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Sample records for induced pressure waves

  1. Pressure induced Superconductivity in the Charge Density Wave Compound Tritelluride

    SciTech Connect

    Hamlin, J.J.; Zocco, D.A.; Sayles, T.A.; Maple, M.B.; Chu, J.-H.; Fisher, I.R.; /Stanford U., Geballe Lab.

    2010-02-15

    A series of high-pressure electrical resistivity measurements on single crystals of TbTe{sub 3} reveal a complex phase diagram involving the interplay of superconducting, antiferromagnetic and charge density wave order. The onset of superconductivity reaches a maximum of almost 4 K (onset) near {approx} 12.4 GPa.

  2. Utilization of sparker induced pressure waves to tenderize meat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study investigated the feasibility of tenderizing meat using high pressure waves generated from a sparker source. Beef strip loins were cut into steaks from the anterior end and one to two steaks from each strip loin were randomly selected to serve as non-treated controls and the remaining ste...

  3. Wave-Induced Pressure Under an Internal Solitary Wave and Its Impact at the Bed

    NASA Astrophysics Data System (ADS)

    Rivera, Gustavo; Diamesis, Peter; Jenkins, James; Berzi, Diego

    2015-11-01

    The bottom boundary layer (BBL) under a mode-1 internal solitary wave (ISW) of depression propagating against an oncoming model barotropic current is examined using 2-D direct numerical simulation based on a spectral multidomain penalty method model. Particular emphasis is placed on the diffusion into the bed of the pressure field driven by the wake and any near-bed instabilities produced under specific conditions. To this end, a spectral nodal Galerkin approach is used for solving the diffusion equation for the wave-induced pressure. At sufficiently high ISW amplitude, the BBL undergoes a global instability which produces intermittent vortex shedding from within the separation bubble in the lee of the wave. The interplay between the bottom shear stress field and pressure perturbations during vortex ejection events and the subsequent evolution of the vortices is examined. The potential for bed failure upon the passage of the ISW trough and implications for resuspension of bottom particulate matter are both discussed in the context of specific sediment transport models.

  4. A simplified physical model of pressure wave dynamics and acoustic wave generation induced by laser absorption in the retina.

    PubMed

    Till, S J; Milsom, P K; Rowlands, G

    2004-07-01

    Shock waves have been proposed in the literature as a mechanism for retinal damage induced by ultra-short laser pulses. For a spherical absorber, we derive a set of linear equations describing the propagation of pressure waves. We show that the formation of shock fronts is due to the form of the absorber rather than the inclusion of nonlinear terms in the equations. The analytical technique used avoids the need for a Laplace transform approach and is easily applied to other absorber profiles. Our analysis suggests that the 'soft' nature of the membrane surrounding retinal melanosomes precludes shock waves as a mechanism for the retinal damage induced by ultra-short pulse lasers. The quantitative estimates of the pressure gradients induced by laser absorption which are made possible by this work, together with detailed meso-scale or molecular modelling, will allow alternative damage mechanisms to be identified. PMID:15210319

  5. Influence of ambient air pressure on the energy conversion of laser-breakdown induced blast waves

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Komurasaki, Kimiya; Arakawa, Yoshihiro

    2013-09-01

    Influence of ambient pressure on energy conversion efficiency from a Nd : glass laser pulse (λ = 1.053 µm) to a laser-induced blast wave was investigated at reduced pressure. Temporal incident and transmission power histories were measured using sets of energy meters and photodetectors. A half-shadowgraph half-self-emission method was applied to visualize laser absorption waves. Results show that the blast energy conversion efficiency ηbw decreased monotonically with the decrease in ambient pressure. The decrease was small, from 40% to 38%, for the pressure change from 101 kPa to 50 kPa, but the decrease was considerable, to 24%, when the pressure was reduced to 30 kPa. Compared with a TEA-CO2-laser-induced blast wave (λ = 10.6 µm), higher fraction absorption in the laser supported detonation regime ηLSD of 90% was observed, which is influenced slightly by the reduction of ambient pressure. The conversion fraction ηbw/ηLSD≈90% was achieved at pressure >50 kPa, which is significantly higher than that in a CO2 laser case.

  6. Rubber-induced uniform laser shock wave pressure for thin metal sheets microforming

    NASA Astrophysics Data System (ADS)

    Shen, Zongbao; Wang, Xiao; Liu, Huixia; Wang, Yayuan; Wang, Cuntang

    2015-02-01

    Laser shock microforming of thin metal sheets is a new high velocity forming technique, which employs laser shock wave to deform the thin metal sheets. The spatial distribution of forming pressure is mainly dependent on the laser beam. A new type of laser shock loading method is introduced which gives a uniform pressure distribution. A low density rubber is inserted between the laser beam and the thin metal sheets. The mechanism of rubber-induced smoothing effect on confined laser shock wave is proposed. Plasticine is used to perform the smoothing effect experiments due to its excellent material flow ability. The influence of rubber on the uniformity of laser shock wave pressure is studied by measuring the surface micro topography of the deformed plasticine. And the four holes forming experiment is used to verify the rubber-induced uniform pressure on thin metal sheets surface. The research results show the possibility of smoothing laser shock wave pressure using rubber. And the good surface quality can be obtained under rubber dynamic loading.

  7. Modeling wave-induced pore pressure and effective stress in a granular seabed

    NASA Astrophysics Data System (ADS)

    Scholtès, Luc; Chareyre, Bruno; Michallet, Hervé; Catalano, Emanuele; Marzougui, Donia

    2014-08-01

    The response of a sandy seabed under wave loading is investigated on the basis of numerical modeling using a multi-scale approach. To that aim, the discrete element method is coupled to a finite volume method specially enhanced to describe compressible fluid flow. Both solid and fluid phase mechanics are upscaled from considerations established at the pore level. Model's predictions are validated against poroelasticity theory and discussed in comparison with experiments where a sediment analog is subjected to wave action in a flume. Special emphasis is put on the mechanisms leading the seabed to liquefy under wave-induced pressure variation on its surface. Liquefaction is observed in both dilative and compactive regimes. It is shown that the instability can be triggered for a well-identified range of hydraulic conditions. Particularly, the results confirm that the gas content, together with the permeability of the medium are key parameters affecting the transmission of pressure inside the soil.

  8. Modeling wave-induced pore pressure and effective stress in a granular seabed

    NASA Astrophysics Data System (ADS)

    Scholtès, Luc; Chareyre, Bruno; Michallet, Hervé; Catalano, Emanuele; Marzougui, Donia

    2015-01-01

    The response of a sandy seabed under wave loading is investigated on the basis of numerical modeling using a multi-scale approach. To that aim, the discrete element method is coupled to a finite volume method specially enhanced to describe compressible fluid flow. Both solid and fluid phase mechanics are upscaled from considerations established at the pore level. Model's predictions are validated against poroelasticity theory and discussed in comparison with experiments where a sediment analog is subjected to wave action in a flume. Special emphasis is put on the mechanisms leading the seabed to liquefy under wave-induced pressure variation on its surface. Liquefaction is observed in both dilative and compactive regimes. It is shown that the instability can be triggered for a well-identified range of hydraulic conditions. Particularly, the results confirm that the gas content, together with the permeability of the medium are key parameters affecting the transmission of pressure inside the soil.

  9. Syrinx fluid transport: modeling pressure-wave-induced flux across the spinal pial membrane.

    PubMed

    Elliott, N S J

    2012-03-01

    Syrinxes are fluid-filled cavities of the spinal cord that characterize syringomyelia, a disease involving neurological damage. Their formation and expansion is poorly understood, which has hindered successful treatment. Syrinx cavities are hydraulically connected with the spinal subarachnoid space (SSS) enveloping the spinal cord via the cord interstitium and the network of perivascular spaces (PVSs), which surround blood vessels penetrating the pial membrane that is adherent to the cord surface. Since the spinal canal supports pressure wave propagation, it has been hypothesized that wave-induced fluid exchange across the pial membrane may play a role in syrinx filling. To investigate this conjecture a pair of one-dimensional (1-d) analytical models were developed from classical elastic tube theory coupled with Darcy's law for either perivascular or interstitial flow. The results show that transpial flux serves as a mechanism for damping pressure waves by alleviating hoop stress in the pial membrane. The timescale ratio over which viscous and inertial forces compete was explicitly determined, which predicts that dilated PVS, SSS flow obstructions, and a stiffer and thicker pial membrane-all associated with syringomyelia-will increase transpial flux and retard wave travel. It was also revealed that the propagation of a pressure wave is aided by a less-permeable pial membrane and, in contrast, by a more-permeable spinal cord. This is the first modeling of the spinal canal to include both pressure-wave propagation along the spinal axis and a pathway for fluid to enter and leave the cord, which provides an analytical foundation from which to approach the full poroelastic problem. PMID:22482686

  10. Landslide stability: Role of rainfall-induced, laterally propagating, pore-pressure waves

    USGS Publications Warehouse

    Priest, G.R.; Schulz, W.H.; Ellis, W.L.; Allan, J.A.; Niem, A.R.; Niem, W.A.

    2011-01-01

    The Johnson Creek Landslide is a translational slide in seaward-dipping Miocene siltstone and sandstone (Astoria Formation) and an overlying Quaternary marine terrace deposit. The basal slide plane slopes sub-parallel to the dip of the Miocene rocks, except beneath the back-tilted toe block, where it slopes inland. Rainfall events raise pore-water pressure in the basal shear zone in the form of pulses of water pressure traveling laterally from the headwall graben down the axis of the slide at rates of 1-6 m/hr. Infiltration of meteoric water and vertical pressure transmission through the unsaturated zone has been measured at ~50 mm/hr. Infiltration and vertical pressure transmission were too slow to directly raise head at the basal shear zone prior to landslide movement. Only at the headwall graben was the saturated zone shallow enough for rainfall events to trigger lateral pulses of water pressure through the saturated zone. When pressure levels in the basal shear zone exceeded thresholds defined in this paper, the slide began slow, creeping movement as an intact block. As pressures exceeded thresholds for movement in more of the slide mass, movement accelerated, and differential displacement between internal slide blocks became more pronounced. Rainfall-induced pore-pressure waves are probably a common landslide trigger wherever effective hydraulic conductivity is high and the saturated zone is located near the surface in some part of a slide. An ancillary finding is apparently greater accuracy of grouted piezometers relative to those in sand packs for measurement of pore pressures at the installed depth.

  11. Seismic attenuation: effects of interfacial impedance on wave-induced pressure diffusion

    NASA Astrophysics Data System (ADS)

    Qi, Qiaomu; Müller, Tobias M.; Rubino, J. Germán

    2014-12-01

    Seismic attenuation and dispersion in layered sedimentary structures are often interpreted in terms of the classical White model for wave-induced pressure diffusion across the layers. However, this interlayer flow is severely dependent on the properties of the interface separating two layers. This interface behaviour can be described by a pressure jump boundary condition involving a non-vanishing interfacial impedance. In this paper, we incorporate the interfacial impedance into the White model by solving a boundary value problem in the framework of quasi-static poroelasticity. We show that the White model predictions for attenuation and dispersion substantially change. These changes can be attributed to petrophysically plausible scenarios such as imperfect hydraulic contacts or the presence of capillarity.

  12. Pressure-induced quenching of the charge-density-wave state observed by x-ray diffraction

    SciTech Connect

    Sacchetti, A.

    2010-05-03

    We report an x-ray diffraction study on the charge-density-wave (CDW) LaTe{sub 3} and CeTe{sub 3} compounds as a function of pressure. We extract the lattice constants and the CDW modulation wave-vector, and provide direct evidence for a pressure-induced quenching of the CDW phase. We observe subtle differences between the chemical and mechanical compression of the lattice. We account for these with a scenario where the effective dimensionality in these CDW systems is dependent on the type of lattice compression and has a direct impact on the degree of Fermi surface nesting and on the strength of fluctuation effects.

  13. Wave numbers and pressure-induced shifts of Ar I atomic lines measured by Fourier transform spectroscopy

    NASA Astrophysics Data System (ADS)

    Veza, Damir; Sansonetti, Craig J.; Salit, Marc L.; Travis, John C.

    2012-06-01

    Wave numbers and pressure-induced shifts of 19 blue argon emission lines belonging to the 3p56p-3p54s and 3p55p-3p54s transition arrays were measured with high accuracy using a UV/visible Fourier transform spectrometer (FTS). The measurements were made using electrodeless lamps containing traces of 198Hg and argon at pressures of 33 Pa (1/4 Torr), 400 Pa (3 Torr), 933 Pa (7 Torr) and 1333 Pa (10 Torr). Calibration of the FTS wave number scale was obtained using the four most prominent lines of 198Hg as internal standards. The pressure-induced shifts of the argon emission lines are in reasonable agreement with theoretical predictions. These results are of importance for astronomers and analytical chemists who use argon lines for practical wavelength standards as well as for theoreticians calculating argon-argon interactions and potential energy curves of diatomic argon molecules.

  14. Pressure-induced superconducting phase in the charge-density-wave compound terbium tritelluride.

    PubMed

    Hamlin, J J; Zocco, D A; Sayles, T A; Maple, M B; Chu, J-H; Fisher, I R

    2009-05-01

    A series of high-pressure electrical resistivity measurements on single crystals of TbTe3 reveal a complex phase diagram involving the interplay of superconducting, antiferromagnetic and charge-density-wave order. The onset of superconductivity reaches a maximum of almost 4 K (onset) near approximately 12.4 GPa. PMID:19518815

  15. Characteristics of pressure waves

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Air blast characteristics generated by most types of explosions are discussed. Data cover both negative and positive blast load phases and net transverse pressure as a function of time. The effects of partial or total confinement, atmospheric propagation, absorption of energy by ground shock or cratering, and transmission over irregular terrain on blast wave properties were also considered.

  16. Numerical simulation of pressure waves in the cochlea induced by a microwave pulse.

    PubMed

    Yitzhak, Nir M; Ruppin, Raphael; Hareuveny, Ronen

    2014-10-01

    The pressure waves developing at the cochlea by the irradiation of the body with a plane wave microwave pulse are obtained by numerical simulation, employing a two-step finite-difference time-domain (FDTD) algorithm. First, the specific absorption rate (SAR) distribution is obtained by solving the Maxwell equations on a FDTD grid. Second, the temperature rise due to this SAR distribution is used to formulate the thermoelastic equations of motion, which are discretized and solved by the FDTD method. The calculations are performed for anatomically based full body human models, as well as for a head model. The dependence of the pressure amplitude at the cochlea on the frequency, the direction of propagation, and the polarization of the incident electromagnetic radiation, as well as on the pulse width, was investigated. PMID:25099875

  17. Shock wave reflection induced detonation (SWRID) under high pressure and temperature condition in closed cylinder

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Qi, Y.; Liu, H.; Zhang, P.; He, X.; Wang, J.

    2016-07-01

    Super-knock is one of the major obstacles for improving power density in advanced internal combustion engines (ICE). This work studied the mechanism of super-knock initiation using a rapid compression machine that simulated conditions relevant to ICEs and provided excellent optical accessibility. Based on the high-speed images and pressure traces of the stoichiometric iso-octane/oxygen/nitrogen combustion under high-temperature and high-pressure conditions, it was observed that detonation was first initiated in the near-wall region as a result of shock wave reflection. Before detonation was initiated, the speed of the combustion wave front was less than that of the Chapman-Jouguet (C-J) detonation speed (around 1840 m/s). In the immediate vicinity of the initiation, the detonation speed was much higher than that of the C-J detonation.

  18. Shear waves in the diamond-anvil cell reveal pressure-induced instability in (Mg,Fe)O.

    PubMed

    Jacobsen, Steven D; Spetzler, Hartmut; Reichmann, Hans J; Smyth, Joseph R

    2004-04-20

    The emerging picture of Earth's deep interior from seismic tomography indicates more complexity than previously thought. The presence of lateral anisotropy and heterogeneity in Earth's mantle highlights the need for fully anisotropic elasticity data from mineral physics. A breakthrough in high-frequency (gigahertz) ultrasound has resulted in transmission of pure-mode elastic shear waves into a high-pressure diamond-anvil cell using a P-to-S elastic-wave conversion. The full elastic tensor (c(ij)) of high-pressure minerals or metals can be measured at extreme conditions without optical constraints. Here we report the effects of pressure and composition on shear-wave velocities in the major lower-mantle oxide, magnesiowüstite-(Mg,Fe)O. Magnesiowüstite containing more than approximately 50% iron exhibits pressure-induced c(44) shear-mode softening, indicating an instability in the rocksalt structure. The oxide closer to expected lower-mantle compositions ( approximately 20% iron) shows increasing shear velocities more similar to MgO, indicating that it also should have a wide pressure-stability field. A complete sign reversal in the c(44) pressure derivative points to a change in the topology of the (Mg,Fe)O phase diagram at approximately 50-60% iron. The relative stability of Mg-rich (Mg,Fe)O and the strong compositional dependence of shear-wave velocities (and partial differential c(44)/ partial differential P) in (Mg,Fe)O implies that seismic heterogeneity in Earth's lower mantle may result from compositional variations rather than phase changes in (Mg,Fe)O. PMID:15079080

  19. Shear waves in the diamond-anvil cell reveal pressure-induced instability in (Mg,Fe)O

    PubMed Central

    Jacobsen, Steven D.; Spetzler, Hartmut; Reichmann, Hans J.; Smyth, Joseph R.

    2004-01-01

    The emerging picture of Earth's deep interior from seismic tomography indicates more complexity than previously thought. The presence of lateral anisotropy and heterogeneity in Earth's mantle highlights the need for fully anisotropic elasticity data from mineral physics. A breakthrough in high-frequency (gigahertz) ultrasound has resulted in transmission of pure-mode elastic shear waves into a high-pressure diamond-anvil cell using a P-to-S elastic-wave conversion. The full elastic tensor (cij) of high-pressure minerals or metals can be measured at extreme conditions without optical constraints. Here we report the effects of pressure and composition on shear-wave velocities in the major lower-mantle oxide, magnesiowüstite-(Mg,Fe)O. Magnesiowüstite containing more than ≈50% iron exhibits pressure-induced c44 shear-mode softening, indicating an instability in the rocksalt structure. The oxide closer to expected lower-mantle compositions (≈20% iron) shows increasing shear velocities more similar to MgO, indicating that it also should have a wide pressure-stability field. A complete sign reversal in the c44 pressure derivative points to a change in the topology of the (Mg,Fe)O phase diagram at ≈50–60% iron. The relative stability of Mg-rich (Mg,Fe)O and the strong compositional dependence of shear-wave velocities (and ∂c44/∂P) in (Mg,Fe)O implies that seismic heterogeneity in Earth's lower mantle may result from compositional variations rather than phase changes in (Mg,Fe)O. PMID:15079080

  20. Fluid Pressure Increases in Hydrothermal Systems Induced by Seismic Waves: Possible Triggers of Earthquakes and Volcanic Eruptions

    NASA Astrophysics Data System (ADS)

    Roeloffs, E.

    2002-12-01

    That seismic waves trigger microseismicity in hydrothermal settings hundreds of km from the epicenter is plausibly linked to seismic-wave-induced fluid pressure changes at these distances. Although fluid pressure decreases have been observed in diverse settings, in the hydrothermal system at Long Valley, California, that seismic waves from earthquakes increase fluid pressure or discharge. Other published data, from thermal springs in Japan, Yellowstone, and Klamath Falls, Oregon, support the idea that seismic waves have induced pressure and discharge changes and that, in hydrothermal systems, these changes are usually increases. Temperature increases in seafloor hydrothermal vents within days after earthquakes as distant as 220 km imply, moreover, that seismic waves enhance conductance of vertical fluid flow pathways. The influence of seismic waves (wavelengths of km), on hot, fluid-filled subsurface fractures (apertures of mm to cm) could proceed by several mechanisms. Local fluid flow induced at crack walls could remove mineral seals. Spatially uniform acceleration can move gas bubbles relative to denser liquid and solid phases. Thermal expansion can elevate pressure around hot fluid that has penetrated upward. By lowering effective stress and directly weakening faults that are themselves flow paths, seismic waves could initiate processes leading to volcanic eruptions or other earthquakes where sufficient subsurface magma or elastic strain energy have previously accumulated. This type of earthquake-volcano linkage could explain why volcanos statistically erupt more frequently up to 5 years after M>7 earthquakes hundreds of km distant. For example, 11 months elapsed after the Ms 7.8 Luzon (Phillipines) earthquake before Mount Pinatubo erupted on June 15, 1991, 100 km away. Steam emission and 3 M4+ earthquakes in the Pinatubo area followed within days of the Luzon event, however, and a hydrothermal explosion on April 2 started the continuous unrest that built to

  1. The Numerical Simulation of Unsteady Cavitation Evolution Induced by Pressure Wave

    NASA Astrophysics Data System (ADS)

    Khoo, B. C.; Zheng, J. G.

    2014-11-01

    The present study is focused on the numerical simulation of pressure wave propagation through the cavitating compressible liquid flow, its interaction with cavitation bubble and the resulting unsteady cavitation evolution. The compressibility effects of liquid water are taken into account and the cavitating flow is governed by one-fluid cavitation model which is based on the compressible Euler equations with the assumption that the cavitation is the homogeneous mixture of liquid and vapour which are locally under both kinetic and thermodynamic equilibrium. Several aspects of the method employed to solve the governing equations are outlined. The unsteady features of cavitating flow due to the external perturbation, such as the cavitation deformation and collapse and consequent pressure increase are resolved numerically and discussed in detail. It is observed that the cavitation bubble collapse is accompanied by the huge pressure surge of order of 100 bar, which is thought to be responsible for the material erosion, noise, vibration and loss of efficiency of operating underwater devices.

  2. Effects of pressure characteristics on transfection efficiency in laser-induced stress wave-mediated gene delivery

    NASA Astrophysics Data System (ADS)

    Ando, Takahiro; Sato, Shunichi; Ashida, Hiroshi; Obara, Minoru

    2013-07-01

    Laser-induced stress waves (LISWs) generated by irradiating a light-absorbing medium with a pulsed laser can transiently increase the permeability of cell membranes for gene delivery. In this study, we investigated the effects of pressure characteristics of LISWs upon gene transfection efficiency using lasers with different pulse durations: a 6-ns pulsed Nd:YAG laser and 20-ns and 200-µs pulsed ruby lasers. LISWs were generated by irradiating a black rubber disk, on which a transparent plastic sheet was adhered for confinement of the laser-produced plasma. Rat dorsal skin was injected with plasmid DNA coding for luciferase, to which LISWs were applied. With nanosecond laser pulses, transfection efficiency increased linearly with increasing positive peak pressure in the range of 35 to 145 MPa, the corresponding impulse ranging from 10 to 40 Paṡs. With 200-µs laser pulses, on the other hand, efficient gene expression was observed by the application of LISWs even with a 10-fold-lower peak pressure (˜5 MPa), the corresponding impulse being as large as 430 Paṡs. These results indicate that even at low peak pressures, efficient transfection can be achieved by extending the pressure duration and hence by increasing the impulse of LISWs, while the averaged expression efficiencies were relatively low.

  3. Arterial pulse wave pressure transducer

    NASA Technical Reports Server (NTRS)

    Kim, C.; Gorelick, D.; Chen, W. (Inventor)

    1974-01-01

    An arterial pulse wave pressure transducer is introduced. The transducer is comprised of a fluid filled cavity having a flexible membrane disposed over the cavity and adapted to be placed on the skin over an artery. An arterial pulse wave creates pressure pulses in the fluid which are transduced, by a pressure sensitive transistor in direct contact with the fluid, into an electric signal. The electrical signal is representative of the pulse waves and can be recorded so as to monitor changes in the elasticity of the arterial walls.

  4. Source duration of stress and water-pressure induced seismicity derived from experimental analysis of P wave pulse width in granite

    NASA Astrophysics Data System (ADS)

    Masuda, K.

    2013-12-01

    Pulse widths of P waves in granite, measured in the laboratory, were analyzed to investigate source durations of rupture processes for water-pressure induced and stress-induced microseismicity. Much evidence suggests that fluids in the subsurface are intimately linked to faulting processes. Studies of seismicity induced by water injection are thus important for understanding the trigger mechanisms of earthquakes as well as for engineering applications such as hydraulic fracturing of rocks at depth for petroleum extraction. Determining the cause of seismic events is very important in seismology and engineering; however, water-pressure induced seismic events are difficult to distinguish from those induced by purely tectonic stress. To investigate this problem, we analyzed the waveforms of acoustic emissions (AEs) produced in the laboratory by both water-pressure induced and stress-induced microseismicity. We used a cylinder (50 mm in diameter and 100 mm in length) of medium-grained granite. We applied a differential stress of about 70% of fracture strength, to the rock sample under 40 MPa confining pressure and held it constant throughout the experiment. When the primary creep stage and acoustic emissions (AEs) caused by the initial loading had ceased, we injected distilled water into the bottom end of the sample at a constant pressure of 17 MPa until macroscopic fracture occurred. We analysed AE waveforms produced by stress-induced AEs which occurred before the water-injection and by water-pressure induced AEs which occurred after the water-injection. Pulse widths were measured from the waveform traces plotted from the digital data. To investigate the source duration of the rupture process, we estimated the pulse width at the source and normalized by event magnitude to obtain a scaled pulse width at the source. After the effects of event size and hypocentral distance were removed from observed pulse widths, the ratio of the scaled source durations of water-pressure

  5. Effects of pressure waves

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Two parameters, side on overpressure and side on impulse loads, and their application to the determination of structural damage to buildings and vehicles in the vicinity of an explosion are investigated. Special consideration was given to what constitutes damage and what level of damage is acceptable. Solutions were sorted through the examination of glass breakage, curve fit to bomb damage, overturning of marginal structures (buses, trucks, mobile homes) subject to toppling, and initiation of yielding in either beam or plate structural components. Three different empirical pressure versus impulse diagrams were presented - the first is for minor structural damage involving wrenched joints and partitions, the second is for major damage structural damage with load bearing members at least partially destroyed, and the third is for 50% to 75% of the building demolished. General guidelines were obtained from the results when the accurate structural details are unknown.

  6. Strong anharmonicity induces quantum melting of charge density wave in 2 H -NbSe2 under pressure

    NASA Astrophysics Data System (ADS)

    Leroux, Maxime; Errea, Ion; Le Tacon, Mathieu; Souliou, Sofia-Michaela; Garbarino, Gaston; Cario, Laurent; Bosak, Alexey; Mauri, Francesco; Calandra, Matteo; Rodière, Pierre

    2015-10-01

    The pressure and temperature dependence of the phonon dispersion of 2 H -NbSe2 is measured by inelastic x-ray scattering. A strong temperature dependent soft phonon mode, reminiscent of the charge density wave (CDW), is found to persist up to a pressure as high as 16 GPa, far above the critical pressure at which the CDW disappears at 0 K. By using ab initio calculations beyond the harmonic approximation, we obtain an accurate, quantitative description of the (P ,T ) dependence of the phonon spectrum. Our results show that the rapid destruction of the CDW under pressure is related to the zero mode vibrations—or quantum fluctuations—of the lattice renormalized by the anharmonic part of the lattice potential. The calculations also show that the low-energy longitudinal acoustic mode that drives the CDW transition barely contributes to superconductivity, explaining the insensitivity of the superconducting critical temperature to the CDW transition.

  7. The behavior of a compressible turbulent boundary layer in a shock-wave-induced adverse pressure gradient. Ph.D. Thesis - Washington Univ., Seattle, Aug. 1972

    NASA Technical Reports Server (NTRS)

    Rose, W. C.

    1973-01-01

    The results of an experimental investigation of the mean- and fluctuating-flow properties of a compressible turbulent boundary layer in a shock-wave-induced adverse pressure gradient are presented. The turbulent boundary layer developed on the wall of an axially symmetric nozzle and test section whose nominal free-stream Mach number and boundary-layer thickness Reynolds number were 4 and 100,000, respectively. The adverse pressure gradient was induced by an externally generated conical shock wave. Mean and time-averaged fluctuating-flow data, including the complete experimental Reynolds stress tensor and experimental turbulent mass- and heat-transfer rates are presented for the boundary layer and external flow, upstream, within and downstream of the pressure gradient. The mean-flow data include distributions of total temperature throughout the region of interest. The turbulent mixing properties of the flow were determined experimentally with a hot-wire anemometer. The calibration of the wires and the interpretation of the data are discussed. From the results of the investigation, it is concluded that the shock-wave - boundary-layer interaction significantly alters the turbulent mixing characteristics of the boundary layer.

  8. Fluid pressure waves trigger earthquakes

    NASA Astrophysics Data System (ADS)

    Mulargia, Francesco; Bizzarri, Andrea

    2015-03-01

    Fluids-essentially meteoric water-are present everywhere in the Earth's crust, occasionally also with pressures higher than hydrostatic due to the tectonic strain imposed on impermeable undrained layers, to the impoundment of artificial lakes or to the forced injections required by oil and gas exploration and production. Experimental evidence suggests that such fluids flow along preferred paths of high diffusivity, provided by rock joints and faults. Studying the coupled poroelastic problem, we find that such flow is ruled by a nonlinear partial differential equation amenable to a Barenblatt-type solution, implying that it takes place in form of solitary pressure waves propagating at a velocity which decreases with time as v ∝ t [1/(n - 1) - 1] with n ≳ 7. According to Tresca-Von Mises criterion, these waves appear to play a major role in earthquake triggering, being also capable to account for aftershock delay without any further assumption. The measure of stress and fluid pressure inside active faults may therefore provide direct information about fault potential instability.

  9. Enhanced Transfection Efficiency in Laser-Induced Stress Wave-Assisted Gene Transfer at Low Laser Fluence by Increasing Pressure Impulse

    NASA Astrophysics Data System (ADS)

    Takano, Shinta; Sato, Shunichi; Terakawa, Mitsuhiro; Asida, Hiroshi; Okano, Hideyuki; Obara, Minoru

    2008-03-01

    To improve transfection efficiency in gene delivery based on nanosecond pulsed laser-induced stress waves, we examined different types of transparent materials, a poly(ethylene terephthalate) sheet, poly(vinyl alcohol) gel, and water, which were placed on a laser target for plasma confinement. We found that the use of water was most effective for maintaining a large pressure impulse during multipulse laser irradiation and, as a result, high transfection efficiency was demonstrated in rat skin in vivo at a relatively low laser fluence of 0.7 J/cm2. At this fluence, steady laser transmission through quartz fibers was confirmed, allowing endoscopic application of our gene delivery technique.

  10. Rhythmic Pressure Waves Induce Mucin5AC Expression via an EGFR-Mediated Signaling Pathway in Human Airway Epithelial Cells

    PubMed Central

    Liu, Chunyi; Li, Qi; Kolosov, Victor P.; Perelman, Juliy M.

    2013-01-01

    Rhythmic pressure waves (RPW), mimicking the mechanical forces generated during normal breathing, play a key role in airway surface liquid (ASL) homeostasis. As a major component of ASL, we speculated that the mucin5AC (MUC5AC) expression must also be regulated by RPW. However, fewer researches have focused on this question. Therefore, our aim was to test the effect and mechanism of RPW on MUC5AC expression in cultured human bronchial epithelial cells. Compared with the relevant controls, the transcriptional level of MUC5AC and the protein expressions of MUC5AC, the phospho-epidermal growth factor receptor (p-EGFR), phospho-extracellular signal-related kinase (p-ERK), and phospho-Akt (p-Akt) were all significantly increased after mechanical stimulation. However, this effect could be significantly attenuated by transfecting with EGFR-siRNA. Similarly, pretreating with the inhibitor of ERK or phosphatidylinositol 3-kinases (PI3K)/Akt separately or jointly also significantly reduced MUC5AC expression. Collectively, these results indicate that RPW modulate MUC5AC expression via the EGFR-PI3K-Akt/ERK-signaling pathway in human bronchial epithelial cells. PMID:23768102

  11. Pressure measurements of nonplanar stress waves

    SciTech Connect

    Carlson, G.H.; Charest, J.A.

    1981-01-01

    Measuring the pressure of non-planar stress waves using thin piezo-resistive gages requires correcting for induced strain parallel to the sensing elements. A technique has been developed that permits such measurements, making use of a dual element gage. One element, Manganin, is sensitive to stress both parallel and perpendicular to the sensing element; the other element, Constantan, is primarily sensitive to stress parallel to the sensing element. The change in resistance in the Constantan element is thereby used to correct for the strain effect parallel to the Manganin element axis. Individual and combined Manganin and Constantan elements were subjected to controlled gas gun impact tests in the pressure and strain ranges of 0 to 50 kbar and 0 to 7%, respectively. From planar wave tests, the piezoresistivity of Constantan was found to be positive but negligible in comparison with Manganin. From combined stress and strain environments, the compression and tension strain factors of Constantan were found to be constant and equal to 2.06. The strain factors of Manganin were found to increase from 1.2 to 2.0 asymptotically in the range of 0 to 3% strain. It was experimentally demonstrated that, because of the closeness of their strain factors, the Manganin-Constantan dual element gage could be used in the differential recording mode to yield pressure directly. In this mode the gage is a strain compensating gage. Analytical techniques have also been developed for more accurate strain compensation.

  12. Non-β-blocking R-carvedilol enantiomer suppresses Ca2+ waves and stress-induced ventricular tachyarrhythmia without lowering heart rate or blood pressure.

    PubMed

    Zhang, Jingqun; Zhou, Qiang; Smith, Chris D; Chen, Haiyan; Tan, Zhen; Chen, Biyi; Nani, Alma; Wu, Guogen; Song, Long-Sheng; Fill, Michael; Back, Thomas G; Chen, S R Wayne

    2015-09-01

    Carvedilol is the current β-blocker of choice for suppressing ventricular tachyarrhythmia (VT). However, carvedilol's benefits are dose-limited, attributable to its potent β-blocking activity that can lead to bradycardia and hypotension. The clinically used carvedilol is a racemic mixture of β-blocking S-carvedilol and non-β-blocking R-carvedilol. We recently reported that novel non-β-blocking carvedilol analogues are effective in suppressing arrhythmogenic Ca(2+) waves and stress-induced VT without causing bradycardia. Thus, the non-β-blocking R-carvedilol enantiomer may also possess this favourable anti-arrhythmic property. To test this possibility, we synthesized R-carvedilol and assessed its effect on Ca(2+) release and VT. Like racemic carvedilol, R-carvedilol directly reduces the open duration of the cardiac ryanodine receptor (RyR2), suppresses spontaneous Ca(2+) oscillations in human embryonic kidney (HEK) 293 cells, Ca(2+) waves in cardiomyocytes in intact hearts and stress-induced VT in mice harbouring a catecholaminergic polymorphic ventricular tachycardia (CPVT)-causing RyR2 mutation. Importantly, R-carvedilol did not significantly alter heart rate or blood pressure. Therefore, the non-β-blocking R-carvedilol enantiomer represents a very promising prophylactic treatment for Ca(2+)- triggered arrhythmia without the bradycardia and hypotension often associated with racemic carvedilol. Systematic clinical assessments of R-carvedilol as a new anti-arrhythmic agent may be warranted. PMID:26348911

  13. Improvement of erectile dysfunction by the active pepide from Urechis unicinctus by high temperature/pressure and ultra - wave assisted lysis in Streptozotocin Induced Diabetic Rats

    PubMed Central

    Kim, Kang Sup; Bae, Woong Jin; Kim, Su Jin; Kang, Kyong-Hwa; Kim, Se-Kwon; Cho, Hyuk Jin; Hong, Sung-Hoo; Lee, Ji Youl; Kim, Sae Woong

    2016-01-01

    ABSTRACT Introduction: We investigate the effect of active peptide from Urechis unicinctus (UU) by high temperature/pressure and ultra-wave assisted lysis on erectile dysfunction in streptozotocin-induced diabetic rats. Materials and Methods: Forty 12-week-old Sprague-Dawley rats were used in this study. Diabetes was induced by a one-time intraperitoneal injection of streptozotocin (50mg/kg). One week later, the diabetic rats were randomly divided into four groups: normal control, untreated diabetes control, and groups treated with 100 or 500mg/kg/d UU peptide. Rats were fed with UU peptide by intragastric administration for 8 weeks. After 8 weeks, penile hemodynamic function was evaluated in all groups by measuring the intracavernosal pressure after electrostimulating the cavernous nerve. Nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) activities were measured and endothelial nitric oxide synthase (eNOS) and neuronal NOS (nNOS) protein expression was determined by Western blot. Results: Maximum intracavernosal pressure in diabetic control rats decreased significantly compared to normal control rats, and was increased significantly compared to untreated diabetic rats after UU peptide supplementation. Treatment with the higher dose of UU peptide significantly increased the NO and cGMP levels compared with the diabetic control group. Decreased activity and expression eNOS and nNOS were found in the diabetic rats compared with the normal control group. Decreased eNOS and nNOS in diabetic rats were improved by UU peptide administration. Conclusions: Active peptide from UU ameliorates erectile function in a streptozotocin induced diabetic rat model of erectile dysfunction. PMID:27564297

  14. Investigation of Pressurized Wave Bearings

    NASA Technical Reports Server (NTRS)

    Keith, Theo G., Jr.; Dimofte, Florin

    2003-01-01

    The wave bearing has been pioneered and developed by Dr. Dimofte over the past several years. This bearing will be the main focus of this research. It is believed that the wave bearing offers a number of advantages over the foil bearing, which is the bearing that NASA is currently pursuing for turbomachinery applications. The wave bearing is basically a journal bearing whose film thickness varies around the circumference approximately sinusoidally, with usually 3 or 4 waves. Being a rigid geometry bearing, it provides precise control of shaft centerlines. The wave profile also provides good load capacity and makes the bearing very stable. Manufacturing techniques have been devised that should allow the production of wave bearings almost as cheaply as conventional full-circular bearings.

  15. Influence of Plasma Pressure Fluctuation on RF Wave Propagation

    NASA Astrophysics Data System (ADS)

    Liu, Zhiwei; Bao, Weimin; Li, Xiaoping; Liu, Donglin; Zhou, Hui

    2016-02-01

    Pressure fluctuations in the plasma sheath from spacecraft reentry affect radio-frequency (RF) wave propagation. The influence of these fluctuations on wave propagation and wave properties is studied using methods derived by synthesizing the compressible turbulent flow theory, plasma theory, and electromagnetic wave theory. We study these influences on wave propagation at GPS and Ka frequencies during typical reentry by adopting stratified modeling. We analyzed the variations in reflection and transmission properties induced by pressure fluctuations. Our results show that, at the GPS frequency, if the waves are not totally reflected then the pressure fluctuations can remarkably affect reflection, transmission, and absorption properties. In extreme situations, the fluctuations can even cause blackout. At the Ka frequency, the influences are obvious when the waves are not totally transmitted. The influences are more pronounced at the GPS frequency than at the Ka frequency. This suggests that the latter can mitigate blackout by reducing both the reflection and the absorption of waves, as well as the influences of plasma fluctuations on wave propagation. Given that communication links with the reentry vehicles are susceptible to plasma pressure fluctuations, the influences on link budgets should be taken into consideration. supported by the National Basic Research Program of China (No. 2014CB340205) and National Natural Science Foundation of China (No. 61301173)

  16. Pressure diffusion waves in porous media

    SciTech Connect

    Silin, Dmitry; Korneev, Valeri; Goloshubin, Gennady

    2003-04-08

    Pressure diffusion wave in porous rocks are under consideration. The pressure diffusion mechanism can provide an explanation of the high attenuation of low-frequency signals in fluid-saturated rocks. Both single and dual porosity models are considered. In either case, the attenuation coefficient is a function of the frequency.

  17. Blast wave parameters at diminished ambient pressure

    NASA Astrophysics Data System (ADS)

    Silnikov, M. V.; Chernyshov, M. V.; Mikhaylin, A. I.

    2015-04-01

    Relation between blast wave parameters resulted from a condensed high explosive (HE) charge detonation and a surrounding gas (air) pressure has been studied. Blast wave pressure and impulse differences at compression and rarefaction phases, which traditionally determine damage explosive effect, has been analyzed. An initial pressure effect on a post-explosion quasi-static component of the blast load has been investigated. The analysis is based on empirical relations between blast parameters and non-dimensional similarity criteria. The results can be directly applied to flying vehicle (aircraft or spacecraft) blast safety analysis.

