WorldWideScience

Sample records for adverse pressure gradients

  1. Characterizing developing adverse pressure gradient flows subject to surface roughness

    Science.gov (United States)

    Brzek, Brian; Chao, Donald; Turan, Özden; Castillo, Luciano

    2010-04-01

    An experimental study was conducted to examine the effects of surface roughness and adverse pressure gradient (APG) on the development of a turbulent boundary layer. Hot-wire anemometry measurements were carried out using single and X-wire probes in all regions of a developing APG flow in an open return wind tunnel test section. The same experimental conditions (i.e., T ∞, U ref, and C p) were maintained for smooth, k + = 0, and rough, k + = 41-60, surfaces with Reynolds number based on momentum thickness, 3,000 carefully designed such that the x-dependence in the flow field was known. Despite this fact, only a very small region of the boundary layer showed a balance of the various terms in the integrated boundary layer equation. The skin friction computed from this technique showed up to a 58% increase due to the surface roughness. Various equilibrium parameters were studied and the effect of roughness was investigated. The generated flow was not in equilibrium according to the Clauser (J Aero Sci 21:91-108, 1954) definition due to its developing nature. After a development region, the flow reached the equilibrium condition as defined by Castillo and George (2001), where Λ = const, is the pressure gradient parameter. Moreover, it was found that this equilibrium condition can be used to classify developing APG flows. Furthermore, the Zagarola and Smits (J Fluid Mech 373:33-79, 1998a) scaling of the mean velocity deficit, U ∞δ*/δ, can also be used as a criteria to classify developing APG flows which supports the equilibrium condition of Castillo and George (2001). With this information a ‘full APG region’ was defined.

  2. Roughness induced flow separation in adverse pressure gradient

    Science.gov (United States)

    Joo, Jongwook; Emory, Mike; Bose, Sanjeeb; Medic, Gorazd; Sharma, Om

    2016-11-01

    Surface roughness does not only increase turbulent mixing, but also thickens boundary-layers, making flows more susceptible to separation. Detailed flow physics related to the separation is not understood well. Bammert and Milsch (1972) demonstrates a clear example of surface roughness induced separation under adverse pressure gradient. In the study, compressor cascades with NACA 65 airfoils are systematically roughened and the flow over suction surface gradually separates early as roughness increases. A set of Large-Eddy Simulations (LES) over the Bammert's case is investigated, since RANS simulations using roughness models suffer from capturing the separation. In the current study, surface roughness is represented in two different approaches; 1) Realistic rough surface represented by stochastically distributed hills and valleys are gridded and solved with unstructured finite volume method, 2) Using block-structured grid, surface roughness is gridded as a staggered array of 3D rectangles, in a similar way of the previous study for roughened low pressure turbine (GT2016-57912). The current LES's capture rich features of the flow phenomena, which will bring comprehensive understanding of the roughness induced separation. This collaboration is made through 2016 CTR Summer Program.

  3. On the impact of adverse pressure gradient on the supersonic turbulent boundary layer

    Science.gov (United States)

    Wang, Qian-Cheng; Wang, Zhen-Guo; Zhao, Yu-Xin

    2016-11-01

    By employing the particle image velocimetry, the mean and turbulent characteristics of a Mach 2.95 turbulent boundary layer are experimentally investigated without the impact of curvature. The physical mechanism with which the streamwise adverse pressure gradient affects the supersonic boundary layer is revealed. The data are compared to that of the concave boundary layer with similar streamwise distributions of wall static pressure to clarify the separate impacts of the adverse pressure gradient and the concave curvature. The logarithmic law is observed to be well preserved for both of the cases. The dip below the logarithmic law is not observed in present investigation. Theoretical analysis indicates that it could be the result of compromise between the opposite impacts of the compression wave and the increased turbulent intensity. Compared to the zero pressure gradient boundary layer, the principal strain rate and the turbulent intensities are increased by the adverse pressure gradient. The shear layer formed due the hairpin packets could be sharpened by the compression wave, which leads to higher principal strain rate and the associated turbulent level. Due to the additional impact of the centrifugal instability brought by the concave wall, even higher turbulent intensities than that of the adverse pressure gradient case are introduced. The existence of velocity modes within the zero pressure gradient boundary layer suggests that the large scale motions are statistically well organized. The generation of new velocity modes due to the adverse pressure gradient indicates that the turbulent structure is changed by the adverse pressure gradient, through which more turbulence production that cannot be effectively predicted by the Reynolds-stress transport equations could be brought.

  4. Turbulence measurements in axisymmetric supersonic boundary layer flow in adverse pressure gradients

    Science.gov (United States)

    Gootzait, E.; Childs, M. E.

    1977-01-01

    Mean flow and turbulence measurements are presented for adiabatic compressible turbulent boundary layer flow in adverse pressure gradients. The gradients were induced on the wall of an axially symmetric wind tunnel by contoured centerbodies mounted on the wind tunnel centerline. The boundary layer turbulence downstream of a boundary layer bleed section in a zero pressure gradient was also examined. The measurements were obtained using a constant temperature hot-wire anemometer. The adverse pressure gradients were found to significantly alter the turbulence properties of the boundary layer. With flow through the bleed holes there was a measureable decrease in the rms longitudinal velocity fluctuations near the wall and the turbulent shear stress in the boundary layer was reduced.

  5. Nonisothermal turbulent boundary-layer adverse pressure gradient large scale thermal structure measurements

    Science.gov (United States)

    Bagheri, Nader; White, Bruce R.; Lei, Ting-Kwo

    1994-01-01

    Hot-wire anemometry measurements in an incompressible turbulent boundary-layer flow over a heated flat plate under equilibrium adverse-pressure-gradient conditions (beta = 1.8) were made for two different temperature difference cases (10 and 15 C) between the wall and the freestream. Space-time correlations of temperature fluctuations (T') were obtained with a pair of subminiature temperature fluctuation probes. The mean convection velocities, the mean inclination angles, and coherence characteristics of the T' large-scale structure were determined. The present temperature structures measurements for a nonisothermal boundary layer are compared to the zero-pressure-gradient case with identical temperature differences previously reported, in which the mean convection velocity of the T' structure was a function of position y(sup +) and independent of the limited temperature-difference cases tested. The three major findings of the present study, as compared to the zero-pressure-gradient case, are (1) the mean convection speed of the T' structure under beta = 1.8 pressure-gradient conditions was found to be substantially lower in the logarithmic core region than the zero-pressure-gradient case. Additionally, the mean convection speed is felt by the authors to be a function of pressure-gradient parameter beta; (2) the mean inclination angle of the T' structure to the wall under the adverse-pressure-gradient flow was 32 deg, which compares favorably to the 30-deg value of the zero-pressure-gradient case; and (3) the limited data suggests that the mean convection velocity of the T' structure is a function of y(sup +) and independent of the limited temperature-difference cases tested.

  6. Coherent structures of a self-similar adverse pressure gradient turbulent boundary layer

    Science.gov (United States)

    Sekimoto, Atsushi; Kitsios, Vassili; Atkinson, Callum; Jiménez, Javier; Soria, Julio

    2016-11-01

    The turbulence statistics and structures are studied in direct numerical simulation (DNS) of a self-similar adverse pressure gradient turbulent boundary layer (APG-TBL). The self-similar APG-TBL at the verged of separation is achieved by a modification of the far-field boundary condition to produce the desired pressure gradient. The turbulence statistics in the self-similar region collapse by using the scaling of the external velocity and the displacement thickness. The coherent structures of the APG-TBL are investigated and compared to those of zero-pressure gradient case and homogeneous shear flow. The support of the ARC, NCI and Pawsey SCC funded by the Australian and Western Australian governments as well as the support of PRACE funded by the European Union are gratefully acknowledged.

  7. DNS of self-similar adverse pressure gradient turbulent boundary layer

    Science.gov (United States)

    Soria, Julio; Kitsios, Vassili; Sekimoto, Atsushi; Atkinson, Callum; Jiménez, Javier

    2016-11-01

    A direct numerical simulation (DNS) of a self-similar adverse pressure gradient (APG) turbulent boundary layer (TBL) at the verge of separation has been set-up and carried out. The DNS APG TBL has a displacement thickness based Reynolds number that ranges up to 30,000. The conditions for self-similarity and appropriate scaling will be highlighted, with the first and second order velocity statistical profiles non-dimensionalised using this scaling. The details of the DNS and the required boundary conditions that are necessary to establish this self-similar APG-TBL will be presented. The statistical properties of the self-similar adverse pressure gradient (APG) turbulent boundary layer (TBL) DNS will presented, as will the profiles of the terms in the momentum equation, spanwise/wall-normal kinetic energy spectrum and two-point correlations, which will be compared to those of a zero pressure gradient turbulent boundary layer. NCI and Pawsey SCC funded by the Australian and Western Australian governments as well as the support of PRACE funded by the European Union are gratefully acknowledged.

  8. Experimental Measurements of a High Reynolds Num- ber Adverse Pressure Gradient Turbulent Boundary Layer

    Science.gov (United States)

    Atkinson, Callum; Amili, Omid; Stanislas, Michel; Cuvier, Christophe; Foucaut, Jean-Marc; Srinath, Sricharan; Laval, Jean-Philippe; Kaehler, Christian; Hain, Rainer; Scharnowski, Sven; Schroeder, Andreas; Geisler, Reinhard; Agocs, Janos; Roese, Anni; Willert, Christian; Klinner, Joachim; Soria, Julio

    2016-11-01

    The study of adverse pressure gradient turbulent boundary layers is complicated by the need to characterise both the local pressure gradient and it's upstream flow history. It is therefore necessary to measure a significant streamwise domain at a resolution sufficient to resolve the small scales features. To achieve this collaborative particle image velocimetry (PIV) measurements were performed in the large boundary layer wind-tunnel at the Laboratoire de Mecanique de Lille, including: planar measurements spanning a streamwise domain of 3.5m using 16 cameras covering 15 δ spanwise wall-normal stereo-PIV measurements, high-speed micro-PIV of the near wall region and wall shear stress; and streamwise wall-normal PIV in the viscous sub layer. Details of the measurements and preliminary results will be presented.

  9. Flow Control Device Evaluation for an Internal Flow with an Adverse Pressure Gradient

    Science.gov (United States)

    Jenkins, Luther N.; Gorton, Susan Althoff; Anders, Scott G.

    2002-01-01

    The effectiveness of several active and passive devices to control flow in an adverse pressure gradient with secondary flows present was evaluated in the 15 Inch Low Speed Tunnel at NASA Langley Research Center. In this study, passive micro vortex generators, micro bumps, and piezoelectric synthetic jets were evaluated for their flow control characteristics using surface static pressures, flow visualization, and 3D Stereo Digital Particle Image Velocimetry. Data also were acquired for synthetic jet actuators in a zero flow environment. It was found that the micro vortex generator is very effective in controlling the flow environment for an adverse pressure gradient, even in the presence of secondary vortical flow. The mechanism by which the control is effected is a re-energization of the boundary layer through flow mixing. The piezoelectric synthetic jet actuators must have sufficient velocity output to produce strong longitudinal vortices if they are to be effective for flow control. The output of these devices in a laboratory or zero flow environment will be different than the output in a flow environment. In this investigation, the output was higher in the flow environment, but the stroke cycle in the flow did not indicate a positive inflow into the synthetic jet.

  10. Mean flow structure of non-equilibrium boundary layers with adverse pressure gradient

    Indian Academy of Sciences (India)

    B C Mandal; H P Mazumdar; S S Dutta

    2014-10-01

    In this paper Spalding’s formulation for the law of the wall with constants modified by Persen is used to describe the inner region (viscous sub-layer and certain portion of logarithmic layer) and a wake law due to Persen is used to describe the wake region (outer region). These two laws are examined in the light of measured data by Marušić and Perry for non-equilibrium adverse pressure gradient layers. It is observed that structure of turbulence for this flow is well-described by these two laws. From the known structure of turbulence eddy viscosity for the flow under consideration is calculated. Self similarity in eddy viscosity is observed in the wall region.

  11. An experimental investigation of a low Reynolds number turbulent boundary layer subject to an adverse pressure gradient

    Science.gov (United States)

    Watmuff, Jonathan H.

    1989-01-01

    A very low Reynolds number turbulent boundary layer subject to an adverse pressure gradient is studied. The aim is to obtain highly accurate mean-flow and turbulence measurements under conditions that can be closely related to the numerical simulations of Philippe Spalart for the purposes of CFD validation. Much of the Boundary Layer Wind Tunnel was completely rebuilt with a new wider contraction and working section which will improve compatibility with the simulations. A unique sophisticated high-speed computer controlled 3-D probe traversing mechanism was integrated into the test section. Construction of the tunnel and traverse is discussed in some detail. The hardware is now complete, and measurements are in progress. The mean-flow data indicate that a suitably two-dimensional base flow was established. Automation of the probe positioning and data acquistion have led to a decreased running time for total pressure measurements. However, the most significant benefits are expected to occur when using hot-wire probes. Calibrations can be performed automatically and there is no need to handle fragile probes when moving between measuring stations. Techniques are being developed which require sampling of the signals from moving hot-wire probes on the basis of their position in the flow. Measurements can be made in high intensity turbulence by flying probes upstream at high speed so that the relative magnitude of the turbulent velocity fluctuations are reduced. In regions, where the turbulence intensity is not too large, the probe can also be repetitively scanned across very dense spatial grids in other directions. With this technique, a complete profile can be measured in about 1/3 the time and with a spatial density about 50 times that obtainable using a stationary probe.

  12. Vertebrate pressure-gradient receivers

    DEFF Research Database (Denmark)

    Christensen-Dalsgaard, Jakob

    2011-01-01

    The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum and stro......The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum....... Recent vertebrates form a continuum from perfect interaural transmission (0 dB in a certain frequency band) and pronounced eardrum directionality (30-40 dB) in the lizards, over somewhat attenuated transmission and limited directionality in birds and frogs, to the strongly attenuated interaural...

  13. Vertebrate pressure-gradient receivers.

    Science.gov (United States)

    Christensen-Dalsgaard, Jakob

    2011-03-01

    The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum and strongly dependent on interaural transmission attenuation. Even though the tympanic middle ear has originated independently in the major tetrapod groups, in each group the ancestral condition probably was that the two middle ears were exposed in the mouth cavity with relatively high interaural transmission. Recent vertebrates form a continuum from perfect interaural transmission (0 dB in a certain frequency band) and pronounced eardrum directionality (30-40 dB) in the lizards, over somewhat attenuated transmission and limited directionality in birds and frogs, to the strongly attenuated interaural transmission and functionally isolated pressure receiver ears in the mammals. Since some of the binaural interaction already takes place at the eardrum in animals with strongly coupled ears, producing enhanced interaural time and level differences, the subsequent neural processing may be simpler. In robotic simulations of lizards, simple binaural subtraction (EI cells, found in brainstem nuclei of both frogs and lizards) produces strongly lateralized responses that are sufficient for steering the animal robustly to sound sources.

  14. Scale analysis of turbulent channel flow with varying pressure gradient

    Institute of Scientific and Technical Information of China (English)

    邱翔; 罗剑平; 黄永祥; 卢志明; 刘宇陆

    2014-01-01

    In this paper orthogonal wavelet transformations are applied to decompose experimental velocity signals in fully develo-ped channel flows with varying pressure gradient into scales. We analyze the time series from turbulent data, to obtain the statistical characteristics, correlations between the adjacent scales and the principal scale of coherent structures in different scales by wavelet transformations. The results show that, in the counter gradient transport (CGT) region, skewness factors and flatness factors deviate strongly from the corresponding values of Gaussian distribution on certain scales. PDFs on each scale confirm this observation. Scale-scale correlations show further that the fluctuations on some certain special scales are more intermittent than nearby. Principal scale of coherent structure is coincident with the scales on which the statistical properties depart from Gaussian distribution. These features are the same for different families of wavelets, and it also shows some different features in the region between favorable pressure gradient and adverse pressure gradient.

  15. Discussion of liquid threshold pressure gradient

    Directory of Open Access Journals (Sweden)

    Xiukun Wang

    2017-06-01

    The correct interpretation is that there are two flow regimes: nonlinear flow regime (non-Darcy flow regime when the pressure gradients are low, and linear flow regime (Darcy flow regime when the pressure gradient is intermediate or high. The nonlinear flow regime starts from the origin point. As the pressure gradient is increased, the curve becomes a straight line demonstrating the linear flow regime. We have verified our views by first analyzing the causes of non-Darcy flow, and then systematically analyzed typical experimental data and correlations in the literature. We conclude that TPG does not exist. We also use several counter examples to support our conclusion.

  16. Pressure Gradient Evolution and Substorm Onset

    Science.gov (United States)

    Zhonghua, Y.; Pu, Z.; Cao, X.; Nishimura, T.; Zhang, H.; Fu, S.; Xie, L.; Guo, R.

    2011-12-01

    Near-Earth current disruption (NECD) and substorm current wedge (SCW) formation are two related key phenomena for substorm onset. They are believed to be in close association with evolution of pressure gradient near the inner edge of plasma sheet. In the past, a few attempts have been made to investigate the pressure gradient in the late growth phase based on one- or two-spacecraft observations (e.g. , Korth et al., 1991; Pu et al., 1992; Shiokawa et al., 1998; Xing et al., 2010, 2011,etc). In this paper, with linearization assumption in the inner-probe region, we use THEMIS three-probe measurements to estimate the pressure gradient near the inner edge of the equatorward and duskward (dawnward) plasma sheet where pressure gradient in the Z-direction is almost vanished. We therefore can roughly get the two-dimensional pressure gradient in the X- and Y-direction simultaneously. Our observations indicate that the pressure gradients in both the X- and Y-direction enhance right after (within one minute) substorm onset. The enhanced pressure gradient in the Y-direction is duskward (dawnward) when the probes are in the duskside (dawnside) of the enhanced earthward flow in the growth phase. The enhanced dawn-dusk pressure gradients can drive downward field-aligned current (FAC) on the dawnside and upward FAC on the duskside, thus make contributions to the NECD and formation of SCW. THEMIS in situ data and all-sky auroral images for two events are presented, followed by a brief discussion.

  17. The effect of pressure gradient on the structure of an equilibrium turbulent boundary layer

    Science.gov (United States)

    Lei, Ting-Kwo

    1993-01-01

    Hot-wire anemometry was used to study the effect of adverse pressure gradient on the large-scale structures of equilibrium turbulent boundary layers. A previously existing zero-pressure gradient wind tunnel was modified into an adverse-pressure gradient wind tunnel, which had the capability of creating designated adverse-pressure gradient equilibrium turbulent boundary layer flows. The range of the equilibrium parameter beta was from 0.0 to 1.8 along a 1.50 m long test section of the wind tunnel. Computer programs were developed to predict the geometric shape of the test section for an equilibrium adverse-pressure gradient turbulent boundary layer flow. The numerical prediction of the test section geometry was found to be satisfactory and a substantial effort was saved in the establishment of an equilibrium boundary layer. Three equilibrium boundary layer flows at values of beta = 0.0, 0.8, and 1.8, which respectively represents zero, mild, and strong adverse pressure gradient, were established and were found to be suitable for turbulence structure measurements. Space-time correlation measurements were carried out to determine the convection velocities and inclination angles of the large-scale structures for the three different pressure gradient cases. The convection velocity measurements were performed at various heights which ranged form y(sup +) = 225 to 525 for each beta value. It was found that, within the range of height of the measurements, the convection velocity was independent of height In the case of the strong adverse-pressure gradient flow, the convection velocity was observed to be much lower than the convection velocity observed in the case of zero-pressure gradient. In the case of the mild-pressure gradient flow, it was observed that the pressure gradient effect on the convection velocity was negligible as compared to the zero-pressure gradient case. The inclination angle in the case of strong-pressure gradient case was found to be much greater than

  18. Effect of pressure gradients on Gortler instability

    Science.gov (United States)

    Ragab, S. A.; Nayfeh, A. H.

    1980-01-01

    Gortler instability for boundary-layer flows over generally curved walls is considered. The full linearized disturbance equations are obtained in an orthogonal curvilinear coordinate system. A perturbation procedure to account for second-order effects is used to determine the effects of the displacement thickness and the variation of the streamline curvature on the neutral stability of the Blasius flow. The pressure gradient in the mean flow is accounted for by solving the nonsimilar boundary-layer equations. Growth rates are obtained for the actual mean flow and the Falkner-Skan flows. The results demonstrate the strong influence of the pressure gradient and the nonsimilarity of the basic flow on the stability characteristics.

  19. Role of the vertical pressure gradient in wave boundary layers

    DEFF Research Database (Denmark)

    Jensen, Karsten Lindegård; Sumer, B. Mutlu; Vittori, Giovanna

    2014-01-01

    By direct numerical simulation (DNS) of the flow in an oscillatory boundary layer, it is possible to obtain the pressure field. From the latter, the vertical pressure gradient is determined. Turbulent spots are detected by a criterion involving the vertical pressure gradient. The vertical pressure...... gradient is also treated as any other turbulence quantity like velocity fluctuations and statistical properties of the vertical pressure gradient are calculated from the DNS data. The presence of a vertical pressure gradient in the near bed region has significant implications for sediment transport....

  20. Large eddies induced by local impulse at wall of boundary layer with pressure gradients

    Institute of Scientific and Technical Information of China (English)

    Changgen Lu; Weidong Cao; Yanmei Zhang; Jintao Peng

    2008-01-01

    Large eddies induced by local impulse at the wall with pressure gradients in the boundary layer was studied by direct numerical sim-ulations. The results show that the amplitude evolution, the high and low speed stripes, the formation of streamwise vortices, the ejection and sweeping, inflexions and distortion at the mean velocity profiles, as well as other characteristics, are consistent with the experimental and other numerical results. It is also found that large eddies are easy to be excited with adverse pressure gradient in the boundary layer,and the growth of amplitudes, formation of streamwise vortices and the influencing area etc., are much larger than those with favorable pressure gradient in the boundary layer. In contrast, large eddies are hardly to be induced through local impulse disturbance at the wall with favorable pressure gradients in the boundary layer.

  1. On determining characteristic length scales in pressure-gradient turbulent boundary layers

    Science.gov (United States)

    Vinuesa, R.; Bobke, A.; Örlü, R.; Schlatter, P.

    2016-05-01

    In the present work, we analyze three commonly used methods to determine the edge of pressure gradient turbulent boundary layers: two based on composite profiles, the one by Chauhan et al. ["Criteria for assessing experiments in zero pressure gradient boundary layers," Fluid Dyn. Res. 41, 021404 (2009)] and the one by Nickels ["Inner scaling for wall-bounded flows subject to large pressure gradients," J. Fluid Mech. 521, 217-239 (2004)], and the other one based on the condition of vanishing mean velocity gradient. Additionally, a new method is introduced based on the diagnostic plot concept by Alfredsson et al. ["A new scaling for the streamwise turbulence intensity in wall-bounded turbulent flows and what it tells us about the `outer' peak," Phys. Fluids 23, 041702 (2011)]. The boundary layers developing over the suction and pressure sides of a NACA4412 wing section, extracted from a direct numerical simulation at chord Reynolds number Rec = 400 000, are used as the test case, besides other numerical and experimental data from favorable, zero, and adverse pressure-gradient flat-plate turbulent boundary layers. We find that all the methods produce robust results with mild or moderate pressure gradients, although the composite-profile techniques require data preparation, including initial estimations of fitting parameters and data truncation. Stronger pressure gradients (with a Rotta-Clauser pressure-gradient parameter β larger than around 7) lead to inconsistent results in all the techniques except the diagnostic plot. This method also has the advantage of providing an objective way of defining the point where the mean streamwise velocity is 99% of the edge velocity and shows consistent results in a wide range of pressure gradient conditions, as well as flow histories. Collapse of intermittency factors obtained from a wide range of pressure-gradient and Re conditions on the wing further highlights the robustness of the diagnostic plot method to determine the

  2. Pressure Gradient Estimation Based on Ultrasonic Blood Flow Measurement

    Science.gov (United States)

    Nitta, Naotaka; Homma, Kazuhiro; Shiina, Tsuyoshi

    2006-05-01

    Mechanical load to the blood vessel wall, such as shear stress and pressure, which occurs in blood flow dynamics, contribute greatly to plaque rupture in arteriosclerosis and to biochemical activation of endothelial cells. Therefore, noninvasive estimations of these mechanical loads are able to provide useful information for the prevention of vascular diseases. Although the pressure is the dominant component of mechanical load, for practical purposes, the pressure gradient is also often important. So far, we have investigated the estimation of the kinematic viscosity coefficient using a combination of the Navier-Stokes equations and ultrasonic velocity measurement. In this paper, a method for pressure gradient estimation using the estimated kinematic viscosity coefficient is proposed. The validity of the proposed method was investigated on the basis of the analysis with the data obtained by computer simulation and a flow phantom experiment. These results revealed that the proposed method can provide a valid estimation of the pressure gradient.

  3. Non-linear aspects of Görtler instability in boundary layers with pressure gradient

    Science.gov (United States)

    Rogenski, J. K.; de Souza, L. F.; Floryan, J. M.

    2016-12-01

    The laminar flow over a concave surface may undergo transition to a turbulent state driven by secondary instabilities initiated by the longitudinal vortices known as Görtler vortices. These vortices distort the boundary layer structure by modifying the streamwise velocity component in both spanwise and wall-normal directions. Numerical simulations have been conducted to identify the role of the external pressure gradients in the development and saturation of the vortices. The results show that flows with adverse pressure gradients reach saturation upstream from the saturation location for neutral and favorable pressure gradients. In the transition region, the mean spanwise shear stress is about three times larger than in the flow without the vortices.

  4. Non-invasive measurement of pressure gradients using ultrasound

    DEFF Research Database (Denmark)

    Olesen, Jacob Bjerring; Traberg, Marie Sand; Pihl, Michael Johannes

    2013-01-01

    A non-invasive method for estimating 2-D pressure gradients from ultrasound vector velocity data is presented. The method relies on in-plane vector velocity fields acquired using the Transverse Oscillation method. The pressure gradients are estimated by applying the Navier-Stokes equations...... Medical 2202 UltraView Pro Focus scanner. The results are validated through finite element simulations of the carotid flow model where the geometry is determined from MR images. This proof of concept study was conducted at nine ultrasound frames per second. Estimated pressure gradients along...... the longitudinal direction of the constriction varied from 0 kPa/m to 10 kPa/m with a normalized bias of -9.1% for the axial component and -7.9% for the lateral component. The relative standard deviation of the estimator, given in reference to the peak gradient, was 28.4% in the axial direction and 64...

  5. Vertical pressure gradient and particle motions in wave boundary layers

    DEFF Research Database (Denmark)

    Jensen, Karsten Lindegård

    The present study covers both a numerical and experimental investigation of the processes in the oscillatory boundary layer. In the first part a direct numerical simulation (DNS) is conducted to study the vertical pressure gradient, and its role in relation to laminar to turbulent transition...... and its role in the fully turbulent boundary layer. The pressure in the flow is obtained from the flow fields of the oscillatory boundary layer. What differs, the vertical pressure gradient, from other turbulent quantities, like e.g. velocity fluctuations is that it can detect newly generated turbulence....... This is in contrast to velocity fluctuations that are diffusive, so they can also contain residual turbulence from the previous half cycle until they are dissipated. Furthermore, the magnitude of the mean value of conditionally averaged vertical pressure gradient (for −∂p∗/∂x∗ 2 > 0) is compared to the submerged...

  6. A study of wake development and structure in constant pressure gradients

    Science.gov (United States)

    Liu, Xiaofeng

    2001-07-01

    Motivated by the application to high-lift aerodynamics for commercial transport aircraft, a systematic investigation into the response of symmetric/asymmetric planar turbulent wake development to constant adverse, zero and favorable pressure gradients has been conducted. The experiments are performed at a Reynolds number of 2.4 × 106 based on the chord of the wake generator. A unique feature of this wake study is that the pressure gradients imposed on the wake flow field are held constant. The experimental measurements involve both conventional Laser Doppler Velocimetry and Hot Wire Anemometry flow field surveys of mean and turbulent quantities including the turbulent kinetic energy budget. In addition, similarity analysis and numerical simulation have also been conducted for this wake study. A focus of the research has been to isolate the effects of both pressure gradient and initial wake asymmetry on the wake development. Experimental results reveal that the pressure gradient has a tremendous influence on the wake development, despite the relatively modest pressure gradients imposed. For a given pressure gradient, the development of an initially asymmetric wake is different from the initially symmetric wake. An explicit similarity solution for the shape parameters of the symmetric wake is obtained and agrees with the experimental results. The turbulent kinetic energy budget measurements of the symmetric wake demonstrate that except for the convection term, the imposed pressure gradient does not change the fundamental flow physics of turbulent kinetic energy transport. Based on the turbulent kinetic energy budget measurements, an approach to correct the bias error associated with the notoriously difficult dissipation estimate is proposed and validated through the comparison of the experimental estimate with a direct numerical simulation result.

  7. Redshift drift in a pressure gradient cosmology

    CERN Document Server

    Balcerzak, Adam

    2012-01-01

    We derive the redshift drift formula for the inhomogeneous pressure spherically symmetric Stephani universes which are complementary to inhomogeneous density Lema\\^itre-Tolman-Bondi (LTB) models. We show that there is a clear difference between the redshift drift predictions for these two models. The Stephani models have positive drift values at small redshift and behave qualitatively as the $\\Lambda$CDM models while the drift for LTB models is always negative. This prediction can be tested in future space experiments such as E-ELT, TMT, GMT or CODEX.

  8. Nonparallel stability of boundary layers with pressure gradients and suction

    Science.gov (United States)

    Saric, W. S.; Nayfeh, A. H.

    1977-01-01

    An analysis is presented for the linear nonparallel stability of boundary layer flows with pressure gradients and suction. The effect of the boundary layer growth is included by using the method of multiple scales. The present analysis is compared with those of Bouthier and Gaster and the roles of the different definitions of the amplification rates are discussed. The results of these theories are compared with experimental data for the Blasius boundary layer. Calculations are presented for stability characteristics of boundary layers with pressure gradients and nonsimilar suction distributions.

  9. Luminescence from cavitation bubbles deformed in uniform pressure gradients

    OpenAIRE

    Supponen, Outi; Obreschkow, Danail; Kobel, Philippe; Farhat, Mohamed

    2017-01-01

    Presented here are observations that demonstrate how the deformation of millimetric cavitation bubbles by a uniform pressure gradient quenches single collapse luminescence. Our innovative measurement system captures a broad luminescence spectrum (wavelength range 300-900 nm) from the individual collapses of laser-induced bubbles in water. By varying the bubble size, driving pressure and the perceived gravity level aboard parabolic flights, we probed the limit from aspherical to highly spheric...

  10. Pressure-gradient-induced Alfven eigenmodes: 2. Kinetic excitation with ion temperature gradient

    CERN Document Server

    Bierwage, Andreas; Zonca, Fulvio

    2009-01-01

    The kinetic excitation of ideal magnetohydrodynamic (MHD) discrete Alfven eigenmodes in the second MHD ballooning stable domain is studied in the presence of a thermal ion temperature gradient (ITG), using linear gyrokinetic particle-in-cell simulations of a local flux tube in shifted-circle tokamak geometry. The instabilities are identified as alpha-induced toroidal Alfven eigenmodes (alphaTAE); that is, bound states trapped between pressure-gradient-induced potential barriers of the Schroedinger equation for shear Alfven waves. Using numerical tools, we examine in detail the effect of kinetic thermal ion compression on alphaTAEs; both non-resonant coupling to ion sound waves and wave-particle resonances. It is shown that the Alfvenic ITG instability thresholds (e.g., the critical temperature gradient) are determined by two resonant absorption mechanisms: Landau damping and continuum damping. The numerical results are interpreted on the basis of a theoretical framework previously derived from a variational f...

  11. Study of the starting pressure gradient in branching network

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In order to increase the production of oil in low permeability reservoirs with high efficiency,it is necessary to fully understand the properties and special behaviors of the reservoirs and correctly describe the flow in the reservoirs.This paper applies the branching network mode to the study of the starting pressure gradient of nonlinear Newtonian fluid (Bingham fluid) in the reservoirs with low permeability based on the fact that the fractured network may exist in the reservoirs.The proposed model for starting pressure gradient is a function of yield stress,microstructural parameters of the network.The proposed model may have the potential in further exploiting the mechanisms of flow in porous media with fractured network.

  12. PRESSURE GRADIENT FROM THE CONTRIBUTION OF BOTH GEOTHERMAL AND GRAVITY IN THE LITHOSPHERE

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The pressure gradient of the lithosphere is a key to explaining various geological processes, and varies also in time and space similar to the geothermal gradient. In this paper a correlation formula of geothermal gradients and pressure gradients was built with the thermocomprestion coefficients. Based on this formula, the article has studied the relation between the pressure gradients and the geothermal gradients in the lithosphere, and the results indicate that the pressure gradient in the lithosphere is nonlinear, and its minimum value is the lithostatic gradient, and that the pressure gradient of the lithosphere will increase obviously with the contribution of both geothermal and gravity, and could be twice times more than the lithostatic gradient.

  13. Influence of pressure gradient on streamwise skewness factor in turbulent boundary layer

    Science.gov (United States)

    Dróżdż, Artur

    2014-08-01

    The paper shows an effect of favourable and adverse pressure gradients on turbulent boundary layer. The skewness factor of streamwise velocity component was chosen as a measure of the pressure gradient impact. It appears that skewness factor is an indicator of convection velocity of coherent structures, which is not always equal to the average flow velocity. The analysis has been performed based upon velocity profiles measured with hot-wire technique in turbulent boundary layer with pressure gradient corresponding to turbomachinery conditions. The results show that the skewness factor decreases in the flow region subjected to FPG and increases in the APG conditions. The changes of convection velocity and skewness factor are caused by influence of large-scale motion through the mechanism called amplitude modulation. The large-scale motion is less active in FPG and more active in APG, therefore in FPG the production of vortices is random (there are no high and low speed regions), while in the APG the large-scale motion drives the production of vortices. Namely, the vortices appear only in the high-speed regions, therefore have convection velocity higher than local mean velocity. The convection velocity affects directly the turbulent sweep and ejection events. The more flow is dominated by large-scale motion the higher values takes both the convection velocity of small-scale structures and sweep events induced by them.

  14. Ice Particles Trapped by Temperature Gradients at mbar Pressure

    CERN Document Server

    Kelling, Thorben; Dürmann, Christoph

    2011-01-01

    In laboratory experiments we observe that ice particles (\\leq100 \\mu m) entrained in a low pressure atmosphere (~1 mbar) get trapped by temperature gradients between three reservoirs at different tempertature. Confining elements are a peltier element at 250 K (bottom), a liquid nitrogen reservoir at 77 K (top) and the surrounding vacuum chamber at 293 K. Particle levitation and trapping is modeled by an interplay of thermophoresis, photophoresis and gravity. A number of ice particles are trapped simultaneously in close spatial distance to each other at least up to minutes and are accessible for further experiments.

  15. Investigation of pressure gradient aware wall modeling in LES

    Science.gov (United States)

    Thiry, Olivier; Winckelmans, Gregoire; Duponcheel, Matthieu

    2015-11-01

    This work focuses on the investigation of various wall modeling strategies for the simulation of high Reynolds number wall-bounded turbulent flows with acceleration and/or deceleration. Our code is based on fourth order finite differences, is momentum conserving, and is energy conserving up to fourth order. We here use a ``channel flow'' set-up, with no slip and wall modeling at the bottom, with slip at the top, and with blowing and/or suction at the top in order to generate the desired acceleration-deceleration profile. Two strategies are investigated and compared. Pressure gradient corrected algebraic models are first considered, and we investigate various local averaging techniques so as to avoid imposing mean profile laws pointwise. RANS sub-layer models are then also considered, where the turbulent viscosity is corrected to account for pressure gradient effects and for resolved LES fluctuations effects. A wall-resolved LES was also performed to provide a reference solution. Research fellow (Ph.D. student) at the F.R.S. - FNRS (Belgium).

  16. PRESSURE AND PRESSURE GRADIENT IN AN AXISYMMETRIC RIGID VESSEL WITH STENOSIS

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Based on an improvement of the Karman-Pohlhausen's method, using nonlinear polynomial fitting and numerical integral, the axial distributions of pressure and its gradient in an axisymmetric rigid vessel with stenosis were obtained, and the distributions related to Reynolds number and the geometry of stenotic vessel were discussed. It shows that with the increasing of stenotic degree or Reynolds number, the fluctuation of pressure and its gradient in stenotic area is intense rapidly, and negative pressure occurs subsequently in the diverging part of stenotic area. Especially when the axial range of stenosis extends, the flow of blood in the diverging part will be more obviously changed.In higher Reynolds number or heavy stenosis, theoretical calculation is mainly in accordance with past experiments.

  17. High Pressure, High Gradient RF Cavities for Muon Beam Cooling

    CERN Document Server

    Johnson, R P

    2004-01-01

    High intensity, low emittance muon beams are needed for new applications such as muon colliders and neutrino factories based on muon storage rings. Ionization cooling, where muon energy is lost in a low-Z absorber and only the longitudinal component is regenerated using RF cavities, is presently the only known cooling technique that is fast enough to be effective in the short muon lifetime. RF cavities filled with high-pressure hydrogen gas bring two advantages to the ionization technique: the energy absorption and energy regeneration happen simultaneously rather than sequentially, and higher RF gradients and better cavity breakdown behavior are possible than in vacuum due to the Paschen effect. These advantages and some disadvantages and risks will be discussed along with a description of the present and desired RF R&D efforts needed to make accelerators and colliders based on muon beams less futuristic.

  18. Measurement of the Turbulence Kinetic Energy Budget of a Turbulent Planar Wake Flow in Pressure Gradients

    Science.gov (United States)

    Liu, Xiao-Feng; Thomas, Flint O.; Nelson, Robert C.

    2001-01-01

    Turbulence kinetic energy (TKE) is a very important quantity for turbulence modeling and the budget of this quantity in its transport equation can provide insight into the flow physics. Turbulence kinetic energy budget measurements were conducted for a symmetric turbulent wake flow subjected to constant zero, favorable and adverse pressure gradients in year-three of research effort. The purpose of this study is to clarify the flow physics issues underlying the demonstrated influence of pressure gradient on wake development and provide experimental support for turbulence modeling. To ensure the reliability of these notoriously difficult measurements, the experimental procedure was carefully designed on the basis of an uncertainty analysis. Four different approaches, based on an isotropic turbulence assumption, a locally axisymmetric homogeneous turbulence assumption, a semi-isotropy assumption and a forced balance of the TKE equation, were applied for the estimate of the dissipation term. The pressure transport term is obtained from a forced balance of the turbulence kinetic energy equation. This report will present the results of the turbulence kinetic energy budget measurement and discuss their implication on the development of strained turbulent wakes.

  19. Coherent structures in a zero-pressure-gradient and a strongly decelerated boundary layer

    Science.gov (United States)

    Simens, Mark P.; Gungor, Ayse G.; Maciel, Yvan

    2016-04-01

    Coherent structures in a strongly decelerated large-velocity-defect turbulent boundary layer (TBL) and a zero pressure gradient (ZPG) boundary layer are analysed by direct numerical simulation (DNS). The characteristics of the one-point velocity stastistics are also considered. The adverse pressure gradient (APG) TBL simulation is a new one carried out by the present authors. The APG TBL begins as a zero pressure gradient boundary layer, decelerates under a strong adverse pressure gradient, and separates near the end of the domain in the form of a very thin separation bubble. The one-point velocity statistics in the outer region of this large-defect boundary layer are compared to those of two other large-velocity-defect APG TBLs (one in dynamic equilibrium, the other in disequilibrium) and a mixing layer. In the upper half of the large-defect boundary layers, the velocity statistics are similar to those of the mixing layer. The dominant peaks of turbulence production and Reynolds stresses are located in the middle of the boundary layers. Three-dimensional spatial correlations of (u, u) and (u, v) show that coherence is lost in the streamwise and spanwise directions as the velocity defect increases. Near-wall streaks tend to disappear in the large-defect zone of the flow to be replaced by more disorganized u motions. Near-wall sweeps and ejections are also less numerous. In the outer region, the u structures tend to be shorter, less streaky, and more inclined with respect to the wall than in the ZPG TBL. The sweeps and ejections are generally bigger with respect to the boundary layer thickness in the large-defect boundary layer, even if the biggest structures are found in the ZPG TBL. Large sweeps and ejections that reach the wall region (wall-attached) are less streamwise elongated and they occupy less space than in the ZPG boundary layer. The distinction between wall-attached and wall-detached structures is not as pronounced in the large-defect TBL.

  20. Modeling of Propagation of Interacting Cracks Under Hydraulic Pressure Gradient

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Hai [Idaho National Laboratory; Mattson, Earl Douglas [Idaho National Laboratory; Podgorney, Robert Karl [Idaho National Laboratory

    2015-04-01

    A robust and reliable numerical model for fracture initiation and propagation, which includes the interactions among propagating fractures and the coupling between deformation, fracturing and fluid flow in fracture apertures and in the permeable rock matrix, would be an important tool for developing a better understanding of fracturing behaviors of crystalline brittle rocks driven by thermal and (or) hydraulic pressure gradients. In this paper, we present a physics-based hydraulic fracturing simulator based on coupling a quasi-static discrete element model (DEM) for deformation and fracturing with conjugate lattice network flow model for fluid flow in both fractures and porous matrix. Fracturing is represented explicitly by removing broken bonds from the network to represent microcracks. Initiation of new microfractures and growth and coalescence of the microcracks leads to the formation of macroscopic fractures when external and/or internal loads are applied. The coupled DEM-network flow model reproduces realistic growth pattern of hydraulic fractures. In particular, simulation results of perforated horizontal wellbore clearly demonstrate that elastic interactions among multiple propagating fractures, fluid viscosity, strong coupling between fluid pressure fluctuations within fractures and fracturing, and lower length scale heterogeneities, collectively lead to complicated fracturing patterns.

  1. Luminescence from cavitation bubbles deformed in uniform pressure gradients

    Science.gov (United States)

    Supponen, Outi; Obreschkow, Danail; Kobel, Philippe; Farhat, Mohamed

    2017-09-01

    Presented here are observations that demonstrate how the deformation of millimetric cavitation bubbles by a uniform pressure gradient quenches single-collapse luminescence. Our innovative measurement system captures a broad luminescence spectrum (wavelength range, 300-900 nm) from the individual collapses of laser-induced bubbles in water. By varying the bubble size, driving pressure, and perceived gravity level aboard parabolic flights, we probed the limit from aspherical to highly spherical bubble collapses. Luminescence was detected for bubbles of maximum radii within the previously uncovered range, R0=1.5 -6 mm, for laser-induced bubbles. The relative luminescence energy was found to rapidly decrease as a function of the bubble asymmetry quantified by the anisotropy parameter ζ , which is the dimensionless equivalent of the Kelvin impulse. As established previously, ζ also dictates the characteristic parameters of bubble-driven microjets. The threshold of ζ beyond which no luminescence is observed in our experiment closely coincides with the threshold where the microjets visibly pierce the bubble and drive a vapor jet during the rebound. The individual fitted blackbody temperatures range between Tlum=7000 and Tlum=11 500 K but do not show any clear trend as a function of ζ . Time-resolved measurements using a high-speed photodetector disclose multiple luminescence events at each bubble collapse. The averaged full width at half-maximum of the pulse is found to scale with R0 and to range between 10 and 20 ns.

  2. Measurement of Threshold Pressure Gradient of Microchannels by Static Method

    Institute of Scientific and Technical Information of China (English)

    SONG Fu-Quan; JIANG Ren-Jie; BIAN Shu-Li

    2007-01-01

    The development of oil fields and laboratory experiment present the threshold pressure gradient (TPG) of liquid flow in low permeability porous media, which is called the micro-size effect in porous media. Some micro-size effects in micro-electro-mechanism systems (MEMS) are not always in agreement with each other. We propose an experiment setup to measure the TPG of microchannels by static method in the microchannels with the diameter ranging from 20-320 μm. The results present the existence of TPG in microchannel, and show an effect that the TPG of microchannel increases with decreasing hydrodynamic diameter. The relation between TPG and diameter is in agreement with single-log normalization. Additionally, the influence of errors in the experiment shows the data of experiment are valid. Finally, the mechanism of micro-size effects is discussed by revealing the facial force between liquid and solid and theory of boundary liquid, but the explanation is still not good, and needs further study.

  3. Multiscale architectured materials with composition and grain size gradients manufactured using high-pressure torsion.

    Science.gov (United States)

    Kang, Ji Yun; Kim, Jung Gi; Park, Hyo Wook; Kim, Hyoung Seop

    2016-05-27

    The concept of multiscale architectured materials is established using composition and grain size gradients. Composition-gradient nanostructured materials are produced from coarse grained interstitial free steels via carburization and high-pressure torsion. Quantitative analyses of the dislocation density using X-ray diffraction and microstructural studies clearly demonstrate the gradients of the dislocation density and grain size. The mechanical properties of the gradient materials are compared with homogeneous nanostructured carbon steel without a composition gradient in an effort to investigate the gradient effect. Based on the above observations, the potential of multiscale architecturing to open a new material property is discussed.

  4. Importance of pressure gradient in solid oxide fuel cell electrodes for modeling study

    Science.gov (United States)

    Ni, Meng; Leung, Dennis Y. C.; Leung, Michael K. H.

    The pressure gradients in the electrodes of a solid oxide fuel cell (SOFC) are frequently neglected without any justification in calculating the concentration overpotentials of the SOFC electrodes in modeling studies. In this short communication, a comparative study has been conducted to study the effect of pressure gradients on mass transfer and the resulting concentration overpotentials of an SOFC running on methane (CH 4) fuel. It is found that the pressure gradients in both anode and cathode are significant in the fuel cell electrochemical activities. Neglecting the anode pressure gradient in the calculation can lead to underestimation of the concentration overpotential by about 20% at a typical current density of 5000 A m -2 and at a temperature of 1073 K. The deviation can be even larger at a higher temperature. At the cathode, neglecting the pressure gradient can result in overestimation of the concentration overpotential by about 10% under typical working conditions.

  5. Noninvasive estimation of 2-D pressure gradients in steady flow using ultrasound

    DEFF Research Database (Denmark)

    Olesen, Jacob Bjerring; Traberg, Marie Sand; Pihl, Michael Johannes;

    2014-01-01

    A noninvasive method for estimating 2-D pressure gradients from ultrasound vector velocity data is presented. It relies on vector velocity fields acquired using the transverse oscillation method during steady flow conditions. The pressure gradients are calculated from the velocity fields using...... of -7% for the axial component and -8% for the lateral component. The relative standard deviation of the estimator is 5% (axial component) and 30% (lateral component) when studying the pressure gradient across the constriction using 3 velocity frames per pressure estimate. The study shows that 2-D...... phantom. The geometry of the model is determined from magnetic resonance imaging. The presented study is conducted assuming steady flow using velocity data acquired at 18 frames per second. The proposed method shows pressure gradients at the constricted region from -8 kPa/m to 9 kPa/m, with a maximum bias...

  6. Thermophoresis of dissolved molecules and polymers: Consideration of the temperature-induced macroscopic pressure gradient.

    Science.gov (United States)

    Semenov, Semen; Schimpf, Martin

    2004-01-01

    The movement of molecules and homopolymer chains dissolved in a nonelectrolyte solvent in response to a temperature gradient is considered a consequence of temperature-induced pressure gradients in the solvent layer surrounding the solute molecules. Local pressure gradients are produced by nonuniform London-van der Waals interactions, established by gradients in the concentration (density) of solvent molecules. The density gradient is produced by variations in solvent thermal expansion within the nonuniform temperature field. The resulting expression for the velocity of the solute contains the Hamaker constants for solute-solvent and solute-solute interactions, the radius of the solute molecule, and the viscosity and cubic coefficient of thermal expansion of the solvent. In this paper we consider an additional force that arises from directional asymmetry in the interaction between solvent molecules. In a closed cell, the resulting macroscopic pressure gradient gives rise to a volume force that affects the motion of dissolved solutes. An expression for this macroscopic pressure gradient is derived and the resulting force is incorporated into the expression for the solute velocity. The expression is used to calculate thermodiffusion coefficients for polystyrene in several organic solvents. When these values are compared to those measured in the laboratory, the consistency is better than that found in previous reports, which did not consider the macroscopic pressure gradient that arises in a closed thermodiffusion cell. The model also allows for the movement of solute in either direction, depending on the relative values of the solvent and solute Hamaker constants.

  7. Comparison of Coral Reef Ecosystems along a Fishing Pressure Gradient

    NARCIS (Netherlands)

    Weijerman, M.W.; Fulton, E.A.; Parrish, F.A.

    2013-01-01

    Three trophic mass-balance models representing coral reef ecosystems along a fishery gradient were compared to evaluate ecosystem effects of fishing. The majority of the biomass estimates came directly from a large-scale visual survey program; therefore, data were collected in the same way for all t

  8. Quantifying dynamic changes in plantar pressure gradient in diabetics with peripheral neuropathy

    Directory of Open Access Journals (Sweden)

    Chi-Wen Lung

    2016-07-01

    Full Text Available Diabetic foot ulcers remain one of the most serious complications of diabetes. Peak plantar pressure (PPP and peak pressure gradient (PPG during walking have been shown to be associated with the development of diabetic foot ulcers. To gain further insight into the mechanical etiology of diabetic foot ulcers, examination of the pressure gradient angle (PGA has been recently proposed. The PGA quantifies directional variation or orientation of the pressure gradient during walking, and provides a measure of whether pressure gradient patterns are concentrated or dispersed along the plantar surface. We hypothesized that diabetics at risk of foot ulceration would have smaller PGA in key plantar regions, suggesting less movement of the pressure gradient over time. A total of 27 participants were studied, including 19 diabetics with peripheral neuropathy and 8 non-diabetic control subjects. A foot pressure measurement system was used to measure plantar pressures during walking. PPP, PPG and PGA were calculated for four foot regions - 1st toe (T1, 1st metatarsal head (M1, 2nd metatarsal head (M2, and heel (HL. Consistent with prior studies, PPP and PPG were significantly larger in the diabetic group compared to non-diabetic controls in the T1 and M1 regions, but not M2 or HL. For example, PPP was 165% (P=0.02 and PPG was 214% (P<0.001 larger in T1. PGA was found to be significantly smaller in the diabetic group in T1 (46%, P=0.04, suggesting a more concentrated pressure gradient pattern under the toe. The proposed PGA may improve our understanding of the role of pressure gradient on the risk of diabetic foot ulcers.

  9. Quantifying Dynamic Changes in Plantar Pressure Gradient in Diabetics with Peripheral Neuropathy

    Science.gov (United States)

    Lung, Chi-Wen; Hsiao-Wecksler, Elizabeth T.; Burns, Stephanie; Lin, Fang; Jan, Yih-Kuen

    2016-01-01

    Diabetic foot ulcers remain one of the most serious complications of diabetes. Peak plantar pressure (PPP) and peak pressure gradient (PPG) during walking have been shown to be associated with the development of diabetic foot ulcers. To gain further insight into the mechanical etiology of diabetic foot ulcers, examination of the pressure gradient angle (PGA) has been recently proposed. The PGA quantifies directional variation or orientation of the pressure gradient during walking and provides a measure of whether pressure gradient patterns are concentrated or dispersed along the plantar surface. We hypothesized that diabetics at risk of foot ulceration would have smaller PGA in key plantar regions, suggesting less movement of the pressure gradient over time. A total of 27 participants were studied, including 19 diabetics with peripheral neuropathy and 8 non-diabetic control subjects. A foot pressure measurement system was used to measure plantar pressures during walking. PPP, PPG, and PGA were calculated for four foot regions – first toe (T1), first metatarsal head (M1), second metatarsal head (M2), and heel (HL). Consistent with prior studies, PPP and PPG were significantly larger in the diabetic group compared with non-diabetic controls in the T1 and M1 regions, but not M2 or HL. For example, PPP was 165% (P = 0.02) and PPG was 214% (P < 0.001) larger in T1. PGA was found to be significantly smaller in the diabetic group in T1 (46%, P = 0.04), suggesting a more concentrated pressure gradient pattern under the toe. The proposed PGA may improve our understanding of the role of pressure gradient on the risk of diabetic foot ulcers. PMID:27486576

  10. Secondary subharmonic instability of boundary layers with pressure gradient and suction

    Science.gov (United States)

    El-Hady, Nabil M.

    1988-01-01

    Three-dimensional linear secondary instability is investigated for boundary layers with pressure gradient and suction in the presence of a finite amplitude TS wave. The focus is on principal parametric resonance responsible for a strong growth of subharmonics in a low disturbance environment. Calculations are presented for the effect of pressure gradients and suction on controlling the onset and amplification of the secondary instability.

  11. Effect of Laser Annealing of Common Solid Pressure Media on Pressure Gradients in a Diamond Anvil Cell

    Science.gov (United States)

    Uts, I.; Glazyrin, K.; Lee, K. K.

    2012-12-01

    Advances in experimental techniques allow for the studying of geophysics and planetary science related materials under high pressure and high temperature conditions. With the intrinsic limits of the multianvil apparatus, compression in a diamond anvil cell (DAC) has become the preferred method for creating the extreme conditions of planetary interiors. High pressures up to 1 Mbar can be routinely obtained in laboratories with the use of DACs. Additionally, as in situ laser heating is becoming progressively more affordable for DACs, it is becoming more common to find laser heating setups in many large scale facilities. After the sample material, the pressure medium is the second most important ingredient for a successful high pressure DAC experiment. Not every pressure medium is equally suitable for every experiment. For example, solid pressure media are more persistent than gaseous pressure media if high temperature heating is required. The melting point of the former is much higher, and melting of pressure media may induce undesirable sample shift in the pressure chamber. However, the most important characteristic of a pressure medium is its ability to maintain hydrostaticity in the DAC. The media, particularly solid pressure media, become less effective with increasing pressure. One of the most popular ways of alleviating pressure gradients is through laser annealing of the sample. We explore the effectiveness of this technique in relation to common pressure media, namely, alkali metal halides NaCl, CsCl, KCl, LiF, and oxide MgO. The samples were laser annealed at temperatures above 2000 K. Pressure gradients were determined through the analysis of diamond Raman and ruby fluorescence peaks before and after annealing the sample with a near-infrared laser. We find that the effect of annealing varies for different materials. For some (NaCl and KCl), it reduces pressure gradients considerably, but for the others (MgO), the effect of annealing is less profound.

  12. On determining characteristic length scales in pressure gradient turbulent boundary layers

    Science.gov (United States)

    Vinuesa, Ricardo; Örlü, Ramis; Schlatter, Philipp

    2016-04-01

    In the present work we analyze three methods used to determine the edge of pressure gradient turbulent boundary layers: two based on composite profiles, the one by Chauhan et al. (Fluid Dyn. Res. 41:021401, 2009) and the one by Nickels (J. Fluid Mech. 521:217-239, 2004), and the other one based on the condition of vanishing mean velocity gradient. Additionally, a new method is introduced based on the diagnostic plot concept by Alfredsson et al. (Phys. Fluids 23:041702, 2011). The boundary layer developing over the suction side of a NACA4412 wing profile, extracted from a direct numerical simulation at Rec = 400,000, is used as the test case. We find that all the methods produce robust results with mild or moderate pressure gradients, but stronger pressure gradients (with β larger than around 7) lead to inconsistent results in all the techniques except the diagnostic plot. This method also has the advantage of providing an objective way of defining the point where the mean streamwise velocity is 99% of the edge velocity, and shows consistent results in a wide range of pressure gradient conditions, as well as flow histories. Therefore, the technique based on the diagnostic plot is a robust method to determine the boundary layer thickness (equivalent to δ99) and edge velocity in pressure gradient turbulent boundary layers.

  13. Portosystemic pressure reduction achieved with TIPPS and impact of portosystemic collaterals for the prediction of the portosystemic-pressure gradient in cirrhotic patients

    Energy Technology Data Exchange (ETDEWEB)

    Grözinger, Gerd, E-mail: gerd.groezinger@med.uni-tuebingen.de [Department of Diagnostic Radiology, Department of Radiology, University of Tübingen (Germany); Wiesinger, Benjamin; Schmehl, Jörg; Kramer, Ulrich [Department of Diagnostic Radiology, Department of Radiology, University of Tübingen (Germany); Mehra, Tarun [Department of Dermatology, University of Tübingen (Germany); Grosse, Ulrich; König, Claudius [Department of Diagnostic Radiology, Department of Radiology, University of Tübingen (Germany)

    2013-12-01

    Purpose: The portosystemic pressure gradient is an important factor defining prognosis in hepatic disease. However, noninvasive prediction of the gradient and the possible reduction by establishment of a TIPSS is challenging. A cohort of patients receiving TIPSS was evaluated with regard to imaging features of collaterals in cross-sectional imaging and the achievable reduction of the pressure gradient by establishment of a TIPSS. Methods: In this study 70 consecutive patients with cirrhotic liver disease were retrospectively evaluated. Patients received either CT or MR imaging before invasive pressure measurement during TIPSS procedure. Images were evaluated with regard to esophageal and fundus varices, splenorenal collaterals, short gastric vein and paraumbilical vein. Results were correlated with Child stage, portosystemic pressure gradient and post-TIPSS reduction of the pressure gradient. Results: In 55 of the 70 patients TIPSS reduced the pressure gradient to less than 12 mmHg. The pre-interventional pressure and the pressure reduction were not significantly different between Child stages. Imaging features of varices and portosystemic collaterals did not show significant differences. The only parameter with a significant predictive value for the reduction of the pressure gradient was the pre-TIPSS pressure gradient (r = 0.8, p < 0.001). Conclusions: TIPSS allows a reliable reduction of the pressure gradient even at high pre-interventional pressure levels and a high collateral presence. In patients receiving TIPSS the presence and the characteristics of the collateral vessels seem to be too variable to draw reliable conclusions concerning the portosystemic pressure gradient.

  14. A General Pressure Gradient Formulation for Ocean Models - Part II: Energy, Momentum, and Bottom Torque Consistency

    Science.gov (United States)

    Song, Y.; Wright, D.

    1998-01-01

    A formulation of the pressure gradient force for use in models with topography-following coordinates is proposed and diagnostically analyzed by Song. We investigate numerical consistency with respect to global energy conservation, depth-integrated momentum changes, and the represent of the bottom pressure torque.

  15. Behavior of a horizontal air curtain subjected to a vertical pressure gradient

    Science.gov (United States)

    Linden, James; Phelps, LeEllen

    2012-09-01

    We present the details on an experiment to investigate the behavior of an air curtain that is subjected to a transverse pressure gradient. The setup simulates the conditions that will be present in the Advanced Technology Solar Telescope (ATST), a 4-meter solar observatory that will be built on Haleakala, Hawaii. A test rig was built to replicate the region at which the optical path crosses a temperature and pressure boundary between the telescope mount region, which is at the ambient temperature and pressure, and a warmer, pressurized lab space directly below. Use of an air curtain in place of an optically-transmitting window at the interface would allow science observations at a wider range of scientific wavelengths. With the air curtain exhibiting transitional flow behavior across the boundary, and applied pressure gradients of up to 6.5 Pa, we found that the air curtain was able to hold a pressure gradient of 0.25 Pa. As the applied pressure was increased, transient turbulent regions formed at the interface, and predictable flow behavior only occurred in the region closest to the air curtain blower. Computer modeling is used to validate the test data, identify laminar regions of the air curtain where minimal image distortion would occur, and explore the relationship between the applied pressure, effective pressure difference, and air curtain profile.

  16. Non-invasive Measurement of Pressure Gradients in Pulsatile Flow using Ultrasound

    DEFF Research Database (Denmark)

    Olesen, Jacob Bjerring; Traberg, Marie Sand; Pihl, Michael Johannes

    2013-01-01

    approach. Pressure gradients are calculated from the measured velocity fields using the Navier-Stokes equation. Velocity fields are measured during constant and pulsating flow on a carotid bifurcation phantom and on a common carotid artery in-vivo. Scanning is performed with a 5 MHz BK8670 linear......This paper demonstrates how pressure gradients in a pulsatile flow environment can be measured non-invasively using ultrasound. The proposed method relies on vector velocity fields acquired from ultrasound data. 2-D flow data are acquired at 18-23 frames/sec using the Transverse Oscillation...... transducer using a BK Medical 2202 UltraView Pro Focus scanner. The calculated pressure gradients are validated through a finite element simulation of the constant flow model. The geometry of the flow simulation model is reproduced using MRI data, thereby providing identical flow domains in measurement...

  17. Pressure Gradient Influence on MHD Flow for Generalized Burgers’ Fluid with Slip Condition

    Directory of Open Access Journals (Sweden)

    Ghada H. Ibraheem,

    2014-07-01

    Full Text Available This paper presents a research for magnetohydrodynamic (MHD flow of an incompressible generalized Burgers' fluid including by an accelerating plate and flowing under the action of pressure gradient. Where the no – slip assumption between the wall and the fluid is no longer valid. The fractional calculus approach is introduced to establish the constitutive relationship of the generalized Burgers' fluid. By using the discrete Laplace transform of the sequential fractional derivatives, a closed form solutions for the velocity and shear stress are obtained in terms of Fox H- function for the following two problems: (i flow due to a constant pressure gradient, and (ii flow due to due to a sinusoidal pressure gradient. The solutions for no – slip condition and no magnetic field, can be derived as special cases of our solutions. Furthermore, the effects of various parameters on the velocity distribution characteristics are analyzed and discussed in detail. Comparison between the two cases is also made.

  18. Semianalytical Solution of the Nonlinear Dual-Porosity Flow Model with the Quadratic Pressure Gradient Term

    Directory of Open Access Journals (Sweden)

    Jiang-Tao Li

    2015-01-01

    Full Text Available The nonlinear dual-porosity flow model, specifically considering the quadratic pressure gradient term, wellbore storage coefficient, well skin factor, and interporosity flow of matrix to natural fractures, was established for well production in a naturally fractured formation and then solved using a semianalytical method, including Laplace transform and a transformation of the pressure function. Analytical solution of the model in Laplace space was converted to numerical solution in real space using Stehfest numerical inversion. Nonlinear flow process for well production in a naturally fractured formation with different external boundaries was simulated and analyzed using standard pressure curves. Influence of the quadratic pressure gradient coefficient on pressure curves was studied qualitatively and quantitatively in conditions of a group of fixed model parameters. The research results show that the semianalytical modelling method is applicable in simulating the nonlinear dual-porosity flow behavior.

  19. The establishment of a new deliverability equation considering threshold pressure gradient

    Institute of Scientific and Technical Information of China (English)

    Li Lezhong; Li Xiangfang; He Dongbo; Xu Hanbing

    2009-01-01

    The flowing mechanism of a low permeability gas reservoir is different from a conventional gas reservoir, espe-cially for that with higher irreducible water saturation the threshold pressure gradient exists. At present, in all the deliverability equation, the additional pressure drop caused by the threshold pressure gradient is viewed as constant, but this method has big error in the practical application. Based on the non-Darcy steady flow equation, the limited integral of the additional pressure drop is solved in this paper and it is realized that the additional pressure drop is not a constant but has something to do with production data, and a new deliverability equation is derived, with the relevant processing method for modified isochronal test data. The new deliverability equation turns out to be practical through onsite applica-tion.

  20. Non-invasive Estimation of Pressure Gradients in Pulsatile Flow using Ultrasound

    DEFF Research Database (Denmark)

    Olesen, Jacob Bjerring; Villagómez Hoyos, Carlos Armando; Traberg, Marie Sand

    2014-01-01

    This paper investigates how pressure gradients in a pulsatile flow environment can be measured non-invasively using ultrasound. The presented set-up is based on vector velocity fields measured on a blood mimicking fluid moving at a peak flow rate of 1 ml/s through a constricted vessel. Fields of ...... and standard deviation of 10% and 13%, respectively, relative to peak estimated gradient. The paper concludes that maps of pressure gradients can be measured non-invasively using ultrasound with a precision of more than 85%......This paper investigates how pressure gradients in a pulsatile flow environment can be measured non-invasively using ultrasound. The presented set-up is based on vector velocity fields measured on a blood mimicking fluid moving at a peak flow rate of 1 ml/s through a constricted vessel. Fields...... of pressure gradients are calculated using the Navier-Stokes equations. Flow data are acquired to a depth of 3 cm using directional synthetic aperture flow imaging on a linear array transducer producing 1500 image frames of velocity estimates per second. Scans of a carotid bifurcation phantom with a 70...

  1. Stabilizing effect of ion pressure gradient on magnetic curvature-driven drift modes located at rational surface of tokamak plasma

    Institute of Scientific and Technical Information of China (English)

    Wang Ai-Ke

    2005-01-01

    In the fluid model, we derive a dispersion relation for the toroidal drift modes of tokamak plasmas, including the ion pressure gradient and the magnetic field gradient and curvature. It is shown that the magnetic field gradient and curvature (MFGC) can cause instabilities at the rational surface, which are of toroidicity-induced (TI) modes. On the other hand, it is discovered that the ion pressure gradient can stabilize the present MFGC instabilities. The critical threshold of ion pressure gradient, which makes the growth rate reduced to zero, is obtained both analytically and numerically.

  2. Polynomial regularization for robust MRI-based estimation of blood flow velocities and pressure gradients.

    Science.gov (United States)

    Delles, Michael; Rengier, Fabian; Ley, Sebastian; von Tengg-Kobligk, Hendrik; Kauczor, Hans-Ulrich; Dillmann, Rüdiger; Unterhinninghofen, Roland

    2011-01-01

    In cardiovascular diagnostics, phase-contrast MRI is a valuable technique for measuring blood flow velocities and computing blood pressure values. Unfortunately, both velocity and pressure data typically suffer from the strong image noise of velocity-encoded MRI. In the past, separate approaches of regularization with physical a-priori knowledge and data representation with continuous functions have been proposed to overcome these drawbacks. In this article, we investigate polynomial regularization as an exemplary specification of combining these two techniques. We perform time-resolved three-dimensional velocity measurements and pressure gradient computations on MRI acquisitions of steady flow in a physical phantom. Results based on the higher quality temporal mean data are used as a reference. Thereby, we investigate the performance of our approach of polynomial regularization, which reduces the root mean squared errors to the reference data by 45% for velocities and 60% for pressure gradients.

  3. Investigation of the effects of pressure gradient, temperature and wall temperature ratio on the stagnation point heat transfer for circular cylinders and gas turbine vanes

    Science.gov (United States)

    Nagamatsu, H. T.; Duffy, R. E.

    1984-01-01

    Low and high pressure shock tubes were designed and constructed for the purpose of obtaining heat transfer data over a temperature range of 390 to 2500 K, pressures of 0.3 to 42 atm, and Mach numbers of 0.15 to 1.5 with and without pressure gradient. A square test section with adjustable top and bottom walls was constructed to produce the favorable and adverse pressure gradient over the flat plate with heat gages. A water cooled gas turbine nozzle cascade which is attached to the high pressure shock tube was obtained to measuse the heat flux over pressure and suction surfaces. Thin-film platinum heat gages with a response time of a few microseconds were developed and used to measure the heat flux for laminar, transition, and turbulent boundary layers. The laminar boundary heat flux on the shock tube wall agreed with Mirel's flat plate theory. Stagnation point heat transfer for circular cylinders at low temperature compared with the theoretical prediction, but for a gas temperature of 922 K the heat fluxes were higher than the predicted values. Preliminary flat plate heat transfer data were measured for laminar, transition, and turbulent boundary layers with and without pressure gradients for free-stream temperatures of 350 to 2575 K and flow Mach numbers of 0.11 to 1.9. The experimental heat flux data were correlated with the laminar and turbulent theories and the agreement was good at low temperatures which was not the case for higher temperatures.

