Showing papers on "Inert gas published in 1977"

Limits on VA/Q distributions from analysis of experimental inert gas elimination.

Abstract: Distributions of ventilation-perfusion ratios (VA/Q) actually present in the lung cannot be exactly recovered using current inert gas elimination methods, principally because of the limited number of gases and errors in their measurement. The amount of information that can be gained is studied here. When six gases are used the results are difficult to visualize so that a graphical analysis is first given for only two gases. Methods are proposed for 1) the probabilistic description of retentions compatible with a set of measured values of all six gases, and 2) the placing of limits on the associated VA/Q distributions. It is found that the variability among distributions with compatible retentions depends greatly on the particular set of data. Distributions consisting of a single or of two separated narrow modes can be identified reliably.

The rate of reduction of iron oxides by carbon

Abstract: The rate of reduction of Fe2O3 and FeO by coconut charcoal, coal char and coke, in an inert atmosphere within the temperature range 900 to 1200°C was investigated. The effects of pressure, particle size, and the amount of carbon were determined. The results indicate that the reaction takes place by means of the gaseous intermediates CO and CO2, and that the overall rate is controlled by the oxidation of the carbon by CO2. The rates of reduction of FeO and Fe2O3 by CO are relatively fast, and the CO2/CO ratio for the oxidation of carbon is determined by their equilibria. The reduction of Fe2O3 by carbon is accomplished in two stages, with FeO forming first. The reduction of Fe2O3 to FeO is faster than that of FeO to Fe because its CO2/CO equilibrium ratio is higher and hence the rate of oxidation of carbon is faster. A direct comparison was made between the rate constants for the reduction of FeO by carbon and those for the oxidation of carbon in the appropriate CO2-CO gas mixtures, and they are in good agreement. Apparently the iron formed by the reduction does not significantly catalyze the oxidation of carbon; whereas for the reduction of NiO by carbon, the Ni formed does catalyze the oxidation of carbon.

Methods and apparatus for recovering solvents

Abstract: methods and apparatus for recovering hydrocarbon solvents evaporated during the curing of solvent borne coatings in an oven include supplying an inert gas to the vicinity of the oven entrance and exit to substantially exclude oxygen therefrom while safely maintaining a solvent vapor partial pressure within the oven of at least 75% of the lower explosive limit of such vapor in air. The oven atmosphere is exhausted and passed to a condenser to enable recovery of at least 85% of the solvent vapor as a liquid. Preferably, condensation of the solvent vapor is effected by heat exchange with liquid nitrogen which is effective to vaporize the liquid nitrogen to produce nitrogen gas which may then be utilized to exclude oxygen from and to inert the oven.

Molecular dynamics and chemical reactivity

Abstract: A computer simulation has been obtained of the atom recombination reaction in which the recombination energy is removed by a third-body. The equations of classical dynamics have been solved for two iodine atoms and six inert gas atoms (He, Ar or Xe) confined to a spherical vessel by a wall potential which is a spatial average of a spherical shell of inert gas atoms. Reactions at a given temperature and concentration are simulated by varying the initial momenta of the atoms and the volume of the sphere. A computer run of 100 trajectories for each physical situation gives the average time for recombination, and from this a macroscopic rate constant has been calculated that agrees well with the experimental result. The model reproduces all the characteristic kinetic mechanisms that have traditionally been used to interpret atom recombination. However, at high inert gas concentrations the steady-state approximation is shown to fail as many of the important intermediate reactions do not reach equilibrium. In t...

Low molecular weight mesophase pitch

Abstract: A low molecular weight, anisotropic pitch consisting of essentially 100 percent mesophase and suitable for spinning into continuous filaments can be prepared by passing an inert gas through an isotropic carbonaceous pitch at a rate of at least 4.0 scfh. per pound of pitch while heating the pitch at a temperature of from about 380° C. to about 430° C. to produce mesophase and simultaneously agitating the pitch so as to produce a homogeneous emulsion of the mesophase produced and the remaining non-mesophase portion of the pitch, said heating and agitation being continued until the pitch has been essentially completely converted to mesophase and the emulsion has been transformed into an essentially single phase system. When examined under polarized light, the pitches of the present invention are seen to consist of a single phase which is essentially completely anisotropic. The fibers spun from such pitch are also essentially completely anisotropic and can be further processed to produce carbon and graphite fibers having a high Young's modulus of elasticity and high tensile strength.

