Application Of Hydrostatic Pressure Research Articles

Controlling phase transitions in MnNiGe using thermal quenching and hydrostatic pressure

Abstract The phase transitions in MnNiGe compounds were explored by manipulating the heat treatment conditions and through hydrostatic pressure application. As the quenching temperature increased, both the first-order martensitic structural transition temperatures and magnetic transition temperatures decreased relative to those in the slowly-cooled samples. When the samples were quenched from 1200 ℃, the first-order martensitic structural transition temperature lowered by more than 200 K. The structural transitions also shifted to lower temperature with the application of hydrostatic pressure during measurement. Temperature-dependent X-ray diffraction results reveal
that the changes of the cell parameters resulting from the structural transitions are nearly identical for all samples regardless of the extensive variation in their structural transition temperatures. In addition, neutron scattering measurements confirm the magnetic structure transition between simple and cycloidal spiral magnetic structures.

Construction of Integral Decellularized Cartilage Using a Novel Hydrostatic Pressure Bioreactor.

The decellularized extracellular matrix (ECM) of cartilage is a widely used natural bioscaffold for constructing tissue-engineered cartilage due to its good biocompatibility and regeneration properties. However, current decellularization methods for accessing decellularized cartilaginous tissues require multiple steps and a relatively long duration to produce decellularized cartilage. In addition, most decellularization strategies lead to damage of the microstructure and loss of functional components of the cartilaginous matrix. In this study, a novel decellularization strategy based on a hydrostatic pressure (HP) bioreactor was introduced, which aimed to improve the efficiency of producing integral decellularized cartilage pieces by combining physical and chemical decellularization methods in a perfusing manner. Two types of cartilaginous tissues, auricular cartilage (AC) and nucleus pulposus (NP) fibrocartilage, were selected for comparison of the effects of ordinary, positive, and negative HP-based decellularization according to the cell clearance ratio, microstructural changes, ECM components, and mechanical properties. The results indicated that applying positive HP improved the efficiency of producing decellularized AC, but no significant differences in decellularization efficiency were found between the ordinary and negative HP-treated groups. However, compared with the ordinary HP treatment, the application of the positive or negative HP did not affect the efficiency of decellularized NP productions. Moreover, neither positive nor negative HP influenced the preservation of the microstructure and components of the AC matrix. However, applying negative HP disarranged the fibril distribution of the NP matrix and reduced glycosaminoglycans and collagen type II contents, two essential ECM components. In addition, the positive HP was beneficial for maintaining the mechanical properties of decellularized cartilage. The recellularization experiments also verified the good biocompatibility of the decellularized cartilage produced by the present bioreactor-based decellularization method under positive HP. Overall, applying positive HP-based decellularization resulted in a superior effect on the production of close-to-natural scaffolds for cartilage tissue engineering. Impact statement In this study, we successfully constructed a novel hydrostatic pressure (HP) bioreactor and used this equipment to produce decellularized cartilage by combining physical and chemical decellularization methods in a perfusing manner. We found that positive HP-based decellularization could improve the production efficiency of integral decellularized cartilage pieces and promote the maintenance of matrix components and mechanical properties. This new decellularization strategy exhibited a superior effect in the production of close-to-natural scaffolds and positively impacts cartilage tissue engineering.

Barocaloric Effects in Dialkylammonium Halide Salts.

Barocaloric effects─solid-state thermal changes induced by the application and removal of hydrostatic pressure─offer the potential for energy-efficient heating and cooling without relying on volatile refrigerants. Here, we report that dialkylammonium halides─organic salts featuring bilayers of alkyl chains templated through hydrogen bonds to halide anions─display large, reversible, and tunable barocaloric effects near ambient temperature. The conformational flexibility and soft nature of the weakly confined hydrocarbons give rise to order-disorder phase transitions in the solid state that are associated with substantial entropy changes (>200 J kg-1 K-1) and high sensitivity to pressure (>24 K kbar-1), the combination of which drives strong barocaloric effects at relatively low pressures. Through high-pressure calorimetry, X-ray diffraction, and Raman spectroscopy, we investigate the structural factors that influence pressure-induced phase transitions of select dialkylammonium halides and evaluate the magnitude and reversibility of their barocaloric effects. Furthermore, we characterize the cyclability of thin-film samples under aggressive conditions (heating rate of 3500 K s-1 and over 11,000 cycles) using nanocalorimetry. Taken together, these results establish dialkylammonium halides as a promising class of pressure-responsive thermal materials.

