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Hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula H2S. It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The underground mine gas term for foul-smelling hydrogen sulfide-rich gas mixtures is stinkdamp. Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777. The British English spelling of this compound is hydrogen sulphide, a spelling no longer recommended by the Royal Society of Chemistry or the International Union of Pure and Applied Chemistry.
Hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is toxic to humans and most other animals by inhibiting cellular respiration in a manner similar to hydrogen cyanide. When it is inhaled or its salts are ingested in high amounts, damage to organs occurs rapidly with symptoms ranging from breathing difficulties to convulsions and death. Despite this, the human body produces small amounts of this sulfide and its mineral salts, and uses it as a signalling molecule.Hydrogen sulfide is often produced from the microbial breakdown of organic matter in the absence of oxygen, such as in swamps and sewers; this process is commonly known as anaerobic digestion, which is done by sulfate-reducing microorganisms. It also occurs in volcanic gases, natural gas deposits, and sometimes in well-drawn water.
Hydrogen sulfide
Properties
Hydrogen sulfide is slightly denser than air. A mixture of H2S and air can be explosive. In general, hydrogen sulfide acts as a reducing agent, although in the presence of a base, it can act as an acid by donating a proton and forming SH−.
Hydrogen sulfide
Properties
Hydrogen sulfide burns in oxygen with a blue flame to form sulfur dioxide (SO2) and water: H2S + 3/2 O2 → SO2 + H2OIf an excess of oxygen is present, sulfur trioxide (SO3) is formed, which quickly hydrates to sulfuric acid: H2S + 2 O2 → H2SO4At high temperatures or in the presence of catalysts, sulfur dioxide reacts with hydrogen sulfide to form elemental sulfur and water. This reaction is exploited in the Claus process, an important industrial method to dispose of hydrogen sulfide.
Hydrogen sulfide
Properties
Hydrogen sulfide is slightly soluble in water and acts as a weak acid (pKa = 6.9 in 0.01–0.1 mol/litre solutions at 18 °C), giving the hydrosulfide ion HS− (also written SH−). Hydrogen sulfide and its solutions are colorless. When exposed to air, it slowly oxidizes to form elemental sulfur, which is not soluble in water. The sulfide anion S2− is not formed in aqueous solution.Hydrogen sulfide reacts with metal ions to form metal sulfides, which are insoluble, often dark colored solids. Lead(II) acetate paper is used to detect hydrogen sulfide because it readily converts to lead(II) sulfide, which is black. Treating metal sulfides with strong acid or electrolysis often liberates hydrogen sulfide. Hydrogen sulfide is also responsible for tarnishing on various metals including copper and silver; the chemical responsible for black toning found on silver coins is silver sulfide (Ag2S), which is produced when the silver on the surface of the coin reacts with atmospheric hydrogen sulfide.At pressures above 90 GPa (gigapascal), hydrogen sulfide becomes a metallic conductor of electricity. When cooled below a critical temperature this high-pressure phase exhibits superconductivity. The critical temperature increases with pressure, ranging from 23 K at 100 GPa to 150 K at 200 GPa. If hydrogen sulfide is pressurized at higher temperatures, then cooled, the critical temperature reaches 203 K (−70 °C), the highest accepted superconducting critical temperature as of 2015. By substituting a small part of sulfur with phosphorus and using even higher pressures, it has been predicted that it may be possible to raise the critical temperature to above 0 °C (273 K) and achieve room-temperature superconductivity.Hydrogen sulfide decomposes without a presence of a catalyst under atmospheric pressure around 1200 °C into hydrogen and sulfur.
Hydrogen sulfide
Production
Hydrogen sulfide is most commonly obtained by its separation from sour gas, which is natural gas with a high content of H2S. It can also be produced by treating hydrogen with molten elemental sulfur at about 450 °C. Hydrocarbons can serve as a source of hydrogen in this process.Sulfate-reducing (resp. sulfur-reducing) bacteria generate usable energy under low-oxygen conditions by using sulfates (resp. elemental sulfur) to oxidize organic compounds or hydrogen; this produces hydrogen sulfide as a waste product.
Hydrogen sulfide
Production
A standard lab preparation is to treat ferrous sulfide with a strong acid in a Kipp generator: FeS + 2 HCl → FeCl2 + H2SFor use in qualitative inorganic analysis, thioacetamide is used to generate H2S: CH3C(S)NH2 + H2O → CH3C(O)NH2 + H2SMany metal and nonmetal sulfides, e.g. aluminium sulfide, phosphorus pentasulfide, silicon disulfide liberate hydrogen sulfide upon exposure to water: 6 H2O + Al2S3 → 3 H2S + 2 Al(OH)3This gas is also produced by heating sulfur with solid organic compounds and by reducing sulfurated organic compounds with hydrogen.
Hydrogen sulfide
Production
Water heaters can aid the conversion of sulfate in water to hydrogen sulfide gas. This is due to providing a warm environment sustainable for sulfur bacteria and maintaining the reaction which interacts between sulfate in the water and the water heater anode, which is usually made from magnesium metal.
Hydrogen sulfide
Production
Biosynthesis in the body Hydrogen sulfide can be generated in cells via enzymatic or non-enzymatic pathways. H2S in the body acts as a gaseous signaling molecule which is known to inhibit Complex IV of the mitochondrial electron transport chain which effectively reduces ATP generation and biochemical activity within cells. Three enzymes are known to synthesize H2S: cystathionine γ-lyase (CSE), cystathionine β-synthetase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). These enzymes have been identified in a breadth of biological cells and tissues, and their activity has been observed to be induced by a number of disease states. It is becoming increasingly clear that H2S is an important mediator of a wide range of cell functions in health and in diseases. CBS and CSE are the main proponents of H2S biogenesis, which follows the trans-sulfuration pathway. These enzymes are characterized by the transfer of a sulfur atom from methionine to serine to form a cysteine molecule. 3-MST also contributes to hydrogen sulfide production by way of the cysteine catabolic pathway. Dietary amino acids, such as methionine and cysteine serve as the primary substrates for the transulfuration pathways and in the production of hydrogen sulfide. Hydrogen sulfide can also be synthesized by non-enzymatic pathway, which is derived from proteins such as ferredoxins and Rieske proteins. There has been continuing interest in exploiting such knowledge of hydrogen sulfide's role in signaling through development of mechanistically related therapeutic agents.Hydrogen sulfide has been shown to be involved in physiological processes such as vasodilation in animals, as well as in increasing seed germination and stress responses in plants. Hydrogen sulfide signaling is also innately intertwined with physiological processes that are known to be moderated by reactive oxygen species (ROS) and reactive nitrogen species (RNS). H2S has been shown to interact with NO resulting in several different cellular effects, as well as the formation of a new signal called nitrosothiol. Hydrogen sulfide is also known to increase the levels of glutathione which acts to reduce or disrupt ROS levels in cells. The field of H2S biology has advanced from environmental toxicology to investigate the roles of endogenously produced H2S in physiological conditions and in various pathophysiological states. According to a current classification, pathophysiological states with H2S overproduction (such as cancer and Down syndrome) and pathophysiological states with H2S deficit (e.g. vascular disease) can be identified. Although the understanding of H2S biology has significantly advanced over the last decade, many questions remain, for instance related to the quantification of endogenous H2S levels.
Hydrogen sulfide
Uses
Production of sulfur, thioorganic compounds, and alkali metal sulfides The main use of hydrogen sulfide is as a precursor to elemental sulfur. Several organosulfur compounds are produced using hydrogen sulfide. These include methanethiol, ethanethiol, and thioglycolic acid.Upon combining with alkali metal bases, hydrogen sulfide converts to alkali hydrosulfides such as sodium hydrosulfide and sodium sulfide: H2S + NaOH → NaSH + H2O NaSH + NaOH → Na2S + H2OThese compounds are used in the paper making industry. Specifically, salts of SH− break bonds between lignin and cellulose components of pulp in the Kraft process.Reversibly sodium sulfide in the presence of acids turns into hydrosulfides and hydrogen sulfide; this supplies hydrosulfides in organic solutions and is utilized in the production of thiophenol.