Low‐energy electron diffraction from inert gas overlayers

Abstract: A low‐energy‐electron‐diffraction (LEED) apparatus for investigation of physically adsorbed gases at low temperatures is described. A flat 75‐mm‐diam channel‐electron‐multiplier plate with phosphor screen permits high resolution operation of low incident beam current densities. The sample holder can be cooled by flowing helium gas and tilted for observation of the specular beam. Preliminary observations of krypton adsorbed on the basal plane of graphite are presented, including evidence for the transition from a monolayer in registry to a compressed monolayer.

Process for the wet oxidation of organic substances

Abstract: of the Disclosure A process has been developed for the oxidation of organic substances, dissolved or dispersed in an aqueous system, with a gas containing molecular oxygen at elevated temperature and under elevated pressure chiefly to carbon dioxide and water, with subsequent phase separation of the reaction mixture into a gaseous phase substantially containing inert gas, carbon dioxide, steam and organic constituents and a liquid phase substantially containing water, characterized in that the pressure is adjusted, at the given temperature, so that by evaporation of water from the aqueous system, more steam than the exotherm-icity of the oxidation reaction gives rise to,goes into the gaseous phase, which is fed to a heat exchanger in which the amount of heat required to maintain the oxidation temperature is completely or partially transferred to a mixture of water and a gas containing molecular oxygen, which mixture flows in on the other side of the heat exchanger and is subsequently fed to the reactor. A particular advantage of the process of the invention is that, in addition to the oxidation of organic substances, it is possible to fed inorganic constituents, after the oxidative degradation of the organic substances, to a re-use or recovery process.

Method and apparatus for analyzing trace components using a gas curtain

Abstract: Apparatus for analyzing trace components contained in a sample gas. The sample gas is directed into a reaction chamber and ionized. The resultant trace ions are drifted by an electric field, out of the sample gas, through an inert gas curtain and then through an orifice into a vacuum chamber where they are focused and analyzed. The curtain gas flow may be greater than the flow through the orifice, in which case the gas curtain acts as an ion window which is transparent to ions but blocks sample gas flow into the vacuum chamber. Alternatively, the curtain gas flow may be controlled to admit a desired flow of sample gas through the curtain into the vacuum chamber, in which case the gas curtain acts as a window for ions and as an infinitely variable orifice for the sample gas. Preferably the curtain gas is cryopumpable and is cryopumped by cooling the interior surface of the vaccum chamber.

Closed loop spray cooling apparatus

Abstract: A closed loop apparatus for spraying coolant against the back of a radiation target. The coolant is circulated through a closed loop with a bubble of inert gas being maintained around the spray. Mesh material is disposed between the bubble and the surface of the liquid coolant which is below the bubble at a predetermined level. In a second embodiment no inert gas is used, the bubble consisting of vapor produced when the coolant is sprayed against the target.

Carbonaceous adsorbents and process for making same

Abstract: A carbonaceous adsorbent in the form of a shaped body which has been heated to about 400 to 1400° C in an inert atmosphere is composed essentially of a mixture of finely divided carbonaceous material of a grain size below 50 and up to below 100 microns with a binder composed of about 1 to 20% by weight of a natural or synthetic elastomer and about 1 to 15% by weight of a thermoplastic material. The adsorbent is made by subjecting the mixture to a shaping step followed by heating to a temperature of about 400° to 1400° C in an inert atmosphere which step may be followed by an activation of the carbonaceous material.

The opposing physiological effects of high pressures and inert gases

Abstract: The physiological effects on mammals of elevated pressures (approximately 100 atmospheres) must be considered in the context of the inert gases breathed. The most striking effect of pressure per se is a central hyperexcitability manifest at first by trembling of the entremities and finally by convulsions. Paralysis and death occur at higher pressures. The primary effects of the inert gases breathed are inert gas narcosis and general anesthesia. The exciting effects of pressure per se and the depressive effects of the inert gases tend to oppose each other. Thus consciousness may be restored to anesthetized mice by raising the pressure, and conversely the threshold pressure that causes convulsions is elevated in the presence of anesthetics. These mutually antagonistic effects can be rationalized in terms of model which proposes that both anesthetics and pressure non-specifically perturb thelipid bilayer regions of neutral membranes. This model is termed the critical volume hypothesis. Anthesthetics dissolve in and expand these lipid bilayer regions, while pressure causes mechanical compression. Expansion leads to anesthesia and compression to convulsions if a critical degree of change is achieved. At elevated partial pressures of inert gas the gas-induced expansion is opposed by the compression of pressure per se. With very insoluble gases, such as helium, this expansion is so small that net compression results and the effects of helium differ little from those of pressure per se. With more soluble gases, such as nitrogen, net expansion results in inert gas narcosis and anesthesia. The critical volume hypothesis enables "safe" mixtures of "expanding" and "compressing" gases to be defined. These enable higher pressures to be better tolerated by mammals.