The effects of physiological and injurious hydrostatic pressure on murine ex vivo articular and growth plate cartilage explants: an RNAseq study.

Chondrocytes are continuously exposed to loads placed upon them. Physiological loads are pivotal to the maintenance of articular cartilage health, while abnormal loads contribute to pathological joint degradation. Similarly, the growth plate cartilage is subject to various loads during growth and development. Due to the high-water content of cartilage, hydrostatic pressure is considered one of the main biomechanical influencers on chondrocytes and has been shown to play an important role in the mechano-regulation of cartilage. Herein, we conducted RNAseq analysis of ex vivo hip cap (articular), and metatarsal (growth plate) cartilage cultures subjected to physiological (5 MPa) and injurious (50 MPa) hydrostatic pressure, using the Illumina platform (n = 4 replicates). Several hundreds of genes were shown to be differentially modulated by hydrostatic pressure, with the majority of these changes evidenced in hip cap cartilage cultures (375 significantly upregulated and 322 downregulated in 5 MPa versus control; 1022 upregulated and 724 downregulated in 50 MPa versus control). Conversely, fewer genes were differentially affected by hydrostatic pressure in the metatarsal cultures (5 significantly upregulated and 23 downregulated in 5 MPa versus control; 7 significantly upregulated and 19 downregulated in 50 MPa versus control). Using Gene Ontology annotations for Biological Processes, in the hip cap data we identified a number of pathways that were modulated by both physiological and injurious hydrostatic pressure. Pathways upregulated in response to 50 MPa versus control, included those involved in the generation of precursor metabolites and cellular respiration. Biological processes that were downregulated in this tissue included ossification, connective tissue development, and chondrocyte differentiation. Collectively our data highlights the divergent chondrocyte phenotypes in articular and growth plate cartilage. Further, we show that the magnitude of hydrostatic pressure application has distinct effects on gene expression and biological processes in hip cap cartilage explants. Finally, we identified differential expression of a number of genes that have previously been identified as osteoarthritis risk genes, including Ctsk, and Chadl. Together these data may provide potential genetic targets for future investigations in osteoarthritis research and novel therapeutics.

Effects of high pressure synergistic enzymatic physical state and concentration on the denaturation of polyphenol oxidase.

The synergistic effect of the initial state of the enzyme and pressure level on the denaturation of PPO has not been clear yet, but it significantly affects the application of high hydrostatic pressure (HHP) in the enzyme-containing food processing. Solid (S-) and low/high concentration liquid (LL-/HL-) polyphenol oxidase (PPO) was used as the study object, and the microscopic conformation, molecular morphology and macroscopic activity of PPO under HHP treatments (100-400MPa, 25°C/30min) were investigated by spectroscopic techniques. The results show that the initial state has a significant effect on the activity, structure, active force and substrate channel of PPO under pressure. The effec can be ranked as follows: physical state>concentration>pressure, S-PPO>LL-PPO>HL-PPO. High concentration has a weakening effect on the pressure denaturation of the PPO solution. Under high pressure, the α-helix and concentration factors play a crucial role in stabilizing the structure.

Release of anthocyanins encapsulated by high hydrostatic pressure-treated micellar casein: Effect of serum Ca2+ level during in vitro digestion

Anthocyanins (ACNs) possess the natural advantage of gastric stabilization and has the potential to be adopted for the delivery system design for prolonged gastric release to enhance its bioavailability. In this study, micellar casein treated with high hydrostatic pressure (100, 300, and 500 MPa) was applied to load ACNs, and exogenous serum Ca2+ (0.15, 2, and 5 mM) controlled the gastric aggregation behavior of casein during in vitro digestion. The results showed that the high level of pressure dissociated the micellar structure and provided more cross-linking possibilities for serum Ca2+. Furthermore, the high serum Ca2+ level enhanced gastric aggregation of casein subunits and submicelles leading to delayed gastric emptying, and controlled the slow release of ACNs, which contributed to prolong the ACN retention in the stomach. Industrial relevanceThe application of high hydrostatic pressure (HHP) in food sterilization has been relatively mature, and there is an urgent need to expand it toward the nutritional and health field in search of high added value. Herein, HHP was applied to solve the problem of low bioavailability of ACNs based on the ingenious relationship between HHP and casein micelles. The research data can help to develop nutraceuticals or high satiety foods with ACNs as the main functional component at low cost.

