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Summary Y M Different criteria have been proposed to include the influence of pressure (or mean normal stress) on the yield behavior of polymers. It is difficult to distinguish among them using the type of experiments that produce data used in two-dimensional plots of yield loci. This is due to the fact that the maximum range of values of mean normal stress is relatively small in such experiments. Marked differences between these criteria do occur however as the hydrostatic pressure or mean stress is altered substantially. Experiments that show the effect of applied pressure on tensile and/or compressive yield strength provide one means for describing such differences. This paper considers two forms of a pressure modified yon Mises criterion and shows a comparison with available experimental information.

Data are presented for the thermal conductivity of standard seawater for temperatures from 0° to 30°C and at pressures from atmospheric to 1400 bars. Good agreement is shown between these data at atmospheric pressure and those reported historically, including semi-empirical calculations given by one author. The thermal conductivity of seawater is also shown to be less pressure dependent than that of pure water.

Carbon-black/elastomer powders were prepared by spray-drying mixtures of aqueous dispersions of high abrasion furnace (HAF) black with styrene-butadiene rubber (SBR) latex. The HAF/SBR ratio was varied in the range 100/0, 95/5, 75/25, 67/33, 50/50, 33/67 and 0/100 parts by weight. The powders were subjected to pressures up to 19 kbar in a piston-cylinder apparatus. The density of the powders was measured at different pressures and it was found that an interaction between carbon-black and polymer occurs which results in the formation of coherent samples. They exhibit a pressure dependent degree of porosity the magnitude of which was calculated from their density and compared to the porosity determined experimentally from the methanol uptake of the samples. At higher carbon-black loadings the specimen become increasingly porous with a corresponding decrease in density. Density measurements on the three-phase system (HAF/SBR/pores) permitted to determine the density of the HAF-black at 19 kbar as 1.97 g/cm3. Density and porosity at 0 kbar of the pressed specimen are a function of the pressure at which they were prepared. The density increases with increasing pressure whereas the porosity decreases due to stronger interaction between carbon-black and elastomer. Aus Mischungen wasriger Dispersionen von hochabriebfestem ol-Rus (HAF) und Styrol-Butadien-Kautschuk-Latex (SBR) wurden durch Spruhtrocknung Rus/Elastomer-Pulver hergestellt. Das Verhaltnis von HAF/SBR wurde zu 100/0, 95/5, 75/25, 67/33, 50/50, 33/67 und 0/100 Gewichtsteilen gewahlt. Die Pulver wurden in einer Kolben/Zylinder-Apparatur Drucken bis zu 19 kbar unterworfen. Unter dem Einflus des Druckes bildeten sich kompakte Prufkorper, deren Dichte bei verschiedenen Drucken bestimmt wurde. Unter bestimmten Bedingungen sind diese Prufkorper poros; der Grad ihrer Porositat wurde sowohl aus ihrer Dichte berechnet als auch aus der Methanolaufnahme experimentell ermittelt. Bei hoheren Rusgehalten werden die Prufkorper zunehmend poroser, wobei ihre Dichte entsprechend abnimmt. Aus Dichtemessungen an dem 3-Phasen-System HAF/SBR/Poren wurde die Dichte des HAF-Ruses bei 19 kbar zu 1,97 g/cm3 bestimmt.

Uniaxial and biaxial stress states were employed so as to investigate the yield behavior of oriented polycarbonate. These experimental results are compared with a theoretical yield locus based upon a yield criterion proposed for solids that are both anisotropic and pressure dependent in regard to macroscopic yield behavior. A good correlation between theory and experiment was found.

A general arrangement of a capillary viscometer is examined with a non-steady flow of aNewtonian liquid. The flow is determined by a pressure dependent upon the time. The velocity is found as a function of the pressure gradient or the length coordinate and the time. The result can serve for the determination of the viscosity.

