Additional Hydrostatic Pressure Research Articles

High-resolution spatio-temporal analysis of snowmelt over Antarctic Peninsula ice shelves from 2015 to 2021 using SAR images

ABSTRACT Ice shelves play an essential role in the dynamics of the Antarctic ice sheet. The surface meltwater is important, as it can irreversibly weaken ice shelves by exerting additional hydrostatic pressure. Therefore, high-resolution snowmelt products are urgently needed to accurately analyze melting patterns of ice shelves and further estimate mass loss. In this study, a new high-resolution (40 m) snowmelt dataset over all of the Antarctic Peninsula ice shelves larger than 100 km was developed based on the modified snowmelt detection framework by using a co-orbit normalization method. The dataset provides detailed snowmelt information on each ice shelf, including the image coverage, melting area and melting ratio every 5 days. The melting patterns of three typical ice shelves (George VI, Wilkins and Larsen C Ice Shelves) and the spatio-temporal melting distribution of the Antarctic Peninsula (AP) were further analyzed. The snowmelt information indicates that both the extent and duration of snowmelt have been increasing in the Antarctic Peninsula from 2015 to 2021, and we found that the snowmelt on the Antarctic Peninsula showed a spatial pattern of significantly intense snowmelt on the western side. We believe this study will provide essential data for ice shelf investigation to support other fields of polar research.

PS-C03-12: FINGER-TO-TOE PULSE WAVE VELOCITY IN RESPONSE TO SITTING POSITION

Objective: Aortic stiffness is a non-traditional risk factor for cardiovascular disease and mortality and is associated with increased central pulse pressure. It is generally measured by carotid-femoral pulse wave velocity (PWV) in a supine position. We hypothesized that, in a sitting position, the additional hydrostatic pressure exerted on the vascular wall could represent a vascular stress test. Two alternative methods can now estimate aortic stiffness and can be used conveniently in different positions: 1) brachial pulse wave analysis approach used by Mobil-O-Graph and 2) transit time approach using finger-to-toe PWV by photoplethysmography with the pOpmetre. The aim of the present study is to determine the impact of postural changes on PWV and central blood pressure estimation using these two distinct methods. Design and method: Central blood pressure and PWV were assessed in 20 healthy subjects using Mobil-O-Graph (PWV-M) and pOpmetre (PWV-pop) in three positions: supine in bed, supine in reclining chair and sitting. Central systolic blood pressure (SBP) was determined by calibration of brachial systolic and diastolic blood pressures by both methods (SBP-M and SBP-pop). Generalized estimating equations were used for analysis. Results: The PWV-M remained relatively constant and generally independent of the position (5.5 ± 1.0, 5.3 ± 1.0 and 5.5 ± 1.0 m/s). While PWV-M and PWV-pop were similar in the supine position (5.5 ± 1.0 vs 5.4 ± 1.3 m/s, P = NS), PWV-pop increased very significantly to 5.9 ± 1.5 m/s in supine in reclining chair position (P = 0.04), and to 9.2 ± 1.7 m/s in sitting position (P < 0.001). Central blood pressure estimation remained similar for SBP-M (110.2 ± 10.3 vs 106.9 ± 10.5 vs 108.8 ± 11.1 mmHg, P = NS) and for SBP-pop (107.7 ± 10.4 vs 110.3 ± 9.6 vs 109.5 ± 9.9 mmHg, P = NS). Conclusions: These results suggest that estimated PWV by brachial pulse wave analysis remains robust independent of position. However, the estimated finger-to-toe PWV by pulse transit time increases remarkably with the imposition of hydrostatic pressure on the vascular wall. We conclude that the finger-to-toe PWV may provide the opportunity to evaluated vascular wall property in a dynamic fashion using postural changes as a stress test.

Comparison of Different Scanning Ion-Conductance Microscopy Methods to Study Local Mechanical Properties of Living Cells

