What is selenium
- Family: Nutritional supplement
- Scientific name: Selenium
- Other names: Selenomethionine
Full Answer
What is Selenium-IDE?
Selenium-IDE was originally created by Shinya Kasatani and donated to the Selenium project in 2006. Selenium IDE was previously little-maintained. Selenium IDE began being actively maintained in 2018. Scripts may be automatically recorded and edited manually providing autocompletion support and the ability to move commands around quickly.
What is the generic name for selenium?
Generic Name: selenium (se LEE nee um) Brand Name: Selenium TR, Selepen, Sele-Pak. Medically reviewed on Jun 26, 2018. Selenium is mineral that is found in soil and occurs naturally in certain foods (such as whole grains, Brazil nuts, sunflower seeds, and seafood).
Is selenium an element or compound?
It rarely occurs in its elemental state in nature, or as pure ore compounds. Selenium (Greek σελήνη selene meaning "Moon") was discovered in 1817 by Jöns Jacob Berzelius, who noted the similarity of the new element to the previously known tellurium (named for the Earth).
Where can selenium be found?
Selenium is found in metal sulfide ores, where it partially replaces the sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores, most often during production. Minerals that are pure selenide or selenate compounds are known but rare.
What is the most stable isotope of Selenium?
Selenium also has numerous unstable synthetic isotopes ranging from 64 Se to 95 Se; the most stable are 75 Se with a half-life of 119.78 days and 72 Se with a half-life of 8.4 days.
How much selenium is produced in 2011?
Selenous acid is bubbled with sulfur dioxide ( reduction step) to give elemental selenium. About 2,000 tonnes of selenium were produced in 2011 worldwide, mostly in Germany (650 t), Japan (630 t), Belgium (200 t), and Russia (140 t), and the total reserves were estimated at 93,000 tonnes.
What is the angle of selenium?
The most stable and dense form of selenium is gray and has a hexagonal crystal lattice consisting of helical polymeric chains, where the Se-Se distance is 237.3 pm and Se-Se-Se angle is 130.1° .
How is selenium oxide formed?
Selenium forms two oxides: selenium dioxide (SeO 2) and selenium trioxide (SeO 3 ). Selenium dioxide is formed by the reaction of elemental selenium with oxygen: Structure of the polymer SeO 2: The (pyramidal) Se atoms are yellow. It is a polymeric solid that forms monomeric SeO 2 molecules in the gas phase.
What is the structure of Selenium?
When rapidly melted, it forms the black, vitreous form, usually sold commercially as beads. The structure of black selenium is irregular and complex and consists of polymeric rings with up to 1000 atoms per ring . Black Se is a brittle, lustrous solid that is slightly soluble in CS 2. Upon heating, it softens at 50 °C and converts to gray selenium at 180 °C; the transformation temperature is reduced by presence of halogens and amines.
How many isotopes does selenium have?
Selenium has seven naturally occurring isotopes. Five of these, 74 Se, 76 Se, 77 Se, 78 Se, 80 Se, are stable, with 80 Se being the most abundant (49.6% natural abundance). Also naturally occurring is the long-lived primordial radionuclide 82 Se, with a half-life of 9.2×10 19 years. The non-primordial radioisotope 79 Se also occurs in minute quantities in uranium ores as a product of nuclear fission. Selenium also has numerous unstable synthetic isotopes ranging from 64 Se to 95 Se; the most stable are 75 Se with a half-life of 119.78 days and 72 Se with a half-life of 8.4 days. Isotopes lighter than the stable isotopes primarily undergo beta plus decay to isotopes of arsenic, and isotopes heavier than the stable isotopes undergo beta minus decay to isotopes of bromine, with some minor neutron emission branches in the heaviest known isotopes.
What is Selenium used for?
Selenium is a semiconductor and is used in photocells. Applications in electronics, once important, have been mostly replaced with silicon semiconductor devices. Selenium is still used in a few types of DC power surge protectors and one type of fluorescent quantum dot .
Why is Selenium called Selenium?
