Showing papers on "Deposition (chemistry) published in 1972"

Dispersion and Deposition of Corn Pollen from Experimental Sources1

Abstract: The atmospheric dispersion and subsequent deposition of corn (Zea mays L.) pollen emitted from plants in two 18-m diameter plots were studied in 39 tests at Brookhaven National Laboratory to compare the spread of this large pollen to that of smaller pollens studied previously. Concentrations were measured by wind-impaction samplers mounted at four heights (0.5 to 4.6 m) and at five distances from the source on 20-degree radii. Deposition was measured by greased microscope slides on the ground. Data were analyzed in terms of current meteorological dispersion theory. Normalized centerline concentrations, crosswind integrated concentrations, plume widths and heights, and mass flux are presented as functions of distance and compared to similar data from ragweed (Ambrosia) and timothy (Phleum pratense) sources of comparable size. Normalized centerline and crosswind integrated deposition and velocity of deposition are also presented as functions of distance and are compared to ragweed and timothy pollen data. The study shows that corn pollen is not transported as far by the wind as smaller pollens, does not disperse as widely in either the horizontal or the vertical direction and settles to earth more quickly, much of it within the source itself. The dispersion of corn pollen is influenced by its large size and rapid settling rate. At 60 m from the source in the downwind direction, concentrations average about 1% of those at 1 m. Width of the pollen plume at 60 m is less than that of smaller pollens under similar conditions. The rate of settling opposes the rate of upward dispersion so that the height of the pollen plume does not increase continuously with downwind distance. At 60 m from the source concentrations integrated in the crosswind direction average from 3 to 6% of those at 1 m. The total amount of pollen remaining airborne at 60 m is 5% of that at 1 m. Total deposition within the source plot is greater than that outside. Deposition per unit area at 60 m downwind is only 0.2% of that near the source. Crosswind integrated deposition at 60 m varies from 0.5 to 0.8% of that at 1 m. The velocity of deposition at 32 m from the source averages about 33 cm/sec.

Diffusion deposition of small-sized particles in the bronchial tree.

Abstract: The deposition pattern of radioactive aerosols (AMD = 0.2–0.4 μm) has been studied in a plastic model of the upper bronchial tree, whose geometry corresponded with the dichotomous lung model of WEIBEL. The deposition probabilities w in the different bronchial regions for inspiration and expiration were measured as function of air-flow rate v in the range of 0.1–50 l./min. In addition radioautographs were prepared to study the fine structure of the deposition pattern. The measured w-values can be approximated by the relation w = k, a−n (n > 0), where k is a characteristic factor for each generation and nearly equal for inspiration and expiration. The slope-coefficient n amounts to 0.65 ± 0.07 for all bronchial generations. The results indicate that deposition due to turbulent diffusion plays an important role in the trachea and larger bronchi. With increasing depth in the bronchial tree, however, the measured ra-values approach the theoretical values, calculated with the theory of Gormley et al. for diffusion in a laminar air stream.

Nearshore Glacial-Marine Deposition from Modern Sediments of the Weddell Sea

Abstract: STUDY of modern deposits collected during the 1968, 69 and 70 International Weddell Sea Oceanographic Expeditions has shown that contrasting glacial and oceanographic conditions are reflected in the present sedimentologic and faunal distributions. There is evidence that both dry-base (freezing) and wet-base (thawing) ice shelves presently exist in the Weddell Sea. Saline shelf waters believed to be formed by a freezing Ronne Ice Shelf (Fig. 1) comprise the dominant water mass of the southwestern continental shelf. At the southwestern continental slope these dense shelf waters mix with warm deep waters to form Antarctic Bottom Water1.

Intensity of deposition from avalanches and the loose packing of avalanche deposits

Abstract: An avalanche of granular solids deposits grains once its snout is arrested at the base of the surface of avalanching. During deposition the avalanche behaves as a settling column of dispersed particles; the surface of deposition within the column is marked by a distinct shadow, or continuity wave, which swiftly climbs the sliding mass. Empirically, the high intensities of deposition expected from avalanches behaving in this manner correspond to degrees of packing in the deposits that are very nearly the loosest possible for natural materials. This appears to explain why cross-stratified sediments have low strengths and are readily deformed.

Deposition of erucic acid in rat tissue lipids.

