Efficiency absorbers

Anhydrous lithium hydroxide [1310-65-2], LiOH, is obtained by heating the monohydrate above 100°C. The salt melts at 462°C. Anhydrous lithium hydroxide is an extremely efficient absorbent for carbon dioxide (qv). The porous stmcture of the salt allows complete conversion to the carbonate with no efficiency loss in the absorption process. Thus LiOH has an important role in the removal of carbon dioxide from enclosed breathing areas such as on submarines or space vehicles. About 750 g of lithium hydroxide is required to absorb the carbon dioxide produced by an individual in a day. 

Phosphors usually contain activator ions in addition to the host material. These ions are dehberately added in the proper proportion during the synthesis. The activators and their surrounding ions form the active optical centers. Table 1 Hsts some commonly used activator ions. Some soflds, made up of complexes such as calcium tungstate [7790-75-2] CaWO, are self-activated. Also in many photolurninescence phosphors, the primary activator does not efficiently absorb the exciting radiation and a second impurity ion is introduced known as the sensitizer. The sensitizer, which is an activator ion itself, absorbs the exciting radiation and transfers this energy to the primary activator. 

Any plant at times produces unwanted isomers. This requires an incinerator, capable of burning chlorinated hydrocarbons to HCl, H2O, and CO2 equipped with an efficient absorber for HCl (see Incinerators). An alternative to burning is dechlorination using hydrogen over a suitable catalyst. The ultimate product could be benzene. 

Fig. 10-8. Single particle scattering to mass ratio for particles of four different compositions. Carbon particles are also very efficient absorbers of light. Source U.S. Environmental Protection Agency, "Protecting Visibility," EPA-450/5-79-008, Office of Air Quality Planning Standards, Research Triangle Park, NC, 1979.

Fig. 1-6. Roentgen s production of secondary x-rays. The secondary x-rays from zinc are most efficiently absorbed by the emulsion and give the maximum darkening.

Since IR detector materials are direct bandgap materials (with no change in electron momentum required), they are very efficient absorbers (and emitters) of light - all IR photons are absorbed within the first few /rm of material. The reason that infrared detectors are 10 to 15 ptm thick is for structural and fabrication reasons, not for light absorption reasons. 

Talavera, S. et al., Anthocyanins are efficiently absorbed from the stomach in anesthetized rats, J. Nutr., 133, 4178, 2003. 

A fairly efficient method of selective detection of active forms of oxygen by means of sensors is the preliminary separation of their mixture with the aid of filters designed for the purpose, filters that vigorously de-excite this or that form of oxygen. It has been mentioned in Section 5.4 that freshly atomized films of Ag efficiently absorb O-atoms from the gaseous phase, mildly de-excite 02 molecules. To de-excite the singlet oxygen molecules proper, use should be made of filters with... 

The paracellular pathway, between the epithelial cells, is both size- (MW, volume) and charge-dependent [60, 109, 110]. In general, compounds that are limited to paracellular transport are not efficiently absorbed due to the small available absorptive area and the restriction by tight junctions. The molecular weight cut-off seems to be around 400 g mol-1 and 300 g mol-1 for the small and large intestine respectively, and 300 g mol-1 for the Caco-2 cell monolayers [60], which shows the more colonic nature of the Caco-2 monolayer model. Compounds with a... 

Some apparently specific effects can, however, arise from the supports. Mineral supports are usually poor heat conductors, i. e. significant temperature gradients can develop inside the vessels under the action of conventional heating, whereas they behave as efficient absorbers of microwave energy with consequently more temperature homogeneity (Scheme 3.2). 

It is to be noted that the reactions mentioned so far were performed under homogeneous conditions and, in most cases, using polar solvents, which are efficient absorbers of MW energy. Rate enhancements were attributed to the superheating of the solvent due to the elevated pressures generated in the closed vessels. 

It must be stressed that a liquid component can be substituted with an efficient absorber of microwave irradiation together with a low-melting component. The use of most typical PTC solvents (nonpolar aromatic or aliphatic hydrocarbons, or highly chlorinated hydrocarbons) is most interesting for microwave activation, because such solvents are transparent or absorb microwaves only weakly. They can, therefore, enable specific absorption of microwave irradiation by the reagents, and the results or product distributions might be different under microwave and conventional conditions [7]. 

The type and amount of carotenoids consumed affects carotenoid absorption. Absorption of (3-carotene from large doses is independent of dose size (Tanumihardjo 2002). The response of (3-carotene in serum and milk was similar in women supplemented with 60 or 210 mg of (3-carotene (Canfield and others 1997). In contrast, small carotenoid doses are more efficiently absorbed than large ones (West and Castenmiller 1998 Furusho and others 2000 Tanumihardjo 2002). 

The accident at the Chernobyl, Ukraine, nuclear reactor on April 26, 1986, contaminated much of the northern hemisphere, especially Europe, by releasing large amounts of radiocesium-137 and other radionuclides into the environment. In the immediate vicinity of Chernobyl at least 30 people died, more than 115,000 others were evacuated, and the consumption of locally produced milk and other foods was banned because of radiocontamination. The most sensitive local ecosystems were the soil fauna and pine forest communities. Elsewhere, fallout from Chernobyl measurably contaminated freshwater, marine, and terrestrial ecosystems, including flesh and milk of domestic livestock. Reindeer (Rangifer tarandus) calves in Norway showed an increasing frequency of chromosomal aberrations that seemed to correlate with cesium-137 tissue concentrations tissue concentrations, in turn, were related to cesium-137 in lichens, an efficient absorber of airborne particles containing radiocesium and the main food source of reindeer during winter. A pattern similar to that of reindeer was documented in moose (Alces) in Scandinavia. 