  18. Turbulence measurements in a compressible boundary layer subjected to a shock-wave-induced adverse pressure gradient.

    NASA Technical Reports Server (NTRS)

    Rose, W. C.

    1973-01-01

    The rms intensities of fluctuating mass flux and total temperature and their correlation coefficients are given for the case of an adiabatic, Mach 4, axisymmetric shock-wave boundary-layer interaction. Data were obtained upstream, within, and downstream of the interaction by the use of constant temperature hot-wire anemometer. Turbulence spectra and quantitative behavior from oscilloscope traces are shown at selected locations. The measurements indicate that certain frequencies of the turbulence are increased as a result of the interaction and that the mass flux and total temperature fluctuations remain highly correlated over most of the boundary layer throughout the interaction. The present data are also transformed to rms intensities of fluctuating static temperature and velocity and compared with existing data obtained in adiabatic flows.

  19. Modulated pressure waves in large elastic tubes.

    PubMed

    Mefire Yone, G R; Tabi, C B; Mohamadou, A; Ekobena Fouda, H P; Kofané, T C

    2013-09-01

    Modulational instability is the direct way for the emergence of wave patterns and localized structures in nonlinear systems. We show in this work that it can be explored in the framework of blood flow models. The whole modified Navier-Stokes equations are reduced to a difference-differential amplitude equation. The modulational instability criterion is therefore derived from the latter, and unstable patterns occurrence is discussed on the basis of the nonlinear parameter model of the vessel. It is found that the critical amplitude is an increasing function of α, whereas the region of instability expands. The subsequent modulated pressure waves are obtained through numerical simulations, in agreement with our analytical expectations. Different classes of modulated pressure waves are obtained, and their close relationship with Mayer waves is discussed. PMID:24089964

  20. Modulated pressure waves in large elastic tubes

    NASA Astrophysics Data System (ADS)

    Mefire Yone, G. R.; Tabi, C. B.; Mohamadou, A.; Ekobena Fouda, H. P.; Kofané, T. C.

    2013-09-01

    Modulational instability is the direct way for the emergence of wave patterns and localized structures in nonlinear systems. We show in this work that it can be explored in the framework of blood flow models. The whole modified Navier-Stokes equations are reduced to a difference-differential amplitude equation. The modulational instability criterion is therefore derived from the latter, and unstable patterns occurrence is discussed on the basis of the nonlinear parameter model of the vessel. It is found that the critical amplitude is an increasing function of α, whereas the region of instability expands. The subsequent modulated pressure waves are obtained through numerical simulations, in agreement with our analytical expectations. Different classes of modulated pressure waves are obtained, and their close relationship with Mayer waves is discussed.

  1. Wave pressure acting on V-shaped floating breakwater in random seas

    NASA Astrophysics Data System (ADS)

    Yu, Yang; Ding, Ning; Lin, Jie; Hou, Jiajia

    2015-12-01

    Wave pressure on the wet surface of a V-shaped floating breakwater in random seas is investigated. Considering the diffraction effect, the unit velocity potential caused by the single regular waves around the breakwater is solved using the finite-depth Green function and boundary element method, in which the Green function is solved by integral method. The Response-Amplitude Operator (RAO) of wave pressure is acquired according to the Longuet-Higgins' wave model and the linear Bernoulli equation. Furthermore, the wave pressure's response spectrum is calculated according to the wave spectrum by discretizing the frequency domain. The wave pressure's characteristic value corresponding to certain cumulative probability is determined according to the Rayleigh distribution of wave heights. The numerical results and field test results are compared, which indicates that the wave pressure calculated in random seas agrees with that of field measurements. It is found that the bigger angle between legs will cause the bigger pressure response, while the increase in leg length does not influence the pressure significantly. The pressure at the side of head sea is larger than that of back waves. When the incident wave angle changes from 0° to 90°, the pressure at the side of back waves decreases clearly, while at the side of head sea, the situation is more complicated and there seems no obvious tendency. The concentration of wave energy around low frequency (long wavelength) will induce bigger wave pressure, and more attention should be paid to this situation for the structure safety.

  2. Pressure wave charged repetitively pulsed gas laser

    DOEpatents

    Kulkarny, Vijay A.

    1982-01-01

    A repetitively pulsed gas laser in which a system of mechanical shutters bracketing the laser cavity manipulate pressure waves resulting from residual energy in the cavity gas following a lasing event so as to draw fresh gas into the cavity and effectively pump spent gas in a dynamic closed loop.

  3. Implications of pressure diffusion for shock waves

    NASA Technical Reports Server (NTRS)

    Ram, Ram Bachan

    1989-01-01

    The report deals with the possible implications of pressure diffusion for shocks in one dimensional traveling waves in an ideal gas. From this new hypothesis all aspects of such shocks can be calculated except shock thickness. Unlike conventional shock theory, the concept of entropy is not needed or used. Our analysis shows that temperature rises near a shock, which is of course an experimental fact; however, it also predicts that very close to a shock, density increases faster than pressure. In other words, a shock itself is cold.

  4. Pressure waves generated by steady flames.

    NASA Technical Reports Server (NTRS)

    Kuhl, A. L.; Kamel, M. M.; Oppenheim, A. K.

    1973-01-01

    Analysis of pressure waves that can be generated by clouds of explosive gas mixtures in a free atmosphere which is initially at a uniform state. The treatment is restricted only to the final stage of constant flame velocity when the flowfield is self-similar. By the introduction of reduced blast-wave parameters as phase-plane coordinates, the problem is resolved into the determination of the appropriate integral curves on this plane. Results, including space profiles of gasdynamic parameters, have been computed for a specific case of a hydrocarbon-air mixture characterized by a specific heat ratio of 1.3, sound speed at NTP of 345 m/sec, and volumetric expansion ratio corresponding to constant pressure deflagration of 7. Maximum overpressure ratios that can be generated by such flames in point-and line-symmetrical waves range from .00053, for the lower bound in the burning speed, up to 6 for the deflagration, while, for the average speeds of 5 to 10 m/sec, they are at a level of 0.05 to 0.10.

  5. Wave-Induced Groundwater Flows in a Freshwater Beach Aquifer

    NASA Astrophysics Data System (ADS)

    Malott, S. S.; Robinson, C. E.; O'Carroll, D. M.

    2014-12-01

    Wave-induced recirculation across the sediment-water interface can impact the transport of pollutants through a beach aquifer and their ultimate flux into coastal waters. The fate of nutrients (e.g. from septic and agricultural sources) and fecal indicator bacteria (e.g. E. coil) near the sediment-water interface are of particular concern as these pollutants often lead to degradation of recreational water quality and nearshore ecosystems. This paper presents detailed field measurements of groundwater flows in a freshwater beach aquifer on Lake Huron over periods of intensified wave conditions. Quantifying wave-driven processes in a freshwater beach aquifer enables wave effects to be studied in isolation from density and tidal effects that complicate groundwater flows in marine beaches. Water exchange across the sediment-water interface and groundwater flow patterns were measured using groundwater wells, arrays of vertically nested pressure transducers and manometers. Results show that wave action induces rapid infiltration/exfiltration across the sediment-water interface and a larger recirculation cell through the beach aquifer. Field data is used to validate a numerical groundwater model of wave-induced groundwater flows. While prior studies have simulated the effects of waves on beach groundwater flows, this study is the first attempt to validate these sophisticated modeling approaches. Finally, field data illustrating the impact of wave-induced groundwater flows on nutrient and bacteria fate and transport in beach aquifers will also be presented.

  6. Surface wave propagation characteristics in atmospheric pressure plasma column

    NASA Astrophysics Data System (ADS)

    Pencheva, M.; Benova, E.; Zhelyazkov, I.

    2007-04-01

    In the typical experiments of surface wave sustained plasma columns at atmospheric pressure the ratio of collision to wave frequency (ν/ω) is much greater than unity. Therefore, one might expect that the usual analysis of the wave dispersion relation, performed under the assumption ν/ω = 0, cannot give adequate description of the wave propagation characteristics. In order to study these characteristics we have analyzed the wave dispersion relationship for arbitrary ν/ω. Our analysis includes phase and wave dispersion curves, attenuation coefficient, and wave phase and group velocities. The numerical results show that a turning back point appears in the phase diagram, after which a region of backward wave propagation exists. The experimentally observed plasma column is only in a region where wave propagation coefficient is higher than the attenuation coefficient. At the plasma column end the electron density is much higher than that corresponding to the turning back point and the resonance.

  7. Numerical Study of Unsteady Supercavitation Perturbed by a Pressure Wave

    NASA Astrophysics Data System (ADS)

    Zheng, J. G.; Khoo, B. C.

    2016-06-01

    The unsteady features of supercavitation disturbed by an introduced pressure wave are investigated numerically using a one-fluid cavitation model. The supercavitating flow is assumed to be the homogeneous mixture of liquid and vapour which are locally under both kinetic and thermodynamic equilibrium. The compressibility effects of liquid water are taken into account to model the propagation of pressure wave through flow and its interaction with supercavitation bubble. The interaction between supercavity enveloping an underwater flat-nose cylinder and pressure wave is simulated and the resulting unsteady behavior of supercavitation is illustrated. It is observed that the supercavity will become unstable under the impact of the pressure wave and may collapse locally, which depends on the strength of perturbation. The huge pressure surge accompanying the collapse of supercavitation may cause the material erosion, noise, vibration and efficiency loss of operating underwater devices.

  8. Coalescence of two pressure waves associated with stream interactions

    NASA Technical Reports Server (NTRS)

    Whang, Y. C.; Burlaga, L. F.

    1984-01-01

    An MHD unsteady 1-D model is used to simulate the interaction and coalescence of two pressure waves in the outer heliosphere. Each of the two pressure waves was a compression region bounded by a shock pair. Computer simulation using Voyager data as input demonstrates the interaction and coalescence process involving one pressure wave associated with a fast stream and the other pressure wave without a fast stream. The process produced a significant change in the magnetic field and plasma signatures. The propagation of the forward and reverse shocks first widened the radial dimension of the shock compression region with increasing heliocentric distances. The shocks belonging to two neighboring compression regions eventually collided and two compression regions began to overlap with each other. This type of interaction is a dominant dynamical process in the outer heliosphere, and significantly and irreversible alters the structure of the medium.

  9. Corotating pressure waves without streams in the solar wind

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.

    1983-01-01

    Voyager 1 and 2 magnetic field and plasma data are presented which demonstrate the existence of large scale, corotating, non-linear pressure waves between 2 AU and 4 AU that are not accompanied by fast streams. The pressure waves are presumed to be generated by corotating streams near the Sun. For two of the three pressure waves that are discussed, the absence of a stream is probably a real, physical effect, viz., a consequence of deceleration of the stream by the associated compression wave. For the third pressure wave, the apparent absence of a stream may be a geometrical effect; it is likely that the stream was at latitudes just above those of the spacecraft, while the associated shocks and compression wave extended over a broader range of latitudes so that they could be observed by the spacecraft. It is suggested that the development of large-scale non-linear pressure waves at the expense of the kinetic energy of streams produces a qualitative change in the solar wind in the outer heliosphere. Within a few AU the quasi-stationary solar wind structure is determined by corotating streams whose structure is determined by the boundary conditions near the Sun.

  10. Induced topological pressure for topological dynamical systems

    SciTech Connect

    Xing, Zhitao; Chen, Ercai

    2015-02-15

    In this paper, inspired by the article [J. Jaerisch et al., Stochastics Dyn. 14, 1350016, pp. 1-30 (2014)], we introduce the induced topological pressure for a topological dynamical system. In particular, we prove a variational principle for the induced topological pressure.

  11. Novel wave power analysis linking pressure-flow waves, wave potential, and the forward and backward components of hydraulic power.

    PubMed

    Mynard, Jonathan P; Smolich, Joseph J

    2016-04-15

    Wave intensity analysis provides detailed insights into factors influencing hemodynamics. However, wave intensity is not a conserved quantity, so it is sensitive to diameter variations and is not distributed among branches of a junction. Moreover, the fundamental relation between waves and hydraulic power is unclear. We, therefore, propose an alternative to wave intensity called "wave power," calculated via incremental changes in pressure and flow (dPdQ) and a novel time-domain separation of hydraulic pressure power and kinetic power into forward and backward wave-related components (ΠP±and ΠQ±). Wave power has several useful properties:1) it is obtained directly from flow measurements, without requiring further calculation of velocity;2) it is a quasi-conserved quantity that may be used to study the relative distribution of waves at junctions; and3) it has the units of power (Watts). We also uncover a simple relationship between wave power and changes in ΠP±and show that wave reflection reduces transmitted power. Absolute values of ΠP±represent wave potential, a recently introduced concept that unifies steady and pulsatile aspects of hemodynamics. We show that wave potential represents the hydraulic energy potential stored in a compliant pressurized vessel, with spatial gradients producing waves that transfer this energy. These techniques and principles are verified numerically and also experimentally with pressure/flow measurements in all branches of a central bifurcation in sheep, under a wide range of hemodynamic conditions. The proposed "wave power analysis," encompassing wave power, wave potential, and wave separation of hydraulic power provides a potent time-domain approach for analyzing hemodynamics. PMID:26873972

  12. Estimating Sinusoidal Pressure Waves In A Pump Volute

    NASA Technical Reports Server (NTRS)

    Szabo, Roland J.; Chon, Juliet T.

    1994-01-01

    Closed-form equation approximates principal traveling-wave sinusoidal components of fluctuations of pressure in volute of centrifugal pump. Equation incorporated into Blade Vane Interaction Code (BVIC) computer program, which produces estimates for various pump speeds and various locations in volute. Intended use of BVIC in analysis of undesired interactions between pressure field and pump structure.

  13. The wave-induced boundary layer under long internal waves

    NASA Astrophysics Data System (ADS)

    Lin, Yuncheng; Redekopp, Larry G.

    2011-08-01

    The boundary layer formed under the footprint of an internal solitary wave is studied by numerical simulation for waves of depression in a two-layer model of the density stratification. The inviscid outer flow, in the perspective of boundary-layer theory, is based on an exact solution for the long wave-phase speed, yielding a family of fully nonlinear solitary wave solutions of the extended Korteweg-de Vries equation. The wave-induced boundary layer corresponding to this outer flow is then studied by means of simulation employing the Reynolds-averaged Navier-Stokes (RANS) formulation coupled with a turbulence closure model validated for wall-bounded flows. Boundary-layer characteristics are computed for an extensive range of environmental conditions and wave amplitudes. Boundary-layer transition, identified by monitoring the eddy viscosity, is correlated in terms of a boundary-layer Reynolds number. The frictional drag is evaluated for laminar, transitional, and turbulent cases, and correlations are presented for the friction coefficient plus relevant measures of the boundary-layer thickness.

  14. Acoustic Wave Propagation in Pressure Sense Lines

    NASA Technical Reports Server (NTRS)

    Vitarius, Patrick; Gregory, Don A.; Wiley, John; Korman, Valentin

    2003-01-01

    Sense lines are used in pressure measurements to passively transmit information from hostile environments to areas where transducers can be used. The transfer function of a sense line can be used to obtain information about the measured environment from the protected sensor. Several properties of this transfer function are examined, including frequency dependence, Helmholtz resonance, and time of flight delay.

  15. Diaphragm Pressure Wave Generator Developments at Industrial Research Ltd

    NASA Astrophysics Data System (ADS)

    Caughley, A. J.; Emery, N.; Glasson, N. D.

    2010-04-01

    Industrial Research Ltd (IRL) have been developing a unique diaphragm based pressure wave generator technology for pulse tube and Stirling cryocoolers. Our system uses a metal diaphragm to separate the clean cryocooler gas circuit from a conventionally lubricated mechanical driver, thus producing a clean pressure wave with a long life drive that does not require the precision manufacture and associated costs of large linear motors. The first successful diaphragm pressure wave generator produced 3.2 kW of acoustic power at an electro-acoustic efficiency of 72% with a swept volume of 200 ml and a prototype has now accumulated over 2500 hours running. This paper describes recent developments in the technology. To explore scaling, a small diaphragm pressure wave generator with a swept volume of 20 ml has been constructed and has delivered 454 W of acoustic power at an electro-acoustic efficiency of 60%. Improvements have been made to the hydraulic force amplifier mechanism for driving the diaphragms resulting in a cheaper and lighter mechanism than the mechanical linkage originally used. To meet a customer's specific requirements, the 200 ml pressure wave generator's stroke was extended to achieve 240 ml of swept volume thereby increasing its acoustic power delivery to 4.1 kW without compromising efficiency.

  16. Dual mode acoustic wave sensor for precise pressure reading

    NASA Astrophysics Data System (ADS)

    Mu, Xiaojing; Kropelnicki, Piotr; Wang, Yong; Randles, Andrew Benson; Chuan Chai, Kevin Tshun; Cai, Hong; Gu, Yuan Dong

    2014-09-01

    In this letter, a Microelectromechanical system acoustic wave sensor, which has a dual mode (lateral field exited Lamb wave mode and surface acoustic wave (SAW) mode) behavior, is presented for precious pressure change read out. Comb-like interdigital structured electrodes on top of piezoelectric material aluminium nitride (AlN) are used to generate the wave modes. The sensor membrane consists of single crystalline silicon formed by backside-etching of the bulk material of a silicon on insulator wafer having variable device thickness layer (5 μm-50 μm). With this principle, a pressure sensor has been fabricated and mounted on a pressure test package with pressure applied to the backside of the membrane within a range of 0 psi to 300 psi. The temperature coefficient of frequency was experimentally measured in the temperature range of -50 °C to 300 °C. This idea demonstrates a piezoelectric based sensor having two modes SAW/Lamb wave for direct physical parameter—pressure readout and temperature cancellation which can operate in harsh environment such as oil and gas exploration, automobile and aeronautic applications using the dual mode behavior of the sensor and differential readout at the same time.

  17. Two-phase flow model for energetic proton beam induced pressure waves in mercury target systems in the planned European Spallation Source

    NASA Astrophysics Data System (ADS)

    Barna, I. F.; Imre, A. R.; Rosta, L.; Mezei, F.

    2008-12-01

    Two-phase flow calculations are presented to investigate the thermo-hydraulical effects of the interaction between 2 ms long 1.3 GeV proton pulses with a closed mercury loop which can be considered as a model system of the target of the planned European Spallation Source (ESS) facility. The two-fluid model consists of six first-order partial differential equations that present one dimensional mass, momentum and energy balances for mercury vapor and liquid phases are capable to describe quick transients like cavitation effects or shock waves. The absorption of the proton beam is represented as instantaneous heat source in the energy balance equations. Densities and internal energies of the mercury liquid-vapor system is calculated from the van der Waals equation, but general method how to obtain such properties using arbitrary equation of state is also presented. A second order accurate high-resolution shock-capturing numerical scheme is applied with different kind of limiters in the numerical calculations. Our analysis show that even 75 degree temperature heat shocks cannot cause considerable cavitation effects in mercury.

  18. Acoustic waves in gases with strong pressure gradients

    NASA Technical Reports Server (NTRS)

    Zorumski, William E.

    1989-01-01

    The effect of strong pressure gradients on the acoustic modes (standing waves) of a rectangular cavity is investigated analytically. When the cavity response is represented by a sum of modes, each mode is found to have two resonant frequencies. The lower frequency is near the Viaesaela-Brundt frequency, which characterizes the buoyant effect, and the higher frequency is above the ordinary acoustic resonance frequency. This finding shows that the propagation velocity of the acoustic waves is increased due to the pressure gradient effect.

  19. Pressure induced ageing of polymers

    NASA Technical Reports Server (NTRS)

    Emri, I.; Knauss, W. G.

    1988-01-01

    The nonlinearly viscoelastic response of an amorphous homopolymer is considered under aspects of time dependent free volume behavior. In contrast to linearly viscoelastic solids, this model couples shear and volume deformation through a shift function which influences the rate of molecular relaxation or creep. Sample computations produce all those qualitative features one observes normally in uniaxial tension including the rate dependent formation of a yield point as a consequence of the history of an imposed pressure.

  20. Theoretical pressure distribution and wave drags for conical boattails

    NASA Technical Reports Server (NTRS)

    Jack, John R

    1953-01-01

    Afterbody pressure distributions and wave drag were calculated using a second-order theory for a variety of conical boattails at zero angle of attack. Results are presented for Mach numbers from 1.5 to 4.5, area ratios from 0.200 to 0.800, and boattail angle from 3 degrees to 11 degrees. The results indicate that for a given boattail angle, the wave drag decreases with increasing Mach number and area ratio. The wave drag, for a constant area ratio, increases with increasing boattail angle. For a specific Mach number, area ratio, and fineness ratio, a comparison of the wave-drag coefficients for conical, tangent-parabolic, and secant-parabolic boattails showed the conical boattail to have the smallest wave drag.

  1. Rapid miniature fiber optic pressure sensors for blast wave measurements

    NASA Astrophysics Data System (ADS)

    Zou, Xiaotian; Wu, Nan; Tian, Ye; Niezrecki, Christopher; Chen, Julie; Wang, Xingwei

    2013-02-01

    Traumatic brain injury (TBI) is a serious potential threat to soldiers who are exposed to explosions. Since the pathophysiology of TBI associated with a blast wave is not clearly defined, it is crucial to have a sensing system to accurately quantify the blast wave dynamics. This paper presents an ultra-fast fiber optic pressure sensor based on Fabry-Perot (FP) interferometric principle that is capable of measuring the rapid pressure changes in a blast event. The blast event in the experiment was generated by a starter pistol blank firing at close range, which produced a more realistic wave profile compared to using compressed air driven shock tubes. To the authors' knowledge, it is also the first study to utilize fiber optic pressure sensors to measure the ballistics shock wave of a pistol firing. The results illustrated that the fiber optic pressure sensor has a rise time of 200 ns which demonstrated that the sensor has ability to capture the dynamic pressure transient during a blast event. Moreover, the resonant frequency of the sensor was determined to be 4.11 MHz, which agrees well with the specific designed value.

  2. Air pressure waves from Mount St. Helens eruptions

    SciTech Connect

    Reed, J.W.

    1987-10-20

    Weather station barograph records as well as infrasonic recordings of the pressure wave from the Mount St. Helens eruption of May 18, 1980, have been used to estimate an equivalent explosion airblast yield for this event. Pressure amplitude versus distance patterns in various directions compared with patterns from other large explosions, such as atmospheric nuclear tests, the Krakatoa eruption, and the Tunguska comet impact, indicate that the wave came from an explosion equivalent of a few megatons of TNT. The extent of tree blowdown is considerably greater than could be expected from such an explosion, and the observed forest damage is attributed to outflow of volcanic material. The pressure-time signature obtained at Toledo, Washington, showed a long, 13-min duration negative phase as well as a second, hour-long compression phase, both probably caused by ejacta dynamics rather than standard explosion wave phenomenology. The peculiar audibility pattern, with the blast being heard only at ranges beyond about 100 km, is explicable by finite amplitude propagation effects. Near the source, compression was slow, taking more than a second but probably less than 5 s, so that it went unnoticed by human ears and susceptible buildings were not damaged. There was no damage as Toledo (54 km), where the recorded amplitude would have broken windows with a fast compression. An explanation is that wave emissions at high elevation angles traveled to the upper stratosphere, where low ambient air pressures caused this energetic pressure oscillation to form a shock wave with rapid, nearly instantaneous compression. Atmospheric refraction then returned part of this wave to ground level at long ranges, where the fast compressions were clearly audible. copyright American Geophysical Union 1987

  3. Measurement of Blast Waves from Bursting Pressureized Frangible Spheres

    NASA Technical Reports Server (NTRS)

    Esparza, E. D.; Baker, W. E.

    1977-01-01

    Small-scale experiments were conducted to obtain data on incident overpressure at various distances from bursting pressurized spheres. Complete time histories of blast overpressure generated by rupturing glass spheres under high internal pressure were obtained using eight side-on pressure transducers. A scaling law is presented, and its nondimensional parameters are used to compare peak overpressures, arrival times, impulses, and durations for different initial conditions and sizes of blast source. The nondimensional data are also compared, whenever possible, with results of theoretical calculations and compiled data for Pentolite high explosive. The scaled data are repeatable and show significant differences from blast waves generated by condensed high-explosives.

  4. Attenuation characteristics of nonlinear pressure waves propagating in pipes

    NASA Technical Reports Server (NTRS)

    Shih, C. C.

    1974-01-01

    A series of experiments was conducted to investigate temporal and spatial velocity distributions of fluid flow in 3-in. open-end pipes of various lengths up to 210 ft, produced by the propagation of nonlinear pressure waves of various intensities. Velocity profiles across each of five sections along the pipes were measured as a function of time with the use of hot-film and hot-wire anemometers for two pressure waves produced by a piston. Peculiar configurations of the velocity profiles across the pipe section were noted, which are uncommon for steady pipe flow. Theoretical consideration was given to this phenomenon of higher velocity near the pipe wall for qualitative confirmation. Experimentally time-dependent velocity distributions along the pipe axis were compared with one-dimensional theoretical results obtained by the method of characteristics with or without diffusion term for the purpose of determining the attenuation characteristics of the nonlinear wave propagation in the pipes.

  5. Free-surface wave-induced separation

    SciTech Connect

    Zhang, Z.J.; Stern, F.

    1996-09-01

    Free-surface wave-induced separation is studied for a surface-piercing NACA 0024 foil over a range of Froude numbers (0, .2, .37, .55) through computational fluid dynamics of the unsteady Reynolds-averaged Navier-Stokes and the continuity equations with the Baldwin-Lomax turbulence model, exact nonlinear kinematic and approximate dynamic free-surface boundary conditions, and a body/free-surface conforming grid. The flow conditions and uncertainty analysis are discussed. A topological rule for a surface-piercing body is derived and verified. Steady-flow results are presented and analyzed with regard to the wave and viscous flow and the nature of the separation.

  6. Gravitational waves induced by spinor fields

    NASA Astrophysics Data System (ADS)

    Feng, Kaixi; Piao, Yun-Song

    2015-07-01

    In realistic model building, spinor fields with various masses are present. During inflation, a spinor field may induce gravitational waves as a second order effect. In this paper, we calculate the contribution of a single massive spinor field to the power spectrum of primordial gravitational wave by using a retarded Green propagator. We find that the correction is scale invariant and of order H4/MP4 for arbitrary spinor mass mψ. Additionally, we also observe that when mψ≳H , the dependence of correction on mψ/H is nontrivial.

  7. Magnetospheric ULF waves with increasing amplitude related to solar wind dynamic pressure changes: The Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations

    NASA Astrophysics Data System (ADS)

    Shen, X. C.; Zong, Q.-G.; Shi, Q. Q.; Tian, A. M.; Sun, W. J.; Wang, Y. F.; Zhou, X. Z.; Fu, S. Y.; Hartinger, M. D.; Angelopoulos, V.

    2015-09-01

    Ultralow frequency (ULF) waves play an important role in transferring energy by buffeting the magnetosphere with solar wind pressure impulses. The amplitudes of magnetospheric ULF waves, which are induced by solar wind dynamic pressure enhancements or shocks, are thought to damp in one half a wave cycle or an entire wave cycle. We report in situ observations of solar wind dynamic pressure impulse-induced magnetospheric ULF waves with increasing amplitudes. We found six ULF wave events induced by solar wind dynamic pressure enhancements with slow but clear wave amplitude increase. During three or four wave cycles, the amplitudes of ion velocities and electric field of these waves increased continuously by 1.3-4.4 times. Two significant events were selected to further study the characteristics of these ULF waves. We found that the wave amplitude growth is mainly contributed by the toroidal mode wave. Three possible mechanisms of causing the wave amplitude increase are discussed. First, solar wind dynamic pressure perturbations, which are observed in a duration of 20-30 min, might transfer energy to the magnetospheric ULF waves continually. Second, the wave amplitude increase in the radial electric field may be caused by superposition of two wave modes, a standing wave excited by the solar wind dynamic impulse and a propagating compressional wave directly induced by solar wind oscillations. When superposed, the two wave modes fit observations as does a calculation that superposes electric fields from two wave sources. Third, the normal of the solar wind discontinuity is at an angle to the Sun-Earth line. Thus, the discontinuity will affect the dayside magnetopause continuously for a long time.

  8. Internal wave-turbulence pressure above sloping sea bottoms

    NASA Astrophysics Data System (ADS)

    van Haren, Hans

    2011-12-01

    An accurate bottom pressure sensor has been moored at different sites varying from a shallow sea strait via open ocean guyots to a 1900 m deep Gulf of Mexico. All sites show more or less sloping bottom topography. Focusing on frequencies (σ) higher than tidal, the pressure records are remarkably similar, to within the 95% statistical significance bounds, in the internal gravity wave continuum (IWC) band up to buoyancy frequency N. The IWC has a relatively uniform spectral slope: log(P(σ)) = -αlog(σ), α = 2 ± 1/3. The spectral collapse is confirmed from independent internal hydrostatic pressure estimate, which suggests a saturated IWC. For σ > N, all pressure-spectra transit to a bulge that differs in magnitude. This bulge is commonly attributed to long surface waves. For the present data it is suggested to be due to stratified turbulence-internal wave coupling, which is typically large over sloping topography. The bulge drops off at a more or less common frequency of 2-3 × 10-2 Hz, which is probably related with typical turbulent overturning scales.

  9. Application of Monochromatic Ocean Wave Forecasts to Prediction of Wave-Induced Currents

    NASA Technical Reports Server (NTRS)

    Poole, L. R.

    1975-01-01

    Stoke's wave-induced currents are compared, for variety of wind conditions resulting in partially developed seas and for two water depths, with currents induced by average and significant monochromatic waves related to Bretschneider spectrum.

  10. Propagation of waves in a medium with high radiation pressure

    NASA Technical Reports Server (NTRS)

    Bisnovatyy-Kogan, G. S.; Blinnikov, S. I.

    1979-01-01

    The propagation and mutual transformation of acoustic and thermal waves are investigated in media with a high radiative pressure. The equations of hydrodynamics for matter and the radiative transfer equations in a moving medium in the Eddington approximation are used in the investigation. Model problems of waves in a homogeneous medium with an abrupt jump in opacity and in a medium of variable opacity are presented. The characteristic and the times of variability are discussed. Amplitude for the brightness fluctuations for very massive stars are discussed.

  11. Plateau Waves of Intracranial Pressure and Partial Pressure of Cerebral Oxygen.

    PubMed

    Lang, Erhard W; Kasprowicz, Magdalena; Smielewski, Peter; Pickard, John; Czosnyka, Marek

    2016-01-01

    This study investigates 55 intracranial pressure (ICP) plateau waves recorded in 20 patients after severe traumatic brain injury (TBI) with a focus on a moving correlation coefficient between mean arterial pressure (ABP) and ICP, called PRx, which serves as a marker of cerebrovascular reactivity, and a moving correlation coefficient between ABP and cerebral partial pressure of oxygen (pbtO2), called ORx, which serves as a marker for cerebral oxygen reactivity. ICP and ICPamplitude increased significantly during the plateau waves, whereas CPP and pbtO2 decreased significantly. ABP, ABP amplitude, and heart rate remained unchanged. In 73 % of plateau waves PRx increased during the wave. ORx showed an increase during and a decrease after the plateau waves, which was not statistically significant. Our data show profound cerebral vasoparalysis on top of the wave and, to a lesser extent, impairment of cerebral oxygen reactivity. The different behavior of the indices may be due to the different latencies of the cerebral blood flow and oxygen level control mechanisms. While cerebrovascular reactivity is a rapidly reacting mechanism, cerebral oxygen reactivity is slower. PMID:27165902

  12. Time-resolved wave profile measurements in copper to Megabar pressures

    SciTech Connect

    Chhabildas, L C; Asay, J R

    1981-01-01

    Many time-resolved techniques have been developed which have greatly aided in the understanding of dynamic material behavior such as the high pressure-dynamic strength of materials. In the paper, time-resolved measurements of copper (at shock-induced high pressures and temperatures) are used to illustrate the capability of using such techniques to investigate high pressure strength. Continuous shock loading and release wave profiles have been made in copper to 93 GPa using velocity interferometric techniques. Fine structure in the release wave profiles from the shocked state indicates an increase in shear strength of copper to 1.5 GPa at 93 GPa from its ambient value of 0.08 GPa.

  13. Computation of the pressure field generated by surface acoustic waves in microchannels.

    PubMed

    Darinskii, A N; Weihnacht, M; Schmidt, H

    2016-07-01

    The high-frequency pressure induced by a surface acoustic wave in the fluid filling a microchannel is computed by solving the full scattering problem. The microchannel is fabricated inside a container attached to the top of a piezoelectric substrate where the surface wave propagates. The finite element method is used. The pressure found in this way is compared with the pressure obtained by solving boundary-value problems formulated on the basis of simplifications which have been introduced in earlier papers by other research studies. The considered example shows that the difference between the results can be significant, ranging from several tens of percent up to several times in different points inside the channel. PMID:27314212

  14. An oxygen pressure sensor using surface acoustic wave devices

    NASA Technical Reports Server (NTRS)

    Leighty, Bradley D.; Upchurch, Billy T.; Oglesby, Donald M.

    1993-01-01

    Surface acoustic wave (SAW) piezoelectric devices are finding widespread applications in many arenas, particularly in the area of chemical sensing. We have developed an oxygen pressure sensor based on coating a SAW device with an oxygen binding agent which can be tailored to provide variable sensitivity. The coating is prepared by dissolving an oxygen binding agent in a toluene solution of a copolymer which is then sprayed onto the surface of the SAW device. Experimental data shows the feasibility of tailoring sensors to measure the partial pressure of oxygen from 2.6 to 67 KPa (20 to 500 torr). Potential applications of this technology are discussed.

  15. Air pressure waves from Mount St. Helens eruptions

    SciTech Connect

    Reed, J.W.

    1980-01-01

    Barograms from a number of National Weather Service stations were assembled for the May 18, 1980, eruption and compared to airblast wave propagations from large explosions. Wave amplitudes at 50 to 300 km distances were about what might be expected from a nuclear explosion of between 1 megaton and 10 megaton yield. Pressure-time signatures could not be resolved for the first compression phase, because of the slow paper recording speed. The 900 s negative phase duration was much too long for comparison with the negative phase of an explosion. Nevertheless, positive and negative amplitudes were about equal, as often observed at long distances from explosions. Calculations have been made for a simple finite amplitude propagation model. These show rough bounds on the source compression rate, to give the observed inaudible waves at least to 54 km distance, yet cause audibly rapid compression at Seattle, near 150 km, and beyond.

  16. Pressure-induced metallization of silane

    SciTech Connect

    Chen,X.; Struzhkin, V.; Song, Y.; Goncharov, A.; Ahart, M.; Liu, Z.; Mao, H.; Hemley, R.

    2008-01-01

    There is a great interest in electronic transitions in hydrogen-rich materials under extreme conditions. It has been recently suggested that the group IVa hydrides such as methane (CH4), silane (SiH4), and germane (GeH4) become metallic at far lower pressures than pure hydrogen at equivalent densities because the hydrogen is chemically compressed in group IVa hydride compounds. Here we report measurements of Raman and infrared spectra of silane under pressure. We find that SiH4 undergoes three phase transitions before becoming opaque at 27-30 GPa. The vibrational spectra indicate the material transforms to a polymeric (framework) structure in this higher pressure range. Room-temperature infrared reflectivity data reveal that the material exhibits Drude-like metallic behavior above 60 GPa, indicating the onset of pressure-induced metallization.

  17. Wavelet analysis of blood pressure waves in vasovagal syncope

    NASA Astrophysics Data System (ADS)

    Marrone, A.; Polosa, A. D.; Scioscia, G.; Stramaglia, S.; Zenzola, A.

    1999-09-01

    We describe the multiresolution wavelet analysis of blood pressure waves in vasovagal syncope affected patients compared with healthy people. We argue that there exist discriminating criteria which allow us to isolate particular features, common to syncope-affected patients sample, indicating a tentative, alternative diagnosis methodology for this syndrome. We perform a throughout analysis both in the Haar basis and in a Gaussian one, with an attempt to grasp the underlying dynamics.

  18. Shock pressures induced in condensed matter by laser ablation

    NASA Astrophysics Data System (ADS)

    Swift, Damian C.; Tierney, Thomas E.; Kopp, Roger A.; Gammel, J. Tinka

    2004-03-01

    The Trident laser was used to induce shock waves in samples of solid elements, with atomic numbers ranging from Be to Au, using pulses of 527 nm light around 1 ns long with irradiances of the order of 0.1 to 10 PW/m2. States induced by the resulting ablation process were investigated using laser Doppler velocimetry to measure the velocity history of the opposite surface. By varying the energy in the laser pulse, relations were inferred between the irradiance and the induced pressure. For samples in vacuo, an irradiance constant in time does not produce a constant pressure. Radiation hydrodynamics simulations were used to investigate the relationship between the precise pulse shape and the pressure history. In this regime of time and irradiance, it was possible to reproduce the experimental data to within their uncertainty by including conductivity-dependent deposition of laser energy, heat conduction, gray radiation diffusion, and three temperature hydrodynamics in the treatment of the plasma, with ionizations calculated using the Thomas-Fermi equation. States induced in the solid sample were fairly insensitive to the details of modeling in the plasma, so Hugoniot points may be estimated from experiments of this type given a reasonable model of the plasma. More useful applications include the generation of dynamic loading to investigate compressive strength and phase transitions, and for sample recovery.

  19. Shock pressures induced in condensed matter by laser ablation.

    PubMed

    Swift, Damian C; Tierney, Thomas E; Kopp, Roger A; Gammel, J Tinka

    2004-03-01

    The Trident laser was used to induce shock waves in samples of solid elements, with atomic numbers ranging from Be to Au, using pulses of 527 nm light around 1 ns long with irradiances of the order of 0.1 to 10 PW/m(2). States induced by the resulting ablation process were investigated using laser Doppler velocimetry to measure the velocity history of the opposite surface. By varying the energy in the laser pulse, relations were inferred between the irradiance and the induced pressure. For samples in vacuo, an irradiance constant in time does not produce a constant pressure. Radiation hydrodynamics simulations were used to investigate the relationship between the precise pulse shape and the pressure history. In this regime of time and irradiance, it was possible to reproduce the experimental data to within their uncertainty by including conductivity-dependent deposition of laser energy, heat conduction, gray radiation diffusion, and three temperature hydrodynamics in the treatment of the plasma, with ionizations calculated using the Thomas-Fermi equation. States induced in the solid sample were fairly insensitive to the details of modeling in the plasma, so Hugoniot points may be estimated from experiments of this type given a reasonable model of the plasma. More useful applications include the generation of dynamic loading to investigate compressive strength and phase transitions, and for sample recovery. PMID:15089414

  20. Pressure-induced phase transition in pentacene

    NASA Astrophysics Data System (ADS)

    Farina, L.; Brillante, A.; Della Valle, R. G.; Venuti, E.; Amboage, M.; Syassen, K.

    2003-07-01

    We have recently studied two solid phases of bulk pentacene (polymorphs H and C) by means of lattice phonon Raman spectroscopy. The assignment, previously based on lattice dynamics calculations alone, is now verified by X-ray diffraction measurements, conclusively confirming the existence of both polymorphs. Furthermore, Raman phonon spectra indicate a pressure-induced phase transition where the polymorph C (lower density phase) transforms to the H form (higher density phase). The onset pressure for the phase transition is only 0.2 GPa. The phase change is irreversible.

  1. Pressure-induced transformations in molecular crystals

    SciTech Connect

    Taylor, R.D.; Hearne, G.R. |; Pasternak, M.P.

    1995-09-01

    A review is given on the unique features of the Moessbauer spectroscopy (MS) which by virtue of the quadrupole interaction and the lattice dynamics allows one to characterize some structural properties in the pressure-induced amorphous state of molecular crystals. Experiments were performed in GeI{sub 4}, SnI{sub 4} and SnBr{sub 4} by means of {sup 119}Sn and {sup 129}I MS with pressures to 35 GPa at cryogenic temperatures using diamond anvil cells.

