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Sample records for high shear blood

  1. Chronic high blood flow potentiates shear stress-induced release of NO in arteries of aged rats

    PubMed Central

    Yan, Changdong; Huang, An; Kaley, Gabor; Sun, Dong

    2011-01-01

    Aging impairs shear-stress-dependent dilation of arteries via increased superoxide production, decreased SOD activity, and decreased activation of endothelial nitric oxide (NO) synthase (eNOS). In the present study, we investigated whether chronic increases in shear stress, elicited by increases in blood flow, would improve vascular endothelial function of aged rats. To this end, second-order mesenteric arteries of young (6 mo) and aged (24 mo) male Fischer-344 rats were selectively ligated for 3 wk to elevate blood flow in a first-order artery [high blood flow (HF)]. An in vitro study was then conducted on first-order arteries with HF and normal blood flow (NF) to assess shear stress (1, 10, and 20 dyn/cm2)-induced release of NO into the perfusate. In HF arteries of both age groups, shear stress-induced NO production increased significantly. In 24-mo-old rats, the reduced shear stress-induced NO production in NF arteries was normalized by HF to a level similar to that in NF arteries of 6-mo-old rats. The increased NO production in HF arteries of 24-mo-old rats was associated with increased shear stress-induced dilation, expression of eNOS protein, and shear stress-induced eNOS phosphorylation. Wortmannin, a phosphatidylinositol 3-kinase inhibitor, reduced shear stress-induced eNOS phosphorylation and vasodilation. Superoxide production decreased significantly in HF compared with NF arteries in 24-mo-old rats. The decreased superoxide production was associated with significant increases in CuZn-SOD and extracellular SOD protein expressions and total SOD activity. These results suggest that stimulation with chronic HF restores shear-stress-induced activation of eNOS and antioxidant ability in aged arteries. PMID:17873019

  2. A new look on blood shear thinning

    NASA Astrophysics Data System (ADS)

    Abkarian, Manouk; Lanotte, Luca; Fromental, Jean-Marc; Mendez, Simon; Fedosov, Dmitry; Gompper, Gerhard; Mauer, Johannes; Claveria, Viviana

    2015-11-01

    Blood is a shear-thinning fluid. At shear rates γ˙ < 1 s-1 , its drop of viscosity has been related primarily to the breaking-up of networks of ``rouleaux'' formed by stacked red blood cells (RBCs). For higher γ˙ in the range 10 - 1000 s-1 , where RBCs flow as single elements, studies demonstrated that RBCs suspended in a viscous fluid mimicking the viscosity of whole blood, deformed into ellipsoids aligned steadily in the direction of the flow, while their membrane rotated about their center of mass like a tank-tread. Such drop-like behavior seemed to explain shear-thinning. Here, using rheometers, microfluidics and simulations, we show that the dynamics of single RBCs in plasma-like fluids display a different sequence of deformation for increasing shear rates going from discocytes to successively, stomatocytes, folded stomatocytes, trilobes and tetralobes, but never ellipsoids. This result is also identical for physiological hematocrits. We correlate this shape diagram to the different regimes in blood rheology for high shear rates and propose a new-look on the interpretation of blood shear-thinning behavior.

  3. Pinched flow coupled shear-modulated inertial microfluidics for high-throughput rare blood cell separation.

    PubMed

    Bhagat, Ali Asgar S; Hou, Han Wei; Li, Leon D; Lim, Chwee Teck; Han, Jongyoon

    2011-06-07

    Blood is a highly complex bio-fluid with cellular components making up >40% of the total volume, thus making its analysis challenging and time-consuming. In this work, we introduce a high-throughput size-based separation method for processing diluted blood using inertial microfluidics. The technique takes advantage of the preferential cell focusing in high aspect-ratio microchannels coupled with pinched flow dynamics for isolating low abundance cells from blood. As an application of the developed technique, we demonstrate the isolation of cancer cells (circulating tumor cells (CTCs)) spiked in blood by exploiting the difference in size between CTCs and hematologic cells. The microchannel dimensions and processing parameters were optimized to enable high throughput and high resolution separation, comparable to existing CTC isolation technologies. Results from experiments conducted with MCF-7 cells spiked into whole blood indicate >80% cell recovery with an impressive 3.25 × 10(5) fold enrichment over red blood cells (RBCs) and 1.2 × 10(4) fold enrichment over peripheral blood leukocytes (PBL). In spite of a 20× sample dilution, the fast operating flow rate allows the processing of ∼10(8) cells min(-1) through a single microfluidic device. The device design can be easily customized for isolating other rare cells from blood including peripheral blood leukocytes and fetal nucleated red blood cells by simply varying the 'pinching' width. The advantage of simple label-free separation, combined with the ability to retrieve viable cells post enrichment and minimal sample pre-processing presents numerous applications for use in clinical diagnosis and conducting fundamental studies.

  4. Yield shear stress and disaggregating shear stress of human blood

    NASA Astrophysics Data System (ADS)

    Jung, Jinmu; Lee, Byoung-Kwon; Shin, Sehyun

    2014-05-01

    This review presents two distinct rheological parameters of blood that have the potential to indicate blood circulation adequacy: yield shear stress (YSS) and disaggregating shear stress (DSS). YSS and DSS reflect the strength of red blood cell (RBC) aggregation in suspension under static and dynamic conditions, respectively. YSS, defined as the critical stress to disperse RBC aggregates under static conditions, was found to be dependent upon hematocrit, fibrinogen, and red cell deformability, but not temperature. DSS, defined as the minimum shear stress to disperse RBC aggregates under dynamic conditions, is dependent upon fibrinogen, red cell deformability, and temperature but not hematocrit. Owing to recent advances in measurement technology, these two parameters can be easily measured, and thus, their clinical significance in blood circulation can be verified.

  5. Differential light scattering cuvettes for the measurement of thromboemboli in high shear blood flow systems

    SciTech Connect

    Reynolds, L.O.; Solen, K.A.; Mohammad, S.F.; Pantalos, G.M.; Kim, J. )

    1990-07-01

    Newly developed optical scattering cuvettes were constructed as a modification of our existing 1.0 mm and 3.0 mm internal diameter (ID) cuvettes to facilitate the measurement of platelet microemboli ranging from 20 microns to 1,000 microns diameter in whole blood in 0.9 mm ID flows ranging from 250 to 4,000 ml/min. A perturbation solution to the one-speed radiative transport equation was used in the design and calibration of these cuvettes. A series of tests were performed with these cuvettes in an extracorporeal left ventricular assist device bovine model, and in a recirculating closed-loop flow system containing anticoagulated whole baboon blood, to determine to what extent they affect platelet and erythrocyte function ex vivo and in vitro. Serial hemolysis tests, thromboxane radioimmunoassay measurements, platelet counts, and activated partial thromboplastin times were measured. All of these tests with cuvettes in the extracorporeal and in vitro circuits were statistically indistinguishable from baseline measurements, suggesting the usefulness of this system for the measurement of microemboli in blood-contacting materials of extracorporeal circuits and cardiac assist devices.

  6. Quantitative characterization of endothelial cell morphologies depending on shear stress in different blood vessels of domestic pigs using a focused ion beam and high resolution scanning electron microscopy (FIB-SEM).

    PubMed

    Pham, Tam Thanh; Maenz, Stefan; Lüdecke, Claudia; Schmerbauch, Christoph; Settmacher, Utz; Jandt, Klaus D; Bossert, Jörg; Zanow, Jürgen

    2015-04-01

    Microstructured surfaces mimicking the endothelial cell (EC) morphology is a new approach to improve the blood compatibility of synthetic vascular grafts. The ECs are capable of changing their shapes depending on different shear conditions. However, the quantitative correlation between EC morphology and shear stress has not yet been investigated statistically. The aim of this study was to quantitatively investigate the morphology of ECs in dependence on the shear stress. Blood flow rates in different types of natural blood vessels (carotid, renal, hepatic and iliac arteries) originated from domestic pigs were first measured in vivo to calculate the shear stresses. The EC morphologies were quantitatively characterized ex vivo by imaging with high resolution scanning electron microscopy (SEM) and cross-sectioning of the cells using a state-of-the-art focused ion beam (FIB). The relationships between EC geometrical parameters and shear stress were statistically analyzed and found to be exponential. ECs under high shear stress conditions had a longer length and narrower width, i.e. a higher aspect ratio, while the cell height was smaller compared to low shear conditions. Based on these results, suitable and valid geometrical parameters of microstructures mimicking EC can be derived for various shear conditions in synthetic vascular grafts to optimize blood compatibility.

  7. High Blood Pressure

    MedlinePlus

    ... this page please turn Javascript on. High Blood Pressure What Is High Blood Pressure? High blood pressure is a common disease in ... at higher than normal pressures. What Is Blood Pressure? Click for more information Blood pressure is the ...

  8. Shear jamming in highly strained granular system without shear banding

    NASA Astrophysics Data System (ADS)

    Zhao, Yiqiu; Barés, Jonathan; Zheng, Hu; Behringer, Robert

    2016-11-01

    Bi et al. have shown that, if sheared, a granular material can jam even if its packing fraction (ϕ) is lower than the critical isotropic jamming point ϕJ. They have introduced a new critical packing fraction value ϕS such that for ϕS< ϕ< ϕJ the system jams if sheared. Nevertheless, the value of ϕS as a function of the shear profile or the strain necessary to observe jamming remain poorly understood because of the experimental complexity to access high strain without shear band. We present a novel 2D periodic shear apparatus made of 21 independent, aligned and mirrored glass rings. Each ring can be moved independently which permits us to impose any desired shear profile. The circular geometry allows access to any strain value. The forces between grains are measured using reflective photoelasticity. By performing different shear profiles for different packing fractions we explored the details of jamming diagram including the location of the yield surface. This work is supported by NSF No.DMR1206351, NASA No.NNX15AD38G and W. M. Keck Foundation.

  9. High Blood Pressure

    MedlinePlus

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  10. Red blood cell damage by shear stress for different blood types

    NASA Astrophysics Data System (ADS)

    Arwatz, Gilad; Bedkowski, Katherine; Smits, Alexander

    2011-11-01

    In surgical practice, blood damage caused by medical devices is often a limiting factor in the duration of an acute procedure or in chronic exposures such as hemodialysis. In order to establish guidelines for designing medical devices, a study was conducted to determine the relationship between shear stress and damage to red blood cells using a concentric Couette device. By measuring the hemolysis level for various shear stresses and exposure times, a non-dimensional relationship between shear stress and blood damage for different blood types was established. Funding provided by Princeton University's Project X.

  11. Shear induced diffusion in a red blood cell suspension

    NASA Astrophysics Data System (ADS)

    Podgorski, Thomas; Grandchamp, Xavier; Srivastav, Aparna; Coupier, Gwennou

    2012-11-01

    In the microcirculation, blood exhibits an inhomogeneous structure which results in the well know Fahraeus-Lindqvist effect : the apparent viscosity decreases when the diameter of the capillary decreases due to the formation of a marginal cell depletion layer (known as plasma skimming). This structure is a consequence of several phenomena, which include i) the migration of cells aways from walls due to lift forces and gradients of shear and ii) shear induced diffusion due to collisions and interactions among cells. We investigated these phenomena through experiments in simple shear and microchannel flows, with dilute suspensions of vesicles and blood cells. Pairwise interactions between suspended objects result in non-linear and flow-dependent diffusion, whose properties have been measured in different experiments for vesicles and blood cells. The injection of a sheet of concentrated blood cell suspension in a microchannel with a rectangular cross-section allows, through the measurement of its widening along the channel, to measure the diffusivity of blood cells, both in the local plane of shear and in the vorticity direction.

  12. Dynamic shear deformation in high purity Fe

    SciTech Connect

    Cerreta, Ellen K; Bingert, John F; Trujillo, Carl P; Lopez, Mike F; Gray, George T

    2009-01-01

    The forced shear test specimen, first developed by Meyer et al. [Meyer L. et al., Critical Adiabatic Shear Strength of Low Alloyed Steel Under Compressive Loading, Metallurgical Applications of Shock Wave and High Strain Rate Phenomena (Marcel Decker, 1986), 657; Hartmann K. et al., Metallurgical Effects on Impact Loaded Materials, Shock Waves and High Strain rate Phenomena in Metals (Plenum, 1981), 325-337.], has been utilized in a number of studies. While the geometry of this specimen does not allow for the microstructure to exactly define the location of shear band formation and the overall mechanical response of a specimen is highly sensitive to the geometry utilized, the forced shear specimen is useful for characterizing the influence of parameters such as strain rate, temperature, strain, and load on the microstructural evolution within a shear band. Additionally, many studies have utilized this geometry to advance the understanding of shear band development. In this study, by varying the geometry, specifically the ratio of the inner hole to the outer hat diameter, the dynamic shear localization response of high purity Fe was examined. Post mortem characterization was performed to quantify the width of the localizations and examine the microstructural and textural evolution of shear deformation in a bcc metal. Increased instability in mechanical response is strongly linked with development of enhanced intergranular misorientations, high angle boundaries, and classical shear textures characterized through orientation distribution functions.

  13. Mathematical Modeling of Intravascular Blood Coagulation under Wall Shear Stress

    PubMed Central

    Rukhlenko, Oleksii S.; Dudchenko, Olga A.; Zlobina, Ksenia E.; Guria, Georgy Th.

    2015-01-01

    Increased shear stress such as observed at local stenosis may cause drastic changes in the permeability of the vessel wall to procoagulants and thus initiate intravascular blood coagulation. In this paper we suggest a mathematical model to investigate how shear stress-induced permeability influences the thrombogenic potential of atherosclerotic plaques. Numerical analysis of the model reveals the existence of two hydrodynamic thresholds for activation of blood coagulation in the system and unveils typical scenarios of thrombus formation. The dependence of blood coagulation development on the intensity of blood flow, as well as on geometrical parameters of atherosclerotic plaque is described. Relevant parametric diagrams are drawn. The results suggest a previously unrecognized role of relatively small plaques (resulting in less than 50% of the lumen area reduction) in atherothrombosis and have important implications for the existing stenting guidelines. PMID:26222505

  14. Simulation of red blood cell aggregation in shear flow.

    PubMed

    Lim, B; Bascom, P A; Cobbold, R S

    1997-01-01

    A simulation model has been developed for red blood cell (RBC) aggregation in shear flow. It is based on a description of the collision rates of RBC, the probability of particles sticking together, and the breakage of aggregates by shear forces. The influence of shear rate, hematocrit, aggregate fractal dimension, and binding strength on aggregation kinetics were investigated and compared to other theoretical and experimental results. The model was used to simulate blood flow in a long large diameter tube under steady flow conditions at low Reynolds numbers. The time and spatial distribution of the state of aggregation are shown to be in qualitative agreement with previous B-mode ultrasound studies in which a central region of low echogenicity was noted. It is suggested that the model can provide a basis for interpreting prior measurements of ultrasound echogenicity and may help relate them to the local state of aggregation.

  15. Prediction of Anomalous Blood Viscosity in Confined Shear Flow

    NASA Astrophysics Data System (ADS)

    Thiébaud, Marine; Shen, Zaiyi; Harting, Jens; Misbah, Chaouqi

    2014-06-01

    Red blood cells play a major role in body metabolism by supplying oxygen from the microvasculature to different organs and tissues. Understanding blood flow properties in microcirculation is an essential step towards elucidating fundamental and practical issues. Numerical simulations of a blood model under a confined linear shear flow reveal that confinement markedly modifies the properties of blood flow. A nontrivial spatiotemporal organization of blood elements is shown to trigger hitherto unrevealed flow properties regarding the viscosity η, namely ample oscillations of its normalized value [η]=(η-η0)/(η0ϕ) as a function of hematocrit ϕ (η0=solvent viscosity). A scaling law for the viscosity as a function of hematocrit and confinement is proposed. This finding can contribute to the conception of new strategies to efficiently detect blood disorders, via in vitro diagnosis based on confined blood rheology. It also constitutes a contribution for a fundamental understanding of rheology of confined complex fluids.

  16. Structure of turbulence at high shear rate

    NASA Technical Reports Server (NTRS)

    Lee, Moon Joo; Kim, John; Moin, Parviz

    1990-01-01

    The structure of homogeneous turbulence subject to high shear rate has been investigated by using three-dimensional, time-dependent numerical simulations of the Navier-Stokes equations. This study indicates that high shear rate alone is sufficient for generation of the streaky structures, and that the presence of a solid boundary is not necessary. Evolution of the statistical correlations is examined to determine the effect of high shear rate on the development of anisotropy in turbulence. It is shown that the streamwise fluctuating motions are enhanced so profoundly that a highly anisotropic turbulence state with a 'one-component' velocity field and 'two-component' vorticity field develops asymptotically as total shear increases. Because of high-shear rate, rapid distortion theory predicts remarkably well the anisotropic behavior of the structural quantities.

  17. 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 ...

  18. High Blood Cholesterol

    MedlinePlus

    ... page from the NHLBI on Twitter. What Is Cholesterol? To understand high blood cholesterol (ko-LES-ter- ... cholesterol from your body. What Is High Blood Cholesterol? High blood cholesterol is a condition in which ...

  19. High blood sugar

    MedlinePlus

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  20. Turbulence structure at high shear rate

    NASA Technical Reports Server (NTRS)

    Lee, Moon Joo; Kim, John; Moin, Parviz

    1987-01-01

    The structure of homogeneous turbulence in the presence of a high shear rate is studied using results obtained from three-dimensional time-dependent numerical simulations of the Navier-Stokes equations on a grid of 512 x 128 x 128 node points. It is shown that high shear rate enhances the streamwise fluctuating motion to such an extent that a highly anisotropic turbulence state with a one-dimensional velocity field and two-dimensional small-scale turbulence develops asymptotically as total shear increases. Instantaneous velocity fields show that high shear rate in homogeneous turbulent shear flow produces structures which are similar to the streaks present in the viscous sublayer of turbulent boundary layers.

  1. Characterization at the individual cell level and in whole blood samples of shear stress preventing red blood cells aggregation.

    PubMed

    Lee, K; Kinnunen, M; Danilina, A V; Ustinov, V D; Shin, S; Meglinski, I; Priezzhev, A V

    2016-05-03

    The aggregation of red blood cells (RBC) is an intrinsic feature of blood that has a strong impact on its microcirculation. For a number of years it has been attracting a great attention in basic research and clinical studies. Here, we study a relationship between the RBC aggregation parameters measured at the individual cell level and in a whole blood sample. The home made optical tweezers were used to measure the aggregating and disaggregating forces for a pair of interacting RBCs, at the individual cell level, in order to evaluate the corresponding shear stresses. The RheoScan aggregometer was used for the measurements of critical shear stress (CSS) in whole blood samples. The correlation between CSS and the shear stress required to stop an RBC pair from aggregating was found. The shear stress required to disaggregate a pair of RBCs using the double channel optical tweezers appeared to be about 10 times higher than CSS. The correlation between shear stresses required to prevent RBCs from aggregation at the individual cell level and in whole blood samples was estimated and assessed quantitatively. The experimental approach developed has a high potential for advancing hemorheological studies.

  2. Shear wave elastography quantification of blood elasticity during clotting.

    PubMed

    Bernal, Miguel; Gennisson, Jean-Luc; Flaud, Patrice; Tanter, Mickael

    2012-12-01

    Deep venous thrombosis (DVT) affects millions of people worldwide. A fatal complication occurs when the thrombi detach and create a pulmonary embolism. The diagnosis and treatment of DVT depends on clot's age. The elasticity of thrombi is closely related to its age. Blood was collected from pigs and anticoagulated using ethylenediaminetetraacetic acid (EDTA). Coagulation was initiated using calcium ions. Supersonic shear wave imaging was used to generate shear waves using 100 μs tone bursts of 8 MHz. Tracking of the shear waves was done by ultrafast imaging. Postprocessing of the data was done using Matlab(®). Two-dimensional (2-D) maps of elasticity were obtained by calculating the speed of shear wave propagation. Elasticity varied with time from around 50 Pa at coagulation to 1600 Pa at 120 min after which the elasticity showed a natural decreased (17%) because of thrombolytic action of plasmin. Ejection of the serum from the clot showed a significant decrease in the elasticity of the clot next to the liquid pool (65% decrease), corresponding to the detachment of the clot from the beaker wall. The use of a thrombolytic agent (Urokinase) on the coagulated blood decreased the shear elasticity close to the point of injection, which varied with time and distance. Supersonic imaging proved to be useful mapping the 2-D clot's elasticity. It allowed the visualization of the heterogeneity of mechanical properties of thrombi and has potential use in predicting thrombi breakage as well as in monitoring thrombolytic therapy.

  3. Structural analysis of red blood cell aggregates under shear flow.

    PubMed

    Chesnutt, J K W; Marshall, J S

    2010-03-01

    A set of measures of red blood cell (RBC) aggregates are developed and applied to examine the aggregate structure under plane shear and channel flows. Some of these measures are based on averages over the set of red blood cells which are in contact with each other at a given time. Other measures are developed by first fitting an ellipse to the planar projection of the aggregate, and then examining the area and aspect ratio of the fit ellipse as well as the orientations of constituent RBCs with respect to the fit ellipse axes. The aggregate structural measures are illustrated using a new mesoscale computational model for blood cell transport, collision and adhesion. The sensitivity of this model to change in adhesive surface energy density and shear rate on the aggregate structure is examined. It is found that the mesoscale model predictions exhibit reasonable agreement with experimental and theoretical data for blood flow in plane shear and channel flows. The new structural measures are used to examine the differences between predictions of two- and three-dimensional computations of the aggregate formation, showing that two-dimensional computations retain some of the important aspects of three-dimensional computations.

  4. Hypertension (High Blood Pressure)

    MedlinePlus

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  5. Shear-induced hemolysis: effects of blood chemistry (including aging in storage) and shearing surfaces.

    PubMed

    Offeman, R D; Williams, M C

    1976-01-01

    Rotating disks were used to hemolyze blood under low-stress laminar flow conditions. In the first sequence of tests, kinetic hemolysis curves (KHC) were obtained with polyethylene disks for three well-characterized bloods and repeated over a period of four weeks. Each blood had a KHC with different shape, which maintained its characteristics while aging. Correlations were sought between D6000 (percent of complete hemolysis, after 6000 sec of shear) and D0 (measured before shear) by two means of data analysis, in terms of blood chemistry. It was found that uric acid and very-low-density lipoprotein levels were most useful in predicting the characteristic D6000 vs. D0 relation for each blood, and that glucose levels correlated the rate of aging as measured by hemolysis. Other chemical factors are also displayed in terms of their influence on D0. The second series of tests consisted of comparing the KHC for four disk materials using a fourth blood, then repeating with a fifth blood. Hemolytic rankings of the materials were the same with these two blood, although the KHC shapes differed. The rankings were: polyvinyl chloride greater than Silastic approximately equal to polyethylene greater than polyether urethane, with PVC most hemolytic. In another sequence for examining materials effects, five different bloods were used to compare the hemolytic properties of Teflon, nylon, and polyethylene disks. Although the KHC for the three disks bore different relationships to each other with each different blood, extrapolation of data beyond 6000 sec suggests a ranking of Teflon greater than nylon greater than polyethylene.

  6. Treating High Blood Pressure

    MedlinePlus

    About High Blood Pressure Many people in the United States die from high blood pressure. This condition usually does not cause symptoms. Most ... until it is too late. A person has high blood pressure when the blood pushes against Visit your doctor ...

  7. Duration of exposure to high fluid shear stress is critical in shear-induced platelet activation-aggregation.

    PubMed

    Zhang, Jian-ning; Bergeron, Angela L; Yu, Qinghua; Sun, Carol; McBride, Latresha; Bray, Paul F; Dong, Jing-fei

    2003-10-01

    Platelet functions are increasingly measured under flow conditions to account for blood hydrodynamic effects. Typically, these studies involve exposing platelets to high shear stress for periods significantly longer than would occur in vivo. In the current study, we demonstrate that the platelet response to high shear depends on the duration of shear exposure. In response to a 100 dyn/cm2 shear stress for periods less than 10-20 sec, platelets in PRP or washed platelets were aggregated, but minimally activated as demonstrated by P-selectin expression and binding of the activation-dependent alphaIIbbeta3 antibody PAC-1 to sheared platelets. Furthermore, platelet aggregation under such short pulses of high shear was subjected to rapid disaggregation. The disaggregated platelets could be re-aggregated by ADP in a pattern similar to unsheared platelets. In comparison, platelets that are exposed to high shear for longer than 20 sec are activated and aggregated irreversibly. In contrast, platelet activation and aggregation were significantly greater in whole blood with significantly less disaggregation. The enhancement is likely via increased collision frequency of platelet-platelet interaction and duration of platelet-platelet association due to high cell density. It may also be attributed to the ADP release from other cells such as red blood cells because increased platelet aggregation in whole blood was partially inhibited by ADP blockage. These studies demonstrate that platelets have a higher threshold for shear stress than previously believed. In a pathologically relevant timeframe, high shear alone is likely to be insufficient in inducing platelet activation and aggregation, but acts synergistically with other stimuli.

  8. Dynamics of model blood cells in shear flow

    NASA Astrophysics Data System (ADS)

    Podgorski, Thomas; Callens, Natacha; Minetti, Christophe; Coupier, Gwennou; Dubois, Frank; Misbah, Chaouqi

    The dynamics of a vesicle suspension in shear flow was investigated by digital holographic microscopy [1] in parabolic flights and in the MASER 11 sounding rocket. Vesicles are lipid membranes which mimic the mechanical behaviour of cells, such as red blood cells in flow. In a simple shear flow between parallel walls, a lift force of purely viscous origin pushes vesicles away from walls. Our parabolic flight experiments [2] reveal that the lift velocity in a dilute suspen-sion is well described by theoretical predictions by Olla. As vesicles gather near the center of the flow chamber due to lift forces from both walls, one expects hydrodynamic interactions of pairs of vesicles to result in shear induced diffusion in the suspension. The BIOMICS experi-ment in the MASER 11 sounding rocket revealed a complex spatial structure of a polydisperse vesicle suspension due to the interplay between lift forces from the walls and hydrodynamic interactions. These phenomena have a strong impact on the structure and rheology of blood in small vessels, and a precise knowledge of the dynamics of migration and diffusion of soft particles in flow can lead to alternative ways to separate and sort blood cells. 1. Dubois, F., Schockaert, C., Callens, N., Yourrassowsky, C., "Focus plane detection criteria in digital holography microscopy by amplitude analysis", Opt. Express, Vol. 14, pp 5895-5908, 2006 2. Callens, N., Minetti, C., Coupier, G., Mader, M.-A., Dubois, F., Misbah, C., Podgorski, T., "Hydrodynamics lift of vesicles under shear flow in microgravity", Europhys. Lett., Vol. 83, p. 24002, 2008

  9. High Blood Pressure Prevention

    MedlinePlus

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  10. High blood pressure - infants

    MedlinePlus

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  11. High Blood Pressure (Hypertension)

    MedlinePlus

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  12. Scaling of shear-induced diffusion and clustering in a blood-like suspension

    NASA Astrophysics Data System (ADS)

    Mountrakis, L.; Lorenz, E.; Hoekstra, A. G.

    2016-04-01

    The transport of cells and substances in dense suspensions like blood heavily depends on the microstructure and the dynamics arising from their interactions with red blood cells (RBCs). Computer simulations are used to probe into the detailed transport-related characteristics of a blood-like suspension, for a wide range of volume fractions and shear rates. The shear-induced diffusion of RBCs does not follow the established linear scaling with shear rate for higher volume fractions. The properties directly related to RBC deformability —stretching and flow orientation— are not sufficient to explain this departure according to the model of Breedveld, pointing to the dominance of collective effects in the suspension. A cluster size analysis confirms that collective effects dominate high volume fractions, as the mean cluster size is above 2 and the number of “free RBCs” is significantly decreased in denser suspensions. The mean duration of RBC contacts in clusters is increased in the high volume fraction and shear rate cases, showing that these clusters live longer.

  13. Measurement of the temperature-dependent threshold shear-stress of red blood cell aggregation

    NASA Astrophysics Data System (ADS)

    Lim, Hyun-Jung; Nam, Jeong-Hun; Lee, Yong-Jin; Shin, Sehyun

    2009-09-01

    Red blood cell (RBC) aggregation is becoming an important hemorheological parameter, which typically exhibits temperature dependence. Quite recently, a critical shear-stress was proposed as a new dimensional index to represent the aggregative and disaggregative behaviors of RBCs. The present study investigated the effect of the temperature on the critical shear-stress that is required to keep RBC aggregates dispersed. The critical shear-stress was measured at various temperatures (4, 10, 20, 30, and 37 °C) through the use of a transient microfluidic aggregometry. The critical shear-stress significantly increased as the blood temperature lowered, which accorded with the increase in the low-shear blood viscosity with the lowering of the temperature. Furthermore, the critical shear-stress also showed good agreement with the threshold shear-stress, as measured in a rotational Couette flow. These findings assist in rheologically validating the critical shear-stress, as defined in the microfluidic aggregometry.

  14. Large scale simulation of red blood cell aggregation in shear flows.

    PubMed

    Xu, Dong; Kaliviotis, Efstathios; Munjiza, Ante; Avital, Eldad; Ji, Chunning; Williams, John

    2013-07-26

    Aggregation of highly deformable red blood cells (RBCs) significantly affects the blood flow in the human circulatory system. To investigate the effect of deformation and aggregation of RBCs in blood flow, a mathematical model has been established by coupling the interaction between the fluid and the deformable solids. The model includes a three-dimensional finite volume method solver for incompressible viscous flows, the combined finite-discrete element method for computing the deformation of the RBCs, a JKR model-Johnson, Kendall and Roberts (1964-1971) (Johnson et al., 1971) to take account of the adhesion forces between different RBCs and an iterative direct-forcing immersed boundary method to couple the fluid-solid interactions. The flow of 49,512 RBCs at 45% concentration under the influence of aggregating forces was examined, improving the existing knowledge on simulating flow and structural characteristics of blood at a large scale: previous studies on the particular issue were restricted to simulating the flow of 13,000 aggregative ellipsoidal particles at a 10% concentration. The results are in excellent agreement with experimental studies. More specifically, both the experimental and the simulation results show uniform RBC distributions under high shear rates (60-100/s) whereas large aggregation structures were observed under a lower shear rate of 10/s. The statistical analysis of the simulation data also shows that the shear rate has significant influence on both the flow velocity profiles and the frequency distribution of the RBC orientation angles.

  15. Embolization: critical thrombus height, shear rates, and pulsatility. Patency of blood vessels.

    PubMed

    Basmadjian, D

    1989-11-01

    The present article builds on elementary fluid dynamics and previous analyses by the author to delineate approximate boundaries of mural thrombus height Hp, maximum shear rate gamma Max, and flow pulsatility beyond which thrombi are subject to either very high or very low probabilities of embolization. A thrombus height of approximately 0.1 mm emerges as a critical dividing line: Below it, the maximum embolizing shear stress tau s is independent of thrombus height and varies only linearly with shear rate. Above it, tau s quickly approaches a strong quadratic dependence on both thrombus height and shear rate: tau s approximately (Hp gamma)2, significantly increasing the likelihood of an embolizing event. By contrast, convective-diffusive removal of blood components during the initial stages of thrombus formation varies only weakly with gamma 1/3 in all but the smallest vessels. These maximum embolizing stresses are due principally to fluid drag. Acceleration (pulsatile) forces only begin to make their presence felt at gamma less than 500 s-1 and reach parity with fluid drag at gamma approximately 10 s-1, i.e., at a level where the presence of pulsatility is questionable. The results are used to provide maps of domains with high and low probabilities of an embolytic event and of vessel patency. The maps reveal that relatively modest changes in shear rate and/or vessel lumen can cause shifts from high to low likelihood of vessel patency, opening up possible ways of controlling blockage by manipulation of these variables.

  16. 'Slings' enable neutrophil rolling at high shear.

    PubMed

    Sundd, Prithu; Gutierrez, Edgar; Koltsova, Ekaterina K; Kuwano, Yoshihiro; Fukuda, Satoru; Pospieszalska, Maria K; Groisman, Alex; Ley, Klaus

    2012-08-16

    Most leukocytes can roll along the walls of venules at low shear stress (1 dyn cm−2), but neutrophils have the ability to roll at tenfold higher shear stress in microvessels in vivo. The mechanisms involved in this shear-resistant rolling are known to involve cell flattening and pulling of long membrane tethers at the rear. Here we show that these long tethers do not retract as postulated, but instead persist and appear as 'slings' at the front of rolling cells. We demonstrate slings in a model of acute inflammation in vivo and on P-selectin in vitro, where P-selectin-glycoprotein-ligand-1 (PSGL-1) is found in discrete sticky patches whereas LFA-1 is expressed over the entire length on slings. As neutrophils roll forward, slings wrap around the rolling cells and undergo a step-wise peeling from the P-selectin substrate enabled by the failure of PSGL-1 patches under hydrodynamic forces. The 'step-wise peeling of slings' is distinct from the 'pulling of tethers' reported previously. Each sling effectively lays out a cell-autonomous adhesive substrate in front of neutrophils rolling at high shear stress during inflammation.

  17. Dynamic adhesion of umbilical cord blood endothelial progenitor cells under laminar shear stress.

    PubMed

    Angelos, Mathew G; Brown, Melissa A; Satterwhite, Lisa L; Levering, Vrad W; Shaked, Natan T; Truskey, George A

    2010-12-01

    Late outgrowth endothelial progenitor cells (EPCs) represent a promising cell source for rapid reendothelialization of damaged vasculature after expansion ex vivo and injection into the bloodstream. We characterized the dynamic adhesion of umbilical-cord-blood-derived EPCs (CB-EPCs) to surfaces coated with fibronectin. CB-EPC solution density affected the number of adherent cells and larger cells preferentially adhered at lower cell densities. The number of adherent cells varied with shear stress, with the maximum number of adherent cells and the shear stress at maximum adhesion depending upon fluid viscosity. CB-EPCs underwent limited rolling, transiently tethering for short distances before firm arrest. Immediately before arrest, the instantaneous velocity decreased independent of shear stress. A dimensional analysis indicated that adhesion was a function of the net force on the cells, the ratio of cell diffusion to sliding speed, and molecular diffusivity. Adhesion was not limited by the settling rate and was highly specific to α(5)β(1) integrin. Total internal reflection fluorescence microscopy showed that CB-EPCs produced multiple contacts of α(5)β(1) with the surface and the contact area grew during the first 20 min of attachment. These results demonstrate that CB-EPC adhesion from blood can occur under physiological levels of shear stress.

  18. Effects of shear rate on propagation of blood clotting determined using microfluidics and numerical simulations.

    PubMed

    Runyon, Matthew K; Kastrup, Christian J; Johnson-Kerner, Bethany L; Ha, Thuong G Van; Ismagilov, Rustem F

    2008-03-19

    This paper describes microfluidic experiments with human blood plasma and numerical simulations to determine the role of fluid flow in the regulation of propagation of blood clotting. We demonstrate that propagation of clotting can be regulated by different mechanisms depending on the volume-to-surface ratio of a channel. In small channels, propagation of clotting can be prevented by surface-bound inhibitors of clotting present on vessel walls. In large channels, where surface-bound inhibitors are ineffective, propagation of clotting can be prevented by a shear rate above a threshold value, in agreement with predictions of a simple reaction-diffusion mechanism. We also demonstrate that propagation of clotting in a channel with a large volume-to-surface ratio and a shear rate below a threshold shear rate can be slowed by decreasing the production of thrombin, an activator of clotting. These in vitro results make two predictions, which should be experimentally tested in vivo. First, propagation of clotting from superficial veins to deep veins may be regulated by shear rate, which might explain the correlation between superficial thrombosis and the development of deep vein thrombosis (DVT). Second, nontoxic thrombin inhibitors with high binding affinities could be locally administered to prevent recurrent thrombosis after a clot has been removed. In addition, these results demonstrate the utility of simplified mechanisms and microfluidics for generating and testing predictions about the dynamics of complex biochemical networks.

  19. High-shear-rate capillary viscometer for inkjet inks

    SciTech Connect

    Wang Xi; Carr, Wallace W.; Bucknall, David G.; Morris, Jeffrey F.

    2010-06-15

    A capillary viscometer developed to measure the apparent shear viscosity of inkjet inks at high apparent shear rates encountered during inkjet printing is described. By using the Weissenberg-Rabinowitsch equation, true shear viscosity versus true shear rate is obtained. The device is comprised of a constant-flow generator, a static pressure monitoring device, a high precision submillimeter capillary die, and a high stiffness flow path. The system, which is calibrated using standard Newtonian low-viscosity silicone oil, can be easily operated and maintained. Results for measurement of the shear-rate-dependent viscosity of carbon-black pigmented water-based inkjet inks at shear rates up to 2x10{sup 5} s{sup -1} are discussed. The Cross model was found to closely fit the experimental data. Inkjet ink samples with similar low-shear-rate viscosities exhibited significantly different shear viscosities at high shear rates depending on particle loading.

  20. High strength semi-active energy absorbers using shear- and mixedmode operation at high shear rates

    NASA Astrophysics Data System (ADS)

    Becnel, Andrew C.

    This body of research expands the design space of semi-active energy absorbers for shock isolation and crash safety by investigating and characterizing magnetorheological fluids (MRFs) at high shear rates ( > 25,000 1/s) under shear and mixed-mode operation. Magnetorheological energy absorbers (MREAs) work well as adaptive isolators due to their ability to quickly and controllably adjust to changes in system mass or impact speed while providing fail-safe operation. However, typical linear stroking MREAs using pressure-driven flows have been shown to exhibit reduced controllability as impact speed (shear rate) increases. The objective of this work is to develop MREAs that improve controllability at high shear rates by using pure shear and mixed shear-squeeze modes of operation, and to present the fundamental theory and models of MR fluids under these conditions. A proof of concept instrument verified that the MR effect persists in shear mode devices at shear rates corresponding to low speed impacts. This instrument, a concentric cylinder Searle cell magnetorheometer, was then used to characterize three commercially available MRFs across a wide range of shear rates, applied magnetic fields, and temperatures. Characterization results are presented both as flow curves according to established practice, and as an alternate nondimensionalized analysis based on Mason number. The Mason number plots show that, with appropriate correction coefficients for operating temperature, the varied flow curve data can be collapsed to a single master curve. This work represents the first shear mode characterization of MRFs at shear rates over 10 times greater than available with commercial rheometers, as well as the first validation of Mason number analysis to high shear rate flows in MRFs. Using the results from the magnetorheometer, a full scale rotary vane MREA was developed as part of the Lightweight Magnetorheological Energy Absorber System (LMEAS) for an SH-60 Seahawk helicopter

  1. A simple model to understand the role of membrane shear elasticity and stress-free shape on the motion of red blood cells in shear flow

    NASA Astrophysics Data System (ADS)

    Viallat, Annie; Abkarian, Manouk; Dupire, Jules

    2015-11-01

    The analytical model presented by Keller and Skalak on the dynamics of red blood cells in shear flow described the cell as a fluid ellipsoid of fixed shape. It was extended to introduce shear elasticity of the cell membrane. We further extend the model when the cell discoid physiological shape is not a stress-free shape. We show that spheroid stress-free shapes enables fitting experimental data with values of shear elasticity typical to that found with micropipettes and optical tweezers. For moderate shear rates (when RBCs keep their discoid shape) this model enables to quantitatively determine an effective cell viscosity, that combines membrane and hemoglobin viscosities and an effective shear modulus of the membrane that combines shear modulus and stress-free shape. This model allows determining RBC mechanical parameters both in the tanktreading regime for cells suspended in a high viscosity medium, and in the tumbling regime for cells suspended in a low viscosity medium. In this regime,a transition is predicted between a rigid-like tumbling motion and a fluid-like tumbling motion above a critical shear rate, which is directly related to the mechanical parameters of the cell. A*MIDEX (n ANR-11-IDEX-0001-02) funded by the ''Investissements d'Avenir'', Region Languedoc-Roussillon, Labex NUMEV (ANR-10-LABX-20), BPI France project DataDiag.

  2. Hypertension (High Blood Pressure)

    MedlinePlus

    ... the results of observational studies further strengthened the causal relationship between high blood pressure and CVD, and ... disease, and those who have additional known risk factors for CVD. SPRINT will also provide information on ...

  3. High Blood Pressure (Hypertension)

    MedlinePlus

    ... already been diagnosed with high blood pressure. Try yoga and meditation. Yoga and meditation not only can strengthen your body ... Accessed Sept. 21, 2015. Hu B, et al. Effects of psychological stress on hypertension in middle-aged ...

  4. High Blood Pressure (Hypertension)

    MedlinePlus

    ... Neuropathy Foot Complications DKA (Ketoacidosis) & Ketones Kidney Disease (Nephropathy) High Blood Pressure (Hypertension) Stroke Hyperosmolar Hyperglycemic Nonketotic Syndrome (HHNS) Gastroparesis Heart Disease Mental Health Pregnancy Related Conditions donate en -- Make Your Donation Count - ...

  5. Controlling your high blood pressure

    MedlinePlus

    ... ency/patientinstructions/000101.htm Controlling your high blood pressure To use the sharing features on this page, ... blood pressure goes up. When is Your Blood Pressure a Concern? If your blood pressure is high, ...

  6. Simulation of erythrocyte deformation in a high shear flow.

    PubMed

    Nakamura, Masanori; Bessho, Sadao; Wada, Shigeo

    2009-01-01

    Deformation of a red blood cell (RBC) in a high-shear flow was investigated. The RBC was modeled as a closed shell membrane consisting of spring networks in the framework of the energy minimum concept. The simulation of RBC in a parallel shear flow showed deformation parameters of RBC were well agreed with experimental results. The simulation of RBC behavior in various flow fields demonstrated that the shape was determined not only by instantaneous fluid force acting on it but also its deformation history. No consistency was found between the maximum of the first principal strain and conventionally used hemolysis index. Those results addressed the importance of considering an RBC deformation for accurately predicting hemolysis.

  7. In vitro thrombogenesis resulting from decreased shear rate and blood coagulability.

    PubMed

    Maruyama, Osamu; Kosaka, Ryo; Nishida, Masahiro; Yamane, Takashi; Tatsumi, Eisuke; Taenaka, Yoshiyuki

    2016-06-15

    In vitro antithrombogenic testing with mock circulation is a useful type of pre-evaluation in ex vivo testing of mechanical assist devices. For effective in vitro testing, we have been developing a clear quantitative thrombogenesis model based on shear stress and blood coagulability. Bovine blood was used as the test medium. The activating clotting time (ACT) was adjusted with trisodium citrate and calcium chloride from 200 to 1,000 seconds. The blood was then applied to a rheometer and subjected to shear at 50 to 2,880 s-1. Blood coagulation time and degree of thrombogenesis were measured by the torque sensor of the rheometer. Prothrombin time (PT) and activated partial thromboplastin time (APTT) of the test blood were also measured after the application of shear. Blood coagulation time increased, and the degree of thrombogenesis decreased, with increases in shear rate to between 50 and 2,880 s-1. for test bloods with ACTs of 200 to 250 seconds. An ACT of 200 to 250 seconds is thus appropriate for in vitro antithrombogenic testing under a shear rate of 2,880 s-1. APTT was prolonged, whereas PT did not change, with increasing shear rate: that is, increasing the shear rate reduced thrombogenesis related to the intrinsic clotting pathway. An ACT of 200 to 250 seconds was suitable for in vitro antithrombogenic testing, and increasing the shear stress generated in the mechanical assist device reduced thrombogenesis via the intrinsic clotting pathway.

  8. PEG-albumin supraplasma expansion is due to increased vessel wall shear stress induced by blood viscosity shear thinning.

    PubMed

    Sriram, Krishna; Tsai, Amy G; Cabrales, Pedro; Meng, Fantao; Acharya, Seetharama A; Tartakovsky, Daniel M; Intaglietta, Marcos

    2012-06-15

    We studied the extreme hemodilution to a hematocrit of 11% induced by three plasma expanders: polyethylene glycol (PEG)-conjugated albumin (PEG-Alb), 6% 70-kDa dextran, and 6% 500-kDa dextran. The experimental component of our study relied on microelectrodes and cardiac output to measure both the rheological properties of plasma-expander blood mixtures and nitric oxide (NO) bioavailability in vessel walls. The modeling component consisted of an analysis of the distribution of wall shear stress (WSS) in the microvessels. Our experiments demonstrated that plasma expansion with PEG-Alb caused a state of supraperfusion with cardiac output 40% above baseline, significantly increased NO vessel wall bioavailability, and lowered peripheral vascular resistance. We attributed this behavior to the shear thinning nature of blood and PEG-Alb mixtures. To substantiate this hypothesis, we developed a mathematical model of non-Newtonian blood flow in a vessel. Our model used the Quemada rheological constitutive relationship to express blood viscosity in terms of both hematocrit and shear rate. The model revealed that the net effect of the hemodilution induced by relatively low-viscosity shear thinning PEG-Alb plasma expanders is to reduce overall blood viscosity and to increase the WSS, thus intensifying endothelial NO production. These changes act synergistically, significantly increasing cardiac output and perfusion due to lowered overall peripheral vascular resistance.

  9. Theory to predict shear stress on cells in turbulent blood flow.

    PubMed

    Morshed, Khandakar Niaz; Bark, David; Forleo, Marcio; Dasi, Lakshmi Prasad

    2014-01-01

    Shear stress on blood cells and platelets transported in a turbulent flow dictates the fate and biological activity of these cells. We present a theoretical link between energy dissipation in turbulent flows to the shear stress that cells experience and show that for the case of physiological turbulent blood flow: (a) the Newtonian assumption is valid, (b) turbulent eddies are universal for the most complex of blood flow problems, and (c) shear stress distribution on turbulent blood flows is possibly universal. Further we resolve a long standing inconsistency in hemolysis between laminar and turbulent flow using the theoretical framework. This work demonstrates that energy dissipation as opposed to bulk shear stress in laminar or turbulent blood flow dictates local mechanical environment of blood cells and platelets universally.

  10. Measurements of gap pressure and wall shear stress of a blood pump model.

    PubMed

    Chua, L P; Akamatsu, T

    2000-04-01

    The centrifugal blood pump with a magnetically suspended impeller has shown its superiority as compared to other artificial hearts. However, there is still insufficient understanding of fluid mechanics related issues in the clearance gap. The design nature of the pump requires sufficient washout in the clearance between the impeller and stationary surfaces. As the gap is only 0.2 mm in width, it is very difficult to conduct measurements with present instrumentation. An enlarged model with 5:1 ratio of the pump has been designed and constructed according to specifications. Dimensionless gap pressure measurements of the model are very close to the prototype. The measurements of wall shear stress of the fluid flow in the clearance gap between the impeller face and inlet casing of a blood pump model were accomplished through hot-wire anemometry and rotating disk apparatus. Regions of relatively high and low shear stresses are identified. These correspond to spots where the likelihood of hemolysis and thrombus formation is high. With the use of dimensional analysis, it is found that the highest wall shear stress is equivalent to 146 Pa which is much lower than the threshold value of 400 Pa for hemolysis reported in the literature.

  11. High Shear Stresses under Exercise Condition Destroy Circulating Tumor Cells in a Microfluidic System

    PubMed Central

    Regmi, Sagar; Fu, Afu; Luo, Kathy Qian

    2017-01-01

    Circulating tumor cells (CTCs) are the primary targets of cancer treatment as they cause distal metastasis. However, how CTCs response to exercise-induced high shear stress is largely unknown. To study the effects of hemodynamic microenvironment on CTCs, we designed a microfluidic circulatory system that produces exercise relevant shear stresses. We explore the effects of shear stresses on breast cancer cells with different metastatic abilities, cancer cells of ovarian, lung and leukemic origin. Three major findings were obtained. 1) High shear stress of 60 dynes/cm2 achievable during intensive exercise killed more CTCs than low shear stress of 15 dynes/cm2 present in human arteries at the resting state. 2) High shear stress caused necrosis in over 90% of CTCs within the first 4 h of circulation. More importantly, the CTCs that survived the first 4 h-circulation, underwent apoptosis during 16–24 h of post-circulation incubation. 3) Prolonged high shear stress treatment effectively reduced the viability of highly metastatic and drug resistant breast cancer cells. As high shear stress had much less damaging effects on leukemic cells mimicking the white blood cells, we propose that intensive exercise may be a good strategy for generating high shear stress that can destroy CTCs and prevent cancer metastasis. PMID:28054593

  12. Prevention of High Blood Pressure

    MedlinePlus

    ... the NHLBI on Twitter. Prevention of High Blood Pressure Healthy lifestyle habits, proper use of medicines, and ... blood pressure or its complications. Preventing High Blood Pressure Onset Healthy lifestyle habits can help prevent high ...

  13. Studying solutions at high shear rates: a dedicated microfluidics setup.

    PubMed

    Wieland, D C F; Garamus, V M; Zander, T; Krywka, C; Wang, M; Dedinaite, A; Claesson, P M; Willumeit-Römer, R

    2016-03-01

    The development of a dedicated small-angle X-ray scattering setup for the investigation of complex fluids at different controlled shear conditions is reported. The setup utilizes a microfluidics chip with a narrowing channel. As a consequence, a shear gradient is generated within the channel and the effect of shear rate on structure and interactions is mapped spatially. In a first experiment small-angle X-ray scattering is utilized to investigate highly concentrated protein solutions up to a shear rate of 300000 s(-1). These data demonstrate that equilibrium clusters of lysozyme are destabilized at high shear rates.

  14. High Red Blood Cell Count

    MedlinePlus

    Symptoms High red blood cell count By Mayo Clinic Staff A high red blood cell count is an increase in oxygen-carrying cells in your bloodstream. Red blood cells transport oxygen from your lungs to tissues throughout ...

  15. Lift and down-gradient shear-induced diffusion in red blood cell suspensions.

    PubMed

    Grandchamp, Xavier; Coupier, Gwennou; Srivastav, Aparna; Minetti, Christophe; Podgorski, Thomas

    2013-03-08

    The distribution of red blood cells (RBCs) in a confined channel flow is inhomogeneous and shows a marked depletion near the walls due to a competition between migration away from the walls and shear-induced diffusion resulting from interactions between particles. We investigated the lift of RBCs in a shear flow near a wall and measured a significant lift velocity despite the tumbling motion of cells. We also provide values for the collective and anisotropic shear-induced diffusion of a cloud of RBCs, both in the direction of shear and in the direction of vorticity. A generic down-gradient subdiffusion characterized by an exponent 1/3 is highlighted.

  16. Elevated Low-Shear Blood Viscosity is Associated with Decreased Pulmonary Blood Flow in Children with Univentricular Heart Defects.

    PubMed

    Cheng, Andrew L; Takao, Cheryl M; Wenby, Rosalinda B; Meiselman, Herbert J; Wood, John C; Detterich, Jon A

    2016-04-01

    After the Fontan procedure, patients with univentricular hearts can experience long-term complications due to chronic low-shear non-pulsatile pulmonary blood flow. We sought to evaluate hemorheology and its relationship to hemodynamics in children with univentricular hearts. We hypothesized that low-shear blood viscosity and red blood cell (RBC) aggregation would be associated with increased pulmonary vascular resistance (PVR) and decreased pulmonary blood flow (PBF). We performed a cross-sectional analysis of 62 children undergoing cardiac catheterization-20 with isolated atrial septal defect (ASD), 22 status post Glenn procedure (Glenn), and 20 status post Fontan procedure (Fontan). Shear-dependent blood viscosity, RBC aggregation and deformability, complete blood count, coagulation panel, metabolic panel, fibrinogen, and erythrocyte sedimentation rate were measured. PVR and PBF were calculated using the Fick equation. Group differences were analyzed by ANOVA and correlations by linear regression. Blood viscosity at all shear rates was higher in Glenn and Fontan, partially due to normocytic anemia in ASD. RBC aggregation and deformability were similar between all groups. Low-shear viscosity negatively correlated with PBF in Glenn and Fontan only (R (2) = 0.27, p < 0.001); it also negatively correlated with pulmonary artery pressure in Glenn (R (2) = 0.15, p = 0.01), and positively correlated with PVR in Fontan (R (2) = 0.28, p = 0.02). Our data demonstrate that elevated low-shear blood viscosity is associated with negative hemodynamic perturbations in a passive univentricular pulmonary circulation, but not in a pulsatile biventricular pulmonary circulation.

  17. In vitro blood flow model with physiological wall shear stress for hemocompatibility testing-An example of coronary stent testing.

    PubMed

    Engels, Gerwin Erik; Blok, Sjoerd Leendert Johannes; van Oeveren, Willem

    2016-09-18

    Hemocompatibility of blood contacting medical devices has to be evaluated before their intended application. To assess hemocompatibility, blood flow models are often used and can either consist of in vivo animal models or in vitro blood flow models. Given the disadvantages of animal models, in vitro blood flow models are an attractive alternative. The in vitro blood flow models available nowadays mostly focus on generating continuous flow instead of generating a pulsatile flow with certain wall shear stress, which has shown to be more relevant in maintaining hemostasis. To address this issue, the authors introduce a blood flow model that is able to generate a pulsatile flow and wall shear stress resembling the physiological situation, which the authors have coined the "Haemobile." The authors have validated the model by performing Doppler flow measurements to calculate velocity profiles and (wall) shear stress profiles. As an example, the authors evaluated the thrombogenicity of two drug eluting stents, one that was already on the market and one that was still under development. After identifying proper conditions resembling the wall shear stress in coronary arteries, the authors compared the stents with each other and often used reference materials. These experiments resulted in high contrast between hemocompatible and incompatible materials, showing the exceptional testing capabilities of the Haemobile. In conclusion, the authors have developed an in vitro blood flow model which is capable of mimicking physiological conditions of blood flow as close as possible. The model is convenient in use and is able to clearly discriminate between hemocompatible and incompatible materials, making it suitable for evaluating the hemocompatible properties of medical devices.

  18. What Causes High Blood Pressure?

    MedlinePlus

    ... the NHLBI on Twitter. Causes of High Blood Pressure Changes, either from genes or the environment, in ... vessel structure and function. Biology and High Blood Pressure Researchers continue to study how various changes in ...

  19. Stroke and High Blood Pressure

    MedlinePlus

    ... Venous Thromboembolism Aortic Aneurysm More How High Blood Pressure Can Lead to Stroke Updated:Dec 2,2016 ... content was last reviewed October 2016. High Blood Pressure • Home • Get the Facts About HBP • Know Your ...

  20. Common High Blood Pressure Myths

    MedlinePlus

    ... Venous Thromboembolism Aortic Aneurysm More Common High Blood Pressure Myths Updated:Apr 7,2017 Knowing the facts ... content was last reviewed October 2016. High Blood Pressure • Home • Get the Facts About HBP Introduction What ...

  1. High Blood Pressure Fact Sheet

    MedlinePlus

    ... this? Submit What's this? Submit Button Related CDC Web Sites Heart Disease Stroke High Blood Pressure Salt ... Prevent and Control Chronic Diseases Million Hearts® WISEWOMAN Web Sites with More Information About High Blood Pressure ...

  2. In vitro shear stress-induced platelet activation: sensitivity of human and bovine blood.

    PubMed

    Lu, Qijin; Hofferbert, Bryan V; Koo, Grace; Malinauskas, Richard A

    2013-10-01

    As platelet activation plays a critical role in physiological hemostasis and pathological thrombosis, it is important in the overall hemocompatibility evaluation of new medical devices and biomaterials to assess their effects on platelet function. However, there are currently no widely accepted in vitro test methods to perform this assessment. In an effort to develop effective platelet tests for potential use in medical device evaluation, this study compared the sensitivity of platelet responses to shear stress stimulation of human and bovine blood using multiple platelet activation markers. Fresh whole blood samples anticoagulated with heparin or anticoagulant citrate dextrose, solution A (ACDA) were exposed to shear stresses up to 40 Pa for 2 min using a cone-and-plate rheometer model. Platelet activation was characterized by platelet counts, platelet surface P-selectin expression, and serotonin release into blood plasma. The results indicated that exposure to shear stresses above 20 Pa caused significant changes in all three of the platelet markers for human blood and that the changes were usually greater with ACDA anticoagulation than with heparin. In contrast, for bovine blood, the markers did not change with shear stress stimulation except for plasma serotonin in heparin anticoagulated blood. The differences observed between human and bovine platelet responses suggest that the value of using bovine blood for in vitro platelet testing to evaluate devices may be limited.

  3. Dynamics of High Pressure Reacting Shear Flows

    DTIC Science & Technology

    2015-10-02

    side recirculation zone should be present DISTRIBUTION A: Approved for public release; distribution unlimited 13 Convection Velocities x y Extract...column of pixels at each time along shear layer edge as a function of time, dark streaks represent convecting liquid structures Positive slope streaks...represent upstream traveling features Structures convect at apparent constant velocity Structures start at slow speed and gradually accelerate

  4. Shear stress variation induced by red blood cell motion in microvessel.

    PubMed

    Xiong, Wenjuan; Zhang, Junfeng

    2010-08-01

    We simulated red blood cells flowing in microvessel to examine the induced wall shear stress variation. A typical peak-valley-peak structure is observed, and it is analyzed in terms of its magnitude, spatial influencing range, and temporal elapsed duration. Effects of red cell deformability, microvessel size, and flow velocity have been investigated. The corresponding variation characters have also been related to cell deformation and flow field. Simulation results show that the variation magnitude is mainly determined by the gap size between cell and vessel wall, while the spatial range of the shear stress variation depends on the cell length as well as the microvessel size. For a certain point on the vessel wall, the shear stress variation lasts a short time at a higher flow velocity, and vice versa. As the cell concentration in the microvessel increases, the shear stress variation structure changes accordingly with the two peaks from two close cells merging together, and eventually only one peak is observed at a hematocrit of 30.72%. However, the effect of hematocrit on the variation magnitude of shear stress is less obvious, and the dynamic nature of shear stress is still significant. This represents the first attempt to study the dynamic shear stress variation on microvessel as red blood cells flow by, and the information obtained in this study could be valuable to relevant research, for example, the mechanotransduction in the endothelia glycocalyx layer.

  5. [Blood viscosity and triglyceridemia. Findings using a co-axial cylindrical viscosimeter at low "shear rates"].

    PubMed

    Bartoli, V; Pasquini, G; Dorigo, B

    1977-09-22

    Examination of blood viscosity at low shear rates using a co-axial cylinder viscometer showed a significant difference between the means of values observed in hypertrigliceridemic patients compared with that of control subjects. This result differs from what has been reported by most workers although generally greater shear rates have been used. Calculation of the "r" coefficient and plotting of the regression line for each shear rate showed that there is no linear correlation between blood viscosity and triglyceridaemia, whose variations occur quite independently. It is suggested that the absence of a correlation between the two parameters examined may depend on various factors, of which the most important are those pertaining to the rheological properties of red blood cells and to the structure and chemical and physical characteristics of the triglyceride molecule and of the lipoproteins and chylomicrons which transport them.

  6. Modeling of the blood rheology in steady-state shear flows

    SciTech Connect

    Apostolidis, Alex J.; Beris, Antony N.

    2014-05-15

    We undertake here a systematic study of the rheology of blood in steady-state shear flows. As blood is a complex fluid, the first question that we try to answer is whether, even in steady-state shear flows, we can model it as a rheologically simple fluid, i.e., we can describe its behavior through a constitutive model that involves only local kinematic quantities. Having answered that question positively, we then probe as to which non-Newtonian model best fits available shear stress vs shear-rate literature data. We show that under physiological conditions blood is typically viscoplastic, i.e., it exhibits a yield stress that acts as a minimum threshold for flow. We further show that the Casson model emerges naturally as the best approximation, at least for low and moderate shear-rates. We then develop systematically a parametric dependence of the rheological parameters entering the Casson model on key physiological quantities, such as the red blood cell volume fraction (hematocrit). For the yield stress, we base our description on its critical, percolation-originated nature. Thus, we first determine onset conditions, i.e., the critical threshold value that the hematocrit has to have in order for yield stress to appear. It is shown that this is a function of the concentration of a key red blood cell binding protein, fibrinogen. Then, we establish a parametric dependence as a function of the fibrinogen and the square of the difference of the hematocrit from its critical onset value. Similarly, we provide an expression for the Casson viscosity, in terms of the hematocrit and the temperature. A successful validation of the proposed formula is performed against additional experimental literature data. The proposed expression is anticipated to be useful not only for steady-state blood flow modeling but also as providing the starting point for transient shear, or more general flow modeling.

  7. What Causes High Blood Cholesterol?

    MedlinePlus

    ... the NHLBI on Twitter. What Causes High Blood Cholesterol? Many factors can affect the cholesterol levels in your blood. You can control some ... but not others. Factors You Can Control Diet Cholesterol is found in foods that come from animal ...

  8. High Blood Pressure in Pregnancy

    MedlinePlus

    ... of the baby. Controlling your blood pressure during pregnancy and getting regular prenatal care are important for ... your baby. Treatments for high blood pressure in pregnancy may include close monitoring of the baby, lifestyle ...

  9. What Is High Blood Pressure?

    MedlinePlus

    ... consistently too high. How your blood pressure and circulatory system work In order to survive and function properly, ... and organs need the oxygenated blood that your circulatory system carries throughout the body. When the heart beats, ...

  10. Diagnosis of High Blood Pressure

    MedlinePlus Videos and Cool Tools

    ... above. Confirming High Blood Pressure A blood pressure test is easy and painless and can be done ... provider’s office or clinic. To prepare for the test: Don’t drink coffee or smoke cigarettes for ...

  11. Shear stress paradigm for perinatal fractal arterial network remodeling in lambs with pulmonary hypertension and increased pulmonary blood flow.

    PubMed

    Ghorishi, Zahra; Milstein, Jay M; Poulain, Francis R; Moon-Grady, Anita; Tacy, Theresa; Bennett, Stephen H; Fineman, Jeffery R; Eldridge, Marlowe W

    2007-06-01

    Congenital heart disease with increased blood flow commonly leads to the development of increased pulmonary vascular reactivity and pulmonary arterial hypertension by mechanisms that remain unclear. We hypothesized a shear stress paradigm of hemodynamic reactivity and network remodeling via the persistence and/or exacerbation of a fetal diameter bifurcation phenotype [parent diameter d(0) and daughters d(1) >or= d(2) with alpha < 2 in (d(1)/d(0))(alpha) + (d(2)/d(0))(alpha) and area ratio beta < 1 in beta = (d(1)(2)+ d(2)(2))/ d(0)(2)] that mechanically acts as a high resistance magnifier/shear stress amplifier to blood flow. Evidence of a hemodynamic influence on network remodeling was assessed with a lamb model of high-flow-induced secondary pulmonary hypertension in which an aortopulmonary graft was surgically placed in one twin in utero (Shunt twin) but not in the other (Control twin). Eight weeks after birth arterial casts were made of the left pulmonary arterial circulation. Bifurcation diameter measurements down to 0.010 mm in the Shunt and Control twins were then compared with those of an unoperated fetal cast. Network organization, cumulative resistance, and pressure/shear stress distributions were evaluated via a fractal model whose dimension D(0) approximately alpha delineates hemodynamic reactivity. Fetus and Control twin D(0) differed: fetus D(0)=1.72, a high-resistance/shear stress amplifying condition; control twin D(0) = 2.02, an area-preserving transport configuration. The Shunt twin (D(0)=1.72) maintained a fetal design but paradoxically remodeled diameter geometry to decrease cumulative resistance relative to the Control twin. Our results indicate that fetal/neonatal pulmonary hemodynamic reactivity remodels in response to shear stress, but the response to elevated blood flow and pulmonary hypertension involves the persistence and exacerbation of a fetal diameter bifurcation phenotype that facilitates endothelial dysfunction/injury.

  12. Dynamics of a single red blood cell in simple shear flow

    NASA Astrophysics Data System (ADS)

    Sinha, Kushal; Graham, Michael D.

    2015-10-01

    This work describes simulations of a red blood cell (RBC) in simple shear flow, focusing on the dependence of the cell dynamics on the spontaneous curvature of the membrane. The results show that an oblate spheroidal spontaneous curvature maintains the dimple of the RBC during tank-treading dynamics as well as exhibits off-shear-plane tumbling consistent with the experimental observations of Dupire et al. [J. Dupire, M. Socol, and A. Viallat, Proc. Natl. Acad. Sci. USA 109, 20808 (2012), 10.1073/pnas.1210236109] and their hypothesis of an inhomogeneous spontaneous shape. As the flow strength (capillary number Ca ) is increased at a particular viscosity ratio between inner and outer fluid, the dynamics undergo transitions in the following sequence: tumbling, kayaking or rolling, tilted tank-treading, oscillating-swinging, swinging, and tank-treading. The tilted tank-treading (or spinning frisbee) regime has been previously observed in experiments but not in simulations. Two distinct classes of regime are identified: a membrane reorientation regime, where the part of membrane that is at the dimple at rest moves to the rim and vice versa, is observed in motions at high Ca such as tilted tank-treading, oscillating-swinging, swinging, and tank-treading, and a nonreorientation regime, where the part of the membrane starting from the dimple stays at the dimple, is observed in motions at low Ca such as rolling, tumbling, kayaking, and flip-flopping.

  13. Red Blood Cell Deformation Under Shear Flow: The Effect of Changing Cell Properties

    NASA Astrophysics Data System (ADS)

    Forsyth, Alison M.; Wan, Jiandi; Ristenpart, William D.; Stone, Howard A.

    2008-11-01

    The deformability of red blood cells plays a major role in the pathology of several diseases, including malaria, sickle cell anemia and spherocytosis. Moreover, deformations are believed to trigger the release of adenosine triphosphate, which helps regulate vascular tone and is consequently an important factor in various vascular diseases. Here we investigate single-cell viscoelastic responses to increased shear stress in poly(dimethylsiloxane) channels with a single constriction 2-4 times larger than a typical erythrocyte. These channels mimic arteriole-sized vessels, and have the advantage that the cell membrane is not in contact with the channel walls which have vastly different mechanical and material properties than living tissue. High-speed video and image analysis were used to quantify the trajectories and deformations of cells exposed to varied doses of diamide, a chemical known to ``rigidify'' erythrocytes. Our results show that (i) deformation is proportional to shear rate and (ii) the deformability of diamide-treated cells is greater than that of untreated cells. The latter is an unforeseen result because micropipette aspiration experiments have shown the opposite. We expect that the experimental procedure described here will be useful for characterizing the effect of different therapeutic agents on cellular deformability.

  14. Mitigation of Shear-Induced Blood Damage of Mechanical Bileaflet Heart Valves using Embedded Vortex Generators

    NASA Astrophysics Data System (ADS)

    Hidalgo, Pablo; Arjunon, Sivakkumar; Saikrishnan, Neelakantan; Yoganathan, Ajit; Glezer, Ari

    2012-11-01

    The strong transitory shear stress generated during the time-periodic closing of the mechanical prosthetic bileaflet aortic heart valve, is considered to be one of the main factors responsible for complications, associated with thrombosis and thromboembolism. These flow transients are investigated using phase and time-averaged PIV in a low-volume (about 150 ml) test setup that simulates the pulsatile physiological conditions associated with a 23 mm St. Jude Medical valve. The PIV measurements are accompanied by continuous monitoring of the ventricular and aortic pressures and valve flow rate. Following the valve closure, the leakage flow between the valve leaflets is caused by the pressure buildup across the leaflets, leading to the formation of a regurgitation jet starting from the BMHV B-datum line. As in a typical starting jet, a counter-rotating vortex pair is formed along each leaflet edge and the vorticity sheet is associated with high shear stress that may be result in blood platelet activation. The present investigation demonstrates that the placement of arrays of mm-scale vortex generators near the edges of the leaflets diffuses the vortex sheet and suppresses the formation of these vortices, weakening the local velocity gradients and small-scale vortical structures. Supported by NIH and NSF.

  15. Improved determination of vascular blood-flow shear rate using Doppler ultrasound

    NASA Astrophysics Data System (ADS)

    Farison, James B.; Begeman, Garett A.; Salles-Cunha, Sergio X.; Beebe, Hugh G.

    1997-05-01

    Shear rate has been linked to endothelial and smooth muscle cell function, neointimal hyperplasia, poststenotic dilation and progression of atherosclerotic plaque. In vivo studies of shear rate have been limited in humans due to the lack of a truly accurate noninvasive method of measuring blood flow. In clinical vascular laboratories, the primary method of wall shear rate estimation is the scaled ratio between the center line systolic velocity and the local arterial radius. The present study compares this method with the shear rate calculated directly from data collected using a Doppler ultrasound scanner. Blood flow in the superficial femoral artery of 20 subjects was measured during three stages of distal resistance. Analysis and display programs were written for use with the MATLAB image processing software package. The experimental values of shear rate were calculated using the formal definition and then compared to the standard estimate. In all three states of distal resistance, the experimental values were significantly higher than the estimated values by a factor of approximately 1.57. These results led to the conclusion that the direct method of measuring shear rate is more precise and should replace the estimation model in the clinical laboratory.