Most of the forementioned studies which examined the influence of various dietary fiber on the bioavailability of calcium by human subjects have depended upon the comparative measurements of calcium content of diets and calcium contents of stools and urine. As reviewed by Allen (3), calcium balance studies have distinct limitations relative to accuracy and precision. However, their ease of application and cost, laboratory equipment requirements, and real (or perceived) safety in comparison to available radioactive or stable isotope methods continue to make their use popular. In calcium balance studies, calcium absorption is assumed to be the difference between calcium excretion in the feces and calcium intake. Usually this is expressed as a percent of the calcium intake. This method assumes that all fecal calcium loss is unabsorbed dietary calcium which is, of course, untrue since appreciable amounts of calcium from the body are lost via the intestinal route through the biliary tract. Hence, calcium absorption by this method may underestimate absorption of dietary calcium but is useful for comparative purposes. It has been estimated that bile salts may contribute about 100 g calcium/day to the intestinal calcium contents. Bile salt calcium has been found to be more efficiently absorbed through the intestinal mucosa than is dietary calcium (20) but less so by other investigators (21). 

Interest in the possible connection between intake of fat and absorption of calcium was generated by the concurrent massive losses of calcium in patients with steatorrhea, fatty diarrhea (46, 47). Ordinarily, however, fat is very efficiently absorbed from the gastrointestinal tract. Results of several studies in human adults and children indicate little or no effect of level of dietary fat on absorption of calcium (48-54). However, influence of level of dietary fat on calcium absorption in rat studies has produced conflicting results (55-57). 

A rigid, planar, conjugated porphyrin ring, which functions as an efficient absorber of light. 

Sunlight is efficiently absorbed throughout the solar spectrum by an antenna system containing bacteriochlorophyll and carotenoid chromophores in a protein environment. 

Nonradiative energy transfer is very often used in practical applications, such as to enhance the efficiency of phosphors and lasers. A nice example is the commercial phosphor Cas(P04)3 (FCl), which is doubly activated by Sb + and Mn + ions. When the phosphor is singly activated by Mn + ions, it turns out to be very inefficient, due to the weak absorption bands of the divalent manganese ion. However, coactivation with Sb + ions produces a very intense emission from the Mn + ions, because the Sb + ions (the donor centers) efficiently absorb the ultraviolet emission (253.6 nm) of... 

Under the reaction conditions described in the patents, methacrolein is always present in nonnegligible amounts, and therefore a commercial process necessitates an economical method for recycling methacrolein. The patents assigned to Asahi Chemical Industry claim the use of an organic solvent, a mixmre of decane, undecane, and dodecane, which can efficiently absorb isobutane and methacrolein from the off-gas, with 99.5% recovery efficiency. Isobutane and methacrolein are then stripped with air and recycled. 

One of the first applications of this chopped-beam irradiation technitriplet spectra was reported by Labhart From a knowledge of the intensity of the irradiation light, he determined the quantum yield of triplet generation to be 0.55 0.11 for outgassed solutions of 1,2-benzanthrazene in hexane at room temperature. Hunziker 32) has applied this method to the study of the gas-phase absorption spectrum of triplet naphthalene. A gas mixture of 500 torr Na, 0.3 mtorr Hg, and about 10 mtorr naphthalene was irradiated by a modulated low-pressure mercury lamp. The mercury vapor in the cell efficiently absorbed the line spectrum of the lamp and acted as a photosensitizer. The triplet state of naphthalene was formed directly through collisional deactivation of the excited mercury atoms. 

After oral administration, BPA is rapidly and efficiently absorbed from the gastrointestinal tract and undergoes extensive first-pass metabolism in the gut wall and hver. BPA is mainly transformed into BPA-glucuronide and to a lesser extent into BPA-sulfate. These highly water-soluble metabolites are rapidly cleared from blood by the kidneys and excreted with urine [205]. Volkel et al. determined that the terminal half-life of BPA is less than 6 h in humans [206]. 

ZaUco D, Jacques C, Duplan H, Bruel S, Perdu E (2011) Viable skin efficiently absorbs and metabolizes bisphenol A. Chemosphere 82 424-430... 

The mechanism of iron and heme uptake by the intestine is becoming better understood 70-72), but clearly heme-iron is more efficiently absorbed from the gastrointestinal tract than inorganic iron 73-75), and there is a receptor for heme in the duodenal brush border membrane 76). Duodenal mucosal cells efficiently catabolize heme, and iron-transferrin can be detected in the plasma of blood vessels draining the intestinal segment shortly after Fe—heme—histidine is administered (75). 

Occasionally, one can increase the Ae by utilizing alternative substrates. For example, 3-acetyl-NAD or thio-NAD can often be used with NAD -dependent dehydrogenases. Note however that an alternative substrate may change the kinetic mechanism, as compared to that observed with the naturally occurring substrate. Alternative substrates are of particular value when the normal substrate(s) and product(s) do not efficiently absorb UV or visible light. For example, many p-nitroaniline or p-nitrophenyl derivatives have proved to be quite useful in enzyme assays because they exhibit intense absorption around 410 nm. 

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