  4. Can postoperative mean transprosthetic pressure gradient predict survival after aortic valve replacement?

    NARCIS (Netherlands)

    Koene, Bart M.; Hamad, Mohamed A. Soliman; Bouma, Wobbe; Mariani, Massimo A.; Peels, Kathinka C.; van Dantzig, Jan-Melle; van Straten, Albert H.

    In this study, we sought to determine the effect of the mean transprosthetic pressure gradient (TPG), measured at 6 weeks after aortic valve replacement (AVR) or AVR with coronary artery bypass grafting (CABG) on late all-cause mortality. Between January 1998 and March 2012, 2,276 patients (mean age

  5. The pressure gradient for heterogeneous flow of coal, sand and iron in pipelines

    NARCIS (Netherlands)

    Yu, X.Q.

    1986-01-01

    The existing relationships based on Durand's method to predict pressure gradients for slurry flow in pipelines appear to be inadequate when accounting for a wide range of variables such as particle size and relative density as well as concentration. Using the coal, sand and iron ore data collected

  6. A Remark on the Regularity Criterion for the 3D Boussinesq Equations Involving the Pressure Gradient

    Directory of Open Access Journals (Sweden)

    Zujin Zhang

    2014-01-01

    Full Text Available We consider the three-dimensional Boussinesq equations and obtain a regularity criterion involving the pressure gradient in the Morrey-Companato space Mp,q. This extends and improves the result of Gala (Gala 2013 for the Navier-Stokes equations.

  7. Equilibrium turbulent boundary layers with wall suction/blowing and pressure gradients

    Science.gov (United States)

    Patwardhan, Saurabh; Ramesh, O. N.

    2012-11-01

    Conditions for the equilibrium conditions in turbulent boundary layers with suction or blowing across a no slip wall and pressure gradients are derived from the governing equations. It is also shown that under these conditions the governing equations show self similarity in the conventional inner co-ordinates as well as ``laminar-like'' co-ordinates. The only turbulent boundary layer in ``perfect equilibrium'' known as sink flow turbulent boundary layer forms a subset of this more general equilibrium concept. Direct numerical simulations were carried out to investigate this hypothesis for the case of favourable pressure gradient with small blowing at the wall. Reynolds number invariance and complete self similarity of mean velocity profile and second order turbulence statistics is observed along the flow direction similar to the sink flow boundary layer. A comparison between the case with wall blowing and imposed favourable pressure gradient and the sink flow case for same value of pressure gradient parameter reveals a shift in log law in mean velocity profile and increase in peak turbulence intensities.

  8. Barrier island breach evolution: Alongshore transport and bay-ocean pressure gradient interactions

    Science.gov (United States)

    Safak, Ilgar; Warner, John C.; List, Jeffrey H.

    2016-12-01

    Physical processes controlling repeated openings and closures of a barrier island breach between a bay and the open ocean are studied using aerial photographs and atmospheric and hydrodynamic observations. The breach site is located on Pea Island along the Outer Banks, separating Pamlico Sound from the Atlantic Ocean. Wind direction was a major control on the pressure gradients between the bay and the ocean to drive flows that initiate or maintain the breach opening. Alongshore sediment flux was found to be a major contributor to breach closure. During the analysis period from 2011 to 2016, three hurricanes had major impacts on the breach. First, Hurricane Irene opened the breach with wind-driven flow from bay to ocean in August 2011. Hurricane Sandy in October 2012 quadrupled the channel width from pressure gradient flows due to water levels that were first higher on the ocean side and then higher on the bay side. The breach closed sometime in Spring 2013, most likely due to an event associated with strong alongshore sediment flux but minimal ocean-bay pressure gradients. Then, in July 2014, Hurricane Arthur briefly opened the breach again from the bay side, in a similar fashion to Irene. In summary, opening and closure of breaches are shown to follow a dynamic and episodic balance between along-channel pressure gradient driven flows and alongshore sediment fluxes.

  9. Viscoelastic fluid flow in circular narrow confinements driven by periodic pressure and potential gradients

    NARCIS (Netherlands)

    Nguyen, T.; Berg, van den A.; Eijkel, J.C.T.

    2015-01-01

    We present an in-depth analysis and analytical solution for AC hydrodynamic flow (driven by a timedependent pressure gradient and/or electric fields) of viscoelastic fluid through cylindrical micro-, nanochannels. Particularly, for this purpose we solve the linearized Poisson-Boltzmann equation tog

  10. Nozzle design in a fiber spinning process for a maximal pressure gradient

    Directory of Open Access Journals (Sweden)

    Yang Zhanping

    2013-01-01

    Full Text Available The thickness of a spinneret is always a geometrical constraint in nozzle design. The geometrical form of a nozzle has a significant effect on the subsequent spinning characteristics. This paper gives an optimal condition for maximal pressure gradient through the nozzle.

  11. Symmetries and Group-Invariant Solutions for Transonic Pressure-Gradient Equations

    Institute of Scientific and Technical Information of China (English)

    王丽真; 黄晴

    2011-01-01

    Lie symmetry group method is applied to study the transonic pressure-gradient equations in two-dimensional space. Its symmetry groups and corresponding optimal systems are determined, and several classes of irrotational groupinvariant solutions associated to the symmetries are obtained and special case of one-dimensional rarefaction wave is found.

  12. Relationship among diastolic intraventricular pressure gradients, relaxation, and preload : impact of age and fitness

    NARCIS (Netherlands)

    Popovic, Z.B.; Prasad, A.; Garcia, M.J.; Arbab-Zadeh, A.; Borowski, A.; Dijk, E.; Greenberg, N.L.; Levine, B.D.; Thomas, J.D.

    2006-01-01

    Diastolic intraventricular pressure gradients (IVPGs) are a measure of the ability of the ventricle to facilitate its filling using diastolic suction. We assessed 15 healthy young but sedentary subjects, aged <50 yr (young subjects; age, 35 +/- 9 yr); 13 healthy but sedentary seniors, aged >65 yr wi

  13. Alveolar septal patterning during compensatory lung growth: Part II the effect of parenchymal pressure gradients.

    Science.gov (United States)

    Haber, Shimon; Weisbord, Michal; Mentzer, Steven J; Tsuda, Akira

    2017-05-21

    In most mammals, compensatory lung growth occurs after the removal of one lung (pneumonectomy). Although the mechanism of alveolar growth is unknown, the patterning of complex alveolar geometry over organ-sized length scales is a central question in regenerative lung biology. Because shear forces appear capable of signaling the differentiation of important cells involved in neoalveolarization (fibroblasts and myofibroblasts), interstitial fluid mechanics provide a potential mechanism for the patterning of alveolar growth. The movement of interstitial fluid is created by two basic mechanisms: 1) the non-uniform motion of the boundary walls, and 2) parenchymal pressure gradients external to the interstitial fluid. In a previous study (Haber et al., Journal of Theoretical Biology 400: 118-128, 2016), we investigated the effects of non-uniform stretching of the primary septum (associated with its heterogeneous mechanical properties) during breathing on generating non-uniform Stokes flow in the interstitial space. In the present study, we analyzed the effect of parenchymal pressure gradients on interstitial flow. Dependent upon lung microarchitecture and physiologic conditions, parenchymal pressure gradients had a significant effect on the shear stress distribution in the interstitial space of primary septa. A dimensionless parameter δ described the ratio between the effects of a pressure gradient and the influence of non-uniform primary septal wall motion. Assuming that secondary septa are formed where shear stresses were the largest, it is shown that the geometry of the newly generated secondary septa was governed by the value of δ. For δ smaller than 0.26, the alveolus size was halved while for higher values its original size was unaltered. We conclude that the movement of interstitial fluid, governed by parenchymal pressure gradients and non-uniform primary septa wall motion, provides a plausible mechanism for the patterning of alveolar growth. Copyright © 2017

  14. Perturbations of the solar wind flow by radial and latitudinal pick-up ion pressure gradients

    Directory of Open Access Journals (Sweden)

    H. J. Fahr

    2004-06-01

    Full Text Available It has been found that pick-up ions at their dynamical incorporation into the solar wind modify the original conditions of the asymptotic solar wind plasma flow. In this respect, it has meanwhile been revealed in many papers that these type of solar wind modifications, i.e. deceleration and decrease of effective Mach number, are not only due to the pick-up ion loading effects, but also to the action of pick-up ion pressure gradients. Up to now only the effects of radial pick-up ion pressure gradients were considered, however, analogously but latitudinal pressure gradients also appear to be important. Here we study the effects of radial and latitudinal pick-up ion pressure gradients, occurring especially during solar minimum conditions at mid-latitude regions where slow solar wind streams change to fast solar wind streams. First, we give estimates of the latitudinal wind components connected with these gradients, and then after revealing its importance, present a more quantitative calculation of solar wind velocity and density perturbations resulting from these pressure forces. It is shown that the relative density perturbations near and in the ecliptic increase with radial distance and thus may well explain the measured non-spherically symmetric density decrease with distance. We also show that the solar wind decelerations actually seen with Voyager-1/2 are in conciliation with interstellar hydrogen densities of nH∞≥0.1cm-3, in contrast to earlier claims for nH∞=0.05cm-3.

  15. Doppler echo evaluation of pulmonary venous-left atrial pressure gradients: human and numerical model studies

    Science.gov (United States)

    Firstenberg, M. S.; Greenberg, N. L.; Smedira, N. G.; Prior, D. L.; Scalia, G. M.; Thomas, J. D.; Garcia, M. J.

    2000-01-01

    The simplified Bernoulli equation relates fluid convective energy derived from flow velocities to a pressure gradient and is commonly used in clinical echocardiography to determine pressure differences across stenotic orifices. Its application to pulmonary venous flow has not been described in humans. Twelve patients undergoing cardiac surgery had simultaneous high-fidelity pulmonary venous and left atrial pressure measurements and pulmonary venous pulsed Doppler echocardiography performed. Convective gradients for the systolic (S), diastolic (D), and atrial reversal (AR) phases of pulmonary venous flow were determined using the simplified Bernoulli equation and correlated with measured actual pressure differences. A linear relationship was observed between the convective (y) and actual (x) pressure differences for the S (y = 0.23x + 0.0074, r = 0.82) and D (y = 0.22x + 0.092, r = 0.81) waves, but not for the AR wave (y = 0. 030x + 0.13, r = 0.10). Numerical modeling resulted in similar slopes for the S (y = 0.200x - 0.127, r = 0.97), D (y = 0.247x - 0. 354, r = 0.99), and AR (y = 0.087x - 0.083, r = 0.96) waves. Consistent with numerical modeling, the convective term strongly correlates with but significantly underestimates actual gradient because of large inertial forces.

  16. The effect of electron thermal conduction on plasma pressure gradient during reconnection of magnetic field lines

    Energy Technology Data Exchange (ETDEWEB)

    Chu, T.K.

    1987-12-01

    The interplay of electron cross-field thermal conduction and the reconnection of magnetic field lines around an m = 1 magnetic island prior to a sawtooth crash can generate a large pressure gradient in a boundary layer adjacent to the reconnecting surface, leading to an enhanced gradient of poloidal beta to satisfy the threshold condition for ideal MHD modes. This narrow boundary layer and the short onset time of a sawtooth crash can be supported by fine-grained turbulent processes in a tokamak plasma. 11 refs.

  17. Asymptotic Analysis of a Turbulent Boundary Layer in a Strong Adverse Pressure Gradient.

    Science.gov (United States)

    1987-07-01

    a ar ax 67/2 ’ar 2 ax2(47a 65( an an) +g P 2 atrr +a2 atrx + 4 (4-.:1 (a 2n + 6 4 a 2n) (.2ba (a ax : 4.nir ar (a -+ + a 7/2 ar 2 ax 2 47b In...8217 [22] 5 n n an) + .2 rrt 52 atrx ~4 a2n 4 5 a 2n (4.27b)’ax + " (a- -- a - -TO + ar ax 2 From an examination of (4.26) and (4.27)’, the Inner-layer

  18. Kinetic performance limits of constant pressure versus constant flow rate gradient elution separations. Part I: theory.

    Science.gov (United States)

    Broeckhoven, K; Verstraeten, M; Choikhet, K; Dittmann, M; Witt, K; Desmet, G

    2011-02-25

    We report on a general theoretical assessment of the potential kinetic advantages of running LC gradient elution separations in the constant-pressure mode instead of in the customarily used constant-flow rate mode. Analytical calculations as well as numerical simulation results are presented. It is shown that, provided both modes are run with the same volume-based gradient program, the constant-pressure mode can potentially offer an identical separation selectivity (except from some small differences induced by the difference in pressure and viscous heating trajectory), but in a significantly shorter time. For a gradient running between 5 and 95% of organic modifier, the decrease in analysis time can be expected to be of the order of some 20% for both water-methanol and water-acetonitrile gradients, and only weakly depending on the value of V(G)/V₀ (or equivalently t(G)/t₀). Obviously, the gain will be smaller when the start and end composition lie closer to the viscosity maximum of the considered water-organic modifier system. The assumptions underlying the obtained results (no effects of pressure and temperature on the viscosity or retention coefficient) are critically reviewed, and can be inferred to only have a small effect on the general conclusions. It is also shown that, under the adopted assumptions, the kinetic plot theory also holds for operations where the flow rate varies with the time, as is the case for constant-pressure operation. Comparing both operation modes in a kinetic plot representing the maximal peak capacity versus time, it is theoretically predicted here that both modes can be expected to perform equally well in the fully C-term dominated regime (where H varies linearly with the flow rate), while the constant pressure mode is advantageous for all lower flow rates. Near the optimal flow rate, and for linear gradients running from 5 to 95% organic modifier, time gains of the order of some 20% can be expected (or 25-30% when accounting for

  19. Power Law or Logarithmic Law?—A data Analysis for Zero Pressure Gradient Turbulent Boundary Layers with Low Reδs

    Institute of Scientific and Technical Information of China (English)

    MatthiasBuschmann

    2000-01-01

    The paper presents an analysis of two-dimensional zero pressure gradient(ZPG) turbulent boundary layers(TBL) with regard to the application of power laws,only TBL with low Reynolds number 300adverse pressure gradient(APG) TBL.To brdge the gap between the wall and the power law region an approach for the turbulent viscosity is suggested.

  20. Two-Dimensional Regular Shock Reflection for the Pressure Gradient System of Conservation Laws

    Institute of Scientific and Technical Information of China (English)

    Yuxi Zheng

    2006-01-01

    We establish the existence of a global solution to a regular reflection of a shock hitting a ramp for the pressure gradient system of equations. The set-up of the reflection is the same as that of Mach's experiment for the compressible Euler system, i.e., a straight shock hitting a ramp. We assume that the angle of the ramp is close to 90 degrees. The solution has a reflected bow shock wave, called the diffraction of the planar shock at the compressive corner, which is mathematically regarded as a free boundary in the self-similar variable plane.The pressure gradient system of three equations is a subsystem, and an approximation, of the full Euler system,and we offer a couple of derivations.

  1. FFT integration of instantaneous 3D pressure gradient fields measured by Lagrangian particle tracking in turbulent flows

    Science.gov (United States)

    Huhn, F.; Schanz, D.; Gesemann, S.; Schröder, A.

    2016-09-01

    Pressure gradient fields in unsteady flows can be estimated through flow measurements of the material acceleration in the fluid and the assumption of the governing momentum equation. In order to derive pressure from its gradient, almost exclusively two numerical methods have been used to spatially integrate the pressure gradient until now: first, direct path integration in the spatial domain, and second, the solution of the Poisson equation for pressure. Instead, we propose an alternative third method that integrates the pressure gradient field in Fourier space. Using a FFT function, the method is fast and easy to implement in programming languages for scientific computing. We demonstrate the accuracy of the integration scheme on a synthetic pressure field and apply it to an experimental example based on time-resolved material acceleration data from high-resolution Lagrangian particle tracking with the Shake-The-Box method.

  2. The transpired turbulent boundary layer in various pressure gradients and the blow-off condition

    Science.gov (United States)

    Georgiou, D. P.; Louis, J. F.

    1984-12-01

    Experimental data are reported from studies of the cooling effectiveness and conditions leading to blow-off in transpiration cooling (TC). The TC configuration used featured a sintered bronze plate in a hot blowdown wind tunnel. Cooled air was pumped through the plate and data were gathered with calorimeters downstream of a piece of sandpaper which tripped the boundary layer. Pressure taps were also used. Local pressure gradient effects were small, but local accelerations reduced the cooling effectiveness. The downstream Stanton numbers were sensitive to the upstream coolant-injection ratio. Increasing the injection rate had, at best, only a small effect on the local heat flux.

  3. Does objective measurement of tracheal tube cuff pressures minimise adverse effects and maintain accurate cuff pressures? A systematic review and meta-analysis.

    Science.gov (United States)

    Hockey, C A; van Zundert, A A J; Paratz, J D

    2016-09-01

    Correct inflation pressures of the tracheal cuff are recommended to ensure adequate ventilation and prevent aspiration and adverse events. However there are conflicting views on which measurement to employ. The aim of this review was to examine whether adjustment of cuff pressure guided by objective measurement, compared with subjective measurement or observation of the pressure value alone, was able to prevent patient-related adverse effects and maintain accurate cuff pressures. A search of PubMed, Web of Science, Embase, CINAHL and ScienceDirect was conducted using keywords 'cuff pressure' and 'measure*' and related synonyms. Included studies were randomised or pseudo-randomised controlled trials investigating mechanically ventilated patients both in the intensive care unit and during surgery. Outcomes included adverse effects and the comparison of pressure measurements. Pooled analyses were performed to calculate risk ratios, effect sizes and 95% confidence intervals. Meta-analysis found preliminary evidence that adjustment of cuff pressure guided by objective measurement as compared with subjective measurement or observation of the pressure value alone, has benefit in preventing adverse effects. These included cough at two hours (odds ratio [OR] 0.42, confidence interval [CI] 0.23 to 0.79, P=0.007), hoarseness at 24 hours (OR 0.49, CI 0.31 to 0.76, P measurement to guide adjustment or observation of the pressure value alone may lead to patient-related adverse effects and inaccuracies. It is recommended that an objective form of measurement be used.

  4. Sound Localization in Lizards: Functioning of a Pressure-Gradient Receiver

    Science.gov (United States)

    van Hemmen, J. Leo

    2009-03-01

    Because of their small interaural distance, lizards as well as some other animals have developed a special hearing mechanism, the ``pressure-gradient receiver''. The lizard peripheral auditory system differs from the mammalian one by a coupling of the two eardrums through the internal mouth cavity. We present a three-dimensional analytical model of the pressure-gradient receiver. The central aspect of the coupling of the membranes through the mouth cavity is realized by means of the boundary conditions. Moreover, the lizard's middle ear, a simple lever construction called columella, is asymmetrically attached to the tympanic membrane. This has motivated us to solve the problem of how the middle ear influences the spatial-amplitude profile and the frequency distribution of the tympanic membrane vibration. Finally, we show results from numerical simulations of the eigenfunctions and eigenfrequencies in a lizard's internal mouth cavity bounded by the eardrums. To this end, we have constructed the complex geometry from a cast imprint of the cavity with the help of three-dimensional scans. Our results led to an interesting speculation regarding the neurobiological use of the pressure-gradient system.

  5. The Difference in Translaminar Pressure Gradient and Neuroretinal Rim Area in Glaucoma and Healthy Subjects

    Directory of Open Access Journals (Sweden)

    Lina Siaudvytyte

    2014-01-01

    Full Text Available Purpose. To assess differences in translaminar pressure gradient (TPG and neuroretinal rim area (NRA in patients with normal tension glaucoma (NTG, high tension glaucoma (HTG, and healthy controls. Methods. 27 patients with NTG, HTG, and healthy controls were included in the prospective pilot study (each group consisted of 9 patients. Intraocular pressure (IOP, intracranial pressure (ICP, and confocal laser scanning tomography were assessed. TPG was calculated as the difference of IOP minus ICP. ICP was measured using noninvasive two-depth transcranial Doppler device. The level of significance P 0.05. The difference between TPG for healthy (5.4(7.7 mmHg and glaucomatous eyes (NTG 6.3(3.1 mmHg, HTG 15.7(7.7 mmHg was statistically significant (P < 0.001. Higher TPG was correlated with decreased NRA (r = −0.83; P = 0.01 in the NTG group. Conclusion. Translaminar pressure gradient was higher in glaucoma patients. Reduction of NRA was related to higher TPG in NTG patients. Further prospective studies are warranted to investigate the involvement of TPG in glaucoma management.

  6. Nonconvective Forces: A Critical and Often Ignored Component in the Echocardiographic Assessment of Transvalvular Pressure Gradients

    Directory of Open Access Journals (Sweden)

    Michael S. Firstenberg

    2012-01-01

    Full Text Available Echocardiography is routinely used to assess ventricular and valvular function, particularly in patients with known or suspected cardiac disease and who have evidence of hemodynamic compromise. A cornerstone to the use of echocardiographic imaging is not only the qualitative assessment, but also the quantitative Doppler-derived velocity characteristics of intracardiac blood flow. While simplified equations, such as the modified Bernoulli equation, are used to estimate intracardiac pressure gradients based upon Doppler velocity data, these modified equations are based upon assumptions of the varying contributions of the different forces that contribute to blood flow. Unfortunately, the assumptions can result in significant miscalculations in determining a gradient if not completely understood or they are misapplied. We briefly summarize the principles of fluid dynamics that are used clinically with some of the inherent limitations of routine broad application of the simplified Bernoulli equation.

  7. In vitro comparison of Doppler and catheter-measured pressure gradients in 3D models of mitral valve calcification.

    Science.gov (United States)

    Herrmann, Tarrah A; Siefert, Andrew W; Pressman, Gregg S; Gollin, Hannah R; Touchton, Steven A; Saikrishnan, Neelakantan; Yoganathan, Ajit P

    2013-09-01

    Mitral annular calcification (MAC) involves calcium deposition in the fibrous annulus supporting the mitral valve (MV). When calcification extends onto the leaflets, valve opening can be restricted. The influence of MAC MV geometry on Doppler gradients is unknown. This study describes a novel methodology to rapid-prototype subject-specific MAC MVs. Replicated valves were used to assess the effects of distorted annular-leaflet geometry on Doppler-derived, transmitral gradients in comparison to direct pressure measurements and to determine if transmitral gradients vary according to measurement location. Three-dimensional echocardiography data sets were selected for two MAC MVs and one healthy MV. These MVs were segmented and rapid prototyped in their middiastolic configuration for in vitro testing. The effects of MV geometry, measurement modality, and measurement location on transmitral pressure gradient were assessed by Doppler and catheter at three locations along the MV's intercommissural axis. When comparing dimensions of the rapid-prototyped valves to the subject echocardiography data sets, mean relative errors ranged from 6.2% to 35%. For the evaluated MVs, Doppler pressure gradients exhibited good agreement with catheter-measured gradients at a variety of flow rates, though with slight systematic overestimation in the recreated MAC valves. For all of the tested MVs, measuring the transmitral pressure gradient at differing valve orifice positions had minimal impact on observed gradients. Upon the testing of additional normal and calcific MVs, these data may contribute to an improved clinical understanding of MAC-related mitral stenosis. Moreover, they provide the ability to statistically evaluate between measurement locations, flow rates, and valve geometries for Doppler-derived pressure gradients. Determining these end points will contribute to greater clinical understanding for the diagnosis MAC patients and understanding the use and application of Doppler

  8. Analysis of mine's air leakage based on pressure gradient matrix between nodes

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jian-rang; WANG Hong-gang; WU Feng-liang; CHANG Xin-tan

    2008-01-01

    Air leakage may significantly affect the effectiveness of mine ventilation by in-creasing the cost of ventilation and arousing problems for ventilation management. Fur-thermore, air leakage may accelerate the process of coal spontaneous combustion andcause gas explosion, thus greatly threatens the safety of coat production. The estimationof air leakage, therefore, have great practical significance. For any ventilation system ofcoal mines, there is a defined pattern of pressure gradient which drived the mine air toflow in the network, drives possible air leakage to go shortcut as well. Air leakage mayoccur through ventilation structures such as ventilation doors and fractures of the surroun-dig coal and rock of airways. A concept and the relevent calculation method of the pres-sure gradient matrix was put forward to assist the analysis of potential air leakage routes.A simplified example was used to introduce the application principle of'pressure gradientmatrix in identifying all the potential air leaking routes, which offers a deeper understand-ing over the ventilation system and the prevention of coal spontaneous combustion.

  9. Invasive assessment of doubtful aortic stenosis by measuring simultaneous transaortic gradient with a pressure wire.

    Science.gov (United States)

    Chopard, Romain; Meneveau, Nicolas; Plastaras, Philoktimon; Janin, Sebastien; Seronde, Marie-France; Ecarnot, Fiona; Schiele, Francois

    2013-06-15

    Two-dimensional transthoracic echocardiography (2D-TTE) is the reference technique for evaluating aortic stenosis (AS) but may be unreliable in some cases. We aimed to assess whether the use of a pressure wire to measure simultaneous transaortic gradient and aortic valve area (AVA) could be helpful in patients in whom initial noninvasive evaluations were considered doubtful for AS. Fifty-seven patients (mean age 76 years; 39 men) underwent cardiac catheterization with single arterial access for assessment of AVA with the Gorlin and Gorlin formula. Transaortic pressure was obtained by 2 invasive methods: (1) conventional pullback method (PM) from the left ventricle toward the aorta and (2) simultaneous method (SM) with transaortic pressure simultaneously recorded with a 0.014-inch pressure wire introduced into the left ventricle and with a diagnostic catheter placed in the ascending aorta. Reasons for inaccurate assessment by 2D-TTE were low flow states (88%) and/or atrial fibrillation (79%). Agreement for severe AS defined by AVA <0.6 cm²/m² between SM and 2D-TTE and between SM and PM was fair, with kappa coefficients of 0.38 (95% confidence interval [CI] 0.14-0.75) and 0.36 (95% CI 0.22-0.7) respectively; agreement was poor between 2D-TTE and PM (kappa: 0.23; 95% CI 0.002-0.36). SM led to a reclassification of the severity of AS in 9 patients (15.8%) compared with 2D-TTE and in 11 patients (19.3%) compared with PM. In conclusion, invasive evaluation of doubtful AS by measuring simultaneous transaortic gradient using a pressure wire may provide an attractive method that can lead to a change in therapeutic strategy in a substantial proportion of patients.

  10. Local pressure gradients due to incipience of boiling in subcooled flows

    Energy Technology Data Exchange (ETDEWEB)

    Ruggles, A.E.; McDuffee, J.L. [Univ. of Tennessee, Knoxville, TN (United States)

    1995-09-01

    Models for vapor bubble behavior and nucleation site density during subcooled boiling are integrated with boundary layer theory in order to predict the local pressure gradient and heat transfer coefficient. Models for bubble growth rate and bubble departure diameter are used to scale the movement of displaced liquid in the laminar sublayer. An added shear stress, analogous to a turbulent shear stress, is derived by considering the liquid movement normal to the heated surface. The resulting mechanistic model has plausible functional dependence on wall superheat, mass flow, and heat flux and agrees well with data available in the literature.

  11. Exact solution of unsteady flow generated by sinusoidal pressure gradient in a capillary tube

    Directory of Open Access Journals (Sweden)

    M. Abdulhameed

    2015-12-01

    Full Text Available In this paper, the mathematical modeling of unsteady second grade fluid in a capillary tube with sinusoidal pressure gradient is developed with non-homogenous boundary conditions. Exact analytical solutions for the velocity profiles have been obtained in explicit forms. These solutions are written as the sum of the steady and transient solutions for small and large times. For growing times, the starting solution reduces to the well-known periodic solution that coincides with the corresponding solution of a Newtonian fluid. Graphs representing the solutions are discussed.

  12. Ion slip effect on unsteady Hartmann flow with heat transfer under exponential decaying pressure gradient

    Directory of Open Access Journals (Sweden)

    Hazem A. Attia

    2006-01-01

    Full Text Available The unsteady Hartmann flow of an electrically conducting, viscous, incompressible fluid bounded by two parallel nonconducting porous plates is studied with heat transfer taking the ion slip into consideration. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates, while the fluid motion is subjected to an exponential decaying pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of the ion slip and the uniform suction and injection on both the velocity and temperature distributions is examined.

  13. Gap heating with pressure gradients. [for Shuttle Orbiter thermal protection system tiles

    Science.gov (United States)

    Scott, C. D.; Maraia, R. J.

    1979-01-01

    The heating rate distribution and temperature response on the gap walls of insulating tiles is analyzed to determine significant phenomena and parameters in flows where there is an external surface pressure gradient. Convective heating due to gap flow, modeled as fully developed pipe flow, is coupled with a two-dimensional thermal model of the tiles that includes conduction and radiative heat transfer. To account for geometry and important environmental parameters, scale factors are obtained by curve-fitting measured temperatures to analytical solutions. These scale factors are then used to predict the time-dependent gap heat flux and temperature response of tile gaps on the Space Shuttle Orbiter during entry.

  14. Nitric oxide synthase 3 deficiency limits adverse ventricular remodeling after pressure overload in insulin resistance

    Science.gov (United States)

    Kurtz, Baptiste; Thibault, Helene B.; Raher, Michael J.; Popovich, John R.; Cawley, Sharon; Atochin, Dmitriy N.; Hayton, Sarah; Shakartzi, Hannah R.; Huang, Paul L.; Bloch, Kenneth D.; Buys, Emmanuel

    2011-01-01

    Insulin resistance (IR) and systemic hypertension are independently associated with heart failure. We reported previously that nitric oxide synthase 3 (NOS3) has a beneficial effect on left ventricular (LV) remodeling and function after pressure-overload in mice. The aim of our study was to investigate the interaction of IR and NOS3 in pressure-overload-induced LV remodeling and dysfunction. Wild-type (WT) and NOS3-deficient (NOS3−/−) mice were fed either a standard diet (SD) or a high-fat diet (HFD) to induce IR. After 9 days of diet, mice underwent transverse aortic constriction (TAC). LV structure and function were assessed serially using echocardiography. Cardiomyocytes were isolated, and levels of oxidative stress were evaluated using 2′,7′-dichlorodihydrofluorescein diacetate. Cardiac mitochondria were isolated, and mitochondrial respiration and ATP production were measured. TAC induced LV remodeling and dysfunction in all mice. The TAC-induced decrease in LV function was greater in SD-fed NOS3−/− mice than in SD-fed WT mice. In contrast, HFD-fed NOS3−/− developed less LV remodeling and dysfunction and had better survival than did HFD-fed WT mice. Seven days after TAC, oxidative stress levels were lower in cardiomyocytes from HFD-fed NOS3−/− than in those from HFD-fed WT. Nω-nitro-l-arginine methyl ester and mitochondrial inhibitors (rotenone and 2-thenoyltrifluoroacetone) decreased oxidative stress levels in cardiomyocytes from HFD-fed WT mice. Mitochondrial respiration was altered in NOS3−/− mice but did not worsen after HFD and TAC. In contrast with its protective role in SD, NOS3 increases LV adverse remodeling after pressure overload in HFD-fed, insulin resistant mice. Interactions between NOS3 and mitochondria may be responsible for increased oxidative stress levels in HFD-fed WT mice hearts. PMID:21856905

  15. Effect of Favorable Pressure Gradients on Turbine Blade Pressure Surface Heat Transfer

    Science.gov (United States)

    Boyle, Robert J.; Giel, P. W.

    2002-01-01

    Recent measurements on a turbine rotor showed significant relaminarization effects. These effects were evident on the pressure surface heat transfer measurements. The character of the heat transfer varied with Reynolds number. Data were obtained for exit Reynolds numbers between 500,000 and 880,000. Tests were done with a high level of inlet turbulence, 7.5%. At lower Reynolds numbers the heat transfer was similar to that for laminar flow, but at a level higher than for laminar flow. At higher Reynolds numbers the heat transfer was similar to turbulent flow, when the acceleration parameter, K, was sufficiently small. The proposed paper discusses the experimental results, and also discusses approaches to calculating the surface heat transfer for the blade surface. Calculations were done using a three-dimensional Navier-Stokes CFD analysis. The results of these tests, when compared with previous blade tests in the same facility, illustrate modeling difficulties that were encountered in CFD predictions. The two blades were in many ways similar. However, the degree of agreement between the same analysis and the experimental data was significantly different. These differences are highlighted to illustrate where improvements in modeling approaches are needed for transitional flows.

  16. Observations of wave-induced pore pressure gradients and bed level response on a surf zone sandbar

    Science.gov (United States)

    Anderson, Dylan; Cox, Dan; Mieras, Ryan; Puleo, Jack A.; Hsu, Tian-Jian

    2017-06-01

    Horizontal and vertical pressure gradients may be important physical mechanisms contributing to onshore sediment transport beneath steep, near-breaking waves in the surf zone. A barred beach was constructed in a large-scale laboratory wave flume with a fixed profile containing a mobile sediment layer on the crest of the sandbar. Horizontal and vertical pore pressure gradients were obtained by finite differences of measurements from an array of pressure transducers buried within the upper several centimeters of the bed. Colocated observations of erosion depth were made during asymmetric wave trials with wave heights between 0.10 and 0.98 m, consistently resulting in onshore sheet flow sediment transport. The pore pressure gradient vector within the bed exhibited temporal rotations during each wave cycle, directed predominantly upward under the trough and then rapidly rotating onshore and downward as the wavefront passed. The magnitude of the pore pressure gradient during each phase of rotation was correlated with local wave steepness and relative depth. Momentary bed failures as deep as 20 grain diameters were coincident with sharp increases in the onshore-directed pore pressure gradients, but occurred at horizontal pressure gradients less than theoretical critical values for initiation of the motion for compact beds. An expression combining the effects of both horizontal and vertical pore pressure gradients with bed shear stress and soil stability is used to determine that failure of the bed is initiated at nonnegligible values of both forces.Plain Language SummaryThe pressure gradient present within the seabed beneath breaking waves may be an important physical mechanism transporting sediment. A large-scale laboratory was used to replicate realistic surfzone conditions in controlled tests, allowing for horizontal and vertical pressure gradient magnitudes and the resulting sediment bed response to be observed with precise instruments. Contrary to previous studies

  17. THE EFFECT OF MAGNETIC FIELDS ON LOW FREQUENCY OSCILLATING NATURAL CONVECTION WITH PRESSURE GRADIENT

    Institute of Scientific and Technical Information of China (English)

    G.C. Sharma; Madhu Jain; Mahesh Chandra

    2003-01-01

    The oscillating natural convection in the presence of transverse magnetic field with time depending pressure gradient is studied. The analysis of the problem is carried out by assuming that the fluid is flowing in a parallel plate configuration. The emphasis is on low frequency oscillating convective flows induced by g-jitter associated with micro gravity because of their importance to the space processing materials. A general solution for an oscillating flow in the presence of transverse magnetic field is carried out. Some special cases of the oscillating flow and its response to an applied magnetic field are performed. It was observed that the behavior of oscillating free convective flows depends on frequency, amplitude of the driving buoyancy forces, temperature gradient, magnetic field and the electric conditions of the channel walls. In the absence of magnetic field, buoyancy force plays a predominant role in driving the oscillatory flow pattern, and velocity magnitude is also affected by temperature gradients. To suppress the oscillating flow external magnetic field can be used. It is also found that the reduction of the velocity is inversely proportional to the square of the applied magnetic field with conducting wall but directly proportional to the inverse of the magnetic field with insulating wall. Detailed calculations and computational results are also carried out to depict the real situation.

  18. Staging of liver fibrosis or cirrhosis: The role of hepaticvenous pressure gradient measurement

    Institute of Scientific and Technical Information of China (English)

    Ki Tae Suk; Dong Joon Kim

    2015-01-01

    Liver fibrosis is a common histological change ofchronic liver injury and it is closely related with portalhypertension which is hemodynamic complication ofchronic liver disease. Currently, liver fibrosis has beenknown as a reversible dynamic process in previousliteratures. Although liver biopsy is a gold standardfor assessing the stage of liver fibrosis, it may notcompletely represent the stage of liver fibrosis becauseof sampling error or semi-quantative measurement.Recent evidences suggested that histologic, clinical,hemodynamic, and biologic features are closelyassociated in patients with chronic liver disease. Hepaticvenous pressure gradient (HVPG) measurement has beenknown as a modality to evaluate the portal pressure.The HVPG measurement has been used clinicallyfor fibrosis diagnosis, risk stratification, preoperativescreening for liver resection, monitoring the efficacy ofmedical treatments, and assessing the prognosis of liverfibrosis. Therefore, the HVPG measurement can be usedto monitor areas the chronic liver disease but also otherimportant areas of chronic liver disease.

  19. Beyond Pressure Gradients: The Effects of Intervention on Heart Power in Aortic Coarctation

    Science.gov (United States)

    Brüning, Jan; Hellmeier, Florian; Nordmeyer, Sarah; da Silva, Tiago Ferreira; Schubert, Stephan; Berger, Felix; Kuehne, Titus; Kelm, Marcus

    2017-01-01

    Background In aortic coarctation, current guidelines recommend reducing pressure gradients that exceed given thresholds. From a physiological standpoint this should ideally improve the energy expenditure of the heart and thus prevent long term organ damage. Objectives The aim was to assess the effects of interventional treatment on external and internal heart power (EHP, IHP) in patients with aortic coarctation and to explore the correlation of these parameters to pressure gradients obtained from heart catheterization. Methods In a collective of 52 patients with aortic coarctation 25 patients received stenting and/or balloon angioplasty, and 20 patients underwent MRI before and after an interventional treatment procedure. EHP and IHP were computed based on catheterization and MRI measurements. Along with the power efficiency these were combined in a cardiac energy profile. Results By intervention, the catheter gradient was significantly reduced from 21.8±9.4 to 6.2±6.1mmHg (p<0.001). IHP was significantly reduced after intervention, from 8.03±5.2 to 4.37±2.13W (p < 0.001). EHP was 1.1±0.3 W before and 1.0±0.3W after intervention, p = 0.044. In patients initially presenting with IHP above 5W intervention resulted in a significant reduction in IHP from 10.99±4.74 W to 4.94±2.45W (p<0.001), and a subsequent increase in power efficiency from 14 to 26% (p = 0.005). No significant changes in IHP, EHP or power efficiency were observed in patients initially presenting with IHP < 5W. Conclusion It was demonstrated that interventional treatment of coarctation resulted in a decrease in IHP. Pressure gradients, as the most widespread clinical parameters in coarctation, did not show any correlation to changes in EHP or IHP. This raises the question of whether they should be the main focus in coarctation interventions. Only patients with high IHP of above 5W showed improvement in IHP and power efficiency after the treatment procedure. Trial Registration clinicaltrials

  20. Relation between change in blood pressure in acute stroke and risk of early adverse events and poor outcome

    DEFF Research Database (Denmark)

    Sandset, Else C; Murray, Gordon D; Bath, Philip M W;

    2012-01-01

    The Scandinavian Candesartan Acute Stroke Trial (SCAST) found no benefits of candesartan in acute stroke. In the present analysis we aim to investigate the effect of change in blood pressure during the first 2 days of stroke on the risk of early adverse events and poor outcome.......The Scandinavian Candesartan Acute Stroke Trial (SCAST) found no benefits of candesartan in acute stroke. In the present analysis we aim to investigate the effect of change in blood pressure during the first 2 days of stroke on the risk of early adverse events and poor outcome....

  1. Pick-up ion pressure gradients modulating the solar wind dynamics

    Science.gov (United States)

    Fahr, Hans J.; Fichtner, Horst

    1995-01-01

    Neutral interstellar atoms penetrate deeply into the inner heliosphere before they become ionized by various processes. As ions they are picked-up by the frozen-in magnetic fields and are convected outwards with the solar wind plasma. Thereby the primary plasma flow is mass, momentum, and energy-loaded. The dynamics of the distant multi-constituent solar wind is, however, not solely determined by these loading processes, but is also affected by the wave-mediated pick-up ion pressure gradients derivable from the pick-up ion distribution function. The action of the radial components of these pressures essentially counter balances the decelerating effect of the solar wind momentum loading, diminishing strongly the deceleration of the distant solar wind. Furthermore the latitudinal components of the pick-up ion pressures induce latitudinal forces acting on the multiconstituent solar plasma outflow and inducing nonradial bulk flow components. The enforced nonradial outflow geometry on the upwind hemisphere may partly be responsible for the magnetic flux deficit which was claimed since several years in the PIONEER-10 magnetic flux data.

  2. A Simple Method for Noninvasive Quantification of Pressure Gradient Across the Pulmonary Valve.

    Science.gov (United States)

    Zhou, Xueying; Xing, Changyang; Feng, Yang; Duan, Yunyou; Zheng, Qiangsun; Wang, Zuojun; Liu, Jie; Cao, Tiesheng; Yuan, Lijun

    2017-02-15

    Pressure gradient across the pulmonary valve (PVPG) is an important hemodynamic variable used in the management of patients with cardiovascular and pulmonary disease. However, a reliable noninvasive method is unavailable. We hypothesized that a progressive Muller maneuver would elicit the pulmonary valve premature opening (PVPO) in diastole and that this event would be detectable by Doppler echocardiography. The intrathoracic pressure (ITP) decrease during this maneuver equals PVPG, which may be assessed with a custom airway pressure measurement device. A total of 102 subjects were enrolled in the study. At the earliest appearance of PVPO, the ITP decrease was recorded as the PVPG. PVPG was also simultaneously measured and compared by other two methods: right heart catheterization in 43 subjects, and routine Doppler echocardiography (pulmonary regurgitation jet) in the other 59 subjects. The results measured by different approaches were compared using the Bland-Altman analysis. PVPG assessed via PVPO showed strong agreement with PVPG measured by catheterization or routine Doppler echocardiography methods, with Lin concordance correlation coefficients of 0.91 and 0.70, respectively. In conclusion, PVPO provides a new noninvasive method of quantification of PVPG.

  3. Implicit Large-Eddy Simulations of Zero-Pressure Gradient, Turbulent Boundary Layer

    Science.gov (United States)

    Sekhar, Susheel; Mansour, Nagi N.

    2015-01-01

    A set of direct simulations of zero-pressure gradient, turbulent boundary layer flows are conducted using various span widths (62-630 wall units), to document their influence on the generated turbulence. The FDL3DI code that solves compressible Navier-Stokes equations using high-order compact-difference scheme and filter, with the standard recycling/rescaling method of turbulence generation, is used. Results are analyzed at two different Re values (500 and 1,400), and compared with spectral DNS data. They show that a minimum span width is required for the mere initiation of numerical turbulence. Narrower domains ((is) less than 100 w.u.) result in relaminarization. Wider spans ((is) greater than 600 w.u.) are required for the turbulent statistics to match reference DNS. The upper-wall boundary condition for this setup spawns marginal deviations in the mean velocity and Reynolds stress profiles, particularly in the buffer region.

  4. Developments in the theory of trapped particle pressure gradient-driven turbulence in tokamaks and stellarators

    Energy Technology Data Exchange (ETDEWEB)

    Diamond, P.H.; Biglari, H.; Gang, F.Y.; Kim, Y.B.; Rosenbluth, M.N.; Wang, X.H.; Xu, X.Q. (California Univ., San Diego, La Jolla, CA (USA). Dept. of Physics); Dominguez, N.; Carreras, B.A.; Leboeuf, J.N.; Lynch, V.E.; Charlton, L.A.; Garcia, L. (Oak Ridge National Lab., TN (USA)); Terry, P.W.; Newman, D.E. (Wisconsin Univ., Madison, WI (USA). Dept. of Physics); Koniges, A.E.; Crotinger, J.; Dannevik, W. (Lawre

    1990-12-01

    Recent advances in the theory of trapped particle pressure gradient driven turbulence are summarized. A novel theory of trapped ion convective cell turbulence is presented. It is shown that nonlinear transfer to small scales occurs, and that saturation levels are not unphysically large, as previously thought. As the virulent saturation mechanism of ion Compton scattering is shown to result in weak turbulence at higher frequencies, it is thus likely that trapped ion convective cells are the major agent of tokamak transport. Fluid-like trapped electron modes at short wavelengths (k{sub {theta}} {rho}{sub i} > 1) are shown to drive an inward particle pinch. The characteristics of convective cell turbulence in flat density discharges are described, as is the stability of dissipative trapped electron modes in stellarators, with flexible magnetic field structure. The role of cross-correlations in the dynamics of multi-field models of drift wave turbulence is discussed. 32 refs., 7 figs., 1 tab.

  5. Direct Numerical Simulation and Theories of Wall Turbulence with a Range of Pressure Gradients

    Science.gov (United States)

    Coleman, G. N.; Garbaruk, A.; Spalart, P. R.

    2014-01-01

    A new Direct Numerical Simulation (DNS) of Couette-Poiseuille flow at a higher Reynolds number is presented and compared with DNS of other wall-bounded flows. It is analyzed in terms of testing semi-theoretical proposals for universal behavior of the velocity, mixing length, or eddy viscosity in pressure gradients, and in terms of assessing the accuracy of two turbulence models. These models are used in two modes, the traditional one with only a dependence on the wall-normal coordinate y, and a newer one in which a lateral dependence on z is added. For pure Couette flow and the Couette-Poiseuille case considered here, this z-dependence allows some models to generate steady streamwise vortices, which generally improves the agreement with DNS and experiment. On the other hand, it complicates the comparison between DNS and models.

  6. Wall mass transfer and pressure gradient effects on turbulent skin friction

    Science.gov (United States)

    Watson, R. D.; Balasubramanian, R.

    1984-01-01

    The effects of mass injection and pressure gradients on the drag of surfaces were studied theoretically with the aid of boundary-layer and Navier-Stokes codes. The present investigation is concerned with the effects of spatially varying the injection in the case of flat-plate drag. Effects of suction and injection on wavy wall surfaces are also explored. Calculations were performed for 1.2 m long surfaces, one flat and the other sinusoidal with a wavelength of 30.5 cm. Attention is given to the study of the effect of various spatial blowing variations on flat-plate skin friction reduction, local skin friction coefficient calculated by finite difference boundary-layer code and Navier-Stokes code, and the effect of phase-shifting sinusoidal mass transfer on the drag of a sinusoidal surface.

  7. Baroclinic pressure gradient difference schemes of subtracting the local averaged density stratification in sigma coordinates models

    Institute of Scientific and Technical Information of China (English)

    ZHU Shouxian; ZHANG Wenjing

    2008-01-01

    Much has been written of the error in computing the baroclinic pressure gradient (BPG) with sigma coordinates in ocean or atmos- pheric numerical models. The usual way to reduce the error is to subtract area-averaged density stratification of the whole computa- tion region. But if there is great difference between the area-averaged and the local averaged density stratification, the error will be obvious. An example is given to show that the error from this method may be larger than that from no correction sometimes. The definition of local area is put forward. Then, four improved BPG difference schemes of subtracting the local averaged density strat- ification are designed to reduce the error. Two of them are for diagnostic calculation (density field is fixed), and the others are for prognostic calculation (density field is not fixed). The results show that the errors from these schemes all significantly decrease.

  8. Effects of Abscisic Acid and of Hydrostatic Pressure Gradient on Water Movement through Excised Sunflower Roots.

    Science.gov (United States)

    Glinka, Z

    1977-05-01

    The effect of abscisic acid on the exudation rate from decapitated roots of sunflower plants (Helianthus annuus L.) was investigated in the presence and absence of an imposed hydrostatic pressure gradient. The magnitude of the abscisic acid effect was constant even when suctions up to 60 cm Hg were applied to the cut stumps.When roots were bathed in a THO-labeled nutrient solution, the course of the appearance of radioactivity in the exudate, expressed as a function of exudate volume, was not affected by abscisic acid treatment but was strongly speeded up by applying suction.The implications of those findings with regard to the water pathway through the root and the location of the abscisic acid effect are discussed.

  9. A Nonlinear k-ε Turbulence Model Applicable to High Pressure Gradient and Large Curvature Flow

    Directory of Open Access Journals (Sweden)

    Xiyao Gu

    2014-01-01

    Full Text Available Most of the RANS turbulence models solve the Reynolds stress by linear hypothesis with isotropic model. They can not capture all kinds of vortexes in the turbomachineries. In this paper, an improved nonlinear k-ε turbulence model is proposed, which is modified from the RNG k-ε turbulence model and Wilcox's k-ω turbulence model. The Reynolds stresses are solved by nonlinear methods. The nonlinear k-ε turbulence model can calculate the near wall region without the use of wall functions. The improved nonlinear k-ε turbulence model is used to simulate the flow field in a curved rectangular duct. The results based on the improved nonlinear k-ε turbulence model agree well with the experimental results. The calculation results prove that the nonlinear k-ε turbulence model is available for high pressure gradient flows and large curvature flows, and it can be used to capture complex vortexes in a turbomachinery.

  10. Turbulent magnetic field amplification driven by cosmic-ray pressure gradients

    CERN Document Server

    Drury, Luke O'C

    2012-01-01

    Observations of non-thermal emission from several supernova remnants suggest that magnetic fields close to the blastwave are much stronger than would be naively expected from simple shock compression of the field permeating the interstellar medium (ISM). We present a simple model which is capable of achieving sufficient magnetic field amplification to explain the observations. We propose that the cosmic-ray pressure gradient acting on the inhomogeneous ISM upstream of the supernova blastwave induces strong turbulence upstream of the supernova blastwave. The turbulence is generated through the differential acceleration of the upstream ISM which occurs as a result of density inhomogeneities in the ISM. This turbulence then amplifies the pre-existing magnetic field. Numerical simulations are presented which demonstrate that amplification factors of 20 or more are easily achievable by this mechanism when reasonable parameters for the ISM and supernova blastwave are assumed. The length scale over which this amplif...

  11. Direct measured systolic pressure gradients across the aorto-iliac segment in multiple-level-obstruction arteriosclerosis

    DEFF Research Database (Denmark)

    Noer, Ivan; Praestholm, J; Tønnesen, K H

    1981-01-01

    to the angiographic findings. A consistent pressure gradient was found in the various types of arterial occlusions. In patients with occlusion of both the aorta and the iliac arteries, the systolic pressure drop was about 60% (range, 50-78%, SD 9%). The various types of iliac artery occlusions resulted in quite...... uniform systolic pressure drops of about 50% (range 35-68%, SD 9%). In contrast, the systolic pressure drop along different types of iliac stenoses showed a wide variation, ranging from a minimal drop to about 60%. The degree of stenosis on the angiogram was correlated significantly with the pressure drop...

  12. RESEARCH AND MATHEMATICAL MODELING OF TURBULENT BOUNDARY LAYER AT POSITIVE PRESSURE GRADIENT

    Directory of Open Access Journals (Sweden)

    Vitaliy Mamchuk

    2016-06-01

    Full Text Available Purpose: Mathematical modeling of complex turbulent near-wall flows, that occur during the flow of airfoils, is impossible without understanding the nature of the flow in boundary layer. From a mathematical point of view, the calculation of such flows, because in practical problems they regarded as turbulent, and the characteristics of turbulence are largely dependent on the geometry of the profile of the longitudinal component of the average velocity of the near-wall flow. Based on this, the purpose of this work is studying and mathematical modeling of turbulent near-wall flows in the interaction with the real streamlined surface, that has certain features, such as the curvature, roughness, etc., as well as the study and research of the influence of the pressure gradient on the empirical coefficients, parameters of the flow, velocity profiles and friction stress. Methods: We performed the calculations using numerical finite-difference marching method with algebraic model of turbulent viscosity coefficient. Results: In this paper we present some results of the numerical study of the effect of the positive pressure gradient on the empirical coefficients of the transition zone and the law of the near-wall and the outer-wall areas. Discussion: Comparison of the calculated results with the experimental data shows that the proposed approaches provide an opportunity to simulate the flow as close as possible to their physical properties. Presented mathematical model for the calculation of turbulent boundary layers and near-wall flows makes it possible to calculate such a complex and valuable from a practical point of view type of the flow as the aerodynamic trail behind the streamlined body.

  13. Sildenafil does not influence hepatic venous pressure gradient in patients with cirrhosis

    Institute of Scientific and Technical Information of China (English)

    Jens Otto Clemmesen; Annamaria Giraldi; Peter Ott; Kim Dalhoff; Bent Adel Hansen; Fin Stolze Larsen

    2008-01-01

    AIM: To investigate if sildenafil increases splanchnic blood flow and changes the hepatic venous pressure gradient (HVPG) in patients with cirrhosis. Phosphodiesterase type-5 inhibitors are valuable in the treatment of erectile dysfunction and pulmonary hypertension in patients with end-stage liver disease. However, the effect of phosphodiesterase type-5 inhibitors on splanchnic blood flow and portal hypertension remains essentially unknown. METHODS: Ten patients with biopsy proven cirrhosis (five females/five males, mean age 54±8 years) and an HVPG above 12 mmHg were studied after informed consent. Measurement of splanchnic blood flow and the HVPG during liver vein catheterization were done before and 80 min after oral administration of 50 mg sildenafil. Blood flow was estimated by use of indocyanine green clearance technique and Fick's principle, with correction for non-steady state. RESULTS: The plasma concentration of sildenafil was 222±136 ng/mL 80 min after administration. Mean arterial blood pressure decreased from 77±7 mmHg to 66±12 mmHg, P=0.003, while the splanchnic blood flow and oxygen consumption remained unchanged at 1.14±0.71 L/min and 2.3±0.6 mmol/ min, respectively. Also the HVPG remained unchanged (18±2 mmHg vs 16±2 mmHg) with individual changes ranging from-8 mmHg to+2 mmHg. In seven patients, HVPG decreased and in three it increased. CONCLUSION: In spite of arterial blood pressure decreases 80 min after administration of the phosphodiesterase type-5 inhibitor sildenafil, the present study could not demonstrate any clinical relevant influence on splanichnic blood flow, oxygen consumption or the HVPG.

  14. Pressure gradients and boiling as mechanisms for localizing ore in porphyry systems

    Science.gov (United States)

    Cunningham, Charles G.

    1978-01-01

    Fluid inclusions in ore zones of porphyry systems indicate that extensive boiling of hydrothermal fluids accompanies deposition of ore and gangue minerals. The boiling commonly accompanied a change from a lithostatic to a hydrostatic environment during evolution of an epizonal stock. Pressure gradients near the margin of the stock can determine whether ore or only a diffuse zone of mineralization is formed. A sharp drop in pressure in an epizonal environment is more likely to cause extensive boiling than a comparable change in a deeper environment, as the slope of the boiling curve steepens with an increase 'in pressure. The drop in pressure causes the hydrothermal fluids to boil and creates a crackle (stockwork) breccia, which hosts the veinlets of gangue quartz and ore minerals. The boiling selectively partitions CO2, H2S, and HCl into the vapor phase, changing the pH, composition, ionic strength, and thus the solubility product of metal complexes in the remaining liquid and causing the ore and gangue to come out of solution. Fluid inclusions trapped from boiling solutions can exhibit several forms, depending on the physical and chemical conditions of the hydrothermal fluid from which they were trapped. In one case, inclusions when heated can homogenize to either liquid or vapor at the same temperature, which is the true boiling temperature. In another case, homogenization of various inclusions can occur through a range of temperatures. The latter case results from the trapping of mixture of liquid and vapor. Variations in salinity can result from boiling of the hydrothermal fluid, or intermittent incorporation of high-salinity fluids from the magma, or trapping of fluids of varying densities at pressure-temperature conditions above the critical point of the fluid. In places, paleopressure-temperature transition zones can be recognized by fluid-inclusion homogenization temperatures and phase relationships and by the presence of anhydrite daughter minerals

  15. Computational evaluation of intraventricular pressure gradients based on a fluid-structure approach.

    Science.gov (United States)

    Redaelli, A; Montevecchi, F M

    1996-11-01

    The dynamics of intraventricular blood flow, i.e. its rapid evolution, implies the rise of intraventricular pressure gradients (IPGs) characteristic of the inertia-driven events as experimentally observed by Pasipoularides (1987, 1990) and by Falsetti et al. (1986). The IPG time course is determined by the wall contraction which, in turn, depends on the load applied, namely the intraventricular pressure which is the sum of the aortic pressure (i.e., the systemic net response) and the IPG. Hence the IPGs account, at least in part, for the wall movement. These considerations suggest the necessity of a comprehensive analysis of the ventricular mechanics involving both ventricular wall mechanics and intraventricular fluid dynamics as each domain determines the boundary conditions of the other. This paper presents a computational approach to ventricular ejection mechanics based on a fluid-structure interaction calculation for the evaluation of the IPG time course. An axisymmetric model of the left ventricle is utilized. The intraventricular fluid is assumed to be Newtonian. The ventricle wall is thin and is composed of two sets of counter-rotating fibres which behave according to the modified version of Wong's sarcomere model proposed by Montevecchi and Pietrabissa and Pietrabissa et al. (1987, 1991). The full Navier-Stokes equations describing the fluid domain are solved using Galerkin's weighted residual approach in conjunction with finite element approximation (FIDAP). The wall displacement is solved using the multiplane quasi-Newton method proposed by Buzzi Ferraris and Tronconi (1985). The interaction procedure is performed by means of an external macro which compares the flow fields and the wall displacement and appropriately modifies the boundary conditions to reach the simultaneous and congruous convergence of the two problems. The results refer to a simulation of the ventricular ejection with a heart rate of 72 bpm. In this phase the ventricle ejects 61 cm3

  16. Intraoperative evaluation of transmitral pressure gradients after edge-to-edge mitral valve repair.

    Directory of Open Access Journals (Sweden)

    Jan N Hilberath

    Full Text Available OBJECTIVE: Edge-to-edge repair of the mitral valve (MV has been described as a viable option used for the surgical management of mitral regurgitation (MR. Based on the significant changes in MV geometry associated with this technique, we hypothesized that edge-to-edge MV repairs are associated with higher intraoperative transmitral pressure gradients (TMPG compared to conventional methods. METHODS: Patient records and intraoperative transesophageal echocardiography (TEE examinations of 552 consecutive patients undergoing MV repair at a single institution over a three year period were assessed. After separation from cardiopulmonary bypass (CPB, peak and mean TMPG were recorded for each patient and subsequently analyzed. RESULTS: 84 patients (15% underwent edge-to-edge MV repair. Peak and mean TMPG were significantly higher compared to gradients in patients undergoing conventional repairs: 10.7 ± 0.5 mmHg vs 7.1 ± 0.2 mmHg; P<0.0001 and 4.3 ± 0.2 mmHg vs 2.8 ± 0.1 mmHg; P<0.0001. Only patients with mean TMPG ≥ 7 mmHg (n = 9 required prompt reoperation for iatrogenic mitral stenosis (MS. No differences in peak and mean TMPG were observed among edge-to-edge repairs performed in isolation, compared to those performed in combination with annuloplasty: 11.0 ± 0.7 mmHg vs 10.3 ± 0.6 mmHg and 4.4 ± 0.3 mmHg vs 4.3 ± 0.3 mmHg. There were no differences in TMPG between various types of annuloplasty techniques used in combination with the edge-to-edge repairs. CONCLUSIONS: Edge-to-edge MV repairs are associated with higher intraoperative peak and mean TMPG after separation from CPB compared to conventional repair techniques. Unless gradients are severely elevated, these findings are not necessarily suggestive of iatrogenic MS. Thus, in the immediate postoperative period mildly elevated TMPG can be expected and tolerated after edge-to-edge mitral repairs.

  17. Scaling properties of the mean wall-normal velocity in zero-pressure-gradient boundary layers

    Science.gov (United States)

    Wei, Tie; Klewicki, Joseph

    2016-12-01

    The scaling properties of the mean wall-normal velocity V (x ,y ) in zero-pressure-gradient laminar and turbulent boundary-layer flows are investigated using numerical simulation data, physical experiment data, and integral analyses of the governing equations. The maximum mean wall-normal velocity V∞ and the boundary-layer thickness δ are evidenced to be the proper scaling for V over most if not all of the boundary layer. This is different from the behavior of the mean streamwise velocity U or the turbulent shear stress T =-ρ , which depend on different characteristic length scales in the regions near and away from the surface, respectively. The reason for this apparent difference in scaling behaviors is described physically relative to the downstream development of the U velocity profile and the mechanisms of boundary-layer growth. Insights pertaining to this are further surmised from an analytical relationship for the ratio of the displacement to momentum thickness, i.e., shape factor H . Integral analyses using the continuity and mean momentum equation show that U∞V∞/uτ2=H , where uτ is the friction velocity. Both the laminar similarity solution and direct numerical simulation data in post-transitional flows convincingly support this relation. Over the transitional regime, data of sufficiently high quality are lacking to check if this relation remains valid.

  18. Hepatic venous pressure gradient predicts development of hepatocellular carcinoma independently of severity of cirrhosis☆

    Science.gov (United States)

    Ripoll, Cristina; Groszmann, Roberto J.; Garcia-Tsao, Guadalupe; Bosch, Jaime; Grace, Norman; Burroughs, Andrew; Planas, Ramon; Escorsell, Angels; Garcia-Pagan, Juan Carlos; Makuch, Robert; Patch, David; Matloff, Daniel S.

    2013-01-01

    Background/Aims A total of 213 patients with compensated cirrhosis, portal hypertension and no varices were included in a trial evaluating beta-blockers in preventing varices. Predictors of the development of hepatocellular carcinoma (HCC), including hepatic venous pressure gradient (HVPG) were analyzed. Methods Baseline laboratory tests, ultrasound and HVPG measurements were performed. Patients were followed prospectively every three months until development of varices or variceal bleeding or end of the study in 09/02. The endpoint was HCC development according to standard diagnostic criteria. Univariate and multivariate Cox regression models were developed to identify predictors of HCC. Results In a median follow-up of 58 months 26/213 (12.2%) patients developed HCC. Eight patients were transplanted and 28 patients died without HCC. Twenty-one (84%) HCC developed in patients with HCV. On multivariate analysis HVPG (HR 1.18; 95%CI 1.08–1.29), albumin (HR 0.34; 95%CI 0.14–0.83) and viral etiology (HR 4.59; 95%CI 1.51–13.92) were independent predictors of HCC development. ROC curves identified 10 mmHg of HVPG as the best cutoff; those who had an HVPG above this value had a 6-fold increase in the HCC incidence. Conclusions Portal hypertension is an independent predictor of HCC development. An HVPG >10 mmHg is associated with a 6-fold increase of HCC risk. PMID:19303163

  19. Direct Numerical Simulation of Zero-Pressure Gradient and Sink Flow Turbulent Boundary Layers

    Science.gov (United States)

    Ramesh, O.; Patwardhan, Saurabh

    2010-11-01

    Direct Numerical Simulations have been performed for the zero pressure gradient (ZPG) (600 < Reθ< 900) and for the sink flow turbulent boundary layers (K = 7.71x10-7). A finite difference code on Cartesian grid was used to perform the simulations. Inflow generation method developed by Lund et al. was used to generate inflow boundary condition for the ZPG case. This method was slightly modified for the case of sink flow in view of self-similarity it possesses in the inner co-ordinates. Hence, there was no need to use empirical relations for the calculation of inlet θ or δ and rescaling in outer co-ordinates. The average statistics obtained from the simulations are in close agreement with the experimental as well as DNS data available in the literature. The intermittency distribution in the case of sink flow approaches zero inside the boundary layer (y = 0.8δ), an observation which is also confirmed by the experiments. This effect could be due to the acceleration near the boundary layer edge which suppresses the turbulent fluctuations near the boundary layer edge.

  20. Heat transfer between two parallel porous plates for Couette flow under pressure gradient and Hall current

    Indian Academy of Sciences (India)

    Hazem A Attia; W Abbas; Mostafa A M Abdeen; Ahmed A M Said

    2015-02-01

    The aim of the present paper is to study the unsteady magneto-hydrodynamic viscous Couette flow with heat transfer in a Darcy porous medium between two infinite parallel porous plates considering Hall effect, and temperature dependent physical properties under constant pressure gradient. The parallel plates are assumed to be porous and subjected to a uniform suction from above and injection from below while the fluid is flowing through a porous medium that is assumed to obey Darcy’s law. A numerical solution for the governing nonlinear partial differential equations coupled with set of momentum equations and the energy equation including the viscous and Joule dissipations is adopted. The effect of the porosity of the medium, the Hall current and the temperature dependent viscosity and thermal conductivity on both the velocity and temperature distributions are investigated. It is found that the porosity numberMhas a marked effect on decreasing the velocity distribution (owing to a simultaneous increase in Darcy porous drag). Also the temperature T is decreased considerably with increasing porosity number.With increasing Hall current parameter m, the velocity component u (x-direction) is considerably increased, whereas velocity component w (z-direction) is reduced. Temperatures are decreased in the early stages of flow but effectively increased in the steady state with increasing m.

  1. Thin-Film Composite Pressure Retarded Osmosis Membranes for Sustainable Power Generation from Salinity Gradients

    KAUST Repository

    Yip, Ngai Yin

    2011-05-15

    Pressure retarded osmosis has the potential to produce renewable energy from natural salinity gradients. This work presents the fabrication of thin-film composite membranes customized for high performance in pressure retarded osmosis. We also present the development of a theoretical model to predict the water flux in pressure retarded osmosis, from which we can predict the power density that can be achieved by a membrane. The model is the first to incorporate external concentration polarization, a performance limiting phenomenon that becomes significant for high-performance membranes. The fabricated membranes consist of a selective polyamide layer formed by interfacial polymerization on top of a polysulfone support layer made by phase separation. The highly porous support layer (structural parameter S = 349 μm), which minimizes internal concentration polarization, allows the transport properties of the active layer to be customized to enhance PRO performance. It is shown that a hand-cast membrane that balances permeability and selectivity (A = 5.81 L m-2 h-1 bar-1, B = 0.88 L m-2 h-1) is projected to achieve the highest potential peak power density of 10.0 W/m2 for a river water feed solution and seawater draw solution. The outstanding performance of this membrane is attributed to the high water permeability of the active layer, coupled with a moderate salt permeability and the ability of the support layer to suppress the undesirable accumulation of leaked salt in the porous support. Membranes with greater selectivity (i.e., lower salt permeability, B = 0.16 L m-2 h-1) suffered from a lower water permeability (A = 1.74 L m-2 h-1 bar-1) and would yield a lower peak power density of 6.1 W/m2, while membranes with a higher permeability and lower selectivity (A = 7.55 L m-2 h-1 bar-1, B = 5.45 L m-2 h-1) performed poorly due to severe reverse salt permeation, resulting in a similar projected peak power density of 6.1 W/m2. © 2011 American Chemical Society.

  2. A new macroscopically anisotropic pressure dependent yield function for metal matrix composite based on strain gradient plasticity for the microstructure

    DEFF Research Database (Denmark)

    Azizi, Reza; Legarth, Brian Nyvang; Niordson, Christian Frithiof

    2013-01-01

    Metal matrix composites with long aligned elastic fibers are studied using an energetic rate independent strain gradient plasticity theory with an isotropic pressure independent yield function at the microscale. The material response is homogenized to obtain a conventional macroscopic model...... that exhibits anisotropic yield properties with a pressure dependence. At the microscale free energy includes both elastic strains and plastic strain gradients, and the theory demands higher order boundary conditions in terms of plastic strain or work conjugate higher order tractions. The mechanical response...... of the composite is inclined compared to a standard pressure independent yield surfaces. The evolution of the macroscopic yield surface is investigated by quantifying both anisotropic hardening (expansion) and kinematic hardening (translation), where the coefficients of anisotropy and the Bauschinger stress...

