Influence Of Hydrostatic Pressure Research Articles

Influence of Hydrostatic Pressure on the Corrosion Behavior of Superhydrophobic Surfaces on Bare and Oxidized Aluminum Substrates.

It is generally recognized that superhydrophobic surfaces in water may be used for corrosion resistance due to the entrapped air in the solid/liquid interface and could find potential applications in the protection of ship hull. For a superhydrophobic surface, as its immersion depth into water increases, the resultant hydrostatic pressure is also increased, and the entrapped air can be squeezed out much more easily. It is therefore predicted that high hydrostatic pressure would cause an unexpected decrease in corrosion resistance for the vessels in deep water (e.g., submarines) because of the unstable entrapped air. In this work, in order to clarify the role of hydrostatic pressure in the corrosion behavior of superhydrophobic surfaces, two typical superhydrophobic surfaces (SHSs) were prepared on bare and oxidized aluminum substrates, respectively, and then were immersed into the NaCl aqueous solutions with different depths of ∼0 cm (hydrostatic pressure ∼0 kPa), 10 cm (1 kPa), and 150 cm (15 kPa). It was found out for the SHSs on the oxidized Al, as the hydrostatic pressure increased, the corrosion behavior became severe. However, for the SHSs on the bare Al, their corrosion behavior was complex due to hydrostatic pressure. It was found that the corrosion resistance under 1 kPa was the highest. Further mechanism analysis revealed that this alleviated corrosion behavior under 1 kPa resulted from suppressing the oxygen diffusion through the liquid and reducing the subsequent corrosion rate as compared with 0 kPa, whereas the relatively low hydrostatic pressure (HP) could stabilize the entrapped air and hence enhance the corrosion resistance, compared with 15 kPa. The present study therefore provided a fundamental understanding for the applications of SHSs to prevent the corrosion, especially for various vessels in deep water.

The Combined Influence of Hydrostatic Pressure and Temperature on Nonlinear Optical Properties of GaAs/Ga0.7Al0.3As Morse Quantum Well in the Presence of an Applied Magnetic Field.

Studies aimed at understanding the nonlinear optical (NLO) properties of GaAs/Ga0.7Al0.3As morse quantum well (QW) have focused on the intersubband optical absorption coefficients (OACs) and refractive index changes (RICs). These studies have taken two complimentary approaches: (1) The compact-density-matrix approach and iterative method have been used to obtain the expressions of OACs and RICs in morse QW. (2) Finite difference techniques have been used to obtain energy eigenvalues and their corresponding eigenfunctions of GaAs/Ga0.7Al0.3As morse QW under an applied magnetic field, hydrostatic pressure, and temperature. Our results show that the hydrostatic pressure and magnetic field have a significant influence on the position and the magnitude of the resonant peaks of the nonlinear OACs and RICs. Simultaneously, a saturation case is observed on the total absorption spectrum, which is modulated by the hydrostatic pressure and magnetic field. Physical reasons have been analyzed in depth.

Preparation of black soybean (Glycine max L) extract with enhanced levels of phenolic compound and estrogenic activity using high hydrostatic pressure and pre-germination

ABSTRACTWe investigated the influence of high hydrostatic pressure (HHP) treatment on the estrogenic properties and conversion of the phenolic compounds in germinated black soybean. The black soybean was germinated for two- or four-days, and then subjected to HHP at 0.1, 50, 100, or 150 MPa for 12 or 24 h. The highest total polyphenol content (3.9 mg GAE/g), flavonoid content (0.8 mg CE/g), phenolic acid content (940 ± 18.96 μg/g), and isoflavonone content (2600 μg/g) were observed after germination for four days and HHP treatment at 100 MPa for 24 h. In terms of isoflavone composition, the malonyl, acetyl and β-glycoside contents decreased, while the aglycone content increased with HHP. The highest proliferative effect (150%) is observed at four days germination and HHP treatment at 100 MPa. These results suggest that application of HHP may provide useful information regarding the utility of black soybean as alternative hormone replacement therapy.

