industrial and Transportation Business to focus on Energy Generation and Energy Management.
In late 2010, the state of Minnesota sued 3M for 5 billion in punitive damages, claiming they released PFCs—classified a toxic chemical by the EPA—into local waterways. A settlement for $850 million was reached in February 2018. In 2019, 3M, along with the Chemours Company and DuPont, appeared before lawmakers to deny responsibility, with company Senior VP of Corporate Affairs Denise Rutherford arguing that the chemicals pose no human health threats at current levels and that there were no victims.
In 2021, research had determined that 3M's Zwijndrecht (Belgium) factory caused PFOS pollution that may be contaminating agricultural products within a 15 kilometer radius of the plant which includes Antwerp. The Flemish Government has paid 63 million euros for cleanup costs so far with 3M contributing 75,000 euros. The Flemish Government issued measures advising against the consumption of, for example, home-grown eggs within a radius of 5 kilometers.
In 2023, 3M reached an agreement to pay a $10.3bn settlement with numerous US public water systems to resolve thousands of lawsuits over PFAS contamination.
Carbon footprint
3M reported Total CO2e emissions (Direct + Indirect) for the twelve months ending December 31, 2020, at 5,280 Kt (-550 /-9.4% y-o-y) and plans to reduce emissions 50% by 2030 from a 2019 base year. The company also aims achieve carbon neutrality by 2050.
Earplug controversy
The Combat Arms Earplugs, Version 2 (CAEv2), was developed by Aearo Technologies for U.S. military and civilian use. The CAEv2 was a double ended earplug that 3M claimed would offer users different levels of protection. Between 2003 and 2015, these earplugs were standard issue to members of the U.S. military. 3M acquired Aearo Technologies in 2008.
In May 2016, Moldex-Metric, Inc., a 3M competitor, filed a whistleblower complaint against 3M under the False Claims Act. Moldex-Metric claimed that 3M made false claims to the U.S. government about the safety of its earplugs and that it knew the earplugs had an inherently defective design. In 2018, 3M agreed to pay $9.1 million to the U.S. government to resolve the allegations, without admitting liability.
Since 2018, more than 140,000 former users of the earplugs (primarily U.S. military veterans) have filed suit against 3M claiming they suffer from hearing loss, tinnitus, and other damage as a consequence of the defective design.
Internal emails showed that 3M officials boasted about charging $7.63 per piece for the earplugs which cost 85 cents to produce. The company's official response indicated that the cost to the government includes R&D costs.
3M settled close to 260,000 lawsuits in August 2023 by agreeing to pay $6 billion to current and former U.S. military members who were affected.
N95 respirators and the COVID-19 pandemic
The N95 respirator mask was developed by 3M and approved in 1972. Due to its ability to filter viral particulates, its use was recommended during the COVID-19 pandemic but supply soon became short. Much of the company's supply had already been sold prior to the outbreak.
The shortages led to the U.S. government asking 3M to stop exporting US-made N95 respirator masks to Canada and to Latin American countries, and President Donald Trump invoked the Defense Production Act to require 3M to prioritize orders from the federal government. The dispute was resolved when 3M agreed to import more respirators, mostly from its factories in China.
3M later struck a CA$70M deal with the federal government of Canada and the Ontario provincial government to produce N95 masks at their plant in Brockville, Ontario.
Operating facilities
3M's general offices, corporate research laboratories, and some division laboratories in the U.S. are in St. Paul, Minnesota. In the United States, 3M operates 80 manufacturing facilities in 29 states, and 125 manufacturing and converting facilities in 37 countries outside the U.S. (in 2017).
During March 2016, 3M completed a research-and-development building on its Maplewood campus that cost $150 million. Seven hundred scientists from various divisions occupy the building. They were previously scattered across the campus. 3M hopes concentrating its research and development in this manner will improve collaboration. 3M received $9.6 million in local tax increment financing and relief from state sales taxes in order to assist with development of the building.
Selected factory detail information:
Cynthiana, Kentucky, U.S. factory producing Post-it Notes (672 SKU) and Scotch Tape (147 SKU). It has 539 employees and was established in 1969.
Newton Aycliffe, County Durham, UK factory producing respirators for workers safety using laser technology. It has 370 employees.
In Minnesota, 3M's Hutchinson facility produces products for more than half of the company's 23 divisions, as of 2019. The "super hub" has manufactured adhesive bandages for Nexcare, furnace filters, and Scotch Tape, among other products. The Cottage Grove plant is one of three operated by 3M for the production of pad conditioners, as of 2011.
3M has operated a manufacturing plant in Columbia, Missouri since 1970. The plant has been used for the production of products including electronic components solar and touchscreen films, and stethoscopes. The facility received a $20 million expansion in 2012 and has approximately 400 employees.
3M opened the Brookings, South Dakota plant in 1971, and announced a $70 million expansion in 2014. The facility manufactures more than 1,700 health care products and employs 1,100 people, as of 2018, making the plant 3M's largest focused on health care. Mask production at the site increased during the 2009 swine flu pandemic, 2002–2004 SARS outbreak, 2018 California wildfires, 2019–20 Australian bushfire season, and COVID-19 pandemic.
