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37,753,134 | https://en.wikipedia.org/wiki/CuproBraze | CuproBraze is a copper-alloy heat exchanger technology for high-temperature and pressure environments such as those in modern diesel engines. The technology, developed by the International Copper Association (ICA), is licensed for free to heat exchanger manufacturers around the world.
Applications for CuproBraze include charge air coolers, radiators, oil coolers, climate control systems, and heat transfer cores. CuproBraze is suited for charge air coolers and radiators in heavy industry where machinery must operate for long periods of time under harsh conditions without failures. The technology is intended for off-road vehicles, trucks, buses, industrial engines, generators, locomotives, and military equipment. It is also used for light trucks, SUVs and passenger cars with special needs.
Compared with previous heat exchanger models CuproBraze creates new materials for heat exchanger parts that have previously been made of soldered copper/brass plate fin, soldered copper brass serpentine fin, and brazed aluminum serpentine fin to suit more demanding applications. Aluminum heat exchangers are viable and economical for cars, light trucks, and other light-duty applications. However, they are not amenable for environments characterized by high operating temperatures, humidity, vibration, salty corrosive air, and air pollution. In these environments, the additional tensile strength, durability, and corrosion resistance that CuproBraze technology provides are useful.
The CuproBraze technology uses brazing instead of soldering to join copper and brass radiator components. The heat exchangers are made with anneal-resistant copper and brass alloys. The tubes are fabricated from brass strip and coated with a brazing filler material in form of a powder-based paste or an amorphous brazing foil is laid between the tube and fin. There is another method of coating the tube in-line on the tube mill. This is done using the twin wire-arc spray process where the wire is the braze alloy, deposited on the tube as it is being manufactured at 200-400 fpm. This saves one process step of coating the tube later. The coated tubes, along with copper fins, headers and side supports made of brass, are fitted together into a core assembly which is brazed in a furnace.
The technology enables brazed serpentine fins to be used in copper-brass heat exchanger designs. The benefits include tougher joints.
Performance properties
CuproBraze has better than other materials in several aspects, as shown in the table below.
Thermal performance
The ability to withstand elevated temperatures is essential in high-heat applications. Aluminum alloys are challenged at higher temperatures due to their lower melting points. The yield strength of aluminum is compromised above 200 °C. Problems with fatigue cracking are exacerbated at elevated temperatures. CuproBraze heat exchangers can operate correctly under temperatures of 290°C and above. Anneal-resistant copper and brass strip ensure that radiator cores maintain their strength without softening, despite exposures to high brazing temperatures.
Heat transfer efficiency
Cooling efficiency is a measure of heat rejection from a given space by a heat exchanger. The overall thermal efficiency of a heat exchanger core depends on many factors, such as thermal conductivity of fins and tubes; strength and weight of the fins and tubes; spacing, size, thickness and shape of fins and tubes; velocity of the air passing through the core; and other factors.
The main performance criterion for heat exchangers is cooling efficiency. Heat exchanger cores made from copper and brass can reject more heat per unit volume than any other material. This is why copper-brass heat exchangers generally have a greater cooling efficiency than alternate materials. Brazed copper-brass heat exchangers are also more rugged than soldered copper-brass and alternate materials, including brazed aluminum serpentine.
Air pressure drop is a factor of heat exchanger design. A heat exchanger core with a smaller air pressure drops from the front to the back of the core (i.e., from the windward to the leeward side in a wind tunnel test) is more efficient. Air pressure drops typically are 24% less for CuproBraze versus aluminum heat exchangers. This advantage, responsible for a 6% increase in heat rejection, contributes to CuproBraze's overall greater efficiency.
Since copper's thermal conductivity is higher than aluminum, copper has a higher capacity to dissipate heat. By using thinner material gauges in combination with higher fin density, heat dissipation capacity with CuproBraze can be increased with air pressure drops still at reasonable levels.
Size
Due to its high heat transfer efficiency, CuproBraze has an efficient heating effect. This is because the same heat rejection level can be achieved with a smaller-sized core. Hence, a significant reduction in frontal area and volume is achievable with CuproBraze versus other materials.
Strength and durability
Three new alloys were developed to enhance the strength and durability of CuproBraze heat exchangers: 1) an anneal-resistant fin material that maintains its strength after brazing; 2) an anneal-resistant tube alloy that retains its fine grain structure after brazing and provides ductility and fatigue strength in the brazed heat exchanger core; and 3) the brazing alloy. Brazing at 650 °C creates a joint that is stronger than a soldered joint and comparable in strength to a welded joint. Unlike welding, brazing does not melt the base metals. Therefore, brazing is better for joining dissimilar alloys.
CuproBraze has more strength at elevated temperatures than soldered copper-brass or aluminum. Due to the lower thermal expansion of copper versus aluminum, there is less thermal stress during the manufacturing of CuproBraze and in its use as a heat exchanger. CuproBraze heat exchangers have stronger tube-to-header joints than other materials. These braze joints are the very important in heat exchangers and must be leak-free. CuproBraze also has higher tolerances to internal pressures because its thin-gauge high strength materials provide stronger support for the tubes. The material is also less sensitive to bad coolants than aluminum heat exchangers.
Test results demonstrate a much longer fatigue life for CuproBraze joints compared to similar soldered copper-brass or brazed aluminum joints. Stronger joints allow for the use of thinner fins and new radiator and cooler designs.
The copper fins are not easily bent when dirty radiators are washed with high pressure water. Anticorrosive coatings further improve strength and resistance against humidity, sand erosion, and stone impingement on copper fins.
For further information, see: CuproBraze: Durability and reliability (Technology Series): and CupropBraze durability (design criteria series).
Emissions
New legislation in Europe, Japan and the U.S. call for strong reductions in NOX and particulate emissions from diesel engines used in trucks, buses, power plants, and other heavy equipment. These goals can in part be accomplished by using cleaner-performing turbocharged diesel engines and charge air coolers. Turbocharging enables better power outputs, and charge air coolers allow power to be produced with more efficiency by reducing the temperature of the air charge entering the engine, thereby increasing its density.
The charge air cooler, located between the turbocharger and the engine air inlet manifold, is an air-to-air heat exchanger. It reduces the inlet air temperatures of turbocharged diesel engines from 200 °C to 45 °C while increasing inlet air densities to increase engine efficiencies. Even higher inlet temperatures (246 °C or higher) and boost pressures may be necessary to comply with the emissions standards in the future.
Present-day charge air cooler systems, based on aluminum alloys, experience durability problems at temperatures and pressures necessary to meet the U.S. Tier 4i standards for stationary and mobile engines. Published reports estimate that the average life of an aluminum charge air cooler is currently about 3,500 hours. Aluminum is near its upper technological limit to accommodate higher temperatures and thermal stress levels because the tensile strength of the metal declines rapidly at 150 °C and repetitive thermal cycling between 150 °C and 200 °C substantially weakens it. Thermal cycling creates weak spots in aluminum tubes, which in turn causes charge air coolers to fail. A potential option is to install stainless steel precoolers in aluminum charge air coolers, but limited space and the complexity of this solution is a tampering factor for this option.
A CuproBraze charge air cooler can operate at temperatures as high as 290 °C without creep, fatigue, or other metallurgical problems.
Corrosion resistance
Exterior corrosion resistance in a heat exchanger is especially important in coastal areas, humid areas, polluted areas, and in mining operations. Corrosion mechanisms of copper and aluminum alloys are different. CuproBraze tube contains 85% copper which provides much resistance against dezincification and stress corrosion cracking. The copper alloys tend to corrode uniformly over entire surfaces at known rates. This predictability of copper corrosion is important for proper maintenance management. Aluminum, on the other hand, is more likely to corrode locally by pitting, resulting eventually in holes.
In accelerated corrosion tests, such as SWAAT for salt spray and marine conditions, CuproBraze performed better than aluminum.
The corrosion resistance of CuproBraze is generally better than soft soldered heat exchangers. This is because the materials in CuproBraze heat exchangers are of equal nobility, so galvanic differences are minimized. On soft soldered heat exchangers, the solder is less noble than fin and tube materials and can suffer from galvanic attack in corrosive environments.
Repairability
CuproBraze can be repaired with little complexities. This advantage of the technology is important in remote areas where spare parts may be limited. CuproBraze can be repaired with lead-free soft solder (for example 97% tin, 3% copper) or with common silver-containing brazing alloys.
Antimicrobial
Biofouling is often a problem in HVAC systems that operate in warm, dark, and humid environments. The antimicrobial properties of CuproBraze alloys eliminate foul odors, thereby improving indoor air quality. CuproBraze is being investigated in mobile air conditioner units as a solution to bad odors from fungus and bacteria in aluminum-based heat exchange systems.
Uses
Russian OEMs, such as Kamaz and Ural Automotive Plant, are using CuproBraze radiators and charge air coolers in heavy-duty trucks for off-highway and on-highway applications. Other manufacturers include UAZ and GAZ (Russia) and MAZ (Belarus). The Finnish Radiator Manufacturing Company, also known as FinnRadiator, produces 95% of its radiators and charge air-coolers with CuproBraze for OEM manufacturers of off-road construction equipment. Nakamura Jico Co., Ltd. (Japan) manufactures CuproBraze heat exchangers for construction equipment, locomotives and on-highway trucks. Young Touchstone supplies CuproBraze radiators to MotivePower's diesel-powered commuter train locomotives in North America. Siemens AG Transportation Systems plans to use the technology for its Asia Runner locomotive for South Vietnam and other Asian markets. Bombardier Transportation heat exchangers cool transformer oil in electric-powered locomotives. These huge oil coolers have been used successfully in coal trains for South African Railways. Kohler Power Systems Americas, one of the largest users of diesel engines for power generation, adopted CuproBraze for diesel engine turbocharger air-to-air cooling in its "gen sets".
See also
Copper in heat exchangers
Further reading
Palmqvist U., Liljedahl M. and Falkenö A., 2007. Copper and its Properties for HVAC Systems; Society of Automotive Engineers (SAE) Technical Paper Series 2007-01-1385; https://web.archive.org/web/20121023013350/http://store.sae.org/
Falkenö A., 2006. Environmentally Driven Development of New Heat Exchanger Materials, SAE Technical Paper Series 2006-01-0727; https://web.archive.org/web/20121023013350/http://store.sae.org/
Falkenö A., Tapper L., Ainali M. and Gustafsson B., 2003. The Influence of the Brazing Parameters on the Quality of the Heat-Exchanger Made by the CuproBraze Process, SAE Technical Paper Series 2003-04-0037; https://web.archive.org/web/20121023013350/http://store.sae.org/
Tapper L, Ainali M., 2001. Interactions between the materials in the 632 tube-fin-joints in brazed copper–brass heat exchangers, SAE 633; 2001-01-1726. 634
Ainali M., Korpinen T. and Forsén O., 2001. External Corrosion Resistance of CuproBraze Radiators; SAE Technical Paper Series 2001-01-1718; https://web.archive.org/web/20121023013350/http://store.sae.org/
Korpinen T., Electrochemical Tests with Copper/Brass Radiator Tube Materials in Coolants, 2001. SAE Technical Paper Series 2001-01-1754; https://web.archive.org/web/20121023013350/http://store.sae.org/
Gustafsson B. and Scheel J. 2000. CuproBraze Mobile Heat Exchanger Technology; SAE Technical Paper Series 2000-01-3456; https://web.archive.org/web/20121023013350/http://store.sae.org/
References
Heat exchangers
Heat transfer
Copper alloys
Brazing and soldering | CuproBraze | [
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37,753,951 | https://en.wikipedia.org/wiki/Internally%20grooved%20copper%20tube | Internally grooved copper tubes, also known as "microfin tubes", are a small diameter coil technology for modern air conditioning and refrigeration systems. Grooved coils facilitate more efficient heat transfer than smooth coils. Small diameter coils have better rates of heat transfer than conventionally-sized condenser and evaporator coils with round copper tubes and aluminum or copper fin that have been the standard in the HVAC industry for many years. Small diameter coils can withstand the higher pressures required by the new generation of environmentally friendlier refrigerants. They have lower material costs because they require less refrigerant, fin, and coil materials. They enable the design of smaller and lighter high-efficiency air conditioners and refrigerators because the evaporator and condenser coils are smaller and lighter.
With MicroGroove technology, heat transfer is enhanced by grooving the inside surface of the tube. This increases the surface to volume ratio, mixes the refrigerant, and homogenizes refrigerant temperatures across the tube.
Tubes with MicroGroove technology can be made with copper or aluminium. Copper fins are an attractive alternative to aluminium due to the better corrosion resistance of copper and its antimicrobial benefits.
Design
To use smaller tubes instead of conventional-sized tubes in air conditioners, heat exchangers must be redesigned including the fin and tube circuits. Design optimization requires the use of computational fluid dynamics to analyze airflow around the tubes and fins, as well as computer simulations of refrigerant flow and temperatures inside the tubes. This is important because the overall heat transfer coefficient of a coil is a function of the convection of the refrigerant inside the tube to the tube wall, conduction through the tube wall, and dissipation through the fins.
Engineering considerations for using MicroGroove include:
Determining the best ratio of transverse tube pitch to longitudinal tube pitch by fin efficiency analysis.
Optimizing transverse and longitudinal tube pitch by performance analysis and material cost.
Optimizing fin pattern by comparing performances of fins with different patterns through computational fluid dynamics-based simulations.
Testing the performance of heat exchangers with smaller diameter tubes.
Developing empirical equations for predicting performance of heat exchangers with smaller diameter tubes.
Published experiments on MicroGroove coil performance and energy efficiency take into account the effects of fin spacing and fin design, tube diameter, and tube circuitry. Tube circuitry is substantially different than for conventional coils. Coils should be optimized with respect to the number of paths between the inlet and outlet manifolds. Typically, smaller diameter tubes require more paths of shorter lengths. Published research on tube circuitry and fin design for heat exchangers made with 4 mm tubes are available.
Research on a heat exchanger redesign with 5-mm diameter tubes demonstrated a 5% greater heat exchange capacity than that of the same size heat exchanger with 7 mm diameter tubes. Also, the refrigerant charge of the 5 mm diameter tubes was less than the 7 mm diameter tubes. In China, Chigo, Gree, and Kelon are producing air conditioners with coils that have 5 mm diameter tubes.
A variety of fin designs have been developed for use with small-diameter copper tubes. The performance of slotted and louvered fin designs have been evaluated and compared as a function of various fin dimensions. Simulations have been used to optimize fin design performance.
Refrigerants
The phasing out of CFC and HCFC refrigerants (e.g., HCFC-22, also known as R22) due to global warming concerns has helped to spur innovations in cooling technologies. Natural refrigerants such as carbon dioxide (R744) and propane (R290), as well as R-410A, have become attractive replacements for air conditioning and refrigeration applications.
Higher pressures are typically required to condense these new environmentally friendly refrigerants compared to those that are being phased out. Small diameter copper tubes are more desirable in applications with higher pressures. For tubes of the same thickness, smaller diameter tubes can withstand higher pressures than larger diameter tubes. Hence, as tube diameters decrease, burst pressures increase. This is because working pressure is directly proportional to wall thickness and inversely proportional to diameter. By designing coils with shorter tube lengths, less work is required to circulate the refrigerant. Therefore, refrigerant pressure drop factors due to small diameter tubes can be offset.
Carbon dioxide (R744) refrigerants are used in modern vending machines, refrigerated supermarket display cases, ice-skating rinks, and other emerging applications. Microgroove's smaller diameter copper tubes have the strength to withstand the very high gas cooler and burst pressures of R744 while allowing for lower overall refrigerant volumes.
Propane (R290) is an eco-friendly refrigerant with outstanding thermodynamic properties. The pressure requirements for R290 are much less than for carbon dioxide, but R290 is extremely flammable. Research has demonstrated that MicroGroove is suitable for R290-charged room air conditioners because the refrigerant charge requirement is dramatically reduced with smaller diameter copper tubes. The risk of tube explosions is dramatically reduced as well. Research conducted with propane in MicroGroove has implications for heat exchanger coils used in refrigerators, heat pumps and commercial air conditioning systems.
Weight savings
In a design study of functionally equivalent 5 kW HVAC heat exchangers, tube materials in the coils weighed 3.09 kg for 9.52 mm diameter tube, 2.12 kg for 7 mm diameter tube, and 1.67 kg for 5 mm diameter tube. Tube weight was reduced by 31% when copper tube diameters were downsized from 3/8 inch to 7 mm. Tube weight was reduced by 46% when copper tube diameters were downsized from 3/8 inch to 5 mm. The weights of the fin materials in the coils was 3.55 kg for the 9.52 mm coils, 2.61 kg for the 7 mm coils, and 1.55 kg for the 5 mm coils.
Antimicrobial
Copper is an antimicrobial material. Bio buildup can be reduced with copper coils. This helps to maintain high levels of energy efficiency for longer periods of time and avoids energy efficiency drop off over time.
The use of copper coils to inhibit the growth of fungi and bacteria is a recent development in innovative air conditioning and refrigeration products. OEM companies, such as Chigo in China and Hydronic in France, are now manufacturing all-copper antimicrobial air conditioning systems to improve indoor air quality.
Materials
Smaller diameter refrigerant paths can also be realized with extruded aluminium tubes. These have been designed with several microchannels in one flat, ribbon-like tube. Aluminium microchannel technology offers significant advantages over conventional copper-aluminium round tube plate fin coil, including improved heat transfer performance and reduced refrigerant charge.
However, copper MicroGroove offers higher heat transfer efficiencies than aluminium microchannel tubes and it enables smaller refrigerant volumes because the tube ends of MicroGroove are connected by small U-joints rather than large headers.
Manufacturing
Copper tubes are often produced by a cast and roll process. Copper ingots are cast into mother tubes and these tubes are then drawn to a final shape, annealed, and enhanced with an inner surface texture to improve heat transfer performance. The production of small diameter copper tubes requires only the addition of one or two additional drawing passes to achieve 5 mm tube diameters.
Existing air conditioner coils made of round copper tubes and aluminium fins (CTAF coils) typically are mechanically assembled using tube expansion.
The equipment used in manufacturing Microgroove products expands the tubes circumferentially (i.e., the circumference of the tube is increased without changing the length). This "non-shrinkage" expansion allows for better control of tube lengths in preparation for subsequent assembly operations. Tubes are inserted, or laced, into the holes in a stack of precisely spaced fins. Expanders are inserted into the tubes and the tube diameters are increased slightly until mechanical contact is achieved between the tubes and fins. The high ductility of copper allows for this process to be performed accurately and precisely. Heat exchanger coils made in this manner have excellent durability and heat transfer properties.
The small-diameter tube project in China involves manufacturers who together account for more than 80 percent of HVAC production of approximately 75 million units. Several OEMs in North America are marketing residential air-conditioner products with copper tubes. Air-conditioner OEMs, including Guangdong Chigo Air Conditioning, the Refrigeration Research Institute of Guangdong Midea Refrigeration Appliances Group, and Shanghai Golden Dragon Refrigeration Technology Co., Ltd. have described the benefits of small-diameter copper tubes versus the standard for various designs and diameters. ACR coils from original equipment manufacturers (OEMs) Gree, Haier, Midea, Chigo and HiSense Kelon are also available.
See also
Copper in heat exchangers
Further reading
Simulation-Based Comparison of Optimized AC Coils Using Small Diameter Copper and Aluminium Microchannel Tubes, by John Hipchen, Robert Weed, Ming Zhang, Dennis Nasuta (2012). The Fourteenth International Refrigeration and Air Conditioning Conference; July 2012; (Purdue)
References
Heat exchangers
Heat transfer
Heat conduction
Heating, ventilation, and air conditioning
Copper | Internally grooved copper tube | [
"Physics",
"Chemistry",
"Engineering"
] | 1,988 | [
"Transport phenomena",
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"Heat transfer",
"Chemical equipment",
"Thermodynamics",
"Heat exchangers",
"Heat conduction"
] |
37,755,119 | https://en.wikipedia.org/wiki/Surface%20and%20bulk%20erosion | Surface and bulk erosion are two different forms of erosion that describe how a degrading polymer erodes. In surface erosion, the polymer degrades from the exterior surface. The inside of the material does not degrade until all the surrounding material around it has been degraded. In bulk erosion, degradation occurs throughout the whole material equally. Both the surface and the inside of the material degrade. Surface erosion and bulk erosion are not exclusive, many materials undergo a combination of surface and bulk erosion. Therefore, surface and bulk erosion can be thought of as a spectrum instead of two separate categories.
Erosion Kinetics
In surface erosion, the erosion rate is directly proportional to the surface area of the material. For very thin materials, the surface area remains relatively constant when the material degrades, which allows surface erosion to be characterized as zero order release since the rate of degradation is constant. In bulk erosion, the erosion rate depends on the volume of the material. Due to degradation, the volume of the material decreases during bulk erosion causing the erosion rate to decrease over time. Therefore, bulk erosion rates are difficult to control since it is not zero order. To determine whether a polymer will undergo surface or bulk erosion, the degradation rate of the polymer in water (how fast the polymer reacts to water) and the rate of diffusion of water penetrating through the material must be considered. If the degradation process is faster than the diffusion process, surface erosion will occur since the material's surface will quickly degrade before water has time to diffuse and penetrate through the material. If the diffusion process is faster than the degradation process bulk erosion will occur because water penetrates through the material before significant erosion occurs on the surface. A kinetics of the erosion of a polymer can be modified by changing the diffusion process or the degradation process. For example, blending a polymer with another polymer that is very reactive to water will speed up the degradation process and cause surface erosion. On the other hand, decreasing the dimensions of a material will allow water to travel to the center of the material more quickly, which speeds up the diffusion process and causes bulk erosion.
Mathematical Model
By mathematically modeling the rate of diffusion of water in the material and the rate of degradation of the material, it is possible to predict whether a certain material will undergo surface or bulk erosion by looking at the ratio between the two rates.
The rate of diffusion of water is modeled by the equation
Where <x> is the mean length of the material and D is the diffusion coefficient of water inside the polymer.
The rate of degradation is modeled by the following equation
Where M = molecular weight of polymer, NA = Avogadro constant, N = degree of polymerization, p = density of polymer, k = degradation rate
The ratio between diffusion time and degradation time gives us a dimensionless parameter ε called the erosion number.
If ε≫1, surface erosion occurs. If ε≪1, bulk erosion occurs.
From the model above, it is clear that certain changing certain parameters can determine what kind of erosion a polymer goes through by either increasing or decreasing the rate of the degradation process or the diffusion process. The table below summarizes how a parameter can be modified to favor surface erosion or bulk erosion.
Applications
Since surface erosion is easier to control than bulk erosion, surface erosion is preferred in drug delivery where the release of the drug must be constant or be controlled by changing the dimensions of the material. A zero order release of a drug can be possible with surface erosion if a very thin material is used or if surface area is kept constant. Surface erosion is also useful for protecting water-soluble drugs until the time of desired drug release, because water will not penetrate through the polymer matrix and reach the drug until all the surrounding polymer has degraded. However, bulk erosion can be useful in situations that do not require controlled release, such as plastic degradation.
References
Polymers
Biomaterials
Biomedical engineering | Surface and bulk erosion | [
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26,463,161 | https://en.wikipedia.org/wiki/Novikov%27s%20compact%20leaf%20theorem | In mathematics, Novikov's compact leaf theorem, named after Sergei Novikov, states that
A codimension-one foliation of a compact 3-manifold whose universal covering space is not contractible must have a compact leaf.
Novikov's compact leaf theorem for S3
Theorem: A smooth codimension-one foliation of the 3-sphere S3 has a compact leaf. The leaf is a torus T2 bounding a solid torus with the Reeb foliation.
The theorem was proved by Sergei Novikov in 1964. Earlier, Charles Ehresmann had conjectured that every smooth codimension-one foliation on S3 had a compact leaf, which was known to be true for all known examples; in particular, the Reeb foliation has a compact leaf that is T2.
Novikov's compact leaf theorem for any M3
In 1965, Novikov proved the compact leaf theorem for any M3:
Theorem: Let M3 be a closed 3-manifold with a smooth codimension-one foliation F. Suppose any of the following conditions is satisfied:
the fundamental group is finite,
the second homotopy group ,
there exists a leaf such that the map induced by inclusion has a non-trivial kernel.
Then F has a compact leaf of genus g ≤ 1.
In terms of covering spaces:
A codimension-one foliation of a compact 3-manifold whose universal covering space is not contractible must have a compact leaf.
References
S. Novikov. The topology of foliations//Trudy Moskov. Mat. Obshch, 1965, v. 14, p. 248–278.
I. Tamura. Topology of foliations — AMS, v.97, 2006.
D. Sullivan, Cycles for the dynamical study of foliated manifolds and complex manifolds, Invent. Math., 36 (1976), p. 225–255.
Foliations
Theorems in topology | Novikov's compact leaf theorem | [
"Mathematics"
] | 416 | [
"Mathematical theorems",
"Mathematical problems",
"Topology",
"Theorems in topology"
] |
26,467,595 | https://en.wikipedia.org/wiki/Bile%20salt%20sulfotransferase | Bile salt sulfotransferase also known as hydroxysteroid sulfotransferase (HST) or sulfotransferase 2A1 (ST2A1) is an enzyme that in humans is encoded by the SULT2A1 gene.
Function
Sulfotransferase enzymes catalyze the sulfate conjugation of many hormones, neurotransmitters, drugs, and xenobiotic compounds. These cytosolic enzymes are different in their tissue distributions and substrate specificities. The gene structure (number and length of exons) is similar among family members. This gene is primarily expressed in liver and adrenal tissues where the encoded protein sulfonates steroids and bile acids.
See also
Steroid sulfotransferase
Steroidogenic enzyme
References
Further reading
External links
Post-translational modification | Bile salt sulfotransferase | [
"Chemistry"
] | 175 | [
"Post-translational modification",
"Gene expression",
"Biochemical reactions"
] |
26,469,213 | https://en.wikipedia.org/wiki/Talampanel | Talampanel (INN; development codes GYKI 537773 and LY300164) is a drug which has been investigated for the treatment of epilepsy, malignant gliomas, and amyotrophic lateral sclerosis (ALS).
As of May 2010, results from the trial for ALS have been found negative. Talampanel is not currently under development.
Talampanel acts as a non-competitive antagonist of the AMPA receptor, a type of ionotropic glutamate receptor in the central nervous system.
It showed effectiveness for epilepsy in clinical trials but its development was suspended due to its poor pharmacokinetic profile, namely a short terminal half-life (3 hours) that necessitated multiple doses per day.
References
Abandoned drugs
AMPA receptor antagonists
Anticonvulsants
Benzodiazepines
Benzodioxoles | Talampanel | [
"Chemistry"
] | 189 | [
"Drug safety",
"Abandoned drugs"
] |
45,214,668 | https://en.wikipedia.org/wiki/WRKY%20transcription%20factor | WRKY transcription factors (pronounced ‘worky’) are proteins that bind DNA. They are transcription factors that regulate many processes in plants and algae (Viridiplantae), such as the responses to biotic and abiotic stresses, senescence, seed dormancy and seed germination and some developmental processes but also contribute to secondary metabolism.
Like many transcription factors, WRKY transcription factors are defined by the presence of a DNA-binding domain; in this case, it is the WRKY domain. The WRKY domain was named in 1996 after the almost invariant WRKY amino acid sequence at the N-terminus and is about 60 residues in length. In addition to containing the ‘WRKY signature’, WRKY domains also possess an atypical zinc-finger structure at the C-terminus (either Cx4-5Cx22-23HxH or Cx7Cx23HxC). Most WRKY transcription factors bind to the W-box promoter element that has a consensus sequence of TTGACC/T.
Individual WRKY proteins do appear in the human protozoan parasite Giardia lamblia and slime mold Dictyostelium discoideum.
Structural diversity
WRKY transcription factors are denoted by a 60-70 amino acid WRKY protein domain composed of a conserved WRKYGQK motif and a zinc-finger region. Based on the amino acid sequence WRKY transcription factors are classified into three major categories, group I, group II, and group III. Group I WRKY proteins are primarily denoted by the presence of two WRKY protein domains, whereas both groups II and III each possess only one domain. Group III WRKY proteins have a C2HC zinc finger instead of the C2H2 motif of group I and II factors. The structure of several plant WRKY domains has been elucidated using crystallography and nuclear magnetic resonance spectroscopy.
As soon as the WRKY domain was characterized, it was suggested that it contained a novel zinc finger structure and the first evidence to support this came from studies with 2-phenanthroline that chelates zinc ions. Addition of 2-phenenthroline to gel retardation assays that contained E. coli expressed WRKY proteins resulted in a loss of binding to the W-box target sequence. The other suggestion was that the WRKY signature amino acid sequence at the N-terminus of the WRKY domain directly binds to the W-box sequence in the DNA of target promoters. These suggestions were shown to be correct by publication of the solution structure of the C-terminal WRKY domain of the Arabidopsis WRKY4 protein. The WRKY domain was found to form a four-stranded β-sheet. Soon afterwards, a crystal structure of the C-terminal WRKY domain of the Arabidopsis WRKY1 protein was reported. This showed a similar result to the solution structure except that it may contain an additional β-strand at the N-terminus of the domain. From these two studies it appears that the conserved WRKYGQK signature amino acid sequence enters the major groove of the DNA to bind to the W-Box. Recently, the first structural determination of the WRKY domain complexed with a W-Box was reported. The NMR solution structure of the WRKY DNA-binding domain of Arabidopsis WRKY4 in complex with W Box DNA revealed that part of a four-stranded β-sheet enters the major groove of DNA in an atypical mode that the authors named the β-wedge, where this sheet is almost perpendicular to the DNA helical axis. As initially predicted, amino acids in the conserved WRKYGQK signature motif contact the W Box DNA bases mainly through extensive apolar contacts with thymine methyl groups. These structural data explain the conservation of both the WRKY signature sequence at the N-terminus of the WRKY domain and the conserved cysteine and histidine residues. It also provides the molecular basis for the previously noted remarkable conservation of both the WRKY amino acid signature sequence and the W Box DNA sequence.
History
In 1994 and 1995, the first two reports of WRKY transcription factors appeared. They described newly discovered but as yet ill-defined DNA binding proteins that played potential roles in the regulation of gene expression by sucrose (SPF1) or during germination (ABF1 and ABF2). A third report appeared in 1996 that identified WRKY1, WRKY2 and WRKY3 from parsley. The authors named the new transcription factor family the WRKY family (pronounced ‘worky’) after a conserved amino acid sequence at the N-terminus of the DNA-binding domain. The parsley WRKY proteins also provided the first evidence that WRKY transcription factors play roles in regulating plant responses to pathogens. Numerous papers have now shown this to be a major function of WRKY transcription factors. Since these initial publications, it has become clear that the WRKY family is among the ten largest families of transcription factors in higher plants and that these transcription factors play key roles in regulating a number of plant processes including the responses to biotic and abiotic stresses, germination, senescence, and some developmental processes.
Evolution
WRKY transcription factor genes are found throughout the plant lineage and also outside of the plant lineage in some diplomonads, social amoebae, fungi incertae sedis, and amoebozoa. This patchy distribution suggests that lateral gene transfer is responsible. These lateral gene transfer events appear to pre-date the formation of the WRKY groups in flowering plants, where there are seven well-defined groups, Groups I + IIc, Groups IIa + IIb, Groups IId + IIe, and Group III. Flowering plants also contain proteins with domains typical for both resistance (R) proteins and WRKY transcription factors. R protein-WRKY genes have evolved numerous times in flowering plants, each type being restricted to specific flowering plant lineages. These chimeric proteins contain not only novel combinations of protein domains but also novel combinations and numbers of WRKY domains.
Several early reports proposed that a group I WRKY transcription factor was the progenitor of the family. It was thought that a single group I WRKY domain occurred first and then duplicated to form the original ancestral WRKY transcription factor. However, more recent evidence suggests that WRKY transcription factors evolved from a single group IIc-like gene, which then diversified into group I, group IIc, and group IIa+b domains. The original WRKY protein domain has been proposed to have arisen from the GCM1 and FLYWCH zinc finger factors. GCM1 and FLYWCH are proposed ancestral proteins base on their crystal structural similarity to the WRKY domain. Both GCM1 and FLYWCH belong to families of DNA-binding factors found in metazoan. The plant specific NAC transcription factor family also shares a common structural shape and origin with WRKY transcription factors.
During plant evolution the WRKY family has dramatically expanded, which is proposed to be a result of through duplication. Some species including Arabidopsis thaliana, rice (Oryza sativa), and tomato (Solanum lycopersicum) have WRKY groups which dramatically expanded and diversified in recent evolutionary history. However, differences in expression, not variation in gene sequences, have likely lead to the diverse functions of WRKY genes. Such a model is plausible as WRKY family members are part of numerous phytohormone, developmental, and defense signaling transcriptional networks. Furthermore, W-box elements for WRKY binding occur in promoters of many other WRKY transcription factors indicating not simply a hierarchical rank in gene activation, but also which genes may have arisen later during evolution after initial WRKY regulatory networks were established.
Function
Over the last two decades great effort has been invested in characterizing WRKY transcription factors. The results show that WRKY transcription factors function in a diverse array of plant response, both to internal and external cues.
Plant development
Studies have demonstrated the function of WRKY transcription factors in plant development. Successful male gametogenesis and tolerance to interploidy crosses both require WRKY transcription factors. Embryo and root development also require WRKY transcription factors. WRKYs also contribute to determination of seed size and seed coat color in Arabidopsis. Furthermore, WRKY transcription factors have been shown to play key roles in regulation of developmentally programmed leaf senescence.
Abiotic and biotic stresses
One of the most notorious roles of the WRKY transcription factor family is the regulation of plant stress tolerance. WRKYs participate in nearly every aspect of plant defense to abiotic and biotic stressors. WRKYs are known to regulate cold, drought, flooding, heat, heavy metal toxicity, low humidity, osmotic, oxidative, salt and UV stresses. Likewise, WRKY transcription factors play an essential role in plant tolerance to biotic stresses, protecting against innumerable viruses, bacterial and fungal pathogens, as well as insect herbivory. Plants are believed to perceive pathogens via pathogen-associated molecular pattern (PAMP) triggered immunity and effector-triggered immunity. WRKY transcription factors participate in regulating responses to pathogens by targeting PAMP and effector triggered immunity.
Hormone signaling
WRKY transcription factors function through a variety of plant hormone signaling cascades. Over half of Arabidopsis thaliana WRKY transcription factors respond to salicylic acid treatment. At least 25% of WRKY transcription factors from Madagascar periwinkle (Catharanthus roseus) are responsive to jasmonate. Similarly, in grape (Vitis vinifera) 63%, 73%, 76%, and 81% or WRKY transcription factors are responsive to salicylic acid, ethylene, abscisic acid, and jasmonate treatment, respectively. In Arabidopsis thaliana, two important WRKY transcription factors are WRKY57 and WRKY70. WRKY57 mediates crosstalk between jasmonate and auxin signaling cascades, whereas WRKY70 moderates signaling between the jasmonate and salicylic acid pathways. Arabidopsis thaliana WRKY23 functions downstream of auxin signaling to positively activate expression of flavonols, which function as polar auxin transport inhibitors, to negatively feedback and suppress further auxin responses. Several WRKY transcription factors also respond to gibberellin treatment.
Primary and secondary metabolism
Due to difficulty in measuring phenotypes, less is known about the roles of WRKY transcription factors in plant metabolism. The earliest reports identified WRKYs based on their ability to regulate β-amylase, a gene involved in catabolism of starch into sugars. Since then, WRKY transcription factors have also been shown to regulate phosphate acquisition and tolerance to arsenic. Additionally, WRKYs are needed for proper expression of lignin biosynthetic pathway genes, which form products necessary for cell wall and xylem formation. Analysis of WRKY transcription factors from numerous plant species indicates the importance of the family in regulating secondary metabolism. WRKY transcription factors also play a role in regulating pathways for the biosynthesis of pharmaceutically valuable plant-specialized metabolites. Efforts to use WRKY transcription factors to improve production of the valuable anti-malarial drug artemisinin have been successful.
Mode of action
A long-standing question of in the field of transcriptional regulation is how large families of regulators binding a consensus DNA sequences dictate expression of different target genes. The WRKY transcription factor family has long exemplified this problem. Plant species contain numerous WRKY transcription factors which predominantly recognize a conserved cis-element. Only recently has it begun to be revealed how different WRKY transcription factors regulate unique sets of target genes.
Variation in cis-element recognition
Early work indicated that the WRKY family could bind W-box (T/A)TGAC(T/A). Later, a barley (Hordeum vulgare) WRKY transcription factor, SUSIBA2, was found to bind the Sugar Response Element (TAAAGATTACTAATAGGAA), illustrating some diversity exists in DNA sequence which WRKYs could recognize. Since then, WRKYs have been found to bind a more generic GAC core cis-element with flanking sequences dictating DNA-protein interactions. On the protein side differences in the consensus motif and downstream arginine or lysine residues dictate the exact flanking sequence recognized. Additionally, contrary to early reports, both WRKY domains of group I family members can bind DNA. Implications of these results are still being resolved.
Protein-protein interactions
One mechanism for determining WRKY binding activity is by protein-protein interactions. WRKY transcription factors have been found to interact with a variety of proteins, some of which occur by a group specific manner. Recent evidence suggests that VQ protein family is an important regulator of group I and group IIc WRKY transcription factors. VQ proteins appear to bind the WRKY domain, thus inhibiting protein-DNA interactions. At least one WRKY transcription factor, Arabidopsis WRKY57, interacts with jasmonate ZIM-domain (JAZ) and auxin/indole acetic acid (AUX/IAA) repressor of the jasmonate and auxin signaling cascade, respectively, indicating a point of crosstalk between these phytohormones. Other WRKYs interact with histone deacetylases. Group IIa WRKY factors form homodimers and heterodimers within the subgroup and with other group II subgroups. Group IId WRKY transcription factors typically possess a domain allowing interaction with calcium bound calmodulin.
Phosphorylation
Protein phosphorylation is a common method to regulate protein activity and WRKY transcription factors are no exception. WRKY gene involved in plant defense, hormone signaling, and secondary metabolism are regulated by phosphorylation via mitogen-activated protein kinase (MAPK) cascades. Additionally, a MAPK can phosphorylate a VQ protein, freeing the WRKY transcription factor for target gene activation. While kinases phosphorylating WRKY transcription factors are known, phosphatases removing phosphate groups have yet to be identified.
Proteasomeal degradation
Protein degradation via the proteasome is a common feature in plant regulatory networks to limit the duration of activation or repression by transcription factors. WRKY transcription factors have also been found to be regulated by proteasomal degradation mechanisms. In Chinese grapevine (Vitis pseudoreticulata) ERYSIPHE NECATOR-INDUCED RING FINGER PROTEIN1 targets WRKY11 for degradation leading to enhanced powdery mildew resistance. In rice, WRKY45 is degraded by the proteasome although the E3 ubiquitin ligase responsible remains unknown
References
External links
WRKY family at PlantTFDB: Plant Transcription Factor Database
WRKY family at Plant Transcription Factor Database at University of Potsdam
WRKY Wide Web
WRKY family at Superfamily
WRKY Transcription Factor Family at The Arabidopsis Information Resource
The Somssich Lab
The Shen Lab
Somssich’s list of WRKY-related publications
The Eulgem Lab
Transcription factors | WRKY transcription factor | [
"Chemistry",
"Biology"
] | 3,133 | [
"Induced stem cells",
"Gene expression",
"Transcription factors",
"Signal transduction"
] |
45,223,069 | https://en.wikipedia.org/wiki/CASS4 | Cas scaffolding protein family member 4 is a protein that in humans is encoded by the CASS4 gene.
History and discovery
CASS4 (Crk associated substrate 4) is the fourth and last described member of the CAS protein family. CASS4 was detected by Singh et al. in 2008 following in silico screening of databases describing expressed sequence tags from an evolutionarily diverse group of organisms, using the CAS-related proteins (p130Cas, NEDD9/HEF1 and EFS) mRNAs as templates. Singh et al. subsequently cloned and characterized the CASS4 gene, originally assigning the name HEPL (HEF1-EFS-p130Cas-like) for similarity to the other three defined CAS genes. The official name was subsequently changed to CASS4 by the Human Genome Organization (HUGO) Gene Nomenclature Committee (HGNC).
Gene
The chromosomal location of the CASS4 gene is 20q13.31, with genomic coordinates of 20: 56411548-56459340 on the forward strand in GRChB38p2. While its HGNC-approved symbol is CASS4, this gene has multiple synonyms, including "HEF-like protein", "HEF1-Efs-p130Cas-like", HEFL, HEPL and C20orf32 ("chromosome 20 open reading frame 32"). Official IDs assigned to this gene include 15878 (HGNC), 57091 (Entrez Gene) and ENSG00000087589 (Ensembl). In humans four transcript variants are known. The first and second each contain 7 exons and encode the same full-length protein isoform a (786 amino acids, considered the major isoform), the third one contains 6 exons and encodes a shorter isoform b (732 amino acids) and the fourth one contains 5 exons and encodes the shortest isoform c (349 amino acids). Cumulatively, the CASS4 transcripts are most highly expressed in spleen and lung among normal tissues, and are highly expressed in ovarian and leukemia cell lines.
To date, little effort has been applied to the direct study of transcriptional regulation of CASS4. The SABiosciences' DECODE database, based on the UCSC Bioinformatics Genome Browser, proposes several transcriptional regulators for CASS4 based on its promoter region sequence: NF-κβ, p53, LCR-F1 (NFE2-L1, nuclear factor, erythroid 2-like1), MAX1, C/EBPα, CHOP-10 (C/EBP homologous protein 10), POU3F1 (POU domain, class 3, transcription factor 1, aka Oct-6), Areb6 (ZEB1, Zinc finger E-box binding homeobox 1). These are compatible with regulation relevant to lymphocytes and deregulation in cancer.
Protein family
In vertebrates, the CAS protein family contains four members: p130Cas/BCAR1, NEDD9/HEF1, EFS and CASS4. There are no paralogous genes for this family in acoelomates, pseudocoelomates, and nematodes, while a single ancestral member is found in Drosophila. Evolutionary divergence of the CAS proteins family members is discussed by Singh et al. in detail.
Structure
All CAS protein family members have common structural characteristics. CAS proteins have an amino terminal SH3 domain enabling interaction with poly-proline motif-containing proteins such as FAK. Carboxy-terminal to this, they possess an unstructured domain containing multiple SH2 binding site motifs, which when tyrosine-phosphorylated allow interaction with SH2 domain containing proteins. Further to the carboxy-terminus, they have a four-helix bundle rich in serine residues, and a second highly conserved four-helix bundle that has been recognized as functionally and structurally similar to a focal adhesion targeting [FAT] domain. For the better studied members of the CAS family (BCAR1 and NEDD9), all of these domains have been defined as crucial for recognition and binding by other proteins, reflecting the primary role of CAS family proteins as cell signaling cascades mediators.
Isoform "a" of human CASS4 is considered the predominant species, and at 786 amino acids is the longest one. Amino acid sequence homology of this isoform of human CASS4 with other family members is 26% overall identity and 42% similarity. Using a yeast two-hybrid approach, the CASS4 protein SH3 domain was shown to interact with the FAK C-terminus, despite the lowest overall similarity to other SH3 domains in the CAS group. In addition, human CASS4 has a limited number of candidate SH2-binding sites, estimated at 10, which is similar to EFS (estimated at 9) and in contrast to p130Cas/BCAR1 and NEDD9, which have 20 and 18 respectively. The CASS4 C-terminus has a short region of CAS family homology, but lacks obvious similarity at the level of primary amino acid sequence. It also lacks a YDYVHL sequence at the N-terminal end of the FAT-like carboxy-terminal domain, even though this motif is conserved among the other three CAS family proteins and is an important binding site for the Src SH2 domain. Although this lack of sequence similarity may mean a reduced functionality of the CASS4 protein, molecular modeling analysis performed by Singh and colleagues using p130CAS/BCAR1 structures as templates suggested an almost identical fold between CASS4 and p130CAS/BCAR1 within their SH3 domains, and substantial similarity within 432-591 residues of CASS4 and 449-610 residues of p130Cas/BCAR1 at the level of secondary and tertiary structures. Also, the similar periodicity of α-helices and β-sheets in both CASS4 and p130Cas/BCAR1 provides another confirmation for the idea of well-conserved structures within the family members.
Function
The exact function of CASS4 and its role in development and human pathologies have been subject to little investigation compared to other family members. The primary study exploring CASS4 function was the initial report by Singh et al., who showed the direct interaction between CASS4 and FAK, and CASS4 regulation of FAK activation, affecting cellular adhesion, migration and motility. Unusually, CASS4 depletion had a bimodal affect, causing some cells to have lower velocity and others to have higher velocity than control cells, suggesting a potential role in maintaining homeostasis. This work also suggested the function of CASS4 may be cell-type specific and dependent upon the presence or absence of expression of other CAS family members. Direct binding has also been identified between CASS4 and CRKL, an SH2- and SH3 domain-containing adaptor protein that has been also shown to interact with another CAS family member, p130Cas/BCAR1, in regulation of cellular motility and migration. Because of the high degree of homology in interaction domains and some identified common partners, CASS4 is likely to share some functions with other CAS family members. These include association with FAK and Src family kinases at focal adhesions to transmit integrin-initiated signals to downstream effectors, which results in cytoskeleton reorganization and changes in motility and invasion.
Disease association
Altered expression or modification of CASS4 has been proposed as relevant to several human pathologies, typically based on detection of changes in CASS4 in high throughput screening, although the role of CASS4 in the pathology of these conditions has not yet been studied directly. These findings are summarized in Table 1; some examples are provided below.
Cancer
Many CAS family proteins have altered activity and functional roles in cancer progression and metastasis, with functional roles in influencing cellular adhesion, migration and drug resistance. Changes in CASS4 may also be associated with human malignancies. CASS4 function was linked to non-small cell lung cancer (NSCLC) in a study by Miao et al. that correlated elevated CASS4 expression with lymph node metastasis and high TNM stage. In addition, this study detected a significant difference in cytoplasmic accumulation of CASS4 protein between high (H1299 and BE1) and low (LTE and A549) metastatic potential lung cancer cell lines. These may suggest CASS4 as a possible prognostic marker in clinical management of NSCLC.
Alzheimer's disease
CASS4 and corresponding SNP - rs7274581 T/C has been identified in a large meta-analysis as a locus for lower susceptibility to Alzheimer's disease (AD). However this SNP was not found predictive in a follow-up study.
In a genome wide association screen (GWAS), CASS4 showed a significant correlation with clinical pathological features of AD such as neurofibrillary tangles and neuritic plaques. Two additional CASS4 SNPs were reported to be associated with AD susceptibility: rs6024870, and rs16979934 T/G. Given the likely conserved CAS-family cytoskeletal function of CASS4, it has been speculated that it may have a role in axonal transport and influence the expression of the amyloid precursor protein (APP) and tau, which are pathologically affected in AD. Several possible mechanisms for CASS4 action in AD have been proposed.
Immunopathological conditions
An association of CASS4 with atopic asthma has been shown. CASS4 has also been reported to be an eosinophil-associated gene, with expression in sputum cells increased more than 1.5-fold after whole lung allergen challenge. Moreover, the CASS4 mRNA was upregulated in cells collected by bronchoalveolar lavage after segmental broncho-provocation with an allergen. Reciprocally, the CASS4 mRNA was downregulated when this procedure was performed following administration of mepolizumab (a humanized monoclonal anti-IL-5 antibodies which reduces excessive eosinophilia). This suggests CASS4 activity may be associated with immune response in the context of atopic asthma development.
Cystic fibrosis
CASS4 has been reported to play a modifying role in cystic fibrosis severity, progression and comorbid conditions. The CAS family member NEDD9 has also been shown to interact directly with AURKA (encoding Aurora-A kinase) to regulate cell cycle and ciliary resorption; it is possible that CASS4 may similarly interact with aurora-A kinase.
Thrombosis
CASS4 signaling may contribute to platelet activation and aggregation. A PKA/PKG phosphorylation site has been identified in CASS4 on residue S305 in the unstructured domain containing SH2-binding motifs; the functional significance of this phosphorylation is currently unknown. Significantly increased phosphorylation on S249 of CASS4, also in the unstructured domain, after platelet stimulation with the oxidized phospholipid KODA-PC (9-keto-12-oxo-10-dodecenoic acid ester of 2-lyso-phosphocholine, a CD36 receptor agonist) versus thrombin treatment, which may implicate CASS4 mediated signaling in platelet hyperreactivity.
Clinical significance
There are currently no therapeutic approaches targeting CASS4, and in the absence of a catalytic domain and no extracellular moieties, it may be challenging to generate such an agent. However, CASS4 may ultimately be relevant in clinical practice as a possible marker to assess prognosis and outcome in cases of NSCLC (and possibly other types of cancer). At present, its greatest clinical value is likely to be as a predictive variant for severity and onset of Alzheimer's disease and cystic fibrosis.
Notes
References
External links
Proteins | CASS4 | [
"Chemistry"
] | 2,543 | [
"Biomolecules by chemical classification",
"Proteins",
"Molecular biology"
] |
48,186,544 | https://en.wikipedia.org/wiki/BgK | BgK is a neurotoxin found within secretions of the sea anemone Bunodosoma granulifera which blocks voltage-gated potassium channels, thus inhibiting neuronal repolarization.
Etymology
The neurotoxin was named BgK, with the Bg representing the Latin taxonomy (Bunodosoma granulifera) of the specific sea anemone from which the toxin was found, and the K standing for the chemical symbol for potassium owing to its observed effects on K+ channels.
Sources in Nature
BgK can be found in the mucus of the Bunodosoma granulifera, a common sea anemone found along the coasts of Cuba. Since it is a contracting sea anemone, it has two forms based on the position of its tentacles: open and closed. BgK is released when the anemone is in the closed form, a position it assumes during the day or during times of agitation. In this form, the anemone’s tentacles retract, releasing a mucus from a fibrous matrix found in the mesoglea, a space between the ectodermis and the gastrodermis. For every gram of freeze-dried mucus, there is 0.5 mg BgK.
Chemistry
BgK is composed of 37 amino acid residues, and three disulfide bonds. The neurotoxin belongs to a family of toxins found within 3 different sea anemones. The two other anemone/toxin combinations are: Stichodactyla helianthus and ShK; Anemonia viridis and AsKs. All three of these toxins have an affinity to dendrotoxin sensitive potassium channels that are found within rat brain membranes. BgK and ShK attenuate K+ channels in the neurons of rat dorsal ganglia, in vitro. AsKs stops potassium channel currents that are present in Xenopus oocytes. These toxins potentially represent a new structural type of potassium channel inhibitor. Compared to the short and well-studied scorpion toxins, these anemone toxins have comparable amino acid content (35-37 residues) and the same number of disulfide bridges (three). However, these anemone toxins do not share any sequential similarity. Specifically, the different position of the cysteine residues found within these toxins suggests that BgK, ShK, and AsKS are a new family of toxins.
The only homology BgK shares is with a double-headed protease inhibitor found in sea turtles, however it is only limited to a part of the inhibitor, with the largest similarity found with the cysteine residues, which compose six of the eight conserved amino acids found in the two sequences.
Target
BgK blocks the Kv1.1, Kv1.2, and Kv1.3 channels with similar affinities. IC50 is 6 nM for Kv1.1, 15 nM for Kv1.2, and 10 nM for Kv1.3. Meanwhile, tests on the Kv3 channel, specifically Kv3.1, show that the ion channel exhibits an insensitivity of up to 0.125 μM BgK.
Mode of Action
BgK competes with I-α-dendrotoxin, a known probe used to indicate the presence of certain potassium channels, over binding to synaptic membranes within rat brains. The binding sites of the toxin between Kv1.1, Kv1.2, and Kv1.3 were found to include three common amino acid residues: Lys-25, Tyr-26, and Ser-23. This combination appear to form the core residues that are the site of binding of all Kv1 channel blockers from sea anemones. In particular with Kv1.1, the major reason for BgK's affinity towards binding to this specific channel stems from an electrostatic connections between the side chain of Lys-25 and the carbonyl oxygens of the amino acids found within the channel's molecular filter. Another aspect of BgK's binding to Kv1.1 involves the hydrophobic reactions between Tyr-379 of Kv1.1 and the dyad of Tyr-26 and Phe-6 formed within BgK. Such interactions have been found to surround the Lys-25 and could potentially strengthen the electrostatic interactions that can form between this specific lysine and the oxygen atoms of the channel's filter.
Toxicity
The median lethal dose (LD50) of BgK for mice is 4.5 ng per gram. Symptoms observed include trembling of the tail, muscle twitch, salivation, and paralysis, which are the generally observed physical manifestation of potassium channel blockers .
Therapeutic Use
While BgK has been produced in Escherichia coli as a functional protein, exhibiting all of the effects on potassium channels found with BgK isolated from its natural source, there has been no research into any potential therapeutic purpose so far, with most of its use being for research on potassium channels.
References
Neurotoxins
Ion channel toxins
Sea anemone toxins
Potassium channel blockers | BgK | [
"Chemistry"
] | 1,067 | [
"Neurochemistry",
"Neurotoxins"
] |
48,187,627 | https://en.wikipedia.org/wiki/Elagolix | Elagolix, sold under the brand name Orilissa, is a gonadotropin-releasing hormone antagonist (GnRH antagonist) medication which is used in the treatment of pain associated with endometriosis in women. It is also under development for the treatment of uterine fibroids and heavy menstrual bleeding in women. The medication was under investigation for the treatment of prostate cancer and enlarged prostate in men as well, but development for these conditions was discontinued. Elagolix is taken by mouth once or twice per day. It can be taken for up to 6 to 24 months, depending on the dosage.
Side effects of elagolix include menopausal-like symptoms such as hot flashes, night sweats, insomnia, amenorrhea, mood changes, anxiety, and decreased bone density, among others. Elagolix is a GnRH antagonist, or an antagonist of the gonadotropin-releasing hormone receptor (GnRHR), the biological target of the hypothalamic hormone gonadotropin-releasing hormone (GnRH). By blocking the GnRHR, it dose-dependently suppresses the gonadal production and hence circulating levels of sex hormones such as estradiol, progesterone, and testosterone. Elagolix is a short-acting GnRH antagonist, and can be used to achieve either partial or more substantial suppression of sex hormone levels. Reduced estrogen levels in the endometrium are responsible for the efficacy of elagolix in the treatment of endometriosis.
Elagolix was first described in 2008 and was approved for medical use in July 2018. It has been described as a "second-generation" GnRH modulator due to its non-peptide and small-molecule nature and its oral activity. Unlike GnRH agonists and older GnRH antagonists, which are peptides and first-generation GnRH modulators, elagolix is not a GnRH analogue as it is not structurally related to GnRH. Elagolix was the first second-generation and orally active GnRH modulator to be introduced for medical use. The introduction of elagolix in the United States and Canada was followed by that of relugolix (brand name Relumina), the next second-generation GnRH antagonist, in Japan in January 2019. The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication.
Medical uses
Elagolix is used in the treatment of moderate to severe pain associated with endometriosis in premenopausal women. Endometriosis is a condition in which the endometrium, the inner lining of the uterus, grows outside of the uterus into surrounding tissues and causes symptoms such as pelvic pain and infertility. Around 10% of women may be affected by endometriosis. Elagolix significantly decreases symptoms of dysmenorrhea (menstrual pelvic pain), non-menstrual pelvic pain, and dyspareunia (pain during sexual intercourse) in women with endometriosis. The medication is used at a lower dosage of 150 mg once per day or at a higher dosage of 200 mg twice per day, depending on the severity of symptoms.
The effectiveness of elagolix in the treatment of symptoms of endometriosis was demonstrated in the 6-month Elaris Endometriosis I and II (EM-I and EM-II) phase III clinical trials. In Elaris EM-I, the percentage of women who had a clinical response with respect to dysmenorrhea was 46.4% in the lower-dose elagolix group and 75.8% in the higher-dose elagolix group, as compared with 19.6% in the placebo group; in Elaris EM-II, the corresponding percentages were 43.4% and 72.4%, as compared with 22.7% (P < 0.001 for all comparisons). In Elaris EM-I, the percentage of women who had a clinical response with respect to non-menstrual pelvic pain was 50.4% in the lower-dose elagolix group and 54.5% in the higher-dose elagolix group, as compared with 36.5% in the placebo group (P < 0.001 for all comparisons); in Elaris EM-II, the corresponding percentages were 49.8% and 57.8%, as compared with 36.5% (P = 0.003 and P < 0.001, respectively). The reductions in symptoms of endometriosis with elagolix resulted in an improved quality of life.
The duration of use of elagolix in the treatment of endometriosis should be limited due to a progressive risk of bone loss, and the lowest effective dosage should be used. Elagolix can be used for up to 24 months at the 150 mg once per day dosage and for up to 6 months at the 200 mg twice per day dosage.
Because of its relatively short duration, elagolix should be taken at approximately the same time each day. In the case of twice-daily administration, elagolix should be taken at approximate 12-hour intervals, for instance once in the morning and once at night. It can be taken with or without food.
Elagolix is approved only for the treatment of endometriosis. Other approved and off-label uses of GnRH antagonists in general are the same as those of GnRHR desensitization therapy with GnRH agonists such as leuprorelin, and include uterine fibroids and breast cancer in premenopausal women, prostate cancer in men, precocious puberty in children, and hormone therapy in transgender adolescents and adults, among others.
Available forms
Elagolix is available in the form of Orilissa 150 and 200 mg oral tablets. The 150 mg tablets are light pink, oblong, and film-coated with "EL 150" debossed on one side, while the 200 mg tablets are light orange, oblong, and film-coated with "EL 200" debossed on one side. The inactive ingredients in the tablets include mannitol, sodium carbonate monohydrate, pregelatinized starch, povidone, magnesium stearate, polyvinyl alcohol, titanium dioxide, polyethylene glycol, talc, and a distinct color additive (carmine high tint in the 150 mg tablets and iron oxide red in the 200 mg tablets).
Contraindications
Contraindications of elagolix include pregnancy, known osteoporosis, severe hepatic impairment, and concomitant use with strong organic anion-transporting polypeptide (OATP) 1B1 inhibitors such as ciclosporin and gemfibrozil. Elagolix may increase the risk of miscarriage in early pregnancy. Women should avoid pregnancy while taking elagolix, for instance by using birth control, and should discontinue the medication if they become or wish to become pregnant. Elagolix should not be used in women with osteoporosis because it may increase the risk of further bone loss. Severe hepatic impairment is associated with 7-fold increased exposure to elagolix, which may increase the risk of bone loss. In women with moderate hepatic impairment, which is associated with 3-fold increased exposure to elagolix, the medication at 200 mg twice per day should not be used, while 150 mg once per day should be used for no more than 6 months. OATP1B1 inhibitors are likely to greatly increase exposure to elagolix similarly to moderate to severe hepatic impairment.
Combined birth control is not contraindicated with elagolix, but because of the estrogen component, is expected to decrease the effectiveness of elagolix in the treatment of endometriosis, and hence is not recommended. Other forms of birth control, such as non-hormonal birth control, can be used instead. Elagolix is not contraindicated in women who are breastfeeding, but it is unknown whether the medication is excreted in breast milk or if it has adverse effects on milk production or the breastfed child. The use of elagolix in women who are breastfeeding should be considered carefully, weighing both benefits and risks.
Side effects
The side effects of elagolix are in general similar to menopausal symptoms. The most common side effects of elagolix (incidence ≥10%) are hot flashes, night sweats, headaches, nausea, and amenorrhea (cessation of menstruation). The next most frequent side effects of elagolix (incidence ≥5%) are insomnia, anxiety, arthralgia (joint pain), depression, and mood changes. Less common side effects of elagolix (incidence ≥3% and <5%) include decreased sex drive, diarrhea, abdominal pain, weight gain, dizziness, constipation, and irritability. Other common side effects of elagolix include decreased bone mineral density (BMD) and changes in the blood lipid profile. Rare but serious adverse effects that were observed during elagolix therapy in clinical trials included appendicitis (0.3%), abdominal pain (0.2%), and back pain (0.2%), though it is unknown if these were due to elagolix. Other serious adverse effects of elagolix may include bone loss, miscarriage, suicidality, and elevated liver enzymes. Elagolix was discontinued due to side effects by 5 to 10% of women in clinical trials, with the most common reasons being hot flashes or night sweats, nausea, and decreased BMD.
Elagolix dose- and duration-dependently decreases BMD in premenopausal women with long-term therapy. After 6 months of treatment with elagolix, lumbar spine BMD was decreased by 0.3 to 1.3% with 150 mg once per day and by 2.5 to 3.1% with 200 mg twice per day. The decrease in BMD during elagolix therapy may not be fully reversible with discontinuation, as only partial recovery was observed 12 months after discontinuation of therapy. The cause of the decrease in BMD with elagolix is estrogen deficiency, and is analogous to that associated with postmenopause. The consequences of the effects of elagolix on BMD are unknown, but may be an increase in the risk of bone loss and fractures. This is why the duration of use of elagolix should be limited. In women with risk factors for bone loss and osteoporosis, such as a history of low-trauma fracture, assessment of BMD may be considered. Elagolix should not be used in premenopausal women with known osteoporosis. Supplementation with calcium and/or vitamin D during treatment with elagolix has not been studied, but may be beneficial for helping to maintain bone health.
Elagolix decreases the amount, intensity, and duration of menstrual bleeding. Amenorrhea, the cessation of menstruation, was observed in 4 to 17% of women with 150 mg once per day and in 7 to 57% of women with 200 mg twice per day, compared to less than 1% of women given placebo. The decreased menstrual bleeding caused by elagolix may impede the ability to recognize pregnancy in a timely manner. Based on its mechanism of action, elagolix may increase the risk of miscarriage in early pregnancy, and so should be discontinued if pregnancy occurs. If pregnancy is suspected, pregnancy testing can be performed. Elagolix decreases the rate of ovulation and thereby decreases the likelihood of pregnancy, but has not been shown to be a fully effective contraceptive and should not be relied on to prevent pregnancy.
The incidence of depression and mood changes in clinical trials with elagolix was increased in premenopausal women taking elagolix relative to placebo. Mood- and depression-type side effects such as altered mood, mood swings, depressed mood, depression, depressive symptoms, and tearfulness occurred in 3 to 6% of women with 150 mg per day and in 5 to 6% of women with 200 mg twice per day, compared to 2 to 3% in women given placebo. Suicidal ideation and behavior occurred in a few women (0.2–0.4%), with one suicide observed. People taking elagolix with new or existing depressive symptoms should be promptly evaluated to determine whether the benefits of treatment outweigh the risks. In those with new or existing depressive symptoms, referral to a mental health professional, as appropriate, may be warranted. Immediate medical attention should be sought for those with suicidal ideation and behavior.
Elagolix dose-dependently produced elevated liver enzymes, including elevations of serum alanine aminotransferase of at least 3-fold the upper limit, in clinical trials. This was observed in one woman (0.2%) with 150 mg once per day and in five women (1.1%) with 200 mg twice per day, compared to one woman (0.1%) given placebo. Medical attention should be sought if signs or symptoms of liver injury, such as jaundice, are noticed. The lowest effective dosage of elagolix may be used to minimize the risk of liver problems, and in those who develop elevated liver enzymes during elagolix therapy, prompt evaluation should be done to determine whether the benefits of treatment outweigh the risks.
Overdose
In the event of an overdose of elagolix, the person should be monitored for any signs or symptoms of adverse reactions and should be treated on a symptomatic basis as needed. Elagolix has been assessed in clinical studies at a dose as high as a single administration of 1,200 mg, which resulted in concentrations of the medication that were 17 times higher than with the typical high clinical dosage of 200 mg twice per day. No adverse effects were mentioned. Chronic overdosage of elagolix may result in greater suppression of estradiol levels and a consequent increased risk of bone loss with long-term therapy.
Interactions
Elagolix has a number of potential drug interactions with other medications. Elagolix is a substrate of the cytochrome P450 (CYP450) enzyme CYP3A, and inhibitors and inducers of CYP3A4 may alter the metabolism of elagolix and increase or decrease its circulating levels. The strong CYP3A4 inhibitor ketoconazole has been found to increase peak levels of and total exposure to a single 150 mg dose of elagolix by about 2-fold. Paradoxically, rifampin, a strong inducer of CYP3A4 and other CYP450 enzymes, increased peak levels of and total exposure to a single 150 mg dose of elagolix as well. A single dose of rifampin increased peak levels of elagolix by 4.4-fold and total exposure by 5.6-fold, whereas continuous rifampin therapy increased peak levels of elagolix by 2-fold and total exposure by 1.7-fold. The use of elagolix at 200 mg twice per day concomitantly with rifampin is not recommended, whereas the concomitant use of elagolix at 150 mg once per day with rifampin should be limited to 6 months. No significant changes in exposure to elagolix were observed with concomitant administration of rosuvastatin (a substrate of OATP1B1, OATP1B3, and BCRP), sertraline (a moderate inhibitor of CYP2D6 and CYP2B6), or fluconazole (a strong inhibitor of CYP2C19 and a moderate inhibitor of CYP2C9 and CYP3A4).
Elagolix is a substrate of the hepatic OATP1B1 transporter. Levels of elagolix have been found to be increased by 78% in people with a genotype characterized by reduced OATP1B1 transporter function. The concomitant use of elagolix with medications that inhibit OATP1B1 may increase elagolix levels, and the use of elagolix with strong OATP1B1 inhibitors like ciclosporin and gemfibrozil, which may markedly increase elagolix exposure, is contraindicated.
Elagolix is a weak to moderate inducer of CYP3A, and may decrease levels of medications that are substrates of CYP3A4. In addition, elagolix is an inhibitor of P-glycoprotein, and may increase levels of medications that are substrates of P-glycoprotein, such as digoxin. Elagolix has been found to increase exposure to digoxin and ethinylestradiol, whereas it has been found to decrease exposure to rosuvastatin, midazolam, norethisterone, norelgestromin, and norgestrel.
Because combined birth control pills and other forms of combined birth control contain an estrogen, and because elagolix treats endometriosis by decreasing estrogen levels in the endometrium, these form of hormonal birth control are likely and expected to decrease the effectiveness of elagolix in the treatment of this condition. The effect of progestogen-only birth control on the effectiveness of elagolix in endometriosis is unknown. However, progestogens are antiestrogenic in the uterus, and high-dose progestin therapy is known to be effective in the treatment of endometriosis similarly to GnRH antagonists. On the basis of limited clinical research, combined birth control pills have also been found to be effective in the treatment of endometriosis, but are likely not as effective as GnRH modulator monotherapy. It is advised that women use non-hormonal methods of birth control during elagolix therapy and for one week following discontinuation of elagolix.
Pharmacology
Pharmacodynamics
Elagolix acts as a potent and selective competitive antagonist of the gonadotropin-releasing hormone receptor (GnRHR), the biological target of the hypothalamic peptide hormone gonadotropin-releasing hormone (GnRH). As such, it is a GnRH antagonist. The affinity (KD) of elagolix for the GnRHR is 54 pM. By blocking the GnRHR in the pituitary gland, elagolix suppresses the GnRH-induced secretion of the gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the anterior pituitary, and thereby decreases the production of sex hormones by the gonads. In women, elagolix dose-dependently suppresses the production of ovarian hormones including estradiol, progesterone, and testosterone, and thereby decreases the circulating levels of these hormones. In men, GnRH modulators suppress the testicular production of testosterone and estradiol, decreasing the circulating levels of these hormones similarly. Unlike previous GnRH agonists and antagonists, referred to collectively as GnRH analogues, elagolix is a non-peptide and small-molecule compound that can be taken orally.
