Showing papers on "Atmospheric pressure published in 1974"

Atmospheric pressure effects on 222Rn transport across the Earth-air interface

Abstract: The effect of large-scale atmospheric pressure changes on the 222Rn flux across the soil-air interface is investigated. Field data collected during 1972 and 1973 show that pressure changes of 1–2% associated with the passage of frontal systems produce changes in the 222Rn flux from 20 to 60%, depending upon the rate of change of pressure and its duration. A simple model of molecular diffusion combined with pressure-induced transport in the soil has been confirmed by laboratory experiments using a vertical column of 226Ra-bearing sand. On the basis of this model, pressure changes of 10–20 mbar occurring over a period of 1–2 days produce Darcy velocities of the order of 10−4 cm s−1 near the surface of a soil having a permeability of 10−8 cm2. The corresponding variations in the 222Rn flux predicted by the model are in agreement with those observed from valley alluvium in central New Mexico.

Cathode spot erosion and ionization phenomena in the transition from vacuum to atmospheric pressure arcs

Abstract: Cathode properties of arcs are investigated for ambient gas pressures of 10−3−725 Torr. Copper, silver, and carbon electrodes are used in controlled ambients of either nitrogen, argon, or helium. Experimental techniques include pressure‐dependent observations of the ionized cathode vapor detected at cylindrical collectors surrounding the electrodes, arc photography, and measurements of the cathode erosion rate for copper at 100 A using the weight loss method. At pressures approaching atmospheric, it is shown that the measured erosion rate is reduced from that in vacuum by about an order of magnitude. Increasing the ambient pressure also decreases the distance from the cathode spots at which the 8% ion current can be detected. Data extrapolation shows that cathode spots at atmospheric pressure, particularly in the lighter gases, are still associated with the fundamental ion current. Comparison between the measured reductions in both the erosion rates and the ion currents indicates that vapor and ion redepo...

Field chamber measurements of co2 flux from soil surface

Abstract: Rates of carbon dioxide exchange were determined using an infrared gas analyzer in an open chamber system in a field. During 1971 a fan was used to draw air through the chamber; the measured CO2 flux was approximately 40 percent greater than the highest rate reported in the literature. In 1972 two chambers were used: one under slight suction and the other under a slight pressure (compared with atmospheric pressure). The CO2 flux from the soil surface inside the “pressure” chamber was nearly an order of magnitude lower than inside the “suction” chamber. Dispersion equations were used to separate mass flow and diffusion components of the total flux. Simplified analysis showed that mass flow could account for the large CO2 flux with slight negative pressures inside the chamber.

Thermal analysis and dilatometry of glasses formed under elevated pressure

Abstract: Densified glasses, formed from the liquid state by cooling at 5°C/hr under elevated pressures of up to 517 MN/m2, were studied by thermal analysis and dilatometry at ambient pressure. The materials studied were polystyrene, poly(methyl methacrylate), phenolphthalein, sucrose, and a 1 : 1 mixture by weight of potassium and calcium nitrate. Enthalpies of the densified glasses were found to be up to 2–6 J/g greater than the enthalpies of the glasses formed at atmospheric pressure. The major enthalpy and volume relaxation on heating the densified glasses was found to be not correlated The upper temperature limit of the glass-transition region remained constant for all glasses cooled at various pressures, while the lower temperature limit of the polymeric glasses decreased up to 55°C with increasing pressure. The interpretation of the data suggests that an additional, significant volume relaxation occurred on depressurization at room temperature for all glasses analyzed.

Air cleaning adsorption process

Abstract: A process for air cleaning by the removal of water and one or more undesirable gases such as NO x , SO x and CO 2 by a continuous atmospheric pressure and low pressure drop system wherein the adsorbent body is a wheel of thin sheets or layers of fibrous material containing about 10 to 90% by weight of a finely divided crystalline molecular sieve material. The process is especially useful for the removal of NO 2 from confined areas.

