Increase In Hydrostatic Pressure Research Articles

New York City Panel on Climate Change 2015 Report. Chapter 3: Static coastal flood mapping.

New York City Panel on Climate Change 2015 Report. Chapter 3: Static coastal flood mapping.

Barrier Thickness and Hydrostatic Pressure Effects on Hydrogenic Impurity States in Wurtzite GaN/AlxGa1−xN Strained Quantum Dots

Within the framework of the effective mass approximation, barrier thickness and hydrostatic pressure effects on the ground‐state binding energy of hydrogenic impurity are investigated in wurtzite (WZ) GaN/AlxGa1−xN strained quantum dots (QDs) by means of a variational approach. The hydrostatic pressure dependence of physical parameters such as electron effective mass, energy band gaps, lattice constants, and dielectric constants is considered in the calculations. Numerical results show that the donor binding energy for any impurity position increases when the hydrostatic pressure increases. The donor binding energy for the impurity located at the central of the QD increases firstly and then begins to drop quickly with the decrease of QD radius (height) in strong built‐in electric fields. Moreover, the influence of barrier thickness along the QD growth direction and Al concentration on donor binding energy is also investigated. In addition, we also found that impurity positions have great influence on the donor binding energy.

An experiment on temperature variations in sandstone during biaxial loading

The temperature response to stress–strain variations in rock is useful in developing an understanding of the thermodynamic property of crust. In this study, the temperature of sandstone during loading was investigated using laboratory biaxial testing. By changing the loading patterns, the deformation of a specimen was controlled to produce two distinct modes of strain: volume strain only and shear strain only. These strain modes were produced separately such that the temperature variation associated with the different deformation modes could be analysed. Experimental results indicate that temperature, as a scalar quantity, is notably sensitive to rock deformation. In the case of the volume strain, the temperature variation is positively correlated with the variation in the bulk stress. The temperature rises with the increase in hydrostatic pressure, and vice versa. In the case of the shear strain, experimental results repeatedly show two characteristics: firstly, there appears obvious increase in temperature in the area of pure shear strain, which is most likely related to local plastic deformation; secondly, the temperature drops in the area of tension during loading, whereas the temperature rises within the area of compression. This is to say, the state of crustal stress–strain should be obtained through the measurement of rock temperature.

Numerical Analysis of Gravity Coring Using Coupled Eulerian-Lagrangian Method and a New Corer

The shortcomings of gravity corers in sampling marine sediments have been observed extensively in various field tests. In order to optimize the coring, this article provides an alternative numerical way to model the gravity coring and analyze the sampling effect. Based on this analysis, a new hydraulic hammer corer is devised. A coupled Eulerian-Lagrangian method with capability of simulating the problem involving extreme deformation, penetration is used to simulate the coring process. The results show that the hydrostatic pressure and deviator stress increase and reach their peak when the pile tip is slightly above or at the level of the observation point and then drop rapidly when the pile tip slides below the observation point. In addition, the stress path indicates that the soil element sustains plastic compression before yielding and then expands until recovering to the original state. The obvious “under-sampling” phenomenon is also well-captured by the finite element model.

Effects of External Hydrostatic Pressure on Finished Surface in Silicon Cutting

In this paper, machining tests of silicon wafer under high hydrostatic pressure are reported. A lathe type machining tester was developed, and machining tests were conducted on the upper surface of silicon wafers whose crystal orientation was (001). Roughness of the finished surface was measured by using AFM, and the effect of hydrostatic pressure on roughness was studied. It was found that roughness decreases with increase of hydrostatic pressure. It was also found that the roughness depends on the cutting direction. The roughness is large when the cutting direction is parallel to the <100> direction, but it is small when the cutting direction is parallel to the <110> direction. Mechanism of effects of hydrostatic pressure and crystal orientation are discussed.

The grapevine tonoplast aquaporin TIP2;1 is a pressure gated water channel

In plants, the vacuole is a multifunctional organelle with an important role in the maintenance of the intracellular space. Tonoplast membranes are highly permeable to water due to their content in aquaporins TIPs (Tonoplast Intrinsic Proteins) that allow the rapid water influx creating an internal turgor pressure responsible for cell expansion, elongation and shape.The aim of the present study was to evaluate if the grapevine Vitis vinifera TIP2;1 would operate as a possible volume regulator gated by membrane surface tension.For that, the wild type VvTIP2;1 and a non-functional mutated form were heterologous expressed in yeast. Using an experimental strategy in which cells are incubated in external media that induce an increase in internal hydrostatic pressure and consequently membrane surface tension, we were able to compare the osmotic permeability (Pf) and the activation energy for water transport (Ea) of yeast strains expressing the functional and a non-functional TIP2;1. We found Pf and Ea dependence on internal turgor pressure only for the strain harboring the functional aquaporin indicating that TIP2;1 activity is regulated by membrane tension changing from an open to a closed state in an internal pressure dependent manner. This turgor dependent gating of TIP2;1 might be a mechanism to regulate vacuolar size and shape in plants withstanding hostile drought conditions such as grapevine.

