Combination Of High Pressure Research Articles

The process of superdeep penetration of high-speed metallic particles in solid body

An explanation of the effects arising at the collision of a stream of metal particles with a size of 10–100 microns, moving at a speed of 1–3 km/s, with a solid target is proposed. It is assumed that at the moment of impact on the target, the particle loses some electrons and for some time, due to the presence of an oxide shell, retains a positive charge. The flow of electrons passing through the target at the moment of impact generates an electromagnetic field pulse. A particle with a charge of about 10–9 C, having penetrated into a solid target, presses on the channel wall with a force of about 500 MPa and moves in it under the action of forces caused by the polarization of the target substance. The combination of high pressure and displacement leads to a significant reduction in the particle-wall friction force. The proposed hypothesis, if confirmed, can help find ways to protect electronic devices of spacecraft from impacts from streams of fast dust particles.

Sintering window and sintering mechanism for diamond

High performance sintered diamond tools, such as those applied to wire drawing and rock drilling, represent a considerable advance in hard materials technology. A dense diamond-metal composite is produced using liquid phase sintering. With a cemented carbide substrate, a cobalt-rich liquid infiltrates between the diamond grains at temperatures near 1400 °C. For small diamond particles (nominally below 20 μm), a combination of high pressure (5 GPa or more) and high temperature (1400 °C or more) gives full density in minutes. A sintering window is defined by the pressure and temperature combination that avoids graphitization while ensuring cobalt melt infiltration. The sintering mechanism is carbon transport by dissolution of graphite from low pressure regions away from grain contacts with precipitation of diamond at grain contacts under high pressure. Sinter bonds preferentially nucleate at surface defects, such as screw dislocation spirals. Bonding rates depend on particle size, carbon solubility, temperature, pressure, and hold time. Calculations are shown for interface reaction site limited growth kinetics.

Kinetic study of the combined effect of high pressure and pH-value on Arthrospira Platensis (Spirulina) proteins extraction

The combined effect of High pressure (HP) and pH-value on the extraction of proteins from Arthrospira (Spirulina) platensis was studied. Fresh Spirulina biomass (81% moisture, 60.2 g/100 g dm total soluble proteins-TSP, 16.1 g/100 g dm C-phycocyanin-C-pc) was suspended in phosphate buffer 0.1 M (1/20 w/v) (pH range 5.7–8.6). During a 24-h HP (100–600 MPa and 25 °C) post-processing period, the C-pc and TSP concentrations and C-pc purity were monitored. Chroma analysis and cells disruption through optical microscopy were also performed. Data were described by first order kinetics. Increased extraction rates of proteins were received for higher pressures and pH values. Pressures ≥400 MPa and pH-values ≥8.0 led to lower C-pc yield, due to denaturation process. Pressure 300 MPa and pH 7.1 resulted in highest purity in C-pc extracts (C-pc/other proteins = 1.14, reagent grade). The required extraction times for maximum TSP and C-pc extraction yield were estimated for all HP-pH combinations studied. Industrial relevanceAlternative proteins are among the trends of food research worldwide, targeting to partial replacement of meat-based proteins for human consumption, due in part to health and environmental concerns as well as animal welfare. Thus, plant-based food and alternative proteins (including proteins from algae) novel products are expected to significantly grow the coming years.Algae like spirulina are sources of proteins, nevertheless, some processes need to be applied for extracting them from the biomass. These processes are time-consuming and in most cases the yield of the extracted material is really poor, thus novel approaches are studied.Combination of High pressure (HP) technology along with different pH values of spirulina biomass are parameters that could result in high extractability of proteins (reaching a yield of even 99%) while simultaneously obtaining extracts of high-purity. In addition, appropriate combinations of HP and pH result in a fast and effective process for spirulina proteins extraction compared to conventional methods, thus reducing dramatically the needed time for extraction, allowing for integration of this approach into the microalgae production line.

Using High Pressure and Alkaline pH for Refolding.

The expression of recombinant proteins as insoluble inclusion bodies (IB) has the advantage to separate insoluble aggregates from soluble bacterial molecules, thus obtaining proteins with a high degree of purity. Even aggregated, the proteins in IB often present native-like secondary and tertiary structures, which can be maintained as long as solubilization is carried out in non-denaturing condition. High pressure solubilizes IB by weakening hydrophobic interactions, while alkaline pH solubilizes aggregates by electrostatic repulsion. The combination of high pressure and alkaline pH is effective for IB solubilization at a mild, non-denaturing condition, which is useful for subsequent refolding. Here, we describe the expression of recombinant proteins in Escherichia coli using a rich medium to obtain high expression levels, bacterial lysis, and washing of the IB to obtain products of high purity, and, finally, the solubilization and high yield of refolded proteins using high pressure and alkaline pH.

