High-pressure Cycle Research Articles

Fecal Lipidomics Analysis using Liquid Chromatography‐ Mass Spectrometry

Methodologies for the analysis of intact lipids from fecal matter will facilitate the understanding of gut (patho)physiology, its role(s) in health and disease and help improve patient care. Because lipids are central to intestinal biology, more stable than many metabolites, and more conserved across microbiota than proteins, they will provide information relevant to the microbiome, host, and environment. We developed a fecal extraction method that utilizes two separate, complementary extraction chemistries, dichloromethane and a methyl tert‐butyl ether/hexafluoroisopropanol mixture, alone or with high pressure cycling (PCT), to provide the most robust and comprehensive lipidome coverage. Extracts were assessed by liquid chromatography‐high resolution mass spectrometry profiling with all ion high energy collisional dissociation fragmentation in both positive and negative ionization modes, which enhances unknown lipid characterization. The platform detected >;500 intact lipids, with >;300, spanning 6 LIPIDMAPS categories, identified. This study offers a non‐invasive method to evaluate the GI tract, complement microbiome studies and assess inflammation, nutritional health, and infectious disease in patient vulnerable populations. Research support: K23NR011320 (KEG), U01ES16048 (BSK) and P30DK040561 (WAW).

Method development for fecal lipidomics profiling.

Robust methodologies for the analysis of fecal material will facilitate the understanding of gut (patho)physiology and its role in health and disease and will help improve care for individual patients, especially high-risk populations, such as premature infants. Because lipidomics offers a biologically and analytically attractive approach, we developed a simple, sensitive, and quantitatively precise method for profiling intact lipids in fecal material. The method utilizes two separate, complementary extraction chemistries, dichloromethane (DCM) and a methyl tert-butyl ether/hexafluoroisopropanol (MTBE) mixture, alone or with high pressure cycling. Extracts were assessed by liquid chromatography-high-resolution mass spectrometry-based profiling with all ion higher energy collisional dissociation fragmentation in both positive and negative ionization modes. This approach provides both class-specific and lipid-specific fragments, enhancing lipid characterization. Solvents preferentially extracted lipids based on hydrophobicity. More polar species preferred MTBE; more hydrophobic compounds preferred DCM. Pressure cycling differentially increased the yield of some lipids. The platform enabled analysis of >500 intact lipophilic species with over 300 lipids spanning 6 LIPID MAPS categories identified in the fecal matter from premature infants. No previous report exists that provides these data; thus, this study represents a new paradigm for assessing nutritional health, inflammation, and infectious disease in vulnerable populations.

Effect of High Hydrostatic Pressure and Pressure Cycling on a Pathogenic Salmonella enterica Serovar Cocktail Inoculated into Creamy Peanut Butter

The ability of Salmonella enterica serovars to survive in high fat content, low water activity foods like peanut butter has been demonstrated by large foodborne illness outbreaks in recent years. This study investigates the potential of high hydrostatic pressure processing, including pressure cycling, to inactivate Salmonella inoculated into creamy peanut butter. A cocktail of pathogenic strains of Salmonella Enteritidis PT30, Salmonella Tennessee, Salmonella Oranienburg, Salmonella Anatum, Salmonella Enteritidis PT 9c, and Salmonella Montevideo obtained from peanut butter- and nut-related outbreaks was inoculated (10(6) to 10(7) CFU/g) into creamy peanut butter and high pressure processed under five different sets of conditions, which varied from 400 to 600 MPa and from 4 to 18 min. The log CFU reductions achieved varied from 1.6 to 1.9. Control experiments in which Salmonella was inoculated (10(9) CFU/g) into 0.1% peptone buffer and high pressure processed at 600 MPa for 18 min showed inactivation to below the detection limit of 100 CFU/g, confirming that high pressure processing is effective at destroying Salmonella in high-moisture environments. Pressure cycling under three sets of conditions consisting of pressures from 400 to 600 MPa, 3 to 10 pressure cycles, and hold times of 6 min for each cycle showed reductions similar to those seen in noncycling experiments. The results of our experiments suggest that the peanut butter food matrix facilitates the survival of Salmonella when exposed to high hydrostatic pressure processing.