The significance of silica precipitation on the formation of the permeable–impermeable boundary within Earth's crust

AbstractThe hydrological system within Earth's crust is divided into the permeable zone and the underlying, much less permeable zone. In this study, we investigated the solubility and precipitation kinetics of silica in water under the conditions of the Kakkonda geothermal field, Japan, where well WD‐1a penetrates the boundary between the hydrothermal convection zone and the heat conduction zone. We found that quartz solubility has a local minimum at the depth of the hydrological boundary, at ~3100‐m depth (380 °C and 24 MPa), in the case of either hydrostatic conditions or fluid pressure increase above hydrostatic at deeper levels. The hydrothermal experiments reveal that rapid quartz precipitation occurs via nucleation when fluids are brought from the liquid region to the supercritical region. The preferential precipitation of quartz at a specific depth plays a significant role in forming and sustaining the permeable–impermeable boundary in the crust.

Hydrostatic pressure effects on deformation mechanisms of nanocrystalline fcc metals

A series of large-scale molecular dynamics (MD) simulations have been performed to investigate hydrostatic pressure effects, and the interplay between pressure and grain size, on the flow stress and the related atomic-level deformation mechanisms in nanocrystalline (NC) Cu. The strength of NC Cu increases with increasing hydrostatic pressures for all grain sizes studies in the present paper (3–15nm). The critical grain size for maximum strength first shifts towards lower values with increasing hydrostatic pressure (0–5GPa), and then shifts towards higher values as the hydrostatic pressure becomes even higher (5–80GPa). Below the critical hydrostatic pressure, the dislocation behaviors increase with increasing hydrostatic pressure for all grain sizes and the dependency of effective modulus as a function of hydrostatic pressure is almost the same for all grain sizes, which should lead to the position shifting of maximum strength towards lower grain sizes. Above the critical hydrostatic pressure, the dislocation behaviors start to decrease with increasing hydrostatic pressure for small grain sizes, and continue to increase with increasing hydrostatic pressure for large grain sizes. The slopes of effective modulus as a function of hydrostatic pressure increase slightly with increasing grain size above the critical hydrostatic pressure. The position shifting of maximum strength towards larger grain sizes at large hydrostatic pressure should be attributed to these two observations. Moreover, GB thickening is observed to increase monotonically with increasing pressure for all grain sizes, and the NC Cu with 3nm grain size has the trend to become amorphous state under hydrostatic pressure of 80GPa, which gives a new way to produce crystalline-to-amorphous transition. The findings in the present study should provide insights to the potential applications of NC metals under extreme environments.

Bleb Formation in a Hela Cell Induced by Temperature Gradient

The ability to sense and respond to temperature changes is necessary for biological systems. However, the response of individual cells to local temperature gradient is poorly understood. We have observed actomyosin dynamics within a cell which responds to local thermo-stimulation produced by focusing infrared (IR) laser. We found that the thermo-stimulation provokes spherical expansions of the membrane, termed blebs, in mitotic HeLa cells along the temperature gradient. Similar blebs are observed during cell migration, cell spreading, cytokinesis, and apoptosis. It has been proposed that the blebs form due to an increase in intracellular hydrostatic pressure, which results in the breakage of actomyosin cortex. Blebs can be induced artificially by laser ablation or by local delivery of actin-depolymerizing drugs (Sedzinski et al., 2011; Paluch et al., 2005). Cortical tension is also important for bleb expansion (Tinevez et al., 2009). However, the specific mechanism of bleb formation remains unclear. In this study, we demonstrate that blebs are induced by temperature gradient. Different types of blebs were observed depending on the steepness of temperature gradient at the ambient temperature between 40 and 50°C. Mitotic cells which responded to the thermo-gradient formed asymmetrical actomyosin network. A similar, but uniform increase in the ambient temperature did not induce the directional bleb formation, suggesting that the temperature gradient within a cell is essential for the bleb formation. When the motor function of myosin II or the polymerization/depolymerization dynamics of actin had been suppressed, smaller blebs were produced. These results hint to a new perspective that individual cells respond to local thermo-stimulation through shifting the protein activity or concentration distribution.

The effect of pressure on potassium currents in the inner hair cells isolated from guinea-pig cochlea.

