Ultra-high Hydrostatic Pressure Research Articles

Study on fracture failure behaviour of sapphire transparent window under ultra-high hydrostatic pressure

ABSTRACT Accurately predicting the fracture damage behaviour of light transmission windows is crucial in the design of deep-sea optoelectronic devices. This study proposes a simulation model based on the exponential cohesive zone law to predict the fracture failure of sapphire transparent windows (STW) under multi-dimensional load conditions. By utilising finite element simulation technology, the model accurately determine the fracture damage morphology and failure location of STW in different assembly structure schemes under a hydrostatic pressure of 127 MPa. These simulation results are then effectively validated through full sea depth pressure test experiments. Furthermore, by analyzing the simulation data, this study uncovers the internal mechanism of the fracture damage process of STW and presents a method to predict the fracture damage of STW. This research enhances the understanding of fracture behaviour in light transmission windows and offers valuable insights for the design and development of deep-sea optoelectronic devices.

Ultra-High Hydrostatic Pressure Pretreatment on White Que Zui Tea: Chemical Constituents, Antioxidant, Cytoprotective, and Anti-Inflammatory Activities.

Herbal tea has numerous biological activities and exhibits broad benefits for human health. In China, the flower buds of Lyonia ovalifolia are traditionally processed as herbal tea, namely White Que Zui tea (WQT). This study was aimed to evaluate the effect of ultra-high hydrostatic pressure (UHHP) pretreatment on the chemical constituents and biological activities of free, esterified, and insoluble-bound phenolic fractions from WQT. A total of 327 chemical constituents were identified by a quasi-targeted metabolomics analysis. UHHP pretreatment extremely inhibited reactive oxygen species (ROS) production and cell apoptosis in H2O2-induced HepG2 cells, and it increased the activities of intracellular antioxidant enzymes (SOD and CAT) and GSH content in different phenolic fractions from WQT. In addition, after UHHP pretreatment, the anti-inflammatory effects of different phenolic fractions from WQT were improved by inhibiting the production of nitric oxide (NO) and pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) in LPS-induced RAW264.7 cells. Thus, the UHHP method might be a potential pretreatment strategy for improving the bioavailability of phytochemicals from natural plants.

An insight into the microstructures and composition of 2,700 m-depth deep-sea limpet shells

Structural and physiochemical properties contribute to the biological adaptation of deep-sea animals to their harsh living environment but have hardly been investigated systematically. In the present study, we for the first time applied various material characterization techniques including transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Fourier-transform infrared (FT-IR) spectroscopy to investigate the shell microstructures and chemical composition of a deep-sea limpet Eulepetopsis crystallina collected from the Tiancheng hydrothermal vent field at a depth of around 2,700 m in the Southwest Indian Ocean. Analyses of shell microstructural morphology and diffraction patterns of E. crystallina explicitly revealed the layered structures, exfoliation characteristics, and crystallographic orientation of each layer’s unit cell which was tilted at a small angle sequentially. In comparison with ordinary shallow-water limpet Cellana toreuma shells, E. crystallina shells showed a unique chemical composition and contained pure calcite of calcium carbonate polymorph and the trace of phosphate originated from regional phosphatic sediments of the Southwest Indian Ocean. The further microscopic analyses indicated that the shell of the deep-sea limpet E. crystallina features integrated and untruncated layer structures with a compressed width, possibly owning to the ultra-high hydrostatic pressure, which confirmed the effects of the living environment on the shell microstructure of deep-sea animals.

