Characteristics heterogeneities

Sampling of slurries and solids, differs fundamentally from sampling a completely mixed liquid or gas, A hulk quantity of sohds incorporates characteristic heterogenity—that is, a sample Sj differs inherently from a sample S2 when both are taken from a thoroughly mixed load of solids as a result of property variances embodied in solids. In contrast, all individual samples from a completely mixed liquid or gas container are statistically identical. 

Phencyclidine (1 -[1-phenylcyclohexyl]pi peridine HC1 PCP) and its active derivatives produce unique behavioral effects in animals and psychotomimetic effects in humans. Drugs of this class have been demonstrated to bind saturably, reversibly, and with high affinity to specific binding sites in brain (Hampton et al. 1982 Quirion et al. 1981 Sircar and Zukin 1983 Vincent et al. 1979 Zukin and Zukin 1979). These sites have been shown to exhibit a characteristic heterogeneous regional distribution pattern (Quirion et al. 1981 Sircar et al., submitted for publication Zukin and Zukin 1979) distinct from that of any other receptor type. 

Soils are characteristically heterogeneous. A trench dug into soil typically reveals several horizontal layers having different colors and textures. As illustrated in Figure 8.1, these multiple layers are often divided into three major horizons ... 

First, the typical characteristics of inspection problems which result in heterogeneous data are presented. Next, typical AI techniques which can be used for the automated data interpretation are presented. The applicabihty of the techniques to various inspection problems is discussed. Two example apphcations for automatic NDT data interpretation are briefly described, and finally, the conclusions are given. 

To determine the influence degree on both types of structure and volume of structural heterogeneity on the frequency spectrum characteristics of an ultrasonic pulse, research work using angle beam and straight beam probes was performed... 

The problem of material type determination was decided on the base of data obtained, that is the value of deviation dispersion characteristics from analogous ultrasonic field characteristics in the model heterogeneous flawless medium with given type of structure. 

The scheme of dispersion effects displayed in engineering materials of different structures was considered and an analysis of the causes of their occurrence was performed in our work. The spectrum of structural noise is considered as an element of unified spectral characteristics, reflected interaction of the ultrasonic field with given parameters and heterogeneous medium... 

Characteristics of the system as nitrating reagents Wibaut, who introduced the competitive method for determining reactivities (his experiments with toluene, benzene and chlorobenzene were performed under heterogeneous conditions and were not successful), pointed out that solutions of nitric acid in acetic anhydride are useful in making comparisons of reactivities because aromatic compounds are soluble in them. ... 

The ohmic drop across the electrolyte and the separator can also be calculated from Ohm s law usiag a modified expression for the resistance. When gas bubbles evolve at the electrodes they get dispersed ia and impart a heterogeneous character to the electrolyte. The resulting conductivity characteristics of the medium are different from those of a pure electrolyte. Although there is no exact description of this system, some approximate treatments are available, notably the treatment of Rousar (9), according to which the resistance of the gas—electrolyte mixture, R, is related to the resistance of the pure electrolyte, R ... 

Thermal Conductivity. More information is available relating thermal conductivity to stmctural variables of cellular polymers than for any other property. Several papers have discussed the relation of the thermal conductivity of heterogeneous materials in general (187,188) and of plastic foams in particular (132,143,151,189—191) with the characteristic stmctural variables of the systems. 

Heterogeneous polymerization is characteristic of a number of monomers, including vinyl chloride and acrylonitrile. A completely satisfactory mechanism for these reactions has not been deterrnined. This is tme for VDC also. Earlier studies have not been broad enough to elucidate the mechanism (26,30,31). Morphologies of as-polymerized poly(vinyl chloride) (PVC) and polyacrylonitrile (PAN) are similar, suggesting a similar mechanism. 

Dispersion Characteristics The chief characteristics of gas-in-liquid dispersions, like those of hquid-in-gas suspensions, are heterogeneity and instabihty. The composition and structure of an unstable dispersion must be obsei ved in the dynamic situation by looking at the mixture, with or without the aid of optical devices, or by photographing it, preferably in nominal steady state photographs usually are required for quantitative treatment. Stable foams may be examined after the fact of their creation if they are sufficiently robust or if an immobilizing technique such as freezing is employed [Chang et al., Ind. Eng Chem., 48, 2035 (1956)]. 

Heterogeneous Mixtures (Zabetakis, Flammability Characteristics of Combustible Gases and Vapors, Bulletin 627, Bureau of Mines, 1965.) Heterogeneous (poorly mixed) gas phase mixtures can lead to fires that normally would be totally unexpec ted. It is important... 

There was studied dependence of sorption rate values of microamounts high listed elements from time of their contact with sorbents, pH media and means of equilibrium concentration. It is shown that owing to exchange of sorbents surface characteristics, its hydrating rate value and heterogeneity of sorbate and hydrolyzed forms of metals investigated interaction with surface can simultaneously proceed on several mechanisms. The contributions of various factors into adsorption of elements-analogues are depended from sorption conditions and nature of sorbent surface. 

For modern analysis, high sensitivity and selectivity of methods for the determination of these elements are important parameters. Catalymetric methods of analysis possess such characteristics. Using of heterogeneous catalytic reactions on the interface also penults to reduce determination time. 

The next major commodity plastic worth discussing is polypropylene. Polypropylene is a thermoplastic, crystalline resin. Its production technology is based on Ziegler s discovery in 1953 of metal alkyl-transition metal halide olefin polymerization catalysts. These are heterogeneous coordination systems that produce resin by stereo specific polymerization of propylene. Stereoregular polymers characteristically have monomeric units arranged in orderly periodic steric configuration. 

---