Estrogens like estradiol stimulate the growth of the endometrium, and thereby aggravate symptoms of endometriosis. By suppressing estrogen production and levels, elagolix decreases the growth of the endometrium and decreases endometriosis symptoms such as pelvic pain.
Elagolix is a short-acting GnRH antagonist, with a terminal half-life of typically about 4 to 6 hours. Because of the short duration of elagolix in the body, the activation of the GnRHR by GnRH is not fully blocked throughout the day with once-daily administration of elagolix. As a result, gonadotropin and sex hormone levels are only partially suppressed when elagolix is taken once per day. In addition, the degree of suppression can be dose-dependently adjusted as needed, for instance with higher-dose twice-daily administration to achieve greater hormonal suppression. Because of its short duration in the body, the effects of elagolix are rapidly reversible upon discontinuation. In addition, due to its partial and incomplete suppression of estradiol levels, the side effects of elagolix, such as hot flashes and decreased BMD, are lower than with first-generation GnRH modulators.
In clinical trials, elagolix produced dose-dependent decreases in gonadotropin, estradiol, and progesterone levels in women. Median levels of estradiol were partially suppressed to 42 pg/mL (follicular phase levels) with 150 mg once daily and were fully or near-fully suppressed to 12 pg/mL (postmenopausal levels) with 200 mg twice daily. In a 21-day study in premenopausal women, the effects of elagolix on FSH levels were found to be maximal at a dosage of 300 mg twice per day or above, whereas its effects on LH and estradiol levels were maximal at a dosage of 200 mg twice per day or above. Levels of progesterone were maintained at anovulatory levels (<2 ng/mL) across the 21-day study period at dosages of elagolix of 100 mg twice per day and above. A dosage of elagolix of 400 mg twice per day appears to produce no greater suppression in gonadotropin or estradiol levels than a dosage of 300 mg twice per day in premenopausal women. Suppression of gonadotropin and sex hormone levels with elagolix occurs rapidly, within hours, and upon discontinuation of elagolix, gonadotropin and sex hormone levels remain suppressed for at least 12 hours, but show recovery within 24 to 48 hours. As a consequence of its suppression of gonadotropin and sex hormone levels, elagolix inhibits ovulation in women. Over the course of three menstrual cycles, the ovulation rate with elagolix was 50% at 150 mg once daily and 32% at 200 mg twice daily. Because ovulation is triggered by a surge in estradiol levels at mid-cycle, estrogen exposure during elagolix therapy might be greater around this time in some women.
In addition to its activity as a GnRH antagonist, elagolix is a weak to moderate inducer of CYP3A and an inhibitor of P-glycoprotein. As a result, elagolix may affect the metabolism and/or transport of other medications, and this may contribute to drug interactions with elagolix.
Pharmacokinetics
Elagolix is taken by the oral route of administration, in contrast to other GnRH modulators. The oral bioavailability of elagolix in humans is not described in the Food and Drug Administration (FDA) label for the medication, but in animal research elagolix showed a low oral bioavailability of 5.8% in rats and 11% in monkeys. Following administration, elagolix is rapidly absorbed, with peak concentrations occurring after 0.5 to 1.5 hours. The drug accumulation ratio of elagolix at 150 mg once per day is 0.98 and at 200 mg twice per day is 0.89, indicating that it is not accumulated in the body with continuous administration. At steady state, peak levels of elagolix at 150 mg once per day are 574 ng/mL and at 200 mg twice per day are 774 ng/mL while area-under-the-curve levels of elagolix at 150 mg once per day are 1,292 ng•hour/mL and at 200 mg twice per day are 1,725 ng•hour/mL. A toxicology study found that levels of elagolix in women after a single dose of 1,200 mg were 17 times higher than in women taking 200 mg twice daily. Taking elagolix with a high-fat meal has been found to decrease its peak levels by 36% and its area-under-the-curve levels by 24%. In terms of distribution, the plasma protein binding of elagolix is 80% and its blood-to-plasma ratio is 0.6. The volume of distribution at steady state is 1,674 L at 150 mg once per day and 881 L at 200 mg twice per day.
Elagolix is metabolized in the liver, with the major pathway being by CYP3A and minor pathways including by CYP2D6, CYP2C8, and -glucuronosyltransferases. The terminal half-life of elagolix is typically about 4 to 6 hours. A study found that its half-life was 2.4 to 6.3 hours with a single dose and was 2.2 to 10.8 hours with continuous administration. The oral clearance of elagolix is 123 L/hour at 150 mg once per day and 144 L/hour at 200 mg twice per day. The major pathway of elimination of elagolix is hepatic metabolism. Elagolix is taken up from the circulation into the liver by the hepatic OATP1B1 carrier. In people with two reduced function alleles of the gene that encodes OATP1B1 (SLCO1B1 521T>C; SLCO1B1 521 C/C genotype), plasma levels of elagolix have been found to be increased by 78% relative to in people with normal OATP1B1 function (SLCO1B1 521T/T genotype). The frequency of this reduced function OATP1B1 genotype is generally less than 5% in most racial and ethnic groups. Elagolix is excreted less than 3% in urine and 90% in feces.
Exposure to elagolix is not affected by renal impairment or mild hepatic impairment, but is increased by approximately 3-fold in women with moderate hepatic impairment and by approximately 7-fold in women with severe hepatic impairment. There were no differences in the pharmacokinetics of elagolix between individuals of different racial and ethnic groups. Similarly, the pharmacokinetics of elagolix were unaffected by body weight and body mass index. Peak and area-under-the-curve levels of elagolix have been shown to be altered by CYP3A4 inhibitors like ketoconazole and CYP3A4 inducers like rifampin. Inhibitors of OATP1B1 may increase circulating levels of elagolix, and elagolix is considered to be contraindicated in combination with strong OATP1B1 inhibitors. Elagolix is a substrate of P-glycoprotein, but the effect of inhibitors and inducers of P-glycoprotein on the pharmacokinetics of elagolix is unknown. Elagolix itself is an inhibitor of P-glycoprotein.
Chemistry
Elagolix is a small-molecule and non-peptide compound. This is in contrast to GnRH analogues such as leuprorelin and cetrorelix, which are peptides and analogues of GnRH. Other small-molecule and non-peptide orally active GnRH antagonists besides elagolix include linzagolix, opigolix, relugolix, and sufugolix, although none of these compounds have been introduced for medical use at this time.
Elagolix is used as elagolix sodium, the sodium salt of elagolix. It is a white to off white to light yellow powder. The compound is freely soluble in water. The chemical name of elagolix sodium is sodium 4-({(1R)-2-[5-(2-fluoro-3-methoxyphenyl)-3-{[2-fluoro-6-(trifluoromethyl)phenyl]methyl}-4-methyl-2,6-dioxo-3,6-dihydropyrimidin-1(2H)-yl]-1-phenylethyl}amino)butanoate. It has a molecular formula of C32H29F5N3O5Na and a molecular weight of 653.58 g/mol. The free acid form of elagolix has a molecular formula of C32H29F5N3O5 and a molecular weight of 631.60 g/mol.
History
Elagolix was first described in the literature in 2005. It was originally developed by the pharmaceutical company Neurocrine Biosciences, and was later developed together by Neurocrine Biosciences and AbbVie (previously Abbott Laboratories). In June 2010, Neurocrine Biosciences and Abbott announced a global agreement to develop and commercialize elagolix for the treatment of endometriosis. The medication completed phase III clinical trials for endometriosis in November 2016. Two phase III clinical trials, the Elaris Endometriosis I and II (EM-I and EM-II) studies, were conducted. The studies included almost 1,700 women, about 950 of whom were treated with elagolix. In September 2017, AbbVie filed a New Drug Application (NDA) for elagolix for the treatment of pain associated with endometriosis in the United States. The medication was approved by the FDA for the treatment of endometriosis-associated pain in the United States on 23 July 2018. It was the first new medication to be approved by the FDA for the treatment of endometriosis in more than a decade. Elagolix was the first member of a new class of GnRH modulators described as "second-generation" due to their non-peptide and small-molecule nature and oral activity to be marketed. A second member of this group, relugolix (brand name Relumina), was introduced in Japan in January 2019. In addition to endometriosis, elagolix is under development for the treatment of uterine fibroids and menorrhagia. It is in phase III clinical trials for these indications.
Society and culture
Generic names
Elagolix is the generic name of the drug and its and . It is also known by its former developmental code names NBI-56418 and ABT-620.
Brand names
Elagolix is marketed under the brand name Orilissa.
Availability
Elagolix is available in the United States and Canada. A similar medication, relugolix, is available in Japan.
Economics
Prior to its introduction, elagolix was estimated to cost about per month. It is not available as a generic medication.
Research
, elagolix in phase III clinical trials for the treatment of uterine fibroids (uterine leiomyoma) and menorrhagia (abnormally heavy bleeding during menstruation) in women. An efficacy and safety study of elagolix in combination with add-back estradiol, an estrogen, and norethisterone acetate, a progestin, for the treatment of menorrhagia associated with uterine fibroids in premenopausal women has been published. The medication was also under investigation for the treatment of prostate cancer and benign prostatic hyperplasia (enlarged prostate) in men, but development for these indications was discontinued.
References
Further reading
External links
Drugs developed by AbbVie
Amines
CYP3A4 inducers
Ethers
Fluoroarenes
GnRH antagonists
Lactams
Pyrimidinediones
Trifluoromethyl compounds
Triketones
Uracil derivatives | Elagolix | [
"Chemistry"
] | 6,939 | [
"Functional groups",
"Organic compounds",
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"Amines",
"Bases (chemistry)"
] |
48,188,195 | https://en.wikipedia.org/wiki/Relugolix | Relugolix, sold under the brand names Orgovyx and Relumina among others, is a gonadotropin-releasing hormone antagonist (GnRH receptor antagonist) medication which is used in the treatment of prostate cancer in men and uterine fibroids in women. It is taken by mouth.
Side effects of relugolix include menstrual abnormalities, hot flashes, excessive sweating, headache, and decreased bone mineral density. Relugolix is a GnRH antagonist, or an antagonist of the gonadotropin-releasing hormone receptor. Unlike most other GnRH modulators, but similarly to elagolix (brand name Orilissa), relugolix is a non-peptide, small-molecule compound and is orally active. It suppresses sex hormone levels to the postmenopausal or castrate range in both women and men.
Relugolix was approved for use for the treatment of uterine fibroids in Japan in January 2019, and for the treatment of prostate cancer in the United States in December 2020.
Medical uses
Relugolix is approved in the United States, Canada and the United Kingdom for the treatment of prostate cancer in men and in Japan for the treatment of uterine fibroids (uterine leiomyoma) in women.
Available forms
Relugolix is available in the form of 40 and 120 mg oral tablets.
Side effects
The main side effects of relugolix for uterine fibroids include abnormal uterine bleeding (24.6–48.6% vs. 6.3% for placebo), hot flashes (42.8–45.5% vs. 0% for placebo), heavy menstrual bleeding (12.1–49.3% vs. 9.4% for placebo), headache (12.3–15.2%), and excessive sweating (9.4–15.2% vs. 0% for placebo). In addition, decreased bone mineral density occurs with relugolix (21.7% decrease by week 12, 24.4% decrease by week 24).
Pharmacology
Pharmacodynamics
Relugolix is a selective antagonist of the gonadotropin-releasing hormone receptor (GnRHR), with a half-maximal inhibitory concentration (IC50) of 0.12 nM.
A dosage of relugolix of 40 mg once per day has been found to suppress estradiol levels to postmenopausal levels (<20 pg/mL) within 24 hours in premenopausal women. In the control group of women, estradiol levels fluctuated between 50 and 250 pg/mL. Estradiol levels have been found to return to normal concentrations within 4 weeks of discontinuation of relugolix in premenopausal women. The medication additionally suppresses levels of progesterone, luteinizing hormone, and follicle-stimulating hormone in premenopausal women. Relugolix at a dosage of 40 mg or more once per day has been found to reduce testosterone levels to sustained castrate levels (<20 ng/dL) in men. It additionally suppresses luteinizing hormone and follicle-stimulating hormone levels in men.
Lower doses of relugolix (<40 mg/day) are under investigation for achieving partial sex hormone suppression in the treatment of endometriosis and uterine fibroids. This is intended to reduce the incidence and severity of menopausal symptoms such as hot flushes and decreased bone mineral density that are secondary to estrogen deficiency.
Pharmacokinetics
A single 40-mg oral dose of relugolix has been found to result in peak levels of relugolix of 29 ng/mL (47 nmol/L) after 1.5 hours. Steady-state levels are reached within 7 days with 40 mg/day relugolix administration. There is an approximate 2-fold accumulation of relugolix by 2 weeks of continuous administration. Food diminishes the oral bioavailability of relugolix by about 50%.
Relugolix is a substrate for P-glycoprotein, which may have a limiting effect on its absorption and distribution. The plasma protein binding of relugolix is approximately 68 to 71% over a concentration range of 0.05 to 5 μg/mL.
Relugolix is not a substrate for CYP3A4. The elimination half-life of relugolix is 36 to 65 hours across a dosage range of 20 to 180 mg/day. There is moderate to high interindividual variability in systemic exposure to relugolix.
Relugolix is excreted mainly in feces (83%) and to a small degree in urine (4%). Only about 6% of a dose of relugolix is excreted unchanged.
Chemistry
Relugolix is a non-peptide, small-molecule compound, and is structurally distinct from GnRH analogues. It is an N-phenyl urea derivative.
History
Relugolix was first described in 2004. It superseded sufugolix (developmental code name TAK-013), which was developed by the same researchers. Relugolix was approved for the treatment of uterine fibroids in Japan in January 2019. It was the second orally active GnRH antagonist to be introduced for medical use, following elagolix (brand name Orilissa) in July 2018. Relugolix was approved for the treatment of prostate cancer in the United States on 18 December 2020.
The FDA approved relugolix based on evidence from a clinical trial (NCT03085095) of 930 participants 48 to 97 years old with advanced prostate cancer. The trial was conducted at 155 sites in the United States, Canada, and countries in South America, Europe and the Asia Pacific region. All participants in the trial had advanced prostate cancer. Participants were randomly assigned to receive either one relugolix tablet daily (on the first day they received three tables) or an active control (leuprolide acetate) which was given as an injection under the skin every three months. The participants and healthcare providers were aware of which treatment was being given. The treatment lasted for 48 weeks. The efficacy of relugolix was assessed by the percentage of participants who achieved and maintained low testosterone level equal to castration.
Society and culture
Names
Relugolix is the generic name of the drug and its , , and . It is also known by its former developmental code names RVT-601 and TAK-385.
Relugolix is sold under the brand name Orgovyx for the treatment of prostate cancer and under the brand name Relumina for the treatment of uterine fibroids. Relugolix compounded with ethinyl estradiol and norethindrone is sold under the brand name Myfembree for the treatment of uterine fibroids.
Availability
Relugolix is available in the United States and in Japan.
Legal status
In February 2022, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Orgovyx, intended for the treatment of prostate cancer. The applicant for this medicinal product is Myovant Sciences Ireland Limited. Relugolix was approved for medical use in the European Union in April 2022, and in the United Kingdom in July 2022 (although not available in NHS England until August 2024).
Research
Relugolix is under development for use in the treatment of endometriosis.
References
Further reading
External links
Dimethylamino compounds
Ethers
Fluoroarenes
GnRH antagonists
Hormonal antineoplastic drugs
Pyridazines
Pyrimidines
Triketones
Ureas | Relugolix | [
"Chemistry"
] | 1,662 | [
"Organic compounds",
"Functional groups",
"Ethers",
"Ureas"
] |
25,068,575 | https://en.wikipedia.org/wiki/Wellcome%E2%80%93MRC%20Cambridge%20Stem%20Cell%20Institute | The Cambridge Stem Cell Institute at the University of Cambridge is a research centre for the nature and potential medical uses of stem cells. It is located on the Cambridge Biomedical Campus in Cambridge, England and was originally funded by the Wellcome Trust and the Medical Research Council.
The main areas of study include pluripotent and neural stem cells, as well as epidermal stem cells. Key advances in stem cell science at the centre include the elucidation of the role of the nanog protein in pluripotency and work on inhibiting cellular differentiation. It also conducts human embryo work as approved by the Human Fertilisation and Embryology Authority.
References
External links
Cambridge Stem Cell Institute
Health in Cambridgeshire
Stem Cell Institute, Cambridge
Medical research institutes in the United Kingdom
Research institutes in Cambridge
Science and technology in Cambridgeshire
Stem cell research
Wellcome Trust | Wellcome–MRC Cambridge Stem Cell Institute | [
"Chemistry",
"Biology"
] | 173 | [
"Translational medicine",
"Tissue engineering",
"Stem cell research"
] |
25,069,073 | https://en.wikipedia.org/wiki/Hammer%20paint | Hammer paint (or hammered paint) is a special lacquer with a surface that looks like hammered metal when dried. It is also known as hammertone.
Composition
The slightly iridescent areas are caused by the different orientation of very small shiny particles, which are suspended in the lacquer. These particles are often made of the mineral mica. Mica is resilient, reflective, refractive, dielectric, chemically inert, insulating, lightweight, and hydrophilic. Alternatively, aluminium or bronze powder may be used. To make the "hammered" effect more pronounced, a small amount of silicone oil may be added directly before application.
Purposes
Hammer paint is often used to beautify technical apparatus or as a protective coating. The optical advantage of hammer paint is that surfaces look acceptable even if the underlying surface is not flat and smooth. To get a regular paint to look smooth, the surface would have to be prepared first, for example, by spackling, sanding, grinding or polishing. With hammer paint, this step can be omitted. Some hammer paints (e.g. by Hammerite) are formulated to be usable directly on rusted steel without surface preparation other than brushing to remove the loose rust.
Beyond that, the mica improves the durability and color of the paint job. The mica reduces aging by protecting the underlying binders from UV radiation. The mica also makes hammer paint relatively hard and scratch-resistant.
References
Paints | Hammer paint | [
"Physics",
"Chemistry"
] | 304 | [
"Paints",
"Materials stubs",
"Coatings",
"Materials",
"Matter"
] |
25,069,467 | https://en.wikipedia.org/wiki/Bennett%20acceptance%20ratio | The Bennett acceptance ratio method (BAR) is an algorithm for estimating the difference in free energy between two systems (usually the systems will be simulated on the computer).
It was suggested by Charles H. Bennett in 1976.
Preliminaries
Take a system in a certain super (i.e. Gibbs) state. By performing a Metropolis Monte Carlo walk it is possible to sample the landscape of states that the system moves between, using the equation
where ΔU = U(Statey) − U(Statex) is the difference in potential energy, β = 1/kT (T is the temperature in kelvins, while k is the Boltzmann constant), and is the Metropolis function.
The resulting states are then sampled according to the Boltzmann distribution of the super state at temperature T.
Alternatively, if the system is dynamically simulated in the canonical ensemble (also called the NVT ensemble), the resulting states along the simulated trajectory are likewise distributed.
Averaging along the trajectory (in either formulation) is denoted by angle brackets
.
Suppose that two super states of interest, A and B, are given. We assume that they have a common configuration space, i.e., they share all of their micro states, but the energies associated to these (and hence the probabilities) differ because of a change in some parameter (such as the strength of a certain interaction).
The basic question to be addressed is, then, how can the Helmholtz free energy change (ΔF = FB − FA) on moving between the two super states be calculated from sampling in both ensembles? The kinetic energy part in the free energy is equal between states so can be ignored. Also the Gibbs free energy corresponds to the NpT ensemble.
The general case
Bennett shows that for every function f satisfying the condition (which is essentially the detailed balance condition), and for every energy offset C, one has the exact relationship
where UA and UB are the potential energies of the same configurations, calculated using potential function A (when the system is in superstate A) and potential function B (when the system is in the superstate B) respectively.
The basic case
Substituting for f the Metropolis function defined above (which satisfies the detailed balance condition), and setting C to zero, gives
The advantage of this formulation (apart from its simplicity) is that it can be computed without performing two simulations, one in each specific ensemble. Indeed, it is possible to define an extra kind of "potential switching" Metropolis trial move (taken every fixed number of steps), such that the single sampling from the "mixed" ensemble suffices for the computation.
The most efficient case
Bennett explores which specific expression for ΔF is the most efficient, in the sense of yielding the smallest standard error for a given simulation time. He shows that the optimal choice is to take
, which is essentially the Fermi–Dirac distribution (satisfying indeed the detailed balance condition).
. This value, of course, is not known (it is exactly what one is trying to compute), but it can be approximately chosen in a self-consistent manner.
Some assumptions needed for the efficiency are the following:
The densities of the two super states (in their common configuration space) should have a large overlap. Otherwise, a chain of super states between A and B may be needed, such that the overlap of each two consecutive super states is adequate.
The sample size should be large. In particular, as successive states are correlated, the simulation time should be much larger than the correlation time.
The cost of simulating both ensembles should be approximately equal - and then, in fact, the system is sampled roughly equally in both super states. Otherwise, the optimal expression for C is modified, and the sampling should devote equal times (rather than equal number of time steps) to the two ensembles.
Multistate Bennett acceptance ratio
The multistate Bennett acceptance ratio (MBAR) is a generalization of the Bennett acceptance ratio that calculates the (relative) free energies of several multi states. It essentially reduces to the BAR method when only two super states are involved.
Relation to other methods
The perturbation theory method
This method, also called Free energy perturbation (or FEP), involves sampling from state A only. It requires that all the high probability configurations of super state B are contained in high probability configurations of super state A, which is a much more stringent requirement than the overlap condition stated above.
The exact (infinite order) result
or
This exact result can be obtained from the general BAR method, using (for example) the Metropolis function, in the limit . Indeed, in that case, the denominator of the general case expression above tends to 1, while the numerator tends to .
A direct derivation from the definitions is more straightforward, though.
The second order (approximate) result
Assuming that and Taylor expanding the second exact perturbation theory expression to the second order, one gets the approximation
Note that the first term is the expected value of the energy difference, while the second is essentially its variance.
The first order inequalities
Using the convexity of the log function appearing in the exact perturbation analysis result, together with Jensen's inequality, gives an inequality in the linear level; combined with the analogous result for the B ensemble one gets the following version of the Gibbs-Bogoliubov inequality:
Note that the inequality agrees with the negative sign of the coefficient of the (positive) variance term in the second order result.
The thermodynamic integration method
writing the potential energy as depending on a continuous parameter,
one has the exact result
This can either be directly verified from definitions or seen from the limit of the above Gibbs-Bogoliubov inequalities when
.
we can therefore write
which is the thermodynamic integration (or TI) result. It can be approximated by dividing the range between states A and B into many values of λ at which the expectation value is estimated, and performing numerical integration.
Implementation
The Bennett acceptance ratio method is implemented in modern molecular dynamics systems, such as Gromacs.
Python-based code for MBAR and BAR is available for download at .
See also
Parallel tempering
References
External links
Bennett Acceptance Ratio from AlchemistryWiki.
Multistate Bennett Acceptance Ratio from AlchemistryWiki.
Weighted Histogram Analysis Method (MBAR being the unbinned case) from AlchemistryWiki.
Thermodynamics
Statistical mechanics | Bennett acceptance ratio | [
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25,069,616 | https://en.wikipedia.org/wiki/Crystal%20cluster | A crystal cluster is a group of crystals which are formed in an open space environment and exhibit euhedral crystal form determined by their internal crystal structure. A cluster of small crystals coating the walls of a cavity are called druse.
See also
References
Further reading
"Mechanical and Physical Properties of Whiskers", CRC Handbook of Chemistry and Physics, 55th edition.
Crystallography
Crystals | Crystal cluster | [
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25,070,208 | https://en.wikipedia.org/wiki/Reversing%20drum%20mixer | A reversing drum mixer (also commonly called a non-tilting mixer) is a type of concrete mixer that produces concrete in single batches. The entire drum rotates around its axis as materials are loaded through a charge chute at one end of the drum and exit through a discharge chute at the opposite end of the drum.
Mixing Action
Mixing blades are mounted on the inside surface of the drum and as the drum rotates the blades mix by lifting and dropping the materials during each rotation.
Once the materials are sufficiently mixed the rotation of the drum is reversed and the blade arrangement pushes the concrete through to the discharge end of the mixer.
Industrial sized reversing drum mixers can have a capacity of 9 m³ and can produce a mid quality concrete mix in as little as 40 seconds. Reversing drum mixers provide for efficient mixing and leave very little build up within the mixer. Wear is reduced as the drum rests on rubber or polyurethane wheels and there is no steel on steel contact. There is no direct contact between the stationary charge and discharge chutes and the rotating drum. The flexible tires, absorb vibration and make for low maintenance and a quiet operation. The efficient mixing within the concrete, results in a reduction in wear of the drum liners. The reversing drum mixers are known for the extremely low maintenance and operating costs, yet a good mixing effect relative to other drum mixers.
References
Concrete | Reversing drum mixer | [
"Engineering"
] | 290 | [
"Structural engineering",
"Concrete",
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25,077,398 | https://en.wikipedia.org/wiki/Lagrangian%20coherent%20structure | Lagrangian coherent structures (LCSs) are distinguished surfaces of trajectories in a dynamical system that exert a major influence on nearby trajectories over a time interval of interest. The type of this influence may vary, but it invariably creates a coherent trajectory pattern for which the underlying LCS serves as a theoretical centerpiece. In observations of tracer patterns in nature, one readily identifies coherent features, but it is often the underlying structure creating these features that is of interest.
As illustrated on the right, individual tracer trajectories forming coherent patterns are generally sensitive with respect to changes in their initial conditions and the system parameters. In contrast, the LCSs creating these trajectory patterns turn out to be robust and provide a simplified skeleton of the overall dynamics of the system. The robustness of this skeleton makes LCSs ideal tools for model validation, model comparison and benchmarking. LCSs can also be used for now-casting and even short-term forecasting of pattern evolution in complex dynamical systems.
Physical phenomena governed by LCSs include floating debris, oil spills, surface drifters and chlorophyll patterns in the ocean; clouds of volcanic ash and spores in the atmosphere; and coherent crowd patterns formed by humans and animals.
While LCSs generally exist in any dynamical system, their role in creating coherent patterns is perhaps most readily observable in fluid flows.
General definitions
Material surfaces
On a phase space and over a time interval , consider a non-autonomous dynamical system defined through the flow map , mapping initial conditions into their position for any time . If the flow map is a diffeomorphism for any choice of , then for any smooth set of initial conditions in , the set
is an invariant manifold in the extended phase space . Borrowing terminology from fluid dynamics, we refer to the evolving time slice of the manifold as a material surface (see Fig. 1). Since any choice of the initial condition set yields an invariant manifold , invariant manifolds and their associated material surfaces are abundant and generally undistinguished in the extended phase space. Only few of them will act as cores of coherent trajectory patterns.
LCSs as exceptional material surfaces
In order to create a coherent pattern, a material surface should exert a sustained and consistent action on nearby trajectories throughout the time interval . Examples of such action are attraction, repulsion, or shear. In principle, any well-defined mathematical property qualifies that creates coherent patterns out of randomly selected nearby initial conditions.
Most such properties can be expressed by strict inequalities. For instance, we call a material surface attracting over the interval if all small enough initial perturbations to are carried by the flow into even smaller final perturbations to . In classical dynamical systems theory, invariant manifolds satisfying such an attraction property over infinite times are called attractors. They are not only special, but even locally unique in the phase space: no continuous family of attractors may exist.
In contrast, in dynamical systems defined over a finite time interval , strict inequalities do not define exceptional (i.e., locally unique) material surfaces. This follows from the continuity of the flow map over . For instance, if a material surface attracts all nearby trajectories over the time interval , then so will any sufficiently close other material surface.
Thus, attracting, repelling and shearing material surfaces are necessarily stacked on each other, i.e., occur in continuous families. This leads to the idea of seeking LCSs in finite-time dynamical systems as exceptional material surfaces that exhibit a coherence-inducing property more strongly than any of the neighboring material surfaces. Such LCSs, defined as extrema (or more generally, stationary surfaces) for a finite-time coherence property, will indeed serve as observed centerpieces of trajectory patterns. Examples of attracting, repelling and shearing LCSs are in a direct numerical simulation of 2D turbulence are shown in Fig.2a.
LCSs vs. classical invariant manifolds
Classical invariant manifolds are invariant sets in the phase space of an autonomous dynamical system. In contrast,
LCSs are only required to be invariant in the extended phase space. This means that even if the underlying dynamical system is autonomous, the LCSs of the system over the interval will generally be time-dependent, acting as the evolving skeletons of observed coherent trajectory patterns. Figure 2b shows the difference between an attracting LCS and a classic unstable manifold of a saddle point, for evolving times, in an autonomous dynamical system.
Objectivity of LCSs
Assume that the phase space of the underlying dynamical system is the material configuration space of a continuum, such as a fluid or a deformable body. For instance, for a dynamical system generated by an unsteady velocity field
the open set of possible particle positions is a material configuration space. In this space, LCSs are material surfaces, formed by trajectories. Whether or not a material trajectory is contained in an LCS is a property that is independent of the choice of coordinates, and hence cannot depend of the observer. As a consequence, LCSs are subject to the basic objectivity (material frame-indifference) requirement of continuum mechanics. The objectivity of LCSs requires them to be invariant with respect to all possible observer changes, i.e., linear coordinate changes of the form
where is the vector of the transformed coordinates; is an arbitrary proper orthogonal matrix representing time-dependent rotations; and is an arbitrary -dimensional vector representing time-dependent translations. As a consequence, any self-consistent LCS definition or criterion should be expressible in terms of quantities that are frame-invariant. For instance, the strain rate and the spin tensor defined as
transform under Euclidean changes of frame into the quantities
A Euclidean frame change is, therefore, equivalent to a similarity transform for , and hence an LCS approach depending only on the eigenvalues and eigenvectors of is automatically frame-invariant. In contrast, an LCS approach depending on the eigenvalues of is generally not frame-invariant.
A number of frame-dependent quantities, such as , , , as well as the averages or eigenvalues of these quantities, are routinely used in heuristic LCS detection. While such quantities may effectively mark features of the instantaneous velocity field , the ability of these quantities to capture material mixing, transport, and coherence is limited and a priori unknown in any given frame. As an example, consider the linear unsteady fluid particle motion
which is an exact solution of the two-dimensional Navier–Stokes equations. The (frame-dependent) Okubo-Weiss criterion classifies the whole domain in this flow as elliptic (vortical) because holds, with referring to the Euclidean matrix norm. As seen in Fig. 3, however, trajectories grow exponentially along a rotating line and shrink exponentially along another rotating line. In material terms, therefore, the flow is hyperbolic (saddle-type) in any frame.
Since Newton’s equation for particle motion and the Navier–Stokes equations for fluid motion are well known to be frame-dependent, it might first seem counterintuitive to require frame-invariance for LCSs, which are composed of solutions of these frame-dependent equations. Recall, however, that the Newton and Navier–Stokes equations represent objective physical principles for material particle trajectories. As long as correctly transformed from one frame to the other, these equations generate physically the same material trajectories in the new frame. In fact, we decide how to transform the equations of motion from an -frame to a -frame through a coordinate change precisely by upholding that trajectories are mapped into trajectories, i.e., by requiring to hold for all times. Temporal differentiation of this identity and substitution into the original equation in the -frame then yields the transformed equation in the -frame. While this process adds new terms (inertial forces) to the equations of motion, these inertial terms arise precisely to ensure the invariance of material trajectories. Fully composed of material trajectories, LCSs remain invariant in the transformed equation of motion defined in the -frame of reference. Consequently, any self-consistent LCS definition or detection method must also be frame-invariant.
Hyperbolic LCSs
Motivated by the above discussion, the simplest way to define an attracting LCS is by requiring it to be a locally strongest attracting material surface in the extended phase space (see. Fig. 4) . Similarly, a repelling LCS can be defined as a locally strongest repelling material surface. Attracting and repelling LCSs together are usually referred to as hyperbolic LCSs, as they provide a finite-time generalization of the classic concept of normally hyperbolic invariant manifolds in dynamical systems.
Diagnostic approach: Finite-time Lyapunov exponent (FTLE) ridges
Heuristically, one may seek initial positions of repelling LCSs as set of initial conditions at which infinitesimal perturbations to trajectories starting from grow locally at the highest rate relative to trajectories starting off of . The heuristic element here is that instead of constructing a highly repelling material surface, one simply seeks points of large particle separation. Such a separation may well be due to strong shear along the set of points so identified; this set is not at all guaranteed to exert any normal repulsion on nearby trajectories.
The growth of an infinitesimal perturbation along a trajectory is governed by the flow map gradient . Let be a small perturbation to the initial condition , with , and with denoting an arbitrary unit vector in . This perturbation generally grows along the trajectory into the perturbation vector . Then the maximum relative stretching of infinitesimal perturbations at the point can be computed as
where denotes the right Cauchy–Green strain tensor. One then concludes that the maximum relative stretching experienced along a trajectory starting from is just . As this relative stretching tends to grow rapidly, it is more convenient to work with its growth exponent , which is then precisely the finite-time Lyapunov exponent (FTLE)
Therefore, one expects hyperbolic LCSs to appear as codimension-one local maximizing surfaces (or ridges) of the FTLE field.
This expectation turns out to be justified in the majority of cases: time positions of repelling LCSs are marked by ridges of . By applying the same argument in backward time,
we obtain that time positions of attracting LCSs are marked by ridges of the backward FTLE field .
The classic way of computing Lyapunov exponents is solving a linear differential equation for the linearized flow map . A more expedient approach is to compute the FTLE field from a simple finite-difference approximation to the deformation gradient.
For example, in a three-dimenisonal flow, we launch a trajectory from any element of a grid of initial conditions. Using the coordinate representation for the evolving trajectory , we approximate the gradient of the flow map as
with a small vector pointing in the coordinate direction. For two-dimensional flows, only the first minor matrix of the above matrix is relevant.
Issues with inferring hyperbolic LCSs from FTLE ridges
FTLE ridges have proven to be a simple and efficient tool for the visualize hyperbolic LCSs in a number of physical problems, yielding intriguing images of initial positions of hyperbolic LCSs in different applications (see, e.g., Figs. 5a-b). However, FTLE ridges obtained over sliding time windows do not form material surfaces. Thus, ridges of under varying cannot be used to define Lagrangian objects, such as hyperbolic LCSs. Indeed, a locally strongest repelling material surface over will generally not play the same role over and hence its evolving position at time will not be a ridge for . Nonetheless, evolving second-derivative FTLE ridges computed over sliding intervals of the form have been identified by some authors broadly with LCSs. In support of this identification, it is also often argued that the material flux over such sliding-window FTLE ridges should necessarily be small.
The "FTLE ridge=LCS" identification, however, suffers form the following conceptual and mathematical problems:
Second-derivative FTLE ridges are necessarily straight lines and hence do not exist in physical problems.
FTLE ridges computed over sliding time windows with a varying are generally not Lagrangian and the flux through them is generally not small.
In particular, a broadly referenced material flux formula for FTLE ridges is incorrect, even for straight FTLE ridges
FTLE ridges mark hyperbolic LCS positions, but also highlight surfaces of high shear. A convoluted mixture of both types of surfaces often arises in applications (see Fig. 6 for an example).
There are several other types LCSs (elliptic and parabolic) beyond the hyperbolic LCSs highlighted by FTLE ridges
Local variational approach: Shrink and stretch surfaces
The local variational theory of hyperbolic LCSs builds on their original definition as strongest repelling or repelling material surfaces in the flow over the time interval . At an initial point , let
denote a unit normal to an initial material surface (cf. Fig. 6). By the invariance of material lines, the tangent space is mapped into the tangent space of
by the linearized flow map . At the same time, the image of the normal normal under generally does not remain normal to .
Therefore, in addition to a normal component of length , the advected normal also develops a tangential component of length (cf. Fig. 7).
If , then the evolving material surface strictly repels nearby trajectories by the end of the time interval . Similarly,
signals that strictly attracts nearby trajectories along its normal directions. A repelling (attracting) LCS over the interval can be defined as a material surface whose net repulsion is pointwise maximal (minimal) with respect to perturbations
of the initial normal vector field . As earlier, we refer to repelling and attracting LCSs collectively as hyperbolic LCSs.
Solving these local extremum principles for hyperbolic LCSs in two and three dimensions yields unit normal vector fields to which hyperbolic LCSs should everywhere be tangent. The existence of such normal surfaces also requires a Frobenius-type integrability condition in the three-dimensional case. All these results can be summarized as follows:
Repelling LCSs are obtained as most repelling shrink lines, starting from local maxima of . Attracting LCSs are obtained as most attracting stretch lines, starting from local minima of . These starting points serve are initial positions of exceptional saddle-type trajectories in the flow. An example of the local variational computation of a repelling LCS is shown in FIg. 8. The computational algorithm is available in LCS Tool.
In 3D flows, instead of solving the Frobenius PDE (see table above) for hyperbolic LCSs, an easier approach is to construct intersections of hyperbolic LCSs with select 2D planes, and fit a surface numerically to a large number of such intersection curves. Let us denote the unit normal of a 2D plane by . The intersection curve of a 2D repelling LCS surface with the plane is normal to both and to the unit normal of the LCS. As a consequence, an intersection curve satisfies the ODE
whose trajectories we refer to as reduced shrink lines. (Strictly speaking, this equation is not an ordinary differential equation, given that its right-hand side is not a vector field, but a direction field, which is generally not globally orientable). Intersections of hyperbolic LCSs with are fastest contracting reduced shrink lines. Determining such shrink lines in a smooth family of nearby planes, then fitting a surface to the curve family so obtained yields a numerical approximation of a 2D repelling LCS.
Global variational approach: Shrink- and stretchlines as null-geodesics
A general material surface experiences shear and strain in its deformation, both of which depend continuously on initial conditions by the continuity of the map .
The averaged strain and shear within a strip of -close material lines, therefore, typically show variation within such a strip.
The two-dimensional geodesic theory of LCSs seeks exceptionally coherent locations where this general trend fails, resulting in an order of magnitude smaller variability in shear or strain than what is normally expected across an strip. Specifically, the geodesic theory searches for LCSs as special material lines around which material strips show no variability either in the material-line
averaged shear (Shearless LCSs) or in the material-line averaged strain (Strainless or Elliptic LCSs). Such LCSs turn out to be null-geodesics of appropriate metric tensors defined by the deformation field—hence the name of this theory.
Shearless LCSs are found to be null-geodesics of a Lorentzian metric tensor defined as
Such null-geodesics can be proven to be tensorlines of the Cauchy–Green strain tensor, i.e., are tangent to the direction field formed by the strain eigenvector fields . Specifically, repelling LCSs are trajectories of starting from local maxima of the eigenvalue field. Similarly, attracting LCSs are trajectories of starting from local minims of the eigenvalue field. This agrees with the conclusion of the local variational theory of LCSs. The geodesic approach, however, also sheds more light on the robustness of hyperbolic LCSs: hyperbolic LCSs only prevail as stationary curves of the averaged shear functional under variations that leave their endpoints fixed. This is to be contrasted with parabolic LCSs (see below), which are also shearless LCSs but prevail as stationary curves to the shear functional even under arbitrary variations. As a consequence, individual trajectories are objective, and statements about the coherent structures they form should also be objective.
A sample application is shown in Fig. 9, where the sudden appearance of a hyperbolic core (strongest attracting part of a stretchline) within the oil spill caused the notable Tiger-Tail instability in the shape of the oil spill.
Elliptic LCSs
Elliptc LCSs are closed and nested material surfaces that act as building blocks of the Lagrangian equivalents of vortices, i.e., rotation-dominated regions of trajectories that generally traverse the phase space without substantial stretching or folding. They mimic the behavior of Kolmogorov–Arnold–Moser (KAM) tori that form elliptic regions in Hamiltonian systems. There coherence can be approached either through their homogeneous material rotation or through their homogeneous stretching properties.
Rotational coherence from the polar rotation angle (PRA)
As a simplest approach to rotational coherence, one may define an elliptic LCS as a tubular material surface along which small material volumes complete the same net rotation over the time intervall of interest.
A challenge in that in each material volume element, all individual material fibers (tangent vectors to trajectories) perform different rotations.
To obtain a well-defined bulk rotation for each material element, one may employ the unique left and right polar decompositions of the flow gradient in the form
where the proper orthogonal tensor is called the rotation tensor and the symmetric, positive definite tensors are called the left stretch tensor and right stretch tensor, respectively.
Since the Cauchy–Green strain tensor can be written as
the local material straining described by the eigenvalues and eigenvectors of are fully captured by the singular values and singular vectors of the stretch tensors. The remaining factor in the deformation gradient is represented by , interpreted as the bulk solid-body rotation component of volume elements. In planar motions, this rotation is defined relative to the normal of the plane. In three dimensions, the rotation is defined relative to the axis defined by the eigenvector of corresponding to its unit eigenvalue. In higher-dimensional flows, the rotation tensor cannot be viewed as a rotation about a single axis.
In two and three dimensions, therefore, there exists a polar rotation angle (PRA) that characterises the material rotation generated by for a volume element centered at the initial condition . This PRA is well-defined up to multiples of . For two-dimensional flows, the PRA can be computed from the invariants of using the formulas
which yield a four-quadrant version of the PRA via the formula
For three-dimensional flows, the PRA can again be computed from the invariants of from the formulas
where is the Levi-Civita symbol, is the eigenvector corresponding to the unit eigenvector of the matrix .
The time positions of elliptic LCSs are visualized as tubular level sets of the PRA distribution . In two-dimensions, therefore, (polar) elliptic LCSs are simply closed level curves of the PRA, which turn out to be objective. In three dimensions, (polar) elliptic LCSs are toroidal or cylindrical level surfaces of the PRA, which are, however, not objective and hence will generally change in rotating frames. Coherent Lagrangian vortex boundaries can be visualized as outermost members of nested families of elliptic LCSs. Two- and three-dimensional examples of elliptic LCS revealed by tubular level surfaces of the PRA are shown in Fig. 10a-b.
Rotational coherence from the Lagrangian-averaged vorticity deviation (LAVD)
The level sets of the PRA are objective in two dimensions but not in three dimensions. An additional shortcoming of the polar rotation tensor is its dynamical inconsistency: polar rotations computed over adjacent sub-intervals of a total deformation do not sum up to the rotation computed for the full-time interval of the same deformation. Therefore, while is the closest rotation tensor to in the norm over a fixed time interval , these piecewise best fits do not form a family of rigid-body rotations as and are varied. For this reason, rotations predicted by the polar rotation tensor over varying time intervals divert from the experimentally observed mean material rotation of fluid elements.
An alternative to the classic polar decomposition provides a resolution to both the non-objectivity and the dynamic inconsistency issue. Specifically, the Dynamic Polar Decomposition (DPD) of the deformation gradient is also of the form
where the proper orthogonal tensor is the dynamic rotation tensor and the non-singular tensors are the left dynamic stretch tensor and right dynamic stretch tensor, respectively. Just as the classic polar decomposition, the DPD is valid in any finite dimension. Unlike the classic polar decomposition, however, the dynamic rotation and stretch tensors are obtained from solving linear differential equations, rather than from matrix manipulations. In particular, is the deformation gradient of the purely rotational flow
and is the deformation gradient of the purely straining flow
.
The dynamic rotation tensor can further be factorized into two deformation gradients: one for a spatially uniform (rigid-body) rotation, and one that deviates from this uniform rotation:
As a spatially independent rigid-body rotation, the proper orthogonal relative rotation tensor is dynamically consistent, serving as the deformation gradient of the relative rotation flow
In contrast, the proper orthogonal mean rotation tensor is the deformation gradient of the mean-rotation flow
The dynamic consistency of implies that the total angle swept by around its own axis of rotation is dynamically consistent. This intrinsic rotation angle is also objective, and turns out to equal to one half of the Lagrangian-averaged vorticity deviation (LAVD). The LAVD is defined as the trajectory-averaged magnitude of the deviation of the vorticity from its spatial mean. With the vorticity and its spatial mean
the LAVD over a time interval therefore takes the form
with denoting the (possibly time-varying) domain of definition of the velocity field . This result applies both in two- and three dimensions, and enables the computation of a well-defined, objective and dynamically consistent material rotation angle along any trajectory.
Outermost complex tubular level curves of the LAVD define initial positions of rotationally coherent material vortex boundaries in two-dimensional unsteady flows (see Fig. 11a). By construction, these boundaries may exhibit transverse filamentation, but any developing filament keeps rotating with the boundary, without global transverse departure form the material vortex. (Exceptions are inviscid flows where such a global departure of LAVD level surfaces from a vortex is possible as fluid elements preserve their material rotation rate for all times). Remarkably, centers of rotationally coherent vortices (defined by local maxima of the LAVD field) can be proven to be the observed centers of attraction or repulsion for finite-size (inertial) particle motion in geophysical flows (see Fig. 11b). In three-dimensional flows, tubular level surfaces of the LAVD define initial positions of two-dimensional eddy boundary surfaces (see Fig. 11c) that remain rotationally coherent over a time intcenter|erval (see Fig. 11d).
Stretching-based coherence from a local variational approach: Shear surfaces
The local variational theory of elliptic LCSs targets material surfaces that locally maximize material shear over the finite time interval of interest. This means that at initial point each point of an elliptic LCS , the tangent space is the plane along which the local Lagrangian shear is maximal (cf. Fig 7).
Introducing the two-dimensional shear vector field
and the three-dimensional shear normal vector field
the criteria for two- and three-dimensional elliptic LCSs can be summarized as follows:
For 3D flows, as in the case of hyperbolic LCSs, solving the Frobenius PDE can be avoided. Instead, one can construct intersections of a tubular elliptic LCS with select 2D planes, and fit a surface numerically to a large number of these intersection curves. As for hyperbolic LCSs above, let us denote the unit normal of a 2D plane by . Again, the intersection curves of elliptic LCSs with the plane are normal to both and to the unit normal of the LCS. As a consequence, an intersection curve satisfies the reduced shear ODE
whose trajectories we refer to as reduced shear lines. (Strictly speaking, the reduced shear ODE is not an ordinary differential equation, given that its right-hand side is not a vector field, but a direction field, which is generally not globally orientable). Intersections of tubular elliptic LCSs with are limit cycles of the reduced shear ODE. Determining such limit cycles in a smooth family of nearby planes, then fitting a surface to the limit cycle family yields a numerical approximation for 2D shear surface. A three-dimensional example of this local variational computation of an elliptic LCS is shown in Fig. 11.
Stretching-based coherence from a global variational approach: lambda-lines
As noted above under hyperbolic LCSs, a global variational approach has been developed in two dimensions to capture elliptic LCSs as closed stationary curves of the material-line-averaged Lagrangian strain functional. Such curves turn out to be closed null-geodesics of the generalized Green–Lagrange strain tensor family , where is a positive parameter (Lagrange multiplier). The closed null-geodesics can be shown to coincide with limit cycles of the family of direction fields
Note that for , the direction field coincides with the direction field for shearlines obtained above from the local variational theory of LCSs.
Trajectories of are referred to as -lines. Remarkably, they are initial positions of material lines that are infinitesimally uniformly stretching under the flow map . Specifically, any subset of a -line is stretched by a factor of between the times and . As an example, Fig. 13 shows elliptic LCSs identified as closed -lines within the Great Red Spot of Jupiter.
Parabolic LCSs
Parabolic LCSs are shearless material surfaces that delineate cores of jet-type sets of trajectories. Such LCSs are characterized by both low stretching (because they are inside a non-stretching structure), but also by low shearing (because material shearing is minimal in jet cores).
Diagnostic approach: Finite-time Lyapunov exponents (FTLE) trenches
Since both shearing and stretching are as low as possible along a parabolic LCS, one may seek initial positions of such material surfaces as trenches of the FTLE field . A geophysical example of a parabolic LCS (generalized jet core) revealed as a trench of the FTLE field is shown in Fig. 14a.
Global variational approach: Heteroclinic chains of null-geodesics
In two dimensions, parabolic LCSs are also solutions of the global shearless variational principle described above for hyperbolic LCSs. As such, parabolic LCSs are composed of shrink lines and stretch lines that represent geodesics of the Lorentzian metric tensor . In contrast to hyperbolic LCSs, however, parabolic LCSs satisfy more robust boundary conditions: they remain stationary curves of the material-line-averaged shear functional even under variations to their endpoints. This explains the high degree of robustness and observability that jet cores exhibit in mixing. This is to be contrasted with the highly sensitive and fading footprint of hyperbolic LCSs away from strongly hyperbolic regions in diffusive tracer patterns.
Under variable endpoint boundary conditions, initial positions of parabolic LCSs turn out to be alternating chains of shrink lines and stretch lines that connect singularities of these line fields. These singularities occur at points where , and hence no infinitesimal deformation takes place between the two time instances and . Fig. 14b shows an example of parabolic LCSs in Jupiter's atmosphere, located using this variational theory. The chevron-type shapes forming out of circular material blobs positioned along the jet core is characteristic of tracer deformation near parabolic LCSs.
Software packages for LCS computations
Particle advection and Finite-Time Lyapunov Exponent calculation:
ManGen (source code)
LCS MATLAB Kit (source code)
FlowVC (source code)
cuda_ftle (source code)
CTRAJ
Newman (source code)
FlowTK (source code)
Jupyter notebooks that guide you through methods used to extract advective, diffusive, stochastic and active transport barriers from discrete velocity data.
TBarrier (source code)
See also
Turbulence
Chaos theory
Dynamical systems theory
Spectral submanifold
Eulerian coherent structure
Coherent turbulent structure
References
Further reading
Dynamical systems
Fluid dynamics
Turbulence
Chaos theory
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39,214,059 | https://en.wikipedia.org/wiki/Rose%E2%80%93Vinet%20equation%20of%20state | The Rose–Vinet equation of state is a set of equations used to describe the equation of state of solid objects. It is a modification of the Birch–Murnaghan equation of state.
The initial paper discusses how the equation only depends on four inputs: the isothermal bulk modulus , the derivative of bulk modulus with respect to pressure , the volume , and the thermal expansion; all evaluated at zero pressure () and at a single (reference) temperature. The same equation holds for all classes of solids and a wide range of temperatures.
Let the cube root of the specific volume be
then the equation of state is:
A similar equation was published by Stacey et al. in 1981.
References
Solid mechanics
Equations of state | Rose–Vinet equation of state | [
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"Equations of state"
] |
39,223,191 | https://en.wikipedia.org/wiki/ISASMELT | The ISASMELT process is an energy-efficient smelting process that was jointly developed from the 1970s to the 1990s by Mount Isa Mines (a subsidiary of MIM Holdings and now part of Glencore) and the Government of Australia's CSIRO. It has relatively low capital and operating costs for a smelting process.
ISASMELT technology has been applied to lead, copper, and nickel smelting. As of 2021, 22 plants were in operation in eleven countries, along with three demonstration plants located at Mt Isa. The installed capacity of copper/nickel operating plants in 2020 was 9.76 million tonnes per year of feed materials and 750 thousand tonnes per year across lead operating plants.
Smelters based on the copper ISASMELT process are among the lowest-cost copper smelters in the world.
The ISASMELT furnace
An ISASMELT furnace is an upright-cylindrical shaped steel vessel that is lined with refractory bricks. There is a molten bath of slag, matte or metal (depending on the application) at the bottom of the furnace. A steel lance is lowered into the bath through a hole in the roof of the furnace, and air or oxygen-enriched air that is injected through the lance into the bath causes vigorous agitation of the bath.
Mineral concentrates or materials for recycling are dropped into the bath through another hole in the furnace roof or, in some cases, injected down the lance. These feed materials react with the oxygen in the injected gas, resulting in an intensive reaction in a small volume (relative to other smelting technologies).
ISASMELT lances contain one or more devices called "swirlers" that cause the injected gas to spin within the lance, forcing it against the lance wall, cooling it. The swirler consists of curved vanes around a central pipe forming an annular flow. They are designed to minimize pressure losses changing the angle from axial to tangential thus creating a strong vortex. The vortex helps mix liquids and solids with oxygen in the bath. The cooling effect results in a layer of slag "freezing" on the outside of the lance. This layer of solid slag protects the lance from the high temperatures inside the furnace. The tip of the lance that is submerged in the bath eventually wears out, and the worn lance is easily replaced with a new one when necessary. The worn tips are subsequently cut off and a new tip welded onto the lance body before it is returned to the furnace.
ISASMELT furnaces typically operate in the range of 1000–1200 °C, depending on the application. The refractory bricks that form the internal lining of the furnace protect the steel shell from the heat inside the furnace.
The products are removed from the furnace through one or more "tap holes" in a process called "tapping". This can be either continuous removal or in batches, with the tap holes being blocked with clay at the end of a tap, and then reopened by drilling or with a thermic lance when it is time for the next tap.
The products are allowed to separate in a settling vessel, such as a rotary holding furnace or an electric furnace.
While smelting sulfide concentrates, most of the energy needed to heat and melt the feed materials is derived from the reaction of oxygen with the sulfur and iron in the concentrate. However, a small amount of supplemental energy is required. ISASMELT furnaces can use a variety of fuels, including coal, coke, petroleum coke, oil and natural gas. The solid fuel can be added through the top of the furnace with the other feed materials, or it can be injected down the lance. Liquid and gaseous fuels are injected down the lance.
Advantages of the ISASMELT process
The advantages of the ISASMELT process include:
High productivity with a small footprint: Glencore's copper smelter in Mount Isa treats over 1 million t/y of copper concentrate through a single furnace 3.75 m in diameter. The small footprint makes the process well suited to retrofitting to existing smelters where there are significant space constraints
Simple operation: the ISASMELT furnace does not require extensive feed preparation as the feed can be discharged from a belt conveyor directly into the furnace
high energy efficiency: installing an ISASMELT furnace in the Mount Isa copper smelter reduced energy consumption by over 80% (through better use of the inherent energy contained in the sulfide concentrate) compared with the roaster and reverberatory furnaces previously used there
Flexibility in feed types: ISASMELT furnaces have been used to smelt copper, lead and nickel concentrates with a wide range of compositions, including high levels of magnetite, and secondary materials, such as copper scrap and lead-acid battery paste
Flexibility in fuel types: ISASMELT furnaces can operate with a variety of fuels, including lump coal of varying ranks, coke (lump or fine), petroleum coke, oil (including recycled oil), natural gas, and liquid petroleum gas, depending on which is the most economic at the smelter's location
High turn-down ratio: the feed rate to a single ISASMELT installation can easily be scaled up or down, depending on the availability of concentrate and the needs of the smelter
Low feed carry over: ISASMELT furnaces typically lose about 1% of the feed as carry-over with the waste gas, meaning that there is less material that needs to be returned to the furnace for retreatment
Effective containment of fugitive emissions: because the furnace has only two openings at the top, any fugitive emissions can easily be captured
High elimination of deleterious minor elements: due to the flushing action of the gases injected into the ISASMELT furnace slags, copper ISASMELT furnaces have a high elimination of minor elements, such as bismuth and arsenic, that can have deleterious effects on the properties of the product copper
High sulfur dioxide concentration in the waste gas: the use of oxygen enrichment gives the ISASMELT plants high sulfur dioxide concentrations in the waste gas stream, making acid plants cheaper to build and operate
Relatively low operating cost: the energy efficiency of the process, the simple feed preparation, the relative lack of moving parts, low feed carry-over rates, low labour requirements and the ease of replacing lances and refractory linings when they are worn give the ISASMELT process relatively low operating costs
Relatively low capital cost: the simplicity of the construction of the ISASMELT furnaces and the ability to treat concentrate without drying make it cheaper than other smelting processes.
History of the process
Early development (1973–1980)
The ISASMELT process began with the invention in 1973 of the Sirosmelt lance by Drs Bill Denholm and John Floyd at the CSIRO. The lance was developed as a result of investigations into improved tin-smelting processes, in which it was found that the use of a top-entry submerged lance would result in greater heat transfer and mass transfer efficiencies.
The idea of top-entry submerged lances goes back to at least 1902, when such a system was attempted in Clichy, France. However, early attempts failed because of the short lives of the lances on submersion in the bath. The Mitsubishi copper smelting process is one alternative approach, wherein lances are used in a furnace, but they are not submerged into the bath. Instead, they blow oxygen-enriched air onto the surface of the slag (top jetting). Similarly, a water-cooled, top-jetting lance was the basis of the LD (Linz-Donawitz) steelmaking process. This does not produce the same intensity of mixing in the bath as a submerged lance.
The CSIRO scientists first tried developing a submerged lance system using a water-cooled lance, but moved to an air-cooled system because "scale up of the water-cooled lance would have been problematic". Introducing any water to a system involving molten metals and slags can result in catastrophic explosions, such as that in the Scunthorpe Steelworks in November 1975 in which 11 men lost their lives.
The inclusion of the swirlers in the Sirosmelt lance and forming a splash coating of slag on the lance were the major innovations that led to the successful development of submerged lance smelting.
From 1973, the CSIRO scientists began a series of trials using the Sirosmelt lance to recover metals from industrial slags in Australia, including lead softener slag at the Broken Hill Associated Smelters in Port Pirie (1973), tin slag from Associated Tin Smelters in Sydney (1974), copper converter slag at the Electrolytic Refining and Smelting ("ER&S") Port Kembla plant (1975) and copper anode furnace slag at Copper Refineries Limited (another subsidiary of MIM Holdings) in Townsville (1976) and of copper converter slag in Mount Isa (1977). The work then proceeded to smelting tin concentrates (1975) and then sulfidic tin concentrates (1977).
MIM and ER&S jointly funded the 1975 Port Kembla converter slag treatment trials and MIM's involvement continued with the slag treatment work in Townsville and Mount Isa.
In parallel with the copper slag treatment work, the CSIRO was continuing to work in tin smelting. Projects included a five tonne ("t") plant for recovering tin from slag being installed at Associated Tin Smelters in 1978, and the first sulfidic smelting test work being done in collaboration with Aberfoyle Limited, in which tin was fumed from pyritic tin ore and from mixed tin and copper concentrates. Aberfoyle was investigating the possibility of using the Sirosmelt lance approach to improve the recovery of tin from complex ores, such as its mine at Cleveland, Tasmania, and the Queen Hill ore zone near Zeehan in Tasmania.
The Aberfoyle work led to the construction and operation in late 1980 of a four t/h tin matte fuming pilot plant at the Western Mining Corporation's Kalgoorlie Nickel Smelter, located to the south of Kalgoorlie, Western Australia.
Lead ISASMELT development
Small-scale work (1978–1983)
In the early 1970s, the traditional blast furnace and sinter plant technology that was the mainstay of the lead smelting industry was coming under sustained pressure from more stringent environmental requirements, increased energy costs, decreasing metal prices and rising capital and operating costs.
Many smelting companies were seeking new processes to replace sinter plants and blast furnaces. Possibilities included the QSL lead smelting process, the Kivcet process, the Kaldo top-blown rotary converter, and adapting Outokumpu's successful copper and nickel flash furnace to lead smelting.
MIM was seeking ways to safeguard the future of its Mount Isa lead smelting operations. It did this in two ways:
working to improve the environmental and operational performance of its existing operations
investigating new technologies.
MIM investigated new technologies by arranging plant testing of large parcels of Mount Isa lead concentrates for all the then process options except for the Kivcet process. At the same time, it had been aware of the use of top-jetting lances in the Mitsubishi and Kaldo processes, and of top-entry submerged combustion lance investigations undertaken by Asarco (which had a long association with MIM, including being a shareholder in MIM Holdings) in the 1960s. This stimulated MIM's interest in the Sirosmelt lance, which was seen as a way to produce a robust submerged lance.
Following the copper slag trials of 1976–1978, MIM initiated a joint project with the CSIRO in 1978 to investigate the possibility of applying Sirosmelt lances to lead smelting.
The work began with computer modelling the equilibrium thermodynamics (1978) and was followed by laboratory bench-scale test work using large alumina silicate crucibles (1978–1979). The results were sufficiently encouraging that MIM built a 120 kg/h test rig in Mount Isa. It began operation in September 1980. This was used to develop a two-stage process to produce lead bullion from Mount Isa lead concentrate. The first stage was an oxidation step that removed virtually all the sulfur from the feed, oxidising the contained lead to lead oxide (PbO) that was largely collected in the slag (some was carried out of the furnace as lead oxide fume that was returned for lead recovery). The second stage was a reduction step in which the oxygen was removed from the lead to form lead metal.
The lead ISASMELT pilot plant (1983–1990)
Following the 120 kg/h test work, MIM decided to proceed to install a 5 t/h lead ISASMELT pilot plant in its Mount Isa lead smelter. It bought Aberfoyle's matte fuming furnace and transported it from Kalgoorlie to Mount Isa, where it was rebuilt and commissioned in 1983 to demonstrate the first stage of the process in continuous operation and for testing the reduction step using batches of high-lead slag.
One of the key features of the pilot plant was that it was run by operations’ personnel in the lead smelter as though it was an operations’ plant. The high lead slag produced by the continuous smelting of the lead concentrate was subsequently treated in the sinter plant, thus increasing the production of the lead smelter by up to 17%. This gave the operations’ people ownership of the plant and an incentive to make it work, thus ensuring management and maintenance priority. It also gave MIM assurance that the process was simple enough to be operable in a production environment, with normal staff and supervision, and that it was robust enough to withstand normal control excursions. In addition to the continuous operation of lead concentrate to produce high-lead slag, the pilot plant was used to produce lead metal from batches of the slag, investigate the wear rates of the furnace's refractory lining and lances, and initial work aimed at developing a low-pressure version of the Sirosmelt lance. The result was a lance design that allowed operation at significantly lower pressure than the initial values of about 250 kilopascal (gauge) ("kPag"), thus reducing operating costs.
MIM built a second, identical furnace next to the first, and commissioned it in August 1985. This combination of furnaces was used to demonstrate the two-stage process in continuous operation in mid-1987. However, for most of the time the two furnaces were not able to operate simultaneously due to a constraint in the capacity of the baghouse used to filter the lead dust from the waste gas.
A series of process improvements, particularly in the waste gas handling system, resulted in increasing the throughput of the plant from the initial design of 5 t/h to 10 t/h. The pilot plant had treated more than 125,000 t of lead concentrate by April 1989.
The two furnaces were also used to develop a process to recover lead from the Mount Isa lead smelter's drossing operations.
The lead ISASMELT demonstration plant (1991–1995)
Based on the results of the pilot plant work, the MIM Holdings Board of Directors approved the construction of an A$65 million demonstration plant, capable of producing 60,000 t/y of lead bullion. This plant operated from early 1991 until 1995. It was initially designed to treat 20 t/h of lead concentrate using lance air enriched to 27%. However, the oxygen originally designated for its use was diverted to the more profitable copper smelting operations, and the feed rate to the lead ISASMELT demonstration plant was severely restricted. When there was sufficient oxygen available in 1993 to increase the enrichment level to 33–35%, treatment rates of up to 36 t/h of concentrate were achieved, with residual lead in the final reduction furnace slag being in the range of 2–5%.
The two-stage approach to ISASMELT lead smelting was partly driven by the relatively low lead content of Mount Isa lead concentrates (typically in the range of 47–52% lead during the lead ISASMELT development period). Trying to produce lead bullion in a single furnace with such low concentrate grades would result in excessive fuming of lead oxide with a huge amount of material that would have to be returned to the furnace to recover the lead and, consequently, a higher energy demand as that material had to be reheated to the furnace temperatures.
Concentrates with higher lead contents can be smelted directly into lead metal in a single furnace without excess fuming. This was demonstrated on the large scale in 1994, when 4000 t of concentrate containing 67% lead were treated at rates up to 32 t/h with lance air enriched to 27%. During these trials, 50% of the lead in the concentrate was converted to lead bullion in the smelting furnace, while most of the rest ended up as lead oxide in the smelting furnace slag.
Like the lead ISASMELT pilot plant, the lead ISASMELT demonstration plant suffered from constraints imposed by the waste gas handling system. In the case of the demonstration plant, the problem was caused by sticky fume that formed an insulating layer on the convection tube bundles of the waste heat boilers, significantly reducing the heat transfer rates and thus the ability of the boilers to reduce the waste gas temperature. As the plant used baghouses to filter lead fume from the waste gas, it was necessary to reduce the temperature of the gas below the point at which the bags would be damaged by high temperatures. The problem was solved by allowing cool air to mix with the hot waste gas to lower the temperature to a level at which the baghouse could operate. This reduced the ISASMELT plant's capacity because it was again limited by the volume of gas that could be filtered by the baghouse.
The lead ISASMELT demonstration plant was mothballed in 1995 because there was insufficient concentrate to keep both it and the rest of the lead smelter operating. It was too small to treat all the Mount Isa lead concentrate by itself.
Commercial primary-lead ISASMELT plants (since 2005)
The first commercial primary-lead ISASMELT furnace was installed at the Yunnan Chihong Zinc and Germanium Company Limited (YCZG) greenfield zinc and lead smelting complex at Qujing in Yunnan Province in China. This furnace was part of a plant consisting of the ISASMELT furnace and a blast furnace specially designed to treat high-lead ISASMELT slag. The ISASMELT furnace was designed to produce both the slag and lead bullion, with about 40% of the lead in the concentrate being converted to lead bullion in the ISASMELT furnace.
The ISASMELT–blast furnace combination was designed to treat 160,000 t/y of lead concentrate.
The second commercial primary-lead ISASMELT furnace was commissioned at Kazzinc's smelting complex at Ust-Kamenogorsk in Kazakhstan in 2012. It is designed to treat 300,000 t/y of lead concentrate, again using an ISASMELT–blast furnace combination.
YCZG is constructing another lead ISASMELT at a new greenfield smelter in Huize in China, and this is due to be commissioned in 2013.
In June 2017, Glencore announced that Nyrstar NV had acquired an Isasmelt licence for its new Ausmelt furnace in Port Pirie. As part of the agreement, Nyrstar engaged training and ramp-up support services for the Ausmelt furnace and blast furnace by personnel from Glencore's Kazzinc operations in Kazakhstan. This involved training Nyrstar personnel at Ust-Kamenogorsk operations and site support by Kazzinc personnel during the commissioning and ramp-up stages of the Ausmelt plant.
Secondary-lead smelting (since 1982)
While the lead ISASMELT 5 t/h pilot plant was being designed in 1982–1983, MIM continued to use the 120 kg/h test rig to develop other processes, including the dross treatment process previously mentioned, and the treatment of lead-acid battery paste for lead recycling.
The MIM Holdings Board of Directors approved the construction of an ISASMELT plant at Britannia Refined Metals, the company's lead refinery at Northfleet in the United Kingdom, for commercial recovery of lead from battery paste to supplement the existing plant, which used a short rotary furnace to produce 10,000 t/y of lead. The new plant increased annual production to 30,000 t/y of recycled lead, and was commissioned in 1991. The ISASMELT furnace was used to produce low-antimony lead bullion from the battery paste and an antimony-rich slag that contained 55–65% lead oxide. While it was possible to recover the lead from the slag in the ISASMELT furnace by a reduction step, the total throughput of the plant was increased by treating the slag in the short rotary furnace when sufficient quantities of the slag had been generated. The plant was designed to treat 7.7 t/h of battery paste, but routinely treated 12 t/h. The plant was shut down in 2004 when Xstrata Zinc, which took over the MIM Holdings lead operations, decided to leave the lead recycling business.
A second lead ISASMELT plant for recovering lead from recycled batteries was commissioned in 2000 in Malaysia at Metal Reclamation Industries’ Pulau Indah plant. This ISASMELT plant has a design capacity of 40,000 t/y of lead bullion.
