Hydrostatic Pressure Gradient Research Articles

On thermal diffusion and gauge transformations for thermodynamic fluxes and forces

We discuss the molecular diffusion transport in infinitely dilute liquid solutions under non-isothermal conditions. This discussion is motivated by an occurring misinterpretation of thermodynamic transport equations written in terms of chemical potential in the presence of temperature gradient. The transport equations contain the contributions owned by a gauge transformation related to the fact that chemical potential is determined up to the summand of form (AT+B) with arbitrary constants A and B, where constant A is owned by the entropy invariance with respect to shifts by a constant value and B is owned by the potential energy invariance with respect to shifts by a constant value. The coefficients of the cross-effect terms in thermodynamic fluxes are contributed by this gauge transformation and, generally, are not the actual cross-effect physical transport coefficients. Our treatment is based on consideration of the entropy balance and suggests a promising hint for attempts of evaluation of the thermal diffusion constant from the first principles. We also discuss the impossibility of the for dilute solutions, understood in a sense of diffusion flux driven by the pressure gradient itself. When one speaks of terms in literature, these terms typically represent the drift in external potential force field (e.g., electric or gravitational fields), where in the final equations the specific force on molecules is substituted with an expression with the hydrostatic pressure gradient this external force field produces. Obviously, the interpretation of the latter as barodiffusion is fragile and may hinder the accounting for the diffusion fluxes produced by the pressure gradient itself.

Effects of Hydrostatic Pressure on Carcinogenic Properties of Epithelia

The relationship between chronic inflammation and cancer is well known. The inflammation increases the permeability of blood vessels and consequently elevates pressure in the interstitial tissues. However, there have been only a few reports on the effects of hydrostatic pressure on cultured cells, and the relationship between elevated hydrostatic pressure and cell properties related to malignant tumors is less well understood. Therefore, we investigated the effects of hydrostatic pressure on the cultured epithelial cells seeded on permeable filters. Surprisingly, hydrostatic pressure from basal to apical side induced epithelial stratification in Madin-Darby canine kidney (MDCK) I and Caco-2 cells, and cavities with microvilli and tight junctions around their surfaces were formed within the multi-layered epithelia. The hydrostatic pressure gradient also promoted cell proliferation, suppressed cell apoptosis, and increased transepithelial ion permeability. The inhibition of protein kinase A (PKA) promoted epithelial stratification by the hydrostatic pressure whereas the activation of PKA led to suppressed epithelial stratification. These results indicate the role of the hydrostatic pressure gradient in the regulation of various epithelial cell functions. The findings in this study may provide clues for the development of a novel strategy for the treatment of the carcinoma.

Feedback Regulation of Intracellular Hydrostatic Pressure in Surface Cells of the Lens

In wild-type lenses from various species, an intracellular hydrostatic pressure gradient goes from ∼340 mmHg in central fiber cells to 0 mmHg in surface cells. This gradient drives a center-to-surface flow of intracellular fluid. In lenses in which gap-junction coupling is increased, the central pressure is lower, whereas if gap-junction coupling is reduced, the central pressure is higher but surface pressure is always zero. Recently, we found that surface cell pressure was elevated in PTEN null lenses. This suggested disruption of a feedback control system that normally maintained zero surface cell pressure. Our purpose in this study was to investigate and characterize this feedback control system. We measured intracellular hydrostatic pressures in mouse lenses using a microelectrode/manometer-based system. We found that all feedback went through transport by the Na/K ATPase, which adjusted surface cell osmolarity such that pressure was maintained at zero. We traced the regulation of Na/K ATPase activity back to either TRPV4, which sensed positive pressure and stimulated activity, or TRPV1, which sensed negative pressure and inhibited activity. The inhibitory effect of TRPV1 on Na/K pumps was shown to signal through activation of the PI3K/AKT axis. The stimulatory effect of TRPV4 was shown in previous studies to go through a different signal transduction path. Thus, there is a local two-legged feedback control system for pressure in lens surface cells. The surface pressure provides a pedestal on which the pressure gradient sits, so surface pressure determines the absolute value of pressure at each radial location. We speculate that the absolute value of intracellular pressure may set the radial gradient in the refractive index, which is essential for visual acuity.