Effect of sugarcane biomass waste in cement slurries submitted to high temperature and pressure

Abstract Cementitious materials are subjected to changes in their microstructure and mechanical behavior when submitted to high service temperatures. In the oil industry, Portland-based slurries are used where conditions imply high temperatures and high pressures, e.g., steam injection or recovery of heavy oils. The present study investigated the hydration behavior and mechanical strength of cement slurries containing sugarcane biomass waste or silica flour, submitted to high temperature and pressure cycles using a curing chamber. The slurries were initially cured for 28 days at 22 °C. After that, they were placed in a curing chamber for 3 days at 280 °C and 17.6 MPa. The results showed a decrease in the compressive strength of the slurries submitted to high temperature high pressure. The decrease in strength was less marked in the slurry containing 40% of sugarcane biomass waste, as a consequence of the formation of silica-rich phases, i.e., xonotlite and tobermorite. When the slurries were placed in the curing chamber at 280 °C and 6.9 MPa for 7 days (after initial curing for 14 days at 38 °C), the slurry containing 59% sugarcane biomass waste showed an increase in compressive strength, contrary to what was observed for all the other slurries tested.

Pressure Cycling Technology-assisted Protein Digestion for Efficient Proteomic Analysis

In typical proteomic analysis, trypsin digestion is one of the most time-consuming steps. Conventional proteomic sample preparation methods use an overnight trypsin digestion method. In this study, we compared high-pressure cycling technology (PCT) during enzyme digestion for proteome analysis to the conventional method. We examined the effect of PCT on enzyme activity at temperatures of 25, 37, and <TEX>$50^{\circ}C$</TEX>. Although a fast digestion (1 h) was used for the standard protein mixture analysis, the PCT-assisted method with urea showed better results for protein sequence coverage and the number of peptides identified compared with the conventional method. There was no significant difference between temperatures for PCT-assisted digestion; however, we selected PCT-assisted digestion with urea at <TEX>$25^{\circ}C$</TEX> as an optimized method for fast enzyme digestion, based on peptide carbamylation at these conditions. The optimized method was used for stem cell proteome analysis. We identified 233, 264 and 137 proteins using the conventional method with urea at <TEX>$37^{\circ}C$</TEX> for 16h, the PCT-assisted digestion with urea at <TEX>$25^{\circ}C$</TEX> for 1 h, and the non-PCT-assisted digestion with urea at <TEX>$25^{\circ}C$</TEX> for 1 h, respectively. A comparison of these results suggests that PCT enhanced the enzyme digestion by permitting better access to cleavage sites on the proteins.

High pressure-induced structural effects in plastic packaging

Today, flexible vacuum packages are predominantly used for products to be subjected to high pressure treatment. However, tray packages with a modified atmosphere are in demand, which provide a high failure rate with respect to gas and water vapour permeability and packaging integrity. Methods to follow permeation processes under high pressure were developed and used together with optical microscopy, confocal scanning laser microscopy, Raman spectroscopy and atomic force microscopy to identify the mechanisms for changes in permeability and damage to the packaging materials. Single film samples and pouch packages filled with model products were studied. Results indicate a reversible decrease in the coefficients of diffusion and permeation under the impact of high pressure, due to the compression of the polymeric bulk. Irreversible changes in the polymeric materials are associated with gases in the packaging head space, which cause high local temperatures and create damage due to rapid deliberation upon the pressure drop at the end of the high pressure cycle.

Pressure cycling of InN to 20 GPa: In situ transport properties and amorphization

Indium nitride was grown on Al2O3 substrate and characterized by x-ray diffraction, Raman, electrical resistivity, Hall, and magnetoresistance studies. Thermoelectric and electrical properties of free-standing films were measured in situ under high pressure (HP) cycling to 20 GPa, across a phase transformation to a rock-salt-structured lattice. HP-cycling-induced amorphization was established. The thermopower (Seebeck effect) data evidence that both crystalline and amorphous InN kept n-type conductivity to 20 GPa. Pressure effect on the carrier concentration and effective mass is analyzed. Two features that can be related to structural transitions in amorphous InN were found near 11 and 17 GPa.

중형 직분식 디젤 엔진의 0-D Multi-zone 연소 모델 및 1-D Cycle Simulation 연계 기법 개발

본 연구에서는 중형 직분식 선박용 엔진의 성능 및 NOx 배출물 예측을 위한 0-D multi-zone 분무 연소 모델이 개발되었다. 모델은 상용 1-D 사이클 해석 프로그램 (Boost)와 연동할 수 있도록 개발되었으며, 흡배기 시스템을 포함한 엔진 전체에 대한 동시 해석이 가능하였다. 연소 모델은 Fortran90 으로 개발되었으며, AVL 에서 제공된‘user defined high pressure cycle (UDHPC) interface’를 통해 Boost 와 연동되었다. 두 가지의 인젝터(8 홀, 10 홀)에 대해 두 가지 부하에서 해석을 수행하였으며, 해석 결과는 실제 엔진의 성능 실험 결과를 잘 추종하였다.