Effects of High-Pressure Treatments (Ultra-High Hydrostatic Pressure and High-Pressure Homogenization) on Bighead Carp (Aristichthys nobilis) Myofibrillar Protein Native State and Its Hydrolysate

The impacts of four treatments, ultra-high hydrostatic pressure (UHP), high-pressure homogenization (HPH), combined UHP + HPH (U-H), and HPH + UHP (H-U), on bighead carp (Aristichthys nobilis) myofibrillar protein (BMP) structure, functional hydrolysis property to pepsin, and antioxidant activity of hydrolysates were investigated. All treatments led to increase in low-molecular-weight BMP, the BMP stability, and hydrophobic group exposure, but decrease in total sulfhydryl content and BMP particle size, thus resulting in increased hydrolysis and antioxidant capacity of enzymatic hydrolysates. U-H treated BMP exhibited the highest surface hydrophobicity (924.5 ± 1.0), zeta potential absolute value (18.88 ± 0.11 mV), hydrolysis degree (54.5 ± 1.6%), and antioxidant activity, but the lowest α-helix (21.84 ± 2.61%), intrinsic fluorescence spectrum intensity, total sulfhydryl (7.24 ± 0.07 μmol/g), and mean particle size (182.57 ± 2.23 nm). Therefore, U-H might be a promising pretreatment to prepare bioactive peptide.

Comparative study: Thermal and non‐thermal treatment on enzyme deactivation and selected quality attributes of fresh carrot juice

SummaryThe combined effect of emerging electro‐technology high‐voltage cold plasma (HVCP) and non‐thermal ultra‐high hydrostatic pressure (UHP) as bioprocess technologies on the quality and stability of carrot juice has been evaluated. Carrot juice was treated with HVCP (70 kV for 3 min), UHP (300, 400, and 500 MPa) at 25 °C for 5 min, and a blanched sample of 100 °C for 5 min (BS) was also prepared. As compared to control and single treatments, the combined treatment (HVCP‐UHP500) has attained better results in terms of enzyme inactivation and electroporation extraction of coloring compounds, phytochemicals, and ascorbic acid. Wherein, the maximum of 25.87 ± 0.12a µg/100 mL of β‐Carotene, 11.89 ± 0.80aGAE (µg g−1) of total phenols, and 24.07 ± 0.12b mg/100 mL of ascorbic acid content in carrot juice were also observed in the combined treatment at 500 MPa. In addition, phytochemical enhancement might be attributed to the disintegration of phenolic dimers into simple aglycones, predominantly because of the electro‐kinetic phenomenon of HVCP, which is subsequently intensified by UHP treatment. Therefore, the current study suggests that the combination of two novel techniques is a highly efficient method in terms of energy, time, and cost, with low yield efficiency and bio‐safety.

Generation of 30 kbar hydrostatic pressure in Bi2Te3 thin films by uniaxial deformation and its effect on the band structure

Generation of ultrahigh hydrostatic pressure by application of a strong one-axis deformation is demonstrated in epitaxial ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ films on a mica substrate. This was followed by measurements of transport properties in $n$-type ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ as a function of temperature (100--300 K) and pressure of up to 30 kbar. This pressure allowed studies of the restructuring of the conduction band. The nonmonotonic pressure dependence of the Hall coefficient and the increase of electrical conductivity \ensuremath{\sigma}($P$) can only be explained using two subband structures in the conduction band: subbands of light and heavy electrons with a mobility ratio of 10. The gap between the electron subbands increases with the hydrostatic pressure.

Physicochemical Properties of Rice Flour Suspension Treated by Ultrahigh Hydrostatic Pressure

This study investigated the physicochemical properties of rice flour suspensions under ultrahigh hydrostatic pressure (UHP) treatment. Rice flour suspensions were subjected to 200, 400, and 600 MPa of pressure for 10 min, and heat treatment was used as a control. Proximate characteristics of different rice cultivar were analyzed to amylose, damage starch content, and particle size. Changes in physicochemical properties of rice flour suspensions according to UHP treatment were analyzed to microscopic structure, iodine reaction, α-amylase hydrolysis rate, and resistant starch content. Microscopic structural analyses showed that the structures of the rice flours were altered under both heat and 600 MPa treatment conditions. Water absorption rates were highest under heat treatment (467.53–554.85%), followed by 600 MPa treatment (269.55–334.57%). Iodine reaction values increased with increasing applied pressure. α-Amylase hydrolysis rates and resistant starch contents were highest under heat treatment and increased with increasing applied pressure. Based on these results, 600 MPa treatment of rice flour suspensions was shown to be comparable to heat treatment; as a result, the development of the new rice processing method with different physicochemical properties is expected from rice cultivars treated under UHP processing methods.