  2. Numerical Investigations of High Pressure Acoustic Waves in Resonators

    NASA Technical Reports Server (NTRS)

    Athavale, Mahesh; Pindera, Maciej; Daniels, Christopher C.; Steinetz, Bruce M.

    2004-01-01

    This presentation presents work on numerical investigations of nonlinear acoustic phenomena in resonators that can generate high-pressure waves using acoustic forcing of the flow. Time-accurate simulations of the flow in a closed cone resonator were performed at different oscillation frequencies and amplitudes, and the numerical results for the resonance frequency and fluid pressure increase match the GRC experimental data well. Work on cone resonator assembly simulations has started and will involve calculations of the flow through the resonator assembly with and without acoustic excitation. A new technique for direct calculation of resonance frequency of complex shaped resonators is also being investigated. Script-driven command procedures will also be developed for optimization of the resonator shape for maximum pressure increase.

  3. Experimental Study Of Metallurgical Evolutions In Metallic Alloys Induced By Laser Generated High Pressure Shocks

    NASA Astrophysics Data System (ADS)

    Fabbro, R.; Fournier, J.; Fabre, E.; Leberichel, E.; Hannau, Th; Corbet, C.

    1986-11-01

    Some preliminary results are presented concerning the damages and the evolutions of metallurgical properties of Fe-C alloys induced by laser shock waves at two different laser wavelengths. In the present work, changes induced by laser shocking have been measured : pressure, microhardness, residual stresses. In addition microstructural variations at the surface and in depth have been observed.

  4. Cavitation inception by the backscattering of pressure waves from a bubble interface

    NASA Astrophysics Data System (ADS)

    Takahira, Hiroyuki; Ogasawara, Toshiyuki; Mori, Naoto; Tanaka, Moe

    2015-10-01

    The secondary cavitation that occurs by the backscattering of focused ultrasound from a primary cavitation bubble caused by the negative pressure part of the ultrasound (Maxwell, et al., 2011) might be useful for the energy exchange due to bubble oscillations in High Intensity Focused Ultrasound (HIFU). The present study is concerned with the cavitation inception by the backscattering of ultrasound from a bubble. In the present experiment, a laser-induced bubble which is generated by a pulsed focused laser beam with high intensity is utilized as a primary cavitation bubble. After generating the bubble, focused ultrasound is emitted to the bubble. The acoustic field and the bubble motion are observed with a high-speed video camera. It is confirmed that the secondary cavitation bubble clouds are generated by the backscattering from the laser-induced bubble. The growth of cavitation bubble clouds is analyzed with the image processing method. The experimental results show that the height and width of the bubble clouds grow in stepwise during their evolution. The direct numerical simulations are also conducted for the backscattering of incident pressure waves from a bubble in order to evaluate a pressure field near the bubble. It is shown that the ratio of a bubble collapse time t0 to a characteristic time of wave propagation tS, η = t0/ts, is an important determinant for generating negative pressure region by backscattering. The minimum pressure location by the backscattering in simulations is in good agreement with the experiment.

  5. Microcantilever Actuation by Laser Induced Photoacoustic Waves

    PubMed Central

    Gao, Naikun; Zhao, Dongfang; Jia, Ran; Liu, Duo

    2016-01-01

    We present here a combined theoretical and experimental investigation on effective excitation of microcantilever by using photoacoustic waves. The photoacoustic waves arose from a vibrating Al foil induced by an intensity-modulated laser. We demonstrate that, superior to photothermal excitation, this new configuration avoids direct heating of the microcantilever, thus minimizing undesired thermal effects on the vibration of microcantilever, while still keeps the advantage of being a remote, non-contact excitation method. We also measured the vibration amplitude of the microcantilever as a function of distance between the microcantilever and the Al foil and found that the amplitudes decay gradually according to the inverse distance law. This method is universal and can be adopted in bio-microelectromechanical systems (BioMEMs) for the detection of small signals where detrimental thermal effects must be avoided. PMID:26814360

  6. Long waves induced motions to rigid spheroids

    NASA Astrophysics Data System (ADS)

    Zhou, Hongkun; Hong, Lianjin

    2015-05-01

    Responses of unconstrained and rigid spheroidal bodies subjected to long sound waves are analyzed by means of approaching hydrodynamic method. It is shown that in the low-frequency approximation the amplitude of translational velocity is completely determined by the density as well as the acoustic added mass which is equal to hydrodynamic one associated with the body. The inconformity of responses to sound waves in virtue of geometric asymmetry is also presented. In addition, rotational movement engendered by acoustic oblique incidence is discussed, and it represents as the modulated angular oscillation similar to the beat-frequency vibration. All these analyses on acoustically induced motions provide a theoretical evidence for developing spheroidal inertial vector receivers.

  7. Microcantilever Actuation by Laser Induced Photoacoustic Waves

    NASA Astrophysics Data System (ADS)

    Gao, Naikun; Zhao, Dongfang; Jia, Ran; Liu, Duo

    2016-01-01

    We present here a combined theoretical and experimental investigation on effective excitation of microcantilever by using photoacoustic waves. The photoacoustic waves arose from a vibrating Al foil induced by an intensity-modulated laser. We demonstrate that, superior to photothermal excitation, this new configuration avoids direct heating of the microcantilever, thus minimizing undesired thermal effects on the vibration of microcantilever, while still keeps the advantage of being a remote, non-contact excitation method. We also measured the vibration amplitude of the microcantilever as a function of distance between the microcantilever and the Al foil and found that the amplitudes decay gradually according to the inverse distance law. This method is universal and can be adopted in bio-microelectromechanical systems (BioMEMs) for the detection of small signals where detrimental thermal effects must be avoided.

  8. Microcantilever Actuation by Laser Induced Photoacoustic Waves.

    PubMed

    Gao, Naikun; Zhao, Dongfang; Jia, Ran; Liu, Duo

    2016-01-01

    We present here a combined theoretical and experimental investigation on effective excitation of microcantilever by using photoacoustic waves. The photoacoustic waves arose from a vibrating Al foil induced by an intensity-modulated laser. We demonstrate that, superior to photothermal excitation, this new configuration avoids direct heating of the microcantilever, thus minimizing undesired thermal effects on the vibration of microcantilever, while still keeps the advantage of being a remote, non-contact excitation method. We also measured the vibration amplitude of the microcantilever as a function of distance between the microcantilever and the Al foil and found that the amplitudes decay gradually according to the inverse distance law. This method is universal and can be adopted in bio-microelectromechanical systems (BioMEMs) for the detection of small signals where detrimental thermal effects must be avoided. PMID:26814360

  9. Radiation-pressure-driven dust waves inside bursting interstellar bubbles

    NASA Astrophysics Data System (ADS)

    Ochsendorf, B. B.; Verdolini, S.; Cox, N. L. J.; Berné, O.; Kaper, L.; Tielens, A. G. G. M.

    2014-06-01

    Massive stars drive the evolution of the interstellar medium through their radiative and mechanical energy input. After their birth, they form "bubbles" of hot gas surrounded by a dense shell. Traditionally, the formation of bubbles is explained through the input of a powerful stellar wind, even though direct evidence supporting this scenario is lacking. Here we explore the possibility that interstellar bubbles seen by the Spitzer- and Herschel space telescopes, blown by stars with log (L/L⊙) ≲ 5.2, form and expand because of the thermal pressure that accompanies the ionization of the surrounding gas. We show that density gradients in the natal cloud or a puncture in the swept-up shell lead to an ionized gas flow through the bubble into the general interstellar medium, which is traced by a dust wave near the star, which demonstrates the importance of radiation pressure during this phase. Dust waves provide a natural explanation for the presence of dust inside H II bubbles, offer a novel method to study dust in H II regions and provide direct evidence that bubbles are relieving their pressure into the interstellar medium through a champagne flow, acting as a probe of the radiative interaction of a massive star with its surroundings. We explore a parameter space connecting the ambient density, the ionizing source luminosity, and the position of the dust wave, while using the well studied H II bubbles RCW 120 and RCW 82 as benchmarks of our model. Finally, we briefly examine the implications of our study for the environments of super star clusters formed in ultraluminous infrared galaxies, merging galaxies, and the early Universe, which occur in very luminous and dense environments and where radiation pressure is expected to dominate the dynamical evolution.

  10. Current-induced spin wave Doppler shift

    NASA Astrophysics Data System (ADS)

    Bailleul, Matthieu

    2010-03-01

    In metal ferromagnets -namely Fe, Co and Ni and their alloys- magnetism and electrical transport are strongly entangled (itinerant magnetism). This results in a number of properties such as the tunnel and giant magnetoresistance (i.e. the dependence of the electrical resistance on the magnetic state) and the more recently addressed spin transfer (i.e. the ability to manipulate the magnetic state with the help of an electrical current). The spin waves, being the low-energy elementary excitations of any ferromagnet, also exist in itinerant magnets, but they are expected to exhibit some peculiar properties due the itinerant character of the carriers. Accessing these specific properties experimentally could shed a new light on the microscopic mechanism governing itinerant magnetism, which -in turn- could help in optimizing material properties for spintronics applications. As a simple example of these specific properties, it was predicted theoretically that forcing a DC current through a ferromagnetic metal should induce a shift of the frequency of the spin waves [1,2]. This shift can be identified to a Doppler shift undergone by the electron system when it is put in motion by the electrical current. We will show how detailed spin wave measurements allow one to access this current-induced Doppler shift [3]. From an experimental point of view, we will discuss the peculiarities of propagating spin wave spectroscopy experiments carried out at a sub-micrometer length-scale and with MHz frequency resolution. Then, we will discuss the measured value of the Doppler shift in the context of both the old two-current model of spin-polarized transport and the more recent model of adiabatic spin transfer torque. [4pt] [1] P.Lederer and D.L. Mills, Phys.Rev. 148, 542 (1966).[0pt] [2] J. Fernandez-Rossier et al., Phys. Rev. B 69, 174412 (2004)[0pt] [3] V. Vlaminck and M. Bailleul, Science 322, 410 (2008).

  11. Mild neurotrauma indicates a range-specific pressure response to low level shock wave exposure.

    PubMed

    Vandevord, Pamela J; Bolander, Richard; Sajja, Venkata Siva Sai Sujith; Hay, Kathryn; Bir, Cynthia A

    2012-01-01

    Identifying the level of overpressure required to create physiological deficits is vital to advance prevention, diagnostic, and treatment strategies for individuals exposed to blasts. In this study, a rodent model of primary blast neurotrauma was employed to determine the pressure at which acute neurological alterations occurred. Rats were exposed to a single low intensity shock wave at a pressure of 0, 97, 117, or 153 kPa. Following exposure, rats were assessed for acute cognitive alterations using the Morris water maze and motor dysfunction using the horizontal ladder test. Subsequently, histological analyses of three brain regions (primary motor cortex, the hippocampal dentate gyrus region, and the posteromedial cortical amygdala) were conducted. Histological parameters included measuring the levels of glial fibrillary acidic protein (GFAP) to identify astrocyte activation, cleaved caspase-3 for early apoptosis identification and Fluoro-Jade B (FJB) which labels degenerating neurons within the brain tissue. The results demonstrated that an exposure to a single 117 kPa shock wave revealed a significant change in overall neurological deficits when compared to controls and the other pressures. The animals showed significant alterations in water maze parameters and a histological increase in the number of GFAP, caspase-3, and FJB-positive cells. It is suggested that when exposed to a low level shock wave, there may be a biomechanical response elicited by a specific pressure range which can cause low level neurological deficits within the rat. These data indicate that neurotrauma induced from a shock wave may lead to cognitive deficits in short-term learning and memory of rats. Additional histological evidence supports significant and diffuse glial activation and cellular damage. Further investigation into the biomechanical aspects of shock wave exposure is required to elucidate this pressure range-specific phenomenon. PMID:21994066

  12. Pressure wave generated by the Mount St. Helens eruption

    SciTech Connect

    Banister, J.B.

    1984-06-20

    Histories of the air pressure wave radiated from the eruption of Mount St. Helens on May 18, 1980, were calculated for two models of the eruption cloud expansion. The first considered the wave radiated from an accelerated plane surface, while the second examined the wave radiated from an expanding hemisphere. Two histories of eruption cloud motion based on photographs were used. Peak positive overpressures were about the same for these cloud motion histories of expansion into a hemisphere was assumed. If an accelerated planar source model was used, the peak positive pressures have again about the same value in east and west direction, but values are about half in the north and south direction. Observed peak overpressures at microbarograph stations are somewhat higher than the calculated with the most marked departures at the greater surface ranges. These observed overpressures may have been about half the correct values, however. Microbarograph records show a weaker rarefaction than calculated histories or none at all. This can be explained, in part, by a lack of a real motion coherence in the slowing eruption cloud. If it is also possible the net ash cloud volume increased considerably after its vertical growth ceased and weakened the negative phase as well as lengthening the positive phase.

  13. Application of monochromatic ocean wave forecasts to prediction of wave-induced currents

    NASA Technical Reports Server (NTRS)

    Poole, L. R.

    1975-01-01

    The use of monochromatic wind-wave forecasts in prediction of wind-wave-induced currents was assessed. Currents were computed for selected combinations of wind conditions by using a spectrum approach which was developed by using the Bretschneider wave spectrum for partially developed wind seas. These currents were compared with currents computed by using the significant and average monochromatic wave parameters related to the Bretschneider spectrum. Results indicate that forecasts of significant wave parameters can be used to predict surface wind-wave-induced currents. Conversion of these parameters to average wave parameters can furnish reasonable estimates of subsurface current values.

  14. Measurement of sound speed vs. depth in South Pole ice: pressure waves and shear waves

    SciTech Connect

    IceCube Collaboration; Klein, Spencer

    2009-06-04

    We have measured the speed of both pressure waves and shear waves as a function of depth between 80 and 500 m depth in South Pole ice with better than 1% precision. The measurements were made using the South Pole Acoustic Test Setup (SPATS), an array of transmitters and sensors deployed in the ice at the South Pole in order to measure the acoustic properties relevant to acoustic detection of astrophysical neutrinos. The transmitters and sensors use piezoceramics operating at {approx}5-25 kHz. Between 200 m and 500 m depth, the measured profile is consistent with zero variation of the sound speed with depth, resulting in zero refraction, for both pressure and shear waves. We also performed a complementary study featuring an explosive signal propagating vertically from 50 to 2250 m depth, from which we determined a value for the pressure wave speed consistent with that determined for shallower depths, higher frequencies, and horizontal propagation with the SPATS sensors. The sound speed profile presented here can be used to achieve good acoustic source position and emission time reconstruction in general, and neutrino direction and energy reconstruction in particular. The reconstructed quantities could also help separate neutrino signals from background.

  15. Pressure-induced diffusion in natural garnets

    NASA Astrophysics Data System (ADS)

    Floess, David; Vrijmoed, Johannes; Baumgartner, Lukas; Podladchikov, Yuri

    2015-04-01

    Recent efforts in metamorphic petrology suggest that significant pressure gradients exist on the grain-scale and provide tools for its quantification [1,2]. Here we propose that pressure gradients around coesite inclusions induced diffusion of major elements within garnet crystals upon exhumation. This is based on the fact that the molar mass of garnet endmembers vary between 403 and 497 g/mol, thus up to 23 %. Whiteschists from the Dora Maira Massive in the Western Alps underwent eclogite facies metamorphism (3.3-4.3 GPa, 720-780 °C) during the Alpine event at 35 Ma [3]. Coesite included in garnet (py0.96gr0.02alm0.02) during the HP stage was partially transformed to quartz during the subsequent, rapid exhumation (from 3.5 to 1 GPa within 2 Ma [4]). Coesite is preserved by maintaining a high pressure on the inclusion wall due to the large volume change of the phase transition. The surface of the host garnet experiences a lower pressure controlled by the exhumation P-T path. This pressure difference should induce diffusion of major elements in the garnet surrounding the inclusion. Element distribution maps show well-defined Fe-rich, Ca-poor halos surrounding the coesite-inclusions. The observed diffusion profiles are in agreement with predictions, assuming a positive ΔP around the inclusions. The results are based on thermodynamic equilibrium calculations assuming heterogeneous pressure [5]. Hence, the observed profiles are interpreted as an equilibrium state reflecting the pressure (stress) distribution within the crystal and can be used as tool to constrain the exhumation path. Understanding the effect of pressure gradients on diffusion and, alternatively, the generation of pressure due to relaxation of chemical gradients by diffusion, is crucial for interpreting P-T-t paths of zoned minerals correctly. [1] Baumgartner et al. (2010), GSA meeting Denver. [2] Tajčmanová et al. (2014) CMP 32, 195-207. [3] Compagnoni & Rolfo (2003), UHP Metamorphism - EMU notes 5

  16. Wave-induced response of poro-elastic offshore foundations

    SciTech Connect

    Toha, F.X.

    1983-01-01

    A plane strain analysis based on Biot's theory of consolidation is utilized to investigate the pore-water pressures and displacements induced by steady-state linear planar waves beneath offshore gravity structures placed on poro-elastic seabed of finite thickness. The response is characterized by three controlling parameters, i.e., poroelasticity factor, fluid compressibility factor, and Poisson's Ratio. A parametric study, using a range of the controlling parameters encountered in practice, indicates that the response is governed primarily by the poro-elasticity factor and to a lesser extent by Poisson's Ratio (fluid compressibility factor has negligible influence for saturated soils). For offshore gravity structures, the wave-induced moment and horizontal force exerted by the structure on the foundation contribute most to the overall response while the influence of sea water pressure penetration through the sea bottom is, in general, negligible. For smaller structures, however, the latter influence dominates the response for soils as fine as silty sand. The maximum shear strain amplitudes evaluated imply that the soil response remains primarily in the linear elastic range, even for severe storm loadings. An experimental procedure was developed for the measurement of a composite poro-elastic property which combines all the pertinent soil properties. Two test configurations were found to be suitable depending on the hydraulic conductivity of the soil considered. The results of test on nine specimens reconstituted from three soil samples conform with the theoretical estimates and indicate that the developed procedure is viable.

  17. Model of a small surface wave discharge at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Ivanov, A.; Kiss'ovski, Zh

    2016-05-01

    Self-consistent model of a small microwave plasma source based on a surface wave sustained discharge at 2.45 GHz is presented in this study. The model includes dispersion relation of azimuthally symmetric surface waves, sustaining the discharge in a high permittivity ceramic tube (εd = 9.3) and the radial distribution of the field components at curtain values of the electron density are obtained. The electron Boltzmann equation under the local approximation is solved together with the heavy particle balance equations. A detailed collisional-radiative model for argon discharge at atmospheric pressure is implemented in the model. The changes in the EEDF shape and the mean electron energy with the value of the electron density are investigated. Results show that the EEDF is close to Maxwellian at our experimental conditions for the plasma density above 2.1020 (m-3).

  18. Wave Acceleration Induced Sediment Transport in the Surf Zone

    NASA Astrophysics Data System (ADS)

    Hoefel, F.; Elgar, S.

    2002-12-01

    A bedload sediment transport formulation (Drake and Calantoni, 2001) that accounts for the effects of near-bottom wave-orbital velocity acceleration skewness predicts onshore sandbar migration observed near Duck, NC. Including acceleration effects in an energetics sediment transport model results in improved skill in reproducing cross-shore sandbar migration patterns observed over a 40 day period during which the bar moved both offshore in storms and onshore between storms. These results suggest that skewed acceleration time series, associated with the pitched forward shapes of nearly breaking and broken waves, play an important role in wave-induced sediment transport in the surf zone. The passage of steep wave fronts results in spikes in acceleration when orbital velocities are directed onshore, producing strong horizontal pressure gradient forces that act on the sediment. In contrast to velocity skewness, which remains approximately constant across the surf zone, acceleration skewness is observed to increase from small values offshore to a maximum near the bar crest, and then to decrease toward the shoreline, producing cross-shore spatial gradients in acceleration-driven transport that are consistent with erosion offshore and accretion onshore of the bar crest. As the sandbar migrates shoreward, the maximum of acceleration skewness also moves onshore, causing a positive feedback mechanism that promotes continued onshore sediment transport motion provided the forcing remains constant. Funded by ARO, ONR, and NOPP.

  19. Spectroscopy During Laser Induced Shock Wave Lithotripsy

    NASA Astrophysics Data System (ADS)

    Engelhardt, R.; Meyer, W.; Hering, P.

    1988-06-01

    In the course of laser induced shock wave lithotripsy (LISL) by means of a flashlamp pumped dye laser a plasma is formed on the stone's surface. Spectral analysis of the plasma flash leads to chemical stone analysis during the procedure. A time resolved integral analysis of scattered and laser induced fluorescence light makes stone detection possible and avoids tissue damage. We used a 200 μm fiber to transmit a 2 μs, 50 mJ pulse to the stone's surface and a second 200 μ fiber for analysis. This transmission system is small and flexible enough for controlled endoscopic use in the treatment of human ureter or common bile duct stones. Under these conditions the stone selective effect of lasertripsy leads only to minor tissue injury.

  20. Estimating explosive performance from laser-induced shock waves

    NASA Astrophysics Data System (ADS)

    Gottfried, Jennifer

    2015-06-01

    A laboratory-scale method for predicting explosive performance (e.g., detonation velocity and pressure) based on milligram quantities of material is currently being developed. This technique is based on schlieren imaging of the shock wave generated in air by the formation of a laser-induced plasma on the surface of an energetic material. A large suite of pure and composite conventional energetic materials has been tested. Based on the observed linear correlation between the laser-induced shock velocity and the measured performance from full-scale detonation testing, this method is a potential screening tool for the development of new energetic materials and formulations prior to detonation testing. Recent results on the extension of this method to metal-containing energetic materials will be presented.

  1. Tunnel pressure waves - A smartphone inquiry on rail travel

    NASA Astrophysics Data System (ADS)

    Müller, Andreas; Hirth, Michael; Kuhn, Jochen

    2016-02-01

    When traveling by rail, you might have experienced the following phenomenon: The train enters a tunnel, and after some seconds a noticeable pressure change occurs, as perceived by your ears or even by a rapid wobbling of the train windows. The basic physics is that pressure waves created by the train travel down the tunnel, are reflected at its other end, and travel back until they meet the train again. Here we will show (i) how this effect can be well understood as a kind of large-scale outdoor case of a textbook paradigm, and (ii) how, e.g., a prediction of the tunnel length from the inside of a moving train on the basis of this model can be validated by means of a mobile phone measurement.

  2. Pressure-induced Polymerization in Substituted Acetylenes

    NASA Astrophysics Data System (ADS)

    Chellappa, Raja; Dattelbaum, Dana; Sheffield, Stephen; Robbins, David

    2011-06-01

    A fundamental understanding of shock-induced chemical reactions in organics is still lacking and there are limited studies devoted to determining reaction mechanisms, evolution of bonding, and effect of functional group substitutions. The fast timescale of reactions occurring during shock compression create significant experimental challenges (diagnostics) to fully quantify the mechanisms involved. Static compression provides a complementary route to investigate the equilibrium phase space and metastable intermediates during high pressure chemistry, although at a much slower timescale. In this study, we present our results from our ongoing high pressure in situ synchrotron x-ray diffraction and vibrational spectroscopy experiments on substituted acetylenes: tert-butyl acetylene [TBA: (CH3)3 -C ≡CH] and ethynyl trimethylsilane [ETMS: (CH3)3 -Si ≡CH]. We observed that the onset pressure of chemical reactions (at room temperature) in these compounds is significantly higher in static compression (TBA: 11 GPa and ETMS: 26 GPa) when compared to shock input pressures (TBA: 6.1 GPa and ETMS: 6.6 GPa). The products were polymeric in nature, recovered to ambient conditions with little degradation and fully characterized using spectroscopy, calorimetry, and other techniques to identify reaction mechanisms. LDRD-DR (PI: Dana Dattelbaum)

  3. On the Generation of Multiple Atmospheric Pressure Waves Observed During Violent Volcanic Eruptions.

    NASA Astrophysics Data System (ADS)

    Medici, E. F.; Waite, G. P.

    2015-12-01

    One or more atmospheric pressure waves followed by a supersonic jet may be generated during the over pressurized vapor-solid-liquid mixture ejection of a violent volcanic eruption. The source of these multiple atmospheric pressure waves could have different origins. Among the physical mechanisms that could explain these behaviors are pulsating eruptions, the dynamics of shock waves, coupled pressure wave-supersonic jet interaction, or a combination of all these factors. In order to elucidate the causes of these complex fluid flow dynamics, a series of analog volcanic eruption experiments using an atmospheric shock tube were performed. During the testing, single and multiple pressure waves and the subsequent supersonic jet were generated. The controlled laboratory conditions enable studies of the most relevant variables potentially responsible for the formation of the multiple pressure waves. The tests were performed using dry, compressed nitrogen at standard room temperature that was free of particles. Yet, under this idealization of a real volcanic eruption, multiple pressure waves were observed on the high-speed video imaging and recorded on the pressure transducer. The amount of energy being released on each test was varied to achieve different discharge dynamics and the formation of single and multiple pressure waves. The preliminary experimental observations indicate a coupled pressure wave-jet interaction as source of multiple pressure waves.

  4. Pressure-Induced Foaming of Metals

    NASA Astrophysics Data System (ADS)

    García-Moreno, Francisco; Mukherjee, Manas; Jiménez, Catalina; Banhart, John

    2015-05-01

    Pressure-induced foaming (PIF) of metals is a foaming technique in which blowing agent free compacted metal powders are foamed. The method consists of heating hot-compacted metallic precursors to above their melting temperature under gas overpressure and foaming them by pressure release. This study focuses on PIF of Al99.7 and AlSi7 alloys under both air or Ar and overpressures up to 9 bar. In situ x-ray radioscopy allows us to follow the foaming process and to perform quantitative analyses of expansion, foam morphology, and coalescence rate. Mass spectrometry helps to identify hydrogen as the foaming gas. Adsorbates on the former powder particles are found to be the primary gas source. Various advantages of this new method are identified and discussed.

  5. Pressure-induced metal-insulator transition in spinel compound CuV 2S 4

    NASA Astrophysics Data System (ADS)

    Okada, H.; Koyama, K.; Hedo, M.; Uwatoko, Y.; Watanabe, K.

    2008-04-01

    In order to investigate the pressure effect on electrical properties of CuV 2S 4, we performed the electrical resistivity measurements under high pressures up to 8 GPa for a high-quality polycrystalline sample. The charge density wave (CDW) transition temperatures increase with increasing pressure. The residual resistivity rapidly increases with increasing pressure over 4 GPa, and the temperature dependence of the electrical resistivity at 8 GPa exhibits a semiconducting behavior below about 150 K, indicating that a pressure-induced metal-insulator transition occurs in CuV 2S 4 at 8 GPa.

  6. Internal wave pressure, velocity, and energy flux from density perturbations

    NASA Astrophysics Data System (ADS)

    Allshouse, Michael R.; Lee, Frank M.; Morrison, Philip J.; Swinney, Harry L.

    2016-05-01

    Determination of energy transport is crucial for understanding the energy budget and fluid circulation in density varying fluids such as the ocean and the atmosphere. However, it is rarely possible to determine the energy flux field J =p u , which requires simultaneous measurements of the pressure and velocity perturbation fields p and u , respectively. We present a method for obtaining the instantaneous J (x ,z ,t ) from density perturbations alone: A Green's function-based calculation yields p ; u is obtained by integrating the continuity equation and the incompressibility condition. We validate our method with results from Navier-Stokes simulations: The Green's function method is applied to the density perturbation field from the simulations and the result for J is found to agree typically to within 1% with J computed directly using p and u from the Navier-Stokes simulation. We also apply the Green's function method to density perturbation data from laboratory schlieren measurements of internal waves in a stratified fluid and the result for J agrees to within 6 % with results from Navier-Stokes simulations. Our method for determining the instantaneous velocity, pressure, and energy flux fields applies to any system described by a linear approximation of the density perturbation field, e.g., to small-amplitude lee waves and propagating vertical modes. The method can be applied using our matlab graphical user interface EnergyFlux.

  7. Wave-induced dynamics of flexible blades

    NASA Astrophysics Data System (ADS)

    Luhar, M.; Nepf, H. M.

    2016-02-01

    We present an experimental and numerical study that describes the motion of flexible blades, scaled to be dynamically similar to natural aquatic vegetation, forced by wave-induced oscillatory flows. For the conditions tested, blade motion is governed primarily by two dimensionless variables: (i) the Cauchy number, $Ca$, which represents the ratio of the hydrodynamic forcing to the restoring force due to blade stiffness, and (ii) the ratio of the blade length to the wave orbital excursion, $L$. For flexible blades with $Ca \\gg 1$, the relationship between drag and velocity can be described by two different scaling laws at the large- and small-excursion limits. For large excursions ($L \\ll 1$), the flow resembles a unidirectional current and the scaling laws developed for steady-flow reconfiguration studies hold. For small excursions ($L \\gg 1$), the beam equations may be linearized and a different scaling law for drag applies. The experimental force measurements suggest that the small-excursion scaling applies even for intermediate cases with $L \\sim O(1)$. The numerical model employs the well-known Morison force formulation, and adequately reproduces the observed blade dynamics and measured hydrodynamic forces without the use of any fitted parameters. For $Ca \\gg 1$, the movement of the flexible blades reduces the measured and modeled hydrodynamic drag relative to a rigid blade of the same morphology. However, in some cases with $Ca \\sim O(1)$, the measured hydrodynamic forces generated by the flexible blades exceed those generated by rigid blades, but this is not reproduced in the model. Observations of blade motion suggest that this unusual behavior is related to an unsteady vortex shedding event, which the simple numerical model cannot reproduce. Finally, we also discuss implications for the modeling of wave energy dissipation over canopies of natural aquatic vegetation.

  8. Optical Estimation of Depth Induced Wave Breaking Distributions over Complex Bathymetry

    NASA Astrophysics Data System (ADS)

    Keen, A. S.; Holman, R. A.

    2012-12-01

    Parametric depth-induced-breaking dissipation models have shown great skill at predicting time averaged wave heights across the surf zone. First proposed by Battjes & Janssen (1978), these models balance the incoming wave energy flux with a roller dissipation term. This roller dissipation term is estimated by calculating the dissipation for one characteristic broken wave and then multiplying this quantity by the fraction of broken waves. To describe the fraction of broken waves, a typical assumption asserts that wave heights are nearly Rayleigh distributed [Thornton & Guza (1983)] allowing a sea state to be described by only a few parameters. While many experiments have validated the cross shore wave height profiles, few field experiments have been performed to analyze the probability distribution of breaking wave heights over a barred beach profile. The goal of the present research is to determine the distribution of broken and unbroken wave heights across a natural barred beach profile. Field data collected during the Surf Zone Optics experiment (a Multi-disciplinary University Research Initiative) in Duck, North Carolina, consisted of an array of in-situ pressure sensors and optical remote sensing cameras. Sea surface elevation time series from the in-situ pressure sensors are used here to resolve wave height distributions at multiple locations across the surf zone. Breaking wave height distributions are resolved based upon a combination of the pressure sensor and optically based breaker detection algorithm. Since breaking is easily able to be tracked by video imaging, breaking waves are flagged in the sea surface elevation series and binned into a broken wave height distribution. Results of this analysis are compared with model predictions based upon the Battjes & Janssen (1978), Thornton & Guza (1983) and Janssen & Battjes (2007) models to assess the validity of each wave height distribution model.

  9. A Boussinesq-scaled, pressure-Poisson water wave model

    NASA Astrophysics Data System (ADS)

    Donahue, Aaron S.; Zhang, Yao; Kennedy, Andrew B.; Westerink, Joannes J.; Panda, Nishant; Dawson, Clint

    2015-02-01

    Through the use of Boussinesq scaling we develop and test a model for resolving non-hydrostatic pressure profiles in nonlinear wave systems over varying bathymetry. A Green-Nagdhi type polynomial expansion is used to resolve the pressure profile along the vertical axis, this is then inserted into the pressure-Poisson equation, retaining terms up to a prescribed order and solved using a weighted residual approach. The model shows rapid convergence properties with increasing order of polynomial expansion which can be greatly improved through the application of asymptotic rearrangement. Models of Boussinesq scaling of the fully nonlinear O (μ2) and weakly nonlinear O (μN) are presented, the analytical and numerical properties of O (μ2) and O (μ4) models are discussed. Optimal basis functions in the Green-Nagdhi expansion are determined through manipulation of the free-parameters which arise due to the Boussinesq scaling. The optimal O (μ2) model has dispersion accuracy equivalent to a Padé [2,2] approximation with one extra free-parameter. The optimal O (μ4) model obtains dispersion accuracy equivalent to a Padé [4,4] approximation with two free-parameters which can be used to optimize shoaling or nonlinear properties. In comparison to experimental results the O (μ4) model shows excellent agreement to experimental data.

  10. Effect of the initial pressure of multicomponent bubble media on the characteristics of detonation waves

    NASA Astrophysics Data System (ADS)

    Sychev, A. I.

    2016-05-01

    The effect of the initial pressure of multicomponent bubble media on the conditions of initiation, the structure, the velocity, and the pressure of detonation waves is experimentally studied. The variation of the initial pressure of a bubble medium is found to be an effective method to control the parameters of bubble detonation waves.

  11. Optimizing OBS data using shielding and by removing ocean wave loading noise with Pressure and Horizontal Pressure Gradient Sensor Data

    NASA Astrophysics Data System (ADS)

    Webb, Spahr C.; Barclay, Andrew H.

    2016-04-01

    Ocean bottom seismometer (OBS) data, particularly from sites in shallow water are notoriously noisy. Ocean currents generate forces on an unshielded OBS sensor causing time varying tilt that greatly raises noise levels. Shallow burial can mitigate this source of noise, but is expensive and difficult to accomplish, particularly for large fleets of instruments. Large shields can provide significant reduction in noise levels as demonstrated with Cascadia Array OBS data. A recent test deployment investigated the relative motion of the shield and the sensor within the shield, providing guidance on the effectiveness of shielding. Even with shielding or burial, deformation of the seafloor caused by loading by the ocean waves raises seismic noise levels. We have previously shown the vertical component noise can be reduced using data from pressure sensors to predict the vertical deformation and remove it from the vertical record. We recently deployed a new OBS instrument in shallow water (80m) that measured two horizontal components of pressure gradient and show these data can be used to reduce wave induced deformation noise from horizontal component seismic data.

  12. Producing ion waves from acoustic pressure waves in pulsed ICP: Modeling vs. Experiments

    NASA Astrophysics Data System (ADS)

    Despiau-Pujo, Emilie; Cunge, Gilles; Darnon, Maxime; Sadeghi, Nader; Braithwaite, Nicholas

    2015-09-01

    Neutral depletion is an important phenomenon in CW high-density plasmas, mostly caused by gas heating - with a small contribution due to electron pressure Pe - under typical material processing conditions. In pulsed ICP, neutral depletion plays an important role on radical transport in the afterglow. At the beginning of the afterglow, Pe drops rapidly (10 μs) by electron cooling and the gas cools down as well. It generates a neutral pressure gradient between the plasma bulk and the reactor walls, which in turn forces the cold surrounding gas to move rapidly towards the center, thus launching an acoustic wave in the reactor. Fast gas displacement is evidenced by measuring Al atoms drift velocity in the early afterglow of a Cl2/Ar discharge by time-resolved LIF, the acoustic wave in the chamber being observed by mass spectrometry. 2D fluid simulations of Cl2 pulsed ICP predict similar results. These phenomena are further studied during both the plasma ignition and afterglow using modeling and experiments. Strong oscillations are observed both on the Cl2 neutral densities and on the ion flux. As neutrals are pushed towards (or outwards) the chamber walls by the pressure gradient, ions are also pushed in that direction through collisions, as well captured by our ion flux probe.

  13. Influence of flow and pressure on wave propagation in the canine aorta.

    NASA Technical Reports Server (NTRS)

    Histand, M. B.; Anliker, M.

    1973-01-01

    Data on wave speed acquired from 20 anesthetized dogs showed that the thoracic aorta was essentially nondispersive for small artificially generated pressure waves traveling in the downstream or the upstream direction and having frequencies between 40 and 120 Hz. The amplitude of these waves decayed exponentially with the distance traveled. Theoretical studies are cited which have shown that changes in wave speed due to variations in pressure and flow produce marked nonlinear effects in hemodynamics.

  14. Mass Spectrometry of Atmospheric Pressure Surface Wave Discharges

    NASA Astrophysics Data System (ADS)

    Ridenti, M. A.; Souza-Corrêa, J. A.; Amorim, J.

    2016-05-01

    By applying mass spectrometry techniques, we carried out measurements of ionic mass spectrum and their energy distribution in order to investigate an atmospheric argon discharge by using a surfatron surface-wave device. The mass and energy distribution measurements were performed with fixed flow rate (2.5 SLM) of pure argon gas (99.999%) and different Ar-O2 gas mixture compositions (99-1, 98-2 and 97-3). The mass spectra and energy distributions were recorded for Ar+, O+, O+ 2, N+ and N2 +. The axial distribution profiles of ionic mass and their energy were obtained for different experimental conditions as a function of the plasma length. The results showed that the peak of the positive ion energy distributions shifted to higher energies and also that the distribution width increased as the distance between the sampling orifice and the launcher gap was increased. It was also found that under certain experimental conditions the ion flux of atomic species were higher than the ion flux of their diatomic counterpart. The motivation of this study was to obtain a better understanding of a surface wave discharge in atmospheric pressure that may play a key role on new second generation biofuel technologies.

  15. Cavitation inception by the backscattering of pressure waves from a bubble interface

    SciTech Connect

    Takahira, Hiroyuki Ogasawara, Toshiyuki Mori, Naoto Tanaka, Moe

    2015-10-28

    The secondary cavitation that occurs by the backscattering of focused ultrasound from a primary cavitation bubble caused by the negative pressure part of the ultrasound (Maxwell, et al., 2011) might be useful for the energy exchange due to bubble oscillations in High Intensity Focused Ultrasound (HIFU). The present study is concerned with the cavitation inception by the backscattering of ultrasound from a bubble. In the present experiment, a laser-induced bubble which is generated by a pulsed focused laser beam with high intensity is utilized as a primary cavitation bubble. After generating the bubble, focused ultrasound is emitted to the bubble. The acoustic field and the bubble motion are observed with a high-speed video camera. It is confirmed that the secondary cavitation bubble clouds are generated by the backscattering from the laser-induced bubble. The growth of cavitation bubble clouds is analyzed with the image processing method. The experimental results show that the height and width of the bubble clouds grow in stepwise during their evolution. The direct numerical simulations are also conducted for the backscattering of incident pressure waves from a bubble in order to evaluate a pressure field near the bubble. It is shown that the ratio of a bubble collapse time t{sub 0} to a characteristic time of wave propagation t{sub S}, η = t{sub 0}/t{sub s}, is an important determinant for generating negative pressure region by backscattering. The minimum pressure location by the backscattering in simulations is in good agreement with the experiment.

  16. Frequency and wavelength prediction of ultrasonic induced liquid surface waves.

    PubMed

    Mahravan, Ehsan; Naderan, Hamid; Damangir, Ebrahim

    2016-12-01

    A theoretical investigation of parametric excitation of liquid free surface by a high frequency sound wave is preformed, using potential flow theory. Pressure and velocity distributions, resembling the sound wave, are applied to the free surface of the liquid. It is found that for impinging wave two distinct capillary frequencies will be excited: One of them is the same as the frequency of the sound wave, and the other is equal to the natural frequency corresponding to a wavenumber equal to the horizontal wavenumber of the sound wave. When the wave propagates in vertical direction, mathematical formulation leads to an equation, which has resonance frequency equal to half of the excitation frequency. This can explain an important contradiction between the frequency and the wavelength of capillary waves in the two cases of normal and inclined interaction of the sound wave and the free surface of the liquid. PMID:27566141

  17. Statistical properties of wave groups described by group-induced long waves

    NASA Astrophysics Data System (ADS)

    Lin, Weiqi; Huang, Peiji

    1992-03-01

    A new method using group-induced second-order long waves (GSLW) to describe wave groups is presented in this paper on the basis of the GSLW theory by Longuet-Higgins and Steward (1964). In the method, the parabolic relationship between GSLW and the wave envelope is first deduced, and then the distribution function of GSLW amplitude is derived. Thus, the formulae in terms of the moments of GSLW and short wave spectra for the average time duration and the mean length of runs of wave heights exceeding a certain level can be derived. A new groupiness factor equivalent to half the mean wave number in wave groups is defined by taking into account the widths of spectra of GSLW and short waves. Compared with theoretical results of others, ours are closer to measured wave data.