A critical approach to the determination of optimal heat rejection pressure in transcritical systems

Abstract In this paper the optimal energy efficiency and high cycle pressure problem in single-stage refrigerating carbon dioxide vapour compressor units operating in transcritical conditions is addressed. Literature approximated solutions to the optimisation problem are analysed and critically discussed. A numerical model for CO 2 heat exchangers and refrigerant systems is developed. Different gas coolers are simulated in order to investigate the effect of literature simplifying assumptions on the optimal pressure determination: the analysis showed a strong sensitivity of the gas cooler outlet temperature from the secondary fluid temperature, from its capacity rate and from the heat exchanger geometry. Nevertheless it resulted that approximated solutions obtained considering the carbon dioxide gas cooler outlet temperature as an independent variable behaved better than solutions correlating it to secondary fluid inlet temperature. A commercial refrigeration plant and a heat pump water heater were finally simulated to verify their energy performances when applying literature approximated solutions in presence of an on-board compressor capacity and supply water temperature control respectively. While in the case of the commercial refrigeration plant no major penalisation resulted from the literature approximated solutions simplifying assumptions, the heat pump performance was strongly deteriorated, up to −30%, as a consequence of the huge variation in the water capacity flow rate resulting from the water temperature control. It was finally concluded that an approximated correlation should be critically evaluated before implementation; a real-time algorithm for determining the optimal (or quasi-optimal) pressure value could provide a more efficient and robust solution.

Stirling engines using working fluids with strong real gas effects

Real gas effects typical of the critical region of working fluids are a powerful tool to increase the energy performances of Stirling cycles, mainly at low top temperatures. To carry out the compression near the critical region the working fluids must have a critical temperature near environmental conditions and the use of organic working substances (pure or in suitable mixtures) as a matter of fact begins compulsory. The moderate thermal stability of the organic working fluids limits the maximum temperatures to 300–400 °C and as a consequence, the achievable cycles efficiencies result rather low. Carbon dioxide, with a critical temperature of 31 °C, is, among the traditionally inorganic gases, an exception and is considered here in comparison with organic substances. But the good thermodynamics of the cycles allows, in the considered cases, conversion efficiencies of about 20%, with good specific powers. The good energy performance of real gas Stirling cycles is obtained at the cost of high maximum cycle pressure, in the range of at least 100–300 bar. These high pressures nevertheless have large positive effects on the heat power transferred per unit of pumping mechanical power, and the low top temperatures have a positive influence on the material problems for the hottest engine parts.

Pasteurization of Fruit Juices by Means of a Pulsed High Pressure Process

The use of pulsed high hydrostatic pressure was investigated as a possible approach to stabilize foodstuffs. The objective of this article was to investigate the effect of the main processing variables (pressure [150 to 300 MPa], temperature levels [25 to 50 degrees C], and pulse number [1 to 10]) on the sanitation of nonpasteurized clear Annurca apple juice as well as freshly-squeezed clear orange juice. The aim of the article was the optimization of the process parameters in step-wise pressure treatment (pressure holding time of each pulse: 60 s, compression rate: 10.5 MPa/s, decompression time: 2 to 5s). The shelf life of the samples, processed at optimized conditions, was evaluated in terms of microbiological stability and quality retention. According to our experimental results, the efficiency of pulsed high pressure processes depends on the combination of pulse holding time and number of pulses. The pulsed high pressure cycles have no additive or synergetic effect on microbial count. The efficacy of the single pulses decreases with the increase of the pulse number and pressure level. Therefore the first pulse cycle is more effective than the following ones. By coupling moderate heating to high pressure, the lethality of the process increases but thermal degradation of the products can be detected. The optimization of the process condition thus results in a compromise between the reduction of the pressure value, due to the synergetic temperature action, and the achievement of quality of the final production. The juices processed under optimal processing conditions show a minimum shelf life of 21 d at a storage temperature of 4 degrees C.

