Aerosol strength

The major effects of air pollution on fabrics are soiling and loss of tensile strength. Sulfur oxides are considered to cause the greatest loss of tensile strength. The most widely publicized example of this type of problem has been damage to women s nylon hose by air pollution, described in newspaper accounts. The mechanism is not understood, but it is postulated that fine droplets of sulfuric acid aerosol deposit on the very thin nylon... 

For the majority of applications, the sample is taken into solution and introduced into the plasma as an aerosol in the argon stream. The sample solution is pumped by a peristaltic pump at a fixed rate and converted into an aerosol by a nebulizer (see atomic absorption spectrometry). Various designs of nebulizer are in use, each having strengths and weaknesses. The reader is directed to the more specialist texts for a detailed consideration of nebulizers. There is an obvious attraction in being able to handle a solid directly, and sample volatilization methods using electric spark ablation, laser ablation and electrothermal volatilization have also been developed. 

Piston type aerosol system, 1 784 PIT (powder-in-tube) conductors, critical current density in, 23 833-834. See also PIT technique Pitch-based carbon fibers, 26 733-735 asbestos substitute, 3 314t compressive strength versus tensile modulus for, 26 742-743 Pitch-based fibers, 26 760 Pitch binders, 12 724-726 Pitchblende, 25 396-397 Pitch control, 10 304 Pitched blade turbine (PBT), 16 672 Pitches... 

A profile of methylene chloride is presented including US production capacities, demand, growth rate, price, uses, strength, weakness and outlook. Paint stripping and removal accounts for 30% of MeC by end-use application, adhesives 20%, metal cleaning 10%, aerosols 10%, pharmaceuticals 10%, chemical processing 10% and flexible PU foams 5%. Because of occupational concerns, users of MeC are under pressure to limit use, restrict... 

Strengths 1. Effective against the complete range of indoor air pollutants including organic- bio-aerosols, VOCs, odors and carbon monoxide 2. New advanced technology 3. Inexpensive material 4. Easy to manufacture. Weaknesses 1. Unable to remedy inorganic aerosols 2. Low clean air delivery rate (< 100 cfm) 3. Produces carbon dioxide. 

The aerosol solution does not require shaking. Two actuations of the 40 meg strength should provide a dose comparable to 1 actuation of the 80 meg strength. The recommended dosage relative to CFC-based beclomethasone dipropionate (CFC-BDP) inhalation aerosols is lower because of differences in delivery characteristics between the products. 

As we have seen, a great deal is known about emission sources and strengths, ambient levels, and mutagenic/carcinogenic properties of the particle-phase PAHs in airborne POM. However, because of the tremendous physical and chemical complexity of the aerosol surfaces on which photolysis, photooxidations, and gas-particle interactions take place in real polluted ambient air, much less is known about the structures, yields, and absolute rates and mechanisms of formation of PAH and PAC reaction products, especially for the more polar PACs. This is one area in which there exists a major gap in our knowledge of their atmospheric chemistry and toxicology. 

Lewis, C. W., and R. B. Zweidinger, Apportionment of Residential Indoor Aerosol VOC and Aldehyde Species to Indoor and Outdoor Sources, and Their Source Strengths, Atmos. Environ., 26A, 2179-2184 (1992). 

CF2)4 mw 200,04 chemically inert dry gas, bp —6°(760mm) high,electric strength. Can be prepd by dimerization of tetrafluoroethylene at high temp. Used for electric equipment and as aerosol proplnt for foods and pharmaceuticals... 

The active component of inhalation aerosol is beclomethasone dipropionate, an anti-inflammatory corticosteroid having the chemical name 9-chloro-ll(beta),17,21-trihy-droxy-16(beta)-methylpregna-l,4-diene-3,20-dione 17,21-dipropionate. It is a pressurized, metered-dose aerosol intended for oral inhalation only. Each unit contains a solution of beclomethasone dipropionate in propellant HFA-134a (1,1,1,2 tetrafluoroethane) and ethanol. The 40-mcg strength delivers 40 meg of beclomethasone dipropionate from the actuator and 50 meg from the valve. The... 

The study described here demonstrates that ESCA provides information regarding the chemical nature of the surface of an unperturbed sample which would be difficult to acquire by other methods. A major weakness of ESCA, the necessity of exposing the sample to vacuum, together with its attendant problem of sample volatilization, can also be one of its strengths. The volatility of some nitrogenous species in atmospheric aerosol particles can be used to provide strong evidence for chemical identity of ionic compounds (e.g., ammonium nitrate) rather than simply ionic identities as provided by wet chemical methods. This volatility is accelerated by x-ray irradiation, so that similar results could be achieved only by extended vacuum exposure alone if another analytical technique were used. Also, with ESCA, volatile losses can be conveniently monitored since the sample remains in the spectrometer throughout the process. 

We became interested in the oxidation of H2S by H202 due to the findings of Zika and co-workers (55-561 of 0.1 jiM concentrations of H202 in surface waters. The concentrations in rainwater can be higher (100 /iM) thus, peroxide may be the preferred oxidant in rainwaters and marine aerosols. To elucidate the kinetics of oxidation of H2S by we have made measurements on the effect of temperature, ionic strength and pH on the reaction (2). 

Estimating the lifetimes of MSA in the aerosol particles themselves is considerably more difficult due to the problem of estimating an OH concentration in what is essentially an add brine. A measurement of k(OH + MSA) as a function of ionic strength, possibly using NaC104 as an ionic strength adjuster, could be carried out using the procedure used in this work. 

Even relatively weak attraction between droplets or solid particles in aerosols suffices to create an enhanced collision rate that can change particle-size distributions and overall stability. Think in kT thermal-energy units. Alone, small suspended bodies do a Brownian bop, randomly jiggling from the kT kicks of the air. Should their mutually random paths bring two particles to separations comparable with their size, their van der Waals attraction energy also approaches kT. To previous randomness, attraction adds strength of purpose and increased chance of collision, aggregation, or fusion.59... 

In this study we have employed the simultaneous collection of atmospheric particles and gases followed by multielement analysis as an approach for the determination of source-receptor relationships. A number of particulate tracer elements have previously been linked to sources (e.g., V to identify oil-fired power plant emissions, Na for marine aerosols, and Pb for motor vehicle contribution). Receptor methods commonly used to assess the interregional impact of such emissions include chemical mass balances (CMBs) and factor analysis (FA), the latter often including wind trajectories. With CMBs, source-strengths are determined (1) from the relative concentrations of marker elements measured at emission sources. When enough sample analyses are available, correlation calculations from FA and knowledge of source-emission compositions may identify groups of species from a common source type and identify potential marker elements. The source composition patterns are not necessary as the elemental concentrations in each sample are normalized to the mean value of the element. Recently a hybrid receptor model was proposed by Lewis and Stevens (2) in which the dispersion, deposition, and conversion characteristics of sulfur species in power-plant emissions... 

In these discussions we will thus use the following explicit definition of a chemical measurement in the atmosphere the collection of a definable atmospheric phase as well as the determination of a specific chemical moiety with definable precision and accuracy. This definition is required since most atmospheric pollutants are not inert gaseous and aerosol species with atmospheric concentrations determined by source strength and physical dispersion processes alone. Instead they may undergo gas-phase, liquid-phase, or surface-mediated conversions (some reversible) and, in certain cases, mass transfer between phases may be kinetically limited. Analytical methods for chemical species in the atmosphere must transcend these complications from chemical transformations and microphysical processes in order to be useful adjuncts to atmospheric chemistry studies. 

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