Research and Analysis of Pressure-Maintaining Trapping Instrument for Macro-Organisms in Hadal Trenches

The ecosystem of the abyss is one of the fields that humans hardly know. The ultra-high hydrostatic pressure makes it very difficult to obtain abyssal organisms. Samples are often severely broken during recovery due to changes in environmental pressure, temperature, and other factors. Currently, there are no macro-organism samplers suitable for the abyss. The development of a pressure-maintaining sampler for the abyss is a prerequisite for abyssal ecosystem research. This paper mainly proposed a pressure-maintaining trapping instrument (PMTI) designed to work at a depth above 10,000 m. Unlike typical deep-sea equipment, this instrument is lightweight (about 65 kg in water). The instrument adopts a new structure, using a hollow piston as the sampling space and sealing the mechanism with O-rings at both ends of the piston, thus avoiding sealing methods such as ball valves and greatly reducing the weight of the equipment. The structure and working process of the instrument are described in detail in this paper. Meanwhile, in this paper, the movement resistance of the piston (mainly the resistance of the O-ring) is analyzed using a dynamic explicit method in Abaqus. The factors affecting the friction of the O-rings are analyzed via the method of orthogonal tests and ANOVA. In addition, high-pressure tests were conducted on key parts of the instrument, and the results showed that the instrument works well at 100 MPa.

Development of a friction test apparatus for simulating the ultra-high pressure environment of the deep ocean

The continued development of deep-ocean equipment requires improved friction and wear resistance of key tribopairs in a high pressure environment. However, there is little research on the effect of high hydrostatic pressure on the tribological properties of different tribopairs as available test rigs are scarce. In this work, a friction test apparatus was developed to help carry out this research. A non-contact gap seal and uniquely shaped loading system were developed to adapt to the high pressure environment and improve measurement accuracy. The fatigue life simulation of key components was conducted to ensure the safety and reliability of the apparatus. Pilot studies on tribopairs consisting of 30 vol% carbon fiber-reinforced polyetheretherketone (CFRPEEK) and AISI 431 stainless steel (431SS) lubricated with high-pressure water were conducted. The results indicated that the apparatus could work stably under an ultra-high hydrostatic pressure of 80 MPa. Friction was found to decrease with increasing hydrostatic pressure. Maximum wear of CFRPEEK occurred at 20 MPa. The results also showed that the CFRPEEK/431SS tribopair could be used in the deep ocean at depths of less than 8000 m as the friction and wear of the tribopair did not degenerate sharply for pressures of 0–80 MPa.

Tissue-engineered submillimeter-diameter vascular grafts for free flap survival in rat model

Vascular grafts for free flap transfers should be of very small diameter and remain patent for approximately three weeks to supply blood until the revascularization from the surrounding tissue is established, with the autologous vein grafts acting as the gold standard. Artificial submillimeter-diameter vascular grafts with clinically useful size of 0.6 mm inner diameter and 5 cm length were prepared and evaluated by replacing the axial artery of free flap in rats. The rat tail artery, selected as a novel bioscaffold material, was decellularized using ultrahigh-hydrostatic pressure (UHP) method and compared with the detergent-based conventional method. To induce rapid endothelialization, the graft lumen was modified with synthesized peptides, having high affinity to the endothelial progenitor cells. The UHP method and peptide modification at 37 °C were found to preserve the extracellular matrix structure well, leading to the stable immobilization of the peptide at the luminal surface. These grafts showed the neointima formation, even at the center position far from the native vessels, remained patent for three weeks, and resulted in the flap survival in the rat free-flap model. The tissue-engineered vascular grafts with functionalized lumen have great future potential as an alternative to autologous vein grafts in free flap transfers.