Hydrogen sulfide
Uses
Analytical chemistry For well over a century hydrogen sulfide was important in analytical chemistry in the qualitative inorganic analysis of metal ions. In these analyses, heavy metal (and nonmetal) ions (e.g., Pb(II), Cu(II), Hg(II), As(III)) are precipitated from solution upon exposure to H2S). The components of the resulting precipitate redissolve with some selectivity, and are thus identified.
Hydrogen sulfide
Uses
Precursor to metal sulfides As indicated above, many metal ions react with hydrogen sulfide to give the corresponding metal sulfides. This conversion is widely exploited. For example, gases or waters contaminated by hydrogen sulfide can be cleaned with metals, by forming metal sulfides. In the purification of metal ores by flotation, mineral powders are often treated with hydrogen sulfide to enhance the separation. Metal parts are sometimes passivated with hydrogen sulfide. Catalysts used in hydrodesulfurization are routinely activated with hydrogen sulfide, and the behavior of metallic catalysts used in other parts of a refinery is also modified using hydrogen sulfide.
Hydrogen sulfide
Uses
Miscellaneous applications Hydrogen sulfide is used to separate deuterium oxide, or heavy water, from normal water via the Girdler sulfide process.
Hydrogen sulfide
Uses
Scientists from the University of Exeter discovered that cell exposure to small amounts of hydrogen sulfide gas can prevent mitochondrial damage. When the cell is stressed with disease, enzymes are drawn into the cell to produce small amounts of hydrogen sulfide. This study could have further implications on preventing strokes, heart disease and arthritis.Depending on the level of toning present, coins that have been subject to toning by hydrogen sulfide and other sulfur-containing compounds may add to the numismatic value of a coin based on the toning's aesthetics. Coins can also be intentionally treated with hydrogen sulfide to induce toning, though artificial toning can be distinguished from natural toning, and is generally criticised among collectors.A suspended animation-like state has been induced in rodents with the use of hydrogen sulfide, resulting in hypothermia with a concomitant reduction in metabolic rate. Oxygen demand was also reduced, thereby protecting against hypoxia. In addition, hydrogen sulfide has been shown to reduce inflammation in various situations.
Hydrogen sulfide
Uses
Occurrence Volcanoes and some hot springs (as well as cold springs) emit some H2S, where it probably arises via the hydrolysis of sulfide minerals, i.e. MS + H2O → MO + H2S. Hydrogen sulfide can be present naturally in well water, often as a result of the action of sulfate-reducing bacteria. Hydrogen sulfide is produced by the human body in small quantities through bacterial breakdown of proteins containing sulfur in the intestinal tract, therefore it contributes to the characteristic odor of flatulence. It is also produced in the mouth (halitosis).A portion of global H2S emissions are due to human activity. By far the largest industrial source of H2S is petroleum refineries: The hydrodesulfurization process liberates sulfur from petroleum by the action of hydrogen. The resulting H2S is converted to elemental sulfur by partial combustion via the Claus process, which is a major source of elemental sulfur. Other anthropogenic sources of hydrogen sulfide include coke ovens, paper mills (using the Kraft process), tanneries and sewerage. H2S arises from virtually anywhere where elemental sulfur comes in contact with organic material, especially at high temperatures. Depending on environmental conditions, it is responsible for deterioration of material through the action of some sulfur oxidizing microorganisms. It is called biogenic sulfide corrosion.
Hydrogen sulfide
Uses
In 2011 it was reported that increased concentrations of H2S were observed in the Bakken formation crude, possibly due to oil field practices, and presented challenges such as "health and environmental risks, corrosion of wellbore, added expense with regard to materials handling and pipeline equipment, and additional refinement requirements".Besides living near gas and oil drilling operations, ordinary citizens can be exposed to hydrogen sulfide by being near waste water treatment facilities, landfills and farms with manure storage. Exposure occurs through breathing contaminated air or drinking contaminated water.In municipal waste landfill sites, the burial of organic material rapidly leads to the production of anaerobic digestion within the waste mass and, with the humid atmosphere and relatively high temperature that accompanies biodegradation, biogas is produced as soon as the air within the waste mass has been reduced. If there is a source of sulfate bearing material, such as plasterboard or natural gypsum (calcium sulfate dihydrate), under anaerobic conditions sulfate reducing bacteria converts this to hydrogen sulfide. These bacteria cannot survive in air but the moist, warm, anaerobic conditions of buried waste that contains a high source of carbon – in inert landfills, paper and glue used in the fabrication of products such as plasterboard can provide a rich source of carbon – is an excellent environment for the formation of hydrogen sulfide.
Hydrogen sulfide
Uses
In industrial anaerobic digestion processes, such as waste water treatment or the digestion of organic waste from agriculture, hydrogen sulfide can be formed from the reduction of sulfate and the degradation of amino acids and proteins within organic compounds. Sulfates are relatively non-inhibitory to methane forming bacteria but can be reduced to H2S by sulfate reducing bacteria, of which there are several genera.
Hydrogen sulfide
Uses
Removal from water A number of processes have been designed to remove hydrogen sulfide from drinking water.
Hydrogen sulfide
Uses
Continuous chlorination For levels up to 75 mg/L chlorine is used in the purification process as an oxidizing chemical to react with hydrogen sulfide. This reaction yields insoluble solid sulfur. Usually the chlorine used is in the form of sodium hypochlorite.Aeration For concentrations of hydrogen sulfide less than 2 mg/L aeration is an ideal treatment process. Oxygen is added to water and a reaction between oxygen and hydrogen sulfide react to produce odorless sulfate.Nitrate addition Calcium nitrate can be used to prevent hydrogen sulfide formation in wastewater streams.
Hydrogen sulfide
Uses
Removal from fuel gases Hydrogen sulfide is commonly found in raw natural gas and biogas. It is typically removed by amine gas treating technologies. In such processes, the hydrogen sulfide is first converted to an ammonium salt, whereas the natural gas is unaffected. RNH2 + H2S ⇌ [RNH3]+ + SH−The bisulfide anion is subsequently regenerated by heating of the amine sulfide solution. Hydrogen sulfide generated in this process is typically converted to elemental sulfur using the Claus Process.
Hydrogen sulfide
Safety
Hydrogen sulfide is a highly toxic and flammable gas (flammable range: 4.3–46%). Being heavier than air, it tends to accumulate at the bottom of poorly ventilated spaces. Although very pungent at first (it smells like rotten eggs), it quickly deadens the sense of smell, creating temporary anosmia, so victims may be unaware of its presence until it is too late. Safe handling procedures are provided by its safety data sheet (SDS).
Hydrogen sulfide
Safety
Toxicity Hydrogen sulfide is a broad-spectrum poison, meaning that it can poison several different systems in the body, although the nervous system is most affected. The toxicity of H2S is comparable with that of carbon monoxide. It binds with iron in the mitochondrial cytochrome enzymes, thus preventing cellular respiration. Its toxic properties were described in detail in 1843 by Justus von Liebig.
Hydrogen sulfide
Safety
Low-level exposure Since hydrogen sulfide occurs naturally in the body, the environment, and the gut, enzymes exist to detoxify it. At some threshold level, believed to average around 300–350 ppm, the oxidative enzymes become overwhelmed. Many personal safety gas detectors, such as those used by utility, sewage and petrochemical workers, are set to alarm at as low as 5 to 10 ppm and to go into high alarm at 15 ppm. Detoxification is affected via oxidation to sulfate, which is harmless. Hence, low levels of hydrogen sulfide may be tolerated indefinitely.