Selenium was so named because Huggins, dissatisfied with testing tools on the market, was seeking a name that would position the product as an alternative to Mercury Interactive QuickTest Professional commercial testing software .
When was Selenium developed?
Selenium was originally developed by Jason Huggins in 2004 as an internal tool at ThoughtWorks. Huggins was later joined by other programmers and testers at ThoughtWorks, before Paul Hammant joined the team and steered the development of the second mode of operation that would later become "Selenium Remote Control" (RC). The tool was open sourced that year.
What is Selenium testing?
Selenium is an open-source umbrella project for a range of tools and libraries aimed at supporting web browser automation. Selenium provides a playback tool for authoring functional tests without the need to learn a test scripting language (Selenium IDE). It also provides a test domain-specific language (Selenese) to write tests in a number of popular programming languages, including JavaScript ( Node.js ), C#, Groovy, Java, Perl, PHP, Python, Ruby and Scala. The tests can then run against most modern web browsers. Selenium runs on Windows, Linux, and macOS. It is open-source software released under the Apache License 2.0 .
What version of Selenium is Firefox?
The 2.x version of the Selenium IDE for Firefox stopped working after the Firefox 55 upgrade and has been replaced by Selenium IDE 3.x.
What languages does Selenium run?
It also provides a test domain-specific language (Selenese) to write tests in a number of popular programming languages, including C#, Groovy, Java, Perl, PHP, Python, Ruby and Scala. The tests can then run against most modern web browsers. Selenium runs on Windows, Linux, and macOS.
Who made the Selenium Grid?
In 2008, Philippe Hanrigou (then at ThoughtWorks) made "Selenium Grid", which provides a hub allowing the running of multiple Selenium tests concurrently on any number of local or remote systems, thus minimizing test execution time.
Is Selenium RC deprecated?
With the release of Selenium 2, Selenium RC has been officially deprecated in favor of Selenium WebDriver.
What is the source of selenium?
Electrolytic copper refinery slimes are the principal source of selenium and its sister element, tellurium ... Slimes generated by the refining of primary copper, copper produced from ores and concentrates, generally contain from 5-25% selenium and 2-10% tellurium. ... Some of the first processes to recover selenium on a commercial basis were based on roasting of copper slimes with soda ash to convert both selenium and tellurium to the +6 oxidation state. ... Slimes are intensively mixed with sodium carbonate, a binder such as bentonite, and water to form a stiff paste. The paste is extruded or pelletized and allowed to dry. ... Roasting occurs between temperatures of 530-650 °C. ... Conversion of both elements to the hexavalent form is complete. The roasted pellets or extrudes are ground and leached in water. The hexavalent selenium dissolves as sodium selenate, Na2SeO4. Sodium tellurate, being highly insoluble in the now very strongly alkaline solution, remains in the residue. The separation between selenium and tellurium is readily achieved, provided all tellurium is oxidized to the hexavalent state. ... There are two processes commonly employed for reducing selenium from solution. ... In the first process, employed commercially for may years, selenium is leached from the slimes in the form of the hexavalent sodium selenate. It is recovered from solution by crystallization and the crystalline sodium selenate is mixed with charcoal. Under controlled conditions of heating, the Na2SeO4 is reduced to sodium selenide. The sodium selenide cake is leached with water to form a typically liver-red solution of sodium selenide, which is readily oxidized to the elemental form by blowing air through the solution. ... In the second process, reduction of the hexavalent selenium is accomplished using concentrated hydrochloric acid or ferrous iron salts catalyzed by chloride ions as the reductant.
What is the metabolite of selenium?
Selenium supplements are typically available in the form of sodium selenite which is metabolized to selenide through either glutathione conjugation and subsequent reduction by glutathione reductase enzymes or reduction by thioredoxin reductases. Selenide is further metabolized to selenocystein by cysteine synthases and to selenophosphate by selenophosphate synthases. Selenide is also metabolized progressively to methyl-selenol, dimethyl selenide, then trimethylselenonium. Selenocysteine is degraded to methyl-selenol, pyruvate and ammonia by cysteine beta lyase. Selenocystein reacts with oxygen to form selenocysteine selenoxide which spontaneously degrades to methylselenic acid, pyruvate and ammonia. Methylselenic acid can be converted to methylselenol via conjugation with thiol groups on proteins like glutathione.
