Magnetic properties of iron monosilicide FeSi: Pressure effects

The crystal structure, magnetic susceptibility as a function of temperature χ(T) in the range 5–400 K, and the hydrostatic pressure effect on χ at fixed temperatures T = 78, 150, and 300 K, were studied in perovskite-like compounds La1−xPrxCoO3 (x = 0, 0.1, 0.2, and 0.3). The obtained experimental data were analyzed using a two-level model with an energy gap Δ between the ground and excited states of the system that correspond to the spin values S = 0 and 1 for Co3+ ions. In this model, the magnetism of Co3+ ions, which determines the features of the χ (T) dependence, is ensured by the temperature-induced change in the population of the excited state. The anomalously large magnitude of the observed pressure effect is associated with the high sensitivity of Δ to changes in the lattice volume, under the influence of both hydrostatic and chemical pressures, when La is replaced by the smaller Pr ion in the considered system. Theoretical calculations of the electronic structure for the boundary compounds LaCoO3 and PrCoO3 confirm the significant increase in the excitation energy Δ with a decrease in the lattice volume, and also support the scenario of a spin crossover between the states of cobalt ions with low and intermediate spin values.

The Role of Water in the Dissociation of Enolase, a Dimeric Enzyme

An investigation into the influence of hydrostatic pressure on the ultimate capacity of tubular joints is presented. Finite element studies of cross (DT) joints subjected to axial compression and in-plane bending are used to assess the effect that varying amounts of external pressure have on joint capacity. The matrix of geometries evaluated include variations in branch to chord diameter ratio (?), chord radius to thickness ratio (?), and branch to chord thickness ratio (?). Variations in yield strength were also considered, but the same value was always assumed for both the branch and chord. Findings can be divided into two categories. First, longitudinal loads resulting from capped end pressures, as deduced from consideration of isolated members or a frame analysis, may be treated merely as additional axial loads. For deeper water, the magnitude of the branch axial loads from hydrostatic pressure can be substantial and, thus can increase the joint strength utilization ratio. The effect of capped end forces on the chord can be estimated from the normal chord stress effect term, Qf, of the joint capacity equations. However, the impact is expected to be trivial in most instances. The second category of results concerns the effect of hydrostatic radial pressure alone on joint capacity. The analyses show that the capacity can be reduced by as much as 25%, depending on joint parameters and the type of longitudinal load in the branch. Parameter ? is the most important one in relating nondimensionalized branch load and nondimensionalized hydrostatic pressure. Based on a limited number of T-joint cases studied, it appears that the DT-joint interaction equation adjustments, suggested in this study, are a conservative representation T-joint behavior. Also, it seems likely that capacities of other joint configurations will be affected by hydrostatic pressure and should be investigated. INTRODUCTION The offshore oil industry is exploring in progressively deeper water in order to locate economic oil reserves. The deeper waters confront the designers of offshore structures with challenging problems. The member and joint dimensions for shallow water structures are designed according to the expected loading and component capacities, which are provided in various design equations. For deep water structures, an important additional source of loading can be hydrostatic pressure. Overall member behavior in the presence of hydrostatic pressure has received some attention latelyl. In fact, the draft version of API RP2A-LRFD2 reflects these recent studies. However, the effect of hydrostatic pressure on joint capacity has received little or no attention to date. The intent of this analysis has been to provide some design guidance by determining correction factors that can be used to adjust existing joint interaction equations to account for the effect of hydrostatic pressure on joint capacity. The following are interaction equation provided by Hoadley3 and the API2 for tubular joints. Mathematical equation (Available in full paper) The out-of-plane bending terms are not included in Eq. 1 or 2. The results presented below will permit the designer to replace the PU and MU terms in the above equations by new terms that include the effect of hydrostatic pressure.

It has been the object of the present study to elucidate the effect of hydrostatic stress on the mechanical behavior of polycrystalline metals at elevated temperatures. In the studies hitherto made by authors, the effect of hydrostatic stress on metallic tensile creep and torsional creep was investigated through the tests under combined hydrostatic pressure at room temperature. The question concerning the pressure effect under the influence of elevated temperatures has, however, been left still for further inquiry. From (The present) analytical and experimental studies on tensile plastic deformation and tensile creep under hydrostatic pressure at elevated temperatures, the following conclusions have been made.(1) The effect of combined hydrostatic pressure on the plastic flow stress of polycrystalline metals at elevated temperature is observable in the region of large plastic deformation. Therefore, it is necessary to consider the influence of hydrostatic stress in the yielding condition at this region.(2) The effect of concentrated pressure on metallic creep results in decrease in the strain rate of second creep stage at elevated temperature as the same behavior at room temperature. The effect of hydrostatic pressure on metallic creep at elevated temperature may be more intensive than that on the static tensile strength at the same temperature.