Copper ISASMELT development
Small-scale test work (1979–1987)
Scientists at the CSIRO conducted small-scale test work on copper sulfide concentrate in 1979, using the CSIRO's 50 kg Sirosmelt test rig. These trials included producing copper matte containing 40–52% copper and, in some cases, converting the matte to produce blister copper.
The results of this work were sufficiently encouraging that MIM in 1983 undertook its own copper smelting test work program using its 120 kg/h test rig, which had by then been rerated to 250 kg/h. It was found that the process was easy to control and that copper loss to slag was low. It was also learned that the process could easily recover copper from copper converter slag concentrate, of which there was a large stockpile at Mount Isa.
The copper ISASMELT demonstration plant (1987–1992)
Construction of a 15 t/h demonstration copper ISASMELT plant began in 1986. The design was based on MIM's 250 kg/h test work and operating experience with the lead ISASMELT pilot plant. It cost A$11 million and was commissioned in April 1987. The initial capital cost was recovered in the first 14 months of operation.
As with the lead ISASMELT pilot plant, the copper ISASMELT demonstration plant was integrated into copper smelter operations and justified by the 20% (30,000 t/y) increase in copper production that it provided. It quickly treated the entire backlog of converter slag concentrate, which could not be treated at high rates in the reverberatory furnaces without generating magnetite ("Fe3O4") accretions that would necessitate shutting down the reverberatory furnaces for their removal.
The demonstration copper ISASMELT plant was used to further develop the copper process. Refractory life was initially shorter than expected and considerable effort was devoted to understanding the reasons and attempting to extend the life of the refractories. At the end of the life of the demonstration plant, the longest refractory life achieved was 90 weeks.
Lance life was also low initially. Inexperienced operators could destroy a lance in as little as 10 minutes. However, as a result of modifications to the lance design, the development of techniques to determine the position of the lance in the bath, and a rise in the operating experience, the typical lance life was extended to a week.
The demonstration plant was commissioned with high-pressure (700 kPag) air injected down the lance. Later, after extensive testing of low-pressure lance designs and trials using oxygen enrichment of the lance air, a 70 t/d oxygen plant and a 5 Nm3/s blower with a discharge pressure of 146 kPag were purchased. The new lance design was capable of operating at pressures below 100 kPag. Using enrichment of the oxygen in the lance air to 35%, the demonstration plant throughput was lifted to 48 t/h of concentrate, and the gross energy used during smelting was reduced from 25.6 GJ/t of contained copper to 4.1 GJ/t.
Commercial primary-copper ISASMELT plants (since 1990)
The successful operation and development of the demonstration copper ISASMELT, and the degree of interest shown in the new process by the global smelting community, gave MIM Holdings sufficient confidence to license the ISASMELT technology to external companies, so an agreement under which MIM could incorporate the Sirosmelt lance into ISASMELT technology was signed with the CSIRO in 1989.
AGIP Australia
MIM signed the first ISASMELT licence agreement with Agip Australia Proprietary Limited ("Agip") in July 1990. Agip, a subsidiary of the Italian oil company ENI, was developing the Radio Hill nickel-copper deposit near Karratha in Western Australia. MIM and representatives of Agip conducted a series of trials in which 4 tonnes of Radio Hill concentrate was smelted in the 250 kg/h test rig at Mount Isa.
The Agip ISASMELT plant was designed to treat 7.5 t/h of the Radio Hill concentrate and produce 1.5 t/h of granulated matte with a combined nickel and copper content of 45% for sale., It was the same size as the copper ISASMELT demonstration plant (2.3 m internal diameter) and had a 5.5 Nm3/s blower to provide the lance air. Commissioning of the plant began in September 1991; however, the Radio Hill mine and smelter complex were forced to close by low nickel prices after less than six months, before commissioning was completed. The ISASMELT furnace achieved its design capacity within three months. Subsequent owners of the mine focussed on mining and mineral processing only, and the ISASMELT plant has been dismantled.
Freeport-McMoRan Copper and Gold
In 1973, the Freeport-McMoRan Copper and Gold ("Freeport") smelter at Miami, Arizona, installed a 51 MW electric furnace at its Miami smelter. The decision was based on a long-term electrical power contract with the Salt River Project that provided the company with a very low rate for electricity. This contract expired in 1990 and the resulting increase in electricity prices prompted the owners of the smelter, Cyprus Miami Mining Corporation ("Cyprus"), to seek alternative smelting technologies for lower operating costs.
The technologies evaluated included:
Contop flame cyclone reactor
Inco flash furnace
ISASMELT
Mitsubishi furnace
Noranda reactor
Outokumpu flash furnace
Teniente furnace.
The Contop, Inco, Mitsubishi and Outokumpu processes "were all eliminated primarily because of their high dust levels, high capital costs and poor adaptability to the existing facility". The Teniente converter was ruled out because it required the use of the electric furnace for partial smelting. The Noranda reactor was not selected "because of its high refractory wear and its poor adaptability to the existing plant due to the handling of the reactor slag". ISASMELT was chosen as the preferred technology and a licence agreement was signed with MIM in October 1990. The major factor in the decision to select the ISASMELT technology was the ability to fit it into the existing plant and to maximise the use of existing equipment and infrastructure, while the major disadvantage was seen to be the risks associated with scaling up the technology from the Mount Isa demonstration plant.
The Miami copper ISASMELT furnace was designed to treat 590,000 t/y (650,000 short tons per year) of copper concentrate, a treatment rate that was constrained by the capacity of the sulfuric acid plant used to capture the sulfur dioxide from the smelter's waste gases. The existing electric furnace was converted from smelting duties to a slag cleaning furnace and providing matte surge capacity for the converters. The ISASMELT furnace was commissioned on 11 June 1992 and in 2002 treated over 700,000 t/y of concentrate. The modernisation of the Miami smelter cost an estimated US$95 million.
In 1993, the Cyprus Minerals Company merged with AMAX to form the Cyprus Amax Minerals company, which was in turn taken over by the Phelps Dodge Corporation in late 1999. After the take-over, Phelps Dodge closed its Hidalgo and Chino smelters. Phelps Dodge was acquired by Freeport in 2006.
The Miami smelter is one of only two remaining operating copper smelters in the United States, down from 16 in 1979.
Mount Isa Mines
The third commercial copper ISASMELT plant was installed in MIM's Mount Isa copper smelter at a cost of approximately A$100 million. It was designed to treat 104 t/h of copper concentrate, containing 180,000 t/y of copper, and it began operation in August 1992.
A significant difference between the Mount Isa copper ISASMELT plant and all the others is that it uses an Ahlstrom Fluxflow waste heat boiler to recover heat from the furnace waste gas. This boiler uses a recirculating fluid bed of particles to rapidly quench the gas as it leaves the furnace, and then uses the enhanced heat transfer properties of solid–solid contact to cool the particles as they are carried past boiler tubes that are suspended in a shaft above the bed. The high heat transfer rate means that the Fluxflow boiler is relatively compact compared with conventional waste heat boilers and the rapid cooling of the waste gas limits the formation of sulfur trioxide ("SO3"), which in the presence of water forms sulfuric acid that can cause corrosion of cool surfaces.
In its early years, the Fluxflow boiler was the cause of significant down time, because the rate of wear of the boiler tubes was much higher than expected. The problems were solved by understanding the gas flows within the boiler and redesigning the boiler tubes to minimise the effects of erosion.
The life of the refractory bricks in the ISASMELT furnace was initially shorter than expected and a water cooling system was briefly considered to extend them; however, this was not installed and operational improvements resulted in a significant extension of the lining life without this capital and operating expense. Since 1998, the refractory lining lives have exceeded their two-year design, with lives of the 8th and 9th linings nearly reaching three years. The most recent lining lasted for 50 months, with the one before that lasting for 44 months.
In the first years of operation at Mount Isa, the throughput of the ISASMELT furnace was constrained by problems with some of the ancillary equipment in the plant, including the boiler, slag granulation system and concentrate filters. The ultimate constraint was the decision during its construction to keep one of the two reverberatory furnaces on line to increase the copper smelter production to 265,000 t/y of anode copper. The smelter's Peirce-Smith converters became a bottleneck and the feed rate of the ISASMELT furnace had to be restrained to allow sufficient matte to be drawn from the reverberatory furnace to prevent it freezing solid. The ISASMELT 12-month rolling average of the feed rate fell just short of 100 t/h for much of this period, not quite reaching the design annual average of 104 t/h. MIM decided to shut down the reverberatory furnace in 1997, and the ISASMELT plant 12-month rolling mean feed rate quickly exceeded the 104 t/h design when this constraint was lifted.
The performance of the ISASMELT plant was sufficiently encouraging that MIM decided to expand the ISASMELT treatment rate to 166 t/h by adding a second oxygen plant to allow higher enrichment of the lance air. As a result, by late 2001 it had achieved a peak rate of 190 t/h of concentrate, and the smelter produced a peak annual total of 240,000 t of anode copper. At that time, the Mount Isa copper smelter, together with its copper refinery in Townsville, was among the lowest cost copper smelters in the world.
Lance life is typically two weeks, with lance changes taking 30 to 40 minutes, and repairs usually being limited to replacement of the lance tips.
In 2006, MIM commissioned a second rotary holding furnace that operates in parallel with the existing holding furnace.
Sterlite Industries
Sterlite Industries ("Sterlite"), a subsidiary of Vedanta Resources, built a copper smelter in Tuticorin using an ISASMELT furnace and Peirce-Smith converters. The smelter was commissioned in 1996 and was designed to produce 60,000 t/y of copper (450,000 t/y of copper concentrate), but by increasing the oxygen content of the lance air and making modifications to other equipment, the ISASMELT furnace feed rate was increased to the point where the smelter was producing 180,000 t/y of copper.
Sterlite commissioned a new ISASMELT furnace in May 2005 that was designed to treat 1.3 million t/y of copper concentrate, and the smelter's production capacity was expanded to 300,000 t/y of copper. The new plant reached its design capacity, measured over a three-month period, six months after it started treating its first feed. Vedanta's website states that the new ISASMELT furnace was successfully ramped up "in a record period of 45 days".
Since then Sterlite decided to further expand its copper production by installing a third ISASMELT smelter and new refinery using IsaKidd technology. The new smelter has a design capacity of 1.36 million t/y of copper concentrate (containing 400,000 t/y of copper), processed through a single ISASMELT furnace.
Yunnan Copper Corporation
In the 1990s, the Chinese government decided to increase the efficiency of the Chinese economy and reduce the environmental effects of heavy industry by modernising plants. As a response, the Yunnan Copper Corporation ("YCC") upgraded its existing plant, which was based on a sinter plant and an electric furnace, with a copper ISASMELT furnace. As with the Miami smelter, the electric furnace was converted from smelting duty to separation of matte and slag and providing matte surge capacity for the converters, and again, the small footprint of the ISASMELT furnace was very important in retrofitting it to the existing smelter.
The YCC ISASMELT plant had a design capacity of 600,000 dry t/y of copper concentrate and started smelting concentrate on 15 May 2002. YCC placed a lot of emphasis on training its operators, sending people to Mount Isa for training over a seven-month period during 2001 ahead of the ISASMELT commissioning. The total cost of the smelter modernisation program, including the ISASMELT furnace, was 640 million yuan (approximately US$80 million) and the smelter's concentrate treatment rate increased from 470,000 t/y to 800,000 t/y as a result.
The transfer of operating knowledge from MIM to YCC was sufficient for the first ISASMELT furnace refractory lining to last for two years, a marked improvement on the life of the initial lining of other plants.
YCC described the modernisation project as "a great success, achieving all that was expected." Energy consumption per tonne of blister copper produced decreased by 34% as a result of installing the ISASMELT furnace, and YCC estimated that during the first 38 months of operation, it saved approximately US$31.4 million through reduced energy costs alone, giving the modernisation a very short payback by industry standards.
In 2004, YCC's management was presented with awards for Innovation in Project Management and the National Medal for High Quality Projects by the Chinese government to mark the success of the smelter modernisation project.
Xstrata subsequently licensed YCC to build three more ISASMELT plants, one in Chuxiong in Yunnan Province, China to treat 500,000 t/y of copper concentrate, one in Liangshan in Sichuan Province, China and the other in Chambishi in Zambia to treat 350,000 t/y of concentrate. Chuxiong and Chambishi were commissioned in 2009. Liangshan was commissioned in 2012.
Mopani Copper Mines, as part of Zambia Consolidated Copper Mines Limited
Southern Peru Copper Corporation
In the 1990s, Southern Peru Copper Corporation ("SPCC") was seeking to modernise its smelter at Ilo in southern Peru as part of 1997 commitment to the Peruvian government to capture at least 91.7% of the sulfur dioxide generated in its smelting operations by January 2007. It initially selected flash smelting technology to replace its reverberatory furnaces, at a cost of almost US$1 billion; however, one of the first actions following Grupo México's acquisition of ASARCO was to review the proposed Ilo smelter modernisation plans.
Kazzinc
Kazzinc selected the copper ISASMELT process for its Ust-Kamenogorsk metallurgical complex. It is designed to treat 290,000 t/y of copper concentrate and was commissioned in 2011. A projected capital cost for the smelter and refinery in 2006 was US$178 million.
Commercial secondary-copper ISASMELT plants
In addition to treating copper concentrates, ISASMELT furnaces have also been built to treat secondary (scrap) copper materials.
Umicore
In the early 1990s, technical personnel from the then Union Miniére worked with MIM Holdings personnel to develop an ISASMELT-based process to treat scrap materials and residues containing copper and lead. Union Miniére operated a smelter at Hoboken, near Antwerpen in Belgium, that specialised in recycling scrap non-ferrous materials. The test work program was undertaken using an ISASMELT test rig at MIM Holdings’ lead refinery, Britannia Refined Metals, at Northfleet in the United Kingdom.
A demonstration plant was designed by MIM Holdings personnel and operated for several months at the Hoboken smelter site. The new smelter was commissioned in the final quarter of 1997 and in 2007 was treating up to 300,000 t/y of secondary materials. The installation of the ISASMELT furnace replaced a roasting plant, a sinter plant, 1 of two sulfuric acid plants, a copper blast furnace and four Hoboken converters. It substantially reduced operating costs at the Hoboken smelter.
Umicore's Hoboken plant uses a two-step process in a single furnace. The first step involves the oxidation of the feed to form a copper matte and a lead-rich slag. The slag is then tapped and the remaining copper matte is then converted to blister copper. The lead-rich slag is subsequently reduced in a blast furnace to produce lead metal, while the copper is refined and the contained precious metals recovered.
Aurubis
The Hüttenwerke Kayser smelter at Lünen in Germany installed an ISASMELT plant in 2002 to replace three blast furnaces and one Peirce-Smith converter used for smelting scrap copper. The company was subsequently bought by Norddeutsche Affinerie AG, which in turn became Aurubis.
The process used at the Lünen smelter involves charging the furnace with copper residues and scrap containing between 1 and 80% copper and then melting it in a reducing environment. This produces a "black copper phase" and a low-copper silica slag. Initially the black copper was converted to blister copper in the ISASMELT furnace. However, in 2011 the smelter was expanded as part of the "KRS Plus" project. A top-blown rotary converter is used to convert the black copper and the ISASMELT furnace runs continuously in smelting mode.
The installation of the ISASMELT furnace increased the overall copper recovery in the plant by reducing losses to slag, reduced the number of furnaces in operation, decreased the waste gas volume, and decreased energy consumption by more than 50%. The production capacity exceeds the original design by 40%.
Kandanshi
Atlantic Copper
References
Metallurgical processes
Industrial furnaces
Industrial ecology
Smelting | ISASMELT | [
"Chemistry",
"Materials_science",
"Engineering"
] | 8,421 | [
"Smelting",
"Metallurgical processes",
"Metallurgy",
"Industrial engineering",
"Industrial furnaces",
"Environmental engineering",
"Industrial ecology"
] |
36,307,450 | https://en.wikipedia.org/wiki/Reactive%20transport%20modeling%20in%20porous%20media | Reactive transport modeling in porous media refers to the creation of computer models integrating chemical reaction with transport of fluids through the Earth's crust. Such models predict the distribution in space and time of the chemical reactions that occur along a flowpath. Reactive transport modeling in general can refer to many other processes, including reactive flow of chemicals through tanks, reactors, or membranes; particles and species in the atmosphere; gases exiting a smokestack; and migrating magma.
Overview
Reactive transport models are constructed to understand the composition of natural waters; the origin of economic mineral deposits; the formation and dissolution of rocks and minerals in geologic formations in response to injection of industrial wastes, steam, or carbon dioxide; and the generation of acidic waters and leaching of metals from mine wastes. They are often relied upon to predict the migration of contaminant plumes; the mobility of radionuclides in waste repositories; and the biodegradation of chemicals in landfills. When applied to the study of contaminants in the environments, they are known as fate and transport models.
Development of reactive transport modeling
Modern reactive transport modeling has arisen from several separate schools of thought. Hydrologists primarily concerned with the physical nature of mass transport assumed relatively simple reaction formulations, such as linear distribution coefficients or linear decay terms, which could be added to the advection-dispersion equation. By assuming linear, equilibrium sorption, for example, the advection-dispersion equation can be modified by a simple retardation factor and solved analytically. Such analytical solutions are limited to relatively simple flow systems and reactions.
Geochemical models, on the other hand, have been developed to provide thermodynamic descriptions of multicomponent systems without regard to transport. Reaction path models were created, for instance, to describe the sequence of chemical reactions resulting from chemical weathering or hydrothermal alteration in batch systems, in terms of the overall reaction progress. By adopting the reference frame of a packet of fluid and treating reaction progress as travel time (or distance along a flowpath), however, a batch reaction path model could be thought of as describing advective transport through an aquifer.
The most sophisticated multi-component reactive transport models consider both reaction and transport. Early studies developed the theoretical basis of reactive transport models, and the numerical tools necessary to solve them, and applied them to problems of reactive contaminant transport and flow through reacting hydrothermal systems.
Reactive transport models have found increased application in recent years with improvements in the power of personal computers and modeling software.
Processes considered in reactive transport models
Reactive transport models couple a large number chemical reactions with mass transport. Certain applications, such as geothermal energy production and ore deposit modeling, require the additional calculation of heat transfer. In modeling carbon sequestration and hydraulic fracturing, moreover, it may be necessary to describe rock deformation resulting from mineral growth or abnormally high fluid pressure. Description of transport through the unsaturated zone and multiphase flow modeling, as applied to transport of petroleum and natural gas; non-aqueous phase liquids (DNAPL or LNAPL); and supercritical carbon dioxide requires increasingly complex models which are prone to considerable uncertainty.
In many cases the processes simulated in reactive transport models are highly related. Mineral dissolution and precipitation, for example, can affect the porosity and permeability of the domain, which in turn affect the flow field and groundwater velocity. Heat transport greatly affects the viscosity of water and its ability to flow. Below are many of the physical and chemical processes which can be simulated with reactive transport models.
Geochemical reactions:
Acid-base reactions
Aqueous complexation
Mineral dissolution and precipitation
Reduction and oxidation (redox) reactions, including those catalyzed by enzymes, surfaces, and microorganisms
Sorption, ion exchange, and surface complexation
Gas dissolution and exsolution
Stable isotope fractionation
Radioactive decay
Mass Transport:
Advection
Molecular scale diffusion
Hydrodynamic dispersion
Colloid-facilitated transport
Heat transport:
Advection
Conduction
Convection
Medium deformation:
Compression or expansion of the domain
Fracture formation
Solving reactive transport models
Some of the simplest reactive transport problems can be solved analytically. Where equilibrium sorption is described by a linear distribution coefficient, for example, the sorbing solute's velocity is retarded relative to that of a nonreactive tracer; the relative velocities can be described with a retardation factor. Analytical solutions are exact solutions of the governing equations.
Complex reactive transport problems are more commonly solved numerically. In this case, the governing equations are approximated so that they can be solved by computer algorithms. The governing equations, including both reaction and transport terms, can be solved simultaneously using a one-step or global implicit simulator. This technique is straightforward conceptually, but computationally very difficult.
Instead of solving all the relevant equations together, the transport and chemical reaction equations can be solved separately. Operator splitting, as this technique is known, uses appropriate numerical techniques to solve the reaction and transport equations at each time step. Various methods exist, including the sequential non-iterative approach (SNIA), Strang splitting, and sequential iterative approach (SIA). Since the reaction and transport terms are handled separately, separate programs for batch reaction and transport can be linked together. Cross-linkable re-entrant software objects designed for this purpose readily enable construction of reactive transport models of any flow configuration.
Challenges
Reactive transport modeling requires input from numerous fields, including hydrology, geochemistry and biogeochemistry, microbiology, soil physics, and fluid dynamics. The numerical formulation and solution of reactive transport problems can be especially difficult due to errors arising in the coupling process, beyond those inherent to the individual processes. Valocchi and Malmstead (1992), for example, reported on the potential errors arising from the operator splitting technique.
Even in the absence of numerical difficulties, the general lack of knowledge available to practitioners creates uncertainty. Field sites are typically heterogeneous, both physically and chemically, and sampling is often sparse. The prevailing assumption of Fickian dispersion is often inadequate. Equilibrium constants and kinetic rate laws for relevant reactions are often poorly known. The complexity of many processes requires expertise in one or more of the aforementioned fields. Many processes, such as long-term nuclear waste storage, cannot be experimentally verified; reactive transport problems can only attempt to predict such long-term behavior. The current descriptions of multi-phase flow and mechanical deformation processes are still being developed.
Software programs in common use
PFLOTRAN*
ChemPlugin
MIN3P
CHESS, HYTEC
CrunchFlow
The Geochemist's Workbench
HYDROGEOCHEM
THMC
PHREEQC,
PHAST
Reaktoro
TOUGHREACT
OpenGeoSys
PHT3D
PNBRNS
HP1 / HP2
See also
Chemical thermodynamics
Chemical kinetics
Geochemistry
Geomicrobiology
Hydrogeology
Groundwater model
Geochemical modeling
Reservoir simulation
Chemical process modeling
Chemical transport model
References
Further reading
Appelo, C.A.J. and D. Postma, 2005, Geochemistry, Groundwater, and Pollution. Taylor & Francis, 683 pp.
Bethke, C.M., 2008, Geochemical and Biogeochemical Reaction Modeling. Cambridge University Press, 547 pp.
Lichtner, P.C., C.I. Steefel, and E.H. Oelkers (eds.), 1996, Reactive Transport in Porous Media. Reviews in Mineralogy 34, 438 pp.
Merkel, B.J., B. Planer-Friedrich, and D.K. Nordstrom, 2008, Groundwater Geochemistry: A Practical Guide to Modeling of Natural and Contaminated Aquatic Systems. Springer, 242 pp.
Zhang, F., G.T. Yeh, and J.C. Parker (eds.), 2012, Groundwater Reactive Transport Models. Behtham Publishers, 254 pp.
Zhu, C. and G. Anderson, 2002, Environmental Applications of Geochemical Modeling. Cambridge University Press, 300 pp.
Geologic modelling
Geochemistry
Transport phenomena | Reactive transport modeling in porous media | [
"Physics",
"Chemistry",
"Engineering"
] | 1,680 | [
"Transport phenomena",
"Chemical engineering",
"Physical phenomena",
"nan"
] |
36,313,540 | https://en.wikipedia.org/wiki/Proton%20spin%20crisis | The proton spin crisis (or proton spin puzzle) is a theoretical crisis precipitated by a 1987 experiment by the European Muon Collaboration (EMC),
which tried to determine the distribution of spin within the proton.
Physicists expected that the quarks carry all a proton's spin. However, not only was the total proton spin carried by quarks far smaller than 100%, these results were consistent with almost zero (4–24%) proton spin being carried by quarks. This surprising and puzzling result was termed the "proton spin crisis".
The problem is considered one of the important unsolved problems in physics.
Background
A key question is how the nucleons' spins are distributed amongst their constituent parts ("partons": quarks and gluons). Components of proton's spin are expectation values of individual sources of angular momentum. These values depend on the renormalization scale, because their operators are not separately conserved.
Physicists originally expected that valence quarks would carry all of the nucleon spin.
A proton is built from three valence quarks (two up quarks and one down quark), virtual gluons, and virtual (or sea) quarks and antiquarks (virtual particles do not influence the proton's quantum numbers). The ruling hypothesis was that since the proton is stable, it exists in the lowest possible energy level. Therefore, it was expected that the quark's wave function is the spherically symmetric s-wave with no spatial contribution to angular momentum. The proton is, like each of its quarks, a spin- particle (a fermion). Therefore, it was hypothesized that two of the quarks would have their spins parallel and the third quark would have its spin antiparallel to that of the proton.
The experiment
In this EMC experiment, a quark of a polarized proton target was hit by a polarized muon beam, and the quark's instantaneous spin was measured. In a polarized proton target, all the protons' spins take the same direction, and therefore it was expected that the spin of two out of the three quarks cancels out and the spin of the third quark is polarized in the direction of the proton's spin. Thus, the sum of the quarks' spin was expected to be equal to the proton's spin.
Instead, the experiment found that the number of quarks with spin in the proton's spin direction was almost the same as the number of quarks whose spin was in the opposite direction. This is the proton spin crisis. Similar results have been obtained in later experiments.
Subsequent work
A paper published in 2008 showed that more than half of the spin of the proton comes from the spin of its quarks, and that the missing spin is produced by the quarks' orbital angular momentum.
This work used relativistic effects together with other quantum chromodynamic properties and explained how they boil down to an overall spatial angular momentum that is consistent with the experimental data. A 2013 paper showed how to calculate the gluon helicity contribution using lattice QCD.
According to physicist Xiangdong Ji in 2017, Lattice QCD shows "the theoretical expectation on the fraction of the nucleon spin carried in quark spin is about 30%. Thus there is no substantial discrepancy between the fundamental theory and data."
Monte Carlo calculations have shown that 50% of the proton spin comes from gluon polarization.
Results from the RHIC, published in 2016, indicate that gluons may carry even more of protons' spin than quarks do.
However, in 2018 lattice QCD calculations indicated that it is the quark orbital angular momentum that is the dominant contribution to the nucleon spin.
In a 2022 AAPPS Bulletin, Keh-Fei Liu calculated that quark spin contributes about 40% of the angular momentum, quark orbital angular momentum contributes about 15%, and gluon orbital angular momentum contributes about 40%. Given various error bars on both theoretical calculations and on experiments, this too is consistent with the observed experimental quark spin contribution of around 30%.
References
External links
Proton
Unsolved problems in physics | Proton spin crisis | [
"Physics"
] | 891 | [
"Unsolved problems in physics"
] |
41,948,238 | https://en.wikipedia.org/wiki/Nurse%20scheduling%20problem | The nurse scheduling problem (NSP), also called the nurse rostering problem (NRP), is the operations research problem of finding an optimal way to assign nurses to shifts, typically with a set of hard constraints which all valid solutions must follow, and a set of soft constraints which define the relative quality of valid solutions. Solutions to the nurse scheduling problem can be applied to constrained scheduling problems in other fields.
While research on computer-assisted employee scheduling goes back to the 1950s, the nurse scheduling problem in its current form was introduced in two parallel publications in 1976. It is known to have NP-hard complexity.
General description
The nurse scheduling problem involves the assignment of shifts and holidays to nurses. Each nurse has their own wishes and restrictions, as does the hospital. The problem is described as finding a schedule that both respects the constraints of the nurses and fulfills the objectives of the hospital. Conventionally, a nurse can work 3 shifts because nursing is shift work:
day shift
night shift
late night shift
In this problem we must search for a solution satisfying as many wishes as possible while not compromising the needs of the hospital.
Constraints
There are two types of constraints:
hard constraints: if this constraint fails then the entire schedule is invalid.
soft constraints: it is desirable that these constraints are met but not meeting them does not make the schedule invalid.
Some examples of constraints are:
A nurse does not work the day shift, night shift and late night shift on the same day (i.e. no 24-hour duties).
A nurse may go on a holiday and will not work shifts during this time.
A nurse does not do a late night shift followed by a day shift the next day.
Two nurses dislike each other and thus cannot work on the same shift because of that.
One nurse is newly qualified and must be paired with an experienced nurse.
A shift requires a charge nurse.
Hard constraints typically include a specification of shifts (e.g. morning, afternoon, and night), that each nurse should work no more than one shift per day, and that all patients should have nursing coverage. Differences in qualifications between nurses also create hard constraints. Soft constraints may include minimum and maximum numbers of shifts assigned to a given nurse in a given week, of hours worked per week, of days worked consecutively, of days off consecutively, and so on. The shift preferences of individual nurses may be treated as a soft constraint, or as a hard constraint.
Solutions
Solutions to the problem use a variety of techniques, including both mathematically exact solutions and a variety of heuristic solutions using decomposition, parallel computing, stochastic optimization, genetic algorithms, colony optimization, simulated annealing, quantum annealing, Tabu search, and coordinate descent.
Burke et al. (2004) summarised the state of art of academic research to the nurse rostering problem, including brief introductions of various then published solutions.
See also
Assignment problem
Constraint programming
Employee scheduling software
References
External links
Why is Scheduling People Hard?
A free solver for nurse scheduling problem
Nursing informatics
Constraint programming
Time management
Optimal scheduling | Nurse scheduling problem | [
"Physics",
"Engineering"
] | 622 | [
"Physical quantities",
"Time",
"Optimal scheduling",
"Industrial engineering",
"Time management",
"Spacetime"
] |
23,558,865 | https://en.wikipedia.org/wiki/Baseflow%20residence%20time | Baseflow residence time (often mean baseflow residence time) is a parameter useful in describing the mixing of waters from the infiltration of precipitation and pre-event groundwater in a watershed. It describes the average amount of time that water within the transient water supply resides in a watershed. Many methods of determining baseflow residence time have been developed, mostly involving mathematical models using a convolution integral approach with isotopic or chemical data as the input. Other methods that do not require such extensive and expensive data collection include Brutsaert and Nieber, which uses aquifer parameters as inputs, and Vitvar et al., which uses the stream flow hydrograph to determine baseflow recession parameters.
See also
Baseflow
Hydrograph
Time of concentration
References
Hydrology | Baseflow residence time | [
"Chemistry",
"Engineering",
"Environmental_science"
] | 157 | [
"Hydrology",
"Environmental engineering"
] |
23,560,902 | https://en.wikipedia.org/wiki/T-26%20variants | More than 50 different modifications and experimental vehicles based on the T-26 light infantry tank chassis were developed in the USSR in the 1930s, with 23 modifications going into series production. The majority were armoured combat vehicles: flame tanks, artillery tractors, radio-controlled tanks (teletanks), military engineering vehicles, self-propelled guns and armoured personnel carriers. They were developed at the Leningrad Factory of Experimental Mechanical Engineering (from 1935 known as the Factory No. 185 named after S.M. Kirov) by talented Soviet engineers P.N. Syachentov, S.A. Ginzburg, L.S. Troyanov, N.V. Tseits, B.A. Andryhevich, M.P. Zigel and others. Many Soviet tank engineers were declared "enemies of the nation" and repressed during Stalin's Great Purge from the middle of the 1930s. As a result, work on self-propelled guns and armoured carriers ceased in the USSR during that time. T-26 light tanks were also modified into armoured combat vehicles in the field during wartime.
Flame-throwing (chemical) tanks
Flame-throwing tanks formed around 12 per cent of the series production of T-26 light tanks. It should be mentioned that the abbreviation "OT" (Ognemetniy Tank which stands for Flame-throwing Tank) appeared only in post-war literature; these tanks were originally called "KhT" (Khimicheskiy Tank which stands for Chemical Tank), or BKhM (Boevaya Khimicheskaya Mashina; Fighting Chemical Vehicle) in the documents of the 1930s. All chemical (flame-throwing) tanks based on the T-26 chassis (KhT-26, KhT-130, KhT-133) were designated BKhM-3. The vehicles were intended for area chemical contamination, smoke screens and for flame-throwing.
The TKhP-3 chemical equipment for smoke screens and chemical contamination was developed in 1932. This equipment could be easily installed on any T-26 light tank and was produced by the "Compressor" Factory, (introduced for smoke screening as the TDP-3 from summer 1934; 1,503 such sets were produced to the end of 1936).
KhT-26 (OT-26) — Flamethrower variant developed in 1933. Based on the twin-turreted T-26 mod. 1931 tank but using a single turret armed with a flamethrower, the second turret was removed.
KhT-130 (OT-130) — Flamethrower variant of model 1933, using a larger 45 mm gun turret (a gun was replaced with a flamethrower).
KhT-133 (OT-133) — Flamethrower variant of model 1939 (a gun was replaced with a flamethrower).
KhT-134 (OT-134) — Flamethrower variant of model 1939, with 45 mm gun intact and hull-mounted flamethrower. Prototype only.
Combat engineer vehicles
(ST stands for saperniy tank or "engineer tank") — engineer tank; a bridge-laying tank based on the twin-turreted T-26 mod. 1931 chassis. According to the "System of armoured engineering armament of the Red Army", the ST-26 was developed by designers from the Academy of Military Engineering (chief engineer of the project - Gutman) in the beginning of 1932. The ST-26 had only one shortened turret in the middle of the hull armed with a DT tank machine gun with 1,008 rounds; arc of fire was 211°. Special equipment consisted of a metal tracked bridge long and weighing , supports for the bridge (a front frame with two forks and two guiding rollers, lower forks with a hoisting mechanism and a roller, a rear frame with mounts and two rollers) and a cable winch (driven by the tank engine with the use of the reversing gear) inside the vehicle. The ST-26 was intended to provide for crossing of trenches and streams wide and barriers up to high by T-27, T-26 and BT light tanks: the bridge had a maximum load rating of . The bridge could be laid with the help of the cable winch in 25–40 seconds without crew exit; the raising operation took 2-3 min and a commander needed to come out from the vehicle in order to control the process. The ST-26 with its cable system for bridge laying was tested in the summer of 1932.
Additional variants of the ST-26 (with a sliding system of bridge laying and with a tipping system of bridge laying) were also tested from 1932. The first had a massive guide frame and a special boom (the bridge could be laid in 3 min 20 sec, the raise operation took 6-7 min), while the second was equipped with a special swinging-boom with a rack-and-pinion drive. All three variants of the ST-26 participated in military maneuvers of the Leningrad Military District in the summer of 1933; subsequently series production of the ST-26 with a cable system of bridge laying was begun as it proved to be more reliable and less complicated to maintain. The Defence Committee of the USSR ordered the production of 100 ST-26 to the end of 1933, but only 44 vehicles were assembled by the Factory No. 174 by 1934, and 20 in 1935. The delay was attributed to the manufacture of the metal bridges, carried out by the Gipstalmost Factory and several workshops using semi-handicraft techniques.
Specifications: weight - ; crew - 2 men (commander and driver); speed - ; range - .
The Armoured Engineering Section of the Red Army's Research Institute of Engineer Equipment (NIIIT RKKA) in co-operation with the Gipstalmost Factory developed an improved engineer tank at the end of 1936, with a lever hydraulic system of bridge laying (similar to the UST-26, see below) and a small turret of new design. The bridge could be laid in 45 sec and the raise operation took 1.5 min (both processes did not require crew exit). The vehicle was assembled by the Podolsk Machine Factory named after S. Ordzhonikidze in July 1937, and was successfully tested at the NIIIT Proving Ground (85 bridge layings were performed and 70 light tanks passed over the bridge). This ST-26 prototype was also tested at the Kubinka Tank Proving Ground, and participated in military exercises of the Leningrad Military District in 1938. A decision was made in 1939 to produce a batch of engineer tanks with the lever hydraulic system, but the Podolsk Machine Factory could assemble only one. The Stalingrad Tractor Factory probably also produced two such vehicles the same year.
An experimental multispan bridge was developed in 1934 which allowed for the coupling together of three or more ST-26 bridges, using special automatic grips in the end of each bridge section. The multispan bridge employed 250 kg metal columns high and was intended for crossings by T-26 and BT light tanks of water obstacles up to wide and deep. The launching of each bridge section took 20-30 min. The bridge had no development after testing.
Engineer Alexandrov from the Research and Technology Division of the Red Army's Engineer Directorate (NTO UNI RKKA) developed a wooden tracked bridge long. The bridge was mounted on standard T-26 light tanks as well as on ST-26 engineer tanks and could be laid in 30-60 sec without crew exit. Trials carried out in July–August 1934 were successful and 20 such bridges were issued to the armed forces.
Seventy-one ST-26 engineer tanks were produced in 1932–1939, including experimental vehicles: 65 ST-26 with a cable-laid bridge system, 1 ST-26 with a sliding bridge, 1 ST-26 with a tipping bridge, 2 UST-26 and 2 ST-26 with a levered bridge-laying system.
Ten ST-26 engineer tanks were used on the Karelian Isthmus during the Winter War (9 with a cable system and 1 with a lever system); they were included in engineer groups for obstacle clearing that were established in each tank brigade during the war. Three ST-26 tanks of the 35th Light Tank Brigade had the most success (in particular they launched two bridges over a trench and then an antitank ditch for a tank battalion during an assault on the fortified High Point 65.5 (Hottinen area) of the Mannerheim Line on February 18, 1940). The ST-26 with the lever system of bridge laying demonstrated good results and that vehicle was used quite actively during the Winter War, while tanks with the cable system were less reliable and had limited use. There were no losses of ST-26 engineer tanks during the Winter War.
Tank units of the Red Army had 57 ST-26 engineer tanks on June 1, 1941: 9 in the Far Eastern Front, 26 in the Moscow Military District, 2 in the Leningrad Military District, 2 in the Kiev Special Military District, 8 in the Western Special Military District, 1 in the Volga Military District, and 9 vehicles were in military supply depots. From those ST-26 engineer tanks only 12 were in good order, the others required repair.
(UST stands for usovershenstvovanniy saperniy tank or "improved engineer tank") - mod. 1936 was an improved version of the ST-26. Operation of the ST-26 engineer tanks had demonstrated their low reliability (frequent breaking of wire cables and bending of bridge supporting mounts), so the improved UST-26 was developed in 1936. The vehicle designers were the Red Army's Research Institute of Engineer Equipment (NIIIT RKKA) and the Gipstalmost Factory (engineers Vayson, Nemets and Markov). The UST-26 used a lever system of bridge laying with two levers and a hydraulic cylinder. The Factory No. 174 in co-operation with the Podolsk Machine Factory assembled two UST-26 in 1936. Trials performed in March 1936 showed the UST-26 was an improvement on the series-produced ST-26 (for example, the bridge raise operation did not require crew exit). Nevertheless, the UST-26 had its own disadvantages.
Remotely controlled tanks
TT-26 — Teletank
Self-propelled guns
SU-1 — Self-propelled gun armed with 76.2 mm regimental gun mod. 1927. The single fully armoured vehicle was built and tested in 1931.
AT-1 — Artillery tank (tank of artillery support) armed with 76.2 mm PS-3 or L-7 tank gun. Two fully armoured vehicles were built and tested in 1935, 10 AT-1 artillery tanks were planned to be built in 1936 but were cancelled (Izhora Works produced 8 armoured hulls for the program).
SU-5-1 — Self-propelled gun armed with the 76 mm divisional gun M1902/30 (open-top type, the single vehicle was built in 1934).
SU-5-2 — Self-propelled gun armed with 122 mm howitzer mod. 1910/30 (open-top type; a single vehicle was built in 1934 and a further 30 vehicles in 1936).
SU-5-3 — Self-propelled gun armed with 152.4 mm divisional mortar mod. 1931 (open-top type, a single vehicle was built in 1934).
SU-6 — Self-propelled gun armed with 76.2 mm 3K anti-aircraft gun (open-top type, a single vehicle was built in 1935 and 4 more vehicles armed with 37 mm anti-aircraft automatic gun were planned to be produced in 1936).
SU-T-26 (SU-26, later SU-76P) — Self-propelled gun of an open-top design armed with a 37 mm gun or a 76.2mm regimental gun mod. 1927. The Factory of Hoisting-and-Conveying Machinery named after S.M. Kirov (in Leningrad) built 14 vehicles in 1941: probably 2 with a 37 mm gun and 12 with a 76 mm gun.
Armoured transport vehicles
TR-4 — Armoured personnel carrier
TR-26 — Armoured personnel carrier
TR4-1 — Ammunition transportation vehicle
TB-26 — Ammunition transportation vehicle
T-26Ts — Fuel transportation vehicle
TTs-26 — Fuel transportation vehicle
Reconnaissance vehicles
(TN stands for tank nablyudeniya or "observation tank")
an experimental observation version based on the T-26T artillery tractor chassis and intended for reconnaissance of front lines and enemy firing-points; also for correction of artillery fire. Developed by the Design Office of the Military Supply Depot No. 37 in Moscow in September 1934. The single vehicle was built by the Factory No. 185 named after S.M. Kirov in Leningrad and tested with some success in 1935 (nevertheless, the further work was stopped). The TN had an armoured cabin instead of a tank turret, armed with a bow DT tank machine gun (4,980 rds.). Equipment consisted of a 71-TK-1 radio station with a hand-rail antenna around the cabin, a Zeiss optical rangefinder (with a 500 mm base length), a PTK tank commander panoramic sight, gyrocompass, course plotter, field dead-reckoning analyzer, predictor, map-board, SPVO signalling lamp and two UNAF telephones with a cable spool.
Specifications: weight - ; crew - 3 men; armour - ; speed - ; range - .
The TN, stored at the Factory No. 185, was subsequently rebuilt as the BSNP (bronirovanniy samokhodniy nablyudatel'niy punkt - "armoured self-propelled observation post"), developed by the Artillery Advanced Courses for Command Staff and the Research Institute No. 22 in 1939. The BSNP was equipped with a 71-TK radio station, an Invert optical rangefinder (with 700 mm base length), PTK tank commander panoramic sight, tank magnetic compass, PDN retractable periscope of long-range observation (with 10x optical magnification and 5° angle), two field telephones with two cable spools and a real-time course plotter developed by the Research Institute No. 22. The vehicle was tested in summer 1939 at the Luga Artillery Proving Ground. The inspection commission came to the conclusion that the BSNP was a very useful vehicle for artillery general-purpose reconnaissance and for co-ordination of artillery with tank and infantry units on the battlefield, but that the quality of equipment and its installation was not a successful use of the vehicle. It was recommended to improve the vehicle but all further work was stopped.
(FT stands for foto tank or "photo tank")
An experimental reconnaissance vehicle based on the T-26 mod. 1933 tank chassis, the T-26FT was intended for filming and photography of enemy defensive positions (both at a halt and while on the move). The T-26FT had the usual cylindrical tank turret with a hand-rail antenna, but the 45 mm gun was removed (replaced with a dummy wooden gun); armament consisted of the DT tank machine gun (441 rds.) only. On the left side of the turret two small holes (80 mm in diameter) with electrically driven armoured lids were fitted for camera lenses. There were two special compartments inside the vehicle: one for filming and photography (equipped with a Kinamo heavy semi-automatic photographic camera, a motion-picture camera, a periscope synchronized with both cameras and a radio station), and one for photographic development (equipped with an Anschütz gyrocompass navigation device, magnifier and developing apparatus). The crew consisted of 3 men (a driver and two camera operators). The single vehicle was built by the Military Supply Depot No. 37 in Moscow in 1937 and tested at the Kubinka Tank Proving Ground in January–February 1938. The vehicle had no further development.
Artillery tractors
(T stands for tyagach or "prime mover", "tractor") — armoured artillery tractor based on the T-26 chassis. Two unarmed variants were developed in 1932 according to the "Program of tank, tractor and armoured car armament of the RKKA": one with a canvas cover designed by the Artillery Design Office of the Bolshevik Factory (some sources mention this vehicle as the T-26T2) and one with an armoured cabin designed by the Artillery Academy. The canvas cover had celluloid windows along the perimeter. The armoured cabin had a double-wing driver hatch in the front, two hatches on the roof and lookout hatches on the sides and rear (some vehicles did not have the rear hatches). T-26T artillery tractors had riveted or welded hulls (late models). The vehicle was equipped with a special towing device for towing 76.2 mm divisional guns, 122–152 mm howitzers and trailers up to weight.
Specifications: weight - ; crew - 1 (driver) + 4-5 (gun crew or landing party); armour - ; speed - , with a 5-t trailer; range - with a 5-t trailer.
One hundred and eighty three T-26T were produced in 1933. Fourteen more with a high-powered engine and improved towing device were produced in 1936 (including 10 with an armoured cabin). The manufacturer was the Factory No. 174 named after K.E. Voroshilov in Leningrad (a plan to produce 200 T-26T with a canvas cover and 150 T-26T with an armoured cabin annually was not carried out due to increases in tank production). Tests and army service showed that T-26T artillery tractors were underpowered for cross-country towing of trailers weighing more than , so these vehicles had no further development. Also around 20 T-26 light tanks of early models were converted into artillery tractors by army units in 1937–1939. A transfer of overhauled old twin-turreted T-26 tanks (without turrets and armament) from some tank units of western military districts for use as artillery tractors for anti-tank and regimental guns in mechanized corps began in May 1941.
Tank and mechanized infantry units of the Red Army had 211 artillery tractors based on the T-26 chassis on June 1, 1941. Almost all T-26T artillery tractors of border and some inner military districts were lost during the first weeks of the Great Patriotic War. A few remained in front-line service until 1942 at least (for example, the 150th Tank Brigade of the Bryansk Front had a T-26T with an armoured cabin on May 15, 1942, which was used as a command vehicle).
No less than 50 old twin-turreted T-26 tanks of the Transbaikal Military District were converted into artillery tractors from 1941; these vehicles participated in combat with the Japanese Kwantung Army in August 1945.
Armoured carriers
. In early 1933, a prototype of armoured personnel carrier for mechanized units based on the T-26 chassis was manufactured according to the "Program of tank, tractor and armoured car armament of the RKKA". The TR-1 armoured personnel carrier was developed by students of the Military Academy of Mechanization and Motorization named after I. Stalin, and produced at the Leningrad Factory of Experimental Mechanical Engineering. An engine ( Hercules) and transmission were located at the front of the vehicle, and an armoured cabin for infantrymen, equipped with a rear door and six portholes in side walls, was located in the rear. The TR-1 was an unarmed vehicle. In August–October 1933 this armoured personnel carrier has passed extensive tests at Kubinka proving ground.
Specifications: full weight - ; crew - 2 (driver and commander) + 14 men (landing party); armour - .
Series production
Around 1,701 armoured combat vehicles based on the T-26 chassis were produced in the USSR from 1932 till 1941.
1Delivered to customer in 1933
2Prototypes
3Teletanks and control tanks of all types
4Prototypes of SU-5-1, SU-5-2, SU-5-3
5Produced in Leningrad at the "Factory of Carrying-and-conveying Machines named after S. Kirov"
Vehicle-mounted engineer equipment
Many different attached implements for the T-26 light tank were developed in the USSR in the 1930s. Among these were mine sweeps, equipment for swimming, snorkels for deep fording, wooden and brushwood fascines for trench crossing, special extra-wide swamp tracks and mats, wire cutters, dozer blades and many others. All of them were tested but despite often excellent test results none (except some mine sweeps) passed into army service.
Tank mine sweeps. Several mine sweeps of different designs for the T-26 and ST-26 (minus its bridge) tanks were developed in the USSR, but none of them were passed into army service. Three models of mine plows (suspended from a front frame, operated with a hand cable winch and with special blades) were tested in 1932–1934. Trials showed very poor performance of such types of mine-sweep on compacted soil or scrubby land. The much more successful KMT-26 mine roller (weight 1.55 t, mine-sweeping speed 6–8 km/h, able to absorb up to 3 anti-tank mine explosions) was developed and tested in July 1934; three such mine-exploding rollers were produced. An experimental mine flail was tested in August–September 1939 also. Mine sweeps could be mounted on T-26 or ST-26 tanks in 1.5 hours and jettisoned without crew exit if necessary.
Design work started again when the Winter War began: Leningrad factories Kirov Factory, Factory No. 185 and Factory No. 174 developed new models of mine sweeps for the T-26 and T-28 tanks in December 1939. Kirov Factory produced 93 new mine sweeps and Factory No. 174 produced an additional 49. These disc mine sweeps (metal discs 700–900 mm in diameter with a thickness of 10–25 mm on a common axis; the weight of the whole construction was 1,800-3,000 kg) were issued to army field forces in February and March 1940. Despite low explosion resistance (the discs would bend after the first mine explosion), these mine sweeps were used successfully by the 35th tank brigade and tank battalions of the 8th Army during the Winter War.
Fascines. Three types of remotely released large fascines (brushwood, wooden and a canvas bag stuffed with straw) for trench crossing were developed for the T-26 and the ST-26 in 1937–1939. These fascines made possible the crossing of trenches and antitank ditches 3.5 m wide and 1.2 m deep. Only ten sets of wooden fascines were produced. The fascines somewhat restricted the field of fire of the main gun.
Wire cutters. Factory No. 174 developed special wire cutters for T-26 tanks in 1940. The automatically operated TN-3 tank wire cutters were intended for breaching enemy wire obstacles. They were located on the rear of the vehicle over the tank tracks, cutting off wire caught in the tracks. Trials performed in October 1940 in Kubinka proving ground demonstrated that the design needed improvement.
Snowplow. The ST-26 engineer tank with a mounted snowplow from the Ya-5 truck was tested in Kubinka proving ground in 1933. In 1935 a special tank snowplow for the ST-26 was developed for clearing roads of 3 m width, in snow up to 1.2 m deep. The snowplow could be mounted on the ST-26 in 15 min. It was officially passed into army service but follow-up trials indicated that it could not clear even 0.6-0.8 m deep snow.
Other equipment. Between 1934 and 1940 the following equipment for the T-26 tank was developed and tested: brushwood mats and wooden planks for swamp crossing, special water/bog tracks (of 520 mm width), automatic coupling equipment for two tanks intended for crossing trenches of 3.8-4.2 m width, an implement for destroying antitank teeth and road-blocks, a magnetic mine detector, different track grousers.
Notes
References
Subscription index in the Rospechat Catalogue 73474.
Zaloga, Steven J., James Grandsen (1984). Soviet Tanks and Combat Vehicles of World War Two. London: Arms and Armour Press. .
External links
T-26T prime movers , photos of T-26T artillery tractors
ST-26 engineer tanks, photos of ST-26 engineer tanks (bridge-laying tanks)
Interwar tanks of the Soviet Union
World War II tanks of the Soviet Union
History of the tank
Soviet chemical weapons program
Chemical weapon delivery systems
ru:ХТ-26 | T-26 variants | [
"Chemistry"
] | 5,115 | [
"Chemical weapon delivery systems",
"Chemical weapons"
] |
31,121,915 | https://en.wikipedia.org/wiki/Discontinuity%20%28geotechnical%20engineering%29 | In geotechnical engineering, a discontinuity (often referred to as a joint) is a plane or surface that marks a change in physical or chemical characteristics in a soil or rock mass. A discontinuity can be, for example, a bedding, schistosity, foliation, joint, cleavage, fracture, fissure, crack, or fault plane. A division is made between mechanical and integral discontinuities. Discontinuities may occur multiple times with broadly the same mechanical characteristics in a discontinuity set, or may be a single discontinuity. A discontinuity makes a soil or rock mass anisotropic.
Mechanical
A mechanical discontinuity is a plane of physical weakness where the tensile strength perpendicular to the discontinuity or the shear strength along the discontinuity is lower than that of the surrounding soil or rock material.
Integral
An integral discontinuity is a discontinuity that is as strong as the surrounding soil or rock material. Integral discontinuities can change into mechanical discontinuities due to physical or chemical processes (e.g. weathering) that change the mechanical characteristics of the discontinuity.
Set or family
Various geological processes create discontinuities at a broadly regular spacing. For example, bedding planes are the result of a repeated sedimentation cycle with a change of sedimentation material or change in structure and texture of the sediment at regular intervals, folding creates joints at regular separations to allow for shrinkage or expansion of the rock material, etc. Normally discontinuities with the same origin have broadly the same characteristics in terms of shear strength, spacing between discontinuities, roughness, infill, etc. The orientations of discontinuities with the same origin are related to the process that has created them and to the geological history of the rock mass. A discontinuity set or family denotes a series of discontinuities for which the geological origin (history, etc.), the orientation, spacing, and the mechanical characteristics (shear strength, roughness, infill material, etc.) are broadly the same.
Single
A discontinuity may exist as a single feature (e.g. fault, isolated joint or fracture) and in some circumstances, a discontinuity is treated as a single discontinuity although it belongs to a discontinuity set, in particular if the spacing is very wide compared to the size of the engineering application or to the size of the geotechnical unit.
Characterization
Various international standards exist to describe and characterize discontinuities in geomechanical terms, such as ISO 14689-1:2003 and ISRM.
See also
Asperity (geotechnical engineering)
Exfoliating granite
Persistence (discontinuity)
Rock mass classification
Rock mechanics
Shear strength (discontinuity)
Sliding criterion (geotechnical engineering)
Tilt test (geotechnical engineering)
References
Further reading
Soil mechanics
Mining engineering
Rock mechanics | Discontinuity (geotechnical engineering) | [
"Physics",
"Engineering"
] | 630 | [
"Soil mechanics",
"Mining engineering",
"Applied and interdisciplinary physics"
] |
31,122,086 | https://en.wikipedia.org/wiki/Polysilazane | In organosilicon chemistry, polysilazanes are polymers in which silicon and nitrogen atoms alternate to form the basic backbone (). Since each silicon atom is bound to two separate nitrogen atoms and each nitrogen atom to two silicon atoms, both chains and rings of the formula occur. R can be hydrogen atoms or organic substituents. If all substituents R are hydrogen atoms, the polymer is designated as perhydropolysilazane, polyperhydridosilazane, or inorganic polysilazane . If hydrocarbon substituents are bound to the silicon atoms, the polymers are designated as Organopolysilazanes. Molecularly, polysilazanes are isoelectronic with and close relatives to polysiloxanes (silicones).
History
The synthesis of polyorganosilazanes was first described in 1964 by Krüger and Rochow. By reacting ammonia with chlorosilanes (ammonolysis), trimeric or tetrameric cyclosilazanes were formed initially and further reacted at high temperatures with a catalyst to yield higher molecular weight polymers. Ammonolysis of chlorosilanes still represents the most important synthetic pathway to polysilazanes. The industrial manufacture of chlorosilanes using the Müller-Rochow process, first reported in the 1940s, served as the cornerstone for the development of silazane chemistry. In the 1960s, the first attempts to transform organosilicon polymers into quasi-ceramic materials were described. At this time, suitable (“pre-ceramic”) polymers heated to 1000 °C or higher were shown to split off organic groups and hydrogen and, in the process, the molecular network is rearranged to form amorphous inorganic materials that show both unique chemical and physical properties. Using polymer derived ceramics (PDCs), new application areas can be opened, especially in the area of high performance materials. The most important pre-ceramic polymers are polysilanes , polycarbosilanes , polysiloxanes and polysilazanes .
Structure
Like all polymers, polysilazanes are built from one or several basic monomer units. Linking together of these basic units can result in polymeric chains, rings or three-dimensionally crosslinked macromolecules with a wide range of molecular mass. While the monomer unit describes the chemical composition and the connectivity of the atoms (coordination sphere) it does not illustrate the macro-molecular structure.
In polysilazanes, each silicon atom is bound to two nitrogen atoms and each nitrogen atom to at least two silicon atoms (three bonds to silicon atoms are also possible). If all remaining bonds are with hydrogen atoms, perhydropolysilazane results (proposed structure is shown to the right). In organopolysilazanes, at least one organic substituent is bound to the silicon atom. The amount and type of organic substituents have a predominant influence on the macro-molecular structure of polysilazanes.
Silazane copolymers are normally produced from ammonolyses of chlorosilane mixtures. In this chemical reaction, different chlorosilanes react at similar rates so that the monomers are statistically distributed in the copolymer.
Preparation
Ammonia and chlorosilanes, both readily available and low-priced, are used as starting materials in the synthesis of polysilazanes. In the ammonolysis reaction, large quantities of ammonium chloride are produced and must be removed from the reaction mixture.
In the laboratory, the reaction is normally carried out in a dry organic solvent (polysilazanes decompose in the presence of water or moisture) and the ammonium chloride is removed by filtration from the reaction mass. Because the filtration step is both time-consuming and cost-intensive, several production methods were developed in which no solid materials are formed during the final reaction step.
The liquid-ammonia-procedure was developed by Commodore/KiON for polysilazane synthesis. It calls for adding chlorosilane or chlorosilane mixtures simultaneously to an excess of liquid ammonia. The resulting ammonium chloride dissolves in the liquid ammonia and phase separates from the polysilazane. Two immiscible liquids form. This allows for the simple isolation of pure polysilazane from the liquid ammonia/ammonium chloride solution. The patented procedure is used today by Merck KGaA, formerly AZ Electronic Materials in the manufacture of polysilazanes.
Previously, Hoechst AG manufactured VT 50 and ET 70 (now discontinued) as polysilsesquiazane solutions. Synthesis took place in two steps: first a trichlorosilane was reacted with dimethylamine and the resulting monomeric aminosilane was separated from dimethylammoniumchloride. In a subsequent salt-free step, the aminosilane was treated with ammonia to afford a polymer solution.
If hexamethyldisilazane (HMDS) is used as a nitrogen source instead of ammonia, transamination takes place. The chlorine atoms liberated from the chlorosilane are tied to the trimethylsilyl groups of HMDS so that no chlorine-containing solid salts are formed. This procedure was used by Dow Corning to manufacture the hydridopolysilazane HPZ.
Numerous additional procedures for the synthesis of Si–N based polymers have been described in the literature (for example a dehydrogenation coupling between Si–H and N–H or ring-opening polymerizations) but none are currently employed commercially.
For the industrial manufacture of perhydropolysilazane , ammonolysis in a solvent is the standard process. Although this results in a higher price, the material is routinely used as a coating in the electronics industry due to its special properties (insulating effect in thin layers). The product is available in different solvents as 20% solutions.
Nomenclature
Silicon-nitrogen compounds with alternating silicon- ("sila") and nitrogen atoms ("aza") are designated as silazanes. Simple examples of silazanes are disilazane and hexamethyldisilazane . If only one silicon atom is bound to the nitrogen atom, the materials are known as silylamines or aminosilanes (for example triethylsilylamine ). If three silicon atoms are bound to each nitrogen atom, the materials are called silsesquiazanes. Small ring-shaped molecules with a basic network of Si-N are named cyclosilazanes (for example cyclotrisilazane ). In contrast to this, polysilazanes are silazane polymers consisting of both large chains and rings showing a range of molecular masses. A polymer with the general formula is designated as poly(dimethylsilazane). According to the IUPAC rules for the designation of linear organic polymers, the compound would actually be named poly[aza(dimethylsilylene)], and according to the preliminary rules for inorganic macromolecules catena-poly[(dimethylsilicon)-m-aza]. The labels normally used to describe the structure of silicones (M, D, T, and Q) are rarely employed for polysilazanes.
Characteristics
Polysilazanes are colorless to pale yellow liquids or solid materials. Conditional of manufacturing, the liquids often contain dissolved ammonia that can be detected by smell. The average molecular weight can range from a few thousand to approximately 100,000 g/mol while the density normally lies around 1 g/cm3. The state of aggregation and the viscosity are both dependent on the molecular mass and the molecular macrostructure. Solid polysilazanes are produced by chemical conversion of the liquid materials (crosslinking of smaller molecules). The solid materials can be fusible or unmeltable and can be soluble or insoluble in organic solvents. As a rule, polysilazane solids behave as thermosetting polymers, but in some cases, thermoplastic processing is possible.
After the synthesis, an aging process frequently takes place in which dissolved ammonia plays an important role. The groups resulting from the ammonolysis reaction form silazane units by splitting off ammonia. If ammonia can not escape, the silazane units can be split again into groups. Therefore, frequent venting of ammonia can lead to an increase in molecular mass. Also, functional groups that are not bound directly into the polymer backbone can react under suitable conditions (for example Si–H with N–H groups) and increase crosslinking of the rings and chains. An increase in molecular weight can also be observed during storage at higher temperatures or in sunlight.
With contact to water or moisture, polysilazanes decompose more or less quickly. Water molecules attack the silicon atom and the Si–N bond is cleaved. The forms and which can further react (condensation) to form (siloxanes). The rate of the reaction with water (or other OH containing materials like alcohols) depends on the molecular structure of the polysilazanes and the substituents. Perhydropolysilazane will decompose very quickly and exothermically with contact to water while polysilazanes with large substituents react very slowly.
Polysilazanes are not vaporizable because of strong intermolecular forces. Heating polysilazanes results in crosslinking to form higher molecular weight polymers. At temperatures of 100-300 °C, further crosslinking of the molecules takes place with evolution of hydrogen and ammonia. If the polysilazane contains further functional groups such as vinyl units, additional reactions can take place. In general, liquid materials will be converted to solids as the temperature increases. At 400-700 °C, the organic groups decompose with the evolution of small hydrocarbon molecules, ammonia and hydrogen. Between 700 and 1200 °C a three-dimensional amorphous network develops containing Si, C and N ("SiCN ceramics") with a density of ca. 2 g/cm3. A further temperature increase can result in crystallization of the amorphous material and the formation of silicon nitride, silicon carbide and carbon. This so-called pyrolysis of the polysilazanes produces ceramic materials from low-viscosity liquids with very high yield (up to 90%). Due to the organic groups that are often used to give good polymer processability, ceramic yield is normally in the range of 60-80%.
Applications
For a long time polysilazanes have been synthesized and characterized, and their great potential for many applications was acknowledged. However, up to now, very few products have been developed into a marketable commodity. The development effort for these rather expensive chemicals is relatively high because of changing commercial availability among other things. Nevertheless, for some applications, polysilazanes proved to be competitive products.
Taking advantage of their reaction with moisture and polar surfaces, polysilazanes are used as coating materials. Many metals, glass, ceramics or plastics with OH groups on the surface are easily wetted by polysilazanes. Reaction of Si–N with OH leads to the formation of Si–O–metal bonds generating good adhesion of the coating to the substrate. The “free” surface of the coating can react with humidity thereby creating a siloxane-like structure with excellent “easy to clean” properties. TutoProm, an organopolysilazane-based product, is used by Deutsche Bahn on their carriages as an anti-graffiti coating. Beyond that, organopolysilazanes can be applied as high temperature coatings or anti-corrosion varnishes.
The inorganic perhydropolysilazane can be used in a similar way. Curing in air yields a carbon-free amorphous coating of . Compared to organopolysilazane-derived materials, these coatings are less flexible but very smooth and dense. They show excellent barrier properties (against water vapor or oxygen) and a low electrical conductivity. This makes them suitable candidates for different application in electronics or solar industry.
Polysilazanes can be used as or in combination with synthetic resins. First experiments on specially treated components have shown that thermally cured materials can withstand temperatures of 400 - 600 °C. Most plastics are not applicable in this temperature range. The resins will be used for the fabrication of non-combustible fiber-reinforced composites.
Polysilazanes are suitable precursors for ceramic materials. Since most ceramic materials are produced by powder processing and sintering, near net shape forming is very difficult for complex components. With the aid of organic binders added to ceramic powders, injection molding or other casting techniques are possible, but removal of the organics (“debinding”) is expensive and results in fragile “white bodies” which are difficult to handle and shrink significantly during sintering. Pre-ceramic polymers can replace these organic binders. After compounding, casting and curing, the thermoset material can be pyrolyzed in one step to give a ceramic component in high yield. However, this application is still in its infancy in the civilian area.
Physical and chemical properties of pre-ceramic polymers can be varied in a wide range by chemical modifications. This is crucial for the production of ceramic fibers, an important topic both at universities and in industrial research. Silicon carbide fibers made from polycarbosilanes were the first to be used for reinforcement of ceramic matrix composites. The production of silicon nitride fibers from perhydropolysilazane was described by Tonen Corp. at the end of the 1980s. Dow Corning modified the HPZ polymer as a precursor for SiCN fibers, and Hoechst AG did successful experiments with VT50. More recently, G. Singh at Kansas State University demonstrated synthesis of boron-modified polysilazane for synthesis of Si(B)CN functionalized carbon nanotubes, which were stable in air up to 1000 C. The PDC-CNT composites are being explored for applications such as damage resistant coatings for high power laser thermal detectors as well as Li-ion battery anodes.
References
Inorganic polymers
Silicon compounds
Nitrogen compounds | Polysilazane | [
"Chemistry"
] | 3,010 | [
"Inorganic polymers",
"Inorganic compounds"
] |
31,122,751 | https://en.wikipedia.org/wiki/C13H12O8 | {{DISPLAYTITLE:C13H12O8}}
The molecular formula C13H12O8 (molar mass: 296.23 g/mol, exact mass: 296.0532 u) may refer to:
Caffeoylmalic acid
Coutaric acid
Molecular formulas | C13H12O8 | [
"Physics",
"Chemistry"
] | 63 | [
"Molecules",
"Set index articles on molecular formulas",
"Isomerism",
"Molecular formulas",
"Matter"
] |
31,122,867 | https://en.wikipedia.org/wiki/Speech%20interference%20level | Speech Interference Level (SIL) is an acoustical parameter calculated from sound pressure levels measured in octave bands. It is used to characterize a noise signal in the frequency range where the human ear has its highest sensitivity.
The Speech Interference Level is calculated as the arithmetic mean of unweighted sound pressure levels in three or four octave bands in the 500 Hz - 4 kHz frequency range
Several variants of the Speech Interference Level are in use:
PSIL: Arithmetic mean of 500 Hz, 1 kHz and 2 kHz octave bands
SIL3: Arithmetic mean of 1 kHz, 2 kHz and 4 kHz octave bands
SIL4: Arithmetic mean of 500 Hz, 1 kHz, 2 kHz and 4 kHz octave bands
External links
Speech Interference Levels in Aircraft Interior Noise Measurement
Sound Metrics: Speech Interference Level, Siemens Knowledge article (2019)
Sound measurements | Speech interference level | [
"Physics",
"Mathematics"
] | 168 | [
"Quantity",
"Sound measurements",
"Physical quantities"
] |
31,124,187 | https://en.wikipedia.org/wiki/Metal%20ions%20in%20aqueous%20solution | A metal ion in aqueous solution or aqua ion is a cation, dissolved in water, of chemical formula [M(H2O)n]z+. The solvation number, n, determined by a variety of experimental methods is 4 for Li+ and Be2+ and 6 for most elements in periods 3 and 4 of the periodic table. Lanthanide and actinide aqua ions have higher solvation numbers (often 8 to 9), with the highest known being 11 for Ac3+. The strength of the bonds between the metal ion and water molecules in the primary solvation shell increases with the electrical charge, z, on the metal ion and decreases as its ionic radius, r, increases. Aqua ions are subject to hydrolysis. The logarithm of the first hydrolysis constant is proportional to z2/r for most aqua ions.
The aqua ion is associated, through hydrogen bonding with other water molecules in a secondary solvation shell. Water molecules in the first hydration shell exchange with molecules in the second solvation shell and molecules in the bulk liquid. The residence time of a molecule in the first shell varies among the chemical elements from about 100 picoseconds to more than 200 years. Aqua ions are prominent in electrochemistry.
