Influence of Atmosphere

The specific effect of oxygen is the decisive factor in the selection of ambient atmosphere during irradiation. 

Left linear polyethylene Right branched polyethylene 

In many cases, plastics degrade in the presence of oxygen at irradiation doses that are without influence or result in crosslinking in vacuum. Because of oxidation, ultimate tensile strength and strain at break in polyethylene, polypropylene, polyvinyl chloride, polystyrene and in styrene-copolymers decrease faster with increasing doses when irradiated in air than when irradiated in a vacuum, whereas this is not the case for polyethylene terephthalate, polyvinyl alcohol, and acetyl cellulose. Oxidative degradation is also the reason for radiation damage doses that are notably smaller when irradiated in air than when irradiated in a vacuum [711], 

Plastics without oxygen in their molecular chains are always subject to strong oxidative degradation. For plastics with intramolecular oxygen (polyether, polyethylene oxide, and polyoxymethylene) the influence of external oxygen during irradiation is small. 

Intramolecular oxygen itself triggers specific degradation reactions compared to which any oxidation by external oxygen is small [711]. 

In general the characteristic temperatures obtained under oxidizing conditions are higher than the reducing counterparts. This can be traced to iron that fluxes clay minerals (aluminosilicates) in the ferrous state (Fe/FeO) much more effective than as ferric oxide (Fe203). Typical iron species show the following behavior under reducing conditions  

The numerical values especially of IDT and ST are strongly related to the iron content. If the iron content increases from 5 to 40wt% in similar bulk ash, IDT and ST can easily decrease 200 K under oxidizing and 400 K imder reducing conditions [11]. It can be stated that under reducing atmosphere, iron contents 20 wt% cause ST 1200 °C if in the bulk ash sihcates are present [10]. 

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Although neither inflammable nor self-igniting, sodium peroxide is highly inflammable when mixed with oxidi2able substances. Such mixtures bum violendy, even ia the absence of air. Tme sodium peroxocarbonates can be formed under the influence of atmospheric moisture and carbon dioxide. At temperatures >50° C and when exposed to pressure or friction, these peroxocarbonates can decompose and generate flame. 

Chapter 2 discussed the possible influence of atmospheric dispersion on vapor cloud explosion or flash fire effects. Factors such as flammable cloud size, homogeneity, and location are largely determined by the manner of flammable material released and turbulent dispersion into the atmosphere following release. Several models for calculating release and dispersion effects have been developed. Hanna and Drivas (1987) provide clear guidance on model selection for various accident scenarios. 

One of the most important properties of commercial glasses is their great resistance to corrosion any chemical laboratory apparatus, any window or windscreen provides an excellent illustration. Windows remain virtually unchanged for centuries, resisting the influences of atmosphere and radiation. A vast range of products may be safely stored in glass for decades at ordinary temperatures, and the fact that gleiss can be used with alkaline, neutral and acid environments allows the same equipment to be used for a variety of processes. 

Influence of atmospheric oxygen. At the time we started our studies, none of the other authors had satisfactorily dealt with the question of whether oxygen as well as water takes part in the POC. 

But also tetra-congeners, including tetra-furans have impact for the total TEQ. This may express the influence of atmospheric deposition within the wastewater treatment plant. At this stage of research and lack of archival samples, it was impossible to compare recent levels with historical ones, so any comments about decreasing or increasing concentrations are not justified. 

The protection of a drug substance from the destructive influences of atmospheric oxygen or humidity (such as coated tablets, sealed ampuls)... 

A problem In the analysis of these data Is the potential masking of some sources of variability by other correlated variables which may be difficult to quantify. For example, the potential meteorological Influences of atmospheric dispersion and mixing, scavenging differences between warm and cold clouds, variable rates of oxidation of sulfur and nitrogen species, and the dilution effect of variable rain volume may mask source-receptor chemical relationships. A particular problem Is that meteorological data and source-receptor locations share directional dependence. 

Poppe, D R. Koppmann, and J. Rudolph, Ozone Formation in Biomass Burning Plumes Influence of Atmospheric Dilution, Geophys. Res. Lett., 25, 3823-3826 (1998). 

Influence of atmospheric chemical composition on the rate of mass loss... 

The influence of atmospheric air on the properties of mineral materials manufactured in thermal processes is generally known. An example of the nature of this phenomenon as regards hardness, is a series of Vickers hardness tests of a material made of sintered corundum modified with 0.6% MgO sintered at 1950-2050 K in various environments. The sintering process is accelerated in the presence of hydrogen and is slowest in air thus allowing a material with optimum parameters to be obtained at a significantly lower temperature. The results, specified in Table 6.2.4, show the gases used as... 