Novel High-Pressure Nanocomposites for Cathode Materials in Sodium Batteries.

A new nanocomposite material was prepared by high pressure processing of starting glass of nominal composition NaFePO4. Thermal, structural, electrical and dielectric properties of the prepared samples were studied by differential thermal analysis (DTA), X-ray diffraction (XRD) and broadband dielectric spectroscopy (BDS). It was demonstrated that high-pressure-high-temperature treatment (HPHT) led to an increase in the electrical conductivity of the initial glasses by two orders of magnitude. It was also shown that the observed effect was stronger than for the lithium analogue of this material studied by us earlier. The observed enhancement of conductivity was explained by Mott's theory of electron hopping, which is more frequent in samples after pressure treatment. The final composite consisted of nanocrystalline NASICON (sodium (Na) Super Ionic CONductor) and alluaudite phases, which are electrochemically active in potential cathode materials for Na batteries. Average dimensions of crystallites estimated from XRD studies were between 40 and 90 nm, depending on the phase. Some new aspects of local dielectric relaxations in studied materials were also discussed. It was shown that a combination of high pressures and BDS method is a powerful method to study relaxation processes and molecular movements in solids. It was also pointed out that high-pressure cathode materials may exhibit higher volumetric capacities compared with commercially used cathodes with carbon additions.

Reduction of the levels of 5-hydroxymethylfurfural and advanced glycation end products in milk by the combination of high pressure and moderate heat pre-incubation

Reduction of the levels of 5-hydroxymethylfurfural and advanced glycation end products in milk by the combination of high pressure and moderate heat pre-incubation

Calcium supplementation of bioinks reduces shear stress-induced cell damage during bioprinting

During bioprinting, cells are suspended in a viscous bioink and extruded under pressure through small diameter printing needles. The combination of high pressure and small needle diameter exposes cells to considerable shear stress, which can lead to cell damage and death. Approaches to monitor and control shear stress-induced cell damage are currently not well established. To visualize the effects of printing-induced shear stress on plasma membrane integrity, we add FM 1-43 to the bioink, a styryl dye that becomes fluorescent when bound to lipid membranes, such as the cellular plasma membrane. Upon plasma membrane disruption, the dye enters the cell and also stains intracellular membranes. Extrusion of alginate-suspended NIH/3T3 cells through a 200 µm printing needle led to an increased FM 1-43 incorporation at high pressure, demonstrating that typical shear stresses during bioprinting can transiently damage the plasma membrane. Cell imaging in a microfluidic channel confirmed that FM 1-43 incorporation is caused by cell strain. Notably, high printing pressure also impaired cell survival in bioprinting experiments. Using cell types of different stiffnesses, we find that shear stress-induced cell strain, FM 1-43 incorporation and cell death were reduced in stiffer compared to softer cell types and demonstrate that cell damage and death correlate with shear stress-induced cell deformation. Importantly, supplementation of the suspension medium with physiological concentrations of CaCl2 greatly reduced shear stress-induced cell damage and death but not cell deformation. As the sudden influx of calcium ions is known to induce rapid cellular vesicle exocytosis and subsequent actin polymerization in the cell cortex, we hypothesize that calcium supplementation facilitates the rapid resealing of plasma membrane damage sites. We recommend that bioinks should be routinely supplemented with physiological concentrations of calcium ions to reduce shear stress-induced cell damage and death during extrusion bioprinting.

Low-energy adsorptive separation by zeolites

Separation of mixture is always necessarily required in modern industry, especially in fine chemical, petrochemical, coal chemical and pharmaceutical industries. The challenge of the separation process is usually associated with small molecules with very similar physical and chemical properties. Among the separation techniques, the commonly used high-pressure cryogenic distillation process with combination of high pressure and very low temperature is heavily energy-consuming, which accounts for the major production costs as well as 10–15% of the world's energy consumption. To this end, the adsorptive separation process based on zeolite sorbents is a promising lower-energy alternative and the performance is directly determined by the zeolite sorbents. In this review, we surveyed the separation mechanisms based on the steric, equilibrium, kinetic and ‘trapdoor’ effect, and summarized the recent advances in adsorptive separation via zeolites including CO2, light olefins, C8 aromatics and hydrogen isotopes. Furthermore, we provided the perspectives on the rational design of zeolite sorbents for the absolute separation of mixtures.