Multilevel porous structured polyvinylidene fluoride/polyurethane fibrous membranes for ultrahigh waterproof and breathable application

Abstract Porous membranes that can resist water droplet and transmit water vapor simultaneously have aroused wide attention due to their promising application in individual protection. However, the fabrication of such materials remains a challenge. Here we fabricated electrospun fibrous membranes exhibiting ultrahigh waterproofness and excellent breathable performance simultaneously by constructing a multilevel porous structure. The careful control over the concentration of polyvinylidene fluoride (PVDF) generated improved hydrostatic pressure and water vapor transmitting rate (WVTR). More importantly, by coupling polyurethane/fluorinated (PU/FPU) membrane with PVDF membrane layer by layer, the resultant composite PVDF/PU membrane presented ultrahigh hydrostatic pressure (140 kPa) and WVTR (11.3 kg m-2 d-1). We unveiled that this excellent waterproof/breathable performance was achieved benefitting from the differentiated pore size and porosity of the two membranes. The creation of such an encouraging membrane could establish a new optimization methodology for waterproof/breathable membranes.

High pressure-promoted xylanase treatment to enhance papermaking properties of recycled pulp.

Industrially produced bleached recycled pulp (R) comprising essentially hardwood fibres was subjected to enzymatic treatment with endo-xylanase from Thermomyces lanuginosus with or without ultra-high hydrostatic pressure (UHP) pre-treatment at 300-600MPa for 10min. The kinetics and the extent of enzymatic hydrolysis after UHP pre-treatment under different conditions have been evaluated by released reducing sugars and the analysis of neutral sugars in pulps, respectively. The changes in surface chemical composition of pulps were assessed by UV-vis diffuse reflectance spectroscopy. UHP-pre-treated R under optimal conditions (400MPa), with or without posterior enzymatic treatment, was used for the production of handsheets and evaluation of its mechanical properties. It was suggested that enzymatic modification improves significantly the papermaking properties of recycled pulp. These improvements were related with selective removal of xylan bound to impurities and to aggregated cellulose fibrils on the fibre surface, thus favouring the ensuing swelling and inter-fibre bonding in paper. UHP pre-treatment and posterior enzymatic treatment revealed a synergetic effect on the mechanical properties of recycled pulp. This fact was assigned to enhanced accessibility of fibres towards xylanase and by forced hydration and favourable rearrangement of cellulosic fibrils in fibres after UHP pre-treatment. The increase of basic strength properties after UHP-promoted xylanase treatment was up to 30% being the most pronounced for the tensile strength and the burst resistance.

Effect of ultra-high hydrostatic pressure on the survival of Chromohalobacter beijerinckii

The aim of the study was to determine the effect of ultra-high hydrostatic pressure on the survival of Chromohalobacter beijerinckii in samples of nutrient broth containing a 6% addition of NaCl and in samples of cold-smoked salmon. Both types of samples were exposed to ultra-high hydrostatic pressure of 300 and 400 MPa for 0, 5, 10 and 15 min. The number of Chromohalobacter beijerinckii was determined in all control samples and samples subjected to high pressure. The total number of aerobic bacteria was additionally determined in the samples of cold-smoked salmon intentionally inoculated with Chromohalobacter beijerinckii. It was found that Chromohalobacter beijerinckii showed a clearly greater sensitivity to high hydrostatic pressure in the nutrient broth (D-values: 300 MPa - 3.72 min; 400 MPa - 1.90 min) than it did in the samples of cold-smoked salmon (D-values: 300 MPa - 5.83 min; 400 MPa - 3.08 min). The results concerning the total number of aerobic bacteria show that Chromohalobacter beijerinckii is more susceptible to high pressure than the accompanying microflora present in cold-smoked salmon. High pressure treatment at 400 MPa applied for 15 min caused a destruction of Chromohalobacter beijerinckii cells that was clearly visible under a scanning electron microscope. Chromohalobacter beijerinckii belongs to bacteria that have average sensitivity to high hydrostatic pressure.

