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Sample records for cycle-to-cycle pressure variations

  1. Characteristic of blended fuel properties and engine cycle-to-cycle variations with butanol additive

    NASA Astrophysics Data System (ADS)

    Ali, Obed M.; Mamat, Rizalman; Abdullah, Nik R.; Abdullah, Abdul Adam

    2015-05-01

    Biodiesel fuel characteristics are one of the most important parameters that limited their application in diesel engines. Though biodiesel-diesel blended fuel can replace diesel satisfactorily at low blending ratios up to 20%, problems related to fuel property persist at high blending ratio. Hence, in the present study, the feasibility of biodiesel-diesel blended fuel B30 was investigated with respect to its properties and engine cyclic variations with increasing butanol additive. The blended fuel with additive were tested experimentally in a diesel engine and the in-cylinder pressure data were collected and analyzed using the coefficient of variation and wavelet power spectrum to evaluate the engine cyclic variations compared to diesel fuel engine test results. The fuel property test results showed slight improvement in density and acid value with significant reduction in viscosity when increasing butanol additive. Furthermore, the blended fuel pour point was reduced to -6 °C at 8% butanol additive. On the other hand, the energy content slightly affected with increasing butanol additive in the blend. From the wavelet power spectrum, it is observed that the short-period oscillations appear intermittently in pure blended fuel, while the long and intermediate-term periodicities tends to appear with increasing additive ratio. Moreover, the spectral power increased with an increase in the additive ratio indicating that the additive has a noticeable effect on increasing the cycle to cycle variation. The coefficient of variation of indicated mean effective pressure for B30 were found to be the lowest and increases with increasing additive ratios. Both the wavelet analysis and coefficient of variation results reveals that blended fuel B30 has engine cyclic variations comparable to diesel fuel with increasing butanol additive up to 4%.

  2. Spatio-temporal structure and cycle to cycle variations of an in-cylinder tumbling flow

    NASA Astrophysics Data System (ADS)

    Voisine, M.; Thomas, L.; Borée, J.; Rey, P.

    2011-05-01

    The aim of this paper is to make use of PIV and high-speed PIV in a research engine of moderate tumbling ratio in order to analyze both the spatial structure of the flow and its temporal evolution during series of consecutive cycles. Appropriate analyzing tools are introduced, and four different points are addressed: (1) the chain of events driving the generation of the three-dimensional mean tumbling motion is investigated; (2) a Lagrangian analysis of the roll-up of the tumbling jet in individual cycles demonstrates a strong cycle to cycle variation during the compression phase (the rms of the position of the jet front being approximately 10% of the piston stroke); (3) focussing on the "breakdown" phase, phase invariant proper orthogonal decomposition enables us to distinguish cycles according to their structure near top dead center (TDC). We show that when the coherent energy of the flow is conserved, there is no increase in the fluctuating kinetic energy; (4) finally, the phase-averaged Reynolds stresses is decomposed into a contribution of the in-cycle coherence and the turbulence carried by the flow states. Approximately 30% of the fluctuating kinetic energy is due to cycle to cycle fluctuations in this chamber near TDC.

  3. Investigation of cycle-to-cycle variations in an engine-like geometry

    NASA Astrophysics Data System (ADS)

    Schmitt, M.; Frouzakis, C. E.; Wright, Y. M.; Tomboulides, A. G.; Boulouchos, K.

    2014-12-01

    The multiple-cycle direct numerical simulation data of the flow in the valve/piston assembly investigated in Schmitt et al. ["Direct numerical simulation of multiple cycles in a valve/piston assembly," Phys. Fluids 26, 035105 (2014)] is revisited to identify the relevant flow features leading to the observed cyclic variations. These are found to be the radial velocity at top dead center (TDC) remaining from the previous cycle, the location of the center of the hollow jet during intake and the strength and orientation of the vortex ring at bottom dead center. Comparisons between these features showed strong correlations in the flow field within a cycle and between two consecutive cycles. The trajectory of the hollow jet during intake is strongly influenced by the remaining radial velocity from the previous cycle. Subsequently, the hollow jet forms a vortex ring whose orientation and strength influences the radial velocity at TDC of the next cycle. This has in turn an effect on the jet trajectory of the following cycle. The results in this simplified geometry are a first attempt to understand the origin of cause-and-effect relationships of cycle-to-cycle variations (CCVs) in the flow field and can serve as a base for investigating CCVs in more realistic engine geometries. Moreover, the reported correlations are a useful validation platform for large Eddy simulation models.

  4. Cycle-to-Cycle Variations in the Diurnal Variation of Galactic Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Thomas, Simon; Owen, Chris; Owens, Matt; Lockwood, Mike

    2016-04-01

    We examine mean profiles of the diurnal variations in galactic cosmic ray flux using a number of neutron monitors at different magnetic latitudes and longitudes. By splitting all of the hourly neutron monitor data by the solar magnetic polarity and analysing the mean normalised neutron monitor count rates between these, we see that the diurnal variation changes phase by 1-2 hours between the two polarity states for the majority of non-polar neutron monitors. The intensity and variability of a heliospheric magnetic field is analysed for every day and found not to be the cause of the phase change. Some polar neutron monitors, however, show different, smaller amplitude variations in phase between polarity cycles. Time series of the time of the maximum in the diurnal variation are presented between 1965 and 2013. Our results agree with previous work by confirming the presence of a 22-year variation in the peak time of the diurnal variation and a 11-year variation in the amplitude, but also show that not all neutron monitors show the same trend. An analysis of the magnetic latitude dependence of the diurnal variation shows that the time-of-day of the peak and trough of this variation gives opposing changes to the amplitude of the 22-year change. We suggest that this could be due to changes in the configeration of the heliospheric magnetic field for consecutive cycles.

  5. Interpretation of engine cycle-to-cycle variation by chaotic time series analysis

    SciTech Connect

    Daw, C.S.; Kahl, W.K.

    1990-01-01

    In this paper we summarize preliminary results from applying a new mathematical technique -- chaotic time series analysis (CTSA) -- to cylinder pressure data from a spark-ignition (SI) four-stroke engine fueled with both methanol and iso-octane. Our objective is to look for the presence of deterministic chaos'' dynamics in peak pressure variations and to investigate the potential usefulness of CTSA as a diagnostic tool. Our results suggest that sequential peak cylinder pressures exhibit some characteristic features of deterministic chaos and that CTSA can extract previously unrecognized information from such data. 18 refs., 11 figs., 2 tabs.

  6. Application of High Performance Computing for Simulating Cycle-to-Cycle Variation in Dual-Fuel Combustion Engines

    DOE PAGES

    Jupudi, Ravichandra S.; Finney, Charles E.A.; Primus, Roy; ...

    2016-04-05

    Interest in operational cost reduction is driving engine manufacturers to consider lower-cost fuel substitution in heavy-duty diesel engines. These dual-fuel (DF) engines could be operated either in diesel-only mode or operated with premixed natural gas (NG) ignited by a pilot flame of compression-ignited direct-injected diesel fuel. One promising application is that of large-bore, medium-speed engines such as those used in locomotives. With realistic natural gas substitution levels in the fleet of locomotives currently in service, such fuel substitution could result in billions of dollars of savings annually in the US alone. However, under certain conditions, dual-fuel operation can result inmore » increased cycle-to-cycle variability (CCV) during combustion, resulting in variations in cylinder pressure and work extraction. In certain situations, the CCV of dual-fuel operation can be notably higher than that of diesel-only combustion under similar operating conditions. Excessive CCV can limit the NG substitution rate and operating range of a dual-fuel engine by increasing emissions and reducing engine stability, reliability and fuel efficiency via incomplete natural-gas combustion. Running multiple engine cycles in series to simulate CCV can be quite time consuming. Hence innovative modelling techniques and large computing resources are needed to investigate the factors affecting CCV in dual-fuel engines. This paper discusses the use of the High Performance Computing resource Titan, at the Oak Ridge Leadership Computing Facility at Oak Ridge National Laboratory, to investigate cycle-to-cycle combustion variability of a dual-fuel engine. The CONVERGE CFD software was used to simulate multiple, parallel single cycles of dual-fuel combustion with perturbed operating parameters and boundary conditions. These perturbations are imposed according to a sparse grids sampling of the parameter space. The sampling scheme chosen is similar to a design of experiments method

  7. Application of High Performance Computing for Simulating Cycle-to-Cycle Variation in Dual-Fuel Combustion Engines

    SciTech Connect

    Jupudi, Ravichandra S.; Finney, Charles E.A.; Primus, Roy; Wijeyakulasuriya, Sameera; Klingbeil, Adam E.; Tamma, Bhaskar; Stoyanov, Miroslav K.

    2016-04-05

    Interest in operational cost reduction is driving engine manufacturers to consider lower-cost fuel substitution in heavy-duty diesel engines. These dual-fuel (DF) engines could be operated either in diesel-only mode or operated with premixed natural gas (NG) ignited by a pilot flame of compression-ignited direct-injected diesel fuel. One promising application is that of large-bore, medium-speed engines such as those used in locomotives. With realistic natural gas substitution levels in the fleet of locomotives currently in service, such fuel substitution could result in billions of dollars of savings annually in the US alone. However, under certain conditions, dual-fuel operation can result in increased cycle-to-cycle variability (CCV) during combustion, resulting in variations in cylinder pressure and work extraction. In certain situations, the CCV of dual-fuel operation can be notably higher than that of diesel-only combustion under similar operating conditions. Excessive CCV can limit the NG substitution rate and operating range of a dual-fuel engine by increasing emissions and reducing engine stability, reliability and fuel efficiency via incomplete natural-gas combustion. Running multiple engine cycles in series to simulate CCV can be quite time consuming. Hence innovative modelling techniques and large computing resources are needed to investigate the factors affecting CCV in dual-fuel engines. This paper discusses the use of the High Performance Computing resource Titan, at the Oak Ridge Leadership Computing Facility at Oak Ridge National Laboratory, to investigate cycle-to-cycle combustion variability of a dual-fuel engine. The CONVERGE CFD software was used to simulate multiple, parallel single cycles of dual-fuel combustion with perturbed operating parameters and boundary conditions. These perturbations are imposed according to a sparse grids sampling of the parameter space. The sampling scheme chosen is similar to a design of experiments method but uses

  8. Cycle-to-cycle variation analysis of in-cylinder flow in a gasoline engine with variable valve lift

    NASA Astrophysics Data System (ADS)

    Liu, Daming; Wang, Tianyou; Jia, Ming; Wang, Gangde

    2012-09-01

    In spark ignition engines, cycle-to-cycle variation (CCV) limits the expansion of the operating range because it induces the load variations and the occurrence of misfire and/or knock. Variable valve actuation (VVA) or variable valve lift (VVL) has been widely used in SI engines to improve the volumetric efficiency or to reduce the pumping losses. It is necessary to investigate the CCV of in-cylinder gas motion and mixing processes in SI engines with VVA/VVL system. This study is aimed to analyze the CCV of the tumble flow in a gasoline direct injection (GDI) engine when VVL is employed. Cycle-resolved digital particle image velocimetry (CRD-PIV) data were acquired for the in-cylinder flow field of a motored four-stroke multi-valve GDI optical engine. The CCV of in-cylinder gas motion with a series of valve profiles and different maximum valve lift (MVL) was analyzed, including cyclic variation characteristics of bulk flow (tumble centre and tumble ratio), large- and small-scale fluctuation, total kinetic energy, and circulation. The results show that the CCV of the in-cylinder flow is increased with reduced MVL. With lower MVLs, stable tumble flow cannot be formed in the cylinder, and the ensemble-averaged tumble ratio decreases to zero before the end of the compression stroke due to violent variation. In addition, the evolution of the circulation shows larger variation with lower MVLs that indicates the `spin' of the small-scale eddy in the flow field presents violent fluctuation from one cycle to another, especially at the end of the compression stroke. Moreover, the analyze of the kinetic energy indicates the total energy of the flow field with lower MVLs increases significantly comparing with higher MVL conditions due to the intake flow jet at the intake valve seat in the intake stroke. However, the CCV of the in-cylinder flow becomes more violent under lower MVL conditions, especially for the low-frequency fluctuation kinetic energy. Thus, present strong

  9. Characterizing cycle-to-cycle variations of the shedding cycle in the turbulent wake of a normal flat plate using generalized phase averages

    NASA Astrophysics Data System (ADS)

    Martinuzzi, Robert

    2016-11-01

    Quasi-periodic vortex shedding in the turbulent wake of a thin-flat plate placed normal to a uniform stream at Reynolds number of 6700 is investigated based on Particle Image Velocimetry experiments. The wake structure and vortex formation are characterized using a generalized phase average (GPA), a refinement of the triple decomposition of Reynolds and Hussain (1970) incorporating elements of mean-field theory (Stuart, 1958). The resulting analysis highlights the importance of cycle-to-cycle variations in characterizing vortex formation, wake topology and the residual turbulent Reynolds Stresses. For example, it is shown that during high-amplitude cycles vorticity is strongly concentrated within the well-organized shed vortices, whereas during low-amplitude cycles the shed vortices are highly distorted resulting in significant modulation of the shedding frequency. It is found that high-amplitude cycles contribute more to the coherent Reynolds stress field while the low-amplitude cycles contribute to the residual stress field. It is further shown that traditional phase-averaging techniques lead to an over-estimation of the residual stress field. Natural Sciences and Engineering Research Council of Canada.

  10. Subfilamentary Networks Cause Cycle-to-Cycle Variability in Memristive Devices.

    PubMed

    Baeumer, Christoph; Valenta, Richard; Schmitz, Christoph; Locatelli, Andrea; Menteş, Tevfik Onur; Rogers, Steven P; Sala, Alessandro; Raab, Nicolas; Nemsak, Slavomir; Shim, Moonsub; Schneider, Claus M; Menzel, Stephan; Waser, Rainer; Dittmann, Regina

    2017-07-25

    A major obstacle for the implementation of redox-based memristive memory or logic technology is the large cycle-to-cycle and device-to-device variability. Here, we use spectromicroscopic photoemission threshold analysis and operando XAS analysis to experimentally investigate the microscopic origin of the variability. We find that some devices exhibit variations in the shape of the conductive filament or in the oxygen vacancy distribution at and around the filament. In other cases, even the location of the active filament changes from one cycle to the next. We propose that both effects originate from the coexistence of multiple (sub)filaments and that the active, current-carrying filament may change from cycle to cycle. These findings account for the observed variability in device performance and represent the scientific basis, rather than prior purely empirical engineering approaches, for developing stable memristive devices.

  11. Discovery of Cycle-to-cycle Modulated Spectral Line Variability and Velocity Gradients in Long-period Cepheids

    NASA Astrophysics Data System (ADS)

    Anderson, Richard I.

    2016-12-01

    This work reports the discovery of cycle-to-cycle modulated spectral line and atmospheric velocity gradient variability in long-period Cepheids based on 925 high-resolution optical spectra of ℓ Carinae (P ˜ 35.5 d) recorded during three heavy duty-cycle monitoring campaigns (in 2014, 2015, and 2016). Spectral line variability is investigated via cross-correlation functions (CCFs) computed using three sets of spectral lines (weak, solar, strong). A metallic line velocity gradient, δvr(t), is computed as the difference between weak and strong-line radial velocities (RVs). CCF shape indicators bisector inverse span (BIS) (asymmetry), full width at half-maximum, and depth all exhibit clear phase-dependent variability patterns that differ from one pulsation cycle to the next. Weak-line CCFs exhibit these effects more clearly than strong-line CCFs. BIS exhibits the most peculiar modulated variability and can be used to identify the presence of cycle-to-cycle modulated line profile variations. δvr(t) clearly exhibits cycle-to-cycle differences that correlate very closely with modulated BIS variability, suggesting perturbations of the atmospheric velocity field as the cause for modulated spectral line variability. These perturbations are most significant during contraction and are not in phase with the pulsation, transmitting information between consecutive pulsation cycles. This work shows RV curve modulation to be a consequence of atmospheric velocity gradient perturbations. Possible origins of these perturbations and their impact on Cepheid RV measurements as well as the projection factor used in Baade-Wesselink-type distance determinations are discussed.

  12. No Random Cycle-to-Cycle Period Changes in the β Cephei Star BW Vulpeculae

    NASA Astrophysics Data System (ADS)

    Percy, John R.; Velocci, Vince; Sterken, Christiaan

    2003-05-01

    We show, using the formalism of Eddington & Plakidis, that the nonevolutionary period changes in the β Cephei star BW Vul are not the result of random cycle-to-cycle period fluctuations, as they are in several cooler types of pulsating variables. The fractional fluctuation per cycle is less than 0.002.

  13. Experimental implementation of automatic 'cycle to cycle' control of a chiral simulated moving bed separation.

    PubMed

    Amanullah, Mohammad; Grossmann, Cristian; Mazzotti, Marco; Morari, Manfred; Morbidelli, Massimo

    2007-09-21

    In the absence of a suitable controller, currently simulated moving beds (SMBs) are operated suboptimally to cope with system uncertainties and to guarantee robustness of operation. Recently, we have developed a 'cycle to cycle' optimizing controller that not only makes use of minimal system information, i.e. only the Henry constants and average bed voidage, but also optimizes the process performance and taps the full economic potential of the SMB technology. The experimental implementation of the 'cycle to cycle' optimizing controller had been carried out for achiral separation. For chiral separation however, application of any online controller has not been possible because an appropriate online monitoring system has not been available. This work reports and discusses the first experimental implementation of the 'cycle to cycle' optimizing control for chiral separations. A mixture of guaifenesin enantiomers is separated on Chiralcel OD columns with ethanol as mobile phase in a eight-column four sections laboratory SMB unit. The results show that the controller, although using minimal information about the retention of the two enantiomers, is able to meet product and process specifications, can optimize the process performance, and is capable of rejecting disturbances that may occur during the operation of the SMB plant.

  14. Experimental implementation of automatic 'cycle to cycle' control to a nonlinear chiral simulated moving bed separation.

    PubMed

    Grossmann, Cristian; Langel, Christian; Mazzotti, Marco; Morari, Manfred; Morbidelli, Massimo

    2010-03-26

    In order to better exploit the economic potential of the simulated moving bed chromatography a 'cycle to cycle' controller which only requires the information about the linear adsorption behavior and the overall average porosity of the columns has been proposed. Recently, an automated on-line HPLC monitoring system which determines the concentrations in the two product streams averaged over one cycle, and returns them as feedback information to the controller was implemented. The new system allows for an accurate determination of the average concentration of the product streams even if the plant is operated at high concentrations. This paper presents the experimental implementation of the 'cycle to cycle' control concept to the separation of guaifenesin enantiomers under nonlinear chromatographic conditions, i.e. at high feed concentrations. Different case studies have been carried out to challenge the controller under realistic operation conditions, e.g. introducing pump disturbances and changing the feed concentration during the operation. The experimental results clearly demonstrate that the controller can indeed deliver the specified purities and improve the process performance.

  15. Diffusion and thermodynamic equilibrium under pressure variations

    NASA Astrophysics Data System (ADS)

    Moulas, Evangelos; Tajčmanová, Lucie; Vrijmoed, Johannes; Podladchikov, Yuri

    2015-04-01

    Pressure is one of the most fundamental variables in mineral thermodynamics. In that respect, pressure-sensitive mineral reactions provide an important constraint on pressure under which the rock was developed. One implicit assumption when interpreting such pressure estimates is that the state-of-stress is close to hydrostatic, homogeneous and that the differential stress is negligible. Recent spectroscopic data from the mineral scale documenting pressure variations do not support this assumption. In addition to observations, mechanical models (numerical and analytical) suggest that rocks can develop and maintain heterogeneous pressure distributions at geological time scales. The recently developed unconventional barometry explains chemical zoning in minerals as a result of a pressure variation. We focus to apply the unconventional barometry in cases where chemical zoning in minerals cannot be explained by sluggish kinetics. In that respect, the unconventional barometry offers an alternative view of the chemical zoning which is consistent with thermodynamic equilibrium. However, to distinguish between a pressure-controlled chemical zoning and a zoning reflecting an incomplete chemical reaction is still challenging, especially for multicomponent systems. In this contribution, different types of chemical zoning are discussed. We investigate plagioclase rims around kyanite from an amphibolitized eclogite from Rhodope Metamorphic Complex (Greece-Bulgaria) as a case study and compare them with similar published textures from the Bohemian Massif. Mineral microstructures and phase equilibrium suggest that both rocks experienced near-isothermal decompression at high (>700C) temperatures. However, several distinct microstructural features suggest the development and/or the decay of mechanically maintained heterogeneous pressure distributions. We discuss our results and interpretations based on phase-equilibrium modeling, unconventional barometry and diffusion modeling under

  16. Intradiscal pressure variation under spontaneous ventilation

    NASA Astrophysics Data System (ADS)

    Roriz, Paulo; Ferreira, J.; Potes, J. C.; Oliveira, M. T.; Santos, J. L.; Simões, J. A.; Frazão, O.

    2014-05-01

    The pressure measured in the intervertebral discs is a response to the loads acting on the spine. External loads, such as the reaction forces resulting from locomotion, manual handling and collisions are probably the most relevant in studying spine trauma. However, the physiological functions such as breathing and hearth rate also participate in subtle variations of intradiscal pressure that can be observed only in vivo at resting. Present work is an effort to measure the effect of breathing on intradiscal pressure of an anesthetized sheep.

  17. Neighborhood Disadvantage and Variations in Blood Pressure

    ERIC Educational Resources Information Center

    Cathorall, Michelle L.; Xin, Huaibo; Peachey, Andrew; Bibeau, Daniel L.; Schulz, Mark; Aronson, Robert

    2015-01-01

    Purpose: To examine the extent to which neighborhood disadvantage accounts for variation in blood pressure. Methods: Demographic, biometric, and self-reported data from 19,261 health screenings were used. Addresses of participants were geocoded and located within census block groups (n = 14,510, 75.3%). Three hierarchical linear models were…

  18. Neighborhood Disadvantage and Variations in Blood Pressure

    ERIC Educational Resources Information Center

    Cathorall, Michelle L.; Xin, Huaibo; Peachey, Andrew; Bibeau, Daniel L.; Schulz, Mark; Aronson, Robert

    2015-01-01

    Purpose: To examine the extent to which neighborhood disadvantage accounts for variation in blood pressure. Methods: Demographic, biometric, and self-reported data from 19,261 health screenings were used. Addresses of participants were geocoded and located within census block groups (n = 14,510, 75.3%). Three hierarchical linear models were…

  19. Cycle-to-cycle extraction synchronization of the Fermilab Booster for multiple batch injection to the Main Injector

    SciTech Connect

    Zwaska, R.; Kopp, S.; Pellico, W.; /Fermilab

    2005-05-01

    We report on a system to ensure cycle-to-cycle synchronization of beam extraction from the Fermilab Booster accelerator to the Main Injector. Such synchronization is necessary for multiple batch operation of the Main Injector for the Run II upgrade of anti-proton production using slip-stacking in the Main Injector, and for the NuMI (Neutrinos at the Main Injector) neutrino beam. To perform this task a system of fast measurements and feedback controls the longitudinal progress of the Booster beam throughout its acceleration period by manipulation of the transverse position maintained by the LLRF (Low-level Radio Frequency) system.

  20. Modeling systolic pressure variation due to positive pressure ventilation.

    PubMed

    Messerges, Joanne

    2006-01-01

    Although many clinical techniques have been proposed to assess blood volume none have been established as an undisputed standard practice, Volume studies suggest systolic pressure variation (SPV) as a promising volume indicator but underlying influences on SPV are not well understood. Successful modeling of SPV will reveal the major SPV influencers, guide algorithm development to accommodate these influencers, and potentially lead to a more clinically relevant interpretation of SPV values, thus improving upon current clinical methods for assessing blood volume. This study takes a first step towards identifying SPV influencers by investigating three variations of an existing pressure-flow cardiovascular model. Each successive version introduces an additional modification in attempt to model SPV under normovolemic and hypovolemic conditions, where the last model accounts for positive pressure ventilation, venous compression, and a rightward septum shift. Under normovolemic conditions, each model yields SPV values of 5.8, 6.4, and 6.7 mmHg, respectively. Under hypovolemic conditions the results do not agree with clinical findings, suggesting these three mechanisms alone do not dictate the clinical SPV response to a decrease in volume. Model results are used to suggest improvements for future work.

  1. Intraocular pressure variations: causes and clinical significance.

    PubMed

    Sit, Arthur J

    2014-12-01

    Reduction of intraocular pressure (IOP) is the only known effective treatment for glaucoma. However, IOP is a highly variable and dynamic parameter, undergoing virtually constant changes from numerous factors, including body position and circadian rhythms. Despite this variability, evidence for the efficacy of IOP reduction in glaucoma is based on studies designed to assess mean IOP and not IOP variations. Post hoc analysis of data from major clinical trials has suggested that IOP variations may be an independent risk factor for the development of glaucoma or glaucomatous progression, at least in some patients, but the evidence is incomplete and further studies are required. In the interim, judicious selection of existing therapies can help to minimize IOP variations. In general, therapies that improve outflow instead of suppressing aqueous humor production result in more stable IOP. However, new technology to allow better monitoring of IOP, ideally in a continuous 24-hour manner, is required to fully understand the role of IOP variations in glaucoma. Copyright © 2014 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved.

  2. 49 CFR 195.104 - Variations in pressure.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Variations in pressure. 195.104 Section 195.104... PIPELINE Design Requirements § 195.104 Variations in pressure. If, within a pipeline system, two or more components are to be connected at a place where one will operate at a higher pressure than another,...

  3. 49 CFR 195.104 - Variations in pressure.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Variations in pressure. 195.104 Section 195.104... PIPELINE Design Requirements § 195.104 Variations in pressure. If, within a pipeline system, two or more components are to be connected at a place where one will operate at a higher pressure than another,...

  4. 49 CFR 195.104 - Variations in pressure.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Variations in pressure. 195.104 Section 195.104... PIPELINE Design Requirements § 195.104 Variations in pressure. If, within a pipeline system, two or more components are to be connected at a place where one will operate at a higher pressure than another,...

  5. 49 CFR 195.104 - Variations in pressure.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Variations in pressure. 195.104 Section 195.104... PIPELINE Design Requirements § 195.104 Variations in pressure. If, within a pipeline system, two or more components are to be connected at a place where one will operate at a higher pressure than another,...

  6. Modeling Cyclic Variation of Intracranial Pressure

    DTIC Science & Technology

    2001-10-25

    with increasing vascular dilation induced by increasing the level of the partial pressure of carbon dioxide (PCO2) within the arterial blood ...ventilation. Simulated model recordings demonstrated that the correlation index between arterial blood pressure and ICP progressively increased... blood pressure (ABP) recording, the ICP Figure 1. Experimental Recordings of ABP and ICP during Normocapnia and Hypercapnia. a) Normocapnia with

  7. Low-temperature pressure variations in a self-clamping pressure cell

    SciTech Connect

    Thompson, J.D.

    1984-02-01

    A simple method is described that permits a consistent determination of thermally induced pressure variations in a piston-cylinder, self-clamping pressure cell at temperatures less than ambient. Significant pressure changes are found to be present even for T<75 K. It is also shown that the pressure coefficient of resistance of a manganin-wire gauge is, to within experimental uncertainty, independent of temperature over the range 0

  8. Techniques for estimating blood pressure variation using video images.

    PubMed

    Sugita, Norihiro; Obara, Kazuma; Yoshizawa, Makoto; Abe, Makoto; Tanaka, Akira; Homma, Noriyasu

    2015-01-01

    It is important to know about a sudden blood pressure change that occurs in everyday life and may pose a danger to human health. However, monitoring the blood pressure variation in daily life is difficult because a bulky and expensive sensor is needed to measure the blood pressure continuously. In this study, a new non-contact method is proposed to estimate the blood pressure variation using video images. In this method, the pulse propagation time difference or instantaneous phase difference is calculated between two pulse waves obtained from different parts of a subject's body captured by a video camera. The forehead, left cheek, and right hand are selected as regions to obtain pulse waves. Both the pulse propagation time difference and instantaneous phase difference were calculated from the video images of 20 healthy subjects performing the Valsalva maneuver. These indices are considered to have a negative correlation with the blood pressure variation because they approximate the pulse transit time obtained from a photoplethysmograph. However, the experimental results showed that the correlation coefficients between the blood pressure and the proposed indices were approximately 0.6 for the pulse wave obtained from the right hand. This result is considered to be due to the difference in the transmission depth into the skin between the green and infrared light used as light sources for the video image and conventional photoplethysmogram, respectively. In addition, the difference in the innervation of the face and hand may be related to the results.

  9. Significant practice pattern variations associated with intracranial pressure monitoring.

    PubMed

    Olson, DaiWai M; Lewis, Lisa S; Bader, Mary Kay; Bautista, Cynthia; Malloy, Rachel; Riemen, Kristina E; McNett, Molly M

    2013-08-01

    The purpose of this study was to describe nursing practice in the care of patients with intracranial pressure monitoring. Although standards for care of such patients have been established, there continue to be variations in the nursing practice. This was an observational study in which data were collected from 28 nurse-patient dyads at 16 different hospitals across the United States. Each dyad was observed for 2 hours; nursing actions and patient responses including intracranial pressure readings were documented. Differences in the care of patients with intracranial pressure monitoring were prevalent. Variations in practice were prompted by healthcare provider prescriptions as well as nursing decisions. Prescriptions and interventions were often not supported by the available scientific evidence. For more insights from the authors, see Supplemental Digital Content 1, at http://links.lww.com/JNN/A7.

  10. Modeling of patient's blood pressure variation during ambulance transportation

    NASA Astrophysics Data System (ADS)

    Sakatani, Kenji; Ono, Takahiko; Kobayasi, Yasuhide; Hikita, Shinichi; Saito, Mitsuyuki

    2007-12-01

    In an emergency transportation by ambulance, a patient is transported in a supine position. In this position, a patient's blood pressure (BP) variation depending on an inertial force which occurs when an ambulance accelerates or decelerates. This BP variation causes a critical damage for a patent with brain disorder. In order to keep a patient stable during transportation, it is required to maintain small BP variation. To analyze the BP variation during transportation, a model of the BP variation has so far been made. But, it can estimate the BP variation only in braking. The purpose of this paper is to make a dynamical model of the BP variation which can simulate it in both braking and accelerating. First, to obtain the data to construct the model, we used a tilting bed to measure a head-to-foot acceleration and BP of fingertip. Based on this data, we build a mathematical model whose input is the head-to-foot acceleration and output is the Mean BP variation. It is a switched model which switches two models depending on the jerk. We add baroreceptor reflex to the model as a offset value.

  11. Diurnal blood pressure variation and related behavioral factors.

    PubMed

    Kawano, Yuhei

    2011-03-01

    Blood pressure (BP) varies according to many internal and external factors, and behavioral factors have an important role in diurnal BP variation. BP rises sharply on waking in the morning and falls during sleep at night, although it varies throughout the day and night. These changes in BP are closely related to mental and physical activities, and the sympathetic nervous system mainly contributes to the diurnal variation in BP. Other behavioral factors, such as food consumption and obesity, dietary intake of sodium, drinking and smoking habits, consumption of coffee and tea, and bathing, also affect the diurnal variation in BP. Alterations in diurnal BP variation due to behavioral factors are frequently seen in patients with hypertension and can be classified as morning hypertension, daytime hypertension and nighttime hypertension. Appropriate lifestyle modifications may normalize or improve both the level and rhythm of BP in these patients.

  12. Time-resolved pulsed spray drop sizing at elevated pressures

    NASA Astrophysics Data System (ADS)

    Drallmeier, J. A.; Peters, J. E.

    1986-04-01

    An experimental program was conducted to measure drop sizes in pulsed sprays for diesel and fuel-injected spark ignition engine applications. A forward-scattering unit was designed with a high-speed data acquisition system to permit the measurement of drop sizes in sprays at 0.4-ms intervals. Data were taken at elevated pressures from 0.345 to 3.45 MPa with a 0-deg pintle nozzle. The Sauter Mean Diameter (SMD) and size distribution were calculated using a computational method that is independent of a predetermined distribution function. Results taken at the spray centerline indicate that for most elevated pressures, the SMD in the secondary injection region tended to increase as the pressure in the fuel line decreased and tended to increase with increasing environmental pressure, both suggesting an inverse relationship between drop size and the pressure drop across the nozzle. Also as the environmental pressure was raised, the distribution width decreased at a slower rate than the SMD increased, indicating a spreading of the drop sizes with injection time at elevated pressures. Significant cycle-to-cycle variation in both the SMD and distribution width indicate that cycle-to-cycle variations must be considered in pulsed sprays. In addition, more variation was seen between random rather than consecutive cycles.

  13. Using Advanced Tensiometers to Monitor Temporal Variations in Pore Pressure

    NASA Astrophysics Data System (ADS)

    Nichols, R. L.; Young, M. H.; Dixon, K. L.; Rossabi, J.; Hyde, W. K.; Holmes-Burns, H.

    2002-12-01

    The Savannah River Site has installed a comprehensive vadose zone monitoring system (VZMS) at it's low level radioactive waste disposal facility to collect the necessary information to calculate contaminant flux. The VZMS includes water content reflectometers, suction lysimeters, advanced tensiometers (ATs), water flux meters, access ports for neutron probes, and a tipping bucket rain gauge. Forty one ATs were installed from 1999 to 2001 at depths ranging from 2 to 60 feet and have been operated continuously. The installation depths were based on a hydrostatigraphic model developed from core logs, cone penetrometer logs, moisture content profiles, water retention curves model that were obtained during the phased installation of the VZMS. An AT consists of a porous cup installed at a prescribed depth with casing back to the surface and a pressure transducer that is lowered into the casing and connects with the porous cup. The pressure transducer transmits it's signal to a datalogger where the data is stored for future retrieval using a cellular phone communications package. Results from the 2 year operating period show that the AT calibrations are stable and t ATs are capable of extended monitoring of pore pressures in the 0 to 300 cm H2 O range. The ATs had sufficient resolution to detect the naturally occurring fluctuations in pore pressure (1 to 100 cm H2 O over 1 to 72 hours) that resulted from infiltration events at the site. The stable performance of the ATs combined with their ability to detect naturally occurring fluctuations in pore pressure make the ATs a useful tool in measuring temporal pore pressure variations for use in calibrating numerical models of fluid flow in variably saturated porous media.

  14. Pressure variation of melting temperatures of alkali halides

    NASA Astrophysics Data System (ADS)

    Arafin, Sayyadul; Singh, Ram N.

    2017-02-01

    The melting temperatures of alkali halides (LiCl, LiF, NaBr, NaCl, NaF, NaI, KBr, KCl, KF, KI, RbBr, RbCl, RbI and CsI) have been evaluated over a wide range of pressures. The solid-liquid transition of alkali halides is of considerable significance due to their huge industrial applications. Our formalism requires a priori knowledge of the bulk modulus and the Grüneisen parameter at ambient conditions to compute Tm at high pressures. The computed values are in very good agreement with the available experimental results. The formalism can satisfactorily be used to compute Tm at high pressures where the experimental data are scanty. Most of the melting curves (Tm versus P) exhibit nonlinear variation with increasing pressure having curvatures downward and exhibit a maximum in some cases like NaCl, RbBr, RbCl and RbI. The values of Tmmax and Pmax corresponding to the maxima of the curves are given.

  15. Pressure variation under the ischial tuberosity during a push cycle.

    PubMed

    Dabnichki, P; Taktak, D

    1998-06-01

    The present study is devoted to the variation of the magnitude of the compressive loading acting on the soft seating parts of a disabled person and the related pressure distribution under the ischial tuberosity during wheelchair propulsion. A combined experimental and computational approach was designed to predict correctly the change in magnitude of the maximum internal shear and compressive stresses produced by different propulsion speeds, cushion characteristics and body position of the subject. The results obtained show that the vertical force acting on the seating parts increases with the propulsion speed and exceeds the body weight by more than 100%. The related pressure under the ischial tuberosity shows a significant increase of 125% on the tissue/seat interface and an estimated increase of 185% in the peak compressive stress. It is concluded that computer modelling using a quasi-static approach provides a reliable estimate of the pressure values by the observed loading frequencies of 0-4 Hz. It can also be noted that the time independent material model utilised for the bulky soft tissue proved adequate for the estimate of the pressure level occurring under the ischial tuberosity during a push cycle.

  16. Latitudinal variation in herbivore pressure in Atlantic Coast salt marshes.

    PubMed

    Pennings, Steven C; Ho, Chuan-Kai; Salgado, Cristiano S; Wieski, Kazimierz; Davé, Nilam; Kunza, Amy E; Wason, Elizabeth L

    2009-01-01

    Despite long-standing interest in latitudinal variation in ecological patterns and processes, there is to date weak and conflicting evidence that herbivore pressure varies with latitude. We used three approaches to examine latitudinal variation in herbivore pressure in Atlantic Coast salt marshes, focusing on five abundant plant taxa: the grass Spartina alterniflora, the congeneric rushes Juncus gerardii and J. roemerianus, the forb Solidago sempervirens, and the shrubs Iva frutescens and Baccharis halimifolia. Herbivore counts indicated that chewing and gall-making herbivores were typically > or = 10 times more abundant at low-latitude sites than at high-latitude sites, but sucking herbivores did not show a clear pattern. For two herbivore taxa (snails and tettigoniid grasshoppers), correctly interpreting latitudinal patterns required an understanding of the feeding ecology of the species, because the species common at high latitudes did not feed heavily on plant leaves whereas the related species common at low latitudes did. Damage to plants from chewing herbivores was 2-10 times greater at low-latitude sites than at high-latitude sites. Damage to transplanted "phytometer" plants was 100 times greater for plants transplanted to low- than to high-latitude sites, and two to three times greater for plants originating from high- vs. low-latitude sites. Taken together, these results provide compelling evidence that pressure from chewing and gall-making herbivores is greater at low vs. high latitudes in Atlantic Coast salt marshes. Sucking herbivores do not show this pattern and deserve greater study. Selective pressure due to greater herbivore damage at low latitudes is likely to partially explain documented patterns of low plant palatability to chewing herbivores and greater plant defenses at low latitudes, but other factors may also play a role in mediating these geographic patterns.

  17. Analysis of Pressure Variations in a Low-Pressure Nickel-Hydrogen Battery - Part 1.

    PubMed

    Purushothaman, B K; Wainright, J S

    2012-05-15

    A low pressure nickel-hydrogen battery using either a metal hydride or gaseous hydrogen for H(2) storage has been developed for use in implantable neuroprosthetic devices. In this paper, pressure variations inside the cell for the gaseous hydrogen version are analyzed and correlated with oxygen evolution side reaction at the end of charging, the recombination of oxygen with hydrogen during charging and a subsequent rest period, and the self-discharge of the nickel electrode. About 70% of the recombination occurred simultaneously with oxygen evolution during charging and the remaining oxygen recombined with hydrogen during the 1(st) hour after charging. Self-discharge of the cell varies linearly with hydrogen pressure at a given state of charge and increased with increasing battery charge levels. The coulometric efficiency calculated based on analysis of the pressure-time data agreed well with the efficiency calculated based on the current-time data. Pressure variations in the battery are simulated accurately to predict coulometric efficiency and the state of charge of the cell, factors of extreme importance for a battery intended for implantation within the human body.

  18. Validity of Pulse Pressure Variation (PPV) Compared with Stroke Volume Variation (SVV) in Predicting Fluid Responsiveness

    PubMed Central

    Rathore, Abhishek; Singh, Shalendra; Lamsal, Ritesh; Taank, Priya; Paul, Debashish

    2017-01-01

    Objective Static monitors for assessing the fluid status during major surgeries and in critically ill patients have been gradually replaced by more accurate dynamic monitors in modern-day anaesthesia practice. Pulse pressure variation (PPV) and systolic pressure variation (SPV) are the two commonly used dynamic indices for assessing fluid responsiveness. Methods In this prospective observational study, 50 patients undergoing major surgeries were monitored for PPV and SPV: after the induction of anaesthesia and after the administration of 500 mL of isotonic crystalloid bolus. Following the fluid bolus, patients with a cardiac output increase of more than 15% were classified as responders and those with an increase of less than 15% were classified as non-responders. Results There were no significant differences in the heart rate (HR), mean arterial pressure (MAP), PPV, SVV, central venous pressure (CVP) and cardiac index (CI) between responders and non-responders. Before fluid bolus, the stroke volume was significantly lower in responders (p=0.030). After fluid bolus, MAP was significantly higher in responders but there were no significant changes in HR, CVP, CI, PPV and SVV. In both responders and non-responders, PPV strongly correlated with SVV before and after fluid bolus. Conclusion Both PPV and SVV are useful to predict cardiac response to fluid loading. In both responders and non-responders, PPV has a greater association with fluid responsiveness than SVV. PMID:28868168

  19. Indicator system provides complete data of engine cylinder pressure variation

    NASA Technical Reports Server (NTRS)

    Mc Jones, R. W.; Morgan, N. E.

    1966-01-01

    Varying reference pressure used together with a balanced pressure pickup /a diaphragm switch/ to switch the electric output of the pressure transducer in a reference pressure line obtains precise engine cylinder pressure data from a high speed internal combustion engine.

  20. Predictions of the cycle-to-cycle aerodynamic loads on a yawed wind turbine blade under stalled conditions using a 3D empirical stochastic model

    NASA Astrophysics Data System (ADS)

    ELGAMMI, MOUTAZ; SANT, TONIO

    2016-09-01

    This paper investigates a new approach to model the stochastic variations in the aerodynamic loads on yawed wind turbines experienced at high angles of attack. The method applies the one-dimensional Langevin equation in conjunction with known mean and standard deviation values for the lift and drag data. The method is validated using the experimental data from the NREL Phase VI rotor in which the mean and standard deviation values for the lift and drag are derived through the combined use of blade pressure measurements and a free-wake vortex model. Given that direct blade pressure measurements are used, 3D flow effects arising from the co-existence of dynamic stall and stall delay are taken into account. The model is an important step towards verification of several assumptions characterized as the estimated standard deviation, Gaussian white noise of the data and the estimated drift and diffusion coefficients of the Langevin equation. The results using the proposed assumptions lead to a good agreement with measurements over a wide range of operating conditions. This provides motivation to implement a general fully independent theoretical stochastic model within a rotor aerodynamics model, such as the free-wake vortex or blade-element momentum code, whereby the mean lift and drag coefficients can be estimated using 2D aerofoil data with correction models for 3D dynamic stall and stall delay phenomena, while the corresponding standard derivations are estimated through CFD.

  1. Ocean bottom pressure variation associated with path variations of the Kuroshio south of Japan

    NASA Astrophysics Data System (ADS)

    Nagano, Akira; Hasegawa, Takuya; Matsumoto, Hiroyuki; Ariyoshi, Keisuke

    2016-04-01

    The Kuroshio south of Japan takes a stable southward meandering path, called the large meander (LM), on interannual to decadal timescales. During the non-LM period, mesoscale disturbances of the Kuroshio path, called small meanders, occasionally occur in the region southeast of Kyushu and propagate eastward. Some of them develop to the LM, possibly associated with deep eddies. In order to reveal the relationship between the development of path disturbances and bottom current (or hydrostatic pressure), we examined variations of ocean bottom pressure obtained by pressure sensors deployed in the region off Shikoku (capes Ashizuri and Muroto). Bottom pressure on the continental slope is found to increase abruptly lagging a few months behind an elevation of sea surface height (SSH) due to the formation of the LM in July 2014. Geopotential distance from the sea surface to 2000 dbar based on hydrographic data at the Affiliated Surveys of the Kuroshio off Cape Ashizuri (ASUKA) line abruptly increases from early to late July. The reduction of density stratification, i.e., the weakened baroclinicity, causes the temporal delay of the increase of bottom pressure relative to the elevation of SSH associated with the formation of the LM.

  2. Ice-Shelf Tidal Flexure and Subglacial Pressure Variations

    NASA Technical Reports Server (NTRS)

    Walker, Ryan T.; Parizek, Byron R.; Alley, Richard B.; Anandakrishnan, Sridhar; Riverman, Kiya L.; Christianson, Knut

    2013-01-01

    We develop a model of an ice shelf-ice stream system as a viscoelastic beam partially supported by an elastic foundation. When bed rock near the grounding line acts as a fulcrum, leverage from the ice shelf dropping at low tide can cause significant (approx 1 cm) uplift in the first few kilometers of grounded ice.This uplift and the corresponding depression at high tide lead to basal pressure variations of sufficient magnitude to influence subglacial hydrology.Tidal flexure may thus affect basal lubrication, sediment flow, and till strength, all of which are significant factors in ice-stream dynamics and grounding-line stability. Under certain circumstances, our results suggest the possibility of seawater being drawn into the subglacial water system. The presence of sea water beneath grounded ice would significantly change the radar reflectivity of the grounding zone and complicate the interpretation of grounded versus floating ice based on ice-penetrating radar observations.

  3. Micrometoric Impact Effects: Peak Pressure versus Spectral Variation

    NASA Technical Reports Server (NTRS)

    Jensen, Elizabeth; Lederer, S. M.; Wooden, D. H.; Lindsay, S. S.; Keller, L. P.; Cintala, M. J.; Zolensky, M. E.

    2013-01-01

    At the Experimental Impact Laboratory at NASA Johnson Space Center, we have investigated the surface properties of asteroids caused by collisions in the mid-infrared (2.5 to 16 microns) by impacting forsterite and enstatite across a range of velocities (as predicted by the Nice Model) and at varying temperatures. The crystal structure in these minerals can be deformed by the shock wave from the impact as well as sheared into smaller particle sizes. Our current focus is on the differing effects between 2.3 and 2.6 km/sec, as well as the differences between a cold sample at -20C and a room temperature sample at 25C. We find that the spectral variation and crystal deformation varies non-linearly with the peak shock pressure.

  4. Pluto's insolation history: Latitudinal variations and effects on atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Earle, Alissa M.; Binzel, Richard P.

    2015-04-01

    Since previous long-term insolation modeling in the early 1990s, new atmospheric pressure data, increased computational power, and the upcoming flyby of the Pluto system by NASA's New Horizons spacecraft have generated new motivation and increased capabilities for the study of Pluto's complex long-term (million-years) insolation history. The two primary topics of interest in studying Pluto's insolation history are the variations in insolation patterns when integrated over different intervals and the evolution of diurnal insolation patterns over the last several decades. We find latitudinal dichotomies when comparing average insolation over timescales of days, decades, centuries, and millennia, where all timescales we consider are short relative to the predicted timescales for Pluto's chaotic orbit. Depending on the timescales of volatile migration, some consequences of these insolation patterns may be manifested in the surface features revealed by New Horizons. We find the Maximum Diurnal Insolation (MDI) at any latitude is driven most strongly when Pluto's obliquity creates a long arctic summer (or "midnight sun") beginning just after perihelion. Pluto's atmospheric pressure, as measured through stellar occultation observations during the past three decades, shows a circumstantial correlation with this midnight sun scenario as quantified by the MDI parameter.

  5. Relationship between activity levels and circadian blood pressure variations.

    PubMed

    Kohno, I; Ishii, H; Nakamura, T; Tamura, K

    1993-01-01

    In 17 healthy Japanese students (14 males and 3 females) an ambulatory activity level monitoring instrument (Actigraph) was attached to the wrist for 48-hour measurement of wrist movement (with 0.01G or higher acceleration). At the same time, an ambulatory blood pressure monitoring apparatus was attached to these subjects to monitor blood pressure (BP) and heart rate (HR) every 30 minutes. Sleeping hours were calculated from the activity levels. The sleeping hours obtained by the Actigraph correlated with those judged from the diary. The correlation was better for the go-to-sleep time than for the awakening time. Activity level, HR and BP showed a similar circadian variation. Activity level differed significantly between the active daytime (4500 counts/hour) and during sleep at night (720 counts/hour). The acrophase of activity level, obtained by the cosinor method, was 235 degrees which did not significantly differ from that of BP and HR. Hourly activity levels correlated with HR and BP at corresponding hours. These results suggest that BP is affected by activity levels even if this rhythm continues to recur in bedrest.

  6. Automatic algorithm for monitoring systolic pressure variation and difference in pulse pressure.

    PubMed

    Pestel, Gunther; Fukui, Kimiko; Hartwich, Volker; Schumacher, Peter M; Vogt, Andreas; Hiltebrand, Luzius B; Kurz, Andrea; Fujita, Yoshihisa; Inderbitzin, Daniel; Leibundgut, Daniel

    2009-06-01

    Difference in pulse pressure (dPP) reliably predicts fluid responsiveness in patients. We have developed a respiratory variation (RV) monitoring device (RV monitor), which continuously records both airway pressure and arterial blood pressure (ABP). We compared the RV monitor measurements with manual dPP measurements. ABP and airway pressure (PAW) from 24 patients were recorded. Data were fed to the RV monitor to calculate dPP and systolic pressure variation in two different ways: (a) considering both ABP and PAW (RV algorithm) and (b) ABP only (RV(slim) algorithm). Additionally, ABP and PAW were recorded intraoperatively in 10-min intervals for later calculation of dPP by manual assessment. Interobserver variability was determined. Manual dPP assessments were used for comparison with automated measurements. To estimate the importance of the PAW signal, RV(slim) measurements were compared with RV measurements. For the 24 patients, 174 measurements (6-10 per patient) were recorded. Six observers assessed dPP manually in the first 8 patients (10-min interval, 53 measurements); no interobserver variability occurred using a computer-assisted method. Bland-Altman analysis showed acceptable bias and limits of agreement of the 2 automated methods compared with the manual method (RV: -0.33% +/- 8.72% and RV(slim): -1.74% +/- 7.97%). The difference between RV measurements and RV(slim) measurements is small (bias -1.05%, limits of agreement 5.67%). Measurements of the automated device are comparable with measurements obtained by human observers, who use a computer-assisted method. The importance of the PAW signal is questionable.

  7. Pressure variations in the Monte Rosa nappe, Western Alps

    NASA Astrophysics Data System (ADS)

    Luisier, Cindy; Vaughan-Hammon, Joshua; Baumgartner, Lukas; Schmalholz, Stefan

    2017-04-01

    internally consistent thermodynamic database on whiteschists result in a minimum P of 2.2 GPa at T of 550 to 570˚C and a water activity close to 1, unlike previous water activities proposed (Le Bayon et al., 2006). Peak alpine pressures and temperatures calculated for the metagranite and associated whiteschists hence result in significant different pressure estimates, corroborating previous results from the literature. The possible explanations for such pressure variations are i) slight underestimation of the metagranite peak pressure, due to water-undersaturation conditions, however a pressure as high as 2 GPa is unlikely, or ii) heterogeneous stress conditions, due to rheologically contrasting lithologies, consisting of weak whiteschist inclusions within strong, undeformed metagranites. References Le Bayon et al., 2006: Contrib. Mineral. Petrol. 151, 395-412 Luisier et al., 2015: GSA conference abstract Massonne and Schreyer, 1987: Contrib. Mineral. Petrol. 96, 212-224 Pawlig, S. 2001: PhD thesis, University of Mainz (Germany) Pawlig and Baumgartner, 2001: SMPM 81,329-346

  8. Pluto's Insolation History: Latitudinal Variations and Effects on Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Earle, Alissa M.; Binzel, Richard P.

    2014-11-01

    Since previous insolation modeling in the early 1990’s, new atmospheric pressure data, increased computational power, and the upcoming flyby of the Pluto system by NASA’s New Horizons spacecraft have generated new motivation and increased capabilities for the study of Pluto’s complex long-term (million-years) insolation history. The two primary topics of interest in studying Pluto’s insolation history are the variations in insolation patterns when integrated over different intervals and the evolution of diurnal insolation patterns over the last several decades. We find latitudinal dichotomies when comparing average insolation over timescales of days, decades, centuries, and millennia. Depending on the timescales of volatile migration, some consequences of these insolation patterns may be manifested in the surface features revealed by New Horizons. For any single rotation of Pluto there is a latitude that receives more insolation relative to the others. Often this is the sub-subsolar latitude but it can also be an arctic circle latitude when near-polar regions of Pluto experience the "midnight sun". We define the amount of that greatest insolation value over the course of one rotation as the "maximum diurnal insolation" (MDI). We find that MDI is driven to its highest values when Pluto’s obliquity creates a long arctic summer (or “midnight sun”) beginning just after perihelion. Pluto’s atmospheric pressure, as measured through stellar occultation observations during the past three decades, appears to correlate with Pluto's currently occurring midnight sun as quantified by the MDI parameter. If insolation (as parameterized by the MDI value) is the single dominant factor driving Pluto's atmospheric pressure, this “Midnight Sun Model” predicts that Pluto's maximum atmospheric pressure will be reached in 2017 followed by a steady decline. Pluto's maximum diurnal insolation value begins dropping after 2017 due to two factors: Pluto’s sub-solar point

  9. Pulse pressure variation and stroke volume variation under different inhaled concentrations of isoflurane, sevoflurane and desflurane in pigs undergoing hemorrhage

    PubMed Central

    Oshiro, Alexandre Hideaki; Otsuki, Denise Aya; Hamaji, Marcelo Waldir M; Rosa, Kaleizu T; Ida, Keila Kazue; Fantoni, Denise T; Auler, José Otavio Costa

    2015-01-01

    OBJECTIVES: Inhalant anesthesia induces dose-dependent cardiovascular depression, but whether fluid responsiveness is differentially influenced by the inhalant agent and plasma volemia remains unknown. The aim of this study was to compare the effects of isoflurane, sevoflurane and desflurane on pulse pressure variation and stroke volume variation in pigs undergoing hemorrhage. METHODS: Twenty-five pigs were randomly anesthetized with isoflurane, sevoflurane or desflurane. Hemodynamic and echocardiographic data were registered sequentially at minimum alveolar concentrations of 1.00 (M1), 1.25 (M2), and 1.00 (M3). Then, following withdrawal of 30% of the estimated blood volume, these data were registered at a minimum alveolar concentrations of 1.00 (M4) and 1.25 (M5). RESULTS: The minimum alveolar concentration increase from 1.00 to 1.25 (M2) decreased the cardiac index and increased the central venous pressure, but only modest changes in mean arterial pressure, pulse pressure variation and stroke volume variation were observed in all groups from M1 to M2. A significant decrease in mean arterial pressure was only observed with desflurane. Following blood loss (M4), pulse pressure variation, stroke volume variation and central venous pressure increased (p<0.001) and mean arterial pressure decreased in all groups. Under hypovolemia, the cardiac index decreased with the increase of anesthesia depth in a similar manner in all groups. CONCLUSION: The effects of desflurane, sevoflurane and isoflurane on pulse pressure variation and stroke volume variation were not different during normovolemia or hypovolemia. PMID:26735220

  10. Integrating environmental variation, predation pressure, phenotypic plasticity and locomotor performance.

    PubMed

    Fu, Shi-Jian; Cao, Zhen-Dong; Yan, Guan-Jie; Fu, Cheng; Pang, Xu

    2013-10-01

    The Wujiang River, a tributary of the Three Gorges Reservoir, has many dams along its length. These dams alter the river's natural habitat and produce various flow regimes and degrees of predator stress. To test whether the swimming performance and external body shape of pale chub (Zacco platypus) have changed as a result of alterations in the flow regime and predator conditions, we measured the steady (U(crit)) and unsteady (fast-start) swimming performances and morphological characteristics of fish collected from different sites along the Wujiang River. We also calculated the maximum respiratory capacity and cost of transport (COT). We demonstrated significant differences in swimming performance and morphological traits among the sampling sites. Steady swimming performance was positively correlated with water velocity and negatively correlated with the abundance of predators, whereas unsteady swimming performance was negatively correlated with water velocity. The body shape was significantly correlated with both swimming performance and ecological parameters. These findings suggested that selection pressure on swimming performance results in a higher U(crit) and a more streamlined body shape in fast-flow and (or) in habitats with low predator stress and subsequently results in a lower COT. These characteristics were accompanied by a poorer fast-start performance than that of the fish from the slow-flow and (or) high-predator habitats. The divergence in U(crit) may also be due in part to variation in respiratory capacity.

  11. Repeat variation of electrocardiogram, blood pressure, and blood cholesterol within one hour and six months1

    PubMed Central

    Simonson, Ernst; Keys, Ancel

    1970-01-01

    The intraindividual repeat variation of the conventional 12-lead electrocardiogram, of blood pressure, and of blood cholesterol was determined in 27 middle-aged healthy men with an interval of one hour and six months. In 7 of 17 analysed electrocardiographic items the variation within six months was significantly greater than that within one hour; in 10 items, the variation was not significantly different. Blood pressure varied as much within one hour as within six months, while the intraindividual variation of serum cholesterol was significantly greater for the six-month period. The intraindividual variation, expressed as the coefficient of variation, was greater for the electrocardiogram than for either blood pressure or cholesterol. There were large differences between various electrocardiographic items in the repeat variation. There was high intraclass correlation of most items analysed, but no significant covariation between electrocardiographic item vs. blood pressure or cholesterol. PMID:5470047

  12. Observation of pressure variation in the cavitation region of submerged journal bearings

    NASA Technical Reports Server (NTRS)

    Etsion, I.; Ludwig, L. P.

    1980-01-01

    Visual observations and pressure measurements in the cavitation zone of a submerged journal bearing are described. Tests were performed at various shaft speeds and ambient pressure levels. Some photographs of the cavitation region are presented showing strong reverse flow at the downstream end of the region. Pressure profiles are presented showing significant pressure variations inside the cavitation zone, contrary to common assumptions of constant cavitation pressure.

  13. Antihypertensive treatments obscure familial contributions to blood pressure variation.

    PubMed

    Cui, Jisheng S; Hopper, John L; Harrap, Stephen B

    2003-02-01

    The linkage and association between inherent blood pressure and underlying genotype is potentially confounded by antihypertensive treatment. We estimated blood pressure variance components (genetic, shared environmental, individual-specific) in 767 adult volunteer families by using a variety of approaches to adjusting blood pressure of the 244 subjects (8.2%) receiving antihypertensive medications. The additive genetic component of variance for systolic pressure was 73.9 mm Hg(2) (SE, 8.8) when measured pressures (adjusted for age by gender within each generation) were used but fell to 61.4 mm Hg(2) (SE, 8.0) when treated subjects were excluded. When the relevant 95th percentile values were substituted for treated systolic pressures, the additive genetic component was 81.9 mm Hg(2) (SE, 9.5), but individual adjustments in systolic pressure ranged from -53.5 mm Hg to +64.5 mm Hg (mean, +17.2 mm Hg). Instead, when 10 mm Hg was added to treated systolic pressure, the additive genetic component rose to 86.6 mm Hg(2) (SE, 10.1). Similar changes were seen in the shared environment component of variance for systolic pressure and for the combined genetic and shared environmental (ie, familial) components of diastolic pressure. There was little change in the individual-specific variance component across any of the methods. Therefore, treated subjects contribute important information to the familial components of blood pressure variance. This information is lost if treated subjects are excluded and obscured by treatment effects if unadjusted measured pressures are used. Adding back an appropriate increment of pressure restores familial components, more closely reflects the pretreatment values, and should increase the power of genomic linkage and linkage disequilibrium analyses.

  14. Black tea lowers the rate of blood pressure variation: a randomized controlled trial.

    PubMed

    Hodgson, Jonathan M; Croft, Kevin D; Woodman, Richard J; Puddey, Ian B; Fuchs, Dagmar; Draijer, Richard; Lukoshkova, Elena; Head, Geoffrey A

    2013-05-01

    Measures of blood pressure variation have been associated with cardiovascular disease and related outcomes. The regular consumption of black tea can lower blood pressure, but its effects on blood pressure variation have yet to be investigated. We aimed to assess the effects of black tea consumption on the rate of ambulatory blood pressure variation. Men and women (n = 111) with systolic blood pressure between 115 and 150 mm Hg at screening were recruited in a randomized, controlled, double-blind, 6-mo parallel-designed trial designed primarily to assess effects on blood pressure. Participants consumed 3 cups/d of either powdered black tea solids (tea) or a flavonoid-free caffeine-matched beverage (control). The 24-h ambulatory blood pressure level and rate of measurement-to-measurement blood pressure variation were assessed at baseline, day 1, and 3 and 6 mo. Across the 3 time points, tea, compared with the control, resulted in lower rates of systolic (P = 0.0045) and diastolic (P = 0.016) blood pressure variation by ~10% during nighttime (2200-0600). These effects, which were immediate at day 1 and sustained over 6 mo, were independent of the level of blood pressure and heart rate. The rate of blood pressure variation was not significantly altered during daytime (0800-2000). These findings indicate that a component of black tea solids, other than caffeine, can influence the rate of blood pressure variation during nighttime. Thus, small dietary changes have the potential to significantly influence the rate of blood pressure variation. This trial was registered at the Australian New Zealand Clinical Trials Registry as ACTR12607000543482.

  15. Variation of Azeotropic Composition and Temperature with Pressure

    ERIC Educational Resources Information Center

    Gibbard, H. Frank; Emptage, Michael R.

    1975-01-01

    Describes an undergraduate physical chemistry experiment in which an azeotropic mixture is studied using the vapor pressures of the components as functions of temperature and the azeotropic composition and temperature at one pressure. Discusses in detail the mathematical treatment of obtained thermodynamic data. (MLH)

  16. Country variations in family members' informal pressure to drink less.

    PubMed

    Holmila, Marja; Raitasalo, Kirsimarja; Knibbe, Ronald; Selin, Klara

    2009-04-01

    The paper examines how family members in 18 countries attempt to influence each other to drink less. Data come from the GENACIS (Gender, Alcohol and Culture: an International Study) dataset. Countries included were Argentina, Costa Rica, Czech Republic, Denmark, Finland, Germany, Hungary, Iceland, India, Japan, Nigeria, Norway, Spain, Sri Lanka, Sweden, Uganda, UK and Uruguay (overall sample 44,115). In each country, the percentage of people who had experienced family member pressure to drink less were compared to country abstinence rate, mean drinking volume per drinker and other societal-level factors. While countries differed greatly on proportion of drinkers having experienced family members' pressure to drink less, in all countries drinking women reported less pressure than drinking men in their own society. In all studied countries, informal pressure was exerted most often by the spouse or sexual partner. However, other family members were also involved. Informal pressure was found to be highly correlated with the country's socioeconomic conditions. Informal pressure to drink less by family members is on one hand an expression of social and family problems, caused by heavy drinking, especially in the economically less developed countries, suggesting alcohol-related deprivation. On the other hand, similar gender differences were seen in all the societies, men reporting receiving more informal pressure than women. Thus, informal pressure to drink less tended to reflect the gender conflict caused by heavy use of alcohol by men.

  17. Country variations in family members' informal pressure to drink less

    PubMed Central

    Holmila, Marja; Raitasalo, Kirsimarja; Knibbe, Ronald; Selin, Klara

    2009-01-01

    The paper examines how family members in 18 countries attempt to influence each other to drink less. Data come from the GENACIS (Gender, Alcohol and Culture: an International Study) dataset. Countries included were Argentina, Costa Rica, Czech Republic, Denmark, Finland, Germany, Hungary, Iceland, India, Japan, Nigeria, Norway, Spain, Sri Lanka, Sweden, Uganda, UK and Uruguay (overall sample 44,115). In each country, the percentage of people who had experienced family member pressure to drink less were compared to country abstinence rate, mean drinking volume per drinker and other societal-level factors. While countries differed greatly on proportion of drinkers having experienced family members' pressure to drink less, in all countries drinking women reported less pressure than drinking men in their own society. In all studied countries, informal pressure was exerted most often by the spouse or sexual partner. However, other family members were also involved. Informal pressure was found to be highly correlated with the country's socioeconomic conditions. Informal pressure to drink less by family members is on one hand an expression of social and family problems, caused by heavy drinking, especially in the economically less developed countries, suggesting alcohol-related deprivation. On the other hand, similar gender differences were seen in all the societies, men reporting receiving more informal pressure than women. Thus, informal pressure to drink less tended to reflect the gender conflict caused by heavy use of alcohol by men. PMID:20084178

  18. Pressure variation of reentrant transition temperature in liquid crystals

    NASA Astrophysics Data System (ADS)

    Srivastava, A.; Sa, D.; Singh, S.

    2007-02-01

    High pressure experimental studies show that in certain mesogenic materials, the nematic-smectic A (N-Sm A) transition temperature TAN exhibits nonlinear pressure dependence. As a consequence, the material shows reentrant phenomena that is a phase sequence nematic — smectic A — reentrant nematic appears. The characteristic features of this phenomenon have been addressed here within the framework of Landau-de-Gennes theory, where the coupling between nematic and smectic A order parameters (γ, λeff) plays an important role. The cubic coupling γ is chosen to be negative in order to form Sm A phase whereas the biquadratic coupling λeff is made large and positive to obtain reentrant behaviour. In the present work, we incorporate the pressure dependence in the theory through γ and λeff which justifies the experimental pressure dependence in the reentrant transition temperature tilde{T}REAN. The pressure dependence of γ and λeff are employed in the calculation of excess specific heat capacity near the reentrant transition. The computed heat capacity shows strong pressure dependence near the reentrant transition which can be confirmed from high pressure measurement.

  19. Variation of plantar pressure in Chinese diabetes mellitus.

    PubMed

    Yang, Chuan; Xiao, Huisheng; Wang, Chuan; Mai, LiFang; Liu, Dan; Qi, Yiqing; Ren, Meng; Yan, Li

    2015-01-01

    To investigate dynamic changes in plantar pressure in Chinese diabetes mellitus patients and to provide a basis for further preventing diabetic foot. This is a cross-sectional investigation including 649 Chinese diabetes mellitus patients (diabetes group) and 808 "normal" Chinese persons (nondiabetes group) with normal blood glucose levels. All the subjects provided a complete medical history and underwent a physical examination and a 75-g oral glucose tolerance test. All subjects walked barefoot with their usual gait, and their dynamic plantar forces were measured using the one-step method with a plantar pressure measurement instrument; 5 measurements were performed for each foot. No significant differences were found in age, height, body weight, or body mass index between the two groups. The fasting blood glucose levels, plantar contact time, maximum force, pressure-time integrals and force-time integrals in the diabetes group were significantly higher than those in the nondiabetes group (p < 0.05). However, the maximum pressure was significantly higher in the nondiabetes group than in the diabetes group (p < 0.05). No difference was found in the contact areas between the two groups (p > 0.05). The maximum plantar force distributions were essentially the same, with the highest force found for the medial heel, followed by the medial forefoot and the first toe. The peak plantar pressure was located at the medial forefoot for the nondiabetes group and at the hallucis for the diabetes group. In the diabetes group, the momentum in each plantar region was higher than that in the nondiabetes group; this difference was especially apparent in the heel, the lateral forefoot and the hallucis. The dynamic plantar pressures in diabetic patients differ from those in nondiabetic people with increased maximum force and pressure, a different distribution pattern and significantly increased momentum, which may lead to the formation of foot ulcers.

  20. Variation of Pressure Waveforms in Measurements of Extracorporeal Shock Wave Lithotripter

    NASA Astrophysics Data System (ADS)

    Inose, Naoto; Ide, Masao

    1993-05-01

    In this paper, we describe measurement of variation in pressure waveforms of the acoustic field of an extra-corporeal shock-wave lithotripter (ESWL). Variations in the measured acoustic fields and pressure waveform of an underwater spark-gap-type ESWL with an exhausted spark plug electrode have been reported by researchers using crystal sensors. If the ESWL spark plugs become exhausted, patients feel pain during kidney, biliary stone disintegration. We studied the relationship between exhaustion of electrodes and the variation of pressure waveforms and shock-wave fields of the ESWL using a newly developed hydrophone.

  1. Development of a Pressure Sensitive Paint System with Correction for Temperature Variation

    NASA Technical Reports Server (NTRS)

    Simmons, Kantis A.

    1995-01-01

    Pressure Sensitive Paint (PSP) is known to provide a global image of pressure over a model surface. However, improvements in its accuracy and reliability are needed. Several factors contribute to the inaccuracy of PSP. One major factor is that luminescence is temperature dependent. To correct the luminescence of the pressure sensing component for changes in temperature, a temperature sensitive luminophore incorporated in the paint allows the user to measure both pressure and temperature simultaneously on the surface of a model. Magnesium Octaethylporphine (MgOEP) was used as a temperature sensing luminophore, with the pressure sensing luminophore, Platinum Octaethylporphine (PtOEP), to correct for temperature variations in model surface pressure measurements.

  2. Spectrum effects of subglottal pressure variation in professional baritone singers

    NASA Astrophysics Data System (ADS)

    Sjölander, Peta; Sundberg, Johan

    2004-03-01

    The audio signal from five professional baritones was analyzed by means of spectrum analysis. Each subject sang syllables [pæ] and [pa] from loudest to softest phonation at fundamental frequencies representing 25%, 50%, and 75% of his total range. Ten subglottal pressures, equidistantly spaced between highest and lowest, were selected for analysis along with the corresponding production of the vowels. The levels of the first formant and singer's formant were measured as a function of subglottal pressure. Averaged across subjects, vowels, and F0, a 10-dB increase at 600 Hz was accompanied by a 16-dB increase at 3 kHz.

  3. Variation of Fracturing Pressures with Depth Near the Valles Caldera

    SciTech Connect

    Dash, Zora; Murphy, Hugh

    1983-12-15

    Hydraulic Fracturing at the Fenton Hill Hot Dry Rock Geothermal site near the Valles Caldera has yielded fracturing pressures from 14 to 81 MPa (2030 to 11,750 psi) at depths ranging from 0.7 to 4.4 km (2250 to 14,400 ft). This data can be fit to a fracture gradient of 19 MPa/km (0.84 psi/ft), except for an anomalous region between 2.6 to 3.2 km where fracturing pressures are about 20 MPa lower than estiamted using the above gradient. This anomaly coincides with a biotite granodiorite intrusive emplaced into a heterogeneous jointed metamorphic complex comprised of gneisses, schists and metavolcanic rocks. Microseismic events detected with sensitive downhole geophones suggest that shear failure is an important process during hydraulic fracturing of such jointed rock. Consequently the usual relation between minimum earth stress and fracture opening pressure, based upon classic tensile failure, cannot be used apriori; fracture opening pressure is instead a complex function of joint orientation and all three components of principal earth stress.

  4. Elk and mule deer responses to variation in hunting pressure.

    Treesearch

    Bruce K. Johnson; Alan A. Ager; James H. Noyes; Norm. Cimon

    2004-01-01

    Hunting can exert a variety of effects on both targeted and nontargeted ungulates, and animals either run or hide in response to hunting pressure. If animals successfully elude hunters by running, the energetic cost may deplete fat reserves needed for survival during winter in temperate regions. If animals successfully elude hunters by hiding, there may be an energetic...

  5. Day-Night Variations in Malate Concentration, Osmotic Pressure, and Hydrostatic Pressure in Cereus validus1

    PubMed Central

    Lüttge, Ulrich; Nobel, Park S.

    1984-01-01

    Malate concentration and stem osmotic pressure concomitantly increase during nighttime CO2 fixation and then decrease during the daytime in the obligate Crassulacean acid metabolism (CAM) plant, Cereus validus (Cactaceae). Changes in malate osmotic pressure calculated using the Van't Hoff relation match the changes in stem osmotic pressure, indicating that changes in malate level affected the water relations of the succulent stems. In contrast to stem osmotic pressure, stem water potential showed little day-night changes, suggesting that changes in cellular hydrostatic pressure occurred. This was corroborated by direct measurements of hydrostatic pressure using the Jülich pressure probe where a small oil-filled micropipette is inserted directly into chlorenchyma cells, which indicated a 4-fold increase in hydrostatic pressure from dusk to dawn. A transient increase of hydrostatic pressure at the beginning of the dark period was correlated with a short period of stomatal closing between afternoon and nighttime CO2 fixation, suggesting that the rather complex hydrostatic pressure patterns could be explained by an interplay between the effects of transpiration and malate levels. A second CAM plant, Agave deserti, showed similar day-night changes in hydrostatic pressure in its succulent leaves. It is concluded that, in addition to the inverted stomatal rhythm, the oscillations of malate markedly affect osmotic pressures and hence water relations of CAM plants. PMID:16663708

  6. Understanding Blood Pressure Variation and Variability: Biological Importance and Clinical Significance.

    PubMed

    James, Gary D

    2017-01-01

    Variability is a normative property of blood pressure necessary for survival which likely contributes to morbidity and mortality through allostatic load. Because of its allostatic and adaptive properties blood pressure responses to peculiar situations like the visit to the clinic can lead to the misdiagnosis of hypertension. Cuff methods of blood pressure measurement can also create blood pressure variation when there really is none. There are also physiological differences between populations related to their evolutionary history that likely further affect the extent of population differences in 24-h blood pressure variability. Quantifying the sources and extent of blood pressure variability can be done using natural experimental models and through the evaluation of ecological momentary data. It is very likely that the results of population studies of blood pressure variability and morbidity and mortality risk are inconclusive because the parameters used to assess blood pressure variability do not reflect the actual nature of blood pressure allostasis.