Introduction to metal aqua ions
{| class=wikitable style=text-align:center
|+Elements that form aqua cations
|-
| H || colspan=30 |
|
|-
| Li|| Be ||colspan=24|
|| || || || || ||
|-
| Na|| Mg ||colspan=24|
| Al
|| || || || ||
|-
| K|| Ca|| colspan=14|
|Sc||Ti||V||Cr||Mn||Fe||Co||Ni||Cu
|Zn||Ga ||Ge*|| || || ||
|-
| Rb|| Sr|| colspan=14|
||Y||Zr||||Mo||||Ru||Rh||Pd||Ag
|Cd||In||Sn||Sb*
|| || ||
|-
|Cs|| Ba|| La
|Ce||Pr||Nd|| Pm ||Sm||Eu||Gd||Tb||Dy||Ho||Er||Tm||Yb||Lu
|Hf||||||||||Ir||Pt||Au
|Hg||Tl||Pb||Bi||Po*||At*
||
|-
|Fr*||Ra*||Ac
| Th||Pa||U||Np||Pu
|Am||Cm||Bk
|Cf||Es*||Fm*||Md*||No*||Lr*||||||||||||||||||||||||||||||
|}
* No experimental information regarding aqua ion structures
Most chemical elements are metallic. Compounds of the metallic elements usually form simple aqua ions with the formula [M(H2O)n]z+ in low oxidation states. With the higher oxidation states the simple aqua ions dissociate losing hydrogen ions to yield complexes that contain both water molecules and hydroxide or oxide ions, such as the vanadium(IV) species [VO(H2O)5]2+. In the highest oxidation states only oxyanions, such as the permanganate(VII) ion, , are known. A few metallic elements that are commonly found only in high oxidation states, such as niobium and tantalum, are not known to form aqua cations; near the metal–nonmetal boundary, arsenic and tellurium are only known as hydrolysed species. Some elements, such as tin and antimony, are clearly metals, but form only covalent compounds in the highest oxidation states: their aqua cations are restricted to their lower oxidation states. Germanium is a semiconductor rather than a metal, but appears to form an aqua cation; similarly, hydrogen forms an aqua cation like metals, despite being a gas. The transactinides have been greyed out due to a lack of experimental data. For some highly radioactive elements, experimental chemistry has been done, and aqua cations may have been formed, but no experimental information is available regarding the structure of those putative aqua ions.
In aqueous solution the water molecules directly attached to the metal ion are said to belong to the first coordination sphere, also known as the first, or primary, solvation shell. The bond between a water molecule and the metal ion is a dative covalent bond, with the oxygen atom donating both electrons to the bond. Each coordinated water molecule may be attached by hydrogen bonds to other water molecules. The latter are said to reside in the second coordination sphere. The second coordination sphere is not a well defined entity for ions with charge 1 or 2. In dilute solutions it merges into the water structure in which there is an irregular network of hydrogen bonds between water molecules. With tripositive ions the high charge on the cation polarizes the water molecules in the first solvation shell to such an extent that they form strong enough hydrogen bonds with molecules in the second shell to form a more stable entity.
The strength of the metal-oxygen bond can be estimated in various ways. The hydration enthalpy, though based indirectly on experimental measurements, is the most reliable measure. The scale of values is based on an arbitrarily chosen zero, but this does not affect differences between the values for two metals. Other measures include the M–O vibration frequency and the M–O bond length. The strength of the M-O bond tends to increase with the charge and decrease as the size of the metal ion increases. In fact there is a very good linear correlation between hydration enthalpy and the ratio of charge squared to ionic radius, z2/r. For ions in solution Shannon's "effective ionic radius" is the measure most often used.
Water molecules in the first and second solvation shells can exchange places. The rate of exchange varies enormously, depending on the metal and its oxidation state. Metal aqua ions are always accompanied in solution by solvated anions, but much less is known about anion solvation than about cation solvation.
Understanding of the nature of aqua ions is helped by having information on the nature of solvated cations in mixed solvents and non-aqueous solvents, such as liquid ammonia, methanol, dimethyl formamide and dimethyl sulfoxide to mention a few.
Occurrence in nature
Aqua ions are present in most natural waters. Na+, K+, Mg2+ and Ca2+ are major constituents of seawater.
{| class="wikitable" style=text-align:center
|+ Aqua ions in seawater (salinity = 35)
|-
! Ion
|
|
|
|
|-
!Concentration (mol kg−1)
| 0.469
| 0.0102
| 0.0528
| 0.0103
|}
Many other aqua ions are present in seawater in concentrations ranging from ppm to ppt. The concentrations of sodium, potassium, magnesium and calcium in blood are similar to those of seawater. Blood also has lower concentrations of essential elements such as iron and zinc. Sports drink is designed to be isotonic and also contains the minerals which are lost in perspiration.
Magnesium and calcium ions are common constituents of domestic water and are responsible for permanent and temporary hardness, respectively. They are often found in mineral water.
Experimental methods
Information obtained on the nature of ions in solution varies with the nature of the experimental method used. Some methods reveal properties of the cation directly, others reveal properties that depend on both cation and anion. Some methods supply information of a static nature, a kind of snapshot of average properties, others give information about the dynamics of the solution.
Nuclear magnetic resonance (NMR)
Ions for which the water-exchange rate is slow on the NMR time-scale give separate peaks for molecules in the first solvation shell and for other water molecules. The solvation number is obtained as a ratio of peak areas. Here it refers to the number of water molecules in the first solvation shell. Molecules in the second solvation shell exchange rapidly with solvent molecules, giving rise to a small change in the chemical shift value of un-coordinated water molecules from that of water itself. The main disadvantage of this method is that it requires fairly concentrated solutions, with the associated risk of ion-pair formation with the anion.
X-ray diffraction (XRD)
A solution containing an aqua ion does not have the long-range order that would be present in a crystal containing the same ion, but there is short-range order. X-ray diffraction on solutions yields a radial distribution function from which the coordination number of the metal ion and metal-oxygen distance may be derived. With aqua ions of high charge some information is obtained about the second solvation shell.
This technique requires the use of relatively concentrated solutions. X-rays are scattered by electrons, so scattering power increases with atomic number. This makes hydrogen atoms all but invisible to X-ray scattering.
Large angle X-ray scattering has been used to characterize the second solvation shell with trivalent ions such as Cr3+ and Rh3+. The second hydration shell of Cr3+ was found to have molecules at an average distance of . This implies that every molecule in the first hydration shell is hydrogen bonded to two molecules in the second shell.
Neutron diffraction
Diffraction by neutrons also give a radial distribution function. In contrast to X-ray diffraction, neutrons are scattered by nuclei and there is no relationship with atomic number. Indeed, use can be made of the fact that different isotopes of the same element can have widely different scattering powers. In a classic experiment, measurements were made on four nickel chloride solutions using the combinations of 58Ni, 60Ni, 35Cl and 37Cl isotopes to yield a very detailed picture of cation and anion solvation. Data for a number of metal salts show some dependence on the salt concentration.
†Figures in brackets are standard deviations on the last significant figure of the value.‡ angle between a M-OH2 bond and the plane of the water molecule.
Most of these data refer to concentrated solutions in which there are very few water molecules that are not in the primary hydration spheres of the cation or anion, which may account for some of the variation of solvation number with concentration even if there is no contact ion pairing. The angle θ gives the angle of tilt of the water molecules relative to a plane in the aqua ion. This angle is affected by the hydrogen bonds formed between water molecules in the primary and secondary solvation shells.
The measured solvation number is a time-averaged value for the solution as a whole. When a measured primary solvation number is fractional there are two or more species with integral solvation numbers present in equilibrium with each other. This also applies to solvation numbers that are integral numbers, within experimental error. For example, the solvation number of 5.5 for a lithium chloride solution could be interpreted as being due to presence of two different aqua ions with equal concentrations.
[Li(H2O)6]+ [Li(H2O)5]+ + H2O
Another possibility is that there is interaction between a solvated cation and an anion, forming an ion pair. This is particularly relevant when measurements are made on concentrated salt solutions. For example, a solvation number of 3 for a lithium chloride solution could be interpreted as being due to the equilibrium
[Li(H2O)4]+ + Cl− [Li(H2O)3Cl] + H2O
lying wholly in favour of the ion pair.
Vibrational spectra
Infrared spectra and Raman spectra can be used to measure the M-O stretching frequency in metal aqua ions. Raman spectroscopy is particularly useful because the Raman spectrum of water is weak whereas the infrared spectrum of water is intense. Interpretation of the vibration frequencies is somewhat complicated by the presence, in octahedral and tetrahedral ions, of two vibrations, a symmetric one measured in the Raman spectrum and an anti-symmetric one, measured in the infrared spectrum.
Although the relationship between vibration frequency and force constant is not simple, the general conclusion that can be taken from these data is that the strength of the M-O bond increases with increasing ionic charge and decreasing ionic size. The M-O stretching frequency of an aqua ion in solution may be compared with its counterpart in a crystal of known structure. If the frequencies are very similar it can be concluded that the coordination number of the metal ion is the same in solution as it is in a compound in the solid state.
Dynamic methods
Data such as conductivity, electrical mobility and diffusion relate to the movement of ions through a solution. When an ion moves through a solution it tends to take both first and second solvation shells with it. Hence solvation numbers measured from dynamic properties tend to be much higher that those obtained from static properties.
{| class="wikitable"
|+Hydration numbers measured by dynamic methods
|-
! !! Li+!! Na+!!Cs+!!Mg2+!!Ca2+!!Ba2+!!Zn2+!!Cr3+||Al3+
|-
| Ion transport number||13-22||7-13||4||12-14||8-12||3-5||10-13|| ||
|-
| Ion mobility||3-21||2-10|| ||10-13||7-11||5-9||10-13|| ||
|-
| Diffusion||5||3||1||9||9||8||11||17||13
|}
Solvation numbers and structures
Hydrogen
Hydrogen is not a metal, but like them it tends to lose its valence electron in chemical reactions, forming a cation H+. In aqueous solution, this immediately attaches itself to a water molecule, forming a species generally symbolised as H3O+ (sometimes loosely written H+). Such hydration forms cations that can in essence be considered as [H(OH2)n]+.
The solvation of H+ in water is not fully characterised and many different structures have been suggested. Two well-known structures are the Zundel cation and the Eigen cation. The Eigen solvation structure has the hydronium ion at the center of an complex in which the hydronium is strongly hydrogen-bonded to three neighbouring water molecules. In the Zundel complex the proton is shared equally by two water molecules in a symmetric hydrogen bond.
Alkali metals
The hydrated lithium cation in water is probably tetrahedral and four-coordinated. There are most probably six water molecules in the primary solvation sphere of the octahedral sodium ion. Potassium is seven-coordinate, and rubidium and caesium are probably eight-coordinate square antiprismatic. No data is available for francium.
Alkaline earth metals
Other values include Zn2+ -2044.3, Cd2+ -1805.8 and Ag+ -475.3 kJ mol−1.
There is an excellent linear correlation between hydration enthalpy and the ratio of charge squared, z2, to M-O distance, reff.
Values for transition metals are affected by crystal field stabilization. The general trend is shown by the magenta line which passes through Ca2+, Mn2+ and Zn2+, for which there is no stabilization in an octahedral crystal field. Hydration energy increases as size decreases. Crystal field splitting confers extra stability on the aqua ion. The maximum crystal field stabilization energy occurs at Ni2+. The agreement of the hydration enthalpies with predictions provided one basis for the general acceptance of crystal field theory.
The hydration enthalpies of the trivalent lanthanide ions show an increasingly negative values at atomic number increases, in line with the decrease in ionic radius known as the lanthanide contraction.
Single ion hydration entropy can be derived. Values are shown in the following table. The more negative the value, the more there is ordering in forming the aqua ion. It is notable that the heavy alkali metals have rather small entropy values which suggests that both the first and second solvation shells are somewhat indistinct.
{| class="wikitable" style=text-align:center
|+Single ion standard hydration entropy at 25 °C /J deg−1 mol−1
| Li+-118.8||
|-
|Na+-87.4||Mg2+-267.8|| || ||Al3+-464.4
|-
|K+-51.9||Ca2+-209.2|| || ...||Ga3+-510.4
|-
|Rb+-40.2||Sr2+-205.0|| ||... ||In3+-426.8
|-
|Cs+-36.8||Ba2+-159.0
||La3+-368.2||... ||
|}
Hydrolysis of aqua ions
There are two ways of looking at an equilibrium involving hydrolysis of an aqua ion. Considering the dissociation equilibrium
[M(H2O)n]z+ - H+ [M(H2O)n-1(OH)](z-1)+
the activity of the hydrolysis product, omitting the water molecules, is given by
The alternative is to write the equilibrium as a complexation or substitution reaction
[M(H2O)n]z+ +OH− :[M(H2O)n-1(OH)](z-1)+ + H2O
In which case
The concentration of hydrogen and hydroxide ions are related by the self-ionization of water, Kw = {H+} {OH−} so the two equilibrium constants are related as
In practice the first definition is more useful because equilibrium constants are determined from measurements of hydrogen ion concentrations. In general,
charges are omitted for the sake of generality and activities have been replaced by concentrations. are cumulative hydrolysis constants.
Modeling the hydrolysis reactions that occur in solution is usually based on the determination of equilibrium constants from potentiometric (pH) titration data. The process is far from straightforward for a variety of reasons. Sometimes the species in solution can be precipitated as salts and their structure confirmed by X-ray crystallography. In other cases, precipitated salts bear no relation to what is postulated to be in solution, because a particular crystalline substances may have both low solubility and very low concentration in the solutions.
First hydrolysis constant
The logarithm of hydrolysis constant, K1,-1, for the removal of one proton from an aqua ion
[M(H2O)n]z+ - H+ [M(H2O)n-1(OH)](z-1)+
[ [M(OH)]{(z-1)+ ] = K1,-1 [Mz+] [H+] −1
shows a linear relationship with the ratio of charge to M-O distance, z/d. Ions fall into four groups. The slope of the straight line is the same for all groups, but the intercept, A, is different.
{| class="wikitable"
|+log K1,-1 = A + 11.0 z/d
!cation||A
|-
|Mg2+, Ca2+, Sr2+, Ba2+ Al3+, Y3+, La3+||
|-
| Li+, Na+, K+Be2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+Sc3+, Ti3+, V3+, Cr3+, Fe3+, Rh3+, Ga3+, In3+ Ce4+, Th4+, Pa4+, U4+, Np4+, Pu4+, ||
|-
| Ag+, Tl+ Pb2+ Ti3+, Bi3+, ||
|-
| Sn2+, Hg2+, Pd2+ ||ca. 12
|}
The cations most resistant to hydrolysis for their size and charge are hard pre-transition metal ions or lanthanide ions. The slightly less resistant group includes the transition metal ions. The third group contains mostly soft ions ion of post-transition metals. The ions which show the strongest tendency to hydrolyze for their charge and size are Pd2+, Sn2+ and Hg2+. This is because of the low coordination numbers of ions in this part of the periodic table (also including Ag+ and Au+), so that fewer water molecules are present around the cation and they experience more electrostatic force than normal. A similar situation affects Be2+, the smallest aqua cation, which is also more acidic than would normally be expected.
The standard enthalpy change for the first hydrolysis step is generally not very different from that of the dissociation of pure water. Consequently, the standard enthalpy change for the substitution reaction
[M(H2O)n]z+ +OH− :[M(H2O)n-1(OH)](z-1)+ + H2O
is close to zero. This is typical of reactions between a hard cation and a hard anion, such as the hydroxide ion. It means that the standard entropy charge is the major contributor to the standard free energy change and hence the equilibrium constant.
The change in ionic charge is responsible for the effect as the aqua ion has a greater ordering effect on the solution than the less highly charged hydroxo complex.
Multiple hydrolysis reactions
The hydrolysis of beryllium shows many of the characteristics typical of multiple hydrolysis reactions. The concentrations of various species, including polynuclear species with bridging hydroxide ions, change as a function of pH up to the precipitation of an insoluble hydroxide. Beryllium hydrolysis is unusual in that the concentration of [Be(H2O)3(OH)]+ is too low to be measured. Instead a trimer ([Be3(H2O)6(OH3))3+ is formed, whose structure has been confirmed in solid salts. The formation of polynuclear species is driven by the reduction in charge density within the molecule as a whole. The local environment of the beryllium ions approximates to [Be(H2O)2(OH)2]+. The reduction in effective charge releases free energy in the form of a decrease of the entropy of ordering at the charge centers.
{| class="wikitable"
|+Some polynuclear hydrolysis products
! Species formula!! cations!! ! scope="col" width="300" |structure
|-
| M2(OH)+|| Be2+, Mn2+, Co2+, Ni2+ Zn2+, Cd2+, Hg2+, Pb2+ ||single hydroxide bridge between two cations
|-
|M2(OH) ||Cu2+, Sn2+ Al3+, Sc3+, Ln3+, Ti3+, Cr3+ Th4+ VO2+, , , || double hydroxide bridge between two cations
|-
| ||Be2+, Hg2+ || six-membered ring with alternate Mn+ and OH− groups
|-
|(OH) ||Sn2+, Pb2+ Al3+, Cr3+, Fe3+, In3+ || Cube with alternate vertices of Mn+ and OH− groups, one vertex missing
|-
| ||Mg2+, Co2+, Ni2+, Cd2+, Pb2+ ||Cube with alternate vertices of Mn+ and OH− groups
|-
| || Zr4+, Th4+ || Square of Mn+ ions with double hydroxide bridges on each side of the square
|}
The hydrolysis product of aluminium formulated as [Al13O4(OH)24(H2O)12]7+ is very well characterized and may be present in nature in water at pH ca. 5.4.
The overall reaction for the loss of two protons from an aqua ion can be written as
[M(H2O)n]z+ - 2 H+ [M(H2O)n-2(OH)2](z-2)+
However, the equilibrium constant for the loss of two protons applies equally well to the equilibrium
[M(H2O)n]z+ - 2 H+ [MO(H2O)n-2](z-2)+ + H2O
because the concentration of water is assumed to be constant. This applies in general: any equilibrium constant is equally valid for a product with an oxide ion as for the product with two hydroxyl ions. The two possibilities can only be distinguished by determining the structure of a salt in the solid state. Oxo bridges tend to occur when the metal oxidation state is high. An example is provided by the molybdenum(IV) complex [Mo3O4(H2O)9]4+ in which there is a triangle of molybdenum atoms joined by σ- bonds with an oxide bridge on each edge of the triangle and a fourth oxide which bridges to all three Mo atoms.
Oxyanions
There are very few oxo-aqua ions of metals in the oxidation state +5 or higher. Rather, the species found in aqueous solution are monomeric and polymeric oxyanions. Oxyanions can be viewed as the end products of hydrolysis, in which there are no water molecules attached to the metal, only oxide ions.
Exchange kinetics
A water molecule in the first solvation shell of an aqua ion may exchange places with a water molecule in the bulk solvent. It is usually assumed that the rate-determining step is a dissociation reaction.
[M(H2O)n]z+ → [M(H2O)n-1]z+* + H2O
The * symbol signifies that this is the transition state in a chemical reaction. The rate of this reaction is proportional to the concentration of the aqua ion, [A].
.
The proportionality constant, k, is called a first-order rate constant at temperature T. The unit of the reaction rate for water exchange is usually taken as mol dm−3s−1.
The half-life for this reaction is equal to loge2 / k. This quantity with the dimension of time is useful because it is independent of concentration. The quantity 1/k, also with dimension of time, equal to the half life divided by 0.6932, is known as the residence time or time constant.
The residence time for water exchange varies from about 10−10 s for Cs+ to about 10+10 s (more than 200 y) for Ir3+. It depends on factors such as the size and charge on the ion and, in the case of transition metal ions, crystal field effects. Very fast and very slow reactions are difficult to study. The most information on the kinetics a water exchange comes from systems with a residence time between about 1 μs and 1 s. The enthalpy and entropy of activation, ΔH‡ and ΔS‡ can be obtained by observing the variation of rate constant with temperature.
{| class="wikitable" style="text-align:center"
|+ Kinetic parameters (at 25 °C) for water exchange: divalent ions, M2+ (aq)
|-
! !!Be||Mg||V||Cr!!Mn!!Fe!!Co !!Ni!!Cu!!Zn||UO2
|-
!Residence time (μs)
| 0.001 ||2 ||0.00013 ||0.0032 ||0.0316 ||0.32 ||0.79 ||40 ||0.0005 ||0.032||1.3
|-
!ΔH‡ (kJ mol−1)
| || 43 ||69 ||13 ||34 ||32 ||33 ||43 ||23 || ||
|-
!ΔS‡ (J deg−1mol−1)
| || 8 ||21 ||-13 ||12 ||-13 ||-17 ||-22 ||25 || ||
|}
Note the general increase in the residence time from vanadium to nickel, which mirrors the decrease in ion size with increasing atomic number, which is a general trend in the periodic table, though given a specific name only in the case of the lanthanide contraction. The effects of crystal field stabilization energy are superimposed on the periodic trend.
{| class="wikitable" style="text-align:center"
|+ Kinetic parameters (at 25 °C) for water exchange - trivalent ions, M3+ (aq)
|-
! || Al|| Ti|| Cr|| Fe|| Ga|| Rh|| In|| La
|-
! residence time (μs)
| 6.3×106 ||16 ||2.0×1012 ||316 ||501 ||3.2×1013 ||50 ||0.050
|-
!ΔH‡ (kJ mol−1)
| 11 ||26 ||109 ||37 ||26 ||134 ||17 ||
|-
!ΔS‡ (J deg−1mol−1)
| 117 ||-63 ||0 ||-54 ||-92 ||59 || ||
|}
Solvent exchange is generally slower for trivalent than for divalent ions, as the higher electrical charge on the cation makes for stronger M-OH2 bonds and, in consequence, higher activation energy for the dissociative reaction step, [M(H2O)n]3+ → [M(H2O)n-1]3+ + H2O. The values in the table show that this is due to both activation enthalpy and entropy factors.
The ion [Al(H2O)6]3+ is relatively inert to substitution reactions because its electrons are effectively in a closed shell electronic configuration, [Ne]3s23p6, making dissociation an energy-expensive reaction. Cr3+, which has an octahedral structure and a d3 electronic configuration is also relatively inert, as are Rh3+ and Ir3+ which have a low-spin d6 configuration.
Formation of complexes
Metal aqua ions are often involved in the formation of complexes. The reaction may be written as
pMx+(aq) + qLy− → [MpLq](px-qy)+
In reality this is a substitution reaction in which one or more water molecules from the first hydration shell of the metal ion are replaced by ligands, L. The complex is described as an inner-sphere complex. A complex such as [ML](p-q)+ may be described as a contact ion pair.
When the water molecule(s) of the second hydration shell are replaced by ligands, the complex is said to be an outer-sphere complex, or solvent-shared ion pair. The formation of solvent-shared or contact ion pairs is particularly relevant to the determination of solvation numbers of aqua ions by methods that require the use of concentrated solutions of salts, as ion pairing is concentration-dependent. Consider, for example, the formation of the complex [MgCl]+ in solutions of MgCl2. The formation constant K of the complex is about 1 but varies with ionic strength. The concentration of the rather weak complex increases from about 0.1% for a 10mM solution to about 70% for a 1M solution (1M = 1 mol dm−3).
Electrochemistry
The standard electrode potential for the half-cell equilibrium Mz+ + z M(s) has been measured for all metals except for the heaviest trans-uranium elements.
{| class=wikitable style=text-align:center
|+Standard electrode potentials /V for couples Mz+/M(s)
|-
| H0
|-
| Li−3.040|| Be2+ −1.85
|-
| Na −2.71|| Mg2+ −2.372|| || || || Al3+−1.66
|-
| K −2.931|| Ca2+ −2.868|| Sc3+−2.90
|...||Zn2+ −0.751||Ga3+ −0.53||Ge2+ +0.1
|-
| Rb −2.98|| Sr2+ −2.899|| Y3+−2.37
|...||Cd2+ −0.403||In3+ −0.342||Sn2+ −0.136||Sb3+ +0.15
|-
|Cs −3.026|| Ba2+ −2.912||Lu3+ −2.25
|...||Hg2+ −0.854||Tl3+ +0.73||Pb2+ −0.126||Bi3+ +0.16||Po4+ +0.76
|-
| Fr−2.9 || Ra2+−2.8||Lr3+ −1.96
|-
|
|-
| || ||La3+−2.52 ||Ce3+ −2.32 ||Pr3+ −2.34||Nd3+ −2.32|| Pm3+−2.30 ||Sm3+ −2.28
|Eu3+ −1.98||Gd3+ −2.27||Tb3+ −2.27
|Dy3+ −2.32||Ho3+ −2.37||Er3+ −2.33
|Tm3+ −2.30||Yb3+ −2.23
|-
| || || Ac3+ −2.18||Th4+ −1.83||Pa4+ −1.46||U4+ −1.51||Np4+ −1.33||Pu4+ −1.80
|Am3+ −2.06||Cm3+ −2.07||Bk3+ −2.03
|Cf3+ −2.01||Es3+ −1.99||Fm3+ −1.97||Md3+ −1.65||No3+ −1.20
|}
{| class=wikitable style=text-align:center
|+Standard electrode potentials /V for 1st. row transition metal ions
!Couple!!Ti!!V!!Cr!!Mn!!Fe!!Co!!Ni!!Cu
|-
|M2+ / M||−1.63||−1.18||−0.91||−1.18||−0.473||−0.28||−0.228||+0.345
|-
|M3+ / M||−1.37||−0.87||−0.74||−0.28||−0.06||+0.41
|}
{| class=wikitable style=text-align:center
|+Miscellaneous standard electrode potentials /V
!Ag+ / Ag!!Pd2+ / Pd!!Pt2+ / Pt!!Zr4+ / Zr!!Hf4+ / Hf!!Au3+ / Au!!Ce4+ / Ce
|-
| +0.799||+0.915||+1.18||−1.53||−1.70|| +1.50||−1.32
|}
As the standard electrode potential is more negative the aqua ion is more difficult to reduce. For example, comparing the potentials for zinc (-0.75 V) with those of iron (Fe(II) -0.47 V, Fe(III) -0.06 V) it is seen that iron ions are more easily reduced than zinc ions. This is the basis for using zinc to provide anodic protection for large structures made of iron or to protect small structures by galvanization.
References
Bibliography
Further reading
H. L. Friedman, F. Franks, Aqueous Solutions of Simple Electrolytes, Springer; reprint of the 1973 edition, 2012
Solutions | Metal ions in aqueous solution | [
"Chemistry"
] | 7,911 | [
"Homogeneous chemical mixtures",
"Solutions"
] |
31,126,328 | https://en.wikipedia.org/wiki/TcoF-DB | The Dragon Database for Human Transcription Co-Factors and Transcription Factor Interacting Proteins (TcoF-DB) is a database that facilitates the exploration of proteins involved in the regulation of transcription in humans by binding to regulatory DNA regions (transcription factors) and proteins involved in the regulation of transcription in humans by interacting with transcription factors and not binding to regulatory DNA regions (transcription co-factors). The database describes a total of 529 (potential) human transcription co-factors interacting with a total of 1365 human transcription factors.
See also
Transcription factor
Transcription coregulator
References
External links
Biological databases
Gene expression
Genetics databases
Transcription factors
Biophysics | TcoF-DB | [
"Physics",
"Chemistry",
"Biology"
] | 126 | [
"Applied and interdisciplinary physics",
"Gene expression",
"Signal transduction",
"Bioinformatics",
"Molecular genetics",
"Biophysics",
"Induced stem cells",
"Cellular processes",
"Molecular biology",
"Biochemistry",
"Biological databases",
"Transcription factors"
] |
31,129,066 | https://en.wikipedia.org/wiki/Reparagen | Reparagen is a joint health product that scientists at Albany Medical College ran clinical trials on to test the theory that the combination of Uncaria guianensis and Lepidium meyenii can turn on Insulin-like growth factor
References
Genetic diseases and disorders | Reparagen | [
"Chemistry"
] | 54 | [
"Pharmacology",
"Pharmacology stubs",
"Medicinal chemistry stubs"
] |
31,131,470 | https://en.wikipedia.org/wiki/Robot-assisted%20double%20heart%20valve%20replacement | The first robot-assisted double heart valve replacement was carried out in the Chennai region of India at Chettinad Health City. This is the first instance of such a procedure using robotic surgery. The surgery was carried out by Dr R. Ravi Kumar, the director of the Institute of Cardiovascular Disease and head of the Robotic Surgery Centre at Chettinad.
References
External links
Press conference discussing the surgery
Computer-assisted surgery | Robot-assisted double heart valve replacement | [
"Biology"
] | 84 | [
"Biotechnology stubs",
"Medical technology stubs",
"Medical technology"
] |
31,131,659 | https://en.wikipedia.org/wiki/Thomsen%E2%80%93Friedenreich%20antigen | Thomsen–Friedenreich antigen (Galβ1-3GalNAcα1-Ser/Thr) is a disaccharide that serves as a core 1 structure in O-linked glycosylation. First described by Thomsen as a red blood cell's antigen, later research have determined it to be an oncofetal antigen. it is present in the body as a part of membrane transport proteins where it is normally masked from the immune system. It is commonly demasked in cancer cells, with it being expressed in up to 90% of carcinomas, making it a potential target for immunotherapy.
References
External links
Glycoproteins | Thomsen–Friedenreich antigen | [
"Chemistry",
"Biology"
] | 146 | [
"Biochemistry",
"Biotechnology stubs",
"Biochemistry stubs",
"Glycoproteins",
"Glycobiology"
] |
46,569,002 | https://en.wikipedia.org/wiki/London%20Security | London Security is a British fire protection company based in Elland, West Yorkshire, England.
London Security has 200,000 customers in the UK, Belgium, the Netherlands, Austria and Luxembourg.
It is 98% owned by its chairman, Tony Murray.
References
External links
Companies based in Elland
Building materials companies of the United Kingdom
Fire protection | London Security | [
"Engineering"
] | 69 | [
"Building engineering",
"Fire protection"
] |
46,571,112 | https://en.wikipedia.org/wiki/Phosphoryl%20group | A phosphoryl group is a trivalent group, consisting of a phosphorus atom (symbol P) and an oxygen atom (symbol O), where the three free valencies are on the phosphorus atom. While commonly depicted as possessing a double bond (P=O) the bonding is in fact non-classical.
Despite that, the meaning of the term "phosphoryl" varies, depending on the branch of scientific discipline. In biology, biochemistry and biomedicine branches, the term "phosphoryl" refers to groups consisting of phosphorus atom attached to three oxygen atoms, with the simplified chemical formula (there are several groups called "phosphoryl" in those branches, with the chemical formulas , , , , and ). In the branches mentioned above, the "phosphoryl" and phosphate groups are sometimes abbreviated by the letter "P", or represented by a symbol of encircled letter "P". "Phosphoryl" groups are covalently bonded by a single bond to an organic molecule, phosphate group(s) or another "phosphoryl" group(s), and those groups are sp3 hybridized at the phosphorus atom. The term "phosphoryl" in the mentioned branches is usually used in the description of catalytic mechanisms in living organisms. The "phosphoryl" group plays a central role in phosphorylation. In biochemical reactions involving phosphate groups (e.g. adenosine triphosphate), a "phosphoryl" group is usually transferred between the substrates by the "phosphoryl transfer reactions" (see phosphorylation). Examples of molecules containing those groups in biology, biochemistry and biomedicine are adenosine monophosphate (AMP), adenosine diphosphate (ADP), adenosine triphosphate (ATP), phosphocreatine (PCr) and DNA.
Contrary to biology, biochemistry and biomedicine branches, in organic and inorganic chemistry branches, and in the branch of chemical nomenclature (see IUPAC), the correct name for the group is not "phosphoryl", but phosphonato, and the correct name for the group is phosphono, and the term phosphoryl correctly refers to the trivalent >P(=O)− group. Example of molecules containing that trivalent phosphoryl group are phosphoryl chloride (), methylphosphonyl dichloride () and phosphoramide ().
A phosphoryl group should not be confused with a phosphate group.
References
Phosphorus compounds
Functional groups | Phosphoryl group | [
"Chemistry"
] | 568 | [
"Functional groups"
] |
46,571,441 | https://en.wikipedia.org/wiki/Bacterial%2C%20archaeal%20and%20plant%20plastid%20code | The bacterial, archaeal and plant plastid code (translation table 11) is the DNA code used by bacteria, archaea, prokaryotic viruses and chloroplast proteins. It is essentially the same as the standard code, however there are some variations in alternative start codons.
The code
As in the standard code, initiation is most efficient at AUG. In addition, GUG and UUG starts are documented in archaea and bacteria. In Escherichia coli, UUG is estimated to serve as initiator for about 3% of the bacterium's proteins. CUG is known to function as an initiator for one plasmid-encoded protein (RepA) in E. coli. In addition to the NUG initiations, in rare cases bacteria can initiate translation from an AUU codon as e.g. in the case of poly(A) polymerase PcnB and the InfC gene that codes for translation initiation factor IF3. The internal assignments are the same as in the standard code though UGA codes at low efficiency for tryptophan in Bacillus subtilis and, presumably, in Escherichia coli.
The NCBI raw format is as follows, with UUG, CUG, AUU, AUC, AUA, AUG, and GUG marked as possible initiators:
AAs = FFLLSSSSYY**CC*WLLLLPPPPHHQQRRRRIIIMTTTTNNKKSSRRVVVVAAAADDEEGGGG
Starts = ---M------**--*----M------------MMMM---------------M------------
Base1 = TTTTTTTTTTTTTTTTCCCCCCCCCCCCCCCCAAAAAAAAAAAAAAAAGGGGGGGGGGGGGGGG
Base2 = TTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGG
Base3 = TCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAG
Initiation at AUC and AUA is not addressed in the NCBI description text, but both are indeed known to occur in E. coli.
See also
List of genetic codes
References
Molecular genetics
Gene expression
Protein biosynthesis | Bacterial, archaeal and plant plastid code | [
"Chemistry",
"Biology"
] | 537 | [
"Protein biosynthesis",
"Gene expression",
"Molecular genetics",
"Biosynthesis",
"Cellular processes",
"Molecular biology",
"Biochemistry"
] |
46,571,676 | https://en.wikipedia.org/wiki/The%20mold%2C%20protozoan%2C%20and%20coelenterate%20mitochondrial%20code%20and%20the%20mycoplasma/spiroplasma%20code | The mold, protozoan, and coelenterate mitochondrial code and the mycoplasma/spiroplasma code (translation table 4) is the genetic code used by various organisms, in some cases with slight variations, notably the use of UGA as a tryptophan codon rather than a stop codon.
The code
AAs = FFLLSSSSYY**CCWWLLLLPPPPHHQQRRRRIIIMTTTTNNKKSSRRVVVVAAAADDEEGGGG
Starts = --MM---------------M------------MMMM---------------M------------
Base1 = TTTTTTTTTTTTTTTTCCCCCCCCCCCCCCCCAAAAAAAAAAAAAAAAGGGGGGGGGGGGGGGG
Base2 = TTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGG
Base3 = TCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAG
Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).
Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), Valine (Val, V).
Differences from the standard code
Alternative initiation codons
Trypanosoma: UUA, UUG, CUG ;
Leishmania: AUU, AUA ;
Tetrahymena: AUU, AUA, AUG ;
Paramecium: AUU, AUA, AUG, AUC, GUG, GUA(?).
(Pritchard et al., 1990)
Systematic range
Bacteria: The code is used in Entomoplasmatales and Mycoplasmatales (Bove et al. 1989). The situation in the Acholeplasmatales is unclear. Based on a study of ribosomal protein genes, it had been concluded that UGA does not code for tryptophan in plant-pathogenic mycoplasma-like organisms (MLO) and the Acholeplasmataceae (Lim and Sears, 1992) and there seems to be only a single tRNA-CCA for tryptophan in Acholeplasma laidlawii (Tanaka et al. 1989). In contrast, in a study of codon usage in Phytoplasmas, it was found that 30 out of 78 open reading frames analysed translated better with this code (UGA for tryptophan) than with the bacterial, archaeal and plant plastid code while the remainder showed no differences between the two codes (Melamed et al. 2003). In addition, the coding reassignment of UGA Stop → Trp can be found in an alpha-proteobacterial symbiont of cicadas: Candidatus Hodgkinia cicadicola (McCutcheon et al. 2009). Mycoplasma pneumoniae also uses the codon UGA to code for tryptophan rather than using it as a stop codon.
Fungi: Emericella nidulans, Neurospora crassa, Podospora anserina, Acremonium (Fox, 1987), Candida parapsilosis (Guelin et al., 1991), Trichophyton rubrum (de Bievre and Dujon, 1992), Dekkera/Brettanomyces, Eeniella (Hoeben et al., 1993), and probably Ascobolus immersus, Aspergillus amstelodami, Claviceps purpureaand Cochliobolus heterostrophus.
Protists: the red algae of Gigartinales (Boyen et al. 1994), the protozoa Trypanosoma brucei, Leishmania tarentolae, Paramecium tetraurelia, Tetrahymena pyriformis and probably Plasmodium gallinaceum (Aldritt et al., 1989), and the stramenopile Cafileria marina.
Metazoa: Coelenterata (Ctenophora and Cnidaria).
Other: this code is also used for the kinetoplast DNA (maxicircles, minicircles). Kinetoplasts are modified mitochondria (or their parts).
See also
List of genetic codes
References
Molecular genetics
Gene expression
Protein biosynthesis | The mold, protozoan, and coelenterate mitochondrial code and the mycoplasma/spiroplasma code | [
"Chemistry",
"Biology"
] | 1,203 | [
"Protein biosynthesis",
"Gene expression",
"Molecular genetics",
"Biosynthesis",
"Cellular processes",
"Molecular biology",
"Biochemistry"
] |
50,602,087 | https://en.wikipedia.org/wiki/Adiabatic%20MRI%20Pulses | Adiabatic radio frequency (RF) pulses are used in magnetic resonance imaging (MRI) to achieve excitation that is insensitive to spatial inhomogeneities in the excitation field or off-resonances in the sampled object.
Nuclear magnetic resonance (NMR) experiments are often performed with surface transceiver coils that have desirable sensitivity, but have the disadvantage of producing an inhomogeneous excitation field. This inhomogeneous field causes spatial variations in spin flip angles, which, in turn, causes errors and degrades the receiver's sensitivity. RF pulses can be designed to create low-variation flip-angles or uniform magnetization inversion across a sample, even in the presence of inhomogeneities such as B1-variation and off-resonance.
Analysis - Adiabatic Excitation Principles
Traditional RF Excitation
In traditional MRI RF excitation, an RF pulse, B1, is applied with a frequency that is resonant with the Larmor precession frequency of the spins of interest. In the frame rotating at the Larmor frequency, the effective field experienced by the spins is in the transverse plane. Observing the spins in this frame shows spins precessing about Beffective at a frequency proportional to . If the RF pulse is applied for a time shorter than the period of this precession, one can engineer the flip-angle (the angle with z-axis) by turning the pulse on and off at the appropriate time.
In RF excitation analysis, the effective field is derived in the rotating frame of reference, which depends on the radial frequency of the radio-frequency field. in the laboratory frame is written as:
Where B0 is the background magnetic field which points along the laboratory z-axis.
In the frame rotating about the z-axis at radial frequency, the effective magnetic field can be derived:
When is equal to the Larmor frequency for a particular spin, defined as , has only an x-component for that spin. Therefore, the spin will precess about the x-axis in the rotating frame.
Adiabatic Passage
In general, the RF magnetic field can be written with a time-varying phase and time-varying amplitude, so that,
And Beffective in the frame rotating at can be written as:
In an “adiabatic passage” process, the parameters A and ω can be varied gradually. Magnetic spin components that are in parallel with Beffective in the rotating frame will “track” Beffective as it changes, provided that Beffective changes “slowly enough.” Similarly, components that are perpendicular to Beffective will remain perpendicular to Beffective as it gradually changes direction. Figure 1 shows how spins track Beffective in an adiabatic passage transition.
The “gradualness” of the changing Beffective is defined as the “adiabaticity,” K, of the pulse, which is given by:
where is defined as the angle of Beffective with the z-axis in the rotating frame of reference.
The term K can be understood by examining the ratio by which it is defined: the precession frequency of a spin about Beffective is proportional to the strength of the effective field, and the angle of the field, phi, must change slower than the precession frequency so that the spin can “track” the effective field as it changes direction. This means that in order for a pulse to be considered adiabatic, the K-factor, or adiabaticity, must be much greater than 1 for the entire duration of the excitation sequence.
Figure 2 shows the magnitude and angle of for a commonly-used type of adiabatic sweep modulation function where A(t) and (t) are given by:
It is common to examine the so-called “sweep-diagram” for adiabatic pulses. Sweep-diagrams plot the trajectory of the effective field for a spin with a particular resonance frequency. Figure 3 shows the sweep diagram for two on-resonance spins: blue sweep trajectory for a spin experiencing a B1 field strength without error, and red sweep trajectory for a spin experiencing a B1 field strength with significant deviation. Since the direction of Beffective is largely independent of B1 strength, adiabatic pulses are considered insensitive to B1 inhomogeneities.
For off-resonance spins, the Beffective sweep diagram is shifted up or down by the amount of off-resonance. Another interpretation: the frequency excursion of the adiabatic pulse is always centered at the presumed Larmor frequency. If we have a spin which is not at the Larmor frequency, the relative frequency excursion of the adiabatic RF pulse will not be centered at that spin's resonance.
Adiabatic Pulse Design
Adiabatic passage can be used to design several different kinds of pulses, which can be insensitive to common variations that are common in modern MRI system design. Several common adiabatic sequences are summarized here: adiabatic half-passage (AHP), adiabatic full-passage (AFP); and B1-insensitive rotation (BIR) pulses.
Adiabatic Half-Passage (AHP)
The sweep diagram for AHP is the same as in Figure 3. Half-passage refers to a 90-degree rotation of Beffective. If the initial magnetization is along the initial axis of Beffective, the magnetization will track Beffective as it rotates. If the initial magnetization has components in the transverse plane, these perpendicular components will precess around Beffective during the time of the AHP pulse. The accumulated phase will depend on the length of the pulse and the strength of Beffective, so signal strength after AHP can be sensitive to initial transverse magnetization.
Adiabatic Full-Passage (AFP)
The sweep diagram for AFP is also shown in Figure 4. AFP pulses are exactly the same as AHP pulses, except that the angle of Beffective is changed to 180 degrees. AFP pulses are also known as adiabatic inversion pulses.
An interesting feature of AFP pulses is their insensitivity to off-resonance spins in a particular bandwidth. Figure 4 shows sweep diagrams for an on-resonance spin (blue) and the same sweep parameters for an off-resonance spin (red). The effective field has a trajectory which is shifted upward, but still has a final ending position which points along the –z-axis. For this reason, AFP pulses are considered insensitive to off-resonance sources, within a certain bandwidth. Spins with off-resonance outside this bandwidth will not experience an inversion, as shown in the sweep diagram.
B1-Insensitive Rotation (BIR) Pulses
BIR pulses, also called “universal rotators,” induce arbitrary flip angles for all spins in a plane perpendicular to the rotation axis defined by Beffective. The plane that is perpendicular to Beffective is only defined by the direction of Beffective, and not the strength of Beffective. As long as adiabaticity is maintained during rotations of Beffective, inhomogeneities in the B1 field strength will not have an effect on the flip-angle of the magnetization after a BIR pulse. Two commonly analyzed BIR pulse sequences are explained and summarized here: the BIR-1 and BIR-4 pulse sequences.
BIR-1
An important BIR pulse is known as the BIR-1. In this sequence, Beffective is applied initially along the +x-axis in the rotating frame, and then adiabatically swept from the +x-axis to the +z-axis. Magnetization in the plane initially perpendicular to Beffective remains perpendicular to Beffective throughout the adiabatic sweep. In the time that it takes the field to sweep, M precesses about the Beffective axis. Spins will have an arbitrary phase accrual due to precession about Beffective in the time period TP/2, and the amount of phase accrual will depend on the strength of B1. In the second half of the pulse, Beffective is applied along the -z-axis and adiabatically swept to point along the -y-axis. If the time of the -z to -y sweep is the same as the original +x to +z sweep, the phase-accrual due to B1 inhomogeneity will be reversed and M will now point along the -x axis. This process is shown in Figure 5, along the 90-degree path.
BIR-1 pulses can be used to achieve an arbitrary flip angle. This is achieved by applying a phase-shift relative to the initial Beffective. In the case described above, the phase shift is 90-degrees. This can be understood by examining how the plane rotates during the second half of the BIR pulse. For a flip-angle of theta, the phase shift is designed:
The BIR-1 pulse with arbitrary flip-angle will rotate M about the x-axis by theta, and then apply a phase-shift of theta. This means that all flip-angles induced by BIR-1 pulses will not lie in the same plane.
BIR-1 pulses can be sensitive to off-resonance effects for several reasons. Firstly, off-resonance spins will have asymmetric phase accrual in the first and second halves of the pulse, meaning that off-resonance spins may not be refocused by the BIR-1. Secondly, the initial Beffective for an off-resonance spin can have a significant component pointing along the z-axis of the rotating frame, which causes the spin to track Beffective during the entire adiabatic pulse (known as “spin-locking”). Spin-locked sources will end up pointing along the -y-axis after a BIR-1 pulse, since that is the final direction for Beffective.
BIR-4
A BIR-4 pulse is designed simply as two BIR-1 pulses back-to-back. For a 180-degree excitation (inversion), the second BIR-1 sequence is performed with Beffective initially pointing along the –y-axis, sweeps to the +z-axis, flips to the –z-axis, and sweeps to the +x-axis. Exactly in the same manner as the first BIR-1 pulse, phase accrual of M occurs in the sweep from –y to +z, and is undone in the sweep from –z to +x.
Arbitrary flip angles are achieved by selecting a phase-shift for each of the BIR-1 parts of the pulse. For a flip-angle of theta, the phase shift of each pulse is set by this design:
;
The BIR-4 pulse with arbitrary flip-angle will always rotate M by theta about the initial direction of the Beffective field, which is not true of the BIR-1 pulse. This means that all flip-angles induced by BIR-4 pulses will lie in the same plane (if the initial Beffective is in the same direction for each of the BIR-4 pulses).
Off-resonance spins will exhibit some degree of spin-locking to the Beffective field, similarly to the BIR-1 case.
Modulation Functions for Adiabatic Inversion Pulses
Many different combinations of phase and amplitude modulated pulses can perform similar adiabatic inversions. The selection and/or design of adiabatic pulses depends on the required adiabaticity of the application. Once a required adiabaticity is defined, the amplitude and phase functions can be optimized against several desired features, such as reduction in the total time of the pulse, insensitivity to off-resonance or constant gradient fields, and reduction in the peak power required in the B1 pulse.
We can examine the cases of AHP and AFP to demonstrate principles in adiabatic pulse design. In NMR excitation, it is desired to create offset-frequency-independent excitation with low RF peak power. Consider a spin which has an offset frequency of . The effective field experienced by this spin is given,
The adiabaticity of an AHP pulse is given,
Considering the time , where for a particular off-resonance, , the K-factor reduces to
This represents the time when the rotating reference frame is rotating in resonance with the frequency-shifted spin. At this time, correlated to the amount of off-resonance, the adiabaticity, K, is at a minimum for the off-resonant spin, which means it is a minimum constraint on the design of and . One way to design and is to examine the minimum K-factor as a function of off-resonance. When this is done, the bandwidth of the adiabatic pulse can be defined by the width of off-resonance that still has a minimum K-factor greater than a minimum K-factor threshold. The pulses can be parameterized with desired constraints, such as pulse length or RF peak power, and the AHP pulse modulation functions can then be selected based on the desired application specifications.
Applications and Current Research
Most applications of adiabatic pulse design are in MR spectroscopy or MR imaging where B1 inhomogeneity or effects like chemical shift cause significant errors. These applications include:
Spectroscopy and imaging with surface coils that are used for both transmission and receiving.;;;
Ultra-high-field NMR, which can induce non-magnetic resonances with non-trivial effects on B1 homogeneity
Imaging in the presence of chemical-shift, where normal excitation would exhibit apparent spatial displacement (error in position) of off-resonant spins
Spectroscopy and imaging applications that have constraints on RF peak power for excitation.
In addition, several research efforts have demonstrated methods for inverse design of adiabatic pulse sequences
References
Magnetic resonance imaging | Adiabatic MRI Pulses | [
"Chemistry"
] | 2,867 | [
"Nuclear magnetic resonance",
"Magnetic resonance imaging"
] |
29,760,118 | https://en.wikipedia.org/wiki/Jansen%27s%20linkage | Jansen's linkage is a planar leg mechanism designed by the kinetic sculptor Theo Jansen to generate a smooth walking motion. Jansen has used his mechanism in a variety of kinetic sculptures which are known as (Dutch for "beach beasts"). Jansen's linkage bears artistic as well as mechanical merit for its simulation of organic walking motion using a simple rotary input. These leg mechanisms have applications in mobile robotics and in gait analysis.
The central 'crank' link moves in circles as it is actuated by a rotary actuator such as an electric motor. All other links and pin joints are unactuated and move because of the motion imparted by the crank. Their positions and orientations are uniquely defined by specifying the crank angle and hence the mechanism has only one degree of freedom (1-DoF). The kinematics and dynamics of the Jansen mechanism have been exhaustively modeled using circle intersection method and bond graphs (Newton–Euler mechanics). These models can be used to rate the actuator torque and in design of the hardware and controller for such a system.
Illustrations
References
External links
Theo Jansen's STRANDBEEST
Theo Jansens Strandbeest-Mechanismus (German)
Strandbeest created with GeoGebra
2D Shadertoy
3D Shadertoy
Walking
Linkages (mechanical)
Walking vehicles
Robot kinematics | Jansen's linkage | [
"Engineering"
] | 282 | [
"Robotics engineering",
"Robot kinematics"
] |
29,763,411 | https://en.wikipedia.org/wiki/Stodola%27s%20cone%20law | The Law of the Ellipse, or Stodola's cone law, is a method for calculating highly nonlinear dependence of extraction pressures with a flow for multistage turbine with high backpressure, when the turbine nozzles are not choked. It is important in turbine off-design calculations.
Description
Stodola's cone law, consider a multistage turbine, like in the picture. The design calculation is done for the design flow rate (, the flow expected for the most uptime). The other parameters for design are the temperature and pressure at the stage group intake, and , respectively the extraction pressure at the stage group outlet (the symbol is used for the pressure after a stage nozzle; pressure does not interfere in relations here).
For off-design calculations, the Stodola's cone law off-design flow rate is , respectively, the temperature and pressure at the stage group intake are and and the outlet pressure is .
Stodola established experimentally that the relationship between these three parameters as represented in the Cartesian coordinate system has the shape of a degenerate quadric surface, the cone directrix being an ellipse. For a constant initial pressure the flow rate depends on the outlet pressure as an arc of an ellipse in a plane parallel to
For very low outlet pressure , like in condensing turbines, flow rates do not change with the outlet pressure, but drops very quickly with the increase in the backpressure. For a given outlet pressure , flow rates change depending on the inlet pressure as an arc of hyperbola in a plane parallel to .
Usually, Stodola's cone does not represent absolute flow rates and pressures, but rather maximum flow rates and pressures, with the maximum values of the diagram having in this case the value of 1. The maximum flow rate has the symbol and the maximum pressures at the inlet and outlet have the symbols and . The pressure ratios for the design flow rate at the intake and outlet are and , and the off-design ratios are and .
If the speed of sound is reached in a stage, the group of stages can be analyzed until that stage, which is the last in the group, with the remaining stages forming another group of analysis. This division is imposed by the stage working in limited (choked) mode. The cone is shifted in the axis direction, appearing as a triangular surface, depending on the critical pressure ratio , where is the outlet critical pressure of the stage group.
The analytical expression of the flow ratio is:
For condensing turbine the ratio is very low, previous relation reduces to:
simplified relationship obtained theoretically by Gustav Flügel (1885–1967).
In the event that the variation of inlet temperature is low, the relationship is simplified:
For condensing turbines , so in this case:
During operation, the above relations allow the assessment of the flow rate depending on the operating pressure of a stage.
References
Gavril Creța, Turbine cu abur și cu gaze [Steam and Gas Turbines], București: Ed. Didactică şi Pedagogică, 1981, 2nd ed. Ed. Tehnică, 1996,
Alexander Leyzerovich, Large Steam Power Turbines, Tulsa, Oklahoma: PennWell Publishing Co., 1997, Romanian version, București: Editura AGIR, 2003,
Further reading
Aurel Stodola, Die Dampfturbinen, Berlin: Springer Verlag, 1903–1924 (six editions)
Aurel Stodola, Steam and Gas Turbines, New York: McGraw-Hill, 1927
Constantin Zietemann, Die Dampfturbinen, 2nd ed., Berlin-Göttingen-Heidelberg: Springer-Verlag, 1955
Walter Traupel, New general theory of multistage axial flow turbomachines. Translated by Dr. C.W. Smith, Washington D.C. Published by Navy Dept.
Sydney Lawrence Dixon, Fluid Mechanics and Thermodynamics of Turbomachinery, Pergamon Press Ltd., 1966, 2nd ed. 1975, 3rd ed. 1978 (reprinted 1979, 1982 [twice], 1986, 1986, 1989, 1992, 1995), 4th ed. 1998
Notes
External links
Modeling of Off-Design Multistage Turbine Pressures by Stodola's Ellipse
Turbines
Jet engines
Power engineering | Stodola's cone law | [
"Chemistry",
"Technology",
"Engineering"
] | 878 | [
"Engines",
"Turbomachinery",
"Turbines",
"Energy engineering",
"Jet engines",
"Power engineering",
"Electrical engineering"
] |
29,763,819 | https://en.wikipedia.org/wiki/Ushiki%27s%20theorem | In mathematics, particularly in the study of functions of several complex variables, Ushiki's theorem, named after S. Ushiki, states that certain well-behaved functions cannot have certain kinds of well-behaved invariant manifolds.
The theorem
A biholomorphic mapping cannot have a 1-dimensional compact smooth invariant manifold. In particular, such a map cannot have a homoclinic connection or heteroclinic connection.
Commentary
Invariant manifolds typically appear as solutions of certain asymptotic problems in dynamical systems. The most common is the stable manifold or its kin, the unstable manifold.
The publication
Ushiki's theorem was published in 1980. The theorem appeared in print again several years later, in a certain Russian journal, by an author apparently unaware of Ushiki's work.
An application
The standard map cannot have a homoclinic or heteroclinic connection. The practical consequence is that one cannot show the existence of a Smale's horseshoe in this system by a perturbation method, starting from a homoclinic or heteroclinic connection. Nevertheless, one can show that Smale's horseshoe exists in the standard map for many parameter values, based on crude rigorous numerical calculations.
See also
Melnikov distance
Equichordal point problem
References
Dynamical systems
Theorems in complex analysis
Several complex variables | Ushiki's theorem | [
"Physics",
"Mathematics"
] | 281 | [
"Theorems in mathematical analysis",
"Functions and mappings",
"Several complex variables",
"Theorems in complex analysis",
"Mathematical objects",
"Mathematical relations",
"Mechanics",
"Dynamical systems"
] |
29,767,475 | https://en.wikipedia.org/wiki/Flat%20lens | A flat lens is a lens whose flat shape allows it to provide distortion-free imaging, potentially with arbitrarily-large apertures. The term is also used to refer to other lenses that provide a negative index of refraction. Flat lenses require a refractive index close to −1 over a broad angular range. In recent years, flat lenses based on metasurfaces were also demonstrated.
History
Russian mathematician Victor Veselago predicted that a material with simultaneously negative electric and magnetic polarization responses would yield a negative refractive index (an isotropic refractive index of −1), a "left-handed" medium in which light propagates with opposite phase and energy velocities.
The first, near-infrared, flat lens was announced in 2012 using nanostructured antennas. It was followed in 2013 by an ultraviolet flat lens that used a bi-metallic sandwich.
In 2014 a flat lens was announced that combined composite metamaterials and transformation optics. The lens works over a broad frequency range.
Traditional lenses
Traditional curved glass lenses can bend light coming from many angles to end up at the same focal point on a piece of photographic film or an electronic sensor. Light captured at the very edges of a curved glass lens does not line up correctly with the rest of the light, creating a fuzzy image at the edge of the frame. (Petzval field curvature and other aberrations.) To correct this, lenses use extra pieces of glass, adding bulk, complexity, and mass.
Metamaterials
Flat lenses employ metamaterials, that is, electromagnetic structures engineered on subwavelength scales to elicit tailored polarization responses.
Left-handed responses typically are implemented using resonant metamaterials composed of periodic arrays of unit cells containing inductive–capacitive resonators and conductive wires. Negative refractive indices that are isotropic in two and three dimensions at microwave frequencies have been achieved in resonant metamaterials with centimetre-scale features.
Metamaterials can image infrared, visible, and, most recently, ultraviolet wavelengths.
Types
Graphene oxide
With the advances in micro- and nanofabrication techniques, continued miniaturization of conventional optical lenses has been requested for applications such as communications, sensors, and data storage. Specifically, smaller and thinner micro lenses are needed for subwavelength optics or nano-optics with small structures, for visible and near-IR applications. As the distance scale for optical communications shrinks, the required feature sizes of micro lenses shrink.
Graphene oxide provides solutions to advance planar focusing devices. Giant refractive index modification (as large as 10^-1 or one order of magnitude larger than earlier materials), between graphene oxide (GO) and reduced graphene oxide (rGO) were demonstrated by manipulating its oxygen content using direct laser writing (DLW) method. The overall lens thickness potentially can be reduced by more than ten times. Also, the linear optical absorption of GO increases as the reduction of GO deepens, which results in transmission contrast between GO and rGO and therefore provides an amplitude modulation mechanism. Moreover, both the refractive index and optical absorption are dispersionless over a wavelength range from visible to near infrared. GO film offers flexible patterning capability by using the maskless DLW method, which reduces manufacturing complexity.
A novel ultrathin planar lens on a GO thin film used the DLW method. Its advantage is that phase modulation and amplitude modulation can be achieved simultaneously, which are attributed to the giant refractive index modulation and the variable linear optical absorption of GO during its reduction process, respectively. Due to the enhanced wavefront shaping capability, the lens thickness is subwavelength scale (~200 nm), which is thinner than dielectric lenses (~ μm scale). The focusing intensities and the focal length can be controlled effectively by varying laser power and lens size, respectively. By using oil immersion high numerical aperture (NA) objective during DLW process, 300 nm fabrication feature size on GO film has been realized, and therefore the minimum lens size reached 4.6 μm in diameter, the smallest planar micro lens. This can only be realized with metasurface by FIB. Thereafter, the focal length can be reduced to as small as 0.8 μm, which would potentially increase the NA and the focusing resolution.
The full-width at half-maximum (FWHM) of 320 nm at the minimum focal spot using a 650 nm input beam has been demonstrated experimentally, which corresponds to an effective NA of 1.24 (n=1.5). Furthermore, ultra-broadband focusing capability from 500 nm to as far as 2 μm have been realized with this planar lens.
Nanoantennas
The first flat lens used a thin wafer of silicon 60 nanometers thick coated with concentric rings of v-shaped gold nanoantennas to produce photographic images. The antennas refract the light so that it all ends up on a single focal plane, a so-called artificial refraction process. The antennas were surrounded by an opaque silver/titanium mask that reflected all light that did not strike the antennas. Varying the arm lengths and angle provided the required range of amplitudes and phases. The distribution of the rings controls focal length.
The refraction angle—more at the edges than in the middle—is controlled by the antennas' shape, size, and orientation. It could focus only a single near-infrared wavelength.
Nanoantennas introduce a radial distribution of phase discontinuities, thereby generating respectively spherical wavefronts and nondiffracting Bessel beams. Simulations show that such aberration-free designs are applicable to high-numerical aperture lenses such as flat microscope objectives.
In 2015 a refined version used an achromatic metasurface to focus different wavelengths of light at the same point, employing a dielectric material rather than a metal. This improves efficiency and can produce a consistent effect by focusing red, blue and green wavelengths at the same point to achieve instant color correction, yielding a color image. This lens does not suffer from the chromatic aberrations, or color fringing, that plague refractive lenses. As such, it does not require the additional lens elements traditionally used to compensate for this chromatic dispersion.
Bi-metallic sandwich
A bi-metallic flat lens is made of a sandwich of alternating nanometer-thick layers of silver and titanium dioxide. It consists of a stack of strongly-coupled plasmonic waveguides sustaining backward waves. It exhibits a negative index of refraction regardless of the incoming light's angle of travel. The waveguides yield an omnidirectional left-handed response for transverse magnetic polarization. Transmission through the metamaterial can be turned on and off using higher frequency light as a switch, allowing the lens to act as a shutter with no moving parts.
Membrane
Membrane optics employ plastic in place of glass to diffract rather than refract or reflect light. Concentric microscopic grooves etched into the plastic provide the diffraction.
Glass transmits light with 90% efficiency, while membrane efficiencies range from 30-55%. Membrane thickness is on the order of that of plastic wrap.
Holographic lenses
Holographic lenses are made from a hologram of a conventional lens. It is flat, and present any drawbacks of the original lens (aberrations), plus the drawbacks of the hologram (diffraction).
The hologram of a mathematical lens is flat, and it has the properties of the mathematical lens, but it has the drawbacks of the hologram (diffraction).
Geometric-phase lenses
Geometric phase lenses, also known as polarization-directed flat lenses are made by depositing liquid crystal polymer in a pattern to make a "holographically recorded wavefront profile". They exhibit a positive focal length for circularly polarized light of one direction, and a negative focal length for circularly polarized light of one direction.
See also
Metamaterial
Superlens
Zone plate
References
External links
Aberration-Free Ultrathin Flat Lenses and Axicons at Telecom Wavelengths Based on Plasmonic Metasurfaces (full text)
Metamaterials
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"Materials_science",
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"Metamaterials",
"Materials science"
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Ligustilide | C12H14O2 | [
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"Isomerism",
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] |
33,693,638 | https://en.wikipedia.org/wiki/Battlefield%204 | Battlefield 4 is a 2013 first-person shooter video game developed by DICE and published by Electronic Arts. The game was released in October and November for Microsoft Windows, PlayStation 3, Xbox 360, PlayStation 4, and Xbox One, and is the sequel to 2011's Battlefield 3, taking place six years later during the fictional "War of 2020".
Battlefield 4 was met with positive reception for its multiplayer mode, gameplay and graphics, but was criticized for its single-player campaign and for numerous bugs and glitches in the multiplayer. It was a commercial success, selling over seven million copies. A successor, Battlefield Hardline, was released in March 2015 and a direct sequel Battlefield 2042, was released in November 2021.
Gameplay
The game's heads-up display (HUD) is composed of two compact rectangles. The lower left-hand corner features a mini-map and compass for navigation, and a simplified objective notice above it; the lower right includes a compact ammo counter and health meter. The top right displays kill notifications of all players in-game. On the Windows version of the game, the top left features a chat window when in multiplayer. The mini-map, as well as the main game screen, shows symbols denoting three kinds of entities: blue for allies, green for squadmates, and orange for enemies, this applies to all interactivity on the battlefield. Battlefield 4 options also allow colour-blind players to change the on-screen colour indicators to: tritanomaly, deuteranomaly and protanomaly.
Weapon customisation is expansive and encouraged. Primary, secondary and melee weapons can all be customised with weapon attachments and camouflage 'skins'. Most weapons can also change between different firing modes (automatic, semi-automatic, and burst fire), allowing the player to adapt to the environment they find themselves in. They can "spot" targets (marking their positions to the player's team's mini-maps) in the single-player campaign (a first in the Battlefield franchise) as well as in multiplayer. The game's bullet-dropping-system has been significantly enhanced, forcing the player to change the way they play medium to long distance combat. In addition, players have more combat capabilities, such as countering melee attacks from the front while standing or crouching, shooting with their sidearm while swimming, and diving underwater to avoid enemy detection. Standard combat abilities are still current including, reloading whilst sprinting, unlimited sprint, prone and vaulting.
Campaign
The single-player campaign has several differences from the main multiplayer component. For the most part, the player must traverse mini-sandbox-style levels, in some cases using vehicles, like tanks and boats, to traverse the environment. As the player character, Recker, the player can use two campaign-only functions: the Engage command and the tactical binocular. The Engage command directs Recker's squadmates, and occasionally other friendly units, to attack any hostiles in Recker's line of sight. The tactical binocular is similar to a laser-designator, in the sense that it allows the player to identify friendly and enemy units, weapon stashes, explosives, and objectives in the field. By identifying enemies, the player can make them visible without using the visor, making them easier to mark for their teammates. At one point, Recker will briefly lose the tactical visor, forcing them to only use the Engage command to direct his squadmates on a limited number of enemies.
The campaign features assignments that require specific actions and unlock weapons for use in multiplayer upon completion. Collectible weapons return along with the introduction of collectible dog tags which can be used in multiplayer. Weapon crates are found throughout all levels, allowing players to obtain ammo and switch weapons. While crates hold default weapons, collectible weapons may be used whenever they are acquired and level-specific weapons may be used once a specific mission assignment has been completed by obtaining enough points in a level.
Multiplayer
Battlefield 4s multiplayer contains three playable factions—the United States, China, and Russia—fighting against each other, in up to 64-player matches on PC, PlayStation 4, and Xbox One (24-Player on Xbox 360 and PS3). A newly reintroduced "Commander Mode", last seen in Battlefield 2142, gives one player on each team a real-time strategy-like view of the entire map and the ability to give orders to teammates. Also, the Commander can observe the battle through the eyes of the players on the battlefield, deploying vehicle and weapon drops to "keep the war machinery going", and order in missile strikes on hostile targets. A spectator mode is included, enabling players to spectate others in first or third person, as well as use a free camera to pan around the map from any angle.
On June 10, 2013, at E3, DICE featured the map "Siege of Shanghai", depicting the People's Liberation Army against the U.S. Marine Corps. The gameplay showcased Commander Mode; new weapons and vehicles; and the "Levolution" gameplay mechanic. The video displays the last of these at various points, including: a player destroying a support pillar to trap an enemy tank above it; and a large skyscraper (with an in-game objective on the top floor) collapsing in the center of the map, kicking up a massive dust cloud throughout the map and bringing the objective closer to ground level. Levolution also includes effects such as shooting a fire extinguisher to fill the room with obscuring clouds, car alarms going off when stepped on, metal detectors going off once passed through, or cutting the power in a room to reduce others' visibility.
The maps included in the main game are "Siege of Shanghai", "Paracel Storm", "Zavod 311", "Lancang Dam", "Flood Zone", "Rogue Transmission", "Hainan Resort", "Dawnbreaker", "Operation Locker" and "Golmud Railway". The game modes on offer include Battlefields Conquest, Domination and Rush; while adding two new game modes called Obliteration and Defuse, along with traditional game modes such as Team Deathmatch and Squad Deathmatch.
The four kits from Battlefield 3 are present in Battlefield 4 with minor tweaks. The Assault kit must now wait for the defibrillator to recharge after reviving teammates in quick succession. The Engineer kit uses PDWs, and carbines are available to all kits. The support kit has access to the new remote mortar and the XM25 allowing for indirect suppressive fire. The Recon kit is now more mobile and is able to equip carbines, designated marksman rifles (DMRs), and C-4. Sniping mechanics also give with the ability to zero in your sights (set an aiming distance), and equip more optics and accessories than previous Battlefield games. The Recon kit is still able to utilize the MAV, T-UGS, and the Radio Beacon.
New vehicles have also been introduced. With the addition of the Chinese faction, new vehicles include the Type 99 MBT, the ZFB-05 armored car, and the Z-10W attack helicopter. Jets have also been rebalanced and put into two classes, "attack" and "stealth". The attack jets focus is mainly air-to-ground capabilities, while stealth jets focus mainly on air-to-air combat. Another vehicle added in Battlefield 4 is the addition of the RCB and DV-15 Interceptor attack boats, which function as heavily armed aquatic assault craft.