It is shown that the partition functions relating to statistical ensembles can be classified as cumulative, distributive or differential with regard to any of the extensive thermodynamic variables. The Laplace transforms involved in the general formulation of transformed partition functions, when extensive parameters are replaced by their conjugate intensive variables, are two-sided and appear in different forms according to the classification mentioned. The petit partition function at constant pressure can be defined for both classical and quantal systems as a Stieltjes integral or dimensionless Laplace transform over the volume-dependent partition function. This expression contains no arbitrary external parameters and satisfies all the conditions formulated by Munster; it can be interpreted as the ratio of two partition functions, the one relating jointly to the system and a macroscopic boundary, and the second to the boundary alone. It is known that the constant pressure grand partition function as def...

Six hundred twenty-one subjects with an applanation pressure of 20 mm Hg or greater in both eyes and a visual acuity of 20/30 or better were examined for glaucomatous field defects by selective perimetry using the 1-2 and 1-4 targets of the Goldmann perimeter. Significant defects included paracentral scotomas, nasal step, and pressure dependent contraction of the isopter. These defects were present in 106 eyes. Only two required the 1-4 target. Eleven required isopter determination with the 1-2. Ninety-three were detected by stationary presentation at 5, 10, and 15 circles. The frequency of field defects increased significantly with age and with applanation pressure level.

A simple linear model was used to determine the influence of a pressure-dependent friction term on the steady-state solution for long waves produced by heating. Resonance effects, which are found in a frictionless atmosphere, were also evident in the case when friction was concentrated in the boundary layer. As friction increased at low pressure, resonance effects were no longer apparent. Net potential and kinetic energy changes did not occur when friction was zero. When friction was allowed, the conversion term for potential energy was balanced by the generation term and the northward heat transport term. The net frictional loss of kinetic energy was balanced by the conversion of potential energy into kinetic energy.

The second-, third-, and fourth-order elastic constants at T = 0 °K have been calculated using the Mie-Lennard-Jones 12-6 potential, the Buckingham 14-6 potential, and the Morse potential. The zero-point contribution to the second- and third-order constants was taken into account using the quasiharmonic approximation by obtaining the second and fourth moments of the harmonic frequency distribution. The pressure dependence of the second-order constants has been evaluated and thus the pressure dependent bulk modulus. From the bulk modulus 0 °K isotherms for Ne have been calculated and compared with experiment. Die elastischen Konstanten zweiter, dritter und vierter Ordnung bei T = 0 °K werden mit dem Mie-Lennard-Jones 12-6 Potential, dem Buckingham 14-6 Potential und dem Morse Potential berechnet. Die Nullpunktsbeitrage zu den elastischen Konstanten zweiter und dritter Ordnung werden in der quasiharmonischen Naherung mit dem zweiten und vierten Moment der harmonischen Frequenzverteilung berucksichtigt. Die Abhangigkeit der elastischen Konstanten zweiter Ordnung und des Elastizitatsmodul vom Druck wurden bestimmt. Die 0 °K-Isothermen fur Ne werden mit dem Elastizitatsmodul berechnet und mit experimentell bestimmten Isothermen verglichen.

The lifetimes of the upper and lower excited-state levels in helium for the five known laser transitions have been measured as a function of pressure. The lifetimes are strongly pressure dependent and the lifetime value at the laser operating pressure, used together with other relevant information, provides a qualitative description of laser action on the five lines.

We have calculated approximate profiles for the concentration gradient in velocity sedimentation of a homogeneous solute when both the diffusion and the sedimentation coefficient depend on pressure. Pressure dependence of the diffusion coefficient narrows the peak but does not seem to shift the maximum appreciably.

The effective thermal conductivities of packed beds with stagnant gas were theoretically computed, and it was found that these are expressed as Each conductivity was illustrated in graph; (ke)COND is highly pressure dependent, (ke)RAD is slightly pressure dependent and (ke)CONTACT is independent of pressure. It is also shown that for fine particles the effective thermal conductivities even at normal pressure is still in the pressure dependent region and is influenced by the gas accommodation coefficient.