3M's Springfield, Missouri plant opened in 1967 and makes industrial adhesives and tapes for aerospace manufacturers. In 2017, 3M had approximately 330 employees in the metropolitan area, and announced a $40 million expansion project to upgrade the facility and redevelop another building.
In Iowa, the Ames plant makes sandpaper products and received funding from the Iowa Economic Development Authority (IEDA) for expansions in 2013 and 2018. The Knoxville plant is among 3M's largest and produces approximately 12,000 different products, including adhesives and tapes.
3M's Southeast Asian operations are based in Singapore, where the company has invested $1 billion over 50 years. 3M has a facility in Tuas, a manufacturing plant and Smart Urban Solutions lab in Woodlands, and a customer technical center in Yishun. 3M expanded a factory in Woodlands in 2011, announced a major expansion of the Tuas plant in 2016, and opened new headquarters in Singapore featuring a Customer Technical Centre in 2018.
The company has operated in China since 1984, and was Shanghai's first Wholly Foreign-Owned Enterprise. 3M's seventh plant, and the first dedicated to health care product production, opened in Shanghai in 2007. By October 2007, the company had opened an eighth manufacturing plant and technology center in Guangzhou. 3M broke ground on its ninth manufacturing facility, for the production of photovoltaics and other renewable energy products, in Hefei in 2011. 3M announced plans to construct a technology innovation center in Chengdu in 2015, and opened a fifth design center in Shanghai in 2019.
Leadership
Board chairs have included: William L. McKnight (1949–1966), Bert S. Cross (1966–1970), Harry Heltzer (1970–1975), Raymond H. Herzog (1975–1980), Lewis W. Lehr (1980–1986), Allen F. Jacobson (1986–1991), Livio DeSimone (1991–2001), James McNerney (2001–2005), George W. Buckley (2005–2012), and Inge Thulin (2012–2018). Thulin continued as executive chairman until Michael F. Roman was appointed in 2019.
3M's CEOs have included: Cross (1966–1970), Heltzer (1970–1975), Herzog (1975–1979), Lehr (1979–1986), Jacobson (1986–1991), DeSimone (1991–2001), McNerney (2001–2005), Robert S. Morrison (2005, interim), Buckley (2005–2012), Thulin (2012–2018), and Roman (2018–present).
3M's presidents have included: Edgar B. Ober (1905–1929), McKnight (1929–1949), Richard P. Carlton (1949–1953), Herbert P. Buetow (1953–1963), Cross (1963–1966), Heltzer (1966–1970), and Herzog (1970–1975). In the late 1970s, the position was separated into roles for U.S. and international operations. The position overseeing domestic operations was first held by Lehr, followed by John Pitblado from 1979 to 1981, then Jacobson from 1984 to 1991. James A. Thwaits led international operations starting in 1979. Buckley and Thulin were president during 2005–2012, and 2012–2018, respectively.
See also
Oakdale Dump
Further reading
V. Huck, Brand of the Tartan: The 3M Story, Appleton-Century-Crofts, 1955. Early history of 3M and challenges, includes employee profiles.
C. Rimington, From Minnesota mining and manufacturing to 3M Australia Pty Ltd (3M Australia: the Story of an Innovative Company), Sid Harta Publishers, 2013. Recollections from 3M Australia employees in context of broader organisational history.
Sharon Lerner "How 3M Discovered, Then Concealed, the Dangers of Forever Chemicals", New Yorker Magazine
References
External links
Historical records of the 3M Company are available for research use at the Minnesota Historical Society
1902 establishments in Minnesota
1940s initial public offerings
American companies established in 1902
Companies listed on the New York Stock Exchange
Conglomerate companies established in 1902
Conglomerate companies of the United States
Companies in the Dow Jones Industrial Average
Companies in the Dow Jones Global Titans 50
Companies in the S&P 500 Dividend Aristocrats
Manufacturing companies based in Minnesota
Manufacturing companies established in 1902
Multinational companies headquartered in the United States
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Office supply companies of the United States
Ramsey County, Minnesota
Renewable energy technology companies | 3M | Materials_science | 4,768 |
28,098,613 | https://en.wikipedia.org/wiki/Crystalline%20silicon | Crystalline silicon or (c-Si) is the crystalline forms of silicon, either polycrystalline silicon (poly-Si, consisting of small crystals), or monocrystalline silicon (mono-Si, a continuous crystal). Crystalline silicon is the dominant semiconducting material used in photovoltaic technology for the production of solar cells. These cells are assembled into solar panels as part of a photovoltaic system to generate solar power from sunlight.
In electronics, crystalline silicon is typically the monocrystalline form of silicon, and is used for producing microchips. This silicon contains much lower impurity levels than those required for solar cells. Production of semiconductor grade silicon involves a chemical purification to produce hyper-pure polysilicon, followed by a recrystallization process to grow monocrystalline silicon. The cylindrical boules are then cut into wafers for further processing.
Solar cells made of crystalline silicon are often called conventional, traditional, or first generation solar cells, as they were developed in the 1950s and remained the most common type up to the present time. Because they are produced from 160 to 190 μm thick solar wafers—slices from bulks of solar grade silicon—they are sometimes called wafer-based solar cells.