Hydrogen sulfide
Safety
Exposure to lower concentrations can result in eye irritation, a sore throat and cough, nausea, shortness of breath, and fluid in the lungs (pulmonary edema). These effects are believed to be due to hydrogen sulfide combining with alkali present in moist surface tissues to form sodium sulfide, a caustic. These symptoms usually subside in a few weeks. Long-term, low-level exposure may result in fatigue, loss of appetite, headaches, irritability, poor memory, and dizziness. Chronic exposure to low level H2S (around 2 ppm) has been implicated in increased miscarriage and reproductive health issues among Russian and Finnish wood pulp workers, but the reports have not (as of 1995) been replicated.
Hydrogen sulfide
Safety
High-level exposure Short-term, high-level exposure can induce immediate collapse, with loss of breathing and a high probability of death. If death does not occur, high exposure to hydrogen sulfide can lead to cortical pseudolaminar necrosis, degeneration of the basal ganglia and cerebral edema. Although respiratory paralysis may be immediate, it can also be delayed up to 72 hours. Diagnostic of extreme poisoning by H2S is the discolouration of copper coins in the pockets of the victim.
Hydrogen sulfide
Safety
Inhalation of H2S resulted in about 7 workplace deaths per year in the U.S. (2011–2017 data), second only to carbon monoxide (17 deaths per year) for workplace chemical inhalation deaths.
Hydrogen sulfide
Safety
Exposure thresholds Exposure limits stipulated by the United States government:10 ppm REL-Ceiling (NIOSH): recommended permissible exposure ceiling (the recommended level that must not be exceeded, except once for 10 min. in an 8-hour shift, if no other measurable exposure occurs) 20 ppm PEL-Ceiling (OSHA): permissible exposure ceiling (the level that must not be exceeded, except once for 10 min. in an 8-hour shift, if no other measurable exposure occurs) 50 ppm PEL-Peak (OSHA): peak permissible exposure (the level that must never be exceeded) 100 ppm IDLH (NIOSH): immediately dangerous to life and health (the level that interferes with the ability to escape) 0.00047 ppm or 0.47 ppb is the odor threshold, the point at which 50% of a human panel can detect the presence of an odor without being able to identify it.
Hydrogen sulfide
Safety
10–20 ppm is the borderline concentration for eye irritation. 50–100 ppm leads to eye damage. At 100–150 ppm the olfactory nerve is paralyzed after a few inhalations, and the sense of smell disappears, often together with awareness of danger. 320–530 ppm leads to pulmonary edema with the possibility of death. 530–1000 ppm causes strong stimulation of the central nervous system and rapid breathing, leading to loss of breathing. 800 ppm is the lethal concentration for 50% of humans for 5 minutes' exposure (LC50). Concentrations over 1000 ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath. Treatment Treatment involves immediate inhalation of amyl nitrite, injections of sodium nitrite, or administration of 4-dimethylaminophenol in combination with inhalation of pure oxygen, administration of bronchodilators to overcome eventual bronchospasm, and in some cases hyperbaric oxygen therapy (HBOT). HBOT has clinical and anecdotal support.
Hydrogen sulfide
Safety
Incidents Hydrogen sulfide was used by the British Army as a chemical weapon during World War I. It was not considered to be an ideal war gas, partially due to its flammability and because the distinctive smell could be detected from even a small leak, alerting the enemy to the presence of the gas. It was nevertheless used on two occasions in 1916 when other gases were in short supply.On September 2, 2005, a leak in the propeller room of a Royal Caribbean Cruise Liner docked in Los Angeles resulted in the deaths of 3 crewmen due to a sewage line leak. As a result, all such compartments are now required to have a ventilation system.A dump of toxic waste containing hydrogen sulfide is believed to have caused 17 deaths and thousands of illnesses in Abidjan, on the West African coast, in the 2006 Côte d'Ivoire toxic waste dump.
Hydrogen sulfide
Safety
In September 2008, three workers were killed and two suffered serious injury, including long term brain damage, at a mushroom growing company in Langley, British Columbia. A valve to a pipe that carried chicken manure, straw and gypsum to the compost fuel for the mushroom growing operation became clogged, and as workers unclogged the valve in a confined space without proper ventilation the hydrogen sulfide that had built up due to anaerobic decomposition of the material was released, poisoning the workers in the surrounding area. Investigator said there could have been more fatalities if the pipe had been fully cleared and/or if the wind had changed directions.In 2014, levels of hydrogen sulfide as high as 83 ppm were detected at a recently built mall in Thailand called Siam Square One at the Siam Square area. Shop tenants at the mall reported health complications such as sinus inflammation, breathing difficulties and eye irritation. After investigation it was determined that the large amount of gas originated from imperfect treatment and disposal of waste water in the building.In 2014, hydrogen sulfide gas killed workers at the Promenade shopping center in North Scottsdale, Arizona, USA after climbing into 15ft deep chamber without wearing personal protective gear. "Arriving crews recorded high levels of hydrogen cyanide and hydrogen sulfide coming out of the sewer." In November 2014, a substantial amount of hydrogen sulfide gas shrouded the central, eastern and southeastern parts of Moscow. Residents living in the area were urged to stay indoors by the emergencies ministry. Although the exact source of the gas was not known, blame had been placed on a Moscow oil refinery.In June 2016, a mother and her daughter were found deceased in their still-running 2006 Porsche Cayenne SUV against a guardrail on Florida's Turnpike, initially thought to be victims of carbon monoxide poisoning. Their deaths remained unexplained as the medical examiner waited for results of toxicology tests on the victims, until urine tests revealed that hydrogen sulfide was the cause of death. A report from the Orange-Osceola Medical Examiner's Office indicated that toxic fumes came from the Porsche's starter battery, located under the front passenger seat.In January 2017, three utility workers in Key Largo, Florida, died one by one within seconds of descending into a narrow space beneath a manhole cover to check a section of paved street. In an attempt to save the men, a firefighter who entered the hole without his air tank (because he could not fit through the hole with it) collapsed within seconds and had to be rescued by a colleague. The firefighter was airlifted to Jackson Memorial Hospital and later recovered. A Monroe County Sheriff officer initially determined that the space contained hydrogen sulfide and methane gas produced by decomposing vegetation.On May 24, 2018, two workers were killed, another seriously injured, and 14 others hospitalized by hydrogen sulfide inhalation at a Norske Skog paper mill in Albury, New South Wales. An investigation by SafeWork NSW found that the gas was released from a tank used to hold process water. The workers were exposed at the end of a 3-day maintenance period. Hydrogen sulfide had built up in an upstream tank, which had been left stagnant and untreated with biocide during the maintenance period. These conditions allowed sulfate-reducing bacteria to grow in the upstream tank, as the water contained small quantities of wood pulp and fiber. The high rate of pumping from this tank into the tank involved in the incident caused hydrogen sulfide gas to escape from various openings around its top when pumping was resumed at the end of the maintenance period. The area above it was sufficiently enclosed for the gas to pool there, despite not being identified as a confined space by Norske Skog. One of the workers who was killed was exposed while investigating an apparent fluid leak in the tank, while the other who was killed and the worker who was badly injured were attempting to rescue the first after he collapsed on top of it. In a resulting criminal case, Norske Skog was accused of failing to ensure the health and safety of its workforce at the plant to a reasonably practicable extent. It pleaded guilty, and was fined AU$1,012,500 and ordered to fund the production of an anonymized educational video about the incident.In October 2019, an Odessa, Texas employee of Aghorn Operating Inc. and his wife were killed due to a water pump failure. Produced water with a high concentration of hydrogen sulfide was released by the pump. The worker died while responding to an automated phone call he had received alerting him to a mechanical failure in the pump, while his wife died after driving to the facility to check on him. A CSB investigation cited lax safety practices at the facility, such as an informal lockout-tagout procedure and a nonfunctioning hydrogen sulfide alert system.
Hydrogen sulfide
Safety
Suicides The gas, produced by mixing certain household ingredients, was used in a suicide wave in 2008 in Japan. The wave prompted staff at Tokyo's suicide prevention center to set up a special hotline during "Golden Week", as they received an increase in calls from people wanting to kill themselves during the annual May holiday.As of 2010, this phenomenon has occurred in a number of US cities, prompting warnings to those arriving at the site of the suicide. These first responders, such as emergency services workers or family members are at risk of death or injury from inhaling the gas, or by fire. Local governments have also initiated campaigns to prevent such suicides.