Time-Dependent Anabolic Response of hMSC-Derived Cartilage Grafts to Hydrostatic Pressure

It is generally accepted that the application of hydrostatic pressure (HP) is beneficial for MSC chondrogenesis. There is, however, evidence to suggest that the timing of application might determine its impact on cell fate and tissue development. Furthermore, understanding how the maturity of engineered cartilage affects its response to the application of HP can provide critical insight into determining when such a graft is ready for in vivo implantation into a mechanically loaded environment. In this study, we systematically examined chondrogenic maturation of hMSCs over 35 days in the presence of TGF-β3 in vitro. At specific timepoints, the response of hMSCs to the application of HP following the removal of TGF-β3 was assessed; this partially models conditions such grafts will experience in vivo upon implantation. In free swelling culture, the expression of chondrogenic (COL2A1 and ACAN) and hypertrophic (COL10A1) markers increased with time. At early timepoints, the expression of such markers continued to increase following TGF-β3 withdrawal; however, this was not observed after prolonged periods of chondrogenic priming (35 days). Interestingly, the application of HP was only beneficial after 35 days of chondrogenic priming, where it enhanced sGAG synthesis and improved key chondrogenic gene ratios. It was also found that HP can facilitate a metabolic shift towards oxidative phosphorylation, which can be viewed as a hallmark of successfully differentiating MSCs. These results point to the importance of mechanical loading as a key stimulus for maintaining a chondrogenic phenotype once MSCs are removed from chemically defined culture conditions.

Simultaneous Hydrostatic and Compressive Loading System for Mimicking the Mechanical Environment of Living Cartilage Tissue.

In vivo, articular cartilage tissue is surrounded by a cartilage membrane, and hydrostatic pressure (HP) and compressive strain increase simultaneously with the compressive stress. However, it has been impossible to investigate the effects of simultaneous loading in vitro. In this study, a bioreactor capable of applying compressive stress under HP was developed to reproduce ex vivo the same physical loading environment found in cartilage. First, a HP stimulation unit was constructed to apply a cyclic HP pressure-resistant chamber by controlling a pump and valve. A compression-loading mechanism that can apply compressive stress using an electromagnetic force was implemented in the chamber. The synchronization between the compression and HP units was evaluated, and the stimulation parameters were quantitatively evaluated. Physiological HP and compressive strain were applied to the chondrocytes encapsulated in alginate and gelatin gels after applying high HP at 25 MPa, which induced damage to the chondrocytes. It was found that compressive stimulation increased the expression of genes related to osteoarthritis. Furthermore, the simultaneous application of compressive strain and HP, which is similar to the physiological environment in cartilage, had an inhibitory effect on the expression of genes related to osteoarthritis. HP alone also suppressed the expression of osteoarthritis-related genes. Therefore, the simultaneous hydrostatic and compressive stress-loading device developed to simulate the mechanical environment in vivo may be an important tool for elucidating the mechanisms of disease onset and homeostasis in cartilage.

From magnetic order to valence-change crossover in EuPd$_2$(Si$_{1-x}$Ge$_x$)$_2$ using He-gas pressure