  3. On axial temperature gradients due to large pressure drops in dense fluid chromatography.

    Science.gov (United States)

    Colgate, Sam O; Berger, Terry A

    2015-03-13

    The effect of energy degradation (Degradation is the creation of net entropy resulting from irreversibility.) accompanying pressure drops across chromatographic columns is examined with regard to explaining axial temperature gradients in both high performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC). The observed effects of warming and cooling can be explained equally well in the language of thermodynamics or fluid dynamics. The necessary equivalence of these treatments is reviewed here to show the legitimacy of using whichever one supports the simpler determination of features of interest. The determination of temperature profiles in columns by direct application of the laws of thermodynamics is somewhat simpler than applying them indirectly by solving the Navier-Stokes (NS) equations. Both disciplines show that the preferred strategy for minimizing the reduction in peak quality caused by temperature gradients is to operate columns as nearly adiabatically as possible (i.e. as Joule-Thomson expansions). This useful fact, however, is not widely familiar or appreciated in the chromatography community due to some misunderstanding of the meaning of certain terms and expressions used in these disciplines. In fluid dynamics, the terms "resistive heating" or "frictional heating" have been widely used as synonyms for the dissipation function, Φ, in the NS energy equation. These terms have been widely used by chromatographers as well, but often misinterpreted as due to friction between the mobile phase and the column packing, when in fact Φ describes the increase in entropy of the system (dissipation, ∫TdSuniv>0) due to the irreversible decompression of the mobile phase. Two distinctly different contributions to the irreversibility are identified; (1) ΔSext, viscous dissipation of work done by the external surroundings driving the flow (the pump) contributing to its warming, and (2) ΔSint, entropy change accompanying decompression of

  4. Involvement of Inflammation and Adverse Vascular Remodelling in the Blood Pressure Raising Effect of Repeatedly Heated Palm Oil in Rats

    Directory of Open Access Journals (Sweden)

    Chun-Yi Ng

    2012-01-01

    Full Text Available Oil thermoxidation during deep frying generates harmful oxidative free radicals that induce inflammation and increase the risk of hypertension. This study aimed to investigate the effect of repeatedly heated palm oil on blood pressure, aortic morphometry, and vascular cell adhesion molecule-1 (VCAM-1 expression in rats. Male Sprague-Dawley rats were divided into five groups: control, fresh palm oil (FPO, one-time-heated palm oil (1HPO, five-time-heated palm oil (5HPO, or ten-time-heated palm oil (10HPO. Feeding duration was six months. Blood pressure was measured at baseline and monthly using tail-cuff method. After six months, the rats were sacrificed and the aortic arches were dissected for morphometric and immunohistochemical analyses. FPO group showed significantly lower blood pressure than all other groups. Blood pressure was increased significantly in 5HPO and 10HPO groups. The aortae of 5HPO and 10HPO groups showed significantly increased thickness and area of intima-media, circumferential wall tension, and VCAM-1 than other groups. Elastic lamellae were disorganised and fragmented in 5HPO- and 10HPO-treated rats. VCAM-1 expression showed a significant positive correlation with blood pressure. In conclusion, prolonged consumption of repeatedly heated palm oil causes blood pressure elevation, adverse remodelling, and increased VCAM-1, which suggests a possible involvement of inflammation.

  5. Calculation of turbulent boundary layers with heat transfer and pressure gradient utilizing a compressibility transformation. Part 2: Constant property turbulent boundary layer flow with simultaneous mass transfer and pressure gradient

    Science.gov (United States)

    Boccio, J.; Economos, C.

    1972-01-01

    An analysis of the incompressible turbulent boundary layer, developing under the combined effects of mass transfer and pressure gradient, is presented in this paper. A strip-integral method is employed whereby two of the three governing equations are obtained by integrating the combined momentum and continuity equation to 50 percent and 100 percent, respectively, of the boundary-layer height. The latter equation is the usual momentum-integral equation; the former equation requires specification of shear. Accordingly, Clauser's equilibrium eddy-viscosity law is assumed valid at this point. The third and final equation is obtained by specifying that Stevenson's velocity profiles apply throughout the domain of interest, from which a skin-friction law can be derived. Comparisons of the numerical results with the experiments of McQuaid, which include combined effects of variable pressure gradient and mass transfer, show good agreement.

  6. High-order accurate finite-volume formulations for the pressure gradient force in layered ocean models

    Science.gov (United States)

    Engwirda, Darren; Kelley, Maxwell; Marshall, John

    2017-08-01

    Discretisation of the horizontal pressure gradient force in layered ocean models is a challenging task, with non-trivial interactions between the thermodynamics of the fluid and the geometry of the layers often leading to numerical difficulties. We present two new finite-volume schemes for the pressure gradient operator designed to address these issues. In each case, the horizontal acceleration is computed as an integration of the contact pressure force that acts along the perimeter of an associated momentum control-volume. A pair of new schemes are developed by exploring different control-volume geometries. Non-linearities in the underlying equation-of-state definitions and thermodynamic profiles are treated using a high-order accurate numerical integration framework, designed to preserve hydrostatic balance in a non-linear manner. Numerical experiments show that the new methods achieve high levels of consistency, maintaining hydrostatic and thermobaric equilibrium in the presence of strongly-sloping layer geometries, non-linear equations-of-state and non-uniform vertical stratification profiles. These results suggest that the new pressure gradient formulations may be appropriate for general circulation models that employ hybrid vertical coordinates and/or terrain-following representations.

  7. A practical approach for predicting retention time shifts due to pressure and temperature gradients in ultra-high-pressure liquid chromatography.

    Science.gov (United States)

    Åsberg, Dennis; Chutkowski, Marcin; Leśko, Marek; Samuelsson, Jörgen; Kaczmarski, Krzysztof; Fornstedt, Torgny

    2017-01-06

    Large pressure gradients are generated in ultra-high-pressure liquid chromatography (UHPLC) using sub-2μm particles causing significant temperature gradients over the column due to viscous heating. These pressure and temperature gradients affect retention and ultimately result in important selectivity shifts. In this study, we developed an approach for predicting the retention time shifts due to these gradients. The approach is presented as a step-by-step procedure and it is based on empirical linear relationships describing how retention varies as a function of temperature and pressure and how the average column temperature increases with the flow rate. It requires only four experiments on standard equipment, is based on straightforward calculations, and is therefore easy to use in method development. The approach was rigorously validated against experimental data obtained with a quality control method for the active pharmaceutical ingredient omeprazole. The accuracy of retention time predictions was very good with relative errors always less than 1% and in many cases around 0.5% (n=32). Selectivity shifts observed between omeprazole and the related impurities when changing the flow rate could also be accurately predicted resulting in good estimates of the resolution between critical peak pairs. The approximations which the presented approach are based on were all justified. The retention factor as a function of pressure and temperature was studied in an experimental design while the temperature distribution in the column was obtained by solving the fundamental heat and mass balance equations for the different experimental conditions. We strongly believe that this approach is sufficiently accurate and experimentally feasible for this separation to be a valuable tool when developing a UHPLC method. After further validation with other separation systems, it could become a useful approach in UHPLC method development, especially in the pharmaceutical industry where

  8. Inelastic compression legging produces gradient compression and significantly higher skin surface pressures compared with an elastic compression stocking.

    Science.gov (United States)

    Kline, Cassie N; Macias, Brandon R; Kraus, Emily; Neuschwander, Timothy B; Angle, Niren; Bergan, John; Hargens, Alan R

    2008-01-01

    The purposes of this study were to (1) investigate compression levels beneath an inelastic legging equipped with a new pressure-adjustment system, (2) compare the inelastic compression levels with those provided by a well-known elastic stocking, and (3) evaluate each support's gradient compression production. Eighteen subjects without venous reflux and 12 patients with previously documented venous reflux received elastic and inelastic compression supports sized for the individual. Skin surface pressures under the elastic (Sigvaris 500, 30-40 mm Hg range, Sigvaris, Inc., Peachtree City, GA) and inelastic (CircAid C3 with Built-in-Pressure System [BPS], CircAid Medical Products, San Diego, CA) supports were measured using a calibrated Tekscan I-Scan device (Tekscan, Inc., Boston, MA). The elastic stocking produced significantly lower skin surface pressures than the inelastic legging. Mean pressures (+/- standard error) beneath the elastic stocking were 26 +/- 2 and 23 +/- 1 mm Hg at the ankle and below-knee regions, respectively. Mean pressures (+/- standard error) beneath the inelastic legging with the BPS were 50 +/- 3 and 38 +/- 2 mm Hg at the ankle and below-knee regions, respectively. Importantly, our study indicates that only the inelastic legging with the BPS produces significant ankle to knee gradient compression (p = .001).

  9. EXACT SOLUTION FOR SPHERICAL FLOW AND TRANSIENT BEHAVIOR OF PRESSURE WITH CONSIDERATION OF EFFECTS OF QUADRATIC-GRADIENT TERM

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Conventional models for fluid flow in well tests have not been consistent with material balance. According to the slightly compressible fluid assumption, the quadratic gradient term in the nonlinear partial differential equation has been usually neglected. This approach is questionable for live oil and low permeability reservoirs. We have already known that linearization by neglecting quadratic gradient terms may lead to errors for large values of well-test time. In this paper, a method that is consistent with material balance was proposed on the spherical flow system. All terms in the nonlinear partial eqiation were retained. Exact solution for the resulting nonlinear partial differential equation in an infinite reservoir was obtained by using the Laplace transform considering wellbore storage. Analytical solution for nonlinear partial differential equation are resulted by using orthogonal transforms under both closed and constant-pressure outer boundary conditions. The law of pressure changes for a fluid compressibility α and a storage coefficient CD were discussed.

  10. An experimental study on laminar-turbulent transition at high free-stream turbulence in boundary layers with pressure gradients

    Directory of Open Access Journals (Sweden)

    Chernoray Valery

    2012-04-01

    Full Text Available We report here the results of a study on measurements and prediction of laminar-turbulent transition at high free-stream turbulence in boundary layers of the airfoil-like geometries with presence of the external pressure gradient changeover. The experiments are performed for a number of flow cases with different flow Reynolds number, turbulence intensity and pressure gradient distributions. The results were then compared to numerical calculations for same geometries and flow conditions. The experiments and computations are performed for the flow parameters which are typical for turbomachinery applications and the major idea of the current study is the validation of the turbulence model which can be used for such engineering applications.

  11. Intrinsic advantages of packed capillaries over narrow-bore columns in very high-pressure gradient liquid chromatography.

    Science.gov (United States)

    Gritti, Fabrice; McDonald, Thomas; Gilar, Martin

    2016-06-17

    250μm×100mm fused silica glass capillaries were packed with 1.8μm high-strength silica (HSS) fully porous particles. They were prepared without bulky stainless steel endfittings and metal frits, which both generate significant sample dispersion. The isocratic efficiencies and gradient peak capacities of these prototype capillary columns were measured for small molecules (n-alkanophenones) using a home-made ultra-low dispersive micro-HPLC instrument. Their resolution power was compared to that of standard 2.1mm×100mm very high-pressure liquid chromatography (vHPLC) narrow-bore columns packed with the same particles. The results show that, for the same column efficiency (25000 plates) and gradient steepness (0.04min(-1)), the peak capacity of the 250μm i.d. capillary columns is systematically 15-20% higher than that of the 2.1mm i.d. narrow-bore columns. A validated model of gradient chromatography enabled one to predict accurately the observed peak capacities of the capillary columns for non-linear solvation strength retention behavior and under isothermal conditions. Thermodynamics applied to the eluent quantified the temperature difference for the thermal gradients in both capillary and narrow-bore columns. Experimental data revealed that the gradient peak capacity is more affected by viscous heating than the column efficiency. Unlike across 2.1mm i.d. columns, the changes in eluent composition across the 250μm i.d. columns during the gradient is rapidly relaxed by transverse dispersion. The combination of (1) the absence of viscous heating and (2) the high uniformity of the eluent composition across the diameter of capillary columns explains the intrinsic advantage of capillary over narrow-bore columns in gradient vHPLC.

  12. Effect of spanwise pressure gradient on flow and heat transfer characteristics of longitudinal vortices embedded in a turbulent boundary layer

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jeong Min; Moon, Joo Hyun; Park, Jae Yong; Kim, Dae Yun; Lee, Seong Hyuk [Chung-Ang University, Seoul (Korea, Republic of)

    2015-02-15

    This study numerically investigated the influence of spanwise pressure gradient on heat transfer of a 3D turbulent boundary layer with longitudinal vortices. A 30° bend in the passage provided the spanwise pressure gradient. The longitudinal pair vortices were generated using a pair of delta winglets. The Reynolds-averaged Navier-Stokes and energy equations based on the conventional Reynolds stress model were used. The predictions agreed well with the experimental data for the straight plate. The turbulent boundary layer was significantly perturbed with the longitudinal vortices. The spanwise pressure gradient contributed to faster degradation of the longitudinal vortices and widened the perturbed flow region. The local Stanton number distributions were asymmetric because of the difference in the evolution of the longitudinal vortices in the curved region. Moreover, comparison showed that the local Stanton number in the downstream of the straight channel increased near the surface because of the secondary re-circulating vortex. The thickness of the thermal boundary layers increased in the streamwise direction because of the significant flow mixing and heat transfer.

  13. Marked discrepancy in pressure gradient between Doppler and catheter examinations on Medtronic Mosaic valve in aortic position.

    Science.gov (United States)

    Ito, Toshiaki; Maekawa, Atsuo; Fujii, Genyo; Sawaki, Sadanari; Hoshino, Satoshi; Hayashi, Yasunari

    2012-12-01

    A 71-year-old woman underwent aortic valve replacement with 23 mm Medtronic Mosaic Ultra valve 4 years ago because of aortic stenosis. Although she had been asymptomatic since the operation, echocardiography showed 4 m/s of transprosthetic valve flow that implied early prosthetic valve failure. Catheter examination revealed that the mean transvalvular pressure gradient during systole was 15.1 mmHg on simultaneous pressure recording, and calculated valve area 1.82 cm(2). Her body surface area was 1.56 m(2). Prosthetic valve failure and prosthesis-patient mismatch were both denied. The discrepancy between Doppler study data and catheter data seemed to be due to fluid dynamical pressure recovery phenomenon. Net pressure difference between the left ventricle and the aorta may be significantly smaller than that estimated using Bernoulli's equation from transvalvular flow speed in some patients after aortic valve replacement.

  14. The diastolic flow velocity-pressure gradient relation and dpv50 to assess the hemodynamic significance of coronary stenoses.

    Science.gov (United States)

    Marques, Koen M J; van Eenige, Machiel J; Spruijt, Hugo J; Westerhof, Nico; Twisk, Jos; Visser, Cees A; Visser, Frans C

    2006-12-01

    To evaluate the hemodynamic impact of coronary stenoses, the fractional (FFR) or coronary flow velocity reserve (CFVR) usually is measured. The combined measurement of instantaneous flow velocity and pressure gradient (v-dp relation) is rarely used in humans. We derived from the v-dp relation a new index, dp(v50) (pressure gradient at flow velocity of 50 cm/s), and compared the diagnostic performance of dp(v50), CFVR, and FFR. Before coronary angiography was performed, patients underwent noninvasive stress testing. In all coronary vessels with an intermediate or severe stenosis, the flow velocity, aortic, and distal coronary pressure were measured simultaneously with a Doppler and pressure guidewire after induction of hyperemia. After regression analysis of all middiastolic flow velocity and pressure gradient data, the dp(v50) was calculated. With the use of the results of noninvasive stress testing, the dp(v50) cutoff value was established at 22.4 mmHg. In 77 patients, 124 coronary vessels with a mean 39% (SD 19) diameter stenosis were analyzed. In 43 stenoses, ischemia was detected. We found a sensitivity, specificity, and accuracy of 56%, 86%, and 76% for CFVR; 77%, 99%, and 91% for FFR; and 95%, 95%, and 95% for dp(v50). To establish that dp(v50) is not dependent on maximal hyperemia, dp(v50) was recalculated after omission of the highest quartile of flow velocity data, showing a difference of 3%. We found that dp(v50) provided the highest sensitivity and accuracy compared with FFR and CFVR in the assessment of coronary stenoses. In contrast to CFVR and FFR, assessment of dp(v50) is not dependent on maximal hyperemia.

  15. Left Ventricular Geometry and Blood Pressure as Predictors of Adverse Progression of Fabry Cardiomyopathy.

    Directory of Open Access Journals (Sweden)

    Johannes Krämer

    Full Text Available In spite of several research studies help to describe the heart in Fabry disease (FD, the cardiomyopathy is not entirely understood. In addition, the impact of blood pressure and alterations in geometry have not been systematically evaluated.In 74 FD patients (mean age 36±12 years; 45 females the extent of myocardial fibrosis and its progression were quantified using cardiac magnetic-resonance-imaging with late enhancement technique (LE. Results were compared to standard echocardiography complemented by 2D-speckle-tracking, 3D-sphericity-index (SI and standardized blood pressure measurement. At baseline, no patient received enzyme replacement therapy (ERT. After 51±24 months, a follow-up examination was performed.Systolic blood pressure (SBP was higher in patients with vs. without LE: 123±17 mmHg vs. 115±13 mmHg; P = 0.04. A positive correlation was found between SI and the amount of LE-positive myocardium (r = 0.51; P<0.001 indicating an association of higher SI in more advanced stages of the cardiomyopathy. SI at baseline was positively associated with the increase of LE-positive myocardium during follow-up. The highest SBP (125±19 mmHg and also the highest SI (0.32±0.05 was found in the subgroup with a rapidly increasing LE (ie, ≥0.2% per year; n = 16; P = 0.04. Multivariate logistic regression analysis including SI, SBP, EF, left ventricular volumes, wall thickness and NT-proBNP adjusted for age and sex showed SI as the most powerful parameter to detect rapid progression of LE (AUC = 0.785; P<0.05.LV geometry as assessed by the sphericity index is altered in relation to the stage of the Fabry cardiomyopathy. Although patients with FD are not hypertensive, the SBP has a clear impact on the progression of the cardiomyopathy.

  16. Analysis of pressure-strain and pressure gradient-scalar covariances in cloud-topped boundary layers: A large-eddy simulation study

    Science.gov (United States)

    Heinze, Rieke; Mironov, Dmitrii; Raasch, Siegfried

    2016-03-01

    A detailed analysis of the pressure-scrambling terms (i.e., the pressure-strain and pressure gradient-scalar covariances) in the Reynolds-stress and scalar-flux budgets for cloud-topped boundary layers (CTBLs) is performed using high-resolution large-eddy simulation (LES). Two CTBLs are simulated — one with trade wind shallow cumuli, and the other with nocturnal marine stratocumuli. The pressure-scrambling terms are decomposed into contributions due to turbulence-turbulence interactions, mean velocity shear, buoyancy, and Coriolis effects. Commonly used models of these contributions, including a simple linear model most often used in geophysical applications and a more sophisticated two-component-limit (TCL) nonlinear model, are tested against the LES data. The decomposition of the pressure-scrambling terms shows that the turbulence-turbulence and buoyancy contributions are most significant for cloud-topped boundary layers. The Coriolis contribution is negligible. The shear contribution is generally of minor importance inside the cloudy layers, but it is the leading-order contribution near the surface. A comparison of models of the pressure-scrambling terms with the LES data suggests that the more complex TCL model is superior to the simple linear model only for a few contributions. The linear model is able to reproduce the principal features of the pressure-scrambling terms reasonably well. It can be applied in the second-order turbulence modeling of cloud-topped boundary layer flows, provided some uncertainties are tolerated.

  17. Inclusion of biotic stress (consumer pressure) alters predictions from the stress gradient hypothesis

    NARCIS (Netherlands)

    Smit, Christian; Rietkerk, Max; Wassen, Martin J.

    2009-01-01

    The stress gradient hypothesis (SGH) predicts a shift from net negative interactions in benign environments towards net positive in harsh environments in ecological communities. While several studies found support for the SGH, others found evidence against it, leading to a debate on how nature and s

  18. Microstructural and hardness gradients in Cu processed by high pressure surface rolling

    DEFF Research Database (Denmark)

    He, Q. Y.; Zhu, X.-M.; Mei, Q. S.

    2017-01-01

    in the topmost surface to the microscale in the bulk. The hardness varies from 1.37 GPa at the topmost surface to about 0.6 GPa in the coarse-grained matrix. The results of the investigation demonstrate that the HPSR process shows good potential for the generation of thick gradient microstructures on the surface...

  19. Inclusion of biotic stress (consumer pressure) alters predictions from the stress gradient hypothesis

    NARCIS (Netherlands)

    Smit, Christian; Rietkerk, Max; Wassen, Martin J.

    2009-01-01

    The stress gradient hypothesis (SGH) predicts a shift from net negative interactions in benign environments towards net positive in harsh environments in ecological communities. While several studies found support for the SGH, others found evidence against it, leading to a debate on how nature and

  20. Dependence of transcutaneous oxygen tension on local arteriovenous pressure gradient in normal subjects.

    Science.gov (United States)

    Wyss, C R; Matsen, F A; King, R V; Simmons, C W; Burgess, E M

    1981-05-01

    1. We studied the relationship between transcutaneous oxygen tension at the foot and local arteriovenous pressure difference in 15 normal men and women; arteriovenous pressure difference was varied by changing the height of the foot with respect to the heart and by applying external pressure to the foot. 2. Control transcutaneous oxygen tension was 67 +/- 9 SD mmHg (8.9 +/- 1.2 kPa) at a control arteriovenous pressure difference of 80 +/- 6 SD mmHg (10.6 +/- 0.8 kPa). 3. In every subject transcutaneous oxygen tension fell non-linearly with a decrease in arteriovenous pressure difference; transcutaneous oxygen tension was relatively insensitive to changes in arteriovenous pressure difference when arteriovenous pressure difference was high, but always fell sharply to zero at some positive arteriovenous pressure difference [range 13-34 mmHg (1.7-4.5 kPa)]. 4. An analysis of the data indicated that transcutaneous oxygen tension varied with arteriovenous pressure difference approximately as the oxygen tension of cutaneous venous blood under the sensor varied (in the absence of changes in cutaneous vascular resistance and oxygen consumption). 5. This analysis was supported by studies in three subjects in whom the oxygen tension of superficial venous drainage from a warmed hand or foot was measured along with transcutaneous oxygen tension while arteriovenous pressure difference was varied.

  1. Onset of hypertension during pregnancy is associated with long-term worse blood pressure control and adverse cardiac remodeling.

    Science.gov (United States)

    Mesquita, Roberto F; Reis, Muriel; Beppler, Ana Paula; Bellinazzi, Vera Regina; Mattos, Sandra S; Lima-Filho, José L; Cipolli, José A; Coelho-Filho, Otavio R; Pio-Magalhães, José A; Sposito, Andrei C; Matos-Souza, José R; Nadruz, Wilson

    2014-11-01

    Up to 20% of women with hypertensive pregnancy disorders might persist with chronic hypertension. This study compared clinical and echocardiographic features between women whose hypertension began as hypertensive pregnancy disorders (PH group) and women whose diagnosis of hypertension did not occur during pregnancy (NPH group). Fifty PH and 100 NPH women were cross-sectionally evaluated by clinical, laboratory, and echocardiography analysis, and the groups were matched by duration of hypertension. PH exhibited lower age (46.6 ± 1.4 vs. 65.3 ± 1.1 years; P < .001), but higher systolic (159.8 ± 3.9 vs. 148.0 ± 2.5 mm Hg; P = .009) and diastolic (97.1 ± 2.4 vs. 80.9 ± 1.3 mm Hg; P < .001) blood pressure than NPH, although used more antihypertensive classes (3.4 ± 0.2 vs. 2.6 ± 0.1; P < .001). Furthermore, PH showed higher left ventricular wall thickness and increased prevalence of concentric hypertrophy than NPH after adjusting for age and blood pressure. In conclusion, this study showed that PH may exhibit worse blood pressure control and adverse left ventricular remodeling compared with NPH.

  2. Adverse prognostic value of persistent office blood pressure elevation in white coat hypertension.

    Science.gov (United States)

    Mancia, Giuseppe; Facchetti, Rita; Grassi, Guido; Bombelli, Michele

    2015-08-01

    Stratification of cardiovascular risk is of fundamental importance in white coat hypertension (WCH) to identify individuals in need of closer follow-up and perhaps antihypertensive drug treatment. In subjects representative of the general population of Monza (Italy), the risk of cardiovascular and all-cause mortality was assessed >16 years in stable and unstable WCH individuals, that is, those in whom ambulatory blood pressure (BP) normality was associated with a persistent or nonpersistent office BP elevation at 2 consecutive visits, respectively. Data were compared with those from an entirely normotensive group, that is, ambulatory and persistent office BP normality. Compared with the normotensive group, the risk of cardiovascular and all-cause death was not significantly different in unstable WCH, whereas in stable WCH the risk was increased also when data were adjusted for baseline confounders, including ambulatory BP (hazard ratio, 16; P=0.001 for cardiovascular death and 1.92; P=0.02 for all-cause death). At a multivariable analysis, office BP was among the factors independently predicting death, and results were superimposable with use of Monza population-derived and guidelines-derived cutoff values for ambulatory BP normality (125/79 and 130/80 mm Hg, respectively). Thus, only when office BP is persistently elevated does WCH reflect the existence of an abnormal long-term mortality risk. This means that in WCH office BP is prognostically relevant and that repeated collection of its values is clinically important to better define patient risk.

  3. A comparison of methods for computing the sigma-coordinate pressure gradient force for flow over sloped terrain in a hybrid theta-sigma model

    Science.gov (United States)

    Johnson, D. R.; Uccellini, L. W.

    1983-01-01

    In connection with the employment of the sigma coordinates introduced by Phillips (1957), problems can arise regarding an accurate finite-difference computation of the pressure gradient force. Over steeply sloped terrain, the calculation of the sigma-coordinate pressure gradient force involves computing the difference between two large terms of opposite sign which results in large truncation error. To reduce the truncation error, several finite-difference methods have been designed and implemented. The present investigation has the objective to provide another method of computing the sigma-coordinate pressure gradient force. Phillips' method is applied for the elimination of a hydrostatic component to a flux formulation. The new technique is compared with four other methods for computing the pressure gradient force. The work is motivated by the desire to use an isentropic and sigma-coordinate hybrid model for experiments designed to study flow near mountainous terrain.

  4. A General Pressure Gradient Formulation for Ocean Models, Part 1: Scheme Design and Diagnostic Analysis, Part II: Energy, Momentum, and Bottom Torque Consistency

    Science.gov (United States)

    Song, Y. T.

    1998-01-01

    A Jacobian formulation of the pressure gradient force for use in models with topography following coordinates is proposed. It can be used in conjunction with any vertical coordinate system and is easily implemented.

  5. Adverse ventricular-ventricular interactions in right ventricular pressure load: Insights from pediatric pulmonary hypertension versus pulmonary stenosis.

    Science.gov (United States)

    Driessen, Mieke M P; Hui, Wei; Bijnens, Bart H; Dragulescu, Andreea; Mertens, Luc; Meijboom, Folkert J; Friedberg, Mark K

    2016-06-01

    Right ventricular (RV) pressure overload has a vastly different clinical course in children with idiopathic pulmonary arterial hypertension (iPAH) than in children with pulmonary stenosis (PS). While RV function is well recognized as a key prognostic factor in iPAH, adverse ventricular-ventricular interactions and LV dysfunction are less well characterized and the pathophysiology is incompletely understood. We compared ventricular-ventricular interactions as hypothesized drivers of biventricular dysfunction in pediatric iPAH versus PS Eighteen iPAH, 16 PS patients and 18 age- and size-matched controls were retrospectively studied. Cardiac cycle events were measured by M-mode and Doppler echocardiography. Measurements were compared between groups using ANOVA with post hoc Dunnet's or ANCOVA including RV systolic pressure (RVSP; iPAH 96.8 ± 25.4 mmHg vs. PS 75.4 ± 18.9 mmHg; P = 0.011) as a covariate. RV-free wall thickening was prolonged in iPAH versus PS, extending beyond pulmonary valve closure (638 ± 76 msec vs. 562 ± 76 msec vs. 473 ± 59 msec controls). LV and RV isovolumetric relaxation were prolonged in iPAH (P < 0.001; LV 102.8 ± 24.1 msec vs. 63.1 ± 13.7 msec; RV 95 [61-165] vs. 28 [0-43]), associated with adverse septal kinetics; characterized by rightward displacement in early systole and leftward displacement in late RV systole (i.e., early LV diastole). Early LV diastolic filling was decreased in iPAH (73 ± 15.9 vs. PS 87.4 ± 14.4 vs. controls 95.8 ± 12.5 cm/sec; P = 0.004). Prolonged RVFW thickening, prolonged RVFW isovolumetric times, and profound septal dyskinesia are associated with interventricular mechanical discoordination and decreased early LV filling in pediatric iPAH much more than PS These adverse mechanics affect systolic and diastolic biventricular efficiency in iPAH and may form the basis for worse clinical outcomes. We used clinically derived data to study the pathophysiology of ventricular

  6. A Study of the Development of Steady and Periodic Unsteady Turbulent Wakes Through Curved Channels at Positive, Zero, and Negative Streamwise Pressure Gradients, Part 1

    Science.gov (United States)

    Schobeiri, M. T.; John, J.

    1996-01-01

    The turbomachinery wake flow development is largely influenced by streamline curvature and streamwise pressure gradient. The objective of this investigation is to study the development of the wake under the influence of streamline curvature and streamwise pressure gradient. The experimental investigation is carried out in two phases. The first phase involves the study of the wake behind a stationary circular cylinder (steady wake) in curved channels at positive, zero, and negative streamwise pressure gradients. The mean velocity and Reynolds stress components are measured using a X-hot-film probe. The measured quantities obtained in probe coordinates are transformed to a curvilinear coordinate system along the wake centerline and are presented in similarity coordinates. The results of the steady wakes suggest strong asymmetry in velocity and Reynolds stress components. However, the velocity defect profiles in similarity coordinates are almost symmetrical and follow the same distribution as the zero pressure gradient straight wake. The results of Reynolds stress distributions show higher values on the inner side of the wake than the outer side. Other quantities, including the decay of maximum velocity defect, growth of wake width, and wake integral parameters, are also presented for the three different pressure gradient cases of steady wake. The decay rate of velocity defect is fastest for the negative streamwise pressure gradient case and slowest for the positive pressure gradient case. Conversely, the growth of the wake width is fastest for the positive streamwise pressure gradient case and slowest for the negative streamwise pressure gradient. The second phase studies the development of periodic unsteady wakes generated by the circular cylinders of the rotating wake generator in a curved channel at zero streamwise pressure gradient. Instantaneous velocity components of the periodic unsteady wakes, measured with a stationary X-hot-film probe, are analyzed by the

  7. NUMERICAL INVESTIGATION OF TURBULENT COUNTER-GRADIENT-TRANSPORT IN ASYMMETRIC FLOW WITH A JET

    Institute of Scientific and Technical Information of China (English)

    QIU Xiang; GUO Hui-fen; LIU Yu-lu

    2004-01-01

    By using the Reynolds Stress Closure Model(RSM), turbulent Counter-Gradient-Transport (CGT) phenomenon was numerically investigated in asymmetric flow with a jet, and the computational results were compared with experimental data. The computational results show that the negative turbulent energy production only appears at some certain stations in CGT region, this fact indicates that the CGT phenomenon exists more widely than the negative turbulent energy production; while the CGT region exists all along,it gradually shrinks in the favorable pressure gradient zone until the position of the wing central part is reached, where it vanishes, but it appears in the adverse pressure gradient region; in addition, the location in the flow where uv = 0 switched sides, relative to where ()U/()y = 0, from favorable pressure gradient to adverse pressure gradient. The pressure gradient takes an important effect on the region of negative turbulent energy production and CGT.

  8. Calculation and analysis of velocity and viscous drag in an artery with a periodic pressure gradient

    Science.gov (United States)

    Alizadeh, M.; Seyedpour, S. M.; Mozafari, V.; Babazadeh, Shayan S.

    2012-07-01

    Blood as a fluid that human and other living creatures are dependent on has been always considered by scientists and researchers. Any changes in blood pressure and its normal velocity can be a sign of a disease. Whatever significant in blood fluid's mechanics is Constitutive equations and finding some relations for analysis and description of drag, velocity and periodic blood pressure in vessels. In this paper, by considering available experimental quantities, for blood pressure and velocity in periodic time of a thigh artery of a living dog, at first it is written into Fourier series, then by solving Navier-Stokes equations, a relation for curve drawing of vessel blood pressure with rigid wall is obtained. Likewise in another part of this paper, vessel wall is taken in to consideration that vessel wall is elastic and its pressure and velocity are written into complex Fourier series. In this case, by solving Navier-Stokes equations, some relations for blood velocity, viscous drag on vessel wall and blood pressure are obtained. In this study by noting that vessel diameter is almost is large (3.7 mm), and blood is considered as a Newtonian fluid. Finally, available experimental quantities of pressure with obtained curve of solving Navier-Stokes equations are compared. In blood analysis in rigid vessel, existence of 48% variance in pressure curve systole peak caused vessel blood flow analysis with elastic wall, results in new relations for blood flow description. The Resultant curve is obtained from new relations holding 10% variance in systole peak.

  9. Limit analysis of viscoplastic thick-walled cylinder and spherical shell under internal pressure using a strain gradient plasticity theory

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Plastic limit load of viscoplastic thick-walled cylinder and spherical shell subjected to internal pressure is investigated analytically using a strain gradient plastic-itv theory. As a result, the current solutions can capture the size effect at the micron scale. Numerical results show that the smaller the inner radius of the cylinder or spherical shell, the more significant the scale effects. Results also show that the size effect is more evident with increasing strain or strain-rate sensitivity index. The classical plastic-based solutions of the same problems are shown to be a special case of the present solution.

  10. Aerodynamic pressure and heating-rate distributions in tile gaps around chine regions with pressure gradients at a Mach number of 6.6

    Science.gov (United States)

    Hunt, L. Roane; Notestine, Kristopher K.

    1990-06-01

    Surface and gap pressures and heating-rate distributions were obtained for simulated Thermal Protection System (TPS) tile arrays on the curved surface test apparatus of the Langley 8-Foot High Temperature Tunnel at Mach 6.6. The results indicated that the chine gap pressures varied inversely with gap width because larger gap widths allowed greater venting from the gap to the lower model side pressures. Lower gap pressures caused greater flow ingress from the surface and increased gap heating. Generally, gap heating was greater in the longitudinal gaps than in the circumferential gaps. Gap heating decreased with increasing gap depth. Circumferential gap heating at the mid-depth was generally less than about 10 percent of the external surface value. Gap heating was most severe at local T-gap junctions and tile-to-tile forward-facing steps that caused the greatest heating from flow impingement. The use of flow stoppers at discrete locations reduced heating from flow impingement. The use of flow stoppers at discrete locations reduced heating in most gaps but increased heating in others. Limited use of flow stoppers or gap filler in longitudinal gaps could reduce gap heating in open circumferential gaps in regions of high surface pressure gradients.

  11. Validation of pressure gradient and peripheral fractional flow reserve measured by a pressure wire for diagnosis of iliofemoral artery disease with intermediate stenosis

    Directory of Open Access Journals (Sweden)

    Murata N

    2015-11-01

    Full Text Available Naotaka Murata,1 Hideaki Aihara,2 Yoshimitsu Soga,1 Yusuke Tomoi,1 Seiichi Hiramori,1 Yohei Kobayashi,1 Kei Ichihashi,1 Nobuhiro Tanaka3 1Department of Cardiology, Kokura Memorial Hospital, Kitakyushu, 2Department of Cardiology, Tsukuba Medical Center Hospital, Ibaraki, 3Department of Cardiology, Tokyo Medical University, Tokyo, Japan Objective: To examine the pressure gradient and peripheral fractional flow reserve (pFFR measured by a pressure wire as indicators of hemodynamic significance in iliofemoral angiographic intermediate stenosis. Background: The utility of pressure measurements using a pressure wire with vasodilators is unclear in cases with intermediate iliofemoral stenosis. Methods: The mean pressure gradient (MPG and mean pressure ratio (MPR were measured at baseline and after injection of isosorbide dinitrate in 23 lesions with angiographically intermediate iliofemoral stenosis. Patients with complex lesions, infrapopliteal artery lesions, chronic total occlusion, and surgical bypass grafts were excluded. Hyperemic MPR was considered equivalent to pFFR. Changes in parameters in response to vasodilators were assessed and correlations of peak systolic velocity ratio (PSVR with hyperemic MPG and pFFR were examined using duplex ultrasound. Results: After injection of isosorbide dinitrate, hyperemic MPG increased significantly (from 9.0±5.7 to 16.3±6.2 mmHg; P<0.05 and hyperemic MPR (pFFR decreased significantly (from 0.92±0.06 to 0.81±0.07; P<0.05. PSVR was significantly correlated with hyperemic MPG (R=0.52; P<0.05 and pFFR (R=–0.50; P<0.05. The optimal cut-off value of pFFR as an indicator of significant hemodynamic stenosis (PSVR >2.5 was 0.85 (area under the curve 0.72; sensitivity 94%; specificity 50%, P<0.05. Conclusion: pFFR measured using a pressure wire is reliable for prediction of hemodynamic significance in iliofemoral intermediate stenosis. Keywords: endovascular therapy, peripheral artery disease, pressure

  12. High-order accurate finite-volume formulations for the pressure gradient force in layered ocean models

    CERN Document Server

    Engwirda, Darren; Marshall, John

    2016-01-01

    The development of a set of high-order accurate finite-volume formulations for evaluation of the pressure gradient force in layered ocean models is described. A pair of new schemes are presented, both based on an integration of the contact pressure force about the perimeter of an associated momentum control-volume. The two proposed methods differ in their choice of control-volume geometries. High-order accurate numerical integration techniques are employed in both schemes to account for non-linearities in the underlying equation-of-state definitions and thermodynamic profiles, and details of an associated vertical interpolation and quadrature scheme are discussed in detail. Numerical experiments are used to confirm the consistency of the two formulations, and it is demonstrated that the new methods maintain hydrostatic and thermobaric equilibrium in the presence of strongly-sloping layer-wise geometry, non-linear equation-of-state definitions and non-uniform vertical stratification profiles. Additionally, one...

  13. Computation of Flow in a Circular Cylinder Driven by Coaxial Screw Rotation and an Opposing Pressure Gradient.

    Science.gov (United States)

    Cotrell, David L.; Pearlstein, Arne J.

    2000-11-01

    We report computations of the velocity field for flows driven by rotation of a screw in a circular cylinder with an applied opposing pressure gradient. Use of a helical coordinate system in a frame rotating with the screw reduces the flow calculation to a steady one, which is taken to be fully-developed in the helical direction. The full incompressible Navier-Stokes equations in primitive-variables form are solved numerically using a finite-element method employing quadrilateral elements with quadratic velocity and linear pressure interpolation. A consistent penalty method is used to satisfy incompressibility. The screw cross-section is rectangular. The effect of screw clearance and other geometric parameters on the velocity field will be discussed for low and intermediate Reynolds numbers and compared to the Stokes flow case.

  14. Social class-related gradient in the association of skeletal growth with blood pressure among adolescent boys in India.

    Science.gov (United States)

    Rao, Shobha; Apte, Priti

    2009-12-01

    In view of the fact that height differences between socio-economic groups are apparent early in childhood, it is of interest to examine whether skeletal growth is reflective of the social class gradient in CVD risk. The present study examined blood pressure levels, adiposity and growth of adolescent boys from high and low social classes. In a cross-sectional study, skeletal growth (height and sitting height), adiposity (weight, BMI and body fat) and blood pressure levels of the adolescents were measured. Pune, India. Adolescent schoolboys (9-16 years) from high socio-economic (HSE; n 1146) and low socio-economic (LSE; n 932) class. LSE boys were thin, short and undernourished (mean BMI: 15.5 kg/m2 v. 19.3 kg/m2 in HSE boys, P = 0.00). Social gradient was revealed in differing health risks. The prevalence of high systolic blood pressure (HSBP) was high in HSE class (10.5 % v. 2.7 % in LSE class, P = 0.00) and was associated with adiposity, while the prevalence of high diastolic blood pressure (HDBP) was high in LSE class (9.8 % v. 7.0 % in HSE class, P = 0.00) and had only a weak association with adiposity. Despite this, lower ratio of leg length to height was associated with significantly higher respective health risks, i.e. for HDBP in LSE class (OR = 1.99, 95 % CI 1.14, 3.47) and for HSBP in HSE class (OR = 1.69, 95 % CI 1.02, 2.77). As stunting in childhood is a major problem in India and Asia, the leg length to height indicator needs to be validated in different populations to understand CVD risks.

  15. End-tidal arterial CO2 partial pressure gradient in patients with severe hypercapnia undergoing noninvasive ventilation

    Directory of Open Access Journals (Sweden)

    Defilippis V

    2013-06-01

    Full Text Available Vito Defilippis,1 Davide D’Antini,2 Gilda Cinnella,2 Michele Dambrosio,2 Fernando Schiraldi,3 Vito Procacci1 1Emergency Department, Riuniti Hospital, 2Department of Anaesthesiology and Intensive Care, University of Foggia, Foggia, 3Emergency Department, San Paolo Hospital, Naples, Italy Background: Patients with severe hypercapnia represent a particularly serious condition in an emergency department (ED, requiring immediate attention. Noninvasive ventilation (NIV is an integral part of the treatment for acute respiratory failure. The present study aimed to validate the measurement of end-tidal CO2 (EtCO2 as a noninvasive technique to evaluate the effectiveness of NIV in acute hypercapnic respiratory failure. Methods: Twenty consecutive patients admitted to the ED with severe dyspnea were enrolled in the study. NIV by means of bilevel positive airway pressure, was applied to the patients simultaneously with standard medical therapy and continued for 12 hours; the arterial blood gases and side-stream nasal/oral EtCO2 were measured at subsequent times: T0 (admission to the ED, T1h (after 1 hour, T6h (after 6 hours, and T12h (after 12 hours during NIV treatment. Results: The arterial CO2 partial pressure (PaCO2–EtCO2 gradient decreased progressively, reaching at T6h and T12h values lower than baseline (P < 0.001, while arterial pH increased during the observation period (P < 0.001. A positive correlation was found between EtCO2 and PaCO2 values (r = 0.89, P < 0.001 at the end of the observation period. Conclusion: In our hypercapnic patients, the effectiveness of the NIV was evidenced by the progressive reduction of the PaCO2–EtCO2 gradient. The measurement of the CO2 gradient could be a reliable method in monitoring the effectiveness of NIV in acute hypercapnic respiratory failure in the ED. Keywords: arterial end-tidal CO2 gradient, noninvasive ventilation, bilevel positive airway pressure, acute respiratory failure

  16. Fountain streaming contributes to fast tip-growth through regulating the gradients of turgor pressure and concentration in pollen tubes.

    Science.gov (United States)

    Liu, ShaoBao; Liu, Han; Feng, ShangSheng; Lin, Min; Xu, Feng; Lu, Tian Jian

    2017-04-19

    Fountain streaming is a typical microfluidic pattern in plant cells, especially for cells with a high aspect ratio such as pollen tubes. Although it has been found that fountain streaming plays crucial roles in the transport of nutrients and metabolites, the positioning of organelles and the mixing of cytoplasms, its implications for the fast tip growth of pollen tubes remain a mystery. To address this, based on the observations of asiatic lily Lilium Casablanca, we developed physical models for reverse fountain streaming in pollen tubes and solved the hydrodynamics and advection-diffusion dynamics of viscous Stokes flow in the shank and apical region of pollen tubes. Theoretical and numerical results demonstrated that the gradients of turgor pressure and concentration of wall materials along the length of pollen tubes provide undamped driving force and high-efficiency materials supply, which are supposed to contribute to the fast tip-growth of pollen tubes. The sample experimental results show that the tip-growth will be abnormal when the gradients of turgor pressure change under osmotic stress induced by different concentrations of PEG-6000 (a dehydrant).

  17. Rationale, design and methodology for Intraventricular Pressure Gradients Study: a novel approach for ventricular filling assessment in normal and falling hearts

    Directory of Open Access Journals (Sweden)

    Vouga Luís

    2011-05-01

    Full Text Available Abstract Background Intraventricular pressure gradients have been described between the base and the apex of the left ventricle during early diastolic ventricular filling, as well as, their increase after systolic and diastolic function improvement. Although, systolic gradients have also been observed, data are lacking on their magnitude and modulation during cardiac dysfunction. Furthermore, we know that segmental dysfunction interferes with the normal sequence of regional contraction and might be expected to alter the physiological intraventricular pressure gradients. The study hypothesis is that systolic and diastolic gradients, a marker of normal left ventricular function, may be related to physiological asynchrony between basal and apical myocardial segments and they can be attenuated, lost entirely, or even reversed when ventricular filling/emptying is impaired by regional acute ischemia or severe aortic stenosis. Methods/Design Animal Studies: Six rabbits will be completely instrumented to measuring apex to outflow-tract pressure gradient and apical and basal myocardial segments lengthening changes at basal, afterloaded and ischemic conditions. Afterload increase will be performed by abruptly narrowing or occluding the ascending aorta during the diastole and myocardial ischemia will be induced by left coronary artery ligation, after the first diagonal branch. Patient Studies: Patients between 65-80 years old (n = 12, both genders, with severe aortic stenosis referred for aortic valve replacement will be selected as eligible subjects. A high-fidelity pressure-volume catheter will be positioned through the ascending aorta across the aortic valve to measure apical and outflow-tract pressure before and after aortic valve replacement with a bioprosthesis. Peak and average intraventricular pressure gradients will be recorded as apical minus outflow-tract pressure and calculated during all diastolic and systolic phases of cardiac cycle

  18. Combined effect of salt concentration and pressure gradients across charged membranes

    DEFF Research Database (Denmark)

    Benavente, Juana; Jonsson, Gunnar Eigil

    2002-01-01

    The combined effect of both concentration and pressure differences on electrical potential (Deltaphi) for two ion-exchanger membranes, one positively charged (AE) and another negatively charged (CE), measured with the membranes in contact with NaCl solutions was studied. Results show a linear...... dependence between Deltaphi and pressure, independently if DeltaC and DeltaP have the same or opposite directions. The ratio of the streaming potential for cation/anion exchange membranes is r = (2.1+/-0.4). A "bipolar" membrane (BM) was obtained by joining together both ion-exchanger membranes. In order...... to correlate the behaviour of the BP membrane with that corresponding to each sublayer, the same kind of measurements was carried out for both opposite external conditions, this means, applying the pressure on the cation exchanger (CABM) or on the anion exchanger membrane (ACBM), respectively. From values...

  19. Salinity-gradient power : Evaluation of pressure-retarded osmosis and reverse electrodialysis

    NARCIS (Netherlands)

    Post, Jan W.; Veerman, Joost; Hamelers, Hubertus V.M.; Euverink, Gerrit J.W.; Metz, Sybrand J.; Nymeijer, Kitty; Buisman, Cees J.N.

    2007-01-01

    A huge potential to obtain clean energy exists from mixing water streams with different salt concentrations. Two membrane-based energy conversion techniques are evaluated: pressure-retarded osmosis and reverse electrodialysis. From the literature, a comparison is not possible since the reported perf

  20. Estimates of pressure gradients in PEMFC gas channels due to blockage by static liquid drops

    Energy Technology Data Exchange (ETDEWEB)

    Venkatraman, M.; Shimpalee, S.; Van Zee, J.W. [Department of Chemical Engineering, University of South Carolina, 301 Main St., Columbia, SC 29208 (United States); Moon, Sung In; Extrand, C.W. [Entegris, Inc., 3500 Lyman Boulevard, Chaska, MN 55318 (United States)

    2009-07-15

    Numerical analyses are presented to explain the effect of drop size and contact angle on local pressures inside small channels. These pressures and channel characteristics are of interest when water condenses in the gas channels of Proton Exchange Membrane Fuel Cells and hence the study uses Reynolds numbers consistent with as typical utilization of reacting gases in 200 cm{sup 2} flow fields (i.e., 200 < Re < 1500 and stoichiometries of 1.2-2.0 at 1.0 A/cm{sup 2}). The analyses were performed using three-dimensional computational fluid dynamic techniques and the results show that pressure drops are minimal until the blockage was greater than 50%. As blockage increased further, due to larger drops or increased hydrophobicity, pressure drop increased. The results of a stagnant drop are supported by visualization experiments, which show minimal distortion of the drop for these low flow rates, small ratios, and hydrophobic contact angles. Proper scaling parameters and design criteria for microchannels validation experiments are presented. (author)

  1. Salinity-gradient power: Evaluation of pressure-retarded osmosis and reverse electrodialysis

    NARCIS (Netherlands)

    Post, J.W.; Veerman, J.; Hamelers, H.V.M.; Euverink, G.J.W.; Metz, S.J.; Nymeijer, K.; Buisman, C.J.N.

    2007-01-01

    A huge potential to obtain clean energy exists from mixing water streams with different salt concentrations. Two membrane-based energy conversion techniques are evaluated: pressure-retarded osmosis and reverse electrodialysis. From the literature, a comparison is not possible since the reported perf

  2. Thermal studies of a high gradient quadrupole magnet cooled with pressurized, stagnant superfluid

    CERN Document Server

    Chiesa, L; Kerby, J S; Lamm, M J; Novitski, I; Orris, D; Ozelis, J P; Peterson, Thomas J; Tartaglia, M; Zlobin, A V

    2001-01-01

    A 2-m long superconducting model of an LHC Interaction Region quadrupole magnet was wound with stabrite coated cable. The resulting low interstrand resistance and high AC losses presented the opportunity to measure magnet quench performance in superfluid as a function of helium temperature and heat deposition in the coil. Our motivation was to duplicate the high radiation heat loads predicted for the inner triplet quadrupoles at LHC and study the coil cooling conditions in the magnet. At the Magnet Test Facility in Fermilab's Technical Division, the magnet quench performance was tested as a function of bulk helium temperature and current ramp rate near the planned high luminosity interaction region field gradient of 205 T/m. AC loss measurements provided a correlation between current ramp rate and heat deposition in the coil. Analysis indicates that the results are consistent with there being little participation of superfluid helium in the small channels inside the inner layer in the heat removal from the co...

  3. Bimatoprost ophthalmic solution 0.03% lowered intraocular pressure of normal-tension glaucoma with minimal adverse events

    Directory of Open Access Journals (Sweden)

    Tsumura T

    2012-09-01

    Full Text Available Toyoaki Tsumura,1 Keiji Yoshikawa,2 Hirotaka Suzumura,3 Tairo Kimura,4 Satoshi Sasaki,5 Itaru Kimura,6 Ryuji Takeda71Department of Ophthalmology, Fussa Hospital, Fussa, Tokyo, Japan; 2Yoshikawa Eye Clinic, Machida, Tokyo, Japan; 3Department of Ophthalmology, Nakano General Hospital, Nakano, Tokyo, Japan; 4Ueno Eye Clinic, Ueno, Tokyo, Japan; 5Sasaki Eye Clinic, Ueno, Tokyo, Japan; 6Department of Ophthalmology, Juntendo University Urayasu Hospital, Urayasu, Chiba, Japan; 7Department of Biological Chemistry, Faculty of Agriculture, Kinki University, Nara, Nara, JapanPurpose: The aim of this study was to evaluate the efficacy and safety of bimatoprost ophthalmic solution 0.03% (bimatoprost in Japanese normal-tension glaucoma (NTG patients with an intraocular pressure (IOP of 18 mmHg or less.Methods: Bimatoprost was instilled into the unilateral conjunctival sac of Japanese NTG patients with a baseline IOP of 18 mmHg or less. The time courses of IOP, conjunctival hyperemia, superficial punctate keratitis, and adverse events were examined at 2, 4, 8, and 12 weeks post bimatoprost instillation.Results: Thirty-two of the 38 enrolled NTG patients (mean age, 64.1 ± 12.6 years; 19 males and 19 females completed the study, with six patients unable to complete the study (two patients discontinued because of side effects and four patients withdrew. The levels of IOP in the treated eyes were significantly reduced (P < 0.0001 from the baseline IOP levels. No significant change in IOP was observed in the fellow eyes. There were significant increases in conjunctival hyperemia. No significant superficial punctate keratitis scores were noted between the baseline and each point examined. Eyelash disorder, eyelid pigmentation, and deepening of the upper eyelid sulcus were observed in 28, six, and three eyes, respectively.Conclusion: Bimatoprost effectively lowered the IOP. It was well tolerated in Japanese NTG patients, with few patients having to discontinue

  4. Performance limiting effects in power generation from salinity gradients by pressure retarded osmosis.

    Science.gov (United States)

    Yip, Ngai Yin; Elimelech, Menachem

    2011-12-01

    Pressure retarded osmosis has the potential to utilize the free energy of mixing when fresh river water flows into the sea for clean and renewable power generation. Here, we present a systematic investigation of the performance limiting phenomena in pressure retarded osmosis--external concentration polarization, internal concentration polarization, and reverse draw salt flux--and offer insights on the design criteria of a high performance pressure retarded osmosis power generation system. Thin-film composite polyamide membranes were chemically modified to produce a range of membrane transport properties, and the water and salt permeabilities were characterized to determine the underlying permeability-selectivity trade-off relationship. We show that power density is constrained by the trade-off between permeability and selectivity of the membrane active layer. This behavior is attributed to the opposing influence of the beneficial effect of membrane water permeability and the detrimental impact of reverse salt flux coupled with internal concentration polarization. Our analysis reveals the intricate influence of active and support layer properties on power density and demonstrates that membrane performance is maximized by tailoring the water and salt permeabilities to the structural parameters. An analytical parameter that quantifies the relative influence of each performance limiting phenomena is employed to identify the dominant effect restricting productivity. External concentration polarization is shown to be the main factor limiting performance at high power densities. Enhancement of the hydrodynamic flow conditions in the membrane feed channel reduces external concentration polarization and thus, yields improved power density. However, doing so will also incur additional operating costs due to the accompanying hydraulic pressure loss. This study demonstrates that by thoughtful selection of the membrane properties and hydrodynamic conditions, the detrimental

  5. Performance Limiting Effects in Power Generation from Salinity Gradients by Pressure Retarded Osmosis

    KAUST Repository

    Yip, Ngai Yin

    2011-12-01

    Pressure retarded osmosis has the potential to utilize the free energy of mixing when fresh river water flows into the sea for clean and renewable power generation. Here, we present a systematic investigation of the performance limiting phenomena in pressure retarded osmosis-external concentration polarization, internal concentration polarization, and reverse draw salt flux-and offer insights on the design criteria of a high performance pressure retarded osmosis power generation system. Thin-film composite polyamide membranes were chemically modified to produce a range of membrane transport properties, and the water and salt permeabilities were characterized to determine the underlying permeability-selectivity trade-off relationship. We show that power density is constrained by the trade-off between permeability and selectivity of the membrane active layer. This behavior is attributed to the opposing influence of the beneficial effect of membrane water permeability and the detrimental impact of reverse salt flux coupled with internal concentration polarization. Our analysis reveals the intricate influence of active and support layer properties on power density and demonstrates that membrane performance is maximized by tailoring the water and salt permeabilities to the structural parameters. An analytical parameter that quantifies the relative influence of each performance limiting phenomena is employed to identify the dominant effect restricting productivity. External concentration polarization is shown to be the main factor limiting performance at high power densities. Enhancement of the hydrodynamic flow conditions in the membrane feed channel reduces external concentration polarization and thus, yields improved power density. However, doing so will also incur additional operating costs due to the accompanying hydraulic pressure loss. This study demonstrates that by thoughtful selection of the membrane properties and hydrodynamic conditions, the detrimental

  6. Extreme Air Pollution Conditions Adversely Affect Blood Pressure and Insulin Resistance: The Air Pollution and Cardiometabolic Disease Study.

    Science.gov (United States)

    Brook, Robert D; Sun, Zhichao; Brook, Jeffrey R; Zhao, Xiaoyi; Ruan, Yanping; Yan, Jianhua; Mukherjee, Bhramar; Rao, Xiaoquan; Duan, Fengkui; Sun, Lixian; Liang, Ruijuan; Lian, Hui; Zhang, Shuyang; Fang, Quan; Gu, Dongfeng; Sun, Qinghua; Fan, Zhongjie; Rajagopalan, Sanjay

    2016-01-01

    Mounting evidence supports that fine particulate matter adversely affects cardiometabolic diseases particularly in susceptible individuals; however, health effects induced by the extreme concentrations within megacities in Asia are not well described. We enrolled 65 nonsmoking adults with metabolic syndrome and insulin resistance in the Beijing metropolitan area into a panel study of 4 repeated visits across 4 seasons since 2012. Daily ambient fine particulate matter and personal black carbon levels ranged from 9.0 to 552.5 µg/m(3) and 0.2 to 24.5 µg/m(3), respectively, with extreme levels observed during January 2013. Cumulative fine particulate matter exposure windows across the prior 1 to 7 days were significantly associated with systolic blood pressure elevations ranging from 2.0 (95% confidence interval, 0.3-3.7) to 2.7 (0.6-4.8) mm Hg per SD increase (67.2 µg/m(3)), whereas cumulative black carbon exposure during the previous 2 to 5 days were significantly associated with ranges in elevations in diastolic blood pressure from 1.3 (0.0-2.5) to 1.7 (0.3-3.2) mm Hg per SD increase (3.6 µg/m(3)). Both black carbon and fine particulate matter were significantly associated with worsening insulin resistance (0.18 [0.01-0.36] and 0.22 [0.04-0.39] unit increase per SD increase of personal-level black carbon and 0.18 [0.02-0.34] and 0.22 [0.08-0.36] unit increase per SD increase of ambient fine particulate matter on lag days 4 and 5). These results provide important global public health warnings that air pollution may pose a risk to cardiometabolic health even at the extremely high concentrations faced by billions of people in the developing world today.

  7. Evanescent pressure gradient response in the upper ocean to subinertial wind stress forcing of finite wavelength

    Science.gov (United States)

    White, Warren B.; Mcnally, Gerard

    1987-01-01

    A schematic model is used to interpret field observations related to the mixed layer response to wind stress at subinertial frequencies. It is shown that subinertial density and pressure fluctuations can arise locally from the finite wavelength character of the wind stress forcing as a fundamental part of the upper ocean transient, wind-driven response on time scales of 2-10 pendulum days. Evanescent vertical motions arise which alter the density field of the pycnocline, and hence the pressure field over the entire upper ocean. It is thus found that in the real ocean driven by wind stress, a transient geostrophic response exists which can be as large or larger than the transient Eckman response.

  8. Control of Separation for Turbulent Boundary Layers Subjected to Wall Curvature and Streamwise Pressure Gradients

    Science.gov (United States)

    2007-11-02

    the pressure side were studied. The same case, at the higher Reynolds number of 148,000, was also studied by Xiaohua and Durbin (2001). They used a...with the Boussinesq- assumption or the explicit algebraic Reynolds stress model (EASM) by Gatski (Gatski and Sepziale 1993, Gatski and Jongen 2000...approximation is employed for computing the Reynolds stresses. When the Explicit Algebraic Stress Model (EASM) is used, the turbulence equations are

  9. Scrape-off Layer Flows With Pressure Gradient Scale Length ~ {rho}{sub p}

    Energy Technology Data Exchange (ETDEWEB)

    Robert J. Goldston

    2013-03-08

    A heuristic model for the plasma scrape-off width balances magnetic drifts against parallel loss at c{sub s} /2, resulting in a SOL width ~ {rho}{sub p}. T{sub sep} is calculated from Spitzer–Härm parallel thermal conduction. This results in a prediction for the power scrape-off width in quantitative agreement both in magnitude and scaling with recent experimental data. To achieve the ~ c{sub s} /2 flow assumed in this model and measured experimentally sets requirements on the ratio of upstream to total SOL particle sources, relative to the square-root of the ratio of target to upstream temperature. The Pfisch-Schlüter model for equilibrium flows has been modified to allow near-sonic flows, appropriate for gradient scale lengths of order {rho}{sub p}, resulting in a new quadrupole radial flow pattern. The strong parallel flows and plasma charging implied by this model suggest a mechanism for H-mode transition, consistent with many observations

  10. Scrape-off layer flows with pressure gradient scale length ∼ρ{sub p}

    Energy Technology Data Exchange (ETDEWEB)

    Goldston, Robert J., E-mail: rgoldston@pppl.gov [Princeton Plasma Physics Laboratory, MS-41, Princeton, NJ 08543 (United States)

    2013-07-15

    A heuristic model for the plasma scrape-off width balances magnetic drifts against parallel loss at c{sub s}/2, resulting in a SOL width ∼ρ{sub p}. T{sub sep} is calculated from Spitzer–Härm parallel thermal conduction. This results in a prediction for the power scrape-off width in quantitative agreement both in magnitude and scaling with recent experimental data. To achieve the ∼c{sub s}/2 flow assumed in this model and measured experimentally sets requirements on the ratio of upstream to total SOL particle sources, relative to the square-root of the ratio of target to upstream temperature. The Pfisch–Schlüter model for equilibrium flows has been modified to allow near-sonic flows, appropriate for gradient scale lengths of order ρ{sub p}, resulting in a new quadrupole radial flow pattern. The strong parallel flows and plasma charging implied by this model suggest a mechanism for H-mode transition, consistent with many observations.

  11. Effects of predation pressure on species packing on a resource gradient: insights from nonlinear dynamics.

    Science.gov (United States)

    Vandermeer, John; Liere, Heidi; Lin, Brenda

    2006-06-01

    The classical case of three competitors arranged on a resource gradient such that the central competitor will be excluded due to competition from the other two is studied from the point of view of the effects of added predators. The basic formulation is motivated by a desire to understand the effects of asymmetries in multidimensional Lotka-Volterra systems. We first study the effects of perfectly specialist predators and find a rich collection of possible behaviors of the system including (1) extinction of all predators and subsequent extinction of the subordinate competitor, (2) dominant competitors and their predators coexist but the subdominant competitor goes extinct, (3) all species except the predator of the subordinate competitor coexist in coordinated phase-reversed chaos, (4) exclusion of one or more species occurs through an expanding heteroclinic cycle, and (5) all species coexist in an uncoordinated chaos. We then study the effects of five qualitatively distinct forms of polyphagy. In one case, corresponding to the well-known vulnerability to predation versus competitive ability trade-off, it is possible to have the subordinate competitor be the only survivor in the system. The other three cases of polyphagy lead to distortions in the basic pattern seen in the previously analyzed specialist case. Studying this case of ecologically motivated asymmetries in the basic Lotka-Volterra formulation is a step in the direction of fully understanding interacting populations.

  12. Two layer dielectric-electrolyte micro-flow with pressure gradient

    Directory of Open Access Journals (Sweden)

    Ganchenko Georgy

    2016-01-01

    Full Text Available The present work considers stability of two-phase dielectric/electrolyte system, consisting of two immiscible liquids in microchannel. The system is set in motion by the constant external electric field, which causes the electroosmotic flow in the electrolyte, and by the pressure driving force. The investigation of its linear stability has shown that there are two types of instability in the system: short-wave and long-wave instability. The short-wave instability occurs for a stronger external field than the long-wave instability but the growth rate of the short-wave instability is much higher than that of the long-wave instability.

  13. A dynamic response model for pressure sensors in continuum and high Knudsen number flows with large temperature gradients

    Science.gov (United States)

    Whitmore, Stephen A.; Petersen, Brian J.; Scott, David D.

    1996-01-01

    This paper develops a dynamic model for pressure sensors in continuum and rarefied flows with longitudinal temperature gradients. The model was developed from the unsteady Navier-Stokes momentum, energy, and continuity equations and was linearized using small perturbations. The energy equation was decoupled from momentum and continuity assuming a polytropic flow process. Rarefied flow conditions were accounted for using a slip flow boundary condition at the tubing wall. The equations were radially averaged and solved assuming gas properties remain constant along a small tubing element. This fundamental solution was used as a building block for arbitrary geometries where fluid properties may also vary longitudinally in the tube. The problem was solved recursively starting at the transducer and working upstream in the tube. Dynamic frequency response tests were performed for continuum flow conditions in the presence of temperature gradients. These tests validated the recursive formulation of the model. Model steady-state behavior was analyzed using the final value theorem. Tests were performed for rarefied flow conditions and compared to the model steady-state response to evaluate the regime of applicability. Model comparisons were excellent for Knudsen numbers up to 0.6. Beyond this point, molecular affects caused model analyses to become inaccurate.

  14. Spatial variation patterns of subtidal seaweed assemblages along a subtropical oceanic archipelago: Thermal gradient vs herbivore pressure

    Science.gov (United States)

    Sangil, Carlos; Sansón, Marta; Afonso-Carrillo, Julio

    2011-10-01

    The structure and composition of subtidal rocky seaweed assemblages were studied at 69 sites on the Canary Islands (northeastern Atlantic). This group of islands are situated at the southern boundary of the warm temperate region and adjacent to the cold waters from the northwest African coastal upwelling, which creates a difference of almost 2 °C in surface seawater temperature from the eastern to the western islands. This thermal variation allows an examination of the transition between the warm temperate and the tropical regions along this longitudinal gradient together with the hypothesised Fucales-dominated assemblages towards the eastern islands in contrast to the Dictyotales-dominated assemblages towards the western ones. Environmental and biological parameters were considered in order to investigate which were the main factors explaining spatial variation along the gradient in a multi-scaled approach. Although seventy-nine macroalgae were identified, 87.63% of the total mean cover was due to six taxa ( Lobophora variegata, nongeniculate corallines, Canistrocarpus cervicornis, Jania adhaerens, Cystoseira abies-marina and Pseudolithoderma adriaticum). At a large scale, sea urchin density explained the highest variation in seaweed assemblages (26.94%), and its pattern of distribution across the islands. The expected pattern of distribution according to the upwelling distance only occurred in restricted areas of the Canarian Archipelago in absence of herbivore pressure and habitat degradation. Spatial variations within islands (medium scale) were mainly related to wave exposure, while at a small scale these were mostly due to the degree of sedimentation.

  15. Two-phase boundary layer flow and heat transfer with temperature-dependent viscosity and nonzero pressure gradient

    Energy Technology Data Exchange (ETDEWEB)

    Randelia, R.R.; Sahai, V.

    1987-01-01

    A numerical analysis of a two-phase, laminar boundary layer is carried out using the Keller Box method. The two phases are assumed to be immiscible. The problem considered involves the boundary layer flow of a compressible gas with variable properties over a flat surface in the presence of a thin liquid film with power law temperature dependent viscosity. Both zero and nonzero pressure gradients are considered. The main purpose of the study was to investigate the effect of the presence of the liquid layer on the velocity and temperature distributions. A limited set of results are presented in terms of varying liquid Prandtl numbers, film thickness, and viscosity exponents on these distributions as well as the shear stress and heat transfer parameters at the wall and at the interface between the two fluids.

  16. Quantifying predation pressure along an urbanisation gradient in Denmark using artificial caterpillars

    DEFF Research Database (Denmark)

    Ferrante, Marco; Lo Cacciato, Alessandro; Lövei, Gabor L

    2014-01-01

    Urbanisation results in a marked modification of habitats and influences several ecological processes, some of which give rise to beneficial ecological services. Natural pest control, the effect of predators on prey is one of such services. We quantified changes in the incidence of predation with.......3% in suburban and 16.4% in urban forest fragments. Mammals exerted the highest predation pressure in suburban habitats (22.2% vs. 4.9% in forest, and 8.1% in urban forest fragments).......Urbanisation results in a marked modification of habitats and influences several ecological processes, some of which give rise to beneficial ecological services. Natural pest control, the effect of predators on prey is one of such services. We quantified changes in the incidence of predation...... of these to carabids, the most common group of ground-active arthropods. Chewing insects exerted the greatest predation pressure in the original forest (52.1%), with lower values recorded in the suburban (10.1%) and urban (16.4%) forest fragments. Ants were responsible for only 4.7% of the attacks in forest, 11...

  17. Trace element concentrations along a gradient of urban pressure in forest and lawn soils of the Paris region (France).