Hydrogen sulfide
Safety
In 2020, H2S ingestion was used as a suicide method by Japanese pro wrestler Hana Kimura.
Hydrogen sulfide
Hydrogen sulfide in the natural environment
Microbial: The sulfur cycle Hydrogen sulfide is a central participant in the sulfur cycle, the biogeochemical cycle of sulfur on Earth.In the absence of oxygen, sulfur-reducing and sulfate-reducing bacteria derive energy from oxidizing hydrogen or organic molecules by reducing elemental sulfur or sulfate to hydrogen sulfide. Other bacteria liberate hydrogen sulfide from sulfur-containing amino acids; this gives rise to the odor of rotten eggs and contributes to the odor of flatulence.
Hydrogen sulfide
Hydrogen sulfide in the natural environment
As organic matter decays under low-oxygen (or hypoxic) conditions (such as in swamps, eutrophic lakes or dead zones of oceans), sulfate-reducing bacteria will use the sulfates present in the water to oxidize the organic matter, producing hydrogen sulfide as waste. Some of the hydrogen sulfide will react with metal ions in the water to produce metal sulfides, which are not water-soluble. These metal sulfides, such as ferrous sulfide FeS, are often black or brown, leading to the dark color of sludge.
Hydrogen sulfide
Hydrogen sulfide in the natural environment
Several groups of bacteria can use hydrogen sulfide as fuel, oxidizing it to elemental sulfur or to sulfate by using dissolved oxygen, metal oxides (e.g., iron oxyhydroxides and manganese oxides), or nitrate as electron acceptors.The purple sulfur bacteria and the green sulfur bacteria use hydrogen sulfide as an electron donor in photosynthesis, thereby producing elemental sulfur. This mode of photosynthesis is older than the mode of cyanobacteria, algae, and plants, which uses water as electron donor and liberates oxygen.
Hydrogen sulfide
Hydrogen sulfide in the natural environment
The biochemistry of hydrogen sulfide is a key part of the chemistry of the iron-sulfur world. In this model of the origin of life on Earth, geologically produced hydrogen sulfide is postulated as an electron donor driving the reduction of carbon dioxide.
Hydrogen sulfide
Hydrogen sulfide in the natural environment
Animals Hydrogen sulfide is lethal to most animals, but a few highly specialized species (extremophiles) do thrive in habitats that are rich in this compound.In the deep sea, hydrothermal vents and cold seeps with high levels of hydrogen sulfide are home to a number of extremely specialized lifeforms, ranging from bacteria to fish. Because of the absence of sunlight at these depths, these ecosystems rely on chemosynthesis rather than photosynthesis.Freshwater springs rich in hydrogen sulfide are mainly home to invertebrates, but also include a small number of fish: Cyprinodon bobmilleri (a pupfish from Mexico), Limia sulphurophila (a poeciliid from the Dominican Republic), Gambusia eurystoma (a poeciliid from Mexico), and a few Poecilia (poeciliids from Mexico). Invertebrates and microorganisms in some cave systems, such as Movile Cave, are adapted to high levels of hydrogen sulfide.
Hydrogen sulfide
Hydrogen sulfide in the natural environment
Interstellar and planetary occurrence Hydrogen sulfide has often been detected in the interstellar medium. It also occurs in the clouds of planets in our solar system.
Hydrogen sulfide
Hydrogen sulfide in the natural environment
Mass extinctions Hydrogen sulfide has been implicated in several mass extinctions that have occurred in the Earth's past. In particular, a buildup of hydrogen sulfide in the atmosphere may have caused, or at least contributed to, the Permian-Triassic extinction event 252 million years ago.Organic residues from these extinction boundaries indicate that the oceans were anoxic (oxygen-depleted) and had species of shallow plankton that metabolized H2S. The formation of H2S may have been initiated by massive volcanic eruptions, which emitted carbon dioxide and methane into the atmosphere, which warmed the oceans, lowering their capacity to absorb oxygen that would otherwise oxidize H2S. The increased levels of hydrogen sulfide could have killed oxygen-generating plants as well as depleted the ozone layer, causing further stress. Small H2S blooms have been detected in modern times in the Dead Sea and in the Atlantic ocean off the coast of Namibia.
Hydrogen sulfide
Additional resources
Committee on Medical and Biological Effects of Environmental Pollutants (1979). Hydrogen Sulfide. Baltimore: University Park Press. ISBN 978-0-8391-0127-7. Siefers, Andrea (2010). A novel and cost-effective hydrogen sulfide removal technology using tire derived rubber particles (MS thesis). Iowa State University. Retrieved 8 February 2013.
Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)
Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)
Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+) (EC 1.1.1.40) or NADP-malic enzyme (NADP-ME) is an enzyme that catalyzes the chemical reaction in the presence of a bivalent metal ion: (S)-malate + NADP+ ⇌ pyruvate + CO2 + NADPHThus, the two substrates of this enzyme are (S)-malate and NADP+, whereas its 3 products are pyruvate, CO2, and NADPH. Malate is oxidized to pyruvate and CO2, and NADP+ is reduced to NADPH.
Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)
Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)
This enzyme belongs to the family of oxidoreductases, to be specific those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is (S)-malate:NADP+ oxidoreductase (oxaloacetate-decarboxylating). This enzyme participates in pyruvate metabolism and carbon fixation. NADP-malic enzyme is one of three decarboxylation enzymes used in the inorganic carbon concentrating mechanisms of C4 and CAM plants. The others are NAD-malic enzyme and PEP carboxykinase. Although often one of the three photosynthetic decarboxylases predominate, the simultaneous operation of all three is also shown to exist.
Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)
Enzyme structure
Based on crystallography data of homologous NADP-dependent malic enzymes of mammalian origin, a 3D model for C4 pathway NADP-ME in plants has been developed, identifying the key residues involved in substrate-binding or catalysis. Dinucleotide binding involves two glycine-rich GXGXXG motifs, a hydrophobic groove involving at least six amino acid residues, and a negatively charged residue at the end of the βB-strand. The primary sequence of the first motif, 240GLGDLG245, is a consensus marker for phosphate binding, evidencing involvement with NADP binding, while the other glycine rich motif adopts a classical Rossmann fold—also a typical marker for NADP cofactor binding. Mutagenesis experiments in maize NADP-ME have supported the current model. Valine substitution for glycine in either motif region rendered the enzyme completely inactive while spectral analysis indicated no major changes from wild-type form. The data is suggestive of direct impairment at a key residue involved in binding or catalysis rather than an inter-domain residue influencing conformational stability. Additionally, a key arginine residue at site 237 has been shown to interact both with malate and NADP+ substrates, forming key favorable electrostatic interactions to the negatively charged carboxylic-acid and phosphate group respectively. Elucidation of whether the residue plays a role in substrate binding or substrate positioning for catalysis has yet to be determined.Lysine residue 255 has been implicated as a catalytic base for the enzymes reactivity; however, further studies are still required to conclusively establish its biochemical role.
Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)
Enzyme structure
Structural studies As of 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes 1GQ2, 1GZ4, and 2AW5.
Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)
Biological function
In a broader context, malic enzymes are found within a wide range of eukaryotic organisms, from fungi to mammals, and beyond that, are shown to localize in range of subcellular locations, including the cytosol, mitochondria, and chloroplast. C4 NADP-ME, specifically, is in plants localized in bundle sheath chloroplasts.During C4 photosynthesis, an evolved pathway to increase localized CO2 concentrations under the threat of enhanced photorespiration, CO2 is captured within mesophyll cells, fixed as oxaloacetate, converted into malate and released internally within bundle sheath cells to directly feed RuBisCO activity. This release of fixed CO2, triggered by the favorable decarboxylation of malate into pyruvate, is mediated by NADP-dependent malic enzyme. In fact, the significance of NADP-ME activity in CO2 conservation is evidenced by a study performed with transgenic plants exhibiting a NADP-ME loss of function mutation. Plants with the mutation experienced 40% the activity of wild-type NADP-ME and achieved significantly reduced CO2 uptake even at high intercellular levels of CO2, evidencing the biological importance of NADP-ME at regulating carbon flux towards the Calvin cycle.
Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)
Enzyme regulation
NADP-ME expression has been shown to be regulated by abiotic stress factors. For CAM plants, drought conditions cause stoma to largely remain shut to avoid water loss by evapotranspiration, which unfortunately leads to CO2 starvation. In compensation, closed stoma activates the translation of NADP-ME to reinforce high efficiency of CO2 assimilation during the brief intervals of CO2 intake, allowing for carbon fixation to continue.
Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)
Enzyme regulation
In addition to regulation at the longer time scale by means of expression control, regulation at the short-time scale can occur through allosteric mechanisms. C4 NADP-ME has been shown to be partially inhibited by its substrate, malate, suggesting two independent binding sites: one at the active site and one at an allosteric site. However, the inhibitory effect exhibits pH-dependence – existent at a pH of 7 but not a pH of 8. The control of enzyme activity due to pH changes align with the hypothesis that NADP-ME is most active while photosynthesis is in progress: Active light reactions leads to a rise in basicity within the chloroplast stroma, the location of NADP-ME, leading to a diminished inhibitory effect of malate on NADP-ME and thereby promoting a more active state. Conversely, slowed light reactions leads to a rise in acidity within the stroma, promoting the inhibition of NADP-ME by malate. Because the high energy products of the light reactions, NADPH and ATP, are required for the Calvin cycle to proceed, a buildup of CO2 without them is not useful, explaining the need for the regulatory mechanism.This protein may use the morpheein model of allosteric regulation.
Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)
Evolution
NADP-malic enzyme, as all other C4 decarboxylases, did not evolve de novo for CO2 pooling to aid RuBisCO. Rather, NADP-ME was directly transformed from a C3 species in photosynthesis, and even earlier origins from an ancient cystolic ancestor. In the cytosol, the enzyme existed as a series of housekeeping isoforms purposed towards a variety of functions including malate level maintenance during hypoxia, microspore separation, and pathogen defense. In regards to the mechanism of evolution, the C4 functionality is thought to have stemmed from gene duplication error both within promoter regions, triggering overexpression in bundle-sheath cells, and within the coding region, generating neofunctionalization. Selection for CO2 preservation function as well as enhanced water and nitrogen utilization under stressed conditions was then shaped by natural pressures.
Steroid ester
Steroid ester
A steroid ester is an ester of a steroid. They include androgen esters, estrogen esters, progestogen esters, and corticosteroid esters. Steroid esters may be naturally occurring/endogenous like DHEA sulfate or synthetic like estradiol valerate. Esterification is useful because it is often able to render the parent steroid into a prodrug of itself with altered chemical properties such as improved metabolic stability, water solubility, and/or lipophilicity. This, in turn, can enhance pharmacokinetics, for instance by improving the steroid's bioavailability and/or conferring depot activity and hence an extended duration with intramuscular or subcutaneous injection.Esterification of steroids with fatty acids was developed to prolong the duration of effect of steroid hormones. By 1957, more than 500 steroid esters had been synthesized, most frequently of androgens. The longer the fatty acid chain, up to a certain optimal length, the longer the duration when prepared as an oil solution and injected. Across a chain length range of 6 to 12 carbon atoms, a length of 9 or 10 carbon atoms (nonanoate or decanoate ester) was found to be optimal in rodents in the case of testosterone esters. Fatty acid esters increase the lipophilicity of steroids, with longer fatty acids resulting in greater lipophilicity. The greater solubility in oil allows the steroid esters to be dissolved in a smaller oil volume, thereby allowing for larger doses with intramuscular injection. In addition, the greater the lipophilicity of the steroid, as measured by the octanol/water partition coefficient (logP), the slower its release from the oily depot at the injection site and the longer its duration.Steroid esters can also be prepared as crystalline aqueous suspensions. Aqueous suspensions of steroid crystals result in prolongation of duration with intramuscular injection similarly to oil solutions. The duration is longer than that of oil solutions, intermediate between oil solutions and subcutaneous pellet implants. The sizes of crystals in suspensions varies and can range from 0.1 μm to some hundreds of μm. The duration of crystalline steroid suspensions increases directly with the size of the crystals. However, crystalline suspensions have an irritating effect in the body, and intramuscular injections of crystalline steroid suspensions result in painful local reactions. These reactions worsen with larger crystals, and for this reason, crystal sizes must be limited to minimize local reactions. Particle sizes of more than 300 μg in the case of estradiol benzoate by intramuscular injection have been found to be too painful for use.In some cases, crystalline steroid suspensions are used not for prolongation of effect, but because the solubility of the steroid result in this preparation being the only practical way to deliver the steroid in a reasonable injection volume. Examples include cortisone acetate and hydrocortisone and its esters. A requirement of long-lasting crystalline steroid administration is that the steroid be sufficiently water-insoluble, so that it dissolves slowly and thereby attains a prolonged therapeutic effect. The crystals in suspensions can sometimes clump together or aggregate and grow in size. This can be avoided by careful formulation. Crystalline suspensions of steroids are prepared either by precipitation or by dispersing finely divided material in an aqueous suspension medium. Desired particle size can be achieved by grinding, for instance through the use of an atomizer.Adolf Butenandt reported in 1932 that estrone benzoate in oil solution had a prolonged duration with injection in animals. No such prolongation of action occurred if it was given by intravenous injection. Estradiol benzoate was synthesized in 1933 and was marketed for use the same year.
Steroid ester
Sulfur-based esters
Certain sulfur-based steroid esters have a sulfamate or sulfonamide moiety as the ester, typically at the C3 and/or C17β positions. Like many other steroid esters, they are prodrugs. Unlike other steroid esters however, they bypass first-pass metabolism with oral administration and have high oral bioavailability and potency, abolished first-pass hepatic impact, and long elimination half-lives and durations of action. They are under development for potential clinical use. Examples include the estradiol esters estradiol sulfamate (E2MATE; also a potent steroid sulfatase inhibitor) and EC508 (estradiol 17β-(1-(4-(aminosulfonyl)benzoyl)-L-proline)), the testosterone ester EC586 (testosterone 17β-(1-((5-(aminosulfonyl)-2-pyridinyl)carbonyl)-L-proline)), and sulfonamide esters of levonorgestrel and etonogestrel.
World Action And Adventure
World Action And Adventure
World Action and Adventure is a role-playing game published by M.S. Kinney Corporation in 1985.
World Action And Adventure
Description
World Action and Adventure is a universal system, with character creation, skill, combat, and mass combat rules. The boxed set includes the Official Guide, a GM's screen, character record sheets, and blank forms.
World Action And Adventure
Publication history
World Action and Adventure was designed by Gregory L. Kinney, and published by M.S. Kinney Corporation in 1985 as a boxed set containing a 160-page hardcover book, a cardstock screen, a packet of blank forms, a small pad of character sheets, and dice.
World Action And Adventure
Reception
Lawrence Schick comments: "WA&A is beyond doubt the nicest RPG ever published. The three books attempt to describe everything on Earth from a staggeringly naive worldview. The rulebooks consist of a multitude of very general tables that list everything the author could think of. The descriptions that accompany the tables are so ingenuous, they're just priceless. Then there's the poem, "World Action and Adventure": 20 verses, each describing a different aspect of adventure. An excerpt: 'Pyramids are being built/the Pharaoh has a suppressed guilt/so many slaves they thirst and die/to build these things that touch the sky" ... it just goes on and on."