Impact of high‐pressure treatments on enzyme activity of fruit‐based beverages: an overview

SummaryWith an ever‐increasing demand for clean label products, there is a greater need for efficient and environmentally friendly processes to compete the conventional thermal or chemical treatments. For instance, high‐pressure processing (HPP) has been widely studied in the fruit industry from the last two decades. HPP can inactivate or activate different enzymes in fruit juices, pulp, and purées. HPP treatment inactivates the enzymes by the alterating the conformation of the protein structure and the active site. Depending on the enzyme, pressure, pH, temperature and treatment time, HPP can increase enzyme activity due to the release of membrane‐bound enzymes and also due to changes in protein conformation and active site that facilitate interaction with the substrate. Furthermore, the combination of high pressure, temperature and reduced treatment times offered greater inactivation of enzymes in fruit beverages. This study aimed to investigate the inactivation kinetics of endogenous enzymes in fruit beverages.

Hemodynamic factor evaluation using computational fluid dynamics analysis for de novo bleb formation in unruptured intracranial aneurysms

BackgroundAlthough bleb formation increases the risk of rupture of intracranial aneurysms, previous computational fluid dynamic (CFD) studies have been unable to identify robust causative hemodynamic factors, due to the morphological differences of prebleb aneurysm models and a small number of aneurysms with de novo bleb formation. This study investigated the influences of differences in the aneurysm-models and identify causative hemodynamic factors for de novo bleb formation.Materials and methodsCFD analysis was conducted on three aneurysm models, actual prebleb, postbleb, and virtual prebleb models of two unruptured aneurysms with de novo bleb formation. A new multipoint method was introduced in this study. We evenly distributed points with a 0.5-mm distance on the aneurysm surface of the actual prebleb models (146 and 152 points in the individual aneurysm, respectively), and we statistically compared hemodynamics at the points in the areas with and without bleb formation (19 and 279 points, respectively).ResultsVisually, blebs formed on an aneurysm surface area with similar hemodynamic characteristics in the actual and virtual prebleb models. Statistical analysis using the multipoint method revealed that the de novo bleb formation area was significantly correlated with high pressure (p < 0.001), low wall shear stress (WSS) (p < 0.001), and the center of divergent WSS vectors (p = 0.025).ConclusionsDe novo bleb formation in intracranial aneurysms may occur in areas associated with the combination of high pressure, low WSS, and the center of divergent WSS vectors. The multipoint method is useful for statistical analysis of hemodynamics in a limited number of aneurysms.

Influence of the gas pressure in a Torr regime capacitively coupled plasma deposition reactor

The adjustment of the gas pressure has been shown to improve the deposition rate and uniformity of a plasma process. This led us to investigate the effect of the gas pressure in a 300 mm wafer reactor. We numerically simulated SiH4/He capacitively coupled plasma discharges for the deposition of a hydrogenated amorphous silicon film. The results indicated that an increase in the gas pressure leads to uniform dissipation of the power coupled to the plasma and deposition profiles. By toggling the sidewall condition from grounded to dielectric while varying the gas pressure, we observed a modification of the plasma distributions and deposition profiles. Based thereupon, we concluded that the combination of high pressure with narrow electrode spacing can guarantee more efficient and uniform deposition. Additionally, this result was experimentally validated using the plasma deposition of hydrogenated amorphous carbon from the mixture C3H6/Ar/He. Even though the mixture differed from that we adopted in the simulation, the combination of high pressure with narrow electrode spacing still induced uniform deposition.

New Cage-Like Cerium Trihydride Stabilized at Ambient Conditions

New Cage-Like Cerium Trihydride Stabilized at Ambient Conditions

Fatigue failure and launch safety assessment of gun barrel

Hundreds or thousands of projectiles have been fired through a gun barrel. Catastrophic fatigue failure of gun barrel due to cyclic loadings by the stresses induced by the combination of high pressure and temperature combustion gas, and projectile with the rotating band interaction with the bore surface, has not yet been understood. In this paper, laboratory hydraulic fatigue tests on simulated gun barrel were performed on MTS Land. The experimental results show that there is an inherent relation between crack propagation in thick-walled tube and the external surface hoop and axial strains. This fact suggests that fatigue failure of gun barrel should be likely prevented by monitoring the external surface strains of the gun barrel and stopping continued firing before a major crack growing up to the critical size.