    Science.gov (United States)

    Foti, Ludovic; Dubs, Florence; Gignoux, Jacques; Lata, Jean-Christophe; Lerch, Thomas Z; Mathieu, Jérôme; Nold, François; Nunan, Naoise; Raynaud, Xavier; Abbadie, Luc; Barot, Sébastien

    2017-11-15

    The concentration, degree of contamination and pollution of 7 trace elements (TEs) along an urban pressure gradient were measured in 180 lawn and wood soils of the Paris region (France). Iron (Fe), a major element, was used as reference element. Copper (Cu), cadmium (Cd), lead (Pb) and zinc (Zn) were of anthropogenic origin, while arsenic (As), chromium (Cr) and nickel (Ni) were of natural origin. Road traffic was identified as the main source of anthropogenic TEs. In addition, the industrial activity of the Paris region, especially cement plants, was identified as secondary source of Cd. Soil characteristics (such as texture, organic carbon (OC) and total nitrogen (tot N) contents) tell the story of the soil origins and legacies along the urban pressure gradient and often can explain TE concentrations. The history of the land-use types was identified as a factor that allowed understanding the contamination and pollution by TEs. Urban wood soils were found to be more contaminated and polluted than urban lawns, probably because woods are much older than lawns and because of the legacy of the historical management of soils in the Paris region (Haussmann period). Lawn soils are similar to the fertile agricultural soils and relatively recently (mostly from the 1950s onwards) imported from the surrounding of Paris, so that they may be less influenced by urban conditions in terms of TE concentrations. Urban wood soils are heavily polluted by Cd, posing a high risk to the biological communities. The concentration of anthropogenic TEs increased from the rural to the urban areas, and the concentrations of most anthropogenic TEs in urban areas were equivalent to or above the regulatory reference values, raising the question of longer-term monitoring. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Evaluation of the effects of pressure gradients on four Brazilian freshwater fish species

    Directory of Open Access Journals (Sweden)

    Paulo dos Santos Pompeu

    2009-02-01

    Full Text Available This work aimed to experimentally evaluate the behavior of Brazilian freshwater fish species when submitted to a gradual increase in pressure, as well as sudden decompression's effects simulating the passage through a hydroelectric turbine. Four species from the São Francisco river basin were tested: Astyanax bimaculatus, Hypostomus sp., Leporinus reinhardti and Prochilodus costatus. For all of them mortality rates due to decompression were extremely low. However, the symptoms related to decompression, such as bulged eyes and hemorrhage, were not observed only in Hypostomus sp., and were more frequent the larger the pressure values were, considering the values from which decompression was performed. All these symptoms decreased significantly after 24 h of observation. With the increase in pressure inside the apparatus, the four tested species moved towards the upper levels. This behavior could make possoble the implementation of bypass downstream fish passages in dams constructed in Brazil.Este trabalho teve como objetivo avaliar experimentalmente o comportamento de espécies brasileiras quando submetidas a um aumento gradual na pressão, bem como os efeitos de uma descompressão rápida simulando a passagem por uma turbina hidrelétrica. Quatro espécies da bacia do rio São Francisco foram testadas: Astyanax bimaculatus, Hypostomus sp., Leporinus reinhardti e Prochilodus costatus. Para todas elas as taxas de mortalidade devido à descompressão foram extremamente baixas. No entanto, sintomas relacionados à descompressão, como exoftalmia e hemorragia só não foram observados em Hypostomus sp., sendo mais freqüentes quanto maior o valor de pressão a partir do qual realizou-se a descompressão. Todos estes sintomas diminuíram significativamente após 24 horas de observação. Com o aumento da pressão no aparato, as espécies testadas se movimentaram em direção aos níveis superiores. Este comportamento sugere a possibilidade de se

  19. Sildenafil does not influence hepatic venous pressure gradient in patients with cirrhosis

    DEFF Research Database (Denmark)

    Clemmesen, Jens-Otto; Giraldi, Annamaria; Ott, Peter

    2008-01-01

    disease. However, the effect of phosphodiesterase type-5 inhibitors on splanchnic blood flow and portal hypertension remains essentially unknown. METHODS: Ten patients with biopsy proven cirrhosis (five females/five males, mean age 54 +/- 8 years) and an HVPG above 12 mmHg were studied after informed...... consent. Measurement of splanchnic blood flow and the HVPG during liver vein catheterization were done before and 80 min after oral administration of 50 mg sildenafil. Blood flow was estimated by use of indocyanine green clearance technique and Fick's principle, with correction for non-steady state....... RESULTS: The plasma concentration of sildenafil was 222 +/- 136 ng/mL 80 min after administration. Mean arterial blood pressure decreased from 77 +/- 7 mmHg to 66 +/- 12 mmHg, P = 0.003, while the splanchnic blood flow and oxygen consumption remained unchanged at 1.14 +/- 0.71 L/min and 2.3 +/- 0.6 mmol...

  20. Gender difference and economic gradients in the secular trend of population systolic blood pressure

    DEFF Research Database (Denmark)

    Andersen, Ulla; Jensen, Gorm B

    2013-01-01

    To a large extent population blood pressure (PBP) affects morbidity and mortality in the society. Reports indicated that PBP decreased in many western countries. The associations between the main cardiovascular risk factors and the changing PBP have been described. The aim of this study....... In addition, there was a trend towards a lowering of risk-factor adjusted SBP in the high income women with time. The mechanism that lies behind the associations between trend in SBP and income is not known but data suggest that poor lifestyle may explain some of the differences. The treated hypertensives...... was to investigate association between income factors and trends in population BP and hypertension. Copenhagen City Heart Study is a prospective longitudinal epidemiological study on almost 20000 individuals through four surveys from 1976 to 2003. The BP measurement was fully standardised. Questionnaires...

  1. Viscosity bio reducer Influence in a non-Newtonian fluid horizontal pipeline pressure gradient

    Directory of Open Access Journals (Sweden)

    Edgardo Jonathan Suarez-Dominguez

    2014-03-01

    Full Text Available Due to increased production of heavy and extra heavy crude in Mexico, it has led to the necessity touse chemicals to facilitate the transport in the pipe of our country. Experimental study was conductedto analyze the influence of a viscosity reducer of biological origin (BRV, on the rheological behaviorof heavy oil in the northern region of Mexico, finding that it exhibits a non-Newtonian viscoelasticbehavior, where a concentration increase of BRV leads to a consistency decrease and an increasedflow order, where dilatant behavior was observed in high temperatures. From these results it wasestimated the pressure losses by friction in a horizontal pipe for single phase and two phase flow. Wefound that in all cases the increase in the concentration of BRV reduces these losses.

  2. Convective heat transfer studies at high temperatures with pressure gradient for inlet flow Mach number of 0.45

    Science.gov (United States)

    Pedrosa, A. C. F.; Nagamatsu, H. T.; Hinckel, J. A.

    1984-01-01

    Heat transfer measurements were determined for a flat plate with and without pressure gradient for various free stream temperatures, wall temperature ratios, and Reynolds numbers for an inlet flow Mach number of 0.45, which is a representative inlet Mach number for gas turbine rotor blades. A shock tube generated the high temperature and pressure air flow, and a variable geometry test section was used to produce inlet flow Mach number of 0.45 and accelerate the flow over the plate to sonic velocity. Thin-film platinum heat gages recorded the local heat flux for laminar, transition, and turbulent boundary layers. The free stream temperatures varied from 611 R (339 K) to 3840 R (2133 K) for a T(w)/T(r,g) temperature ratio of 0.87 to 0.14. The Reynolds number over the heat gages varied from 3000 to 690,000. The experimental heat transfer data were correlated with laminar and turbulent boundary layer theories for the range of temperatures and Reynolds numbers and the transition phenomenon was examined.

  3. Experimental study on the flow regimes and pressure gradients of air-oil-water three-phase flow in horizontal pipes.

    Science.gov (United States)

    Al-Hadhrami, Luai M; Shaahid, S M; Tunde, Lukman O; Al-Sarkhi, A

    2014-01-01

    An experimental investigation has been carried out to study the flow regimes and pressure gradients of air-oil-water three-phase flows in 2.25 ID horizontal pipe at different flow conditions. The effects of water cuts, liquid and gas velocities on flow patterns and pressure gradients have been studied. The experiments have been conducted at 20 °C using low viscosity Safrasol D80 oil, tap water and air. Superficial water and oil velocities were varied from 0.3 m/s to 3 m/s and air velocity varied from 0.29 m/s to 52.5 m/s to cover wide range of flow patterns. The experiments were performed for 10% to 90% water cuts. The flow patterns were observed and recorded using high speed video camera while the pressure drops were measured using pressure transducers and U-tube manometers. The flow patterns show strong dependence on water fraction, gas velocities, and liquid velocities. The observed flow patterns are stratified (smooth and wavy), elongated bubble, slug, dispersed bubble, and annular flow patterns. The pressure gradients have been found to increase with the increase in gas flow rates. Also, for a given superficial gas velocity, the pressure gradients increased with the increase in the superficial liquid velocity. The pressure gradient first increases and then decreases with increasing water cut. In general, phase inversion was observed with increase in the water cut. The experimental results have been compared with the existing unified Model and a good agreement has been noticed.

  4. Association between Selective Beta-adrenergic Drugs and Blood Pressure Elevation: Data Mining of the Japanese Adverse Drug Event Report (JADER) Database.

    Science.gov (United States)

    Ohyama, Katsuhiro; Inoue, Michiko

    2016-01-01

    Selective beta-adrenergic drugs are used clinically to treat various diseases. Because of imperfect receptor selectivity, beta-adrenergic drugs cause some adverse drug events by stimulating other adrenergic receptors. To examine the association between selective beta-adrenergic drugs and blood pressure elevation, we reviewed the Japanese Adverse Drug Event Reports (JADERs) submitted to the Japan Pharmaceuticals and Medical Devices Agency. We used the Medical Dictionary for Regulatory Activities (MedDRA) Preferred Terms extracted from Standardized MedDRA queries for hypertension to identify events related to blood pressure elevation. Spontaneous adverse event reports from April 2004 through May 2015 in JADERs, a data mining algorithm, and the reporting odds ratio (ROR) were used for quantitative signal detection, and assessed by the case/non-case method. Safety signals are considered significant if the ROR estimates and lower bound of the 95% confidence interval (CI) exceed 1. A total of 2021 reports were included in this study. Among the nine drugs examined, significant signals were found, based on the 95%CI for salbutamol (ROR: 9.94, 95%CI: 3.09-31.93) and mirabegron (ROR: 7.52, 95%CI: 4.89-11.55). The results of this study indicate that some selective beta-adrenergic drugs are associated with blood pressure elevation. Considering the frequency of their indications, attention should be paid to their use in elderly patients to avoid adverse events.

  5. Multiphase Transport in Porous Media: Gas-Liquid Separation Using Capillary Pressure Gradients International Space Station (ISS) Flight Experiment Development

    Science.gov (United States)

    Wheeler, Richard R., Jr.; Holtsnider, John T.; Dahl, Roger W.; Deeks, Dalton; Javanovic, Goran N.; Parker, James M.; Ehlert, Jim

    2013-01-01

    Advances in the understanding of multiphase flow characteristics under variable gravity conditions will ultimately lead to improved and as of yet unknown process designs for advanced space missions. Such novel processes will be of paramount importance to the success of future manned space exploration as we venture into our solar system and beyond. In addition, because of the ubiquitous nature and vital importance of biological and environmental processes involving airwater mixtures, knowledge gained about fundamental interactions and the governing properties of these mixtures will clearly benefit the quality of life here on our home planet. The techniques addressed in the current research involving multiphase transport in porous media and gas-liquid phase separation using capillary pressure gradients are also a logical candidate for a future International Space Station (ISS) flight experiment. Importantly, the novel and potentially very accurate Lattice-Boltzmann (LB) modeling of multiphase transport in porous media developed in this work offers significantly improved predictions of real world fluid physics phenomena, thereby promoting advanced process designs for both space and terrestrial applications.This 3-year research effort has culminated in the design and testing of a zero-g demonstration prototype. Both the hydrophilic (glass) and hydrophobic (Teflon) media Capillary Pressure Gradient (CPG) cartridges prepared during the second years work were evaluated. Results obtained from ground testing at 1-g were compared to those obtained at reduced gravities spanning Martian (13-g), Lunar (16-g) and zero-g. These comparisons clearly demonstrate the relative strength of the CPG phenomena and the efficacy of its application to meet NASAs unique gas-liquid separation (GLS) requirements in non-terrestrial environments.LB modeling software, developed concurrently with the zero-g test effort, was shown to accurately reproduce observed CPG driven gas-liquid separation

  6. Climatic gradients and human development pressure determine spatial patterns of forest fragmentation in the Great Lakes basin, USA

    Science.gov (United States)

    Currie, W. S.; Hart, S.

    2015-12-01

    Over half of temperate forest area globally has been fragmented or deforested by human activities. Our objective was to gain insight into the combination of climatic, ecological, and social factors that control complex spatial patterns of forest cover and fragmentation at the regional scale. Our study area was the US portion of the land area of the Laurentian Great Lakes basin (USGL basin) of the Upper Midwest, USA, covering ca. 300,000 km2 and home to 25 million people. While this region was historically forested, today there are regional gradients in forest cover as well as complex spatial patterns of agriculture, human settlements, and tree cover. This includes large expanses of fragmented forests in the wildland-urban interface or the forest transition zone. We used structural equation modeling to test models of social and climatic-ecological factors to explain spatial patterns of forest cover and fragmentation. This is a model-driven approach to statistical analysis that is used to test proposed causal "structures" of direct and indirect relationships among variables. It is an innovative approach that makes use of large spatial datasets to test understanding. We assembled numerous spatial data layers at 1 km2 resolution across the USGL basin. We found that 64% to 75% of variance in tree cover and forest connectivity was explained through a relatively simple model combining climatic gradients and human development pressure. Human development pressure was best represented as a measurement model that explained 45% of variance in road density and 87% of housing unit density, while significantly explaining patterns of forest fragmentation. Climate could be represented by a single variable, temperature: where temperature was higher, tree cover and forest connectivity was lower due to human land use. Temperatures did not help to explain patterns of human development as roads and housing, but did affect forest fragmentation through land use as cropland. This suggests

  7. Intraperitoneal and retroperitoneal carbon dioxide insufflation evoke different effects on caval vein pressure gradients in humans: evidence for the starling resistor concept of abdominal venous return.

    Science.gov (United States)

    Giebler, R M; Behrends, M; Steffens, T; Walz, M K; Peitgen, K; Peters, J

    2000-06-01

    The authors hypothesized that intraperitoneal and retroperitoneal carbon dioxide insufflation during surgical procedures evoke markedly different effects on the venous low-pressure system, induce different inferior caval vein pressure gradients at similar insufflation pressures, and may provide evidence for the Starling resistor concept of abdominal venous return. Intra- and extrathoracic caval vein pressures were measured using micromanometers during carbon dioxide insufflation at six cavity pressures (baseline and 10, 15, 20, and 24 mmHg and desufflation) in 20 anesthetized patients undergoing laparoscopic (supine, n = 8) or left (n = 6) or right (n = 6) retroperitoneoscopic (prone position) surgery. Intracavital, esophageal, and gastric pressures also were assessed. Data were analyzed for insufflation pressure-dependent and group effects by one-way and two-way analysis of variance for repeated measurements, respectively, followed by the Newman-Keuls post hoc test (P < 0.05). Intraperitoneal, unlike retroperitoneal, insufflation markedly increased, in an insufflation pressure-dependent fashion, the inferior-to-superior caval vein pressure gradient (P < 0.00001) at the level of the diaphragm. In contrast to what was observed with retroperitoneal insufflation, transmural intrathoracic caval vein pressure increased at 10 mmHg insufflation pressure, but the increase flattened with an insufflation pressure of more than 10 mmHg, and pressure decreased with an inflation pressure of 20 mmHg (P = 0.0397). These data are consistent with a zone 2 or 3 abdominal vascular condition during intraperitoneal and a zone 3 abdominal vascular condition during retroperitoneal insufflation. Intraperitoneal but not retroperitoneal carbon dioxide insufflation evokes a transition of the abdominal venous compartment from a zone 3 to a zone 2 condition, presumably impairing venous return, supporting the Starling resistor concept of abdominal venous return in humans.

  8. An experimental investigation of heat transfer to reusable surface insulation tile array gaps in a turbulent boundary layer with pressure gradient. M.S. Thesis

    Science.gov (United States)

    Throckmorton, D. A.

    1975-01-01

    An experimental investigation was performed to determine the effect of pressure gradient on the heat transfer to space shuttle reusable surface insulation (RSI) tile array gaps under thick, turbulent boundary layer conditions. Heat transfer and pressure measurements were obtained on a curved array of full-scale simulated RSI tiles in a tunnel wall boundary layer at a nominal freestream Mach number of 10.3 and freestream unit Reynolds numbers of 1.6, 3.3, and and 6.1 million per meter. Transverse pressure gradients were induced over the model surface by rotating the curved array with respect to the flow. Definition of the tunnel wall boundary layer flow was obtained by measurement of boundary layer pitot pressure profiles, and flat plate wall pressure and heat transfer. Flat plate wall heat transfer data were correlated and a method was derived for prediction of smooth, curved array heat transfer in the highly three-dimensional tunnel wall boundary layer flow and simulation of full-scale space shuttle vehicle pressure gradient levels was assessed.

  9. CATALYTIC COMBUSTION OF PROPANE IN A MEMBRANE REACTOR WITH SEPARATE FEED OF REACTANTS .2. OPERATION IN PRESENCE OF TRANS-MEMBRANE PRESSURE-GRADIENTS

    NARCIS (Netherlands)

    SARACCO, G; VELDSINK, JW; VERSTEEG, GF; VANSWAAIJ, WPM

    This is the second communication of a series dealing with an experimental and modelling study on propane catalytic combustion in a membrane reactor with separate feed of reactants. In paper I the behaviour of the reactor in the absence of trans-membrane pressure gradients was presented and

  10. Catalytic combustion of propane in a membrane reactor with separate feed of reactants—II. Operation in presence of trans-membrane pressure gradients

    NARCIS (Netherlands)

    Saracco, Guido; Veldsink, Jan Willem; Versteeg, Geert F.; Swaaij, Wim P.M. van

    1995-01-01

    This is the second communication of a series dealing with an experimental and modelling study on propane catalytic combustion in a membrane reactor with separate feed of reactants. In paper I the behaviour of the reactor in the absence of trans-membrane pressure gradients was presented and

  11. Catalytic combustion of propane in a membrane reactor with separate feed of reactants II. Operation in presence of transmembrane pressure gradients

    NARCIS (Netherlands)

    Saracco, Guido; Veldsink, J.W.; Veldsink, Jan Willem; Versteeg, Geert; van Swaaij, Willibrordus Petrus Maria

    1995-01-01

    This is the second communication of a series dealing with an experimental and modelling study on propane catalytic combustion in a membrane reactor with separate feed of reactants. In paper I the behaviour of the reactor in the absence of trans-membrane pressure gradients was presented and

  12. The Role of Postintervention Pullback Pressure Gradient in Percutaneous Transluminal Angioplasty for Central Vein Stenosis in Dialysis Patients

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Yu-Sheng, E-mail: dissertlin@yahoo.com.tw [Chang Gung Memorial Hospital, Chiayi, Chang Gung Institute of Technology, Division of Cardiology (China); Yang, Cheng-Hsu, E-mail: yangch@adm.cgmh.org.tw [Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Division of Cardiology and Department of Internal Medicine (China); Chu, Chi-Ming, E-mail: chuchiming@ndmctsgh.edu.tw [National Defense Medical Center and University, Section of Health Informatics, Institute of Public Health (China); Fang, Chi-Yung, E-mail: cyfang@seed.net.tw; Chen, Chien-Jen, E-mail: cjchen@adm.cgmh.org.tw [Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Division of Cardiology and Department of Internal Medicine (China); Hsu, Jen-Te, E-mail: hsujente@gmail.com; Yang, Teng-Yao, E-mail: 2859@adm.cgmh.org.tw [Chang Gung Memorial Hospital, Chiayi, Chang Gung Institute of Technology, Division of Cardiology (China); Hang, Chi-Ling, E-mail: samuelhang@hotmail.com; Wu, Chiung-Jen, E-mail: cvcjwu@adm.cgmh.org.tw [Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Division of Cardiology and Department of Internal Medicine (China)

    2013-10-15

    Purpose: The severity of residual stenosis (RS) sometimes cannot be accurately measured by angiography during central vein intervention. This study evaluated the role of pullback pressure measurement during central vein stenosis (CVS) intervention. Methods: A retrospective review enrolled 94 consecutive dialysis patients who underwent CVS interventions but not stenting procedures. Patients were classified into 2 groups by either angiography or pressure gradient (PG) criteria, respectively. Groups divided by angiographic result were successful group (RS {<=}30 %) and acceptable group (50 % {>=} RS > 30 %), while groups divided by PG were low PG group (PG {<=}5 mmHg) and high PG group (PG >5 mmHg). Baseline characteristics and 12-month patency rates between the groups were analyzed. Results: The angiography results placed 63 patients in the successful group and 31 patients in the acceptable group. The patency rate at 12 month was not statistically different (P = 0.167). When the patients were reclassified by the postintervention pullback PG, the patency rate at 12 months was significant (P = 0.048). Further analysis in groups redivided by different combinations of RS and PG criteria identified significant differences in the group with both RS {<=}30 % and PG {<=}5 mmHg compared with those with either RS >30 % (P = 0.047) or PG >5 mmHg (P = 0.027). In addition, there was a significant difference between those with both RS {<=}30 % and PG {<=}5 mmHg compared with those with both RS >30 % and PG >5 mmHg (P = 0.027). Conclusion: Postintervention PG can better predict long-term outcomes after angioplasty for CVS in nonstented dialysis patients than angiography.

  13. The fluid mechanics of a high aspect ratio slot with an impressed pressure gradient and secondary injection

    Science.gov (United States)

    Sobanik, John Bertram

    1993-01-01

    A high aspect ratio slot flow (which emulates the gas leakage path in a gas turbine engine outer turbine air seal) is studied by use of a high aspect ratio slot using water as the working fluid. The cross section of the geometry is similar to a 'T', the slot being the vertical stroke and the main flow being the cross bar. A pressure gradient in the axial direction is created by blocking the main flow at a discreet location with an orifice plate (or blade tip simulator), located above the slot. Seven individually metered secondary flow injectors are located periodically along the bottom of the wall of the slot. Two slot widths, 1/8 and 1/4 inch, were investigated for length to width aspect ratios of 384 and 192 and height to width aspect ratios 33.2 and 16.6 respectively. Orifice plate pressure drops sufficient to give Reynolds numbers based upon half width of the slot, without secondary injection turned on, of 2350 and 4700 in the 1/8 inch slot and 4700 and 9400 in the 1/4 inch slot were run. Various secondary injection scenarios were added to the flow, the cases most studied being the no-injection and the all injectors flowing equal mass rates. Total injection rates for all seven injectors of 3.78 and 7.56 slot volumes per second were run. Laser velocimetry data and flow visualization pictures using fluorescein dye in the secondary flow are compared with computational results form the TEACH 3-D computer code. Major features and trends of the flow are captured by the computational model. Recommendations for further improvement of the numerical accuracy involves modification of the TEACH 3-D code to allow the 'slip condition' on all confining boundaries of the flow, or using a code which permits the 'slip condition' on all boundaries as a built-in option.

  14. A study of the three-dimensional spectral energy distribution in a zero pressure gradient turbulent boundary layer

    Energy Technology Data Exchange (ETDEWEB)

    LeHew, J.; McKeon, B.J. [California Institute of Technology, Graduate Aerospace Laboratories, Pasadena, CA (United States); Guala, M. [California Institute of Technology, Graduate Aerospace Laboratories, Pasadena, CA (United States); University of Minnesota, Department of Civil Engineering, Minneapolis, MN (United States)

    2011-10-15

    Time-resolved particle image velocimetry (PIV) measurements performed in wall parallel planes at three wall normal locations, y{sup +} = 34, 108, and 278, in a zero pressure gradient turbulent boundary layer at Re{sub {tau}}=470 are used to illuminate the distribution of streamwise velocity fluctuations in a three-dimensional energy spectrum (2D in space and 1D in time) over streamwise, spanwise, and temporal wavelengths. Two high-speed cameras placed side by side in the streamwise direction give a 10{delta}x 5{delta} streamwise by spanwise field of view with a vector spacing of {delta}x{sup +}={delta}z{sup +}{approx} 37 and a time step of {delta}t{sup +}=0.5. Although 3D wavenumber-frequency spectra have been calculated in acoustics studies, to the authors' knowledge this is the first time they has been calculated and presented for a turbulent boundary layer. The calculation and normalization of this spectrum, its relation to 2D and 1D spectra, and the effects of the PIV algorithm on its shape are carefully analyzed and outlined. (orig.)

  15. Experimental Evidence of Near-Wall Reverse Flow Events in a Zero Pressure Gradient Turbulent Boundary Layer

    CERN Document Server

    Willert, Christian E

    2015-01-01

    This study reports on experimentally observed near-wall reverse flow events in a fully developed flat plate boundary layer at zero pressure gradient with Reynolds numbers between $Re_\\tau = 1000$ and $Re_\\tau = 2700$. The reverse flow events are captured using high magnification particle image velocimetry sequences with record lengths varying from 50,000 to 126,000 samples. Time resolved particle image sequences allow singular reverse flow events to be followed over several time steps whereas long records of nearly statistically independent samples provide a variety of single snapshots at a higher spatial resolution. The probability of occurrence lies in the range of 0.01% to 0.1% which matches predictions made with direct numerical simulations (DNS). The self-similar size of the reverse flow bubble is about 30-50 wall units in length and 5 wall units in height which also agrees well to DNS data provided by Lenaers et al. (ETC13, Journal of Physics: Conference Series 318 (2011) 022013).

  16. Gastroesophageal pressure gradients in gastroesophageal reflux disease: relations with hiatal hernia, body mass index, and esophageal acid exposure.

    Science.gov (United States)

    de Vries, Durk R; van Herwaarden, Margot A; Smout, André J P M; Samsom, Melvin

    2008-06-01

    The roles of intragastric pressure (IGP), intraesophageal pressure (IEP), gastroesophageal pressure gradient (GEPG), and body mass index (BMI) in the pathophysiology of gastroesophageal reflux disease (GERD) and hiatal hernia (HH) are only partly understood. In total, 149 GERD patients underwent stationary esophageal manometry, 24-h pH-metry, and endoscopy. One hundred three patients had HH. Linear regression analysis showed that each kilogram per square meter of BMI caused a 0.047-kPa increase in inspiratory IGP (95% confidence interval [CI] 0.026-0.067) and a 0.031-kPa increase in inspiratory GEPG (95% CI 0.007-0.055). Each kilogram per square meter of BMI caused expiratory IGP to increase with 0.043 kPa (95% CI 0.025-0.060) and expiratory IEP with 0.052 kPa (95% CI 0.027-0.077). Each added year of age caused inspiratory IEP to decrease by 0.008 kPa (95% CI -0.015-0.001) and inspiratory GEPG to increase by 0.008 kPa (95% CI 0.000-0.015). In binary logistic regression analysis, HH was predicted by inspiratory and expiratory IGP (odds ratio [OR] 2.93 and 2.62, respectively), inspiratory and expiratory GEPG (OR 3.19 and 2.68, respectively), and BMI (OR 1.72/5 kg/m(2)). In linear regression analysis, HH caused an average 5.09% increase in supine acid exposure (95% CI 0.96-9.22) and an average 3.46% increase in total acid exposure (95% CI 0.82-6.09). Each added year of age caused an average 0.10% increase in upright acid exposure and a 0.09% increase in total acid exposure (95% CI 0.00-0.20 and 0.00-0.18). BMI predicts IGP, inspiratory GEPG, and expiratory IEP. Age predicts inspiratory IEP and GEPG. Presence of HH is predicted by IGP, GEPG, and BMI. GEPG is not associated with acid exposure.

  17. Effects of blood-pressure-lowering treatment in hypertension: 9. Discontinuations for adverse events attributed to different classes of antihypertensive drugs: meta-analyses of randomized trials.

    Science.gov (United States)

    Thomopoulos, Costas; Parati, Gianfranco; Zanchetti, Alberto

    2016-10-01

    Choice of antihypertensive drugs is also based on the expected burden of adverse events associated with each class of agents, and we have recently identified treatment discontinuation for adverse events as a measure of treatment tolerability frequently reported in randomized controlled trials (RCTs). To investigate whether all classes of blood pressure (BP) lowering drugs increase discontinuations for adverse events when compared with placebo and whether risk of discontinuation is similar for all classes when compared in head-to-head RCTs. RCTs of BP-lowering treatment were subdivided in groups according to class of drug compared with placebo or with other classes. Risk ratios and 95% confidence intervals of major cardiovascular events and of treatment discontinuations for adverse events were calculated (random-effects model). Thirty-eight placebo-controlled RCTs (147 788 patients) and 37 head-to-head RCTs (242 481 patients) provided comparative information on discontinuations for adverse events. All classes of drugs significantly increased discontinuations for adverse events over those occurring on placebo: risk ratio diuretics 2.23 (1.32-3.76), beta-blockers 2.88 (1.58-5.28), calcium antagonists 2.03 (1.17-3.56), angiotensin-converting enzyme inhibitors 2.78 (1.37-5.47), central agents 1.74 (1.24-2.45), with the single exception of angiotensin receptor blockers, which did not significantly increase adverse events over placebo [risk ratio 1.13 (0.78-1.62)]. Similarly, in head-to-head comparison RCTs with other classes, angiotensin receptor blockers were the only class associated with a significantly lower risk of adverse events [risk ratio 0.71 (0.58-0.87)] when head-to-head compared with other classes. Regression analysis also shows that incidence of discontinuations for adverse events is proportional to the number of antihypertensive and other cardiovascular drugs, which accounts for the high incidence of this outcome often found in groups randomized to

  18. Association of variants in NEDD4L with blood pressure response and adverse cardiovascular outcomes in hypertensive patients treated with thiazide diuretics

    Science.gov (United States)

    McDonough, Caitrin W.; Burbage, Sarah E.; Duarte, Julio D.; Gong, Yan; Langaee, Taimour Y.; Turner, Stephen T.; Gums, John G.; Chapman, Arlene B.; Bailey, Kent R.; Beitelshees, Amber L.; Boerwinkle, Eric; Pepine, Carl J.; Cooper-DeHoff, Rhonda M.; Johnson, Julie A.

    2013-01-01

    Objective Single-nucleotide polymorphisms (SNPs) in NEDD4L may influence the ability of the NEDD4L protein to reduce epithelial sodium channel expression. A variant in NEDD4L, rs4149601, was associated with antihypertensive response and cardiovascular outcomes during treatment with thiazide diuretics and β-blockers in a Swedish population. We sought to further evaluate associations between NEDD4L polymorphisms, blood pressure response and cardiovascular outcomes with thiazide diuretics and β-blockers. Methods Four SNPs, rs4149601, rs292449, rs1008899 and rs75982813, were genotyped in 767 patients from the Pharmacogenomic Evaluation of Antihypertensive Responses (PEAR) clinical trial and association was assessed with blood pressure response to hydrochlorothiazide and atenolol. One SNP, rs4149601, was also genotyped in 1345 patients from the International Verapmil SR Trandolapril Study (INVEST), and association was examined with adverse cardiovascular outcomes relative to hydrochlorothiazide treatment. Results Significant associations or trends were found between rs4149601, rs292449, rs75982813 and rs1008899 and decreases in blood pressure in whites on hydrochlorothiazide, and a significant association was observed with increasing copies of the GC rs4149601-rs292449 haplotype and greater blood pressure response to hydrochlorothiazide in whites (P = 0.0006 and 0.006, SBP and DBP, respectively). Significant associations were also seen with rs4149601 and an increased risk for adverse cardiovascular outcomes in whites not treated with hydrochlorothiazide [P = 0.022, odds ratio (95% confidence interval) = 10.65 (1.18–96.25)]. Conclusion NEDD4L rs4149601, rs292449 and rs75982813 may be predictors for blood pressure response to hydrochlorothiazide in whites, and NEDD4L rs4149601 may be a predictor for adverse cardiovascular outcomes in whites not treated with hydrochlorothiazide. PMID:23353631

  19. Accurate prediction of retention in hydrophilic interaction chromatography (HILIC) by back calculation of high pressure liquid chromatography (HPLC) gradient profiles.

    Science.gov (United States)

    Wang, Nu; Boswell, Paul G

    2017-08-26

    Gradient retention times are difficult to project from the underlying retention factor (k) vs. solvent composition (φ) relationships. A major reason for this difficulty is that gradients produced by HPLC pumps are imperfect - gradient delay, gradient dispersion, and solvent mis-proportioning are all difficult to account for in calculations. However, we recently showed that a gradient "back-calculation" methodology can measure these imperfections and take them into account. In RPLC, when the back-calculation methodology was used, error in projected gradient retention times is as low as could be expected based on repeatability in the k vs. φ relationships. HILIC, however, presents a new challenge: the selectivity of HILIC columns drift strongly over time. Retention is repeatable in short time, but selectivity frequently drifts over the course of weeks. In this study, we set out to understand if the issue of selectivity drift can be avoid by doing our experiments quickly, and if there any other factors that make it difficult to predict gradient retention times from isocratic k vs. φ relationships when gradient imperfections are taken into account with the back-calculation methodology. While in past reports, the accuracy of retention projections was >5%, the back-calculation methodology brought our error down to ∼1%. This result was 6-43 times more accurate than projections made using ideal gradients and 3-5 times more accurate than the same retention projections made using offset gradients (i.e., gradients that only took gradient delay into account). Still, the error remained higher in our HILIC projections than in RPLC. Based on the shape of the back-calculated gradients, we suspect the higher error is a result of prominent gradient distortion caused by strong, preferential water uptake from the mobile phase into the stationary phase during the gradient - a factor our model did not properly take into account. It appears that, at least with the stationary phase

  20. Trace metal concentrations in forest and lawn soils of Paris region (France) along a gradient of urban pressure

    Science.gov (United States)

    Ludovic, Foti

    2017-04-01

    concentrations and subsequent risks in soils of Paris and Paris region (Île-de-France). Our study aims at filling this knowledge gap, focusing on contamination and pollution by TMs in lawns and forests that constitute the main types of vegetation in urban areas of Paris region. Considering the rational described above, the aims of the present study were (i) to examine the concentration of eight selected TMs (As, Cd, Cr, Cu, Fe, Ni, Pb, Zn) in soils of two land-uses (public lawns and woods) along an urban pressure gradient in Paris region, (ii) to distinguish origins and sources of contamination or pollution, (iii) to evaluate the individual and overall TM contamination degree as well as the individual and overall TM pollution degree, (iiii) to use soil characteristics to better understand soil origins and histories along the urban pressure gradient and the relationship between these characteristics and TM concentrations. Ultimately, this study provides a baseline TM assessment for the long-term monitoring of the evolution of TM soil contents in urban area of the Paris region.

  1. Adverse effects of social pressure to be thin on young women: an experimental investigation of the effects of "fat talk".

    Science.gov (United States)

    Stice, Eric; Maxfield, Jennifer; Wells, Tony

    2003-07-01

    Experiments have found that pressure to be thin from the media promotes body dissatisfaction and negative affect, but the effects of social pressure to be thin have not been examined experimentally. Thus, this study tested whether social pressure to be thin fosters body dissatisfaction and negative affect. Young women (N = 120) were randomly assigned to a condition wherein an ultra-thin confederate complained about how fat she felt and voiced intentions to lose weight or a control condition wherein she discussed a neutral topic. Exposure to social pressure to be thin resulted in increased body dissatisfaction but not negative affect. The effects were not moderated by initial thin-ideal internalization, body dissatisfaction, or social support. Results support the assertion that peer pressure to be thin promotes body dissatisfaction but suggest that this factor may not contribute to negative affect. Copyright 2003 by Wiley Periodicals, Inc.

  2. Evidence for impact induced pressure gradients on the Allende CV3 parent body: Consequences for fluid and volatile transport

    Science.gov (United States)

    Tait, Alastair W.; Fisher, Kent R.; Srinivasan, Poorna; Simon, Justin I.

    2016-11-01

    Carbonaceous chondrites, such as those associated with the Vigarano (CV) parent body, exhibit a diverse range of oxidative/reduced alteration mineralogy (McSween, 1977). Although fluids are often cited as the medium by which this occurs (Rubin, 2012), a mechanism to explain how this fluid migrates, and why some meteorite subtypes from the same planetary body are more oxidized than others remains elusive. In our study we examined a slab of the well-known Allende (CV3OxA) meteorite. Using several petrological techniques (e.g., Fry's and Flinn) and Computerized Tomography (CT) we discover it exhibits a strong penetrative planar fabric, resulting from strain partitioning among its major components: Calcium-Aluminum-rich Inclusions (CAIs) (64.5%CT) > matrix (21.5%Fry) > chondrules (17.6%CT). In addition to the planar fabric, we found a strong lineation defined by the alignment of the maximum elongation of flattened particles interpreted to have developed by an impact event. The existence of a lineation could either be non-coaxial deformation, or the result of a mechanically heterogeneous target material. In the later case it could have formed due to discontinuous patches of sub-surface ice and/or fabrics developed through prior impact compaction (MacPherson and Krot, 2014), which would have encouraged preferential flow within the target material immediately following the impact, compacting pore spaces. We suggest that structurally controlled movement of alteration fluids in the asteroid parent body along pressure gradients contributed to the formation of secondary minerals, which may have ultimately lead to the different oxidized subtypes.

  3. A high-pressure thermal gradient block for investigating microbial activity in multiple deep-sea samples

    DEFF Research Database (Denmark)

    Kallmeyer, J.; Ferdelman, TG; Jansen, KH

    2003-01-01

    of the sample vessels, a back-pressure system with a constant leak rate was installed. Pressure is applied through high-pressure liquid chromatography (HPLC) pumps that run in constant pressure mode with variable flow rate, thereby regulating any pressure fluctuations. The device allows incubations along a wide...

  4. The influence of a transmembrane pH gradient on protonation probabilities of bacteriorhodopsin: the structural basis of the back-pressure effect.

    Science.gov (United States)

    Calimet, Nicolas; Ullmann, G Matthias

    2004-06-01

    Bacteriorhodopsin pumps protons across a membrane using the energy of light. The proton pumping is inhibited when the transmembrane proton gradient that the protein generates becomes larger than four pH units. This phenomenon is known as the back-pressure effect. Here, we investigate the structural basis of this effect by predicting the influence of a transmembrane pH gradient on the titration behavior of bacteriorhodopsin. For this purpose we introduce a method that accounts for a pH gradient in protonation probability calculations. The method considers that in a transmembrane protein, which is exposed to two different aqueous phases, each titratable residue is accessible for protons from one side of the membrane depending on its hydrogen-bond pattern. This method is applied to several ground-state structures of bacteriorhodopsin, which residues already present complicated titration behaviors in the absence of a proton gradient. Our calculations show that a pH gradient across the membrane influences in a non-trivial manner the protonation probabilities of six titratable residues which are known to participate in the proton transfer: D85, D96, D115, E194, E204, and the Schiff base. The residues connected to one side of the membrane are influenced by the pH on the other side because of their long-range electrostatic interactions within the protein. In particular, D115 senses the pH at the cytoplasmic side of the membrane and transmits this information to D85 and the Schiff base. We propose that the strong electrostatic interactions found between D85, D115, and the Schiff base as well as the interplay of their respective protonation states under the influence of a transmembrane pH gradient are responsible for the back-pressure effect on bacteriorhodopsin.

  5. [Impact of the practising anesthesiologist team member on the laryngeal mask cuff pressures and adverse event rate].

    Science.gov (United States)

    Yurtlu, Bülent Serhan; Hanci, Volkan; Köksal, Bengü; Okyay, Dilek; Ayoğlu, Hilal; Turan, Işıl Özkoçak

    2015-01-01

    We have planned to evaluate the laryngeal mask cuff pressures (LMcp) inflated by anesthesia workers of several seniority, without using manometer. 180 patients scheduled to have short duration surgery with laryngeal mask were included in the study. Five anesthesia specialists (Group S), 10 residents (Group R) and 6 technicians (Group T) inflated the LMc; thereafter LMcp were measured with pressure manometer. Participants have repeated this practice in at least five different cases. LMcp higher than 60cm H2O at the initial placement or intraoperative period were adjusted to normal range. Sore throat was questioned postoperatively. Groups were compared in terms of mean LMcp and occupational experience. At the settlement of LM, LMcp pressures within the normal range were determined in 26 (14.4%) cases. Mean LMcp after LM placement in Group S, R and T were 101.2±14.0, 104.3±20.5cm H2O and 105.2±18.4cm H2O respectively (p>0.05). Mean LMcp values in all measurement time periods within the groups were above the normal limit (60cm H2O). When groups were compared in terms of LMcp, no difference has been found among pressure values. Occupational experience was 14.2±3.9; 3.3±1.1 and 6.6±3.8 years for specialists, residents and technicians respectively and measured pressure values were not different in regard of occupational experience. Seven (3.9%) patients had sore throat at the 24th hour interview. Considering lower possibility of normal adjustment of LMcp and ineffectiveness of occupational experience to obtain normal pressure values, it is suitable that all anesthesia practitioners should adjust LMcp with manometer. Copyright © 2013 Sociedade Brasileira de Anestesiologia. Publicado por Elsevier Editora Ltda. All rights reserved.

  6. Impact of the practising anesthesiologist team member on the laryngeal mask cuff pressures and adverse event rate

    Directory of Open Access Journals (Sweden)

    Bülent Serhan Yurtlu

    2015-12-01

    Full Text Available OBJECTIVE: We have planned to evaluate the laryngeal mask cuff pressures (LMcp inflated by anesthesia workers of several seniority, without using manometer. METHODS: 180 patients scheduled to have short duration surgery with laryngeal mask were included in the study. Five anesthesia specialists (Group S, 10 residents (Group R and 6 technicians (Group T inflated the LMc; thereafter LMcp were measured with pressure manometer. Participants have repeated this practice in at least five different cases. LMcp higher than 60 cm H2O at the initial placement or intraoperative period were adjusted to normal range. Sore throat was questioned postoperatively. Groups were compared in terms of mean LMcp and occupational experience. RESULTS: At the settlement of LM, LMcp pressures within the normal range were determined in 26 (14.4% cases. Mean LMcp after LM placement in Group S, R and T were 101.2 ± 14.0, 104.3 ± 20.5 cm H2O and 105.2 ± 18.4 cm H2O respectively (p > 0.05. Mean LMcp values in all measurement time periods within the groups were above the normal limit (60 cm H2O. When groups were compared in terms of LMcp, no difference has been found among pressure values. Occupational experience was 14.2 ± 3.9; 3.3 ± 1.1 and 6.6 ± 3.8 years for specialists, residents and technicians respectively and measured pressure values were not different in regard of occupational experience. Seven (3.9% patients had sore throat at the 24th hour interview. CONCLUSION: Considering lower possibility of normal adjustment of LMcp and ineffectiveness of occupational experience to obtain normal pressure values, it is suitable that all anesthesia practitioners should adjust LMcp with manometer.

  7. Experimental investigation and calibration of surface pressure modeling for trailing edge noise

    DEFF Research Database (Denmark)

    Bertagnolio, Franck

    2011-01-01

    The modeling of the surface pressure spectrum under a turbulent boundary layer is investigated in the presence of an adverse pressure gradient along the flow direction. It is shown that discrepancies between measurements and results from a well-known model increase as the pressure gradient...... increases. This model is modified by introducing anisotropy in the definition of the vertical velocity component spectrum across the boundary layer. The degree of anisotropy is directly related to the strength of the pressure gradient. It is shown that by appropriately normalizing the pressure gradient...... and by tuning the anisotropy factor, experimental results can be closely reproduced by the modified model....

  8. Hardness-gradient reversion in FeMnSiCr shape memory alloy modules produced by high-speed high pressure torsion

    Directory of Open Access Journals (Sweden)

    Bujoreanu Leandru-Gheorghe

    2015-01-01

    Full Text Available High pressure torsion (HPT processing technology, consisting in the obtainment of (ultrafine bulk metallic structure during 2–3 complete rotations of the superior anvil at low speed (~10-1 rpm under high applied pressure (~ GPa applied on the lower anvil, has been modified as to allow the application of elevated number of rotation numbers (~102 rpm. By high-speed high pressure torsion (HS-HPT, coned-disk spring shape modules were processed from an as cast Fe-28Mn-6Si-5Cr (mass % shape memory alloy (SMA. Scanning electron microscopy (SEM and X-ray diffraction (XRD studies revealed that the modules became nanostructured as an effect of HS-HPT processing. After processing, a hardness gradient was obtained along the truncated cone generator, increasing from inner to outer areas, due to different deformation degrees in these zones. After complete flattening, the measurements revealed that the hardness gradient maintained its value but reversed its variation sense.

  9. Weight gain is associated with improved glycaemic control but with adverse changes in plasma lipids and blood pressure isn Type 1 diabetes.

    LENUS (Irish Health Repository)

    Ferriss, J B

    2012-02-03

    AIMS: To assess the effects of weight gain on metabolic control, plasma lipids and blood pressure in patients with Type 1 diabetes. METHODS: Patients in the EURODIAB Prospective Complications Study (n = 3250) were examined at baseline and 1800 (55%) were re-examined a mean of 7.3 years later. Patients had Type 1 diabetes, defined as a diagnosis made before age 36 years and with a need for continuous insulin therapy within a year of diagnosis. Patients were aged 15-60 years at baseline and were stratified for age, sex and duration of diabetes. RESULTS: The change in HbA(1c) from baseline to follow-up examination was significantly more favourable in those who gained 5 kg or more during follow-up (\\'marked weight gain\\') than in patients who gained less or no weight or lost weight (\\'less or no weight gain\\'). In those with marked weight gain, there was a significantly greater rise in plasma triglycerides and total cholesterol and significantly less favourable changes in low-density lipoprotein and high-density lipoprotein cholesterol compared with those with less or no weight gain, with or without adjustment for HbA(1c). Systolic and diastolic blood pressure also rose significantly more in the group with marked weight gain. CONCLUSION: Weight gain in patients with Type 1 diabetes has adverse effects on plasma lipids and blood pressure, despite a small improvement in glycaemic control.

  10. Electrohydrodynamics within electrical double layer in a pressure-driven flow in presence of finite temperature gradients

    CERN Document Server

    Ghonge, Tanmay; Chakraborty, Jeevanjyoti; Chakraborty, Suman

    2012-01-01

    A wide spectrum of electrokinetic studies is modelled as isothermal ones to expedite analysis even when such conditions may be extremely difficult to realize in practice. As a clear and novel departure from this trend, we address the case of flow-induced electrohydrodynamics, commonly referred to as streaming potential, in a situation where finite temperature gradients do indeed exit. By way of analysing a model problem of flow through a narrow parallel plate channel, we show that the temperature gradients have a significant effect on the streaming potential, and, consequently, on the flow itself. We incorporate thermoelectic effects in our model by a full-fledged coupling among the electric potential, the ionic species distribution, the fluid velocity and the local fluid temperature fields without resorting to ad hoc simplifications. We expect this expository study to contribute towards more sophisticated future inquiries into practical micro-/nano-fluidic applications coupling thermal field focusing with el...

  11. Model-based decision making in early clinical development: minimizing the impact of a blood pressure adverse event.

    Science.gov (United States)

    Stroh, Mark; Addy, Carol; Wu, Yunhui; Stoch, S Aubrey; Pourkavoos, Nazaneen; Groff, Michelle; Xu, Yang; Wagner, John; Gottesdiener, Keith; Shadle, Craig; Wang, Hong; Manser, Kimberly; Winchell, Gregory A; Stone, Julie A

    2009-03-01

    We describe how modeling and simulation guided program decisions following a randomized placebo-controlled single-rising oral dose first-in-man trial of compound A where an undesired transient blood pressure (BP) elevation occurred in fasted healthy young adult males. We proposed a lumped-parameter pharmacokinetic-pharmacodynamic (PK/PD) model that captured important aspects of the BP homeostasis mechanism. Four conceptual units characterized the feedback PD model: a sinusoidal BP set point, an effect compartment, a linear effect model, and a system response. To explore approaches for minimizing the BP increase, we coupled the PD model to a modified PK model to guide oral controlled-release (CR) development. The proposed PK/PD model captured the central tendency of the observed data. The simulated BP response obtained with theoretical release rate profiles suggested some amelioration of the peak BP response with CR. This triggered subsequent CR formulation development; we used actual dissolution data from these candidate CR formulations in the PK/PD model to confirm a potential benefit in the peak BP response. Though this paradigm has yet to be tested in the clinic, our model-based approach provided a common rational framework to more fully utilize the limited available information for advancing the program.

  12. Study on the effects of gradient mechanical pressures on the proliferation, apoptosis, chondrogenesis and hypertrophy of mandibular condylar chondrocytes in vitro.

    Science.gov (United States)

    Li, Hui; Huang, Linjian; Xie, Qianyang; Cai, Xieyi; Yang, Chi; Wang, Shaoyi; Zhang, Min

    2017-01-01

    To investigate the effects of gradient mechanical pressure on chondrocyte proliferation, apoptosis, and the expression of markers of chondrogenesis and chondrocyte hypertrophy. Mandibular condylar chondrocytes from 5 rabbits were cultured in vitro, and pressed with static pressures of 50kPa, 100kPa, 150kPa and 200kPa for 3h, respectively. The chondrocytes cultured without pressure (0kPa) were used as control. Cell proliferation, apoptosis, and the expression of aggrecan (AGG), collagen II (COL2), collagen X (COL10), alkaline phosphatase (ALP) were investigated. Ultrastructures of the pressurized chondrocytes under transmission electron microscopy (TEM) were observed. Chondrocyte proliferation increased at 100kPa and decreased at 200kPa. Chondrocyte apoptosis increased with peak pressure at 200kPa in a dose-dependent manner. Chondrocyte necrosis increased at 200kPa. The expression of AGG increased at 200kPa. The expression of COL2 decreased at 50kPa and increased at 150kPa. The expression of COL10 and ALP increased at 150kPa. Ultrastructure of the pressurized chondrocytes under TEM showed: at 100kPa, cells were enlarged with less cellular microvillus and a bigger nucleus; at 200kPa, cells shrank with the sign of apoptosis, and apoptosis cells were found. The mechanical loading of 150kPa is the moderate pressure for chondrocyte: cell proliferation and apoptosis is balanced, necrosis is reduced, and chondrogenesis and chondrocyte hypertrophy are promoted. When the pressure is lower, chondrogenesis and chondrocyte hypertrophy are inhibited. At 200kPa, degeneration of cartilage is implied. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. The effects of sulfonylureas plus metformin on lipids, blood pressure, and adverse events in type 2 diabetes: a meta-analysis of randomized controlled trials.

    Science.gov (United States)

    Zhang, Fan; Xiang, Hao; Fan, Yunzhou; Ganchuluun, Tsend-Ayush; Kong, Wenhua; Ouyang, Qian; Sun, Jingwen; Cao, Beibei; Jiang, Hongbo; Nie, Shaofa

    2013-12-01

    To compare the effects of sulfonylureas and metformin versus metformin on lipid profiles, blood pressure, and adverse events. PubMed, EMbase, Chinese BioMedical Literature on disc, China National Knowledge Infrastructure, VIP database, and Wanfang database were searched for randomized controlled trials (RCTs), from inception to August 2012. Key outcomes were low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), total cholesterol (TC), blood pressure (BP), hemoglobin A1c (HbA1c), fasting insulin, and adverse events. Twenty RCTs were included in the analysis. Compared to metformin, the combination therapy of sulfonylureas and metformin slightly reduced HDL-C [-0.03, 95 % CI (-0.06, -0.01)] and HbA1c (-0.79, 95 % CI -0.96 to -0.63). However, it showed little effects on LDL-C, TG, TC, and BP. Glipizide plus metformin significantly increased fasting insulin [2.33, 95 % CI (1.94, 2.73)]. Hypoglycemia and nervous system side events were more frequent among patients treated with sulfonylureas plus metformin than metformin alone (RR = 6.79, 95 % CI 3.79-12.17; RR = 1.27, 95 % CI 1.03-1.57; respectively), but less in digestive symptoms (RR = 0.75, 95 % CI 0.67-0.84). Combination therapy with sulfonylureas and metformin may be more effective than metformin alone in improving HbA1c and reducing gastrointestinal reactions. But it had disadvantage of decreasing HDL-C, increasing the risk of hypoglycemia and nervous system side events.

  14. Influence of a pressure gradient distal to implanted bare-metal stent on in-stent restenosis after percutaneous coronary intervention

    DEFF Research Database (Denmark)

    Jensen, Lisette Okkels; Thayssen, Per; Thuesen, Leif

    2007-01-01

    BACKGROUND: Fractional flow reserve predicts cardiac events after coronary stent implantation. The aim of the present study was to assess the 9-month angiographic in-stent restenosis rate in the setting of optimal stenting and a persisting gradient distal to the stent as assessed by a pressure wire...... performed in the target vessel: (1) P(d)/P(a) as distal to the artery as possible (fractional flow reserve per definition); (2) P(d)/P(a) just distal to the stent; (3) P(d)/P(a) just proximal to the stent; and (4) P(d)/P(a) at the ostium. Residual abnormal P(d)/P(a) was defined as a pressure drop between P......(d)/P(a) measured at points 1 and 2. Fractional flow reserve distal to the artery after stenting was significantly lower (0.88+/-0.21 versus 0.97+/-0.05; P

  15. Effects of Drought, Pest Pressure and Light Availability on Seedling Establishment and Growth: Their Role for Distribution of Tree Species across a Tropical Rainfall Gradient.

    Science.gov (United States)

    Gaviria, Julian; Engelbrecht, Bettina M J

    2015-01-01

    Tree species distributions associated with rainfall are among the most prominent patterns in tropical forests. Understanding the mechanisms shaping these patterns is important to project impacts of global climate change on tree distributions and diversity in the tropics. Beside direct effects of water availability, additional factors co-varying with rainfall have been hypothesized to play an important role, including pest pressure and light availability. While low water availability is expected to exclude drought-intolerant wet forest species from drier forests (physiological tolerance hypothesis), high pest pressure or low light availability are hypothesized to exclude dry forest species from wetter forests (pest pressure gradient and light availability hypothesis, respectively). To test these hypotheses at the seed-to-seedling transition, the potentially most critical stage for species discrimination, we conducted a reciprocal transplant experiment combined with a pest exclosure treatment at a wet and a dry forest site in Panama with seeds of 26 species with contrasting origin. Establishment success after one year did not reflect species distribution patterns. However, in the wet forest, wet origin species had a home advantage over dry forest species through higher growth rates. At the same time, drought limited survival of wet origin species in the dry forest, supporting the physiological tolerance hypothesis. Together these processes sort species over longer time frames, and exclude species outside their respective home range. Although we found pronounced effects of pests and some effects of light availability on the seedlings, they did not corroborate the pest pressure nor light availability hypotheses at the seed-to-seedling transition. Our results underline that changes in water availability due to climate change will have direct consequences on tree regeneration and distributions along tropical rainfall gradients, while indirect effects of light and pests

  16. Effects of Drought, Pest Pressure and Light Availability on Seedling Establishment and Growth: Their Role for Distribution of Tree Species across a Tropical Rainfall Gradient.

    Directory of Open Access Journals (Sweden)

    Julian Gaviria

    Full Text Available Tree species distributions associated with rainfall are among the most prominent patterns in tropical forests. Understanding the mechanisms shaping these patterns is important to project impacts of global climate change on tree distributions and diversity in the tropics. Beside direct effects of water availability, additional factors co-varying with rainfall have been hypothesized to play an important role, including pest pressure and light availability. While low water availability is expected to exclude drought-intolerant wet forest species from drier forests (physiological tolerance hypothesis, high pest pressure or low light availability are hypothesized to exclude dry forest species from wetter forests (pest pressure gradient and light availability hypothesis, respectively. To test these hypotheses at the seed-to-seedling transition, the potentially most critical stage for species discrimination, we conducted a reciprocal transplant experiment combined with a pest exclosure treatment at a wet and a dry forest site in Panama with seeds of 26 species with contrasting origin. Establishment success after one year did not reflect species distribution patterns. However, in the wet forest, wet origin species had a home advantage over dry forest species through higher growth rates. At the same time, drought limited survival of wet origin species in the dry forest, supporting the physiological tolerance hypothesis. Together these processes sort species over longer time frames, and exclude species outside their respective home range. Although we found pronounced effects of pests and some effects of light availability on the seedlings, they did not corroborate the pest pressure nor light availability hypotheses at the seed-to-seedling transition. Our results underline that changes in water availability due to climate change will have direct consequences on tree regeneration and distributions along tropical rainfall gradients, while indirect effects of

  17. Towards improved estimation of the unsaturated soil hydraulic conductivity in the near saturated range by a fully automated, pressure controlled unit gradient experiment.

    Science.gov (United States)

    Werisch, Stefan; Müller, Marius

    2017-04-01

    Determination of soil hydraulic properties has always been an important part of soil physical research and model applications. While several experiments are available to measure the water retention of soil samples, the determination of the unsaturated hydraulic conductivity is often more complicated, bound to strong assumption and time consuming. Although, the application of unit gradient experiments is recommended since the middle of the last century, as one method towards a (assumption free) direct measurement of the unsaturated hydraulic conductivity, data from unit gradient experiments is seldom to never reported in literature. We developed and build a fully automated, pressure controlled, unit gradient experiment, which allows a precise determination of the unsaturated soil hydraulic conductivity K(h) and water retention VWC(h), especially in the highly dynamic near saturated range. The measurement apparatus applies the concept of hanging water columns and imposes the required soil water pressure by dual porous plates. This concepts allows the simultaneous and direct measurement of water retention and hydraulic conductivity. Moreover, this approach results in a technically less demanding experiment than related flux controlled experiments, and virtually any flux can be measured. Thus, both soil properties can be measured in mm resolution, for wetting and drying processes, between saturation and field capacity for all soil types. Our results show, that it is important to establish separate measurements of the unsaturated hydraulic conductivity in the near saturated range, as the shape of the retention function and hydraulic conductivity curve do not necessarily match. Consequently, the prediction of the hydraulic conductivity curve from measurements of the water retention behavior in combination with a value for the saturated hydraulic conductivity can be misleading. Thus, separate parameterizations of the individual functions might be necessary and are

  18. Low dose of hydrochlorothiazide, in combination with angiotensin receptor blocker, reduces blood pressure effectively without adverse effect on glucose and lipid profiles.

    Science.gov (United States)

    Fujiwara, Wakaya; Izawa, Hideo; Ukai, Gen; Yokoi, Hiroatsu; Mukaide, Daisuke; Kinoshita, Kohsuke; Morimoto, Shin-ichiro; Ishii, Junichi; Ozaki, Yukio; Nomura, Masanori

    2013-05-01

    Previous studies have shown highly effective lowering of blood pressure with thiazide diuretics in combination with angiotensin receptor blockers. However, thiazide diuretics may cause the development of diabetes and abnormal lipid metabolism. Little is known as to whether dysmetabolic potential of thiazide diuretics could be neutralized when adding angiotensin receptor blockers. This study consisted of 26 patients with essential hypertension. Patients were randomized to 24 weeks of treatment with either candesartan, 12 mg monotherapy (n = 13, group A), or hydrochlorothiazide (HCTZ), 6.25 mg in combination with candesartan, 8 mg (n = 13, group B). Before and after treatment, we assessed glucose and lipid profiles including adiponectin, resistin, and active glucagon-like peptide-1 (GLP-1) levels. At baseline, there were no differences in age, body mass index, systolic blood pressure (SBP), and diastolic blood pressure (DBP), as well as plasma levels of hemoglobin A1c, insulin, low-density lipoprotein cholesterol, triglycerides, adiponectin, resistin, and active GLP-1 between the two groups. There were significant reductions in SBP (from 152 ± 10 mmHg at baseline to 134 ± 12 mmHg after treatment) and DBP (from 84 ± 5 mmHg at baseline to 71 ± 8 mmHg after treatment) in group A. There were also significant reductions in SBP (from 148 ± 10 at baseline to 128 ± 7 mmHg after treatment) and DBP (from 90 ± 9 at baseline to 74 ± 12 mmHg after treatment) in group B. There were no differences in reduction of SBP or DBP after 24 weeks of treatment between the two groups. There were no changes of the glucose and lipid profiles, including adiponectin, resistin, insulin, and active GLP-1 levels after 24 weeks of treatment in both groups. A low dose of HCTZ in combination with candesartan reduces blood pressure effectively without adverse effects on the glucose and lipid profiles. Therefore, the combination of thiazide diuretics and angiotensin receptor blockers could

  19. What Sets Temperature Gradients in Galaxy Clusters? Implications for non-thermal pressure support and mass-observable scaling relations

    CERN Document Server

    McCourt, Michael; Parrish, Ian J

    2012-01-01

    We present a spherically symmetric model for the origin and evolution of the temperature profiles in the hot plasma filling galaxy groups and clusters. We find that the gas in clusters is generically not isothermal, and that the temperature declines with radius at large distances from the cluster center (outside the core- and scale radii). This temperature profile is determined by the accretion history of the halo, and is not quantitatively well-described by a polytropic model. We explain quantitatively how the large-scale temperature gradient persists in spite of thermal conduction and convection. These results are a consequence of the cosmological assembly of clusters and cannot be reproduced with non-cosmological simulations of isolated halos. We show that the variation in halo assembly histories produces a ~10% scatter in temperature at fixed mass. On top of this scatter, conduction decreases the temperature of the gas near the scale radius in massive clusters, which may bias hydrostatic mass estimates in...

  20. 新型压差式吸附式制冷机的设计%Design of the pressure gradient adsorption refrigerator

    Institute of Scientific and Technical Information of China (English)

    张艳飞; 余晓明

    2011-01-01

    In this paper, the pressure gradient adsorption refrigerator system was introduced, this system based on the solar energy as the energy source used the osmotic pressure which could take the water from evaporator to the condenser. Water was absorbed by the absorption plate firstly, and then arrived the last circle by the osmotic pressure, and then extruded out from absorption material to condenser intermittently so as to take water out from the evaporator to produce refrigerating effect. The continuous adsorption refrigeration could be achieved by virtue of changing open direction of four - way directional control valve in the solar refrigeration system.%设计了一种以太阳能为驱动力,利用渗透压将水分从蒸发器端传输到冷凝器端的压差式吸附制冷机.水分先在蒸发器端被吸附板吸收,再通过渗透压自动运输到最后环节段,并被膨胀物质间歇式地挤压出吸水材料,进入冷凝器,从而保证水分不断从蒸发器抽出,产生制冷效果.通过改变太阳能制冷系统的四通换向阀的开启方向,实现吸附式制冷系统的连续制冷.

  1. Postoperative pharyngolaryngeal adverse events with laryngeal mask airway (LMA Supreme) in laparoscopic surgical procedures with cuff pressure limiting 25 cmH₂O: prospective, blind, and randomised study.

    Science.gov (United States)

    Kang, Joo-Eun; Oh, Chung-Sik; Choi, Jae Won; Son, Il Soon; Kim, Seong-Hyop

    2014-01-01

    To reduce the incidence of postoperative pharyngolaryngeal adverse events, laryngeal mask airway (LMA) manufacturers recommend maximum cuff pressures not exceeding 60 cmH₂O. We performed a prospective randomised study, comparing efficacy and adverse events among patients undergoing laparoscopic surgical procedures who were allocated randomly into low (limiting 25 cmH₂O, L group) and high (at 60 cmH₂O, H group) LMA cuff pressure groups with LMA Supreme. Postoperative pharyngolaryngeal adverse events were evaluated at discharge from postanaesthetic care unit (PACU) (postoperative day 1, POD 1) and 24 hours after discharge from PACU (postoperative day 2, POD 2). All patients were well tolerated with LMA without ventilation failure. Before pneumoperitoneum, cuff volume and pressure and oropharyngeal leak pressure (OLP) showed significant differences. Postoperative sore throat at POD 2 (3 versus 12 patients) and postoperative dysphagia at POD 1 and POD 2 (0 versus 4 patients at POD 1; 0 versus 4 patients at POD 2) were significantly lower in L group, compared with H group. In conclusion, LMA with cuff pressure limiting 25 cmH₂O allowed both efficacy of airway management and lower incidence of postoperative adverse events in laparoscopic surgical procedures. This clinical trial is registered with KCT0000334.

  2. Postoperative Pharyngolaryngeal Adverse Events with Laryngeal Mask Airway (LMA Supreme in Laparoscopic Surgical Procedures with Cuff Pressure Limiting 25 cmH2O: Prospective, Blind, and Randomised Study

    Directory of Open Access Journals (Sweden)

    Joo-Eun Kang

    2014-01-01

    Full Text Available To reduce the incidence of postoperative pharyngolaryngeal adverse events, laryngeal mask airway (LMA manufacturers recommend maximum cuff pressures not exceeding 60 cmH2O. We performed a prospective randomised study, comparing efficacy and adverse events among patients undergoing laparoscopic surgical procedures who were allocated randomly into low (limiting 25 cmH2O, L group and high (at 60 cmH2O, H group LMA cuff pressure groups with LMA Supreme. Postoperative pharyngolaryngeal adverse events were evaluated at discharge from postanaesthetic care unit (PACU (postoperative day 1, POD 1 and 24 hours after discharge from PACU (postoperative day 2, POD 2. All patients were well tolerated with LMA without ventilation failure. Before pneumoperitoneum, cuff volume and pressure and oropharyngeal leak pressure (OLP showed significant differences. Postoperative sore throat at POD 2 (3 versus 12 patients and postoperative dysphagia at POD 1 and POD 2 (0 versus 4 patients at POD 1; 0 versus 4 patients at POD 2 were significantly lower in L group, compared with H group. In conclusion, LMA with cuff pressure limiting 25 cmH2O allowed both efficacy of airway management and lower incidence of postoperative adverse events in laparoscopic surgical procedures. This clinical trial is registered with KCT0000334.

  3. Postoperative Pharyngolaryngeal Adverse Events with Laryngeal Mask Airway (LMA Supreme) in Laparoscopic Surgical Procedures with Cuff Pressure Limiting 25 cmH2O: Prospective, Blind, and Randomised Study

    Science.gov (United States)

    Kang, Joo-Eun; Choi, Jae Won; Son, Il Soon

    2014-01-01

    To reduce the incidence of postoperative pharyngolaryngeal adverse events, laryngeal mask airway (LMA) manufacturers recommend maximum cuff pressures not exceeding 60 cmH2O. We performed a prospective randomised study, comparing efficacy and adverse events among patients undergoing laparoscopic surgical procedures who were allocated randomly into low (limiting 25 cmH2O, L group) and high (at 60 cmH2O, H group) LMA cuff pressure groups with LMA Supreme. Postoperative pharyngolaryngeal adverse events were evaluated at discharge from postanaesthetic care unit (PACU) (postoperative day 1, POD 1) and 24 hours after discharge from PACU (postoperative day 2, POD 2). All patients were well tolerated with LMA without ventilation failure. Before pneumoperitoneum, cuff volume and pressure and oropharyngeal leak pressure (OLP) showed significant differences. Postoperative sore throat at POD 2 (3 versus 12 patients) and postoperative dysphagia at POD 1 and POD 2 (0 versus 4 patients at POD 1; 0 versus 4 patients at POD 2) were significantly lower in L group, compared with H group. In conclusion, LMA with cuff pressure limiting 25 cmH2O allowed both efficacy of airway management and lower incidence of postoperative adverse events in laparoscopic surgical procedures. This clinical trial is registered with KCT0000334. PMID:24778598

  4. Investigation of the effects of time periodic pressure and engpotential gradients on viscoelastic fluid flow in circular narrow confinements

    DEFF Research Database (Denmark)

    Nguyen, Trieu; van der Meer, Devaraj; van den Berg, Albert

    2017-01-01

    -Boltzmann equation, together with the incompressible Cauchy momentum equation under no-slip boundary conditions for viscoelastic fluid in the case of a combination of time periodic pressure-driven and electro-osmotic flow. The resulting solutions allow us to predict the electrical current and solution flow rate....... As expected from the assumption of linear viscoelasticity, the results satisfy the Onsager reciprocal relation, which is important since it enables an analogy between fluidic networks in this flow configuration and electric circuits. The results especially are of interest for micro-and nanofluidic energy...