What is Selenium 75 used for?
Selenium-75, incorporated into the aerosols, was used to determine the Se content in the whole animal, excreta, and individual tissues as a function of time. Virtually all inhaled selenious acid aerosol was rapidly absorbed into the blood from the lungs, gastrointestinal tract, and the nasal membranes.
What is trace element?
A group of chemical elements that are needed in minute quantities for the proper growth, development, and physiology of an organism. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) (See all compounds classified as Trace Elements .)
How long does selenium 75 stay in the body?
Selenium-75 in these organs had a biological half-life of 30 to 40 days. Approximately 50% of the deposited Se was eliminated with a biological half life of 1.2 days.
What is the NCI Thesaurus?
NCI Thesaurus (NCIt) Selenium is a naturally occurring mineral element that is distributed widely in nature in most rocks and soils. In its pure form, it exists as metallic gray to black hexagonal crystals, but in nature it is usually combined with sulfide or with silver, copper, lead, and nickel minerals.
Where is selenium soluble?
Most selenium compounds are water -soluble and can efficiently be taken up in the intestine. Soluble as well as non-soluble compounds can be taken up by the lungs. When given in excess, selenium compounds are rapidly distributed to major organs of the body. ...
What foods contain selenium?
Includes a variety of protein foods such as lean meats; poultry; eggs; seafood; beans, peas, and lentils; nuts and seeds; and soy products. Pork, beef, turkey, chicken, fish, shellfish, and eggs contain high amounts of selenium . Some beans and nuts, especially Brazil nuts, contain selenium.
What are the most commonly used measures of selenium?
The most commonly used measures of selenium status are plasma and serum selenium concentrations [ 1 ]. Concentrations in blood and urine reflect recent selenium intake. Analyses of hair or nail selenium content can be used to monitor longer-term intakes over months or years.
Why is selenium low in HIV?
Selenium levels are often low in people living with HIV, possibly because of inadequate intakes (especially in developing countries), excessive losses due to diarrhea, and malabsorption [ 2, 25 ]. Observational studies have found an association between lower selenium concentrations in people with HIV and an increased risk of cardiomyopathy, death, and, in pregnant women, HIV transmission to offspring and early death of offspring [ 26-30 ]. Some randomized clinical trials of selenium supplementation in adults with HIV have found that selenium supplementation can reduce the risk of hospitalization and prevent increases of HIV-1 viral load; preventing HIV-1 viral load progression can lead to increases in numbers of CD4 cells, a type of white blood cell that fights infection [ 31, 32 ]. However, one trial showed that selenium supplementation in pregnant women can prevent early death in infants but has no effects on maternal viral load or CD4 counts [ 33, 34 ].
What are the factors that affect the amount of selenium in plant based food?
The amount of selenium in a given type of plant-based food depends on the amount of selenium in the soil and several other factors, such as soil pH, amount of organic matter in the soil, and whether the selenium is in a form that is amenable to plant uptake [ 2, 6, 8, 9 ].
What is the role of selenium in the body?
Selenium, which is nutritionally essential for humans, is a constituent of more than two dozen selenoproteins that play critical roles in reproduction, thyroid hormone metabolism, DNA synthesis, and protection from oxidative damage and infection [ 1 ].
Where is the lowest selenium level?
The lowest selenium intakes in the world are in certain parts of China , where large proportions of the population have a primarily vegetarian diet and soil selenium levels are very low [ 5 ]. Average selenium intakes are also low in some European countries, especially among populations consuming vegan diets [ 5, 9, 23 ]. Although intakes in New Zealand were low in the past, they rose after the country increased its importation of high-selenium wheat [ 9 ].
Which muscle is the main source of selenium?