Method for preparing reduced metal catalyst having metal surface area

Abstract: This invention pertains to a method of stabilizing, with respect to atmospheric air, a bed containing pyrophoric reduced metal catalyst with high active metal surface area formed by reduction of a compound of said metal at an elevated temperature ranging from 200° to 500° C. which comprises: (a) continuously circulating through said bed a stream of inert gas while maintaining a catalyst temperature of at least 300° F. (149° C.); (b) cooling the catalyst throughout the bed with said inert gas until the catalyst in said bed attains a temperature ranging from 50° F. (10° C.) to 100° F. (38° C.); (c) decreasing the inert gas flow and progressively adding CO 2 until the CO 2 concentration in the gas stream is at least 80%; (d) adding O 2 to the gas stream to obtain about 0.05 vol % O 2 in the gas stream and continuing this flow until a sufficient amount of O 2 has passed though the catalyst bed to attain about 25% of a monolayer coverage of oxygen on the active metal surface; (e) increasing the O 2 concentration in the gas stream at a rate that will have passed enough O 2 through the catalyst bed to form about a monolayer on the active metal surface by the time the concentration reaches about 1 vol. % O 2 ; and (f) increasing the O 2 concentration and decreasing the CO 2 until said catalyst is stabilized with respect to atmospheric air, said stabilization treatments being characterized as providing a stabilized catalyst without loss of the initial metal surface area.

Elevated alveolar PCO2 relative to predicted values during normal gas exchange

Abstract: A negative aADCO2 has been demonstrated during ventilation with hypercarbic gas mixtures and during rebreathing, but has never been demonstrated during normal gas exchange. This anomalous behavior of CO2 was studied by comparing it to the behavior of five infused inert gases during normal gas exchange in 10 anesthetized mongrel dogs. The distribution of VA/Q heterogeneity and the respiratory dead space in the animals was quantitated using excretion-solubility data from the five infused inert gases. The predicted excretion fraction (PACO2/PVCO2) for CO2 was obtained from the inert gas excretion-solubility curve, using a measured solubility for CO2. The measured excretion fraction for CO2 (PACO2/PVCO2), even after correction for Haldane effect, was significantly greater than the predicted fraction (P less than 0.001). This corresponded to an alveolar PCO2 that exceeded the predicted value by a mean of 5.0 Torr.

Optical fibers having high infrared transmittancy

Abstract: Optical fibers having high infrared transmittancies are produced by chemical vapor deposition of vitreous layers composed predominantly of anions S, Se and/or Te onto tubes or rods. Cations are Ge, Si, P, B, As, Sb and/or Ti. Conventional CVD techniques are employed to produce stepped-refractive index gradient profiles in the fibers except that an inert gas and/or a halogen(s) is used as the propellant gas.

Stable solutions and processes for their preparation

Abstract: Solutions of certain hydrogenated ergopeptide alkaloids in mixtures of pharmacologically acceptable alcohols and water have improved stability. Preferred solvents are mixtures of ethanol, propylene glycol and glycerol containing from 15-40% wt. of water and having dielectric constants between 34 and 46. With these solutions it is not essential to carry out the filing operation under an inert atmosphere.

Chromatographic apparatus and method

Abstract: Apparatus and method for liquid chromatography applicable to systems employing more than one solvent for the carrier. The forming of bubbles in the pumping means employed is prevented by special pretreatment of at least one solvent of the carrier, the pretreatment involving sparging of the solvent with inert gas.

Venous gas bubbles: production by transient, deep isobaric counterdiffusion of helium against nitrogen

Abstract: When awake goats were subjected to isobaric gas switching from saturation (17 hours) on 4.7 atmospheres of nitrogen (0.3 atmosphere of oxygen) to 4.7 atmospheres of helium (0.3 atmosphere of oxygen), bubbles detected by 5-megahertz Doppler ultrasound in the posterior vena cava 20 to 60 minutes after the switch continued for 4 hours. Similar experiments carried out at 6.7 atmospheres of inert gas and 0.3 atmosphere of oxygen produced more bubbles for as long as 12 hours after the gas switch. This is believed to be the first objective demonstration of the phenomenon of deep isobaric supersaturation under transient operational diving conditions at relatively shallow diving depths. Detection of bubbles by Doppler ultrasound confirms the potential importance of the phenomenon to shallow saturation diving and holds promise for better quantitification of its effects as well as those of its counterpart, isobaric undersaturation, which can confer a decompression advantage.