  16. [Determining wall shear stress in artificial blood pumps of heart assist devices].

    PubMed

    Debaene, P; Aguilera, D; Kertzscher, U; Affeld, K

    2002-01-01

    The walls in blood pumps are made of artificial material and thus are thrombogenic to a lesser or larger degree. Also the flow plays a role: a blood flow with no flow separations and stagnation zones is required to avoid the generation of thrombi. A precondition for solving this problem is the assessment of the wall shear rate. However this parameter is difficult to assess because of the deformability of the walls and the pulsation of the flow. Two methods are proposed to estimate the wall shear stress in bloodpumps. The paint erosion method allows a characterisation of the flow near the wall. The second method is a special development of standard Particle Image Velocimetry (PIV). A vector field of the flow close to the wall results. Both methods should permit the assessment of the wall shear stress in bloodpumps.

  17. High Blood Pressure (Hypertension)

    MedlinePlus

    ... Practice healthy coping techniques, such as muscle relaxation, deep breathing or meditation. Getting regular physical activity and ... blood pressure at home. Practice relaxation or slow, deep breathing. Practice taking deep, slow breaths to help ...

  18. Hypertension (High Blood Pressure)

    MedlinePlus

    ... heart creates as it pumps blood through the circulatory system the force that comes from the arteries resisting ... Relief Yoga: Meditation and Breathing Alcohol Heart and Circulatory System Stop Smoking: Your Personal Plan Why Exercise Is ...

  19. Neutrophil rolling at high shear: flattening, catch bond behavior, tethers and slings

    PubMed Central

    Sundd, Prithu; Pospieszalska, Maria K.; Ley, Klaus

    2012-01-01

    Neutrophil recruitment to sites of inflammation involves neutrophil rolling along the inflamed endothelium in the presence of shear stress imposed by blood flow. Neutrophil rolling in post-capillary venules in vivo is primarily mediated by P-selectin on the endothelium binding to P-selectin glycoprotein ligand-1 (PSGL-1) constitutively expressed on neutrophils. Blood flow exerts a hydrodynamic drag on the rolling neutrophil which is partially or fully balanced by the adhesive forces generated in the P-selectin-PSGL-1 bonds. Rolling is the result of rapid formation and dissociation of P-selectin-PSGL-1 bonds at the center and rear of the rolling cell, respectively. Neutrophils roll stably on P-selectin in post-capillary venules in vivo and flow chambers in vitro at wall shear stresses greater than 6 dyn cm−2. However, the mechanisms that enable neutrophils to roll at such high shear stress are not completely understood. In vitro and in vivo studies have led to the discovery of four potential mechanisms, viz. cell flattening, catch bond behavior, membrane tethers, and slings. Rolling neutrophils undergo flattening at high shear stress, which not only increases the size of the cell footprint but also reduces the hydrodynamic drag experienced by the rolling cell. P-selectin-PSGL-1 bonds behave as catch bonds at small detachment forces and thus become stronger with increasing force. Neutrophils rolling at high shear stress form membrane tethers which can be longer than the cell diameter and promote the survival of P-selectin-PSGL-1 bonds. Finally, neutrophils rolling at high shear stress form slings, which act as cell autonomous adhesive substrates and support step-wise peeling. Tethers and slings act together and contribute to the forces balancing the hydrodynamic drag. How the synergy between the four mechanisms leads to stable rolling at high shear stress is an area that needs further investigation. PMID:23141302

  20. Role of fluid shear stress in regulating VWF structure, function and related blood disorders.

    PubMed

    Gogia, Shobhit; Neelamegham, Sriram

    2015-01-01

    Von Willebrand factor (VWF) is the largest glycoprotein in blood. It plays a crucial role in primary hemostasis via its binding interaction with platelet and endothelial cell surface receptors, other blood proteins and extra-cellular matrix components. This protein is found as a series of repeat units that are disulfide bonded to form multimeric structures. Once in blood, the protein multimer distribution is dynamically regulated by fluid shear stress which has two opposing effects: it promotes the aggregation or self-association of multiple VWF units, and it simultaneously reduces multimer size by facilitating the force-dependent cleavage of the protein by various proteases, most notably ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type repeats, motif 1 type 13). In addition to these effects, fluid shear also controls the solution and substrate-immobilized structure of VWF, the nature of contact between blood platelets and substrates, and the biomechanics of the GpIbα-VWF bond. These features together regulate different physiological and pathological processes including normal hemostasis, arterial and venous thrombosis, von Willebrand disease, thrombotic thrombocytopenic purpura and acquired von Willebrand syndrome. This article discusses current knowledge of VWF structure-function relationships with emphasis on the effects of hydrodynamic shear, including rapid methods to estimate the nature and magnitude of these forces in selected conditions. It shows that observations made by many investigators using solution and substrate-based shearing devices can be reconciled upon considering the physical size of VWF and the applied mechanical force in these different geometries.

  1. Shear and shear friction of ultra-high performance concrete bridge girders

    NASA Astrophysics Data System (ADS)

    Crane, Charles Kennan

    Ultra-High Performance Concrete (UHPC) is a new class of concrete characterized by no coarse aggregate, steel fiber reinforcement, low w/c, low permeability, compressive strength exceeding 29,000 psi (200 MPa), tensile strength ranging from 1,200 to 2,500 psi (8 to 17 MPa), and very high toughness. These properties make prestressed precast UHPC bridge girders a very attractive replacement material for steel bridge girders, particularly when site demands require a comparable beam depth to steel and a 100+ year life span is desired. In order to efficiently utilize UHPC in bridge construction, it is necessary to create new design recommendations for its use. The interface between precast UHPC girder and cast-in-place concrete decks must be characterized in order to safely use composite design methods with this new material. Due to the lack of reinforcing bars, all shear forces in UHPC girders have to be carried by the concrete and steel fibers. Current U.S. codes do not consider fiber reinforcement in calculating shear capacity. Fiber contribution must be accurately accounted for in shear equations in order to use UHPC. Casting of UHPC may cause fibers to orient in the direction of casting. If fibers are preferentially oriented, physical properties of the concrete may also become anisotropic, which must be considered in design. The current research provides new understanding of shear and shear friction phenomena in UHPC including: (1) Current AASHTO codes provide a non-conservative estimate of interface shear performance of smooth UHPC interfaces with and without interface steel. (2) Fluted interfaces can be created by impressing formliners into the surface of plastic UHPC. AASHTO and ACI codes for roughened interfaces are conservative for design of fluted UHPC interfaces.(3) A new equation for the calculation of shear capacity of UHPC girders is presented which takes into account the contribution of steel fiber reinforcement. (4) Fibers are shown to preferentially

  2. Blood contamination effect on shear bond strength of an orthodontic hydrophilic resin

    PubMed Central

    da CUNHA, Taís de Morais Alves; BEHRENS, Bruna Ariela; NASCIMENTO, Denise; RETAMOSO, Luciana Borges; LON, Luís Filipe Siu; TANAKA, Orlando; GUARIZA FILHO, Odilon

    2012-01-01

    Objective The aim of this study was to assess the impact of blood contamination on shear bond strength (SBS) and bond failure pattern of metallic brackets bonded using a new hydrophilic resin. Material and Methods Eighty human premolars were randomly allocated into 4 groups (n=20) according to the bonding material and contamination pattern. GI: brackets bonded with the Transbond XT conventional system without contamination; GII: brackets bonded with the Transbond XT conventional system with blood contamination; GIII: brackets bonded with the Transbond Self Etching Primer and Transbond Plus Color without contamination; GIV: brackets bonded with the Transbond Self Etching Primer and Transbond Plus Color with blood contamination. The specimens were stored in distilled water at 37ºC for 24 h and then submitted to SBS test at a crosshead speed of 0.5 mm/min. After bond failure, the enamel surfaces were observed under an optical microscope at 40x magnification. Results Blood contamination decreased (P<0.05) shear bond strength when both the hydrophobic (GII) and the hydrophilic resin (GIV) were used. However, the bond strength of Transbond Color Change group was significantly higher (P<0.05) than that of the Transbond XT conventional system group under blood contamination condition. Under dry conditions no difference was observed between the hydrophobic and hydrophilic resin groups. Regarding the bond failure pattern, when blood contaminated the enamel, the adhesive remnant index (ARI) showed predominance of scores 0 and 1, which indicates low adhesion to enamel. Conclusions Although there was a significant decrease in the shear bond strength for both adhesive systems under blood contamination, the hydrophilic system showed significantly higher bond strength than the hydrophobic resin adhesive. Therefore, it is advisable to use the hydrophilic resin under risk of blood contamination. PMID:22437684

  3. Medications for High Blood Pressure

    MedlinePlus

    ... Products For Consumers Home For Consumers Consumer Updates Medications for High Blood Pressure Share Tweet Linkedin Pin ... all their lives. back to top Types of Medications FDA has approved many medications to treat high ...

  4. Label-free cancer cell separation from human whole blood using inertial microfluidics at low shear stress.

    PubMed

    Lee, Myung Gwon; Shin, Joong Ho; Bae, Chae Yun; Choi, Sungyoung; Park, Je-Kyun

    2013-07-02

    We report a contraction-expansion array (CEA) microchannel device that performs label-free high-throughput separation of cancer cells from whole blood at low Reynolds number (Re). The CEA microfluidic device utilizes hydrodynamic field effect for cancer cell separation, two kinds of inertial effects: (1) inertial lift force and (2) Dean flow, which results in label-free size-based separation with high throughput. To avoid cell damages potentially caused by high shear stress in conventional inertial separation techniques, the CEA microfluidic device isolates the cells with low operational Re, maintaining high-throughput separation, using nondiluted whole blood samples (hematocrit ~45%). We characterized inertial particle migration and investigated the migration of blood cells and various cancer cells (MCF-7, SK-BR-3, and HCC70) in the CEA microchannel. The separation of cancer cells from whole blood was demonstrated with a cancer cell recovery rate of 99.1%, a blood cell rejection ratio of 88.9%, and a throughput of 1.1 × 10(8) cells/min. In addition, the blood cell rejection ratio was further improved to 97.3% by a two-step filtration process with two devices connected in series.

  5. High shear flow induces migration of adherent human platelets.

    PubMed

    Kraemer, Bjoern F; Schmidt, Christine; Urban, Benjamin; Bigalke, Boris; Schwanitz, Laura; Koch, Miriam; Seizer, Peter; Schaller, Martin; Gawaz, Meinrad; Lindemann, Stephan

    2011-01-01

    Shear forces are generated in all parts of the vascular system and contribute directly and indirectly to vascular disease progression. Endothelial cells are able to adapt to flow conditions, and are known to polarize and migrate in response to shear forces. Platelets exposed to shear stress are activated and release bioactive molecules from their alpha granules. So far, platelets have been considered to be static cells that do not leave the site of tight adhesion. However, we have recently been able to demonstrate the capacity of platelets to migrate in response to stromal derived factor-1 (SDF-1). In this project, we have demonstrated that platelets accumulate in areas with a high concentration of SDF-1 under flow conditions and respond to high shear stress by cellular polarization, cytoskeletal reorganisation, and flow-directed migration. In this context, we have shown increased Wiskott-Aldrich Syndrome protein (WASP) phosphorylation and intracellular redistribution of focal adhesion kinase (FAK) under high-shear stress conditions. The effect of flow-induced platelet migration has not previously been recognized and offers a new role for platelets as mobile cells. Their migratory potential may enable platelets to cover intimal lesions and contribute to vascular repair.

  6. Characteristics of a magnetorheological fluid in high shear rate

    NASA Astrophysics Data System (ADS)

    Kikuchi, Takehito; Abe, Isao; Inoue, Akio; Iwasaki, Akihiko; Okada, Katsuhiko

    2016-11-01

    The information on the properties of the magnetorheological fluid (MRF) in high shear rate, in particular a shear rate greater than 10 000 s-1, is important for the design of devices utilizing the MRF with very narrow fluid gaps, which are used in high-speed applications. However, very little research has been conducted on this subject. The objective of this study is to provide such information. MRF-140CG (Lord Corp.) is chosen as an example MRF. The plastic viscosity, thermal sensitivity, and durability of the fluid, especially under a shear rate greater than 10 000 s-1, are reported. The plastic viscosity is almost constant under a wide range of magnetic input. In contrast, MRF-140CG is sensitive to the shear rate; its sensitivity is relatively low at high shear rates. The thermal sensitivity shows negative values, and the effect of temperature decreases with increasing magnetic input. According to the result of the duration test at 30 000 s-1 and at a temperature of 120 °C, the lifetime dissipation energy is 5.48 MJ ml-1.

  7. Red blood cell: from its mechanics to its motion in shear flow.

    PubMed

    Viallat, A; Abkarian, M

    2014-06-01

    There is a number of publications on red blood cell deformability, that is, on the remarkable cell ability to change its shape in response to an external force and to pass through the narrowest blood capillaries and splenic sinuses. Cell deformability is postulated to be a major determinant of impaired perfusion, increase of blood viscosity, and occlusion in microvessels. Current deformability tests like ektacytometry measure global parameters, related to shape changes at the whole cell scale. Despite strong advances in our understanding of the molecular organization of red blood cells, the relationships between the rheology of each element of the cell composite structure, the global deformability tests, and the cell behavior in microflows are still not elucidated. This review describes recent advances in the description of the dynamics of red blood cells in shear flow and in the mechanistic understanding of this dynamics at the scale of the constitutive rheological and structural elements of the cell. These developments could open up new horizons for the determination of red blood cell mechanical parameters by analyzing their motion under low shear flows.

  8. High Blood Pressure Increasing Worldwide

    MedlinePlus

    ... other ways to control blood pressure, including healthy lifestyle choices and maintaining a normal weight, Roth said. Murray said some of the factors responsible for the worldwide increase in high blood pressure are unhealthy diets and obesity. In addition, in developing countries, more people are ...

  9. Platelet adhesion from shear blood flow is controlled by near-wall rebounding collisions with erythrocytes.

    PubMed

    Tokarev, A A; Butylin, A A; Ataullakhanov, F I

    2011-02-16

    The efficacy of platelet adhesion in shear flow is known to be substantially modulated by the physical presence of red blood cells (RBCs). The mechanisms of this regulation remain obscure due to the complicated character of platelet interactions with RBCs and vascular walls. To investigate this problem, we have created a mathematical model that takes into account shear-induced transport of platelets across the flow, platelet expulsion by the RBCs from the near-wall layer of the flow onto the wall, and reversible capture of platelets by the wall and their firm adhesion to it. This model analysis allowed us to obtain, for the first time to our knowledge, an analytical determination of the platelet adhesion rate constant as a function of the wall shear rate, hematocrit, and average sizes of platelets and RBCs. This formula provided a quantitative description of the results of previous in vitro adhesion experiments in perfusion chambers. The results of the simulations suggest that under a wide range of shear rates and hematocrit values, the rate of platelet adhesion from the blood flow is mainly limited by the frequency of their near-wall rebounding collisions with RBCs. This finding reveals the mechanism by which erythrocytes physically control platelet hemostasis.

  10. Mitigation of Shear-Induced Blood Damage by Mechanical Bileaflet Heart Valves

    NASA Astrophysics Data System (ADS)

    Zakharin, Boris; Arjunon, Sivakkumar; Saikrishnan, Neelakantan; Yoganathan, Ajit; Glezer, Ari

    2010-11-01

    The strong transitory shear stress generated during the time-periodic closing of bileaflet mechanical heart valves that is associated with the formation of counter-rotating vortices near the leaflet edges may be damaging to blood elements and may result in platelet activation and therefore thrombosis and thromboembolism complications. These flow transients are investigated using fluorescent PIV in a new, low-volume test setup that reproduces the pulsatile physiological conditions associated with a 25 mm St. Jude Medical valve. The flow transients are partially suppressed and the platelet activation is minimized using miniature vortex generator arrays that are embedded on the surface of the leaflets. Measurements of the ensuing flow taken phase-locked to the leaflet motion demonstrate substantial modification of the transient vertical structures and concomitant reduction of Reynolds shear stresses. Human blood experiments validated the effectiveness of miniature vortex generators in reducing thrombus formation by over 42 percent.

  11. High shear stress induces atherosclerotic vulnerable plaque formation through angiogenesis

    PubMed Central

    Wang, Yi; Qiu, Juhui; Luo, Shisui; Xie, Xiang; Zheng, Yiming; Zhang, Kang; Ye, Zhiyi; Liu, Wanqian; Gregersen, Hans; Wang, Guixue

    2016-01-01

    Rupture of atherosclerotic plaques causing thrombosis is the main cause of acute coronary syndrome and ischemic strokes. Inhibition of thrombosis is one of the important tasks developing biomedical materials such as intravascular stents and vascular grafts. Shear stress (SS) influences the formation and development of atherosclerosis. The current review focuses on the vulnerable plaques observed in the high shear stress (HSS) regions, which localizes at the proximal region of the plaque intruding into the lumen. The vascular outward remodelling occurs in the HSS region for vascular compensation and that angiogenesis is a critical factor for HSS which induces atherosclerotic vulnerable plaque formation. These results greatly challenge the established belief that low shear stress is important for expansive remodelling, which provides a new perspective for preventing the transition of stable plaques to high-risk atherosclerotic lesions. PMID:27482467

  12. Role of fluid shear stress in regulating VWF structure, function and related blood disorders

    PubMed Central

    Gogia, Shobhit; Neelamegham, Sriram

    2015-01-01

    Von Willebrand factor (VWF) is the largest glycoprotein in blood. It plays a crucial role in primary hemostasis via its binding interaction with platelet and endothelial cell surface receptors, other blood proteins and extra-cellular matrix components. This protein is found as a series of repeat units that are disulfide bonded to form multimeric structures. Once in blood, the protein multimer distribution is dynamically regulated by fluid shear stress which has two opposing effects: it promotes the aggregation or self-association of multiple VWF units, and it simultaneously reduces multimer size by facilitating the force-dependent cleavage of the protein by various proteases, most notably ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type repeats, motif 1 type 13). In addition to these effects, fluid shear also controls the solution and substrate-immobilized structure of VWF, the nature of contact between blood platelets and substrates, and the biomechanics of the GpIbα–VWF bond. These features together regulate different physiological and pathological processes including normal hemostasis, arterial and venous thrombosis, von Willebrand disease, thrombotic thrombocytopenic purpura and acquired von Willebrand syndrome. This article discusses current knowledge of VWF structure–function relationships with emphasis on the effects of hydrodynamic shear, including rapid methods to estimate the nature and magnitude of these forces in selected conditions. It shows that observations made by many investigators using solution and substrate-based shearing devices can be reconciled upon considering the physical size of VWF and the applied mechanical force in these different geometries. PMID:26600266

  13. Managing High Blood Pressure Medications

    MedlinePlus

    ... Thromboembolism Aortic Aneurysm More Managing High Blood Pressure Medications Updated:Jan 3,2017 When your doctor prescribes ... Download a printable medicine tracker . Quick Tips for Medication Use Understand your medication. Know what it's for, ...

  14. Shear-induced in-vitro haemostasis/thrombosis tests: the benefit of using native blood.

    PubMed

    Yamamoto, Junichiro; Kovacs, Iren B

    2003-12-01

    The historical development of in-vitro bleeding time tests, using solely shear forces to initiate haemostatic plug formation, in the absence of the vessel wall or its components, is described. Techniques that have no potential for routine use in clinical practice, such as flow chambers and cone-and-plate viscometers, are excluded. The problems related to the use of citrated blood in platelet function tests are discussed. In light of the pivotal role of thrombin and platelet-dependent thrombin generation in haemostasis/thrombosis, the advantage and clinical benefits of testing unadulterated native blood is discussed.

  15. When Blood Sugar Is Too High

    MedlinePlus

    ... A Week of Healthy Breakfasts Shyness When Blood Sugar Is Too High KidsHealth > For Teens > When Blood ... often can be unhealthy. What Is High Blood Sugar? The blood glucose level is the amount of ...

  16. High resolution weak lensing mass mapping combining shear and flexion

    NASA Astrophysics Data System (ADS)

    Lanusse, F.; Starck, J.-L.; Leonard, A.; Pires, S.

    2016-06-01

    Aims: We propose a new mass mapping algorithm, specifically designed to recover small-scale information from a combination of gravitational shear and flexion. Including flexion allows us to supplement the shear on small scales in order to increase the sensitivity to substructures and the overall resolution of the convergence map without relying on strong lensing constraints. Methods: To preserve all available small scale information, we avoid any binning of the irregularly sampled input shear and flexion fields and treat the mass mapping problem as a general ill-posed inverse problem, which is regularised using a robust multi-scale wavelet sparsity prior. The resulting algorithm incorporates redshift, reduced shear, and reduced flexion measurements for individual galaxies and is made highly efficient by the use of fast Fourier estimators. Results: We tested our reconstruction method on a set of realistic weak lensing simulations corresponding to typical HST/ACS cluster observations and demonstrate our ability to recover substructures with the inclusion of flexion, which are otherwise lost if only shear information is used. In particular, we can detect substructures on the 15'' scale well outside of the critical region of the clusters. In addition, flexion also helps to constrain the shape of the central regions of the main dark matter halos. Our mass mapping software, called Glimpse2D, is made freely available at http://www.cosmostat.org/software/glimpse

  17. High blood cholesterol levels

    MedlinePlus

    ... Outlook (Prognosis) High cholesterol levels can lead to hardening of the arteries , also called atherosclerosis. This occurs ... and safe drinking Coronary heart disease Cushing syndrome Hardening of the arteries Hypothyroidism Overweight Stroke Triglyceride level ...

  18. Effect of Blood Shear Forces on Platelet Mediated Thrombosis Inside Arterial Stenosis.

    NASA Astrophysics Data System (ADS)

    Maalej, Nabil

    Shear induced activation of platelets plays a major role in the onset of thrombosis in atherosclerotic arteries. Blood hemodynamics and its effect on platelet kinetics has been studied mainly in in vitro and in ex vivo experiments. We designed new in vivo methods to study blood hemodynamic effects on platelet kinetics in canine stenosed carotid arteries. A carotid artery-jugular vein anastomotic shunt was produced. Intimal damage and controlled variations in the degree of stenosis were produced on the artery. An inflatable cuff was placed around the jugular vein to control vascular resistance. An electromagnetic flowmeter was used to measure blood flow. Doppler ultrasound crystals were used to measure the velocity profiles inside and distal to the stenosis. Stenosis geometry was obtained using digital subtraction angiography and quantitative arteriography. Using these measurements we calculated the wall shear stress using the finite difference solution of the Navier-Stokes equations. To study platelet kinetics, autologous platelets were labeled with Indium Oxine and injected IV. A collimated Nal gamma counter was placed over the stenosis to detect radio-labeled platelet accumulation as platelet mediated thrombi formed in the stenosis. The radioactive count rate increased in an inverse parallel fashion to the decline in flow rate during thrombus formation. The platelet accumulation increased with the increase of percent stenosis and was maximal at the narrow portion of the stenosis. Acute thrombus formation leading to arterial occlusion was only observed for stenosis higher than 70 +/- 5%. Platelet accumulation rate was not significant until the pressure gradient across the stenosis exceeded 40 +/- 10 mmHg. Totally occlusive thrombus formation was only observed for shear stresses greater than a critical value of 100 +/- 10 Pa. Beyond this critical value acute platelet thrombus formation increased exponentially with shear. Increased shear stresses were found to

  19. Diamond anvil cell for spectroscopic investigation of materials at high temperature, high pressure and shear

    DOEpatents

    Westerfield, C.L.; Morris, J.S.; Agnew, S.F.

    1997-01-14

    Diamond anvil cell is described for spectroscopic investigation of materials at high temperature, high pressure and shear. A cell is described which, in combination with Fourier transform IR spectroscopy, permits the spectroscopic investigation of boundary layers under conditions of high temperature, high pressure and shear. 4 figs.

  20. Diamond anvil cell for spectroscopic investigation of materials at high temperature, high pressure and shear

    DOEpatents

    Westerfield, Curtis L.; Morris, John S.; Agnew, Stephen F.

    1997-01-01

    Diamond anvil cell for spectroscopic investigation of materials at high temperature, high pressure and shear. A cell is described which, in combination with Fourier transform IR spectroscopy, permits the spectroscopic investigation of boundary layers under conditions of high temperature, high pressure and shear.

  1. Effects of shear rate and suspending viscosity on deformation and frequency of red blood cells tank-treading in shear flows.

    PubMed

    Oulaid, Othmane; Saad, Abdul-Khalik W; Aires, Pedro S; Zhang, Junfeng

    2016-01-01

    The tank-treading rotation of red blood cells (RBCs) in shear flows has been studied extensively with experimental, analytical, and numerical methods. Even for this relatively simple system, complicated motion and deformation behaviors have been observed, and some of the underlying mechanisms are still not well understood. In this study, we attempt to advance our knowledge of the relationship among cell motion, deformation, and flow situations with a numerical model. Our simulation results agree well with experimental data, and confirm the experimental finding of the decrease in frequency/shear-rate ratio with shear rate and the increase of frequency with suspending viscosity. Moreover, based on the detailed information from our simulations, we are able to interpret the frequency dependency on shear rate and suspending viscosity using a simple two-fluid shear model. The information obtained in this study thus is useful for understanding experimental observations of RBCs in shear and other flow situations; the good agreement to experimental measurements also shows the potential usefulness of our model for providing reliable results for microscopic blood flows.

  2. Red Blood Cell Aggregation and Dissociation in Shear Flows Simulated by Lattice Boltzmann Method

    PubMed Central

    Zhang, Junfeng; Johnson, Paul C.; Popel, Aleksander S.

    2008-01-01

    In this paper we develop a lattice Boltzmann algorithm to simulate red blood cell (RBC) behavior in shear flows. The immersed boundary method is employed to incorporate the fluid-membrane interaction between the flow field and deformable cells. The cell membrane is treated as a neo-Hookean viscoelastic material and a Morse potential is adopted to model the intercellular interaction. Utilizing the available mechanical properties of RBCs, multiple cells have been studied in shear flows using a two-dimensional approximation. These cells aggregate and form a rouleau under the action of intercellular interaction. The equilibrium configuration is related to the interaction strength. The end cells exhibit concave shapes under weak interaction and convex shapes under strong interaction. In shear flows, such a rouleau-like aggregate will rotate or be separated, depending on the relative strengths of the intercellular interaction and hydrodynamic viscous forces. These behaviors are qualitatively similar to experimental observations and show the potential of this numerical scheme for future studies of blood flow in microvessels. PMID:17888442

  3. Winged inclusions under high-strain simple shear

    NASA Astrophysics Data System (ADS)

    Grasemann, Bernhard; Dabrowski, Marcin

    2014-05-01

    In this study we investigate pinch-and-swell objects, which have been subjected to layer parallel shear deformation. We use a high-resolution mechanical numerical model, which allows to model finite strains up to γ = 40. The developing structures have been called winged inclusions, which have geometrically similarities with δ-clast systems and rolling structures. However, our model results suggest markedly different mechanical evolution for winged inclusions, which has to be considered when these structures are used as shear sense indicator or finite strain gauge. During the early stages of formation winged inclusions may resemble mirror images of sigmoidal objects and miss-interpretations will lead to a wrong interpretation of the shear sense. During high-shear strain, the structures may be approximately described as consisting of a pulsating faster rotating core and thinning tails that experience differential slower rotation. The viscosity ratio and the shape of the winged inclusion have a significant influence on the rotation rate. The tails are subject to ptygmatic folding when they rotate through the field of instantaneous shortening and may unfold again in the field of instantaneous stretching. During on-going shearing the trailing wing may become the leading wing and finally unfold after rotation of 180° resulting again in a pinch and swell shaped objects. Therefore winged inclusions record little information about the finite strain. Rootless intrafolial folds with opposing closures have geometrically strong similarities with winged inclusions. It is speculated that the formation of winged inclusions might be an efficient mechanisms to produce rootless intrafolial folds, which might influence the rheological behaviour of natural highly strained rocks.

  4. Probe Oscillation Shear Elastography (PROSE): A High Frame-Rate Method for Two-Dimensional Ultrasound Shear Wave Elastography.

    PubMed

    Mellema, Daniel C; Song, Pengfei; Kinnick, Randall R; Urban, Matthew W; Greenleaf, James F; Manduca, Armando; Chen, Shigao

    2016-09-01

    Ultrasound shear wave elastography (SWE) utilizes the propagation of induced shear waves to characterize the shear modulus of soft tissue. Many methods rely on an acoustic radiation force (ARF) "push beam" to generate shear waves. However, specialized hardware is required to generate the push beams, and the thermal stress that is placed upon the ultrasound system, transducer, and tissue by the push beams currently limits the frame-rate to about 1 Hz. These constraints have limited the implementation of ARF to high-end clinical systems. This paper presents Probe Oscillation Shear Elastography (PROSE) as an alternative method to measure tissue elasticity. PROSE generates shear waves using a harmonic mechanical vibration of an ultrasound transducer, while simultaneously detecting motion with the same transducer under pulse-echo mode. Motion of the transducer during detection produces a "strain-like" compression artifact that is coupled with the observed shear waves. A novel symmetric sampling scheme is proposed such that pulse-echo detection events are acquired when the ultrasound transducer returns to the same physical position, allowing the shear waves to be decoupled from the compression artifact. Full field-of-view (FOV) two-dimensional (2D) shear wave speed images were obtained by applying a local frequency estimation (LFE) technique, capable of generating a 2D map from a single frame of shear wave motion. The shear wave imaging frame rate of PROSE is comparable to the vibration frequency, which can be an order of magnitude higher than ARF based techniques. PROSE was able to produce smooth and accurate shear wave images from three homogeneous phantoms with different moduli, with an effective frame rate of 300 Hz. An inclusion phantom study showed that increased vibration frequencies improved the accuracy of inclusion imaging, and allowed targets as small as 6.5 mm to be resolved with good contrast (contrast-to-noise ratio ≥ 19 dB) between the target and

  5. Rheometrical Studies of Blood Clot Formation by Oscillatory Shear, Thromboelastography, Sonoclot Analysis and Free Oscillation Rheometry

    NASA Astrophysics Data System (ADS)

    Evans, P. Adrian; Hawkins, Karl M.; Lawrence, Matthew J.; Williams, P. Rhodri; Williams, Rhodri L.

    2008-07-01

    We report studies of the coagulation of samples of whole human blood by oscillatory shear techniques, including Fourier Transform Mechanical Spectroscopy (FTMS). These techniques are used herein to identify the Gel Point of coagulating blood in terms of the Chambon-Winter Gel Point criterion which provides a rheometrical basis for detecting the establishment of an incipient clot. A comparison of the results of FTMS with those obtained from measurements involving a Thromboelastograph (TEG), a Sonoclot Analyzer and a Free Oscillation Rheometer (FOR) indicate that the latter techniques are not capable of detecting the incipient clot, whose establishment occurs several minutes prior to TEG or FOR-based assessments of clot formation time. The results of the present study suggest that FTMS is a useful tool in blood clotting research, being capable of providing a global coagulation profile in addition to detecting the instant of incipient clot formation.

  6. Dynamic evaluation and control of blood clotting using a microfluidic platform for high-throughput diagnostics

    NASA Astrophysics Data System (ADS)

    Combariza, Miguel E.; Yu, Xinghuo; Nesbitt, Warwick; Tovar-Lopez, Francisco; Rabus, Dominik G.; Mitchell, Arnan

    2015-12-01

    Microfluidic technology has the potential to revolutionise blood-clotting diagnostics by incorporating key physiological blood flow conditions like shear rate. In this paper we present a customised dynamic microfluidic system, which evaluates the blood clotting response to multiple conditions of shear rate on a single microchannel. The system can achieve high-throughput testing through use of an advanced fluid control system, which provides with rapid and precise regulation of the blood flow conditions in the platform. We present experimental results that demonstrate the potential of this platform to develop into a high-throughput, low-cost, blood-clotting diagnostics device.

  7. Numerical simulations of deformation and aggregation of red blood cells in shear flow.

    PubMed

    Low, Hong-Tong; Ju, M; Sui, Y; Nazir, T; Namgung, B; Kim, Sangho

    2013-01-01

    This article reviews numerical simulations of red blood cells (RBCs) mainly using the lattice Boltzmann method (LBM), focusing on the 2-dimensional deformation and aggregation of the cells in simple shear flow. We outline the incorporation of the immersed boundary method into the LBM, in which the membrane forces are obtained from the membrane model. The RBCs are simulated as a single biconcave capsule and as a doublet of biconcave capsules. The transition from swinging to tumbling motions of the RBCs, as induced by reducing the shear rate or increasing the membrane bending stiffness, is discussed. Also discussed is the aggregation tendency of the doublet of RBCs, for which homogenous deformability maintained RBC aggregation, whereas an increased deformability difference resulted in RBC dissociation.

  8. Anxiety: A Cause of High Blood Pressure?

    MedlinePlus

    ... Conditions High blood pressure (hypertension) Can anxiety cause high blood pressure? Answers from Sheldon G. Sheps, M.D. Anxiety doesn't cause long-term high blood pressure (hypertension). But episodes of anxiety can cause dramatic, ...

  9. On the effect of dynamic flow conditions on blood microstructure investigated with optical shearing microscopy and rheometry.

    PubMed

    Kaliviotis, E; Yianneskis, M

    2007-11-01

    Red blood cell (RBC) aggregation affects significantly the flow of blood at low shear rates. Increased RBC aggregation is associated with various pathological conditions; hence an accurate quantification and better understanding of the phenomenon is important. The present study aims to improve understanding of the effect of dynamic flow conditions on aggregate formation; whole blood samples from healthy volunteers, adjusted at 0.45 haematocrit were tested in different flow conditions with a plate-plate optical shearing system, image analysis, and a double-walled Couette rheometric cell. Results are presented in terms of aggregation index Aa, aggregate size index As and number of aggregates, which are shown to vary with shear rate gamma and with different shear rate variations with time gamma. The aggregation index Aa was observed to increase as the shear rate decreased between 10 and 3 s(-1). Above 10 s(-1), Aa was found to have a minimum value indicating minimal aggregation while, at approximately 3 s(-1), Aa reaches a maximum. The aggregation size index As, the number of aggregates, and the blood viscosity were found to vary considerably when the same sample was examined over the same shear rate range, but for different variations of shear rate with time, gamma.

  10. High temperature steady shear and oscillatory rheometry of basaltic melt

    NASA Astrophysics Data System (ADS)

    Petford, N.; English, R.; Williams, R.; Rogers, N.

    2012-04-01

    There is a paucity of linear viscoelastic data on low viscosity (basaltic) silicate melts. We report here the initial results of a rheometrical characterisation (steady rotation, small angle oscillation) study on a geochemically well constrained aphyric basalt from Ethiopia (SiO2 48.51 wt.%, Mg# 0.44), in the temperature range 1200-1400 Celsius. Experiments were done using a recently developed commercial instrument (Anton Paar FRS 1600) and a wide gap Couette geometry. To the best of our knowledge these are the first reported silicate melt viscosity data obtained using small amplitude oscillatory shear and a rheometer with a high performance electrically commutated actuator. Results show that in the temperature range the system was very fluid, with the measured shear viscosity falling to ~ 2.3 Pa s at T = 1400 C. The melt exhibited a linear (Newtonian) response, with the shear viscosity remaining constant across two decades of deformation rate. As expected for a Newtonian fluid, the phase angle was 90 degrees across the entire range of angular frequencies studied. Correspondingly, the storage modulus (G') was zero and the loss modulus finite exhibiting a linear increase with frequency. The complex viscosity (oscillation) and shear viscosity (steady rotation) were equal in magnitude ('Cox-Merz' equivalence). These data are best interpreted in terms of a system with relatively low 'connectivity'/polymeric character and rapid relaxation dynamics, consistent with the mafic composition of the melt. As detailed compositional data are available the experimentally determined shear viscosity values are compared with those predicted from multicomponent chemical models in the literature. Discrepancies between the experimental and theoretical values are discussed.

  11. Search for New Highly Energetic Phases under Compression and Shear

    DTIC Science & Technology

    2015-05-01

    corresponding finite element algorithms and subroutines are developed. (c) Problems on compression and shear of a sample in rotational diamond anvil...release, using the diamond anvil cell. Polymeric N2 appears above 110 GPa pressure and above the temperature of 2000K but cannot be retained under...ambient conditions. In these studies, phase transformations (PTs) are obtained in a diamond anvil cell under high quasi-hydrostatic pressure. While it

  12. Local shear texture formation in adiabatic shear bands by high rate compression of high manganese TRIP steels

    NASA Astrophysics Data System (ADS)

    Li, J.; Yang, P.; Mao, W. M.; Cui, F. E.

    2015-04-01

    Local shear textures in ASBs of high manganese TRIP steels under high rate straining are determined and the influences of initial microstructure is analyzed using EBSD technique. It is seen that even at the presence of majority of two types of martensite before deformation, ASB is preferred to evolve in austenite, rather than in martenite, due to reverse transformation. Ultrafine grains of thress phases due to dynamic recrystallization are formed and all show shear textures. The less ε-martensite in ASB is distributed as islands and its preferred orientation can be found to originate from the variants in matrix. The grain orientation rotation around ASB in multi-phase alloy reveals significant influence of α'- martensite on texture in ASB. The mechanism of local texture formation in ASB of high manganese TRIP steel is proposed in terms of the interaction of early TRIP and later reverse transformation.

  13. High blood pressure and eye disease

    MedlinePlus

    ... medlineplus.gov/ency/article/000999.htm High blood pressure and eye disease To use the sharing features on this page, please enable JavaScript. High blood pressure can damage blood vessels in the retina . The ...

  14. Influence of wall shear rate on parameters of blood compatibility of intravascular catheters.

    PubMed

    Rhodes, N P; Kumary, T V; Williams, D F

    1996-10-01

    Three polymeric materials (silicone, PVC and nylon) were compared in an in vitro perfusion model, whereby 5 ml whole blood were perfused along 1 m lengths of polymeric tubing of 1 mm internal diameter at wall shear rates of up to 1000 s-1. Perfusion took place at 37 degrees C for 30 min. The polymers were investigated for platelet activation, granulocyte secretion, complement activation and contact phase activation. These parameters were also analysed in static contact for comparison. All the parameters measured displayed a dependence on wall shear rate. In all the materials studied, platelet adhesion and platelet activation increased with increasing flow rate. Granulocyte elastase release increased slightly with increasing flow rate up to 300 s-1. Complement activation was greatest for PVC at 1000 s-1, greatest for nylon at 100 s-1, but there was no measurable difference at either rate for silicone. All samples caused an increase in clotting time with increasing wall shear rate. PVC was the most platelet compatible material, nylon the worst. Silicone caused least contact phase activation, PVC and nylon the most.

  15. Wall Shear Stress in Aorta with Coarctation and Post-Stenotic Dilatation - Scale Resolved Simulation of Pulsatile Blood Flow

    NASA Astrophysics Data System (ADS)

    Gardhagen, Roland; Karlsson, Matts

    2012-11-01

    Large eddy simulations of pulsating blood flow in an idealized model of a human aorta with a coarctation and a post-stenotic dilatation were conducted before and after treatment of the stenosis using Ansys Fluent. The aim was to study wall shear stress (WSS), which influences the function of endothelial cells, and turbulence, which may play a role in thrombus formation. Phase average values of WSS before the treatment revealed high shear in the stenosis at peak systole, as expected, but also at the end of the dilatation. In the dilatation backflow causes a negative peak. Diastolic WSS is characterized by low amplitude oscillations, which promotes atherogenesis. Also noticeable is the asymmetric pattern between the inner and outer sides of the vessel caused by the arch upstream of the stenosis. Thus, large spatial, temporal, and probably asymmetric WSS gradients in the already diseased region suggest increased risk for further endothelial dysfunction. This reflects a complex, partly turbulent, flow pattern that may disturb the blood flow in the abdominal aorta. After treatment of the stenosis, but not the dilatation, fluctuations of velocity and WSS were still found, thus harmful flow conditions still exist.

  16. Effects of shear rate, confinement, and particle parameters on margination in blood flow.

    PubMed

    Mehrabadi, Marmar; Ku, David N; Aidun, Cyrus K

    2016-02-01

    The effects of flow and particle properties on margination of particles in red blood cell (RBC) suspensions is investigated using direct numerical simulation (DNS) of cellar blood flow. We focus on margination of particles in the flow of moderately dense suspensions of RBCs. We hypothesize that margination rate in nondilute suspensions is mainly driven by the RBC-enhanced diffusion of marginating particles in the RBC-filled region. We derive a scaling law for margination length in a straight channel. Margination length increases cubically with channel height and is independent of shear rate. We verify this scaling law for margination length by DNS of flowing RBCs and marginating particles. We also show that rigidity and size both lead to particle margination with rigidity having a more significant effect compared to size within the range of parameters in this study.

  17. High Blood Pressure (Hypertension) (For Parents)

    MedlinePlus

    ... Old Feeding Your 1- to 2-Year-Old High Blood Pressure (Hypertension) KidsHealth > For Parents > High Blood Pressure (Hypertension) A ... posture, and medications. continue Long-Term Effects of High Blood Pressure When someone has high blood pressure, the heart ...

  18. Influence of non-Newtonian Properties of Blood on the Wall Shear Stress in Human Atherosclerotic Right Coronary Arteries

    PubMed Central

    Liu, Biyue; Tang, Dalin

    2011-01-01

    The objective of this work is to investigate the effect of non-Newtonian properties of blood on the wall shear stress (WSS) in atherosclerotic coronary arteries using both Newtonian and non-Newtonian models. Numerical simulations were performed to examine how the spatial and temporal WSS distributions are influenced by the stenosis size, blood viscosity, and flow rate. The computational results demonstrated that blood viscosity properties had considerable effect on the magnitude of the WSS, especially where disturbed flow was observed. The WSS distribution is highly non-uniform both temporally and spatially, especially in the stenotic region. The maximum WSS occurred at the proximal side of the stenosis, near the outer wall in the curved artery with no stenosis. The lumen area near the inner wall distal to the stenosis region experienced a lower WSS during the entire cardiac cycle. Among the factors of stenosis size, blood viscosity, and flow rate, the size of the stenosis has the most significant effect on the spatial and temporal WSS distributions qualitatively and quantitatively. PMID:21379375

  19. Disinclusion of unerupted teeth by mean of self-ligating brackets: Effect of blood contamination on shear bond strength

    PubMed Central

    Sfondrini, Maria F.; Gatti, Sara; Gandini, Paola

    2013-01-01

    Objectives: The aim of this study was to assess the effect of blood contamination on the shear bond strength and failure site of three different orthodontic self-ligating brackets. Study Design: 240 bovine permanent mandibular incisors were randomly divided into 12 groups of 20 specimens each. Orthodontic self-ligating brackets were tested under four different enamel surface conditions: a) dry, b) blood contamination before priming, c) blood contamination after priming, d) blood contamination before and after priming. Brackets were bonded to the teeth and subsequently tested using a Instron universal testing machine. Shear bond strength values and adhesive failure rate were recorded. Statistical analysis was performed using ANOVA and Tukey tests (strength values), and Chi squared test (ARI Scores). Results: Non-contaminated enamel surfaces showed highest bond strengths for all self ligating brackets. Under blood-contamination shear bond strengths lowered for all brackets tested. Groups contaminated before and after primer application showed the lowest shear bond strength. Significant differences in debond locations were found among the groups under the various enamel surface conditions. Conclusions: Blood contamination of enamel during the bonding procedure lowers bond strength values of self ligating brackets, expecially when contamination occur in different times of the bonding procedure. Key words:Disinclusion, self ligating brackets, blood, contamination, enamel, orthodontics, oral surgery. PMID:23229253

  20. Rheology of red blood cells under flow in highly confined microchannels: I. effect of elasticity.

    PubMed

    Lázaro, Guillermo R; Hernández-Machado, Aurora; Pagonabarraga, Ignacio

    2014-10-07

    We analyze the rheology of dilute red blood cell suspensions in pressure driven flows at low Reynolds number, in terms of the morphologies and elasticity of the cells. We focus on narrow channels of width similar to the cell diameter, when the interactions with the walls dominate the cell dynamics. The suspension presents a shear-thinning behaviour, with a Newtonian-behaviour at low shear rates, an intermediate region of strong decay of the suspension viscosity, and an asymptotic regime at high shear rates in which the effective viscosity converges to that of the solvent. We identify the relevant aspects of cell elasticity that contribute to the rheological response of blood at high confinement. In a second paper, we will explore the focusing of red blood cells while flowing at high shear rates and how this effect is controlled by the geometry of the channel.

  1. Treatment of oily wastes using high-shear rotary ultrafiltration

    SciTech Connect

    Reed, B.E.; Viadero, R. Jr.; Young, J.; Lin, W.

    1997-12-01

    The high-shear rotary ultrafiltration (UF) system uses membrane rotation to provide the turbulence required to minimize concentration polarization and flux decline. The high-shear UF system was effective in concentrating oily wastes from about 5% to as high as 65%. The decoupling of turbulence promotion from feed pressurization/recirculation by rotating the membrane was the primary reason for the improvement in performance over that observed with conventional UF systems. Transitional and gel layer oil concentrations (20% and 50--59%, respectively) were higher than values reported in the literature. Permeate flux was dependent on the temperature and rotational speed. Flux increased by about 45% when the temperature was increased from 43 to 60 C. A larger decrease in waste viscosity, over that predicted for water alone, and increased oil droplet diffusivity were hypothesized as reasons for the stronger than expected flux-temperature relationship. The flux-rotational speed ({omega}) relationship was described by J = f({omega}){sup 0.90}; however, the gel layer exhibited stability with increasing {omega}. The ceramic membrane was superior to the polymeric membrane in regards to permeate flux and quality as well as cleaning and durability.

  2. High blood pressure tests (image)

    MedlinePlus

    ... factors. These lab tests include urinalysis, blood cell count, blood chemistry (potassium, sodium, creatinine, fasting glucose, total cholesterol and HDL cholesterol), and an ECG (electrocardiogram). ...

  3. The effect of turbulent viscous shear stress on red blood cell hemolysis.

    PubMed

    Yen, Jen-Hong; Chen, Sheng-Fu; Chern, Ming-Kai; Lu, Po-Chien

    2014-06-01

    Non-physiologic turbulent flow occurs in medical cardiovascular devices resulting in hemodynamic stresses that may damage red blood cells (RBC) and cause hemolysis. Hemolysis was previously thought to result from Reynolds shear stress (RSS) in turbulent flows. A more recent hypothesis suggests that turbulent viscous shear stresses (TVSS) at spatial scales similar in size to RBCs are related to their damage. We applied two-dimensional digital particle image velocimetry to measure the flow field of a free-submerged axisymmetric jet that was utilized to hemolyze porcine RBCs in selected locations. Assuming a dynamic equilibrium for the sub-grid scale (SGS) energy flux between the resolved and the sub-grid scales, the SGS energy flux was calculated from the strain rate tensor computed from the resolved velocity fields. The SGS stress was determined by the Smagorinsky model, from which the turbulence dissipation rate and then TVSS were estimated. Our results showed the hemolytic threshold of the Reynolds stresses was up to 517 Pa, and the TVSSs were at least an order of magnitude less than the RSS. The results provide further insight into the relationship between turbulence and RBC damage.

  4. Shape Recovery of Elastic Red Blood Cells from Shear Flow Induced Deformation in Three Dimensions

    NASA Astrophysics Data System (ADS)

    Peng, Yan; Gounley, John

    2015-11-01

    Red blood cells undergo substantial shape changes in vivo. Modeled as an elastic capsule, the shape recovery of a three dimensional biconcave capsule from shear flow is studied for different preferred elastic and bending configuration. The fluid-structure interaction is modeled using the multiple-relaxation time lattice Boltzmann (LBM) and immersed boundary (IBM) methods. Based on the studies of the limited shape memory observed in three dimensions, the shape recovery is caused by the preferred elastic configuration, at least when paired with a constant spontaneous curvature. For these capsules, the incompleteness of the shape recovery observed precludes any conjecture about whether a single or multiple phase(s) are necessary to describe the recovery process. Longer simulations and a more stable methodology will be necessary. Y. Peng acknowledges support from Old Dominion University Research Foundation Grant #503921 and National Science Foundation Grant DMS-1319078.

  5. High-Energy-Density Shear Flow and Instability Experiments

    NASA Astrophysics Data System (ADS)

    Doss, F. W.; Flippo, K. A.; Merritt, E. C.; di Stefano, C. A.; Devolder, B. G.; Kurien, S.; Kline, J. L.

    2016-10-01

    High-energy-density shear experiments have been performed by LANL at the OMEGA Laser Facility and National Ignition Facility (NIF). The experiments have been simulated using the LANL radiation-hydrocode RAGE and have been used to assess turbulence models' ability to function in the high-energy-density, inertial-fusion-relevant regime. Beginning with the basic configuration of two counter-oriented shock-driven flows of > 100 km/s, which initiate a strong shear instability across an initially solid-density, 20 μm thick Al plate, variations of the experiment to details of the initial conditions have been performed. These variations have included increasing the fluid densities (by modifying the plate material from Al to Ti and Cu), imposing sinusoidal seed perturbations on the plate, and directly modifying the plate's intrinsic surface roughness. Radiography of the unseeded layer has revealed the presence of emergent Kelvin-Helmholtz structures which may be analyzed to infer fluid-mechanical properties including turbulent energy density. This work is conducted by the US DOE by LANL under contract DE-AC52-06NA25396.

  6. High-frequency shear-horizontal surface acoustic wave sensor

    DOEpatents

    Branch, Darren W

    2013-05-07

    A Love wave sensor uses a single-phase unidirectional interdigital transducer (IDT) on a piezoelectric substrate for leaky surface acoustic wave generation. The IDT design minimizes propagation losses, bulk wave interferences, provides a highly linear phase response, and eliminates the need for impedance matching. As an example, a high frequency (.about.300-400 MHz) surface acoustic wave (SAW) transducer enables efficient excitation of shear-horizontal waves on 36.degree. Y-cut lithium tantalate (LTO) giving a highly linear phase response (2.8.degree. P-P). The sensor has the ability to detect at the pg/mm.sup.2 level and can perform multi-analyte detection in real-time. The sensor can be used for rapid autonomous detection of pathogenic microorganisms and bioagents by field deployable platforms.

  7. High-frequency shear-horizontal surface acoustic wave sensor

    DOEpatents

    Branch, Darren W

    2014-03-11

    A Love wave sensor uses a single-phase unidirectional interdigital transducer (IDT) on a piezoelectric substrate for leaky surface acoustic wave generation. The IDT design minimizes propagation losses, bulk wave interferences, provides a highly linear phase response, and eliminates the need for impedance matching. As an example, a high frequency (.about.300-400 MHz) surface acoustic wave (SAW) transducer enables efficient excitation of shear-horizontal waves on 36.degree. Y-cut lithium tantalate (LTO) giving a highly linear phase response (2.8.degree. P-P). The sensor has the ability to detect at the pg/mm.sup.2 level and can perform multi-analyte detection in real-time. The sensor can be used for rapid autonomous detection of pathogenic microorganisms and bioagents by field deployable platforms.

  8. Hydrodynamic lubrication in nanoscale bearings under high shear velocity

    NASA Astrophysics Data System (ADS)

    Chen, Yunfei; Li, Deyu; Jiang, Kai; Yang, Juekuan; Wang, Xiaohui; Wang, Yujuan

    2006-08-01

    The setting up process in a nanoscale bearing has been modeled by molecular dynamics simulation. Contrary to the prediction from the classical Reynolds' theory, simulation results show that the load capacity of the nanoscale bearing does not increase monotonically with the operation speed. This is attributed to the change of the local shear rate, which will decrease with the shear velocity of the bearing as the shear velocity exceeds a critical value, i.e., the local shear rate has an upper limit. A simple nonlinear dynamic model indicates that the momentum exchange between the liquid and the solid wall is reduced with the shear velocity when the shear velocity is above a critical value. The weak momentum exchange results in a decrease of the local shear rate, which in turn causes a sharp increase of the slip length.

  9. Comminution of Ceramic Materials Under High-Shear Dynamic Compaction

    NASA Astrophysics Data System (ADS)

    Homel, Michael; Loiseau, Jason; Higgins, Andrew; Herbold, Eric; Hogan, Jamie

    The post-failure ``granular flow'' response of high-strength lightweight ceramics has important implications on the materials' effectiveness for ballistic protection. We study the dynamic compaction and shear flow of ceramic fragments and powders using computational and experimental analysis of a collapsing thick-walled cylinder geometry. Using newly developed tools for mesoscale simulation of brittle materials, we study the effect of fracture, comminution, shear-enhanced dilatation, and frictional contact on the continuum compaction response. Simulations are directly validated through particle Doppler velocimetry measurements at the inner surface of the cylindrical powder bed. We characterize the size distribution and morphologies of the initial and compacted material fragments to both validate the computational model and to elucidate the dominant failure processes. A portion of this work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC. LLNL-ABS-678862.

  10. How Is High Blood Cholesterol Treated?

    MedlinePlus

    ... the NHLBI on Twitter. How Is High Blood Cholesterol Treated? High blood cholesterol is treated with lifestyle ... need to follow a heart healthy diet . Lowering Cholesterol Using Therapeutic Lifestyle Changes TLC is a set ...

  11. Avoid the Consequences of High Blood Pressure

    MedlinePlus

    ... Aneurysm More Avoid the Consequences of High Blood Pressure Infographic Updated:Oct 31,2016 View a downloadable version of this infographic High Blood Pressure • Home • Get the Facts About HBP • Know Your ...

  12. Managing Stress to Control High Blood Pressure

    MedlinePlus

    ... Aneurysm More Managing Stress to Control High Blood Pressure Updated:Jan 10,2017 The importance of stress ... content was last reviewed October 2016. High Blood Pressure • Home • Get the Facts About HBP • Know Your ...

  13. Hemodynamic analysis in an idealized artery tree: differences in wall shear stress between Newtonian and non-Newtonian blood models.

    PubMed

    Weddell, Jared C; Kwack, JaeHyuk; Imoukhuede, P I; Masud, Arif

    2015-01-01

    Development of many conditions and disorders, such as atherosclerosis and stroke, are dependent upon hemodynamic forces. To accurately predict and prevent these conditions and disorders hemodynamic forces must be properly mapped. Here we compare a shear-rate dependent fluid (SDF) constitutive model, based on the works by Yasuda et al in 1981, against a Newtonian model of blood. We verify our stabilized finite element numerical method with the benchmark lid-driven cavity flow problem. Numerical simulations show that the Newtonian model gives similar velocity profiles in the 2-dimensional cavity given different height and width dimensions, given the same Reynolds number. Conversely, the SDF model gave dissimilar velocity profiles, differing from the Newtonian velocity profiles by up to 25% in velocity magnitudes. This difference can affect estimation in platelet distribution within blood vessels or magnetic nanoparticle delivery. Wall shear stress (WSS) is an important quantity involved in vascular remodeling through integrin and adhesion molecule mechanotransduction. The SDF model gave a 7.3-fold greater WSS than the Newtonian model at the top of the 3-dimensional cavity. The SDF model gave a 37.7-fold greater WSS than the Newtonian model at artery walls located immediately after bifurcations in the idealized femoral artery tree. The pressure drop across arteries reveals arterial sections highly resistive to flow which correlates with stenosis formation. Numerical simulations give the pressure drop across the idealized femoral artery tree with the SDF model which is approximately 2.3-fold higher than with the Newtonian model. In atherosclerotic lesion models, the SDF model gives over 1 Pa higher WSS than the Newtonian model, a difference correlated with over twice as many adherent monocytes to endothelial cells from the Newtonian model compared to the SDF model.

  14. Hemodynamic Analysis in an Idealized Artery Tree: Differences in Wall Shear Stress between Newtonian and Non-Newtonian Blood Models

    PubMed Central

    Weddell, Jared C.; Kwack, JaeHyuk; Imoukhuede, P. I.; Masud, Arif

    2015-01-01

    Development of many conditions and disorders, such as atherosclerosis and stroke, are dependent upon hemodynamic forces. To accurately predict and prevent these conditions and disorders hemodynamic forces must be properly mapped. Here we compare a shear-rate dependent fluid (SDF) constitutive model, based on the works by Yasuda et al in 1981, against a Newtonian model of blood. We verify our stabilized finite element numerical method with the benchmark lid-driven cavity flow problem. Numerical simulations show that the Newtonian model gives similar velocity profiles in the 2-dimensional cavity given different height and width dimensions, given the same Reynolds number. Conversely, the SDF model gave dissimilar velocity profiles, differing from the Newtonian velocity profiles by up to 25% in velocity magnitudes. This difference can affect estimation in platelet distribution within blood vessels or magnetic nanoparticle delivery. Wall shear stress (WSS) is an important quantity involved in vascular remodeling through integrin and adhesion molecule mechanotransduction. The SDF model gave a 7.3-fold greater WSS than the Newtonian model at the top of the 3-dimensional cavity. The SDF model gave a 37.7-fold greater WSS than the Newtonian model at artery walls located immediately after bifurcations in the idealized femoral artery tree. The pressure drop across arteries reveals arterial sections highly resistive to flow which correlates with stenosis formation. Numerical simulations give the pressure drop across the idealized femoral artery tree with the SDF model which is approximately 2.3-fold higher than with the Newtonian model. In atherosclerotic lesion models, the SDF model gives over 1 Pa higher WSS than the Newtonian model, a difference correlated with over twice as many adherent monocytes to endothelial cells from the Newtonian model compared to the SDF model. PMID:25897758

  15. Visualization of Simulated Endothelial Shear Stress and Blood Flow in Coronary Arteries

    NASA Astrophysics Data System (ADS)

    Borkin, Michelle; Feldman, Charles L.; Pfister, Hanspeter; Melchionna, Simone; Kaxiras, Efthimios

    2010-11-01

    Low endothelial shear stress (ESS) identifies areas of atherosclerotic disease lesion formation in the coronary arteries. However, it is impossible to directly measure ESS in vivo for an entire arterial tree. As part of the Multiscale Hemodynamics Project, computed tomography angiography (CTA) data is being used to obtain patient specific heart and coronary system geometries and then MUPHY, a multi-physics and multi-scale simulation code combining microscopic Molecular Dynamics (MD) with a hydro-kinetic Lattice Boltzmann (LB) method, is applied in order to simulate blood flow through the coronary arteries. Having effective visualizations of the simulation's multidimensional output, including ESS, is vital for the quick and thorough non-invasive evaluation of the patient. To this end, we have developed new visualization tools and techniques to make the simulation's output useful in a clinical diagnostic setting, examined the effectiveness of 2D versus 3D representations, and explored blood flow representations. The visualization methods developed are also applicable to other areas of fluid dynamics.

  16. Study of blood viscosity at low shear rate and its flow through viscoelastic tubes and ducts

    NASA Astrophysics Data System (ADS)

    Misra, N.; Sarkar, A.; Srinivas, A.; Kapusetti, G.

    2012-02-01

    A nonlinear mathematical model is developed analytically to study the flow characteristics of visco-elastic fluid through a visco-elastic pipe when it is subjected to external body acceleration. The equations governing the motion of the system are solved analytically with the use of appropriate boundary conditions. For the present scope of study the flow of visco-elastic fluid (blood) in smaller artery which is visco-elastic in nature has been taken. The artery is assumed to be a flexible cylindrical tube containing a non-Newtonian fluid. The unsteady flow mechanism in the artery is subjected to a pulsatile pressure gradient arising from the normal functioning of the heart and also the external body acceleration. Numerical models have finally been developed for Newtonian and Non-Newtonian fluid in order to have a thorough quantitative measure of the effects of body acceleration on the flow velocity, volume flow rate and the wall shear stress of blood in normal human artery and when the artery gets stiffer, just to validate the applicability of the present mathematical model.

  17. High Blood Pressure in Pregnancy

    MedlinePlus

    ... Public Health Topics Education & Awareness Resources Heart & Vascular Lung Blood Sleep Selected Audiences Contact The Health Information Center ... agencies. NHBPEP is coordinated by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health. ...

  18. The high-energy-density counterpropagating shear experiment and turbulent self-heating

    SciTech Connect

    Doss, F. W.; Fincke, J. R.; Loomis, E. N.; Welser-Sherrill, L.; Flippo, K. A.

    2013-12-06

    The counterpropagating shear experiment has previously demonstrated the ability to create regions of shockdriven shear, balanced symmetrically in pressure and experiencing minimal net drift. This allows for the creation of a high-Mach-number high-energy-density shear environment. New data from the counterpropagating shear campaign is presented, and both hydrocode modeling and theoretical analysis in the context of a Reynolds-averaged-Navier-Stokes model suggest turbulent dissipation of energy from the supersonic flow bounding the layer is a significant driver in its expansion. A theoretical minimum shear flow Mach number threshold is suggested for substantial thermal-turbulence coupling.

  19. Effects of arterial blood flow on walls of the abdominal aorta: distributions of wall shear stress and oscillatory shear index determined by phase-contrast magnetic resonance imaging.

    PubMed

    Sughimoto, Koichi; Shimamura, Yoshiaki; Tezuka, Chie; Tsubota, Ken'ichi; Liu, Hao; Okumura, Kenichiro; Masuda, Yoshitada; Haneishi, Hideaki

    2016-07-01

    Although abdominal aortic aneurysms (AAAs) occur mostly inferior to the renal artery, the mechanism of the development of AAA in relation to its specific location is not yet clearly understood. The objective of this study was to evaluate the hypothesis that even healthy volunteers may manifest specific flow characteristics of blood flow and alter wall shear or oscillatory shear stress in the areas where AAAs commonly develop. Eight healthy male volunteers were enrolled in this prospective study, aged from 24 to 27. Phase-contrast magnetic resonance imaging (MRI) was performed with electrocardiographic triggering. Flow-sensitive four-dimensional MR imaging of the abdominal aorta, with three-directional velocity encoding, including simple morphological image acquisition, was performed. Information on specific locations on the aortic wall was applied to the flow encodes to calculate wall shear stress (WSS) and oscillatory shear index (OSI). While time-framed WSS showed the highest peak of 1.14 ± 0.25 Pa in the juxtaposition of the renal artery, the WSS plateaued to 0.61 Pa at the anterior wall of the abdominal aorta. The OSI peaked distal to the renal arteries at the posterior wall of the abdominal aorta of 0.249 ± 0.148, and was constantly elevated in the whole abdominal aorta at more than 0.14. All subjects were found to have elevated OSI in regions where AAAs commonly occur. These findings indicate that areas of constant peaked oscillatory shear stress in the infra-renal aorta may be one of the factors that lead to morphological changes over time, even in healthy individuals.

  20. Monitoring high-shear granulation using sound and vibration measurements.

    PubMed

    Briens, L; Daniher, D; Tallevi, A

    2007-02-22

    Sound and vibration measurements were investigated as monitoring methods for high-shear granulation. Five microphones and one accelerometer were placed at different locations on a 10 and a 25 l granulator and compared to find the optimum location and the effect of scale. The granulation process could be monitored using the mean frequency and root mean square sound pressure levels from acoustic emissions measured using a microphone in the filtered air exhaust of the granulators. These acoustic monitoring methods were successful for both the 10 and the 25 l granulation scales. The granulation phases, however, were more clearly defined for the larger scale granulation. The root mean square acceleration level from vibration measurements was also able to monitor the granulation, but only for the larger 25 l granulator.

  1. High spin spectroscopy and shears mechanism in {sup 107}In

    SciTech Connect

    Negi, D.; Mohanto, G.; Kumar, R.; Singh, R. P.; Muralithar, S.; Bhowmik, R. K.; Trivedi, T.; Dhal, A.; Kumar, S.; Kumar, V.; Roy, S.; Raju, M. K.; Appannababu, S.; Kaur, J.; Bhati, A. K.; Sinha, R. K.; Pancholi, S. C.

    2010-05-15

    High spin states of {sup 107}In have been investigated using the reaction {sup 94}Mo({sup 16}O,p2n){sup 107}In at a beam energy of 70 MeV. A total of 62 new gamma transitions have been placed in the level scheme and several DELTAI=1 sequences and one DELTAI=2 sequence have been found. Lifetime measurements using the Doppler-shift attenuation method (DSAM) have been carried out for band states of DELTAI=1 and DELTAI=2. A decreasing trend of B(M1) strengths with increasing spin deduced for the DELTAI=1 band indicates the presence of a shears mechanism. The experimental data for this band are compared with the tilted axis cranking (TAC) calculations. The DELTAI=2 band has been found to be a deformed band with beta{sub 2}approx0.2.

  2. Manufacture of concentrated, lipid-based oxygen microbubble emulsions by high shear homogenization and serial concentration.

    PubMed

    Thomson, Lindsay M; Polizzotti, Brian D; McGowan, Frances X; Kheir, John N

    2014-05-26

    Gas-filled microbubbles have been developed as ultrasound contrast and drug delivery agents. Microbubbles can be produced by processing surfactants using sonication, mechanical agitation, microfluidic devices, or homogenization. Recently, lipid-based oxygen microbubbles (LOMs) have been designed to deliver oxygen intravenously during medical emergencies, reversing life-threatening hypoxemia, and preventing subsequent organ injury, cardiac arrest, and death. We present methods for scaled-up production of highly oxygenated microbubbles using a closed-loop high-shear homogenizer. The process can produce 2 L of concentrated LOMs (90% by volume) in 90 min. Resulting bubbles have a mean diameter of ~2 μm, and a rheologic profile consistent with that of blood when diluted to 60 volume %. This technique produces LOMs in high capacity and with high oxygen purity, suggesting that this technique may be useful for translational research labs.

  3. Comparison of two platelet activation markers using flow cytometry after in vitro shear stress exposure of whole human blood.

    PubMed

    Lu, Qijin; Malinauskas, Richard A

    2011-02-01

    Platelet activation is the initiating step to thromboembolic complications in blood-contacting medical devices. Currently, there are no widely accepted testing protocols or relevant metrics to assess platelet activation during the in vitro evaluation of new medical devices. In this article, two commonly used platelet activation marker antibodies, CD62P (platelet surface P-selectin) and PAC1 (activated GP IIb/IIIa), were evaluated using flow cytometry. Anticoagulant citrate dextrose solution A (ACDA) and heparin anticoagulated human blood from healthy donors were separately exposed to shear stresses of 0, 10, 15, and 20 Pa for 120 s using a cone-plate rheometer model, and immediately mixed with the platelet marker antibodies for analysis. To monitor for changes in platelet reactivity between donors and over time, blood samples were also evaluated after exposure to 0, 2, and 20 µM of adenosine diphosphate (ADP). Following ADP stimulation, the percentage of both CD62P and PAC1 positive platelets increased in a dose dependent fashion, even 8 h after the blood was collected. After shear stress stimulation, both CD62P and PAC1 positive platelets increased significantly at shear stress levels of 15 and 20 Pa when ACDA was used as the anticoagulant. However, for heparinized blood, the PAC1 positive platelets decreased with increasing shear stress, while the CD62P positive platelets increased. Besides the anticoagulant effect, the platelet staining buffer also impacted PAC1 response, but had little effect on CD62P positive platelets. These data suggest that CD62P is a more reliable marker compared with PAC1 for measuring shear-dependent platelet activation and it has the potential for use during in vitro medical device testing.

  4. Whole blood of mammalian species in the oscillating shear field: influence of erythrocyte aggregation

    NASA Astrophysics Data System (ADS)

    Windberger, U.; Pöschl, Ch; Peters, S.; Huber, J.; van den Hoven, R.

    2017-02-01

    This is the rheologicalanalysis of mammalian blood of species with a high (horse), medium (man), and low (sheep) erythrocyte (RBC) aggregability by small amplitude oscillation technique. Amplitude and frequency sweep tests in linear mode were performed with blood from healthy adult volunteers, horses, and sheep in CSS-mode. Blood samples were hematocrit (HCT) adjusted (40%, 50%, 60%) and tested at 7°C, 22°C, and 37°C. Storage modulus (G‧) increased with HCT and decreased with temperature in each species, but the gradient of this increase was species-specific. The lower dependency of G‧ on the equine HCT value could be a benefit during physical performance when high numbers of RBCs are released from the spleen in the horse. In sheep, a HCT-threshold had to be overcome before elasticity of the blood sample could be measured, suggesting that the cohesive forces between RBCs, and between RBCs and plasma molecules must be very low. The frequencies for tests under quasi-staticcondition were in a narrow range around the physiologic heart rate of the species. In horse, time-dependent influences concurred at frequencies lower than 3 rad.s-1 probably due to sedimentation of RBC aggregates. In conclusion, elasticity of blood depends not only on the amount of blood cells, but also on their mechanical and functional properties.

  5. Risk Factors for High Blood Pressure

    MedlinePlus

    ... to achieve target blood pressure goals with treatment. Overweight You are more likely to develop prehypertension or high blood pressure if you’re overweight or obese . The terms “overweight” and “obese” refer ...