A better understanding of molecular biophysical basics of the mechanism of mechanotransduction will bring about new methods of treatment of a wide range of disorders. It is assumed that microscopic changes in cellular mechanics could break the regulation of the molecular mechanism of mechanotransduction - the process by which cells sense mechanical signals and convert them into chemical responses. There are plenty of abnormalities arisen from alterations of mechanical properties of the matrix, e.g. enhanced cancer cell metastasis. Therefore, studying of mechanical properties of live cells is very important. Noncontact topography images can be acquired via the Scanning Ion-Conductance Microscopy (SICM), which uses an electrolytic current through a nanopipette as a measure for pipette-surface distance. There are two definitely different methods of topography mapping allowed by SICM. The first one calculates cell stiffness depending on the current drop, due to the probe approach to the cell surface. The second one uses additional hydrostatic pressure through a nanopipette while the pipette-sample separation is kept constant above the cell surface. These approaches have been validated on living cells (Human prostate adenocarcinoma). As a result, two different SICM scanning methods were compared. The first method with the pipette-tip radius of 38 nm showed 895.69 ± 195.95 Pa membrane stiffness. The second one, with the tip radius 120 nm and additional pressure from 3kPa to 6kPa, showed 887.41 ± 178.31 Pa membrane stiffness. In connection with that, these methods are comparable, and give the same mechanical properties. The biological part of research was funded by the Ministry of Education and Science of the Russian Federation implemented by a governmental decree dated 16 March 2013, no. 211, The Russian Science Foundation, grant number No 19-79-30062, funded SICM method.

Deformation and stability of compressible rubber O-rings

BackgroundIn rubber elastic models it is generally assumed that the bulk modulus is infinite, resulting in a material that does not change its volume and a pressure that cannot be evaluated from the material model.MethodsWe have developed a general procedure that incorporates a finite bulk modulus. Using the developed framework accurate results can be obtained without the need for special finite elements. It gives the correct results even in the limit of infinite bulk modulus.ResultsIt was shown that material compressibility causes additional stresses mostly associated with an additional hydrostatic pressure. It was also demonstrated that once a bulk modulus is included in the constitutive model, stability analyses of rubber-like materials subject to large deformation become numerically stable and accurate. Hence, it is essential to use compressibility with neo-Hookean solids for accurate stress and lifing predictions. The role of twist in the formation of stress-strain states in rubber O-rings has been evaluated. Such a twist causes elastic instabilities resulting in highly deformed O-ring shapes. Numerical analysis using compressible material models predicted the stable deformed states that O-ring do not remain circular. The ring is buckled and reaches a “chair” –type non-planar shape just beyond inside-out twist.ConclusionsThe results indicate that elastic material volume change causes additional stresses mostly associated with an additional hydrostatic pressure. Simulations using various rubber elastic models showed that allowing volume changes allows accurate stress state prediction, reduces numerical difficulties and improves the numerical stability.

Pressure-Assisted Selective Preconcentration in a Straight Nanochannel

We investigate the preconcentration profiles of a fluorescein and bovine serum albumin derivatized with this fluorescent tag in a microfluidic chip bearing a nanoslit. A new preconcentration method in which a hydrodynamic pressure is added to both electroosmotic and electrophoretic contributions is proposed to monitor the location of the preconcentration frontline. A simple predictive model of this pressure-assisted electropreconcentration is proposed for the evolution of the flow profile along this micro/nano/microfluidic structure. We show with a small analyte such as fluorescein that the additional hydrostatic pressure mode enables to stabilize the concentration polarization (CP) effect, resulting in better control of the cathodic focusing (CF) peak. For BSA (bovine serum albumin), we exhibit that the variation of the hydrodynamic pressure can have an even more drastic effect on the preconcentration. We show that, depending on this hydrodynamic pressure, the preconcentration can be chosen, either in the cathodic side or in the anodic one. For the first time, we prove here that both anodic focusing (AF) and cathodic focusing (CF) regimes can be reached in the same structures. These results also open new routes for the detection and the quantification of low abundance biomarkers.

Hydrostatic pressure effects on the state density and optical transitions in quantum dots

Using the effective mass approximation and variational method we have computed the effects of hydrostatic pressure on the absorption and photoluminescence spectra in spherical quantum dot GaAs-(Ga, Al) As, considering a finite confinement potential of this particular work we show the optical transitions in quantum of various sizes in the presence of hydrogenic impurities and hydrostatic pressure effects. Our first result describes the spectrum of optical absorption of 500 A QD for different values of hydrostatic pressure P = 0, 20 and 40 Kbar. The absorption peaks are sensitive to the displacement of the impurity center to the edge of the quantum dot and even more when the hydrostatic pressure changes in both cases showing that to the extent that these two effects are stronger quantum dots respond more efficiently. Also this result can be seen in the study of the photoluminescence spectrum as in the case of acceptor impurities consider them more efficiently capture carriers or electrons that pass from the conduction band to the valence band. Density states with randomly distributed impurity show that the additional peaks in the curves of the density of impurity states appear due to the presence of the additional hydrostatic pressure effects.