Customization options have also been increased in Battlefield 4, with all new camos available for every gun and vehicle. A new "adaptive" camo has been introduced that can adapt the camo to the map being played without the player having to change camos every map. Camos can now be applied to jets, helicopters, tanks, transport vehicles, guns, and soldiers themselves. Previously this option was introduced to parachutes but has been removed, emblems are now printed onto parachutes.
Synopsis
Setting and characters
Battlefield 4s single-player Campaign takes place during the fictional "War of 2020", six years after the events of its predecessor. Tensions between Russia and the United States have been running at a record high, due to a conflict between the two countries that has been running for the last six years. On top of this, China is also on the brink of war, as Admiral Chang, the main antagonist, plans to overthrow China's current government. If he succeeds, Chang will have full support from the Russians, helping spark war between China and the United States.
The player controls Sgt. Daniel "Reck" Recker, second-in-command of a U.S. Marine Corps Force Recon squad callsigned "Tombstone". His squadmates include squad leader SSgt. William Dunn, Heavy Weapon Specialist SSgt. Kimble "Irish" Graves, and field medic Sgt. Clayton "Pac" Pakowski. Early in the Campaign, Tombstone is joined by CIA operative Laszlo W. Kovic, originally known as "Agent W." from Battlefield 3s Campaign; and Chinese Secret Service agent Huang "Hannah" Shuyi. The Campaign also sees the return of Dimitri "Dima" Mayakovsky from Battlefield 3s Campaign—still alive after the nuclear detonation in Paris six years ago, and under the Chinese military's custody for unknown reasons.
Plot
Six years after the events in Battlefield 3, a squad of US Marines, codenamed "Tombstone" (consisting of Dunn, the squad's leader, Sergeant Recker, Irish, and Pac) attempts to escape from Azerbaijan with vital intelligence about a potential military uprising in China. After being trapped underwater in a car while being pursued by Russian special forces, Dunn, critically wounded and trapped, sacrifices himself by ordering the squad to break the windshield and escape, leaving Recker in charge of Tombstone. Reuniting with their commanding officer Captain Garrison, codenamed "Fortress", Tombstone learns that Admiral Chang, head of the Chinese army, has taken control of China with Russian support, and eliminated Chinese presidential candidate Jin Jié, a progressive politician seeking reforms within the Chinese government. The group finds itself sent to Shanghai with orders to rescue two VIPs: a woman named Hannah, and her husband, with assistance from an intelligence agent named Kovic.
Although the rescue is a success and Kovic takes the VIPs back to the USS Valkyrie, a Wasp-class amphibious assault ship, Tombstone becomes trapped in the city and is forced to rescue civilians against Pac's protests. Shortly after returning to the Valkyrie, Garrison assigns Kovic as head of the squad, and sends them to the USS Titan, a Nimitz-class aircraft carrier that had just been attacked, to recover its voyage data recorder before the wreckage sinks. Upon returning to the Valkyrie, Tombstone finds the ship under assault by Chinese Marines. The squad rescues Garrison and the VIPs, but Kovic is fatally wounded and passes control of the squad to Recker. Learning that China's air force is grounded due to a storm, Garrison assigns Tombstone to assist US forces planning to assault the Chinese-controlled Singapore airfield to weaken the Chinese air superiority. Hannah volunteers to join Tombstone on their mission, much to Irish's chagrin.
Despite the airfield being destroyed by a missile strike, Pac is separated from Tombstone during evacuation and assumed killed in the blast. Hannah then ostensibly betrays Recker and Irish, allowing both to be captured by Chinese soldiers. Both men are imprisoned in the Kunlun Mountains for interrogation under Chang's orders. In his cell, Recker finds himself befriended by a Russian prisoner named "Dima" (a survivor of the Paris nuclear blast, now suffering from radiation poisoning). The two escape from their cell, start a mass prison riot and use the chaos to make their escape, with Recker rescuing Irish along the way. As the Chinese military arrives to quell the riot, Hannah prevents the group from being recaptured by a group of soldiers. Although Irish mistrusts her, Hannah reveals her action was necessary for her mission, revealing her husband is in fact Jin Jié, who survived Chang's assassination attempt.
The group uses a tram to leave the mountains, only for it to be shot down by an enemy helicopter, killing Dima in the crash. Forced to make their way down on foot with privation, the group eventually finds a jeep and drives towards the US-occupied city of Tashgar. During the journey, Hannah reveals how she lost her family to Chang's men after bringing Jin Jié to meet them, causing Irish to make amends with her for his behavior. Upon reaching Tashgar, the squad finds US troops being besieged by both Chinese and Russian forces, and offers assistance to the US commander by destroying a nearby dam, flooding the area and eliminating the opposing forces. Learning the Valkyrie is within the region of the Suez Canal, Tombstone is airlifted to the ship, and arrives to warn the vessel that they are blindly heading towards Chang's navy. Stopping Chinese forces from boarding the ship, the squad soon finds Jin Jié amongst other survivors, including Pac (who had survived the events in Singapore).
Knowing he must show his face, as Chinese forces had been fighting under the assumption he was dead, Jin Jié convinces Recker to let him show his face and calm tensions between the three forces. The assault quickly ends with Chinese soldiers beginning to spread the news of Jin Jié's return. Chang, wanting to prevent this and conceal the truth, proceeds to barrage the Valkyrie with his personal warship. Recker, Irish, and Hannah decide to board Chang's warship and destroy it with C-4 explosives. However, when they fail to detonate, Irish and Hannah each volunteer to manually replace the charges, sacrificing his or her own life. If the player does nothing, Chang destroys the Valkyrie, killing Pac, Garrison and Jin Jié; if the player chooses Irish or Hannah to rearm the explosives, he or she will be reported missing in action after the warship's destruction, while the survivor and Recker are recovered by the Valkyrie. During the credits, the player hears new dialogue between Irish and Hannah, discussing their pasts, and how they have to keep moving forward with no regrets.
Development
Electronic Arts president Frank Gibeau confirmed the company's intention to release a sequel to Battlefield 3 during a keynote at the University of Southern California where he said "There is going to be a Battlefield 4". Afterwards, an EA spokesperson told IGN: "Frank was speaking broadly about the Battlefield brand—a brand that EA is deeply passionate about and a fan community that EA is committed to." On the eve of Battlefield 3s launch, EA Digital Illusions CE told Eurogamer it was the Swedish studio's hope that it would one day get the opportunity to make Battlefield 4. "This feels like day one now," executive producer Patrick Bach said. "It's exciting. The whole Frostbite 2 thing has opened up a big landscape ahead of us so we can do whatever we want."
Battlefield 4 is built on the new Frostbite 3 engine. The new Frostbite engine enables more realistic environments with higher resolution textures and particle effects. A new "networked water" system is also being introduced, allowing all players in the game to see the same wave at the same time. Tessellation has also been overhauled. An Alpha Trial commenced on June 17, 2013, with invitations randomly emailed to Battlefield 3 players the day prior. The trial ran for two weeks and featured the Siege of Shanghai map with all of its textures removed, essentially making it a "whitebox" test.
Due to mixed reception of the two-player Co-op Mode in Battlefield 3, DICE decided to omit the mode from Battlefield 4 to focus on improving both the campaign and multiplayer components instead.
AMD and DICE have partnered for AMD's Mantle API to be used on Battlefield 4. The goal was to boost performance on AMD GCN Radeon graphic cards providing a higher level of hardware-optimized performance than was previously possible with OpenGL or DirectX. Initial tests of AMD's Mantle showed it was an effective enhancement for slower processors.
DICE released an Open Beta for the game that was available on Windows (64 bit only), Xbox 360 and PlayStation 3. It featured the game-modes Domination, Conquest and Obliteration which were playable on the map Siege of Shanghai. The Open Beta started on October 4, 2013, and ended on October 15, 2013.
Technical issues and legal troubles
Upon release, Battlefield 4 was riddled with major technical bugs, glitches and crashes across all platforms. EA and DICE soon began releasing several patches for the game on all systems and DICE later revealed that work on all of its future games (including Mirror's Edge, Star Wars: Battlefront and Battlefield 4 DLC) would be halted until Battlefield 4 was working properly. In December 2013, more than a month after the game's initial release, an EA representative said, "We know we still have a ways to go with fixing the game – it is absolutely our #1 priority. The team at DICE is working non-stop to update the game."
EA President Peter Moore announced in January 2014 that the company did not see any negative impact to sales as a result of the myriad technical issues. He said any negative impacts to sales were actually due to the transition from current-generation (PS3, Xbox 360) to next-generation consoles (PS4, Xbox One), and that other video game franchises like FIFA and Need for Speed were experiencing similar effects. As a reward for players who bought the game early and continued to play it despite all of the bugs and glitches, DICE rewarded players in February 2014 with all-month-long, free multi-player content such as: bronze and silver Battlepacks, XP boosts and events, camouflage skins, shortcut bundles for weapons and additional content for Premium members.
Because of the widespread bugs and glitches that were present, EA became the target of multiple law firms. The firm Holzer Holzer & Fistel, LLC launched an investigation into EA's public statements made between July 24 and December 4, 2013, to determine if the company intentionally misled its investors with information pertaining to, "the development and sales of the Company's Battlefield 4 video game and the game's impact on EA's revenue and projects moving forward." Shortly thereafter, the law firm Robbins Geller Rudman & Dowd LLP similarly filed a class action lawsuit against EA for releasing false or misleading statements about the quality of Battlefield 4. A second class action lawsuit was announced only days later from the firm Bower Piven, which alleged that EA violated the Securities Exchange Act of 1934 by not properly informing its investors about the major bugs and glitches during development that may have prevented the investors from making an informed decision about Battlefield 4. Bower Piven sought out investors who lost more than US$200,000 to become the lead plaintiff. In October 2014, Judge Susan Illston dismissed one of the class action suits' original case on the grounds that EA did not intentionally mislead investors, instead its pre-release claims about Battlefield 4 were a "vague statement of corporate optimism", "an inactionable opinion" and "puffery".
Six months after the initial release of the game, in April 2014, DICE released a program called Community Test Environment (CTE), which let a limited number of PC gamers play a different version of Battlefield 4 that was designed to test new patches and updates before giving them a wide-release. One of the major patches tested was an update to the game's netcode, specifically the "tickrate", which is how frequently the game and server would update, measured in cycles per second. Because of the size of Battlefield 4 in terms of information, DICE initially chose to have a low tickrate. However, the low tickrate resulted in a number of issues including damage registration and "trade kills". The CTE program tested the game at a higher tickrate, among other common problems, and began rolling out patches in mid-2014.
In October 2014, nearly a full year after the official release with major updates still being put out, DICE LA producer David Sirland said the company acknowledged that the release of Battlefield 4 "absolutely" damaged the trust of the franchise's fanbase. Sirland said that the shaky release of Battlefield 4 caused the company to reevaluate their release model, and plan on being more transparent and offer earlier beta tests with future installments, namely (at the time) with Battlefield Hardline (2015). Sirland also said: "We still probably have a lot of players who won't trust us to deliver a stable launch or a stable game. I don't want to say anything because I want to do. I want them to look at what we're doing and what we are going to do and that would be my answer. I think we have to do things to get them to trust us, not say things to get them to trust us. Show by doing."
Marketing
In March 2013, Electronic Arts opened the Battlefield 4 website with three official teasers, entitled "Prepare 4 Battle". Each hints at three kinds of battlespace: air, land and sea. EA then continued to release teaser trailers leading up to the unveiling of Battlefield 4 at the Game Developers Conference on March 26, 2013. The following day, Battlefield 4s first gameplay trailer, which doubled as a showcase for the Frostbite 3 engine was released. Shortly thereafter, EA listed the game for pre-order on Origin for Microsoft Windows, PlayStation 3, and Xbox 360; however, EA excluded any mention of the next generation consoles.
In July 2012, Battlefield 4 was announced when EA advertised on their Origin client that those who pre-ordered Medal of Honor: Warfighter (either Digital Deluxe or the limited edition) would receive early access to the Battlefield 4 beta, this has since been expanded to include any Battlefield 3 Premium owners, and any Origin users who pre-purchase Battlefield 4 Digital Deluxe Edition. Although players who qualify for access in more than one way will only be granted one beta pass for their account and is non transferable to other players. The "Exclusive" beta started on October 1, 2013, with the open beta that went live on October 4. The beta will be on three platforms, PC, Xbox 360, and PlayStation 3 and features the Siege of Shanghai map on the Conquest game mode.
DICE revealed more Battlefield 4 content in the E3 2013 event at June 10, 2013, such as multiplayer modes, and allowed participants to play the game at the same event. More information was released at Gamescom 2013 in Cologne, Germany, such as the "Paracel Storm" multiplayer map and Battlefield 4 Premium. Battlefield 4 Premium includes five digital expansion packs featuring new maps and in-game content. Two-weeks early access to all expansion packs. Personalization options including camos, paints, emblems, dog tags and more. Priority position in server queues. Weekly updates with new content. Double XP events, 12 Battle Packs. Battle Packs are digital packages that contain a combination of new weapon accessories, dog tags, knives, XP boosts, and character customization items, three are included with all pre-orders of the Origin Digital Deluxe edition. The service will also transfer your Premium membership from Xbox 360 to Xbox One or PS3 to PS4. Premium membership pre-orders started the day the service was announced (August 21, 2013). DICE has also announced that if you purchase the game for a current generation system (PlayStation 3 or Xbox 360) you will be able to trade it in for a PlayStation 4 or Xbox One version of the game for as little as $10. Additionally all PlayStation 3 and 4 copies will include a code in the box to redeem a digital copy on the PlayStation Store.
An important strategy of DICE's market strategy to promote Battlefield 4 was the series of TV and web advertisements entitled Only in Battlefield 4. Each one of these TV spots was narrated by a player of Battlefield 4 describing one of the unique experiences they encountered, along with a re-creation of the event using gameplay footage. These advertisements highlighted the free-form nature of the upcoming game, such as the destructibility of the environment and the dynamic nature of the game's combat engine. These events included things such as demonstrating the new Levolution feature, upgrades to gameplay, and unscripted moments that cannot occur in other games' multiplayer mode.
Due to poor reception from gamers, on May 30, 2013, EA discontinued the online pass for all existing and future EA games including Battlefield 4.
A companion application was also released for iOS and Android.
Downloadable content
Battlefield 4 featured a total of five downloadable content (DLC) packs that included new maps and additions to gameplay. All five DLC packs were developed by DICE LA and were available two weeks prior to their scheduled release by players who had purchased Premium. Once support for Battlefield 4 Premium ended, DICE LA announced all future DLC would be free.
China Rising
On May 21, 2013, DICE unveiled Battlefield 4: China Rising on a Battlelog post and stated that it would include four new maps (Silk Road, Altai Range, Dragon Pass, and Guilin Peaks) on the Chinese mainland, ten new assignments, new vehicles, as well as the Air Superiority gametype. It is available to those who pre-ordered the game at no extra cost. It was released to premium players on December 3, 2013, followed by a general release on December 17, 2013.
Second Assault
On June 10, 2013, DICE LA unveiled Battlefield 4: Second Assault during the Microsoft Press Conference at E3 2013. It was announced that it would be the first expansion pack to be released for Battlefield 4 and would debut on the Xbox One. It was released on November 22, 2013, the same day the Xbox One was launched. The expansion features the return of four fan-favorite maps from Battlefield 3 and introduces Capture the Flag as a new gametype. On February 18, 2014, Second Assault became available as Premium exclusive for Xbox 360, PlayStation 3, PlayStation 4, and PC. It became available for non-Premium users on March 4, 2014.
During January 29 – February 28, 2015, the expansion was free of charge to all EA Access subscribers.
Naval Strike
On August 20, 2013, DICE LA unveiled Battlefield 4: Naval Strike at Gamescom 2013. It involves dynamic combat on four new maps, Wave Breaker, Nansha Strike, Operation Mortar, and Lost Islands, which take place in the South China Sea and features a new mode called "Carrier Assault" inspired by Battlefield 2142. The original release date was planned for March 25, 2014 for premium members and April 8, 2014, for non-premium members but was delayed several hours before release for Xbox One and PC without a new release date being set. On March 26, 2014, Naval Strike was released for premium members on PlayStation 3, PlayStation 4 and Xbox 360. The Xbox One version was released for premium members on March 27, 2014, and the PC version was released on March 31, 2014.
Dragon's Teeth
At Gamescom 2013, DICE LA unveiled Battlefield 4: Dragon's Teeth. Its maps take place in war-torn cities locked down by the People's Liberation Army. Dragon's Teeth was released on July 15, 2014, for Battlefield 4 Premium Members. For Non-Premium members it was released 2 weeks later on July 29, 2014. A new game mode included in this Dragon's Teeth DLC is called "Chain Link". There are four new maps included in Dragon's Teeth called "Lumphini Garden, Pearl Market, Propaganda, and Sunken Dragon". There are 11 new Assignments and a new assault drone called the "RAWR" that can be found on those four maps.
Final Stand
On August 20, 2013, DICE LA unveiled Battlefield 4: Final Stand at Gamescom 2013. Final Stand focuses on the conclusion of the in-game war of 2020. It includes four new maps and "secret prototype weapons and vehicles". The four maps that are included are "Operation Whiteout", "Giants of Karelia", "Hammerhead" and "Hangar 21". New weapons include the Rorsch X1 Handheld Railgun and some gadgets including the DS-3 Decoy and XD-1 Accipiter MKV, as well as a hovercraft tank based on the Levkov 1937 Hovercraft MBT. It was released for Battlefield 4 Premium members on November 18, 2014, 00:01 and for non-Premium Battlefield 4 players on December 2, 2014, 00:01.
Weapons Crate
The Weapons Crate DLC was announced by DICE LA on March 30, 2015, as a free DLC. The DLC added five weapons into the game: the Mare's Leg, AN-94, Groza-1, Groza-4 and the L86A2 along with the gamemode from Battlefield 3 'Gun Master' and many other stat changes. It was released in an alpha form in the Community Test Environment. It was released along with the Spring 2015 Patch on May 26, 2015.
Night Operations
In August 2015, DICE and DICE LA announced the expansion pack Night Operations, a free DLC pack. The first map to be released was Zavod: Graveyard shift, a night time version of the Battlefield 4 map Zavod 311, it was released with the Summer 2015 Patch. Two other night maps were also in development, a night time version of the map Siege of Shanghai and Golmud Railway, these maps were playable in the Battlefield 4 Community Test Environment but would remain unreleased as further development on Battlefield 4 ended. All three maps were developed by DICE LA and tested in the Community Test Environment with player feedback taken on board.
Community Operations
Community Operations was released on October 27, 2015, a free DLC pack. The map, Outbreak, is a medium-sized with much vegetation such as trees, shrubs, and grass for ambushing the enemies within. There are limited amounts of heavy vehicles such as tanks, LAVs and no anti-air vehicles. The map does not include air dominance such as stealth jets, scout helicopters and attack aircraft. This map was created by DICE Los Angeles and the Battlefield 4 gaming community. The update contains major changes to weapons and vehicles.
Legacy Operations
Legacy Operations was released on December 15, 2015, a free DLC pack. The map is an updated version of the Battlefield 2 map, Dragon Valley. It was released alongside the Winter Patch content update.
Premium
Premium is a downloadable pass that offers all of the downloadable content for a discounted price. Premium offers a range of personalization options and items, such as exclusive dog tags or camos. Premium contributes to the game by offering select days in which special events take place only for premium members.
Reception
Critical reception
Battlefield 4 received positive reviews from critics. Chris Watters of GameSpot gave praise to Obliteration Mode and the multiplayer elements but was otherwise unimpressed with the campaign. IGN's Mitch Dyer stated that "Battlefield 4 is a greatest hits album of DICE's multiplayer legacy" for same versions. Evan Lahti of PC Gamer stated that although the game strongly resembles Battlefield 3 it still manages to remain "a visually and sonically satisfying, reliably intense FPS". Commander Mode and the diverse map selection within multiplayer were also praised as being good additions to the game. Joystiq'''s David Hinkle said that the game "drops players into a sandbox and unhooks all tethers, loosing scores of soldiers to squad up and take down the opposition however they choose". Hinkle praised the campaign elements, but found the multiplayer to not hold any surprises. GameZone Lance Liebl stated "Your success in Battlefield is up to you and how well you work as a team. And it's one of the most rewarding games I've played. Battlelog needs some refinement, and there's still way too many crashes, but the multiplayer more than makes up for all of it." Machinima's Lawrence Sonntag praised the Levolution feature and the multiplayer mode.
However, several reviewers noted that the multiplayer part of the game had been released with a lot of game-breaking bugs on PC, PlayStation 4 and Xbox One, such as server crashes and lag. Polygon reviewed the game the day of its release, and gave it 7.5, then later downgraded their score to 4 after acknowledging that the game "was still barely playable for many players".
DICE later acknowledged the issues with the multiplayer part of the game and said they were working to fix them, and that they would not work on expansions or future projects until the game problems were resolved. Despite this promise, the game's second expansion was released while numerous recurring problems had yet to be resolved.
Ban in China
In late December 2013, shortly after the release of the "China Rising" DLC pack, China banned the sale of Battlefield 4, requesting stores and online vendors to remove the game and encouraging those who have already purchased the game to remove it from their consoles and/or PCs. The game was viewed as a national security risk in the form of a cultural invasion as the DLC includes four maps on the Chinese mainland.
An editorial from the China National Defense Newspaper (a subsidiary of the PLA Daily) published in December 2013 criticized the game for discrediting China's national sovereignty, and stated that while in the past the Soviet Union would often be used as an imaginary enemy in video games, the game has recently shifted to China.
Sales
During the first week of sales in the United Kingdom, Battlefield 4 became the second best-selling game on all available formats, only behind Assassin's Creed IV: Black Flag. The game's sales were down 69% compared to 2011's Battlefield 3. EA blamed the fall in demand on uncertainty caused by the upcoming transition to eighth generation consoles.
The PlayStation 3 version of Battlefield 4 topped the Media Create sales charts in Japan during its first week of release, ahead of Pokémon X and Y which has topped the charts for the past four weeks, by selling 121,699 copies. The PlayStation 3 version of Battlefield 4 Sales in Japan however fell 84.148% to only 19,291 copies in its second week of release, and losing number one to God Eater 2.
According to NPD Group figures, Battlefield 4 was the second best-selling game of November in the United States, only behind Call of Duty: Ghosts. In February 2014, EA announced that the Premium service for the game had sold more than 1.6 million copies. In May 2014, the game had sold more than 7 million copies.
Awards
According to EA, Battlefield 4 received awards from over 30 gaming publications prior to its release. Battlefield 4 appeared on several year-end lists of the best First-person shooter games of 2013, receiving wins from 18th Satellite Awards, and GamesRadar. During the 17th Annual D.I.C.E. Awards, the Academy of Interactive Arts & Sciences nominated Battlefield 4'' for "Action Game of the Year", "Online Game of the Year", "Outstanding Achievement in Sound Design", and "Outstanding Achievement in Visual Engineering".
Notes
References
External links
Battlefield 4 at MobyGames
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Video games that support Mantle (API)
Video games using Havok
Windows games
Works banned in China
World War III video games
Xbox Cloud Gaming games
Xbox 360 games
Xbox One games | Battlefield 4 | [
"Physics"
] | 7,504 | [
"Asymmetrical multiplayer video games",
"Symmetry",
"Asymmetry"
] |
33,694,818 | https://en.wikipedia.org/wiki/Pheophorbide | Pheophorbide or phaeophorbide is a product of chlorophyll breakdown and a derivative of pheophytin where both the central magnesium has been removed and the phytol tail has been hydrolyzed. It is used as a photosensitizer in photodynamic therapy.
Pheophorbide may be generated by digestion of ingested plant matter. Both worm (Caenorhabditis elegans) and mouse mitochondria are able to use the molecule in a form of ad hoc photoheterotrophy.
References
Biochemistry
Light therapy
Tetrapyrroles | Pheophorbide | [
"Chemistry",
"Biology"
] | 133 | [
"Biochemistry stubs",
"Biotechnology stubs",
"Biochemistry",
"nan"
] |
33,698,097 | https://en.wikipedia.org/wiki/CPS%20operon | The capsule biosynthesis, or CPS operon, is a section of the genome present in some Escherichia coli, of which regulates the production of polysaccharides making up the bacterial capsule. These polysaccharides help protect the bacteria from harsh environments, toxic chemicals, and bacteriophages.
The CPS operon contains genes which code for the following proteins:
Wza - a lipoprotein which may form a channel in the bacterial outer membrane.
Wzb - a cytoplasmic regulatory phosphatase which dephosphorylates Wzc.
Wzc - a tyrosine kinase found in the bacterial inner membrane. Participates in polymerization of capsule polysaccharides.
Wzx - Transfers new polysaccharide units across the inner membrane.
Wzy - Assembles longer polysaccharide chains using units introduced by Wzx.
The CPS operon is likely transcriptionally regulated by the Rcs (regulation of capsule synthesis) proteins. Reduced levels of membrane-derived oligosaccharides result in autophosphorylation of RcsC. This results in a phosphate group being transferred from RcsC to RcsB. RcsB then binds to RcsA, forming a complex which acts on the CPS promoter and activates transcription of the CPS genes.
The same operon is present in Klebsiella species, possibly as a result of horizontal gene transfer.
References
Escherichia coli genes
Operons | CPS operon | [
"Chemistry"
] | 316 | [
"Operons",
"Gene expression"
] |
33,700,433 | https://en.wikipedia.org/wiki/List%20of%20steam%20technology%20patents | List of steam technology patents. This is a list of patents relating to steam engines, steam locomotives, boilers, steam accumulators, condensers, etc.
Belgian patents
BE 904602 (A1), 1986, Boiler fed water heater - has flue gas closed-circuit heat exchanger contg. pure water with self-regulating operation
British patents
GB 189718087 (A), 1897, Improvements in means for providing for the free circulation of air in steam cylinders when the pistons are running and the steam cut off
GB 189921940 (A), 1899, Improvements in feed water purifiers and heaters for steam generators
GB 189922137 (A), 1899, Improvement in rotary steam engines
GB 189923234 (A), 1899, Improvements in steam generators
GB 190006487 (A), 1901, An improvement in starting valves for compound steam engines
GB 190022906 (A), 1901, Improvements in valves for use in compound locomotives and other compound engines
GB 190504645 (A), 1905, Improvements relating to the working of compound engines and in regulator valves therefor
GB 190516372 (A), 1906, Improvements in valve gear for locomotives or similar coupled steam engines
GB 190604729 (A), 1907, Improvements in locomotive superheaters
GB 190605839 (A), 1907, Combined spark arrester and ash ejector for locomotive engines
GB 191321689 (A), 1914, Improvements in and relating to power systems
GB 125433 (A), 1919, Improvements in or relating to fireless steam locomotives and engines
GB 235249 (A), 1925, Improvements in closed cycle steam power installations
GB 446060 (A), 1936, Improvements in or relating to steam power plants comprising feedwater heaters and hot-water accumulators
GB 446061 (A), 1936, Improvements in or relating to steam plants including hot-water accumulators
GB 522279 (A), 1940, Improvements in or relating to plant for operating fireless locomotives
GB 541689 (A), 1941, Improvements in or relating to steam generators
GB 626087 (A), 1949, Improvements in or relating to the conversion of fired locomotives into fireless locomotives
GB 629296 (A), 1949, Improvements in or relating to apparatus for electrically heating high-pressure steam generators or high-pressure steam accumulators
GB 634497 (A), 1950, Improvements in or relating to fireless locomotives having high pressure steam accumulators
GB 636122 (A), 1950, Improvements in or relating to charging cranes for fireless locomotives
GB 637797 (A), 1950, Improvements in or relating to throttle valves for high-pressure steam accumulator fireless locomotives
GB 639989 (A), 1950, Improvements in or relating to the arrangement of controls in the cabs of fireless locomotives
GB 640235 (A), 1950, Improvements in or relating to high pressure steam accumulator locomotives
GB 738935 (A), 1955, Fireless steam-driven vehicle
GB 888793 (A), 1962, Solid fuel grates for locomotive fire boxes
GB 929486 (A), 1963, Means for supplying solid fuel to locomotive fire boxes
Canadian patents
CA 2039935 (A1), 1992, Electrical steam locomotive
French patents
FR 2609152 (A1), 1988, Removable furnace body, burning poor-grade (lean) fuel, for an industrial generator
German patents
DE 4005467 (A1), 1990, Blast pipe for steam locomotive - has control systems for varying pipe opening
DE 4311775 (A1), 1994, Feedwater-preheater construction for preheating temperatures above 100 deg C for steam generators, in particular locomotive-type boilers
DE 19746384 (A1), 1999, Steam locomotive with steam storage boiler coupled to running gear, and used for shunting and industrial purposes
Japanese patents
JP 8144702 (A), 1996, Rotary steam engine
Russian patents
RU 2421619 (C1), 2011, Method of operating steam locomotive tandem compound steam engine
US patents
US 4425763 (A), 1984, Coal-fired steam locomotive
US 4633818 (A), 1987, Mobile coal-fired fluidized bed power unit
US 2011180024 (A1), 2011, Steam boiler with radiants
References
steam technology patents
Steam power | List of steam technology patents | [
"Physics"
] | 939 | [
"Power (physics)",
"Steam power",
"Physical quantities"
] |
33,702,384 | https://en.wikipedia.org/wiki/T1%20process | A T1 process (or topological rearrangement process of the first kind) is one of the main processes by which cellular materials such as foams or biological tissues change shapes. It involves four discrete objects such as bubbles, drops, cells, etc. The four objects are initially arranged in a plane in the following way. Objects A and B are in contact and objects C and D are on either side of the AB group and touching both A and B. The T1 process consists in breaking the contact between A and B and establishing the contact between C and D.
When a significant number of rearrangement events such as T1 processes with similar orientations occur inside a foam or a tissue, the material correspondingly undergoes a deformation: it elongates in the direction in which neighbours depart (here, AB) while it contracts in the direction in which new neighbour pairs form (here, CD).
As a result of the existence of the T1 and similar processes, materials made of these objects have a number of similar rheological properties. Among these, plasticity allows them to be deformed irreversibly. For such materials, such irreversible deformations arise from the ability to rearrange their constitutive objects. Thus, the T1 process is the major mesoscopic ingredient of plasticity for these materials.
References
Topology | T1 process | [
"Physics",
"Mathematics"
] | 278 | [
"Spacetime",
"Topology",
"Space",
"Geometry"
] |
33,702,893 | https://en.wikipedia.org/wiki/Surface%20rheology | Surface rheology is a description of the rheological properties of a free surface. When perfectly pure, the interface between fluids usually displays only surface tension. The stress within a fluid interface can be affected by the adsorption of surfactants in several ways:
Change in the surface concentration of surfactants when the in-plane flow tends to alter the surface area of the interface (Gibbs' elasticity).
Adsorption/desorption of the surfactants to/from the interface.
Importance of surface rheology
The mechanical properties (rheology) of dispersed media such as liquid foams and emulsions is strongly affected by surface rheology. Indeed, when they consist of two (or more) fluid phases, deforming the material implies deforming the constitutive phases (bubbles, drops) and thus their interfaces.
The measurement of surface rheological properties is described by storage and loss moduli. In the case of a linear response to a sinusoidal deformation, the loss modulus is the product of the viscosity by the frequency. One of the difficulties of surface rheology measurements come from the fact that the adsorbed layers are usually rather compressible (at the difference of bulk fluids which are essentially incompressible), and both compression and shear parameters should be determined. This determination requires different type of rheometric instruments, for instance oscillating drops for the compression properties and oscillating bicones for the shear properties. These two methods allow investigating the variation of the parameters upon the amplitude of the deformation. The responses of adsorbed layers to deformations are frequently non-linear, making this variation measurement relevant to rheological studies.
References
Rheology | Surface rheology | [
"Chemistry"
] | 361 | [
"Rheology",
"Fluid dynamics"
] |
40,510,551 | https://en.wikipedia.org/wiki/Screened%20porch | A screened porch, also known as a screen room, is a type of porch or similar structure on or near the exterior of a house that has been covered by window screens in order to hinder insects, debris, and other undesirable objects from entering the area inside the screen. Typically created to enhance the livability of a structure that would otherwise be exposed to the annoyances of the outdoors, screened porches often permit residents to enjoy an indoor environment outdoors.
Construction
bugs Screened porches can be built in a manner similar to that of pole barns, with the screens added after the structure of the walls and the roof is completed. While screen porches are often attached to houses, they are sometimes built separately in order to simplify the construction process. In order to ensure that the porch be impervious to insects and other intrusions, a screen door is typically added to facilitate entry. Because screens can reduce the amount of light that enters the porch's interior, some screened porches are built so that the screens can be removed at times when insects and sunlight are less of a problem to the resident. Some homeowners fill their porches with furniture and amenities typically found indoors, such as tables, chairs, and couches, ceiling fans, imitation hardwood floors, electrical outlets, painted elements, and even built-in furniture and plumbing.
Uses
Homeowners sometimes use their screened porches in lieu of climate control when the latter is unavailable. For example, when the loss of electricity prevents air conditioning systems from working, a screened porch may be a cooler sleeping location. At the same time, screened porches can be used to permit an outdoors experience while being sheltered from direct sunlight and flying insects; some builders even include skylights in their designs when a porch would otherwise be excessively dark. Some people experience a sense of intimacy and quiet privacy when spending their leisure hours on a screened porch. In the field of landscape architecture, a screened porch may even be used to divide surrounding gardens or lawns into smaller zones; at the Walter Gropius House in the northeastern United States, the screened porch serves as a transitional zone between a normal room of the house and a normal outdoors area, and its extended roof supports help to create the appearance of a frame around the surrounding terrain, dividing the land into multiple zones comparable to the rooms of a house.
See also
Arizona room
Gazebo
Sleeping porch
Sunroom
References
Architectural elements
Insect repellents
Landscape architecture
Leisure
Rooms | Screened porch | [
"Technology",
"Engineering"
] | 497 | [
"Building engineering",
"Landscape architecture",
"Rooms",
"Architectural elements",
"Components",
"Architecture"
] |
40,512,332 | https://en.wikipedia.org/wiki/Continuum%20percolation%20theory | In mathematics and probability theory, continuum percolation theory is a branch of mathematics that extends discrete percolation theory to continuous space (often Euclidean space ). More specifically, the underlying points of discrete percolation form types of lattices whereas the underlying points of continuum percolation are often randomly positioned in some continuous space and form a type of point process. For each point, a random shape is frequently placed on it and the shapes overlap each with other to form clumps or components. As in discrete percolation, a common research focus of continuum percolation is studying the conditions of occurrence for infinite or giant components. Other shared concepts and analysis techniques exist in these two types of percolation theory as well as the study of random graphs and random geometric graphs.
Continuum percolation arose from an early mathematical model for wireless networks, which, with the rise of several wireless network technologies in recent years, has been generalized and studied in order to determine the theoretical bounds of information capacity and performance in wireless networks. In addition to this setting, continuum percolation has gained application in other disciplines including biology, geology, and physics, such as the study of porous material and semiconductors, while becoming a subject of mathematical interest in its own right.
Early history
In the early 1960s Edgar Gilbert proposed a mathematical model in wireless networks that gave rise to the field of continuum percolation theory, thus generalizing discrete percolation. The underlying points of this model, sometimes known as the Gilbert disk model, were scattered uniformly in the infinite plane according to a homogeneous Poisson process. Gilbert, who had noticed similarities between discrete and continuum percolation, then used concepts and techniques from the probability subject of branching processes to show that a threshold value existed for the infinite or "giant" component.
Definitions and terminology
The exact names, terminology, and definitions of these models may vary slightly depending on the source, which is also reflected in the use of point process notation.
Common models
A number of well-studied models exist in continuum percolation, which are often based on homogeneous Poisson point processes.
Disk model
Consider a collection of points in the plane that form a homogeneous Poisson process with constant (point) density . For each point of the Poisson process (i.e. ), place a disk with its center located at the point . If each disk has a random radius (from a common distribution) that is independent of all the other radii and all the underlying points , then the resulting mathematical structure is known as a random disk model.
Boolean model
Given a random disk model, if the set union of all the disks is taken, then the resulting structure is known as a Boolean–Poisson model (also known as simply the Boolean model), which is a commonly studied model in continuum percolation as well as stochastic geometry. If all the radii are set to some common constant, say, , then the resulting model is sometimes known as the Gilbert disk (Boolean) model.
Germ-grain model
The disk model can be generalized to more arbitrary shapes where, instead of a disk, a random compact (hence bounded and closed in ) shape is placed on each point . Again, each shape has a common distribution and independent to all other shapes and the underlying (Poisson) point process. This model is known as the germ–grain model where the underlying points are the germs and the random compact shapes are the grains. The set union of all the shapes forms a Boolean germ-grain model. Typical choices for the grains include disks, random polygon and segments of random length.
Boolean models are also examples of stochastic processes known as coverage processes. The above models can be extended from the plane to general Euclidean space .
Components and criticality
In the Boolean–Poisson model, disks there can be isolated groups or clumps of disks that do not contact any other clumps of disks. These clumps are known as components. If the area (or volume in higher dimensions) of a component is infinite, one says it is an infinite or "giant" component. A major focus of percolation theory is establishing the conditions when giant components exist in models, which has parallels with the study of random networks. If no big component exists, the model is said to be subcritical. The conditions of giant component criticality naturally depend on parameters of the model such as the density of the underlying point process.
Excluded area theory
The excluded area of a placed object is defined as the minimal area around the object into which an additional object cannot be placed without overlapping with the first object. For example, in a system of randomly oriented homogeneous rectangles of length , width and aspect ratio , the average excluded area is given by:
In a system of identical ellipses with semi-axes and and ratio , and perimeter , the average excluded areas is given by:
The excluded area theory states that the critical number density (percolation threshold) of a system is inversely proportional to the average excluded area :
It has been shown via Monte-Carlo simulations that percolation threshold in both homogeneous and heterogeneous systems of rectangles or ellipses is dominated by the average excluded areas and can be approximated fairly well by the linear relation
with a proportionality constant in the range 3.1–3.5.
Applications
The applications of percolation theory are various and range from material sciences to wireless communication systems. Often the work involves showing that a type of phase transition occurs in the system.
Wireless networks
Wireless networks are sometimes best represented with stochastic models owing to their complexity and unpredictability, hence continuum percolation have been used to develop stochastic geometry models of wireless networks. For example, the tools of continuous percolation theory and coverage processes have been used to study the coverage and connectivity of sensor networks. One of the main limitations of these networks is energy consumption where usually each node has a battery and an embedded form of energy harvesting. To reduce energy consumption in sensor networks, various sleep schemes have been suggested that entail having a subcollection of nodes go into a low energy-consuming sleep mode. These sleep schemes obviously affect the coverage and connectivity of sensor networks. Simple power-saving models have been proposed such as the simple uncoordinated 'blinking' model where (at each time interval) each node independently powers down (or up) with some fixed probability. Using the tools of percolation theory, a blinking Boolean Poisson model has been analyzed to study the latency and connectivity effects of such a simple power scheme.
See also
Stochastic geometry models of wireless networks
Random graphs
Boolean model (probability theory)
Percolation thresholds
References
Percolation theory
Probability theory
Phase transitions | Continuum percolation theory | [
"Physics",
"Chemistry",
"Mathematics"
] | 1,383 | [
"Physical phenomena",
"Phase transitions",
"Percolation theory",
"Phases of matter",
"Critical phenomena",
"Combinatorics",
"Statistical mechanics",
"Matter"
] |
40,513,454 | https://en.wikipedia.org/wiki/Clohessy%E2%80%93Wiltshire%20equations | The Clohessy–Wiltshire equations describe a simplified model of orbital relative motion, in which the target is in a circular orbit, and the chaser spacecraft is in an elliptical or circular orbit. This model gives a first-order approximation of the chaser's motion in a target-centered coordinate system. It is used to plan the rendezvous of the chaser with the target.
History
Early results about relative orbital motion were published by George William Hill in 1878. Hill's paper discussed the orbital motion of the moon relative to the Earth.
In 1960, W. H. Clohessy and R. S. Wiltshire published the Clohessy–Wiltshire equations to describe relative orbital motion of a general satellite for the purpose of designing control systems to achieve orbital rendezvous.
System Definition
Suppose a target body is moving in a circular orbit and a chaser body is moving in an elliptical orbit.
Let be the relative position of the chaser relative to the target with radially outward from the target body, is along the orbit track of the target body, and is along the orbital angular momentum vector of the target body (i.e., form a right-handed triad).
Then, the Clohessy–Wiltshire equations are
where is the orbital rate (in units of radians/second) of the target body, is the radius of the target body's circular orbit, is the standard gravitational parameter,
If we define the state vector as , the Clohessy–Wiltshire equations can be written as a linear time-invariant (LTI) system,
where the state matrix is
For a satellite in low Earth orbit, and , implying , corresponding to an orbital period of about 93 minutes.
If the chaser satellite has mass and thrusters that apply a force then the relative dynamics are given by the LTI control system
where is the applied force per unit mass and
Solution
We can obtain closed form solutions of these coupled differential equations in matrix form, allowing us to find the position and velocity of the chaser at any time given the initial position and velocity.where:Note that and . Since these matrices are easily invertible, we can also solve for the initial conditions given only the final conditions and the properties of the target vehicle's orbit.
See also
Orbital maneuver
Orbital mechanics
Space rendezvous
References
Further reading
Prussing, John E. and Conway, Bruce A. (2012). Orbital Mechanics (2nd Edition), Oxford University Press, NY, pp. 179–196.
External links
The Clohessy-Wiltshire Equations of Relative Motion
Derivation Of Approximate Equations For Solving The Planar Rendezvous Problem
Orbits
Astrodynamics
Spaceflight | Clohessy–Wiltshire equations | [
"Astronomy",
"Engineering"
] | 538 | [
"Astrodynamics",
"Spaceflight",
"Outer space",
"Aerospace engineering"
] |
40,517,576 | https://en.wikipedia.org/wiki/Hydrology%20of%20Fishing%20Creek%20%28North%20Branch%20Susquehanna%20River%20tributary%29 | Fishing Creek is a tributary of the Susquehanna River, in Columbia County, Pennsylvania, in the United States. Hydrology involves the discharge, the pH, the chemical hydrology, the dams, and the water temperature. Data has been gathered from a United States Geological Survey gauging station near Bloomsburg, Pennsylvania. The pH of the waters in the Fishing Creek watershed ranges from 4.9 to 8.5 in various places.
Discharge
Approximately downstream of Orangeville, Fishing Creek's discharge averages per second and its median discharge is second. The creek's lowest recorded discharge rate in that location is in 1962 and its highest was in 1981. Further upstream, in Benton, Fishing Creek's discharge is almost always less than , and is far lower during the summer, usually approaching 0. The typical discharge of Fishing Creek at this location is around . The streambeds of West Branch and East Branch Fishing Creeks commonly run dry in the summer. In dry years, they are dry for 105 days on average, while in wet years they are on average dry for 5 days.
At a stream gauging station near Bloomsburg, Fishing Creek's discharge ranged between and between 2002 and 2012. The lowest discharge recorded during this time occurred on November 9, 2004. The highest discharge recorded during this time occurred on September 23, 2003.
pH
Near Benton, Fishing Creek's pH ranges from around 5.6 to around 7.25. Near Camp Lavigne, it ranges from 5.5 to 7.1. East Branch Fishing Creek is the only stream in the watershed whose pH drops below 5.5. Its pH can be as low as 4.9. West Creek and Coles Creek are the least acidic streams in the Fishing Creek watershed. Their pH is usually above 6.3 and often above 7. Typically, Fishing Creek and its tributaries are not at risk for being too acidic for the optimal health of fish, but in early spring during snowmelts, the pH levels near the limit that brook trout can tolerate. Fishing Creek's waters are acidic due to acid rain.
The waters of Fishing Creek at a gauging station near Bloomsburg had pH levels ranging from 5.8 to 8.5 between 2002 and 2012. The lowest pH during that time (5.8) occurred on December 17, 2003. The highest pH during that time (8.5) occurred on February 14, 2012. The average pH during that time and at that location was 7.242.
Dissolved nonmetals
The concentration of dissolved oxygen in Fishing Creek has been measured to range from approximately 5 to 17.5 milligrams per liter at Benton. In a 14-month period from May 2010 to July 2011, the dissolved oxygen level for the streams in the Fishing Creek watershed was highest in February 2011 and lowest in June, July, or August 2010, depending on the stream. A site on Fishing Creek, near Camp Lavigne, had slightly less fluctuation; there it ranged from 8 to 17 milligrams per liter of dissolved oxygen.
The concentration of hydrogen ions in the waters of Fishing Creek near Bloomsburg between 2002 and 2012 ranged from 0.00001 to 0.00153 milligrams per liter. The date of the lowest concentration of hydrogen ions at that location was on March 1 and July 16, 2003. The date of the highest concentration of hydrogen ions at the location on the creek was December 17, 2003. The average concentration of hydrogen ions was 0.0001 milligrams per liter.
The total concentration of nitrogen in the waters of Fishing Creek at the gauging station near Bloomsburg between 2002 and 2012 ranged from 0.52 to 2.8 milligrams per liter. The date during which the lowest concentration of nitrogen occurred was October 14, 2009. The date of the highest concentration was on January 13, 2003. The average concentration of nitrogen between 2002 and 2012 was 1.212 milligrams per liter.
Dissolved metals
The concentration of dissolved oxygen in Fishing Creek near Bloomsburg between 2002 and 2012 ranged between 4.1 and 17.1 milligrams per liter. The lowest concentration of dissolved oxygen in the creek during that period and at that location occurred on July 25, 2005. The highest concentration of dissolved oxygen occurred on January 6, 2009. The average concentration of dissolved oxygen was 10.942 milligrams per liter.
Fishing Creek contains dissolved aluminum but in most places not enough to be toxic, although some of its tributaries have aluminum concentrations approaching lethal levels for fish. The only tributary of Fishing Creek which contains dissolved aluminum in concentrations of over 100 micrograms per liter is East Branch Fishing Creek . Fishing Creek itself and all of its other tributaries had dissolved aluminum concentrations of less than 70 micrograms per liter. This concentration is linked to the thawing of soils, as demonstrated by the fact that aluminum levels in Fishing Creek peak in March and April and drop to almost zero in the summer.
The total concentration of calcium in the waters of Fishing Creek at the gauging station near Bloomsburg between 2002 and 2012 ranged from 5.5 milligrams per liter to 26 milligrams per liter. The lowest concentration of calcium occurred on February 6, 2008. The highest concentration of calcium occurred on June 18, 2012. The average concentration of calcium was 7.532 milligrams per liter.
The total concentration of magnesium in the waters of Fishing Creek at the gauging station near Bloomsburg between 2002 and 2012 ranged from 1.5 milligrams per liter to 6.7 milligrams per liter. The lowest concentration of magnesium occurred on November 1, 2006. The highest concentration of magnesium occurred on June 18, 2012. The average concentration of calcium is 1.748 milligrams per liter.
The total concentration of iron in the waters of Fishing Creek at the gauging station near Bloomsburg between 2002 and 2012 ranged from 40 micrograms per liter to 5730 micrograms per liter. The lowest concentration of iron occurred on April 6, 2006, November 12, 2008, and June 18, 2012. The highest concentration of iron occurred on July 5, 2011. The average concentration of iron was 397.37 micrograms per liter.
The total concentration of manganese in the waters of Fishing Creek at the gauging station near Bloomsburg between 2002 and 2012 ranged from less than 10 to 240 micrograms per liter, not counting the times that its presence was "verified but not quantified". The lowest concentration of manganese occurred on November 20, 2002. The highest concentration of manganese occurred on September 23, 2003. The average concentration was approximately 42 micrograms per liter.
In all times between 2002 and 2012 that the concentration of copper in the waters of Fishing Creek at the gauging station near Bloomsburg was measured, it was under 10 milligrams per liter. The concentration was under 4 micrograms per liter all but one of the times that it was measured. The concentration of lead in the waters of Fishing Creek was always under 1 microgram per liter, as measured between 2002 and 2012 at the gauging station near Bloomsburg. The concentration of nickel was always under 4 micrograms per liter all the times it was measured and its presence quantified between 2002 and 2012. The concentration of strontium was only measured once, on February 14, 2012. The concentration was 90 micrograms per liter.
The concentration of zinc in the waters of Fishing Creek has been under 5 micrograms per liter all the times that it was detected and measured. The other time, on April 11, 2012, it was 10 micrograms per liter. The concentration of selenium has only been measured once, on February 14, 2012. It was under 7 micrograms per liter.
Simple compounds
The concentration of carbon dioxide in the waters of Fishing Creek near Bloomsburg between 2002 and 2012 ranged from 0.3 to 34 milligrams per liter. The date during which there was the lowest concentration of carbon dioxide was April 6, 2006 and February 14, 2012. The date during which there was the highest concentration of carbon dioxide at the location on the creek was December 17, 2003. The average concentration of carbon dioxide was 2.04 milligrams per liter.
The total concentration of ammonia in the waters of Fishing Creek at the gauging station near Bloomsburg between 2002 and 2012 ranged from less than 0.02 milligrams per liter to 0.06 milligrams per liter. The highest concentration of ammonia occurred on May 19, 2009. The total concentration of nitrates in the waters of Fishing Creek at the gauging station near Bloomsburg between 2002 and 2012 was always less than 0.04 milligrams per liter.
The total concentration of phosphates in the waters of Fishing Creek at the gauging station near Bloomsburg between 2002 and 2012 ranged from less than 0.031 milligrams per liter to 0.11 milligrams per liter. The highest concentration of phosphates occurred on May 19, 2009. The total concentration of phosphorus itself in the waters of Fishing Creek at the gauging station near Bloomsburg between 2002 and 2012 ranged from less than 0.01 milligrams per liter to 0.575 milligrams per liter. The highest phosphorus concentration occurred on July 5, 2011.
The total concentration of sulfates in the waters of Fishing Creek at the gauging station near Bloomsburg between 2002 and 2012 ranged from 6.8 to 34.5 milligrams per liter. However, the second highest concentration was only 15.2 milligrams per liter. The highest concentration of sulfates occurred on February 14, 2012. The lowest concentration occurred on September 23, 2003. The average concentration was 10.57 milligrams per liter.
Complex compounds
The total concentration of caffeine in the waters of Fishing Creek near Bloomsburg between 2002 and 2012 ranged from an estimated 0.012 micrograms per liter to less than 0.2 micrograms per liter. The highest concentration occurred on November 12, 2008 and May 19, 2009. The lowest concentration occurred on February 6, 2008. The average concentration was approximately 0.099 micrograms per liter.
The total concentration of acetaminophen in the waters of Fishing Creek near Bloomsburg between 2002 and 2012 ranged from an estimated 7 nanograms per liter to 88 nanograms per liter. The lowest concentration occurred on August 25, 2008 and the highest concentration occurred on March 17, 2009. The average concentration was approximately 63 nanograms per liter.
The total concentration of codeine in the waters of Fishing Creek near Bloomsburg has been measured several times. It was under 0.04 micrograms per liter all the times that it was measured.
The total concentration of phenols in the waters of Fishing Creek near Bloomsburg has been measured once, on November 9, 2004. The concentration was less than five micrograms per liter. The total concentration of chlortetracycline and oxytetracycline in the waters of Fishing Creek near Bloomsburg between 2002 and 2012 have also both been measured several times. The concentrations of both compounds was always less than 0.01 micrograms per liter. Sulfamethazine is another chemical whose concentration has been measured in the waters of Fishing Creek. Its concentration is always less than 5 nanograms per liter.
The concentration of dehydronifedipine in the waters of Fishing Creek has also been measured a number of times. On February 6, 2008, April 3, 2008, June 10, 2008, and August 25, 2008, the concentration was the lowest, at less than 0.06 micrograms per liter. On November 12, 2008, March 17, 2009, May 19, 2009, and July 8, 2009, the concentration was at its highest, at less than 0.08 micrograms per liter. The average concentration is 0.07 micrograms per liter.
The concentration of cotinine in the waters of Fishing Creek was measured eight times in 2008 and 2009. All of these times, the concentration was less than 26 nanograms per liter. The concentration of diltiazem was also measured eight times in 2008 and 2009.
The total concentration of dissolved solids at Fishing Creek near Bloomsburg between 2002 and 2012 ranged from less than 2 to 166 milligrams per liter. The lowest concentration during that time occurred on January 13, 2003; May 19, 2003; October 21, 2003; December 17, 2003; March 14, 2005; May 5, 2005; February 8, 2006; April 6, 2006; August 3, 2006; January 4, 2007; May 24, 2007; July 11, 2007; December 4, 2007; and April 3, 2008. The highest concentration during that time occurred on September 23, 2003.
The total concentration of azithromycin in Fishing Creek near Bloomsburg between 2002 and 2012 was less than 5 nanograms per liter every time it was measured. The total concentration of carbamazepine in Fishing Creek in the same place and time ranged from approximately 1 nanogram per liter to less than 40 nanograms per liter. The lowest concentration occurred on February 6, 2008. The highest concentration occurred several times in 2008 and 2009.
The total concentration of diphenhydramine in Fishing Creek ranged from approximately 2 to less than 40 nanograms per liter. The lowest concentration occurred on June 10, 2008. The highest concentration occurred once in 2008 and three times in 2009. The average concentration was 22.125 nanograms per liter.
Biological contaminants
The concentration of fecal coliform has been measured once, on November 9, 2004. Its concentration was under 20 M-FC 0.45uMF col per 100 milliliters.
The concentration of E coli in the waters of Fishing Creek at the gauging station near Bloomsburg between 2002 and 2012 ranged from less than 3 to 150 m-TEC MF water col per 100 milliliters. The lowest concentration occurred on April 3, 2008. The highest concentration occurred on February 6, 2008. The average concentration was 58.14 m-TEC MF water col per 100 milliliters.
The concentration of enterococcus in the waters of Fishing Creek at the gauging station near Bloomsburg has ranged from under 3 to 680 m-E MF water col per 100 milliliters. The lowest concentration occurred on November 12, 2008 and the highest concentration occurred on February 6, 2008. The average concentration was 120.71 m-E MF water col per 100 milliliters.
Dams
There is a lowhead dam referred to by locals as Boone's Dam on Fishing Creek near where the creek flows past Bloomsburg. A dam was built on Fishing Creek in the northern reaches of Bloomsburg with the purpose of powering nearby Irondale furnaces. Additionally, a dam was built on Fishing Creek about north of Bloomsburg in 1818 by John Barton. In the 1800s and early 1900s there were two other dams on Fishing Creek. One was in Orange Township, and the other, a concrete dam, was in Orangeville. A dam known as the Benton Dam was built on upper Fishing Creek, directly upstream of Benton.
Water temperature
The highest water temperature of a stream in the Fishing Creek watershed is that of West Creek, which can reach in the summer. The water temperature of Fishing Creek in Benton can reach in the summer. The water temperature of Coles Creek, a tributary of Fishing Creek, only reaches in the summer. In the winter, the water temperature of the main stem of Fishing Creek is around , and West Branch Fishing Creek's temperature can reach as low as in the winter, making it the coldest stream in the watershed during winter.
At a gauging station near Bloomsburg, the water temperature ranged from 32°F (0.1°C) to 78°F (25.7°C) between November 2002 and November 2012. The lowest water temperature of the creek occurred on January 10, 2011. The highest water temperature of the creek in this location occurred on August 3, 2006. The average water temperature in August on Fishing Creek near Bloomsburg is approximately 22.67°C. The average water temperature in January on Fishing Creek near Bloomsburg is approximately 1.92°C. The average water temperature of Fishing Creek for every water temperature measurement on the creek near Bloomsburg between 2002 and 2012 is approximately 12.03°C.
References
Hydrology
Columbia County, Pennsylvania
Water in Pennsylvania | Hydrology of Fishing Creek (North Branch Susquehanna River tributary) | [
"Chemistry",
"Engineering",
"Environmental_science"
] | 3,384 | [
"Hydrology",
"Environmental engineering"
] |
40,518,246 | https://en.wikipedia.org/wiki/Tube-based%20nanostructure | Tube-based nanostructures are nanolattices made of connected tubes and exhibit nanoscale organization above the molecular level.
Lattices
Lattices are structures formed of arrays of uniformly sized cells. Ceramic lattice nanostructures have been formed using hollow tubes of titanium nitride (TiN). Using vertex-connected, tessellated octahedra with 7-nm hollow struts with elliptical cross-sections and wall thickness of 75-nm produced approximately cubic cells 100-nm on a side at a scale of up to 1 cubic millimeter. The material's relative density was of the order of 0.013 (similar to aerogels).
Compression experiments with multiple deformation cycles revealed tensile strengths of 1.75 GPa without failure.
The material was constructed from a digital design with direct laser writing onto a photopolymer using 2-photon lithography followed by conformal deposition of TiN using atomic layer deposition and a final etching to remove the polymer.
An earlier metallic tube lattice produced hollow tube nickel microlattices with a density of .9 milligram per cubic centimeter and complete recovery after compression exceeding 50% strain with energy absorption similar to elastomers. Young's modulus E scales with density as E ~ ρ2, in contrast to the E ~ ρ3 scaling observed for ultralight aerogels and carbon nanotube nanofoams with stochastic architecture. Hardness of 6 GPa and a modulus of 210 GPa were measured by nanoindentation and hollow tube compression experiments, respectively. These materials are fabricated by starting with a template formed by self-propagating photopolymer waveguide prototyping, coating the template by electroless nickel plating, and subsequently etching away the template.
Organic nanostructures
Nanostructured hollow multilayered tubes can be created by combining layer-by-layer (LbL) and template leaching.
Such materials are of particular interest for tissue engineering since they allow the precise control of physical and biochemical cues of implantable devices. The tubes are based on polyelectrolyte multilayer films. The final tubular structures can be characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), microscopy, swelling and mechanical tests, including dynamic mechanical analysis (DMA) in physiological simulated conditions. More robust films could be produced via chemical cross-linking with genipin. Water uptake decreases from about 390% to 110% after cross-linking. The cross-linked tubes are more suitable structures for cell adhesion and spreading. Potential applications include tissue engineering.
References
See also
Nanolattice
Superlattice
Nanostructure
Condensed matter physics
Ceramic materials
Nanomaterials | Tube-based nanostructure | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 566 | [
"Ceramic engineering",
"Phases of matter",
"Materials science",
"Ceramic materials",
"Condensed matter physics",
"Nanotechnology",
"Nanomaterials",
"Matter"
] |
37,759,555 | https://en.wikipedia.org/wiki/International%20Radiation%20Protection%20Association | The International Radiation Protection Association (IRPA) is an independent non-profit association of national and regional radiation protection societies, and its mission is to advance radiation protection throughout the world. It is the international professional association for radiation protection.
IRPA is recognized by the IAEA as a Non Governmental Organization (NGO) and is an observer on the IAEA Radiation Safety Standards Committee (RASSC).
IRPA was formed on June 19, 1965, at a meeting in Los Angeles; stimulated by the desire of radiation protection professionals to have a world-wide body. Membership includes 50 Associate Societies covering 65 countries, totaling approximately 18,000 individual members.
Structure
The General Assembly, made up of representatives from the Associate Societies, is the representative body of the Association. It delegates authority to the Executive Council for the efficient administration of the affairs of the Association.
Specific duties are carried out by IRPA Commissions, Committees, Task Groups and Working Groups:
Commission on Publications
Societies Admission and Development Committee
International Congress Organising Committee
International Congress Programme Committee
Montreal Fund Committee
Radiation Protection Strategy and Practice Committee
Regional Congresses Co-ordinating Committee
Rules Committee
Sievert Award Committee
Task Group on Security of Radioactive Sources
Task Group on Public Understanding of Radiation Risk
Working Group on Radiation Protection Certification and Qualification
Associate societies
The following is a list of the 50 Associate Societies (covering 65 countries):
List of International Congresses
The 2032 Congress (IRPA18) will be in Australia.
The 2028 Congress (IRPA17) will be in Spain.
Past Congresses
IRPA 16 Orlando, July 2024
IRPA 15 Seoul, January 2021
IRPA 14 Cape Town, May 2016
IRPA 13 Glasgow, May 2012
IRPA 12 Buenos Aires, October 2008
IRPA 11 Madrid, May 2004
IRPA 10 Hiroshima, May 2000
IRPA 9 Vienna, April 1996
IRPA 8 Montreal, May 1992
IRPA 7 Sydney, April 1988
IRPA 6 Berlin, May 1984
IRPA 5 Jerusalem, March 1980
IRPA 4 Paris, April 1977
IRPA 3 Washington, September 1973
IRPA 2 Brighton, May 1970
IRPA 1 Rome, September 1966
International Cooperation
IRPA maintains relations with many other international organizations in the field of radiation protection, such as those listed here.
Inter-Governmental Organizations
Non-Governmental Organizations
Professional Organizations
Awards
Rolf M. Sievert Award
Commencing with the 1973 IRPA Congress, each International Congress has been opened by the Sievert Lecture which is presented by the winner of the Sievert Award. This award is in honour of Rolf M. Sievert, a pioneer in radiation physics and radiation protection.
The Sievert Award consists of a suitable scroll, certificate or parchment, containing the name of the recipient, the date it is presented, and an indication that the award honours the memory of Professor Rolf M. Sievert.
The recipients of the Sievert Award are listed below:
1973 Prof. (Sweden), Radiation and Man Health Physics 31 (September), pp 265–272, 1976
1977 Prof. W.V. Mayneord (United Kingdom), The Time Factor in Carcinogenesis Health Physics 34 (April), pp 297–309, 1978
1980 Lauriston S. Taylor (USA), Some Nonscientific Influences on Radiation Protection Standards and Practice Health Physics 39 (December), pp 851–874, 1980
1984 Sir Edward Pochin (United Kingdom), Sieverts and Safety Health Physics 46(6), pp 1173–1179, 1984
1988 Prof. Dr. (Germany), Environmental Radioactivity and Man Health Physics 55(6), pp 845–853, 1988
1992 Dr. Giovanni Silini (Italy), Ethical Issues in Radiation Protection Health Physics 63(2), pp 139–148, 1992
1996 Dr. Daniel Beninson (Argentina), Risk of Radiation at Low Doses Health Physics 71(2), pp 122–125, 1996
2000 Prof. Dr. Itsuzo Shigematsu (Japan), Lessons from Atomic Bomb Survivors in Hiroshima and Nagasaki Health Physics 78(3), pp 234–241, 2000
2004 Dr. Abel J. Gonzalez (Argentina), Protecting Life against the Detrimental Effects Attributable to Radiation Exposure: Towards a Globally Harmonized Radiation Protection Regime Paper prepared for IRPA
2008 Prof. (Germany), Radiological Protection: Challenges and Fascination of Biological Research Stralenschutz Praxis 2009/2, pp 35–45, 2009
2012 Dr. Richard Osborne (Canada), A Story of T Lightly edited transcript of Dr. Osborne's lecture
2016 Dr. John Boice (USA), How to Protect the Public When you Can't Measure the Risk - The Role of Radiation Epidemiology
2020 Prof. Dr. Eliseo Vañó (Spain)
See also
Radioactivity
Ionizing radiation
Radiation protection
International Atomic Energy Agency (IAEA)
International Commission on Radiological Protection (ICRP)
United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)
International Commission on Non-Ionizing Radiation Protection (ICNIRP)
Index of radiation articles
References
External links
IRPA website
Radiation
Nuclear energy
Nuclear organizations
1965 establishments in California
Radiation protection | International Radiation Protection Association | [
"Physics",
"Chemistry",
"Engineering"
] | 1,043 | [
"Transport phenomena",
"Physical phenomena",
"Nuclear organizations",
"Waves",
"Radiation",
"Nuclear energy",
"Nuclear physics",
"Energy organizations",
"Radioactivity"
] |
37,761,264 | https://en.wikipedia.org/wiki/Grothendieck%E2%80%93Teichm%C3%BCller%20group | In mathematics, the Grothendieck–Teichmüller group GT is a group closely related to (and possibly equal to) the absolute Galois group of the rational numbers. It was introduced by and named after Alexander Grothendieck and Oswald Teichmüller, based on Grothendieck's suggestion in his 1984 essay Esquisse d'un Programme to study the absolute Galois group of the rationals by relating it to its action on the Teichmüller tower of Teichmüller groupoids Tg,n, the fundamental groupoids of moduli stacks of genus g curves with n points removed. There are several minor variations of the group: a discrete version, a pro-l version, a k-pro-unipotent version, and a profinite version; the first three versions were defined by Drinfeld, and the version most often used is the profinite version.
References
General references
Translation in Leningrad Math. J. 2 (1991), no. 4, 829–860.
Further reading
Relation to algebraic topology via the little disks operads
Relation to combinatorial anabelian geometry
Number theory
Galois theory | Grothendieck–Teichmüller group | [
"Mathematics"
] | 246 | [
"Discrete mathematics",
"Number theory"
] |
37,763,802 | https://en.wikipedia.org/wiki/2014%20aluminium%20alloy | 2014 aluminium alloy (aluminum) is an aluminium-based alloy often used in the aerospace industry.
It is easily machined in certain tempers, and among the strongest available aluminium alloys, as well as having high hardness. However, it is difficult to weld, as it is subject to cracking.
2014 is the second most popular of the 2000-series aluminium alloys, after 2024 aluminium alloy. It is commonly extruded and forged. The corrosion resistance of this alloy is particularly poor. To combat this, it is often clad with pure aluminium. If unclad 2014 aluminium is to be exposed to the elements, it should be painted as a corrosion protection measure.
Prior to the adoption of The Aluminum Association alloy designations in 1954, 2014 was known by the industry conventional designation "14S".
Chemical composition
The alloy composition of 2014 is:
Aluminium: Remainder
Chromium: 0.1% max
Copper: 3.9% - 5%
Iron: 0.7% max
Magnesium: 0.2% - 0.8%
Manganese: 0.4 - 1.2%
Remainder: Each 0.05% max
Remainder: Total 0.15% max
Silicon: 0.5% - 1.2%
Titanium: 0.15% max
Titanium + Zinc: 0.2% max
Zinc: 0.25% max
2014A Aluminium Alloy
2014A is an alloy of aluminium that is very similar (but not entirely identical) to 2014. Because of the naming similarity, the two can be confused. The alloy composition of 2014A is:
Aluminium: Remainder
Chromium: 0.1% max
Copper: 3.9% - 5%
Iron: 0.5% max (versus 0.7 for 2014)
Magnesium: 0.2% - 0.8%
Manganese: 0.4 - 1.2%
Remainder: Each 0.05% max
Remainder: Total 0.15% max
Silicon: 0.5% - 0.9% (versus 0.5-1.2 for 2014)
Titanium: 0.15% max
Titanium + Zinc: 0.2% max
Zinc: 0.25% max
Properties
Typical material properties for 2014 aluminium alloy are:
Density: 2.80 g/cm3, or 175 lb/ft3.
Young's modulus: 73 GPa, or 11 Msi.
Electrical conductivity: 34 to 50% IACS.
Ultimate tensile strength: 190 to 480 MPa, or 28 to 70 ksi.
Thermal Conductivity: 130 to 190 W/m-K.
Thermal Expansion: 23 μm/m-K.
Standards
2014 aluminium alloy is discussed in the following standards:
ASTM B 209: Standard Specification for Aluminium and Aluminium-Alloy Sheet and Plate
ASTM B 210: Standard Specification for Aluminium and Aluminium-Alloy Drawn Seamless Tubes
ASTM B 211: Standard Specification for Aluminium and Aluminium-Alloy Bar, Rod, and Wire
ASTM B 221: Standard Specification for Aluminium and Aluminium-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
References
Further reading
"Properties of Wrought Aluminium and Aluminium Alloys: 2014, Alclad 2014". Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Vol 2, ASM Handbook, ASM International, 1990, p. 67-68.