  7. Pressure Variations in Metamorphic Rocks: Implications for the Interpretation of Petrographic Observations

    NASA Astrophysics Data System (ADS)

    Tajčmanová, Lucie

    2014-05-01

    Metamorphic petrologists and structural geologists, using direct measurements, bring the only direct observational constrains for validating geodynamic models. Therefore, petrological and structural geological observations are essential for the quality and reproducibility of geodynamic reconstructions and models. One of the important assumptions for geodynamic reconstructions arises from the pressure and temperature estimates in the petrology analysis. Pressure is commonly converted to depth through the equation for lithostatic pressure and so the original position of the rock sample within the Earth's interior can be constrained. The current assumption that the studied sample corresponds to uniform pressure may not be correct, and if so, it has serious implications. Increasing evidence from analytical data shows that pressure is not constant even on a grain scale, posing new challenges because, if ignored, it leads to an incorrect use of petrology data in constraining geodynamic models. Well known examples of the preservation of coesite and diamond in a host mineral like garnet show that high pressure inclusions are preserved during decompression. Tajčmanová et al. (2014) has shown that grain-scale pressure variations can develop and that these pressure variations allow compositional zoning in minerals preserved over geological time scales. A new unconventional barometric method based on equilibrium under pressure variations has been developed . Such pressure variations are also connected with differences in fluid pressure in open systems and can be thus observed at all scales. Tajčmanová L., Podladchikov Y., Powell R., Moulas E., Vrijmoed J. and Connolly J. (2014). Grain scale pressure variations and chemical equilibrium in high-grade metamorphic rocks.Journal of Metamorphic Geology, doi:10.1111/jmg.12066 This work was supported by ERC starting grant 335577 to Lucie Tajcmanova

  8. Endogamy and variation in blood pressure levels in Croatian island isolates.

    PubMed

    Narancić, N S; Rudan, I

    2001-03-01

    Blood pressure variation was investigated among populations inhabiting islands and peninsula of Middle Dalmatia, Croatia. The number of previous anthropological studies pointed to isolation and different genetic population structure in this environmentally fairly homogeneous area. Variation in blood pressure (systolic and diastolic) among the populations of the islands of Brac, Hvar, Korcula, and the Peljesac peninsula was assessed at three levels involving village populations, regional (western and eastern) populations and the entire island populations. The blood pressure data were collected from 3834 adult individuals inhabiting 37 rural communities and were adjusted for age and body mass index. Variation in blood pressure levels existed among regions and villages. Due to the history of differential settlement, small village sizes and high levels of reproductive isolation, the observed blood pressure variation could be attributed to founder effect, genetic drift and inbreeding. The involvement of genetic factors was tested by relating blood pressure variation among villages to degree of isolation among them. Blood pressure means and proportions of hypertensives increased with endogamy levels in males. In females, this effect could not be observed. However, in both sexes the highest proportions of hypertensives (more than 40%) were found in villages that are most reproductively closed (endogamy greater than 80%). These populations are considered particularly promising for further genetic epidemiological research.

  9. Variation of the pressure limits of flame propagation with tube diameter for propane-air mixtures

    NASA Technical Reports Server (NTRS)

    Belles, Frank E; Simon, Dorothy M

    1951-01-01

    An investigation was made of the variation of the pressure limits of flame propagation with tube diameter for quiescent propane with tube diameter for quiescent propane-air mixtures. Pressure limits were measured in glass tubes of six different inside diameters, with a precise apparatus. Critical diameters for flame propagation were calculated and the effect of pressure was determined. The critical diameters depended on the pressure to the -0.97 power for stoichiometric mixtures. The pressure dependence decreased with decreasing propane concentration. Critical diameters were related to quenching distance, flame speeds, and minimum ignition energy.

  10. A method to account for variation of average compressor inlet pressure during instantaneous distortion analyses

    NASA Technical Reports Server (NTRS)

    Burstadt, P. L.; Wenzel, L. M.

    1976-01-01

    A method is presented to calculate the available surge margin as a function of time and incorporate it into an instantaneous distortion analysis. Results show that inlet pressure variations which cause only a small change at the compressor exit can cause a significant variation in the available surge margin.

  11. Blood pressure measurement under standardized indoor condition may mask seasonal blood pressure variation in men with mildly elevated blood pressure.

    PubMed

    Hattori, Tomomi; Munakata, Masanori

    2015-01-01

    Blood pressure (BP) is generally higher in cold than in warm seasons. This seasonal BP change is largely attributable to outdoor temperature changes. However, if such a typical seasonal change is observed in BP measured under a standardized indoor condition remains unclear. Resting supine BPs and heart rate (HR) were measured under a standardized room temperature during summer and the next winter in 104 untreated men (38.1 ± 4.4 years). Subjects were classified as having normotension (NT group: n = 79) or mildly elevated BP (ME group: n = 25) according to the summer measurements. Seasonal variation was defined as the difference from winter to summer measurements. We also examined body composition, endocrine parameters, and renal function. Age did not differ in the two groups (37.6 ± 4.2 versus 39.1 ± 4.9 years). The mean seasonal change in systolic BP was 2.7 ± 1.1 mmHg for the NT group and -4.6 ± 1.9 mmHg for the ME group (p = 0.001). Laboratory and outdoor temperatures did not differ between the two groups in either season. HR, noradrenaline, and estimated glomerular filtration rate were significantly higher during winter in the NT group but not in ME group. Typical seasonal change in BP may be masked in mildly elevated BP measured under a standardized indoor condition. The mechanisms are multifactorial. Our data suggest that out-of-office BP measurements are necessary for correctly understanding seasonal BP change especially in individuals with mildly elevated BP.

  12. Analysis of Pressure Variations in a Low-Pressure Nickel-Hydrogen Battery- Part 2: Cells with Metal Hydride Storage.

    PubMed

    Purushothaman, B K; Wainright, J S

    2012-05-15

    A sub-atmospheric pressure nickel hydrogen (Ni-H(2)) battery with metal hydride for hydrogen storage is developed for implantable neuroprosthetic devices. Pressure variations during charge and discharge of the cell are analyzed at different states of charge and are found to follow the desorption curve of the pressure composition isotherm (PCI) of the metal hydride. The measured pressure agreed well with the calculated theoretical pressure based on the PCI and is used to predict the state of charge of the battery. Hydrogen equilibration with the metal hydride during charge/discharge cycling is fast when the pressure is in the range from 8 to 13 psia and slower in the range from 6 to 8 psia. The time constant for the slower hydrogen equilibration, 1.37h, is similar to the time constant for oxygen recombination and therefore pressure changes due to different mechanisms are difficult to estimate. The self-discharge rate of the cell with metal hydride is two times lower in comparison to the cell with gaseous hydrogen storage alone and is a result of the lower pressure in the cell when the metal hydride is used.

  13. Analysis of Pressure Variations in a Low-Pressure Nickel-Hydrogen Battery– Part 2: Cells with Metal Hydride Storage

    PubMed Central

    Purushothaman, B. K.; Wainright, J. S.

    2012-01-01

    A sub-atmospheric pressure nickel hydrogen (Ni-H2) battery with metal hydride for hydrogen storage is developed for implantable neuroprosthetic devices. Pressure variations during charge and discharge of the cell are analyzed at different states of charge and are found to follow the desorption curve of the pressure composition isotherm (PCI) of the metal hydride. The measured pressure agreed well with the calculated theoretical pressure based on the PCI and is used to predict the state of charge of the battery. Hydrogen equilibration with the metal hydride during charge/discharge cycling is fast when the pressure is in the range from 8 to 13 psia and slower in the range from 6 to 8 psia. The time constant for the slower hydrogen equilibration, 1.37h, is similar to the time constant for oxygen recombination and therefore pressure changes due to different mechanisms are difficult to estimate. The self-discharge rate of the cell with metal hydride is two times lower in comparison to the cell with gaseous hydrogen storage alone and is a result of the lower pressure in the cell when the metal hydride is used. PMID:22711974

  14. Spatial Variation of Pressure in the Lyophilization Product Chamber Part 1: Computational Modeling.

    PubMed

    Ganguly, Arnab; Varma, Nikhil; Sane, Pooja; Bogner, Robin; Pikal, Michael; Alexeenko, Alina

    2017-04-01

    The flow physics in the product chamber of a freeze dryer involves coupled heat and mass transfer at different length and time scales. The low-pressure environment and the relatively small flow velocities make it difficult to quantify the flow structure experimentally. The current work presents the three-dimensional computational fluid dynamics (CFD) modeling for vapor flow in a laboratory scale freeze dryer validated with experimental data and theory. The model accounts for the presence of a non-condensable gas such as nitrogen or air using a continuum multi-species model. The flow structure at different sublimation rates, chamber pressures, and shelf-gaps are systematically investigated. Emphasis has been placed on accurately predicting the pressure variation across the subliming front. At a chamber set pressure of 115 mtorr and a sublimation rate of 1.3 kg/h/m(2), the pressure variation reaches about 9 mtorr. The pressure variation increased linearly with sublimation rate in the range of 0.5 to 1.3 kg/h/m(2). The dependence of pressure variation on the shelf-gap was also studied both computationally and experimentally. The CFD modeling results are found to agree within 10% with the experimental measurements. The computational model was also compared to analytical solution valid for small shelf-gaps. Thus, the current work presents validation study motivating broader use of CFD in optimizing freeze-drying process and equipment design.

  15. Pulse pressure variation to predict fluid responsiveness in spontaneously breathing patients: tidal vs. forced inspiratory breathing.

    PubMed

    Hong, D M; Lee, J M; Seo, J H; Min, J J; Jeon, Y; Bahk, J H

    2014-07-01

    We evaluated whether pulse pressure variation can predict fluid responsiveness in spontaneously breathing patients. Fifty-nine elective thoracic surgical patients were studied before induction of general anaesthesia. After volume expansion with hydroxyethyl starch 6 ml.kg(-1) , patients were defined as responders by a ≥ 15% increase in the cardiac index. Haemodynamic variables were measured before and after volume expansion and pulse pressure variations were calculated during tidal breathing and during forced inspiratory breathing. Median (IQR [range]) pulse pressure variation during forced inspiratory breathing was significantly higher in responders (n = 29) than in non-responders (n = 30) before volume expansion (18.2 (IQR 14.7-18.2 [9.3-31.3])% vs. 10.1 (IQR 8.3-12.6 [4.8-21.1])%, respectively, p < 0.001). The receiver-operating characteristic curve revealed that pulse pressure variation during forced inspiratory breathing could predict fluid responsiveness (area under the curve 0.910, p < 0.0001). Pulse pressure variation measured during forced inspiratory breathing can be used to guide fluid management in spontaneously breathing patients.

  16. Thermodynamic analysis of helium boil-off experiments with pressure variations

    NASA Astrophysics Data System (ADS)

    Cha, Y. S.; Niemann, R. C.; Hull, J. R.

    A thermodynamic analysis by calorimetric experiments in a system with changing pressure is presented. A general equation is derived for use in calculating the rate of heat loss from measured mass flow rate. The results show that the largest contribution from pressure variation is the sensible heat of liquid helium in a Dewar. A dimensionless parameter that was identified provides an indication of the importance of pressure variation relative to the latent heat of vaporization during an experiment. This dimensionless parameter is a function of system pressure land the thermodynamic properties of helium), rate of change of system pressure, liquid helium inventory in the Dewar and measured mass flow rate. In the special case when the effect of pressure variation is small compared to the latent heat of vaporization, the heat loss rate is the product of the measured mass flow rate and the latent heat of vaporization, multiplied by a correction factor that is a function of the ratio of vapour density to liquid density. This correction factor is significant for helium at pressures near or above 1 atm and should always be included in the calculation.

  17. Selective Pressure along a Latitudinal Gradient Affects Subindividual Variation in Plants

    PubMed Central

    Sobral, Mar; Guitián, José; Guitián, Pablo; Larrinaga, Asier R.

    2013-01-01

    Individual plants produce repeated structures such as leaves, flowers or fruits, which, although belonging to the same genotype, are not phenotypically identical. Such subindividual variation reflects the potential of individual genotypes to vary with micro-environmental conditions. Furthermore, variation in organ traits imposes costs to foraging animals such as time, energy and increased predation risk. Therefore, animals that interact with plants may respond to this variation and affect plant fitness. Thus, phenotypic variation within an individual plant could be, in part, an adaptive trait. Here we investigated this idea and we found that subindividual variation of fruit size of Crataegus monogyna, in different populations throughout the latitudinal gradient in Europe, was explained at some extent by the selective pressures exerted by seed-dispersing birds. These findings support the hypothesis that within-individual variation in plants is an adaptive trait selected by interacting animals which may have important implications for plant evolution. PMID:24069297

  18. Observation of pressure variation in the cavitation region of submerged journal bearings

    NASA Technical Reports Server (NTRS)

    Etsion, I.; Ludwig, L. P.

    1981-01-01

    Visual observations and pressure measurements in the cavitation zone of a submerged journal bearing are described. Tests are run at speeds of 1840 and 3000 rpm, and at each speed, four different levels of the ambient supply pressure are applied, ranging from 13.6 KPa to 54.4 KPa. A strong reverse flow is detected inside the cavitation area adjacent to its downstream end, and significant pressure variations on the order of 50 KPa are found inside the cavitation region at the downstream portion of its circumferential extent. Results indicate that the assumption of a constant cavitation pressure is incorrect in the case of enclosed cavitations, and it is postulated that oil which is saturated with air under atmospheric pressure becomes oversaturated in the subcavity pressure loop.

  19. A biometrical genome search in rats reveals the multigenic basis of blood pressure variation.

    PubMed

    Schork, N J; Krieger, J E; Trolliet, M R; Franchini, K G; Koike, G; Krieger, E M; Lander, E S; Dzau, V J; Jacob, H J

    1995-09-01

    A genome-wide search for multiple loci influencing salt-loaded systolic blood pressure (NaSBP) variation among 188 F2 progeny from a cross between the Brown-Norway and spontaneously hypertensive rat strains was pursued in an effort to gain insight into the polygenic basis of blood pressure regulation. The results suggest that loci within five to six genomic regions collectively explain approximately 43% of the total NaSBP variation exhibited among the 188 F2 progeny. Many of these loci are in regions that previous studies have not implicated in blood pressure regulation. Ultimately, however, this study not only sheds light on the multigenic basis of blood pressure but provides further evidence that the identification of the genetic determinants of polygenic traits in mammals is possible with modern biometrical and molecular genetic tools in controlled settings (i.e., breeding paradigm and model organism).

  20. Time Rate of Blood Pressure Variation Is Associated With Endothelial Function in Patients With Metabolic Syndrome.

    PubMed

    Ruan, Yanping; Wei, Wanlin; Yan, Jianhua; Sun, Lixian; Lian, Hui; Zhao, Xiaoyi; Liang, Ruijuan; Xiaole, Liu; Fan, Zhongjie

    2016-01-01

    The time rate of blood pressure (BP) variation indicates the speed of BP fluctuations. Previous studies have demonstrated that the time rate of BP variation was associated with target organ damage. However, the association between time rate of BP variation and endothelial function has not been evaluated.24-hour ambulatory blood pressure monitoring (ABPM) was performed in 61 patients with metabolic syndrome. Time rate of BP variation was calculated from BP recordings of ABPM. Endothelial function was assessed using reactive hyperemia-peripheral arterial tonometry index (RHI) by EndoPat2000. Multiple linear regression models were used to detect the association between time rate of BP variation and RHI.Among all the subjects (n = 61), the multiple linear regression models revealed that the daytime rate of systolic blood pressure (SBP) variation was independently associated with RHI (β = -0.334, P = 0.008). A 0.1 mmHg/minute increase in the daytime rate of SBP variation correlated with a decline of 0.20 in RHI. The same effect was also found in the subjects with eGFR ≥ 60 mL/ (minute*1.73 m(2)). A greater association was found in those who were not taking a statin, β-blocker, ACEI/ARB, or diuretic and those without diabetes compared with those with any antihypertensive medication or with diabetes. Other ambulatory blood pressure parameters and central hemodynamics were not found to be associated with RHI.Our findings have shown that the daytime rate of SBP variation was associated with endothelial function in patients with metabolic syndrome, independent of other BP parameters and central hemodynamics.

  1. High pressure phase transition and variation of elastic constants of diluted magnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Varshney, Dinesh; Sharma, P.; Kaurav, N.; Shah, S.; Singh, R. K.

    2004-11-01

    A theoretical study of the high-pressure phase transition and elastic behavior in diluted magnetic semiconductors Zn0.83Mn0.17Se, using a three-body interaction (TBI) potential caused by the electron-shell deformation of the overlapping ions is carried out. The estimated values of phase transition pressure and the vast volume discontinuity in pressure-volume (PV) phase diagram indicate the structural phase transition from zincblende (B3) to rock salt (B1). The variation of second-order elastic constants with pressure resembles that observed in some binary semiconductors. The inconsistency in the deduced value of pressure derivative of second order elastic constant with the available data is attributed to the fact that we derive expressions neglecting thermal effects and assuming the overlap repulsion significant only up to nearest neighbors. The vdW interaction is effective in obtaining the thermodynamical parameters such as Debye temperature, Gruneisen parameter, thermal expansion coefficient, compressibility as well phase stability in diluted magnetic semiconductors. It is revealed that TBI model has a promise to predict the phase transition pressure and the pressure variation of elastic constants of other semiconductors as well.

  2. Simulations of the general circulation of the Martian atmosphere. II - Seasonal pressure variations

    NASA Astrophysics Data System (ADS)

    Pollack, J. B.; Haberle, R. M.; Murphy, J. R.; Schaeffer, J.; Lee, H.

    1993-02-01

    The CO2 seasonal cycle of the Martian atmosphere and surface is simulated with a hybrid energy balance model that incorporates dynamical and radiation information from a large number of general circulation model runs. This information includes: heating due to atmospheric heat advection, the seasonally varying ratio of the surface pressure at the two Viking landing sites to the globally averaged pressure, the rate of CO2 condensation in the atmosphere, and solar heating of the atmosphere and surface. The predictions of the energy balance model are compared with the seasonal pressure variations measured at the two Viking landing sites and the springtime retreat of the seasonal polar cap boundaries. The following quantities are found to have a strong influence on the seasonal pressures at the Viking landing sites: albedo of the seasonal CO2 ice deposits, emissivity of this deposit, atmospheric heat advection, and the pressure ratio.

  3. Inactivation kinetics of Listeria monocytogenes by high-pressure processing: pressure and temperature variation.

    PubMed

    Doona, Christopher J; Feeherry, Florence E; Ross, Edward W; Kustin, Kenneth

    2012-08-01

    The enhanced quasi-chemical kinetics (EQCK) model is presented as a methodology to evaluate the nonlinear inactivation kinetics of baro-resistant Listeria monocytogenes in a surrogate protein food system by high-pressure processing (HPP) for various combinations of pressure (P= 207 to 414 MPa) and temperature (T= 20 to 50 °C). The EQCK model is based on ordinary differential equations derived from 6 "quasi-chemical reaction" steps. The EQCK model continuously fits the conventional stages of the microbial lifecycle: lag, growth, stationary phase, and death; and tailing. Depending on the conditions, the inactivation kinetics of L. monocytogenes by HPP show a lag, inactivation, and tailing. Accordingly, we developed a customized, 4-step subset version of the EQCK model sufficient to evaluate the HPP inactivation kinetics of L. monocytogenes and obtain values for the model parameters of lag (λ), inactivation rate (μ), rate constants (k), and "processing time" (tp). This latter parameter was developed uniquely to evaluate kinetics data showing tailing. Secondary models are developed by interrelating the fitting parameters with experimental parameters, and Monte Carlo simulations are used to evaluate parameter reproducibility. This 4-step model is also compared with the empirical Weibull and Polylog models. The success of the EQCK model (as its 4-step subset) for the HPP inactivation kinetics of baro-resistant L. monocytogenes showing tailing establishes several advantages of the EQCK modeling approach for investigating nonlinear microbial inactivation kinetics, and it has implications for determining mechanisms of bacterial spore inactivation by HPP. Results of this study will be useful to the many segments of the food processing industry (ready-to-eat meats, fresh produce, seafood, dairy) concerned with ensuring the safety of consumers from the health hazards of Listeria monocytogenes, particularly through the use of emerging food preservation technologies such as

  4. Effect of material and structure of compression bandage on interface pressure variation over time.

    PubMed

    Kumar, B; Das, A; Alagirusamy, R

    2014-07-01

    Compression bandage consists of fibrous materials which are viscoelastic in nature due to which the internal stress developed in the compression bandage under wrapped position may decay over time. The viscoelastic behaviour of a textile material depends on the fibre type as well as on its structure, and hence these factors could play a prominent role in interface pressure variation over time. To explore the influence of different materials and varying structures on the interface pressure profile generated by the bandages over time during static state of the limb. The material and construction of several compression bandages were engineered first and based on that different knitted bandages were prepared using several yarns (cotton, viscose, polyethylene terephthalate [PET], cotton-Lycra and PET-Lycra) and varying thread density in the structure. Three important factors, namely the material type, the applied tension and the tightness of the structure, were selected to examine their influence on interface pressure variation over time. The interface pressure measurement over time was done using a leg-segment prototype, which allows continuous online measurement of interface pressure over a static mannequin leg. More than 40% reduction of interface pressure was obtained for bandages made of spun yarns (cotton or viscose) in eight hours. Reduction of interface pressure for these bandages was higher when wrapped at a higher tension level. Lower reduction of interface pressure was obtained for the sample having higher thread density as compared with lower thread density in the structure, for the same applied tension level during wrapping. Bandages containing elastomeric yarn in the structure showed good sustenance of pressure for longer period. Bandages made up of elastic core spun yarns are effective for maintaining uniform interface pressure for longer period due to sustained compression developed by the elastic filament and tight structure of these bandages. © The

  5. Temporal variation of the leak pressure of uncuffed endotracheal tubes following pediatric intubation: an observational study.

    PubMed

    Patel, Shreya; Lalwani, Kirk; Koh, Jeffrey; Wu, Lei; Fu, Rongwei

    2014-06-01

    Uncuffed endotracheal tubes are still preferred over cuffed tubes in certain situations in pediatric anesthesia. Inaccurately sized uncuffed endotracheal tubes may lead to inadequate ventilation or tracheal mucosal damage during anesthesia. Endotracheal tube size in children is usually assessed by measuring the audible leak pressure; if the fit of the tube and the leak pressure decrease significantly with time, reintubation during surgery as a result of inability to ventilate effectively may be challenging, and could lead to patient morbidity. There is no evidence to indicate whether leak pressure increases or decreases with time following endotracheal intubation with uncuffed tubes in children. We measured leak pressure for 30 min following tracheal intubation in 46 ASA I children age 0-7 years after excluding factors known to modify leak pressure. The largest mean change in leak pressure occurred between time points 0 and 15 min, an increase of 3.5 cmH2O. Endotracheal tube size and type of procedure were associated with the leak pressure. In the final linear mixed model, there were no statistically significant variations in leak pressure over time (P = 0.129) in this group of children. We did not identify a consistent change in leak pressure within 30 min following tracheal intubation with uncuffed endotracheal tubes in this group of children.

  6. Variation in Sodium Intake and Intra-individual Change in Blood Pressure in Chronic Kidney Disease.

    PubMed

    Pathak, Chetna M; Ix, Joachim H; Anderson, Cheryl A M; Woodell, Tyler B; Smits, Gerard; Persky, Martha S; Block, Geoffrey A; Rifkin, Dena E

    2017-08-30

    In the kidney disease clinic setting, higher-than-usual blood pressure is often ascribed to recent dietary sodium indiscretion. While clinical trials demonstrate a clear relationship between salt intake and blood pressure on the population level, it is uncertain whether real-world variation in sodium intake within individual chronic kidney disease (CKD) patients is associated with fluctuations in blood pressure. We analyzed data from the Phosphorus Normalization Trial, in which participants with CKD eating their usual diets completed at least three 24-hour urine collections over 9 months, from which we measured sodium. Blood pressure was measured at the time of 24-hour urine collections. For each individual participant, we assessed the slope of the relationship between sodium intake and mean arterial blood pressure (MAP). Among 119 participants (mean age 67 years and mean estimated glomerular filtration rate 31 mL/minute/1.73 m(2)), there was substantial variation in sodium intake as measured by 24-hour urine collections (mean intake 3,903 mg/day, standard deviation 1037 mg/day). Individual participants had highly variable associations between their sodium intake and their MAP; 47% (n = 56) had inverse associations between sodium and MAP, whereas the remainder had positive (salt-sensitive) associations. Among CKD patients, there is substantial variation in sodium intake but no predictable relationship between dietary sodium and blood pressure in individuals. The frequent dismissal of elevated blood pressure readings as related to recent sodium intake in clinic may be a misapplication of large-scale population data to explain individual variability and may contribute to clinical inertia regarding high blood pressure treatment. Copyright © 2017 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

  7. Skeletal muscle hemoglobin content measured by near-infrared spectroscopy during oscillatory venous pressure variation

    NASA Astrophysics Data System (ADS)

    Marcu, Laura; Maarek, Jean-Michel I.; Bembi, Atul; Howell, Sandra

    1995-04-01

    Changes in oxidized (HbO), reduced (Hbr), and total hemoglobin (Hbt) contents were monitored by near infrared spectroscopy in human forearm skeletal muscle during oscillatory variations of the effective venous pressure. Laser diode pulses (wavelength, 775, 810, 865, 904; duration, 60 ns) were directed to the muscle by means of an optic fiber bundle and detected with a sensing fiber positioned at 1.5 cm from the emitting bundle. Sinusoidal pressure waves (frequency, 1 and 2 cycles/min; amplitude, 10-15 mm Hg) generated by a piston pump were transmitted to a sphygmomanometer cuff placed on the arm, the mean cuff pressure (Pc) being 20, 40 and 60 mm Hg. Variations of HbO, Hbr and Hbt were computed from the optical signals and processed by Fourier analysis to characterize their amplitude and phase relative to the cuff mean pressure oscillations (Posc). Oscillations of HbO, Hbr, Hbt were observed for all mean cuff pressures, the amplitude of the variations being decreased with increasing Pc. For Pc equals 20 mm Hg, the oscillations of HbO and Hbt were nearly in phase with Posc whereas the oscillation of Hbr were out of phase with HbO and Posc. Increasing Pc resulted in an increase of the phase difference between HbO and Posc, Hbr remaining out of phase with Posc. These trends could be predicted with a lumped model of the forearm vasculature, suggesting that the technique could be used to asses mechanical characteristics of vascular beds.

  8. Implications of Dynamic Pressure Transducer Mounting Variations on Measurements in Pyrotechnic Test Apparatus

    NASA Technical Reports Server (NTRS)

    Dibbern, Andreas; Crisafulli, Jeffrey; Hagopia, Michael; McDougle, Stephen H.; Saulsberry, Regor L.

    2009-01-01

    Accurate dynamic pressure measurements are often difficult to make within small pyrotechnic devices, and transducer mounting difficulties can cause data anomalies that lead to erroneous conclusions. Delayed initial pressure response followed by data ringing has been observed when using miniaturized pressure transducer mounting adapters required to interface transducers to small test chambers. This delayed pressure response and ringing, combined with a high data acquisition rate, has complicated data analysis. This paper compares the output signal characteristics from different pressure transducer mounting options, where the passage distance from the transducer face to the pyrotechnic chamber is varied in length and diameter. By analyzing the data and understating the associated system dynamics, a more realistic understanding of the actual dynamic pressure variations is achieved. Three pressure transducer mounting configurations (elongated, standard, and face/flush mount) were simultaneously tested using NASA standard initiators in closed volume pressure bombs. This paper also presents results of these pressure transducer mounting configurations as a result of a larger NASA Engineering and Safety Center pyrovalve test project. Results from these tests indicate the improved performance of using face/flush mounted pressure transducers in this application. This type of mounting improved initial pressure measurement response time by approximately 19 s over standard adapter mounting, eliminating most of the lag time; provided a near step-function type initial pressure increase; and greatly reduced data ringing in high data acquisition rate systems. The paper goes on to discuss other issues associated with the firing and instrumentation that are important for the tester to understand.

  9. Heart rate and blood pressure variations after transvascular patent ductus arteriosus occlusion in dogs.

    PubMed

    De Monte, Valentina; Staffieri, Francesco; Caivano, Domenico; Nannarone, Sara; Birettoni, Francesco; Porciello, Francesco; Di Meo, Antonio; Bufalari, Antonello

    2017-09-05

    The objective of the study was to retrospectively analyse the cardiovascular effects that occurs following the transvascular occlusion of patent ductus arteriosus in dogs. Sixteen anaesthesia records were included. Variables were recorded at the time of placing the arterial introducer, occlusion of the ductus, and from 5 to 60min thereafter, including, among the other, heart rate, systolic, diastolic and mean arterial blood pressure. The maximal percentage variation of the aforementioned physiological parameters within 60min of occlusion, compared with the values recorded at the introducer placing, was calculated. The time at which maximal variation occurred was also computed. Correlations between maximal percentage variation of physiological parameters and the diameter of the ductus and systolic and diastolic flow velocity through it were evaluated with linear regression analysis. Heart rate decreased after occlusion of the ductus with a mean maximal percentage variation of 41.0±14.8% after 21.2±13.7min. Mean and diastolic arterial blood pressure increased after occlusion with a mean maximal percentage variation of 30.6±18.1 and 55.4±27.1% after 19.6±12.1 and 15.7±10.8min, respectively. Mean arterial blood pressure variation had a significant and moderate inverse correlation with diastolic and systolic flow velocity through the ductus. Transvascular patent ductus arteriosus occlusion in anaesthetised dogs causes a significant reduction in heart rate and an increase in diastolic and mean blood arterial pressure within 20min of closure of the ductus. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Endurance and Cycle-to-cycle Uniformity Improvement in Tri-Layered CeO2/Ti/CeO2 Resistive Switching Devices by Changing Top Electrode Material

    NASA Astrophysics Data System (ADS)

    Rana, Anwar Manzoor; Akbar, Tahira; Ismail, Muhammad; Ahmad, Ejaz; Hussain, Fayyaz; Talib, Ijaz; Imran, Muhammad; Mehmood, Khalid; Iqbal, Khalid; Nadeem, M. Younus

    2017-01-01

    Resistance switching characteristics of CeO2/Ti/CeO2 tri-layered films sandwiched between Pt bottom electrode and two different top electrodes (Ti and TaN) with different work functions have been investigated. RRAM memory cells composed of TaN/CeO2/Ti/CeO2/Pt reveal better resistive switching performance instead of Ti/CeO2/Ti/CeO2/Pt memory stacks. As compared to the Ti/CeO2 interface, much better ability of TaN/CeO2 interface to store and exchange plays a key role in the RS performance improvement, including lower forming/SET voltages, large memory window (~102) and no significant data degradation during endurance test of >104 switching cycles. The formation of TaON thinner interfacial layer between TaN TE and CeO2 film is found to be accountable for improved resistance switching behavior. Partial charge density of states is analyzed using density functional theory. It is found that the conductive filaments formed in CeO2 based devices is assisted by interstitial Ti dopant. Better stability and reproducibility in cycle-to-cycle (C2C) resistance distribution and Vset/Vreset uniformity were achieved due to the modulation of current conduction mechanism from Ohmic in low field region to Schottky emission in high field region.

  11. Endurance and Cycle-to-cycle Uniformity Improvement in Tri-Layered CeO2/Ti/CeO2 Resistive Switching Devices by Changing Top Electrode Material.

    PubMed

    Rana, Anwar Manzoor; Akbar, Tahira; Ismail, Muhammad; Ahmad, Ejaz; Hussain, Fayyaz; Talib, Ijaz; Imran, Muhammad; Mehmood, Khalid; Iqbal, Khalid; Nadeem, M Younus

    2017-01-12

    Resistance switching characteristics of CeO2/Ti/CeO2 tri-layered films sandwiched between Pt bottom electrode and two different top electrodes (Ti and TaN) with different work functions have been investigated. RRAM memory cells composed of TaN/CeO2/Ti/CeO2/Pt reveal better resistive switching performance instead of Ti/CeO2/Ti/CeO2/Pt memory stacks. As compared to the Ti/CeO2 interface, much better ability of TaN/CeO2 interface to store and exchange plays a key role in the RS performance improvement, including lower forming/SET voltages, large memory window (~10(2)) and no significant data degradation during endurance test of >10(4) switching cycles. The formation of TaON thinner interfacial layer between TaN TE and CeO2 film is found to be accountable for improved resistance switching behavior. Partial charge density of states is analyzed using density functional theory. It is found that the conductive filaments formed in CeO2 based devices is assisted by interstitial Ti dopant. Better stability and reproducibility in cycle-to-cycle (C2C) resistance distribution and Vset/Vreset uniformity were achieved due to the modulation of current conduction mechanism from Ohmic in low field region to Schottky emission in high field region.

  12. Endurance and Cycle-to-cycle Uniformity Improvement in Tri-Layered CeO2/Ti/CeO2 Resistive Switching Devices by Changing Top Electrode Material

    PubMed Central

    Rana, Anwar Manzoor; Akbar, Tahira; Ismail, Muhammad; Ahmad, Ejaz; Hussain, Fayyaz; Talib, Ijaz; Imran, Muhammad; Mehmood, Khalid; Iqbal, Khalid; Nadeem, M. Younus

    2017-01-01

    Resistance switching characteristics of CeO2/Ti/CeO2 tri-layered films sandwiched between Pt bottom electrode and two different top electrodes (Ti and TaN) with different work functions have been investigated. RRAM memory cells composed of TaN/CeO2/Ti/CeO2/Pt reveal better resistive switching performance instead of Ti/CeO2/Ti/CeO2/Pt memory stacks. As compared to the Ti/CeO2 interface, much better ability of TaN/CeO2 interface to store and exchange plays a key role in the RS performance improvement, including lower forming/SET voltages, large memory window (~102) and no significant data degradation during endurance test of >104 switching cycles. The formation of TaON thinner interfacial layer between TaN TE and CeO2 film is found to be accountable for improved resistance switching behavior. Partial charge density of states is analyzed using density functional theory. It is found that the conductive filaments formed in CeO2 based devices is assisted by interstitial Ti dopant. Better stability and reproducibility in cycle-to-cycle (C2C) resistance distribution and Vset/Vreset uniformity were achieved due to the modulation of current conduction mechanism from Ohmic in low field region to Schottky emission in high field region. PMID:28079056

  13. Variation in predator species abundance can cause variable selection pressure on warning signaling prey

    PubMed Central

    Valkonen, Janne K; Nokelainen, Ossi; Niskanen, Martti; Kilpimaa, Janne; Björklund, Mats; Mappes, Johanna

    2012-01-01

    Predation pressure is expected to drive visual warning signals to evolve toward conspicuousness. However, coloration of defended species varies tremendously and can at certain instances be considered as more camouflaged rather than conspicuous. Recent theoretical studies suggest that the variation in signal conspicuousness can be caused by variation (within or between species) in predators' willingness to attack defended prey or by the broadness of the predators' signal generalization. If some of the predator species are capable of coping with the secondary defenses of their prey, selection can favor reduced prey signal conspicuousness via reduced detectability or recognition. In this study, we combine data collected during three large-scale field experiments to assess whether variation in avian predator species (red kite, black kite, common buzzard, short-toed eagle, and booted eagle) affects the predation pressure on warningly and non-warningly colored artificial snakes. Predation pressure varied among locations and interestingly, if common buzzards were abundant, there were disadvantages to snakes possessing warning signaling. Our results indicate that predator community can have important consequences on the evolution of warning signals. Predators that ignore the warning signal and defense can be the key for the maintenance of variation in warning signal architecture and maintenance of inconspicuous signaling. PMID:22957197

  14. Responses of Venus Ionosphere and Induced Magnetosphere to Solar Wind Pressure Variations

    NASA Astrophysics Data System (ADS)

    Ma, Yingjuan; Toth, Gabor; Nagy, Andrew F.; Russell, Christopher T.

    2016-04-01

    Often regarded as the Earth's 'sister planet', Venus has similar size and mass as Earth. But it is also remarkably different from Earth in many respects. Even though we have some basic knowledge of the solar wind interaction with Venus based on spacecraft observations, little is known about how the interaction and the resulting plasma escape rates vary in response to solar wind variations due to the lack of coordinated observations of both upstream solar wind conditions and simultaneous plasma properties in the Venus ionosphere. Furthermore, recent observations suggest that plasma escape rates are significantly enhanced during stormy space weather in response to solar wind pressure pulses (Edberg et al., 2011). Thus it is important to understand the plasma interaction under varying solar wind conditions. In this study, we use a sophisticated multi-species MHD model that has been recently developed for Venus (Ma et al., 2013) to characterize the responses of the ionosphere and the induced magnetosphere of Venus to a typical variation of the solar wind: dynamic pressure change. We will examine the response of the ionosphere and the induced magnetosphere to both pressure enhancements and decreases. We will quantify the total plasma escape-rate change in response to such variations and to identify the underlying driver for changes in escape rate. We will also quantify the time scale of the Venus ionosphere and induced magnetosphere in responding to the pressure change of the external solar wind driver.

  15. Geographic variation of melanisation patterns in a hornet species: genetic differences, climatic pressures or aposematic constraints?

    PubMed

    Perrard, Adrien; Arca, Mariangela; Rome, Quentin; Muller, Franck; Tan, Jiangli; Bista, Sanjaya; Nugroho, Hari; Baudoin, Raymond; Baylac, Michel; Silvain, Jean-François; Carpenter, James M; Villemant, Claire

    2014-01-01

    Coloration of stinging insects is often based on contrasted patterns of light and black pigmentations as a warning signal to predators. However, in many social wasp species, geographic variation drastically modifies this signal through melanic polymorphism potentially driven by different selective pressures. To date, surprisingly little is known about the geographic variation of coloration of social wasps in relation to aposematism and melanism and to genetic and developmental constraints. The main objectives of this study are to improve the description of the colour variation within a social wasp species and to determine which factors are driving this variation. Therefore, we explored the evolutionary history of a polymorphic hornet, Vespa velutina Lepeletier, 1836, using mitochondrial and microsatellite markers, and we analysed its melanic variation using a colour space based on a description of body parts coloration. We found two main lineages within the species and confirmed the previous synonymy of V. auraria Smith, 1852, under V. velutina, differing only by the coloration. We also found that the melanic variation of most body parts was positively correlated, with some segments forming potential colour modules. Finally, we showed that the variation of coloration between populations was not related to their molecular, geographic or climatic differences. Our observations suggest that the coloration patterns of hornets and their geographic variations are determined by genes with an influence of developmental constraints. Our results also highlight that Vespa velutina populations have experienced several convergent evolutions of the coloration, more likely influenced by constraints on aposematism and Müllerian mimicry than by abiotic pressures on melanism.

  16. Geographic Variation of Melanisation Patterns in a Hornet Species: Genetic Differences, Climatic Pressures or Aposematic Constraints?

    PubMed Central

    Perrard, Adrien; Arca, Mariangela; Rome, Quentin; Muller, Franck; Tan, Jiangli; Bista, Sanjaya; Nugroho, Hari; Baudoin, Raymond; Baylac, Michel; Silvain, Jean-François; Carpenter, James M.; Villemant, Claire

    2014-01-01

    Coloration of stinging insects is often based on contrasted patterns of light and black pigmentations as a warning signal to predators. However, in many social wasp species, geographic variation drastically modifies this signal through melanic polymorphism potentially driven by different selective pressures. To date, surprisingly little is known about the geographic variation of coloration of social wasps in relation to aposematism and melanism and to genetic and developmental constraints. The main objectives of this study are to improve the description of the colour variation within a social wasp species and to determine which factors are driving this variation. Therefore, we explored the evolutionary history of a polymorphic hornet, Vespa velutina Lepeletier, 1836, using mitochondrial and microsatellite markers, and we analysed its melanic variation using a colour space based on a description of body parts coloration. We found two main lineages within the species and confirmed the previous synonymy of V. auraria Smith, 1852, under V. velutina, differing only by the coloration. We also found that the melanic variation of most body parts was positively correlated, with some segments forming potential colour modules. Finally, we showed that the variation of coloration between populations was not related to their molecular, geographic or climatic differences. Our observations suggest that the coloration patterns of hornets and their geographic variations are determined by genes with an influence of developmental constraints. Our results also highlight that Vespa velutina populations have experienced several convergent evolutions of the coloration, more likely influenced by constraints on aposematism and Müllerian mimicry than by abiotic pressures on melanism. PMID:24740142

  17. Lack of family-based association between common variations in WNK1 and blood pressure level.

    PubMed

    Liu, Fuqiang; Lian, Qiufang; Ren, Jie; Ren, Keyu; Wang, Yang; Wang, Dan; Chu, Chao; Wang, Lan; Guo, Tongshuai; Liu, Enqi; Mu, Jianjun; Yuan, Zuyi

    2014-10-16

    WNK1 (With No-lysine Kinase 1) modulates numerous sodium transport-related ion channels involved in regulation of blood pressure. Several studies have indicated associations between the common variants of the WNK1 gene and hypertension or blood pressure levels. However, little data exists on Asian populations and normotensive or pre-hypertensive subjects. Our aim was to detect whether the common variations in the WNK1 gene are potential contributors to individual variations in blood pressure in a family-based sample. 525 individuals from 116 families were selected from a rural community of Northern China. Five single-nucleotide polymorphisms were selected from the WNK1 gene. Single-marker and haplotype analyses were conducted using the Family-Based Association Test program. Regretful, no associations for the 5 WNK1 SNPs and the constructed haplotype blocks of WNK1 with blood pressure level reached nominal statistical significance. We conclude that although multiple candidate genes are involved in development of hypertension, the genetic polymorphism in WNK1 is not a major contributor to the observed variability in blood pressure and familial clustering risk of hypertension.

  18. Simulation Research of Vaporization and Pressure Variation in a Cryogenic Propellant Tank at the Launch Site

    NASA Astrophysics Data System (ADS)

    Chen, Liang; Liang, Guo-zhu

    2013-12-01

    In order to improve depiction of pressure variation and investigate the interrelation among the physical processes in propellant tanks, a 2D axial symmetry Volume-of-Fluid (VOF) CFD model is established to simulate a large-sized liquid propellant tank when the rocket is preparing for launch with propellant loaded at the launch site. The numerical model is considered with propellant free convection, heat transfer between the tank and the external environment, thermal exchange between propellant and inner tank wall surfaces, gas compressibility, and phase change modeled under the assumption of thermodynamic equilibrium. Vaporization rate of the vented LH2 tank and prediction of pressure change in the tank pressurized with GHe are obtained through simulation. We analysis the distributions of phase, temperature, and velocity vectors to reveal interactions among the propellant's own convection motion, heat transfer and phase change. The results show that the vaporization rate is mainly affected by heat leaks though the tank wall when the tank is vented, but it does not completely accord with the trend of the leakage because of convection motion and temperature nonuniformity of the liquid propellant in the tank. We also find that the main factors on pressure variation in the pressurized tank are the heat transfer on the tank wall surface bonding the ullage and propellant vaporization which has comparatively less influence.

  19. Variation of output with atmospheric pressure and ambient temperature for Therac-20 linear accelerator.

    PubMed

    Sharma, S C; Wilson, D L; Jose, B

    1983-01-01

    The Therac-20 (a linear accelerator manufactured by the Atomic Energy of Canada, Ltd.) employs an unsealed monitor chamber to control the dose output. Daily fluctuations in machine output for both x rays and electron beams were observed to vary with ambient temperature and atmospheric pressure. These variations were not related to any other machine parameters. Variations as large as 3.5% were seen by monitoring 18-MV x-ray output over several months. We recommend that the manufacturers take steps to eliminate the atmospheric dependence of dose rate.

  20. Resistivity Variation due to CO2 Migration in Different Temperature and Pressure Conditions

    NASA Astrophysics Data System (ADS)

    Nakatsuka, Y.; Onishi, K.; Yamada, Y.; Matsuoka, T.; Xue, Z.

    2007-12-01

    CO2 geological sequestration is one of the effective approaches solving the global warming problem. Captured CO2 is injected to the deep aquifers or depleted oil and gas fields. Injected CO2 migrates thorough the reservoir rock, however, the details behavior of injected CO2 under the ground at super critical phase is not yet fully understood. Migration of injected CO2 will change by the condition of the injected reservoir such as the temperature and pressure. Also density and permeability of the rock may be changed due to temperature or pressure variations. These changes control the migration behavior of injected CO2. In this study, experiments of resistivity measurements were conducted to detect the migration difference of CO2 in different temperature and pressure conditions by using sandstone core samples. Core sample was taken from Berea sandstone and processed to 5cm diameter and 12cm length. For the resistivity measurement, impression electrode was set on the both end and the measurement electrode of ring condition was set on the side of the rock sample. We stetted the core sample in the pressure vessel and recreated the condition of underground reservoir which is high pressure and high temperature. We injected supercritical CO2 in different pressure and temperature for each experiment. Pressure was changed in range of 8 to 11MPa and temperature was changed in range of 35° to 45°. This means that all the experiments were conducted in supercritical phase. From the measured resistivity variation, we verified the migration of CO2 and compared the migration behavior of CO2 in different conditions.

  1. External cavity diode laser with frequency drift following natural variation in air pressure.

    PubMed

    Takamizawa, Akifumi; Yanagimachi, Shinya; Ikegami, Takeshi; Kawabata, Ryuzo

    2015-06-20

    A compact and mechanically very robust external cavity diode laser was made by removing any position adjusters such as precision screws and piezo actuators, taking advantage of a cat's eye retroreflector insensitive to misalignment. Under free-running operation during 150 h, the frequency drift followed natural variation in air pressure with a ratio of -66.6±0.1  MHz/hPa in a range between 1001.5 and 1013.6 hPa. The ratio was in good agreement with that estimated from variation in the effective cavity length derived from the relation between the pressure and the refractive index of air. These results indicate that an external cavity diode laser with predictable frequency drift was successfully created.

  2. Variations of energetic electrons associated with solar wind dynamic pressure enhancement in the outer radiation belt

    NASA Astrophysics Data System (ADS)

    Lee, J.; Lee, E.; Kim, K. H.; Lee, D. H.; Lee, J.; Spence, H. E.

    2015-12-01

    Earth's outer radiation belt varies dynamically under the variations of the solar wind. In this study, we investigated the variations of energetic electrons in the outer radiation belt caused by an enhancement of the solar wind dynamic pressure associated with an interplanetary shock using the measurements from the Van Allen Probes (VAP) satellites. The enhanced dynamic pressure lasted for about 24 hours, but magnetic storm was not occurred. The impact of the interplanetary shock on 13 April 2013 produced dipolarization of the magnetic field for a few minutes, which was simultaneously observed by VAP A and B moving in the nightside region. The enhancement of the electron fluxes with E < ~600 keV coincidentally occurred during the dipolarization. Later, drift echoes with energy dispersion and ULF-like modulations were observed. By comparing the measurements from VAP A and B we will discuss spatial and temporal characteristics of the enhancement of the energetic electron fluxes.

  3. Genome-wide association analyses using electronic health records identify new loci influencing blood pressure variation.

    PubMed

    Hoffmann, Thomas J; Ehret, Georg B; Nandakumar, Priyanka; Ranatunga, Dilrini; Schaefer, Catherine; Kwok, Pui-Yan; Iribarren, Carlos; Chakravarti, Aravinda; Risch, Neil

    2017-01-01

    Longitudinal electronic health records on 99,785 Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort individuals provided 1,342,814 systolic and diastolic blood pressure measurements for a genome-wide association study on long-term average systolic, diastolic, and pulse pressure. We identified 39 new loci among 75 genome-wide significant loci (P ≤ 5 × 10(-8)), with most replicating in the combined International Consortium for Blood Pressure (ICBP; n = 69,396) and UK Biobank (UKB; n = 152,081) studies. Combining GERA with ICBP yielded 36 additional new loci, with most replicating in UKB. Combining all three studies (n = 321,262) yielded 241 additional genome-wide significant loci, although no replication sample was available for these. All associated loci explained 2.9%, 2.5%, and 3.1% of variation in systolic, diastolic, and pulse pressure, respectively, in GERA non-Hispanic whites. Using multiple blood pressure measurements in GERA doubled the variance explained. A normalized risk score was associated with time to onset of hypertension (hazards ratio = 1.18, P = 8.2 × 10(-45)). Expression quantitative trait locus analysis of blood pressure loci showed enrichment in aorta and tibial artery.

  4. Upstream pressure variations associated with the bow shock and their effects on the magnetosphere

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.; Baumjohann, W.; Paschmann, G.; Luehr, H.; Sibeck, D. G.

    1990-01-01

    The AMPTE IRM solar wind data are analyzed to determine the relationship between upstream pressure fluctuations and magnetospheric perturbations. It is argued that the upstream pressure variations are not inherent in the solar wind but rather are associated with the bow shock. This conclusion follows from the fact that the upstream field strength and density associated with perturbations are highly correlated with each other, while they tend to be anticorrelated in the undisturbed solar wind, and that the upstream perturbations occur within the foreshock or at its boundary. The results imply a mode of interaction between the solar wind upstream and the magnetosphere whereby density changes produced in the foreshock subsequently convect through the bow shock and impinge on the magnetosphere. Upstream pressure perturbations should create significant effects on the magnetopause and at the foot of nearby field lines that lead to the polar cusp ionosphere.

  5. Assimilation of scatterometer winds into surface pressure fields using a variational method

    NASA Technical Reports Server (NTRS)

    Harlan, J., Jr.; Obrien, J. J.

    1986-01-01

    A variational formulation was used to assimilate Seasat-A scatterometer (SASS) surface wind measurements near and during a severe storm in the North Atlantic into conventional National Meteorological Center sea level pressure fields. An estimate of the relative vorticity at every point on a grid was calculated using each of these two data sets. A solution to a modified geostrophic stream function is found subject to the constraints that (1) the relative vorticities calculated from the data agree as closely as possible with the relative vorticities from the variational solution, and that (2) the average kinetic energy is a minimum. Results are obtained which support the idea that averaged satellite data can be treated as synoptic data. Direct substitution rather than a time-weighted insertion made from SASS winds generally resulted in more accurate pressure analyses. In addition, this relatively simple model provides surface pressure fields which agree extremely well with surface truth and the results of other investigators who required additional sources of input data into more complex models. It will be possible to obtain improved wind field maps from future scatterometer pressure fields in mid-latitudes.

  6. Indexes of aortic pressure augmentation markedly underestimate the contribution of reflected waves toward variations in aortic pressure and left ventricular mass.

    PubMed

    Booysen, Hendrik L; Woodiwiss, Angela J; Sibiya, Moekanyi J; Hodson, Bryan; Raymond, Andrew; Libhaber, Elena; Sareli, Pinhas; Norton, Gavin R

    2015-03-01

    Although indexes of wave reflection enhance risk prediction, the extent to which measures of aortic systolic pressure augmentation (augmented pressures [Pa] or augmentation index) underestimate the effects of reflected waves on cardiovascular risk is uncertain. In participants from a community sample (age >16), we compared the relative contribution of reflected (backward wave pressures and the reflected wave index [RI]) versus augmented (Pa and augmentation index) pressure wave indexes to variations in central aortic pulse pressure (PPc; n=1185), and left ventricular mass index (LVMI; n=793). Aortic hemodynamics and LVMI were determined using radial applanation tonometry (SphygmoCor) and echocardiography. Independent of confounders, RI and backward wave pressures contributed more than forward wave pressures, whereas Pa and augmentation index contributed less than incident wave pressure to variations in PPc (P<0.0001 for comparison of partial r values). In those <50 years of age, while backward wave pressures (partial r=0.28, P<0.0001) contributed more than forward wave pressures (partial r=0.15, P<0.001; P<0.05 for comparison of r values), Pa (partial r=0.13, P<0.005) contributed to a similar extent as incident wave pressure (partial r=0.22, P<0.0001) to variations in LVMI. Furthermore, in those ≥50 years of age, backward wave pressures (partial r=0.21, P<0.0001), but not forward wave pressures (P=0.98), while incident wave pressure (partial r=0.23, P<0.0001), but not Pa (P=0.80) were associated with LVMI. Pa and augmentation index underestimated the effect of wave reflection on PPc and LVMI in both men and women. Thus, as compared with relations between indexes of aortic pressure augmentation and PPc or LVMI, strikingly better relations are noted between aortic wave reflection and PPc or LVMI. © 2014 American Heart Association, Inc.

  7. Variations in the WNK1 gene modulates the effect of dietary intake of sodium and potassium on blood pressure determination.

    PubMed

    Osada, Yuko; Miyauchi, Rie; Goda, Toshinao; Kasezawa, Nobuhiko; Horiike, Hiromi; Iida, Mariko; Sasaki, Satoshi; Yamakawa-Kobayashi, Kimiko

    2009-08-01

    WNK lysine-deficient protein kinase 1 (WNK1) is a member of the WNK family of serine/threonine kinases with no lysine (K), and these kinases have been implicated as important modulators of salt homeostasis in the kidney. It is well known that high dietary sodium and low dietary potassium have been implicated in the etiology of increased blood pressure. However, the blood pressure response to dietary sodium and potassium intake varies considerably among individuals. In this study, we have detected that the haplotypes of the WNK1 gene are associated with blood pressure variations in the general Japanese population. In addition, we investigated the interactions between the haplotypes of the WNK1 gene and dietary sodium and potassium intake for determining inter-individual variations in blood pressure. Our data support the hypothesis that part of the variation in blood pressure response to dietary sodium and potassium intake among individuals can be explained by variations in the WNK1 gene.

  8. Pulse-pressure variation predicts fluid responsiveness during heart displacement for off-pump coronary artery bypass surgery.

    PubMed

    Lee, Jong-Hwan; Jeon, Yunseok; Bahk, Jae-Hyon; Gil, Nam-Su; Kim, Ki-Bong; Hong, Deok Man; Kim, Hyun Joo

    2011-12-01

    The aim of this study was to evaluate the ability of pulse-pressure variation to predict fluid responsiveness during heart displacement for off-pump coronary artery bypass surgery using receiver operating characteristic analysis. A prospective study. A clinical study in a single cardiac anesthesia institution. Thirty-five patients undergoing elective off-pump coronary artery bypass surgery. Central venous pressure, pulmonary arterial occlusion pressure, pulse-pressure variation, and cardiac index were measured 5 minutes after revascularization of the left anterior descending coronary artery and before heart displacement. Immediately after heart displacement for revascularization of the left circumflex artery, and 10 minutes after fluid loading with hydroxyethyl starch 6% (10 mL/kg) during heart displacement, the measurements were repeated. Patients whose cardiac indices increased by ≥15% from fluid loading were defined as responders. After heart displacement, only pulse-pressure variation showed significant difference between the responders and nonresponders (13.48 ± 6.42 v 7.33 ± 3.81, respectively; p < 0.01). Moreover, receiver operating characteristic analysis showed that pulse-pressure variation successfully predicted fluid responsiveness (area under the curve = 0.839, p = 0.0001). Pulse-pressure variation >7.69% identified the responders, with a sensitivity of 86% and a specificity of 83%. Pulse-pressure variation successfully predicted fluid responsiveness and would be useful in guiding fluid management during heart displacement for off-pump coronary artery bypass surgery. Copyright © 2011 Elsevier Inc. All rights reserved.

  9. Synthetic Glucocorticoids and Early Variations of Blood Pressure: A Population-Based Cohort Study.

    PubMed

    Fardet, Laurence; Nazareth, Irwin; Petersen, Irene

    2015-07-01

    Endogenous glucocorticoids are known to increase blood pressure, but very little is known about the early effects of synthetic glucocorticoids (eg, prednisone, dexamethasone) on blood pressure. To assess longitudinal variations of blood pressure before and after initiation of systemic glucocorticoid therapy. Adult patients prescribed synthetic glucocorticoid therapy for at least 3 months and registered between 2004 and 2012 in The Health Improvement Network (THIN) primary care database. Systolic and diastolic blood pressure as measured in primary care. Among the 16,351 patients prescribed antihypertensive drug within the year before glucocorticoid initiation (women, 57.1%; age [mean ± SD], 72.0 ± 11.4 y), the mean (SD) blood pressure within the year before glucocorticoid initiation was 140 (18)/78 (9) mm Hg. It was 139 (19)/77 (11), 139 (19)/77 (10), and 139 (19)/77 (11) mm Hg during the first, second, and third months of exposure, respectively. We did not find any evidence of the effects of glucocorticoids on blood pressure in these patients. Among the 6914 patients not prescribed antihypertensive drug within the year before glucocorticoid initiation (women, 64.9%; age, 60.0 ± 17.8 y), the figures were 133 (17)/78 (10), 135 (20)/79 (11), 133 (19)/78 (11), and 133 (19)/78 (11) mm Hg before exposure and during the first, second, and third months of exposure, respectively. In this group of patients, glucocorticoid exposure was associated with a slight (<1 mm Hg; P = .03) increase of systolic but not diastolic (P = .52) blood pressure. However, in 4% of people or fewer, extreme increases or decreases (ie, ≥30 mm Hg for systolic blood pressure) in blood pressure were observed after glucocorticoid initiation. Prednisone/prednisolone use was associated with a higher risk of extreme increase in systolic blood pressure than the other synthetic glucocorticoids (odds ratio, 4.9 [95% confidence interval, 1.9-12.6]; P = .001). Contrary to what is usually thought, the

  10. Cortical representation of tympanic membrane movements due to pressure variation: an fMRI study.

    PubMed

    Job, Agnès; Paucod, Jean-Charles; O'Beirne, Greg A; Delon-Martin, Chantal

    2011-05-01

    Middle ear sensory information has never been localized in the homunculus of the somatosensory cortex (S1). We investigated the somatosensory representation of the middle ear in 15 normal hearing subjects. We applied small air pressure variations to the tympanic membrane while performing a 3T-fMRI study. Unilateral stimulations of the right ear triggered bilateral activations in the caudal part of the postcentral gyrus in Brodmann area 43 (BA 43) and in the auditory associative areas 42 (BA 42) and 22 (BA 22). BA 43 has been found to be involved in activities accompanying oral intake and could be more largely involved in pressure activities in the oropharynx area. The tympanic membrane is indirectly related to the pharynx area through the action of tensor tympani, which is a Eustachian tube muscle. The Eustachian tube muscles have a role in pressure equalization in the middle ear and also have a role in the pharyngeal phase of swallowing. Activation of BA 42 and BA 22 could reflect activations associated with the bilateral acoustic reflex triggered prior to self-vocalization to adjust air pressure in the oropharynx during speech. We propose that BA 43, 42, and 22 are the cortical areas associated with middle ear function. We did not find representation of tympanic membrane movements due to pressure in S1, but its representation in the postcentral gyrus in BA 43 seems to suggest that at least part of this area conveys pure somatosensory information.

  11. Effects of injection pressure variation on mixing in a cold supersonic combustor with kerosene fuel

    NASA Astrophysics Data System (ADS)

    Liu, Wei-Lai; Zhu, Lin; Qi, Yin-Yin; Ge, Jia-Ru; Luo, Feng; Zou, Hao-Ran; Wei, Min; Jen, Tien-Chien

    2017-10-01

    Spray jet in cold kerosene-fueled supersonic flow has been characterized under different injection pressures to assess the effects of the pressure variation on the mixing between incident shock wave and transverse cavity injection. Based on the real scramjet combustor, a detailed computational fluid dynamics model is developed. The injection pressures are specified as 0.5, 1.0, 2.0, 3.0 and 4.0 MPa, respectively, with the other constant operation parameters (such as the injection diameter, angle and velocity). A three dimensional Couple Level Set & Volume of Fluids approach incorporating an improved Kelvin-Helmholtz & Rayleigh-Taylor model is used to investigate the interaction between kerosene and supersonic air. The numerical simulations primarily concentrate on penetration depth, span expansion area, angle of shock wave and sauter mean diameter distribution of the kerosene droplets with/without evaporation. Validation has been implemented by comparing the calculated against the measured in literature with good qualitative agreement. Results show that the penetration depth, span-wise angle and expansion area of the transverse cavity jet are all increased with the injection pressure. However, when the injection pressure is further increased, the value in either penetration depth or expansion area increases appreciably. This study demonstrates the feasibility and effectiveness of the combination of Couple Level Set & Volume of Fluids approach and an improved Kelvin-Helmholtz & Rayleigh-Taylor model, in turn providing insights into scramjet design improvement.

  12. Diurnal variations in axial length, choroidal thickness, intraocular pressure, and ocular biometrics.

    PubMed

    Chakraborty, Ranjay; Read, Scott A; Collins, Michael J

    2011-07-11

    To investigate the pattern of diurnal variations in axial length (AL), choroidal thickness, intraocular pressure (IOP), and ocular biometrics over 2 consecutive days. Measurements of ocular biometrics and IOP were collected for 30 young adult subjects (15 myopes, 15 emmetropes) at 10 different times over 2 consecutive days. Five sets of measurements were collected each day at approximately 3-hour intervals, with the first measurement taken at ~9 AM and final measurement at ~9 PM. AL underwent significant diurnal variation (P < 0.0001) that was consistently observed across the 2 measurement days. The longest AL was typically observed at the second measurement session (mean time, 12:26) and the shortest AL at the final session of each day (mean time, 21:06). The mean diurnal change in AL was 0.032 ± 0.018 mm. Choroidal thickness underwent significant diurnal variation (mean change, 0.029 ± 0.016 mm; P < 0.001) and varied approximately in antiphase to the AL changes. Significant diurnal variations were also found in vitreous chamber depth (VCD; mean change, 0.06 ± 0.029 mm; P < 0.0001) and IOP (mean change, 3.54 ± 0.84 mm Hg; P < 0.0001). A positive association was found between the variations of AL and IOP (r(2) = 0.17, P < 0.0001) and AL and VCD (r(2) = 0.31, P < 0.0001) and a negative association between AL and choroidal thickness (r(2) = 0.13, P < 0.0001). There were no significant differences in the magnitude and timing of diurnal variations associated with refractive error. Significant diurnal variations in AL, choroidal thickness, and IOP were consistently observed over 2 consecutive days of testing.

  13. Variations in tongue-palate swallowing pressures when swallowing xanthan gum-thickened liquids.

    PubMed

    Steele, Catriona M; Molfenter, Sonja M; Péladeau-Pigeon, Melanie; Polacco, Rebecca C; Yee, Clemence

    2014-12-01

    Thickened liquids are frequently recommended to reduce the risk of aspiration in patients with oropharyngeal dysphagia. Although it has previously been reported that tongue-palate pressures increase when swallowing spoon-thick and semi-solid consistencies compared to thin liquids, relatively little is known about how swallowing behaviors differ when swallowing liquids of nectar- or honey-thick consistency. Furthermore, previous studies have primarily used starch-based thickeners, and little is known about swallowing behaviors with xanthan gum-thickened liquids, which have recently been introduced for dysphagia management. In this study, we measured variations in tongue-palate pressures during the swallowing of liquids thickened to apparent viscosities of 190, 250, and 380 mPa s at 50/s using increasing concentrations of xanthan gum (0.5, 0.63 and 0.87 w/w%). The viscosity differences between these nectar- and honey-thick stimuli were confirmed to exceed sensory perceptual discrimination thresholds. Data were collected from 78 healthy adults in two sex-balanced age-groups (young; mature) and compared to reference values obtained during water swallowing. The results confirm that increased amplitudes of tongue-palate pressure were used when swallowing the thickened liquid stimuli, compared to swallows of water, and for the honey-thick liquid compared to the two nectar-thick liquids. Age-related reductions were seen in tongue strength but not in swallowing pressures, which fell below 40 % of maximum isometric pressure values. Thus, the use of xanthan gum-thickened liquids is unlikely to tax the swallowing system in terms of tongue pressure generation requirements, even in seniors with reduced maximum isometric tongue pressure measures.

  14. Load variation effects on the pressure fluctuations exerted on a Kaplan turbine runner

    NASA Astrophysics Data System (ADS)

    Amiri, K.; Mulu, B.; Raisee, M.; Cervantes, M. J.

    2014-03-01

    Introduction of intermittent electricity production systems like wind power and solar systems to electricity market together with the consumption-based electricity production resulted in numerous start/stops, load variations and off-design operation of water turbines. The hydropower systems suffer from the varying loads exerted on the stationary and rotating parts of the turbines during load variations which they are not designed for. On the other hand, investigations on part load operation of single regulated turbines, i.e., Francis and propeller, proved the formation of rotating vortex rope (RVR) in the draft tube. The RVR induces oscillating flow both in plunging and rotating modes which results in oscillating force with two different frequencies on the runner blades, bearings and other rotating parts of the turbine. The purpose of this study is to investigate the effect of transient operations on the pressure fluctuations on the runner and mechanism of the RVR formation/mitigation. Draft tube and runner blades of the Porjus U9 model, a Kaplan turbine, were equipped with pressure sensors. The model was run in off-cam mode during different load variation conditions to check the runner performance under unsteady condition. The results showed that the transients between the best efficiency point and the high load happens in a smooth way while transitions to/from the part load, where rotating vortex rope (RVR) forms in the draft tube induces high level of fluctuations with two frequencies on the runner; plunging and rotating mode of the RVR.

  15. A variational model of disjoining pressure: Liquid film on a nonplanar surface

    SciTech Connect

    Silin, D.; Virnovsky, G.

    2009-06-01

    Variational methods have been successfully used in modelling thin liquid films in numerous theoretical studies of wettability. In this paper, the variational model of the disjoining pressure is extended to the general case of a two-dimensional solid surface. The Helmgoltz free energy functional depends both on the disjoining pressure isotherm and the shape of the solid surface. The augmented Young-Laplace equation (AYLE) is a nonlinear second-order partial differential equation. A number of solutions describing wetting films on spherical grains have been obtained. In the case of cylindrical films, the phase portrait technique describes the entire variety of mathematically feasible solutions. It turns out that a periodic solution, which would describe wave-like wetting films, does not satisfy the Jacobi's condition of the classical calculus of variations. Therefore, such a solution is nonphysical. The roughness of the solid surface significantly affects liquid film stability. AYLE solutions suggest that film rupture is more likely at a location where the pore-wall surface is most exposed into the pore space and the curvature is positive.

  16. The contribution of pleiotropy of blood pressure and body-mass index variation: The Gubbio study

    SciTech Connect

    Schork, N.J.; Weder, A.B. ); Trevisan, M. Univ. of Naples Northwestern Univ., Chicago, IL ); Laurenzi, M. Center for Epidemiological Research, Merck, Sharp and Dohme Center for Preventive Medicine, Gubbio )

    1994-02-01

    Blood pressure (BP), body-mass index (BMI), and quantitative phenotypes thought to influence BP (e.g., lithium-sodium countertransport activity) were studied in 2,184 households comprising 5,376 people in Gubbio, Italy. Variance-components models were used to partition the variation of these phenotypes into components characterizing the effects of age-related, measured environmental, additive genetic, pleiotropic, unmeasured shared-household, and individual-specific (or random) factors. The goal of the investigation was to estimate the contribution of pleiotropy to variation in BP and BMI in population-based samples. Although the results suggest that numerous significant bivariate genetic correlations exist between BP and some of the traits investigated, they ultimately lead to rejection of a prominent role for any individual bivariate pleiotropic system influencing the natural variation of BP. However, because the authors found evidence that many traits enter into small-impact pleiotropic relationships with BP, they cannot rule out the possibility that pleiotropic genes, when considered collectively, may contribute to BP variation at the population level. Similar results were obtained when BMI was taken as the primary variable of interest. The authors argue that the small but significant portion of BP variation explained by individual genes displaying bivariate pleiotropic effects is intuitive, in light of the relatively low heritabilities associated with quantitative cardiovascular phenotypes and the low phenotypic correlations between BP, BMI, and many other physiologically linked measures of cardiovascular function. The results not only bear directly on both the nature of the multifactorial determinants of BP and the maintenance of BP variation in the population genetics research. 37 refs., 5 tabs.

  17. Colour variation in cichlid fish: Developmental mechanisms, selective pressures and evolutionary consequences☆

    PubMed Central

    Maan, Martine E.; Sefc, Kristina M.

    2013-01-01

    Cichlid fishes constitute one of the most species-rich families of vertebrates. In addition to complex social behaviour and morphological versatility, they are characterised by extensive diversity in colouration, both within and between species. Here, we review the cellular and molecular mechanisms underlying colour variation in this group and the selective pressures responsible for the observed variation. We specifically address the evidence for the hypothesis that divergence in colouration is associated with the evolution of reproductive isolation between lineages. While we conclude that cichlid colours are excellent models for understanding the role of animal communication in species divergence, we also identify taxonomic and methodological biases in the current research effort. We suggest that the integration of genomic approaches with ecological and behavioural studies, across the entire cichlid family and beyond it, will contribute to the utility of the cichlid model system for understanding the evolution of biological diversity. PMID:23665150

  18. A controlled variation scheme for convection treatment in pressure-based algorithm

    NASA Technical Reports Server (NTRS)

    Shyy, Wei; Thakur, Siddharth; Tucker, Kevin

    1993-01-01

    Convection effect and source terms are two primary sources of difficulties in computing turbulent reacting flows typically encountered in propulsion devices. The present work intends to elucidate the individual as well as the collective roles of convection and source terms in the fluid flow equations, and to devise appropriate treatments and implementations to improve our current capability of predicting such flows. A controlled variation scheme (CVS) has been under development in the context of a pressure-based algorithm, which has the characteristics of adaptively regulating the amount of numerical diffusivity, relative to central difference scheme, according to the variation in local flow field. Both the basic concepts and a pragmatic assessment will be presented to highlight the status of this work.

  19. Stochastic Modelling and Estimation for Cyclic Pressure Variations in Spark Ignition Engines

    NASA Astrophysics Data System (ADS)

    Roberts, J. B.; Peyton Jones, J. C.; Landsborough, K. J.

    2001-03-01

    A new method of fitting linearised, parametric stochastic models of cycle-by-cycle variations of pressure, during the combustion region of a spark ignition petrol engine, is described. The technique is based on stochastically fitting the combustion models to the covariance function of the measured pressure fluctuations, obtained by averaging over the entire ensemble of measured cycles. Comparisons, for two specific combustion models, with corresponding results obtained by deterministic fitting on a cycle-by-cycle basis, show that the new method gives a similar degree of fit, but with much improved computational efficiency. It is also demonstrated that the degree of fit to the data can be further improved by modelling the residual error between the data and the combustion models in terms of Chebyshev polynomials: the parameters in these polynomials may be determined by stochastic fitting. The technique has wider applications in the condition monitoring of rotating machinery.

  20. Sound pressure level variations across the Pacific based on IMS data

    NASA Astrophysics Data System (ADS)

    Yamada, Tomoaki; Haralabus, Georgios; Zampolli, Mario; Heaney, Kevin

    2017-04-01

    Low frequency hydro-acoustic waves can be detected at great distances due to low attenuation of acoustic energy in the SOund Fixing And Ranging (SOFAR) channel. These waves contain both acoustic source and propagation medium information which is difficult to separate at the receiving end. This study examines sound pressure level variations across the pacific using 100 underwater controlled sources near a landward slope zone in Japan to minimize source uncertainty. The data were acquired at water-column hydrophones of the hydroacoustic station HA03 at Chile that is part of the International Monitoring System (IMS) of the Comprehensive Nuclear Test Ban Treaty. Acoustics waves were detected over 15,000 km across the Pacific and initial analysis indicates a maximum difference of the pressure level is 17 dB re. micro Pa.

  1. Atmospheric pressure, density, temperature and wind variations between 50 and 200 km

    NASA Technical Reports Server (NTRS)

    Justus, C. G.; Woodrum, A.

    1972-01-01

    Data on atmospheric pressure, density, temperature and winds between 50 and 200 km were collected from sources including Meteorological Rocket Network data, ROBIN falling sphere data, grenade release and pitot tube data, meteor winds, chemical release winds, satellite data, and others. These data were analyzed by a daily difference method and results on the distribution statistics, magnitude, and spatial structure of the irregular atmospheric variations are presented. Time structures of the irregular variations were determined by the analysis of residuals from harmonic analysis of time series data. The observed height variations of irregular winds and densities are found to be in accord with a theoretical relation between these two quantities. The latitude variations (at 50 - 60 km height) show an increasing trend with latitude. A possible explanation of the unusually large irregular wind magnitudes of the White Sands MRN data is given in terms of mountain wave generation by the Sierra Nevada range about 1000 km west of White Sands. An analytical method is developed which, based on an analogy of the irregular motion field with axisymmetric turbulence, allows measured or model correlation or structure functions to be used to evaluate the effective frequency spectra of scalar and vector quantities of a spacecraft moving at any speed and at any trajectory elevation angle.

  2. Variations in nanomechanical properties of back-end Zr-2.5Nb pressure tube material

    NASA Astrophysics Data System (ADS)

    Gallaugher, Matthew; Peykov, Daniel; Brodusch, Nicolas; Chromik, Richard R.; Rodrigue, Lisa; Trudeau, Michel L.; Gauvin, Raynald

    2013-11-01

    The Zr-2.5Nb pressure tube alloy used in Canada Deuterium Uranium (CANDU) nuclear reactors consists of a dual-phase microstructure produced by a multi-step manufacturing process. The metallurgical characteristics of the pressure tubes influence their in-reactor behavior, especially with respect to reactor life-limiting properties such as diametral creep. In order to predict the in-reactor behavior of pressure tubes, a greater understanding of the influence of tube-to-tube variations in metallurgical factors such as texture, grain size, and β-phase percentage would be greatly beneficial. In this paper, a testing method combining high temperature nanoindentation with subsequent electron channeling contrast imaging (ECCI) in the scanning electron microscope (SEM) is presented to compare two back end pressure tube off-cuts. Nanoindentation was used to measure local mechanical properties such as hardness, modulus, and strain rate sensitivity. Post-examination of residual indents with ECCI allowed for the correlation of microstructural characteristics to nanomechanical properties. A difference in hardness was observed between the two tubes in the axial normal plane, which was correlated to differences in β-phase area percentage and/or morphology.

  3. Influence of tidal volume on pulse pressure variation and stroke volume variation during experimental intra-abdominal hypertension.