Abnormal liquid loading in gas wells of the Samandepe Gasfield in Turkmenistan and countermeasures

With complicated formation mechanisms, liquid loading in gas wells during gasfield development may significantly affect the productivity of gas wells and the ultimate recovery rate. Dynamic monitoring data of the Samandepe Gasfield in Turkmenistan shows that liquid loading can be found extensively in gas wells. Their formation mechanisms and negative impacts on gasfield development severely restrict the productivity enhancement of this gasfield. With their origins taken into consideration, liquid loads in gas wells were classified into three types: formation water, condensed liquid, and external liquid. By using the hydrostatic pressure gradient method and through PLT monitoring, properties of liquid loads in the Samandepe Gasfield were determined. In addition, formation mechanisms related to liquid loading in gas wells were obtained through analyses of critical fluid-carrying capacities and by using gas-reservoir production data. The following findings were obtained. Liquid loading was commonly found in this gas well with majority of reservoir formations in lower well intervals flooded. However, the formation mechanisms for these liquid loads are different from those of other gasfields. Due to long-term shut-down of gas wells, killing fluids precipitated and pores in lower reservoir formations were plugged. As a result, natural gas had no access to boreholes, killing fluids were impossibly carried out of the borehole. Instead, the killing fluid was detained at the bottomhole to generate liquid load and eliminate the possibility of formation water coning. Moreover, since the gasfield was dominated by block reservoirs with favorable physical properties and connectivity, impacts of liquid load on gasfield development were insignificant. Thus, to enhance the recovery rate of the Samandepe Gasfield significantly, it is necessary to expand the gasfield development scale and strengthen the development of marginal gas reservoirs.

Body height and arterial pressure in seated and supine young males during +2 G centrifugation.

It is known that arterial pressure correlates positively with body height in males, and it has been suggested that this is due to the increasing vertical hydrostatic gradient from the heart to the carotid baroreceptors. Therefore, we tested the hypothesis that a higher gravito-inertial stress induced by the use of a human centrifuge would increase mean arterial pressure (MAP) more in tall than in short males in the seated position. In short (162-171 cm; n = 8) and tall (194-203 cm; n = 10) healthy males (18-41 yr), brachial arterial pressure, heart rate (HR), and cardiac output were measured during +2G centrifugation, while they were seated upright with the legs kept horizontal (+2Gz). In a separate experiment, the same measurements were done with the subjects supine (+2Gx). During +2Gz MAP increased in the short (22 ± 2 mmHg, P < 0.0001) and tall (23 ± 2 mmHg, P < 0.0001) males, with no significant difference between the groups. HR increased more (P < 0.05) in the tall than in the short group (14 ± 2 vs. 7 ± 2 bpm). Stroke volume (SV) decreased in the short group (26 ± 4 ml, P = 0.001) and more so in the tall group (39 ± 5 ml, P < 0.0001; short vs. tall, P = 0.047). During +2Gx, systolic arterial pressure increased (P < 0.001) and SV (P = 0.012) decreased in the tall group only. In conclusion, during +2Gz, MAP increased in both short and tall males, with no difference between the groups. However, in the tall group, HR increased more during +2Gz, which could be caused by a larger hydrostatic pressure gradient from heart to head, leading to greater inhibition of the carotid baroreceptors.

VEGF Receptor-2-Linked PI3K/Calpain/SIRT1 Activation Mediates Retinal Arteriolar Dilations to VEGF and Shear Stress.