Aluminium alloy table
Aluminium–copper alloys
Aerospace materials | 2014 aluminium alloy | [
"Chemistry",
"Engineering"
] | 682 | [
"Aerospace engineering",
"Aerospace materials",
"Alloys",
"Aluminium alloys"
] |
37,763,925 | https://en.wikipedia.org/wiki/Torque%20amplifier | A torque amplifier is a mechanical device that amplifies the torque of a rotating shaft without affecting its rotational speed. It is mechanically related to the capstan seen on ships. Its most widely known use is in power steering on automobiles. Another use is on the differential analyser, where it was used to increase the output torque of the otherwise limited ball-and-disk integrator. The term is also applied to some gearboxes used on tractors, although this is unrelated. It differs from a torque converter, in which the rotational speed of the output shaft decreases as the torque increases.
History
The first electric-powered torque amplifier was invented in 1925 by Henry W. Nieman of the Bethlehem Steel Company of Bethlehem, Pennsylvania. It was intended to allow manual control of heavy equipment; e.g., industrial cranes, artillery, etc.
Vannevar Bush used Nieman's torque amplifier as part of his differential analyzer project at M.I.T in the early 1930s. Lord Kelvin had already discussed the possible construction of such calculators as early as the 1880s, but had been stymied by the limited output torque of the ball-and-disk integrators. These integrators used a ball bearing pressed between the surface of a rotating shaft and a disk, transmitting the rotational force of the shaft to the disk. By moving the ball along the shaft, the speed of the disk could be smoothly varied. The torque on the output shaft was limited by the friction between the bearing and the disk, and as these were generally made out of friction-limiting metals such as bronze to allow smooth motion, the output torque was quite low. Some calculating devices could use the output directly, and Kelvin and others built several systems, but in the case of a differential analyzer, the output of one integrator drove the input of the next integrator, or a graphing output. The torque amplifier was the advance that allowed these machines to work.
Principle
A torque amplifier is essentially two capstans connected together. A capstan consists of a drum that is connected to a powerful rotary source, typically the steam engine of the ship, or an electric motor in modern examples. To use the device, a rope is wrapped a few turns around the drum, with one end attached to a load, and the other hand-held by the user. Initially the rope has little tension and slips easily as the drum turns. However, if the user pulls on their end of the rope, the tension increases, increasing friction between the rope and the drum. Now the entire torque of the driver is applied to the other end of the rope, pulling the load. If the user does nothing, the capstan will briefly pull the load toward itself, thereby loosening the rope and stopping further motion. If the user instead takes up the slack, the tension is maintained and the load continues to be pulled. In this way, the user can easily control the motion of a very large load.
Construction
A typical torque amplifier consists of two capstans positioned end-to-end along a common line of rotation, typically horizontal. A single source of torque is supplied, typically from an electric motor, which is geared to power the two drums to spin in opposite directions. A single rope (or band) is wrapped around the two drums. If tension is applied to one end of the rope, its capstan pulls on it, which in turn tensions the output. Like the single capstan, the motion starts and stops as soon as the tension is applied or released, but generally the motion is smooth with varying degrees of torque being applied to the input.
Running through the middle of the drums are two separate shafts, for input and output. Both end with a cam (obscured in the attached sketch), which via a follower and a rocking arm holds one end of each rope. If the input shaft rotates from the null position, its cam raises or lowers the input follower, which via the rocking input arm tensions the rope on one drum and slackens the other. In that state, one drum applies much greater traction than the other, resulting in both the output shaft and a cage mounting the input and output arms moving to track the input. As soon as the cage and the output shaft have moved to the correct position, the tension in the two ropes regains equilibrium and relative motion stops. In this way, the motion of the output shaft closely tracks the motion of the input, although the torque applied to it is the torque of the motor driving the system, as opposed to the much smaller torque applied to the input shaft.
Applications
Early autopilot units designed by Elmer Ambrose Sperry incorporated a mechanical amplifier using belts wrapped around rotating drums; a slight increase in the tension of the belt caused the drum to move the belt. A paired, opposing set of such drives made up a single amplifier. This amplified small gyro errors into signals large enough to move aircraft control surfaces.
A similar mechanism was used in the Vannevar Bush differential analyzer.
The electrostatic drum amplifier used a band wrapped partway around a rotating drum, and fixed at its anchored end to a spring. The other end connected to a speaker cone. The input signal was transformed up to high voltage, and added to a high voltage DC supply line. This voltage was connected between drum and belt. Thus the input signal varied the electric field between belt and drum, and thus the friction between them, and thus the amount of lateral movement of the belt and thus speaker cone.
See also
Servomechanism
Torque converter
References
Citations
Further reading
Mechanical power control
Mechanical power transmission
Mechanical amplifiers | Torque amplifier | [
"Physics",
"Technology"
] | 1,142 | [
"Mechanical amplifiers",
"Mechanical power control",
"Mechanics",
"Mechanical power transmission",
"Amplifiers"
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37,764,606 | https://en.wikipedia.org/wiki/Oxychlorination | In chemistry, oxychlorination is a process for generating the equivalent of chlorine gas (Cl2) from hydrogen chloride and oxygen. This process is attractive industrially because hydrogen chloride is less expensive than chlorine.
Mechanism
The reaction is usually initiated by copper(II) chloride (CuCl2), which is the most common catalyst in the production of 1,2-dichloroethane. In some cases, CuCl2 is supported on silica in presence of KCl, LaCl3, or AlCl3 as cocatalysts. Aside from silica, a variety of supports have also been used including various types of alumina, diatomaceous earth, or pumice. Because this reaction is highly exothermic (238 kJ/mol), the temperature is monitored, to guard against thermal degradation of the catalyst. The reaction is as follows:
CH2=CH2 + 2 CuCl2 → 2 CuCl + ClH2C-CH2Cl
The copper(II) chloride is regenerated by sequential reactions of the cuprous chloride with oxygen and then hydrogen chloride:
½ O2 + 2 CuCl → CuOCuCl2
2 HCl + CuOCuCl2 → 2 CuCl2 + H2O
Applications
Oxychlorination is employed in the conversion of ethylene into vinyl chloride. In the first step in this process, ethylene undergoes oxychlorination to give ethylene chloride:
CH2=CH2 + 2 HCl + ½ O2 → ClCH2CH2Cl + H2O
Oxychlorination is of special importance in the making of 1,2-dichloroethane, which is then converted into vinyl chloride. As can be seen in the following reaction, 1,2-dichloroethane is cracked:
ClCH2CH2Cl → CH2=CHCl + HCl
The HCl from this cracking process is recycled by oxychlorination in order to reduce the consumption of raw material HCl (or Cl2, if direct chlorination of ethylene is chosen as main way to produce 1,2-dichloroethane).
Iron(III) chloride is produced commercially by oxychlorination (and other methods). For example, dissolution of iron ores in hydrochloric acid gives a mixture of ferrous and ferric chlorides:
The iron(II) chloride is converted to the iron(III) derivative by treatment with oxygen and hydrochloric acid:
References
Organic reactions
Inorganic reactions
Halogens | Oxychlorination | [
"Chemistry"
] | 538 | [
"Inorganic reactions",
"Organic reactions"
] |
37,765,984 | https://en.wikipedia.org/wiki/Flattop%20%28critical%20assembly%29 | Flattop is a benchmark critical assembly that is used to study the nuclear characteristics of uranium-233, uranium-235, and plutonium-239 in spherical geometries surrounded by a relatively thick natural uranium neutron reflector.
Flattop assemblies are used to measure neutron activation and reactivity coefficients. Since the neutron energies gradually decrease in the reflector, experiments may be run in various energy spectra based on the location in which they are placed.
Specifications
Flattop is a natural-uranium-reflected, benchmarked, fixed-geometry critical assembly machine that can accommodate plutonium or uranium cores. The fast neutron spectrum is used to provide benchmarked neutronic measurements in spherical geometry with different fissile driver materials. Key missions for Flattop include fundamental reactor physics studies, sample irradiation for radiochemical research, actinide minimum critical mass studies, detector calibration, and training. The U-233 core is no longer usable because of its high gamma-ray activity.
The experiment was originally located at the Los Alamos National Laboratory Critical Experiments Facility (LACEF) located at the Los Alamos Pajarito Site, otherwise known as Technical Area 18. In 2005 the Pajarito Site started to shut down and nuclear material was moved to the National Criticality Experiments Research Center (NCERC) which is located at the Nevada National Security Site. However, NCERC continues to be operated by the Los Alamos National Laboratory. The core capabilities at NCERC include Flattop along with three other critical assemblies, Comet, Planet, and Godiva-IV and a significant inventory of nuclear material items available for experimental use. NCERC critical operations commenced in 2011 and continue to be operational today.
Space power research
In 2012, Flattop was used for key demonstration of the use of nuclear power for space applications. The Demonstration Using Flattop Fission, or DUFF, test was planned by Los Alamos National Laboratory to use Flattop as a nuclear heat source. A team from the NASA Glenn Research Center in partnership with the LANL reactor design team designed, built, and tested a heat pipe and power conversion system to couple to Flattop with the end goal of demonstrating electrical power production using technology applicable to space application.
Controls
Flattop consists of a hemispherical fixed reflector and two movable quarter-spheres of reflector that can close down on the central core. One movable reflector is controlled by hydraulic pressure, while the other is actuated by a motor.
References
Nuclear technology
Nuclear research reactors | Flattop (critical assembly) | [
"Physics"
] | 509 | [
"Nuclear technology",
"Nuclear physics"
] |
37,771,398 | https://en.wikipedia.org/wiki/NRF51%20series | The nRF51 Series SoCs are a family of ultra low-power wireless SoCs from Nordic Semiconductor. The nRF51 series are designed to enable a wide range of wireless embedded systems and consumer electronic products in many different fields of wireless connectivity including wearable devices, computer peripherals, mobile phone accessories, security devices and sensor applications. The nRF51 series devices support a range of ultra low-power wireless communication protocols including: Bluetooth low energy, ANT, ANT+ and 2.4 GHz proprietary protocols.
Radio architecture
The nRF51 series devices employ Nordic Semiconductor's 3rd generation 2.4 GHz radio architecture. This radio uses narrow-band GFSK modulation and is frequency adaptable across the 2.4 GHz ISM band.
Key features
ARM Cortex-M0 microcontroller
Programmable GPIO
Bespoke power management system
Programmable Peripheral Interconnect system
Radio packet DMA (Direct Memory Access)
4dBm output power
Independent software architecture
External Links
Nordic Semi Bluetooth Low Energy Products
Microtechnology | NRF51 series | [
"Materials_science",
"Engineering"
] | 211 | [
"Materials science",
"Microtechnology"
] |
35,314,773 | https://en.wikipedia.org/wiki/Kai-Ming%20Ho | Kai-Ming Ho is a senior physicist at Ames Laboratory and distinguished professor in Department of Physics and Astronomy at Iowa State University.
Honors
2012 Aneesur Rahman Prize for Computational Physics (American Physical Society)
External links
Personal website
21st-century American physicists
Iowa State University faculty
University of California, Berkeley alumni
Year of birth missing (living people)
Living people
Hong Kong physicists
Alumni of the University of Hong Kong
Computational physicists | Kai-Ming Ho | [
"Physics"
] | 86 | [
"Computational physicists",
"Computational physics"
] |
35,314,983 | https://en.wikipedia.org/wiki/Viability%20theory | Viability theory is an area of mathematics that studies the evolution of dynamical systems under constraints on the system state. It was developed to formalize problems arising in the study of various natural and social phenomena, and has close ties to the theories of optimal control and set-valued analysis.
Motivation
Many systems, organizations, and networks arising in biology and the social sciences do not evolve in a deterministic way, nor even in a stochastic way. Rather they evolve with a Darwinian flavor, driven by random fluctuations but yet constrained to remain "viable" by their environment. Viability theory started in 1976 by translating mathematically the title of the book Chance and Necessity by Jacques Monod to the differential inclusion for chance and
for necessity. The differential inclusion is a type of “evolutionary engine” (called an evolutionary system associating with any initial state x a subset of evolutions starting at x. The system is said to be deterministic if this set is made of one and only one evolution and contingent otherwise.
Necessity is the requirement that at each instant, the evolution is viable (remains) in the environment K described by viability constraints, a word encompassing polysemous concepts as stability, confinement, homeostasis, adaptation, etc., expressing the idea that some variables must obey some constraints (representing physical, social, biological and economic constraints, etc.) that can never be violated. So, viability theory starts as the confrontation of evolutionary systems governing evolutions and viability constraints that such evolutions must obey. They share common features:
Systems designed by human brains, in the sense that agents, actors, decision-makers act on the evolutionary system, as in engineering (control theory and differential games)
Systems observed by human brains, more difficult to understand since there is no consensus on the actors piloting the variable, who, at least, may be myopic, lazy but explorers, conservative but opportunist. This is the case of economics, less in finance, where the viability constraints are the scarcity constraints among many other ones, in connectionist networks and/or cooperative games, in population and social dynamics, in neurosciences and some biological issues.
Viability theory thus designs and develops mathematical and algorithmic methods for investigating the "adaptation to viability constraints" of evolutions governed by complex systems under uncertainty that are found in many domains involving living beings, from biological evolution to economics, from environmental sciences to financial markets, from control theory and robotics to cognitive sciences. It needed to forge a differential calculus of set-valued maps (set-valued analysis), differential inclusions and differential calculus in metric spaces (mutational analysis).
Viability kernel
The basic problem of viability theory is to find the "viability kernel" of an environment, the subset of initial states in the environment such that there exists at least one evolution "viable" in the environment, in the sense that at each time, the state of the evolution remains confined to the environment. The second question is then to provide the regulation map selecting such viable evolutions starting from the viability kernel. The viability kernel may be equal to the environment, in which case the environment is called viable under the evolutionary system, and the empty set, in which case it is called a repellor, because all evolutions eventually violate the constraints.
The viability kernel assumes that some kind of "decision maker" controls or regulates evolutions of the system. If not, the next problem looks at the "tychastic kernel" (from tyche, meaning chance in Greek) or "invariance kernel", the subset of initial states in the environment such that all evolutions are "viable" in the environment, an alternative way to stochastic differential equations encapsulating the concept of "insurance" against uncertainty, providing a way of eradicating it instead of evaluating it.
See also
Autonomous agency theory
Viable system theory
Notes
References
Aubin J.-P. (2010) La mort du devin, l’émergence du démiurge : Essai sur la contingence, la viabilité et l’inertie des systèmes, Beauchesne
Aubin J.-P. (2000) Mutational and morphological analysis: tools for shape regulation and morphogenesis, Birkhäuser
Aubin J.-P. (1997) Dynamic economic theory: a viability approach, Springer-Verlag
Aubin J.-P. (1996) Neural networks and qualitative physics: a viability approach, Cambridge University Press
Aubin J.-P. & Frankowska H. (1990) Set-valued analysis, Birkhäuser
Aubin J.-P. & Cellina A. (1984) Differential Inclusions. Set-valued Maps and Viability Theory Springer-Verlag
Dordan O. (1995) Analyse qualitative Masson
Dynamical systems | Viability theory | [
"Physics",
"Mathematics"
] | 995 | [
"Mechanics",
"Dynamical systems"
] |
35,317,869 | https://en.wikipedia.org/wiki/List%20of%20isomers%20of%20nonane | This is the list of structural isomers of nonane. There are 35.
Straight-chain
Nonane
Octanes
2-Methyloctane
3-Methyloctane
4-Methyloctane
Heptanes
Dimethylheptanes
2,2-Dimethylheptane
2,3-Dimethylheptane
2,4-Dimethylheptane
2,5-Dimethylheptane
2,6-Dimethylheptane
3,3-Dimethylheptane
3,4-Dimethylheptane
3,5-Dimethylheptane
4,4-Dimethylheptane
Ethylheptanes
3-Ethylheptane
4-Ethylheptane
Hexane
Isomers where hexane is the longest chain:
Trimethyl
2,2,3-Trimethylhexane
2,2,4-Trimethylhexane
2,2,5-Trimethylhexane
2,3,3-Trimethylhexane
2,3,4-Trimethylhexane
2,3,5-Trimethylhexane
2,4,4-Trimethylhexane
3,3,4-Trimethylhexane
Methyl+Ethyl
3-Ethyl-2-methylhexane
4-Ethyl-2-methylhexane
3-Ethyl-3-methylhexane
3-Ethyl-4-methylhexane
Pentane
Isomers where pentane is the longest chain
Tetramethyl
2,2,3,3-Tetramethylpentane
2,2,3,4-Tetramethylpentane
2,2,4,4-Tetramethylpentane
2,3,3,4-Tetramethylpentane
Dimethyl+ethyl
3-Ethyl-2,2-dimethylpentane
3-Ethyl-2,3-dimethylpentane
3-Ethyl-2,4-dimethylpentane
Diethyl
3,3-Diethylpentane
Lists of isomers of alkanes
Isomerism
Hydrocarbons | List of isomers of nonane | [
"Chemistry"
] | 473 | [
"Hydrocarbons",
"Stereochemistry",
"Organic compounds",
"Lists of isomers of alkanes",
"Isomerism"
] |
35,318,832 | https://en.wikipedia.org/wiki/List%20of%20isomers%20of%20dodecane | This is the list of 355 isomers of dodecane.
Straight-chain
Dodecane
Undecane
2-Methylundecane
3-Methylundecane
4-Methylundecane
5-Methylundecane
6-Methylundecane
Decane
Dimethyl
2,2-Dimethyldecane
2,3-Dimethyldecane
2,4-Dimethyldecane
2,5-Dimethyldecane
2,6-Dimethyldecane
2,7-Dimethyldecane
2,8-Dimethyldecane
2,9-Dimethyldecane
3,3-Dimethyldecane
3,4-Dimethyldecane
3,5-Dimethyldecane
3,6-Dimethyldecane
3,7-Dimethyldecane
3,8-Dimethyldecane
4,4-Dimethyldecane
4,5-Dimethyldecane
4,6-Dimethyldecane
4,7-Dimethyldecane
5,5-Dimethyldecane
5,6-Dimethyldecane
Ethyl
3-Ethyldecane
4-Ethyldecane
5-Ethyldecane
Nonane
Trimethyl
2,2,3-Trimethylnonane
2,2,4-Trimethylnonane
2,2,5-Trimethylnonane
2,2,6-Trimethylnonane
2,2,7-Trimethylnonane
2,2,8-Trimethylnonane
2,3,3-Trimethylnonane
2,3,4-Trimethylnonane
2,3,5-Trimethylnonane
2,3,6-Trimethylnonane
2,3,7-Trimethylnonane
2,3,8-Trimethylnonane
2,4,4-Trimethylnonane
2,4,5-Trimethylnonane
2,4,6-Trimethylnonane
2,4,7-Trimethylnonane
2,4,8-Trimethylnonane
2,5,5-Trimethylnonane
2,5,6-Trimethylnonane
2,5,7-Trimethylnonane
2,5,8-Trimethylnonane
2,6,6-Trimethylnonane
2,6,7-Trimethylnonane
2,7,7-Trimethylnonane
3,3,4-Trimethylnonane
3,3,5-Trimethylnonane
3,3,6-Trimethylnonane
3,3,7-Trimethylnonane
3,4,4-Trimethylnonane
3,4,5-Trimethylnonane
3,4,6-Trimethylnonane
3,4,7-Trimethylnonane
3,5,5-Trimethylnonane
3,5,6-Trimethylnonane
3,5,7-Trimethylnonane
3,6,6-Trimethylnonane
4,4,5-Trimethylnonane
4,4,6-Trimethylnonane
4,5,5-Trimethylnonane
4,5,6-Trimethylnonane
Ethyl+Methyl
3-Ethyl-2-methylnonane
3-Ethyl-3-methylnonane
3-Ethyl-4-methylnonane
3-Ethyl-5-methylnonane
3-Ethyl-6-methylnonane
3-Ethyl-7-methylnonane
4-Ethyl-2-methylnonane
4-Ethyl-3-methylnonane
4-Ethyl-4-methylnonane
4-Ethyl-5-methylnonane
4-Ethyl-6-methylnonane
5-Ethyl-2-methylnonane
5-Ethyl-3-methylnonane
5-Ethyl-4-methylnonane
5-Ethyl-5-methylnonane
6-Ethyl-2-methylnonane
6-Ethyl-3-methylnonane
7-Ethyl-2-methylnonane
Propyl
4-Propylnonane
5-Propylnonane
4-(1-Methylethyl)nonane /(4-isopropylnonane)
5-(1-Methylethyl)nonane /(5-isopropylnonane)
Octane
Tetramethyl
2,2,3,3-Tetramethyloctane
2,2,3,4-Tetramethyloctane
2,2,3,5-Tetramethyloctane
2,2,3,6-Tetramethyloctane
2,2,3,7-Tetramethyloctane
2,2,4,4-Tetramethyloctane
2,2,4,5-Tetramethyloctane
2,2,4,6-Tetramethyloctane
2,2,4,7-Tetramethyloctane
2,2,5,5-Tetramethyloctane
2,2,5,6-Tetramethyloctane
2,2,5,7-Tetramethyloctane
2,2,6,6-Tetramethyloctane
2,2,6,7-Tetramethyloctane
2,2,7,7-Tetramethyloctane
2,3,3,4-Tetramethyloctane
2,3,3,5-Tetramethyloctane
2,3,3,6-Tetramethyloctane
2,3,3,7-Tetramethyloctane
2,3,4,4-Tetramethyloctane
2,3,4,5-Tetramethyloctane
2,3,4,6-Tetramethyloctane
2,3,4,7-Tetramethyloctane
2,3,5,5-Tetramethyloctane
2,3,5,6-Tetramethyloctane
2,3,5,7-Tetramethyloctane
2,3,6,6-Tetramethyloctane
2,3,6,7-Tetramethyloctane
2,4,4,5-Tetramethyloctane
2,4,4,6-Tetramethyloctane
2,4,4,7-Tetramethyloctane
2,4,5,5-Tetramethyloctane
2,4,5,6-Tetramethyloctane
2,4,5,7-Tetramethyloctane
2,4,6,6-Tetramethyloctane
2,5,5,6-Tetramethyloctane
2,5,6,6-Tetramethyloctane
3,3,4,4-Tetramethyloctane
3,3,4,5-Tetramethyloctane
3,3,4,6-Tetramethyloctane
3,3,5,5-Tetramethyloctane
3,3,5,6-Tetramethyloctane
3,3,6,6-Tetramethyloctane
3,4,4,5-Tetramethyloctane
3,4,4,6-Tetramethyloctane
3,4,5,5-Tetramethyloctane
3,4,5,6-Tetramethyloctane
4,4,5,5-Tetramethyloctane
Ethyl+Dimethyl
3-Ethyl-2,2-dimethyloctane
3-Ethyl-2,3-dimethyloctane
3-Ethyl-2,4-dimethyloctane
3-Ethyl-2,5-dimethyloctane
3-Ethyl-2,6-dimethyloctane
3-Ethyl-2,7-dimethyloctane
3-Ethyl-3,4-dimethyloctane
3-Ethyl-3,5-dimethyloctane
3-Ethyl-3,6-dimethyloctane
3-Ethyl-4,4-dimethyloctane
3-Ethyl-4,5-dimethyloctane
3-Ethyl-4,6-dimethyloctane
3-Ethyl-5,5-dimethyloctane
4-Ethyl-2,2-dimethyloctane
4-Ethyl-2,3-dimethyloctane
4-Ethyl-2,4-dimethyloctane
4-Ethyl-2,5-dimethyloctane
4-Ethyl-2,6-dimethyloctane
4-Ethyl-2,7-dimethyloctane
4-Ethyl-3,3-dimethyloctane
4-Ethyl-3,4-dimethyloctane
4-Ethyl-3,5-dimethyloctane
4-Ethyl-3,6-dimethyloctane
4-Ethyl-4,5-dimethyloctane
5-Ethyl-2,2-dimethyloctane
5-Ethyl-2,3-dimethyloctane
5-Ethyl-2,4-dimethyloctane
5-Ethyl-2,5-dimethyloctane
5-Ethyl-2,6-dimethyloctane
5-Ethyl-3,3-dimethyloctane
5-Ethyl-3,4-dimethyloctane
5-Ethyl-3,5-dimethyloctane
5-Ethyl-4,4-dimethyloctane
6-Ethyl-2,2-dimethyloctane
6-Ethyl-2,3-dimethyloctane
6-Ethyl-2,4-dimethyloctane
6-Ethyl-2,5-dimethyloctane
6-Ethyl-2,6-dimethyloctane
6-Ethyl-3,3-dimethyloctane
6-Ethyl-3,4-dimethyloctane
Diethyl
3,3-Diethyloctane
3,4-Diethyloctane
3,5-Diethyloctane
3,6-Diethyloctane
4,4-Diethyloctane
4,5-Diethyloctane
Methyl+Propyl
2-Methyl-4-propyloctane
3-Methyl-4-propyloctane
4-Methyl-4-propyloctane
4-Methyl-5-propyloctane
2-Methyl-5-propyloctane
3-Methyl-5-propyloctane
2-Methyl-3-(1-methylethyl)octane
2-Methyl-4-(1-methylethyl)octane
3-Methyl-4-(1-methylethyl)octane
4-Methyl-4-(1-methylethyl)octane
4-Methyl-5-(1-methylethyl)octane
2-Methyl-5-(1-methylethyl)octane
3-Methyl-5-(1-methylethyl)octane
tert-Butyl
4-(1,1-Dimethylethyl)octane or 4-tert-Butyloctane
Heptane
Pentamethyl
2,2,3,3,4-Pentamethylheptane
2,2,3,3,5-Pentamethylheptane
2,2,3,3,6-Pentamethylheptane
2,2,3,4,4-Pentamethylheptane
2,2,3,4,5-Pentamethylheptane
2,2,3,4,6-Pentamethylheptane
2,2,3,5,5-Pentamethylheptane
2,2,3,5,6-Pentamethylheptane
2,2,3,6,6-Pentamethylheptane
2,2,4,4,5-Pentamethylheptane
2,2,4,4,6-Pentamethylheptane
2,2,4,5,5-Pentamethylheptane
2,2,4,5,6-Pentamethylheptane
2,2,4,6,6-Pentamethylheptane
2,2,5,5,6-Pentamethylheptane
2,3,3,4,4-Pentamethylheptane
2,3,3,4,5-Pentamethylheptane
2,3,3,4,6-Pentamethylheptane
2,3,3,5,5-Pentamethylheptane
2,3,3,5,6-Pentamethylheptane
2,3,4,4,5-Pentamethylheptane
2,3,4,4,6-Pentamethylheptane
2,3,4,5,5-Pentamethylheptane
2,3,4,5,6-Pentamethylheptane
2,4,4,5,5-Pentamethylheptane
3,3,4,4,5-Pentamethylheptane
3,3,4,5,5-Pentamethylheptane
Ethyl+Trimethyl
3-Ethyl-2,2,3-trimethylheptane
3-Ethyl-2,2,4-trimethylheptane
3-Ethyl-2,2,5-trimethylheptane
3-Ethyl-2,2,6-trimethylheptane
3-Ethyl-2,3,4-trimethylheptane
3-Ethyl-2,3,5-trimethylheptane
3-Ethyl-2,3,6-trimethylheptane
3-Ethyl-2,4,4-trimethylheptane
3-Ethyl-2,4,5-trimethylheptane
3-Ethyl-2,4,6-trimethylheptane
3-Ethyl-2,5,5-trimethylheptane
3-Ethyl-2,5,6-trimethylheptane
3-Ethyl-3,4,4-trimethylheptane
3-Ethyl-3,4,5-trimethylheptane
3-Ethyl-3,5,5-trimethylheptane
3-Ethyl-4,4,5-trimethylheptane
4-Ethyl-2,2,3-trimethylheptane
4-Ethyl-2,2,4-trimethylheptane
4-Ethyl-2,2,5-trimethylheptane
4-Ethyl-2,2,6-trimethylheptane
4-Ethyl-2,3,3-trimethylheptane
4-Ethyl-2,3,4-trimethylheptane
4-Ethyl-2,3,5-trimethylheptane
4-Ethyl-2,3,6-trimethylheptane
4-Ethyl-2,4,5-trimethylheptane
4-Ethyl-2,4,6-trimethylheptane
4-Ethyl-2,5,5-trimethylheptane
4-Ethyl-3,3,4-trimethylheptane
4-Ethyl-3,3,5-trimethylheptane
4-Ethyl-3,4,5-trimethylheptane
5-Ethyl-2,2,3-trimethylheptane
5-Ethyl-2,2,4-trimethylheptane
5-Ethyl-2,2,5-trimethylheptane
5-Ethyl-2,2,6-trimethylheptane
5-Ethyl-2,3,3-trimethylheptane
5-Ethyl-2,3,4-trimethylheptane
5-Ethyl-2,3,5-trimethylheptane
5-Ethyl-2,4,4-trimethylheptane
5-Ethyl-2,4,5-trimethylheptane
5-Ethyl-3,3,4-trimethylheptane
Diethyl+Methyl
3,3-Diethyl-2-methylheptane
3,3-Diethyl-4-methylheptane
3,3-Diethyl-5-methylheptane
3,4-Diethyl-2-methylheptane
3,4-Diethyl-3-methylheptane
3,4-Diethyl-4-methylheptane
3,4-Diethyl-5-methylheptane
3,5-Diethyl-2-methylheptane
3,5-Diethyl-3-methylheptane
3,5-Diethyl-4-methylheptane
4,4-Diethyl-2-methylheptane
4,4-Diethyl-3-methylheptane
4,5-Diethyl-2-methylheptane
5,5-Diethyl-2-methylheptane
Dimethyl+Propyl
2,2-Dimethyl-4-propylheptane
2,3-Dimethyl-4-propylheptane
2,4-Dimethyl-4-propylheptane
2,5-Dimethyl-4-propylheptane
2,6-Dimethyl-4-propylheptane
3,3-Dimethyl-4-propylheptane
3,4-Dimethyl-4-propylheptane
3,5-Dimethyl-4-propylheptane
2,2-Dimethyl-3-(1-methylethyl)heptane
2,3-Dimethyl-3-(1-methylethyl)heptane
2,4-Dimethyl-3-(1-methylethyl)heptane
2,5-Dimethyl-3-(1-methylethyl)heptane
2,6-Dimethyl-3-(1-methylethyl)heptane
2,2-Dimethyl-4-(1-methylethyl)heptane
2,3-Dimethyl-4-(1-methylethyl)heptane
2,4-Dimethyl-4-(1-methylethyl)heptane
2,5-Dimethyl-4-(1-methylethyl)heptane
2,6-Dimethyl-4-(1-methylethyl)heptane
3,3-Dimethyl-4-(1-methylethyl)heptane
3,4-Dimethyl-4-(1-methylethyl)heptane
3,5-Dimethyl-4-(1-methylethyl)heptane
Ethyl+Propyl
3-Ethyl-4-propylheptane
4-Ethyl-4-propylheptane
3-Ethyl-4-(1-methylethyl)heptane
4-Ethyl-4-(1-methylethyl)heptane
Propyl+Methyl
4-(1,1-Dimethylethyl)-2-methylheptane
4-(1,1-Dimethylethyl)-3-methylheptane
4-(1,1-Dimethylethyl)-4-methylheptane
Hexane
Hexamethyl
2,2,3,3,4,4-Hexamethylhexane
2,2,3,3,4,5-Hexamethylhexane
2,2,3,3,5,5-Hexamethylhexane
2,2,3,4,4,5-Hexamethylhexane
2,2,3,4,5,5-Hexamethylhexane
2,3,3,4,4,5-Hexamethylhexane
Ethyl+Tetramethyl
3-Ethyl-2,2,3,4-tetramethylhexane
3-Ethyl-2,2,3,5-tetramethylhexane
3-Ethyl-2,2,4,4-tetramethylhexane
3-Ethyl-2,2,4,5-tetramethylhexane
3-Ethyl-2,2,5,5-tetramethylhexane
3-Ethyl-2,3,4,4-tetramethylhexane
3-Ethyl-2,3,4,5-tetramethylhexane
4-Ethyl-2,2,3,3-tetramethylhexane
4-Ethyl-2,2,3,4-tetramethylhexane
4-Ethyl-2,2,3,5-tetramethylhexane
4-Ethyl-2,2,4,5-tetramethylhexane
4-Ethyl-2,3,3,4-tetramethylhexane
4-Ethyl-2,3,3,5-tetramethylhexane
Diethyl+Dimethyl
3,3-Diethyl-2,2-dimethylhexane
3,3-Diethyl-2,4-dimethylhexane
3,3-Diethyl-2,5-dimethylhexane
3,3-Diethyl-4,4-dimethylhexane
3,4-Diethyl-2,2-dimethylhexane
3,4-Diethyl-2,3-dimethylhexane
3,4-Diethyl-2,4-dimethylhexane
3,4-Diethyl-2,5-dimethylhexane
3,4-Diethyl-3,4-dimethylhexane
4,4-Diethyl-2,2-dimethylhexane
4,4-Diethyl-2,3-dimethylhexane
Triethyl
3,3,4-Triethylhexane
Trimethyl+Propyl
2,2,3-Trimethyl-3-(1-methylethyl)hexane
2,2,4-Trimethyl-3-(1-methylethyl)hexane
2,2,5-Trimethyl-3-(1-methylethyl)hexane
2,3,4-Trimethyl-3-(1-methylethyl)hexane
2,3,5-Trimethyl-3-(1-methylethyl)hexane
2,4,4-Trimethyl-3-(1-methylethyl)hexane
2,3,5-Trimethyl-4-(1-methylethyl)hexane
2,2,5-Trimethyl-4-(1-methylethyl)hexane
Ethyl+Methyl+Propyl
3-Ethyl-2-methyl-3-(1-methylethyl)hexane
4-Ethyl-2-methyl-3-(1-methylethyl)hexane
tert-Butyl+Dimethyl
3-(1,1-Dimethylethyl)-2,2-dimethylhexane
Pentane
Ethyl+Pentamethyl
3-Ethyl-2,2,3,4,4-pentamethylpentane
Diethyl+Trimethyl
3,3-Diethyl-2,2,4-trimethylpentane
Tetramethyl+Propyl
2,2,3,4-Tetramethyl-3-(1-methylethyl)pentane
2,2,4,4-Tetramethyl-3-(1-methylethyl)pentane
Ethyl+Dimethyl+Propyl
3-Ethyl-2,4-dimethyl-3-(1-methylethyl)pentane
References
Lists of isomers of alkanes
Hydrocarbons | List of isomers of dodecane | [
"Chemistry"
] | 5,369 | [
"Organic compounds",
"Isomerism",
"Hydrocarbons",
"Lists of isomers of alkanes"
] |
35,319,154 | https://en.wikipedia.org/wiki/Occupational%20safety%20and%20health | Occupational safety and health (OSH) or occupational health and safety (OHS) is a multidisciplinary field concerned with the safety, health, and welfare of people at work (i.e., while performing duties required by one's occupation). OSH is related to the fields of occupational medicine and occupational hygiene and aligns with workplace health promotion initiatives. OSH also protects all the general public who may be affected by the occupational environment.
According to the official estimates of the United Nations, the WHO/ILO Joint Estimate of the Work-related Burden of Disease and Injury, almost 2 million people die each year due to exposure to occupational risk factors. Globally, more than 2.78 million people die annually as a result of workplace-related accidents or diseases, corresponding to one death every fifteen seconds. There are an additional 374 million non-fatal work-related injuries annually. It is estimated that the economic burden of occupational-related injury and death is nearly four per cent of the global gross domestic product each year. The human cost of this adversity is enormous.
In common-law jurisdictions, employers have the common law duty (also called duty of care) to take reasonable care of the safety of their employees. Statute law may, in addition, impose other general duties, introduce specific duties, and create government bodies with powers to regulate occupational safety issues. Details of this vary from jurisdiction to jurisdiction.
Prevention of workplace incidents and occupational diseases is addressed through the implementation of occupational safety and health programs at company level.
Definitions
The International Labour Organization (ILO) and the World Health Organization (WHO) share a common definition of occupational health. It was first adopted by the Joint ILO/WHO Committee on Occupational Health at its first session in 1950:
In 1995, a consensus statement was added:
An alternative definition for occupational health given by the WHO is: "occupational health deals with all aspects of health and safety in the workplace and has a strong focus on primary prevention of hazards."
The expression "occupational health", as originally adopted by the WHO and the ILO, refers to both short- and long-term adverse health effects. In more recent times, the expressions "occupational safety and health" and "occupational health and safety" have come into use (and have also been adopted in works by the ILO), based on the general understanding that occupational health refers to hazards associated to disease and long-term effects, while occupational safety hazards are those associated to work accidents causing injury and sudden severe conditions.
History
Research and regulation of occupational safety and health are a relatively recent phenomenon. As labor movements arose in response to worker concerns in the wake of the industrial revolution, workers' safety and health entered consideration as a labor-related issue.
Beginnings
Written works on occupational diseases began to appear by the end of the 15th century, when demand for gold and silver was rising due to the increase in trade and iron, copper, and lead were also in demand from the nascent firearms market. Deeper mining became common as a consequence. In 1473, , a German physician, wrote a short treatise On the Poisonous Wicked Fumes and Smokes, focused on coal, nitric acid, lead, and mercury fumes encountered by metal workers and goldsmiths. In 1587, Paracelsus (1493–1541) published the first work on the mine and smelter workers diseases. In it, he gave accounts of miners' "lung sickness". In 1526, Georgius Agricola's (1494–1553) De re metallica, a treaty on metallurgy, described accidents and diseases prevalent among miners and recommended practices to prevent them. Like Paracelsus, Agricola mentioned the dust that "eats away the lungs, and implants consumption."
The seeds of state intervention to correct social ills were sown during the reign of Elizabeth I by the Poor Laws, which originated in attempts to alleviate hardship arising from widespread poverty. While they were perhaps more to do with a need to contain unrest than morally motivated, they were significant in transferring responsibility for helping the needy from private hands to the state.
In 1713, Bernardino Ramazzini (1633–1714), often described as the father of occupational medicine and a precursor to occupational health, published his De morbis artificum diatriba (Dissertation on Workers' Diseases), which outlined the health hazards of chemicals, dust, metals, repetitive or violent motions, odd postures, and other disease-causative agents encountered by workers in more than fifty occupations. It was the first broad-ranging presentation of occupational diseases.
Percivall Pott (1714–1788), an English surgeon, described cancer in chimney sweeps (chimney sweeps' carcinoma), the first recognition of an occupational cancer in history.
The Industrial Revolution in Britain
The United Kingdom was the first nation to industrialize. Soon shocking evidence emerged of serious physical and moral harm suffered by children and young persons in the cotton textile mills, as a result of exploitation of cheap labor in the factory system. Responding to calls for remedial action from philanthropists and some of the more enlightened employers, in 1802 Sir Robert Peel, himself a mill owner, introduced a bill to parliament with the aim of improving their conditions. This would engender the Health and Morals of Apprentices Act 1802, generally believed to be the first attempt to regulate conditions of work in the United Kingdom. The act applied only to cotton textile mills and required employers to keep premises clean and healthy by twice yearly washings with quicklime, to ensure there were sufficient windows to admit fresh air, and to supply "apprentices" (i.e., pauper and orphan employees) with "sufficient and suitable" clothing and accommodation for sleeping. It was the first of the 19th century Factory Acts.
Charles Thackrah (1795–1833), another pioneer of occupational medicine, wrote a report on The State of Children Employed in Cotton Factories, which was sent to the Parliament in 1818. Thackrah recognized issues of inequalities of health in the workplace, with manufacturing in towns causing higher mortality than agriculture.
The Act of 1833 created a dedicated professional Factory Inspectorate. The initial remit of the Inspectorate was to police restrictions on the working hours in the textile industry of children and young persons (introduced to prevent chronic overwork, identified as leading directly to ill-health and deformation, and indirectly to a high accident rate).
In 1840 a Royal Commission published its findings on the state of conditions for the workers of the mining industry that documented the appallingly dangerous environment that they had to work in and the high frequency of accidents. The commission sparked public outrage which resulted in the Mines and Collieries Act of 1842. The act set up an inspectorate for mines and collieries which resulted in many prosecutions and safety improvements, and by 1850, inspectors were able to enter and inspect premises at their discretion.
On the urging of the Factory Inspectorate, a further act in 1844 giving similar restrictions on working hours for women in the textile industry introduced a requirement for machinery guarding (but only in the textile industry, and only in areas that might be accessed by women or children). The latter act was the first to take a significant step toward improvement of workers' safety, as the former focused on health aspects alone.
The first decennial British Registrar-General's mortality report was issued in 1851. Deaths were categorized by social classes, with class I corresponding to professionals and executives and class V representing unskilled workers. The report showed that mortality rates increased with the class number.
Continental Europe
Otto von Bismarck inaugurated the first social insurance legislation in 1883 and the first worker's compensation law in 1884 – the first of their kind in the Western world. Similar acts followed in other countries, partly in response to labor unrest.
United States
The United States are responsible for the first health program focusing on workplace conditions. This was the Marine Hospital Service, inaugurated in 1798 and providing care for merchant seamen. This was the beginning of what would become the US Public Health Service (USPHS).
The first worker compensation acts in the United States were passed in New York in 1910 and in Washington and Wisconsin in 1911. Later rulings included occupational diseases in the scope of the compensation, which was initially restricted to accidents.
In 1914 the USPHS set up the Office of Industrial Hygiene and Sanitation, the ancestor of the current National Institute for Safety and Health (NIOSH). In the early 20th century, workplace disasters were still common. For example, in 1911 a fire at the Triangle Shirtwaist Company in New York killed 146 workers, mostly women and immigrants. Most died trying to open exits that had been locked. Radium dial painter cancers,"phossy jaw", mercury and lead poisonings, silicosis, and other pneumoconioses were extremely common.
The enactment of the Federal Coal Mine Health and Safety Act of 1969 was quickly followed by the 1970 Occupational Safety and Health Act, which established the Occupational Safety and Health Administration (OSHA) and NIOSH in their current form`.
Workplace hazards
A wide array of workplace hazards can damage the health and safety of people at work. These include but are not limited to, "chemicals, biological agents, physical factors, adverse ergonomic conditions, allergens, a complex network of safety risks," as well a broad range of psychosocial risk factors. Personal protective equipment can help protect against many of these hazards. A landmark study conducted by the World Health Organization and the International Labour Organization found that exposure to long working hours is the occupational risk factor with the largest attributable burden of disease, i.e. an estimated 745,000 fatalities from ischemic heart disease and stroke events in 2016. This makes overwork the globally leading occupational health risk factor.
Physical hazards affect many people in the workplace. Occupational hearing loss is the most common work-related injury in the United States, with 22 million workers exposed to hazardous occupational noise levels at work and an estimated $242 million spent annually on worker's compensation for hearing loss disability. Falls are also a common cause of occupational injuries and fatalities, especially in construction, extraction, transportation, healthcare, and building cleaning and maintenance. Machines have moving parts, sharp edges, hot surfaces and other hazards with the potential to crush, burn, cut, shear, stab or otherwise strike or wound workers if used unsafely.
Biological hazards (biohazards) include infectious microorganisms such as viruses, bacteria and toxins produced by those organisms such as anthrax. Biohazards affect workers in many industries; influenza, for example, affects a broad population of workers. Outdoor workers, including farmers, landscapers, and construction workers, risk exposure to numerous biohazards, including animal bites and stings, urushiol from poisonous plants, and diseases transmitted through animals such as the West Nile virus and Lyme disease. Health care workers, including veterinary health workers, risk exposure to blood-borne pathogens and various infectious diseases, especially those that are emerging.
Dangerous chemicals can pose a chemical hazard in the workplace. There are many classifications of hazardous chemicals, including neurotoxins, immune agents, dermatologic agents, carcinogens, reproductive toxins, systemic toxins, asthmagens, pneumoconiotic agents, and sensitizers. Authorities such as regulatory agencies set occupational exposure limits to mitigate the risk of chemical hazards. International investigations are ongoing into the health effects of mixtures of chemicals, given that toxins can interact synergistically instead of merely additively. For example, there is some evidence that certain chemicals are harmful at low levels when mixed with one or more other chemicals. Such synergistic effects may be particularly important in causing cancer. Additionally, some substances (such as heavy metals and organohalogens) can accumulate in the body over time, thereby enabling small incremental daily exposures to eventually add up to dangerous levels with little overt warning.
Psychosocial hazards include risks to the mental and emotional well-being of workers, such as feelings of job insecurity, long work hours, and poor work-life balance. Psychological abuse has been found present within the workplace as evidenced by previous research. A study by Gary Namie on workplace emotional abuse found that 31% of women and 21% of men who reported workplace emotional abuse exhibited three key symptoms of post-traumatic stress disorder (hypervigilance, intrusive imagery, and avoidance behaviors). Sexual harassment is a serious hazard that can be found in workplaces.
By industry
Specific occupational safety and health risk factors vary depending on the specific sector and industry. Construction workers might be particularly at risk of falls, for instance, whereas fishermen might be particularly at risk of drowning. Similarly psychosocial risks such as workplace violence are more pronounced for certain occupational groups such as health care employees, police, correctional officers and teachers.
Primary sector
Agriculture
Agriculture workers are often at risk of work-related injuries, lung disease, noise-induced hearing loss, skin disease, as well as certain cancers related to chemical use or prolonged sun exposure. On industrialized farms, injuries frequently involve the use of agricultural machinery. The most common cause of fatal agricultural injuries in the United States is tractor rollovers, which can be prevented by the use of roll over protection structures which limit the risk of injury in case a tractor rolls over. Pesticides and other chemicals used in farming can also be hazardous to worker health, and workers exposed to pesticides may experience illnesses or birth defects. As an industry in which families, including children, commonly work alongside their families, agriculture is a common source of occupational injuries and illnesses among younger workers. Common causes of fatal injuries among young farm worker include drowning, machinery and motor vehicle-related accidents.
The 2010 NHIS-OHS found elevated prevalence rates of several occupational exposures in the agriculture, forestry, and fishing sector which may negatively impact health. These workers often worked long hours. The prevalence rate of working more than 48 hours a week among workers employed in these industries was 37%, and 24% worked more than 60 hours a week. Of all workers in these industries, 85% frequently worked outdoors compared to 25% of all US workers. Additionally, 53% were frequently exposed to vapors, gas, dust, or fumes, compared to 25% of all US workers.
Mining and oil and gas extraction
The mining industry still has one of the highest rates of fatalities of any industry. There are a range of hazards present in surface and underground mining operations. In surface mining, leading hazards include such issues as geological instability, contact with plant and equipment, rock blasting, thermal environments (heat and cold), respiratory health (black lung), etc. In underground mining, operational hazards include respiratory health, explosions and gas (particularly in coal mine operations), geological instability, electrical equipment, contact with plant and equipment, heat stress, inrush of bodies of water, falls from height, confined spaces, ionising radiation, etc.
According to data from the 2010 NHIS-OHS, workers employed in mining and oil and gas extraction industries had high prevalence rates of exposure to potentially harmful work organization characteristics and hazardous chemicals. Many of these workers worked long hours: 50% worked more than 48 hours a week and 25% worked more than 60 hours a week in 2010. Additionally, 42% worked non-standard shifts (not a regular day shift). These workers also had high prevalence of exposure to physical/chemical hazards. In 2010, 39% had frequent skin contact with chemicals. Among nonsmoking workers, 28% of those in mining and oil and gas extraction industries had frequent exposure to secondhand smoke at work. About two-thirds were frequently exposed to vapors, gas, dust, or fumes at work.
Secondary sector
Construction
Construction is one of the most dangerous occupations in the world, incurring more occupational fatalities than any other sector in both the United States and in the European Union. In 2009, the fatal occupational injury rate among construction workers in the United States was nearly three times that for all workers. Falls are one of the most common causes of fatal and non-fatal injuries among construction workers. Proper safety equipment such as harnesses and guardrails and procedures such as securing ladders and inspecting scaffolding can curtail the risk of occupational injuries in the construction industry. Due to the fact that accidents may have disastrous consequences for employees as well as organizations, it is of utmost importance to ensure health and safety of workers and compliance with HSE construction requirements. Health and safety legislation in the construction industry involves many rules and regulations. For example, the role of the Construction Design Management (CDM) Coordinator as a requirement has been aimed at improving health and safety on-site.
The 2010 National Health Interview Survey Occupational Health Supplement (NHIS-OHS) identified work organization factors and occupational psychosocial and chemical/physical exposures which may increase some health risks. Among all US workers in the construction sector, 44% had non-standard work arrangements (were not regular permanent employees) compared to 19% of all US workers, 15% had temporary employment compared to 7% of all US workers, and 55% experienced job insecurity compared to 32% of all US workers. Prevalence rates for exposure to physical/chemical hazards were especially high for the construction sector. Among nonsmoking workers, 24% of construction workers were exposed to secondhand smoke while only 10% of all US workers were exposed. Other physical/chemical hazards with high prevalence rates in the construction industry were frequently working outdoors (73%) and frequent exposure to vapors, gas, dust, or fumes (51%).
Tertiary sector
The service sector comprises diverse workplaces. Each type of workplace has its own health risks. While some occupations have become mobile, others still require desk work. As the number of service sector jobs has risen in developed countries, many jobs have turned sedentary, presenting an array of health problems that differ from previous health concerns associated with manufacturing and the primary sector. Contemporary health problems include obesity. Some working conditions, such as occupational stress, workplace bullying, and overwork, have negative consequences for physical and mental health.
Tipped wage workers are at a higher risk of negative mental health outcomes like addiction or depression. The higher rates of mental health issues may be attributed to the precarious nature of their employment, characterized by low and unpredictable incomes, inadequate access to benefits, wage exploitation, and minimal control over work schedules and assigned shifts. Close to 70% of tipped wage workers are women. Additionally, "almost 40 percent of people who work for tips are people of color: 18 percent are Latino, 10 percent are African American, and 9 percent are Asian. Immigrants are also overrepresented in the tipped workforce." According to data from the 2010 NHIS-OHS, hazardous physical and chemical exposures in the service sector were lower than national averages. However, harmful organizational practices and psychosocial risks were fairly prevalent in this sector. Among all workers in the service industry, 30% experienced job insecurity in 2010, 27% worked non-standard shifts (not a regular day shift), 21% had non-standard work arrangements (were not regular permanent employees).
In addition to these organizational risks, some industries pose significant physical dangers due to the manual labor involved. For instance, on a per employee basis, the US Postal Service, UPS and FedEx are the 4th, 5th and 7th most dangerous companies to work for in the United States, respectively.
Healthcare and social assistance
In general, healthcare workers are exposed to many hazards that can adversely affect their health and well-being. Long hours, changing shifts, physically demanding tasks, violence, and exposures to infectious diseases and harmful chemicals are examples of hazards that put these workers at risk for illness and injury. Musculoskeletal injury (MSI) is the most common health hazard in for healthcare workers and in workplaces overall. Injuries can be prevented by using proper body mechanics.
According to the Bureau of Labor statistics, US hospitals recorded 253,700 work-related injuries and illnesses in 2011, which is 6.8 work-related injuries and illnesses for every 100 full-time employees. The injury and illness rate in hospitals is higher than the rates in construction and manufacturing – two industries that are traditionally thought to be relatively hazardous.
Workplace fatality and injury statistics
Worldwide
An estimated 2.90 million work-related deaths occurred in 2019, increased from 2.78 million death from 2015. About, one-third of the total work-related deaths (31%) were due to circulatory diseases, while cancer contributed 29%, respiratory diseases 17%, and occupational injuries contributed 11% (or about 319,000 fatalities). Other diseases such as work-related communicable diseases contributed 6%, while neuropsychiatric conditions contributed 3% and work-related digestive disease and genitourinary diseases contributed 1% each. The contribution of cancers and circulatory diseases to total work-related deaths increased from 2015, while deaths due to occupational injuries decreased. Although work-related injury deaths and non-fatal injuries rates were on a decreasing trend, the total deaths and non-fatal outcomes were on the rise. Cancers represented the most significant cause of mortality in high-income countries. The number of non-fatal occupational injuries for 2019 was estimated to be 402 million.
Mortality rate is unevenly distributed, with male mortality rate (108.3 per 100,000 employed male individuals) being significantly higher than female rate (48.4 per 100,000). 6.7% of all deaths globally are represented by occupational fatalities.
European Union
Certain EU member states admit to having lacking quality control in occupational safety services, to situations in which risk analysis takes place without any on-site workplace visits and to insufficient implementation of certain EU OSH directives. Disparities between member states result in different impact of occupational hazards on the economy. In the early 2000s, the total societal costs of work-related health problems and accidents varied from 2.6% to 3.8% of the national GDPs across the member states.
In 2021, in the EU-27 as a whole, 93% of deaths due to injury were of males.
Russia
One of the decisions taken by the communist regime under Stalin was to reduce the number of accidents and occupational diseases to zero. The tendency to decline remained in the Russian Federation in the early 21st century. However, as in previous years, data reporting and publication was incomplete and manipulated, so that the actual number of work-related diseases and accidents are unknown. The ILO reports that, according to the information provided by the Russian government, there are 190,000 work-related fatalities each year, of which 15,000 due to occupational accidents.
After the demise of the USSR, enterprises became owned by oligarchs who were not interested in upholding safe and healthy conditions in the workplace. Expenditure on equipment modernization was minimal and the share of harmful workplaces increased. The government did not interfere in this, and sometimes it helped employers. At first, the increase in occupational diseases and accidents was slow, due to the fact that in the 1990s it was compensated by mass deindustrialization. However, in the 2000s deindustrialization slowed and occupational diseases and injuries started to rise in earnest. Therefore, in the 2010s the Ministry of Labor adopted federal law no. 426-FZ. This piece of legislation has been described as ineffective and based on the superficial assumption that the issuance of personal protective equipment to the employee means real improvement of working conditions. Meanwhile, the Ministry of Health made significant changes in the methods of risk assessment in the workplace. However, specialists from the Izmerov Research Institute of Occupational Health found that the post-2014 apparent decrease in the share of employees engaged in hazardous working conditions is due to the change in definitions consequent to the Ministry of Health's decision, but does not reflect actual improvements. This was most clearly shown in the results for the aluminum industry.
Further problems in the accounting of workplace fatalities arise from the fact that multiple Russian federal entities collect and publish records, a practice that should be avoided. In 2008 alone, 2074 accidents at work may have not been reported in official government sources.
United Kingdom
In the UK there were 135 fatal injuries at work in financial year 2022–2023, compared with 651 in 1974 (the year when the Health and Safety at Work Act was promulgated). The fatal injury rate declined from 2.1 fatalities per 100,000 workers in 1981 to 0.41 in financial year 2022–2023. Over recent decades reductions in both fatal and non-fatal workplace injuries have been very significant. However, illnesses statistics have not uniformly improved: while musculoskeletal disorders have diminished, the rate of self-reported work-related stress, depression or anxiety has increased, and the rate of mesothelioma deaths has remained broadly flat (due to past asbestos exposures).
United States
The Occupational Safety and Health Statistics (OSHS) program in the Bureau of Labor Statistics of the United States Department of Labor compiles information about workplace fatalities and non-fatal injuries in the United States. The OSHS program produces three annual reports:
Counts and rates of nonfatal occupational injuries and illnesses by detailed industry and case type (SOII summary data)
Case circumstances and worker demographic data for nonfatal occupational injuries and illnesses resulting in days away from work (SOII case and demographic data)
Counts and rates of fatal occupational injuries (CFOI data)
The Bureau also uses tools like AgInjuryNews.org to identify and compile additional sources of fatality reports for their datasets.
Between 1913 and 2013, workplace fatalities dropped by approximately 80%. In 1970, an estimated 14,000 workers were killed on the job. By 2021, in spite of the workforce having since more than doubled, workplace deaths were down to about 5,190. According to the census of occupational injuries 5,486 people died on the job in 2022, up from the 2021 total of 5,190. The fatal injury rate was 3.7 per 100,000 full-time equivalent workers. The decrease in the mortality rate is only partly (about 10–15%) explained by the deindustrialization of the US in the last 40 years.
About 3.5 million nonfatal workplace injuries and illnesses were reported by private industry employers in 2022, occurring at a rate of 3.0 cases per 100 full-time workers.
Management systems
Companies may adopt a safety and health management system (SMS), either voluntarily or because required by applicable regulations, to deal in a structured and systematic way with safety and health risks in their workplace. An SMS provides a systematic way to assess and improve prevention of workplace accidents and incidents based on structured management of workplace risks and hazards. It must be adaptable to changes in the organization's business and legislative requirements. It is usually based on the Deming cycle, or plan-do-check-act (PDCA) principle. An effective SMS should:
Define how the organization is set up to manage risk
Identify workplace hazards and implement suitable controls
Implement effective communication across all levels of the organization
Implement a process to identify and correct non-conformity and non-compliance issues
Implement a continual improvement process
Management standards across a range of business functions such as environment, quality and safety are now being designed so that these traditionally disparate elements can be integrated and managed within a single business management system and not as separate and stand-alone functions. Therefore, some organizations dovetail other management system functions, such as process safety, environmental resource management or quality management together with safety management to meet both regulatory requirements, industry sector requirements and their own internal and discretionary standard requirements.
Standards
International
The ILO published ILO-OSH 2001 on Guidelines on Occupational Safety and Health Management Systems to assist organizations with introducing OSH management systems. These guidelines encouraged continual improvement in employee health and safety, achieved via a constant process of policy; organization; planning and implementation; evaluation; and action for improvement, all supported by constant auditing to determine the success of OSH actions.
From 1999 to 2018, OHSAS 18001 was adopted and widely used internationally. It was developed by a selection of national standards bodies, academic bodies, accreditation bodies, certification bodies and occupational health and safety institutions to address a gap where no third-party certifiable international standard existed. It was designed for integration with ISO 9001 and ISO 14001.
OHSAS 18001 was replaced by ISO 45001, which was published in March 2018 and implemented in March 2021.
National
National management system standards for occupational health and safety include AS/NZS 4801 for Australia and New Zealand (now superseded by ISO 45001), CSA Z1000:14 for Canada (which is due to be discontinued in favor of CSA Z45001:19, the Canadian adoption of ISO 45000) and ANSI/ASSP Z10 for the United States. In Germany, the Bavarian state government, in collaboration with trade associations and private companies, issued their OHRIS standard for occupational health and safety management systems. A new revision was issued in 2018. The Taiwan Occupational Safety and Health Management System (TOSHMS) was issued in 1997 under the auspices of Taiwan's Occupational Safety and Health Administration.
Identifying OSH hazards and assessing risk
Hazards, risks, outcomes
The terminology used in OSH varies between countries, but generally speaking:
A hazard is something that can cause harm if not controlled.
The outcome is the harm that results from an uncontrolled hazard.
A risk is a combination of the probability that a particular outcome may occur and the severity of the harm involved.
"Hazard", "risk", and "outcome" are used in other fields to describe e.g., environmental damage or damage to equipment. However, in the context of OSH, "harm" generally describes the direct or indirect degradation, temporary or permanent, of the physical, mental, or social well-being of workers. For example, repetitively carrying out manual handling of heavy objects is a hazard. The outcome could be a musculoskeletal disorder (MSD) or an acute back or joint injury. The risk can be expressed numerically (e.g., a 0.5 or 50/50 chance of the outcome occurring during a year), in relative terms (e.g., "high/medium/low"), or with a multi-dimensional classification scheme (e.g., situation-specific risks).
Hazard identification
Hazard identification is an important step in the overall risk assessment and risk management process. It is where individual work hazards are identified, assessed and controlled or eliminated as close to source (location of the hazard) as reasonably practicable. As technology, resources, social expectation or regulatory requirements change, hazard analysis focuses controls more closely toward the source of the hazard. Thus, hazard control is a dynamic program of prevention. Hazard-based programs also have the advantage of not assigning or implying there are "acceptable risks" in the workplace. A hazard-based program may not be able to eliminate all risks, but neither does it accept "satisfactory" – but still risky – outcomes. And as those who calculate and manage the risk are usually managers, while those exposed to the risks are a different group, a hazard-based approach can bypass conflict inherent in a risk-based approach.
The information that needs to be gathered from sources should apply to the specific type of work from which the hazards can come from. Examples of these sources include interviews with people who have worked in the field of the hazard, history and analysis of past incidents, and official reports of work and the hazards encountered. Of these, the personnel interviews may be the most critical in identifying undocumented practices, events, releases, hazards and other relevant information. Once the information is gathered from a collection of sources, it is recommended for these to be digitally archived (to allow for quick searching) and to have a physical set of the same information in order for it to be more accessible. One innovative way to display the complex historical hazard information is with a historical hazards identification map, which distills the hazard information into an easy-to-use graphical format.
Risk assessment
Modern occupational safety and health legislation usually demands that a risk assessment be carried out prior to making an intervention. This assessment should:
Identify the hazards
Identify all affected by the hazard and how
Evaluate the risk
Identify and prioritize appropriate control measures.
The calculation of risk is based on the likelihood or probability of the harm being realized and the severity of the consequences. This can be expressed mathematically as a quantitative assessment (by assigning low, medium and high likelihood and severity with integers and multiplying them to obtain a risk factor), or qualitatively as a description of the circumstances by which the harm could arise.
The assessment should be recorded and reviewed periodically and whenever there is a significant change to work practices. The assessment should include practical recommendations to control the risk. Once recommended controls are implemented, the risk should be re-calculated to determine if it has been lowered to an acceptable level. Generally speaking, newly introduced controls should lower risk by one level, i.e., from high to medium or from medium to low.
National legislation and public organizations
Occupational safety and health practice vary among nations with different approaches to legislation, regulation, enforcement, and incentives for compliance. In the EU, for example, some member states promote OSH by providing public monies as subsidies, grants or financing, while others have created tax system incentives for OSH investments. A third group of EU member states has experimented with using workplace accident insurance premium discounts for companies or organizations with strong OSH records.
Australia
In Australia, four of the six states and both territories have enacted and administer harmonized work health and safety legislation in accordance with the Intergovernmental Agreement for Regulatory and Operational Reform in Occupational Health and Safety. Each of these jurisdictions has enacted work health and safety legislation and regulations based on the Commonwealth Work Health and Safety Act 2011 and common codes of practice developed by Safe Work Australia. Some jurisdictions have also included mine safety under the model approach. However, most have retained separate legislation for the time being. In August 2019, Western Australia committed to join nearly every other state and territory in implementing the harmonized Model WHS Act, Regulations and other subsidiary legislation. Victoria has retained its own regime, although the Model WHS laws themselves drew heavily on the Victorian approach.
Canada
In Canada, workers are covered by provincial or federal labor codes depending on the sector in which they work. Workers covered by federal legislation (including those in mining, transportation, and federal employment) are covered by the Canada Labour Code; all other workers are covered by the health and safety legislation of the province in which they work. The Canadian Centre for Occupational Health and Safety (CCOHS), an agency of the Government of Canada, was created in 1978 by an act of parliament. The act was based on the belief that all Canadians had "a fundamental right to a healthy and safe working environment." CCOHS is mandated to promote safe and healthy workplaces and help prevent work-related injuries and illnesses.
China
In China, the Ministry of Health is responsible for occupational disease prevention and the State Administration of Work Safety workplace safety issues. The Work Safety Law (安全生产法) was issued on 1 November 2002. The Occupational Disease Control Act came into force on 1 May 2002. In 2018, the National Health Commission (NHC) was formally established to formulating national health policies. The NHC formulated the "National Occupational Disease Prevention and Control Plan (2021–2025)" in the context of the activities leading to the "Healthy China 2030" initiative.
European Union
The European Agency for Safety and Health at Work was founded in 1994. In the European Union, member states have enforcing authorities to ensure that the basic legal requirements relating to occupational health and safety are met. In many EU countries, there is strong cooperation between employer and worker organizations (e.g., unions) to ensure good OSH performance, as it is recognized this has benefits for both the worker (through maintenance of health) and the enterprise (through improved productivity and quality).
Member states have all transposed into their national legislation a series of directives that establish minimum standards on occupational health and safety. These directives (of which there are about 20 on a variety of topics) follow a similar structure requiring the employer to assess workplace risks and put in place preventive measures based on a hierarchy of hazard control. This hierarchy starts with elimination of the hazard and ends with personal protective equipment.
Denmark
In Denmark, occupational safety and health is regulated by the Danish Act on Working Environment and Cooperation at the Workplace. The Danish Working Environment Authority (Arbejdstilsynet) carries out inspections of companies, draws up more detailed rules on health and safety at work and provides information on health and safety at work. The result of each inspection is made public on the web pages of the Danish Working Environment Authority so that the general public, current and prospective employees, customers and other stakeholders can inform themselves about whether a given organization has passed the inspection.
Netherlands
In the Netherlands, the laws for safety and health at work are registered in the Working Conditions Act (Arbeidsomstandighedenwet and Arbeidsomstandighedenbeleid). Apart from the direct laws directed to safety and health in working environments, the private domain has added health and safety rules in Working Conditions Policies (Arbeidsomstandighedenbeleid), which are specified per industry. The Ministry of Social Affairs and Employment (SZW) monitors adherence to the rules through their inspection service. This inspection service investigates industrial accidents and it can suspend work and impose fines when it deems the Working Conditions Act has been violated. Companies can get certified with a VCA certificate for safety, health and environment performance. All employees have to obtain a VCA certificate too, with which they can prove that they know how to work according to the current and applicable safety and environmental regulations.
Ireland
The main health and safety regulation in Ireland is the Safety, Health and Welfare at Work Act 2005, which replaced earlier legislation from 1989. The Health and Safety Authority, based in Dublin, is responsible for enforcing health and safety at work legislation.
Spain
In Spain, occupational safety and health is regulated by the Spanish Act on Prevention of Labor Risks. The Ministry of Labor is the authority responsible for issues relating to labor environment. The National Institute for Safety and Health at Work (Instituto Nacional de Seguridad y Salud en el Trabajo, INSST) is the government's scientific and technical organization specialized in occupational safety and health.
Sweden
In Sweden, occupational safety and health is regulated by the Work Environment Act. The Swedish Work Environment Authority (Arbetsmiljöverket) is the government agency responsible for issues relating to the working environment. The agency works to disseminate information and furnish advice on OSH, has a mandate to carry out inspections, and a right to issue stipulations and injunctions to any non-compliant employer.
India
In India, the Ministry of Labour and Employment formulates national policies on occupational safety and health in factories and docks with advice and assistance from its Directorate General Factory Advice Service and Labour Institutes (DGFASLI), and enforces its policies through inspectorates of factories and inspectorates of dock safety. The DGFASLI provides technical support in formulating rules, conducting occupational safety surveys and administering occupational safety training programs.
Indonesia
In Indonesia, the Ministry of Manpower (Kementerian Ketenagakerjaan, or Kemnaker) is responsible to ensure the safety, health and welfare of workers. Important OHS acts include the Occupational Safety Act 1970 and the Occupational Health Act 1992. Sanctions, however, are still low (with a maximum of 15 million rupiahs fine and/or a maximum of one year in prison) and violations are still very frequent.