    PubMed

    Díaz, F; Erranz, B; Donoso, A; Salomon, T; Cruces, Pablo

    2015-09-22

    Pulse pressure variation (PPV) and stroke volume variation (SVV) are frequently used to assess fluid responsiveness in critically ill patients on mechanical ventilation (MV). There are many factors, in addition to preload that influence the magnitude of these cyclic variations. We sought to investigate the effect of tidal volume (V(T)) on PPV and SVV, and prediction of fluid responsiveness in a model of intra-abdominal hypertension (IAH). Twelve anesthetized and mechanically ventilated piglets on continuous pulse contour cardiac output monitoring. Hypovolemia was ruled out with 2 consecutive fluid boluses after instrumentation. IAH was induced by intraperitoneal instillation of colloid solution with a goal of reducing respiratory system compliance by 50 %. Subjects were classified as fluid responders if stroke volume increased >15 % after each fluid challenge. SVV and PPV were recorded with tidal volumes (VT) of 6, 12 and 18 ml/kg before IAH after IAH induction and after a fluid challenge during IAH. V(T) influenced PPV and SVV at baseline and during IAH, being significantly larger with higher V(T). These differences were attenuated after fluid administration in both conditions. After IAH induction, there was a significant increase in SVV with the three-tested V(T), but the magnitude of that change was larger with high V(T): with 6 ml/kg from 3 % (3, 4) to 5 % (4, 6.25) (p = 0.05), with 12 ml/kg from 5 % (4, 6) to 11 % (8.75, 17) (p = 0.02) and 18 ml/kg from 5 % (4,7.5) to 15 % (8.75, 19.5) (p = 0.02). Similarly, PPV increased with all the tested VT after IAH induction, being this increase larger with high VT: with 6 ml/kg from 3 % (2, 4.25) to 6 % (4.75, 7) (p = 0.05), with 12 ml/kg from 5 % (4, 6) to 13.5 % (10.25, 15.5) (p = 0.02) and 18 ml/kg from 7 % (5.5, 8.5) to 24 % (13.5, 30.25) (p = 0.02). One third of subjects responded to fluid administration after IAH, but neither SVV nor PPV were able to identify the fluid responders with the

  4. Methods for quantifying the influences of pressure and temperature variation on metal hydride reaction rates measured under isochoric conditions.

    PubMed

    Voskuilen, Tyler G; Pourpoint, Timothée L

    2013-11-01

    Analysis techniques for determining gas-solid reaction rates from gas sorption measurements obtained under non-constant pressure and temperature conditions often neglect temporal variations in these quantities. Depending on the materials in question, this can lead to significant variations in the measured reaction rates. In this work, we present two new analysis techniques for comparison between various kinetic models and isochoric gas measurement data obtained under varying temperature and pressure conditions in a high pressure Sievert system. We introduce the integral pressure dependence method and the temperature dependence factor as means of correcting for experimental variations, improving model-measurement fidelity, and quantifying the effect that such variations can have on measured reaction rates. We use measurements of hydrogen absorption in LaNi5 and TiCrMn to demonstrate the effect of each of these methods and show that their use can provide quantitative improvements in interpretation of kinetics measurements.

  5. Effects of stroke volume variation, pulse pressure variation, and pleth variability index in predicting fluid responsiveness during different positive end expiratory pressure in prone position.

    PubMed

    Chen, Yu; Fu, Qiang; Mi, Wei-dong

    2015-04-01

    To investigate the effects of different positive end expiratory pressures (PEEP) on functional hemodynamic parameters in patients lying in prone position during operation under general anesthesia. Totally 60 patients undergoing cervical vertebra operation or lumbar vertebra operation were studied. All patients were also monitored with Vigileo/FloTrac system. The functional hemodynamic parameters including stroke volume variation (SVV), pulse pressure variation (PPV), and pleth variability index (PVI) under PEEP levels of 0 mmHg, 5 mmHg, 10 mmHg, and 15 mmHg were recorded before and after volume expansion (hydroxyethyl starch 6%,7 ml/kg). Fluid responsiveness was defined as an increase in stroke volume index (SVI) ≥ 15%(△SVI ≥ 15%). Responders were defined as patients demonstrating an increase in SVI ≥ 15% after intravascular volume expansion and non-responders as patients whose SVI changed <15%. Receiver operating characteristic (ROC) curves were generated for SVV, PPV, and PVI under different PEEP levels to determine their diagnosis accuracies and thresholds and their potential correlations. In the prone position, SVV, PPV, and PVI were significantly higher compared to those in the supine position (P<0.05) and the mean arterial pressure significantly decreased (P<0.05); however, the changes of heart rate, stroke volume, SVI, cardiac output, and cardiac index showed no significant difference (P>0.05). In the prone position, along with the elevation of PEEP (0 mmHg, 5 mmHg, 10 mmHg, and 15 mmHg), the areas under the ROC curves of SVV were 0.864, 0.759, 0.718, and 0.521, the area under the ROC of PPV were 0.873, 0.792,0.705, and 0.505, and the area under the ROC of PVI were 0.851, 0.765 ,0.709, and 0.512. Under PEEP=0 mmHg, the diagnostic thresholds of SVV, PPV, and PVI were 10.5, 11.5, and 13.5. Under PEEP=5 mmHg, the diagnostic thresholds of SVV,PPV, and PVI were 11.5,13.5, and 14.5.Under PEEP=10 mmHg,the diagnostic thresholds of SVV, PPV, and PVI were 13

  6. Passenger comfort on high-speed trains: effect of tunnel noise on the subjective assessment of pressure variations.

    PubMed

    Sanok, Sandra; Mendolia, Franco; Wittkowski, Martin; Rooney, Daniel; Putzke, Matthias; Aeschbach, Daniel

    2015-01-01

    When passing through a tunnel, aerodynamic effects on high-speed trains may impair passenger comfort. These variations in atmospheric pressure are accompanied by transient increases in sound pressure level. To date, it is unclear whether the latter influences the perceived discomfort associated with the variations in atmospheric pressure. In a pressure chamber of the DLR-Institute of Aerospace Medicine, 71 participants (M = 28.3 years ± 8.1 SD) rated randomised pressure changes during two conditions according to a crossover design. The pressure changes were presented together with tunnel noise such that the sound pressure level was transiently elevated by either +6 dB (low noise condition) or +12 dB (high noise condition) above background noise level (65 dB(A)). Data were combined with those of a recent study, in which identical pressure changes were presented without tunnel noise (Schwanitz et al., 2013, 'Pressure Variations on a Train - Where is the Threshold to Railway Passenger Discomfort?' Applied Ergonomics 44 (2): 200-209). Exposure-response relationships for the combined data set comprising all three noise conditions show that pressure discomfort increases with the magnitude and speed of the pressure changes but decreases with increasing tunnel noise. Practitioner Summary: In a pressure chamber, we systematically examined how pressure discomfort, as it may be experienced by railway passengers, is affected by the presence of tunnel noise during pressure changes. It is shown that across three conditions (no noise, low noise (+6 dB), high noise (+12 dB)) pressure discomfort decreases with increasing tunnel noise.

  7. Noise in pressure transducer readings produced by variations in solar radiation

    USGS Publications Warehouse

    Cain, S. F.; Davis, G.A.; Loheide, S.P.; Butler, J.J.

    2004-01-01

    Variations in solar radiation can produce noise in readings from gauge pressure transducers when the transducer cable is exposed to direct sunlight. This noise is a result of insolation-induced heating and cooling of the air column in the vent tube of the transducer cable. A controlled experiment was performed to assess the impact of variations in solar radiation on transducer readings. This experiment demonstrated that insolation-induced fluctuations in apparent pressure head can be as large as 0.03 m. The magnitude of these fluctuations is dependent on cable color, the diameter of the vent tube, and the length of the transducer cable. The most effective means of minimizing insolation-induced noise is to use integrated transducer-data logger units that fit within a well. Failure to address this source of noise can introduce considerable uncertainty into analyses of hydraulic tests when the head change is relatively small, as is often the case for tests in highly permeable aquifers or for tests using distant observation wells.

  8. Variation of 24-hour intraocular pressure in healthy individuals: right eye versus left eye.

    PubMed

    Liu, John H K; Sit, Arthur J; Weinreb, Robert N

    2005-10-01

    An assumption for the one-eye therapeutic trial of ocular hypotensive drugs is the symmetrical variation of intraocular pressure (IOP) between the two eyes. We evaluated whether or not 24-hour variations of IOP in the two eyes are similar in healthy individuals. Experimental study with human subjects. Ninety-one healthy individuals. We reviewed bilateral IOP data collected from 38 younger (18-25 years) and 53 older (40-74 years) experimental subjects housed for 24 hours in a sleep laboratory. Intraocular pressure was measured every 2 hours using a pneumatonometer in the sitting and supine positions during the 16-hour diurnal/wake period and in the supine position during the 8-hour nocturnal/sleep period. Measurements were always taken first in the right eye. For each age group, the two eyes' means, peaks, troughs, and ranges of IOP during office hours, the diurnal period, the nocturnal period, and the 24-hour period were compared. The coefficient of determination was used to examine the strength of association between the right and left IOPs. Bilateral IOP. For each age group, the profiles of IOP variations were similar in the two eyes with either the habitual body positions (diurnal sitting and nocturnal supine) or the 24-hour supine position. Mean, peak, and trough IOPs in the right eye were slightly higher than those in the left eye during the defined periods. There was no difference in the IOP range, except for the supine IOP in the younger group during the diurnal period. Cosine fits of the 24-hour supine IOP indicate no difference in the estimated phase timing or the 24-hour variation between the two eyes. Coefficients of determination for single pairs of right and left IOPs were in the range of 0.311 to 0.741. Variations of 24-hour IOP in the right and left eyes are similar. However, because the strength of association between the two eyes is only moderate, it may be difficult to perform a one-eye therapeutic trial using single pairs of right and left eye

  9. Simulation of spatio-temporal variation of OH radical density in atmospheric-pressure streamer discharge

    NASA Astrophysics Data System (ADS)

    Komuro, Atsushi; Ando, Akira

    2017-06-01

    The spatio-temporal variation of OH radical density in an atmospheric-pressure plasma discharge is investigated via two-dimensional numerical simulation. The behaviours of OH are characterized in four regions in the inter-electrode gap, namely the ‘Hot anode’, ‘Secondary streamer’, ‘Primary streamer’, and ‘Near-cathode’ regions. In these regions, temporal variations of averaged reduced electric field, electron density, and gas temperature differ and they affect the temporal variation of OH density. In all regions, a relatively large amount of OH is produced by the dissociation reactions of H2O with electronically excited nitrogen molecules and oxygen atom rather than the direct electron-impact dissociation reactions. In the Hot anode and Secondary streamer regions, the instantaneous density of OH just after the discharge is high. However, the subsequent OH decay rates differ in these regions owing to the difference in gas temperatures. The reaction mechanism is discussed by dividing the effect of the diffusion-convection term and chemical reaction term in the continuous equation for OH radical density.

  10. Variation in blood pressure is associated with white matter microstructure but not cognition in African Americans.

    PubMed

    Leritz, Elizabeth C; Salat, David H; Milberg, William P; Williams, Victoria J; Chapman, Caroline E; Grande, Laura J; Rudolph, James L; Schnyer, David M; Barber, Colleen E; Lipsitz, Lewis A; McGlinchey, Regina E

    2010-03-01

    Although hypertension is a major risk factor for cerebrovascular disease (CVD) and is highly prevalent in African Americans, little is known about how blood pressure (BP) affects brain-behavior relationships in this population. In predominantly Caucasian populations, high BP is associated with alterations in frontal-subcortical white matter and in executive functioning aspects of cognition. We investigated associations among BP, brain structure, and neuropsychological functioning in 52 middle-older-age African Americans without diagnosed history of CVD. All participants underwent diffusion tensor imaging for examination of white matter integrity, indexed by fractional anisotropy (FA). Three regions of interest were derived in the anterior (genu) and posterior (splenium) corpus callosum and across the whole brain. A brief neuropsychological battery was administered from which composite scores of executive function and memory were derived. Blood pressure was characterized by mean arterial blood pressure (MABP). When controlling for age, higher MABP was associated with lower FA in the genu, and there was a trend for this same relationship with regard to whole-brain FA. When the sample was broken into groups on the basis of treatment for BP regulation (medicated vs. nonmedicated), MABP was related to genu and whole-brain FA only in the nonmedicated group. Neither MABP nor FA was significantly related to either neuropsychological composite score regardless of medication use. These data provide important evidence that variation in BP may contribute to significant alterations in specific neural regions of white matter in nonmedicated individuals without symptoms of overt CVD.

  11. Variation in barometric pressure in Melbourne does not significantly affect the BTPS correction factor.

    PubMed

    Johns, David P; Hartley, M Faizel; Burns, Graham; Thompson, Bruce R

    2004-08-01

    The conventional BTPS (body temperature and pressure, saturated with water vapour) correction factor varies with ambient barometric pressure (P(B)) and many lung function laboratories measure P(B) daily. The aim was to investigate whether a fixed value for P(B) could replace daily measurements. P(B) was measured daily over a 12-month period. The highest and lowest values in Melbourne in the last century were also recorded from data published by the Bureau of Meteorology. Using these P(B) values, the BTPS factor was determined for a range of spirometer temperatures and compared to the BTPS factors obtained using a fixed ambient pressure of 101.3 kPa. The mean (SD) P(B) measured over the 12-month period was 102.2 kPa (0.64) with a range of 99.9-103.6 kPa. The level of disagreement between the BTPS factor calculated using a P(B) of 101.3 kPa instead of the measured value was greater at lower temperatures. Over the extremes of P(B) during the last century (98.0-104.3 kPa) the use of a standard pressure (101.3 kPa) produced an error in the BTPS factor of variations in P(B) do not significantly affect the magnitude of the conventional BTPS correction factor and a fixed value, such as 101.3 kPa at sea level, can be used with little error.

  12. Micrometeorite Impact Effects on Comets and Asteroids: Peak Pressure versus Spectral Variation

    NASA Astrophysics Data System (ADS)

    Jensen, Elizabeth; Lederer, S. M.; Strojia, C.; Smith, D. C.; Wooden, D. H.; Lindsay, S. S.; Keller, L. P.; Cintala, M. J.; Zolensky, M. E.

    2013-10-01

    At the Experimental Impact Laboratory at NASA Johnson Space Center, we have investigated the surface properties of asteroids caused by collisions in the mid-infrared (2.5 to 16 microns) by impacting forsterite and enstatite across a range of velocities (as predicted by the Nice Model) and at varying temperatures. The crystal structure in these minerals can be deformed by the shock wave from the impact as well as sheared into smaller particle sizes. Our current focus is on the differing effects between 2.3 and 2.6 km/sec, as well as the differences between a cold sample at -20C and a room temperature sample at 25C. We find that the spectral variation and crystal deformation varies non-linearly with the peak theoretical shock pressure. Funding was provided by the NASA PG&G grant 09-PGG09-0115, NSF grant AST-1010012, and a Cottrell College Scholarship through the Research Corporation.

  13. Modeling the dynamics of pressure propagation and diameter variation in tree sapwood.

    PubMed

    Perämäki, Martti; Vesala, Timo; Nikinmaa, Eero

    2005-09-01

    A non-steady-state model of water tension propagation in tree stems was developed. The model is based on the cohesion theory and the assumption that fluctuating water tension driven by transpiration together with the elasticity of wood cause variations in the diameter of a tree stem. The change in xylem diameter can be linked to water tension in accordance with Hooke's law. The model was tested against field measurements of the diurnal change in xylem diameter at different heights in a 180-year-old Scots pine tree at Hyytiälä, southern Finland. Model predictions agreed well with measurements. The effect of tree dimensions on pressure propagation was examined with the model. The model outcomes were also consistent with results of several field measurements presented in the literature.

  14. Observational features of field line resonances excited by solar wind pressure variations on 4 September 1984

    NASA Technical Reports Server (NTRS)

    Warnecke, J.; Luehr, H.; Takahashi, K.

    1990-01-01

    The purpose of the study is to establish the most probable excitation mechanism of the magnetic storm occurred after an inverse sudden impulse on September 4, 1984. Geomagnetic pulsations in the Pc5-frequency range observed at magnetometer stations are evaluated. Attention is focused on two events of the enhanced activity: for the first one, conjugate observations on the ground are assessed and then compared with satellite-based observations on adjacent field lines; for the second event two hours later, data from an extended azimuthal range is employed. It is pointed out that the observations are consistent with the theory of filed-line resonance, and may be interpreted as excitations caused by pressure variations in the solar wind. Both magnetopause-surface waves and cavity resonances are excited; the cavity mode drives toroidal field-line oscillations at locations where its frequency matches the resonance frequency of the field lines.

  15. Effect of azilsartan versus candesartan on nocturnal blood pressure variation in Japanese patients with essential hypertension.

    PubMed

    Rakugi, Hiromi; Kario, Kazuomi; Enya, Kazuaki; Igeta, Masataka; Ikeda, Yoshinori

    2013-09-01

    Abnormal variations in night-time hypertension such as "non-dipping" type (< 10% decrease in nocturnal systolic blood pressure [SBP] from daytime SBP) are a risk factor for cardiovascular events independent of 24-h BP. As part of a randomized, double-blind study of azilsartan (20-40 mg once daily) and candesartan (8-12 mg once daily) in Japanese patients with essential hypertension, an exploratory analysis was performed using ambulatory BP monitoring (ABPM) at baseline and Week 14. Effects of study drugs on nocturnal BP variations according to patients' nocturnal SBP dipping status were evaluated. ABPM data were available for 273 patients treated with azilsartan and 275 with candesartan. In the dipping group (≥ 10% decrease from daytime SBP), azilsartan produced a greater reduction from baseline in daytime than in night-time SBP (- 14.1 and - 10.9 mmHg, respectively), and the change in daytime SBP was significantly greater with azilsartan than with candesartan (p = 0.0077). In the non-dipping group, azilsartan produced a greater reduction from baseline in night-time than in daytime SBP (- 20.2 and - 9.9 mmHg, respectively), and reductions in both night-time SBP (p = 0.02) and daytime SBP (p = 0.0042) were significantly greater with azilsartan than with candesartan. Once-daily azilsartan improved non-dipping night-time SBP to a greater extent than candesartan in Japanese patients with grade I-II essential hypertension.

  16. A biometrical genome-scan in rats reveals the multigenic basis of blood pressure variation

    SciTech Connect

    Schork, N.J.; Trolliet, M.R.; Koike, G.

    1994-09-01

    Well-designed breeding programs involving model organisms and modern DNA marker technologies have the potential to reveal loci whose evolutionary homologs influence human traits. Researchers investigating particular human traits can exploit this fact by studying the genetic basis of those traits in model organisms in an effort to gain insight into which genes might be influencing the trait in humans. This strategy is especially useful for researchers studying human quantitative traits (QTs), since the genetic architecture of human QTs is complex enough to preclude easy characterization with limited extant human gene mapping tools. We performed a genome-wide search for loci influencing salt-loaded systolic blood pressure (NaSBP) in 188 F2 rats produced from a Brown-Norway x Spontaneously Hypertensive rat cross. From genotype information available at 184 marker loci dispersed throughout the rat genome, we were able to determine 6 loci that collectively explain some 43% of the total NaSBP variation exhibited by our F2 progeny. Our results not only shed light on potential candidate loci for human BP variation, but also suggest that the genetic basis of classically-defined polygenic traits of higher organisms may yield to modern biometrical analyses in controlled settings.

  17. North Atlantic meridional overturning circulation variations from GRACE ocean bottom pressure anomalies

    NASA Astrophysics Data System (ADS)

    Landerer, Felix W.; Wiese, David N.; Bentel, Katrin; Boening, Carmen; Watkins, Michael M.

    2015-10-01

    Concerns about North Atlantic Meridional Overturning Circulation (NAMOC) changes imply the need for a continuous, large-scale observation capability to detect changes on interannual to decadal time scales. Here we present the first measurements of Lower North Atlantic Deep Water (LNADW) transport changes using only time-variable gravity observations from Gravity Recovery and Climate Experiment (GRACE) satellites from 2003 until now. Improved monthly gravity field retrievals allow the detection of North Atlantic interannual bottom pressure anomalies and LNADW transport estimates that are in good agreement with those from the Rapid Climate Change-Meridional Overturning Circulation and Heatflux Array (RAPID/MOCHA). Concurrent with the observed AMOC transport anomalies from late 2009 through early 2010, GRACE measured ocean bottom pressures changes in the 3000-5000 m deep western North Atlantic on the order of 20 mm-H2O (200 Pa), implying a southward volume transport anomaly in that layer of approximately -5.5 sverdrup. Our results highlight the efficacy of space gravimetry for observing AMOC variations to evaluate latitudinal coherency and long-term variability.

  18. [Salt taste threshold, 24 hour natriuresis and blood pressure variation in normotensive individuals].

    PubMed

    Antonello, Vicente Sperb; Antonello, Ivan Carlos Ferreira; Santos, Carlos Abaeté de Los

    2007-01-01

    The study evaluates salt taste sensibility, urinary sodium excretion and blood pressure (BP) in normotensive persons. The hypothesis was that a higher salt taste threshold (STT) can be associated to a higher 24 hour natriuresis and increased BP levels. Twenty four not hypertensive volunteers were selected. To evaluate STT, different concentrations of sodium chloride were used. Individuals were submitted to 24 hour ambulatory blood pressure monitoring (ABPM) and the 24 hour urine was collected for sodium dosage. Patients were divided in two groups related to higher or normal STT. Both groups did not differ regarding age or body mass index (BMI). There was no difference between the groups regarding demographic variables, alcohol or tobacco use, and ABPM. Twenty-four hour natriuresis was significantly higher in the group with increased STT. Using Pearson's correlation coefficient, with the significance determined by Student-t test, there was a strong correlation between 24 hour Systolic BP and BMI, Diastolic BP and BMI, and a regular correlation between STT with 24 hour natriuresis and Systolic BP with 24 hour natriuresis. Twenty four hour natriuresis was significantly higher in individuals with higher STT, suggesting that this avidity for salt is followed by higher ingestion of sodium. There was strong association between BP and BMI. The association between STT and BP levels was not confirmed. Increasing the number of persons, the age bracket, and of hypertensive patients may lead to a better understanding of the relations between STT, natriuresis and BP variation.

  19. The physics of pressure variation in microchannels within corotating or static discs

    NASA Astrophysics Data System (ADS)

    Guha, Abhijit; Sengupta, Sayantan

    2016-10-01

    We formulate a comprehensive analysis for the radial pressure variation in flow through microchannels within corotating (or static) discs, which is important for its fundamental value and application potential in macrofluidic and microfluidic devices. The uniqueness and utility of the present approach emanate from our ability to describe the physics completely in terms of non-dimensional numbers and to determine quantitatively the separate roles of inertia, centrifugal force, Coriolis force, and viscous effects in the overall radial pressure difference (Δpio). It is established here that the aspect ratio (ratio of inter-disc spacing and disc radius) plays only a secondary role as an independent parameter, its major role being contained within a newly identified dynamic similarity number (Ds). For radial inflow, it is shown that the magnitude of Δpio decreases monotonically as the tangential speed ratio (γ) increases but exhibits a minima when Ds is varied. For radial outflow, it is shown that Δpio increases monotonically as the flow coefficient (ϕ) decreases but evinces a maxima when Ds is varied. It is further shown that for the radial inflow case, the minima in the magnitude of Δpio exist even when the rotational speed of the discs is reduced to zero (static discs). The demonstrated existence of these extrema (i.e., minima for radial inflow and maxima for radial outflow) creates the scope for device optimization.

  20. North Atlantic meridional overturning circulation variations from GRACE ocean bottom pressure anomalie

    NASA Astrophysics Data System (ADS)

    Landerer, F. W.; Wiese, D. N.; Bentel, K.; Boening, C.; Watkins, M. M.

    2015-12-01

    The important role of the North-Atlantic Meridonal Overturning Circulation (AMOC) for regional as well as global climate is well recognized. Concerns about potential future AMOC changes imply the need for a continuous, large-scale observation capability to detect any such changes on interannual to decadal time scales. Here, we present the first measurements of lower North-Atlantic-Deep-Water (LNADW) monthly transport changes using only space-based time-variable gravity observations from Gravity Recovery and Climate Experiment (GRACE) satellites, continuously covering the time period from 2003 until now. Improved monthly gravity field retrievals allow the detection of North Atlantic interannual bottom pressure anomalies and yield LNADW transport estimates that are in good agreement with those from the ocean in-situ RAPID-MOCA array at 26.5N. Concurrent with the observed AMOC transport anomalies from late-2009 through early-2010, GRACE measured ocean bottom pressures changes in the 3000-5000 m deep western North Atlantic of -20 mm-H2O, implying a southward volume transport anomaly in that layer of approximately -5.5 Sv. Our results highlight the efficacy of space-gravimetry to observe and detect meridional ocean transport variations that can potentially be retrieved over all latitude ranges in the Atlantic.

  1. Variation in intracranial pressure monitoring and outcomes in pediatric traumatic brain injury.

    PubMed

    Bennett, Tellen D; Riva-Cambrin, Jay; Keenan, Heather T; Korgenski, E Kent; Bratton, Susan L

    2012-07-01

    To describe between-hospital and patient-level variation in intracranial pressure (ICP) monitoring and to evaluate ICP monitoring in association with hospital features and outcome in children with traumatic brain injury (TBI). Retrospective cohort study. SETTING Children's hospitals participating in the Pediatric Health Information System database (January 2001 to June 2011). Children (aged <18 years) with TBI and head Abbreviated Injury Scale scores of at least 3 who were ventilated for at least 96 consecutive hours or who died in the first 4 days after hospital admission. Monitoring of ICP. A total of 4667 children met the study criteria. Hospital mortality was 41% (n = 1919). Overall, 55% of patients (n = 2586) received ICP monitoring. Expected hospital ICP monitoring rates after adjustment for patient age, cardiac arrest, inflicted injury, craniotomy or craniectomy, head Abbreviated Injury Scale score, and Injury Severity Score were 47% to 60%. Observed hospital ICP monitoring rates were 14% to 83%. Hospitals with more observed ICP monitoring, relative to expected, and hospitals with higher patient volumes had lower rates of mortality or severe disability. After adjustment for between-hospital variation and patient severity of injury, ICP monitoring was independently associated with age 1 year and older (odds ratio, 3.1; 95% CI, 2.5-3.8) vs age younger than 1 year. There was significant between-hospital variation in ICP monitoring that cannot be attributed solely to differences in case mix. Hospitals that monitor ICP more frequently and hospitals with higher patient volumes had better patient outcomes. Infants with TBI are less likely to receive ICP monitoring than are older children.

  2. Cardiac cycle efficiency and dicrotic pressure variations: new parameters for fluid therapy: A pilot observational study.

    PubMed

    Messina, Antonio; Romano, Salvatore M; Bonicolini, Eleonora; Colombo, Davide; Cammarota, Gianmaria; Chiostri, Marco; Della Corte, Francesco; Navalesi, Paolo; Payen, Didier; Romagnoli, Stefano

    2017-06-19

    During a fluid challenge, the changes in cardiac performance and peripheral circulatory tone are closely related to the position of the ventricle on the Frank-Starling curve. Some patients have a good haemodynamic response to a fluid challenge, others hardly any response. The early haemodynamic effects of a fluid challenge could predict the final response before the entire fluid volume has been administered. To assess whether a multivariate logistic regression model, including pulse pressure variation (PPV), cardiac cycle efficiency (CCE), arterial elastance and the difference between the dicrotic pressure and both systolic and mean arterial pressure (SAP - Pdic and MAP - Pdic) can predict cardiac responsiveness early during a fluid challenge in comparison with the standard procedure described elsewhere. Observational pilot study. Elective surgical patients undergoing laparotomy, enrolled in two Italian University Hospitals. Fifty adult surgical patients, ventilated with a lung protective strategy, were enrolled and data from 46 were analysed. A fluid challenge consisting of 500 ml of crystalloid infused over 10 min. The changes in CCE, arterial elastance, SAP - Pdic and MAP - Pdic were compared using analysis of variance. A multivariate logistic regression analysis utilising baseline values and the first minute measuring a variation statistically significant for the considered variables. At baseline, PPV correctly identified 70% of patients (89% of non-responders; 42% of responders). The model, including baseline PPV, ΔCCE and ΔSAP - Pdic, correctly identified the efficiency of fluid challenge in 87% of patients (84.2% of responders; 92.5 of non-responders) after 5 min from fluid challenge infusion. In this pilot study conducted in a population of surgical patients mechanically ventilated with a VT less than 8 ml kg, a dynamic model of fluid challenge assessment, including PPV, ΔCCE and ΔSAP - Pdic, enhances the prediction of

  3. Hydromechanical Rock Mass Fatigue in Deep-Seated Landslides Accompanying Seasonal Variations in Pore Pressures

    NASA Astrophysics Data System (ADS)

    Preisig, Giona; Eberhardt, Erik; Smithyman, Megan; Preh, Alexander; Bonzanigo, Luca

    2016-06-01

    The episodic movement of deep-seated landslides is often governed by the presence of high pore pressures and reduced effective stresses along active shear surfaces. Pore pressures are subject to cyclic fluctuation under seasonal variations of groundwater recharge, resulting in an intermittent movement characterized by acceleration-deceleration phases. However, it is not always clear why certain acceleration phases reach alarming levels without a clear trigger (i.e., in the absence of an exceptional pore pressure event). This paper presents a conceptual framework linking hydromechanical cycling, progressive failure and fatigue to investigate and explain the episodic behavior of deep-seated landslides using the Campo Vallemaggia landslide in Switzerland as a case study. A combination of monitoring data and advanced numerical modeling is used. The principal processes forcing the slope into a critical disequilibrium state are analyzed as a function of rock mass damage and fatigue. Modeling results suggest that during periods of slope acceleration, the rock slope experiences localized fatigue and gradual weakening through slip along pre-existing natural fractures and yield of critically stressed intact rock bridges. At certain intervals, pockets of critically weakened rock may produce a period of enhanced slope movement in response to a small pore pressure increase similar to those routinely experienced each year. Accordingly, the distribution and connectivity of pre-existing permeable planes of weakness play a central role. These structures are often related to the rock mass's tectonic history or initiate (and dilate) in response to stress changes that disturb the entire slope, such as glacial unloading or seismic loading via large earthquakes. The latter is discussed in detail in a companion paper to this (Gischig et al., Rock Mech Rock Eng, 2015). The results and framework presented further demonstrate that episodic movement and progressive failure of deep

  4. Stroke volume variation (SVV) and pulse pressure variation (PPV) as indicators of fluid responsiveness in sevoflurane anesthetized mechanically ventilated euvolemic dogs

    PubMed Central

    ENDO, Yusuke; TAMURA, Jun; ISHIZUKA, Tomohito; ITAMI, Takaharu; HANAZONO, Kiwamu; MIYOSHI, Kenjiro; SANO, Tadashi; YAMASHITA, Kazuto; MUIR, William W.

    2017-01-01

    Changes in stroke volume variation (SVV) and pulse pressure variation (PPV) in response to fluid infusion were experimentally evaluated during vecuronium infusion and sevoflurane anesthesia in 5 adult, mechanically ventilated, euvolemic, beagle dogs. Sequential increases in central venous pressure (CVP; 3–7[baseline], 8–12, 13–17, 18–22 and 23–27 mmHg) were produced by infusing lactated Ringer’s solution and 6% hydroxyethyl starch solution. Heart rate (beats/min), right atrial pressure (RAP, mmHg), pulmonary arterial pressure (PAP, mmHg), pulmonary capillary wedge pressure (PCWP, mmHg), transpulmonary thermodilution cardiac output (TPTDCO, l/min), stroke volume (SV, ml/beat), arterial blood pressure (ABP, mmHg), extravascular lung water (EVLW, ml), pulmonary vascular permeability index (PVPI, calculated), SVV (%), PPV (%) and systemic vascular resistance (SVR, dynes/sec/cm5) were determined at each predetermined CVP range. Heart rate (P=0.019), RAP (P<0.001), PAP (P<0.001), PCWP (P<0.001), TPTDCO (P=0.009) and SV (P=0.04) increased and SVR (P<0.001), SVV (P<0.001) and PPV (P<0.001) decreased associated with each stepwise increase in CVP. Arterial blood pressure, EVLW, PVPI and the arterial partial pressures of oxygen and carbon dioxide did not change. The changes in SVV and PPV directly reflected the fluid load and the minimum threshold values for detecting fluid responsiveness were SVV ≥11% and PPV ≥7% in dogs. PMID:28690287

  5. Vertical laryngeal position and oral pressure variations during resonance tube phonation in water and in air. A pilot study.

    PubMed

    Wistbacka, Greta; Sundberg, Johan; Simberg, Susanna

    2016-10-01

    Resonance tube phonation in water (RTPW) is commonly used in voice therapy, particularly in Finland and Sweden. The method is believed to induce a lowering of the vertical laryngeal position (VLP) in phonation as well as variations of the oral pressure, possibly inducing a massage effect. This pilot study presents an attempt to measure VLP and oral pressure in two subjects during RTPW and during phonation with the free tube end in air. VLP is recorded by means of a dual-channel electroglottograph. RTPW was found to lower VLP in the subjects, while it increased during phonation with the tube end in air. RTPW caused an oral pressure modulation with a bubble frequency of 14-22 Hz, depending mainly on the depth of the tube end under the water surface. The results indicate that RTPW lowers the VLP instantly and creates oral pressure variations.

  6. Possible origins of time variability in Jupiter's outer magnetosphere. I - Variations in solar wind dynamic pressure. II - Variations in solar wind magnetic field

    NASA Technical Reports Server (NTRS)

    Coroniti, F. V.; Kennel, C. F.

    1977-01-01

    Attention is given to the effect of changes in the dynamic pressure of the solar wind on the structure of a centrifugally driven planetary wind from Jupiter. It is suggested that dynamic pressure variations can induce a transition between a super-Alfvenic wind and a sub-Alfvenic wind breeze on Jupiter's dayside. This could possibly account for the observed large-scale changes in the structure of Jupiter's outer magnetosphere. An attempt is then made to conceptually merge planetary wind models of Jupiter's outer magnetosphere with reconnection models of Jupiter's outer magnetosphere.

  7. CO2 Exsolution from CO2 Saturated Water: Core-Scale Experiments and Focus on Impacts of Pressure Variations.

    PubMed

    Xu, Ruina; Li, Rong; Ma, Jin; Jiang, Peixue

    2015-12-15

    For CO2 sequestration and utilization in the shallow reservoirs, reservoir pressure changes are due to the injection rate changing, a leakage event, and brine withdrawal for reservoir pressure balance. The amounts of exsolved CO2 which are influenced by the pressure reduction and the subsequent secondary imbibition process have a significant effect on the stability and capacity of CO2 sequestration and utilization. In this study, exsolution behavior of the CO2 has been studied experimentally using a core flooding system in combination with NMR/MRI equipment. Three series of pressure variation profiles, including depletion followed by imbibitions without or with repressurization and repetitive depletion and repressurization/imbibition cycles, were designed to investigate the exsolution responses for these complex pressure variation profiles. We found that the exsolved CO2 phase preferentially occupies the larger pores and exhibits a uniform spatial distribution. The mobility of CO2 is low during the imbibition process, and the residual trapping ratio is extraordinarily high. During the cyclic pressure variation process, the first cycle has the largest contribution to the amount of exsolved CO2. The low CO2 mobility implies a certain degree of self-sealing during a possible reservoir depletion.

  8. Pressure and temperature variation of octahedral Na and tetrahedral Al in amphiboles in metamafic rocks

    NASA Astrophysics Data System (ADS)

    Jenkins, D. M.; Lei, J.

    2013-12-01

    The sodium content in the M4 site of amphibole (BNa) was calibrated by Brown (1977, J Petrol, 18, 53-72) in a study that continues to be highly cited to this day. This study, based on empirical observations of amphibole compositional changes in the presence of the buffering assemblage plagioclase, chlorite, epidote, iron oxide, and water, demonstrated a systematic variation in the BNa and tetrahedral Al (TAl) content with pressure. Recent experimental work in this lab aimed at defining the extent of miscibility along the tremolite-glaucophane and hornblende-glaucophane joins in the Na2O-CaO-MgO-Al2O3-SiO2-H2O system has provided some additional information on the cation mixing along these joins. These joins also serve as the chemically-simplified framework of the BNa versus TAl correlation reported by Brown (1977). There are now sufficient, though still a bare minimum, of experimentally-confirmed mixing data for sodium-rich amphiboles to test this correlation and for quantifying the pressure-temperature (P-T) dependence of amphibole compositions in metamafic rocks relevant to subduction zones. From experimental results obtained over the range of 500-800°C, 1.5-2.0 GPa, and using a variety of amphibole synthesis and re-equilibration methods, the following set of asymmetric formalism (ASF) macroscopic interaction and mixing parameters have been derived that can be used with THERMOCALC dataset 55: Wtrgl = 70 kJ, Wglts = Wtrts =20 kJ, α(tr) = 1.0, α(ts) = 1.2, and α(gl) = 0.52. Using a fixed MORB bulk composition, the composition of amphiboles within the P-T stability field of the buffering assemblage were calculated for the above chemical system with FeO added (i.e., NCFMASH) over the range of 0.2 - 2.0 GPa and 400 - 700°C. The following main observations can be made. First, the empirical amphibole compositions at low TAl and high BNa contents are well modeled by the miscibility gap in the amphibole ternary sub-system tremolite

  9. Pressure variation assisted fiber extraction and development of high performance natural fiber composites and nanocomposites

    NASA Astrophysics Data System (ADS)

    Markevicius, Gediminas

    It is believed, that due to the large surface areas provided by the nano scale materials, various composite properties could be enhanced when such particles are incorporated into a polymer matrix. There is also a trend of utilizing natural resources or reusing and recycling materials that are already available for the fabrication of the new composite materials. Cellulose is the most abundant natural polymer on the planet, and therefore it is not surprising to be of interest for composite fabrication. Basic structures of cellulose, comprised of long polysaccharide chains, are the building blocks of cellulose nano fibers. Nano fibers are further bound into micro fibrils and macro fibers. Theoretically pure cellulose nano fibers have tremendous strengths, and therefore are some of the most sought after nano particles. The fiber extraction however is a complex task. The ultrasound, which creates pressure variation in the medium, was employed to extract nano-size cellulose particles from microcrystalline cellulose (MCC). The length and the intensity of the cavitations were evaluated. Electron microscopy studies revealed that cellulose nanoparticles were successfully obtained from the MCC after ultrasound treatment of just 30 minutes. Structure of the fractionated cellulose was also analyzed with the help of X-ray diffraction, and its thermal properties were evaluated with the help of differential scanning calorimetry (DSC). Ultrasound treatment performed on the wheat straw, kenaf, and miscanthus particles altered fiber structure as a result of the cavitation. The micro fibers were generated from these materials after they were subjected to NaOH treatment followed by the ultrasound processing. The potential of larger than nano-sized natural fibers to be used for composite fabrication was also explored. The agricultural byproducts, such as wheat or rice straw, as well as other fast growing crops as miscanthus or kenaf, are comprised of three basic polymers. Just like in

  10. The face of appearance-related social pressure: gender, age and body mass variations in peer and parental pressure during adolescence.

    PubMed

    Helfert, Susanne; Warschburger, Petra

    2013-05-17

    Appearance-related social pressure plays an important role in the development of a negative body image and self-esteem as well as severe mental disorders during adolescence (e.g. eating disorders, depression). Identifying who is particularly affected by social pressure can improve targeted prevention and intervention, but findings have either been lacking or controversial. Thus the aim of this study is to provide a detailed picture of gender, weight, and age-related variations in the perception of appearance-related social pressure by peers and parents. 1112 German students between grades 7 and 9 (mean age: M = 13.38, SD = .81) filled in the Appearance-Related Social Pressure Questionnaire (German: FASD), which considers different sources (peers, parents) as well as various kinds of social pressure (e.g. teasing, modeling, encouragement). Girls were more affected by peer pressure, while gender differences in parental pressure seemed negligible. Main effects of grade-level suggested a particular increase in indirect peer pressure (e.g. appearance-related school and class norms) from early to middle adolescence. Boys and girls with higher BMI were particularly affected by peer teasing and exclusion as well as by parental encouragement to control weight and shape. The results suggest that preventive efforts targeting body concerns and disordered eating should bring up the topic of appearance pressure in a school-based context and should strengthen those adolescents who are particularly at risk - in our study, girls and adolescents with higher weight status. Early adolescence and school transition appear to be crucial periods for these efforts. Moreover, the comprehensive assessment of appearance-related social pressure appears to be a fruitful way to further explore social risk-factors in the development of a negative body image.

  11. The face of appearance-related social pressure: gender, age and body mass variations in peer and parental pressure during adolescence

    PubMed Central

    2013-01-01

    Background Appearance-related social pressure plays an important role in the development of a negative body image and self-esteem as well as severe mental disorders during adolescence (e.g. eating disorders, depression). Identifying who is particularly affected by social pressure can improve targeted prevention and intervention, but findings have either been lacking or controversial. Thus the aim of this study is to provide a detailed picture of gender, weight, and age-related variations in the perception of appearance-related social pressure by peers and parents. Methods 1112 German students between grades 7 and 9 (mean age: M = 13.38, SD = .81) filled in the Appearance-Related Social Pressure Questionnaire (German: FASD), which considers different sources (peers, parents) as well as various kinds of social pressure (e.g. teasing, modeling, encouragement). Results Girls were more affected by peer pressure, while gender differences in parental pressure seemed negligible. Main effects of grade-level suggested a particular increase in indirect peer pressure (e.g. appearance-related school and class norms) from early to middle adolescence. Boys and girls with higher BMI were particularly affected by peer teasing and exclusion as well as by parental encouragement to control weight and shape. Conclusion The results suggest that preventive efforts targeting body concerns and disordered eating should bring up the topic of appearance pressure in a school-based context and should strengthen those adolescents who are particularly at risk - in our study, girls and adolescents with higher weight status. Early adolescence and school transition appear to be crucial periods for these efforts. Moreover, the comprehensive assessment of appearance-related social pressure appears to be a fruitful way to further explore social risk-factors in the development of a negative body image. PMID:23680225

  12. Migration of impurity level reflected in the electrical conductivity variation for natural pyrite at high temperature and high pressure

    NASA Astrophysics Data System (ADS)

    Liu, Kaixiang; Dai, Lidong; Li, Heping; Hu, Haiying; Wu, Lei; Zhuang, Yukai; Pu, Chang; Yang, Linfei

    2017-06-01

    This report presents the variations of the electrical conductivity and the migration of natural pyrite impurity levels at temperatures range from 298 to 573 K and pressures range from 1 atm. to 20.9 GPa. The electrical conductivity increases with temperature at a fixed pressure, displaying the semiconductor behavior of the sample. In spite of the positive correlations of electrical conductivity and pressure, there exists an acceleration in the rate of conductivity increase after 13 GPa. No indication of a chemical reaction or structural phase transition of pyrite was detected by Raman spectroscopy. The main trace elements that affect the electrical properties of pyrite are determined by inductively coupled plasma with mass spectrometry (ICPMS). The transport activation energy of natural pyrite is 0.045 eV at ambient pressure, which corresponds to the activation of the CoFe donor level ( 1/2 E D), and decreases with increasing pressure.

  13. Simulation for spatio-temporal variation of chemically active species in an atmospheric pressure streamer discharge.

    NASA Astrophysics Data System (ADS)

    Komuro, Atsushi; Takaahshi, Kazunori; Ando, Akira

    2016-09-01

    Spatiotemporal variation of radical density in an atmospheric pressure plasma discharge has been investigated by two-dimensional numerical simulation. Behaviors of radicals are characterized by four areas as ``Hot anode region'', ``Secondary streamer region'', ``Primary streamer region'', and ``Near-cathode region''. Although the reduced electric field in ``Hot anode region'' is relatively high, the gas temperature also increases and the ozone destruction process proceed. On the other hand, in ``Near-cathode region'', the high-energy radicals such as N(4S) is effectively produced because the instantaneous value of reduced electric field is high. Behaiviour of OH is also investigated. The results show that OH is effectively produced in ``Secondary streamer region'' and is not effective in ``Hot anode region''. This is because the reduced electric filed in ``Secondary streamer region'' is sufficiently high for the dissociation of H2O by O(D) and N2(a) and the gas temperature in ``Hot anode region'' is too high for the production of OH.

  14. Ice flow dynamics forced by water pressure variations in subglacial granular beds

    NASA Astrophysics Data System (ADS)

    Damsgaard, Anders; Egholm, David L.; Beem, Lucas H.; Tulaczyk, Slawek; Larsen, Nicolaj K.; Piotrowski, Jan A.; Siegfried, Matthew R.

    2016-12-01

    Glaciers and ice streams can move by deforming underlying water-saturated sediments, and the nonlinear mechanics of these materials are often invoked as the main reason for initiation, persistence, and shutdown of fast-flowing ice streams. Existing models have failed to fully explain the internal mechanical processes driving transitions from stability to slip. We performed computational experiments that show how rearrangements of load-bearing force chains within the granular sediments drive the mechanical transitions. Cyclic variations in pore water pressure give rise to rate-dependent creeping motion at stress levels below the point of failure, while disruption of the force chain network induces fast rate-independent flow above it. This finding contrasts previous descriptions of subglacial sediment mechanics, which either assume rate dependence regardless of mechanical state or unconditional stability before the sediment yield point. Our new micromechanical computational approach is capable of reproducing important transitions between these two end-member models and can explain multimodal velocity patterns observed in glaciers, landslides, and slow-moving tremor zones.

  15. Seasonal Variations of the Earth's Gravitational Field: An Analysis of Atmospheric Pressure, Ocean Tidal, and Surface Water Excitation

    NASA Technical Reports Server (NTRS)

    Dong, D,; Gross, R.S.; Dickey, J.

    1996-01-01

    Monthly mean gravitational field parameters (denoted here as C(sub even)) that represent linear combinations of the primarily even degree zonal spherical harmonic coefficients of the Earth's gravitational field have been recovered using LAGEOS I data and are compared with those derived from gridded global surface pressure data of the National meteorological center (NMC) spanning 1983-1992. The effect of equilibrium ocean tides and surface water variations are also considered. Atmospheric pressure and surface water fluctuations are shown to be the dominant cause of observed annual C(sub even) variations. Closure with observations is seen at the 1sigma level when atmospheric pressure, ocean tide and surface water effects are include. Equilibrium ocean tides are shown to be the main source of excitation at the semiannual period with closure at the 1sigma level seen when both atmospheric pressure and ocean tide effects are included. The inverted barometer (IB) case is shown to give the best agreement with the observation series. The potential of the observed C(sub even) variations for monitoring mass variations in the polar regions of the Earth and the effect of the land-ocean mask in the IB calculation are discussed.

  16. Variation.

    ERIC Educational Resources Information Center

    Hamilton City Board of Education (Ontario).

    Suggestions for studying the topic of variation of individuals and objects (balls) to help develop elementary school students' measurement, comparison, classification, evaluation, and data collection and recording skills are made. General suggestions of variables that can be investigated are made for the study of human variation. Twelve specific…

  17. Grain-scale pressure variations recorded in orthopyroxene from the diamond grade ultra-high pressure Svartberget peridotite body, Western Gneiss Region, Norway

    NASA Astrophysics Data System (ADS)

    Vrijmoed, Johannes C.

    2014-05-01

    The ultra-high pressure (UHP) area in the Western Gneiss Region (WGR) in Norway is recognized as a giant UHP domain that resulted from the collision of Baltica and Laurentia during the Caledonian Orogeny. Recent geochronological data suggest the WGR resided at UHP for several tens of millions of years and slowly exhumed near- isothermally to amphibolite facies conditions. The Svartberget peridotite body is located in the north-westernmost part of the UHP area of the WGR. The rocks record diamond grade peak metamorphism at ~800 ° C in crosscutting pyroxenite veins as evidenced by micro-diamond inclusions in Caledonian metamorphic garnet. The peridotite body preserves primary spinel-garnet-peridotite assemblages stable at much lower pressure (~2.0 GPa at ~800 ° C). Orthopyroxene typically shows bowl-shaped aluminium (Al) zoning and conventional geothermobarometry using core compositions of garnet-opx mineral pairs yields P-T estimates of 5.5 GPa at ~800 ° C. Besides Al increasing toward the rims of orthopyroxene grains, concentrations also increase in cracks and veins crosscutting the mineral. Here, recently developed unconventional geobarometry and Gibbs minimization methods are used to derive the grain-scale pressure variations corresponding to the observed Al-zoning. The methods independently result in pressure variations from core to rim on the order of 2.0 GPa. Interestingly, low-Al cores correspond to low pressures whereas high-Al rims correspond to high pressures, opposite to conventional geothermobarometry results. However, the new estimates are in agreement with the consideration that at high pressure the high density phases become more stable. In a binary orthopyroxene in the MAS-system, the Mg-Tschermak endmember thought to be the dominant Al-species in the mineral has a higher density then the Al-free enstatite endmember. Therefore at higher pressure the Mg-Tschermak endmember in orthopyroxene is favoured over the enstatite endmember. This is similar

  18. A novel pressure variation study on electronic structure, mechanical stability and thermodynamic properties of potassium based fluoroperovskite

    NASA Astrophysics Data System (ADS)

    Erum, Nazia; Azhar Iqbal, Muhammad

    2017-09-01

    The effect of pressure variation on stability, structural parameters, elastic constants, mechanical, electronic and thermodynamic properties of cubic SrKF3 fluoroperovskite have been investigated by using the full-potential linearized augmented plane wave (FP-LAPW) method combined with Quasi-harmonic Debye model in which the phonon effects are considered. The calculated lattice parameters show a prominent decrease in lattice constant and bonds length with the increase in pressure. The application of pressure from 0 to 25 GPa reveals a predominant characteristic associated with widening of bandgap with GGA and GGA plus Tran–Blaha modified Becke–Johnson (TB-mBJ) potential. The influence of pressure on elastic constants and their related mechanical parameters have been discussed in detail. Apart of linear dependence of elastic coefficients, transition from brittle to ductile behavior is also observed at elevated pressure ranges. We have successfully computed variation of lattice constant, volume expansion, bulk modulus, Debye temperature and specific heat capacities at pressure and temperature in the range of 0–25 GPa and 0–600 K.

  19. Effects of diurnal variation and anesthetic agents on intraocular pressure in Syrian hamsters (Mesocricetus auratus).

    PubMed

    Rajaei, Seyed Mehdi; Mood, Maneli Ansari; Paryani, Mohammad Reza; Williams, David L

    2017-01-01

    OBJECTIVE To determine effects of diurnal variation and anesthetic agents on intraocular pressure (IOP) in Syrian hamsters (Mesocricetus auratus). ANIMALS 90 healthy adult Syrian hamsters (45 males and 45 females). PROCEDURES IOP was measured with a rebound tonometer. In phase 1, IOP was measured in all hamsters 3 times during a 24-hour period (7 am, 3 pm, and 11 pm). In phase 2, hamsters were assigned to 5 groups (18 animals [9 males and 9 females]/group). Each group received an anesthetic agent or combination of anesthetic agents (ketamine hydrochloride, xylazine hydrochloride, diazepam, ketamine-diazepam [KD], or ketamine-xylazine [KX] groups) administered via the IP route. The IOP was measured before (time 0 [baseline]) and 10, 30, 60, 90, 120, and 150 minutes after administration of drugs. RESULTS Mean ± SD IOP values were 2.58 ± 0.87 mm Hg, 4.46 ± 1.58 mm Hg, and 5.96 ± 1.23 mm Hg at 7 am, 3 pm, and 11 pm, respectively. Mean baseline IOP was 6.25 ± 0.28 mm Hg, 6.12 ± 0.23 mm Hg, 5.75 ± 0.64 mm Hg, 5.12 ± 1.40 mm Hg, and 4.50 ± 1.30 mm Hg for the ketamine, xylazine, diazepam, KD, and KX groups, respectively. A significant decrease in IOP, compared with baseline IOP, was detected in only the KX group at 30, 60, and 90 minutes after drug administration. CONCLUSIONS AND CLINICAL RELEVANCE Maximum IOP in Syrian hamsters was detected at night. The ketamine-xylazine anesthetic combination significantly decreased IOP in Syrian hamsters.

  20. THE RELATIONSHIP BETWEEN CIRCADIAN BLOOD PRESSURE VARIATION AND AGE ANALYSED FROM 7-DAY MONITORING

    PubMed Central

    SIEGELOVÁ, J.; DUŠEK, J.; FIŠER, B.; HOMOLKA, P.; VANK, P.; MAŠEK, M.; HAVELKOVÁ, A.; CORNÉLISSEN, G.; HALBERG, F.

    2009-01-01

    The relationship between age and circadian blood pressure (BP) variation was the aim of the present study. One hundred and eighty-seven subjects (130 males, 57 females), 20-77 years old, were recruited for seven-day BP monitoring. Colin medical instruments (Komaki, Japan) were used for ambulatory BP monitoring (oscillation method, 30-minute interval between measurements). A sinusoidal curve was fitted (minimum square method) and the mean value and amplitude of the curve (double amplitude corresponds to the night-day difference) were evaluated on every day of monitoring. The average 7-day values of the mean (M) and of double amplitude (2A) for systolic BP (SBP), diastolic BP (DBP), and heart rate (HR) were determined in each subject. The mean values of M (±SD) for the whole group were: SBP- 127±8, DBP - 79±6 mmHg, HR - 70±6 bpm; of 2A: SBP - 21±7, DBP - 15±5 mmHg, HR - 15±6 bpm. A linear relationship between M of SBP and age (r=0.341, p< 0.001) and DBP and age (r=0.384, p<0.001) was found (difference between 20 and 77 years: SBP - 16, DBP - 12 mmHg). 2A of SBP and DBP was increasing with age up to 35 years, then the curve remained relatively flat up to 55 years (maximum at 45 years), and then it decreased again (difference between 45 and 77 years: SBP - 13mmHg, DBP - 12 mmHg). Heart rate M and 2A were age-independent. The mean values of SBP and DBP were increasing with age up to 75 years, but the night-day difference of SBP and DBP reached its maximum value at 45 years and then decreased. PMID:19436777

  1. Widespread sequence variations in VAMP1 across vertebrates suggest a potential selective pressure from botulinum neurotoxins.

    PubMed

    Peng, Lisheng; Adler, Michael; Demogines, Ann; Borrell, Andrew; Liu, Huisheng; Tao, Liang; Tepp, William H; Zhang, Su-Chun; Johnson, Eric A; Sawyer, Sara L; Dong, Min

    2014-07-01

    Botulinum neurotoxins (BoNT/A-G), the most potent toxins known, act by cleaving three SNARE proteins required for synaptic vesicle exocytosis. Previous studies on BoNTs have generally utilized the major SNARE homologues expressed in brain (VAMP2, syntaxin 1, and SNAP-25). However, BoNTs target peripheral motor neurons and cause death by paralyzing respiratory muscles such as the diaphragm. Here we report that VAMP1, but not VAMP2, is the SNARE homologue predominantly expressed in adult rodent diaphragm motor nerve terminals and in differentiated human motor neurons. In contrast to the highly conserved VAMP2, BoNT-resistant variations in VAMP1 are widespread across vertebrates. In particular, we identified a polymorphism at position 48 of VAMP1 in rats, which renders VAMP1 either resistant (I48) or sensitive (M48) to BoNT/D. Taking advantage of this finding, we showed that rat diaphragms with I48 in VAMP1 are insensitive to BoNT/D compared to rat diaphragms with M48 in VAMP1. This unique intra-species comparison establishes VAMP1 as a physiological toxin target in diaphragm motor nerve terminals, and demonstrates that the resistance of VAMP1 to BoNTs can underlie the insensitivity of a species to members of BoNTs. Consistently, human VAMP1 contains I48, which may explain why humans are insensitive to BoNT/D. Finally, we report that residue 48 of VAMP1 varies frequently between M and I across seventeen closely related primate species, suggesting a potential selective pressure from members of BoNTs for resistance in vertebrates.

  2. High-frequency pressure variations in the vicinity of a surface CO2 flux chamber

    Treesearch

    Eugene S. Takle; James R. Brandle; R. A. Schmidt; Rick Garcia; Irina V. Litvina; William J. Massman; Xinhua Zhou; Geoffrey Doyle; Charles W. Rice

    2003-01-01

    We report measurements of 2Hz pressure fluctuations at and below the soil surface in the vicinity of a surface-based CO2 flux chamber. These measurements were part of a field experiment to examine the possible role of pressure pumping due to atmospheric pressure fluctuations on measurements of surface fluxes of CO2. Under the moderate wind speeds, warm temperatures,...

  3. Response of nightside ionosphere and ionotail of Venus to variations in solar EUV and solar wind dynamic pressure

    NASA Technical Reports Server (NTRS)

    Brace, L. H.; Theis, R. F.; Mihalov, J. D.

    1990-01-01

    Pioneer Venus in situ measurements of N(e), total solar EUV flux, and solar wind dynamic pressure P(sw) are used to investigate the solar cycle and orbit-to-orbit variations of the Venus nightside ionosphere. It is found that the density of the main body of the nightside ionosphere below 600 km responds to the solar wind dynamic pressure variations in much the same way that the density of the ionotail does: both regions are depleted at times of high P(sw). Solar cycle variations in the EUV flux near solar minimum produce very large changes in the electron density in ionotail, changes that are consistent with the ionotail being supplied by nightward ion flow. However, short-term variations in the EUV flux produce a weak negative response in the density at altitudes between 150 and 600 km, at least at solar maximum. The nightside variations are consistent with enhanced solar wind scavenging of plasma from the nightside ionosphere during periods of higher P(sw).

  4. Sunspot random walk and 22-year variation

    USGS Publications Warehouse

    Love, Jeffrey J.; Rigler, E. Joshua

    2012-01-01

    We examine two stochastic models for consistency with observed long-term secular trends in sunspot number and a faint, but semi-persistent, 22-yr signal: (1) a null hypothesis, a simple one-parameter random-walk model of sunspot-number cycle-to-cycle change, and, (2) an alternative hypothesis, a two-parameter random-walk model with an imposed 22-yr alternating amplitude. The observed secular trend in sunspots, seen from solar cycle 5 to 23, would not be an unlikely result of the accumulation of multiple random-walk steps. Statistical tests show that a 22-yr signal can be resolved in historical sunspot data; that is, the probability is low that it would be realized from random data. On the other hand, the 22-yr signal has a small amplitude compared to random variation, and so it has a relatively small effect on sunspot predictions. Many published predictions for cycle 24 sunspots fall within the dispersion of previous cycle-to-cycle sunspot differences. The probability is low that the Sun will, with the accumulation of random steps over the next few cycles, walk down to a Dalton-like minimum. Our models support published interpretations of sunspot secular variation and 22-yr variation resulting from cycle-to-cycle accumulation of dynamo-generated magnetic energy.

  5. Sunspot random walk and 22-year variation

    NASA Astrophysics Data System (ADS)

    Love, Jeffrey J.; Rigler, E. Joshua

    2012-05-01

    We examine two stochastic models for consistency with observed long-term secular trends in sunspot number and a faint, but semi-persistent, 22-yr signal: (1) a null hypothesis, a simple one-parameter log-normal random-walk model of sunspot-number cycle-to-cycle change, and, (2) an alternative hypothesis, a two-parameter random-walk model with an imposed 22-yr alternating amplitude. The observed secular trend in sunspots, seen from solar cycle 5 to 23, would not be an unlikely result of the accumulation of multiple random-walk steps. Statistical tests show that a 22-yr signal can be resolved in historical sunspot data; that is, the probability is low that it would be realized from random data. On the other hand, the 22-yr signal has a small amplitude compared to random variation, and so it has a relatively small effect on sunspot predictions. Many published predictions for cycle 24 sunspots fall within the dispersion of previous cycle-to-cycle sunspot differences. The probability is low that the Sun will, with the accumulation of random steps over the next few cycles, walk down to a Dalton-like minimum. Our models support published interpretations of sunspot secular variation and 22-yr variation resulting from cycle-to-cycle accumulation of dynamo-generated magnetic energy.

  6. Investigation of temperature and barometric pressure variation effects on radon concentration in the Sopronbánfalva Geodynamic Observatory, Hungary.

    PubMed

    Mentes, Gyula; Eper-Pápai, Ildikó

    2015-11-01

    Radon concentration variation has been monitored since 2009 in the artificial gallery of the Sopronbánfalva Geodynamic Observatory, Hungary. In the observatory, the radon concentration is extremely high, 100-600 kBq m(-3) in summer and some kBq m(-3) in winter. The relationships between radon concentration, temperature and barometric pressure were separately investigated in the summer and winter months by Fast Fourier Transform, Principal Component Analysis, Multivariable Regression and Partial Least Square analyses in different frequency bands. It was revealed that the long-period radon concentration variation is mainly governed by the temperature (20 kBq m(-1) °C(-1)) both in summer and winter. The regression coefficients between long-period radon concentration and barometric pressure are -1.5 kBq m(-3) hPa(-1) in the summer and 5 kBq m(-3) hPa(-1) in the winter months. In the 0.072-0.48 cpd (cycles per day) frequency band the effect of the temperature is about -1 kBq m(-3) °C(-1) and that of the barometric pressure is -5 kBq m(-3) hPa(-1) in summer and -0.5 kBq m(-3) hPa(-1) in winter. In the high frequency range (>0.48 cpd) all regression coefficients are one order of magnitude smaller than in the range of 0.072-0.48 cpd. Fast Fourier Transform of the radon concentration, temperature and barometric pressure time series revealed S1, K1, P1, S2, K2, M2 tidal constituents in the data and weak O1 components in the radon concentration and barometric pressure series. A detailed tidal analysis, however, showed that the radon tidal components are not directly driven by the gravitational force but rather by solar radiation and barometric tide. Principal Component Analysis of the raw data was performed to investigate the yearly, summer and winter variability of the radon concentration, temperature and barometric pressure. In the summer and winter periods the variability does not change. The higher variability of the radon concentration compared to the variability of

  7. Blood Pressure Variation Throughout Pregnancy According to Early Gestational BMI: A Brazilian Cohort.

    PubMed

    Rebelo, Fernanda; Farias, Dayana Rodrigues; Mendes, Roberta Hack; Schlüssel, Michael Maia; Kac, Gilberto

    2015-02-13

    Background: The maternal cardiovascular system undergoes progressive adaptations throughout pregnancy, causing blood pressure fluctuations. However, no consensus has been established on its normal variation in uncomplicated pregnancies. Objective: To describe the variation in systolic blood pressure (SBP) and diastolic blood pressure (DBP) levels during pregnancy according to early pregnancy body mass index (BMI). Methods: SBP and DBP were measured during the first, second and third trimesters and at 30-45 days postpartum in a prospective cohort of 189 women aged 20-40 years. BMI (kg/m2) was measured up to the 13th gestational week and classified as normal-weight (<25.0) or excessive weight (≥25.0). Longitudinal linear mixed-effects models were used for statistical analysis. Results: A decrease in SBP and DBP was observed from the first to the second trimester (βSBP=-0.394; 95%CI: -0.600- -0.188 and βDBP=-0.617; 95%CI: -0.780- -0.454), as was an increase in SBP and DBP up to 30-45 postpartum days (βSBP=0.010; 95%CI: 0.006-0.014 and βDBP=0.015; 95%CI: 0.012-0.018). Women with excessive weight at early pregnancy showed higher mean SBP in all gestational trimesters, and higher mean DBP in the first and third trimesters. Excessive early pregnancy BMI was positively associated with prospective changes in SBP (βSBP=7.055; 95%CI: 4.499-9.610) and in DBP (βDBP=3.201; 95%CI: 1.136-5.266). Conclusion: SBP and DBP decreased from the first to the second trimester and then increased up to the postpartum period. Women with excessive early pregnancy BMI had higher SBP and DBP than their normal-weight counterparts throughout pregnancy, but not in the postpartum period.Fundamento: O sistema cardiovascular materno sofre adaptações progressivas durante a gestação, acarretando flutuações da pressão arterial. Entretanto, não há consenso sobre a variação pressórica normal na gravidez saudável. Objetivo: Descrever a variação da pressão arterial sistólica (PAS) e

  8. Effects of autogenic training and antihypertensive agents on circadian and circaseptan variation of blood pressure.

    PubMed

    Watanabe, Yoshihiko; Cornélissen, Germaine; Watanabe, Misako; Watanabe, Fumihiko; Otsuka, Kuniaki; Ohkawa, Shi-ichiro; Kikuchi, Takenori; Halberg, Franz

    2003-10-01

    Even when the daily blood pressure mean is acceptable, too large a circadian amplitude of blood pressure largely increases cardiovascular disease risk. Autogenic training (N = 11), a non-pharmacologic intervention capable of lowering an excessive blood pressure variability, may be well-suited for MESOR-normotensive patients diagnosed with circadian-hyper-amplitude-tension (CHAT). Not all anti-hypertensive drugs affect blood pressure variability. Accordingly, long-acting carteolol (N = 11) and/or atenolol (N = 8) may be preferred to captopril retard (N = 13), nilvadipine (N = 8), or amlodipine (N = 7) for midline-estimating statistic of rhythm (MESOR)-hypertensive patients with CHAT. Prospective outcome studies are needed to assess whether the relative merits of these treatments are in keeping with their effects on blood pressure and blood pressure variability.

  9. Pressure driven currents near magnetic islands in 3D MHD equilibria: Effects of pressure variation within flux surfaces and of symmetry

    NASA Astrophysics Data System (ADS)

    Reiman, Allan H.

    2016-07-01

    In toroidal, magnetically confined plasmas, the heat and particle transport is strongly anisotropic, with transport along the field lines sufficiently strong relative to cross-field transport that the equilibrium pressure can generally be regarded as constant on the flux surfaces in much of the plasma. The regions near small magnetic islands, and those near the X-lines of larger islands, are exceptions, having a significant variation of the pressure within the flux surfaces. It is shown here that the variation of the equilibrium pressure within the flux surfaces in those regions has significant consequences for the pressure driven currents. It is further shown that the consequences are strongly affected by the symmetry of the magnetic field if the field is invariant under combined reflection in the poloidal and toroidal angles. (This symmetry property is called "stellarator symmetry.") In non-stellarator-symmetric equilibria, the pressure-driven currents have logarithmic singularities at the X-lines. In stellarator-symmetric MHD equilibria, the singular components of the pressure-driven currents vanish. These equilibria are to be contrasted with equilibria having B ṡ∇p =0 , where the singular components of the pressure-driven currents vanish regardless of the symmetry. They are also to be contrasted with 3D MHD equilibrium solutions that are constrained to have simply nested flux surfaces, where the pressure-driven current goes like 1 /x near rational surfaces, where x is the distance from the rational surface, except in the case of quasi-symmetric flux surfaces. For the purpose of calculating the pressure-driven currents near magnetic islands, we work with a closed subset of the MHD equilibrium equations that involves only perpendicular force balance, and is decoupled from parallel force balance. It is not correct to use the parallel component of the conventional MHD force balance equation, B ṡ∇p =0 , near magnetic islands. Small but nonzero values of B

  10. The influence of thermal inertia on Mars' seasonal pressure variation and the effect of the weather component

    NASA Technical Reports Server (NTRS)

    Wood, S. E.; Paige, D. A.

    1993-01-01

    Using a Leighton-Murray type diurnal and seasonal Mars thermal model, we found that it is possible to reproduce the seasonal variation in daily-averaged pressures (approximately 680-890 Pa) measured by Viking Lander 1 (VL1), during years without global dust storms, with a standard deviation of less than 5 Pa. In this simple model, surface CO2, frost condensation, and sublimation rates at each latitude are determined by the net effects of radiation, latent heat, and heat conduction in subsurface soil layers. An inherent assumption of our model is that the seasonal pressure variation is due entirely to the exchange of mass between the atmosphere and polar caps. However, the results of recent Mars GCM modeling have made it clear that there is a significant dynamical contribution to the seasonal pressure variation. This 'weather' component is primarily due to large-scale changes in atmospheric circulation, and its magnitude depends somewhat on the dust content of the atmosphere. The overall form of the theoretical weather component at the location of VL1, as calculated by the AMES GCM, remains the same over the typical range of Mars dust opacities.

  11. Pulse pressure variation-guided fluid therapy after cardiac surgery: a pilot before-and-after trial.

    PubMed

    Suzuki, Satoshi; Woinarski, Nicholas C Z; Lipcsey, Miklos; Candal, Cristina Lluch; Schneider, Antoine G; Glassford, Neil J; Eastwood, Glenn M; Bellomo, Rinaldo

    2014-12-01

    The aim of this study is to study the feasibility, safety, and physiological effects of pulse pressure variation (PPV)-guided fluid therapy in patients after cardiac surgery. We conducted a pilot prospective before-and-after study during mandatory ventilation after cardiac surgery in a tertiary intensive care unit. We introduced a protocol to deliver a fluid bolus for a PPV≥13% for at least >10 minutes during the intervention period. We studied 45 control patients and 53 intervention patients. During the intervention period, clinicians administered a fluid bolus on 79% of the defined PPV trigger episodes. Median total fluid intake was similar between 2 groups during mandatory ventilation (1297 mL [interquartile range 549-1968] vs 1481 mL [807-2563]; P=.17) and the first 24 hours (3046 mL [interquartile range 2317-3982] vs 3017 mL [2192-4028]; P=.73). After adjusting for several baseline factors, PPV-guided fluid management significantly increased fluid intake during mandatory ventilation (P=.004) but not during the first 24 hours (P=.47). Pulse pressure variation-guided fluid therapy, however, did not significantly affect hemodynamic, renal, and metabolic variables. No serious adverse events were noted. Pulse pressure variation-guided fluid management was feasible and safe during mandatory ventilation after cardiac surgery. However, its advantages may be clinically small. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. 40 CFR 53.56 - Test for effect of variations in ambient pressure.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    .... (4) Barometer, range 600 mm Hg to 800 mm Hg, certified accurate to 2 mm Hg. Ambient air pressure... meter. (4) The barometer shall be installed in the test chamber such that it will accurately measure the... corresponding ambient (chamber) pressure measured by the barometer specified in paragraph (c)(4) of this...

  13. 40 CFR 53.56 - Test for effect of variations in ambient pressure.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    .... (4) Barometer, range 600 mm Hg to 800 mm Hg, certified accurate to 2 mm Hg. Ambient air pressure... meter. (4) The barometer shall be installed in the test chamber such that it will accurately measure the... corresponding ambient (chamber) pressure measured by the barometer specified in paragraph (c)(4) of this...

  14. 40 CFR 53.56 - Test for effect of variations in ambient pressure.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    .... (4) Barometer, range 600 mm Hg to 800 mm Hg, certified accurate to 2 mm Hg. Ambient air pressure... meter. (4) The barometer shall be installed in the test chamber such that it will accurately measure the... corresponding ambient (chamber) pressure measured by the barometer specified in paragraph (c)(4) of this...

  15. 40 CFR 53.56 - Test for effect of variations in ambient pressure.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    .... (4) Barometer, range 600 mm Hg to 800 mm Hg, certified accurate to 2 mm Hg. Ambient air pressure... meter. (4) The barometer shall be installed in the test chamber such that it will accurately measure the... corresponding ambient (chamber) pressure measured by the barometer specified in paragraph (c)(4) of this...

  16. 40 CFR 53.56 - Test for effect of variations in ambient pressure.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    .... (4) Barometer, range 600 mm Hg to 800 mm Hg, certified accurate to 2 mm Hg. Ambient air pressure... meter. (4) The barometer shall be installed in the test chamber such that it will accurately measure the... corresponding ambient (chamber) pressure measured by the barometer specified in paragraph (c)(4) of this...

  17. Effects of pressure variations on electronic-resonance-enhanced coherent anti-Stokes Raman scattering of nitric oxide

    NASA Astrophysics Data System (ADS)

    Kulatilaka, Waruna D.; Chai, Ning; Naik, Sameer V.; Roy, Sukesh; Laurendeau, Normand M.; Lucht, Robert P.; Kuehner, Joel P.; Gord, James R.

    2007-06-01

    The effects of pressure variations on the electronic-resonance-enhanced coherent anti-Stokes Raman scattering (ERE-CARS) signal of nitric oxide (NO) were studied at pressures ranging from 0.1 to 8 bar. ERE-CARS signals were recorded in a gas cell filled with a mixture of 300 ppm NO in N 2 buffer gas at room temperature. The ERE-CARS signal was found to increase with rising pressure up to 2 bar and to remain nearly constant thereafter. The spectra recorded at different cell pressures were modeled using a modified version of the Sandia CARSFT code. Laser-saturation effects were accounted for by systematically varying the theoretical ultraviolet probe-laser linewidth. Excellent agreement was obtained between theory and experiment for the pressure-scaling behavior of the ERE-CARS signal of NO. This finding, along with a negligible influence of electronic quenching on the ERE-CARS signal, provides strong incentive for the application of ERE-CARS to measurements of NO concentrations in high-pressure combustion environments.

  18. Measurements of reed vibration and pressure variation of the sho, the Japanese mouth organ

    NASA Astrophysics Data System (ADS)

    Hikichi, Takafumi; Osaka, Naotoshi

    2002-05-01

    Measurements of reed vibration and pressure vibration of the sho were carried out. Reed displacement, sound pressure at both sides of the reed, and radiated sound pressure at the open end of the pipe were measured using an experimental sho model made from an acrylic pipe and a metal reed. The kashira, or cavity, was also made from an acrylic box, where the pipe is mounted so that the reed vibration can be measured by a laser displacement sensor. The measurement results show that reeds vibrate as a sinusoidal, and that, in contrast with earlier results obtained by experiments on harmonium reeds [J. P. Cottingham, C. J. Lilly, and C. H. Reed, 137th meeting of the ASA and the 2nd Convention of the EAA, pp. 14-19 (1999)], the amplitude of reed vibration increases with increasing blowing/drawing pressure. The sound pressure inside the tube shows peaks when the reed reaches its maximum displacement, and the sound pressure oscillates twice when the reed oscillates once. Further, sound pressure inside the kashira, i.e., at the upstream of the reed, shows high frequency oscillation compared with reed vibration. This result implies that the shape and volume of the kashira may significantly affect the sound characteristics.

  19. Therapeutic Consequences of Variation in Intraarterial Pressure Measurements After Iliac Angioplasty

    SciTech Connect

    Tetteroo, Eric; Haaring, Cees; Engelen, Andries D. van; Graaf, Yolanda van der; Mali, Willem P.T.M.