Solar cells made from c-Si are single-junction cells and are generally more efficient than their rival technologies, which are the second-generation thin-film solar cells, the most important being CdTe, CIGS, and amorphous silicon (a-Si). Amorphous silicon is an allotropic variant of silicon, and amorphous means "without shape" to describe its non-crystalline form.
Overview
Classification
The allotropic forms of silicon range from a single crystalline structure to a completely unordered amorphous structure with several intermediate varieties. In addition, each of these different forms can possess several names and even more abbreviations, and often cause confusion to non-experts, especially as some materials and their application as a PV technology are of minor significance, while other materials are of outstanding importance.
PV industry
In photovoltaic industry,materials are commonly grouped into the following two categories:
Crystalline silicon (c-Si), used in conventional wafer-based solar cells.
Monocrystalline silicon (mono-Si)
Polycrystalline silicon (multi-Si)
Ribbon silicon (ribbon-Si), has currently no market
Other materials, not classified as crystalline silicon, used in thin-film and other solar-cell technologies.
Amorphous silicon (a-Si)
Nanocrystalline silicon (nc-Si)
Protocrystalline silicon (pc-Si)
Other established non-silicon materials, such as CdTe, CIGS
Emerging photovoltaics
Multi-junction solar cells (MJ) commonly used for solar panels on spacecraft for space-based solar power. They are also used in concentrator photovoltaics (CPV, HCPV), an emerging technology best suited for locations that receive much sunlight.
Generations
Alternatively, different types of solar cells and/or their semiconducting materials can be classified by generations:
First generation solar cells are made of crystalline silicon, also called, conventional, traditional, wafer-based solar cells and include monocrystalline (mono-Si) and polycrystalline (multi-Si) semiconducting materials.
Second generation solar cells or panels are based on thin-film technology and are of commercially significant importance. These include CdTe, CIGS and amorphous silicon.
Third generation solar cells are often labeled as emerging technologies with little or no market significance and include a large range of substances, mostly organic, often using organometallic compounds.
Arguably, multi-junction photovoltaic cells can be classified to neither of these generations. A typical triple junction semiconductor is made of InGaP/(In)GaAs/Ge.
Comparison of technical specifications
Market share
In 2013, conventional crystalline silicon technology dominated worldwide PV production, with multi-Si leading the market ahead of mono-Si, accounting for 54% and 36%, respectively. For the last ten years, worldwide market-share of thin-film technologies stagnated below 18% and currently stand at 9%. In the thin-film market, CdTe leads with an annual production of 2 GWp or 5%, followed by a-Si and CIGS, both around 2%.
Alltime deployed PV capacity of 139 gigawatts (cumulative as of 2013) splits up into 121 GW crystalline silicon (87%) and 18 GW thin-film (13%) technology.
Efficiency
The conversion efficiency of PV devices describes the energy-ratio of the outgoing electrical power compared to the incoming radiated light. A single solar cells has generally a better, or higher efficiency than an entire solar module. Additionally, lab efficiency is always far superior to that of goods that are sold commercially.
Lab cells
In 2013, record Lab cell efficiency was highest for crystalline silicon. However, multi-silicon is followed closely by cadmium telluride and copper indium gallium selenide solar cells.
25.6% — mono-Si cell
20.4% — multi-Si cell
21.7% — CIGS cell
21.5% — CdTe cell
Both-sides-contacted silicon solar cells as of 2021: 26% and possibly above.
Modules
The average commercial crystalline silicon module increased its efficiency from about 12% to 16% over the last ten years. In the same period CdTe-modules improved their efficiency from 9 to 16%.
The modules performing best under lab conditions in 2014 were made of monocrystalline silicon.
They were 7% above the efficiency of commercially produced modules (23% over 16%) which indicated that the conventional silicon technology still had potential to improve and therefore maintain its leading position.
Energy costs of manufacture
Crystalline silicon has a high cost in energy because silicon is produced by the reduction of high-grade quartz sand in an electric furnace. The electricity generated for this process may produce greenhouse gas emissions. This coke-fired smelting process occurs at high temperatures of more than 1,000 °C and is very energy intensive, using about 11 kilowatt-hours (kW⋅h) per kilogram of silicon.
The energy requirements of this process per unit of silicon metal produced may be relatively inelastic. But major energy cost reductions per (photovoltaic) product have been made as silicon cells have become more efficient at converting sunlight, larger silicon metal ingots are cut with less waste into thinner wafers, silicon waste from manufacture is recycled, and material costs have reduced.
Toxicity
With the exception of amorphous silicon, most commercially established PV technologies use toxic heavy metals. CIGS often uses a CdS buffer layer, and the semiconductor material of CdTe-technology itself contains the toxic cadmium (Cd). In the case of crystalline silicon modules, the solder material that joins the copper strings of the cells, it contains about 36% of lead (Pb). Moreover, the paste used for screen printing front and back contacts contains traces of Pb and sometimes Cd as well. It is estimated that about 1,000 metric tonnes of Pb have been used for 100 gigawatts of c-Si solar modules. However, there is no fundamental need for lead in the solder alloy.
