Logarithm Of Pressure Research Articles

Shift in the chemical equilibrium of the LaCo 5H system by strong magnetic fields

The equilibrium hydrogen pressure in the β+γ region of the LaCo 5-H system has been observed under the influence of magnetic fields up to 14 T. The logarithmic pressure change, In( P H/ P 0), is 0.19 in 14 T. This corresponds to a 21% change in the equilibrium constant.

Nitridation of polycrystalline titanium as studied by in situ angle‐resolved x‐ray photoelectron spectroscopy

AbstractNitridation of polycrystalline titanium was investigated in situ at about 550°C by angle‐resolved x‐ray photoelectron spectroscopy (XPS). The nitrogen pressure was varied from 10−4mbar to 1 mbar. The distribution of nitrogen in the titanium and the chemical bonding present were deduced from XPS measurements. Titanium nitridation passes through several stages as a function of the nitrogen exposure. The nitrogen concentration varies linearly with the logarithm of pressure and dose. Using the modified Ritchie‐Hund theory it was shown that the kinetics of titanium nitridation follows a cubic law.

Field-effect transistor using a solid electrolyte as a new oxygen sensor

A field-effect transistor (FET) using a solid electrolyte is proposed in the present study as a new oxygen sensor. The sensor is fabricated by depositing a thin layer of yttria-stabilized zirconia (YSZ) on a gate insulator of an insulated gate field-effect transistor (IGFET). As an IGFET has an ability to transform impedance, the potential change produced at the interface between the YSZ layer and a platinum gate electrode can be detected stably, even if the impedance of the YSZ is very high. The response of the fabricated sensor showed good reproducibility at 20 °C. A linear relationship between output voltage and logarithmic partial pressure of oxygen was obtained in the range from 0.01 to 1 atm. Sensitivity of the sensor was found to depend on the thickness of the Pt-gate electrode and sputtering conditions of the YSZ layer. Although selectivity to hydrogen and carbon monoxide was not good at room temperature, it could be improved by increasing the operating temperature to 100 °C. The developed sensor has several advantages including small size, low output impedance, and solid-state construction. It is potentially applicable to medical uses, process control, and automobiles.

Effect of a strong magnetic field on the chemical equilibrium of the ferromagnetic hydride-hydrogen system

The hydrogen pressure of the ferromagnetic SmCo 5H x and LaCo 5H x systems has been measured as a function of magnetic fields up to 7 T. Magnetic fields cause considerable rises in the pressure. The logarithmic pressure change, ln( P H/ P 0), in the β + γ region of LaCo 5H x is 0.095 in 7 T at room temperature.

Pressure dependence of the electric field gradient at Cd impurities in antimony

The electric field gradient at111Cd in Antimony was studied at hydrostatic pressures up to 7 kbar at 150 K, 293 K and 473 K. The logarithmic pressure derivatives, dlnq/dP, were found to be −67, −37 and −26 Mbar−1 respectively. The isotropic volume dependence derived from these values was found to be positive and largely responsible for the anomalous temperature dependence, previously observed.

Evaluation of an index of peripheral vascular resistance in human subjects.

Based on evidence in animal studies, an index of resistance in man has been evaluated. In 10 human subjects, ranging in age from 31 to 60 years, direct brachial arterial pressure was measured, and a computer program using linear regression calculated the index of resistance from the slope of the logarithm of the pressure versus time during the second half of diastole. Resistance was independently calculated from 20-s averages of pressure and cardiac output obtained by thermodilution. Resistance was varied by infusion of phenylephrine and nitroprusside. The values of the index of resistance were compared with independently calculated resistance by linear regression and correlation. The index of resistance was variably correlated with independently calculated resistance. However, when the comparison was limited to points with a model correlation coefficient greater than or equal to 0.98 (i.e. a good fit of a straight line to the logarithm of pressure versus time), the correlation of the index of resistance with calculated resistance approached or exceeded 0.9 in eight of 10 subjects. In the two subjects showing poor correlation of the index with calculated resistance, estimated compliance from the same model was much lower than in the other subjects. In the same two subjects pressure dependence of estimated compliance was much higher than in the other subjects, suggesting the presence of significant atherosclerosis. We concluded that the diastolic decay of pressure may be used to calculate a useful index of resistance, provided that a single exponential decay fits the observed diastolic waveform well, and arterial compliance is not significantly reduced by atherosclerosis.

