Gaseous environments

The two inert gases used in anaerobic gas-solid fluidized bed fermenters are carbon dioxide (Moebus and Teuber, 1982a) and nitrogen (Rottenbacher, 1985). The former found that the addition of air at the beginning of the run substantially increased carbon dioxide production compared to a bed run under pure carbon dioxide. An identical bed operated under strict anaerobiosis appeared to ferment glucose 

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Highly protective layers can also fonn in gaseous environments at ambient temperatures by a redox reaction similar to that in an aqueous electrolyte, i.e. by oxygen reduction combined with metal oxidation. The thickness of spontaneously fonned oxide films is typically in the range of 1-3 nm, i.e., of similar thickness to electrochemical passive films. Substantially thicker anodic films can be fonned on so-called valve metals (Ti, Ta, Zr,. ..), which allow the application of anodizing potentials (high electric fields) without dielectric breakdown. 

Thermal ionization. Takes place when an atom or molecule interacts with a heated surface or is in a gaseous environment at high temperatures. Examples of the latter include a capillary arc plasma, a microwave plasma, or an inductively coupled plasma. 

Impurities that can negatively affect the physical and electrical properties of the metallisation layer can originate from several sources, particularly the deposition source and the gaseous environment. Impurities stemming from the source bombard the surface of the growing film and get trapped in the metal layer. 

By far the largest proportion of gas sampling operations in industry is carried out for environmental reasons and the sampling methods employed have been thoroughly researched and are well documented (5—12). The preparation, precautions and equipment requirements involved in the sampling of air pollution sources are appHcable to most other gaseous environments (see Airpollution control methods). 

Flame retardants (qv) are incorporated into the formulations in amounts necessary to satisfy existing requirements. Reactive-type diols, such as A/ A/-bis(2-hydroxyethyl)aminomethylphosphonate (Fyrol 6), are preferred, but nonreactive phosphates (Fyrol CEF, Fyrol PCF) are also used. Often, the necessary results are achieved using mineral fillers, such as alumina trihydrate or melamine. Melamine melts away from the flame and forms both a nonflammable gaseous environment and a molten barrier that helps to isolate the combustible polyurethane foam from the flame. Alumina trihydrate releases water of hydration to cool the flame, forming a noncombustible inorganic protective char at the flame front. Flame-resistant upholstery fabric or liners are also used (27). 

The stmcture of residual char particles after devolatilization depends on the nature of the coal and the pyrolysis conditions such as heating rate, peak temperature, soak time at the peak temperature, gaseous environment, and the pressure of the system (72). The oxidation rate of the chat is primarily influenced by the physical and chemical nature of the chat, the rate of diffusion and the nature of the reactant and product gases, and the temperature and pressure of the operating system. The physical and chemical characteristics that influence the rate of oxidation ate chemical stmctural variations, such as the... 

Corrosion products formed as thin layers on metal surfaces in either aqueous or gaseous environments, and the nature and stability of passive and protective films on metals and alloys, have also been major areas of XPS application. XPS has been used in two ways, one in which materials corroded or passivated in the natural environment are analyzed, and another in which well-characterized, usually pure metal surfaces are studied after exposure to controlled conditions. 

In most processes of coal conversion the corrosive action of the gaseous environment may be aggravated to some degree by the erosive action of the entrained solids, the ashes or partly-burned fuel termed char. 

It has been established that salts can deposit or form on metals during gas-metal reactions. Molten layers could then develop at high operating temperatures. Consequently, the laboratory testing of corrosion resistance in molten salts could yield valuable results for evaluating resistance to some high-temperature gaseous environments. 

The ER system has been used successfully in a range of industries for process plant monitoring. As ER can be applied in any liquid or gaseous environment the areas of application are considerable. However, there is a problem with ER if a conductive corrosion product is produced as is the case with sour crude oil or gas due to the deposition of iron sulphide. 

Erosion-corrosion the wastage of a material caused by the conjoint action of erosion and corrosion by a liquid or gaseous environment, with or without solid particles. 

Life originated in an aqueous environment enzyme reactions, cellular and subcellular processes, and so forth have therefore evolved to work in this milieu. Since mammals live in a gaseous environment, how is the aqueous state maintained Membranes accomplish this by internalizing and compartmentalizing body water. 

Weaver MJ. 2002. Surface-enhanced Raman spectroscopy as a versatile in situ probe of chemisorption in catalytic electrochemical and gaseous environments. J Raman Spectrosc 33 309. 

An individual automated device within a fully automated assay system that usually performs a complete single assay step or procedure. A fully enclosed MODULE may allow for the control of temperature, humidity, and the gaseous environment. 

Conductive sample coatings are not needed because the gas molecules in the chamber replenish electrons on the sample surface to prevent charging. Direct observation of either wet or dry specimens is possible based on the continuously variable specimen environment. The instrument accommodates a micromanipulator, heatable stage, and gaseous environment. Energy dispersive x-ray (EDX) units can also be added to the sample chamber for elemental analysis. Samples can be analyzed in their natural state, at elevated relative humidities, elevated temperatures, and in various gas environments (including 100% relative humidity). 

DEPTH PROFILE. The secondary electrons produced by ionization processes from an incident beam of high-energy electrons are randomly directed in space. Spatial "equilibrium" is achieved only after a minimum distance from the surface of a polymer in contact with a vacuum or gaseous environment (of much lower density). Consequently, the absorbed radiation dose increases to a maximum at a distance from the surface (2 mm for 1 MeV electrons) which depends on the energy of the electrons. The energy deposition then decreases towards zero at a limiting penetration depth. 

The resistivities of typical cell components at 1000°C (1832°F) under fuel cell gaseous environments are (6) 10 ohm cm (ionic) for the electrolyte (8-10 mol% Y2O3 doped Z1O2),... 

Carbon dioxide, CO2, is a typical component of the gaseous environment for reactions in air or in the presence of air traces. Therefore, both interactions between CO2 and organic ion-radicals as well as reactions of 62 with uncharged molecules of organic compounds should be considered. Interaction of CO2 with organic anion-radicals leads, as a rule, to carboxylic acids COj" anion-radicals are not formed. Even such a one-electron reductant as the superoxide ion (in aprotic medium) simply adds to carbon dioxide CO2 + O2 -> 00-C02. The additional product accepts an electron ... 

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