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Hydrostatic Pressure (hydrostatic + pressure)
Kinds of Hydrostatic Pressure Terms modified by Hydrostatic Pressure Selected AbstractsEFFECT OF HIGH HYDROSTATIC PRESSURE ON SPORES OF GEOBACILLUS STEAROTHERMOPHILUS SUSPENDED IN SOYMILKJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 5 2007YOKIUSHIRDHILGILMARA ESTRADA-GIRÓN ABSTRACT The inactivation of Geobacillus stearothermophilus spores (ATCC 7953) inoculated in soymilk was investigated using high hydrostatic pressure (550, 585 and 620 MPa) in combination with temperature (70, 80 and 90C) for selected times (2 s to 15 min). Inactivation of spores occurred at all selected treatments. Less than 10 CFU/mL of G. stearothermophilus were observed after 7 min of treatment at 620 MPa and 90C. An increase in the inactivation rate constant, at the highest pressure, was observed, resulting in a decrease in D values at all temperatures. D values were calculated as 10.6, 6.2 and 3.5 min for 70, 80 and 90C, respectively after pressurization at 620 MPa. zp values decreased as temperature increased with values ranging from 142 to 238 MPa. The activation energy required for inactivation of G. stearothermophilus spores in soymilk, at the selected treatments, was in the range of 37.9,57.4 kJ/mol. [source] INACTIVATION OF BACTERIAL SPORES BY COMBINED ACTION OF HYDROSTATIC PRESSURE AND BACTERIOCINS IN ROAST BEEFJOURNAL OF FOOD SAFETY, Issue 4 2003N. KALCHAYANAND ABSTRACT Foodborne bacterial spores are normally resistant to high hydrostatic pressure; however, at moderate pressure, they can be induced to germinate and outgrow. At this stage, they can be killed by bacteriocin-based biopreservatives (BP-containing pediocin and nisin at 3:7 ratio; BPX, BP + 100 ,g/mL lysozyme; BPY, BPX+ 500 ,g/mL Na-EDTA). Based on this principle, spores of the meat spoilage organism, Clostridium laramie (1,2 × 102 spores/bag) alone or a mixture of four clostridial spores (5 × 103 spores/bag), Clostridium sporogenes, Clostridium perfringens, Clostridium tertium, and Clostridium laramie, were inoculated in roast beef in the presence of 5000 AU/g of bacteriocin-based biopreservatives. The roast beef samples were subjected to hydrostatic pressure (HP) at 345 MPa for 5 min at 60C and stored at 4 or 12C for 84 days or at 25C for 7 days. The HP treatment of roast beef samples inoculated with a mixture of clostridial spores could be stored for 42 days at 4C. The HP in combination with either BPX or BPY extended the shelf-life of roast beef up to 7 days at 25C. The combined treatment of HP and BP controlled the growth of C. laramie spores and extended the shelf-life of roast beef for 84 days when stored at 4C. [source] Image Analysis Based Quantification of Bacterial Volume Change with High Hydrostatic PressureJOURNAL OF FOOD SCIENCE, Issue 9 2008M. Pilavtepe-Çelik ABSTRACT:, Scanning electron microscopy (SEM) images of Staphylococcus aureus 485 and Escherichia coli O157:H7 933 were taken after pressure treatments at 200 to 400 MPa. Software developed for this purpose was used to analyze SEM images and to calculate the change in view area and volume of cells. Significant increase in average cell view area and volume for S. aureus 485 was observed in response to pressure treatment at 400 MPa. Cell view area for E. coli O157:H7 933 significantly increased at 325 MPa, the maximum pressure treatment tested against this pathogen. In contrast to S. aureus, cells of E. coli O157:H7 exhibited significant increase in average view area and volume at 200 MPa. The pressure-induced increase in these parameters may be attributed to modifications in membrane properties, for example, denaturation of membrane-bound proteins and pressure-induced phase transition of membrane lipid bilayer. [source] Stability of Copigmented Anthocyanins and Ascorbic Acid in Muscadine Grape Juice Processed by High Hydrostatic PressureJOURNAL OF FOOD SCIENCE, Issue 4 2007D. Del Pozo-Insfran ABSTRACT:, Intermolecular copigmentation is one of the mechanisms of stabilization of anthocyanins in nature and is also responsible for the characteristic color and stability of aged red wines. In the present study, the effect of polyphenol oxidase (PPO) activity on phytochemical stability of an ascorbic acid-fortified muscadine grape juice following high hydrostatic pressure (HHP) processing (400 and 550 MPa for 15 min) and after 21 d of storage at 25 °C was investigated. Addition of rosemary and thyme polyphenolic extracts (copigmentation) was evaluated as a means to stabilize anthocyanins and ascorbic acid during pressurization and subsequent storage. Polyphenolic extracts were partially purified in order to reduce their content of PPO substrates, and improve their stabilization properties within juice matrix. Overall PPO activity increased (3- and 2.5-fold) following HHP at 400 and 550 MPa, respectively, although it was significantly lower in copigmented treatments. Higher anthocyanin losses occurred at 400 (,70%) than at 550 MPa (,46%), which were correlated to antioxidant losses (r= 0.89). Similarly, greater ascorbic acid losses were observed at 400 (84%) than at 550 MPa (18%). Copigmentation increased anthocyanin retention in reference to pressurized controls (3- and 3.2-fold for rosemary and thyme treatments, respectively) and decreased ascorbic degradation (20 to 32%). In stored samples, higher anthocyanin content (>2-fold) and antioxidant capacity (>1.5-fold) was observed for copigmented treatments when compared to control juices. Addition of partially purified copigments increased muscadine grape juice color, antioxidant activity and also reduced phytochemical losses during HHP processing and storage. [source] The Effects of Irradiation, High Hydrostatic Pressure, and Temperature during Pressurization on the Characteristics of Cooked-reheated Salmon and Catfish FilletsJOURNAL OF FOOD SCIENCE, Issue 1 2003D.R. McKenna ABSTRACT: Fully-cooked salmon and catfish