  18. Experimental particle acceleration by water evaporation induced by shock waves

    NASA Astrophysics Data System (ADS)

    Scolamacchia, T.; Alatorre Ibarguengoitia, M.; Scheu, B.; Dingwell, D. B.; Cimarelli, C.

    2010-12-01

    Shock waves are commonly generated during volcanic eruptions. They induce sudden changes in pressure and temperature causing phase changes. Nevertheless, their effects on flowfield properties are not well understood. Here we investigate the role of gas expansion generated by shock wave propagation in the acceleration of ash particles. We used a shock tube facility consisting of a high-pressure (HP) steel autoclave (450 mm long, 28 mm in internal diameter), pressurized with Ar gas, and a low-pressure tank at atmospheric conditions (LP). A copper diaphragm separated the HP autoclave from a 180 mm tube (PVC or acrylic glass) at ambient P, with the same internal diameter of the HP reservoir. Around the tube, a 30 cm-high acrylic glass cylinder, with the same section of the LP tank (40 cm), allowed the observation of the processes occurring downstream from the nozzle throat, and was large enough to act as an unconfined volume in which the initial diffracting shock and gas jet expand. All experiments were performed at Pres/Pamb ratios of 150:1. Two ambient conditions were used: dry air and air saturated with steam. Carbon fibers and glass spheres in a size range between 150 and 210 μm, were placed on a metal wire at the exit of the PVC tube. The sudden decompression of the Ar gas, due to the failure of the diaphragm, generated an initial air shock wave. A high-speed camera recorded the processes between the first 100 μsec and several ms after the diaphragm failure at frame rates ranging between 30,000 and 50,000 fps. In the experiments with ambient air saturated with steam, the high-speed camera allowed to visualize the condensation front associated with the initial air shock; a maximum velocity of 788 m/s was recorded, which decreases to 524 m/s at distance of 0.5 ±0.2 cm, 1.1 ms after the diaphragm rupture. The condensation front preceded the Ar jet front exhausting from the reservoir, by 0.2-0.5 ms. In all experiments particles velocities following the initial

  19. A thoracic mechanism of mild traumatic brain injury due to blast pressure waves.

    PubMed

    Courtney, A C; Courtney, M W

    2009-01-01

    The mechanisms by which blast pressure waves cause mild-to-moderate traumatic brain injury (mTBI) are an open question. Possibilities include acceleration of the head, direct passage of the blast wave via the cranium, and propagation of the blast wave to the brain via a thoracic mechanism. The hypothesis that the blast pressure wave reaches the brain via a thoracic mechanism is considered in light of ballistic and blast pressure wave research. Ballistic pressure waves, caused by penetrating ballistic projectiles or ballistic impacts to body armor, can only reach the brain via an internal mechanism and have been shown to cause cerebral effects. Similar effects have been documented when a blast pressure wave has been applied to the whole body or focused on the thorax in animal models. While vagotomy reduces apnea and bradycardia due to ballistic or blast pressure waves, it does not eliminate neural damage in the brain, suggesting that the pressure wave directly affects the brain cells via a thoracic mechanism. An experiment is proposed which isolates the thoracic mechanism from cranial mechanisms of mTBI due to blast wave exposure. Results have implications for evaluating risk of mTBI due to blast exposure and for developing effective protection. PMID:18829180

  20. Effects of Blood Pressure and Sex on the Change of Wave Reflection: Evidence from Gaussian Fitting Method for Radial Artery Pressure Waveform

    PubMed Central

    Liu, Chengyu; Zhao, Lina; Liu, Changchun

    2014-01-01

    An early return of the reflected component in the arterial pulse has been recognized as an important indicator of cardiovascular risk. This study aimed to determine the effects of blood pressure and sex factor on the change of wave reflection using Gaussian fitting method. One hundred and ninety subjects were enrolled. They were classified into four blood pressure categories based on the systolic blood pressures (i.e., ≤110, 111–120, 121–130 and ≥131 mmHg). Each blood pressure category was also stratified for sex factor. Electrocardiogram (ECG) and radial artery pressure waveforms (RAPW) signals were recorded for each subject. Ten consecutive pulse episodes from the RAPW signal were extracted and normalized. Each normalized pulse episode was fitted by three Gaussian functions. Both the peak position and peak height of the first and second Gaussian functions, as well as the peak position interval and peak height ratio, were used as the evaluation indices of wave reflection. Two-way ANOVA results showed that with the increased blood pressure, the peak position of the second Gaussian significantly shorten (P<0.01), the peak height of the first Gaussian significantly decreased (P<0.01) and the peak height of the second Gaussian significantly increased (P<0.01), inducing the significantly decreased peak position interval and significantly increased peak height ratio (both P<0.01). Sex factor had no significant effect on all evaluation indices (all P>0.05). Moreover, the interaction between sex and blood pressure factors also had no significant effect on all evaluation indices (all P>0.05). These results showed that blood pressure has significant effect on the change of wave reflection when using the recently developed Gaussian fitting method, whereas sex has no significant effect. The results also suggested that the Gaussian fitting method could be used as a new approach for assessing the arterial wave reflection. PMID:25384042

  1. Autapse-induced target wave, spiral wave in regular network of neurons

    NASA Astrophysics Data System (ADS)

    Qin, HuiXin; Ma, Jun; Wang, ChunNi; Chu, RunTong

    2014-10-01

    Autapse is a type of synapse that connects axon and dendrites of the same neuron, and the effect is often detected by close-loop feedback in axonal action potentials to the owned dendritic tree. An artificial autapse was introduced into the Hindmarsh-Rose neuron model, and a regular network was designed to detect the regular pattern formation induced by autapse. It was found that target wave emerged in the network even when only a single autapse was considered. By increasing the (autapse density) number of neurons with autapse, for example, a regular area (2×2, 3×3, 4×4, 5×5 neurons) under autapse induced target wave by selecting the feedback gain and time-delay in autapse. Spiral waves were also observed under optimized feedback gain and time delay in autapses because of coherence-like resonance in the network induced by some electric autapses connected to some neurons. This confirmed that the electric autapse has a critical role in exciting and regulating the collective behaviors of neurons by generating stable regular waves (target waves, spiral waves) in the network. The wave length of the induced travelling wave (target wave, spiral wave), because of local effect of autapse, was also calculated to understand the waveprofile in the network of neurons.

  2. Visualization of ultrasonically induced shear wave propagation using phase sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Nguyen, Thu-Mai; Song, Shaozhen; Arnal, Bastien; Wong, Emily Y.; Wang, Ruikang K.; O'Donnell, Matthew

    2014-02-01

    Shear wave elastography measures the stiffness of soft tissues from the speed of propagating shear waves induced in tissue. Optical coherence tomography (OCT) is a promising detection modality given its high sensitivity and spatial resolution, making it suitable for elastic characterization of skin, peripheral vasculature or ocular tissues. For clinical applications, it would be valuable to use a non-contact shear source. Thus, we propose acoustic radiation force as a remote shear source combined with OCT for visualization. A single-element focused transducer (central frequency 7.5 MHz) was used to apply a maximal pressure of ~3 MPa for 100 μs in agar phantoms. It induced shear waves with an amplitude of several hundreds of nanometers and a broadband spectrum in the kilohertz range. Phasesensitive OCT was used to track shear waves at an equivalent frame rate of 47 kHz. We reconstructed shear modulus maps in a heterogeneous phantom. In addition, we use 3-ms long coded excitation to increase the displacement signal-to-noise ratio. We applied digital pulse compression to the resulting displacement field to obtain a gain of ~15 dB compared to standard pulse excitation while maintaining the US pressure level and the shear wave spatial and temporal resolution. This is a promising result for shear wave generation at low US pressures (~ 1 MPa).

  3. Wave energy and wave-induced flow reduction by full-scale model Posidonia oceanica seagrass

    NASA Astrophysics Data System (ADS)

    Manca, E.; Cáceres, I.; Alsina, J. M.; Stratigaki, V.; Townend, I.; Amos, C. L.

    2012-12-01

    This paper presents results from experiments in a large flume on wave and flow attenuation by a full-scale artificial Posidonia oceanica seagrass meadow in shallow water. Wave height and in-canopy wave-induced flows were reduced by the meadow under all tested regular and irregular wave conditions, and were affected by seagrass density, submergence and distance from the leading edge. The energy of irregular waves was reduced at all components of the spectra, but reduction was greater at the peak spectral frequency. Energy dissipation factors were largest for waves with small orbital amplitudes and at low wave Reynolds numbers. An empirical model, commonly applied to predict friction factors by rough beds, proved applicable to the P. oceanica bed. However at the lowest Reynolds numbers, under irregular waves, the data deviated significantly from the model. In addition, the wave-induced flow dissipation in the lower canopy increased with increasing wave orbital amplitude and increasing density of the mimics. The analysis of the wave-induced flow spectra confirm this trend: the reduction of flow was greatest at the longer period component of the spectra. Finally, we discuss the implications of these findings for sediment dynamics and the role of P. oceanica beds in protecting the shore from erosion.

  4. Earthquake Induced Water Waves in Washington State

    NASA Astrophysics Data System (ADS)

    Barberopoulou, A.; Qamar, A.; Pratt, T. L.

    2003-12-01

    The Mw 7.9 Denali earthquake of 3 November 2002 caused minor damage to at least 20 houseboats by initiating water waves in Lake Union, Seattle, Washington. Damage caused by unusual water activity is not uncommon in Washington State. Newspaper reports show that damage also has been caused by water waves in the Seattle area during local or distant earthquakes in 1899 (Yakutat Bay Alaska earthquake), 1949 (Olympia earthquake) and 1965 (Seattle-Tacoma earthquake). Analysis of Pacific Northwest Seismic Network (PNSN) recordings of the Denali earthquake demonstrates that large water waves are due in part to local amplification of seismic waves by the underlying Seattle sedimentary basin. Simple formulae predict water wave amplitudes only half or smaller than those reported for swimming pools and lakes. Resonance initiated by multiple cycles of surface waves, focusing, and near-shore effects could further amplify the water waves. To understand the type and origins of these water waves, we are examining the response of a water body of rectangular shape and rectangular cross-section subjected to hypothetical forcing functions, and to forcing functions derived from seismograph records of major earthquakes. The results provide estimates of the potential wave heights during future large earthquakes on the nearby subduction zone or on local faults.

  5. Mechanism of membrane poration by shock wave induced nanobubble collapse: a molecular dynamics study.

    PubMed

    Adhikari, Upendra; Goliaei, Ardeshir; Berkowitz, Max L

    2015-05-21

    We performed coarse-grained molecular dynamics simulations in order to understand the mechanism of membrane poration by shock wave induced nanobubble collapse. Pressure profiles obtained from the simulations show that the shock wave initially hits the membrane and is followed by a nanojet produced by the nanobubble collapse. While in the absence of the nanobubble, the shock wave with an impulse of up to 18 mPa s does not create a pore in the membrane, in the presence of a nanobubble even a smaller impulse leads to the poration of the membrane. Two-dimensional pressure maps depicting the pressure distributed over the lateral area of the membrane reveal the differences between these two cases. In the absence of a nanobubble, shock pressure is evenly distributed along the lateral area of the membrane, while in the presence of a nanobubble an unequal distribution of pressure on the membrane is created, leading to the membrane poration. The size of the pore formed depends on both shock wave velocity and shock wave duration. The results obtained here show that these two properties can be tuned to make pores of various sizes. PMID:25903048

  6. Investigations of High Pressure Acoustic Waves in Resonators with Seal-Like Features

    NASA Technical Reports Server (NTRS)

    Daniels, Christopher C.; Steinetz, Bruce M.; Finkbeiner, Joshua R.; Li, Xiao-Fan; Raman, Ganesh

    2004-01-01

    1) Standing waves with maximum pressures of 188 kPa have been produced in resonators containing ambient pressure air; 2) Addition of structures inside the resonator shifts the fundamental frequency and decreases the amplitude of the generated pressure waves; 3) Addition of holes to the resonator does reduce the magnitude of the acoustic waves produced, but their addition does not prohibit the generation of large magnitude non-linear standing waves; 4) The feasibility of reducing leakage using non-linear acoustics has been confirmed.

  7. An application of Love SH waves for the viscosity measurement of triglycerides at high pressures

    NASA Astrophysics Data System (ADS)

    Rostocki, A. J.; Siegoczyński, R. M.; Kiełczyński, P.; Szalewski, M.

    2010-03-01

    A new ultrasonic method of viscosity measurements at a high-pressure conditions has been presented. The method is based on the Love wave amplitude measurement. The same electronic setup as in the Bleustein-Gulyaev (B-G) wave method applied by the authors recently for a high-pressure measurement was adopted. The new sensors were made of metallic materials, which make them more reliable at high-pressure conditions. The method has been successfully applied for the viscosity measurement of some triglycerides at high-pressure conditions up to 1 GPa. The results have been compared with the earlier results obtained using B-G waves. This comparison has shown that Love wave method sensors are more reliable than B-G wave sensors and are also cheaper in fabrication, although the sensitivity of Love wave sensors is lower. During the measurement, the phase transitions in the investigated liquids were observed.

  8. a Low Cost Pressure Wave Generator Using Diaphragms

    NASA Astrophysics Data System (ADS)

    Caughley, A. J.; Haywood, D. J.; Wang, C.

    2008-03-01

    The high cost of Pressure Wave Generators (PWGs) is a major barrier to the more widespread use of high-efficiency pulse tube and Stirling cryocoolers. This paper describes the development and testing of a low-cost industrial-style PWG which employs metal diaphragms. The use of diaphragms removes the need for rubbing or clearance seals, and eliminates contamination problems by hermetically separating the gas circuit and the lubricated driving mechanism. A conventional low-cost electric motor is used for power input, via a novel high-efficiency kinematic linkage. A first prototype of the diaphragm PWG produced 3.2 kW of PV power with a measured electro-acoustic efficiency of 72%. Accelerated testing predicts a diaphragm life time in excess of 40,000 hours. An additional advantage of the use of diaphragms is the ability to directly cool the gas in the compression space. This eliminates or significantly reduces the requirement for an after cooler, and further decreases the cost of the whole cryocooler system. A pulse tube cryocooler has been successfully run at Industrial Research Ltd to 59K with the diaphragm PWG and no aftercooler. Another pulse tube cryocooler with the diaphragm PWG is undergoing development at Cryomech, the results of which will be given in another presentation.

  9. Laser induced plane acoustic wave generation, propagation, and interaction with rigid structures in water

    NASA Astrophysics Data System (ADS)

    Ko, Seung H.; Ryu, Sang G.; Misra, Nipun; Pan, Heng; Grigoropoulos, Costas P.; Kladias, Nick; Panides, Elias; Domoto, Gerald A.

    2008-10-01

    Short pulsed laser induced single acoustic wave generation, propagation, interaction with rigid structures, and focusing in water are experimentally and numerically studied. A large area short duration single plane acoustic wave was generated by the thermoelastic interaction of a homogenized nanosecond pulsed laser beam with a liquid-solid interface and propagated at the speed of sound in water. Laser flash schlieren photography was used to visualize the transient interaction of the plane acoustic wave with various submerged rigid structures [(a) a single block, (b) double blocks, (c) 33° tilted single block, and (d) concave cylindrical acoustic lens configurations]. Excellent agreement between the experimental results and numerical simulation is observed. Our simulation results demonstrate that the laser induced planar acoustic wave can be focused down to several tens of micron size and several bars in pressure.

  10. Nonlinear upper hybrid waves and the induced density irregularities

    SciTech Connect

    Kuo, Spencer P.

    2015-08-15

    Upper hybrid waves are excited parametrically by the O-mode high-frequency heater waves in the ionospheric heating experiments. These waves grow to large amplitudes and self-induced density perturbations provide nonlinear feedback. The lower hybrid resonance modifies the nonlinear feedback driven by the ponderomotive force; the nonlinear equation governing the envelope of the upper hybrid waves is derived. Solutions in symmetric alternating functions, in non-alternating periodic functions, as well as in solitary functions are shown. The impact of lower hybrid resonance on the envelope of the upper hybrid waves is explored; the results show that both the spatial period and amplitude are enlarged. The average fluctuation level of induced density irregularities is also enhanced. In the soliton form, the induced density cavity is widened considerably.

  11. Predicting S-wave velocities for unconsolidated sediments at low effective pressure

    USGS Publications Warehouse

    Lee, Myung W.

    2010-01-01

    Accurate S-wave velocities for shallow sediments are important in performing a reliable elastic inversion for gas hydrate-bearing sediments and in evaluating velocity models for predicting S-wave velocities, but few S-wave velocities are measured at low effective pressure. Predicting S-wave velocities by using conventional methods based on the Biot-Gassmann theory appears to be inaccurate for laboratory-measured velocities at effective pressures less than about 4-5 megapascals (MPa). Measured laboratory and well log velocities show two distinct trends for S-wave velocities with respect to P-wave velocity: one for the S-wave velocity less than about 0.6 kilometer per second (km/s) which approximately corresponds to effective pressure of about 4-5 MPa, and the other for S-wave velocities greater than 0.6 km/s. To accurately predict S-wave velocities at low effective pressure less than about 4-5 MPa, a pressure-dependent parameter that relates the consolidation parameter to shear modulus of the sediments at low effective pressure is proposed. The proposed method in predicting S-wave velocity at low effective pressure worked well for velocities of water-saturated sands measured in the laboratory. However, this method underestimates the well-log S-wave velocities measured in the Gulf of Mexico, whereas the conventional method performs well for the well log velocities. The P-wave velocity dispersion due to fluid in the pore spaces, which is more pronounced at high frequency with low effective pressures less than about 4 MPa, is probably a cause for this discrepancy.

  12. Defect induced guided waves mode conversion

    NASA Astrophysics Data System (ADS)

    Wandowski, Tomasz; Kudela, Pawel; Malinowski, Pawel; Ostachowicz, Wieslaw

    2016-04-01

    This paper deals with analysis of guided waves mode conversion phenomenon in fiber reinforced composite materials. Mode conversion phenomenon may take place when propagating elastic guided waves interact with discontinuities in the composite waveguide. The examples of such discontinuities are sudden thickness change or delamination between layers in composite material. In this paper, analysis of mode conversion phenomenon is based on full wave-field signals. In the full wave-field approach signals representing propagation of elastic waves are gathered from dense mesh of points that span over investigated area of composite part. This allow to animate the guided wave propagation. The reported analysis is based on signals resulting from numerical calculations and experimental measurements. In both cases defect in the form of delamination is considered. In the case of numerical research, Spectral Element Method (SEM) is utilized, in which a mesh is composed of 3D elements. Numerical model includes also piezoelectric transducer. Full wave-field experimental measurements are conducted by using piezoelectric transducer for guided wave excitation and Scanning Laser Doppler Vibrometer (SLDV) for sensing.

  13. The Pressure in a Deep-Water Stokes Wave of Greatest Height

    NASA Astrophysics Data System (ADS)

    Lyons, Tony

    2016-02-01

    In this paper we investigate the qualitative behaviour of the pressure function beneath an extreme Stokes wave over infinite depth. The presence of a stagnation point at the wave-crest of an extreme Stokes wave introduces a number of mathematical difficulties resulting in the irregularity of the free surface profile. It will be proven that the pressure decreases in the horizontal direction between a crest-line and subsequent trough-line, except along these lines themselves where the pressure is stationary with respect to the horizontal coordinate. In addition we will prove that the pressure strictly increases with depth throughout the fluid body.

  14. The Pressure in a Deep-Water Stokes Wave of Greatest Height

    NASA Astrophysics Data System (ADS)

    Lyons, Tony

    2016-06-01

    In this paper we investigate the qualitative behaviour of the pressure function beneath an extreme Stokes wave over infinite depth. The presence of a stagnation point at the wave-crest of an extreme Stokes wave introduces a number of mathematical difficulties resulting in the irregularity of the free surface profile. It will be proven that the pressure decreases in the horizontal direction between a crest-line and subsequent trough-line, except along these lines themselves where the pressure is stationary with respect to the horizontal coordinate. In addition we will prove that the pressure strictly increases with depth throughout the fluid body.

  15. Biological effect of shock waves on rat brain: pathological evaluation by compact Ho:YAG-laser-induced cavitational shock wave generator

    NASA Astrophysics Data System (ADS)

    Nakagawa, Atsuhiro; Hirano, T.; Kusaka, Y.; Sato, Motoyuki; Shirane, R.; Takayama, Kazuya; Yoshimoto, Takashi

    2003-07-01

    To introduce shock wave as a new treatment modality for the lesions in the vicinity of brain and skull, pressure-dependent brain damages after exposure of shock wave were investigated. A novel compact Ho:YAG laser-induced cavitational shock wave generator (diameter: 15 mm, weight: 20g) was used intstead of clinical lithotriptors due to their wide distribution of shock waves. In the first part, we have developed and investigated characteristics of present generator by means of high-speed photography, shadowgraphy, and pressure measurement. Generation of localized shock wave without harmful effect of laser was observed after irradiation of Ho:YAG laser in the brass tube with internal water supply. Mechanical effect of accompanying laser-induced liquid jet was mitigated after placement of latex diaphragm with acrylic water reservoir. Maximum overpressure of generated shock wave was 15 MPa before placement of diaphragm, and 5 MPa after placement of diaphragm. In the second part, shock wave-induced brain damages were investigated in 5 male Sprague-Dawley rats. While subarachnoid hemorrhage could be observed between 1 and 5 MPa, intracerebral hemorrhage, and laceration of tissue were also observed above 5 MPa. We therefore conclude that overpressure of exposing shock wave over brain surface should be managed under 1 MPa.

  16. Trichoscopy of Noncicatricial Pressure-induced Alopecia Resembling Alopecia Areata

    PubMed Central

    Papaiordanou, Francine; da Silveira, Bruno Rebelo Lages; Piñeiro-Maceira, Juan; Pirmez, Rodrigo

    2016-01-01

    Pressure-induced alopecia is an unusual cause of hair loss, and reports of its trichoscopic features are scarce. In this paper, we describe a case of pressure-induced alopecia in which trichoscopic and histopathological findings overlap with those described for alopecia areata. PMID:27601865

  17. Trichoscopy of Noncicatricial Pressure-induced Alopecia Resembling Alopecia Areata.

    PubMed

    Papaiordanou, Francine; da Silveira, Bruno Rebelo Lages; Piñeiro-Maceira, Juan; Pirmez, Rodrigo

    2016-01-01

    Pressure-induced alopecia is an unusual cause of hair loss, and reports of its trichoscopic features are scarce. In this paper, we describe a case of pressure-induced alopecia in which trichoscopic and histopathological findings overlap with those described for alopecia areata. PMID:27601865

  18. Influence of the initial pressure in bubble media on the detonation wave parameters

    NASA Astrophysics Data System (ADS)

    Sychev, A. I.

    2015-04-01

    The influence of the initial pressure in bubble media on the initiation, structure, velocity, and pressure of detonation waves in single-component bubble media is studied. The test medium (bubbles of a stoichiometric acetylene-oxygen mixture in a hydroglyceric solution) falls under the category of "chemically inactive liquid—bubbles of a chemically active gas." It is found that one can effectively control the parameters of bubble detonation waves by varying the initial pressure in the bubble medium.

  19. Practical and highly sensitive elemental analysis for aqueous samples containing metal impurities employing electrodeposition on indium-tin oxide film samples and laser-induced shock wave plasma in low-pressure helium gas.

    PubMed

    Kurniawan, Koo Hendrik; Pardede, Marincan; Hedwig, Rinda; Abdulmadjid, Syahrun Nur; Lahna, Kurnia; Idris, Nasrullah; Jobiliong, Eric; Suyanto, Hery; Suliyanti, Maria Margaretha; Tjia, May On; Lie, Tjung Jie; Lie, Zener Sukra; Kurniawan, Davy Putra; Kagawa, Kiichiro

    2015-09-01

    We have conducted an experimental study exploring the possible application of laser-induced breakdown spectroscopy (LIBS) for practical and highly sensitive detection of metal impurities in water. The spectrochemical measurements were carried out by means of a 355 nm Nd-YAG laser within N2 and He gas at atmospheric pressures as high as 2 kPa. The aqueous samples were prepared as thin films deposited on indium-tin oxide (ITO) glass by an electrolysis process. The resulting emission spectra suggest that concentrations at parts per billion levels may be achieved for a variety of metal impurities, and it is hence potentially feasible for rapid inspection of water quality in the semiconductor and pharmaceutical industries, as well as for cooling water inspection for possible leakage of radioactivity in nuclear power plants. In view of its relative simplicity, this LIBS equipment offers a practical and less costly alternative to the standard use of inductively coupled plasma-mass spectrometry (ICP-MS) for water samples, and its further potential for in situ and mobile applications. PMID:26368882

  20. Pressure-induced disproportionation in CuBr

    NASA Astrophysics Data System (ADS)

    Skelton, E. F.; Webb, A. W.; Qadri, S. B.; Ingalls, R. G.; Traquada, J. M.

    1983-04-01

    CuBr has been pressurized to 8.3 GPa in four separate runs. Prima facie evidence of pressure-induced disproportionation of cuprous bromide into cupric bromide has been observed on release of pressure from 7 GPa. Evidence is also seen of a phase change in CuBr2 above 5.5 GPa.

  1. Relationship between orientation to a blast and pressure wave propagation inside the rat brain.

    PubMed

    Chavko, Mikulas; Watanabe, Tomas; Adeeb, Saleena; Lankasky, Jason; Ahlers, Stephen T; McCarron, Richard M

    2011-01-30

    Exposure to a blast wave generated during an explosion may result in brain damage and related neurological impairments. Several mechanisms by which the primary blast wave can damage the brain have been proposed, including: (1) a direct effect of the shock wave on the brain causing tissue damage by skull flexure and propagation of stress and shear forces; and (2) an indirect transfer of kinetic energy from the blast, through large blood vessels and cerebrospinal fluid (CSF), to the central nervous system. To address a basic question related to the mechanisms of blast brain injury, pressure was measured inside the brains of rats exposed to a low level of blast (~35kPa), while positioned in three different orientations with respect to the primary blast wave; head facing blast, right side exposed to blast and head facing away from blast. Data show different patterns and durations of the pressure traces inside the brain, depending on the rat orientation to blast. Frontal exposures (head facing blast) resulted in pressure traces of higher amplitude and longer duration, suggesting direct transmission and reflection of the pressure inside the brain (dynamic pressure transfer). The pattern of the pressure wave inside the brain in the head facing away from blast exposures assumes contribution of the static pressure, similar to hydrodynamic pressure to the pressure wave inside the brain. PMID:21129403

  2. Head-on collision of shock wave induced vortices with solid and perforated walls

    NASA Astrophysics Data System (ADS)

    Kontis, K.; An, R.; Zare-Behtash, H.; Kounadis, D.

    2008-01-01

    An experimental study has been conducted to examine the interaction of shock wave induced vortices with a flat plate and a perforated plate. The experiments were carried out using a 30mm internal diameter shock-tube at Mach numbers 1.31, 1.49, and 1.61 under critical driver conditions. Air was used both in the driver and driven sections. High-speed schlieren photography was employed to study the flow development and the resulting interactions with the plates. Wall pressure measurements on both plates were also carried out in order to study the flow interactions quantitatively. The experimental results indicated that a region of strong flow development is generated near the wall surface, due to the flow interactions of reflected waves and oncoming induced vortices. This flow behavior causes the generation of multiple pressure fluctuations on the wall. In the case of the perforated plate, a weaker initial reflected wave is produced, which is followed by compression waves, due to the internal reflections within the plate. The transmitted wave is reduced in strength, compared to the initial incident shock wave.

  3. A Non-Intrusive Pressure Sensor by Detecting Multiple Longitudinal Waves.

    PubMed

    Zhou, Hongliang; Lin, Weibin; Ge, Xiaocheng; Zhou, Jian

    2016-01-01

    Pressure vessels are widely used in industrial fields, and some of them are safety-critical components in the system-for example, those which contain flammable or explosive material. Therefore, the pressure of these vessels becomes one of the critical measurements for operational management. In the paper, we introduce a new approach to the design of non-intrusive pressure sensors, based on ultrasonic waves. The model of this sensor is built based upon the travel-time change of the critically refracted longitudinal wave (LCR wave) and the reflected longitudinal waves with the pressure. To evaluate the model, experiments are carried out to compare the proposed model with other existing models. The results show that the proposed model can improve the accuracy compared to models based on a single wave. PMID:27527183

  4. Rogue wave formation under the action of quasi-stationary pressure

    NASA Astrophysics Data System (ADS)

    Abrashkin, A. A.; Oshmarina, O. E.

    2016-05-01

    The process of rogue wave formation on deep water is considered. A wave of extreme amplitude is born against the background of uniform waves (Gerstner waves) under the action of external pressure on free surface. The pressure distribution has a form of a quasi-stationary "pit". The fluid motion is supposed to be a vortex one and is described by an exact solution of equations of 2D hydrodynamics for an ideal fluid in Lagrangian coordinates. Liquid particles are moving around circumferences of different radii in the absence of drift flow. Values of amplitude and wave steepness optimal for rogue wave formation are found numerically. The influence of vorticity distribution and pressure drop on parameters of the fluid is investigated.

  5. Propagation of pore pressure diffusion waves in saturated dual-porosity media (II)

    NASA Astrophysics Data System (ADS)

    Yang, Duoxing; Li, Qi; Zhang, Lianzhong

    2016-04-01

    A mechanism has been established for pressure diffusion waves in dual-porosity media. Pressure diffusion waves are heavily damped with relatively low velocities and short wavelengths. The characteristic frequency dominates the attenuation behavior of pressure diffusions and separates wave fields into two asymptotic regimes: relaxed and unrelaxed. Characteristic delay times control the pressure diffusion between the matrix and the fractures. The transition zones in wavelength and attenuation peak shift toward high frequencies when the characteristic delay time decreases. In contrast, the transition zones in both phase and group velocity shift toward low frequencies as the characteristic time of the delay increases. In a spatially dependent diffusivity field, the pressure diffusion waves in dual-porosity media obey an accumulation-depletion law.

  6. Biological effects of laser-induced stress waves

    SciTech Connect

    Doukas, A.; Lee, S.; McAuliffe, D.

    1995-12-31

    Laser-induced stress waves can be generated by one of the following mechanisms: Optical breakdown, ablation or rapid heating of an absorbing medium. These three modes of laser interaction with matter allow the investigation of cellular and tissue responses to stress waves with different characteristics and under different conditions. The most widely studied phenomena are those of the collateral damage seen in photodisruption in the eye and in 193 run ablation of cornea and skin. On the other hand, the therapeutic application of laser-induced stress waves has been limited to the disruption of noncellular material such as renal stones, atheromatous plaque and vitreous strands. The effects of stress waves to cells and tissues can be quite disparate. Stress waves can fracture tissue, damage cells, and increase the permeability of the plasma membrane. The viability of cell cultures exposed to stress waves increases with the peak stress and the number of pulses applied. The rise time of the stress wave also influences the degree of cell injury. In fact, cell viability, as measured by thymidine incorporation, correlates better with the stress gradient than peak stress. Recent studies have also established that stress waves induce a transient increase of the permeability of the plasma membrane in vitro. In addition, if the stress gradient is below the damage threshhold, the cells remain viable. Thus, stress waves can be useful as a means of drug delivery, increasing the intracellular drug concentration and allowing the use of drugs which are impermeable to the cell membrane. The present studies show that it is important to create controllable stress waves. The wavelength tunability and the micropulse structure of the free electron laser is ideal for generating stress waves with independently adjustable parameters, such as rise time, duration and peak stress.

  7. Quench-induced correlation waves, and quantum grenades

    NASA Astrophysics Data System (ADS)

    Corson, John; Bohn, John

    2016-05-01

    We investigate the wave packet dynamics of a pair of particles that undergoes a rapid change of scattering length. Such quenches have recently become experimentally feasible with fast magnetic-field ramps and optical switching in the vicinity of a Feshbach resonance. The short-range interactions are modelled in the zero-range limit, where the quench is accomplished by switching the boundary condition of the wave function at vanishing particle separation. This generates a correlation wave that propagates rapidly to nonzero particle separations. We have derived universal, analytic results for this process that lead to a simple phase-space picture of quench-induced scattering. Intuitively, the strength of the correlation wave relates to the initial contact of the system. A natural consequence is that the waves are significant when the quench dissociates, at least partially, a bound state. These waves can propagate with high energy from one lattice site to another, potentially triggering highly non-equilibrium dynamics.

  8. Wave-induced extreme water levels in the Puerto Morelos fringing reef lagoon

    NASA Astrophysics Data System (ADS)

    Torres-Freyermuth, A.; Mariño-Tapia, I.; Coronado, C.; Salles, P.; Medellín, G.; Pedrozo-Acuña, A.; Silva, R.; Candela, J.; Iglesias-Prieto, R.

    2012-12-01

    Wave-induced extreme water levels in the Puerto Morelos fringing reef lagoon are investigated by means of a phase-resolving non-hydrostatic wave model (SWASH). This model solves the nonlinear shallow water equations including non-hydrostatic pressure. The one-dimensional version of the model is implemented in order to investigate wave transformation in fringing reefs. Firstly, the numerical model is validated with (i) laboratory experiments conducted on a physical model (Demirbilek et al., 2007)and (ii) field observations (Coronado et al., 2007). Numerical results show good agreement with both experimental and field data. The comparison against the physical model results, for energetic wave conditions, indicates that high- and low-frequency wave transformation is well reproduced. Moreover, extreme water-level conditions measured during the passage of Hurricane Ivan in Puerto Morelos are also estimated by the numerical tool. Subsequently, the model is implemented at different along-reef locations in Puerto Morelos. Extreme water levels, wave-induced setup, and infragravity wave energy are estimated inside the reef lagoon for different storm wave conditions (Hs >2 m). The numerical results revealed a strong correlation between the offshore sea-swell wave energy and the setup. In contrast, infragravity waves are shown to be the result of a more complex pattern which heavily relies on the reef geometry. Indeed, the southern end of the reef lagoon provides evidence of resonance excitation, suggesting that the reef barrier may act as either a natural flood protection morphological feature, or as an inundation hazard enhancer depending on the incident wave conditions.

  9. Particle transport induced by electrostatic wave fluctuations

    NASA Astrophysics Data System (ADS)

    Rosalem, K. C.; Roberto, M.; Caldas, I. L.

    2015-10-01

    Particle transport driven by electrostatic waves at the plasma edge is numerically investigated, for large aspect ratio tokamaks, by considering a kinetic model derived from guiding-center equations of motion. Initially, the transport is estimated for trajectories obtained from differential equations for a wave spectrum generated by a dominant spatial mode and three time modes. Then, in case of infinite time modes, the differential equations of motion are used to introduce a symplectic map that allows to analyze the particle transport. The particle transport barriers are observed for spatial localized dominant perturbation and infinite modes. In presence of infinite spatial modes, periodic islands arise in between chaotic trajectories at the plasma edge.

  10. On pressure-shear plate impact for studying the kinetics of stress-induced phase transformations

    NASA Astrophysics Data System (ADS)

    Escobar, Joanne C.; Clifton, Rodney J.

    1992-07-01

    Pressure-shear plate impact experiments are proposed for studying the kinetics of stress-induced phase transformations. The purpose of this paper is to determine loading conditions and specimen orientations which can be expected to activate a single habit plane variant parallel to the impact plane, thereby simplifying the study of the kinetics of the transformation through monitoring the wave profiles associated with the propagating phase boundary. The Wechsler Lieberman-Read phenomenological theory was used to determine habit plane indices and directions of shape deformation for a Cu-Al-Ni shape memory alloy which undergoes a martensitic phase transformation under stress. Elastic waves generated by pressure-shear impact were analyzed for wave propagation in the direction of the normal to a habit plane. A critical resolved shear stress criterion was used to predict variants which are expected to be activated for a range of impact velocities and relative magnitudes of the normal and transverse components of the impact velocity.

  11. Impact induced solitary wave propagation through a woodpile structure

    NASA Astrophysics Data System (ADS)

    Kore, R.; Waychal, A.; Agarwal, S.; Yadav, P.; Uddin, Ahsan; Sahoo, N.; Shelke, A.

    2016-02-01

    In this paper, we investigate solitary wave propagation through a one-dimensional woodpile structure excited by low and high velocity impact. Woodpile structures are a sub-class of granular metamaterial, which supports propagation of nonlinear waves. Hertz contact law governs the behavior of the solitary wave propagation through the granular media. Towards an experimental study, a woodpile structure was fabricated by orthogonally stacking cylindrical rods. A shock tube facility has been developed to launch an impactor on the woodpile structure at a velocity of 30 m s-1. Embedded granular chain sensors were fabricated to study the behavior of the solitary wave. The impact induced stress wave is studied to investigate solitary wave parameters, i.e. contact force, contact time, and solitary wave velocity. With the aid of the experimental setup, numerical simulations, and a theoretical solution based on the long wavelength approximation, formation of the solitary wave in the woodpile structure is validated to a reasonable degree of accuracy. The nondispersive and compact supported solitary waves traveling at sonic wave velocity offer unique properties that could be leveraged for application in nondestructive testing and structural health monitoring.

  12. Pressure-induced referred pain is expanded by persistent soreness.

    PubMed

    Doménech-García, V; Palsson, T S; Herrero, P; Graven-Nielsen, T

    2016-05-01

    Several chronic pain conditions are accompanied with enlarged referred pain areas. This study investigated a novel method for assessing referred pain. In 20 healthy subjects, pressure pain thresholds (PPTs) were recorded and pressure stimuli (120% PPT) were applied bilaterally for 5 and 60 seconds at the infraspinatus muscle to induce local and referred pain. Moreover, PPTs were measured bilaterally at the shoulder, neck, and leg before, during, and after hypertonic saline-induced referred pain in the dominant infraspinatus muscle. The pressure and saline-induced pain areas were assessed on drawings. Subsequently, delayed onset muscle soreness was induced using eccentric exercise of the dominant infraspinatus muscle. The day-1 assessments were repeated the following day (day 2). Suprathreshold pressure stimulations and saline injections into the infraspinatus muscle caused referred pain to the frontal aspect of the shoulder/arm in all subjects. The 60-second pressure stimulation caused larger referred pain areas compared with the 5-second stimulation (P < 0.01). Compared with pressure stimulation, the saline-induced referred pain area was larger (P < 0.02). After saline-induced pain, the PPTs at the infraspinatus and supraspinatus muscles were reduced (P < 0.05), and the 5-second pressure-induced referred pain area was larger than baseline. Pressure pain thresholds at the infraspinatus and supraspinatus muscles were reduced at day 2 in the delayed onset muscle soreness side (P < 0.05). Compared with day 1, larger pressure and saline-induced referred pain areas were observed on day 2 (P < 0.05). Referred pain to the shoulder/arm was consistently induced and enlarged after 1 day of muscle soreness, indicating that the referred pain area may be a sensitive biomarker for sensitization of the pain system. PMID:26808146

  13. The pressure-induced calcium deposition on crosslinked polyurethanes.

    PubMed

    Shunmugakumar, N; Jayabalan, M

    1992-06-01

    The pressure-induced calcium deposition in crosslinked polyurethane was studied. Two polyurethane systems, IPDI-PTMG/PPG-TMP and SMDI-PTMG/PPG-TMP were subjected to calcification under induced pressure. Calcium deposition in IPDI polymers was linear with the increase of soft segment (PTMG) content whereas in SMDI polymers the reverse trend was observed. Decreased phase mixing and hydrophilicity in the polymer (SMDI based) having increased soft segment content was attributed to the decreased calcification. The enhanced amount of calcium deposition under pressure indicates the possible influence of pressure on calcification. PMID:10078255

  14. Pressure induced swelling in microporous materials

    DOEpatents

    Vogt, Thomas; Hriljac, Joseph A.; Lee, Yongjae

    2006-07-11

    A method for capturing specified materials which includes contacting a microporous material with a hydrostatic fluid having at least one specified material carried therein, under pressure which structurally distorts the lattice sufficiently to permit entry of the at least one specified material. The microporous material is capable of undergoing a temporary structural distortion which alters resting lattice dimensions under increased ambient pressure and at least partially returning to rest lattice dimensions when returned to ambient pressure. The pressure of the fluid is then reduced to permit return to at least partial resting lattice dimension while the at least one specified material is therein. By this method, at least one specified material is captured in the microporous material to form a modified microporous material.