Abstract: The effects of diets containing olive oil, corn oil-ethyl erucate (1:5), rapeseed oil (B. campestris) or zero-erucic rapeseed oil (var. Canbra) on the tissue fatt

Influence of Deposition Temperature on Composition and Growth Rate of GaAsx P1−x Layers

Abstract: Epitaxial layers of GaAsxP1−x alloys were deposited in an open‐tube vapor‐transport apparatus It was found that the growth rate and the composition of the deposited alloy strongly depend on the deposition temperature Higher deposition temperatures lead to an increase in the P content of the alloy The growth rate reached a maximum at 830°C and then decreased with further decrease in the deposition temperature, contrary to expectations based on the thermodynamics of the growth system A time‐of‐flight mass spectrometer was coupled to the growth system, and the composition and the chemical reactivity of the vapor species was studied The results of these studies offer an explanation for the observed dependence of the composition of the deposited alloy on the deposition temperature

A Mississippian echinoderm site in Alabama

Abstract: In situ fauna, abundance and diversity, conditions of deposition, Monteagle Limestone, Weatherly Mountain region

Method of producing metallized thermoplastic articles

Abstract: Heating metallised thermoplastic, particularly polyethylene terephthalate film, either before or after deposition of the metal coating.

A Random-Walk Simulation Model of Alluvial-Fan Deposition

Abstract: A digital model based on a random walk is used in an experiment to determine how well such a model is able to simulate alluvial-fan deposition. The model is three dimensional, and is dynamic with respect to both time and space. Two principal stochastic events are employed: (1) a relative uplift of the mountain area that is the source of the fan sediments, and (2) a storm event of sufficient magnitude to result in the deposition of material on the fan. These two events are assumed to follow independent Poisson processes with exponentially distributed interoccurrence times. The pattern of deposition is determined by a random walk from the canyon mouth at the mountain front, and each depositional event is assumed to occur instantaneously. The direction that each step in the walk takes is determined probabilistically by the gradient in the direction of flow, the momentum of flow, and the boundary conditions stipulated in the model. The type of flow — whether a debris flow, water flow, or eroding water flow — depends upon the thickness of erodible material in the basin. Deposition is assumed to occur over the entire length of the channel as a bad tapered in the direction of flow. Grain size of the water-flow deposits is governed by slope and velocity. Erosion is considered negative deposition and results from the exponential decline in elevation of the main stream channel at the fan apex or from water flows containing little basin sediment. Results of the simulation are printed as geologic and topographic maps of the fan surface and as geologic sections through the deposits.

Transport and Deposition of SiO2 with H2O under Supercritical Conditions

Abstract: Transport and deposition of silica in different forms: quartz, chalcedony, cristobalite, tridymite and hyalite were investigated between 400-800°C and 200 to 2000 bar. The conditions of formation of the forms are discussed. The crystallization of quartz whiskers is reported and ideas of the formation of hyalite are given. Conclusions are drawn to natural occurences. Transport und Abscheidung von SiO2 in seinen verschiedenen Formen: Quarz, Chalzedon, Cristobalit, Tridymit und Hyalit wurden zwischen 400-800°C bei 200-2000 bar untersucht. Es werden die Bildungsbedingungen fur die verschiedenen Formen diskutiert. Dabei wird auch uber die Bildung von Quarz-Whiskern berichtet, sowie eine Vorstellung uber die Entstehung und die Struktur von Hyalit entwickelt. Beziehungen zu entsprechenden SiO2-Vorkommen in der Natur werden hergestellt.

On the Deposition of Acroal Particles to the Horisontal Pipe Wall from Turbulent Stream

Abstract: 従来なされなかった乱流下での水平円管, 管壁への粒子沈着に関して, 重力および慣性力が大となるタングステン, 亜鉛両粒子を用いて実験を行ない, 重力, 乱流拡散, 管径, 角度などが粒子沈着速度に及ぼす影響をたしかめた。理論的には, 従来垂直管のみにしか適用できなかったFriedlanderらの理論式に重力を加味して全ての場合に適用できる沈着速度式を提出し, 実験とかなりよい一致をみた。さらに, 水平管によるサンプリングの際のサンプリング誤差を最小とする条件の存在を理論的にたしかめるとともに, その関係式を提出した

An Electrodeposited Bright Tin-Cobalt Intermetallic Compound, CoSn

Abstract: The cobalt analogue of electrodeposited NiSn (BS 3597:1963) was plated from an acid fluoride bath. Tin deposition had to be hindered more than necessary in tin-nickel baths. The Co alloy was fine-g...