    1997-11-15

    Purpose: To assess the accuracy of intraarterial measurement of transstenotic pressure gradients for the detection of hemodynamically suboptimal iliac angioplasty. Methods: In 14 patients, referred for diagnostic angiography, mean pressure gradients in the aorta and iliac artery were obtained twice, using a double-sensor pressure catheter. Additional iliac measurements were performed during pharmacologically induced flow augmentation. Repeatability was assessed by calculation of the mean difference plus standard deviation (MD {+-} SD) and repeatability coefficient (2 x SD). These results were extrapolated to 137 iliac angioplasty procedures with secondary stenting where there was a residual pressure gradient > 10 mmHg. Results: MD {+-} SD for repeated measurements at rest and during flow augmentation were 0 {+-} 2 mmHg and 1 {+-} 3 mmHg, respectively. Repeatability coefficients were 3 and 6 mmHg. Mean pressure gradients after hemodynamically insufficient angioplasty were 8 {+-} 7 mmHg at rest and 17 {+-} 5 mmHg following vasodilatation. Inaccurate pressure recordings may have led to inappropriate stent placement in less than 2.5%, and inappropriate denial of stent placement in less than 5% of the lesions. Conclusion: Variability of intraarterial pressure measurements has little consequence in the detection of hemodynamically significant stenosis after angioplasty.

  20. Effect of ambient pressure variation on closed loop gas system for India based Neutrino Observatory (INO)

    NASA Astrophysics Data System (ADS)

    Satyanarayana, B.; Majumder, G.; Mondal, N. K.; Kalmani, S. D.; Shinde, R. R.; Joshi, A.

    2014-10-01

    Pilot unit of a closed loop gas mixing and distribution system for the INO project was designed and is being operated with 1.8meters × 1.9meters RPCs for about two years. A number of studies on controlling the flow and optimisation of the gas mixture through the RPC stack were carried out during this period. The gas system essentially measures and attempts to maintain absolute pressure inside the RPC gas volume. During typical Mumbai monsoon seasons, the barometric pressure changes rather rapidly, due to which the gas system fails to maintain the set differential pressure between the ambience and the RPC gas volume. As the safety bubblers on the RPC gas input lines are set to work on fixed pressure differentials, the ambient pressure changes lead to either venting out and thus wasting gas through safety bubblers or over pressuring the RPCs gas volume and thus degrading its performance. The above problem also leads to gas mixture contamination through minute leaks in gas gap. The problem stated above was solved by including the ambient barometric pressure as an input parameter in the closed loop. Using this, it is now possible to maintain any set differential pressure between the ambience and RPC gas volumes between 0 to 20mm of water column, thus always ensuring a positive pressure inside the RPC gas volume with respect to the ambience. This has resulted in improved performance of the gas system by maintaining the constant gas flow and reducing the gas toping up frequency. In this paper, we will highlight the design features and improvements of the closed loop gas system. We will present some of the performance studies and considerations for scaling up the system to be used with the engineering module and then followed by Iron Calorimeter detector (ICAL), which is designed to deploy about 30,000 RPCs of 1.8meters × 1.9 meters in area.

  1. Influence of variations in systemic blood flow and pressure on cerebral and systemic oxygen saturation in cardiopulmonary bypass patients.

    PubMed

    Moerman, A; Denys, W; De Somer, F; Wouters, P F; De Hert, S G

    2013-10-01

    Although both pressure and flow are considered important determinants of regional organ perfusion, the relative importance of each is less established. The aim of the present study was to evaluate the impact of variations in flow, pressure, or both on cerebral and whole-body oxygen saturation. Thirty-four consenting patients undergoing elective cardiac surgery on cardiopulmonary bypass were included. Using a randomized cross-over design, four different haemodynamic states were simulated: (i) 20% flow decrease, (ii) 20% flow decrease with phenylephrine to restore baseline pressure, (iii) 20% pressure decrease with sodium nitroprusside (SNP) under baseline flow, and (iv) increased flow with baseline pressure. The effect of these changes was evaluated on cerebral (Sc(O₂)) and systemic (Sv(O₂)) oxygen saturation, and on systemic oxygen extraction ratio (OER). Data were assessed by within- and between-group comparisons. Decrease in flow was associated with a decrease in [from 63.5 (7.4) to 62.0 (8.5) %, P<0.001]. When arterial pressure was restored with phenylephrine during low flow, Sc(O₂) further decreased from 61.0 (9.7) to 59.2 (10.2) %, P<0.001. Increase in flow was associated with an increase in Sc(O₂) from 62.6 (7.7) to 63.6 (8.9) %, P=0.03, while decreases in pressure with the use of SNP did not affect Sc(O₂). Sv(O₂) was significantly lower (P<0.001) and OER was significantly higher (P<0.001) in the low flow arms. In the present elective cardiac surgery population, Sc(O₂) and Sv(O₂) were significantly lower with lower flow, regardless of systemic arterial pressure. Moreover, phenylephrine administration was associated with a reduced cerebral and systemic oxygen saturation.

  2. Evaluating the BD-100R [Bubble Technology Industries] as a neutron spectrometer through pressure variation

    SciTech Connect

    White, B.; Ebert, D.; Munno, F.

    1990-07-01

    Other investigators have evaluated the dose response of neutron bubble dosimeters for possible use as personnel monitors for the U.S. Navy in low level radiation fields. In addition to dose measurements, these devices have been modified to measure the neutron energy spectra. These methods tend to be cumbersome, inaccurate, or both and do not use the same devices as employed in the dosimetry. The BD-100R dosimeter used in this work consists of a test tube containing an elastic polymer with interspersed droplets of two types of Freon; Freon-12 and Freon-114. Each superheated liquid droplet is a potential nucleation site. The minimum energy needed to form a bubble from the nucleation site is given by, E = 16{pi}{gamma}{sup 3}(T)/3({delta}P){sup 2}, where {delta}P is the difference between the vapor pressure of the droplet and the applied pressure. Upon reaching a critical radius, a bubble becomes unstable and grows in size. It may be seen from this equation that the energy deposition required for bubble formation is inversely proportional to the square of the pressure difference. The number of bubbles formed continually decreases with increasing applied pressure, until a pressure is reached where no bubbles are formed since the energy transferred can no longer vaporize the Freon. This investigation is intended to demonstrate the determination of an unknown spectrum utilizing the dosimeter response (number of bubbles formed) as a function of the neutron energy (applied pressure). A set of 12 dosimeters was initially exposed outside the East Beam Port (EBP) at the Maryland University Training Reactor (MUTR). The dosimeters were inside a pressure chamber which could accommodate up to 18 dosimeters. The same set of dosimeters were irradiated using a paraffin moderated PuBe source for which the neutron energy spectrum is unknown. There were eight exposures of six dosimeters at varied pressures in the EBP. The average number of bubbles and standard deviation was measured

  3. [Variation in inspiratory gas flow in pressure support ventilation. The effect on respiratory mechanics and respiratory work].

    PubMed

    Sydow, M; Thies, K; Engel, J; Golisch, W; Buscher, H; Zinserling, J; Burchardi, H

    1996-11-01

    During pressure support ventilation (PSV), the timing of the breathing cycle is mainly controlled by the patient. Therefore, the delivered flow pattern during PSV might be better synchronised with the patient's demands than during volume-assisted ventilation. In several modern ventilators, inspiration is terminated when the inspiratory flow decreases to 25% of the initial peak value. However, this timing algorithm might cause premature inspiration termination if the initial peak flow is high. This could result not only in an increased risk of dyssynchronization between the patient and the ventilator, but also in reduced ventilatory support. On the other hand, a decreased peak flow might inappropriately increase the patient's inspiratory effort. The aim of our study was to evaluate the influence of the variation of the initial peak-flow rate during PSV on respiratory pattern and mechanical work of breathing. Six patients with chronic obstructive pulmonary disease (COPD) and six patients with no or minor nonobstructive lung pathology (control) were studied during PSV with different inspiratory flow rates by variations of the pressurisation time (Evita I, Drägerwerke, Lübeck, Germany). During the study period all patients were in stable circulatory conditions and in the weaning phase. Patients were studied in a 45 degrees semirecumbent position. Using the medium pressurization time (l s) during PSV the inspiratory pressure was individually adjusted to obtain a tidal volume of about 8 ml/kg body weight. Thereafter, measurements were performed during five pressurization times (< 0.1, 0.5, 1, 1.5, 2 s defined as T 0.1, T 0.5, T 1, T 1.5 and T 2) in random order, while maintaining the pressure support setting at the ventilator. Between each measurement steady-state was attained. Positive end-exspiratory pressure (PEEP) and FIO2 were maintained at prestudy levels and remained constant during the study period. Informed consent was obtained from each patient or his next of

  4. Sediment budget variation at watershed scale due to anthropogenic pressures, and its relationship to coastal erosion

    NASA Astrophysics Data System (ADS)

    Aiello, Antonello; Adamo, Maria; Canora, Filomena

    2014-05-01

    The transfer of sediments from hydrographic basins towards the coast is a significant pathway of material transfer on Earth. In sedimentary environment, the main portion of sediment that enters the coastal areas is derived originally from erosion in the coastal watersheds. Extensive anthropogenic pressures carried out within coastal basins have long shown negative impacts on littoral environments. In fluvial systems, sediments trapped behind dams and in-stream gravel mining cause the reduction in sediment supply to the coast. Along the Jonian littoral of the Basilicata Region (southern Italy), natural coastal processes have been severely disrupted since the second half of the 20th century as a result of riverbed sand and gravel mining and dam construction, when economic advantages were measured in terms of the development of infrastructure, water storage, and hydropower production for the agricultural, industrial and socio-economic development of the area. Particularly, the large numbers of dams and impoundments that have been built in the hydrographic basins have led a signi?cant reduction on river sediment loads. As a result, the Jonian littoral is experiencing a catalysed erosion phenomenon. In order to increase understanding of the morpho-dynamics of the Jonian littoral environment and more fully appreciate the amount of coastal erosion, an evaluation of the sediment budget change due to dam construction within the hydrographic basins of the Basilicata Region needs to be explored. Since quantitative data on decadal trends in river sediment supply before and after dam construction are lacking, as well as updated dam silting values, river basin assessment of the spatial patterns and estimated amount of sediment erosion and deposition are important in evaluating changes in the sediment budget. As coastal areas are being affected by an increasing number of population and socio-economic activities, the amount of sediment deficit at the littoral can permit to

  5. Investigation of pressure variations over stepped spillways using smooth particle hydrodynamics

    NASA Astrophysics Data System (ADS)

    Husain, Sarhang M.; Muhammed, Jowhar R.; Karunarathna, Harshinie U.; Reeve, Dominic E.

    2014-04-01

    In this paper the smoothed particle hydrodynamics, (SPH), technique is used to investigate the pressure distribution on steps located in the non-aerated flow region of a stepped spillway for different discharges typical of skimming flow conditions. The open source code 2D SPHysics has been employed after being validated against the laboratory model studies of flow over broad crested weirs and flow over stepped spillways. The numerical results, in terms of the water surface and velocity profiles at different sections, are in good agreement with the corresponding experimental results. The code is then applied to determine the pressure distribution on the vertical and horizontal step faces. Also, the aspects of the pressure pattern are described and the positions/magnitudes of the maximum and minimum pressure values are presented.

  6. Variation of antioxidative activity and growth enhancement of Brassicaceae induced by low-pressure oxygen plasma

    NASA Astrophysics Data System (ADS)

    Ono, Reoto; Hayashi, Nobuya

    2015-06-01

    The mechanism of growth enhancement induced by active oxygen species generated in an oxygen plasma is investigated. The plant growth enhancement induced by the active oxygen species would relate to an antioxidative activity, which is one of the biological responses. The amount of generated active oxygen species is varied by the oxygen gas pressure in a low-pressure RF glow discharge plasma. The antioxidative activity of sprouts of Brassicaceae induced by the oxygen plasma is maximized at pressures between 30 and 40 Pa, whereas the antioxidative activity becomes small at around 60 and 80 Pa. The pressure dependence of the antioxidative activity of sprout stems is opposite to that of the stem length of the sprouts. The growth enhancement would be induced by the increase in the concentration of active oxygen species in plants owing to the decrease in the amount of antioxidative substances.

  7. Visually evoked blood flow responses and interaction with dynamic cerebral autoregulation: correction for blood pressure variation.

    PubMed

    Gommer, Erik D; Bogaarts, Guy; Martens, Esther G H J; Mess, Werner H; Reulen, Jos P H

    2014-05-01

    Visually evoked flow responses recorded using transcranial Doppler ultrasonography are often quantified using a dynamic model of neurovascular coupling. The evoked flow response is seen as the model's response to a visual step input stimulus. However, the continuously active process of dynamic cerebral autoregulation (dCA) compensating cerebral blood flow for blood pressure fluctuations may induce changes of cerebral blood flow velocity (CBFV) as well. The effect of blood pressure variability on the flow response is evaluated by separately modeling the dCA-induced effects of beat-to-beat measured blood pressure related CBFV changes. Parameters of 71 subjects are estimated using an existing, well-known second order dynamic neurovascular coupling model proposed by Rosengarten et al., and a new model extending the existing model with a CBFV contributing component as the output of a dCA model driven by blood pressure as input. Both models were evaluated for mean and systolic CBFV responses. The model-to-data fit errors of mean and systolic blood pressure for the new model were significantly lower compared to the existing model: mean: 0.8%±0.6 vs. 2.4%±2.8, p<0.001; systolic: 1.5%±1.2 vs. 2.2%±2.6, p<0.001. The confidence bounds of all estimated neurovascular coupling model parameters were significantly (p<0.005) narrowed for the new model. In conclusion, blood pressure correction of visual evoked flow responses by including cerebral autoregulation in model fitting of averaged responses results in significantly lower fit errors and by that in more reliable model parameter estimation. Blood pressure correction is more effective when mean instead of systolic CBFV responses are used. Measurement and quantification of neurovascular coupling should include beat-to-beat blood pressure measurement.

  8. Theory and observations of mechanically heterogeneous critical-taper wedges: the role of spatial variation in fluid pressure

    NASA Astrophysics Data System (ADS)

    Yeh, E.; Suppe, J.

    2008-12-01

    It is easily shown that many well-imaged accretionary wedges are mechanically heterogeneous based on spatial variations in wedge taper. For example, the toes of active accretionary wedges such as the Nankai trough and Barbados display deceasing surface slope α away from the toe, with no associated variation in the detachment dip β. Likely sources of this heterogeneity in taper are spatial variations in fluid pressure, cohesion and fault strength. However progress in understanding the mechanics of these active accretionary wedges is challenging because of [1] the obvious in-situ observational difficulties, combined with [2] the substantial complexity of heterogeneous wedge theory, making it difficult to apply to natural wedges. Here we present progress on both fronts, emphasizing the role of heterogeneity in pore-fluid pressure. We show that the spatial gradients in pore-fluid pressure can be effectively constrained using seismic velocity data, as well as borehole data, using standard petroleum techniques. Furthermore, the gradients in fluid pressure can be approximated by a single easily observable parameter, the fluid-retention depth zFRD below which compaction is strongly diminished. The Hubbert-Rubey weakening (1- λ) is a simple function of fluid-retention depth and depth (1-λ)=(1-λh)[zFRD/z]. We find that the heterogeneous critical taper wedge theory of Dahlen (1990) can be recast in terms of this fluid-retention depth, which leads to more concise and easily applied critical-taper wedge equations. The key observable parameters in addition to wedge taper (α, β) are zFRD/H, where H is the depth to detachment, and d zFRD/d z. We illustrate the application of these results with several natural examples, including the Barbados accretionary wedge and the Brazos area of offshore Texas, which is an extensional critical-taper wedge with extensive data.

  9. Modeling modulation of intracranial pressure by variation of cerebral venous resistance induced by ventilation.

    PubMed

    Pasley, Richard L; Leffler, Charles W; Daley, Michael L

    2003-11-01

    To test, theoretically, the hypothesis that: (1) cyclic extravascular compressional modulation of the terminal venous bed occurs with positive pressure inhalation; and (2) the degree of modulation is diminished with increasing vascular dilation induced by increasing the level of the partial pressure of arterial blood carbon dioxide (PCO2), two modifications of Ursino's model of cerebrospinal fluid dynamics were made: (1) terminal venous bed resistance was synchronously modulated with the ventilation cycle; and (2) both the depth of modulation and cerebrovascular resistance were progressively reduced with increasing levels of PCO2. Recordings of intracranial pressure (ICP) and arterial blood pressure of piglets were obtained and correlated at different levels of hypercapnia. Simulated and experimental correlation values progressively increased monotonically as the level of PCO2 increased. Group (n = 4) mean values of correlation (+/- standard deviation) were 0.54 (+/- 0.17), 0.61 (+/- 0.08), 0.79 (+/- 0.06), 0.86 (+/- 0.04), 0.87 (+/- 0.05) for respective mean PCO2 levels (+/- standard deviation) of 32.9 (+/- 1.75), 41.4 (+/- 2.5), 55.9 (+/- 4.0), 72.5 (+/- 6.45), and 87.4 (+/- 7.25) mmHg. These results support the stated premise that dilation of the cerebrovasculature reduces the influence of positive pressure ventilation on the ICP recording by increasing the venous pressure and thus diminishing the likelihood of vascular compression.

  10. [Factors influencing physiologic pressure variations of the lower esophageal sphincter in healthy probands].

    PubMed

    Bilic, A; Vuckovic, B; Pilas, V; Bakula, B; Hrgovic, Z; Kesselman-Evans, Z; Radosevic, J

    1990-01-01

    Manometric characteristics of lower esophageal sphincter (LES) in 59 healthy persons have been investigated. The aim of the investigation was to find out possible physiological changes of LES pressures considering posture, part of the day, maximal inspiration and expiration, empty or partially full stomach and abdominal compression. It has been proved that the minimal value of lower esophageal sphincter pressure in all the investigated patients was 1.77 kPA (13.3 mm Hg) while the maximal one was 4.53 kPa (34.0 mm Hg). The absolute difference between the lowest and the highest measured lower esophageal sphincter pressure was 1.43 kPa (10.77 mm Hg). The mean value of all pressures was 2.99 kPa (22.4 mm Hg). It seems that the posture during pressure measuring is irrelevant. The pressure does not vary more significantly considering neither the time of the day nor any exertion of the examinee.

  11. Gender differences in associations of diurnal blood pressure variation, awake physical activity, and sleep quality with negative affect: the work site blood pressure study.

    PubMed

    Kario, K; Schwartz, J E; Davidson, K W; Pickering, T G

    2001-11-01

    This study reports on the associations among depression, anxiety, awake physical activity, sleep quality (assessed by nocturnal physical activity), and diurnal blood pressure (BP) variation in a nonpsychiatric sample (The Work Site Blood Pressure Study). We conducted ambulatory BP (ABP) monitoring and actigraphy in 231 working men and women. Depression and anxiety were measured by the Brief Symptom Inventory. There were gender-specific associations between depression or anxiety and ABP parameters. In men, depression was associated positively with the sleep/awake systolic BP (SBP) ratio (r=0.24, P=0.006). After controlling for age, body mass index, and awake and sleep activity, depression remained significantly associated with the sleep/awake SBP ratio (r=0.25, P=0.005) and was also significantly related to sleep SBP (r=0.21, P=0.02). Anxiety, which was related to depression (r=0.73, P<0.0001), had a similar but slightly weaker pattern of associations with ABP and activity. These associations were not found in women, but there were associations of anxiety with awake SBP (r=0.24, P=0.01) and pulse rate (r=0.27, P=0.006). In conclusion, depression is associated with disrupted diurnal BP variation independent of ambulatory physical activity in working men, whereas anxiety is associated with awake SBP and pulse rate in women.

  12. Circadian variations of catecholamines and blood pressure in patients with pseudohypoparathyroidism and hypertension.

    PubMed

    Brickman, A S; Stern, N; Sowers, J R

    1990-01-01

    The relationship between 24-h recumbent blood pressure levels and secretory patterns of catecholamines was investigated in 4 patients with pseudohypoparathyroidism (PsHP) and hypertension and in 9 patients with essential hypertension. A clear circadian rhythm of blood pressure and catecholamines was documented in both groups with lowest levels of blood pressures and catecholamines occurring during sleep. During the 24-h period of recumbency mean arterial blood pressure (MAP) was correlated (r = 0.63, p less than or equal to 0.01) with plasma norepinephrine (N) in the patients with essential hypertension, but this correlation was weaker in patients with PsHP (r = 0.38, p less than or equal to 0.05). MAP was more closely related to plasma epinephrine (E) (r = 0.62, p less than or equal to 0.01) than to plasma NE in patients with PsHP. Plasma NE and E levels were considerably lower in patients with PsHP than in patients with essential hypertension throughout the 24-h recumbent period. The sleep-related decline in blood pressure and NE was less than in patients with essential hypertension. These results suggest that while the sympathetic nervous system may have a role in hour-to-hour maintenance of blood pressure in patients with PsHP and hypertension, it does not appear to be responsible for the elevated arterial pressure in these patients. Factors other than those investigated, such as obesity, alterations in sodium homeostasis of refractoriness of the vascular smooth muscle to the vasodilatory effect of PTH may be involved in the pathogenesis of hypertension in PsHP.

  13. Use of systolic pressure variation to predict the cardiovascular response to mini-fluid challenge in anaesthetised dogs.

    PubMed

    Rabozzi, R; Franci, P

    2014-11-01

    Systolic pressure variation (SPV), the maximum variation in systolic pressure values following a single positive pressure breath delivered by controlled mechanical ventilation (CMV), is highly correlated with volaemia in dogs. The aim of this study was to determine an SPV value that would indicate when fluid administration would be beneficial in clinical practice. Twenty-six client-owned dogs were anaesthetised, following which CMV with a peak inspiratory pressure (PIP) of 8 cmH2O was applied. After SPV measurement and recording of heart rate (HR) and blood pressure (BP), 3 mL/kg fluid were administered, then HR and BP were recorded again. Dogs exhibiting a 10% decrease in HR and/or an increase in BP were defined as responders, and their SPV pre-bolus was analysed retrospectively. SPV values > 4 mmHg or >4.5% predicted haemodynamic improvement in dogs with normal cardiovascular function, with a sensitivity of 90% and a specificity of 87%. The area under the curve receiver operating characteristic value for SPV was 0.931 mmHg (95% confidence interval, CI, 0.76-0.99 mmHg) and 0.944% (95% CI 0.78-0.99%). It is proposed that SPV values > 4.5% in dogs with a normal cardiovascular function, anaesthetised with isoflurane in oxygen and air, and on CMV (PIP 8 cmH2O), can be used to predict a cardiovascular response (>10% increase in mean arterial BP and/or >10% decrease in heart rate).

  14. Response of a catalytic reaction to periodic variation of the CO pressure: increased CO2 production and dynamic phase transition.

    PubMed

    Machado, Erik; Buendía, Gloria M; Rikvold, Per Arne; Ziff, Robert M

    2005-01-01

    We present a kinetic Monte Carlo study of the dynamical response of a Ziff-Gulari-Barshad model for CO oxidation with CO desorption to periodic variation of the CO pressure. We use a square-wave periodic pressure variation with parameters that can be tuned to enhance the catalytic activity. We produce evidence that, below a critical value of the desorption rate, the driven system undergoes a dynamic phase transition between a CO2 productive phase and a nonproductive one at a critical value of the period and waveform of the pressure oscillation. At the dynamic phase transition the period-averaged CO2 production rate is significantly increased and can be used as a dynamic order parameter. We perform a finite-size scaling analysis that indicates the existence of power-law singularities for the order parameter and its fluctuations, yielding estimated critical exponent ratios beta/nu approximately 0.12 and gamma/nu approximately 1.77. These exponent ratios, together with theoretical symmetry arguments and numerical data for the fourth-order cumulant associated with the transition, give reasonable support for the hypothesis that the observed nonequilibrium dynamic phase transition is in the same universality class as the two-dimensional equilibrium Ising model.

  15. Effects of chamber pressure variation on the grid temperature in an inertial electrostatic confinement device

    SciTech Connect

    Murali, S. Krupakar; Emmert, G. A.; Santarius, J. F.; Kulcinski, G. L.

    2010-10-15

    Inertial electrostatic confinement fusion devices are compact sources of neutrons, protons, electrons, and x rays. Such sources have many applications. Improving the efficiency of the device also increases the applications of this device. Hence a thorough understanding of the operation of this device is needed. In this paper, we study the effect of chamber pressure on the temperature of the cathode. Experimentally, the grid temperature decreases as the chamber pressure increases; numerical simulations suggest that this is caused by the reduction of the hot ion current to the cathode as the pressure increases for constant power supply current. Such an understanding further supports the conclusion that the asymmetric heating of the cathode can be decreased by homogenizing the ion flow around the cathode.

  16. Variation with Mach Number of Static and Total Pressures Through Various Screens

    NASA Technical Reports Server (NTRS)

    Adler, Alfred A

    1946-01-01

    Tests were conducted in the Langley 24-inch highspeed tunnel to ascertain the static-pressure and total-pressure losses through screens ranging in mesh from 3 to 12 wires per inch and in wire diameter from 0.023 to 0.041 inch. Data were obtained from a Mach number of approximately 0.20 up to the maximum (choking) Mach number obtainable for each screen. The results of this investigation indicate that the pressure losses increase with increasing Mach number until the choking Mach number, which can be computed, is reached. Since choking imposes a restriction on the mass rate of flow and maximum losses are incurred at this condition, great care must be taken in selecting the screen mesh and wire dimmeter for an installation so that the choking Mach number is

  17. Use of the BD-100R as a neutron spectrometer through applied pressure variation

    SciTech Connect

    White, B.; Ebert, D.; Munno, F. )

    1991-05-01

    A study was undertaken to demonstrate the feasibility of using the well-characterized BD-100R neutron bubble dosimeter as a neutron spectrometer in low-level radiation fields. The BD-100R dosimeters used in this work consisted of a test tube containing an elastic polymer with interspersed droplets of two types of Freon: Freon-12 and Freon-114. Each superheated liquid droplet is a potential nucleation site, with the minimum energy needed to form a bubble at the nucleation site being inversely proportional to the square of the difference between the applied and the vapor pressure (i.e., Emin alpha(delta P)-2). For a given dose, the number of bubbles formed continually decreases with increasing applied pressure, until a pressure is reached where no bubbles are formed, since the energy transferred can no longer vaporize the Freon. This investigation is intended to demonstrate the feasibility of measuring an unknown spectrum utilizing the dosimeter response (number of bubbles formed) as a function of the neutron energy (applied pressure). A set of 12 dosimeters was exposed under various applied pressures in a well-characterized neutron energy spectrum at the East Beam Port (EBP) of the Maryland University Training Reactor (MUTR). The dosimeters were placed inside a pressure chamber that could accommodate up to 18 dosimeters. Energy response coefficients (cross-sections) were obtained by spectral unfolding techniques on the known spectrum. The same set of dosimeters were then irradiated using a paraffin-moderated Pu/Be source. Measured spectral estimates obtained using the response coefficients were compared with numerical computations generated using the ANISN computer code. The results indicate that further research using the BD-100R as a neutron spectrometer in low radiation fields is warranted.

  18. Within-Tunnel Variations in Pressure Data for Three Transonic Wind Tunnels

    NASA Technical Reports Server (NTRS)

    DeLoach, Richard

    2014-01-01

    This paper compares the results of pressure measurements made on the same test article with the same test matrix in three transonic wind tunnels. A comparison is presented of the unexplained variance associated with polar replicates acquired in each tunnel. The impact of a significance component of systematic (not random) unexplained variance is reviewed, and the results of analyses of variance are presented to assess the degree of significant systematic error in these representative wind tunnel tests. Total uncertainty estimates are reported for 140 samples of pressure data, quantifying the effects of within-polar random errors and between-polar systematic bias errors.

  19. Drip flow variations under a stalactite of the Père Noël cave (Belgium). Evidence of seasonal variations and air pressure constraints

    NASA Astrophysics Data System (ADS)

    Genty, Dominique; Deflandre, Guy

    1998-11-01

    The study of drip rate and seepage water electrical conductivity (hereafter called conductivity) under one stalactite in the Père Noël cave (Belgium), with data produced from an automatic station since 1991, demonstrates several previously unobserved features: (1) measurement of drop volume shows that, for 94% of the time series, drop volume is constant (=0.14 ml), but when discharge exceeds 48.2 drips min -1, drop volume decreases, probably because of secondary drop formation; (2) the interannual drip rate variation is correlated to the annual water excess and its correlant, rainfall (R 2=0.98; exponential model); this result introduces a new improvement in the understanding of the previously investigated relationships between stalagmite annual laminae thickness and mean annual rainfall; (3) the drip rate shows a well marked seasonality: it increases abruptly in late fall or early winter and decreases slowly during spring, summer and fall. Increased discharge is accompanied by an increase in conductivity, which suggests that the flushed water is more mineralized and was stored in the karst aquifer for several months; (4) superimposed on these seasonal variations, there are two kinds of flow regimes which are driven by the atmospheric pressure: (i) a "wiggles regime", whose duration is 1-7 days in length and which is inversely proportional to the air pressure wiggles; it is explained by either a "shut-off faucet" process due to the rock formation stress, or to a change in the two-phases flow component proportions (air/water); (ii) an "unstable regime" characterized by abrupt switches (<2 h) or oscillations with variable periodicities, from a few minutes to a few hours. These occur when the drip rate reaches a threshold (i.e. 240 drops 10 min -1); the chaotic behaviour of this phenomenon is discussed.

  20. Positive Selection Pressure Drives Variation on the Surface-Exposed Variable Proteins of the Pathogenic Neisseria

    PubMed Central

    Hill, Stuart

    2016-01-01

    Pathogenic species of Neisseria utilize variable outer membrane proteins to facilitate infection and proliferation within the human host. However, the mechanisms behind the evolution of these variable alleles remain largely unknown due to analysis of previously limited datasets. In this study, we have expanded upon the previous analyses to substantially increase the number of analyzed sequences by including multiple diverse strains, from various geographic locations, to determine whether positive selective pressure is exerted on the evolution of these variable genes. Although Neisseria are naturally competent, this analysis indicates that only intrastrain horizontal gene transfer among the pathogenic Neisseria principally account for these genes exhibiting linkage equilibrium which drives the polymorphisms evidenced within these alleles. As the majority of polymorphisms occur across species, the divergence of these variable genes is dependent upon the species and is independent of geographical location, disease severity, or serogroup. Tests of neutrality were able to detect strong selection pressures acting upon both the opa and pil gene families, and were able to locate the majority of these sites within the exposed variable regions of the encoded proteins. Evidence of positive selection acting upon the hypervariable domains of Opa contradicts previous beliefs and provides evidence for selection of receptor binding. As the pathogenic Neisseria reside exclusively within the human host, the strong selection pressures acting upon both the opa and pil gene families provide support for host immune system pressure driving sequence polymorphisms within these variable genes. PMID:27532335

  1. Positive Selection Pressure Drives Variation on the Surface-Exposed Variable Proteins of the Pathogenic Neisseria.

    PubMed

    Wachter, Jenny; Hill, Stuart

    2016-01-01

    Pathogenic species of Neisseria utilize variable outer membrane proteins to facilitate infection and proliferation within the human host. However, the mechanisms behind the evolution of these variable alleles remain largely unknown due to analysis of previously limited datasets. In this study, we have expanded upon the previous analyses to substantially increase the number of analyzed sequences by including multiple diverse strains, from various geographic locations, to determine whether positive selective pressure is exerted on the evolution of these variable genes. Although Neisseria are naturally competent, this analysis indicates that only intrastrain horizontal gene transfer among the pathogenic Neisseria principally account for these genes exhibiting linkage equilibrium which drives the polymorphisms evidenced within these alleles. As the majority of polymorphisms occur across species, the divergence of these variable genes is dependent upon the species and is independent of geographical location, disease severity, or serogroup. Tests of neutrality were able to detect strong selection pressures acting upon both the opa and pil gene families, and were able to locate the majority of these sites within the exposed variable regions of the encoded proteins. Evidence of positive selection acting upon the hypervariable domains of Opa contradicts previous beliefs and provides evidence for selection of receptor binding. As the pathogenic Neisseria reside exclusively within the human host, the strong selection pressures acting upon both the opa and pil gene families provide support for host immune system pressure driving sequence polymorphisms within these variable genes.

  2. Variation in heat and pressure resistance of verotoxigenic and nontoxigenic Escherichia coli.

    PubMed

    Liu, Yang; Gill, Alex; McMullen, Lynn; Gänzle, Michael G

    2015-01-01

    This study evaluated the heat and pressure resistance of 112 strains of Escherichia coli, including 102 strains of verotoxigenic E. coli (VTEC) representing 23 serotypes and four phylogenetic groups. In an initial screening, the heat and pressure resistance of 100 strains, including 94 VTEC strains, were tested in phosphate-buffered saline (PBS). Treatment at 60°C for 5 min reduced cell counts by 2.0 to 5.5 log CFU/ml; treatment at 600 MPa for 3 min at 25°C reduced the cell counts by 1.1 to 5.5 log CFU/ml. Heat or pressure resistance did not correlate to the phylogenetic group or the serotype. A smaller group of E. coli strains was evaluated for heat and pressure resistance in Luria-Bertani (LB) broth. Generally, the levels of heat resistance of E. coli strains in LB and PBS were similar; however, the levels of pressure resistance observed for treatments in LB broth or PBS were variable. The cell counts of pressure-resistant strains of VTEC were reduced by less than 1.5 log CFU/ml after treatment at 600 MPa for 3 min. E. coli strains were also treated with 600 MPa for 3 min in ground beef or inoculated into beef patties and grilled to 63 or 71°C. The cell counts of the VTEC E. coli O26:H11 strain 05-6544 were reduced by 2 log CFU/g by pressure treatment in ground beef. The cell counts of the heat-resistant E. coli strain AW1.7 were reduced by 1.4 and 3.4 log CFU/g in beef patties grilled to internal temperatures of 63 and 71°C, respectively. The cell counts of E. coli 05-6544 were reduced by less than 3 and 6 log CFU/g in beef patties grilled to internal temperatures of 63 and 71°C, respectively. To study whether the composition of the beef patties influenced heat resistance, E. coli strains AW1.7, AW1.7 Δ pHR1, MG1655, and LMM1030 were mixed into beef patties containing 15 or 35% fat and 0 or 2% NaCl, and the patties were grilled to an internal temperature of 63°C. The highest heat resistance of E. coli was observed in patties containing 15% fat and 2% NaCl.

  3. The influence of bandage characteristics and inter-individual application variations on underneath bandage pressures.

    PubMed

    Morlock, MM; Nassutt, R; Bonin, V

    1997-04-01

    INTRODUCTION:: Cohesive bandages are applied to the legs of racehorses and horses with limb injuries for protection (prevention of abrasion) and support (reduction of movement at the fetlock joint). The support capacity of all commercially available bandages has been questioned. Consequently, the protection aspect of bandaging and the negative side effects, which can be caused by bandaging (eg pressure induced ischemia with subsequent necrosis), were emphasized. High pressures underneath bandages were shown to cause reduced blood flow. Pressures underneath certain types of bandages were shown to be higher than under others. It is unclear if these differences were due to differences in material characteristics between the bandage types or caused by differences in application by the trainers. The purpose of this study was to determine (a) if differences between different types of bandages are observed if these are applied similarly and (b) if earlier observed differences in pressures underneath bandages are reproducible when wrapped by different trainers. METHODS AND MATERIAL:: (a) A wrapping machine for the application of bandages to an artificial joint (simulating the human knee joint) was designed and built. The machine allows to wrap bandages with adjustable, constant tension under well defined wrapping angles in order to simulate a wrapping technique similar to the wrapping by trainers. The artificial joint is equipped with two pressure sensors (Parotec, Germany). After bandage application, the artificial joint was placed in a specially designed testing machine and cycled through 200 cycles from 0 degrees to 90 degrees of flexion at a frequency of 0.5 Hz. Pressure data were collected at a frequency of 20 Hz. The force required to unwind the bandage from its core was measured with a material testing machine. Five samples each of four different 4" wide cohesive bandages were tested: 'E': high modulus latex, 'V': low mod. latex, 'C': low mod. latex, 'F': medium mod

  4. Seasonal variation in self-measured home blood pressure among patients on antihypertensive medications: HOMED-BP study.

    PubMed

    Hanazawa, Tomohiro; Asayama, Kei; Watabe, Daisuke; Hosaka, Miki; Satoh, Michihiro; Yasui, Daisaku; Obara, Taku; Inoue, Ryusuke; Metoki, Hirohito; Kikuya, Masahiro; Imai, Yutaka; Ohkubo, Takayoshi

    2017-03-01

    Seasonal variation of blood pressure (BP) has been reported in small populations or by BP levels captured at only a few points in a year, for example, summer and winter. We aimed to investigate the multiyear seasonal variation in self-measured home BP among hypertensive patients receiving antihypertensive medications. We selected 1649 eligible patients receiving antihypertensive drug treatment, and weekly averaged home BPs were analyzed throughout the follow-up period. Systolic and diastolic home BPs were fitted with the cosine function: 'Variation+Other Effects+Intercept', in which the 'Variation' was expressed by a cosine curve with three parameters representing: (1) maximum-minimum difference of home BP in one cycle of the cosine curve; (2) time required for one cycle of the cosine curve for home BP variation; and (3) time at which home BP reached the maximum point. Maximum-minimum differences in home BP were 6.7/2.9 mm Hg, and the highest home BPs were observed in mid-to-late January. In the multivariable-adjusted model, a large maximum-minimum difference in home BP was associated with lower body mass index and older age, and larger differences were observed in men compared with women. Summer-winter difference in home BP was essentially similar every year, though it was marginally reduced by 0.14/0.04 mm Hg per year, under long-term antihypertensive treatment. Records of daily home BP measurements enable us to capture long-term factors such as seasonal variation. Home BP should therefore be carefully monitored, particularly in patients with increased BP in winter, to mitigate cardiovascular risk.

  5. Sea Level and Ocean Bottom Pressure Variations From Altimetry, Mercator Model and GRACE Mission in the Argentine Basin

    NASA Astrophysics Data System (ADS)

    Garcia-Garcia, D.; Boy, J.; Chao, B. F.

    2008-12-01

    Sea Level Variations (SLV) in the Argentine basin, as already observed from space altimetry missions, show one of the most prominent variances in the oceans. Here we study two major signals in the Argentine basin, the annual and submonthly SLV signals, based on altimetry, various hydrographic data, and the time-variable gravity data from the GRACE mission. We demonstrate that the annual variation is mainly driven by density variations of the water column, that is the steric-SLV. In contrast, the submonthly SLV in the form of the so- called Argentine gyre, a barotropic counterclockwise gyre with a period around 25 days, is mainly mass- induced, that is, mostly produced by mass variations in the region [Fu et al. 2000]. The Argentine gyre signal is well reproduced by the MERCATOR ocean circulation (and bottom pressure) model, unlike the annual signal. We show that now the aliased form (into monthly sampling) is also captured in the GRACE time- variable gravity data after applying appropriated filters; further study awaits higher temporal-resolution GRACE data.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. AGT genetic variation, plasma AGT, and blood pressure: An analysis of the Utah Genetic Reference Project pedigrees.

    PubMed

    Watkins, W Scott; Rohrwasser, Andreas; Peiffer, Andy; Leppert, Mark F; Lalouel, Jean-Marc; Jorde, Lynn B

    2010-08-01

    Much remains unknown about the genetic factors that contribute to essential hypertension. The Utah Genetic Reference Project (UGRP) large pedigree collection provides new opportunities to study quantitative relationships between genetic variation, endophenotypes, and blood pressure. We analyzed the relationship between common single-nucleotide polymorphisms (SNPs) and haplotypes spanning the angiotensinogen (AGT) gene and promoter region, plasma AGT levels, and systolic (SBP) and diastolic blood pressure (DBP) in 424 individuals from 41 two-generation UGRP families. Plasma AGT levels are significantly correlated among UGRP family members. Correlations are higher for males than for females. Parent-offspring correlations for plasma AGT (0.30) are higher than those for SBP (0.26) and DBP (0.17) (all P values <0.01). The additive heritability (h(2)) for plasma AGT is high (0.74) and substantially exceeds heritability estimates for SBP (0.26) and DBP (0.16) (all P values <0.01). Significant linkage (logarithm of the odds (LOD) >3) is found between six AGT SNPs and plasma AGT. A model that utilizes three AGT haplotype groups produces the best LOD score (5.1) that exceeds the best single SNP LOD score (3.8). Plasma AGT and blood pressure were not significantly correlated. Plasma AGT levels demonstrate high heritability in 41 UGRP families. Locus-specific heritability estimates for AGT SNPs and haplotypes approach 67%, indicating that variation at AGT accounts for a large percentage of the heritability of plasma AGT. A three-way haplotype model outperforms single SNPs for quantitative linkage analysis to plasma AGT. In these predominantly normotensive individuals, plasma AGT did not correlate significantly with blood pressure.

  8. TEMPORAL VARIATIONS OF X-RAY SOLAR FLARE LOOPS: LENGTH, CORPULENCE, POSITION, TEMPERATURE, PLASMA PRESSURE, AND SPECTRA

    SciTech Connect

    Jeffrey, Natasha L. S.; Kontar, Eduard P.

    2013-04-01

    The spatial and spectral properties of three solar flare coronal X-ray loops are studied before, during, and after the peak X-ray emission. Using observations from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), we deduce the temporal changes in emitting X-ray length, corpulence, volume, position, number density, and thermal pressure. We observe a decrease in the loop length, width, and volume before the X-ray peak, and an increasing number density and thermal pressure. After the X-ray peak, volume increases and loop corpulence grows due to increasing width. The volume variations are more pronounced than the position variations, often known as magnetic field line contraction. We believe this is the first dedicated study examining the temporal evolution of X-ray loop lengths and widths. Collectively, the observations also show for the first time three temporal phases given by peaks in temperature, X-ray emission, and thermal pressure, with the minimum volume coinciding with the X-ray peak. Although the volume of the flaring plasma decreases before the peak in X-ray emission, the relationship between temperature and volume does not support simple compressive heating in a collapsing magnetic trap model. Within a low {beta} plasma, shrinking loop widths perpendicular to the guiding field can be explained by squeezing the magnetic field threading the region. Plasma heating leads to chromospheric evaporation and growing number density. This produces increasing thermal pressure and decreasing loop lengths as electrons interact at shorter distances and we believe after the X-ray peak, the increasing loop corpulence.

  9. Is gold solubility subject to pressure variations in ascending arc magmas?

    NASA Astrophysics Data System (ADS)

    Jégo, Sébastien; Nakamura, Michihiko; Kimura, Jun-Ichi; Iizuka, Yoshiyuki; Chang, Qing; Zellmer, Georg F.

    2016-09-01

    Magmas play a key role in the genesis of epithermal and porphyry ore deposits, notably by providing the bulk of ore metals to the hydrothermal fluid phase. It has been long shown that the formation of major deposits requires a multi-stage process, including the concentration of metals in silicate melts at depth and their transfer into the exsolved ore fluid in more superficial environments. Both aspects have been intensively studied for most of noble metals in subsurface conditions, whereas the effect of pressure on the concentration (i.e., solubility) of those metals in magmas ascending from the sublithospheric mantle to the shallow arc crust has been quite neglected. Here, we present new experimental data aiming to constrain the processes of gold (Au) dissolution in subduction-linked magmas along a range of depth. We have conducted hydrous melting experiments on two dacitic/adakitic magmas at 0.9 and 1.4 GPa and ∼1000 °C in an end-loaded piston cylinder apparatus, under fO2 conditions close to NNO as measured by solid Co-Pd-O sensors. Experimental charges were carried out in pure Au containers, the latter serving as the source of gold, in presence of variable amounts of H2O and, for half of the charges, with elemental sulfur (S) so as to reach sulfide saturation. Au concentrations in melt quenched to glass were determined by LA-ICPMS. When compared to previous data obtained at lower pressures and variable redox conditions, our results show that in both S-free and sulfide-saturated systems pressure has no direct, detectable effect on melt Au solubility. Nevertheless, pressure has a strong, negative effect on sulfur solubility. Since gold dissolution is closely related to the behavior of sulfur in reducing and moderately oxidizing conditions, pressure has therefore a significant but indirect effect on Au solubility. The present study confirms that Au dissolution is mainly controlled by fO2 in S-free melts and by a complex interplay of fO2 and melt S2

  10. Fluctuations in syringe-pump infusions: association with blood pressure variations in infants.

    PubMed

    Capes, D F; Dunster, K R; Sunderland, V B; McMillan, D; Colditz, P B; McDonald, C

    1995-08-01

    Flow continuity of two brands of syringe pumps and four brands of syringes was studied as a possible cause of hemodynamic fluctuations observed in neonates. Cyclical fluctuations were observed in the blood pressure of 14 neonates receiving dopamine infusions by syringe pump at flow rates from 0.2 to 1 mL/hr. Atom 235 and IVAC 770 pumps and various sizes of Terumo, Becton Dickinson, Omnifix, and IVAC syringes were evaluated. Flow continuity was assessed by using a gravimetric technique. The force needed to initiate and maintain syringe plunger motion was also measured. Noncontinuous flow was encountered most commonly with Terumo syringes, which delivered boluses at regular intervals at flow rates up to 5 mL/hr. The interval was dependent on flow rate and was similar to the time between the blood pressure fluctuations observed clinically. The syringe plunger force exhibited regular fluctuations indicative of the plunger sticking, and simultaneous measurement of flow established a direct temporal relationship with boluses. The other syringes tested did not exhibit such fluctuations. No differences were found between the two syringe pumps. Syringe plunger sticking, resulting in intermittent boluses and potential blood pressure fluctuations, may occur at low flow rates and with certain syringe brands. This appeared to be the cause of hemodynamic fluctuations in neonates receiving dopamine infusions.

  11. Impact of Wall Shear Stress and Pressure Variation on the Stability of Atherosclerotic Plaque

    NASA Astrophysics Data System (ADS)

    Taviani, V.; Li, Z. Y.; Sutcliffe, M.; Gillard, J.

    Rupture of vulnerable atheromatous plaque in the carotid and coronary arteries often leads to stroke and heart attack respectively. The mechanism of blood flow and plaque rupture in stenotic arteries is still not fully understood. A three dimensional rigid wall model was solved under steady and unsteady conditions assuming a time-varying inlet velocity profile to investigate the relative importance of axial forces and pressure drops in arteries with asymmetric stenosis. Flow-structure interactions were investigated for the same geometry and the results were compared with those retrieved with the corresponding one dimensional models. The Navier-Stokes equations were used as the governing equations for the fluid. The tube wall was assumed linearly elastic, homogeneous isotropic. The analysis showed that wall shear stress is small (less than 3.5%) with respect to pressure drop throughout the cycle even for severe stenosis. On the contrary, the three dimensional behavior of velocity, pressure and wall shear stress is in general very different from that predicted by one dimensional models. This suggests that the primary source of mistakes in one dimensional studies comes from neglecting the three dimensional geometry of the plaque. Neglecting axial forces only involves minor errors.

  12. Ultra-high temperature stability Joule-Thomson cooler with capability to accomodate pressure variations

    NASA Technical Reports Server (NTRS)

    Bard, Steven (Inventor); Wu, Jiunn-Jeng (Inventor); Trimble, Curtis A. (Inventor)

    1992-01-01

    A Joule-Thomson cryogenic refrigeration system capable of achieving high temperature stabilities in the presence of varying temperature, atmospheric pressure, and heat load is provided. The Joule-Thomson cryogenic refrigeration system includes a demand flow Joule-Thomson expansion valve disposed in a cryostat of the refrigeration system. The expansion valve has an adjustable orifice that controls the flow of compressed gas therethrough and induces cooling and partial liquefaction of the gas. A recuperative heat exchanger is disposed in the cryostat and coupled to the expansion valve. A thermostatically self-regulating mechanism is disposed in the cryostat and coupled to the J-T expansion valve. The thermostatically self-regulating mechanism automatically adjusts the cross sectional area of the adjustable valve orifice in response to environmental temperature changes and changes in power dissipated at a cold head. A temperature sensing and adjusting mechanism is coupled to a cold head for adjusting the temperature of the cold head in response to the change in heat flow in the cold head. The temperature sensing and adjusting mechanism comprises a temperature sensitive diode, a wound wire heater, and an electrical feedback control circuit coupling the diode to the heater. An absolute pressure relief valve is interposed between the output of the cryostat and an exhaust port for maintaining a constant exhaust temperature in the refrigerating system, independent of the changes in atmospheric pressure.

  13. Inter- versus Intramolecular Structural Manipulation of a Dichromium(II) Pacman Complex through Pressure Variation.

    PubMed

    Stevens, Charlotte J; Prescimone, Alessandro; Tuna, Floriana; McInnes, Eric J L; Parsons, Simon; Morrison, Carole A; Arnold, Polly L; Love, Jason B

    2016-01-04

    The effect of pressure on the intranuclear M···M separation and intermolecular secondary interactions in the dinuclear chromium Pacman complex [Cr2(L)](C6H6) was evaluated because this compound contains both a short Cr···Cr separation and an exogenously bound molecule of benzene in the solid state. The electronic structure of [Cr2(L)] was determined by electron paramagnetic resonance spectroscopy, SQUID magnetometry, and density functional theory calculations and shows a diamagnetic ground state through antiferromagnetic exchange, with no evidence for a Cr-Cr bond. Analysis of the solid-state structures of [Cr2(L)](C6H6) at pressures varying from ambient to 3.0 GPa shows little deformation in the Cr···Cr separation, i.e., no Cr-Cr bond formation, but instead a significantly increased interaction between the exogenous arene and the chromium iminopyrrolide environment. It is therefore apparent from this analysis that [Cr2(L)] would be best exploited as a rigid chemical synthon, with pressure regulation being used to mediate the approach and secondary interactions of possible substrates.

  14. Understanding Depth Variation of Deep Seismicity from in situ Measurements of Mineral Strengths at High Pressures

    SciTech Connect

    Chen, J.

    2010-01-01

    Strengths of major minerals of Earth's mantle have been measured using in situ synchrotron X-ray diffraction at high pressures. Analysis of the diffraction peak widths is used to derive the yield strengths. Systematic analysis of the experimental result for olivine, wadsleyite, ringwoodite and perovskite indicates that minerals in the upper mantle, the transition zone and the lower mantle have very distinct strength character. Increasing temperature weakens the upper mantle mineral, olivine, significantly. At high temperature and high pressure, the transition zone minerals, wadsleyite and ringwoodite, have higher strengths than the upper mantle mineral. Among all the minerals studied, the lower mantle mineral, perovskite, has the highest strength. While both the upper mantle and the transition zone minerals show a notable strength drop, the strength of the lower mantle mineral shows just an increase of relaxation rate (no strength drop) when the temperature is increased stepwise by 200 K. The strength characteristics of these major mantle minerals at high pressures and temperatures indicate that yield strength may play a crucial role in defining the profile of deep earthquake occurrence with depth.

  15. Exercise-induced albuminuria vs circadian variations in blood pressure in type 1 diabetes

    PubMed Central

    Tadida Meli, Isabelle Hota; Tankeu, Aurel T; Dehayem, Mesmin Y; Chelo, David; Noubiap, Jean Jacques N; Sobngwi, Eugene

    2017-01-01

    AIM To investigated the relationship between exercise-induced ambulatory blood pressure measurement (ABPM) abnormalities in type 1 diabetes mellitus (T1DM) adolescents. METHODS We conducted a case-control at the National Obesity Center of the Yaoundé Central Hospital, Cameroon. We compared 24 h ABPM and urinary albumin-to-creatinine ratio (ACR) at rest and after a standardized treadmill exercise between 20 Cameroonian T1DM patients and 20 matched controls. T1DM adolescents were aged 12-18 years, with diabetes for at least one year, without proteinuria, with normal office blood pressure (BP) and renal function according to the general reference population. Non-diabetic controls were adolescents of general population matched for sex, age and BMI. RESULTS Mean duration of diabetes was 4.2 ± 2.8 years. The mean 24 h systolic blood pressure (SBP) and diastolic blood pressure (DBP) were respectively 116 ± 9 mmHg in the diabetic group vs 111 ± 8 mmHg in the non-diabetic (P = 0.06), and 69 ± 7 mm Hg vs 66 ± 5 mm Hg (P = 0.19). There was no difference in the diurnal pattern of BP in diabetes patients and non-diabetic controls (SBP: 118 ± 10 mmHg vs 114 ± 10 mmHg, P = 0.11; DBP: 71 ± 7 mmHg vs 68 ± 6 mmHg, P = 0.22). Nighttime BP was higher in the diabetic group with respect to SBP (112 ± 11 mmHg vs 106 ± 7 mmHg, P = 0.06) and to the mean arterial pressure (MAP) (89 ± 9 mmHg vs 81 ± 6 mmHg, P = 0.06). ACR at rest was similar in both groups (5.5 mg/g vs 5.5 mg/g, P = 0.74), but significantly higher in diabetes patients after exercise (10.5 mg/g vs 5.5 mg/g, P = 0.03). SBP was higher in patients having exercise-induced albuminuria (116 ± 10 mmHg vs 108 ± 10 mmHg, P = 0.09). CONCLUSION Exercise-induced albuminuria could be useful for early diagnosis of kidney damage in adolescents with T1DM. PMID:28265345

  16. Are conformational changes, induced by osmotic pressure variations, the underlying mechanism of controlling the adhesive activity of mussel adhesive proteins?

    PubMed

    van der Leeden, Mieke C

    2005-11-22

    The mussel adhesive protein Mefp-1, under physiological conditions, presumably has a self-avoiding random walk conformation with helix-like or turned deca-peptide segments. Such a conformation may coil up under osmotic pressure induced by surrounding macromolecules. As a consequence, the orientation of the 3,4-dihydroxy-phenylalanine groups (dopa), essential for the adhesive strength as well as the cohesive strength in Mefp-1, will be altered. Changing the concentration of the protein itself or of different-type surrounding macromolecules may therefore be a tool to control the protein's adhesive activity. The effect of osmotic pressure on the conformation and dopa reactivity of Mefp-1 is studied by the addition of (poly)ethylene oxide (PEO) as a model macromolecule (Mw = 100 kD). From UV-spectroscopy measurements, it can be concluded that dopa reactivity in Mefp-1 changes with increasing PEO concentration. Fitting of the measured absorbance intensity data of the oxidation product dopaquinone versus time with a kinetic model points to the decreased accessibility of dopa groups in the Mefp-1 structure, a faster oxidation, and diminished cross linking under the influence of increasing PEO concentration up to 2.4 g/L, corresponding to an osmotic pressure of approximately 73 Pa. At higher PEO concentrations, the accessibility of the dopa groups for oxidation as well as cross-link formation decreases until about 20% of the dopa groups are oxidized at a PEO concentration of 3.8 g/L, corresponding to an osmotic pressure of approximately 113 Pa. FTIR measurements on the basis of amide I shifts qualitatively point to a transition to a more continuously turned structure of Mefp-1 in the presence of PEO. Therefore, it seems that conformational changes caused by variations of osmotic pressure determine the extent of steric hindrance of the dopa groups and hence the adhesive reactivity of Mefp-1.

  17. Geographic variation in host-specificity and parasitoid pressure of an herbivore (geometridae) associated with the tropical genus piper (piperaceae).

    PubMed

    Connahs, Heidi; Rodríguez-Castañeda, Genoveva; Walters, Toni; Walla, Thomas; Dyer, Lee

    2009-01-01

    The extraordinary diversity of tropical herbivores may be linked to hostplant specialization driven in part by variation in pressure from natural enemies. We quantified levels of host-specificity and parasitoid attack for the specialist herbivore, Eois (Geometridae). The goals of this research were to examine: 1) whether Eois are specialized on the genus Piper (Piperaceae) and if hostplant specialization varies geographically; 2) whether Eois are equally vulnerable to parasitoid attack across different geographic regions and by the same parasitoid families; and 3) whether parasitism levels vary with precipitation and elevation. Based on over 15,000 rearings, we found Eois caterpillars feeding exclusively on Piper. However, we did not detect geographic differences in host-specificity; each Eois species fed on an average of two Piper species. Parasitism levels of Eois varied significantly with climate and topography; Eois were most vulnerable to parasitoid attack in moist versus dry and wet forests and at low versus high elevations. The diversity of parasitoid families reared from Eois was greater in Ecuador and Costa Rica than in Panama, where parasitoids were primarily in the family Braconidae. The quantitative evidence for host-specificity provides support for the hypothesis that Eois are specialized on Piper. Our results also reveal that Eois are exposed to a mosaic of potential selective pressures due to variation in parasitoid attack over a large spatial scale.

  18. Exploring variation in pressure ulcer prevalence in Sweden and the USA: benchmarking in action.

    PubMed

    Gunningberg, Lena; Donaldson, Nancy; Aydin, Carolyn; Idvall, Ewa

    2012-08-01

    To compare overall unit-level pressure ulcer (PU) prevalence, hospital-acquired pressure ulcer (HAPU) prevalence and prevention strategies, as well as nurse staffing and workload in two hospitals in Sweden with data from the USA. Medical and surgical units in a university hospital and a general hospital in Sweden were compared with 207 hospitals in the USA participating in the Collaborative Alliance for Nursing Outcomes (CALNOC) benchmarking registry. All adult inpatients in university hospital (n = 630), general hospital (n = 253) and CALNOC hospitals (n = 3506) were included in the study. Outcome indicators were pressure ulcer prevalence for all types (PU) and HAPU prevalence, specifically. Process indicators were risk assessment and PU prevention strategies. Structure indicators were nurse staffing (hours of care, and skill mix) and workload (admissions, discharges and transfers). The prevalence of PU (categories 1-4) was 17.6% (university hospital) and 9.5% (general hospital) compared with 6.3-6.7% in the CALNOC sample. The prevalence of full thickness HAPU (categories 3 and 4) was 2.7% (university hospital) and 2.0% (general hospital) compared with 0-0.5% in the CALNOC sample. Risk and skin assessment varied between 6% and 60% in the Swedish hospitals compared with 100% in the CALNOC sample. Total hours per patient day were 8.4 in both Swedish hospitals and 9.5 to 9.8 in the CALNOC hospitals The findings suggest a link between processes of care and outcomes that is exciting to observe internationally and suggest the opportunity to expedite performance improvement through global benchmarking. Using HAPU as a complement to point prevalence of PU in Sweden has revealed this indicator as a more valid measure for patient care quality. © 2011 Blackwell Publishing Ltd.

  19. Association of Temporal Variations in Staffing With Hospital-Acquired Pressure Injury in Military Hospitals.

    PubMed

    Patrician, Patricia A; McCarthy, Mary S; Swiger, Pauline; Raju, Dheeraj; Breckenridge-Sproat, Sara; Su, Xiaogang; Randall, Kelly H; Loan, Lori A

    2017-04-01

    To more precisely evaluate the effects of nurse staffing on hospital-acquired pressure injury (HAPI) development, data on nursing care hours per patient day (NCHPPD), nursing skill mix, patient turnover (i.e., admissions, transfers, and discharges), and patient acuity were merged with patient information from pressure injury prevalence surveys that were collected annually for the Military Nursing Outcomes Database (MilNOD) project. The MilNOD included staffing and adverse events from 56 medical-surgical, stepdown, and critical care units in 13 military hospitals over a 4-year-period. Data on 1,643 patients were analyzed with Cox proportional hazards models and generalized estimating equations. Staffing was not associated with pressure injuries in stepdown or critical care patients. However, among the 1,104 medical-surgical patients, higher licensed practical nurse (LPN) nursing care hours per patient day (NCHPPD) 3 days and 1 week prior to the HAPI discovery date were associated with fewer HAPI (HR 0.27, p < .001), after controlling for patient age, Braden mobility score, and albumin level. Neither total staff number, nor RN NCHPPD, nor the proportion of staff who were RNs (RN skill mix) were associated with HAPI. These findings suggest that on military medical-surgical units, LPNs play a major role in HAPI prevention. Although the national trend in acute care is to staff hospital units with more RNs and patient care technicians, and fewer LPNs, hospitals should reconsider LPNs as valuable members of the nursing care team. © 2016 Wiley Periodicals, Inc.

  20. A combined experimental and numerical study of pore water pressure variations in sub-permafrost groundwater

    NASA Astrophysics Data System (ADS)

    Rivière, A.; Anne, J.; Goncalves, J.

    2013-12-01

    The past few decades have seen a rapid development and progress in research on past and current hydrologic impacts of permafrost evolution. In permafrost area, groundwater is subdivided into two zones: supra-permafrost and sub-permafrost which are separated by permafrost. Knowledge of the sub-permafrost aquifers is often lacking due to the difficulty to access those systems. The few available data show that this aquifers are generally artesian below the continuous permafrost. In the literature, there are two plausible explanations for the relatively high pore pressures in the sub-permafrost aquifer; the recharge related to the ice sheet melting and the expulsion of water related to the ice expansion. In this study, we investigated areas where ice sheets have never developed like in the Paris basin region. The ice expansion induces also soil surface uplift. Our study focuses on modifications of pore water pressure in the sub-permafrost aquifer and the soil surface motion during the permafrost development (freezing front deepening). To fill in the gaps to the field data availability, we developed an experimental approach. Experimental design was undertaken at the Laboratory M2C (Université de Caen-Basse Normandie, CNRS, France). The device consisted in a 2 m2 box insulated at all sides except on the top where a surface temperature was prescribed. The box is filled with silty sand of which hydraulics and thermal parameters are known. Soil temperatures, pore water pressure and soil motion are continuously recorded at different elevations in the sand-box. We developed a two-dimensional transient fully coupled heat and water transport model to simulate thawing and freezing processes taking into account the phase change (Latent heat effects). The balance equations are solved using of a finite difference numerical scheme. Experimental results are used to verify the implementation of the hydro-mechanical processes in our numerical simulations. Experimental and numerical

  1. Pore water pressure variations in Subpermafrost groundwater : Numerical modeling compared with experimental modeling

    NASA Astrophysics Data System (ADS)

    Rivière, Agnès.; Goncalves, Julio; Jost, Anne; Font, Marianne

    2010-05-01

    Development and degradation of permafrost directly affect numerous hydrogeological processes such as thermal regime, exchange between river and groundwater, groundwater flows patterns and groundwater recharge (Michel, 1994). Groundwater in permafrost area is subdivided into two zones: suprapermafrost and subpermafrost which are separated by permafrost. As a result of the volumetric expansion of water upon freezing and assuming ice lenses and frost heave do not form freezing in a saturated aquifer, the progressive formation of permafrost leads to the pressurization of the subpermafrost groundwater (Wang, 2006). Therefore disappearance or aggradation of permafrost modifies the confined or unconfined state of subpermafrost groundwater. Our study focuses on modifications of pore water pressure of subpermafrost groundwater which could appear during thawing and freezing of soil. Numerical simulation allows elucidation of some of these processes. Our numerical model accounts for phase changes for coupled heat transport and variably saturated flow involving cycles of freezing and thawing. The flow model is a combination of a one-dimensional channel flow model which uses Manning-Strickler equation and a two-dimensional vertically groundwater flow model using Richards equation. Numerical simulation of heat transport consisted in a two dimensional model accounting for the effects of latent heat of phase change of water associated with melting/freezing cycles which incorporated the advection-diffusion equation describing heat-transfer in porous media. The change of hydraulic conductivity and thermal conductivity are considered by our numerical model. The model was evaluated by comparing predictions with data from laboratory freezing experiments. Experimental design was undertaken at the Laboratory M2C (Univesité de Caen-Basse Normandie, CNRS, France). The device consisted of a Plexiglas box insulated on all sides except on the top. Precipitation and ambient temperature are

  2. Common genetic variation in the type A endothelin-1 receptor is associated with ambulatory blood pressure: a family study.

    PubMed

    Rahman, T; Baker, M; Hall, D H; Avery, P J; Keavney, B

    2008-04-01

    The endothelins are among the most potent vasoconstrictors known. Pharmacological inhibition of endothelin receptors lowers blood pressure (BP). It is unknown whether naturally occurring genetic variation in the endothelin receptors influences BP. We have evaluated the type A endothelin receptor (EDNRA) as a candidate gene for hypertension in a large family study. A total of 1425 members of 248 families selected via a proband with hypertension were studied. Ambulatory BP monitoring was conducted using the A&D TM2421 device. Four haplotype-tagging single nucleotide polymorphisms (SNPs) spanning the EDNRA gene were typed. There was evidence of association between genotype at the rs5335 (C+70G) SNP and night systolic blood pressure (+1.24% (s.e. 0.64) per G allele; P=0.05); night diastolic blood pressure (+1.64% (s.e. 0.71) per G allele; P=0.021) and night mean BP (+1.51% (s.e. 0.64) per G allele; P=0.017). Borderline significant trends in the same direction were seen for daytime BPs. Proportions of hypertensives in each of the three genotype groups were C/C 34.7%, C/G 37.9%, G/G 42.4% yielding an odds ratio for hypertension per G allele of 1.19 (95% confidence interval 1.00-1.41; P=0.05). In conclusion, the rs5335 (C+70G) polymorphism of the EDNRA gene has small effects on the risk of hypertension. Natural variation in other genes in the endothelin-signalling pathway should be explored to identify additional influences on BP regulation.

  3. SEASONAL MORTALITY PATTERNS IN NON-HUMAN PRIMATES: IMPLICATIONS FOR VARIATION IN SELECTION PRESSURES ACROSS ENVIRONMENTS

    PubMed Central

    Gogarten, Jan F.; Brown, Leone M.; Chapman, Colin A.; Cords, Marina; Doran-Sheehy, Diane; Fedigan, Linda M.; Grine, Frederick E.; Perry, Susan; Pusey, Anne E.; Sterck, Elisabeth H. M.; Wich, Serge A.; Wright, Patricia C.

    2014-01-01

    Examining seasonal mortality patterns can yield insights into the drivers of mortality and thus potential selection pressures acting on individuals in different environments. We compiled adult and juvenile mortality data from nine wild non-human primate taxa to investigate the role of seasonality in patterns of mortality and address the following questions: Is mortality highly seasonal across species? Does greater environmental seasonality lead to more seasonal mortality patterns? If mortality is seasonal, is it higher during wet seasons or during periods of food scarcity? and Do folivores show less seasonal mortality than frugivores? We found seasonal mortality patterns in five of nine taxa, and mortality was more often tied to wet seasons than food-scarce periods, a relationship that may be driven by disease. Controlling for phylogeny, we found a positive relationship between the degree of environmental seasonality and mortality, with folivores exhibiting more seasonal mortality than frugivores. These results suggest that mortality patterns are influenced both by diet and degree of environmental seasonality. Applied to a wider array of taxa, analyses of seasonal mortality patterns may aid understanding of life-history evolution and selection pressures acting across a broad spectrum of environments and spatial and temporal scales. PMID:23025613

  4. Seasonal mortality patterns in non-human primates: implications for variation in selection pressures across environments.

    PubMed

    Gogarten, Jan F; Brown, Leone M; Chapman, Colin A; Cords, Marina; Doran-Sheehy, Diane; Fedigan, Linda M; Grine, Frederick E; Perry, Susan; Pusey, Anne E; Sterck, Elisabeth H M; Wich, Serge A; Wright, Patricia C

    2012-10-01

    Examining seasonal mortality patterns can yield insights into the drivers of mortality and thus potential selection pressures acting on individuals in different environments. We compiled adult and juvenile mortality data from nine wild non-human primate taxa to investigate the role of seasonality in patterns of mortality and address the following questions: Is mortality highly seasonal across species? Does greater environmental seasonality lead to more seasonal mortality patterns? If mortality is seasonal, is it higher during wet seasons or during periods of food scarcity? and Do folivores show less seasonal mortality than frugivores? We found seasonal mortality patterns in five of nine taxa, and mortality was more often tied to wet seasons than food-scarce periods, a relationship that may be driven by disease. Controlling for phylogeny, we found a positive relationship between the degree of environmental seasonality and mortality, with folivores exhibiting more seasonal mortality than frugivores. These results suggest that mortality patterns are influenced both by diet and degree of environmental seasonality. Applied to a wider array of taxa, analyses of seasonal mortality patterns may aid understanding of life-history evolution and selection pressures acting across a broad spectrum of environments and spatial and temporal scales.

  5. Solar wind dynamic pressure variations and possible ground signatures of flux transfer events

    NASA Technical Reports Server (NTRS)

    Sibeck, D. G.; Croley, D. J., Jr.

    1991-01-01

    The effects of a series of solar wind dynamic pressure pulses are followed through the solar wind, across the bow shock and magnetosheath, into the magnetosphere, and down to the dayside ionosphere. Each pressure pulse had an intrinsic solar wind origin, i.e., was not generated by processes occurring at the earth's bow shock. Both upstream and downstream of the earth's bow shock, the pulses were identified by depressed magnetic field strengths and enhanced plasma densities. The pulses compressed the magnetosheath and magnetosphere, causing satellites in the magnetosphere to briefly observe enhanced magnetic field strengths, and/or enter the low-latitude boundary layer or magnetosheath. Satellites already in the magnetosheath observed a brief burst of enhanced magnetosheath flow caused by the relative inward motion of magnetosheath flow patterns. Alfven and fast mode compressional waves propagated rapidly down to the polar ionosphere, where they produced transient ionospheric flows at latitudes equatorward of the convection reversal boundary. The flow patterns moved westward around the auroral oval.

  6. Effects of mental workload and caffeine on catecholamines and blood pressure compared to performance variations.

    PubMed

    Papadelis, Christos; Kourtidou-Papadeli, Chrysoula; Vlachogiannis, Emmanouil; Skepastianos, Petros; Bamidis, Panayiotis; Maglaveras, Nikos; Pappas, Kostantinos

    2003-02-01

    Caffeine is characterised as a central nervous system stimulant, also affecting metabolic and cardiovascular functions. A number of studies have demonstrated an effect of caffeine on the excretion of catecholamines and their metabolites. Urinary epinephrine and norepinephrine have been shown to increase after caffeine administration. Similar trends were observed in our study in adrenaline (ADR) and noradrenaline (NORADR) levels and additionally a dose dependent effect of caffeine. The effect of caffeine on cognitive performance, blood pressure, and catecholamines was tested under resting conditions and under mental workload. Each subject performed the test after oral administration of 1 cup and then 3 cups of coffee. Root mean square error (RMSE) for the tracking task was continuously monitored. Blood pressure was also recorded before and after each stage of the experiment. Catecholamines were collected and measured for three different conditions as: at rest, after mental stress alone, after one dose of caffeine under stress, and after triple dose of caffeine under stress. Comparison of the performance of each stage with the resting conditions revealed statistically significant differences between group of smokers/coffee drinkers compared with the other two groups of non-coffee drinkers/non-smokers and non-smokers/coffee drinkers. There was no statistically significant difference between the last two groups. There was an increase of urine adrenaline with 1 cup of coffee and statistically significant increase of urine noradrenaline. Both catecholamines were significantly increased with triple dose of caffeine. Mental workload increased catecholamines. There was a dose dependent effect of caffeine on catecholamines.

  7. SIRT1 Polymorphisms Associate with Seasonal Weight Variation, Depressive Disorders, and Diastolic Blood Pressure in the General Population.

    PubMed

    Kovanen, Leena; Donner, Kati; Partonen, Timo

    2015-01-01

    SIRT1 polymorphisms have previously been associated with depressive and anxiety disorders. We aimed at confirming these earlier findings and extending the analyses to seasonal variations in mood and behavior. Three tag single-nucleotide polymorphisms (SNPs) were selected to capture the common variation in the SIRT1 gene. 5910 individuals (with blood sample, diagnostic interview, self-report of on seasonal changes in mood and behavior) were selected from a representative Finnish nationwide population-based sample. Logistic and linear regression models were used to analyze the associations between the SNPs and depressive and anxiety disorders, metabolic syndrome (EGIR criteria) and its components, and health examination measurements, Homeostasis Model Assessments, and diagnoses of type 2 and type 1 diabetes. SIRT1 rs2273773 showed evidence of association with seasonal variation in weight (C-allele, OR = 0.85, 95% CI = 0.76-0.95, p = 0.005). In addition, our study gave further support for the association of SIRT1 gene with depressive disorders (rs3758391) and diastolic blood pressure (rs2273773).

  8. SIRT1 Polymorphisms Associate with Seasonal Weight Variation, Depressive Disorders, and Diastolic Blood Pressure in the General Population

    PubMed Central

    Kovanen, Leena; Donner, Kati; Partonen, Timo

    2015-01-01

    SIRT1 polymorphisms have previously been associated with depressive and anxiety disorders. We aimed at confirming these earlier findings and extending the analyses to seasonal variations in mood and behavior. Three tag single-nucleotide polymorphisms (SNPs) were selected to capture the common variation in the SIRT1 gene. 5910 individuals (with blood sample, diagnostic interview, self-report of on seasonal changes in mood and behavior) were selected from a representative Finnish nationwide population-based sample. Logistic and linear regression models were used to analyze the associations between the SNPs and depressive and anxiety disorders, metabolic syndrome (EGIR criteria) and its components, and health examination measurements, Homeostasis Model Assessments, and diagnoses of type 2 and type 1 diabetes. SIRT1 rs2273773 showed evidence of association with seasonal variation in weight (C-allele, OR = 0.85, 95% CI = 0.76–0.95, p = 0.005). In addition, our study gave further support for the association of SIRT1 gene with depressive disorders (rs3758391) and diastolic blood pressure (rs2273773). PMID:26509718

  9. Identification of the characteristics of motorcycle and scooter tyres in the presence of large variations in inflation pressure

    NASA Astrophysics Data System (ADS)

    Cossalter, V.; Doria, A.; Giolo, E.; Taraborrelli, L.; Massaro, M.

    2014-10-01

    Stability and safety of road vehicles are largely affected by tyre properties. Single-track vehicles are characterised by weakly damped modes of vibration (weave and wobble) and therefore this phenomenon is even more important. This article focuses on the study of both steady-state and transient properties of motorcycle and scooter tyres in the presence of very low and very high inflation pressures. The steady-state properties are defined as lateral forces (side-slip and camber forces) and yaw torques (self-aligning and twisting). The transient properties are described in terms of relaxation length, which represents the distance needed to reach a certain percentage of the steady-state value of the tyre force. Experimental tests are carried out on a specific rotating disk machine. Three sets of tyres are analysed. Steady-state properties are measured by increasing step by step the values of camber and side-slip angles. Transient properties are studied carrying out tests with harmonic side-slip excitation and measuring the phase lag between the excitation (input) and the tyre force (output). Experimental results show important variations in tyre properties with inflation pressure with general trends of all the tested tyres and particular features related to the tyre's geometry. After the analysis and discussion of experimental results, the measured data are fitted by means of a specific version of the Magic Formula. The dependence of the Magic Formula's coefficients on inflation pressure is analysed and interpolation curves are given.