Byssochlamys nivea inactivation in pineapple juice and nectar using high pressure cycles

The aim of this work was to assess the inactivation of Byssochlamys nivea ascospores in pineapple juice and nectar by combining pressure sequences involving high pressure cycles with relatively mild thermal processing. The effect of 550 and 600 MPa sustained pressures (holding time of 15 min), combinations of sustained pressures and pressure pulses (holding time of 10 s), and pressure cycles (two, three and five cycles of 550 and 600 MPa for 7.5, 5 and 3 min, respectively), at 20, 40, 60, 70, 80 and 90 °C were compared. B. nivea ascospores were inactivated by applying sustained a pressure of 600 MPa at 90 °C for 5 min (juice) and 15 min (nectar), and three and five cycles of pressure at 600 MPa and 80 °C for nectar with holding time of 5 and 3 min, respectively, and in all pressure cycles for juice. In general, pressure cycles were more effective for inactivating B. nivea ascospores than the application of sustained high pressures.

Preparation and Characterization of Expandable St/MMA Copolymers Produced by Suspension Polymerization

Free radical suspension copolymerization of styrene (St) with methyl methacrylate (MMA) in the presence of n-pentane was investigated. The batch polymerization was performed in a stirred reactor via a two-stage process. First, free radical suspension polymerization of St and MMA in aqueous media was carried out at about 80—90°C with the aid of a monofunctional initiator to the monomer conversions up to about 70%. Second process, called impregnation stage, consisted of a high temperature—high pressure cycle (110—120°C and 10 bars) in which the blowing agent was charged in the reactor and polymerization was carried out with the aid of a high temperature initiator. Fine particles of micron sizes of St/MMA copolymer were synthesized by manipulation of some experimental parameters governing the copolymerization system. Polymerization was carried out at different agitation rates, suspending agent and aqueous phase initiator concentrations as well as emulsifier amounts, while keeping constant the MMA/St ratio. To reach a desired bead size, the above parameters were optimized using the Taguchi method for experimental design and the relative importance of the mentioned parameters was analyzed. Particles with a spherical shape of 250—350 μm were formed. The obtained copolymers were also characterized in terms of molecular weight, polydispersity index, copolymer composition, morphology of the polymer beads, thermal behavior, and particle size and particle size distribution.

Formation of clathrasil layers by secondary growth of DOH-type nuclei for gas separation applications

Dodecasil 1H (D1H) possessing the zeolite framework type DOH is one of the all-silica zeolites and therefore offers high chemical, thermal and hydrothermal stability. D1H is a 6-ring clathrasil with small pore apertures of about 3Å and may be able to selectively transport hydrogen or helium while rejecting other gasses such as CO2. These properties make D1H an interesting microporous membrane material for precombustion applications. Moreover, it has been shown that D1H crystals can be prepared practically structure directing agent-free.Prior to the attempt to prepare complete layers of D1H crystals, the general crystallisation behaviour of D1H was investigated. To obtain optimal crystallisation conditions a large number of synthesis experiments were performed aiming, in particular, at the preparation of pure material consisting of small and very thin crystals with a reduced number of organic molecules occupying the cage-like voids of the structure. The syntheses were performed in the system aminoadamantane/silica/ethylenediamine or ammonia/water and by systematically varying synthesis parameters like temperature, gel composition, aging of the synthesis mixture, seeding and the type of agitation during the synthesis run. In some additional runs aminoadamantane was replaced by other structure directing agents.Moreover, the removal the organics filling the zeolite cages was studied by different approaches, including calcination at atmospheric pressure and by applying high pressure cycling and calcination of ball milled crystals. The obtained materials were then characterized by powder XRD, SEM, thermal analysis, chemical analysis and optical microscopy. Knowing favourable synthesis conditions, D1H layers have been prepared on a α-Al2O3 support by using secondary growth of small D1H nuclei.

Pickling brine treatment for possible recycling using high‐pressure homogenization

AbstractPickling is a preservation method of vegetables by brine immersion. Residual pickling solutions cannot be reused owing to high yeast content and the presence of polygalacturonase, which may produce vegetable softening. It has been reported that high‐pressure homogenization can reduce enzyme activity and microbial population in liquid foods. An investigation was aimed at studying the effect of high‐pressure homogenization cycles on polygalacturonase activity and yeast survival of residual pickling solutions, from processing of six vegetables. Each pickling solution was pumped through a homogenizing valve at 69 MPa pressure and was recirculated up to 15 times. Yeast counts and polygalacturonase activity were determined in treated solutions after being subjected to 1, 2, 5, 10, and 15 pressure cycles. Untreated and thermally treated solutions were used for comparison. Up to 4 log reductions in yeast inactivation was observed after five high‐pressure cycles treatments, contrasted with only 2 log reductions in thermal treatment. No clear relationship between enzyme inactivation and the number of high pressure cycles, or a thermal parallel effect, were observed. Copyright © 2007 Society of Chemical Industry

