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The effect of Γ-X crossover due to the external hydrostatic pressure on the ground state donor binding energy as well as for some low lying excited states for a Quantum well has been investigated by considering the non-parabolicity of the conduction band and pressure dependent spatial dielectric screening. It is observed that the effect of Γ-X crossover is predominant for ground state than for low lying excited states.

Apparent pressure dependent shifting of the peak positions of rotational lines, which is a consequence of unresolved hyperfine structures, is analyzed. In addition, possible line profile asymmetries and their influences on the ultimately achievable measurement accuracy are discussed for rotational transitions of ammonia and acetonitrile. These effects are caused by partially overlapped, but unresolved line profiles of individual hyperfine components.

In the evaluation of patients with local pathologic dilatation inside the upper airway a pressure-related testing seems important for understanding its pathophysiology and for developing a concept of intra-individually adjusted therapy. Commonly used diagnostic techniques like endoscopy or medical imaging including ultrasound, barium swallow or computer-assisted tomography (CT) have shown limitations either in evaluating a dynamic process or assessing the entirety of cervical structures. This article presents a case report of a professional trumpet player with bilateral pharyngoceles, introducing real-time and three-dimensional (3D) MRI as a helpful tool in the diagnosis of pressure dependent pathologies in the upper airway. With the use of MRI the complete sub- and supraglottic airway can be viewed simultaneously, avoiding the distortion which can occur with endoscopy. Thus, it was possible to evaluate the pharyngoceles pressure-related pathophysiology, from which a successful therapy could be conceived which included modifying the musician's blowing technique.

We show that simple expressions can be derived from the Vogel–Fulcher–Tammann (VFT) law relating the glass transition temperature Tg, the VFT temperature T0, their pressure derivatives, the steepness index of the ‘Angell plot’ and the strength parameter D of the VFT equation, in good agreement with experimental data. In the same way one can describe the dependence of the dTg/dP on the relaxation time τg chosen to define the temperature Tg. Thus, this procedure allows a consistent rescaling and comparison of pressure dependent parameters obtained from different experiments and simulations.

An experimental study of the inelastic deformation of bulk metallic glass Zr41.2Ti13.8Cu12.5Ni10Be22.5 under multiaxial compression using a confining sleeve technique is presented. In contrast to the catastrophic shear failure (brittle) in uniaxial compression, the metallic glass exhibited large inelastic deformation of more than 10% under confinement, demonstrating the nature of ductile deformation under constrained conditions in spite of the long-range disordered characteristic of the material. It was found that the metallic glass followed a pressure (p) dependent Tresca criterion τ = τ0 + βp, and the coefficient of the pressure dependence β was 0.17. Multiple parallel shear bands oriented at 45° to the loading direction were observed on the surfaces of the deformed specimens and were responsible for the overall inelastic deformation.

The algorithm proposed by Aravas to integrate a special type of elastic-plastic constitutive equations has been extended to incorporate kinematic hardening. Like in the case of isotropic hardening, the number of primary unknowns for the Newton iteration can be reduced to two scalar strain variables. Furthermore, the consistent tangent can be obtained explicitly. The modified algorithm has been applied to a Gurson-type model which takes into account kinematic hardening and the predictions of the Gurson-like model are compared with results obtained by unit cell calculations.

In addition to lightweight and moldable characteristics, polymeric foams possess an excellent energy-absorbing capability that can be used for a wide range of commercial applications, especially for crash protection in automobiles. The purpose of the present study is to develop an experimental methodology to characterize the pressure dependent yield behavior of energy-absorbing polymeric foams. A device was designed to perform a compression test in a triaxial stress state. For the test material, polyurethane foams of two different densities were used. The displacement of the specimen, the load applied to the specimen, and hydrostatic pressure applied to the specimen were measured and controlled. Stress–strain curves and yield stresses for different hydrostatic pressures were obtained. The experiments conducted in this study revealed that the polyurethane foams exhibited significant increase in yield stress with applied hydrostatic pressure or mean normal stress. Based on this observation, a yield criterion which included the effect of the stress invariant was established for the foams. The experimental constants obtained which constituted the pressure-dependent yield criterion were verified.