Vasomotor responses of retinal arterioles to luminal flow/shear stress and VEGF have a critical role in governing retinal blood flow possibly via nitric oxide synthase (NOS) activation. However, the cellular mechanism for flow-sensitive vasomotor activity in relation to VEGF signaling in retinal arterioles has not been characterized. We used an isolated vessel approach to specifically address this issue. Porcine retinal arterioles were isolated, cannulated, and pressurized to 55 cm H2O luminal pressure by two independent reservoir systems. Luminal flow was increased stepwise by creating hydrostatic pressure gradients across two reservoirs. Diameter changes and associated signaling mechanisms corresponding to increased flow and VEGF receptor 2 (VEGFR2) activation were assessed using videomicroscopic, pharmacological, and molecular tools. Retinal arterioles developed basal tone under zero-flow condition and dilated concentration-dependently to VEGF165. Stepwise increases in flow produced graded vasodilation. Vasodilations to VEGF165 and increased flow were abolished by endothelial removal, and inhibited by pharmacological blockade of VEGFR2, NOS, phosphoinositide 3-kinase (PI3K), calpains, or sirtuin-1 (SIRT1) deacetylase. A VEGF165 antibody blocked vasodilation to VEGF165 but not flow. Immunostaining indicated that VEGFR2 was expressed in the endothelial and smooth muscle layers of retinal arterioles. Ligand-dependent and ligand-independent activation of VEGFR2 in the endothelium mediates NO-dependent dilations of porcine retinal arterioles in response to VEGF165 and luminal flow/shear stress, respectively. It appears that NOS stimulation via PI3K, calpain proteases, and SIRT1-dependent deacetylation downstream from VEGFR2 activation contributes to these vasodilator responses.

Analytical solution of magnetohydrodynamic flow of Jeffrey fluid through a circular microchannel

The magnetohydrodynamic (MHD) flow of Jeffrey fluid in a circular microchannel is presented. Using the method of variable separation, the analytical solutions to both DC-operated MHD and AC-operated MHD micropumps are found. The flow is assumed to be laminar, unidirectional, one dimensional and driven by the Lorentz force. The Lorentz force can be taken as hydrostatic pressure gradient in the momentum equation of the MHD microchannel flow model. The effects of Hartmann number Ha, dimensionless relaxation time λ¯1 and retardation time λ¯2 on the velocity and volumetric flow rate are investigated. The velocity and volumetric flow rate grow and then reduce with Hartmann number Ha. There is a critical value of the Ha for MHD velocity and an optimum Ha for maximum volumetric flow rate. In addition, a comparison with previous works is also provided to confirm the validity of the present results.

Abstract 5500: A 3D tumor tissue microphysiological system for realistic tumor microenvironment mimicry and therapeutic modeling

Abstract Introduction: Although cancer is a heterogeneous disease, current chemotherapy is based on the use of anti-cancer agents that broadly affect cell proliferation. As a result of this non-specific tumor therapy there is often high toxicity and therapeutic resistance, which increases the risk of disease progression. There is thus a critical need to find novel anti-cancer compounds, however, as a result of preliminary screens often performed in 2D systems, and the use of mouse models for secondary screens, many drugs fail during full clinical trials. Replicating a complex, 3D microenvironment incorporating human cells is therefore likely to improve drug screening efficiency. Methods: Here we have developed a system for high throughput screening of drug efficacy. Our system features 3D tumor tissues incorporating human cells co-cultured with stromal cells and connected by human microvessels in a naturally occurring 3D matrix in a PDMS microdevice. Transduced colorectal cancer cells (CRC) such as HCT116, SW480 and SW620s that express green fluorescent protein (GFP) constitutively are introduced into the device in co-culture with human endothelial colony-forming cell-derived EC (ECFC-EC) and fibroblasts. ECFC-EC or fibroblasts that express longer wavelength fluorescent proteins are also used to track both tumor cells and vasculature/fibroblast growth. The tri-culture is resuspended in fibrinogen (10 mg/ml) and mixed with thrombin before injecting into the microchambers. Cells are fed with endothelial growth media-2 and drugs are delivered through the microfluidic channels using a hydrostatic pressure gradient. Results: A complete vascular network was formed in the chambers by 7-10 days and this carried medium into the tissue. CRC showed continuous growth, often forming spheroids. After 7-10 days of culture, cells were exposed to various FDA-approved drugs at concentrations reported for plasma levels in patients. Tumor growing in the device responded differently to most drugs compared to cells growing in 2D. We identified cytotoxic and cytostatic drug actions in the device with IC50s close to the in vivo pharmacologic plasma concentration, but higher than those obtained in parallel 2D experiments. Importantly, we also identified drugs that were active in our 3D-device but not in 2D cultures. Conclusions: Preliminary results using our 3D microphysiological system, in which we have created a more complex microenvironment than used in 2D cultures, support an improved strategy for drug validation. In addition, future experiments will include the use of non-invasive optical imaging techniques to better understand the human 3D tumor microenvironment, including the study of different tumor behaviors, tumor metabolism and pathological angiogenesis. This proof-of-concept study validates the use of 3D microphysiological systems in place of more simplistic 2D systems. Citation Format: Agua Sobrino, Dúc Phan, Steven C George, Christopher C.W Hughes. A 3D tumor tissue microphysiological system for realistic tumor microenvironment mimicry and therapeutic modeling. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5500. doi:10.1158/1538-7445.AM2015-5500