Observations on two dissimilar z-pinched discharges have revealed a sharp transition in their behaviour as the initial filling pressure is varied. Measurements have been made interferometrically, spectroscopically and with a framing camera. The results are most striking for the variation of the peak electron density reached in the plasma, but other parameters also show changes at a critical value of the filling pressure. The interpretation of the observations is briefly discussed.

Positive and negative corona characteristics of air and nitrogen are determined experimentally for coaxial cylindrical electrode geometry with gas temperatures from 300°K to 1100°K and with pressures from 0.1 to 8 atmospheres. Over this range, positive corona characteristics appear to be functions of gas density only. On the other hand, negative corona characteristics depend on gas temperature as well as gas density. At high temperatures both positive and negative coronas show instabilities which are pressure dependent.

A detailed analytical study of the formation of the products of the pyrolysis of n-butane in the temperature range 420 to 530 °C and at initial pressures between 10 and 150 mm Hg has been carried out. A free-radical mechanism incorporating that originally proposed by Rice is shown to give an excellent quantitative account of the reactions occurring Rate parameters for some of the reactions involved have been calculated. The unimolecular decomposition of the ethyl radical is shown to be in its pressure dependent region throughout the range of conditions employed, and the fall-off of the rate constant with pressure is shown to be well described by the classical theory of Kassel. The important role of the ethyl radical in determining the kinetic features of paraffin pyrolyses is outlined.

Ionization and attachment coefficients α and η have been obtained in C4F10 under uniform field conditions at pressures in the range 1-20 torr and reduced fields of 80-150 V cm−1 torr−1. The reduced coefficient α/p rises from 0·11 at E/p=80 to 0·79 at E/p=150, while η/p is found to be pressure dependent, at least in the pressure range 1-20 torr. There was no evidence of the presence of detachment at these pressures.

A framing camera has been used to study the initial collapse of the linear Z pinch in argon and nitrogen over a pressure range of 25 to 750 μmHg. A comparison of the computed and observed dynamics of the discharge column reveals the existence of a delayed collapse at the higher pressures, which is interpreted in terms of the breakdown characteristics of gas left near the walls of the discharge vessel during the early stages of the discharge. At the lower pressures the `snow-plough' model is found to be a good representation of the dynamics of the discharge in both gases in spite of the streamers observed in the nitrogen discharge columns.

The photolysis of nitrous oxide at 1470 A has been studied and the quantum yields measured for N2O disappearance and NO, O2, and N2 appearance. The average of 38 measurements gives φN2O=1.70, φO2=0.50, and φN2=1.44 with φNO being pressure dependent. The data obtained here can be explained by a mechanism involving initial dissociation of nitrous oxide into nitrogen molecules and oxygen atoms. The source of NO can be in the reaction O+N2O→2NO. These results are discussed in the light of previous work.

This paper describes the start of an investigation into the factors affecting cage and roller slip in high-speed roller bearings. Cage and roller speeds, for different radial clearances, are measured over a range of steady radial loads and shaft speeds, using several lubricants. These results are analysed and compared with existing theoretical evidence. To improve the correlation between theory and practice further theoretical results of cage and roller motion are obtained for bearing conditions relevant to the regime where the fluid pro-perties are pressure dependent. The theoretical extent of cage and roller slip shows only a fair agreement with the experimental findings. However, the load below which cage slip will occur is much more accurately forecast.

The absorption of 26 lines of a CO2 laser by BCl3 has been measured over a wide range of pressures. At low pressures, saturation effects occurred for powers as low as 200 mW cm−2. Above 1 Torr, the absorption coefficient is found to increase linearly with pressure. A theoretical model, taking the effects of saturation and line overlapping into account, has been formulated to interpret these results.

This paper deals with design methods for Pirani and related gauges. The analytical approach is discussed, with particular reference to bridge classification and `gauge sensitivity'. The application of the load-line technique is also discussed, in some detail. It is shown that a useful insight may be gained, by this method, into the interdependence of the element and its associated bridge, that it may be used over the whole range for which the output is pressure dependent and with equal facility for both metallic filament and thermistor elements.