Influence of Atmospheric Precipitation on the Operation of a Natural Draught Indirect-Contact Cooling Tower... 

The results of molecular-weight measurements on a freshly prepared solution in benzene suggest a dimeric structure (found M = 886 calcd., M = 895). In the solid state, [IrCl(C8 H14 )2 ] 2 decomposes slowly under the influence of atmospheric moisture. The compound is moderately soluble in benzene, chloroform, and carbon tetrachloride, but in general, these solutions are unstable for long periods of time. In comparison with the corresponding... 

Hodge, V, Johnson, S.R. and Goldberg, E.D. (1978) Influence of atmospherically transported aerosols on surface ocean water composition. Geochem.f., 12, 7-20. 

Gromadzinska J, Wasowicz W, Sklodowska M, et al. 1996. The influence of atmospheric chromium on selenium content and glutathione peroxidase activity in blood of tannery workers. Environ Health Perspect 104(12) 1312-1316. 

Arsenic is a frequent contaminant in metal ores (especially sulfides) and therefore appears in hydrometallurgical processes applied to these ores. Because of its toxicity, it must be efficiently removed from aqueous process streams before discharge. Traditionally this has been done with lime, but a large excess is required and the product (calcium arsenite and arsenate) can re-release some arsenic under the influence of atmospheric carbon dioxide. A more reliable process is co-precipitation with iron salts under near-neutral conditions. This requires both element ores to be in their higher oxidation states and hydrogen... 

Potassium magnesium ferrocyanide, K2MgFe(CN)6, is obtained in the anhydrous condition by mixing cold concentrated solutions of potassium ferrocyanide and magnesium chloride.3 After a short time a white micro-crystalline precipitate is formed, which is not affected by heating to 120° C. When moist the salt soon becomes cream-coloured, owing to slight decomposition, possibly under the influence of atmospheric carbon dioxide. 

Irritant Smokes ami Screcniftg Smokes.— The smokes are comparatively iMv from the influence of atmospheric temj)erature insofar as the formation of the original cloud is concenied. The cloud once formed i.v affcHTtcd in the same way as clouds of nonpersisteiit agents. 

Silicone coatings used in the construction industry are one-component silicone rubber dispersions. They cure at room temperature, vulcanisation being effected by the influence of atmospheric humidity. The process evolves various primary aliphatic amines and the solvent evaporates. 

Conventional processing equipment (mixers, granulators, roller compactors, drying equipment, and mills) can be used to produce effervescent preparations if the influence of atmospheric moisture is considered. As a rule, tablet presses have to be adapted to handle effervescent products, except for tablets with a sufficient proportion of a self-lubricating substance, such as acetylsalicylic acid. 

With the substitution of equations 37 and 39, equation 35 can now be solved for [H" ] It is probably more convenient to plot the various equilibria double logarithmically, as discussed in Sections 4.3 and 4.7. The results can be read from the graph (Figures 4.15 and 7.10). Comparing this result with that of Model lb (Figure 7.9), we see that the influence of atmospheric CO2 has depressed the pH markedly and that [Ca ] and [Aik] have been raised to values veiy representative of those in natural waters. 

Medina, B., Augagneur, S., Barbaste, M., Grousset, F.E. and Buat-Menard, P. (2000) Influence of atmospheric pollution on the lead content of wines. Food Addit. Contam., 17, 435M45. 

A comparative DTA study [86] of some 25 oxalates in Nj and in Oj has been pubhshed. The onset temperatures of dehydration and decomposition reactions are given and the influence of atmosphere upon the temperatures and products of decomposition is discussed. Variations in the surface areas of the solid products fi om decomposition of a number of oxalates have been reported by Dollimore and Nicholson [87]. 

The first attempts to model flow and transport in plant canopies that accommodated (i) the distinct microclimates of different stands of vegetation (ii) the separation of soil surface and layers of canopy as distinct sources and sinks of heat and mass and (iii) the influence of atmospheric stability or advection effects, applied gradient transfer to diffusion within the canopy space ([493]). In this procedure, a flux density is expressed as the product of a diffusion coefficient (turbuient or eddy diffusivity) and the gradient of the time average of the quantity of interest, as in the following examples ... 

Omstedt, A., Chen, D., 2001. Influence of atmospheric circulation on the maximum ice extent in the Baltic Sea. Journal of Geophysical Research, 106, 4493 4500. 

Diaminobenzidine hydrochloride (DAB), 0.5% solution in boiled and cooled water. The solution is stable for a few hours, then turns brown under the influence of atmospheric oxygen. 

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