Thermal conductivity of B2O3 glass under pressure

The thermal conductivity, λ, of vitreous boron trioxide was measured, using a hot-wire procedure, from 170 to 570 K and under pressures of up to 1.7 GPa. The thermal conductivity at room temperature and zero pressure was found to be 0.52 W · m−1 · K−1. The values of the logarithmic pressure derivative, g = d(ln λ)/d(ln ρ), where ρ is the density, were found to be 1.1 for uncompacted glass and 0.7 for glass compacted to 1.2 GPa. The variation of λ with temperature at constant density was approximately linear, with a positive slope of 1.38×10−3W·m−1·K−2.

Pressure dependence of the electron cyclotron effective mass in potassium

The hydrostatic pressure dependence of cyclotron effective mass of potassium up to 4.4 kbar in solid helium was obtained from de Haas-van Alphen measurements using the field modulation technique. The logarithmic pressure derivative of the cyclotron effective mass was found to be -(0.71+or-0.12)*10-2 kbar-1 and the zero-pressure mass was (1.211+or-0.005)m0, where m0 is the free-electron mass. The decrease of the quasiparticle mass with increasing pressure is compared with theoretical predictions of the changes of band mass, electron-electron and electron-phonon mass enhancement parameters with pressure.

Wellbore Storage Effects in Geothermal Wells

Abstract The early-time response in the well testing of a homogeneous reservoir customarily is expected to give a unit slope when the logarithm of pressure is plotted vs. the logarithm of time. It is shown that this response is a special case and that another non-dimensional parameter must be defined to describe the set of curves that could take place for each value of the wellbore storage coefficient CD. In addition, the effect of temperature changes along the bore is shown to increase the time when wellbore storage is important.

A quantitative analysis of elastic, entropic, electrostatic, and osmotic forces within relaxed skinned muscle fibers.

The elastic behavior of mechanically skinned skeletal muscle fibers in relaxing solution is modelled using equations developed by Flory (1953) for the elasticity of non-biological polymers. Mechanically, the relaxed skinned fiber is considered to be a semi-crystalline network of inextensible polymer chains, which are periodically cross-linked and which are bathed in an aqueous medium. We consider (1) configurational elastic forces in the network, (2) entropic forces due to mixing of polymer and water, (3) electrostatic forces due to fixed charges on the muscle proteins and mobile charges in the bathing solution, and (4) compressive forces due to large colloids in the bathing solution. Van der Waals forces are not considered since calculations show that they are probably negligible under our conditions. We derive an expression which relates known quantities (ionic strength, osmotic compressive pressure, and fiber width), experimentally estimated quantities (fixed charge density and volume fraction of muscle proteins), and derived quantities (concentration of cross-links and a parameter reflecting the interaction energy between protein and water). The model was tested by comparison with observed changes in skinned fiber width under a variety of experimental conditions which included changes in osmotic compressive pressure, pH, sarcomere length, and ionic strength. Over a wide range of compressive pressure (0-36 atm) the theory predicted the nonlinear relation between fiber width and logarithm of pressure. The direction and magnitude of the decrease in width when pH was decreased to 4 could be modelled assuming the fixed charge density on the protein network was 0.34 moles of electrons per liter protein, a value in accordance with the estimates of others. The relation between width and sarcomere length over the complete range of compressive pressures could be modelled with the assumption that the number of cross-links increases somewhat with sarcomere length. Changes of width with ionic strength were modelled assuming that increasing salt concentration both increased the electrostatic shielding of fixed charges and decreased the number of cross-links. The decrease of fiber width in 1% glutaraldehyde was modelled by assuming that the concentration of crosslinks increased by some 10%. The theory predicted the order of magnitude but not the detailed shape of the passive tension-length relation which may indicate that, as with non-biological polymers, the theory does not adequately describe the behavior of semi-crystalline networks at high degrees of deformation. In summary, the theory provides a semiquantitative approach to an understanding of the nature and relative magnitudes of the forces underlying the mechanical behavior of relaxed skinned fibers. It indicates, for instance, that when fibers are returned to near their in vivo size with 3% PVP, the forces in order of their importance are: (elastic forces) approximately (entropic forces) greater than (electrostatic forces) approximately (osmotic compressive forces).