fillets were treated by ionizing radiation (0, 3, or 6 kGy), high hydrostatic pressure (HHP) (0, 414, or 690 MPa), 2 different temperatures during pressurization (ambient-HHP approximately equal to 21 °C, or heated-HHP = 70 °C), and combinations of the treatments. Kramer shear values increased for salmon and catfish fillets treated by HHP, heated-HHP, and a combination treatment. Tenderness and juiciness scores of salmon and catfish fillets were lower with HHP, heated-HHP, and a combination treatment. Irradiation decreased CIE a* values of salmon, and CIE b* values of salmon and catfish. Irradiation increased tenderness and juiciness scores of salmon and increased flavor intensity of catfish. [source] The Lifetimes of Pharaonis Phoborhodopsin Signaling States Depend on the Rates of Proton Transfers,Effects of Hydrostatic Pressure and Stopped Flow Experiments,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2008Takashi Kikukawa Pharaonis phoborhodopsin (ppR), a negative phototaxis receptor of Natronomonas pharaonis, undergoes photocycle similar to the light-driven proton pump bacteriorhodopsin (BR), but the turnover rate is much slower due to much longer lifetimes of the M and O intermediates. The M decay was shown to become as fast as it is in BR in the L40T/F86D mutant. We examined the effects of hydrostatic pressure on the decay of these intermediates. For BR, pressure decelerated M decay but slightly affected O decay. In contrast, with ppR and with its L40T/F86D mutant, pressure slightly affected M decay but accelerated O decay. Clearly, the pressure-dependent factors for M and O decay are different in BR and ppR. In order to examine the deprotonation of Asp75 in unphotolyzed ppR we performed stopped flow experiments. The pH jump-induced deprotonation of Asp75 occurred with 60 ms, which is at least 20 times slower than deprotonation of the equivalent Asp85 in BR and about 10-fold faster than the O decay of ppR. These data suggest that proton transfer is slowed not only in the cytoplasmic channel but also in the extracellular channel of ppR and that the light-induced structural changes in the O intermediate of ppR additionally decrease this rate. [source] Effects of Cyclic Hydrostatic Pressure on the Metabolism of Human Osteoarthritic Chondrocytes Cultivated in a Collagen GelARTIFICIAL ORGANS, Issue 2 2007Karsten Gavénis Abstract:, Among other parameters, the application of mechanical force may provide an important stimulus in modulating the structure and function of tissue-engineered articular cartilage. We developed a cultivation chamber in which six collagen type-I gel samples, seeded with human osteoarthritic chondrocytes, can be cultivated simultaneously. A cyclic hydrostatic pressure of up to 40 kPa with a frequency of 0.0125 Hz was applied, and cultivation was performed for 1, 4, 7, or 14 days. Histological examinations revealed a spheroidal cell morphology in the treatment group. In contrast, control samples of the same patients represented a more fibroblastic appearance. Collagen type-II (col-II) protein was found in the very pericellular region of all investigated samples; the col-II content did not obviously vary between the control and treatment groups. In the treatment group, col-II and aggrecan gene expression were elevated. A spectrophotometric quantification of proteoglycan concentrations in media supernatants revealed a statistically significant enhancement in the treatment group. [source] ChemInform Abstract: Structural Properties of Multiferroic BiFeO3 under Hydrostatic Pressure.CHEMINFORM, Issue 44 2009Alexei A. Belik Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Kinetic, Thermodynamic, and Mechanistic Patterns for Free (Unbound) Cytochrome c at Au/SAM Junctions: Impact of Electronic Coupling, Hydrostatic Pressure, and Stabilizing/Denaturing AdditivesCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2006Dimitri E. Khoshtariya Prof. Dr. Abstract Combined kinetic (electrochemical) and thermodynamic (calorimetric) investigations were performed for an unbound (intact native-like) cytochrome c (CytC) freely diffusing to and from gold electrodes modified by hydroxyl-terminated self-assembled monolayer films (SAMs), under a unique broad range of experimental conditions. Our approach included: 1) fine-tuning of the charge-transfer (CT) distance by using the extended set of Au-deposited hydroxyl-terminated alkanethiol SAMs [-S-(CH2)n -OH] of variable thickness (n=2, 3, 4, 6, 11); 2) application of a high-pressure (up to 150,MPa) kinetic strategy toward the representative Au/SAM/CytC assemblies (n=3, 4, 6); 3) complementary electrochemical and microcalorimetric studies on the impact of some stabilizing and denaturing additives. We report for the first time a mechanistic changeover detected for "free" CytC by three independent kinetic methods, manifested through 1) the abrupt change in the dependence of the shape of the electron exchange standard rate constant (ko) versus the SAM thickness (resulting in a variation of estimated actual CT range within ca. 15 to 25 Å including ca. 11 Å of an "effective" heme-to-,-hydroxyl distance). The corresponding values of the electronic coupling matrix element vary within the range from ca. 3 to 0.02 cm,1; 2) the change in activation volume from +6.7 (n=3), to ,0 (n=4), and ,5.5 (n=6) cm3,mol,1 (disclosing at n=3 a direct pressure effect on the protein's internal viscosity); 3) a "full" Kramers-type viscosity dependence for ko at n=2 and 3 (demonstrating control of an intraglobular friction through the external dynamic properties), and its gradual transformation to the viscosity independent (nonadiabatic) regime at n=6 and 11. Multilateral cross-testing of "free" CytC in a native-like, glucose-stabilized and urea-destabilized (molten-globule-like) states revealed novel intrinsic links between local/global structural and functional characteristics. Importantly, our results on the high-pressure and solution-viscosity