Substance dependence

The observed rotation a of an optically pure substance depends on how many mol ecules the light beam encounters A filled polarimeter tube twice the length of another produces twice the observed rotation as does a solution twice as concentrated To account for the effects of path length and concentration chemists have defined the term specific rotation, given the symbol [a] Specific rotation is calculated from the observed rotation according to the expression... 

Individual ammo acids differ m their acid-base properties This is important m peptides and proteins where the properties of the substance depend on its ammo acid constituents especially on the nature of the side chains It is also important m analyses m which a complex mixture of ammo acids is separated into its components by taking advantage of the differences m their proton donating and accepting power... 

Vacuum distillation. This expression is commonly used to denote a distillation under reduced pressure lower than that of the normal atmosphere. Because the boiling point of a substance depends on the pressure, it is often possible by sufficiently lowering the pressure to distil materials at a temperature low enough to avoid partial or complete decomposition, even if they are unstable when boiled at atmospheric pressure. 

As stated earlier, inhalation is the main route of absorption for occupational exposure to chemicals. Absorption of gaseous substances depends on solubility ifi blood and tissues (as presented in Sections 2.3.3-2.3.5), blood flow, and pulmonary ventilation. Particle size has an important influence on the absorption of aerosols (see Sections 2.3.7 and 3.1.1). 

Dose-response relationship 1 he toxicological concept that the toxicity of a substance depends not only on its toxic properties, but also on the amount of exposure or dose. 

The mp of this substance depends on the solvent used for recrystallization. A mp of 171-174 was reported for a sample recrystallized from ether-petroleum ether [K. Heusler, J. Kalvoda, Ch. Meystre, P. Wieland, G. Anner, A. Wettstein, G. Cainelli, D. Arigoni and O. Jeger, Helv. Chim. Acta, 44, 502 (1961)]. 

The energy of a system can be changed by means of thermal energy or work energy, but a further possibility is to add or subtract moles of various substances to or from the system. The free energy of a pure substance depends upon its chemical nature, its quantity (AG is an extensive property), its state (solid, liquid or gas), and temperature and pressure. Gibbs called the partial molar free heat content (free energy) of the component of a system its chemical potential... 

The intensity and colour of the fluorescence of many substances depend upon the pH of the solution indeed, some substances are so sensitive to pH that they can be used as pH indicators. These are termed fluorescent or luminescent indicators. Those substances which fluoresce in ultraviolet light and change in colour or have their fluorescence quenched with change in pH can be used as fluorescent indicators in acid-base titrations. The merit of such indicators is that they can be employed in the titration of coloured (and sometimes of intensely coloured) solutions in which the colour changes of the usual indicators would... 

Thermodynamics has explained the puzzling form of K it is a direct consequence of Eq. 4b, which shows how the Gibbs free energy of a substance depends on its activity. 

Clinical situations in which detoxification is indicated can be grouped into three categories 1) for patients who have been taking a maintenance therapeutic dosage for moderate to long periods of time and for whom a trial without medication is warranted, 2) for patients taking supratherapeutic doses (usually in the context of benzodiazepine dependence), and 3) for patients who use benzodiazepines as part of mixed substance dependence. Detoxification should be approached differently in each category. 

Kosten TR, Biegel D Therapeutic vaccines for substance dependence. Expert Rev... 

The visual detection limits for fluorimetric detection are substance-dependent and lie between 5 ng (adrenaline, noradrenaline) and 30 ng (homovanillic acid) substance per chromatogram zone. 

The reagent sequence produces colored chromatogram zones of substance-dependent color, some of which appear before the final heating step. The background remains colorless. Some of the zones fluoresce with various colors, when examined under UV light (X. = 280 mn). 

The heat of formation of a substance depends on its phase, because heat is required to melt or boil a substance. A for... 

The boiling point of a substance depends on the magnitude of its intermolecular forces, which in turn depends on the polarizability of its electron cloud. Monatomic gases contain atoms rather than molecules, so we must assess interatomic forces for these substances. 

The stable phase of a substance depends on temperature and pressure. A phase diagram is a map of the pressure-temperature world showing the phase behavior of a substance. As Figure 11-38 shows, a phase diagram is aP-r graph that shows the ranges of temperature and pressure over which each phase is stable. Pressure is plotted along... 

The absolute entropy of a substance depends on its phase. For example, compare three substances that are quite similar except for their phase at 298 K, 1 bar (Figure 14-141 ... 

The absolute entropies of otherwise similar substances depend on their phases ... 

The frequency of testing of a reference substances depends on the known or suspected stability and of its prescribed use. Reference substances used as assay standards are re-examined on a two-yearly basis whilst the other reference substances are... 

The reactivity of a substance depends on its ability to gain or lose electrons. It is possible to arrange the elements into a series based upon their reactivity. Such a list is called an activity series. 

Determine when a patient meets criteria for substance dependence. 

Individuals with a pattern of chronic use of commonly abused substances should be assessed to determine if they meet Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) criteria for substance dependence (addiction). 

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