RESPIRATORY MOVEMENTS AND ENDURANCE OF FROGS AT LOW PRESSURES

1957 ◽  
Vol 35 (5) ◽  
pp. 593-601
Author(s):  
James C. Hall ◽  
Helen I. Battle
Keyword(s):  
Atmospheric Pressure ◽  
Prolonged Exposure ◽  
Low Pressure ◽  
Reduced Pressure ◽  
Lung Inflation ◽  
Initial Effect ◽  
Advanced Stages ◽  
Normal Atmospheric Pressure ◽  
Low Pressures ◽  
Respiratory Movements

Exposure of three species of frogs (Rana pipiens, R. clamitans, and R. sylvatica) to pressures of 1.5, 3.0, and 5.0 cm. Hg induces characteristic changes in the frequency and type of breathing. The immediate initial effect is that of increasing both mouth and lung oscillations for a brief period, prior to a gradual decline in rate. Lung oscillations persist longer than mouth oscillations, and on return to normal atmospheric pressure, are initiated earlier and at a rapid rate. During advanced stages of decompression, excess lung inflation is resultant from several consecutive inhalations, prior to a deep exhalation. R. pipiens is most resistant to low pressure, and R. sylvatica least resistant. Large individuals of a species survive longer than small. Survival is better with little oxygen in an atmosphere of nitrogen at normal atmospheric pressure than with a comparable oxygen supply at a reduced pressure. A brief acclimatization to pressures of 1.5 and 3.0 cm. Hg can be produced by prolonged exposure to 15 cm. Hg but not by intermittent exposures to low pressure.

scholarly journals The influence of pressure on the boiling points of metals

1910 ◽  
Vol 83 (565) ◽  
pp. 483-491 ◽  
Keyword(s):  
Atmospheric Pressure ◽  
Boiling Point ◽  
High Vacuum ◽  
Similar Type ◽  
Exact Relation ◽  
Reduced Pressure ◽  
Boiling Points ◽  
Experimental Values ◽  
Low Pressures ◽  
Very High

Part I. — Pressures below 760 mm . In a previous communication (‘Proc.’, A, vol. 82, 1909, p. 396) the approximate boiling points of a number of metals were determined at atmospheric pressure. Apart from the question of finding the exact relation between the boiling point and pressure, it is an important criterion of any method for fixing the temperatures of ebullition to demonstrate that the experimental values obtained are dependent on the pressure. It is specially desirable when dealing with substances boiling at temperatures above 2000° to have some evidence that the points indicated are true boiling points. Previous work on the vaporisation of metals at different pressures has been confined to experiments in a very high vacuum except for metals like bismuth, cadmium, and zinc, which boil at relatively low temperatures under atmospheric pressure. The observations were limited to very low pressures on account of the difficulty of obtaining any material capable of withstanding a vacuum at temperatures over 1400° and the consequent necessity for keeping the boiling point below this limit by using very low pressures. Moreover in the case of the majority of the metals, e. g. , copper, tin, ebullition under reduced pressure has never been observed. The difficulties indicated above were avoided by using a similar type of apparatus to that previously described, and arranging the whole furnace inside a vacuum enclosure, thus permitting of the use of graphite crucibles to contain the metal.

An improved system for prolonged exposure of small animals to artificial low pressures

1965 ◽  
Vol 20 (4) ◽  
pp. 742-744 ◽  
Author(s):  
James Kollias ◽  
John Patrick Jordan
Keyword(s):  
High Altitude ◽  
Environmental Temperature ◽  
Prolonged Exposure ◽  
Pressure Control ◽  
Low Pressure ◽  
High Oxygen ◽  
Small Animals ◽  
Oxygen Environment ◽  
Artificial Environment ◽  
Low Pressures

A system has been developed for exposing small animals to a low pressure-high oxygen environment. Several unique features such as 1) pressure control, 2) an electronic watering device, and 3) a constant environmental temperature are discussed. artificial environment; high altitude; high oxygen; watering device Submitted on July 24, 1964

scholarly journals Exploring the Low-Pressure Growth Limit: Evolution of Bacillus subtilis in the Laboratory to Enhanced Growth at 5 Kilopascals