By constructing rigid-ion models (RIMs) at ambient and high pressures we present a comprehensive study of lattice-dynamics and thermodynamical properties in cubic III-nitrides. Murnaghan's equation of state is adopted for relating the volume dependence to pressure. The force constants in the RIM scheme are optimized using non-linear least square fitting procedures with constrained parameters and weighting of the data on critical-point phonons, lattice and elastic constants. Theoretical results for the phonon dispersions, density of states, mode Gruneisen parameters, specific heat, and thermal expansion coefficients are compared and discussed with the existing experimental and ab initio data.

The solubility of alumina in orthopyroxene coexisting with sapphirine and quartz was determined over the P–T interval 1,250–1,350 °C and 10–16 kbar in the system MgO–Al2O3–SiO2. Five isobaric experiments were reversed at 12 kbar at 25 °C intervals between 1,250 and 1,350 °C, and two isothermal experiments at 1,325 °C at 14 and 16 kbar. These constrain the P–T–X relationships of the reaction: \({\rm Mg - Tschermak's}\;{\rm orthopyroxene = Mg - sapphirine}_{{\rm 221}} \;{\rm + quartz}\) . The reaction is strongly temperature dependent and slightly pressure dependent (dP/dT=ca. 94 b K–1) and alumina in orthopyroxene increases by ca. 1 wt% per 26 °C over the temperature interval studied. No corresponding compositional trend in sapphirine was resolvable, an effect attributed to only small changes in alumina solubility with temperature and sluggish kinetics of sapphirine. Entropy calculations for sapphirine based on a recent dataset and minimum constraints from an oxide sum approach fall within the 90% confidence limits of our data, but above a linear-best fit of our data. The latter discrepancy suggests that disequilibrium in sapphirine and/or configurational disorder in orthopyroxene may have been important in the experiments. When taken into account these factors bring our data into reasonable agreement with an oxide sum calculation.

Obtaining bubbles on demand at precise times and locations in a non-contact fashion can be useful in a variety of applications. Of special importance is the combination of laser nucleation with acoustics, so that bubbles are only just nucleated by the optics but grown to macroscopic size solely by the acoustics. We present theory and experiment for the non-thermal laser nucleation of bubbles in an acoustic field in the absence of significant absorbing/scattering particles. First we present theory and experiment for the threshold for dielectric breakdown in water, resolving the distinct minimum at 20 bar. Then, we present a method and results for nucleating single and multiple bubbles with temporal uncertainty of 5 ns, and spatial uncertainty of 1 mm. Results for bubble number and first cycle expansion are reported as functions of the timing of the nucleating laser pulse with respect to the acoustic field. [Work supported by Impulse Devices, Inc.]

The non-linear elastic bending of a thin axi-symmetrical film layer clamped at its edges has been investigated under pressure in the framework of the Foppl–von Karman theory of thin plates. The mechanical equilibrium equations have been solved for the pressurized layer by developing the relaxed stress and layer deflection in power of a pressure dependent parameter. The obtained expression allows for a better understanding of the different terms of the empirical bulge test formula and validates the use of this empirical expression by the materials science community for determining the elastic coefficients of thin films and coatings.

In this paper we study three filtration problems through porous media, assuming that the viscosity of the fluid depends on pressure. After showing that in this case Darcy’s law is “formally” preserved (meaning that the formal relation remains unchanged except for viscosity that now depends on pressure), we focus on the following problems: Green–Ampt infiltration through a dry porous medium; the Dam problem; the Muskat problem. For each model (free boundary problems) we obtain explicit solutions that allow to quantify the detachment from the classical case, where with the word “classical” we mean that viscosity is taken constant.

The goal of this article is to provide some essential results for the solution of a regularized viscoplastic frictional flow model adapted from the extensive mathematical analysis of the Bingham model. The Bingham model is a standard for the description of viscoplastic flows and it is widely used in many application areas. However, wet granular viscoplastic flows necessitate the introduction of additional non-linearities and coupling between velocity and stress fields. This article proposes a step toward a frictional coupling, characterized by a dependence of the yield stress to the pressure field. A regularized version of this viscoplastic frictional model is analysed in the framework of stationary flows. Existence, uniqueness and regularity are investigated, as well as finite-dimensional and algorithmic approximations. It is shown that the model can be solved and approximated as far as a frictional parameter is small enough. Getting similar results for the non-regularized model remains an issue. Numerical investigations are postponed to further works.