effects, together with matching literature data, strongly support the concept of "dynamic slaving", which implies that fluctuations involving "small" solution components control the proteins' intrinsic dynamics and function in a highly cooperative manner as far as CT processes under adiabatic conditions are concerned. [source] Carrier recombination mechanisms in mid-infrared GaInAsSb quantum well lasersPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2007K. O'Brien Abstract Hydrostatic pressure and spontaneous emission techniques have been used to examine the important recombination mechanisms in type-I GaInAsSb/GaSb quantum well lasers. High pressure results indicate that Auger recombination dominates the threshold current of 2.11 ,m and 2.37 ,m devices and is the origin of their temperature sensitivity around room temperature. While the characteristics of the 2.37 ,m devices are much improved by the suppression of the CHSH Auger process, since its spin,orbit splitting energy is greater than its band gap, other important Auger processes such as CHHL and CHCC persist. In the larger band gap 2.11 ,m devices, an increase in threshold current with pressure is observed suggesting that CHSH Auger is present in these devices at atmospheric pressure and contributes to performance degradation at these shorter wavelengths. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Tubular reabsorption and diabetes-induced glomerular hyperfiltrationACTA PHYSIOLOGICA, Issue 1 2010P. Persson Abstract Elevated glomerular filtration rate (GFR) is a common observation in early diabetes mellitus and closely correlates with the progression of diabetic nephropathy. Hyperfiltration has been explained to be the result of a reduced load of sodium and chloride passing macula densa, secondarily to an increased proximal reabsorption of glucose and sodium by the sodium-glucose co-transporters. This results in an inactivation of the tubuloglomerular feedback (TGF), leading to a reduced afferent arteriolar vasoconstriction and subsequently an increase in GFR. This hypothesis has recently been questioned due to the observation that adenosine A1 -receptor knockout mice, previously shown to lack a functional TGF mechanism, still display a pronounced hyperfiltration when diabetes is induced. Leyssac demonstrated in the 1960s (Acta Physiol Scand58, 1963:236) that GFR and proximal reabsorption can work independently of each other. Furthermore, by the use of micropuncture technique a reduced hydrostatic pressure in Bowman's space or in the proximal tubule of diabetic rats has been observed. A reduced pressure in Bowman's space will increase the pressure gradient over the filtration barrier and can contribute to the development of diabetic hyperfiltration. When inhibiting proximal reabsorption with a carbonic anhydrase inhibitor, GFR decreases and proximal tubular pressure increases. Measuring intratubular pressure allows a sufficient time resolution to reveal that net filtration pressure decreases before TGF is activated which highlights the importance of intratubular pressure as a regulator of GFR. Taken together, these results imply that the reduced intratubular pressure observed in diabetes might be crucial for the development of glomerular hyperfiltration. [source] Optical studies of defects generated in neutron-irradiated Cz-Si during HP-HT treatmentCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4-5 2005B. Surma Abstract Neutron-irradiated Czochralski grown silicon subjected to heat treatment (HT) at 350 °C and 1000 °C under enhanced hydrostatic pressure (HP) was studied in this work. It has been shown that external hydrostatic pressure enhances the creation of VO2 defects in neutron irradiated silicon subjected to the HP - HT treatment at 350 °C. Enhanced formation of platelet-like oxygen precipitates was found in the samples treated at 1000 °C under 1.1 GPa. This effect was more pronounced in the samples with VO2 defects. Presented results seem to suggest that probably HP helps to transform VO2 to some kind of defects or change alone VO2 defects in the form that can act as an additional nucleus for an additional oxygen precipitation at 1000°C. No correlation between the plate-like oxygen precipitates related absorption at 1225 cm -1 and dislocation-related emission has been confirmed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural and functional effects of hydrostatic pressure on centrosomes from vertebrate cellsCYTOSKELETON, Issue 4 2001A. Rousselet Abstract In an attempt to better understand the role of centrioles in vertebrate centrosomes, hydrostatic pressure was applied to isolated centrosomes as a means to disassemble centriole microtubules. Treatments of the centrosomes were monitored by analyzing their protein composition, ultrastructure, their ability to nucleate microtubules from pure tubulin, and their capability to induce parthenogenetic development of Xenopus eggs. Moderate hydrostatic pressure (95 MPa) already affected the organization of centriole microtubules in isolated centrosomes, and also impaired microtubule nucleation. At higher pressure, the protein composition of the peri-centriolar matrix (PCM) was also altered and the capacity to nucleate microtubules severely impaired. Incubation of the treated centrosomes in Xenopus egg extract could restore their capacity to nucleate microtubules after treatment at 95 MPa, but not after higher pressure treatment. However, the centriole structure was in no case restored. It is noteworthy that centrosomes treated with mild pressure did not allow parthenogenetic development after injection into Xenopus eggs, even if they had recovered their capacity to nucleate microtubules. This suggested that, in agreement with previous results, centrosomes in which centriole architecture is impaired, could not direct the biogenesis of new centrioles in Xenopus eggs. Centriole structure could also be affected by applying mild hydrostatic pressure directly