Induced in mixtures

Activation analysis was first applied by von Hevesy and Levi two years after the discovery of artificial radioactivity (38). Determination of 0.1% dysprosium in rare earth mixtures was made by activation with neutrons from a 300-millicurie radium emanation-beryllium neutron source. The 2.3-hr half-life induced activity due to Dy was compared with that induced in mixtures of known dysprosium content. A similar method was used to determine europium in gadolinium. 

The importance of linked scanning of metastable ions or of ions formed by induced decomposition is discussed in this chapter and in Chapter 34. Briefly, linked scanning provides information on which ions give which others in a normal mass spectrum. With this sort of information, it becomes possible to examine a complex mixture of substances without prior separation of its components. It is possible to look highly specifically for trace components in mixtures under circumstances in which other techniques could not succeed. Finally, it is possible to gain information on the molecular structures of unknown compounds, as in peptide and protein sequencing (see Chapter 40). 

FIG. 27-33 Inspirator (gas-jet) mixer feeding a large port premix nozzle of the flame retention type. High-velocity gas emerging from the spud entrains and mixes with air induced in proportion to the gas flow. The mixture velocity is reduced and pressure is recovered in the ventnii section. (F om North Ameiioan Comhnstion Handbook, 3d ed., Notih American Manufacturing Company Cleveland 1996. )... 

In most cases of interest, shock-induced chemical reactions in solids are studied in mixtures of powders of the potential reactants. In the earlier description of conceptual models it was emphasized that the pores provide space in which the potential reactants can be more intimately mixed in order... 

Abstract The characterization of toxicological impact of chemicals and mixtures from environmental matrices is a critical point in the assessment of adverse effects induced in human and ecological targets. In fact, the toxicity of most of the environmental mixtures is still under investigation due to the possibility of synergic or antagonistic effects of the components. Moreover, in some cases, the toxicity of identified chemicals is not already well known and it could be an additional matter of concern. 

Chromium has proved effective in counteracting the deleterious effects of cadmium in rats and of vanadium in chickens. High mortality rates and testicular atrophy occurred in rats subjected to an intraperitoneal injection of cadmium salts however, pretreatment with chromium ameliorated these effects (Stacey et al. 1983). The Cr-Cd relationship is not simple. In some cases, cadmium is known to suppress adverse effects induced in Chinese hamster (Cricetus spp.) ovary cells by Cr (Shimada et al. 1998). In southwestern Sweden, there was an 80% decline in chromium burdens in liver of the moose (Alces alces) between 1982 and 1992 from 0.21 to 0.07 mg Cr/kg FW (Frank et al. 1994). During this same period in this locale, moose experienced an unknown disease caused by a secondary copper deficiency due to elevated molybdenum levels as well as chromium deficiency and trace element imbalance (Frank et al. 1994). In chickens (Gallus sp.), 10 mg/kg of dietary chromium counteracted adverse effects on albumin metabolism and egg shell quality induced by 10 mg/kg of vanadium salts (Jensen and Maurice 1980). Additional research on the beneficial aspects of chromium in living resources appears warranted, especially where the organism is subjected to complex mixtures containing chromium and other potentially toxic heavy metals. 

A suppressor is a device that selectively removes ions from a flowing solution. In an ion exchange HPLC experiment in which the mobile phase contains ions, a suppressor must be used to remove these ions so that the ions of the mixture can be detected. A conductivity detector measures ions by the conductivity that they induce in the mobile phase, so the mobile phase ions constituent an interference. 

When a reaction which transforms the reactants into nonchiral products is started, AH and AD, owing to the KIE, are consumed at different rates and an optical rotation is induced in the mixture. For a reaction that follows first-order or pseudo-first-order kinetics with the rate constants kH and kD, the time dependence of the optical rotation, a, is described by a two-exponential function (64). 

The explosive phenomena produced by contact of liquefied gases with water were studied. Chlorodifluoromethane produced explosions when the liquid-water temperature differential exceeded 92°C, and propene did so at differentials of 96-109°C. Liquid propane did, but ethylene did not, produce explosions under the conditions studied [1], The previous literature on superheated vapour explosions has been critically reviewed, and new experimental work shows the phenomenon to be more widespread than had been thought previously. The explosions may be quite violent, and mixtures of liquefied gases may produce overpressures above 7 bar [2], Alternative explanations involve detonation driven by phase changes [3,4] and do not involve chemical reactions. Explosive phase transitions from superheated liquid to vapour have also been induced in chlorodifluoromethane by 1.0 J pulsed ruby laser irradiation. Metastable superheated states (of 25°C) achieved lasted some 50 ms, the expected detonation pressure being 4-5 bar [5], See LIQUEFIED NATURAL GAS, SUPERHEATED LIQUIDS, VAPOUR EXPLOSIONS... 

Fig. 12. Procedure for analyzing and determining the TU of the eighth PAH compound in mixture 8-C1 (i.e., TU8 for fluoranthene, Table 9) that would induce 50% growth inhibition for the fresh water alga Selenastrum capricornutum...

For example, conversion after two hours reaction time (T=70°C, p(H2/CO) = 50 bar) dropped from 99% in the absence of CO2 to 66.4% at a density d(C02) = 0.35 g mL to 0% at d(C02) = 0.57 g mL The observation of a yellow-orange solid precipitated during the addition of CO2 confirmed the efficient separation of catalyst and substrate. The same separation was induced in the product mixture if CO2 was introduced after the hydroformylation was completed. The mixture of regioisomeric nonanals formed during the reaction was extracted quantitatively with SCCO2 leaving an active hydroformylation catalyst behind in the reactor. 

However, coffee beverages are complex mixtures of several hundred chemicals that either occur naturally or are later induced in coffee by the roasting process in the form of nicotinic acid or melanoidins. 

Fig. 28. Isothermal solvent-induced helix-coil transition of PBLG in mixtures of CHd3 and DCA over the entire range of composition (100) filled circles for [a] and open circles for [rf)...

Subsequent work has revealed that collision-induced absorption is observable even in mixtures of monatomic gases, albeit not in unmixed monatomic gases. In rare gas mixtures, the translational absorption profile occurs in the microwave and far infrared regions. In mixtures of molecular gases, such translational absorption profiles are sometimes discernible but they are generally masked by the induced rotational bands mentioned. 

Method of moments. In rare gas mixtures, the induced dipole consists of just one B component, with Ai AL = 0001, Eq. 4.14. Alternatively, one particular B(c) component may cause the overwhelming part of a measured spectrum, like the quadrupole-induced component in mixtures of small amounts of H2 in highly polarizable rare gases ((c) = Ai AL = 2023, Eq. 4.59) in a given spectral range, other components (like 0001, 2021,...) are often relatively insignificant. In such cases, one can write down more or less discriminating relationships between certain spectral moments of low order n that are obtainable from measurements of the collision-induced spectral profile, g Al(o>),... 

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