Ab-initio study of (Ga,Cr)N and (Ga,Mn)N DMSs: under hydrostatic pressure

The influence of hydrostatic pressure between 0–100 GPa on structural, electronic and magnetic properties of CrxGa1−xN and MnxGa1−xN (x = 0.25) diluted magnetic semiconductors has been studied. The calculations have been performed using DFT as implemented in code SIESTA. LDA + U as exchange-correlation (XC) potential have been used to study the parameters. Under external pressure, shifting in both valence band and conduction band energy levels from their actual positions has been observed, which lead to modification of electronic properties. Also, N0α, s-d exchange constant and p-d exchange constants, N0β have been calculated at different pressures. Both the compounds show half metallic nature at studied pressure range.

Influence of microstructural defects and hydrostatic pressure on water absorption in composite materials for tidal energy

The lifespan and economic viability of tidal energy devices are constrained, in part, by the complex degradation of the tidal turbine blade materials due to prolonged immersion in a hostile sub-sea environment. Seawater penetration is a significant degradation mechanism in composite materials. This work aims to investigate the influence of microstructure and hydrostatic pressure on water absorption in four polymer composites which are candidate materials for use in tidal energy devices. These materials are: a glass fibre powder epoxy, a carbon fibre powder epoxy, glass fibre Ampreg epoxy and a chopped fibre glass fibre Polyether Ether Ketone. X-ray computed tomography is used to characterise the voids, resin-rich areas and other manufacturing defects present in each material. These defects are known to significantly alter the rate of moisture diffusion, as well as the total uptake of water at saturation. The samples are then exposed to accelerated water aging and hydrostatic pressurisation in order to simulate a range of expected sub-sea operating conditions. The material micro-structure, the matrix material and pressurisation level are shown to strongly influence both the moisture absorption rate and total water uptake. Significant volumetric changes are also noted for all samples, both during and after aging. X-ray computed tomography scans of specimens also provide a unique insight into the role of voids in storing water once a material has reached saturation.

Temperature and hydrostatic pressure effects on single dopant states in hollow cylindrical core-shell quantum dot

This work reports on theoretical investigation of the temperature and hydrostatic pressure effects on the confined donor impurity in a AlGaAs-GaAs hollow cylindrical core-shell quantum dot. The charges are assumed to be completely confined to the interior of the shell with approximately rigid walls. Within the framework of the effective-mass approximation and by using a variational approach, we have computed the donor binding energies as a function of the shell size in order to study the behavior of the electron-impurity attraction for a very small thickness under the influence of both temperature and hydrostatic pressure. Our results show that the temperature and hydrostatic pressure have a significant influence on the impurity binding energy for large shell quantum dots. It will be shown that the binding energy is more pronounced with increasing pressure and decreasing temperature for any impurity position and quantum dot size. The photoionization cross section is also analyzed by considering only the in-plane incident radiation polarization. Its behavior is investigated as a function of photon energy for different values of pressure and temperature. The opposite effects caused by temperature and hydrostatic pressure reveal a big practical interest and offer an alternative way to tuning of correlated electron-impurity transitions in optoelectronic devices.

Influence of hydrostatic pressure on the sound speed of surficial seafloor sediments

ABSTRACTChanges in seawater depth could cause variations of hydrostatic pressure and temperature conditions in surficial seafloor sediments. As a result, the sound speed of the sediments would change. Studies seldom have focused on the influence of hydrostatic pressure on such. According to calculations of the general model of sound speed (GMSS), the sound speed of sediment increased linearly when the hydrostatic pressure increased, the same trend as that of the seawater. Pressure-controlled experiments in the laboratory verified that the influence of hydrostatic pressure on the sediment sound speed was highly related to the pore water, which was consistent with the theoretical calculations from the GMSS. Hydrostatic pressure was found to have the same effect on sound speed for the three kinds of sediments: gravel-silty sand, clayey silt, and silty clay. For different hydrostatic pressures up to 40 MPa, the fluctuation of sound speed ratio calculated with the theoretical model was less than 1.96%, while that measured in the controlled experiment was less than 2.63%. This means that if the sound speed ratio is used as a constant to correct for the difference at different seawater depths of no more than 4000 m, the estimable error is about 2.63%.