to living cells. Comparison of the effect of hydrostatic pressure on cells at the G1/S border or on the corresponding cytoplasts suggests that pro-centrioles are very sensitive to pressure. However, cells can regrow a centriole after pressure-induced disassembly. In that case, centrosomes eventually recover an apparently normal duplication cycle although with some delay. Cell Motil. Cytoskeleton 48:262,276, 2001. © 2001 Wiley-Liss, Inc. [source] Scanning Electrochemical Microscopy as an In Vitro Technique for Measuring Convective Flow Rates Across Dentine and the Efficacy of Surface Blocking TreatmentsELECTROANALYSIS, Issue 3 2005Julie Abstract Scanning electrochemical microscopy (SECM) is shown to be a powerful technique for both the measurement of local solution velocities through human dentine slices, in vitro, and for assessing quantitatively the effect of surface treatments on the flow process. SECM employs a small ultramicroelectrode (micron dimensions) as an imaging probe to provide information on the topography and transport characteristics of dentine, with high spatial resolution. In these studies the dentine sample is a membrane in a two compartment cell, which contains solutions of identical composition, including a redox active mediator (Fe(CN). In the absence of an applied pressure, the transport-limited current response at the probe electrode is due to diffusion of Fe(CN) to the UME, which depends on the probe to sample separation. Under an applied hydrostatic pressure, hydrodynamic flow across the sample enhances mass transport to the UME. With this methodology it was possible to accurately measure effective fluid velocities, by recording tip currents with and without pressure, and assess the efficacy of potential flow retarding agents for the treatment of dentinal hypersensitivity. For native dentine, the solution velocity was found to vary dramatically with location on the sample. The application of a glycerol monooleate - base paste treatment to the surface of dentine was found to lower local flow velocities significantly. This electroanalytical methodology is simple to implement and is generally applicable to assessing the efficacy and mode of action of a wide variety of potential fluid flow retarding agents. [source] Electrochemistry at High Pressures: A ReviewELECTROANALYSIS, Issue 10 2004Debora Giovanelli Abstract High pressure electrochemical studies are potentially dangerous and less immediately implemented than conventional investigations. Technical obstacles related to properties of the working electrode material, preparation of its surface, availability of suitable reference electrodes, and the need for specially designed high pressure equipment and cells may account for the relative lack of experimental data on electrochemistry at high pressures. However, despite the stringent requirements for system and equipment stability, significant developments have been made in recent years and the combination of electrochemical methods with high hydrostatic pressure has provided useful insights into the thermodynamics, kinetics, and other physico-chemical characteristics of a wide range of redox reactions. In addition to fundamental information, high pressure electrochemistry has also lead to a better understanding of a variety of processes under non-classical conditions with potential applications in today's industrial environment from extraction and electrosynthesis in supercritical fluids to measurement of the pH at the bottom of the ocean. The purpose of this article is to detail the experimental pressurizing apparatus for electroanalytical measurements at high pressures and to review the relevant literature on the effect of pressure on electrode processes and on the properties of aqueous electrolyte solutions. [source] CEC-ESI ion trap MS of multiple drugs of abuseELECTROPHORESIS, Issue 7 2010Zeineb Aturki Abstract This article describes a method for the separation and determination of nine drugs of abuse in human urine, including amphetamines, cocaine, codeine, heroin and morphine. This method was based on SPE on a strong cation exchange cartridge followed by CEC-MS. The CEC experiments were performed in fused silica capillaries (100,,m×30,cm) packed with a 3,,m cyano derivatized silica stationary phase. A laboratory-made liquid junction interface was used for CEC-MS coupling. The outlet capillary column was connected with an emitter tip that was positioned in front of the MS orifice. A stable electrospray was produced at nanoliter per minute flow rates applying a hydrostatic pressure (few kPa) to the interface. The coupling of packed CEC columns with mass spectrometer as detector, using a liquid junction interface, provided several advantages such as better sensitivity, low dead volume and independent control of the conditions used for CEC separation and ESI analysis. For this purpose, preliminary experiments were carried out in CEC-UV to optimize the proper mobile phase for CEC analysis. Good separation efficiency was achieved for almost all compounds, using a mixture containing ACN and 25,mM ammonium formate buffer at pH 3 (30:70, v/v), as mobile phase and applying a voltage of 12,kV. ESI ion-trap MS detection was performed in the positive ionization mode. A spray liquid, composed by methanol,water (80:20, v/v) and 1% formic acid, was delivered at a nano-flow rate of ,200,nL/min. Under optimized CEC-ESI-MS conditions, separation of the investigated drugs was performed within 13,min. CEC-MS and CEC-MS2 spectra were obtained by providing the unambiguous confirmation of these drugs in urine samples. Method precision was determined with RSDs values ,3.3% for retention times and ,16.3% for peak areas in both intra-day and day-to-day experiments. LODs were established between 0.78 and 3.12,ng/mL for all compounds. Linearity was satisfactory in the concentration range of interest for all compounds (r2,0.995). The developed CEC-MS method was then applied