Sample preparation for two-dimensional gel electrophoresis using pressure cycling technology

Sample preparation for two-dimensional gel electrophoresis using pressure cycling technology

P-20 Fatigue crack propagation life of the autofrettaged compound cylinder

The autofrettage process is commonly used to produce compressive tangential residual stresses near the bore of high-pressure compound cylinder. The multi-layered cylinders can be manufactured with combining autofrettage and shrink fit process to extend fatigue lifetimes. And compressive stresses improve the fatigue life of the vessel during the loading-unloading high-pressure cycles. This paper presents the fatigue design of an autofrettaged compound cylinder for gun barrel which working at high internal pressure(707 MPa). To ensure the structural integrity of the autofrettaged compound cylinder subjected to cyclic internal pressure loading, the fatigue crack propagation life of the cylinder was evaluated. Stress intensity factors of the external cracked compound cylinder due to internal pressure and autofrettage loadings were calculated using the finite element method. The fatigue crack propagation life of the compound cylinder based on the fracture mechanics concepts were predicted and compared to the fatigue crack propagation life of the single cylinder. For FE simulations, the material has been modeled considering an elasto-plastic behaviour for the loading phase. As a result, predicted fatigue crack propagation life of the compound cylinder was about 1.3〜3.3 times more than those of the single cylinder depending on the level of autofrettage.

Examination of the Performance of an Unconventional Combination of Rankine, Brayton, and Inverse Brayton Cycles

The study presented in this article examined the thermodynamic performance of a proposed system constructed from Brayton, inverse Brayton, and steam Rankine cycles. The theoretical examination was performed by varying the Brayton cycle pressure ratio for different values of inlet pressure and expansion pressures of the inverse Brayton cycle and for different ratios of the inverse Brayton power turbine mass flow to the gas generator mass flow. The results indicated that for the three values of mass flow ratio examined, better performance could be achieved when the proposed system is operated at high Brayton cycle pressure ratio (high maximum system temperature and the highest value of inverse Brayton cycle expansion pressure). It was revealed that in the case of the mass flow equal to 0.25, the proposed system achieved the highest value of Brayton cycle pressure ratio and attained a maximum thermal efficiency of 57.7 per cent.

Fatigue behaviour of an autofrettaged high-pressure vessel for the food industry

The autofrettage technique is commonly used to produce compressive tangential residual stresses near the bore of high-pressure vessels. These compression stresses improve the fatigue life of the vessel during the loading–unloading high-pressure cycles. The present paper presents the fatigue design of an autofrettaged thick-walled vessel for the food industry, working at an internal pressure of 500 MPa. A finite element analysis has been performed in order to obtain the residual stresses after the autofrettage at an internal pressure of 925 MPa. The material of the vessel was a 15-5PH stainless steel hardened by precipitation, which shows a strong Bauschinger effect. For FE simulations, the material has been modelled considering an elastic–perfectly plastic behaviour for the loading phase and a Ramberg–Osgood behaviour for the unloading phase, with its coefficients depending on the previous equivalent plastic strain reached during the loading process. The simulation procedure is explained in detail. Finally, the fatigue life of the vessel was obtained using the residual stresses obtained in the previous simulations stage.

Design of an autofrettaged high-pressure vessel, considering the Bauschinger effect

High-pressure processing is a method by which food products are subjected to a high level of hydrostatic pressure for a certain period of time. To achieve this process, it is necessary to correctly design high-pressure vessels capable of supporting at least 100 000 loading—unloading high-pressure cycles. The autofrettage technique is commonly used to produce compressive tangential residual stresses near the bore, which improve the fatigue life of the pressure vessel. This article shows the design of an autofrettaged thick-walled vessel that works at an internal pressure of 500 MPa, with an internal diameter of 300 mm and a length of 4500 mm. A finite element (FE) analysis was performed to obtain the residual stresses after the autofrettage at an internal pressure of 925 MPa. The material of the vessel was a 15–15 PH stainless steel hardened by precipitation, which shows a strong Bauschinger effect. For FE simulations, the material has been modelled considering an elastic—perfectly plastic behaviour for the loading phase and a Ramberg—Osgood behaviour for the unloading phase, with its coefficients depending on the previous equivalent plastic strain reached during the loading process. The simulation procedure is explained in detail and the results allow it to be applied for other autofrettage designs that need the Bauschinger effect of the material to be considered.