Oxygen air enrichment method

Abstract: Inlet air under pressure is supplied to a container having a bed of sorbent material wherein all gaseous air components are adsorbed in varying amounts by the sorbent material, with oxygen being the least adsorbed. Oxygen enriched air flowing from the container is stored and can be utilized at the same time for breathing purposes. Supply of the pressurized inlet air to the container is inversely controlled in accordance with pressure variations of the stored enriched air to limit production of enriched air to demand. Periodically the container is opened to the outside atmosphere, which is at a lower pressure than the inlet air pressure, and some of the stored enriched air is passed through the container to remove adsorbed gases from the sorbent bed and purge them to the outside atmosphere. The sorbent bed is thus cleansed of adsorbed gases and prepared to receive more inlet air under pressure from which gaseous components can be further adsorbed and inlet air enriched.

Climatic variations on Mars. 2. Evolution of carbon dioxide atmosphere and polar caps.

Abstract: The long-term variations in the atmospheric pressure and the polar cap temperature of Mars resulting from the obliquity oscillations (presented by W. R. Ward, 1974) are discussed. In performing these calculations, the assumption is made that the atmosphere is in equilibrium with perennial CO_2 ice deposits at the north pole, as is proposed by R. B. Leighton and B. C. Murray (1966). If heat transport by the atmosphere is neglected, the temperature of CO_2 ice at the poles ranges from ∼130°K to ∼160°K, the corresponding atmospheric pressure rising from a few tenths of a millibar to ∼30 mbar, respectively. The neglect of atmospheric heat transport probably underestimates the peak pressure. Because the altitude of the south cap is ∼2 km higher than that of the north cap, CO_2 ice is unstable there and will migrate to the north cap at a rate ∼10 g/cm^2 yr, the implication being that the south residual cap is water ice. A simplified model of the annual polar caps and pressure fluctuations is also presented. This indicates that when the obliquity is at its maximum, the annual caps may be greatly enlarged in both mass and maximum coverage. The modifications introduced by including significant atmospheric heat transport are then discussed. Finally, the implications of different past climatic conditions on the mechanism of eolian erosion are briefly considered.

Elastic Properties of Dental Resin Restorative Materials

Abstract: The elastic constants of several commercially available filled and unfilled dental resin restorative materials were determined in the 0 to 50 kilobar range of pressure. Measurements of the velocities of propagation of longitudinal and shear ultrasonic waves were used to obtain the Young's, bulk, and shear moduli and Poisson's ratio as a function of pressure; atmospheric pressure values were obtained by back extrapolation from the high pressure data.

Desiccant apparatus and method

Abstract: A process and apparatus for drying air by a continuous atmospheric pressure and low pressure drop system wherein the adsorbent body is a wheel of thin sheets or layers of fibrous material containing about 10 to 90% by weight of a finely divided crystalline molecular sieve material. The process and apparatus is especially useful for drying air for confined areas down to and less than 0.001 lbs. of moisture per pound of air.

Pressure and temperature dependences of the elastic constants of compression‐annealed pyrolytic graphite

Abstract: Changes of ultrasonic transit times in compression‐annealed pyrolytic graphite (CAPG) were measured as a function of temperature (4–300°K at atmospheric pressure) and of pressure (0–20 kbar at 295°K). From the low‐temperature results, obtained for five independent acoustic modes, the temperature variations of all five elastic constants were calculated using the thermal expansion data of Bailey and Yates. From the high‐pressure data, taken for four independent modes, the changes of all five elastic constants and of the unit cell dimensions with pressure were calculated under the assumption that the small a‐axis compressibility is independent of pressure. The initial pressure derivatives of C33 and C44 are, respectively, about 25 and 35% lower than those obtained by Green et al. for CAPG. The pressure dependences of the volume and c‐axis compressibilities are in good agreement with measurements on natural graphite crystals by Lynch and Drickamer and by Bridgman, and in less satisfactory agreement with data of Kabalkina and Vereshchagin. The results support the contention that CAPG has bulk elastic properties very similar to those of single‐crystalline graphite.