  10. Singular Currents Near Magnetic Islands in MHD Equilibria: Effects of Pressure Variation Within Flux Surfaces and of Symmetry

    NASA Astrophysics Data System (ADS)

    Reiman, Allan

    2016-10-01

    We present an analytic calculation of the MHD equilibrium current near a magnetic island that includes the effect of the pressure variation on the flux surfaces in that region. The current has logarithmic singularities at the X-lines of magnetic islands in non-stellarator-symmetric equilibria. The singular components vanish in stellarator-symmetric MHD equilibria. (Equilibria invariant under combined reflection in the poloidal and toroidal angles. Tokamaks with balanced double-null divertors are stellarator symmetric, but single-null tokamaks are not.) These equilibrium solutions are to be contrasted with equilibria having B . ∇p = 0 , where the singular components of the pressure-driven currents vanish regardless of the symmetry. They are also to be contrasted with 3D MHD equilibrium solutions that have simply nested flux surfaces, where the pressure-driven current goes like 1 / x near rational surfaces, where x is the distance from the rational surface. (Except in the case of quasi-symmetric flux surfaces.) We work with a closed subset of the MHD equilibrium equations that involves only perpendicular force balance, and is decoupled from parallel force balance. It is not correct to use the parallel component of the conventional MHD force balance equation, B . ∇p = 0 , near magnetic islands. DOE contract DEAC02-76CH03073.

  11. Intrathoracic pressure variations in an anthropomorphic dummy exposed to air blast, blunt impact, and missiles.

    PubMed

    Jönsson, A; Arvebo, E; Schantz, B

    1988-01-01

    Experiments with an anthropomorphic dummy for blast research demonstrated that pressures recorded in the lung model of the dummy could be correlated to primary air blast effects on the lungs of experimental animals. The results presented here were obtained with a dummy of the type mentioned above, but with the lung model modified to improve geometric similarity to man. Blast experiments were performed in a shock tube, and impact experiments in a special impact machine. Experiments with nonpenetrating missiles were performed with small-caliber firearms and the dummy protected by body armor. Severity indices derived from the blast experiments were related to established criteria for primary lung injury in man. Impacts delivered in the impact machine and by nonpenetrating missiles are compared. Relationships between severity of impact based on experiments with animals and primary lung injury in man are discussed.

  12. Some aspects of the interannual variation of mean monthly sea level pressure on the Southern Hemisphere

    NASA Technical Reports Server (NTRS)

    Mo, K. C.; Van Loon, H.

    1984-01-01

    We calculate the seasonal changes that are largely associated with the half-yearly wave, autocorrelation functions, and the mean planetary waves in the monthly mean sea level pressure from two data sources. One covers the period from 1951 to 1958 (from the South African Weather Bureau) and the other the period from 1972 to 1980 (from the Australian Bureau of Meteorology). Thirty years of data from stations over the southern hemisphere are used to assess the reliability of the differences between the two periods that the grid-point data show. These differences are especially large over the Atlantic Ocean and the Pacific Ocean. The station data confirm the changes between the two periods and thus the observed differences in the mean waves, which are especially large for wave number 3.

  13. Variation in genes that regulate blood pressure are associated with glomerular filtration rate in Chinese.

    PubMed

    Montasser, May E; Shimmin, Lawrence C; Gu, Dongfeng; Chen, Jing; Gu, Charles; Kelly, Tanika N; Jaquish, Cashell E; Rice, Treva K; Rao, Dabeeru C; Cao, Jie; Chen, Jichun; De-PeLiu; Whelton, Paul K; Hamm, Lotuce Lee; He, Jiang; Hixson, James E

    2014-01-01

    Chronic kidney disease (CKD) can be a consequence of diabetes, hypertension, immunologic disorders, and other exposures, as well as genetic factors that are still largely unknown. Glomerular filtration rate (GFR), which is widely used to measure kidney function, has a heritability ranging from 25% to 75%, but only 1.5% of this heritability is explained by genetic loci that have been identified to date. In this study we tested for associations between GFR and 234 SNPs in 26 genes from pathways of blood pressure regulation in 3,025 rural Chinese participants of the "Genetic Epidemiology Network of Salt Sensitivity" (GenSalt) study. We estimated GFR (eGFR) using baseline serum creatinine measurements obtained prior to dietary intervention. We identified significant associations between eGFR and 12 SNPs in 6 genes (ACE, ADD1, AGT, GRK4, HSD11B1, and SCNN1G). The cumulative effect of the protective alleles was an increase in mean eGFR of 4 mL/min per 1.73 m2, while the cumulative effect of the risk alleles was a decrease in mean eGFR of 3 mL/min per 1.73 m2. In addition, we identified a significant interaction between SNPs in CYP11B1 and ADRB2. We have identified common variants in genes from pathways that regulate blood pressure and influence kidney function as measured by eGFR, providing new insights into the genetic determinants of kidney function. Complex genetic effects on kidney function likely involve interactions among genes as we observed for CYP11B1 and ADRB2.

  14. Variations of blood pressure in stroke unit patients may result from alternating body positions.

    PubMed

    Aries, Marcel J H; Elting, Jan Willem; Stewart, Roy E; de Keyser, Jacques; Thien, Theo; Kremer, Berry P; Vroomen, Patrick C A J

    2012-08-01

    Blood pressure (BP) is one of the major vital parameters monitored in the stroke unit. The accuracy of indirect BP measurement is strongly influenced by the position of both patient and arm during the measurement. Acute stroke patients are often nursed in lateral decubitus positions. The effect of these alternating body positions in relation to affected body side on the outcome and reliability of BP readings in acute stroke patients is unknown. An automatic oscillometric BP device was used. BP was measured in both arms in the (back) supine and both lateral decubitus positions. In total, 54 consecutive acute stroke patients were included. Thirty-five patients had right-sided deficits and 19 patients had left-sided deficits. Supine BP readings were similar in the right and left arms regardless of side of deficit. Measurements of BP in the lateral decubitus positions resulted in significantly lower BP readings in the uppermost arm (around 12 mm Hg in both arms) and significantly higher readings in the right lowermost arm (around 6 mm Hg) compared to the supine position. This effect seemed less pronounced when the left lowermost arm was measured. There was no relation between change of BP readings in various lateral positions and side of stroke. Alternating lateral decubitus positions according to nursing standards in acute stroke patients lead to a mean 18 mm Hg BP fluctuation. This may largely be explained by hydrostatic pressure effects, partly by anatomic factors in the left lowermost arm, but not by the side of stroke. Copyright © 2012 National Stroke Association. Published by Elsevier Inc. All rights reserved.

  15. Ontogenetic Variation of Four Cytokinins in Soybean Root Pressure Exudate 1

    PubMed Central

    Heindl, Josephine C.; Carlson, Dale R.; Brun, William A.; Brenner, Mark L.

    1982-01-01

    Cytokinins exported from the root may be involved in the correlative control of plant development. To test this hypothesis in soybean ((Glycine max [L.] Merr. cv. McCall, cv Chippewa 64, and cv Hodgson 78), cytokinins were intercepted en route from the root to the shoot by collecting root pressure exudate from detopped roots. The quantities of four cytokinins in the exudate were studied throughout the development of plants grown in the field and in controlled environment chambers. Zeatin, zeatin riboside, and their dihydro derivatives, dihydrozeatin and dihydrozeatin riboside, were isolated and quantitated using high-performance liquid chromatography. Cytokinin fluxes (pmoles per plant per hour) were independent of exudate flux (grams per plant per hour). All fluxes are averages for a 6- or 8-h collection period. The ribosides accounted for the majority of the observed cytokinin transport. The fluxes of zeatin riboside and dihydrozeatin riboside increased from low levels during vegetative growth to maxima during late flowering or early pod formation. Before the seeds began rapid dry matter accumulation, zeatin riboside and dihydrozeatin riboside fluxes decreased and remained at low levels through maturation. The fluxes of zeatin and dihydrozeatin were low throughout development. No correlation was found between cytokinin fluxes and nodule dry weight or specific nodule activity (acetylene reduction). The timing of distinct peaks in zeatin riboside and dihydrozeatin riboside fluxes during flowering or pod formation suggests that cytokinins exported from the root may function in the regulation of reproductive growth in soybean. PMID:16662731

  16. Upper Airway Variation and Frequent Alcohol Consumption Can Affect Compliance With Continuous Positive Airway Pressure

    PubMed Central

    Jeong, Jong In; Kim, Hyo Yeol; Hong, Sang Duk; Ryu, Gwanghui; Kim, Su Jin; Lee, Kyung Eun; Dhong, Hun-Jong; Chung, Seung-Kyu

    2016-01-01

    Objectives Compliance with continuous positive airway pressure (CPAP) treatment remains a primary concern for improving treatment outcomes of obstructive sleep apnea. There are few studies that have considered the role of upper airway anatomy on the compliance with CPAP. We hypothesized that upper airway anatomy would influence the compliance with CPAP. Methods One hundred out of 161 consecutive patients were enrolled in this study. The following possible determinants were tested against CPAP use: demographic and anthropometric data, minimal cross-sectional area on acoustic rhinometry, cephalometric and polysomnographic data, questionnaires of Epworth sleepiness scale and Beck depression index, and histories of previous upper airway surgery, degree of nasal obstruction, daily cigarette consumption, and weekly frequency of alcohol intake. Results Univariate analysis showed that histories of previous upper airway surgery and less frequent alcohol consumption, and longer mandibular plane-hyoid length (MP-H) on cephalometry were associated with longer average daily CPAP use. After adjustment for the confounding factors with multiple linear regression analysis, alcohol consumption and MP-H were still associated with the compliance with CPAP significantly. Conclusion To improve compliance with CPAP, careful evaluations of upper airway problems and life style are important before initiating CPAP. PMID:27334512

  17. Diurnal variations of cardiac rhythm, arterial pressure, and urinary catecholamines in borderline and established essential hypertension.

    PubMed

    Messerli, F H; Glade, L B; Ventura, H O; Dreslinski, G R; Suarez, D H; MacPhee, A A; Aristimuno, G G; Cole, F E; Frohlich, E D

    1982-07-01

    Ambulatory continuous ECG and arterial pressure (BP) were recorded simultaneously (Delmar Avionics Pressurometer II) for 24 hours in 13 age-matched normotensive subjects, 11 patients with borderline hypertension (HBP), and in 10 patients with uncomplicated established essential HBP. Urinary concentrations of epinephrine, norepinephrine, and dopamine were simultaneously collected over four successive 4-hour periods and one 8-hour period. Prevalence and total number of ventricular and supraventricular ectopic beats was low and not affected by arterial BP. Twenty-four-hour rate (HR) and 4-hourly excretion of epinephrine, norepinephrine, and dopamine were comparable between normotensive and HBP persons and no correlation between urinary catecholamines and arterial BP (systolic, diastolic, or mean), HR, or prevalence of ectopic beats was found in any of the three groups or in the total study population. We conclude that HBP patients without ECG evidence of left ventricular hypertrophy do not have a higher prevalence of supraventricular or ventricular ectopic beats. Urinary catecholamines are not related to circadian fluctuations or variability in arterial BP, HR, or prevalence of ectopic beats.

  18. Intraocular pressure variation associated with body length in young American alligators (Alligator mississippiensis).

    PubMed

    Whittaker, C J; Heaton-Jones, T G; Kubilis, P S; Smith, P J; Brooks, D E; Kosarek, C; Mackay, E O; Gelatt, K N

    1995-10-01

    Using an applanation tonometer, 5 replicate intraocular pressure (IOP) measurements were obtained from each eye of 12 young clinically normal, American alligators. Alligator length ranged from 46 to 117 cm, measured from snout to tail tip. All IOP were recorded by a single observer at an ambient temperature of approximately 25 C, and ranged from 5 to 35 mm of Hg. Observer reliability was excellent (intraclass r = 0.93), and IOP did not change over the ordered sequence of 5 replicate measurements/eye. Replicate IOP) measurements were, therefore, averaged in each eye for comparison between eyes of the same alligator. Left and right eve IOP were highly correlated within individual alligators (r = 0.92), whereas the mean within animal difference between left and right eye IOP was not statistically significant (95% confidence interval [CI] for the left eye-right eye mean difference, - 1.9 to 1.3 min of Hg). Mean IOP determined for 5 confirmed females and 3 confirmed males did not differ significantly between the sexes (95% CI for the male-female difference in means, -2.1 to 3.7 mm of Hg). Mean +/- SEM IOP of 23.7 + 2.1 mm of Hg determined for 4 alligators < -50 cm long was significantly (P = 0.009) greater than mean IOP of 11.6 + 0.5 mm of Hg determined for 8 alligators > 50 cm long (95% CI for the difference in means, 8.5 to 15.7 mm of Hg). In young alligators, the relation between body length and IOP appears to be nonlinear, possibly with a negative exponent.

  19. Study of Variation in Intraocular Pressure Spike (IOP) Following Nd- YAG Laser Capsulotomy

    PubMed Central

    Sridhar, Sriya

    2016-01-01

    Introduction Posterior Capsular Opacifications (PCO) is a frequent complication of cataract surgery following posterior chamber intraocular lens implantation. Nd –Yag laser capsulotomy is the treatment of choice for PCO and is known to be associated with complications like Raised Intraocular Pressure (IOP), Intraocular lens pitting, intraocular lens cracks, cystoid macular oedema, retinal detachment, corneal burns. Raised IOP is the most common complication and prescribing anti-glaucoma drugs post capsulotomy is a common practise. Our study helps us to anticipate the post procedural IOP rise in specific patients and treat only selected group of patients with anti- glaucoma medications. Aim To study and correlate the effect of energy used and number of shots with post procedural IOP spike following Nd-YAG laser capsulotomy cases. Materials and Methods All patients with PCO presenting to Ophthalmology Out Patient Department at Sri Siddhartha Medical College between November 2014 to November 2015 were included. All the patients with glaucoma, uveitis and high myopia were excluded from the study. Data relevant to history, ocular examination and IOP were recorded. Results Significant correlation of IOP spike with the number of Nd- YAG Laser shots delivered was found by One-way ANOVA Post-Hoc Tukeys Test. The p-value was significant for shots more than 40, provided the energy was restricted to 20 mJ and below. Correlation of energy with IOP spike was not significant as found by One-way ANOVA, Post-Hoc Tukey test. Predictability of 2 hours post-procedure IOP regarding persistent IOP rise was significant. Conclusion It was observed that all pseudophakic patients may not require anti-glaucoma medication pre, or post Nd YAG laser capsulotomy. Only patients who required more than 40 shots during the procedure would need a close observation and if persistent rise is documented, ocular hypotensives may be advised. PMID:28208899

  20. Pulsed resources and climate-induced variation in the reproductive traits of wild boar under high hunting pressure.

    PubMed

    Sabrina, Servanty; Jean-Michel, Gaillard; Carole, Toïgo; Serge, Brandt; Eric, Baubet

    2009-11-01

    1. Identifying which factors influence age and size at maturity is crucial for a better understanding of the evolution of life-history strategies. In particular, populations intensively harvested, hunted or fished by humans often respond by displaying earlier age and decreased size at first reproduction. 2. Among ungulates wild boar (Sus scrofa scrofa L.) exhibit uncommon life-history traits, such as high fertility and early reproduction, which might increase the demographic impact of varying age at first reproduction. We analysed variation in female reproductive output from a 22-year long study of an intensively hunted population. We assessed how the breeding probability and the onset of oestrus responded to changes of female body mass at different ages under varying conditions of climate and food availability. 3. Wild boar females had to reach a threshold body mass (27-33 kg) before breeding for the first time. This threshold mass was relatively low (33-41% of adult body mass) compared to that reported in most other ungulates (about 80%). 4. Proportions of females breeding peaked when rainfall and temperature were low in spring and high in summer. Climatic conditions might act through the nutritional condition of females. The onset of oestrus varied a lot in relation to resources available at both current and previous years. Between none and up to 90% of females were in oestrus in November depending on the year. 5. Past and current resources accounted for equivalent amount of observed variations in proportions of females breeding. Thus, wild boar rank at an intermediate position along the capital-income continuum rather than close to the capital end where similar-sized ungulates rank. 6. Juvenile females made a major contribution to the yearly reproductive output. Comparisons among wild boar populations facing contrasted hunting pressures indicate that a high demographic contribution of juveniles is a likely consequence of a high hunting pressure rather than a

  1. Spatial Variation of Pressure in the Lyophilization Product Chamber Part 2: Experimental Measurements and Implications for Scale-up and Batch Uniformity.

    PubMed

    Sane, Pooja; Varma, Nikhil; Ganguly, Arnab; Pikal, Michael; Alexeenko, Alina; Bogner, Robin H

    2017-02-01

    Product temperature during the primary drying step of freeze-drying is controlled by a set point chamber pressure and shelf temperature. However, recent computational modeling suggests a possible variation in local chamber pressure. The current work presents an experimental verification of the local chamber pressure gradients in a lab-scale freeze-dryer. Pressure differences between the center and the edges of a lab-scale freeze-dryer shelf were measured as a function of sublimation flux and clearance between the sublimation front and the shelf above. A modest 3-mTorr difference in pressure was observed as the sublimation flux was doubled from 0.5 to 1.0 kg·h(-1)·m(-2) at a clearance of 2.6 cm. Further, at a constant sublimation flux of 1.0 kg·h(-1)·m(-2), an 8-fold increase in the pressure drop was observed across the shelf as the clearance was decreased from 4 to 1.6 cm. Scale-up of the pressure variation from lab- to a manufacturing-scale freeze-dryer predicted an increased uniformity in drying rates across the batch for two frequently used pharmaceutical excipients (mannitol and sucrose at 5% w/w). However, at an atypical condition of shelf temperature of +10°C and chamber pressure of 50 mTorr, the product temperature in the center vials was calculated to be a degree higher than the edge vial for a low resistance product, thus reversing the typical edge and center vial behavior. Thus, the effect of local pressure variation is more significant at the manufacturing-scale than at a lab-scale and accounting for the contribution of variations in the local chamber pressures can improve success in scale-up.

  2. Seasonal Variation in Blood Pressure in 162,135 Patients With Type 1 or Type 2 Diabetes Mellitus.

    PubMed

    Hermann, Julia M; Rosenbauer, Joachim; Dost, Axel; Steigleder-Schweiger, Claudia; Kiess, Wieland; Schöfl, Christof; Holl, Reinhard W

    2016-04-01

    Seasonal variation in blood pressure (BP) has been observed in different populations. However, only few studies have focused on BP seasonality in diabetic patients. This study examined the seasonal patterns in BP in 62,589 patients with type 1 diabetes mellitus (T1DM) and in 99,546 patients with type 2 diabetes mellitus (T2DM) from the German/Austrian Diabetes Follow-up Registry. Adjusted mean BP values revealed seasonal cycles of 12 months, with higher BP in colder months. Using harmonic regression models, the estimated systolic BP difference throughout the year was 2.28/2.48 mm Hg in T1DM/T2DM (both P<.001). Interestingly, seasonal variation in diastolic BP was larger in T1DM than in T2DM (1.24/0.64 mm Hg, P<.001). A sex difference was observed in T1DM only, while age differences occurred in both types of diabetes. Correlations between BP and potentially related factors such as outdoor temperature indicated that reasons underlying BP seasonality are likely to be complex and vary by subgroup.

  3. Influence of Different Patellofemoral Design Variations Based on Genesis II Total Knee Endoprosthesis on Patellofemoral Pressure and Kinematics

    PubMed Central

    Lange, Barbara; Herzog, Yvonne; Schnauffer, Peter; Leichtle, Carmen I.; Wülker, Nikolaus

    2017-01-01

    In total knee arthroplasty (TKA), patellofemoral groove design varies greatly and likely has a distinct influence on patellofemoral biomechanics. To analyse the selective influence, five patellofemoral design variations were developed based on Genesis II total knee endoprosthesis (original design, being completely flat, being laterally elevated, being medially elevated, and both sides elevated) and made from polyamide using rapid prototyping. Muscle-loaded knee flexion was simulated on 10 human knee specimens using a custom-made knee simulator, measuring the patellofemoral pressure distribution and tibiofemoral and patellofemoral kinematics. The measurements were carried out in the native knee as well as after TKA with the 5 design prototypes. The overall influence of the different designs on the patellofemoral kinematics was small, but we found detectable effects for mediolateral tilt (p < 0.05 for 35°–80° flexion) and translation of the patella (p < 0.045 for 20°–65° and 75°–90°), especially for the completely flat design. Considering patellofemoral pressures, major interindividual differences were seen between the designs, which, on average, largely cancelled each other out. These results suggest that the elevation of the lateral margin of the patellofemoral groove is essential for providing mediolateral guidance, but smooth contouring as with original Genesis II design seems to be sufficient. The pronounced interindividual differences identify a need for more patellofemoral design options in TKA. PMID:28255225

  4. Influence of Different Patellofemoral Design Variations Based on Genesis II Total Knee Endoprosthesis on Patellofemoral Pressure and Kinematics.

    PubMed

    Leichtle, Ulf G; Lange, Barbara; Herzog, Yvonne; Schnauffer, Peter; Leichtle, Carmen I; Wülker, Nikolaus; Lorenz, Andrea

    2017-01-01

    In total knee arthroplasty (TKA), patellofemoral groove design varies greatly and likely has a distinct influence on patellofemoral biomechanics. To analyse the selective influence, five patellofemoral design variations were developed based on Genesis II total knee endoprosthesis (original design, being completely flat, being laterally elevated, being medially elevated, and both sides elevated) and made from polyamide using rapid prototyping. Muscle-loaded knee flexion was simulated on 10 human knee specimens using a custom-made knee simulator, measuring the patellofemoral pressure distribution and tibiofemoral and patellofemoral kinematics. The measurements were carried out in the native knee as well as after TKA with the 5 design prototypes. The overall influence of the different designs on the patellofemoral kinematics was small, but we found detectable effects for mediolateral tilt (p < 0.05 for 35°-80° flexion) and translation of the patella (p < 0.045 for 20°-65° and 75°-90°), especially for the completely flat design. Considering patellofemoral pressures, major interindividual differences were seen between the designs, which, on average, largely cancelled each other out. These results suggest that the elevation of the lateral margin of the patellofemoral groove is essential for providing mediolateral guidance, but smooth contouring as with original Genesis II design seems to be sufficient. The pronounced interindividual differences identify a need for more patellofemoral design options in TKA.

  5. Changes of blood pressure, sodium excretion and sodium balance due to variations of the renin-angiotensin-aldosterone system.

    PubMed

    Reinhardt, H W; Seeliger, E; Lohmann, K; Corea, M; Boemke, W

    1996-03-07

    Studies were performed in partly free moving Beagle dogs, kept under standardized environmental and dietetic conditions (food intake: once daily at 8:30 a.m., 5.5 mmol Na/kg body weight per 24 h). The dogs were chronically instrumented with an inflatable cuff around the aorta above the renal arteries, two aortic catheters above and below the cuff, and a bladder catheter. Three protocols were performed in 7 dogs each: (i) urine collection in 20-min intervals and measurement of Na excretion, continuous registration of mean arterial blood pressure (MABP) and heart rate for 4 consecutive days. (ii) As (i), but additional servocontrolled reduction of the renal perfusion pressure (rRPP) to stimulate renin secretion and the formation of angiotensin II and aldosterone. (iii) As (ii), but additional constant infusion of the angiotensin converting enzyme inhibitor Captopril. Despite rRPP Na is only transiently retained (pressure escape). MABP level is elevated, as long as total-body Na is augmented. In protocol iii no Na retention occurs, indicating that rRPP per se causes no Na retention. MABP level remained unchanged. Independent of the preset MABP level similar diurnal variation in MABP are present in all protocols. During control days major amounts of Na are excreted postprandially. Up to 5:00 p.m. 65% of the daily Na intake is excreted. After disturbance of Na control (protocols ii and iii) the Na excretion is shifted to the evening and night. Probably due to this shift Na retention can be prevented. Furthermore, these results demonstrate that rRPP-induced increases of total body Na and MABP are solely mediated by the activation of the renin-angiotensin-aldosterone system.

  6. The coefficient variation of home blood pressure is a novel factor associated with macroalbuminuria in type 2 diabetes mellitus.

    PubMed

    Ushigome, Emi; Fukui, Michiaki; Hamaguchi, Masahide; Senmaru, Takafumi; Sakabe, Kazumi; Tanaka, Muhei; Yamazaki, Masahiro; Hasegawa, Goji; Nakamura, Naoto

    2011-12-01

    The purpose of this study was to investigate the association between day-by-day variability in home blood pressure (HBP) on 14 consecutive days and macroalbuminuria in patients with type 2 diabetes. We compared the coefficient of variation (CV) of HBP in 858 Japanese patients with and without macroalbuminuria. Next, we analyzed the relationship between the logarithm of urinary albumin excretion (UAE) and the CV of HBP using linear regression analysis. Then, we evaluated the association between the CV of HBP and macroalbuminuria, defined as UAE ≥300 mg g(-1) creatinine, using logistic regression analysis. The CVs of morning and evening systolic blood pressure (SBP) were significantly greater in patients with macroalbuminuria than in those without (8.08±3.35 vs. 7.19±2.25%, P<0.05 and 9.01±3.58 vs. 7.98±2.57%, P<0.05, respectively). Multivariate linear regression analyses indicated that the CVs of morning SBP (P<0.05) and diastolic blood pressure (DBP; P<0.05), and those of evening SBP (P<0.05) were the independent explanatory variables for the logarithm of UAE. Multivariate logistic regression analyses also demonstrated that the odds ratio for the CVs of morning SBP, morning DBP and evening SBP for macroalbuminuria were 1.35 (P<0.05), 1.29 (P<0.05) and 1.44 (P<0.05), respectively. We conclude that the CV of HBP is correlated with macroalbuminuria, independent of the known risk factors, in Japanese patients with type 2 diabetes.

  7. Single-shot temperature- and pressure-sensitive paint measurements on an unsteady helicopter blade

    NASA Astrophysics Data System (ADS)

    Disotell, Kevin J.; Peng, Di; Juliano, Thomas J.; Gregory, James W.; Crafton, Jim W.; Komerath, Narayanan M.

    2014-02-01

    Unsteady pressure-sensitive paint (PSP) measurements were acquired on an articulated model helicopter rotor of 0.26 m diameter in edgewise flow to simulate forward flight conditions. The rotor was operated at advance ratios (free stream velocity normalized by hover tip speed) of 0.15 and 0.30 at a cycle-averaged tip chord Reynolds number of 1.1 × 105, with collective and longitudinal cyclic pitch inputs of 10° and 2.5°, respectively. A single-shot data acquisition technique allowed a camera to record the paint luminescence after a single pulse of high-energy laser excitation, yielding sufficient signal-to-noise ratio to avoid image averaging. Platinum tetra(pentafluorophenyl) porphyrin (PtTFPP) in a porous polymer/ceramic binder served as the PSP. To address errors caused by image blurring and temperature sensitivity, a previously reported motion deblurring algorithm was implemented and the temperature correction was made using temperature-sensitive paint measurements on a second rotor blade. Instantaneous, unsteady surface pressure maps at a rotation rate of 82 Hz captured different aerodynamic responses between the two sides of the rotor disk and were compared to the nominally steady hover case. Cycle-to-cycle variations in tip unsteadiness on the retreating blade were also observed, causing oblique pressure features which may be linked to three-dimensional stall.

  8. The added value of cardiac index and pulse pressure variation monitoring to mean arterial pressure-guided volume therapy in moderate-risk abdominal surgery (COGUIDE): a pragmatic multicentre randomised controlled trial.

    PubMed

    Stens, J; Hering, J-P; van der Hoeven, C W P; Boom, A; Traast, H S; Garmers, L E; Loer, S A; Boer, C

    2017-09-01

    There is disagreement regarding the benefits of goal-directed therapy in moderate-risk abdominal surgery. Therefore, we tested the hypothesis that the addition of non-invasive cardiac index and pulse pressure variation monitoring to mean arterial pressure-based goal-directed therapy would reduce the incidence of postoperative complications in patients having moderate-risk abdominal surgery. In this pragmatic multicentre randomised controlled trial, we randomly allocated 244 patients by envelope drawing in a 1:1 fashion, stratified per centre. All patients had mean arterial pressure, cardiac index and pulse pressure variation measured continuously. In one group, healthcare professionals were blinded to cardiac index and pulse pressure variation values and were asked to guide haemodynamic therapy only based on mean arterial pressure (control group). In the second group, cardiac index and pulse pressure variation values were displayed and kept within target ranges following a pre-defined algorithm (CI-PPV group). The primary endpoint was the incidence of postoperative complications within 30 days. One hundred and seventy-five patients were eligible for final analysis. Overall complication rates were similar (42/94 (44.7%) vs. 38/81 (46.9%) in the control and CI-PPV groups, respectively; p = 0.95). The CI-PPV group had lower mean (SD) pulse pressure variation values (9.5 (2.0)% vs. 11.9 (4.6)%; p = 0.003) and higher mean (SD) cardiac indices (2.76 (0.62) l min(-1) .m(-2) vs. 2.53 (0.66) l min(-1) .m(-2) ; p = 0.004) than the control group. In moderate-risk abdominal surgery, we observed no additional value of cardiac index and pulse pressure variation-guided haemodynamic therapy to mean arterial pressure-guided volume therapy with regard to postoperative complications. © 2017 The Association of Anaesthetists of Great Britain and Ireland.

  9. [The specific features of circadian blood pressure variations in patients with hypertensive disease in different types of weather].

    PubMed

    Kulakov, Iu V; Nasonova, E V

    2004-01-01

    The specific features of circadian blood pressure (BP) variations were studied in 162 patients aged 20 to 60 years who had hypertensive disease (HD) in the warm period of a year in different types of weather. In accordance with the type of weather in which daily BP monitoring (DBPM) was performed, the examinees were divided into 2 groups: 1) those examined in droughty (anticyclonic) weather; 2) those examined in moist (cyclonic) weather, The groups were matched by the number (81) of patients, age, gender, duration of the disease, and office BP values. The mean BP during a day, daylight and night hours, the maximum and minimum BP during wake and sleep was significantly high in moist weather. Examining the magnitude of a nocturnal BP decrease indicated that in Group 1, its adequate decrease (the dipper daily curve) was recorded in 72.3% of the patients; inadequate BP decrease (the non-dipper daily curve) was in 24.2%; paradoxical nocturnal hypertension (night peaker) was seen in 1.8%. In Group 2, adequate and inadequate nocturnal BP decreases were observed in 44.4 and 41.3%, respectively; paradoxical nocturnal hypertension was in 7.7%. Statistical processing confirmed the validity of the findings. Moist (cyclonic) weather was ascertained to be marked by the changes in adequate circadian BP variations: a significant mean daily, maximum, and minimum systolic BP (SBP) and diastolic BP (DBP), as well as by the inadequate nocturnal lowering of SBP and DBP, which determines a poor prognosis and may serve as a basis for preventing HD complications in this period of a year.

  10. Different predictivity of fluid responsiveness by pulse pressure variation in children after surgical repair of ventricular septal defect or tetralogy of Fallot.

    PubMed

    Han, Ding; Pan, Shoudong; Wang, Xiaonan; Jia, Qingyan; Luo, Yi; Li, Jia; Ou-Yang, Chuan

    2017-10-01

    Pulse pressure variation derived from the varied pulse contour method is based on heart-lung interaction during mechanical ventilation. It has been shown that pulse pressure variation is predictive of fluid responsiveness in children undergoing surgical repair of ventricular septal defect. Right ventricle compliance and pulmonary vascular capacitance in children with tetralogy of Fallot are underdeveloped as compared to those in ventricular septal defect. We hypothesized that the difference in the right ventricle-pulmonary circulation in the two groups of children would affect the heart-lung interaction and therefore pulse pressure variation predictivity of fluid responsiveness following cardiac surgery. Infants undergoing complete repair of ventricular septal defect (n=38, 1.05±0.75 years) and tetralogy of Fallot (n=36, 1.15±0.68 years) clinically presenting with low cardiac output were enrolled. Fluid infusion with 5% albumin or fresh frozen plasma was administered. Pulse pressure variation was recorded using pressure recording analytical method along with cardiac index before and after fluid infusion. Patients were considered as responders to fluid loading when cardiac index increased ≥15%. Receiver operating characteristic curves analysis was used to assess the accuracy and cutoffs of pulse pressure variation to predict fluid responsiveness. The pulse pressure variation values before and after fluid infusion were lower in tetralogy of Fallot children than those in ventricular septal defect children (15.2±4.4% vs 19.3±4.4%, P<.001; 11.6±3.8 vs 15.4±4.3%, P<.001, respectively). In ventricular septal defect children, 27 were responders and 11 nonresponders. Receiver operating characteristic curve area was 0.89 (95% confidence interval, 0.77-1.01) and cutoff value 17.4% with a sensitivity of 0.89 and a specificity of 0.91. In tetralogy of Fallot children, 26 were responders and 10 were nonresponders. Receiver operating characteristic curve area was 0

  11. Periodic structures and diurnal variation in blood pressure and heart rate in relation to microgravity on space station MIR.

    PubMed

    Shiraishi, M; Kamo, T; Kamegai, M; Baevsky, R M; Funtova, I I; Chernikova, A; Nemoto, S; Hotta, M; Nomura, Y; Suzuki, T

    2004-10-01

    Four Russian crew members were studied on space station MIR, and blood pressure (BP) and heart rate (HR) data were continuously collected. BP and HR data were collected on earth 1 day before orbital flight to the space station, then at weeks 8, 16 and 24 during space flight, and again 1 or 2 days after returning to earth. Time serial data for BP and HR were analyzed by spectral analysis with the MemCalc system (Suwa Trust, Sapporo, Japan). Periodic structures of diurnal variation in systolic blood pressure (SBP), diastolic blood pressure (DBP) and HR were compared at 24-hour, 12-hour and 8-hour intervals, these being determined as the main periodic components for the assessment of BP and HR variability. The 24-h mean levels of SBP and HR during space flight were unchanged. Waking SBP was not different from pre-flight values. During sleep, in-flight changes in HR did not differ from pre-flight values. SBP during sleep in orbit increased to over pre-flight values. Waking DBP was reduced during flight. The SBP and HR phases over a 24-hour cycle were shortened with a more pronounced shortening in weeks 8 and 16 compared with pre-flight values, and at week 24 recovered to preflight values. The 12, 8-hour-cycle remained unchanged, and were similar to pre-flight values. At the space station, the astronauts' mission was carried out under strict control of sleeping and waking hours; therefore, their 24-hour schedule is an artificially constructed situation. Main periodicity structures were maintained by strict control of lifestyle during long-term space flight. The conclusions reached were as follows: 1) SBP levels during sleep in a space environment increased compared with those on earth; 2) the periodicity phase of BP and HR shifted toward to 24-hour cycle as a result of long-term space flight, even though these periods shortened after a few months compared with pre-space flight values.

  12. Seasonal Variations in the CO Line Profile and the Retrieved Thermal/Pressure Structures in the Atmosphere of Mars

    NASA Astrophysics Data System (ADS)

    Khayat, Alain; Villanueva, G. L.; Mumma, M. J.; Riesen, T. E.; Tokunaga, A. T.

    2013-10-01

    We report retrievals of temperature vertical profiles up to 100 km over Tharsis and Syrtis regions on Mars obtained by inverting the strong rotational (3-2) line of carbon monoxide (CO) at 346 GHz. Observations of CO were made from mid Northern Spring to early Northern Summer on Mars (Ls= 36°-108°, 23 Nov, 2011 - 13 May, 2012) using the Caltech Submillimeter Observatory's (CSO) high-resolution heterodyne receiver (Barney) on top of Mauna Kea, Hawai'i. The temperature profiles were derived using our radiative transfer model that considers the latest spectroscopic constants for CO collisionally broadened by CO2. We observe notable changes of the line profile for different dates, which are directly related to seasonal variations in the thermal/pressure structure of the atmosphere. The seasonal variability of the martian CO line profile, the extracted temperature profiles, and comparisons with modeled profiles from the Mars Climate Database (Lewis et al, 1999) will be presented. We gratefully acknowledge support from the NASA Planetary Astronomy Program , NASA Astrobiology Institute, Planetary Atmospheres programs. This material is based upon work at the Caltech Submillimeter Observatory, which is operated by the California Institute of Technology under cooperative agreement with the National Science Foundation, grant number AST-0838261.

  13. A Variational Nodal Approach to 2D/1D Pin Resolved Neutron Transport for Pressurized Water Reactors

    DOE PAGES

    Zhang, Tengfei; Lewis, E. E.; Smith, M. A.; ...

    2017-04-18

    A two-dimensional/one-dimensional (2D/1D) variational nodal approach is presented for pressurized water reactor core calculations without fuel-moderator homogenization. A 2D/1D approximation to the within-group neutron transport equation is derived and converted to an even-parity form. The corresponding nodal functional is presented and discretized to obtain response matrix equations. Within the nodes, finite elements in the x-y plane and orthogonal functions in z are used to approximate the spatial flux distribution. On the radial interfaces, orthogonal polynomials are employed; on the axial interfaces, piecewise constants corresponding to the finite elements eliminate the interface homogenization that has been a challenge for method ofmore » characteristics (MOC)-based 2D/1D approximations. The angular discretization utilizes an even-parity integral method within the nodes, and low-order spherical harmonics (PN) on the axial interfaces. The x-y surfaces are treated with high-order PN combined with quasi-reflected interface conditions. Furthermore, the method is applied to the C5G7 benchmark problems and compared to Monte Carlo reference calculations.« less

  14. Kinetics of the Ar-Hg Plasma of Fluorescent Lamp Discharges. I. Model - Basic Equations - Hg Partial Pressure Variation

    NASA Astrophysics Data System (ADS)

    Winkler, R. B.; Wilhelm, J.; Winkler, R.

    A kinetic description of the dc Hg-Ar mixture plasma of fluorescent lamp discharges is given on the basis of the main microphysical processes and corresponding atomic data. The investigation comprises particle balances for the excited Hg atoms of the triplet 63P0,1,2 and singulet 61P1 state, the balance of the discharge current and an adequate form of the electron Boltzmann equation for such a mixture plasma, the latter including also the various binary collision processes with excited Hg atoms and the Coulomb interaction between the electrons. By simultaneously solving the balances together with the kinetic equation the densities of electrons and excited Hg atoms, the electron energy distribution, the resulting mean energy, mobility and various energy transfer rates of the electrons and the ultraviolet radiation output were determined and in part compared with measured data from the literature. This paper presents and analyses the macroscopic plasma properties mentioned for a wide range of the wall temperature or the corresponding Hg partial pressure variation, where a good agreement of calculated results with experimental data is obtained. In a second paper the change of the macroscopic plasma behaviour due to variation of buffer gas pressure and discharge current will be dealt with.Translated AbstractKinetik des Ar-Hg-Plasmas von Leuchtstofflampenentladungen I. Modell - Grundgleichungen - Hg-PartialdruckvariationDie Arbeit befaßt sich auf der Grundlage der wesentlichen mikrophysikalischen Prozesse und der entsprechenden atomaren Daten mit der kinetischen Beschreibung des de Hg-Ar-Mischplasmas von Leuchtstofflampenentladungen. Die Untersuchung verwendet die Teilchenbilanzen für die angeregten Hg-Atome des Tripletts 63P0,1,2 und des Singuletts 61P1, die Bilanz für den Entladungsstrom und eine adäquate Form der Elektronen-Boltzmann-Gleichung für ein solches Mischplasma, wobei in letzterer auch die verschiedenen Zweierstoßprozesse mit angeregten Hg-Atomen und

  15. Passive leg-raising and end-expiratory occlusion tests perform better than pulse pressure variation in patients with low respiratory system compliance.

    PubMed

    Monnet, Xavier; Bleibtreu, Alexandre; Ferré, Alexis; Dres, Martin; Gharbi, Rim; Richard, Christian; Teboul, Jean-Louis

    2012-01-01

    We tested whether the poor ability of pulse pressure variation to predict fluid responsiveness in cases of acute respiratory distress syndrome was related to low lung compliance. We also tested whether the changes in cardiac index induced by passive leg-raising and by an end-expiratory occlusion test were better than pulse pressure variation at predicting fluid responsiveness in acute respiratory distress syndrome patients. Prospective study. Medical intensive care unit. We included 54 patients with circulatory shock (63 ± 13 yrs; Simplified Acute Physiology Score II, 63 ± 24). Twenty-seven patients had acute respiratory distress syndrome (compliance of the respiratory system, 22 ± 3 mL/cm H2O). In nonacute respiratory distress syndrome patients, the compliance of the respiratory system was 45 ± 9 mL/cm H2O. We measured the response of cardiac index (transpulmonary thermodilution) to fluid administration (500 mL saline). Before fluid administration, we recorded pulse pressure variation and the changes in pulse contour analysis-derived cardiac index induced by passive leg-raising and end-expiratory occlusion. Fluid increased cardiac index ≥ 15% (44% ± 39%) in 30 "responders." Pulse pressure variation was significantly correlated with compliance of the respiratory system (r = .58), but not with tidal volume. The higher the compliance of the respiratory system, the better the prediction of fluid responsiveness by pulse pressure variation. A compliance of the respiratory system of 30 mL/cm H2O was the best cut-off for discriminating patients regarding the ability of pulse pressure variation to predict fluid responsiveness. If compliance of the respiratory system was >30 mL/cm H2O, then the area under the receiver-operating characteristics curve for predicting fluid responsiveness was not different for pulse pressure variation and the passive leg-raising and end-expiratory occlusion tests (0.98 ± 0.03, 0.91 ± 0.06, and 0.97 ± 0.03, respectively). By contrast

  16. Magnitude of long-term non-lithostatic pressure variations in lithospheric processes: insight from thermo-mechanical subduction/collision models

    NASA Astrophysics Data System (ADS)

    Gerya, Taras

    2014-05-01

    On the one hand, the principle of lithostatic pressure is habitually used in metamorphic geology to calculate paleo-depths of metamorphism from mineralogical pressure estimates given by geobarometry. On the other hand, it is obvious that this lithostatic (hydrostatic) pressure principle should only be valid for an ideal case of negligible deviatoric stresses during the long-term development of the entire tectono-metamorphic system - the situation, which newer comes to existence in natural lithospheric processes. The question is therefore not "Do non-lithostatic pressure variations exist?" but " What is the magnitude of long-term non-lithostatic pressure variations in various lithospheric processes, which can be recorded by mineral equilibria of respective metamorphic rocks?". The later question is, in particular, relevant for various types of high-pressure (HP) and ultrahigh-pressure (UHP) rocks, which are often produced in convergent plate boundary settings (e.g., Hacker and Gerya, 2013). This question, can, in particular, be answered with the use of thermo-mechanical models of subduction/collision processes employing realistic P-T-stress-dependent visco-elasto-brittle/plastic rheology of rocks. These models suggest that magnitudes of pressure deviations from lithostatic values can range >50% underpressure to >100% overpressure, mainly in the regions of bending of rheologically strong mantle lithosphere (Burg and Gerya, 2005; Li et al., 2010). In particular, strong undepresures along normal faults forming within outer rise regions of subducting plates can be responsible for downward water suction and deep hydration of oceanic slabs (Faccenda et al., 2009). Weaker HP and UHP rocks of subduction/collision channels are typically subjected to lesser non-lithostatic pressure variations with characteristic magnitudes ranging within 10-20% from the lithostatic values (Burg and Gerya, 2005; Li et al., 2010). The strength of subducted crustal rocks and the degree of

  17. Pressure-induced wall thickness variations in multi-layered wall of a pollen tube and Fourier decomposition of growth oscillations.

    PubMed

    Pietruszka, Mariusz; Haduch-Sendecka, Aleksandra

    2015-04-01

    The augmented growth equation introduced by Ortega is solved for the apical portion of the pollen tube as an oscillating volume, which we approach in the framework of a two-fluid model in which the two fluids represent the constant pressure and the fluctuating features of the system. Based on routine Fourier analysis, we calculate the energy spectrum of the oscillating pollen tube, and discuss the resonant frequency problem of growth rate oscillations. We also outline a descriptive model for cell wall thickness fluctuations associated with small, yet regular variations (~ 0.01 MPa) observed in turgor pressure. We propose that pressure changes must lead to the sliding of wall layers, indirectly resulting in a wave of polarization of interlayer bonds. We conclude that pollen tube wall thickness may oscillate due to local variations in cell wall properties and relaxation processes. These oscillations become evident because of low amplitude/high frequency pressure fluctuations δP being superimposed on turgor pressure P. We also show that experimentally determined turgor pressure oscillates in a strict periodical manner. A solitary frequency f0 ≈ 0.066 Hz of these (~ 0.01 MPa in magnitude) oscillations for lily pollen tubes was established by the discrete Fourier transform and Lorentz fit.

  18. Fluid Pressure Variation in a Sedimentary Geothermal Reservoir in the North German Basin: Case Study Groß Schönebeck

    NASA Astrophysics Data System (ADS)

    Huenges, Ernst; Trautwein, Ute; Legarth, Björn; Zimmermann, Günter

    2006-10-01

    The Rotliegend of the North German basin is the target reservoir of an interdisciplinary investigation program to develop a technology for the generation of geothermal electricity from low-enthalpy reservoirs. An in situ downhole laboratory was established in the 4.3 km deep well Groβ Schönebeck with the purpose of developing appropriate stimulation methods to increase permeability of deep aquifers by enhancing or creating secondary porosity and flow paths. The goal is to learn how to enhance the inflow performance of a well from a variety of rock types in low permeable geothermal reservoirs. A change in effective stress due to fluid pressure was observed to be one of the key parameters influencing flow properties both downhole and in laboratory experiments on reservoir rocks. Fluid pressure variation was induced using proppant-gel-frac techniques as well as waterfrac techniques in several different new experiments in the borehole. A pressure step test indicates generation and extension of multiple fractures with closure pressures between 6 and 8.4 MPa above formation pressure. In a 24-hour production test 859 m3 water was produced from depth indicating an increase of productivity in comparison with former tests. Different depth sections and transmissibility values were observed in the borehole depending on fluid pressure. In addition, laboratory experiments were performed on core samples from the sandstone reservoir under uniaxial strain conditions, i.e., no lateral strain, constant axial load. The experiments on the borehole and the laboratory scale were realized on the same rock types under comparable stress conditions with similar pore pressure variations. Nevertheless, stress dependences of permeability are not easy to compare from scale to scale. Laboratory investigations reflect permeability variations due to microstructural heterogeneities and the behavior in the borehole is dominated by the generation of connections to large-scale structural patterns.

  19. Genetic Loci and Novel Discrimination Measures Associated with Blood Pressure Variation in African Americans Living in Tallahassee

    PubMed Central

    Quinlan, Jacklyn; Pearson, Laurel N.; Mitchell, Miaisha M.; Boston, Qasimah; Gravlee, Clarence C.; Mulligan, Connie J.

    2016-01-01

    Sequencing of the human genome and decades of genetic association and linkage studies have dramatically improved our understanding of the etiology of many diseases. However, the multiple causes of complex diseases are still not well understood, in part because genetic and sociocultural risk factors are not typically investigated concurrently. Hypertension is a leading risk factor for cardiovascular disease and afflicts more African Americans than any other racially defined group in the US. Few genetic loci for hypertension have been replicated across populations, which may reflect population-specific differences in genetic variants and/or inattention to relevant sociocultural factors. Discrimination is a salient sociocultural risk factor for poor health and has been associated with hypertension. Here we use a biocultural approach to study blood pressure (BP) variation in African Americans living in Tallahassee, Florida by genotyping over 30,000 single nucleotide polymorphisms (SNPs) and capturing experiences of discrimination using novel measures of unfair treatment of self and others (n = 157). We perform a joint admixture and genetic association analysis for BP that prioritizes regions of the genome with African ancestry. We only report significant SNPs that were confirmed through our simulation analyses, which were performed to determine the false positive rate. We identify eight significant SNPs in five genes that were previously associated with cardiovascular diseases. When we include measures of unfair treatment and test for interactions between SNPs and unfair treatment, we identify a new class of genes involved in multiple phenotypes including psychosocial distress and mood disorders. Our results suggest that inclusion of culturally relevant stress measures, like unfair treatment in African Americans, may reveal new genes and biological pathways relevant to the etiology of hypertension, and may also improve our understanding of the complexity of gene

  20. Gravimetric phenotyping of whole plant transpiration responses to atmospheric vapour pressure deficit identifies genotypic variation in water use efficiency.

    PubMed

    Ryan, Annette C; Dodd, Ian C; Rothwell, Shane A; Jones, Ros; Tardieu, Francois; Draye, Xavier; Davies, William J

    2016-10-01

    There is increasing interest in rapidly identifying genotypes with improved water use efficiency, exemplified by the development of whole plant phenotyping platforms that automatically measure plant growth and water use. Transpirational responses to atmospheric vapour pressure deficit (VPD) and whole plant water use efficiency (WUE, defined as the accumulation of above ground biomass per unit of water used) were measured in 100 maize (Zea mays L.) genotypes. Using a glasshouse based phenotyping platform with naturally varying VPD (1.5-3.8kPa), a 2-fold variation in WUE was identified in well-watered plants. Regression analysis of transpiration versus VPD under these conditions, and subsequent whole plant gas exchange at imposed VPDs (0.8-3.4kPa) showed identical responses in specific genotypes. Genotype response of transpiration versus VPD fell into two categories: 1) a linear increase in transpiration rate with VPD with low (high WUE) or high (low WUE) transpiration rate at all VPDs, 2) a non-linear response with a pronounced change point at low VPD (high WUE) or high VPD (low WUE). In the latter group, high WUE genotypes required a significantly lower VPD before transpiration was restricted, and had a significantly lower rate of transpiration in response to VPD after this point, when compared to low WUE genotypes. Change point values were significantly positively correlated with stomatal sensitivity to VPD. A change point in stomatal response to VPD may explain why some genotypes show contradictory WUE rankings according to whether they are measured under glasshouse or field conditions. Furthermore, this novel use of a high throughput phenotyping platform successfully reproduced the gas exchange responses of individuals measured in whole plant chambers, accelerating the identification of plants with high WUE.

  1. Relationship between Ocean Bottom Pressure Variations and Baroclinic Eddy off Kushiro-Tokachi from 2004 to 2013

    NASA Astrophysics Data System (ADS)

    Hasegawa, Takuya; Nagano, Akira; Matsumoto, Hiroyuki; Ariyoshi, Keisuke

    2016-04-01

    The scope of this study is to explore relationships between ocean bottom pressure (OBP) variations related to ocean plate changes, and oceanic climate changes like El Nino/Southern Oscillation (ENSO). We analyzed OBP data at stations PG1 (41.7040N-144.4375E) and PG2 (42.2365N-144.8454E) obtained from the Long-Term Deep Sea Floor Observatory off Kushiro-Tokachi in the Kuril Trench, gridded daily sea surface height (SSH) data provided by AVISO, and conductivity-temperature-depth (CTD) data at a repeated observation line off Akkeshi (A-line) from 2004 to 2013. In addition, we used Nino-3 index, which is one of the major indices for ENSO and is given by the CPC/NOAA. It is suggested that SSH at PG1 and PG2 similarly vary affected by the Oyashio, the western boundary current of the North Pacific subarctic gyre, and El Nino events in 2006 and 2007 via atmospheric telconnections. OBP time series at PG1 and PG2 are almost in phase in most of the analysis period, but from the early 2006 to the end of 2007, are quit discrepant in amplitude; at that occasion, OBP at PG1 is much higher than that at PG2. Expecting a peculiar hydrographic feature at the occasion, CTD data along the A-line in January 2007 are analyzed. A lenticular eddy was found to exist in a layer between 1500 and 3000 dbar and to deepen substantially isopycnals of approximately 27.7 sigma-theta around a depth of 2000 dbar. Probably due to the baroclinic eddy feature, OBP is kept low at PG2, while high at PG1. The subthermocline water occupying the deep eddy are considered not to be originated in the North Pacific but to be derived from the Southern Ocean.

  2. Common variation in the WNK1 gene and blood pressure in childhood: the Avon Longitudinal Study of Parents and Children.

    PubMed

    Tobin, Martin D; Timpson, Nicholas J; Wain, Louise V; Ring, Susan; Jones, Louise R; Emmett, Pauline M; Palmer, Thomas M; Ness, Andrew R; Samani, Nilesh J; Smith, George Davey; Burton, Paul R

    2008-11-01

    WNK1 gene variants have been associated with adult blood pressure. We aimed to investigate relationships between WNK1 variants and blood pressure, as well as blood pressure change with age, in a longitudinal childhood study. Associations between single nucleotide polymorphisms in WNK1 and blood pressure and the rate of blood pressure change between 7 and 11 years were examined in the Avon Longitudinal Study of Parent and Children Study (n=5326 for systolic blood pressure at 11 years). We observed associations (P<0.05) with diastolic blood pressure gradient with age for 33 of 82 typed and imputed polymorphisms, including polymorphisms in exons 4, 10, and 11 (rs10774466, rs1012729, and rs9804992). The minor allele (G) of rs1012729 (frequency: 25.6%) was associated with a gender-adjusted change in a diastolic blood pressure gradient of -0.11 mm Hg/y (95% CI: -0.20 to -0.03 mm Hg/y; P=0.0054). No associations were shown with the systolic blood pressure gradient. At age 11 years, 30 polymorphisms showed association (P<0.05) with systolic blood pressure, including variants in exons 4 and 10 (rs10774466 and rs1012729). Only 3 polymorphisms were associated with diastolic blood pressure at 11 years. In exploration of polymorphism-dietary cation interactions on systolic blood pressure at 11 years, 59 reached significance (P<0.05; 12.3 expected by chance), mostly (n=33) related to dietary calcium. The findings show that common intronic and exonic WNK1 variants are associated with diastolic blood pressure gradient from 7 to 11 years and with systolic blood pressure at 11 years. Our study suggests that previously reported effects of WNK1 variants on blood pressure are mediated via effects on the gradient of blood pressure change with age.

  3. Variation of Pressure with Depth of Water: Working with High-Tech and Low-Cost Materials

    ERIC Educational Resources Information Center

    Ornek, Funda; Zziwa, Byansi Jude; Taganahan, Teresita D.

    2013-01-01

    When you dive underwater, you feel the pressure on your ears and, as you dive deeper, more pressure is felt. This article presents an activity that teachers might find useful for demonstrating the relationship between water depth and pressure. (Contains 5 figures and 1 table.)

  4. Variation of Pressure with Depth of Water: Working with High-Tech and Low-Cost Materials

    ERIC Educational Resources Information Center

    Ornek, Funda; Zziwa, Byansi Jude; Taganahan, Teresita D.

    2013-01-01

    When you dive underwater, you feel the pressure on your ears and, as you dive deeper, more pressure is felt. This article presents an activity that teachers might find useful for demonstrating the relationship between water depth and pressure. (Contains 5 figures and 1 table.)

  5. Short-term variation of subglottal pressure for expressive purposes in singing and stage speech: a preliminary investigation.

    PubMed

    Sundberg, J; Elliot, N; Gramming, P; Nord, L

    1993-09-01

    According to previous investigations, subglottal pressure in singing is adapted not only to loudness but also to fundamental frequency. Here the significance of musical expression to subglottal pressure is analyzed in terms of alternations between stressed and unstressed bar positions. Esophageal pressure was recorded together with the audio signal in a male and a female professional singer using a paranasally introduced pressure transducer while the subjects performed vocal exercises. Also, the subjects gave examples of actors' speech by reading poetry aloud. The results show that subglottal pressure can be used for stressing the first beat in bars and also for increasing the sound level in voiced consonants in actor's speech.

  6. Basic Pressure Measurements at Transonic Speeds on a Thin 45 deg Sweptback Highly Tapered Wing with Systematic Spanwise Twist Variations

    NASA Technical Reports Server (NTRS)

    Mugler, John P., Jr.

    1958-01-01

    Pressure distributions are presented for a thin highly tapered untwisted 45 deg sweptback wing in combination with a body. These tests were made in the Langley 8-foot transonic pressure tunnel at both 1.0 and 0.5 atmosphere stagnation pressures at Mach numbers from 0.800 to 1.200 through an angle-of-attack range of -4 deg to 12 deg.

  7. Long-term spatial and temporal variation of CO2 partial pressure in the Yellow River, China

    NASA Astrophysics Data System (ADS)

    Ran, L.; Lu, X. X.; Richey, J. E.; Sun, H.; Han, J.; Yu, R.; Liao, S.; Yi, Q.

    2015-02-01

    Carbon transport in river systems is an important component of the global carbon cycle. Most rivers of the world act as atmospheric CO2 sources due to high riverine CO2 partial pressure (pCO2). By determining the pCO2 from alkalinity and pH, we investigated its spatial and temporal variation in the Yellow River watershed using historical water chemistry records (1950s-1984) and recent sampling along the mainstem (2011-2012). Except the headwater region where the pCO2 was lower than the atmospheric equilibrium (i.e. 380 μatm), river waters in the remaining watershed were supersaturated with CO2. The average pCO2 for the watershed was estimated at 2810 ± 1985 μatm, which is 7-fold the atmospheric equilibrium. As a result of severe soil erosion and dry climate, waters from the Loess Plateau in the middle reaches had higher pCO2 than that from the upper and lower reaches. From a seasonal perspective, the pCO2 varied from about 200 μatm to > 30 000 μatm with higher pCO2 usually occurring in the dry season and lower pCO2 in the wet season (at 73% of the sampling sites), suggesting the dilution effect of water. While the pCO2 responded exponentially to total suspended solids (TSS) export when the TSS concentration was less than 100 kg m-3, it decreased slightly and remained stable if the TSS concentration exceeded 100 kg m-3. This stable pCO2 is largely due to gully erosion that mobilizes subsoils characterized by low organic carbon for decomposition. In addition, human activities have changed the pCO2 dynamics. Particularly, flow regulation by dams can diversely affect the temporal changes of pCO2, depending on the physiochemical properties of the regulated waters and adopted operation scheme. Given the high pCO2 in the Yellow River waters, large potential for CO2 evasion is expected and warrants further investigation.

  8. Variation of pressure limits of flame propagation with tube diameter for various isooctane-oxygen-nitrogen mixtures

    NASA Technical Reports Server (NTRS)

    Spakowski, Adolph, A; Belles, Frank E

    1952-01-01

    An investigation was made of the change in the pressure limits of flame propagation with tube diameter for various isooctane-oxygen-nitrogen mixtures. Pressure limits were measured in cylindrical glass tubes of four different inside diameters at six different oxygen-nitrogen ratios. Under the experimental conditions, flame propagation was found to be impossible in isooctane-oxygen mixtures with oxygen concentrations less than 11 to 12 percent. Critical tube diameters for flame propagation were calculated and the effect of pressure was determined and compared with the effect of pressure on quenching distance. Critical diameters were related to flame speeds for various isooctane-oxygen-nitrogen mixtures.

  9. Significance of Dynamic Pore Pressure Variations - Comparison of Observations on Mud Volcanoes on the Costa Rica Margin and in the Gulf of Cadiz

    NASA Astrophysics Data System (ADS)

    Brueckmann, W.; Linke, P.; Pieper, M.; Hensen, C.; Tuerk, M.

    2006-12-01

    Research in the cooperative research center (SFB) 574 "Volatiles and Fluids in Subduction Zones" at the University Kiel focuses on volatile and fluid exchange processes at subduction zones. These have a significant impact on the long-term geochemical evolution of the hydrosphere and atmosphere. In the SFB 574 working area off Central America more than 120 mud volcanoes, mud diapirs and cold seeps have been identified and sampled. To better understand the internal dynamics of these structures and the temporal variability of fluid expulsion an in-situ tool for monitoring shallow pore pressure variations was devised. The tool (PWPL) monitors pore pressure variations along a 2m profile in the shallow subsurface using a stinger with 4 pressure ports. Positioned with a video-guided lander the stinger is gently pushed into the seafloor where it remains for several weeks or months in autonomous mode before being retrieved. While particular emphasis was placed on the convergent margin of Central America, mud volcanoes in other tectonic settings suitable for long-term observations of fluid flux are used for comparison. Here we will present data and interpretations from two mud volcanoes off Costa Rica and in the Gulf of Cadiz where we have conducted successful tests. Pore pressure data from short-term tests on Mound 11 on the continental slope off Costa Rica are compared with new results from a long-term (3-month) campaign on the Captain Arutjunov deep water mud volcano in the Gulf of Cadiz. Rates of fluid flow at both structures have been thoroughly characterized and quantified with geochemical methods providing a frame of reference for judging the significance of dynamic pore pressure variations.

  10. [Effects of surgical treatment on circadian variations of arterial pressure in patients with primary aldosteronism and renovascular hypertension].

    PubMed

    Kosmacheva, E D; Minkin, S E; Chikhladze, N M; Arabidze, G G; At'kov, O Iu

    1990-05-01

    Noninvasive recording of blood pressure (BP) with a portable Del Mar Avionics monitor (USA) revealed its abnormal circadian rhythm in patients with renovascular hypertension or arterial hypertension caused by adrenal aldosteroma. Surgical treatment was shown to result in a significant decrease in blood pressures and normalization of its circadian rhythm in the early postoperative period.

  11. Dynamic and Steady Characteristics of Polymer-Ceramic Pressure-Sensitive Paint with Variation in Layer Thickness

    PubMed Central

    Hayashi, Tatsunori; Sakaue, Hirotaka

    2017-01-01

    Polymer-ceramic pressure-sensitive paint (PC-PSP) has been investigated as a surface-pressure sensor for unsteady aerodynamics and short duration measurements. This PSP provides a fast response to a change in pressures with a spray-coating ability. Because it is sprayed onto an aerodynamic surface, the thickness of PC-PSP may play an important role in determining the performance of this sensor. The thickness of other fast PSPs, such as anodized aluminum pressure-sensitive paint, is a major factor in determining its performance. We vary the thickness of PC-PSP from 10 to 240 μm in order to study its effects on PSP measurement characteristics including time response, signal level, pressure sensitivity, and temperature dependency. It is found that the thickness does affect these characteristics. However, a thickness over 80 μm provides uniform performance in these characteristics. PMID:28505122

  12. Variation in Resistance of Natural Isolates of Escherichia coli O157 to High Hydrostatic Pressure, Mild Heat, and Other Stresses

    PubMed Central

    Benito, Amparo; Ventoura, Georgia; Casadei, Maria; Robinson, Tobin; Mackey, Bernard

    1999-01-01

    Strains of Escherichia coli O157 isolated from patients with clinical cases of food-borne illness and other sources exhibited wide differences in resistance to high hydrostatic pressure. The most pressure-resistant strains were also more resistant to mild heat than other strains. Strain C9490, a representative pressure-resistant strain, was also more resistant to acid, oxidative, and osmotic stresses than the pressure-sensitive strain NCTC 12079. Most of these differences in resistance were observed only in stationary-phase cells, the only exception being acid resistance, where differences were also apparent in the exponential phase. Membrane damage in pressure-treated cells was revealed by increased uptake of the fluorescent dyes ethidium bromide and propidium iodide. When strains were exposed to the same pressure for different lengths of time, the pressure-sensitive strains took up stain sooner than the more resistant strain, which suggested that the differences in resistance may be related to susceptibility to membrane damage. Our results emphasize the importance of including stress-resistant strains of E. coli O157 when the efficacy of a novel or mild food preservation treatment is tested. PMID:10103251

  13. Change in serum TSH levels within the reference range was associated with variation of future blood pressure: a 5-year follow-up study.

    PubMed

    Jiang, F; Liu, A; Lai, Y; Yu, X; Li, C; Han, C; Zhang, Y; Wang, X; Wang, Z; Bao, S; Lv, N; Jin, M; Yang, F; Fan, Y; Jin, T; Zhao, W; Shan, Z; Teng, W

    2017-04-01

    Controversy exists on the relationship between serum thyrotropin (TSH) and blood pressure, and only a few prospective studies are available up to now. The study aimed to investigate the association between serum TSH within the reference range and blood pressure through a 5-year follow-up study. A total of 623 subjects with normal TSH were followed up for 5 years, including the measurement of demographic data, blood pressure, height, weight and serum TSH. Finally, 531 subjects were included in this prospective study. Body mass index (BMI), prevalence of hypertension, and systolic and diastolic blood pressure were all higher at follow-up than at baseline. Adjusted for age, gender, smoking status, BMI and homoeostasis model assessment of insulin resistance (HOMA-IR) at baseline, multiple linear regression analyses found no relationship between serum TSH at baseline and levels of blood pressure at follow-up, but the changes in serum TSH levels during follow-up was positively associated with the changes in systolic blood pressure (B=2.134, P<0.05), which became more significant in women but not significant in men. The change of systolic blood pressure in group of TSH increase >0.5 mIU l(-1) was significantly higher than in group of TSH decrease >0.5 mIU l(-1) within reference, after adjusting for age, gender, smoking status, BMI and HOMA-IR at baseline. This result became more significant in women, but no statistical significance was observed in men. Co-variation with serum TSH levels and blood pressure was observed during 5-year follow-up among people with normal TSH.

  14. Pressure difference-flow rate variation in a femoral artery branch casting of man for steady flow

    NASA Technical Reports Server (NTRS)

    Cho, Y. I.; Back, L. H.; Crawford, D. W.

    1983-01-01

    In-vitro, steady flow in a casting of the profunda femoris branch of the femoral artery of man was studied by measuring pressure differences in the main lumen and also in the branch over a large Reynolds number range from 200 to 1600. Effects of viscous and inviscid flows in this femoral artery branch were demonstrated quantitatively. The critical ratio of the flow rate in the branch to the upstream main lumen in this casting was found to be 0.4, above which the inviscid flow analysis indicated a pressure rise and below which it yielded a pressure drop in the main lumen across the branch junction. Pressure rises were experimentally found to occur both in the main lumen and in the branch for certain ranges of the aforementioned ratio.

  15. Pressure difference-flow rate variation in a femoral artery branch casting of man for steady flow

    NASA Technical Reports Server (NTRS)

    Cho, Y. I.; Back, L. H.; Crawford, D. W.

    1983-01-01

    In-vitro, steady flow in a casting of the profunda femoris branch of the femoral artery of man was studied by measuring pressure differences in the main lumen and also in the branch over a large Reynolds number range from 200 to 1600. Effects of viscous and inviscid flows in this femoral artery branch were demonstrated quantitatively. The critical ratio of the flow rate in the branch to the upstream main lumen in this casting was found to be 0.4, above which the inviscid flow analysis indicated a pressure rise and below which it yielded a pressure drop in the main lumen across the branch junction. Pressure rises were experimentally found to occur both in the main lumen and in the branch for certain ranges of the aforementioned ratio.

  16. The 24 h pattern of arterial pressure in mice is determined mainly by heart rate‐driven variation in cardiac output

    PubMed Central

    Kurtz, Theodore W.; Lujan, Heidi L.; DiCarlo, Stephen E.

    2014-01-01

    Abstract Few studies have systematically investigated whether daily patterns of arterial blood pressure over 24 h are mediated by changes in cardiac output, peripheral resistance, or both. Understanding the hemodynamic mechanisms that determine the 24 h patterns of blood pressure may lead to a better understanding of how such patterns become disturbed in hypertension and influence risk for cardiovascular events. In conscious, unrestrained C57BL/6J mice, we investigated whether the 24 h pattern of arterial blood pressure is determined by variation in cardiac output, systemic vascular resistance, or both and also whether variations in cardiac output are mediated by variations in heart rate and or stroke volume. As expected, arterial pressure and locomotor activity were significantly (P < 0.05) higher during the nighttime period compared with the daytime period when mice are typically sleeping (+12.5 ± 1.0 mmHg, [13%] and +7.7 ± 1.3 activity counts, [254%], respectively). The higher arterial pressure during the nighttime period was mediated by higher cardiac output (+2.6 ± 0.3 mL/min, [26%], P < 0.05) in association with lower peripheral resistance (−1.5 ± 0.3 mmHg/mL/min, [−13%] P < 0.05). The increased cardiac output during the nighttime was mainly mediated by increased heart rate (+80.0 ± 16.5 beats/min, [18%] P < 0.05), as stroke volume increased minimally at night (+1.6 ± 0.5 μL per beat, [6%] P < 0.05). These results indicate that in C57BL/6J mice, the 24 h pattern of blood pressure is hemodynamically mediated primarily by the 24 h pattern of cardiac output which is almost entirely determined by the 24 h pattern of heart rate. These findings suggest that the differences in blood pressure between nighttime and daytime are mainly driven by differences in heart rate which are strongly correlated with differences in locomotor activity. PMID:25428952

  17. Low-Frequency Ocean Bottom Pressure Variations in the North Pacific in Response to Time-Variable Surface Winds

    NASA Astrophysics Data System (ADS)

    Dobslaw, H.; Petrick, C.; Bergmann-Wolf, I.; Matthes, K. B.; Thomas, M.

    2014-12-01

    One decade of time-variable gravity field observations from the GRACE satellite mission reveals low-frequency ocean bottom pressure (OBP) variability of up to 2.5 hPa centered at the northern flank of the subtropical gyre in the North Pacific. From a 145 year-long simulation with a coupled chemistry climate model, OBP variability is found to be related to the prevailing atmospheric sea-level pressure and surface wind conditions in the larger North Pacific area. The dominating atmospheric pressure patterns obtained from the climate model run allow in combination with ERA-Interim sea-level pressure and surface winds a reconstruction of the OBP variability in the North Pacific from atmospheric model data only, which correlates favourably (r=0.7) with GRACE ocean bottom pressure observations. The regression results indicate that GRACE-based OBP observations are indeed sensitive to changes in the prevailing sea-level pressure and thus surface wind conditions in the North Pacific, thereby opening opportunities to constrain atmospheric models from satellite gravity observations over the oceans.

  18. Circadian variation in heart rate, blood pressure, body temperature and EEG of immature broiler breeder chickens in restricted-fed and ad libitum-fed states.

    PubMed

    Savory, C J; Kostal, L; Nevison, I M

    2006-10-01

    1. Heart rate, intra-aortic blood pressure, deep body temperature and telencephalic EEG were monitored by radiotelemetry in 6 freely moving immature broiler breeders (three in each of two years), during routine food restriction and then ad libitum feeding, over two 24-h periods in each feeding state.2. Heart rate, blood pressure and body temperature were all higher during ad libitum than restricted feeding, and heart rate and body temperature were higher by day (12 h) than at night (12 h). The decreases in heart rate and body temperature at night were greater during restricted than ad libitum feeding. Blood pressure tended to be higher at night, except in year 2 during restricted feeding. Body temperature and ambient temperature were higher in year 2 than year 1.3. During restricted feeding, marked peaks in heart rate, blood pressure and body temperature in the 15 min after provision of the daily food ration at 09:00 h, when birds were eating, were equivalent to corresponding values seen during ad libitum feeding.4. Relative powers in delta (1 to 4 Hz) and theta (4 to 8 Hz) frequency bands of the EEG power spectrum were higher at night in year 2 only, while power in the alpha (8 to 12 Hz) band was higher at night in both years.5. It is concluded that most of the variation in heart rate, blood pressure and body temperature between feeding states and times of day/night can be accounted for in terms of variation in food intake and energy expenditure. The greater slow wave (delta, theta) EEG activity seen after lights-off in year 2 may reflect non-paradoxical sleep at that time.

  19. Variation law of gas holdup in an autoclave during the pressure leaching process by using a mixed-flow agitator

    NASA Astrophysics Data System (ADS)

    Tian, Lei; Liu, Yan; Tang, Jun-jie; Lü, Guo-zhi; Zhang, Ting-an

    2017-08-01

    The multiphase reaction process of pressure leaching is mainly carried out in the liquid phase. Therefore, gas holdup is essential for the gas-liquid-solid phase reaction and the extraction rate of valuable metals. In this paper, a transparent quartz autoclave, a six blades disc turbine-type agitator, and a high-speed camera were used to investigate the gas holdup of the pressure leaching process. Furthermore, experiments determining the effects of agitation rate, temperature, and oxygen partial pressure on gas holdup were carried out. The results showed that when the agitation rate increased from 350 to 600 r/min, the gas holdup increased from 0.10% to 0.64%. When the temperature increased from 363 to 423 K, the gas holdup increased from 0.14% to 0.20%. When the oxygen partial pressure increased from 0.1 to 0.8 MPa, the gas holdup increased from 0.13% to 0.19%. A similar criteria relationship was established by Homogeneous Principle and Buckingham's theorem. Comprehensively, empirical equation of gas holdup was deduced on the basis of experimental data and the similarity theory, where the criterion equation was determined as ɛ = 4.54 × 10-11 n 3.65 T 2.08 P g 0.18. It can be seen from the formula that agitation rate made the most important impact on gas holdup in the pressure leaching process using the mixed-flow agitator.

  20. Genetic Variation in the Human SORBS1 Gene is Associated With Blood Pressure Regulation and Age at Onset of Hypertension: A SAPPHIRe Cohort Study.