Bessel–Maitland function
Bessel–Maitland function
In mathematics, the Bessel–Maitland function, or Wright generalized Bessel function, is a generalization of the Bessel function, introduced by Edward Maitland Wright (1934). The word "Maitland" in the name of the function seems to be the result of confusing Edward Maitland Wright's middle and last names. It is given by Jμ,ν(z)=∑k≥0(−z)kΓ(kμ+ν+1)k!.
Embroidery of India
Embroidery of India
Embroidery in India includes dozens of embroidery styles that vary by region and clothing styles. Designs in Indian embroidery are formed on the basis of the texture and the design of the fabric and the stitch. The dot and the alternate dot, the circle, the square, the triangle, and permutations and combinations of these constitute the design.
Embroidery of India
Aari
Aari work involves a hook, plied from the top but fed by silk thread from below with the material spread out on a frame. This movement creates loops, and repeats of these lead to a line of chain stitches. The fabric is stretched on a frame and stitching is done with a long needle ending with a hook such as a crewel, tambour (a needle similar to a very fine crochet hook but with a sharp point) or Luneville work. The other hand feeds the thread from the underside, and the hook brings it up, making a chainstitch, but it is much quicker than chainstitch done in the usual way: looks like machine-made and can also be embellished with sequins and beads - which are kept on the right side, and the needle goes inside their holes before plunging below, thus securing them to the fabric.there are many types of materials used like zari threads, embellishments,sequins etc..
Embroidery of India
Aari
Aari embroidery is practiced in various regions such as in Kashmir and Kutch (Gujarat).
Embroidery of India
Banjara embroidery
Practiced by the Lambada gypsy tribes of Andhra Pradesh, Banjara embroidery is a mix of applique with mirrors and beadwork. Bright red, yellow, black and white coloured cloth is laid in bands and joined with a white criss-cross stitch. The Banjaras of Madhya Pradesh who are found in the districts of Malwa and Nimar have their own style of embroidery where designs are created according to the weave of the cloth, and the textured effect is achieved by varying colours and stitches of the geometric patterns and designs. Motifs are generally highlighted by cross-stitch.
Embroidery of India
Banni or Heer Bharat (Gujarat)
The Banni or Heer Bharat embroidery originates in Gujarat, and is practiced mainly by the Lohana community. It is done with silk floss (Heer means "silk floss") and it is famous for its vibrancy and richness in color pallets & design patterns, which include shisha (mirror) work. Bagh and phulkari embroidery of the Punjab region has influenced Heer Bharat embroidery in its use of geometrical motifs and stitchery.
Embroidery of India
Chamba Rumal (Himachal Pradesh)
It originated in Chamba kingdom of Himachal Pradesh in 17th century. This embroidery flourished in the princely hill states of Kangra, Chamba, Basholi, and other neighbouring provinces. The Chamba region has highly skilled craftsmen. Chamba embroidery has its own distinctive style, small squares or rectangles of clothe embroidered with untwisted silk threads. While untwisted silk is most common some Chamba embroidery make use of thin metal wires or metallic yarn. While the chamba rumal originated in the 17th century it reached widespread popularity in the 18th century after rulers in the Himalayan region patronized Chamba Rumal embroiderers. The original Chamba embroideries were done by women or young children, the embroideries often depicted gods or goddesses. Original Chamba embroideries were very important in marriages as the embroideries were kept as the brides dowry. Chamba embroideries often began by drawing an outline on the rectangular square of fabric, while originally embroidered by women at the height of popularity in the 18th century many male painters drew the outlines and embroidered the clothe themselves to ensure high quality work. Not long after its height of popularity in the 18th century the chamba rumal's popularity declined. The rumals began to lose their sacredness, today most rumals are made by families trying to sell them to survive, and the Chamba Rumals are not of the same quality as they were in the 17th and 18th century. While this art style has declined over the years and almost been lost, in 2009 Lalita Vakil was given the Shilp Guru award for her ability and skill in Chamba embroidery.
Embroidery of India
Chikankari (Uttar Pradesh)
The present form of chikan (meaning elegant patterns on fabric) work is associated with the city of Lucknow, in Uttar Pradesh. Chikan embroidery on silk is Lucknow's own innovation. The other chikan styles are that of Calcutta and Dacca. However, characteristic forms of stitch were developed in Lucknow: phanda and murri.Chikan embroidery is believed to have been introduced by Nur Jahan, the wife of Jahangir. Chikan embroidery involves the use of white thread on white muslin (tanzeb), fine cotton (mulmul), or voile, fine almost sheer fabrics which showcases shadow work embroidery the best. Other colours can also be used. The artisans usually create individual motifs or butis of animals and flowers (rose, lotus, jasmine, creepers). The designs are first printed onto the fabric not with chaulk, but with a mixture of glue and indigo.
Embroidery of India
Chikankari (Uttar Pradesh)
At least 40 different stitches are documented, of which about 30 are still practiced today and include flat, raised and embossed stitches, and the open trellis-like jaali work. Some of the stitches that are used in Chikankari work include: taipchi, pechni, pashni, bakhia (ulta bakhia and sidhi bakhia), gitti, jangira, murri, phanda, jaalis etc. In English: chain stitch, buttonhole stitch, French knots and running stitch, shadow work. Another is the khatao (also called khatava or katava).
Embroidery of India
Gota (Jaipur, Rajasthan)
It is a form of appliqué in gold thread, used for women's formal attire. Small pieces of zari ribbon are applied onto the fabric with the edges sewn down to create elaborate patterns. Lengths of wider golden ribbons are stitched on the edges of the fabric to create an effect of gold zari work. Khandela in Shekhawati is famous for its manufacture. The Muslim community uses Kinari or edging, a fringed border decoration. Gota-kinari practiced mainly in Jaipur, utilising fine shapes of bird, animals, human figures which are cut and sewn on to the material.it is very famous in rajasthan as well as in many other parts of the world.
Embroidery of India
Kamal kadai (Andhra Pradesh)
Is an embroidery from native Andhra Pradesh. Woven Trellis stitch is used to make flowers and leaves and other stitches are done on fabric to complete the embroidery.
Embroidery of India
Kantha (Bengal)
Naksha is embroidery on many layers of cloth (like quilting), with running stitch. It is also known as dorukha which mean the designs/motifs are equally visible in both sides: there is no right or wrong side so both side are usable. Traditionally, worn out clothes and saris were piled together and stitched into quilts. Rural Bengali women still do this with cotton saris, the embroidery thread being taken from the sari border. It started as a method of making quilts, but the same type of embroidery can also be found on saris, salwar suits, stoles, napkins, etc. Themes include human beings, animals, flowers, geometric designs and mythological figures.
Embroidery of India
Karchobi - Rajasthan
It is a raised zari metallic thread embroidery created by sewing flat stitches on cotton padding. This technique is commonly used for bridal and formal costumes as well as for velvet coverings, tent hangings, curtains and the coverings of animal carts and temple chariots.
Embroidery of India
Kasuti or Kasuthi (Karnataka)
Kasuti (Kai=hand and Suti = weave /wrap) comes from the state of Karnataka, Kasuti is originated in Karnataka during chalukya period (6th to 12th century) [5] and done with single thread and involves counting of each thread on the cloth. The patterns are stitched without knots, so that both sides of the cloth look alike. Stitches like Gavanti, Murgi, Negi and Menthi form intricate patterns like gopura, chariot, palanquin, lamps and conch shells, as well as peacocks and elephants, in fixed designs and patterns.
Embroidery of India
Kathi (Gujarat)
Kathi embroidery was introduced by 'Kathi' the cattle breeders, who were wanderers. This technique combines chain stitch, appliqué work and mirror-like insertions.
Embroidery of India
Kaudi (Karnataka)
Kaudi (ಕೌದಿ) is a blanket or bedspread and applique embroidery from Karnataka. Old Fabrics are cut into pieces and stitched with simple running stitch, and Gubbi Kaalu stitch.