We present results of magnetic susceptibility and thermal expansion measurements performed on high-quality single crystals of EuPd_22(Si_{1-x}1−xGe_xx)_22 for 0 \leq x \leq≤x≤ 0.2 and temperatures 2 K \leq T \leq≤T≤ 300 K. Data were taken at ambient pressure and finite He-gas pressure pp\leq≤ 0.5 GPa. For x = 0x=0 and ambient pressure we observe a pronounced valence-change crossover centred around T'_VT′V\approx≈ 160 K with a non-magnetic ground state. This valence-change crossover is characterized by an extraordinarily strong pressure dependence of dT'_VT′V /dpp = (80 \pm 10)±10) K/GPa. We observe a shift of T'_VT′V to lower temperatures with increasing Ge-concentration, reaching T'_VT′V\approx≈ 90 K for x = 0.1x=0.1, while still showing a non-magnetic ground state. Remarkably, on further increasing xx to 0.2 we find a stable Eu^{(2+\delta)+}(2+δ)+ valence with long-range antiferromagnetic order below T_NTN = (47.5 \pm± 0.1) K, reflecting a close competition between two energy scales in this system. In fact, by the application of hydrostatic pressure as small as 0.1 GPa, the ground state of this system can be changed from long-range antiferromagnetic order for pp<< 0.1 GPa to an intermediate-valence state for pp\geq≥ 0.1 GPa.

Using pressure to unravel the structure–dynamic-disorder relationship in metal halide perovskites

The exceptional optoelectronic properties of metal halide perovskites (MHPs) are presumed to arise, at least in part, from the peculiar interplay between the inorganic metal-halide sublattice and the atomic or molecular cations enclosed in the cage voids. The latter can exhibit a roto-translative dynamics, which is shown here to be at the origin of the structural behavior of MHPs as a function of temperature, pressure and composition. The application of high hydrostatic pressure allows for unraveling the nature of the interaction between both sublattices, characterized by the simultaneous action of hydrogen bonding and steric hindrance. In particular, we find that under the conditions of unleashed cation dynamics, the key factor that determines the structural stability of MHPs is the repulsive steric interaction rather than hydrogen bonding. Taking as example the results from pressure and temperature-dependent photoluminescence and Raman experiments on MAPbBr_3 but also considering the pertinent MHP literature, we provide a general picture about the relationship between the crystal structure and the presence or absence of cationic dynamic disorder. The reason for the structural sequences observed in MHPs with increasing temperature, pressure, A-site cation size or decreasing halide ionic radius is found principally in the strengthening of the dynamic steric interaction with the increase of the dynamic disorder. In this way, we have deepened our fundamental understanding of MHPs; knowledge that could be coined to improve performance in future optoelectronic devices based on this promising class of semiconductors.

An assessment of the response of human MSCs to hydrostatic pressure in environments supportive of differential chondrogenesis

Mechanical stimulation can modulate the chondrogenic differentiation of stem/progenitor cells and potentially benefit tissue engineering (TE) of functional articular cartilage (AC). Mechanical cues like hydrostatic pressure (HP) are often applied to cell-laden scaffolds, with little optimization of other key parameters (e.g. cell density, biomaterial properties) known to effect lineage commitment. In this study, we first sought to establish cell seeding densities and fibrin concentrations supportive of robust chondrogenesis of human mesenchymal stem cells (hMSCs). High cell densities (15*106 cells/ml) were more supportive of sGAG deposition on a per cell basis, while collagen deposition was higher at lower seeding densities (5*106 cells/ml). Employment of lower fibrin (2.5 %) concentration hydrogels supported more robust chondrogenesis of hMSCs, with higher collagen type II and lower collagen type X deposition compared to 5 % hydrogels. The application of HP to hMSCs maintained in identified chondro-inductive culture conditions had little effect on overall levels of cartilage-specific matrix production. However, if hMSCs were first temporally primed with TGF-β3 before its withdrawal, they responded to HP by increased sGAG production. The response to HP in higher cell density cultures was also associated with a metabolic shift towards glycolysis, which has been linked with a mature chondrocyte-like phenotype. These results suggest that mechanical stimulation may not be necessary to engineer functional AC grafts using hMSCs if other culture conditions have been optimised. However, such bioreactor systems can potentially be employed to better understand how engineered tissues respond to mechanical loading in vivo once removed from in vitro culture environments.