The Collapse and Expansion of Liquid-Filled Elastic Channels and Cracks.

The rate at which fluid drains from a collapsing channel or crack depends on the interaction between the elastic properties of the solid and the fluid flow. The same interaction controls the rate at which a pressurized fluid can flow into a crack. In this paper, we present an analysis for the interaction between the viscous flow and the elastic field associated with an expanding or collapsing fluid-filled channel. We first examine an axisymmetric problem for which a completely analytical solution can be developed. A thick-walled elastic cylinder is opened by external surface tractions, and its core is filled by a fluid. When the applied tractions are relaxed, a hydrostatic pressure gradient drives the fluid to the mouth of the cylinder. The relationship between the change in dimensions, time, and position along the cylinder is given by the diffusion equation, with the diffusion coefficient being dependent on the modulus of the substrate, the viscosity of the fluid, and the ratio of the core radius to the exterior radius of the cylinder. The second part of the paper examines the collapse of elliptical channels with arbitrary aspect ratios, so as to model the behavior of fluid-filled cracks. The channels are opened by a uniaxial tension parallel to their minor axes, filled with a fluid, and then allowed to collapse. The form of the analysis follows that of the axisymmetric calculations, but is complicated by the fact that the aspect ratio of the ellipse changes in response to the local pressure. Approximate analytical solutions in the form of the diffusion equation can be found for small aspect ratios. Numerical solutions are given for more extreme aspect ratios, such as those appropriate for cracks. Of particular note is that, for a given cross-sectional area, the rate of collapse is slower for larger aspect ratios. With minor modifications to the initial conditions and the boundary conditions, the analysis is also valid for cracks being opened by a pressurized fluid.

Characteristics of stratified laminar flows in inclined pipes

Exact solutions for laminar stratified flows in inclined pipes are presented. These include all possible configurations of stratified flows with concave and convex interfaces. The exact solution is used to study the effect of the flow geometry and pipe inclination on the holdup and pressure gradient. In particular, the possibility of reducing the pressure gradient of a viscous fluid in upward inclined flows by adding a lubricating phase is investigated. It is shown that independently of the density of the lubricant, namely, whether it is lighter or heavier than the viscous fluid, the effect of hydrostatic pressure gradient always adversely affects the possibility to reduce the pumping requirement for the flow of the viscous phase. In addition, the countercurrent flow limits and the boundaries of the multiple solution regions in concurrent inclined flow are identified and discussed. The susceptibility of the system to the Ledinegg instability when using separate pumps for each of the fluids is also examined.