Cell technologies
PERC solar cell
Passivated emitter rear contact (PERC) solar cells consist of the addition of an extra layer to the rear-side of a solar cell. This dielectric passive layer acts to reflect unabsorbed light back to the solar cell for a second absorption attempt increasing the solar cell efficiency.
A PERC is created through an additional film deposition and etching process. Etching can be done either by chemical or laser processing. About 80% of solar panels worldwide use the PERC design. Martin Green, Andrew Blakers, Jianhua Zhao and Aihua Wang won the Queen Elizabeth Prize for Engineering in 2023 for development of the PERC solar cell.
HIT solar cell
A HIT solar cell is composed of a mono thin crystalline silicon wafer surrounded by ultra-thin amorphous silicon layers. The acronym HIT stands for "heterojunction with intrinsic thin layer". HIT cells are produced by the Japanese multinational electronics corporation Panasonic (see also ). Panasonic and several other groups have reported several advantages of the HIT design over its traditional c-Si counterpart:
An intrinsic a-Si layer can act as an effective surface passivation layer for c-Si wafer.
The p+/n+ doped a-Si functions as an effective emitter/BSF for the cell.
The a-Si layers are deposited at much lower temperature, compared to the processing temperatures for traditional diffused c-Si technology.
The HIT cell has a lower temperature coefficient compared to c-Si cell technology.
Owing to all these advantages, this new hetero-junction solar cell is a considered to be a promising low cost alternative to traditional c-Si based solar cells.
Fabrication of HIT cells
The details of the fabrication sequence vary from group to group. Typically in good quality, CZ/FZ grown c-Si wafer (with ~1 ms lifetimes) are used as the absorber layer of HIT cells. Using alkaline etchants, such as, NaOH or (CH3)4NOH the (100) surface of the wafer is textured to form the pyramids of 5–10 μm height. Next, the wafer is cleaned
using peroxide and HF solutions. This is followed by deposition of intrinsic a-Si passivation layer, typically through PECVD or Hot-wire CVD. The silane (SiH4) gas diluted with H2 is used as a precursor. The deposition temperature and pressure is maintained at 200 °C and 0.1−1 Torr. Precise control over this step is essential to avoid the formation of defective epitaxial Si.
Cycles of deposition and annealing and H2 plasma treatment are shown to have provided excellent surface passivation. Diborane or Trimethylboron gas mixed with SiH4 is used to deposit p-type a-Si layer, while, Phosphine gas mixed with SiH4 is used to deposit n-type a-Si layer. Direct deposition of doped a-Si layers on c-Si wafer is shown to have very poor passivation properties. This is most likely due to dopant induced defect generation in a-Si layers. Sputtered Indium Tin Oxide (ITO) is commonly used as a transparent conductive oxide (TCO) layer on top of the front and back a-Si layer in bi-facial design, as a-Si has high lateral resistance.
It is generally deposited on the back side as well fully metallized cell to avoid diffusion of back metal and also for impedance matching for the reflected light. The silver/aluminum grid of 50-100μm thick is deposited through stencil printing for the front contact and back contact for bi-facial design. The detailed description of the fabrication process can be found in.
Opto-electrical modeling and characterization of HIT cells
The literature discusses several studies to interpret carrier transport bottlenecks in these cells. Traditional light and dark I–V are extensively studied and are observed to have several non-trivial features, which cannot be explained using the traditional solar cell diode theory. This is because of the presence of hetero-junction between the intrinsic a-Si layer and c-Si wafer which introduces additional complexities to current flow. In addition, there has been significant efforts to characterize this solar cell using C-V, impedance spectroscopy, surface photo-voltage, suns-Voc to produce complementary information.
Further, a number of design improvements, such as, the use of new emitters, bifacial configuration, interdigitated back contact (IBC) configuration bifacial-tandem configuration are actively being pursued.
Mono-silicon
Monocrystalline silicon (mono c-Si) is a form in which the crystal structure is homogeneous throughout the material; the orientation, lattice parameter, and electronic properties are constant throughout the material. Dopant atoms such as phosphorus and boron are often incorporated into the film to make the silicon n-type or p-type respectively. Monocrystalline silicon is fabricated in the form of silicon wafers, usually by the Czochralski Growth method, and can be quite expensive depending on the radial size of the desired single crystal wafer (around $200 for a 300 mm Si wafer). This monocrystalline material, while useful, is one of the chief expenses associated with producing photovoltaics where approximately 40% of the final price of the product is attributable to the cost of the starting silicon wafer used in cell fabrication.
Polycrystalline silicon
Polycrystalline silicon is composed of many smaller silicon grains of varied crystallographic orientation, typically > 1 mm in size. This material can be synthesized easily by allowing liquid silicon to cool using a seed crystal of the desired crystal structure. Additionally, other methods for forming smaller-grained polycrystalline silicon (poly-Si) exist such as high temperature chemical vapor deposition (CVD).
Not classified as Crystalline silicon
These allotropic forms of silicon are not classified as crystalline silicon. They belong to the group of thin-film solar cells.
