Aerosol orientation

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). 

The DEP of numerous particle types has been studied, and many apphcations have been developed. Particles studied have included aerosols, glass, minerals, polymer molecules, hving cells, and cell organelles. Apphcations developed include filtration, orientation, sorting or separation, characterization, and levitation and materials handhng. Effects of DEP are easily exhibited, especially by large particles, and can be apphed in many useful and desirable ways. DEP effects can, however, be observed on particles ranging in size even down to the molecular level in special cases. Since thermal effects tend to disrupt DEP with molecular-sized particles, they can be controlled only under special conditions such as in molecular beams. 

L. M. Folan and S. Arnold, Determination of molecular orientation at the surface of an aerosol particle by morphology-dependent photoselection, Opt. Lett. 13, 1-3 (1988). 

Whipple, Chen, and Wang S showed that the distribution of an inhaled aerosol bolus depends on the orientation of the successive airway bifurcations and the volume of the bolus. On the basis of skewed velocity profiles, they made theoretical calculations of the distribution of aerosol boli in branching airways that were in fair agreement with the experimental data. Their results suggested that slow and shallow breaths should show greater differences in dispersion of irritant gases in the airways. 

The first ESI design at the end of the 1980s proved to work properly as the HPLC interface with mobile phase flow rates between 1 and lOpL/min. Meanwhile, the development of the HPLC instrumentation and columns was oriented in the mL/min flow rate mode. In addition, the nebulization process based only on the application of an electrical field does not produce a stable spray from aqueous mobile phases. A modified ESI source, called ionspray, was then introduced [39], in which the nebulization of a liquid solution is pneumatically assisted by a coaxial flow of nitrogen (sheath gas) that allows the formation of a stable aerosol at mobile-phase flow rates between 10 and 500 pL/ min and the use of aqueous mobile phases. When working at higher flow rates (500-1000 pL/min), an additional nittogen flow rate can be used (auxiliary gas) to assist the desolvation of the droplets. This modified source is called turboionspray. 

Urban aerosols are complicated systems composed of material from many different sources. Achieving cost-effective air particle reductions in airsheds not meeting national ambient air quality standards requires identification of major aerosol sources and quantitative determination of their contribution to particle concentrations. Quantitative source Impact assesment, however, requires either calculation of a source s impact from fundamental meteorological principles using source oriented dispersion models, or resolving source contributions with receptor models based on the measurement of characteristic chemical and physical aerosol features. Q)... 

While the source-oriented model begins with measurements at the source (i.e., emission rates for the period under study), and estimates ambient concentrations, the receptor-oriented model begins with the actual ambient measurements and estimates the source contributions to them. The receptor model relies on properties of the aerosol which are common to source and receptor and that are unique to specific source types. These properties are composition, size and variability. 

Pinnick, R. G., D. E. Carroll, and D. J. Hoffmann, 1976. Polarized light scattered from monodisperse randomly oriented nonspherical aerosol particles measurements, Appl. Opt., 15, 384-393. 

As Mitra (2004) pointed out, the Indian oceanic experiment (INDOEX) was the first complex problem-oriented observational international program aimed mainly at studies of the aerosol-induced radiative and climatic forcing of regional and global climate that take respective feedbacks into account. The preliminary stage of the accomplishment of INDOEX began in 1996-1997, and the basic part of complex observations was accomplished in 1998-1999 with the participation of specialists from different countries (India, U.S.A., Western Europe, Mauritius, and the Maldives). The obtained results were based on the use of surface, ship, aircraft, and satellite observational means. 

Fourier-transformed infrared spectroscopy (FT1R), either in the transmission mode(70), the grazing incidence reflection (GI) mode(7,5) or the attenuated total reflection (ATR) mode(7,2), has been the most widely used experimental tool for the characterization and structure determination of SA monolayers. GI-IR is especially useful in determining the molecular orientation in the film structures because it senses only the vibrational component perpendicular to the substrate surface(7,5). Polarized ATR-IR can also be used to study molecular orientation(7,77). McKeigue and Gula-ri(72) have used ATR-IR to quantitatively study the adsorption of the surfactant Aerosol-OT. 

Aerosol delivery of the precursors was chosen because it was expected that although the species were monomeric, their volatility was likely to be low based on the TGA results described earlier, and that the crown ether might dissociate on heating for extended periods. The compound Ca(SOCMe)2(15-crown-5) was dissolved in ethanol and delivered in a nitrogen gas stream to a cold-wall atmospheric pressure CVD reactor where the substrate temperature was varied between 300 and 400°C. Analysis of films deposited at 310°C revealed that crystalline CaS was deposited, approximately 100 nm thick, with a deposition rate of 10 nm/min. The X-ray powder pattern indicates that CaS was formed with preferential (200) orientation (see Fig. 63). The SEM data showed that the films comprised cubic crystallites with dimensions consistent with the linewidth of the peaks observed by X-ray diffraction. The bulk composition corresponded to CaS as determined by AES. 

Most aerosol materials will vary in their refractive index depending on the wavelength of light used, their chemical composition, and, in some cases, their orientation with respect to the light source and receptor. Since complex indices of refraction are not well established for most materials (Deirmendjian, 1969), optical models of aerosols may contain errors because of the uncertainty of these values. 

The choice of the chemical and aerosol models for using with or implementation into HIRLAM/HARMONIE depends on specific tasks (e.g. for atmospheric pollution or for improvement of NWP). Current ACTMs of HIRLAM institutes (e.g. DACFOS, EMEP, MATCH, SELAM, etc.) are problem-oriented (air quality) and not very flexible for simple modifications. In CAC and Enviro-HIRLAM different... 

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