Apparatus and method for preparing and presenting serum chemistries for analyzation

Abstract: Apparatus for handling and preparing for analyzation serum chemistries composed of serum specimens and chemical reagents. Serum specimens are loaded into a plurality of specimen cups in a specimen conveyor, and chosen ones of said cups are successively pressurized by a transfer apparatus to a predetermined pressure level. The transfer apparatus has a water-filled pickup tube having one end received in the specimen in a pressurized serum cup, and the other end couplable by a vent valve to atmospheric pressure for a closely controlled time period to allow the pressure within the serum cup to cause flow of a predetermined amount of the specimen into said pickup tube. The transfer apparatus transfers the picked-up specimen to above a chemistry cup in a chemistry conveyor where the other end of the pickup tube is selectively coupled by a pressure valve to a pressurized water supply for a predetermined time period to cause deposition of a predetermined amount of picked-up specimen into the underlying chemistry cup. Each of the reagents is contained in a reagent bottle which is maintained by pressurizing means at a substantially constant pressure level. A delivery tube has one end received in the reagent and the other end couplable by a delivery valve to a position above one of the chemistry cups of the chemistry conveyor. The delivery valve is selectively operable for a predetermined time period to allow deposition of a predetermined amount of reagent into the underlying chemistry cup.

Ice particulates in the mesosphere

Abstract: The observations of noctilucent clouds, the measurements of hydrated and of large immobile ions, and the light-scattering layer detected by the OGO-6 satellite suggest the presence of particulates, probably ice, in the mesosphere. The correlation between temperature and positive ion conductivity where the vapor pressure over ice becomes greater than atmospheric pressure in the stratopause region indicates the presence of ice crystals throughout the mesosphere over a wide range of latitudes during all seasons. Between one and ten billion ice crystals per cubic meter of order 10 nanometers in diameter can dominate ionization loss processes in the mesosphere, and can explain a variety of experimental observations, including observed solar angle dependence and seasonal variability of electron density.

Atmospheric pressure pulsed HF chemical laser

Abstract: Experiments are described on a pulsed chemical laser operating on the reaction between hydrogen and fluorine at pressures above the second explosion limit. A laser energy density of 80 J/liter‐atm is obtained for a mixture of 0.1 F2/0.1 H2/0.8 He mole fraction at 1.1 atm total pressure. This performance corresponds to a chemical efficiency of 4% and an over‐all electrical efficiency of 1.3% for the particular photolysis geometry employed. Various diagnostic experiments are developed to measure the initial fraction of F2 dissociated by the photolysis, the temporal extent of the over‐all reaction, and measurements of medium homogeneity. These data together with measurements of over‐all laser performance are compared with calculations from a comprehensive theoretical model which includes the photolysis process, chemical kinetic reactions, vibrational energy transfer processes, and stimulated emission. The major features of this laser appear to be understood and described by the existing kinetic rate data. Ho...

Anode Phenomena in Vacuum and Atmospheric Pressure Arcs

Abstract: This paper summarizes recent experimental data related to anode phenomena in both vacuum and atmospheric pressure arcs. Currents in the range 10A to 3OkA are discussed, and particular emphasis is placed on the effect of plasma flow from the cathode. For vacuum arcs this plasma flow is the directed motion of metal ions from the cathode spots. These ions reduce the anode voltage drop, and maintain a diffuse anode termination. At atmospheric pressure the ion flow is impeded by gas-atom collisions. However, a plasma flow towards the anode can result from magnetic pinch forces at the constricted cathode termination. In the absence of plasma flow, the anode termination constricts to a vigorously evaporating anode spot. For a typical non-refractory electrode such as copper, the spot operates at a temperature close to the boiling point irrespective of the gas pressure. The spot temperature is dictated by the balance between electrical input power and evaporative losses. These anode phenomena are discussed in relation to vacuum switchgear, arc welding and arc furnaces.

Martian tidal pressure and wind fields obtained from the Mariner 9 infrared spectroscopy experiment

Abstract: Using temperature fields derived from the Mariner 9 infrared spectroscopy experiment, the Martian atmospheric tidal pressure and wind fields are calculated. Temperature as a function of local time, latitude, and atmospheric pressure level is obtained by secular and longitudinal averaging of the data. The resulting temperature field is approximated by a spherical harmonic expansion, retaining one symmetric and one asymmetric term for wavenumber zero and wavenumber one. Vertical averaging of the linearized momentum and continuity equations results in an inhomogeneous tidal equation for surface pressure fluctuations with the driving function related to the temperature field through the geopotential function and the hydrostatic equation. Solutions of the tidal equation show a diurnal fractional pressure amplitude approximately equal to one half of the vertically averaged diurnal fractional temperature amplitude.