3D‐Printed Anisotropic Nanofiber Composites with Gradual Mechanical Properties

Abstract3D printing of bio‐based nanomaterials into complex structures with design flexibility, structural anisotropy, and long‐term stability is a key issue for biomedical applications. Herein, 3D‐printed and ionically crosslinked structures with anisotropic, water‐proof, and tunable mechanical properties are fabricated using a polysaccharide ink composed of nanocellulose, alginate, and CaCO3 nanoparticles. The excellent shear thinning properties of the ink, combined with double or even triple extrusion, allow printing of complex structures (tubes, buckets, ears, and boat models) with high shape fidelity even after crosslinking. The anisotropically printed and crosslinked structures can be mechanically tuned by controlling the fiber orientation via the printing path, the amount of crosslinker, the type of acid used for crosslinking (weak to strong), and the storage medium. This allows for tailored flexibility and a tensile modulus of the materials in wet state ranging from 1 to 30 MPa. Application of hydrostatic pressure of 160–600 mmHg for 24 h with a physiological fluid to a tubular structure, a model for the cardiovascular system, shows no leakage or rupture in the tube. The great design freedom offered by 3D printing and spatially controlled structural anisotropy enable the production of tailored materials for soft robotics or biomedical applications.

Potential Application of High Hydrostatic Pressure on the Production of Hydrolyzed Proteins with Antioxidant and Antihypertensive Properties and Low Allergenicity: A Review.

The high hydrostatic pressure (HHP) process has been studied for several applications in food technology and has been commercially implemented in several countries, mainly for non-thermal pasteurization and shelf-life extension of food products. HHP processing has been demonstrated to accelerate proteolytic hydrolysis at a specific combination of pressure and pressure-holding time for a given protein source and enzyme. The enzymatic hydrolysis of proteins is a well-known alternative to producing biologically active peptides, with antioxidant and antihypertensive capacity, from different food protein sources. However, some of these protein sources contain allergenic epitopes which are often not degraded by traditional hydrolysis. Moreover, the peptide profile and related biological activity of a hydrolysate depend on the protein source, the enzymes used, the parameters of the proteolysis process (pH, temperature, time of hydrolysis), and the use of other technologies such as HHP. The present review aims to provide an update on the use of HHP for improving enzymatic hydrolysis, with a particular focus on studies which evaluated hydrolysate antihypertensive and antioxidant capacity, as well as residual allergenicity. Overall, HHP has been shown to improve the biological properties of hydrolysates. While protein allergenicity can be reduced with traditional hydrolysis, HHP can further reduce the allergenicity. Compared with traditional hydrolysis methods, HHP-assisted protein hydrolysis offers a greater opportunity to add value to protein-rich products through conversion into high-end hydrolysate products with enhanced nutritional and functional properties.

Superconductivity in medium- and high-entropy alloy thin films: Impact of thickness and external pressure

We have prepared and investigated superconducting ${\mathrm{Nb}}_{67}{\mathrm{Hf}}_{11}{\mathrm{Ti}}_{11}{\mathrm{Zr}}_{11}$ and ${\mathrm{Nb}}_{35}{\mathrm{Ta}}_{35}{\mathrm{Hf}}_{10}{\mathrm{Ti}}_{10}{\mathrm{Zr}}_{10}$ medium- and high-entropy alloys in form of thin films with thicknesses of 600, 100, and 30 nm, and compared their properties with bulk counterparts. We show that the superconducting transition temperature ${T}_{c}$ as well as the upper critical magnetic field ${B}_{c2}(0)$ decrease with decreasing thickness. Application of hydrostatic pressure up to 33 kbar on the 600-nm ${\mathrm{Nb}}_{35}{\mathrm{Ta}}_{35}{\mathrm{Hf}}_{10}{\mathrm{Ti}}_{10}{\mathrm{Zr}}_{10}$ film shows a decrease of ${T}_{c}$ with pressure, which differs from that observed on bulk sample. However, no clear ${T}_{c}$ dependence was observed if pressure was applied on the 100-nm film. This result is most likely related to increasing disorder (tendency to structure amorphization) in thinner films. Moreover, we performed point-contact spectroscopy measurements on the 600-nm ${\mathrm{Nb}}_{67}{\mathrm{Hf}}_{11}{\mathrm{Ti}}_{11}{\mathrm{Zr}}_{11}$ and ${\mathrm{Nb}}_{35}{\mathrm{Ta}}_{35}{\mathrm{Hf}}_{10}{\mathrm{Ti}}_{10}{\mathrm{Zr}}_{10}$ films and were able to observe directly the temperature development of the superconducting energy gap $\mathrm{\ensuremath{\Delta}}(T)$ and determine the superconducting coupling strength $2\mathrm{\ensuremath{\Delta}}/{k}_{B}{T}_{c}=3.54$ and $2\mathrm{\ensuremath{\Delta}}/{k}_{B}{T}_{c}=4.21$, respectively, which is consistent with that of conventional $s$-wave phonon-mediated Bardeen-Cooper-Schrieffer superconductors.