Skeletal muscle is the major site of selenium storage, accounting for approximately 28% to 46% of the total selenium pool [ 3 ]. Both selenocysteine and selenite are reduced to generate hydrogen selenide, which in turn is converted to selenophosphate for selenoprotein biosynthesis [ 4 ].
What foods have selenium?
The amount of selenium in food depends on where it is grown or raised. Crab, liver, fish, poultry, and wheat are generally good selenium sources. The amount of selenium in soils varies a lot around the world, which means that the foods grown in these soils also have differing selenium levels.
Why is Selenium important?
Selenium is important for making many body processes work correctly. It seems to increase the action of antioxidants.
What are the names of birth control pills?
Some birth control pills include ethinyl estradiol and levonorgestrel (Triphasil), ethinyl estradiol and norethindrone (Ortho-Novum 1/35, Ortho-Novum 7/7/7), and others. Gold salts interacts with SELENIUM. Gold salts bind to selenium and decrease selenium in parts of the body.
Can you get preeclampsia from low selenium levels?
Pregnant women with low levels of selenium in the blood might have a higher chance of developing pre-eclampsia. Pre-eclampsia is a serious complication of pregnancy. Pregnant women taking selenium 60-100 mcg daily for up to 6 months during pregnancy might have a lower chance of having pre-eclampsia. Asthma.
Does selenium cause tremors?
Selenium can cause muscle tenderness, tremor, lightheadedness, facial flushing, blood clotting problems, liver and kidney problems, and other side effects. High doses of selenium can cause significant side effects including nausea, vomiting, nail changes, loss of energy, and irritability.
Does selenium help with arthritis?
Evidence on the effects of selenium on rheumatoid arthritis is mixed. Some research suggests that taking yeast enriched with 200 mcg of selenium does not improve RA. However, other research suggests that taking 200 mcg of selenium daily for 3 months reduces joint swelling, tenderness, and stiffness in people with RA.
Does selenium reduce the risk of death?
Other research suggests that sele nium, taken alone or with other nutrients, does not reduce the risk of death.
What are the health conditions that are associated with low selenium levels?
But some health conditions -- such as HIV, Crohn's disease, and others -- are associated with low selenium levels. People who are fed intravenously are also at risk for low selenium. Doctors sometimes suggest that people with these conditions use selenium supplements.
What foods contain selenium?
Good natural food sources of selenium include: 1 Nuts, like Brazil nuts and walnuts 2 Many fresh and saltwater fish, like tuna, cod, red snapper, and herring 3 Beef and poultry 4 Grains
What is the best source of selenium?
Good natural food sources of selenium include: Nuts, like Brazil nuts and walnuts. Many fresh and saltwater fish, like tuna, cod, red snapper, and herring. Beef and poultry.
What fish are in the salt water?
Many fresh and saltwater fish, like tuna, cod, red snapper, and herring
Where is selenium found in 2021?
Medically Reviewed by Melinda Ratini, DO, MS on March 26, 2021. Selenium is a mineral found in the soil. Selenium naturally appears in water and some foods. While people only need a very small amount, selenium plays a key role in their metabolism.
Is Selenium good for asthma?
Selenium has also been studied for the treatment of dozens of conditions. They range from asthma to arthritis to dandruffto infertility. However, the results have been inconclusive.
Can selenium cause nausea?
Taken at normal doses, selenium does not usually have side effects. An overdose of selenium may cause bad breath, fever, and nausea, as well as liver, kidney and heart problems and other symptoms. At high enough levels, selenium could cause death. Interactions.
What is Selenium?
Selenium is a free (open-source) automated testing framework used to validate web applications across different browsers and platform s. You can use multiple programming languages like Java, C#, Python etc to create Selenium Test Scripts. Testing done using the Selenium testing tool is usually referred to as Selenium Testing.
Why is Selenium called Selenium?
Since Selenium is a well-known antidote for Mercury poisoning, Jason suggested that name and his teammates took it. So that is how we got to call this framework up to the present.
What is Selenium Remote Control?
Selenium Remote Control, also known as Selenium 1, which is the first Selenium tool that allowed users to use programming languages in creating complex tests.