Amorphous silicon
Amorphous silicon (a-Si) has no long-range periodic order. The application of amorphous silicon to photovoltaics as a standalone material is somewhat limited by its inferior electronic properties. When paired with microcrystalline silicon in tandem and triple-junction solar cells, however, higher efficiency can be attained than with single-junction solar cells. This tandem assembly of solar cells allows one to obtain a thin-film material with a bandgap of around 1.12 eV (the same as single-crystal silicon) compared to the bandgap of amorphous silicon of bandgap. Tandem solar cells are then attractive since they can be fabricated with a bandgap similar to single-crystal silicon but with the ease of amorphous silicon.
Nanocrystalline silicon
Nanocrystalline silicon (nc-Si), sometimes also known as microcrystalline silicon (μc-Si), is a form of porous silicon. It is an allotropic form of silicon with paracrystalline structure—is similar to amorphous silicon (a-Si), in that it has an amorphous phase. Where they differ, however, is that nc-Si has small grains of crystalline silicon within the amorphous phase. This is in contrast to polycrystalline silicon (poly-Si) which consists solely of crystalline silicon grains, separated by grain boundaries. The difference comes solely from the grain size of the crystalline grains. Most materials with grains in the micrometre range are actually fine-grained polysilicon, so nanocrystalline silicon is a better term. The term 'nanocrystalline silicon' refers to a range of materials around the transition region from amorphous to microcrystalline phase in the silicon thin film.
Protocrystalline silicon
Protocrystalline silicon has a higher efficiency than amorphous silicon (a-Si) and it has also been shown to improve stability, but not eliminate it. A Protocrystalline phase is a distinct phase occurring during crystal growth which evolves into a microcrystalline form.
Protocrystalline Si also has a relatively low absorption near the band gap owing to its more ordered crystalline structure. Thus, protocrystalline and amorphous silicon can be combined in a tandem solar cell where the top layer of thin protocrystalline silicon absorbs short-wavelength light whereas the longer wavelengths are absorbed by the underlying a-Si substrate.
Transformation of amorphous into crystalline silicon
Amorphous silicon can be transformed to crystalline silicon using well-understood and widely implemented high-temperature annealing processes. The typical method used in industry requires high-temperature compatible materials, such as special high temperature glass that is expensive to produce. However, there are many applications for which this is an inherently unattractive production method.
Low temperature induced crystallization
Flexible solar cells have been a topic of interest for less conspicuous-integrated power generation than solar power farms. These modules may be placed in areas where traditional cells would not be feasible, such as wrapped around a telephone pole or cell phone tower. In this application, a photovoltaic material may be applied to a flexible substrate, often a polymer. Such substrates cannot survive the high temperatures experienced during traditional annealing. Instead, novel methods of crystallizing the silicon without disturbing the underlying substrate have been studied extensively. Aluminum-induced crystallization (AIC) and local laser crystallization are common in the literature, however not extensively used in industry.
In both of these methods, amorphous silicon is grown using traditional techniques such as plasma-enhanced chemical vapor deposition (PECVD). The crystallization methods diverge during post-deposition processing.
In aluminum-induced crystallization, a thin layer of aluminum (50 nm or less) is deposited by physical vapor deposition onto the surface of the amorphous silicon. This stack of material is then annealed at a relatively low temperature between 140 °C and 200 °C in a vacuum. The aluminum that diffuses into the amorphous silicon is believed to weaken the hydrogen bonds present, allowing crystal nucleation and growth. Experiments have shown that polycrystalline silicon with grains on the order of 0.2–0.3 μm can be produced at temperatures as low as 150 °C. The volume fraction of the film that is crystallized is dependent on the length of the annealing process.
Aluminum-induced crystallization produces polycrystalline silicon with suitable crystallographic and electronic properties that make it a candidate for producing polycrystalline thin films for photovoltaics. AIC can be used to generate crystalline silicon nanowires and other nano-scale structures.
Another method of achieving the same result is the use of a laser to heat the silicon locally without heating the underlying substrate beyond some upper-temperature limit. An excimer laser or, alternatively, green lasers such as a frequency-doubled Nd:YAG laser is used to heat the amorphous silicon, supplying the energy necessary to nucleate grain growth. The laser fluence must be carefully controlled in order to induce crystallization without causing widespread melting. Crystallization of the film occurs as a very small portion of the silicon film is melted and allowed to cool. Ideally, the laser should melt the silicon film through its entire thickness, but not damage the substrate. Toward this end, a layer of silicon dioxide is sometimes added to act as a thermal barrier. This allows the use of substrates that cannot be exposed to the high temperatures of standard annealing, polymers for instance. Polymer-backed solar cells are of interest for seamlessly integrated power production schemes that involve placing photovoltaics on everyday surfaces.
A third method for crystallizing amorphous silicon is the use of a thermal plasma jet. This strategy is an attempt to alleviate some of the problems associated with laser processing – namely the small region of crystallization and the high cost of the process on a production scale. The plasma torch is a simple piece of equipment that is used to anneal the amorphous silicon thermally. Compared to the laser method, this technique is simpler and more cost-effective.
Plasma torch annealing is attractive because the process parameters and equipment dimensions can be changed easily to yield varying levels of performance. A high level of crystallization (~ 90%) can be obtained with this method. Disadvantages include difficulty achieving uniformity in the crystallization of the film. While this method is applied frequently to silicon on a glass substrate, processing temperatures may be too high for polymers.