Nano-crystalline diamond (NCD) films have been synthesized using H2, CH4 and N2 gases with a deposition pressure ranging from 90-130 Torr and characterized by Raman spectroscopy, XRD, SEM, optical emission spectroscopy (OES) and EDX techniques. SEM micrographs confirmed the existence of ball-shaped morphology of the aggregated nano-sized grains of diamond with average crystallite size in the range of 26-32nm. Formation of nanocrystalline diamond phase was further confirmed by Raman spectra recorded for these samples, which also showed the existence of sp2 hybridized carbon phase in these samples. Carbon dimers (C2) have been identified as the imperative growth species for NCD and its presence has been confirmed by OES. A plausible explanation for the reduction in grain size of diamond nano-particles with deposition pressure has been provided in terms of CN species.

Pressure-induced decreases in arterial diameter are accompanied by membrane depolarization and Ca2+ entry via voltage-gated Ca2+ channels. Recent evidence also suggests the involvement of Ca2+ sensitization of the contractile proteins. Both PKC and Rho kinase are candidate second messengers for the mediation of the sensitization process. We investigated the signaling pathways of pressure-induced decreases in rat cerebral artery diameter in vessels that were depolarized with a 60 mM potassium-physiological salt solution (KPSS). Arteries were mounted on a pressure myograph, and pressure-induced constrictions were recorded. In some experiments simultaneous changes in intracellular Ca2+ concentration ([Ca2+]i) were recorded by using fura 2 fluorescence photometry. Pressure increases induced constriction with significant changes in [Ca2+]i at high pressures (60–100 mmHg). The ratio of the change in diameter to change in [Ca2+]i was greater for pressure-induced constriction compared with constriction produced by depolarization with 60 mM KPSS, suggesting that in addition to increases in [Ca2+]i, enhanced myofilament Ca2+ sensitivity occurs during pressure-induced decreases in arterial diameter. Depolarizing the membrane with 60 mM KPSS increased [Ca2+]i via a Ca2+influx pathway insensitive to PKC inhibition. Cerebral arteries were able to maintain their diameters in the continued presence of 60 mM KPSS. Pressure-induced constriction under these conditions was not associated with further increases in Ca2+ but was abolished by selective inhibitors of PLC, PKC, and Rho kinase. We report for the first time that in rat cerebral arteries, pressure-induced decreases in arterial diameter are not only due to increases in voltage-gated Ca2+ influx but also to accompanying increases in myofilament sensitivity to Ca2+ mediated by PKC/Rho kinase activation.

Amino alcohol-catalyzed asymmetric alkylation of benzaldehydes by dialkylzincs can be achieved in supercritical fluoroform (scCHF 3 ) and supercritical ethane (scC 2 H 6 ) with high conversion and enantioselectivity. The higher enantioselectivity in ethane compared to CHF 3 suggests that solvent polarity affects the reaction. The enantioselectivity in scCHF 3 is strongly pressure dependent.

The background and theoretical and experimental requirements of powder compaction equations have been briefly reviewed. There have been many equations proposed. However, the equations most commonly used today are the Heckel and Kawakita ones, because they alone have claimed to be able to relate to the physical properties of the materials being compacted. There has been much discussion about their relative merits, and in their form, they appear very different. The two equations are discussed in detail and examples are given, and their relative merits are discussed. However, it is first shown for applied pressures, which are low compared to the yield strength of the particles, that they are identical in form. It is then shown mathematically that if a pressure dependent term is used in the Heckel equation then the resulting modified equation is very similar to the Kawakita one and, in fact, becomes identical in form for a particular, likely value of the pressure dependency term. It is concluded that the Kawakita equation is a special case of the more general, modified Heckel equation. It is further concluded that compaction equations need further development to take into account the anisotropy in compacts made by uniaxial compaction. It is shown that the Poisson's ratio of compacts will also increase with applied pressure, and this must be considered.