  5. Comments on Evanescent Pressure Gradient Response in the Upper Ocean to Subinertial Wind Stress Forcing of Finite Wavelength

    Science.gov (United States)

    1988-07-01

    IIl/r’ (b). The dashed curve is the solution presented by response in the upper ocean to subinertial wind stress forcing Codes WM and the solid curve...especially as c hand side of Eq. (3). approaches the inertial frequency f,. h nd s re is 0 With pressure terms included, the expression for The wind ... stress is mixed layer velocities are [Eq. (3.1) in WM], in the 7 = [0, r’ Re(e""’ C)] (6) usual fluid mechanical notation. and following WM. we are

  6. Pressure gradient of a two-region solid-liquid flow in horizontal wells; Gradiente de presion de un flujo bifasico solido-liquido de dos regiones en pozos horizontales

    Energy Technology Data Exchange (ETDEWEB)

    Salazar Mendoza, R.; Garcia Gutierrez, A. [Centro Nacional de Investigacion y Desarrollo Tecnologico (CENIDET), Cuernavaca, Morelos (Mexico); Espinosa Paredes, G. [Universidad Autonoma Metropolitana-Iztapalapa, Mexico, D.F. (Mexico)

    2005-12-01

    A theoretical analysis is presented for the problem of cutting transport in a two-region, slurry-flow system in horizontal pipes, with a stationary bed of drill cuttings as a porous medium (w-region) below a two-phase dispersed flow (n-region). Volume averaging was applied to derive a rigorous mathematical model where each variable is precisely defined. The model includes volume-averaged transport equations for both the two-phase dispersed flow and the porous-medium regions, and terms from a macroscopic forces balance. The solution of the two-region model allowed evaluation of the behavior of the pressure gradient as a function of velocity, total volume fraction of cuttings, and the relationship between the height of the stationary bed and pipe diameter. It is based on a backward, finite-difference explicit scheme. The simulated physical system is a pipe diameter. It is based on a backward, finite-difference explicit scheme. The simulated physical system is a pipe of 4.135 m in horizontal length and 0.0508 m in diameter. A one dimensional, mesh-centered grid is used, consisting of 10 nodes. The numerical results were compared with experimental data on slurry flows and a good agreement was found. [Spanish] Se presenta un analisis teorico del problema de transporte de recortes de perforacion en pozos horizontales. Se estudia el flujo bifasico solido-liquido en dos regiones donde la region inferior es un lecho estacionario de recortes, considerado como medio poroso, mientras que la region superior es un flujo bifasico disperso solido-liquido. Se aplica el metodo de promediado en volumen para derivar de manera matematicamente rigurosa el modelo de dos regiones. El modelo incluye las ecuaciones de transporte promediadas en volumen para cada region y terminos que resultan de un balance de fuerzas macroscopico. La solucion del modelo permite evaluar el comportamiento del gradiente de presion como funcion de la velocidad, la fraccion de volumen de recortes total y la

  7. Improper use of the starting pressure gradient of linear flow in the plane radial flow equation%线性流的启动压力梯度不能用于平面径向流方程

    Institute of Scientific and Technical Information of China (English)

    陈元千

    2011-01-01

    Bear first presented a physical concept and discriminant of the starting pressure gradient in 1972 when he studied the applied lower limit of the Darcy law. And then Professor Ge Jiali introduced the starting pressure gradient to China in 1982. The so-called starting pressure gradient refers to a pressure gradient that makes a fluid in fluid-saturated cores begin to flow. It should be pointed out that the pressure gradient of linear flow is directly proportional to the flow rate, while the starting pressure gradient is a constant. The pressure gradient of plane radial flow is directly proportional to the flow rate but inversely to the radial radius. Moreover, the starting pressure7 gradient at a position of different radial radius is variable. It is controversial for the correctness to have directly applied the Bear's starting pressure gradient and discriminant of linear flow to the plane radial flow equation by some researchers. Theoretically, the paper analyzed both the pressure gradient and starting pressure gradient of linear flow and plane radial flow and proposed the conception of starting flow rate. At the same time, a more applicable method to evaluate the starting drawdown pressure and starting bottomhole flowing pressure of low permeability tight reservoirs was proposed.%启动压力梯度的物理概念及判别式是Bear于1972年在利用岩心测试资料研究达西定律的应用下限时提出来的,葛家理教授首次介绍到我国.所谓启动压力梯度,是指流体在饱和的岩心开始发生流动时的压力梯度.应当指出,线性流的压力梯度与流量成正比,启动压力梯度为常数;平面径向流的压力梯度与流量成正比,与径向半径成反比,而且,不同径向半径位置的启动压力梯度是不同的.有关学者将线性流启动的压力梯度及判别式直接用于平面径向流方程的正确性值得质疑.笔者对线性流和平面径向流的压力梯度和启动压力梯度问题进行了

  8. Pressure shifts and abundance gradients in the atmosphere of the DAZ white dwarf GALEX J193156.8+011745

    CERN Document Server

    Vennes, S; Nemeth, P

    2011-01-01

    We present a detailed model atmosphere analysis of high-dispersion and high signal-to-noise ratio spectra of the heavily polluted DAZ white dwarf GALEX J1931+0117. The spectra obtained with the VLT-Kueyen/UV-Visual Echelle Spectrograph show several well-resolved Si II spectral lines enabling a study of pressure effects on line profiles. We observed large Stark shifts in silicon lines in agreement with theoretical predictions and laboratory measurements. Taking into account Stark shifts in the calculation of synthetic spectra we reduced the scatter in individual line radial velocity measurements from ~ 3 to < 1 km/s. We present revised abundances of O, Mg, Si, Ca, and Fe based on a critical review of line broadening parameters and oscillator strengths. The new measurements are generally in agreement with our previous analysis with the exception of magnesium with a revised abundance a factor of two lower than previously estimated. The magnesium, silicon and iron abundances exceed solar abundances, but the ox...

  9. Transitional Boundary Layers Under the Influence of High Free Stream Turbulence, Intensive Wall Cooling and High Pressure Gradients in Hot Gas Circulation. Ph.D. Thesis - Technische Hochschule, Karlsruhe, 1985

    Science.gov (United States)

    Rued, Klaus

    1987-01-01

    The requirements for fundamental experimental studies of the influence of free stream turbulence, pressure gradients and wall cooling are discussed. Under turbine-like free stream conditions, comprehensive tests of transitional boundary layers with laminar, reversing and turbulent flow increments were performed to decouple the effects of the parameters and to determine the effects during mutual interaction.

  10. Buoyancy-Driven Heat Transfer During Application of a Thermal Gradient for the Study of Vapor Deposition at Low Pressure Using and Ideal Gas

    Science.gov (United States)

    Frazier, D. O.; Hung, R. J.; Paley, M. S.; Penn, B. G.; Long, Y. T.

    1996-01-01

    A mathematical model has been developed to determine heat transfer during vapor deposition of source materials under a variety of orientations relative to gravitational accelerations. The model demonstrates that convection can occur at total pressures as low as 10-2 mm Hg. Through numerical computation, using physical material parameters of air, a series of time steps demonstrates the development of flow and temperature profiles during the course of vapor deposition. These computations show that in unit gravity vapor deposition occurs by transport through a fairly complicated circulating flow pattern when applying heat to the bottom of the vessel with parallel orientation with respect to the gravity vector. The model material parameters for air predict the effect of kinematic viscosity to be of the same order as thermal diffusivity, which is the case for Prandtl number approx. 1 fluids. Qualitative agreement between experiment and the model indicates that 6-(2-methyl-4-nitroanilino)-2,4-hexadiyn-l-ol (DAMNA) at these pressures indeed approximates an ideal gas at the experiment temperatures, and may validate the use of air physical constants. It is apparent that complicated nonuniform temperature distribution in the vapor could dramatically affect the homogeneity, orientation, and quality of deposited films. The experimental test i's a qualitative comparison of film thickness using ultraviolet-visible spectroscopy on films generated in appropriately oriented vapor deposition cells. In the case where heating of the reaction vessel occurs from the top, deposition of vapor does not normally occur by convection due to a stable stratified medium. When vapor deposition occurs in vessels heated at the bottom, but oriented relative to the gravity vector between these two extremes, horizontal thermal gradients induce a complex flow pattern. In the plane parallel to the tilt axis, the flow pattern is symmetrical and opposite in direction from that where the vessel is

  11. Portal hypertension in patients with cirrhosis: indirect assessment of hepatic venous pressure gradient by measuring azygos flow with 2D-cine phase-contrast magnetic resonance imaging.

    Science.gov (United States)

    Gouya, Hervé; Grabar, Sophie; Vignaux, Olivier; Saade, Anastasia; Pol, Stanislas; Legmann, Paul; Sogni, Philippe

    2016-07-01

    To measure azygos, portal and aortic flow by two-dimensional cine phase-contrast magnetic resonance imaging (2D-cine PC MRI), and to compare the MRI values to hepatic venous pressure gradient (HVPG) measurements, in patients with cirrhosis. Sixty-nine patients with cirrhosis were prospectively included. All patients underwent HVPG measurements, upper gastrointestinal endoscopy and 2D-cine PC MRI measurements of azygos, portal and aortic blood flow. Univariate and multivariate regression analyses were used to evaluate the correlation between the blood flow and HVPG. The performance of 2D-cine PC MRI to diagnose severe portal hypertension (HVPG ≥ 16 mmHg) was determined by receiver operating characteristic curve (ROC) analysis, and area under the curves (AUC) were compared. Azygos and aortic flow values were associated with HVPG in univariate linear regression model. Azygos flow (p cine PC MRI is a promising technique to evaluate significant portal hypertension in patients with cirrhosis. • Noninvasive HVPG assessment can be performed with MRI azygos flow. • Azygos MRI flow is an easy-to-measure marker to detect significant portal hypertension. • MRI flow is more specific that varice grade to detect portal hypertension.

  12. Tuning of turbulent boundary layer anisotropy for improved surface pressure and trailing-edge noise modeling

    DEFF Research Database (Denmark)

    Bertagnolio, Franck; Fischer, Andreas; Zhu, Wei Jun

    2014-01-01

    The modeling of the surface pressure spectrum beneath a turbulent boundary layer is investigated, focusing on the case of airfoil flows and associated trailing edge noise prediction using the so-called TNO model. This type of flow is characterized by the presence of an adverse pressure gradient a...

  13. Effect of canagliflozin on blood pressure and adverse events related to osmotic diuresis and reduced intravascular volume in patients with type 2 diabetes mellitus.

    Science.gov (United States)

    Weir, Matthew R; Januszewicz, Andrzej; Gilbert, Richard E; Vijapurkar, Ujjwala; Kline, Irina; Fung, Albert; Meininger, Gary

    2014-12-01

    The effects of canagliflozin, a sodium glucose co-transporter 2 inhibitor, on blood pressure (BP) and osmotic diuresis- and intravascular volume reduction-related adverse events (AEs) were evaluated using pooled data from four placebo-controlled, phase 3 studies in patients with type 2 diabetes mellitus (T2DM; N=2313). At baseline, 1332 (57.6%) patients were taking an antihypertensive medication. Canagliflozin 100 mg and 300 mg provided reductions (95% confidence interval [CI]) from baseline in systolic BP (SBP) compared with placebo (-4.3 mm Hg [-5.0 to -3.5], -5.0 mm Hg [-5.8 to -4.2], and -0.3 mm Hg [-1.2 to 0.5], respectively) and in diastolic BP (DBP; -2.5 mm Hg [-2.9 to -2.0], -2.4 mm Hg [-2.9 to -1.9], and -0.6 mm Hg [-1.1 to -0.02], respectively). Placebo-subtracted reductions (95% CI) in SBP with canagliflozin 100 mg and 300 mg were -4.0 mm Hg (-5.1 to -2.8) and -4.7 mm Hg (-5.8 to -3.5) and reductions in DBP were -1.9 mm Hg (-2.6 to -1.2) and -1.9 mm Hg (-2.6 to -1.1), respectively. Compared with the overall population, patients with elevated baseline SBP (≥140 mm Hg) had numerically greater absolute SBP reductions (95% CI) with canagliflozin 100 mg and 300 mg and placebo (-12.8 mm Hg [-15.2 to -10.5], -14.2 mm Hg [-16.4 to -12.0], and -6.8 mm Hg [-9.1 to -4.5], respectively). Numerically greater DBP reductions were seen in patients with DBP ≥90 mm Hg at baseline (-5.9 mm Hg [-8.2 to -3.6], -9.0 mm Hg [-11.1 to -6.9], and -7.4 mm Hg [-9.6 to -5.1], respectively). In patients with elevated SBP at baseline, placebo-subtracted reductions (95% CI) in SBP with canagliflozin 100 mg and 300 mg were -6.0 mm Hg (-9.1 to -2.9) and -7.4 mm Hg (-10.4 to -4.4), respectively. Placebo-subtracted changes in DBP were 1.5 mm Hg (-1.6 to 4.5) and -1.6 mm Hg (-4.5 to 1.2), respectively, in those with elevated DBP at baseline. Canagliflozin 100 mg and 300 mg were associated with increased incidence of osmotic diuresis-related AEs (e.g., pollakiuria [increased urine volume

  14. Revisiting the quest for a universal log-law and the role of pressure gradient in "canonical" wall-bounded turbulent flows

    Science.gov (United States)

    Monkewitz, Peter A.

    2017-09-01

    The trinity of so-called "canonical" wall-bounded turbulent flows, comprising the zero pressure gradient turbulent boundary layer, abbreviated ZPG TBL, turbulent pipe flow, and channel/duct flows has continued to receive intense attention as new and more reliable experimental data have become available. Nevertheless, the debate on whether the logarithmic part of the mean velocity profile, in particular the Kármán constant κ , is identical for these three canonical flows or flow-dependent is still ongoing. In this paper, the asymptotic matching requirement of equal κ in the logarithmic overlap layer, which links the inner and outer flow regions, and in the expression for the centerline/free-stream velocity is reiterated and shown to preclude a universal logarithmic overlap layer in the three canonical flows. However, the majority of pipe and channel flow studies at friction Reynolds numbers Reτ below ≈104 extract from near-wall profiles the same κ of 0.38-0.39 as in the ZPG TBL. This apparent contradiction is resolved by a careful reanalysis of high-quality mean velocity profiles in the Princeton "Superpipe" and other pipes, channels, and ducts, which shows that the mean velocity in a near-wall region extending to around 700 "+" units in channels and ducts and 500 "+" units in pipes is the same as in the ZPG TBL. In other words, all the "canonical" flow profiles contain the lower end of the ZPG TBL log-region, which starts at a wall distance of 150 -200 "+" units with a universal κ of κZPG≈0.384 . This interior log-region is followed by a second logarithmic region with a flow specific κ >κZPG , which increases monotonically with pressure gradient. This second, exterior log-layer is the actual overlap layer matching up to the outer expansion, which implies equality of the exterior κ and κCL obtained from the evolution of the respective centerline velocity with Reynolds number. The location of the switch-over point implies furthermore that this second

  15. Blood pressure gradients and cardiovascular risk factors in urban and rural populations in Abia State South Eastern Nigeria using the WHO STEPwise approach.

    Directory of Open Access Journals (Sweden)

    Ikechi Gareth Okpechi

    Full Text Available BACKGROUND: Developing countries of sub-Saharan Africa (SSA face a double burden of non-communicable diseases (NCDs and communicable diseases. As high blood pressure (BP is a common global cardiovascular (CV disorder associated with high morbidity and mortality, the relationship between gradients of BP and other CV risk factors was assessed in Abia State, Nigeria. METHODS: Using the WHO STEPwise approach to surveillance of chronic disease risk factors, we conducted a population-based cross-sectional survey in Abia state, Nigeria from August 2011 to March 2012. Data collected at various steps included: demographic and behavioral risk factors (Step 1; BP and anthropometric measurements (Step 2, and fasting blood cholesterol and glucose (Step 3. RESULTS: Of the 2983 subjects with complete data for analysis, 52.1% were females and 53.2% were rural dwellers. Overall, the distribution of selected CV disease risk factors was diabetes (3.6%, hypertension (31.4%, cigarette smoking (13.3%, use of smokeless tobacco (4.8%, physical inactivity (64.2% and being overweight or obese (33.7%. Presence of hypertension, excessive intake of alcohol, smoking (cigarette and smokeless tobacco and physical inactivity occurred more frequently in males than in females (p<0.05; while low income, lack of any formal education and use of smokeless tobacco were seen more frequently in rural dwellers than in those living in urban areas (p<0.05. The frequency of selected CV risk factors increased as BP was graded from optimal, normal to hypertension; and high BP correlated with age, gender, smokeless tobacco, overweight or obesity, annual income and level of education. CONCLUSION: Given the high prevalence of hypertension in this part of Nigeria, there is an urgent need to focus on the reduction of preventable CV risk factors we have observed to be associated with hypertension, in order to effectively reduce the burden of NCDs in Africa.

  16. Gradient networks

    Science.gov (United States)

    Toroczkai, Zoltán; Kozma, Balázs; Bassler, Kevin E.; Hengartner, N. W.; Korniss, G.

    2008-04-01

    Gradient networks are defined (Toroczkai and Bassler 2004 Nature 428 716) as directed graphs formed by local gradients of a scalar field distributed on the nodes of a substrate network G. We present the derivation for some of the general properties of gradient graphs and give an exact expression for the in-degree distribution R(l) of the gradient network when the substrate is a binomial (Erd{\\;\\kern -0.10em \\raise -0.35ex \\{{^{^{\\prime\\prime}}}}\\kern -0.57em \\o} s-Rényi) random graph, G_{N,p} , and the scalars are independent identically distributed (i.i.d.) random variables. We show that in the limit N \\to \\infty, p \\to 0, z = pN = \\mbox{const} \\gg 1, R(l)\\propto l^{-1} for l Bassler (2004 Nature 428 716).

  17. Maternal Fish Oil Supplementation during Lactation May Adversely Affect Long-Term Blood Pressure, Energy Intake, and Physical Activity of 7-Year-Old Boys

    DEFF Research Database (Denmark)

    Asserhøj, M.; Nehammer, S.; Matthiessen, Jeppe

    2009-01-01

    . Danish mothers (n = 122) were randomized to FO [1.5 g/d (n-3) LCPUFA] or olive oil (OO) supplementations during the first 4 mo of lactation. The trial also included a high-fish intake reference group (n = 53). Ninety-eight children were followed-up with blood pressure and anthropometry measurements at 7......Early nutrition may program obesity and cardiovascular risk later in life, and one of the potential agents is (n-3) long-chain PUFA (LCPUFA). In this study, our objective was to examine whether fish oil (FO) supplementation during lactation affects blood pressure and body composition of children...

  18. Monitoring and Analysis of Suspected Adverse Events on Disposable High Pressure Syringe in Anhui%安徽省一次性使用高压注射器不良事件重点监测分析

    Institute of Scientific and Technical Information of China (English)

    梁燕; 朱凤仪; 杨建林; 黄萍; 汪峰

    2016-01-01

    Objective: To investigate and analysis suspicious adverse events induced by disposable high pressure syringe through emphasis on monitoring in Anhui province, and put forward some opinioins to take precautions against the similar adverse events. Methods:Information of suspicious adverse events caused by disposable high pressure syringe through emphasis on monitoring in Anhui were anayzed statistical y by Excel and the reason of adverse events were analysis through investigation and literature. Results:The percentage of equipment failure as connection pipeline, needle tube and piston were 84.0% in suspected adverse events. The adverse events were mainly caused by product factors, fol owed by non normal use of medical personnel factors and patients with aging, cancer and other factors of the original disease. Conclusion: The 25 cases as alert as a condition, the production enterprises should pay at ention to the connection pipeline, needle tube and piston components such as material selection, design and quality, and strengthen to instal training to medical staff. Medical staff should strengthen the observation and nursing of elderly patients, cancer patients and choose the appropriate injection pressure, observe the patient's reaction, to reduce the occurrence of similar adverse events.%目的:针对安徽省内一次性使用高压注射器导致的可疑不良事件,进行调查、分析,提出相应的措施,预防同类不良事件的发生。方法:用 Excel 对我省重点监测期间收集到的一次性使用高压注射器可疑不良事件数据进行统计,并通过调研、查阅文献等方式对不良事件案例进行原因分析。结果:25例一次性使用高压注射器可疑不良事件报告中,连接管路、针筒、活塞等发生的器械故障占84.0%。调研发现引起不良事件的原因主要为产品因素。其次为医护人员非正常使用的因素和患者老龄、肿瘤等原患疾病

  19. Potential Deaths Averted and Serious Adverse Events Incurred from Adoption of the SPRINT Intensive Blood Pressure Regimen in the U.S.: Projections from NHANES.

    Science.gov (United States)

    Bress, Adam P; Kramer, Holly; Khatib, Rasha; Beddhu, Srinivasan; Cheung, Alfred K; Hess, Rachel; Bansal, Vinod K; Cao, Guichan; Yee, Jerry; Moran, Andrew E; Durazo-Arvizu, Ramon A; Muntner, Paul; Cooper, Richard S

    2017-02-13

    Background -The Systolic Blood Pressure Intervention Trial (SPRINT) demonstrated a 27% reduction in all-cause mortality with a systolic blood-pressure (SBP) goal of SBP treatment goal was implemented in all eligible U.S. adults. Methods -SPRINT eligibility criteria were applied to the 1999-2006 National Health and Nutrition Examination Survey and linked with the National Death Index through December 2011. SPRINT eligibility included age ≥ 50 years, SBP of 130-180 mmHg (depending on the number of antihypertensive medications being taken), and high CVD risk. Exclusion criteria were diabetes, history of stroke, >1 gram of proteinuria, heart failure, estimated glomerular filtration rate SBP treatment. Results -The mean age was 68.6 years and 83.2% and 7.4% were non-Hispanic white and non-Hispanic black, respectively. The annual mortality rate was 2.20% (95%CI 1.91%-2.48%) and intensive SBP treatment was projected to prevent about 107,500 deaths per year (95%CI 93,300-121,200) and give rise to 56,100 (95%CI 50,800-61,400) episodes of hypotension, 34,400 (95%CI 31,200-37,600) episodes of syncope, 43,400 (95%CI 39,400-47,500) serious electrolyte disorders, and 88,700 (95%CI 80,400-97,000) cases of acute kidney injury per year. The analysis of extremes approach indicated that the range of estimated lower and upper bound number of deaths prevented per year with intensive SBP control was 34,600 to 179,600. Intensive SBP control was projected to prevent 46,100 (95%CI 41,800-50,400) cases of heart failure annually. Conclusions -If fully implemented in eligible U.S. adults, intensive SBP treatment could prevent about 107,500 deaths per year. A consequence of this treatment strategy, however, could be an increase in SAEs.

  20. Effect of pressure on Fe3+/ΣFe ratio in a mafic magma and consequences for magma ocean redox gradients

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H. L.; Hirschmann, M. M.; Cottrell, E.; Withers, A. C.

    2017-05-01

    Experiments establishing the effect of pressure on the Fe3+/ΣFe ratio of andesitic silicate melts buffered by coexisting Ru and RuO2 were performed from 100 kPa to 7 GPa and 1400–1750 °C. Fe3+/ΣFe ratios were determined by room temperature Mössbauer spectroscopy, but corrected for the effects of recoilless fraction. Fe3+/ΣFe ratios in quenched glasses decrease with increasing pressure consistent with previous results between 100 kPa and 3 GPa (O’Neill et al., 2006), but show only small pressure effects above 5 GPa. Ratios also decrease with increasing temperature. Mössbauer hyperfine parameters indicate mean coordination of Fe3+ ions of ~5 in glasses, with no dependence on the pressure from which the glasses were quenched, but show an increase with pressure in mean coordination of Fe2+ ions, from ~5 to ~6. XANES spectra on these glasses show variations in pre-edge intensities and centroid positions that are systematic with Fe3+/ΣFe, but are displaced from those established from otherwise identical andesitic glasses quenched at 100 kPa (Zhang et al., 2016). These systematics permit construction of a new XANES calibration curve relating pre-edge sub-peak intensities to Fe3+/ΣFe applicable to high pressure glasses. Consistent with interpretations of the Mössbauer hyperfine parameters, XANES pre-edge peak features in high pressure glasses are owing chiefly to the effects of pressure on the coordination of Fe2+ ions from ~5.5 to ~6, with negligible effects evident for Fe3+ ions. We use the new data to construct a thermodynamic model relating the effects of oxygen fugacity and pressure on Fe3+/ΣFe. We apply this model to calculate variations in oxygen fugacity in isochemical (constant Fe3+/ΣFe) columns of magma representative of magma oceans, in which fO2 is fixed at the base by equilibration with molten Fe. These calculations

  1. Effect of pressure on Fe3+/ΣFe ratio in a mafic magma and consequences for magma ocean redox gradients

    Science.gov (United States)

    Zhang, H. L.; Hirschmann, M. M.; Cottrell, E.; Withers, A. C.

    2017-05-01

    Experiments establishing the effect of pressure on the Fe3+/ΣFe ratio of andesitic silicate melts buffered by coexisting Ru and RuO2 were performed from 100 kPa to 7 GPa and 1400-1750 °C. Fe3+/ΣFe ratios were determined by room temperature Mössbauer spectroscopy, but corrected for the effects of recoilless fraction. Fe3+/ΣFe ratios in quenched glasses decrease with increasing pressure consistent with previous results between 100 kPa and 3 GPa (O'Neill et al., 2006), but show only small pressure effects above 5 GPa. Ratios also decrease with increasing temperature. Mössbauer hyperfine parameters indicate mean coordination of Fe3+ ions of ∼5 in glasses, with no dependence on the pressure from which the glasses were quenched, but show an increase with pressure in mean coordination of Fe2+ ions, from ∼5 to ∼6. XANES spectra on these glasses show variations in pre-edge intensities and centroid positions that are systematic with Fe3+/ΣFe, but are displaced from those established from otherwise identical andesitic glasses quenched at 100 kPa (Zhang et al., 2016). These systematics permit construction of a new XANES calibration curve relating pre-edge sub-peak intensities to Fe3+/ΣFe applicable to high pressure glasses. Consistent with interpretations of the Mössbauer hyperfine parameters, XANES pre-edge peak features in high pressure glasses are owing chiefly to the effects of pressure on the coordination of Fe2+ ions from ∼5.5 to ∼6, with negligible effects evident for Fe3+ ions. We use the new data to construct a thermodynamic model relating the effects of oxygen fugacity and pressure on Fe3+/ΣFe. We apply this model to calculate variations in oxygen fugacity in isochemical (constant Fe3+/ΣFe) columns of magma representative of magma oceans, in which fO2 is fixed at the base by equilibration with molten Fe. These calculations indicate that oxygen fugacities at the surface of shallow magma oceans are more reduced than at depth. For magma oceans in

  2. Valor do gradiente de pressão retal e anal na evacuação em megacólon adquirido Rectal and anal pressure variation during defecation in patients with acquired megacolon

    Directory of Open Access Journals (Sweden)

    Chia Bin Fang

    2007-09-01

    Full Text Available O megacólon resulta de lesão extensa dos plexos mioentéricos, a qual se traduz por incoordenação motora do cólon com inércia funcional e acalasia do esfíncter anal. Disso resulta duplo distúrbio, em que à dificuldade motora agrega-se o obstáculo para evacuar. Para que haja eliminação fecal é necessário que a pressão retal ultrapasse a anal, havendo um gradiente reto-anal. O objetivo do trabalho foi avaliar este gradiente em 29 pacientes portadores de megacólon, em que as pressões retais e anais foram medidas ao evacuar, comparadas com pessoas normais. Os resultados mostraram que havia pressão retal em centímetros de água aumentada em homens (72,2 ± 29,1 e mulheres (64,5 ± 20,1, superando as respectivas pressões anais de evacuação (66,4 ± 23,2 e 62,1 ± 28,7. As pressões de evacuação, por sua vez, eram muito maiores que as do grupo controle. Isto permitiu concluir haver uma reação adaptativa com maior esforço muscular para evacuar, a fim de superar o obstáculo da acalasia.Megacolon is the result of an extensive lesion of the mioenteric plexus, with lack of motor coordination and achalasia of the anal sphincter. The motility disorder caused by the muscle contraction problems added to a mechanical obstacle results cause constipation. The defecation rectal pressure increases and reaches its peak with the start of fecal flow, exceeding the anal pressure. The objective of this work was to assess the ratio of rectal / anal pressure on 29 megacolon sufferers, compared to normal subjects. Results have shown that defecation rectal pressure was higher than expected for both men (72,2 ± 29,1 cm water and women (64,5 ± 20,1 cm water exceeding the defecation anal pressure (66,4 ± 23,2 and 62,1 ± 28,7 cm water, for men and women, respectively. The defecation pressures were much higher than those of the control group, what led to the conclusion that as an adaptive reaction, muscular effort increases to make evacuation

  3. Exact analytical solutions for moving boundary problems of one-dimensional flow in semi-infinite porous media with consideration of threshold pressure gradient

    Institute of Scientific and Technical Information of China (English)

    王晓冬; 朱光亚; 王磊

    2015-01-01

    By defining new dimensionless variables, nonlinear mathematical models for one-dimensional flow with unknown moving boundaries in semi-infinite porous media are modified to be solved analytically. The exact analytical solutions for both constant-rate and constant-pressure inner boundary constraint problems are obtained by applying the Green’s function. Two transcendental equations for moving boundary problems are obtained and solved using the Newton-Raphson iteration. The exact analytical solutions are then compared with the approximate solutions. The Pascal’s approximate formula in reference is fairly accurate for the moving boundary development under the constant-rate condition. But another Pascal’s approximate formula given in reference is not very robust for constant-pressure condition problems during the early production period, and could lead to false results at the maximum moving boundary distance. Our results also show that, in presence of larger TPG, more pressure drop is required to maintain a constant-rate production. Under the constant-pressure producing condition, the flow rate may decline dramatically due to a large TPG. What’s more, there exists a maximum distance for a given TPG, beyond which the porous media is not disturbed.

  4. Demonstration of a Piston Plug feed System for Feeding Coal/Biomass Mixtures across a Pressure Gradient for Application to a Commercial CBTL System

    Energy Technology Data Exchange (ETDEWEB)

    Santosh Gangwal

    2011-06-30

    Producing liquid transportation fuels and power via coal and biomass to liquids (CBTL) and integrated gasification combined cycle (IGCC) processes can significantly improve the nation's energy security. The Energy Independence and Security Act of 2007 mandates increasing renewable fuels nearly 10-fold to >2.3 million barrels per day by 2022. Coal is abundantly available and coal to liquids (CTL) plants can be deployed today, but they will not become sustainable without large scale CO{sub 2} capture and storage. Co-processing of coal and biomass in CBTL processes in a 60 to 40 ratio is an attractive option that has the potential to produce 4 million barrels of transportation fuels per day by 2020 at the same level of CO{sub 2} emission as petroleum. In this work, Southern Research Institute (Southern) has made an attempt to address one of the major barriers to the development of large scale CBTL processes - cost effective/reliable dry-feeding of coal-biomass mixtures into a high pressure vessel representative of commercial entrained-flow gasifiers. Present method for dry coal feeding involves the use of pressurized lock-hopper arrangements that are not only very expensive with large space requirements but also have not been proven for reliably feeding coal-biomass mixtures without the potential problems of segregation and bridging. The project involved the development of a pilot-scale 250 lb/h high pressure dry coal-biomass mixture feeder provided by TKEnergi and proven for feeding biomass at a scale up to 6 ton/day. The aim of this project is to demonstrate cost effective feeding of coal-biomass mixtures (50:50 to 70:30) made from a variety of coals (bituminous, lignite) and biomass (wood, corn stover, switch grass). The feeder uses a hydraulic piston-based approach to produce a series of plugs of the mixture that act as a seal against high back-pressure of the gasification vessel in to which the mixture is being fed. The plugs are then fed one by one via a

  5. Double-Twisted Conductive Smart Threads Comprising a Homogeneously and a Gradient-Coated Thread for Multidimensional Flexible Pressure-Sensing Devices

    KAUST Repository

    Tai, Yanlong

    2016-03-17

    Fiber-based, flexible pressure-sensing systems have attracted attention recently due to their promising application as electronic skins. Here, a new kind of flexible pressure-sensing device based on a polydimethylsiloxane membrane instrumented with double-twisted smart threads (DTSTs) is reported. DTSTs are made of two conductive threads obtained by coating cotton threads with carbon nanotubes. One thread is coated with a homogeneous thickness of single-walled carbon nanotubes (SWCNTs) to detect the intensity of an applied load and the other is coated with a graded thickness of SWCNTs to identify the position of the load along the thread. The mechanism and capacity of DTSTs to accurately sense an applied load are systematically analyzed. Results demonstrate that the fabricated 1D, 2D, and 3D sensing devices can be used to predict both the intensity and the position of an applied load. The sensors feature high sensitivity (between ≈0.1% and 1.56% kPa) and tunable resolution, good cycling resilience (>104 cycles), and a short response time (minimum 2.5 Hz). The presented strategy is a viable alternative for the design of simple, low-cost pressure sensors.

  6. A New Way to Calculate the Critical Pressure Gradient of Sand Production%计算砂岩出砂临界压力梯度的新方法

    Institute of Scientific and Technical Information of China (English)

    聂向荣; 杨胜来; 丁景辰; 李芳芳; 章星

    2013-01-01

    A capillary-tube model is proposed which could transform the porous medium solid liquid coupling problems to duct flow problems,and the dynamic mechanism of sand production is studied according to the fluid mechanics as well as skin effect considered.The critical pressure gradient formula is as a quantifying characterization for the sand production.Based on sensitivity analysis,the critical pressure gradient rises with its thickness increasing.With the sand particle radius increasing,the critical pressure gradient also rises.In order to validate the effectiveness of the formula,a physical simulation experiment is designed.The formulae has a good agreement with experimental,and the average error is only 16%.%将毛管束模型引入到出砂问题的研究中,同时考虑了表皮效应,建立了出砂毛管束物理模型,该模型能够将复杂的多孔介质固液耦合问题转化为宏观的管流流动问题,通过分析砂岩颗粒在毛管束中的受力和运动,建立了砂岩出砂数学模型,分析了出砂过程动态机理,推导了出砂临界压力梯度公式,该公式从理论上对出砂问题进行了定量表征.敏感性分析表明:随着表皮厚度的增大,临界压力梯度增大;随着砂粒半径的增大,临界压力梯度也随之增大.为了验证公式的有效性,设计了砂岩出砂物理模拟实验,结果表明平均误差为16%,和实验符合较好.

  7. Numerical simulation of coupled heat and mass transfer under the effect of pressure gradient in porous media%多孔介质在压力梯度作用下的热质耦合数值模拟

    Institute of Scientific and Technical Information of China (English)

    朱正刚; KALISKE Michel

    2011-01-01

    Drying porous media leads to a coupled process of heat and mass transfer. Based on the macroscopic viewpoint of continuum mechanics, coupled heat, moisture movement and gas phase flow is numerically simulated. The effect of pressure gradient on the heat and mass transfer is studied. Diffusional and convectional flow of water vapor and air; moisture flow driven by gradient of moisture and temperature (Soret effect) are basic mechanisms of mass transfer in porous media. A 3-D coupled model under Dirichlet and mixed type of boundary conditions, based on the Galerkin weighted residual finite element method, is presented to account for the coupling among temperature, moisture content and gas pressure of the porous media dried at high temperature.%多孔介质干燥导致热质耦合传输过程。本文基于连续介质力学的宏观尺度,对多孔介质的热、湿和气三者耦合迁移进行数值模拟,研究压力梯度对热质传输的影响。多孔介质传质机理主要为水汽和空气的对流和扩散传输、吸附水在含湿量梯度作用下的自由扩散和其在温度梯度即Soret效应驱动下的流动。采用Galerkin加权余量的有限元方法,提出了温度、含温量和气相压力在Dirichlet边界条件及混合边界条件下的三维耦合数值模型,并对介质受高温干燥条件进行了数值模拟。

  8. Gradient changes of bilateral cerebral hemisphere pressure in patients with lateral hemisphere injury%一侧大脑损伤患者两侧半球压力梯度的变化

    Institute of Scientific and Technical Information of China (English)

    姜启周; 裘五四; 方蓉; 徐海松

    2008-01-01

    Objective To investigate the gradient changes of bilateral cerebral hemisphere pressure after lateral hemisphere injury and observe their effects on craniotomy. Methods Twenty-four patients with cerebral contusion and subdural intracerebral hematoma were included in this study. All patients received brain parenehyma pressure (BPP) monitoring by introducing optic fibro sensor into each cerebral hemisphere via the frontal lobe. All patients underwent surgical craniotomy for evacuation of space occupying lesions such as cerebral hemisphere contusion, subdural and/or intracerebral hematoma.Preoperative and postoperative BPP data at different time points were recorded and analyzed. Results Preoperative BPP value of the injured hemispheres was significantly higher than that of the other hemisphere (P < 0. 01 ). There was no significant statistical difference upon BPP value at 0, 24 and 48 hours after operation between both hemispheres ( P > 0.05 ). The postoperative BPP value of bilateral hemispheres was lower than the preoperative one. Conclusions BPP monitoring sensors should be introduced into the injured hemisphere so that the valuable information can be timely showed. When the cerebral hemisphere has lesions after brain injury, such lesion becomes the source of elevated intracranial pressure and can result in bilateral hemisphere pressure gradient. Craniotomy can not only effectively lower the intracranial pressure, but also eliminate the BPP gradient, which contritbutes to reposition of the oppressed brain tissue.%目的 了解一侧大脑损伤后两侧半球压力梯度的变化及开颅手术的影响.方法 选择24例一侧大脑额、颞叶脑挫伤、硬膜下脑内血肿的患者,CT显示伤侧有占位效应、中线向对侧移位.入院后即分别于两侧额部钻颅置入光导纤维传感器行两侧大脑半球脑组织压(BPP)监护,所有患者都接受开颅血肿清除手术.分别于术前、术后收集两侧大脑

  9. [Laser trabeculoplasty: therapeutic options and adverse effects].

    Science.gov (United States)

    Wacker, T; Eckert, S

    2010-01-01

    Laser trabeculoplasty is a simple method for treating glaucoma and ocular hypertension and has few adverse effects. There are different laser systems for reducing the intraocular pressure of patients with glaucoma and ocular hypertension. Complications include transient intraocular pressure elevation, iritis, and anterior synechiae.

  10. Numerical Simulation of Turbulence Having Adverse Pressure Gradient in a Conical Diffuser%锥形渐扩管内逆压梯度紊流场的数值仿真

    Institute of Scientific and Technical Information of China (English)

    肖瑞

    2009-01-01

    用DLR(近壁低雷诺数)型k-ε紊流模型·BFC(边界拟合曲线坐标变换)法,对总扩散角为8°,扩散度为4的锥形渐扩管内充分发展的不可压粘性紊流进行数值仿真,研究不同数值入流边界条件对计算结果的影响以及整个流场主要流动参数的分布特性.

  11. Results of correlations for transition location on a clean-up glove installed on an F-14 aircraft and design studies for a laminar glove for the X-29 aircraft accounting for spanwise pressure gradient

    Science.gov (United States)

    Goradia, S. H.; Bobbitt, P. J.; Morgan, H. L.; Ferris, J. C.; Harvey, William D.

    1989-01-01

    Results of correlative and design studies for transition location, laminar and turbulent boundary-layer parameters, and wake drag for forward swept and aft swept wings are presented. These studies were performed with the use of an improved integral-type boundary-layer and transition-prediction methods. Theoretical predictions were compared with flight measurements at subsonic and transonic flow conditions for the variable aft swept wing F-14 aircraft for which experimental pressure distributions, transition locations, and turbulent boundary-layer velocity profiles were measured. Flight data were available at three spanwise stations for several values of sweep, freestream unit Reynolds number, Mach numbers, and lift coefficients. Theory/experiment correlations indicate excellent agreement for both transition location and turbulent boundary-layer parameters. The results of parametric studies performed during the design of a laminar glove for the forward swept wing X-29 aircraft are also presented. These studies include the effects of a spanwise pressure gradient on transition location and wake drag for several values of freestream Reynolds numbers at a freestream Mach number of 0.9.

  12. Drivers of radial growth and carbon isotope discrimination of bur oak (Quercus macrocarpa Michx.) across continental gradients in precipitation, vapour pressure deficit and irradiance.

    Science.gov (United States)

    Voelker, Steven L; Meinzer, Frederick C; Lachenbruch, Barbara; Brooks, J Renée; Guyette, Richard P

    2014-03-01

    Tree-ring characteristics are commonly used to reconstruct climate variables, but divergence from the assumption of a single biophysical control may reduce the accuracy of these reconstructions. Here, we present data from bur oaks (Quercus macrocarpa Michx.) sampled within and beyond the current species bioclimatic envelope to identify the primary environmental controls on ring-width indices (RWIs) and carbon stable isotope discrimination (Δ(13) C) in tree-ring cellulose. Variation in Δ(13) C and RWI was more strongly related to leaf-to-air vapour pressure deficit (VPD) at the centre and western edge of the range compared with the northern and wettest regions. Among regions, Δ(13) C of tree-ring cellulose was closely predicted by VPD and light responses of canopy-level Δ(13) C estimated using a model driven by eddy flux and meteorological measurements (R(2)  = 0.96, P = 0.003). RWI and Δ(13) C were positively correlated in the drier regions, while they were negatively correlated in the wettest region. The strength and direction of the correlations scaled with regional VPD or the ratio of precipitation to evapotranspiration. Therefore, the correlation strength between RWI and Δ(13) C may be used to infer past wetness or aridity from paleo wood by determining the degree to which carbon gain and growth have been more limited by moisture or light. © 2013 John Wiley & Sons Ltd.

  13. Estudio coste-efectividad sobre la medición del gradiente de presión venosa hepática en la profilaxis secundaria de la hemorragia digestiva varicosa A cost-effectiveness study of hepatic venous pressure gradient measurement in the secondary prevention of variceal bleeding

    Directory of Open Access Journals (Sweden)

    A. Amorós

    2008-07-01

    favorable comparado con la no realización del mismo.Objective: variceal rebleeding is common following a first episode of hemorrhage in cirrhotic patients. The objective of this study was to determine the cost-effectiveness of monitoring hepatic venous pressure gradient (HVPG to guide secondary prophylaxis. Methods: we created a Markov decision model to calculate cost-effectiveness for two strategies: Group 1: HVPG monitoring to decide treatment -when portal pressure was reduced by at least 20 percent or HVPG was less than 12 mmHg after beta-blocker administration, patients received beta-blockers; when portal pressure did not meet these criteria therapy was endoscopic band ligation. Group 2: in this group there was no monitoring of HVPG. Patients with large varices received treatment with beta-blockers combined with EBL; patients with small varices received beta-blockers plus isosorbide mononitrate. Results: there was no recurrent variceal bleeding in group 1 for good responders, and for 17% of poor responders. In group 2 a 25% rebleeding rate was detected in patients with small varices and 13% for those with big varices. Overall cost in group 1 was 14,100.49 euros, and 14,677.16 in group 2. Conclusions: HVPG measurement is cost-effective for the secondary prophylaxis of variceal bleeding.

  14. Double Exposure to Adverse Psychosocial Work Factors and High Family Responsibilities as Related to Ambulatory Blood Pressure at Work: A 5-Year Prospective Study in Women With White-Collar Jobs.

    Science.gov (United States)

    Gilbert-Ouimet, Mahée; Brisson, Chantal; Milot, Alain; Vézina, Michel

    2017-06-01

    Accumulating evidence shows that psychosocial work factors of the demand-control and effort-reward imbalance models may contribute to increase blood pressure (BP). Women are more likely to be exposed to these psychosocial factors than men. Moreover, women spend twice as much time per week performing family responsibilities than men. This study aimed to evaluate the longitudinal association of the double exposure to psychosocial work factors and high family responsibilities in women with BP for a 5-year follow-up. At baseline, the study sample was composed of 1215 working women. Psychosocial work factors were measured using validated scales. Family responsibilities were measured using items related to "the number of children and their age" and "housework and children care." Ambulatory BP measures were taken every 15 minutes during a working day. Associations between psychosocial measures and BP were examined using analyses of covariance. Women with a double exposure to effort-reward imbalance and high family responsibilities had significantly higher BP means than women not exposed to these factors at baseline (diastolic: +2.75 mm Hg), at 3-year follow-up (systolic: +2.22 mm Hg and diastolic: +2.55 mm Hg), and at 5-year follow-up (systolic: +2.94 mm Hg and diastolic: + 3.10 mm Hg). No adverse effect on BP was observed for the double exposure to the psychosocial work factors of the demand-control model and high family responsibilities. A double exposure to effort-reward imbalance at work and high family responsibilities might contribute to elevated ambulatory BP at work among women. BP elevations related to this double exposure may persist for several years.

  15. Modified gradient ratio (GR) test system with micro pore pressure transducer measurement%结合微孔隙水压力计改良型GR试验系统分析研究

    Institute of Scientific and Technical Information of China (English)

    张达德; 郦能惠; 陈柏麟; 傅新民

    2004-01-01

    本研究针对结合微孔隙水压力计改良型GR试验系统与一般GR试验系统进行了一系列的试验分析比较,研究中所使用的试验材料包含4种不同针轧不织布及5种不同比例渥太华砂与风化泥岩混合土壤.试验结果发现,由改良型GR试验系统所得的GR试验值都高于一般GR试验系统所得结果,同时也验证了微孔隙水压力计在GR试验系统中可提供较好的孔隙水压力量测与抗阻塞潜势评估.%A series of gradient ratio (GR) tests with conventional GR test device, modified implanted GR test device with and without micro pore pressure transducers were done. 4 different types of needle-punched nonwoven geotextiles and 5 mixtures of Ottawa sand and weathered mudstone with various percentages were used as testing materials. It was found that the GR values from modified GR tests are generally greater than that obtained from the conventional GR tests. It is believed the transducers installed in the GR test systems provide better measurement on pore pressure distribution and better evaluation of the clogging potential.

  16. Adverse reactions to sulfites

    OpenAIRE

    Yang, William H; Purchase, Emerson C.R.

    1985-01-01

    Sulfites are widely used as preservatives in the food and pharmaceutical industries. In the United States more than 250 cases of sulfite-related adverse reactions, including anaphylactic shock, asthmatic attacks, urticaria and angioedema, nausea, abdominal pain and diarrhea, seizures and death, have been reported, including 6 deaths allegedly associated with restaurant food containing sulfites. In Canada 10 sulfite-related adverse reactions have been documented, and 1 death suspected to be su...

  17. Estimation of Joule heating effect on temperature and pressure distribution in electrokinetic-driven microchannel flows.

    Science.gov (United States)

    Chein, Reiyu; Yang, Yeong Chin; Lin, Yushan

    2006-02-01

    In this study we present simple analytical models that predict the temperature and pressure variations in electrokinetic-driven microchannel flow under the Joule heating effect. For temperature prediction, a simple model shows that the temperature is related to the Joule heating parameter, autothermal Joule heating parameter, external cooling parameter, Peclet number, and the channel length to channel hydraulic diameter ratio. The simple model overpredicted the thermally developed temperature compared with the full numerical simulation, but in good agreement with the experimental measurements. The factors that affect the external cooling parameters, such as the heat transfer coefficient, channel configuration, and channel material are also examined based on this simple model. Based on the mass conservation, a simple model is developed that predicts the pressure variations, including the temperature effect. An adverse pressure gradient is required to satisfy the mass conservation requirement. The temperature effect on the pressure gradient is via the temperature-dependent fluid viscosity and electroosmotic velocity.

  18. Adverse reactions to sulfites

    Science.gov (United States)

    Yang, William H.; Purchase, Emerson C.R.

    1985-01-01

    Sulfites are widely used as preservatives in the food and pharmaceutical industries. In the United States more than 250 cases of sulfite-related adverse reactions, including anaphylactic shock, asthmatic attacks, urticaria and angioedema, nausea, abdominal pain and diarrhea, seizures and death, have been reported, including 6 deaths allegedly associated with restaurant food containing sulfites. In Canada 10 sulfite-related adverse reactions have been documented, and 1 death suspected to be sulfite-related has occurred. The exact mechanism of sulfite-induced reactions is unknown. Practising physicians should be aware of the clinical manifestations of sulfite-related adverse reactions as well as which foods and pharmaceuticals contain sulfites. Cases should be reported to health officials and proper advice given to the victims to prevent further exposure to sulfites. The food industry, including beer and wine manufacturers, and the pharmaceutical industry should consider using alternative preservatives. In the interim, they should list any sulfites in their products. PMID:4052897

  19. Prediction of Pressure Gradient and Holdup in Small E(o)tv(o)s Number Liquid-Liquid Segregated Flow%预测小E(o)tv(o)s数液-液分离流的压力梯度和平均界面含水率

    Institute of Scientific and Technical Information of China (English)

    刘夷平; 张华; 王淑华; 王经

    2008-01-01

    The segregated flow pattern, which occurs in a 26.1 mm diameter, horizontal, stainless steel test section,is investigated. Pressure gradient and in situ phase distribution data were obtained for different combinations of system (E0D=4.77), the dominant effect of interracial tension and wall-wetting properties of the liquids over the gravity is considered. The approach introduces the closure relationship for the case of turbulent flow in a rough pipe,and attempts to modify the two-fluid model to account for the curved interface. In present flow rates range, wave amplitudes were found small, while interfacial mixing was observed. An adjustable definition for hydraulic diame-ters of two fluids and interfacial friction factor is adopted. The predicted pressure gradient and in situ phase distri-bution data have been compared with present experimental data and those reported in the literature.

  20. Therapeutic evaluation of intensive lipid lowering combined with intensive blood pressure reduction in adverse event of stroke%强化降脂联合强化降压预防脑卒中不良事件的疗效评价

    Institute of Scientific and Technical Information of China (English)

    赵锦华; 康永刚; 鱼丽萍

    2015-01-01

    Objective To investigate the clinical effects of intensive lipid lowering combined with intensive blood pressure reduction in preventing adverse event of stroke.Methods190 patients with stroke who seek medical treatment in our hospital were divided into observation group and control group, patients in observation group were treated with intensive blood lipid low-ering combined with intensive blood pressure reduction, while patients in control group were cured with conventional blood lipid lowering combined with conventional blood pressure reduction, the differences of blood lipid, blood pressure and adverse event of these two groups were compared after12 months of treatment.Results The follow-up results of12 months after treatment showed that, DBP, SBP and LDL-C of observation group were significantly lower than control group, incidence rates of primary end point events and secondary end point events of adverse events were significantly lower than control group.Conclusion In-tensive lipid lowering combined with intensive blood pressure reduction would contribute to improve the blood lipid and blood pressure of patients with stroke and effectively prevent adverse events, so they could be used as a priority in curing stroke.%目的:探讨强化降脂联合强化降压预防脑卒中患者不良事件方面的临床价值。方法:将我院收治的190例脑卒中患者随机分为观察组和对照组,观察组的采用强化降脂联合强化降压治疗,对照组采用常规降脂联合常规降压治疗,治疗12个月后,比较两组患者血脂、血压水平及不良事件发生情况。结果:观察组的舒张压、收缩压、LDL-C水平明显低于对照组,不良事件的主要终点事件和次要终点事件的发生率显著低于对照组。结论:强化降脂联合强化降压有助于改善脑卒中患者的血压和血脂,还可有效预防心血管不良事件的发生,故可将其作为治疗脑卒中的优先考虑方案。

  1. Adverse outcomes after colposcopy

    Directory of Open Access Journals (Sweden)

    Damery Sarah L

    2011-01-01

    Full Text Available Abstract Background Colposcopy is an essential part of the National Health Service Cervical Screening Programme (NHSCSP. It is used for both diagnosis and treatment of pre-cancerous cells of the cervix. Despite colposcopy being a commonly performed and relatively invasive procedure, very little research has explored the potential long-term impacts of colposcopic examination upon patient quality of life. The aim of this study is to investigate and quantify any potential reduction in women's quality of life following a colposcopy procedure. More specifically, the degree of female sexual dysfunction and the excess risk of adverse events in those undergoing colposcopy will be explored. If such risks are identified, these can be communicated to women before undergoing colposcopy. It will also assist in identifying whether there are particular sub-groups at greater risk and if so, this may lead to a re-evaluation of current recommendations concerning colposcopically directed treatments. Methods/design Cohort study using postal surveys to assess sexual function and quality of life in women who have attended for colposcopy (cases, compared with those who have not attended colposcopy (controls. The prevalence and excess risk of female sexual dysfunction will be determined. Logistic regression will identify the predictors of adverse outcomes. Discussion There are more than 400,000 colposcopy appointments each year in England, of which 134,000 are new referrals. There is some evidence that there may be long-term implications for women treated under colposcopy with respect to adverse obstetric outcomes, persisting anxiety, increased rates of sexual dysfunction and reduced quality of life. Reliably establishing whether such adverse outcomes exist and the excess risk of adverse events will facilitate informed decision-making and patient choice.

  2. Adverse reactions to cosmetics

    Directory of Open Access Journals (Sweden)

    Dogra A

    2003-03-01

    Full Text Available Adverse reaction to cosmetics constitute a small but significant number of cases of contact dermatitis with varied appearances. These can present as contact allergic dermatitis, photodermatitis, contact irritant dermatitis, contact urticaria, hypopigmentation, hyperpigmentotion or depigmentation, hair and nail breakage. Fifty patients were included for the study to assess the role of commonly used cosmetics in causing adverse reactions. It was found that hair dyes, lipsticks and surprisingly shaving creams caused more reaction as compared to other cosmetics. Overall incidence of contact allergic dermatitis seen was 3.3% with patients own cosmetics. Patch testing was also done with the basic ingredients and showed positive results in few cases where casual link could be established. It is recommended that labeling of the cosmetics should be done to help the dermatologists and the patients to identify the causative allergen in cosmetic preparation.

  3. Adverse Effects of Bisphosphonates

    DEFF Research Database (Denmark)

    Abrahamsen, Bo

    2010-01-01

    Use of bisphosphonates has been growing steadily in the last decade. This follows the introduction of simpler dosing regimes, the availability of lower-priced generics, and concerns about the safety of hormone-replacement therapy. Bisphosphonates have a relatively good safety record and are toler......Use of bisphosphonates has been growing steadily in the last decade. This follows the introduction of simpler dosing regimes, the availability of lower-priced generics, and concerns about the safety of hormone-replacement therapy. Bisphosphonates have a relatively good safety record...... and are tolerated by the majority of patients, but serious adverse events have been recorded in some cases. Only the most common of adverse effects are robustly observable in clinical trials. In general, studies were not powered to detect effects that were lower in incidence than fractures. This review of adverse...... compared with the risk of osteoporotic fractures, at least in patients with the same risk of fractures as those in the phase III trials. It is biologically plausible that atypical fragility fractures could follow from suppression of bone remodeling, but high-quality studies proving causality are lacking...

  4. Adverse effects of bisphosphonates

    DEFF Research Database (Denmark)

    Abrahamsen, Bo

    2010-01-01

    Use of bisphosphonates has been growing steadily in the last decade. This follows the introduction of simpler dosing regimes, the availability of lower-priced generics, and concerns about the safety of hormone-replacement therapy. Bisphosphonates have a relatively good safety record and are toler......Use of bisphosphonates has been growing steadily in the last decade. This follows the introduction of simpler dosing regimes, the availability of lower-priced generics, and concerns about the safety of hormone-replacement therapy. Bisphosphonates have a relatively good safety record...... and are tolerated by the majority of patients, but serious adverse events have been recorded in some cases. Only the most common of adverse effects are robustly observable in clinical trials. In general, studies were not powered to detect effects that were lower in incidence than fractures. This review of adverse...... compared with the risk of osteoporotic fractures, at least in patients with the same risk of fractures as those in the phase III trials. It is biologically plausible that atypical fragility fractures could follow from suppression of bone remodeling, but high-quality studies proving causality are lacking...

  5. Gradients are shaping up.

    Science.gov (United States)

    Bollenbach, Tobias; Heisenberg, Carl-Philipp

    2015-04-23

    In animal embryos, morphogen gradients determine tissue patterning and morphogenesis. Shyer et al. provide evidence that, during vertebrate gut formation, tissue folding generates graded activity of signals required for subsequent steps of gut growth and differentiation, thereby revealing an intriguing link between tissue morphogenesis and morphogen gradient formation.

  6. Fast Distributed Gradient Methods

    CERN Document Server

    Jakovetic, Dusan; Moura, Jose M F

    2011-01-01

    The paper proposes new fast distributed optimization gradient methods and proves convergence to the exact solution at rate O(\\log k/k), much faster than existing distributed optimization (sub)gradient methods with convergence O(1/\\sqrt{k}), while incurring practically no additional communication nor computation cost overhead per iteration. We achieve this for convex (with at least one strongly convex,) coercive, three times differentiable and with Lipschitz continuous first derivative (private) cost functions. Our work recovers for distributed optimization similar convergence rate gains obtained by centralized Nesterov gradient and fast iterative shrinkage-thresholding algorithm (FISTA) methods over ordinary centralized gradient methods. We also present a constant step size distributed fast gradient algorithm for composite non-differentiable costs. A simulation illustrates the effectiveness of our distributed methods.

  7. Vaccine adverse events.

    Science.gov (United States)

    Follows, Jill

    2012-01-01

    Millions of adults are vaccinated annually against the seasonal influenza virus. An undetermined number of individuals will develop adverse events to the influenza vaccination. Those who suffer substantiated vaccine injuries, disabilities, and aggravated conditions may file a timely, no-fault and no-cost petition for financial compensation under the National Vaccine Act in the Vaccine Court. The elements of a successful vaccine injury claim are described in the context of a claim showing the seasonal influenza vaccination was the cause of Guillain-Barré syndrome.

  8. Laser textured surface gradients

    Science.gov (United States)

    Ta, Van Duong; Dunn, Andrew; Wasley, Thomas J.; Li, Ji; Kay, Robert W.; Stringer, Jonathan; Smith, Patrick J.; Esenturk, Emre; Connaughton, Colm; Shephard, Jonathan D.

    2016-05-01

    This work demonstrates a novel technique for fabricating surfaces with roughness and wettability gradients and their subsequent applications for chemical sensors. Surface roughness gradients on brass sheets are obtained directly by nanosecond laser texturing. When these structured surfaces are exposed to air, their wettability decreases with time (up to 20 days) achieving both spatial and temporal wettability gradients. The surfaces are responsive to organic solvents. Contact angles of a series of dilute isopropanol solutions decay exponentially with concentration. In particular, a fall of 132° in contact angle is observed on a surface gradient, one order of magnitude higher than the 14° observed for the unprocessed surface, when the isopropanol concentration increased from 0 to 15.6 wt%. As the wettability changes gradually over the surface, contact angle also changes correspondingly. This effect offers multi-sensitivity at different zones on the surface and is useful for accurate measurement of chemical concentration.

  9. Second gradient poromechanics

    CERN Document Server

    Sciarra, Giulio; Coussy, Olivier

    2010-01-01

    Second gradient theories have been developed in mechanics for treating different phenomena as capillarity in fluids, plasticity and friction in granular materials or shear band deformations. Here, there is an attempt of formulating a second gradient Biot like model for porous materials. In particular the interest is focused in describing the local dilatant behaviour of a porous material induced by pore opening elastic and capillary interaction phenomena among neighbouring pores and related micro-filtration phenomena by means of a continuum microstructured model. The main idea is to extend the classical macroscopic Biot model by including in the description second gradient effects. This is done by assuming that the surface contribution to the external work rate functional depends on the normal derivative of the velocity or equivalently assuming that the strain work rate functional depends on the porosity and strain gradients. According to classical thermodynamics suitable restrictions for stresses and second g...

  10. Avaliação do gradiente pressórico aorto-radial em pacientes submetidos à intervenção cirúrgica com circulação extracorpórea Evaluación del gradiente presórico aorto-radial en pacientes sometidos a la intervención quirúrgica con circulación extracorpórea Evaluation of the aorta-to-radial artery pressure gradient in patients undergoing surgery with cardiopulmonary bypass

    Directory of Open Access Journals (Sweden)

    Maria José Carvalho Carmona

    2007-12-01

    presión aórtica durante revascularización del miocardio (RM con CEC y su correlación con la resistencia vascular sistémica. MÉTODO: Después de la aprobación por el Comité de Ética hospitalaria, 16 pacientes sometidos a la RM con CEC hipotérmica fueron estudiados. Presiones sistólica, diastólica y media fueron obtenidas en la raíz de la aorta y en la arteria radial, a través de catéteres específicos. Débito cardíaco se obtuvo usando catéter de arteria pulmonar o directamente de la máquina de CEC y Resistencia Vascular Sistémica indexada (RVSi fue calculada en los momentos pre-CEC, inicio de la CEC, después de la última RM, al final de la CEC y pos-CEC. El análisis estadístico se realizó a través de Análisis de Variancia para medidas repetidas y correlación de orden de Spearman y el nivel de significancia se estableció en 0,05. RESULTADOS: Después del inicio de la CEC, la presión arterial radial fue sistemáticamente menor que la presión aórtica en 3 a 5 mmHg. Se observó correlación significativa entre el gradiente medio de presión aorto-radial y la RVSi solamente después de la ultima RM, correspondiendo al calentamiento del paciente (Rho = 0,67, p = 0,009. CONCLUSIONES: La medida de presión en la arterial radial subestimó sistemáticamente la presión arterial en la raíz de la aorta después de la CEC y la RVSi no suministró estimación puntual de la magnitud del gradiente de presión aorto-radial.BACKGROUND AND OBJECTIVES: Several studies have demonstrated a significant difference between the aortic and radial artery pressures in patients on cardiopulmonary bypass (CPB. The objectives of this study were to evaluate the behavior of the aorta-to-radial artery pressure gradient during myocardial revascularization (MR with CPB and its correlation with the systemic vascular resistance. METHODS: After approval by the Ethics Committee of the hospital, 16 patients undergoing MR with hypothermic CPB were studied. Systolic, diastolic and

  11. High Gradient Accelerator Research

    Energy Technology Data Exchange (ETDEWEB)

    Temkin, Richard [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Physics. Plasma Science and Fusion Center

    2016-07-12

    The goal of the MIT program of research on high gradient acceleration is the development of advanced acceleration concepts that lead to a practical and affordable next generation linear collider at the TeV energy level. Other applications, which are more near-term, include accelerators for materials processing; medicine; defense; mining; security; and inspection. The specific goals of the MIT program are: • Pioneering theoretical research on advanced structures for high gradient acceleration, including photonic structures and metamaterial structures; evaluation of the wakefields in these advanced structures • Experimental research to demonstrate the properties of advanced structures both in low-power microwave cold test and high-power, high-gradient test at megawatt power levels • Experimental research on microwave breakdown at high gradient including studies of breakdown phenomena induced by RF electric fields and RF magnetic fields; development of new diagnostics of the breakdown process • Theoretical research on the physics and engineering features of RF vacuum breakdown • Maintaining and improving the Haimson / MIT 17 GHz accelerator, the highest frequency operational accelerator in the world, a unique facility for accelerator research • Providing the Haimson / MIT 17 GHz accelerator facility as a facility for outside users • Active participation in the US DOE program of High Gradient Collaboration, including joint work with SLAC and with Los Alamos National Laboratory; participation of MIT students in research at the national laboratories • Training the next generation of Ph. D. students in the field of accelerator physics.

  12. Procedural Success and Adverse Events in Pulmonary Artery Stenting: Insights From the NCDR.

    Science.gov (United States)

    Lewis, Matthew J; Kennedy, Kevin F; Ginns, Jonathan; Crystal, Matthew A; Torres, Alejandro; Vincent, Julie; Rosenbaum, Marlon S

    2016-03-22

    Risk factors associated with outcomes for pulmonary artery (PA) stenting remain poorly defined. The goal of this study was to determine the effect of patient and procedural characteristics on rates of adverse events and procedural success. Registry data were collected, and 2 definitions of procedural success were pre-specified for patients with biventricular circulation: 1) 20% reduction in right ventricular pressure or 50% increase in PA diameter; and 2) 25% reduction in right ventricular pressure or 50% decrease in PA gradient or post-procedure ratio of in-stent minimum to pre-stent distal diameter >80%. A separate definition of procedural success based on normalization of PA diameter was pre-specified for patients with single ventricle palliation. Between January 2011 and January 2014, a total of 1,183 PA stenting procedures were performed at 59 institutions across 1,001 admissions; 262 (22%) procedures were performed in patients with a single ventricle. The rate of procedural success was 76% for definition 1, 86% for definition 2, and 75% for single ventricle patients. In the multivariate analysis, ostial stenosis was significantly associated with procedural success for biventricular patients according to both definitions. The overall complication rate was 14%, with 9% of patients experiencing death or a major adverse event (MAE). According to multivariate analysis, weight 75% across all definitions, and adverse events were relatively common. Biventricular patients with an ostial stenosis had a higher probability of a successful outcome. Patients who had a single ventricle, weight <4 kg, or who underwent an emergency procedure had a higher risk of death or MAE. These findings may help inform patient selection for PA stenting. Copyright © 2016 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  13. 规范健康教育联合行为矫正技术在减少高血压患者脑血管不良事件中的作用研究%Standard health education joint behavior modification technology in patients with high blood pressure to reduce the role of cerebral adverse events

    Institute of Scientific and Technical Information of China (English)

    吴江平

    2012-01-01

    Objective To explore the role of standard health education and behavior modification technology in reducing hypertension cerebrovascular adverse events. Methods 224 cases of patients with high blood pressure in random digital tables were randomly divided into observation group and control group each 112 cases, The observation group based on routine treatment given standard health education and bad behavior modification, and the control group was given only to conventional therapy, compared between the two groups in different periods in patients with cerebral incidence of aderse events. Results The observation group cerebrovascular adverse events in patients with a rate of 0.89%, to 8.04% in the control group, adverse events incidence of the observation group was significantly lower than the control group, and comparative differences between groups were statistically significant (χ2 = 8.547, P < 0.05). Conclusion Standard health education and behavior modification to improve hypertension treatment adherence and blood pressure control, so as to reduce the incidence of cardiovascular adverse events, worth clinical promotion.%目的 探讨规范健康教育和行为矫正技术在减少高血压脑血管不良事件中的作用.方法 将224例高血压患者按照随机数字表法分为观察组和对照组各112例,观察组在常规治疗的基础上给予规范健康教育和不良行为矫正,对照组只给予常规治疗,比较两组患者不同时期脑血管不良事件的发生率.结果 观察组患者脑血管不良事件发生率为0.89%,对照组为8.04%,观察组不良事件发生率明显低于对照组,差异有高度统计学意义(χ2 = 8.547,P < 0.01).结论规范健康教育和不良行为矫正有助于提高高血压患者治疗依从性和血压控制率,从而降低脑血管不良事件的发生率,值得临床推广.

  14. Uniform gradient expansions

    Directory of Open Access Journals (Sweden)

    Massimo Giovannini

    2015-06-01

    Full Text Available Cosmological singularities are often discussed by means of a gradient expansion that can also describe, during a quasi-de Sitter phase, the progressive suppression of curvature inhomogeneities. While the inflationary event horizon is being formed the two mentioned regimes coexist and a uniform expansion can be conceived and applied to the evolution of spatial gradients across the protoinflationary boundary. It is argued that conventional arguments addressing the preinflationary initial conditions are necessary but generally not sufficient to guarantee a homogeneous onset of the conventional inflationary stage.