This article is a continuation of our discussion of the role of oxides in thiuram vulcanization. The following additional results were obtained: The reaction of TETD and ZnO gives off gaseous products and is pressure dependent. By taking this into account, both the conductometric and the spectrophotometric methods of analysis furnish identical results for the DEDC yields as a function of reaction times. The reaction of TETD with Bi2O3 produces in the presence or absence of NR (independent of the temperature) approximately 82 mole per cent BiDEDC based on the initial amount of TETD. However, no vulcanization takes place. The reaction between TETD and TeO2 produces in the presence or absenee of NR (independent of the temperature) a maximum yield of Te-II-DEDC of 60 to 70 mole per cent based on the initial amount of TETD. Such a yield of DEDC is also observed during a TETD vulcanization with ZnO. Nevertheless, no normal thiuram vulcanization takes place when TETD, TeO2 and NR are heated together. When Te-IV-DEDC is dissolved in various organic solvents, it undergoes disproportionation and equimolar amounts of Te-II-DEDC and TETD are formed. The limiting value of the Te-II-DEDC formation of 60 to 70 mole per cent during the reaction of TETD with TeO5 in the presence or absence of NR can be explained by a primary formation of Te-IV-DEDC in a maximum yield of 80 mole per cent followed by a disproportionation of the Te-IV-DEDC (the same as with a corresponding reaction in the presence of Bi2O3). Of course, it is assumed that the metal oxides during their reaction with TETD give maximum yields of 80 to 90 mole per cent DEDC based on the initial amount of TETD. Furthermore, the experiments showed that thiuram vulcanization obviously is due to the reaction of TETD with ZnO in which NR participates with formation of crosslinks. This concept is supported by the identical activation energies of the TETD decrease and DEDC increase during the reaction of ZnO with TETD in the presence and absence of NR.

An investigation of arc zone pressures during CEVAR (consumable-electrode vacuum-arc remelting) experiments has shown that pressure differences and gradients within furnaces are functions of pressure itself, electrode composition, and the degree of arc-zone confinement. There is evidence also that some previously puzzling contrasts in arc-furnace behavior may be explainable on the basis that two pressure dependent forms of electrical discharge operate with distinct potentials. The lower voltage form tends to become unstable at pressures 1 Torr. The higher voltage form seems to be most stable at pressures

It is known that liquid CS2 when subjected to high pressure forms a stable solid polymer. Our studies revealed the existence of two distinct forms designated here A and B. Chemical evidence suggests that type A has the composition CS2 and contains no free sulphur, while type B does contain free sulphur and may be a sub-sulphide. Infrared structural studies suggest that type A has a highly conjugated polymeric chain structure. X-ray evidence suggests absence of long range order in both the A and B materials. The dc resistivity of type A is about 1013 Ωcm at 300 °K with an activation energy of 0.7 eV and that of type B is about 103 Ωcm with about 0.02 eV activation energy. The resistivity of both is strongly pressure dependent. Both types show strong frequency dependence of conductivity and permittivity with a region of σ ∼ f2 at high frequencies and saturating at 109 and 1010 Hz, respectively. Although it is impossible to prove that the observed ac data are not related to some form of Maxwell-Wagner mechanism, it is pointed out that, at least in the case of the A material, the pressure, frequency, and temperature dependences of resistivity are more likely to be associated with two processes in which partially localized electrons hop within chains at high frequencies and between chains at lower frequencies. Es ist bekannt, das flussiges CS2 unter hohem Druck zu einem stabilen Festkorper polymerisiert. Nach unseren Untersuchungen bestehen zwei verschiedene Formen (als A und B bezeichnet). Chemische Analyse ergibt fur die Form A eine Zusammensetzung CS2 ohne freien Schwefel, wahrend die Form B als ein Sub-Sulfid charakterisiert wird und freien Schwefel enthalten kann. Eine hochkonjugierte polymere Kettenstruktur wird auf Grund der Spektralanalyse im Infrarot fur die Form A vorgeschlagen. Beide Formen besitzen nach der Rontgenstrahlenanalyse keinerlei Fernordnung. Der spezifische Gleichstromwiderstand der Form A betragt 1013 Ωcm bei Zimmertemperatur mit einer Aktivierungsenergie von 0,7 eV, wahrend fur die Form B die entsprechenden Werte 103 Ωcm beziehungsweise 0,02 eV sind. Beide Formen sind durch starke Frequenzabhangigkeit der Leitfahigkeit σ und der dielektrischen Konstante ausgezeichnet, mit σ ∼ f2 im Hochfrequenzintervall und mit nachfolgender Sattigung bei 109 und 1010 Hz fur die A- beziehungsweise B-Formen. Obwohl es moglich ware, die beschriebene Frequenzabhangigkeit auf eine Art Maxwell-Wagner-Mechanismus zuruckzufuhren, deuten die experimentell bestimmten Druck-, Frequenz- und Temperaturabhangigkeiten des Widerstandes eher auf eine sprunghafte Bewegung quasi-lokalisierter Elektronen (hopping) zwischen naheliegenden Polymerketten bei tiefen Frequenzen und innerhalb der Ketten bei hohen Frequenzen hin.