Influence of hydrostatic pressure on creeping discharge characteristics over solid/liquid insulating interfaces under AC and DC voltages

This study deals with the influence of hydrostatic pressure on discharges propagating at solid/liquid insulating interface submitted to a divergent electric field under AC and DC voltages. The investigated insulator samples are of phenoplast resin (bakelite) and the considered liquid is mineral oil. The experimental results show that the hydrostatic pressure and the waveform, amplitude and polarity of voltage greatly influence the characteristic parameters of creepage discharges. The stopping (or final) length, L f, which is the maximum extension of these discharges increases with voltage; it is reduced when applying a hydrostatic pressure. L f increases quasi-linearly with the voltage and decreases quasi-linearly when the hydrostatic pressure is increased, whatever the voltage waveform. These results are of great interest especially for design and dimensioning of insulation systems in high voltage oil-filled apparatus and especially non-breathing components.

Влияние изотропного давления на вольт-амперную характеристику поверхностно-барьерных диодов Sb-p-Si<Mn>-Au

AbstractThe influence of hydrostatic pressure on the current–voltage characteristics of surface-barrier diode structures of the Sb– p -Si〈Mn〉–Au type are investigated. The potential-barrier height and the baric coefficient of its variation are found to be e ϕ_δ = 0.75 eV and δ =–1.54 × 10^–11 eV/Pa, respectively.

Hydrostatic pressure and magnetic field effect on the excited states in inverse parabolic quantum dot

The hydrostatic pressure (P) influence of the degenerate energy states inside an inverse parabolic quantum dot (IPQD), with and without an external magnetic field, was performed within the frame of the effective mass approximation. Our theoretical results showed that the effect of relatively high pressure clearly appeared to induce a crossing between the excited states in the strong confinement region. But in the weak confinement region, such crossing disappeared and, in addition, the excited states got reordered. In the presence of an external magnetic field the hydrostatic pressure modified the crossing points of the degenerate states. We investigated the electron-heavy hole transition energy. It displayed a blue shift with increasing the pressure values and the magnetic field strength. But it showed an adhesive red shift by increasing the IPQD size.

Influence of magnetic field, chemical pressure and hydrostatic pressure on the structural and magnetocaloric properties of the Mn–Ni–Ge system

The magnetic, structural and thermomagnetic properties of the MM’X material system of MnNiGe are evaluated with respect to their utilization in magnetocaloric refrigeration. The effects of separate and simultaneous substitution of Fe for Mn and Si on the Ge site are analysed in detail to highlight the benefits of the isostructural alloying method. A large range of compounds with precisely tunable structural and magnetic properties and the tuning of the phase transition by chemical pressure are compared to the effect of hydrostatic pressure on the martensitic transition.We obtained very large isothermal entropy changes of up to J based on magnetic measurements for (Mn,Fe)NiGe in moderate fields of 2 T. The enhanced magnetocaloric properties for transitions around room temperature are demonstrated for samples with reduced Ge, a resource critical element. An adiabatic temperature change of 1.3 K in a magnetic field change of 1.93 T is observed upon direct measurement for a sample with Fe and Si substitution. However, the high volume change of 2.8% results in an embrittlement of large particles into several smaller fragments and leads to a sensitivity of the magnetocaloric properties towards sample shape and size. On the other hand, this large volume change enables to induce the phase transition with a large shift of the transition temperature by application of hydrostatic pressure (72 K ). Thus, the effect of 1.88 GPa is equivalent to a substitution of 10% Fe for Mn and can act as an additional stimulus to induce the phase transition and support the low magnetic field dependence of the phase transition temperature for multicaloric applications.

