Different Levels Of Hydrostatic Pressure Research Articles

EFFECT OF HYDROSTATIC PRESSURE ON THE VIABILITY OF EPN NATIVE ITALIAN STRAINS STEINERNEMA FELTIAEAND HETERORHABDITIS BACTERIOPHORA

The use of entomopathogenic nematodes (EPNs)as a non-chemical treatment system is one of the most mo-dern techniques promoted by the 2008/128/EC standards for the biological control of plant pathogens. The distri-bution ofEPNscould be carried out with the same sprayers used for the distribution of pesticides. This research is focusedon the effects of the mechanical stress due to hydraulic compression on EPNsItalianstrains,Stei-nernemafeltiaeand Heterorhabditisbacteriophora, to assess their residual strength and vitality under laboratory tests. Liquid suspensions of nematodes were subjected to 8 different levels of hydrostatic pressure from 5 to 40 bar. The hydraulic compression test was conducted through a hydrostatic compression system specifically de-signed for the experimental test. Although correlation curves show an increment of14%in nematode mortality, the statistical analysisdid not show any significant effect of static pressure on the vitality and infectivity of EPNs, that makes them suitable for field application with sprayers. These preliminary positive results on the effects of compression on the viability of EPNsare preparatory to subsequent field tests under high pressure

An in vitro pressure model towards studying the response of primary retinal ganglion cells to elevated hydrostatic pressures

Glaucoma is a leading cause of blindness characterized by progressive degeneration of retinal ganglion cells (RGCs). A well-established risk factor for the development and progression of glaucoma is elevation of intraocular pressure (IOP). However, how elevated IOP leads to RGC degeneration remains poorly understood. Here, we fabricate a facile, tunable hydrostatic pressure platform to study the effect of increased hydrostatic pressure on RGC axon and total neurite length, cell body area, dendritic branching, and cell survival. The hydrostatic pressure can be adjusted by varying the height of a liquid reservoir attached to a three-dimensional (3D)-printed adapter. The proposed platform enables long-term monitoring of primary RGCs in response to various pressure levels. Our results showed pressure-dependent changes in the axon length, and the total neurite length. The proportion of RGCs with neurite extensions significantly decreased by an average of 38 ± 2% (mean ± SEM) at pressures 30 mmHg and above (p < 0.05). The axon length and total neurite length decreased at a rate of 1.65 ± 0.18 μm and 4.07 ± 0.34 μm, respectively (p < 0.001), for each mmHg increase in pressure after 72 hours pressure treatment. Dendritic branching increased by 0.20 ± 0.05 intersections/day at pressures below 25 mmHg, and decreased by 0.07 ± 0.01 intersections/day at pressures above 25 mmHg (p < 0.001). There were no significant changes in cell body area under different levels of hydrostatic pressure (p ≥ 0.05). Application of this model will facilitate studies on the biophysical mechanisms that contribute to the pathophysiology of glaucoma and provide a channel for the screening of potential pharmacological agents for neuroprotection.

High hydrostatic pressure induces apoptosis of retinal ganglion cells via regulation of the NGF signalling pathway.

High pressure is the most important factor inducing retinal ganglion cell (RGC) apoptosis. However, the underlying mechanisms remain obscure. The present study investigated the effects of different levels of hydrostatic pressure (HP) on RGCs and the potential mechanisms involved. Primary cultured rat RGCs were exposed to five levels of HP (0, 20, 40, 60 and 80 mmHg) for 24 h. Morphological changes in RGCs were observed. The viability and apoptosis rate of RGCs were detected using a Cell Counting Kit-8 assay and Annexin V-fluorescein isothiocyanate/propidium iodide flow cytometry, respectively. Western blotting, reverse transcription-quantitative polymerase chain reaction and immunofluorescence were used to detect the expression and mRNA levels of nerve growth factor (NGF), protein kinase B (AKT), apoptosis signal-regulating kinase 1 (ASK1), forkhead box O1 (FoxO1) and cAMP response element binding protein (CREB). In the 0- and 20-mmHg groups, there were no apoptotic morphological changes. In the 40 mmHg group, parts of the cell were shrunken or disrupted. In the 60 mmHg group, neurite extension was weakened and parts of the cells were disintegrating or dying. In the 80 mmHg group, the internal structures of the cells were not visible at all. The apoptosis rates of RGCs were significantly higher and the viability rates significantly lower under 40, 60 and 80 mmHg compared with under 0 or 20 mmHg (all P<0.01). The expression and mRNA levels of NGF, AKT and CREB decreased in a dose-dependent manner in the 40-, 60- and 80-mmHg groups (all P<0.05), but those of ASK1 and FoxO1 increased in a dose-dependent manner (all P<0.05). Interestingly, the alterations to the expression and mRNA levels of CREB were significantly larger compared with the changes in ASK1 or FoxO1 in the 40-, 60- and 80-mmHg groups (all P<0.01). The results of the present study demonstrate that elevated HP of 40, 60 or 80 mmHg reduces viability and induces apoptosis in RGCs, which may occur through effects on the NGF/ASK1/FoxO1 and NGF/AKT/CREB pathways, of which the latter is more strongly affected.