Why does Selenium Core need to be installed on local computer?
Unfortunately; testers using Selenium Core had to install the whole application under test and the web server on their own local computers because of the restrictions imposed by the same origin policy. So another ThoughtWork's engineer, Paul Hammant, decided to create a server that will act as an HTTP proxy to "trick" the browser into believing that Selenium Core and the web application being tested come from the same domain. This system became known as the Selenium Remote Control or Selenium 1.
When was WebDriver created?
Birth of WebDriver. Simon Stewart created WebDriver circa 2006 when browsers and web applications were becoming more powerful and more restrictive with JavaScript programs like Selenium Core. It was the first cross-platform testing framework that could control the browser from the OS level.
Which is better, Selenium or QTP?
Selenium is more advantageous than QTP in terms of costs and flexibility. It also allows you to run tests in parallel, unlike in QTP where you are only allowed to run tests sequentially.
When did Selenium 2 come out?
Birth of Selenium 2. In 2008, the whole Selenium Team decided to merge WebDriver and Selenium RC to form a more powerful tool called Selenium 2, with WebDriver being the core. Currently, Selenium RC is still being developed but only in maintenance mode.
Overview
Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic. It seldom occurs in its elemental state or as pure ore compounds in the Earth's crust. Selenium – from
Characteristics
Selenium forms several allotropes that interconvert with temperature changes, depending somewhat on the rate of temperature change. When prepared in chemical reactions, selenium is usually an amorphous, brick-red powder. When rapidly melted, it forms the black, vitreous form, usually sold commercially as beads. The structure of black selenium is irregular and complex and consists of
Chemical compounds
Selenium compounds commonly exist in the oxidation states −2, +2, +4, and +6.
Selenium forms two oxides: selenium dioxide (SeO2) and selenium trioxide (SeO3). Selenium dioxide is formed by the reaction of elemental selenium with oxygen:
It is a polymeric solid that forms monomeric SeO2 molecules in the gas phase. …
History
Selenium (Greek σελήνη selene meaning "Moon") was discovered in 1817 by Jöns Jacob Berzelius and Johan Gottlieb Gahn. Both chemists owned a chemistry plant near Gripsholm, Sweden, producing sulfuric acid by the lead chamber process. The pyrite from the Falun Mine created a red precipitate in the lead chambers which was presumed to be an arsenic compound, so the pyrite's use to make acid was discontinued. Berzelius and Gahn wanted to use the pyrite and they also o…
Occurrence
Native (i.e., elemental) selenium is a rare mineral, which does not usually form good crystals, but, when it does, they are steep rhombohedra or tiny acicular (hair-like) crystals. Isolation of selenium is often complicated by the presence of other compounds and elements.
Selenium occurs naturally in a number of inorganic forms, including selenide, s…
Production
Selenium is most commonly produced from selenide in many sulfide ores, such as those of copper, nickel, or lead. Electrolytic metal refining is particularly productive of selenium as a byproduct, obtained from the anode mud of copper refineries. Another source was the mud from the lead chambers of sulfuric acid plants, a process that is no longer used. Selenium can be refined from these muds by a number of methods. However, most elemental selenium comes as a byproduc…
Applications
Researchers found that application of selenium fertilizer to lettuce crops decreased the accumulation of lead and cadmium. Peaches and pears given a foliar selenium spray contained higher levels of selenium and also stayed firm and ripe longer when in storage. In low doses, selenium has shown a beneficial effect on plant resistance to various environmental stress factors including drought, UV-B, soil salinity, and cold or hot temperatures. However, it can dama…
Pollution
In high concentrations, selenium acts as an environmental contaminant. Sources of pollution include waste materials from certain mining, agricultural, petrochemical, and industrial manufacturing operations. In Belews Lake North Carolina, 19 species of fish were eliminated from the lake due to 150-200 μg Se/L wastewater discharged from 1974 to 1986 from a Duke Energy coal-fired power plant. At the Kesterson National Wildlife Refuge in California, thousands of fish a…