Impact of Conservation Processes on the Lipid Profile and Immunological Factors IL-10 and TGF-β1 in Whey Separated from Discarded Human Milk

Reuse made by the separation of whey can reduce the waste of human milk. However, the authors are not aware of the literature on treatments in human whey, made available by pasteurization holder, freeze-drying, spray drying, and high hydrostatic pressure. In this context, the present study applied treatments to human whey and evaluated their lipid and immunological quality. Among the results, a different formation in the triacylglycerol profile was evidenced after the application of spray drying and high hydrostatic pressure, while pasteurization and freezedrying presented ion intensity close to the control human whey. In addition, pasteurization proved to be adequate for lipid nutritional quality and transformation factor-β1 (TGF-β1) concentration, while an increase in interleukin-10 (IL-10) levels was promoted, between 73 and 80%, after freeze-drying, spray drying, and high hydrostatic pressure. Through the principal component analysis, it is noteworthy that the processes presented divergences in terms of the effects caused, with similarity only between pasteurization and freeze-drying in the composition of fatty acids. However, it was observed that all processes were able to maintain the nutrients. Nevertheless, it is relevant to consider individual characteristics presented and the interest in the desired quality, which can be promising as a complementary product to infant feeding.

Design and development of submersible hydrostatic level sensor using a GMR sensor

In this article, an innovative Hydrostatic Level Sensor (HLS) is presented for measuring water height as well as any other liquid height. This HLS is designed using a magnetic sensor based on giant magnetoresistance (GMR) technology to measure the hydrostatic pressure. This unique HLS has stainless steel (SS) diaphragm attached with a permanent magnet that deflects on the application of hydrostatic pressure resulting in a change in magnetic field gradient at the GMR sensor. The GMR sensor chip develops a voltage output with respect to hydrostatic pressure-induced magnetic field gradient which is further, amplified and corrected using signal conditioning chip. The sensor showed 0.05% of the full-scale resolution, the nonlinearity of <± 1%, and excellent reproducibility. Sensors are tested in laboratory set up and in real-time applications. This GMR-based HLS technology was found to be cost-effective to compete with the existing sensors.

Prediction of Magnetocaloric Effect Induced by Continuous Modulation of Exchange Interaction: A Monte Carlo Study.

A magnetic-to-thermal energy conversion, derived from the continuous modulation of intrinsic exchange energy, is conceived and studied by performing Monte Carlo simulations. On the basis of thermodynamics and Weiss's molecular field theories, we modified the Maxwell formula, where the magnetic entropy change (∆SM) is calculated by integrating the temperature derivative of magnetization under a continuously increasing exchange interaction, rather than an external magnetic field, from zero to a given value. For the conventional ∆SM induced through increasing magnetic field, the ∆SM maximum value is enhanced with increasing magnetic field, while the ∆SM peak temperature is weakly influenced by the magnetic field. On the contrary, the ∆SM induced by changing the exchange interaction is proportional to the exchange interaction while suppressed by a magnetic field. Another feature is that the relative cooling power calculated from the ∆SM induced by changing the exchange interaction is fully independent of the magnetic field perspective for obtaining the magnetically stabilized self-converted refrigerants. The controlled variation of exchange interaction could be realized by partial substitution or the application of hydrostatic pressure to lower the cost of magnetic energy at no expense of magnetocaloric response, which opens an avenue to develop the practical and energy-saving devices of conversion from magnetic energy to thermal energy, highly extending the material species of the magnetocaloric effect.

Chemical Tuning, Pressure, and Temperature Behavior of Mn4+ Photoluminescence in Ga2O3-Al2O3 Alloys.