2010 ◽  
Vol 76 (22) ◽  
pp. 7559-7565 ◽  
Author(s):  
Wayne L. Nicholson ◽  
Patricia Fajardo-Cavazos ◽  
Jeffrey Fedenko ◽  
José L. Ortíz-Lugo ◽  
Andrea Rivas-Castillo ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Growth Inhibition ◽  
Atmospheric Pressure ◽  
Low Pressure ◽  
Stepwise Increase ◽  
Normal Atmospheric Pressure ◽  
Preliminary Study ◽  
Growth Limit ◽  
Ancestral Strain

ABSTRACT Growth of Bacillus subtilis cells, normally adapted at Earth-normal atmospheric pressure (∼101.3 kPa), was progressively inhibited by lowering of pressure in liquid LB medium until growth essentially ceased at 2.5 kPa. Growth inhibition was immediately reversible upon return to 101.3 kPa, albeit at a slower rate. A population of B. subtilis cells was cultivated at the near-inhibitory pressure of 5 kPa for 1,000 generations, where a stepwise increase in growth was observed, as measured by the turbidity of 24-h cultures. An isolate from the 1,000-generation population was obtained that showed an increase in fitness at 5 kPa when compared to the ancestral strain or a strain obtained from a parallel population that evolved for 1,000 generations at 101.3 kPa. The results from this preliminary study have implications for understanding the ability of terrestrial microbes to grow in low-pressure environments such as Mars.

Epitaxial Silicon Layers Made by Reduced Pressure/Temperature CVD

1988 ◽  
Vol 129 ◽  
Author(s):  
J.L. Regolini ◽  
D. Bensahel ◽  
J. Mercier ◽  
C. D'Anterroches ◽  
A. Perio
Keyword(s):  
Thermal Processing ◽  
Atmospheric Pressure ◽  
Rapid Thermal Processing ◽  
Processing System ◽  
Epitaxial Silicon ◽  
Reduced Pressure ◽  
Selective Epitaxial Growth ◽  
Main Decomposition ◽  
Rate Limiting ◽  
Reactive Gas

ABSTRACTIn a rapid thermal processing system working at a total pressure of a few Torr, we have obtained selective epitaxial growth of silicon at temperatures as low as 650°C. When using SiH2Cl2 (DCS) as the reactive gas, no addition of HCl is needed. Nevertheless, using SiH4 below 950°C a small amount of HCl should be added.Some kinetic aspects of the two systems, DCS/HCI/H2 and SiH4/HCl/H2, are presented and discussed. For the DCS system, we show that the rate-limiting reactions are slightly different from those commonly accepted in the literature, where the results are from systems working at atmospheric pressure or in the 20-100 Torr range.Our model is based on the main decomposition of DCS, SiH2Cl→SiHCl + HCl, instead of the widely accepted reaction SiH2Cl2→SiCl2 + H2. This is the main reason why no extra HCl is required in the DCS/H2 system to obtain full selectivity from above 1000°C down to 650°C.

scholarly journals Static and Motional Feedthrough Capacitance of Flexural Microresonator

2011 ◽  
Vol 2011 ◽  
pp. 1-6
Author(s):  
Wen-Teng Chang
Keyword(s):  
Silicon Carbide ◽  
Atmospheric Pressure ◽  
Network Analyzer ◽  
Reduced Pressure ◽  
Flexural Mode ◽  
Microelectromechanical System ◽  
Order Of Magnitude ◽  
Bode Plots

The present paper evaluates the static and motional feedthrough capacitance of a silicon carbide-based flexural-mode microelectromechanical system resonator. The static feedthrough capacitance was measured by a network analyzer under atmospheric pressure. The motional feedthrough was obtained by introducing various values into the modeling circuit in order to fit the Bode plots measured under reduced pressure. The static feedthrough capacitance was 0.02 pF, whereas the motional feedthrough capacitance of an identical device was about 0.2 pF, which is one order of magnitude larger than the static feedthrough capacitance.

scholarly journals The rate of evaporation of droplets. Evaporation and diffusion coefficients, and vapour pressures of dibutyl phthalate and butyl stearate