  15. Uniform gradient expansions

    Energy Technology Data Exchange (ETDEWEB)

    Giovannini, Massimo, E-mail: massimo.giovannini@cern.ch [Department of Physics, Theory Division, CERN, 1211 Geneva 23 (Switzerland); INFN, Section of Milan-Bicocca, 20126 Milan (Italy)

    2015-06-30

    Cosmological singularities are often discussed by means of a gradient expansion that can also describe, during a quasi-de Sitter phase, the progressive suppression of curvature inhomogeneities. While the inflationary event horizon is being formed the two mentioned regimes coexist and a uniform expansion can be conceived and applied to the evolution of spatial gradients across the protoinflationary boundary. It is argued that conventional arguments addressing the preinflationary initial conditions are necessary but generally not sufficient to guarantee a homogeneous onset of the conventional inflationary stage.

  16. Farmer Health and Adaptive Capacity in the Face of Climate Change and Variability. Part 1: Health as a Contributor to Adaptive Capacity and as an Outcome from Pressures Coping with Climate Related Adversities

    Directory of Open Access Journals (Sweden)

    Anne Parkinson

    2011-10-01

    Full Text Available This paper examines the role farmers’ health plays as an element of adaptive capacity. The study examines which of twenty aspects of adaptation may be related to overall health outcomes, controlling for demographic and on-farm-factors in health problems. The analysis is based on 3,993 farmers’ responses to a national survey of climate risk and adaptation. Hierarchical linear regression modelling was used examine the extent to which, in a multivariate analysis, the use of adaptive practices was predictively associated with self-assessed health, taking into account the farmer’s rating of whether their health was a barrier to undertaking farm work. We present two models, one excluding pre-existing health (model 1 and one including pre-existing health (model 2. The first model accounted for 21% of the variance. In this model better health was most strongly predicted by an absence of on-farm risk, greater financial viability, greater debt pressures, younger age and a desire to continue farming. Social capital (trust and reciprocity was moderately associated with health as was the intention to adopt more sustainable practices. The second model (including the farmers’ health as a barrier to undertaking farm work accounted for 43% of the variance. Better health outcomes were most strongly explained, in order of magnitude, by the absence of pre-existing health problems, greater access to social support, greater financial viability, greater debt pressures, a desire to continue farming and the condition of on-farm resources. Model 2 was a more parsimonious model (only nine predictors, compared with 15 in model 1, and explained twice as much variance in health outcomes. These results suggest that (i pre-existing health problems are a very important factor to consider when designing adaptation programs and policies and (ii these problems may mediate or modify the relationship between adaptation and health.

  17. Gradient systems and mechanical systems

    Institute of Scientific and Technical Information of China (English)

    Fengxiang Mei; Huibin Wu

    2016-01-01

    All types of gradient systems and their properties are discussed. Two problems connected with gradient sys-tems and mechanical systems are studied. One is the direct problem of transforming a mechanical system into a gradi-ent system, and the other is the inverse problem, which is transforming a gradient system into a mechanical system.

  18. A universal equation for calculating the energy gradient function in the energy gradient theory

    CERN Document Server

    Dou, Hua-Shu

    2016-01-01

    The relationship for the energy variation, work done, and energy dissipation in unit volumetric fluid of incompressible flow is derived. A universal equation for calculating the energy gradient function is presented for situations where both pressure driven flow and shear driven flow are present simultaneously.

  19. Estudio coste-efectividad sobre la medición del gradiente de presión venosa hepática en la profilaxis secundaria de la hemorragia digestiva varicosa A cost-effectiveness study of hepatic venous pressure gradient measurement in the secondary prevention of variceal bleeding

    OpenAIRE

    Amorós, A; J. M. Palazón; Zapater, P; E. de Madaria; Pérez-Mateo, M

    2008-01-01

    Objetivo: la hemorragia digestiva es una complicación frecuente en pacientes con cirrosis hepática. La tasa de recidiva tras un primer episodio oscila en torno al 60%, motivo por el cual la profilaxis está recomendada. Esta puede realizarse mediante fármacos (betabloqueantes y nitratos) combinados o no con ligadura endoscópica con bandas. El objetivo de este estudio es valorar el coste-efectividad de la medición del gradiente de presión venosa hepática (GPVH) previo a la elección de la profil...

  20. Selection of the Most Appropriate Nyquist Velocity for Applying Hemispherical Flow Convergenee Equation According to the Transorifice Pressure Gradient%根据跨瓣压差选择适用于半球体血流会聚公式的最佳Nyquist速度

    Institute of Scientific and Technical Information of China (English)

    邓又斌; 王新房; 王加恩; 李治安; Takahico SHiota; David J.Sahn

    1995-01-01

    应用数字计算机分析彩色多普勒血流会聚区,证明计算流量与实际流量之比为1时,半球体血流会聚公式中所用速度与跨瓣压差间有明显的相关性,协方差分析示这种关系在不同瓣口间无明显差异.本研究为准确应用半球体血流会聚公式提供了一种根据临床可测踌瓣压差选择最佳Nyquist速度的方法.%By analyzing,the flow convergence region with digital computer technique,this in vitro study demonstrated that the most appropriate Nyquist velocity for applying the hemispheric flow convergence equation was correlated well with the transorifice pressure gradient when the calculated flow to actual flow rate ratio wwaS 1.Furthermore,the coveriance analysis indicated that this relation was indepenaent of orifiee size.The Present study provided us a Way to select the most Suitable Nyquist Veloeity for applying the hemispheric flow convergence equation based on the clinically measurable transorifice pressure gradient.

  1. Dual gradient drilling - simulations during connection operations

    OpenAIRE

    Time, André

    2014-01-01

    As oilfields are ageing and depleting, operators are forced to start searching for oil in more hostile environments. These new environments can introduce new drilling challenges. Prospects like ultra deep water reservoirs and depleted offshore reservoirs are difficult to drill with conventional drilling. This has lead the industry to developing the Dual Gradient Drilling (DGD) system. DGD is an unconventional drilling method and it is classified as a Managed Pressure Drilling ...

  2. Adverse Reactions to Hallucinogenic Drugs.

    Science.gov (United States)

    Meyer, Roger E. , Ed.

    This reports a conference of psychologists, psychiatrists, geneticists and others concerned with the biological and psychological effects of lysergic acid diethylamide and other hallucinogenic drugs. Clinical data are presented on adverse drug reactions. The difficulty of determining the causes of adverse reactions is discussed, as are different…

  3. Bigravity from gradient expansion

    Energy Technology Data Exchange (ETDEWEB)

    Yamashita, Yasuho [Yukawa Institute for Theoretical Physics, Kyoto University,606-8502, Kyoto (Japan); Tanaka, Takahiro [Yukawa Institute for Theoretical Physics, Kyoto University,606-8502, Kyoto (Japan); Department of Physics, Kyoto University,606-8502, Kyoto (Japan)

    2016-05-04

    We discuss how the ghost-free bigravity coupled with a single scalar field can be derived from a braneworld setup. We consider DGP two-brane model without radion stabilization. The bulk configuration is solved for given boundary metrics, and it is substituted back into the action to obtain the effective four-dimensional action. In order to obtain the ghost-free bigravity, we consider the gradient expansion in which the brane separation is supposed to be sufficiently small so that two boundary metrics are almost identical. The obtained effective theory is shown to be ghost free as expected, however, the interaction between two gravitons takes the Fierz-Pauli form at the leading order of the gradient expansion, even though we do not use the approximation of linear perturbation. We also find that the radion remains as a scalar field in the four-dimensional effective theory, but its coupling to the metrics is non-trivial.

  4. Increasing SLEDed Linac Gradient

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, Zoltan D

    2001-11-08

    This note will show how to increase the SLED [1] gradient by varying Q{sub e}, the external Q of the SLED cavity, by increasing its Q{sub 0} and by increasing the compression ratio. If varying the external Q is to be effective, then the copper losses should be small so that Q{sub 0} >> Q{sub e}. Methods of varying Q{sub e} will be indicated but no experimental data will be presented. If we increase the klystron pulse width from 3.5 to 5 {micro}S and increase Q{sub 0} from the present 100000 to 300000, then the gradient increases by 19% and the beam energy increases from 50 to 60 GeV. This note will also discuss SLED operation at 11424 MHz, the NLC frequency. Without Q{sub e} switching, using SLED at 11424 MHz increases the SLAC gradient from 21 MV/m to 34 MV/m, and at the same repetition rate, uses about 1/5 of rf average power. If we also double the compression ratio, we reach 47 MV/m and over 100 GeV beam energy.

  5. Reinforcement Learning by Value Gradients

    CERN Document Server

    Fairbank, Michael

    2008-01-01

    The concept of the value-gradient is introduced and developed in the context of reinforcement learning. It is shown that by learning the value-gradients exploration or stochastic behaviour is no longer needed to find locally optimal trajectories. This is the main motivation for using value-gradients, and it is argued that learning value-gradients is the actual objective of any value-function learning algorithm for control problems. It is also argued that learning value-gradients is significantly more efficient than learning just the values, and this argument is supported in experiments by efficiency gains of several orders of magnitude, in several problem domains. Once value-gradients are introduced into learning, several analyses become possible. For example, a surprising equivalence between a value-gradient learning algorithm and a policy-gradient learning algorithm is proven, and this provides a robust convergence proof for control problems using a value function with a general function approximator.

  6. MEASURING SYSTEM OF ADVERSE WEATHER PHENOMENA

    Directory of Open Access Journals (Sweden)

    M. Ćurić

    2012-03-01

    Full Text Available Measuring system of adverse weather phenomena. The adverse weather phenomena in nowadays are becoming an extraordinary problem in human life and human activity. Therefore, it seems very important to know the thresholds of adverse weather phenomena. These thresholds can be calculated in different ways, but some experience has shown that for weather elements which departures from normal follow the normal distribution suits to use the Gaussian curve of frequency distribution (temperature and pressure. For such weather elements the normal curve of frequency distribution may be used for classification of thresholds. For weather elements which departures do not depend on such a frequency distribution configuration (precipitation amounts may be used a decile method. For wind speed thresholds, the Beaufort scale units can be used for calculation. In this paper the threshold scales for four basic weather elemnts are presented. All these scales contain four steps each. They are defined: normal, above normal, much above normal and extraordinary above normal or normal, below normal, much below normal and extraordinary below normal. The examples by observations of Meteorological Observatory in Belgrade are presented.

  7. Synthesis of large diamond crystals containing high-nitrogen concentration at high pressure and high temperature using Ni-based solvent by temperature gradient methodHuang Guo-Feng1, Jia Xiao-Peng1,2, Li Shang-Sheng2,

    Institute of Scientific and Technical Information of China (English)

    Huang Guo-Feng; Jia Xiao-Peng; Li Shang-Sheng; Zhang Ya-Fei; Li Yong; Zhao Ming; Ma Hong-An

    2010-01-01

    This paper reprots that with Ni-based catalyst/solvent and with a dopant of NaN3>, large green single crystal diamonds with perfect shape are successfully synthesized by temperature gradient method under high pressure and high temperature in a China-type cubic anvil high-pressure apparatus (SPD-6×1200), and the highest nitrogen concentration reaches approximately 1214-1257 ppm calculated by infrared absorption spectra. The synthesis conditions are about 5.5 GPa and 1240-1300℃. The growth behaviour of diamond with high-nitrogen concentration is investigated in detail. The results show that, with increasing the content of NaN3> added in synthesis system, the width of synthesis temperature region for growth high-quality diamonds becomes narrower, and the morphology of diamond crystal is changed from cube-octahedral to octahedral at same temperature and pressure, the crystal growth rate is slowed down,nevertheless, the nitrogen concentration doped in synthetic diamond increases.

  8. Study on Microstructure and Property of Low Pressure Plasma Sprayed MoB/CoCr Gradient Coatings by Laser Remelting%激光重熔低压等离子喷涂MoB/CoCr梯度涂层组织与性能研究

    Institute of Scientific and Technical Information of China (English)

    陈枭

    2012-01-01

    MoB/CoCr gradient coatings were sprayed on 310S stainless steel using low pressure plasma spraying method) and then MoB/CoCr gradient coatings were laser remelted. The microstructure and property of MoB/CoCr coatings were studied. Results show that the surface morphology of MoB/CoCr coating is smooth and dense, cross sectional microstucture of MoB/CoCr gradient coatings consists of dentrite crystal, cystiform crystal and flat crystal from the surface to the bottom of coatings; There is convection-diffusion phenomena occurred between element of 310S stainless steel and that of coatings, Fe element appears in the coatings; Microhardness of MoB/CoCr coating increases obviously after laser remelting.%采用低压等离子喷涂技术在310S不锈钢表面制备MoB/CoCr梯度涂层,然后对MoB/CoCr涂层进行激光重熔处理,对重熔后涂层的组织结构及性能进行了研究.研究结果表明,激光重熔后,涂层表面平整致密,截面的显微组织呈树枝晶-胞状晶-平面晶过渡;激光重熔过程中,微熔的310S基体元素与熔化的涂层元素发生对流扩散现象,涂层中出现Fe元素成分;激光重熔后,MoB/CoCr层的硬度明显提高.

  9. Adverse Event Reporting System (AERS)

    Data.gov (United States)

    U.S. Department of Health & Human Services — The Adverse Event Reporting System (AERS) is a computerized information database designed to support the FDA's post-marketing safety surveillance program for all...

  10. Pollution adverse tourists and growth

    OpenAIRE

    Cerina, Fabio; Giannoni, Sauveur

    2008-01-01

    We build a growth model in which tourism development generates pollution while tourists are pollution adverse. We establish that long run positive growth exists only for a particular value of tourists pollution adversion. Furthermore, we show that an intensive use of facilities is associated with a lower growth rate for destinations specialized in green tourism. We also see that if the destination can choose the degree of use of facilities, tourism will generate positive growth only if touris...

  11. Reverse Engineering Adverse Outcome Pathways

    Energy Technology Data Exchange (ETDEWEB)

    Perkins, Edward; Chipman, J.K.; Edwards, Stephen; Habib, Tanwir; Falciani, Francesco; Taylor, Ronald C.; Van Aggelen, Graham; Vulpe, Chris; Antczak, Philipp; Loguinov, Alexandre

    2011-01-30

    The toxicological effects of many stressors are mediated through unknown, or poorly characterized, mechanisms of action. We describe the application of reverse engineering complex interaction networks from high dimensional omics data (gene, protein, metabolic, signaling) to characterize adverse outcome pathways (AOPs) for chemicals that disrupt the hypothalamus-pituitary-gonadal endocrine axis in fathead minnows. Gene expression changes in fathead minnow ovaries in response to 7 different chemicals, over different times, doses, and in vivo versus in vitro conditions were captured in a large data set of 868 arrays. We examined potential AOPs of the antiandrogen flutamide using two mutual information theory methods, ARACNE and CLR to infer gene regulatory networks and potential adverse outcome pathways. Representative networks from these studies were used to predict a network path from stressor to adverse outcome as a candidate AOP. The relationship of individual chemicals to an adverse outcome can be determined by following perturbations through the network in response to chemical treatment leading to the nodes associated with the adverse outcome. Identification of candidate pathways allows for formation of testable hypotheses about key biologic processes, biomarkers or alternative endpoints, which could be used to monitor an adverse outcome pathway. Finally, we identify the unique challenges facing the application of this approach in ecotoxicology, and attempt to provide a road map for the utilization of these tools. Key Words: mechanism of action, toxicology, microarray, network inference

  12. Gradient dynamics models for liquid films with soluble surfactant

    CERN Document Server

    Thiele, Uwe; Pismen, Len M

    2016-01-01

    In this paper we propose equations of motion for the dynamics of liquid films of surfactant suspensions that consist of a general gradient dynamics framework based on an underlying energy functional. This extends the gradient dynamics approach to dissipative non-equilibrium thin film systems with several variables, and casts their dynamic equations into a form that reproduces Onsager's reciprocity relations. We first discuss the general form of gradient dynamics models for an arbitrary number of fields and discuss simple well-known examples with one or two fields. Next, we develop the gradient dynamics (three field) model for a thin liquid film covered by soluble surfactant and discuss how it automatically results in consistent convective (driven by pressure gradients, Marangoni forces and Korteweg stresses), diffusive, adsorption/desorption, and evaporation fluxes. We then show that in the dilute limit, the model reduces to the well-known hydrodynamic form that includes Marangoni fluxes due to a linear equat...

  13. Reliability and Validity of Self-rating Adverse Reaction Scale of Continuous Positive Airway Pressure among Patients with Obstructive Sleep Apnea Hypopnea Syndrome%阻塞性睡眠呼吸暂停低通气综合征患者持续正压通气治疗副作用自评量表的信度与效度研究

    Institute of Scientific and Technical Information of China (English)

    贾雯碧; 杨希; 曾继红; 余林

    2013-01-01

    目的:评价阻塞性睡眠呼吸暂停低通气综合征(obstructive sleep apnea hypopnea syndrome, OSAHS)患者持续正压通气(continuous positive airway pressure, CPAP)治疗副作用自评量表的信度与效度。方法根据相关文献和临床工作自制CPAP治疗副作用自评量表,采用内部一致性分析和重测信度法检测量表的信度;采用专家评议,选用副反应量表(Treatment Emergent Symptom Scale, TESS)、汉密尔顿焦虑量表(Hamilton Anxiety Scale, HAMA)、健康调查简表(the MOS 36-item Short-form Health Survey, SF-36)作为效标并结合因子分析法测量量表效度。结果量表内部一致性信度Cronbach’sα系数为0.825,重测信度为0.687;内容效度指数为0.870,量表与TESS、HAMA、SF-36显著相关(P0.4。结论 CPAP治疗副作用自评量表具有较好的信度与效度,可应用于OSAHS患者CPAP治疗副作用以及其对依从性影响的评估。%Objective To evaluate the reliability and validity of self-rating adverse reaction of continuous positive airway pressure (CPAP) scale among patients with obstructive sleep apnea hypopnea syndrome (OSAHS). Methods A self-rating adverse reaction of CPAP scale was developed based on literatures and clinical practice. The reliability of the scale was evaluated by internal consistency and test-retest reliability. Through expert review, taking Treatment Emergent Symptom Scale (TESS), Hamilton Anxiety Scale (HAMA) and the MOS 36-item Short-form Health Survey (SF-36) as criterion, the validity of the scale was evaluated with factor analysis. Results Cronbach’sαcoefficient was 0.825, ICC 0.687 and CVI 0.870. The scale was significantly related with TESS, HAMA and SF-36 (P<0.01) with the accumulative variance contribution rate of 77.271% and the load of every item on corresponding factor was higher than 0.4. Conclusion The self-rating adverse reaction of CPAP scale among OSAHS patients is with good reliability and

  14. Energy in density gradient

    CERN Document Server

    Vranjes, J

    2015-01-01

    Inhomogeneous plasmas and fluids contain energy stored in inhomogeneity and they naturally tend to relax into lower energy states by developing instabilities or by diffusion. But the actual amount of energy in such inhomogeneities has remained unknown. In the present work the amount of energy stored in a density gradient is calculated for several specific density profiles in a cylindric configuration. This is of practical importance for drift wave instability in various plasmas, and in particular in its application in models dealing with the heating of solar corona because the instability is accompanied with stochastic heating, so the energy contained in inhomogeneity is effectively transformed into heat. It is shown that even for a rather moderate increase of the density at the axis in magnetic structures in the corona by a factor 1.5 or 3, the amount of excess energy per unit volume stored in such a density gradient becomes several orders of magnitude greater than the amount of total energy losses per unit ...

  15. Energy in density gradient

    Energy Technology Data Exchange (ETDEWEB)

    Vranjes, J., E-mail: jvranjes@yahoo.com [Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife (Spain); Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife (Spain); Kono, M., E-mail: kono@fps.chuo-u.ac.jp [Faculty of Policy Studies, Chuo University, Tokyo (Japan)

    2015-01-15

    Inhomogeneous plasmas and fluids contain energy stored in inhomogeneity and they naturally tend to relax into lower energy states by developing instabilities or by diffusion. But the actual amount of energy in such inhomogeneities has remained unknown. In the present work, the amount of energy stored in a density gradient is calculated for several specific density profiles in a cylindrical configuration. This is of practical importance for drift wave instability in various plasmas, and, in particular, in its application in models dealing with the heating of solar corona because the instability is accompanied with stochastic heating, so the energy contained in inhomogeneity is effectively transformed into heat. It is shown that even for a rather moderate increase of the density at the axis in magnetic structures in the corona by a factor 1.5 or 3, the amount of excess energy per unit volume stored in such a density gradient becomes several orders of magnitude greater than the amount of total energy losses per unit volume (per second) in quiet regions in the corona. Consequently, within the life-time of a magnetic structure such energy losses can easily be compensated by the stochastic drift wave heating.

  16. Generalized conjugate gradient squared

    Energy Technology Data Exchange (ETDEWEB)

    Fokkema, D.R.; Sleijpen, G.L.G. [Utrecht Univ. (Netherlands)

    1994-12-31

    In order to solve non-symmetric linear systems of equations, the Conjugate Gradient Squared (CGS) is a well-known and widely used iterative method. In practice the method converges fast, often twice as fast as the Bi-Conjugate Gradient method. This is what you may expect, since CGS uses the square of the BiCG polynomial. However, CGS may suffer from its erratic convergence behavior. The method may diverge or the approximate solution may be inaccurate. BiCGSTAB uses the BiCG polynomial and a product of linear factors in an attempt to smoothen the convergence. In many cases, this has proven to be very effective. Unfortunately, the convergence of BiCGSTAB may stall when a linear factor (nearly) degenerates. BiCGstab({ell}) is designed to overcome this degeneration of linear factors. It generalizes BiCGSTAB and uses both the BiCG polynomial and a product of higher order factors. Still, CGS may converge faster than BiCGSTAB or BiCGstab({ell}). So instead of using a product of linear or higher order factors, it may be worthwhile to look for other polynomials. Since the BiCG polynomial is based on a three term recursion, a natural choice would be a polynomial based on another three term recursion. Possibly, a suitable choice of recursion coefficients would result in method that converges faster or as fast as CGS, but less erratic. It turns out that an algorithm for such a method can easily be formulated. One particular choice for the recursion coefficients leads to CGS. Therefore one could call this algorithm generalized CGS. Another choice for the recursion coefficients leads to BiCGSTAB. It is therefore possible to mix linear factors and some polynomial based on a three term recursion. This way one may get the best of both worlds. The authors will report on their findings.

  17. ANALYSIS ON INCLINATION ANGLE OF SHEAR BAND UNDER LOW CONFINING PRESSURE BASED ON GRADIENT-DEPENDENT PLASTICITY%围压对剪切带倾角影响的梯度塑性理论分析

    Institute of Scientific and Technical Information of China (English)

    王学滨; 姚再兴; 潘一山

    2004-01-01

    The inclination angle of shear band is analyzed considering heterogeneity of rock material when a single shear band is formed in the center of specimen under triaxial compression. The analytical solution of post-peak axial stress-axial strain curve is deduced using the assumption that the total post-peak deformation is composed of entire uniform elastic deformation and localized shear plastic deformation dependent on the thickness of shear band. The obtained solution shows that the post-peak stiffness is related to the inclination angle of shear band,confining pressure,thickness of shear band and elastic modulus,etc. Using the solution,the expression for the inclination angle of shear band can be presented easily and it is dependent on constitutive parameters of rock material and geometry parameters of rock specimen. Larger dilation angle or loading rate leads to increment of the inclination angle. In addition,the inclination angle increases with the thickness of the shear band,which cannot be explained or forecasted by other existing solutions,such as Coulomb inclination,Roscoe inclination and Arthur inclination,etc.

  18. Magnetic Field Gradient Waveform Monitoring for Magnetic Resonance

    Science.gov (United States)

    Han, Hui

    Linear magnetic field gradients have played a central role in Magnetic Resonance Imaging (MRI) since Fourier Transform MRI was proposed three decades ago. Their primary function is to encode spatial information into MR signals. Magnetic field gradients are also used to sensitize the image contrast to coherent and/or incoherent motion, to selectively enhance an MR signal, and to minimize image artifacts. Modern MR imaging techniques increasingly rely on the implementation of complex gradient waveforms for the manipulation of spin dynamics. However, gradient system infidelities caused by eddy currents, gradient amplifier imperfections and group delays, often result in image artifacts and other errors (e.g., phase and intensity errors). This remains a critical problem for a wide range of MRI techniques on modern commercial systems, but is of particular concern for advanced MRI pulse sequences. Measuring the real magnetic field gradients, i.e., characterizing eddy currents, is critical to addressing and remedying this problem. Gradient measurement and eddy current calibration are therefore a general topic of importance to the science of MRI. The Magnetic Field Gradient Monitor (MFGM) idea was proposed and developed specifically to meet these challenges. The MFGM method is the heart of this thesis. MFGM methods permit a variety of magnetic field gradient problems to be investigated and systematically remedied. Eddy current effects associated with MR compatible metallic pressure vessels were analyzed, simulated, measured and corrected. The appropriate correction of eddy currents may enable most MR/MRI applications with metallic pressure vessels. Quantitative imaging (1D/2D) with model pressure vessels was successfully achieved by combining image reconstruction with MFGM determined gradient waveform behaviour. Other categories of MR applications with metallic vessels, including diffusion measurement and spin echo SPI T2 mapping, cannot be realized solely by MFGM guided

  19. The Application Value of end tidal carbon dioxide partial pressure on mechanical ventilation adverse events%呼气末二氧化碳分压监测在机械通气不良事件中的应用价值

    Institute of Scientific and Technical Information of China (English)

    梁章荣; 李旷怡; 张英俭; 陈景利; 魏华; 吴智鑫; 李莹莹

    2016-01-01

    Objective To investigate the application value of end tidal carbon dioxide partial pressure on mechanical venti-lation adverse events.Method 114 patients with mechanical ventilation in department of emergency were selected,they were randomly divided into two groups.57 patients treated end tidal carbon dioxide partial pressure as observation group.57 patients did not implement end tidal carbon dioxide partial pressure as control group.Occurrence of mechanical ventilation adverse e-vents and prognosis were compared between two groups.Response to mechanical ventilation adverse events were analyzed in two groups.Results Incidence of error intubation (1.8%);ventilator pipe twisted or discount (10.5%);ventilator pipe shed (8.8%);inadequate ventilation (5.3%)in the observation group were lower than control group (5.3%);(15.8%);(14%);(8.8%).Cured rate(98.2%)in observation group was higher than control group (96.5%).Differences were not statistically significant (P >0.05).Response time of error intubation (0.57 ±0.18 min);ventilator pipe twisted or discount (1.06 ±0.35)min;ventilator pipe shed (0.25 ±0.11)min;inadequate ventilation (4.13 ±0.79)min in observation group were significantly less than control group (2.10 ±0.42)min;(1.89 ±0.27)min;(0.87 ±0.16)min;(7.62 ±1.24) min.Differences were statistically significant (P <0.05).Conclusion End tidal carbon dioxide partial pressure can early dis-cover mechanical ventilation adverse events,which is helpful to improve prognosis of patients.That is worthy of clinical use.%目的:探讨呼气末二氧化碳分压(PETCO2)监测在机械通气不良事件中的应用价值。方法:选取急诊科机械通气患者114例,采用随机数字表法分为两组,57例患者实施 PETCO2监测为观察组,57例患者未实施 PETCO2监测为对照组,比较两组患者机械通气不良事件的发生情况、预后情况、响应情况。结果:观察组患者错误插管发生率(1.8%)、呼吸机管

  20. Dynamic Insurance and Adverse Selection

    NARCIS (Netherlands)

    M.C.W. Janssen (Maarten); V.A. Karamychev (Vladimir)

    2001-01-01

    textabstractWe take a dynamic perspective on insurance markets under adverse selection and study a generalized Rothschild and Stiglitz model where agents may differ with respect to the accidental probability and their expenditure levels in case an accident occurs. We investigate the nature of dynami

  1. Adverse Effects of Hormonal Contraception

    Directory of Open Access Journals (Sweden)

    Sabatini R

    2011-01-01

    Full Text Available contraception acceptability, compliance and continuation. Despite the safety profile of current COCs, fears of adverse metabolic and vascular effects caused by estrogen component, and possible neoplastic effects of these formulations remain. Misperceptions and concerns about side-effects, especially those affecting the menstrual cycle and increased body weight, are often given as reason for discontinuation. Besides, severe adverse effects exist; perhaps they are very rare, but it might be that other cases were underestimated or ignored. It is important to take into account that COCs, as all medications, have some contraindications, which is mandatory to consider. The „pill“ could be not for everyone. In any case, also mild or moderate adverse effects of COCs may impair the woman’s quality of life. It is well known that even small increases in frequency of adverse effects, in COCs-users, could have a general critical health impact because of their widespread use, which is currently expanding to potential risk groups. To avoid adverse events by COC use the exclusion of patients with known risk factors including patient history and family history is necessary. Furthermore the patient should be informed about possible side effects and side effects during OC use should be carefully monitored. Finally the risk benefit analysis for oral contraceptive pills which are worldwide used since more than 50 years for healthy patients is positive. Most women will benefit from additional noncontraceptive benefits such as improvement of acne vulgaris, dysmenorrhoea, stabilization of menstrual bleeding pattern, less ovarian cysts and finally a lower risk for ovarian and breast cancer, which persists even after withdrawl of COC for several years.

  2. Gradient chromatography under constant frictional heat: realization and application.

    Science.gov (United States)

    Gritti, Fabrice; Guiochon, Georges

    2013-05-10

    A new mode of gradient elution in liquid chromatography is proposed. It is derived from simple theoretical considerations and is particularly suitable for applications to fast, very-high pressure gradients. It is designed to improve the injection-to-injection repeatability of chromatographic runs at either constant flow (cF, cooling case scenario) or constant pressure (cP, heating case scenario). The purpose of this original gradient mode is to minimize the variations of the temperatures and the pressures across and along the column during the gradient time. These variations are caused by the heat generated in the column due to the friction of the eluent percolating the bed. Any temperature fluctuation affects to some extent the precision of the measurements of retention times and bandwidths of eluted compounds. The minimization of this effect was achieved by maintaining constant the frictional heat power (i.e., the product of the flow rate by the column pressure drop) generated during the gradient run, the washing step, and the re-equilibration time. The eluent temperature was recorded at the column outlet. One useful application of gradient chromatography at constant frictional heat (cFH) is illustrated for a 50-100% volume gradient of acetonitrile in water using a 4.6mm × 150 mm column packed with 3.5 μm BEH-C18 particles and operated with an Agilent 1290 Infinity liquid chromatograph. The reproducibility (eleven consecutive injections) of the retention times and peak variances of nine small molecules (RPLC check-out sample mixture) using cF, cP, and cFH gradients were compared for the same amount of heat produced (403 J) during each run time. The RSDs of the retention times and the peak variances for four consecutive injections were systematically below 0.035 and 0.50% in constant frictional heat gradient chromatography, after three initial injections. These RSDs were markedly higher for cF (0.050 and 0.90%) and cP (0.070 and 1.80%) gradients. Copyright

  3. Sobolev gradients and differential equations

    CERN Document Server

    Neuberger, J W

    2010-01-01

    A Sobolev gradient of a real-valued functional on a Hilbert space is a gradient of that functional taken relative to an underlying Sobolev norm. This book shows how descent methods using such gradients allow a unified treatment of a wide variety of problems in differential equations. For discrete versions of partial differential equations, corresponding Sobolev gradients are seen to be vastly more efficient than ordinary gradients. In fact, descent methods with these gradients generally scale linearly with the number of grid points, in sharp contrast with the use of ordinary gradients. Aside from the first edition of this work, this is the only known account of Sobolev gradients in book form. Most of the applications in this book have emerged since the first edition was published some twelve years ago. What remains of the first edition has been extensively revised. There are a number of plots of results from calculations and a sample MatLab code is included for a simple problem. Those working through a fair p...

  4. Gradient zone boundary control in salt gradient solar ponds

    Energy Technology Data Exchange (ETDEWEB)

    Hull, John R. (Downers Grove, IL)

    1984-01-01

    A method and apparatus for suppressing zone boundary migration in a salt gradient solar pond includes extending perforated membranes across the pond at the boundaries, between the convective and non-convective zones, the perforations being small enough in size to prevent individual turbulence disturbances from penetrating the hole, but being large enough to allow easy molecular diffusion of salt thereby preventing the formation of convective zones in the gradient layer. The total area of the perforations is a sizable fraction of the membrane area to allow sufficient salt diffusion while preventing turbulent entrainment into the gradient zone.

  5. Optimal Contracting under Adverse Selection

    DEFF Research Database (Denmark)

    Lenells, Jonatan; Stea, Diego; Foss, Nicolai Juul

    2015-01-01

    We study a model of adverse selection, hard and soft information, and mentalizing ability--the human capacity to represent others' intentions, knowledge, and beliefs. By allowing for a continuous range of different information types, as well as for different means of acquiring information, we dev...... of that information. This strategy affects the properties of the optimal contract, which grows closer to the first best. This research provides insights into the implications of mentalizing for agency theory....

  6. Large scale patterns of antimicrofouling defenses in the hard coral Pocillopora verrucosa in an environmental gradient along the Saudi Arabian coast of the Red Sea.

    Directory of Open Access Journals (Sweden)

    Martin Wahl

    Full Text Available Large scale patterns of ecologically relevant traits may help identify drivers of their variability and conditions beneficial or adverse to the expression of these traits. Antimicrofouling defenses in scleractinian corals regulate the establishment of the associated biofilm as well as the risks of infection. The Saudi Arabian Red Sea coast features a pronounced thermal and nutritional gradient including regions and seasons with potentially stressful conditions to corals. Assessing the patterns of antimicrofouling defenses across the Red Sea may hint at the susceptibility of corals to global change. We investigated microfouling pressure as well as the relative strength of 2 alternative antimicrofouling defenses (chemical antisettlement activity, mucus release along the pronounced environmental gradient along the Saudi Arabian Red Sea coast in 2 successive years. Microfouling pressure was exceptionally low along most of the coast but sharply increased at the southernmost sites. Mucus release correlated with temperature. Chemical defense tended to anti-correlate with mucus release. As a result, the combined action of mucus release and chemical antimicrofouling defense seemed to warrant sufficient defense against microbes along the entire coast. In the future, however, we expect enhanced energetic strain on corals when warming and/or eutrophication lead to higher bacterial fouling pressure and a shift towards putatively more costly defense by mucus release.

  7. Sobolev gradients and differential equations

    CERN Document Server

    Neuberger, John William

    1997-01-01

    A Sobolev gradient of a real-valued functional is a gradient of that functional taken relative to the underlying Sobolev norm. This book shows how descent methods using such gradients allow a unified treatment of a wide variety of problems in differential equations. Equal emphasis is placed on numerical and theoretical matters. Several concrete applications are made to illustrate the method. These applications include (1) Ginzburg-Landau functionals of superconductivity, (2) problems of transonic flow in which type depends locally on nonlinearities, and (3) minimal surface problems. Sobolev gradient constructions rely on a study of orthogonal projections onto graphs of closed densely defined linear transformations from one Hilbert space to another. These developments use work of Weyl, von Neumann and Beurling.

  8. Conjugate Gradient with Subspace Optimization

    CERN Document Server

    Karimi, Sahar

    2012-01-01

    In this paper we present a variant of the conjugate gradient (CG) algorithm in which we invoke a subspace minimization subproblem on each iteration. We call this algorithm CGSO for "conjugate gradient with subspace optimization". It is related to earlier work by Nemirovsky and Yudin. We apply the algorithm to solve unconstrained strictly convex problems. As with other CG algorithms, the update step on each iteration is a linear combination of the last gradient and last update. Unlike some other conjugate gradient methods, our algorithm attains a theoretical complexity bound of $O(\\sqrt{L/l} \\log(1/\\epsilon))$, where the ratio $L/l$ characterizes the strong convexity of the objective function. In practice, CGSO competes with other CG-type algorithms by incorporating some second order information in each iteration.

  9. Flame Propagation Through Concentration Gradient

    Institute of Scientific and Technical Information of China (English)

    JunyaIINO; MitsuakiTANABE; 等

    2000-01-01

    The experiment was carried out in homogeneous propane-air mixture and in several concentration gradient of mixture.Igniter is put on the upper side of the combustion chamber,In concentration gradient experiment.ixture was ignited from lean side.An experimental study was conducted in a combustion chamber.The combustion chamber has glass windows for optical measurements at any side.For the measurement of distribution of fuel concentration,infraed absorption method using 3.39μm He-Ne laser was used,and for the observation of proagating flams,Schlieren method was employed.As a measurment result of flame propagation velocity and flammable limit,for a mixture of an identical local equivalence ratio.flame propagation velocity in concentration gradient is faster than that in homogeneous mixture,and rich flammable limit in concentration gradient shows a tendency to be higher than that in homogeneous mixture.

  10. Adverse responses to local anaesthetics.

    Science.gov (United States)

    Fisher, M M; Graham, R

    1984-11-01

    Progressive challenge was used to investigate twenty-seven patients with a history of an adverse response to local anaesthesia. True allergy was detected in only one patient. The method does not exclude reactions to additives and preservatives in local anaesthetics. If preservative-free local anaesthetics are used for subsequent exposure in patients with no response to progressive challenge, subsequent exposure is safe. The possibility that some of these patients may be reacting to preservatives in the solutions cannot be excluded by such testing. Where possible preservative-free local anaesthetic preparations should be used for subsequent anaesthesia.

  11. [Adverse ocular effects of vaccinations].

    Science.gov (United States)

    Ness, T; Hengel, H

    2016-07-01

    Vaccinations are very effective measures for prevention of infections but are also associated with a long list of possible side effects. Adverse ocular effects following vaccination have been rarely reported or considered to be related to vaccinations. Conjunctivitis is a frequent sequel of various vaccinations. Oculorespiratory syndrome and serum sickness syndrome are considered to be related to influenza vaccinations. The risk of reactivation or initiation of autoimmune diseases (e. g. uveitis) cannot be excluded but has not yet been proven. Overall the benefit of vaccination outweighs the possible but very low risk of ocular side effects.

  12. Family skills for overcoming adversity

    Directory of Open Access Journals (Sweden)

    Mónica Patricia Ardila Hernández

    2013-12-01

    Full Text Available This section draws on research four families in displacement in Tunja Boyacá step of this research is to present the problem of displacement from another different look that has embargoed regarding this topic. Critical reflection was raised from resilient approach Parsons theory in order to understand families immersed in this conflict as change agents capable of adapting to a new system and overcome adversity. Within this scheme is used to obtain qualitative research of the following categories : adaptation to the new social context risk factors present in families and protective factors.

  13. Long pendulums in gravitational gradients

    Energy Technology Data Exchange (ETDEWEB)

    Suits, B H [Physics Department, Michigan Technological University, Houghton, MI 49931 (United States)

    2006-03-01

    Previous results for long pendulums above a spherical Earth are generalized for arbitrary non-uniform gravitational fields in the limit of small oscillation. As is the case for the previous results, gravitational gradients are multiplied by the length of the string even though the string is assumed massless. The effect is shown to arise from the constraint on the motion imposed by the string. The significance of these results for real gradients is discussed. (letters and comments)

  14. Low-gradient aortic stenosis.

    Science.gov (United States)

    Clavel, Marie-Annick; Magne, Julien; Pibarot, Philippe

    2016-09-07

    An important proportion of patients with aortic stenosis (AS) have a 'low-gradient' AS, i.e. a small aortic valve area (AVA <1.0 cm(2)) consistent with severe AS but a low mean transvalvular gradient (<40 mmHg) consistent with non-severe AS. The management of this subset of patients is particularly challenging because the AVA-gradient discrepancy raises uncertainty about the actual stenosis severity and thus about the indication for aortic valve replacement (AVR) if the patient has symptoms and/or left ventricular (LV) systolic dysfunction. The most frequent cause of low-gradient (LG) AS is the presence of a low LV outflow state, which may occur with reduced left ventricular ejection fraction (LVEF), i.e. classical low-flow, low-gradient (LF-LG), or preserved LVEF, i.e. paradoxical LF-LG. Furthermore, a substantial proportion of patients with AS may have a normal-flow, low-gradient (NF-LG) AS: i.e. a small AVA-low-gradient combination but with a normal flow. One of the most important clinical challenges in these three categories of patients with LG AS (classical LF-LG, paradoxical LF-LG, and NF-LG) is to differentiate a true-severe AS that generally benefits from AVR vs. a pseudo-severe AS that should be managed conservatively. A low-dose dobutamine stress echocardiography may be used for this purpose in patients with classical LF-LG AS, whereas aortic valve calcium scoring by multi-detector computed tomography is the preferred modality in those with paradoxical LF-LG or NF-LG AS. Although patients with LF-LG severe AS have worse outcomes than those with high-gradient AS following AVR, they nonetheless display an important survival benefit with this intervention. Some studies suggest that transcatheter AVR may be superior to surgical AVR in patients with LF-LG AS.

  15. Graded/Gradient Porous Biomaterials

    Directory of Open Access Journals (Sweden)

    Xigeng Miao

    2009-12-01

    Full Text Available Biomaterials include bioceramics, biometals, biopolymers and biocomposites and they play important roles in the replacement and regeneration of human tissues. However, dense bioceramics and dense biometals pose the problem of stress shielding due to their high Young’s moduli compared to those of bones. On the other hand, porous biomaterials exhibit the potential of bone ingrowth, which will depend on porous parameters such as pore size, pore interconnectivity, and porosity. Unfortunately, a highly porous biomaterial results in poor mechanical properties. To optimise the mechanical and the biological properties, porous biomaterials with graded/gradient porosity, pores size, and/or composition have been developed. Graded/gradient porous biomaterials have many advantages over graded/gradient dense biomaterials and uniform or homogenous porous biomaterials. The internal pore surfaces of graded/gradient porous biomaterials can be modified with organic, inorganic, or biological coatings and the internal pores themselves can also be filled with biocompatible and biodegradable materials or living cells. However, graded/gradient porous biomaterials are generally more difficult to fabricate than uniform or homogenous porous biomaterials. With the development of cost-effective processing techniques, graded/gradient porous biomaterials can find wide applications in bone defect filling, implant fixation, bone replacement, drug delivery, and tissue engineering.

  16. Coastal Trapped Waves, Alongshore Pressure Gradients, and the California Undercurrent

    Science.gov (United States)

    2014-01-01

    D. NM W. J. Teague. C. N. Bairon. M. R. Carnes . and C. M. Lee. 2002: The Modular Ocean Dala Assimilation System (MODAS). J. Annoy Oieanic Tniwol...waves by irreimlarilies in coastline and topouraphy. J. llns. ()i»m<w.. 20." 396 421. Willmott. C J.. 1981: On the validation of models. Ph \\s. Gnffr

  17. Volume Integral of the Pressure Gradient and Archimedes' Principle

    CERN Document Server

    Pickett, Galen T

    2014-01-01

    The theorems of vector analysis (divergence theorem, etc.) are typically first applied in the undergraduate physics curriculum in the context of the electromagnetic field and the differential forms of Maxwell's equations. However, these tools are analyzed in depth several courses later in the junior-senior level. I discuss here a "bridge" problem, using the language of vector calculus in a mechanics setting to understand Archimedes' principle as a consequence of hydrostatic equilibrium and the superposition of the external forces. It is my hope that this treatment will help students better integrate and understand understand these and similar vector analysis results in contexts beyond electromagnetism.

  18. Volume Integral of the Pressure Gradient and Archimedes' Principle

    OpenAIRE

    Pickett, Galen T.

    2014-01-01

    The theorems of vector analysis (divergence theorem, etc.) are typically first applied in the undergraduate physics curriculum in the context of the electromagnetic field and the differential forms of Maxwell's equations. However, these tools are analyzed in depth several courses later in the junior-senior level. I discuss here a "bridge" problem, using the language of vector calculus in a mechanics setting to understand Archimedes' principle as a consequence of hydrostatic equilibrium and th...

  19. The causal relation between turbulent particle flux and density gradient

    Energy Technology Data Exchange (ETDEWEB)

    Milligen, B. Ph. van; Martín de Aguilera, A.; Hidalgo, C. [CIEMAT - Laboratorio Nacional de Fusión, Avda. Complutense 40, 28040 Madrid (Spain); Carreras, B. A. [BACV Solutions, 110 Mohawk Road, Oak Ridge, Tennessee 37830 (United States); García, L.; Nicolau, J. H. [Universidad Carlos III, 28911 Leganés, Madrid (Spain)

    2016-07-15

    A technique for detecting the causal relationship between fluctuating signals is used to investigate the relation between flux and gradient in fusion plasmas. Both a resistive pressure gradient driven turbulence model and experimental Langmuir probe data from the TJ-II stellarator are studied. It is found that the maximum influence occurs at a finite time lag (non-instantaneous response) and that quasi-periodicities exist. Furthermore, the model results show very long range radial influences, extending over most of the investigated regions, possibly related to coupling effects associated with plasma self-organization. These results clearly show that transport in fusion plasmas is not local and instantaneous, as is sometimes assumed.

  20. Acoustic beam control in biomimetic projector via velocity gradient

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Xiaowei; Dong, Erqian; Song, Zhongchang [Key Laboratory of Underwater Acoustic Communication and Marine Information Technology of the Ministry of Education, Xiamen University, Xiamen 361005 (China); Zhang, Yu, E-mail: yuzhang@xmu.edu.cn, E-mail: dzk@psu.edu; Tang, Liguo [Key Laboratory of Underwater Acoustic Communication and Marine Information Technology of the Ministry of Education, Xiamen University, Xiamen 361005 (China); State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005 (China); Cao, Wenwu, E-mail: yuzhang@xmu.edu.cn, E-mail: dzk@psu.edu [Department of Mathematics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Li, Songhai [Sanya Key Laboratory of Marin Mammal and Marine Bioacoustics, Sanya Institute of Deep-Sea Science and Engineering, Chinese Academy of Science, Sanya 57200 (China); Zhang, Sai [Faculty of Science, Jiangsu University, Zhenjiang 212013 (China)

    2016-07-04

    A biomimetic projector (BioP) based on computerized tomography of pygmy sperm whale's biosonar system has been designed using gradient-index (GRIN) material. The directivity of this BioP device was investigated as function of frequency and the velocity gradient of the GRIN material. A strong beam control over a broad bandwidth at the subwavelength scale has been achieved. Compared with a bare subwavelength source, the main lobe pressure of the BioP is about five times as high and the angular resolution is one order of magnitude better. Our results indicate that this BioP has excellent application potential in miniaturized underwater sonars.

  1. 管路内逆压梯度紊流场数值仿真网格条件影响的研究%Study on Effect of the Grid Condition of Numerical Simulation of Adverse Pressure Gradient Turbulence Field in Pipe System

    Institute of Scientific and Technical Information of China (English)

    孙勇

    2007-01-01

    用DHR型κ-ε紊流模型及其壁面函数·BFC(边界拟合曲线坐标变换)法,对总扩散角为8°、扩散度为4的锥形渐扩管路内完全发展的不可压粘性紊流场进行了数值仿真.在不同的网格数和网格系统等计算条件下分别给出了时均流速、紊流动能分布的计算结果,并分别与实验结果进行比较和分析,得知在不同计算条件下对计算结果的影响程度.

  2. Numerical Simulation for Inner Turbulent Flow having Adverse Pressure Gradient by DLR k - ε Turbulent Model——Effects of Model Constances and Grid Disposition%用DLR型k-ε紊流模型对逆压梯度内部紊流数值仿真——模型常数和网格布局的影响

    Institute of Scientific and Technical Information of China (English)

    何永森; 肖瑞; 孙勇

    2007-01-01

    用DLR型k-ε紊流模型·BFC(边界拟合曲线坐标变换)法,对总扩散角为8°,扩散度为4的锥形渐扩管内充分发展的不可压粘性紊流进行数值仿真.应用实例的人口雷诺数分别为1.16×105和2.93× 105.在不同的模型常数和网格布局下进行数值仿真,给出14种算例的时均速度ū和紊流动能k分布的计算结果,并分别将其与实验结果进行比较,分析不同计算条件对计算结果的影响程度,计算结果与实验结果较好符合.

  3. CDC Wonder Vaccine Adverse Event Reporting System

    Data.gov (United States)

    U.S. Department of Health & Human Services — The Vaccine Adverse Event Reporting System (VAERS) online database on CDC WONDER provides counts and percentages of adverse event case reports after vaccination,...

  4. "Adversative Conjunction": The Poetics of Linguistic Opposition.

    Science.gov (United States)

    Wallerstein, Nicholas

    1992-01-01

    The general use of adversative conjunction in (primarily) English and U.S. poetry is outlined. The contention is that the adversative is not merely a grammatical convenience but sometimes a highly functional tool of rhetorical strategy. (36 references) (LB)

  5. Optimal Contracting under Adverse Selection

    DEFF Research Database (Denmark)

    Lenells, Jonatan; Stea, Diego; Foss, Nicolai Juul

    2015-01-01

    We study a model of adverse selection, hard and soft information, and mentalizing ability--the human capacity to represent others' intentions, knowledge, and beliefs. By allowing for a continuous range of different information types, as well as for different means of acquiring information, we dev...... of that information. This strategy affects the properties of the optimal contract, which grows closer to the first best. This research provides insights into the implications of mentalizing for agency theory....... develop a model that captures how principals differentially obtain information on agents. We show that principals that combine conventional data collection techniques with mentalizing benefit from a synergistic effect that impacts both the amount of information that is accessed and the overall cost...

  6. Adverse reactions to drug additives.

    Science.gov (United States)

    Simon, R A

    1984-10-01

    There is a long list of additives used by the pharmaceutical industry. Most of the agents used have not been implicated in hypersensitivity reactions. Among those that have, only reactions to parabens and sulfites have been well established. Parabens have been shown to be responsible for rare immunoglobulin E-mediated reactions that occur after the use of local anesthetics. Sulfites, which are present in many drugs, including agents commonly used to treat asthma, have been shown to provoke severe asthmatic attacks in sensitive individuals. Recent studies indicate that additives do not play a significant role in "hyperactivity." The role of additives in urticaria is not well established and therefore the incidence of adverse reactions in this patient population is simply not known. In double-blind, placebo-controlled studies, reactions to tartrazine or additives other than sulfites, if they occur at all, are indeed quite rare for the asthmatic population, even for the aspirin-sensitive subpopulation.

  7. Gradient expansion for anisotropic hydrodynamics

    Science.gov (United States)

    Florkowski, Wojciech; Ryblewski, Radoslaw; Spaliński, Michał

    2016-12-01

    We compute the gradient expansion for anisotropic hydrodynamics. The results are compared with the corresponding expansion of the underlying kinetic-theory model with the collision term treated in the relaxation time approximation. We find that a recent formulation of anisotropic hydrodynamics based on an anisotropic matching principle yields the first three terms of the gradient expansion in agreement with those obtained for the kinetic theory. This gives further support for this particular hydrodynamic model as a good approximation of the kinetic-theory approach. We further find that the gradient expansion of anisotropic hydrodynamics is an asymptotic series, and the singularities of the analytic continuation of its Borel transform indicate the presence of nonhydrodynamic modes.

  8. Gradient expansion for anisotropic hydrodynamics

    CERN Document Server

    Florkowski, Wojciech; Spaliński, Michał

    2016-01-01

    We compute the gradient expansion for anisotropic hydrodynamics. The results are compared with the corresponding expansion of the underlying kinetic-theory model with the collision term treated in the relaxation time approximation. We find that a recent formulation of anisotropic hydrodynamics based on an anisotropic matching principle yields the first three terms of the gradient expansion in agreement with those obtained for the kinetic theory. This gives further support for this particular hydrodynamic model as a good approximation of the kinetic-theory approach. We further find that the gradient expansion of anisotropic hydrodynamics is an asymptotic series, and the singularities of the analytic continuation of its Borel transform indicate the presence of non-hydrodynamic modes.

  9. EXACT SOLUTIONS FOR NONLINEAR TRANSIENT FLOW MODEL INCLUDING A QUADRATIC GRADIENT TERM

    Institute of Scientific and Technical Information of China (English)

    曹绪龙; 同登科; 王瑞和

    2004-01-01

    The models of the nonlinear radial flow for the infinite and finite reservoirs including a quadratic gradient term were presented. The exact solution was given in real space for flow equation including quadratic gradiet term for both constant-rate and constant pressure production cases in an infinite system by using generalized Weber transform. Analytical solutions for flow equation including quadratic gradient term were also obtained by using the Hankel transform for a finite circular reservoir case. Both closed and constant pressure outer boundary conditions are considered. Moreover, both constant rate and constant pressure inner boundary conditions are considered. The difference between the nonlinear pressure solution and linear pressure solution is analyzed. The difference may be reached about 8% in the long time. The effect of the quadratic gradient term in the large time well test is considered.

  10. Bond Growth under Temperature Gradient.

    Directory of Open Access Journals (Sweden)

    P.K. Satyawali

    1999-12-01

    Full Text Available Grain and bond growth for dry snow are determined by the distribution of temperature andtemperature gradient in the snow matrix. From the standpoint of particle approach and based oncubic packing structure, a bond growth model has been developed for TG metamorphism. The paper.highlights the importance of bond formation and its effect on snow viscosity and finally on the rateof settlement. This is very important for developing a numerical snow pack model if microstructureis considered to be a basic parameter. A few experiments have been carried out to validate bond formation under temperature gradient.

  11. Human impact gradient on mammalian biodiversity

    Directory of Open Access Journals (Sweden)

    Mariana Munguía

    2016-04-01

    Full Text Available Drastic changes have been caused by human influence in natural landscapes, which may exert an intensive effect on species loss. However, species loss from human pressure is not random but depends on a series of environmentally associated factors. Linking species traits to environmental attributes may allow us to detect the ecological impacts of habitat so that meaningful habitat degradation gradients can be identified. The relationships between environmental factors and species traits provide the basis for identifying those biological traits that make species more sensitive to disturbance. These relationships are also helpful to detect the geographic distribution of latent risk to reveal areas where biodiversity is threatened. Here, we identify a “Human Impact Gradient for Biodiversity (HIGB” based on a three-table ordination method (RLQ analysis and fourth-corner analysis to identify key species traits that are associated with environmental gradient. Species distribution and environmental geographic data were gathered nationwide to analyze 68 localities, which represent 27% of Mexico’s surface, including 211 species of mammals. Nine environmental variables (including biophysical, geophysical and land-use impacts were analyzed by using the Geographic Information System. Three types of species’ traits were evaluated: locomotion, trophic habit and body size. We identified a human impact gradient, which was mainly determined by the percentage of the area that was covered by seedlings, the plant richness, the understory coverage percentage and the human settlement index. The most important species traits that are associated with non-human-impacted sites were carnivores, frugivores–herbivores and a body size that was greater than 17.8 kg; 25 species were selected by the decision criteria framework for species that were sensitive to degradation based on ecological function information. Conversely, granivores, fossorial and semifossorial

  12. Adverse effects of antihypertensive drugs.

    Science.gov (United States)

    Husserl, F E; Messerli, F H

    1981-09-01

    Early essential hypertension is asymptomatic and should remain so throughout treatment. In view of the increasing number of available antihypertensive agents, clinicians need to become familiar with the potential side effects of these drugs. By placing more emphasis on non-pharmacological treatment (sodium restriction, weight loss, exercise) and thoroughly evaluating each case in particular, the pharmacological regimen can be optimally tailored to the patient's needs. Potential side effects should be predicted and can often be avoided; if they become clinically significant they should be rapidly recognised and corrected. These side effects can be easily remembered in most instances, as they fall into 3 broad categories: (a) those caused by an exaggerated therapeutic effect; (b) those due to a non-therapeutic pharmacological effect; and (c) those caused by a non-therapeutic, non-pharmacological effect probably representing idiosyncratic reactions. This review focuses mainly on adverse effects of the second and third kind. Each group of drugs in general shares the common side effects of the first two categories, while each individual drug has its own idiosyncratic side effects.

  13. The geomagnetic field gradient tensor

    DEFF Research Database (Denmark)

    Kotsiaros, Stavros; Olsen, Nils

    2012-01-01

    We develop the general mathematical basis for space magnetic gradiometry in spherical coordinates. The magnetic gradient tensor is a second rank tensor consisting of 3 × 3 = 9 spatial derivatives. Since the geomagnetic field vector B is always solenoidal (∇ · B = 0) there are only eight independe...... of the small-scale structure of the Earth’s lithospheric field....

  14. Surface gradients under electrochemical control

    NARCIS (Netherlands)

    Krabbenborg, Sven Olle

    2014-01-01

    Gradients are systems in which the physicochemical properties of a solution and/or surface change gradually in space and/or time. They are used for a myriad of technological and biological applications, for example for high-throughput screening, or for the investigation of biological systems. The de

  15. Compositional gradients in Gramineae genes

    DEFF Research Database (Denmark)

    Wong, Gane Ka-Shu; Wang, Jun; Tao, Lin

    2002-01-01

    In this study, we describe a property of Gramineae genes, and perhaps all monocot genes, that is not observed in eudicot genes. Along the direction of transcription, beginning at the junction of the 5'-UTR and the coding region, there are gradients in GC content, codon usage, and amino-acid usage...

  16. GOCE level 2 gravity gradients

    NARCIS (Netherlands)

    Bouman, J.; Fiorot, S.; Fuchs, M.; Gruber, T.; Schrama, E.J.O.; Tscherning, C.C.; Veicherts, M.; Visser, P.N.A.M.

    2011-01-01

    Two of the GOCE Level 2 products are the gravity gradients (GGs) in the Gradiometer Reference Frame (GRF) and the GGs in the Local North-Oriented Frame (LNOF). The GRF is an instrument frame and the GGs are derived from the L1b GGs. The L1b to L2 GG processing involves corrections for temporal gravi

  17. Reinforcement Learning Through Gradient Descent

    Science.gov (United States)

    1999-05-14

    Reinforcement learning is often done using parameterized function approximators to store value functions. Algorithms are typically developed for...practice of existing types of algorithms, the gradient descent approach makes it possible to create entirely new classes of reinforcement learning algorithms

  18. Consolidation by Prefabricated Vertical Drains with a Threshold Gradient

    Directory of Open Access Journals (Sweden)

    Xiao Guo

    2014-01-01

    Full Text Available This paper shows the development of an approximate analytical solution of radial consolidation by prefabricated vertical drains with a threshold gradient. To understand the effect of the threshold gradient on consolidation, a parametric analysis was performed using the present solution. The applicability of the present solution was demonstrated in two cases, wherein the comparisons with Hansbo’s results and observed data were conducted. It was found that (1 the flow with the threshold gradient would not occur instantaneously throughout the whole unit cell. Rather, it gradually occurs from the vertical drain to the outside; (2 the moving boundary would never reach the outer radius of influence if R+1pressure will not be dissipated completely, but it will maintain a long-term stable value at the end of consolidation; (4 the larger the threshold gradient is, the greater the long-term excess pore pressure will be; and (5 the present solution could predict the consolidation behavior in soft clay better than previous methods.

  19. Shaping and timing gradient pulses to reduce MRI acoustic noise.

    Science.gov (United States)

    Segbers, Marcel; Rizzo Sierra, Carlos V; Duifhuis, Hendrikus; Hoogduin, Johannes M

    2010-08-01

    A method to reduce the acoustic noise generated by gradient systems in MRI has been recently proposed; such a method is based on the linear response theory. Since the physical cause of MRI acoustic noise is the time derivative of the gradient current, a common trapezoid current shape produces an acoustic gradient coil response mainly during the rising and falling edge. In the falling edge, the coil acoustic response presents a 180 degrees phase difference compared to the rising edge. Therefore, by varying the width of the trapezoid and keeping the ramps constant, it is possible to suppress one selected frequency and its higher harmonics. This value is matched to one of the prominent resonance frequencies of the gradient coil system. The idea of cancelling a single frequency is extended to a second frequency, using two successive trapezoid-shaped pulses presented at a selected interval. Overall sound pressure level reduction of 6 and 10 dB is found for the two trapezoid shapes and a single pulse shape, respectively. The acoustically optimized pulse shape proposed is additionally tested in a simulated echo planar imaging readout train, obtaining a sound pressure level reduction of 12 dB for the best case.

  20. OAE: The Ontology of Adverse Events.

    Science.gov (United States)

    He, Yongqun; Sarntivijai, Sirarat; Lin, Yu; Xiang, Zuoshuang; Guo, Abra; Zhang, Shelley; Jagannathan, Desikan; Toldo, Luca; Tao, Cui; Smith, Barry

    2014-01-01

    A medical intervention is a medical procedure or application intended to relieve or prevent illness or injury. Examples of medical interventions include vaccination and drug administration. After a medical intervention, adverse events (AEs) may occur which lie outside the intended consequences of the intervention. The representation and analysis of AEs are critical to the improvement of public health. The Ontology of Adverse Events (OAE), previously named Adverse Event Ontology (AEO), is a community-driven ontology developed to standardize and integrate data relating to AEs arising subsequent to medical interventions, as well as to support computer-assisted reasoning. OAE has over 3,000 terms with unique identifiers, including terms imported from existing ontologies and more than 1,800 OAE-specific terms. In OAE, the term 'adverse event' denotes a pathological bodily process in a patient that occurs after a medical intervention. Causal adverse events are defined by OAE as those events that are causal consequences of a medical intervention. OAE represents various adverse events based on patient anatomic regions and clinical outcomes, including symptoms, signs, and abnormal processes. OAE has been used in the analysis of several different sorts of vaccine and drug adverse event data. For example, using the data extracted from the Vaccine Adverse Event Reporting System (VAERS), OAE was used to analyse vaccine adverse events associated with the administrations of different types of influenza vaccines. OAE has also been used to represent and classify the vaccine adverse events cited in package inserts of FDA-licensed human vaccines in the USA. OAE is a biomedical ontology that logically defines and classifies various adverse events occurring after medical interventions. OAE has successfully been applied in several adverse event studies. The OAE ontological framework provides a platform for systematic representation and analysis of adverse events and of the factors (e

  1. Thyroid-disrupting chemicals: interpreting upstream biomarkers of adverse outcomes.

    Science.gov (United States)

    Miller, Mark D; Crofton, Kevin M; Rice, Deborah C; Zoeller, R Thomas

    2009-07-01

    There is increasing evidence in humans and in experimental animals for a relationship between exposure to specific environmental chemicals and perturbations in levels of critically important thyroid hormones (THs). Identification and proper interpretation of these relationships are required for accurate assessment of risk to public health. We review the role of TH in nervous system development and specific outcomes in adults, the impact of xenobiotics on thyroid signaling, the relationship between adverse outcomes of thyroid disruption and upstream causal biomarkers, and the societal implications of perturbations in thyroid signaling by xenobiotic chemicals. We drew on an extensive body of epidemiologic, toxicologic, and mechanistic studies. THs are critical for normal nervous system development, and decreased maternal TH levels are associated with adverse neuropsychological development in children. In adult humans, increased thyroid-stimulating hormone is associated with increased blood pressure and poorer blood lipid profiles, both risk factors for cardiovascular disease and death. These effects of thyroid suppression are observed even within the "normal" range for the population. Environmental chemicals may affect thyroid homeostasis by a number of mechanisms, and multiple chemicals have been identified that interfere with thyroid function by each of the identified mechanisms. Individuals are potentially vulnerable to adverse effects as a consequence of exposure to thyroid-disrupting chemicals. Any degree of thyroid disruption that affects TH levels on a population basis should be considered a biomarker of adverse outcomes, which may have important societal outcomes.

  2. Gradient B drift transport of high current electron beams

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J.R.; Backstrom, R.C.; Halbleib, J.A.; Quintenz, J.P.; Wright, T.P.

    1984-12-01

    A 1-MeV, 200-kA electron beam was transported 89 cm in a low pressure background gas via gradient B drift in the 1/r azimuthal magnetic field of a current carrying wire. The electron drift velocity was measured and found to be in good agreement with theory. Measurements of x-ray production in the target indicated high transport efficiency.

  3. Moving-Temperature-Gradient Heat-Pipe Furnace Element

    Science.gov (United States)

    Gillies, Donald C.; Lehoczky, Sandor L.; Gernert, Nelson J.

    1993-01-01

    In improved apparatus, ampoule of material directionally solidified mounted in central hole of annular heat pipe, at suitable axial position between heated and cooled ends. Heated end held in fixed position in single-element furnace; other end left in ambient air or else actively cooled. Gradient of temperature made to move along heat pipe by changing pressure of noncondensable gas. In comparison with prior crystal-growing apparatuses, this one simpler, smaller, and more efficient.

  4. [Cutaneous adverse effects of TNFalpha antagonists].

    Science.gov (United States)

    Failla, V; Sabatiello, M; Lebas, E; de Schaetzen, V; Dezfoulian, B; Nikkels, A F

    2012-01-01

    The TNFalpha antagonists, including adalimumab, etanercept and infliximab, represent a class of anti-inflammatory and immunosuppressive drugs. Although cutaneous adverse effects are uncommon, they are varied. There is no particular risk profile to develop cutaneous adverse effects. The principal acute side effects are injection site reactions and pruritus. The major long term cutaneous side effects are infectious and inflammatory conditions. Neoplastic skin diseases are exceptional. The association with other immunosuppressive agents can increase the risk of developing cutaneous adverse effects. Some adverse effects, such as lupus erythematosus, require immediate withdrawal of the biological treatment, while in other cases temporary withdrawal is sufficient. The majority of the other cutaneous adverse effects can be dealt without interrupting biologic treatment. Preclinical and clinical investigations revealed that the new biologics, aiming IL12/23, IL23 and IL17, present a similar profile of cutaneous adverse effects, although inflammatory skin reactions may be less often encountered compared to TNFalpha antagonists.

  5. Early adversity, neural development, and inflammation.

    Science.gov (United States)

    Chiang, Jessica J; Taylor, Shelley E; Bower, Julienne E

    2015-12-01

    Early adversity is a risk factor for poor mental and physical health. Although altered neural development is believed to be one pathway linking early adversity to psychopathology, it has rarely been considered a pathway linking early adversity to poor physical health. However, this is a viable pathway because the central nervous system is known to interact with the immune system via the hypothalamic-pituitary-adrenal (HPA) axis and autonomic nervous system (ANS). In support of this pathway, early adversity has been linked to changes in neural development (particularly of the amygdala, hippocampus, and prefrontal cortex), HPA axis and ANS dysregulation, and higher levels of inflammation. Inflammation, in turn, can be detrimental to physical health when prolonged. In this review, we present these studies and consider how altered neural development may be a pathway by which early adversity increases inflammation and thus risk for adverse physical health outcomes.

  6. Asymmetric Information – Adverse Selection Problem

    Directory of Open Access Journals (Sweden)

    Dumitru MARIN

    2007-01-01

    Full Text Available The present paper makes an introduction in the contract theory starting with the definitions of asymmetric information and some of the problems that generate: moral hazard and adverse selection. We provide an insight of the latest empirical studies in adverse selection in different markets. An adverse selection model, based on Rothchild and Stiglitz is also present to give a perspective of the theoretical framework.

  7. Hospital deaths and adverse events in Brazil

    Directory of Open Access Journals (Sweden)

    Pavão Ana Luiza B

    2011-09-01

    Full Text Available Abstract Background Adverse events are considered a major international problem related to the performance of health systems. Evaluating the occurrence of adverse events involves, as any other outcome measure, determining the extent to which the observed differences can be attributed to the patient's risk factors or to variations in the treatment process, and this in turn highlights the importance of measuring differences in the severity of the cases. The current study aims to evaluate the association between deaths and adverse events, adjusted according to patient risk factors. Methods The study is based on a random sample of 1103 patient charts from hospitalizations in the year 2003 in 3 teaching hospitals in the state of Rio de Janeiro, Brazil. The methodology involved a retrospective review of patient charts in two stages - screening phase and evaluation phase. Logistic regression was used to evaluate the relationship between hospital deaths and adverse events. Results The overall mortality rate was 8.5%, while the rate related to the occurrence of an adverse event was 2.9% (32/1103 and that related to preventable adverse events was 2.3% (25/1103. Among the 94 deaths analyzed, 34% were related to cases involving adverse events, and 26.6% of deaths occurred in cases whose adverse events were considered preventable. The models tested showed good discriminatory capacity. The unadjusted odds ratio (OR 11.43 and the odds ratio adjusted for patient risk factors (OR 8.23 between death and preventable adverse event were high. Conclusions Despite discussions in the literature regarding the limitations of evaluating preventable adverse events based on peer review, the results presented here emphasize that adverse events are not only prevalent, but are associated with serious harm and even death. These results also highlight the importance of risk adjustment and multivariate models in the study of adverse events.