Embroidery of India
Khneng (Meghalaya)
Is an embroidery from meghalaya. Mustoh village is only known place for khneng embroidery and the embroidery is traditionally Done on eri silk shawls. [6]
Embroidery of India
Kutch or Aribharat
The best known of the Kutch (Gujarat) embroidery techniques is Aribharat, named after the hooked needle which forms the chainstitch. It is also known as Mochibharat, as it used to be done by mochis (cobblers).
Embroidery of India
Kutchi bharat/Sindhi stitch (Gujarat)
A variation of Kutch work, this geometric embroidery starts with a foundation framework of herringbone stitch or Cretan stitch, and then this framework is completely filled with interlacing. It is said that this technique originated in far away land of Armenia and found its way to Gujarat by travelling Nomads. Sindhi stitch or Maltese cross stitch is also similar but the innovation of the Kutchi women have taken it beyond the traditional designs meow Kutch work
Embroidery of India
Kashmiri embroidery
Kashmiri Kashida Kashmiri embroidery (also Kashida) is originated during Mughal period and used for phirans (woollen kurtas) and namdahs (woollen rugs) as well as stoles. It draws inspiration from nature. Birds, blossoms and flowers, creepers, chinar leaves, ghobi, mangoes, lotus, and trees are the most common themes. The entire pattern is made with one or two embroidery stitches, and mainly chain stitch on a base of silk, wool and cotton: the colour is usually white, off-white or cream but nowadays one can find stoles and salwar-kameez sets in many other colours such as brown, deep blue, sky blue, maroon and rani pink. Kashida is primarily done on canvas with crystal threads, but Kashida also employs pashmina and leather threads. Apart from clothes, it is found on home furnishings like bed spreads, sofa and floor cushions, and pillow covers.
Embroidery of India
Kashmiri embroidery
The base cloth, whether wool or cotton, is generally white or cream or a similar shade. Pastel colors are also often used. The craftsmen use shades that blend with the background. Thread colors are inspired by local flowers. Only one or two stitches are employed on one fabric. Kashmiri embroidery is known for the skilled execution of a single stitch, which is often called the Kashmiri stitch and which may comprise the chain stitch, the satin stitch, the slanted darn stitch, the stem stitch, and the herringbone stitch. Sometimes, the doori (knot) stitches are used but not more than one or two at a time.
Embroidery of India
Kashmiri embroidery
Kashmiri stitches The stitches include sozni (satin), zalakdozi (chain) and vata chikan (button hole). Other styles include dorukha in which the motif appears on both sides of the shawl with each side having a different color; papier-mâché; aari (hook) embroidery; shaaldaar; chinar-kaam; samovar (the antique Kashimiri tea-pot) is a very typical and popular design used in Kashmiri embroidery. The samovar pattern is then filled up with intricate flowers and leaves and twigs; Kashir-jaal which implies fine network of embroidery, particularly on the neckline and sleeves of a dress material.
Embroidery of India
Kashmiri embroidery
Further styles include naala jaal which involves embroidery particularly on the neckline and chest/yoke: naala means neck in the Koshur dialect of Kashmiri language; jaama is a very dense embroidery covering the whole base fabric with a thick spread of vine/creepers and flowers, badaam and heart shapes, a variation of this form is neem-jaama, where neem means demi or half, because the embroidery is less dense, allowing a view of the fabric underneath; and jaal consisting of bel-buti: a fine and sparse net of vine/creepers and flowers. Variation of this form is neem-jaal, where again the work is less dense.
Embroidery of India
Mukaish Work- (similar to chikankari) -Lucknow
Small rectangular pieces of metal are squeezed shut around some threads of the fabric. Mukesh work (known also as badla or fardi), includes women making shiny stitches amid chikan embroidery using a needle and long, thin strips of metal.
Embroidery of India
Phool Patti ka Kaam (Uttar Pradesh)
Flower embroidery of Uttar Pradesh, especially in Aligarh.
Embroidery of India
Phulkari (Punjab and Haryana)
Phulkari (Phul=flower, Kari=work) is originated in the late 17th century in Punjab region. the most famous rural embroidery tradition of Punjab, mentioned in the Punjabi folklore of Heer Ranjha by Waris Shah. Its present form and popularity goes back to 15th century, during Maharaja Ranjit Singh's reign Phulkari also means headscarf, and it comes from the 19th century tradition of carrying an odhani or a head-scarf with flower patterns. Its distinctive property is that the base is a dull hand-spun or khadi cloth, with bright coloured threads that cover it completely, leaving no gaps. It uses a darn stitch done from the wrong side of the fabric using darning needles, one thread at a time, leaving a long stitch below to form the basic pattern. Famous for Phulkari are the cities of Amritsar, Jalandhar, Ambala, Ludhiana, Nabha, Jind, Faridkot, and Kapurthala. Other cities include Gurgaon (Haryana), Karnal, Hissar, Rohtak and Delhi. Bagh is an offshoot of phulkari and almost always follows a geometric pattern, with green as its basic colour.
Embroidery of India
Phulkari (Punjab and Haryana)
Other styles The embroidery styles of the Punjab region include kalabatun embroidery using thin wires. Kalabatan surkh involves using gold wires on orange coloured and red silk. Kalabatan safed involves using silver wires on white material. There are two kinds of gold embroidery, one of a solid and rich kind called kar-chob and the other called tila-kar or kar-chikan utilising gold thread. The former is used for carpets and saddle cloths whereas the latter is used for dresses. The Punjab region also uses mukesh embroidery: mukesh bati-hui, twisted tinsel, mukesh gokru, flattened gold wire for embroidery of a heavy kind, and waved mukesh, made by crimping mukesh batihui with iron tongs. Ludhiana and Amritsar are known for embroidery using white, silver and gold threads on clothes such as chogas and waistcoats (phatuhi). Patchwork is also a tradition of the region.
Embroidery of India
Pichwai (Rajasthan)
Colourful embroidered cloth-hangings made in Nathdwara, Rajasthan. The central themes focus on Lord Krishna.
Embroidery of India
Pipli (Odisha)
Appliqué or Pipli work originates from the Pipli village in Odisha and some parts of Gujarat. It is called Chandua based on patchwork: brightly coloured and patterned fabric pieces are sewn together on a plain background mostly velvet along with Mirror and lace work. Designs include Hindu gods, human forms, animals, flowers and vehicles. Originally Chandua work was done to build the chariots for Puri Rath Yatra and was also used for parasols, canopies and pillows for the Rath Yatra. Nowadays different home décor items can be found, such as lamp shades, garden umbrellas and bed covers and utility products like Hand bags, Wallets, Files.
Embroidery of India
Rabari (Rajasthan and Gujarat)
This embroidery style is made by the Rabari or Rewari community of Rajasthan and Gujarat. This very colourful embroidery style, using stark contrast was traditionally used only for garments, but now it can be found on bags, accessories, home furnishings, etc. Mirrors of all shapes and sizes are incorporated in the embroidery, as a result of the belief that mirrors protect from evil spirits. Designs include not only flowers and fruit and animals such as parrots and elephants, but also temples, women carrying pots, and the ubiquitous mango shape.
Embroidery of India
Shamilami (Manipur)
A combination of weaving and embroidery and was once a high status symbol.
Embroidery of India
Shisha or Mirrorwork (Gujarat, Haryana, Rajasthan)
This ornamentation method originated in Persia during 13th century and involves little pieces of mirror in various sizes which are encased in the decoration of the fabric first by interlacing threads and then with buttonhole stitch.Originally, pieces of mica were used as the mirrors, but later, people started using thin blown-glass pieces, hence the name, which in Hindi means "little glass". Until recently they were all irregular, made by hand, and used mercury, nowadays one can also find them machine made and regularly shaped. It's usually found in combination with other types of stitches like cross stitch, buttonhole stitch and satin stitch, nowadays not only by hand but also by machine. Mirrorwork is very popular for cushion covers and bedcovers, purses and decorative hangings as well as in decorative borders in women's salwar-kameez and sari. Thousands of women from kutch (Gujarat) and sikar, churu (Rajasthan) are engaged in doing hand embroidery work like tie, mirror work, beads on fabric.