Investigations on the methane sorption capacity of marine shales from Sichuan Basin, China

High-pressure methane sorption isotherms measured at 30, 50 and 80°C and pressure up to 20MPa were measured on Lower Silurian marine shales from Sichuan Basin of China. The effect of total organic carbon content, temperature, thermal maturity, mineral composition, and pore structure on methane sorption capacity has been investigated. A linear combination approach has been developed to predict the Langmuir sorption capacity of shales based on the mass fractions of their organic and inorganic components. This information can be used to estimate the in situ sorption capacity of shale layers as a function of burial depth (formation pressure and temperature), and composition.Methane sorption capacity of the dry shales shows a positive relationship with TOC and specific surface area. The Langmuir pressure decreases with increasing maturity, but the TOC-normalized Langmuir sorption capacity of over-mature shales also decreases with increasing thermal maturity. This may be related to the carbonization of highly over-mature organic matter. For the samples investigated, approximately 16.3%–46.7% (average 28.6%) of the methane sorption can be attributed to clay minerals and 46.5%–81.5% to (average 67.6%) organic matter in these shales, respectively. Using the linear combination approach, the calculated Langmuir sorption capacity function matches the measured values reasonably. Methane sorption capacity computed as a function of depth (for a mean hydrostatic pressure gradient of 0.01MPa/m and a geothermal gradient of 0.03°C /m) shows a rapid increase and reaches a maximum between 900 and 1800m followed by a slow decrease with increasing depth. At shallow burial depths (<900–1800m), the sorption capacity is controlled by the combination of hydrostatic pressure and geothermal gradients. At deeper burial (>900–1800m) sorption capacity is controlled by the geothermal gradient. Higher geothermal gradients result in a steeper decline of sorption capacity.

Molecular Dynamics Modeling of Sodium And Water Transport through a Claudin Pore

BackgroundClaudin‐2 is a paracellular channel. Na and water flow through it driven by an osmotic or Na concentration gradient, suggesting that Na and water pass through a common pore and that their fluxes are frictionally coupled. We investigated the mechanism by molecular dynamics simulations.MethodsThe claudin pore was modeled either as a double cone or a cylindrical nanotube with narrowest diameter of 6.5 Å and 6 negatively charged sites in the middle of the pore (each ‐0.2e). A hydrostatic pressure gradient was applied via an additional constant force in the channel axis direction to a layer of water molecules parallel to the membrane interface. Simulations were performed using the CHARMM27 force field and the TIP3P water model, with full electrostatics was included.ResultsWith an osmotic gradient, water molecules oriented within the pore in 2 water wires and exhibited directional flow with Pf= 4.7 x 10‐13 cm3/s and a water:Na flux ratio of 233. Increasing the magnitude of the negative charge increased permeability only when the charges were smeared evenly along the pore surface. Application of a Na concentration gradient, also drove water flow with water:Na flux of 14.6. Increasing the pore diameter to 7Å also increased water flow significantly by allowing 3 water wires to form.ConclusionsOur findings confirm that water can permeate through claudin‐2 via a water wire mechanism, demonstrate that water permeability is dependent on the magnitude and distribution of intrapore charges and on the pore diameter, and provide a molecular explanation for the frictional coupling of Na and water fluxes within the pore.

Differential responses in brachial and ankle blood pressure during blood pressure reactivity tests

Blood pressure (BP) reactivity has been assessed by a variety of stimuli, including physical, psychological, and physiological perturbations, that can be further classified into cardiac or vascular in regard to the effector organs. In many BP reactivity studies, changes in brachial BP are taken as systemic changes and are combined with leg measurements to assess vasoactive states. Currently, it is unknown if leg BP behaves similarly to arm BP.PurposeWe compared BP changes between the brachial and post‐tibial arteries during acute BP perturbations.MethodsThirty apparently healthy subjects (57% males, 46±4 years) were studied. Both brachial and ankle systolic BP (SBP) were measured simultaneously with the oscillometric technique during resting baseline, head‐up tilt (HUT), head‐down tilt (HDT), mental stress (MS), isometric hand‐grip exercise (HG), and a cold pressor test (CPT).ResultsBrachial (bSBP) and ankle (aSBP) SBP at rest were significantly and highly correlated (r=0.81). Changes in bSBP were significantly and positively associated with changes in aSBP in response to HUT (r=0.46), HDT (r=0.53), MS (r=0.70), HG (r=0.63), and CPT (r=0.75). The magnitudes of bSBP and aSBP changes were not different n response to MS, HG, and CPT since all were within 5 mmHG. There were significant differences in the magnitude of changes in bSBP and aSBP in response to HDT (12±1 mmHg) and HUT (40±2 mmHg).ConclusionBoth brachial and ankle BP respond similarly in many vascular reactivity maneuvers. During head‐down and head‐up tilt, however, differences in their responses may be quite large, presumably due to the hydrostatic pressure gradients created during the maneuvers.Supported by Fukuda Denshi.