  8. Segmental blood pressure after total hip replacement

    DEFF Research Database (Denmark)

    Gebuhr, Peter Henrik; Soelberg, M; Henriksen, Jens Henrik Sahl

    1992-01-01

    Twenty-nine patients due to have a total hip replacement had their systemic systolic and segmental blood pressures measured prior to operation and 1 and 6 weeks postoperatively. No patients had signs of ischemia. The segmental blood pressure was measured at the ankle and at the toes. A significant...... drop was found in all pressures 1 week postoperatively. The decrease followed the systemic pressure and was restored to normal after 6 weeks. In a group of six patients with preoperatively decreased ankle pressure, a significant transient further decrease in the ankle-toe gradient pressure was found...

  9. Abnormal pressure in hydrocarbon environments

    Science.gov (United States)

    Law, B.E.; Spencer, C.W.

    1998-01-01

    Abnormal pressures, pressures above or below hydrostatic pressures, occur on all continents in a wide range of geological conditions. According to a survey of published literature on abnormal pressures, compaction disequilibrium and hydrocarbon generation are the two most commonly cited causes of abnormally high pressure in petroleum provinces. In young (Tertiary) deltaic sequences, compaction disequilibrium is the dominant cause of abnormal pressure. In older (pre-Tertiary) lithified rocks, hydrocarbon generation, aquathermal expansion, and tectonics are most often cited as the causes of abnormal pressure. The association of abnormal pressures with hydrocarbon accumulations is statistically significant. Within abnormally pressured reservoirs, empirical evidence indicates that the bulk of economically recoverable oil and gas occurs in reservoirs with pressure gradients less than 0.75 psi/ft (17.4 kPa/m) and there is very little production potential from reservoirs that exceed 0.85 psi/ft (19.6 kPa/m). Abnormally pressured rocks are also commonly associated with unconventional gas accumulations where the pressuring phase is gas of either a thermal or microbial origin. In underpressured, thermally mature rocks, the affected reservoirs have most often experienced a significant cooling history and probably evolved from an originally overpressured system.

  10. Bacterial accumulation in viscosity gradients

    Science.gov (United States)

    Waisbord, Nicolas; Guasto, Jeffrey

    2016-11-01

    Cell motility is greatly modified by fluid rheology. In particular, the physical environments in which cells function, are often characterized by gradients of viscous biopolymers, such as mucus and extracellular matrix, which impact processes ranging from reproduction to digestion to biofilm formation. To understand how spatial heterogeneity of fluid rheology affects the motility and transport of swimming cells, we use hydrogel microfluidic devices to generate viscosity gradients in a simple, polymeric, Newtonian fluid. Using video microscopy, we characterize the random walk motility patterns of model bacteria (Bacillus subtilis), showing that both wild-type ('run-and-tumble') cells and smooth-swimming mutants accumulate in the viscous region of the fluid. Through statistical analysis of individual cell trajectories and body kinematics in both homogeneous and heterogeneous viscous environments, we discriminate passive, physical effects from active sensing processes to explain the observed cell accumulation at the ensemble level.

  11. Computational Strain Gradient Crystal Plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2011-01-01

    A model for strain gradient crystal visco-plasticity is formulated along the lines proposed by Fleck andWillis (2009) for isotropic plasticity. Size-effects are included in the model due to the addition of gradient terms in both the free energy as well as through a dissipation potential. A finite...... element solution method is presented, which delivers the slip-rate field and the velocity-field based on two minimum principles. Some plane deformation problems relevant for certain specific orientations of a face centered cubic crystal under plane loading conditions are studied, and effective in......-plane parameters are developed based on the crystallographic properties of the material. The problem of cyclic shear of a single crystal between rigid platens is studied as well as void growth of a cylindrical void....

  12. Biomimetic Gradient Index (GRIN) Lenses

    Science.gov (United States)

    2006-01-01

    optics include single lenses inspired by cephalopod (octopus) eyes and a three-lens, wide field of view, optical system for a surveillance sensor...camera. Details are easily resolv- able with the polymer lens. This lens system was installed on an Evolution unmanned aerial vehicle (UAV) with a...lens system was installed in an NRL Evolution UAV and used to record video images at a height of up to 1000 ft. The index gradients in the polymer

  13. Multilayer coating for high gradients

    CERN Document Server

    Kubo, Takayuki

    2016-01-01

    The multilayer coating for high gradients is reviewed. Not only the S-I-S structure, but also the S-S bilayer structure are also treated. This is an incomplete manuscript of an invited article which will be submitted to a journal. I have uploaded this version in order to help the understanding on my talk at the TESLA Technology Collaboration meeting at Saclay, France.

  14. Using contemporary liquid chromatography theory and technology to improve capillary gradient ion-exchange separations.

    Science.gov (United States)

    Wouters, Bert; Broeckhoven, Ken; Wouters, Sam; Bruggink, Cees; Agroskin, Yury; Pohl, Christopher A; Eeltink, Sebastiaan

    2014-11-28

    The gradient-performance limits of capillary ion chromatography have been assessed at maximum system pressure (34.5 MPa) using capillary columns packed with 4.1 μm macroporous anion-exchange particles coated with 65 nm positively-charged nanobeads. In analogy to the van-Deemter curve, the gradient performance was assessed applying different flow rates, while decreasing the gradient time inversely proportional to the increase in flow rate in order to maintain the same retention properties. The gradient kinetic-performance limits were determined at maximum system pressure, applying tG/t0=5, 10, and 20. In addition, the effect of retention on peak width was assessed in gradient mode for mono-, di-, and trivalent inorganic anions. The peak width of late-eluting ions can be significantly reduced by using concave gradient, resulting in better detection sensitivity. A signal enhancement factor of 8 was measured for a late-eluting ion when applying a concave instead of a linear gradient. For the analysis of a complex anion mixture, a coupled column with a total length of 1.05 m was operated at the kinetic-performance limit applying a linear 250 min gradient (tG/t0=10). The peak capacity varied between 200 and 380 depending on analyte retention, and hence on charge and size of the ion.

  15. Future of gradient index optics

    Science.gov (United States)

    Hashizume, Hideki; Hamanaka, Kenjiro; Graham, Alan C., III; Zhu, X. Frank

    2001-11-01

    First developed over 30 years ago, gradient index lenses play an important role not only in telecommunications technology, but also in applications such as information interface and biomedical technology. Traditional manufacturing consists of doping a certain ion, A+ into the mother glass, drawing the glass into rods and then immersing the rods into s molten salt bath containing another certain ion B+. During a thermal ion exchange process, the original ion migrates out of the mother glass, and is replaced by the alternate ion, creating a refractive index variation. Current research is being conducted to improve the thermal ion exchange technology, and open new applications. This research includes extending working distances to greater than 100mm, decreasing the lens diameter, increasing the effective radius, and combining the technology with other technologies such as photolithographically etched masks to produce arrays of gradient index lenses. As a result of this ongoing research, the gradient index lens is expected to continue to be the enabling optical technology in the first decade of the new millennium and beyond.

  16. Primordial vorticity and gradient expansion

    Science.gov (United States)

    Giovannini, Massimo; Rezaei, Zahra

    2012-02-01

    The evolution equations of the vorticities of the electrons, ions and photons in a pre-decoupling plasma are derived, in a fully inhomogeneous geometry, by combining the general relativistic gradient expansion and the drift approximation within the Adler-Misner-Deser decomposition. The vorticity transfer between the different species is discussed in this novel framework and a set of general conservation laws, connecting the vorticities of the three-component plasma with the magnetic field intensity, is derived. After demonstrating that a source of large-scale vorticity resides in the spatial gradients of the geometry and of the electromagnetic sources, the total vorticity is estimated to lowest order in the spatial gradients and by enforcing the validity of the momentum constraint. By acknowledging the current bounds on the tensor to scalar ratio in the (minimal) tensor extension of the ΛCDM paradigm, the maximal comoving magnetic field induced by the total vorticity turns out to be, at most, of the order of 10-37 G over the typical comoving scales ranging between 1 and 10 Mpc. While the obtained results seem to be irrelevant for seeding a reasonable galactic dynamo action, they demonstrate how the proposed fully inhomogeneous treatment can be used for the systematic scrutiny of pre-decoupling plasmas beyond the conventional perturbative expansions.

  17. Primordial vorticity and gradient expansion

    CERN Document Server

    Giovannini, Massimo

    2012-01-01

    The evolution equations of the vorticities of the electrons, ions and photons in a pre-decoupling plasma are derived, in a fully inhomogeneous geometry, by combining the general relativistic gradient expansion and the drift approximation within the Adler-Misner-Deser decomposition. The vorticity transfer between the different species is discussed in this novel framework and a set of general conservation laws, connecting the vorticities of the three-component plasma with the magnetic field intensity, is derived. After demonstrating that a source of large-scale vorticity resides in the spatial gradients of the geometry and of the electromagnetic sources, the total vorticity is estimated to lowest order in the spatial gradients and by enforcing the validity of the momentum constraint. By acknowledging the current bounds on the tensor to scalar ratio in the (minimal) tensor extension of the $\\Lambda$CDM paradigm the maximal comoving magnetic field induced by the total vorticity turns out to be, at most, of the or...

  18. 16 CFR 901.7 - Adverse determination.

    Science.gov (United States)

    2010-01-01

    ... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Adverse determination. 901.7 Section 901.7... APPLICATION FOR EXEMPTION FROM THE PROVISIONS OF THE ACT § 901.7 Adverse determination. (a) If, after... of the information before it that it cannot make a favorable determination in connection with the...

  19. Salinity Gradients for Sustainable Energy: Primer, Progress, and Prospects.

    Science.gov (United States)

    Yip, Ngai Yin; Brogioli, Doriano; Hamelers, Hubertus V M; Nijmeijer, Kitty

    2016-11-15

    Combining two solutions of different composition releases the Gibbs free energy of mixing. By using engineered processes to control the mixing, chemical energy stored in salinity gradients can be harnessed for useful work. In this critical review, we present an overview of the current progress in salinity gradient power generation, discuss the prospects and challenges of the foremost technologies - pressure retarded osmosis (PRO), reverse electrodialysis (RED), and capacitive mixing (CapMix) and provide perspectives on the outlook of salinity gradient power generation. Momentous strides have been made in technical development of salinity gradient technologies and field demonstrations with natural and anthropogenic salinity gradients (for example, seawater-river water and desalination brine-wastewater, respectively), but fouling persists to be a pivotal operational challenge that can significantly ebb away cost-competitiveness. Natural hypersaline sources (e.g., hypersaline lakes and salt domes) can achieve greater concentration difference and, thus, offer opportunities to overcome some of the limitations inherent to seawater-river water. Technological advances needed to fully exploit the larger salinity gradients are identified. While seawater desalination brine is a seemingly attractive high salinity anthropogenic stream that is otherwise wasted, actual feasibility hinges on the appropriate pairing with a suitable low salinity stream. Engineered solutions are foulant-free and can be thermally regenerative for application in low-temperature heat utilization. Alternatively, PRO, RED, and CapMix can be coupled with their analog separation process (reverse osmosis, electrodialysis, and capacitive deionization, respectively) in salinity gradient flow batteries for energy storage in chemical potential of the engineered solutions. Rigorous techno-economic assessments can more clearly identify the prospects of low-grade heat conversion and large-scale energy storage

  20. Socioeconomic gradients in cardiovascular risk in Canadian children and adolescents

    Directory of Open Access Journals (Sweden)

    Y. Shi

    2016-02-01

    Full Text Available Introduction: Cardiovascular disease (CVD and its risk factors show clear socioeconomic gradients in Canadian adults. Whether socioeconomic gradients in cardiovascular risk emerge in childhood remains unclear. The objective of this study was to determine whether there are socioeconomic gradients in physiological markers of CVD risk in Canadian children and adolescents. Methods: Using combined cross-sectional data from the Canadian Health Measures Survey 2007–2011, we examined the following cardiovascular risk markers: overweight (including obesity, aerobic fitness score (AFS, blood pressure (BP, blood lipids (total as well as HDL and LDL cholesterol and triglycerides, glucose metabolism and C-reactive protein (CRP by sex in 2149 children (ages 6–11 years and 2073 adolescents (ages 12–17 years. Multivariate linear and logistic regression analyses were used to identify patterns in cardiovascular risk across strata of household income adequacy and parental educational attainment, adjusting for age and ethnicity, and stratified by age group and sex. Results: Young boys showed markedly higher prevalence of obesity than young girls (prevalence of 18.5%, 95% confidence interval [CI]: 15.6–21.5 vs. 7.7%, 95% CI: 5.2–10.3. However, negative SES gradients in adiposity risk were seen in young and adolescent girls rather than boys. Young and adolescent boys were more physically fit than girls (mean AFS of 541, 95% CI: 534–546 vs. 501, 95% CI: 498–505 in children; 522, 95% CI: 514–529 vs. 460, 95% CI: 454–466 in adolescents; p < .001. Although a positive income gradient in AFS was observed in both boys and girls, statistical significance was reached only in girls (p = .006. A negative gradient of parental education in BP was observed in young children. While we observed substantial sex differences in systolic BP, total and HDL cholesterol, fasting glucose and CRP in adolescents, sex-specific socioeconomic gradients were only observed for

  1. On the structure of gradient Yamabe solitons

    CERN Document Server

    Cao, Huai-Dong; Zhang, Yingying

    2011-01-01

    We show that every complete nontrivial gradient Yamabe soliton admits a special global warped product structure with a one-dimensional base. Based on this, we prove a general classification theorem for complete nontrivial locally conformally flat gradient Yamabe solitons.

  2. Community and ecosystem responses to elevational gradients

    DEFF Research Database (Denmark)

    Sundqvist, Maja K.; Sanders, Nate; Wardle, David A.

    2013-01-01

    Community structure and ecosystem processes often vary along elevational gradients. Their responses to elevation are commonly driven by changes in temperature, and many community- and ecosystem-level variables therefore frequently respond similarly to elevation across contrasting gradients. There...

  3. Multiple adverse experiences and child cognitive development.

    Science.gov (United States)

    Guinosso, Stephanie A; Johnson, Sara B; Riley, Anne W

    2016-01-01

    During childhood and adolescence, children's social environments shape their cognitive development. Children exposed to multiple adversities in their social environment are more likely to have poorer cognitive outcomes. These findings have prompted interest among pediatric and public health communities to screen and connect youth to appropriate interventions that ameliorate the detrimental effects of adverse exposures. Such intervention efforts can be improved with a stronger conceptual understanding of the relationship between multiple adverse exposures and child cognitive development. This includes disentangling adverse exposures from other risk factors or underlying mechanisms, specifying mechanisms of action, and determining when adverse exposures are most detrimental. This review summarizes findings from the literature on each of these areas and proposes a conceptual model to guide further research and intervention.

  4. Distribution et assemblages des macrophytes le long d’un gradient d'hydrodynamisme : application au lac de Lacanau (Gironde)

    OpenAIRE

    F. Grigoletto

    2014-01-01

    The objective of the internship is to study the macrophytes distribution and assemblages on Lacanau lake along a gradient of hydrodynamics, including waves. It is also to characterize this gradient at different spatial scales near the coastal areas. The first method of measuring the gradient of hydrodynamics is based on field data acquired using hydrostatic pressure sensor made for exploratory purposes in 2013. This method is used for observations on a small scale (a few square meters). The r...

  5. Gradient Flow Convolutive Blind Source Separation

    DEFF Research Database (Denmark)

    Pedersen, Michael Syskind; Nielsen, Chinton Møller

    2004-01-01

    Experiments have shown that the performance of instantaneous gradient flow beamforming by Cauwenberghs et al. is reduced significantly in reverberant conditions. By expanding the gradient flow principle to convolutive mixtures, separation in a reverberant environment is possible. By use of a circ......Experiments have shown that the performance of instantaneous gradient flow beamforming by Cauwenberghs et al. is reduced significantly in reverberant conditions. By expanding the gradient flow principle to convolutive mixtures, separation in a reverberant environment is possible. By use...

  6. An education gradient in health, a health gradient in education, or a confounded gradient in both?

    Science.gov (United States)

    Lynch, Jamie L; von Hippel, Paul T

    2016-04-01

    There is a positive gradient associating educational attainment with health, yet the explanation for this gradient is not clear. Does higher education improve health (causation)? Do the healthy become highly educated (selection)? Or do good health and high educational attainment both result from advantages established early in the life course (confounding)? This study evaluates these competing explanations by tracking changes in educational attainment and Self-rated Health (SRH) from age 15 to age 31 in the National Longitudinal Study of Youth, 1997 cohort. Ordinal logistic regression confirms that high-SRH adolescents are more likely to become highly educated. This is partly because adolescent SRH is associated with early advantages including adolescents' academic performance, college plans, and family background (confounding); however, net of these confounders adolescent SRH still predicts adult educational attainment (selection). Fixed-effects longitudinal regression shows that educational attainment has little causal effect on SRH at age 31. Completion of a high school diploma or associate's degree has no effect on SRH, while completion of a bachelor's or graduate degree have effects that, though significant, are quite small (less than 0.1 points on a 5-point scale). While it is possible that educational attainment would have greater effect on health at older ages, at age 31 what we see is a health gradient in education, shaped primarily by selection and confounding rather than by a causal effect of education on health.

  7. Latitudinal gradients in ecosystem engineering by oysters vary across habitats.

    Science.gov (United States)

    McAfee, Dominic; Cole, Victoria J; Bishop, Melanie J

    2016-04-01

    Ecological theory predicts that positive interactions among organisms will increase across gradients of increasing abiotic stress or consumer pressure. This theory has been supported by empirical studies examining the magnitude of ecosystem engineering across environmental gradients and between habitat settings at local scale. Predictions that habitat setting, by modifying both biotic and abiotic factors, will determine large-scale gradients in ecosystem engineering have not been tested, however. A combination of manipulative experiments and field surveys assessed whether along the east Australian coastline: (1) facilitation of invertebrates by the oyster Saccostrea glomerata increased across a latitudinal gradient in temperature; and (2) the magnitude of this effect varied between intertidal rocky shores and mangrove forests. It was expected that on rocky shores, where oysters are the primary ecosystem engineer, they would play a greater role in ameliorating latitudinal gradients in temperature than in mangroves, where they are a secondary ecosystem engineer living under the mangrove canopy. On rocky shores, the enhancement of invertebrate abundance in oysters as compared to bare microhabitat decreased with latitude, as the maximum temperatures experienced by intertidal organisms diminished. By contrast, in mangrove forests, where the mangrove canopy resulted in maximum temperatures that were cooler and of greater humidity than on rocky shores, we found no evidence of latitudinal gradients of oyster effects on invertebrate abundance. Contrary to predictions, the magnitude by which oysters enhanced biodiversity was in many instances similar between mangroves and rocky shores. Whether habitat-context modifies patterns of spatial variation in the effects of ecosystem engineers on community structure will depend, in part, on the extent to which the environmental amelioration provided by an ecosystem engineer replicates that of other co-occurring ecosystem engineers.

  8. Nonlinear cross Gramians and gradient systems

    NARCIS (Netherlands)

    Ionescu, T. C.; Scherpen, J. M. A.

    2007-01-01

    We study the notion of cross Gramians for nonlinear gradient systems, using the characterization in terms of prolongation and gradient extension associated to the system. The cross Gramian is given for the variational system associated to the original nonlinear gradient system. We obtain

  9. 40 CFR 230.25 - Salinity gradients.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Salinity gradients. 230.25 Section 230... Physical and Chemical Characteristics of the Aquatic Ecosystem § 230.25 Salinity gradients. (a) Salinity... fresh or salt water may change existing salinity gradients. For example, partial blocking of...

  10. Effect of Regrown Graphite on the Growth of Large Gem Diamonds by Temperature Gradient Method

    Institute of Scientific and Technical Information of China (English)

    ZANG Chuan-Yi; JIA Xiao-Peng; MA Hong-An; TIAN Yu; XIAO Hong-Yu

    2005-01-01

    @@ Generally, when growing high-quality large gem diamond crystals by temperature gradient method under high pressure and high temperature, the crystal growth rate is only determined by the temperature gradient. However,we find that the seed crystal cannot completely absorb all the diffused carbon sources, when growing gem diamonds under a higher temperature gradient. Other influence factors appear, and the growth rate of growing diamonds is partly dependent on the crystalline form of superfluous unabsorbed carbon source, flaky regrown graphite or small diamond crystals nucleated spontaneously. The present form is determined by the growth temperature if the pressure isfixed. Different from spontaneous diamond nuclei, the appearance of regrown graphite in the diamondstable region can retard the growth rate of gem diamonds substantially, even if the temperature gradient keeps unchanged. On the other hand, the formation mechanism of metastable regrown graphite in the diamond-stable region is also explained.

  11. Stringy bounces and gradient instabilities

    CERN Document Server

    Giovannini, Massimo

    2017-01-01

    Bouncing solutions are obtained from a generally covariant action characterized by a potential which is a nonlocal functional of the dilaton field at two separated space-time points. Gradient instabilities are shown to arise in this context but they are argued to be nongeneric. After performing a gauge-invariant and frame-invariant derivation of the evolution equations of the fluctuations, a heuristic criterium for the avoidance of pathological instabilities is proposed and corroborated by a number of explicit examples that turn out to be compatible with a quasi-flat spectrum of curvature inhomogeneities for typical wavelengths larger than the Hubble radius.

  12. Temperature Gradient in Hall Thrusters

    Energy Technology Data Exchange (ETDEWEB)

    D. Staack; Y. Raitses; N.J. Fisch

    2003-11-24

    Plasma potentials and electron temperatures were deduced from emissive and cold floating probe measurements in a 2 kW Hall thruster, operated in the discharge voltage range of 200-400 V. An almost linear dependence of the electron temperature on the plasma potential was observed in the acceleration region of the thruster both inside and outside the thruster. This result calls into question whether secondary electron emission from the ceramic channel walls plays a significant role in electron energy balance. The proportionality factor between the axial electron temperature gradient and the electric field is significantly smaller than might be expected by models employing Ohmic heating of electrons.

  13. Synergistic childhood adversities and complex adult psychopathology.

    Science.gov (United States)

    Putnam, Karen T; Harris, William W; Putnam, Frank W

    2013-08-01

    Numerous studies find a cumulative effect of different types of childhood adversities on increasing risk for serious adult mental and medical outcomes. This study uses the National Comorbidity Survey-Replication sample to investigate the cumulative impact of 8 childhood adversities on complex adult psychopathology as indexed by (a) number of lifetime diagnoses according to the Diagnostic and Statistical Manual of Mental Disorders (4th ed., DSM-IV; American Psychiatric Association, 1994); (b) number of 4 DSM-IV disorder categories (mood, anxiety, impulse control, and substance abuse disorders); and (c) coexistence of internalizing and externalizing disorders. Seven of the 8 childhood adversities were significantly associated with complex adult psychopathology. Individuals with 4 or more childhood adversities had an odds ratio of 7.3, 95% confidence interval [4.7, 11.7] for 4 disorder categories. Additive and multiplicative synergistic effects increasing adult psychopathology were found for specific pairwise combinations of childhood adversities. Synergistic patterns differed by gender suggesting that women are more impacted by sexual abuse and men by economic hardship. The absence of childhood adversities was protective, in that it significantly decreased an individual's risk for subsequent adult mental illness. The results support the clinical impression that increased childhood adversity is associated with more complex adult psychopathology.

  14. On the thermal gradient in the Earth's deep interior

    Directory of Open Access Journals (Sweden)

    M. Tirone

    2015-09-01

    Full Text Available Temperature variations in large portions of the mantle are mainly controlled by the reversible and irreversible transformation of mechanical energy related to pressure and viscous forces into internal energy along with diffusion of heat and chemical reactions. The simplest approach to determine the temperature gradient is to assume that the dynamic process involved is adiabatic and reversible, which means that entropy remains constant in the system. However heat conduction and viscous dissipation during dynamic processes effectively create entropy. The adiabatic and non-adiabatic temperature variation under the influence of a constant or varying gravitational field are discussed in this study from the perspective of the Joule–Thomson (JT throttling system in relation to the transport equation for change of entropy. The JT model describes a dynamic irreversible process in which entropy in the system increases but enthalpy remains constant (at least in an equipotential gravitational field. A comparison is made between the thermal gradient from the JT model and the thermal gradient from two models, a mantle convection and a plume geodynamic model coupled with thermodynamics including a complete description of the entropy variation. The results show that the difference is relatively small and suggests that thermal structure of the asthenospheric mantle can be well approximated by an isenthalpic model when the formulation includes the effect of the gravitational field. For non-dynamic or parameterized mantle dynamic studies the JT formulation provides a better description of the thermal gradient than the classic isentropic formulation.

  15. Mechanisms of FGF gradient formation during embryogenesis.

    Science.gov (United States)

    Balasubramanian, Revathi; Zhang, Xin

    2016-05-01

    Fibroblast growth factors (FGFs) have long been attributed to influence morphogenesis in embryonic development. Signaling by FGF morphogen encodes positional identity of tissues by creating a concentration gradient over the developing embryo. Various mechanisms that influence the development of such gradient have been elucidated in the recent past. These mechanisms of FGF gradient formation present either as an extracellular control over FGF ligand diffusion or as a subcellular control of FGF propagation and signaling. In this review, we describe our current understanding of FGF as a morphogen, the extracellular control of FGF gradient formation by heparan sulfate proteoglycans (HSPGs) and mechanisms of intracellular regulation of FGF signaling that influence gradient formation.

  16. MILLIMETER-SCALE GENETIC GRADIENTS AND COMMUNITY-LEVEL MOLECULAR CONVERGENCE IN A HYPERSALINE MICROBIAL MAT

    Energy Technology Data Exchange (ETDEWEB)

    Fenner, Marsha W; Kunin, Victor; Raes, Jeroen; Harris, J. Kirk; Spear, John R.; Walker, Jeffrey J.; Ivanova, Natalia; Mering, Christian von; Bebout, Brad M.; Pace, Norman R.; Bork, Peer; Hugenholtz, Philip

    2008-04-30

    To investigate the extent of genetic stratification in structured microbial communities, we compared the metagenomes of 10 successive layers of a phylogenetically complex hypersaline mat from Guerrero Negro, Mexico. We found pronounced millimeter-scale genetic gradients that are consistent with the physicochemical profile of the mat. Despite these gradients, all layers displayed near identical and acid-shifted isoelectric point profiles due to a molecular convergence of amino acid usage indicating that hypersalinity enforces an overriding selective pressure on the mat community.

  17. [Muscle-related adverse effects of statins].

    Science.gov (United States)

    Pohjola-Sintonen, Sinikka; Julkunen, Heikki

    2014-01-01

    Adverse effects on muscles occur in approximately 5 to 10% of patients taking statins. Drug interactions, associated diseases, agedness, low body weight, high statin dose and hereditary factors increase the risk of adverse effects. In most cases the muscle effects are mild and disappear upon discontinuation of the medication. Rhabdomyolysis is a severe though rare complication that can possibly result in renal damage. A totally different muscle-related adverse effect, necrotizing myopathy, has recently been linked to the use of statins. Its characteristic feature is progression of the symptoms in spite of discontinuation of the statin.

  18. NIF optics phase gradient specfication

    Energy Technology Data Exchange (ETDEWEB)

    Williams, W.; Auerbach, J.; Hunt, J.; Lawson, L.; Manes, K.; Orth, C.; Sacks, R.; Trenholme, J.; Wegner, P.

    1997-05-02

    A root-mean-square (rms) phase gradient specification seems to allow a good connection between the NIP optics quality and focal spot requirements. Measurements on Beamlet optics individually, and as a chain, indicate they meet the assumptions necessary to use this specification, and that they have a typical rms phase gradient of {approximately}80 {angstrom}/cm. This may be sufficient for NIP to meet the proposed Stockpile Stewardship Management Program (SSMP) requirements of 80% of a high- power beam within a 200-250 micron diameter spot. Uncertainties include, especially, the scale length of the optics phase noise, the ability of the adaptive optic to correct against pump-induced distortions and optics noise, and the possibility of finding mitigation techniques against whole-beam self-focusing (e.g. a pre- correction optic). Further work is needed in these areas to better determine the NIF specifications. This memo is a written summary of a presentation on this topic given by W. Williams 24 April 1997 to NIP and LS&T personnel.

  19. Pressure ulcers

    National Research Council Canada - National Science Library

    Reddy, Madhuri

    2011-01-01

    Unrelieved pressure or friction of the skin, particularly over bony prominences, can lead to pressure ulcers in up to one third of people in hospitals or community care, and one fifth of nursing home residents...

  20. Pressure Sores

    Science.gov (United States)

    Pressure sores are areas of damaged skin caused by staying in one position for too long. They ... wheelchair, or are unable to change your position. Pressure sores can cause serious infections, some of which ...

  1. Urban-to-Rural Environmental Gradients in Houston Metropolitan Area

    Science.gov (United States)

    Gramann, J.; Schade, G. W.; Barta, C.

    2011-12-01

    The Houston Metropolitan area composes an extensive urban heat island and is the largest emitter of atmospheric pollutants in Texas, affecting regional air quality far beyond its borders. Three self-powered weather stations that include carbon dioxide (CO2) and ozone (O3) analyzers were set up to evaluate urban to rural environmental gradients in support of an NSF project investigating isoprene emissions and corresponding oak tree physiology. One station was installed at a participating high school in downtown Houston, one at a junior high school in The Woodlands, a forested suburban community about 40 km from downtown, and the third near the ranger station in Sam Houston National Forest (SHNF) 90 km from downtown. As a consequence of the sea breeze and typical summer wind patterns, these locations are often in line with the Houston urban pollution plume, allowing us to observe the development of ozone concentrations as winds move ozone precursors emitted in Houston toward the north. Here, we analyze the urban to rural gradients for the 2011 ozone season, a period of extreme high temperatures and exceptional drought. Night time (0:00-5:00 LT) temperatures indicated a 2°C gradient between downtown and SHNF; however, this gradient was not mirrored in daytime (10:00-18:00LT) temperatures, which were instead strongly influenced by the sea breeze typically arriving at the downtown station around 13:45 local time (LT), and in The Woodlands around 15:00 LT. Vapor pressure values also showed a gradient between downtown and SHNF with Houston being the more humid, as would be expected with its closer proximity to the Gulf of Mexico. O3 tended to be lowest in downtown for all time periods: night, morning (10:00-13:00 LT), and afternoon (13:00-18:00 LT). The largest O3 gradient, 9 ppb, occurred between downtown Houston and the Woodlands during the afternoon. CO2 gradients were detected as well with lowest daytime values at SHNF, and highest night time values in The Woodlands

  2. Elevated blood pressure in offspring of rats exposed to diverse chemicals during pregnancy

    Science.gov (United States)

    Adverse intrauterine environments are associated with increased risk of later disease, including cardiovascular disease and hypertension. As a potential bioindicator of such an adverse environment, we measured blood pressure (BP), renal nephron endowment, renal glucocorticoid rec...

  3. Pressure ulcers

    OpenAIRE

    Monfre, Jill M.

    2011-01-01

    Unrelieved pressure or friction of the skin, particularly over bony prominences, can lead to pressure ulcers, which affect up to one third of people in hospitals or community care, and one fifth of nursing home residents. Pressure ulcers are more likely in people with reduced mobility and poor skin condition, such as older people or those with vascular disease.

  4. [Cardiovascular pharmacotherapy. Risks and adverse effects].

    Science.gov (United States)

    Voigt, N; Heijman, J; Dobrev, D

    2014-03-01

    Adverse side effects of drugs are a significantly underestimated problem in modern medicine. In this review article, we summarize common adverse side effects of cardiovascular drugs. In particular, we highlight the factors promoting these adverse side effects in patients, including reduced hepatic or renal clearance in elderly patients that often requires dosage adjustment. Pharmacodynamic and pharmacokinetic interactions between drugs (e.g. through the cytochrome P450 system or P-glycoproteins) can modify the plasma concentration of many compounds, thereby also increasing the likelihood of unwanted side effects. The most prominent cardiac side effects include arrhythmias, e.g. atrioventricular (AV) block, drug-induced long-QT syndrome and torsade de pointes and altered inotropy. Non-cardiac side effects are subsequently discussed grouped by drug class. A better understanding of the risks and side effects of cardiovascular drugs is expected to reduce the mortality and morbidity associated with adverse side effects.

  5. [Allergies and adverse events associated with fluoroquinolones].

    Science.gov (United States)

    Muller, Y; Andrey, D; Emonet, S; Harr, T; Spoerl, D

    2015-04-08

    The prescription ot fluoroquinolones has been constantly increasing over the past decade. consequently, an increasing number of hyper-sensitivity reactions and adverse events have been reported. The aim of the review is to discuss the incidence of hypersensitivity reactions either IgE (immediate) or T cells mediated (delayed). We will make an overview ofthe diagnostic tools available to detect such hypersensitivity reactions. Finally, the specific adverse events associated with fluoroquinolones, including tendinopathy, chondrotoxicity, peripheral neuropathy or retinal detachment will be discussed.

  6. Adverse drug reactions in hospitalized Colombian children.

    Science.gov (United States)

    de Las Salas, Roxana; Díaz-Agudelo, Daniela; Burgos-Flórez, Francisco Javier; Vaca, Claudia; Serrano-Meriño, Dolores Vanessa

    2016-09-30

    The occurrence of adverse drug reactions is an important issue due to the lack of drug safety data in children. To describe the Adverse Drug Reactions in inpatient children under 6 years of age in two general pediatrics wards located in Barranquilla, Colombia. A prospective cohort study based on intensive pharmacovigilance was conducted during six months in order to monitor the emergence of Adverse Drug Reactions in inpatients children under 6 years of age with at least one medication prescribed. The study was conducted in two pediatric wards of two hospitals located in Barranquilla, Colombia. Naranjo´s Algorithm was used to evaluate imputability, the modified Hartwig and Siegel assessment scale to establish severity and the Schumock and Thornton criteria to determine preventability. Of a total of 772 monitored patients, 156 Adverse Drug Reactions were detected on 147 children. The cumulative incidence of Adverse Drug Reactions was 19.0% (147/772); the incidence density was 37.6 Adverse Drug Reactions per 1,000 patients-days (147/3,913). The frequency was higher in children under 2 years of age (12.7%). Emergence of Adverse Drug Reactions was higher in male patients (RR= 1.66; 95% CI= 1.22-2.22, p= 0.001) and in those who used systemic antibiotics (RR= 1.82; 95% CI= 1.17-2.82, p= 0.005). Adverse Drug Reactions are common among hospitalized children and represent an additional burden of morbidity and risk, particularly in those who used several medicines, including antibiotics.

  7. Development of paradoxical low-flow, low-gradient severe aortic stenosis

    DEFF Research Database (Denmark)

    Dahl, Jordi S; Eleid, Mackram F; Pislaru, Sorin V

    2015-01-01

    OBJECTIVE: Among patients with severe aortic stenosis (sAS) and preserved LVEF, those with low-flow, low-gradient sAS (LFLG-sAS) have an adverse prognosis. It has been proposed that LFLG-sAS represents an end-stage point of sAS, but longitudinal information has not been described. The aim...... was to determine whether LFLG-sAS represents an end-stage consequence of normal-flow, high-gradient sAS (NFHG-sAS) or a different entity. METHODS: From our transthoracic echocardiogram (TTE) database, we identified patients with sAS (aortic valve area

  8. Intrinsic parallel rotation drive by electromagnetic ion temperature gradient turbulence

    Science.gov (United States)

    Peng, Shuitao; Wang, Lu; Pan, Yuan

    2017-03-01

    The quasilinear intrinsic parallel flow drive including parallel residual stress, kinetic stress, cross Maxwell stress and parallel turbulent acceleration by electromagnetic ion temperature gradient (ITG) turbulence is calculated analytically using electromagnetic gyrokinetic theory. Both the kinetic stress and cross Maxwell stress also enter the mean parallel flow velocity equation via their divergence, as for the usual residual stress. The turbulent acceleration driven by ion pressure gradient along the total magnetic field (including equilibrium magnetic field and fluctuating radial magnetic field) cannot be written as a divergence of stress, and so should be treated as a local source/sink. All these terms can provide intrinsic parallel rotation drive. Electromagnetic effects reduce the non-resonant electrostatic stress force and even reverse it, but enhance the resonant stress force. Both the non-resonant and resonant turbulent acceleration terms are also enhanced by electromagnetic effects. The possible implications of our results for experimental observations are discussed.

  9. Intrinsic parallel rotation drive by electromagnetic ion temperature gradient turbulence

    CERN Document Server

    Peng, Shuitao; Pan, Yuan

    2016-01-01

    The quasilinear intrinsic parallel flow drive including parallel residual stress, kinetic stress, cross Maxwell stress and parallel turbulent acceleration by electromagnetic ion temperature gradient (ITG) turbulence is calculated analytically using electromagnetic gyrokinetic theory. Both the kinetic stress and cross Maxwell stress also enter the mean parallel flow velocity equation via their divergence, as for the usual residual stress. The turbulent acceleration driven by ion pressure gradient along the total magnetic field (including equilibrium magnetic field and fluctuating radial magnetic field) cannot be written as a divergence of stress, and so should be treated as a local source/sink. All these terms can provide intrinsic parallel rotation drive. Electromagnetic effects reduce the non-resonant electrostatic stress force and even reverse it, but enhance the resonant stress force. Both the non-resonant and resonant turbulent acceleration terms are also enhanced by electromagnetic effects. The possible ...

  10. Thermal-gradient-induced non-mass-dependent isotope fractionation.

    Science.gov (United States)

    Sun, Tao; Bao, Huiming

    2011-03-30

    Isotope fractionation resulting from gas diffusion along a thermal gradient has always been considered entirely mass-dependent. A previous report, however, showed that non-mass-dependent (17)O anomalies can be generated simply by subjecting O(2) gas in an enclosure to a thermal gradient. To explore the underlying mechanism for the anomalies, we tested the effect of gas pressure, duration of experiment, and geometry of the apparatus on the (17)O anomalies for O(2) as well as on the (33)S or (36)S anomalies for SF(6) gas. The results are consistent with our proposal that a previously ignored nuclear spin effect on gas diffusion coefficient may be largely responsible for generating the observed anomalies. This discovery provides clues to some of the puzzling non-mass-dependent isotope signatures encountered in experiments and in nature, including the triple oxygen or quadruple sulfur isotope heterogeneity in the solar system. Copyright © 2011 John Wiley & Sons, Ltd.

  11. Childhood adversities, adulthood life events and depression.

    Science.gov (United States)

    Korkeila, Jyrki; Vahtera, Jussi; Nabi, Hermann; Kivimäki, Mika; Korkeila, Katariina; Sumanen, Markku; Koskenvuo, Karoliina; Koskenvuo, Markku

    2010-12-01

    The role of childhood adversities in predicting adulthood depression has been suggested to be complex and in need of additional comprehensive studies. This investigation set out to examine whether increased exposure to life events (LEs) in adulthood mediates the association between childhood adversities and adulthood depression. This study is based on a random health survey sample from the Finnish working-aged population (n=16,877) with a follow-up of up to 7 years. Depression was identified by Beck Depression Inventory, records of antidepressant prescriptions and hospitalization due to depression obtained from national health registers. Childhood adversities were associated with an increased likelihood of experiencing a high number of LEs in adulthood and their perceived burdensomeness. The mean number of new LEs correlated significantly (Pchildhood adversities. Reporting childhood adversities was associated with a 1.28-2.70-fold increase in the odds of depression as indicated by BDI score, a 1.29-1.94-fold increase in the rate of antidepressant prescriptions and a 1.17-4.04-fold increase in the risk of hospitalization due to depression. Adjustment for new LE attenuated these associations by 21-24%, but did not render them insignificant. Increased exposure to adult negative life events proximal to adult depression may partially explain the association between childhood adversities and adult depression. Copyright © 2010 Elsevier B.V. All rights reserved.

  12. Leg intravenous pressure during head-up tilt.

    NARCIS (Netherlands)

    Groothuis, J.T.; Poelkens, F.; Wouters, C.W.; Kooijman, M.; Hopman, M.T.E.

    2008-01-01

    Leg vascular resistance is calculated as the arterial-venous pressure gradient divided by blood flow. During orthostatic challenges it is assumed that the hydrostatic pressure contributes equally to leg arterial, as well as to leg venous pressure. Because of venous valves, one may question whether,

  13. Wnt Secretion and Gradient Formation

    Directory of Open Access Journals (Sweden)

    Vladimir L. Katanaev

    2013-03-01

    Full Text Available Concentration gradients formed by the lipid-modified morphogens of the Wnt family are known for their pivotal roles during embryogenesis and adult tissue homeostasis. Wnt morphogens are also implicated in a variety of human diseases, especially cancer. Therefore, the signaling cascades triggered by Wnts have received considerable attention during recent decades. However, how Wnts are secreted and how concentration gradients are formed remains poorly understood. The use of model organisms such as Drosophila melanogaster has provided important advances in this area. For instance, we have previously shown that the lipid raft-associated reggie/flotillin proteins influence Wnt secretion and spreading in Drosophila. Our work supports the notion that producing cells secrete Wnt molecules in at least two pools: a poorly diffusible one and a reggie/flotillin-dependent highly diffusible pool which allows morphogen spreading over long distances away from its source of production. Here we revise the current views of Wnt secretion and spreading, and propose two models for the role of the reggie/flotillin proteins in these processes: (i reggies/flotillins regulate the basolateral endocytosis of the poorly diffusible, membrane-bound Wnt pool, which is then sorted and secreted to apical compartments for long-range diffusion, and (ii lipid rafts organized by reggies/flotillins serve as “dating points” where extracellular Wnt transiently interacts with lipoprotein receptors to allow its capture and further spreading via lipoprotein particles. We further discuss these processes in the context of human breast cancer. A better understanding of these phenomena may be relevant for identification of novel drug targets and therapeutic strategies.

  14. Childhood adversities and laboratory pain perception

    Directory of Open Access Journals (Sweden)

    Pieritz K

    2015-08-01

    Full Text Available Karoline Pieritz, Winfried Rief, Frank EuteneuerDivision of Clinical Psychology and Psychotherapy, Philipps University Marburg, Marburg, GermanyAbstract: Childhood adversity has frequently been related to a wide range of psychosomatic complaints in adulthood. The present study examined the relationship between different forms of childhood adversity and laboratory measures of pain. Heat pain tolerance and perceived heat pain intensity were measured in a community-based sample of 62 women (aged 20–64 years. Participants completed the Childhood Trauma Questionnaire (CTQ, which assesses five forms of childhood adversity: physical abuse, sexual abuse, emotional abuse, physical neglect, and emotional neglect. Somatic symptoms, depressive symptoms, and pain catastrophizing were assessed as potential mediators. Bivariate analyses indicated that emotional abuse but no other forms of childhood adversity were significantly related to decreased heat pain tolerance (r=-0.27; P<0.05. Accordingly, multiple regression analyses revealed that only emotional abuse was a significant predictor of heat pain tolerance (β=-0.62; P=0.034 when entering all CTQ subscales simultaneously. Although emotional abuse was also related to somatic symptoms, depressive symptoms, and pain catastrophizing, none of these variables mediated the relationship between childhood adversity and laboratory pain (P>0.1. No significant associations were found between any forms of childhood adversity and heat pain intensity. Our findings indicate that the severity of emotional childhood abuse is associated with decreased pain tolerance, an affective component of pain, but not with heat pain intensity, which has been described as a sensory component of pain.Keywords: childhood adversity, emotional abuse, pain tolerance, pain intensity, somatic symptoms

  15. Biomimetic Gradient Polymers with Enhanced Damping Capacities.

    Science.gov (United States)

    Wang, Dong; Zhang, Huan; Guo, Jing; Cheng, Beichen; Cao, Yuan; Lu, Shengjun; Zhao, Ning; Xu, Jian

    2016-04-01

    Designing gradient structures, mimicking biological materials, such as pummelo peels and tendon, is a promising strategy for developing advanced materials with superior energy damping capacities. Here a facile and effective approach for fabricating polymers with composition gradients at millimeter length scale is presented. The gradient thiol-ene polymers (TEPs) are created by the use of density difference of ternary thiol-ene-ene precursors and the subsequent photo-crosslinking via thiol-ene reaction. The compositional gradients are analyzed via differential scanning calorimeter (DSC), compressive modulus testing, atomic force microscopy (AFM) indentation, and swelling measurements. In contrast to homogeneous TEPs networks, the resultant gradient polymer shows a broader effective damping temperature range combining with good mechanical properties. The present result provides an effective route toward high damping materials by the fabrication of gradient structures.

  16. Strain gradient effects on cyclic plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Legarth, Brian Nyvang

    2010-01-01

    hardening materials it is quantified how dissipative and energetic gradient effects promote hardening above that of conventional predictions. Usually, increased hardening is attributed to energetic gradient effects, but here it is found that also dissipative gradient effects lead to additional hardening...... in the presence of conventional material hardening. Furthermore, it is shown that dissipative gradient effects can lead to both an increase and a decrease in the dissipation per load cycle depending on the magnitude of the dissipative length parameter, whereas energetic gradient effects lead to decreasing...... dissipation for increasing energetic length parameter. For dissipative gradient effects it is found that dissipation has a maximum value for some none zero value of the material length parameter, which depends on the magnitude of the deformation cycles....

  17. Mathematics of Experimentally Generated Chemoattractant Gradients.

    Science.gov (United States)

    Postma, Marten; van Haastert, Peter J M

    2016-01-01

    Many eukaryotic cells move in the direction of a chemical gradient. Several assays have been developed to measure this chemotactic response, but no complete mathematical models of the spatial and temporal gradients are available to describe the fundamental principles of chemotaxis. Here we provide analytical solutions for the gradients formed by release of chemoattractant from a point source by passive diffusion or forced flow (micropipettes) and gradients formed by laminar diffusion in a Zigmond chamber. The results show that gradients delivered with a micropipette are formed nearly instantaneously, are very steep close to the pipette, and have a steepness that is strongly dependent on the distance from the pipette. In contrast, gradients in a Zigmond chamber are formed more slowly, are nearly independent of the distance from the source, and resemble the temporal and spatial properties of the natural cAMP wave that Dictyostelium cells experience during cell aggregation.

  18. Rainfall seasonality and pest pressure as determinants of tropical tree species' distributions

    OpenAIRE

    2012-01-01

    Drought and pests are primary abiotic and biotic factors proposed as selective filters acting on species distributions along rainfall gradients in tropical forests and may contribute importantly to species distributional limits, performance, and diversity gradients. Recent research demonstrates linkages between species distributions along rainfall gradients and physiological drought tolerance; corresponding experimental examinations of the contribution of pest pressure to distributional limit...

  19. Hemodynamics in arterial reconstructions of the lower limb. II. Blood pressure.

    Science.gov (United States)

    Dedichen, H

    1976-01-01

    In order to demonstrate common pressure gradients and peripheral arterial pressure in ileo-femoro-popliteal arteries before and after reconstruction for atherosclerosis, intra-operative pressure measurements were performed on 204 patients. Before reconstruction, the pressure differential was 44.3 mmHg in femoro-popliteal arteries and 29.0 mmHg in the iliac arteries. This was reduced to 8.4 and 4.1 mmHg by the reconstructions. In patients with femoro-popliteal disease, the pressure gradient was higher when gangrena or rest pain were present than when claudication was the principal symptom. When the iliac arteries were mainly involved, no such difference was seen. Postoperative gradients were slightly higher in arteries subjected to primary failure than in vessels remaining patent. The blood flow increase from intra-arterial papaverine injections accentuated existing pressure gradients and frequently disclosed gradients not manifest at basal flow rates.

  20. Segmental blood pressure after total hip replacement

    DEFF Research Database (Denmark)

    Gebuhr, Peter Henrik; Soelberg, M; Henriksen, Jens Henrik

    1992-01-01

    drop was found in all pressures 1 week postoperatively. The decrease followed the systemic pressure and was restored to normal after 6 weeks. In a group of six patients with preoperatively decreased ankle pressure, a significant transient further decrease in the ankle-toe gradient pressure was found......Twenty-nine patients due to have a total hip replacement had their systemic systolic and segmental blood pressures measured prior to operation and 1 and 6 weeks postoperatively. No patients had signs of ischemia. The segmental blood pressure was measured at the ankle and at the toes. A significant...... on the operated side. None of the patients had symptoms from the lowered pressure. We conclude that in patients without signs of ischemia, the postoperative segmental pressure decrease is reversible and therefore not dangerous....

  1. Nonlinear cross Gramians and gradient systems

    OpenAIRE

    Ionescu, T. C.; Scherpen, J.M.A.

    2007-01-01

    We study the notion of cross Gramians for nonlinear gradient systems, using the characterization in terms of prolongation and gradient extension associated to the system. The cross Gramian is given for the variational system associated to the original nonlinear gradient system. We obtain linearization results that precisely correspond to the notion of a cross Gramian for symmetric linear systems. Furthermore, first steps towards relations with the singular value functions of the nonlinear Han...

  2. First trimester predictors of adverse pregnancy outcomes.

    Science.gov (United States)

    Brameld, Kate J; Dickinson, Jan E; O'Leary, Peter; Bower, Carol; Goldblatt, Jack; Hewitt, Beverley; Murch, Ashleigh; Stock, Rosanne

    2008-12-01

    To identify first trimester indicators of adverse pregnancy outcomes. Data were obtained from the statewide evaluation of first trimester screening for Down syndrome in Western Australia which included 22,695 pregnancies screened between August 2001 and October 2003. Screening data were linked with pregnancy outcome information from the Hospital Morbidity Database and the Birth Defects Registry. The odds ratios (OR) of adverse outcomes were analysed for combined risk incorporating maternal age, nuchal translucency (NT) and biochemical parameters and then separately for each parameter (pregnancy-associated plasma protein-A (PAPP-A), free beta human chorionic gonadotropin (beta-hCG) and NT). Risk assessments for first trimester combined screening are derived from maternal age, ultrasound measurement of fetal NT, maternal serum free beta-hCG and PAPP-A. Increased combined risk for Down syndrome was significantly (P beta-hCG and increased NT were less consistently associated with adverse outcomes and high levels of free beta-hCG showed limited use as an indicator. The detection rates for all outcomes other than Down syndrome were less than 40%. Biochemical indicators and NT that are measured during first trimester screening for Down syndrome show a number of associations with adverse outcomes, but do not show appropriate performance characteristics for screening tests. These data are consistent with the view that the individual components, specifically low PAPP-A levels alone, do not provide an effective screening tool for adverse pregnancy outcomes.

  3. The complement system and adverse pregnancy outcomes.

    Science.gov (United States)

    Regal, Jean F; Gilbert, Jeffrey S; Burwick, Richard M

    2015-09-01

    Adverse pregnancy outcomes significantly contribute to morbidity and mortality for mother and child, with lifelong health consequences for both. The innate and adaptive immune system must be regulated to insure survival of the fetal allograft, and the complement system is no exception. An intact complement system optimizes placental development and function and is essential to maintain host defense and fetal survival. Complement regulation is apparent at the placental interface from early pregnancy with some degree of complement activation occurring normally throughout gestation. However, a number of pregnancy complications including early pregnancy loss, fetal growth restriction, hypertensive disorders of pregnancy and preterm birth are associated with excessive or misdirected complement activation, and are more frequent in women with inherited or acquired complement system disorders or complement gene mutations. Clinical studies employing complement biomarkers in plasma and urine implicate dysregulated complement activation in components of each of the adverse pregnancy outcomes. In addition, mechanistic studies in rat and mouse models of adverse pregnancy outcomes address the complement pathways or activation products of importance and allow critical analysis of the pathophysiology. Targeted complement therapeutics are already in use to control adverse pregnancy outcomes in select situations. A clearer understanding of the role of the complement system in both normal pregnancy and complicated or failed pregnancy will allow a rational approach to future therapeutic strategies for manipulating complement with the goal of mitigating adverse pregnancy outcomes, preserving host defense, and improving long term outcomes for both mother and child.

  4. Environmental adversity and uncertainty favour cooperation

    Science.gov (United States)

    Andras, Peter; Lazarus, John; Roberts, Gilbert

    2007-01-01

    Background A major cornerstone of evolutionary biology theory is the explanation of the emergence of cooperation in communities of selfish individuals. There is an unexplained tendency in the plant and animal world – with examples from alpine plants, worms, fish, mole-rats, monkeys and humans – for cooperation to flourish where the environment is more adverse (harsher) or more unpredictable. Results Using mathematical arguments and computer simulations we show that in more adverse environments individuals perceive their resources to be more unpredictable, and that this unpredictability favours cooperation. First we show analytically that in a more adverse environment the individual experiences greater perceived uncertainty. Second we show through a simulation study that more perceived uncertainty implies higher level of cooperation in communities of selfish individuals. Conclusion This study captures the essential features of the natural examples: the positive impact of resource adversity or uncertainty on cooperation. These newly discovered connections between environmental adversity, uncertainty and cooperation help to explain the emergence and evolution of cooperation in animal and human societies. PMID:18053138

  5. Environmental adversity and uncertainty favour cooperation

    Directory of Open Access Journals (Sweden)

    Lazarus John

    2007-11-01

    Full Text Available Abstract Background A major cornerstone of evolutionary biology theory is the explanation of the emergence of cooperation in communities of selfish individuals. There is an unexplained tendency in the plant and animal world – with examples from alpine plants, worms, fish, mole-rats, monkeys and humans – for cooperation to flourish where the environment is more adverse (harsher or more unpredictable. Results Using mathematical arguments and computer simulations we show that in more adverse environments individuals perceive their resources to be more unpredictable, and that this unpredictability favours cooperation. First we show analytically that in a more adverse environment the individual experiences greater perceived uncertainty. Second we show through a simulation study that more perceived uncertainty implies higher level of cooperation in communities of selfish individuals. Conclusion This study captures the essential features of the natural examples: the positive impact of resource adversity or uncertainty on cooperation. These newly discovered connections between environmental adversity, uncertainty and cooperation help to explain the emergence and evolution of cooperation in animal and human societies.

  6. Putative adverse outcome pathways relevant to neurotoxicity

    Science.gov (United States)

    Bal-Price, Anna; Crofton, Kevin M.; Sachana, Magdalini; Shafer, Timothy J.; Behl, Mamta; Forsby, Anna; Hargreaves, Alan; Landesmann, Brigitte; Lein, Pamela J.; Louisse, Jochem; Monnet-Tschudi, Florianne; Paini, Alicia; Rolaki, Alexandra; Schrattenholz, André; Suñol, Cristina; van Thriel, Christoph; Whelan, Maurice; Fritsche, Ellen

    2016-01-01

    The Adverse Outcome Pathway (AOP) framework provides a template that facilitates understanding of complex biological systems and the pathways of toxicity that result in adverse outcomes (AOs). The AOP starts with an molecular initiating event (MIE) in which a chemical interacts with a biological target(s), followed by a sequential series of KEs, which are cellular, anatomical, and/or functional changes in biological processes, that ultimately result in an AO manifest in individual organisms and populations. It has been developed as a tool for a knowledge-based safety assessment that relies on understanding mechanisms of toxicity, rather than simply observing its adverse outcome. A large number of cellular and molecular processes are known to be crucial to proper development and function of the central (CNS) and peripheral nervous systems (PNS). However, there are relatively few examples of well-documented pathways that include causally linked MIEs and KEs that result in adverse outcomes in the CNS or PNS. As a first step in applying the AOP framework to adverse health outcomes associated with exposure to exogenous neurotoxic substances, the EU Reference Laboratory for Alternatives to Animal Testing (EURL ECVAM) organized a workshop (March 2013, Ispra, Italy) to identify potential AOPs relevant to neurotoxic and developmental neurotoxic outcomes. Although the AOPs outlined during the workshop are not fully described, they could serve as a basis for further, more detailed AOP development and evaluation that could be useful to support human health risk assessment in a variety of ways. PMID:25605028

  7. Wireless SAW Based Temperature Gradient Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Prime Photonics proposes design and development of a surface acoustic wave (SAW) based temperature gradient sensor for instrumentation of thermal protection systems...

  8. On lower order strain gradient plasticity theories

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Hutchinson, J. W.

    2003-01-01

    the tangent moduli governing increments of stress and strain. It is shown that the modification is far from benign from a mathematical standpoint, changing the qualitative character of solutions and leading to a new type of localization that is at odds with what is expected from a strain gradient theory......By way of numerical examples, this paper explores the nature of solutions to a class of strain gradient plasticity theories that employ conventional stresses, equilibrium equations and boundary conditions. Strain gradients come into play in these modified conventional theories only to alter....... The findings raise questions about the physical acceptability of this class of strain gradient theories....

  9. INFLUENCES OF SLOPE GRADIENT ON SOIL EROSION

    Institute of Scientific and Technical Information of China (English)

    刘青泉; 陈力; 李家春

    2001-01-01

    The main factors influencing soil erosion include the net rain excess, the water depth, the velocity, the shear stress of overland flows , and the erosion-resisting capacity of soil. The laws of these factors varying with the slope gradient were investigated by using the kinematic wave theory. Furthermore, the critical slope gradient of erosion was driven. The analysis shows that the critical slope gradient of soil erosion is dependent on grain size , soil bulk density , surface roughness, runoff length, net rain excess, and the friction coefficient of soil, etc. The critical slope gradient has been estimated theoretically with its range between 41. 5 °~ 50°.

  10. Night time blood pressure dip

    Institute of Scientific and Technical Information of China (English)

    Dennis; Bloomfield; Alex; Park

    2015-01-01

    The advent of ambulatory blood pressure monitoring permitted examination of blood pressures during sleep and recognition of the associated circadian fall in pressure during this period. The fall in pressure,called the "dip",is defined as the difference between daytime mean systolic pressure and nighttime mean systolic pressure expressed as a percentage of the day value. Ten percent to 20% is considered normal. Dips less than 10%,referred to as blunted or absent,have been considered as predicting an adverse cardiovascular event. This view and the broader concept that white coat hypertension itself is a forerunner of essential hypertension is disputable. This editorial questions whether mean arterial pressures over many hours accurately represent the systolic load,whether nighttime dipping varies from measure to measure or is a fixed phenomenon,whether the abrupt morning pressure rise is a risk factor or whether none of these issues are as important as the actual night time systolic blood pressure itself. The paper discusses the difference between medicated and nonmedicated white coat hypertensives in regard to the cardiovascular risk and suggests that further work is necessary to consider whether the quality and duration of sleep are important factors.

  11. Aldosterone deficiency adversely affects pregnancy outcome in mice.

    Science.gov (United States)

    Todkar, Abhijeet; Di Chiara, Marianna; Loffing-Cueni, Dominique; Bettoni, Carla; Mohaupt, Markus; Loffing, Johannes; Wagner, Carsten A

    2012-10-01

    Circulating aldosterone levels are increased in human pregnancy. Inadequately low aldosterone levels as present in preeclampsia, a life-threatening disease for both mother and child, are discussed to be involved in its pathogenesis or severity. Moreover, inactivating polymorphisms in the aldosterone synthase gene have been detected in preeclamptic women. Here, we used aldosterone synthase-deficient (AS(-/-)) mice to test whether the absence of aldosterone is sufficient to impair pregnancy or even to cause preeclampsia. AS(-/-) and AS(+/+) females were mated with AS(+/+) and AS(-/-) males, respectively, always generating AS(+/-) offspring. With maternal aldosterone deficiency in AS(-/-) mice, systolic blood pressure was low before and further reduced during pregnancy with no increase in proteinuria. Yet, AS(-/-) had smaller litters due to loss of fetuses as indicated by a high number of necrotic placentas with massive lymphocyte infiltrations at gestational day 18. Surviving fetuses and their placentas from AS(-/-) females were smaller. High-salt diet before and during pregnancy increased systolic blood pressure only before pregnancy in both genotypes and abolished the difference in blood pressure during late pregnancy. Litter size from AS(-/-) was slightly improved and the differences in placental and fetal weights between AS(+/+) and AS(-/-) mothers disappeared. Overall, an increased placental efficiency was observed in both groups paralleled by a normalization of elevated HIF1α levels in the AS(-/-) placentas. Our results demonstrate that aldosterone deficiency has profound adverse effects on placental function. High dietary salt intake improved placental function. In this animal model, aldosterone deficiency did not cause preeclampsia.

  12. Patch testing for adverse drug reactions.

    Science.gov (United States)

    Sekhon, Sahil; Nedorost, Susan T

    2017-01-01

    Adverse drug reactions result in a substantial number of hospital admissions and inpatient events. Diagnosis usually is made with clinical judgment and circumstantiality without diagnostic testing. Furthermore, even in situations where diagnostic testing is performed, no safe gold standard tests exist. Oral rechallenge is currently the gold standard but carries the risk of recrudescence of severe allergic symptoms. Other tests include skin prick tests, the lymphocyte transformation test, immunohistochemistry, and patch testing. This article provides a review of patch testing in cases of adverse drug reactions and presents new data on this topic.

  13. Adverse motor effects induced by antiepileptic drugs.

    Science.gov (United States)

    Zaccara, G; Cincotta, M; Borgheresi, A; Balestrieri, F

    2004-09-01

    Cognitive effects of anti-epileptic drugs (AEDs) have been already extensively reported. In contrast, motor disturbances, frequently induced by these drugs, have not received similar attention. We review subjective and objective adverse motor effects of traditional and new AEDs. We discuss the methodological issues caused by the heterogeneous sources of information on drug adverse effects (controlled clinical studies, open studies, and case reports). We describe specific disturbances (vestibulocerebellar, dyskinesias, parkinsonism, tics, myoclonus, and tremor) as the effects of different AEDs on distinct motor circuitries. Finally, we summarize the role of sophisticated technical studies which provide a valuable insight into the specific or subtle effects of AEDs on the central nervous system.

  14. Psychiatric Adverse Effects of Dermatological Drugs

    Directory of Open Access Journals (Sweden)

    Mine Özmen

    2010-07-01

    Full Text Available Dermatological drugs, mostly corticosteroids and isotretinoin, cause different psychiatric adverse effects. During steroid therapy, a wide range of psychiatric conditions, from minor clinical symptoms like insomnia and anxiety to serious psychiatric syndromes like psychosis and delirium might be seen. In medical literature, a causal connection is usually suggested between “isotretinoin”, which is used for treatment of acne vulgaris and depression and suicide attempts. However, there are no statistically significant double-blind randomized studies that support this connection. Clinicians must know patient’s psychiatric history before using any dermatological treatment known as causing psychiatric adverse effects, and psychiatric consultation should be established whenever necessary.

  15. Treatment of refractory low-pressure hydrocephalus with an active pumping negative-pressure shunt system.

    Science.gov (United States)

    Kalani, M Yashar S; Turner, Jay D; Nakaji, Peter

    2013-03-01

    Low-pressure hydrocephalus is a rare type of hydrocephalus characterized by negative intracranial pressure (ICP) and ventriculomegaly. Given the shortcomings of available methods to treat refractory low-pressure hydrocephalus, we set out to develop a new system for evacuation of cerebrospinal fluid (CSF) from the ventricular system where existing shunt systems do not produce the necessary gradient for CSF drainage. We retrospectively reviewed the charts of two patients with the diagnosis of negative-pressure hydrocephalus refractory to traditional treatments. We combined a traditional low-pressure, non-siphoning valve with a pumping chamber placed distal to the valve to create a system that could be actively pumped to remove excess CSF. Treatment of negative-pressure hydrocephalus requires the establishment of a lower ventricular drainage pressure than the drainage pressure in the subarachnoid space. In refractory cases, we propose the use of this active negative-pressure pumping system.

  16. Peer Pressure

    Science.gov (United States)

    ... who are unsure of themselves, new to the group, or inexperienced with peer pressure may also be more likely to give in. ... stand that makes you look uncool to your group. But these situations can be ... up to peer pressure, but it does take courage — yours: Listen to ...

  17. An adverse drug event manager facilitates spontaneous reporting of adverse drug reactions

    DEFF Research Database (Denmark)

    Vinther, Siri; Klarskov, Pia; Borgeskov, Hanne

    2017-01-01

    INTRODUCTION: Spontaneous reporting of adverse drug reactions (ADRs) is used for continuous risk-benefit evaluation of marketed pharmaceutical products and for signal detection. The Adverse Drug Event Manager (ADEM) is a service offered to clinicians employed at hospitals in the Capital Region...

  18. Newton's method in the context of gradients

    Directory of Open Access Journals (Sweden)

    John W. Neuberger

    2007-09-01

    Full Text Available This paper gives a common theoretical treatment for gradient and Newton type methods for general classes of problems. First, for Euler-Lagrange equations Newton's method is characterized as an (asymptotically optimal variable steepest descent method. Second, Sobolev gradient type minimization is developed for general problems using a continuous Newton method which takes into account a "boundary condition" operator.

  19. An Inexpensive Digital Gradient Controller for HPLC.

    Science.gov (United States)

    Brady, James E.; Carr, Peter W.

    1983-01-01

    Use of gradient elution techniques in high performance liquid chromatography (HPLC) is often essential for direct separation of complex mixtures. Since most commercial controllers have features that are of marginal value for instructional purposes, a low-cost controller capable of illustrating essential features of gradient elution was developed.…

  20. NUMERICAL METHODS IN MARINE ECOLOGY 2. GRADIENT ...

    African Journals Online (AJOL)

    GRADIENT ANALYSIS OF ROCKY SHORE SAMPL~S FROM FALSE BAY ... could be applied to marine studies and it showed quantitatively that the fauna varied with changes ... tigator and the computational facilities at his disposal. ... the major environmental gradients affecting distribution in a more complex situation with.

  1. An Inexpensive Digital Gradient Controller for HPLC.

    Science.gov (United States)

    Brady, James E.; Carr, Peter W.

    1983-01-01

    Use of gradient elution techniques in high performance liquid chromatography (HPLC) is often essential for direct separation of complex mixtures. Since most commercial controllers have features that are of marginal value for instructional purposes, a low-cost controller capable of illustrating essential features of gradient elution was developed.…

  2. Effects of pressure and temperature on the yield strength of tantalum and rhenium

    Science.gov (United States)

    Crow, Joseph Allan

    The effects of pressure and temperature on the yield strength of tantalum and the effects of pressure on the yield strength of rhenium were investigated using ruby fluorescence. A new Raman system with a motorized stage and near diffraction limit was built to map 2-dimensionally, the pressures inside of a diamond anvil cell. The 2-dimensional data is used to create contour maps and surface plots of the pressures and calculate the pressure gradients induced in the samples. Using the Birch-Murnaghan equation of state, the final sample thickness, and the pressure gradients, the yield strength as a function of temperature and pressure are calculated.

  3. Density Gradient Stabilization of Electron Temperature Gradient Driven Turbulence in a Spherical Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Y; Mazzucato, E; Guttenfelder, W; Bell, R E; Domier, C W; LeBlanc, B P; Lee, K C; Luhmann Jr, N C; Smith, D R

    2011-03-21

    In this letter we report the first clear experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k⊥ρs ≤10, are most stabilized by density gradient, and the stabilization is accompanied by about a factor of two decrease in the plasma effective thermal diffusivity.

