Movement, selective

To investigate the crystallization phenomena induced by the external field, a cyclic force is imposed on a small portion of molecules in the amorphous structure, in addition to tiie inherent intermolecular forces. As a practical matter, this force may be applied to susceptor molecules (molecules witii dangling or floating bonds, or other defects) tiirough direct electric fields, electric fields induced by the external magnetic field, or other excitation sources. In tiiis study, it is assumed that some molecules can act as susceptors of the external field, for tiie sole purpose of inducing artificial molecular movements selectively and of observing tiie subsequent crystallization behavior. As discussed previously, the results of this study could provide a clue to mechanisms involved in the athermal crystallization of a-Si to poly-Si, which is induced by the field-enhanced molecular movements. 

These are not replacements for effective fall prevention practices. Only where the use of platforms, nets or other access and personal suspension equipment is impracticable is their use permissible. The functions of belts and harnesses are to limit the height of any fall, and to assist in rescues from confined spaces. In addition to comfort and freedom of movement, selection of this equipment must... 

An agitator consists of blades attached to a rotating shaft. Impellers have flat blades and provide radial flowpattems whereas propellers provide axial flow movement Paddle agitators consist of tilted flat blades providing a combination of radial and axial flow movement Selection of the appropriate agitator depends on the processing requirements, the fluid properties, and the materials of construction. 

Following the movement of airborne pollutants requires a natural or artificial tracer (a species specific to the source of the airborne pollutants) that can be experimentally measured at sites distant from the source. Limitations placed on the tracer, therefore, governed the design of the experimental procedure. These limitations included cost, the need to detect small quantities of the tracer, and the absence of the tracer from other natural sources. In addition, aerosols are emitted from high-temperature combustion sources that produce an abundance of very reactive species. The tracer, therefore, had to be both thermally and chemically stable. On the basis of these criteria, rare earth isotopes, such as those of Nd, were selected as tracers. The choice of tracer, in turn, dictated the analytical method (thermal ionization mass spectrometry, or TIMS) for measuring the isotopic abundances of... 

From equation 12.1 it is clear that resolution may be improved either by increasing Afr or by decreasing wa or w-q (Figure 12.9). We can increase Afr by enhancing the interaction of the solutes with the column or by increasing the column s selectivity for one of the solutes. Peak width is a kinetic effect associated with the solute s movement within and between the mobile phase and stationary phase. The effect is governed by several factors that are collectively called column efficiency. Each of these factors is considered in more detail in the following sections. 

From 760 to 960°C, circulating fans, normally without baffles, are used to improve temperature uniformity and overall heat transfer by adding some convection heat transfer. They create a directional movement of the air or atmosphere but not the positive flow past the heating elements to the work as in a convection furnace. Heating elements ate commonly chrome—nickel alloys in the forms described previously. Sheathed elements are limited to the very low end of the temperature range, whereas at the upper end silicon carbide resistors may be used. In this temperature range the selection of heating element materials, based on the combination of temperature and atmosphere, becomes critical (1). 

A particular type of support assembly is selected according to the amount of restraint tolerable by the piping system and the movement to be allowed at each location. Support types ate classified as rigid, resiUent, and constant-effort hanging and resting are the two basic arrangements. 

The movement-absorbing devices used in semirigid and nonrigid piping systems are usually called expansion joints. Based on the method by which the pressure seal is effected, joints are either of the packed type or the packless or bellows type. Selection depends not only on the required movement but also on the severity of service in terms of pressure and temperature, tolerabiUty of leakage, and the number of service cycles. 

Physiological Role of Citric Acid. Citric acid occurs ia the terminal oxidative metabolic system of virtually all organisms. This oxidative metabohc system (Fig. 2), variously called the Krebs cycle (for its discoverer, H. A. Krebs), the tricarboxyUc acid cycle, or the citric acid cycle, is a metaboHc cycle involving the conversion of carbohydrates, fats, or proteins to carbon dioxide and water. This cycle releases energy necessary for an organism s growth, movement, luminescence, chemosynthesis, and reproduction. The cycle also provides the carbon-containing materials from which cells synthesize amino acids and fats. Many yeasts, molds, and bacteria conduct the citric acid cycle, and can be selected for thek abiUty to maximize citric acid production in the process. This is the basis for the efficient commercial fermentation processes used today to produce citric acid. 

LandtiUing of Solid Wastes Landfilling involves the controlled disposal of solid wastes on or in the upper layer of the earth s mantle. Important aspects in the implementation of sanitary landfills include (1) site selection, (2) landfimng methods and operations, (3) occurrence of gases and leachate in landfills, (4) movement and control of landfill gases and leachate, and (5) landfill design. The landfilling of hazardous wastes is considered separately. 

Proper selection and sizing of ventilation systems require knowledge of emissions from internal contaminant and heat sources and an understanding of the mechanisms and characteristics of air and contaminant movement. 

Flow to select predominant factors affecting air and contaminant movement in ventilated spaces,... 

The application of the strategies in system selection can be illustrated by using a simple example. Let us think about an industrial hail with some internal heat sources but without any remarkable internal movement that would disturb the stratification. 

The measured pressure differences in ventilation applications are low or very low. The measurement range varies from a few pascals to several thousand pascals. At the lower end are typically building leakage and air movement-related measurements, where only a few pascals can cause a remarkably large air-tlow. The largest pressure differences probably occur in fan performance determination and similar applications. This wide range requires special demands on the measuring equipment and selection of the correct instrument for each application (Fig. 12.15). 

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