    PubMed

    Chang, Tien-Jyun; Wang, Wen-Chang; Hsiung, Chao A; He, Chih-Tsueng; Lin, Ming-Wei; Sheu, Wayne Huey-Herng; Chang, Yi-Cheng; Quertermous, Tom; Chen, Ida; Rotter, Jerome; Chuang, Lee-Ming

    2016-03-01

    Essential hypertension is a complex disease involving multiple genetic and environmental factors. A human gene containing a sorbin homology domain and 3 SH3 domains in the C-terminal region, termed SORBS1, plays a significant role in insulin signaling. We previously found a significant association between the T228A polymorphism and insulin resistance, obesity, and type 2 diabetes. It has been hypothesized that a set of genes responsible for insulin resistance may be closely linked with genes susceptible to the development of hypertension. Identification of insulin resistance-related genetic factors may, therefore, enhance our understanding of essential hypertension. This study aimed to examine whether common SORBS1 genetic variations are associated with blood pressure and age at onset of hypertension in an ethnic Chinese cohort.We genotyped 9 common tagged single nucleotide polymorphisms of the SORBS1 gene in 1136 subjects of Chinese origin from the Stanford Asia-Pacific Program for Hypertension and Insulin Resistance family study. Blood pressure was measured upon enrolment. The associations of the SORBS1 single nucleotide polymorphisms with blood pressure and the presence of hypertension were analyzed with a generalized estimating equation model. We used the false-discovery rate measure Q value with a cutoff <0.1 to adjust for multiple comparisons. In the Cox regression analysis for hypertension-free survival, a robust sandwich variance estimator was used to deal with the within-family correlations with age at onset of hypertension. Gender, body mass index, and antihypertension medication were adjustment covariates in the Cox regression analysis.In this study, genetic variants of rs2281939 and rs2274490 were significantly associated with both systolic and diastolic blood pressure. A genetic variant of rs2274490 was also significantly associated with the presence of hypertension. Furthermore, genetic variants of rs2281939 and rs2274490 were associated with age at

  1. Abacus giving the variation of the mean pressure of an aviation engine as a function of its speed of rotation

    NASA Technical Reports Server (NTRS)

    Margoulis, W

    1921-01-01

    Comparing the results of the calculations for computing the mean pressure of an aviation engine for any number of revolutions, with those of experiment, the writer, by numerous examples, shows the perfect agreement between them. This report will show that, by means of a special abacus, an engineer can instantly plot the characteristics of an engine.

  2. The relation between the properties of pressure variations in the lower corona and solar energetic particle events

    NASA Astrophysics Data System (ADS)

    Rouillard, A. P.; Vourlidas, A.; Tylka, A. J.; Cohen, C. M.; Mewaldt, R. A.; Mason, G. M.; Thernisien, A. F.

    2012-12-01

    We combine ultraviolet and white-light images obtained by the Solar Dynamics Observatory (SDO) and the Solar-Terrestrial Relations Observatory (STEREO) to track, in the lower corona, the spatial and temporal evolution of pressure waves associated with the onset of Coronal Mass Ejections (CMEs). We use in-situ measurements of the onset of solar energetic particle events (SEPs) to determine their release time near the Sun. We concentrate on the proton-rich events detected by the near-Earth spacecraft and the STEREOs during 2011 and 2012. We use a simple model of the distribution of interplanerary magnetic field lines to determine the foopoint locations of field lines connecting the lower corona to the points of in-situ measurements. We (1) determine the height and spatial extent of the pressure waves at the SEP release times, (2) compare the longitudinal extent of SEP events with the extent of the pressure waves, (3) compare the kinematic properties of pressure waves launched over widely separated longitudes. We discuss the successes and challenges faced when interpreting these observations in terms of the acceleration of particles at coronal shocks.

  3. Mass-induced sea level variations in the Red Sea from GRACE, steric-corrected altimetry, in situ bottom pressure records, and hydrographic observations

    NASA Astrophysics Data System (ADS)

    Feng, W.; Lemoine, J.-M.; Zhong, M.; Hsu, H. T.

    2014-08-01

    An annual amplitude of ∼18 cm mass-induced sea level variations (SLV) in the Red Sea is detected from the Gravity Recovery and Climate Experiment (GRACE) satellites and steric-corrected altimetry from 2003 to 2011. The annual mass variations in the region dominate the mean SLV, and generally reach maximum in late January/early February. The annual steric component of the mean SLV is relatively small (<3 cm) and out of phase of the mass-induced SLV. In situ bottom pressure records at the eastern coast of the Red Sea validate the high mass variability observed by steric-corrected altimetry and GRACE. In addition, the horizontal water mass flux of the Red Sea estimated from GRACE and steric-corrected altimetry is validated by hydrographic observations.

  4. Association of genetic variation with systolic and diastolic blood pressure among African Americans: the Candidate Gene Association Resource study.

    PubMed

    Fox, Ervin R; Young, J Hunter; Li, Yali; Dreisbach, Albert W; Keating, Brendan J; Musani, Solomon K; Liu, Kiang; Morrison, Alanna C; Ganesh, Santhi; Kutlar, Abdullah; Ramachandran, Vasan S; Polak, Josef F; Fabsitz, Richard R; Dries, Daniel L; Farlow, Deborah N; Redline, Susan; Adeyemo, Adebowale; Hirschorn, Joel N; Sun, Yan V; Wyatt, Sharon B; Penman, Alan D; Palmas, Walter; Rotter, Jerome I; Townsend, Raymond R; Doumatey, Ayo P; Tayo, Bamidele O; Mosley, Thomas H; Lyon, Helen N; Kang, Sun J; Rotimi, Charles N; Cooper, Richard S; Franceschini, Nora; Curb, J David; Martin, Lisa W; Eaton, Charles B; Kardia, Sharon L R; Taylor, Herman A; Caulfield, Mark J; Ehret, Georg B; Johnson, Toby; Chakravarti, Aravinda; Zhu, Xiaofeng; Levy, Daniel

    2011-06-01

    The prevalence of hypertension in African Americans (AAs) is higher than in other US groups; yet, few have performed genome-wide association studies (GWASs) in AA. Among people of European descent, GWASs have identified genetic variants at 13 loci that are associated with blood pressure. It is unknown if these variants confer susceptibility in people of African ancestry. Here, we examined genome-wide and candidate gene associations with systolic blood pressure (SBP) and diastolic blood pressure (DBP) using the Candidate Gene Association Resource (CARe) consortium consisting of 8591 AAs. Genotypes included genome-wide single-nucleotide polymorphism (SNP) data utilizing the Affymetrix 6.0 array with imputation to 2.5 million HapMap SNPs and candidate gene SNP data utilizing a 50K cardiovascular gene-centric array (ITMAT-Broad-CARe [IBC] array). For Affymetrix data, the strongest signal for DBP was rs10474346 (P= 3.6 × 10(-8)) located near GPR98 and ARRDC3. For SBP, the strongest signal was rs2258119 in C21orf91 (P= 4.7 × 10(-8)). The top IBC association for SBP was rs2012318 (P= 6.4 × 10(-6)) near SLC25A42 and for DBP was rs2523586 (P= 1.3 × 10(-6)) near HLA-B. None of the top variants replicated in additional AA (n = 11 882) or European-American (n = 69 899) cohorts. We replicated previously reported European-American blood pressure SNPs in our AA samples (SH2B3, P= 0.009; TBX3-TBX5, P= 0.03; and CSK-ULK3, P= 0.0004). These genetic loci represent the best evidence of genetic influences on SBP and DBP in AAs to date. More broadly, this work supports that notion that blood pressure among AAs is a trait with genetic underpinnings but also with significant complexity.

  5. Association of genetic variation with systolic and diastolic blood pressure among African Americans: the Candidate Gene Association Resource study

    PubMed Central

    Fox, Ervin R.; Young, J. Hunter; Li, Yali; Dreisbach, Albert W.; Keating, Brendan J.; Musani, Solomon K.; Liu, Kiang; Morrison, Alanna C.; Ganesh, Santhi; Kutlar, Abdullah; Ramachandran, Vasan S.; Polak, Josef F.; Fabsitz, Richard R.; Dries, Daniel L.; Farlow, Deborah N.; Redline, Susan; Adeyemo, Adebowale; Hirschorn, Joel N.; Sun, Yan V.; Wyatt, Sharon B.; Penman, Alan D.; Palmas, Walter; Rotter, Jerome I.; Townsend, Raymond R.; Doumatey, Ayo P.; Tayo, Bamidele O.; Mosley, Thomas H.; Lyon, Helen N.; Kang, Sun J.; Rotimi, Charles N.; Cooper, Richard S.; Franceschini, Nora; Curb, J. David; Martin, Lisa W.; Eaton, Charles B.; Kardia, Sharon L.R.; Taylor, Herman A.; Caulfield, Mark J.; Ehret, Georg B.; Johnson, Toby; Chakravarti, Aravinda; Zhu, Xiaofeng; Levy, Daniel; Munroe, Patricia B.; Rice, Kenneth M.; Bochud, Murielle; Johnson, Andrew D.; Chasman, Daniel I.; Smith, Albert V.; Tobin, Martin D.; Verwoert, Germaine C.; Hwang, Shih-Jen; Pihur, Vasyl; Vollenweider, Peter; O'Reilly, Paul F.; Amin, Najaf; Bragg-Gresham, Jennifer L.; Teumer, Alexander; Glazer, Nicole L.; Launer, Lenore; Zhao, Jing Hua; Aulchenko, Yurii; Heath, Simon; Sõber, Siim; Parsa, Afshin; Luan, Jian'an; Arora, Pankaj; Dehghan, Abbas; Zhang, Feng; Lucas, Gavin; Hicks, Andrew A.; Jackson, Anne U.; Peden, John F.; Tanaka, Toshiko; Wild, Sarah H.; Rudan, Igor; Igl, Wilmar; Milaneschi, Yuri; Parker, Alex N.; Fava, Cristiano; Chambers, John C.; Kumari, Meena; JinGo, Min; van der Harst, Pim; Kao, Wen Hong Linda; Sjögren, Marketa; Vinay, D.G.; Alexander, Myriam; Tabara, Yasuharu; Shaw-Hawkins, Sue; Whincup, Peter H.; Liu, Yongmei; Shi, Gang; Kuusisto, Johanna; Seielstad, Mark; Sim, Xueling; Nguyen, Khanh-Dung Hoang; Lehtimäki, Terho; Matullo, Giuseppe; Wu, Ying; Gaunt, Tom R.; Charlotte Onland-Moret, N.; Cooper, Matthew N.; Platou, Carl G.P.; Org, Elin; Hardy, Rebecca; Dahgam, Santosh; Palmen, Jutta; Vitart, Veronique; Braund, Peter S.; Kuznetsova, Tatiana; Uiterwaal, Cuno S.P.M.; Campbell, Harry; Ludwig, Barbara; Tomaszewski, Maciej; Tzoulaki, Ioanna; Palmer, Nicholette D.; Aspelund, Thor; Garcia, Melissa; Chang, Yen-Pei C.; O'Connell, Jeffrey R.; Steinle, Nanette I.; Grobbee, Diederick E.; Arking, Dan E.; Hernandez, Dena; Najjar, Samer; McArdle, Wendy L.; Hadley, David; Brown, Morris J.; Connell, John M.; Hingorani, Aroon D.; Day, Ian N.M.; Lawlor, Debbie A.; Beilby, John P.; Lawrence, Robert W.; Clarke, Robert; Collins, Rory; Hopewell, Jemma C.; Ongen, Halit; Bis, Joshua C.; Kähönen, Mika; Viikari, Jorma; Adair, Linda S.; Lee, Nanette R.; Chen, Ming-Huei; Olden, Matthias; Pattaro, Cristian; Hoffman Bolton, Judith A.; Köttgen, Anna; Bergmann, Sven; Mooser, Vincent; Chaturvedi, Nish; Frayling, Timothy M.; Islam, Muhammad; Jafar, Tazeen H.; Erdmann, Jeanette; Kulkarni, Smita R.; Bornstein, Stefan R.; Grässler, Jürgen; Groop, Leif; Voight, Benjamin F.; Kettunen, Johannes; Howard, Philip; Taylor, Andrew; Guarrera, Simonetta; Ricceri, Fulvio; Emilsson, Valur; Plump, Andrew; Barroso, Inês; Khaw, Kay-Tee; Weder, Alan B.; Hunt, Steven C.; Bergman, Richard N.; Collins, Francis S.; Bonnycastle, Lori L.; Scott, Laura J.; Stringham, Heather M.; Peltonen, Leena; Perola, Markus; Vartiainen, Erkki; Brand, Stefan-Martin; Staessen, Jan A.; Wang, Thomas J.; Burton, Paul R.; SolerArtigas, Maria; Dong, Yanbin; Snieder, Harold; Wang, Xiaoling; Zhu, Haidong; Lohman, Kurt K.; Rudock, Megan E.; Heckbert, Susan R.; Smith, Nicholas L.; Wiggins, Kerri L.; Shriner, Daniel; Veldre, Gudrun; Viigimaa, Margus; Kinra, Sanjay; Prabhakaran, Dorairajan; Tripathy, Vikal; Langefeld, Carl D.; Rosengren, Annika; Thelle, Dag S.; MariaCorsi, Anna; Singleton, Andrew; Forrester, Terrence; Hilton, Gina; McKenzie, Colin A.; Salako, Tunde; Iwai, Naoharu; Kita, Yoshikuni; Ogihara, Toshio; Ohkubo, Takayoshi; Okamura, Tomonori; Ueshima, Hirotsugu; Umemura, Satoshi; Eyheramendy, Susana; Meitinger, Thomas; Wichmann, H.-Erich; Cho, Yoon Shin; Kim, Hyung-Lae; Lee, Jong-Young; Scott, James; Sehmi, Joban S.; Zhang, Weihua; Hedblad, Bo; Nilsson, Peter; Smith, George Davey; Wong, Andrew; Narisu, Narisu; Stančáková, Alena; Raffel, Leslie J.; Yao, Jie; Kathiresan, Sekar; O'Donnell, Chris; Schwartz, Steven M.; Arfan Ikram, M.; Longstreth, Will T.; Seshadri, Sudha; Shrine, Nick R.G.; Wain, Louise V.; Morken, Mario A.; Swift, Amy J.; Laitinen, Jaana; Prokopenko, Inga; Zitting, Paavo; Cooper, Jackie A.; Humphries, Steve E.; Danesh, John; Rasheed, Asif; Goel, Anuj; Hamsten, Anders; Watkins, Hugh; Bakker, Stephan J.L.; van Gilst, Wiek H.; Janipalli, Charles S.; Radha Mani, K.; Yajnik, Chittaranjan S.; Hofman, Albert; Mattace-Raso, Francesco U.S.; Oostra, Ben A.; Demirkan, Ayse; Isaacs, Aaron; Rivadeneira, Fernando; Lakatta, Edward G.; Orru, Marco; Scuteri, Angelo; Ala-Korpela, Mika; Kangas, Antti J.; Lyytikäinen, Leo-Pekka; Soininen, Pasi; Tukiainen, Taru; Würz, Peter; Twee-Hee Ong, Rick; Dörr, Marcus; Kroemer, Heyo K.; Völker, Uwe; Völzke, Henry; Galan, Pilar; Hercberg, Serge; Lathrop, Mark; Zelenika, Diana; Deloukas, Panos; Mangino, Massimo; Spector, Tim D.; Zhai, Guangju; Meschia, James F.; Nalls, Michael A.; Sharma, Pankaj; Terzic, Janos; Kranthi Kumar, M.J.; Denniff, Matthew; Zukowska-Szczechowska, Ewa; Wagenknecht, Lynne E.; Fowkes, Gerald R.; Charchar, Fadi J.; Schwarz, Peter E.H.; Hayward, Caroline; Guo, Xiuqing; Bots, Michiel L.; Brand, Eva; Samani, Nilesh J.; Polasek, Ozren; Talmud, Philippa J.; Nyberg, Fredrik; Kuh, Diana; Laan, Maris; Hveem, Kristian; Palmer, Lyle J.; van der Schouw, Yvonne T.; Casas, Juan P.; Mohlke, Karen L.; Vineis, Paolo; Raitakari, Olli; Wong, Tien Y.; Shyong Tai, E.; Laakso, Markku; Rao, Dabeeru C.; Harris, Tamara B.; Morris, Richard W.; Dominiczak, Anna F.; Kivimaki, Mika; Marmot, Michael G.; Miki, Tetsuro; Saleheen, Danish; Chandak, Giriraj R.; Coresh, Josef; Navis, Gerjan; Salomaa, Veikko; Han, Bok-Ghee; Kooner, Jaspal S.; Melander, Olle; Ridker, Paul M.; Bandinelli, Stefania; Gyllensten, Ulf B.; Wright, Alan F.; Wilson, James F.; Ferrucci, Luigi; Farrall, Martin; Tuomilehto, Jaakko; Pramstaller, Peter P.; Elosua, Roberto; Soranzo, Nicole; Sijbrands, Eric J.G.; Altshuler, David; Loos, Ruth J.F.; Shuldiner, Alan R.; Gieger, Christian; Meneton, Pierre; Uitterlinden, Andre G.; Wareham, Nicholas J.; Gudnason, Vilmundur; Rettig, Rainer; Uda, Manuela; Strachan, David P.; Witteman, Jacqueline C.M.; Hartikainen, Anna-Liisa; Beckmann, Jacques S.; Boerwinkle, Eric; Boehnke, Michael; Larson, Martin G.; Järvelin, Marjo-Riitta; Psaty, Bruce M.; Abecasis, Gonçalo R.; Elliott, Paul; van Duijn , Cornelia M.; Newton-Cheh, Christopher

    2011-01-01

    The prevalence of hypertension in African Americans (AAs) is higher than in other US groups; yet, few have performed genome-wide association studies (GWASs) in AA. Among people of European descent, GWASs have identified genetic variants at 13 loci that are associated with blood pressure. It is unknown if these variants confer susceptibility in people of African ancestry. Here, we examined genome-wide and candidate gene associations with systolic blood pressure (SBP) and diastolic blood pressure (DBP) using the Candidate Gene Association Resource (CARe) consortium consisting of 8591 AAs. Genotypes included genome-wide single-nucleotide polymorphism (SNP) data utilizing the Affymetrix 6.0 array with imputation to 2.5 million HapMap SNPs and candidate gene SNP data utilizing a 50K cardiovascular gene-centric array (ITMAT-Broad-CARe [IBC] array). For Affymetrix data, the strongest signal for DBP was rs10474346 (P= 3.6 × 10−8) located near GPR98 and ARRDC3. For SBP, the strongest signal was rs2258119 in C21orf91 (P= 4.7 × 10−8). The top IBC association for SBP was rs2012318 (P= 6.4 × 10−6) near SLC25A42 and for DBP was rs2523586 (P= 1.3 × 10−6) near HLA-B. None of the top variants replicated in additional AA (n = 11 882) or European-American (n = 69 899) cohorts. We replicated previously reported European-American blood pressure SNPs in our AA samples (SH2B3, P= 0.009; TBX3-TBX5, P= 0.03; and CSK-ULK3, P= 0.0004). These genetic loci represent the best evidence of genetic influences on SBP and DBP in AAs to date. More broadly, this work supports that notion that blood pressure among AAs is a trait with genetic underpinnings but also with significant complexity. PMID:21378095

  6. Role of twins in variations in the conductivity characteristics of single-crystal HoBa2Cu3O7-δ during reversible changes in hydrostatic pressure

    NASA Astrophysics Data System (ADS)

    Khadzhai, G. Ya.; Nazyrov, Z. F.; Vovk, R. V.

    2016-09-01

    The in-plane electrical resistivity of single-crystal HoBa2Cu3O7-δ (Tc = 62-66 K) is studied at temperatures Tc-300 K under conditions such that the measurement current flows parallel to twins or at an angle of 45° to them during reversible changes in hydrostatic pressure. The variations in Tc, in the parameters of the Bloch-Grueneisen equations, and in the parameters of the Aslamasov-Larkin model for fluctuation conductivity are analyzed. Application of a pressure facilitates the formation of a second phase with lower Tc that shows up more clearly when the measurement current flows across the twinning plane. In this case, the transverse coherence length and the interval within which the fluctuation conductivity exists are smaller than in the first configuration. The relaxation of the parameters characterizing the scatting of charge carriers on phonons and defects is related to the redistribution of oxygen between the two phases.

  7. Seasonal variation in blood pressure and its relationship with outdoor temperature in 10 diverse regions of China: the China Kadoorie Biobank

    PubMed Central

    LEWINGTON, Sarah; LI, LiMing; SHERLIKER, Paul; GUO, Yu; MILLWOOD, Iona; BIAN, Zheng; WHITLOCK, Gary; YANG, Ling; COLLINS, Rory; CHEN, Junshi; WU, Xianping; WANG, Shaojie; HU, Yihe; JIANG, Li; YANG, Liqiu; LACEY, Ben; PETO, Richard; CHEN, Zhengming

    2015-01-01

    Objectives Mean blood pressure varies moderately with outdoor air temperature in many Western populations. Substantial uncertainty exists, however, about the strength of the relationship in other populations, and the relevance to it of age, adiposity, medical treatment, climate and housing conditions. Methods To investigate the relationship of blood pressure with season and outdoor temperature, we analysed cross-sectional data from the China Kadoorie Biobank study of 506 673 adults aged 30-79 recruited from ten diverse urban and rural regions in China. Analyses related mean blood pressure – overall and in various subgroups – to mean local outdoor temperature. Results The mean difference in systolic blood pressure (SBP) between summer (June-August) and winter (December-February) was 10 mmHg overall, and was more extreme, on average, in rural than in urban areas (12 vs. 8 mmHg; p for interaction<0.0001). Above 5°C, SBP was strongly inversely associated with outdoor temperature in all ten areas studied, with 5.7 (SE 0.04) mmHg higher SBP per 10°C lower outdoor temperature. The association was stronger in older people and in those with lower body mass index. At lower temperatures there was no evidence of an association among participants who reported having home central heating. Conclusions Blood pressure was strongly inversely associated with outdoor temperature in Chinese adults across a range of climatic conditions, although access to home central heating appeared to remove much of the association during the winter months. Seasonal variation in blood pressure should be considered in the clinical management of hypertension. PMID:22688260

  8. Diagnosis Accuracy of Mean Arterial Pressure Variation during a Lung Recruitment Maneuver to Predict Fluid Responsiveness in Thoracic Surgery with One-Lung Ventilation

    PubMed Central

    Kang, Woon-Seok; Oh, Chung-Sik; Park, Chulmin; Shin, Bo Mi; Yoon, Tae-Gyoon; Rhee, Ka-Young; Woo, Nam-Sik

    2016-01-01

    Background. Lung recruitment maneuver (LRM) during thoracic surgery can reduce systemic venous return and resulting drop in systemic blood pressure depends on the patient's fluid status. We hypothesized that changes in systemic blood pressure during the transition in LRM from one-lung ventilation (OLV) to two-lung ventilation (TLV) may provide an index to predict fluid responsiveness. Methods. Hemodynamic parameters were measured before LRM (T0); after LRM at the time of the lowest mean arterial blood pressure (MAP) (T1) and at 3 minutes (T2); before fluid administration (T3); and 5 minutes after ending it (T4). If the stroke volume index increased by >25% following 10 mL/kg colloid administration for 30 minutes, then the patients were assigned to responder group. Results. Changes in MAP, central venous pressure (CVP), and stroke volume variation (SVV) between T0 and T1 were significantly larger in responders. Areas under the curve for change in MAP, CVP, and SVV were 0.852, 0.759, and 0.820, respectively; the optimal threshold values for distinguishment of responders were 9.5 mmHg, 0.5 mmHg, and 3.5%, respectively. Conclusions. The change in the MAP associated with LRM at the OLV to TLV conversion appears to be a useful indicator of fluid responsiveness after thoracic surgery. Trial Registration. This trial is registered at Clinical Research Information Service with KCT0000774. PMID:27819002

  9. Measurement and Analysis of the Periodic Variation of Total Pressure in an Axial-Flow Compressor Stage.

    DTIC Science & Technology

    1980-11-01

    interaction has been established through the work of Meyer (1958), Lefcort (1965), Smith (1966), Kerrebrock and Mikolajczak (1970), Brandone and...pressure side of a chopping blade can also be seen in terms of a so- called "slip velocity" (Kerrebrock and Mikolajczak (1970)) as demon- strated in the... Mikolajczak (1970). They used this wake transport model to explain the shape of measured transonic compressor stator exit stagnation-temperature profiles

  10. Variations in Alveolar Partial Pressure for Carbon Dioxide and Oxygen Have Additive Not Synergistic Acute Effects on Human Pulmonary Vasoconstriction

    PubMed Central

    Croft, Quentin P. P.; Formenti, Federico; Talbot, Nick P.; Lunn, Daniel; Robbins, Peter A.; Dorrington, Keith L.

    2013-01-01

    The human pulmonary vasculature constricts in response to hypercapnia and hypoxia, with important consequences for homeostasis and adaptation. One function of these responses is to direct blood flow away from poorly-ventilated regions of the lung. In humans it is not known whether the stimuli of hypercapnia and hypoxia constrict the pulmonary blood vessels independently of each other or whether they act synergistically, such that the combination of hypercapnia and hypoxia is more effective than the sum of the responses to each stimulus on its own. We independently controlled the alveolar partial pressures of carbon dioxide (Paco2) and oxygen (Pao2) to examine their possible interaction on human pulmonary vasoconstriction. Nine volunteers each experienced sixteen possible combinations of four levels of Paco2 (+6, +1, −4 and −9 mmHg, relative to baseline) with four levels of Pao2 (175, 100, 75 and 50 mmHg). During each of these sixteen protocols Doppler echocardiography was used to evaluate cardiac output and systolic tricuspid pressure gradient, an index of pulmonary vasoconstriction. The degree of constriction varied linearly with both Paco2 and the calculated haemoglobin oxygen desaturation (1-So2). Mixed effects modelling delivered coefficients defining the interdependence of cardiac output, systolic tricuspid pressure gradient, ventilation, Paco2 and So2. No interaction was observed in the effects on pulmonary vasoconstriction of carbon dioxide and oxygen (p>0.64). Direct effects of the alveolar gases on systolic tricuspid pressure gradient greatly exceeded indirect effects arising from concurrent changes in cardiac output. PMID:23935847

  11. Large variation of magnetic properties of amorphous Fe–Zr thin films with Ar pressure during sputtering

    NASA Astrophysics Data System (ADS)

    Kim, Miri; Sung, Nark-Eon; Lim, Sang Ho

    2017-01-01

    A large change is observed in the magnetic properties of amorphous Fe–Zr thin films sputtered at different Ar pressures. The change depends on the composition of the alloys and at compositions near 60 at.% Fe, for example, the magnetisation measured at 10 kOe increases 30-fold with an increase in the Ar pressure from 2 to 10 mTorr. The magnetic properties are well explained by a combination of two phenomena—superparamagnetism and spin glass behaviours—and the large change is partly related to the number density of a magnetically correlated region. Examinations of the microstructure by X-ray diffraction, transmission electron microscopy, and X-ray absorption fine structure spectroscopy reveal no appreciable difference in it as a function of the Ar pressure. This indicates that even a very slight change in the microstructure can greatly affect the magnetic properties of amorphous Fe–Zr thin films, thereby opening up the possibility of employing the magnetic properties of amorphous alloys for the characterisation of amorphous microstructures.

  12. Large variation of magnetic properties of amorphous Fe–Zr thin films with Ar pressure during sputtering

    PubMed Central

    Kim, Miri; Sung, Nark-Eon; Lim, Sang Ho

    2017-01-01

    A large change is observed in the magnetic properties of amorphous Fe–Zr thin films sputtered at different Ar pressures. The change depends on the composition of the alloys and at compositions near 60 at.% Fe, for example, the magnetisation measured at 10 kOe increases 30-fold with an increase in the Ar pressure from 2 to 10 mTorr. The magnetic properties are well explained by a combination of two phenomena—superparamagnetism and spin glass behaviours—and the large change is partly related to the number density of a magnetically correlated region. Examinations of the microstructure by X-ray diffraction, transmission electron microscopy, and X-ray absorption fine structure spectroscopy reveal no appreciable difference in it as a function of the Ar pressure. This indicates that even a very slight change in the microstructure can greatly affect the magnetic properties of amorphous Fe–Zr thin films, thereby opening up the possibility of employing the magnetic properties of amorphous alloys for the characterisation of amorphous microstructures. PMID:28139773

  13. The sensitivity of physical and spectral properties of silica glass to variations of interatomic potentials under high pressure

    NASA Astrophysics Data System (ADS)

    Rustad, James R.; Yuen, David A.; Spera, Frank J.

    We have investigated with molecular dynamics various aspects of the structure and vibrational properties of silica glass at a temperature near 330 K to pressures of 40 GPa for three sets of interatomic potentials using 1500 atoms. The potentials were chosen from previous works. Only one of these potentials shows a transition from tetrahedral silicon coordination to octahedral silicon coordination. For this potential the percentage of five-fold coordinated silicon increases from 12% at 10 GPa to 35% at 15 GPa. The geometry of the five-coordinated complexes is that of a distorted pyramid with the silicon situated at the base, or, equivalently, it is an octahedron with one vertex missing. The shape of the OSiO distribution for the five-fold-coordinated complex is similar for all three potentials, but they are present in lesser amounts in the two which do not show the tetrahedral to octahedral transition. In the potential that shows the transition the distribution of SiOSi angles is bimodal at pressures above 30 GPa, coinciding with large populations of two-silicon rings. Analysis of the density of states reveals that two of the potentials give enhanced contributions from the frequencies in the 800-900 cm -1 range which agrees with in situ infrared spectroscopic studies of silica glass. The major effect of pressure on the velocity autocorrelation function is to increase the amount of negatively correlated motion for silicon atoms during the approach to the first maximum.

  14. Common variation in with no-lysine kinase 1 (WNK1) and blood pressure responses to dietary sodium or potassium interventions- family-based association study.

    PubMed

    Liu, Fuqiang; Zheng, Shuhui; Mu, Jianjun; Chu, Chao; Wang, Lan; Wang, Yang; Xiao, Hongyu; Wang, Dan; Cao, Yu; Ren, Keyu; Liu, Enqi; Yuan, Zuyi

    2013-01-01

    Common variations in the gene with no-lysine kinase 1 (WNK1) are associated with hypertension, but because of gene-environment interaction, it is difficult to fully identify the genetic contribution of WNK1 gene polymorphism to blood pressure (BP) variability. The aim of this study was to identify the effect of common WNK1 variants on the shift of BP during strict dietary interventions of salt or potassium intake. A total of 342 subjects from 126 families were selected and sequentially maintained on normal diet for 3 days at baseline, a low-salt diet for 7 days (3g/day, NaCl), then a high-salt diet for 7 days (18 g/day), and high-salt diet with potassium supplementation for another 7 days (4.5 g/day, KCl). Five single nucleotide polymorphisms (SNPs) were selected from the WNK1 gene. rs880054 and rs12828016 were associated with diastolic BP (DBP) response during the low-or high-sodium intervention, and rs2301880 was significantly associated with systolic BP, DBP and mean arterial pressure responses to the high-sodium intervention (all P<0.05). Unfortunately, no associations for WNK1 SNPs and the constructed haplotype blocks of WNK1 with BP responses to high-salt-and-potassium supplement intervention reached nominal statistical significance. The WNK1 gene might be mechanistically involved in the variation in BP response to dietary sodium and potassium intake among individuals, and might contribute to the variation of this complex phenotype.

  15. Temporal variation of the arterial pressure in healthy young people and its relation to geomagnetic activity in Mexico

    NASA Astrophysics Data System (ADS)

    Azcárate, T.; Mendoza, B.; Sánchez de la Peña, S.; Martínez, J. L.

    2012-11-01

    We present a study of the temporal behavior of the systolic (SBP) and diastolic (DBP) blood pressure for a sample of 51 normotensive, healthy volunteers, 18 men and 33 women with an average age of 19 years old in Mexico City, Mexico, during April and May, 2008. We divided the data by sex along the circadian rhythm. Three geomagnetic storms occurred during the studied time-span. The strongest one, a moderate storm, is attributed to a coronal hole border that reached the Earth. The ANOVA test applied to the strongest storm showed that even though we are dealing with a moderate geomagnetic storm, there are statistically significant responses of the blood pressure. The superposed epoch analysis during a three-day window around the strongest storm shows that on average the largest changes occurred for the SBP. Moreover, the SBP largest increases occurred two days before and one day after this storm, and women are the most sensitive group as they present larger SBP and DBP average changes than men. Finally, given the small size of the sample, we cannot generalize our results.

  16. Meta-analysis of genome-wide association studies identifies common variants associated with blood pressure variation in East Asians

    PubMed Central

    Kato, Norihiro; Takeuchi, Fumihiko; Tabara, Yasuharu; Kelly, Tanika N.; Go, Min Jin; Sim, Xueling; Tay, Wan Ting; Chen, Chien-Hsiun; Zhang, Yi; Yamamoto, Ken; Katsuya, Tomohiro; Yokota, Mitsuhiro; Kim, Young Jin; Ong, Rick Twee Hee; Nabika, Toru; Gu, Dongfeng; Chang, Li-ching; Kokubo, Yoshihiro; Huang, Wei; Ohnaka, Keizo; Yamori, Yukio; Nakashima, Eitaro; Jaquish, Cashell E.; Lee, Jong-Young; Seielstad, Mark; Isono, Masato; Hixson, James E.; Chen, Yuan-Tsong; Miki, Tetsuro; Zhang, Xuegong; Sugiyama, Takao; Jeon, Jae-Pil; Liu, Jian Jun; Takayanagi, Ryoichi; Kim, Sung Soo; Aung, Tin; Sung, Yun Ju; Zhou, Xueya; Wong, Tien Yin; Han, Bok-Ghee; Kobayashi, Shotai; Ogihara, Toshio; Zhu, Dingliang; Iwai, Naoharu; Wu, Jer-Yuarn; Teo, Yik Ying; Tai, E Shyong; Cho, Yoon Shin; He, Jiang

    2011-01-01

    We conducted a meta-analysis of genome-wide association studies of systolic (SBP) and diastolic (DBP) blood pressure in 19,608 subjects of East Asian ancestry from the AGEN-BP consortium followed by de novo genotypingin 2 stages of replication involving 10,518 and 20,247 East Asian samples. We identified novel genome-wide significant (P < 5 × 10−8) associations between SBP or DBP and variants at four novel loci: ST7L-CAPZA1, FIGN-GRB14, ENPEP, and NPR3, as well as a novel variant near TBX3. Except for NPR3, all novel findings were significantly replicated for SBP or DBP in independent samples. Sevenloci previously reported in populations of European descent were confirmed. On 12q24.13, we observed an ethnic specific association(implicating rs671 at the ALDH2 locus as the causal variant) that affected SBP, DBP and multiple traits related to coronary artery disease. These findings provide novel insights into blood pressure regulation and potential targets for intervention. PMID:21572416

  17. Mass-induced sea level variations in the Red Sea from steric-corrected altimetry, GRACE, in-situ bottom pressure records, and hydrographic observations

    NASA Astrophysics Data System (ADS)

    Feng, Wei; Lemoine, Jean-Michel; Zhong, Min; Xu, Houze

    2014-05-01

    An annual amplitude of ~18 cm mass-induced sea level variations (SLV) in the Red Sea is detected from steric-corrected altimetry and the Gravity Recovery and Climate Experiment (GRACE) satellites from 2003 to 2011, which dominates the mean sea level in the region. Seawater mass variations here generally reach maximum in late January/early February. The steric component of SLV calculated from oceanographic temperature and salinity data is relatively small and peaks about seven months later than mass variations. The phase difference between the steric SLV and the mass-induced SLV indicates that when the Red Sea gains the mass from inflow water in winter, the steric SLV fall, and vice versa in summer. In-situ bottom pressure records in the eastern coast of the Red Sea validate the high mass variability observed by steric-corrected altimetry and GRACE. Furthermore, we compare the horizontal water mass flux in the Red Sea from steric-corrected altimetry and GRACE with that estimated from hydrographic observations.

  18. Study of growth rate and composition variations in metalorganic vapour phase selective area epitaxy at atmospheric pressure and application to the growth of strained layer DBR lasers

    NASA Astrophysics Data System (ADS)

    Silvestre, L.; Ougazzaden, A.; Delprat, D.; Ramdane, A.; Daguet, C.; Patriarche, G.

    1997-01-01

    In selective area epitaxy (SAE), a lateral variation of thickness accompanied by a variation of composition occurs because of the presence of dielectric masks on the substrate surface. To take advantage of these behaviours for monolithic integration of electronic devices, a good control of growth rate and composition is necessary. For this aim, different bulk materials InP, InGaAs and InGaAsP have been systematically investigated as a function of the geometry of dielectric masks specially designed for this work. All growths were performed by metalorganic vapour phase epitaxy (MOVPE) at atmospheric pressure. An estimation of growth rate enhancement and composition variation between the open regions in dielectric masks and the unmasked region has been established, allowing the choice of specific mask geometry for each application. Following this study, a strained multiple quantum well (MQW) structure for a distributed Bragg reflector (DBR) laser has been selectively grown. The standard buried ridge structure (BRS) processed presents good characteristics (8 mA threshold current) and we obtained a 7 nm tuning range with a ridge structure, which constitutes the best value reported with SAE.

  19. Study of the Effect of Water Pressure on Plasma and Cavitation Bubble Induced by Pulsed Laser Ablation in Liquid of Silver and Missed Variations of Observable Nanoparticle Features.

    PubMed

    Dell'Aglio, Marcella; Santagata, Antonio; Valenza, Gabriele; De Stradis, Angelo; De Giacomo, Alessandro

    2017-05-05

    In this work the effects of the pressure between 1-150 Bar on pulsed laser ablation in liquids (PLAL) during the production of silver nanoparticles (AgNPs) in water was investigated. The produced NPs are the results of two different well-known stages which are the plasma and the bubble evolution occurring until the generated material is released into the solution. The main aim of this work is to show which roles is played by the variation of water pressure on the laser induced plasma and the cavitation bubble dynamics during the NPs formation. Their implication on the comprehension of the as-produced NPs formation mechanisms is treated. The typical timescales of the different stages occurring in water at different pressures have been studied by optical emission spectroscopy (OES), imaging and shadowgraph experiments. Finally surface plasmon resonance (SPR) spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS) and scanning electron microscopy (SEM) for characterization of the material released in solution, have been used. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Variations in aortic pressure affect the mechanics of the intra-aortic balloon: an in vitro investigation.

    PubMed

    Biglino, Giovanni; Kolyva, Christina; Whitehorne, Michael; Pepper, John R; Khir, Ashraf W

    2010-07-01

    This study aims to investigate the mechanics of the intra-aortic balloon (IAB) under different aortic pressure (P(ao)) and inclination (0-75 degrees). Pressure and flow were measured in an artificial aorta during IAB pumping with a frequency of 1:3. Volume displaced toward the "coronary arteries" during inflation (V(prox)) and "intra-aortic" pressure reduction during deflation (P(r)) were derived. IAB duration of inflation and deflation was determined with a high-speed camera visualization. When the aorta was horizontal, P(ao) raised from 45 mm Hg to 115 mm Hg, V(prox) reduced by 18% (25.0 +/- 1.0 mL vs. 30.4 +/- 1.9 mL) and P(r) increased by 117% (106.4 +/- 0.3 mm Hg vs. 48.9 +/- 0.6 mm Hg). When the aorta was inclined, at low P(ao) of 45 mm Hg, V(prox) was reduced by 30% from 0 degrees to 45 degrees (19.8 +/- 2.3 mL vs. 28.3 +/- 1.7 mL) and P(r) was reduced by 66% (16.5 +/- 0.1 mm Hg vs. 48.9 +/- 0.6 mm Hg). However, at high P(ao) of 115 mm Hg, V(prox) remained unchanged with increasing angle (20.0 +/- 1.0 mL) and P(r) was reduced by 24% (80.6 +/- 0.8 mm Hg vs. 106.4 +/- 0.3 mm Hg). Increasing P(ao) increased duration of inflation. At low P(ao), increasing angle resulted in increasing duration of inflation, but at high P(ao), increasing angle had the opposite effect. Duration of deflation generally decreased with P(ao) and increased with increasing angle. The IAB pump is affected by both P(ao) and angle, indicating that non-normotensive patients or patients in the semi-recumbent position might not receive the full benefits of IAB counterpulsation.

  1. Negating the Yearly Eccentricity Magnitude Variation of Super-synchronous Disposal Orbits due to Solar Radiation Pressure

    NASA Astrophysics Data System (ADS)

    Jones, S. L.

    Solar radiation pressure alters satellites' eccentricity by accelerating and decelerating them during each orbit. The accumulated perturbation cancels yearly for geostationary satellites, but meanwhile the perigee radius changes. Disposed satellites must be reorbited higher to compensate, using more fuel. The examined disposal orbit points toward the Sun and uses the satellite's natural eccentricity. This causes the eccentricity vector to only change direction, keeping the perigee radius constant. This thesis verifies this behavior over one year with an analytical derivation and MATLAB simulation, gaining useful insights into its cause. The traditional and proposed disposal orbits are then modeled using NASA's GMAT for more realistic simulations. The proposed orbit's sensitivity to satellite and initialization errors is also examined. Relationships are developed to show these errors' effect on the perigee radius. In conclusion, while this orbit can be used in the short term, margins are necessary to guarantee protection of the geostationary belt.

  2. Expected improvements in determining continental hydrology, ice mass variations, ocean bottom pressure signals, and earthquakes using two pairs of dedicated satellites for temporal gravity recovery

    NASA Astrophysics Data System (ADS)

    Wiese, David N.; Nerem, Robert S.; Han, Shin-Chan

    2011-11-01

    The Gravity Recovery and Climate Experiment mission has demonstrated the ability to quantify global mass variations at large spatial scales with monthly to sub-monthly temporal resolution. Future missions of this type taking advantage of improved measurement technologies will be limited by temporal aliasing errors. We suggest the addition of a second pair of satellites to reduce these errors. Using an optimized mission architecture consisting of a polar pair of satellites coupled with a lower inclined pair of satellites (72°), both in 13-day repeating orbits, we quantify the expected scientific improvements that having two pairs of satellites will provide over one pair. Numerical simulations to spherical harmonic degree 100 are run over one full year. Analysis using empirical orthogonal functions reveals that two satellite pairs determine annual mass variations in small basins which are undetected using one pair of satellites. Averaging kernels are used to show that two satellite pairs offer an 80% reduction in the level of error in determining mass variations in 53 hydrological basins and 12 Greenland basins over the year. After standard GRACE post-processing techniques have been applied to the one-pair solutions, it is seen that two satellite pairs (with no post-processing) still offer a 25%-75% improvement in determining the mass variations. Spatiospectral localization analysis is used to show increased spatial resolution and higher signal-to-noise ratios in recovering hydrology in the Amazon River basin, ocean bottom pressure signals in the Southeast Pacific basin, and a simulated earthquake signal representative of the 2010 Maule, Chile earthquake.

  3. Modification of a variational objective analysis model for new equations for pressure gradient and vertical velocity in the lower troposphere and for spatial resolution and accuracy of satellite data

    NASA Technical Reports Server (NTRS)

    Achtemeier, G. L.

    1986-01-01

    Since late 1982 NASA has supported research to develop a numerical variational model for the diagnostic assimilation of conventional and space-based meteorological data. In order to analyze the model components, four variational models are defined dividing the problem naturally according to increasing complexity. The first of these variational models (MODEL I), the subject of this report, contains the two nonlinear horizontal momentum equations, the integrated continuity equation, and the hydrostatic equation. This report summarizes the results of research (1) to improve the way the large nonmeteorological parts of the pressure gradient force are partitioned between the two terms of the pressure gradient force terms of the horizontal momentum equations, (2) to generalize the integrated continuity equation to account for variable pressure thickness over elevated terrain, and (3) to introduce horizontal variation in the precision modulus weights for the observations.

  4. Assessment of Human Tribbles Homolog 3 Genetic Variation (rs2295490) Effects on Type 2 Diabetes Patients with Glucose Control and Blood Pressure Lowering Treatment.

    PubMed

    He, Fazhong; Liu, Mouze; Chen, Zhangren; Liu, Guojing; Wang, Zhenmin; Liu, Rong; Luo, Jianquan; Tang, Jie; Wang, Xingyu; Liu, Xin; Zhou, Honghao; Chen, Xiaoping; Liu, Zhaoqian; Zhang, Wei

    2016-11-01

    Effects of human tribbles homolog 3 (TRIB3) genetic variation (c.251 A>G, Gln84Arg, rs2295490) on the clinical outcomes of vascular events has not been evaluated in patients with type 2 diabetes after blood pressure lowering and glucose controlling treatment. We did an analysis of a 2×2 factorial (glucose control axis and blood pressure lowering axis) randomized controlled clinical trial at 61 centers in China, with a follow-up period of 5years. The major vascular endpoints were the composites of death from cardio-cerebral vascular diseases, non-fatal stroke and myocardial infraction, new or worsening renal and diabetic eye disease. A total of 1884 participants were included in our research with a 4.8years median follow-up. For glucose lowering axis, patients with TRIB3 (rs2295490) AA (n=609) genotype exhibited significantly reduced risk of major vascular events compared with AG+GG (n=335) genotype carriers (Hazard ratio 0.72, 95% CI 0.55-0.94, p=0.016), Paradoxically, the risk of vascular events were significantly increased in patients with AA (n=621) compared to AG+GG (n=319) genotype for intensive glucose control (Hazard ratio 1.46, 95% CI, 1.06-2.17, 35 p=0.018). For blood pressure lowering axis, marginally significant difference was found between TRIB3 variant and coronary events. Our findings suggest that good glucose and blood pressure control exhibited greater benefits on vascular outcomes in patients with TRIB3 (rs2295490) G allele.

  5. Strength variation and deformational behavior in anisotropic granitic mylonites under high-temperature and -pressure conditions - An experimental study

    NASA Astrophysics Data System (ADS)

    Liu, Gui; Zhou, Yongsheng; Shi, Yaolin; Miao, Sheqiang; He, Changrong

    2017-03-01

    We performed deformation experiments on foliated granitic mylonites under high-temperature and -pressure conditions. To investigate the effects of pre-existing fabric properties on the rheology of the rocks, these experiments were carried out at different compression directions 30°, 45°, and 60° relative to the foliation, at temperatures of 600-850 °C, under confining pressures of 800-1200 MPa, within a strain rate range of 1 × 10-4/S - 2.5 × 10-6/S. The results of the experiments show that the deformation of three group samples is in the semi-brittle region at temperatures between 600 and 700 °C, and that the deformation of the samples transforms to plastic deformation by power-law creep with the stress exponent n = 3 ± 0.3 at temperatures between 800 and 850 °C. In the semi-brittle region, the mechanical data show that strength reaches its minimum value at an angle of 30° between the compression direction and the original foliation. In the plastic deformation regime, strength reaches its minimum value at an angle of 45° between the foliation and the orientation of the maximum principal stress. The strength with angles between 30° and 60° is lower than that of the compression direction perpendicular to foliation and the compression direction parallel to foliation. Microstructure analysis based on optical and electron microscopy of the deformation microstructures showed plastic deformation of aggregates of biotite and quartz at 800-850 °C. This deformation was extensive and formed new foliation. Quartz c-axis fabrics analysis by EBSD show that at temperatures of 600-700 °C, the c-axis fabric patterns could have been formed by the dominant activity of basal slip, similar with the starting granitic mylonite samples, but the dominant slip systems have been changed and transformed from basal slip to rhomb slip and prism slip at temperature of 800 °C and 850 °C. Microfractures were developed in hornblende and feldspar grains with local

  6. A molecular dynamics study of ambient and high pressure phases of silica: Structure and enthalpy variation with molar volume

    NASA Astrophysics Data System (ADS)

    Rajappa, Chitra; Sringeri, S. Bhuvaneshwari; Subramanian, Yashonath; Gopalakrishnan, J.

    2014-06-01

    Extensive molecular dynamics studies of 13 different silica polymorphs are reported in the isothermal-isobaric ensemble with the Parrinello-Rahman variable shape simulation cell. The van Beest-Kramer-van Santen (BKS) potential is shown to predict lattice parameters for most phases within 2%-3% accuracy, as well as the relative stabilities of different polymorphs in agreement with experiment. Enthalpies of high-density polymorphs - CaCl2-type, α-PbO2-type, and pyrite-type - for which no experimental data are available as yet, are predicted here. Further, the calculated enthalpies exhibit two distinct regimes as a function of molar volume—for low and medium-density polymorphs, it is almost independent of volume, while for high-pressure phases a steep dependence is seen. A detailed analysis indicates that the increased short-range contributions to enthalpy in the high-density phases arise not only from an increased coordination number of silicon but also shorter Si-O bond lengths. Our results indicate that amorphous phases of silica exhibit better optimization of short-range interactions than crystalline phases at the same density while the magnitude of Coulombic contributions is lower in the amorphous phase.

  7. A molecular dynamics study of ambient and high pressure phases of silica: structure and enthalpy variation with molar volume.

    PubMed

    Rajappa, Chitra; Sringeri, S Bhuvaneshwari; Subramanian, Yashonath; Gopalakrishnan, J

    2014-06-28

    Extensive molecular dynamics studies of 13 different silica polymorphs are reported in the isothermal-isobaric ensemble with the Parrinello-Rahman variable shape simulation cell. The van Beest-Kramer-van Santen (BKS) potential is shown to predict lattice parameters for most phases within 2%-3% accuracy, as well as the relative stabilities of different polymorphs in agreement with experiment. Enthalpies of high-density polymorphs - CaCl2-type, α-PbO2-type, and pyrite-type - for which no experimental data are available as yet, are predicted here. Further, the calculated enthalpies exhibit two distinct regimes as a function of molar volume-for low and medium-density polymorphs, it is almost independent of volume, while for high-pressure phases a steep dependence is seen. A detailed analysis indicates that the increased short-range contributions to enthalpy in the high-density phases arise not only from an increased coordination number of silicon but also shorter Si-O bond lengths. Our results indicate that amorphous phases of silica exhibit better optimization of short-range interactions than crystalline phases at the same density while the magnitude of Coulombic contributions is lower in the amorphous phase.

  8. Tomographic inverse estimation of aquifer properties based on pressure variations caused by transient water-supply pumping

    NASA Astrophysics Data System (ADS)

    Vesselinov, V. V.; Harp, D. R.; Koch, R. J.; Birdsell, K. H.

    2008-12-01

    Groundwater pumping of water-supply wells frequently exhibits substantial temporal and spatial variability. Wells are typically operated periodically (on daily and seasonal temporal scales), and the total production is controlled by the water-supply demand,. The pumping causes temporal and spatial variability in the water levels around the pumping wells. During the wellfield operation, water-level data are collected from the production and nearby observation wells. Water level fluctuations are a result of the manner in which the pumping is conducted, aquifer heterogeneity, and variations in other influences such as recharge, poroelastic effects, etc. The variability in aquifer stresses due to pumping can provide valuable information about aquifer properties. The supply-well pumping can be viewed as a single prolonged pumping test extending over multiple pumping cycles and including multiple pumping and observation wells. Here we discuss water level and pumping production data acquired during water-supply production from the regional aquifer at Los Alamos, New Mexico. We have performed extensive interpretation of the data using analytical and numerical techniques. The analytical techniques are applied to provide (1) initial screening of the data for measurement errors, (2) identification of correlations between the pumping and water-level variability, and (3) estimation of the large-scale properties of the aquifer. The numerical models are applied to characterize the spatial heterogeneity of the aquifer using an approach based on tomographic inverse analysis. Our results demonstrate that there are large-scale features in the aquifer that appear to control the spatial propagation of transient pumping effects. The identified aquifer heterogeneities were not previously recognized and are expected to have important effects on the potential migration of contaminants in the regional aquifer.

  9. Variation in predation pressure as a mechanism underlying differences in numerical abundance between populations of the poeciliid fish Heterandria formosa

    USGS Publications Warehouse

    Richardson, J.M.L.; Gunzburger, M.S.; Travis, J.

    2006-01-01

    We explored whether a variation in predation and habitat complexity between conspecific populations can drive qualitatively different numerical dynamics in those populations. We considered two disjunct populations of the least killifish, Heterandria formosa, that exhibit long-term differences in density, top fish predator species, and dominant aquatic vegetation. Monthly censuses over a 3-year period found that in the higher density population, changes in H. formosa density exhibited a strong negative autocorrelation structure: increases (decreases) at one census tended to be followed by decreases (increases) at the next one. However, no such correlation was present in the lower density population. Monthly census data also revealed that predators, especially Lepomis sp., were considerably more abundant at the site with lower H. formosa densities. Experimental studies showed that the predation by Lepomis gulosus occurred at a much higher rate than predation by two other fish and two dragonfly species, although L. gulosus and L. punctatus had similar predation rates when the amount of vegetative cover was high. The most effective predator, L. gulosus, did not discriminate among life stages (males, females, and juveniles) of H. formosa. Increased predation rates by L. gulosus could keep H. formosa low in one population, thereby eliminating strong negative density-dependent regulation. In support of this, changes in H. formosa density were positively correlated with changes in vegetative cover for the population with a history of lower density, but not for the population with a history of higher density. Our results are consistent with the hypothesis that the observed differences among natural populations in numerical abundance and dynamics are caused in part by the differences in habitat complexity and the predator community. ?? Springer-Verlag 2005.

  10. Cortical Response Variation with Different Sound Pressure Levels: A Combined Event-Related Potentials and fMRI Study

    PubMed Central

    Arrubla, Jorge; Warbrick, Tracy; Hitz, Konrad; Wyss, Christine; Boers, Frank; Shah, N. Jon

    2014-01-01

    Introduction Simultaneous recording of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) provides high spatial and temporal resolution. In this study we combined EEG and fMRI to investigate the structures involved in the processing of different sound pressure levels (SPLs). Methods EEG data were recorded simultaneously with fMRI from 16 healthy volunteers using MR compatible devices at 3 T. Tones with different SPLs were delivered to the volunteers and the N1/P2 amplitudes were included as covariates in the fMRI data analysis in order to compare the structures activated with high and low SPLs. Analysis of variance (ANOVA) and ROI analysis were also performed. Additionally, source localisation analysis was performed on the EEG data. Results The integration of averaged ERP parameters into the fMRI analysis showed an extended map of areas exhibiting covariation with the BOLD signal related to the auditory stimuli. The ANOVA and ROI analyses also revealed additional brain areas other than the primary auditory cortex (PAC) which were active with the auditory stimulation at different SPLs. The source localisation analyses showed additional sources apart from the PAC which were active with the high SPLs. Discussion The PAC and the insula play an important role in the processing of different SPLs. In the fMRI analysis, additional activation was found in the anterior cingulate cortex, opercular and orbito-frontal cortices with high SPLs. A strong response of the visual cortex was also found with the high SPLs, suggesting the presence of cross-modal effects. PMID:25279457

  11. Cortical response variation with different sound pressure levels: a combined event-related potentials and FMRI study.

    PubMed

    Neuner, Irene; Kawohl, Wolfram; Arrubla, Jorge; Warbrick, Tracy; Hitz, Konrad; Wyss, Christine; Boers, Frank; Shah, N Jon

    2014-01-01

    Simultaneous recording of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) provides high spatial and temporal resolution. In this study we combined EEG and fMRI to investigate the structures involved in the processing of different sound pressure levels (SPLs). EEG data were recorded simultaneously with fMRI from 16 healthy volunteers using MR compatible devices at 3 T. Tones with different SPLs were delivered to the volunteers and the N1/P2 amplitudes were included as covariates in the fMRI data analysis in order to compare the structures activated with high and low SPLs. Analysis of variance (ANOVA) and ROI analysis were also performed. Additionally, source localisation analysis was performed on the EEG data. The integration of averaged ERP parameters into the fMRI analysis showed an extended map of areas exhibiting covariation with the BOLD signal related to the auditory stimuli. The ANOVA and ROI analyses also revealed additional brain areas other than the primary auditory cortex (PAC) which were active with the auditory stimulation at different SPLs. The source localisation analyses showed additional sources apart from the PAC which were active with the high SPLs. The PAC and the insula play an important role in the processing of different SPLs. In the fMRI analysis, additional activation was found in the anterior cingulate cortex, opercular and orbito-frontal cortices with high SPLs. A strong response of the visual cortex was also found with the high SPLs, suggesting the presence of cross-modal effects.

  12. Facility-level variation in diabetes and blood pressure control in patients with diabetes: Findings from the Veterans Affairs national database.

    PubMed

    Rehman, Hasan; Akeroyd, Julia M; Ramsey, David; Ahmed, Sarah T; Merchant, Anwar T; Navaneethan, Sankar D; Petersen, Laura A; Virani, Salim S

    2017-08-25

    Intensive glycemic and blood pressure (BP) control in diabetic patients is associated with improved cardiovascular outcomes. We hypothesized that there is suboptimal glycemic and BP control with significant facility-level variation in patients with diabetes. We identified patients with diabetes receiving care in 130 facilities in the Veterans Affairs Health Care System. We assessed facility-level rates of glycemic (hemoglobin [Hb]A1c <7%), BP (BP <140/90 mmHg), and combined glycemic and BP control (HbA1c <7% and BP <140/90 mmHg), and their facility-level variation in using median rate ratios (MRR). Among 1 103 302 patients with diabetes, 50.2% participants had an HbA1c <7%, 77.5% had a BP <140/90 mmHg, and 39.8% had both, HbA1c <7% and BP <140/90 mmHg. Median facility-level rates were 50.3% (interquartile range [IQR], 47.9%-52.4%) for glycemic control, 78.4% (IQR, 75.2%-80.0%) for BP control, and 39.9% (IQR, 38.14%-42.34%) for combined glycemic and BP control. Unadjusted MRR for glycemic control was 1.61 (95% confidence interval [CI]: 1.51-1.70) which decreased to 1.16 (95% CI: 1.14-1.19) after adjusting for patient and facility-level variables, indicating a 16% variation in glycemic control between 2 identical patients receiving care at 2 random facilities. Unadjusted MRR for BP control was 1.49 (95% CI: 1.41-1.56), which decreased to 1.25 (95% CI: 1.21-1.28), whereas unadjusted MRR for combined glycemic and BP control was 1.59 (95% CI: 1.50-1.68), which decreased to 1.15 (95% CI: 1.13-1.17) after adjustment. Facility-level rates for BP control and glycemic control remain low with significant facility-level variation. Much of this is explained by patient and facility-level variables although 16%, 25%, and 15% variation in glycemic, BP, and combined glycemic and BP control remains unexplained. © 2017 Wiley Periodicals, Inc.

  13. Genetic variations in sterol regulatory element binding protein cleavage-activating protein (SCAP) are associated with blood pressure in overweight/obese Chinese children.

    PubMed

    Yang, Yi-De; Song, Jie-Yun; Wang, Shuo; Liu, Fang-Hong; Zhang, Yi-Ning; Shang, Xiao-Rui; Wang, Hai-Jun; Ma, Jun

    2017-01-01

    Previous studies demonstrated a role of variations in sterol regulatory element binding protein (SREBP) cleavage-activating protein (SCAP) in obesity and blood lipids. But the associations between SCAP polymorphisms and blood pressure (BP) are not clear. This study aimed to investigate the relationship between genetic variations in SCAP and BP phenotypes in a Chinese pediatric population. A case-control study on 702 high blood pressure (HBP) children and 1319 controls was conducted to explore the correlation between single nucleotide polymorphism markers (rs12487736 and rs12490383) of SCAP and BP phenotypes. The associations with continuous and categorical variables were examined by linear regression and logistic regression models under a dominant genetic model for the minor rs12487736 A allele and rs12490383 T allele. The rs12487736 polymorphism was significantly associated with systolic BP (SBP) (β = 1.66, P = 0.003) and diastolic BP (DBP) (β = 1.35, P = 0.024) with age, age-squared, sex, study population and body mass index (BMI) adjusted under the dominant genetic model. The rs12490383 polymorphism was significantly associated with SBP (β = 1.71, P = 0.004) and SHBP (OR = 1.39, 95%CI: 1.04-1.86, P = 0.027). When analyzed by BMI categories, in the normal-weight children, no significant association between the SCAP polymorphisms and BP phenotypes was observed (all P > 0.05). However, in the overweight/obese children, rs12487736 was significantly associated with SBP (β = 1.6, P = 0.019) and SHBP (OR = 1.36, 95%CI: 1.02-1.82; P = 0.037), rs12490383 was associated with SBP (β = 2.04, P = 0.004) and SHBP (OR = 1.50, 95%CI: 1.10-2.05; P = 0.01). This study demonstrated that SCAP rs12487736 and rs12490383 were significantly associated with SBP and SHBP in overweight/obese Chinese children. It provided the evidence for association of SCAP with SBP.

  14. Correlations of life-span variation parameters in 128 successive generations of Drosophila melanogaster with changes in atmospheric pressure and geomagnetic activity.

    PubMed

    Izmaylov, D M; Obukhova, L K; Konradov, A A

    2005-05-01

    Correlations between the parameters of life-span (LS) distribution of Drosophila melanogaster, including mean LS (MLS) and the time of 10 and 90% population mortality, and some geophysical parameters that are usually beyond the control of researchers dealing with laboratory cultures, including atmospheric pressure, solar activity indices (Wolf's sunspot numbers and 2,800-MHz radio flux), and geomagnetic activity (planetary index, K(p)), were studied. Geophysical data were obtained from free-access official web sites of the National Oceanic & Atmospheric Administration of the US Department of Commerce and the Institute of Terrestrial Magnetism and Radiowave Propagation of the Russian Academy of Sciences. The geophysical parameters were calculated only for the period corresponding to 10 days of preimaginal development of the flies from egg to imago. Canonical correlation analysis, calculation of the non-parametric Spearman rank-order correlation coefficients, and graphical data analysis were used. Highly significant correlations between parameters of LS distribution in males and females and environmental factors, such as the atmospheric pressure on the 4th and 5th day of development and geomagnetic activity indices (K(p)) on the 6th and 10th day of development were found, with correlation coefficients varying from 0.31 to 0.37 (P<0.02). Assuming a causal relationship between geophysical factors and LS, it may be hypothesized that energetically weak environmental factors determine the formation of LS oscillatory dynamics in laboratory populations. The possible mechanisms underlying the contribution of these environmental factors to the LS variation in successive generations are discussed.

  15. Long-term variations of the solar wind parameters and their geoeffciency

    NASA Astrophysics Data System (ADS)

    Makarova, Liudmila; Shirochkov, Alexander

    One of the contradictory problems of the contemporary state of the solar-terrestrial physics is impact of the solar activity of different kinds on the near-Earth space. For a long time solar activity having cyclical variations of sunspots and solar flares were considered as a main factor in the study of the solar - terrestrial links. State of the solar wind, which depends on the processes occurring in the Sun, is an important indicator of the solar - terrestrial links. Right now geoeffeciency of the solar wind influence on the processes in the near-Earth space is commonly accepted fact. In this paper we study the long-term variations in the solar wind parameters using satellite data from 1966 to 2013. So, sporadic variability associated with casual short-term disturbances in the solar wind were excluded from consideration. We analyzed annual values of such parameters as the solar wind interplanetary field full magnetic vector (B), speed (V) and density (n), as well as its dynamic pressure (nV2). It was confirmed that in the long term variations of the total magnetic field vector B coincides with cyclic variability of the number of sunspots. The long-term variations in the solar wind velocity clearly demonstrated maximum at decreasing phase of solar activity cycle. Solar wind density values were minimal at the maxima of solar activity cycles and they increased in the decay phase of the cyclic activity. These results were mentioned in the previous literature. The new fact was that the density of the solar wind has increased from cycle to cycle from 1966 to 1993, and it began to decrease values after 1996. Dynamic pressure of the solar wind from 1966 to 1993 increased in proportion to the density of the solar wind. It was also found that since 1998 the dynamic pressure is determined of the total magnetic field vector IMF and the solar wind velocity. Analysis of long-term variations of ionospheric parameters at F region showed a high correlation with the values of

  16. Between-Habitat Variation of Benthic Cover, Reef Fish Assemblage and Feeding Pressure on the Benthos at the Only Atoll in South Atlantic: Rocas Atoll, NE Brazil.

    PubMed

    Longo, G O; Morais, R A; Martins, C D L; Mendes, T C; Aued, A W; Cândido, D V; de Oliveira, J C; Nunes, L T; Fontoura, L; Sissini, M N; Teschima, M M; Silva, M B; Ramlov, F; Gouvea, L P; Ferreira, C E L; Segal, B; Horta, P A; Floeter, S R

    2015-01-01

    The Southwestern Atlantic harbors unique and relatively understudied reef systems, including the only atoll in South Atlantic: Rocas atoll. Located 230 km off the NE Brazilian coast, Rocas is formed by coralline red algae and vermetid mollusks, and is potentially one of the most "pristine" areas in Southwestern Atlantic. We provide the first comprehensive and integrative description of the fish and benthic communities inhabiting different shallow reef habitats of Rocas. We studied two contrasting tide pool habitats: open pools, which communicate with the open ocean even during low tides, thus more exposed to wave action; and closed pools, which remain isolated during low tide and are comparatively less exposed. Reef fish assemblages, benthic cover, algal turfs and fish feeding pressure on the benthos remarkably varied between open and closed pools. The planktivore Thalassoma noronhanum was the most abundant fish species in both habitats. In terms of biomass, the lemon shark Negaprion brevirostris and the omnivore Melichtys niger were dominant in open pools, while herbivorous fishes (mainly Acanthurus spp.) prevailed in closed pools. Overall benthic cover was dominated by algal turfs, composed of articulated calcareous algae in open pools and non-calcified algae in closed pools. Feeding pressure was dominated by acanthurids and was 10-fold lower in open pools than in closed pools. Besides different wave exposure conditions, such pattern could also be related to the presence of sharks in open pools, prompting herbivorous fish to feed more in closed pools. This might indirectly affect the structure of reef fish assemblages and benthic communities. The macroalgae Digenea simplex, which is uncommon in closed pools and abundant in the reef flat, was highly preferred in herbivory assays, indicating that herbivory by fishes might be shaping this distribution pattern. The variations in benthic and reef fish communities, and feeding pressure on the benthos between open and

  17. Evaluation of augmented pulse pressure variation using the Valsalva manoeuvre as a predictor of fluid responsiveness under open-chest conditions: A prospective observational study.

    PubMed

    Min, Jeong Jin; Kim, Tae Kyong; Lee, Jong-Hwan; Park, Jiyeon; Cho, Hyun Sung; Kim, Wook Sung; Lee, Young Tak

    2017-05-01

    Pulse pressure variation (PPV) is a well known dynamic preload indicator of fluid responsiveness. However, its usefulness in open-chest conditions remains controversial. We evaluated whether augmented PPV during a Valsalva manoeuvre can predict fluid responsiveness after sternotomy. A prospective, observational study. Single-centre trial, study period from October 2014 to June 2015. Forty-nine adult patients who underwent off-pump coronary arterial bypass grafting. After midline sternotomy, haemodynamic parameters were measured before and after volume expansion (6 ml kg of crystalloids). PPV was calculated both automatically (PPVauto) and manually (PPVmanual). For PPV augmentation, we performed Valsalva manoeuvres with manual holding of the rebreathing bag and constant airway pressure of 30 cmH2O for 10 s before fluid loading and calculated PPV during the Valsalva manoeuvre (PPVVM). The predictive ability of PPVVM for fluid responsiveness using receiver-operating characteristic curve analysis. Responders were identified when an increase in cardiac index of at least 12% occurred after fluid loading. Twenty-one patients were responders and 28 were nonresponders. PPVVM successfully predicted fluid responsiveness with an area under the curve (AUC) of 0.88 [95% confidence interval (95% CI) 0.75 to 0.95; sensitivity 91%, specificity 79%, P < 0.0001] and a threshold value of 55%. Baseline PPVauto and PPVmanual also predicted fluid responsiveness [AUC 0.75 (0.62 to 0.88); sensitivity 79%, specificity 75%; and 0.76 (0.61 to 0.87]; sensitivity 71%, specificity 71%, respectively). However, only PPVVM showed a significant AUC-difference from that of central venous pressure (P = 0.008) and correlated with the change of cardiac index induced by volume expansion (r = 0.6, P < 0.001). Augmented PPV using a Valsalva manoeuvre can be used as a clinically reliable predictor of fluid responsiveness under open-chest condition. ClinicalTrials.gov identifier: NCT

  18. Between-Habitat Variation of Benthic Cover, Reef Fish Assemblage and Feeding Pressure on the Benthos at the Only Atoll in South Atlantic: Rocas Atoll, NE Brazil

    PubMed Central

    Longo, G. O.; Morais, R. A.; Martins, C. D. L.; Mendes, T. C.; Aued, A. W.; Cândido, D. V.; de Oliveira, J. C.; Nunes, L. T.; Fontoura, L.; Sissini, M. N.; Teschima, M. M.; Silva, M. B.; Ramlov, F.; Gouvea, L. P.; Ferreira, C. E. L.; Segal, B.; Horta, P. A.; Floeter, S. R.

    2015-01-01

    The Southwestern Atlantic harbors unique and relatively understudied reef systems, including the only atoll in South Atlantic: Rocas atoll. Located 230 km off the NE Brazilian coast, Rocas is formed by coralline red algae and vermetid mollusks, and is potentially one of the most “pristine” areas in Southwestern Atlantic. We provide the first comprehensive and integrative description of the fish and benthic communities inhabiting different shallow reef habitats of Rocas. We studied two contrasting tide pool habitats: open pools, which communicate with the open ocean even during low tides, thus more exposed to wave action; and closed pools, which remain isolated during low tide and are comparatively less exposed. Reef fish assemblages, benthic cover, algal turfs and fish feeding pressure on the benthos remarkably varied between open and closed pools. The planktivore Thalassoma noronhanum was the most abundant fish species in both habitats. In terms of biomass, the lemon shark Negaprion brevirostris and the omnivore Melichtys niger were dominant in open pools, while herbivorous fishes (mainly Acanthurus spp.) prevailed in closed pools. Overall benthic cover was dominated by algal turfs, composed of articulated calcareous algae in open pools and non-calcified algae in closed pools. Feeding pressure was dominated by acanthurids and was 10-fold lower in open pools than in closed pools. Besides different wave exposure conditions, such pattern could also be related to the presence of sharks in open pools, prompting herbivorous fish to feed more in closed pools. This might indirectly affect the structure of reef fish assemblages and benthic communities. The macroalgae Digenea simplex, which is uncommon in closed pools and abundant in the reef flat, was highly preferred in herbivory assays, indicating that herbivory by fishes might be shaping this distribution pattern. The variations in benthic and reef fish communities, and feeding pressure on the benthos between open

  19. Evaluation of physiological risk factors, oxidant-antioxidant imbalance, proteolytic and genetic variations of matrix metalloproteinase-9 in patients with pressure ulcer.

    PubMed

    Latifa, Khlifi; Sondess, Sahli; Hajer, Graiet; Manel, Ben-Hadj-Mohamed; Souhir, Khelil; Nadia, Bouzidi; Abir, Jaballah; Salima, Ferchichi; Abdelhedi, Miled

    2016-07-11

    Pressure ulcer (PU) remains a common worldwide problem in all health care settings, it is synonymous with suffering. PU is a complex disease that is dependent on a number of interrelated factors. It involves multiple mechanisms such as physiological risk factors, chronic inflammation, oxidant-antioxidant imbalance and proteolytic attack on extracellular matrix by matrix metalloproteinases (MMP). Therefore, we propose that these wounds lead to molecular variations that can be detected by assessing biomarkers. In this study, we aimed to evaluate the major clinical elements and biological scars in Tunisian patients suffering from PU. Consistently, non-healing wound remains a challenging clinical problem. The complex challenges of the wound environment, involving nutrient deficiencies, bacterial infection, as well as the critical role played by inflammatory cells, should be considered because of their negative impact on wound healing. In addition, an imbalance between pro-oxidants and antioxidant systems seems to be more aggravated in patients with PU compared to healthy subjects. Of interest, this study provides further evidence to support a core role of the biological activity of MMP-9 in the pathogenesis of PU and indicates that the MMP9-1562 C/T (rs 3918242) functional polymorphism is associated with protection against this disease.

  20. Comparison between respiratory changes in the inferior vena cava diameter and pulse pressure variation to predict fluid responsiveness in postoperative patients.

    PubMed

    de Oliveira, Olivia Haun; Freitas, Flávio Geraldo Rezende de; Ladeira, Renata Teixeira; Fischer, Claudio Henrique; Bafi, Antônio Tonete; Azevedo, Luciano Cesar Pontes; Machado, Flávia Ribeiro

    2016-08-01

    The objective of our study was to assess the reliability of the distensibility index of the inferior vena cava (dIVC) as a predictor of fluid responsiveness in postoperative, mechanically ventilated patients and compare its accuracy with that of the pulse pressure variation (PPV) measurement. We included postoperative mechanically ventilated and sedated patients who underwent volume expansion with 500mL of crystalloids over 15minutes. A response to fluid infusion was defined as a 15% increase in the left ventricular outflow tract velocity time integral according to transthoracic echocardiography. The inferior vena cava diameters were recorded by a subcostal view using the M-mode and the PPV by automatic calculation. The receiver operating characteristic (ROC) curves were generated for the baseline dIVC and PPV. Twenty patients were included. The area under the ROC curve for dIVC was 0.84 (95% confidence interval, 0.63-1.0), and the best cutoff value was 16% (sensitivity, 67%; specificity, 100%). The area under the ROC curve for PPV was 0.92 (95% confidence interval, 0.76-1.0), and the best cutoff was 12.4% (sensitivity, 89%; specificity, 100%). A noninferiority test showed that dIVC cannot replace PPV to predict fluid responsiveness (P=.28). The individual PPV discriminative properties for predicting fluid responsiveness in postoperative patients seemed superior to those of dIVC. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Evaluation of physiological risk factors, oxidant-antioxidant imbalance, proteolytic and genetic variations of matrix metalloproteinase-9 in patients with pressure ulcer

    PubMed Central

    Latifa, Khlifi; Sondess, Sahli; Hajer, Graiet; Manel, Ben-Hadj-Mohamed; Souhir, Khelil; Nadia, Bouzidi; Abir, Jaballah; Salima, Ferchichi; Abdelhedi, Miled

    2016-01-01

    Pressure ulcer (PU) remains a common worldwide problem in all health care settings, it is synonymous with suffering. PU is a complex disease that is dependent on a number of interrelated factors. It involves multiple mechanisms such as physiological risk factors, chronic inflammation, oxidant–antioxidant imbalance and proteolytic attack on extracellular matrix by matrix metalloproteinases (MMP). Therefore, we propose that these wounds lead to molecular variations that can be detected by assessing biomarkers. In this study, we aimed to evaluate the major clinical elements and biological scars in Tunisian patients suffering from PU. Consistently, non-healing wound remains a challenging clinical problem. The complex challenges of the wound environment, involving nutrient deficiencies, bacterial infection, as well as the critical role played by inflammatory cells, should be considered because of their negative impact on wound healing. In addition, an imbalance between pro-oxidants and antioxidant systems seems to be more aggravated in patients with PU compared to healthy subjects. Of interest, this study provides further evidence to support a core role of the biological activity of MMP-9 in the pathogenesis of PU and indicates that the MMP9-1562 C/T (rs 3918242) functional polymorphism is associated with protection against this disease. PMID:27405842

  2. A Novel Mobile Phone Application for Pulse Pressure Variation Monitoring Based on Feature Extraction Technology: A Method Comparison Study in a Simulated Environment.

