Sentences with phrase «by hydroxyl»

Third, although many of the individual steps have been established experimentally (18), surprisingly, the mechanism of production of MSA from OSC gas phase oxidation by hydroxyl radicals (OH, daytime) and nitrate radicals (nighttime) remains unclear (31).

The natural enzyme has two zinc ions bridged by a hydroxyl group as the active catalytic site.

The reactions are performed by hydroxyl radicals (· OH) created by the decomposition of hydrogen peroxide, a powerful oxidizing agent that is used in both household and industrial settings.

Methane is normally held in check by the hydroxyl radical (OH), which scrubs nearly all of it out of the atmosphere within a decade.

Not exact matches

Most SETI projects tune in to the 1.42 to 1.72 - gigahertz range, reasoning that alien astronomers might expect earthly scientists to be looking there anyway as this is the frequency of radiation emitted by interstellar hydrogen and hydroxyl clouds.

The team succeeded by using deuteration, or the substitution of deuterium atoms for hydrogen atoms, to study how hydroxyl is produced.

Instead, scientists gauge OH abundance by looking to proxies — chemicals that react with hydroxyl.

Formed in the presence of sunlight by water vapor and pollutants like ozone and nitrogen oxides, hydroxyl is hard to measure, because it persists for just a second in the air before it reacts away.

«All three of these molecules are removed by the same process — reaction with hydroxyl,» a radical formed from water in the atmosphere, explains Nobel Prize - winning chemist F. Sherwood Rowland, who participated in the research.

In one scenario, methane's rise may come in part from a drop in hydroxyl, a chemical that acts as an atmospheric detergent; in the other, the gas is emanating from tropical wetlands flooded by heavy rains in recent years.

Methane can be destroyed, however, by reactions involving an atmospheric «cleanser» called the hydroxyl free radical (OH).

A final possibility is that there has been increased formation of the hydroxyl radical in the atmosphere — perhaps caused by the thinning of the ozone layer, which allows more ultraviolet radiation to reach low levels.

But in recent years chemists have been increasingly concerned that the atmosphere's reservoir of the hydroxyl radical, and hence the efficiency of its «cleansing service», has been overstretched by the build - up of pollutants such as methane, carbon monoxide and sulphur dioxide.

Specifically, the scientists measured the yields of hydroxyl radicals and nitrite ions produced by the so - called acoustic cavitation of the bubbles.

It would allow hydroxyl to cheat by digging through the reaction's energy «barrier».

The reaction combines the hydroxyl molecule (OH, produced by reaction of oxygen and water) and carbon monoxide (CO, a byproduct of incomplete fossil fuel combustion) to form hydrogen (H) and carbon dioxide (CO2, a «greenhouse gas» contributing to global warming), as well as heat.

Lower in the atmosphere, oxygen atoms and hydroxyl radicals (OH), which form when water molecules are broken apart by ultraviolet photons, oxidize methane.

These experiments will first quantify the poorly - known production rates of a) nitric oxide (NO) and b) hydroxyl radicals (OH) by cosmic radiation.

AOES Medialab, ESA Alternative, larger and jumbo illustrations of hydroxyl in Venus» nightside by ESA and C. Carreau.

One theory is that a small amount of silver goes into solution by forming a compound of AgOH with the free hydroxyl radicals in the water.

The two most common ways of creating what is a false alkalinity are use of bicarbonates or drinking water from machines that make alkaline water by chemically splitting water into a retained hydroxyl radical that is alkaline and an acid proton that is flushed away.

These free radicals (such as: superoxide, hydroxyl radical, and peroxynitrite) are controlled by antioxidant systems and when these systems can't cope with the amount of free radicals produced these free radicals scavenge for electrons from proteins, cell membranes, and DNA.

Polysaccharides and glycans are made by the sequential addition of monosaccharides by glycosyltransferase from a reactive sugar - phosphate donor such as uridine diphosphate glucose (UDP - glucose) to an acceptor hydroxyl group on the growing polysaccharide.

Fat soluble antioxidants such as vitamin E's and A's may help prevent lipid membrane oxidation and methoxylated flavonoids (flavonoids [plant antioxidants] with free hydroxyl groups are much more easily disposed of by the liver and kidneys and have trouble entering the brain, and usually have very little biological effect) may also prevent damage and prevent the toxic aggregation of amyloid beta peptides.

Antioxidant activity of natural flavonoids is governed by number and location of their aromatic hydroxyl groups.

and 1998 snippets Methane now contributes about 20 % to the increased direct radiative forcing by greenhouse gases compared to preindustrial times [Shine et al., 1995] Oxidation of CH4 in the troposphere produces carbon monoxide (CO), can lead production of ozone (03), and involves atmospheric oxidant, the hydroxyl radical (OH).

This water photolysis must have happened to the primordial Earth, with loss of Hydrogen to space but it was stopped, as it is today, by the presence of ozone (O3) which requires high oxygen tension to form and it quickly reoxidises hydrogen via OH hydroxyls back to water.