  15. Using Clifford Algebra to Understand the Nature of Negative Pressure Waves

    NASA Astrophysics Data System (ADS)

    McClellan, Gene

    2014-03-01

    The geometric algebra of 3-D Euclidean space, a sub-discipline of Clifford algebra, is a useful tool for analyzing wave propagation. We use geometric algebra to explore the concept of negative pressure. In free space a straightforward extension of Maxwell's equations using geometric algebra yields a theory in which classical electromagnetic waves coexist with nonelectromagnetic waves having retrograde momentum. By retrograde momentum we mean waves carrying momentum pointing in the opposite direction of energy flow. If such waves exist, they would have negative pressure. In rebounding from a wall, they would pull rather than push. In this presentation we use standard methods of analyzing energy and momentum conservation and their flow through the surface of an enclosed volume to illustrate the properties of both the electromagnetic and nonelectromagnetic solutions of the extended Maxwell equations. The nonelectromagnetic waves consist of coupled scalar and electric waves and coupled magnetic and pseudoscalar waves. They superimpose linearly with electromagnetic waves. We show that the nonelectromagnetic waves, besides having negative pressure, propagate with the speed of light and do not interact with conserved electric currents. Hence, they have three properties in common with dark energy.

  16. Elastic wave velocities of a MORB at pressures of the mantle transition region

    NASA Astrophysics Data System (ADS)

    Kono, Y.; Higo, Y.; Ohfuji, H.; Ohnishi, I.; Inoue, T.; Irifune, T.

    2006-12-01

    Ultrasonic P- and S-wave velocities of synthetic basalt at around 18 GPa and 1100 °C with MORB composition were measured up to 16 GPa under room temperature conditions. The basalt was synthesized in advance from MORB glass, and was found to consist of well-sintered, microcrystalline garnet and stishovite. Ultrasonic measurement was carried out in a multi-anvil apparatus. Details of the experimental procedures were described in Higo et al. (2006). Pressures were estimated from the load-pressure calibration using ZnTe pressure standard. The result showed a significant increase in both P- and S-wave velocities with increasing pressure, while the pressure dependence of P-wave velocity was larger than that of S-wave velocity. The pressure derivatives of P- and S-wave velocities are 0.07 and 0.02 (km/s)/GPa, respectively. Bulk (K) and shear (G) moduli and their pressure derivatives were calculated directly from the experimentally determined P- and S-wave velocities. The calculated K0 and G0 values were 174 and 104 GPa, respectively. The pressure derivatives of K (4.8) and G (1.5) of the basalt are markedly higher than those of major mineral constituents of mantle transition zone, that is, wadsleyite (4.2 and 1.5, respectively) (Li et al., 2001), ringwoodite (Fo91) (4.3 and 1.2, respectively) and majorite with pyrolite minus olivine composition (4.3 and 1.1, respectively) (Higo et al., unpublished data), for example. Stronger pressure dependence of P- and S-wave velocities is indicated in basaltic composition, as compared with those in pyrolitic or peridotitic compositions under the P-T conditions of the mantle transition zone. Combined ultrasonic and in situ X-ray measurements under high pressure and high temperature conditions for the present MORB composition are also currently being pursued at SPring-8.

  17. Transition from 1D to 2D Laser-Induced Ultrasonic Wave Propagation in an Extended Plate

    NASA Astrophysics Data System (ADS)

    Laloš, Jernej; Požar, Tomaž; Možina, Janez

    2016-05-01

    Optodynamic interaction between a laser pulse and the surface of an opaque, solid elastic object produces transient waves that propagate and reverberate within the object. They can be, in general, categorized into three distinctive types which are all formed through different mechanisms: ablation-induced waves, light-pressure-induced waves, and thermoelastic waves. In this paper, out-of-plane displacements of such waves are simulated at the epicentral position on the opposite side of an extended plane-parallel elastic plate. Wave propagation is mathematically described by Green's transfer functions convolved with suitable time profiles of the incoming laser pulses. The simulated size of the circularly symmetric laser-illuminated area on the plate surface is varied to show the limit-to-limit transition of the displacement waveforms: from a 2D point source to an infinite 1D source.

  18. Xe/+/ -induced ion-cyclotron harmonic waves

    NASA Astrophysics Data System (ADS)

    Jones, D.

    Xenon ion sources on an ejectable package separated from the main payload during the flights of Porcupine rockets F3 and F4 which were launched from Kiruna, Sweden on March 19 and 31, 1979, respectively. The effects of the xenon ion beam, detected by the LF (f less than 16 kHz) wideband electric field experiment and analyzed by using a sonograph, are discussed. Particular attention is given to the stimulation of the ion-cyclotron harmonic waves which are usually linked to the local proton gyro-frequency, but are sometimes related to half that frequency. It was found that in a plasma dominated by O(+) ions, a small amount (1-10%) of protons could cause an effect such that the O(+) cyclotron harmonic waves are set up by the hydrogen ions, the net result being the observation of harmonic emissions separated by the hydrogen ion gyro frequency.

  19. Inducing Peer Pressure to Promote Cooperation

    PubMed Central

    Mani, Ankur; Rahwan, Iyad; Pentland, Alex

    2013-01-01

    Cooperation in a large society of self-interested individuals is notoriously difficult to achieve when the externality of one individual's action is spread thin and wide on the whole society. This leads to the ‘tragedy of the commons’ in which rational action will ultimately make everyone worse-off. Traditional policies to promote cooperation involve Pigouvian taxation or subsidies that make individuals internalize the externality they incur. We introduce a new approach to achieving global cooperation by localizing externalities to one's peers in a social network, thus leveraging the power of peer-pressure to regulate behavior. The mechanism relies on a joint model of externalities and peer-pressure. Surprisingly, this mechanism can require a lower budget to operate than the Pigouvian mechanism, even when accounting for the social cost of peer pressure. Even when the available budget is very low, the social mechanisms achieve greater improvement in the outcome. PMID:23619166

  20. Inducing Peer Pressure to Promote Cooperation

    NASA Astrophysics Data System (ADS)

    Mani, Ankur; Rahwan, Iyad; Pentland, Alex

    2013-04-01

    Cooperation in a large society of self-interested individuals is notoriously difficult to achieve when the externality of one individual's action is spread thin and wide on the whole society. This leads to the `tragedy of the commons' in which rational action will ultimately make everyone worse-off. Traditional policies to promote cooperation involve Pigouvian taxation or subsidies that make individuals internalize the externality they incur. We introduce a new approach to achieving global cooperation by localizing externalities to one's peers in a social network, thus leveraging the power of peer-pressure to regulate behavior. The mechanism relies on a joint model of externalities and peer-pressure. Surprisingly, this mechanism can require a lower budget to operate than the Pigouvian mechanism, even when accounting for the social cost of peer pressure. Even when the available budget is very low, the social mechanisms achieve greater improvement in the outcome.

  1. Inducing peer pressure to promote cooperation.

    PubMed

    Mani, Ankur; Rahwan, Iyad; Pentland, Alex

    2013-01-01

    Cooperation in a large society of self-interested individuals is notoriously difficult to achieve when the externality of one individual's action is spread thin and wide on the whole society. This leads to the 'tragedy of the commons' in which rational action will ultimately make everyone worse-off. Traditional policies to promote cooperation involve Pigouvian taxation or subsidies that make individuals internalize the externality they incur. We introduce a new approach to achieving global cooperation by localizing externalities to one's peers in a social network, thus leveraging the power of peer-pressure to regulate behavior. The mechanism relies on a joint model of externalities and peer-pressure. Surprisingly, this mechanism can require a lower budget to operate than the Pigouvian mechanism, even when accounting for the social cost of peer pressure. Even when the available budget is very low, the social mechanisms achieve greater improvement in the outcome. PMID:23619166

  2. Pressure-induced polyamorphism in salty water.

    PubMed

    Bove, L E; Klotz, S; Philippe, J; Saitta, A M

    2011-03-25

    We investigated the metastable phase diagram of an ionic salt aqueous solution, LiCl:6D₂O, at high pressure and low temperature by neutron diffraction measurements and computer simulations. We show that the presence of salt triggers a stepwise transformation, under annealing at high pressure, to a new very high-density amorphous form. The transition occurs abruptly at 120 K and 2 GPa, is reversible, and is characterized by a sizeable enthalpy release. Simulations suggest that the polyamorphic transition is linked to a local structural reorganization of water molecules around the Li ions. PMID:21517327

  3. Measuring high pressure equation of state of polystyrene using laser driven shock wave

    NASA Astrophysics Data System (ADS)

    Shu, Hua; Huang, Xiuguang; Ye, Junjian; Wu, Jiang; Jia, Guo; Fang, Zhiheng; Xie, Zhiyong; Zhou, Huazhen; Fu, Sizu

    2015-11-01

    High precision polystyrene equation of state data were measured using laser-driven shock waves with pressures from 180 GPa to 700 GPa. α quartz was used as standard material, the shock wave trajectory in quartz and polystyrene was measured using the Velocity Interferometer for Any Reflector (VISAR). Instantaneous shock velocity in quartz and polystyrene was obtained when the shock wave pass the interface. This provided ~1% precision in shock velocity measurements.

  4. Theoretical calculation of plane wave speeds for alkali metals under pressure.

    NASA Technical Reports Server (NTRS)

    Eftis, J.; Macdonald, D. E.; Arkilic, G. M.

    1971-01-01

    Theoretical calculations of the variation with pressure of small amplitude plane wave speeds are performed for sodium and potassium at zero temperature. The results obtained for wave speeds associated with volume dependent second-order elastic coefficients show better agreement with experimental data than for wave speeds associated with shear dependent coefficients. This result is believed to be due to omission of the band structure correction to the strain energy density.

  5. Laser control of filament-induced shock wave in water

    NASA Astrophysics Data System (ADS)

    Potemkin, F. V.; Mareev, E. I.; Podshivalov, A. A.; Gordienko, V. M.

    2014-09-01

    We discovered that tight focusing of Cr:forsterite femtosecond laser radiation in water provides the unique opportunity of long filament generation. The filament becomes a source of numerous spherical shock waves whose radius tends to saturate with the increase of energy. These overlapping waves create a contrast cylindrical shock wave. The laser-induced shock wave parameters such as shape, amplitude and speed can be effectively controlled by varying energy and focusing geometry of the femtosecond pulse. Aberrations added to the optical scheme lead to multiple dotted plasma sources for shock wave formation, spaced along the optical axis. Increasing the laser energy launches filaments at each dot that enhance the length of the entire filament and as a result, the shock impact on the material.

  6. Ion radial transport induced by ICRF waves in tokamaks

    SciTech Connect

    Chen, L.; Vaclavik, J.; Hammett, G.W.

    1987-05-01

    The wave-induced fluxes of energetic-trapped ions during ICRF heating of tokamak plasmas are calculated using quasilinear equations. A simple single particle model of this transport mechanism is also given. Both a convective flux proportional to k/sub phi/vertical bar E/sub +/vertical bar/sup 2/ and a diffusive flux proportional to k/sub phi//sup 2/vertical bar E/sub +/vertical bar/sup 2/ are found. Here, k/sub phi/ is the toroidal wave number and E/sub +/ is the left-hand polarized wave field. The convective flux may become significant for large k/sub phi/ if the wave spectrum is asymmetric in k/sub phi/. But for the conditions of most previous experiments, these calculations indicate that radial transport driven directly by the ICRF wave is unimportant.

  7. Pacemaker interactions induce reentrant wave dynamics in engineered cardiac culture

    NASA Astrophysics Data System (ADS)

    Borek, Bartłomiej; Shajahan, T. K.; Gabriels, James; Hodge, Alex; Glass, Leon; Shrier, Alvin

    2012-09-01

    Pacemaker interactions can lead to complex wave dynamics seen in certain types of cardiac arrhythmias. We use experimental and mathematical models of pacemakers in heterogeneous excitable media to investigate how pacemaker interactions can be a mechanism for wave break and reentrant wave dynamics. Embryonic chick ventricular cells are cultured invitro so as to create a dominant central pacemaker site that entrains other pacemakers in the medium. Exposure of those cultures to a potassium channel blocker, E-4031, leads to emergence of peripheral pacemakers that compete with each other and with the central pacemaker. Waves emitted by faster pacemakers break up over the slower pacemaker to form reentrant waves. Similar dynamics are observed in a modified FitzHugh-Nagumo model of heterogeneous excitable media with two distinct sites of pacemaking. These findings elucidate a mechanism of pacemaker-induced reentry in excitable media.

  8. [Research on the Method of Blood Pressure Monitoring Based on Multiple Parameters of Pulse Wave].

    PubMed

    Miao, Changyun; Mu, Dianwei; Zhang, Cheng; Miao, Chunjiao; Li, Hongqiang

    2015-10-01

    In order to improve the accuracy of blood pressure measurement in wearable devices, this paper presents a method for detecting blood pressure based on multiple parameters of pulse wave. Based on regression analysis between blood pressure and the characteristic parameters of pulse wave, such as the pulse wave transit time (PWTT), cardiac output, coefficient of pulse wave, the average slope of the ascending branch, heart rate, etc. we established a model to calculate blood pressure. For overcoming the application deficiencies caused by measuring ECG in wearable device, such as replacing electrodes and ECG lead sets which are not convenient, we calculated the PWTT with heart sound as reference (PWTT(PCG)). We experimentally verified the detection of blood pressure based on PWTT(PCG) and based on multiple parameters of pulse wave. The experiment results showed that it was feasible to calculate the PWTT from PWTT(PCG). The mean measurement error of the systolic and diastolic blood pressure calculated by the model based on multiple parameters of pulse wave is 1.62 mm Hg and 1.12 mm Hg, increased by 57% and 53% compared to those of the model based on simple parameter. This method has more measurement accuracy. PMID:26964321

  9. Pressure pulse induced-damage in live biological samples

    NASA Astrophysics Data System (ADS)

    Bo, C.; Balzer, J.; Godfrey, S.; Francois, M.; Saffell, J. L.; Rankin, S. M.; Proud, W. G.; Brown, K. A.

    2012-08-01

    Developing a cellular and molecular understanding of the nature of traumatic and post-traumatic effects of blast on live biological samples is critical for improving clinical outcomes. To analyze the effects of blast waves upon the cellular structures and the underlying physiological and biochemical changes, we have constructed an experimental platform capable of delivering compression waves, of amplitudes relevant to blast, to cell suspensions in a contained environment. Initial characterization of the system shows that cell cultures can be subjected to high-intensity compression waves up to 15 MPa in pressure and duration of 80 ± 10μs. Studies of mouse mesenchymal stem cells subjected to two different pressure impulses were analysed by cell counting, cell viability assays and microscopic evaluation: the experiments present evidence suggestive of increased levels of damage and loss of cellular integrity compared to uncompressed cell cultures.

  10. Observable induced gravitational waves from an early matter phase

    SciTech Connect

    Alabidi, Laila; Sasaki, Misao; Kohri, Kazunori; Sendouda, Yuuiti E-mail: kohri@post.kek.jp E-mail: sendouda@cc.hirosaki-u.ac.jp

    2013-05-01

    Assuming that inflation is succeeded by a phase of matter domination, which corresponds to a low temperature of reheating T{sub r} < 10{sup 9}GeV, we evaluate the spectra of gravitational waves induced in the post-inflationary universe. We work with models of hilltop-inflation with an enhanced primordial scalar spectrum on small scales, which can potentially lead to the formation of primordial black holes. We find that a lower reheat temperature leads to the production of gravitational waves with energy densities within the ranges of both space and earth based gravitational wave detectors.

  11. Current-induced spin-wave Doppler shift.

    PubMed

    Vlaminck, Vincent; Bailleul, Matthieu

    2008-10-17

    Spin transfer appears to be a promising tool for improving spintronics devices. Experiments that quantitatively access the magnitude of the spin transfer are required for a fundamental understanding of this phenomenon. By inductively measuring spin waves propagating along a permalloy strip subjected to a large electrical current, we observed a current-induced spin wave Doppler shift that we relate to the adiabatic spin transfer torque. Because spin waves provide a well-defined system for performing spin transfer, we anticipate that they could be used as an accurate probe of spin-polarized transport in various itinerant ferromagnets. PMID:18927387

  12. Monochromatic waves induced by large-scale parametric forcing.

    PubMed

    Nepomnyashchy, A; Abarzhi, S I

    2010-03-01

    We study the formation and stability of monochromatic waves induced by large-scale modulations in the framework of the complex Ginzburg-Landau equation with parametric nonresonant forcing dependent on the spatial coordinate. In the limiting case of forcing with very large characteristic length scale, analytical solutions for the equation are found and conditions of their existence are outlined. Stability analysis indicates that the interval of existence of a monochromatic wave can contain a subinterval where the wave is stable. We discuss potential applications of the model in rheology, fluid dynamics, and optics. PMID:20365907

  13. Observations of height-dependent pressure-perturbation structure of a strong mesoscale gravity wave

    NASA Technical Reports Server (NTRS)

    Starr, David O'C.; Korb, C. L.; Schwemmer, Geary K.; Weng, Chi Y.

    1992-01-01

    Airborne observations using a downward-looking, dual-frequency, near-infrared, differential absorption lidar system provide the first measurements of the height-dependent pressure-perturbation field associated with a strong mesoscale gravity wave. A pressure-perturbation amplitude of 3.5 mb was measured within the lowest 1.6 km of the atmosphere over a 52-km flight line. Corresponding vertical displacements of 250-500 m were inferred from lidar-observed displacement of aerosol layers. Accounting for probable wave orientation, a horizontal wavelength of about 40 km was estimated. Satellite observations reveal wave structure of a comparable scale in concurrent cirrus cloud fields over an extended area. Smaller-scale waves were also observed. Local meteorological soundings are analyzed to confirm the existence of a suitable wave duct. Potential wave-generation mechanisms are examined and discussed. The large pressure-perturbation wave is attributed to rapid amplification or possible wave breaking of a gravity wave as it propagated offshore and interacted with a very stable marine boundary layer capped by a strong shear layer.

  14. Pressure-induced superconductivity in europium metal

    SciTech Connect

    Debessai, M.; Matsuoka, T.; Hamlin, J.J.; Bi, W.; Meng, Y.; Shimizu, K.; Schilling, J.S.

    2010-05-24

    Of the 52 known elemental superconductors among the 92 naturally occurring elements in the periodic table, fully 22 only become superconducting under sufficiently high pressure. In the rare-earth metals, the strong local magnetic moments originating from the 4f shell suppress superconductivity. For Eu, however, Johansson and Rosengren have suggested that sufficiently high pressures should promote one of its 4f electrons into the conduction band, changing Eu from a strongly magnetic (J=7/2) 4f{sup 7}-state into a weak Van Vleck paramagnetic (J=0) 4f{sup 6}-state, thus opening the door for superconductivity, as in Am (5f{sup 6}). We report that Eu becomes superconducting above 1.8 K for pressures exceeding 80 GPa, T{sub c} increasing linearly with pressure to 142 GPa at the rate +15 mK/GPa. Eu thus becomes the 53rd elemental superconductor in the periodic table. Synchrotron x-ray diffraction studies to 92 GPa at ambient temperature reveal four structural phase transitions.

  15. Electromagnetic cyclotron waves in the dayside subsolar outer magnetosphere generated by enhanced solar wind pressure: EMIC wave coherency

    NASA Astrophysics Data System (ADS)

    Remya, B.; Tsurutani, B. T.; Reddy, R. V.; Lakhina, G. S.; Hajra, R.

    2015-09-01

    Electromagnetic ion (proton) cyclotron (EMIC) waves and whistler mode chorus are simultaneously detected in the Earth's dayside subsolar outer magnetosphere. The observations were made near the magnetic equator 3.1°-1.5° magnetic latitude at 1300 magnetic local time from L = 9.9 to 7.0. It is hypothesized that the solar wind external pressure caused preexisting energetic 10-100 keV protons and electrons to be energized in the T⊥ component by betatron acceleration and the resultant temperature anisotropy (T⊥>T∥) formed led to the simultaneous generation of both EMIC (ion) and chorus (electron) waves. The EMIC waves had maximum wave amplitudes of ˜6 nT in a ˜60 nT ambient field B0. The observed EMIC wave amplitudes were about ˜10 times higher than the usually observed chorus amplitudes (˜0.1-0.5 nT). The EMIC waves are found to be coherent to quasi-coherent in nature. Calculations of relativistic ˜1-2 MeV electron pitch angle transport are made using the measured wave amplitudes and wave packet lengths. Wave coherency was assumed. Calculations show that in a ˜25-50 ms interaction with an EMIC wave packet, relativistic electron can be transported ˜27° in pitch. Assuming dipole magnetic field lines for a L = 9 case, the cyclotron resonant interaction is terminated ˜±20° away from the magnetic equator due to lack of resonance at higher latitudes. It is concluded that relativistic electron anomalous cyclotron resonant interactions with coherent EMIC waves near the equatorial plane is an excellent loss mechanism for these particles. It is also shown that E > 1 MeV electrons cyclotron resonating with coherent chorus is an unlikely mechanism for relativistic microbursts. Temporal structures of ˜30 keV precipitating protons will be ˜2-3 s which will be measurable at the top of the ionosphere.

  16. Engineering biphoton wave packets with an electromagnetically induced grating

    SciTech Connect

    Wen Jianming; Xiao Min; Zhai Yanhua; Du Shengwang

    2010-10-15

    We propose to shape biphoton wave packets with an electromagnetically induced grating in a four-level double-{Lambda} cold atomic system. We show that the induced hybrid grating plays an essential role in directing the new fields into different angular positions, especially for the zeroth-order diffraction. A number of interesting features appears in the shaped two-photon wave forms. For example, broadening or narrowing the spectrum would be possible in the proposed scheme even without the use of a cavity.

  17. Wave Journal Bearing. Part 2: Experimental Pressure Measurements and Fractional Frequency Whirl Threshold for Wave and Plain Journal Bearings

    NASA Technical Reports Server (NTRS)

    Walker, James F.; Dimofte, Florin; Addy, Harold E., Jr.

    1995-01-01

    A new hydrodynamic bearing concept, the wave journal bearing, is being developed because it has better stability characteristics than plain journal bearings while maintaining similar load capacity. An analysis code to predict the steady state and dynamic performance of the wave journal bearing is also part of the development. To verify numerical predictions and contrast the wave journal bearing's stability characteristics to a plain journal bearing, tests were conducted at NASA Lewis Research Center using an air bearing test rig. Bearing film pressures were measured at 16 ports located around the bearing circumference at the middle of the bearing length. The pressure measurements for both a plain journal bearing and a wave journal bearing compared favorably with numerical predictions. Both bearings were tested with no radial load to determine the speed threshold for self-excited fractional frequency whirl. The plain journal bearing started to whirl immediately upon shaft start-up. The wave journal did not incur self-excited whirl until 800 to 900 rpm as predicted by the analysis. Furthermore, the wave bearing's geometry limited the whirl orbit to less than the bearing's clearance. In contrast, the plain journal bearing did not limit the whirl orbit, causing it to rub.

  18. The Propagation of Nonlinear Pressure Waves Through Regions of Non-Uniform Temperature

    NASA Astrophysics Data System (ADS)

    Dizinno, Nicholas; Vradis, George; Otugen, Volkan

    2006-11-01

    A numerical study of wave propagation through gases with non-uniform temperature distributions will be presented. The aim of this study is to determine the impact of temperature gradients on high-intensity pressure waves of various initial wave forms. Emphasis is paid to wave reflection and transmission. Ultimately, the performance of thermal barriers in attenuating nonlinear waves is evaluated. The concept of using regions of hot gas inside an ambient environment has potential in aeroacoustic applications, such as jet screech mitigation. This analysis considers the one-dimensional compressible unsteady Euler's equations with an ideal gas state equation. The domain is composed of two regions with uniform and equal gas properties separated by a third region with higher gas temperature (lower density). Pressure is uniform throughout the domain. We introduce various high-intensity wave forms into this medium. Our investigation studies how the shape and extent of the thermal zone affect transmission and reflection of the wave. This is done for a range of wave and thermal field parameters. A Fourier analysis will study the frequency content of the incident, transmitted and reflected waves. These results will help determine the effectiveness of using thermal barriers for nonlinear wave attenuation.

  19. Bicycling induced pudendal nerve pressure neuropathy.

    PubMed

    Silbert, P L; Dunne, J W; Edis, R H; Stewart-Wynne, E G

    1991-01-01

    Pudendal neuropathies are well recognised as part of more generalised peripheral neuropathies; however, focal abnormalities of the pudendal nerve due to cycling-related injuries have been infrequently reported. We describe two patients who developed pudendal neuropathies secondary to pressure effects on the perineum from racing-bicycle saddles. Both were male competitive athletes, one of whom developed recurrent numbness of the penis and scrotum after prolonged cycling; the other developed numbness of the penis, an altered sensation of ejaculation, with disturbance of micturition and reduced awareness of defecation. Both patients improved with alterations in saddle position and riding techniques. We conclude that pudendal nerve pressure neuropathy can result from prolonged cycling, particularly when using a poor riding technique. PMID:1821826

  20. Pressure gradient induced generation of microbubbles

    NASA Astrophysics Data System (ADS)

    Evangelio, Alvaro; Campo-Cortes, Francisco; Gordillo, Jose Manuel

    2015-11-01

    It is well known that the controlled production of monodisperse bubbles possesses uncountable applications in medicine, pharmacy and industry. Here we provide with a detailed physical description of the bubble formation processes taking place in a type of flow where the liquid pressure gradient can be straightforwardly controlled. In our experiments, a gas flow rate discharges through a cylindrical needle into a pressurized chamber. The pressure gradient created from the exit of the injection needle towards the entrance of a extraction duct promotes the stretching of the gas ligament downstream. In our analysis, which is supported by an exhaustive experimental study in which the liquid viscosity is varied by three orders of magnitude, different regimes can be distinguished depending mainly on the Reynolds number. Through our physical modeling, we provide closed expressions for both the bubbling frequencies and for the bubble diameters as well as the conditions under which a monodisperse generation is obtained in all regimes found. The excellent agreement between our expressions and the experimental data fully validates our physical modeling.

  1. Ultrafast Time Response Pressure-Sensitive Paint for Unsteady Shock-Wave Research

    NASA Astrophysics Data System (ADS)

    Numata, Daiju; Asai, Keisuke

    Pressure-Sensitive Paint (PSP) is an optical pressure measurement technique widely used in aerodynamic experiments, and has been applied to unsteady shock-wave phenomena [1, 2]. However, one of the largest problems to apply PSP to high-speed and unsteady phenomena is the response time of PSP.

  2. Wave-particle interactions induced by SEPAC on Spacelab 1 Wave observations

    NASA Technical Reports Server (NTRS)

    Taylor, W. W. L.; Obayashi, T.; Kawashima, N.; Sasaki, S.; Yanagisawa, M.; Burch, J. L.; Reasoner, D. L.; Roberts, W. T.

    1985-01-01

    Space experiments with particle accelerators (SEPAC) flew on Spacelab 1 in November and December 1983. SEPAC included an accelerator which emitted electrons into the ionospheric plasma with energies up to 5 keV and currents up to 300 mA. The SEPAC equipment also included an energetic plasma generator, a neutral gas generator, and an extensive array of diagnostics. The diagnostics included plasma wave detectors, and energetic electron analyzer, a photometer, a high sensitivity television camera, a Langmuir probe and a pressure gage. Twenty-eight experiments were performed during the mission to investigate beam-plasma interactions, electron beam dynamics, plasma beam propagation, and vehicle charging. The wave-particle interactions were monitored by the plasma wave instrumentation, by the energetic electron detector and by the optical detectors. All show evidence of wave-particle interactions, which are described in this paper.

  3. Two Dimensional Finite Element Analysis for the Effect of a Pressure Wave in the Human Brain

    NASA Astrophysics Data System (ADS)

    Ponce L., Ernesto; Ponce S., Daniel

    2008-11-01

    Brain injuries in people of all ages is a serious, world-wide health problem, with consequences as varied as attention or memory deficits, difficulties in problem-solving, aggressive social behavior, and neuro degenerative diseases such as Alzheimer's and Parkinson's. Brain injuries can be the result of a direct impact, but also pressure waves and direct impulses. The aim of this work is to develop a predictive method to calculate the stress generated in the human brain by pressure waves such as high power sounds. The finite element method is used, combined with elastic wave theory. The predictions of the generated stress levels are compared with the resistance of the arterioles that pervade the brain. The problem was focused to the Chilean mining where there are some accidents happen by detonations and high sound level. There are not formal medical investigation, however these pressure waves could produce human brain damage.

  4. Atmospheric planetary waves induced by solar rotation

    NASA Technical Reports Server (NTRS)

    Krivolutsky, A. A.

    1989-01-01

    It is known that there are variations in the atmospheric processes with a period close to that of the rotation of the Sun (27 days). The variations are discovered in tropospheric processes, rainfalls, geopotential and in stratosphere. The main theoretical problem is the identification of the physical process by which these heterogeneous solar and meteorological phenomena are connected. Ivanovsky and Krivolutsky proposed that the periodic heating of the ozone layer by the short wave radiation would be the reason of excitation the 27-day oscillations. It was also assumed that excitement takes place in condition of resonance with an excited mode corresponding to the conditions present in the stratospheric circulations. The possibility is discussed of the resonant excitation and presentation is made of the data analysis results which support this idea.

  5. Amplification of Pressure Waves during Vibrational Equilibration of Excited Chemical Reaction Products

    SciTech Connect

    Tarver, C M

    2004-05-11

    The Non-Equilibrium Zeldovich - von Neumann - Doring (NEZND) theory of self-sustaining detonation identified amplification of pressure wavelets during equilibration of vibrationally excited reaction products in the reaction zone as the physical mechanism by which exothermic chemical energy release sustains detonation waves. This mechanism leads to the formation of the well-known, complex three-dimensional structure of a self-sustaining detonation wave. This amplification mechanism is postulated to be a general property of subsonic and supersonic reactive flows occurring during: shock to detonation transition (SDT); hot spot ignition and growth; deflagration to detonation transition (DDT); flame acceleration by shock or compression waves; and acoustic (sound) wave amplification. The existing experimental and theoretical evidence for pressure wave amplification by chemical energy release into highly vibrationally excited product molecules under these reactive flow conditions is reviewed in this paper.

  6. Characterization of laser-driven shock waves in solids using a fiber optic pressure probe

    SciTech Connect

    Cranch, Geoffrey A.; Lunsford, Robert; Grun, Jacob; Weaver, James; Compton, Steve; May, Mark; Kostinski, Natalie

    2013-11-08

    Measurement of laser-driven shock wave pressure in solid blocks of polymethyl methacrylate is demonstrated using fiber optic pressure probes. Three probes based on a fiber Fabry–Perot, fiber Bragg grating, and interferometric fiber tip sensor are tested and compared. Shock waves are generated using a high-power laser focused onto a thin foil target placed in close proximity to the test blocks. The fiber Fabry–Perot sensor appears capable of resolving the shock front with a rise time of 91 ns. As a result, the peak pressure is estimated, using a separate shadowgraphy measurement, to be 3.4 GPa.

  7. Barocaloric effect and the pressure induced solid state refrigerator

    SciTech Connect

    Oliveira, N. A. de

    2011-03-01

    The current refrigerators are based on the heating and cooling of fluids under external pressure variation. The great inconvenience of this refrigeration technology is the damage caused to the environment by the refrigerant fluids. In this paper, we discuss the magnetic barocaloric effect, i.e., the heating or cooling of magnetic materials under pressure variation and its application in the construction of refrigerators using solid magnetic compounds as refrigerant materials and pressure as the external agent. The discussion presented in this paper points out that such a pressure induced solid state refrigerator can be very interesting because it is not harmful to the environment and can exhibit a good performance.

  8. Slipstream-induced pressure fluctuations on a wing panel

    NASA Astrophysics Data System (ADS)

    Ljunggren, Sten; Samuelsson, Ingemar; Widig, Kurt

    1989-10-01

    Propeller-induced pressure fluctuations have been measured on a wind-tunnel model. The results show that the main contribution on the wing panels can be attributed to the propeller tip vortex, which gives a pressure level at least 20 dB above the level from the inner parts of the propeller. The pressure fluctuations are predominantly periodic and the spectrum shows strong peaks at the blade passage frequency and its harmonics. The pressure level at the blade passage frequency is approximately the same on wing panel and fuselage, while the level of the higher harmonics is substantially higher on the wing panel than on the fuselage.

  9. Pressure-induced magnetic instability in Pd-Ni alloys

    NASA Astrophysics Data System (ADS)

    Oomi, Gendo; Iwai, Sadanori; Ohashi, Masashi; Nakano, Tomohito

    2012-12-01

    The electrical resistivity ρ(T) of dilute Pd-Ni alloys has been measured at high pressure up to 3 GPa. It is found that the ρ(T) of the ferromagnetic Pd-Ni alloy shows an anomalous temperature dependence near the critical pressure Pc, where the ferromagnetism disappears. The results are analysed in the framework of quantum critical behaviour induced by pressure. The effect of magnetic field on the ρ(T) is also examined. Different behaviour of magnetoresistance against pressure was found depending on the alloy concentration and discussed in connection with an instability of ferromagnetism.

  10. Surface modification by subsurface pressure induced diffusion

    SciTech Connect

    Zimmermann, Claus G.

    2012-01-23

    Polycrystalline Ag, covered with a nm thin siloxane layer, was irradiated with ultraviolet light in vacuum at 500 K. Ag particles of different aspect ratios, 50-1000 nm in size, formed on the surface, including a small fraction of nanorods. Pressurized water vapor bubbles are created in the subsurface region by hydrogen radicals photo-chemically released by the siloxane layer. They provide the driving force for a diffusive material flux along grain boundaries to the surface. This mechanism was modeled and found to agree with the experimental timescale: approximately 300 h are required for a 1000 nm particle to form.

  11. Quantification of wave reflection in the human aorta from pressure alone: a proof of principle.

    PubMed

    Westerhof, Berend E; Guelen, Ilja; Westerhof, Nico; Karemaker, John M; Avolio, Alberto

    2006-10-01

    Wave reflections affect the proximal aortic pressure and flow waves and play a role in systolic hypertension. A measure of wave reflection, receiving much attention, is the augmentation index (AI), the ratio of the secondary rise in pressure and pulse pressure. AI can be limiting, because it depends not only on the magnitude of wave reflection but also on wave shapes and timing of incident and reflected waves. More accurate measures are obtainable after separation of pressure in its forward (P(f)) and reflected (P(b)) components. However, this calculation requires measurement of aortic flow. We explore the possibility of replacing the unknown flow by a triangular wave, with duration equal to ejection time, and peak flow at the inflection point of pressure (F(tIP)) and, for a second analysis, at 30% of ejection time (F(t30)). Wave form analysis gave forward and backward pressure waves. Reflection magnitude (RM) and reflection index (RI) were defined as RM=P(b)/P(f) and RI=P(b)/(P(f)+P(b)), respectively. Healthy subjects, including interventions such as exercise and Valsalva maneuvers, and patients with ischemic heart disease and failure were analyzed. RMs and RIs using F(tIP) and F(t30) were compared with those using measured flow (F(m)). Pressure and flow were recorded with high fidelity pressure and velocity sensors. Relations are: RM(tIP)=0.82RM(mf)+0.06 (R(2)=0.79; n=24), RM(t30)=0.79RM(mf)+0.08 (R(2)=0.85; n=29) and RI(tIP)=0.89RI(mf)+0.02 (R(2)=0.81; n=24), RI(t30)=0.83RI(mf)+0.05 (R(2)=0.88; n=29). We suggest that wave reflection can be derived from uncalibrated aortic pressure alone, even when no clear inflection point is distinguishable and AI cannot be obtained. Epidemiological studies should establish its clinical value. PMID:16940207

  12. Low-pressure sustainment of surface-wave microwave plasma with modified microwave coupler

    NASA Astrophysics Data System (ADS)

    Sasai, Kensuke; Suzuki, Haruka; Toyoda, Hirotaka

    2016-01-01

    Sustainment of long-scale surface-wave plasma (SWP) at pressures below 1 Pa is investigated for the application of the SWP as an assisting plasma source for roll-to-roll sputter deposition. A modified microwave coupler (MMC) for easier surface-wave propagation is proposed, on the basis of the concept of the power direction alignment of the slot antenna and surface-wave propagation. The superiority of the MMC-SWP over conventional SWPs is shown at a sustainment pressure as low as 0.6 Pa and an electron density as high as 3 × 1017 m-3. A polymer film is treated with the MMC-SWP at a low pressure of 0.6 Pa, and surface modification at a low pressure is proved using Ar plasma. These results show the availability of the MMC-SWP as the surface treatment plasma source that is compatible with sputter deposition in the same processing chamber.

  13. New ultrasonic Bleustein-Gulyaev wave method for measuring the viscosity of liquids at high pressure

    NASA Astrophysics Data System (ADS)

    Kiełczyński, P.; Szalewski, M.; Siegoczyński, R. M.; Rostocki, A. J.

    2008-02-01

    In this paper, a new method for measuring the viscosity of liquids at high pressure is presented. To this end the authors have applied an ultrasonic method using the Bleustein-Gulyaev (BG) surface acoustic wave. By applying the perturbation method, we can prove that the change in the complex propagation constant of the BG wave produced by the layer of liquid loading the waveguide surface is proportional to the shear mechanical impedance of the liquid. In the article, a measuring setup employing the BG wave for the purpose of measuring the viscosity of liquids at high pressure (up to 1GPa) is presented. The results of high-pressure viscosity measurements of triolein and castor oil are also presented. In this paper the model of a Newtonian liquid was applied. Using this new method it is also possible to measure the viscosity of liquids during the phase transition and during the decompression process (hysteresis of the dependence of viscosity on pressure).

  14. Inositol 1,4,5-trisphosphate induced calcium waves

    NASA Astrophysics Data System (ADS)

    Falcke, M.

    Traveling waves of high concentration of Ca2+ are observed in many different cells and have attracted great interest in experimental and theoretical biological research in recent years. They are created by the nonlinear dynamics of the release and uptake of Ca2+ by intracellular Ca2+ stores like the endoplasmatic or sarcoplasmatic reticulum. Their characteristics depend on other cellular organelles and components like mitochondria and Ca2+ buffers too. Here, we present some mathematical models and results of recent research on intracellular Ca2+ waves generated by the inositol 1,4,5-trisphosphate receptor channel including the modeling of Calcium induced Calcium release, buffer dynamics, impact of mitochondria on wave formation and the effect of the spatial discreteness of the channels releasing Ca2+. Modeling of the communication of Ca2+ waves to adjacent cells through gap junctions concludes this report.

  15. Modelling and Experimental Verification of Pressure Wave Following Gaseous Helium Storage Tank Rupture

    NASA Astrophysics Data System (ADS)

    Chorowski, M.; Grabowski, M.; Jędrusyna, A.; Wach, J.

    Helium inventory in high energy accelerators, tokamaks and free electron lasers may exceed tens of tons. The gaseous helium is stored in steel tanks under a pressure of about 20 bar and at environment temperature. Accidental rupture of any of the tanks filled with the gaseous helium will create a rapid energy release in form of physical blast. An estimation of pressure wave distribution following the tank rupture and potential consequences to the adjacent research infrastructure and buildings is a very important task, critical in the safety aspect of the whole cryogenic system. According to the present regulations the TNT equivalent approach is to be applied to evaluate the pressure wave following a potential gas storage tank rupture. A special test stand was designed and built in order to verify experimentally the blast effects in controlled conditions. In order to obtain such a shock wave a pressurized plastic tank was used. The tank was ruptured and the resulting pressure wave was recorded using a spatially-distributed array of pressure sensors connected to a high-speed data acquisition device. The results of the experiments and the comparison with theoretical values obtained from thermodynamic model of the blast are presented. A good agreement between the simulated and measured data was obtained. Recommendations regarding the applicability of thermodynamic model of physical blast versus TNT approach, to estimate consequences of gas storage tank rupture are formulated. The laboratory scale experimental results have been scaled to ITER pressurized helium storage tanks.