Plasma polymerization of TEMPO shows promise

A combination of high pressure and low power in plasma polymerization of a monomer containing NO-like functional groups can produce well-controlled films.

Control of pathogenic and spoilage bacteria in meat and meat products by high pressure: Challenges and future perspectives.

High-pressure processing is among the most widely used nonthermal intervention to reduce pathogenic and spoilage bacteria in meat and meat products. However, resistance of pathogenic bacteria strains in meats at the current maximum commercial equipment of 600MPa questions the ability of inactivation by its application in meats. Pathogens including Escherichia coli, Listeria, and Salmonelle, and spoilage microbiota including lactic acid bacteria dominate in raw meat, ready-to-eat, and packaged meat products. Improved understanding on the mechanisms of the pressure resistance is needed for optimizing the conditions of pressure treatment to effectively decontaminate harmful bacteria. Effective control of the pressure-resistant pathogens and spoilage organisms in meats can be realized by the combination of high pressure with application of mild temperature and/or other hurdles including antimicrobial agents and/or competitive microbiota. This review summarized applications, mechanisms, and challenges of high pressure on meats from the perspective of microbiology, which are important for improving the understanding and optimizing the conditions of pressure treatment in the future.

Discovery of new boron-rich chalcogenides: orthorhombic B6X (X=S, Se)

New boron-rich sulfide B6S and selenide B6Se have been discovered by combination of high pressure – high temperature synthesis and ab initio evolutionary crystal structure prediction, and studied by synchrotron X-ray diffraction and Raman spectroscopy at ambient conditions. As it follows from Rietveld refinement of powder X-ray diffraction data, both chalcogenides have orthorhombic symmetry and belong to Pmna space group. All experimentally observed Raman bands have been attributed to the theoretically calculated phonon modes, and the mode assignment has been performed. Prediction of mechanical properties (hardness and elastic moduli) of new boron-rich chalcogenides has been made using ab initio calculations, and both compounds were found to be members of a family of hard phases.

Comparing thermal inactivation to a combined process of moderate heat and high pressure: Effect on ascospores in strawberry puree

High pressure processing is a mild preservation process that inactivates pathogenic and spoilage micro-organisms in food products, but preserves the fresh characteristics of a product. Compared to untreated product, an enhanced shelf life is obtained during refrigerated storage. Knowledge on the use of high pressure pasteurisation aimed for ambient storage is limited.The aim of this research was to investigate if a combination of high pressure and moderate heat could be used to produce a shelf-stable high-acid fruit product. Ascospores of the heat resistant fungi Talaromyces macrosporus and Aspergillus fischeri were added to fresh strawberry puree that served as a model system. The effect of the processing steps and storage at ambient temperature for 2 weeks was studied on viability of the ascospores.A preheating step at 69 °C/2 min resulted in full or partial activation of A. fischeri and T. macrosporus spores, respectively. The pressure build-up by the process without any holding time resulted in additional activation of spores. A combination of moderate heat (maximum 85–90 °C) and high pressure (500–700 MPa) for holding times up to 13 min inactivated these highly resistant spores much faster than a heat treatment alone. At Tmax = 85 °C and 600 MPa the spores of T. macrosporus and A. fischeri were inactivated by 5.0 and 5.5 log10 after 13 and 7 min, respectively. At Tmax = 85 °C the heat treatment alone did not reduce the viability of these spores up to 60 min of treatment. At Tmax = 90 °C the holding time of the combined pressure-heat treatment could be reduced to obtain the same degree of inactivation of the heat resistant fungi.In addition, treated and untreated ascospores in strawberry puree were stored for 14 days at room temperature to evaluate delayed outgrowth of spores. Untreated ascospores of A. fischeri were activated by storage in the puree. However, at conditions combining high pressure ≥ 600 MPa with Tmax ≥ 85 °C for 13 min, heat resistant fungi were successfully inactivated.This research showed that a combination of moderate heat and pressure can drastically improve the effectiveness to inactivate heat-resistant ascospores in a high-acid fruit product compared to a heat treatment, potentially resulting in a better product quality.