See also
List of types of solar cells
References
Silicon, crystalline
Silicon solar cells
Allotropes of silicon | Crystalline silicon | Chemistry | 4,146 |
268,042 | https://en.wikipedia.org/wiki/American%20Astronomical%20Society | The American Astronomical Society (AAS, sometimes spoken as "double-A-S") is an American society of professional astronomers and other interested individuals, headquartered in Washington, DC. The primary objective of the AAS is to promote the advancement of astronomy and closely related branches of science, while the secondary purpose includes enhancing astronomy education and providing a political voice for its members through lobbying and grassroots activities. Its current mission is to enhance and share humanity's scientific understanding of the universe as a diverse and inclusive astronomical community.
History
The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the "Astronomical and Astrophysical Society of America". One proposed name that preceded this interim name was "American Astrophysical Society".
The AAS today has over 8,000 members and six divisions – the Division for Planetary Sciences (1968), the Division on Dynamical Astronomy (1969), the High Energy Astrophysics Division (1969), the Solar Physics Division (1969), the Historical Astronomy Division (1980) and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy. The annual meeting of the AAS is held in the spring and constitutes the largest gathering of astronomers, numbering over 3,000 in 2023.
In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.
The AAS established the AAS Fellows program in 2019 to "confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society." The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.
Divisions
Because the field of astronomy is diverse, several divisions have been formed each of which promotes and enables a different branch of astronomy or astronomy-related science as well as working within the overall charter of the AAS. Many of the divisions hold separate meetings in addition to meeting with the main group. The divisions of the AAS, together with their main research interests, are:
The Division for Planetary Sciences (DPS) supports planetology and exploration of the Solar System.
The Division on Dynamical Astronomy (DDA) supports research on the dynamics (orbits, evolution, and history) of astronomical systems from the Solar System to superclusters of galaxies on cosmological scales.
The High Energy Astrophysics Division (HEAD) supports knowledge about high energy events, particles, quanta, relativistic gravitational fields, and related phenomena in the astrophysical universe.
The Historical Astronomy Division (HAD) supports topics relevant to the history of astronomy as a field, and research using historical astronomical records to solve current problems in astronomy.
The Solar Physics Division (SPD) supports solar physics (astrophysical research on the Sun), and its interactions with the Solar System and Earth.
In 2012, a new division was formed: the Laboratory Astrophysics Division (LAD) to advance humanity's understanding of the Universe through the promotion of fundamental theoretical and experimental research into the underlying processes that drive the Universe.
Publications
Astronomical Journal
Astronomy Education Review [no longer published]
The Astrophysical Journal
The Planetary Science Journal
Bulletin of the American Astronomical Society
Research Notes of the AAS (scientific publication of brief communications, non peer-reviewed)
AAS Nova, an online publication with highlights from the research journals of the Society.
In June 2019 AAS announced that it would be the new publisher of Sky & Telescope.
In August 2020 AAS announced that it had acquired the inventory, author contracts and related assets of Willmann-Bell, Inc. a publisher of astronomical books, atlases and software.
Prizes
The Henry Norris Russell Lectureship, for lifetime achievement in astronomy
The Newton Lacy Pierce Prize in Astronomy, for outstanding early career in observational astronomy
The Helen B. Warner Prize for Astronomy, for outstanding early career in theoretical astronomy
The Beatrice M. Tinsley Prize, for a creative or innovating contribution to astronomy
The Joseph Weber Award, for a significant advance in astronomical instrumentation
The Dannie Heineman Prize for Astrophysics (joint award with the American Institute of Physics), for outstanding work in astrophysics
The George Van Biesbroeck Prize, for outstanding service to astronomy
The Annie J. Cannon Award in Astronomy (awarded in concert with the American Association of University Women), for outstanding early career by a female astronomer
the Chambliss Astronomical Writing Award for astronomy writing for an academic audience
The Beth Brown Memorial Award for exemplary poster and oral research presentation by undergraduate and graduate students
The Chambliss Astronomy Achievement Student Award for exemplary research by undergraduate and graduate students
The Chambliss Amateur Achievement Award for exemplary research by an amateur astronomer
The AAS Education Prize for outstanding contributions to astronomy education (formerly called the Annenberg Foundation Award)
Similar prizes are awarded by AAS divisions. These include:
The Gerard P. Kuiper Prize (DPS), for lifetime achievement in planetary science
The Harold C. Urey Prize (DPS), for outstanding early career in planetary science
The Harold Masursky Meritorious Service Award (DPS), for outstanding service to planetary science
The Brouwer Award (DDA), for lifetime achievement in dynamical astronomy
The Bruno Rossi Prize (HEAD), for a significant recent contribution to high-energy astrophysics
The LeRoy E. Doggett Prize (HAD), for work in the history of astronomy
The George Ellery Hale Prize (SPD), for lifetime achievement in solar astronomy
The Karen Harvey Prize (SPD), for outstanding early career in solar astronomy
The AAS also manages an International Travel Grant program, which any astronomer working in the US may apply to for travel to international astronomy-related conferences and other smaller grant and award programs. American Astronomical Society won the 2020 Webby People's Voice Award for Association in the category Web.