The lower chlorides of zirconium

Published work on the preparation and disproportionation of the lower chlorides of zirconium is outlined. A detailed comparison is made of the quantitative aspects of the disproportionation of ZrCl 3 as studied by an effusion method and with a quartz membrane manometer. It is shown that the results of the two studies are in agreement with each other and it is postulated that the first-stage disproportionation, ZrCl 3.0 → ZrCl 2.8, proceeds in a step-wise manner via intermediate Magneli-type phases. A scheme is proposed for further disproportionation through the sequence ZrCl 2.8 → ZrCl 1.6 → ZrCl → Zr and, using measured or estimated disproportionation pressure data, values for the formation enthalpies for a mean temperature of 400 °C are obtained as follows: ZrCl, —67 kcal mol −1; ZrCl 1.6, —106 kcal mol −1; ZrCl 2.8, —180 kcal mol −1; ZrCl 3, —189 kcal mol −1. A stability diagram for these lower chlorides is constructed in terms of logarithmic pressure of ZrCl 4 and temperature. This is used to discuss the preparative methods, which are based on the Zr + ZrCl 4 reaction.

Photochemistry and Dynamics of the Ozone Layer

The paper presents a broad review of the photochemical and dynamic theories of the ozone layer. The two theories are combined into the MIT three-dimensional dynamic-chemical quasi-geostrophic model with 26 levels in the vertical spaced in logarithmic pressure coordinates between the ground and 72-km altitude. The chemical scheme incorporates the important odd nitrogen, odd hydrogen, and odd oxygen chemistry, but is simplified in the sense that it requires specification of the distributions of NO2, OH and HO2. The prognostic equations are the vorticity equation, the perturbation thermodynamic equation, and the global mean and perturbation continuity equations for ozone; diagnostic equations include the hydrostatic equation, the balance condition, and the mass continuity equation. The model is applied to the investigation of the impact of supersonic aircraft on the ozone layer.

Critical Displacement Ratio and Its Effect on Wellbore Measurement of Residual Oil Saturation