Effect of high hydrostatic pressure challenge on biogenic amines, microbiota, and sensory profile in traditional poultry- and pork-based semidried fermented sausage.

The processing of traditional poultry- and pork-based semidried fermented smoked sausages needs to be modernized to improve product quality and further extend its shelf life. The aim of the present study was to apply different combinations of high pressure (300 to 600MPa) and time (154 to 1,800 s) on the sausages using an experimental design based on response surface methodology. The chemical, microbial, and sensory characteristics of sausages treated with high-pressure processing (HPP) were investigated. HPP application to semidried fermented sausages resulted in color changes, which could be dependent on the ingredients, formulation, and smoking conditions used. Nevertheless, none of the HPP treatments applied resulted in detectable changes in sensory properties, as tested in a triangle test and confirmed by the analysis of focus groups assessment. Significant differences were detected for lactic acid bacteria (LAB) counts from 344MPa and 1,530 s onward, with a marked decrease for the combination of 600MPa and 960 s (P < 0.05). Coagulase-negative staphylococci showed higher tolerance to the increase in pressure than LAB. HPP induced a microbial reduction on Enterobacteriaceae, molds, and yeasts, minimizing the production of the main biogenic amines. However, the polyamines (spermine and spermidine) increased since their metabolic use by microorganisms did not occur. Given the reduction of the main spoilage microbial indicators with no detectable sensory changes observed with the binomial condition of 600MPa and 960 s, this was chosen as the optimal combination to be further applied. PRACTICAL APPLICATION: The results from sensory analysis revealed that any of the HPP treatments applied resulted in detectable changes in sensory properties, as tested in a triangle test and confirmed by the analysis of the focus groups speeches.

The validity of high pressure IR for detecting the interactions between β-cyclodextrin and imidazolium based ionic liquids

The effects of alkyl side-chain length on the interactions between imidazolium ionic liquids (ILs) and β-cyclodextrin (β-CD) were studied at ambient pressure and up to 2.5GPa. No noticeable changes in the C-H band frequencies of 1-methyl-3-propylimidazolium hexafluorophosphate ([MPIM][PF6]) were observed upon β-CD addition under ambient pressure. Nevertheless, β-CD addition inhibited the formation of the [MPIM][PF6] aggregated structure under pressures of ≤0.7 GPa. As the pressure was raised to 1.1–2.5 GPa, [MPIM][PF6] aggregated and formed self-associated configurations. This pressure-induced dissociation was not detected in the 1-butyl-3-methylimidazolium hexafluorophosphate and β-CD mixture ([BMIM][PF6]-β-CD) due to the long side chain in the [BMIM] cation. This indicates that the alkyl side-chain length of the imidazolium ILs plays a non-negligible role in controlling the order and strength of IL-β-CD interactions. It is well known that the validity of infrared spectroscopy for detecting the inclusion complexation is questionable in the literature. However, this study demonstrates that the combination of high pressure and IR spectroscopy may provide a suitable way to monitor the IL-β-CD interactions.

High pressure sensitization of heat-resistant and pathogenic foodborne spores to nisin

Today, there is no effective non-thermal method to inactivate unwanted bacterial spores in foods. High-Pressure (HP) process has been shown to act synergistically with moderate heating and the bacteriocin nisin to inactivate spores but the mechanisms have not been elucidated. The purpose of the present work was to investigate in depth the synergy of HP and nisin on various foodborne spore species and to bring new elements of understandings.For this purpose, spores of Bacillus pumilus, B. sporothermodurans, B. licheniformis, B. weihenstephanensis, and Clostridium sp. were suspended in MES buffer, in skim milk or in a liquid medium simulating cooked ham brine and treated by HP at 500 MPa for 10 min at 50 °C or 20 °C. Nisin (20 or 50 IU/mL) was added at three different points during treatment: during HP, during and or in the plating medium of enumeration. In the latter two cases, a high synergy was observed with the inhibition of the spores of Bacillus spp. The evaluation of the germinated fraction of Bacillus spp. spores after HP revealed that this synergy was likely due to the action of nisin on HP-sensitized spores, rather than on HP-germinated spores. Thus, the combination of nisin and HP can lead to Bacillus spp. spore inhibition at 20 °C. And Nisin can act on HP-treated spores, even if they are not germinated.This paper provides new information about the inhibition of spores by the combination of HP and nisin. The high synergy observed at low temperature has not been reported yet and could allow food preservation without the use of any thermal process.