The antiferromagnetic ordering temperatures of Sm2RuO5, Tb2RuO5 and the ferromagnetic ordering temperature of Nd3RuO7 are reduced by the application of high hydrostatic pressure, whereas that of antiferromagnetic Gd2RuO5 remains unchanged. The results are discussed in terms of the enhancement of the crystalline electric field interaction on the Ln cation constituents. A versatile method of measuring magnetization in high fields and high pressure is presented.

The effects of collisions and magnetic fields on quantum beat are treated by the density matrix method. Some experimental quantum beat results of biacetyl in the presence of collisions are presented and theoretically analysed. It is shown that in this case not only pure dephasing but also pressure dependent inherent decay rate constants can be observed; this implies that the Schrodinger method cannot be employed for this case. The magnetic field effect on quantum beat is examined also and it is shown that for the biacetyl molecule magnetic splitting can be observed even in fields of a few gauss.

Published isobaric semilogarithmic survival curves of E. coli were fitted with logS(t) a = b(P)t n(P) where b(P) and n(P) are pressure dependent coefficients. Pressure profiles, P(t), were generated with a double logistic model and the corresponding inactivation rate is only a function of the momentary CO 2 pressure and survival ratio, then dlogS(t)/dt = - b(t)-n(t).{-logS(t)/b(t)] [n(t)-1]/n(t) . This differential equation was solved numerically to produce nonisobaric survival curves, which demonstrated the effects of the pressure level, treatment duration, and the come up time. They also enabled thearetical compartison of processes consisting of single and multiple compressiondecompression cycles of equivalent duration. Les objectifs de cette etude sont de demontrer l'efficacite du modele logS(t) a = b(P)t n(P) ou b(P) et n(P) sont des coefficients dependant de la pression dans une etude theorique des parametres d'inactivation de E. coli par du dioxyde de carbone sous pression. L'equation differentielle developpee dans cette etude est resolue numeriquement pour produire des courbes de survie non isobares, ce qui demontre les effets de la pression et de la duree du traitement.

A kinetic model has been developed for the thermal decomposition of vinyl bromide at temperatures below approximately 750 K. The decomposition is initiated by two channels, a pressure dependent mol...

In this article, we derive a rate model, the “cooperative free volume” (CFV) model, to explain relaxation dynamics in terms of a system’s free volume, Vfree, and its temperature, T, over widely varied pressure dependent conditions. In the CFV model, the rate a molecule moves a distance on the order of its own size is dependent on the cooperation of surrounding molecules to open up enough free space. To test CFV, we have generated extensive T,V dependent simulation data for structural relaxation times, τ, on a Kob and Andersen type Lennard-Jones (KA-LJ) fluid. The Vfree = V − Vhc values are obtained by estimating the limiting hard core volume, Vhc, through analysis of the KA-LJ PVT data. We provide the first simulation evidence that shows ln τ to be linearly proportional to 1/Vfree on isotherms, with T-dependent slopes, thus confirming our recent analysis of experimental systems. The linear relationship exhibited by the simulation data is further shown to occur at temperatures both above and below the tran...

We report pressure (0–28 kbar) and temperature (1.1–4.3 K) dependent photon echo results for tetra-tert-butyl-terrylene (TBT) in a polyisobutylene (PIB) host. Increased pressure is found to increase the homogeneous dephasing rate over the temperature range of this study, in contrast to pressure dependent hole burning results reported for other polymer systems at somewhat higher temperatures (⩾4.2 K). A relatively small pressure increase (0 to 9 kbar) resulted in a change in the temperature dependence of the dephasing characterized by a lowering of the temperature power law exponent from ∼1.3 to ∼0.9. Further pressure increase above 9 kbar was characterized by an additional increase in the homogeneous dephasing rate without further change in the temperature exponent. The results are compared to high pressure photon echo studies of other polymer systems, and discussed in terms of the TLS (two-level-systems) model.

Positive ion mobility in normal liquid 3He has been measured as a function of external magnetic fields up to 15 T at various pressures and temperatures down to 3 mK. At 20 mK, a monotonic decrease of the mobility with increasing the magnetic field has been observed at the pressures above 10 bars. At 3.2 mK, the field dependence for pressures above 20 bars is found to exhibit a pressure dependent broad peak, followed by a big decrease. Possible origins for these anomalous behaviors are discussed.