On the Mechanical Behavior of Granite Material With Particular Emphasis on the Influence From Pre-Existing Cracks and Defects

Abstract In this investigation, experiments were carried out in order to determine the mechanical properties of Bohus granite considering the influence from pre-existing cracks and defects. The experimental investigation aimed at a complete material characterization, for the purpose of mechanical analyses using advanced constitutive models, based on a variety of tests. In doing so, direct tensile and compression tests were performed to evaluate the stiffness and strength; quasi-oedometric tests were carried out in order to obtain the deviatoric and volumetric behavior of the material at different levels of hydrostatic pressure (up to 860 MPa); three-point bend tests were performed to evaluate the quasi-static strength of the rock and its distribution. Weibull statistics was then employed to describe the strength distribution. The intact specimens indicated a rather low scatter in the mechanical properties such as Young’s modulus and tensile strength. However, specimens with large initial defects behaved differently. The failure mechanism in these specimens was not as brittle as the intact ones. The crack was opened on the tensile surface of such specimens during the three-point bend test at an early stage during loading, as demonstrated by digital image correlation results.

RESEARCH OF HYDRAULIC IMPACT ON THE TECHNOLOGICAL STABILITY OF SHALLOW METROTUNNEL IN DREDGING MASSIVES

Purpose. On the basis of the results analysis of the computer simulation and laboratory studies it is necessary to determine the changes impact dependence of the hydraulic level of groundwater on the tunnels processing stability in the underground due to the deformations development of the surrounding dredging massif. Methodology. The methodological basis of the research complex consists of the analysis, generalization of known scientific results and practical experience of forecasting and preconditioning of deformations of tunnel and surrounding soil mass processing, as well as computer simulation of the critical stress-strain state of the tunnel processing at changes in the hydraulic level of groundwater. Findings. In the process of technological construction and under the non-pressure groundwaters impact, when operating tunnels of subway lines of shallow foundation, the stability of all-section machining is ensured due to the uniform hydrostatic reduction of processing. At this the sediments are within the permissible values. The results of the research show that different levels of hydrostatic pressure can occur when the groundwater level changes from both sides of the tunnel. At the same time, there is a redistribution of stresses of the soil mass around the cross section of the tunnel, which, in turn, leads to the appearance of additional non-uniform deformations and the opening of cracks in the tunnels during operation. Originality. The authors of the work firstly established the effect of changes in hydrostatic pressure, which may arise due to fluctuations in the level of groundwater on the whole-section processing of tunnels of metro lines of shallow foundation due to secondary sedimentation. The conditions of occurrence of the secondary sediment have been determined and the nature of the deformation course has been established during the operation of the shallow subway. Practical value. At the stage of designing the metro lines of the shallow foundation, it is necessary to take into account the possibility of uneven precipitation from the action of hydrostatic pressure during operation. This will avoid additional deformations during the seasonal period, reduce the number of current repairs, increase reliability and the useful life of the tunnel processing structures.

Cohesive/adhesive failure interaction in ductile adhesive joints Part II: Quasi-static and fatigue analysis of double lap-joint specimens subjected to through-thickness compressive loading

This paper proposes a new methodology for the finite element (FE) modelling of failure in adhesively bonded joints. Cohesive and adhesive failure are treated separately which allows accurate failure predictions for adhesive joints of different thicknesses using a single set of material parameters. In a companion paper (part I), a new smeared-crack model for adhesive joint cohesive failure was proposed and validated. The present contribution gives an in depth investigation into the interaction among plasticity, cohesive failure and adhesive failure, with application to structural joints. Quasi-static FE analyses of double lap-joint specimens with different thicknesses and under different levels of hydrostatic pressure were performed and compared to experimental results. In all the cases studied, the numerical analysis correctly predicts the driving mechanisms and the specimens’ final failure. Accurate fatigue life predictions are made with the addition of a Paris based damage law to the interface elements used to model the adhesive failure.

Pressure-Dependent Gene Activation in Yeast Cells.