A general relationship for the compressibility of organic solvents

Applying an additional hydrostatic pressure, which is determined by the difference (B i –B j ) in Tait's equation coefficients, to liquids (S j ) with a higher compressibility coefficient equalizes the compressibility of all the liquids studied (S i ). The correlation obtained makes it possible to predict the compression curve of any liquid over a wide pressure range based on the value of β T determined at ambient pressure.

Pressure Increase Due to Hydrostatic Pressure of Perfluorocarbon

With great interest we read the recent article by Kacmarek and colleagues (1). In the trial reported therein, the authors conclude that partial liquid ventilation (PLV) results in a greater number of serious adverse effects and does not improve outcome compared with conventional ventilation in patients with severe ARDS. As one of the reasons for a higher complication rate, the authors suggest the high peak alveolar pressure due to the additional hydrostatic pressure exerted by the perfluorocarbon (PFC), which has to be added to the measured airway pressure. It is obvious that a measurement of the hydrostatic pressure is associated with technical difficulties, though it is possible to estimate it. In this study the PFC was instilled to the carina in the supine position. Therefore, the maximal hydrostatic pressure (cm H2O) can be calculated by multiplying the distance between the liquid surface and the deepest point in the thorax, the dorsovisceral pleura (in cm), and the specific density of the PFC, which is 1.92. To evaluate the effective additional hydrostatic pressure, we measured 40 patients, ages between 18 and 60 yr, median 44.6 12.8 yr, 60% male sex, who had a thoracic CT in the supine position. On the Diagnostic Workstation (Diagnostic DICOM 3.0 Workstation; Agfa-Gevaert Group, Morstel, Belgium), the distance between the level of the carina and the lowest point of the dorsovisceral pleura was measured with the on-screen tool. The median distance retrieved was 7.5 cm 1.2 cm. Using these findings for estimating the actual resulting airway pressure, the distance was multiplied by 1.92. Therefore in the “low-dose” group, the hydrostatic pressure of 14.4 2.36 cm H2O has to be added to the measured plateau pressure as well as to the measured PEEP. Following this estimation, the median plateau pressure would be as high as 45.8 cm H2O with a PEEP of 28.7 cm H2O. These excessively high pressures could explain the higher rate of adverse effects in the “low-dose” group. For the “high-dose” group the resulting pressure would even exceed these findings. As is known from the literature (2), increased airway pressures lead to a worse outcome. Therefore, to avoid barotrauma to the lung during PLV, which probably contributes to a worse outcome, the measured pressure levels during PLV should have been significantly reduced. Therefore, the conclusion based on the findings of this study should be reconsidered.

Pressure Increase Due to Hydrostatic Pressure of Perfluorocarbon

With great interest we read the recent article by Kacmarek and colleagues (1). In the trial reported therein, the authors conclude that partial liquid ventilation (PLV) results in a greater number of serious adverse effects and does not improve outcome compared with conventional ventilation in patients with severe ARDS. As one of the reasons for a higher complication rate, the authors suggest the high peak alveolar pressure due to the additional hydrostatic pressure exerted by the perfluorocarbon (PFC), which has to be added to the measured airway pressure. It is obvious that a measurement of the hydrostatic pressure is associated with technical difficulties, though it is possible to estimate it. In this study the PFC was instilled to the carina in the supine position. Therefore, the maximal hydrostatic pressure (cm H2O) can be calculated by multiplying the distance between the liquid surface and the deepest point in the thorax, the dorsovisceral pleura (in cm), and the specific density of the PFC, which is 1.92. To evaluate the effective additional hydrostatic pressure, we measured 40 patients, ages between 18 and 60 yr, median 44.6 12.8 yr, 60% male sex, who had a thoracic CT in the supine position. On the Diagnostic Workstation (Diagnostic DICOM 3.0 Workstation; Agfa-Gevaert Group, Morstel, Belgium), the distance between the level of the carina and the lowest point of the dorsovisceral pleura was measured with the on-screen tool. The median distance retrieved was 7.5 cm 1.2 cm. Using these findings for estimating the actual resulting airway pressure, the distance was multiplied by 1.92. Therefore in the “low-dose” group, the hydrostatic pressure of 14.4 2.36 cm H2O has to be added to the measured plateau pressure as well as to the measured PEEP. Following this estimation, the median plateau pressure would be as high as 45.8 cm H2O with a PEEP of 28.7 cm H2O. These excessively high pressures could explain the higher rate of adverse effects in the “low-dose” group. For the “high-dose” group the resulting pressure would even exceed these findings. As is known from the literature (2), increased airway pressures lead to a worse outcome. Therefore, to avoid barotrauma to the lung during PLV, which probably contributes to a worse outcome, the measured pressure levels during PLV should have been significantly reduced. Therefore, the conclusion based on the findings of this study should be reconsidered.