  4. End-inspiratory rebreathing reduces the end-tidal to arterial PCO2 gradient in mechanically ventilated pigs

    NARCIS (Netherlands)

    Fierstra, Jorn; Machina, Matthew; Battisti-Charbonney, Anne; Duffin, James; Fisher, Joseph Arnold; Minkovich, Leonid

    Noninvasive monitoring of the arterial partial pressures of CO2 (PaCO2) of critically ill patients by measuring their end-tidal partial pressures of CO2 (PetCO(2)) would be of great clinical value. However, the gradient between PetCO(2) and PaCO2 (Pet-aCO(2)) in such patients typically varies over a

  5. End-inspiratory rebreathing reduces the end-tidal to arterial PCO2 gradient in mechanically ventilated pigs

    NARCIS (Netherlands)

    Fierstra, Jorn; Machina, Matthew; Battisti-Charbonney, Anne; Duffin, James; Fisher, Joseph Arnold; Minkovich, Leonid

    2011-01-01

    Noninvasive monitoring of the arterial partial pressures of CO2 (PaCO2) of critically ill patients by measuring their end-tidal partial pressures of CO2 (PetCO(2)) would be of great clinical value. However, the gradient between PetCO(2) and PaCO2 (Pet-aCO(2)) in such patients typically varies over a

  6. High order compact schemes for gradient approximation

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In this paper, we propose three gradient recovery schemes of higher order for the linear interpolation. The first one is a weighted averaging method based on the gradients of the linear interpolation on the uniform mesh, the second is a geometric averaging method constructed from the gradients of two cubic interpolation on macro element, and the last one is a local least square method on the nodal patch with cubic polynomials. We prove that these schemes can approximate the gradient of the exact solution on the symmetry points with fourth order. In particular, for the uniform mesh, we show that these three schemes are the same on the considered points. The last scheme is more robust in general meshes. Consequently, we obtain the superconvergence results of the recovered gradient by using the aforementioned results and the supercloseness between the finite element solution and the linear interpolation of the exact solution. Finally, we provide several numerical experiments to illustrate the theoretical results.

  7. Dual fuel gradients in uranium silicide plates

    Energy Technology Data Exchange (ETDEWEB)

    Pace, B.W. [Babock and Wilcox, Lynchburg, VA (United States)

    1997-08-01

    Babcock & Wilcox has been able to achieve dual gradient plates with good repeatability in small lots of U{sub 3}Si{sub 2} plates. Improvements in homogeneity and other processing parameters and techniques have allowed the development of contoured fuel within the cladding. The most difficult obstacles to overcome have been the ability to evaluate the bidirectional fuel loadings in comparison to the perfect loading model and the different methods of instilling the gradients in the early compact stage. The overriding conclusion is that to control the contour of the fuel, a known relationship between the compact, the frames and final core gradient must exist. Therefore, further development in the creation and control of dual gradients in fuel plates will involve arriving at a plausible gradient requirement and building the correct model between the compact configuration and the final contoured loading requirements.

  8. A new family of conjugate gradient methods

    Science.gov (United States)

    Shi, Zhen-Jun; Guo, Jinhua

    2009-02-01

    In this paper we develop a new class of conjugate gradient methods for unconstrained optimization problems. A new nonmonotone line search technique is proposed to guarantee the global convergence of these conjugate gradient methods under some mild conditions. In particular, Polak-Ribiére-Polyak and Liu-Storey conjugate gradient methods are special cases of the new class of conjugate gradient methods. By estimating the local Lipschitz constant of the derivative of objective functions, we can find an adequate step size and substantially decrease the function evaluations at each iteration. Numerical results show that these new conjugate gradient methods are effective in minimizing large-scale non-convex non-quadratic functions.

  9. Adverse skin reactions following intravitreal bevacizumab injection

    Science.gov (United States)

    Ameen, S; Entabi, M; Lee, N; Stavrakoglou, A

    2011-01-01

    The authors describe two separate cases of skin eruption following intravitreal bevacizumab injection with evidence to suggest that these were adverse drug reactions to bevacizumab. The authors also discuss how each case was treated and report on the final outcome. PMID:22715260

  10. Enduring psychobiological effects of childhood adversity.

    Science.gov (United States)

    Ehlert, Ulrike

    2013-09-01

    This mini-review refers to recent findings on psychobiological long-term consequences of childhood trauma and adverse living conditions. The continuum of trauma-provoked aftermath reaches from healthy adaptation with high resilience, to severe maladjustment with co-occurring psychiatric and physical pathologies in children, adolescents and adults. There is increasing evidence of a strong interconnectivity between genetic dispositions, epigenetic processes, stress-related hormonal systems and immune parameters in all forms of (mal)-adjustment to adverse living conditions. Unfavorable constellations of these dispositions and systems, such as low cortisol levels and elevated markers of inflammation in maltreated children, seem to promote the (co)-occurrence of psychiatric and physical pathologies such as posttraumatic stress disorder, obesity, or diabetes. Although findings from prospective study designs support a deepened understanding of causal relations between adverse living conditions, including traumatic experiences, during childhood and its psychobiological effects, so far, little is known about the temporal coincidence of stress-sensitive developmental stages during childhood and adolescence and trauma consequences. Taken together, childhood adversity is a severe risk factor for the onset of psychobiological (mal)-adjustment, which has to be explained under consideration of diverse physiological systems and developmental stages of childhood and adolescence. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. The Public Health Burden of Early Adversity

    Science.gov (United States)

    Schlueter, Lisa J.; Watamura, Sarah Enos

    2017-01-01

    Severe and chronic stress in early childhood has enormous physical and mental health costs across an individual's lifespan. Unfortunately, exposure to early life adversity is common, and costs accrue to individuals and society. This article highlights several promising approaches to buffer children from the negative health consequences associated…

  12. Adverse reactions to injectable soft tissue fillers

    DEFF Research Database (Denmark)

    Requena, Luis; Requena, Celia; Christensen, Lise

    2011-01-01

    In recent years, injections with filler agents are often used for wrinkle-treatment and soft tissue augmentation by dermatologists and plastic surgeons. Unfortunately, the ideal filler has not yet been discovered and all of them may induce adverse reactions. Quickly biodegradable or resorbable...

  13. The Public Health Burden of Early Adversity

    Science.gov (United States)

    Schlueter, Lisa J.; Watamura, Sarah Enos

    2017-01-01

    Severe and chronic stress in early childhood has enormous physical and mental health costs across an individual's lifespan. Unfortunately, exposure to early life adversity is common, and costs accrue to individuals and society. This article highlights several promising approaches to buffer children from the negative health consequences associated…

  14. Inverse adverse selection: the market for gems

    NARCIS (Netherlands)

    Dari-Mattiacci, G.; Onderstal, S.; Parisi, F.

    2011-01-01

    This paper studies markets plagued with asymmetric information on the quality of the goods traded. In Akerlof’s setting, sellers are better informed than buyers. In contrast, we examine cases where buyers are better informed than sellers. This creates an inverse adverse-selection problem: The market

  15. Inverse adverse selection: the market for gems

    NARCIS (Netherlands)

    Dari-Mattiacci, G.; Onderstal, S.; Parisi, F.

    2011-01-01

    This paper studies markets plagued with asymmetric information on the quality of traded goods. In Akerlof’s setting, sellers are better informed than buyers. In contrast, we examine cases where buyers are better informed than sellers. This creates an inverse adverse selection problem: The market ten

  16. Adverse effects of dental local anaesthesia.

    Science.gov (United States)

    Meechan, J G; Rood, J P

    1997-10-01

    This paper considers the adverse effects that a patient may suffer as a result of anticipating an injection of dental local anaesthetic. Although most of these are extremely rare (a testimony to good technique), the dental practitioner should be aware of the possibility of their occurrence and of ways to deal with them.

  17. Antiretroviral adverse drug reactions and their management

    African Journals Online (AJOL)

    as first-line therapy for treatment-naïve adults starting antiretroviral .... Her particular interests are in HIV pharmacology, adherence to ART and long-term retention in care. ... LIST OF ADVERSE EFFECTS OF THESE MEDICATIONS. TDF ABC 3TC. AZT. ddI D4T. Low risk .... central obesity, a buffalo hump, and enlarged.

  18. [Analysis of Spontaneously Reported Adverse Events].

    Science.gov (United States)

    Nakamura, Mitsuhiro

    2016-01-01

    Observational study is necessary for the evaluation of drug effectiveness in clinical practice. In recent years, the use of spontaneous reporting systems (SRS) for adverse drug reactions has increased and they have become an important resource for regulatory science. SRS, being the largest and most well-known databases worldwide, are one of the primary tools used for postmarketing surveillance and pharmacovigilance. To analyze SRS, the US Food and Drug Administration Adverse Event Reporting System (FAERS) and the Japanese Adverse Drug Event Report Database (JADER) are reviewed. Authorized pharmacovigilance algorithms were used for signal detection, including the reporting odds ratio. An SRS is a passive reporting database and is therefore subject to numerous sources of selection bias, including overreporting, underreporting, and a lack of a denominator. Despite the inherent limitations of spontaneous reporting, SRS databases are a rich resource and data mining index that provide powerful means of identifying potential associations between drugs and their adverse effects. Our results, which are based on the evaluation of SRS databases, provide essential knowledge that could improve our understanding of clinical issues.

  19. Revisiting fracture gradient: Comments on “A new approaching method to estimate fracture gradient by correcting Matthew–Kelly and Eaton's stress ratio”

    KAUST Repository

    Hakiki, Farizal

    2017-07-25

    A study performed by Marbun et al. [1] claimed that “A new methodology to predict fracture pressure from former calculations, Matthew–Kelly and Eaton are proposed.” Also, Marbun et al.\\'s paper stated that “A new value of Poisson\\'s and a stress ratio of the formation were generated and the accuracy of fracture gradient was improved.” We found those all statements are incorrect and some misleading concepts are revealed. An attempt to expose the method of fracture gradient determination from industry practice also appears to solidify that our arguments are acceptable to against improper Marbun et al.\\'s claims.

  20. Optimal management of acute nonrenal adverse reactions to iodine-based contrast media

    Directory of Open Access Journals (Sweden)

    Nielsen YW

    2013-06-01

    Full Text Available Yousef W Nielsen, Henrik S Thomsen Department of Radiology, Copenhagen University Hospital Herlev, Copenhagen, Denmark Abstract: Acute adverse reactions to iodine-based contrast media occur within 60 minutes of administration. The reactions range from mild (flushing, arm pain, nausea/vomiting, headache to moderate (bronchospasm, hypotension, and severe (cardiovascular collapse, laryngeal edema, convulsions, arrhythmias. Most acute adverse reactions occur in an unpredictable manner. Use of the older group of ionic iodine-based contrast agents increases the risk of acute adverse reactions. Other risk factors include previous reactions to contrast media, asthma, and allergic conditions. The exact pathophysiology of the acute adverse reactions is unknown, but some of the reactions are pseudoallergic mimicking type 1 allergic reactions. As antibodies against contrast media have not been consistently demonstrated, the reactions are, in most cases, not truly allergic in nature. Most of the severe and fatal adverse reactions occur within the first 20 minutes after injection. Thus, it is important that patients are observed in the radiology department during this period. The radiologist should be near the room where contrast media is administered, and be ready to treat any acute nonrenal adverse reaction. Appropriate drugs and resuscitation equipment should be in/near the room where the contrast media is administered. The important first-line management of acute adverse reactions includes the establishment of an adequate airway, oxygen supplementation by mask, intravenous fluid administration, and measurement of blood pressure and heart rate. When severe anaphylactoid reactions occur, adrenaline should be given intramuscularly. Only one concentration of adrenaline (1:1000–1 mg/mL should be available in the radiology department to avoid dosing errors in stressful acute settings. Resuscitation team specialists should be the only ones giving intravenous

  1. The pressure tensor in tangential equilibria

    Directory of Open Access Journals (Sweden)

    F. Mottez

    2004-09-01

    Full Text Available The tangential equilibria are characterized by a bulk plasma velocity and a magnetic field that are perpendicular to the gradient direction. Such equilibria can be spatially periodic (like waves, or they can separate two regions with asymptotic uniform conditions (like MHD tangential discontinuities. It is possible to compute the velocity moments of the particle distribution function. Even in very simple cases, the pressure tensor is not isotropic and not gyrotropic. The differences between a scalar pressure and the pressure tensor derived in the frame of the Maxwell-Vlasov theory are significant when the gradient scales are of the order of the Larmor radius; they concern mainly the ion pressure tensor.

  2. An Adverse Reaction in the Pediatric Sleep Laboratory

    Directory of Open Access Journals (Sweden)

    Diana Reppucci

    2016-01-01

    Full Text Available We present a case of a 15-month-old boy with Cornelia de Lange Syndrome (NIPBL gene mutation. On a PSG, central sleep apnea (central apnea-hypopnea index of 19/hour and nocturnal hypoventilation (transcutaneous CO2 > 50 mmHg for 53% of the night were found. A positive pressure initiation study was aborted because the patient developed a serious adverse reaction. The differential diagnosis included a skin fragility condition versus an allergic contact dermatitis to the interface; this could be from the povidone-iodine solution used to clean the NiPPV interface or from the plastic of the interface itself. A skin biopsy was performed which was normal. The reaction was likely secondary to an allergic contact dermatitis from the povidone-iodine solution used to clean the NiPPV interface. The patient is currently tolerating NiPPV.

  3. Adverse health effects of high-effort/low-reward conditions.

    Science.gov (United States)

    Siegrist, J

    1996-01-01

    In addition to the person-environment fit model (J. R. French, R. D. Caplan, & R. V. Harrison, 1982) and the demand-control model (R. A. Karasek & T. Theorell, 1990), a third theoretical concept is proposed to assess adverse health effects of stressful experience at work: the effort-reward imbalance model. The focus of this model is on reciprocity of exchange in occupational life where high-cost/low-gain conditions are considered particularly stressful. Variables measuring low reward in terms of low status control (e.g., lack of promotion prospects, job insecurity) in association with high extrinsic (e.g., work pressure) or intrinsic (personal coping pattern, e.g., high need for control) effort independently predict new cardiovascular events in a prospective study on blue-collar men. Furthermore, these variables partly explain prevalence of cardiovascular risk factors (hypertension, atherogenic lipids) in 2 independent studies. Studying adverse health effects of high-effort/low-reward conditions seems well justified, especially in view of recent developments of the labor market.

  4. Magnetic compressibility and ion-temperature-gradient-driven microinstabilities in magnetically confined plasmas

    CERN Document Server

    Zocco, A; Connor, J W

    2015-01-01

    The electromagnetic theory of the strongly driven ion-temperature-gradient (ITG) instability in magnetically confined toroidal plasmas is developed. Stabilizing and destabilizing effects are identified, and a critical $\\beta_{e}$ (the ratio of the electron to magnetic pressure) for stabilization of the toroidal branch of the mode is calculated for magnetic equilibria independent of the coordinate along the magnetic field. Its scaling is $\\beta_{e}\\sim L_{Te}/R,$ where $L_{Te}$ is the characteristic electron temperature gradient length, and $R$ the major radius of the torus. We conjecture that a fast particle population can cause a similar stabilization due to its contribution to the equilibrium pressure gradient. For sheared equilibria, the boundary of marginal stability of the electromagnetic correction to the electrostatic mode is also given. For a general magnetic equilibrium, we find a critical length (for electromagnetic stabilization) of the extent of the unfavourable curvature along the magnetic field....

  5. Characterization of peak capacity of microbore liquid chromatography columns using gradient kinetic plots.

    Science.gov (United States)

    Hetzel, Terence; Blaesing, Christina; Jaeger, Martin; Teutenberg, Thorsten; Schmidt, Torsten C

    2017-02-17

    The performance of micro-liquid chromatography columns with an inner diameter of 0.3mm was investigated on a dedicated micro-LC system for gradient elution. Core-shell as well as fully porous particle packed columns were compared on the basis of peak capacity and gradient kinetic plot limits. The results for peak capacity showed the superior performance of columns packed with sub-2μm fully porous particles compared to 3.0μm fully porous and 2.7μm core-shell particles within a range of different gradient time to column void time ratios. For ultra-fast chromatography a maximum peak capacity of 16 can be obtained using a 30s gradient for the sub-2μm fully porous particle packed column. A maximum peak capacity of 121 can be achieved using a 5min gradient. In addition, the influence of an alternative detector cell on the basis of optical waveguide technology and contributing less to system variance was investigated showing an increased peak capacity for all applied gradient time/column void time ratios. Finally, the influence of pressure was evaluated indicating increased peak capacity for maximum performance whereas a limited benefit for ultra-fast chromatography with gradient times below 30s was observed. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Characterization of vibration and acoustic noise in a gradient-coil insert.

    Science.gov (United States)

    Yao, G Z; Mechefske, C K; Rutt, B K

    2004-09-01

    High-speed switching of current in gradient coils within high magnetic field strength magnetic resonance imaging (MRI) scanners results in high acoustic sound pressure levels (SPL) in and around these machines. To characterize the vibration properties as well as the acoustic noise properties of the gradient coil, a finite-element (FE) model was developed using the dimensional design specifications of an available gradient-coil insert and the concentration of the copper windings in the coil. This FE model was then validated using experimentally collected vibration data. A computational acoustic noise model was then developed based on the validated FE model. The validation of the finite-element analysis results was done using experimental modal testing of the same gradient coil in a free-free state (no boundary constraints). Based on the validated FE model, boundary conditions (supports) were added to the model to simulate the operating condition when the gradient-coil insert is in place in an MRI machine. Vibration analysis results from the FE model were again validated through experimental vibration testing with the gradient-coil insert installed in the MRI scanner and excited using swept sinusoidal time waveforms. The simulation results from the computational acoustic noise model were also validated through experimental noise measurement from the gradient-coil insert in the MRI scanner using swept sinusoidal time waveform inputs. Comparisons show that the FE model predicts the vibration properties and the computational acoustic noise model predicts the noise characteristic properties extremely accurately.

  7. A closure for Lagrangian velocity gradient evolution in turbulence using recent deformation mapping of initially Gaussian fields

    CERN Document Server

    Johnson, Perry L

    2016-01-01

    The statistics of the velocity gradient tensor in turbulent flows are of both theoretical and practical importance. The Lagrangian view provides a privileged perspective for studying the dynamics of turbulence in general, and of the velocity gradient tensor in particular. Stochastic models for the Lagrangian evolution of velocity gradients in isotropic turbulence, with closure models for the pressure Hesssian and viscous Laplacian, have been shown to reproduce important features such as non-Gaussian probability distributions, skewness and vorticity strain-rate alignments. The Recent Fluid Deformation (RFD) closure introduced the idea of mapping an isotropic Lagrangian pressure Hessian as upstream initial condition using the fluid deformation tensor. Recent work on a Gaussian fields closure, however, has shown that even Gaussian isotropic velocity fields contain significant anisotropy for the conditional pressure Hessian tensor due to the inherent velocity-pressure couplings, and that assuming an isotropic pre...

  8. Dependence of Growing High-Quality Gem Diamonds on Growth Rates by Temperature Gradient Method

    Institute of Scientific and Technical Information of China (English)

    ZANG Chuan-Yi; JIA Xiao-Peng; REN Guo-Zhong; WANG Xian-Cheng

    2004-01-01

    @@ Using the temperature gradient method under high pressure and high temperature, we investigate the dependence of growing high-quality gem diamond crystals on the growth rates. It is found that the lower the growth rate of gem diamond crystals, the larger the temperature range of growing high-quality gem diamond crystals, and the easier the control of temperature.

  9. The Effects of Synthetic Cannabinoids on Alveolar-Arterial Oxygen Gradient

    Directory of Open Access Journals (Sweden)

    Egemen Kucuk

    2016-09-01

    Full Text Available Aim: Synthetic cannabinoids are chemicals that produce several marijuana-like effects in humans. Aim of this study is to investigate the effects of synthetic cannabinoids on to alveolar-arterial oxygen gradient. Material and Method: A total of 112 patients, who admitted directly to emergency clinic with synthetic cannabinoid usage, were determined between February 2014 and August 2014. Blood gases of 41 patients were determined as arterial blood gases on room air, and included in to study. Patients were evaluated according to age, sex, decade, partial pressure of arterial oxygen, partial pressure of arterial carbon dioxide, pH, bicarbonate, metabolic status, age consistent expected alveolar-arterial oxygen gradient and calculated alveolar-arterial oxygen gradient. Results: Synthetic cannabinoid using was higher in males, mean age of patients was 23.32±6.14 years. Number of patients in the third decade were significantly higher than the other decades. The calculated alveolar-arterial oxygen gradient value of patients was significantly higher than age consistent expected alveolar-arterial oxygen gradient value. Respiratory acidosis, was significantly higher than the other types of the metabolic disorders. The best cutoff point for calculated alveolar-arterial oxygen gradient was 12.70, with sensitivity of 90% and specifity of 85%. Area under curve was 0.70 for calculated alveolar-arterial oxygen gradient. Discussion: The value of alveolar-arterial oxygen gradient has been increased due to synthetic cannabinoid usage. This can be used as a supportive parameter in the diagnosis of synthetic cannabinoid usage.

  10. Nf=2+1 QCD thermodynamics from gradient flow

    CERN Document Server

    Taniguchi, Yusuke; Iwami, Ryo; Kanaya, Kazuyuki; Kitazawa, Masakiyo; Suzuki, Hiroshi; Umeda, Takashi; Wakabayashi, Naoki

    2016-01-01

    The energy-momentum tensor is a very important quantity in QCD thermodynamics. Its expectation value contains information of the pressure and the energy density as its diagonal part. Further properties like viscosity and specific heat can be extracted from its correlation functions. A non-perturbative evaluation on lattice has been successful only for the pressure and the energy density by making use of property of the thermodynamical free energy intelligently. Recently a new method was introduced to calculate the energy-momentum tensor on lattice using the gradient flow. The method has been applied to quenched QCD and proved to be successful. In this paper we apply the gradient flow method to the Nf=2+1 flavors QCD. We adopt a single but fine lattice spacing which corresponds to $a\\simeq0.07$ fm. A wide range of temperature is covered from $T\\simeq174$ MeV to $697$ MeV. The $u$ and $d$ quarks are rather heavy $m_\\pi/m_\\rho\\simeq0.63$ but the $s$ quark is set to almost its physical mass $m_{\\eta_{ss}}/m_\\phi\\...

  11. CSF concentration gradients of monoamine metabolites in patients with hydrocephalus.

    Science.gov (United States)

    Malm, J; Kristensen, B; Ekstedt, J; Wester, P

    1994-09-01

    Concentration gradients of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and 3-methoxy-4-hydroxyphenylglycol (MHPG), were assessed in 762 successive CSF fractions (2 ml lumbar CSF) from 15 patients with the adult hydrocephalus syndrome (AHS) and 11 patients with hydrocephalus of other causes (mixed group). A mean volume of 49.6 (SD 11.8) ml CSF was removed in the AHS group and 56.4 (10.2) ml in the mixed group. The CSF was collected with a specially designed carousel fraction collector and the corresponding CSF dynamics were continuously registered by a constant pressure CSF infusion method. Pronounced gradients in CSF HVA and CSF 5-HIAA were seen in both patient groups in the first 25 ml of CSF removed. The concentration curves levelled off, despite the removal of larger amounts of CSF and stabilised at about twice the initial concentrations. This phenomenon has not been described before. Concentrations of HVA and 5-HIAA in the first CSF fraction correlated strongly with concentrations in fractions up to about 40 ml. A positive correlation between the first fraction of CSF HVA and CSF 5-HIAA concentrations and CSF outflow conductance was found in the AHS group. There was no gradient in MHPG. It is suggested that the rostrocaudal gradients in CSF HVA and 5-HIAA may be explained by a downward flow of CSF along the spinal cord with absorption of metabolites occurring during passage. Mixing of CSF from different CSF compartments, extraventricular production sites of CSF, clearance of metabolites to venous blood or extracellular fluid, and CSF outflow conductance are probably important determinants of the plateau phase in patients with hydrocephalus. It is concluded that lumbar CSF does not exclusively reflect the concentrations of HVA, 5-HIAA, or MHPG in the ventricles. It should be noted that these results obtained in patients with hydrocephalus may not be applicable to other groups of patients or normal subjects.

  12. Pressure Sores

    Science.gov (United States)

    ... injury. Some chronic diseases, such as diabetes and hardening of the arteries, make it hard for pressure ... Use a mild soap and warm (not hot) water. Apply moisturizers so your skin doesn’t get ...

  13. Pressure sensor

    Science.gov (United States)

    Mee, David K.; Ripley, Edward B.; Nienstedt, Zachary C.; Nienstedt, Alex W.; Howell, Jr., Layton N.

    2015-09-29

    Disclosed is a passive, in-situ pressure sensor. The sensor includes a sensing element having a ferromagnetic metal and a tension inducing mechanism coupled to the ferromagnetic metal. The tension inducing mechanism is operable to change a tensile stress upon the ferromagnetic metal based on a change in pressure in the sensing element. Changes in pressure are detected based on changes in the magnetic switching characteristics of the ferromagnetic metal when subjected to an alternating magnetic field caused by the change in the tensile stress. The sensing element is embeddable in a closed system for detecting pressure changes without the need for any penetrations of the system for power or data acquisition by detecting changes in the magnetic switching characteristics of the ferromagnetic metal caused by the tensile stress.

  14. Intracellular chemical gradients: morphing principle in bacteria

    Directory of Open Access Journals (Sweden)

    Endres Robert G

    2012-09-01

    Full Text Available Abstract Advances in computational biology allow systematic investigations to ascertain whether internal chemical gradients can be maintained in bacteria – an open question at the resolution limit of fluorescence microscopy. While it was previously believed that the small bacterial cell size and fast diffusion in the cytoplasm effectively remove any such gradient, a new computational study published in BMC Biophysics supports the emerging view that gradients can exist. The study arose from the recent observation that phosphorylated CtrA forms a gradient prior to cell division in Caulobacter crescentus, a bacterium known for its complicated cell cycle. Tropini et al. (2012 postulate that such gradients can provide an internal chemical compass, directing protein localization, cell division and cell development. More specifically, they describe biochemical and physical constraints on the formation of such gradients and explore a number of existing bacterial cell morphologies. These chemical gradients may limit in vitro analyses, and may ensure timing control and robustness to fluctuations during critical stages in cell development.

  15. Satellite gravity gradient grids for geophysics.

    Science.gov (United States)

    Bouman, Johannes; Ebbing, Jörg; Fuchs, Martin; Sebera, Josef; Lieb, Verena; Szwillus, Wolfgang; Haagmans, Roger; Novak, Pavel

    2016-02-11

    The Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite aimed at determining the Earth's mean gravity field. GOCE delivered gravity gradients containing directional information, which are complicated to use because of their error characteristics and because they are given in a rotating instrument frame indirectly related to the Earth. We compute gravity gradients in grids at 225 km and 255 km altitude above the reference ellipsoid corresponding to the GOCE nominal and lower orbit phases respectively, and find that the grids may contain additional high-frequency content compared with GOCE-based global models. We discuss the gradient sensitivity for crustal depth slices using a 3D lithospheric model of the North-East Atlantic region, which shows that the depth sensitivity differs from gradient to gradient. In addition, the relative signal power for the individual gradient component changes comparing the 225 km and 255 km grids, implying that using all components at different heights reduces parameter uncertainties in geophysical modelling. Furthermore, since gravity gradients contain complementary information to gravity, we foresee the use of the grids in a wide range of applications from lithospheric modelling to studies on dynamic topography, and glacial isostatic adjustment, to bedrock geometry determination under ice sheets.

  16. A Resistivity Gradient Piezoelectric FGM Actuator

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A resistivity gradient actuator based on lead zirconate titanate ceramics was successfully developed and the bending deflections up to 140 μm were obtained. The actuator material was a matrix of PZT ceramic into which smooth gradient of piezoelectric activity was introduced. The application of an electric field then causes the actuator to bend due to differential strains induced by the piezoelectric effect. The resistivity gradient of the actuator was achieved by doping PZT with suitable donor and acceptor dopants. PZT powder was modified and synthesized by using two stage powder fabrication method. The actuator was fabricated by uniaxial pressing followed by isostatic pressing with two layers of different resistivities.

  17. GRADIENT ENERGY DETECTION OF LSB STEGANOGRAPHY

    Institute of Scientific and Technical Information of China (English)

    Li Zhi; Sui Aifen; Niu Xinxin; Yang Yixian

    2005-01-01

    The spatial Least Significant Bit (LSB) steganography results in the alteration of the smooth characteristics between adjoining pixels of the raw image. The relation between the length of embedded message and the gradient energy is theoretically analyzed, and then a steganalysis and detection method, named Gradient Energy-Flipping Rate (GEFR) detection is proposed. Based on the analysis of the variation of the gradient energy, which results from the LSB steganography in color and grayscale image, the secret message embedded in the target image is detected, and the length of the embedded message is estimated. The method is proved effective and accurate by simulation (detection rate reaches 0.01bit per pixel).

  18. Colour and stellar population gradients in galaxies

    CERN Document Server

    Tortora, C; Cardone, V F; Capaccioli, M; Jetzer, P; Molinaro, R

    2010-01-01

    We discuss the colour, age and metallicity gradients in a wide sample of local SDSS early- and late-type galaxies. From the fitting of stellar population models we find that metallicity is the main driver of colour gradients and the age in the central regions is a dominant parameter which rules the scatter in both metallicity and age gradients. We find a consistency with independent observations and a set of simulations. From the comparison with simulations and theoretical considerations we are able to depict a general picture of a formation scenario.

  19. Strain gradient effects in surface roughening

    DEFF Research Database (Denmark)

    Borg, Ulrik; Fleck, N.A.

    2007-01-01

    A thin aluminium sheet comprising of large polycrystals is pulled in uniaxial tension and the resulting surface profile is measured in a scanning electron microscope. The surface profile near the grain boundaries reveals a local deformation pattern of width of a few micrometres and is strong...... evidence for strain gradient effects. Numerical analyses of a bicrystal undergoing in-plane tensile deformation are also studied using a strain gradient crystal plasticity theory and also by using a strain gradient plasticity theory for an isotropic solid. Both theories include an internal material length...

  20. Speciation gradients and the distribution of biodiversity.

    Science.gov (United States)

    Schluter, Dolph; Pennell, Matthew W

    2017-05-31

    Global patterns of biodiversity are influenced by spatial and environmental variations in the rate at which new species form. We relate variations in speciation rates to six key patterns of biodiversity worldwide, including the species-area relationship, latitudinal gradients in species and genetic diversity, and between-habitat differences in species richness. Although they sometimes mirror biodiversity patterns, recent rates of speciation, at the tip of the tree of life, are often highest where species richness is low. Speciation gradients therefore shape, but are also shaped by, biodiversity gradients and are often more useful for predicting future patterns of biodiversity than for interpreting the past.

  1. Colour and stellar population gradients in galaxies

    Science.gov (United States)

    Tortora, C.; Napolitano, N. R.; Cardone, V. F.; Capaccioli, M.; Jetzer, P.; Molinaro, R.

    We discuss the colour, age and metallicity gradients in a wide sample of local SDSS early- and late-type galaxies. From the fitting of stellar population models we find that metallicity is the main driver of colour gradients and the age in the central regions is a dominant parameter which rules the scatter in both metallicity and age gradients. We find a consistency with independent observations and a set of simulations. From the comparison with simulations and theoretical considerations we are able to depict a general picture of a formation scenario.

  2. Droplet Motion on a Shape Gradient Surface.

    Science.gov (United States)

    Zheng, Yanfen; Cheng, Jiang; Zhou, Cailong; Xing, Haiting; Wen, Xiufang; Pi, Pihui; Xu, Shouping

    2017-05-02

    We demonstrate a facile method to induce water droplet motion on an wedge-shaped superhydrophobic copper surface combining with a poly(dimethylsiloxane) (PDMS) oil layer on it. The unbalanced interfacial tension from the shape gradient offers the actuating force. The superhydrophobicity critically eliminates the droplet contact line pinning and the slippery PDMS oil layer lubricates the droplet motion, which makes the droplet move easily. The maximum velocity and furthest position of droplet motion were recorded and found to be influenced by the gradient angle. The mechanism of droplet motion on the shape gradient surface is systematically discussed, and the theoretical model analysis is well matched with the experimental results.

  3. Snake antivenoms: adverse reactions and production technology

    Directory of Open Access Journals (Sweden)

    VM Morais

    2009-01-01

    Full Text Available Antivenoms have been widely used for more than a century for treating snakebites and other accidents with poisonous animals. Despite their efficacy, the use of heterologous antivenoms involves the possibility of adverse reactions due to activation of the immune system. In this paper, alternatives for antivenom production already in use were evaluated in light of their ability to minimize the occurrence of adverse reactions. These effects were classified according to their molecular mechanism as: anaphylactic reactions mediated by IgE, anaphylactoid reactions caused by complement system activation, and pyrogenic reactions produced mainly by the presence of endotoxins in the final product. In the future, antivenoms may be replaced by humanized antibodies, specific neutralizing compounds or vaccination. Meanwhile, improvements in antivenom quality will be focused on the obtainment of a more purified and specific product in compliance with good manufacturing practices and at an affordable cost.

  4. Adverse selection model regarding tobacco consumption

    Directory of Open Access Journals (Sweden)

    Dumitru MARIN

    2006-01-01

    Full Text Available The impact of introducing a tax on tobacco consumption can be studied trough an adverse selection model. The objective of the model presented in the following is to characterize the optimal contractual relationship between the governmental authorities and the two type employees: smokers and non-smokers, taking into account that the consumers’ decision to smoke or not represents an element of risk and uncertainty. Two scenarios are run using the General Algebraic Modeling Systems software: one without taxes set on tobacco consumption and another one with taxes set on tobacco consumption, based on an adverse selection model described previously. The results of the two scenarios are compared in the end of the paper: the wage earnings levels and the social welfare in case of a smoking agent and in case of a non-smoking agent.

  5. Early Life Adversity, Genomic Plasticity, and Psychopathology

    Science.gov (United States)

    Turecki, Gustavo; Ota, Vanessa Kiyomi; Belangero, Sintia Iole; Jackowski, Andrea; Kaufman, Joan

    2017-01-01

    Child maltreatment is associated with increased risk for psychiatric disorders, and a range of health problems later in life. The aim of this paper is to review emerging data on the role of epigenetic mechanisms in the etiology of stress-related psychiatric disorders with a focus on future avenues of investigation. Epigenetic processes are described, key findings in the field presented, clinical implications of the research discussed, methodological issues, and future avenues of research considered. Research suggests that adverse early experiences can lead to changes in gene expression through epigenetic mechanisms that can alter stress reactivity, brain function, and behavior. While these changes are frequently long lasting, they can be reversed through pharmacological and environmental manipulations. The complexity of the epigenome is not fully understood. Future studies should investigate epigenetic marks other than methylcytosine, and assess the efficacy of interventions to reverse epigenetic processes associated with early-life adversity. PMID:26361201

  6. Adverse consequences of lysergic acid diethylamide.

    Science.gov (United States)

    Abraham, H D; Aldridge, A M

    1993-10-01

    The continued endemic use of hallucinogenic drugs, and of LSD in particular, raises concern regarding their short and long term adverse consequences. The epidemiology of LSD abuse is reviewed suggesting an increase in LSD use among the young as the prevalence rates for other substances continues to fall. Evidence supports the association of LSD use with panic reactions, prolonged schizoaffective psychoses and post-hallucinogen perceptual disorder, the latter being present continually for as long as 5 years. Evidence does not support claims of genetic disorders arising from hallucinogens. In light of the foregoing, current data confirm earlier findings of long lasting psychopathology arising in vulnerable individuals from the use of LSD. A hypothetical long term molecular mechanism of adverse effects is proposed.

  7. Ruby fluorescence pressure scale: Revisited

    Science.gov (United States)

    Liu, Lei; Bi, Yan; Xu, Ji-An

    2013-05-01

    Effect of non-hydrostatic stress on X-ray diffraction in a diamond anvil cell (DAC) is studied. The pressure gradient in the sample chamber leads to the broadening of the diffraction peaks, which increase with the hkl index of the crystal. It is found that the difference between the determined d-spacing compressive ratio d/d0 and the real d-spacing compressive ratio dr/d0 is determined by the yield stress of the pressure transmitting media (if used) and the shear modulus of the sample. On the basis of the corrected experiment data of Mao et al. (MXB86), which was used to calibrate the most widely used ruby fluorescence scale, a new relationship of ruby fluorescence pressure scale is corrected, i.e., P = (1904/9.827)[(1 + Δλ/λ0)9.827-1].

  8. The lesser of two adverse reactions.

    Science.gov (United States)

    Chakraborti, Chayan; Egan, John

    2010-01-01

    Fundamental to complex systems are interconnected processes involved in providing high-quality patient care. A case study and a root cause analysis (RCA) illustrate a patient safety effort with unintended consequences. A 38-year-old woman presented to the hospital for odynophagia and vomiting. The patient developed Mobitz type 2, second-degree heart block temporally associated with the administration of intravenous ondansetron. RESPONSE TO THE EVENT: An Ishikawa, or fishbone, diagram conducted to enumerate potential contributing factors indicated that a key factor appeared to be an institutional restriction against using intravenous (i.v.) promethazine, which resulted in ondansetron being the only readily available i.v. anti-emetic on formulary. The anesthesia department requested that i.v. promethazine be removed from all operating and recovery room automated medication dispensing machines. The pharmacy department, given the realization that individual departments were taking independent action regarding promethazine, discussed the matter with the medical director, who issued a memo banning the use of i.v. promethazine. An institutional ban on i.v. anti-emetics such as promethazine may have resulted in an increase in the use of ondansetron and contributed to this adverse reaction. The reason to restrict promethazine is not well reported in the literature. In limiting the use of promethazine for patient safety concerns, the inadvertent increase in adverse reactions of the alternative medication, ondansetron, may have been overlooked. The resultant RCA underscores the need for careful cataloguing of adverse medication effects. Stakeholders should anticipate as many "downstream effects" of quality and patient safety improvements as possible. Comprehensive reporting of adverse medication effects will augment the emerging science of patient safety.

  9. The Role of Leasing under Adverse Selection

    OpenAIRE

    Igal Hendel; Alessandro Lizzeri

    2002-01-01

    Leasing contracts specify a rental rate and an option price at which the used good can be bought at the termination of the lease. This option price cannot be controlled when the car is sold. We show that in a world with symmetric information this additional control variable is useless; equilibrium allocations and profits to lessors are unaffected by the option prices. In contrast, under adverse selection, leasing contracts affect equilibrium allocations in a way that matches observed behavior...

  10. Adverse drug reactions in West Africa

    OpenAIRE

    Cliff-Eribo, Kennedy O.

    2016-01-01

    Adverse drug reaction (ADR) reports of countries varies due to differences in the prevalence of diseases and hence the types of drugs used. ADRs are a major health and economic burden worldwide. National health authorities monitor the safety of medicines to protect consumers from the hazards of drugs. ADR databases are also maintained from where reports are regularly evaluated to detect signals of new ADRs and determine the increase of those already known. A review of paediatric and genera...

  11. Major adverse cardiac events during endurance sports.

    Science.gov (United States)

    Belonje, Anne; Nangrahary, Mary; de Swart, Hans; Umans, Victor

    2007-03-15

    Major adverse cardiac events in endurance exercise are usually due to underlying and unsuspected heart disease. The investigators present an analysis of major adverse cardiac events that occurred during 2 consecutive annual long distance races (a 36-km beach cycling race and a 21-km half marathon) over the past 5 years. All patients with events were transported to the hospital. Most of the 62,862 participants were men (77%; mean age 40 years). Of these, 4 men (3 runners, 1 cyclist; mean age 48 years) collapsed during (n = 2) or shortly after the races, rendering a prevalence of 0.006%. Two patients collapsed after developing chest pain, 1 of whom needed resuscitation at the event site, which was successful. These patients had acute myocardial infarctions and underwent primary angioplasty. The third patient was resuscitated at the site but did not have coronary disease or inducible ventricular tachycardia or ventricular fibrillation and collapsed presumably because of catecholamine-induced ventricular fibrillation. The fourth patient experienced heat stroke and had elevated creatine kinase-MB and troponins in the absence of electrocardiographic changes. In conclusion, the risk for major adverse cardiac events during endurance sports in well-trained athletes is very low.

  12. Tetany: possible adverse effect of bevacizumab.

    Science.gov (United States)

    Anwikar, S R; Bandekar, M S; Patel, T K; Patel, P B; Kshirsagar, N A

    2011-01-01

    Bevacizumab a recombinant humanized monoclonal antibody was approved in 2004 by US FDA for metastatic colorectal cancer. It is reported to cause potentially serious toxicities including severe hypertension, proteinuria, and congestive heart failure. To correlate adverse event tetany with the use of bevacizumab. World Health Organization's Uppsala Monitoring Centre, Sweden, for reporting of adverse drug reactions from all over the world, identified 7 cases with tetany-related symptoms to bevacizumab from four different countries. These 7 patients reported to UMC database developed adverse events described as musculoskeletal stiffness (1), muscle spasm (1), muscle cramps (1), lock jaw or jaw stiffness (4), and hypertonia (1), with hypocalcaemia. After detailed study of the possible mechanism of actions of bevacizumab and factors causing tetany, it is proposed that there is a possibility of tetany by bevacizumab, which may occur by interfering with calcium metabolism. Resorption of bone through osteoclasts by affecting VEGF may interfere with calcium metabolism. Another possibility of tetany may be due to associated hypomagnesaemia, hypokalemia, or hyponatremia. Tetany should be considered as a one of the signs. Patient on bevacizumab should carefully watch for tetany-related symptoms and calcium and magnesium levels for their safety.

  13. Managing adverse effects of hormonal contraceptives.

    Science.gov (United States)

    Grossman Barr, Nancy

    2010-12-15

    Adverse effects of hormonal contraceptives usually diminish with continued use of the same method. Often, physi- cians only need to reassure patients that these symptoms will likely resolve within three to five months. Long-acting injectable depot medroxyprogesterone acetate is the only hormonal contraceptive that is consistently associated with weight gain; other hormonal methods are unlikely to increase weight independent of lifestyle choices. Switching com- bined oral contraceptives is not effective in treating headaches, nor is the use of multivitamins or diuretics. There are no significant differences among various combined oral contraceptives in terms of breast tenderness, mood changes, and nausea. Breakthrough bleeding is common in the first months of combined oral contraceptive use. If significant abnormal bleeding persists beyond three months, other methods can be considered, and the patient may need to be evaluated for other causes. Studies of adverse sexual effects in women using hormonal contraceptives are inconsistent, and the pharmacologic basis for these symptoms is unclear. If acne develops or worsens with progestin-only contra- ceptives, the patient should be switched to a combination method if she is medically eligible. There is insufficient evidence of any effect of hormonal contraceptives on breast milk quantity and quality. Patient education should be encouraged to decrease the chance of unanticipated adverse effects. Women can also be assessed for medical eligibility before and during the use of hormonal contraceptives.

  14. Metabolic and adverse effects of diuretics.

    Science.gov (United States)

    Wilcox, C S

    1999-11-01

    Diuretics are among the most frequently prescribed drugs. They enjoy a very high clinical reputation for safety and efficacy. However, more than 3 decades of clinical investigation have disclosed a number of abnormalities in fluid electrolyte handling, metabolism, and other adverse effects that can complicate therapy with diuretic drugs. Some of these complications are a direct extension of the wanted action of the drug. These include extracellular fluid volume depletion, associated orthostatic hypotension, and prerenal azotemia. Others are not a direct action of the diuretic, but can be explained as an intranephronal compensation to the diuretic action. These include hypokalemia, in part to increased potassium secretion secondary to the enhanced tubular fluid flow and aldosterone secretion induced by diuretic administration. Metabolic abnormalities are usually mild. Hyperglycemia and carbohydrate intolerance have been related to diuretic-induced hypokalemia, which inhibits insulin secretion by the beta cells, and reductions in extracellular fluid volume and cardiac output. This is compounded by increases in catecholamines from sympathetic nerve activity which decrease peripheral glucose utilization. A mild increase in serum cholesterol concentration is seen frequently during initiation of diuretic therapy, but during steady state therapy after 6 to 12 months, values usually return to baseline. Knowledge of the more common adverse effects induced by diuretics helps the physician in predicting patients at risk and taking effective steps to anticipate or treat adverse responses.

  15. Tetany: Possible adverse effect of bevacizumab

    Directory of Open Access Journals (Sweden)

    S R Anwikar

    2011-01-01

    Full Text Available Background: Bevacizumab a recombinant humanized monoclonal antibody was approved in 2004 by US FDA for metastatic colorectal cancer. It is reported to cause potentially serious toxicities including severe hypertension, proteinuria, and congestive heart failure. Aim: To correlate adverse event tetany with the use of bevacizumab. Materials and Methods : World Health Organization′s Uppsala Monitoring Centre, Sweden, for reporting of adverse drug reactions from all over the world, identified 7 cases with tetany-related symptoms to bevacizumab from four different countries. These 7 patients reported to UMC database developed adverse events described as musculoskeletal stiffness (1, muscle spasm (1, muscle cramps (1, lock jaw or jaw stiffness (4, and hypertonia (1, with hypocalcaemia. Results: After detailed study of the possible mechanism of actions of bevacizumab and factors causing tetany, it is proposed that there is a possibility of tetany by bevacizumab, which may occur by interfering with calcium metabolism. Resorption of bone through osteoclasts by affecting VEGF may interfere with calcium metabolism. Another possibility of tetany may be due to associated hypomagnesaemia, hypokalemia, or hyponatremia. Conclusions: Tetany should be considered as a one of the signs. Patient on bevacizumab should carefully watch for tetany-related symptoms and calcium and magnesium levels for their safety.

  16. Signal Detection of Adverse Drug Reaction of Amoxicillin Using the Korea Adverse Event Reporting System Database

    OpenAIRE

    Soukavong, Mick; Kim, Jungmee; Park, Kyounghoon; Yang, Bo Ram; Lee, Joongyub; Jin, Xue-Mei; Park, Byung-Joo

    2016-01-01

    We conducted pharmacovigilance data mining for a β-lactam antibiotics, amoxicillin, and compare the adverse events (AEs) with the drug labels of 9 countries including Korea, USA, UK, Japan, Germany, Swiss, Italy, France, and Laos. We used the Korea Adverse Event Reporting System (KAERS) database, a nationwide database of AE reports, between December 1988 and June 2014. Frequentist and Bayesian methods were used to calculate disproportionality distribution of drug-AE pairs. The AE which was de...

  17. Hierarchically nanotextured surfaces maintaining superhydrophobicity under severely adverse conditions

    Science.gov (United States)

    Maitra, Tanmoy; Antonini, Carlo; Auf der Mauer, Matthias; Stamatopoulos, Christos; Tiwari, Manish K.; Poulikakos, Dimos

    2014-07-01

    nanostructured, environmentally friendly, metal-based (aluminum) superhydrophobic surfaces, which maintain their performance under severely adverse conditions. Based on their functionality, we superpose selected hydrophobic layers (i.e. self-assembled monolayers, thin films, or nanofibrous coatings) on hierarchically textured aluminum surfaces, collectively imparting high level robustness of superhydrophobicity under adverse conditions. These surfaces simultaneously exhibit chemical stability, mechanical durability and droplet impalement resistance. They impressively maintained their superhydrophobicity after exposure to severely adverse chemical environments like strong alkaline (pH ~ 9-10), acidic (pH ~ 2-3), and ionic solutions (3.5 weight% of sodium chloride), and could simultaneously resist water droplet impalement up to an impact velocity of 3.2 m s-1 as well as withstand standard mechanical durability tests. Electronic supplementary information (ESI) available: Contact angles on intermediate surfaces; changes in PDMS film thickness with n-hexane immersion; the chemical stability of surfaces with (C3) and without PDMS film (C2) and the impalement pressure balance. See DOI: 10.1039/c4nr01368a

  18. Vegetation patterns and environmental gradients in Benin

    NARCIS (Netherlands)

    Adomou, A.

    2005-01-01

    Key words: West Africa, Benin, vegetation patterns, floristic areas, phytogeography, chorology, floristic gradients, climatic factors, water availability, Dahomey Gap, threatened plants, biodiversity, conservation.Understanding plant species distribution patterns and the underlying factors is a cruc

  19. Unimodal and crossmodal gradients of spatial attention

    DEFF Research Database (Denmark)

    Föcker, J.; Hötting, K.; Gondan, Matthias

    2010-01-01

    Behavioral and event-related potential (ERP) studies have shown that spatial attention is gradually distributed around the center of the attentional focus. The present study compared uni- and crossmodal gradients of spatial attention to investigate whether the orienting of auditory and visual...... spatial attention is based on modality specific or supramodal representations of space. Auditory and visual stimuli were presented from five speaker locations positioned in the right hemifield. Participants had to attend to the innermost or outmost right position in order to detect either visual...... or auditory deviant stimuli. Detection rates and event-related potentials (ERPs) indicated that spatial attention is distributed as a gradient. Unimodal spatial ERP gradients correlated with the spatial resolution of the modality. Crossmodal spatial gradients were always broader than the corresponding...

  20. Full Gradient Solution to Adaptive Hybrid Control

    Science.gov (United States)

    Bean, Jacob; Schiller, Noah H.; Fuller, Chris

    2017-01-01

    This paper focuses on the adaptation mechanisms in adaptive hybrid controllers. Most adaptive hybrid controllers update two filters individually according to the filtered reference least mean squares (FxLMS) algorithm. Because this algorithm was derived for feedforward control, it does not take into account the presence of a feedback loop in the gradient calculation. This paper provides a derivation of the proper weight vector gradient for hybrid (or feedback) controllers that takes into account the presence of feedback. In this formulation, a single weight vector is updated rather than two individually. An internal model structure is assumed for the feedback part of the controller. The full gradient is equivalent to that used in the standard FxLMS algorithm with the addition of a recursive term that is a function of the modeling error. Some simulations are provided to highlight the advantages of using the full gradient in the weight vector update rather than the approximation.

  1. On lower order strain gradient plasticity theories

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Hutchinson, J. W.

    2002-01-01

    By way of numerical examples, this paper explores the nature of solutions to a class of strain gradient plasticity theories that employ conventional stresses, equilibrium equations and boundary conditions. Strain gradients come into play in these modified conventional theories only to alter the t...... the tangential moduli governing increments of stress and strain. It is shown that the modification is far from benign from a mathematical standpoint, changing the qualitative character of solutions and leading to a new type of localization that appears to be unphysical.......By way of numerical examples, this paper explores the nature of solutions to a class of strain gradient plasticity theories that employ conventional stresses, equilibrium equations and boundary conditions. Strain gradients come into play in these modified conventional theories only to alter...

  2. Improving GOCE cross-track gravity gradients

    Science.gov (United States)

    Siemes, Christian

    2017-07-01

    The GOCE gravity gradiometer measured highly accurate gravity gradients along the orbit during GOCE's mission lifetime from March 17, 2009, to November 11, 2013. These measurements contain unique information on the gravity field at a spatial resolution of 80 km half wavelength, which is not provided to the same accuracy level by any other satellite mission now and in the foreseeable future. Unfortunately, the gravity gradient in cross-track direction is heavily perturbed in the regions around the geomagnetic poles. We show in this paper that the perturbing effect can be modeled accurately as a quadratic function of the non-gravitational acceleration of the satellite in cross-track direction. Most importantly, we can remove the perturbation from the cross-track gravity gradient to a great extent, which significantly improves the accuracy of the latter and offers opportunities for better scientific exploitation of the GOCE gravity gradient data set.

  3. Optimizing sampling approaches along ecological gradients

    DEFF Research Database (Denmark)

    Schweiger, Andreas; Irl, Severin D. H.; Steinbauer, Manuel

    2016-01-01

    1. Natural scientists and especially ecologists use manipulative experiments or field observations along gradients to differentiate patterns driven by processes from those caused by random noise. A well-conceived sampling design is essential for identifying, analysing and reporting underlying...

  4. Integral Field Spectroscopy Surveys: Oxygen Abundance Gradients

    Science.gov (United States)

    Sánchez, S. F.; Sánchez-Menguiano, L.

    2017-07-01

    We present here the recent results on our understanding of oxygen abundance gradients derived using Integral Field Spectroscopic surveys. In particular we analyzed more than 2124 datacubes corresponding to individual objects observed by the CALIFA (˜ 734 objects) and the public data by MaNGA (˜ 1390 objects), deriving the oxygen abundance gradient for each galaxy. We confirm previous results that indicate that the shape of this gradient is very similar for all galaxies with masses above 109.5M⊙, presenting in average a very similar slope of ˜ -0.04 dex within 0.5-2.0 re, with a possible drop in the inner regions (r109.5M⊙) the gradient seems to be flatter than for more massive ones. All these results agree with an inside-out growth of massive galaxies and indicate that low mass ones may still be growing in an outside in phase.

  5. Artificial photosynthesis: Light-activated calcium gradients

    Science.gov (United States)

    Thompson, David H.

    2002-12-01

    Photosynthetic organisms use light to create chemical gradients across bilayer membranes that drive energetically unfavourable reactions. Synthetic systems that accomplish the same feat may find uses in a variety of biological and non-biological applications.

  6. CMB Anisotropies from a Gradient Mode

    CERN Document Server

    Mirbabayi, Mehrdad

    2014-01-01

    A pure gradient mode must have no observable dynamical effect at linear level. We confirm this by showing that its contribution to the dipolar power asymmetry of CMB anisotropies vanishes, if Maldacena's consistency condition is satisfied. To this end, the existing second order Sachs-Wolfe formula in the squeezed limit is extended to include a gradient in the long mode and to account for the change in the location of the last scattering surface induced by this mode. At second order, a gradient mode generated in Single-field inflation is shown to induce a quadrupole moment. For instance in a matter-dominated model it is equal to 5/18 times the square of the linear gradient part. This quadrupole can be cancelled by superposing a quadratic perturbation. The result is shown to be a non-linear extension of Weinberg's adiabatic modes: a long-wavelength physical mode which looks locally like a coordinate transformation.

  7. Psychiatric adverse effects of pediatric corticosteroid use.

    Science.gov (United States)

    Drozdowicz, Linda B; Bostwick, J Michael

    2014-06-01

    Corticosteroids, highly effective drugs for myriad disease states, have considerable neuropsychiatric adverse effects that can manifest in cognitive disorders, behavioral changes, and frank psychiatric disease. Recent reviews have summarized these effects in adults, but a comprehensive review on corticosteroid effects in children has not been published since 2005. Here, we systematically review articles published since then that, we find, naturally divide into 3 main areas: (1) chronic effects of acute prenatal and neonatal exposure associated with prematurity and congenital conditions; (2) immediate behavioral effects of acute exposure via oncological protocols; and (3) acute behavioral effects of sporadic use in children and adolescents with other conditions. PsycInfo, MEDLINE, Embase, and Scopus were queried to identify articles reporting psychiatric adverse effects of corticosteroids in pediatric patients. Search terms included corticosteroids, adrenal cortex hormones, steroid psychosis, substance-induced psychoses, glucocorticoids, dexamethasone, hydrocortisone, prednisone, adverse effects, mood disorders, mental disorders, psychosis, psychotic, psychoses, side effect, chemically induced, emotions, affective symptoms, toxicity, behavior, behavioral symptoms, infant, child, adolescent, pediatric, paediatric, neonatal, children, teen, and teenager. Following guidelines for systematic reviews from the Potsdam Consultation on Meta-Analysis, we have found it difficult to draw specific conclusions that are more than general impressions owing to the quality of the available studies. We find a mixed picture with neonates exposed to dexamethasone, with some articles reporting eventual deficits in neuropsychiatric functioning and others reporting no effect. In pediatric patients with acute lymphoblastic leukemia, corticosteroid use appears to correlate with negative psychiatric and behavioral effects. In children treated with corticosteroids for noncancer conditions

  8. Thermal gradient analysis of solidifying casting

    Directory of Open Access Journals (Sweden)

    J. Suchoń

    2008-08-01

    Full Text Available For description of casting solidification and crystallization process the thermal derivative analysis (TDA is commonly used. Besides the process kinetics considered in TDA method to describe the solidification process, the thermal gradient analysis can be also used for this purpose [1, 2]. In conducted studies analysis of thermal gradient distribution inside the solidifying wedge casting was shown which enabled determination of heat flow intensity on casting section.

  9. The local power of the gradient test

    CERN Document Server

    Lemonte, Artur

    2010-01-01

    The asymptotic expansion of the distribution of the gradient test statistic is derived for a composite hypothesis under a sequence of Pitman alternative hypotheses converging to the null hypothesis at rate $n^{-1/2}$, $n$ being the sample size. Comparisons of the local powers of the gradient, likelihood ratio, Wald and score tests reveal no uniform superiority property. The power performance of all four criteria in one-parameter exponential family is examined.

  10. NEW STRAIN GRADIENT THEORY AND ANALYSIS

    Institute of Scientific and Technical Information of China (English)

    Dake Yi; Tzu Chiang Wang; Shaohua Chen

    2009-01-01

    A new strain gradient theory which is based on energy nonlocal model is proposed in this paper, and the theory is applied to investigate the size effects in thin metallic wire torsion, ultra-thin beam bending and micro-indentation of polycrystalline copper. First, an energy nonlocal model is suggested. Second, based on the model, a new strain gradient theory is derived. Third, the new theory is applied to analyze three representative experiments.

  11. The gradient flow in a twisted box

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, Alberto [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

    2013-08-15

    We study the perturbative behavior of the gradient flow in a twisted box. We apply this information to define a running coupling using the energy density of the flow field. We study the step-scaling function and the size of cutoff effects in SU(2) pure gauge theory. We conclude that the twisted gradient flow running coupling scheme is a valid strategy for step-scaling purposes due to the relatively mild cutoff effects and high precision.

  12. Study on Purifying Technology of Andrographolide by Supercritical CO2 Secondary Gradient Crystallization

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wen-cheng; PAN Jian

    2004-01-01

    The effects of the secondary gradient crystallizing pressure, temperature and time on the purity and crystallization ratio of andrographolide were investigated via single factor experiments. The shape of crystal was observed with scanning electron microscopy (SEM). The purity of andrographolide was determined by high pressure liquid chromatography (HPLC). It was found that the optimized parameters were pressure 14 MPa, temperature 55℃,time 60 min, and CO2 flow rate 15 L min-1, under these conditions the particle of andrographolide was much smaller, the crystal of andrographolide was distributed in floccule on crystal board, with the purity of andrographolide 92.5%, the crystallization ratio 48.9%.

  13. Interplay between transport barriers and density gradient

    Science.gov (United States)

    Sarazin, Y.; Grandgirard, V.; Dif-Pradalier, G.; Garbet, X.; Ghendrih, Ph.

    2006-09-01

    The present paper addresses two critical issues of zonal flows: the evidence of control parameters of their driving term, namely the Reynolds stress, and how they back-react on turbulence and transport. Kinetic nonlinear simulations are performed with the GYSELA code [V. Grandgirard et al., J. Comput. Phys. (to be published)], which models the slab branch of the ion temperature gradient driven instability in the four-dimensional drift-kinetic regime. First, the numerical results show that the gradient of the guiding center density, related to the general potential vorticity, is stabilizing both linearly, by increasing the instability threshold, and nonlinearly, by activating zonal flows. Accordingly, the Reynolds stress is found to scale like LΩ-2 in the quasilinear regime, LΩ being the gradient length of the guiding center density. Second, the local temperature gradient appears to increase linearly with the curvature of the zonal flows, regardless of its sign. Such behavior agrees qualitatively with a perturbative theory. Indeed, while linear eigenmodes are localized at the maximum of the temperature gradient in the absence of zonal flows, they tend to be expelled if both exhibit a maximum at the same location. In this case, the reduction mechanism of the turbulent transport results from the ability of large zonal flow curvatures to render strong temperature gradients stable with respect to perturbations.

  14. Gradient-based compressive image fusion

    Institute of Scientific and Technical Information of China (English)

    Yang CHEN‡; Zheng QIN

    2015-01-01

    We present a novel image fusion scheme based on gradient and scrambled block Hadamard ensemble (SBHE) sam-pling for compressive sensing imaging. First, source images are compressed by compressive sensing, to facilitate the transmission of the sensor. In the fusion phase, the image gradient is calculated to reflect the abundance of its contour information. By com-positing the gradient of each image, gradient-based weights are obtained, with which compressive sensing coefficients are achieved. Finally, inverse transformation is applied to the coefficients derived from fusion, and the fused image is obtained. Information entropy (IE), Xydeas’s and Piella’s metrics are applied as non-reference objective metrics to evaluate the fusion quality in line with different fusion schemes. In addition, different image fusion application scenarios are applied to explore the scenario adaptability of the proposed scheme. Simulation results demonstrate that the gradient-based scheme has the best per-formance, in terms of both subjective judgment and objective metrics. Furthermore, the gradient-based fusion scheme proposed in this paper can be applied in different fusion scenarios.

  15. pressure analysis and fluid contact prediction for alpha reservoir

    African Journals Online (AJOL)

    HOD

    As pressure data was not acquired in the water leg of the reservoir, pressure gradient analysis was done with the field-wide hydrostatic profile for contact and fluid prediction. Also, an ... within this depth range (Figure 4). The presence of an.

  16. Shared and unique patterns of phenotypic diversification along a stream gradient in two congeneric species

    Science.gov (United States)

    Jourdan, Jonas; Krause, Sarah T.; Lazar, V. Max; Zimmer, Claudia; Sommer-Trembo, Carolin; Arias-Rodriguez, Lenin; Klaus, Sebastian; Riesch, Rüdiger; Plath, Martin

    2016-12-01

    Stream ecosystems show gradual variation of various selection factors, which can result in a zonation of species distributions and gradient evolution of morphological and life-history traits within species. Identifying the selective agents underlying such phenotypic evolution is challenging as different species could show shared and/or unique (species-specific) responses to components of the river gradient. We studied a stream gradient inhabited by two mosquitofishes (genus Gambusia) in the Río Grijalva basin in southern Mexico and found a patchy distribution pattern of both congeners along a stretch of 100 km, whereby one species was usually dominant at a given site. We uncovered both shared and unique patterns of diversification: some components of the stream gradient, including differences in piscine predation pressure, drove shared patterns of phenotypic divergence, especially in females. Other components of the gradient, particularly abiotic factors (max. annual temperature and temperature range) resulted in unique patterns of divergence, especially in males. Our study highlights the complexity of selective regimes in stream ecosystems. It exemplifies that even closely related, congeneric species can respond in unique ways to the same components of the river gradient and shows how both sexes can exhibit quite different patterns of divergence in multivariate phenotypic character suites.

  17. Irreducible decomposition of strain gradient tensor in isotropic strain gradient elasticity

    CERN Document Server

    Lazar, Markus

    2016-01-01

    In isotropic strain gradient elasticity, we decompose the strain gradient tensor into its irreducible pieces under the n-dimensional orthogonal group O(n). Using the Young tableau method for traceless tensors, four irreducible pieces (n>2), which are canonical, are obtained. In three dimensions, the strain gradient tensor can be decomposed into four irreducible pieces with 7+5+3+3 independent components whereas in two dimensions, the strain gradient tensor can be decomposed into three irreducible pieces with 2+2+2 independent components. The knowledge of these irreducible pieces is extremely useful when setting up constitutive relations and strain energy.

  18. Improving the accuracy of pulsed field gradient NMR diffusion experiments: Correction for gradient non-uniformity

    Science.gov (United States)

    Connell, Mark A.; Bowyer, Paul J.; Adam Bone, P.; Davis, Adrian L.; Swanson, Alistair G.; Nilsson, Mathias; Morris, Gareth A.

    2009-05-01

    Pulsed field gradient NMR is a well-established technique for the determination of self-diffusion coefficients. However, a significant source of systematic error exists in the spatial variation of the applied pulsed field gradient. Non-uniform pulsed field gradients cause the decay of peak amplitudes to deviate from the expected exponential dependence on gradient squared. This has two undesirable effects: the apparent diffusion coefficient will deviate from the true value to an extent determined by the choice of experimental parameters, and the error estimated by the nonlinear least squares fitting will contain a significant systematic contribution. In particular, the apparent diffusion coefficient determined by exponential fitting of the diffusional attenuation of NMR signals will depend both on the exact pulse widths used and on the range of gradient amplitudes chosen. These problems can be partially compensated for if experimental attenuation data are fitted to a function corrected for the measured spatial dependence of the gradient and signal strength. This study describes a general alternative to existing methods for the calibration of NMR diffusion measurements. The dominant longitudinal variation of the pulsed field gradient amplitude and the signal strength are mapped by measuring pulsed field gradient echoes in the presence of a weak read gradient. These data are then used to construct a predicted signal decay function for the whole sample, which is parameterised as the exponential of a power series. Results are presented which compare diffusion coefficients obtained using the new calibration method with previous literature values.

  19. Adverse effects of statins - myths and reality.

    Science.gov (United States)

    Šimić, Iveta; Reiner, Željko

    2015-01-01

    Statins reduce cardiovascular mortality and morbidity as well as cardiovascular events in patients with a very high risk of cardiovascular disease (CVD) and also in subjects with high or moderate risk by reducing the levels of low-density lipoprotein cholesterol (LDL-C). Although they are considered to be drugs with a very good safety profile, because of their wide use there are many concerns that their adverse effects might compromise their proven beneficial effects. Therefore this article reviews all the data and provides an evidence- based insight what are the proven adverse effects of statins and what are the "myths" about them. The most important side effects include myopathy and rhabdomyolysis. Another side effect is increased activity of liver tests which occurs occasionally and is reversible. However, recent studies even suggest that statin therapy can improve hepatic steatosis. It is beyond any doubt that statins do slightly increase the incidence of type 2 diabetes mellitus in people with two or more components of metabolic syndrome but the cardiovascular benefits of such a treatment by far exceed this risk. Statin therapy has also been associated with some adverse renal effects, eg. acute renal failure, but recent data suggest even a possible protective effect of these drugs on renal dysfunction. Concerns that statins might increase cancer have not been proven. On the contrary, several studies have indicated a possible benefit of these drugs in patients with different types of cancer. Early concerns about cognitive dysfunction and memory loss associated with statins use could not be proven and most recent data even suggest a possible beneficial effect of statins in the prevention of dementia. Systematic reviews and clinical guidelines suggest that the cardiovascular benefits of statins by far out-weight non-cardiovascular harms in patients with cardiovascular risk.

  20. Regional maps of subsurface geopressure gradients of the onshore and offshore Gulf of Mexico basin

    Science.gov (United States)

    Burke, Lauri A.; Kinney, Scott A.; Dubiel, Russell F.; Pitman, Janet K.

    2013-01-01

    The U.S. Geological Survey created a comprehensive geopressure-gradient model of the regional pressure system spanning the onshore and offshore Gulf of Mexico basin, USA. This model was used to generate ten maps that included (1) five contour maps characterizing the depth to the surface defined by the first occurrence of isopressure gradients ranging from 0.60 psi/ft to 1.00 psi/ft, in 0.10-psi/ft increments; and (2) five supporting maps illustrating the spatial density of the data used to construct the contour maps. These contour maps of isopressure-gradients at various increments enable the identification and quantification of the occurrence, magnitude, location, and depth of the subsurface pressure system, which allows for the broad characterization of regions exhibiting overpressured, underpressured, and normally pressured strata. Identification of overpressured regions is critical for exploration and evaluation of potential undiscovered hydrocarbon accumulations based on petroleum-generation pressure signatures and pressure-retention properties of reservoir seals. Characterization of normally pressured regions is essential for field development decisions such as determining the dominant production drive mechanisms, evaluating well placement and drainage patterns, and deciding on well stimulation methods such as hydraulic fracturing. Identification of underpressured regions is essential for evaluating the feasibility of geological sequestration and long-term containment of fluids such as supercritical carbon dioxide for alternative disposal methods of greenhouse gases. This study is the first, quantitative investigation of the regional pressure systems of one of the most important petroleum provinces in the United States. Although this methodology was developed for pressure studies in the Gulf of Mexico basin, it is applicable to any basin worldwide.