Hydrostatic pressure is one of the physical factors affecting cellular physiology. Hydrostatic pressure of a few tens MPa decreases the growth rate and a few hundred MPa decreases the cellular viability. To find clues to understand how such pressure effects on living cells relating to damages on protein molecules, we employed yeast DNA microarrays and analyzed genome-wide gene-expression levels in yeast cells which have been exposed to different levels of hydrostatic pressure. These include the cells temporarily adapted to a high pressure (from 0.1 to 30MPa) and to a low pressure (from 30 to 0.1MPa). These conditions cause yeast cells decreases of growth rate. We also analyzed gene expression profiles from the cells recovering after the sublethal pressure treatment at 180MPa at 4°C for 0min and at 40MPa at 4°C for 16h. These conditions cause yeast cells decreases of cellular viability. The activated genes by the temporary adaptations to both of the high pressure and the low pressure suggest that proteins related to membrane biosynthesis and cell wall biosynthesis can be crucial targets of pressure-induced damages, whereas the activated genes under recovering conditions after exposure to the sublethal high pressure suggest that proteasome activity and proteins localized in endoplasmic reticulum can be the crucial targets or the essential factors to survive.

Effect of high hydrostatic pressure on the expression of glutamine synthetase in rat retinal Müller cells cultured in vitro

The aim of the present study was to examine the expression of glutamine synthetase (GS) in rat retinal Müller cells induced by different levels of hydrostatic pressure using a novel pressure mechanism. pH, PCO(2) or PO2 in culture medium as determined by gas analysis was used to examine the pressure mechanism. GS expression in the Müller cells at different levels of hydrostatic pressure (0, 20, 40, 60 and 80 mmHg/24 h) was examined using immunofluorescence, real-time PCR and Western blotting. There was no significant difference in pH, PCO(2) or PO(2) in the culture medium by gas analysis at the different hydrostatic pressure levels (p>0.05). Immunofluorescence staining showed that GS was expressed in the Müller cells. The expression of GS in the 40 mmHg/24 h and the 60 mmHg/24 h groups was increased significantly compared to that in the 0 mmHg/24 h group (p<0.05). These results suggest that the pressure mechanism which was constructed was effective and that moderate pressure promotes the up-regulation of GS in active Müller cells.

Shear Stress and Cyclic Circumferential Stretch, But Not Pressure, Alter Connexin43 Expression in Endothelial Cells

Hemodynamic forces play a critical role in atherogenesis, as evidenced by the focal pattern of development of atherosclerotic lesions. Whereas disturbed flow in the branches and curved regions of large arteries is proatherogenic, laminar flow in the straight parts of vessels is atheroprotective. In addition, hypertension and age-related changes in arterial stiffness are important risk factors of the disease. Hemodynamic forces induce various changes in the structure and function of vascular endothelium, many of which reflect alterations in gene expression. Endothelial cells are linked by gap junctions, which facilitate the propagation of electrical and chemical signals along the vascular wall. Using an in vitro perfusion system, we investigated the effects of pulsed unidirectional and oscillatory flows in combination with different levels of hydrostatic pressure and circumferential stretch on the expression of Cx43 in endothelial cells. Our results show that shear stress and circumferential stretch, but not pressure, modulate the expression of Cx43. In view of the distribution of this protein along the vascular tree, our findings provide new insights into the role of mechanical forces on gap junctional communication in regions prone to the development of atherosclerosis.

Effects of pressure on swimming behavior in planula larvae of the coral Porites astreoides (Cnidaria, Scleractinia)

Mechanisms governing the behavior of coral planulae are not well understood, particularly those manifesting themselves between the time when the larvae are released and when they settle. Larvae from the hermatypic coral Porites astreoides Lamarck were exposed to different levels of hydrostatic pressure—103.4, 206.9, 310.3, 413.8, and 517.1 kPa (including ambient pressure). Data were collected at stops of the above pressures for 15 min each, respectively. This was done in both an increasing sequence and a decreasing one. When exposed to increases in pressure from 103.4 kPa, larvae swam upward (negative barotaxis) in a spiraling motion. Upon exposure to decreasing pressure from 517.1 kPa, larvae moved downward (positive barotaxis), but the magnitude of the vertical movement was much less than in the case of increasing pressure. This suggests that these larvae are more sensitive to increased pressure than decreasing pressure. High variance was also observed in the responses of these larvae at both the intra- and inter-colony levels. Thus, this behavioral trait is variable within the population. The trait may be genetically based, and thus may be susceptible to alteration by natural selection, although this remains to be demonstrated. This study is the first to document these behavioral mechanisms in coral larvae.

Tensile strength of single-walled carbon nanotubes with defects under hydrostatic pressure

Elastic properties and tensile strength of single-walled carbon nanotubes, which have topological and coordinated defects, under hydrostatic pressure have been studied by using molecular-dynamics simulations and ab initio electronic structure calculations. The Young's moduli in both the axial direction and the radial direction are determined under different levels of hydrostatic pressure. It is found that the stiffness of the nanotubes changes with the strain in a graded manner. When the strain is larger than 0.10, the tubes become softened. The strength at failure of the tubes is lowered by the existence of the defects.