MRI measurements of intracranial pressure in the upright posture: The effect of the hydrostatic pressure gradient.

To add the hydrostatic component of the cerebrospinal fluid (CSF) pressure to magnetic resonance imaging (MRI)-derived intracranial pressure (ICP) measurements in the upright posture for derivation of pressure value in a central cranial location often used in invasive ICP measurements. Additional analyses were performed using data previously collected from 10 healthy subjects scanned in supine and sitting positions with a 0.5T vertical gap MRI scanner (GE Medical). Pulsatile blood and CSF flows to and from the brain were quantified using cine phase-contrast. Intracranial compliance and pressure were calculated using a previously described method. The vertical distance between the location of the CSF flow measurement and a central cranial location was measured manually in the mid-sagittal T1 -weighted image obtained in the upright posture. The hydrostatic pressure gradient of a CSF column with similar height was then added to the MR-ICP value. After adjustment for the hydrostatic component, the mean ICP value was reduced by 7.6 mmHg. Mean ICP referenced to the central cranial level was -3.4 ± 1.7 mmHg compared to the unadjusted value of +4.3 ± 1.8 mmHg. In the upright posture, the hydrostatic pressure component needs to be added to the MRI-derived ICP values for compatibility with invasive ICP at a central cranial location.

CO2 injection simulation into the South Georgia Rift Basin for geologic storage: A preliminary assessment

This study simulated the injection of supercritical phase into the South Georgia Rift (SGR) basin to evaluate the feasibility of long-term storage. Because of the lack of basin data, an equilibrium model was used to estimate the initial hydrostatic pressure, temperature, and salinity gradients that represent our study area. For the equilibrium model, the USGS SEAWAT program was used and for the injection simulation, TOUGH2-ECO2N was used. A stochastic approach was used to populate the permeability in the injection layer within the model domain. The statistical method to address permeability uncertainty and heterogeneity was sequential Gaussian simulation. The target injection depths are well below the 1 km (∼0.62 mi) depth required to maintain as a supercritical fluid. There were very little data pertaining to the properties in the deep Jurassic/Triassic SGR basin formations. So, conservative porosity and permeability starting points were postulated using data from analogous basins. This study simulated 30 million tons of injected at a rate of 1 million tons per year for 30 yr, which is the minimum capacity requirement by the U.S. Department of Energy (DOE) for a viable storage reservoir. In addition to this requirement, a 970-yr shut-in time (no injection) was also simulated to better determine the long-term fate and migration of the injected and to ensure that the SGR basin could effectively contain 30 million tons of . The preliminary modeling of injection indicated that the SGR basin is suitable for geologic storage of this U.S. DOE stated minimum capacity.

Physiology of the pleural space.

The pleural cavity is created between the 4(th) and 7(th) week of embryologic development. These embryonic components of visceral and parietal pleurae develop different anatomic characteristics with regard to vascular, lymphatic, and nervous supply. There are two layers: a superficial mesothelial cell layer facing the pleural space and an underlying connective tissue layer. The pleura might present inflammatory response and maintenance of the pleural fluid is observed. The latter function is especially important in the mechanical coupling of the lung and chest wall. Fluid is filtered into the pleural space according to the net hydrostatic oncotic pressure gradient. It flows downward along a vertical pressure gradient, presumably determined by hydrostatic pressure and resistance to viscous flow. There also may be a net movement of fluid from the costal pleura to the mediastinal and interlobar regions. In these areas, pleural fluid is resorbed primarily through lymphatic stomata on the parietal pleural surface. In the current review we will present the physiology of the pleural space in a step by step manner.