    PubMed

    Desebbe, Olivier; Joosten, Alexandre; Suehiro, Koichi; Lahham, Sari; Essiet, Mfonobong; Rinehart, Joseph; Cannesson, Maxime

    2016-07-01

    Pulse pressure variation (PPV) can be used to assess fluid status in the operating room. This measurement, however, is time consuming when done manually and unreliable through visual assessment. Moreover, its continuous monitoring requires the use of expensive devices. Capstesia™ is a novel Android™/iOS™ application, which calculates PPV from a digital picture of the arterial pressure waveform obtained from any monitor. The application identifies the peaks and troughs of the arterial curve, determines maximum and minimum pulse pressures, and computes PPV. In this study, we compared the accuracy of PPV generated with the smartphone application Capstesia (PPVapp) against the reference method that is the manual determination of PPV (PPVman). The Capstesia application was loaded onto a Samsung Galaxy S4 phone. A physiologic simulator including PPV was used to display arterial waveforms on a computer screen. Data were obtained with different sweep speeds (6 and 12 mm/s) and randomly generated PPV values (from 2% to 24%), pulse pressure (30, 45, and 60 mm Hg), heart rates (60-80 bpm), and respiratory rates (10-15 breaths/min) on the simulator. Each metric was recorded 5 times at an arterial height scale X1 (PPV5appX1) and 5 times at an arterial height scale X3 (PPV5appX3). Reproducibility of PPVapp and PPVman was determined from the 5 pictures of the same hemodynamic profile. The effect of sweep speed, arterial waveform scale (X1 or X3), and number of images captured was assessed by a Bland-Altman analysis. The measurement error (ME) was calculated for each pair of data. A receiver operating characteristic curve analysis determined the ability of PPVapp to discriminate a PPVman > 13%. Four hundred eight pairs of PPVapp and PPVman were analyzed. The reproducibility of PPVapp and PPVman was 10% (interquartile range, 7%-14%) and 6% (interquartile range, 3%-10%), respectively, allowing a threshold ME of 12%. The overall mean bias for PPVappX1 was 1.1% within limits of

  3. Variations in dark respiration and mitochondrial numbers within needles of Pinus radiata grown in ambient or elevated CO2 partial pressure.

    PubMed

    Griffin, Kevin L; Anderson, O Roger; Tissue, David T; Turnbull, Matthew H; Whitehead, David

    2004-03-01

    Within-leaf variations in cell size, mitochondrial numbers and dark respiration rates were compared in the most recently expanded tip, the mid-section and base of needles of Pinus radiata D. Don trees grown for 4 years in open-top chambers at ambient (36 Pa) or elevated (65 Pa) carbon dioxide partial pressure (p(CO2)a). Mitochondrial numbers and respiratory activity varied along the length of the needle, with the highest number of mitochondria per unit cytoplasm and the highest rate of respiration per unit leaf area at the base of the needle. Regardless of the location of the cells (tip, middle or basal sections), needles collected from trees grown in elevated p(CO2)a had nearly twice the number of mitochondria per unit cytoplasm as those grown in ambient p(CO2)a. This stimulation of mitochondrial density by growth at elevated p(CO2)a was greater at the tip of the needle (2.7 times more mitochondria than in needles grown in ambient CO2) than at the base of the needle (1.7 times). The mean size of individual mitochondria was unaffected either by growth at elevated p(CO2)a or by position along the needle. Tree growth at elevated p(CO2)a had a variable effect on respiration per unit leaf area, significantly increasing respiration in the tip of the needles (+25%) and decreasing respiration at the mid-section and base of the needles (-14% and -25%, respectively). Although a simple relationship between respiration per unit leaf area and mitochondrial number per unit cytoplasm was found within each CO2 treatment, the variable effect of growth at elevated p(CO2)a on respiration along the length of the needles indicates that a more complex relationship must determine the association between structure and function in these needles.

  4. Agreement between diurnal variations of intraocular pressure by Tono-Pen and Goldmann applanation tonometer in patients on topical anti-glaucoma medication.

    PubMed

    Gupta, Shikha; Sinha, Gautam; Sharma, Reetika; Nayak, Bhagabat; Patil, Bharat; Kashyap, Bibhuti; Shameer, Abdul; Dada, Tanuj

    2016-02-01

    To estimate agreement in diurnal variations of intraocular pressure (IOP) by Tono-Pen (TP) and Goldmann applanation tonometer (GAT) in glaucoma patients on topical anti-glaucoma medication(s). IOP was measured at every 3 h from 7 a.m. to 10 a.m. in 50 eyes of glaucoma patients on topical medication(s). Diurnal fluctuation of IOP by each method was calculated as maximum-minimum IOP in a day. Central corneal thickness (CCT) was measured by ultrasonic pachymeter. There was good correlation between TP and GAT at all times during a day, minimum, and maximum IOPs during a day (Correlation coefficient, 0.706 at 7 a.m., 0.624 at 10 a.m., 0.682 at 1 p.m., 0.814 at 4 p.m., 0.652 at 7 p.m., 0.572 at 10 p.m., 0.668 minimum IOP, 0.689 maximum IOP). Mean IOPs by TP were always higher than GAT at all times during a day. Bland-Altman plots suggested a close relationship between the two sets of readings, and that this relationship was consistent at different times in a day, in maximum IOPs, minimum IOPs and also in fluctuation of IOPs. Linear regression analysis between the differences of diurnal fluctuation (diurnal fluctuation by GAT-diurnal fluctuation by TP) and CCT showed strong association (R 2 = 0.857, p < 0.001). The mean change in difference of diurnal fluctuation (GAT-TP) for a 10-micron increase in CCT was 0.69 mmHg. TP can be considered a reliable alternative to GAT in glaucoma patients for knowing the diurnal control of IOP; however these two methods should not be used interchangeably. Difference of diurnal fluctuation between two methods is dependent on CCT.

  5. Cycle-to-cycle variability of neuromuscular activity in Aplysia feeding behavior.

    PubMed

    Horn, Charles C; Zhurov, Yuriy; Orekhova, Irina V; Proekt, Alex; Kupfermann, Irving; Weiss, Klaudiusz R; Brezina, Vladimir

    2004-07-01

    Aplysia consummatory feeding behavior, a rhythmic cycling of biting, swallowing, and rejection movements, is often said to be stereotyped. Yet closer examination shows that cycles of the behavior are very variable. Here we have quantified and analyzed the variability at several complementary levels in the neuromuscular system. In reduced preparations, we recorded the motor programs produced by the central pattern generator, firing of the motor neurons B15 and B16, and contractions of the accessory radula closer (ARC) muscle while repetitive programs were elicited by stimulation of the esophageal nerve. In other similar experiments, we recorded firing of motor neuron B48 and contractions of the radula opener muscle. In intact animals, we implanted electrodes to record nerve or ARC muscle activity while the animals swallowed controlled strips of seaweed or fed freely. In all cases, we found large variability in all parameters examined. Some of this variability reflected systematic, slow, history-dependent changes in the character of the central motor programs. Even when these trends were factored out, however, by focusing only on the differences between successive cycles, considerable variability remained. This variability was apparently random. Nevertheless, it too was the product of central history dependency because regularizing merely the high-level timing of the programs also regularized many of the downstream neuromuscular parameters. Central motor program variability thus appears directly in the behavior. With regard to the production of functional behavior in any one cycle, the large variability may indicate broad tolerances in the operation of the neuromuscular system. Alternatively, some cycles of the behavior may be dysfunctional. Overall, the variability may be part of an optimal strategy of trial, error, and stabilization that the CNS adopts in an uncertain environment.

  6. Anomalous scattering behavior of selected impact parabola features: Magellan cycle-to-cycle comparisons

    NASA Technical Reports Server (NTRS)

    Plaut, Jeffrey J.; Saunders, R. Stephen; Stofan, E. R.; Kirk, R. L.; Schaber, G. G.; Soderblom, L. A.; Ford, P. G.; Pettengill, G. H.; Campbell, D. B.; Stacy, N. J. S.

    1992-01-01

    Magellan observations indicate that many venusian impact craters have associated surfaces, typically lower in backscatter and emissivity than the surroundings, that extend up to hundreds of kilometers to the west of craters, in parabolic planforms. During Magellan's second mapping cycle, a number of these parabolic features were imaged for a second time, under a different viewing geometry. In some cases, the SAR backscatter appearance of portions of the parabolic features was quite different in the two datasets. We present a description and preliminary interpretations of the anomalous appearance of these features as observed during Magellan's first and second mapping cycles.

  7. Hemispheric Preference and Cyclic Variation of Solar Filament Chirality

    NASA Astrophysics Data System (ADS)

    Hazra, Soumitra; Mahajan, Sushant S.; Douglas, William; Martens, Petrus C.

    2017-08-01

    Although the hemispheric preference of magnetic topological features in the solar atmosphere is a well-established fact, strength and cyclic variation of the hemispheric rule is a debatable issue. In this work, we study the chirality of 3480 solar filaments from 2000 to 2016. We determine the chirality of filaments manually and compare with the results obtained from the Advanced Automated Filament Detection and Characterization Code (AAFDCC). We find that 83% of our manually determined filaments follow the hemispheric chirality rule, while 58% of automatically determined filamentsfollow the same. We also compare our result with an other manually compiled list by Pevtsov et al. (2003). We find that our list matches Pevtsovs manually compiled list with 90% accuracy. We also find that the hemispheric chirality rule does not vary from cycle to cycle. However, the strength of the hemispheric preference decreases at the end and beginning phase of the solar cycle.

  8. Interfacial heat transfer in squeeze casting of magnesium alloy AM60 with variation of applied pressures and casting wall-thicknesses

    NASA Astrophysics Data System (ADS)

    Zhang, Xuezhi; Fang, Li; Sun, Zhizhong; Hu, Henry; Nie, Xueyuan; Tjong, Jimi

    2016-10-01

    The heat transfer coefficient at the casting-die interface is the most important factor on the solidification process. With the 75-ton hydraulic press machine and P20 steel die mold, 5-step castings of magnesium alloy AM60 with different wall-thicknesses (3, 5, 8, 12, 20 mm) were poured under various hydraulic pressures (30, 60, and 90 MPa) using an indirect squeeze casting process. Thermal histories throughout the die wall and the casting surface have been recorded by fine type-K thermocouples. The in-cavity local pressures measured by pressure transducers were explored at the casting-die interfaces of 5 steps. The casting-die interfacial heat transfer coefficients (IHTC) initially reached a maximum peak value followed by a gradually decline to the lower level. Similar characteristics of IHTC peak values can be observed at the applied pressures of 30, 60 and 90 MPa. With the applied pressure of 90 MPa, the peak IHTC values from steps 1 to 5 varied from 5623 to 10,649 W/m2 K. As the applied hydraulic pressure increased, the IHTC peak value of each step was increased accordingly. The wall thickness also affected IHTC peak values significantly. The peak IHTC value and heat flux increased as the step became thicker. The empirical equations relating the IHTCs to the local pressures and the solidification temperature at the casting surface were developed based on the multivariate linear and polynomial regression.

  9. Determination of the variation of the fluorescence line positions of ruby, strontium tetraborate, alexandrite, and samarium-doped yttrium aluminum garnet with pressure and temperature

    NASA Astrophysics Data System (ADS)

    Raju, Selva Vennila; Zaug, Joseph M.; Chen, Bin; Yan, Jinyuan; Knight, Jason W.; Jeanloz, Raymond; Clark, Simon M.

    2011-07-01

    The pressure and temperature dependent fluorescence line-shift of strontium tetraborate has been measured concurrently with x-ray diffraction from the pressure standards sodium chloride or gold. Temperature was found to have a small effect on the fluorescence line-shift under pressure. We found a maximum pressure uncertainty of ±1.8 GPa at 25 GPa (7.2%) and 857 K when making no temperature correction. The fluorescence line-shifts for ruby, Alexandrite, and samarium-doped yttrium aluminum garnet were also determined, using our strontium tetraborate calibration to determine pressure and a thermocouple to measure temperature. Fluorescence measurements were extended up to 800 K for ruby and Alexandrite. Temperature was found to have a small effect on the fluorescence line-shift of samarium-doped yittrium aluminum garnet. We found a maximum uncertainty of ±2.7 GPa at 25 GPa (11.1%) and 857 K when no temperature correction was applied. We determined equations relating to the fluorescence line position from these data, which include a cross derivative term to account for the combined effect of pressure and temperature. We present a method to independently determine pressure and/or temperature from combined fluorescence line-shift measurements of a pair of optical sensors.

  10. Yearly variation of bacterial production in the Arraial do Cabo protection area (Cabo Frio upwelling region): an evidence of anthropogenic pressure.

    PubMed

    Coelho-Souza, Sérgio A; Pereira, Gilberto C; Coutinho, Ricardo; Guimarães, Jean R D

    2013-12-01

    Arraial do Cabo is where upwelling occurs more intensively on the Brazilian coast. Although it is a protection area it suffers anthropogenic pressure such as harbor activities and sporadic sewage emissions. Short-time studies showed a high variability of bacterial production (BP) in this region but none of them evaluated BP during long periods in a large spatial scale including stations under different natural (upwelling and cold fronts) and anthropogenic pressures. During 2006, we sampled surface waters 10 times (5 in upwelling and 5 in subsidence periods) in 8 stations and we measured BP, temperature as well as the concentrations of inorganic nutrients, pigments and particulate organic matter (POM). BP was up to 400 times higher when sewage emissions were observed visually and it had a positive correlation with ammonia concentrations. Therefore, in 2007, we did two samples (each during upwelling and subsidence periods) during sewage emissions in five stations under different anthropogenic pressure and we also measured particles abundance by flow cytometry. The 12 samples in the most impacted area confirmed that BP was highest when ammonia was higher than 2 μM, also reporting the highest concentrations of chlorophyll a and suspended particles. However, considering all measured variables, upwelling was the main disturbing factor but the pressure of fronts should not be neglected since it had consequences in the auto-heterotrophic coupling, increasing the concentrations of non fluorescent particles and POM. Stations clustered in function of natural and anthropogenic pressures degrees and both determined the temporal-spatial variability.

  11. Yearly variation of bacterial production in the Arraial do Cabo protection area (Cabo Frio upwelling region): An evidence of anthropogenic pressure

    PubMed Central

    Coelho-Souza, Sérgio A.; Pereira, Gilberto C.; Coutinho, Ricardo; Guimarães, Jean R.D.

    2013-01-01

    Arraial do Cabo is where upwelling occurs more intensively on the Brazilian coast. Although it is a protection area it suffers anthropogenic pressure such as harbor activities and sporadic sewage emissions. Short-time studies showed a high variability of bacterial production (BP) in this region but none of them evaluated BP during long periods in a large spatial scale including stations under different natural (upwelling and cold fronts) and anthropogenic pressures. During 2006, we sampled surface waters 10 times (5 in upwelling and 5 in subsidence periods) in 8 stations and we measured BP, temperature as well as the concentrations of inorganic nutrients, pigments and particulate organic matter (POM). BP was up to 400 times higher when sewage emissions were observed visually and it had a positive correlation with ammonia concentrations. Therefore, in 2007, we did two samples (each during upwelling and subsidence periods) during sewage emissions in five stations under different anthropogenic pressure and we also measured particles abundance by flow cytometry. The 12 samples in the most impacted area confirmed that BP was highest when ammonia was higher than 2 μM, also reporting the highest concentrations of chlorophyll a and suspended particles. However, considering all measured variables, upwelling was the main disturbing factor but the pressure of fronts should not be neglected since it had consequences in the auto-heterotrophic coupling, increasing the concentrations of non fluorescent particles and POM. Stations clustered in function of natural and anthropogenic pressures degrees and both determined the temporal-spatial variability. PMID:24688533

  12. Predicting pressure-dependent unimolecular rate constants using variational transition state theory with multidimensional tunneling combined with system-specific quantum RRK theory: a definitive test for fluoroform dissociation.

    PubMed

    Bao, Junwei Lucas; Zhang, Xin; Truhlar, Donald G

    2016-06-22

    Understanding the falloff in rate constants of gas-phase unimolecular reaction rate constants as the pressure is lowered is a fundamental problem in chemical kinetics, with practical importance for combustion, atmospheric chemistry, and essentially all gas-phase reaction mechanisms. In the present work, we use our recently developed system-specific quantum RRK theory, calibrated by canonical variational transition state theory with small-curvature tunneling, combined with the Lindemann-Hinshelwood mechanism, to model the dissociation reaction of fluoroform (CHF3), which provides a definitive test for falloff modeling. Our predicted pressure-dependent thermal rate constants are in excellent agreement with experimental values over a wide range of pressures and temperatures. The present validation of our methodology, which is able to include variational transition state effects, multidimensional tunneling based on the directly calculated potential energy surface along the tunneling path, and torsional and other vibrational anharmonicity, together with state-of-the-art reaction-path-based direct dynamics calculations, is important because the method is less empirical than models routinely used for generating full mechanisms, while also being simpler in key respects than full master equation treatments and the full reduced falloff curve and modified strong collision methods of Troe.

  13. Environmental variation in the prevalence of hypertension in children and adolescents - is blood pressure higher in children and adolescents living in rural areas?

    PubMed

    Krzywinska-Wiewiorowska, Małgorzata; Stawińska-Witoszyńska, Barbara; Krzyżaniak, Alicja; Kaczmarek, Maria; Siwinska, Aldona

    2017-03-31

    Despite considerable progress in diagnostic methods and treatment options, cardiovascular diseases constitute a serious health issue in Poland, and hypertension is considered one of the main risk factors in the incidence of the diseases. The aim of this study is to assess the values of arterial blood pressure among adolescents in the context of urban and rural environments. The study was carried out on a representative, randomly selected group of youths aged 10-18 years, participating in the ADOPOLNOR project. Prior to blood pressure measurement, each pupil was assessed according to anthropomorphic principles. The BP measurements strictly followed the guidelines of the Fourth Protocol of the American Working Group of High Blood pressure in Children and Adolescents. Mean values of systolic blood pressure (SBP) in boys in rural areas were higher in every age group than in the boys in urban areas. Higher values of systolic and diastolic blood pressure were observed also in girls in rural areas. BP values sufficiently high for the diagnosis of hypertension were observed in 12.8% of the rural boy population but only in 6.7% of the boys from the urban environment. The difference is statistically significant. The girls in rural areas (13.3%) had twice the incidence of elevated BP values in comparison with the girls in urban areas (7.2%) and, as in boys, the difference is statistically significant. The high proportion of pupils with elevated arterial blood pressure observed in the rural areas of Wielkopolska calls for regularly performed BP assessment and monitoring in this populatio.

  14. Pressure-driven variations of hydrogen bonding energy in ammonium azide (NH4N3): IR absorption and Raman scattering studies.

    PubMed

    Wu, Xiaoxin; Ma, Fengxian; Ma, Chunli; Cui, Hang; Liu, Zhenxian; Zhu, Hongyang; Wang, Xiaoli; Cui, Qiliang

    2014-07-14

    In this study, high pressure infrared (IR) absorption and Raman scattering studies for ammonium azide (NH4N3) were carried out at room temperature up to 20 GPa and 22 GPa, respectively. For comparison and further assignment, the vibrational spectra at ambient conditions were calculated using CASTEP code, particularly for the far- and mid-IR modes. The recorded vibrational data consistently indicated a pressure-induced phase transition at 2.9 GPa. All observed vibrational modes maintained their identities at the high pressure phase, indicating that NH4N3 was still presented in the form of ammonium cations and azide anions linked by the hydrogen bond (N-H⋯N). Above 2.9 GPa, the relative magnitude of the torsional mode weakened and the N-H symmetric stretch displayed a redshift, indicating strengthened hydrogen bonding energy. The opposite effects were observed above 12 GPa, where the relative magnitude of the torsional mode strengthened and the N-H symmetric stretch reverted to a blueshift, indicating weakened hydrogen bonding energy. It can be concluded that the hydrogen bonding energy exhibited a weakening (0-2.9 GPa), strengthening (2.9-12 GPa), and then again weakening (12-22 GPa) phenomena with the increasing of compression. The hydrogen bonding energy changing with the increase of pressure can be ascribed to a phase transition at 2.9 GPa and a rotational or bending behavior of azide ions at 12 GPa.

  15. High-pressure resistance variation of Escherichia coli O157:H7 strains and Salmonella serovars in tryptic soy broth, distilled water, and fruit juice.

    PubMed

    Whitney, Brooke M; Williams, Robert C; Eifert, Joseph; Marcy, Joseph

    2007-09-01

    The effect of high pressure on the log reduction of six strains of Escherichia coli O157:H7 and five serovars of Salmonella enterica was investigated in tryptic soy broth, sterile distilled water, and commercially sterile orange juice (for Salmonella) and apple cider (for E. coli). Samples were subjected to high-pressure processing treatment at 300 and 550 MPa for 2 min at 6 degrees C. Samples were plated onto tryptic soy agar directly after pressurization and after being held for 24 h at 4 degrees C. At 300 MPa, little effect was seen on E. coli O157:H7 strains, while Salmonella serovars varied in resistance, showing reductions between 0.26 and 3.95 log CFU/ml. At 550 MPa, E. coli O157:H7 strains exhibited a range of reductions (0.28 to 4.39 log CFU/ml), while most Salmonella populations decreased beyond the detection limit (> 5-log CFU/ml reduction). The most resistant strains tested were E. coli E009 and Salmonella Agona. Generally, bacterial populations in fruit juices showed larger decreases than did populations in tryptic soy broth and distilled water. E. coli O157:H7 cultures held for 24 h at 4 degrees C after treatment at 550 MPa showed a significant log decrease as compared with cultures directly after treatment (P < or = 0.05), while Salmonella serovars did not show this significant decrease (P > 0.05). All Salmonella serovars tested in orange juice treated at 550 MPa for 2 min at 6 degrees C and held for 24 h showed a > 5-log decrease, while E. coli O157:H7 strains require a higher pressure, higher temperature, longer pressurization, or a chemical additive to achieve a 5-log decrease.

  16. [Variations in the prevalence and patient profile of white-coat syndrome, according to its definition using self-measurement of blood pressure at home].

    PubMed

    Torres Jiménez, J I; Martínez Peña, E; Adrián, N; Galicia Paredes, M A; Britt, M J; Cordero Guevara, J

    2001-09-15

    To calculate the prevalence of white-coat syndrome (WCS) in patients with hypertension, comparing the two most common definitions and their effect on the profile of the patient with WCS. Cross-sectional, descriptive study.Setting. Urban health centre.Patients. Hypertense patients selected by simple randomised sampling from among those included in the hypertension programme. Clinical blood pressure (CBP) from the previous year was collected. Home blood pressure (HBP) was measured by the patient with an electronic sphygmomanometer. Age, sex, further tests (analysis and electrocardiogram) and other clinical features were also recorded. WCS was defined as when CBP was above/equal to 140/90 mmHg and HBP was under 135/85 mmHg or when the difference between CBP and HBP was more than/equal to 20 mmHg systolic and/or 10 mmHg diastolic pressure. In 154 hypertense patients (60.4% women) between 38 and 92 years old, mean CBP (141.1/85.3) was higher than mean HBP (136.8/79.8). WCS prevalence varied (p = 0.001), depending on the definition used (20.1% and 36.4%). The systolic and diastolic mean CBP of the last year were higher in those patients with WCS (p < 0.001 for diastolic pressure). The profile of hypertense patients with WCS varied according to the definition used. WCS is common in hypertense patients treated in Primary Care and may condition an inadequate assessment of the degree of blood pressure monitoring. As the way of defining WCS conditions its prevalence, its profile and clinical decision-taking, it is essential to agree a uniform definition for practical use.

  17. Upper crustal structure, seismicity and pore pressure variations in an extensional seismic belt through 3-D and 4-D VP and VP/VS models: The example of the Val d'Agri area (southern Italy)

    NASA Astrophysics Data System (ADS)

    Valoroso, L.; Improta, L.; de Gori, P.; Chiarabba, C.

    2011-07-01

    We use local earthquake tomography and background seismicity to investigate static and transient features of the crustal velocity structure in the Val d'Agri (southern Apennines, Italy), one of the regions in central Mediterranean with the highest seismogenic potential. The upper crust is dominated by two broad high-velocity anticlines of the buried Apulia Carbonate Platform ramping on two parallel high-angle thrusts interpreted as preexisting inverted normal faults. The deep core of the anticlines consists of very high VP (up to 6.9 km/s) and low VP/VS rocks, suggesting the involvement of the Apulian crystalline basement in the Apennine belt. These results provide valuable constraints on the Apennine belt tectonic evolution, supporting a thick-skinned interpretation for the Pliocene terminal phase of the compressional tectonics. The geometry of the Val d'Agri Quaternary basin is controlled by these inherited compressive features, whereas the presently active extensional tectonics barely reworked the structure. We find inconsistency between the structure of the Apulia Carbonate Platform and the location and geometry of the Quaternary normal faults mapped at the surface. This suggests either the immaturity of the normal faults or their secondary role in accommodating the extension. We observe spatiotemporal (4-D) changes of VP and VP/VS models defining transient variations of pore fluid pressure in the upper crust. A strong change in the VP/VS ratio heralds a raise in the seismicity rate that can be related to large water level changes in a nearby artificial lake. This evidence is consistent with a mechanism of reservoir-induced seismicity by fluid pressure increase and pore pressure diffusion. The 4-D velocity variations are confined in the shallow portion of the upper crust (3-6 km depth) where fluids are stored in a highly fractured medium. Pore pressure fluctuations can affect the strength of fault segments, favoring seismicity rate changes along the active

  18. Spatial and Temporal Variations in the Partial Pressure and Emission of CO2 and CH4 in and Amazon Floodplain Lake

    NASA Astrophysics Data System (ADS)

    Forsberg, B. R.; Amaral, J. H.; Barbosa, P.; Kasper, D.; MacIntyre, S.; Cortes, A.; Sarmento, H.; Borges, A. V.; Melack, J. M.; Farjalla, V.

    2015-12-01

    The Amazon floodplain contains a variety of wetland environments which contribute CO2 and CH4 to the regional and global atmospheres. The partial pressure and emission of these greenhouse gases (GHGs) varies: 1) between habitats, 2) seasonally, as the characteristics these habitats changes and 3) diurnally, in response to diurnal stratification. In this study, we investigated the combined influence of these factors on the partial pressure and emission of GHGs in Lago Janauacá, a central Amazon floodplain lake (3o23' S; 60o18' O). All measurements were made between August of 2014 and April of 2015 at two different sites and in three distinct habitats: open water, flooded forest, flooded macrophytes. Concentrations of CO2 and CH4 in air were measured continuously with a cavity enhanced absorption spectrometer, Los Gatos Research´s Ultraportable Greenhouse Gas Analyzer (UGGA). Vertical profiles o pCO2 and pCH4 were measured using the UGGA connected to an electric pump and equilibrator. Diffusive surface emissions were estimated with the UGGA connected to a static floating chamber. To investigate the influence of vertical stratification and mixing on GHG partial pressure and emissions, a meteorological station and submersible sensor chain were deployed at each site. Meteorological sensors included wind speed and direction. The submersible chains included thermistors and oxygen sensors. Depth profiles of partial pressure and diffusive emissions for both CO2 and CH4 varied diurnally, seasonally and between habitats. Both pCO2 and pCH4 were consistently higher in bottom than surface waters with the largest differences occurring at high water when thermal stratification was most stable. Methane emissions and partial pressures were highest at low water while pCO2 and CO2 fluxes were highest during high water periods, with 35% of CO2 fluxes at low water being negative. The highest average surface value of pCO2 (5491 μatm), encountered during rising water, was ~3 times

  19. Magnetic activity of red secondaries: clues from the outburst cycle variations of dwarf novae

    NASA Astrophysics Data System (ADS)

    Chinarova, L. L.

    Photometric variations of 6 dwarf novae stars are studied based on the photographic observations from the Odessa, Moscow and Sonneberg plate collections and published visual monitoring data from the AFOEV database (Schweitzer E.: 1993, Bull. AFOEV, 64, 14). The moments of maxima are determined by using the "running parabola" fit (Andronov I.L., 1990, Kinematika Fizika Nebesn. Tel., v.6,,N 6, 87) with automatically determined filter half-width (Andronov I.L., 1997, As.Ap. Suppl., in press). All investigated stars exhibit significant changes not only from cycle-to-cycle, but from season-to-season as well. Secondary decade-scale cycles of smooth variations (Bianchini A., 1990, AJ 99, 1941) and abrupt switchings (Andronov I.L., Shakun L.I., 1990, ASS 169, 237) were interpreted by a solar-type activity of the red dwarf secondary in a binary system and may argue for existence of two different subgroups of the dwarf novae.

  20. Structural Variations in β-(BDA-TTP)2FeCl4 at Low Temperature and under Pressure: Charge-Ordered State with a Two-Fold Crystal Structure

    NASA Astrophysics Data System (ADS)

    Sasamori, Kota; Takahashi, Kazuyuki; Kodama, Takeshi; Fujita, Wataru; Kikuchi, Koichi; Yamada, Jun-ichi

    2013-05-01

    The pressure-induced organic superconductor β-(BDA-TTP)2FeCl4 [BDA-TTP = 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene], which shows a metal--insulator (MI) transition at TMI = 113 K under ambient pressure, has been found by X-ray study to have a two-fold crystal structure along the c-axis in the insulating state at 10 K. In the donor layer, there are four independent BDA-TTP molecules, which are divided into two charge-poor ones and two charge-rich ones on the basis of the folding dihedral angles around the intramolecular sulfur-to-sulfur axes of two outer dithiane rings in BDA-TTP. The charge separation leads to the formation of two types of dimers: a dimer consisting of two charge-poor donors and a dimer consisting of two charge-rich ones. The tight-binding band calculation revealed a band gap of 5.3 meV in the energy dispersion. The MI transition can be therefore accounted for by the charge separation. In addition, we investigated the crystal and electronic structures of β-(BDA-TTP)2FeCl4 at different pressures up to 21 kbar, and found that the application of pressures causes variations in both the conformation of donor molecule and the donor arrangement, which are responsible for almost uniform interaction in the donor stacking and for an increase in bandwidth (W). As a result, the suppression of MI transition and subsequent occurrence of superconductivity in β-(BDA-TTP)2FeCl4 would be observed with increasing pressure.

  1. Flow-compensating pressure regulator

    NASA Technical Reports Server (NTRS)

    Baehr, E. F.

    1979-01-01

    Pressure regulator developed for use with cataract-surgery instrument controls intraocular pressure during substantial variations in flow rate of infusion fluid. Device may be applicable to variety of eye-surgery instruments.

  2. Variations in battery life of a heart-lung machine using different pump speeds, pressure loads, boot material, centrifugal pump head, multiple pump usage, and battery age.

    PubMed

    Marshall, Cornelius; Hargrove, Martin; O'Donnell, Aonghus; Aherne, Thomas

    2005-09-01

    Electrical failure during cardiopulmonary bypass (CPB) has previously been reported to occur in 1 of every 1500 cases. Most heart-lung machine pump consoles are equipped with built-in battery back-up units. Battery run times of these devices are variable and have not been reported. Different conditions of use can extend battery life in the event of electrical failure. This study was designed to examine the run time of a fully charged battery under various conditions of pump speed, pressure loads, pump boot material, multiple pump usage, and battery life. Battery life using a centrifugal pump also was examined. The results of this study show that battery life is affected by pump speed, circuit pressure, boot stiffness, and the number of pumps in service. Centrifugal pumps also show a reduced drain on battery when compared with roller pumps. These elements affect the longevity and performance of the battery. This information could be of value to the individual during power failure as these are variables that can affect the battery life during such a challenging scenario.

  3. Variations in Battery Life of a Heart—Lung Machine Using Different Pump Speeds, Pressure Loads, Boot Material, Centrifugal Pump Head, Multiple Pump Usage, and Battery Age

    PubMed Central

    Marshall, Cornelius; Hargrove, Martin; O’Donnell, Aonghus; Aherne, Thomas

    2005-01-01

    Abstract: Electrical failure during cardiopulmonary bypass (CPB) has previously been reported to occur in 1 of every 1500 cases. Most heart—lung machine pump consoles are equipped with built-in battery back-up units. Battery run times of these devices are variable and have not been reported. Different conditions of use can extend battery life in the event of electrical failure. This study was designed to examine the run time of a fully charged battery under various conditions of pump speed, pressure loads, pump boot material, multiple pump usage, and battery life. Battery life using a centrifugal pump also was examined. The results of this study show that battery life is affected by pump speed, circuit pressure, boot stiffness, and the number of pumps in service. Centrifugal pumps also show a reduced drain on battery when compared with roller pumps. These elements affect the longevity and performance of the battery. This information could be of value to the individual during power failure as these are variables that can affect the battery life during such a challenging scenario. PMID:16350380

  4. A concept for transition mapping on a 10 deg-cone in the National Transonic Facility using flow-pressure variation

    NASA Technical Reports Server (NTRS)

    Gartenberg, Ehud

    1995-01-01

    A conceptual study was performed to define a technique for mapping the boundary-layer transition on a 10 deg-Cone in the National Transonic Facility (NTF) as a means of determining this cryogenic-tunnel suitability for laminar flow testing. A major challenge was to devise a test matrix using a fixed surface pitot probe, varying the flow pressure to pr oduce the actual Reynolds numbers for boundary-layer transition. This constraint resulted from a lack of a suitable and reliable electrical motor to drive the probe along the cone's surface under cryogenic flow conditions. The initial phase of this research was performed by the author in collaboration with the late Dr. William B. Igoe from the Aerodynamics Division at NASA Langley Research Center. His comments made during the drafting of this document were invaluable and a source of inspiration.

  5. Goal-Directed Fluid Therapy Using Stroke Volume Variation for Resuscitation after Low Central Venous Pressure-Assisted Liver Resection: A Randomized Clinical Trial.

    PubMed

    Correa-Gallego, Camilo; Tan, Kay See; Arslan-Carlon, Vittoria; Gonen, Mithat; Denis, Stephanie C; Langdon-Embry, Liana; Grant, Florence; Kingham, T Peter; DeMatteo, Ronald P; Allen, Peter J; D'Angelica, Michael I; Jarnagin, William R; Fischer, Mary

    2015-08-01

    The optimal perioperative fluid resuscitation strategy for liver resections remains undefined. Goal-directed therapy (GDT) embodies a number of physiologic strategies to achieve an ideal fluid balance and avoid the consequences of over- or under-resuscitation. In a prospective randomized trial, patients undergoing liver resection were randomized to GDT using stroke volume variation as an end point or to standard perioperative resuscitation. Primary outcomes measure was 30-day morbidity. Between 2012 and 2014, one hundred and thirty-five patients were randomized (GDT: n = 69; standard perioperative resuscitation: n = 66). Median age was 57 years and 56% were male. Metastatic disease comprised 81% of patients. Overall (35% GDT vs 36% standard perioperative resuscitation; p = 0.86) and grade 3 morbidity (28% GDT vs 18% standard perioperative resuscitation; p = 0.22) were equivalent. Patients in the GDT arm received less intraoperative fluid (mean 2.0 L GDT vs 2.9 L standard perioperative resuscitation; p < 0.001). Perioperative transfusions were required in 4% (6% GDT vs 2% standard perioperative resuscitation; p = 0.37) and boluses in the postanesthesia care unit were administered to 24% (29% GDT vs 20% standard perioperative resuscitation; p = 0.23). Mortality rate was 1% (2 of 135 patients; both in GDT). On multivariable analysis, male sex, age, combined procedures, higher intraoperative fluid volume, and fluid boluses in the postanesthesia care unit were associated with higher 30-day morbidity. Stroke volume variation-guided GDT is safe in patients undergoing liver resection and led to less intraoperative fluid. Although the incidence of postoperative complications was similar in both arms, lower intraoperative resuscitation volume was independently associated with decreased postoperative morbidity in the entire cohort. Future studies should target extensive resections and identify patients receiving large resuscitation volumes, as this population is more likely

  6. Effect of Visit-to-Visit Variation of Heart Rate and Systolic Blood Pressure on Outcomes in Chronic Systolic Heart Failure: Results From the Systolic Heart Failure Treatment With the If Inhibitor Ivabradine Trial (SHIFT) Trial.

    PubMed

    Böhm, Michael; Robertson, Michele; Borer, Jeffrey; Ford, Ian; Komajda, Michel; Mahfoud, Felix; Ewen, Sebastian; Swedberg, Karl; Tavazzi, Luigi

    2016-02-12

    Elevated resting heart rate (HR) and low systolic blood pressure (SBP) are related to poor outcomes in heart failure (HF). The association between visit-to-visit variation in SBP and HR and risk in HF is unknown. In Systolic Heart Failure Treatment with the If inhibitor ivabradine Trial (SHIFT) patients, we evaluated relationships between mean HR, mean SBP, and visit-to-visit variations (coefficient of variation [CV]=SD/mean×100%) in SBP and HR (SBP-CV and HR-CV, respectively) and primary composite endpoint (cardiovascular mortality or HF hospitalization), its components, all-cause mortality, and all-cause hospitalization. High HR and low SBP were closely associated with risk for primary endpoint, all-cause mortality, and HF hospitalization. The highest number of primary endpoint events occurred in the highest HR tertile (38.8% vs 16.4% lowest tertile; P<0.001). For HR-CV, patients at highest risk were those in the lowest tertile. Patients in the lowest thirds of mean SBP and SBP-CV had the highest risk. The combination of high HR and low HR-CV had an additive deleterious effect on risk, as did that of low SBP and low SBP-CV. Ivabradine reduced mean HR and increased HR-CV, and increased SBP and SBP-CV slightly. Beyond high HR and low SBP, low HR-CV and low SBP-CV are predictors of cardiovascular outcomes with additive effects on risk in HF, but with an unknown effect size. Beyond HR reduction, ivabradine increases HR-CV. Low visit-to-visit variation of HR and SBP might signal risk of cardiovascular outcomes in systolic HF. URL: http://www.isrctn.com/. Unique identifier: ISRCTN70429960. © 2016 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

  7. Indoor air pollution and its association with poor lung function, microalbuminuria and variations in blood pressure among kitchen workers in India: a cross-sectional study.

    PubMed

    Singh, Amarnath; Kesavachandran, Chandrasekharan Nair; Kamal, Ritul; Bihari, Vipin; Ansari, Afzal; Azeez, Parappurath Abdul; Saxena, Prem Narain; Ks, Anil Kumar; Khan, Altaf Hussain

    2017-04-04

    The present study is an attempt to explore the association between kitchen indoor air pollutants and physiological profiles in kitchen workers with microalbuminuria (MAU) in north India (Lucknow) and south India (Coimbatore). The subjects comprised 145 control subjects, 233 kitchen workers from north India and 186 kitchen workers from south India. Information related to the personal and occupational history and health of the subjects at both locations were collected using a custom-made questionnaire. Worker lung function was measured using a spirometer. Blood pressure was monitored using a sphygmomanometer. Urinary MAU was measured using a urine analyzer. Indoor air monitoring in kitchens for particulate matter (PM), total volatile organic compounds (TVOC), carbon dioxide (CO2) and carbon monoxide (CO) was conducted using indoor air quality monitors. The size and shape of PM in indoor air was assessed using a scanning electron microscope (SEM). Fourier transform infrared (FTIR) spectroscopy was used to detect organic or inorganic compounds in the air samples. Particulate matter concentrations (PM2.5 and PM1) were significantly higher in both north and south Indian kitchens than in non-kitchen areas. The concentrations of TVOC, CO and CO2 were higher in the kitchens of north and south India than in the control locations (non-kitchen areas). Coarse, fine and ultrafine particles and several elements were also detected in kitchens in both locations by SEM and elemental analysis. The FTIR spectra of kitchen indoor air at both locations show the presence of organic chemicals. Significant declines in systolic blood pressure and lung function were observed in the kitchen workers with MAU at both locations compared to those of the control subjects. A higher prevalence of obstruction cases with MAU was observed among the workers in the southern region than in the controls (p < 0.01). Kitchen workers in south India have lower lung capacities and a greater risk of

  8. Genetic variation in angiotensin II type 2 receptor gene influences extent of left ventricular hypertrophy in hypertrophic cardiomyopathy independent of blood pressure.

    PubMed

    Carstens, Nadia; van der Merwe, Lize; Revera, Miriam; Heradien, Marshall; Goosen, Althea; Brink, Paul A; Moolman-Smook, Johanna C

    2011-09-01

    Hypertrophic cardiomyopathy (HCM), an inherited primary cardiac disorder mostly caused by defective sarcomeric proteins, serves as a model to investigate left ventricular hypertrophy (LVH). HCM manifests extreme variability in the degree and distribution of LVH, even in patients with the same causal mutation. Genes coding for renin-angiotensin-aldosterone system components have been studied as hypertrophy modifiers in HCM, with emphasis on the angiotensin (Ang) II type 1 receptor (AT(1)R). However, Ang II binding to Ang II type 2 receptors (AT(2)R) also has hypertrophy-modulating effects. We investigated the effect of the functional +1675 G/A polymorphism (rs1403543) and additional single nucleotide polymorphisms in the 3' untranslated region of the AT(2)R gene (AGTR2) on a heritable composite hypertrophy score in an HCM family cohort in which HCM founder mutations segregate. We find significant association between rs1403543 and hypertrophy, with each A allele decreasing the average wall thickness by ~0.5 mm, independent of the effects of the primary HCM causal mutation, blood pressure and other hypertrophy covariates (p = 0.020). This study therefore confirms a hypertrophy-modulating effect for AT(2)R also in HCM and implies that +1675 G/A could potentially be used in a panel of markers that profile a genetic predisposition to LVH in HCM.

  9. Effects of microstructural variation on Charpy impact properties in heavy-section Mn-Mo-Ni low alloy steel for reactor pressure vessel

    NASA Astrophysics Data System (ADS)

    Hong, Seokmin; Song, Jaemin; Kim, Min-Chul; Choi, Kwon-Jae; Lee, Bong-Sang

    2016-03-01

    The effects of microstructural changes in heavy-section Mn-Mo-Ni low alloy steel on Charpy impact properties were investigated using a 210 mm thick reactor pressure vessel. Specimens were sampled from 5 different positions at intervals of 1/4 thickness from the inner surface to the outer surface. A detailed microstructural analysis of impact-fractured specimens showed that coarse carbides along the lath boundaries acted as fracture initiation sites, and cleavage cracks deviated at prior-austenite grain boundaries and bainite lath boundaries. Upper shelf energy was higher and energy transition temperature was lower at the surface positon, where fine bainitic microstructure with homogeneously distributed fine carbides were present. Toward the center, coarse upper bainite and precipitation of coarse inter-lath carbides were observed, which deteriorated impact properties. At the 1/4T position, the Charpy impact properties were worse than those at other positions owing to the combination of elongated-coarse inter-lath carbides and large effective grain size.

  10. Predictive modeling and reducing cyclic variability in autoignition engines

    DOEpatents

    Hellstrom, Erik; Stefanopoulou, Anna; Jiang, Li; Larimore, Jacob

    2016-08-30

    Methods and systems are provided for controlling a vehicle engine to reduce cycle-to-cycle combustion variation. A predictive model is applied to predict cycle-to-cycle combustion behavior of an engine based on observed engine performance variables. Conditions are identified, based on the predicted cycle-to-cycle combustion behavior, that indicate high cycle-to-cycle combustion variation. Corrective measures are then applied to prevent the predicted high cycle-to-cycle combustion variation.

  11. Short-term blood pressure variability - variation between arm side, body position and successive measurements: a population-based cohort study.

    PubMed

    Lacruz, Maria Elena; Kluttig, Alexander; Kuss, Oliver; Tiller, Daniel; Medenwald, Daniel; Nuding, Sebastian; Greiser, Karin Halina; Frantz, Stefan; Haerting, Johannes

    2017-01-18

    Precise blood pressure (BP) measurements are central for the diagnosis of hypertension in clinical and epidemiological studies. The purpose of this study was to quantify the variability in BP associated with arm side, body position, and successive measurements in the setting of a population-based observational study. Additionally, we aimed to evaluate the influence of different measurement conditions on prevalence of hypertension. The sample included 967 men and 812 women aged 45 to 83 years at baseline. BP was measured according to a standardized protocol with oscillometric devices including three sitting measurements at left arm, one simultaneous supine measurement at both arms, and four supine measurements at the arm with the higher BP. Hypertension was defined as systolic BP (SBP) ≥140 mmHg and/or diastolic BP (DBP) ≥90 mmHg. Variability in SBP and DBP were analysed with sex-stratified linear covariance pattern models. We found that overall, no mean BP differences were measured according to arm-side, but substantial higher DBP and for men also higher SBP was observed in sitting than in supine position and there was a clear BP decline by consecutive measurement. Accordingly, the prevalence of hypertension depends strongly on the number and scheme of BP measurements taken to calculate the index values. Thus, BP measurements should only be compared between studies applying equal measurement conditions and index calculation. Moreover, the first BP measurement should not be used to define hypertension since it overestimates BP. The mean of second and third measurement offers the advantage of better reproducibility over single measurements.

  12. Application of thermodynamic modelling to natural mantle xenoliths: examples of density variations and pressure-temperature evolution of the lithospheric mantle

    NASA Astrophysics Data System (ADS)

    Ziberna, L.; Klemme, S.

    2016-02-01

    In this paper, we show how the results of phase equilibria calculations in different mantle compositions can be reconciled with the evidence from natural mantle samples. We present data on the response of bulk rock density to pressure (P), temperature (T) and compositional changes in the lithospheric mantle and obtain constraints on the P-T evolution recorded by mantle xenoliths. To do this, we examine the mantle xenolith suite from the Quaternary alkali basalts of Pali-Aike, Patagonia, using phase equilibria calculation in six representative compositions. The calculations were done subsolidus and in volatile-free conditions. Our results show that the density change related to the spinel peridotite to garnet peridotite transition is not sharp and strongly depends on the bulk composition. In a depleted mantle composition, this transition is not reflected in the density profile, while in a fertile mantle it leads to a relative increase in density with respect to more depleted compositions. In mantle sections characterized by hot geothermal gradients (~70 mW/m2), the spinel-garnet transition may overlap with the lithosphere-asthenosphere boundary. Phase equilibria calculations in peridotitic compositions representative of the Pali-Aike mantle were also used to constrain the origin and evolution of the mantle xenoliths. Our results indicate that the mineral modes and compositions, and the mineral zonation reported for the low-temperature peridotites (spinel and spinel + garnet harzburgites and lherzolites), are linked to a cooling event in the mantle which occurred long before the eruption of the host basalts. In addition, our phase equilibria calculations show that kelyphitic rims around garnets, as those observed in the high-temperature garnet peridotites from Pali-Aike, can be explained simply by decompression and do not require additional metasomatic fluid or melt.

  13. Chaos in atmospheric-pressure plasma jets

    NASA Astrophysics Data System (ADS)

    Walsh, J. L.; Iza, F.; Janson, N. B.; Kong, M. G.

    2012-06-01

    We report detailed characterization of a low-temperature atmospheric-pressure plasma jet that exhibits regimes of periodic, quasi-periodic and chaotic behaviors. Power spectra, phase portraits, stroboscopic section and bifurcation diagram of the discharge current combine to comprehensively demonstrate the existence of chaos, and this evidence is strengthened with a nonlinear dynamics analysis using two control parameters that maps out periodic, period-multiplication, and chaotic regimes over a wide range of the input voltage and gas flow rate. In addition, optical emission signatures of excited plasma species are used as the second and independent observable to demonstrate the presence of chaos and period-doubling in both the concentrations and composition of plasma species, suggesting a similar array of periodic, quasi-periodic and chaotic regimes in plasma chemistry. The presence of quasi-periodic and chaotic regimes in structurally unbounded low-temperature atmospheric plasmas not only is important as a fundamental scientific topic but also has interesting implications for their numerous applications. Chaos may be undesirable for industrial applications where cycle-to-cycle reproducibility is important, yet for treatment of cell-containing materials including living tissues it may offer a novel route to combat some of the major challenges in medicine such as drug resistance. Chaos in low-temperature atmospheric plasmas and its effective control are likely to open up new vistas for medical technologies.

  14. The E23K and A190A variations of the KCNJ11 gene are associated with early-onset type 2 diabetes and blood pressure in the Chinese population.

    PubMed

    Zhuang, Langen; Zhao, Yu; Zhao, Weijing; Li, Ming; Yu, Ming; Lu, Ming; Zhang, Rong; Ge, Xiaoxu; Zheng, Taishan; Li, Can; Yin, Jun; Yin, Jingyuan; Bao, Yuqian; Liu, Limei; Jia, Weiping; Liu, Yanjun

    2015-06-01

    Conflicting associations between define (KCNJ11) variations and susceptibility to late-onset (>40 years old) type 2 diabetes mellitus (T2DM) have been reported in different ethnic groups. We investigated whether the E23K (G→A, rs5219) or A190A (C→T, rs5218) variations in KCNJ11 are associated with early-onset T2DM and blood pressure in the Chinese population. Case-control study of 175 unrelated Chinese patients with early-onset T2DM (age of onset <40 years old) who receive (ins+, n = 57) or do not receive insulin (ins-, n = 118), and 182 non-diabetic control subjects. PCR-direct sequencing was performed to genotype E23K and A190A; the genotypic frequencies and associations with clinical characteristics were analyzed. The genotypic frequencies of E23K-GA+AA were higher and A190A-TT was lower in the early-onset T2DM group, especially the T2D-ins+ group, compared to the non-diabetic control group (p < 0.01 or 0.05, respectively). In non-diabetic subjects, E23K-AA carriers had significantly higher 2 h plasma glucose and lower 2 h insulin than E23K-GG carriers (both p < 0.05). A190A-TT or E23K-GG carriers had higher systolic blood pressure (SBP) than CC or AA carriers in the non-diabetic control and T2DM groups (both p < 0.05). In the T2DM ins+ group, E23K-AA carriers had lower onset age and duration of diabetes and higher BMI than GG carriers, and A190A-TT carriers had higher SBP than CC carriers (all p < 0.05). The E23K-GA or AA genotypes may increase the susceptibility to early-onset T2DM, while A190A-TT may protect against early-onset T2DM. On the other hand the A190A-TT or E23K-GG genotypes may increase the risk of hypertension in the Chinese population.

  15. X-ray Monitoring of eta Carinae: Variations on a Theme

    NASA Technical Reports Server (NTRS)

    Corcoran, M. F.

    2004-01-01

    We present monitoring observations by the Rossi X-ray Timing Explorer of the 2-10 keV X-ray emission from the supermassive star eta Carinae from 1996 through late 2003. These data cover more than one of the stellar variability cycles in temporal detail and include especially detailed monitoring through two X-ray minima. We compare the current X-ray minimum which began on June 29, 2003 to the previous X-ray minimum which began on December 15, 1997, and refine the X-ray period to 2024 days. We examine the variations in the X-ray spectrum with phase and with time, and also refine our understanding of the X-ray peaks which have a quasi-period of 84 days, with significant variation. Cycle-to-cycle differences are seen in the level of X-ray intensity and in the detailed variations of the X-ray flux on the rise to maximum just prior to the X-ray minimum. Despite these differences the similarities between the decline to minimum, the duration of the minimum, and correlated variations of the X-ray flux and other measures throughout the electromagnetic spectrum leave little doubt that that the X-ray variation is strictly periodic and produced by orbital motion as the wind from eta Carinae collides with the wind of an otherwise unseen companion.

  16. Shoulder Pain and Cycle to Cycle Kinematic Spatial Variability during Recovery Phase in Manual Wheelchair Users: A Pilot Investigation

    PubMed Central

    Jayaraman, Chandrasekaran; Moon, Yaejin; Rice, Ian M.; Hsiao Wecksler, Elizabeth T.; Beck, Carolyn L.; Sosnoff, Jacob J.

    2014-01-01

    Wheelchair propulsion plays a significant role in the development of shoulder pain in manual wheelchair users (MWU). However wheelchair propulsion metrics related to shoulder pain are not clearly understood. This investigation examined intra-individual kinematic spatial variability during semi-circular wheelchair propulsion as a function of shoulder pain in MWU. Data from 10 experienced adult MWU with spinal cord injury (5 with shoulder pain; 5 without shoulder pain) were analyzed in this study. Participants propelled their own wheelchairs on a dynamometer at 3 distinct speeds (self-selected, 0.7 m/s, 1.1 m/s) for 3 minutes at each speed. Motion capture data of the upper limbs were recorded. Intra-individual kinematic spatial variability of the steady state wrist motion during the recovery phase was determined using principal component analysis (PCA). The kinematic spatial variability was calculated at every 10% intervals (i.e at 11 interval points, from 0% to 100%) along the wrist recovery path. Results Overall, spatial variability was found to be highest at the start and end of the recovery phase and lowest during the middle of the recovery path. Individuals with shoulder pain displayed significantly higher kinematic spatial variability than individuals without shoulder pain at the start (at 10% interval) of the recovery phase (p<.004). Conclusions Analysis of intra-individual kinematic spatial variability during the recovery phase of manual wheelchair propulsion distinguished between those with and without shoulder pain. Variability analysis of wheelchair propulsion may offer a new approach to monitor the development and rehabilitation of shoulder pain. PMID:24614232

  17. Pressure Sores

    MedlinePlus

    ... night. Pressure sores also are called bedsores or pressure ulcers. The sores change appearance over 4 stages. In ... SeniorsTags: antibiotics, Dermatologic, elderly, higher, older adults, Overview, Pressure Ulcers Family Health, Seniors September 2000 Copyright © American Academy ...

  18. Blood pressure

    MedlinePlus Videos and Cool Tools

    Normal blood pressure is important for proper blood flow to the body's organs and tissues. The force of the blood on the walls of the arteries is called blood pressure. Blood pressure is measured both as the heart ...

  19. Peer Pressure

    MedlinePlus

    ... Surgery? A Week of Healthy Breakfasts Shyness Peer Pressure KidsHealth > For Teens > Peer Pressure A A A ... for the school play. previous continue When the Pressure's On Sometimes, though, the stresses in your life ...

  20. Variational filtering.

    PubMed

    Friston, K J

    2008-07-01

    This note presents a simple Bayesian filtering scheme, using variational calculus, for inference on the hidden states of dynamic systems. Variational filtering is a stochastic scheme that propagates particles over a changing variational energy landscape, such that their sample density approximates the conditional density of hidden and states and inputs. The key innovation, on which variational filtering rests, is a formulation in generalised coordinates of motion. This renders the scheme much simpler and more versatile than existing approaches, such as those based on particle filtering. We demonstrate variational filtering using simulated and real data from hemodynamic systems studied in neuroimaging and provide comparative evaluations using particle filtering and the fixed-form homologue of variational filtering, namely dynamic expectation maximisation.

  1. Atmospheric Pressure During Landing

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This figure shows the variation with time of pressure (dots) measured by the Pathfinder MET instrument during the landing period shown in image PIA00797. The two diamonds indicate the times of bridal cutting and 1st impact. The overall trend in the data is of pressure increasing with time. This is almost certainly due to the lander rolling downhill by roughly 10 m. The spacing of the horizontal dotted lines indicates the pressure change expected from 10 m changes in altitude. Bounces may also be visible in the data.

  2. System accurately controls pressure in cryogenic tanks

    NASA Technical Reports Server (NTRS)

    Kirchmeier, W. E., Jr.

    1971-01-01

    High-resolution differential pressure transducer senses very small positive or negative pressure variations in the cryogenic tank relative to absolute reference pressure. System is useful in calibrating instruments where working fluid must be maintained at closely controlled temperature, or in processes requiring very fine pressure control.

  3. Estimation of trapped mass by in-cylinder pressure resonance in HCCI engines

    NASA Astrophysics Data System (ADS)

    Luján, José Manuel; Guardiola, Carlos; Pla, Benjamín; Bares, Pau

    2016-01-01

    High pressure gradients at homogeneous charge compression ignition (HCCI) engines heavily excite the pressure resonance. The pressure resonant frequency depends on speed of sound in the cylinder, and thus on the bulk gas temperature. Present paper profits this relation estimating the trapped mass inside the cylinder. In contrast to other estimation methods in the literature, the presented method is based on the trace of the in-cylinder pressure during the cycle; therefore, it permits a cycle-to-cycle mass estimation, and avoids errors associated with other assumptions, such as heat transfer during compression or initial temperature of the in-cylinder gases. The proposed strategy only needs the pressure signal, a volume estimation and a composition assumption to obtain several trapped mass estimates during one cycle. These estimates can be later combined for providing an error estimate of the measurement, with the assumption of negligible blow-by. The method is demonstrated in two HCCI engines of different size, showing good performance in steady operation and presenting great potential to control transient operation.

  4. Pressure Sores

    MedlinePlus

    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 ...

  5. Pressure levels and pulsation frequencies can be varied on high pressure/frequency testing device

    NASA Technical Reports Server (NTRS)

    Routson, J. W.

    1967-01-01

    Hydraulic system components test device obtains a pulsating pressure from a hydraulic actuator that is being driven by a vibration exciter of sufficient force and displacement. Input to the exciter controls the frequency of pressure variation.

  6. Barometric pressure

    NASA Technical Reports Server (NTRS)

    Billings, C. E.

    1973-01-01

    The effects of alterations in barometric pressure on human beings are described. Human tolerances for gaseous environments and low and high barometric pressure are discussed, including effects on specific areas, such as the ear, lungs, teeth, and sinuses. Problems due to trapped gas within the body, high dynamic pressures on the body, and blasts are also considered.

  7. Pressurizer tank upper support

    DOEpatents

    Baker, Tod H.; Ott, Howard L.

    1994-01-01

    A pressurizer tank in a pressurized water nuclear reactor is mounted between structural walls of the reactor on a substructure of the reactor, the tank extending upwardly from the substructure. For bearing lateral loads such as seismic shocks, a girder substantially encircles the pressurizer tank at a space above the substructure and is coupled to the structural walls via opposed sway struts. Each sway strut is attached at one end to the girder and at an opposite end to one of the structural walls, and the sway struts are oriented substantially horizontally in pairs aligned substantially along tangents to the wall of the circular tank. Preferably, eight sway struts attach to the girder at 90.degree. intervals. A compartment encloses the pressurizer tank and forms the structural wall. The sway struts attach to corners of the compartment for maximum stiffness and load bearing capacity. A valve support frame carrying the relief/discharge piping and valves of an automatic depressurization arrangement is fixed to the girder, whereby lateral loads on the relief/discharge piping are coupled directly to the compartment rather than through any portion of the pressurizer tank. Thermal insulation for the valve support frame prevents thermal loading of the piping and valves. The girder is shimmed to define a gap for reducing thermal transfer, and the girder is free to move vertically relative to the compartment walls, for accommodating dimensional variation of the pressurizer tank with changes in temperature and pressure.

  8. Pressurizer tank upper support

    DOEpatents

    Baker, T.H.; Ott, H.L.

    1994-01-11

    A pressurizer tank in a pressurized water nuclear reactor is mounted between structural walls of the reactor on a substructure of the reactor, the tank extending upwardly from the substructure. For bearing lateral loads such as seismic shocks, a girder substantially encircles the pressurizer tank at a space above the substructure and is coupled to the structural walls via opposed sway struts. Each sway strut is attached at one end to the girder and at an opposite end to one of the structural walls, and the sway struts are oriented substantially horizontally in pairs aligned substantially along tangents to the wall of the circular tank. Preferably, eight sway struts attach to the girder at 90[degree] intervals. A compartment encloses the pressurizer tank and forms the structural wall. The sway struts attach to corners of the compartment for maximum stiffness and load bearing capacity. A valve support frame carrying the relief/discharge piping and valves of an automatic depressurization arrangement is fixed to the girder, whereby lateral loads on the relief/discharge piping are coupled directly to the compartment rather than through any portion of the pressurizer tank. Thermal insulation for the valve support frame prevents thermal loading of the piping and valves. The girder is shimmed to define a gap for reducing thermal transfer, and the girder is free to move vertically relative to the compartment walls, for accommodating dimensional variation of the pressurizer tank with changes in temperature and pressure. 10 figures.

  9. The vapor pressures of explosives

    SciTech Connect

    Ewing, Robert G.; Waltman, Melanie J.; Atkinson, David A.; Grate, Jay W.; Hotchkiss, Peter

    2013-01-05

    The vapor pressures of many explosive compounds are extremely low and thus determining accurate values proves difficult. Many researchers, using a variety of methods, have measured and reported the vapor pressures of explosives compounds at single temperatures, or as a function of temperature using vapor pressure equations. There are large variations in reported vapor pressures for many of these compounds, and some errors exist within individual papers. This article provides a review of explosive vapor pressures and describes the methods used to determine them. We have compiled primary vapor pressure relationships traceable to the original citations and include the temperature ranges for which they have been determined. Corrected values are reported as needed and described in the text. In addition, after critically examining the available data, we calculate and tabulate vapor pressures at 25 °C.

  10. Pressure gauge

    SciTech Connect

    Morita, S.

    1985-04-02

    A pressure receiving element for receiving an external pressure is attached to one end of a body and a temperature compensating diaphragm is attached to the other end of the body. A coupling shaft disposed in the body is fixed at both ends to the pressure receiving element and the diaphragm, respectively. A liquid is sealed in the body and means is provided for detecting displacement or force applied to the coupling shaft in accordance with a pressure received by the pressure receiving element. The diaphragm has corrugations of concentric circles and the crests of a plurality of them are made flat and one of the flat crests is fixed to the body. The effective area of the diaphragm inside of the flat crest that is fixed to the body is selected substantially to be equal to the effective area of the pressure receiving element.

  11. A study on the effects of inhibition of prostaglandin biosynthesis with flunixin meglumine and later administration of prostaglandin F2 alpha on the intraluminal pressure variations in the isthmus of the oviduct in unrestrained gilts.

    PubMed

    Pettersson, A; Einarsson, S; Kindahl, H

    1993-01-01

    Three gilts were each equipped with 2 ultra-miniature pressure sensors, placed at 2 different points along the same isthmus of the oviduct. Following base recordings of isthmic intraluminal pressure, the gilts were treated with 2.2 mg flunixin meglumine (FM) per kg body weight. After FM treatment, the peripheral plasma levels of 15-ketodihydro-PGF2 alpha, the major metabolite of prostaglandin F2 alpha (PGF2 alpha), decreased within 30 min. The frequency of the phasic pressure fluctuations in the isthmus of the oviduct decreased after FM treatment. Exogenous administration of PGF2 alpha increased the peripheral plasma levels of 15-ketodihydro-PGF2 alpha. When administered at a dose of 0.1 mg, PGF2 alpha produced an increase in the frequency of the phasic pressure fluctuations in the oviductal isthmus. When the PGF2 alpha dose was increased to 0.5 mg, a marked increase in the base and total pressures was seen in addition to the increase in the frequency of the phasic pressure fluctuations.

  12. High-pressure microfluidics

    NASA Astrophysics Data System (ADS)

    Hjort, K.

    2015-03-01

    When using appropriate materials and microfabrication techniques, with the small dimensions the mechanical stability of microstructured devices allows for processes at high pressures without loss in safety. The largest area of applications has been demonstrated in green chemistry and bioprocesses, where extraction, synthesis and analyses often excel at high densities and high temperatures. This is accessible through high pressures. Capillary chemistry has been used since long but, just like in low-pressure applications, there are several potential advantages in using microfluidic platforms, e.g., planar isothermal set-ups, large local variations in geometries, dense form factors, small dead volumes and precisely positioned microstructures for control of reactions, catalysis, mixing and separation. Other potential applications are in, e.g., microhydraulics, exploration, gas driven vehicles, and high-pressure science. From a review of the state-of-art and frontiers of high pressure microfluidics, the focus will be on different solutions demonstrated for microfluidic handling at high pressures and challenges that remain.

  13. Pressurized Sleeve

    NASA Technical Reports Server (NTRS)

    Lerner, Amy

    1988-01-01

    Garment part sustains pressure differential without unduly restricting the user. Sleeve withstands pressure difference of 8 lb/in2 while allowing wearer fairly easy movement. Sleeve consists of low-torque joint hardware, sewn fabric sections, and lengthwise strips of fabric that restrain sections.

  14. Cough gastric pressure and maximum expiratory mouth pressure in humans.

    PubMed

    Man, William D-C; Kyroussis, Dimitris; Fleming, Tracey A; Chetta, Alfredo; Harraf, Farzaneh; Mustfa, Naveed; Rafferty, Gerrard F; Polkey, Michael I; Moxham, John

    2003-09-15

    Maximal expiratory mouth pressure is a well established test that is used to assess expiratory muscle strength. However, low values are difficult to interpret, as they may result from technical difficulties in performing the test, particularly in patients with facial muscle weakness or bulbar dysfunction. We hypothesized that measuring the gastric pressure during a cough, a natural maneuver recruiting the expiratory muscles, might prove to be a useful additional test in the assessment of expiratory muscle function. Mouth expiratory and cough gastric pressures were measured in 99 healthy volunteers to obtain normal values and in 293 patients referred for respiratory muscle assessment to compare the two measurements. Between-occasion within-subject coefficient of variation, assessed in 24 healthy volunteers, was 10.3% for mouth pressure and 6.9% for cough. Mean +/- SD cough gastric pressure for normal males was 214.4 +/- 42.2 and 165.1 +/- 34.8 cm H2O for females. In 171 patients deemed weak by a low mouth expiratory pressure, 42% had a normal cough gastric pressure. In 105 patients deemed weak by a low cough gastric pressure, 5.7% had a normal expiratory mouth pressure. Low maximal expiratory mouth pressures do not always indicate expiratory muscle weakness. Cough gastric pressure provides a useful complementary test for the assessment of expiratory muscle strength.

  15. Pressure sensor

    DOEpatents

    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.

  16. Pressure Drop

    NASA Technical Reports Server (NTRS)

    Lawson, Mike

    2010-01-01

    Mike Lawson briefly discussed pressure drop for aerospace applications and presented short stories about adventures experienced while working at NASA and General Dynamics, including exposure to technologies like the Crew and Equipment Translation Aid (CETA) cart and the SWME.

  17. PRESSURE TRANSDUCER

    DOEpatents

    Sander, H.H.

    1959-10-01

    A pressure or mechanical force transducer particularly adaptable to miniature telemetering systems is described. Basically the device consists of a transistor located within a magnetic field adapted to change in response to mechanical force. The conduction characteristics of the transistor in turn vary proportionally with changes in the magnetic flux across the transistor such that the output (either frequency of amplitude) of the transistor circuit is proportional to mechanical force or pressure.

  18. Pressure regulator

    DOEpatents

    Ebeling, Jr., Robert W.; Weaver, Robert B.

    1979-01-01

    The pressure within a pressurized flow reactor operated under harsh environmental conditions is controlled by establishing and maintaining a fluidized bed of uniformly sized granular material of selected density by passing the gas from the reactor upwardly therethrough at a rate sufficient to fluidize the bed and varying the height of the bed by adding granular material thereto or removing granular material therefrom to adjust the backpressure on the flow reactor.

  19. Ambulatory blood pressure monitoring in hypertensive adolescents.

    PubMed

    Fixler, D E; Wallace, J M; Thornton, W E; Dimmitt, P

    1990-04-01

    The purpose of this study was to determine the ability of ambulatory blood pressure monitoring to identify youths with chronic blood pressure elevation. Nineteen adolescent boys were studied, ten had 5-year average systolic or diastolic pressures above the 95th percentile, nine had normal pressure. A Del Mar Avionics Pressurometer III system recorded an average of 121 readings on each subject. The coefficients of variation for pressure were similar for hypertensive and normotensive individuals. During classes, eight of the ten hypertensive youths had elevated pressures in over half of the measurements. Also during these classes eight of ten hypertensive boys had average systolic or diastolic pressure above the 95th percentile, whereas only one of nine normotensive boys had average pressures above this level. We suggest that schooltime ambulatory pressures may be most useful in classifying the blood pressure trend in a youth.

  20. Tolerance of intrinsic device variation in fuzzy restricted Boltzmann machine network based on memristive nano-synapses

    NASA Astrophysics Data System (ADS)

    Zhang, Teng; Yin, Minghui; Lu, Xiayan; Cai, Yimao; Yang, Yuchao; Huang, Ru

    2017-06-01

    Inspired by the architecture and principle of the human brain, neuromorphic computing has attracted enormous research interest due to its potential for massively parallel and energy-efficient computing, where nanoscale memristors are considered as perfect building blocks for hardware neural networks, serving as compact, analog synapses. However, the inherent variation in memristors has been regarded as a major obstacle to their practical application in neuromorphic computing. Here, for the first time, we demonstrate that this long-standing issue can be addressed by introducing fuzziness into the neural networks. We found that the cycle-to-cycle and device-to-device conductance variations in the on and off states of Pt/TaOx/Ta memristors statistically follow Gaussian distributions, and using an experimentally verified compact synapse model based on the electrical characteristics of Pt/TaOx/Ta devices, a fuzzy restricted Boltzmann machine (FRBM) network was constructed where all the weight states were fuzzified to accommodate device stochasticity. The FRBM network has shown significantly improved tolerance to device variation, as confirmed by increased accuracy in the benchmark test of MNIST handwritten digit classifications. This study thus provides a new route towards highly robust neuromorphic computing, even if the computing elements can be stochastic and inhomogeneous.

  1. Variation in pediatric surgical care.

    PubMed

    Cameron, Danielle B; Rangel, Shawn J

    2015-12-01

    Variation in care and outcomes are common in the management of children with surgical diseases. Differences in the availability of resources, patient and family preferences, ever-increasing fiscal pressure, and lack of high-quality data to guide clinical decision making are just a few factors that contribute to both the over and under-utilization of healthcare resources. Identification of data-driven, value-based "best practices" that are sensitive to differences in resource availability and patient preferences may be an important first step in establishing a practical framework for reducing unwarranted practice variation. The goal of this article is to explore the causes and influence of practice variation using appendicitis as a common condition to illustrate key concepts, and to propose solutions to mitigate unwarranted practice variation while preserving the spirit of innovation necessary to advance the field. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Pressure and temperature variation of the electrical conductivity of poly(propylene glycol) containing LiCF{sub 3}SO{sub 3}. Technical report, 1 June 1998--31 May 1999

    SciTech Connect

    Fontanella, J.J.

    1999-07-01

    Electrical conductivity, dielectric relaxation and DSC studies have been carried out on poly(propylene glycol) (PPG, average molecular weight 1025) and PPG containing LiCF{sub 3}SO{sub 3}. The complex impedance studies were made at frequencies from about 1 mHz to 100 MHz at pressures up to 0.3 GPa (3 kbar) over the temperature range 215--365 K. Both the complex impedance and DSC studies were carried out in vacuum or at atmospheric pressure over a temperature range of about 100--375K. The inadequacy of the widely used Vogel Tammann Filcher (VTF) or Williams Landel Ferry (WLF) equations to describe the vacuum electrical conductivity data is discussed. It is shown that the Bendler-Shlesinger (BENSH) formalism is a better representation of the data, particularly in the region close to the glass transition. The first pressure derivative of the electrical conductivity decreases strongly with temperature giving rise to a large decrease in the apparent activation volume as temperature increases.

  3. Pressure Inactivation of Bacillus Endospores

    PubMed Central

    Margosch, Dirk; Gänzle, Michael G.; Ehrmann, Matthias A.; Vogel, Rudi F.

    2004-01-01

    The inactivation of bacterial endospores by hydrostatic pressure requires the combined application of heat and pressure. We have determined the resistance of spores of 14 food isolates and 5 laboratory strains of Bacillus subtilis, B. amyloliquefaciens, and B. licheniformis to treatments with pressure and temperature (200 to 800 MPa and 60 to 80°C) in mashed carrots. A large variation in the pressure resistance of spores was observed, and their reduction by treatments with 800 MPa and 70°C for 4 min ranged from more than 6 log units to no reduction. The sporulation conditions further influenced their pressure resistance. The loss of dipicolinic acid (DPA) from spores that varied in their pressure resistance was determined, and spore sublethal injury was assessed by determination of the detection times for individual spores. Treatment of spores with pressure and temperature resulted in DPA-free, phase-bright spores. These spores were sensitive to moderate heat and exhibited strongly increased detection times as judged by the time required for single spores to grow to visible turbidity of the growth medium. The role of DPA in heat and pressure resistance was further substantiated by the use of the DPA-deficient mutant strain B. subtilis CIP 76.26. Taken together, these results indicate that inactivation of spores by combined pressure and temperature processing is achieved by a two-stage mechanism that does not involve germination. At a pressure between 600 and 800 MPa and a temperature greater than 60°C, DPA is released predominantly by a physicochemical rather than a physiological process, and the DPA-free spores are inactivated by moderate heat independent of the pressure level. Relevant target organisms for pressure and temperature treatment of foods are proposed, namely, strains of B. amyloliquefaciens, which form highly pressure-resistant spores. PMID:15574932

  4. Chemical Variations Affect Seismic Velocities Less Than Grain Size Variations

    NASA Astrophysics Data System (ADS)

    de Jong, B. H.; Jacobs, M. H.