Embroidery of India
Shisha or Mirrorwork (Gujarat, Haryana, Rajasthan)
There are various types of Chikan work: Taipchi, Bakhia, Phunda, Murri, Jaali, Hathkati, Pechni, Ghas Patti, and Chaana Patti.
Embroidery of India
Toda embroidery
The Toda embroidery has its origins in Tamil Nadu. The Nilgiri Hills, inhabited by the Todu community have their own style called pugur, means flower. This embroidery, like Kantha, is practiced by women. The embroidery adorns the shawls. The shawl, called poothkuli, has red and black bands between which the embroidery is done. As Todas worship the buffaloes, buffalo becomes an important motif in the Toda embroidery among mettvi kaanpugur, Izhadvinpuguti and others. Stylized sun, moon, stars and the eye of the peacock feathers are used in Toda embroidery.
Embroidery of India
Zardozi or Zari or kalabattu
The most opulent form of Indian embroidery is the Zari and the Zardozi or Zardosi, known since the late 16th century, brought in India by the Moghuls. The word Zardozi comes from the two Persian words, Zar (gold) and Dozi (embroidery). This form uses metallic thread.
Embroidery of India
Zardozi or Zari or kalabattu
Once real gold and silver thread was used, on silk, brocade and velvet fabric. Metal ingots were melted and pressed through perforated steel sheets to convert into wires, which then were hammered to the required thinness. Plain wire is called 'badla', and when wound round a thread, it is called 'kasav'. Smaller spangles are called 'sitara' and tiny dots made of badla are called 'mukais' or 'mukesh'.
Embroidery of India
Zardozi or Zari or kalabattu
Zardozi is either a synonym or a more elaborate version of zari where the gold or silver embroidery is embellished with pearls and precious stones, gota and kinari, making this art only affordable by rich people. Nowadays Zardosi thread has a plastic core and a golden-coloured outside. The thread consists of coiled metal wires placed on the right side of the fabric and couched with a thinner thread.
Sequence learning
Sequence learning
In cognitive psychology, sequence learning is inherent to human ability because it is an integrated part of conscious and nonconscious learning as well as activities. Sequences of information or sequences of actions are used in various everyday tasks: "from sequencing sounds in speech, to sequencing movements in typing or playing instruments, to sequencing actions in driving an automobile." Sequence learning can be used to study skill acquisition and in studies of various groups ranging from neuropsychological patients to infants. According to Ritter and Nerb, “The order in which material is presented can strongly influence what is learned, how fast performance increases, and sometimes even whether the material is learned at all.” Sequence learning, more known and understood as a form of explicit learning, is now also being studied as a form of implicit learning as well as other forms of learning. Sequence learning can also be referred to as sequential behavior, behavior sequencing, and serial order in behavior.
Sequence learning
History
In the first half of the 20th century, Margaret Floy Washburn, John B. Watson, and other behaviorists believed behavioral sequencing to be governed by the reflex chain, which states that stimulation caused by an initial movement triggers an additional movement, which triggers another additional movement, and so on. In 1951, Karl Lashley, a neurophysiologist at Harvard University, published “The Problem of Serial Order in Behavior,” addressing the current beliefs about sequence learning and introducing his hypothesis. He criticized the previous view on the basis of six lines of evidence: The first line is that movements can occur even when sensory feedback is interrupted. The second is that some movement sequences occur too quickly for elements of the sequences to be triggered by feedback from the preceding elements. Next is that the errors in behavior suggest internal plans for what will be done later. Also, the time to initiate a movement sequence can increase with the length or complexity of the sequence. The next line is the properties of movements occurring early in a sequence can anticipate later features. Then lastly the neural activity can indicate preparation of upcoming behavior events, including upcoming behavior events in the relatively long-term future.
Sequence learning
History
Lashley argued that sequence learning, or behavioral sequencing or serial order in behavior, is not attributable to sensory feedback. Rather, he proposed that there are plans for behavior since the nervous system prepares for some behaviors but not others. He said that there was a hierarchical organization of plans. He came up with several lines of evidence. The first of these is that the context changes functional interpretations of the same behaviors, such as the way “wright, right, right, rite, and write” are interpreted based on the context of the sentence. “Right” can be interpreted as a direction or as something good depending on the context. A second line of evidence says that errors are involved in human behavior as hierarchical organization. In addition, “hierarchical organization of plans comes from the timing of behavioral sequences.” The larger the phrase, the longer the response time, which factors into “decoding” or “unpacking” hierarchical plans. Additional evidence is how easy or hard it is to learn a sequence. The mind can create a “memory for what is about to happen” as well as a “memory for what has happened.” The final evidence for the hierarchical organization of plans is characterized by "chunking". This skill combines multiple units into larger units.
Sequence learning
Types of sequence learning
There are two broad categories of sequence learning—explicit and implicit—with subcategories. Explicit sequence learning has been known and studied since the discovery of sequence learning. However, recently, implicit sequence learning has gained more attention and research. As a form of implicit learning, implicit sequence learning concerns underlying learning methods of which people are unaware—in other words, learning without knowing. The exact properties and number of mechanisms of implicit learning are debated. Other forms of implicit sequence learning include motor sequence learning, temporal sequence learning, and associative sequence learning.
Sequence learning
Sequence learning problems
Sequence learning problems are used to better understand the different types of sequence learning. There are four basic sequence learning problems: sequence prediction, sequence generation, sequence recognition, and sequential decision making. These “problems” show how sequences are formulated. They show the patterns sequences follow and how these different sequence learning problems are related to each other.
Sequence learning
Sequence learning problems
Sequence prediction attempts to predict the next immediate element of a sequence based on all the preceding elements. Sequence generation is basically the same as sequence prediction: an attempt to piece together a sequence one by one the way it naturally occurs. Sequence recognition takes certain criteria and determines whether the sequence is legitimate. Sequential decision making or sequence generation through actions breaks down into three variations: goal-oriented, trajectory-oriented, and reinforcement-maximizing. These three variations all want to pick the action(s) or step(s) that will lead to the goal in the future.These sequence learning problems reflect hierarchical organization of plans because each element in the sequences builds on the previous elements.
Sequence learning
Sequence learning problems
In a classic experiment published in 1967, Alfred L. Yarbus demonstrated that though subjects viewing portraits reported apprehending the portrait as a whole, their eye movements successively fixated on the most informative parts of the image. These observations suggest that underlying an apparently parallel process of face perception, a serial oculomotor process is concealed. It is a common observation that when a skill is being acquired, we are more attentive in the initial phase, but after repeated practice, the skill becomes nearly automatic; this is also known as unconscious competence. We can then concentrate on learning a new action while performing previously learned actions skillfully. Thus, it appears that a neural code or representation for the learned skill is created in our brain, which is usually called procedural memory. The procedural memory encodes procedures or algorithms rather than facts.
Sequence learning
Ongoing research
There are many other areas of application for sequence learning. How humans learn sequential procedures has been a long-standing research problem in cognitive science and currently is a major topic in neuroscience. Research work has been going on in several disciplines, including artificial intelligence, neural networks, and engineering. For a philosophical perspective, see Inductive reasoning and Problem of induction. For a theoretical computer-science perspective, see Solomonoff's theory of inductive inference and Inductive programming. For a mathematical perspective, see Extrapolation.
Sparse Fourier transform
Sparse Fourier transform
The sparse Fourier transform (SFT) is a kind of discrete Fourier transform (DFT) for handling big data signals. Specifically, it is used in GPS synchronization, spectrum sensing and analog-to-digital converters.:The fast Fourier transform (FFT) plays an indispensable role on many scientific domains, especially on signal processing. It is one of the top-10 algorithms in the twentieth century. However, with the advent of big data era, the FFT still needs to be improved in order to save more computing power. Recently, the sparse Fourier transform (SFT) has gained a considerable amount of attention, for it performs well on analyzing the long sequence of data with few signal components.