An increase in hydrostatic pressure in the endolymphatic system causes hydrops-related inner ear diseases such as Meniere's disease or low tone sensorineural hearing loss. In the present study, we investigated the effects of pressure exerted on potassium currents in acutely isolated inner hair cells of the guinea-pig cochlea using whole-cell voltage-clamp techniques. By applying negative or positive pressure via the patch pipette using a syringe, intracellular hydropressure was changed between -40 cm H2O to +20 cm H2O. Negative pressure potentiated the amplitude of potassium currents, whereas positive pressure suppressed the amplitude of potassium currents. Gadolinium, a blocker of stretch-activated cation channels, did not influence pressure-dependent changes in potassium currents; however, cinnarizine blocked pressure-dependent changes in potassium currents. The current changes were not dependent on the sign of the pressure change, that is, similar increases in negative pressures (between -10 cm H2O and -40 cm H2O) and similar decreases in positive pressures (between +10 cm H2O and +20 cm H2O) were observed.

AKT activation promotes PTEN hamartoma tumor syndrome–associated cataract development

Mutations in the human phosphatase and tensin homolog (PTEN) gene cause PTEN hamartoma tumor syndrome (PHTS), which includes cataract development among its diverse clinical pathologies. Currently, it is not known whether cataract formation in PHTS patients is secondary to other systemic problems, or the result of the loss of a critical function of PTEN within the lens. We generated a mouse line with a lens-specific deletion of Pten (PTEN KO) and identified a regulatory function for PTEN in lens ion transport. Specific loss of PTEN in the lens resulted in cataract. PTEN KO lenses exhibited a progressive age-related increase in intracellular hydrostatic pressure, along with, increased intracellular sodium concentrations, and reduced Na+/K+-ATPase activity. Collectively, these defects lead to lens swelling, opacities and ultimately organ rupture. Activation of AKT was highly elevated in PTEN KO lenses compared to WT mice. Additionally, pharmacological inhibition of AKT restored normal Na+/K+-ATPase activity in primary cultured lens cells and reduced lens pressure in intact lenses from PTEN KO animals. These findings identify a direct role for PTEN in the regulation of lens ion transport through an AKT-dependent modulation of Na+/K+-ATPase activity, and provide a new animal model to investigate cataract development in PHTS patients.

Iron reduction and mineralization of deep‐sea iron reducing bacterium Shewanella piezotolerans WP3 at elevated hydrostatic pressures

In this study, iron reduction and concomitant biomineralization of a deep-sea iron reducing bacterium (IRB), Shewanella piezotolerans WP3, were systematically examined at different hydrostatic pressures (0.1, 5, 20, and 50MPa). Our results indicate that bacterial iron reduction and induced biomineralization are influenced by hydrostatic pressure. Specifically, the iron reduction rate and extent consistently decreases with the increase in hydrostatic pressure. By extrapolation, the iron reduction rate should drop to zero by ~68MPa, which suggests a possible shut-off of enzymatic iron reduction of WP3 at this pressure. Nano-sized superparamagnetic magnetite minerals are formed under all the experimental pressures; nevertheless, even as magnetite production decreases, the crystallinity and grain size of magnetite minerals increase at higher pressure. These results imply that IRB may play an important role in iron reduction, biomineralization, and biogeochemical cycling in deep-sea environments.

Solid–extracellular fluid interaction and damage in the mechanical response of rat brain tissue under confined compression

The mechanical processes that underlie mild traumatic brain injury from physical insults are not well understood. One aspect in particular that has not been examined is the tissue fluid, which is known to be critical in the mechanical function of other organs. To investigate the contributions of solid–fluid interactions to brain tissue mechanics, we performed confined compression tests, that force the extracellular fluid (ECF) to flow in the direction of the deformation, on 6.35mm diameter, 3mm long cylindrical samples excised from various regions of rat brains. Two types of tests in deformation control, (1) quasi-static, slow and moderate constant strain rate tests at 0.64×10−5/s, 0.001/s and 1/s to large strains and (2) several applications of slow linear deformation to 5% strain each followed by stress relaxation are employed to explore the solid–fluid interaction. At slow and moderate compressive strain rates, we observed stress peaks in the applied strain range at about 11%, whose magnitudes exhibited statistically significant dependence on strain rate. These data suggest that the ECF carries load until the tissue is sufficiently damaged to permit pathological fluid flow. Under the slow ramp rate in the ramp-relaxation cycles protocol, commonly used to estimate permeability, the stress relaxes to zero after the first cycle, rather than to a non-zero equilibrium stress corresponding to the applied strain, which further implicates mechanical damage. Magnetic resonance imaging (MRI) of changes in tissue microstructure during confined compression, before and after compression, provides further evidence of tissue damage. The solid–fluid interactions, reflected in the morphology of the stress–stretch curves and supported by the MRI data, suggest that increases in hydrostatic pressure in the ECF may contribute to mechanical damage of brain tissue.