Process for purification of argon from oxygen

Abstract: A process for purification of argon from oxygen comprises the step of absorption of oxygen by passing argon through synthetic zeolites of the A type with a diameter of the entry voids from 2.8 to 4.2A. Oxygen is adsorbed under a pressure of argon of 21.38-427 p.s.i.a. Then oxygen is desorbed from zeolites by reducing the pressure from 21.38-427 p.s.i.a. to atmospheric pressure with subsequent vacuum treatment of the zeolites at a pressure of 1-10 - 2 mm Hg. The steps of adsorption, desorption and vacuum treatment are carried out under thermostatic treatment of zeolites with a refrigerant so that a temperature of zeolites at the adsorption stage is maintained at -186° C to -133° C.

Effect of Pressure on the Absorption Spectra of Oriented and Amorphous Organic Films

Abstract: The absorption spectra of oriented and amorphous naphthacene and pentacene film have been measured at high pressure. The Davydov splitting of 0–0 band in oriented films increase with increasing pressure at the rate of 37 cm−1/kbar for naphthacene and 70 cm−1/kbar for pentacene. The 0–2 vibronic bands of both oriented films show the large red shifts compared with the 0–1 vibronic band. For amorphous films the Davydov splitting is not observed at atmospheric pressure. The pressure induced spectral red shifts in the amorphous state are slightly larger than those in the crystalline-state.

Carbonylation of Alcohols, Olefins, and Saturated Hydrocarbons by CO in the Ag(I)–H 2 SO 4 System

Abstract: In the presence of an Ag carbonyl-ion catalyst, prepared in situ from the Ag compound and carbon monoxide in H2SO4, olefins or alcohols reacted with carbon monoxide at room temperature and atmospheric pressure to produce exclusively tertiary carboxylic acids in high yields. The amount of Ag compound sufficient for carrying out the reaction is ca. 0.2 mol/l. The optimum reaction temperature is 0–40°C. The reaction proceeds practically at above a 90% H2SO4 concentration. Saturated hydrocarbons, containing a tertiary hydrogen, also reacted with carbon monoxide in the presence of alcohols or olefins as carbonium ion precursors, thus producing tertiary carboxylic acids.

Radiative and Electrical Properties of Exploding Silver Wires

Abstract: The radiative properties of silver wires exploded by capacitive discharge are studied using time-integrated and time-resolved spectroscopy. Discharge current measurements are obtained from a calibrated current shunt and are correlated with time-resolved spectra to obtain a model for the current conduction processes during wire explosions. Two basic explosion mechanisms are described, both of which begin with the conversion of the wire from a conducting solid to a rapidly expanding dielectric cylinder of metal vapor. This results in a rapid reduction of discharge current. Current then may resume in one of two ways. In He at atmospheric and reduced pressure and in air at reduced pressure dielectric breakdown of the gas surrounding the wire occurs with current conduction peripheral to the expanding metal vapor cylinder. In air at atmospheric pressure, dielectric breakdown occurs through the metal vapor. This results in current conduction along the vapor cylinder axis. The advantages of peripheral current conduction for the analysis of metals electroplated on the surface of silver wires are discussed. Parametric studies with Cd-plated silver wires indicate that the intensity of the background continuum can be reduced by nearly 2 orders of magnitude with little effect on Cd line intensities by reducing the pressure from 730 Torr to 50 Torr in He where peripheral current conduction occurs.

Photographic photosensitive element and developing method thereof

Abstract: A silver halide photographic photosensitive element having a hydrophilic colloidal layer prepared by dispersing photographic additives in a fatty oil which is liquid at room temperature; which boils at temperatures higher than 250°C under atmospheric pressure; which is soluble in water in a proportion of less than about 10% by weight at 25°C; and which dissolves water in a proportion of less than about 5% by weight at 25°C, and a developing method thereof.