Introduction Residual oil saturation is one of the most basic concepts in reservoir engineering; knowledge of its value is virtually indispensable in determining the economic attractiveness of a waterflood project or a tertiary recovery operation. Its measurement, which is frequently made in situ, depends on the condition of true residual oil saturation around the wellbore. This condition is usually created by injecting a fluid to reduce the existing oil saturation to a residual value. Measurement techniques include various log-inject-log schemes, minitests, the tracer method, and even the conventional method of movable oil determination from logs, which depend on the true residual oil saturation created by mud filtrate in the flushed zone. All these methods sample the relatively small part of the formation that is subjected to the largest pressure gradients because of the logarithmic pressure distribution around the wellbore. In this region close to the well, the large pressure drop (or high velocity of the displacing phase) may cause the parameter Delta p/L sigma to exceed the "critical" value and mobilize some of the residual oil in this region. The result may be a conservative value of measured residual oil saturation and an optimistic value of movable oil saturation. Others have commented on this danger and have recommended that injection rates be kept low enough to minimize the possible displacement of residual oil before the logging test possible displacement of residual oil before the logging test is run. An extreme case of stripping of the residual oil may occur in coring operations when very large pressure gradients exist near the core bit. pressure gradients exist near the core bit. While it is undesirable to mobilize the residual oil before its in-situ measurement, there are cases in which the reduction of oil saturation immediately adjacent to the wellbore is highly desirable. The relative permeability to water increases with even a small reduction of permeability to water increases with even a small reduction of residual oil saturation; since most of the pressure drop in an injection well takes place within the first few feet from the wellbore, the well injection pressure can be reduced significantly by a deliberate displacement or reduction of the residual oil in that area of the wellbore. A preinjection well treatment is then necessary and the displacement ratio, Delta p/L sigma, during the well treatment must exceed the critical value. This paper describes a method for determining the injection rates that will not disturb the residual oil saturation for any specified distance from the injection well. The method also will be useful for determining the combinations of interfacial tension and injection rates that can be used to reduce the residual oil saturation at various distances from the injection well. Displacement Ratio in Linear and Radial Systems The fact that some residual oil can be displaced from most porous materials, if the ratio of viscous to capillary forces is large enough, has been reported by a number of researchers. Some authors reported their results in terms of a dimensionless group such as v mu/sigma, where v and mu are linear velocity and viscosity, respectively, of the water phase and sigma is the interfacial tension between the oil and water. For convenience, we prefer to use the ratio Delta p/L sigma, where Delta p is the prefer to use the ratio Delta p/L sigma, where Delta p is the pressure drop (psi) across the distance L (ft) and sigma is pressure drop (psi) across the distance L (ft) and sigma is the interfacial tension (dynes/cm) between oil and water. JPT P. 865

Effect of propranolol on left ventricular function, segmental wall motion, and diastolic pressure-volume relation in man.

Precise quantitation of the effects of the non-selective beta adrenergic blocking drug propranolol (3.15 mg/kg body weight) on left ventricular function, segmental wall motion, and diastolic pressure-volume relation in man has been performed. High fidelity left ventricular pressure measurements and simultaneous single-plane angiocardiograms were recorded on a video disc and volumes calculated by a light-pen computer system. Systolic segmental wall motion was computer analysed using the long axis-quadrasection method. Patients were transvenously atrially paced to maintain a constant heart rate. The haemodynamic effects of propranolol may vary depending upon the extent of pre-existing myocardial disease. In some patients ventricular function, as measured by ejection fraction, may be reduced. This reduction in ejection fraction appears to result from overall reduction in segmental wall motion, but also from accentuation of segmental wall abnormalities. These results are consistent with the thesis that beta adrenergic blocking drugs may inhibit compensatory sympathetic mechanisms. The diastolic effects of propranolol may include quite substantial increases in ventricular volumes in those patients with impaired cardiac function. With respect to the intact human ventricle, propranolol may increase diastolic volume for a given level of ventricular pressure. Thus, in a static sense, the ventricle in these patients could be viewed as being more compliant after propranolol administration. However, the fact that the length-tension relation, as measured by the slope of the logarithmic pressure versus volume plot is unaltered by propranolol, suggests that the muscle comprising the ventricle itself exhibits no alteration in its passive elastic properties.

Biomechanical study of the constitutive laws of vascular walls

Static mechanical behaviors of three different arterial walls were examined through changes in external radius due to distending pressure. In order to examine the distensibility of these vessels, distension ratio was defined as the ratio of eternal radius at each pressure to that at zero pressure. Linear relations were observed between the logarithmic pressure and the distension ration, and they were described by on exponential function. Two parameters used in this equation were related quantitatively to the area fraction of elastin or collagen component occupied in the cross section of wall. Stress-strain relation was then determined from their pressure-diameter data by using finite-deformation theory. An exponential function was established between tangential stress and tangenital strain. These results can be used to study the resistance of arterial walls to cardio-vascular disease.

ChemInform Abstract: THE VAPOR PRESSURE OF IRON PENTACARBONYL

Vapor pressure measurements have been made on pure iron pentacarbonyl between +31 and -19 C. The experimental results may be expressed by the logarithm of pressure (mm Hg) to the base 10 equals -(2096.7 K/T) + 8.4959, which corresponds to a heat of vaporization for the liquid carbonyl of delta H ? (9.588 plus or minus 0.12) kcal/mole. This result confirms and extends the earlier measurements made by Trautz and Badstuebner between 0 and 140 C. The need for careful purification of commercially available iron pentacarbonyl is emphasized, particularly for establishing the correct vapor pressure below 45 C.