    2001-12-01

    It is well known that mantle velocities depend on the ``Magnesium number'' of constituent minerals. According to our recently developed equation of state (Jacobs & Oonk, Calphad 24, 133--147, 2000) this speed varies almost linearly between 6.7422 (Mg2SiO4) and 6.0113 (Fe2SiO4) km/sec at 10 GPa and 1500 K, i.e. a velocity contrast of 730 m/sec, the canonical mantle composition at 400 km depth being 52% Mg2SiO4 in accordance with the estimates by Lee et al. (1998). We have shown experimentally elsewhere that grain size variations of isochemical, equal density, holocrystalline alkali disilicates affect acoustic velocities. These vary at room temperature and ambient pressure between 6.6 km/sec (coarse grained) and 7.7 km/sec (fine grained), a difference of 1100 m/sec, i.e. substantially larger than the above mentioned 730 m/sec for chemical variations. Such differences in grain size occur because of variations in time, temperature, transformation (TTT) conditions to which a material is subjected. Thus velocity variations as observed in the mantle do not necessarily reflect current hottter or colder localities or compositional variations. They more likely reflect different TTT conditions with concomitant fabric variation during subduction.

  5. Pressure Alopecia

    PubMed Central

    Davies, Kate E; Yesudian, PD

    2012-01-01

    Postoperative or pressure alopecia (PA) is an infrequently reported group of scarring and non-scarring alopecias. It has been reported after immobilization of the head during surgery and following prolonged stays on intensive care units, and may be analogous to a healed pressure ulcer. This review presents a summary of cases published in pediatrics and after cardiac, gynecological, abdominal and facial surgeries. PA may manifest as swelling, tenderness, and ulceration of the scalp in the first few postoperative days; in other cases, the alopecia may be the presenting feature with a history of scalp immobilization in the previous four weeks. The condition may cause considerable psychological distress in the long term. Regular head turning schedules and vigilance for the condition should be used as prophylaxis to prevent permanent alopecia. A multi-center study in high-risk patients would be beneficial to shed further light on the etiology of the condition. PMID:23180911

  6. Pressurized hopper

    SciTech Connect

    Densley, P.J.; Goldmann, L.H. Jr.

    1980-04-01

    A Secure Automated Fuel Fabrication Line is being developed to reduce personnel exposure and to improve safeguards. Fertile and fissile fuel powders are blended in the line for making fuel pellets. A pressurized hopper was developed for use not only as a blender, but also as a storage and feeding device. It works with or without injection tubes to produce a well-blended powder with reduced agglomerate population. Results of blending experiments using dry Kaolin clay and Tempra pigment are given. (DLC)

  7. Pressure transducer

    DOEpatents

    Anderson, T.T.; Roop, C.J.; Schmidt, K.J.; Gunchin, E.R.

    1987-02-13

    A pressure transducer suitable for use in high temperature environments includes two pairs of induction coils, each pair being bifilarly wound together, and each pair of coils connected as opposite arms of a four arm circuit; an electrically conductive target moveably positioned between the coil pairs and connected to a diaphragm such that deflection of the diaphragm causes axial movement of the target and an unbalance in the bridge output. 7 figs.

  8. Pressure transducer

    DOEpatents

    Anderson, Thomas T.; Roop, Conard J.; Schmidt, Kenneth J.; Gunchin, Elmer R.

    1989-01-01

    A pressure transducer suitable for use in high temperature environments includes two pairs of induction coils, each pair being bifilarly wound together, and each pair of coils connected as opposite arms of a four arm circuit; an electrically conductive target moveably positioned between the coil pairs and connected to a diaphragm such that deflection of the diaphragm causes axial movement of the target and an unbalance in the bridge output.

  9. Induced topological pressure for topological dynamical systems

    SciTech Connect

    Xing, Zhitao; Chen, Ercai

    2015-02-15

    In this paper, inspired by the article [J. Jaerisch et al., Stochastics Dyn. 14, 1350016, pp. 1-30 (2014)], we introduce the induced topological pressure for a topological dynamical system. In particular, we prove a variational principle for the induced topological pressure.

  10. Pressure-Letdown Plates for Coal Gasifiers

    NASA Technical Reports Server (NTRS)

    Collins, E. R., Jr.

    1985-01-01

    Variation of pseudoporous plates used with coal gasifiers in pressure letdown stage of processing minimize clogging. Rotating plates containing variable gap annuli continually change flow path to enable erosionless reduction of gas pressure. Particles that otherwise clog porous plugs pass through gaps.

  11. Simple device to determine the pressure applied by pressure clips for the treatment of earlobe keloids

    PubMed Central

    Sasidharan, Aashish; David, Ann; Gohil, Amish; Gupta, Ashish Kumar

    2015-01-01

    Background: Keloids of the ear are common problems. Various treatment modalities are available for the treatment of ear keloids. Surgical excision with intralesional steroid injection along with compression therapy has the least recurrence rate. Various types of devices are available for pressure therapy. Pressure applied by these devices is uncontrolled and is associated with the risk of pressure necrosis. We describe here a simple and easy to use device to measure pressure applied by these clips for better outcome. Objectives: To devise a simple method to measure the pressure applied by various pressure clips used in ear keloid pressure therapy. Materials and Methods: By using a force sensitive resistor (FSR), the pressure applied gets converted into voltage using electrical wires, resistors, capacitors, converter, amplifier, diode, nine-volt (9V) cadmium battery and the voltage is measured using a multimeter. The measured voltage is then converted into pressure using pressure voltage graph that depicts the actual pressure applied by the pressure clip. Results: The pressure applied by different clips was variable. The spring clips were adjustable by slight variation in the design whereas the pressure applied by binder clips and magnet discs was not adjustable. Conclusion: The uncontrolled/suboptimal pressure applied by certain pressure clips can be monitored to provide optimal pressure therapy in ear keloid for better outcome. PMID:26933284

  12. A film pressure sensor based on optical fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Zhang, Zhichun; Deng, Gang; Dai, Yongbo; Liu, Yanju; Leng, Jinsong

    2010-03-01

    The measurement of pressure is essential for the design and flying controlling of aircraft. In order to measure the surface pressures of the aircraft, the common pressure tube method and Pressure sensitive paint measurement method have their own disadvantages, and are not applicable to all aircraft structures and real time pressure monitoring. In this paper, a novel thin film pressure sensor based on Fiber Bragg Grating (FBG) is proposed, using FBG measuring the tangential strain of the disk sensing film. Theoretical circle strain of the disk sensing film of the pressure sensor under pressure and temperature variation are analyzed, and the linear relationship between FBG center wavelength shift and pressure, temperature variation is gotten. The pressure and temperature calibration experiments prove the theoretical analysis. But the calibration sensing parameters are small than the calculating ones, which is caused by the constraint of optical fibre to the thin sensing film.

  13. Organic electronics based pressure sensor towards intracranial pressure monitoring

    NASA Astrophysics Data System (ADS)

    Rai, Pratyush; Varadan, Vijay K.

    2010-04-01

    The intra-cranial space, which houses the brain, contains cerebrospinal fluid (CSF) that acts as a fluid suspension medium for the brain. The CSF is always in circulation, is secreted in the cranium and is drained out through ducts called epidural veins. The venous drainage system has inherent resistance to the flow. Pressure is developed inside the cranium, which is similar to a rigid compartment. Normally a pressure of 5-15 mm Hg, in excess of atmospheric pressure, is observed at different locations inside the cranium. Increase in Intra-Cranial Pressure (ICP) can be caused by change in CSF volume caused by cerebral tumors, meningitis, by edema of a head injury or diseases related to cerebral atrophy. Hence, efficient ways of monitoring ICP need to be developed. A sensor system and monitoring scheme has been discussed here. The system architecture consists of a membrane less piezoelectric pressure sensitive element, organic thin film transistor (OTFT) based signal transduction, and signal telemetry. The components were fabricated on flexible substrate and have been assembled using flip-chip packaging technology. Material science and fabrication processes, subjective to the device performance, have been discussed. Capability of the device in detecting pressure variation, within the ICP pressure range, is investigated and applicability of measurement scheme to medical conditions has been argued for. Also, applications of such a sensor-OTFT assembly for logic sensor switching and patient specific-secure monitoring system have been discussed.

  14. Naturally occurring human genetic variation in the 3’-untranslated region of the secretory protein chromogranin A (CHGA) is associated with autonomic blood pressure regulation and hypertension in sex-dependent fashion

    PubMed Central

    Chen, Yuqing; Rao, Fangwen; Rodriguez-Flores, Juan L.; Mahata, Manjula; Fung, Maple M.; Stridsberg, Mats; Vaingankar, Sucheta M.; Wen, Gen; Salem, Rany M.; Das, Madhusudan; Cockburn, Myles G.; Schork, Nicholas J.; Ziegler, Michael G.; Hamilton, Bruce A.; Mahata, Sushil K.; Taupenot, Laurent; O’Connor, Daniel T.

    2008-01-01

    Objective Determination whether common variation at the CHGA locus increases susceptibility to hypertension. Background Chromogranin A (CHGA) regulates catecholamine storage and release. Previously we systematically identified genetic variants across CHGA. Methods Dense genotyping across the CHGA locus in >1000 individuals with the most extreme BPs in the population, as well twin pairs with autonomic phenotypes. Characterizing function of a trait-associated 3'-UTR variant with transfected CHGA 3'-UTR/luciferase reporter plasmids. Results CHGA was overexpressed in patients with hypertension, especially hypertensive men, and CHGA predicted catecholamines. In individuals with extreme BPs, CHGA genetic variants predicted BP, especially in men, with a peak association occurred in the 3'-UTR at C+87T, accounting for up to ~12/~9 mmHg. The C+87T genotype predicted CHGA secretion in vivo, with the +87T allele (associated with lower BP) also diminishing plasma CHGA by ~10%. The C+87T 3'-UTR variant also predicted the BP response to environmental (cold) stress; the same allele (+87T) that diminished basal BP in the population also decreased the SBP response to stress by ~12 mmHg, and the response was smaller in women (by ~6 mmHg). In a chromaffin cell-transfected CHGA 3'-UTR/luciferase reporter plasmid, the +87T allele associated with lower BP also decreased reporter expression by ~30%. In cultured chromaffin cells, reducing endogenous Chga expression by si-RNA caused ~2/3 depletion of catecholamine storage vesicles. Conclusions Common variant C+87T in the CHGA 3'-UTR is a functional polymorphism causally associated with hypertension especially in men of the population, and propose steps ("intermediate phenotypes") whereby in sex-dependent fashion this genetic variant influences the ultimate disease trait. These observations suggest new molecular strategies to probe the pathophysiology, risk, and rational treatment of hypertension. PMID:19017515

  15. Pressure calibration in solid pressure transmitting medium in large volume press.

    PubMed

    Yan, Xiaozhi; Ren, Xiangting; He, Duanwei

    2016-12-01

    The pressure limit in the large-volume-press (LVP) is increasing, but the in situ pressure calibration in LVP is still not a well resolved problem. The variation of the electrical resistance of the manganin with pressure in a hydrostatic condition is well known and is widely used in the pressure calibration in LVP. However, the hydrostatic pressure condition is hard to be maintained for the unavoidable solidification of the pressure transmitting medium (PTM) with pressure increasing. Moreover, our understanding about the relationship between pressure and manganin's resistance in a solid transmitting medium is still limited. Therefore, it is difficult to calibrate higher pressure using manganin. We measured the electrical resistance of manganin under pressure in pyrophyllite, MgO, and NaCl, respectively. The results show a linear relationship between the resistance and pressure in the same PTM with good reproducibility. In addition, the resistance-pressure relationships of manganin in different PTM are obviously different. So the resistance of manganin in a given solid PTM can be satisfactorily used as a pressure gauge only in the same PTM but cannot be used in other pressure media. Our results make it possible to calibrate higher pressure in a solid pressure transmitting medium in LVP.

  16. Solar cycle variations in the solar wind

    NASA Technical Reports Server (NTRS)

    Freeman, John W.; Lopez, Ramon E.

    1986-01-01

    The solar cycle variations of various solar wind parameters are reviewed. It is shown that there is a gradual decrease in the duration of high-speed streams from the declining phase of solar cycle 20 through the ascending phase of cycle 21 and a corresponding decrease in the annual average of the proton speed toward solar maximum. Beta, the ratio of the proton thermal pressure to magnetic pressure, undergoes a significant solar cycle variation, as expected from the variation in the IMF. Individual hourly averages of beta often exceed unity with 20 cases exceeding 10 and one case as high as 25. The Alfven Mach number shows a solar cycle variation similar to beta, lower aboard solar maximum. High-speed streams can be seen clearly in epsilon and the y component of the interplanetary magnetic field.

  17. Measurement of static pressure on aircraft

    NASA Technical Reports Server (NTRS)

    Gracey, William

    1958-01-01

    Existing data on the errors involved in the measurement of static pressure by means of static-pressure tubes and fuselage vents are presented. The errors associated with the various design features of static-pressure tubes are discussed for the condition of zero angle of attack and for the case where the tube is inclined to flow. Errors which result from variations in the configuration of static-pressure vents are also presented. Errors due to the position of a static-pressure tube in the flow field of the airplane are given for locations ahead of the fuselage nose, ahead of the wing tip, and ahead of the vertical tail fin. The errors of static-pressure vents on the fuselage of an airplane are also presented. Various methods of calibrating static-pressure installations in flight are briefly discussed.

  18. Low Blood Pressure

    MedlinePlus

    ... a problem. Sometimes blood pressure that is too low can also cause problems. Blood pressure is the ... reading is 90/60 or lower, you have low blood pressure. Some people have low blood pressure ...

  19. Blood Pressure Test

    MedlinePlus

    ... blood pressure readings at home. Tracking your blood pressure readings It can be helpful in diagnosing or ... options might work best for you. Low blood pressure Low blood pressure that either doesn't cause ...

  20. 49 CFR 195.406 - Maximum operating pressure.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Maximum operating pressure. 195.406 Section 195... HAZARDOUS LIQUIDS BY PIPELINE Operation and Maintenance § 195.406 Maximum operating pressure. (a) Except for surge pressures and other variations from normal operations, no operator may operate a pipeline at...

  1. 49 CFR 195.406 - Maximum operating pressure.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Maximum operating pressure. 195.406 Section 195... HAZARDOUS LIQUIDS BY PIPELINE Operation and Maintenance § 195.406 Maximum operating pressure. (a) Except for surge pressures and other variations from normal operations, no operator may operate a pipeline at...

  2. 49 CFR 195.406 - Maximum operating pressure.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Maximum operating pressure. 195.406 Section 195... HAZARDOUS LIQUIDS BY PIPELINE Operation and Maintenance § 195.406 Maximum operating pressure. (a) Except for surge pressures and other variations from normal operations, no operator may operate a pipeline at...

  3. 49 CFR 195.406 - Maximum operating pressure.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Maximum operating pressure. 195.406 Section 195... HAZARDOUS LIQUIDS BY PIPELINE Operation and Maintenance § 195.406 Maximum operating pressure. (a) Except for surge pressures and other variations from normal operations, no operator may operate a pipeline at...

  4. Variation and Mathematics Pedagogy

    ERIC Educational Resources Information Center

    Leung, Allen

    2012-01-01

    This discussion paper put forwards variation as a theme to structure mathematical experience and mathematics pedagogy. Patterns of variation from Marton's Theory of Variation are understood and developed as types of variation interaction that enhance mathematical understanding. An idea of a discernment unit comprising mutually supporting variation…

  5. PRESSURE TRANSDUCER RESEARCH.

    DTIC Science & Technology

    PIEZOELECTRIC TRANSDUCERS, PRESSURE), UNDERGROUND EXPLOSIONS, ELECTRICAL RESISTANCE, SEEBECK EFFECT , PRESSURE GAGES, SHOCK WAVES, STRESSES, COMPUTER PROGRAMMING, NUCLEAR EXPLOSIONS, NUCLEAR RADIATION.

  6. Implementation of an automated on-line high-performance liquid chromatography monitoring system for 'cycle to cycle' control of simulated moving beds.

    PubMed

    Langel, Christian; Grossmann, Cristian; Morbidelli, Massimo; Morari, Manfred; Mazzotti, Marco

    2009-12-11

    In continuous chromatography simulated moving bed (SMB) is a firmly established powerful technique for the separation of fine chemicals and enantiomers. The use of a controller could improve the operation conditions and increase the productivity of an SMB unit. However, the performance of any controller is greatly affected by the reliability and the quality of the feedback information from the plant. Therefore, to overcome the limitations of optical detectors, such as UV and polarimeter, an automated on-line HPLC monitoring system was developed and installed to monitor the product streams. The performance of the system is tested experimentally separating a mixture of guaifenesin enantiomers on Chiralcel OD columns with ethanol as mobile phase in our laboratory SMB unit under both linear and nonlinear chromatographic conditions. The results show that the new monitoring system provides precise and accurate data about the concentration of the components in the two product streams. Moreover, they prove that despite disturbances a combination of the controller and the new on-line monitoring system allows to fulfill the product specifications and to improve the performance of the process in terms of feed throughput and solvent consumption.

  7. Pressure Characteristics of a Diffuser in a Ram RDE Propulsive Device

    DTIC Science & Technology

    2017-07-21

    pressure variation seen near the inlet is very sensitive to the shape of the forcing function. The broad pressure rise of the lower area ratios tend to...of pressure variation seen near the inlet is very sensitive to the shape of the forcing function. The broad pressure rise of the lower area ratios...very sensitive to the shape of the forcing function. The broad pressure rise of the lower area ratios tend to remain intact through the diffuser to

  8. Determinants of blood pressure in Navajo adolescents.

    PubMed

    Coulehan, J L; Topper, M D; Arena, V C; Welty, T K

    1990-01-01

    Hypertension is becoming more common among Navajo people, especially among young men. In a group of 580 Navajo adolescents, we looked for factors associated with variations in blood pressure level. Using our criteria, 11.1% of adolescent males and 1.6% of females had an elevated screening blood pressure. In males, blood pressure was a function of age only, and not significantly related either to obesity (body mass index) or measures of acculturation and personal adjustment. In females, blood pressure was not related to age, but was associated with body mass index. Systolic pressure in females was also associated with poor personal adjustment. Level of acculturation (by our index) had no bearing on blood pressure level in this population.

  9. Total pressure averaging in pulsating flows

    NASA Technical Reports Server (NTRS)

    Krause, L. N.; Dudzinski, T. J.; Johnson, R. C.

    1972-01-01

    A number of total-pressure tubes were tested in a non-steady flow generator in which the fraction of period that pressure is a maximum is approximately 0.8, thereby simulating turbomachine-type flow conditions. Most of the tubes indicated a pressure which was higher than the true average. Organ-pipe resonance which further increased the indicated pressure was encountered within the tubes at discrete frequencies. There was no obvious combination of tube diameter, length, and/or geometry variation used in the tests which resulted in negligible averaging error. A pneumatic-type probe was found to measure true average pressure, and is suggested as a comparison instrument to determine whether nonlinear averaging effects are serious in unknown pulsation profiles. The experiments were performed at a pressure level of 1 bar, for Mach number up to near 1, and frequencies up to 3 kHz.

  10. Laser techniques in high-pressure geophysics

    NASA Technical Reports Server (NTRS)

    Hemley, R. J.; Bell, P. M.; Mao, H. K.

    1987-01-01

    Laser techniques in conjunction with the diamond-anvil cell can be used to study high-pressure properties of materials important to a wide range of problems in earth and planetary science. Spontaneous Raman scattering of crystalline and amorphous solids at high pressure demonstrates that dramatic changes in structure and bonding occur on compression. High-pressure Brillouin scattering is sensitive to the pressure variations of single-crystal elastic moduli and acoustic velocities. Laser heating techniques with the diamond-anvil cell can be used to study phase transitions, including melting, under deep-earth conditions. Finally, laser-induced ruby fluorescence has been essential for the development of techniques for generating the maximum pressures now possible with the diamond-anvil cell, and currently provides a calibrated in situ measure of pressure well above 100 gigapascals.

  11. Laser techniques in high-pressure geophysics

    NASA Technical Reports Server (NTRS)

    Hemley, R. J.; Bell, P. M.; Mao, H. K.

    1987-01-01

    Laser techniques in conjunction with the diamond-anvil cell can be used to study high-pressure properties of materials important to a wide range of problems in earth and planetary science. Spontaneous Raman scattering of crystalline and amorphous solids at high pressure demonstrates that dramatic changes in structure and bonding occur on compression. High-pressure Brillouin scattering is sensitive to the pressure variations of single-crystal elastic moduli and acoustic velocities. Laser heating techniques with the diamond-anvil cell can be used to study phase transitions, including melting, under deep-earth conditions. Finally, laser-induced ruby fluorescence has been essential for the development of techniques for generating the maximum pressures now possible with the diamond-anvil cell, and currently provides a calibrated in situ measure of pressure well above 100 gigapascals.

  12. Decadal trends in the diurnal variation of galactic cosmic rays observed using neutron monitor data

    NASA Astrophysics Data System (ADS)

    Thomas, Simon; Owens, Mathew; Lockwood, Mike; Owen, Chris

    2017-07-01

    The diurnal variation (DV) in galactic cosmic ray (GCR) flux is a widely observed phenomenon in neutron monitor data. The background variation considered primarily in this study is due to the balance between the convection of energetic particles away from the Sun and the inward diffusion of energetic particles along magnetic field lines. However, there are also times of enhanced DV following geomagnetic disturbances caused by coronal mass ejections or corotating interaction regions. In this study we investigate changes in the DV over four solar cycles using ground-based neutron monitors at different magnetic latitudes and longitudes at Earth. We divide all of the hourly neutron monitor data into magnetic polarity cycles to investigate cycle-to-cycle variations in the phase and amplitude of the DV. The results show, in general, a similarity between each of the A < 0 cycles and A > 0 cycles, but with a phase change between the two. To investigate this further, we split the neutron monitor data by solar magnetic polarity between times when the dominant polarity was either directed outward (positive) or inward (negative) at the northern solar pole. We find that the maxima and minima of the DV changes by, typically, 1-2 h between the two polarity states for all non-polar neutron monitors. This difference between cycles becomes even larger in amplitude and phase with the removal of periods with enhanced DV caused by solar wind transients. The time difference between polarity cycles is found to vary in a 22-year cycle for both the maximum and minimum times of the DV. The times of the maximum and minimum in the DV do not always vary in the same manner between A > 0 and A < 0 polarity cycles, suggesting a slight change in the anisotropy vector of GCRs arriving at Earth between polarity cycles. Polar neutron monitors show differences in phase between polarity cycles which have asymptotic directions at mid-to-high latitudes. All neutron monitors show changes in the amplitude

  13. A wireless blood pressure monitoring system for personal health management.

    PubMed

    Li, Wun-Jin; Luo, Yuan-Long; Chang, Yao-Shun; Lin, Yuan-Hsiang

    2010-01-01

    In this paper, we developed a wireless blood pressure monitoring system which provides a useful tool for users to measure and manage their daily blood pressure values. This system includes an ARM-based blood pressure monitor with a ZigBee wireless transmission module and a PC-based management unit with graphic user interface and database. The wireless blood pressure monitor can measure the blood pressure and heart rate and then store and forward the measuring information to the management unit through the ZigBee wireless transmission. On the management unit, user can easy to see their blood pressure variation in the past using a line chart. Accuracy of blood pressure measurement has been verified by a commercial blood pressure simulator and shown the bias of systolic blood pressure is ≤ 1 mmHg and the bias of diastolic blood pressure is ≤ 1.4 mmHg.

  14. Genetics and variation

    Treesearch

    John R. Jones; Norbert V. DeByle

    1985-01-01

    The broad genotypic variability in quaking aspen (Populus tremuloides Michx.), that results in equally broad phenotypic variability among clones is important to the ecology and management of this species. This chapter considers principles of aspen genetics and variation, variation in aspen over its range, and local variation among clones. For a more...

  15. Bedsores (Pressure Sores)

    MedlinePlus

    ... Berlowitz D. Treatment of pressure ulcers. http://www.uptodate.com/home. Accessed Nov. 12, 2013. Gestring M. Negative pressure wound therapy. http://www.uptodate.com/home. Accessed Nov. 12, 2013. AskMayoExpert. Pressure ...

  16. Dealing with Peer Pressure

    MedlinePlus

    ... Video: Getting an X-ray Dealing With Peer Pressure KidsHealth > For Kids > Dealing With Peer Pressure Print ... talk about how to handle it. Defining Peer Pressure Peers influence your life, even if you don' ...

  17. Intracranial pressure monitoring

    MedlinePlus

    ... head. The monitor senses the pressure inside the skull and sends measurements to a recording device. ... are 3 ways to monitor pressure in the skull (intracranial pressure). INTRAVENTRICULAR CATHETER The intraventricular catheter is ...

  18. Yield-pressure determination

    NASA Technical Reports Server (NTRS)

    Wakefield, M. E.

    1977-01-01

    Stress/strain relationship of complex-shape vessel is recorded under hydrostatic pressure. Technique is used to test pressurized gas cylinders and tubular transition joints made of dissimilar metals and to determine burst or system-failure pressures.

  19. Dealing with Peer Pressure

    MedlinePlus

    ... Happens in the Operating Room? Dealing With Peer Pressure KidsHealth > For Kids > Dealing With Peer Pressure A ... talk about how to handle it. Defining Peer Pressure Peers influence your life, even if you don' ...

  20. High Blood Pressure

    MedlinePlus

    ... normal blood pressure 140/90 or higher is high blood pressure Between 120 and 139 for the top number, ... prehypertension. Prehypertension means you may end up with high blood pressure, unless you take steps to prevent it. High ...

  1. High Blood Pressure (Hypertension)

    MedlinePlus

    ... Print Page Text Size: A A A Listen High Blood Pressure (Hypertension) Nearly 1 in 3 American adults has ... weight. How Will I Know if I Have High Blood Pressure? High blood pressure is a silent problem — you ...

  2. High blood pressure

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/000468.htm High blood pressure To use the sharing features on this page, ... body. Hypertension is the term used to describe high blood pressure. Blood pressure readings are given as two numbers. ...

  3. High blood pressure medicines

    MedlinePlus

    Hypertension - medicines ... blood vessel diseases. You may need to take medicines to lower your blood pressure if lifestyle changes ... blood pressure to the target level. WHEN ARE MEDICINES FOR HIGH BLOOD PRESSURE USED Most of the ...

  4. Barocaloric effect and the pressure induced solid state refrigerator

    NASA Astrophysics Data System (ADS)

    de Oliveira, N. A.

    2011-03-01

    The current refrigerators are based on the heating and cooling of fluids under external pressure variation. The great inconvenience of this refrigeration technology is the damage caused to the environment by the refrigerant fluids. In this paper, we discuss the magnetic barocaloric effect, i.e., the heating or cooling of magnetic materials under pressure variation and its application in the construction of refrigerators using solid magnetic compounds as refrigerant materials and pressure as the external agent. The discussion presented in this paper points out that such a pressure induced solid state refrigerator can be very interesting because it is not harmful to the environment and can exhibit a good performance.

  5. Estimation of central systolic blood pressure using an oscillometric blood pressure monitor.

    PubMed

    Cheng, Hao-Min; Wang, Kang-Ling; Chen, Ying-Hwa; Lin, Shing-Jong; Chen, Lung-Ching; Sung, Shih-Hsien; Ding, Philip Yu-An; Yu, Wen-Chung; Chen, Jaw-Wen; Chen, Chen-Huan

    2010-06-01

    Current noninvasive techniques for assessing central aortic pressure require the recording of an arterial pressure wave using a high-fidelity applanation tonometer. We therefore developed and validated a novel method to estimate the central aortic systolic pressure using an oscillometric blood pressure monitor alone. Invasive high-fidelity right brachial and central aortic pressure waves, and left-brachial pulse volume plethysmography from an oscillometric blood pressure monitor, were obtained at baseline and 3 min after administration of sublingual nitroglycerin in 100 patients during cardiac catheterization. In the initial 50 patients (Generation Group), Central systolic blood pressure was predicted by a multi-variate prediction model generated from the comprehensive analysis of the invasive brachial pressure wave, including brachial late-systolic shoulder pressure value and parameters related to wave reflection and arterial compliance. Another prediction model was similarly constructed from the noninvasively calibrated pulse volume plethysmography. Both models were validated in the subsequent 50 patients (Validation Group) with results: r=0.98 (P<0.001) and mean difference=0.5+/-4.5 (95% confidence interval -8.3 to 9.3) mm Hg for the invasive model, and r=0.93 (P<0.001) and mean difference=-0.1+/-7.6 (95% confidence interval -15.0 to 14.8) mm Hg for the noninvasive model. Thus, our results indicate that central aortic systolic blood pressure could be estimated by analysis of the noninvasive brachial pressure wave alone from an oscillometric blood pressure monitor.

  6. Ultrasonic detection of atmospheric humidity variations

    NASA Astrophysics Data System (ADS)

    Harrison, R. Giles

    2001-03-01

    The small variation of the speed of sound in air with water vapor concentration is evaluated as a method of measuring atmospheric humidity. Laboratory acoustic phase measurements were made, using inexpensive piezoelectric transducers and electret microphones with dew point temperature independently monitored in the same enclosure. Phase variations from an acoustic path gave fair agreement with the measured humidity variations, when temperature and cross-wind variations were removed. Thermal stabilization and filtering were necessary to reduce the random phase noise contributions from the detectors, leading to errors in mean vapor pressure of ˜5 mbar at 20 °C. The approach is therefore more suited to determine turbulent humidity fluctuations, for meteorological latent heat flux measurements.

  7. NQR investigation of halogenate crystals under pressure

    NASA Astrophysics Data System (ADS)

    Baisa, D. F.; Barabash, A. I.; Vertegel, I. G.

    It is shown that the phase transition in the KIO 3 crystal at 120K is caused bv the ordering of an impurity in an asymmetrical two-minimum potential. The shape of this potential changes under hydrostatic pressure and the role of proton tunnel effect increases with increasing pressure. The transformation of intemoiecular hydrogen bond. length in the ∝ -HIO 3 crystal under pressure is studied. The value of the O-H....O bond length variation and the compressibility factor for the ∝-HIO 3 crystal is estimated.

  8. Ambient pressure and single-bubble sonoluminescence

    NASA Astrophysics Data System (ADS)

    Kondic, Ljubinko; Yuan, Chi; Chan, C. K.

    1998-01-01

    We present a theoretical analysis of the influence of ambient pressure on single-bubble sonoluminescence (SBSL). By combining simulations of gas dynamics, mass diffusion theory, and stability analysis we find a narrow region of the parameter space where stable SBSL is possible. In particular, the theory predicts a 200% increase in SL radiation if ambient pressure is decreased only 5%. The results are compared with preliminary experimental data, and a good agreement is found. Variation of ambient pressure provides a simple and interesting test for the validity of various SL theories, diffusive or nondiffusive mass flow ideas, and stability analyses.

  9. Development of a dynamic pressure calibration technique

    NASA Technical Reports Server (NTRS)

    Vezzetti, C. F.; Hilten, J. S.; Lederer, P. S.

    1975-01-01

    The report deals with work continuing on the development of a method of producing sinusoidally varying pressures of at least 34 kPa zero-to-peak with amplitude variations within plus or minus 5% up to 2 kHz for the dynamic calibration of pressure transducers. Sinusoidally varying pressures of 34 kPa zero-to-peak were produced between 40 Hz and 750 Hz by vibrating a 10-cm column of a dimethyl siloxane liquid at 36gn zero-to-peak. Damping of the liquid column was accomplished by packing the fixture tube with a number of smaller diameter tubes.

  10. Idiopathic recurrent calcium urolithiasis (IRCU): pathophysiology evaluated in light of oxidative metabolism, without and with variation of several biomarkers in fasting urine and plasma - a comparison of stone-free and -bearing male patients, emphasizing mineral, acid-base, blood pressure and protein status

    PubMed Central

    2011-01-01

    Background IRCU is traditionally considered as lifestyle disease (associations with, among others, overweight, obesity, hypertension, type-2 diabetes), arising from excess, in 24 h urine, of calcium (Ca) salts (calcium oxalate (CaOx), calcium phosphate (CaPi)), supersaturation of, and crystallization in, tubular fluid and urine, causing crystal-induced epithelial cell damage, proteinuria, crystal aggregation and uroliths. Methods Another picture emerges from the present uncontrolled study of 154 male adult IRCU patients (75 stone-bearing (SB) and 79 age-matched stone-free (SF)), in whom stone-forming and other parameters in fasting urine and plasma were contrasted with five biomarkers (see footnote) of oxidative metabolism (OM), without and with variation of markers. Results 1) In SB vs. SF unstratified OM biomarkers were statistically unchanged, but the majority of patients was overweight; despite, in SB vs. SF urine pH, total and non-albumin protein concentration were elevated, fractional urinary uric acid excretion and blood bicarbonate decreased, whereas urine volume, sodium, supersaturation with CaOx and CaPi (as hydroxyapatite) were unchanged; 2) upon variation of OM markers (strata below and above median) numerous stone parameters differed significant!)', among others urine volume, total protein, Ca/Pi ratio, pH, sodium, potassium, plasma Ca/Pi ratio and parathyroid hormone, blood pressure, renal excretion of non-albumin protein and other substances; 3) a significant shift from SF to SB patients occurred with increase of urine pH, decrease of blood bicarbonate, and increase of diastolic blood pressure, whereas increase of plasma uric acid impacted only marginally; 4) in both SF and SB patients a strong curvilinear relationship links a rise of urine Ca/Pi to urine Ca/Pi divided by plasma Ca/Pi, but in SB urine Ca/Pi failed to correlate significantly with urine hydroxyapatite supersaturation; 5) also in SB, plasma Ca/Pi and urinary nitrate were negatively

  11. Variable pressure ionization detector for gas chromatography

    DOEpatents

    Buchanan, Michelle V.; Wise, Marcus B.

    1988-01-01

    Method and apparatus for differentiating organic compounds based on their electron affinity. An electron capture detector cell (ECD) is operated at pressures ranging from atmospheric to less than 1 torr. Through variation of the pressure within the ECD cell, the organic compounds are induced to either capture or emit electrons. Differentiation of isomeric compounds can be obtianed when, at a given pressure, one isomer is in the emission mode and the other is in the capture mode. Output of the ECD is recorded by chromatogram. The invention also includes a method for obtaining the zero-crossing pressure of a compound, defined as the pressure at which the competing emission and capture reactions are balanced and which may be correlated to the electron affinity of a compound.

  12. Periodic Heat Transfer at Small Pressure Fluctuations

    NASA Technical Reports Server (NTRS)

    Pfriem, H.

    1943-01-01

    The effect of cyclic gas pressure variations on the periodic heat transfer at a flat wall is theoretically analyzed and the differential equation describing the process and its solution for relatively. Small pressure fluctuations developed, thus explaining the periodic heat cycle between gas and wall surface. The processes for pure harmonic pressure and temperature oscillations, respectively, in the gas space are described by means of a constant heat transfer coefficient and the equally constant phase angle between the appearance of the maximum values of the pressure and heat flow most conveniently expressed mathematically in the form of a complex heat transfer coefficient. Any cyclic pressure oscillations, can be reduced by Fourier analysis to harmonic oscillations, which result in specific, mutual relationships of heat-transfer coefficients and phase angles for the different harmonics.

  13. Personal Cabin Pressure Monitor and Warning System

    NASA Technical Reports Server (NTRS)

    Zysko, Jan A. (Inventor)

    2002-01-01

    A cabin pressure altitude monitor and warning system provides a warning when a detected cabin pressure altitude has reached a predetermined level. The system is preferably embodied in a portable, pager-sized device that can be carried or worn by an individual. A microprocessor calculates the pressure altitude from signals generated by a calibrated pressure transducer and a temperature sensor that compensates for temperature variations in the signals generated by the pressure transducer. The microprocessor is programmed to generate a warning or alarm if a cabin pressure altitude exceeding a predetermined threshold is detected. Preferably, the microprocessor generates two different types of warning or alarm outputs, a first early warning or alert when a first pressure altitude is exceeded. and a second more serious alarm condition when either a second. higher pressure altitude is exceeded, or when the first pressure altitude has been exceeded for a predetermined period of time. Multiple types of alarm condition indicators are preferably provided, including visual, audible and tactile. The system is also preferably designed to detect gas concentrations and other ambient conditions, and thus incorporates other sensors, such as oxygen, relative humidity, carbon dioxide, carbon monoxide and ammonia sensors, to provide a more complete characterization and monitoring of the local environment.

  14. Personal Cabin Pressure Monitor and Warning System

    NASA Astrophysics Data System (ADS)

    Zysko, Jan A.

    2002-09-01

    A cabin pressure altitude monitor and warning system provides a warning when a detected cabin pressure altitude has reached a predetermined level. The system is preferably embodied in a portable, pager-sized device that can be carried or worn by an individual. A microprocessor calculates the pressure altitude from signals generated by a calibrated pressure transducer and a temperature sensor that compensates for temperature variations in the signals generated by the pressure transducer. The microprocessor is programmed to generate a warning or alarm if a cabin pressure altitude exceeding a predetermined threshold is detected. Preferably, the microprocessor generates two different types of warning or alarm outputs, a first early warning or alert when a first pressure altitude is exceeded. and a second more serious alarm condition when either a second. higher pressure altitude is exceeded, or when the first pressure altitude has been exceeded for a predetermined period of time. Multiple types of alarm condition indicators are preferably provided, including visual, audible and tactile. The system is also preferably designed to detect gas concentrations and other ambient conditions, and thus incorporates other sensors, such as oxygen, relative humidity, carbon dioxide, carbon monoxide and ammonia sensors, to provide a more complete characterization and monitoring of the local environment.

  15. Personal Cabin Pressure Monitor and Warning System

    NASA Technical Reports Server (NTRS)

    Zysko, Jan A. (Inventor)

    2002-01-01

    A cabin pressure altitude monitor and warning system provides a warning when a detected cabin pressure altitude has reached a predetermined level. The system is preferably embodied in a portable, pager-sized device that can be carried or worn by an individual. A microprocessor calculates the pressure altitude from signals generated by a calibrated pressure transducer and a temperature sensor that compensates for temperature variations in the signals generated by the pressure transducer. The microprocessor is programmed to generate a warning or alarm if a cabin pressure altitude exceeding a predetermined threshold is detected. Preferably, the microprocessor generates two different types of warning or alarm outputs, a first early warning or alert when a first pressure altitude is exceeded. and a second more serious alarm condition when either a second. higher pressure altitude is exceeded, or when the first pressure altitude has been exceeded for a predetermined period of time. Multiple types of alarm condition indicators are preferably provided, including visual, audible and tactile. The system is also preferably designed to detect gas concentrations and other ambient conditions, and thus incorporates other sensors, such as oxygen, relative humidity, carbon dioxide, carbon monoxide and ammonia sensors, to provide a more complete characterization and monitoring of the local environment.

  16. Hypertension (High Blood Pressure)

    MedlinePlus

    ... Loss Surgery? A Week of Healthy Breakfasts Shyness Hypertension (High Blood Pressure) KidsHealth > For Teens > Hypertension (High Blood Pressure) A ... rest temperature diet emotions posture medicines Why Is High Blood Pressure Bad? High blood pressure means a person's heart ...

  17. High Blood Pressure

    MedlinePlus

    ... version of this page please turn Javascript on. High Blood Pressure What Is High Blood Pressure? High blood pressure is a common disease in ... the heart, kidneys, brain, and eyes. Types of High Blood Pressure There are two main types of high blood ...

  18. Confusion about Pressure.

    ERIC Educational Resources Information Center

    Kuethe, Dean O.

    1991-01-01

    Listed are errors students make by accepting misconceptions about pressure and precautions teachers might take to avoid fostering those misconceptions. Misconceptions discussed include pressure as a measure of energy per unit volume, fluid flow only from high to low pressure, and the lack of pressures lower than a vacuum. (CW)

  19. Pressurized Submarine Rescue

    DTIC Science & Technology

    1984-06-07

    4 V. PROBLEMS RESULTING FROM PRESSURIZATION A. Mechanical ......................................... 5 B. Decompression...RESULTING FROM PRESSURIZATION The problems resulting from. increased pressure inside the DISUB simplify to three categories: mechanical , decompression...obligation and toxicity of respired gases. Each will be discussed in detail. A. Mechanical Pressurization of the DISUB creates several uniquely mechanical

  20. A variational principle for turbulent flow

    NASA Astrophysics Data System (ADS)

    Stern, M. E.

    1980-11-01

    A general control theory is proposed to select the realized stationary state whenever the equations of motion are densely nonunique (degenerate). For the turbulent flow in a pipe with given pressure gradient, the theory implies that the discharge is an extremum. Quantitative results, such as von Karman's constant, emerge when this variational principle is combined with inequalities pertaining to the mean field. The control theory is also applied to fully turbulent thermal convection, and a variational principle for this problem is obtained which is also consistent with measurements.

  1. Constant-pressure Blowers

    NASA Technical Reports Server (NTRS)

    Sorensen, E

    1940-01-01

    The conventional axial blowers operate on the high-pressure principle. One drawback of this type of blower is the relatively low pressure head, which one attempts to overcome with axial blowers producing very high pressure at a given circumferential speed. The Schicht constant-pressure blower affords pressure ratios considerably higher than those of axial blowers of conventional design with approximately the same efficiency.

  2. Variations in Sexual Behavior.

    ERIC Educational Resources Information Center

    Juhasz, Anne McCreary

    1983-01-01

    Questions are raised about the difficulty of defining normal and atypical sexual behavior. Variations from normalcy that students, parents, and educators are most likely to encounter are discussed. The importance of dealing with variations in ways that are best for the individual and the group is emphasized. (PP)

  3. Causes and significance of variation in mammalian basal metabolism.

    PubMed

    Raichlen, David A; Gordon, Adam D; Muchlinski, Magdalena N; Snodgrass, J Josh

    2010-02-01

    Mammalian basal metabolic rates (BMR) increase with body mass, whichs explains approximately 95% of the variation in BMR. However, at a given mass, there remains a large amount of variation in BMR. While many researchers suggest that the overall scaling of BMR with body mass is due to physiological constraints, variation at a given body mass may provide clues as to how selection acts on BMR. Here, we examine this variation in BMR in a broad sample of mammals and we test the hypothesis that, across mammals, body composition explains differences in BMR at a given body mass. Variation in BMR is strongly correlated with variation in muscle mass, and both of these variables are correlated with latitude and ambient temperature. These results suggest that selection alters BMR in response to thermoregulatory pressures, and that selection uses muscle mass as a means to generate this variation.

  4. [Cardiac preload and central venous pressure].

    PubMed

    Weyland, A; Grüne, F

    2009-05-01

    The force of cardiac contraction is strongly influenced by myocardial fibre length at the beginning of systole. Because the length of cardiac sarcomers and muscle fibres primarily depends on the end-diastolic ventricular volume, filling pressures a priori can only act as indirect parameters of cardiac preload. Central venous pressure (CVP) gives information on right ventricular end-diastolic pressure, which parallels changes in left ventricular end-diastolic pressure as long as ventricular function is not impaired. Since the pressure-volume relationship of cardiac ventricles is not linear and shows great variability, filling of the ventricles cannot be directly derived from end-diastolic pressure. Further limitations of CVP as a surrogate variable of preload are caused by the influence of intrathoracic and intra-abdominal pressures. A valid parameter of preload should describe the relationship between preload and stroke volume as given by the Frank-Starling law. Furthermore, estimates of cardiac preload should enable prediction of fluid responsiveness. Many studies have demonstrated that under clinical conditions CVP cannot meet these demands and thus does not appear to be a useful predictor of cardiac preload. Variables which more directly represent end-diastolic ventricular volume (e.g. intrathoracic blood volume or end-diastolic ventricular area) offer a higher validity as estimates of cardiac preload. Furthermore, dynamic parameters of ventricular preload, such as pulse pressure variation or stroke volume variation, seem to be more predictive of volume responsiveness in ventilated patients than CVP. These limitations, however, do not impair the importance of CVP as the downstream pressure of the systemic venous system.

  5. Pressure Dome for High-Pressure Electrolyzer

    NASA Technical Reports Server (NTRS)

    Norman, Timothy; Schmitt, Edwin

    2012-01-01

    A high-strength, low-weight pressure vessel dome was designed specifically to house a high-pressure [2,000 psi (approx. = 13.8 MPa)] electrolyzer. In operation, the dome is filled with an inert gas pressurized to roughly 100 psi (approx. = 690 kPa) above the high, balanced pressure product oxygen and hydrogen gas streams. The inert gas acts to reduce the clamping load on electrolyzer stack tie bolts since the dome pressure acting axially inward helps offset the outward axial forces from the stack gas pressure. Likewise, radial and circumferential stresses on electrolyzer frames are minimized. Because the dome is operated at a higher pressure than the electrolyzer product gas, any external electrolyzer leak prevents oxygen or hydrogen from leaking into the dome. Instead the affected stack gas stream pressure rises detectably, thereby enabling a system shutdown. All electrical and fluid connections to the stack are made inside the pressure dome and require special plumbing and electrical dome interfaces for this to be accomplished. Further benefits of the dome are that it can act as a containment shield in the unlikely event of a catastrophic failure. Studies indicate that, for a given active area (and hence, cell ID), frame outside diameter must become ever larger to support stresses at higher operating pressures. This can lead to a large footprint and increased costs associated with thicker and/or larger diameter end-plates, tie-rods, and the frames themselves. One solution is to employ rings that fit snugly around the frame. This complicates stack assembly and is sometimes difficult to achieve in practice, as its success is strongly dependent on frame and ring tolerances, gas pressure, and operating temperature. A pressure dome permits an otherwise low-pressure stack to operate at higher pressures without growing the electrolyzer hardware. The pressure dome consists of two machined segments. An O-ring is placed in an O-ring groove in the flange of the bottom

  6. Total variation regularization with bounded linear variations

    NASA Astrophysics Data System (ADS)

    Makovetskii, Artyom; Voronin, Sergei; Kober, Vitaly

    2016-09-01

    One of the most known techniques for signal denoising is based on total variation regularization (TV regularization). A better understanding of TV regularization is necessary to provide a stronger mathematical justification for using TV minimization in signal processing. In this work, we deal with an intermediate case between one- and two-dimensional cases; that is, a discrete function to be processed is two-dimensional radially symmetric piecewise constant. For this case, the exact solution to the problem can be obtained as follows: first, calculate the average values over rings of the noisy function; second, calculate the shift values and their directions using closed formulae depending on a regularization parameter and structure of rings. Despite the TV regularization is effective for noise removal; it often destroys fine details and thin structures of images. In order to overcome this drawback, we use the TV regularization for signal denoising subject to linear signal variations are bounded.

  7. Electrical power generation from salinity gradients using pressure retarded osmosis

    SciTech Connect

    Emery, A.F.; Yourstone, W.H.

    1983-08-01

    The use of a pressure retarded osmosis system (PRO) to generate electricity form naturally available or artificially generated salt is described. Variations in overall system efficiency are analyzed in terms of freshwater and brine flow rates, fluid pressure levels, and membrane permeability. It is shown that the PRO system is economically competitive with other alternative energy systems.

  8. Pressure sensitivity of low permeability sandstones

    USGS Publications Warehouse

    Kilmer, N.H.; Morrow, N.R.; Pitman, J.K.

    1987-01-01

    Detailed core analysis has been carried out on 32 tight sandstones with permeabilities ranging over four orders of magnitude (0.0002 to 4.8 mD at 5000 psi confining pressure). Relationships between gas permeability and net confining pressure were measured for cycles of loading and unloading. For some samples, permeabilities were measured both along and across bedding planes. Large variations in stress sensitivity of permeability were observed from one sample to another. The ratio of permeability at a nominal confining pressure of 500 psi to that at 5000 psi was used to define a stress sensitivity ratio. For a given sample, confining pressure vs permeability followed a linear log-log relationship, the slope of which provided an index of pressure sensitivity. This index, as obtained for first unloading data, was used in testing relationships between stress sensitivity and other measured rock properties. Pressure sensitivity tended to increase with increase in carbonate content and depth, and with decrease in porosity, permeability and sodium feldspar. However, scatter in these relationships increased as permeability decreased. Tests for correlations between pressure sensitivity and various linear combinations of variables are reported. Details of pore structure related to diagenetic changes appears to be of much greater significance to pressure sensitivity than mineral composition. ?? 1987.

  9. The measurement of maximum cylinder pressures

    NASA Technical Reports Server (NTRS)

    Hicks, Chester W

    1929-01-01

    The work presented in this report was undertaken at the Langley Memorial Aeronautical Laboratory of the National Advisory Committee for Aeronautics to determine a suitable method for measuring the maximum pressures occurring in aircraft engine cylinders. The study and development of instruments for the measurement of maximum cylinder pressures has been conducted in connection with carburetor and oil engine investigations on a single cylinder aircraft-type engine. Five maximum cylinder-pressure devices have been designed, and tested, in addition to the testing of three commercial indicators. Values of maximum cylinder pressures are given as obtained with various indicators for the same pressures and for various kinds and values of maximum cylinder pressures, produced chiefly by variation of the injection advance angle in high-speed oil engine. The investigations indicate that the greatest accuracy in determining maximum cylinder pressures can be obtained with an electric, balanced-pressure, diaphragm or disk-type indicator so constructed as to have a diaphragm or disk of relatively large area and minimum seat width and mass.

  10. Responses of jawbone to pressure.

    PubMed

    Carlsson, Gunnar E

    2004-06-01

    To provide a literature review of bone resorption of edentulous jaws focusing on responses to pressure. After the extraction of all teeth in a jaw there is a continuous reduction of the residual ridge. The individual variation of bone resorption is great, and the aetiology is complex and not yet well understood. A search of the literature published up to May 2003 on bone resorption and pressure was performed using PubMed/Medline. Animal studies have demonstrated that excessive and constant pressure induces bone resorption. Recent experimental research has indicated that bone resorption is a pressure-regulated phenomenon with a lower threshold for continuous than for intermittent pressure. Clinical studies have suggested that residual ridge resorption is due more to the effects of denture wearing than to disuse atrophy. However, the results of leaving out dentures at night are not conclusive. Nor does the literature offer any strong evidence for the so-called combination syndrome, which has been described as a result of unfavourable loading. Clinical studies using multivariate analyses indicate that female gender and systemic factors may be of greater importance than oral and denture factors. Implant-supported prostheses have a bone preserving effect rather than the continuing resorption under complete dentures. The best way to reduce bone resorption is to avoid total extraction, preserve a few teeth and fabricate overdentures. In edentulous jaws, placement of implant-supported prostheses will lead to less bone loss and may even promote bone growth. To increase our knowledge of residual ridge resorption extended experimental, clinical and statistical methods will be needed, preferably including collaboration between dental and medical researchers.

  11. On the pressure field of nonlinear standing water waves

    NASA Technical Reports Server (NTRS)

    Schwartz, L. W.

    1980-01-01

    The pressure field produced by two dimensional nonlinear time and space periodic standing waves was calculated as a series expansion in the wave height. The high order series was summed by the use of Pade approximants. Calculations included the pressure variation at great depth, which was considered to be a likely cause of microseismic activity, and the pressure distribution on a vertical barrier or breakwater.

  12. High Blood Pressure in Pregnancy

    MedlinePlus

    ... The Health Information Center High Blood Pressure in Pregnancy What Is High Blood Pressure? Blood pressure is ... Are the Effects of High Blood Pressure in Pregnancy? Although many pregnant women with high blood pressure ...

  13. Variational Transition State Theory

    SciTech Connect

    Truhlar, Donald G.

    2016-09-29

    This is the final report on a project involving the development and applications of variational transition state theory. This project involved the development of variational transition state theory for gas-phase reactions, including optimized multidimensional tunneling contributions and the application of this theory to gas-phase reactions with a special emphasis on developing reaction rate theory in directions that are important for applications to combustion. The development of variational transition state theory with optimized multidimensional tunneling as a useful computational tool for combustion kinetics involved eight objectives.

  14. Effects of Geometric Variations on the Buckling of Arteries.

    PubMed

    Datir, Parag; Lee, Avione Y; Lamm, Shawn D; Han, Hai-Chao

    2011-10-05

    Arteries often demonstrate geometric variations such as elliptic and eccentric cross sections, stenosis, and tapering along the longitudinal axis. Effects of these variations on the mechanical stability of the arterial wall have not been investigated. The objective of this study was to determine the buckling behavior of arteries with elliptic, eccentric, stenotic, and tapered cross sections. The arterial wall was modeled as a homogenous anisotropic nonlinear material. Finite element analysis was used to simulate the buckling process of these arteries under lumen pressure and axial stretch. Our results demonstrated that arteries with an oval cross section buckled in the short axis direction at lower critical pressures compared to circular arteries. Eccentric cross-sections, stenosis, and tapering also decreased the critical pressure. Stenosis led to dramatic pressure variations along the vessel and reduced the buckling pressure. In addition, tapering shifted the buckling deformation profile of the artery towards the distal end. We conclude that geometric variations reduce the critical pressure of arteries and thus make the arteries more prone to mechanical instability than circular cylindrical arteries. These results improve our understanding of the mechanical behavior of arteries.

  15. An instrument for measuring turbulent pressure fluctuations

    NASA Astrophysics Data System (ADS)

    Papadimitrakis, Yiannis Alex; Hsu, En Yu; Street, Robert L.

    1986-04-01

    An instrument is described for laboratory measurements of the fluctuating static pressure in the turbulent boundary layer above progressive water waves. It consists of a disk-shaped sensing head properly designed to minimize the dynamic pressure variation to an acceptable level, a commercially available piezocrystal transducer housed inside a casing, and a forward-bent connecting tube. Pressure fluctuations sampled by the disk are converted into an electrical signal by the piezocrystal transducer. Through low-pass filtering, only the frequency range of interest is retained. The instrument was tested successfully for frequency response, dynamic and mechanical noise sensitivity, and response to spurious pressure fluctuations (produced when operating in a Eulerian wave-following mode) inside a cylindrical chamber and in a wind-wave facility, and some sample results along with the calibration procedures and data analysis are presented.

  16. Lipid decorated liquid crystal pressure sensors

    NASA Astrophysics Data System (ADS)

    Lopatkina, Tetiana; Popov, Piotr; Honaker, Lawrence; Jakli, Antal; Mann, Elizabeth; Mann's Group Collaboration; Jakli's Group Collaboration

    Surfactants usually promote the alignment of liquid crystal (LC) director parallel to the surfactant chains, and thus on average normal to the substrate (homeotropic), whereas water promotes tangential (planar) alignment. A water-LC interface is therefore very sensitive to the presence of surfactants, such as lipids: this is the principle of LC-based chemical and biological sensing introduced by Abbott et al.Using a modified configuration, we found that at higher than 10 micro molar lipid concentration, the uniformly dark texture seen for homeotropic alignment between left-, and right-handed circular polarizers becomes unstable and slowly brightens again. This texture shows extreme sensitivity to external air pressure variations offering its use for sensitive pressure sensors. Our analysis indicates an osmotic pressure induced bending of the suspended films explaining both the birefringence and pressure sensitivity. In the talk we will discuss the experimental details of these effects. This work was financially supported by NSF DMR No. DMR-0907055.

  17. Phonon Drag Dislocations at High Pressures

    SciTech Connect

    Wolfer, W.G.

    1999-10-19

    Phonon drag on dislocations is the dominant process which determines the flow stress of metals at elevated temperatures and at very high plastic deformation rates. The dependence of the phonon drag on pressure or density is derived using a Mie-Grueneisen equation of state. The phonon drag is shown to increase nearly linearly with temperature but to decrease with density or pressure. Numerical results are presented for its variation for shock-loaded copper and aluminum. In these cases, density and temperature increase simultaneously, resulting in a more modest net increase in the dislocation drag coefficient. Nevertheless, phonon drag increases by more than an order of magnitude during shock deformations which approach melting. Since the dependencies of elastic moduli and of the phonon drag coefficient on pressure and temperature are fundamentally different, the effect of pressure on the constitutive law for plastic deformation can not simply be accounted for by its effect on the elastic shear modulus.

  18. Pressure Sensitive Paints

    NASA Technical Reports Server (NTRS)

    Liu, Tianshu; Bencic, T.; Sullivan, J. P.

    1999-01-01

    This article reviews new advances and applications of pressure sensitive paints in aerodynamic testing. Emphasis is placed on important technical aspects of pressure sensitive paint including instrumentation, data processing, and uncertainty analysis.

  19. Blood pressure measurement

    MedlinePlus

    ... have this problem. High blood pressure is often discovered during a visit to the provider for another ... to develop high blood pressure. If you have diabetes, heart disease, or kidney problems, or if you ...

  20. Low blood pressure

    MedlinePlus

    Hypotension; Blood pressure - low; Postprandial hypotension; Orthostatic hypotension; Neurally mediated hypotension; NMH ... Blood pressure varies from one person to another. A drop as little as 20 mmHg, can cause problems for ...

  1. Blood Pressure Quiz

    MedlinePlus

    ... high blood pressure can lead to… stroke. kidney failure. heart attack and heart failure. all of the above. ... high blood pressure can lead to stroke, kidney failure, heart attack and heart failure A is the correct ...

  2. Atmospheric Pressure Indicator.

    ERIC Educational Resources Information Center

    Salzsieder, John C.

    1995-01-01

    Discusses observable phenomena related to air pressure. Describes a simple, unobtrusive, semiquantitative device to monitor the changes in air pressure that are associated with altitude, using a soft-drink bottle and a balloon. (JRH)

  3. Atmospheric Pressure Indicator.

    ERIC Educational Resources Information Center

    Salzsieder, John C.

    1995-01-01

    Discusses observable phenomena related to air pressure. Describes a simple, unobtrusive, semiquantitative device to monitor the changes in air pressure that are associated with altitude, using a soft-drink bottle and a balloon. (JRH)

  4. High blood pressure - infants

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/007329.htm High blood pressure - infants To use the sharing features on this page, please enable JavaScript. High blood pressure (hypertension) is an increase in the force of ...

  5. High Blood Pressure Prevention

    MedlinePlus

    ... version of this page please turn Javascript on. High Blood Pressure Prevention Steps You Can Take You can take steps to prevent high blood pressure by adopting these healthy lifestyle habits. Follow a ...

  6. Blood Pressure Medicines

    MedlinePlus

    High blood pressure, also called hypertension, usually has no symptoms. But it can cause serious problems such as stroke, ... and kidney failure. If you cannot control your high blood pressure through lifestyle changes such as losing weight and ...

  7. Hypertension (High Blood Pressure)

    MedlinePlus

    ... Visitor Information RePORT NIH Fact Sheets Home > Hypertension (High Blood Pressure) Small Text Medium Text Large Text Hypertension (High Blood Pressure) YESTERDAY Hypertension is a silent killer because it ...

  8. The Root Pressure Phenomenon

    ERIC Educational Resources Information Center

    Marsh, A. R.

    1972-01-01

    Describes experiments demonstrating that root pressure in plants is probably controlled by a circadian rhythm (biological clock). Root pressure phenomenon plays significant part in water transport in contradiction with prevalent belief. (PS)

  9. Pressure surge attenuator

    DOEpatents

    Christie, Alan M.; Snyder, Kurt I.

    1985-01-01

    A pressure surge attenuation system for pipes having a fluted region opposite crushable metal foam. As adapted for nuclear reactor vessels and heads, crushable metal foam is disposed to attenuate pressure surges.

  10. The Root Pressure Phenomenon

    ERIC Educational Resources Information Center

    Marsh, A. R.

    1972-01-01

    Describes experiments demonstrating that root pressure in plants is probably controlled by a circadian rhythm (biological clock). Root pressure phenomenon plays significant part in water transport in contradiction with prevalent belief. (PS)

  11. Middle ear pressure change as a function of body position.

    PubMed

    Cinamon, Udi; Russo, Eyal; Levy, Dalia

    2009-02-01

    To verify and assess immediate middle ear (ME) pressure changes as a function of body position. A prospective clinical trail. Twenty-six adult volunteers having 52 normal, healthy ears had tympanometric ME pressures measured in an upright and recumbent positions. Recordings were obtained immediately after positioning and after 3 minutes. The main outcome measure was the pressure difference between upright and recumbent measurements, that is, positional ME pressure change. All ME pressure recordings were within (-)100 to (+)55 mmH(2)O. An instant and significant (P < .001) pressure elevation was recorded in all ears once position changed from upright to recumbent. The average pressure increment was 19 mmH(2)O. Once a recumbent ear was repositioned upright it demonstrated an immediate pressure drop and regaining the initial ME pressure. Assuming the volume of a normal ME cleft as 8 mL and following Boyle's law, an ME volume alteration of about 17 microL was required to induce such pressure change. Positional pressure changes were within the range of normal daily ME pressure variations. The instantaneous pressure changes and reversibility may be explained by filling and emptying of blood vessels within the ME cleft, following gravity causing an alteration of the aerated volume. Individual differences of pressure change may follow variability of ME cleft volume, its surface, and vessel density.

  12. Relative microvascular pressure sensing

    NASA Astrophysics Data System (ADS)

    Choi, Min; Zemp, Roger

    2016-03-01

    Microcirculation may be characterized by the vascular pressure as it is influenced by pressure-driven perfusion. Crosssections of blood vessels can be visualized by photoacoustic imaging and compressing on vessels causes deformation. The photoacoustic signals of blood, when compressed to the point of vessel collapse, may or may not vanish depending on the buckling process it undergoes. We form relative pressure images of microvessels by tracking vessel collapse as a function of externally applied pressure using photoacoustic imaging.

  13. PRESSURE SYSTEM CONTROL

    DOEpatents

    Esselman, W.H.; Kaplan, G.M.

    1961-06-20

    The control of pressure in pressurized liquid systems, especially a pressurized liquid reactor system, may be achieved by providing a bias circuit or loop across a closed loop having a flow restriction means in the form of an orifice, a storage tank, and a pump connected in series. The subject invention is advantageously utilized where control of a reactor can be achieved by response to the temperature and pressure of the primary cooling system.

  14. Pressure-sensitive optrode

    DOEpatents

    Hirschfeld, Tomas B.

    1986-01-01

    An apparatus is provided for sensing changes in pressure and for generating optical signals related to said changes in pressure. Light from a fiber optic illuminates a fluorescent composition causing it to fluoresce. The fluorescent composition is caused to more relative to the end of the fiber optic in response to changes in pressure so that the intensity of fluorescent emissions collected by the same fiber optic used for illumination varies monotonically with pressure.

  15. Pressure-sensitive optrode

    DOEpatents

    Hirschfeld, T.B.

    1986-07-15

    An apparatus is provided for sensing changes in pressure and for generating optical signals related to said changes in pressure. Light from a fiber optic illuminates a fluorescent composition causing it to fluoresce. The fluorescent composition is caused to fluoresce more relative to the end of the fiber optic in response to changes in pressure so that the intensity of fluorescent emissions collected by the same fiber optic used for illumination varies monotonically with pressure. 10 figs.

  16. Pressure sensing by flexible, organic, field effect transistors

    NASA Astrophysics Data System (ADS)

    Manunza, I.; Sulis, A.; Bonfiglio, A.

    2006-10-01

    A mechanical sensor based on a pentacene field effect transistor has been fabricated. The pressure dependence of the output current has been investigated by applying a mechanical stimulus by means of a pressurized air flow. Experimental results show a reversible current dependence on pressure. Data analysis suggests that variations of threshold voltage, mobility and contact resistance are responsible for current variations. Thanks to the flexibility of the substrate and the low cost of the technology, this device opens the way for flexible mechanical sensors that can be used in a variety of innovative applications such as e-textiles and robotic interfaces.

  17. Nonaxisymmetric incompressible hydrostatic pressure effects in radial face seals

    NASA Technical Reports Server (NTRS)

    Etsion, I.

    1976-01-01

    A flat seal having an angular misalinement is analyzed, taking into account the radial variations in seal clearance. An analytical solution for axial force, tilting moment, and leakage is presented that covers the whole range from zero to full angular misalinement. Nonaxisymmetric hydrostatic pressures due to the radial variations in the film thickness have a considerable effect on seal stability. When the high pressure is on the outer periphery of the seal, both the axial force and the tilting moment are nonrestoring. The case of high-pressure seals where cavitation is eliminated is discussed, and the possibility of dynamic instability is pointed out.

  18. Understanding Blood Pressure Readings

    MedlinePlus

    ... Disease Venous Thromboembolism Aortic Aneurysm More Understanding Blood Pressure Readings Updated:Mar 22,2017 What do your ... it’s too high for blood pressure High Blood Pressure • Home • Get the Facts About HBP • Know Your ...

  19. Low Blood Pressure

    MedlinePlus

    ... Disease Venous Thromboembolism Aortic Aneurysm More Low Blood Pressure - When Blood Pressure Is Too Low Updated:Dec 13,2016 How ... content was last reviewed October 2016 High Blood Pressure • Home • Get the Facts About HBP Introduction What ...

  20. A soundproof pressure chamber.

    PubMed

    Kitahara, M; Kodama, A; Ozawa, H; Inoue, S

    1994-01-01

    For neurotological research we designed a soundproof pressure chamber in which pressure can be adjusted +/- 1000 mmH2O at the rate of less than 100 mmH2O per second. Noise in the chamber can be maintained under 30-35 dB while pressure is kept at a given level.

  1. Brain Pressure Monitoring

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A transducer originally used to measure air pressure in aircraft wind tunnel tests is the basis for a development important in diagnosis and treatment of certain types of brain damage. A totally implantable device, tbe intracranial pressure monitor measures and reports brain pressure by telemetry.

  2. High Blood Pressure (Hypertension)

    MedlinePlus

    ... For Consumers Consumer Information by Audience For Women High Blood Pressure (Hypertension) Share Tweet Linkedin Pin it More sharing ... En Español Who is at risk? How is high blood pressure treated? Understanding your blood pressure: What do the ...

  3. Glottal Adduction and Subglottal Pressure in Singing.

    PubMed

    Herbst, Christian T; Hess, Markus; Müller, Frank; Švec, Jan G; Sundberg, Johan

    2015-07-01

    Previous research suggests that independent variation of vocal loudness and glottal configuration (type and degree of vocal fold adduction) does not occur in untrained speech production. This study investigated whether these factors can be varied independently in trained singing and how subglottal pressure is related to average glottal airflow, voice source properties, and sound level under these conditions. A classically trained baritone produced sustained phonations on the endoscopic vowel [i:] at pitch D4 (approximately 294 Hz), exclusively varying either (a) vocal register; (b) phonation type (from "breathy" to "pressed" via cartilaginous adduction); or (c) vocal loudness, while keeping the others constant. Phonation was documented by simultaneous recording of videokymographic, electroglottographic, airflow and voice source data, and by percutaneous measurement of relative subglottal pressure. Register shifts were clearly marked in the electroglottographic wavegram display. Compared with chest register, falsetto was produced with greater pulse amplitude of the glottal flow, H1-H2, mean airflow, and with lower maximum flow declination rate (MFDR), subglottal pressure, and sound pressure. Shifts of phonation type (breathy/flow/neutral/pressed) induced comparable systematic changes. Increase of vocal loudness resulted in increased subglottal pressure, average flow, sound pressure, MFDR, glottal flow pulse amplitude, and H1-H2. When changing either vocal register or phonation type, subglottal pressure and mean airflow showed an inverse relationship, that is, variation of glottal flow resistance. The direct relation between subglottal pressure and airflow when varying only vocal loudness demonstrated independent control of vocal loudness and glottal configuration. Achieving such independent control of phonatory control parameters would be an important target in vocal pedagogy and in voice therapy. Copyright © 2015 The Voice Foundation. Published by Elsevier Inc

  4. Human genomic variation

    PubMed Central

    Disotell, Todd R

    2000-01-01

    The recent completion and assembly of the first draft of the human genome, which combines samples from several ethnically diverse males and females, provides preliminary data on the extent of human genetic variation. PMID:11178257

  5. Masks: Interpretations and Variations.

    ERIC Educational Resources Information Center

    Basso, Robert

    1990-01-01

    Presents a high school art teacher's views of and experiences with masks. Outlines a maskmaking activity in which students were required to create variations on existing masks. Emphasizes use of experimental materials. Displays examples of student-created masks. (DB)

  6. Multiclass Total Variation Clustering

    DTIC Science & Technology

    2014-12-01

    Multiclass Total Variation Clustering Xavier Bresson University of Lausanne Lausanne, Switzerland xavier.bresson@unil.ch Thomas Laurent Loyola...recently motivated a new set of clustering algorithms that rely on the concept of total variation. While these al- gorithms perform well for bi-partitioning...tasks, their recursive extensions yield unimpressive results for multiclass clustering tasks. This paper presents a general framework for multiclass

  7. Generalized quasi variational inequalities

    SciTech Connect

    Noor, M.A.

    1996-12-31

    In this paper, we establish the equivalence between the generalized quasi variational inequalities and the generalized implicit Wiener-Hopf equations using essentially the projection technique. This equivalence is used to suggest and analyze a number of new iterative algorithms for solving generalized quasi variational inequalities and the related complementarity problems. The convergence criteria is also considered. The results proved in this paper represent a significant improvement and refinement of the previously known results.

  8. The Schwinger Variational Method

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.

    1995-01-01

    Variational methods have proven invaluable in theoretical physics and chemistry, both for bound state problems and for the study of collision phenomena. For collisional problems they can be grouped into two types: those based on the Schroedinger equation and those based on the Lippmann-Schwinger equation. The application of the Schwinger variational (SV) method to e-molecule collisions and photoionization has been reviewed previously. The present chapter discusses the implementation of the SV method as applied to e-molecule collisions.

  9. Pressure Relief Devices

    NASA Astrophysics Data System (ADS)

    Manha, William D.

    2010-09-01

    Pressure relief devices are used in pressure systems and on pressure vessels to prevent catastrophic rupture or explosion from excessive pressure. Pressure systems and pressure vessels have manufacturers maximum rated operating pressures or maximum design pressures(MDP) for which there are relatively high safety factors and minimum risk of rupture or explosion. Pressure systems and pressure vessels that have a potential to exceed the MDP by being connected to another higher pressure source, a compressor, or heat to water(boiler) are required to have over-pressure protecting devices. Such devices can be relief valves and/or burst discs to safely relieve potentially excessive pressure and prevent unacceptable ruptures and explosions which result in fail-safe pressure systems and pressure vessels. Common aerospace relief valve and burst disc requirements and standards will be presented. This will include the NASA PSRP Interpretation Letter TA-88-074 Fault Tolerance of Systems Using Specially Certified Burst Disks that dictates burst disc requirements for payloads on Shuttle. Two recent undesirable manned space payloads pressure relief devices and practices will be discussed, as well as why these practices should not be continued. One example for discussion is the use of three burst discs that have been placed in series to comply with safety requirements of three controls to prevent a catastrophic hazard of the over-pressurization and rupture of pressure system and/or vessels. The cavities between the burst discs are evacuated and are the reference pressures for activating the two upstream burst discs. If the upstream burst disc leaks into the reference cavity, the reference pressure increases and it can increase the burst disc activating pressure and potentially result in the burst disc assembly being ineffective for over pressure protection. The three burst discs-in-series assembly was found acceptable because the burst discs are designed for minimum risk(DFMR) of

  10. Dynamic Pressure Calibration Standard

    NASA Technical Reports Server (NTRS)

    Schutte, P. C.; Cate, K. H.; Young, S. D.

    1986-01-01

    Vibrating columns of fluid used to calibrate transducers. Dynamic pressure calibration standard developed for calibrating flush diaphragm-mounted pressure transducers. Pressures up to 20 kPa (3 psi) accurately generated over frequency range of 50 to 1,800 Hz. System includes two conically shaped aluminum columns one 5 cm (2 in.) high for low pressures and another 11 cm (4.3 in.) high for higher pressures, each filled with viscous fluid. Each column mounted on armature of vibration exciter, which imparts sinusoidally varying acceleration to fluid column. Signal noise low, and waveform highly dependent on quality of drive signal in vibration exciter.

  11. Air pressure measurement

    NASA Technical Reports Server (NTRS)

    Ballard, H. N.

    1978-01-01

    The pressure measurement was made by a Model 830J Rosemont sensor which utilized the principle of a changing pressure to change correspondingly the capacitance of the pressure sensitive element. The sensor's range was stated to be from zero to 100 Torr (14 km); however, the sensor was not activated until an altitude of 20 km (41 Torr) was reached during the balloon ascent. The resolution of the sensor was specified by the manufacturer as infinitesimal; however, associated electronic and pressure readout systems limit the resolution to .044 Torr. Thus in the vicinity of an altitude of 30 km the pressure resolution corresponded to an altitude resolution of approximately 33 meters.

  12. Fracture analysis of axially cracked pressure tube of pressurized heavy water reactor

    SciTech Connect

    Krishnan, S.; Bhasin, V.; Mahajan, S.C.

    1997-04-01

    Three Dimensional (313) finite element elastic plastic fracture analysis was done for through wall axially cracked thin pressure tubes of 220 MWe Indian Pressurized Heavy Water Reactor. The analysis was done for Zr-2 and Zr-2.5Nb pressure tubes operating at 300{degrees}C and subjected to 9.5 Mpa internal pressure. Critical crack length was determined based on tearing instability concept. The analysis included the effect of crack face pressure due to the leaking fluid from tube. This effect was found to be significant for pressure tubes. The available formulae for calculating J (for axially cracked tubes) do not take into account the effect of crack face pressure. 3D finite element analysis also gives insight into variation of J across the thickness of pressure tube. It was observed that J is highest at the mid-surface of tube. The results have been presented in the form of across the thickness average J value and a peak factor on J. Peak factor on J is ratio of J at mid surface to average J value. Crack opening area for different cracked lengths was calculated from finite element results. The fracture assessment of pressure tubes was also done using Central Electricity Generating Board R-6 method. Ductile tearing was considered.

  13. The Thermal Pressure in Low Metallicity Galaxies

    NASA Astrophysics Data System (ADS)

    Wolfire, Mark; McKee, Christopher; Ostriker, Eve C.; Bolatto, Alberto; Jenkins, Edward

    2015-08-01

    The thermal pressure in the diffuse interstellar medium (ISM) is a relatively small fraction of the total ISM pressure yet it is extremely important for the evolution of the ISM phases. A multi-phase medium can exist between a range of thermal pressures Pmin < Pth < Pmax. The phase separation is driven by thermal instability and produces a cold (T ˜ 100 K) neutral atomic gas and a warm (T ˜ 8000 K) neutral atomic gas separated by thermally unstable gas. At thermal pressures<