Japan
The Japanese Ministry of Health, Labor and Welfare (MHLW) is the governmental agency overseeing occupational safety and health in Japan. The MHLW is responsible for enforcing Industrial Safety and Health Act of 1972 – the key piece of OSH legislation in Japan –, setting regulations and guidelines, supervising labor inspectors who monitor workplaces for compliance with safety and health standards, investigating accidents, and issuing orders to improve safety conditions. The Labor Standards Bureau is an arm of MHLW tasked with supervising and guiding businesses, inspecting manufacturing facilities for safety and compliance, investigating accidents, collecting statistics, enforcing regulations and administering fines for safety violations, and paying accident compensation for injured workers.
The (JISHA) is a non-profit organization established under the Industrial Safety and Health Act of 1972. It works closely with MHLW, the regulatory body, to promote workplace safety and health. The responsibilities of JISHA include: Providing education and training on occupational safety and health, conducting research and surveys on workplace safety and health issues, offering technical guidance and consultations to businesses, disseminating information and raising awareness about occupational safety and health, and collaborating with international organizations to share best practices and improve global workplace safety standards.
The (JNIOSH) conducts research to support governmental policies in occupational safety and health. The organization categorizes its research into project studies, cooperative research, fundamental research, and government-requested research. Each category focuses on specific themes, from preventing accidents and ensuring workers' health, to addressing changes in employment structure. The organization sets clear goals, develops road maps, and collaborates with the Ministry of Health, Labor and Welfare to discuss progress and policy contributions.
Malaysia
In Malaysia, the Department of Occupational Safety and Health (DOSH) under the Ministry of Human Resources is responsible to ensure that the safety, health and welfare of workers in both the public and private sector is upheld. DOSH is responsible to enforce the Factories and Machinery Act 1967 and the Occupational Safety and Health Act 1994. Malaysia has a statutory mechanism for worker involvement through elected health and safety representatives and health and safety committees. This followed a similar approach originally adopted in Scandinavia.
Saudi Arabia
In Saudi Arabia, the Ministry of Human Resources and Social Development administrates workers' rights and the labor market as a whole, consistent with human rights rules upheld by the Human Rights Commission of the kingdom.
Singapore
In Singapore, the Ministry of Manpower (MOM) is the government agency in charge of OHS policies and enforcement. The key piece of legislation regulating aspects of OHS is the Workplace Safety and Health Act. The MOM promotes and manages campaigns against unsafe work practices, such as when working at height, operating cranes and in traffic management. Examples include Operation Cormorant and the Falls Prevention Campaign.
South Africa
In South Africa the Department of Employment and Labour is responsible for occupational health and safety inspection and enforcement in the commercial and industrial sectors, with the exclusion of mining, where the Department of Mineral Resources is responsible. The main statutory legislation on health and safety in the jurisdiction of the Department of Employment and Labour is the OHS Act or OHSA (Act No. 85 of 1993: Occupational Health and Safety Act, as amended by the Occupational Health and Safety Amendment Act, No. 181 of 1993). Regulations implementing the OHS Act include:
General Safety Regulations, 1986
Environmental Regulations for Workplaces, 1987
Driven Machinery Regulations, 1988
General Machinery Regulations, 1988
Noise Induced Hearing Loss Regulations, 2003
Pressure Equipment Regulations, 2004
General Administrative Regulations, 2003
Diving Regulations, 2009
Construction Regulations, 2014
Syria
In Syria, health and safety is the responsibility of the Ministry of Social Affairs and Labor ().
Taiwan
In Taiwan, the of the Ministry of Labor is in charge of occupational safety and health. The matter is governed under the .
United Arab Emirates
In the United Arab Emirates, national OSH legislation is based on the Federal Law on Labor (1980). Order No. 32 of 1982 on Protection from Hazards and Ministerial Decision No. 37/2 of 1982 are also of importance. The competent authority for safety and health at work at the federal level is the Ministry of Human Resources and Emiratisation (MoHRE).
United Kingdom
Health and safety legislation in the UK is drawn up and enforced by the Health and Safety Executive and local authorities under the Health and Safety at Work etc. Act 1974 (HASAWA or HSWA). HASAWA introduced (section 2) a general duty on an employer to ensure, so far as is reasonably practicable, the health, safety and welfare at work of all his employees, with the intention of giving a legal framework supporting codes of practice not in themselves having legal force but establishing a strong presumption as to what was reasonably practicable (deviations from them could be justified by appropriate risk assessment). The previous reliance on detailed prescriptive rule-setting was seen as having failed to respond rapidly enough to technological change, leaving new technologies potentially unregulated or inappropriately regulated. HSE has continued to make some regulations giving absolute duties (where something must be done with no "reasonable practicability" test) but in the UK the regulatory trend is away from prescriptive rules, and toward goal setting and risk assessment. Recent major changes to the laws governing asbestos and fire safety management embrace the concept of risk assessment. The other key aspect of the UK legislation is a statutory mechanism for worker involvement through elected health and safety representatives and health and safety committees. This followed a similar approach in Scandinavia, and that approach has since been adopted in countries such as Australia, Canada, New Zealand and Malaysia.
The Health and Safety Executive service dealing with occupational medicine has been the Employment Medical Advisory Service. In 2014 a new occupational health organization, the Health and Work Service, was created to provide advice and assistance to employers in order to get back to work employees on long-term sick-leave. The service, funded by the government, offers medical assessments and treatment plans, on a voluntary basis, to people on long-term absence from their employer; in return, the government no longer foots the bill for statutory sick pay provided by the employer to the individual.
United States
In the United States, President Richard Nixon signed the Occupational Safety and Health Act into law on 29 December 1970. The act created the three agencies which administer OSH: the Occupational Safety and Health Administration (OSHA), the National Institute for Occupational Safety and Health (NIOSH), and the Occupational Safety and Health Review Commission (OSHRC). The act authorized OSHA to regulate private employers in the 50 states, the District of Columbia, and territories. It includes a general duty clause (29 U.S.C. §654, 5(a)) requiring an employer to comply with the Act and regulations derived from it, and to provide employees with "employment and a place of employment which are free from recognized hazards that are causing or are likely to cause [them] death or serious physical harm."
OSHA was established in 1971 under the Department of Labor. It has headquarters in Washington, DC, and ten regional offices, further broken down into districts, each organized into three sections: compliance, training, and assistance. Its stated mission is "to ensure safe and healthful working conditions for workers by setting and enforcing standards and by providing training, outreach, education and assistance." The original plan was for OSHA to oversee 50 state plans with OSHA funding 50% of each plan, but this did not work out that way: there are 26 approved state plans (with four covering only public employees) and OSHA manages the plan in the states not participating.
OSHA develops safety standards in the Code of Federal Regulations and enforces those safety standards through compliance inspections conducted by Compliance Officers; enforcement resources are focused on high-hazard industries. Worksites may apply to enter OSHA's Voluntary Protection Program (VPP). A successful application leads to an on-site inspection; if this is passed, the site gains VPP status and OSHA no longer inspect it annually nor (normally) visit it unless there is a fatal accident or an employee complaint until VPP revalidation (after three–five years). VPP sites generally have injury and illness rates less than half the average for their industry.
OSHA has a number of specialists in local offices to provide information and training to employers and employees at little or no cost. Similarly OSHA produces a range of publications and funds consultation services available for small businesses.
OSHA has strategic partnership and alliance programs to develop guidelines, assist in compliance, share resources, and educate workers in OHS. OSHA manages Susan B. Harwood grants to non-profit organizations to train workers and employers to recognize, avoid, and prevent safety and health hazards in the workplace. Grants focus on small business, hard-to-reach workers and high-hazard industries.
The National Institute for Occupational Safety and Health (NIOSH), also created under the Occupational Safety and Health Act, is the federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the Centers for Disease Control and Prevention (CDC) within the Department of Health and Human Services.
Professional roles and responsibilities
Those in the field of occupational safety and health come from a wide range of disciplines and professions including medicine, occupational medicine, epidemiology, physiotherapy and rehabilitation, psychology, human factors and ergonomics, and many others. Professionals advise on a broad range of occupational safety and health matters. These include how to avoid particular pre-existing conditions causing a problem in the occupation, correct posture, frequency of rest breaks, preventive actions that can be undertaken, and so forth. The quality of occupational safety is characterized by (1) the indicators reflecting the level of industrial injuries, (2) the average number of days of incapacity for work per employer, (3) employees' satisfaction with their work conditions and (4) employees' motivation to work safely.
The main tasks undertaken by the OSH practitioner include:
Inspecting, testing and evaluating workplace environments, programs, equipment, and practices to ensure that they follow government safety regulation.
Designing and implementing workplace programs and procedures that control or prevent chemical, physical, or other risks to workers.
Educating employers and workers about maintaining workplace safety.
Demonstrating use of safety equipment and ensuring proper use by workers.
Investigating incidents to determine the cause and possible prevention.
Preparing written reports of their findings.
OSH specialists examine worksites for environmental or physical factors that could harm employee health, safety, comfort or performance. They then find ways to improve potential risk factors. For example, they may notice potentially hazardous conditions inside a chemical plant and suggest changes to lighting, equipment, materials, or ventilation. OSH technicians assist specialists by collecting data on work environments and implementing the worksite improvements that specialists plan. Technicians also may check to make sure that workers are using required protective gear, such as masks and hardhats. OSH specialists and technicians may develop and conduct employee training programs. These programs cover a range of topics, such as how to use safety equipment correctly and how to respond in an emergency. In the event of a workplace safety incident, specialists and technicians investigate its cause. They then analyze data from the incident, such as the number of people impacted, and look for trends in occurrence. This evaluation helps them to recommend improvements to prevent future incidents.
Given the high demand in society for health and safety provisions at work based on reliable information, OSH professionals should find their roots in evidence-based practice. A new term is "evidence-informed decision making". Evidence-based practice can be defined as the use of evidence from literature, and other evidence-based sources, for advice and decisions that favor the health, safety, well-being, and work ability of workers. Therefore, evidence-based information must be integrated with professional expertise and the workers' values. Contextual factors must be considered related to legislation, culture, financial, and technical possibilities. Ethical considerations should be heeded.
The roles and responsibilities of OSH professionals vary regionally but may include evaluating working environments, developing, endorsing and encouraging measures that might prevent injuries and illnesses, providing OSH information to employers, employees, and the public, providing medical examinations, and assessing the success of worker health programs.
The Netherlands
In the Netherlands, the required tasks for health and safety staff are only summarily defined and include:
Providing voluntary medical examinations.
Providing a consulting room on the work environment to the workers.
Providing health assessments (if needed for the job concerned).
Dutch law influences the job of the safety professional mainly through the requirement on employers to use the services of a certified working-conditions service for advice. A certified service must employ sufficient numbers of four types of certified experts to cover the risks in the organizations which use the service:
A safety professional
An occupational hygienist
An occupational physician
A work and organization specialist.
In 2004, 14% of health and safety practitioners in the Netherlands had an MSc and 63% had a BSc. 23% had training as an OSH technician.
Norway
In Norway, the main required tasks of an occupational health and safety practitioner include:
Systematic evaluations of the working environment.
Endorsing preventive measures which eliminate causes of illnesses in the workplace.
Providing information on the subject of employees' health.
Providing information on occupational hygiene, ergonomics, and environmental and safety risks in the workplace.
In 2004, 37% of health and safety practitioners in Norway had an MSc and 44% had a BSc. 19% had training as an OSH technician.
Education and training
Formal education
There are multiple levels of training applicable to the field of occupational safety and health. Programs range from individual non-credit certificates and awareness courses focusing on specific areas of concern, to full doctoral programs. The University of Southern California was one of the first schools in the US to offer a PhD program focusing on the field. Further, multiple master's degree programs exist, such as that of the Indiana State University who offer MSc and MA programs. Other masters-level qualifications include the MSc and Master of Research (MRes) degrees offered by the University of Hull in collaboration with the National Examination Board in Occupational Safety and Health (NEBOSH). Graduate programs are designed to train educators, as well as high-level practitioners.
Many OSH generalists focus on undergraduate studies; programs within schools, such as that of the University of North Carolina's online BSc in environmental health and safety, fill a large majority of hygienist needs. However, smaller companies often do not have full-time safety specialists on staff, thus, they appoint a current employee to the responsibility. Individuals finding themselves in positions such as these, or for those enhancing marketability in the job-search and promotion arena, may seek out a credit certificate program. For example, the University of Connecticut's online OSH certificate provides students familiarity with overarching concepts through a 15-credit (5-course) program. Programs such as these are often adequate tools in building a strong educational platform for new safety managers with a minimal outlay of time and money. Further, most hygienists seek certification by organizations that train in specific areas of concentration, focusing on isolated workplace hazards. The American Society of Safety Professionals (ASSP), Board for Global EHS Credentialing (BGC), and American Industrial Hygiene Association (AIHA) offer individual certificates on many different subjects from forklift operation to waste disposal and are the chief facilitators of continuing education in the OSH sector.
In the US, the training of safety professionals is supported by NIOSH through their NIOSH Education and Research Centers.
In the UK, both NEBOSH and the Institution of Occupational Safety and Health (IOSH) develop health and safety qualifications and courses which cater to a mixture of industries and levels of study. Although both organizations are based in the UK, their qualifications are recognized and studied internationally as they are delivered through their own global networks of approved providers. The Health and Safety Executive has also developed health and safety qualifications in collaboration with the NEBOSH.
In Australia, training in OSH is available at the vocational education and training level, and at university undergraduate and postgraduate level. Such university courses may be accredited by an accreditation board of the Safety Institute of Australia. The institute has produced a Body of Knowledge which it considers is required by a generalist safety and health professional and offers a professional qualification. The Australian Institute of Health and Safety has instituted the national Eric Wigglesworth OHS Education Medal to recognize achievement in OSH doctorate education.
Field training
One form of training delivered in the workplace is known as toolbox talk. According to the UK's Health and Safety Executive, a toolbox talk is a short presentation to the workforce on a single aspect of health and safety. Such talks are often used, especially in the construction industry, by site supervisors, frontline managers and owners of small construction firms to prepare and deliver advice on matters of health, safety and the environment and to obtain feedback from the workforce.
Use of virtual reality
Virtual reality is a novel tool to deliver safety training in many fields. Some applications have been developed and tested especially for fire and construction safety training. Preliminary findings seem to support that virtual reality is more effective than traditional training in knowledge retention.
Contemporary developments
On an international scale, the World Health Organization (WHO) and the International Labour Organization (ILO) have begun focusing on labor environments in developing nations with projects such as Healthy Cities. Many of these developing countries are stuck in a situation in which their relative lack of resources to invest in OSH leads to increased costs due to work-related illnesses and accidents. The ILO estimates that work-related illness and accidents cost up to 10% of GDP in Latin America, compared with just 2.6% to 3.8% in the EU. There is continued use of asbestos, a notorious hazard, in some developing countries. So asbestos-related disease is expected to continue to be a significant problem well into the future.
Artificial intelligence
There are several broad aspects of artificial intelligence (AI) that may give rise to specific hazards.
Many hazards of AI are psychosocial in nature due to its potential to cause changes in work organization. For example, AI is expected to lead to changes in the skills required of workers, requiring retraining of existing workers, flexibility, and openness to change. Increased monitoring may lead to micromanagement or perception of surveillance, and thus to workplace stress. There is also the risk of people being forced to work at a robot's pace, or to monitor robot performance at nonstandard hours. Additionally, algorithms may show algorithmic bias through being trained on past decisions may mimic undesirable human biases, for example, past discriminatory hiring and firing practices. Some approaches to accident analysis may be biased to safeguard a technological system and its developers by assigning blame to the individual human operator instead.
Physical hazards in the form of human–robot collisions may arise from robots using AI, especially collaborative robots (cobots). Cobots are intended to operate in close proximity to humans, which makes it impossible to implement the common hazard control of isolating the robot using fences or other barriers, which is widely used for traditional industrial robots. Automated guided vehicles are a type of cobot in common use, often as forklifts or pallet jacks in warehouses or factories.
Both applications and hazards arising from AI can be considered as part of existing frameworks for occupational health and safety risk management. As with all hazards, risk identification is most effective and least costly when done in the design phase. AI, in common with other computational technologies, requires cybersecurity measures to stop software breaches and intrusions, as well as information privacy measures. Communication and transparency with workers about data usage is a control for psychosocial hazards arising from security and privacy issues. Workplace health surveillance, the collection and analysis of health data on workers, is challenging for AI because labor data are often reported in aggregate, does not provide breakdowns between different types of work, and is focused on economic data such as wages and employment rates rather than skill content of jobs.
Coronavirus
The National Institute of Occupational Safety and Health (NIOSH) National Occupational Research Agenda Manufacturing Council established an externally-lead COVID-19 workgroup to provide exposure control information specific to working in manufacturing environments. The workgroup identified disseminating information most relevant to manufacturing workplaces as a priority, and that would include providing content in Wikipedia. This includes evidence-based practices for infection control plans, and communication tools.
Nanotechnology
Nanotechnology is an example of a new, relatively unstudied technology. A Swiss survey of 138 companies using or producing nanoparticulate matter in 2006 resulted in forty completed questionnaires. Sixty-five per cent of respondent companies stated they did not have a formal risk assessment process for dealing with nanoparticulate matter. Nanotechnology already presents new issues for OSH professionals that will only become more difficult as nanostructures become more complex. The size of the particles renders most containment and personal protective equipment ineffective. The toxicology values for macro sized industrial substances are rendered inaccurate due to the unique nature of nanoparticulate matter. As nanoparticulate matter decreases in size its relative surface area increases dramatically, increasing any catalytic effect or chemical reactivity substantially versus the known value for the macro substance. This presents a new set of challenges in the near future to rethink contemporary measures to safeguard the health and welfare of employees against a nanoparticulate substance that most conventional controls have not been designed to manage.
Occupational health inequalities
Occupational health inequalities refer to differences in occupational injuries and illnesses that are closely linked with demographic, social, cultural, economic, and/or political factors. Although many advances have been made to rectify gaps in occupational health within the past half century, still many persist due to the complex overlapping of occupational health and social factors. There are three main areas of research on occupational health inequities:
Identifying which social factors, either individually or in combination, contribute to the inequitable distribution of work-related benefits and risks.
Examining how the related structural disadvantages materialize in the lives of workers to put them at greater risk for occupational injury or illness.
Translating these findings into intervention research to build an evidence base of effective ways for reducing occupational health inequities.
Transnational and immigrant worker populations
Immigrant worker populations often are at greater risk for workplace injuries and fatalities. For example within the United States, immigrant Mexican workers have one of the highest rates of fatal workplace injuries out of all of the working population. Statistics like these are explained through a combination of social, structural, and physical aspects of the workplace. These workers struggle to access safety information and resources in their native languages because of lack of social and political inclusion. In addition to linguistically tailored interventions, it is also critical for the interventions to be culturally appropriate.
Those residing in a country to work without a visa or other formal authorization may also not have access to legal resources and recourse that are designed to protect most workers. Health and Safety organizations that rely on whistleblowers instead of their own independent inspections may be especially at risk of having an incomplete picture of worker health.
See also
Regulations
Related fields
Notes
References
Sources
Further reading
External links
International agencies
(EU) European Agency for Safety & Health at Work (EU-OSHA)
(UN) International Labour Organization (ILO)
National bodies
(Canada) Canadian Centre for Occupational Health and Safety
(Japan) Japan Industrial Safety and Health Association
(Japan) Ministry of Health, Labor and Welfare
(Japan) Japan National Institute of Occupational Safety and Health
(UK) Health and Safety Executive
(US) National Institute for Occupational Safety and Health (NIOSH)
(US) Occupational Safety and Health Administration (OSHA)
Legislation
(Canada) EnviroOSH Legislation plus Standards
Publications
American Journal of Industrial Medicine
Education
National Examination Board in Occupational Safety and Health (NEBOSH)
Risk management in business
Industrial hygiene
Safety engineering
Environmental social science
Working conditions
Infectious diseases
Industrial and organizational psychology
Health promotion
ky:Өндүрүштөгү гигиена | Occupational safety and health | [
"Engineering",
"Environmental_science"
] | 13,089 | [
"Safety engineering",
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35,324,195 | https://en.wikipedia.org/wiki/C34H22O22 | The molecular formula C34H22O22 (molar mass: 782.52 g/mol, exact mass: 782.060272 u) may refer to:
Punicalin, an ellagitannin found in pomegranates
4,6-isoterchébuloyl-D-glucose, an ellagitannin found in Terminalia macroptera
Molecular formulas | C34H22O22 | [
"Physics",
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45,227,429 | https://en.wikipedia.org/wiki/Monier%20Ventilation%20Shaft%201 | Monier Ventilation Shaft 1 is a heritage-listed ventilation shaft at 500 Wickham Terrace, Spring Hill, City of Brisbane, Queensland, Australia. It was designed by Joseph Monier and built . It was added to the Queensland Heritage Register on 4 August 1998.
History
The Monier Ventilation Shafts are thought to have been constructed , as part of a system of ventilation shafts (either concrete or steel/iron) located at intervals along some of Brisbane's inner city arterial stormwater drains. Three concrete shafts survive (of at least five erected) and may be the first pre-cast reinforced concrete structures in Queensland.
The Wickham Terrace shaft, on the footpath at the eastern end of Albert Park, opposite Twine Street, was one of a pair, the other having been erected just inside the park, opposite Lilley Street, but since removed. A concrete shaft of identical dimensions exists on the footpath of St Paul's Terrace, opposite Gloucester Street. Both the Wickham Terrace and St Paul's Terrace shafts appear to have been associated with the first Spring Hill stormwater drainage system, laid in the 1880s. A third shaft (Monier Ventilation Shaft 3), of similar but smaller dimensions, exists on the footpath near the former Queensland Primary Producers' Woolstore No. 8, in Florence Street, Teneriffe. Stormwater drains were laid in Florence and Ethel streets in mid-1904, and the concrete ventilation shaft at the east end of the Florence Street drain may have been constructed shortly afterwards.
In the 19th century, the distinction between drainage and sewerage was not well defined. Drains were described as sewers and they received a combination of sullage, roof and surface run-off. They relied on rainwater for flushing, and discharged to the nearest watercourse.
When Brisbane acquired municipal status in late 1859, there was no system of drainage or sewerage in the town. Most people dumped refuse in the creeks and channels, trusting that stormwater would carry it away to the river, and for some years the Municipal Council considered drainage and sewerage as one and the same thing. However, from about 1868 the Council adopted the policy of "rainfall to the river" and "sewerage to the land", developing a city drainage scheme to carry off stormwater and an earth closet sanitary service.
The Brisbane Drainage Act of 1875, under which the colonial government agreed to set aside crown land for sale to finance Brisbane's drainage scheme, provided the impetus for construction of Brisbane's early arterial stormwater drains. The systems were designed by the colonial government's Engineer for Harbours and Rivers, William David Nisbet, and carried out by government contractors under government supervision. Upon completion they became the property and responsibility of the Brisbane Municipal Council, which was responsible also for laying branch drains.
By 1878, the inner city was drained by three separate systems:
the Frog's Hollow system – a main drain down Albert and Margaret Streets with branches laid by the Brisbane Municipal Council
the Adelaide Street–Creek Street system, which drained the centre of the town from Makerston Street to Queen Street and the lower sections of Elizabeth and Charlotte Streets
the Makerston Street system, which served the area between Makerston Street and Petrie Terrace, and between Wickham Terrace and College Road and the Brisbane River
Between 1879 and 1886 the Brisbane Municipal Council, with government loans, developed an arterial drainage system for the densely populated suburbs of Spring Hill and Fortitude Valley (even though Fortitude Valley then lay outside the Brisbane town boundary). Much of this work comprised open drains, which were covered in the late 1890s. South Brisbane and Kangaroo Point drainage systems were constructed in 1885–1886. In the late 1880s, the Brisbane Municipal Council drained parts of New Farm, and a drainage system for Petrie Terrace, begun in 1883, was completed in the late 1880s. By 1890, the Brisbane Municipal Council had completed an arterial drainage scheme for the city core, at a total cost of nearly .
The densely populated Booroodabin Division was annexed to the Municipality of Brisbane in 1903, and in 1908 a loan was secured to enable the council to complete the drainage of Merthyr, New Farm, Teneriffe, Bowen Hills, Mayne and Newstead by the end of 1909.
Without a proper sewerage system, Brisbane residents still tended to dispose of household and trade waste into the stormwater drainage systems. This led to the chronic pollution of local creeks, and foul smells emanating from the stormwater drains. Prior to bacterial theory being widely accepted, such miasma was thought to cause disease.
The situation was compounded in 1900 with the arrival of bubonic plague in Australia, carried by rats aboard ships arriving from foreign ports. The first case of human plague in Sydney was reported in January 1900, and in Brisbane (a day and a half away by steamer) on 27 April 1900. Between 1900 and 1909, plague broke out in most of Queensland's ports, galvanising the State into developing tighter controls over public health and sanitation.
In the early 20th century, the Commissioner of Public Health, using the strong coercive powers given to him under the provisions of the Health Act of 1900, required the Brisbane Municipal Council to erect ventilators in city streets to remove foul and unhealthy smells from the drainage systems. In 1900, the Council called tenders for the construction and erection of a ventilating shaft at Thorn Street, Kangaroo Point. No trace remains of this vent, except for its design, which was in the Monier system of re-inforced concrete, and identical with that of the vents that have survived on Wickham Terrace and St Paul's Terrace.
The Monier system of reinforced concrete (invented by Frenchman Joseph Monier and patented in 1867) was introduced to Australia in the early 1890s by WJ Baltzer, a New South Wales engineer. Monier's was the first true reinforced concrete, based on calculations which ensured that the steel was dispersed so as to take tension and shear forces. Baltzer, in association with contracting engineers Carter Gummow and Co. of Sydney, gained the Australian rights to this innovative fabric. The company constructed the first Monier system structure (a small arch for a storm water culvert) in Burwood, New South Wales, in 1894 and a sewer aqueduct linking the Sydney suburbs of Annandale and Balmain in 1895. The first use of the Monier system in Victoria was in 1897 with the Anderson Street Bridge over the Yarra River, designed and constructed by Carter Gummow & Co.
Carter Gummow and Co. began manufacture of Monier pipes in Sydney in 1897, and John Monash's Reinforced Concrete & Monier Pipe Construction Co. commenced production in Melbourne in 1903.
During the financial year 1903–1904, the Brisbane Municipal Council authorised the spending of on erecting sewer (drain) ventilating shafts wherever they were urgently needed. It is thought that the surviving concrete ventilation shafts were constructed in consequence.
Description
The three surviving concrete ventilation shafts are located in Brisbane's inner city suburbs of Spring Hill and Teneriffe. Two are in Spring Hill – one at the eastern end of Albert Park, on the footpath on Wickham Terrace opposite Twine Street; another on the footpath on St Paul's Terrace, opposite Gloucester Street. A third is located on the footpath in Florence Street, Teneriffe, west of the intersection with Macquarie Street. They ventilate stormwater drains rather than sewers.
The Spring Hill ventilators are located on ridges, but the Teneriffe ventilator is on low ground near the Brisbane River. It is not known what rationale was adopted in deciding where the vents were to be placed.
The ventilators are constructed of reinforced concrete, hexagonal in shape, with simple ornamentation at half height and apex. The Spring Hill ventilators are tall with a base width of . They have a wall thickness of at the base, tapering to at the top. The Teneriffe ventilator is of slightly smaller dimensions.
All three ventilators are thought to have been constructed in accordance with the patented Monier ventilation system for venting public sewers and drains, and probably pre-cast in an hexagonal mould, with the top face open.
Heritage listing
Monier Ventilation Shaft 1 (Spring Hill) was listed on the Queensland Heritage Register on 4 August 1998 having satisfied the following criteria.
The place is important in demonstrating the evolution or pattern of Queensland's history.
The Monier Ventilation Shafts, constructed , are important in illustrating late 19th/early 20th century attitudes toward public health and sanitation, and survive as visible evidence of Brisbane's early and extensive stormwater drainage scheme and venting system. The three surviving concrete shafts are thought to be the first pre-cast reinforced concrete structures in Queensland, and examples of the earliest application of the Monier system of reinforced concrete construction in Queensland.
The place demonstrates rare, uncommon or endangered aspects of Queensland's cultural heritage.
They provide rare surviving evidence of this early use of true reinforced concrete, and are significant as indicators of the technically advanced state of municipal engineering and construction in Brisbane at the turn of the 20th century.
The place has potential to yield information that will contribute to an understanding of Queensland's history.
They have the potential to contribute further to our understanding of:
community attitudes toward public health in the late 19th/early 20th centuries
Brisbane's early stormwater drainage scheme
early pre-cast reinforced concrete technology in Queensland.
The place is important in demonstrating the principal characteristics of a particular class of cultural places.
They remain highly intact examples of their type and demonstrate engineering skill and involvement in creating aesthetically pleasing but functional structures.
The place is important because of its aesthetic significance.
They remain highly intact examples of their type and demonstrate engineering skill and involvement in creating aesthetically pleasing but functional structures.
The place is important in demonstrating a high degree of creative or technical achievement at a particular period.
They provide rare surviving evidence of this early use of true reinforced concrete, and are significant as indicators of the technically advanced state of municipal engineering and construction in Brisbane at the turn of the 20th century.
See also
Monier Ventilation Shaft 2
Monier Ventilation Shaft 3
References
Attribution
External links
Queensland Heritage Register
Spring Hill, Queensland
Ventilation
Articles incorporating text from the Queensland Heritage Register
Stormwater management | Monier Ventilation Shaft 1 | [
"Chemistry",
"Environmental_science"
] | 2,103 | [
"Water treatment",
"Stormwater management",
"Water pollution"
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45,228,541 | https://en.wikipedia.org/wiki/TaxiBot | The TaxiBot, developed by the Lahav Division of Israel Aerospace Industries, is a semi-robotic, towbarless aircraft tractor.
Its primary function is to transport an aircraft from the terminal gate to the take-off area (taxi-out phase) and back to the gate post-landing (taxi-in phase). TaxiBot has been suspected to be able to reduce the need for airplane engines during these phases. Operational control of the TaxiBot is maintained by the aircraft's pilot from the cockpit, using standard pilot controls.
There are two models of the TaxiBot available. The Narrow-Body (NB) model is compatible with single-aisle aircraft, including the Airbus A320 and Boeing 737 series. The Wide-Body (WB) model is meant for twin-aisle aircraft, such as the Airbus A380 and Boeing 747.
History
The TaxiBot completed certification tests in July 2014, was approved for airport towing in November 2014, and had the first commercial flight dispatch-towed (Lufthansa LH140 from Frankfurt to Nuremberg) on November 25, 2014. In February 2015, the TaxiBot entered regular flight operations by Lufthansa at Frankfurt Airport. Certification tests of the Wide-Body model occurred from 2016 to 2018.
In October 2019, Air India became the first airline to "regularly" use the TaxiBot by deploying the unit to dispatch a Delhi–Mumbai flight from Terminal 3 of Indira Gandhi International Airport in New Delhi, one of the Top 10 airports in the world by annual passenger traffic.
References
External links
Vehicles of Israel
Aircraft ground handling
Tractors | TaxiBot | [
"Engineering"
] | 325 | [
"Engineering vehicles",
"Tractors"
] |
45,230,173 | https://en.wikipedia.org/wiki/Intramolecular%20vibrational%20energy%20redistribution | Intramolecular vibrational energy redistribution (IVR) is a process in which energy is redistributed between different quantum states of a vibrationally excited molecule, which is required by successful theories explaining unimolecular reaction rates such as RRKM theory. Such theories assume a full statistical redistribution between all vibrational modes, but restricted redistribution could enable bond selective chemistry for which deposited energy must remain in a particular mode for as long as it takes for the required reaction to take place.
References
Chemical processes
Chemical physics
Quantum chemistry
Molecular physics
Chemical kinetics | Intramolecular vibrational energy redistribution | [
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"Chemistry"
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"Quantum mechanics",
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"Theoretical chemistry",
" molecular",
"nan",... |
45,233,993 | https://en.wikipedia.org/wiki/Design%20space%20exploration | Design Space Exploration (DSE) refers to systematic analysis and pruning of unwanted design points based on parameters of interest. While the term DSE can apply to any kind of system, we refer to electronic and embedded system design in this article.
Given the complex specification of electronic systems and the plethora of design choices ranging from the choice of components, number of components, operating modes of each of the components, connections between the components, choice of algorithm, etc.; design decisions need to be based on a systematic exploration process. However, the exploration process is complex because of a variety of ways in which the same functionality can be implemented. A tradeoff analysis between each of the implementation option based on a certain parameter of interest forms the basis of DSE. The parameter of interest could vary across systems, but the commonly used parameters are power, performance, and cost. Additional factors like size, shape, weight, etc. can be important for some handheld systems like cellphone and tablets. With growing usage of mobile devices, energy is also becoming a mainstream optimization parameter along with power and performance.
Owing to the complexity of the exploration process, researchers have proposed automated DSE where the exploration software is able to take decisions and comes up with the optimal solution. However, it is not possible to have an automated DSE for all kind of systems and hence there are semi-automated methods of DSE where the designer has to steer the tool after every iteration towards convergence. Since the exploration is a complex process which takes large computational time, researchers have developed exploration tools which can give an approximate analysis of the system behavior in a fraction of time compared to accurate analysis. Such tools are very important for quick comparison of design decisions and are becoming more important with increasing complexity of designs.
To simplify the complexity of DSE, researchers have been continuously striving to raise the abstractions of component and system definition to be able to cater to larger and complex systems. For example, instead of modeling a digital system at transistor or gate level, there have been attempts to use RTL or behavioral modeling. Further higher abstractions like SystemC or block diagram based modeling are also used depending on the system requirements. Modeling at higher abstractions allows fast exploration of various design choices for the lower level implementation.
The ability to operate on the space of design candidates makes DSE useful for many engineering tasks, such as rapid prototyping, optimization, and system integration.
See also
Computer experiment
Design of experiment
MULTICUBE
Multifactor design of experiments software
Probabilistic design
Randomized block design
References
Design of experiments
Industrial engineering
Systems engineering
Quantitative research
Experiments | Design space exploration | [
"Engineering"
] | 531 | [
"Systems engineering",
"Industrial engineering"
] |
48,191,313 | https://en.wikipedia.org/wiki/Allendeite | Allendeite, Sc4Zr3O12, is an oxide mineral. Allendeite was discovered in a small ultrarefractory inclusion within the Allende meteorite. This inclusion has been named ACM-1. It is one of several scandium rich minerals that have been found in meteorites. Allendeite is trigonal, with a calculated density of 4.84 g/cm3. The new mineral was found along with hexamolybdenum. These minerals, are believed to demonstrate conditions during the early stages of the Solar System, as is the case with many CV3 carbonaceous chondrites such as the Allende meteorite. It is named after the Allende meteorite that fell in 1969 near Pueblito de Allende, Chihuahua, Mexico.
Occurrence
Allendeite was found as nano-crystals in an ultrarefractory inclusion in the Allende meteorite. The Allende meteorite has shown to be full of new minerals, after nearly forty years it has produced one in ten of the now known minerals in meteorites. This CV3 carbonaceous chondrite was the largest ever recovered on earth and is referred to as the best-studied meteorite in history. The inclusion has only been viewed via electron microscopy. The sample is one centimeter in diameter and has been entrusted to the Smithsonian Institution's National Museum of Natural History with the catalog number USNM7554. One crystal studied is a single 15 x 25 micron size with included perovskite, various osmium-iridium-molybdenum-tungsten alloys, and scandium-stabilized tazheranite. In fact, all allendeite was in contact with perovskite. The grains are anhedral, with no observable crystal forms or twinning.
Significance
Various scandium rich minerals have been found in meteorites, including; davisite, panguite, kangite, tazheranite, thortveitite, and eringaite. Of these, allendeite is the most Sc rich, with only pretulite containing substantially more scandium.
Appearance
Color, streak, luster, hardness, tenacity, cleavage, fracture, density, and refractive index could not be observed because the grain size was too small and the section bearing the mineral was optically thick.
See also
Classification of minerals
List of minerals
References
Natural materials
Trigonal minerals
Minerals in space group 148
Oxide minerals | Allendeite | [
"Physics"
] | 505 | [
"Natural materials",
"Materials",
"Matter"
] |
48,201,742 | https://en.wikipedia.org/wiki/GPOPS-II | GPOPS-II (pronounced "GPOPS 2") is a general-purpose MATLAB software for solving continuous optimal control problems using hp-adaptive Gaussian quadrature collocation and sparse nonlinear programming. The acronym GPOPS stands for "General Purpose OPtimal Control Software", and the Roman numeral "II" refers to the fact that GPOPS-II is the second software of its type (that employs Gaussian quadrature integration).
Problem Formulation
GPOPS-II is designed to solve multiple-phase optimal control problems of the following mathematical form (where is the number of phases):
subject to the dynamic constraints
the event constraints
the inequality path constraints
the static parameter constraints
and the integral constraints
where
and the integrals in each phase are defined as
It is important to note that the event constraints can contain any functions that relate information at the start and/or terminus of any phase (including relationships that include both static parameters and integrals) and that the phases themselves need not be sequential. It is noted that the approach to linking phases is based on well-known formulations in the literature.
Method Employed by GPOPS-II
GPOPS-II uses a class of methods referred to as -adaptive Gaussian quadrature collocation where the collocation points are the nodes of a Gauss quadrature (in this case, the Legendre-Gauss-Radau [LGR] points). The mesh consists of intervals into which the total time interval in each phase is divided, and LGR collocation is performed in each interval. Because the mesh can be adapted such that both the degree of the polynomial used to approximate the state and the width of each mesh interval can be different from interval to interval, the method is referred to as an -adaptive method (where "" refers to the width of each mesh interval, while "" refers to the polynomial degree in each mesh interval). The LGR collocation method has been developed rigorously in Refs., while -adaptive mesh refinement methods based on the LGR collocation method can be found in Refs., .
Development
The development of GPOPS-II began in 2007. The code development name for the software was OptimalPrime, but was changed to GPOPS-II in late 2012 in order to keep with the lineage of the original version of GPOPS which implemented global collocation using the Gauss pseudospectral method. The development of GPOPS-II continues today, with improvements that include the open-source algorithmic differentiation package ADiGator and continued development of -adaptive mesh refinement methods for optimal control.
Applications of GPOPS-II
GPOPS-II has been used extensively throughout the world both in academia and industry. Published academic research where GPOPS-II has been used includes Refs. where the software has been used in applications such as performance optimization of Formula One race cars, Ref. where the software has been used for minimum-time optimization of low-thrust orbital transfers, Ref. where the software has been used for human performance in cycling, Ref. where the software has been used for soft lunar landing, and Ref. where the software has been used to optimize the motion of a bipedal robot.
References
External links
GPOPS-II home page
GPOPS-II Journal Article Appearing in the ACM Transactions on Mathematical Software
Website of Anil V. Rao
Mathematical optimization software
Optimal control
Mathematical software
Numerical software | GPOPS-II | [
"Mathematics"
] | 707 | [
"Numerical software",
"Mathematical software"
] |
48,204,219 | https://en.wikipedia.org/wiki/Thermogalvanic%20cell | In electrochemistry, a thermogalvanic cell is a kind of galvanic cell in which heat is employed to provide electrical power directly. These cells are electrochemical cells in which the two electrodes are deliberately maintained at different temperatures. This temperature difference generates a potential difference between the electrodes. The electrodes can be of identical composition and the electrolyte solution homogeneous. This is usually the case in these cells. This is in contrast to galvanic cells in which electrodes and/or solutions of different compositions provide the electromotive potential. As long as there is a difference in temperature between the electrodes a current will flow through the circuit. A thermogalvanic cell can be seen as analogous to a concentration cell but instead of running on differences in the concentration/pressure of the reactants they make use of differences in the "concentrations" of thermal energy. The principal application of thermogalvanic cells is the production of electricity from low-temperature heat sources (waste heat and solar heat). Their energetic efficiency is low, in the range of 0.1% to 1% for conversion of heat into electricity.
History
The use of heat to empower galvanic cells was first studied around 1880. However it was not until the decade of 1950 that more serious research was undertaken in this field.
Working mechanism
Thermogalvanic cells are a kind of heat engine. Ultimately the driving force behind them is the transport of entropy from the high temperature source to the low temperature sink. Therefore, these cells work thanks to a thermal gradient established between different parts of the cell. Because the rate and enthalpy of chemical reactions depend directly on the temperature, different temperatures at the electrodes imply different chemical equilibrium constants. This translates into unequal chemical equilibrium conditions on the hot side and on the cold side. The thermocell tries to approach a homogeneous equilibrium and, in doing so, produces a flow of chemical species and electrons. The electrons flow through the path of least resistance (the outer circuit) making it possible to extract power from the cell.
Types
Different thermogalvanic cells have been constructed attending to their uses and properties. Usually they are classified according to the electrolyte employed in each specific type of cell.
Aqueous electrolytes
In these cells the electrolyte between the electrodes is a water solution of some salt or hydrophylic compound. An essential property of these compounds is that they must be able to undergo redox reactions in order to shuttle electrons from one electrode to the other during the cell operation.
Non-aqueous electrolytes
The electrolyte is a solution of some other solvent different from water. Solvents like methanol, acetone, dimethyl sulphoxide and dimethyl formamide have been successfully employed in thermogalvanic cells running on copper sulfate.
Molten salts
In this type of thermocell the electrolyte is some kind of salt with a relatively low melting point. Their use solves two problems. On one hand the temperature range of the cell is much larger. This is an advantage as these cells produce more power the larger the difference between the hot and cold sides. On the other hand, the liquid salt directly provides the anions and cations necessary for sustainment of a current through the cell. Therefore, no additional current-carrying compounds are necessary as the melted salt is the electrolyte itself. Typical hot source temperatures are between 600–900 K, but can get as high as 1730 K. Cold sink temperatures are in the 400–500 K range.
Solid electrolytes
Thermocells in which the electrolyte connecting the electrodes is an ionic material have been considered and constructed too. The temperature range is also elevated as compared to liquid electrolytes. Studied systems fall in the 400–900 K. Some solid ionic materials that have been employed to construct thermogalvanic cells are AgI, PbCl2 and PbBr2.
Uses
Given the advantages provided by the working mechanism of thermogalvanic cells, their main application is electricity production under conditions where there is an excess of heat available. In particular thermogalvanic cells are being used to produce electricity in the following areas.
Solar energy
The heat collected from this process generates steam, which can be used in a conventional steam turbine system to make electricity. In contrast to the low-temperature solar thermal systems that are used for air or water heating in domestic or commercial buildings, these solar thermal electricity plants operate at high temperatures, requiring both concentrated sunlight and a large collection area, making the Moroccan desert an ideal location.
This is an alternative approach to the more widely used “photovoltaic” technology for producing electricity from sunlight. In a photovoltaic system, the sunlight is absorbed in the photovoltaic device (commonly called a solar cell) and energy is passed to electrons in the material, converting the solar energy directly into electricity. Sometimes, solar thermal electricity and photovoltaics are portrayed as competing technologies and, while this may be true when deciding on the way forward for a specific site, in general they are complementary, using solar energy as extensively as possible.
Thermal generators
Waste heat sources
Thermogalvanic cells can be used to extract a useful quantity of energy from waste heat sources even when the temperature gradient is less than 100C (sometimes only a few tens of degrees). This is often the case in many industrial areas.
See also
Concentration cell
Electrochemical cell
Electrochemical potential
Galvanic cell
Ion transport number
Alkali-metal thermal to electric converter
Search for the Super Battery (2017 PBS film)
Thermoelectric effect
Thermoelectric generator
OTEC
References
Electrochemistry | Thermogalvanic cell | [
"Chemistry"
] | 1,169 | [
"Electrochemistry"
] |
26,477,771 | https://en.wikipedia.org/wiki/Capillary%20action%20through%20synthetic%20mesh | Capillary action through synthetic mesh is the result of the intermolecular attraction between moisture and semi-synthetic polymers, causing a current of thermionic energy through a specific pathway within a mesh material. The combination of the adhesive forces and the surface tension that arises from cohesion produces the characteristic upward curve in a fluid, such as water. Capillarity is the result of cohesion of water molecules and adhesion of those molecules to the solid material forming the void. As the edges of the material are brought closer together, such as in a very narrow path, the interaction causes the liquid to be drawn away from the original source. The more narrow the pathway, the greater the rise of the liquid. Greater surface tension and increased ratio of adhesion to cohesion also result in greater rise. Synthetic materials using conductive polymer as found in polypyrrole to reduce liquid density to a manageable state.
The force with which water is held by capillary action varies with the quantity of water being held. As part of a demonstration conducted by Bright Idea and Webb development: Water entering a natural void, such as a pore within a synthetic mesh material, forms a film on the surface of the material surrounding the pore. The adhesion of the water molecules nearest the solid material is greatest. As water is added to the pore, the thickness of the film increases, the capillary force is reduced in magnitude, and water molecules on the outer portion of the film may begin to flow away from its source. As more water enters the pore the capillary force is reduced to zero when the pore is saturated, unless a hydrophilic body is introduced. The movement of moisture through the mesh is controlled by this capillary action.
References
Thermionic and field electron emission from nanostructured carbon materials for energy conversion and vacuum electronics
Capillary Action at the Nanoscale
Three-Dimensional Multi-mesh Material Point Method for Solving Collision Problems
Fluid dynamics
Organic polymers
Molecular electronics
Organic semiconductors | Capillary action through synthetic mesh | [
"Chemistry",
"Materials_science",
"Engineering"
] | 410 | [
"Organic polymers",
"Molecular physics",
"Chemical engineering",
"Semiconductor materials",
"Molecular electronics",
"Organic compounds",
"Piping",
"Fluid dynamics",
"Nanotechnology",
"Organic semiconductors"
] |
26,478,301 | https://en.wikipedia.org/wiki/SRAS | SRAS (spatially resolved acoustic spectroscopy) a non-destructive acoustic microscopy microstructural-crystallographic characterization technique commonly used in the study of crystalline or polycrystalline materials. The technique can provide information about the structure and crystallographic orientation of the material. Traditionally, the information provided by SRAS has been acquired by using diffraction techniques in electron microscopy - such as EBSD. The technique was patented in 2005, .
SRAS measures the surface acoustic wave velocity across a specimen, the surface acoustic wave (SAW) velocity is in turn a function of the material state, including parameters such as crystallographic orientation, elastic constants, temperature and stress.
Measurement
In a SRAS measurement, as in most laser ultrasound techniques, two lasers are used, one for the generation of acoustic waves and one for the subsequent detection of these waves. Considering first the generation of acoustic waves, an optical amplitude grating, illuminated by the a short pulse pump laser (typically ~1ns), is imaged onto the sample surface. The incident light is thermoelastically absorbed, creating surface acoustic waves, such as Rayleigh waves. As the laser pulse contains a broad range of frequencies, only the frequencies which match the grating spacing and acoustic velocity of that sample point will be generated. Using a second, continuous wave, laser these surface acoustic waves can then be measured through a number of interferometry techniques. Detection is usually achieved by optical beam deflection.
As Rayleigh waves are non-dispersive the phase velocity of the acoustic wave can be found by
where is the distance between the grating fringes imaged onto the sample surface and is the dominant frequency of the wave packet, found by fast Fourier transform.
As the measurement probes the frequency of the wave packet, which does not change along the propagation length, the measured SAW velocity is determined by only the properties of the specimen at the area where the grating pattern is imaged, unlike more traditional time of flight measurements that are influenced by the sample properties along the propagation length. This makes SRAS robust and immune to the aberrating and scattering effects of the microstructure.
Microstructure imaging
By raster scanning the sample, making measurements at several points across the surface, multi-megapixel images of the SAW velocity can be built up - providing rich microstructural maps. On samples with a good surface finish measurements can be made without averaging, allowing samples to be rapidly scanned. In-theory, means the acquisition rate is limited only by the repetition rate of the pump laser; modern laser repetition rates can exceed 10 kHz. As the measurements do not require a vacuum chamber or acoustic couplant there is little restriction, beyond the limit of scanning stages, to the size of sample which can be interrogated. The elastic anisotropy of most engineering materials means the acoustic response is a function of the loading direction. Hence, a unique velocity map exists for each propagation direction of the SAW direction. It is possible to combine multiple velocity maps to improve contrast between grains.
Orientation mapping
An acoustic slowness surface can be determined for each pixel by propagating the acoustic wave in several directions. Having measured the SAW velocity in multiple directions the challenge is then to convert this information into the measurement of crystallographic orientation. The direct calculation of the orientation from velocity is a difficult problem. However, the numerical calculation of the SAW velocity as a function of SAW velocity is relatively simple, as first outlined by Farnell. Therefore, a database of possible slowness surfaces can be pre-calculated and compared to the measurement values. For each measurement pixel the orientation is given by the orientation of the pre-calculated velocity surface which best matches the measured data. These maps can spatially describe the crystal orientation of the material being interrogated and can be used to examine microtexture and sample morphology. The technique is applicable to any crystal structure, however transverse isotropy means the full orientation cannot be determined in hexagonal materials, such as titanium.
In order to calculate the predicted SAW velocity of the sample, the materials density and elastic constants must be known. Elastic constants are typically measured by ultrasonic techniques such as resonant ultrasound spectroscopy, with well-established values for most common engineering materials. However, it is possible to attempt the full inverse problem to determine both the elastic constants and crystallographic orientation from only the measured SAW velocity.
From orientation data, a wealth of information can be devised that aids in the understanding of the sample's microstructure and processing history. Recent developments include understanding: the prior texture of parent phases at elevated temperature; the storage and residual deformation after mechanical testing; the population of various microstructural features, including precipitates and grain boundary character.
Single crystal elasticity matrix measuring (SRAS++)
SRAS++ utilises SRAS imaging to provide the raw measurement of single grain velocity surfaces, this is input to a novel inverse solver that mitigates the problem of the inversion being very ill-conditioned, by simultaneously solving for multiple uniquely orientated grains at once in a brute-force approach. This allows simultaneous determination of the elastic constants and crystallographic orientation. Furthermore, this technique has the potential to work on polycrystalline materials with minimal preparation and is capable of high accuracy, with the potential to realise errors in the determination of elastic constants values of less than 1 GPa.
Rough surfaces
Smooth mirror-like surfaces provide specular reflections, allowing easy detection of the acoustic wave. However, as surfaces become rougher the reflections become more diffuse, making detection of the acoustic wave more challenging for two reasons. Firstly, the reflected beam is spread out in a cone, as this cone increases in diameter less light is returned to the system - decreasing detection efficiency. Secondly, the light which is returned to the detector no longer exabits a gaussian intensity, instead the interfering wave fronts create a stochastic speckle pattern. However, many engineering processes impart an optically rough surface, for example additive manufacturing or forging, and there is a desire to make measurements on such components in their 'as manufactured state'. To achieve this, an interferometric technique compatible with rough surfaces is required. For example, a Fabry–Pérot interferometer - which is inherently tolerant to speckle, two-wave mixing - which can adapt to the speckle pattern, or a speckle knife edge detector. With the use of such detection techniques, it is possible to make SRAS measurements on optically rough surfaces.
References
Spectroscopy
Crystallography
Lasers
Ultrasound | SRAS | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 1,355 | [
"Molecular physics",
"Spectrum (physical sciences)",
"Instrumental analysis",
"Materials science",
"Crystallography",
"Condensed matter physics",
"Spectroscopy"
] |
26,480,606 | https://en.wikipedia.org/wiki/Arcade%20Creek%20Project | The Mira Loma Arcade Creek Project was a project studying the riparian corridor of an urban watershed in Sacramento, California. It consisted of eleven studies which measured the health of Arcade Creek and was run entirely by students of Mira Loma High School and five faculty advisers. As of 2017, there were 346 students participating in the project.
The project was initiated in 1998 as part of the school's IB Group 4 project.
In 2004, the project was recognised by Governor Schwarzenegger when it was awarded the Governor's Environmental and Economic Leadership Award, California's most prestigious environmental honour.
The project was also awarded a $10,000 environmental excellence award from SeaWorld in 2010.
List of studies
Bio Assay
Bio Assay tested the health of the creek's water using the indicator species Ceriodaphnia dubia which is highly sensitive to toxins and other changes in the creek's water.
Biological Assessment
Biological Assessment monitored populations of macroinvertebrates in the creek bed. Large populations of species in the insect orders Ephemeroptera, Plecoptera and Trichoptera indicate good health of the creek.
Botany
The Botany Study monitored the populations of plant life in the riparian corridor of the creek with a special emphasis on controlling invasive species.
Chemistry
The Chemistry Study monitored the chemical content of the creek water. Measurements of dissolved oxygen, pH, temperature, and various metallic ions were taken. This data could then be used to determine if the water was chemically appropriate for most life at the creek.
Habitat
The Habitat Study measured various physical features of the creek to provide a general description of its health. The group measured water depth, vegetation density, and average tree diameters.
Long Mapping
The Long Mapping Study mapped the general shape and flow of the creek bed including creek bank height and soil build-up or erosion. The Long Mapping group provided a geographical reference for other studies to pinpoint locations at the creek.
Outreach
The Outreach group presents the tasks, results, and accomplishments of the Arcade Creek Project to the wider community and organizes events to educate schoolchildren, politicians, and environmentalists.
Restoration
The Restoration group removed garbage, toxins, and invasive species from Arcade Creek in hopes of restoring it to a more natural state.
Sediment
The Sediment Study monitored the composition of the benthic layer of the creek bed. The presence of an excess of rocks, clay, or silt indicates that the creek's soil is inappropriate for most life at the creek.
Technology
The Technology team was responsible for compiling creek data and publicizing the Arcade Creek Project through informational videos and the Arcade Creek Project website.
Vertebrates
The Vertebrate Study monitored the populations of vertebrate species at the creek. By tracking population changes over time, this study aimed to determine the ecological health of Arcade Creek.
References
External links
Website
Organizations based in Sacramento, California
Ecological restoration | Arcade Creek Project | [
"Chemistry",
"Engineering"
] | 580 | [
"Ecological restoration",
"Environmental engineering"
] |
26,480,895 | https://en.wikipedia.org/wiki/Eterobarb | Eterobarb (Antilon) is a barbiturate derivative. It has mainly anticonvulsant action with less sedative effects than the closely related compound phenobarbital. It saw reasonable success in clinical trials, but is not in widespread medical use.
Synthesis
Eterobarb can be synthesized by reacting phenobarbital with chloromethyl methyl ether in presence of a base.
References
Barbiturates
Ethers | Eterobarb | [
"Chemistry"
] | 96 | [
"Organic compounds",
"Functional groups",
"Ethers"
] |
26,481,832 | https://en.wikipedia.org/wiki/Parabola%20of%20safety | In classical mechanics and ballistics, the parabola of safety or safety parabola is the envelope of the parabolic trajectories of projectiles shot from a certain point with a given speed at different angles to horizon in a fixed vertical plane. The fact that this envelope is a parabola had been first established by Evangelista Torricelli and was later reproven by Johann Bernoulli using the infinitesimal calculus methods of Leibniz.
The paraboloid of revolution obtained by rotating the safety parabola around the vertical axis is the boundary of the safety zone, consisting of all points that cannot be hit by a projectile shot from the given point with the given speed.
Equations
In 2D and shooting on a horizontal plane, parabola of safety can be represented by the equation
where is the initial speed of projectile and is the gravitational field.
Properties
Focus of the parabola is the shooting position.
Maximum height () can be calculated by absolute value of in standard form of parabola. It is given as
Range () of the projectile can be calculated by the value of latus rectum of the parabola given shooting to the same level. It is given as
References
Philip Robinson, On the Geometrical Approach to Projectile Motion, The Mathematical Gazette, Vol. 82, No. 493, 1998, pp. 118–122
Ballistics
Conic sections | Parabola of safety | [
"Physics"
] | 276 | [
"Applied and interdisciplinary physics",
"Ballistics"
] |
26,482,358 | https://en.wikipedia.org/wiki/Elliptic%20flow | Relativistic heavy-ion collisions produce very large numbers of subatomic particles in all directions. In such collisions, flow refers to how energy, momentum, and number of these particles varies with direction, and elliptic flow is a measure of how the flow is not uniform in all directions when viewed along the beam-line. Elliptic flow is strong evidence for the existence of quark–gluon plasma, and has been described as one of the most important observations measured at the Relativistic Heavy Ion Collider (RHIC).
Elliptic flow describes the azimuthal momentum space anisotropy of particle emission from non-central heavy-ion collisions in the plane transverse to the beam direction, and is defined as the second harmonic coefficient of the azimuthal Fourier decomposition of the momentum distribution. Elliptic flow is a fundamental observable since it directly reflects the initial spatial anisotropy, of the nuclear overlap region in the transverse plane, directly translated into the observed momentum distribution of identified particles. Since the spatial anisotropy is largest at the beginning of the evolution, elliptic flow is especially sensitive to the early stages of system evolution. A measurement of elliptic flow thus provides access to the fundamental thermalization time scale and many more things in the early stages of a relativistic heavy-ion collision.
Notes
References
Quark matter | Elliptic flow | [
"Physics"
] | 277 | [
"Nuclear physics",
"Astrophysics",
"Quark matter"
] |
26,486,063 | https://en.wikipedia.org/wiki/Substrate-integrated%20waveguide | A substrate-integrated waveguide (SIW) (also known as post-wall waveguide or laminated waveguide) is a synthetic rectangular electromagnetic waveguide formed in a dielectric substrate by densely arraying metallized posts or via holes that connect the upper and lower metal plates of the substrate. The waveguide can be easily fabricated with low-cost mass-production using through-hole techniques, where the post walls consists of via fences. SIW is known to have similar guided wave and mode characteristics to conventional rectangular waveguide with equivalent guide wavelength.
Since the emergence of new communication technologies in the 1990s, there has been an increasing need for high-performance millimeter-wave systems. These need to be reliable, low-cost, compact, and compatible with high-frequencies. Unfortunately, above 10 GHz, the well known microstrip and coplanar lines technologies cannot be used because they have high insertion and radiation losses at these frequencies. The rectangular waveguide topology can overcome these issues, as it offers an excellent immunity against radiation losses and presents low insertion losses. But in their classical form, rectangular waveguide is not compatible with the miniaturization required by modern applications.
The concept of SIW was developed in the early 2000s by Ke Wu to reconcile those requirements. The authors presented a platform for integrating all the components of a microwave circuit inside a single substrate, with a rectangular cross-section. Using a single substrate guarantees a limited volume and a simplicity of manufacture, while the rectangular cross-section of the line provides the advantages of the waveguide topology in terms of losses.
Principles of SIW
Geometry
A SIW is composed of a thin dielectric substrate covered on both faces by a metallic layer. The substrate embeds two parallel rows of metallic via holes delimiting the wave propagation area. The organization of the vias and the geometric parameters are described in the attached figure.
The width of a SIW is the distance between its two vias rows, which is defined from center to center. An effective width may be used to characterize more precisely the wave propagation. The distance between two successive vias of the same row is , and the vias diameter is denoted by .
Transverse magnetic propagation modes
In classical solid-walled rectangular waveguide, the general formulation of propagation involves a superposition of transverse electric (TE) and transverse magnetic (TM) modes. Each of these is associated with particular fields and currents. In the case of TM modes, the current in the vertical walls is longitudinal, i.e. parallel to the propagation axis, usually denoted as . Then, given the vertical geometry of the vias, it is impossible for such modes to appear in SIWs: the electrical current cannot propagate from via to via. Only TE modes are able to propagate through SIW.
Each mode appears above a precise cut-off frequency determined by the waveguide dimensions and the filling medium. For TM modes, decreasing the waveguide thickness (usually denoted as ) increases the cut-off frequency with . In the case of SIW, the thickness is so low that the cut-off frequency of TM modes is much higher than the dominant mode.
Effective width
One of the objectives of the SIW geometry is to reproduce the characteristic propagation modes of rectangular waveguides inside a thin template. The width of the waveguide is an essential parameter of those modes. In the typical SIW geometry, is the distance between the two vias rows from center to center (see figure). Due to the vias geometry, this distance cannot be used directly; because of the space between successive vias and their circular shape, the signal inside the guide does not behave exactly as it would in a perfectly rectangular waveguide of the same width.
To apply waveguide theory to SIWs, an effective width can be used. It takes into account the shape of the vias and the space in-between. Its value lies between and .
A common simple definition is
and a more refined definition used for large values of is
With this effective width, the propagation constant of a SIW is similar to that of a classical rectangular waveguide whose width is . The formulas given above are empirical: they were established comparing the dispersion characteristics of different SIWs to those of rectangular waveguide filled with the same dielectric material.
Transitions
SIWs are promising structures that can be used in complex microwave systems as interconnects, filters, etc. However, a problem may arise: the connection of the SIWs with other kinds of transmission lines (TL), mainly microstrip, coplanar and coaxial cable. The goal of such transitions between two different topologies of TL is to excite the correct transmission mode in the SIW cavity with the minimum loss of power and on the broadest possible frequency range.
Rapidly after the presentation of the concept of SIW by Ke Wu, two different transitions were mainly used. First, the tapered transition allowing to convert a microstrip line into a SIW, and secondly, a transition between a coplanar line and a SIW (see attached figure). The tapered transition from microstrip to SIW is useful for thin substrates. In this case, the radiation losses associated with microstrip lines are not too significant. This transition is widely used and different optimizing process have been proposed. But this is not applicable to thick substrates, where leakages are important. In that situation, a coplanar excitation of the SIW is recommended. The drawback of the coplanar transition is the narrower bandwidth.
These two kinds of transitions involve lines that are embedded in the same substrate, which is not the case for coaxial lines. There exists no direct transition between a coaxial line and a SIW: an other planar line have to be used to convert properly the coaxial TEM propagation modes to the TE modes in SIW.
Several studies have been carried out to optimize the transition between topologies without being able to determine a universal rule making it possible to draw the absolute transition. The architecture, the frequency range, the used materials, etc. are examples of parameters that make specific the design procedure.
Losses in SIW
The propagation constant of a transmission line is often decomposed as follow:
and the oscillating electric and magnetic fields in the guide have the form
It is then clear that, while the imaginary part of stands for the propagating component, the real component describes the loss of intensity during the propagation. This loss is generated by different phenomena, and each of them is represented by a term . The most common terms are the following:
the loss due to the external metal conductivity,
the loss due to loss tangent of the dielectric medium filling the waveguide,
the loss due to conductivity of the dielectric medium filling the waveguide,
the loss due to radiation.
This decomposition is valid for all kinds of transmission lines. However, for rectangular waveguides, the attenuation due to radiations and substrate conductivity is negligible. Indeed, usually, the substrate is an insulator such that . In the same way, if the wall thickness is much thicker than the skin depth of the signal, no radiation will appear. This is in fact one of the advantages of closed waveguides compared to open lines such as microstrips.
The SIWs show comparable or lower losses compared the other traditional planar structures like microstrip or coplanar lines, especially at high frequencies. If the substrate is thick enough, the losses are dominated by the dielectric behavior of the substrate.
Attenuation due to conduction currents
Part of the signal attenuation is due to the surface current density flowing through the metallic walls of the waveguide. These currents are induced by the propagating electromagnetic fields. These losses may also be named ohmic losses for obvious reasons. They are linked to the finite conductivity of the metals: the better the conduction, the lower the losses. The power lost per unit length can be calculated by integrating the current densities on a path enclosing the waveguide walls:
It can be shown that in a classical rectangular waveguide, the attenuation of the dominant mode due to conduction currents is given, in nepers per meter, by
where
is the width of the waveguide,
its height,
the wave impedance,
the wave vector,
the skin depth in the conductor,
is the sheet resistance (of surface impedance).
It is noticeable that is directly linked to the substrate thickness : the thinner the substrate, the higher the conduction losses. This can be explained keeping in mind that this ohmic losses are determined by integrating the current density on a path enclosing the waveguide walls.
On the top and bottom horizontal metallic plates, the current is scaled with , due to the modification of the field intensity on these plates: when increases, the field intensity decreases, as well as the currents. In the vertical walls, this variation of is compensated by the lengthening of the integration path . As a result, the contribution of the vertical vias to the conductor losses is unchanged with . This is why there is two terms in the expression of : the first is independent of , while the second one varies with .
Another key point of the conduction losses experienced by the SIWs is linked to the roughness of the surfaces that may appear due to the synthesis processes. This roughness decreases the effective conductivity of the metallic walls and subsequently increases the losses. This observation is of crucial importance for the design of SIWs, as they are integrated on very thin substrates. In this case, the contribution of the conduction losses on the global attenuation is predominant.
Attenuation due to dielectric substrate
The attenuation due to the dielectric behavior of the filling medium can be determined directly from the propagation constant. Indeed, it can be proven that, making use of a Taylor expansion of the function for , the propagation constant is
where is the loss tangent of the dielectric substrate. This approximation is correct if , which is usually the case in microwave electronics (at 10 GHz, in air, in Teflon, and in bulk alumina). Then the following identification can be made:
This relation is correct for both electrical and magnetic transverse modes.
The dielectric losses depend only on the substrate and not on the geometry: unlike the conduction losses, is not influenced by the substrate thickness. It transpires that the only way to reduce consists in choosing a template with better dielectric properties: the lower the loss tangent , the lower the attenuation.
Attenuation due to radiation
Because the vertical walls of the SIW are not continuous, radiation leakages may flow between the vias. These leakages can significantly affect the global transmission quality if the vias geometry is not chosen carefully. Some studies have been conducted to describe, predict and reduce the radiation losses. They have resulted in some simple geometric rules that have to be satisfied in order to reduce the radiation losses.
The geometric parameters of interest are the diameter , the width of the SIW and the center-to-center distance between the vias . They must be tuned in such a way to approximate the behavior of a continuous metallic wall: the spacing of the vias has to remain small compared to their diameter, while the diameter must be small compared to the waveguide guided wavelength (). To keep the radiation losses reasonably small, the recommended values are
For a specific traveling mode, the leakages decrease with the increasing frequency and are maximal at the cut-off frequency of the mode. The radiation leakage factor is independent of the substrate properties and independent of the height of the guide.
Design Assistant
There are some applications available to ease the design of SIW and microstrip-to-SIW transitions. For example, the iOS-based app SIW Cal can provide the initial parameters for microstrip, SIW, and microstrip-to-SIW transitions.
See also
, also
References
External links
Substrate Integrated Waveguide, at microwave101.com
Planar transmission lines
Electronic design
Microwave technology
Electronics manufacturing | Substrate-integrated waveguide | [
"Engineering"
] | 2,484 | [
"Electronic design",
"Electronic engineering",
"Electronics manufacturing",
"Design"
] |
49,459,416 | https://en.wikipedia.org/wiki/IEC%2061000-4-5 | IEC 61000-4-5 is an international standard by the International Electrotechnical Commission on surge immunity. In an electrical installation, disruptive surges can appear on power and data lines. Their sources include abrupt load switching and faults in the power system, as well as induced lightning transients from an indirect lightning strike (direct lightning is out of scope in this standard). It necessitates the test of surge immunity in electrical or electronic equipment. IEC 61000-4-5 defines test set-up, procedures, and classification levels.
In particular, it standardizes the required surge voltage and current waveforms for laboratory testing, with the "1.2/50-8/20 μs" impulse being the most frequently used surge waveform. Although this standard is designed for testing equipment as a whole at system level, not for individual protection devices, in practice this surge waveform is often also used for rating Transient Voltage Suppressors (TVS), Gas Discharge Tubes (GDT), Metal Oxide Varistors (MOV), and other surge protection devices.
The current version is Third Edition (2014), amended in 2017.
Test Setup
Two major components are defined in this standard: two types of Combination Wave Generators (CWG) and various Coupling/Decoupling Networks (CDN) depending on the test level and type.