Elasto–plastic behavior of the third generation Fortiform 1050 steel has been analysed using cyclic tension–compression tests. At the same time, the pseudo elastic modulus evolution with plastic strain was analysed using cyclic loading and unloading tests. From the experiments, it was found that the cyclic behavior of the steel is strongly kinematic and elastic modulus decrease with plastic strain is relevant for numerical modelling. In order to numerically analyse a U-Drawing process, strip drawing tests have been carried out at different contact pressures and Filzek model has been used to fit the experimental data and implement a pressure dependent friction law in Autoform software. Finally, numerical predictions of springback have been compared with the experimentally ones obtained using a sensorized U-Drawing tooling. Different material and contact models have been examined and most influencing parameters have been identified to model the forming of these new steels.

Tantalum pentoxide Ta2O5 with the orthorhombic L-Ta2O5 structure has been experimentally studied up to 28.3 GPa (at ambient temperature) using synchrotron angle-dispersive powder X-ray diffraction (XRD). The ambient pressure phase remains stable up to 25 GPa where with increased pressure a crystalline to amorphous phase transition occurs. A detailed equation of state (EOS), including pressure dependent lattice parameters, is reported. The results of this study were compared with a previous high-pressure XRD study by Li et al. A clear discrepancy between the ambient-pressure crystal structures and, consequently, the reported EOSs between the two studies was revealed. The origin of this discrepancy is attributed to two different crystal structures used to index the XRD patterns.

The effect of hydrostatic pressure on photo-induced surface expansion in As0.2Se0.8 thin films has been studied in the pressure range of 0–0.5 GPa. The development of the surface relief was investigated at different intensities and exposure of laser irradiation. We have observed that the applied pressure suppressed the rate of the surface relief formation, therefore the pressure dependent components of the structural transformations in glasses should be included to the model of this phenomenon.

An integrated unconventional reservoir model that accounts for known mechanisms and nonlinearities affecting modeling of hydraulically fractured wells is developed. In general, modeling and simulation of multi-fractured reservoirs are highly challenging due to the complexity attributed to the flow in this very low permeability and dense structured rock. Pressure- dependent phenomena in reservoir modeling are considered as combined hydraulic and natural fracture conductivity losses, desorption, Klinkenberg gas slippage effect and non-Darcy flow. Integrating these phenomena and analyzing the importance of each parameter in a reservoir model are essential. The proposed model includes three zones, Rock Matrix (I), Induced-Fracture (II) and Hydraulic Fracture (III) that are defined with different characteristics. Pressure dependent permeability is considered for zone II and III, with an exponential relationship between permeability and reservoir pressure. Governing equations of gas flow are non-linear partial differential equations, for all three zones, due to incorporated pressure-dependent phenomena that are solved using the finite difference method. A synthetic case is defined in order to investigate the effect of each individual phenomenon on long-term production. Moreover, a history matching process with Marcellus Shale field production data is performed in order to obtain the most uncertain parameters in the model. Results showed that combined effect of permeability losses of hydraulic and induced-fracture zones results in 15 percent gas production drop in 30 years. Also, it is observed that Klinkenberg effect and non-Darcy flow have insignificant effect on the modeling of shale gas reservoirs, whereas desorption has great contribution on long-term production. It is concluded that the minimum ingredients for an accurate shale reservoir modeling are considering gas desorption phenomena alongside with pressure-dependent permeability for the hydraulic and induced-fractures network. Our simple reservoir modeling approach helps in understanding complex behavior of flow mechanisms in shale plays. Also, this integrated model can be used during optimization of key factors in hydraulic fracturing process and fracture characterization by history matching of production.