The electrical properties of niobium pentoxide scales during their formation on niobium

A study of the electrical properties of compact scales growing on niobium has revealed several new properties of the oxidation reaction. The growth of the oxide follows two parabolic rates, with the latter approximately four times the former. Both the rate constants and the time of transition between the rates are sensitive to oxygen pressure, but it is the latter property that largely explains the extreme sensitivity of the oxidation reaction to oxygen pressure reported previously. Concomitant with the change to the faster oxidation rate is the development of a voltage across the scale (metal negative). The voltage has a value of 0.3 V at 1 atm and decreases approximately linearly with the logarithm of pressure to 0 V at 10−3 atm. The oxidation rate is essentially insensitive to induced changes in the voltage. These properties of the oxidation reaction cannot be explained by the usual formalization of point defect theory.

Graphical representation of homogeneous chemical equilibria in volcanic gas systems

The logarithms of the partial pressures of the components of the gaseous phase are plotted against the logarithm of the partial pressureof the oxygen under conditions of constant temperature, constant total pressure, and constant ratios of all elements except oxygen. The result is a quantitative survey of the effect of oxidation on the gases present. The equilibrium composition of an individual volcanic gas sample or of any mixture of gases may be obtained from the diagram when the atomic ratio of the oxygen is also fixed. In constructing logarithmic partial pressure diagrams, it is essential to know which molecular species may become dominant (contain virtually all of a certain element) under the conditions of the diagram.

High-Pressure Compaction Studies and Chemistry of Solutions Squeezed Out of Muds at Different Stages of Compaction: ABSTRACT

Remaining moisture content (% dry basis) was determined for various clays (montmorillonite, hectorite, illite, kaolinite, dickite, halloysite), marine mud, and soil samples and plotted versus the logarithm of pressure (up to 500,000 psi.). The straight-line relation at pressures above 40-1,000 psi. (depending on type of clay) suggests that compaction is more or less a simple continuous process in the pressure range studied. The resistance to compression apparently increases with higher packing density and more strongly coalesced structures. Most of the water is squeezed out during a relatively short period of time (1-4 days), and equilibrium is reached after about 7-60 days (depending on type of clay). The calculated (from water loss) permeability of clay at high overburd n pressures (15,000-400,000 psi.) is in the order of 10-10-10-13 darcys, values characteristic of nearly impervious soils. Consequently, compaction appears not to be limited by low permeability, but rather by resistance to grain deformation. The salinity of squeezed-out solutions (using fresh marine mud, various types of clay, and sea water) progressively decreases with increase in overburden pressure. Consequently, mineralization of interstitial solutions in shale should be less than that of waters in associated sandstone. Reliable results in determining the chemistry of interstitial solutions of marine mud require that nearly all fluid be squeezed from each sample and require pressures in the 150,000-400,000 psi. range. Experiments concerning X-ray analysis of compacted clay for deciphering the magnitude of overburden pressure were inconclusive. End_of_Article - Last_Page 608------------

Relationship Between High Overburden Pressures and Moisture Content of Halloysite and Dickite Clays

High-pressure compaction studies (up to 386,000 psi) were conducted on halloysite and dickite clays. The remaining moisture content in per cent (dry weight) was plotted versus the logarithm of pressure in psi. For halloysite clay there is a straight-line relationship between 1000 and 260,000 psi ( M = 40.1 − 6.66.1og P ), and for dickite clay the relationship between the pressure (psi) and the moisture content (per cent) can be expressed by the formula M = 26.7 − 5.04.1og P between 200 and 120,000 psi. X-ray analyses were made on compacted samples in order to determine any possible mineralogic changes with increasing overburden pressure. In addition, the permeability of dickite clay at an overburden pressure of 15,000 psi was calculated.