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101.
In the current contribution, investigations of the high hydrostatic pressure process up to 400 MPa and temperatures up to 353 K are carried out by means of dimensional analysis. The thermofluiddynamical mechanisms are analysed for three different sizes of a high pressure chamber, two different pressure generation systems and two model-fluids that differ in viscosity. Forced convection during compression/decompression and free convection during constant pressure phase are considered separately. The results contain process parameter study based on dimensionless numbers derived from conservation equations of mass, momentum and energy. Either dimensionless process parameters or the fluid dynamical and thermodynamical time scales are presented as a function of pressure and temperature. Relations according to heat transfer and fluid flow mechanisms during high pressure treatment are discussed. 相似文献
102.
C. Luz‐Lima G. D. Saraiva A. G. Souza Filho W. Paraguassu P. T. C. Freire J. Mendes Filho 《Journal of Raman spectroscopy : JRS》2010,41(5):576-581
Raman spectroscopy measurements of polycrystalline Na2MoO4·2H2O (NMHO) and Na2MoO4 (NM) under hydrostatic pressure (from 0 to 10 GPa) were performed. This study allowed us to monitor the stretching and bending vibrations of MoO4 ions as well as the translational modes as a function of pressure. The pressure dependence of the wavenumbers of the modes indicates that the Na2MoO4·2H2O undergoes two phase transitions at about ∼3 and ∼4 GPa. When releasing pressure, we have observed that the original spectrum is recovered, thereby pointing to a reversible process. The Na2MoO4 (NM) starting phase was found to be stable up to 10 GPa. The pressure‐dependent Raman data for NM did not reveal any structural modification. The influence of the pressure‐transmitting medium on the phase transitions is also discussed. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Alicyclobacillus acidoterrestris is a spore-forming bacterium, causing spoilage of juices. The spores of these bacteria have the ability to survive in the typical conditions used for thermal pasteurization. Therefore, the use of other techniques such as high hydrostatic pressure is considered for their inactivation. The effect of hydrostatic pressure of 200–500 MPa, at temperatures 4–50 °C for 15 min, on the dynamics of germination of A. acidoterrestris spores in apple juice and pH 4 buffer was studied. To estimate the share of germinated spores, the method of determining the optical density at a wavelength of 660 nm (OD660) was used. Parameters of hydrostatic pressure treatment used in this work affected the dynamics of germination of A. acidoterrestris spores in apple juice, and the temperature had the greatest effect. The results indicate that nutrients present in apple juice can promote the germination of A. acidoterrestris spores. 相似文献
106.
High hydrostatic pressure (HP) inhibits growth and inactivates microorganisms by destabilizing non-covalent molecular interactions. Arginine contributes to stress resistance because it has a guanidine side chain, which assists in the refolding of aggregated proteins. We attempted to analyze the contribution of arginine to high HP stress using a pressure-sensitive mutant strain of Saccharomyces cerevisiae and a metabolomics approach. Our results showed that the content of 136 out of 250 detected metabolites differed in the mutant and parent strains. Decreased metabolites were involved in the tricarboxylic acid cycle and arginine biosynthesis. The expression of genes contributing to arginine biosynthesis was significantly lower in the mutant strain than in the parent strain. When arginine was supplemented to the medium, the mutant strain showed more tolerance to pressure. These results suggest that yeast cells survived due to the contribution of arginine to high pressure resistance. This indicates that depletion of arginine caused by decreased activity of the biosynthesis pathway confers sensitivity to HP. 相似文献
107.
The shape and gravitational field of ellipsoidal satellites are studied by using the tidal theory. For ellipsoidal satellites, the following conclusions were obtained: Firstly, in the early stage of the satellite formation, strong tidal friction allowed the satellites move in a synchronous orbit and evolve into a triaxial ellipsoidal shape. Because the tidal potential from the associated primary and the centrifugal potential from the satellite spin are nearly fixed at the surface, the early satellites are the viscoelastic celestial body, and their surfaces are nearly in the hydrostatic equilibrium state. The deformation is fixed in the surface of the satellite. By using the related parameters of primary and satellite, the tidal height and the theoretical lengths of three primary radii of the ellipsoidal satellite are calculated. Secondly, the current ellipsoidal satellites nearly maintain their ellipsoidal shape from solidification, which happened a few billion years ago. According to the satellite shape, we estimated the orbital period and spinning angular velocity, and then determined the evolution of the orbit. Lastly, assuming an ellipsoidal satellite originated in the hydrostatic equilibrium state, the surface shape could be determined by tidal, rotation, and additional potentials. However, the shape of the satellite’s geoid differs from its surface shape. The relationship between these shapes is discussed and a formula for the gravitational harmonic coefficients is presented. 相似文献
108.
Xingke Duan Yu Zhu Congying Shu Jihui Gao Fengxia Liu Siyi Pan 《Molecules (Basel, Switzerland)》2022,27(12)
Satsuma mandarin peel pectin was extracted by high hydrostatic pressure-assisted citric acid (HHPCP) or hydrochloric acid (HHPHP), and the physiochemical, structural, rheological and emulsifying characteristics were compared to those from conventional citric acid (CCP) and hydrochloric acid (CHP). Results showed that HHP and citric acid could both increase the pectin yield, and HHPCP had the highest yield (18.99%). Structural characterization, including NMR and FTIR, demonstrated that HHPHP showed higher Mw than the other pectins. The viscosity of the pectin treated with HHP was higher than that obtained with the conventional method, with HHPHP exhibiting significantly higher viscosity. Interestingly, all the pectin emulsions showed small particle mean diameters (D4,3 being 0.2–1.3 μm) and extremely good emulsifying stability with centrifugation and 30-day storage assays, all being 100%. Satsuma mandarin peel could become a highly promising pectin source with good emulsifying properties, and HHP-assisted acid could be a more efficient method for pectin extraction. 相似文献
109.
Mohamed Cherif Gaixia Zhang Yang Gao Shuhui Sun Franois Vidal 《Molecules (Basel, Switzerland)》2022,27(6)
We use computational materials methods to study the sequential appearance of zinc-based zeolitic imidazolate frameworks (ZIFs) generated in the mechanochemical conversion process. We consider nine ZIF topologies, namely RHO, ANA, QTZ, SOD, KAT, DIA, NEB, CAG and GIS, combined with the two ligands 2-methylimidazolate and 2-ethylimidazolate. Of the 18 combinations obtained, only six (three for each ligand) were actually observed during the mechanosynthesis process. Energy and porosity calculations based on density functional theory, in combination with the Ostwald rule of stages, were found to be insufficient to distinguish the experimentally observed ZIFs. We then show, using classical molecular dynamics, that only ZIFs withstanding quasi-hydrostatic pressure P ≥ 0.3 GPa without being destroyed were observed in the laboratory. This finding, along with the requirement that successive ZIFs be generated with decreasing porosity and/or energy, provides heuristic rules for predicting the sequences of mechanically generated ZIFs for the two ligands considered. 相似文献
110.
David Henry 《Applicable analysis》2013,92(2):238-245
In the following note we investigate the occurrence of non-trivial free-surfaces for hydrostatic flows. We show that, for travelling-wave solutions of the full Euler equations where we invoke the hydrostatic approximation, no non-flat travelling wave flows occur unless the resulting flow is outside the domain of current local or global existence results for travelling water waves. 相似文献