  6. High Blood Pressure: Unique to Older Adults

    MedlinePlus

    ... below to read more. High Blood Pressure and Edema : You may notice swelling in some parts of ... blood pressure. This buildup of fluids, called peripheral edema, usually occurs in your ankles, feet, lower legs, ...

  7. A comparison of granules produced by high-shear and fluidized-bed granulation methods.

    PubMed

    Morin, Garett; Briens, Lauren

    2014-08-01

    Placebo granules were manufactured by both wet high-shear and fluidized-bed techniques. The granules were compared based on size, shape, surface morphology, and a variety of different flowability measurements. This comparison showed that granule formation and growth were different, with induction growth for high-shear granulation and steady growth for fluidized-bed granulation. Final granules from high-shear granulation were more spherical and dense compared with the irregular granules from fluidized-bed granulation. The high-shear granules demonstrated better overall flow properties.

  8. Quantifying the deformation of the red blood cell skeleton in shear flow

    NASA Astrophysics Data System (ADS)

    Peng, Zhangli; Zhu, Qiang

    2012-02-01

    To quantitatively predict the response of red blood cell (RBC) membrane in shear flow, we carried out multiphysics simulations by coupling a three-level multiscale approach of RBC membranes with a Boundary Element Method (BEM) for surrounding flows. Our multiscale approach includes a model of spectrins with the domain unfolding feature, a molecular-based model of the junctional complex with detailed protein connectivity and a whole cell Finite Element Method (FEM) model with the bilayer-skeleton friction derived from measured transmembrane protein diffusivity based on the Einstein-Stokes relation. Applying this approach, we investigated the bilayer-skeleton slip and skeleton deformation of healthy RBCs and RBCs with hereditary spherocytosis anemia during tank-treading motion. Compared with healthy cells, cells with hereditary spherocytosis anemia sustain much larger skeleton-bilayer slip and area deformation of the skeleton due to deficiency of transmembrane proteins. This leads to extremely low skeleton density and large bilayer-skeleton interaction force, both of which may cause bilayer loss. This finding suggests a possible mechanism of the development of hereditary spherocytosis anemia.

  9. High blood pressure in women.

    PubMed

    Calhoun, D A; Oparil, S

    1997-01-01

    There is a sexual dimorphism in blood pressure of humans and experimental animals: males tend to have higher blood pressure than females with functional ovaries, while ovariectomy or menopause tends to abolish the sexual dimorphism and cause females to develop a "male" pattern of blood pressure. Hypertensive male laboratory animals tend to have NaCl-sensitive blood pressure, while females are NaCl resistant unless their ovaries are removed, in which case NaCl sensitivity appears. The hormonal basis of NaCl sensitivity of blood pressure and of the sexual dimorphism of hypertension remains to be defined. Synthetic estrogens and progestins, as found in oral contraceptives, tend to elevate blood pressure, while naturally occurring estrogens lower it, or have no effect. Hypertension increases cardiovascular risk in women, as well as men, although the benefits of antihypertensive treatment have been more difficult to demonstrate in women. In the population of the United States, women are more aware of their hypertension, more likely to be treated medically, and more likely to have their blood pressure controlled.

  10. Thermoplastic encapsulation of waste surrogates by high-shear mixing

    SciTech Connect

    Lageraaen, P.R.; Kalb, P.D.; Patel, B.R.

    1995-12-01

    Brookhaven National Laboratory (BNL) has developed a robust, extrusion-based polyethylene encapsulation process applicable to a wide range of solid and aqueous low-level radioactive, hazardous and mixed wastes. However, due to the broad range of physical and chemical properties of waste materials, pretreatment of these wastes is often required to make them amenable to processing with polyethylene. As part of the scope of work identified in FY95 {open_quotes}Removal and Encapsulation of Heavy Metals from Ground Water,{close_quotes} EPA SERDP No. 387, that specifies a review of potential thermoplastic processing techniques, and in order to investigate possible pretreatment alternatives, BNL conducted a vendor test of the Draiswerke Gelimat (thermokinetic) mixer on April 25, 1995 at their test facility in Mahwah, NJ. The Gelimat is a batch operated, high-shear, high-intensity fluxing mixer that is often used for mixing various materials and specifically in the plastics industry for compounding additives such as stabilizers and/or colorants with polymers.

  11. Evaluation of shear stress accumulation on blood components in normal and dysfunctional bileaflet mechanical heart valves using smoothed particle hydrodynamics.

    PubMed

    Shahriari, S; Maleki, H; Hassan, I; Kadem, L

    2012-10-11

    Evaluating shear induced hemodynamic complications is one of the major concerns in design of the mechanical heart valves (MHVs). The monitoring of these events relies on both numerical simulations and experimental measurements. Currently, numerical approaches are mainly based on a combined Eulerian-Lagrangian approach. A more straightforward evaluation can be based on the Lagrangian analysis of the whole blood. As a consequence, Lagrangian meshfree methods are more adapted to such evaluation. In this study, smoothed particle hydrodynamics (SPH), a fully meshfree particle method originated to simulate compressible astrophysical flows, is applied to study the flow through a normal and a dysfunctional bileaflet mechanical heart valves (BMHVs). The SPH results are compared with the reference data. The accumulation of shear stress patterns on blood components illustrates the important role played by non-physiological flow patterns and mainly vortical structures in this issue. The statistical distribution of particles with respect to shear stress loading history provides important information regarding the relative number of blood components that can be damaged. This can be used as a measure of the response of blood components to the presence of the valve implant or any implantable medical device. This work presents the first attempt to simulate pulsatile flow through BMHVs using SPH method.

  12. Living with High Blood Pressure

    MedlinePlus

    ... closely and work with your health care team. Healthy Lifestyle Changes You can help control your blood pressure by making these healthy lifestyle changes: Follow a healthy diet. Be physically active. ...

  13. `Sausage string' patterns in blood vessels at high blood pressures

    NASA Astrophysics Data System (ADS)

    Alstrøm, Preben; Eguíluz, Victor M.; Gustafsson, Finn; Holstein-Rathlou, Niels-Henrik

    A new Rayleigh-type instability is proposed to explain the `sausage-string' pattern of alternating constrictions and dialtations formed in blood vessels at high blood pressure conditions. Our theory involves the nonlinear stress-strain characteristics of the vessel wall, and provides predictions for the conditions under which the normal cylindrical geometry of a blood vessel becomes unstable. The theory explains key features observed experimentally, e.g. the limited occurrence of the sausage-string pattern to small arteries and large arterioles, and only in those with small wall-to-lumen ratios.

  14. Effect of cytoskeleton stress-free state on red blood cell responses in low shear rate flows

    NASA Astrophysics Data System (ADS)

    Zhu, Qiang; Peng, Zhangli; Mashayekh, Adel

    2013-11-01

    Inspired by the recent experiment on erythrocytes (red blood cells, or RBCs) in weak shear flows (Dupire et al. 2012), we conduct a numerical investigation to study the dynamics of RBCs in low shear rate flows by applying a multiscale fluid-structure interaction model. By employing a spheroidal stress-free state in the cytoskeleton we are able to numerically predict an important feature that the cell maintains its biconcave shape during tank treading motions. This has not been achieved by any existing models. Furthermore, we numerically confirm the hypothesis that as the stress-free state approaches a sphere, the threshold shear rates corresponding to the establishment of tank treading decrease. By comparing with the experimental measurements, our study suggests that the stress-free state of RBCs is a spheroid which is close to a sphere, rather than a biconcave shape applied in existing models (the implication is that the RBC skeleton is prestressed in its natural biconcave state). It also suggests that the response of RBCs in low shear rate flows may provide a measure to quantitatively determine the distribution of shear stress in RBC cytoskeleton at the natural state.

  15. Compositional evolution of high-temperature sheared lherzolite PHN 1611

    SciTech Connect

    Smith, D. ); Griffin, W.L.; Ryan, C.G. )

    1993-02-01

    The evolution of fertile' mantle has been studied by proton microprobe (PIXE) analysis of minerals of a high-temperature sheared xenolith from the Thaba Putsoa kimerlite in Lesotho, southern Africa. Analyzed elements include Ni, Cu, Zn, Ga, Sr, Y, and Zr. Garnets are homogeneous in Ni and Zn but have rims enriched relative to cores in Zr and Y. Compositions of olivine neoblasts define intergranular gradients of Fe, Zn, and Ni; Fe-rich olivine is relatively Zn-rich but Ni-poore. Although individual clinopyroxene grains are nearly homogeneous, clinopyroxene associated with Fe-rich olivine is relatively Fe- and Zn-rich but Sr- and Cr-poor. The trace-element abundances and compositional gradients constrain the processes of periodotite enrichment and the thermal history. Enrichment of Zr, Y, and Fe in garnet rims documents infiltration of a silica-undersaturated melt. The Fe-rich olivine compositions and the Zn and Fe gradients establish that the xenolith was sampled from near a melt conduit. Mechanical mixing of inhomogeneous peridotite and melt infiltration may have been concurrent. Because garnets appear homogeneous in Ni, mantle temperature changes affecting PHN 1611 occurred before or over a longer period than the melt infiltration. Measured and calculated abundances of many incompatible trace elements in the rock are similar to those proposed for primitive mantle. Calculated chondrite-normalized abundances of Sr, Ti, Zr, and Y are like those of appropriate REE. Enrichment processes in PHN 1611 proceeded at unusually high recorded temperature and in the apparent absence of minor phases common in lower-temperature metasomatized rocks, but similar processes may be common. In particular, mechanical mixing near mantle dikes may frequently occur. These enrichment mechanisms may produce xenolith compositions that resemble some proposed for primitive mantle but that have different implications for mantle evolution. 61 refs., 7 figs., 2 tabs.

  16. High Blood Pressure: MedlinePlus Health Topic

    MedlinePlus

    ... and taking medicines , if needed. NIH: National Heart, Lung, and Blood Institute Start Here Blood Pressure Matters: Keep Hypertension ... Institutes of Health) High Blood Pressure (National Heart, Lung, and Blood Institute) Also in Spanish High Blood Pressure (Hypertension) ( ...

  17. FE Analysis on Shear Deformation for Asymmetrically Hot-Rolled High-Manganese Steel Strip

    NASA Astrophysics Data System (ADS)

    Sui, Feng-Li; Wang, Xin; Li, Chang-Sheng; Zhao, Jun

    2016-11-01

    Shear deformation along the longitudinal cross section of the high-manganese steel strip has been analyzed in hot asymmetrical rolling process using rigid-plastic finite element model. The friction coefficient between the rolls and the strip surfaces, the diameter of the work rolls, the speed ratio for the lower/upper rolls, the reduction rate and the initial temperature of the billet were all taken into account. Influence of these process parameters on the shear stress, the shear strain and the related shear strain energy in the center layer of the hot-rolled strip was analyzed. It is indicated that increasing the speed ratio, the reduction rate and the work roll diameter is an effective way to accumulate more shear strain energy in the strip center. A mathematical model reflecting the relationship between the shear strain energy and the process parameters has been established.

  18. Transition in high-speed free shear layers

    NASA Technical Reports Server (NTRS)

    Demetriades, A.

    1990-01-01

    The laminar free-shear layers considered in the study are formed by combinations of the velocities and momentum thicknesses of two adjacent parallel flows. Transition in wakes, pure free-shear layers of the Chapman type, and separate and partition flows are discussed. A stability-transition connection is emphasized, and it is suggested that a recurring deficiency in some stability calculations is the use of overly simplified laminar profiles. It is also noted that physical principles can be used for estimating the transition location or providing the factors affecting it. One such approach, a threshold theory, is discussed by way of example.

  19. Real-Life Stories about High Blood Pressure

    MedlinePlus

    ... turn Javascript on. Feature: High Blood Pressure Real-life Stories About High Blood Pressure Past Issues / Fall ... High Blood Pressure / Keep the Beat Recipes / Real-life Stories About High Blood Pressure / Treatment: Types of ...

  20. High Blood Pressure Often Undiagnosed, Untreated

    MedlinePlus

    ... Health, or the U.S. Department of Health and Human Services. More Health News on: Heart Attack High Blood Pressure Stroke Recent Health News Related MedlinePlus Health Topics Heart Attack High Blood Pressure Stroke ... Bethesda, MD 20894 U.S. Department of Health and Human Services National Institutes of Health Page last updated ...

  1. Exact two-dimensional zonal wavefront reconstruction with high spatial resolution in lateral shearing interferometry

    NASA Astrophysics Data System (ADS)

    Dai, Fengzhao; Li, Jie; Wang, Xiangzhao; Bu, Yang

    2016-05-01

    A novel zonal method is proposed for exact discrete reconstruction of a two-dimensional wavefront with high spatial resolution for lateral shearing interferometry. Four difference wavefronts measured in the x and y shear directions are required. Each of the two shear directions is measured twice with different shear amounts. The shear amounts of the second measurements of the x and y directions are Sx+1 pixels and Sy+1 pixels, where Sx pixels and Sy pixels are the shear amounts of the first measurements in the x and y directions, respectively. The shear amount in each direction can be chosen freely, provided that it is below a maximum value determined by the pupil shape and the number of samples N in that direction; thus, the choices are not limited by the more stringent condition required by previous methods, namely, that the shear amounts must be divisors of N. This method can exactly reconstruct any wavefront at evaluation points up to an arbitrary constant if the data is noiseless, and high spatial resolution can be achieved even with large shear amounts. The method is applicable not only to square pupils, but also to general pupil shapes if a sufficient number of Gerchberg iterations are employed. In this study, the validity and capability of the method were confirmed by numerical experiments. In addition, the experiments demonstrated that the method is stable with respect to noise in the difference wavefronts.

  2. CHRONOBIOLOGY OF HIGH BLOOD PRESSURE

    PubMed Central

    Cornélissen, G.; Halberg, F.; Bakken, E. E.; Wang, Z.; Tarquini, R.; Perfetto, F.; Laffi, G.; Maggioni, C.; Kumagai, Y.; Homolka, P.; Havelková, A.; Dušek, J.; Svačinová, H.; Siegelová, J.; Fišer, B.

    2008-01-01

    BIOCOS, the project aimed at studying BIOlogical systems in their COSmos, has obtained a great deal of expertise in the fields of blood pressure (BP) and heart rate (HR) monitoring and of marker rhythmometry for the purposes of screening, diagnosis, treatment, and prognosis. Prolonging the monitoring reduces the uncertainty in the estimation of circadian parameters; the current recommendation of BIOCOS requires monitoring for at least 7 days. The BIOCOS approach consists of a parametric and a non-parametric analysis of the data, in which the results from the individual subject are being compared with gender- and age-specified reference values in health. Chronobiological designs can offer important new information regarding the optimization of treatment by timing its administration as a function of circadian and other rhythms. New technological developments are needed to close the loop between the monitoring of blood pressure and the administration of antihypertensive drugs. PMID:19122770

  3. Structure of Highly Sheared Tropical Storm Chantal during CAMEX-4

    NASA Technical Reports Server (NTRS)

    Heymsfield, G. M.; Halverson, J.; Ritchie, E.; Simpson, Joanne; Molinari, J.; Tian, L.

    2006-01-01

    Tropical Storm Chantal during August 2001 was a storm that failed to intensify over the few days prior to making landfall on the Yucatan Peninsula. An observational study of Tropical Storm Chantal is presented using a diverse dataset including remote and in situ measurements from the NASA ER-2 and DC-8 and the NOAA WP-3D N42RF aircraft and satellite. The authors discuss the storm structure from the larger-scale environment down to the convective scale. Large vertical shear (850-200-hPa shear magnitude range 8-15 m/s) plays a very important role in preventing Chantal from intensifying. The storm had a poorly defined vortex that only extended up to 5-6-km altitude, and an adjacent intense convective region that comprised a mesoscale convective system (MCS). The entire low-level circulation center was in the rain-free western side of the storm, about 80 km to the west-southwest of the MCS. The MCS appears to have been primarily the result of intense convergence between large-scale, low-level easterly flow with embedded downdrafts, and the cyclonic vortex flow. The individual cells in the MCS such as cell 2 during the period of the observations were extremely intense, with reflectivity core diameters of 10 km and peak updrafts exceeding 20 m/s. Associated with this MCS were two broad subsidence (warm) regions, both of which had portions over the vortex. The first layer near 700 hPa was directly above the vortex and covered most of it. The second layer near 500 hPa was along the forward and right flanks of cell 2 and undercut the anvil divergence region above. There was not much resemblance of these subsidence layers to typical upper-level warm cores in hurricanes that are necessary to support strong surface winds and a low central pressure. The observations are compared to previous studies of weakly sheared storms and modeling studies of shear effects and intensification. The configuration of the convective updrafts, low-level circulation, and lack of vertical

  4. Highly Efficient Prion Transmission by Blood Transfusion

    PubMed Central

    Andréoletti, Olivier; Litaise, Claire; Simmons, Hugh; Corbière, Fabien; Lugan, Séverine; Costes, Pierrette; Schelcher, François; Vilette, Didier; Grassi, Jacques; Lacroux, Caroline

    2012-01-01

    It is now clearly established that the transfusion of blood from variant CJD (v-CJD) infected individuals can transmit the disease. Since the number of asymptomatic infected donors remains unresolved, inter-individual v-CJD transmission through blood and blood derived products is a major public health concern. Current risk assessments for transmission of v-CJD by blood and blood derived products by transfusion rely on infectious titers measured in rodent models of Transmissible Spongiform Encephalopathies (TSE) using intra-cerebral (IC) inoculation of blood components. To address the biological relevance of this approach, we compared the efficiency of TSE transmission by blood and blood components when administrated either through transfusion in sheep or by intra-cerebral inoculation (IC) in transgenic mice (tg338) over-expressing ovine PrP. Transfusion of 200 µL of blood from asymptomatic infected donor sheep transmitted prion disease with 100% efficiency thereby displaying greater virulence than the transfusion of 200 mL of normal blood spiked with brain homogenate material containing 103ID50 as measured by intracerebral inoculation of tg338 mice (ID50 IC in tg338). This was consistent with a whole blood titer greater than 103.6 ID50 IC in tg338 per mL. However, when the same blood samples were assayed by IC inoculation into tg338 the infectious titers were less than 32 ID per mL. Whereas the transfusion of crude plasma to sheep transmitted the disease with limited efficacy, White Blood Cells (WBC) displayed a similar ability to whole blood to infect recipients. Strikingly, fixation of WBC with paraformaldehyde did not affect the infectivity titer as measured in tg338 but dramatically impaired disease transmission by transfusion in sheep. These results demonstrate that TSE transmission by blood transfusion can be highly efficient and that this efficiency is more dependent on the viability of transfused cells than the level of infectivity measured by IC

  5. Nanometric Gouge in High-Speed Shearing Experiments: Superplasticity?

    NASA Astrophysics Data System (ADS)

    Green, H. W.; Lockner, D. A.; Bozhilov, K. N.; Maddon, A.; Beeler, N. M.; Reches, Z.

    2010-12-01

    High-speed shearing experiments on solid rock samples typically generate a gouge with sub-micron grain size that appears to control the frictional resistance at velocities approaching 1 m/s (Reches & Lockner, Nature, in press). We conducted experiments on Kasota dolomite samples and observed profound weakening (friction drops from ~0.8 to ~ 0.2) under earthquake conditions (up to slip-velocity ~ 0.95 m/s and normal stress 28.4 MPa). During these runs the experimental fault had T ≥ 800°C and developed a shining, dark surface. We report here analysis of such a surface with scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM analysis shows a slickensided gouge made up of particles all ≤ 50nm with a large fraction ≤ 20nm. The spacing of the slickenside striations is less than 1 µm. Over large areas of the slickensided surface the nanometric gouge has been replaced by an undeformed, interlocking crystalline pavement of 100-300 nm grain size. Qualitative chemical analysis of this pavement surface by energy-dispersive X-ray spectroscopy reveals only a weak carbon peak, suggesting that the dolomite has been decarbonated. The development of a “pavement” of grain size ~200 nm in our experiments is remarkably similar to the observations of Han et al. (JGR, 2010, Fig. 14(d)). However, their experiments either did not develop such a nanometric gouge or it was completely replaced by the coarser pavement. These present observations of nanometric gouge that recrystallizes during the short time interval of elevated temperature following termination of deformation are reminiscent of the nanometric “gouge” produced in very high-pressure experiments (1-14 GPa) that have failed by transformation-induced faulting during the olivine-spinel transformation (Green and Burnley, Nature, 1989; Green et al., Nature, 1990). In the high-pressure experiments, the gouge consists of a nanocrystalline aggregate of the spinel phase that flowed at very high strain

  6. Shear wave measurements in shock-induced, high-pressure phases

    SciTech Connect

    Aidun, J.B.

    1993-01-01

    Structural phase transformations under shock loading are of considerable interest for understanding the response of solids under nonhydrostatic stresses and at high strain-rates. Examining shock-induced transformations from continuum level measurements is fundamentally constrained by the inability to directly identify microscopic processes, and also by the limited number of material properties that can be directly measured. ne latter limitation can be reduced by measuring both shear and compression waves using Lagrangian gauges in combined, compression and shear loading. The shear wave serves as an important, real-time probe of the shocked state and unloading response. Using results from a recent study of CaCO[sub 3], the unique information obtained from the shear wave speed and the detailed structure of the shear wave are shown to be useful for distinguishing the effects of phase transformations from yielding, as well as in characterizing the high-pressure phases and the yielding process under shock loading.

  7. Shear wave measurements in shock-induced, high-pressure phases

    SciTech Connect

    Aidun, J.B.

    1993-07-01

    Structural phase transformations under shock loading are of considerable interest for understanding the response of solids under nonhydrostatic stresses and at high strain-rates. Examining shock-induced transformations from continuum level measurements is fundamentally constrained by the inability to directly identify microscopic processes, and also by the limited number of material properties that can be directly measured. ne latter limitation can be reduced by measuring both shear and compression waves using Lagrangian gauges in combined, compression and shear loading. The shear wave serves as an important, real-time probe of the shocked state and unloading response. Using results from a recent study of CaCO{sub 3}, the unique information obtained from the shear wave speed and the detailed structure of the shear wave are shown to be useful for distinguishing the effects of phase transformations from yielding, as well as in characterizing the high-pressure phases and the yielding process under shock loading.

  8. Extrusion granulation and high shear granulation of different grades of lactose and highly dosed drugs: a comparative study.

    PubMed

    Keleb, E I; Vermeire, A; Vervaet, C; Remon, Jean Paul

    2004-07-01

    Formulations containing different lactose grades, paracetamol, and cimetidine were granulated by extrusion granulation and high shear granulation. Granules were evaluated for yield, friability, and compressibility. Tablets were prepared from those granules and evaluated for tensile strength, friability, disintegration time, and dissolution. The different lactose grades had an important effect on the extrusion granulation process. Particle size and morphology affected powder feeding and power consumption, but had only a minor influence on the granule and tablet properties obtained by extrusion granulation. In contrast, the lactose grades had a major influence on the granule properties obtained by high shear granulation. Addition of polyvinylpyrrolidone (PVP) was required to process pure paracetamol and cimetidine by high shear granulation, whereas it was feasible to granulate these drugs without PVP by extrusion granulation. Granules prepared by extrusion granulation exhibited a higher yield and a lower friability than those produced by high shear granulation. Paracetamol and cimetidine tablets compressed from granules prepared by extrusion granulation showed a higher tensile strength, lower friability, and lower disintegration time than those prepared from granules produced by high shear granulation. Paracetamol tablets obtained via extrusion granulation exhibited faster dissolution than those obtained via high shear granulation. For all lactose grades studied, extrusion granulation resulted in superior granule and tablet properties in comparison with those obtained by high shear granulation. These results indicate that extrusion granulation is more efficient than high shear granulation.

  9. High speed all optical shear wave imaging optical coherence elastography (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Song, Shaozhen; Hsieh, Bao-Yu; Wei, Wei; Shen, Tueng; O'Donnell, Matthew; Wang, Ruikang K.

    2016-03-01

    Optical Coherence Elastography (OCE) is a non-invasive testing modality that maps the mechanical property of soft tissues with high sensitivity and spatial resolution using phase-sensitive optical coherence tomography (PhS-OCT). Shear wave OCE (SW-OCE) is a leading technique that relies on the speed of propagating shear waves to provide a quantitative elastography. Previous shear wave imaging OCT techniques are based on repeated M-B scans, which have several drawbacks such as long acquisition time and repeated wave stimulations. Recent developments of Fourier domain mode-locked high-speed swept-source OCT system has enabled enough speed to perform KHz B-scan rate OCT imaging. Here we propose ultra-high speed, single shot shear wave imaging to capture single-shot transient shear wave propagation to perform SW-OCE. The frame rate of shear wave imaging is 16 kHz, at A-line rate of ~1.62 MHz, which allows the detection of high-frequency shear wave of up to 8 kHz. The shear wave is generated photothermal-acoustically, by ultra-violet pulsed laser, which requires no contact to OCE subjects, while launching high frequency shear waves that carries rich localized elasticity information. The image acquisition and processing can be performed at video-rate, which enables real-time 3D elastography. SW-OCE measurements are demonstrated on tissue-mimicking phantoms and porcine ocular tissue. This approach opens up the feasibility to perform real-time 3D SW-OCE in clinical applications, to obtain high-resolution localized quantitative measurement of tissue biomechanical property.

  10. What Are High Blood Cholesterol and Triglycerides?

    MedlinePlus

    ANSWERS by heart Lifestyle + Risk Reduction Cholesterol What Are High Blood Cholesterol and Triglycerides? Cholesterol travels to the body’s cells through the bloodstream by way of lipoproteins (LDL and ...

  11. High Blood Pressure: Medicines to Help You

    MedlinePlus

    ... Types of High Blood Pressure Medicines ACE Inhibitors Beta Blockers Calcium Channel Blockers Peripherally Acting Alpha-Adrenergic Blockers ... side effects for each drug, check Drugs@FDA . Beta Blockers Brand Name Generic Name Bystolic Nebivolol Timolol Coreg ...

  12. Deformation and fragmentation of human red blood cells in turbulent shear flow.

    PubMed Central

    Sutera, S P; Mehrjardi, M H

    1975-01-01

    By means of glutaraldehyde fixation, human erythrocytes are "frozen" while suspended in turbulent shear flow. As the shearing is increased in steps from 100 to 2,500 dyn/cm2, the deformed cells evolve gradually toward a smooth ellipsoidal shape. At stresses above 2,500 dyn/cm2, approximately, fragmentation of the cells occurs with a concomitant increase in free hemoglobin content of the suspending medium. The photographic evidence suggests that the cells rupture in tension in the bulk flow. Images FIGURE 1 FIGURE 2 FIGURE 6 PMID:1174639

  13. High-Sensitivity Optical Pulse Characterization Using Sagnac Electro-Optic Spectral Shearing Interferometry

    SciTech Connect

    Dorrer, C.; Bromage, J.

    2010-05-04

    An electro-optic spectral shearing interferometer for high-sensitivity optical pulse characterization is described. Two replicas of the test pulse counterpropagate in a Sagnac interferometer with orthogonal polarization states, resulting in two relatively sheared copolarized replicas after temporal phase modulation. The polarization interferometer is intrinsically stable, and its birefringence sets the delay between interfering replicas to reduce the spectrometer resolution requirement. Experimental implementations demonstrate real-time pulse characterization at average powers as low as 1 nWwith spectral shears as high as 280 GHz.

  14. High temperature and deformation field measurements at the vicinity of dynamically growing shear bands

    SciTech Connect

    Rosakis, A.J.; Ravichandran, G.; Zhou, M.

    1995-12-31

    The phenomenon of dynamic initiation and propagation of adiabatic shear bands is experimentally and numerically investigated. Pre-notched metal plates are subjected to asymmetric impact load histories (dynamic mode-II loading). Dynamic shear bands emanate from the notch tip and propagate rapidly in a direction nearly parallel to the direction of the impact. Real time temperature histories along a line intersecting and perpendicular to the shear band paths are recorded by means of a high-speed infrared detector system. The materials studied are C-300 (a maraging steel) and Ti - 6 Al - 4 V alloy. Experiments show that the peak temperatures inside the propagating shear bands are approaching 90% of the melting point for C-300 and are significantly lower for the titanium alloy (up to 600{degrees}C). Additionally, measured distances of shear band propagation indicate stronger resistance to shear banding by the Ti - 6Al - 4V alloy. Deformation fields around the propagating shear bands are recorded using high-speed photography. Shear band speeds are found to strongly depend on impact velocities, and are as high as 1200 m/s for C-300 steels. Finite Element simulations of the experiments are carried out under the context of plane strain, considering finite deformations, inertia, heat conduction, thermal softening, strain hardening and strain-rate hardening. In the simulations, the shear band propagation is assumed to be governed by a critical plastic strain criterion. The results are compared with experimental measurements obtained using the high-speed infrared detectors and high-speed photography.

  15. Strain localization in direct shear experiments on Solnhofen limestone at high temperature Effects of transpression

    NASA Astrophysics Data System (ADS)

    Llana-Fúnez, Sergio; Rutter, Ernest H.

    2008-11-01

    Some features of natural shear zones formed under non-coaxial strain geometries, including some effects of transpression, can be simulated in the laboratory by using the direct shear experimental configuration. Slices of ˜1 mm thick Solnhofen limestone were deformed in direct shear between two stronger forcing blocks of cores of Tennessee sandstone pre-cut at 45° to the cylinder axis. Experiments were run dry at 600 °C, 200 MPa confining pressure and bulk shear strain rates of ˜5 × 10 -3 s -1, at which conditions Solnhofen limestone deformed by dislocation creep with a stress exponent of 4.7. When loaded, strain concentrates in the limestone band, producing non-coaxial deformation as one pre-cut block slides past the other. The orientation and intensity of the shape fabric developed in calcite grains indicate that strain is heterogeneous across the specimen, with the formation of two high-strain shear bands close to the limestone-sandstone interface, separated by a central zone of low strain. Crystallographic preferred orientation patterns in the calcite grains measured by electron backscatter diffraction are consistent with a switch in deformation geometry from flattening-dominated in the middle of the specimen towards shear-dominated in the high-strain bands. From tests on thin slices of the same material compressed axisymmetrically (without shearing) normal to the layer, heterogeneous thinning of the slice develops, from a maximum in the centre of the slice to zero at the edges. The formation of the paired shear zones observed in the sheared experiments is interpreted in terms of superposed strain fields, with shearing in the centre of the slice being inhibited by the strain hardening that accompanies the higher flattening strain in the centre of the specimen.

  16. Stretching Behavior of Red Blood Cells at High Strain Rates

    NASA Astrophysics Data System (ADS)

    Mancuso, Jordan; Ristenpart, William

    2016-11-01

    Most work on the mechanical behavior of red blood cells (RBCs) has focused on simple shear flows. Relatively little work has examined RBC deformations in the physiologically important extensional flow that occurs at the entrance to a constriction. In particular, previous work suggests that RBCs rapidly stretch out and then retract upon entering the constriction, but to date no model predicts this behavior for the extremely high strain rates typically experienced there. In this work, we use high speed video to perform systematic measurements of the dynamic stretching behavior of RBCs as they enter a microfluidic constriction. We demonstrate that a simple viscoelastic model captures the observed stretching dynamics, up to strain rates as high as 1000 s-1. The results indicate that the effective elastic modulus of the RBC membrane at these strain rates is an order of magnitude larger than moduli measured by micropipette aspiration or other low strain rate techniques.

  17. Turbulence Decorrelation via Controlled Ex B Shear in High-Performance Plasmas

    NASA Astrophysics Data System (ADS)

    McKee, G. R.

    2015-11-01

    Multi-scale spatiotemporal turbulence properties are significantly altered as toroidal rotation and resulting ExB shearing rate profile are systematically varied in advanced-inductive H-mode plasmas on DIII-D (βN ~ 2.7, q95=5.1). Density, electron and ion temperature profiles and dimensionless parameters (βN, q95, ν*, ρ*, and Te/Ti) are maintained nearly fixed during the rotation scan. Low-wavenumber turbulence (k⊥ρS < 1), measured with Beam Emission Spectroscopy, exhibits increased decorrelation rates (reduced eddy lifetime) as the ExB shear rises across the radial zone of maximum shearing rate (0.55 < ρ < 0 . 75), while the fluctuation amplitude undergoes little change. The poloidal wavenumber is reduced at higher shear, indicating a change in the wavenumber spectrum: eddies elongate in the direction orthogonal to shear and field. At both low and high shear, the 2D turbulence correlation function exhibits a tilted structure, consistent with flow shear. At mid-radius (ρ ~ 0.5), low-k density fluctuations show localized amplitude reduction, consistent with linear GYRO growth rates and ωExB shearing rates. Intermediate and high wavenumber fluctuations measured with Doppler Back-Scattering (k⊥ρS ~ 2.5-3.5) at ρ=0.7 and Phase Contrast Imaging (k⊥ρS > 5) exhibit decreasing amplitude at higher rotation. The energy confinement time increases from 105 ms to 150 ms as the toroidal Mach number (M=vTOR / vth , i) increases to Mo ~ 0.5, while transport decreases. TGLF calculations match the Ti profile with modest discrepancies in the Te and ne profiles. These results clarify the complex mechanisms by which ExB shear affects turbulence. Work supported in part by the US DOE under DE-FG02-08ER54999, DE-FC02-04ER54698.

  18. Membrane stress and internal pressure in a red blood cell freely suspended in a shear flow.

    PubMed Central

    Tran-Son-Tay, R; Sutera, S P; Zahalak, G I; Rao, P R

    1987-01-01

    Presented is an algorithm for the approximate calculation of the membrane stress distribution and the internal pressure of a steadily tank-treading red cell. The algorithm is based on an idealized ellipsoidal model of the tank-treading cell (Keller, S.R., and R. Skalak, 1982, J. Fluid Mech., 120:27-47) joined with experimental observations of projected length, width, and tank-treading frequency. The results are inexact because the membrane shape and velocity are assumed a priori, rather than being determined via appropriate material constitutive relations for the membrane; these results are, nevertheless, believed to be approximately correct, and show that internal pressure builds up slowly as cell elongation increases, rising more rapidly as the deformed cell approaches the limiting geometry of a prolate ellipsoid. The maximum shear stress resultant in the membrane was found to be below but approaching the yield point range at the highest shear rate applied. Images FIGURE 1 PMID:3607212

  19. High spatial resolution PIV and CH-PLIF measurements of a Shear Layer Stabilized Flame

    NASA Astrophysics Data System (ADS)

    Foley, Christopher; Chterev, Ianko; Seitzman, Jerry; Lieuwen, Tim

    2014-11-01

    In practical combustors, flames stabilize in thin shear layers with very high strain rates, which alter the flame burning rate - either enhancing or diminishing reaction rates, and even leading to extinction. Therefore, the bulk velocity that provides stable operation in these combustors is limited, presumably due to the associated maximum stretch rate that the flame is able to withstand. The focus of this work is to develop a deeper understanding of the interaction between flow and flame for a shear layer stabilized, premixed flame. This study consists of planar, high resolution, simultaneous PIV and CH-PLIF measurements, in a 8 x 6 mm plane with 0.11 mm and 0.16 mm PIV vector and CH-PLIF image resolution, respectively, of the flame stabilization region in a swirling jet. The hydrodynamic strain induced stretch rate along the high CH concentration layer of the flame front is calculated from these measurements. In addition, this study elucidates the unsteady behavior of the flame in the thin shear layer. The measured flame stretch is highly spatially and temporally dependent, and dominated by contributions from normal and shear strain terms of axial velocity. Although normal strain is much greater than shear, the near horizontal flame orientation results in neither strain term dominating flame stretch. Furthermore, the flame angle changes the sign of the shear strain contributions as observed experimentally, an important implication for reduced order modeling approaches.

  20. Experimental Reacting Hydrogen Shear Layer Data at High Subsonic Mach Number

    NASA Technical Reports Server (NTRS)

    Chang, C. T.; Marek, C. J.; Wey, C.; Wey, C. C.

    1996-01-01

    The flow in a planar shear layer of hydrogen reacting with hot air was measured with a two-component laser Doppler velocimeter (LDV) system, a schlieren system, and OH fluorescence imaging. It was compared with a similar air-to-air case without combustion. The high-speed stream's flow speed was about 390 m/s, or Mach 0.71, and the flow speed ratio was 0.34. The results showed that a shear layer with reaction grows faster than one without; both cases are within the range of data scatter presented by the established data base. The coupling between the streamwise and the cross-stream turbulence components inside the shear layers was low, and reaction only increased it slightly. However, the shear layer shifted laterally into the lower speed fuel stream, and a more organized pattern of Reynolds stress was present in the reaction shear layer, likely as a result of the formation of a larger scale structure associated with shear layer corrugation from heat release. Dynamic pressure measurements suggest that coherent flow perturbations existed inside the shear layer and that this flow became more chaotic as the flow advected downstream. Velocity and thermal variable values are listed in this report for a computational fluid dynamics (CFD) benchmark.

  1. Shallow Water Sediment Properties Derived from High-Frequency Shear and Interface Waves

    DTIC Science & Technology

    1992-04-10

    FREQUENCY SHEAR ONR N00014-88-C-1238 AND INTERFACE WAVES 6. AUTHOR(S) JOHN EWING, JERRY A. CARTER, GEORGE H. SUTTON AND NOEL BARSTOW 7. PERFORMING...B4. PAGES 4739--4762. APRIL 10. 1992 Shallow Water Sediment Properties Derived From High-Frequency Shear and Interface Waves JOHN EWING Woods Hole...calculating thickness. The amplitude falloff with range establishes a Q velocity gradients and penetration depths [ Nettleton . 19401 estimate of 40 in

  2. Too Many Americans Have High Blood Pressure, Doctors Warn

    MedlinePlus

    ... 163468.html Too Many Americans Have High Blood Pressure, Doctors Warn With February designated National Heart Month, ... that too many Americans struggle with high blood pressure. High blood pressure is a major risk factor ...

  3. What about African Americans and High Blood Pressure?

    MedlinePlus

    ANSWERS by heart Lifestyle + Risk Reduction High Blood Pressure What About African Americans and High Blood Pressure? The prevalence of high blood pressure in African Americans is among the highest in ...

  4. Suppression of endothelial t-PA expression by prolonged high laminar shear stress

    SciTech Connect

    Ulfhammer, Erik; Carlstroem, Maria; Bergh, Niklas; Larsson, Pia; Karlsson, Lena; Jern, Sverker

    2009-02-06

    Primary hypertension is associated with an impaired capacity for acute release of endothelial tissue-type plasminogen activator (t-PA), which is an important local protective response to prevent thrombus extension. As hypertensive vascular remodeling potentially results in increased vascular wall shear stress, we investigated the impact of shear on regulation of t-PA. Cultured human endothelial cells were exposed to low ({<=}1.5 dyn/cm{sup 2}) or high (25 dyn/cm{sup 2}) laminar shear stress for up to 48 h in two different experimental models. Using real-time RT-PCR and ELISA, shear stress was observed to time and magnitude-dependently suppress t-PA transcript and protein secretion to approximately 30% of basal levels. Mechanistic experiments revealed reduced nuclear protein binding to the t-PA specific CRE element (EMSA) and an almost completely abrogated shear response with pharmacologic JNK inhibition. We conclude that prolonged high laminar shear stress suppresses endothelial t-PA expression and may therefore contribute to the enhanced risk of arterial thrombosis in hypertensive disease.

  5. Shear flow-induced optical inhomogeneity of blood assessed in vivo and in vitro by spectral domain optical coherence tomography in the 1.3 μm wavelength range

    NASA Astrophysics Data System (ADS)

    Cimalla, Peter; Walther, Julia; Mittasch, Matthaeus; Koch, Edmund

    2011-11-01

    The optical inhomogeneity of flowing blood, which appears as a waisted double fan-shaped intensity pattern inside vessels in cross-sectional optical coherence tomography (OCT) images, was investigated for the first time. High resolution spectral domain OCT in the 1.3 μm wavelength region is used to assess this inhomogeneous intravascular backscattering of light in an in vivo mouse model and flow phantom measurements. Based on a predicted alignment of the red blood cells toward laminar shear flow, an angular modulation of the corresponding backscattering cross-section inside the vessels is assumed. In combination with the signal attenuation in depth by absorption and scattering, a simple model of the intravascular intensity modulation is derived. The suitability of the model is successfully demonstrated in the in vivo experiments and confirmed by the in vitro measurements. The observed effect appears in flowing blood only and shows a strong dependency on the shear rate. In conclusion, the shear-induced red blood cell alignment in conjunction with the vessel geometry is responsible for the observed intensity distribution. This inherent effect of blood imaging has to be considered in attenuation measurements performed with OCT. Furthermore, the analysis of the intravascular intensity pattern might be useful to evaluate flow characteristics.

  6. Measurements in the annular shear layer of high subsonic and under-expanded round jets

    NASA Astrophysics Data System (ADS)

    Feng, Tong; McGuirk, James J.

    2016-01-01

    An experimental study has been undertaken to document compressibility effects in the annular shear layers of axisymmetric jets. Comparison is made of the measured flow development with the well-documented influence of compressibility in planar mixing layers. High Reynolds number (~106) and high Mach number jets issuing from a convergent nozzle at nozzle pressure ratios (NPRs) from 1.28 to 3.0 were measured using laser Doppler anemometry instrumentation. Detailed radial profile data are reported, particularly within the potential core region, for mean velocity, turbulence rms, and turbulence shear stress. For supercritical NPRs the presence of the pressure waves in the inviscid shock cell region as the jet expanded back to ambient pressure was found to exert a noticeable effect on shear layer location, causing this to shift radially outwards at high supercritical NPR conditions. After a boundary layer to free shear layer transition zone, the turbulence development displayed a short region of similarity before adjustment to near-field merged jet behaviour. Peak turbulence rms reduction due to compressibility was similar to that observed in planar layers with radial rms suppression much stronger than axial. Comparison of the compressibility-modified annular shear layer growth rate with planar shear layer data on the basis of the convective Mach number ( M C) showed notable differences; in the annular shear layer, compressibility effects began at lower M C and displayed a stronger reduction in growth. For high Mach number aerospace propulsion applications involving round jets, the current measurements represent a new data set for the calibration/validation of compressibility-affected turbulence models.

  7. Increase in blood viscosity in the sprinting horse: can it account for the high pulmonary arterial pressure?

    PubMed

    Fedde, M R; Erickson, H H

    1998-07-01

    Blood was taken from 49 Thoroughbred horses before and after racing at the track to determine if frusemide modified the apparent viscosity of the blood and to determine the effects of changes in shear rate and packed cell volume (PCV), associated with strenuous exercise, on apparent and relative viscosities. Small increases in apparent viscosity of the blood (at a specified PCV and shear rate) occurred in horses given frusemide compared to those receiving no frusemide; however, no differences were seen in relative viscosity. Although 2 groups of horses, those receiving frusemide before racing and those not receiving this drug were studied, the results suggest no influence of frusemide on any red blood cell variable that might modify apparent blood viscosity. Apparent viscosity of the blood was slightly (but significantly) higher after racing than before racing at any given PCV and shear rate, but relative viscosity was lower in the post race than in the prerace blood sample. The most important contributing factor to the increase in apparent viscosity in blood during racing is the increase in PCV, because the blood becomes nearly shear rate independent at shear rates likely to exist in the cardiovascular system during exercise. With an increase in PCV from 40 to 65% at shear rates above 225/s, apparent viscosity approximately doubled. However, this increase alone cannot account for the elevated pulmonary vascular pressure in the running horse, and additional factors, especially those causing the high left atrial pressure, must be considered. The cause of the elevated pressure may be multifactorial in nature.

  8. High wall shear stress and high-risk plaque: an emerging concept.

    PubMed

    Eshtehardi, Parham; Brown, Adam J; Bhargava, Ankit; Costopoulos, Charis; Hung, Olivia Y; Corban, Michel T; Hosseini, Hossein; Gogas, Bill D; Giddens, Don P; Samady, Habib

    2017-01-10

    In recent years, there has been a significant effort to identify high-risk plaques in vivo prior to acute events. While number of imaging modalities have been developed to identify morphologic characteristics of high-risk plaques, prospective natural-history observational studies suggest that vulnerability is not solely dependent on plaque morphology and likely involves additional contributing mechanisms. High wall shear stress (WSS) has recently been proposed as one possible causative factor, promoting the development of high-risk plaques. High WSS has been shown to induce specific changes in endothelial cell behavior, exacerbating inflammation and stimulating progression of the atherosclerotic lipid core. In line with experimental and autopsy studies, several human studies have shown associations between high WSS and known morphological features of high-risk plaques. However, despite increasing evidence, there is still no longitudinal data linking high WSS to clinical events. As the interplay between atherosclerotic plaque, artery, and WSS is highly dynamic, large natural history studies of atherosclerosis that include WSS measurements are now warranted. This review will summarize the available clinical evidence on high WSS as a possible etiological mechanism underlying high-risk plaque development.

  9. Major Risk Factors for Heart Disease: High Blood Cholesterol

    MedlinePlus

    ... Major Risk Factors for Heart Disease High Blood Cholesterol High blood cholesterol is another major risk factor for heart disease ... can do something about. The higher your blood cholesterol level, the greater your risk for developing heart ...

  10. High Shear Deformation to Produce High Strength and Energy Absorption in Mg Alloys

    SciTech Connect

    Joshi, Vineet V.; Jana, Saumyadeep; Li, Dongsheng; Garmestani, Hamid; Nyberg, Eric A.; Lavender, Curt A.

    2014-02-01

    Magnesium alloys have the potential to reduce the mass of transportation systems however to fully realize the benefits it must be usable in more applications including those that require higher strength and ductility. It has been known that fine grain size in Mg alloys leads to high strength and ductility. However, the challenge is how to achieve this optimal microstructure in a cost effective way. This work has shown that by using optimized high shear deformation and second phase particles of Mg2Si and MgxZnZry the energy absorption of the extrusions can exceed that of AA6061. The extrusion process under development described in this presentation appears to be scalable and cost effective. In addition to process development a novel modeling approach to understand the roles of strain and state-of-strain on particle fracture and grain size control has been developed

  11. Texture Development in High-Silicon Iron Sheet Produced by Simple Shear Deformation

    NASA Astrophysics Data System (ADS)

    Kustas, Andrew B.; Sagapuram, Dinakar; Trumble, Kevin P.; Chandrasekar, Srinivasan

    2016-06-01

    Sheet processing of high Si-Fe alloys (up to 6.5 wt pct Si) is demonstrated by application of highly confined shear deformation in cutting-extrusion. This alloy system, of major interest to electromagnetic applications, is characterized by poor workability. By a suitable interactive combination of simple shear, high strain rates, near-adiabatic heating, and large hydrostatic pressure in the deformation zone, flow localization, and cracking inherent to this alloy system are suppressed. This enables creation of sheet and foil forms from bulk ingots, cast or wrought, in a single deformation step, unlike rolling. The sheet is characterized by strong shear textures, described by partial {110} and <111> fibers, and fine-grained microstructures ( 20 µm grain size). The orientation (inclination) of these fibers, with respect to the sheet surface, can be varied over a range of 35 deg through selection of the deformation path. In contrast to rolling textures, the current shear deformation textures are negligibly influenced by recrystallization annealing. A recovery-based continuous recrystallization mechanism is proposed to explain the texture retention. Some general implications for shear-based processing of alloys of limited workability are discussed.

  12. Influence of high deformation rate, brain region, transverse compression, and specimen size on rat brain shear stress morphology and magnitude.

    PubMed

    Haslach, Henry W; Gipple, Jenna M; Leahy, Lauren N

    2017-01-26

    An external mechanical insult to the brain, such as a blast, may create internal stress and deformation waves, which have shear and longitudinal components that can induce combined shear and compression of the brain tissue. To isolate the consequences of such interactions for the shear stress and to investigate the role of the extracellular fluid in the mechanical response, translational shear stretch at 10/s, 60/s, and 100/s translational shear rates under either 0% or 33% fixed transverse compression is applied without preconditioning to rat brain specimens. The specimens from the cerebrum, the cerebellum grey matter, and the brainstem white matter are nearly the full length of their respective regions. The translational shear stress response to translational shear deformation is characterized by the effect that each of four factors, high deformation rate, brain region, transverse compression, and specimen size, have on the shear stress magnitude averaged over ten specimens for each combination of factors. Increasing the deformation rate increases the magnitude of the shear stress at a given translational shear stretch, and as tested by ANOVAs so does applying transverse fixed compression of 33% of the thickness. The stress magnitude differs by the region that is the specimen source: cerebrum, cerebellum or brainstem. The magnitude of the shear stress response at a given deformation rate and stretch depends on the specimen length, called a specimen size effect. Surprisingly, under no compression a shorter length specimen requires more shear stress, but under 33% compression a shorter length specimen requires less shear stress, to meet a required shear deformation rate. The shear specimen size effect calls into question the applicability of the classical shear stress definition to hydrated soft biological tissue.

  13. Microturbulence and Flow Shear in High-performance JET ITB Plasma

    SciTech Connect

    R.V. Budny; A. Andre; A. Bicoulet; C. Challis; G.D. Conway; W. Dorland; D.R. Ernst; T.S. Hahm; T.C. Hender; D. McCune; G. Rewoldt; S.E. Sharapov

    2001-12-05

    The transport, flow shear, and linear growth rates of microturbulence are studied for a Joint European Torus (JET) plasma with high central q in which an internal transport barrier (ITB) forms and grows to a large radius. The linear microturbulence growth rates of the fastest growing (most unstable) toroidal modes with high toroidal mode number are calculated using the GS2 and FULL gyrokinetic codes. These linear growth rates, gamma (subscript lin) are large, but the flow-shearing rates, gamma (subscript ExB) (dominated by the toroidal rotation contribution) are also comparably large when and where the ITB exists.

  14. Dynamic characteristics of Bridgestone low shear modulus-high damping seismic isolation bearings

    SciTech Connect

    Chang, Y.W.; Seidensticker, R.W.

    1993-06-01

    Bridgestone Company of Japan is one of the leading seismic bearing manufacturers in the world. Their bearings have very good performance records. It appears that Bridgestone`s high damping bearings are made of a blend of filled natural and synthetic rubbers with fillers and plastizers whereas in the United States, the high damping compound is a carbon filled natural rubber. To compare the properties of the two different kinds of high damping compounds, Argonne National Laboratory (ANL) purchased eight bearings from Bridgestone: four of which were made of high shear modulus-high damping rubber compound KL401; the other four were made of low shear modulus-high damping rubber compounds: two with KL301 elastomer and two with KL302 elastomer. Tests of the Bridgestone bearings were performed at the Earthquake Engineering Research Center. The dynamic characteristics of the high shear modulus Bridgestone bearings, KL401, are described in ANL/Shimizu Report ANL-003. This report describes the dynamic and failure characteristics of the low shear modulus Bridgestone bearings, KL301 and KL302.

  15. Probing the dynamics of high-viscosity entangled polymers under shear using Neutron Spin Echo spectroscopy

    NASA Astrophysics Data System (ADS)

    Kawecki, M.; Gutfreund, P.; Adlmann, F. A.; Lindholm, E.; Longeville, S.; Lapp, A.; Wolff, M.

    2016-09-01

    Neutron Spin Echo spectroscopy provides unique insight into molecular and submolecular dynamics as well as intra- and inter-molecular interactions in soft matter. These dynamics may change drastically under shear flow. In particular in polymer physics a stress plateau is observed, which might be explained by an entanglement-disentanglement transition. However, such a transition is difficult to identify directly by experiments. Neutron Spin Echo has been proven to provide information about entanglement length and degree by probing the local dynamics of the polymer chains. Combining shear experiments and neutron spin echo is challenging since, first the beam polarisation has to be preserved during scattering and second, Doppler scattered neutrons may cause inelastic scattering. In this paper we present a new shear device adapted for these needs. We demonstrate that a high beam polarisation can be preserved and present first data on an entangled polymer solution under shear. To complement the experiments on the dynamics we present novel SANS data revealing shear- induced conformational changes in highly entangled polymers.

  16. Gas-Enhanced Ultra-High Shear Mixing: A Concept and Applications

    NASA Astrophysics Data System (ADS)

    Czerwinski, Frank; Birsan, Gabriel

    2017-04-01

    The processes of mixing, homogenizing, and deagglomeration are of paramount importance in many industries for modifying properties of liquids or liquid-based dispersions at room temperature and treatment of molten or semi-molten alloys at high temperatures, prior to their solidification. To implement treatments, a variety of technologies based on mechanical, electromagnetic, and ultrasonic principles are used commercially or tested at the laboratory scale. In a large number of techniques, especially those tailored toward metallurgical applications, the vital role is played by cavitation, generation of gas bubbles, and their interaction with the melt. This paper describes a novel concept exploring an integration of gas injection into the shear zone with ultra-high shear mixing. As revealed via experiments with a prototype of the cylindrical rotor-stator apparatus and transparent media, gases injected radially through the high-speed rotor generate highly refined bubbles of high concentration directly in the shear zone of the mixer. It is believed that an interaction of large volume of fine gas bubbles with the liquid, superimposed on ultra-high shear, will enhance mixing capabilities and cause superior refining and homogenizing of the liquids or solid-liquid slurries, thus allowing their effective property modification.

  17. Gas-Enhanced Ultra-High Shear Mixing: A Concept and Applications

    NASA Astrophysics Data System (ADS)

    Czerwinski, Frank; Birsan, Gabriel

    2016-12-01

    The processes of mixing, homogenizing, and deagglomeration are of paramount importance in many industries for modifying properties of liquids or liquid-based dispersions at room temperature and treatment of molten or semi-molten alloys at high temperatures, prior to their solidification. To implement treatments, a variety of technologies based on mechanical, electromagnetic, and ultrasonic principles are used commercially or tested at the laboratory scale. In a large number of techniques, especially those tailored toward metallurgical applications, the vital role is played by cavitation, generation of gas bubbles, and their interaction with the melt. This paper describes a novel concept exploring an integration of gas injection into the shear zone with ultra-high shear mixing. As revealed via experiments with a prototype of the cylindrical rotor-stator apparatus and transparent media, gases injected radially through the high-speed rotor generate highly refined bubbles of high concentration directly in the shear zone of the mixer. It is believed that an interaction of large volume of fine gas bubbles with the liquid, superimposed on ultra-high shear, will enhance mixing capabilities and cause superior refining and homogenizing of the liquids or solid-liquid slurries, thus allowing their effective property modification.

  18. Method for obtaining simple shear material properties of the intervertebral disc under high strain rates.

    PubMed

    Ott, Kyle A; Armiger, Robert S; Wickwire, Alexis C; Carneal, Catherine M; Trexler, Morgana M; Lennon, Andrew M; Zhang, Jiangyue; Merkle, Andrew C

    2012-01-01

    Predicting spinal injury under high rates of vertical loading is of interest, but the success of computational models in modeling this type of loading scenario is highly dependent on the material models employed. Understanding the response of these biological materials at high strain rates is critical to accurately model mechanical response of tissue and predict injury. While data exists at lower strain rates, there is a lack of the high strain rate material data that are needed to develop constitutive models. The Split Hopkinson Pressure Bar (SHPB) has been used for many years to obtain properties of various materials at high strain rates. However, this apparatus has mainly been used for characterizing metals and ceramics and is difficult to apply to softer materials such as biological tissue. Recently, studies have shown that modifications to the traditional SHPB setup allow for the successful characterization of mechanical properties of biological materials at strain rates and peak strain values that exceed alternate soft tissue testing techniques. In this paper, the previously-reported modified SHPB technique is applied to characterize human intervertebral disc material under simple shear. The strain rates achieved range from 5 to 250 strain s-1. The results demonstrate the sensitivity to the disc composition and structure, with the nucleus pulposus and annulus fibrosus exhibiting different behavior under shear loading. Shear tangent moduli are approximated at varying strain levels from 5 to 20% strain. This data and technique facilitates determination of mechanical properties of intervertebral disc materials under shear loading, for eventual use in constitutive models.

  19. High Rate Plasticity under Pressure using a Windowed Pressure-Shear Impact Experiment

    SciTech Connect

    Florando, J N; Jiao, T; Grunschel, S E; Clifton, R J; Ferranti, L; Becker, R C; Minich, R W; Bazan, G

    2009-07-29

    An experimental technique has been developed to study the strength of materials under conditions of moderate pressures and high shear strain rates. The technique is similar to the traditional pressure-shear plate-impact experiments except that window interferometry is used to measure both the normal and transverse particle velocities at a sample-window interface. Experimental and simulation results on vanadium samples backed with a sapphire window show the utility of the technique to measure the flow strength under dynamic loading conditions. The results show that the strength of the vanadium is 600 MPa at a pressure of 4.5 GPa and a plastic strain of 1.7%.

  20. Impact of triacylglycerol composition on shear-induced textural changes in highly saturated fats.

    PubMed

    Gregersen, Sandra B; Andersen, Morten D; Hammershøj, Marianne; Wiking, Lars

    2017-01-15

    This study demonstrates a strong interaction between triacylglycerol (TAG) composition and effects of shear rate on the microstructure and texture of fats. Cocoa butter alternatives with similar saturated fat content, but different major TAGs (PPO-, PSO-, SSO-, POP- and SOS-rich blends) were evaluated. Results show how shear can create a harder texture in fat blends based on symmetric monounsaturated TAGs (up to ∼200%), primarily due to reduction in crystal size, whereas shear has little effect on hardness of asymmetric monounsaturated TAGs. Such differences could not be ascribed to differences in the degree of supercooling, but was found to be a consequence of differences in the crystallisation behaviour of different TAGs. The fractal dimension was evaluated by dimensional detrended fluctuation analysis and Fourier transformation of microscopy images. However, the concept of fractal patterns was found to be insufficient to describe microstructural changes of fat blends with high solid fat content.

  1. Optical Properties of Compressible Inhomogeneous Shear Layers Relevant to High Power Lasers.

    DTIC Science & Technology

    1987-04-30

    191 615 OPTICAL PROPERTIES OF COMPRESSIBLE INb4ONOGENEOUS SHEAR 1/1 LAYERS RELEVANT TO HIGH PONER LASERS(U) WASHINGTON UNIV SEATTLE II H...so that a near-diffraction- limited laser beam may be attained. With the general trend of laser development towards shorter wavelengths, the fluid

  2. High Blood Pressure and Kidney Disease

    MedlinePlus

    ... Kidney disease is diagnosed with urine and blood tests. Health care providers measure blood pressure with a blood pressure ... the sample to a lab for analysis. A health care provider may order a blood test to estimate how much blood the kidneys filter ...

  3. Dietary spermidine for lowering high blood pressure.

    PubMed

    Eisenberg, Tobias; Abdellatif, Mahmoud; Zimmermann, Andreas; Schroeder, Sabrina; Pendl, Tobias; Harger, Alexandra; Stekovic, Slaven; Schipke, Julia; Magnes, Christoph; Schmidt, Albrecht; Ruckenstuhl, Christoph; Dammbrueck, Christopher; Gross, Angelina S; Herbst, Viktoria; Carmona-Gutierrez, Didac; Pietrocola, Federico; Pieber, Thomas R; Sigrist, Stephan J; Linke, Wolfgang A; Mühlfeld, Christian; Sadoshima, Junichi; Dengjel, Joern; Kiechl, Stefan; Kroemer, Guido; Sedej, Simon; Madeo, Frank

    2017-01-24

    Loss of cardiac macroautophagy/autophagy impairs heart function, and evidence accumulates that an increased autophagic flux may protect against cardiovascular disease. We therefore tested the protective capacity of the natural autophagy inducer spermidine in animal models of aging and hypertension, which both represent major risk factors for the development of cardiovascular disease. Dietary spermidine elicits cardioprotective effects in aged mice through enhancing cardiac autophagy and mitophagy. In salt-sensitive rats, spermidine supplementation also delays the development of hypertensive heart disease, coinciding with reduced arterial blood pressure. The high blood pressure-lowering effect likely results from improved global arginine bioavailability and protection from hypertension-associated renal damage. The polyamine spermidine is naturally present in human diets, though to a varying amount depending on food type and preparation. In humans, high dietary spermidine intake correlates with reduced blood pressure and decreased risk of cardiovascular disease and related death. Altogether, spermidine represents a cardio- and vascular-protective autophagy inducer that can be readily integrated in common diets.

  4. Dietary spermidine for lowering high blood pressure

    PubMed Central

    Zimmermann, Andreas; Schroeder, Sabrina; Pendl, Tobias; Harger, Alexandra; Stekovic, Slaven; Schipke, Julia; Magnes, Christoph; Schmidt, Albrecht; Ruckenstuhl, Christoph; Dammbrueck, Christopher; Gross, Angelina S; Herbst, Viktoria; Carmona-Gutierrez, Didac; Pietrocola, Federico; Pieber, Thomas R; Sigrist, Stephan J; Linke, Wolfgang A; Mühlfeld, Christian; Sadoshima, Junichi; Dengjel, Joern; Kiechl, Stefan; Kroemer, Guido; Sedej, Simon; Madeo, Frank

    2017-01-01

    Loss of cardiac macroautophagy/autophagy impairs heart function, and evidence accumulates that an increased autophagic flux may protect against cardiovascular disease. We therefore tested the protective capacity of the natural autophagy inducer spermidine in animal models of aging and hypertension, which both represent major risk factors for the development of cardiovascular disease. Dietary spermidine elicits cardioprotective effects in aged mice through enhancing cardiac autophagy and mitophagy. In salt-sensitive rats, spermidine supplementation also delays the development of hypertensive heart disease, coinciding with reduced arterial blood pressure. The high blood pressure-lowering effect likely results from improved global arginine bioavailability and protection from hypertension-associated renal damage. The polyamine spermidine is naturally present in human diets, though to a varying amount depending on food type and preparation. In humans, high dietary spermidine intake correlates with reduced blood pressure and decreased risk of cardiovascular disease and related death. Altogether, spermidine represents a cardio- and vascular-protective autophagy inducer that can be readily integrated in common diets. PMID:28118075

  5. The plane strain shear fracture of the advanced high strength steels

    NASA Astrophysics Data System (ADS)

    Sun, Li

    2013-12-01

    The "shear fracture" which occurs at the high-curvature die radii in the sheet metal forming has been reported to remarkably limit the application of the advanced high strength steels (AHSS) in the automobile industry. However, this unusual fracture behavior generally cannot be predicted by the traditional forming limit diagram (FLD). In this research, a new experimental system was developed in order to simulate the shear fracture, especially at the plane strain state which is the most common state in the auto-industry and difficult to achieve in the lab due to sample size. Furthermore, the system has the capability to operate in a strain rate range from quasi-static state to the industrial forming state. One kinds of AHSS, Quenching-Partitioning (QP) steels have been performed in this test and the results show that the limiting fracture strain is related to the bending ratio and strain rate. The experimental data support that deformation-induced heating is an important cause of "shear fracture" phenomena for AHSS: a deformation-induced quasi-heating caused by smaller bending ratio and high strain rate produce a smaller limiting plane strain and lead a "shear fracture" in the component.

  6. The plane strain shear fracture of the advanced high strength steels

    SciTech Connect

    Sun, Li

    2013-12-16

    The “shear fracture” which occurs at the high-curvature die radii in the sheet metal forming has been reported to remarkably limit the application of the advanced high strength steels (AHSS) in the automobile industry. However, this unusual fracture behavior generally cannot be predicted by the traditional forming limit diagram (FLD). In this research, a new experimental system was developed in order to simulate the shear fracture, especially at the plane strain state which is the most common state in the auto-industry and difficult to achieve in the lab due to sample size. Furthermore, the system has the capability to operate in a strain rate range from quasi-static state to the industrial forming state. One kinds of AHSS, Quenching-Partitioning (QP) steels have been performed in this test and the results show that the limiting fracture strain is related to the bending ratio and strain rate. The experimental data support that deformation-induced heating is an important cause of “shear fracture” phenomena for AHSS: a deformation-induced quasi-heating caused by smaller bending ratio and high strain rate produce a smaller limiting plane strain and lead a “shear fracture” in the component.

  7. High blood pressure and visual sensitivity

    NASA Astrophysics Data System (ADS)

    Eisner, Alvin; Samples, John R.

    2003-09-01

    The study had two main purposes: (1) to determine whether the foveal visual sensitivities of people treated for high blood pressure (vascular hypertension) differ from the sensitivities of people who have not been diagnosed with high blood pressure and (2) to understand how visual adaptation is related to standard measures of systemic cardiovascular function. Two groups of middle-aged subjects-hypertensive and normotensive-were examined with a series of test/background stimulus combinations. All subjects met rigorous inclusion criteria for excellent ocular health. Although the visual sensitivities of the two subject groups overlapped extensively, the age-related rate of sensitivity loss was, for some measures, greater for the hypertensive subjects, possibly because of adaptation differences between the two groups. Overall, the degree of steady-state sensitivity loss resulting from an increase of background illuminance (for 580-nm backgrounds) was slightly less for the hypertensive subjects. Among normotensive subjects, the ability of a bright (3.8-log-td), long-wavelength (640-nm) adapting background to selectively suppress the flicker response of long-wavelength-sensitive (LWS) cones was related inversely to the ratio of mean arterial blood pressure to heart rate. The degree of selective suppression was also related to heart rate alone, and there was evidence that short-term changes of cardiovascular response were important. The results suggest that (1) vascular hypertension, or possibly its treatment, subtly affects visual function even in the absence of eye disease and (2) changes in blood flow affect retinal light-adaptation processes involved in the selective suppression of the flicker response from LWS cones caused by bright, long-wavelength backgrounds.

  8. High-frequency photoacoustic imaging of erythrocyte aggregation and oxygen saturation: probing hemodynamic relations under pulsatile blood flow

    NASA Astrophysics Data System (ADS)

    Bok, Tae-Hoon; Hysi, Eno; Kolios, Michael C.

    2015-03-01

    In this paper, we investigate the feasibility of high-frequency photoacoustic (PA) imaging to study the shear rate dependent relationship between red blood cell (RBC) aggregation and oxygen saturation (SO2) in a simulated blood flow system. The PA signal amplitude increased during the formation of aggregates and cyclically varied at intervals corresponding to the beat rate (30, 60, 120, 180 and 240 bpm) for all optical wavelengths of illumination (750 and 850 nm).The SO2 also cyclically varied in phase with the PA signal amplitude for all beat rates. In addition, the mean blood flow velocity cyclically varied at the same interval of beat rate, and the shear rate (i.e. the radial gradient of flow velocity) also cyclically varied. On the other hand, the phase of the cyclic variation in the shear rate was reversed compared to that in the PA signal amplitude. This study indicates that RBC aggregation induced by periodic changes in the shear rate can be correlated with the SO2 under pulsatile blood flow. Furthermore, PA imaging of flowing blood may be capable of providing a new biomarker for the clinical application in terms of monitoring blood viscosity, oxygen delivery and their correlation.

  9. CDC Vital Signs: High Blood Pressure and Cholesterol

    MedlinePlus

    ... the MMWR Science Clips High Blood Pressure and Cholesterol Out of Control Recommend on Facebook Tweet Share ... cdc.gov/GISCVH2/ High Blood Pressure and High Cholesterol Among US Adults SOURCES: National Health and Nutrition ...

  10. Dynamic Strengthening During High Velocity Shear Experiments with Siliceous Rocks

    NASA Astrophysics Data System (ADS)

    Liao, Z.; Chang, J. C.; Boneh, Y.; Chen, X.; Reches, Z.

    2011-12-01

    It is generally accepted that dynamic-weakening is essential for earthquake instability, and many experimental works have documented this weakening. Recent observations revealed also opposite trends of dynamic-strengthening in experiments (Reches & Lockner, 2010). We present here our experimental results of this dynamic-strengthening and discuss possible implications to earthquake behavior. We ran hundreds of experiments on experimental faults made of siliceous rock including granite, syenite, diorite, and quartzite. The experimental fault is comprised of two solid cylindrical blocks with a raised-ring contact of 7 cm diameter and 1 cm width. We recognized general, three regimes of strength-velocity relations: (I) Dynamic weakening (drop of 20-60% of static strength) as slip velocity increased from ~0.0003 m/s (lowest experimental velocity) to a critical velocity, Vc=0.008-0.16 m/s; (II) Abrupt transition to dynamic strengthening regime during which the fault strength almost regains its static strength; and (III) Quasi-constant strength with further possible drops as velocity approaches ~1 m/s. The critical velocity depends on the sample lithology: Vc is ~0.06 m/s for granite, ~0.008 m/s for syenite, ~0.01 m/s for diorite, and ~0.16 m/s for quartzite. The strengthening stage is associated with temperature increase, wear-rate increase, and the occurrence of intense, high frequency stick-slip events (Reches & Lockner, 2010). Sammis et al., (this meeting) attributed this strengthening to dehydration of the thin water layer that covers the gouge particles as the temperature increases. On the other hand, we note that tens of experiments with dolomite samples (non-siliceous), which were deformed under similar conditions, did not exhibit the velocity strengthening (unpublished). Based on the analyses by Andrews (2004, 2005), we speculate that velocity strengthening may bound the slip velocity. The numerical models of Andrews show that the slip velocity along a slip

  11. Crack initiation observation and local stress analysis in shear fracture tests of ultra-high strength steels

    NASA Astrophysics Data System (ADS)

    Ma, Ninshu; Takada, Kenji; Sugimoto, Nao

    2016-08-01

    To investigate the local strain and stress at the crack initiation position in shear fracture test pieces of ultra-high strength steels, a butterfly shear fracture specimen was employed. The crack initiation position and propagation direction were observed during shear fracture tests by high speed cameras and investigated through analysing the fracture surface by scanning electron microscope. Further, the finite element method was employed and the stress-triaxiality at the crack initiation position was investigated. It can be obtained that the crack initiated at the position where the stress state is close to uniaxial tensile state or plane strain state more than pure shear stress state.