OH-formation in the reactions of CH3CO (R1) and HOCH2CO (R4) with O2 was studied in He, N2 and air (27 to 400 mbar) using OH-detection by laser induced fluorescence (LIF). 248 nm laser photolysis of COCl2 in the presence of CH3CHO or HOCH2CHO was used as source of the acyl radicals CH3CO and HOCH2CO. The LIF-system was calibrated in back-to-back experiments by the 248 nm laser photolysis of H2O2 as OH radical precursor. A straight-forward analytical expression was used to derive OH yields (α) for both reactions. A Stern-Volmer-analysis results in α1b(-1)(N2) = 1 + (9.4 ± 1.7) × 10(-18) cm(3) molecule(-1) × [M], α1b(-1)(He) = 1 + (3.6 ± 0.6) × 10(-18) cm(3) molecule(-1) × [M] and α4b(-1)(N2) = 1 + (1.85 ± 0.38) × 10(-18) cm(3) molecule(-1) × [M]. Our results for CH3CO are compared to the previous (divergent) literature values whilst that for HOCH2CO, for which no previous data were available, provide some insight into the factors controlling the yield of OH in these reactions.

The objective of this study is to investigate the pressure-induced redox-sensitive signaling pathway in the regulation of pressure-dependent myogenic rat cerebral arterial constriction. Methods. We...

In order to accurately simulate fine blanking processes, a finite element model valid for numerically describing of such operations has been developed. The numerical simulation of the damage evolution and crack initiation and propagation have been described by means of continuum damage approach. In this paper, two models for damage accumulation has been implemented in the finite element code ABAQUS by means of the user routine (UMAT). The Lemaitre damage model (referred to LMD model) taking into account the influence of triaxiality has been implemented as well as a damage model accumulation, based on the Rice and Tracey ductile fracture criterion allowing for the description of the exponential dependence on triaxiality of the stress field. The comparative study between the results obtained by the simulations using the different damage models and the experimental ones, showed that the LMD model is not able to predict the fracture propagation path in a realistic way. Only the exponential damage evolution gives good results.

Computer tools to automatically generate large gas-phase kinetic models find increasing use in industry. Until recently, mechanism generation algorithms have been restricted to generating kinetic models in the high-pressure limit, unless special adjustments are made for particular cases. A new approach, recently presented, allows the automated generation of pressure-dependent reaction networks for chemically and thermally activated reactions (Grenda et al., 2000; Grenda and Dean, in preparation; Grenda et al., 1998; see Refs. [1–3]). These pressure-dependent reaction networks can be quite large and can contain a large number of unimportant pathways. We thus present an algorithm for the automated screening of pressure-dependent reaction networks. It allows a computer to discover and incorporate pressure-dependent reactions in a manner consistent with the existing rate-based model generation method. The new algorithm works by using a partially-explored (or “screened”) pressure-dependent reaction network to predict rate constants, and updating predictions as more parts of the network are discovered. It requires only partial knowledge of the network connectivity, and allows the user to explore only the important channels at a given temperature and pressure. Applications to vinyl + O 2 , 1-naphthyl + acetylene and phenylvinyl radical dissociation are presented. We show that the error involved in using a truncated pressure-dependent network to predict a rate constant is insignificant, for all channels whose yields are significantly greater than a user-specified tolerance. A bound for the truncation error is given. This work demonstrates the feasibility of using screened networks to predict pressure-dependent rate constants k(T,P) .

We have studied the pressure and magnetic field dependence of the antiferromagnetic transition of U0.45Y0.55Pd3. TN increases with pressure whereas there is very little magnetic field dependence up to 7 T. These results indicate that (U, Y)Pd3 is located in the weak-coupling regime of the Doniach phase diagram, contradicting some previous suggestions. From a comparative study of the resistivity of U0.2Y0.8Pd3 under pressure and magnetic field, we have shown that the non-Fermi-liquid behaviour seen in this composition is very robust against pressure and field. By considering the metallurgical aspect of these two samples, we propose that disorder in the U concentration is likely to be responsible for the decrease of TN with increasing Y concentration, and eventually the appearance of non-Fermi-liquid behaviour in U0.2Y0.8Pd3.