  16. Shock pressure induced by glass-confined laser shock peening: Experiments, modeling and simulation

    SciTech Connect

    Wu Xianqian; Song Hongwei; Wei Yanpeng; Wang Xi; Huang Chenguang; Duan Zhuping

    2011-09-01

    The shock pressure generated by the glass confined regime in laser shock peening and its attenuation in the target material are investigated. First, the particle velocity of the target back free surface induced by laser generated shock pressure of this regime is measured using a photonic Doppler velocimetry system. The temporal profile of the particle velocity at the back free surface, where the elastic precursor is captured, manifests a powerful diagnostic capability of this newly developed photonic Doppler velocimetry system for tracking the velocity on short time scales in shock-wave experiments. Second, a coupling pressure analytical model, in which the material constitutive models of confined layers and target material are considered, is proposed to predict the plasma pressure profile at the surface of target. Furthermore, using the predicted shock pressure profile as the input condition, the dynamic response of the target under the shock pressure is simulated by LS-DYNA. The simulated back free surface velocity profile agrees well with that measured by the photonic Doppler velocimetry system. Finally, the attenuation behavior of stress waves and particle velocities in the depth of the target is analyzed, and it indicates an exponential decay. The corresponding empirical formulas for the attenuation behavior are given based on the numerical results.

  17. Eliminating pulse-induced artifacts in Urethral Pressure data.

    PubMed

    Klunder, Mario; Feuer, Ronny; Amend, Bastian; Kelp, Alexandra; Stenzl, Arnulf; Sievert, Karl-Dietrich; Sawodny, Oliver; Ederer, Michael

    2015-08-01

    Urethral Pressure Profilometry (UPP) is a tool in the diagnosis of urinary incontinence. The pressure profile along the urethra is measured by a special catheter in order to assess the contraction strength of the sphincter muscle. The use of microtip catheters with several pressure sensors and an integrated acceleration sensor enables signal reconstruction of the pressure distribution on the urethra's inside. Experimental data from minipigs exhibit artifact patterns in the pressure data. It is shown that these artifacts are caused by vascular pulsation in the sphincter structure. We therefore investigate different methods exploiting the time-correlation of the artifacts to eliminate pulse-induced artifacts in the pressure data without compromising the actual signal. Evaluation of these methods applied to experimental data conclude this work showing that both an Input-Model and Principal Component Analysis Decorrelation are effective at removing the artifacts. PMID:26736868

  18. Pressure-induced metallization of molybdenum disulfide.

    PubMed

    Chi, Zhen-Hua; Zhao, Xiao-Miao; Zhang, Haidong; Goncharov, Alexander F; Lobanov, Sergey S; Kagayama, Tomoko; Sakata, Masafumi; Chen, Xiao-Jia

    2014-07-18

    X-ray diffraction, Raman spectroscopy, and electrical conductivity measurements of molybdenum disulfide MoS(2) are performed at pressures up to 81 GPa in diamond anvil cells. Above 20 GPa, we find discontinuous changes in Raman spectra and x-ray diffraction patterns which provide evidence for isostructural phase transition from 2H(c) to 2H(a) modification through layer sliding previously predicted theoretically. This first-order transition, which is completed around 40 GPa, is characterized by a collapse in the c-lattice parameter and volume and also by changes in interlayer bonding. After the phase transition completion, MoS(2) becomes metallic. The reversibility of the phase transition is identified from all these techniques. PMID:25083660

  19. The impact of hepatic pressurization on liver shear wave speed estimates in constrained versus unconstrained conditions

    NASA Astrophysics Data System (ADS)

    Rotemberg, V.; Palmeri, M.; Nightingale, R.; Rouze, N.; Nightingale, K.

    2012-01-01

    Increased hepatic venous pressure can be observed in patients with advanced liver disease and congestive heart failure. This elevated portal pressure also leads to variation in acoustic radiation-force-derived shear wave-based liver stiffness estimates. These changes in stiffness metrics with hepatic interstitial pressure may confound stiffness-based predictions of liver fibrosis stage. The underlying mechanism for this observed stiffening behavior with pressurization is not well understood and is not explained with commonly used linear elastic mechanical models. An experiment was designed to determine whether the stiffness increase exhibited with hepatic pressurization results from a strain-dependent hyperelastic behavior. Six excised canine livers were subjected to variations in interstitial pressure through cannulation of the portal vein and closure of the hepatic artery and hepatic vein under constrained conditions (in which the liver was not free to expand) and unconstrained conditions. Radiation-force-derived shear wave speed estimates were obtained and correlated with pressure. Estimates of hepatic shear stiffness increased with changes in interstitial pressure over a physiologically relevant range of pressures (0-35 mmHg) from 1.5 to 3.5 m s-1. These increases were observed only under conditions in which the liver was free to expand while pressurized. This behavior is consistent with hyperelastic nonlinear material models that could be used in the future to explore methods for estimating hepatic interstitial pressure noninvasively.

  20. A mechanism for sustained groundwater pressure changes induced by distant earthquakes

    USGS Publications Warehouse

    Brodsky, E.E.; Roeloffs, E.; Woodcock, D.; Gall, I.; Manga, M.

    2003-01-01

    Large sustained well water level changes (>10 cm) in response to distant (more than hundreds of kilometers) earthquakes have proven enigmatic for over 30 years. Here we use high sampling rates at a well near Grants Pass, Oregon, to perform the first simultaneous analysis of both the dynamic response of water level and sustained changes, or steps. We observe a factor of 40 increase in the ratio of water level amplitude to seismic wave ground velocity during a sudden coseismic step. On the basis of this observation we propose a new model for coseismic pore pressure steps in which a temporary barrier deposited by groundwater flow is entrained and removed by the more rapid flow induced by the seismic waves. In hydrothermal areas, this mechanism could lead to 4 ?? 10-2 MPa pressure changes and triggered seismicity.

  1. Characteristics of laser-induced shock wave injury to the inner ear of rats.

    PubMed

    Kurioka, Takaomi; Matsunobu, Takeshi; Niwa, Katsuki; Tamura, Atsushi; Kawauchi, Satoko; Satoh, Yasushi; Sato, Shunichi; Shiotani, Akihiro

    2014-12-01

    Recently, the number of blast injuries of the inner ear has increased in the general population. In blast-induced inner ear injury, a shock wave (SW) component in the blast wave is considered to play an important role in sensorineural hearing loss. However, the mechanisms by which an SW affects inner ear tissue remain largely unknown. We aimed to establish a new animal model for SW-induced inner ear injury by using laser-induced SWs (LISWs) on rats. The LISWs were generated by irradiating an elastic laser target with 694-nm nanosecond pulses of a ruby laser. After LISW application to the cochlea through bone conduction, auditory measurements revealed the presence of inner ear dysfunction, the extent of which depended on LISW overpressure. A significantly lower survival rate of hair cells and spiral ganglion neurons, as well as severe oxidative damage, were observed in the inner ear exposed to an LISW. Although considerable differences in the pressure characteristics exist between LISWs and SWs in real blast waves, the functional and morphological changes shown by the present LISW-based model were similar to those observed in real blast-induced injury. Thus, our animal model is expected to be useful for laboratory-based research of blast-induced inner ear injury. PMID:25467523

  2. Characteristics of laser-induced shock wave injury to the inner ear of rats

    NASA Astrophysics Data System (ADS)

    Kurioka, Takaomi; Matsunobu, Takeshi; Niwa, Katsuki; Tamura, Atsushi; Kawauchi, Satoko; Satoh, Yasushi; Sato, Shunichi; Shiotani, Akihiro

    2014-12-01

    Recently, the number of blast injuries of the inner ear has increased in the general population. In blast-induced inner ear injury, a shock wave (SW) component in the blast wave is considered to play an important role in sensorineural hearing loss. However, the mechanisms by which an SW affects inner ear tissue remain largely unknown. We aimed to establish a new animal model for SW-induced inner ear injury by using laser-induced SWs (LISWs) on rats. The LISWs were generated by irradiating an elastic laser target with 694-nm nanosecond pulses of a ruby laser. After LISW application to the cochlea through bone conduction, auditory measurements revealed the presence of inner ear dysfunction, the extent of which depended on LISW overpressure. A significantly lower survival rate of hair cells and spiral ganglion neurons, as well as severe oxidative damage, were observed in the inner ear exposed to an LISW. Although considerable differences in the pressure characteristics exist between LISWs and SWs in real blast waves, the functional and morphological changes shown by the present LISW-based model were similar to those observed in real blast-induced injury. Thus, our animal model is expected to be useful for laboratory-based research of blast-induced inner ear injury.

  3. Wave-induced topographic formstress in baroclinic channel flow

    NASA Astrophysics Data System (ADS)

    Olbers, Dirk; Lettmann, Karsten; Wolff, Jörg-Olaf

    2007-12-01

    Large-scale zonal flow driven across submarine topography establishes standing Rossby waves. In the presence of stratification, the wave pattern can be represented by barotropic and baroclinic Rossby waves of mixed planetary topographic nature, which are locked to the topography. In the balance of momentum, the wave pattern manifests itself as topographic formstress. This wave-induced formstress has the net effect of braking the flow and reducing the zonal transport. Locally, it may lead to acceleration, and the parts induced by the barotropic and baroclinic waves may have opposing effects. This flow regime occurs in the circumpolar flow around Antarctica. The different roles that the wave-induced formstress plays in homogeneous and stratified flows through a zonal channel are analyzed with the BARBI (BARotropic-Baroclinic-Interaction ocean model, Olbers and Eden, J Phys Oceanogr 33:2719-2737, 2003) model. It is used in complete form and in a low-order version to clarify the different regimes. It is shown that the barotropic formstress arises by topographic locking due to viscous friction and the baroclinic one due to eddy-induced density advection. For the sinusoidal topography used in this study, the transport obeys a law in which friction and wave-induced formstress act as additive resistances, and windstress, the effect of Ekman pumping on the density stratification, and the buoyancy forcing (diapycnal mixing of the stratified water column) of the potential energy stored in the stratification act as additive forcing functions. The dependence of the resistance on the system parameters (lateral viscosity ɛ, lateral diffusivity κ of eddy density advection, Rossby radius λ, and topography height δ) as well as the dependence of transport on the forcing functions are determined. While the current intensity in a channel with homogeneous density decreases from the viscous flat bottom case in an inverse quadratic law ~ δ -2 with increasing

  4. Optimization of pressure waveform, distribution and sequence in shock wave lithotripsy

    NASA Astrophysics Data System (ADS)

    Zhou, Yufeng

    This work aims to improve shock wave lithotripsy (SWL) technology by increasing stone comminution efficiency while reducing simultaneously the propensity of tissue injury. First, the mechanism of vascular injury in SWL was investigated. Based on in vitro vessel phantom experiment and theoretical calculation, it was found that SWL-induced large intraluminal bubble expansion may constitute a primary mechanism for the rupture of capillaries and small blood vessels. However, when the large intraluminal bubble expansion is suppressed by inversion of the pressure waveform of the lithotripter shock wave (LSW), rupture of a 200-mum cellulose hollow fiber vessel phantom can be avoided. Based on these experimental observations and theoretical assessment of bubble dynamics using the Gilmore model an in situ pulse superposition technique was developed to reduce tissue injury without compromising stone comminution in SWL. A thin shell ellipsoidal reflector insert was fabricated to fit snugly with the original HM-3 reflector. Using the Hamilton model, the effects of reflector geometry on the pulse profile and sequence of the shock waves were evaluated qualitatively. Guided by this analysis, the design of the reflector insert had been refined to suppress the intraluminal bubble expansion, which was confirmed by high-speed imaging of bubble dynamics both in free field and inside a vessel phantom. The pulse pressure, beam size and stone comminution efficiency of the upgraded reflector were all found to be comparable to those of the original reflector. However, the greatest difference lies in the propensity for tissue injury. At the lithotripter focus, about 30 shocks are needed to cause a rupture of the vessel phantom using the original reflector, but no rupture can be produced after 200 shocks by the upgraded reflector. Overall, the upgraded reflector could significantly reduce the propensity of vessel rupture while maintaining satisfactory stone comminution. Second, to improve

  5. Prediction of the characteristics of two types of pressure waves in the cochlea: Theoretical considerations

    NASA Astrophysics Data System (ADS)

    Andoh, Masayoshi; Wada, Hiroshi

    2004-07-01

    The aim of this study was to predict the characteristics of two types of cochlear pressure waves, so-called fast and slow waves. A two-dimensional finite-element model of the organ of Corti (OC), including fluid-structure interaction with the surrounding lymph fluid, was constructed. The geometry of the OC at the basal turn was determined from morphological measurements of others in the gerbil hemicochlea. As far as mechanical properties of the materials within the OC are concerned, previously determined mechanical properties of portions within the OC were adopted, and unknown mechanical features were determined from the published measurements of static stiffness. Time advance of the fluid-structure scheme was achieved by a staggered approach. Using the model, the magnitude and phase of the fast and slow waves were predicted so as to fit the numerically obtained pressure distribution in the scala tympani with what is known about intracochlear pressure measurement. When the predicted pressure waves were applied to the model, the numerical result of the velocity of the basilar membrane showed good agreement with the experimentally obtained velocity of the basilar membrane documented by others. Thus, the predicted pressure waves appeared to be reliable. Moreover, it was found that the fluid-structure interaction considerably influences the dynamic behavior of the OC at frequencies near the characteristic frequency.

  6. Wave-induced seepage and its possible contribution to the formation of pockmarks in the Huanghe (Yellow) River delta

    NASA Astrophysics Data System (ADS)

    Wang, Hu; Liu, Hongjun; Zhang, Minsheng; Wang, Xiuhai

    2016-01-01

    Wave-induced seepage and its possible contribution to the formation of pockmarks in the Huanghe (Yellow) River delta were investigated experimentally and numerically. Laboratory experiments were carried out to explore the response of a layered silty seabed with various saturation conditions under cyclic wave loads, in which the pore pressure and seepage-related phenomena were particularly monitored. Numerical models to simulate wave-induced seepage in the seabed were presented and evaluated, then applied to the Huanghe River delta. The experimental results show that the excess pore pressure decreases more rapidly at the surface layer, while the seepage-related phenomena are more pronounced when large cyclic loads are applied and the underlying layer is less saturated. The proposed numerical models were verified by comparing with the experiments. The calculated seepage depth agreed well with the depth of the pockmarks in the Huanghe River delta. The experimental and numerical results and the existing insitu investigations indicate that the wave-induced seepage may be a direct cause of the pockmarks in the Huanghe River delta. Extreme storm waves and the dual-layered structure of hard surface layer and weak underlying layer are essential external and internal factors, respectively. Wave- or current-induced scour and transport are possible contributors to the reformation of pockmarks at a later stage.

  7. Pressure waves generated by metastable intermolecular composites in an aqueous environment

    NASA Astrophysics Data System (ADS)

    Maines, G.; Radulescu, M.; Bacciochini, A.; Jodoin, B.; Lee, J. J.

    2014-05-01

    In the present study, pressure waves generated by a metastable intermolecular composite (MIC) have been measured experimentally in an aqueous environment and correlated with flame speed measurements. Underwater experiments were performed in a 1.0 L high-pressure chamber mounted with high-resolution pressure transducers and designed with optical access. Samples consisting of a stoichiometric mixture of aluminium and copper(II)-oxide particles were evaluated. Two types of samples were synthesized; a mixture of micron-sized raw powders, and ball-milled powders with a fine-scale nano-structure. A planetary mill was used to refine reactant powders from micron- to nano-scale dimensions. The dynamics of the pressure wave and high-pressure gas bubble were monitored via pressure histories and high-speed Schlieren visualization. The effect of reactant particle size has been evaluated quantitatively. The dynamics of the pressure wave were correlated with the rate of expansion of the high-pressure gas bubble.

  8. Transport induced by ion cyclotron range of frequencies waves

    SciTech Connect

    Zhang, Debing Xu, Yingfeng; Wang, Shaojie

    2014-11-15

    The Vlasov equation, which includes the effect of the ion cyclotron range of frequencies (ICRF) waves, can be written as the Fokker-Planck equation which describes the quasilinear transport in phase space by using the Lie-transform method. The radial transport fluxes of particle, energy and parallel momentum driven by ICRF waves in the slab geometry have been derived. The results show that the ICRF-induced radial redistributions of particle, energy and parallel momentum are driven by the inhomogeneity in energy of the equilibrium distribution function, and related to the correlation between the excursion in the real space and the excursion in energy. For the case with strong asymmetry of k{sub y} spectrum, the ICRF-induced radial transport driven by the energy inhomogeneity dominates the ICRF-induced radial transport driven by the spatial inhomogeneity.

  9. Dehydration-induced porosity waves and episodic tremor and slip

    NASA Astrophysics Data System (ADS)

    Skarbek, Rob M.; Rempel, Alan W.

    2016-02-01

    Episodic tremor and slip (ETS) along the subduction interface takes place where there is abundant evidence for elevated, near-lithostatic pore pressures, at sufficiently great depths (30-45 km) that chemical dehydration reactions must act as their dominant source. We simulate fluid and heat flow while tracking the location of a vertically oriented, one-dimensional column of material as it subducts through the slow slip and tremor zone. The material in the column is transformed through a pressure-dependent and temperature-dependent dehydration reaction that we describe with a generalized nonlinear kinetic rate law. Column deformation is largely dominated by viscous creep, with a closure rate that depends linearly on porosity. This behavior causes the dehydration reaction to generate traveling porosity waves that transport increased fluid pressures within the slow slip region. To explore the possibility that the observed periodicity of slow slip and tremor in subduction zones can be explained by the migration of such porosity waves, we derive a dispersion relation that accurately describes our numerical results. We also obtain an expression for how the thickness of the dehydrating layer is expected to vary as a function of the parameters in the reaction rate law. Although the amplitudes of pore pressure perturbations rival those that are produced by known external forcings (e.g., tides or passing surface waves), our analysis suggests that given reasonable estimates of rock viscosity, permeabilities in the range 6.5×10-15 to 5×10-10 m2 are required for porosity wave trains to form at periods comparable to those of slow slip and tremor.

  10. A computational study of pressure wave reflections in the pulmonary arteries.

    PubMed

    Qureshi, M Umar; Hill, N A

    2015-12-01

    Experiments using wave intensity analysis suggest that the pulmonary circulation in sheep and dogs is characterized by negative or open-end type wave reflections, that reduce the systolic pressure. Since the pulmonary physiology is similar in most mammals, including humans, we test and verify this hypothesis by using a subject specific one-dimensional model of the human pulmonary circulation and a conventional wave intensity analysis. Using the simulated pressure and velocity, we also analyse the performance of the P-U loop and sum of squares techniques for estimating the local pulse wave velocity in the pulmonary arteries, and then analyse the effects of these methods on linear wave separation in the main pulmonary artery. P-U loops are found to provide much better estimates than the sum of squares technique at proximal locations, but both techniques accumulate progressive error at distal locations away from heart, particularly near junctions. The pulse wave velocity estimated using the sum of squares method also gives rise to an artificial early systolic backward compression wave. Finally, we study the influence of three types of pulmonary hypertension viz. pulmonary arterial hypertension, chronic thromboembolic pulmonary hypertension and pulmonary hypertension associated with hypoxic lung disease. Simulating these conditions by changing the relevant parameters in the model and then applying the wave intensity analysis, we observe that for each group the early systolic backward decompression wave reflected from proximal junctions is maintained, whilst the initial forward compression and the late systolic backward compression waves amplify with increasing pathology and contribute significantly to increases in systolic pressure. PMID:25754476

  11. Pressure induced phase transitions in ceramic compounds containing tetragonal zirconia

    SciTech Connect

    Sparks, R.G.; Pfeiffer, G.; Paesler, M.A.

    1988-12-01

    Stabilized tetragonal zirconia compounds exhibit a transformation toughening process in which stress applied to the material induces a crystallographic phase transition. The phase transition is accompanied by a volume expansion in the stressed region thereby dissipating stress and increasing the fracture strength of the material. The hydrostatic component of the stress required to induce the phase transition can be investigated by the use of a high pressure technique in combination with Micro-Raman spectroscopy. The intensity of Raman lines characteristic for the crystallographic phases can be used to calculate the amount of material that has undergone the transition as a function of pressure. It was found that pressures on the order of 2-5 kBar were sufficient to produce an almost complete transition from the original tetragonal to the less dense monoclinic phase; while a further increase in pressure caused a gradual reversal of the transition back to the original tetragonal structure.

  12. Experimental and Numerical Investigation of Pressure Wave Attenuation due to Bubbly Layers

    NASA Astrophysics Data System (ADS)

    Jayaprakash, Arvind; Fourmeau, Tiffany; Hsiao, Chao-Tsung; Chahine, Georges; Dynaflow Inc. Team

    2013-03-01

    In this work, the effects of dispersed microbubbles on a steep pressure wave and its attenuation are investigated both numerically and experimentally. Numerical simulations were carried out using a compressible Euler equation solver, where the liquid-gas mixture was modeled using direct numerical simulations involving discrete deforming bubbles. To reduce computational costs a 1D configuration is used and the bubbles are assumed distributed in layers and the initial pressure profile is selected similar to that of a one-dimensional shock tube problem. Experimentally, the pressure pulse was generated using a submerged spark electric discharge, which generates a large vapor bubble, while the microbubbles in the bubbly layer are generated using electrolysis. High speed movies were recorded in tandem with high fidelity pressure measurements. The dependence of pressure wave attenuation on the bubble radii, the void fraction, and the bubbly layer thickness were parametrically studied. It has been found that the pressure wave attenuation can be seen as due to waves reflecting and dispersing in the inter-bubble regions, with the energy absorbed by bubble volume oscillations and re-radiation. Layer thickness and small bubble sizes were also seen as having a strong effect on the attenuation with enhanced attenuation as the bubble size is reduced for the same void fraction. This study was supported by the Department of Energy, under SBIR Phase II Contract DE-FG02-07ER84839.

  13. Wave reflection quantification based on pressure waveforms alone--methods, comparison, and clinical covariates.

    PubMed

    Hametner, Bernhard; Wassertheurer, Siegfried; Kropf, Johannes; Mayer, Christopher; Holzinger, Andreas; Eber, Bernd; Weber, Thomas

    2013-03-01

    Within the last decade the quantification of pulse wave reflections mainly focused on measures of central aortic systolic pressure and its augmentation through reflections based on pulse wave analysis (PWA). A complementary approach is the wave separation analysis (WSA), which quantifies the total amount of arterial wave reflection considering both aortic pulse and flow waves. The aim of this work is the introduction and comparison of aortic blood flow models for WSA assessment. To evaluate the performance of the proposed modeling approaches (Windkessel, triangular and averaged flow), comparisons against Doppler measurements are made for 148 patients with preserved ejection fraction. Stepwise regression analysis between WSA and PWA parameters are performed to provide determinants of methodological differences. Against Doppler measurement mean difference and standard deviation of the amplitudes of the decomposed forward and backward pressure waves are comparable for Windkessel and averaged flow models. Stepwise regression analysis shows similar determinants between Doppler and Windkessel model only. The results indicate that the Windkessel method provides accurate estimates of wave reflection in subjects with preserved ejection fraction. The comparison with waveforms derived from Doppler ultrasound as well as recently proposed simple triangular and averaged flow waves showed that this approach may reduce variability and provide realistic results. PMID:23107159

  14. Radiation-induced decomposition of PETN and TATB under pressure

    SciTech Connect

    Giefers, Hubertus; Pravica, Michael; Liermann, Hanns-Peter; Yang, Wenge

    2008-10-02

    We have investigated decomposition of PETN and TATB induced by white synchrotron X-ray radiation in a diamond anvil cell at ambient temperature and two pressures, nearly ambient and about 6 GPa. The decomposition rate of TATB decreases significantly when it is pressurized to 5.9 GPa. The measurements were highly reproducible and allowed us to obtain decomposition rates and the order parameters of the reactions.

  15. Transepithelial pressure pulses induce nucleotide release in polarized MDCK cells.

    PubMed

    Praetorius, H A; Frøkiaer, J; Leipziger, J

    2005-01-01

    The release of nucleotides is involved in mechanosensation in various epithelial cells. Intriguingly, kidney epithelial cells are absolutely dependent on the primary cilium to sense changes in apical laminar flow. During fluid passage, the renal epithelial cells are subjected to various mechanical stimuli in addition to changes in the laminar flow rate. In the distal part of the collecting duct, the epithelial cells are exposed to pressure changes and possibly distension during papillary contractions. The aim of the present study was to determine whether nucleotide release contributes to mechanosensation in kidney epithelial cells, thereby establishing whether pressure changes are sufficient to produce nucleotide-mediated responses. Madin-Darby canine kidney (MDCK) cells grown on permeable supports were mounted in a closed double perfusion chamber on an inverted microscope. The intracellular Ca(2+) concentration ([Ca(2+)](i)) was monitored with the Ca(2+)-sensitive fluorescence probe fluo 4. Transepithelial pressure pulses of 30-80 mm Hg produced a transient increase in [Ca(2+)](i) of MDCK cells. This response is independent of the primary cilium, since it is readily observed in immature cells that do not yet express primary cilia. The amplitudes of the pressure-induced Ca(2+) transients varied with the applied chamber pressure in a quantity-dependent manner. The ATPase apyrase and the P2Y antagonist suramin significantly reduced the pressure-induced Ca(2+) transients. Applying apyrase or suramin to both sides of the preparation simultaneously nearly abolished the pressure-induced Ca(2+) response. In conclusion, these observations suggest that rapid pressure changes induce both apical and basolateral nucleotide release that contribute to mechanosensation in kidney epithelial cells. PMID:15367389

  16. Generation and Propagation of Long Waves due to Spatial and Temporal Pressure Distributions

    NASA Astrophysics Data System (ADS)

    Metin, A. D.; Yalçıner, A. C.; Ozyurt Tarakcıoglu, G.; Zaytsev, A.

    2015-12-01

    An abnormal wave event was observed between 23 and 27 June 2014 in the Mediterranean and Black Seas. First, sea level oscillations began in Ciutadella Inlet (Spain) after midnight of 22 June. The phenomena continued with observation of strong oscillations (up to 3 m wave height) in the Adriatic Sea, Mediterranean Sea and Black Sea on 25-26 June. Finally, at noon on 27 June on a calm and sunny day, the abnormal waves suddenly struck coasts of Odessa with 1-2 m wave height injuring a number of people. This tsunami-like event which is called meteotsunami is generated by different types of meteorological disturbances such as atmospheric gravity waves, pressure jumps and squall lines and the significant consequences necessitates the research to understand, model and simulate such events accurately. Thus, using the 2014 event as a case study, the waves generated by the change of atmospheric pressure distribution is studied. A static water level drop due to high atmospheric pressure in a region and rise due to low atmospheric pressure in another region deform the water level throughout the entire sea area. To compute the sea level change, the relation between the pressure difference and change of water level from normal position (ζ=0.99ΔP) is used where ζ is the change of water level (cm) according to the pressure difference from normal pressure ΔP. This relation gives that 1 hPa (1millibar) depression in air pressure from normal water level position (under 1000millibar) creates almost 1 cm rise in mean sea level. The respective small amplitude long waves propagate along the sea which is continuously excited by the spatial and temporal changes of atmospheric pressure. And, the amplification becomes important to understand the occurrence of unexpected water level changes, especially near the coastal zone. In this study, this long wave propagation due to water surface deformation is modelled by solving nonlinear shallow water equations. The model results are compared

  17. Structure of an oblique detonation wave induced by a wedge

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Liu, Y.-S.; Wu, D.; Wang, J.-P.

    2016-03-01

    The structure of an oblique detonation wave (ODW) induced by a wedge is investigated via numerical simulations and Rankine-Hugoniot analysis. The two-dimensional Euler equations coupled with a two-step chemical reaction model are solved. In the numerical results, four configurations of the Chapman-Jouguet (CJ) ODW reflection (overall Mach reflection, Mach reflection, regular reflection, and non-reflection) are observed to take place sequentially as the inflow Mach number increases. According to the numerical and analytical results, the change of the CJ ODW reflection configuration results from the interaction among the ODW, the CJ ODW, and the centered expansion wave.

  18. Pressure-induced structural phase transition, elastic and thermodynamic properties of ReC under high pressure

    NASA Astrophysics Data System (ADS)

    Lei, Hui-Ru; Zhu, Jun; Hao, Yan-Jun; Zhang, Lin; Zhao, Yu-Xin; Zhan, Guo-Fu

    2015-10-01

    The pressure-induced structural phase transition of rhenium monocarbon (ReC) is investigated via the projector augmented wave (PAW) method with the generalized gradient approximation (GGA). Using the first-principles calculations, the equilibrium structural parameters of ReC in rocksalt (NaCl), cesium chloride (CsCl), zinc blende (ZB), wurtzite (WZ), nickel arsenide (NiAs) and tungsten carbide (WC) types are successfully obtained, and the results are well consistent with other theoretical data. It is firstly noted that WC-ReC translates into CsCl-ReC at 510.50 GPa by analyzing the enthalpy difference versus pressure. From the calculated elastic constants, the aggregate elastic modulus (B, G, E), the Poisson's ratio (σ) and the Debye temperature ΘD of WC-type are also derived. It is observed that all the data of WC-ReC obtained increase monotonically with increasing pressure. Meanwhile, the thermodynamic properties of WC-ReC under high temperature and high pressure are investigated applying nonempirical Debye model in the quasi-harmonic approximation.

  19. Pressure dependence of the charge-density-wave gap in rare-earth tritellurides.

    PubMed

    Sacchetti, A; Arcangeletti, E; Perucchi, A; Baldassarre, L; Postorino, P; Lupi, S; Ru, N; Fisher, I R; Degiorgi, L

    2007-01-12

    We investigate the pressure dependence of the optical properties of CeTe3, which exhibits an incommensurate charge-density-wave (CDW) state already at 300 K. Our data are collected in the midinfrared spectral range at room temperature and at pressures between 0 and 9 GPa. The energy for the single particle excitation across the CDW gap decreases upon increasing the applied pressure, similarly to the chemical pressure by rare-earth substitution. The broadening of the bands upon lattice compression removes the perfect nesting condition of the Fermi surface and therefore diminishes the impact of the CDW transition on the electronic properties of RTe3. PMID:17358625

  20. Wave-induced fluid flow in random porous media: attenuation and dispersion of elastic waves.

    PubMed

    Müller, Tobias M; Gurevich, Boris

    2005-05-01

    A detailed analysis of the relationship between elastic waves in inhomogeneous, porous media and the effect of wave-induced fluid flow is presented. Based on the results of the poroelastic first-order statistical smoothing approximation applied to Biot's equations of poroelasticity, a model for elastic wave attenuation and dispersion due to wave-induced fluid flow in 3-D randomly inhomogeneous poroelastic media is developed. Attenuation and dispersion depend on linear combinations of the spatial correlations of the fluctuating poroelastic parameters. The observed frequency dependence is typical for a relaxation phenomenon. Further, the analytic properties of attenuation and dispersion are analyzed. It is shown that the low-frequency asymptote of the attenuation coefficient of a plane compressional wave is proportional to the square of frequency. At high frequencies the attenuation coefficient becomes proportional to the square root of frequency. A comparison with the 1-D theory shows that attenuation is of the same order but slightly larger in 3-D random media. Several modeling choices of the approach including the effect of cross correlations between fluid and solid phase properties are demonstrated. The potential application of the results to real porous materials is discussed. PMID:15957744

  1. Slowly breaking waves: the longevity of tidally induced spiral structure

    NASA Astrophysics Data System (ADS)

    Struck, Curtis; Dobbs, Clare L.; Hwang, Jeong-Sun

    2011-07-01

    We have discovered long-lived waves in two sets of numerical models of fast (marginally bound or unbound) flyby galaxy collisions, carried out independently with two different codes. In neither simulation set are the spirals the result of a collision-induced bar formation. Although there is variation in the appearance of the waves with time, they do not disappear and reform recurrently, as seen in other cases described in the literature. We also present an analytic theory that can account for the wave structure, not as propagating transients, nor as a fixed pattern propagating through the disc. While these waves propagate through the disc, they are mantained by the coherent oscillations initiated by the impulsive disturbance. Specifically, the analytic theory suggests that they are caustic waves in ensembles of stars pursuing correlated epicyclic orbits after the disturbance. This theory is an extension of that developed by Struck and collaborators for colliding ring galaxies. The models suggest that this type of wave may persist for a couple of Gyr, and galaxy interactions occur on comparable time-scales, so waves produced by the mechanism may be well represented in observed spirals. In particular, this mechanism can account for the tightly wound, and presumably long-lived, spirals seen in some nearby early-type galaxies. These spirals are also likely to be common in groups and clusters, where fast encounters between galaxies occur relatively frequently. However, as the spirals become tightly wound, and evolve to modest amplitudes, they may be difficult to resolve unless they are nearby. None the less, the effect may be one of several processes that result from galaxy harassment, and via wave-enhanced star formation, contributes to the Butcher-Oemler effect.

  2. Molecular modeling of high-pressure ramp waves in tantalum

    NASA Astrophysics Data System (ADS)

    Lane, J. Matthew D.; Lim, Hojun; Brown, Justin L.

    2015-03-01

    Ramp wave compression experiments of bcc metals under extreme conditions have produced differing measurements of material strength response. These variations are often attributed to differing experimental techniques, and varying material factors such as microstructure, and strain-rate. We present non-equilibrium molecular dynamics simulations of tantalum for single crystal and two polycrystalline nanostructures out to 250 GPa, over strain states ranging from 108 to 1011 1/s. Results will be compared to recent Z-machine strength experiments, meso-scale crystal plasticity models and continuum-scale polycrystalline model. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  3. Wave pattern in the wake of an arbitrary moving surface pressure disturbance

    NASA Astrophysics Data System (ADS)

    Miao, Sha; Liu, Yuming

    2015-12-01

    We study the problem of wave pattern in the wake of an arbitrary surface pressure disturbance that moves forward at constant speed U in deep water. We seek the dependence of the location of the maximum amplitude of waves upon the pressure distribution and the Froude number F ≡ U / √{ g L } , where L is the characteristic length of the pressure disturbance and g is the gravitational acceleration. We show by theoretical analysis and direct numerical evaluation that half of the included angle (ϕmax) of the V-shape corresponding to the maximum amplitude of the waves in the wake at large Froude numbers behaves asymptotically as ϕ max = C F - a for F > F c , with the constant a, coefficient C, and threshold value of Froude number F c all being functions of the pressure distribution. It is found that for most pressure disturbances, a equals 1, but a can equal 2 for special non-smooth pressure disturbances. The condition in terms of the order of discontinuity and distribution shape of the pressure disturbance for the result of a = 2 is provided. These findings imply that for ship wakes, ϕmax generally decreases with increasing F at large Froude numbers, while the exact value of ϕmax is dependent on ship geometry and F .

  4. Pressure waves generated by metastable intermolecular composites in an aqueous environment

    NASA Astrophysics Data System (ADS)

    Maines, Geoff; Radulescu, Matei; Bacciochini, Antoine; Jodoin, Bertrand; Lee, Julian

    2013-06-01

    In the present study, pressure waves generated by a metastable intermolecular composite (MIC) have been measured experimentally in an aqueous environment. Experiments were performed in a 1.0 L high pressure chamber mounted with high resolution pressure transducers and designed with optical access. Samples consisting of a stoichiometric mixture of aluminum and copper(II)oxide particles were evaluated. Two types of samples were constructed; a mixture of micron-sized raw powders, and ball milled powders with a lamellated nanostructure. A planetary mill was used to refine reactant powders from micron- to nano-scale dimensions. Manual compaction and cold spray deposition techniques were used to consolidate powders in various densities. The dynamics of the pressure wave and high pressure gas bubble were monitored via pressure data and high-speed Schlieren visualization. The effects of reactant particle size and sample density have been evaluated quantitatively and compared with equilibrium calculations. Dynamics of the pressure wave were correlated with the amount of gas released and the rate of burning of the sample material. Work supported by DRDC Suffield (Dr. Julian J. Lee).

  5. The effect of convection and shear on the damping and propagation of pressure waves

    NASA Astrophysics Data System (ADS)

    Kiel, Barry Vincent

    Combustion instability is the positive feedback between heat release and pressure in a combustion system. Combustion instability occurs in the both air breathing and rocket propulsion devices, frequently resulting in high amplitude spinning waves. If unchecked, the resultant pressure fluctuations can cause significant damage. Models for the prediction of combustion instability typically include models for the heat release, the wave propagation and damping. Many wave propagation models for propulsion systems assume negligible flow, resulting in the wave equation. In this research the effect of flow on wave propagation was studied both numerically and experimentally. Two experiential rigs were constructed, one with axial flow to study the longitudinal waves, the other with swirling flow to study circumferential waves. The rigs were excited with speakers and the resultant pressure was measured simultaneously at many locations. Models of the rig were also developed. Equations for wave propagation were derived from the Euler Equations. The resultant resembled the wave equation with three additional terms, two for the effect of the convection and a one for the effect of shear of the mean flow on wave propagation. From the experimental and numerical data several conclusions were made. First, convection and shear both act as damping on the wave propagation, reducing the magnitude of the Frequency Response Function and the resonant frequency of the modes. Second, the energy extracted from the mean flow as a result of turbulent shear for a given condition is frequency dependent, decreasing with increasing frequency. The damping of the modes, measured for the same shear flow, also decreased with frequency. Finally, the two convective terms cause the anti-nodes of the modes to no longer be stationary. For both the longitudinal and circumferential waves, the anti-nodes move through the domain even for mean flow Mach numbers less than 0.10. It was concluded that convection

  6. The wave-induced sediment responses in the subaquous Yellow River delta, China: new insights into seabed inhomogeneity

    NASA Astrophysics Data System (ADS)

    Liu, X.; Jia, Y.; Zheng, J.; Shan, H.

    2014-12-01

    This paper presents the results of an experimental study of the wave-induced sediment responses in the subaqueous Yellow River delta. The pore pressure, sediment particle size composition, microstructure, physical and mechanical properties at different depths inside the seabed were observed during the experimental process under the weight of the soil and under the action of waves of different heights. The results showed that wave-induced sediment responses significantly controlled the occurrence and evolution of inhomogeneity in the strength and sediment distribution of a uniform-originated silty seabed. The variations in the strength, composition and structure of during the wave-sediment interaction processes are closely related to the pore water seepage inside the seabed. The driving machanism can be devided into three modes: transient seepage caused by pore pressure oscillation, seepage failure caused by pore pressure accumulation and liquefaction failure caused by pore pressure accumulation, during which the latter is the main cause of vertical transport of pore water carrying a large amount of fine particles inside the seabed of the subaqueous Yellow River delta. The array of features observed in these experiments can be incorporated into a new model of seabed stratification in uniform-originated silty sediments during wave-sediment interaction. In addition, the implications of this model for traditional sedimentology are explored from a sediment dynamic perspective.