  12. High blood pressure in children and adolescents.

    PubMed

    Riley, Margaret; Bluhm, Brian

    2012-04-01

    High blood pressure in children and adolescents is a growing health problem that is often overlooked by physicians. Normal blood pressure values for children and adolescents are based on age, sex, and height, and are available in standardized tables. Prehypertension is defined as a blood pressure in at least the 90th percentile, but less than the 95th percentile, for age, sex, and height, or a measurement of 120/80 mm Hg or greater. Hypertension is defined as blood pressure in the 95th percentile or greater. A secondary etiology of hypertension is much more likely in children than in adults, with renal parenchymal disease and renovascular disease being the most common. Overweight and obesity are strongly correlated with primary hypertension in children. A history and physical examination are needed for all children with newly diagnosed hypertension to help rule out underlying medical disorders. Children with hypertension should also be screened for other risk factors for cardiovascular disease, including diabetes mellitus and hyperlipidemia, and should be evaluated for target organ damage with a retinal examination and echocardiography. Hypertension in children is treated with lifestyle changes, including weight loss for those who are overweight or obese; a healthy, low-sodium diet; regular physical activity; and avoidance of tobacco and alcohol. Children with symptomatic hypertension, secondary hypertension, target organ damage, diabetes, or persistent hypertension despite nonpharmacologic measures should be treated with antihypertensive medications. Thiazide diuretics, angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, beta blockers, and calcium channel blockers are safe, effective, and well tolerated in children.

  13. Effect of blood contamination on shear bond strength of brackets bonded with a self-etching primer combined with a resin-modified glass ionomer.

    PubMed

    Cacciafesta, Vittorio; Sfondrini, Maria Francesca; Scribante, Andrea; De Angelis, Marco; Klersy, Catherine

    2004-12-01

    This study assessed the effect of blood contamination on the shear bond strength and bond failure site of a resin-modified glass ionomer (Fuji Ortho LC, GC Europe, Leuven, Belgium) used with 3 enamel conditioners (10% polyacrylic acid, 37% phosphoric acid, and self-etching primer). One hundred twenty bovine permanent mandibular incisors were randomly divided into 8 groups; each group consisted of 15 specimens. Two enamel surface conditions were studied: dry and contaminated with blood. One hundred twenty stainless steel brackets were bonded with the resin-modified glass ionomer. After bonding, all samples were stored in distilled water for 24 hours and then tested in shear mode on a testing machine. The groups conditioned with self-etching primer and 37% phosphoric acid had the highest bond strengths for both dry and blood-contaminated enamel. The groups conditioned with 10% polyacrylic acid showed significantly lower shear bond strength value, and the unconditioned groups had the lowest bond strengths. For each enamel conditioner, no significant difference was reported between dry and blood-contaminated groups. Significant differences in debond locations were found among the groups bonded with the different conditioners. Blood contamination of enamel during the bonding procedure of Fuji Ortho LC did not affect its bond strength values, no matter which enamel conditioner was used.

  14. Flush mounted hot film anemometer measurement of wall shear stress distal to a tri-leaflet valve for Newtonian and non-Newtonian blood analog fluids.

    PubMed

    Nandy, S; Tarbell, J M

    1987-01-01

    Wall shear stress has been measured by flush-mounted hot film anemometry distal to an Ionescu-Shiley tri-leaflet valve under pulsatile flow conditions. Both Newtonian (aqueous glycerol) and non-Newtonian (aqueous polyacrylamide) blood analog fluids were investigated. Significant differences in the axial distribution of wall shear stress between the two fluids are apparent in flows having nearly identical Reynolds numbers. The Newtonian fluid exhibits a (peak) wall shear rate which is maximized near the valve seat (30 mm) and then decays to a fully developed flow value (by 106 mm). In contrast, the shear rate of the non-Newtonian fluid at 30 mm is less than half that of the Newtonian fluid and at 106 mm is more than twice that of the Newtonian fluid. It is suggested that non-Newtonian rheology influences valve flow patterns either through alterations in valve opening associated with low shear separation zones behind valve leaflets, or because of variations in the rate of jet spreading. More detailed studies are required to clarify the mechanisms. The Newtonian wall shear stresses for this valve are low. The highest value observed anywhere in the aortic chamber was 2.85 N/m2 at a peak Reynolds number of 3694.

  15. [Hypertensive urgency or high blood pressure variability?

    PubMed

    Rodionov, A V

    2017-01-01

    Hypertensive urgency (HU) is a common reason particularly for elderly patients to seek medical advice. Severe asymptomatic hypertension and situational high blood pressure (BP) in patients with its high variability is frequently taken as HU. The use of short-acting antihypertensive drugs is not only indicated in these situations, but it may also increase the risk of cardiovascular events (CVE). Over the past decade, increased BP variability is an independent predictor for a higher risk of CVE. Among the major groups of antihypertensive drugs, there are calcium antagonists, mainly amlodipine, which has the greatest potential to reduce BP variability. Thus, calcium antagonists can be considered as first-line drugs for patients with high BP variability.

  16. Analysing calcium signalling of cells under high shear flows using discontinuous dielectrophoresis

    NASA Astrophysics Data System (ADS)

    Soffe, Rebecca; Baratchi, Sara; Tang, Shi-Yang; Nasabi, Mahyar; McIntyre, Peter; Mitchell, Arnan; Khoshmanesh, Khashayar

    2015-07-01

    Immobilisation of cells is an important feature of many cellular assays, as it enables the physical/chemical stimulation of cells; whilst, monitoring cellular processes using microscopic techniques. Current approaches for immobilising cells, however, are hampered by time-consuming processes, the need for specific antibodies or coatings, and adverse effects on cell integrity. Here, we present a dielectrophoresis-based approach for the robust immobilisation of cells, and analysis of their responses under high shear flows. This approach is quick and label-free, and more importantly, minimises the adverse effects of electric field on the cell integrity, by activating the field for a short duration of 120 s, just long enough to immobilise the cells, after which cell culture media (such as HEPES) is flushed through the platform. In optimal conditions, at least 90% of the cells remained stably immobilised, when exposed to a shear stress of 63 dyn/cm2. This approach was used to examine the shear-induced calcium signalling of HEK-293 cells expressing a mechanosensitive ion channel, transient receptor potential vaniloid type 4 (TRPV4), when exposed to the full physiological range of shear stress.

  17. Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

    NASA Astrophysics Data System (ADS)

    Javanbakht, Mahdi; Levitas, Valery I.

    2016-12-01

    Pressure and shear strain-induced phase transformations (PTs) in a nanograined bicrystal at the evolving dislocations pile-up have been studied utilizing a phase field approach (PFA). The complete system of PFA equations for coupled martensitic PT, dislocation evolution, and mechanics at large strains is presented and solved using the finite element method (FEM). The nucleation pressure for the high-pressure phase (HPP) under hydrostatic conditions near a single dislocation was determined to be 15.9 GPa. Under shear, a dislocation pile-up that appears in the left grain creates strong stress concentration near its tip and significantly increases the local thermodynamic driving force for PT, which causes nucleation of HPP even at zero pressure. At pressures of 1.59 and 5 GPa and shear, a major part of a grain transforms to HPP. When dislocations are considered in the transforming grain as well, they relax stresses and lead to a slightly smaller stationary HPP region than without dislocations. However, they strongly suppress nucleation of HPP and require larger shear. Unexpectedly, the stationary HPP morphology is governed by the simplest thermodynamic equilibrium conditions, which do not contain contributions from plasticity and surface energy. These equilibrium conditions are fulfilled either for the majority of points of phase interfaces or (approximately) in terms of stresses averaged over the HPP region or for the entire grain, despite the strong heterogeneity of stress fields. The major part of the driving force for PT in the stationary state is due to deviatoric stresses rather than pressure. While the least number of dislocations in a pile-up to nucleate HPP linearly decreases with increasing applied pressure, the least corresponding shear strain depends on pressure nonmonotonously. Surprisingly, the ratio of kinetic coefficients for PT and dislocations affect the stationary solution and the nanostructure. Consequently, there are multiple stationary solutions

  18. Evaluation of Aortic Blood Flow and Wall Shear Stress in Aortic Stenosis and Its Association With Left Ventricular Remodeling

    PubMed Central

    von Knobelsdorff-Brenkenhoff, Florian; Karunaharamoorthy, Achudhan; Trauzeddel, Ralf Felix; Barker, Alex J; Blaszczyk, Edyta; Markl, Michael; Schulz-Menger, Jeanette

    2016-01-01

    Background Aortic stenosis (AS) leads to variable stress for the left ventricle (LV) and consequently a broad range of LV remodeling. Study aim was to describe blood flow patterns in the ascending aorta of AS patients and determine their association with remodeling. Methods and Results Thirty-seven patients with AS (14 mild, 8 moderate, 15 severe; age 63±13 years) and 37 healthy controls (age 60±10 years) underwent 4D-flow MRI. Helical and vortical flow formations and flow eccentricity were assessed in the ascending aorta. Normalized flow displacement from the vessel center and peak systolic wall shear stress (WSSpeak) in the ascending aorta were quantified. LV remodeling was assessed based on LV mass index (LVMI-I) and the ratio of LV mass to enddiastolic volume (relative wall mass; RWM). Marked helical and vortical flow formation and eccentricity were more prevalent in patients with AS than in healthy subjects, and AS patients exhibited an asymmetric and elevated distribution of WSSpeak. In AS, aortic orifice area was strongly negatively associated with vortical flow formation (p=0.0274), eccentricity (p=0.0070) and flow displacement (p=0.0021). Bicuspid aortic valve was associated with more intense helical (p=0.0098) and vortical flow formation (p=0.0536), higher flow displacement (p=0.11) and higher WSSpeak (p=0.0926). LVM-I and RWM were significantly associated with aortic orifice area (p=0.0611, p=0.0058) and flow displacement (p=0.0058, p=0.0283). Conclusions In this pilot study, AS leads to abnormal blood flow pattern and WSSpeak in the ascending aorta. In addition to aortic orifice area, normalized flow displacement was significantly associated with LV remodeling. PMID:26917824

  19. Measurement of whole blood of different mammalian species in the oscillating shear field: influence of erythrocyte aggregation

    NASA Astrophysics Data System (ADS)

    Windberger, U.; Pöschl, Ch; Peters, S.; Huber, J.; van den Hoven, R.

    2017-01-01

    This is the first systematic analysis of mammalian blood of species with a high (horse), medium (man), and low (sheep) erythrocyte (RBC) aggregability by small amplitude oscillation technique. Amplitude and frequency sweep tests (linear viscoelastic mode) were performed with blood from healthy adult volunteers, horses, and sheep in CSS-mode. Blood samples were hematocrit (HCT) adjusted (40%, 50%, 60%) and tested at 7°C, 22°C, and 37°C. Generally, storage modulus (G´) increased with HCT and decreased with temperature in each species, but the gradient of this increase was species-specific. The lower dependency of G´ on the equine HCT value could be a benefit during physical performance when high numbers of RBCs are released from the spleen. In sheep, an HCT-threshold had to be overcome before the desired quasi-static condition of the blood sample could be achieved, suggesting that the contact between RBCs, and between RBCs and plasma molecules must be very low. The frequencies for tests under linear viscoelastic condition were in a narrow range around the physiologic heart rate of the species. In horse, time-dependent influences concurred at frequencies lower than 3 rad.s-1probably due to sedimentation of RBC aggregates. In conclusion, blood is a fragile suspension that shows its best stability around the resting heart rate of the species.

  20. Sleep Deprivation: A Cause of High Blood Pressure?

    MedlinePlus

    ... High blood pressure (hypertension) Is it true that sleep deprivation can cause high blood pressure? Answers from Sheldon ... Cirelli C, et al. Definition and consequences of sleep deprivation. http://www.uptodate.com/home. Accessed March 24, ...

  1. High blood pressure - what to ask your doctor

    MedlinePlus

    What to ask your doctor about high blood pressure; Hypertension - what to ask your doctor ... problems? What medicines am I taking to treat high blood pressure? Do they have any side effects? What should ...

  2. Changes You Can Make to Manage High Blood Pressure

    MedlinePlus

    ... Changes You Can Make to Manage High Blood Pressure Updated:Mar 10,2017 Fighting back against the “ ... on Twitter Follow us on Facebook High Blood Pressure • Home • Get the Facts About HBP • Know Your ...

  3. Heart and Artery Damage and High Blood Pressure

    MedlinePlus

    ... Venous Thromboembolism Aortic Aneurysm More How High Blood Pressure Can Lead to a Heart Attack Updated:Dec ... content was last reviewed October 2016. High Blood Pressure • Home • Get the Facts About HBP • Know Your ...

  4. What You Should Know About High Blood Pressure and Medications

    MedlinePlus

    ... More What You Should Know About High Blood Pressure and Medications Updated:Jan 18,2017 Is medication ... content was last reviewed October 2016. High Blood Pressure • Home • Get the Facts About HBP • Know Your ...

  5. How Potassium Can Help Control High Blood Pressure

    MedlinePlus

    ... More How Potassium Can Help Control High Blood Pressure Updated:Dec 13,2016 Understanding the heart-healthy ... content was last reviewed October 2016. High Blood Pressure • Home • Get the Facts About HBP • Know Your ...

  6. A Nutritional Strategy for the Treatment of High Blood Pressure.

    ERIC Educational Resources Information Center

    Podell, Richard N.

    1984-01-01

    Some physicians wonder if high blood pressure can be controlled without the use of drugs and their potential side effects. Current findings concerning nutrition and high blood pressure are presented. (RM)

  7. Observations of subsonic and supersonic shear flows in laser driven high-energy-density plasmas

    NASA Astrophysics Data System (ADS)

    Harding, E. C.

    2009-11-01

    Shear layers containing strong velocity gradients appear in many high-energy-density (HED) systems and play important roles in mixing and the transition to turbulence. Yet few laboratory experiments have been carried out to study their detailed evolution in this extreme environment where plasmas are compressible, actively ionizing, often involve strong shock waves and have complex material properties. Many shear flows produce the Kelvin-Helmholtz (KH) instability, which initiates the mixing at a fluid interface. We present results from two dedicated shear flow experiments that produced overall subsonic and supersonic flows using novel target designs. In the subsonic case, the Omega laser was used to drive a blast wave along a rippled interface between plastic and foam, shocking both the materials to produce two fluids separated by a sharp shear layer. The interface subsequently rolled-upped into large KH vortices that were accompanied by bubble-like structures of unknown origin. This was the first time the evolution of a well-resolved KH instability was observed in a HED plasma in the laboratory. We have analyzed the properties and dynamics of the plasma based on the data and fundamental models, without resorting to simulated values. In the second, supersonic experiment the Nike laser was used to drive a supersonic flow of Al plasma along a rippled, low-density foam surface. Here again the flowing plasma drove a shock into the second material, so that two fluids were separated by a shear layer. In contrast to the subsonic case, the flow developed shocks around the ripples in response to the supersonic flow of Al. Collaborators: R.P. Drake, O.A. Hurricane, J.F. Hansen, Y. Aglitskiy, T. Plewa, B.A. Remington, H.F. Robey, J.L. Weaver, A.L. Velikovich, R.S. Gillespie, M.J. Bono, M.J. Grosskopf, C.C. Kuranz, A. Visco.

  8. Experimental and numerical study of plastic shear instability under high-speed loading conditions

    SciTech Connect

    Sokovikov, Mikhail E-mail: naimark@icmm.ru; Chudinov, Vasiliy E-mail: naimark@icmm.ru; Bilalov, Dmitry E-mail: naimark@icmm.ru; Oborin, Vladimir E-mail: naimark@icmm.ru; Uvarov, Sergey E-mail: naimark@icmm.ru; Plekhov, Oleg E-mail: naimark@icmm.ru; Terekhina, Alena E-mail: naimark@icmm.ru; Naimark, Oleg E-mail: naimark@icmm.ru

    2014-11-14

    The behavior of specimens dynamically loaded during the split Hopkinson (Kolsky) bar tests in a regime close to simple shear conditions was studied. The lateral surface of the specimens was investigated in a real-time mode with the aid of a high-speed infra-red camera CEDIP Silver 450M. The temperature field distribution obtained at different time made it possible to trace the evolution of plastic strain localization. The process of target perforation involving plug formation and ejection was examined using a high-speed infra-red camera and a VISAR velocity measurement system. The microstructure of tested specimens was analyzed using an optical interferometer-profilometer and a scanning electron microscope. The development of plastic shear instability regions has been simulated numerically.

  9. [High blood pressure and physical exercise].

    PubMed

    Sosner, P; Gremeaux, V; Bosquet, L; Herpin, D

    2014-06-01

    High blood pressure is a frequent pathology with many cardiovascular complications. As highlighted in guidelines, the therapeutic management of hypertension relies on non-pharmacological measures, which are diet and regular physical activity, but both patients and physicians are reluctant to physical activity prescription. To acquire the conviction that physical activity is beneficial, necessary and possible, we can take into account some fundamental and clinical studies, as well as the feedback of our clinical practice. Physical inactivity is a major risk factor for cardiovascular morbidity and mortality, and hypertension contributes to increase this risk. Conversely, regular practice of physical activity decreases very significantly the risk by up to 60%. The acute blood pressure changes during exercise and post-exercise hypotension differs according to the dynamic component (endurance or aerobic and/or strength exercises), but the repetition of the sessions leads to the chronic hypotensive benefit of physical activity. Moreover, physical activity prescription must take into account the assessment of global cardiovascular risk, the control of the hypertension, and the opportunities and desires of the patient in order to promote good adherence and beneficial lifestyle change.

  10. Exposure of human megakaryocytes to high shear rates accelerates platelet production.

    PubMed

    Dunois-Lardé, Claire; Capron, Claude; Fichelson, Serge; Bauer, Thomas; Cramer-Bordé, Elisabeth; Baruch, Dominique

    2009-08-27

    Platelets originate from megakaryocytes (MKs) by cytoplasmic elongation into proplatelets. Direct platelet release is not seen in bone marrow hematopoietic islands. It was suggested that proplatelet fragmentation into platelets can occur intravascularly, yet evidence of its dependence on hydrodynamic forces is missing. Therefore, we investigated whether platelet production from MKs could be up-regulated by circulatory forces. Human mature MKs were perfused at a high shear rate on von Willebrand factor. Cells were observed in real time by videomicroscopy, and by confocal and electron microscopy after fixation. Dramatic cellular modifications followed exposure to high shear rates: 30% to 45% adherent MKs were converted into proplatelets and released platelets within 20 minutes, contrary to static conditions that required several hours, often without platelet release. Tubulin was present in elongated proplatelets and platelets, thus ruling out membrane tethers. By using inhibitors, we demonstrated the fundamental roles of microtubule assembly and MK receptor GPIb. Secretory granules were present along the proplatelet shafts and in shed platelets, as shown by P-selectin labeling. Platelets generated in vitro were functional since they responded to thrombin by P-selectin expression and cytoskeletal reorganization. In conclusion, MK exposure to high shear rates promotes platelet production via GPIb, depending on microtubule assembly and elongation.

  11. Enhanced Actuation Performance and Reduced Heat Generation in Shear-Bending Mode Actuator at High Temperature.

    PubMed

    Chen, Jianguo; Liu, Guoxi; Cheng, Jinrong; Dong, Shuxiang

    2016-08-01

    The actuation performance, strain hysteresis, and heat generation of the shear-bending mode actuators based on soft and hard BiScO3-PbTiO3 (BS-PT) ceramics were investigated under different thermal (from room temperature to 300 °C) and electrical loadings (from 2 to 10 kV/cm and from 1 to 1000 Hz). The actuator based on both soft and hard BS-PT ceramics worked stably at the temperature as high as 300 °C. The maximum working temperature of this shear-bending actuators is 150 °C higher than those of the traditional piezoelectric actuators based on commercial Pb(Zr, Ti)O3 materials. Furthermore, although the piezoelectric properties of soft-type ceramics based on BS-PT ceramics were superior to those of hard ceramics, the maximum displacement of the actuator based on hard ceramics was larger than that fabricated by soft ceramics at high temperature. The maximum displacement of the actuator based on hard ceramics was [Formula: see text] under an applied electric field of 10 kV/cm at 300 °C. The strain hysteresis and heat generation of the actuator based on hard ceramics was smaller than those of the actuator based on soft ceramics in the wide temperature range. These results indicated that the shear-bending actuator based on hard piezoelectric ceramics was more suitable for high-temperature piezoelectric applications.

  12. ‘Sausage-string’ deformations of blood vessels at high blood pressures

    NASA Astrophysics Data System (ADS)

    Alstrøm, P.; Mikkelsen, R.; Gustafsson, F.; Holstein-Rathlou, N.-H.

    1999-12-01

    A new instability is proposed to explain the ‘sausage-string’ patterns of alternating constrictions and dilatations formed in blood vessels at high blood pressure conditions. Our theory provides predictions for the conditions under which the cylindrical geometry of a blood vessel becomes unstable. The theory is related to experimental observations in rats, where high blood pressure is induced by intravenous infusion of angiotensin II.

  13. Design and simulation of high-energy-density shear experiments on OMEGA and the NIF

    NASA Astrophysics Data System (ADS)

    Doss, F. W.; Devolder, B.; di Stefano, C.; Flippo, K. A.; Kline, J. L.; Kot, L.; Loomis, E. N.; Merritt, E. C.; Perry, T. S.; MacLaren, S. A.; Wang, P.; Zhou, Y. K.

    2015-11-01

    High-energy-density shear experiments have been performed by LANL at the OMEGA Laser Facility and National Ignition Facility (NIF). The experiments have been simulated using the LANL radiation-hydrocode RAGE and have been used to assess turbulence models' ability to function in the high-energy-density, inertial-fusion-relevant regime. Beginning with the basic configuration of two counter-oriented shock-driven flows of > 100 km/s, which initiate a strong shear instability across an initially solid density, 20 micron thick Al plate, variations of the experiment have been performed and are studied. These variations have included increasing the fluid density (by modifying the metal plate material from Al to Ti), imposing sinusoidal perturbations on the plate, and directly modifying the plate's intrinsic surface roughness. In addition to examining the shear-induced mixing, the simulations reveal other physics, such as how the interaction of our indirect-drive halfraums with a mated shock tube's ablator impedes a stagnation-driven shock. This work is conducted by the US DOE by LANL under contract DE-AC52-06NA25396, and NIF facility operations by LLNL under contract DE-AC52-07NA27344.

  14. Venous levels of shear support neutrophil-platelet adhesion and neutrophil aggregation in blood via P-selectin and beta2-integrin

    NASA Technical Reports Server (NTRS)

    Konstantopoulos, K.; Neelamegham, S.; Burns, A. R.; Hentzen, E.; Kansas, G. S.; Snapp, K. R.; Berg, E. L.; Hellums, J. D.; Smith, C. W.; McIntire, L. V.; Simon, S. I.

    1998-01-01

    BACKGROUND: After activation, platelets adhere to neutrophils via P-selectin and beta2-integrin. The molecular mechanisms and adhesion events in whole blood exposed to venous levels of hydrodynamic shear in the absence of exogenous activation remain unknown. METHODS AND RESULTS: Whole blood was sheared at approximately 100 s(-1). The kinetics of neutrophil-platelet adhesion and neutrophil aggregation were measured in real time by flow cytometry. P-selectin was upregulated to the platelet surface in response to shear and was the primary factor mediating neutrophil-platelet adhesion. The extent of neutrophil aggregation increased linearly with platelet adhesion to neutrophils. Blocking either P-selectin, its glycoprotein ligand PSGL-1, or both simultaneously by preincubation with a monoclonal antibody resulted in equivalent inhibition of neutrophil-platelet adhesion (approximately 30%) and neutrophil aggregation (approximately 70%). The residual amount of neutrophil adhesion was blocked with anti-CD11b/CD18. Treatment of blood with prostacyclin analogue ZK36374, which raises cAMP levels in platelets, blocked P-selectin upregulation and neutrophil aggregation to baseline. Complete abrogation of platelet-neutrophil adhesion required both ZK36374 and anti-CD18. Electron microscopic observations of fixed blood specimens revealed that platelets augmented neutrophil aggregation both by forming bridges between neutrophils and through contact-mediated activation. CONCLUSIONS: The results are consistent with a model in which venous levels of shear support platelet adherence to neutrophils via P-selectin binding PSGL-1. This interaction alone is sufficient to mediate neutrophil aggregation. Abrogation of platelet adhesion and aggregation requires blocking Mac-1 in addition to PSGL-1 or P-selectin. The described mechanisms are likely of key importance in the pathogenesis and progression of thrombotic disorders that are exacerbated by leukocyte-platelet aggregation.

  15. What Are the Signs, Symptoms, and Complications of High Blood Pressure?

    MedlinePlus

    ... the Signs, Symptoms, and Complications of High Blood Pressure? Because diagnosis is based on blood pressure readings, ... chronic high blood pressure. Complications of High Blood Pressure When blood pressure stays high over time, it ...

  16. High Blood Cholesterol: What You Need to Know

    MedlinePlus

    ... Audiences Contact The Health Information Center High Blood Cholesterol: What You Need To Know Table of Contents ... Lifestyle Changes (TLC) Drug Treatment Resources Why Is Cholesterol Important? Your blood cholesterol level has a lot ...

  17. 10 Ways to Control High Blood Pressure without Medication

    MedlinePlus

    ... Conditions High blood pressure (hypertension) By making these 10 lifestyle changes, you can lower your blood pressure ... or reduce the need for medication. Here are 10 lifestyle changes you can make to lower your ...

  18. A Study of the Unstable Modes in High Mach Number Gaseous Jets and Shear Layers

    NASA Astrophysics Data System (ADS)

    Bassett, Gene Marcel

    1993-01-01

    Instabilities affecting the propagation of supersonic gaseous jets have been studied using high resolution computer simulations with the Piecewise-Parabolic-Method (PPM). These results are discussed in relation to jets from galactic nuclei. These studies involve a detailed treatment of a single section of a very long jet, approximating the dynamics by using periodic boundary conditions. Shear layer simulations have explored the effects of shear layers on the growth of nonlinear instabilities. Convergence of the numerical approximations has been tested by comparing jet simulations with different grid resolutions. The effects of initial conditions and geometry on the dominant disruptive instabilities have also been explored. Simulations of shear layers with a variety of thicknesses, Mach numbers and densities perturbed by incident sound waves imply that the time for the excited kink modes to grow large in amplitude and disrupt the shear layer is taug = (546 +/- 24) (M/4)^{1.7 } (Apert/0.02) ^{-0.4} delta/c, where M is the jet Mach number, delta is the half-width of the shear layer, and A_ {pert} is the perturbation amplitude. For simulations of periodic jets, the initial velocity perturbations set up zig-zag shock patterns inside the jet. In each case a single zig-zag shock pattern (an odd mode) or a double zig-zag shock pattern (an even mode) grows to dominate the flow. The dominant kink instability responsible for these shock patterns moves approximately at the linear resonance velocity, nu_ {mode} = cextnu_ {relative}/(cjet + c_ {ext}). For high resolution simulations (those with 150 or more computational zones across the jet width), the even mode dominates if the even penetration is higher in amplitude initially than the odd perturbation. For low resolution simulations, the odd mode dominates even for a stronger even mode perturbation. In high resolution simulations the jet boundary rolls up and large amounts of external gas are entrained into the jet. In low

  19. Ductility of Advanced High-Strength Steel in the Presence of a Sheared Edge

    NASA Astrophysics Data System (ADS)

    Ruggles, Tim; Cluff, Stephen; Miles, Michael; Fullwood, David; Daniels, Craig; Avila, Alex; Chen, Ming

    2016-07-01

    The ductility of dual-phase (DP) 980 and transformation-induced plasticity (TRIP) assisted bainitic ferritic (TBF) 980 steels was studied in the presence of a sheared edge. Specimens were tested in uniaxial tension in a standard test frame as well as in situ in the scanning electron microscope (SEM). Incremental tensile straining was done in the SEM with images taken at each strain increment. Then digital image correlation (DIC) was used to compute the effective strain at the level of the individual phases in the microstructure. Shear banding across multiple phases was seen in strained TBF specimens, while the DP specimens exhibited more of a patchwork strain pattern, with high strains concentrated in ferrite and low strains observed in the martensite. Two-point statistics were applied to the strain data from the DIC work and the corresponding microstructure images to evaluate the effect of phase hardness on localization and fracture. It was observed that the DP 980 material had a greater tendency for localization around hard phases compared to the TBF 980. This at least partially explains the greater ductility of the TBF material, especially in specimens where a sheared edge was present.

  20. Understanding High Recession Rates of Carbon Ablators Seen in Shear Tests in an Arc Jet

    NASA Technical Reports Server (NTRS)

    Driver, David M.; Olson, Michael W.; Barnhardt, Michael D.; MacLean, Matthew

    2010-01-01

    High rates of recession in arc jet shear tests of Phenolic Impregnated Carbon Ablator (PICA) inspired a series of tests and analysis on FiberForm (a carbon preform used in the fabrication of PICA). Arc jet tests were performed on FiberForm in both air and pure nitrogen for stagnation and shear configurations. The nitrogen tests showed little or no recession, while the air tests of FiberForm showed recession rates similar to that of PICA (when adjusted for the difference in density). While mechanical erosion can not be ruled out, this is the first step in doing so. Analysis using a carbon oxidation boundary condition within DPLR was used to predict the recession rate of FiberForm. The analysis indicates that much of the anomalous recession behavior seen in shear tests may simply be an artifact of the non-flight like test configuration (copper upstream of the test article) a result of dissimilar enthalpy and oxygen concentration profiles on the copper. Shape change effects were also investigated and shown to be relatively small.

  1. Diverse forms of pulmonary hypertension remodel the arterial tree to a high shear phenotype.

    PubMed

    Allen, Roblee P; Schelegle, Edward S; Bennett, Stephen H

    2014-08-01

    Pulmonary hypertension (PH) is associated with progressive changes in arterial network complexity. An allometric model is derived that integrates diameter branching complexity between pulmonary arterioles of generation n and the main pulmonary artery (MPA) via a power-law exponent (X) in dn = dMPA2(-n/X) and the arterial area ratio β = 2(1-2/X). Our hypothesis is that diverse forms of PH demonstrate early decrements in X independent of etiology and pathogenesis, which alters the arteriolar shear stress load from a low-shear stress (X > 2, β > 1) to a high-shear stress phenotype (X < 2, β < 1). Model assessment was accomplished by comparing theoretical predictions to retrospective morphometric and hemodynamic measurements made available from a total of 221 PH-free and PH subjects diagnosed with diverse forms (World Health Organization; WHO groups I-IV) of PH: mitral stenosis, congenital heart disease, chronic obstructive pulmonary lung disease, chronic thromboembolism, idiopathic pulmonary arterial hypertension (IPAH), familial (FPAH), collagen vascular disease, and methamphetamine exposure. X was calculated from pulmonary artery pressure (PPA), cardiac output (Q) and body weight (M), utilizing an allometric power-law prediction of X relative to a PH-free state. Comparisons of X between PAH-free and PAH subjects indicates a characteristic reduction in area that elevates arteriolar shear stress, which may contribute to mechanisms of endothelial dysfunction and injury before clinically defined thresholds of pulmonary vascular resistance and PH. We conclude that the evaluation of X may be of use in identifying reversible and irreversible phases of PH in the early course of the disease process.

  2. Stability of LAPONITE®-stabilized high internal phase Pickering emulsions under shear.

    PubMed

    Dinkgreve, M; Velikov, K P; Bonn, D

    2016-08-17

    Colloidal particles are often used to make Pickering emulsions that are reported to be very stable. Commonly the stabilization is a combined effect of particle adsorbing at the fluid interface and a particle network in the continuous phase; the contribution of each to the overall stability is difficult to assess. We investigate the role of LAPONITE® particles on high internal phase emulsion stability by considering three different situations: emulsion stabilization by surfactant only, by surfactant plus clay particles, and finally clay particles only. To clarify the structure of the emulsion and the role of the clay particles, we have succeeded in fluorescently labelling the clay particles by adsorbing the dye onto the particle surfaces. This allows us to show directly using confocal microscopy, that the clay particles are not only located at the interface but also aggregate and form a gel in the continuous aqueous phase. We show that the emulsions in the presence of surfactant (with or without clay) are stable to coalescence and shear. Without surfactant (with only LAPONITE® as stabilizer) the emulsions are stable to coalescence for several weeks, however they destabilize rapidly under shear. Our results suggest that the formation of the emulsions is mostly due to gel formation of the clay particles in the continuous phase, rather than that the clay is an emulsifier. This gel formation also accounts for the instability of the emulsions to shear that we observe caused by shear thinning of the continuous gel and inability of the adsorbed particles to rearrange effectively around the droplets due to their attractive nature.

  3. Monitoring of high-intensity focused ultrasound treatment by shear wave elastography induced by two-dimensional-array therapeutic transducer

    NASA Astrophysics Data System (ADS)

    Iwasaki, Ryosuke; Takagi, Ryo; Nagaoka, Ryo; Jimbo, Hayato; Yoshizawa, Shin; Saijo, Yoshifumi; Umemura, Shin-ichiro

    2016-07-01

    Shear wave elastography (SWE) is expected to be a noninvasive monitoring method of high-intensity focused ultrasound (HIFU) treatment. However, conventional SWE techniques encounter difficulty in inducing shear waves with adequate displacements in deep tissue. To observe tissue coagulation at the HIFU focal depth via SWE, in this study, we propose using a two-dimensional-array therapeutic transducer for not only HIFU exposure but also creating shear sources. The results show that the reconstructed shear wave velocity maps detected the coagulated regions as the area of increased propagation velocity even in deep tissue. This suggests that “HIFU-push” shear elastography is a promising solution for the purpose of coagulation monitoring in deep tissue, because push beams irradiated by the HIFU transducer can naturally reach as deep as the tissue to be coagulated by the same transducer.

  4. Shallow water sediment properties derived from high-frequency shear and interface waves

    NASA Astrophysics Data System (ADS)

    Ewing, John; Carter, Jerry A.; Sutton, George H.; Barstow, Noel

    1992-04-01

    Low-frequency sound propagation in shallow water environments is not restricted to the water column but also involves the subbottom. Thus, as well as being important for geophysical description of the seabed, subbottom velocity/attenuation structure is essential input for predictive propagation models. To estimate this structure, bottom-mounted sources and receivers were used to make measurements of shear and compressional wave propagation in shallow water sediments of the continental shelf, usually where boreholes and high-resolution reflection profiles give substantial supporting geologic information about the subsurface. This colocation provides an opportunity to compare seismically determined estimates of physical properties of the seabed with the "ground truth" properties. Measurements were made in 1986 with source/detector offsets up to 200 m producing shear wave velocity versus depth profiles of the upper 30-50 m of the seabed (and P wave profiles to lesser depths). Measurements in 1988 were made with smaller source devices designed to emphasize higher frequencies and recorded by an array of 30 sensors spaced at 1-m intervals to improve spatial sampling and resolution of shallow structure. These investigations with shear waves have shown that significant lateral and vertical variations in the physical properties of the shallow seabed are common and are principally created by erosional and depositional processes associated with glacial cycles and sea level oscillations during the Quaternary. When the seabed structure is relatively uniform over the length of the profiles, the shear wave fields are well ordered, and the matching of the data with full waveform synthetics has been successful, producing velocity/attenuation models consistent with the subsurface lithology indicated by coring results. Both body waves and interface waves have been modeled for velocity/attenuation as a function of depth with the aid of synthetic seismograms and other analytical

  5. Effect of moisture, saliva, and blood contamination on the shear bond strength of brackets bonded with a conventional bonding system and self-etched bonding system

    PubMed Central

    Prasad, Mandava; Mohamed, Shamil; Nayak, Krishna; Shetty, Sharath Kumar; Talapaneni, Ashok Kumar

    2014-01-01

    Background: The success of bonding brackets to enamel with resin bonding systems is negatively affected by contamination with oral fluids such as blood and saliva. The new self-etch primer systems combine conditioning and priming agents into a single application, making the procedure more cost effective. Objective: The purpose of the study was to investigate the effect of moisture, saliva and blood contamination on shear bond strength of orthodontic brackets bonded with conventional bonding system and self-etch bonding system. Materials and Methods: Each system was examined under four enamel surface conditions (dry, water, saliva, and blood), and 80 human teeth were divided into two groups with four subgroups each of 10 according to enamel surface condition. Group 1 used conventional bonding system and Group 2 used self-etched bonding system. Subgroups 1a and 2a under dry enamel surface conditions; Subgroups 1b and 2b under moist enamel surface condition; Subgroups 3a and 3b under saliva enamel surface condition and Subgroup 4a and 4b under blood enamel surface condition. Brackets were bonded, and all the samples were then submitted to a shear bond test with a universal testing machine with a cross head speed of 1mm/sec. Results: The results showed that the contamination reduced the shear bond strength of all groups. In self-etch bonding system water and saliva had significantly higher bond strength when compared to other groups. Conclusion: It was concluded that the blood contamination showed lowest bond strength from both bonding systems. Self-etch bonding system resulted in higher bond strength than conventional bonding system under all conditions except the dry enamel surface. PMID:24678210

  6. Rotational and magnetic shear stabilization of magnetohydrodynamic modes and turbulence in DIII-D high performance discharges

    SciTech Connect

    Lao, L.L.; Burrell, K.H.; Casper, T.S.

    1996-08-01

    The confinement and the stability properties of the DIII-D tokamak high performance discharges are evaluated in terms of rotational and magnetic shear with emphasis on the recent experimental results obtained from the negative central magnetic shear (NCS) experiments. In NCS discharges, a core transport barrier is often observed to form inside the NCS region accompanied by a reduction in core fluctuation amplitudes. Increasing negative magnetic shear contributes to the formation of this core transport barrier, but by itself is not sufficient to fully stabilize the toroidal drift mode (trapped- electron-{eta}{sub i}mode) to explain this formation. Comparison of the Doppler shift shear rate to the growth rate of the {eta}{sub i} mode suggests that the large core {bold E x B} flow shear can stabilize this mode and broaden the region of reduced core transport . Ideal and resistive stability analysis indicates the performance of NCS discharges with strongly peaked pressure profiles is limited by the resistive interchange mode to low {Beta}{sub N} {lt} 2.3. This mode is insensitive to the details of the rotational and the magnetic shear profiles. A new class of discharges which has a broad region of weak or slightly negative magnetic shear (WNS) is described. The WNS discharges have broader pressure profiles and higher values than the NCS discharges together with high confinement and high fusion reactivity.

  7. Effect of high molecular weight plasticizers on the gelatinization of starch under static and shear conditions.

    PubMed

    Taghizadeh, Ata; Favis, Basil D

    2013-02-15

    Starch gelatinization in the presence of high molecular weight polyol plasticizers and water was studied under static and dynamic conditions and was compared to a glycerol reference. For static gelatinization, glycerol, sorbitol, diglycerol and polyglycerol were examined using polarized light microscopy and differential scanning calorimetry. A wide range of starch/water/plasticizer compositions were prepared to explore the gelatinization regime for each plasticizer. The plasticizers show that the onset and conclusion temperatures for sorbitol and glycerol are in the same range and are lower than the other two plasticizers. On the other hand, polyglycerol shows a higher gelatinization temperature than diglycerol because of its higher molecular weight and viscosity. The results indicate that in the case of all plasticizers, increasing the water content tends to decrease the gelatinization temperature and, except for polyglycerol, increasing the plasticizer content increases the gelatinization temperature. In the case of polyglycerol, however, increasing the plasticizer content had the opposite effect and this was found to be related to the borderline solubility of polyglycerol in water. When the polyglycerol/water solubility was increased by increasing the temperature of the water/plasticizer/starch slurry, the gelatinization temperature dependence was found to be similar to the other polyols. A rheological technique was developed to study the dynamic gelatinization process by tracking the influence of shear on the complex viscosity in a couette flow system. Glycerol, diglycerol and sorbitol were subjected to different dynamic gelatinization treatments and the results were compared with static gelatinization. It is quantitatively shown that shear has a major effect on the gelatinization process. The conclusion temperature of gelatinization is significantly diminished (up to 21 °C) in the presence of shear whereas the onset temperature of gelatinization remains

  8. [Quality by design based high shear wet granulation process development for the microcrystalline cellulose].

    PubMed

    Luo, Gan; Xu, Bing; Sun, Fei; Cui, Xiang-long; Shi, Xin-yuan; Qiao, Yan-jiang

    2015-03-01

    The design space of the high shear wet granulation process was established and validated within the framework of quality by design (QbD). The system of microcrystalline cellulose-de-ioned water was used in this study. The median granule size and bulk density of granules were identified as critical quality attributes. Plackeet-Burmann experimental design was used to screen these factors as follows: dry mixing time, the impeller and chopper speed of dry mixing, water amount, water addition time, wet massing time, the impeller and chopper speed of wet massing and drying time. And the optimization was implemented with the central composite experimental design based on screened critical process parameters. The design space of the high shear wet granulation process was established based on the quadratic polynomial regression model. Since the P-values of both models were less than 0.05 and values of lack of fit were more than 0.1, the relationship between critical quality attributes and critical process parameters could be well described by the two models. The reliability of design space, illustrated by overlay plot, was improved with the addition of 95% confidence interval. For those granules whose process parameters were in the design space, the granule size could be controlled within 250 to 355 μm, and the bulk density could be controlled within a range of 0.4 to 0.6 g x cm(-3). The robustness and flexibility of the high shear wet granulation process have been enhanced via the establishment of the design space based on the QbD concept.

  9. Demonstration of high performance negative central magnetic shear discharges on the DIII-D tokamak

    SciTech Connect

    Rice, B.W.; Burrell, K.H.; Lao, L.L.

    1996-01-01

    Reliable operation of discharges with negative central magnetic shear has led to significant increases in plasma performance and reactivity in both low confinement, L-mode, and high confinement, H-mode, regimes in the DIII-D tokamak. Using neutral beam injection early in the initial current ramp, a large range of negative shear discharges have been produced with durations lasting up to 3.2 s. The total non- inductive current (beam plus bootstrap) ranges from 50% to 80% in these discharges. In the region of shear reversal, significant peaking of the toroidal rotation [f{sub {phi}} {approx} 30-60 kHz] and ion temperature [T{sub i}(0) {approx} 15-22 keV] profiles are observed. In high power discharges with an L-mode edge, peaked density profiles are also observed. Confinement enhancement factors up to H {equivalent_to} {tau}{sub E}/{tau}{sub ITER-89P} {approx} 2.5 with an L-mode edge, and H {approx} 3.3 in an Edge Localized Mode (ELM)-free H-mode, are obtained. Transport analysis shows both ion thermal diffusivity and particle diffusivity to be near or below standard neoclassical values in the core. Large pressure peaking in L- mode leads to high disruptivity with {Beta}{sub N} {equivalent_to} {Beta}{sub T}/(I/aB) {<=} 2.3, while broader pressure profiles in H- mode gives low disruptivity with {Beta}{sub N} {<=} 4.2.

  10. How Is High Blood Pressure Treated?

    MedlinePlus

    ... and eat foods that are heart healthy. Limiting Sodium and Salt A low-sodium diet can help you manage your blood pressure. You should try to limit the amount of sodium that you eat. This means choosing and preparing ...

  11. How to Prevent High Blood Pressure

    MedlinePlus

    ... provider will use a gauge, a stethoscope or electronic sensor, and a blood pressure cuff. For most ... pressure. Stress management techniques include exercising, listening to music, focusing on something calm or peaceful, and meditating. ...

  12. When Blood Sugar is Too High

    MedlinePlus

    ... elevado Glucose , or sugar, is the body's main fuel source. That means your body — including your brain — needs glucose to work properly. But even though we need glucose for energy, too much glucose in the blood can be ...

  13. High Blood Pressure (Hypertension) (For Parents)

    MedlinePlus

    ... pumps blood into the arteries and through the circulatory system, and the other is from the arteries as ... with the kidneys (most commonly), lungs, heart, or circulatory system. These problems can include bronchopulmonary dysplasia , an immaturity ...

  14. Application of MMC model on simulation of shearing process of thick hot-rolled high strength steel plate

    NASA Astrophysics Data System (ADS)

    Dong, Liang; Li, Shuhui; Yang, Bing; Gao, Yongsheng

    2013-12-01

    Shear operation is widely used as the first step in sheet metal forming to cut the sheet or plate into the required size. The shear of thick hot-rolled High Strength Steel (HSS) requires large shearing force and the sheared edge quality is relatively poor because of the large thickness and high strength compared with the traditional low carbon steel. Bad sheared edge quality will easily lead to edge cracking during the post-forming process. This study investigates the shearing process of thick hot-rolled HSS plate metal, which is generally exploited as the beam of heavy trucks. The Modified Mohr-Coulomb fracture criterion (MMC) is employed in numerical simulation to calculate the initiation and propagation of cracks during the process evolution. Tensile specimens are designed to obtain various stress states in tension. Equivalent fracture strains are measured with Digital Image Correlation (DIC) equipment to constitute the fracture locus. Simulation of the tension test is carried out to check the fracture model. Then the MMC model is applied to the simulation of the shearing process, and the simulation results show that the MMC model predicts the ductile fracture successfully.

  15. Momentum Transport Studies in High E x B Shear Plasmas in NSTX

    SciTech Connect

    Solomon, W M; Bell, R E; LeBlanc, B P; Menard, J E; Rewoldt, G; Wang, W; Levinton, F M; Yuh, H

    2008-06-26

    Experiments have been conducted on NSTX to study both steady state and perturbative mo mentum transport. These studies are unique in their parameter space under investigation, where the low aspect ratio of NSTX results in rapid plasma rotation with E x B shearing rates high enough to suppress low-k turbulence. In some cases, the ratio of momentum to energy confinement time is found to exceed five. Momentum pinch velocities of order 10-40 m/s are inferred from the measured angular momentum flux evolution after non-resonant magnetic perturbations are applied to brake the plasma.

  16. Are integrin alpha(2)beta(1), glycoprotein Ib and vWf levels correlated with their contributions to platelet adhesion on collagen under high-shear flow?

    PubMed

    Jung, Stephanie M; Sonoda, Mamiko; Tsuji, Kayoko; Jimi, Atsuo; Nomura, Shosaku; Kanaji, Taisuke; Moroi, Masaaki

    2010-01-01

    Platelets in flowing blood at high-shear stress are recruited to exposed subendothelial collagen of injured vessels by GPIb-von Willebrand factor (vWf) and integrin alpha(2)beta(1) (alpha(2)beta(1))-collagen interactions. Platelet adhesion to type I collagen depends mainly on the alpha(2)beta(1)-collagen interaction and that to type III collagen depends on the GPIb-vWf interaction due to vWf's weak affinity for type I collagen. Contributions of these two interactions would differ depending on expressions of alpha(2)beta(1), vWf, or GPIb. We quantitated platelet adhesion to low- and high-density collagen under high-shear flow conditions in the presence of anti-alpha(2)beta(1) (Gi9) and anti-GPIb (NNKY5-5) antibodies to determine if their inhibitory effects were correlated with the amounts of alpha(2)beta(1), GPIb and vWf. Gi9 inhibition of adhesion to type I collagen was decreased in platelets with more integrin alpha(2)beta(1). Gi9 and NNKY5-5 are more inhibitory against adhesion to low-density type III and I, respectively. Higher alpha(2)beta(1) expression decreases adhesion to low-density type III and increases Gi9 inhibition of adhesion to high-density type III, suggesting crosstalk between the alpha(2)beta(1)-collagen and GPIb-vWf interactions in adhesion to type III. Integrin alpha(2)beta(1)-collagen and GPIb-vWf interactions both contribute to platelet adhesion to collagen under high-shear flow. In adhesion under high-shear stress, the two interactions would compensate for each other, when there is a deficiency in one or the other. The alpha(2)beta(1)-collagen interaction was also suggested to have an inhibitory effect on platelet adhesion to type III collagen, through a yet undefined mechanism.

  17. Turbulence measurement in a reacting and non-reacting shear layer at a high subsonic Mach number

    NASA Technical Reports Server (NTRS)

    Chang, C. T.; Marek, C. J.; Wey, C.; Jones, R. A.; Smith, M. J.

    1993-01-01

    The results of two component velocity and turbulence measurements are presented which were obtained on a planar reacting shear layer burning hydrogen. Quantitative LDV and temperature measurements are presented with and without chemical reaction within the shear layer at a velocity ratio of 0.34 and a high speed Mach number of 0.7. The comparison showed that the reacting shear layer grew faster than that without reaction. Using a reduced width coordinate, the reacting and non-reacting profiles were very similar. The peak turbulence for both cases was 20 percent.

  18. Dissolution and reconstitution of casein micelle containing dairy powders by high shear using ultrasonic and physical methods.

    PubMed

    Chandrapala, Jayani; Martin, Gregory J O; Kentish, Sandra E; Ashokkumar, Muthupandian

    2014-09-01

    The effect of shear on the solubilization of a range of dairy powders was investigated. The rate of solubilization of low solubility milk protein concentrate and micellar casein powders was examined during ultrasonication, high pressure homogenization and high-shear rotor-stator mixing and compared to low-shear overhead stirring. The high shear techniques were able to greatly accelerate the solubilization of these powders by physically breaking apart the powder agglomerates and accelerating the release of individual casein micelles into solution. This was achieved without affecting the structure of the solubilized proteins. The effect of high shear on the re-establishment of the mineral balance between the casein micelles and the serum was examined by monitoring the pH of the reconstituted skim milk powder after prior exposure to ultrasonication. Only minor differences in the re-equilibration of the pH were observed after sonication for up to 3 min, suggesting that the localized high shear forces exerted by sonication did not significantly affect the mass transfer of minerals from within the casein micelles.

  19. Announcement: National High Blood Pressure Education Month - May 2016.

    PubMed

    2016-05-27

    May is National High Blood Pressure Education Month. High blood pressure (hypertension) is a major contributor to heart disease and stroke, two leading causes of death in the United States.* High blood pressure affects one third of U.S. adults, or approximately 75 million persons, yet approximately 11 million of these persons are not aware they have hypertension, and approximately 18 million are not being treated (unpublished data) (1,2).

  20. Turbulence modeling of free shear layers for high-performance aircraft

    NASA Technical Reports Server (NTRS)

    Sondak, Douglas L.

    1993-01-01

    The High Performance Aircraft (HPA) Grand Challenge of the High Performance Computing and Communications (HPCC) program involves the computation of the flow over a high performance aircraft. A variety of free shear layers, including mixing layers over cavities, impinging jets, blown flaps, and exhaust plumes, may be encountered in such flowfields. Since these free shear layers are usually turbulent, appropriate turbulence models must be utilized in computations in order to accurately simulate these flow features. The HPCC program is relying heavily on parallel computers. A Navier-Stokes solver (POVERFLOW) utilizing the Baldwin-Lomax algebraic turbulence model was developed and tested on a 128-node Intel iPSC/860. Algebraic turbulence models run very fast, and give good results for many flowfields. For complex flowfields such as those mentioned above, however, they are often inadequate. It was therefore deemed that a two-equation turbulence model will be required for the HPA computations. The k-epsilon two-equation turbulence model was implemented on the Intel iPSC/860. Both the Chien low-Reynolds-number model and a generalized wall-function formulation were included.

  1. High temperature gradient micro-sensor for wall shear stress and flow direction measurements

    NASA Astrophysics Data System (ADS)

    Ghouila-Houri, C.; Claudel, J.; Gerbedoen, J.-C.; Gallas, Q.; Garnier, E.; Merlen, A.; Viard, R.; Talbi, A.; Pernod, P.

    2016-12-01

    We present an efficient and high-sensitive thermal micro-sensor for near wall flow parameters measurements. By combining substrate-free wire structure and mechanical support using silicon oxide micro-bridges, the sensor achieves a high temperature gradient, with wires reaching 1 mm long for only 3 μm wide over a 20 μm deep cavity. Elaborated to reach a compromise solution between conventional hot-films and hot-wire sensors, the sensor presents a high sensitivity to the wall shear stress and to the flow direction. The sensor can be mounted flush to the wall for research studies such as turbulence and near wall shear flow analysis, and for technical applications, such as flow control and separation detection. The fabrication process is CMOS-compatible and allows on-chip integration. The present letter describes the sensor elaboration, design, and micro-fabrication, then the electrical and thermal characterizations, and finally the calibration experiments in a turbulent boundary layer wind tunnel.

  2. High-order face-shear modes of relaxor-PbTiO3 crystals for piezoelectric motor applications

    NASA Astrophysics Data System (ADS)

    Ci, Penghong; Liu, Guoxi; Chen, Zhijiang; Zhang, Shujun; Dong, Shuxiang

    2014-06-01

    The face-shear vibration modes of [011] poled Zt ± 45° cut relaxor-PT crystals and their applications for linear piezoelectric motors were investigated. Unlike piezoelectric ceramics, the rotated crystal was found to exhibit asymmetric face-shear deformations, and its two high-order face-shear modes degraded into two non-isomorphic modes. As an application example, a standing wave ultrasonic linear motor (10 × 10 × 2 mm3) operating in high-order face-shear vibration modes was developed. The motor exhibits a large driving force (1.5 N) under a low driving voltage (22 Vpp). These findings could provide guidance for design of crystal resonance devices.

  3. Microstructural characteristics of adiabatic shear localization in a metastable beta titanium alloy deformed at high strain rate and elevated temperatures

    SciTech Connect

    Zhan, Hongyi; Zeng, Weidong; Wang, Gui; Kent, Damon; Dargusch, Matthew

    2015-04-15

    The microstructural evolution and grain refinement within adiabatic shear bands in the Ti6554 alloy deformed at high strain rates and elevated temperatures have been characterized using transmission electron microscopy. No stress drops were observed in the corresponding stress–strain curve, indicating that the initiation of adiabatic shear bands does not lead to the loss of load capacity for the Ti6554 alloy. The outer region of the shear bands mainly consists of cell structures bounded by dislocation clusters. Equiaxed subgrains in the core area of the shear band can be evolved from the subdivision of cell structures or reconstruction and transverse segmentation of dislocation clusters. It is proposed that dislocation activity dominates the grain refinement process. The rotational recrystallization mechanism may operate as the kinetic requirements for it are fulfilled. The coexistence of different substructures across the shear bands implies that the microstructural evolution inside the shear bands is not homogeneous and different grain refinement mechanisms may operate simultaneously to refine the structure. - Graphical abstract: Display Omitted - Highlights: • The microstructure within the adiabatic shear band was characterized by TEM. • No stress drops were observed in the corresponding stress–strain curve. • Dislocation activity dominated the grain refinement process. • The kinetic requirements for rotational recrystallization mechanism were fulfilled. • Different grain refinement mechanisms operated simultaneously to refine the structure.

  4. Ultrafast Harmonic Coherent Compound (UHCC) imaging for high frame rate echocardiography and Shear Wave Elastography

    PubMed Central

    Correia, Mafalda; Provost, Jean; Chatelin, Simon; Villemain, Olivier; Tanter, Mickael; Pernot, Mathieu

    2016-01-01

    Transthoracic shear wave elastography of the myocardium remains very challenging due to the poor quality of transthoracic ultrafast imaging and the presence of clutter noise, jitter, phase aberration, and ultrasound reverberation. Several approaches, such as, e.g., diverging-wave coherent compounding or focused harmonic imaging have been proposed to improve the imaging quality. In this study, we introduce ultrafast harmonic coherent compounding (UHCC), in which pulse-inverted diverging-waves are emitted and coherently compounded, and show that such an approach can be used to enhance both Shear Wave Elastography (SWE) and high frame rate B-mode Imaging. UHCC SWE was first tested in phantoms containing an aberrating layer and was compared against pulse-inversion harmonic imaging and against ultrafast coherent compounding (UCC) imaging at the fundamental frequency. In-vivo feasibility of the technique was then evaluated in six healthy volunteers by measuring myocardial stiffness during diastole in transthoracic imaging. We also demonstrated that improvements in imaging quality could be achieved using UHCC B-mode imaging in healthy volunteers. The quality of transthoracic images of the heart was found to be improved with the number of pulse-inverted diverging waves with reduction of the imaging mean clutter level up to 13.8-dB when compared against UCC at the fundamental frequency. These results demonstrated that UHCC B-mode imaging is promising for imaging deep tissues exposed to aberration sources with a high frame-rate. PMID:26890730

  5. A quality by design approach to scale-up of high-shear wet granulation process.

    PubMed

    Pandey, Preetanshu; Badawy, Sherif

    2016-01-01

    High-shear wet granulation is a complex process that in turn makes scale-up a challenging task. Scale-up of high-shear wet granulation process has been studied extensively in the past with various different methodologies being proposed in the literature. This review article discusses existing scale-up principles and categorizes the various approaches into two main scale-up strategies - parameter-based and attribute-based. With the advent of quality by design (QbD) principle in drug product development process, an increased emphasis toward the latter approach may be needed to ensure product robustness. In practice, a combination of both scale-up strategies is often utilized. In a QbD paradigm, there is also a need for an increased fundamental and mechanistic understanding of the process. This can be achieved either by increased experimentation that comes at higher costs, or by using modeling techniques, that are also discussed as part of this review.

  6. Structure of the Highly Sheared Tropical Storm Chantal During CAMEX-4

    NASA Technical Reports Server (NTRS)

    Heymsfield, G. M.; Halverson, J.; Ritchie, E.; Simpson, Joanne; Molinari, J.; Tian, L.

    2004-01-01

    NASA's 4th Convection and Moisture Experiment (CAMEX-4) focused on Atlantic hurricanes during the 2001 hurricane season and it involved both NASA and NOAA participation. The NASA ER-2 and DC-8 aircraft were instrumented with unique remote sensing instruments to help increase the overall understanding of hurricanes. This paper is concerned about one of the storms studied, Tropical Storm Chantal, that was a weak storm which failed to intense into a hurricane. One of the practical questions of high importance is why some tropical stoins intensify into hurricanes, and others remain weak or die altogether. The magnitude of the difference between the horizontal winds at lower levels and upper altitudes in a tropical storm, i.e., the wind shear, is one important quantity that can affect the intensification of a tropical storm. Strong shear as was present during Tropical Storm Chantal s lifetime and it was detrimental to its intensification. The paper presents an analysis of unique aircraft observations collected from Chantal including an on-board radar, radiometers, dropsondes, and flight level measurements. These measurements have enabled us to examine the internal structure of the winds and thermal structure of Chantal. Most of the previous studies have involved intense hurricanes that overcame the effects of shear and this work has provided new insights into what prevents a weaker storm from intensifying. The storm had extremely intense thunderstorms and rainfall, yet its main circulation was confined to low levels of the atmosphere. Chantal's thermal structure was not configured properly for the storm to intensify. It is most typical that huricanes have a warm core structure where warm temperatures in upper levels of a storm s circulation help intensify surface winds and lower its central pressure. Chantal had two weaker warm layers instead of a well-defined warm core. These layers have been related to the horizontal and vertical winds and precipitation structure and

  7. High Temperature Shear Horizontal Electromagnetic Acoustic Transducer for Guided Wave Inspection

    PubMed Central

    Kogia, Maria; Gan, Tat-Hean; Balachandran, Wamadeva; Livadas, Makis; Kappatos, Vassilios; Szabo, Istvan; Mohimi, Abbas; Round, Andrew

    2016-01-01

    Guided Wave Testing (GWT) using novel Electromagnetic Acoustic Transducers (EMATs) is proposed for the inspection of large structures operating at high temperatures. To date, high temperature EMATs have been developed only for thickness measurements and they are not suitable for GWT. A pair of water-cooled EMATs capable of exciting and receiving Shear Horizontal (SH0) waves for GWT with optimal high temperature properties (up to 500 °C) has been developed. Thermal and Computational Fluid Dynamic (CFD) simulations of the EMAT design have been performed and experimentally validated. The optimal thermal EMAT design, material selection and operating conditions were calculated. The EMAT was successfully tested regarding its thermal and GWT performance from ambient temperature to 500 °C. PMID:27110792

  8. Deformation and failure of OFHC copper under high strain rate shear compression

    NASA Astrophysics Data System (ADS)

    Ruggiero, Andrew; Testa, Gabriel; Bonora, Nicola; Iannitti, Gianluca; Persechino, Italo; Colliander, Magnus Hörnqvist

    2017-01-01

    Hat-shaped specimen geometries were developed to generate high strain, high-strain-rates deformation under prescribed conditions. These geometries offer also the possibility to investigate the occurrence of ductile rupture under low or negative stress triaxiality, where most failure models fail. In this work, three tophat geometries were designed, by means of extensive numerical simulation, to obtain desired stress triaxiality values within the shear region that develops across the ligament. Material failure was simulated using the Continuum Damage Model (CDM) formulation with a unilateral condition for damage accumulation and validated by comparing with quasi-static and high strain rate compression tests results on OFHC copper. Preliminary results seem to indicate that ductile tearing initiates at the specimen corner location where positive stress triaxiality occurs because of local rotation and eventually propagates along the ligament.

  9. Identification of high shears and compressive discontinuities in the inner heliosphere

    SciTech Connect

    Greco, A.; Perri, S.

    2014-04-01

    Two techniques, the Partial Variance of Increments (PVI) and the Local Intermittency Measure (LIM), have been applied and compared using MESSENGER magnetic field data in the solar wind at a heliocentric distance of about 0.3 AU. The spatial properties of the turbulent field at different scales, spanning the whole inertial range of magnetic turbulence down toward the proton scales have been studied. LIM and PVI methodologies allow us to identify portions of an entire time series where magnetic energy is mostly accumulated, and regions of intermittent bursts in the magnetic field vector increments, respectively. A statistical analysis has revealed that at small time scales and for high level of the threshold, the bursts present in the PVI and the LIM series correspond to regions of high shear stress and high magnetic field compressibility.

  10. When Blood Sugar is Too High

    MedlinePlus

    ... the body gets desperate for a source of fuel. The body wants to use glucose (sugar). But without insulin, that glucose stays stuck in the blood — and isn't available to the cells — so the body uses fat instead. But that ...

  11. When Blood Sugar Is Too High

    MedlinePlus

    ... stored fat instead in an attempt to provide fuel to hungry cells. Feeling tired: Because the body can't use ... blood and can't get into the body's cells to be used for energy. This can ... body can't use glucose for fuel, it starts to use fat. When this happens, ...

  12. New Membrane Concept Applied to the Analysis of Fluid Shear- and Micropipette-Deformed Red Blood Cells

    PubMed Central

    Evans, E. A.

    1973-01-01

    A two-dimensional elastomer material concept of the red cell membrane is applied to the analysis of fluid shear-deformed, point-attached red cells and micropipette aspiration of red cell disks. The elastic constant (corresponding to the “shear” modulus multiplied by the membrane thickness) is of the order 10-2 dyn/cm for both cases. Additional experimental observations are in agreement with the membrane model, e.g. teardrop and “tether” formation of the sheared disks, pressure difference vs. aspirated length of the cell for micropipette experiments, etc PMID:4733701

  13. Development of K-Basin High-Strength Homogeneous Sludge Simulants and Correlations Between Unconfined Compressive Strength and Shear Strength

    SciTech Connect

    Onishi, Yasuo; Baer, Ellen BK; Chun, Jaehun; Yokuda, Satoru T.; Schmidt, Andrew J.; Sande, Susan; Buchmiller, William C.

    2011-02-20

    K-Basin sludge will be stored in the Sludge Transport and Storage Containers (STSCs) at an interim storage location on Central Plateau before being treated and packaged for disposal. During the storage period, sludge in the STSCs may consolidate/agglomerate, potentially resulting in high-shear-strength material. The Sludge Treatment Project (STP) plans to use water jets to retrieve K-Basin sludge after the interim storage. STP has identified shear strength to be a key parameter that should be bounded to verify the operability and performance of sludge retrieval systems. Determining the range of sludge shear strength is important to gain high confidence that a water-jet retrieval system can mobilize stored K-Basin sludge from the STSCs. The shear strength measurements will provide a basis for bounding sludge properties for mobilization and erosion. Thus, it is also important to develop potential simulants to investigate these phenomena. Long-term sludge storage tests conducted by Pacific Northwest National Laboratory (PNNL) show that high-uranium-content K-Basin sludge can self-cement and form a strong sludge with a bulk shear strength of up to 65 kPa. Some of this sludge has 'paste' and 'chunks' with shear strengths of approximately 3-5 kPa and 380-770 kPa, respectively. High-uranium-content sludge samples subjected to hydrothermal testing (e.g., 185 C, 10 hours) have been observed to form agglomerates with a shear strength up to 170 kPa. These high values were estimated by measured unconfined compressive strength (UCS) obtained with a pocket penetrometer. Due to its ease of use, it is anticipated that a pocket penetrometer will be used to acquire additional shear strength data from archived K-Basin sludge samples stored at the PNNL Radiochemical Processing Laboratory (RPL) hot cells. It is uncertain whether the pocket penetrometer provides accurate shear strength measurements of the material. To assess the bounding material strength and potential for erosion, it

  14. Frictional strength of wet- and dry- talc gouge in high-velocity shear experiments

    NASA Astrophysics Data System (ADS)

    Chen, X.; Reches, Z.; Elwood Madden, A. S.

    2015-12-01

    The strength of the creeping segment of the San Andres fault may be controlled by the distinct weakness and stability of talc (Moore & Rymer, 2007). We analyze talc frictional strength at high slip-velocity of 0.002 - 0.66 m/s, long slip-distances of 0.01 m to 33 m, and normal stresses up to 4.1 MPa. This analysis bridges the gap between nucleation stage of low velocity/distance, and the frictional behavior during large earthquakes. We tested wet and dry samples of pure talc gouge in a confined rotary cell, and continuously monitored the slip-velocity, stresses, dilation and temperature. We run 29 experiments of single and stepped velocities to obtain 243 values of quasi-static frictional coefficients. Dry talc gouge showed distinct slip-strengthening: friction coefficient of µ ~0.4 at short slip-distances of D < 0.1 m, and it increased systematically to µ ~0.8 at slip-distances of D = 0.1- 1 m; at D > 1 m, the frictional strength saturated at µ= 0.8 - 1 level. Wet talc gouge (16-20% water) displayed low frictional strength of µ= 0.1-0.3, in agreement with published triaxial tests. The stepped-velocity runs revealed a consistent velocity-strengthening trend. For a velocity jump from V1 to V2, we used VD = (µ2 -µ1)/ln (V2/V1), and found that on average VD = 0.06 and 0.03 for dry and wet talc, respectively, and for slip distances shorter than 1 m. Microstructural analysis of post-shearing wet talc gouge revealed extreme slip localization to a principal-slip-zone of a few microns, and significant shear compaction of 10-30%. In contrast, dry talc gouge exhibited distributed shear in a wide zone and systematic shear dilation (10-50%). We propose slip along weak interlayer talc plates and thermal-pressurization as the possible weakening mechanisms for wet talc. The development of distributed secondary fault network along with substantial grain crushing is responsible for slip-strengthening in dry condition. Fig. 1. Friction maps of talc gouge as function of slip

  15. Experimental and Computational Study of the Shearing Resistance of Polyurea at High Pressures and High Strain Rates

    NASA Astrophysics Data System (ADS)

    Grujicic, Mica; Yavari, R.; Snipes, J. S.; Ramaswami, S.; Jiao, T.; Clifton, R. J.

    2015-02-01

    Mechanical response of polyurea, a nanophase segregated elastomeric co-polymer, is investigated using all-atom, equilibrium, molecular-dynamics methods and tools. Specifically, the effects of high pressure (1-30 GPa) and high strain rate (105-106 s-1) on the shearing resistance of polyurea are examined. Such loading conditions are encountered by polyurea coatings subjected to impact by high-velocity projectiles, shell shrapnel, and improvised explosive device fragments. Computed results are compared with their experimental counterparts obtained using the so-called pressure-shear plate impact experiments. Computed results have also been rationalized in terms of the nanosegregated polyurea microstructure consisting of rod-shaped, discrete, the so-called hard domains embedded in a highly compliant, the so-called soft matrix. By analyzing molecular-level microstructure and its evolution during high-rate deformation and under high imposed pressures, an attempt is made to identify and quantify main phenomena in viscous/inelastic deformation and microstructure-reorganization processes that are most likely responsible for the observed mechanical response of polyurea.