Pressure–volume relations in different arteries have been observed to be nonlinear. This gives rise to the pressure-dependent behavior of the overall arterial system compliance. Using a nonlinear pressure-dependent compliance arterial system model, we have shown that this compliance varies continuously throughout the cardiac cycle. However, the overall significance of this nonlinear compliance under different vasoactive conditions has been examined only to a limited extent. In addition, its frequency domain characteristics have not been investigated. We studied these aspects under varied physiological conditions. Systemic arterial compliance of the nonlinear compliance model was expressed as C(P) = a · exp(−bP). It is determined, through optimization, from the following equations: Pao(ti) = Qao(ti)Z0 + P(ti) and P(ti + 1) = P(ti) +Δt (Qao(ti) − P(ti)/Rs)/C(Pti), where Pao and Qao are aortic pressure and flow respectively, Z0 is aortic characteristic impedance, and Rs is the peripheral resistance. Results showed that C(P) increased during vasodilation and decreased during vasoconstriction, as expected. Frequency domain analysis of C(P) revealed a rapid and significant reduction in magnitude with increasing frequency, with a dominant presence at low frequencies, and a near absence at high frequencies, and its mean value approximates that of the windkessel. Thus, the systemic arterial system compliance varies continuously throughout the cardiac cycle with its predominant effect occurring at low frequencies. These features are not observed in the classical windkessel model.

First principle calculations are used to determine the pressure dependent phase stability transformations for GaS polytypes at pressures up to 1000 GPa. Our results indicate that the relative stability sequence changes with the increase in pressure. With the increase in pressure, the phase stability sequence is β-GaS, GaS-II, rocksalt GaS, CsCl structure of GaS and β-GaS, and the corresponding transformation pressures are 2, 19, 75 and 680 GPa. Finally, we discuss the influence of pressure dependence of these GaS polytypes on their electronic properties.

In a variety of high-temperature superconductors the transition temperature ${T}_{\mathrm{c}}$ has been found to depend on the sample's detailed temperature and pressure history. ${\mathrm{Tl}}_{2}{\mathrm{Ba}}_{2}{\mathrm{CuO}}_{6+\ensuremath{\delta}}$ (Tl-2201) exhibits two distinct relaxation channels, one activated below 100 K and the other above 150 K, that have been attributed to oxygen ordering effects. In the present studies to 0.8 GPa we find that the activation energy for the low-temperature process, ${E}_{\mathrm{A}}^{\mathrm{LT}}(1 \mathrm{bar})\ensuremath{\approx}0.25$ eV, is independent of pressure, whereas the activation energy for the high-temperature process, ${E}_{\mathrm{A}}^{\mathrm{HT}}(1 \mathrm{bar})\ensuremath{\approx}0.75$ eV, appears to increase with pressure yielding an activation volume $\ensuremath{\sim}1.5 {\mathrm{cm}}^{3}/\mathrm{mol}.$ The activation volumes for the diffusion of oxygen defects in the high-temperature superconductors Tl-2201, ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ (Y-123), and ${\mathrm{HgBa}}_{2}{\mathrm{CuO}}_{4+\ensuremath{\delta}}$ (Hg-1201) are estimated using a simple hard-sphere model and found to be roughly half the experimental values. For Tl-2201 this comparison supports an indirect ``interstitialcy'' diffusion path for oxygen defects, whereas for Y-123 and Hg-1201 direct ``interstitial'' diffusion paths are indicated.

The relations among enthalpy, temperature and quality of nonazeotropic refrigerant mixtures (NARMs) in the phase change region (temperature gliding region) are investigated to seek a possibility for linear approximations. Using REFPROP, a refrigerant property calculation package developed by NIST, temperature-enthalpy, temperature-quality, quality-enthalpy relations are investigated for 4 binary and 15 ternary NARMs. Those 19 NARMs tested are the most promising alternative refrigerants for conventional CFC and HCFC refrigerants. A normalized enthalpy. which is a pseudo-quality in a sense, is defined based on the dew and bubble point enthalpies to compare with the conventional quality. The results show that the pseudo-quality and the conventional quality are almost identical independent of system pressure for all the NARMs tested while enthalpy-temperature and quality-temperature relations are diverse and highly pressure dependent depending on mixture combinations. The significance of the near-identical re...