The Gruneisen parameters and the thermal expansion coefficients of CaO and SrO are calculated from a pressure dependent shell model.

An investigation has been made of the kinetics of reactions between various guest molecules and α-phenol and α-quinol crystals. The reactions were strongly promoted by shaking the crystals with small steel ball bearings, and reactions did not normally occur in absence of shaking. With α-quinol a small initial uptake of gas was followed, after an initiation time τ, by a second large uptake. With α-phenol the initiation time was not preceded by any initial uptake. Initiation times proved to be pressure dependent, but temperature independent. In the uptake following the initiation time the amount of clathrate phase formed at first tended to vary linearly with time but at a later stage varied with the square of the amount of unreacted α-phase. The properties of τ and the study of kinetic runs with interrupted shaking, and with preliminary shaking in vacuo followed by permanent cessation of shaking, have led to a possible explanation of the catalysis of the reactions through mechanical agitation.

The rotational profile of the (11, 7) first positive band in active nitrogen is shown to be pressure dependent in the range 0.05 to 1.0 torr. The effect is ascribed to rotational relaxation of nitrogen molecules in the B 3Π(v=11) level, and this interpretation leads to an estimation of tentative lower limits to the radiative lifetimes of B 3Π(v=11) and A 3Σ(v=0) of (2.4±0.5)×10−6 sec and 12±2.4 sec, respectively.

The piezoresistivity coefficients for Manganin have been determined from the static and shock pressure dependence of the resistance. An analysis is presented which relates the piezoresistivity coefficients to resistance changes under conditions of one‐, two‐, and three‐dimensional dynamic strains and hydrostatic strain. This analysis shows that the piezoresistance values depend on the mode of strain and reconciles the different piezoresistance values, reported in the literature, to a unique but pressure dependent piezoresistivity coefficient. The dynamic piezoresistance predicted from static piezoresistance pressure data and mechanical data using this analysis is in good agreement with the observed values. The observed piezoresistivity which is of opposite sign to that predicted from the pressure dependence of the lattice scattering, is discussed in terms of an s‐d scattering model for Manganin and other alloys of copper containing elements with unfilled 3d electron states. This model suggests that severa...

Spectra of self-broadened vibration-rotation lines of the 5.3μ NO fundamental band were obtained on an Ebert grating spectrometer which had a spectral slit width of about 0.1 cm−1. The integrated absorptances of the observed vibration-rotation lines of each sub-band were measured at 300°K for different path lengths and total pressures of NO. The pressure dependent behavior of the integrated absorptances is compared with the effects expected from the unresolved Λ doubling of each line. The self-broadened half-widths and the line strengths of over 70 lines of the band were measured by using a curve of growth technique. The half-widths decrease with increasing | m | values and no measurable difference in half-widths is observed for lines of the same | m | value in the R and P branches of each sub-band. From the individual line strengths a total band strength of 122 ± 6 cm−2 atm−1 was obtained. No vibration-rotation interaction effect on line intensities was observed.