Investigation of the influence of hydrostatic pressure on the magnetic and magnetocaloric properties of Ni2−XMn1+XGa (X = 0, 0.15) Heusler alloys

The effect of hydrostatic pressure on the magnetic and magnetocaloric properties of Ni2−XMn1+XGa (X = 0, 0.15) Heusler alloys around the martensitic transformation temperature (TM) has been investigated. We find that magnetic field increases and decreases the characteristic transitions temperature for X = 0 and 0.15, respectively, and increases the saturation magnetization of martensite phase for both the alloys. However, the hysteresis width decreases for both the alloys as we increase the magnetic field to 5 T. Application of hydrostatic pressure increases (decreases) the TM for X = 0 and 0.15. Pressure stabilizes the martensite phase with the increase of TM for Ni2MnGa, whereas the austenite phase gets stabilized with the decrease of TM in Ni1.85Mn1.15Ga (x = 0.15). Metamagnetic-like transition is suppressed for both the specimens with increasing pressure. The maximum magnetic entropy change (ΔSM max) is found to reduce from 19.2 J kg−1 K−1 (P = 0) to 6.04 J kg−1 K−1 (P = 9.69 kilobars) around TM for Ni2MnGa and it decreases from 8.9 J kg−1 K−1 (P = 0) to 1.27 J kg−1 K−1 (P = 7.4 kilobars) around TM for Ni1.85Mn1.15Ga.

Prolonged steep Trendelenburg position: risk of postoperative upper airway obstruction

Robot-assisted laparoscopic radical prostatectomy (RALRP) is the procedure of choice for the surgical treatment of prostatic cancer. Following induction of anesthesia, the patient is placed in a steep Trendelenburg position (40 – 45 ) in combination with a CO2 pneumoperitoneum. The steep Trendelenburg position is required for an optimal surgical exposure and to utilize the technical advantages of the robot. Besides the physiological effect of this position on the cardiovascular, respiratory and central nervous system, complications such as brachial plexus injuries, corneal abrasions and ischemic optic neuropathy have also been reported [1]. In our experience with RALRP over the last 8 years, upper airway obstruction in the postoperative period is another complication of RALRP which has not been widely reported. Some patients develop an obstructed breathing pattern after extubation associated with agitation and sometimes desaturation despite an adequate reversal of neuromuscular blockade. This is more common in patients who have had prolonged head-down position of more than 3 h or over-enthusiastic fluid therapy exceeding 3 L. Patients who have a large neck circumference or suffer from chronic obstructive airway disease (COPD) are also more prone to develop a similar obstruction. Although there is a report of laryngeal edema following RALRP [2], none of our patients has developed laryngeal edema. The upper airway obstruction usually resolves either with the insertion of a nasopharyngeal airway or with the application of continuous positive airway pressure. In the postanaesthesia care unit, these patients are then nursed in a head-up position and the symptoms resolve in 1–2 h. It has been reported that, in the 45 Trendelenburg position, central venous pressure increases almost threefold compared with the initial value [3]. The head-down position along with pneumoperitoneum also increases the abdominal pressure, which impedes the venous return from the head and neck. This increase in the capillary hydrostatic pressure leads to interstitial accumulation of fluid in the dependent tissues. This is most apparent in the form of periorbital and conjunctival edema. However, edema also forms in the neck and peripharyngeal tissues, which causes constriction of the upper airway lumen. Chiu et al. [4] showed that displacement of a small amount of fluid (340 ml) from the legs is sufficient to cause a 102 % increase in pharyngeal resistance in healthy, non-obese subjects. The degree of fluid accumulation is often directly proportional to the amount of fluid transfused and the length of the surgery. This theory is also corroborated by the fact that fluid overload in fluid-retension states such as heart and renal failure is responsible for the increased incidence of obstructive sleep apnea in these patients [4]. The effect of dependent edema in the upper airway would logically be exaggerated in obese patients with increased neck circumference who already have a compromised upper airway lumen due to fat deposition. In patients with COPD, it has been postulated that cigarette smoking may affect the upper-airway dilator muscles or that treatment with inhaled corticosteroids may cause local pharyngeal muscle myopathy which could lead to obstructive sleep apnea [5]. Therefore, a small amount of edema formation in the upper airway in these patients would make them V. Rewari (&) R. Ramachandran Department of Anaesthesiology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India e-mail: vimirewari@gmail.com; vimirewari@hotmail.com