In situ study starch gelatinization under ultra-high hydrostatic pressure using synchrotron SAXS

The gelatinization of waxy (very low amylose) corn and potato starches by high hydrostatic pressure (HHP) (up to ∼1 GPa) was investigated in situ using synchrotron small-angle X-ray scattering (SAXS) on samples held in a diamond anvil cell (DAC). The starch pastes, made by mixing starch and water in a 1:1 ratio (by weight), were pressurized and measured at room temperature. During HHP, both SAXS peak areas (corresponding to the lamellar phase) of waxy corn and potato starches decreased suggesting the starch gelatinization increases with increasing pressure. As pressure increased, lamellar peak broadened and the power law exponent increased in low q region. 1D linear correlation function was further employed to analyse SAXS data. For both waxy potato and waxy corn starches, the long period length and the average thickness of amorphous layers decreased when the pressure increased. While for both of waxy starches, the thickness of the crystalline layer first increased, then decreased when the pressure increased. The former is probably due to the out-phasing of starch molecules, and the latter is due to the water penetrating into the crystalline region during gelatinization and to pressure induced compression.

Combined effects of ultra-high hydrostatic pressure and mild heat on the inactivation of Bacillus subtilis

Effects of combined ultra-high hydrostatic pressure and mild heat (HPMH) treatments on the food-borne microorganism Bacillus subtilis were evaluated in this study. The B. subtilis culture (counted spores less than 2 log [CFU/mL]) was subjected to 100–500 MPa at 40 °C–60 °C for 15 min at pH 7.0. Treatment with HPMH increased membrane permeability by 10%–89% as determined by the uptake of propidium iodide. Changes in membrane lipids, proteins and DNA were detected in regions 3000 to 2800 cm−1 and 1300 to 900 cm−1 by Fourier transform–infrared spectroscopy (FT-IR). The membrane phospholipid molecules changed from a liquid crystalline state to a gel state, with a decrease in membrane fluidity. HPMH decreased the α-helix content（about 8–22%）while increased the random coil content (about 5–19%) of the cellular protein, which resulted in protein denaturation. Flow cytometry results indicated that HPMH treatment at 60 °C caused 63% damage to the esterase activity of the cells more than HPMH treatment at 40 °C. All of these results revealed the mechanism of HPMH, which is essential for the successful application of high hydrostatic pressure in neutral-pH food processing.

X-ray diffraction investigation of amorphous calcium phosphate and hydroxyapatite under ultra-high hydrostatic pressure

The changes in the crystal structures of synthetically prepared amorphous calcium phosphate (ACP) and hydroxyapatite (HAP) in water (1:1 mass ratio) were studied by synchrotron X-ray diffraction (XRD) under ultra-high hydrostatic pressures as high as 2.34 GPa for ACP and 4 GPa for HAP. At ambient pressure, the XRD patterns of the ACP and HAP samples in capillary tubes and their environmental scanning electron micrographs indicated amorphous and crystalline characteristics for ACP and HAP, respectively. At pressures greater than 0.25 GPa, an additional broad peak was observed in the XRD pattern of the ACP phase, indicating a partial phase transition from an amorphous phase to a new high-pressure amorphous phase. The peak areas and positions of the ACP phase, as obtained through fitting of the experimental data, indicated that the ACP exhibited increased pseudo-crystalline behavior at pressures greater than 0.96 GPa. Conversely, no structural changes were observed for the HAP phase up to the highest applied pressure of 4 GPa. For HAP, a unit-cell reduction during compression was evidenced by a reduction in both refined lattice parameters a and c. Both ACP and HAP reverted to their original structures when the pressure was fully released to ambient pressure.