Effects of External Hydrostatic Pressure on Orthogonal Cutting Characteristics

On the effect of hydrostatic pressure on the auxetic character of NAT-type silicates

Magnetic properties of RCoO3 cobaltites (R = La, Pr, Nd, Sm, Eu). Effects of hydrostatic and chemical pressure

In this study, we have investigated the effects of temperature (T) and hydrostatic pressure (P) on both the nonlinear and linear optical properties of an InAs/GaAs core/shell quantum dot (QD) system with a Screened-Modified Kratzer potential (SMKP). To achieve this objective, we calculated the energy levels and their corresponding wave functions of the structure using the diagonalization method within the framework of the effective mass approximation. Analytical expressions for the absorption coefficients (ACs) and relative refractive index changes (RRICs) were derived using the compact-density-matrix approach. In our numerical calculations, we first determined the variation of the SMKP dependence, the dipole transition matrix element, and the electron energies of the ground (1s) and first excited state (1p) over a range of hydrostatic pressure (P) and temperature (T). As a result, the obtained numerical calculations revealed that changes in P and T influence both the magnitude and position of the resonant peaks that define the ACs and RRICs

The effects of temperature and hydrostatic pressure have been measured on the velocities of longitudinal and shear ultrasonic waves propagated in ceramic specimens of a composite comprising YBa2Cu3O7-x together with 15 vol.% metallic silver. At room temperature and atmospheric pressure the bulk modulus B0 of the composite is 1.8 times larger than that of the pure YBa2Cu3O7-x ceramic of similar porosity. The ultrasonic wave velocities increase smoothly with decreasing temperature from 300 to 10 K and do not show the anomalous step-like changes including the hysteresis effects in the temperature range 190-235 K, which characterize the elastic behaviour of pure YBa2Cu3O7-x ceramic. The ultrasonic attenuation shows peaks resembling those observed in YBa2Cu3O7-x itself, which result from low-activation-energy anelastic relaxation processes. The effects of hydrostatic pressure on the velocities of ultrasonic waves propagated in the composite and hence the hydrostatic pressure derivatives ( delta CL/ delta P)P=0 and ( delta mu / delta P)P=0 of the elastic stiffnesses and ( delta B/ delta P)P=0 of the bulk modulus are substantially smaller than those found previously for pure YBa2Cu3O7-x ceramics.

Magnetic properties and hydrostatic pressure effect on the curie temperature of (Co, Mn) 2B amorphous alloys

π-Pimer, π-Dimer, π-Trimer, and 1D π-Stacks in a Series of Benzene Triimide Radical Anions: Substituent-Modulated π Interactions and Physical Properties in Crystalline State

Experiments are carried out to determine the molecular and mechanical components of the specific friction force under the effect of hydrostatic pressure of up to 140 MPa. The molecular component of the friction coefficient declines by up to two times under the effect of the hydrostatic pressure in various fluids. It is found that the combined influence of the temperature and hydrostatic pressure on the mechanical properties and the contact pressure leads to considerable variations in the deformation component of the static friction coefficient in plastic contact at temperatures of up to 200°C and under pressures of up to 140 MPa. The dependence of the hardness of structural materials on the hydrostatic pressure is analyzed to predict the effect of the latter on the deformation component of friction. It is shown that with increasing pressure within the above range the hardness grows in proportion to the square of the pressure and is inversely proportional to the initial hardness. The formula for calculating the dependence of the indentation depth of a spherical indenter in elastic contact on the hydrostatic pressure is derived.

The effects of mechanical stimuli on TMJ disc cells have yet to be investigated. This study examined for the first time the effect of constant and intermittent hydrostatic pressure (HP) on TMJ disc cells. Guided by studies on articular chondrocytes, the chosen amplitude was 10 MPa, the frequency was 1 Hz for intermittent HP, and the duration was 4 h. A one-time application of the HP stimulus was applied in 2-D and 3-D for gene expression studies. A duty cycle of 2 days on, 1 day off for 1 week of HP stimulus was used for biochemical content studies. In monolayer, the intermittent HP regimen increased collagen II expression, while constant HP increased collagen I expression when compared to the non-loaded control. However, the overall expression of collagen I was much higher than collagen II in both constant and intermittent HP. The expression results correlated well with gross morphology, histology, and biochemical content. At Week 1, the intermittent HP group had a lower content of collagen, 7.5 +/- 0.2 microg/construct, than the non-loaded control group, 18.2 +/- 4.0 microg/construct. The constant HP group showed the highest amount of collagen, 24.5 +/- 1.6 microg/construct. These data show that constant HP at 10 MPa for 4 h produces more collagen I than do the non-loaded control or intermittent HP at 10 MPa and 1 Hz.

Effect of hydrostatic pressure on the conductivity of YBa2Cu3O7-δsingle crystals in a broad range of temperature and oxygen content

A barotolerant member of the genus Pseudomonas was isolated from deep-sea sediment obtained from the Japan Trench, at a depth of 4418 m. The growth temperature was found to affect the hydrostatic pressure range in which the bacterium could grow; the optimum hydrostatic pressure for growth shifted to a higher pressure with increasing temperature. We examined the lipid composition of the inner membrane of cells grown at various hydrostatic pressures and temperatures. The fatty acid components of the inner membrane lipids were C16:0, C16:1, C18:0, and C18:1. The phospholipid components of the inner membrane were phosphatidylethanolamine, cardiolipin, phosphatidylglycerol, and phosphatidylserine. It is evident that the effects of elevated hydrostatic pressure are comparable to the effects of low temperature on both the fatty acid composition of the inner membrane lipids and the phospholipid composition of the inner membrane of this bacterium.