Particle Deposition

Ramsden J J and Mate M 1998 Kinetics of monolayer particle deposition J. Chem. Soc. Faraday Trans. 94 783-8... 

Splelman L A and Friedlander S K 1974 Role of the electrical double layer In particle deposition by convective diffusion J. Colloid. Interfaoe. Sol. 46 22-31... 

Second, the a-particles deposit energy locally, breaking many bonds and causiag much tissue damage. 

A nonproportional sampler is suitable for near-constant flow conditions. The sample is simply drawn from the waste stream at a constant flow rate. Sampling lines should be as short as possible and free from sharp bends, which can lead to particle deposition. Proportional samplers are designed to collect either definite volumes at irregular time intervals or variable volumes at equal time intervals. Both types depend on flow rate. Examples of some of these are the vacuum and chain-driven wastewater samplers. Other types, which have cups mounted on motor driven wheels, vacuum suction samplers, and peristaltic pump samplers, are also available (26,27). 

Fig. 2. Skin of a suspension PVC grain showing 0.1-p.m dia particles deposited from the water phase.

Fiber-Bed Scrubbers Fibrous-bed structures are sometimes used as gas-liquid contactors, with cocnrrent flow of the gas and hqnid streams. In such contactors, both scrubbing (particle deposition on droplets) and filtration (particle deposition on fibers) may take place. If only mists are to be collected, small fibers may be used, but if solid particles are present, the use of fiber beds is limited by the tendency of the beds to phig. For dnst-cohectiou service, the fiber bed must be composed of coarse fibers and have a high void fraction, so as to minimize the tendency to plug. The fiber bed may be made from metal or... 

Bouncing may be regarded as a defect in the particle-deposition process. However, particles that have been deposited in filters may subsequently be blown off and reentrained into the air stream (Corn, Adhesion of Particles, in Davies, Aerosol Science, Academic, New York, 1966 and Davies, op. cit.). 

Be, and °Be. Radioisotopes of hydrogen and carbon are of particular interest because they are major biological elements, and thus can be used as both chemical and biological tracers. Recently, particle reactive Be = 53.3 day) has been utilized as a valuable coastal tracer of short-term particle deposition and remobilization. ... 

Fig. 7-2. Particle deposition as a function of particle diameter in various regions of the lung. The nasopharyngeal region consists of the nose and throat the tracheobronchial region consists of the windpipe and large airways and the pulmonary region consists of the small bronchi and the alveolar sacs. Source Task Group on Lung Dynamics, Health Phys. 12, 173 (1966).

How is particle deposition and removal from the lung influenced by the size of the particles ... 

The mass of particles deposited on the pore walls will be x dq, and the thickness of this particle layer in each pore is dr. Hence... 

For Sm, Eu, and Yb, on the other hand, nanocapsules containing carbides were not found in the cathode deposit by either TEM or XRD. To see where these elements went, the soot particles deposited on the walls of the reaction chamber was investigated for Sm. XRD of the soot produced from Sm203/C composite anodes showed the presence of oxide (Sm203) and a small amount of carbide (SmC2). TEM, on the other hand, revealed that Sm oxides were naked, while Sm carbides were embedded in flocks of amorphous carbon[12J. The size of these compound particles was in a range from 10 to 50 nm. However, no polyhedral nanocapsules encaging Sm carbides were found so far. 

Consequently, any breathing pattern which increases pulmonary residence times, such as breath-holding, increases fine particle deposition throughout the airway. 

Hygroscopic Particle Deposition Determined by Initial MMAD... 

Airstream neutralization of acid aerosols by NH3 present in the airway-lumen reduces the health risk associated with acid particles by reducing the acid concentration prior to particle deposition.- In addition, the liquid lining of the respiratory tract probably acts as a chemical buffer," further reducing the health hazard posed by inspired acid particles. Principal factors controlling airstream neutralization of acid aerosols, which is considered to be a diffusion-limited process, are particle surface area, and particle... 

The particle size is the most important factor that contributes to the clearance of particles. For particles deposited in the anterior parts of the nose, wiping and blowing are important mechanisms whereas particles on the other areas of the nose are removed with mucus. The cilia move the mucus toward the glottis where the mucus and the particles are swallowed. In the tracheobronchial area, the mucus covering the tracheobronchial tree is moved upward by the cilia beating under the mucus. This mucociliary escalator transports deposited particles and particle-filled macrophages to the pharynx, where they are also swallowed. Mucociliary clearance is rapid in healthy adults and is complete within one to two days for particles in the lower airways. Infection and inflammation due to irritation or allergic reaction can markedly impair this form of clearance. 

Resistance and arc welding operations, and plasma and laser cutting produce fumes by expulsion or evaporation of the base material, coating, and electrode wear. Larger particles deposit on the surrounding surfaces, while smaller particles move upward with convective flows. Specific contaminants associated with different welding and cutting operations are listed in AWS. ... 

Particles are present in outdoor air and are also generated indoors from a large number of sources including tobacco smoking and other combustion processes. Particle size, generally expressed in microns (10-6 m) is important because it influences the location where particles deposit in the respiratory system (U.S. Environmental Protection Agency 1995), the efficiency of particle removal by air filters, and the rate of particle removal from indoor air by deposition on surfaces. 

Diffusion—dust particles deposited on the liquid droplets. Predominant for the submicron and particles up to about 5p. 

The principal mechanisms of disposition in dust collectors are (1) gravitational deposition, (2) flow-line interception, (3) inertial deposition, (4) diffusional deposition, and (5) electrostatic deposition. During the initial operating period, particle deposition takes place mainly by inertial and flow-line interception, diffusion, and gravity. Once the dust layer has been fully established, sieving is probably the dominant deposition mechanism. 

The pores of tire separating membrane are to be most uniformly distributed and of minimum size to avoid deposition of metallic particles and thus electronic bridging. One distinguishes between macroporous and microporous separators, the latter having to show pore diameters below I micron (/urn ), i.e., below one-thousandth of a millimeter. Thus the risk of metal particle deposition and subsequent shorting is quite low, since active materials in storage batteries usually have particle diameters of several microns. 

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