Physicochemical properties, structural properties, and in vitro digestibility of pea starch treated with high hydrostatic pressure

The influence of high hydrostatic pressure (HHP) treatment at 150, 300, 450, and 600 MPa for 25 min on the physicochemical properties, structural properties, and in vitro digestibility of pea starch was studied. Compared to native and pea starch treated at 150–450 MPa, the morphology of pea starch at 600 MPa was completely destroyed and the particle size became larger, indicating complete gelatinization. The X‐ray diffraction results showed that the native pea starch was gradually changed from the C‐type into the B‐type pattern after 150–600 MPa HHP treatment. At 30–70°C, pea starch treated at 600 MPa had a higher water absorption index (p < 0.05), swelling power, and solubility than other samples did, but opposite results were obtained at 90°C. The rapid visco analyzer (RVA) results indicated that pea starch treated with high pressure at 600 MPa showed lower values of peak viscosity, trough, breakdown, final viscosity, and setback (p < 0.05), reflecting lower retrogradation. Gelatinization temperatures and enthalpy determined by differential scanning calorimetry (DSC) decreased with the increase of pressure. Furthermore, the in vitro digestibility of HHP treated pea starches was lower than that of native pea starch (p < 0.05). Therefore, it is an effective method for HHP treatment to modify the properties of pea starches.

Noise-Induced Total Optical Absorption Coefficient and Refractive Index Change of Impurity Doped Quantum Dots Under Simultaneous Influence of Hydrostatic Pressure and Temperature

Aims: Present study explores two important nonlinear optical (NLO) properties of impurity doped quantum dots (QDs) under the purview of hydrostatic pressure (HP) and temperature. Method: The NLO properties are the total optical absorption coefficient (TOAC) and the total optical refractive index change (TRIC). Simultaneously, the role of Gaussian white noise on these optical properties has also been minutely examined. A change in HP and temperature affects the above NLO properties reflected through alteration of peak height and peak position. Objective: Under a given temperature and HP, the magnitude of above NLO properties has been found to be severely depleted in the presence of noise and the extent of depletion prominently depends on the mode through which noise is applied to the system. Result: The study highlights important interplay between HP, temperature and noise (obviously taking care of its mode of application) that finally governs the profiles of TOAC and TRIC of doped QD systems. Keywords: Quantum dot, absorption coefficient, refractive index change, hydrostatic pressure, temperature, gaussian white noise.

First-principles investigation of structural, elastic, lattice dynamical and thermodynamic properties of lithium sulfur under pressure

In this study we report on the influence of hydrostatic pressure on structural, elastic, lattice dynamical and thermal properties of Li2S in the anti-fluorite structure using ab initio pseudopotential approach based on the density functional perturbation theory. Our results are found to be in good agreement with those existing in the literature. The present phonon dispersion spectra, dielectric constants and Born effective charges may be seen as the first investigation for the material under load. The pressure dependence of all features of interest has been examined and discussed. Besides, the temperature dependence of the lattice parameter and bulk modulus is predicted. The generalized elastic stability criteria showed that the material of interest is mechanically unstable for pressures beyond 55 GPa.

Evaluation of the impact of high pressure on the storage of filled traditional chocolates

Abstract The aim of this study was to evaluate the influence of high hydrostatic pressure (HHP) (400 MPa for 2.5 min and 500 MPa for 1 min) and storage temperature (4 °C and 20 °C), on the physicochemical, rheological and microbiological properties of filled chocolates during storage time. The results showed that the physicochemical (moisture, water activity and pH) and microbiological parameters (total aerobic mesophiles, moulds and yeasts) were particularly affected, at 20 °C, during storage time (P Industrial relevance The preservation of traditional filled chocolates can present some hurdles due to the use of perishable raw materials, physical changes during processing, and also to the influence of external factors, which tend to shorten shelf-life. The most important factors that contribute to the shelf-life of filled chocolates include physical properties (i.e. drying, sugar bloom or fat bloom), microbiological stability (i.e. the use of ingredients with high water content will ease the development of moulds and yeasts) and chemical properties (i.e. oxidation of fatty acids or hydrolysis of fatty acids or saponification). The use of HHP in filled chocolates could be an important contribution to improve the food safety of high quality filled chocolates as an alternative to conventional heating treatments or refrigeration.