  7. New experimental capabilities and theoretical insights of high pressure compression waves

    NASA Astrophysics Data System (ADS)

    Orlikowski, Daniel

    2007-06-01

    While some high pressure, compression wave research seeks ever high pressures(>10 Mbar), the exciting developments of high pressure research for gas-gun generated compression waves have spawned novel compression experiments as well as new theoretical insights into compression wave dissipation. The first half of the discussion covers the unique gradient density impactor (GDI) developed at LLNL, that has just matured into a viable tool to examine the material response along and significantly away from the principal paths of the Hugoniot and isentrope. This gives direct access to hot planetary isentropes or cyclic paths to understand hysteretic response at moderately high pressures (<5 Mbar). Recently, significant material design challenges pertaining to material control, planarity, parallel layers, and reproducibility have been overcome in the manufacturing of these impactors used to create (within 2μs) compression waves. These compression waves consist of the standard monotonic compression and of unique non-monotonic compression waves, which widens the field of research to include previously inaccessible parts of the thermodynamic phase diagram for a given material. These developments will be addressed in conjunction with hydrodynamic simulations discussing several interesting experiments that have taken place in the pursuit of understanding the high-pressure phase diagram of water and of understanding high-pressure strength. Closely connected to these compression experiments, in general, is the interpretation of the recorded particle velocity histories and the assumptions used to quantify those results, e.g. stress versus density. Therefore, a second theoretical discussion of solitary wave structure is given suggested by recent experimental observations. Dissipative and dispersive effects are expected to exist in general, however, these effects are not usually discussed within the context of the Korteweg-de Vries(KdV)-Burgers equation, thus, leading to a possible

  8. Helical guided waves in liquid-filled cylindrical shells subjected to static pressurization stress

    NASA Astrophysics Data System (ADS)

    Dubuc, Brennan; Ebrahimkhanlou, Arvin; Salamone, Salvatore

    2016-04-01

    Helical guided waves in pipelines are studied under the effects of pressurization stresses from a contained liquid. The pipeline is approximated by an "unwrapped" plate waveguide, and a transfer matrix method is used to solve for guided wave velocity and attenuation dispersion curves in a multilayered plate waveguide subject to an arbitrary triaxial state of initial stress. The matrix-based model is able to incorporate both elastic and viscoelastic solid materials, as well as approximate non-uniform distributions in initial stress through the thickness of a waveguide. Experiments on a steel pipe filled with pressurized water are carried out to validate the modeling approach.

  9. Cosmic shear from scalar-induced gravitational waves

    SciTech Connect

    Sarkar, Devdeep; Serra, Paolo; Cooray, Asantha; Ichiki, Kiyotomo; Baumann, Daniel

    2008-05-15

    Weak gravitational lensing by foreground density perturbations generates a gradient mode in the shear of background images. In contrast, cosmological tensor perturbations induce a nonzero curl mode associated with image rotations. In this note, we study the lensing signatures of both primordial gravitational waves from inflation and second-order gravitational waves generated from the observed spectrum of primordial density fluctuations. We derive the curl mode for galaxy lensing surveys at redshifts of 1-3 and for lensing of the cosmic microwave background at a redshift of 1100. We find that the curl mode angular power spectrum associated with secondary tensor modes for galaxy lensing surveys dominates over the corresponding signal generated by primary gravitational waves from inflation. However, both tensor contributions to the shear curl mode spectrum are below the projected noise levels of upcoming galaxy and cosmic microwave background lensing surveys and therefore are unlikely to be detectable.

  10. Finite-amplitude pressure waves in the radial mode of a cylinder

    NASA Technical Reports Server (NTRS)

    Kubo, I.; Moore, F. K.

    1972-01-01

    A numerical study of finite-strength, isentropic pressure waves transverse to the axis of a circular cylinder was made for the radial resonant mode. The waves occur in a gas otherwise at rest, filling the cylinder. A method of characteristics was used for the numerical solution. For small but finite amplitudes, calculations indicate the existence of waves of permanent potential form. For larger amplitudes, a shock is indicated to occur. The critical value of the initial amplitude parameter in the power series is found to be 0.06 to 0.08, under various types of initial conditions.

  11. In-situ determination of SH-channel wave velocity and the influence of overburden pressure

    SciTech Connect

    Reeves, J.J.; Major, M.W.

    1982-04-01

    In the Dutch Creek 1 Mine at Coal Basin, Colorado, SH-channel waves have been transmitted through floor coal underneath a gob (cave darea) produced by an advancing longwall panel. For any given source, only the receiver directly adjacent or closest to the source was monitored by the Geometrics ES 1210 F seismograph. Two sources were used to excite channel waves at each source location; one an explosive charge, the other a hammer blow. Tests showed that variation in overburden pressure on coal can be detected seismically using channel waves passing through the coal.

  12. Enhancement of airborne shock wave by laser-induced breakdown of liquid column in laser shock cleaning

    SciTech Connect

    Jang, Deoksuk; Kim, Dongsik; Park, Jin-Goo

    2011-04-01

    In laser shock cleaning (LSC), the shock wave is generated by laser-induced breakdown of the ambient gas. The shock wave intensity has thus been a factor limiting the performance of the LSC process. In this work, a novel method of amplifying a laser-induced plasma-generated shock wave by the breakdown of a liquid column is proposed and analyzed. When the laser beam is focused on a microscale liquid column, a shock wave having a significantly amplified intensity compared to that generated by air breakdown alone can be generated in air. Therefore, substantially amplified cleaning force can be obtained. The dynamics of a shock wave induced by a Q-switched Nd:YAG laser was analyzed by laser flash shadowgraphy. The peak pressure of the laser-induced shock wave was approximately two times greater than that of air breakdown at the same laser fluence. The proposed method of shock wave generation is expected to be useful in various applications of laser shock processing, including surface cleaning.

  13. Wave induced density modification in RF sheaths and close to wave launchers

    SciTech Connect

    Van Eester, D.; Lu, Ling-Feng

    2015-12-10

    With the return to full metal walls - a necessary step towards viable fusion machines - and due to the high power densities of current-day ICRH (Ion Cyclotron Resonance Heating) or RF (radio frequency) antennas, there is ample renewed interest in exploring the reasons for wave-induced sputtering and formation of hot spots. Moreover, there is experimental evidence on various machines that RF waves influence the density profile close to the wave launchers so that waves indirectly influence their own coupling efficiency. The present study presents a return to first principles and describes the wave-particle interaction using a 2-time scale model involving the equation of motion, the continuity equation and the wave equation on each of the time scales. Through the changing density pattern, the fast time scale dynamics is affected by the slow time scale events. In turn, the slow time scale density and flows are modified by the presence of the RF waves through quasilinear terms. Although finite zero order flows are identified, the usual cold plasma dielectric tensor - ignoring such flows - is adopted as a first approximation to describe the wave response to the RF driver. The resulting set of equations is composed of linear and nonlinear equations and is tackled in 1D in the present paper. Whereas the former can be solved using standard numerical techniques, the latter require special handling. At the price of multiple iterations, a simple ’derivative switch-on’ procedure allows to reformulate the nonlinear problem as a sequence of linear problems. Analytical expressions allow a first crude assessment - revealing that the ponderomotive potential plays a role similar to that of the electrostatic potential arising from charge separation - but numerical implementation is required to get a feeling of the full dynamics. A few tentative examples are provided to illustrate the phenomena involved.

  14. Wave induced density modification in RF sheaths and close to wave launchers

    NASA Astrophysics Data System (ADS)

    Van Eester, D.; Crombé, K.; Lu, Ling-Feng

    2015-12-01

    With the return to full metal walls - a necessary step towards viable fusion machines - and due to the high power densities of current-day ICRH (Ion Cyclotron Resonance Heating) or RF (radio frequency) antennas, there is ample renewed interest in exploring the reasons for wave-induced sputtering and formation of hot spots. Moreover, there is experimental evidence on various machines that RF waves influence the density profile close to the wave launchers so that waves indirectly influence their own coupling efficiency. The present study presents a return to first principles and describes the wave-particle interaction using a 2-time scale model involving the equation of motion, the continuity equation and the wave equation on each of the time scales. Through the changing density pattern, the fast time scale dynamics is affected by the slow time scale events. In turn, the slow time scale density and flows are modified by the presence of the RF waves through quasilinear terms. Although finite zero order flows are identified, the usual cold plasma dielectric tensor - ignoring such flows - is adopted as a first approximation to describe the wave response to the RF driver. The resulting set of equations is composed of linear and nonlinear equations and is tackled in 1D in the present paper. Whereas the former can be solved using standard numerical techniques, the latter require special handling. At the price of multiple iterations, a simple 'derivative switch-on' procedure allows to reformulate the nonlinear problem as a sequence of linear problems. Analytical expressions allow a first crude assessment - revealing that the ponderomotive potential plays a role similar to that of the electrostatic potential arising from charge separation - but numerical implementation is required to get a feeling of the full dynamics. A few tentative examples are provided to illustrate the phenomena involved.

  15. Propagation of terahertz waves in an atmospheric pressure microplasma with Epstein electron density profile

    SciTech Connect

    Yuan Chengxun; Zhou Zhongxiang; Zhang, Jingwen W.; Sun Hongguo; Wang He; Du Yanwei; Xiang Xiaoli

    2011-03-15

    Propagation properties of terahertz (THz) waves in a bounded atmospheric-pressure microplasma (AMP) are analyzed in this study. A modified Epstein profile model is used to simulate the electron density distribution caused by the plasma sheaths. By introducing the dielectric constant of a Drude-Lorentz model and using the method of dividing the plasma into a series of subslabs with uniform electron density, the coefficients of power reflection, transmission, and absorption are derived for a bounded microplasma structure. The effects of size of microplasma, electron density profile, and collision frequency on the propagation of THz waves are analyzed numerically. The results indicate that the propagation of THz waves in AMPs depend greatly on the above three parameters. It is demonstrated that the THz wave can play an important role in AMPs diagnostics; meanwhile, the AMP can be used as a novel potential tool to control THz wave propagation.

  16. Experimental observation of standing wave effect in low-pressure very-high-frequency capacitive discharges

    SciTech Connect

    Liu, Yong-Xin; Gao, Fei; Liu, Jia; Wang, You-Nian

    2014-07-28

    Radial uniformity measurements of plasma density were carried out by using a floating double probe in a cylindrical (21 cm in electrode diameter) capacitive discharge reactor driven over a wide range of frequencies (27–220 MHz). At low rf power, a multiple-node structure of standing wave effect was observed at 130 MHz. The secondary density peak caused by the standing wave effect became pronounced and shifts toward the axis as the driving frequency further to increase, indicative of a much more shortened standing-wave wavelength. With increasing rf power, the secondary density peak shift toward the radial edge, namely, the standing-wave wavelength was increased, in good qualitative agreement with the previous theory and simulation results. At higher pressures and high frequencies, the rf power was primarily deposited at the periphery of the electrode, due to the fact that the waves were strongly damped as they propagated from the discharge edge into the center.

  17. Modeling and simulation of pressure waves generated by nano-thermite reactions

    NASA Astrophysics Data System (ADS)

    Martirosyan, Karen S.; Zyskin, Maxim; Jenkins, Charles M.; (Yuki) Horie, Yasuyuki

    2012-11-01

    This paper reports the modeling of pressure waves from the explosive reaction of nano-thermites consisting of mixtures of nanosized aluminum and oxidizer granules. Such nanostructured thermites have higher energy density (up to 26 kJ/cm3) and can generate a transient pressure pulse four times larger than that from trinitrotoluene (TNT) based on volume equivalence. A plausible explanation for the high pressure generation is that the reaction times are much shorter than the time for a shock wave to propagate away from the reagents region so that all the reaction energy is dumped into the gaseous products almost instantaneously and thereby a strong shock wave is generated. The goal of the modeling is to characterize the gas dynamic behavior for thermite reactions in a cylindrical reaction chamber and to model the experimentally measured pressure histories. To simplify the details of the initial stage of the explosive reaction, it is assumed that the reaction generates a one dimensional shock wave into an air-filled cylinder and propagates down the tube in a self-similar mode. Experimental data for Al/Bi2O3 mixtures were used to validate the model with attention focused on the ratio of specific heats and the drag coefficient. Model predictions are in good agreement with the measured pressure histories.

  18. a New Approach of Dynamic Blood Pressure Measurement Based on the Time Domain Analysis of the Pulse Wave

    NASA Astrophysics Data System (ADS)

    Zimei, Su; Wei, Xu; Hui, Yu; Fei, Du; Jicun, Wang; Kexin, Xu

    2009-08-01

    In this study the pulse wave characteristics were used as a new approach to measure the human blood pressure. Based the principle of pulse wave and theory of the elastic vascular, the authors analyzed the characteristic of the pulse waveforms and revealed the characteristics points which could be used to represent the blood pressure. In this investigation the relevant mathematical feature was used to identify the relationship between the blood pressure and pulse wave parameters in a more accurate way. It also provided an experimental basis to carry out continuing non-invasive blood pressure monitoring using the pulse wave method.

  19. On the toroidal plasma rotations induced by lower hybrid waves

    SciTech Connect

    Guan Xiaoyin; Fisch, Nathaniel J.; Qin Hong; Liu Jian

    2013-02-15

    A theoretical model is developed to explain the plasma rotations induced by lower hybrid waves in Alcator C-Mod. In this model, torodial rotations are driven by the Lorentz force on the bulk-electron flow across flux surfaces, which is a response of the plasma to the resonant-electron flow across flux surfaces induced by the lower hybrid waves. The flow across flux surfaces of the resonant electrons and the bulk electrons are coupled through the radial electric field initiated by the resonant electrons, and the friction between ions and electrons transfers the toroidal momentum to ions from electrons. An improved quasilinear theory with gyrophase dependent distribution function is developed to calculate the perpendicular resonant-electron flow. Toroidal rotations are determined using a set of fluid equations for bulk electrons and ions, which are solved numerically by a finite-difference method. Numerical results agree well with the experimental observations in terms of flow profile and amplitude. The model explains the strong correlation between torodial flow and internal inductance observed experimentally, and predicts both counter-current and co-current flows, depending on the perpendicular wave vectors of the lower hybrid waves.

  20. Ballistic quench-induced correlation waves in ultracold gases

    NASA Astrophysics Data System (ADS)

    Corson, John P.; Bohn, John L.

    2016-08-01

    We investigate the wave-packet dynamics of a pair of particles that undergoes a rapid change of scattering length. The short-range interactions are modeled in the zero-range limit, where the quench is accomplished by switching the boundary condition of the wave function at vanishing particle separation. This generates a correlation wave that propagates rapidly to nonzero particle separations. We have derived universal, analytic results for this process that lead to a simple phase-space picture of the quench-induced scattering. Intuitively, the strength of the correlation wave relates to the initial contact of the system. We find that, in one spatial dimension, the k-4 tail of the momentum distribution contains a ballistic contribution that does not originate from short-range pair correlations, and a similar conclusion can hold in other dimensionalities depending on the quench protocol. We examine the resultant quench-induced transport in an optical lattice in one dimension, and a semiclassical treatment is found to give quantitatively accurate estimates for the transport probabilities.

  1. On the Toroidal Plasma Rotations Induced by Lower Hybrid Waves

    SciTech Connect

    Guan, Xiaoyin; Qin, Hong; Liu, Jian; Fisch, Nathaniel J.

    2012-11-14

    A theoretical model is developed to explain the plasma rotations induced by lower hybrid waves in Alcator C-Mod. In this model, torodial rotations are driven by the Lorentz force on the bulk electron flow across flux surfaces, which is a response of the plasma to the resonant-electron flow across flux surfaces induced by the lower hybrid waves. The flow across flux surfaces of the resonant electrons and the bulk electrons are coupled through the radial electric fi eld initiated by the resonant electrons, and the friction between ions and electrons transfers the toroidal momentum to ions from electrons. An improved quasilinear theory with gyrophase dependent distribution function is developed to calculate the perpendicular resonant-electron flow. Toroidal rotations are determined using a set of fluid equations for bulk electrons and ions, which are solved numerically by a fi nite- difference method. Numerical results agree well with the experimental observations in terms of flow pro file and amplitude. The model explains the strong correlation between torodial flow and internal inductance observed experimentally, and predicts both counter-current and co-current flows, depending on the perpendicular wave vectors of the lower hybrid waves. __________________________________________________

  2. The quality of high pressure-induced and heat-induced yuzu marmalade

    NASA Astrophysics Data System (ADS)

    Kuwada, Hiroko; Jibu, Yuri; Teramoto, Ai; Fuchigami, Michiko

    2010-12-01

    Yuzu is a typical Japanese citrus with a desirable smell. The objectives of this study are to establish a process for pressure-induced marmalade (without both heating or the addition of pectin) and compare it with heat-induced marmalade. Sliced peel (flavedo) was soaked in 2% citric acid solution (pH 2.0). Albedo, endocarp and juice sacs were homogenized with 0.3% citric acid solution (pH 2.5). After soaking for 24 h, these were mixed and 50% or 60% sucrose of the total weight was added, then pressurized at 500 MPa or boiled (process A). Process B: all processing was done at pH 2.7. Peel of high pressure-induced marmalade maintained a natural color. Flavedo in heat-induced marmalade was softer than that of pressure-induced marmalade. There was no difference in viscosity between heat-induced and high pressure-induced marmalade. High pressure-induced marmalade with 50% sugar was preferred by a sensory test because fresh flavor and color were maintained.

  3. High-pressure-induced water penetration into 3-isopropylmalate dehydrogenase

    SciTech Connect

    Nagae, Takayuki; Kawamura, Takashi; Chavas, Leonard M. G.; Niwa, Ken; Hasegawa, Masashi; Kato, Chiaki; Watanabe, Nobuhisa

    2012-03-01

    Structures of 3-isopropylmalate dehydrogenase were determined at pressures ranging from 0.1 to 650 MPa. Comparison of these structures gives a detailed picture of the swelling of a cavity at the dimer interface and the generation of a new cleft on the molecular surface, which are accompanied by water penetration. Hydrostatic pressure induces structural changes in proteins, including denaturation, the mechanism of which has been attributed to water penetration into the protein interior. In this study, structures of 3-isopropylmalate dehydrogenase (IPMDH) from Shewanella oneidensis MR-1 were determined at about 2 Å resolution under pressures ranging from 0.1 to 650 MPa using a diamond anvil cell (DAC). Although most of the protein cavities are monotonically compressed as the pressure increases, the volume of one particular cavity at the dimer interface increases at pressures over 340 MPa. In parallel with this volume increase, water penetration into the cavity could be observed at pressures over 410 MPa. In addition, the generation of a new cleft on the molecular surface accompanied by water penetration could also be observed at pressures over 580 MPa. These water-penetration phenomena are considered to be initial steps in the pressure-denaturation process of IPMDH.

  4. Pore-pressure gradients, stresses, and induced earthquakes

    SciTech Connect

    Segall, P. . Geophysics Dept. Geological Survey, Menlo Park, CA )

    1992-01-01

    In the theory of poroelasticity, spatial gradients in pore-pressure enter the equilibrium equations in the same way as distributed body forces. Pore-pressure gradients are thus associated with poroelastic stresses in the same way that temperature gradients associated with thermoelastic stresses. The author has suggested that pore-pressure gradients caused by pumping are responsible for earthquakes near some oil and gas fields. Seismic data from a number of active oil and gas fields in California, Texas, Alberta, and elsewhere clearly show that earthquakes are occurring near fields where pore pressures have declined by several 10's of MPa. These observations can not be explained by changes in effective stress alone, which predicts that decreasing pore-fluid pressures tend to stabilize faults. He believes that poro-elastic stresses resulting from pore-fluid extraction are responsible for earthquakes in these situations. Fluid injection also induces poro-elastic stresses, however it is difficult to separate this effect from the destabilizing effect of increased pore-pressure within fault zones. To test the poroelastic model for induced seismicity, theoretical predictions are compared to data from a deep gas field in the Pyrenean foreland. Hundreds of shallow, small to moderate earthquakes have occurred there since 1969. The earthquakes are tightly clustered near the gas field. Reservoir pressure had declined by 30 MPa at the onset of seismicity. The relationship between average reservoir pressure decline and subsidence is remarkably linear, lending support to the linear poroelastic model. Using laboratory derived material parameters and in situ reservoir pressure measurements, it is possible to predict the surface deformations and the change in stress field without adjustable parameters. The computed vertical displacements are in good agreement with the observed subsidence. The poroelastic stress changes at the onset of seismicity are of the order of a few bars.

  5. Pressure-induced conformational switch of an interfacial protein.

    PubMed

    Johnson, Quentin R; Lindsay, Richard J; Nellas, Ricky B; Shen, Tongye

    2016-06-01

    A special class of proteins adopts an inactive conformation in aqueous solution and activates at an interface (such as the surface of lipid droplet) by switching their conformations. Lipase, an essential enzyme for breaking down lipids, serves as a model system for studying such interfacial proteins. The underlying conformational switch of lipase induced by solvent condition is achieved through changing the status of the gated substrate-access channel. Interestingly, a lipase was also reported to exhibit pressure activation, which indicates it is drastically active at high hydrostatic pressure. To unravel the molecular mechanism of this unusual phenomenon, we examined the structural changes induced by high hydrostatic pressures (up to 1500 MPa) using molecular dynamics simulations. By monitoring the width of the access channel, we found that the protein undergoes a conformational transition and opens the access channel at high pressures (>100 MPa). Particularly, a disordered amphiphilic α5 region of the protein becomes ordered at high pressure. This positive correlation between the channel opening and α5 ordering is consistent with the early findings of the gating motion in the presence of a water-oil interface. Statistical analysis of the ensemble of conformations also reveals the essential collective motions of the protein and how these motions contribute to gating. Arguments are presented as to why heightened sensitivity to high-pressure perturbation can be a general feature of switchable interfacial proteins. Further mutations are also suggested to validate our observations. Proteins 2016; 84:820-827. © 2016 Wiley Periodicals, Inc. PMID:26967808

  6. Irreversibility of pressure induced boron speciation change in glass.

    PubMed

    Smedskjaer, Morten M; Youngman, Randall E; Striepe, Simon; Potuzak, Marcel; Bauer, Ute; Deubener, Joachim; Behrens, Harald; Mauro, John C; Yue, Yuanzheng

    2014-01-01

    It is known that the coordination number (CN) of atoms or ions in many materials increases through application of sufficiently high pressure. This also applies to glassy materials. In boron-containing glasses, trigonal BO3 units can be transformed into tetrahedral BO4 under pressure. However, one of the key questions is whether the pressure-quenched CN change in glass is reversible upon annealing below the ambient glass transition temperature (Tg). Here we address this issue by performing (11)B NMR measurements on a soda lime borate glass that has been pressure-quenched at ~0.6 GPa near Tg. The results show a remarkable phenomenon, i.e., upon annealing at 0.9Tg the pressure-induced change in CN remains unchanged, while the pressurised values of macroscopic properties such as density, refractive index, and hardness are relaxing. This suggests that the pressure-induced changes in macroscopic properties of soda lime borate glasses compressed up to ~0.6 GPa are not attributed to changes in the short-range order in the glass, but rather to changes in overall atomic packing density and medium-range structures. PMID:24442182

  7. Irreversibility of Pressure Induced Boron Speciation Change in Glass

    PubMed Central

    Smedskjaer, Morten M.; Youngman, Randall E.; Striepe, Simon; Potuzak, Marcel; Bauer, Ute; Deubener, Joachim; Behrens, Harald; Mauro, John C.; Yue, Yuanzheng

    2014-01-01

    It is known that the coordination number (CN) of atoms or ions in many materials increases through application of sufficiently high pressure. This also applies to glassy materials. In boron-containing glasses, trigonal BO3 units can be transformed into tetrahedral BO4 under pressure. However, one of the key questions is whether the pressure-quenched CN change in glass is reversible upon annealing below the ambient glass transition temperature (Tg). Here we address this issue by performing 11B NMR measurements on a soda lime borate glass that has been pressure-quenched at ~0.6 GPa near Tg. The results show a remarkable phenomenon, i.e., upon annealing at 0.9Tg the pressure-induced change in CN remains unchanged, while the pressurised values of macroscopic properties such as density, refractive index, and hardness are relaxing. This suggests that the pressure-induced changes in macroscopic properties of soda lime borate glasses compressed up to ~0.6 GPa are not attributed to changes in the short-range order in the glass, but rather to changes in overall atomic packing density and medium-range structures. PMID:24442182

  8. Mechanism of pressure-induced gelation of milk.

    PubMed

    Keenan, R D; Young, D J; Tier, C M; Jones, A D; Underdown, J

    2001-07-01

    The pressure-induced gelation of concentrated skimmed milk and milk-sugar mixtures was studied to discover the main components responsible for gelation. The major protein component responsible for gelation is micellar casein. Gelation occurs at similar pressures to casein micelle disintegration in dilute milk, and both can be prevented by inclusion of excess calcium chloride. Transmission electron micrographs show that the protein network is formed from particles with diameters approximately an order of magnitude smaller than those of intact casein micelles. Gelation occurs on decompression and is found to be baroreversible. Concentrations of sugar up to 30% reduce the critical concentration of casein required for gelation, but higher sugar concentrations inhibit gelation. A mechanism of gelation based on the aggregation of casein submicelles formed by pressure-induced disintegration of casein micelles is proposed. Observations on the effect of sucrose on gelation are discussed in terms of the influence of sugars on the solvent quality in aqueous casein systems. PMID:11453781

  9. Magnetic field induced spin-wave energy focusing

    NASA Astrophysics Data System (ADS)

    Perez, Noel; Lopez-Diaz, Luis

    2015-07-01

    Local temperature variations induced by spin-wave propagation are studied using a model that couples nonuniform magnetization dynamics and heat flow. We show that the remote heating at the sample edge reported recently [T. An et al., Nat. Mater. 12, 549 (2013)], 10.1038/nmat3628 is due to the geometry-induced gradual reduction of the effective field. We demonstrate that the same effect can be achieved by a reduction in the external field instead of a constriction at the edge and, furthermore, that both the location and the amount of energy to be delivered to the lattice can be controlled accurately this way.

  10. Plasma transport induced by kinetic Alfven wave turbulence

    SciTech Connect

    Izutsu, T.; Hasegawa, H.; Fujimoto, M.; Nakamura, T. K. M.

    2012-10-15

    At the Earth's magnetopause that separates the hot-tenuous magnetospheric plasma from the cold dense solar wind plasma, often seen is a boundary layer where plasmas of both origins coexist. Plasma diffusions of various forms have been considered as the cause of this plasma mixing. Here, we investigate the plasma transport induced by wave-particle interaction in kinetic Alfven wave (KAW) turbulence, which is one of the candidate processes. We clarify that the physical origin of the KAW-induced cross-field diffusion is the drift motions of those particles that are in Cerenkov resonance with the wave: E Multiplication-Sign B-like drift that emerges in the presence of non-zero parallel electric field component and grad-B drift due to compressional magnetic fluctuations. We find that KAW turbulence, which has a spectral breakpoint at which an MHD inertial range transits to a dissipation range, causes selective transport for particles whose parallel velocities are specified by the local Alfven velocity and the parallel phase velocity at the spectral breakpoint. This finding leads us to propose a new data analysis method for identifying whether or not a mixed plasma in the boundary layer is a consequence of KAW-induced transport across the magnetopause. The method refers to the velocity space distribution function data obtained by a spacecraft that performs in situ observations and, in principle, is applicable to currently available dataset such as that provided by the NASA's THEMIS mission.

  11. The effects of pressure, temperature, and pore water on velocities in Westerly granite. [for seismic wave propagation

    NASA Technical Reports Server (NTRS)

    Spencer, J. W., Jr.; Nur, A. M.

    1976-01-01

    A description is presented of an experimental assembly which has been developed to conduct concurrent measurements of compressional and shear wave velocities in rocks at high temperatures and confining pressures and with independent control of the pore pressure. The apparatus was used in studies of the joint effects of temperature, external confining pressure, and internal pore water on sonic velocities in Westerly granite. It was found that at a given temperature, confining pressure has a larger accelerating effect on compressional waves in dry rock, whereas at a given confining pressure, temperature has a larger retarding effect on shear waves.

  12. Influence of pore pressure and production-induced changes in pore pressure on in situ stress

    SciTech Connect

    Teufel, L.W.

    1996-02-01

    Knowledge of in situ stress and how stress changes with reservoir depletion and pore pressure drawdown is important in a multi-disciplinary approach to reservoir characterization, reservoir management, and improved oil recovery projects. This report summarizes a compilation of in situ stress data from six fields showing the effects of pore pressure and production-induced changes in pore pressure on the minimum horizontal stress. The in situ stress data and corresponding pore pressure data were obtained from field records of the operating companies and published reports. Horizontal stress was determined from closure pressure data of hydraulic fractures and leak-off tests. The stress measurements clearly demonstrate that the total minimum-horizontal stress is dependent on pore pressure. A decrease in pore pressure either by geologic processes or production of a reservoir will result in a decrease in the total minimum-horizontal stress. The magnitude of changes in stress state with net changes in pore pressure is dependent on local field conditions and cannot be accurately predicted by the uniaxial strain model that is commonly used by the petroleum industry.

  13. Effect of osmolytes on pressure-induced unfolding of proteins: a high-pressure SAXS study.

    PubMed

    Krywka, Christina; Sternemann, Christian; Paulus, Michael; Tolan, Metin; Royer, Catherine; Winter, Roland

    2008-12-22

    Herein, we explore the effect of different types of osmolytes on the high-pressure stability and tertiary structure of a well-characterized monomeric protein, staphylococcal nuclease (SNase). Changes in the denaturation pressure and the radius of gyration are obtained in the presence of different concentrations of trimethylamine N-oxide (TMAO), glycerol and urea. To reveal structural changes in the protein upon compression at various osmolyte conditions, small-angle X-ray scattering (SAXS) experiments were carried out. To this end, a new high-pressure cell suitable for high-precision SAXS studies at synchrotron sources was built, which allows one to carry out scattering experiments up to maximum pressures of about 7 kbar. Our data clearly indicate that the osmolytes that stabilize proteins against temperature-induced unfolding drastically increase their pressure stability and that the elliptically shaped curve of the pressure-temperature-stability diagram of proteins is shifted to higher temperatures and pressures with increasing osmolyte concentration. A drastic stabilization is observed for the osmolyte TMAO, which exhibits not only a significant stabilization against temperature-induced unfolding, but also a particularly strong stabilization of the protein against pressure. In fact, such findings are in accordance with in vivo studies (for example P. J. Yancey, J. Exp. Biol. 2005, 208, 2819-2830), where unusually high TMAO concentrations in some deep-sea animals were found. Conversely, chaotropic agents such as urea have a strong destabilizing effect on both the temperature and pressure stability of the protein. Our data also indicate that sufficiently high TMAO concentrations might be able to largely offset the destabilizing effect of urea. The different scenarios observed are discussed in the context of recent experimental and theoretical studies. PMID:18924198

  14. Pressure-induced phase transformations during femtosecond-laser doping of silicon

    NASA Astrophysics Data System (ADS)

    Smith, Matthew J.; Lin, Yu-Ting; Sher, Meng-Ju; Winkler, Mark T.; Mazur, Eric; Gradečak, Silvija

    2011-09-01

    Silicon hyperdoped with chalcogens via femtosecond-laser irradiation exhibits unique near-unity sub-bandgap absorptance extending into the infrared region. The intense light-matter interactions that occur during femtosecond-laser doping produce pressure waves sufficient to induce phase transformations in silicon, resulting in the formation of metastable polymorphic phases, but their exact formation mechanism and influence on the doping process are still unknown. We report direct observations of these phases, describe their formation and distribution, and consider their potential impact on sub-bandgap absorptance. Specifically, the transformation from diamond cubic Si-I to pressure-induced polymorphic crystal structures (amorphous Si, Si-XII, and Si-III) during femtosecond-laser irradiation was investigated using scanning electron microscopy, Raman spectroscopy, and transmission electron microscopy. Amorphous Si, Si-XII, and Si-III were found to form in femtosecond-laser doped silicon regardless of the presence of a gaseous or thin-film dopant precursor. The rate of pressure loading and unloading induced by femtosecond-laser irradiation kinetically limits the formation of pressure-induced phases, producing regions of amorphous Si 20 to 200 nm in size and nanocrystals of Si-XII and Si-III. The surface texturing that occurs during femtosecond-laser irradiation produces inhomogeneous pressure distributions across the surface and causes delayed development of high-pressure silicon polymorphs over many laser pulses. Finally, we find that the polymorph phases disappear during annealing more rapidly than the sub-bandgap absorptance decreases, enabling us to decouple these two processes through post-treatment annealing.

  15. Development of Laser-induced Grating Spectroscopy for Underwater Temperature Measurement in Shock Wave Focusing Regions

    NASA Technical Reports Server (NTRS)

    Gojani, Ardian B.; Danehy, Paul M.; Alderfer, David W.; Saito, Tsutomu; Takayama, Kazuyoshi

    2003-01-01

    In Extracorporeal Shock Wave Lithotripsy (ESWL) underwater shock wave focusing generates high pressures at very short duration of time inside human body. However, it is not yet clear how high temperatures are enhanced at the spot where a shock wave is focused. The estimation of such dynamic temperature enhancements is critical for the evaluation of tissue damages upon shock loading. For this purpose in the Interdisciplinary Shock Wave Research Center a technique is developed which employs laser induced thermal acoustics or Laser Induced Grating Spectroscopy. Unlike most of gasdynamic methods of measuring physical quantities this provides a non-invasive one having spatial and temporal resolutions of the order of magnitude of 1.0 mm3 and 400 ns, respectively. Preliminary experiments in still water demonstrated that this method detected sound speed and hence temperature in water ranging 283 K to 333 K with errors of 0.5%. These results may be used to empirically establish the equation of states of water, gelatin or agar cells which will work as alternatives of human tissues.

  16. Development of laser-induced grating spectroscopy for underwater temperature measurement in shock wave focusing regions

    NASA Astrophysics Data System (ADS)

    Gojani, Ardian B.; Danehy, Paul M.; Alderfer, David W.; Saito, Tsutomu; Takayama, Kazuyoshi

    2004-02-01

    In Extracorporeal Shock Wave Lithotripsy (ESWL) underwater shock wave focusing generates high pressures at very short duration of time inside human body. However, it is not yet clear how high temperatures are enhanced at the spot where a shock wave is focused. The estimation of such dynamic temperature enhancements is critical for the evaluation of tissue damages upon shock loading. For this purpose in the Interdisciplinary Shock Wave Research Center a technique is developed which employs laser induced thermal acoustics or Laser Induced Grating Spectroscopy. Unlike most of gas-dynamic methods of measuring physical quantities this provides a non-invasive one having spatial and temporal resolutions of the order of magnitude of 1.0 mm 3 and 400 ns, respectively. Preliminary experiments in still water demonstrated that this method detected sound speed and hence temperature in water ranging 283 K to 333 K with errors of 0.5%. These results are used to empirically establish the equation of states of water, gelatin or agar cell which will work as alternatives of human tissues.

  17. A Boussinesq-type model simulating wave and wave-induced current fields

    NASA Astrophysics Data System (ADS)

    Klonaris, Georgios; Memos, Constantine

    2015-04-01

    A two-dimensional high order Boussinesq-type model is developed able to simulate wave propagation in the coastal zone. The model reproduces very accurately the linear dispersion up to the traditional limit of deep water, kd ≈ 3, and it is derived to embed enhanced nonlinear characteristics compared to its weakly nonlinear counterparts. In particular the description of the nonlinear amplitude dispersion is improved over the entire depth range. In order to form an integrated tool the model was extended to the surf and swash zones. The model is also capable of estimating satisfactorily the wave-induced depth-averaged current field. Due to its nonlinear character, this estimation is possible without the need to decouple the wave and current motion as imposed by the traditional spitting method. This capability is of great importance, not only because of the saving of computational time, but also because the wave-current interaction can be also taken into account. In addition, the undertow effect is included in the cross-shore current computations. The model's response to the wave-current interaction is checked through the simulation of a demanding test including a rip channel. In addition, both 1DH and 2DH model's versions were validated against a variety of experimental tests including plane beaches and submerged bars. The agreement, in general, is found fairly good and most of the nearshore phenomena are adequately described.

  18. Pressure-induced phase transformation of In2Se3

    NASA Astrophysics Data System (ADS)

    Rasmussen, Anya; Teklemichael, Samuel; Mafi, Elham; Gu, Yi; McCluskey, Matthew

    2013-06-01

    Phase-change memory, with fast read-write speeds and small dimensions, will soon replace flash memory in our cell phones and tablets. This type of memory relies on phase change materials like indium selenide, In2Se3, a III-VI semiconductor that exists in multiple crystalline phases. To achieve controlled switching between phases, it is important to understand both the thermal and elastic properties of In2Se3. Using synchrotron x-ray diffraction and a diamond-anvil cell, a pressure-induced phase transition in powder In2Se3 from the α phase to β phase was discovered at 0.7 GPa. This pressure is an order of magnitude lower than phase-transition pressures in most semiconductors. Raman spectroscopy experiments confirm this result. The bulk moduli are reported for both α and β phases, and the c / a ratio for the β phase is shown to have a nonlinear dependence on pressure.

  19. Pressure-Induced Order in the Gapped Quantum Magnet DTN

    NASA Astrophysics Data System (ADS)

    Mannig, Alexandra; Moeller, Johannes; Zheludev, Andrey; Garlea, V. Ovidiu; Dela Cruz, Clarina; Guguchia, Zurab; Khasanov, Rustem; Morenzoni, Elvezio

    We present muon-spin relaxation, neutron diffraction and magnetic susceptibility data under applied hydrostatic pressure on the organometallic S = 1 quantum magnet NiCl2 . 4 [ SC(NH2)2 ] . The material consists of weakly coupled antiferromagnetic chains and has a spin gap resulting from a large single-ion anisotropy. Our muon spin rotation experiments provide local field dependencies on temperature as well as pressure and allow for the mapping of a detailed phase diagram up to 22kbar. Thus, we demonstrate that the compound may be driven through two subsequent pressure-induced transitions into apparently distinct magnetically ordered phases. Neutron diffraction and susceptibility measurements support those results and show the potential of low-pressure transitions to be investigated by various techniques.

  20. Increasing pulse wave velocity in a realistic cardiovascular model does not increase pulse pressure with age

    PubMed Central

    Mohiuddin, Mohammad W.; Rihani, Ryan J.; Laine, Glen A.

    2012-01-01

    The mechanism of the well-documented increase in aortic pulse pressure (PP) with age is disputed. Investigators assuming a classical windkessel model believe that increases in PP arise from decreases in total arterial compliance (Ctot) and increases in total peripheral resistance (Rtot) with age. Investigators assuming a more sophisticated pulse transmission model believe PP rises because increases in pulse wave velocity (cph) make the reflected pressure wave arrive earlier, augmenting systolic pressure. It has recently been shown, however, that increases in cph do not have a commensurate effect on the timing of the reflected wave. We therefore used a validated, large-scale, human arterial system model that includes realistic pulse wave transmission to determine whether increases in cph cause increased PP with age. First, we made the realistic arterial system model age dependent by altering cardiac output (CO), Rtot, Ctot, and cph to mimic the reported changes in these parameters from age 30 to 70. Then, cph was theoretically maintained constant, while Ctot, Rtot, and CO were altered. The predicted increase in PP with age was similar to the observed increase in PP. In a complementary approach, Ctot, Rtot, and CO were theoretically maintained constant, and cph was increased. The predicted increase in PP was negligible. We found that increases in cph have a limited effect on the timing of the reflected wave but cause the system to degenerate into a windkessel. Changes in PP can therefore be attributed to a decrease in Ctot. PMID:22561301

  1. Chemical excitation of Limulus photoreceptors. I. Phosphatase inhibitors induce discrete-wave production in the dark

    PubMed Central

    1983-01-01

    Molybdate, tungstate, fluoride, vanadate, and GTP-gamma-S [guanosine-5'- 0-(3-thiotriphosphate)] were injected into Limulus ventral photoreceptors by ionophoresis from microelectrodes. All of these drugs induce discrete waves of depolarization similar in waveform to, but smaller in amplitude than, those normally elicited by dim light. As for light-evoked waves, the amplitude of drug-induced waves decreases with light adaptation. For the compounds examined so far (fluoride, vanadate, GTP-gamma-S), the drug-induced waves share a reversal potential with light-induced discrete waves at about +15 mV. The induction of discrete waves by fluoride, vanadate, and molybdate was found to be reversible, whereas the induction of waves by GTP-gamma-S was not. Unlike fluoride and vanadate, which induce waves when added to the bath, molybdate appears to be ineffective when applied extracellularly. Because of the similarity of the drug-induced waves to light-induced discrete waves, we conclude that the drug-induced waves arise from a process similar or perhaps identical to visual excitation of the photoreceptor. However, the smaller size of drug-induced waves suggests that they arise at a stage of phototransduction subsequent to the isomerization of rhodopsin. On the basis of the chemical properties and action of the drugs, we suggest that discrete waves may arise through the activation of a GTP-binding protein. PMID:6315860

  2. Stress-induced chemical waves in sediment burial diagenesis.

    PubMed

    Wang, Yifeng; Budd, David A

    2012-01-01

    Lateral metre-scale periodic variations in porosity and composition are found in many dolomite strata. Such variations may embed important information about dolomite formation and transformation. Here we show that these variations could be fossilized chemical waves emerging from stress-mediated mineral-water interaction during sediment burial diagenesis. Under the overlying loading, crystals in higher porosity domains are subjected to a higher effective stress, causing pressure solution. The dissolved species diffuse to and precipitate in neighbouring lower porosity domains, further reducing the porosity. This positive feedback leads to lateral porosity and compositional patterning in dolomite. The pattern geometry depends on fluid flow regimes. In a diffusion-dominated case, the low- and high-porosity domains alternate spatially with no directional preference, while, in the presence of an advective flow, this alternation occurs only along the flow direction, propagating like a chemical wave. Our work provides a new perspective for interpreting diagenetic signatures in sedimentary rocks. PMID:22353716

  3. Control and reduction of unsteady pressure loads in separated shock wave turbulent boundary layer interaction

    NASA Technical Reports Server (NTRS)

    Dolling, David S.; Barter, John W.