to the analysis of drugs of abuse in spiked urine samples, obtaining recovery data in the range 80,95%. [source] Dentine sealing provided by smear layer/smear plugs vs. adhesive resins/resin tagsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 4 2007Marcela R. Carrilho The aim of this study was to evaluate the ability of five experimental resins, which ranged from hydrophobic to hydrophilic blends, to seal acid-etched dentine saturated with water or ethanol. The experimental resins (R1, R2, R3, R4, and R5) were evaluated as neat bonding agents (100% resin) or as solutions solvated with absolute ethanol (70% resin/30% ethanol). Fluid conductance was measured at 20 cm H2O hydrostatic pressure after sound dentine surfaces were: (i) covered with a smear layer; (ii) acid-etched; or (iii) bonded with neat or solvated resins, which were applied to acid-etched dentine saturated with water or ethanol. In general, the fluid conductance of resin-bonded dentine was significantly higher than that of smear layer-covered dentine. However, when the most hydrophobic neat resins (R1 and R2) were applied to acid-etched dentine saturated with ethanol, the fluid conductance was as low as that produced by smear layers. The fluid conductance of resin-bonded dentine saturated with ethanol was significantly lower than for resin bonded to water-saturated dentine, except for resin R4. Application of more hydrophobic resins may provide better sealing of acid-etched dentine if the substrate is saturated with ethanol instead of with water. [source] The rapidly adapting receptors in mammalian airways and their responses to changes in extravascular fluid volumeEXPERIMENTAL PHYSIOLOGY, Issue 4 2006C. Tissa Kappagoda In this short review, we shall focus on some recent findings on the physiological stimulus for the rapidly adapting receptors (RAR) of the airways. They are readily activated by a sustained inflation of the lungs and they are usually identified by their rapid adaptation to this stimulus. They are also activated by both tactile stimuli and irritant gases applied to the epithelium of the airways. The investigations reviewed here suggest that these receptors are activated by changes in extravascular fluid volume. The principal factors governing fluid flux from the microcirculation are identified in the Starling equation. These are the hydrostatic pressure, plasma oncotic pressure and capillary permeability. Findings from recent studies suggest that all these factors increase the activity of RAR. In addition, these receptors are also activated by obstruction of lymph drainage from the lung. Evidence is presented to show that manipulation of Starling forces also increases the extravascular fluid volume of the airways in areas where the RAR are located. On the basis of these findings, it is suggested that, along with mechanosensitivity to stimuli such as stretch, inflation and deflation, another physiological stimulus to the RAR is a change in extravascular fluid volume in the regions of the airways where these receptors are located. [source] Effects of methylcyclodextrin on lysosomesFEBS JOURNAL, Issue 5 2001Michel Jadot The cholesterol complexing agent methyl-cyclodextrin (MCD) provides an efficient mean for the removal of cholesterol from biological membranes. In order to study the effects of this agent on the lysosomal membrane in situ, we treated HepG2 cells with MCD and studied the effects of this treatment on lysosomes in isolated fractions. We found that lysosomes prepared from treated cells are more sensitive to various membrane perturbing treatments such as: incubation of lysosomes in isotonic glucose, in hypotonic sucrose or in the presence of the lytic agent glycyl- l -phenylalanine 2-naphthylamide. The lysosomal membrane is also less resistant to increased hydrostatic pressure. Centrifugation methods were used to analyse the effect of MCD on lysosomes. Isopycnic centrifugation in sucrose density gradients demonstrates that the drug induces a reversible density increase of the lysosomes. Our study indicates that extracellularly added MCD can modify the properties of the lysosomal membrane in living cells. It suggests that MCD could be an effective tool to modulate the physical properties of lysosomes within intact cells and to monitor the cellular responses to such modifications. [source] Hydraulic observations from a 1 year fluid production test in the 4000 m deep KTB pilot boreholeGEOFLUIDS (ELECTRONIC), Issue 1 2006W. GRÄSLE Abstract A long-term pump test was conducted in the KTB pilot borehole (KTB-VB), located in the Oberpfalz area, Germany. It produced 22 300 m3 of formation fluid. Initially, fluid production rate was 29 l min,1 for 4 months, but was then raised to an average of 57 l min,1 for eight more months. The aim of this study was to examine the fluid parameters and hydraulic properties of fractured, crystalline crusts as part of the new KTB programme ,Energy and Fluid Transport in Continental Fault Systems'. KTB-VB has an open-hole section from 3850 to 4000 m depth that is in hydraulic contact with a prominent continental fault system in the area, called SE2. Salinity and temperature of the fluid inside the borehole, and consequently hydrostatic pressure, changed significantly throughout the test. Influence of these quantities on variations in fluid density had to be taken into account for interpretation of the pump test. Modelling of the pressure response related to the pumping was achieved assuming the validity of linear Darcy flow and permeability to be independent of the flow rate. Following the principle ,minimum in model dimension', we first examined whether the pressure response can be explained by an equivalent model where rock properties around the borehole are axially symmetric. Calculations show that the observed pressure data in KTB-VB can in fact be reproduced through such a configuration. For the period of high pumping rate (57 l min,1) and the following recovery