Secondary absorption

During occupational exposure, respiratory absorption of soluble and insoluble nickel compounds is the major route of entry, with gastrointestinal absorption secondary (WHO 1991). Inhalation exposure studies of nickel in humans and test animals show that nickel localizes in the lungs, with much lower levels in liver and kidneys (USPHS 1993). About half the inhaled nickel is deposited on bronchial mucosa and swept upward in mucous to be swallowed about 25% of the inhaled nickel is deposited in the pulmonary parenchyma (NAS 1975). The relative amount of inhaled nickel absorbed from the pulmonary tract is dependent on the chemical and physical properties of the nickel compound (USEPA 1986). Pulmonary absorption into the blood is greatest for nickel carbonyl vapor about half the inhaled amount is absorbed (USEPA 1980). Nickel in particulate matter is absorbed from the pulmonary tract to a lesser degree than nickel carbonyl however, smaller particles are absorbed more readily than larger ones (USEPA 1980). Large nickel particles (>2 pm in diameter) are deposited in the upper respiratory tract smaller particles tend to enter the lower respiratory tract. In humans, 35% of the inhaled nickel is absorbed into the blood from the respiratory tract the remainder is either swallowed or expectorated. Soluble nickel compounds... 

Matrix absorption, secondary fluorescence and scattering phenomena limit sensitivity and precision in many cases, especially with dense matrices. The sensitivity falls off with atomic number elements with Z < 15 are particularly difficult to analyse. Analysis is characteristic of surface layers (5-500 pm depth) only for a solid specimen. Instruments are often large, complicated and costly. 

High phosphate diets cause decreased Ca absorption, secondary hyperparathyroidism, accelerated bone resorption and soft tissue calcification in some animals, but not in normal humans. Although phosphates may decrease Ca absorption in man at very high (> 2000 mg/day) Ca intakes, they do not do so at more moderate Ca levels and enhance Ca absorption at very low levels (< 500 mg/day). Phosphates increase renal tubular reabsorption and net retention of Ca. At low Ca intakes, phosphates stimulate parathyroid hormone (PTH) secretion without causing net bone resorption. 

Full-thickness burns are unlikely to be painful since the nerve endings have been damaged. Partial-thickness burns, however, are known to cause variable degrees and types of pain because the nerve endings have lost protection. Intravenous narcotics are usually sufficient to maintain adequate pain control. Continuous infusions are appropriate for those who are mechanically ventilated. Oral and subcutaneous routes should not be used to treat burns greater than 20% TBSA because of decreased absorption secondary to burn shock. 

Decreased absorption secondary to defecation of the rectally administered pharmaceutical product... 

There are three main matrix effects in XRF primary absorption, secondary absorption and secondary fluorescence. Primary absorption refers to the radiation that is absorbed on the beam s path to reach the atoms to be excited. Secondary absorption refers to absorption of fluorescent radiation from atoms that occur along its path inside the specimen to the detector. Secondary fluorescence refers to the fluorescent radiation from the atoms which are excited by the fluorescent radiation of atoms with a higher atomic number in the same specimen. This phenomenon is possible when energy of the primary fluorescent radiation from heavier atoms is sufficient to excite secondary fluorescence from lighter atoms in the specimen. The absorption effects reduce the intensity of characteristic X-ray lines in spectrum, while secondary fluorescence increases the intensity of lighter elements. The matrix factors of EDS analysis in an electron microscope (EM) are described later in Section 6.8. 

In an article which is critical of many generally accepted molecular fluorescence parameters of aromatic molecules (and by inference the parameters for other systems), Birks emphasizes the precautions necessary to eliminate errors due to self-absorption secondary fluorescence and/or self-quenching.1 The points are made that reliable data for rf and Of are available for only a few compounds, e.g. diphenylanthracene (DPA), perylene, quinine bisulphate, and acridone, and that these provide suitable standards. The value of Of (DPA) is now set at 0.83. The importance of solvent effects on Of and t( of DPA is stressed in a publication which reports Tf for DPA in cyclohexane and benzene.2 The value of 6.95 0.04 ns for benzene solution is in good agreement with the earlier work of Birks and Dyson3 and Ware and Baldwin 4 7 (7.35 0.05 ns). The value obtained for cyclohexane solution, 7.58 0.04 ns, although in poor agreement with earlier results, is probably the most acceptable. The absolute fluorescence quantum yield of quinine bisulphate has also been redetermined (Of = 0.56).8... 

Given the inherent statistical nature of the discrete processes (such as photon absorption, secondary electron generation, PAG excitation, acid-quencher annihilation, deprotection, etc.) involved in advanced resist imaging, say, with EUV lithography, a credible concern has been reported that resists may reach a shot noise limit whereby low doses of high-energy EUV photons may cause the number of photons to fall to such low levels that the statistical variations inevitably will cause the LER to increase beyond an acceptable limit.This acceptable limit is referred to as the shot noise limit, and it is defined as the limit imposed by the statistical probability of underexposing a pixel. ... 