The Corrosion Performance of Galvanized Steel in Closed Rusty Seawater

The corrosion performance of galvanized steel in closed rusty seawater (CRS) was investigated using weight loss, Tafel polarization curve, and electrochemical impedance spectroscopy. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were carried out for morphological and chemical characterization of the rust layer absorbed on the zinc coating. Effects of temperature and hydrostatic pressure on corrosion resistance of galvanized steel were studied. Results indicated that rust layer could induce pitting corrosion on the zinc coating under the Cl−erosion; high temperature accelerated the corrosion rate of zinc coating and inhibited the absorption of rust layer; the polarization resistance (Rp) of galvanized steel increased with the increase of hydrostatic pressure in CRS.

Rheological behaviour of hydraulic lime-based grouts. Shear-time and temperature dependence

This paper deals with the coupled effect of temperature and fly ash (FA) addition on rheological behaviour of natural hydraulic lime (NHL5) based grouts, currently used in masonry consolidation. The use of a grout injection technique for masonry consolidation may lead to an increase of hydrostatic pressure and lead to structural damage. This means that the thixotropic effects become self-evident in grout design. It was shown that there is a relation between the structuration rate of each grout and the pressure that occurs inside masonry during its consolidation. According to the results, it seems also that there is a grout threshold temperature (Tlimit) that separates a domain where the grout build-up structure area is almost constant, from another where flocculation area starts to increase significantly. We believe that in the first region the thixotropic effects are almost isolated from the irreversible effects (due to hydration). For the NHL5 based grout Tlimit = 20 °C and for the grout with NHL5 + 15 % of FA Tlimit = 15 °C. Grouts' characterization based on maximum resisting time, structuration rate and on the analysis of the hydraulic lime grout behaviour tested at different shear rates was performed using a shear thinning model and assuming that the structure is shear- and time-dependent. The goal is to use this methodology during mix proportioning and design for masonry injection purpose. The tested grout compositions were optimized compositions obtained in previous research using the design of experiments method.

Effect of hydrostatic pressure on shear banding behaviors in bulk metallic glasses

We report the effect of hydrostatic pressure on shear banding behaviors of a bulk metallic glass (BMG) Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit 1). A confining sleeve technique was used to apply multiaxial compression. The density of shear bands increased along a direction with the increase of hydrostatic pressure from 0MPa to 550MPa. Interestingly, as the hydrostatic pressure increased to 680MPa, branching phenomenon was emerged in the shear band, and shear bands were intersected with the hydrostatic pressure further increased to 960MPa. At the maximum hydrostatic pressure of 1940MPa, intersection sites increased and branching phenomenon could be also observed simultaneously. The present results suggest that the hydrostatic pressure has an important influence on the formation and propagation of the shear band in BMGs.

Study on the pressure self-adaptive water-tight junction box in underwater vehicle

Underwater vehicles play a very important role in underwater engineering. Water-tight junction box (WJB) is one of the key components in underwater vehicle. This paper puts forward a pressure self-adaptive water-tight junction box (PSAWJB) which improves the reliability of the WJB significantly by solving the sealing and pressure problems in conventional WJB design. By redundancy design method, the pressure self-adaptive equalizer (PSAE) is designed in such a way that it consists of a piston pressure-adaptive compensator (PPAC) and a titanium film pressure-adaptive compensator (TFPAC). According to hydro-mechanical simulations, the operating volume of the PSAE is more than or equal to 11.6 % of the volume of WJB liquid system. Furthermore, the required operating volume of the PSAE also increases as the gas content of oil, hydrostatic pressure or temperature difference increases. The reliability of the PSAWJB is proved by hyperbaric chamber tests.

Study on the pressure self-adaptive water-tight junction box in underwater vehicle

Underwater vehicles play a very important role in underwater engineering. Water-tight junction box (WJB) is one of the key components in underwater vehicle. This paper puts forward a pressure self-adaptive water-tight junction box (PSAWJB) which improves the reliability of the WJB significantly by solving the sealing and pressure problems in conventional WJB design. By redundancy design method, the pressure self-adaptive equalizer (PSAE) is designed in such a way that it consists of a piston pressure-adaptive compensator (PPAC) and a titanium film pressure-adaptive compensator (TFPAC). According to hydro-mechanical simulations, the operating volume of the PSAE is more than or equal to 11.6 % of the volume of WJB liquid system. Furthermore, the required operating volume of the PSAE also increases as the gas content of oil, hydrostatic pressure or temperature difference increases. The reliability of the PSAWJB is proved by hyperbaric chamber tests.