The equations of motion are derived and solved for the component parts of the oscillating plate viscometer.4 A linear relation √ηρ= Qδliq–K, is found at constant pressure, where η, ρ, are the viscosity and density of the liquid under test, δliq is the logarithmic decrement of the oscillations of a thin flat plate immersed in the liquid, and Q, K are apparatus constants. Both Q and K have been derived analytically, so that if desired the method may be employed without calibration using liquids of known viscosity; K is slightly pressure dependent. The derivations of Q and K involve certain approximations, but values of these can readily be computed to within 1 %; even better accuracy can be achieved using the viscometer as a comparative device.

The microscopic Grueneisen parameters and the temperature dependence of the thermal Grueneisen parameter of NaCl are calculated from a shell model with six parameters, five of which are taken as pressure dependent. All parameters are determined from experimental elastic, optical, and dielectric data at absolute-zero temperature. The results agree within 6-8% with experimental data. The discrepancy is primarily attributed to the experimental error of the input data that are used to determine the parameters of the model. Calculations have also been made for two versions of the rigid-ion model (RIM) which indicate that the apparent success previously attributed to the Kellermann model is mainly due to cancellation of errors arising from omitting second-nearest-neighbor interaction and electronic polarizability.

The presence of an absorption maximum at 360 mμ indicates the formation of I3− in the fcc phase of AgI at approximately 4 kbar. The concentration of I3− is pressure dependent above 4 kbar and falls to zero somewhere below the transition to the new phase at approximately 100 kbar. A mechanism is proposed to explain the presence (in the fcc structure) and subsequent disappearance of I3−.

The performance of a transversely excited pulsed CO2-N2-He laser is examined at pressures up to 3 atm. The electrical discharge determines an optimum partial pressure of carbon dioxide plus nitrogen, which remains constant when the total gas pressure is varied.

Measurement made under hydrostatic conditions to 7 kbar of the relative thermal emf's of chromel/alumel and platinum/platinum−10% rhodium thermocouples indicates a pressure correction for platinum couples of 0.57 ± 0.03°C/kbar from about 600 to 1000°C. Chromel/alumel couples are found to be pressure dependent above about 720°C and to degrade rapidly at temperatures above 800°C. Systematic differences of unknown origin are found between pressure corrections measured with increasing and decreasing pressure.

The thermal expansion coefficient of MgO is calculated from a six parameter pressure dependent shell model.

The photolysis of nitrous oxide at 1849 A has been studied and the quantum yield ratios φN2O/φN2, φN2O/φO2, and φN2O/φNO measured. The former two ratios compare well with the same ratios at 1470 A and the latter ratio is pressure dependent. It appears that the photolysis mechanism at 1849 A is similar to that at 1470 A. The absorption coefficient of N2O is calculated from the photolysis data and found to compare well with previous work.

Obstructions of the central airways (thoracic trachea and main bronchi) can be divided in two main categories, namely: 1) fixed stenoses independent of the thoracic pressure, and 2) non-fixed stenoses dependent on the thoracic pressure. Methods of diagnosing central airway obstructions are the forced expiration curve, bronchoscopy, the tracheal diameter/transmural pressure diagram and, most important, the measurement of intrabronchial pressure in the different segments of the intrathoracic airways. Preliminary experiments in dogs showed that the patterns of the expiratory alveoto-glottic pressure drop changed considerably when the normally taut dorsal membrane of trachea was replaced by a loose skin-flap indicating exactly the site of the artificial weakness of the airways. In four patients with non-fixed, pressure dependent obstructions of the central airways, patterns of expiratory transbronchial pressure-drop were plotted and the share of peripheral and central bronchi in total expiratory flow resistance measured and compared with the findings in healthy man as well as before and after reinforcement of the relaxed dorsal tracheobronchial membrane by application of a strip from the sheath of the straight abdominal muscle. Effects on clinical features such as efficiency of cough and breathlessness during exercise and on pulmonary function tests are evaluated and indications for the intervention discussed.