  16. Experimental analysis of the effect of vegetation on flow and bed shear stress distribution in high-curvature bends

    NASA Astrophysics Data System (ADS)

    Termini, Donatella

    2016-12-01

    The cross-sectional circulation, which develops in meandering bends, exerts an important role in velocity and the boundary shear stress redistributions. This paper considers the effect of vegetation on cross-sectional flow and bed shear distribution along a high-curvature bend. The analysis is conducted with the aid of data collected in a large-amplitude meandering flume during a reference experiment without vegetation and an experiment with vegetation on the bed. The results show that the presence of vegetation modifies the curvature-induced flow pattern and the directionality of turbulent structures. In fact, in the presence of vegetation, the turbulent structures tend to develop within and between the vegetated elements. The pattern of cross-sectional flow, modified by the presence of vegetation, affects the bed shear stress distribution along the bend so that the core of the highest value of the bed shear stress does not reach the outer bank.

  17. Lower hybrid current drive in FTU high density shear reversed discharges

    NASA Astrophysics Data System (ADS)

    Tuccillo, A. A.; Barbato, E.; Crisanti, F.; Panaccione, L.; Pericoli, V.; Podda, S.; Cirant, S.; Acitelli, L.; Alladio, F.; Amadeo, P.; Angelini, B.; Apicella, M. L.; Apruzzese, G.; Bertocchi, A.; Borra, M.; Bracco, G.; Bruschi, A.; Buceti, G.; Buratti, P.; Cardinali, A.; Centioli, C.; Cesario, R.; Ciattaglia, S.; Ciotti, M.; Cocilovo, V.; De Angelis, R.; De Marco, F.; Esposito, B.; Frigione, D.; Gabellieri, L.; Gatti, G.; Giovannozzi, E.; Gourlan, C.; Granucci, G.; Grolli, M.; Imparato, A.; Kroegler, H.; Leigheb, M.; Lovisetto, L.; Maddaluno, G.; Maffia, G.; Mancuso, A.; Marinucci, M.; Mazzitelli, G.; Micozzi, P.; Mirizzi, F.; Orsitto, P.; Pacella, D.; Panella, M.; Pieroni, L.; Righetti, G. B.; Romanelli, F.; Santini, F.; Simonetto, A.; Sozzi, C.; Sternini, S.; Tudisco, O.; Valente, F.; Vitale, V.; Vlad, G.; Zanza, V.; Zerbini, M.

    1997-04-01

    Results are reported of the 8 GHz Lower Hybrid experiments on FTU after the installation of the new toroidal limiter. A figure of merit of the Current Drive efficiency ηCD≈0.11ṡ1020 A/Wm2 is estimated for plasma density n¯e=1020 m-3 and no appreciable broadening of the launched frequency is detected. In low density experiments sawteeth are stabilised and m=1 activity is present in the plasma. Shear reversed discharges with large reversal radius, rs/a≈0.5, are obtained at higher density, lower temperature, BT=4 T, qa≈5.5, by off-axis LH CD. The reversed configurations exhibit high central temperature coexisting with regular m=2, n=1 relaxations of large amplitude and are maintained up to LH switch off. At higher magnetic field, B=5.2 T, qa≈7, irregular DTM crashes are present during the whole LH pulse. Confinement time of radiofrequency heated discharges (PLH=0.5÷2ṡPOH) exhibits the same behaviour of FTU ohmic discharges following the ITER89-P scaling. Preliminary results of central 140 GHz Electron Cyclotron Resonant Heating (ECRH) during the plasma current ramp-up, aimed at obtaining shear reversed configurations are also reported.

  18. High Blood Pressure - Multiple Languages: MedlinePlus

    MedlinePlus

    ... ارتفاع ضغط الدم - العربية Bilingual PDF Health Information Translations Bosnian (Bosanski) High Blood Pressure Visoki krvni tlak - Bosanski (Bosnian) Bilingual PDF Health Information Translations Chinese - Simplified (简体中文) High Blood Pressure 高血压 - 简体中文 ( ...

  19. High Blood Pressure in Pregnancy - Multiple Languages: MedlinePlus

    MedlinePlus

    ... الدم أثناء الحمل - العربية Bilingual PDF Health Information Translations Bosnian (Bosanski) High Blood Pressure in Pregnancy Visok ... u trudnoći - Bosanski (Bosnian) Bilingual PDF Health Information Translations Chinese - Simplified (简体中文) High Blood Pressure in Pregnancy ...

  20. High-spin states in {sup 205}Rn: A new shears band structure?

    SciTech Connect

    Novak, J.R.; Beausang, C.W.; Casten, R.F.; Cata Danil, G.; Cooper, J.R.; Juutinen, S.; Kruecken, R.; Liu, B.; Socci, T.; Thomas, J.T.; Zamfir, N.V.; Zhang, J.; Amzal, N.; Greenlees, P.T.; Cata Danil, G.; Zamfir, N.V.; Cocks, J.F.; Greenlees, P.T.; Helariutta, K.; Jones, P.; Julin, R.; Kankaanpaeae, H.; Kettunen, H.; Kuusiniemi, P.; Leino, M.; Muikku, M.; Savelius, A.; Hannachi, F.; Zamfir, N.V.; Zhang, J.; Frauendorf, S.

    1999-06-01

    The high-spin structure of {sup 205}Rn has been investigated for the first time following the {sup 170}Er({sup 40}Ar,5n) and {sup 197}Au({sup 14}N,6n) reactions at beam energies of 183 MeV and 90{endash}110 MeV, respectively, using the Jurosphere and YRAST Ball arrays. Two new cascades have been identified which dominate the high-spin decay. One of these, consisting of ten stretched M1 transitions with unobserved E2 crossover transitions, is interpreted as a shears structure based on the {nu}i{sub 13/2}{sup {minus}1}{circle_times}{pi}i{sub 13/2}{sup 2} (or {nu}i{sub 13/2}{sup {minus}1}{circle_times}{pi}h{sub 9/2}i{sub 13/2}) configuration. {copyright} {ital 1999} {ital The American Physical Society}

  1. Calculation of high frequency ultrasonic signals for shear wave insonification in solid material.

    PubMed

    Schmitz, V; Langenberg, K J; Chakhlov, S

    2004-04-01

    The goal of the theoretical part is to simulate an automatic ultrasonic inspection with contact technique shear wave probes, where the high frequency signals are captured and used to perform a reconstruction based on the synthetic aperture focusing method "SAFT". Therefore the ultrasonic probe, the scanning path and the defects are parameters in a CAD model. The scattering behavior of the defect is calculated by the Kirchhoff approximation in its elastodynamic version. The result of the simulation--the high frequency data--and the result of the SAFT-reconstructions are compared with experimental results on a steel test block with side drilled and flat bottom holes. The model is validated by the experiment. One of the applications of the model is to identify multiple reflections.

  2. High blood pressure in acute ischemic stroke and clinical outcome.

    PubMed

    Manabe, Yasuhiro; Kono, Syoichiro; Tanaka, Tomotaka; Narai, Hisashi; Omori, Nobuhiko

    2009-11-16

    This study aimed to evaluate the prognostic value of acute phase blood pressure in patients with acute ischemic stroke by determining whether or not it contributes to clinical outcome. We studied 515 consecutive patients admitted within the first 48 hours after the onset of ischemic strokes, employing systolic and diastolic blood pressure measurements recorded within 36 hours after admission. High blood pressure was defined when the mean of at least 2 blood pressure measurements was ≥200 mmHg systolic and/or ≥110 mmHg diastolic at 6 to 24 hours after admission or ≥180 mmHg systolic and/or ≥105 mmHg diastolic at 24 to 36 hours after admission. The high blood pressure group was found to include 16% of the patients. Age, sex, diabetes mellitus, hypercholesterolemia, atrial fibrillation, ischemic heart disease, stroke history, carotid artery stenosis, leukoaraiosis, NIH Stroke Scale (NIHSS) on admission and mortality were not significantly correlated with either the high blood pressure or non-high blood pressure group. High blood pressure on admission was significantly associated with a past history of hypertension, kidney disease, the modified Rankin Scale (mRS) on discharge and the length of stay. On logistic regression analysis, with no previous history of hypertension, diabetes mellitus, atrial fibrillation, and kidney disease were independent risk factors associated with the presence of high blood pressure [odds ratio (OR), 1.85 (95% confidence interval (CI): 1.06-3.22), 1.89 (95% CI: 1.11-3.22), and 3.31 (95% CI: 1.36-8.04), respectively]. Multi-organ injury may be presented in acute stroke patients with high blood pressure. Patients with high blood pressure had a poor functional outcome after acute ischemic stroke.

  3. Microfluidic Pipette Tip for High-Purity and High-Throughput Blood Plasma Separation from Whole Blood.

    PubMed

    Kim, Byeongyeon; Oh, Sein; You, Dongwon; Choi, Sungyoung

    2017-02-07

    Blood plasma separation from whole blood is often limited by numerous blood cells which can compromise separation processes and thus deteriorate separation performance such as purity and throughput. To address this challenge, we present a microfluidic pipet tip composed of slant array ridges that enable autonomous blood cell focusing without significant deviation as well as facilitating a high degree of parallelization without compromising separation purity. With these advantages, we achieved high-purity (99.88%) and high-throughput (904.3 μL min(-1)) plasma separation from whole blood. In combination with a smart pipet, we successfully demonstrated rapid, inexpensive, and equipment-free blood plasma preparation for pretransfusion testing.

  4. Vortex Formation in a High Speed Dust Flow with Large Velocity Shear in RF Plasmas

    SciTech Connect

    Iizuka, Satoru; Gohda, Takuma

    2008-09-07

    We have investigated a rotation of a dust cloud disc with strong velocity shear in a radio frequency (RF) plasma. The flow pattern of the dusts was evaluated by the Navier Stokes Equation with shear viscosity due to the Coulomb interactions. We have clarified dynamic behaviors of the dusts and observed generation of micro-vortices around rotational center, when the velocity shear is enhanced.

  5. Rotational and magnetic shear stabilization of magnetohydrodynamic modes and turbulence in DIII-D high performance discharges

    SciTech Connect

    Lao, L.L.; Burrell, K.H.; Casper, T.S.; Chan, V.S.; Chu, M.S.; DeBoo, J.C.; Doyle, E.J.; Durst, R.D.; Forest, C.B.; Greenfield, C.M.; Groebner, R.J.; Hinton, F.L.; Kawano, Y.; Lazarus, E.A.; Lin-Liu, Y.R.; Mauel, M.E.; Meyer, W.H.; Miller, R.L.; Navratil, G.A.; Osborne, T.H.; Peng, Q.; Rettig, C.L.; Rewoldt, G.; Rhodes, T.L.; Rice, B.W.; Schissel, D.P.; Stallard, B.W.; Strait, E.J.; Tang, W.M.; Taylor, T.S.; Turnbull, A.D.; Waltz, R.E.; the DIII-D Team

    1996-05-01

    The confinement and the stability properties of the DIII-D tokamak [{ital Plasma} {ital Physics} {ital and} {ital Controlled} {ital Nuclear} {ital Fusion} {ital Research} 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 159] high-performance discharges are evaluated in terms of rotational and magnetic shear, with an emphasis on the recent experimental results obtained from the negative central magnetic shear (NCS) experiments. In NCS discharges, a core transport barrier is often observed to form inside the NCS region accompanied by a reduction in core fluctuation amplitudes. Increasing negative magnetic shear contributes to the formation of this core transport barrier, but by itself is not sufficient to fully stabilize the toroidal drift mode (trapped-electron-{eta}{sub {ital i}} mode) to explain this formation. Comparison of the Doppler shift shear rate to the growth rate of the {eta}{sub {ital i}} mode suggests that the large core {ital E}{times}{ital B} flow shear can stabilize this mode and broaden the region of reduced core transport. Ideal and resistive stability analysis indicates the performance of NCS discharges with strongly peaked pressure profiles is limited by the resistive interchange mode to low {beta}{sub {ital N}}{le}2.3. This mode is insensitive to the details of the rotational and the magnetic shear profiles. A new class of discharges, which has a broad region of weak or slightly negative magnetic shear (WNS), is described. The WNS discharges have broader pressure profiles and higher {beta} values than the NCS discharges, together with high confinement and high fusion reactivity. {copyright} {ital 1996 American Institute of Physics.}

  6. Structure of the Highly Sheared Tropical Storm Chantal During CAMEX -4

    NASA Technical Reports Server (NTRS)

    Heymsfield, Gerald M.; Halverson, J.; Black, M.; Marks, F.; Zipser, E.; Tian, L.; Belcher, L.; Bui, P.; Im, E.; Starr, David OC. (Technical Monitor)

    2002-01-01

    On 20 August 2001 during the Convection and Moisture Experiment 4 (CAMEX-4) and NOAA Hurricane Field Program (HFP2001), the NASA high-altitude ER-2 and medium-altitude DC-8, and lower-altitude NOAA P3 aircraft conducted a coordinated Quantitative Precipitation Estimation (QPE) mission focused on convection in Tropical Storm Chantal. This storm first became a depression on 14 August, a tropical storm on 17 August, and it maintained maximum winds of about 65-70 mph during 19-20 August with minimum pressures ranging from 1008 mb on 19 August to 1001 mb late on 20 August. The storm was westward moving and was forecasted to intensify and landfall near the Yucatan-Belize border late on 20 August. Chanter failed to intensify and instead exhibited a highly sheared structure with an open low-level circulation and intense convection well to the northeast of this circulation center. The NASA ER-2 and DC-8 aircraft were closely coordinated with the NOAA P3 (NOAA-42). The NASA aircraft collected remote sensing and in situ data sets, while the P3 collected lower level in situ and radar data; both the DC-8 and P3 released 7 and 24 dropsondes, respectively. These aircraft measurements provided a unique opportunity to examine the structure of a sheared system and why it did not develop as forecasted a few days earlier. This paper will describe a preliminary study of the precipitation and wind structure provided by the NASA aircraft within the context of the NOAA P3 measurements.

  7. Enhancement of USM3D Unstructured Flow Solver for High-Speed High-Temperature Shear Flows

    NASA Technical Reports Server (NTRS)

    Pandya, Mohagna J.; Abdol-Hamid, Khaled S.; Frink, Neal T.

    2009-01-01

    Large temperature and pressure fluctuations have a profound effect on turbulence development in transonic and supersonic jets. For high-speed, high-temperature jet flows, standard turbulence models lack the ability to predict the observed mixing rate of a shear layer. Several proposals to address this deficiency have been advanced in the literature to modify the turbulence transport equations in a variety of ways. In the present study, some of the most proven and simple modifications to two-equation turbulence models have been selected and implemented in NASA's USM3D tetrahedral Navier-Stokes flow solver. The modifications include the addition of compressibility correction and pressure dilatation terms in the turbulence transport equations for high-speed flows, and the addition of a simple modification to the Boussinesq's closure model coefficient for high-temperature jets. The efficacy of the extended models is demonstrated by comparison with experimental data for two supersonic axisymmetric jet test cases at design pressure ratio.

  8. Differential roles for endothelial ICAM-1, ICAM-2, and VCAM-1 in shear-resistant T cell arrest, polarization, and directed crawling on blood-brain barrier endothelium.

    PubMed

    Steiner, Oliver; Coisne, Caroline; Cecchelli, Roméo; Boscacci, Rémy; Deutsch, Urban; Engelhardt, Britta; Lyck, Ruth

    2010-10-15

    Endothelial ICAM-1 and ICAM-2 were shown to be essential for T cell diapedesis across the blood-brain barrier (BBB) in vitro under static conditions. Crawling of T cells prior to diapedesis was only recently revealed to occur preferentially against the direction of blood flow on the endothelial surface of inflamed brain microvessels in vivo. Using live cell-imaging techniques, we prove that Th1 memory/effector T cells predominantly crawl against the direction of flow on the surface of BBB endothelium in vitro. Analysis of T cell interaction with wild-type, ICAM-1-deficient, ICAM-2-deficient, or ICAM-1 and ICAM-2 double-deficient primary mouse brain microvascular endothelial cells under physiological flow conditions allowed us to dissect the individual contributions of endothelial ICAM-1, ICAM-2, and VCAM-1 to shear-resistant T cell arrest, polarization, and crawling. Although T cell arrest was mediated by endothelial ICAM-1 and VCAM-1, T cell polarization and crawling were mediated by endothelial ICAM-1 and ICAM-2 but not by endothelial VCAM-1. Therefore, our data delineate a sequential involvement of endothelial ICAM-1 and VCAM-1 in mediating shear-resistant T cell arrest, followed by endothelial ICAM-1 and ICAM-2 in mediating T cell crawling to sites permissive for diapedesis across BBB endothelium.

  9. Motivating Factors and Potential Deterrents to Blood Donation in High School Aged Blood Donors

    PubMed Central

    Phan-Tang, Michelle

    2016-01-01

    Background. To ensure an adequate supply of blood, collection centers must design campaigns that successfully recruit and maintain an active donor pool. Understanding factors that motivate and deter individuals from donating may help centers develop targeted recruitment campaigns. These factors among high school aged blood donors have not yet been fully investigated. Study Design and Methods. A voluntary, anonymous survey was administered to student donors at high school mobile blood drives. The survey instrument asked the students to rate several potential motivating factors in their importance in the decision to donate blood and several potential deterring factors in their future decision whether or not to donate blood again. The survey also asked the students to rate the desirability of several potential incentives. Results. Motivating factors that reflected prosocial, empathetic, and altruistic thoughts and beliefs were rated highly by students. Pain from phlebotomy was most commonly chosen as potential deterrent. Movie tickets and cookies/snacks at the drive were rated as the most attractive incentives. Conclusion. High school aged blood donors are similar to other donor groups in their expressed motives for donating blood. This group may be unique in the factors that deter them from donating and in their preferences for different incentives. PMID:27293985

  10. Earthquake Energy Dissipation in Light of High-Velocity, Slip-Pulse Shear Experiments

    NASA Astrophysics Data System (ADS)

    Reches, Z.; Liao, Z.; Chang, J. C.

    2014-12-01

    We investigated the energy dissipation during earthquakes by analysis of high-velocity shear experiments conducted on room-dry, solid samples of granite, tonalite, and dolomite sheared at slip-velocity of 0.0006-1m/s, and normal stress of 1-11.5MPa. The experimental fault were loaded in one of three modes: (1) Slip-pulse of abrupt, intense acceleration followed by moderate deceleration; (2) Impact by a spinning, heavy flywheel (225 kg); and (3) Constant velocity loading. We refer to energy dissipation in terms of power-density (PD=shear stress*slip-velocity; units of MW/m^2), and Coulomb-energy-density (CED= mechanical energy/normal stress; units of m). We present two aspects: Relative energy dissipation of the above loading modes, and relative energy dissipation between impact experiments and moderate earthquakes. For the first aspect, we used: (i) the lowest friction coefficient of the dynamic weakening; (ii) the work dissipated before reaching the lowest friction; and (iii) the cumulative mechanical work during the complete run. The results show that the slip-pulse/impact modes are energy efficient relatively to the constant-velocity mode as manifested by faster, more intense weakening and 50-90% lower energy dissipation. Thus, for a finite amount of pre-seismic crustal energy, the efficiency of slip-pulse would amplify earthquake instability. For the second aspect, we compare the experimental CED of the impact experiments to the reported breakdown energy (EG) of moderate earthquakes, Mw = 5.6 to 7.2 (Chang et al., 2012). In is commonly assumed that the seismic EG is a small fraction of the total earthquake energy, and as expected in 9 out of 11 examined earthquakes, EG was 0.005 to 0.07 of the experimental CED. We thus speculate that the experimental relation of Coulomb-energy-density to total slip distance, D, CED = 0.605 × D^0.933, is a reasonable estimate of total earthquake energy, a quantity that cannot be determined from seismic data.

  11. High-velocity deformation of Al0.3CoCrFeNi high-entropy alloy: Remarkable resistance to shear failure

    NASA Astrophysics Data System (ADS)

    Li, Z.; Zhao, S.; Diao, H.; Liaw, P. K.; Meyers, M. A.

    2017-02-01

    The mechanical behavior of a single phase (fcc) Al0.3CoCrFeNi high-entropy alloy (HEA) was studied in the low and high strain-rate regimes. The combination of multiple strengthening mechanisms such as solid solution hardening, forest dislocation hardening, as well as mechanical twinning leads to a high work hardening rate, which is significantly larger than that for Al and is retained in the dynamic regime. The resistance to shear localization was studied by dynamically-loading hat-shaped specimens to induce forced shear localization. However, no adiabatic shear band could be observed. It is therefore proposed that the excellent strain hardening ability gives rise to remarkable resistance to shear localization, which makes this material an excellent candidate for penetration protection applications such as armors.

  12. High-velocity deformation of Al0.3CoCrFeNi high-entropy alloy: Remarkable resistance to shear failure.

    PubMed

    Li, Z; Zhao, S; Diao, H; Liaw, P K; Meyers, M A

    2017-02-17

    The mechanical behavior of a single phase (fcc) Al0.3CoCrFeNi high-entropy alloy (HEA) was studied in the low and high strain-rate regimes. The combination of multiple strengthening mechanisms such as solid solution hardening, forest dislocation hardening, as well as mechanical twinning leads to a high work hardening rate, which is significantly larger than that for Al and is retained in the dynamic regime. The resistance to shear localization was studied by dynamically-loading hat-shaped specimens to induce forced shear localization. However, no adiabatic shear band could be observed. It is therefore proposed that the excellent strain hardening ability gives rise to remarkable resistance to shear localization, which makes this material an excellent candidate for penetration protection applications such as armors.

  13. High-velocity deformation of Al0.3CoCrFeNi high-entropy alloy: Remarkable resistance to shear failure

    PubMed Central

    Li, Z.; Zhao, S.; Diao, H.; Liaw, P. K.; Meyers, M. A.

    2017-01-01

    The mechanical behavior of a single phase (fcc) Al0.3CoCrFeNi high-entropy alloy (HEA) was studied in the low and high strain-rate regimes. The combination of multiple strengthening mechanisms such as solid solution hardening, forest dislocation hardening, as well as mechanical twinning leads to a high work hardening rate, which is significantly larger than that for Al and is retained in the dynamic regime. The resistance to shear localization was studied by dynamically-loading hat-shaped specimens to induce forced shear localization. However, no adiabatic shear band could be observed. It is therefore proposed that the excellent strain hardening ability gives rise to remarkable resistance to shear localization, which makes this material an excellent candidate for penetration protection applications such as armors. PMID:28210000

  14. Vorticity Based (External) Intermittency measurements in a High Rθ Single-Stream Shear Layer

    NASA Astrophysics Data System (ADS)

    Foss, John F.; Hellum, Aren

    2006-11-01

    The MSU four-sensor (transverse) vorticity probe has been used to determine the intermittency function (I(t)=0,1) in a single-stream shear layer. The measurements were taken in the self-preserving region (x/θ(0)=484) with R[θ(x)=9x10^4]. The I(t) signal permits conditionally sampled measures of the intermittent turbulence field. The mean intermittency distribution is compared with that previously reported (1) and (2). It is also compared with the distribution created from the use of an advanced surrogate method (3). Distinctive conditionally sampled results include: i) a constant [mean(u'v')]/[σ(u)σ(v)] distribution for the I=1 condition, ii) clear evidence of fluid from both high- and low-speed irrotational streams to the peak location (u/Uo=0.5), and iii) robust dissipation even as -> for large values of [(y-y/2)/θ(x)]. 1. Wygnanski, I. and Fiedler, H. E., (1970). ``The two-dimensional mixing region''. JFM, Vol. 41, pp. 327-361. 2. R.C. Haw, J.K. Foss and J.F. Foss, ``Vorticity Based Intermittency Measurements in a Single Stream Shear Layer'' proc. Second European Turb. Conf. Advance in Turbulence 2, Ed. H.H. Fernholz and H.E. Fiedler Spring Verlag, Berlin (1989). 3. Hedley, T.B., and Keffer, J.F., (1974). ``Turbulent/non-turbulent decisions in an intermittent flow''. JFM, Vol. 64, pp. 625-644

  15. Magnetically applied pressure-shear : a new technique for direct strength measurement at high pressure (final report for LDRD project 117856).

    SciTech Connect

    Lamppa, Derek C.; Haill, Thomas A.; Alexander, C. Scott; Asay, James Russell

    2010-09-01

    A new experimental technique to measure material shear strength at high pressures has been developed for use on magneto-hydrodynamic (MHD) drive pulsed power platforms. By applying an external static magnetic field to the sample region, the MHD drive directly induces a shear stress wave in addition to the usual longitudinal stress wave. Strength is probed by passing this shear wave through a sample material where the transmissible shear stress is limited to the sample strength. The magnitude of the transmitted shear wave is measured via a transverse VISAR system from which the sample strength is determined.

  16. Rapid distortion analysis of high speed homogeneous turbulence subject to periodic shear

    DOE PAGES

    Bertsch, Rebecca L.; Girimaji, Sharath S.

    2015-12-30

    The effect of unsteady shear forcing on small perturbation growth in compressible flow is investigated. In particular, flow-thermodynamic field interaction and the resulting effect on the phase-lag between applied shear and Reynolds stress are examined. Simplified linear analysis of the perturbation pressure equation reveals crucial differences between steady and unsteady shear effects. The analytical findings are validated with numerical simulations of inviscid rapid distortion theory (RDT) equations. In contrast to steadily sheared compressible flows, perturbations in the unsteady (periodic) forcing case do not experience an asymptotic growth phase. Further, the resonance growth phenomenon found in incompressible unsteady shear turbulence ismore » absent in the compressible case. Overall, the stabilizing influence of both unsteadiness and compressibility is compounded leading to suppression of all small perturbations. As a result, the underlying mechanisms are explained.« less

  17. Rapid distortion analysis of high speed homogeneous turbulence subject to periodic shear

    SciTech Connect

    Bertsch, Rebecca L. Girimaji, Sharath S.

    2015-12-15

    The effect of unsteady shear forcing on small perturbation growth in compressible flow is investigated. In particular, flow-thermodynamic field interaction and the resulting effect on the phase-lag between applied shear and Reynolds stress are examined. Simplified linear analysis of the perturbation pressure equation reveals crucial differences between steady and unsteady shear effects. The analytical findings are validated with numerical simulations of inviscid rapid distortion theory (RDT) equations. In contrast to steadily sheared compressible flows, perturbations in the unsteady (periodic) forcing case do not experience an asymptotic growth phase. Further, the resonance growth phenomenon found in incompressible unsteady shear turbulence is absent in the compressible case. Overall, the stabilizing influence of both unsteadiness and compressibility is compounded leading to suppression of all small perturbations. The underlying mechanisms are explained.

  18. Rapid distortion analysis of high speed homogeneous turbulence subject to periodic shear

    SciTech Connect

    Bertsch, Rebecca L.; Girimaji, Sharath S.

    2015-12-30

    The effect of unsteady shear forcing on small perturbation growth in compressible flow is investigated. In particular, flow-thermodynamic field interaction and the resulting effect on the phase-lag between applied shear and Reynolds stress are examined. Simplified linear analysis of the perturbation pressure equation reveals crucial differences between steady and unsteady shear effects. The analytical findings are validated with numerical simulations of inviscid rapid distortion theory (RDT) equations. In contrast to steadily sheared compressible flows, perturbations in the unsteady (periodic) forcing case do not experience an asymptotic growth phase. Further, the resonance growth phenomenon found in incompressible unsteady shear turbulence is absent in the compressible case. Overall, the stabilizing influence of both unsteadiness and compressibility is compounded leading to suppression of all small perturbations. As a result, the underlying mechanisms are explained.

  19. In-Plane Shear Testing of Medium and High Modulus Woven Graphite Fiber Reinforced/Polyimide Composites

    NASA Technical Reports Server (NTRS)

    Gentz, M.; Armentrout, D.; Rupnowski, P.; Kumosa, L.; Shin, E.; Sutter, J. K.; Kumosa, M.

    2004-01-01

    Iosipescu shear tests were performed at room temperature and at 316 C (600 F) o woven composites with either M40J or M60J graphite fibers and PMR-II-50 polyimide resin matrix. The composites were tested as supplied and after thermo-cycling, with the thermo-cycled composites being tested under dry and wet conditions. Acoustic emission (AE) was monitored during the room and high temperature Iosipescu experiments. The shear stresses at the maximum loads and the shear stresses at the significant onset of AE were determined for the composites as function of temperature and conditioning. The combined effects of thermo-cycling and moisture on the strength and stiffness properties of the composites were evaluated. It was determined that the room and high temperature shear stresses at the maximum loads were unaffected by conditioning. However, at room temperature the significant onset of AE was affected by conditioning; the thermal conditioned wet specimens showed the highest shear stress at the onset of AE followed by thermal-conditioned and then as received specimens. Also, at igh temperature the significant onset of AE occurred in some specimens after the maximum load due to the viscoelastoplastic nature of the matrix material.

  20. Late Oligocene high-temperature shear zones in the core of the Higher Himalayan Crystallines (Lower Dolpo, western Nepal)

    NASA Astrophysics Data System (ADS)

    Carosi, R.; Montomoli, C.; Rubatto, D.; Visonã, D.

    2010-08-01

    A high-temperature shear zone, Toijem shear zone, with a top-to-the-SW sense of shear affects the core of the Higher Himalayan Crystallines (HHC) in western Nepal. The shear zone developed during the decompression, in the sillimanite stability field, of rocks that previously underwent relatively high-pressure metamorphism deformed under the kyanite stability field. PT conditions indicate that the footwall experienced higher pressure (˜9 kbar) than the hanging wall (˜7 kbar) and similar temperatures (675°-700°C). Monazite growth constrains the initial activity of the shear zone at 25.8 ± 0.3 Ma, before the onset of the Main Central Thrust zone, whereas the late intrusion of a crosscutting granitic dike at 17 ± 0.2 Ma limits its final activity. Monazites in kyanite-bearing gneisses from the footwall record prograde metamorphism in the HHC from ˜43 to 33 Ma. The new data confirm that exhumation of the HHC started earlier in western Nepal than in other portions of the belt and before the activity of both the South Tibetan Detachment System (STDS) and Main Central Thrust (MCT) zones. As a consequence, western Nepal represents a key area where the channel-flow-driven mechanism of exhumation, supposed to be active from Bhutan to central-eastern Nepal, does terminate. In this area, exhumation of crystalline units occurred by foreland propagation of ductile and, subsequently, brittle deformation.

  1. Frictional properties of DFDP-1 Alpine Fault rocks under hydrothermal conditions and high shear strain

    NASA Astrophysics Data System (ADS)

    Niemeijer, André R.; Boulton, Carolyn; Toy, Virginia; Townend, John; Sutherland, Rupert

    2015-04-01

    The Alpine Fault, New Zealand, is a major plate-bounding fault that accommodates 65-75% of the total relative motion between the Australian and Pacific plates. Paleoseismic evidence of large-displacement surface-rupturing events, as well as an absence of measurable contemporary surface deformation, indicates that the fault slips mostly in quasi-periodic large-magnitude earthquakes (< Mw 8.0). To understand the mechanics of earthquakes, it is important to study the evolution of frictional properties of the fault rocks under conditions representative of the potential hypocentral depth. Here, we present data obtained on drill core samples of rocks that surround the principal slip zone(s) (PSZ) of the Alpine Fault and the PSZ itself. The drill core samples were obtained during phase 1 of the Deep Fault Drilling Project (DFDP-1) in 2011 at relatively shallow depths (down to ~150 m). Simulated fault gouges were sheared under elevated pressure and temperature conditions in a hydrothermal ring shear apparatus. We performed experiments at temperatures of 25, 150, 300, 450 ° C, and 600 oC. Using the shallow geothermal gradient of 63 ° C/km determined in DFDP-1, our highest temperature corresponds to a depth of ~7 km (Sutherland et al. 2012); it would correspond to 10 km depth using a more moderate geotherm of 45 oC/km (Toy et al. 2010). All samples show a transition from velocity-strengthening behavior, i.e. a positive value of (a-b), to velocity-weakening behavior, i.e. a negative value of (a-b) at a temperature of 150 ° C. The transition depends on the absolute value of sliding velocity, with velocity-weakening dominating at lower sliding velocities. At 600 oC, velocity-strengthening dominates at low sliding velocity, whereas the high-velocity steps are all velocity-weakening. Moreover, shear stress depends linearly on effective normal stress at 600 oC, indicating that shearing is essentially frictional and that no transition to ductile (normal stress independent) flow

  2. Yoga Called Good Medicine for High Blood Pressure

    MedlinePlus

    ... fullstory_162446.html Yoga Called Good Medicine for High Blood Pressure People who added this practice to a healthy ... in people who are at risk for developing hypertension, a new study finds. "Patients with pre-hypertension [ ...

  3. High Blood Pressure and Sex: Overcome the Challenges

    MedlinePlus

    ... Treatment for high blood pressure and satisfaction with sex can go hand in hand — if you're ... signs or symptoms. But the impact on your sex life may be obvious. Although sexual activity is ...

  4. Supersonic shear wave elastography of in vivo pig kidney: influence of blood pressure, urinary pressure and tissue anisotropy.

    PubMed

    Gennisson, Jean-Luc; Grenier, Nicolas; Combe, Christian; Tanter, Mickaël

    2012-09-01

    The in vivo influence of renal anisotropy and of urinary and vascular pressure on elasticity values using ultrasonic supersonic shear wave elastography was studied in pigs. Experiments were conducted in agreement with the European Commission guidelines and directives of the French Research Ministry. Six kidneys in three pigs were studied in vivo. Elasticity of renal cortex and medulla was quantified through the shear modulus (μ) by using the supersonic shear imaging technique with an 8 MHz linear ultrasound probe. All measurements were done peroperatively both in the axis and perpendicular to the main axis of pyramids, in normal condition, after progressive increase of urinary pressure, and after renal artery and renal vein ligation. In normal conditions, cortical (C) and medullary (M) elasticity values were always higher when acquisitions were realized with the ultrasound main axis perpendicular to main pyramid axis (C(//): 7.7 ± 2.3 kPa; M(//): 8.7 ± 2.5 kPa) than parallel (C(⊥): 6.9 ± 1.4 kPa; M(⊥): 6.6 ± 2.3 kPa), demonstrating an effect of renal anisotropy. In renal cortex, two bands were separated, inner cortex showing higher elasticity values (IC(⊥): 8.1 ± 1.9 kPa) than outer cortex (OC(⊥): 6.9 ± 1.4 kPa). Renal artery and renal vein ligation induced a decrease and an increase of elasticity respectively. Parenchymal elasticity increased linearly with elevation of urinary pressure. Intrarenal elasticity values vary with tissue anisotropy and, with vascular and urinary pressure levels. These parameters have to be taken into account for interpretation of tissue changes. Separation of outer and inner cortex could be attributable to perfusion differences.

  5. Blood flow regulation and oxygen uptake during high-intensity forearm exercise.

    PubMed

    Nyberg, S K; Berg, O K; Helgerud, J; Wang, E

    2017-04-01

    The vascular strain is very high during heavy handgrip exercise, but the intensity and kinetics to reach peak blood flow, and peak oxygen uptake, are uncertain. We included 9 young (25 ± 2 yr) healthy males to evaluate blood flow and oxygen uptake responses during continuous dynamic handgrip exercise with increasing intensity. Blood flow was measured using Doppler-ultrasound, and venous blood was drawn from a deep forearm vein to determine arteriovenous oxygen difference (a-vO2diff) during 6-min bouts of 60, 80, and 100% of maximal work rate (WRmax), respectively. Blood flow and oxygen uptake increased (P < 0.05) from 60%WRmax [557 ± 177(SD) ml/min; 56.0 ± 21.6 ml/min] to 80%WRmax (679 ± 190 ml/min; 70.6 ± 24.8 ml/min), but no change was seen from 80%WRmax to 100%WRmax Blood velocity (49.5 ± 11.5 to 58.1 ± 11.6 cm/s) and brachial diameter (0.49 ± 0.05 to 0.50 ± 0.06 cm) showed concomitant increases (P < 0.05) with blood flow from 60% to 80%WRmax, whereas no differences were observed in a-vO2diff Shear rate also increased (P < 0.05) from 60% (822 ± 196 s(-1)) to 80% (951 ± 234 s(-1)) of WRmax The mean response time (MRT) was slower (P < 0.05) for blood flow (60%WRmax 50 ± 22 s; 80%WRmax 51 ± 20 s; 100%WRmax 51 ± 23 s) than a-vO2diff (60%WRmax 29 ± 9 s; 80%WRmax 29 ± 5 s; 100%WRmax 20 ± 5 s), but not different from oxygen uptake (60%WRmax 44 ± 25 s; 80%WRmax 43 ± 14 s; 100%WRmax 41 ± 32 s). No differences were observed in MRT for blood flow or oxygen uptake with increased exercise intensity. In conclusion, when approaching maximal intensity, oxygen uptake appeared to reach a critical level at ~80% of WRmax and be regulated by blood flow. This implies that high, but not maximal, exercise intensity may be an optimal stimulus for shear stress-induced small muscle mass training adaptations.NEW & NOTEWORTHY This study evaluated blood flow regulation and oxygen uptake during small muscle mass forearm exercise with high to maximal intensity. Despite

  6. Fluid-loss control for high-permeability rocks in hydraulic fracturing under realistic shear conditions

    SciTech Connect

    Navarrete, R.C.; Mitchell, J.P.

    1995-12-31

    A study is presented on the effectiveness of different combinations of fluid and fluid-loss additives to control fluid loss in high-permeability formations under high shear rates. The impact on matrix damage and proppant-pack damage is also studied. Borate-crosslinked guars, hydroxyethylcellulose (HEC) and a surfactant water-base gravel packing fluid were investigated. The fluid-loss additive considered was silica flour. All fluid-loss tests were run in dynamic fluid-loss cells. To properly test high-permeability cores, new long core dynamic fluid-loss cells were used. The matrix damage caused by the invasion of the fluid was determined using pressure taps along the core. Conductivity tests were also run to determine the damage to the proppant pack. Results show that the effectiveness of particulate fluid-loss additives under dynamic conditions is strongly dependent on the initial leakoff rate, which depends on the pressure gradient across the core, permeability of the core and viscosity of the invading fluid. The use of silica flour helps matrix flowback, and it has a minimal effect on proppant-pack conductivity in clean fluids (e.g., surfactant water-base gravel packing fluid). With the exception of the borate-crosslinked guar with no fluid-loss additive, the variety of fluids used in these tests (with and without silica flour) have a negligible effect on postproduction.

  7. High temperature pseudotachylytes and ductile shear zones in dry rocks from the continental lower crust (Lofoten, Norway)

    NASA Astrophysics Data System (ADS)

    Menegon, Luca; Pennacchioni, Giorgio; Harris, Katherine; Wood, Elliot

    2014-05-01

    Understanding the mechanisms of initiation and growth of shear zones under lower crustal conditions is of fundamental importance when assessing lithosphere rheology and strength. In this study we investigate brittle-ductile shear zones developed under lower crustal conditions in anorthosites from Nusfjord, Lofoten (northern Norway). Steep ductile shear zones trend E-W to ESE-WSW and have a stretching lineation plunging steeply to the SSW or SSE. The shear sense is normal (south block down to the south) as indicated by SC and SC' fabrics and sigmoidal foliations. The shear zone show a mylonitic to ultramylonitic fabric, sharp boundaries to the host anorthosites, and abundant anastomosing dark fine-grained layers along the main foliation. The fine-grained layers localized much of the strain. Relatively lower strain domains within or adjacent to shear zones indicate that the fine dark bands of mylonites represent transposed pseudotachylyte which still locally preserve the pristine structures such as chilled margins, breccia textures with angular clasts of the host rock and injection veins; intersecting veins of pseudotachylyte record multiple stages of seismic slip. The orientation of injection veins and marker offset along the most preserved pseudotachylyte fault veins indicate approximately a sinistral strike slip kinematic during faulting event responsible for the friction-induced melting. These observations indicate that ductile shear zones exploited pre-existing brittle fault zones including a network of pseudotachylytes, and that the fine-grained "ultramylonites" derive from former fine-grained pseudotachylytes. The pseudotachylyte microstructure is dominated by plagioclase microlites dispersed in a groundmass of fine-grained clinopyroxene. Clinopyroxene recrystallizes in the damage zone flanking the pseudotachylytes, indicating high metamorphic grade during pseudotachylyte formation. Small idioblastic or cauliflower garnet are scattered through the matrix and

  8. High blood pressure in older subjects with cognitive impairment.

    PubMed

    Mossello, Enrico; Simoni, David

    2016-06-22

    High blood pressure and cognitive impairment often coexist in old age, but their pathophysiological association is complex. Several longitudinal studies have shown that high blood pressure at midlife is a risk factor for cognitive impairment and dementia, although this association is much less clear in old age. The effect of blood pressure lowering in reducing the risk of dementia is only borderline significant in clinical trials of older subjects, partly due to the insufficient follow-up time. Conversely, dementia onset is associated with a decrease of blood pressure values, probably secondary to neurodegeneration. Prognostic effect of blood pressure values in cognitively impaired older subjects is still unclear, with aggressive blood pressure lowering being potentially harmful in this patients category. Brief cognitive screening, coupled with simple motor assessment, are warranted to identify frail older subjects who need a more cautious approach to antihypertensive treatment. Values obtained with ambulatory blood pressure monitoring seem more useful than clinical ones to predict the outcome of cognitively impaired older subjects. Future studies should identify the most appropriate blood pressure targets in older subjects with cognitive impairment.

  9. Frictional processes in smectite-rich gouges sheared at slow to high slip rates

    NASA Astrophysics Data System (ADS)

    Aretusini, Stefano; Mittempergher, Silvia; Gualtieri, Alessandro; Di Toro, Giulio

    2015-04-01

    The slipping zones of shallow sections of megathrusts and of large landslides are often smectite-rich (e.g., montmorillonite type). Consequently, similar "frictional" processes operating at high slip rates (> 1 m/s) might be responsible of the large slips estimated in megathrust (50 m for the 2011 Tohoku Mw 9.1 earthquake) and measured in large landslides (500 m for the 1963 Vajont slide, Italy). At present, only rotary shear apparatuses can reproduce simultaneously the large slips and slip rates of these events. Noteworthy, the frictional processes proposed so far (thermal and thermochemical pressurization, etc.) remain rather obscure. Here we present preliminary results obtained with the ROtary Shear Apparatus (ROSA) installed at Padua University. Thirty-one experiments were performed at ambient conditions on pure end-members of (1) smectite-rich standard powders (STx-1b: ~68 wt% Ca-montmorillonite, ~30 wt% opal-CT and ~2 wt% quartz), (2) quartz powders (qtz) and (3) on 80:20 = Stx-1b:qtz mixtures. The gouges were sandwiched between two (1) hollow (25/15 mm external/internal diameter) or (2) solid (25 mm in diameter) stainless-steel made cylinders and confined by inner and outer Teflon rings (only outer for solid cylinders). Gouges were sheared at a normal stress of 5 MPa, slip rates V from 300 μm/s to 1.5 m/s and total slip of 3 m. The deformed gouges were investigated with quantitative (Rietveld method with internal standard) X-ray powder diffraction (XRPD) and Scanning Electron Microscopy (SEM). In the smectite-rich standard endmember, (1) for 300 μm/s ≤ V ≤ 0.1 m/s, initial friction coefficient (μi) was 0.6±0.05 whereas the steady-state friction coefficient (μss) was velocity and slip strengthening (μss 0.85±0.05), (2) for 0.1 m/s < V < 0.3 m/s, velocity and slip neutral (μi = μss = 0.62±0.08) and (3) for V > 0.8 m/s, velocity and slip weakening (μi = 0.7±0.1 and μss = 0.25±0.05). In the 80:20 Stx-1b:qtz mixtures, (1) for 300 μm/s ≤ V

  10. Comminution of solids caused by kinetic energy of high shear strain rate, with implications for impact, shock, and shale fracturing.

    PubMed

    Bazant, Zdenek P; Caner, Ferhun C

    2013-11-26

    Although there exists a vast literature on the dynamic comminution or fragmentation of rocks, concrete, metals, and ceramics, none of the known models suffices for macroscopic dynamic finite element analysis. This paper outlines the basic idea of the macroscopic model. Unlike static fracture, in which the driving force is the release of strain energy, here the essential idea is that the driving force of comminution under high-rate compression is the release of the local kinetic energy of shear strain rate. The density of this energy at strain rates >1,000/s is found to exceed the maximum possible strain energy density by orders of magnitude, making the strain energy irrelevant. It is shown that particle size is proportional to the -2/3 power of the shear strain rate and the 2/3 power of the interface fracture energy or interface shear stress, and that the comminution process is macroscopically equivalent to an apparent shear viscosity that is proportional (at constant interface stress) to the -1/3 power of this rate. A dimensionless indicator of the comminution intensity is formulated. The theory was inspired by noting that the local kinetic energy of shear strain rate plays a role analogous to the local kinetic energy of eddies in turbulent flow.

  11. Shear deformation and division of cylindrical walls in free-standing nematic films under high electric fields.

    PubMed

    Tadapatri, Pramod; Krishnamurthy, K S

    2008-10-30

    We report on the behavior of cylindrical walls formed in a substrate-free nematic film of PCH5 under the action of an in-plane ac field. In the film, with vertical molecular alignment at all the limiting surfaces, annular Brochard-Leger walls are induced well above the bend-Freedericksz threshold. They exhibit, at high field strengths, a new type of instability not encountered in sandwich, or any other, cell configuration. It manifests as a shearing of the loop-wall between the opposite free-surfaces. The shear strain is measured as a function of time, field strength, frequency, and temperature. Significantly, the strain is linear in field strength. The origin of shear and its dependence on field variables are explained through an adaptation of the Carr-Helfrich mechanism of charge separation. The sheared wall is stable against pincement up to several times the threshold field, and divides itself into two fragments under a large enough strain. With the shear distortion, linear defects appear in the opposite splay-bend regions, just as Neel lines in Bloch walls of magnetic systems. At very low frequencies, flexoelectric influence on distortion is revealed.

  12. Influence of loading-rate and steel fibers on the shear strength of ultra high performance concrete

    NASA Astrophysics Data System (ADS)

    Bratislav, Lukic; Pascal, Forquin

    2015-09-01

    The paper describes quasi-static and dynamic experimental methods used to examine the confined shear strength of an Ultra High Performance Concrete, with and without the presence of steel fibers in the concrete composition. An experimental setup was created to investigate the concrete shear strength under quasi-static loading regime using a hydraulic press Schenk while dynamic shear strength was characterized by subjecting concrete samples to dynamic loading through a modified Split Hopkinson Pressure Bar. Both methods are based on a Punch Through Shear (PTS) test with a well-instrumented aluminum passive confinement ring that allows measuring the change of radial stress in the shear ligament throughout the test. Firstly, four equally distributed radial notches have been performed in order to deduce the radial stress by suppressing a self-confinement of the sample peripheral part. However, by analyzing the strain gauge data from the confinement ring, it has been noticed that these were apparently insufficient, especially for fiber-reinforced samples, resulting in subsequently practicing eight radial notches through the sample peripheral part. The results obtained from both procedures are reported and discussed.

  13. High blood pressure in pregnancy and coronary calcification.

    PubMed

    Sabour, Siamak; Franx, Arie; Rutten, Annemarieke; Grobbee, Diederick E; Prokop, Mathias; Bartelink, Marie-Louise; van der Schouw, Yvonne T; Bots, Michiel L

    2007-04-01

    A considerable proportion of pregnant women develop high blood pressure in pregnancy. Although it is assumed that this condition subsides after pregnancy, many of these women develop the metabolic syndrome later in life and are at increased risk to develop coronary heart disease. Atherosclerosis development is considered in between risk factors and occurrence of vascular symptoms. We set out to cross-sectionally study the relation of high blood pressure during pregnancy with risk of coronary calcification. The study population was composed 491 healthy postmenopausal women selected from a population-based cohort study. Information on high blood pressure during pregnancy was obtained using a questionnaire. Between 2004 and 2005, the women underwent a multidetector computed tomography (Philips Mx 8000 IDT 16) to assess coronary calcium. The Agatston score, volume, and mass measurements were used to quantify coronary calcium. A total of 30.7% of the women reported to have had high blood pressure in pregnancy. Body mass index (odds ratio [OR]: 1.05; 95% CI: 1.01 to 1.09) and diastolic blood pressure (OR: 1.03; 95% CI: 1.01 to 1.05) were significantly related to a history of high blood pressure in pregnancy. Age was significantly related to increased coronary calcification. Women with a history of high blood pressure during pregnancy had a 57% increased risk of having coronary calcification compared with those women without this condition (OR: 1.57; 95% CI: 1.04 to 2.37). After adjusting for age, the relation did not change (OR: 1.64; 95% CI: 1.07 to 2.53). We concluded that high blood pressure during pregnancy is associated with an increased risk of coronary calcification later in life.

  14. Investigation of high-speed free shear flows using improved pressure-strain correlated Reynolds stress turbulence model

    NASA Technical Reports Server (NTRS)

    Tiwari, S. N.; Lakshmanan, B.

    1993-01-01

    A high-speed shear layer is studied using compressibility corrected Reynolds stress turbulence model which employs newly developed model for pressure-strain correlation. MacCormack explicit prediction-corrector method is used for solving the governing equations and the turbulence transport equations. The stiffness arising due to source terms in the turbulence equations is handled by a semi-implicit numerical technique. Results obtained using the new model show a sharper reduction in growth rate with increasing convective Mach number. Some improvements were also noted in the prediction of the normalized streamwise stress and Reynolds shear stress. The computed results are in good agreement with the experimental data.

  15. High-speed ultrasound imaging in dense suspensions reveals impact-activated solidification due to dynamic shear jamming

    NASA Astrophysics Data System (ADS)

    Han, Endao; Peters, Ivo R.; Jaeger, Heinrich M.

    2016-07-01

    A remarkable property of dense suspensions is that they can transform from liquid-like at rest to solid-like under sudden impact. Previous work showed that this impact-induced solidification involves rapidly moving jamming fronts; however, details of this process have remained unresolved. Here we use high-speed ultrasound imaging to probe non-invasively how the interior of a dense suspension responds to impact. Measuring the speed of sound we demonstrate that the solidification proceeds without a detectable increase in packing fraction, and imaging the evolving flow field we find that the shear intensity is maximized right at the jamming front. Taken together, this provides direct experimental evidence for jamming by shear, rather than densification, as driving the transformation to solid-like behaviour. On the basis of these findings we propose a new model to explain the anisotropy in the propagation speed of the fronts and delineate the onset conditions for dynamic shear jamming in suspensions.

  16. Optimization of curcumin loaded lipid nanoparticles formulated using high shear homogenization (HSH) and ultrasonication (US) methods.

    PubMed

    Puglia, Carmelo; Offerta, Alessia; Rizza, Luisa; Zingale, Giuseppe; Bonina, Francesco; Ronsisvalle, Simone

    2013-10-01

    Lipid nanoparticles (LN) are drug carriers possessing advantages with respect to stability, drug release profile, and biocompatibility. There are several production methods for lipid nanoparticles. Recently high shear homogenization (HSH) and ultrasound (US) techniques have been used to produce these systems in a cheaper and easier way. The objective of the present study was to evaluate the effect of same important instrumental parameters, such as homogenization time (HT) and ultrasonication time (UT), on particle size (MD) and polydispersity index (PDI) of LNs obtained by HSH-US techniques. Curcumin was used as a model drug to be incapsulated in the LNs. LN were prepared by HSH-US technique using tripalmitin (Dynasan 116) and poloxamer 188 (Lutrol F68) as solid lipid and surfactant, respectively. The preparations were characterized and then evaluated using a factorial design study. From the results obtained, LNs produced by HSH-US method were characterized by nanodimension, high homogeneity and encapsulation efficiency. US technology plays an important role in controlling the final dimension of LN dispersion, while longer times of HSH seem mainly to exert a positive effect on the final homogeneity of particle dispersion. Additional studies are in progress to evaluate drug release profile from LNs, for further in vitro/in vivo correlation studies.

  17. Remotely-Controlled Shear for Dismantling Highly Radioactive Tools In Rokkasho Vitrification Facility - 12204

    SciTech Connect

    Mitsui, Takashi; Sawa, Shusuke; Sadaki, Akira; Awano, Toshihiko; Cole, Matt; Miura, Yasuhiko; Ino, Tooru

    2012-07-01

    A high-level liquid waste vitrification facility in the Japanese Rokkasho Reprocessing Plant (RRP) is right in the middle of hot commissioning tests toward starting operation in fall of 2012. In these tests, various tools were applied to address issues occurring in the vitrification cell. Because of these tools' unplanned placement in the cell it has been necessary to dismantle and dispose of them promptly. One of the tools requiring removal is a rod used in the glass melter to improve glass pouring. It is composed of a long rod made of Inconel 601 or 625 and has been highly contaminated. In order to dismantle these tools and to remotely put them in a designated waste basket, a custom electric shear machine was developed. It was installed in a dismantling area of the vitrification cell by remote cranes and manipulators and has been successfully operated. It can be remotely dismantled and placed in a waste basket for interim storage. This is a very good example of a successful deployment of a specialty remote tool in a hot cell environment. This paper also highlights how commissioning and operations are done in the Japanese Rokkasho Reprocessing Plant. (authors)

  18. Identification of highly active flocculant proteins in bovine blood.

    PubMed

    Piazza, George J; Nuñez, Alberto; Garcia, Rafael A

    2012-03-01

    Synthetic polymeric flocculants are used extensively for wastewater remediation, soil stabilization, and reduction in water leakage from unlined canals. Sources of highly active, inexpensive, renewable flocculants are needed to replace synthetic flocculants. High kaolin flocculant activity was documented for bovine blood (BB) and blood plasma with several anticoagulant treatments. BB serum also had high flocculant activity. To address the hypothesis that some blood proteins have strong flocculating activity, the BB proteins were separated by SEC. Then, the major proteins of the flocculant-active fractions were separated by SDS-PAGE. Identity of the major protein components was determined by tryptic digestion and peptide analysis by MALDI TOF MS. The sequence of selected peptides was confirmed using TOF/TOF-MS/MS fragmentation. Hemoglobin dimer (subunits α and β) was identified as the major protein component of the active fraction in BB; its high flocculation activity was confirmed by testing a commercial sample of hemoglobin. In the same manner, three proteins from blood plasma (fibrinogen, γ-globulin, α-2-macroglobulin) were found to be highly active flocculants, but bovine serum albumin, α-globulin, and β-globulin were not flocculants. On a mass basis, hemoglobin, γ-globulin, α-2-macroglobulin were as effective as anionic polyacrylamide (PAM), a widely used synthetic flocculant. The blood proteins acted faster than PAM, and unlike PAM, the blood proteins flocculants did not require calcium salts for their activity.

  19. Comparison of reacting and non-reacting shear layers at a high subsonic Mach number

    NASA Technical Reports Server (NTRS)

    Chang, C. T.; Marek, C. J.; Wey, C.; Jones, R. A.; Smith, M. J.

    1993-01-01

    The flow field in a hydrogen-fueled planar reacting shear layer was measured with an LDV system and is compared with a similar air to air case without combustion. Measurements were made with a speed ratio of 0.34 with the highspeed stream at Mach 0.71. They show that the shear layer with reaction grows faster than one without, and both cases are within the range of data scatter presented by the established database. The coupling between the streamwise and the cross-stream turbulence components inside the shear layer is slow, and reaction only increased it slightly. However, a more organized pattern of the Reynolds stress is present in the reacting shear layer, possibly as a result of larger scale structure formation in the layer associated with heat release.

  20. Timing of initiation of left-lateral shearing along the Ailao Shan-Red River shear zone: microstructural and geochronological constraints from high temperature mylonites in Diancang Shan, SW China

    NASA Astrophysics Data System (ADS)

    Cao, S.; Liu, J.; Leiss, B.; Neubauer, F.; Genser, J.

    2009-04-01

    The high grade metamorphic massifs (e.g. Xuelong Shan, Diancang Shan, Ailao Shan in China and Day Nui Con Voi metamorphic massif in Vietnam) along the Ailao Shan-Red River shear zone in Southwestern China bear much information on the large-scale left-lateral strike-slip shearing in eastern Tibet during Indian-Eurasian plate collision and post-collisional accommodation process in late Oligocene-early Miocene. The metamorphic massifs are narrow zones bounded by brittle faults. Low-grade metamorphic rocks are lying on the west and sedimentary rocks to the east. Rocks in these massifs are partly sheared with widespread occurrence of high temperature mylonites that have subhorizontal stretching lineations. Left-lateral shearing is indicated by mesoscale and microscale shear indicators in the mylonites. Debates exist on the timing of initiation and duration of left-lateral shearing, and mechanism of exhumation of the high grade metamorphic rocks along Ailao Shan Red River shear zone. The Diancang Shan complex, a typical metamorphic massif, is constituted by three units, i.e. a central high strain shear zone, a western low-grade metamorphic volcanic-sedimentary sequence in the Lanping basin, and an eastern superimposed retrograde metamorphic belt. The central high grade metamorphic complex consists of metamorphic rocks of amphibolite facies conditions. High-grade metamorphic mineral assemblages and structural elements indicate a deep level crustal metamorphism and deformation of the rocks. L-tectonites are typical indicators of high-temperature deformation in the highly sheared granitic mylonites. Widespread occurrence of different shear criteria (e.g. sheared veins, sigmoid and delta -porphyroclasts) suggests that these gneisses experienced very intensive high-temperature progressive left-lateral strike-slip shearing. A large synkinematic augen monzogranitic intrusion is recognized in the central belt by the present work. The intrusion has an obvious porphyritic texture

  1. A shear gradient-activated microfluidic device for automated monitoring of whole blood haemostasis and platelet function

    PubMed Central

    Jain, Abhishek; Graveline, Amanda; Waterhouse, Anna; Vernet, Andyna; Flaumenhaft, Robert; Ingber, Donald E.

    2016-01-01

    Accurate assessment of blood haemostasis is essential for the management of patients who use extracorporeal devices, receive anticoagulation therapy or experience coagulopathies. However, current monitoring devices do not measure effects of haemodynamic forces that contribute significantly to platelet function and thrombus formation. Here we describe a microfluidic device that mimics a network of stenosed arteriolar vessels, permitting evaluation of blood clotting within small sample volumes under pathophysiological flow. By applying a clotting time analysis based on a phenomenological mathematical model of thrombus formation, coagulation and platelet function can be accurately measured in vitro in patient blood samples. When the device is integrated into an extracorporeal circuit in pig endotoxemia or heparin therapy models, it produces real-time readouts of alterations in coagulation ex vivo that are more reliable than standard clotting assays. Thus, this disposable device may be useful for personalized diagnostics and for real-time surveillance of antithrombotic therapy in clinic. PMID:26733371

  2. A shear gradient-activated microfluidic device for automated monitoring of whole blood haemostasis and platelet function.

    PubMed

    Jain, Abhishek; Graveline, Amanda; Waterhouse, Anna; Vernet, Andyna; Flaumenhaft, Robert; Ingber, Donald E

    2016-01-06

    Accurate assessment of blood haemostasis is essential for the management of patients who use extracorporeal devices, receive anticoagulation therapy or experience coagulopathies. However, current monitoring devices do not measure effects of haemodynamic forces that contribute significantly to platelet function and thrombus formation. Here we describe a microfluidic device that mimics a network of stenosed arteriolar vessels, permitting evaluation of blood clotting within small sample volumes under pathophysiological flow. By applying a clotting time analysis based on a phenomenological mathematical model of thrombus formation, coagulation and platelet function can be accurately measured in vitro in patient blood samples. When the device is integrated into an extracorporeal circuit in pig endotoxemia or heparin therapy models, it produces real-time readouts of alterations in coagulation ex vivo that are more reliable than standard clotting assays. Thus, this disposable device may be useful for personalized diagnostics and for real-time surveillance of antithrombotic therapy in clinic.

  3. Deformation and Shear Band Development in an Ultrahigh Carbon Steel During High Strain Rate Deformation

    SciTech Connect

    Lesuer, D R; Syn, C K; Sherby, O D

    2004-07-06

    The mechanical response of a pearlitic UHCS-1.3C steel deformed at approximately 4000 s{sup -1} to large strains ({var_epsilon} = -0.9) has been studied. Failure, at both the macroscopic and the microscopic levels has been evaluated, and the ability of the material to absorb energy in compression has been examined. Failure occurred by the development of a shear band. However before failure, extensive buckling of the carbide plates was observed and the UHCS-1.3C material exhibited significant potential for compressive ductility and energy absorption due to the distributed buckling of these plates. Strain localization during adiabatic shear band development resulted in the formation of austenite. Subsequent cooling produced a divorced-eutectoid transformation with associated deformation, which resulted in a microstructure consisting of 50 to 100 nm sized grains. The stress-strain behavior within the shear band has also been determined. The results are used to critically evaluate the maximum shear stress criterion of shear band development. New criteria for the development of shear bands are developed based on a strain energy concept.

  4. Hexagonal-structured ε-NbN: ultra-incompressibility, high shear rigidity, and a possible hard superconducting material.

    PubMed

    Zou, Yongtao; Wang, Xuebing; Chen, Ting; Li, Xuefei; Qi, Xintong; Welch, David; Zhu, Pinwen; Liu, Bingbing; Cui, Tian; Li, Baosheng

    2015-06-01

    Exploring the structural stability and elasticity of hexagonal ε-NbN helps discover correlations among its physical properties for scientific and technological applications. Here, for the first time, we measured the ultra-incompressibility and high shear rigidity of polycrystalline hexagonal ε-NbN using ultrasonic interferometry and in situ X-ray diffraction, complemented with first-principles density-functional theory calculations up to 30 GPa in pressure. Using a finite strain equation of state approach, the elastic bulk and shear moduli, as well as their pressure dependences are derived from the measured velocities and densities, yielding BS0 = 373.3(15) GPa, G0 = 200.5(8) GPa, ∂BS/∂P = 3.81(3) and ∂G/∂P = 1.67(1). The hexagonal ε-NbN possesses a very high bulk modulus, rivaling that of superhard material cBN (B0 = 381.1 GPa). The high shear rigidity is comparable to that for superhard γ-B (G0 = 227.2 GPa). We found that the crystal structure of transition-metal nitrides and the outmost electrons of the corresponding metals may dominate their pressure dependences in bulk and shear moduli. In addition, the elastic moduli, Vickers hardness, Debye temperature, melting temperature and a possible superconductivity of hexagonal ε-NbN all increase with pressures, suggesting its exceptional suitability for applications under extreme conditions.

  5. Concentration polarization of high-density lipoprotein and its relation with shear stress in an in vitro model.

    PubMed

    Meng, Wei; Yu, Fengxu; Chen, Huaiqing; Zhang, Jianmin; Zhang, Eryong; Dian, Ke; Shi, Yingkang

    2009-01-01

    The purpose of this study was to determine the concentration polarization of high-density lipoprotein (HDL) at the surface of the carotid artery under conditions of steady flow and to establish its relationship with shear stress using an in vitro vascular simulation model of carotid bifurcation. Shear stress, HDL concentration at the surface, and the ratio of HDL concentration at the surface to concentration in bulk flow were measured at different locations within the model under high-speed (1.451 m/s) and low-speed (0.559 m/s) flow. HDL showed concentration polarization at the surface of the carotid artery model, particularly in the internal carotid artery sinus. With decreasing flow velocity, the shear stress at the surface also decreased, and HDL concentration polarization increased. The concentration polarization of HDL was negatively and strongly correlated with shear stress at both low- (r = -0.872, P < .001) and high-speed flow (r = -0.592, P = .0018).

  6. Hexagonal-structured epsilon-NbN. Ultra-incompressibility, high shear rigidity, and a possible hard superconducting material

    DOE PAGES

    Zou, Y.; Wang, X.; Chen, T.; ...

    2015-06-01

    Exploring the structural stability and elasticity of hexagonal ε-NbN helps discover correlations among its physical properties for scientific and technological applications. Here, for the first time, we measured the ultra-incompressibility and high shear rigidity of polycrystalline hexagonal ε-NbN using ultrasonic interferometry and in situ X-ray diffraction, complemented with first-principles density-functional theory calculations up to 30 GPa in pressure. Using a finite strain equation of state approach, the elastic bulk and shear moduli, as well as their pressure dependences are derived from the measured velocities and densities, yielding BS0 = 373.3(15) GPa, G0 = 200.5(8) GPa, ∂BS/∂P = 3.81(3) and ∂G/∂Pmore » = 1.67(1). The hexagonal ε-NbN possesses a very high bulk modulus, rivaling that of superhard material cBN (B0 = 381.1 GPa). The high shear rigidity is comparable to that for superhard γ-B (G0 = 227.2 GPa). We found that the crystal structure of transition-metal nitrides and the outmost electrons of the corresponding metals may dominate their pressure dependences in bulk and shear moduli. In addition, the elastic moduli, Vickers hardness, Debye temperature, melting temperature and a possible superconductivity of hexagonal ε-NbN all increase with pressures, suggesting its exceptional suitability for applications under extreme conditions.« less

  7. Hexagonal-structured epsilon-NbN. Ultra-incompressibility, high shear rigidity, and a possible hard superconducting material

    SciTech Connect

    Zou, Y.; Wang, X.; Chen, T.; Li, X.; Qi, X; Welch, D.; Zhu, P.; Liu, B.; Cui, T.; Li, B.

    2015-06-01

    Exploring the structural stability and elasticity of hexagonal ε-NbN helps discover correlations among its physical properties for scientific and technological applications. Here, for the first time, we measured the ultra-incompressibility and high shear rigidity of polycrystalline hexagonal ε-NbN using ultrasonic interferometry and in situ X-ray diffraction, complemented with first-principles density-functional theory calculations up to 30 GPa in pressure. Using a finite strain equation of state approach, the elastic bulk and shear moduli, as well as their pressure dependences are derived from the measured velocities and densities, yielding BS0 = 373.3(15) GPa, G0 = 200.5(8) GPa, ∂BS/∂P = 3.81(3) and ∂G/∂P = 1.67(1). The hexagonal ε-NbN possesses a very high bulk modulus, rivaling that of superhard material cBN (B0 = 381.1 GPa). The high shear rigidity is comparable to that for superhard γ-B (G0 = 227.2 GPa). We found that the crystal structure of transition-metal nitrides and the outmost electrons of the corresponding metals may dominate their pressure dependences in bulk and shear moduli. In addition, the elastic moduli, Vickers hardness, Debye temperature, melting temperature and a possible superconductivity of hexagonal ε-NbN all increase with pressures, suggesting its exceptional suitability for applications under extreme conditions.

  8. Fractal properties of isovelocity surfaces in high Reynolds number laboratory shear flows

    NASA Astrophysics Data System (ADS)

    Praskovsky, Alexander A.; Foss, John F.; Kleis, Stanley J.; Karyakin, Mikhail Yu.

    1993-08-01

    The fractal properties of isovelocity surfaces are studied in three high Reynolds number (Rλ≊2.0×102-3.2×103) laboratory shear flows using the standard box-counting method. The fractal dimension D=-d(log Nr)/d(log r) was estimated within the range of box sizes r from several Kolmogorov scales up to several integral scales (Nr is the number of boxes with size r required to cover the line intersection of an isovelocity surface). The inertial subrange was of particular interest in this investigation. Measurements were carried out for external intermittency factors γ≊0.6-1.0. The data were processed using threshold levels U±2.5u' (U and u' denote mean and rms values of longitudinal velocity). Over the parameters studied, no wide range of constant fractal dimension was found. On the other hand, the accuracy of constant fractal dimension approximation with D≊0.4 over the inertial subranges was shown to be similar to that of the Kolmogorov [Dokl. Akad. Nauk SSSR 30, 301 (1941)] ``two-thirds law.''

  9. Optimization of β-carotene loaded solid lipid nanoparticles preparation using a high shear homogenization technique

    NASA Astrophysics Data System (ADS)

    Triplett, Michael D.; Rathman, James F.

    2009-04-01

    Using statistical experimental design methodologies, the solid lipid nanoparticle design space was found to be more robust than previously shown in literature. Formulation and high shear homogenization process effects on solid lipid nanoparticle size distribution, stability, drug loading, and drug release have been investigated. Experimentation indicated stearic acid as the optimal lipid, sodium taurocholate as the optimal cosurfactant, an optimum lecithin to sodium taurocholate ratio of 3:1, and an inverse relationship between mixing time and speed and nanoparticle size and polydispersity. Having defined the base solid lipid nanoparticle system, β-carotene was incorporated into stearic acid nanoparticles to investigate the effects of introducing a drug into the base solid lipid nanoparticle system. The presence of β-carotene produced a significant effect on the optimal formulation and process conditions, but the design space was found to be robust enough to accommodate the drug. β-Carotene entrapment efficiency averaged 40%. β-Carotene was retained in the nanoparticles for 1 month. As demonstrated herein, solid lipid nanoparticle technology can be sufficiently robust from a design standpoint to become commercially viable.