Absorption of toxic compounds that may alter thdr own absorption secondary to cutaneous toxieity of the penetrant has been studied using the chemical vesicant sulfur mustard (Riviere et al., 1995). In this model, absorption profiles could ordy be preeisely described if the vascular compartment was modulated as a function of sulfur mustard in the skin. This was independently correlated to vascular volume/pCT-meabihty using inuhn infusions to measure vascular space. 

Toxicology Exposure is by inhalation and by skin absorption (secondary). Diacetone alcohol is an irritant (eyes and mucous membranes), and a narcotic at high concentrations. Its odour threshold is rather low 0.3 ppm. 

Another factor responsible for negative departures from linearity at high concentration is. secondary absorption. Secondary absorption occurs when the wavelength of emission overlaps an absorption band. Fluorescence is then decreased as the emission traverses the solution and is reabsorbed by other molecules in solution. Secondary absorption can be absorption by the analyte species itself or absorption by other species in the solution. The effects of these phenomena are such that a plot of fluorescence versus concentration may exhibit a maximum Absorption effects are often termed inner filler effects. 

In addition to the characteristic C=0 stretching absorption of amides, primary and secondary amides also have N—H stretching absorptions in the 3200-3400 cm region. Amides without alkyl or aryl groups bonded to nitrogen (primary amides) have two N—H absorptions secondary amides have one N—H absorption. Of course, tertiary amides have no absorption in this r ion. Figures 21.6 and 21.7 show the infrared spectra of acetamide, a primary amide, and Af-methylacetamide, a secondary amide. 

Transmission through free-standing m-plane substrate was measured as a function of wavelength at different parts of the wafer (see Figure 12.30). It can be seen that there is a significant amount of absorption in the wafer, especially in the blue spectral range. To explain the increased absorption, secondary-ion-mass-spectroscopy (SIMS) was performed on the underside of... 

Ema data can be quantitated to provide elemental concentrations, but several corrections are necessary to account for matrix effects adequately. One weU-known method for matrix correction is the 2af method (7,31). This approach is based on calculated corrections for major matrix-dependent effects which alter the intensity of x-rays observed at a particular energy after being emitted from the corresponding atoms. The 2af method corrects for differences between elements in electron stopping power and backscattering (the correction), self-absorption of x-rays by the matrix (the a correction), and the excitation of x-rays from one element by x-rays emitted from a different element, or in other words, secondary fluorescence (the f correction). 

The alcohols are toxic orally, through skin absorption, and through inhalation. The secondary alcohols are more toxic than the tertiary. The glycols are relatively low in toxicity. 

Polypropylene fibers are used in every aspect of carpet constmetion from face fiber to primary and secondary backings. Polypropylene s advantages over jute as carpet backing are dimensional stabiUty and minimal moisture absorption. Drawbacks include difficulty in dyeing and higher cost. Bulked-continuous-filament (BCF) carpet yams provide face fiber with improved crimp and elasticity. BCF carpet yams are especially important in contract carpets, characterized by low dense loops, where easy cleaning is an advantage. 

Absorption Systems. Absorption refrigeration cycles employ a secondary fluid, the absorbent, to absorb the primary fluid, refrigerant vapor, which has been vaporized in the evaporator. The two materials that serve as the refrigerant—absorbent pair must meet a number of requirements however, only two have found extensive commercial use ammonia—water and water—Hthium bromide. 

This secondary reaction starts at about 180°C, but the mass must be heated to 350—400°C to bring the reaction to completion and produce a nitrate-free product. The off-gases are extremely corrosive and poisonous, and considerable attention and expense is required for equipment maintenance and caustic-wash absorption towers. Treatment of the alkaline wash Hquor for removal of mercury is required both for economic reasons and to comply with governmental regulations pertaining to mercury ia plant effluents. 

Ultraviolet. Benzene has a series of relatively low intensity absorption bands in the region of 230 to 270 nm. When there is a substituent on the ring with nonbonding electrons, such as an amino group, there is a pronounced increase in the intensity of these bands and a shift to longer wavelength. Aniline shows an absorption band at 230 nm (e = 8600) and a secondary band at 280 nm (e = 1430). Protonation of the amino groups reduces these effects and the spectmm resembles that of the unsubstituted benzene. 

In addition to the fundamental property of particle si2e (and surface area), carbon black possesses a secondary characteristic of stmcture, best described as the tendency of individual particles to agglomerate or associate with one another. These two properties or characteristics of the carbon control the degree and nature of the reinforcing character of the black in mbber. The stmcture of the carbon black is deterrnined by dibutyl phthalate absorption and surface area is estimated by N2 absorption (Table 10). 

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