First, a Combination Wave Generator is a standardized impulse generator (sometimes also referred to as a lightning surge generator), it's used for producing simulated, standard voltage and current surges under laboratory conditions. Subsequently, the surge is transmitted into a port of the Device-Under-Test (DUT) via a coupling network. Finally, to prevent surges from reaching other devices via the power system during the test, a decoupling network is also inserted between the power line and the DUT.
Surge Waveforms
The Combination Wave Generator is required to have an output floating from ground, and be capable of generating both positive and negative impulses. Its repetition rate should be at least one impulse per 60 seconds.
The surge is defined by the Combination Wave Generator's open-circuit voltage and short-circuit current waveforms, characterized by front time, duration, and peak values. With an open circuit output, the surge voltage is a double exponential pulse in the form of . With a short circuit output, the surge current waveform is a damped sine wave. The ratio between the peak open-circuit voltage and the peak short-circuit current is 2, giving an effective output impedance of 2 Ω.
Usually, the voltage waveform has a 1.2 μs front time and a 50 μs duration, and the current waveform has a 8 μs front time and 20 μs duration. This is the most commonly used surge waveform for most applications, often referred to as a "1.2/50-8/20 μs" surge.
Alternatively, for outdoor telecommunication networks that experience a higher surge level, the standard also defines a more energetic generator with a 10/700 μs voltage waveform and a 5/320 μs current waveform.
Front time and duration are not measured directly, but as virtual parameters derived from measurements. For open-circuit voltage, front time is defined to be 1.67 times the 30%-90% rise time, duration is defined as the time interval between the 50% point of its rising edge and the 50% point of its falling edge. For short-circuit current, front time is defined to be 1.25 times the 10%-90% rise time, duration is defined as 1.18 times time interval between the 50% point of its rising edge and the 50% point of its falling edge.
At the output of the generator, a 30% undershoot below zero is allowed. There's no overshoot or overshoot limit at the output of the Coupling Network.
Comparison with different standards
IEC 60060-1
It's worth noting that both "1.2/50 μs" voltage and "8/20 μs" current impulses are classic waveforms with a well-established history of use in high-voltage testing for electric power transmission. Thus, these waveforms are also defined by IEC 60060-1 "High-Voltage Test Techniques" and other standards in this context. In fact, the waveform definitions in IEC 61000-4-5 were originally based on IEC 60060-1.
Nevertheless, there are important differences. In traditional high-voltage testing, voltage and current impulses are tested separately, not in combination. The "1.2/50 μs" generator is designed for insulation testing, and produces a high-voltage, low-current impulse into a high-impedance load. The output current of this generator is on the milliampere scale. The "8/20 μs" generator is designed for surge arrester testing, and produces a high-current surge into a low-impedance load. On the other hand, modern electronic devices can be high and low-impedance loads simultaneously due to non-linear devices, protection circuits, and arcing in a dielectric breakdown. As a result, it motivated the creation of the Combination Wave Generator with the ability to generate a high-voltage, high-current output during the same surge. In addition, both standards have different waveform tolerances and other technical requirements. Thus, IEC 61000-4-5 is not to be confused with IEC 60060-1 and other high-voltage tests that also use a "1.2/50 μs" or "8/20 μs" impulse.
IEC 61000-4-5 Ed. 2 and Ed. 3
When a Coupling Network is used, past experience has shown inconsistent waveforms between different generators. Thus, an important change in IEC 61000-4-5 Ed. 3 is that a Combination Wave Generator must be verified only with a 18 μF capacitor attached at the output. This causes a significant impact to the short-circuit current waveform. If the generator is to be designed without the coupling capacitor in mind, the output would no longer be standard compliant.
Third Edition also simplified waveform definitions. The earlier standard contained two definitions of "1.2/50-8/20 μs" waveform parameters, based on either IEC 60060-1 or IEC 60469-1, and two definitions of "10/700-5/320 μs" waveform parameters, based on either IEC 60060-1 or ITU-T K series. Ed. 3 removed references to these standards and gives standalone definitions. Especially, front time has been redefined in terms of rise time, rather than a time interval from an extrapolated "virtual origin" using IEC 60060-1's approach. This allows one to use the built-in measurement feature on an oscilloscope, simplifying test procedures. For practical purposes, the differences between both definitions are negligible. However, because the new definition was created using IEC 60060-1 as its basis, a generator calibrated according to IEC 60469-1's definitions may no longer be standard compliant.
Circuit Analysis
1.2/50-8/20 μs Generator
The Combination Wave Generator is essentially a capacitor discharge circuit. Initially, the switch is open, a high voltage source charges the energy-storage capacitor through a current-limiting resistor , which is assumed to be sufficiently large to isolate the high-voltage source from the load (the voltage source only charges the capacitor, the impulse current from the voltage source itself is negligible). The switch is then closed to deliver an impulse from the capacitor to the load through a pulse-forming network, which consists of a rise time shaping inductor , two impulse duration shaping resistors and , and an impedance matching resistor .
The standard does not specify component values or practical circuits, any suitable design that conforms to the standard requirements can be used.
A complete circuit analysis of the ideal surge generator, including design equations and component values, is available in the presentation Introduction To Voltage Surge Immunity Testing by Hesterman et, al. An updated derivation for the Third Edition is given in the paper Elementary and ideal equivalent circuit model of the 1,2/50-8/20 μs combination wave generator by Carobbi et, al.
Design Equations
The following design equations are derived by Carobbi et, al. In these equations, the charging voltage is , and the components are , , , , and .
Open-Circuit Voltage
For open-circuit voltage, its Laplace transform is:
Where:
Thus, open-circuit voltage is a double exponential waveform:
The voltage reaches its peak value at:
And the peak voltage is:
Short-Circuit Current
When the output is shorted, note that the last resistor ( in the schematic) is effectively removed.
For short-circuit current, its Laplace transform is:
Where:
Thus, short-circuit current is a damped sine wave (from an underdamped RLC circuit):
The current reaches its peak value at:
And the peak current is:
Solution
Ignore the amplitude in , it becomes:
By substituting :
The ratio should be selected to make 's waveform have a duration over front-time ratio of . By numerically evaluating 's waveform (including its front time and duration) while varying this ratio, the solution is found to be . Next, and are computed by numerically varying until 's waveform has a front time of 1.2 μs. The solution is = 68.2 μs. Therefore, = 0.4 μs.
Ignore the amplitude in , it becomes:
By substituting :
The value should be selected to make 's waveform have a duration over front time ratio of . By numerically evaluating 's waveform (including its front time and duration) while varying , the solution is found to be . Next, is computed by varying it numerically until 's waveform has a duration of 20 μs. With the correct duration, front time is also automatically satisfied. The solution is .
Once , , and are solved, the circuit component values can be obtained, is derived first.
Note that the effective output impedance is (by dividing by ):
And can be rearranged as:
Set output impedance = 2 Ω, the solution is = 26.1 Ω.
Finally, the closed-form solution of other component values is:
The solution is = 5.93 μF, = 10.9 μH, = 20.2 Ω, and = 0.814 Ω.
Output peak voltage is slightly lower than the charging voltage. To scale the voltage, use the amplitude in and set E = 1, this yields . Thus, the capacitor charging voltage is times the output peak voltage.
Note that this solution doesn't consider the coupling capacitor, and also has an undershoot of . The solution to both problems are discussed in the following sections.
Coupling Capacitor
An extra 18 μF series coupling capacitor has almost no effect on the open-circuit voltage, but affects short-circuit current significantly.
Carobbi et, al. suggested the following iterative, trial-and-error design procedure to take the effect of the series coupling capacitor into account. First, without considering the capacitor, the original circuit analysis is reused, and circuit components values are obtained through a numerical solver. Next, the capacitor is added and the change of short-circuit waveform is noted. Then, the target waveform parameters for the numerical solver are "pre-distorted", obtaining a new set of component values (by changing front time, duration, and effective output impedance). For example, if the peak current becomes too low, component values are recalculated for a higher peak current by adjusting the effective output impedance target. These steps are repeated until the desired waveform is obtained. The result given here is accurate within 1.5% after two iterations, more iterations are required for higher accuracy.
Results
Both sources showed that it's not possible to exactly meet the waveform requirements without violating the 30% short-circuit current overshoot limit. Nevertheless, Hesterman, et. al. presented an approximate solution by adjusting the waveform parameters within tolerance. The derivation by Carobbi et, al. ignored the undershoot requirement, pointing out that a practical circuit may reduce overshoot to even practically zero in some cases if an unidirectional switch is used. Also, IEC 61000-4-5 states that there's no overshoot or undershoot requirement at the output of a coupling network.
These solutions are only valid for an ideal generator, suitable for circuit simulation. It can be used as a starting point of practical generator design, but component values have to be adjusted further due to switch non-idealities. In an ideal circuit, open-circuit voltage rise time is governed by the time constant , but a practical switch may cause rise time degradation. Further, due to the use of different switch types, a real generator may produce either a bidirectional impulse with undershoot, or an unidirectional impulse without undershoot. An ideal circuit model cannot predict these non-linear effects, and should not be treated as a complete circuit model of practical generators.
10/700-5/320 μs Generator
A different Combination Wave Generator is used for the 10/700-5/320 μs surge.
Test Levels
The following table shows the peak open-circuit voltage and short-circuit current of the Combination Wave Generator.
The full current is not always actually applied to the DUT. Depending on the test setup and port type, an additional resistor may be used as a part of the coupling network to reduce the peak surge current into the DUT, raising the output impedance to 12 Ω or 42 Ω.
See also
IEC 61000-4-2
IEC 61000-4-4
Surge protection
List of common EMC test standards
List of IEC standards
List of EN standards
References
External links
IEC Webstore
STMicroelectronics' Application note AN4275 IEC 61000-4-5 standard overview
Electromagnetic compatibility
61000-4-5 | IEC 61000-4-5 | [
"Technology",
"Engineering"
] | 2,941 | [
"Electromagnetic compatibility",
"Radio electronics",
"Computer standards",
"IEC standards",
"Electrical engineering"
] |
49,462,636 | https://en.wikipedia.org/wiki/2016%20Italian%20oil%20drilling%20referendum | An abrogative referendum on oil and natural gas drilling was held in Italy on 17 April 2016. The referendum was on the proposed repealing of a law that allows gas and oil drilling concessions extracting hydrocarbon within 12 nautical miles of the Italian coast to be prolonged until the exhaustion of the useful life of the fields.
Although 86% voted in favour of repealing the law, the turnout of 31% was below the majority threshold required to validate the result.
It was the first referendum requested by at least five Regional Councils in the history of the Italian Republic: all 66 previous referendum questions since 1974 were called after the collection of signatures.
Background
The search for hydrocarbon liquids and/or gases in the Italian sea is possible - with some restrictions for the coastal and environmental protection - only in certain "marine areas" identified by the Italian Parliament or by the Ministry of Economic Development. From 2013, new drilling is prohibited in the Tyrrhenian Sea, in the marine protected areas and in the waters within 12 nautical miles from the coast; however, the concessions approved before 2013 may continue until all of the resources are extracted.
Italy authorized a total of 79 offshore platforms: 31 are located over 12 miles from and 48 within 12 miles.
Off-shore production of hydrocarbons in Italy
Within 12 miles, 9 concessions are authorized (with 39 platforms) and their permits have expired and they have asked for an extension: if the "yes" vote wins in the referendum, the 9 expired concessions can not be extended. During 2015 those installations extracted about 622 million cubic meters of natural gas (equivalent to 9% of the national production and 1.1% of total consumption in 2014).
Under the 12 mile limit, there are 17 other concessions expiring between 2017 and 2027, which in 2015 extracted 1.21 billion cubic meters of gas (17.6% of national production and 2.1% of national consumption in 2014) and 500,000 tons of oil (about 9.1% of national production and 0.8% of consumption in 2014). These concessions, in the event of a victory for 'yes' in the referendum, will not be extended after 2027.
Referendum initiative
The referendum was proposed by several regional governments after the national government passed a law allowing drilling concessions to last until oilfields or gasfields are empty. On 19 January 2016 the Constitutional Court approved the referendum. On 12 February the Five Star Movement asked President Sergio Mattarella to delay the referendum until June to allow it to be held alongside local elections in order to raise turnout and save money.
Position of main political parties
Opinion polls
Results
Notes
References
Oil
Italy
Referendums in Italy
Energy in Italy
Oil wells
Energy policy referendums
Oil | 2016 Italian oil drilling referendum | [
"Chemistry"
] | 548 | [
"Petroleum technology",
"Oil wells"
] |
49,466,458 | https://en.wikipedia.org/wiki/Rapid%20tooling | Rapid tooling (RT) in the plastic injection molding industry refers to molds that are manufactured in a very short period of time, also known as prototype tooling. Some of the main advantages to rapid tooling trades is that it decreases the time and cost of the product. With rapid tools being fast and easily reproducible, it requires less stock for finished tools. These tools will be produced on demand and are available almost immediately. Special tools or tools where no supplier is existing on the market any more can be reproduced without bigger design and production efforts. However, the disadvantages are that it is not as accurate and also shortens the lifespan of the product.
Rapid tooling is mainly used for specific needs including prototyping and troubleshooting existing problems. Rapid prototyping is not often used for large scale and long term operations for a part. Nevertheless, rapid tooling is starting to be used to create molds for commercial operations because the time lag is so short between start to finish and since a CAD file is the only thing needed for the design stage. Since alternate methods require precious time and resources, rapid tooling provides a way to quickly provide molds for the required products. This allows companies to quickly make commercial products with the advances of rapid prototyping.
In addition, rapid tooling provides the customization necessary for personal applications. Instead of tedious trial and error measurements, rapid prototyping processes allow scientists and doctors the ability to scan and digitize the item or patient. Then by putting it through a CAD program, a personal custom mold can be created to fix the problem. An example of this procedure is for dental patients. Originally to fabricate an oral application, an alginate impression or a wax registration is used to fit the teeth with the mold. With new advances, doctors can take a scan of the dental arches to correctly and quickly make a mold out of silicone for the patient. This allows for better accuracy and more acute customization of the mold in the future.
Unlike rapid tooling, production tooling (PT) refers to molds that are manufactured according to a normal process in a normal production time. some of the main advantages of production tooling are that it has a larger Life Cycle and is suitable for mass production.
References
Manufacturing
Prototypes
Computer-aided design
3D printing | Rapid tooling | [
"Engineering"
] | 472 | [
"Computer-aided design",
"Design engineering",
"Manufacturing",
"Mechanical engineering"
] |
32,107,744 | https://en.wikipedia.org/wiki/DIN%201025 | DIN 1025 is a DIN standard which defines the dimensions, masses and sectional properties of hot rolled I-beams.
The standard is divided in 5 parts:
DIN 1025-1: Hot rolled I-sections - Part 1: Narrow flange I-sections, I-serie - Dimensions, masses, sectional properties
DIN 1025-2: Hot rolled I-beams - Part 2: Wide flange I-beams, IPB-serie; dimensions, masses, sectional properties
DIN 1025-3: Hot rolled I-beams; wide flange I-beams, light pattern, IPBl-serie; dimensions, masses, sectional properties
DIN 1025-4: Hot rolled I-beams; wide flange I-beams heavy pattern, IPBv-serie; dimensions, masses, sectional properties
DIN 1025-5: Hot rolled I-beams; medium flange I-beams, IPE-serie; dimensions, masses, sectional properties
See also
EN 1993
1025
Structural engineering standards
Structural steel | DIN 1025 | [
"Engineering"
] | 205 | [
"Structural engineering",
"Structural steel",
"Structural engineering standards"
] |
32,109,190 | https://en.wikipedia.org/wiki/Chantiers%20et%20Ateliers%20Augustin%20Normand | Chantiers et Ateliers A. Normand was a French shipyard in Le Havre. They were notable for building small warships since the late 1850s to the early part of the 20th century.
They also developed the Normand boiler, an early design of three-drum water-tube boiler.
Shipyards of France
Le Havre
Former submarine builders | Chantiers et Ateliers Augustin Normand | [
"Engineering"
] | 69 | [
"Mechanical engineering stubs",
"Mechanical engineering"
] |
32,115,422 | https://en.wikipedia.org/wiki/Geographical%20centre%20of%20Ireland | The Geographical Centre of Ireland, according to an investigation and calculation carried out by the Official Irish Government Mapping Agency, Ordnance Survey Ireland (OSI) published on the official OSI website on 24 February 2022 is near the village of Castletown Geoghegan, County Westmeath.
The exact location lies at the Irish Transverse Mercator (ITM) coordinates 633015.166477, 744493.046768, and at Latitude: 53.4494762 and Longitude : -7.5029786.
It sits in the townland of Adamstown within a National Monuments Zone, on the location of an ancient graveyard and near the remains of Kilbride church.
This investigation to identify the exact geographic centre of Ireland assumed a calculation that would take in the whole of the mainland Island of Ireland but exclude the islands of which there are approximately 8,000 mapped islands, outcrops etc.
It is however based on current data and based on current coastal data and any coastal erosion or accretion historically or in the future would change the data and change the exact location calculated. Various locations have claimed in the past to be the geographical centre of Ireland using various methodologies (though sometimes without any updated references or supporting academic methodology).
OSI have determined that the most appropriate methodology to use currently is the one published in February 2022 and which determined the location to be just outside Castletown Geoghegan.
In Irish mythology the Hill of Uisneach, which is about 17.7 kilometres west of Mullingar and two kilometres from the village of Loughanavally was generally considered to be the ceremonial and ancient spiritual centre of Ireland, though at times the Hill of Tara was also regarded in a similar manner.
The Hill of Uisneach is the nearest of the alternative historical locations to the location calculated by the OSI and is approximately 5 kilometres south east in a direct line from the Hill of Uisneach.
References
Ordnance Survey Ireland website Blog : https://osi.ie/blog/where-is-the-centre-of-ireland/ 24 February 2022
Geography of Ireland
Ireland | Geographical centre of Ireland | [
"Physics",
"Mathematics"
] | 439 | [
"Point (geometry)",
"Geometric centers",
"Geographical centres",
"Symmetry"
] |
32,122,623 | https://en.wikipedia.org/wiki/Additive%20manufacturing%20file%20format | Additive manufacturing file format (AMF) is an open standard for describing objects for additive manufacturing processes such as 3D printing. The official ISO/ASTM 52915:2016 standard is an XML-based format designed to allow any computer-aided design software to describe the shape and composition of any 3D object to be fabricated on any 3D printer via a computer-aided manufacturing software. Unlike its predecessor STL format, AMF has native support for color, materials, lattices, and constellations.
Structure
An AMF can represent one object, or multiple objects arranged in a constellation. Each object is described as a set of non-overlapping volumes. Each volume is described by a triangular mesh that references a set of points (vertices). These vertices can be shared among volumes belonging to the same object. An AMF file can also specify the material and the color of each volume, as well as the color of each triangle in the mesh. The AMF file is compressed using the zip compression format, but the ".amf" file extension is retained. A minimal AMF reader implementation must be able to decompress an AMF file and import at least geometry information (ignoring curvature).
Basic file structure
The AMF file begins with the XML declaration line specifying the XML version and encoding. The remainder of the file is enclosed between an opening element and a closing element. The unit system can also be specified (millimeter, inch, feet, meter or micrometer). In absence of a units specification, millimeters are assumed.
Within the AMF brackets, there are five top level elements. Only a single object element is required for a fully functional AMF file.
The object element defines a volume or volumes of material, each of which are associated with a material ID for printing. At least one object element must be present in the file. Additional objects are optional.
The optional material element defines one or more materials for printing with an associated material ID. If no material element is included, a single default material is assumed.
The optional texture element defines one or more images or textures for color or texture mapping, each with an associated texture ID.
The optional constellation element hierarchically combines objects and other constellations into a relative pattern for printing.
The optional metadata element specifies additional information about the object(s) and elements contained in the file.
Geometry specification
The format uses a Face-vertex polygon mesh layout. Each top-level element specifies a unique . The element can also optionally specify a material. The entire mesh geometry is contained in a single element. The mesh is defined using one element and one or more elements. The required element lists all vertices that are used in this object. Each vertex is implicitly assigned a number in the order in which it was declared, starting at zero. The required child element gives the position of the point in 3D space using the , and elements.
After the vertex information, at least one element must be included. Each volume encapsulates a closed volume of the object, Multiple volumes can be specified in a single object. Volumes may share vertices at interfaces but may not have any overlapping volume.
Within each volume, the child element is used to define triangles that tessellate the surface of the volume. Each element will list three vertices from the set of indices of the previously defined vertices given in the element. The indices of the three vertices of the triangles are specified using the , and elements. The order of the vertices must be according to the right-hand rule, such that vertices are listed in counter-clockwise order as viewed from the outside. Each triangle is implicitly assigned a number in the order in which it was declared, starting at zero.
Color specification
Colors are introduced using the element by specifying the red, green, blue and alpha (transparency) channels in the sRGB color space as numbers in the range of 0 to 1. The element can be inserted at the material, object, volume, vertex, or triangle levels, and takes priority in reverse order (triangle color is highest priority). The transparency channel specifies to what degree the color from the lower level is blended in. By default, all values are set to zero.
A color can also be specified by referring to a formula that can use a variety of coordinate-dependent functions.
Texture maps
Texture maps allow assigning color or material to a surface or a volume, borrowing from the idea of Texture mapping in graphics. The element is first used to associate a with particular texture data. The data can be represented as either a 2D or a 3D array, depending on whether the color or material need to be mapped to a surface or a volume. The data is represented as a string of bytes in Base64 encoding, one byte per pixel specifying the grayscale level in the 0-255 range.
Once the texture-id is assigned, the texture data can be referenced in a color formula, such as in the example below.
Usually, however, the coordinates will not be used directly as shown above, but transformed first to bring them from object coordinates to texture coordinates. For example, where are some functions, typically linear.
Material specification
Materials are introduced using the <material> element. Each material is assigned a unique id.
Geometric volumes are associated with materials by specifying a material-id within the <volume> element.
Mixed, graded, lattice, and random materials
New materials can be defined as compositions of other materials. The element is used to specify the proportions of the composition, as a constant or as a formula dependent of the x, y, and z coordinates. A constant mixing proportion will lead to a homogenous material. A coordinate-dependent composition can lead to a graded material. More complex coordinate-dependent proportions can lead to nonlinear material gradients as well as periodic and non-periodic substructure. The proportion formula can also refer to a texture map using the function. Reference to material-id "0" (void) is reserved and may be used to specify porous structures. Reference to the function can be used to specify pseudo-random materials. The function returns a random number between 0 and 1 that is persistent for that coordinate.
Print constellations
Multiple objects can be arranged together using the element. A constellation can specify the position and orientation of objects to increase packing efficiency and to describe large arrays of identical objects. The element specifies the displacement and rotation an existing object needs to undergo to arrive into its position in the constellation. The displacement and rotation are always defined relatively to the original position and orientation in which the object was defined. A constellation can refer to another constellation as long as cyclic references are avoided.
If multiple top-level constellations are specified, or if multiple objects without constellations are specified, each of them will be imported with no relative position data. The importing program can then freely determine the relative positioning.
Meta-data
The element can optionally be used to specify additional information about the objects, geometries and materials being defined. For example, this information can specify a name, textual description, authorship, copyright information and special instructions. The element can be included at the top level to specify attributes of the entire file, or within objects, volumes and materials to specify attributes local to that entity.
Optional curved triangles
In order to improve geometric fidelity, the format allows curving the triangle patches. By default, all triangles are assumed to be flat and all triangle edges are assumed to be straight lines connecting their two vertices. However, curved triangles and curved edges can optionally be specified in order to reduce the number of mesh elements required to describe a curved surface. The curvature information has been shown to reduce the error of a spherical surface by a factor of 1000 as compared to a surface described by the same number of planar triangles. Curvature should not create a deviation from the plane of the flat triangle that exceeds 50% of the largest dimension of the triangle.
To specify curvature, a vertex can optionally contain a child element to specify desired surface normal at the location of the vertex. The normal should be unit length and pointing outwards. If this normal is specified, all triangle edges meeting at that vertex are curved so that they are perpendicular to that normal and in the plane defined by the normal and the original straight edge. When the curvature of a surface at a vertex is undefined (for example at a cusp, corner or edge), an element can be used to specify the curvature of a single non-linear edge joining two vertices. The curvature is specified using the tangent direction vectors at the beginning and end of that edge. The element will take precedence in case of a conflict with the curvature implied by a element.
When curvature is specified, the triangle is decomposed recursively into four sub-triangles. The recursion must be executed five levels deep, so that the original curved triangle is ultimately replaced by 1024 flat triangles. These 1024 triangles are generated "on the fly" and stored temporarily only while layers intersecting that triangle are being processed for manufacturing.
Formulas
In both the and elements, coordinate-dependent formulas can be used instead of constants. These formulas can use various standard algebraic and mathematical operators and expressions.
Compression
An AMF can be stored either as plain text or as compressed text. If compressed, the compression is in ZIP archive format. A compressed AMF file is typically about half the size of an equivalent compressed binary STL file. The compression can be done manually using compression software, or automatically by the exporting software during write. Both the compressed and uncompressed files have the extension and it is the responsibility of the parsing program to determine whether or not the file is compressed, and if so to perform decompression during import.
Design considerations
When the ASTM Design subcommittee began developing the AMF specifications, a survey of stakeholders revealed that the key priority for the new standard was the requirement for a non-proprietary format. Units and buildability issues were a concern lingering from problems with the STL format. Other key requirements were the ability to specify geometry with high fidelity and small file sizes, multiple materials, color, and microstructures. In order to be successful across the field of additive manufacturing, this file format was designed to address the following concerns
Technology independence: The file format must describe an object in a general way such that any machine can build it to the best of its ability. It is resolution and layer-thickness independent, and does not contain information specific to any one manufacturing process or technique. This does not negate the inclusion of properties that only certain advanced machines support (for example, color, multiple materials, etc.), but these are defined in such a way as to avoid exclusivity.
Simplicity: The file format must be easy to implement and understand. The format should be readable and editable in a simple text viewer, in order to encourage understanding and adoption. No identical information should be stored in multiple places.
Scalability: The file format should scale well with increase in part complexity and size, and with the improving resolution and accuracy of manufacturing equipment. This includes being able to handle large arrays of identical objects, complex repeated internal features (e.g. meshes), smooth curved surfaces with fine printing resolution, and multiple components arranged in an optimal packing for printing.
Performance: The file format must enable reasonable duration (interactive time) for read and write operations and reasonable file sizes for a typical large object.
Backwards compatibility: Any existing STL file should be convertible directly into a valid AMF file without any loss of information and without requiring any additional information. AMF files are also easily convertible back to STL for use on legacy systems, although advanced features will be lost.
Future compatibility: In order to remain useful in a rapidly changing industry, this file format must be easily extensible while remaining compatible with earlier versions and technologies. This allows new features to be added as advances in technology warrant, while still working flawlessly for simple homogenous geometries on the oldest hardware.
History
Since the mid-1980s, the STL file format has been the de facto industry standard for transferring information between design programs and additive manufacturing equipment. The STL format only contained information about a surface mesh, and had no provisions for representing color, texture, material, substructure, and other properties of the fabricated target object. As additive manufacturing technology evolved from producing primarily single-material, homogenous shapes to producing multi-material geometries in full color with functionally graded materials and microstructures, there was a growing need for a standard interchange file format that could support these features. A second factor that ushered the development of the standard was the improving resolution of additive manufacturing technologies. As the fidelity of printing processes approached micron scale resolution, the number of triangles required to describe smooth curved surfaces resulted in unacceptably large file sizes.
During the 1990s and 2000s, a number of proprietary file formats have been in use by various companies to support specific features of their manufacturing equipment, but the lack of an industry-wide agreement prevented widespread adoption of any single format. In 2006, Jonathan D. Hiller and Hod Lipson presented an initial version of AMF dubbed "STL 2.0". In January 2009, a new ASTM Committee F42 on Additive Manufacturing Technologies was established, and a design subcommittee was formed to develop a new standard. A survey was conducted in late 2009 leading to over a year of deliberations on the new standard. The resulting first revision of the AMF standard became official on May 2, 2011.
During the July 2013 meetings of ASTM's F42 and ISO's TC261 in Nottingham (UK), the Joint Plan for Additive Manufacturing Standards Development was approved. Since then, the AMF standard is managed jointly by ISO and ASTM.
Sample file
Below is a simple AMF file describing a pyramid made of two materials, adapted from the AMF tutorial (548 bytes compressed). To create this AMF file, copy and paste the text below into a text editor or an xml editor, and save the file as "pyramid.amf". Then compress the file with ZIP, and rename the file extension from ".zip" to ".zip.amf".
<?xml version="1.0" encoding="utf-8"?>
<amf unit="inch" version="1.1">
<metadata type="name">Split Pyramid</metadata>
<metadata type="author">John Smith</metadata>
<object id="1">
<mesh>
<vertices>
<vertex><coordinates><x>0</x><y>0</y><z>0</z></coordinates></vertex>
<vertex><coordinates><x>1</x><y>0</y><z>0</z></coordinates></vertex>
<vertex><coordinates><x>0</x><y>1</y><z>0</z></coordinates></vertex>
<vertex><coordinates><x>1</x><y>1</y><z>0</z></coordinates></vertex>
<vertex><coordinates><x>0.5</x><y>0.5</y><z>1</z></coordinates></vertex>
</vertices>
<volume materialid="2">
<metadata type="name">Hard side</metadata>
<triangle><v1>2</v1><v2>1</v2><v3>0</v3></triangle>
<triangle><v1>0</v1><v2>1</v2><v3>4</v3></triangle>
<triangle><v1>4</v1><v2>1</v2><v3>2</v3></triangle>
<triangle><v1>0</v1><v2>4</v2><v3>2</v3></triangle>
</volume>
<volume materialid="3">
<metadata type="name">Soft side</metadata>
<triangle><v1>2</v1><v2>3</v2><v3>1</v3></triangle>
<triangle><v1>1</v1><v2>3</v2><v3>4</v3></triangle>
<triangle><v1>4</v1><v2>3</v2><v3>2</v3></triangle>
<triangle><v1>4</v1><v2>2</v2><v3>1</v3></triangle>
</volume>
</mesh>
</object>
<material id="2">
<metadata type="name">Hard material</metadata>
<color><r>0.1</r><g>0.1</g><b>0.1</b></color>
</material>
<material id="3">
<metadata type="name">Soft material</metadata>
<color><r>0</r><g>0.9</g><b>0.9</b><a>0.5</a></color>
</material>
</amf>
See also
X3D
3D Printing Marketplace
3D Manufacturing Format
glTF - a Khronos Group file format for 3D Scenes and models.
Notes
External links
AMF Wiki: A repository of AMF resources, sample files, and source code
Jon Hiller's AMF page
Open standards
XML-based standards
3D graphics file formats
CAD file formats | Additive manufacturing file format | [
"Technology"
] | 3,730 | [
"Computer standards",
"XML-based standards"
] |
32,122,937 | https://en.wikipedia.org/wiki/Systems%20of%20Logic%20Based%20on%20Ordinals | Systems of Logic Based on Ordinals was the PhD dissertation of the mathematician Alan Turing.
Turing's thesis is not about a new type of formal logic, nor was he interested in so-called "ranked logic" systems derived from ordinal or relative numbering, in which comparisons can be made between truth-states on the basis of relative veracity. Instead, Turing investigated the possibility of resolving the Gödelian incompleteness condition using Cantor's method of infinites.
The thesis is an exploration of formal mathematical systems after Gödel's theorem. Gödel showed that for any formal system S powerful enough to represent arithmetic, there is a theorem G that is true but the system is unable to prove. G could be added as an additional axiom to the system in place of a proof. However this would create a new system S' with its own unprovable true theorem G''', and so on. Turing's thesis looks at what happens if you simply iterate this process repeatedly, generating an infinite set of new axioms to add to the original theory, and even goes one step further in using transfinite recursion to go "past infinity", yielding a set of new theories Gα, one for each ordinal number α''.
The thesis was completed at Princeton under Alonzo Church and was a classic work in mathematics that introduced the concept of ordinal logic.
Martin Davis states that although Turing's use of a computing oracle is not a major focus of the dissertation, it has proven to be highly influential in theoretical computer science, e.g. in the polynomial-time hierarchy.
References
External links
https://rauterberg.employee.id.tue.nl/lecturenotes/DDM110%20CAS/Turing/Turing-1939%20Sysyems%20of%20logic%20based%20on%20ordinals.pdf
https://www.dcc.fc.up.pt/~acm/turing-phd.pdf
https://web.archive.org/web/20121023103503/https://webspace.princeton.edu/users/jedwards/Turing%20Centennial%202012/Mudd%20Archive%20files/12285_AC100_Turing_1938.pdf
History of logic
Systems of formal logic
Alan Turing
Ordinal numbers
Mathematics papers | Systems of Logic Based on Ordinals | [
"Mathematics"
] | 504 | [
"Ordinal numbers",
"Mathematical logic",
"Mathematical objects",
"Mathematical logic stubs",
"Order theory",
"Numbers"
] |
39,224,245 | https://en.wikipedia.org/wiki/YDS%20algorithm | YDS is a scheduling algorithm for dynamic speed scaling processors which minimizes the total energy consumption. It was named after and developed by Yao et al. There is both an online and an offline version of the algorithm.
Offline Algorithm
Definitions:
There is a set of n Jobs , where each job has a release time , deadline and a processing volume .
is a certain time interval.
Also we have , the work density in .
And finally is the set of Jobs that must be processed in , that means Jobs with .
The algorithm then works as follows:
While
Determine the time interval of maximum density .
In process the jobs of at speed according to EDF
Set .
Remove from the time horizon and update the release times and deadlines of unscheduled jobs accordingly.
end While
In other terms it's a recursive algorithm that will follow these steps until all jobs are scheduled:
Calculate all intensities for all possible combinations of intervals. This means that for every start time and end time combination the intensity of work is calculated. For this the times of all jobs whose arrival time and deadline lie inside the interval are added and divided by the interval length. To speed up the process, only combinations of arrival times and later deadlines need to be considered, as times without arrival of a process or deadline can be shrunk to a smaller interval with the same processes, thus increasing intensity, and negative intervals are invalid. Then the maximum intensity interval is selected. In case of multiple equally intense intervals, one can be chosen at will, as intensities of non-overlapping intervals do not influence each other, and removing a part of an interval will not change the intensity of the rest, as processes are removed proportionally.
The processes inside this interval are scheduled using Earliest Deadline First, meaning that the job inside this interval whose deadline will arrive soonest is scheduled first, and so on. The jobs are executed at the above calculated intensity to fit all jobs inside the interval.
The interval is removed from the timeline, as no more calculations can be scheduled here. To simplify further calculations, all arrival times and deadlines of remaining jobs are recalculated to omit already occupied times. For example, assume a job with arrival time , deadline and a workload , and a job with , and . Assume the previous interval was from time to . To omit this interval the times of and need to be adjusted; workloads are unaffected, as no work has been done for either or . stays the same, as it's unaffected by later omissions. , however, needs to be changed to , as . This is the time job has left before its deadline. The arrival time becomes , as it would have been inside the removed interval. also becomes , as the time left after the removed interval is . It is important, however, to remember the actual arrival and deadline times for later assembly of the scheduling.
Repeat steps 1-3 until all jobs have been scheduled.
Assemble jobs into final scheduling according to their allotted time intervals. Remember, though, that an interval may be split in two by another interval calculated earlier.
For any Job instance, the algorithm computes an optimal schedule minimizing the total energy consumption.
See also
Earliest deadline first scheduling
References
Real-time computing
Processor scheduling algorithms
Optimal scheduling | YDS algorithm | [
"Technology",
"Engineering"
] | 669 | [
"Optimal scheduling",
"Real-time computing",
"Industrial engineering"
] |
39,230,475 | https://en.wikipedia.org/wiki/Configurational%20mechanics | Configurational mechanics is a subdiscipline of continuum mechanics in which particular emphasis is placed on reckoning from the perspective of the material manifold. By contrast, in classical mechanics, reckoning is commonly made from the perspective of spatial coordinates.
Configurational mechanics has been applied to the analysis of crack growth. In these applications, growth of the crack corresponds to a material displacement, and the configurational force causing crack growth emerges as the Energy release rate.
References
Continuum mechanics | Configurational mechanics | [
"Physics"
] | 96 | [
"Classical mechanics stubs",
"Classical mechanics",
"Continuum mechanics"
] |
31,134,176 | https://en.wikipedia.org/wiki/Phyre | Phyre and Phyre2 (Protein Homology/AnalogY Recognition Engine; pronounced as fire) are free web-based services for protein structure prediction. Phyre is among the most popular methods for protein structure prediction having been cited over 1,500 times. Like other remote homology recognition techniques (see protein threading), it is able to regularly generate reliable protein models when other widely used methods such as PSI-BLAST cannot. Phyre2 has been designed to ensure a user-friendly interface for users inexpert in protein structure prediction methods. Its development is funded by the Biotechnology and Biological Sciences Research Council.
Description
The Phyre and Phyre2 servers predict the three-dimensional structure of a protein sequence using the principles and techniques of homology modeling.
Because the structure of a protein is more conserved in evolution than its amino acid sequence, a protein sequence of interest (the target) can be modeled with reasonable accuracy on a very distantly related sequence of known structure (the template), provided that the relationship between target and template can be discerned through sequence alignment. Currently the most powerful and accurate methods for detecting and aligning remotely related sequences rely on profiles or hidden Markov models (HMMs). These profiles/HMMs capture the mutational propensity of each position in an amino acid sequence based on observed mutations in related sequences and can be thought of as an 'evolutionary fingerprint' of a particular protein.
Typically, the amino acid sequences of a representative set of all known three-dimensional protein structures is compiled, and these sequences are processed by scanning against a large protein sequence database. The result is a database of profiles or HMMs, one for each known 3D structure. A user sequence of interest is similarly processed to form a profile/HMM. This user profile is then scanned against the database of profiles using profile-profile or HMM-HMM alignment techniques. These alignments can also take into account patterns of predicted or known secondary structure elements and can be scored using various statistical models. See protein structure prediction for more information.
The first Phyre server was released in June 2005 and uses a profile-profile alignment algorithm based on each protein's position-specific scoring matrix. The Phyre2 server was publicly released February 2011 as a replacement for the original Phyre server and provides extra functions over Phyre, a more advanced interface, fully updated fold library and uses the HH-suite (HHpred, HHsearch) package for homology detection among other improvements.
Standard use
After pasting a protein amino acid sequence into the Phyre or Phyre2 submission form, a user will typically wait between 30 minutes and several hours (depending on factors such as sequence length, number of homologous sequences and frequency and length of insertions and deletions) for a prediction to complete. An email containing summary information and the predicted structure in PDB format are sent to the user together with a link to a web page of results. The Phyre2 results screen is divided into three main sections, described below.
Secondary structure and disorder prediction
The user-submitted protein sequence is first scanned against a large sequence database using PSI-BLAST. The profile generated by PSI-BLAST is then processed by the neural network secondary structure prediction program PsiPred and the protein disorder predictor Disopred. The predicted presence of alpha-helices, beta-strands and disordered regions is shown graphically together with a color-coded confidence bar.
Domain analysis
Many proteins contain multiple protein domains. Phyre2 provides a table of template matches color-coded by confidence and indicating the region of the user sequence matched. This can aid in the determination of the domain composition of a protein.
Detailed template information
The main results table in Phyre2 provides confidence estimates, images and links to the three-dimensional predicted models and information derived from either Structural Classification of Proteins database (SCOP) or the Protein Data Bank (PDB) depending on the source of the detected template. For each match a link takes the user to a detailed view of the alignment between the user sequence and the sequence of known three-dimensional structure.
Alignment view
The detailed alignment view permits a user to examine individual aligned residues, matches between predicted and known secondary structure elements and the ability to toggle information regarding patterns of sequence conservation and secondary structure confidence. In addition Jmol is used to permit interactive 3D viewing of the protein model.
Improvements in Phyre2
Phyre2 uses a fold library that is updated weekly as new structures are solved. It uses a more up-to-date interface and offers additional functions over the Phyre server as described below.
Added functions
Batch processing
The batch processing feature permits users to submit more than one sequence to Phyre2 by uploading a file of sequences in FASTA format. By default, users have a limit of 100 sequences in a batch. This limit can be raised by contacting the administrator.
Batch jobs are processed in the background on free computing power as it becomes available. Thus, batch jobs will often take longer than individually submitted jobs, but this is necessary to allow a fair distribution of computing resources to all Phyre2 users.
One to one threading
One to one threading allows you to upload both a sequence you wish modelled AND the template on which to model it. Users sometimes have a protein sequence that they wish to model on a specific template of their choice. This may be for example a newly solved structure that is not in the Phyre2 database or because of some additional biological information that indicates the chosen template would produce a more accurate model than the one(s) automatically chosen by Phyre2.
Backphyre
Instead of predicting the 3D structure of a protein sequence, often users have a solved structure and they are interested in determining if there is a related structure in a genome of interest. In Phyre2 an uploaded protein structure can be converted into a hidden Markov model and then scanned against a set of genomes (more than 20 genomes as of March 2011). This function is called BackPhyre to indicate how Phyre2 is being used in reverse.
Phyrealarm
Sometimes Phyre2 can't detect any confident matches to known structures. However, the fold library database increases by about 40-100 new structures each week. So even though there might be no decent templates this week, there may well be in the coming weeks.
Phyrealarm allows users to submit a protein sequence to be automatically scanned against new entries added to the fold library every week. If a confident hit is detected, the user is automatically notified by email together with the results of the Phyre2 search. Users can also control the level of alignment coverage and confidence in the match required to trigger an email alert.
3DLigandSite
Phyre2 is coupled to the 3DLigandSite server for protein binding site prediction. 3DLigandSite has been one of the top performing servers for binding site prediction at the Critical Assessment of Structure Prediction (CASP) in (CASP8 and CASP9). Confident models produced by Phyre2 (confidence >90%) are automatically submitted to 3DLigandSite.
Transmembrane topology prediction
The program memsat_svm is used to predict the presence and topology of any transmembrane helices present in the user protein sequence.
Multi-template modelling
Phyre2 permits users to choose 'Intensive' modelling from the main submission screen. This mode:
Examines the list of hits and applies heuristics in order to select templates that maximise sequence coverage and confidence.
Constructs models for each selected template.
Uses these models to provide pairwise distance constraints that are input to the ab initio and multi-template modelling tool Poing.
Poing synthesises the user protein in the context of these distance constraints, modelled by springs. Regions for which there is no template information are modelled by the ab initio simplified physics model of Poing.
The complete model generated by Poing is combined with the original templates as input to MODELLER.
Applications
Applications of Phyre and Phyre2 include protein structure prediction, function prediction, domain prediction, domain boundary prediction, evolutionary classification of proteins, guiding site-directed mutagenesis and solving protein crystal structures by molecular replacement.
There are two linked resources that use Phyre predictions for the structure-based analysis of missense variants typically resulting from single-nucleotide polymorphisms.
PhyreRisk is a database which maps genetic variants to experimental and Phyre-predicted protein structures. The protein page displays the experimental and predicted structures. Users can map variants from either genetic or protein coordinates.
Missense3D is a tool which provides a stereochemical report on the effect of a missense variant on protein structure. Users can upload their own variants and coordinates, including both PDB structures and Phyre-predicted models.
History
Phyre and Phyre2 are the successors to the 3D-PSSM protein structure prediction system which has over 1,400 citations to date. 3D-PSSM was designed and developed by Lawrence Kelley and Bob MacCallum in the Biomolecular modelling Lab at the Cancer Research UK. Phyre and Phyre2 were Lawrence Kelley in the structural bioinformatics group, Imperial College London. Components of the Phyre and Phyre2 systems were developed by Benjamin Jefferys, Alex Herbert, and Riccardo Bennett-Lovsey. Research and development of both servers was supervised by Michael Sternberg.
References
Bioinformatics software
Computational science | Phyre | [
"Mathematics",
"Biology"
] | 1,928 | [
"Computational science",
"Applied mathematics",
"Bioinformatics",
"Bioinformatics software"
] |
31,135,900 | https://en.wikipedia.org/wiki/Edith%20Creek%20Chlorination%20House | The Edith Creek Chlorination House is a historic structure in Mount Rainier National Park, built by the National Park Service in 1930. The rustic structure was built as part of the water supply system to the Paradise area. The low concrete building with stone veneer cladding was built to withstand very heavy snow loads. It was fed by a small dam on Edith Creek, which was replaced in 1970. The chlorination house contained equipment to chlorinate the water from this source and to regulate the level of the reservoir.
The Edith Creek Chlorination House was placed on the National Register of Historic Places on March 13, 1991. It is part of the Mount Rainier National Historic Landmark District, which encompasses the entire park and which recognizes the park's inventory of Park Service-designed rustic architecture.
References
National Register of Historic Places in Mount Rainier National Park
Infrastructure completed in 1930
Rustic architecture in Washington (state)
Buildings and structures in Mount Rainier National Park
Water treatment facilities
Buildings and structures in Pierce County, Washington
Industrial buildings and structures in Washington (state)
Park buildings and structures on the National Register of Historic Places in Washington (state)
1930 establishments in Washington (state) | Edith Creek Chlorination House | [
"Chemistry"
] | 238 | [
"Water treatment",
"Water treatment facilities"
] |
31,136,418 | https://en.wikipedia.org/wiki/Octaazacubane | Octaazacubane is a hypothetical explosive allotrope of nitrogen with formula N8, whose molecules have eight atoms arranged into a cube. (By comparison, nitrogen usually occurs as the diatomic molecule N2.) It can be regarded as a cubane-type cluster, where all eight corners are nitrogen atoms bonded along the edges. It is predicted to be a metastable molecule, in which despite the thermodynamic instability caused by bond strain, and the high energy of the N–N single bonds, the molecule remains kinetically stable for reasons of orbital symmetry.
Explosive and fuel
Octaazacubane is predicted to have an energy density (assuming decomposition into N2) of 22.9 MJ/kg, which is over 5 times the standard value of TNT. It has therefore been proposed (along with other exotic nitrogen allotropes) as an explosive, and as a component of high performance rocket fuel. Its velocity of detonation is predicted to be 15,000 m/s, much (48.5%) more than octanitrocubane, the fastest known nonnuclear explosive.
A prediction for cubic gauche nitrogen energy density is 33 MJ/kg, exceeding octaazacubane by 44%, though a more recent one is of 10.22 MJ/kg, making it less than half of octaazacubane.
See also
Tetranitrogen (Nitrogen allotrope with formula N4)
Hexazine (Nitrogen allotrope with formula N6)
Pentazole
1,1′-Azobis-1,2,3-triazole
1-Diazidocarbamoyl-5-azidotetrazole
References
External links
Explosive chemicals
Hypothetical chemical compounds
Allotropes of nitrogen | Octaazacubane | [
"Chemistry"
] | 373 | [
"Allotropes",
"Allotropes of nitrogen",
"Hypotheses in chemistry",
"Theoretical chemistry",
"Hypothetical chemical compounds",
"Explosive chemicals"
] |
31,142,113 | https://en.wikipedia.org/wiki/3-pronged%20parts%20retriever | A 3-pronged parts retriever, also known as a Pearl-Catcher, is a tool used by computer technicians.
Design
It consists of a length of tube of around 4 mm to 6 mm in diameter, often made of coiled steel springs, with a push-button on one end. Three metal wires protrude from the other end, each sprung to bend outwards, away from the tube's axis, but with their tips bent inwards to form teeth. The push-button drives the wires down the tube, where their natural springiness causes them to spread further outwards, opening the teeth. When the button is released, an internal spring withdraws the wires which, constrained by the tube, are forced together, closing the teeth.
By pressing the end of it, the user allows the teeth to open up and by releasing their hold, the teeth will grab whatever object is below the grabber.
They mainly come in sizes ranging from about 4 to 9 inches. The outer shell is usually plastic, although higher end retrievers can have metal casing and reinforced inner material.
Use
The tool is mainly used to retrieve screws, although is also helpful in retrieving jammed bits in the motherboard.
Other uses include paper removal, device handling, and item maneuvering.
References
Lifting equipment | 3-pronged parts retriever | [
"Physics",
"Technology"
] | 265 | [
"Physical systems",
"Machines",
"Lifting equipment"
] |
31,142,581 | https://en.wikipedia.org/wiki/Lyapunov%E2%80%93Schmidt%20reduction | In mathematics, the Lyapunov–Schmidt reduction or Lyapunov–Schmidt construction is used to study solutions to nonlinear equations in the case when the implicit function theorem does not work. It permits the reduction of infinite-dimensional equations in Banach spaces to finite-dimensional equations. It is named after Aleksandr Lyapunov and Erhard Schmidt.
Problem setup
Let
be the given nonlinear equation, and are
Banach spaces ( is the parameter space). is the
-map from a neighborhood of some point to
and the equation is satisfied at this point
For the case when the linear operator is invertible, the implicit function theorem assures that there exists
a solution satisfying the equation at least locally close to .
In the opposite case, when the linear operator is non-invertible, the Lyapunov–Schmidt reduction can be applied in the following
way.
Assumptions
One assumes that the operator is a Fredholm operator.
and has finite dimension.
The range of this operator has finite co-dimension and
is a closed subspace in .
Without loss of generality, one can assume that
Lyapunov–Schmidt construction
Let us split into the direct product , where .
Let be the projection operator onto .
Consider also the direct product .
Applying the operators and to the original equation, one obtains the equivalent system
Let and , then the first equation
can be solved with respect to by applying the implicit function theorem to the operator
(now the conditions of the implicit function theorem are fulfilled).
Thus, there exists a unique solution satisfying
Now substituting into the second equation, one obtains the final finite-dimensional equation
Indeed, the last equation is now finite-dimensional, since the range of is finite-dimensional. This equation is now to be solved with respect to , which is finite-dimensional, and parameters :
Applications
Lyapunov–Schmidt reduction has been used in economics, natural sciences, and engineering often in combination with bifurcation theory, perturbation theory, and regularization. LS reduction is often used to rigorously regularize partial differential equation models in chemical engineering resulting in models that are easier to simulate numerically but still retain all the parameters of the original model.
References
Bibliography
Louis Nirenberg, Topics in nonlinear functional analysis, New York Univ. Lecture Notes, 1974.
Aleksandr Lyapunov, Sur les figures d’équilibre peu différents des ellipsoides d’une masse liquide homogène douée d’un mouvement de rotation, Zap. Akad. Nauk St. Petersburg (1906), 1–225.
Aleksandr Lyapunov, Problème général de la stabilité du mouvement, Ann. Fac. Sci. Toulouse 2 (1907), 203–474.
Erhard Schmidt, Zur Theory der linearen und nichtlinearen Integralgleichungen, 3 Teil, Math. Annalen 65 (1908), 370–399.
Functional analysis | Lyapunov–Schmidt reduction | [
"Mathematics"
] | 609 | [
"Functional analysis",
"Mathematical objects",
"Functions and mappings",
"Mathematical relations"
] |
31,142,742 | https://en.wikipedia.org/wiki/K-independent%20hashing | In computer science, a family of hash functions is said to be k-independent, k-wise independent or k''-universal if selecting a function at random from the family guarantees that the hash codes of any designated k keys are independent random variables (see precise mathematical definitions below). Such families allow good average case performance in randomized algorithms or data structures, even if the input data is chosen by an adversary. The trade-offs between the degree of independence and the efficiency of evaluating the hash function are well studied, and many k-independent families have been proposed.
Background
The goal of hashing is usually to map keys from some large domain (universe) into a smaller range, such as bins (labelled ). In the analysis of randomized algorithms and data structures, it is often desirable for the hash codes of various keys to "behave randomly". For instance, if the hash code of each key were an independent random choice in , the number of keys per bin could be analyzed using the Chernoff bound. A deterministic hash function cannot offer any such guarantee in an adversarial setting, as the adversary may choose the keys to be the precisely the preimage of a bin. Furthermore, a deterministic hash function does not allow for rehashing: sometimes the input data turns out to be bad for the hash function (e.g. there are too many collisions), so one would like to change the hash function.
The solution to these problems is to pick a function randomly from a large family of hash functions. The randomness in choosing the hash function can be used to guarantee some desired random behavior of the hash codes of any keys of interest. The first definition along these lines was universal hashing, which guarantees a low collision probability for any two designated keys. The concept of -independent hashing, introduced by Wegman and Carter in 1981, strengthens the guarantees of random behavior to families of designated keys, and adds a guarantee on the uniform distribution of hash codes.
Definitions
The strictest definition, introduced by Wegman and Carter under the name "strongly universal hash family", is the following. A family of hash functions is -independent if for any distinct keys and any hash codes (not necessarily distinct) , we have:
This definition is equivalent to the following two conditions:
for any fixed , as is drawn randomly from , is uniformly distributed in .
for any fixed, distinct keys , as is drawn randomly from , are independent random variables.
Often it is inconvenient to achieve the perfect joint probability of due to rounding issues. Following, one may define a -independent family to satisfy:
distinct and ,
Observe that, even if is close to 1, are no longer independent random variables, which is often a problem in the analysis of randomized algorithms. Therefore, a more common alternative to dealing with rounding issues is to prove that the hash family is close in statistical distance to a -independent family, which allows black-box use of the independence properties.
Techniques
Polynomials with random coefficients
The original technique for constructing -independent hash functions, given by Carter and Wegman, was to select a large prime number , choose random numbers modulo , and use these numbers as the coefficients of a polynomial of degree whose values modulo are used as the value of the hash function. All polynomials of the given degree modulo are equally likely, and any polynomial is uniquely determined by any -tuple of argument-value pairs with distinct arguments, from which it follows that any -tuple of distinct arguments is equally likely to be mapped to any -tuple of hash values.
In general the polynomial can be evaluated in any finite field.
Besides the fields modulo prime, a popular choice is the field of size , which supports fast finite field arithmetic on modern computers.
This was the approach taken by Daniel Lemire and Owen Kaser for CLHash.
Tabulation hashing
Tabulation hashing is a technique for mapping keys to hash values by partitioning each key into bytes, using each byte as the index into a table of random numbers (with a different table for each byte position), and combining the results of these table lookups by a bitwise exclusive or operation. Thus, it requires more randomness in its initialization than the polynomial method, but avoids possibly-slow multiplication operations. It is 3-independent but not 4-independent. Variations of tabulation hashing can achieve higher degrees of independence by performing table lookups based on overlapping combinations of bits from the input key, or by applying simple tabulation hashing iteratively.
Independence needed by different types of collision resolution
The notion of k''-independence can be used to differentiate between different collision resolution in hashtables, according to the level of independence required to guarantee constant expected time per operation.
For instance, hash chaining takes constant expected time even with a 2-independent family of hash functions, because the expected time to perform a search for a given key is bounded by the expected number of collisions that key is involved in. By linearity of expectation, this expected number equals the sum, over all other keys in the hash table, of the probability that the given key and the other key collide. Because the terms of this sum only involve probabilistic events involving two keys, 2-independence is sufficient to ensure that this sum has the same value that it would for a truly random hash function.
Double hashing is another method of hashing that requires a low degree of independence. It is a form of open addressing that uses two hash functions: one to determine the start of a probe sequence, and the other to determine the step size between positions in the probe sequence. As long as both of these are 2-independent, this method gives constant expected time per operation.
On the other hand, linear probing, a simpler form of open addressing where the step size is always one can be guaranteed to work in constant expected time per operation with a 5-independent hash function, and there exist 4-independent hash functions for which it takes logarithmic time per operation.
For Cuckoo hashing the required k-independence is not known as of 2021.
In 2009 it was shown that -independence suffices, and at least 6-independence is needed.
Another approach is to use Tabulation hashing, which is not 6-independent, but was shown in 2012 to have other properties sufficient for Cuckoo hashing.
A third approach from 2014 is to slightly modify the cuckoo hashtable with a so-called stash, which makes it possible to use nothing more than 2-independent hash functions.
Other applications
Kane, Nelson and David Woodruff improved the Flajolet–Martin algorithm for the Distinct Elements Problem in 2010.
To give an approximation to the correct answer, they need a -independent hash function.
The Count sketch algorithm for dimensionality reduction requires two hash functions, one 2-independent and one 4-independent.
The Karloff–Zwick algorithm for the MAX-3SAT problem can be implemented with 3-independent random variables.
The MinHash algorithm can be implemented using a -independent hash function as was proven by Piotr Indyk in 1999
References
Further reading
Hash functions
Search algorithms
Error detection and correction | K-independent hashing | [
"Engineering"
] | 1,460 | [
"Error detection and correction",
"Reliability engineering"
] |
31,144,433 | https://en.wikipedia.org/wiki/Cunninghamella%20elegans | Cunninghamella elegans is a species of fungus in the genus Cunninghamella found in soil.
It can be grown in Sabouraud dextrose broth, a liquid medium used for cultivation of yeasts and molds from liquid which are normally sterile.
As opposed to C. bertholletiae, it is not a human pathogen, with the exception of two documented patients.
Description
Cunninghamella elegans is a filamentous fungus that produces purely gray colonies.
Electron microscopy studies show that the conidia are covered with spines.
Use as a fungal organism capable of xenobiotics metabolism
Cunninghamella elegans is able to degrade xenobiotics. It has a variety of enzymes of phases I (modification enzymes acting to introduce reactive and polar groups into their substrates) and II (conjugation enzymes) of the xenobiotic metabolism, as do mammals.
Cytochrome P450 monooxygenase, aryl sulfotransferase, glutathione S-transferase, UDP-glucuronosyltransferase, UDP-glucosyltransferase activities have been detected in cytosolic or microsomal fractions.
Cytochrome P-450 and cytochrome P-450 reductase in C. elegans are part of the phase I enzymes. They are induced by the corticosteroid cortexolone and by phenanthrene. C. elegans also possesses a lanosterol 14-alpha demethylase, another enzyme in the cytochrome P450 family.
Cunninghamella elegans also possesses a glutathione S-transferase.
Use as a fungal model organism of mammalian drug metabolism
Cunninghamella elegans is a microbial model of mammalian drug metabolism. The use of this fungus could reduce the over-all need for laboratory animals.
Cunninghamella elegans is able to transform the tricyclic antidepressants amitriptyline and doxepin, the tetracyclic antidepressant mirtazapine, the muscle relaxant cyclobenzaprine, the typical antipsychotic chlorpromazine as well as the antihistamine and anticholinergic methdilazine and azatadine. It is also able to transform the antihistamines brompheniramine, chlorpheniramine and pheniramine.
It forms a glucoside with the diuretic furosemide.
The transformation of oral contraceptive mestranol by C. elegans yields two hydroxylated metabolites, 6beta-hydroxymestranol and 6beta,12beta-dihydroxymestranol.
Metabolism of polycyclic aromatic hydrocarbons
The phase I cytochrome P450 enzyme systems of C. elegans has been implicated in the neutralization of numerous polycyclic aromatic hydrocarbons (PAH).
It can degrade molecules such as anthracene, 7-methylbenz[a]anthracene and 7-hydroxymethylbenz[a]anthracene, phenanthrene, acenaphthene, 1- and 2-methylnaphthalene, naphthalene, fluorene or benzo(a)pyrene.
In the case of phenanthrene, C. elegans produces a glucoside conjugate of 1-hydroxyphenanthrene (phenanthrene 1-O-beta-glucose).
Metabolism of pesticides
Cunninghamella elegans is also able to degrade the herbicides alachlor, metolachlor and isoproturon as well as the fungicide mepanipyrim.
Metabolism of phenolics
Cunninghamella elegans can be used to study the metabolism of phenols. This type of molecules already have reactive and polar groups comprised within their structure therefore phases I enzymes are less active than phase II (conjugation) enzymes.
Metabolism of flavonoids
Flavonols
In flavonols, an hydroxyl group is available in the 3- position allowing the glycosylation at that position. The biotransformation of quercetin yields three metabolites, including quercetin 3-O-β-D-glucopyranoside, kaempferol 3-O-β-D-glucopyranoside and isorhamnetin 3-O-β-D-glucopyranoside. Glucosylation and O-methylation are involved in the process.
Flavones
In flavones, there is no hydroxyl group available at the 3- position. Conjugation, in the form of sulfation occurs at the 7- or 4'- positions. Apigenin and chrysin are also transformed by C. elegans and produce apigenin 7-sulfate, apigenin 7,4′-disulfate, chrysin 7-sulfate.
Sulfation also occurs on naringenin and produces naringenin-7-sulfate.
Glucosylation may nevertheless occur but in 3'- position, as happens during the microbial transformation of psiadiarabin and its 6-desmethoxy analogue, 5,3′ dihydroxy-7,2′,4′,5′-tetramethoxyflavone, by Cunninghamella elegans NRRL 1392 that gives the 3′-glucoside conjugates of the two flavones.
flavanones
As in flavones, there is no hydroxyl groups available at the 3- position for glycosylation in flavanones. Therefore, sulfation occurs at the 7- position. In compounds like 7-methoxylated flavanones like 7-O-methylnaringenin (sakuranetin), demethylation followed by sulfation occur.
Metabolism of synthetic phenolics
It is also able to degrade synthetic phenolic compounds like bisphenol A.
Metabolism of heterocyclic organic compounds
Cunninghamella elegans can transform the nitrogen containing compound phthalazine It is also able to oxidize the organosulfur compound dibenzothiophene.
Uses in biotechnology
Methods for efficient C. elegans genomic DNA isolation and transformation have been developed.
The cytochrome P450 of C. elegans has been cloned in Escherichia coli as well as an enolase.
Use in bioconversion
Techniques employed
Cunninghamella elegans can be grown in stirred tank batch bioreactor. Protoplasts cultures have been used.
Examples of uses
Cunninghamella elegans can be used for phenanthrene bioconversion or for steroid transformation. It has been used to produce from 10,11-dimethoxyaporphine, triptoquinone from the synthetic abietane diterpene triptophenolide or for the rational and economical bioconversion of antimalarial drug artemisinin to 7beta-hydroxyartemisinin.
Environmental biotechnology
Cunninghamella elegans has been used in environmental biotechnology for the treatment of textile wastewaters, for instance those discoloured by azo dyes or malachite green.
Chitin and chitosan isolated from C. elegans can be used for heavy metal biosorption. Production can be made on yam bean (Pachyrhizus erosus L. Urban) medium.
Strains
Cunninghamella elegans ATCC 9245
Cunninghamella elegans ATCC 36112
Cunninghamella elegans ATCC 26269
Cunninghamella elegans NRRL 1393
Cunninghamella elegans IFM 46109
Cunninghamella elegans UCP 542
References
External links
Cunninghamella elegans on the Fungal Genomics Project
Cunninghamellaceae
Fungi described in 1907
Fungal models
Biotechnology
Alternatives to animal testing
Fungus species | Cunninghamella elegans | [
"Chemistry",
"Biology"
] | 1,695 | [
"Animal testing",
"Fungi",
"Fungus species",
"Biotechnology",
"Model organisms",
"Alternatives to animal testing",
"nan",
"Fungal models"
] |
25,082,219 | https://en.wikipedia.org/wiki/Supersonic%20airfoils | A supersonic airfoil is a cross-section geometry designed to generate lift efficiently at supersonic speeds. The need for such a design arises when an aircraft is required to operate consistently in the supersonic flight regime.
Supersonic airfoils generally have a thin section formed of either angled planes or opposed arcs (called "double wedge airfoils" and "biconvex airfoils" respectively), with very sharp leading and trailing edges. The sharp edges prevent the formation of a detached bow shock in front of the airfoil as it moves through the air. This shape is in contrast to subsonic airfoils, which often have rounded leading edges to reduce flow separation over a wide range of angle of attack. A rounded edge would behave as a blunt body in supersonic flight and thus would form a bow shock, which greatly increases wave drag. The airfoils' thickness, camber, and angle of attack are varied to achieve a design that will cause a slight deviation in the direction of the surrounding airflow.
Drag
At supersonic conditions, aircraft drag is originated due to:
Skin-friction drag due to shearing.
The wave drag due to the thickness (or volume) or zero-lift wave drag
Drag due to lift
Therefore, the Drag coefficient on a supersonic airfoil is described by the following expression:
CD= CD,friction+ CD,thickness+ CD,lift
Experimental data allow us to reduce this expression to:
CD= CD,O + KCL2
Where CDO is the sum of C(D,friction) and C D,thickness, and k for supersonic flow is a function of the Mach number. The skin-friction component is derived from the presence of a viscous boundary layer which is infinitely close to the surface of the aircraft body. At the boundary wall, the normal component of velocity is zero; therefore an infinitesimal area exists where there is no slip. The zero-lift wave drag component can be obtained based on the supersonic area rule which tells us that the wave-drag of an aircraft in a steady supersonic flow is identical to the average of a series of equivalent bodies of revolution. The bodies of revolution are defined by the cuts through the aircraft made by the tangent to the fore Mach cone from a distant point of the aircraft at an azimuthal angle. This average is over all azimuthal angles. The drag due-to lift component is calculated using lift-analysis programs. The wing design and the lift-analysis programs are separate lifting-surfaces methods that solve the direct or inverse problem of design and lift analysis.
Supersonic wing design
Years of research and experience with the unusual conditions of supersonic flow have led to some interesting conclusions about airfoil design. Considering a rectangular wing, the pressure at a point P with coordinates (x,y) on the wing is defined only by the pressure disturbances originated at points within the upstream Mach cone emanating from point P. As result, the wing tips modify the flow within their own rearward Mach cones. The remaining area of the wing does not suffer any modification by the tips and can be analyzed with two-dimensional theory. For an arbitrary planform the supersonic leading and trailing are those portions of the wing edge where the components of the freestream velocity normal to the edge are supersonic. Similarly the subsonic leading and trailing are those portions of the wing edge where the components of the free stream velocity normal to the edge are subsonic.
Delta wings have supersonic leading and trailing edges; in contrast arrow wings have a subsonic leading edge and a supersonic trailing edge.
When designing a supersonic airfoil two factors that must be considered are shock and expansion waves. Whether a shock or expansion wave is generated at different locations along an airfoil depends on the local flow speed and direction along with the geometry of the airfoil.
Summary
Aerodynamic efficiency for supersonic aircraft increases with thin section airfoils with sharp leading and trailing edges. Swept wings where the leading edge is subsonic have the advantage of reducing the wave drag component at supersonic speeds; however experiments show that the theoretical benefits are not always attained due to separation of the flow over the surface of the wing; however this can be corrected with design factors. Double-Wedge and Bi-convex airfoils are the most common airfoils used for supersonic aircraft.
See also
Area rule
Mach number
Sonic boom
Sound barrier
Stall (fluid mechanics)
Supersonic aerodynamics
Supersonic speed
References
Aerodynamics
Airspeed
Dimensionless numbers of physics
Fluid dynamics
Aircraft wing design | Supersonic airfoils | [
"Physics",
"Chemistry",
"Engineering"
] | 919 | [
"Physical quantities",
"Chemical engineering",
"Aerodynamics",
"Airspeed",
"Aerospace engineering",
"Piping",
"Wikipedia categories named after physical quantities",
"Fluid dynamics"
] |
25,082,257 | https://en.wikipedia.org/wiki/Reach%20%28mathematics%29 | Let X be a subset of Rn. Then the reach of X is defined as
Examples
Shapes that have reach infinity include
a single point,
a straight line,
a full square, and
any convex set.
The graph of ƒ(x) = |x| has reach zero.
A circle of radius r has reach r.
References
Geometric measurement
Real analysis
Topology | Reach (mathematics) | [
"Physics",
"Mathematics"
] | 72 | [
"Geometric measurement",
"Physical quantities",
"Quantity",
"Topology",
"Space",
"Geometry",
"Spacetime"
] |
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