Synthesis of Bulk Nanocrystalline Materials by Repeated Cold Rolling

AbstractThe article gives an overview on the preparation and characterization of bulk nanocrystalline or bulk amorphous metallic materials by repeated cold rolling with intermediate folding. The results that are highlighted for pure fcc and hcp metals and one binary glass‐forming alloy indicate that truly nanocrystalline materials with grain sizes below 10 nm can be obtained by this process that does not apply an additional hydrostatic pressure and that is compatible with continuous processing routes.

Effect of X-ray irradiation on CdS 1− xSe x quantum dots optical absorption

Optical absorption spectra of X-ray irradiated CdS 1− x Se x quantum dots embedded in a borosilicate matrix are studied. As the irradiation dose is increased up to 3240 Gy, the quantum-size-related maxima are smeared and the absorption edge is blue shifted. The observed effects are related to the X-ray ionization of the quantum dots with charge-carrier transfer between the nanocrystals and the host matrix as well as to the additional hydrostatic pressure upon the quantum dots due to the radiation-induced swelling of the glass matrix. The radiation-induced changes vanish completely at post-irradiation annealing up to 575 K.

Discussion on measurement and calculation principle of petrogenetic depth

Geologic and geophysical data certificate that lithosphere and its down rock behave as solid, therefore, it is better to measure petrogenetic and metallogenetic depth according to internal stress of solid states. Lithomechanic experiment found that the bigger the confining pressure, the bigger the tensile and shear strength of rocks,so rock can bear very high differential stress but it is not broken. Sibson put forward that the property of rocks under 10–15km of the surface changes from brittle to ductile (rather than from elastic to plastic). Rock with ductile deformation is still solid with elasticity, and it is not in the hydrostatic pressure state. Now ingored differential stress has already been measured at deeper place, it cannot be used to measure depth with the static fluid model but with the elastic model for lack of rheological experiment data. The more correct depth could be calculated by the elastic model rather than the static fluid model. It is an advance to describe rock property with the viscoelastic or elastic-viscosity model, but it is not the progress to come back to the static fluid model from the elastic model. Generally speaking, isotropic equante normal stress in the tectonic stress field, namely tectono-original additional hydrostatic pressure is one order of magnitute more than differential stress in the tectonic stress field, which, superimposed on additional hydrostatic stress of gravity, will bring about ultrahigh pressure metamorphism (UHPM), no matter how big the differential stress is.

A finite-element simulation on deformational energy in structural deformed zone

Under the same conditions of external force, simulations on differences of deforma-tional energy in structural zones, which have different deformational behavior, and that on the distribution of the differences have been carried out by means of finite-element method. Shear deformational energy UW is higher than volume deformational energy UT by about one order of magnitude, and deformational energy UB( = UW + UT) and Uw show a trend to be larger→ largest→small in quantity in structural zones of different deformational properties, which correspond to compressive, shear, tensile zones, respectively, but UT shows a trend to be large→ small gradually. This has a considerable significance in the study of tectonic heat and mineral liquid migration in association with the research on tectonic additional hydrostatic pressure.

The formation depth of coesitebearing eclogite, Dabie UHPM zone, China, modified by tectonooriginal additional hydrostatic pressure

The knowledge that hydrostatic pressure is equal to the gravity value of the overlying rocks in studying a dynamic state of certain underground site is argued. It is suggested that the stress field Τ in the crust is a combination or superposition of total hydrostatic pressureP with differential stress σ, and the total hydrostatic pressureP at any point in the crust comprises two parts: one is spherical stress tensor PG, caused by the gravity, and the other is spherical stress tensor PS caused by tectonic stress; thereforeP could not be attributed to the gravity of overlying rocks only.