phase, the resulting parameters are 2.4 × 10,13 m3 in hydraulic transmissivity and 3.7 × 10,9 m Pa,1 in storativity for radial distances up to 187 m, and 4.7 × 10,14 m3 and 6.0 × 10,9 m Pa,1, respectively, for radial distances between 187 and 1200 m. The former pair of values mainly reflect the hydraulic properties of the fault zone SE2. For a more realistic hydraulic study on a greater scale, program FEFLOW was used. Parameter values were obtained by matching the calculated induced pressure signal to fluid-level variations observed in the KTB main hole (KTB-HB) located at 200 m radial distance from KTB-VB. KTB-HB is uncased from 9031 to 9100 m and shows indications of leakage in the casing at depths 5200,5600 m. Analysis of the pressure record and hydraulic modelling suggest the existence of a weak hydraulic communication between the two boreholes, probably at depths around the leakage. Hydraulic modelling of a major slug-test in KTB-HB that was run during the pumping in KTB-VB reveals the effective transmissivity of the connected formation to be 1 to 2 orders of magnitude lower than the one determined for the SE2 fault zone. [source] Near-lithostatic pore pressure at seismogenic depths: a thermoporoelastic modelGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2006Francesca Zencher SUMMARY A model is presented for pore pressure migration through a transition layer separating a meteoric aquifer at hydrostatic pressure from a deeper reservoir at lithostatic pressure. This configuration is thought to be pertinent to the South Iceland seismic zone (SISZ) and to other tectonically active regions of recent volcanism, where volatiles are continuously released by ascending magma below the brittle,ductile transition. Poroelastic parameters are computed for basaltic rock. The model is 1-D, the fluid viscosity is temperature dependent and rock permeability is assumed to be pressure dependent according to a dislocation model of a fractured medium. Environment conditions are considered, pertinent to basalt saturated with water at shallow depth (case I) and at mid-crustal depth (case II). If the intrinsic permeability of the rock is high, no significant effects are observed in the pressure field but advective heat transfer shifts the brittle,ductile transition to shallower depths. If the intrinsic permeability is low, the pressure-dependent permeability can propagate near-lithostatic pore pressures throughout most of the transition layer, while the temperature is practically unaffected by advective contributions so that the rock in the transition layer remains in brittle condition. Geometrical parameters characterizing the fracture distribution are important in determining the effective permeability: in particular, if an interconnected system of fractures develops within the transition layer, the effective permeability may increase by several orders of magnitude and near-lithostatic pore pressure propagates upwards. These modelling results have important bearings on our understanding of seismogenic processes in geothermal areas and are consistent with several geophysical observations in the SISZ, in connection with the two 2000 June M= 6.5 earthquakes, including: (i) fluid pressure pulses in deep wells, (ii) low resistivity at the base of the seismogenic layer, (iii) low VP/VS ratio and time-dependent seismic tomography, (iv) heterogeneity of focal mechanisms, (v) shear wave splitting, (vi) high b -value of deep foreshocks, (vii) triggered seismicity and (viii) Radon anomalies. [source] Elastic properties of dry clay mineral aggregates, suspensions and sandstonesGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2003Tiziana Vanorio SUMMARY The presence of clay minerals can alter the elastic behaviour of rocks significantly. Although clay minerals are common in sedimentary formations and seismic measurements are our main tools for studying subsurface lithologies, measurements of elastic properties of clay minerals have proven difficult. Theoretical values for the bulk modulus of clay are reported between 20 and 50 GPa. The only published experimental measurement of Young's modulus in a clay mineral using atomic force acoustic microscopy (AFAM) gave a much lower value of 6.2 GPa. This study has concentrated on using independent experimental methods to measure the elastic moduli of clay minerals as functions of pressure and saturation. First, ultrasonic P - and S -wave velocities were measured as functions of hydrostatic pressure in cold-pressed clay aggregates with porosity and grain density ranging from 4 to 43 per cent and 2.13 to 2.83 g cm,3, respectively. In the second experiment, P - and S -wave velocities in clay powders were measured under uniaxial stresses compaction. In the third experiment, P -wave velocity and attenuation in a kaolinite,water suspension with clay concentrations between 0 and 60 per cent were measured at ambient conditions. Our elastic moduli measurements of kaolinite, montmorillonite and smectite are consistent for all experiments and with reported AFAM measurements on a nanometre scale. The bulk modulus values of the solid clay phase (Ks) lie between 6 and 12 GPa and shear (,s) modulus values vary between 4 and 6 GPa. A comparison is made between the accuracy of velocity prediction in shaley sandstones and clay,water and clay,sand mixtures using the values measured in this study and those from theoretical models. Using Ks= 12 GPa and ,s= 6 GPa from this study, the models give a much better prediction both of experimental velocity reduction due to increase in clay content in sandstones and velocity measurements in a kaolinite,water suspension. [source] In vitro evaluation of reactive astrocyte migration, a component of tissue remodeling in glaucomatous optic nerve headGLIA, Issue 3 2001Gülgün Tezel Abstract In order to improve understanding of remodeling events in the glaucomatous optic nerve head, the migration of optic nerve head astrocytes was studied