In this study, we carried out a detailed investigation of the photoluminescence of Mn4+ in Ga2O3-Al2O3 solid solutions as a function of the chemical composition, temperature, and hydrostatic pressure. For this purpose, a series of (Al1-xGax)2O3:Mn4+,Mg phosphors (x = 0, ..., 0.1.0) were synthesized and characterized for the first time. A detailed crystal structure analysis of the obtained materials was done by the powder X-ray diffraction technique. The results of the crystal structure and luminescence studies evidence the transformation of the ambient-pressure-synthesized material from the rhombohedral (α-type) to monoclinic (β-type) phase as the Ga content exceeds 15%. Spectroscopic features of the Mn4+ deep-red emission, including the temperature-dependent emission efficiency and decay time, as well as the possibility of their tuning through chemical pressure in each of these two phases were examined. Additionally, it has been shown that the application of hydrostatic pressure of ≥19 GPa allows one to obtain a corundum-like α-Ga2O3:Mn4+ phase. The luminescence properties of this material were compared with β-Ga2O3:Mn4+, which is normally synthesized at ambient pressure. Finally, we evaluated the possibility of application of the studied phosphor materials for low-temperature luminescence thermometry.

Pressure-driven tunable properties of the small-gap chalcopyrite topological quantum material ZnGeSb2 : A first-principles study

Search for new topological quantum materials is the demand of time and the theoretical prediction plays a crucial role besides the obvious experimental verification. Divination of topological properties in already well-known narrow gap semiconductors is a flourishing area in quantum material. In this view we revisited the semiconductor compound in the chalcopyrite series, with a very small gap near the Fermi energy. Using the density functional theory-based first-principles calculations, we report a strong topologically nontrivial phase in chalcopyrite ${\mathrm{ZnGeSb}}_{2}$, which can act as a model system of strained HgTe. The calculations reveal the nonzero topological invariant (${Z}_{2}$), the presence of Dirac cone crossing in the surface spectral functions with spin-momentum locked spin texture. We also study the interplay between the structural parameters and electronic properties, and report the tunable topological properties due to a very small band gap, from nontrivial to trivial phase under the application of moderate hydrostatic pressure within $\ensuremath{\approx}7$ GPa. A small modification of a lattice parameter is enough to achieve this topological phase transition which is easily accomplished in an experimental laboratory. The calculations show that a discontinuity in the tetragonal distortion of noncentrosymmetric ${\mathrm{ZnGeSb}}_{2}$ plays a crucial role in driving this topological phase transition. Our results are further collaborated with a low energy $\mathbf{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{p}$ model Hamiltonian to validate our $\mathit{ab}\mathit{initio}$ findings. We showed that the evaluation of the model band energy dispersion under the hydrostatic pressure is consistent with the obtained results.

Integrative Physiological and Transcriptome Analysis Reveals the Mechanism for the Repair of Sub-Lethally Injured Escherichia coli O157:H7 Induced by High Hydrostatic Pressure

The application of high hydrostatic pressure (HHP) technology in the food industry has generated potential safety hazards due to sub-lethally injured (SI) pathogenic bacteria in food products. To address these problems, this study explored the repair mechanisms of HHP-induced SI Escherichia coli O157:H7. First, the repair state of SI E. coli O157:H7 (400 MPa for 5 min) was identified, which was cultured for 2 h (37 °C) in a tryptose soya broth culture medium. We found that the intracellular protein content, adenosine triphosphate (ATP) content, and enzyme activities (superoxide dismutase, catalase, and ATPase) increased, and the morphology was repaired. The transcriptome was analyzed to investigate the molecular mechanisms of SI repair. Using cluster analysis, we identified 437 genes enriched in profile 1 (first down-regulated and then tending to be stable) and 731 genes in profile 2 (up-regulated after an initial down-regulation). KEGG analysis revealed that genes involved in cell membrane biosynthesis, oxidative phosphorylation, ribosome, and aminoacyl-tRNA biosynthesis pathways were enriched in profile 2, whereas cell-wall biosynthesis was enriched in profile 1. These findings provide insights into the repair process of SI E. coli O157:H7 induced by HHP.