Phase characterization and stabilization due to grain size effects of nanostructured Y 2O 3

X-ray diffraction and micro-Raman scattering studies of nanostructured Y 2O 3 prepared by gas phase synthesis are reported. The as-prepared material has the monoclinic structure of the high pressure polymorph, γ-Y 2O 3. The high-pressure phase is stable in the nanostructured grains at ambient conditions resulting from the additional hydrostatic pressure component due to the Gibbs-Thomson effect. At temperatures exceeding 600°C monoclinic γ-transforms to cubic α- Y 2 O 3. The dependence of the phase transition temperature on the state of compaction of the nanostructured powders indicates that the stability of the high pressure phase at ambient conditions results from the nanostructured particle size.

Effect of Experimental Ocular Hypertension on Macrovacuolation in Schlemm’s Canal Endothelial Cells of Monkey Eyes

The severance of all the extraocular muscles (tenotomy) caused temporary ocular hypertension, lasting a few days, in Japanese monkey (Macaca fuscata) eyes. We studied the morphology of Schlemm's canal endothelium of the eyes under a light microscope after quick fixation through continuous irrigation of the anterior chamber with a 10% acrolein solution, with precise control of the hydrostatic pressure on the eyes during fixation. A statistically significant increase in macrovacuolation in endothelial cells of Schlemm's canal of normal eyes was observed when additional hydrostatic pressure was applied. However, such an increase was not observed in the case of tenotomized temporary hypertensive eyes.

Fluid shift across the placenta: I. The effect of dextran T 40 in the isolated guinea-pig placenta

In an effort to understand better the transplacental water flux induced by osmotic forces, 17 near-term guinea-pig placentae were perfused on both sides with an artificial cell-free fluid containing dextran. Maternal and fetal arterial inflow rates were kept constant by syringe pumps and inflow and outflow pressures were recorded continuously. Precise measurements of outflow rates were made by weight determination and transplacental fluid shifts calculated by weight changes during placental passage. The content of dextran T 40 in the perfusion fluid was altered in stepwise manner from 0 to 60 to 120 g/l, and the effects of all possible combinations of fetal--maternal concentration differences on the transplacental fluid shift were observed. On the average, about 1 X 10(-3) ml/min/g placenta was moved per 1 g/l concentration difference. In two experiments venous colloid osmotic pressures were recorded continuously. In ten experiments the oncotic fluid shift was counterbalanced by an additional hydrostatic pressure difference; an average 1 mmHg hydrostatic pressure counterbalancing 15 g/l of dextran concentration osmotic force. The calculated hydraulic conductance, Lp, was approximately 0.017 ml/min/mmHg/g and the reflection coefficient, s, for dextran T 40 was 0.1. Both parameters characterize the isolated guinea-pig placenta as leaky.

Cellular convection in a salinity gradient along a heated inclined wall

Natural convection along a heated inclined wall in a salinity gradient has been studied experimentally. The experiments were carried out in a tank with one wall inclined at 45°. The dimensions of the tank were 20 cm in height and depth, 30 cm wide at the top, and 10 cm wide at the bottom. The inclined wall and the opposite vertical wall were made of aluminum and they were kept at different constant temperatures. The other two walls were of plexiglass. Shadowgraph technique was used to visualize the fluid motion. The onset of celular motion was quite similar to the case of heating along a vertical wall. In the subcritical regime, the fluid moved along the heated wall almost imperceptibly. In the transition regime, convection cells were generated successfully from the bottom boundary. In the supercritical regime, simultaneous occurrence of the convection cells were observed. These cells then grew clear across the tank. The motions in the fully developed cells were quite different from those observed in tanks with vertical walls. The governing parameter which characterizes the fluid motion is the Rayleigh number defined in terms of the height of rise of a heated fluid particle and the reduced gravity. It was found that the Rayleigh number range for the transitional regime is somewhat higher than that for the vertical heated wall. This was due to the stabilizing effect of the additional hydrostatic pressure normal to the wall. Longitudinal vortices along the inclined wall were observed only in a large bottom cell 6 days into the experiment. At that time, the fluid within the cell was of constant salinity. In no other case longitudinal vortices were observed.

Punching tests on disks of rock under hydrostatic pressure

A simple apparatus for making punching tests on disks of rock subjected to an additional hydrostatic pressure is described. Experiments have been made on marble, slate, and sandstone. They give an approximate value for the variation of shear strength with confining pressure. For marble and slate, confining pressure has a considerable strengthening effect, but for sandstone this effect is relatively small. The method is applicable to a number of situations not covered by the triaxial test; when both methods are applicable, there are considerable differences between the results obtained.