in vitro. Since elevated intraocular pressure is an important stress factor identified in glaucomatous eyes, optic nerve head astrocytes were incubated under physical stress created by elevated hydrostatic pressure. In addition, they were incubated in the presence of a chemical stimulus, lipolysaccharide (LPS). Migration of reactivated astrocytes in the presence of these stressors was examined using chambers in which cell migration through extracellular matrix-coated pores is only possible following proteolytic digestion of the matrix. We observed that the migratory ability of optic nerve head astrocytes was approximately 4,6 times greater following exposure to elevated hydrostatic pressure or LPS for up to 48 h. Phosphoinositide 3-kinase, protein kinase C, and tyrosine kinase were found to be involved in the signal transduction for activated migration of optic nerve head astrocytes in response to elevated hydrostatic pressure or LPS. In addition, we observed that the stress-induced migration of optic nerve head astrocytes, which is accompanied by proteolytic degradation, resulted in the formation of culture cavities containing mucopolysaccharides. These in vitro findings provide a clearer understanding of the pathophysiologic mechanisms of characteristic tissue remodeling events that occur, in vivo, in the glaucomatous optic nerve head. GLIA 34:178,189, 2001. © 2001 Wiley-Liss, Inc. [source] Recharge and Preservation of Laurentide Glacial Melt Water in the Canadian ShieldGROUND WATER, Issue 5 2000Ian D. Clark Ground water inflows to drifts ranging from 700 to 1615 m below ground surface at the Con Mine, Yellowknife, Northwest Territories, Canada, were used to study deep hydrogeological flow regimes in Shield terrain. Salinity trends are due to mixing between low-TDS ground water and deep Ca(Na)-C1 brines (>290 g/L) likely derived from Devonian sea water. C1 - ,,18O relationships demonstrate that all inflows are a mixture of three distinct components: modern meteoric ground water (,18O ,,18.9 ± 0.1%o), brine (,18O ,,10%o), and an isotopically depleted water (,18O ,,28%o). The origin of this third endmember is attributed to glacial melt water injected into the subsurface during ablation of the Laurentide Ice Sheet at ca. 10 ka. A mechanism is proposed where high hydrostatic pressure in the ablation zone imposes strong downward gradients beneath the ice sheet margin. Numerical simulation with the SWIFT II finite-difference code recreates the observed salinity gradients within a modeled 50-year interval, corresponding with the rate of retreat of the ice sheet across the landscape at this time. The persistence of this melt water in the subsurface for some 10,000 years following retreat of the ice and decay of the steep hydraulic gradients highlights the importance of gradient, in addition to permeability, as a major control on ground water flow and transport in deep crystalline settings. [source] Finite element modelling of free-surface flows with non-hydrostatic pressure and k,, turbulence modelINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2005C. Leupi Abstract Validation of 3D finite element model for free-surface flow is conducted using a high quality and high spatial resolution data set. The commonly numerical models with the conventional hydrostatic pressure still remain the most widely used approach for the solution of practical engineering problems. However, when a 3D description of the velocity field is required, it is useful to resort to a more accurate model in which the hydrostatic assumption is removed. The present research finds its motivation in the increasing need for efficient management of geophysical flows such as estuaries (multiphase fluid flow) or natural rivers with the presence of short waves and/or strong bathymetry gradient, and/or strong channel curvature. A numerical solution is based on the unsteady Reynolds-averaged Navier,Stokes equations on the unstructured grid. The eddy viscosity is calculated from the efficient k,, turbulence model. The model uses implicit fractional step time stepping, and the characteristics method is used to compute the convection terms in the multi-layers system (suitable for the vertical stratified fluid flow), in which the vertical grid is located at predefined heights and the number of elements in the water column depends on water depth. The bottommost and topmost elements of variable height allow a faithful representation of the bed and the time-varying free-surface, respectively. The model is applied to the 3D open channel flows of various complexity, for which experimental data are available for comparison. Computations with and without non-hydrostatic are compared for the same trench to test the validity of the conventional hydrostatic pressure assumption. Good agreement is found between numerical computations and experiments. Copyright © 2005 John Wiley & Sons, Ltd. [source] Technology options for new nutritional conceptsINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 2 2002Hannu Korhonen Recent advances in the food and nutrition sciences support the concept that the diet has a significant role in the modulation of various functions in the body. The diet and/or its components may contribute to an improved state of well-being, a reduction of risks related to certain diseases and even an improvement in the quality of life. These new concepts have led to the introduction of a new category of health-promoting foodstuffs, i.e. functional foods. The concern about health embraces a number of driving issues, needs and opportunities which may be approached by designing specific diets from various food raw materials. These tailor-made products provide physiological benefits that are targeted at particular consumer groups. The functionality of functional foods is based on bioactive components, which may be contained naturally in the product but usually require formulation by appropriate technologies in order to optimise