Do the intervertebral disc cells respond to different levels of hydrostatic pressure?

Objective. To test the hypothesis that hydrostatic pressure directly affects the synthesis of collagen and proteoglycan by intervertebral disc cells. Design. By the use of pressure vessels, hydrostatic pressure was applied to intervertebral disc cells cultured in alginate. Background. The influence of compression (both hydrostatic and axial) on chondrocyte metabolism was examined in a number of earlier studies. However, in most of these studies, articular cartilage, not intervertebral disc was used, and in none of these was hydrostatic pressure applied to intervertebral disc cells cultured in alginate. Methods. Fresh cells were harvested from the lumbar intervertebral discs of dogs. Before their suspension in an alginate gel system, the cells were plated and expanded until they reached confluence. Then, by use of the alginate gel system, the cells were exposed (for up to 9 days) to specific values of hydrostatic pressure inside two stainless steel pressure vessels. One vessel was kept at 0.35 MPa and the other at atmospheric pressure (approximately 0.1 MPa). The effects of 0.35 MPa were compared against atmospheric pressure by measuring the incorporation of [ 3 H] -proline and [ 35 S] -sulfate into collagen and proteoglycans, respectively, for the anulus cells and nucleus cells separately, and by determining whether this incorporation was reflected by changes in the levels of mRNA for aggrecan and Types I and II collagen. Results. Proteoglycan synthesis was inhibited at 0.35 MPa as compared to atmospheric pressure for both the nucleus and anulus cells, whereas collagen synthesis was stimulated in the nucleus cells, but inhibited in the anulus cells. The mRNA levels of collagen 1A and collagen 2A decreased in the anulus but showed a differential response in the nucleus (collagen 1A increased, while collagen 2A decreased). The mRNA levels for aggrecan core protein decreased in the anulus and increased in the nucleus. Conclusion. Hydrostatic pressure directly affects the synthesis of collagen and proteoglycan by the intervertebral disc cells. Relevance This in vitro study reveals the direct effect of hydrostatic pressure on disc cells, in the absence of other factors. However, circumspection must be applied when comparisons between these results, from in vitro experiments on dog disc cells, are extrapolated and applied to the whole discs of humans.

Effects of hydrostatic pressure on cultured bovine trabecular meshwork cells.

In order to explore the effects of pressure on trabecular meshwork cells, bovine trabecular meshwork cells were cultured in vitro and subjected to different levels of hydrostatic pressure. The cellular morphology, ultrastructure and phagocytosis were studied with inverted phase-contrast microscopy, light microscopy and transmission electron microscopy, etc. It was found that the cells subjected to 2.0 kPa or 2.67 kPa for 48 h had no remarkable difference as compared with the controls in terms of parameters observed. Those under 4.0 kPa for 24 h showed slight changes in structure and a mild decrease in phagocytic function. The damage appeared more severe if the pressure was higher or lasted longer. From the above we conclude that trabecular meshwork cells can only bear pressure below a certain level. They may be destroyed structurally or impaired functionally by pressure over this level.

Formation and elimination of voids during the processing of thermoplastic of matrix composites

AbstractThe mechanisms of void formation and elimination during the stamping process of a polypropylene/glass fiber composite have been infestigated as a function of temperature, pressure, and time. Experiments were performed in a temperature and pressure controlled chamber, equipped with a rapid cooling facility. Samples of the composite as well as model polypropylene specimens containing calibrated voids were held at 200°C at different levels of hydrostatic pressure (1,10,100, and 300 bars), for a period of either 1 or 10 min. The speciments were subsequently characterized by denstiy measurements and morphologival observation. It was shown that: i) the expansion of the composite observed during the heating at 200°C under atmospheric pressure is largely induced by the gases previously dissolved in the polymeric matrix, ii) the rapid increase of the pressure during the stamping process leads to the closing of voids and, iii) the final holding under high calculation of void growth and shrinkage is in agreement with the morphological observations.

Influence of hydrostatic Pressure in Cold-Pressure Welding

Earlier work by Bay has shown the introduction of brittle surface coatings by electrochemical or chemical plating to be useful when roll bonding A-A. The coating layers fracture during deformation and decover virgin surfaces which extrude through the cracks and establish contact and metallic bonding to the adjacent surface. This paper presents a systematic study of the influence of hydrostatic pressure on the fracture of Various types of surface layers. By cold pressure welding AI-AI, Cu-Cu, Al-alloy-Al-alloy and Fe-Fe in simple upsetting the ductility of different coatings have been studied at lour different levels of hydrostatic pressure. The ductility of electrochemical matt Ni is very pressure sensitive, chemical M is somewhat less sensitive whereas hard chromium is almost brittle even at large pressures.