Improved Model for Predicting Annulus Pressure Drop during Underbalanced Drilling

Most time during underbalanced drilling or cleaning of well, formation fluid (oil and water) influx is usually experienced as soon as productive zone is penetrated because formation pore pressure gradient are higher than hydrostatic pressure gradient. Successful flow of fine drilling cuttings and formation fluid (gas, oil and water) to the surface flow facilities therefore demands for accurate prediction of pressure drop along the well bore during underbalanced drilling. Previous studies on pressure profile prediction in the wellbore during underbalanced drilling have not taken into account the effect of cuttings volume. The purpose of this study is therefore to develop an improved model that predicts the effect of cuttings volume on annulus pressure drop in the wellbore during underbalanced drilling. This is an extension of Guo and Fadairo model for investigating the effect of cutting volume pressure drop during underbalanced drilling. The result of the study shows that the cutting flow rate increases with small pressure differential while it decreases with large pressure differential. This depicts that cutting retards fluid flow and increases bottom-hole pressure and fluid density, resulting in low fluid velocity and cutting lifting capacity of the drilling fluid. This may result in cutting accumulation, ultimately reducing the ability of the drilling fluid to effectively lift drill cuttings from bottom-hole to the surface and eventually lead into stuck drilling string.

Problems in estimation of the formation depth of hydrothermal deposits by data on pressure of mineralizing fluids

In this paper, the formation depth of hydrothermal deposits is proposed to be roughly estimated by data on pressure variations in fluid inclusions from maximum Pmax to minimum Pmin values, taking into account the restrictions to the physical limits of this range based on lithostatic and hydrostatic fluid pressure. Under the assumption of a regressive trend in the PT conditions throughout the geological history of the deposits, it is possible to estimate the minimum depth at the beginning of the mineralization process, using a Pmax value and lithostatic fluid pressure gradient (∼260 bar/km), and the maximum depth at the completion of mineralization process, using a Pmin value and hydrostatic gradient (∼100 bar/km). If the mineral deposition depth estimated from the values of Pmax and lithostatic fluid pressure gradient is consistent with the depth estimate from the values of Pmin and hydrostatic fluid pressure gradient, then the resulting depth estimates correspond to the deposit formation depth unchanged throughout the mineral deposition process. In case of the ratio Pmax/Pmin > 2.6–3.0, the deposit is mineralized under variable depth coordinates with an upward movement of mineral deposition level, according to obtained estimates, over a depth range of up to >15 km. In case of the ratio Pmax/Pmin < 2.6, the data on fluid pressure variations does not allow making any definite conclusions on the trends in the deposit formation depth. In deposits with an upward movement of the mineral deposition level, the trends in depth variations based on fluid pressure data are in qualitative agreement with the data on minimum temperature Tmin recorded in deposit fluid inclusions under the assumption of its physical restriction to geothermal field values.

Numerical Simulation of Fluid Flow in Magnetohydrodynamic (MHD) Micropumps Using Hydrostatic Pressure Gradient

In this paper the fluid flow of a particular type of micropumps, so-called Magnetohydrodynamic (MHD) micropump, has been simulated numerically. In this investigation, the governing equations of a fluid flow in MHD micropumps with the incompressible, steady state, laminar and fully developed assumptions, have been derived and solved. In the momentum equation associated with the considered flow model, the foregoing Lorentz force has been replaced by a uniform hydrostatic pressure gradient throughout the channel. The effects of channel geometry, electric and magnetic fields on the flow velocity produced by the micropump have been investigated. Finally, the comparison of numerical results with the experimental data issued by other researchers proved that the presented method simulates the fluid flow with a good agreement and the least amount of time and cost.

Understanding negative pressure pulmonary edema.

Understanding negative pressure pulmonary edema.