the desired beneficial properties. To this end, it is often necessary to develop and apply novel technologies, e.g. membrane separation, high hydrostatic pressure and supercritical fluid extraction techniques. Also the minimal processing concept could be employed in this context. This review discusses the current technological options available and the future challenges faced in the area. Particular attention is paid to the exploitation of bovine colostrum and milk-derived bioactive compounds for the development of functional foods. [source] Effect of initial concentration of bacterial suspensions on their inactivation by high hydrostatic pressureINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 5 2002S. Furukawa The effects of initial concentration [104,109 colony forming units (CFU) mL,1] on the inactivation of vegetative cell suspensions (Escherichia coli) and spore suspensions (Bacillus subtilis) by hydrostatic pressure treatment were investigated. The inactivation rates of E. coli and B. subtilis decreased as the initial concentration of cell and spore suspensions increased. In the practical application of hydrostatic pressure treatment, it was considered that the initial concentration of the bacteria suspensions should be as low as possible. [source] Evaluation of the chondral modeling theory using fe-simulation and numeric shape optimizationJOURNAL OF ANATOMY, Issue 5 2009Jeffrey H. Plochocki Abstract The chondral modeling theory proposes that hydrostatic pressure within articular cartilage regulates joint size, shape, and congruence through regional variations in rates of tissue proliferation. The purpose of this study is to develop a computational model using a nonlinear two-dimensional finite element analysis in conjunction with numeric shape optimization to evaluate the chondral modeling theory. The model employed in this analysis is generated from an MR image of the medial portion of the tibiofemoral joint in a subadult male. Stress-regulated morphological changes are simulated until skeletal maturity and evaluated against the chondral modeling theory. The computed results are found to support the chondral modeling theory. The shape-optimized model exhibits increased joint congruence, broader stress distributions in articular cartilage, and a relative decrease in joint diameter. The results for the computational model correspond well with experimental data and provide valuable insights into the mechanical determinants of joint growth. The model also provides a crucial first step toward developing a comprehensive model that can be employed to test the influence of mechanical variables on joint conformation. [source] History of science , sporesJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2006Lewis B Perry Memorial Lecture 200 Abstract Bacterial endospores were first studied 130 years ago by Cohn in 1876 and independently by Koch in the same year. Although spore dormancy and resistance have been much studied since then, questions still remain concerning the basic mechanisms and the kinetics of heat inactivation in particular. Likewise, the extreme dormancy and longevity of spores was recognized early on and later greatly extended but still evade complete understanding. Evidence has accumulated for the involvement of specific spore components such as calcium, dipicolinic acid, small acid soluble proteins in the core and peptidoglycan in the cortex. Involvement of physical factors too, such as the relative dehydration of the core, maybe in a high-viscosity state or even in a glassy state, has added to appreciation of the multicomponent nature of dormancy and resistance. Spore-former morphology formed the basis for early classification systems of sporeformers from about 1880 and consolidated in the mid-1900s, well prior to the use of modern genetic procedures. With respect to sporulation, groundbreaking sequence studies in the 1950s provided the basis for later elucidation of the genetic control widely relevant to many cell differentiation mechanisms. With respect to the breaking of dormancy (activation and germination), the elucidation of mechanisms began in the 1940s following the observations of Hills at Porton who identified specific amino acid and riboside ,germinants', and laid the basis for the later genetic analyses, the identification of germinant receptor genes and the elucidation of key germination reactions. The nonexponential nature of germination kinetics has thwarted the development of practical Tyndallization-like processing. So inactivation by heat remains the premier method of spore control, the basis of a huge worldwide industry, and still relying on the basic kinetics of inactivation of Clostridium botulinum spores, and the reasoning regarding safety first evolved by Bigelow et al. in 1920 and Esty and Meyer in 1922. ,Newer' processes such as treatment with ionizing radiation (first proposed in 1905) and high hydrostatic pressure (first proposed in 1899) may be introduced if consumer resistance and some remaining technical barriers could be overcome. [source] Protein disaggregation and refolding using high hydrostatic pressureJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2007David J Phelps Abstract Production of recombinant proteins often leads to aggregate formation. These aggregates may make it impossible to solubilize the protein for downstream applications such as assay development or structural studies by X-ray crystallography or nuclear magnetic resonance spectroscopy. High hydrostatic pressure technology has been developed which offers significant advantages over traditional methods of protein disaggregation and refolding. Pressure induced disruption of protein aggregates and subsequent refolding can take place at high concentrations in a single process step, without the need for high concentrations of chaotropic agents. Copyright © 2007 Society of Chemical Industry [source] | |||||||||||||||||||||||||||||||||||||||||||