Physical and Chemical Properties of Particles

Physical and Chemical Properties of Particles A. Arctic Aerosol 

Numerous studies have documented both the chemistry and physics of aerosol particulates in several locations, including studies of Arctie haze in the late winter and the aerosol under much cleaner conditions in the Arctie summer. The most complete set of particle size distribution measurements is reported by Covert et 

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Heintzenberg and Leek (36) reported that the average total number concentration of aerosol particles observed in summer was more than twice that in winter. During winter, however, concentrations of black carbon and sea salt (Na ) in the aerosol were higher than in summer, whereas the methanesulfonic acid (MSA oxidation product from DMS) concentration was higher in summer. 

A study by Heintzenberg et al. (37) found that the winter Arctic aerosol was dominated by anthropogenic pollution from midlatitude sources. Size-fractionated chemical measurements showed that S, Cu, Zn, and Pb were found mainly in the submicrometer particles. 

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Hays M.D., Fine P.M., Geron C.D., Kleeman M.J., and Gullett B.K. (2005). Open burning of agricultural biomass Physical and chemical properties of particle-phase emissions. Atmospheric Environment, 39(36), 6747-6764. 

Surface area of a powder increases geometrically with decreasing particle size, so that the volume fraction of the outermost layer of ions on the surface increase significantly, which has a significant effect on properties of the powder. With the development of nanotechnology, it is readily to synthesize powders with nanosized particles (1-100 nm). Therefore, characterization of surface properties becomes more and more important. Specifically for ceramics or transparent ceramics, the consolidation of fine ceramic powders with liquid suspensions to produce more uniform green bodies has been shown to play an important role in the fabrication ceramics, especially when special or complex structures are required. Because the quality of microstructure of the consolidated body is determined by the dispersion behavior of the powder and the interaction between the particles in the suspension, which is closely related to the surface properties of the particles, controlling the physical and chemical properties of particles is a critical to ceramics fabrication. 

The constants a and y depend on the physical and chemical properties of the system, the scmbbing device, and the particle-size distribution in the entering gas stream. 

The abihty to enlarge tiny objects to macroscopic dimensions immediately suggests the need to make measurements and other observations helptiil in documenting what is seen and thus enabling others to confirm that a specimen has been identified with certainty. Many physical and chemical properties of a microscopic substance can be measured, even on particles nearing atomic dimensions. 

Bioavailability, Bioequivalence, and Pharmacokinetics. Bioavailabihty can be defined as the amount and rate of absorption of a dmg into the body from an adrninistered dmg product. It is affected by the excipient ingredients in the product, the manufacturing technologies employed, and physical and chemical properties of the dmg itself, eg, particle size and polymorphic form. Two dmg products of the same type, eg, compressed tablets, that contain the same amount of the same dmg are pharmaceutical equivalents, but may have different degrees of bioavailabihty. These are chemical equivalents but are not necessarily bioequivalents. For two pharmaceutically equivalent dmg products to be bioequivalent, they must achieve the same plasma concentration in the same amount of time, ie, have equivalent bioavadabihties. 

Water leaves the field either as surface mnoff, carrying pesticides dissolved in the water or sorbed to soil particles suspended in water, or as water draining through the soil profile, carrying dissolved pesticides to deeper depths. The distribution of water between drainage and mnoff is dependent on the amount of water appHed to the field, the physical and chemical properties of the soil, and the cultural practices imposed on the field. These factors also impact the retention and transformation processes affecting the pesticide. 

FIG. 19-68 The schematic diagram showing the relationship between the physical and chemical properties of fine particles and their behavior in flotation. (G) and (R) refer to whether the phenomena affects grade and/or recovery. The arrows indicate the various factors contributing to a particular phenomena observed in flotation of fine particles (Fiierstenaii, 1980). 

The physical and chemical properties of sufficiently small particles, in particular their magnetism, must depend on their size, whence the idea of using NMR to study them. Because of the theoretical and technical difficulties associated with the NMR detection of metals, and specially since only a few can be detected, NMR work has been mainly devoted to the indirect study of metallic properties, by the intenuediary of easily detected chemisorbed phases ( F1, C) or of physically adsorbed probes ( Xe). We will develop the cases of Pt and Pd. 

The use of highly dispersed metals at low concentration levels has found wide use In Industry, particularly for electronic and catalytic uses. The desire to optimize the size and mass uniformity of these metal particles Is of particular Interest. Characterization of these materials Is difficult especially when metal particle sizes are on the order of 5 nm or less and concentrations are below 1 wt-Z. Development of highly sophisticated techniques In recent years has provided new approaches to understanding the physical and chemical properties of these materials. Electron microscopy has proven quite valuable In the acquisition of data and subsequent generation of information, which Is necessary to understand the physical-chemical properties of Individual nm-slzed particles. 

To measure the strength of the forces exerted on particles, various analytical techniques have been developed [6, 7]. Unfortunately, since most of these techniques are based on hydrodynamics, assumption of the potential profiles is required and the viscosities of the fiuid and the particle sizes must be precisely determined in separate experiments, for example, using the viscous flow technique [8,9] and power spectrum analysis of position fluctuation [10]. Furthermore, these methods provide information on ensemble averages for a mass of many particles. The sizes, shapes, and physical and chemical properties of individual particles may be different from each other, which will result in a variety of force strengths. Thus, single-particle... 

The physical and chemical properties of MgO films prepared by the sol-gel technique were the area interest of the examinations presented by Shukla75. The aim of mentioned work was to produce films with nano size particles so as to employ them for the sensor applications, as adsorption in such films increases many folds due to the increase of surface area. Infra-red spectroscopic studies indicated the presence of solvent in the precursor, which helped in decomposition to nano-particles during nucleation of the film. The MgO sol-gel films were deposited on the glass rod bend in U-shape for humidity sensor. 

The concept of the atom as the smallest particle of matter (from the Greek word for indivisible) was promulgated by John Dalton about 1803. Within about a century and a quarter of scientific investigation which will be briefly described in this chapter, this concept yielded the idea of the periodic table and the understanding of the periodic table including the nuclear atom, the concept of isotopes, and the discovery of the majority of the isotopes which are used in the studies of the isotope effects. It is appropriate to point out that this book deals with the study of the effect of isotopic substitution on the physical and chemical properties of molecular (or atomic) systems. The book does not deal with the use of isotopes as tracers, a use which usually depends on the assumption that isotope effects are small and can be ignored in tracer studies. 

The real density of coke is obtained when the particle size of the specimen is smaller than 75 mm. The real density (or the particle size) exerts a direct influence on the physical and chemical properties of the carbon and graphite products that are manufactured from the coke. 

Literature data regarding the fate and transport of hexachlorobutadiene are limited. Much of the available information consists of modeling based on the physical and chemical properties of hexachlorobutadiene, and the monitoring data. These data indicate that hexachlorobutadiene will bind to soil particles and sediments, and is found in air and water bound to particulates. Some volatilization of hexachlorobutadiene from surface waters and soils may also occur. The bioconcentration of hexachlorobutadiene has been reported in fish and shellfish with considerable variability between species (EPA 1976 Oliver and Niimi 1983 Pearson and McConnell 1975). 

The first steps in traditional analysis of the physical and chemical properties of atmospheric particulate matter are sampling, that is, obtaining a representative sample over the desired size range, and collection, that is, separating the particles from air. During sampling and collection, such parameters as humidity, temperature, and particle concentration must be controlled to maintain the sample integrity. 

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