Past presidents
The following past and present members served as president of the society during the listed periods:
Simon Newcomb (1899–1905)
Edward Charles Pickering (1905–1919)
Frank Schlesinger (1919–1922)
William Wallace Campbell (1922–1925)
George Cary Comstock (1925–1928)
Ernest William Brown (1928–1931)
Walter Sydney Adams (1931–1934)
Henry Norris Russell (1934–1937)
Robert Grant Aitken (1937–1940)
Joel Stebbins (1940–1943)
Harlow Shapley (1943–1946)
Otto Struve (1946–1949)
Alfred Harrison Joy (1949–1952)
Robert Raynolds McMath (1952–1954)
Donald Howard Menzel (1954–1956)
Paul Willard Merrill (1956–1958)
Gerald Maurice Clemence (1958–1960)
Lyman Spitzer Jr. (1960–1962)
Carlyle Smith Beals (1962–1964)
Leo Goldberg (1964–1966)
Bengt Strömgren (1966–1967)
Albert E. Whitford (1967–1970)
Martin Schwarzschild (1970–1972)
Bart J. Bok (1972–1974)
Robert Paul Kraft (1974–1976)
E. Margaret Burbidge (1976–1978)
Ivan R. King (1978–1980)
David S. Heeschen (1980–1982)
Arthur D. Code (1982–1984)
Maarten Schmidt (1984–1986)
Bernard F. Burke (1986–1988)
Donald Edward Osterbrock (1988–1990)
John Norris Bahcall (1990–1992)
Sidney C. Wolff (1992–1994)
Frank Shu (1994–1996)
Andrea K. Dupree (1996–1998)
Robert D. Gehrz (1998–2000)
Anneila I. Sargent (2000–2002)
Catherine A. Pilachowski (2002–2004)
Robert P. Kirshner (2004–2006)
J. Craig Wheeler (2006–2008)
John Peter Huchra (2008–2010)
Debra M. Elmegreen (2010–2012)
David Helfand (2012–2014)
Meg Urry (2014–2016)
Christine Jones-Foreman (2016–2018)
Megan Donahue (2018–2020)
Paula Szkody (2020–2022)
Kelsey Johnson (2022-2024)
See also
215th meeting of the American Astronomical Society
List of astronomical societies
References
External links
Archival collections
Niels Bohr Library & Archives
American Astronomical Society Harlow Shapley Visiting Lectureship Program records, 1980-1999
American Astronomical Society miscellaneous publications, 1910-2017
American Astronomical Society records, 1897-1988 (bulk 1920-1980)
AAS Division on Dynamical Astronomy addition to records, 1967-2004
American Astronomical Society Education Office records, 1959-1984
Personal histories of x-ray astronomy records, 1967-2013, American Astronomical Society. High Energy Astrophysics Division
AAS Historical Astronomy Division records of Chairman Thomas R. Williams, 1979-2005
American Astronomical Society Historical Astronomy Division addition to records, 1898-1998 (bulk 1996-1998)
American Astronomical Society Historical Astronomy Division records of Secretary-Treasurer Joseph S. Tenn, 2007-2015
American Astronomical Society Historical Astronomy Division records of the Secretary/Treasurer, 1974-2000, (bulk 1985-1992)
AAS Office of Secretary Arlo Landolt records addition, 1990-2000
American Astronomical Society Office of the Treasurer records of Frank K. Edmondson, 1898-1979
AAS Solar Physics Division records, 1966-1996
Astronomy societies
Scientific organizations established in 1899
Scientific societies based in the United States
1899 establishments in the United States
Open access publishers | American Astronomical Society | Astronomy | 1,990 |
70,358,540 | https://en.wikipedia.org/wiki/Angkor%20Wat%20Equinox | The Angkor Wat equinox is a solar phenomenon considered as a hierophany that happens twice a year with spring and autumn equinox, as part of the many astronomical alignments indicative of a "fairly elaborate system of astronomy" and of the Hindu influence in the construction of the vast temple complex of Angkor Wat, in Cambodia.
Description
The sunrise on Angkor Wat during the equinox is such that someone standing in front of the western entrance on the equinox is able to see the sun rising directly over the central lotus tower. In fact, it would be more correct to describe the phenomenon as the exact match of the shadow formed by the sunrise on Angkor Wat's central prang and the western entrance bridge.
Architecture
Like most celestial cities, Angkor Wat contains many astronomically inspired symbols and alignments. Angkor Wat was built by Suryvarman II, literally the Sun-King, during his reign for 1113 to 1150 with "astronomical and cosmic rhythm". It was dedicated as a tribute to Vishnu, a solar deity according to the Rigveda.
In fact, it appears that most of the vast complex of Angkor Wat was determined by the equinox. In the bas-relief at Angkor Wat, the position of the churning pivot would correspond to the position of the spring equinox. The 91 asuras in the south represent the 91 days from equinox to winter solstice, and the 88 northern devas represent the 88 days from equinox to summer solstice. In fact, there are either 88 or 89 devas in the scene, 89 if the deva atop Mount Mandara is counted with the others. There are 88 or 89 days from the spring equinox, counted from the first day of the new year, to the summer solstice.