Molecular dynamics simulations of a methane pair in water are used to calculate the thermodynamic properties of the hydrophobic interaction as a function of pressure. Pressure is found to decrease the tendency to form methane aggregates. The entropic contribution to the free energy, which at atmospheric pressure greatly stabilizes aggregation, is highly pressure dependent. As the pressure increases, the entropic stabilization steadily decreases until, at 7 kbar, the entropy of the contact pair is equal to the entropy of the solvent separated pair. The heat capacity change between the contact and solvent separated pair is shown to be large and positive at 1 atm, as is characteristic of hydrophobic processes. At higher pressures, the heat capacity change is zero, indicating that two of the significant properties of the hydrophobic effect, the large entropy decrease and heat capacity increase are lost at high pressures. The free energy, volume and entropy changes are consistent with the corresponding changes...

In a related paper (Jones et al., Comput Mech, 1998;22:413) the problem of maximizing the depth of penetration by a normally impacting cylindrical projectile by optimizing the nose geometry was considered. These results were accomplished by neglecting any frictional resistance offered by the target and only considering the normal pressure acting against the penetrator nose. The problem of maximizing the penetration depth achieved by the normal impact of a cylindrical projectile including the effects of friction acting on the penetrator nose is a much more challenging problem. In this paper, the normal impact and penetration problem is considered including the effects of pressure-dependent friction.

The composition of the Xe system changed from mainly atomic at low pressure to molecular at high pressure. The energy levels of this system varied also. By using the fluorescence of the first and second continuum measured near the resonant line of Xe at 147 nm at various pressure conditions, we observed the formation of Xe 2 and the energy levels for the excited states A1 u , B0 u + and B′1 u states. In a potential energy diagram, this corresponds to the change of energy levels from R ≈∞ to finite R .

Computer-aided processing of the results obtained with the intrathecal infusion test using our newly developed mathematical model simplifies the investigation technique and thus the diagnosis of normal pressure hydrocephalus. Simultaneous determination of resistance and compliance in a single session markedly reduces the examination-related stress on the patient. In contrast to the classical methods, the new calculation does not require the ICP to reach a plateau. Unlike the static approach, our model describes the functional pressure-dependent course of the resistance. This means that account is taken of the non-linearity of the CSF dynamics during the processing of the biosignal. The intrathecal infusion test used to measure resistance and compliance is a reliable diagnostic method in patients with a normal pressure hydrocephalus.

The internationally accepted calculation methods concerning cerebrospinal fluid dynamics proceed from a pressure independent resistance to cerebrospinal fluid outflow. In a new model we focus our attention on the pressure dependency of resistance. In our calculation model we are monitoring the complete pressure course p(t) over the time during and after the infusion. The comparison of the pressure rise On(p) during the infusion and the descent Off(p) after the infusion at the same pressure level allows one to construct all formulas for the compliance C(p) and resistance R(p). The computerized analysis of the results of the intrathecal infusion test using our mathematical computation leads to a simplification of this investigation. The simultaneous measurement of the resistance and compliance during a single investigation allows one to minimize the patient's discomfort. In contrast to the classical methods it is not necessary that the ICP reaches a plateau. Our mathematical method diverges with the description of a pressure dependent slope of the function for the resistance from the static examination models. For that we are able to take the non-linearity of the cerebrospinal fluid resorption into consideration.

Our studies show that hydrostatic pressure causes a substantial increase in Kondo temperature TK and suppresses the magnetic order of the Ce-rich side of (Ce,U)Al2. For example, the magnetic transition of (Ce0.7U0.3)Al2 disappears above 5.5 kbar. Spin fluctuations dominant in the U-rich side become suppressed too, and simultaneously the U-rich systems are driven with pressure towards a simple metallic regime. A new scaling is found of the pressure-dependent resistivity of U-rich samples.

As fluids and porous media are compressible, particularly if free gases are present in the fluid and/or at the pore wall, the permeability of such media varies as a function of the fluid pressure. Under high fluid pressure the permeability increases and under low pressure it decreases. Mechanical vibrations discharged into porous media make the fluid pressure vary and, thus, cause flow by vibration which is directed out of the vibration source. With regard to the specific use of mechanical vibrations for soil remediation methods or injection techniques, for example, a Darcy equation based theory and the fundamental principles of such flows are presented. Hereby, the permeability included in the Darcy equation is a pressure-dependent parameter. The stationary pressure line equation and, in the case of a sine vibration, the equation of the time averaged Darcy velocity are given as a function of the gas content in the fluid and at the pore wall