1946 ◽  
Vol 186 (1006) ◽  
pp. 368-390 ◽  
Keyword(s):  
Diffusion Coefficients ◽  
Atmospheric Pressure ◽  
Dibutyl Phthalate ◽  
Droplet Evaporation ◽  
Medium Size ◽  
Good Accordance ◽  
Butyl Stearate ◽  
Rate Of Evaporation ◽  
Low Pressures ◽  
And Diffusion

The rate of evaporation of drops of dibutyl phthalate and butyl stearate of radius approx. 0.5 mm. has been studied by means of a microbalance over a range of atmospheric pressures down to approx. 0*1 mm. of mercury. Wide departures from Langmuir’s evaporation formula were found to occur at these low pressures, but results are in good accordance with the theory of droplet evaporation advanced by Fuchs which hitherto has not been tested experimentally. This experimental verification of Fuch’s theory for droplets of medium size evaporating at low pressures shows that the theory can be applied to the evaporation of very small drops at atmospheric pressure. The vapour pressures of the above liquids have been measured by Knudsen’s method and the evaporation and diffusion coefficients calculated fro n the experimental data.

Development of a New Design Method for High Efficiency Swept Low Pressure Axial Fans With Small Hub/Tip Ratio

2014 ◽  
Author(s):  
Thore Bastian Lindemann ◽  
Jens Friedrichs ◽  
Udo Stark
Keyword(s):  
High Efficiency ◽  
Design Method ◽  
Tangential Velocity ◽  
Pressure Rise ◽  
Low Pressure ◽  
Aerodynamic Performance ◽  
Low Noise ◽  
Angle Distribution ◽  
Sweep Angle ◽  
Reduced Pressure

For a competitive low pressure axial fan design low noise emission is as important as high efficiency. In this paper a new design method for low pressure fans with a small hub to tip ratio including blade sweep is introduced and discussed based on experimental investigations. Basis is an empirical axial and tangential velocity distribution at the rotor outlet combined with a distinctive sweep angle distribution along the stacking line. Several fans were designed, built and tested in order to analyze the aerodynamic as well as the aeroacoustic behavior. For the aerodynamic performance particular attention was paid to compensate the influence of reduced pressure rise and efficiency due to increasing blade sweep. This was achieved by a method of increasing the blade chord depending on the local sweep angle which is based on single airfoil data. The tested fans without this compensation revealed a significant noise reduction effect of up to approx. 6 dB(A) for a tip sweep angle of 64° which was accompanied by an unsatisfactory effect of reduced overall aerodynamic performance. The second group of fans did not only confirm the method of the aerodynamic compensation by a nearly unchanged pressure rise and efficiency characteristic but also revealed an increased aeroacoustic benefit of in average 9.5 dB(A) compared to the unswept version. Beside the overall characteristics the individual differences between the designs are also discussed using results of wall pressure measurements which show some significant changes of the blade tip flow structure.

Large Cryogenic Storage of Hydrogen in Carbon Nanotubes at Low Pressures

2001 ◽  
Vol 706 ◽  
Author(s):  
B. K. Pradhan ◽  
A. Harutyunyan ◽  
D. Stojkovic ◽  
P. Zhang ◽  
M. W. Cole ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Zero Point ◽  
Isosteric Heat ◽  
Low Pressure ◽  
Quantum Mechanical ◽  
Strong Adsorption ◽  
Point Motion ◽  
Post Synthesis ◽  
Walled Carbon Nanotubes ◽  
Low Pressures

AbstractWe report (6 wt %) storage of H2 at T=77 K in processed bundles of single-walled carbon nanotubes at P=2 atmospheres. The hydrogen storage isotherms are completely reversible. D2 isotherms confirm this anomalous low-pressure adsorption and further reveal the effects of quantum mechanical zero point motion. We propose that our post-synthesis treatment of the sample not only improves access for hydrogen to the central pores within individual nanotubes, but also may create a roughened tube surface with an enhanced binding energy for hydrogen. Such an enhancement is needed to understand the strong adsorption at low pressure. We obtain an experimental isosteric heat qst=125 ± 5 meV for processed SWNT materials.

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