Aerosols density

Phase 1. Low precursor supersaturation leads to slow nucleation at average rates <0.1-10 2/cm3s, connected with the formation of stable neutral clusters following the recombination of large ambient ions generates ultrafine aerosol densities of up to 100 s-1000 s/cm3 [19]. 

Little is known of this electrification mechanism. For one thing, aerosol densities are generally so small that even though one would expect... 

From data of measurements at the South Polar Plateau the mean bulk aerosol density varies from 15 particles/cm (in winter) to 100-150 particles/cm (in summer). A prevailing size of particles lies within 0.02-0.2 pm. In summer, at the expense of downward air fluxes, the values Cn = 500-1,500 cm were registered. This jump attributed to the appearance in the Antarctic air of considerable concentrations of particles... 

Specially shaped cells are required for special uses. One case in point is the cell depicted in Fig. 9.4C, which was designed to correct the variation of aerosol density in LA-ICP-MS and was a laboratory-made laser light-scattering cell for insertion into the aerosol transport tube between the laser ablation system and the torch. In this way, the temporal variation of signals from the laser light-scattering cell was correlated with that of the ion signals from the mass spectrometer [28]. 

A low aerosol density, n rl <plasma chemistry. In this case, considered by Fridman (1976), the combination of the Poisson equation with the Boltzmatm distribution leads to equations for the potential cp r) and electron density n r) around a spherical thermally ionized particle ... 

In a dynamic system, one has to take into account that the concentration of aerosols originating from the control rod materials in the gas-steam flow is not constant over time. Experiments reported by Beard et al. (1988 b) showed that the initial burst release upon failure of the claddings at about 1700 K produced an aerosol density (mainly cadmium) higher by about two orders of magnitude than the subsequent diffusional release. 

In the gas—steam flow which enters the containment in the low-pressure accident sequence, maximum aerosol densities in the range of 20 g/m may occur. When the core — concrete interaction begins, about 1 to 3 Mg of aerosols in total are assumed to be present in the containment atmosphere, according to corresponding calculations. 

In addition, both the physical properties of the liquid aerosol (density, viscosity, surface tension) and the operation conditions of the filtration process such as pressure, temperature, fluid velocity, and humidity all influence the degree to which coalescence occurs, and the fibre selections and structural design of nonwoven coalescing filters need to be engineered in agreement with those system configurations. 

Tanaka,T.,Yamamoto, K., Nomizu,T, and Kawaguchi, H. (1995). Laser ablation/inductively coupled plasma mass spectrometry with aerosol density nortnaUzation. Anal. Sci. Int.J. Jpn. Soc.Anal. Chem. 11(6),967. 

In the higher atmosphere the aerosol density decreases rapidly with altitude and other detection schemes may become more advantageous. Raman spectroscopy or detection of laser-induced fluorescence excited by frequency-doubled pulsed lasers has been utilized [14.22]. Both Raman and fluorescence intensities excited by the laser at a location x are proportional to the density n. (x) of scattering particles. However, because of the high pressure (p latm) the fluorescence is quenched if the collisional deactivation na v becomes faster than the spontaneous decay A. = 1/t. (see Sect. 12.2). Transition probabilities and quenching cross sections must therefore be known if quantitative results are to be obtained from measurements of the fluorescence intensity. 

Eimb-tangent observations are much better suited for inferring the vertical structure of an absorbing aerosol. Density rather than spectral variations are responsible for providing vertical contrast. As long as the particles are sufficiently small and absorbing, Eq. (8.3.9) can be used to infer their vertical distribution and abundance. 

Difluorophosphoric Acid. Difluorophosphoric acid (2) is a mobile, colorless Hquid. It fumes on contact with air, probably owing to HE aerosol formation. The mp of anhydrous difluorophosphoric acid has been reported to be —96.5 1°C (63) and —91.3 1°C (64). The density at 25°C is 1.583 g/mL. It partially decomposes on heating above 80—100°C. An extrapolated normal boiling point is 116°C (63) although it boils at 107—111°C... 

Elastic scattering is also the basis for Hdar, in which a laser pulse is propagated into a telescope s field of view, and the return signal is collected for detection and in some cases spectral analysis (14,196). The azimuth and elevation of the scatterers (from the orientation of the telescope), their column density (from the intensity), range (from the temporal delay), and velocity (from Doppler shifts) can be deterrnined. Such accurate, rapid three-dimensional spatial information about target species is useful in monitoring air mass movements and plume transport, and for tracking aerosols and pollutants (197). 

Airborne partieulate matter may eomprise liquid (aerosols, mists or fogs) or solids (dust, fumes). Refer to Figure 5.2. Some eauses of dust and aerosol formation are listed in Table 4.3. In either ease dispersion, by spraying or fragmentation, will result in a eonsiderable inerease in the surfaee area of the ehemieal. This inereases the reaetivity, e.g. to render some ehemieals pyrophorie, explosive or prone to spontaneous eombustion it also inereases the ease of entry into the body. The behaviour of an airborne partiele depends upon its size (e.g. equivalent diameter), shape and density. The effeet of partiele diameter on terminal settling veloeity is shown in Table 4.4. As a result ... 

The catalyst is formed by reaction of HF on SbClj. The Freons have a unique combination of properties which make them ideally suited for use as refrigerants and aerosol propellants. They have low bp, low viscosity, low surface tension and high density, and are non-toxic, non-flammable, odourless, chemically inert and thermally stable. The most commonly used is CF2CI2, bp, —29.8°. The market for Freons... 

When trying to understand and to manipulate matter and materials, chemistry does not start by looking at the natural world in all its complexity. Rather, it seeks to establish what have been termed exemplar phenomena ideal or simplified examples that are capable of investigation with the tools available at the time (Gilbert, Borrlter, Elmer, 2000). This level consists of representatiorrs of the empirical properties of solids, liquids (taken to include solutions, especially aqueous solutiorts), colloids, gases and aerosols. These properties are perceptible in chemistry laboratories and in everyday life and are therefore able to be meastrred. Examples of such properties are mass, density, concentration, pH, temperatrrre and osmotic presstrre. 

Activity Median Aerodynamic Diameter (AMAD)—The diameter of a unit-density sphere with the same terminal settling velocity in air as that of the aerosol particle whose activity is the median for the entire size distribution of the aerosol. 

Equation (1) points to a number of important particle properties. Clearly the particle diameter, by any definition, plays a role in the behavior of the particle. Two other particle properties, density and shape, are of significance. The shape becomes important if particles deviate significantly from sphericity. The majority of pharmaceutical aerosol particles exhibit a high level of rotational symmetry and consequently do not deviate substantially from spherical behavior. The notable exception is that of elongated particles, fibers, or needles, which exhibit shape factors, kp, substantially greater than 1. Density will frequently deviate from unity and must be considered in comparing aerodynamic and equivalent volume diameters. 

Inertial impaction is the method of choice for evaluating particle or droplet size delivery from pharmaceutical aerosol systems. This method lends itself readily to theoretical analysis, ft has been evaluated in general terms [39] and for specific impactors [40]. Inertial impaction employs Stokes law to determine aerodynamic diameter of particles being evaluated. This has the advantage of incorporating shape and density effects into a single term. 

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