  10. Particle-turbulence-acoustic interactions in high-speed free-shear flows

    NASA Astrophysics Data System (ADS)

    Shallcross, Gregory; Buchta, David; Capecelatro, Jesse

    2016-11-01

    Experimental studies have shown that the injection of micro-water droplets in turbulent flows can be used to reduce the intensity of near-field pressure fluctuations. In this study, direct numerical simulation (DNS) is used to evaluate the effects of particle-turbulence-acoustic coupling for the first time. Simulations of temporally developing mixing layers are conducted for a range of Mach numbers and mass loadings. Once the turbulence reaches a self-similar state, the air-density shear layer is seeded with a random distribution of mono disperse water-density droplets. For M =0.9 to M =1.75, preliminary results show reductions in the near-field pressure fluctuations for moderate mass loadings, consistent with experimental studies under similar conditions. At high speed, the principle reduction of the normal velocity fluctuations, which increases with particle mass loading, appears to correlate to the reduction of the near-field radiated pressure fluctuations. These findings demonstrate that the DNS reproduces the observed particle-turbulence-acoustic phenomenology, and its complete space-time database can be used to further understand their interactions.

  11. Nitric oxide generation by endothelial cells exposed to shear stress in glass tubes perfused with red blood cell suspensions: role of aggregation.

    PubMed

    Yalcin, Ozlem; Ulker, Pinar; Yavuzer, Ugur; Meiselman, Herbert J; Baskurt, Oguz K

    2008-05-01

    Endothelial function is modulated by wall shear stress acting on the vessel wall, which is determined by fluid velocity and the local viscosity near the vessel wall. Red blood cell (RBC) aggregation may affect the local viscosity by favoring axial migration. The aim of this study was to investigate the role of RBC aggregation, with or without altered plasma viscosity, in the mechanically induced nitric oxide (NO)-related mechanisms of endothelial cells. Human umbilical vein endothelial cells (HUVEC) were cultured on the inner surface of cylindrical glass capillaries that were perfused with RBC suspensions having normal and increased aggregation at a nominal shear stress of 15 dyn/cm(2). RBC aggregation was enhanced by two different approaches: 1) poloxamer-coated RBC suspended in normal, autologous plasma, resulting in enhanced aggregation but unchanged plasma viscosity and 2) normal RBC suspended in autologous plasma containing 0.5% dextran (mol mass 500 kDa), with a similar level of RBC aggregation but higher plasma viscosity. Compared with normal cells in unmodified plasma, perfusion with suspensions of poloxamer-coated RBC in normal plasma resulted in decreased levels of NO metabolites and serine 1177 phosphorylation of endothelial nitric oxide synthase (eNOS). Perfusion with normal RBC in plasma containing dextran resulted in a NO level that remained elevated, whereas only a modest decrease of phosphorylated eNOS level was observed. The results of this study suggest that increases of RBC aggregation tendency affect endothelial cell functions by altering local blood composition, especially if the alterations of RBC aggregation are due to modified cellular properties and not to plasma composition changes.

  12. The Malaria-High Blood Pressure Hypothesis

    PubMed Central

    Smeeth, Liam; Cruickshank, J. Kennedy; Scott, J. Anthony G.

    2016-01-01

    Rationale: Several studies have demonstrated links between infectious diseases and cardiovascular conditions. Malaria and hypertension are widespread in many low- and middle-income countries, but the possible link between them has not been considered. Objective: In this article, we outline the basis for a possible link between malaria and hypertension and discuss how the hypothesis could be confirmed or refuted. Methods and Results: We reviewed published literature on factors associated with hypertension and checked whether any of these were also associated with malaria. We then considered various study designs that could be used to test the hypothesis. Malaria causes low birth weight, malnutrition, and inflammation, all of which are associated with hypertension in high-income countries. The hypothetical link between malaria and hypertension can be tested through the use of ecological, cohort, or Mendelian randomization studies, each of which poses specific challenges. Conclusions: Confirmation of the existence of a causative link with malaria would be a paradigm shift in efforts to prevent and control hypertension and would stimulate wider research on the links between infectious and noncommunicable disease. PMID:27151400

  13. Studies of wall shear and mass transfer in a large scale model of neonatal high-frequency jet ventilation.

    PubMed

    Muller, W J; Gerjarusek, S; Scherer, P W

    1990-01-01

    The problem of endotracheal erosion associated with neonatal high-frequency jet ventilation (HFJV) is investigated through measurement of air velocity profiles in a scaled up model of the system. Fluid mechanical scaling principles are applied in order to construct a model within which velocity profiles are measured by hot-wire anemometry. The effects of two different jet geometries are investigated. Velocity gradients measured near the tracheal wall are used to measure the shear stresses caused by the jet flow on the wall. The Chilton-Colburn analogy between the transport of momentum and mass is applied to investigate tracheal drying caused by the high shear flow. Shear forces are seen to be more than two times higher for jets located near the endotracheal tube wall than for those located axisymmetrically in the center of the tube. Since water vapor fluxes are dependent on these shears, they are also higher for the asymmetric case. Fluxes are shown to be greatly dependent on the temperature and relative humidity of the inspired gas. Water from the tracheal surface may be depleted within one second if inspired gases are inadequately heated and humidified. It is recommended that the design of neonatal HFJV devices include delivery of heated (near body temperature), humidified (as close to 100% humidity as possible) gases through an axisymmetric jet to best avoid the problem of endotracheal erosion.

  14. Effective Blending of Ultrahigh Molecular Weight Polyethylene with High-Density Polyethylene via Solid-State Shear Pulverization (SSSP)

    NASA Astrophysics Data System (ADS)

    Diop, Mirian; Torkelson, John

    2014-03-01

    Compared with conventional polyolefins, ultrahigh molecular weight polyethylene (UHMWPE) possesses outstanding mechanical properties, including impact strength and crack resistance, that make it it highly desirable for applications ranging from body armor to implants. Unfortunately, UHMWPE has an ultrahigh melt viscosity that renders common melt processes ineffective for making products from UHMWPE. Attempts to overcome this problem by blending UHMWPE with polyethylene (PE) by conventional melt mixing have been unsuccessful because of the enormous viscosity mismatch between blend components and have led to large suspensions of UHMWPE particles within a PE matrix. Here, we show the utility of solid-state shear pulverization (SSSP) in achieving effectively and intimately mixed UHMWPE/PE blends. For blends with up to 50 wt% UHMWPE we observe only slight increases in viscosity (η) at high shear rates but major increases in η with increasing UHMWPE content at low shear rates. Using extensional rheology, we confirm the strain hardening behavior of SSSP blends. Additionally, shear rheology and differential scanning calorimetry data indicate that the degree of mixing between UHMWPE and HDPE domains can be increased dramatically with subsequent passes of SSSP and single screw extrusion. Finally, blends prepared via SSSP show dramatic increases in impact strength; e.g., for a 30/70 wt% UHMWPE/HDPE blend, impact strength increases by about 300 % (relative to the parent neat HDPE).

  15. Blood

    MedlinePlus

    ... The liquid part, called plasma, is made of water, salts, and protein. Over half of your blood is plasma. The solid part of your blood contains red blood cells, white blood cells, and platelets. Red ...

  16. Viral metagenomics applied to blood donors and recipients at high risk for blood-borne infections

    PubMed Central

    Sauvage, Virginie; Laperche, Syria; Cheval, Justine; Muth, Erika; Dubois, Myriam; Boizeau, Laure; Hébert, Charles; Lionnet, François; Lefrère, Jean-Jacques; Eloit, Marc

    2016-01-01

    Background Characterisation of human-associated viral communities is essential for epidemiological surveillance and to be able to anticipate new potential threats for blood transfusion safety. In high-resource countries, the risk of blood-borne agent transmission of well-known viruses (HBV, HCV, HIV and HTLV) is currently considered to be under control. However, other unknown or unsuspected viruses may be transmitted to recipients by blood-derived products. To investigate this, the virome of plasma from individuals at high risk for parenterally and sexually transmitted infections was analysed by high throughput sequencing (HTS). Materials and methods Purified nucleic acids from two pools of 50 samples from recipients of multiple transfusions, and three pools containing seven plasma samples from either HBV−, HCV− or HIV-infected blood donors, were submitted to HTS. Results Sequences from resident anelloviruses and HPgV were evidenced in all pools. HBV and HCV sequences were detected in pools containing 3.8×103 IU/mL of HBV-DNA and 1.7×105 IU/mL of HCV-RNA, respectively, whereas no HIV sequence was found in a pool of 150 copies/mL of HIV-RNA. This suggests a lack of sensitivity in HTS performance in detecting low levels of virus. In addition, this study identified other issues, including laboratory contaminants and the uncertainty of taxonomic assignment of short sequence. No sequence suggestive of a new viral species was identified. Discussion This study did not identify any new blood-borne virus in high-risk individuals. However, rare and/or viruses present at very low titre could have escaped our protocol. Our results demonstrate the positive contribution of HTS in the detection of viral sequences in blood donations. PMID:27136432

  17. Highly sensitive optical sensor system for blood leakage detection

    NASA Astrophysics Data System (ADS)

    Ueda, Masahiro; Ishikawa, Kazuhiko; Jie, Chen; Sanae, Mizuno; Touma, Yasunori

    A highly sensitive method for the detection of blood leakage has been developed, and a practical sensor system for blood concentration measurement has been constructed. The present method is based on the attenuation of laser light by blood cells. The effects of the fluctuations of the incident laser light power are eliminated by normalizing the attenuated light intensity by the incident light intensity. A part of the incident laser light is reflected by a beam splitter mounted at the entrance of the test cell, of which the power is measured to provide base data for normalization. The optical path is extended to enhance sensitivity by using a pair of side mirrors. This multi-reflection method is very effective to increase sensitivity; the maximum sensitivity obtained for blood concentration is about 4 X 10 -6 by volume, which is significantly higher than that of the conventional sensors.

  18. Racial differences in hypertension: implications for high blood pressure management.

    PubMed

    Lackland, Daniel T

    2014-08-01

    The racial disparity in hypertension and hypertension-related outcomes has been recognized for decades with African Americans with greater risks than Caucasians. Blood pressure levels have consistently been higher for African Americans with an earlier onset of hypertension. Although awareness and treatment levels of high blood pressure have been similar, racial differences in control rates are evident. The higher blood pressure levels for African Americans are associated with higher rates of stroke, end-stage renal disease and congestive heart failure. The reasons for the racial disparities in elevated blood pressure and hypertension-related outcomes risk remain unclear. However, the implications of the disparities of hypertension for prevention and clinical management are substantial, identifying African American men and women with excel hypertension risk and warranting interventions focused on these differences. In addition, focused research to identify the factors attributed to these disparities in risk burden is an essential need to address the evidence gaps.

  19. Fabrication of shallow microchannels for highly uniform blood smear preparation

    NASA Astrophysics Data System (ADS)

    Raveendran, Jeethu; Stanley, John; Satheesh Babu, T. G.

    2016-09-01

    Polydimethylsiloxane (PDMS) based microfluidic channels for blood cell analysis were fabricated using etched glass as the master for soft lithography. The design consisted of shallow microchannels with uniformly spaced micropillars that aid in the formation of thin blood films (smear) through capillary filling of the microchannels. The concentration of hydrofluoric acid (HF) and the time duration of etching were varied and conditions optimized for fabrication of microstructures of different depths. Morphological analysis revealed the structure and dimension of the microstructures to be highly consistent. It was also noted that the micropillars formed during soft lithography prevented the roof of the PDMS microchannel from collapsing, a common phenomena observed while using shallow microfluidic channels. The fabricated prototype was used for blood cell analysis and the blood smear formed due to capillary flow was found to eliminate the drawbacks associated with manual smear preparation. Thus, a novel cost effective microfluidic device for cell analysis using glass etching was successfully developed and tested.

  20. Leisure-Time Exercise Could Lower Your Risk of High Blood Pressure

    MedlinePlus

    ... exercise could lower your risk of high blood pressure American Heart Association Rapid Access Journal Report September ... Heart Association Download (1.4 MB) High Blood Pressure A high blood pressure reading. copyright American Heart ...

  1. Conductometric study of shear-dependent processes in red cell suspensions. I. Effect of red blood cell aggregate morphology on blood conductance.

    PubMed

    Pribush, A; Meyerstein, D; Meyerstein, N

    2004-01-01

    The conductance and capacitance of flowing and quiescent red blood cell (RBC) suspensions were measured at a frequency of 0.2 MHz. The results demonstrate that the time-dependent changes in the conductance recorded during the aggregation process differ in nature for suspensions of short linear rouleaux, branched aggregates and RBC networks. It is shown that the conductance of RBC suspensions measured during the aggregation and disaggregation processes follows the morphological transformations of the RBC aggregates. Thus, this method enables characterization of the morphology of RBC aggregates formed in whole blood and in suspensions with physiological hematocrits both under flow conditions and in stasis. These results in combination with previous ones suggest that this technique can be used for studies of dynamic RBC aggregation and probably for diagnostic use.

  2. Observation and modeling of mixing-layer development in high-energy-density, blast-wave-driven shear flow

    SciTech Connect

    Di Stefano, C. A. Kuranz, C. C.; Klein, S. R.; Drake, R. P.; Malamud, G.; Henry de Frahan, M. T.; Johnsen, E.; Shimony, A.; Shvarts, D.; Smalyuk, V. A.; Martinez, D.

    2014-05-15

    In this work, we examine the hydrodynamics of high-energy-density (HED) shear flows. Experiments, consisting of two materials of differing density, use the OMEGA-60 laser to drive a blast wave at a pressure of ∼50 Mbar into one of the media, creating a shear flow in the resulting shocked system. The interface between the two materials is Kelvin-Helmholtz unstable, and a mixing layer of growing width develops due to the shear. To theoretically analyze the instability's behavior, we rely on two sources of information. First, the interface spectrum is well-characterized, which allows us to identify how the shock front and the subsequent shear in the post-shock flow interact with the interface. These observations provide direct evidence that vortex merger dominates the evolution of the interface structure. Second, simulations calibrated to the experiment allow us to estimate the time-dependent evolution of the deposition of vorticity at the interface. The overall result is that we are able to choose a hydrodynamic model for the system, and consequently examine how well the flow in this HED system corresponds to a classical hydrodynamic description.

  3. Study of the strength of molybdenum under high pressure using electromagnetically applied compression-shear ramp loading

    NASA Astrophysics Data System (ADS)

    Ding, Jow; Alexander, C. Scott; Asay, James

    2015-06-01

    MAPS (Magnetically Applied Pressure Shear) is a new technique that has the potential to study material strength under mega-bar pressures. By applying a mixed-mode pressure-shear loading and measuring the resultant material responses, the technique provides explicit and direct information on material strength under high pressure. In order to apply sufficient shear traction to the test sample, the driver must have substantial strength. Molybdenum was selected for this reason along with its good electrical conductivity. In this work, the mechanical behavior of molybdenum under MAPS loading was studied. To understand the experimental data, a viscoplasticity model with tension-compression asymmetry was also developed. Through a combination of experimental characterization, model development, and numerical simulation, many unique insights were gained on the inelastic behavior of molybdenum such as the effects of strength on the interplay between longitudinal and shear stresses, potential interaction between the magnetic field and molybdenum strength, and the possible tension-compression asymmetry of the inelastic material response. Sandia National Labs is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Dept. of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  4. EXTREMELY RAPID STAR CLUSTER DISRUPTION IN HIGH-SHEAR CIRCUMNUCLEAR STARBURST RINGS: THE UNUSUAL CASE OF NGC 7742

    SciTech Connect

    De Grijs, Richard; Anders, Peter E-mail: anders@pku.edu.cn

    2012-10-10

    All known mass distributions of recently formed star cluster populations resemble a 'universal' power-law function. Here we assess the impact of the extremely disruptive environment in NGC 7742's circumnuclear starburst ring on the early evolution of the galaxy's high-mass ({approx}10{sup 5}-10{sup 7} M{sub Sun }) star cluster population. Surprisingly, and contrary to expectations, at all ages-including the youngest, {approx}< 15 Myr-the cluster mass functions are robustly and verifiably represented by lognormal distributions that resemble those commonly found only for old, evolved globular cluster systems in the local universe. This suggests that the high-shear conditions in the NGC 7742 starburst ring may significantly speed up dynamical star cluster destruction. This enhanced mass-dependent disruption rate at very young ages might be caused by a combination of the starburst ring's high density and the shear caused by the counterrotating gas disk.

  5. Shearing stability of lubricants

    NASA Technical Reports Server (NTRS)

    Shiba, Y.; Gijyutsu, G.

    1984-01-01

    Shearing stabilities of lubricating oils containing a high mol. wt. polymer as a viscosity index improver were studied by use of ultrasound. The oils were degraded by cavitation and the degradation generally followed first order kinetics with the rate of degradation increasing with the intensity of the ultrasonic irradiation and the cumulative energy applied. The shear stability was mainly affected by the mol. wt. of the polymer additive and could be determined in a short time by mechanical shearing with ultrasound.

  6. An analysis of the contact phase of blood coagulation: effects of shear rate and surface are intertwined.

    PubMed

    Gregory, K; Basmadjian, D

    1994-01-01

    This work analyzes, for the first time, the combined role of blood flow, protein transport and the reaction network of the contact phase up to the "common pathway" of the blood coagulation cascade. The model is comprised of a set of 20 dominant reactions with 11 components. Systems of ODEs reducible to 4 coupled equations describe rigorously the dynamic behavior, while systems of algebraic equations, reducible to a single polynomial equation, model the steady state concentrations of the coagulants. The analysis showed that there is never more than one stable steady state. This is in contrast to the analysis of common pathway that gives rise to multiple concentration states. It also revealed a general robustness of the system to changes in procoagulant concentrations, inhibition rates and most activation rate constants. The system is largely impervious to the level of activated Factor XII, given that a trace (non-zero) level is present. In contrast, the system displays a dual response to flow and surface activity: A change in either of these factors alone can promote, have no effect on, or (in the case of flow) impede the progress of coagulation, depending on the value of the other factor. Their effects must therefore be examined in unison. These results may help resolve contradictory findings attributed to one or the other factor alone.

  7. Dynamic thermal field-induced gradient soft-shear for highly oriented block copolymer thin films.

    PubMed

    Singh, Gurpreet; Yager, Kevin G; Berry, Brian; Kim, Ho-Cheol; Karim, Alamgir

    2012-11-27

    As demand for smaller, more powerful, and energy-efficient devices continues, conventional patterning technologies are pushing up against fundamental limits. Block copolymers (BCPs) are considered prime candidates for a potential solution via directed self-assembly of nanostructures. We introduce here a facile directed self-assembly method to rapidly fabricate unidirectionally aligned BCP nanopatterns at large scale, on rigid or flexible template-free substrates via a thermally induced dynamic gradient soft-shear field. A localized differential thermal expansion at the interface between a BCP film and a confining polydimethylsiloxane (PDMS) layer due to a dynamic thermal field imposes the gradient soft-shear field. PDMS undergoes directional expansion (along the annealing direction) in the heating zone and contracts back in the cooling zone, thus setting up a single cycle of oscillatory shear (maximum lateral shear stress ∼12 × 10(4) Pa) in the system. We successfully apply this process to create unidirectional alignment of BCP thin films over a wide range of thicknesses (nm to μm) and processing speeds (μm/s to mm/s) using both a flat and patterned PDMS layer. Grazing incidence small-angle X-ray scattering measurements show absolutely no sign of isotropic population and reveal ≥99% aligned orientational order with an angular spread Δθ(fwhm) ≤ 5° (full width at half-maximum). This method may pave the way to practical industrial use of hierarchically patterned BCP nanostructures.

  8. Effect of starch 1500 as a binder and disintegrant in lamivudine tablets prepared by high shear wet granulation.

    PubMed

    Rahman, Bytul M; Ibne-Wahed, Mir Imam; Khondkar, Proma; Ahmed, Maruf; Islam, Robiul; Barman, Ranjan K; Islam, M Anwarul

    2008-10-01

    High shear wet granulation is a preferred manufacturing method of tablets. It allowed for rapid production of compressible granulations. The resultant granulation characteristics depend on a combination of formulation properties and processing parameters. Fully pregelatinized starches are currently being used as binders in wet granulated formulations. But due to the gelatinization, much of the disintegration properties are lost. Partially pregelatinized starches (starch 1,500) have a mixture of properties of both native and fully gelatinized starches; made them useful as both a binder and a disintegrant in wet granulated formulations. Starch 1,500 performed as an excellent binder producing a granulation that was compressible and produced lamivudine tablets of improved hardness and friability compared with those prepared with povidone. The formulation of lamivudine tablets with starch 1,500 exceeded the disintegration and dissolution performance of the povidone formulation that utilized a super disintegrant. High shear wet granulation is also well suited for the use of partially pregelatinized starches.

  9. High magnetic shear gain in a liquid sodium stable couette flow experiment A prelude to an alpha - omega dynamo

    SciTech Connect

    Colgate, Stirling; Li, Jui; Finn, John; Pariev, Vladimir; Beckley, Howard; Si, Jiahe; Martinic, Joe; Westpfahl, David; Slutz, James; Westrom, Zeb; Klein, Brianna

    2010-11-08

    The {Omega}-phase of the liquid sodium {alpha}-{Omega} dynamo experiment at NMIMT in cooperation with LANL has successfully demonstrated the production of a high toroidal field, B{sub {phi}} {approx_equal} 8 x B{sub r} from the radial component of an applied poloidal magnetic field, B{sub r}. This enhanced toroidal field is produced by rotational shear in stable Couette Row within liquid sodium at Rm {approx_equal} 120. The small turbulence in stable Taylor-Couette Row is caused by Ekman Row where ({delta}v/v){sup 2} {approx} 10{sup -3}. This high {Omega}-gain in low turbulence flow contrasts with a smaller {Omega}-gain in higher turbulence, Helmholtz-unstable shear flows. This result supports the ansatz that large scale astrophysical magnetic fields are created within semi-coherent large scale motions in which turbulence plays a diffusive role that enables magnetic flux linkage.

  10. Development and application of a volume penalization immersed boundary method for the computation of blood flow and shear stresses in cerebral vessels and aneurysms.

    PubMed

    Mikhal, Julia; Geurts, Bernard J

    2013-12-01

    A volume-penalizing immersed boundary method is presented for the simulation of laminar incompressible flow inside geometrically complex blood vessels in the human brain. We concentrate on cerebral aneurysms and compute flow in curved brain vessels with and without spherical aneurysm cavities attached. We approximate blood as an incompressible Newtonian fluid and simulate the flow with the use of a skew-symmetric finite-volume discretization and explicit time-stepping. A key element of the immersed boundary method is the so-called masking function. This is a binary function with which we identify at any location in the domain whether it is 'solid' or 'fluid', allowing to represent objects immersed in a Cartesian grid. We compare three definitions of the masking function for geometries that are non-aligned with the grid. In each case a 'staircase' representation is used in which a grid cell is either 'solid' or 'fluid'. Reliable findings are obtained with our immersed boundary method, even at fairly coarse meshes with about 16 grid cells across a velocity profile. The validation of the immersed boundary method is provided on the basis of classical Poiseuille flow in a cylindrical pipe. We obtain first order convergence for the velocity and the shear stress, reflecting the fact that in our approach the solid-fluid interface is localized with an accuracy on the order of a grid cell. Simulations for curved vessels and aneurysms are done for different flow regimes, characterized by different values of the Reynolds number (Re). The validation is performed for laminar flow at Re = 250, while the flow in more complex geometries is studied at Re = 100 and Re = 250, as suggested by physiological conditions pertaining to flow of blood in the circle of Willis.

  11. Aging, High Altitude, and Blood Pressure: A Complex Relationship.

    PubMed

    Parati, Gianfranco; Ochoa, Juan Eugenio; Torlasco, Camilla; Salvi, Paolo; Lombardi, Carolina; Bilo, Grzegorz

    2015-06-01

    Parati, Gianfranco, Juan Eugenio Ochoa, Camilla Torlasco, Paolo Salvi, Carolina Lombardi, and Grzegorz Bilo. Aging, high altitude, and blood pressure: A complex relationship. High Alt Biol Med 16:97-109, 2015.--Both aging and high altitude exposure may induce important changes in BP regulation, leading to significant increases in BP levels. By inducing atherosclerotic changes, stiffening of large arteries, renal dysfunction, and arterial baroreflex impairment, advancing age may induce progressive increases in systolic BP levels, promoting development and progression of arterial hypertension. It is also known, although mainly from studies in young or middle-aged subjects, that exposure to high altitude may influence different mechanisms involved in BP regulation (i.e., neural central and reflex control of sympathetic activity), leading to important increases in BP levels. The evidence is less clear, however, on whether and to what extent advancing age may influence the BP response to acute or chronic high altitude exposure. This is a question not only of scientific interest but also of practical relevance given the consistent number of elderly individuals who are exposed for short time periods (either for leisure or work) or live permanently at high altitude, in whom arterial hypertension is frequently observed. This article will review the evidence available on the relationship between aging and blood pressure levels at high altitude, the pathophysiological mechanisms behind this complex association, as well as some questions of practical interest regarding antihypertensive treatment in elderly subjects, and the effects of antihypertensive drugs on blood pressure response during high altitude exposure.

  12. National High Blood Pressure 12-Month Kit. May 1988.

    ERIC Educational Resources Information Center

    National Heart and Lung Inst. (DHHS/NIH), Bethesda, MD. National High Blood Pressure Education Program.

    Part I of this kit provides information for program planners and health professionals on ways to overcome barriers to health care among the medically underserved, promote high blood pressure control through the media and other community channels, and improve adherence to treatment among hypertensive patients. It lists additional resources for…

  13. A Nutrition Curriculum for Families with High Blood Pressure.

    ERIC Educational Resources Information Center

    Farris, Rosanne P.; And Others

    1985-01-01

    A nutrition curriculum for elementary and secondary school students with high blood pressure was implemented as part of a Dietary/Exercise Alteration Program trial. Reduced sodium and energy intake and increased potassium intake were promoted. Materials and methods of the program are described. (Author/DF)

  14. [High blood pressure care: beyond the clinical setting].

    PubMed

    Ordúñez García, Pedro; Pérez Flores, Enrique; Hospedales, James

    2010-10-01

    The recommendations from the seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) were compared with those of a recent article by Aram V. Chobanian, Chairman of the JNC 7. The purpose was to identify the changes that this author proposed and determine how they might affect clinical work, as well as the health services and public health implications. The JNC 7 and the article in question coincide on all essential points, except that the article is more flexible when it comes to the use of diuretics at the start of treatment for high blood pressure. Chronic disease management should take place in health systems with primary care approach, where the epidemiology of such diseases and scientific advances in prevention offer an excellent opportunity for redesigning the health services and making them more effective. High blood pressure, as a public health problem, demands health interventions aimed not only at reducing harm but modifying its etiologic determinants. The challenge is to recognize that an integrated approach to clinical medicine, health services, and public health would offer an attractive opportunity to interrupt and prevent the continuous and costly vicious circle that managing high blood pressure and its complications implies.

  15. A High Energy Density Shock Driven Kelvin-Helmholtz Shear Layer Experiment

    NASA Astrophysics Data System (ADS)

    Hurricane, Omar

    2008-11-01

    In 2002, a high energy density Kelvin-Helmholtz (KH) instability experiment was designed (O.A. Hurricane, High Energy Density Phys., 2008) for the National Ignition Facility (NIF) Early Light experiment. However, the long backlighter delay, required for the experiments success, could not be accommodated by NIF at that time. In early 2008, this experiment proposal was resurrected by our team, the target was fabricated at Livermore with final assembly at the University of Michigan, and then fielded at the Omega laser facility. The data return from the four shots of the experiment series exceeded expectation. In this paper, we describe the theory and simulation behind the experiment design, the unusual target construction, and present the radiographic data from the Omega experiment in raw form and a preliminary analysis of the data. Discussion of the target design theory and simulations focuses on the key role played by baroclinic vorticity production in the functioning of the target and also illuminates the key design parameters. The data shows the complete evolution of large distinct KH eddies, from formation to turbulent break-up. The data appears to graphically confirm a theoretical fluid dynamics conjecture about the existence of supersonic bubbles over the vortical structure [transonic convective Mach numbers (D. Papamoschou and A. Roshko, J. Fluid Mech., 197, 1988)] that support localized shocks (shocklets) not extending into the free-stream^ (P.E. Dimotakis, AIAA 91-1724, Proc. 22^nd Fluid Dyn., Plasma Dyn., & Lasers Conf., 1991). The consequences of these observations on understanding the turbulent transition, growth-rates and mixing in compressible supersonic turbulent shear layers will be discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. A National Laser Users Facility grant also supported this work. Collaborators: J.F. Hansen, E.C. Harding , R

  16. Blood

    MedlinePlus

    ... that die or are lost from the body. White Blood Cells White blood cells (WBCs, and also ... of severe pain. previous continue Diseases of the White Blood Cells Neutropenia (pronounced: new-truh-PEE-nee- ...

  17. High speed optical holography of retinal blood flow

    NASA Astrophysics Data System (ADS)

    Pellizzari, M.; Simonutti, M.; Degardin, J.; Sahel, J.-A.; Fink, M.; Paques, M.; Atlan, M.

    2016-08-01

    We performed non-invasive video imaging of retinal blood flow in a pigmented rat by holographic interferometry of near-infrared laser light backscattered by retinal tissue, beating against an off-axis reference beam sampled at a frame rate of 39 kHz with a high throughput camera. Local Doppler contrasts emerged from the envelopes of short-time Fourier transforms and the phase of autocorrelation functions of holograms rendered by Fresnel transformation. This approach permitted imaging of blood flow in large retinal vessels (30 microns diameter) over 400 by 400 pixels with a spatial resolution of 8 microns and a temporal resolution of 6.5 ms.

  18. Hexagonal-structured ε-NbN: ultra-incompressibility, high shear rigidity, and a possible hard superconducting material

    PubMed Central

    Zou, Yongtao; Wang, Xuebing; Chen, Ting; Li, Xuefei; Qi, Xintong; Welch, David; Zhu, Pinwen; Liu, Bingbing; Cui, Tian; Li, Baosheng

    2015-01-01

    Exploring the structural stability and elasticity of hexagonal ε-NbN helps discover correlations among its physical properties for scientific and technological applications. Here, for the first time, we measured the ultra-incompressibility and high shear rigidity of polycrystalline hexagonal ε-NbN using ultrasonic interferometry and in situ X-ray diffraction, complemented with first-principles density-functional theory calculations up to 30 GPa in pressure. Using a finite strain equation of state approach, the elastic bulk and shear moduli, as well as their pressure dependences are derived from the measured velocities and densities, yielding BS0 = 373.3(15) GPa, G0 = 200.5(8) GPa, ∂BS/∂P = 3.81(3) and ∂G/∂P = 1.67(1). The hexagonal ε-NbN possesses a very high bulk modulus, rivaling that of superhard material cBN (B0 = 381.1 GPa). The high shear rigidity is comparable to that for superhard γ-B (G0 = 227.2 GPa). We found that the crystal structure of transition-metal nitrides and the outmost electrons of the corresponding metals may dominate their pressure dependences in bulk and shear moduli. In addition, the elastic moduli, Vickers hardness, Debye temperature, melting temperature and a possible superconductivity of hexagonal ε-NbN all increase with pressures, suggesting its exceptional suitability for applications under extreme conditions. PMID:26028439

  19. Management of high blood pressure in children and adolescents.

    PubMed

    Kavey, Rae-Ellen W; Daniels, Stephen R; Flynn, Joseph T

    2010-11-01

    Hypertension in childhood is now recognized to be a common and serious problem with a prevalence of 2% to 5%. Large epidemiologic studies have established normative tables for blood pressure beginning in early childhood based on age, gender, and height. Making a diagnosis of hypertension in a child or adolescent identifies an individual at increased risk for early-onset cardiovascular disease who requires specific treatment. Routine blood pressure measurement is recommended at every health care encounter beginning at 3 years of age, but often this is not being accomplished. This measurement is especially important in relation to the obesity epidemic, because approximately one-third of obese children have high blood pressure. Hypertension can be effectively managed with effective lifestyle change and medication when necessary.

  20. High-speed imaging of blood splatter patterns

    SciTech Connect

    McDonald, T.E.; Albright, K.A.; King, N.S.P.; Yates, G.J. ); Levine, G.F. . Bureau of Forensic Services)

    1993-01-01

    The interpretation of blood splatter patterns is an important element in reconstructing the events and circumstances of an accident or crime scene. Unfortunately, the interpretation of patterns and stains formed by blood droplets is not necessarily intuitive and study and analysis are required to arrive at a correct conclusion. A very useful tool in the study of blood splatter patterns is high-speed photography. Scientists at the Los Alamos National Laboratory, Department of Energy (DOE), and Bureau of Forensic Services, State of California, have assembled a high-speed imaging system designed to image blood splatter patterns. The camera employs technology developed by Los Alamos for the underground nuclear testing program and has also been used in a military mine detection program. The camera uses a solid-state CCD sensor operating at approximately 650 frames per second (75 MPixels per second) with a microchannel plate image intensifier that can provide shuttering as short as 5 ns. The images are captured with a laboratory high-speed digitizer and transferred to an IBM compatible PC for display and hard copy output for analysis. The imaging system is described in this paper.

  1. High-speed imaging of blood splatter patterns

    SciTech Connect

    McDonald, T.E.; Albright, K.A.; King, N.S.P.; Yates, G.J.; Levine, G.F.

    1993-05-01

    The interpretation of blood splatter patterns is an important element in reconstructing the events and circumstances of an accident or crime scene. Unfortunately, the interpretation of patterns and stains formed by blood droplets is not necessarily intuitive and study and analysis are required to arrive at a correct conclusion. A very useful tool in the study of blood splatter patterns is high-speed photography. Scientists at the Los Alamos National Laboratory, Department of Energy (DOE), and Bureau of Forensic Services, State of California, have assembled a high-speed imaging system designed to image blood splatter patterns. The camera employs technology developed by Los Alamos for the underground nuclear testing program and has also been used in a military mine detection program. The camera uses a solid-state CCD sensor operating at approximately 650 frames per second (75 MPixels per second) with a microchannel plate image intensifier that can provide shuttering as short as 5 ns. The images are captured with a laboratory high-speed digitizer and transferred to an IBM compatible PC for display and hard copy output for analysis. The imaging system is described in this paper.

  2. High blood pressure and syncope: orthostatic hypotension as a link.

    PubMed

    Rafanelli, Martina; Ungar, Andrea

    2016-06-22

    The prevalence of hypertension increases with the age. Diagnostic criteria are the same as for the young, but in older adults isolated systolic hypertension is more frequent, due to loss of vascular compliance. Blood pressure should be measured on both sides in the seated position, moreover in the supine and upright position to detect orthostatic hypotension. Ambulatory blood pressure monitoring is useful to detect white coat hypertension and masked hypertension, to tailor the treatment and search for diurnal and nocturnal blood pressure pattern abnormalities. Given that frailty can affect the relationship between blood pressure and mortality, the clinician should properly evaluate and monitor physical performance and cognitive status, throughout specific tools, as the Fried Frailty Phenotype, aiming at a systolic blood pressure target between 130 and 150 mmHg. Before starting hypotensive drugs, a careful risk and benefits' evaluation should be performed given the high risk of hypertension and hypotension consequences and the frequent coexistence of orthostatic hypotension, which predisposes to syncope and falls.

  3. Efficacy of flavonoids in the management of high blood pressure.

    PubMed

    Clark, Jaime L; Zahradka, Peter; Taylor, Carla G

    2015-12-01

    Plant compounds such as flavonoids have been reported to exert beneficial effects in cardiovascular disease, including hypertension. Information on the effects of isolated individual flavonoids for management of high blood pressure, however, is more limited. This review is focused on the flavonoids, as isolated outside of the food matrix, from the 5 main subgroups consumed in the Western diet (flavones, flavonols, flavanones, flavan-3-ols, and anthocyanins), along with their effects on hypertension, including the potential mechanisms for regulating blood pressure. Flavonoids from all 5 subgroups have been shown to attenuate a rise in or to reduce blood pressure during several pathological conditions (hypertension, metabolic syndrome, and diabetes mellitus). Flavones, flavonols, flavanones, and flavanols were able to modulate blood pressure by restoring endothelial function, either directly, by affecting nitric oxide levels, or indirectly, through other pathways. Quercetin had the most consistent blood pressure-lowering effect in animal and human studies, irrespective of dose, duration, or disease status. However, further research on the safety and efficacy of the flavonoids is required before any of them can be used by humans, presumably in supplement form, at the doses required for therapeutic benefit.

  4. Frictional Behavior of Amphibolite at Seismic Slip Rates from High-velocity Rotary Shear Experiments

    NASA Astrophysics Data System (ADS)

    Jung, S.; Ree, J.; Hirose, T.; Lee, S.

    2012-12-01

    Gabbroic rocks of oceanic crust transform into amphibolite with depth at subduction zone, and thus frictional property of amphibolite may be important for a better understanding of subduction zone earthquakes. We report preliminary results of high-velocity rotary shear experiments on amphibolite at a seismic slip rate (~1.05 m/s) and normal stresses of 2-15 MPa. Amphibolite from the Imjingang belt of South Korea is composed of hornblende (0.5-1.5 mm) and plagioclase (0.25-0.5 mm) with rare occurrence of quartz. The frictional behavior of the amphibolite is characterized by two phases of unstable slip weakening separated by strengthening, followed by a final weakening with a very low steady-state friction coefficient of 0.07. The average coefficient of the first, second and final peak frictions is 0.48, 0.36 and 0.22, respectively. The fault zone consists of a principal slip zone (PSZ, 200-300 μm thick) with molten material mantled by damage zone (1-3 mm thick). In the damage zone, the color of hornblende grains becomes darker toward the PSZ and thin, black stripes occur along cleavage planes of hornblende in plane-polarized light. Also fracture density of hornblende and plagioclase increases relative to those of wall rock. The PSZ comprises molten material and mineral clasts (25-50 μm) and the clasts tend to concentrate along the center of the PSZ. The surface temperature of the fault zones measured by a radiation thermography during experiments is about 1060°C and the internal temperature of the fault zones could be higher than the measured temperature in view of the melting of hornblende and plagioclase. The frictional behavior of amphibolite is much different from that of gabbro where the overall friction is much higher with the final peak friction of 0.84-1.09 and steady-state friction of ~0.6 (Hirose and Shimamoto, 2005 in Journal of Geophysical Research). This difference may be due to dehydration of hornblende by frictional heating and lower viscosity of

  5. Scalable shear-exfoliation of high-quality phosphorene nanoflakes with reliable electrochemical cycleability in nano batteries

    NASA Astrophysics Data System (ADS)

    Xu, Feng; Ge, Binghui; Chen, Jing; Nathan, Arokia; Xin, Linhuo L.; Ma, Hongyu; Min, Huihua; Zhu, Chongyang; Xia, Weiwei; Li, Zhengrui; Li, Shengli; Yu, Kaihao; Wu, Lijun; Cui, Yiping; Sun, Litao; Zhu, Yimei

    2016-06-01

    Atomically thin black phosphorus (called phosphorene) holds great promise as an alternative to graphene and other two-dimensional transition-metal dichalcogenides as an anode material for lithium-ion batteries (LIBs). However, bulk black phosphorus (BP) suffers from rapid capacity fading and poor rechargeable performance. This work reports for the first time the use of in situ transmission electron microscopy (TEM) to construct nanoscale phosphorene LIBs. This enables direct visualization of the mechanisms underlying capacity fading in thick multilayer phosphorene through real-time capture of delithiation-induced structural decomposition, which serves to reduce electrical conductivity thus causing irreversibility of the lithiated phases. We further demonstrate that few-layer-thick phosphorene successfully circumvents the structural decomposition and holds superior structural restorability, even when subject to multi-cycle lithiation/delithiation processes and concomitant huge volume expansion. This finding provides breakthrough insights into thickness-dependent lithium diffusion kinetics in phosphorene. More importantly, a scalable liquid-phase shear exfoliation route has been developed to produce high-quality ultrathin phosphorene using simple means such as a high-speed shear mixer or even a household kitchen blender with the shear rate threshold of ˜1.25 × 104 s-1. The results reported here will pave the way for industrial-scale applications of rechargeable phosphorene LIBs.

  6. The function of ultra-large von Willebrand factor multimers in high shear flow controlled by ADAMTS13.

    PubMed

    Reininger, A J

    2015-01-01

    The paradigm that platelet aggregation, which contributes to bleeding arrest and also to thrombovascular disorders, initiates after signaling-induced platelet activation has been refuted in past recent years. Platelets can form aggregates independently of activation when soluble von Willebrand factor (VWF) is present and the shear rate exceeds a certain threshold where active A1 domains become exposed in soluble VWF multimers and can bind to platelet glycoprotein Ib. Subsequently - fostering each other - VWF can self-assemble into large nets combining with platelets into large conglomerates, which are entirely reversible when they enter a flow region with shear rates below the threshold. In addition the threshold changes from approximately 20 000 s⁻¹ in wall parallel flow to approximately 10 000 s⁻¹ in stagnation point flow. VWF containing ultra-large multimers - as when just released from endothelial storage sites - has been shown to have the highest binding potential to platelets and to each other, thus facilitating rapid platelet accrual to sites of vessel injury and exposed subendothelial structures, i.e. collagen. The VWF nets as well as the platelet-VWF conglomerates are controlled by the cleaving protease ADAMTS13 within minutes under high shear flow. Therewith the hemostatic potential is delivered where needed and the thrombogenic potential is highly controlled twofold: by flow and enzymatic proteolytic cleavage.

  7. Scalable shear-exfoliation of high-quality phosphorene nanoflakes with reliable electrochemical cycleability in nano batteries

    DOE PAGES

    Xu, Feng; Ge, Binghui; Chen, Jing; ...

    2016-03-30

    Atomically thin black phosphorus (called phosphorene) holds great promise as an alternative to graphene and other two-dimensional transition-metal dichalcogenides as an anode material for lithium-ion batteries (LIBs). But, bulk black phosphorus (BP) suffers from rapid capacity fading and poor rechargeable performance. This work reports for the first time the use of in situ transmission electron microscopy (TEM) to construct nanoscale phosphorene LIBs. This enables direct visualization of the mechanisms underlying capacity fading in thick multilayer phosphorene through real-time capture of delithiation-induced structural decomposition, which serves to reduce electrical conductivity thus causing irreversibility of the lithiated phases. Furthermore, we demonstrate thatmore » few-layer-thick phosphorene successfully circumvents the structural decomposition and holds superior structural restorability, even when subject to multi-cycle lithiation/delithiation processes and concomitant huge volume expansion. This finding provides breakthrough insights into thickness-dependent lithium diffusion kinetics in phosphorene. More importantly, a scalable liquid-phase shear exfoliation route has been developed to produce high-quality ultrathin phosphorene using simple means such as a high-speed shear mixer or even a household kitchen blender with the shear rate threshold of ~1.25 × 104 s-1. Our results reported here will pave the way for industrial-scale applications of rechargeable phosphorene LIBs.« less

  8. Scalable shear-exfoliation of high-quality phosphorene nanoflakes with reliable electrochemical cycleability in nano batteries

    SciTech Connect

    Xu, Feng; Ge, Binghui; Chen, Jing; Nathan, Arokia; Xin, Linhuo L.; Ma, Hongyu; Zhu, Chongyang; Xia, Weiwei; Li, Zhengrui; Li, Shengli; Yu, Kaihao; Wu, Lijun; Cui, Yiping; Sun, Litao; Zhu, Yimei

    2016-03-30

    Atomically thin black phosphorus (called phosphorene) holds great promise as an alternative to graphene and other two-dimensional transition-metal dichalcogenides as an anode material for lithium-ion batteries (LIBs). But, bulk black phosphorus (BP) suffers from rapid capacity fading and poor rechargeable performance. This work reports for the first time the use of in situ transmission electron microscopy (TEM) to construct nanoscale phosphorene LIBs. This enables direct visualization of the mechanisms underlying capacity fading in thick multilayer phosphorene through real-time capture of delithiation-induced structural decomposition, which serves to reduce electrical conductivity thus causing irreversibility of the lithiated phases. Furthermore, we demonstrate that few-layer-thick phosphorene successfully circumvents the structural decomposition and holds superior structural restorability, even when subject to multi-cycle lithiation/delithiation processes and concomitant huge volume expansion. This finding provides breakthrough insights into thickness-dependent lithium diffusion kinetics in phosphorene. More importantly, a scalable liquid-phase shear exfoliation route has been developed to produce high-quality ultrathin phosphorene using simple means such as a high-speed shear mixer or even a household kitchen blender with the shear rate threshold of ~1.25 × 104 s-1. Our results reported here will pave the way for industrial-scale applications of rechargeable phosphorene LIBs.

  9. [Uncontrolled factors of blood pressure in essential hypertension: from "patient's high blood pressure" to "hypertensive patient"].

    PubMed

    Xiong, Xing-Jiang; Wang, Jie

    2014-04-01

    Hypertension is a significant medical and public health issue which puts an enormous burden on health care resources and the community. It is a chronic medical condition in which the systemic arterial blood pressure (BP) is elevated. Serious complications including cardiovascular and cerebrovascular diseases would be preventable if the rise in BP with age could be prevented or diminished. The majority of hypertensive patients require long-term treatment. Oral antihypertensive drugs, lifestyle modification including exercise and dietary modification are milestones for hypertension therapy. However, the control rate of hypertension hasn't reached the expected requirements currently. "Three lows" status quo, just low awareness, low treatment, and low control, are still the major problems confronting modern medicine. Recently, uncontrolled factors of blood pressure are widely concerned, which include insomnia, constipation, mood disorders, exogenous, etc. What's more, the control strategies of hypertension should not only pay close attention to "patient's high blood pressure", but also to "hypertensive patient". Therefore, the treatment of uncontrolled factors of blood pressure plays an important role in hypertensive therapy, which could be further research priorities.

  10. Dynamics of a high viscosity layer in response to shear flow

    NASA Astrophysics Data System (ADS)

    Esmaili, Ehsan; Staples, Anne

    2016-11-01

    We use the Shan-Chen multicomponent Lattice Boltzmann method (LBM) to investigate the time evolution of a thin liquid film (phase I) coating a solid surface under the action of a shearing force imposed by a surrounding fluid (phase II), whose viscosity is significantly lower than that of the film. The goal of this study is to use LBM to capture the contact line motion and interfacial dynamics for an oil-like liquid film which is driven by the upper phase (water) movement as a first approach to modeling thin film dewetting in wave swept marine environments. Lubrication theory is used to validate the results for the driven thin film, and the LBM simulations investigate the effects of the upper phase movement, lower phase thickness, and angle of the imposed shearing force on the thin film profile. This work was supported by the National Science Foundation under Grant Number 1437387.

  11. Cryogenic High-Pressure Shear-Coaxial Jets Exposed to Transverse Acoustic Forcing

    DTIC Science & Technology

    2011-12-13

    Air Force Research Laboratory (AFMC) AFRL/RZSA 10 E. Saturn Blvd. Edwards AFB CA 93524-7680 9. SPONSORING / MONITORING AGENCY NAME(S) AND...pressure antinode ( PAN ). The role of injector exit geometry on the flow response was examined using two shear coaxial injectors with different outer-to...jets to pressure perturbations due to transverse acoustic forcing at a pressure antinode ( PAN ). The role of injector exit geometry on the flow

  12. The elusiveness of population-wide high blood pressure control.

    PubMed

    Whelton, Paul K

    2015-03-18

    High blood pressure (hypertension) is a leading risk factor for cardiovascular disease. It is highly prevalent in the US general population, especially in those who are old, African American, or socially disadvantaged. Prevalence is also high and increasing worldwide. Awareness, treatment, and control of hypertension have improved over time, but there is still considerable room for improvement. The optimal solution to this health challenge varies by country. Several nonpharmacologic and pharmacologic interventions are well proven as effective means to prevent hypertension and improve control rates in those with established hypertension. Better prevention and control of hypertension will yield substantial general population health benefits and remain high priorities in public health.

  13. High shear strain behaviour of synthetic muscovite fault gouges under hydrothermal conditions

    NASA Astrophysics Data System (ADS)

    Van Diggelen, Esther W. E.; De Bresser, Johannes H. P.; Peach, Colin J.; Spiers, Christopher J.

    2010-11-01

    Major continental fault zones typically contain phyllosilicates and have long been recognised as zones of persistent weakness. To establish whether the presence of micas can explain this weakness, we studied the frictional behaviour of simulated muscovite fault gouge by performing rotary shear experiments in the temperature range 20-700 °C, under constant effective normal stresses of 20-100 MPa, a fixed fluid pressure of 100 MPa and at sliding velocities of 0.03-3.7 μm/s, reaching shear strains up to 100. Cataclasis causes substantial grain size reduction up to 600 °C. With increasing strain, both pervasive and localized cataclasis and related compaction result in strain hardening, until steady state is reached. This reflects the progressive development of a continuous network of fine grained, hardening bands. Coarse grained relict lenses between these bands show folded and kinked muscovite grains indicative of ductile mechanisms. Samples deformed at 700 °C show evidence for chemical alteration and partial melting. Since our data suggest that muscovite gouge strengthens with depth and strain, it is questionable whether its presence can contribute to the long-term weakness of major crustal fault zones, unless a substantial decrease in strength occurs at shear strain rates lower than attained in our study.

  14. Microfluidic Thrombosis under Multiple Shear Rates and Antiplatelet Therapy Doses

    PubMed Central

    Ku, David N.; Forest, Craig R.

    2014-01-01

    The mainstay of treatment for thrombosis, the formation of occlusive platelet aggregates that often lead to heart attack and stroke, is antiplatelet therapy. Antiplatelet therapy dosing and resistance are poorly understood, leading to potential incorrect and ineffective dosing. Shear rate is also suspected to play a major role in thrombosis, but instrumentation to measure its influence has been limited by flow conditions, agonist use, and non-systematic and/or non-quantitative studies. In this work we measured occlusion times and thrombus detachment for a range of initial shear rates (500, 1500, 4000, and 10000 s−1) and therapy concentrations (0–2.4 µM for eptifibatide, 0–2 mM for acetyl-salicylic acid (ASA), 3.5–40 Units/L for heparin) using a microfluidic device. We also measured complete blood counts (CBC) and platelet activity using whole blood impedance aggregometry. Effects of shear rate and dose were analyzed using general linear models, logistic regressions, and Cox proportional hazards models. Shear rates have significant effects on thrombosis/dose-response curves for all tested therapies. ASA has little effect on high shear occlusion times, even at very high doses (up to 20 times the recommended dose). Under ASA therapy, thrombi formed at high shear rates were 4 times more prone to detachment compared to those formed under control conditions. Eptifibatide reduced occlusion when controlling for shear rate and its efficacy increased with dose concentration. In contrast, the hazard of occlusion from ASA was several orders of magnitude higher than that of eptifibatide. Our results show similar dose efficacy to our low shear measurements using whole blood aggregometry. This quantitative and statistically validated study of the effects of a wide range of shear rate and antiplatelet therapy doses on occlusive thrombosis contributes to more accurate understanding of thrombosis and to models for optimizing patient treatment. PMID:24404131

  15. Arginine-glycine-aspartic acid- and fibrinogen gamma-chain carboxyterminal peptides inhibit platelet adherence to arterial subendothelium at high wall shear rates. An effect dissociable from interference with adhesive protein binding.

    PubMed Central

    Lawrence, J B; Kramer, W S; McKeown, L P; Williams, S B; Gralnick, H R

    1990-01-01

    Arg-Gly-Asp (RGD)- and fibrinogen gamma-chain carboxyterminal (GQQHHLGGAKQAGDV) peptides inhibit fibrinogen, fibronectin (Fn), vitronectin, and von Willebrand factor (vWF) binding to the platelet glycoprotein IIb-IIIa complex (GP IIb-IIIa). GP IIb-IIIa, vWF, and Fn are essential for normal platelet adherence to subendothelium. We added peptides to normal citrated whole blood before perfusion over human umbilical artery subendothelium and evaluated platelet adherence morphometrically at high (2,600 s-1) and low (800 s-1) wall shear rates. We also examined the effects of the peptides on platelet adhesion to collagen in a static system. At the high wall shear rate, RGDS and GQQHHLGGAKQAGDV caused dose-dependent reduction in the surface coverage with spread and adherent platelets. Amino acid transposition and conservative substitutions of RGD peptides and the AGDV peptide significantly inhibited platelet adherence at 2,600 s-1. By contrast, the modified RGD peptides and AGDV do not affect adhesive protein binding to platelets. None of the native or modified RGD- or fibrinogen gamma-chain peptides significantly inhibited either platelet adherence to subendothelium at 800 s-1 or platelet adhesion to collagen. Our findings demonstrate that peptides that interfere with adhesive protein binding to GP IIb-IIIa inhibit platelet adherence to vascular subendothelium with flowing blood only at high wall shear rates. Platelet adherence to subendothelium at high wall shear rates appears to be mediated by different recognition specificities from those required for fluid-phase adhesive protein binding or static platelet adhesion. PMID:2243140

  16. Vesicle dynamics in shear and capillary flows

    NASA Astrophysics Data System (ADS)

    Noguchi, Hiroshi; Gompper, Gerhard

    2005-11-01

    The deformation of vesicles in flow is studied by a mesoscopic simulation technique, which combines multi-particle collision dynamics for the solvent with a dynamically triangulated surface model for the membrane. Shape transitions are investigated both in simple shear flows and in cylindrical capillary flows. We focus on reduced volumes, where the discocyte shape of fluid vesicles is stable, and the prolate shape is metastable. In simple shear flow at low membrane viscosity, the shear induces a transformation from discocyte to prolate with increasing shear rate, while at high membrane viscosity, the shear induces a transformation from prolate to discocyte, or tumbling motion accompanied by oscillations between these two morphologies. In capillary flow, at small flow velocities the symmetry axis of the discocyte is found not to be oriented perpendicular to the cylinder axis. With increasing flow velocity, a transition to a prolate shape occurs for fluid vesicles, while vesicles with shear-elastic membranes (like red blood cells) transform into a coaxial parachute-like shape.

  17. Effect of high altitude on blood glucose meter performance.

    PubMed

    Fink, Kenneth S; Christensen, Dale B; Ellsworth, Allan

    2002-01-01

    Participation in high-altitude wilderness activities may expose persons to extreme environmental conditions, and for those with diabetes mellitus, euglycemia is important to ensure safe travel. We conducted a field assessment of the precision and accuracy of seven commonly used blood glucose meters while mountaineering on Mount Rainier, located in Washington State (elevation 14,410 ft). At various elevations each climber-subject used the randomly assigned device to measure the glucose level of capillary blood and three different concentrations of standardized control solutions, and a venous sample was also collected for later glucose analysis. Ordinary least squares regression was used to assess the effect of elevation and of other environmental potential covariates on the precision and accuracy of blood glucose meters. Elevation affects glucometer precision (p = 0.08), but becomes less significant (p = 0.21) when adjusted for temperature and relative humidity. The overall effect of elevation was to underestimate glucose levels by approximately 1-2% (unadjusted) for each 1,000 ft gain in elevation. Blood glucose meter accuracy was affected by elevation (p = 0.03), temperature (p < 0.01), and relative humidity (p = 0.04) after adjustment for the other variables. The interaction between elevation and relative humidity had a meaningful but not statistically significant effect on accuracy (p = 0.07). Thus, elevation, temperature, and relative humidity affect blood glucose meter performance, and elevated glucose levels are more greatly underestimated at higher elevations. Further research will help to identify which blood glucose meters are best suited for specific environments.

  18. Review on Joint Shear Strength of Nano-Silver Paste and Its Long-Term High Temperature Reliability

    NASA Astrophysics Data System (ADS)

    Khazaka, R.; Mendizabal, L.; Henry, D.

    2014-07-01

    Soldering has been the main die attach technology for several decades. Recently, in order to meet the high temperature electronic requirements (high temperature-operating SiC and GaN devices) as well as the health recommendations (replacing the toxic lead present in common solder alloys with lead-free alternatives), several new attach technologies have been developed. Among others, the sintering of nano-silver particles seems to be one of the most interesting choices, and has been extensively investigated during recent years. The emergence of this technology is mainly due to the desired high electrical and high thermal conductivities of the sintered joint, its low elastic modulus offering a good thermo-mechanical reliability, its low process temperature, and its high operating temperature. In this paper, a review of parameters affecting the initial shear strength of the sintered silver joint will be summarized as well as the high temperature long-term reliability issues. The sintering cycle (bonding pressure, bonding temperature, sintering dwell time, heating rate, and the sintering atmosphere), the joint size, and the attached materials properties (nature, roughness), are found to closely affect the initially measured shear strength of the joint. The long-term reliability of the joint has been shown to suffer initially from three phenomena: the silver electro-migration, the decrease of shear strength under harsh thermo-mechanical stresses, and the swelling of the sintered layer. While the latter phenomenon is observed during the storage at temperatures above 350°C, the electro-migration and thermo-mechanical stresses can influence the package reliability at temperatures as low as 250°C. However, some suggested precautions during the module fabrication can lead to the minimizing of the effects of these phenomena and the achievem a more reliable joint.

  19. Accuracy of Handheld Blood Glucose Meters at High Altitude

    PubMed Central

    de Vries, Suzanna T.; Fokkert, Marion J.; Dikkeschei, Bert D.; Rienks, Rienk; Bilo, Karin M.; Bilo, Henk J. G.

    2010-01-01

    Background Due to increasing numbers of people with diabetes taking part in extreme sports (e.g., high-altitude trekking), reliable handheld blood glucose meters (BGMs) are necessary. Accurate blood glucose measurement under extreme conditions is paramount for safe recreation at altitude. Prior studies reported bias in blood glucose measurements using different BGMs at high altitude. We hypothesized that glucose-oxidase based BGMs are more influenced by the lower atmospheric oxygen pressure at altitude than glucose dehydrogenase based BGMs. Methodology/Principal Findings Glucose measurements at simulated altitude of nine BGMs (six glucose dehydrogenase and three glucose oxidase BGMs) were compared to glucose measurement on a similar BGM at sea level and to a laboratory glucose reference method. Venous blood samples of four different glucose levels were used. Moreover, two glucose oxidase and two glucose dehydrogenase based BGMs were evaluated at different altitudes on Mount Kilimanjaro. Accuracy criteria were set at a bias <15% from reference glucose (when >6.5 mmol/L) and <1 mmol/L from reference glucose (when <6.5 mmol/L). No significant difference was observed between measurements at simulated altitude and sea level for either glucose oxidase based BGMs or glucose dehydrogenase based BGMs as a group phenomenon. Two GDH based BGMs did not meet set performance criteria. Most BGMs are generally overestimating true glucose concentration at high altitude. Conclusion At simulated high altitude all tested BGMs, including glucose oxidase based BGMs, did not show influence of low atmospheric oxygen pressure. All BGMs, except for two GDH based BGMs, performed within predefined criteria. At true high altitude one GDH based BGM had best precision and accuracy. PMID:21103399

  20. High-speed ultrasound imaging in dense suspensions reveals impact-activated solidification due to dynamic shear jamming

    PubMed Central

    Han, Endao; Peters, Ivo R.; Jaeger, Heinrich M.

    2016-01-01

    A remarkable property of dense suspensions is that they can transform from liquid-like at rest to solid-like under sudden impact. Previous work showed that this impact-induced solidification involves rapidly moving jamming fronts; however, details of this process have remained unresolved. Here we use high-speed ultrasound imaging to probe non-invasively how the interior of a dense suspension responds to impact. Measuring the speed of sound we demonstrate that the solidification proceeds without a detectable increase in packing fraction, and imaging the evolving flow field we find that the shear intensity is maximized right at the jamming front. Taken together, this provides direct experimental evidence for jamming by shear, rather than densification, as driving the transformation to solid-like behaviour. On the basis of these findings we propose a new model to explain the anisotropy in the propagation speed of the fronts and delineate the onset conditions for dynamic shear jamming in suspensions. PMID:27436628

  1. Anomalous Shear Properties of Coesite at High Pressure and Implications for the X-discontinuity in the Earth's Upper Mantle

    NASA Astrophysics Data System (ADS)

    Chen, T.; Gwanmesia, G. D.; Wang, X.; Zou, Y.; Liebermann, R. C.; Michaut, C.; Li, B.

    2013-12-01

    The X-discontinuity (250-350km) in the upper mantle has been revealed under some continental or oceanic plates by a number of seismic studies, at which depth the P and S wave velocities increase by about 2%. One possible cause for this discontinuity, as suggested in previous studies, is the coesite-stishovite phase transition. Although the compressional behavior of coesite was determined by a previous single crystal study, its shear properties at high pressure have not yet been assessed experimentally. In this study, we conducted ultrasonic interferometry measurements on polycrystalline coesite up to 12.5GPa at ambient temperature. The sample was hot-pressed at 6.5GPa and 920°C and confirmed to be single phased by X-ray diffraction. We find that while the P wave velocities of coesite continuously increase with pressure, the S wave velocities exhibit a monotonic decrease to the peak pressure of the current experiment followed by a reversible recovery upon release of pressure. By fitting to finite strain equations, the elastic bulk and shear moduli and their pressure derivatives are precisely determined using the data collected during compression and decompression. Comparing with stishovite, coesite has lower pressure derivatives for both the bulk and shear moduli that is especially pronounced for the shear modulus. The volume-pressure relations obtained in the current study are in excellent agreement with those from single crystal compression of coesite. These results indicate that the velocity and impedance contrasts of the coesite-stishovite transition will increase with pressure, and its seismic signatures will be greatly enhanced at the depths of the X-discontinuity.

  2. [The oral cavity condition in patients with high blood pressure].

    PubMed

    Rosiak, Joanna; Kubić-Filiks, Beata; Szymańska, Jolanta

    2015-10-01

    The incidence of high blood pressure in adults is estimated at ca. 30-40% of the general population. Both hypertension disease and hypertensive drugs affect the condition of the patients' oral cavity. A review of the current literature shows that disorders most frequently found in the masticatory organ of patients with hypertension include: xerostomia, changes in salivary glands, gum hypertrophy, lichenoid lesions, taste disorders, and paraesthesias. The authors emphasize that patients with high blood pressure, along with the treatment of the underlying disease, should receive prophylactic and therapeutic dental care. This would enable reduction and/or elimination of unpleasant complaints, and also help prevent the emergence of secondary disorders in the patients' oral cavity as a result of hypertension pharmacotherapy.

  3. Shear Thinning of Noncolloidal Suspensions

    NASA Astrophysics Data System (ADS)

    Vázquez-Quesada, Adolfo; Tanner, Roger I.; Ellero, Marco

    2016-09-01

    Shear thinning—a reduction in suspension viscosity with increasing shear rates—is understood to arise in colloidal systems from a decrease in the relative contribution of entropic forces. The shear-thinning phenomenon has also been often reported in experiments with noncolloidal systems at high volume fractions. However its origin is an open theoretical question and the behavior is difficult to reproduce in numerical simulations where shear thickening is typically observed instead. In this letter we propose a non-Newtonian model of interparticle lubrication forces to explain shear thinning in noncolloidal suspensions. We show that hidden shear-thinning effects of the suspending medium, which occur at shear rates orders of magnitude larger than the range investigated experimentally, lead to significant shear thinning of the overall suspension at much smaller shear rates. At high particle volume fractions the local shear rates experienced by the fluid situated in the narrow gaps between particles are much larger than the averaged shear rate of the whole suspension. This allows the suspending medium to probe its high-shear non-Newtonian regime and it means that the matrix fluid rheology must be considered over a wide range of shear rates.

  4. Structure of the Highly Sheared Tropical Storm Chantal During CAMEX-4

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Tropical Storm Chantal during August 2001 was a storm that failed to intensify over the few days prior to making landfall on the Yucatan Peninsula. An observational study of Tropical Storm Chantal is presented using a diverse data set including remote and in situ measurements from the NASA ER-2 and DC-8 and the NOAA WP-3D N42RF aircraft and satellite data. The authors discuss the storm structure from the larger scale environment down to the convective scale. Large vertical shear (850-200 hPa shear magnitude range 8-15 m/s) plays a very important role in preventing Chantal from intensifying. The storm had a poorly defined vortex that only extended up to 5-6 km altitude, and an adjacent intense convective region that comprised an MCS. The entire low-level circulation center was in the rain-free western side of the storm, about 80 km to the west-southwest of the MCS. The MCS appears to have been primarily the result of intense convergence between large-scale, low-level easterly flow with embedded downdrafts, and the cyclonic vortex flow. The individual cells in the MCS such as Cell 2 during the period of the observations, were extremely intense with reflectivity core diameters of 10 km and peak updrafts exceeding 20 m/s. Associated with this MCS were two broad subsidence (warm) regions both of which had portions over the vortex. The first layer near 700 hPa was directly above the vortex and covered most of it. The second layer near 500 hPa was along the forward and right flanks of Cell 2 and undercut the anvil divergence region above. There was not much resemblance of these subsidence layers to typical upper level warm cores in hurricanes that are necessary to support strong surface winds and a low central pressure. The observations are compared to previous studies of weakly sheared storms and modeling studies of shear effects and intensification. Additional information is included in the original extended abstract.

  5. Shear wave transmissivity measurement by color Doppler shear wave imaging

    NASA Astrophysics Data System (ADS)

    Yamakoshi, Yoshiki; Yamazaki, Mayuko; Kasahara, Toshihiro; Sunaguchi, Naoki; Yuminaka, Yasushi

    2016-07-01

    Shear wave elastography is a useful method for evaluating tissue stiffness. We have proposed a novel shear wave imaging method (color Doppler shear wave imaging: CD SWI), which utilizes a signal processing unit in ultrasound color flow imaging in order to detect the shear wave wavefront in real time. Shear wave velocity is adopted to characterize tissue stiffness; however, it is difficult to measure tissue stiffness with high spatial resolution because of the artifact produced by shear wave diffraction. Spatial average processing in the image reconstruction method also degrades the spatial resolution. In this paper, we propose a novel measurement method for the shear wave transmissivity of a tissue boundary. Shear wave wavefront maps are acquired by changing the displacement amplitude of the shear wave and the transmissivity of the shear wave, which gives the difference in shear wave velocity between two mediums separated by the boundary, is measured from the ratio of two threshold voltages required to form the shear wave wavefronts in the two mediums. From this method, a high-resolution shear wave amplitude imaging method that reconstructs a tissue boundary is proposed.

  6. Formation and Stability of Shear-Induced Shish-Kebab Structure in Highly Entangled Melts of UHMWPE/HDPE Blends

    SciTech Connect

    Keum,J.; Zuo, F.; Hsiao, B.

    2008-01-01

    The formation and stability of a shear-induced shish-kebab structure was investigated by in situ rheo-SAXS (small-angle X-ray scattering) and -WAXD (wide-angle X-ray diffraction) measurements of highly entangled polyethylene melts based on two polymer blends, containing small fractions (2 and 5 wt %) of ultra-high molecular weight polyethylene (UHMWPE) and high-density polyethylene (HDPE). Immediately after shear, the combined SAXS and WAXD results at 142 C confirmed the sole formation of shish without kebabs, indicating the interplay between the topological deformation of highly entangled UHMWPE chains and the extended-chain crystallization of stretched segments without the participation of coiled segments. The presence of HDPE chains influenced the entanglement of UHMWPE but they were not involved in the shish-kebab formation at the initial stage of crystallization. The final shish lengths in both blends were nearly identical at the same strain (e = 500), even though the UHMWPE concentration was different. When the temperature was cooled to 134 C, both sheared blends exhibited the kebab formation, following the diffusion-controlled growth process. Although the total kebab nucleation was higher in the 5/95 wt % UHMWPE/HDPE blend, the kebab density per shish was higher in the 2/98 wt % UHMWPE/HDPE blend. The thermal stability of the shish-kebab structure was also investigated by constrained melting. Both blends exhibited identical melting behavior of kebabs but different melting behavior of shish that is governed by the entanglement restraints of the stretched-chain network.

  7. Enzymatic hydrolysis combined with mechanical shearing and high-pressure homogenization for nanoscale cellulose fibrils and strong gels.