Shelf life studies on apple juice pasteurised by ultrahigh hydrostatic pressure

Shelf life of Golden Delicious apple juice treated by ultrahigh hydrostatic pressure (HPP) was evaluated in terms of colour, total polyphenol content, antioxidant capacity, ascorbic acid content, pH, titratable acidity, total soluble solids, polyphenol oxidase (PPO) activity, pectin methylesterase (PME) activity and sensory testing. Using response surface methodology it was determined to process the apple juice in a HPP unit at 430 MPa for 7 min, and stored at room temperature (20 °C) and in refrigeration (4 °C) for 34 days. No significant changes (p < 0.05) in physicochemical properties, nutritive value or sensory attributes were detected in the treated apple juice, but the PPO started recovering its activity during the storage without causing significant difference (p < 0.05) in its colour. PME was completely inactivated in the HPP treatment, while indigenous micro-biota of the raw juice was also eliminated. The applied processing conditions preserved the physicochemical and sensory quality of apple juice, and kept polyphenols content and antioxidant capacity unaltered.

In situ study of maize starch gelatinization under ultra-high hydrostatic pressure using X-ray diffraction

The gelatinization of waxy (very low amylose) and high-amylose maize starches by ultra-high hydrostatic pressure (up to 6GPa) was investigated in situ using synchrotron X-ray powder diffraction on samples held in a diamond anvil cell (DAC). The starch pastes, made by mixing starch and water in a 1:1 ratio, were pressurized and measured at room temperature. X-ray diffraction pattern showed that at 2.7GPa waxy starch, which displayed A-type XRD pattern at atmospheric pressure, exhibited a faint B-type-like pattern. The B-type crystalline structures of high-amylose starch were not affected even when 1.5GPa pressure was applied. However, both waxy and high-amylose maize starches can be fully gelatinized at 5.9GPa and 5.1GPa, respectively. In the case of waxy maize starch, upon release of pressure (to atmospheric pressure) crystalline structure appeared as a result of amylopectin aggregation.

Effect of Ultrahigh Hydrostatic Pressure on the Activity and Structure of Mushroom (Agaricus bisporus) Polyphenoloxidase

High hydrostatic pressure (HHP, treatment pressure ≤700 MPa) is approved to be the most successful commercial nonthermal processing due to its minimal modifications in nutritional and sensory quality. However, for some pressure stable enzymes such as PPO, this unique technology can hardly inactivate them at treatment pressure below of 700 MPa. This study investigated the effects of ultrahigh hydrostatic pressure (UHHP, treatment pressure >700 MPa) on the activity of Agaricus bisporus mushroom polyphenoloxidase (PPO) both in the phosphate buffer and in the mushroom puree, and on the structure of the enzyme by means of circular dichroism (CD), fluorescence emission spectra, and sulphydryl group detection. The results showed that UHHP treatment at pressure from 800 to 1600 MPa caused significant inactivation on the PPO both in the phosphate buffer and in the mushroom puree. UHHP treatment at 1400 and 1600 MPa for 1 min reduced the enzyme activity by 90.4% and 99.2% in the buffer;, however, higher enzyme activity remained in the puree after UHHP treatment at the same condition. CD and fluorescence spectra analysis showed that the secondary and tertiary structures of UHHP treated mushroom PPO were changed. The sulphydryl group (SH) detection revealed that the SH content on the surface of UHHP treated mushroom PPO was increased. It has been suggested that the inactivation of mushroom PPO by UHHP treatment at pressure higher than 1000 MPa was due to the synergistic effect of the pressure and the heat arising from pressurization, in which heat plays a major role.

High pressure treatment as a tool for engineering of enzymatic reactions in cellulosic fibres

Ultrahigh hydrostatic pressure (UHP) was applied to enhance the enzymatic hydrolysis of xylan in cellulosic fibers. The pretreatment improved xylan accessibility in the fiber cell wall and a 5–10-fold increase in the initial hydrolysis rate of xylan by xylanase was observed when Eucalyptus globulus kraft bleached pulp was pretreated at hydrostatic pressures of 300–400MPa for 15–45min. The rate and the extent of hydrolysis can be controlled by varying the pressure and the exposure time of UHP treatment prior to enzymatic hydrolysis. Sequential UHP pretreatment and hydrolysis by xylanase disaggregated the hydrated cellulose fibrils and led to the gelation of cell wall regions accessible to enzymatic attack. UHP could therefore become a tool for the engineering of enzymatic reactions within cellulosic fibers to obtain products with tailored properties.