To optimize intraaortic balloon pulsation, the inflation and deflation mechanisms of different intraaortic balloons were studied in a model aorta with pressure volume characteristics approximating those of a natural aorta and in anesthetized dogs by cineangiography. It could be demonstrated that inflation of straight balloons begins at the tip and proceeds from there to the end of the balloon. The distention of the aortic arch balloons is first observed in the aortic arch; inflation than proceeds to the end of the balloon. Deflation of both balloon types has the same direction as inflation, beginning at the tip.From the model investigations it can be concluded that the balloon dynamics are definitely pressure dependent: inflation begins in that balloon part, where the pressure is lowest; deflation where the highest pressure is exerted. These results explain the behavior of balloons in vivo.In the aorta of living dogs in the early diastole, the pressure nearest to the heart is less than in lower parts of t...

Introduction The equation generally used to describe unsteady-state fluid flow in porous media is the diffusivity equation porous media is the diffusivity equation either in terms of potential, head, pressure, or density. Terzaghi used pressure, or density. Terzaghi used the equation to describe changes of head within permeable layers of rock which resulted in fluid flow and rock compaction. Use of this equation to describe rock compaction requires the assumptions that permeability, porosity, formation compressibility coefficient, and formation thickness are constants. It is also assumed that grain volume is constant and that bulk-volume reduction equals pore-volume reduction. Terzaghi's results have been applied to many engineering problems, including the compaction of oil-reservoir rocks due to fluid-pressure decreases caused by fluid withdrawals. For a horizontal, isotropic, homogeneous layer bounded on the top by an impermeable boundary and on the bottom by a high-permeability layer which acts as a drainage channel and in which there is a sudden drop of head from hi to ho at t = o Terzaghi gives the head as a function of time and distance: (1) Overburden loads are supported by a combination of the rock grain-to-grain "pressure", PG and the interstitial fluid pressure, Pf: (2) Compaction of the rock is a function of changes of PG, which is often designated "compaction pressure." From equation (2) therefore, it may be seen that rock compaction, designated "shrinkage" by Terzaghi, is a function of Pf if Pob is constant.

After introductory remarks on advanced techniques for producing silicon carbide of high density and strength the phase stability of silicon carbide against nitrogen is discussed. Thermodynamic calculations are in agreement with experimental results. The stability of silicon nitride in contact with carbon is strongly pressure dependent. In the temperature range between 2200°C and 2500°C nitrogen induces transformation of α-SiC into β-SiC. Under suitable conditions the conversion can be forced repeatedly into both directions.

The role of the capillary filtration pressure and secretory activity in determining the rate of net inward movement of solute and water across the ciliary processes is examined theoretically using previously published experimental data. The theoretical approach, based on a dimensionless diffusion model ( Weinbaum and Goldgraben, 1972 ) has yielded results which are in close agreement with experimental data for both living and dead eyes. It is concluded that the formation of the aqueous humor is a pressure dependent mechanism associated with an active transport of solute; the latter being responsible for 30–40% of the total flow. In keeping with present concepts of solute-water coupled flow in epithelial systems it is assumed that the solute is actively transported into the extracellular channels of the ciliary epithelium from the adjacent cells and that the water movement is passive.

The large exchange induced ESR g‐shifts of S‐state ions present as trace impurities in the samarium monochalcogenides SmS and SmSe have been investigated as functions of quasihydrostatic pressure at liquid helium temperatures. While roughly comparable with expectations based on intercompound variations the results suggest that local compressibilities may differ significantly from those of the hosts.