    PubMed

    Pääkkö, M; Ankerfors, M; Kosonen, H; Nykänen, A; Ahola, S; Osterberg, M; Ruokolainen, J; Laine, J; Larsson, P T; Ikkala, O; Lindström, T

    2007-06-01

    Toward exploiting the attractive mechanical properties of cellulose I nanoelements, a novel route is demonstrated, which combines enzymatic hydrolysis and mechanical shearing. Previously, an aggressive acid hydrolysis and sonication of cellulose I containing fibers was shown to lead to a network of weakly hydrogen-bonded rodlike cellulose elements typically with a low aspect ratio. On the other hand, high mechanical shearing resulted in longer and entangled nanoscale cellulose elements leading to stronger networks and gels. Nevertheless, a widespread use of the latter concept has been hindered because of lack of feasible methods of preparation, suggesting a combination of mild hydrolysis and shearing to disintegrate cellulose I containing fibers into high aspect ratio cellulose I nanoscale elements. In this work, mild enzymatic hydrolysis has been introduced and combined with mechanical shearing and a high-pressure homogenization, leading to a controlled fibrillation down to nanoscale and a network of long and highly entangled cellulose I elements. The resulting strong aqueous gels exhibit more than 5 orders of magnitude tunable storage modulus G' upon changing the concentration. Cryotransmission electron microscopy, atomic force microscopy, and cross-polarization/magic-angle spinning (CP/MAS) 13C NMR suggest that the cellulose I structural elements obtained are dominated by two fractions, one with lateral dimension of 5-6 nm and one with lateral dimensions of about 10-20 nm. The thicker diameter regions may act as the junction zones for the networks. The resulting material will herein be referred to as MFC (microfibrillated cellulose). Dynamical rheology showed that the aqueous suspensions behaved as gels in the whole investigated concentration range 0.125-5.9% w/w, G' ranging from 1.5 Pa to 105 Pa. The maximum G' was high, about 2 orders of magnitude larger than typically observed for the corresponding nonentangled low aspect ratio cellulose I gels, and G' scales

  8. Effect of High Temperature on Mineralogy, Microstructure, Shear Stiffness and Tensile Strength of Two Australian Mudstones

    NASA Astrophysics Data System (ADS)

    Liu, Xianfeng; Zhang, Chonglei; Yuan, Shengyang; Fityus, Stephen; Sloan, Scott William; Buzzi, Olivier

    2016-09-01

    This study aims at providing quality experimental data on the effects of temperature on tensile strength and small strain shear stiffness of two Australian mudstones. The objective is to provide multiscale data in view of developing a numerical model that can capture and simulate the complex multiphysics of underground coal fire propagation. Two mudstones were collected in the Hunter Valley, close to a known underground coal fire, referred to as "Burning Mountain." The rock specimens were heated to a range of temperatures (maximum of 900 °C) for 24 h, and the materials were comprehensively characterized by X-ray diffraction, thermal gravimetric analyses, optical microscopy and scanning electron microscopy. In addition, mercury intrusion porosimetry was used in order to track changes in pore size distribution with temperature. Investigations at microscale were complemented by testing at the macroscale. In particular, the paper focuses on the evolution of the tensile strength and small strain shear stiffness as the materials are subjected to heating treatment. Results show that both parameters evolve in a non-monotonic manner with temperature. The observed mechanical responses are fully explained and corroborated by microstructural observations.

  9. High sensitivity micro-elastometry: applications in blood coagulopathy.

    PubMed

    Wu, Gongting; Krebs, Charles R; Lin, Feng-Chang; Wolberg, Alisa S; Oldenburg, Amy L

    2013-10-01

    Highly sensitive methods for the assessment of clot structure can aid in our understanding of coagulation disorders and their risk factors. Rapid and simple clot diagnostic systems are also needed for directing treatment in a broad spectrum of cardiovascular diseases. Here we demonstrate a method for micro-elastometry, named resonant acoustic spectroscopy with optical vibrometry (RASOV), which measures the clot elastic modulus (CEM) from the intrinsic resonant frequency of a clot inside a microwell. We observed a high correlation between the CEM of human blood measured by RASOV and a commercial thromboelastograph (TEG), (R = 0.966). Unlike TEG, RASOV requires only 150 μL of sample and offers improved repeatability. Since CEM is known to primarily depend upon fibrin content and network structure, we investigated the CEM of purified clots formed with varying amounts of fibrinogen and thrombin. We found that RASOV was sensitive to changes of fibrinogen content (0.5-6 mg/mL), as well as to the amount of fibrinogen converted to fibrin during clot formation. We then simulated plasma hypercoagulability via hyperfibrinogenemia by spiking whole blood to 150 and 200% of normal fibrinogen levels, and subsequently found that RASOV could detect hyperfibrinogenemia-induced changes in CEM and distinguish these conditions from normal blood.

  10. High Sensitivity Micro-Elastometry: Applications in Blood Coagulopathy

    PubMed Central

    Wu, Gongting; Krebs, Charles R.; Lin, Feng-Chang; Wolberg, Alisa S.; Oldenburg, Amy L.

    2013-01-01

    Highly sensitive methods for the assessment of clot structure can aid in our understanding of coagulation disorders and their risk factors. Rapid and simple clot diagnostic systems are also needed for directing treatment in a broad spectrum of cardiovascular diseases. Here we demonstrate a method for micro-elastometry, named Resonant Acoustic Spectroscopy with Optical Vibrometry (RASOV), which measures the clot elastic modulus (CEM) from the intrinsic resonant frequency of a clot inside a microwell. We observed a high correlation between the CEM of human blood measured by RASOV and a commercial Thromboelastograph (TEG), (R=0.966). Unlike TEG, RASOV requires only 150 μL of sample and offers improved repeatability. Since CEM is known to primarily depend upon fibrin content and network structure, we investigated the CEM of purified clots formed with varying amounts of fibrinogen and thrombin. We found that RASOV was sensitive to changes of fibrinogen content (0.5–6 mg/mL), as well as to the amount of fibrinogen converted to fibrin during clot formation. We then simulated plasma hypercoagulability via hyperfibrinogenemia by spiking whole blood to 150% and 200% of normal fibrinogen levels, and subsequently found that RASOV could detect hyperfibrinogenemia-induced changes in CEM and distinguish these conditions from normal blood. PMID:23649979

  11. Momentum-transport studies in high E x B shear plasmas in the National Spherical Torus Experiment.

    PubMed

    Solomon, W M; Kaye, S M; Bell, R E; Leblanc, B P; Menard, J E; Rewoldt, G; Wang, W; Levinton, F M; Yuh, H; Sabbagh, S A

    2008-08-08

    Experiments have been conducted at the National Sperical Torus Experiment (NSTX) to study both steady state and perturbative momentum transport. These studies are unique in their parameter space under investigation, where the low aspect ratio of NSTX results in rapid plasma rotation with ExB shearing rates high enough to suppress low-k turbulence. In some cases, the ratio of momentum to energy confinement time is found to exceed five. Momentum pinch velocities of order 10-40 m/s are inferred from the measured angular momentum flux evolution after nonresonant magnetic perturbations are applied to brake the plasma.

  12. A comparative study of several compressibility corrections to turbulence models applied to high-speed shear layers

    NASA Technical Reports Server (NTRS)

    Viegas, John R.; Rubesin, Morris W.

    1991-01-01

    Several recently published compressibility corrections to the standard k-epsilon turbulence model are used with the Navier-Stokes equations to compute the mixing region of a large variety of high speed flows. These corrections, specifically developed to address the weakness of higher order turbulence models to accurately predict the spread rate of compressible free shear flows, are applied to two stream flows of the same gas mixing under a large variety of free stream conditions. Results are presented for two types of flows: unconfined streams with either (1) matched total temperatures and static pressures, or (2) matched static temperatures and pressures, and a confined stream.

  13. On the Derivation of a High-Velocity Tail from the Boltzmann-Fokker-Planck Equation for Shear Flow

    NASA Astrophysics Data System (ADS)

    Acedo, L.; Santos, A.; Bobylev, A. V.

    2002-12-01

    Uniform shear flow is a paradigmatic example of a nonequilibrium fluid state exhibiting non-Newtonian behavior. It is characterized by uniform density and temperature and a linear velocity profile U x ( y)= ay, where a is the constant shear rate. In the case of a rarefied gas, all the relevant physical information is represented by the one-particle velocity distribution function f( r, v)= f( V), with V≡ v- U( r), which satisfies the standard nonlinear integro-differential Boltzmann equation. We have studied this state for a two-dimensional gas of Maxwell molecules with a collision rate K( θ)∝lim ∈→0 ∈ -2 δ( θ- ∈), where θ is the scattering angle, in which case the nonlinear Boltzmann collision operator reduces to a Fokker-Planck operator. We have found analytically that for shear rates larger than a certain threshold value a th≃0.3520 ν (where ν is an average collision frequency and a th/ ν is the real root of the cubic equation 64 x 3+16 x 2+12 x-9=0) the velocity distribution function exhibits an algebraic high-velocity tail of the form f( V; a)˜| V|-4- σ( a) Φ( ϕ; a), where ϕ≡tan V y / V x and the angular distribution function Φ( ϕ; a) is the solution of a modified Mathieu equation. The enforcement of the periodicity condition Φ( ϕ; a)= Φ( ϕ+ π; a) allows one to obtain the exponent σ( a) as a function of the shear rate. It diverges when a→ a th and tends to a minimum value σ min≃1.252 in the limit a→∞. As a consequence of this power-law decay for a> a th, all the velocity moments of a degree equal to or larger than 2+ σ( a) are divergent. In the high-velocity domain the velocity distribution is highly anisotropic, with the angular distribution sharply concentrated around a preferred orientation angle ~ϕ( a), which rotates from ~ϕ=- π/4,3 π/4 when a→ a th to ~ϕ=0, π in the limit a→∞.

  14. The effect of plasma beta on high-n ballooning stability at low magnetic shear

    NASA Astrophysics Data System (ADS)

    Connor, J. W.; Ham, C. J.; Hastie, R. J.

    2016-08-01

    An explanation of the observed improvement in H-mode pedestal characteristics with increasing core plasma pressure or poloidal beta, {β\\text{pol}} , as observed in MAST and JET, is sought in terms of the impact of the Shafranov shift, {{Δ }\\prime} , on ideal ballooning MHD stability. To illustrate this succinctly, a self-consistent treatment of the low magnetic shear region of the ‘s-α ’ stability diagram is presented using the large aspect ratio Shafranov equilibrium, but enhancing both α and {{Δ }\\prime} so that they compete with each other. The method of averaging, valid at low s, is used to simplify the calculation and demonstrates how α , {{Δ }\\prime} , plasma shaping and ‘average favourable curvature’ all contribute to stability.

  15. High altitude hypoxia and blood pressure dysregulation in adult chickens.

    PubMed

    Herrera, E A; Salinas, C E; Blanco, C E; Villena, M; Giussani, D A

    2013-02-01

    Although it is accepted that impaired placental perfusion in complicated pregnancy can slow fetal growth and programme an increased risk of cardiovascular dysfunction at adulthood, the relative contribution of reductions in fetal nutrition and in fetal oxygenation as the triggering stimulus remains unclear. By combining high altitude (HA) with the chick embryo model, we have previously isolated the direct effects of HA hypoxia on embryonic growth and cardiovascular development before hatching. This study isolated the effects of developmental hypoxia on cardiovascular function measured in vivo in conscious adult male and female chickens. Chick embryos were incubated, hatched and raised at sea level (SL, nine males and nine females) or incubated, hatched and raised at HA (seven males and seven females). At 6 months of age, vascular catheters were inserted under general anaesthesia. Five days later, basal blood gas status, basal cardiovascular function and cardiac baroreflex responses were investigated. HA chickens had significantly lower basal arterial PO2 and haemoglobin saturation, and significantly higher haematocrit than SL chickens, independent of the sex of the animal. HA chickens had significantly lower arterial blood pressure than SL chickens, independent of the sex of the animal. Although the gain of the arterial baroreflex was decreased in HA relative to SL male chickens, it was increased in HA relative to SL female chickens. We show that development at HA lowers basal arterial blood pressure and alters baroreflex sensitivity in a sex-dependent manner at adulthood.

  16. Impact comminution of solids due to local kinetic energy of high shear strain rate: II-Microplane model and verification

    NASA Astrophysics Data System (ADS)

    Caner, Ferhun C.; Bažant, Zdeněk P.

    2014-03-01

    The new theory presented in the preceding paper, which models the dynamic comminution of concrete due to very high shear strain rate, is now compared to recent test data on the penetration of projectiles through concrete walls of different thicknesses, ranging from 127 to 254 mm. These data are analyzed by an explicit finite element code using the new microplane constitutive model M7 for concrete, which was previously shown to provide the most realistic description of the quasi-static uni-, bi- and tri-axial test data with complex loading path and unloading. Model M7 incorporates the quasi-static strain rate effects due viscoelasticity and to the rate of cohesive crack debonding based on activation energy of bond ruptures, which are expected to extend to very high rates. Here model M7 is further enhanced by apparent viscosity capturing the energy dissipation due to the strain-rate effect of comminution. The maximum shear strain rates in the computations are of the order of 105 s-1. The simulations document that, within the inevitable uncertainties, the measured exit velocities of the projectiles can be matched quite satisfactorily and the observed shapes of the entry and exit craters can be reproduced correctly.

  17. Scale-up studies on high shear wet granulation process from mini-scale to commercial scale.

    PubMed

    Aikawa, Shouhei; Fujita, Naomi; Myojo, Hidetoshi; Hayashi, Takashi; Tanino, Tadatsugu

    2008-10-01

    A newly developed mini-scale high shear granulator was used for scale-up study of wet granulation process from 0.2 to 200 L scales. Under various operation conditions and granulation bowl sizes, powder mixture composed of anhydrous caffeine, D-mannitol, dibasic calcium phosphate, pregelatinized starch and corn starch was granulated by adding water. The granules were tabletted, and disintegration time and hardness of the tablets were evaluated to seek correlations of granulation conditions and tablet properties. As the granulation proceeded, disintegration time was prolonged and hardness decreased. When granulation processes were operated under the condition that agitator tip speed was the same, similar relationship between granulation time and tablet properties, such as disintegration time and hardness, between 0.2 L and 11 L scales were observed. Likewise, between 11 L and 200 L scales similar relationship was observed when operated under the condition that the force to the granulation mass was the same. From the above results, the mini-scale high shear granulator should be useful tool to predict operation conditions of large-scale granulation from its mini-scale operation conditions, where similar tablet properties should be obtained.

  18. Shear-horizontal surface acoustic wave phononic device with high density filling material for ultra-low power sensing applications

    SciTech Connect

    Richardson, M.; Bhethanabotla, V. R.; Sankaranarayanan, S. K. R. S.

    2014-06-23

    Finite element simulations of a phononic shear-horizontal surface acoustic wave (SAW) sensor based on ST 90°-X Quartz reveal a dramatic reduction in power consumption. The phononic sensor is realized by artificially structuring the delay path to form an acoustic meta-material comprised of a periodic microcavity array incorporating high-density materials such as tantalum or tungsten. Constructive interference of the scattered and secondary reflected waves at every microcavity interface leads to acoustic energy confinement in the high-density regions translating into reduced power loss. Tantalum filled cavities show the best performance while tungsten inclusions create a phononic bandgap. Based on our simulation results, SAW devices with tantalum filled microcavities were fabricated and shown to significantly decrease insertion loss. Our findings offer encouraging prospects for designing low power, highly sensitive portable biosensors.

  19. Double Sided Irradiation for Laser-assisted Shearing of Ultra High Strength Steels with Process Integrated Hardening

    NASA Astrophysics Data System (ADS)

    Brecher, Christian; Emonts, Michael; Eckert, Markus; Weinbach, Matthias

    Most small or medium sized parts produced in mass production are made by shearing and forming of sheet metal. This technology is cost effective, but the achievable quality and geometrical complexity are limited when working high and highest strength steel. Based on the requirements for widening the process limits of conventional sheet metal working the Fraunhofer IPT has developed the laser-assisted sheet metal working technology. With this enhancement it is possible to produce parts made of high and highest strength steel with outstanding quality, high complexity and low tool wear. Additionally laser hardening has been implemented to adjust the mechanical properties of metal parts within the process. Currently the process is limited to lower sheet thicknesses (<2 mm) to maintain short cycle times. To enable this process for larger geometries and higher sheet thicknesses the Fraunhofer IPT developed a system for double sided laser-assisted sheet metal working within progressive dies.

  20. High red blood cell nitric oxide synthase activation is not associated with improved vascular function and red blood cell deformability in sickle cell anaemia.

    PubMed

    Grau, Marijke; Mozar, Anaïs; Charlot, Keyne; Lamarre, Yann; Weyel, Linda; Suhr, Frank; Collins, Bianca; Jumet, Stéphane; Hardy-Dessources, Marie-Dominique; Romana, Marc; Lemonne, Nathalie; Etienne-Julan, Maryse; Antoine-Jonville, Sophie; Bloch, Wilhelm; Connes, Philippe

    2015-03-01

    Human red blood cells (RBC) express an active and functional endothelial-like nitric oxide (NO) synthase (RBC-NOS). We report studies on RBC-NOS activity in sickle cell anaemia (SCA), a genetic disease characterized by decreased RBC deformability and vascular dysfunction. Total RBC-NOS content was not significantly different in SCA patients compared to healthy controls; however, using phosphorylated RBC-NOS-Ser(1177) as a marker, RBC-NOS activation was higher in SCA patients as a consequence of the greater activation of Akt (phosphorylated Akt-Ser(473) ). The higher RBC-NOS activation in SCA led to higher levels of S-nitrosylated α- and β-spectrins, and greater RBC nitrite and nitrotyrosine levels compared to healthy controls. Plasma nitrite content was not different between the two groups. Laser Doppler flowmetric experiments demonstrated blunted microcirculatory NO-dependent response under hyperthermia in SCA patients. RBC deformability, measured by ektacytometry, was reduced in SCA in contrast to healthy individuals, and pre-shearing RBC in vitro did not improve deformability despite an increase of RBC-NOS activation. RBC-NOS activation is high in freshly drawn blood from SCA patients, resulting in high amounts of NO produced by RBC. However, this does not result in improved RBC deformability and vascular function: higher RBC-NO is not sufficient to counterbalance the enhanced oxidative stress in SCA.

  1. Clinical significance of home blood pressure measurements for the prevention and management of high blood pressure.

    PubMed

    Imai, Yutaka; Hosaka, Miki; Elnagar, Noha; Satoh, Michihiro

    2014-01-01

    1. Ambulatory blood pressure (ABP) monitoring (M) provides BP information at many points on any particular day during unrestricted routine daily activities, whereas home blood pressure (HBP) monitoring provides a lot of BP information obtained under fixed times and conditions over a long period of time, thus mean values of HBP provide high reproducibility, and thus an overall superiority compared with ABP.  2. HBP is at least equally or better able than ABP to predict hypertensive target organ damage and prognosis of cardiovascular disease.  3. HBPM allows for ongoing disease monitoring by patients, improves adherence to antihypertensive treatment, and can provide health-care providers with timely clinical data and direct and immediate feedback regarding diagnosis and treatment of hypertension.  4. HBPM provides BP information in relation to time; that is, BP in the morning, in the evening and at night during sleep, and it is an essential tool for the diagnosis of white-coat and masked hypertension.  5. HBPM yields minimal alerting affects and no or minimal placebo effect, and can therefore distinguish small, but significant, serial changes in BP. It is thus the most practical method for monitoring BP in the day-to-day management of hypertension. 6. The superiority of HBPM over ABPM and clinic BPM is apparent from almost all practical and clinical research perspectives.

  2. Fault rupture as a series of nano-seismic events during high-velocity shear experiments

    NASA Astrophysics Data System (ADS)

    Zu, X.; Reches, Z.; Chen, X.; Chang, J. C.; Carpenter, B. M.

    2015-12-01

    The rupture process of experimental faults is investigated here by monitoring nano-seismic events (NSE) during slip in a rotary shear apparatus. Our experimental faults are made of two rock blocks with one to four miniature 3D accelerometers that are glued to the stationary block at distance of ~ 2 cm from the fault surface. Accelerations in the frequency range of 1 Hz to 200 kHz are recorded in slip-parallel (x), slip-transverse (y), and slip-vertical (z) directions. We conducted a series of 45 experiments on diorite and dolomite samples in two loading styles: classical velocity controlled loading, and power-density loading, in which the power-density (shear stress times slip velocity) is selected, and stick-slip events develop spontaneously according to the experimental fault response. The 3D accelerometer data were recorded at 106 samples/s, with acceleration resolution of 10 mV/g in recoding range of +/- 5 V. The experiments were conducted at slip-velocity of 0.001-0.8 m/s and slip distance up to 1.38 m. The accelerometer observations revealed tens to hundreds of NSEs per slip in both loading styles; peak acceleration ranged from 1g to over 500g. A typical stick-slip with tens of NSEs in Fig. 1, shows: (1) An initial NSE at ~59.72 s (green) that coincides with a small stress drop (~10%, red); (2) Simultaneous macroscopic slip initiation (blue); (3) A swarm of NSEs occur as the fault slips, each NSE lasts 1-2 milliseconds; and (4) Details of the initial NSE are shown in Fig. 2. Based on waveform cross-correlation between frequency band from 20 kHz to 70kHz, we identify several groups of NSE clusters, and apply empirical Green's function method to analyze event source spectra based on Brune-type source model. These NSEs are indicators of rupture propagation during the experimental fault slip.

  3. Slip-localization within confined gouge powder sheared at moderate to high slip-velocity

    NASA Astrophysics Data System (ADS)

    Reches, Zeev; Chen, Xiaofeng; Morgan, Chance; Madden, Andrew

    2015-04-01

    Slip along faults in the upper crust is always associated with comminution and formation of non-cohesive gouge powder that can be lithified to cataclasite. Typically, the fine-grained powders (grain-size < 1 micron) build a 1-10 cm thick inner-core of a fault-zone. The ubiquitous occurrence of gouge powder implies that gouge properties may control the dynamic weakening of faults. Testing these properties is the present objective. We built a Confined ROtary Cell, CROC, with a ring-shape, ~3 mm thick gouge chamber, with 62.5 and 81.2 mm of inner and outer diameters. The sheared powder is sealed by two sets of seals pressurized by nitrogen. In CROC, we can control the pore-pressure and to inject fluids, and to monitor CO2 and H2O concentration; in addition, we monitor the standard mechanical parameters (slip velocity, stresses, dilation, and temperature). We tested six types of granular materials (starting grain-size in microns): Talc (<250), Kasota dolomite (125-250), ooides grains (125-250), San Andreas fault zone powder (< 840), montmorillonite powder (1-2), kaolinite powder and gypsum. The experimental slip-velocity ranged 0.001-1 m/s, slip distances from a few tens of cm to tens of m, effective normal stress up to 6.1 MPa. The central ultra-microscopic (SEM) observation is that almost invariably the slip was localized along principal-slip-zone (PSZ) within the granular layer. Even though the starting material was loose, coarse granular material, the developed PSZ was cohesive, hard, smooth and shining. The PSZ is about 1 micron thick, and built of agglomerated, ultra-fine grains (20-50 nm) that were pulverized from the original granular material. We noted that PSZs of the different tested compositions display similar characteristics in terms of structure, grain size, and roughness. Further, we found striking similarities between PSZ in the granular samples and the PZS that developed along experimental faults made of solid rock that were sheared at similar

  4. Shear flow induced unfolding of collapsed polymers.

    NASA Astrophysics Data System (ADS)

    Alexander-Katz, Alfredo; Netz, Roland

    2006-03-01

    In the process of clotting in small vessels, platelets form a plug in an injured zone only in the presence of a protein known as the von Willebrand Factor (vWF). The absence or malfunction of the vWF leads to a bleeding disorder, the so-called von Willebrand disease. It is believed that the protein is collapsed (or globular) when released into the blood flow, and that it undergoes a transition at high shear rates that allows it to bind platelets. Using hydrodynamic simulations of a simple model of the vWF in shear flow, we show that a globular polymer undergoes a globule-stretch transition at a critical shear rate. Below this threshold shear rate the polymer remains collapsed and slightly deformed, while above it the chain displays strong elongations in the direction of the flow. Finally, we discuss the relevance of our results in the case of blood flow, and compare them to the physiological values present in the body.

  5. Functional properties of whey proteins affected by heat treatment and hydrodynamic high-pressure shearing.

    PubMed

    Dissanayake, M; Vasiljevic, T

    2009-04-01

    Two batches of native whey proteins (WP) were subjected to microfluidization or heat denaturation accompanied by microfluidization, followed by spray drying. Powders were assessed for their solubility, heat stability, coagulation time, and emulsifying and foaming properties. Effects of denaturation and shearing were examined by particle size analysis, differential scanning calorimetry, reducing and nonreducing sodium dodecyl sulfate-PAGE, and size exclusion-HPLC. Heat treatment significantly decreased solubility, whereas the number of microfluidization passes markedly improved solubility. The combined effect of heat and pressure significantly increased heat coagulation time. Emulsifying activity index substantially increased upon heat denaturation and was further enhanced by microfluidization. Emulsion stability appeared unaffected by the combined treatment, but the concentration of adsorbed protein on fat droplets was significantly increased. Foaming properties were diminished by heating. Particle size distribution patterns, sodium dodecyl sulfate-PAGE, and size exclusion-HPLC revealed disappearance of major WP and creation of relatively higher, as well as smaller, molecular weight aggregates as a result of the 2 treatments. The use of heat and microfluidization in combination could be used to stabilize WP against heat by producing microparticulated species that have different surface and colloidal properties compared with native WP. These results have implications for the use of WP as an additive in heat-processed foods.

  6. Reducing the Ideal Shear Strengths of ZrB2 by High Efficient Alloying Elements (Ag, Au, Pd and Pt).

    PubMed

    Dai, Fu-Zhi; Zhou, Yanchun

    2017-02-24

    Activating the plasticity of ZrB2 is a promising approach to improve its key properties for applications in hypersonic vehicles, including high temperature strength and thermal shock resistance. The present work demonstrates that ideal shear strength of ZrB2, which is a good indicator of the critical stress for dislocation nucleation, can be significantly reduced by dissolving of appropriate alloying elements. Analyzing on the bonding nature of ZrB2 reveals that choosing alloying elements with low energy valence electrons will prevent electron transferring from alloying element to the electron deficient B-B π orbits, which will reduce the local stability of the region surrounding the alloying element. Under the criterion, elements with d electrons tending to be full-filled (Ag, Au, Pd and Pt, the full-filled state is associated with low energy level) are selected as promising candidates with their prominent efficiency in reducing ideal shear strengths verified by first-principles calculations. The results provide useful guidelines for further designs of ZrB2 based materials, especially for improving their mechanical properties.

  7. Reducing the Ideal Shear Strengths of ZrB2 by High Efficient Alloying Elements (Ag, Au, Pd and Pt)

    NASA Astrophysics Data System (ADS)

    Dai, Fu-Zhi; Zhou, Yanchun

    2017-02-01

    Activating the plasticity of ZrB2 is a promising approach to improve its key properties for applications in hypersonic vehicles, including high temperature strength and thermal shock resistance. The present work demonstrates that ideal shear strength of ZrB2, which is a good indicator of the critical stress for dislocation nucleation, can be significantly reduced by dissolving of appropriate alloying elements. Analyzing on the bonding nature of ZrB2 reveals that choosing alloying elements with low energy valence electrons will prevent electron transferring from alloying element to the electron deficient B-B π orbits, which will reduce the local stability of the region surrounding the alloying element. Under the criterion, elements with d electrons tending to be full-filled (Ag, Au, Pd and Pt, the full-filled state is associated with low energy level) are selected as promising candidates with their prominent efficiency in reducing ideal shear strengths verified by first-principles calculations. The results provide useful guidelines for further designs of ZrB2 based materials, especially for improving their mechanical properties.

  8. Reducing the Ideal Shear Strengths of ZrB2 by High Efficient Alloying Elements (Ag, Au, Pd and Pt)

    PubMed Central

    Dai, Fu-Zhi; Zhou, Yanchun

    2017-01-01

    Activating the plasticity of ZrB2 is a promising approach to improve its key properties for applications in hypersonic vehicles, including high temperature strength and thermal shock resistance. The present work demonstrates that ideal shear strength of ZrB2, which is a good indicator of the critical stress for dislocation nucleation, can be significantly reduced by dissolving of appropriate alloying elements. Analyzing on the bonding nature of ZrB2 reveals that choosing alloying elements with low energy valence electrons will prevent electron transferring from alloying element to the electron deficient B-B π orbits, which will reduce the local stability of the region surrounding the alloying element. Under the criterion, elements with d electrons tending to be full-filled (Ag, Au, Pd and Pt, the full-filled state is associated with low energy level) are selected as promising candidates with their prominent efficiency in reducing ideal shear strengths verified by first-principles calculations. The results provide useful guidelines for further designs of ZrB2 based materials, especially for improving their mechanical properties. PMID:28233838

  9. Many People Don't Take Their High Blood Pressure Meds

    MedlinePlus

    ... Many People Don't Take Their High Blood Pressure Meds: Study Failure to follow doctors' orders leads ... of patients seeking care for stubborn high blood pressure take all the medicine they're supposed to, ...

  10. Hispanics, Blacks Less Likely to Get High Blood Pressure Treatment: Study

    MedlinePlus

    ... Hispanics, Blacks Less Likely to Get High Blood Pressure Treatment: Study Less than half from any group ... less likely than whites to get high blood pressure under control, a new study suggests. Researchers reviewed ...

  11. Novel, high-yield red blood cell production methods from CD34-positive cells derived from human embryonic stem, yolk sac, fetal liver, cord blood, and peripheral blood.

    PubMed

    Olivier, Emmanuel; Qiu, Caihong; Bouhassira, Eric E

    2012-08-01

    The current supply of red blood cells expressing rare blood groups is not sufficient to cover all the existing transfusion needs for chronically transfused patients, such as sickle cell disease homozygous carriers, because of alloimmunization. In vitro production of cultured red blood cells is slowly emerging as a possible complement to the existing collection-based red blood cell procurement system. The yield of cultured red blood cells can theoretically be maximized by amplifying the stem, progenitor, or precursor compartment. Here, we combined methods designed to expand these three compartments to optimize the yield of cultured red blood cells and found that exposing CD34(+) cells to a short pulse of cytokines favorable for erythroid differentiation prior to stem cell expansion followed by progenitor expansion produced the highest yield of erythroid cells. This novel serum-free red blood cell production protocol was efficient on CD34(+) cells derived from human embryonic stem cells, 6-8-week yolk sacs, 16-18-week fetal livers, cord blood, and peripheral blood. The yields of cells obtained with these new protocols were larger by an order of magnitude than the yields observed previously. Globin expression analysis by high-performance liquid chromatography revealed that these expansion protocols generally yielded red blood cells that expressed a globin profile similar to that expected for the developmental age of the CD34(+) cells.

  12. Step by Step: Eating To Lower Your High Blood Cholesterol. Revised.

    ERIC Educational Resources Information Center

    National Heart, Lung, and Blood Inst. (DHHS/NIH), Bethesda, MD.

    This booklet offers advice for adults who want to lower their blood cholesterol level. The first section, "What You Need To Know about High Blood Cholesterol," discusses blood cholesterol and why it matters, what cholesterol numbers mean, and what affects blood cholesterol levels. Section 2, "What You Need To Do To Lower Blood…

  13. New high blood pressure guidelines create new at-risk classification: changes in blood pressure classification by JNC 7.

    PubMed

    Miller, Edgar R; Jehn, Megan L

    2004-01-01

    High blood pressure has become increasingly prevalent and is an important risk factor for cardiovascular disease. The Seventh Report of the Joint National Committee on the Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) has redefined normal blood pressure as less than 120/80 mm Hg and created a new blood pressure category called "prehypertension" for those with a systolic BP of 120 to 139 mm Hg or a diastolic BP of 80 to 89 mm Hg. This new blood pressure category was created to identify adults considered to be at risk for developing hypertension and to alert both patients and healthcare providers of the importance of adopting lifestyle changes. Recognition of prehypertension provides important opportunities to prevent hypertension and cardiovascular disease.

  14. Shear Yielding and Shear Jamming of Dense Hard Sphere Glasses

    NASA Astrophysics Data System (ADS)

    Urbani, Pierfrancesco; Zamponi, Francesco

    2017-01-01

    We investigate the response of dense hard sphere glasses to a shear strain in a wide range of pressures ranging from the glass transition to the infinite-pressure jamming point. The phase diagram in the density-shear strain plane is calculated analytically using the mean-field infinite-dimensional solution. We find that just above the glass transition, the glass generically yields at a finite shear strain. The yielding transition in the mean-field picture is a spinodal point in presence of disorder. At higher densities, instead, we find that the glass generically jams at a finite shear strain: the jamming transition prevents yielding. The shear yielding and shear jamming lines merge in a critical point, close to which the system yields at extremely large shear stress. Around this point, highly nontrivial yielding dynamics, characterized by system-spanning disordered fractures, is expected.

  15. The Effect of Job Strain on Nighttime Blood Pressure Dipping among Men and Women with High Blood Pressure

    PubMed Central

    Fan, Lin-bo; Blumenthal, James A.; Hinderliter, Alan L.; Sherwood, Andrew

    2013-01-01

    Objectives Blunted nighttime blood pressure dipping is an established cardiovascular risk factor. This study examined the effect of job strain on nighttime blood pressure dipping among men and women with high blood pressure. Methods The sample consisted of 122 blue collar and white collar workers (men=72, women=50). Job psychological demands, job control and social support were measured by the Job Content Questionnaire. Job strain was assessed by the ratio of job demands/job control. Nighttime blood pressure dipping was evaluated from 24-hour ambulatory blood pressure monitoring performed on three workdays. Results Men with high job strain had a 5.4 mm Hg higher sleep systolic blood pressure (P=0.03) and 3.5 mm Hg higher sleep pulse pressure (P=0.02) compared to men with low job strain. Men with high job strain had a smaller fall in systolic blood pressure and pulse pressure from awake to sleep than those with low job strain (P<0.05). Hierarchical analyses showed that job strain was an independent determinant of systolic blood pressure dipping (P=0.03) among men after adjusting for ethnicity, body mass index, anxiety and depression symptoms, current smoking status, and alcohol consumption. Further exploratory analyses indicated that job control was the salient component of job strain associated with blood pressure dipping (p=.03). Conclusions High job strain is associated with a blunting of the normal diurnal variation in blood pressure and pulse pressure, which may contribute to the relationship between job strain and cardiovascular disease. PMID:22460541

  16. A High shear stress segment along the San Andreas Fault: Inferences based on near-field stress direction and stress magnitude observations in the Carrizo Plain Area

    SciTech Connect

    Castillo, D. A.,; Younker, L.W.

    1997-01-30

    Nearly 200 new in-situ determinations of stress directions and stress magnitudes near the Carrizo plain segment of the San Andreas fault indicate a marked change in stress state occurring within 20 km of this principal transform plate boundary. A natural consequence of this stress transition is that if the observed near-field ``fault-oblique`` stress directions are representative of the fault stress state, the Mohr-Coulomb shear stresses resolved on San Andreas sub-parallel planes are substantially greater than previously inferred based on fault-normal compression. Although the directional stress data and near-hydrostatic pore pressures, which exist within 15 km of the fault, support a high shear stress environment near the fault, appealing to elevated pore pressures in the fault zone (Byerlee-Rice Model) merely enhances the likelihood of shear failure. These near-field stress observations raise important questions regarding what previous stress observations have actually been measuring. The ``fault-normal`` stress direction measured out to 70 km from the fault can be interpreted as representing a comparable depth average shear strength of the principal plate boundary. Stress measurements closer to the fault reflect a shallower depth-average representation of the fault zone shear strength. If this is true, only stress observations at fault distances comparable to the seismogenic depth will be representative of the fault zone shear strength. This is consistent with results from dislocation monitoring where there is pronounced shear stress accumulation out to 20 km of the fault as a result of aseismic slip within the lower crust loading the upper locked section. Beyond about 20 km, the shear stress resolved on San Andreas fault-parallel planes becomes negligible. 65 refs., 15 figs.

  17. Quaternary layer anomalies around the Carlsberg Fault zone mapped with high-resolution shear-wave seismics south of Copenhagen

    NASA Astrophysics Data System (ADS)

    Kammann, Janina; Hübscher, Christian; Nielsen, Lars; Boldreel, Lars Ole

    2015-04-01

    The Carlsberg Fault zone is located in the N-S striking Höllviken Graben and traverses the city of Copenhagen. The fault zone is a NNW-SSE striking structure in direct vicinity to the transition zone of the Danish Basin and the Baltic Shield. Recent small earthquakes indicate activity in the area, although none of the mapped earthquakes appear to have occurred on the Carlsberg Fault. We examined the fault evolution by a combination of very high resolution onshore shear-wave seismic data, one conventional onshore seismic profile and marine reflection seismic profiles. The chalk stratigraphy and the localization of the fault zone at depth was inferred from previous studies by other authors. We extrapolated the Jurassic and Triassic stratigraphy from the Pomeranian Bay to the area of investigation. The fault zone shows a flower structure in the Triassic as well as in Cretaceous sediments. The faulting geometry indicates strong influence of Triassic processes when subsidence and rifting prevailed in the Central European Basin System. Growth strata within the surrounding Höllviken Graben reveal syntectonic sedimentation in the lower Triassic, indicating the opening to be a result of Triassic rifting. In the Upper Cretaceous growth faulting documents continued rifting. This finding contrasts the Late Cretaceous to Paleogene inversion tectonics in neighbouring structures, as the Tornquist Zone. The high-resolution shear-wave seismic method was used to image structures in Quaternary layers in the Carlsberg Fault zone. The portable compact vibrator source ElViS III S8 was used to acquire a 1150 m long seismic section on the island Amager, south of Copenhagen. The shallow subsurface in the investigation area is dominated by Quaternary glacial till deposits in the upper 5-11 m and Danian limestone below. In the shear-wave profile, we imaged the 30 m of the upward continuation of the Carlsberg Fault zone. In our area of investigation, the fault zone appears to comprise

  18. High blood pressure in Latin America: a call to action.

    PubMed

    Rubinstein, Adolfo; Alcocer, Luis; Chagas, Antonio

    2009-08-01

    High blood pressure (BP) is an enormous global problem, and is especially challenging for low- and middle-income countries such as those of Latin America. Although developed countries have benefited from significant reductions in cardiovascular and cerebrovascular disease in recent decades, comparable reductions have not been achieved in Latin America. In fact, the prevalence of high BP is increasing in many Latin American countries, and the situation will worsen without definitive efforts to correct it. The growing preponderance of hypertension and chronic diseases, coupled with expected increases in population growth, present a mounting threat to Latin American economies. This report provides a comprehensive overview of the burden of high BP throughout Latin America, and presents recommendations for change. The dismal observations warrant a call to action for improved control of high BP and other cardiovascular risk factors across Latin America. Achieving these ambitious goals will require collaborative efforts by many groups, including policymakers, international organizations, healthcare providers, schools and society as a whole.

  19. Understanding the implications of the data from recent high-energy-density Kelvin-Helmholtz shear layer experiments

    SciTech Connect

    Hurricane, O A; Hansen, J F; Harding, E C; Drake, R P; Robey, H F; Remington, B A; Kuranz, C C; Grosskopf, M J; Gillespie, R S; Park, H

    2009-10-26

    The first successful high energy density Kelvin-Helmholtz (KH) shear layer experiments (O.A. Hurricane, et al., Phys. Plasmas, 16, 056305, 2009; E.C. Harding, et al., Phys. Rev. Lett., 103, 045005, 2009) demonstrated the ability to design and field a target that produces an array of large diagnosable KH vortices in a controlled fashion. Data from these experiments vividly showed the complete evolution of large distinct eddies, from formation to apparent turbulent break-up. Unexpectedly, low-density bubbles/cavities comparable to the vortex size ({approx} 300 - 400 {micro}m) appeared to grow up in the free-stream flow above the unstable material interface. In this paper, the basic principles of the experiment will be discussed, the data reviewed, and the progress on understanding the origin of the above bubble structures through theory and simulation will be reported on.

  20. High Magnetic Shear Gain in a Liquid Sodium Stable Couette Flow Experiment: A Prelude to an {alpha}-{Omega} Dynamo

    SciTech Connect

    Colgate, Stirling A.; Beckley, Howard; Si, Jiahe; Martinic, Joe; Westpfahl, David; Slutz, James; Westrom, Cebastian; Klein, Brianna; Schendel, Paul; Scharle, Cletus; McKinney, Travis; Ginanni, Rocky; Bentley, Ian; Mickey, Timothy; Ferrel, Regnar; Li, Hui; Pariev, Vladimir; Finn, John

    2011-04-29

    The {Omega} phase of the liquid sodium {alpha}-{Omega} dynamo experiment at New Mexico Institute of Mining and Technology in cooperation with Los Alamos National Laboratory has demonstrated a high toroidal field B{sub {phi}} that is {approx_equal}8xB{sub r}, where B{sub r} is the radial component of an applied poloidal magnetic field. This enhanced toroidal field is produced by the rotational shear in stable Couette flow within liquid sodium at a magnetic Reynolds number Rm{approx_equal}120. Small turbulence in stable Taylor-Couette flow is caused by Ekman flow at the end walls, which causes an estimated turbulence energy fraction of ({delta}v/v){sup 2{approx}}10{sup -3}.

  1. High-frequency viscoelastic shear properties of vocal fold tissues: implications for vocal fold tissue engineering.

    PubMed

    Teller, Sean S; Farran, Alexandra J E; Xiao, Longxi; Jiao, Tong; Duncan, Randall L; Clifton, Rodney J; Jia, Xinqiao

    2012-10-01

    The biomechanical function of the vocal folds (VFs) depends on their viscoelastic properties. Many conditions can lead to VF scarring that compromises voice function and quality. To identify candidate replacement materials, the structure, composition, and mechanical properties of native tissues need to be understood at phonation frequencies. Previously, the authors developed the torsional wave experiment (TWE), a stress-wave-based experiment to determine the linear viscoelastic shear properties of small, soft samples. Here, the viscoelastic properties of porcine and human VFs were measured over a frequency range of 10-200 Hz. The TWE utilizes resonance phenomena to determine viscoelastic properties; therefore, the specimen test frequency is determined by the sample size and material properties. Viscoelastic moduli are reported at resonance frequencies. Structure and composition of the tissues were determined by histology and immunochemistry. Porcine data from the TWE are separated into two groups: a young group, consisting of fetal and newborn pigs, and an adult group, consisting of 6-9-month olds and 2+-year olds. Adult tissues had an average storage modulus of 2309±1394 Pa and a loss tangent of 0.38±0.10 at frequencies of 36-200 Hz. The VFs of young pigs were significantly more compliant, with a storage modulus of 394±142 Pa and a loss tangent of 0.40±0.14 between 14 and 30 Hz. No gender dependence was observed. Histological staining showed that adult porcine tissues had a more organized, layered structure than the fetal tissues, with a thicker epithelium and a more structured lamina propria. Elastin fibers in fetal VF tissues were immature compared to those in adult tissues. Together, these structural changes in the tissues most likely contributed to the change in viscoelastic properties. Adult human VF tissues, recovered postmortem from adult patients with a history of smoking or disease, had an average storage modulus of 756±439 Pa and a loss tangent of 0

  2. Shear-stress sensitive lenticular vesicles for targeted drug delivery.

    PubMed

    Holme, Margaret N; Fedotenko, Illya A; Abegg, Daniel; Althaus, Jasmin; Babel, Lucille; Favarger, France; Reiter, Renate; Tanasescu, Radu; Zaffalon, Pierre-Léonard; Ziegler, André; Müller, Bert; Saxer, Till; Zumbuehl, Andreas

    2012-08-01

    Atherosclerosis results in the narrowing of arterial blood vessels and this causes significant changes in the endogenous shear stress between healthy and constricted arteries. Nanocontainers that can release drugs locally with such rheological changes can be very useful. Here, we show that vesicles made from an artificial 1,3-diaminophospholipid are stable under static conditions but release their contents at elevated shear stress. These vesicles have a lenticular morphology, which potentially leads to instabilities along their equator. Using a model cardiovascular system based on polymer tubes and an external pump to represent shear stress in healthy and constricted vessels of the heart, we show that drugs preferentially release from the vesicles in constricted vessels that have high shear stress.

  3. Instability and ``Sausage-String'' Appearance in Blood Vessels during High Blood Pressure

    NASA Astrophysics Data System (ADS)

    Alstrøm, Preben; Eguíluz, Victor M.; Colding-Jørgensen, Morten; Gustafsson, Finn; Holstein-Rathlou, Niels-Henrik

    1999-03-01

    A new Rayleigh-type instability is proposed to explain the ``sausage-string'' pattern of alternating constrictions and dilatations formed in blood vessels under influence of a vasoconstricting agent. Our theory involves the nonlinear elasticity characteristics of the vessel wall, and provides predictions for the conditions under which the cylindrical form of a blood vessel becomes unstable.

  4. Nursing Education in High Blood Pressure Control. Report of the Task Force on the Role of Nursing in High Blood Pressure Control.

    ERIC Educational Resources Information Center

    National Institutes of Health (DHEW), Bethesda, MD. High Blood Pressure Information Center.

    This curriculum guide on high blood pressure (hypertension) for nursing educators has five sections: (1) Introduction and Objectives provides information regarding the establishment and objectives of the National Task Force on the Role of Nursing in High Blood Pressure Control and briefly discusses nursing's role in hypertension control; (2) Goals…

  5. Versatility of Biofilm Matrix Molecules in Staphylococcus epidermidis Clinical Isolates and Importance of Polysaccharide Intercellular Adhesin Expression during High Shear Stress

    PubMed Central

    Schaeffer, Carolyn R.; Hoang, Tra-My N.; Sudbeck, Craig M.; Alawi, Malik; Tolo, Isaiah E.; Robinson, D. Ashley; Horswill, Alexander R.; Rohde, Holger

    2016-01-01

    ABSTRACT Staphylococcus epidermidis is a leading cause of hospital-associated infections, including those of intravascular catheters, cerebrospinal fluid shunts, and orthopedic implants. Multiple biofilm matrix molecules with heterogeneous characteristics have been identified, including proteinaceous, polysaccharide, and nucleic acid factors. Two of the best-studied components in S. epidermidis include accumulation-associated protein (Aap) and polysaccharide intercellular adhesin (PIA), produced by the enzymatic products of the icaADBC operon. Biofilm composition varies by strain as well as environmental conditions, and strains producing PIA-mediated biofilms are more robust. Clinically, biofilm-mediated infections occur in a variety of anatomical sites with diverse physiological properties. To test the hypothesis that matrix composition exhibits niche specificity, biofilm-related genetic and physical properties were compared between S. epidermidis strains isolated from high-shear and low-shear environments. Among a collection of 105 clinical strains, significantly more isolates from high-shear environments carried the icaADBC operon than did those from low-shear settings (43.9% versus 22.9%, P < 0.05), while there was no significant difference in the presence of aap (77.2% versus 75.0%, P > 0.05). Additionally, a significantly greater number of high-shear isolates were capable of forming biofilm in vitro in a microtiter assay (82.5% versus 45.8%, P < 0.0001). However, even among high-shear clinical isolates, less than half contained the icaADBC locus; therefore, we selected for ica-negative variants with increased attachment to abiotic surfaces to examine PIA-independent biofilm mechanisms. Sequencing of selected variants identified substitutions capable of enhancing biofilm formation in multiple genes, further highlighting the heterogeneity of S. epidermidis biofilm molecules and mechanisms. IMPORTANCE Staphylococcus epidermidis is a leading cause of

  6. Versatility of Biofilm Matrix Molecules in Staphylococcus epidermidis Clinical Isolates and Importance of Polysaccharide Intercellular Adhesin Expression during High Shear Stress.

    PubMed

    Schaeffer, Carolyn R; Hoang, Tra-My N; Sudbeck, Craig M; Alawi, Malik; Tolo, Isaiah E; Robinson, D Ashley; Horswill, Alexander R; Rohde, Holger; Fey, Paul D

    2016-01-01

    Staphylococcus epidermidis is a leading cause of hospital-associated infections, including those of intravascular catheters, cerebrospinal fluid shunts, and orthopedic implants. Multiple biofilm matrix molecules with heterogeneous characteristics have been identified, including proteinaceous, polysaccharide, and nucleic acid factors. Two of the best-studied components in S. epidermidis include accumulation-associated protein (Aap) and polysaccharide intercellular adhesin (PIA), produced by the enzymatic products of the icaADBC operon. Biofilm composition varies by strain as well as environmental conditions, and strains producing PIA-mediated biofilms are more robust. Clinically, biofilm-mediated infections occur in a variety of anatomical sites with diverse physiological properties. To test the hypothesis that matrix composition exhibits niche specificity, biofilm-related genetic and physical properties were compared between S. epidermidis strains isolated from high-shear and low-shear environments. Among a collection of 105 clinical strains, significantly more isolates from high-shear environments carried the icaADBC operon than did those from low-shear settings (43.9% versus 22.9%, P < 0.05), while there was no significant difference in the presence of aap (77.2% versus 75.0%, P > 0.05). Additionally, a significantly greater number of high-shear isolates were capable of forming biofilm in vitro in a microtiter assay (82.5% versus 45.8%, P < 0.0001). However, even among high-shear clinical isolates, less than half contained the icaADBC locus; therefore, we selected for ica-negative variants with increased attachment to abiotic surfaces to examine PIA-independent biofilm mechanisms. Sequencing of selected variants identified substitutions capable of enhancing biofilm formation in multiple genes, further highlighting the heterogeneity of S. epidermidis biofilm molecules and mechanisms. IMPORTANCEStaphylococcus epidermidis is a leading cause of infections related

  7. Hemodynamic shear stress and the endothelium in cardiovascular pathophysiology

    PubMed Central

    Davies, Peter F

    2010-01-01

    SUMMARY Endothelium lining the cardiovascular system is highly sensitive to hemodynamic shear stresses that act at the vessel luminal surface in the direction of blood flow. Physiological variations of shear stress regulate acute changes in vascular diameter and when sustained induce slow, adaptive, structural-wall remodeling. Both processes are endothelium-dependent and are systemically and regionally compromised by hyperlipidemia, hypertension, diabetes and inflammatory disorders. Shear stress spans a range of spatiotemporal scales and contributes to regional and focal heterogeneity of endothelial gene expression, which is important in vascular pathology. Regions of flow disturbances near arterial branches, bifurcations and curvatures result in complex spatiotemporal shear stresses and their characteristics can predict atherosclerosis susceptibility. Changes in local artery geometry during atherogenesis further modify shear stress characteristics at the endothelium. Intravascular devices can also influence flow-mediated endothelial responses. Endothelial flow-induced responses include a cell-signaling repertoire, collectively known as mechanotransduction, that ranges from instantaneous ion fluxes and biochemical pathways to gene and protein expression. A spatially decentralized mechanism of endothelial mechanotransduction is dominant, in which deformation at the cell surface induced by shear stress is transmitted as cytoskeletal tension changes to sites that are mechanically coupled to the cytoskeleton. A single shear stress mechanotransducer is unlikely to exist; rather, mechanotransduction occurs at multiple subcellular locations. PMID:19029993

  8. High-Obliquity Impact of a Compact Penetrator on a Thin Plate: Penetrator Splitting and Adiabatic Shear

    DTIC Science & Technology

    1998-01-01

    stress deviator set to zero. On the time scale of our simulations, shear bands are hot and thus weak in tension as well as shear. To account for this...LIVERMORE CA 94550 R DAMINITY CODE U43 J P MATRA 7 DIRECTOR P WALTER SANDIA NATL LABS L MENSI E S HERTEL JR MS 0819 K KIDDY A ROBINSON MS 0819 F J

  9. Family Adaptability and Cohesion and High Blood Pressure among Urban African American women.

    PubMed

    Brittain, Kelly; Taylor, Jacquelyn Y; Wu, Chun Yi

    2010-11-01

    African American women are at greater risk for complications related to high blood pressure. This study examined relationships between high blood pressure, pulse pressure, body mass index, family adaptability, family cohesion and social support among 146 Urban African American women. Significant relationships were found between family adaptability and systolic blood pressure (p = .03) and between adaptability and pulse pressure (p ≤ .01). Based on study results, practitioners should routinely assess family functioning, specifically family adaptability, in African American women who are at risk for high blood pressure or diagnosed with high blood pressure to minimize complications associated with hypertension.

  10. MEMS shear stress sensors for cardiovascular diagnostics.

    PubMed

    Soundararajan, Gopikrishnan; Hsiai, Tzung K; DeMaio, Lucas; Chang, Michael; Chang, Stanley

    2004-01-01

    Coronary artery disease is the leading cause of morbidity and mortality in the industrialized nations. Both biochemical and biomechanical stimuli modulate the pathogenesis of coronary artery diseases. Shear stress acting on the lumen of blood vessels intimately modulates the biological activities of vascular endothelial cells (ECs). We hereby develop microelectro mechanical system (MEMS)-based sensors at the dimension comparable to a single EC to monitor realtime shear stress in fluidic channel. Our goal is to fabricate sensors for ex vivo or in vivo shear stress measurement at Reynolds number commonly encountered in human circulation. The MEMS sensors were designed based on the previously described heat transfer principles. The polysilicon was doped with phosphorous to render the sensing element a high resistivity at 2.5 KOmega. The development of backside wire bonding enabled the application for the vascular geometry. The small dimension (80x2 mum) and the gain amplitude at 71 KHz offered an entry point to measure shear stress with high spatial and temporal resolution.

  11. Blood

    MedlinePlus

    ... increased red blood cell destruction can affect teens: G6PD deficiency. G6PD is an enzyme that helps to protect ... can cause red cells to hemolyze, or burst. G6PD deficiency is a common hereditary disease among people of ...

  12. Blood-Brain Barrier Changes in High Altitude.

    PubMed

    Lafuente, José V; Bermudez, Garazi; Camargo-Arce, Lorena; Bulnes, Susana

    2016-01-01

    Cerebral syndromes related to high-altitude exposure are becoming more frequent as the number of trips to high altitudes has increased in the last decade. The commonest symptom is headache, followed by acute mountain sickness (AMS) and high-altitude cerebral edema (HACE), which can be fatal. The pathophysiology of these syndromes is not fully understood. The classical "tight-fit hypothesis" posits that there are some anatomical variations that would obstruct the sinovenous outflow and worsen vasogenic edema and intracranial hypertension reactive to hypoxia. This could explain microhemorrhages seen in autopsies. However, recent magnetic resonance imaging studies have demonstrated some components of cytotoxic edema in HACE absent in AMS, suggesting a dysfunction in water balance at the cellular level. Currently, the "red-ox theory" supports trigemino-vascular system activation by free radicals formed after hypoxia and the consequent oxidative stress cascades. Apart from trigemino-vascular system activation, free radicals can also provoke membrane destabilisation mediated by lipid peroxidation, inflammation, and local hypoxia inducible factor-1α and vascular endothelial growth factor activation, resulting in gross blood-brain barrier (BBB) dysfunction. Besides alterations in endothelial cells such as increased pinocytotic vesicles and disassembly of interendothelial tight junction proteins, capillary permeability may also increase with subsequent swelling of astrocyte end-feet. In conclusion, although the pathophysiology of AMS and HACE is not completely understood, recent evidence proposes a multifactorial entity, with brain swelling and compromise of the BBB considered to play an important role. A fuller comprehension of these processes is crucial to reduce and prevent BBB alterations during high-altitude exposure.

  13. Activation and shedding of platelet glycoprotein IIb/IIIa under non-physiological shear stress.

    PubMed

    Chen, Zengsheng; Mondal, Nandan K; Ding, Jun; Koenig, Steven C; Slaughter, Mark S; Griffith, Bartley P; Wu, Zhongjun J

    2015-11-01

    The purpose of this study was to investigate the influence of non-physiological high shear stress on activation and shedding of platelet GP IIb/IIIa receptors. The healthy donor blood was exposed to three levels of high shear stresses (25, 75, 125 Pa) from the physiological to non-physiological status with three short exposure time (0.05, 0.5, 1.5 s), created by a specific blood shearing system. The activation and shedding of the platelet GPIIb/IIIa were analyzed using flow cytometry and enzyme-linked immunosorbent assay. In addition, platelet P-selectin expression of sheared blood, which is a marker for activated platelets, was also analyzed. The results from the present study showed that the number of activated platelets, as indicated by the surface GPIIb/IIIa activation and P-selectin expression, increased with increasing the shear stress level and exposure time. However, the mean fluorescence of GPIIb/IIIa on the platelet surface, decreased with increasing the shear stress level and exposure time. The reduction of GPIIb/IIIa on the platelet surface was further proved by the reduction of further activated platelet GPIIb/IIIa surface expression induced by ADP and the increase in GPIIb/IIIa concentration in microparticle-free plasma with increasing the applied shear stress and exposure time. It is clear that non-physiological shear stress induce a paradoxical phenomenon, in which both activation and shedding of the GPIIb/IIIa on the platelet surface occur simultaneously. This study may offer a new perspective to explain the reason of both increased thrombosis and bleeding events in patients implanted with high shear blood-contacting medical devices.

  14. Intensive trapping of blood-fed Anopheles darlingi in Amazonian Peru reveals unexpectedly high proportions of avian blood-meals.

    PubMed

    Moreno, Marta; Saavedra, Marlon P; Bickersmith, Sara A; Prussing, Catharine; Michalski, Adrian; Tong Rios, Carlos; Vinetz, Joseph M; Conn, Jan E

    2017-02-01

    Anopheles darlingi, the main malaria vector in the Neotropics, has been considered to be highly anthropophilic. However, many behavioral aspects of this species remain unknown, such as the range of blood-meal sources. Barrier screens were used to collect resting Anopheles darlingi mosquitoes from 2013 to 2015 in three riverine localities (Lupuna, Cahuide and Santa Emilia) in Amazonian Peru. Overall, the Human Blood Index (HBI) ranged from 0.58-0.87, with no significant variation among years or sites. Blood-meal analysis revealed that humans are the most common blood source, followed by avian hosts (Galliformes-chickens and turkeys), and human/Galliforme mixed-meals. The Forage Ratio and Selection Index both show a strong preference for Galliformes over humans in blood-fed mosquitoes. Our data show that 30% of An. darlingi fed on more than one host, including combinations of dogs, pigs, goats and rats. There appears to be a pattern of host choice in An. darlingi, with varying proportions of mosquitoes feeding only on humans, only on Galliformes and some taking mixed-meals of blood (human plus Galliforme), which was detected in the three sites in different years, indicating that there could be a structure to these populations based on blood-feeding preferences. Mosquito age, estimated in two localities, Lupuna and Cahuide, ranged widely between sites and years. This variation may reflect the range of local environmental factors that influence longevity or possibly potential changes in the ability of the mosquito to transmit the parasite. Of 6,204 resting An. darlingi tested for Plasmodium infection, 0.42% were infected with P. vivax. This study provides evidence for the first time of the usefulness of barrier screens for the collection of blood-fed resting mosquitoes to calculate the Human Blood Index (HBI) and other blood-meal sources in a neotropical malaria endemic setting.

  15. Intensive trapping of blood-fed Anopheles darlingi in Amazonian Peru reveals unexpectedly high proportions of avian blood-meals

    PubMed Central

    Saavedra, Marlon P.; Bickersmith, Sara A.; Prussing, Catharine; Michalski, Adrian; Tong Rios, Carlos; Vinetz, Joseph M.; Conn, Jan E.

    2017-01-01

    Anopheles darlingi, the main malaria vector in the Neotropics, has been considered to be highly anthropophilic. However, many behavioral aspects of this species remain unknown, such as the range of blood-meal sources. Barrier screens were used to collect resting Anopheles darlingi mosquitoes from 2013 to 2015 in three riverine localities (Lupuna, Cahuide and Santa Emilia) in Amazonian Peru. Overall, the Human Blood Index (HBI) ranged from 0.58–0.87, with no significant variation among years or sites. Blood-meal analysis revealed that humans are the most common blood source, followed by avian hosts (Galliformes-chickens and turkeys), and human/Galliforme mixed-meals. The Forage Ratio and Selection Index both show a strong preference for Galliformes over humans in blood-fed mosquitoes. Our data show that 30% of An. darlingi fed on more than one host, including combinations of dogs, pigs, goats and rats. There appears to be a pattern of host choice in An. darlingi, with varying proportions of mosquitoes feeding only on humans, only on Galliformes and some taking mixed-meals of blood (human plus Galliforme), which was detected in the three sites in different years, indicating that there could be a structure to these populations based on blood-feeding preferences. Mosquito age, estimated in two localities, Lupuna and Cahuide, ranged widely between sites and years. This variation may reflect the range of local environmental factors that influence longevity or possibly potential changes in the ability of the mosquito to transmit the parasite. Of 6,204 resting An. darlingi tested for Plasmodium infection, 0.42% were infected with P. vivax. This study provides evidence for the first time of the usefulness of barrier screens for the collection of blood-fed resting mosquitoes to calculate the Human Blood Index (HBI) and other blood-meal sources in a neotropical malaria endemic setting. PMID:28231248

  16. High-shear, jet-cooking, and alkali treatment of corn distillers' dried grains to obtain products with enhanced protein, oil and phenolic antioxidants.

    PubMed

    Inglett, G E; Chen, D; Rose, D J; Berhow, M

    2010-08-01

    Distillers dried grains (DDG) have potential to be a nutritionally important source of protein, oil and phenolic antioxidants. DDG was subjected to high-shear and jet-cooking, with or without alkaline pH adjustment and autoclaving. Soluble and insoluble fractions were analyzed for protein, oil and ash. Extracts were analyzed for phenolic acids and antioxidant activity. Protein contents were significantly elevated in the insoluble fractions after treatment and the oil content was drastically increased in the insoluble fraction after high-shear and jet-cooking without pH adjustment. Alkaline pH adjustment resulted in a soluble fraction that was highest in phenolic acids, but not antioxidant activity. The highest antioxidant activity was found in the 50% ethanol extract from DDG that had been subjected to high-shear and jet-cooking. These results suggest that high-shear and jet-cooking may be useful processing treatments to increase the value of DDG by producing fractions high in protein, oil and extractable phenolic acids with high antioxidant activity. The DDG fractions and extracts described herein may be useful as food and nutraceutical ingredients, and, if used for these applications, will increase the value of DDG and ease economic burdens on ethanol producers, allowing them to compete in the bio-fuel marketplace.

  17. Identification of highly active flocculant proteins in bovine blood

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bovine blood is an excellent flocculating agent, faster acting and as effective on a mass basis as polyacrylamide, the most widely utilized polymeric flocculant. To determine the molecular basis of flocculation activity, whole bovine blood (BB) and BB plasma were fractionated by size exclusion chro...

  18. The changes in serum and whole blood rheological properties of rabbits during the progression of atherosclerosis.

    PubMed

    K Abdelhalim, Mohamed Anwar; Al-Ayed, Mohammed Suliman; Abdelmottaleb Moussa, Sherif A; Al-Mohy, Yanallah Hussain

    2016-05-01

    This study aimed to evaluate the role of zinc (Zn)-supplemented with high cholesterol diet (HCD) on the serum and whole blood rheological properties of rabbits fed a HCD. Twenty-four New Zealand white rabbits were divided into three groups. The HCD group was fed a diet with 1.0% cholesterol and 1.0% olive oil. The HCD + Zn group was fed a diet with 1.0% cholesterol, 1.0% olive oil, and Zn. Blood viscosity, shear stress, and torque (%) were measured at shear rates ranging from 225 to 1875 s-1 for serum and 75-900 s-1 for whole blood. Serum viscosity and shear stress in HCD rabbits were significantly higher at all shear rates compared to controls; while whole blood viscosity and shear stress in HCD rabbits were significantly lower at all shear rates compared to controls. Viscosity and shear stress in both serum and whole blood from rabbits in the HCD + Zn group returned to normal values at all shear rates. The Zn supplemented to HCD rabbits, delays the progression of atherosclerosis. Changes in blood serum viscosity could reflect changes in non-clotting proteins, glucose, nutrients and trace elements; while changes in whole blood viscosity could result from changes in hematocrit, hemoglobin, and erythrocyte count. One of the factors responsible for increasing the serum viscosity values of HCD rabbits might be attributed to increase in Fe and decrease in Zn levels in the blood serum.

  19. Multiscale modeling of blood flow: from single cells to blood rheology.

    PubMed

    Fedosov, Dmitry A; Noguchi, Hiroshi; Gompper, Gerhard

    2014-04-01

    Mesoscale simulations of blood flow, where the red blood cells are described as deformable closed shells with a membrane characterized by bending rigidity and stretching elasticity, have made much progress in recent years to predict the flow behavior of blood cells and other components in various flows. To numerically investigate blood flow and blood-related processes in complex geometries, a highly efficient simulation technique for the plasma and solutes is essential. In this review, we focus on the behavior of single and several cells in shear and microcapillary flows, the shear-thinning behavior of blood and its relation to the blood cell structure and interactions, margination of white blood cells and platelets, and modeling hematologic diseases and disorders. Comparisons of the simulation predictions with existing experimental results are made whenever possible, and generally very satisfactory agreement is obtained.

  20. High-resolution compact shear stress sensor for direct measurement of skin friction in fluid flow

    NASA Astrophysics Data System (ADS)

    Xu, Muchen; Kim, Chang-Jin ``Cj''

    2015-11-01

    The high-resolution measurement of skin friction in complex flows has long been of great interest but also a challenge in fluid mechanics. Compared with indirect measurement methods (e.g., laser Doppler velocimetry), direct measurement methods (e.g., floating element) do not involve any analogy and assumption but tend to suffer from instrumentation challenges, such as low sensing resolution or misalignments. Recently, silicon micromachined floating plates showed good resolution and perfect alignment but were too small for general purposes and too fragile to attach other surface samples repeatedly. In this work, we report a skin friction sensor consisting of a monolithic floating plate and a high-resolution optical encoder to measure its displacement. The key for the high resolution is in the suspension beams, which are very narrow (e.g., 0.25 mm) to sense small frictions along the flow direction but thick (e.g., 5 mm) to be robust along all other directions. This compact, low profile, and complete sensor is easy to use and allows repeated attachment and detachment of surface samples. The sheer-stress sensor has been tested in water tunnel and towing tank at different flow conditions, showing high sensing resolution for skin friction measurement. Supported by National Science Foundation (NSF) (No. 1336966) and Defense Advanced Research Projects Agency (DARPA) (No. HR0011-15-2-0021).

  1. Instabilities in shear and simple shear deformations of gold crystals

    NASA Astrophysics Data System (ADS)

    Pacheco, A. A.; Batra, R. C.

    We use the tight-binding potential and molecular mechanics simulations to study local and global instabilities in shear and simple shear deformations of three initially defect-free finite cubes of gold single crystal containing 3480, 7813, and 58,825 atoms. Displacements on all bounding surfaces are prescribed while studying simple shear deformations, but displacements on only two opposite surfaces are assigned during simulations of shear deformations with the remaining four surfaces kept free of external forces. The criteria used to delineate local instabilities in the system include the following: (i) a component of the second-order spatial gradients of the displacement field having large values relative to its average value in the body, (ii) the minimum eigenvalue of the Hessian of the energy of an atom becoming non-positive, and (iii) structural changes represented by a high value of the common neighborhood parameter. It is found that these criteria are met essentially simultaneously at the same atomic position. Effects of free surfaces are evidenced by different deformation patterns for the same specimen deformed in shear and simple shear. The shear strength of a specimen deformed in simple shear is more than three times that of the same specimen deformed in shear. It is found that for each cubic specimen deformed in simple shear the evolution with the shear strain of the average shear stress, prior to the onset of instabilities, is almost identical to that in an equivalent hyperelastic material with strain energy density derived from the tight-binding potential and the assumption that it obeys the Cauchy-Born rule. Even though the material response of the hyperelastic body predicted from the strain energy density is stable over the range of the shear strain simulated in this work, the molecular mechanics simulations predict local and global instabilities in the three specimens.

  2. Red Blood Cell Dysfunction Induced by High-Fat Diet

    PubMed Central

    Unruh, Dusten; Srinivasan, Ramprasad; Benson, Tyler; Haigh, Stephen; Coyle, Danielle; Batra, Neil; Keil, Ryan; Sturm, Robert; Blanco, Victor; Palascak, Mary; Franco, Robert S.; Tong, Wilson; Chatterjee, Tapan; Hui, David Y.; Davidson, W. Sean; Aronow, Bruce J.; Kalfa, Theodosia; Manka, David; Peairs, Abigail; Blomkalns, Andra; Fulton, David J.; Brittain, Julia E.; Weintraub, Neal L.; Bogdanov, Vladimir Y.