The Effect of high hydrostatic pressure on the viability and mutagenesis of Salmonella typhimurium

This work is devoted to the study of the influence of high hydrostatic pressure (HHP) on the viability and level of mutagenesis of Salmonella typhimurium. It was established that the viability of bacteria significantly decreases under hydrostatic pressure of 200 MPa or higher. In addition, the viability index of the bacteria is six orders of magnitude lower with respect to the number of colony-forming units (CFUs) compared to the data of the flow cytofluorometry analysis. This is probably due to the transition of some part of the bacterial population to a viable but nonculturable state (VBNC). HHP of 50 MPa caused a 1.9-fold increase in the number of His+ revertants of the S. typhimurium strain TA98, which indicates the potential of the induction of gene mutations under these conditions. The mechanisms to reduce the viability and genetic changes in bacterial cells under HHP conditions are discussed.

Hydrostatic pressure and the experimental toxicology of marine fishes: The elephant in the room

Hydrostatic pressure (HP) increases linearly with depth in aquatic environments, so that many fish species routinely experience moderate-to-high HP levels (i.e., from a few to dozens of MPa). Biological effects of this thermodynamic variable are evidenced by a reduced functionality of many biomolecular systems, even in barotolerant and barophilic species. It is likely that environmentally-relevant HP levels (i.e., above atmospheric) could also modulate the responsiveness to and toxic effects of pollutants in fish. Still, only a few laboratories have investigated this possibility. The already-published ecobarotoxicological studies have brought strong support to the notion that HP can indeed modulate pollutant response in shallow-water and deep-sea animals. A careful reassessment of toxicity responses is therefore required. To quantify the exact influence of HP in marine fish toxicology, a research framework is proposed that should ensure the collection of meaningful data for risk assessment, using standard toxicity testing and mechanistic approaches.

Characteristics and in vitro anti-inflammatory activities of protein extracts from pre-germinated black soybean [ Glycine max (L.)] treated with high hydrostatic pressure

Abstract We investigated the influence of high hydrostatic pressure (HHP) and pre-germination on black soybean protein and peptide characteristics. Black soybean was germinated (2 or 4 d) and subjected to HHP (0.1–150 MPa; 24 h), followed by preparation of extracts and testing for anti-inflammatory activity. The highest soluble protein content (815.85 mg/g) was in soybeans subjected to HHP (100 MPa) after germination (4 d). Germination and HHP caused the degradation of high molecular weight proteins; we detected the highest content of

Investigation of the influence of high hydrostatic pressure on the abrasive wear of hard-alloy materials

This paper outlines the results of an experimental study of the influence of high hydrostatic pressure on the abrasive wear of hard-alloy materials based on tungsten carbide (~90% WC ± 10% Co), as well as alloys based on iron with high contents of chromium. A specially developed setup has been described in the paper that makes it possible to test materials under the hydrostatic pressure of up to 250 MPa at different friction speeds. An investigation of the surfaces of samples using the Scanning Electron Microscopy method has revealed that the main damage of alloy surface occurs due to the delamination and spalling of hard particles. It has been revealed that the hydrostatic pressure significantly influences the wear rate of the investigated materials. When the pressure increases to 200 MPa, the wear of materials with high contents of chromium increases seven times, while for the material based on tungsten carbide, it increases twice.

Optimisation of high hydrostatic pressure assisted extraction of anthocyanins from rabbiteye blueberry pomace

The purpose of this study was to evaluate the influence of high hydrostatic pressure assisted extraction (HHPE) on the anthocyanins from blueberry (Vaccinium ashei) pomace. From the Plackett-Burman Experimental Design (PBD) only the liquid-solid ratio, ethanol concentration, and extraction pressure were found to significantly affect the extraction yield of anthocyanin content. Hence, the outcome of Box-Behnken Design suggested that the optimal operating conditions of the HHPE for the yield of anthocyanin content were liquid-solid ratio 41 ml/g, ethanol concentration 63%, and extraction pressure 443 MPa. At these conditions, 107.9 mg/100 g anthocyanins was obtained, which was more than by the control extraction (67.63 mg/100 g). 10 anthocyanins were identified by HPLC-ESI-MS, malvidin-3-galactoside and malvidin-3-glucoside were the major anthocyanins.