In fact, the solar alignment is not limited to Angkor Wat, but includes many other temples of the Khmer civilization, as it connects Angkor Wat with other temples on the Ancient Khmer Highway from the West Mebon to the Preah Khan of Kompong Svay.
Interpretation
An eternal reminder of Suryavarman II's ascension to the throne
Scholars theorize that Suryavarman II was crowned sovereign in Angkor Wat during the equinox. The temples' calibrated use of equinox sunrises to highlight the central tower and the bas-relief of the churning of the ocean of milk would have served as an eternal reminder of this king's "ringing in a new golden age."
A solar city
While Angkor is also known as an hydraulic city since Bernard Philippe Groslier, the Angkor Wat equinox manifests how Angkor was also a solar city. According to Eleanor Manikka, "measurements of the temple recorded data, fixed solar and lunar alignments, defined pathways into and out of sanctuaries, and put segments of the temple in precise association with rays of sunlight during the equinox and solstice days". Accordingly, the gigantic representation of the churning of the sea actually works as a calendar: it positions the two solstice days at the extreme north and south, counts the days between them, and measures 54 units for the north- and southbound arcs of the sun and moon, emulating the symbolism on the bridge or in the western entrances, which repeat the 54/54-unit pairs several times.
An ancient Khmer New Year
The spring equinox, which receives such a special treatment at Angkor Wat, evidently marked the onset of the calendar year. However, during the thirteenth century, many years after the reign of Suryavarman II, the Khmer New Year was moved to the fifth lunar month, Chate, which corresponds to mid-April, in order for farmers to have more time to celebrate once the dry season was over. The astrological New Year that was celebrated before then occurred when the constellation of Aries or Ram appeared. This phenomenon occurred on the vernal equinox on March 21, but because of the precession of the equinoxes, the sun at the vernal equinox is not seen in the constellation of Pisces and enters Aries around April 13 or 14.
Tourism
The solar alignment of equinox at Angkor Wat is attracting a growing number of tourists, in a new trend of tourism connected to solar phenomena, also seen in such places such as Luxor and Vezelay Abbey.
In 2022, Angkor Wat ranked No. 1 as the best place in the world to watch sunrise and sunset, in part because of the Angkor Wat equinox phenomenon.
See also
Orientation of churches
Spring equinox in Teotihuacán
References
Bibliography
Astronomical events of the Solar System
Geography of Cambodia
Khmer folklore
March
September
Solar alignment
Solar phenomena
Spring equinox
Autumn equinox
Angkor Wat | Angkor Wat Equinox | Physics,Astronomy | 994 |
71,731,723 | https://en.wikipedia.org/wiki/2-Iodophenol | 2-Iodophenol (o-iodophenol) is an aromatic organic compound with the formula IC6H4OH. It is a pale yellow solid that melts near room temperature. It undergoes a variety of coupling reactions in which the iodine substituent is replaced by a new carbon group ortho to the hydroxy group of the phenol, which can be followed by cyclization to form heterocycles.
It can be prepared by treatment of 2-chloromercuriphenol with iodine:
Direct reaction of phenol with iodine gives a mixture of 2- and 4-iodo derivatives.
References
Cited sources
2-Iodophenyl compounds
2-Hydroxyphenyl compounds | 2-Iodophenol | Chemistry | 159 |
23,041,963 | https://en.wikipedia.org/wiki/Metfendrazine | Metfendrazine (developmental code names HM-11, MO-482), also known as methphendrazine, is an irreversible and nonselective monoamine oxidase inhibitor (MAOI) of the hydrazine family. It was investigated as an antidepressant, but was never marketed.
Chemistry
Metfendrazine, also known as methamphetamine hydrazide, is a phenethylamine, amphetamine, and hydrazine derivative.
It is an analogue and derivative of phenelzine (phenethylamine hydrazide) and pheniprazine (amphetamine hydrazide), as well as of phenethylamine, amphetamine, and methamphetamine.
References
Abandoned drugs
Hydrazines
Methamphetamines
Monoamine oxidase inhibitors | Metfendrazine | Chemistry | 181 |
37,067,590 | https://en.wikipedia.org/wiki/Delta2%20Gruis | {{DISPLAYTITLE:Delta2 Gruis}}
Delta2 Gruis, Latinized from δ2 Gruis, is a solitary, red-hued star in the southern constellation of Grus. It is visible to the naked eye with an apparent visual magnitude of about 4. Based upon an annual parallax shift of 9.88 mas as seen from the Earth, the star is located around 330 light years from the Sun. It is moving further away from the Sun with a radial velocity of +3 km/s.
This is an evolved red giant star with a stellar classification of M4.5 IIIa. It is a pulsating variable with multiple periods, including 20.6, 24.1, 24.5, and 32.3 days. The strongest period is 33.3 days with an amplitude of 0.043 magnitude. It has a magnitude 9.71 visual companion at an angular separation of 60.4 arc seconds along a position angle of 210°, as of 2013.
References
M-type giants
Semiregular variable stars
Grus (constellation)
Gruis, Delta2
Durchmusterung objects
213080
111043
8560 | Delta2 Gruis | Astronomy | 243 |
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