Selenium and zinc are commonly referred to as antioxidant nutrients, but these chemical elements have no antioxidant action themselves and are instead required for the activity of some antioxidant enzymes, as is discussed below.

Selenium ( ) is a chemical element with symbol Se and atomic number 34.

Selenium is found impurely in metal sulfide ores, where it partially replaces the sulfur.

Selenium is a semiconductor and is used in photocells.

Selenium is a component of the antioxidant enzymes glutathione peroxidase and thioredoxin reductase ( which indirectly reduce certain oxidized molecules in animals and some plants ).

Selenium dioxide is formed by the reaction of elemental selenium with oxygen:

Selenium trioxide is produced in the laboratory by the reaction of anhydrous potassium selenate ( K < sub > 2 </ sub > SeO < sub > 4 </ sub >) and sulfur trioxide ( SO < sub > 3 </ sub >).

Selenium trioxide may be synthesized by dehydrating selenic acid, H < sub > 2 </ sub > SeO < sub > 4 </ sub >, which is itself produced by the oxidation of selenium dioxide with hydrogen peroxide:

Selenium dichloride is an important reagent in the preparation of selenium compounds ( e. g. the preparation of Se < sub > 7 </ sub >).

Selenium sulfide is being studied in the manufacture of photovoltaic solar cells.

Selenium is an occurring semimetallic trace element that occurs naturally in some soils and minute amounts are necessary for animal life.

The longer N-terminal domain is likely an enzymatic domain, and the shorter C-terminal domain is likely a means of safely transporting the very reactive Selenium atom throughout the body.

Selenium is also specifically incorporated into modified bases of some tRNAs ( as 2-seleno-5-methylaminomethyl-uridine ).

Selenium is a vital nutrient in animals, including humans.

Selenium is a trace element involved in proteins that are antioxidants.

Selenium is thus recovered as a by-product of copper mining.

Selenium toning is especially effective in this regard.

Selenium toning is a popular archival toning process, converting metallic silver to silver selenide.

Selenium can be dangerous if overfed, so it is best to have a blood test to confirm that the horse is in need of supplemental selenium.

Selenium sulfide is also used to treat tinea versicolor, a fungal infection of the skin.

XX, # 118, October 1880, pp. 305 – 324 ; also published as " Selenium and the Photophone " in Nature, September 1880.

Selenium and sodium may also be beneficial.

Selenium and tellurium also show variants of these structural motifs.

Selenium continues to be used in a few types of DC power surge protectors and one type of fluorescent quantum dot.

Selenium salts are toxic in large amounts, but trace amounts are necessary for cellular function in many organisms, including all animals.

Selenium requirements in plants differ by species, with some plants requiring relatively large amounts, and others apparently requiring none.

Selenium exists in several allotropes that interconvert upon heating and cooling carried out at different temperatures and rates.

Selenium does not exhibit the unusual changes in viscosity that sulfur undergoes when gradually heated.

Selenium has six naturally occurring isotopes, five of which are stable: < sup > 74 </ sup > Se, < sup > 76 </ sup > Se, < sup > 77 </ sup > Se, < sup > 78 </ sup > Se, and < sup > 80 </ sup > Se.

Selenium compounds commonly exist in the oxidation states − 2, + 2, + 4, and + 6.

Selenium disulfide consists of 8-membered rings of a nearly statistical distribution of sulfur and selenium atoms.

Selenium disulfide has been use in shampoo as an anti-dandruff agent, an inhibitor in polymer chemistry, a glass dye, and a reducing agent in fireworks.

Though in 1847 he published a paper in Liebig's Annalen der Chemie on the ' Mercaptan of Selenium ,' his mind was busy with the new ideas upon the nature of heat which were promulgated by Carnot, Clapeyron, Joule, Clausius, Mayer, Thomson, and Rankine.

Selenium and silicon light meters use sensors that are photovoltaic: they generate a voltage proportional to light exposure.

Selenium sensors generate enough voltage for direct connection to a meter ; they need no battery to operate and this made them very convenient in completely mechanical cameras.

Selenium sensors however cannot measure low light accurately ( ordinary lightbulbs can take them close to their limits ) and are altogether unable to measure very low light, such as candlelight, moonlight, starlight etc.

If the deficiency persists long enough, it is reasonable to suppose that the Af label will reflect the Af distribution in the thyroglobulin.

this is really a deficiency in the scalar field, namely, that it is not algebraically closed.

This is clearly a deficiency in T.

In West Africa, for example, where meat is a luxury and babies must be weaned early to make room at the breast for later arrivals, a childhood menace is kwashiorkor, or `` Red Johnny '', a growth-stunting protein deficiency ( signs: reddish hair, bloated belly ) that kills more than half its victims, leaves the rest prey for parasites and lingering tropical disease.

An atom containing an equal number of protons and electrons is electrically neutral, otherwise it has a positive charge if there are fewer electrons ( electron deficiency ) or negative charge if there are more electrons ( electron excess ).

"... Baeyer is an excellent experimentor, but he is only an empiricist, lacking sense and capability, and his interpretations of his experiments show particular deficiency in his familiarity with the principles of true science ..."

Chromium deficiency is controversial or is at least extremely rare.

Common competition policy is also helpful to avoid competition deficiency.

Cretinism is a condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormones ( congenital hypothyroidism ) usually due to maternal hypothyroidism.

Dyslexia is distinct from reading difficulties resulting from other causes, such as a non-neurological deficiency with vision or hearing, or from poor or inadequate reading instruction.

For instance, 30 % of the world's population either has, or is at risk for developing, iodine deficiency.

It is estimated that at least 3 million children are blind due to vitamin A deficiency.

If total cash available is less than cash needs, a deficiency exists.

The Edelman algorithm works equally well for sparse and non-sparse data, since it is based on the compressibility ( rank deficiency ) of the Fourier matrix itself rather than the compressibility ( sparsity ) of the data.

Worldwide, the most common cause for goitre is iodine deficiency, usually seen in countries that do not use iodized salt.

Hemoglobin deficiency is, in general, strictly distinguished from hypoxemia, defined as decreased partial pressure of oxygen in blood, although both are causes of hypoxia ( insufficient oxygen supply to tissues ).

The major deficiency of Q1 is in the language: particularly noticeable in the opening lines of the famous " To be, or not to be " soliloquy: " To be, or not to be, aye there's the point.

Other classifications used also include: ḥasan ( good ), which refers to an otherwise ṣaḥīḥ report suffering from minor deficiency, or a weak report strengthened due to numerous other corroborating reports ; and munkar ( denounced ) which is a report that is rejected due to the presence of an unreliable transmitter contradicting another more reliable narrator.

This is a great deficiency as trade theory, for intermediate goods occupy the major part of the world international trade.