    2015-01-01

    Background High-fat diet (HFD) promotes endothelial dysfunction and proinflammatory monocyte activation, which contribute to atherosclerosis in obesity. We investigated whether HFD also induces the dysfunction of red blood cells (RBCs), which serve as a reservoir for chemokines via binding to Duffy antigen receptor for chemokines (DARC). Methods and Results A 60% HFD for 12 weeks, which produced only minor changes in lipid profile in C57/BL6 mice, markedly augmented the levels of monocyte chemoattractant protein-1 bound to RBCs, which in turn stimulated macrophage migration through an endothelial monolayer. Levels of RBC-bound KC were also increased by HFD. These effects of HFD were abolished in DARC−/− mice. In RBCs from HFD-fed wild-type and DARC−/− mice, levels of membrane cholesterol and phosphatidylserine externalization were increased, fostering RBC-macrophage inflammatory interactions and promoting macrophage phagocytosis in vitro. When labeled ex vivo and injected into wild-type mice, RBCs from HFD-fed mice exhibited ≈3-fold increase in splenic uptake. Finally, RBCs from HFD-fed mice induced increased macrophage adhesion to the endothelium when they were incubated with isolated aortic segments, indicating endothelial activation. Conclusions RBC dysfunction, analogous to endothelial dysfunction, occurs early during diet-induced obesity and may serve as a mediator of atherosclerosis. These findings may have implications for the pathogenesis of atherosclerosis in obesity, a worldwide epidemic. PMID:26467254

  3. High spatial and temporal resolution observations of pulsatile changes in blood echogenicity in the common carotid artery of rats.

    PubMed

    Nam, Kweon-Ho; Bok, Tae-Hoon; Kong, Qi; Paeng, Dong-Guk

    2013-09-01

    Previous studies have found that ultrasound backscatter from blood in vascular flow systems varies under pulsatile flow, with the maximum values occurring during the systolic period. This phenomenon is of particular interest in hemorheology because it is contrary to the well-known fact that red blood cell (RBC) aggregation, which determines the intensity of ultrasound backscatter from blood, decreases at a high systolic shear rate. In the present study, a rat model was used to provide basic information on the characteristics of blood echogenicity in arterial blood flow to investigate the phenomenon of RBC aggregation under pulsatile flow. Blood echogenicity in the common carotid arteries of rats was measured using a high-frequency ultrasound imaging system with a 40-MHz probe. The electrocardiography-based kilohertz visualization reconstruction technique was employed to obtain high-temporal-resolution and high-spatial-resolution time-course B-mode cross-sectional and longitudinal images of the vessel. The experimental results indicate that blood echogenicity in rat carotid arteries varies during a cardiac cycle. Blood echogenicity tends to decrease during early systole and reaches its peak during late systole, followed by a slow decline thereafter. The time delay of the echogenicity peak from peak systole in the present results is the main difference from previous in vitro and in vivo observations of backscattering peaks during early systole, which may be caused by the very rapid heart rates and low RBC aggregation tendency of rats compared with humans and other mammalian species. The present study may provide useful information elucidating the characteristics of RBC aggregation in arterial blood flow.

  4. Design, analysis, and initial testing of a fiber-optic shear gage for three-dimensional, high-temperature flows

    NASA Astrophysics Data System (ADS)

    Orr, Matthew W.

    This investigation concerns the design, analysis, and initial testing of a new, two-component wall shear gage for 3D, high-temperature flows. This gage is a direct-measuring, non-nulling design with a round head surrounded by a small gap. Two flexure wheels are used to allow small motions of the floating head. Fiber-optic displacement sensors measure how far the polished faces of counterweights on the wheels move in relation to a fixed housing as the primary measurement system. No viscous damping was required. The gage has both fiber-optic instrumentation and strain gages mounted on the flexures for validation of the newer fiber optics. The sensor is constructed of Haynes RTM 230RTM, a high-temperature nickel alloy. The gage housing is made of 316 stainless steel. All components of the gage in pure fiber-optic form can survive to a temperature of 1073 K. The bonding methods of the backup strain gages limit their maximum temperature to 473 K. The dynamic range of the gage is from 0--500 Pa (0--10g) and higher shears can be measured by changing the floating head size. Extensive use of finite element modeling was critical to the design and analysis of the gage. Static structural, modal, and thermal analyses were performed on the flexures using the ANSYS finite element package. Static finite element analysis predicted the response of the flexures to a given load, and static calibrations using a direct force method confirmed these results. Finite element modal analysis results were within 16.4% for the first mode and within 30% for the second mode when compared with the experimentally determined modes. Vibration characteristics of the gage were determined from experimental free vibration data after the gage was subjected to an impulse. Uncertainties in the finished geometry make this level of error acceptable. A transient thermal analysis examined the effects of a very high heat flux on the exposed head of the gage. The 100,000 W/m2 heat flux used in this analysis is

  5. Artificial Intelligence Tools for Scaling Up of High Shear Wet Granulation Process.

    PubMed

    Landin, Mariana

    2017-01-01

    The results presented in this article demonstrate the potential of artificial intelligence tools for predicting the endpoint of the granulation process in high-speed mixer granulators of different scales from 25L to 600L. The combination of neurofuzzy logic and gene expression programing technologies allowed the modeling of the impeller power as a function of operation conditions and wet granule properties, establishing the critical variables that affect the response and obtaining a unique experimental polynomial equation (transparent model) of high predictability (R(2) > 86.78%) for all size equipment. Gene expression programing allowed the modeling of the granulation process for granulators of similar and dissimilar geometries and can be improved by implementing additional characteristics of the process, as composition variables or operation parameters (e.g., batch size, chopper speed). The principles and the methodology proposed here can be applied to understand and control manufacturing process, using any other granulation equipment, including continuous granulation processes.

  6. High shear rate flow in a linear stroke magnetorheological energy absorber

    NASA Astrophysics Data System (ADS)

    Hu, W.; Wereley, N. M.; Hiemenz, G. J.; Ngatu, G. T.

    2014-05-01

    To provide adaptive stroking load in the crew seats of ground vehicles to protect crew from blast or impact loads, a magnetorheological energy absorber (MREA) or shock absorber was developed. The MREA provides appropriate levels of controllable stroking load for different occupant weights and peak acceleration because the viscous stroking load generated by the MREA force increases with velocity squared, thereby reducing its controllable range at high piston velocity. Therefore, MREA behavior at high piston velocity is analyzed and validated experimentally in order to investigate the effects of velocity and magnetic field on MREA performance. The analysis used to predict the MREA force as a function of piston velocity squared and applied field is presented. A conical fairing is mounted to the piston head of the MREA in order reduce predicted inlet flow loss by 9% at nominal velocity of 8 m/s, which resulted in a viscous force reduction of nominally 4%. The MREA behavior is experimentally measured using a high speed servo-hydraulic testing system for speeds up to 8 m/s. The measured MREA force is used to validate the analysis, which captures the transient force quite accurately, although the peak force is under-predicted at the peak speed of 8 m/s.

  7. Evaluation of High Temperature Properties and Microstructural Characterization of Resistance Spot Welded Steel Lap Shear Joints

    NASA Astrophysics Data System (ADS)

    Gupta, R. K.; Anil Kumar, V.; Panicker, Paul G.

    2016-02-01

    Joining of thin sheets (0.5 mm) of stainless steel 304 and 17-4PH through resistance spot welding is highly challenging especially when joint is used for high temperature applications. Various combinations of stainless steel sheets of thickness 0.5 mm are spot welded and tested at room temperature as well as at high temperatures (800 K, 1,000 K, 1,200 K). Parent metal as well as spot welded joints are tested and characterized. It is observed that joint strength of 17-4PH steel is highest and then dissimilar steel joint of 17-4PH with SS-304 is moderate and of SS-304 is lowest at all the temperatures. Joint strength of 17-4PH steel is found to be >80% of parent metal properties up to 1,000 K then drastic reduction in strength is noted at 1,200 K. Gradual reduction in strength of SS-304 joint with increase in temperature from 800 to 1,200 K is noted. At 1,200 K, joint strength of all combinations of joints is found to be nearly same. Microstructural evaluation of weld nugget after testing at different temperatures shows presence of tempered martensite in 17-4PH containing welds and homogenized structure in stainless steel 304 weld.

  8. Development of a New Method for Platelet Function Test and Its Shearing Condition in Microfludic System

    NASA Astrophysics Data System (ADS)

    Lee, Hoyoon; Kim, Gyehyu; Choi, Seawhan; Shin, Sehyun; Korea University Department of Mechanical Engineering Team

    2015-11-01

    Platelet is a crucial blood cell on hemostasis. As platelet exposed to high shear stress, it can be activated showing morphological and functional changes to stop bleeding. When platelet is abnormal, there is high risk of cardiovascular diseases. Thus, quick and precise assay for platelet function is important in clinical treatment. In this study, we design a microfluidic system, which can test platelet function exposed with the stimulation of shear and agonists. The microfluidic system consists of three parts: 1) a shear mechanism with rotating stirrer; 2) multiple microchannels to flow samples and to stop; 3) camera-interfaced migration distance(MD) analyzing system. When sheared blood is driven by pressure through the microchannel, shear-activated platelets adhere to a collagen-coated surface, causing blood flow to significantly slow and eventually stop. As the micro-stirrer speed increases, MD decreases exponentially at first, but it increases beyond a critical rpm after all. These results are coincident with data measured by FACS flowcytometry. These results imply that the present system could quantitatively measure the degree of activation, aggregation and adhesion of platelets and that blood MD is potent index for measuring the shear-dependence of platelet function.

  9. Validation of a turbulent Kelvin-Helmholtz shear layer model using a high-energy-density OMEGA laser experiment.

    PubMed

    Hurricane, O A; Smalyuk, V A; Raman, K; Schilling, O; Hansen, J F; Langstaff, G; Martinez, D; Park, H-S; Remington, B A; Robey, H F; Greenough, J A; Wallace, R; Di Stefano, C A; Drake, R P; Marion, D; Krauland, C M; Kuranz, C C

    2012-10-12

    Following the successful demonstration of an OMEGA laser-driven platform for generating and studying nearly two-dimensional unstable plasma shear layers [Hurricane et al., Phys. Plasmas 16, 056305 (2009); Harding et al., Phys. Rev. Lett. 103, 045005 (2009)], this Letter reports on the first quantitative measurement of turbulent mixing in a high-energy-density plasma. As a blast wave moves parallel to an unperturbed interface between a low-density foam and a high-density plastic, baroclinic vorticity is deposited at the interface and a Kelvin-Helmholtz instability-driven turbulent mixing layer is created in the postshock flow due to surface roughness. The spatial scale and density profile of the turbulent layer are diagnosed using x-ray radiography with sufficiently small uncertainty so that the data can be used to ~0.17 μm) in the postshock plasma flow are consistent with an "inertial subrange," within which a Kolmogorov turbulent energy cascade can be active. An illustration of comparing the data set with the predictions of a two-equation turbulence model in the ares radiation hydrodynamics code is also presented.

  10. Validation of a Turbulent Kelvin-Helmholtz Shear Layer Model Using a High-Energy-Density OMEGA Laser Experiment

    NASA Astrophysics Data System (ADS)

    Hurricane, O. A.; Smalyuk, V. A.; Raman, K.; Schilling, O.; Hansen, J. F.; Langstaff, G.; Martinez, D.; Park, H.-S.; Remington, B. A.; Robey, H. F.; Greenough, J. A.; Wallace, R.; Di Stefano, C. A.; Drake, R. P.; Marion, D.; Krauland, C. M.; Kuranz, C. C.

    2012-10-01

    Following the successful demonstration of an OMEGA laser-driven platform for generating and studying nearly two-dimensional unstable plasma shear layers [Hurricane et al., Phys. Plasmas 16, 056305 (2009)PHPAEN1070-664X10.1063/1.3096790; Harding et al., Phys. Rev. Lett. 103, 045005 (2009)PRLTAO0031-900710.1103/PhysRevLett.103.045005], this Letter reports on the first quantitative measurement of turbulent mixing in a high-energy-density plasma. As a blast wave moves parallel to an unperturbed interface between a low-density foam and a high-density plastic, baroclinic vorticity is deposited at the interface and a Kelvin-Helmholtz instability-driven turbulent mixing layer is created in the postshock flow due to surface roughness. The spatial scale and density profile of the turbulent layer are diagnosed using x-ray radiography with sufficiently small uncertainty so that the data can be used to constrain turbulent mixing models. The estimated Reynolds number (˜106), Liepmann-Taylor scale (˜0.5μm), and inner viscous scale (˜0.17μm) in the postshock plasma flow are consistent with an “inertial subrange,” within which a Kolmogorov turbulent energy cascade can be active. An illustration of comparing the data set with the predictions of a two-equation turbulence model in the ares radiation hydrodynamics code is also presented.

  11. Multi-channel analysis of surface waves MASW of models with high shear-wave velocity contrast

    USGS Publications Warehouse

    Ivanov, J.; Miller, R.D.; Peterie, S.; Zeng, C.; Xia, J.; Schwenk, T.

    2011-01-01

    We use the multi-channel analysis of surface waves MASW method to analyze synthetic seismic data calculated using models with high shear-wave velocity Vs contrast. The MASW dispersion-curve images of the Rayleigh wave are obtained using various sets of source-offset and spread-size configurations from the synthetic seismic data and compared with the theoretically calculated fundamental- and higher-mode dispersion-curves. Such tests showed that most of the dispersion-curve images are dominated by higher-mode energy at the low frequencies, especially when analyzing data from long receiver offsets and thus significantly divert from numerically expected dispersion-curve trends, which can lead to significant Vs overestimation. Further analysis showed that using data with relatively short spread lengths and source offsets can image the desired fundamental-mode of the Rayleigh wave that matches the numerically expected dispersion-curve pattern. As a result, it was concluded that it might be possible to avoid higher-mode contamination at low frequencies at sites with high Vs contrast by appropriate selection of spread size and seismic source offset. ?? 2011 Society of Exploration Geophysicists.

  12. Fluid-structure Interaction Modeling of Aneurysmal Conditions with High and Normal Blood Pressures

    NASA Astrophysics Data System (ADS)

    Torii, Ryo; Oshima, Marie; Kobayashi, Toshio; Takagi, Kiyoshi; Tezduyar, Tayfun E.

    2006-09-01

    Hemodynamic factors like the wall shear stress play an important role in cardiovascular diseases. To investigate the influence of hemodynamic factors in blood vessels, the authors have developed a numerical fluid-structure interaction (FSI) analysis technique. The objective is to use numerical simulation as an effective tool to predict phenomena in a living human body. We applied the technique to a patient-specific arterial model, and with that we showed the effect of wall deformation on the WSS distribution. In this paper, we compute the interaction between the blood flow and the arterial wall for a patient-specific cerebral aneurysm with various hemodynamic conditions, such as hypertension. We particularly focus on the effects of hypertensive blood pressure on the interaction and the WSS, because hypertension is reported to be a risk factor in rupture of aneurysms. We also aim to show the possibility of FSI computations with hemodynamic conditions representing those risk factors in cardiovascular disease. The simulations show that the transient behavior of the interaction under hypertensive blood pressure is significantly different from the interaction under normal blood pressure. The transient behavior of the blood-flow velocity, and the resulting WSS and the mechanical stress in the aneurysmal wall, are significantly affected by hypertension. The results imply that hypertension affects the growth of an aneurysm and the damage in arterial tissues.

  13. Access to sustained high-beta with internal transport barrier and negative central magnetic shear in DIII-Da)

    NASA Astrophysics Data System (ADS)

    Garofalo, A. M.; Doyle, E. J.; Ferron, J. R.; Greenfield, C. M.; Groebner, R. J.; Hyatt, A. W.; Jackson, G. L.; Jayakumar, R. J.; Kinsey, J. E.; La Haye, R. J.; McKee, G. R.; Murakami, M.; Okabayashi, M.; Osborne, T. H.; Petty, C. C.; Politzer, P. A.; Reimerdes, H.; Scoville, J. T.; Solomon, W. M.; St. John, H. E.; Strait, E. J.; Turnbull, A. D.; Wade, M. R.; VanZeeland, M. A.

    2006-05-01

    High values of normalized β (βN˜4) and safety factor (qmin˜2) have been sustained simultaneously for ˜2s in DIII-D [J.L. Luxon, Nucl. Fusion 42, 64 (2002)], suggesting a possible path to high fusion performance, steady-state tokamak scenarios with a large fraction of bootstrap current. The combination of internal transport barrier and negative central magnetic shear at high β results in high confinement (H89P>2.5) and large bootstrap current fraction (fBS>60%) with good alignment. Previously, stability limits in plasmas with core transport barriers have been observed at moderate values of βN (<3) because of the pressure peaking which normally develops from improved core confinement. In recent DIII-D experiments, the internal transport barrier is clearly observed in the electron density and in the ion temperature and rotation profiles at ρ ˜0.5 but not in the electron temperature profile, which is very broad. The misalignment of Ti and Te gradients may help to avoid a large local pressure gradient. Furthermore, at low internal inductance ˜0.6, the current density gradients are close to the vessel and the ideal kink modes are strongly wall-coupled. Simultaneous feedback control of both external and internal sets of n =1 magnetic coils was used to maintain optimal error field correction and resistive wall mode stabilization, allowing operation above the free-boundary β limit. Large particle orbits at high safety factor in the core help to broaden both the pressure and the beam-driven current profiles, favorable for steady-state operation. At plasma current flat top and β ˜5%, a noninductive current fraction of ˜100% has been observed. Stability modeling shows the possibility for operation up to the ideal-wall limit at β ˜6%.

  14. A high energy density shock driven Kelvin-Helmholtz shear layer experiment

    SciTech Connect

    Hurricane, O. A.; Hansen, J. F.; Robey, H. F.; Remington, B. A.; Bono, M. J.; Harding, E. C.; Drake, R. P.; Kuranz, C. C.

    2009-05-15

    Radiographic data from a novel and highly successful high energy density Kelvin-Helmholtz (KH) instability experiment is presented along with synapses of the theory and simulation behind the target design. Data on instability growth are compared to predictions from simulation and theory. The key role played by baroclinic vorticity production in the functioning of the target and the key design parameters are also discussed. The data show the complete evolution of large distinct KH eddies, from formation to turbulent break-up. Unexpectedly, low density bubbles comparable to the vortex size are observed forming in the free-stream region above each vortex at late time. These bubbles have the appearance of localized shocks, possibly supporting a theoretical fluid dynamics conjecture about the existence of supersonic bubbles over the vortical structure [transonic convective Mach numbers, D. Papamoschou and A. Roshko, J. Fluid Mech. 197, 453 (1988)] that support localized shocks (shocklets) not extending into the free stream (P. E. Dimotakis, Proceedings of the 22nd Fluid Dynamics, Plasma Dynamics and Lasers Conference, 1991, Paper No. AIAA 91-1724). However, it is also possible that these low density bubbles are the result of a cavitationlike effect. Hypothesis that may explain the appearance of low density bubbles will be discussed.

  15. High Blood Pressure Dangers: Hypertension's Effects on Your Body

    MedlinePlus

    ... supply to your brain. It's often caused by atherosclerosis or a blood clot — both of which can ... kidney (renal) artery aneurysm. One potential cause is atherosclerosis, which weakens and damages the artery wall. Over ...

  16. Americans with High Blood Pressure Still Eating Too Much Salt

    MedlinePlus

    ... Blood Pressure Still Eating Too Much Salt Average sodium intake more than double the recommended daily limit ... did in 1999. Between 1999 and 2012, salt (sodium) consumption rose from about 2,900 milligrams a ...

  17. High Blood Pressure, Afib and Your Risk of Stroke

    MedlinePlus

    ... irregular atrial heart rhythm — a condition called atrial fibrillation — is present in about one out of five ... blood pressure is the chief culprit, and atrial fibrillation isn’t far behind. Yet there’s good news — ...

  18. Acoustic emission monitoring from a lab scale high shear granulator--a novel approach.

    PubMed

    Watson, N J; Povey, M J W; Reynolds, G K; Xu, B H; Ding, Y

    2014-04-25

    A new approach to the monitoring of granulation processes using passive acoustics together with precise control over the granulation process has highlighted the importance of particle-particle and particle-bowl collisions in acoustic emission. The results have shown that repeatable acoustic results could be obtained but only when a spray nozzle water addition system was used. Acoustic emissions were recorded from a transducer attached to the bowl and an airborne transducer. It was found that the airborne transducer detected very little from the granulation and only experienced small changes throughout the process. The results from the bowl transducer showed that during granulation the frequency content of the acoustic emission shifted towards the lower frequencies. Results from the discrete element model indicate that when larger particles are used the number of collisions the particles experience reduces. This is a result of the volume conservation methodology used in this study, therefore larger particles results in less particles. These simulation results coupled with previous theoretical work on the frequency content of an impacting sphere explain why the frequency content of the acoustic emissions reduces during granule growth. The acoustic system used was also clearly able to identify when large over-wetted granules were present in the system, highlighting its benefit for detecting undesirable operational conditions. High-speed photography was used to study if visual changes in the granule properties could be linked with the changing acoustic emissions. The high speed photography was only possible towards the latter stages of the granulation process and it was found that larger granules produced a higher magnitude of acoustic emission across a broader frequency range.

  19. Application of high-velocity friction experiments to the shear rupture of a fault in an elastic half-space

    NASA Astrophysics Data System (ADS)

    Liao, Zonghu; Reches, Zeev

    2013-04-01

    We developed a physics-based model for earthquake rupture by numerically simulating shear rupture along a 2D vertical fault with the dynamic frictional strength of granite under high slip velocity. Recent experimental observations indicated that the steady-state frictional strength of silica-rich igneous rocks (granite, syenite, diorite) alternate between dynamic-weakening under low velocity (V < 0.03 m/s) and dynamic-strengthening under higher velocities (V > 0.03 m/s). This strength alternation was attributed to powder-lubrication (weakening), and powder dehydration (strengthening) (Sammis et al., 2011). We used the dynamic friction law which was determined on samples of Sierra White granite under experimental velocities approaching 1 m/s (Reches and Lockner, 2010). We converted their observed friction-distance-velocity relations into an empirical friction model referred to as WEST (WEakening - STrengthening). For the simulation calculations, we used the spectral element code of Ampuero (web.gps.caltech.edu/~ampuero/software), which computes the spontaneous rupture propagation along an anti-plane shear (mode III) fracture in an elastic half-space. In the present analysis, the WEST friction model is used as the fault strength while keeping all other parameters (crust properties and stresses) the same as Version 3 of the Southern California Earthquake Center (SCEC) benchmark problem (Harris et al., 2004). This approach allows for direct comparison between the WEST rupture and the benchmark rupture with a fault of slip-weakening friction model (Rojas et al., 2008). We found the following differences between the ruptures of the two models: (1) WEST-based rupture occurs earlier at all observation points away from the nucleation zone; (2) WEST-based model has lower (~ 35%) peak velocity and shorter rise-time; and (3) WEST-based rupture shows rich, frequent alteration of slip velocity, and consequently, the simulated rupture is more complex in stress drop, displacements

  20. Optimization of a high shear wet granulation process using focused beam reflectance measurement and particle vision microscope technologies.

    PubMed

    Arp, Zane; Smith, Ben; Dycus, Eric; O'grady, Des

    2011-08-01

    Application of process analytical technology in the pharmaceutical industry has led to a great number of studies into inline instrumentation. Near-infrared moisture monitoring in fluid bed drying and content uniformity assurance in blending are gaining acceptance for monitoring and quality control of these processes. Although these techniques are a great improvement over traditional methods, each is performed at points in processing wherein processing is well understood and interfacing equipment is relatively easy. More complex unit operations have largely been unexplored due to complexities interfacing inline analytical equipment to unit operations or a lack of methodologies that can be applied to measure attributes of interest. This paper reports results from a study utilizing a focused beam reflectance measurement system equipped with window scraper technology for the inline measurement and control of a high shear wet granulation (HSWG) process. In addition to this, offline results obtained with a particle vision microscope system are compared to verify the results obtained inline. It is shown that using these technologies in monitoring the HSWG process greatly increases process understanding of physical changes occurring during processing through real-time observation of particle size, leading to real-time control of the process.

  1. Nanoparticles and nanocapsules created using the Ouzo effect: spontaneous emulisification as an alternative to ultrasonic and high-shear devices.

    PubMed

    François, Ganachaud; Katz, Joseph L

    2005-02-01

    The preparation of polymeric particles and capsules by means of spontaneous droplet formation and subsequent polymer precipitation or synthesis is well-known. However, spontaneous emulsification is a phenomenon that has often been erroneously interpreted. This Minireview provides new insights into the preparation of metastable liquid dispersions by homogeneous liquid-liquid nucleation, and is based primarily on a recent study by Vitale and Katz (Langmuir, 2003, 19, 4105-4110). This spontaneous emulsification, which they named the Ouzo effect, occurs upon pouring, into water, a mixture of a totally water-miscible solvent and a hydrophobic oil--and optionally some water--thus generating long-lived small droplets, which are formed even though no surfactant is present. Herein, we review and reinterpret the most relevant publications on the synthesis of a variety of dispersions (pseudolatexes, silicone emulsions, biodegradable polymeric nanocapsules, etc.), which we believe have actually been synthesized using the Ouzo effect. The Ouzo effect may also become a substitute for high-shear techniques, which, to date have only been of limited utility on industrial scales.

  2. Excitation of high-n toroidicity-induced shear Alfven eigenmodes by energetic particles and fusion alpha particles in tokamaks

    SciTech Connect

    Fu, G.Y.; Cheng, C.Z.

    1992-07-01

    The stability of high-n toroidicity-induced shear Alfven eigenmodes (TAE) in the presence of fusion alpha particles or energetic ions in tokamaks is investigated. The TAE modes are discrete in nature and thus can easily tap the free energy associated with energetic particle pressure gradient through wave particle resonant interaction. A quadratic form is derived for the high-n TAE modes using gyro-kinetic equation. The kinetic effects of energetic particles are calculated perturbatively using the ideal MHD solution as the lowest order eigenfunction. The finite Larmor radius (FLR) effects and the finite drift orbit width (FDW) effects are included for both circulating and trapped energetic particles. It is shown that, for circulating particles, FLR and FDW effects have two opposite influences on the stability of the high-n TAE modes. First, they have the usual stabilizing effects by reducing the wave particle interaction strength. Second, they also have destabilizing effects by allowing more particles to resonate with the TAE modes. It is found that the growth rate induced by the circulating alpha particles increase linearly with toroidal mode number n for small {kappa}{sub {theta}}{rho}{sub {alpha}}, and decreases as 1/n for {kappa}{sub {theta}}{rho}{sub {alpha}} {much_gt} 1. The maximum growth rate is obtained at {kappa}{sub {theta}}{rho}{sub {alpha}} on the order of unity and is nearly constant for the range of 0.7 < {upsilon}{sub {alpha}}/{upsilon}{sub A} < 2.5. On the other hand, the trapped particle response is dominated by the precessional drift resonance. The bounce resonant contribution is negligible. The growth rate peaks sharply at the value of {kappa}{sub {theta}}{rho}{sub {alpha}} such that the precessional drift resonance occurs for the most energetic trapped particles. The maximum growth rate due to the energetic trapped particles is comparable to that of circulating particles.

  3. Excitation of high-n toroidicity-induced shear Alfven eigenmodes by energetic particles and fusion alpha particles in tokamaks

    SciTech Connect

    Fu, G.Y.; Cheng, C.Z.

    1992-07-01

    The stability of high-n toroidicity-induced shear Alfven eigenmodes (TAE) in the presence of fusion alpha particles or energetic ions in tokamaks is investigated. The TAE modes are discrete in nature and thus can easily tap the free energy associated with energetic particle pressure gradient through wave particle resonant interaction. A quadratic form is derived for the high-n TAE modes using gyro-kinetic equation. The kinetic effects of energetic particles are calculated perturbatively using the ideal MHD solution as the lowest order eigenfunction. The finite Larmor radius (FLR) effects and the finite drift orbit width (FDW) effects are included for both circulating and trapped energetic particles. It is shown that, for circulating particles, FLR and FDW effects have two opposite influences on the stability of the high-n TAE modes. First, they have the usual stabilizing effects by reducing the wave particle interaction strength. Second, they also have destabilizing effects by allowing more particles to resonate with the TAE modes. It is found that the growth rate induced by the circulating alpha particles increase linearly with toroidal mode number n for small {kappa}{sub {theta}}{rho}{sub {alpha}}, and decreases as 1/n for {kappa}{sub {theta}}{rho}{sub {alpha}} {much gt} 1. The maximum growth rate is obtained at {kappa}{sub {theta}}{rho}{sub {alpha}} on the order of unity and is nearly constant for the range of 0.7 < {upsilon}{sub {alpha}}/{upsilon}{sub A} < 2.5. On the other hand, the trapped particle response is dominated by the precessional drift resonance. The bounce resonant contribution is negligible. The growth rate peaks sharply at the value of {kappa}{sub {theta}}{rho}{sub {alpha}} such that the precessional drift resonance occurs for the most energetic trapped particles. The maximum growth rate due to the energetic trapped particles is comparable to that of circulating particles.

  4. Ultrasonic shear wave couplant

    DOEpatents

    Kupperman, David S.; Lanham, Ronald N.

    1985-01-01

    Ultrasonically testing of an article at high temperatures is accomplished by the use of a compact layer of a dry ceramic powder as a couplant in a method which involves providing an ultrasonic transducer as a probe capable of transmitting shear waves, coupling the probe to the article through a thin compact layer of a dry ceramic powder, propagating a shear wave from the probe through the ceramic powder and into the article to develop echo signals, and analyzing the echo signals to determine at least one physical characteristic of the article.

  5. Analysis of high gradient magnetic field effects on distribution of nanoparticles injected into pulsatile blood stream

    NASA Astrophysics Data System (ADS)

    Reza Habibi, Mohammad; Ghassemi, Majid; Hossien Hamedi, Mohammad

    2012-04-01

    Magnetic nanoparticles are widely used in a wide range of applications including data storage materials, pharmaceutical industries as magnetic separation tools, anti-cancer drug carriers and micro valve applications. The purpose of the current study is to investigate the effect of a non-uniform magnetic field on bio-fluid (blood) with magnetic nanoparticles. The effect of particles as well as mass fraction on flow field and volume concentration is investigated. The governing non-linear differential equations, concentration and Navier-stokes are coupled with the magnetic field. To solve these equations, a finite volume based code is developed and utilized. A real pulsatile velocity is utilized as inlet boundary condition. This velocity is extracted from an actual experimental data. Three percent nanoparticles volume concentration, as drug carrier, is steadily injected in an unsteady, pulsatile and non-Newtonian flow. A power law model is considered for the blood viscosity. The results show that during the systole section of the heartbeat when the blood velocity increases, the magnetic nanoparticles near the magnetic source are washed away. This is due to the sudden increase of the hydrodynamic force, which overcomes the magnetic force. The probability of vein blockage increases when the blood velocity reduces during the diastole time. As nanoparticles velocity injection decreases (longer injection time) the wall shear stress (especially near the injection area) decreases and the retention time of the magnetic nanoparticles in the blood flow increases.

  6. Failure During Sheared Edge Stretching

    NASA Astrophysics Data System (ADS)

    Levy, B. S.; van Tyne, C. J.

    2008-12-01

    Failure during sheared edge stretching of sheet steels is a serious concern, especially in advanced high-strength steel (AHSS) grades. The shearing process produces a shear face and a zone of deformation behind the shear face, which is the shear-affected zone (SAZ). A failure during sheared edge stretching depends on prior deformation in the sheet, the shearing process, and the subsequent strain path in the SAZ during stretching. Data from laboratory hole expansion tests and hole extrusion tests for multiple lots of fourteen grades of steel were analyzed. The forming limit curve (FLC), regression equations, measurement uncertainty calculations, and difference calculations were used in the analyses. From these analyses, an assessment of the primary factors that contribute to the fracture during sheared edge stretching was made. It was found that the forming limit strain with consideration of strain path in the SAZ is a major factor that contributes to the failure of a sheared edge during stretching. Although metallurgical factors are important, they appear to play a somewhat lesser role.

  7. Tunable shear thickening in suspensions

    PubMed Central

    Lin, Neil Y.C.; Ness, Christopher; Cates, Michael E.; Sun, Jin; Cohen, Itai

    2016-01-01

    Shear thickening, an increase of viscosity with shear rate, is a ubiquitous phenomenon in suspended materials that has implications for broad technological applications. Controlling this thickening behavior remains a major challenge and has led to empirical strategies ranging from altering the particle surfaces and shape to modifying the solvent properties. However, none of these methods allows for tuning of flow properties during shear itself. Here, we demonstrate that by strategic imposition of a high-frequency and low-amplitude shear perturbation orthogonal to the primary shearing flow, we can largely eradicate shear thickening. The orthogonal shear effectively becomes a regulator for controlling thickening in the suspension, allowing the viscosity to be reduced by up to 2 decades on demand. In a separate setup, we show that such effects can be induced by simply agitating the sample transversely to the primary shear direction. Overall, the ability of in situ manipulation of shear thickening paves a route toward creating materials whose mechanical properties can be controlled. PMID:27621472

  8. [Childhood's determinants for high blood pressure in adulthood].

    PubMed

    Bucher, Barbara S; Tschumi, Sibyelle; Simonetti, Giacomo D

    2012-05-01

    Hypertension has been estimated to affect 20 - 25% of the adult population and represents an important risk factor for cardiovascular disease like coronary heart disease, stroke and peripheral artery occlusive disease. In addition, hypertension supports the development and progression of chronic kidney insufficiency. The interaction of multiple genetic and environmental factors are felt to influence the level of blood pressure. Epidemiological data in the sixties and seventies demonstrated a correlation between cardiovascular disease and infant mortality in the same population. In the late eighties Barker and coworkers described a strong correlation between low birth weight and increased risk for the development of cardiovascular complications. It has been supposed that factors influencing the intrauterine growth and development can lead to adult cardiovascular diseases, known as the concept of "fetal programming". Beside the effect of fetal programming, multiple (preventable and non-preventable) factors determine the blood pressure level in childhood, which will define adult blood pressure level through the blood pressure tracking from childhood to adulthood. Hence, the prevention of cardiovascular disease in adulthood begins in childhood through identification of preventable risk factors as for example obesity and passive smoking and recognition of risk groups like small for gestational age or preterm children.

  9. High Blood Pressure in Adolescents of Curitiba: Prevalence and Associated Factors

    PubMed Central

    Bozza, Rodrigo; de Campos, Wagner; Barbosa Filho, Valter Cordeiro; Stabelini Neto, Antonio; da Silva, Michael Pereira; Maziero, Renato Silva Barbosa

    2016-01-01

    Background Arterial hypertension is a major public health problem and has increased considerably in young individuals in past years. Thus, identifying factors associated with this condition is important to guide intervention strategies in this population. Objective To determine high blood pressure prevalence and its associated factors in adolescents. Methods A random sample of 1,242 students enrolled in public schools of the city of Curitiba (PR) was selected. Self-administered questionnaires provided family history of hypertension, daily energy expenditure, smoking habit, daily fat intake, and socioeconomic status. Waist circumference was measured following standardized procedures, and blood pressure was measured with appropriate cuffs in 2 consecutive days to confirm high blood pressure. Relative frequency and confidence interval (95%CI) indicated high blood pressure prevalence. Bivariate and multivariate analyses assessed the association of risk factors with high blood pressure. Results The high blood pressure prevalence was 18.2% (95%CI 15.2-21.6). Individuals whose both parents had hypertension [odds ratio (OR), 2.22; 95%CI 1.28-3.85] and those with high waist circumference (OR, 2.1; 95%CI 1.34-3.28) had higher chances to develop high blood pressure. Conclusion Positive family history of hypertension and high waist circumference were associated with high blood pressure in adolescents. These factors are important to guide future interventions in this population. PMID:27058256

  10. A Piezoelectric Shear Stress Sensor

    NASA Technical Reports Server (NTRS)

    Kim, Taeyang; Saini, Aditya; Kim, Jinwook; Gopalarathnam, Ashok; Zhu, Yong; Palmieri, Frank L.; Wohl, Christopher J.; Jiang, Xiaoning

    2016-01-01

    In this paper, a piezoelectric sensor with a floating element was developed for shear stress measurement. The piezoelectric sensor was designed to detect the pure shear stress suppressing effects of normal stress generated from the vortex lift-up by applying opposite poling vectors to the: piezoelectric elements. The sensor was first calibrated in the lab by applying shear forces and it showed high sensitivity to shear stress (=91.3 +/- 2.1 pC/Pa) due to the high piezoelectric coefficients of PMN-33%PT (d31=-1330 pC/N). The sensor also showed almost no sensitivity to normal stress (less than 1.2 pC/Pa) because of the electromechanical symmetry of the device. The usable frequency range of the sensor is 0-800 Hz. Keywords: Piezoelectric sensor, shear stress, floating element, electromechanical symmetry

  11. Hypoalbuminemia causes high blood viscosity by increasing red cell lysophosphatidylcholine.

    PubMed

    Joles, J A; Willekes-Koolschijn, N; Koomans, H A

    1997-09-01

    Albumin deficiency is accompanied by a reduction in red cell deformability and blood hyperviscosity. Albumin deficiency increases plasma fibrinogen and triglyceride levels and may alter red cell membrane lipid composition. These options, which could all contribute to reduced red cell deformability (RCD) and hyperviscosity, were studied in the Nagase analbuminemic rat (NAR), a mutant Sprague Dawley rat (CON), characterized by normal total protein levels, with an absolute deficiency of albumin, but elevated levels of non-albumin proteins and hyperlipidemia. Plasma protein-binding of the polar phopholipid lysophosphatidylcholine (LPC) was markedly decreased. LPC comprised only 26 +/- 1% of total plasma phospholipids as compared to 42 +/- 2% in CON. NAR red cells in CON plasma had a viscosity that was similar to CON red cells in CON plasma. Conversely, CON red cells in NAR plasma show an increased viscosity as compared to CON red cells in CON plasma. The maximum deformation index of both NAR and CON red cells was markedly decreased in NAR plasma as compared to either NAR or CON cells in CON plasma (0.04 +/- 0.03 and 0.02 +/- 0.02 vs. 0.22 +/- 0.06 and 0.15 +/- 0.04, respectively; P < 0.05). Thus, plasma composition causes hyperviscosity and reduced RCD in NAR. Fibrinogen is not responsible since red cells in serum and red cells in plasma had a similar viscosity and differences in viscosity and RCD between NAR and CON were maintained. Plasma triglycerides are also not responsible since the viscosity of red cells in serum with a 50% reduction in triglycerides was not reduced. LPC levels in red cells were increased in NAR (8.7 +/- 0.2 vs. 5.5 +/- 0.3% of total phospholipids; P < 0.01). Adding albumin to NAR blood dose-dependently decreased whole blood viscosity, despite marked increases in plasma viscosity, and increased RCD of NAR cells (from 0.04 +/- 0.03 to 0.21 +/- 0.01; P < 0.05). There was also some effect on CON RCD of similar albumin addition to CON blood (from 0

  12. Wave-front analysis with high accuracy by use of a double-grating lateral shearing interferometer.

    PubMed

    Leibbrandt, G W; Harbers, G; Kunst, P J

    1996-11-01

    A phase-stepped double-grating lateral shearing interferometer to be used for wave-front analysis is presented. The resulting interference patterns are analyzed with a differential Zernike polynomial matrix-inversion method. Possible error sources are analyzed in the design stage, and it is shown that the inaccuracy can be kept within 2-5 mλ rms. The apparatus was tested and evaluated in practice. Comparison with a phase-stepped Twyman-Green interferometer demonstrates that the accuracy of the two methods is comparable. Lateral shearing interferometry scores better on reproducibility, owing to the stability and robustness of the method.

  13. Interaction between a normal shock wave and a turbulent boundary layer at high transonic speeds. II - Wall shear stress

    NASA Technical Reports Server (NTRS)

    Liou, M. S.; Adamson, T. C., Jr.

    1980-01-01

    Asymptotic methods are used to calculate the shear stress at the wall for the interaction between a normal shock wave and a turbulent boundary layer on a flat plate. A mixing length model is used for the eddy viscosity. The shock wave is taken to be strong enough that the sonic line is deep in the boundary layer and the upstream influence is thus very small. It is shown that unlike the result found for laminar flow an asymptotic criterion for separation is not found; however, conditions for incipient separation are computed numerically using the derived solution for the shear stress at the wall. Results are compared with available experimental measurements.

  14. The impact of high-frequency magnetic stimulation of peripheral nerves: muscle hardness, venous blood flow, and motor function of upper extremity in healthy subjects.

    PubMed

    Okudera, Yoshihiko; Matsunaga, Toshiki; Sato, Mineyoshi; Chida, Satoaki; Hatakeyama, Kazutoshi; Watanabe, Motoyuki; Shimada, Yoichi

    2015-01-01

    The purpose of this study was to investigate the impact of high-frequency peripheral nerve magnetic stimulation on the upper limb function. Twenty-five healthy adults (16 men and 9 women) participated in this study. The radial nerve of the non-dominant hand was stimulated by high-frequency magnetic stimulation device. A total of 600 impulses were applied at a frequency of 20 Hz and intensity of 1.2 resting motor threshold (rMT). At three time points (before, immediately after, and 15 min after stimulation), muscle hardness of the extensor digitorum muscle on the stimulated side was measured using a mechanical tissue hardness meter and a shear wave imaging device, cephalic venous blood flow on the stimulated side was measured using an ultrasound system, and the Box and Block test (BBT) was performed. Mechanical tissue hardness results did not show any significant differences between before, immediately after, and 15 min after stimulation. Measurements via shear wave imaging showed that muscle hardness significantly decreased both immediately and 15 min after stimulation compared to before stimulation (P < 0.05). Peripheral venous blood flow and BBT score significantly increased both immediately and 15 min after stimulation compared to before stimulation (P < 0.01). High-frequency peripheral nerve magnetic stimulation can achieve effects similar to electrical stimulation in a less invasive manner, and may therefore become an important element in next-generation rehabilitation.

  15. High-Resolution Crystal Structures Elucidate the Molecular Basis of Cholera Blood Group Dependence.

    PubMed

    Heggelund, Julie Elisabeth; Burschowsky, Daniel; Bjørnestad, Victoria Ariel; Hodnik, Vesna; Anderluh, Gregor; Krengel, Ute

    2016-04-01

    Cholera is the prime example of blood-group-dependent diseases, with individuals of blood group O experiencing the most severe symptoms. The cholera toxin is the main suspect to cause this relationship. We report the high-resolution crystal structures (1.1-1.6 Å) of the native cholera toxin B-pentamer for both classical and El Tor biotypes, in complexes with relevant blood group determinants and a fragment of its primary receptor, the GM1 ganglioside. The blood group A determinant binds in the opposite orientation compared to previously published structures of the cholera toxin, whereas the blood group H determinant, characteristic of blood group O, binds in both orientations. H-determinants bind with higher affinity than A-determinants, as shown by surface plasmon resonance. Together, these findings suggest why blood group O is a risk factor for severe cholera.

  16. High-Resolution Crystal Structures Elucidate the Molecular Basis of Cholera Blood Group Dependence

    PubMed Central

    Heggelund, Julie Elisabeth; Burschowsky, Daniel; Bjørnestad, Victoria Ariel; Hodnik, Vesna; Anderluh, Gregor; Krengel, Ute

    2016-01-01

    Cholera is the prime example of blood-group-dependent diseases, with individuals of blood group O experiencing the most severe symptoms. The cholera toxin is the main suspect to cause this relationship. We report the high-resolution crystal structures (1.1–1.6 Å) of the native cholera toxin B-pentamer for both classical and El Tor biotypes, in complexes with relevant blood group determinants and a fragment of its primary receptor, the GM1 ganglioside. The blood group A determinant binds in the opposite orientation compared to previously published structures of the cholera toxin, whereas the blood group H determinant, characteristic of blood group O, binds in both orientations. H-determinants bind with higher affinity than A-determinants, as shown by surface plasmon resonance. Together, these findings suggest why blood group O is a risk factor for severe cholera. PMID:27082955

  17. Precision blood-leak detector with high long-time stability

    NASA Astrophysics Data System (ADS)

    Georgiadis, Christos; Kleuver, Wolfram

    1999-11-01

    With this publication a precision blood-leak-detector is presented. The blood-leak-detector is used for recognition of fractures in the dialyzer of a kidney-machine. It has to detect safely a blood flow of ml/min to exclude any risk for the patient. A lot of systems exist for blood-leak-detection. All of them use the same principle. They detect the light absorption in the dialyze fluid. The actual used detectors are inferior to the new developed sensor in resolution and long-time stability. Regular test of the existing systems and high failure rates are responsible for the high maintenance.

  18. High Blood Cholesterol Q&A Dr. Michael Lauer | NIH MedlinePlus the Magazine

    MedlinePlus

    ... this page please turn Javascript on. Feature: High Cholesterol High Blood Cholesterol Q&A with Dr. Michael Lauer Past Issues / ... heavier and older, what does recent research on cholesterol and heart health tell us that Americans need ...

  19. All in the Family: When High Blood Cholesterol Occurs in Families

    MedlinePlus

    ... page please turn Javascript on. Feature: High Cholesterol All in the Family: When High Blood Cholesterol Occurs ... A / Cholesterol Levels: What You Need to Know / All In The Family Summer 2012 Issue: Volume 7 ...

  20. Predictability of Sheared Tropical Cyclones

    NASA Astrophysics Data System (ADS)

    Zhang, F.; Tao, D.

    2015-12-01

    Predictability of the formation, rapid intensification and eyewall replacement of sheared tropical cyclones (TCs) are explored through a series of convection-permitting ensemble simulations using the Weather Research and Forecasting (WRF) model with different environmental vertical wind shear, sea-surface temperature (SST), and ambient moisture conditions. It is found that the intrinsic predictability of the RI onset time is more limited with increasing shear magnitude until the shear magnitude is large enough to prevent the TC formation. Based on ensemble sensitivity and correlation analysis, the RI onset timing within one set is largely related to the vortex tilt magnitude, the diabatic heating distribution and the strength of the primary vortex circulation. Systematic differences amongst the ensemble members begin to arise right after the initial burst of moist convection associated with the incipient vortex. This difference from the randomness inherent in moist convection in terms of both location and intensity first changes the TC vortex structure subtly and then leads to the deviations in system scales and eventually in the development (and precession) of the TC. On average, a higher SST has a positive effect on the TC formation and reduces the uncertainty of development under all shear conditions, while a drier environment has a negative impact on the TCs development and either broadens the ensemble spread of RI onset time or prevents the storm from forming when the shear-induced tilt is large. Nevertheless, the uncertainty in environmental shear magnitudes may dominate over the effect of randomness in moist convection in terms of TC formation and predictability. A byproduct of tropical cyclones under vertical wind shear is the secondary eyewall formation (SEF). It is found that the eyewall formation is more often observed in TCs with moderate to high shear, which was inherently more unpredictable. The inward contraction/axisymmeterization of shear

  1. Interaction between a normal shock wave and a turbulent boundary layer at high transonic speeds. Part 2: Wall shear stress

    NASA Technical Reports Server (NTRS)

    Liou, M. S.; Adamson, T. C., Jr.

    1979-01-01

    An analysis is presented of the flow in the two inner layers, the Reynolds stress sublayer and the wall layer. Included is the calculation of the shear stress at the wall in the interaction region. The limit processes considered are those used for an inviscid flow.

  2. Blood group genotyping: from patient to high-throughput donor screening.

    PubMed

    Veldhuisen, B; van der Schoot, C E; de Haas, M

    2009-10-01

    Blood group antigens, present on the cell membrane of red blood cells and platelets, can be defined either serologically or predicted based on the genotypes of genes encoding for blood group antigens. At present, the molecular basis of many antigens of the 30 blood group systems and 17 human platelet antigens is known. In many laboratories, blood group genotyping assays are routinely used for diagnostics in cases where patient red cells cannot be used for serological typing due to the presence of auto-antibodies or after recent transfusions. In addition, DNA genotyping is used to support (un)-expected serological findings. Fetal genotyping is routinely performed when there is a risk of alloimmune-mediated red cell or platelet destruction. In case of patient blood group antigen typing, it is important that a genotyping result is quickly available to support the selection of donor blood, and high-throughput of the genotyping method is not a prerequisite. In addition, genotyping of blood donors will be extremely useful to obtain donor blood with rare phenotypes, for example lacking a high-frequency antigen, and to obtain a fully typed donor database to be used for a better matching between recipient and donor to prevent adverse transfusion reactions. Serological typing of large cohorts of donors is a labour-intensive and expensive exercise and hampered by the lack of sufficient amounts of approved typing reagents for all blood group systems of interest. Currently, high-throughput genotyping based on DNA micro-arrays is a very feasible method to obtain a large pool of well-typed blood donors. Several systems for high-throughput blood group genotyping are developed and will be discussed in this review.

  3. Zipper and freeway shear zone junctions

    NASA Astrophysics Data System (ADS)

    Passchier, Cees; Platt, John

    2016-04-01

    Ductile shear zones are usually presented as isolated planar high-strain domains in a less deformed wall rock, characterised by shear sense indicators such as characteristic deflected foliation traces. Many shear zones, however, form branched systems and if movement on such branches is contemporaneous, the resulting geometry can be complicated and lead to unusual fabric geometries in the wall rock. For Y-shaped shear zone junctions with three simultaneously operating branches, and with slip directions at a high angle to the branch line, eight basic types of shear zone triple junctions are possible, divided into three groups. The simplest type, called freeway junctions, have similar shear sense on all three branches. If shear sense is different on the three branches, this can lead to space problems. Some of these junctions have shear zone branches that join to form a single branch, named zipper junctions, or a single shear zone which splits to form two, known as wedge junctions. Closing zipper junctions are most unusual, since they form a non-active high-strain zone with opposite deflection of foliations. Shear zipper and shear wedge junctions have two shear zones with similar shear sense, and one with the opposite sense. All categories of shear zone junctions show characteristic flow patterns in the shear zone and its wall rock. Shear zone junctions with slip directions normal to the branch line can easily be studied, since ideal sections of shear sense indicators lie in the plane normal to the shear zone branches and the branch line. Expanding the model to allow slip oblique and parallel to the branch line in a full 3D setting gives rise to a large number of geometries in three main groups. Slip directions can be parallel on all branches but oblique to the branch line: two slip directions can be parallel and a third oblique, or all three branches can have slip in different directions. Such more complex shear zone junctions cannot be studied to advantage in a

  4. Shear piezoelectricity in bone at the nanoscale

    NASA Astrophysics Data System (ADS)

    Minary-Jolandan, Majid; Yu, Min-Feng

    2010-10-01

    Recent demonstration of shear piezoelectricity in an isolated collagen fibril, which is the origin of piezoelectricity in bone, necessitates investigation of shear piezoelectric behavior in bone at the nanoscale. Using high resolution lateral piezoresponse force microcopy (PFM), shear piezoelectricity in a cortical bone sample was studied at the nanoscale. Subfibrillar structure of individual collagen fibrils with a periodicity of 60-70 nm were revealed in PFM map, indicating the direct contribution of collagen fibrils to the shear piezoelectricity of bone.

  5. Characteristics of the response of the iliac artery to wall shear stress in the anaesthetized pig.

    PubMed

    Kelly, R F; Snow, H M

    2007-07-15

    The functional significance of shear stress-induced vasodilatation in large conduit arteries is unclear since changes in the diameter have little effect on the resistance to blood flow. However, changes in diameter have a relatively large effect on wall shear stress which suggests that the function of flow-mediated dilatation is to reduce wall shear stress. The mean and pulsatile components of shear stress vary widely throughout the arterial system and areas of low mean and high amplitude of wall shear stress are prone to the development of atheroma. In this study, using an in vivo model with the ability to control flow rate and amplitude of flow independently, we investigated the characteristics of the response of the iliac artery to variations in both the mean and amplitude of wall shear stress. The results of this study confirm that increases in mean wall shear stress are an important stimulus for the release of nitric oxide by the endothelium as indicated by changes in arterial diameter and show for the first time, in vivo, that increases in the amplitude of the pulsatile component of shear stress have a small but significant inhibitory effect on this response. A negative feedback mechanism was identified whereby increases in shear stress brought about by increases in blood flow are reduced by the release of nitric oxide from the endothelium causing dilatation of the artery, thus decreasing the stimulus to cell adhesion and, through a direct action of nitric oxide, inhibiting the process of cell adhesion. The results also provide an explanation for the uneven distribution of atheroma throughout the arterial system, which is related to the ratio of pulsatile to mean shear stress and consequent variability in the production of NO.

  6. Anthropometric indicators of obesity as screening tools for high blood pressure in the elderly.

    PubMed

    Leal Neto, João de Souza; Coqueiro, Raildo da Silva; Freitas, Roberta Souza; Fernandes, Marcos Henrique; Oliveira, Daniela Sousa; Barbosa, Aline Rodrigues

    2013-08-01

    The study objectives were to investigate the indicators of obesity most associated with high blood pressure in community-dwelling elderly and identify among these which one best discriminates high blood pressure. This is an epidemiological, population, cross-sectional and home-based study of elderly people (≥ 60 years, n = 316) residing in northeastern Brazil. The results showed that the body mass index and the body adiposity index were the indicators more closely associated with high blood pressure in both sexes. Both in female and male genders, body mass index showed high values of specificity and low sensitivity values for discriminating high blood pressure, whereas the body adiposity index showed high sensitivity and moderate specificity values. In clinical practice and health surveillance, it is suggested that both indicators be used as screening tools for hypertension in the elderly.

  7. Effects of growth, diving history, and high altitude on blood oxygen capacity in harbor seals

    NASA Technical Reports Server (NTRS)

    Kodama, A. M.; Elsner, R.; Pace, N.

    1977-01-01

    Blood volume and body composition for diving and nondiving harbor seals were measured at six-week intervals during a 10-month period of captitivity. Whole body hematocrit, red cell volume per kg of lean body mass, and total circulating hemoglobin per kg lean body mass were significantly higher in the diving group, but relatively large blood volumes expressed in terms of body weight (11-12%) were found in both groups. A pair of harbor seals exposed to high altitude for about three months registered significant increases in red cell volume, blood hemoglobin levels, and blood volume expressed in terms of body weight; results of alveolar gas analyses indicate that hyperventilation also occurred. These typical mammalian responses to hypoxia suggest that the harbor seal's large blood volume and high hemoglobin content are an expression of phylogenetic control, and that in spite of its adaptability to apnea during its diving life, the animal cannot be considered preacclimatized to high altitude.

  8. Multiprofessional Treatment of High Blood Pressure in Very Elderly Patients

    PubMed Central

    Jardim, Luciana Muniz Sanches Siqueira Veiga; Jardim, Thiago Veiga; de Souza, Weimar Kunz Sebba Barroso; Pimenta, Camila Dutra; Sousa, Ana Luiza Lima; Jardim, Paulo César Brandão Veiga

    2017-01-01

    Background As the world population ages, patients older than 80 years, known as very elderly, are more frequently found. There are no studies in this age group aimed at analyzing the multidisciplinary intervention in the treatment of systemic arterial hypertension (SAH) and some comorbidities. Objectives To assess the effect of a multidisciplinary approach in very elderly hypertensives cared for at a specialized service. Methods Longitudinal retrospective cohort study in a multidisciplinary service specialized in the SAH treatment in the Brazilian West-Central region. Patients aged 80 years and older by June 2015 were included. Data from the first (V1) and last visit (Vf) were assessed. Anthropometric variables, blood pressure (BP), renal function, pharmacological treatment, lifestyle, comorbidities and cardiovascular events were studied, comparing data from V1 and Vf. Controlled BP was defined as systolic blood pressure (SBP) lower than 140 mm Hg and diastolic blood pressure (DBP) lower than 90 mm Hg. Statistical analyses were performed with SPSSR software, version 21.0. Values of p<0,05 were considered significant. Results Data of 71 patients were assessed with a mean follow-up time of 15,22 years. Their mean age at V1 was 69.2 years, and, at Vf, 84.53 years, and 26.8% of them were males. There was a significant reduction in mean SBP (157.3 x 142.1 mm Hg; p<0.001) and DBP (95.1 x 77.8 mm Hg; p<0.001), with an increase in BP control rates from V1 to Vf (36.6 x 83.1%; p<0.001). The number of antihypertensive drugs used increased (1.49 x 2.85; p<0.001), with an increase in the use of angiotensin-converting enzyme inhibitors (22.5 x 46.5%; p=0.004), angiotensin II receptor blockers (4.2 x 35.2%; p<0.001) and calcium-channel blockers (18.3 x 67.6%; p<0.001). There was a reduction in total cholesterol (217.9 x 191 mg/dL; p<0.001) and LDL-cholesterol (139.6 x 119.0 mg/dL; p<0.001), but worsening of the glomerular filtration rate (62.5 x 45.4 mL/min; p<0.001). Conclusion

  9. Blood pressure measurement

    MedlinePlus

    ... reading; Measuring blood pressure; Hypertension - blood pressure measurement; High blood pressure - blood pressure measurement ... High blood pressure has no symptoms so you may not know if you have this problem. High blood pressure ...

  10. Laboratory Earthquake Measurements with the High-speed Digital Image Correlation Method and Applications to Super-shear Transition

    NASA Astrophysics Data System (ADS)

    Rubino, V.; Lapusta, N.; Rosakis, A.

    2012-12-01

    Mapping full-field displacements and strains on the Earth's surface during an earthquake is of paramount importance to enhance our understanding of earthquake mechanics. In this study, the feasibility of such measurements using image correlation methods is investigated in a laboratory earthquake setup. Earthquakes are mimicked in the laboratory by dynamic rupture propagating along an inclined frictional interface formed by two Homalite plates under compression, using the configuration developed by Rosakis and coworkers (e.g., Rosakis et al., 2007). In our study, the interface is partially glued, in order to confine the rupture before it reaches the ends of the specimen. The specimens are painted with a speckle pattern to provide the surface with characteristic features for image matching. Images of the specimens are taken before and after dynamic rupture with a 4 Megapixels resolution CCD camera. The digital images are analyzed with two software packages: VIC-2D (Correlated Solutions Inc.) and COSI-Corr (Leprince et. al, 2007). Both VIC-2D and COSI-Corr are able to characterize the full-field static displacement of a dynamic crack. For example, in a case with secondary mode I cracks, the correlation analysis performed with either software clearly shows (i) the relative displacement (slip) along the frictional interface, (ii) the rupture arrest on the glued boundaries, and (iii) the presence of two wing cracks. The obtained displacement measurements are converted to strains, using de-noising techniques. The digital image correlation method is then used in combination with high-speed photography. We will report our progress on the study of a spontaneously expanding sub-Rayleigh shear crack advancing along an interface containing a patch of favorable heterogeneity, such as a preexisting subcritical crack or a patch with higher prestress. According to the predictions of Liu and Lapusta (2008), intersonic transition and propagation can be achieved in the presence of a

  11. Exact closed-form solutions for the natural frequencies and stability of elastically connected multiple beam system using Timoshenko and high-order shear deformation theory

    NASA Astrophysics Data System (ADS)

    Stojanović, Vladimir; Kozić, Predrag; Janevski, Goran

    2013-02-01

    A general procedure for the determination of the natural frequencies and buckling load for a set of beam system under compressive axial loading is investigated using Timoshenko and high-order shear deformation theory. It is assumed that the set beams of the system are simply supported and continuously joined by a Winkler elastic layer. The model of beam includes the effects of axial loading, shear deformation and rotary inertia. In the special case of identical beams, explicit expressions for the natural frequencies and the critical buckling load are determined using a trigonometric method. The influences of the compressive axial loading and the number of beams in the system on the natural frequencies and the critical buckling load are discussed. These results are of considerable practical interest and have wide application in engineering practice of frameworks.

  12. Locally-brewed Nigerian lager beers and high blood pressure

    SciTech Connect

    Adeniyi, F.A.A.

    1986-01-01

    Volunteers who consumed 88g alcohol/day (= 2.48L of lager beer) had elevated levels of systolic and mean arterial Blood Pressure. The association between consumption of locally brewed Nigerian lager beer with arterial hypertension was independent of age and weight. The true mechanism for the development of hypertension in these alcohol-users is at present not clear. All brands of lager beer investigated contain as much as five times the sodium content of potable water. It is desirable to evaluate the consequences of ingesting such quantities of sodium in lager beers. The effect of alcohol on other monovalent and divalent cations may shed some light onto the true mechanism for the pathogenesis of alcohol-induced hypertension. 15 references, 3 tables.

  13. Ultrasonic shear velocities of MgSiO3-perovskite at high pressure and temperature and lower mantle composition

    SciTech Connect

    Sinelnikov,Y.; Chen, G.; Neuville, D.; Liebermann, R.

    1998-01-01

    Ultrasonic interferometric measurements of the shear elastic properties of MgSiO{sub 3} perovskite were conducted on three polycrystalline specimens at conditions up to pressures of 8 gigapascals and temperatures of 800 kelvin. The acoustic measurements produced the pressure (P) and temperature (T) derivatives of the shear modulus (G), namely ({partial_derivative}G/{partial_derivative}P){sub T} = 1.8 {+-} 0.4 and ({partial_derivative}G/{partial_derivative}T){sub P} = 2.9 {+-} 0.3 x 10{sup 2} gigapascals per kelvin. Combining these derivatives with the derivatives that were measured for the bulk modulus and thermal expansion of MgSiO{sub 3} perovskite provided data that suggest lower mantle compositions between pyrolite and C1 carbonaceous chondrite and a lower mantle potential temperature of 1500 {+-} 200 kelvin.

  14. High quality genome-wide genotyping from archived dried blood spots without DNA amplification.

    PubMed

    St Julien, Krystal R; Jelliffe-Pawlowski, Laura L; Shaw, Gary M; Stevenson, David K; O'Brodovich, Hugh M; Krasnow, Mark A

    2013-01-01

    Spots of blood are routinely collected from newborn babies onto filter paper called Guthrie cards and used to screen for metabolic and genetic disorders. The archived dried blood spots are an important and precious resource for genomic research. Whole genome amplification of dried blood spot DNA has been used to provide DNA for genome-wide SNP genotyping. Here we describe a 96 well format procedure to extract DNA from a portion of a dried blood spot that provides sufficient unamplified genomic DNA for genome-wide single nucleotide polymorphism (SNP) genotyping. We show that SNP genotyping of the unamplified DNA is more robust than genotyping amplified dried blood spot DNA, is comparable in cost, and can be done with thousands of samples. This procedure can be used for genome-wide association studies and other large-scale genomic analyses that require robust, high-accuracy genotyping of dried blood spot DNA.

  15. Blood hyperviscosity with reduced skin blood flow in scleroderma

    PubMed Central

    McGrath, M. A.; Peek, R.; Penny, R.

    1977-01-01

    The vascular complications of scleroderma have previously been attributed to the progressive obliteration of small vessels. Our study was carried out to determine whether abnormalities of blood viscosity occur in this disease, thereby contributing to the ischaemic process. Blood viscosity was measured in 20 patients using a rotational viscometer. At a high rate of shear, blood hyperviscosity was found in 35% of the patients and at a low rate of shear, in 70%. In addition there was a significant increase in the plasma viscosity which implicates changes in plasma proteins (fibrinogen, immunoglobulins) as causing the hyperviscosity. Measurement of the hand blood flow by venous occlusion plethysmography showed reduced flow at 32°, 27°, and 20°C. A unique finding was a delayed recovery of the blood flow after cooling. These observations suggest that the increased resistance to blood flow in skin affected by scleroderma may be caused by an interaction between the occlusive vascular lesion and blood hyperviscosity. In addition, blood flow patterns and hyperviscosity could help distinguish scleroderma from primary Raynaud's disease. PMID:596950

  16. Macroscopic Discontinuous Shear Thickening versus Local Shear Jamming in Cornstarch

    NASA Astrophysics Data System (ADS)

    Fall, A.; Bertrand, F.; Hautemayou, D.; Mezière, C.; Moucheront, P.; Lemaître, A.; Ovarlez, G.

    2015-03-01

    We study the emergence of discontinuous shear thickening (DST) in cornstarch by combining macroscopic rheometry with local magnetic resonance imaging measurements. We bring evidence that macroscopic DST is observed only when the flow separates into a low-density flowing and a high-density jammed region. In the shear-thickened steady state, the local rheology in the flowing region is not DST but, strikingly, is often shear thinning. Our data thus show that the stress jump measured during DST, in cornstarch, does not capture a secondary, high-viscosity branch of the local steady rheology but results from the existence of a shear jamming limit at volume fractions quite significantly below random close packing.

  17. High blood pressure in children: clinical and health policy implications.

    PubMed

    Falkner, Bonita; Lurbe, Empar; Schaefer, Franz

    2010-04-01

    Hypertension is a global problem, affecting both developed and developing nations. In addition to being a major cause of morbidity and mortality, hypertension places a heavy burden on health care systems, families, and society as a whole. Despite evidence of an increasing prevalence of hypertension among youth, the consequences of early onset are poorly established and often overlooked. Childhood hypertension is often asymptomatic and easily missed, even by health professionals. Target organ damage is detectable in children and adolescents, however, and hypertension continues into adulthood. Additional strategies to improve cardiovascular health among children and adolescents are needed, including methods to achieve healthy lifestyles at home and in school, improved systems for diagnosis, and research on mechanisms and timing of interventions. The burden of hypertension in the young will continue to grow unless it is given the attention it deserves by policy makers, health care providers, schools, parents, and society. This report aims to increase awareness of the problem of hypertension in childhood. Recent reports on prevalence and target organ injury are discussed and health policy initiatives to improve blood pressure control are proposed.

  18. High blood pressure in the pediatric age group.

    PubMed

    Andrade, Helena; Antonio, Natália; Rodrigues, Dina; Da Silva, Marinho; Pêgo, Mariano; Providência, Luís Augusto

    2010-03-01

    The definition of hypertension (HT) in the pediatric age group is based on the normal distribution of blood pressure (BP) in healthy children. Normal BP is defined as being below the 90th percentile for gender, age and height, and hypertension as equal to or higher than the 95th percentile on at least three separate occasions. If the values are above the 90th percentile but below the 95th percentile, the child should be considered prehypertensive. Ambulatory BP monitoring is useful in the assessment of BP levels in the young. P values in children and adolescents have creased in the last decade, in parallel with increases in body mass index, and HT now has a prevalence of 2-5%. Obesity in childhood and adolescence is one of the main predictors of HT in adulthood, but it is also associated with other cardiovascular risk factors such as dyslipidemia, abnormal glucose metabolism, insulin resistance, inflammation and impaired vascular function. Left ventricular hypertrophy is the most prominent evidence of target organ damage caused by hypertension in children and adolescents. The goal for antihypertensive treatment is to reduce BP below the 95th percentile. Weight control, with regular physical activity and dietary changes, is the primary therapy for obesity-related hypertension. Weight loss decreases not only BP but also other cardiovascular risk factors. The indications for use of antihypertensive drugs are: symptomatic hypertension, secondary hypertension, established hypertensive target organ damage, stage 2 hypertension and failure of nonpharmacologic measures.

  19. Modifying mixing and instability growth through the adjustment of initial conditions in a high-energy-density counter-propagating shear experiment on OMEGA

    SciTech Connect

    Merritt, E. C.; Doss, F. W.; Loomis, E. N.; Flippo, K. A.; Kline, J. L.

    2015-06-24

    Counter-propagating shear experiments conducted at the OMEGA Laser Facility have been evaluating the effect of target initial conditions, specifically the characteristics of a tracer foil located at the shear boundary, on Kelvin-Helmholtz instability evolution and experiment transition toward nonlinearity and turbulence in the high-energy-density (HED) regime. Experiments are focused on both identifying and uncoupling the dependence of the model initial turbulent length scale in variable-density turbulence models of k-ϵ type on competing physical instability seed lengths as well as developing a path toward fully developed turbulent HED experiments. We present results from a series of experiments controllably and independently varying two initial types of scale lengths in the experiment: the thickness and surface roughness (surface perturbation scale spectrum) of a tracer layer at the shear interface. We show that decreasing the layer thickness and increasing the surface roughness both have the ability to increase the relative mixing in the system, and thus theoretically decrease the time required to begin transitioning to turbulence in the system. In addition, we also show that we can connect a change in observed mix width growth due to increased foil surface roughness to an analytically predicted change in model initial turbulent scale lengths.

  20. Modifying mixing and instability growth through the adjustment of initial conditions in a high-energy-density counter-propagating shear experiment on OMEGA

    DOE PAGES

    Merritt, E. C.; Doss, F. W.; Loomis, E. N.; ...

    2015-06-24

    Counter-propagating shear experiments conducted at the OMEGA Laser Facility have been evaluating the effect of target initial conditions, specifically the characteristics of a tracer foil located at the shear boundary, on Kelvin-Helmholtz instability evolution and experiment transition toward nonlinearity and turbulence in the high-energy-density (HED) regime. Experiments are focused on both identifying and uncoupling the dependence of the model initial turbulent length scale in variable-density turbulence models of k-ϵ type on competing physical instability seed lengths as well as developing a path toward fully developed turbulent HED experiments. We present results from a series of experiments controllably and independently varyingmore » two initial types of scale lengths in the experiment: the thickness and surface roughness (surface perturbation scale spectrum) of a tracer layer at the shear interface. We show that decreasing the layer thickness and increasing the surface roughness both have the ability to increase the relative mixing in the system, and thus theoretically decrease the time required to begin transitioning to turbulence in the system. In addition, we also show that we can connect a change in observed mix width growth due to increased foil surface roughness to an analytically predicted change in model initial turbulent scale lengths.« less