    1995-01-01

    The focus was on developing means of controlling and reducing unsteady pressure loads in separated shock wave turbulent boundary layer interactions. Section 1 describes how vortex generators can be used to effectively reduce loads in compression ramp interaction, while Section 2 focuses on the effects of 'boundary-layer separators' on the same interaction.

  4. Internal combustion engine supercharging: turbocharger vs. pressure wave compressor. Performance comparison

    NASA Astrophysics Data System (ADS)

    George, Atanasiu; Chiru, Anghel

    2014-06-01

    This paper aims on comparison between a turbocharged engine and a pressure wave charged engine. The comparison was accomplished using the engine simulation software AVL Boost, version 2010. The grahps were extracted using AVL Impress, version 2010. The performance increase is limited by the mechanical side of the simulated engine.

  5. Continuous-wave dye laser pumped by a high-pressure argon arc

    SciTech Connect

    Thiel, E.; Zander, C.; Drexhage, K.

    1988-11-01

    Continuous-wave operation of a Rhodamine 6G dye laser, incoherently pumped by a high-pressure argon arc, has been achieved. A special electrode design reduces melting of the electrode tips, and thus the arc provides the necessary brightness for periods of the order of hours.

  6. Arterial blood pressure measurement and pulse wave analysis--their role in enhancing cardiovascular assessment.

    PubMed

    Avolio, Alberto P; Butlin, Mark; Walsh, Andrew

    2010-01-01

    The most common method of clinical measurement of arterial blood pressure is by means of the cuff sphygmomanometer. This instrument has provided fundamental quantitative information on arterial pressure in individual subjects and in populations and facilitated estimation of cardiovascular risk related to levels of blood pressure obtained from the brachial cuff. Although the measurement is taken in a peripheral limb, the values are generally assumed to reflect the pressure throughout the arterial tree in large conduit arteries. Since the arterial pressure pulse becomes modified as it travels away from the heart towards the periphery, this is generally true for mean and diastolic pressure, but not for systolic pressure, and so pulse pressure. The relationship between central and peripheral pulse pressure depends on propagation characteristics of arteries. Hence, while the sphygmomanometer gives values of two single points on the pressure wave (systolic and diastolic pressure), there is additional information that can be obtained from the time-varying pulse waveform that enables an improved quantification of the systolic load on the heart and other central organs. This topical review will assess techniques of pressure measurement that relate to the use of the cuff sphygmomanometer and to the non-invasive registration and analysis of the peripheral and central arterial pressure waveform. Improved assessment of cardiovascular function in relation to treatment and management of high blood pressure will result from future developments in the indirect measurement of arterial blood pressure that involve the conventional cuff sphygmomanometer with the addition of information derived from the peripheral arterial pulse. PMID:19940350

  7. Pressure fluctuations beneath instability wave packets and turbulent spots in a hypersonic boundary layer

    NASA Astrophysics Data System (ADS)

    Casper, Katya M.

    During atmospheric reentry, hypersonic vehicles are subjected to high levels of boundary-layer pressure fluctuations that cause vibration of internal components. Current models are not adequate to predict these fluctuations. A more physics-based approach can be obtained by using a turbulent-spot model of transition. In order to gain a better understanding of the pressure-fluctuation field and the growth of turbulent spots in a hypersonic boundary layer, the development of disturbances was studied on the nozzle wall of the Boeing/AFOSR Mach-6 Quiet Tunnel. Under quiet flow conditions, the nozzle wall boundary layer remains laminar and grows very thick over the long nozzle length. This allows the development of large disturbances that can be well-resolved with high-frequency pressure transducers. For a controlled study, disturbances were created by pulsed glow perturbations and studied at various freestream conditions. Both the centerline and the spanwise distribution of pressure fluctuations were measured as boundary-layer disturbances grew from linear instability wave packets into turbulent spots. A disturbance first grows into a linear instability wave packet and then quickly becomes nonlinear. At this point, the wave packet is still concentrated near the disturbance centerline, but weaker disturbances are seen spreading from the center. Throughout the nonlinear growth of the wave packets, large harmonics are visible in the power spectra. Breakdown to turbulence begins in the core of the wave packets where the wave amplitudes are largest. As breakdown begins, the peak amplitudes of the instability waves and harmonics decrease into the rising broadband frequencies. Second-mode waves are still evident in front of and behind the breakdown point and can be seen propagating in the spanwise direction at a spreading angle. The turbulent core grows downstream, resulting in a turbulent spot with a typical arrowhead shape. However, the spot is not merely a localized patch

  8. Wave induced velocities inside and outside a riparian seagrass bed.

    NASA Astrophysics Data System (ADS)

    El-Allaoui, N.; Serra, T.; Soler, M.

    2012-04-01

    Coastal wetlands landscapes, such as salt marshes and mangroves, form and evolve by dynamic feedbacks between vegetation establishment, flow hydrodynamics, and landforms changes. The vegetation-flow feedbacks make coastal vegetation very useful for coastal defense against storms and erosion, therefore importance of conservation of both aquatic and riparian vegetation is today commonly recognized. Experiments were carried out in order to study the flow structure within and outside a riparian seagrass bed in a laboratory flume subject to propagating waves. Different canopy densities, vegetation heights and wave frequencies were studied. Experiments were conducted in a 5m-long, 50cm-wide and 50 cm-deep flume equipped with a wave maker. Flow velocity measurements were undertaken with a microADV (Sontek, Inc) in two different points situated in the transversal section of the flume, one within the canopy and the other outside (in the centre of the flume). A mean return current was found in both regions studied (outside and within the vegetation) only for emergent vegetation. The mean current induced within the emergent vegetation was found larger for lower densities and found at the bottom layer of the flume (from the flume bottom to the half of the depth of the water). In contrast, this current was shifted to shallower depths for larger densities (from the half of the flume water up to 4 cm depth). On the other hand, induced current velocities outside the vegetation were found higher for emergent vegetation patterns than for submerged, decreasing the differences when the canopy density increases. For submerged vegetation of different densities similar values of the mean current velocity were found outside the canopy. Within the meadow horizontal wave velocity behavior is independent on both the vegetation density and height, but above the vegetation it appears a clear differentiation, becoming higher the wave velocity in the submerged vegetation case.

  9. Pressure estimation for a low-speed detonation wave in pressed TEN

    SciTech Connect

    Martynyuk, V.F.; Sulimov, A.A.; Sukoyan, M.K.; Obmenin, A.V.

    1988-05-01

    This paper examined the dynamic deformation in steel shells with stationary low-speed detonation propagating in pressed TEN. Shell expansion was recorded with a ZhLV-2 triggered photographic system with the shell seen against a bright screen. The pressure pattern behind the front was shown to be stationary by the constant mode of shell expansion. Pressure in the stationary low-speed detonation was estimated from the photographic data. An expression was derived for calculating the estimated pressure from an equation for radial expansion of the shell. A dynamic deformation pattern was found which was used to calculate the explosive burnup in stationary low-speed detonation waves.

  10. Amplified-response-spectrum analysis of sodium-water reaction pressure waves. [LMFBR

    SciTech Connect

    Knittle, D.E.

    1981-10-28

    This report deals with a frequency spectrum evaluation of the SWAAM I predicted double rupture disc assembly operation pressure wave generated in the LLTR Series II A-2 test. It also evaluates the same wave predicted by the TRANSWRAP II code and the pressure wave actually measured upstream of the rupture disc assembly by the test instrumentation in Test A-2. The SWAAM I and TRANSWRAP II codes currently use the same analytical model to characterize the rupture disc until the disc strikes the knife edges. Thereafter, the SWAAM I code relies on analytical techniques to characterize the phenomena, whereas the TRANSWRAP II code uses empirical parameters based on A-2 test data to represent the disc behavior. Any differences in the predicted dynamic pipe loads caused by double rupture disc assembly operation, using the forcing functions predicted by the codes can, therefore, be traced to this difference.

  11. Effect of the dynamic pressure on the shock wave structure in a rarefied polyatomic gas

    SciTech Connect

    Taniguchi, Shigeru Sugiyama, Masaru; Arima, Takashi; Ruggeri, Tommaso

    2014-01-15

    We study the shock wave structure in a rarefied polyatomic gas based on a simplified model of extended thermodynamics in which the dissipation is due only to the dynamic pressure. In this case the differential system is very simple because it is a variant of Euler system with a new scalar equation for the dynamic pressure [T. Arima, S. Taniguchi, T. Ruggeri, and M. Sugiyama, Phys. Lett. A 376, 2799–2803 (2012)]. It is shown that this theory is able to describe the three types of the shock wave structure observed in experiments: the nearly symmetric shock wave structure (Type A, small Mach number), the asymmetric structure (Type B, moderate Mach number), and the structure composed of thin and thick layers (Type C, large Mach number)

  12. Three-dimensional visualization of shear wave propagation generated by dual acoustic radiation pressure

    NASA Astrophysics Data System (ADS)

    Mochizuki, Yuta; Taki, Hirofumi; Kanai, Hiroshi

    2016-07-01

    An elastic property of biological soft tissue is an important indicator of the tissue status. Therefore, quantitative and noninvasive methods for elasticity evaluation have been proposed. Our group previously proposed a method using acoustic radiation pressure irradiated from two directions for elastic property evaluation, in which by measuring the propagation velocity of the shear wave generated by the acoustic radiation pressure inside the object, the elastic properties of the object were successfully evaluated. In the present study, we visualized the propagation of the shear wave in a three-dimensional space by the synchronization of signals received at various probe positions. The proposed method succeeded in visualizing the shear wave propagation clearly in the three-dimensional space of 35 × 41 × 4 mm3. These results show the high potential of the proposed method to estimate the elastic properties of the object in the three-dimensional space.

  13. Ultrafast high strain rate acoustic wave measurements at high static pressure in a diamond anvil cell

    SciTech Connect

    Armstrong, M; Crowhurst, J; Reed, E; Zaug, J

    2008-02-04

    We have used sub-picosecond laser pulses to launch ultra-high strain rate ({approx} 10{sup 9} s{sup -1}) nonlinear acoustic waves into a 4:1 methanol-ethanol pressure medium which has been precompressed in a standard diamond anvil cell. Using ultrafast interferometry, we have characterized acoustic wave propagation into the pressure medium at static compression up to 24 GPa. We find that the velocity is dependent on the incident laser fluence, demonstrating a nonlinear acoustic response which may result in shock wave behavior. We compare our results with low strain, low strain-rate acoustic data. This technique provides controlled access to regions of thermodynamic phase space that are otherwise difficult to obtain.

  14. Turbulence modeling for sharp-fin-induced shock wave/turbulent boundary-layer interactions

    NASA Technical Reports Server (NTRS)

    Horstman, C. C.

    1990-01-01

    Solutions of the Reynolds averaged Navier-Stokes equations are presented and compared with a family of experimental results for the 3-D interaction of a sharp fin induced shock wave with a turbulent boundary layer. Several algebraic and two equation eddy viscosity turbulence models are employed. The computed results are compared with experimental surface pressure, skin friction, and yaw angle data as well as the overall size of the interaction. Although the major feature of the flow fields are correctly predicted, several discrepancies are noted. Namely, the maximum skin friction values are significantly underpredicted for the strongest interaction cases. These and other deficiencies are discussed.

  15. Interface motion and nucleation of solid helium-4 induced by acoustic waves.

    PubMed

    Nomura, R; Suzuki, Y; Kimura, S; Okuda, Y

    2003-02-21

    Crystallization and melting of helium-4 was experimentally observed to be induced by acoustic radiation pressure where the liquid-solid interface is highly mobile at low temperatures. We discuss the observed anomalous reversal of this effect as a function of temperature and the nucleation by acoustic wave pulses of crystals in the liquid phase or liquid bubbles in the solid phase. A high-speed camera was used for the in situ observation of large interface velocities as high as 1 m/sec. PMID:12633239

  16. Shock wave induced phase transition in α -FePO 4

    NASA Astrophysics Data System (ADS)

    Joshi, K. D.; Suresh, N.; Jyoti, G.; Kulshreshtha, S. K.; Gupta, S. C.; Sikka, S. K.

    Shock wave induced response of the berlinite form of FePO 4 has been investigated up to 8.5 GPa. The X-ray diffraction measurements on the shock recovered samples reveal transition to the mixture of an amorphous phase and an orthorhombic phase around 5 GPa. The proportion of the amorphous material in the recovered sample is found to decrease at higher pressure. The results are interpreted in terms of a three-level free energy diagram for the crystal to amorphous transitions.

  17. Impact-induced shock pressure distribution in a heterogeneous planetary interior

    NASA Astrophysics Data System (ADS)

    Arkani-Hamed, J.

    2012-12-01

    The shock pressure distribution inside planetary interiors has been investigated on the basis of scaling laws [1,2] and using numerical hydrocode models [2,3]. Here I present a new shock ray formulations derived on the basis of the Hugoniot equations to calculate the impact-induced shock pressure distribution inside heterogeneous terrestrial planets with radially varying physical parameters both in the solid mantle and in the underlying liquid core. Considering a single vertical impact, the formulations are derived in an axi-symmetric spherical coordinate system where the impact is assumed to occur at the north pole. In previous studies the scaling laws of shock pressure distribution [5] have been used to determine the impact heating of the planetary interiors by direct shock waves [2]. Because the main concern was the impact heating of the core, the heating of the antipodal region of the mantle was not investigated. The present study not only considers the impact heating of the entire planetary mantle by direct shock waves but also investigates the effects of the reflected shock waves inside the core. The direct shockwave propagating southward in the core intersects the core mantle boundary in the antipodal region where it partly transmits to the mantle and partly reflects back into the core. Both transmitted and reflected waves converge toward the axis of symmetry and create strong shock pressure near the axis in the antipodal region. Consequently, the antipodal region is significantly heated. In particular, the antipodal region of the core is heated twice, first by the direct shock wave as it propagates southward, and second by the reflected waves which actually increases in intensity close to the axis of symmetry. This feature has been demonstrated by the hydrocode models [3,4] but not by the scaling models based on direct shock wave propagation [1]. The new algorithm is applied to the impact heating of Mars, and the results are compared with those determined

  18. Giant Deformations of a Liquid-Liquid Interface Induced by the Optical Radiation Pressure

    SciTech Connect

    Casner, Alexis; Delville, Jean-Pierre

    2001-07-30

    Because of the small momentum of photons, very intense fields are generally required to bend a liquid interface with the optical radiation pressure. We explore this issue in a near-critical phase-separated liquid mixture to vary continuously the meniscus softness by tuning the temperature. Low power continuous laser waves become sufficient to induce huge stationary bulges. Using the beam size to build an ''optical'' Bond number, Bo , we investigate the crossover from low to large Bo . The whole set of data collapses onto a single master curve which illustrates the universality of the phenomenon.

  19. A New Mechanism for Pore Pressure Changes Induced by Distant Earthquakes

    NASA Astrophysics Data System (ADS)

    Brodsky, E. E.; Roeloffs, E.; Woodcock, D.; Gall, I.; Manga, M.

    2001-12-01

    Observations during the Mw=7.3 1992 Landers earthquake, Mw=7.4 Izmit earthquake and Mw=7.2 Hector Mine earthquake suggest that seismicity is triggered hundreds of kilometers from a mainshock epicenter. This puzzling phenomenon is not explained by traditional elastic models of seismic stresses. The fact that the triggered sites are often geothermal or magmatic suggests that fluids may be an important part of the triggering process. Rapid changes in pore pressure either reduce the effective stress on faults locally or prompt hydrofracturing to initiate local earthquakes. The challenge is to discover how the seismic waves generate a change in pore fluid pressure. We constrain a mechanism for seismically-induced pore pressure changes by studying coseismic water level drops at a well in Grants Pass, Oregon. Water level drops at the site have been associated with earthquakes for nearly 20 years. High-sample rate (up to 1 Hz) digital water level data is available for the two coseismic drops that have occurred since 1994. The approach of this study is to use the amplification of the seismic waves in the well to constrain variations of the aquifer properties during the water level drops. We find that the amplification of the seismic waves in the well is consistent with standard theory for 7 digitally recorded events without drops, but during an earthquake with a drop a dramatic change in amplification occurs during the passage of the Rayleigh waves. The change in amplification indicates that the transmissivity increases by a factor of 50 during the 11 cm coseismic water level drop accompanying the 1999 Mw=7.5 1999 Oaxaca, Mexico earthquake. Based on these observations, we propose a new model for coseismic pore pressure changes. Drops occur if an earthquake occurs when the well has become temporarily clogged by a solid precipitate or sediment. The seismic shaking induces a flow which removes the obstruction. Once a barrier is removed, water flows rapidly to generate dramatic

  20. Effects of Shelves on Amplification of Long Waves Generated by Atmospheric Pressure Differences

    NASA Astrophysics Data System (ADS)

    Duha Metin, Ayse; Cevdet Yalciner, Ahmet; Ozyurt Tarakcıoglu, Gulizar; Zaytsev, Andrey

    2016-04-01

    Meteotsunami is a type of long period ocean wave generated by different types of meteorological disturbances such as atmospheric gravity waves, spatial and temporal pressure distributions and squall lines. The main idea behind the occurrence of this type of long wave is that low atmospheric pressure leads to static water level rise in a part of the marine area and high atmospheric pressure leads to static water level drop in another zone. Then, it causes deformation of the water level throughout the entire sea area. The relation between the pressure difference and change of water level from normal position (η =0.99Δ P where η is the water level change (cm) according to the pressure difference from normal pressure Δ P) can be used to determine the sea level deformation. The relation represents that 1 hPa decrease in air pressure causes 1 cm rise in mean sea level. Due to the spatial and temporal changes of atmospheric pressure, the respective small amplitude long waves propagate along the entire marine area. This type of tsunami-like waves can propagate through long distances and can also be amplified due to resonant effects in the enclosed basins, offshore shelves, and nearshore/offshore coastal morphology. Therefore, it can result in considerable amplifications and causes unexpected effects in some coastal regions. This study is mainly focused on understanding of amplification of long waves generated by atmospheric pressure differences when they encounter the offshore shelves while it is propagating towards to the shore. The problem is investigated by numerically solving nonlinear shallow water equations by using regular shaped basins with different depth and shelf characteristics. In all cases, the rectangular shape large basin is triggered by spatial and temporal distributions of atmospheric pressure. The water depth and shelf formation is changed for different cases. Initially, a deep flat bottom basin is used in simulations and the reference data of water

  1. Shock-wave-induced fracturing of calcareous nannofossils from the Chesapeake Bay impact crater

    USGS Publications Warehouse

    Self-Trail J.M.

    2003-01-01

    Fractured calcareous nannofossils of the genus Discoaster from synimpact sediments within the Chesapeake Bay impact crater demonstrate that other petrographic shock indicators exist for the cratering process in addition to quartz minerals. Evidence for shock-induced taphonomy includes marginal fracturing of rosette-shaped Discoaster species into pentagonal shapes and pressure- and temperature-induced dissolution of ray tips and edges of discoasters. Rotational deformation of individual crystallites may be the mechanism that produces the fracture pattern. Shock-wave-fractured calcareous nannofossils were recovered from synimpact matrix material representing tsunami or resurge sedimentation that followed impact. Samples taken from cohesive clasts within the crater rubble show no evidence of shock-induced fracturing. The data presented here support growing evidence that microfossils can be used to determine the intensity and timing of wet-impact cratering.

  2. Dynamic Modelling of Fault Slip Induced by Stress Waves due to Stope Production Blasts

    NASA Astrophysics Data System (ADS)

    Sainoki, Atsushi; Mitri, Hani S.

    2016-01-01

    Seismic events can take place due to the interaction of stress waves induced by stope production blasts with faults located in close proximity to stopes. The occurrence of such seismic events needs to be controlled to ensure the safety of the mine operators and the underground mine workings. This paper presents the results of a dynamic numerical modelling study of fault slip induced by stress waves resulting from stope production blasts. First, the calibration of a numerical model having a single blast hole is performed using a charge weight scaling law to determine blast pressure and damping coefficient of the rockmass. Subsequently, a numerical model of a typical Canadian metal mine encompassing a fault parallel to a tabular ore deposit is constructed, and the simulation of stope extraction sequence is carried out with static analyses until the fault exhibits slip burst conditions. At that point, the dynamic analysis begins by applying the calibrated blast pressure to the stope wall in the form of velocities generated by the blast holes. It is shown from the results obtained from the dynamic analysis that the stress waves reflected on the fault create a drop of normal stresses acting on the fault, which produces a reduction in shear stresses while resulting in fault slip. The influence of blast sequences on the behaviour of the fault is also examined assuming several types of blast sequences. Comparison of the blast sequence simulation results indicates that performing simultaneous blasts symmetrically induces the same level of seismic events as separate blasts, although seismic energy is more rapidly released when blasts are performed symmetrically. On the other hand when nine blast holes are blasted simultaneously, a large seismic event is induced, compared to the other two blasts. It is concluded that the separate blasts might be employed under the adopted geological conditions. The developed methodology and procedure to arrive at an ideal blast sequence can

  3. Continuous blood pressure monitoring during exercise using pulse wave transit time measurement.

    PubMed

    Lass, J; Meigas, K; Karai, D; Kattai, R; Kaik, J; Rossmann, M

    2004-01-01

    This paper gives an overview of a research, which is focused on the development of the convenient device for continuous non-invasive monitoring of arterial blood pressure. The blood pressure estimation method is based on a presumption that there is a singular relationship between the pulse wave propagation time in arterial system and blood pressure. The parameter used in this study is pulse wave transit time (PWTT). The measurement of PWTT involves the registration of two time markers, one of which is based on ECG R peak detection and another on the detection of pulse wave in peripheral arteries. The reliability of beat to beat systolic blood pressure calculation during physical exercise was the main focus for the current paper. Sixty-one subjects (healthy and hypertensive) were studied with the bicycle exercise test. As a result of current study it is shown that with the correct personal calibration it is possible to estimate the beat to beat systolic arterial blood pressure during the exercise with comparable accuracy to conventional noninvasive methods. PMID:17272172

  4. Experimental Study on a Standing Wave Thermoacoustic Prime Mover with Air Working Gas at Various Pressures

    NASA Astrophysics Data System (ADS)

    Setiawan, Ikhsan; Achmadin, Wahyu N.; Murti, Prastowo; Nohtomi, Makoto

    2016-04-01

    Thermoacoustic prime mover is an energy conversion device which converts thermal energy into acoustic work (sound wave). The advantages of this machine are that it can work with air as the working gas and does not produce any exhaust gases, so that it is environmentally friendly. This paper describes an experimental study on a standing wave thermoacoustic prime mover with air as the working gas at various pressures from 0.05 MPa to 0.6 MPa. We found that 0.2 MPa is the optimum pressure which gives the lowest onset temperature difference of 355 °C. This pressure value would be more preferable in harnessing low grade heat sources to power the thermoacoustic prime mover. In addition, we find that the lowest onset temperature difference is obtained when rh /δ k ratio is 2.85, where r h is the hydraulic radius of the stack and δ k is the thermal penetration depth of the gas. Moreover, the pressure amplitude of the sound wave is significantly getting larger from 2.0 kPa to 9.0 kPa as the charged pressure increases from 0.05 MPa up to 0.6 MPa.

  5. Dynamics of quantum-classical hybrid systems: Effect of matter-wave pressure

    SciTech Connect

    Shen, J.; Huang, X. L.; Yi, X. X.; Wu Chunfeng; Oh, C. H.

    2010-12-15

    Radiation pressure affects the kinetics of a system exposed to radiation and it constitutes the basis of laser cooling. In this article, we study matter-wave pressure through examining the dynamics of a quantum-classical hybrid system. The quantum and classical subsystems are affected mutually via a changing boundary condition. Two systems, that is, an atom and a Bose-Einstein condensate (BEC), are considered as the quantum subsystems, while an oscillating wall is taken as the classical subsystem. We show that the classical subsystem would experience a force proportional to Q{sup -3} from the quantum atom, where Q denotes the distance between the two walls, whereas it acquires an additional force proportional to Q{sup -2} from the BEC due to the atom-atom interaction in the BEC. These forces can be understood as the matter-wave pressure.

  6. Measurement of the normal component of compressive wave pressure in a rock with Manganin sensors

    SciTech Connect

    Virchenko, V.A.; Egorov, A.P.; Krasavin, S.V.

    1985-03-01

    Measurement of dynamic pressures in compressed media with manganin wire sensors has become common in the past few years. The increased interest in this method is due to the technological simplicity of measurement and the ease of manufacturing the manganin pickup. The method has been continually improved and put to new applications. In this paper the authors describe an experiment using manganin sensors to measure the normal component of a compressive pressure wave in rocks (marble, schist, and diabase) generated by industrial blasts. Subtle effects not previously identified include: decomposition of the shockwave in the rock and identification of an elastic precursor; features of damping of the normal component of compressive wave pressure as a function of distance from the load application point; and the pattern of destruction of brittle materials. The authors conclude that manganin sensors can be broadly applied in mining for studies of the efficacy of various types of explosives and in investigations of the mechanism of rock destruction.

  7. Chiral primordial gravitational waves from dilaton induced delayed chromonatural inflation

    NASA Astrophysics Data System (ADS)

    Obata, Ippei; Soda, Jiro; CLEO Collaboration

    2016-06-01

    We study inflation driven by a dilaton and an axion, both of which are coupled to a SU(2) gauge field. We find that the inflation driven by the dilaton occurs in the early stage of inflation during which the gauge field grows due to the gauge-kinetic function. When the energy density of magnetic fields catches up with that of electric fields, chromonatural inflation takes over in the late stage of inflation, which we call delayed chromonatural inflation. Thus, the delayed chromonatural inflation driven by the axion and the gauge field is induced by the dilaton. The interesting outcome of the model is the generation of chiral primordial gravitational waves on small scales. Since the gauge field is inert in the early stage of inflation, it is viable in contrast to the conventional chromonatural inflation. We find the parameter region where chiral gravitational waves are generated in a frequency range higher than nHz, which are potentially detectable in future gravitational wave interferometers and pulsar-timing arrays such as DECi-hertz Interferometer Gravitational wave Observatory (DECIGO), evolved Laser Interferometer Space Antenna (eLISA), and Square Kilometer Array (SKA).

  8. Analysis of Wave Fields induced by Offshore Pile Driving

    NASA Astrophysics Data System (ADS)

    Ruhnau, M.; Heitmann, K.; Lippert, T.; Lippert, S.; von Estorff, O.

    2015-12-01

    Impact pile driving is the common technique to install foundations for offshore wind turbines. With each hammer strike the steel pile - often exceeding 6 m in diameter and 80 m in length - radiates energy into the surrounding water and soil, until reaching its targeted penetration depth. Several European authorities introduced limitations regarding hydroacoustic emissions during the construction process to protect marine wildlife. Satisfying these regulations made the development and application of sound mitigation systems (e.g. bubble curtains or insulation screens) inevitable, which are commonly installed within the water column surrounding the pile or even the complete construction site. Last years' advances have led to a point, where the seismic energy tunneling the sound mitigation systems through the soil and radiating back towards the water column gains importance, as it confines the maximum achievable sound mitigation. From an engineering point of view, the challenge of deciding on an effective noise mitigation layout arises, which especially requires a good understanding of the soil-dependent wave field. From a geophysical point of view, the pile acts like a very unique line source, generating a characteristic wave field dominated by inclined wave fronts, diving as well as head waves. Monitoring the seismic arrivals while the pile penetration steadily increases enables to perform quasi-vertical seismic profiling. This work is based on datasets that have been collected within the frame of three comprehensive offshore measurement campaigns during pile driving and demonstrates the potential of seismic arrivals induced by pile driving for further soil characterization.

  9. Evidence of the Correspondence of EIT Waves and Coronal Mass Ejections Induced Waves Using a Three-Dimensional Magnetohydrodynamic Simulation

    NASA Astrophysics Data System (ADS)

    Wu, S. T.; Wu, C.-C.; Liou, K.

    2013-04-01

    Before the discovery of EIT waves and coronal mass ejections (CMEs) it was already known that Moreton waves were observed to propagate across the solar disk during some solar flares. This magnetohydrodynamic wave was explained as the intersecting line between the edge of an expanding global coronal wavefront and the chromosphere (Uchida, 1968) where Uchida concluded that the Moreton wave was a fast mode MHD wave. In this presentation, we will show that the EIT wave could be a part of a CME induced wave propagating across the solar disk. To illustrate this scenario, we have employed a global 3D MHD model (Wu et al. 2001) to simulate this phenomenon for the May 12, 1997 event which was an Earth-directed CME observed by SOHO/EIT (Thompson et al. 1998). To carry out this simulation, the measured global magnetic fields obtained from the Stanford University Wilcox Solar Observatory (WSO) were used as the inputs to the simulation model. We were able to show that the scenario suggested by Uchida (1968), namely, the observed EIT wave propagating across the solar disk could be caused by the intersection line between the edge of an expanding CME induced wave front and the chromosphere. In addition to the flare source scenario, we concluded that an EIT (or EUV) wave can also be a part of a flare induced coronal wave with its foot print on the Sun's surface.

  10. Comparison of actinide production in traveling wave and pressurized water reactors

    SciTech Connect

    Osborne, A.G.; Smith, T.A.; Deinert, M.R.

    2013-07-01

    The geopolitical problems associated with civilian nuclear energy production arise in part from the accumulation of transuranics in spent nuclear fuel. A traveling wave reactor is a type of breed-burn reactor that could, if feasible, reduce the overall production of transuranics. In one possible configuration, a cylinder of natural or depleted uranium would be subjected to a fast neutron flux at one end. The neutrons would transmute the uranium, producing plutonium and higher actinides. Under the right conditions, the reactor could become critical, at which point a self-stabilizing fission wave would form and propagate down the length of the reactor cylinder. The neutrons from the fission wave would burn the fissile nuclides and transmute uranium ahead of the wave to produce additional fuel. Fission waves in uranium are driven largely by the production and fission of {sup 239}Pu. Simulations have shown that the fuel burnup can reach values greater than 400 MWd/kgIHM, before fission products poison the reaction. In this work we compare the production of plutonium and minor actinides produced in a fission wave to that of a UOX fueled light water reactor, both on an energy normalized basis. The nuclide concentrations in the spent traveling wave reactor fuel are computed using a one-group diffusion model and are verified using Monte Carlo simulations. In the case of the pressurized water reactor, a multi-group collision probability model is used to generate the nuclide quantities. We find that the traveling wave reactor produces about 0.187 g/MWd/kgIHM of transuranics compared to 0.413 g/MWd/kgIHM for a pressurized water reactor running fuel enriched to 4.95 % and burned to 50 MWd/kgIHM. (authors)

  11. Pressure fluctuations beneath turbulent spots and instability wave packets in a hypersonic boundary layer.

    SciTech Connect

    Beresh, Steven Jay; Casper, Katya M.; Schneider, Steven P.

    2010-12-01

    The development of turbulent spots in a hypersonic boundary layer was studied on the nozzle wall of the Boeing/AFOSR Mach-6 Quiet Tunnel. Under quiet flow conditions, the nozzle wall boundary layer remains laminar and grows very thick over the long nozzle length. This allows the development of large turbulent spots that can be readily measured with pressure transducers. Measurements of naturally occurring wave packets and developing turbulent spots were made. The peak frequencies of these natural wave packets were in agreement with second-mode computations. For a controlled study, the breakdown of disturbances created by spark and glow perturbations were studied at similar freestream conditions. The spark perturbations were the most effective at creating large wave packets that broke down into turbulent spots. The flow disturbances created by the controlled perturbations were analyzed to obtain amplitude criteria for nonlinearity and breakdown as well as the convection velocities of the turbulent spots. Disturbances first grew into linear instability waves and then quickly became nonlinear. Throughout the nonlinear growth of the wave packets, large harmonics are visible in the power spectra. As breakdown begins, the peak amplitudes of the instability waves and harmonics decrease into the rising broad-band frequencies. Instability waves are still visible on either side of the growing turbulent spots during this breakdown process.

  12. Pressure-induced phase transitions in GeS under high pressures

    NASA Astrophysics Data System (ADS)

    Dias, Ranga; Yoo, Choong-Shik

    2012-02-01

    We have studied the pressure-induced structural and electronic phase transitions of layered GeS (Pnma) to 30 GPa, using micro-Raman spectroscopy and electrical resistivity measurements in diamond anvil cells. The result shows a steady decrease in resistivity to that of metal at around 18 GPa. The visual appearance of GeS supports the insulator-metal transition: initially black GeS becomes opaque and eventually reflective with increasing pressure. The Raman result indicates that the metallization is preceded by a structural phase transition, presumably to the previously predicted Cmcm structure.

  13. Induced movements of giant vesicles by millimeter wave radiation.

    PubMed

    Albini, Martina; Dinarelli, Simone; Pennella, Francesco; Romeo, Stefania; Zampetti, Emiliano; Girasole, Marco; Morbiducci, Umberto; Massa, Rita; Ramundo-Orlando, Alfonsina

    2014-07-01

    Our previous study of interaction between low intensity radiation at 53.37GHz and cell-size system - such as giant vesicles - indicated that a vectorial movement of vesicles was induced. This effect among others, i.e. elongation, induced diffusion of fluorescent dye di-8-ANEPPS, and increased attractions between vesicles was attributed to the action of the field on charged and dipolar residues located at the membrane-water interface. In an attempt to improve the understanding on how millimeter wave radiation (MMW) can induce this movement we report here a real time evaluation of changes induced on the movement of giant vesicles. Direct optical observations of vesicles subjected to irradiation enabled the monitoring in real time of the response of vesicles. Changes of the direction of vesicle movement are demonstrated, which occur only during irradiation with a "switch on" of the effect. This MMW-induced effect was observed at a larger extent on giant vesicles prepared with negatively charged phospholipids. The monitoring of induced-by-irradiation temperature variation and numerical dosimetry indicate that the observed effects in vesicle movement cannot be attributed to local heating. PMID:24704354

  14. Gravity-wave induced CO2 clouds on Mars

    NASA Astrophysics Data System (ADS)

    Yiǧit, Erdal; Medvedev, Alexander S.; Hartogh, Paul

    2016-07-01

    We present the first general circulation model simulations that quantify and reproduce patches of extremely cold air required for CO2 condensation and cloud formation in the Martian mesosphere. They are created by subgrid-scale gravity waves (GWs) accounted for in the model with the whole atmosphere GW parameterization of Yiǧit et al. (2008)}. Distributions of GW-induced temperature fluctuations and occurrences of supersaturation conditions are in a good agreement with observations of high-altitude CO2 ice clouds. Our study confirms the key role of GWs in facilitating CO2 cloud formation, discusses their tidal modulation, and predicts clouds at altitudes higher than have been observed to date. Reference: Yiǧit, E., A. D. Aylward, and A. S. Medvedev (2008), Parameterization of the effects of vertically propagating gravity waves for thermosphere general circulation models: Sensitivity study, J. Geophys. Res., 113, D19106, doi:10.1029/2008JD010135.

  15. Thermal-hydraulic behaviors of vapor-liquid interface due to arrival of a pressure wave

    SciTech Connect

    Inoue, Akira; Fujii, Yoshifumi; Matsuzaki, Mitsuo

    1995-09-01

    In the vapor explosion, a pressure wave (shock wave) plays a fundamental role for triggering, propagation and enhancement of the explosion. Energy of the explosion is related to the magnitude of heat transfer rate from hot liquid to cold volatile one. This is related to an increasing rate of interface area and to an amount of transient heat flux between the liquids. In this study, the characteristics of transient heat transfer and behaviors of vapor film both on the platinum tube and on the hot melt tin drop, under same boundary conditions have been investigated. It is considered that there exists a fundamental mechanism of the explosion in the initial expansion process of the hot liquid drop immediately after arrival of pressure wave. The growth rate of the vapor film is much faster on the hot liquid than that on the solid surface. Two kinds of roughness were observed, one due to the Taylor instability, by rapid growth of the explosion bubble, and another, nucleation sites were observed at the vapor-liquid interface. Based on detailed observation of early stage interface behaviors after arrival of a pressure wave, the thermal fragmentation mechanism is proposed.

  16. The dynamics of pressure and form drag on a sloping headland: Internal waves versus eddies

    NASA Astrophysics Data System (ADS)

    Warner, Sally J.; MacCready, Parker

    2014-03-01

    Topographically generated eddies and internal waves have traditionally been studied separately even though bathymetry that creates both phenomena is abundant in coastal regions. Here a numerical model is used to understand the dynamics of eddy and wave generation as tidal currents flow past Three Tree Point, a 1 km long, 200 m deep, sloping headland in Puget Sound, WA. Bottom pressure anomalies due to vertical perturbations of the sea surface and isopycnals are used to calculate form drag in different regions of the topography to assess the relative importance of eddies versus internal waves. In regions where internal waves dominate, sea surface and isopycnal perturbations tend to work together to create drag, whereas in regions dominated by eddies, sea surface, and isopycnal perturbations tend to counteract each other. Both phenomena are found to produce similar amounts of form drag even though the bottom pressure anomalies from the eddy have much larger magnitudes than those created by the internal waves. Topography like Three Tree Point is common in high latitude, coastal regions, and therefore the findings here have implications for understanding how coastal topography removes energy from tidal currents.

  17. Direct analysis of dispersive wave fields from near-field pressure measurements.

    PubMed

    Hörchens, Lars

    2011-10-01

    Flexural waves play a significant role for the radiation of sound from plates. The analysis of flexural wave fields enables the detection of sources and transmission paths in plate-like structures. The measurement of these wave fields can be carried out indirectly by means of near-field acoustic holography, which determines the vibrational wave field from pressure information measured in a plane close to the plate under investigation. The reconstruction of the plate vibration is usually obtained by inverting the forward radiation problem, i.e., by inversion of an integral operator. In this article, it is shown that a pressure measurement taken in the extreme near-field of a vibrating plate can directly be used for the approximate analysis of the dispersive flexural wave field. The inversion step of near-field acoustic holography is not necessarily required if such an approximate solution is sufficient. The proposed method enables fast and simple analysis of dispersion characteristics. Application of dispersion compensation to the measured field allows for visualizations of propagating wavefronts, such that sources and scatterers in the plate can be detected. The capabilities of the described approach are demonstrated on several measurements. PMID:21973358

  18. Carbon dioxide pressure-induced coagulation of microalgae.

    PubMed

    Lee, Roland; Jessop, Philip G; Champagne, Pascale

    2015-12-28

    The move to a low-carbon economy has generated renewed interest in microalgae for the production of biofuels with the potential mutual benefit of wastewater treatment. However, harvesting has been identified as a limiting factor to the economic viability of this process. This paper explores the harvesting of microalgae using high-pressure gas without the addition of coagulants. Coagulation of microalgae under high-pressure gas was found to be an efficient method to separate algae from suspension. The critical coagulation pressures (CCPs) for H(2) and CO(2) were determined to be 6.1 and 6.2 MPa, respectively. The CO(2)-induced decrease in solution pH positively influenced coagulation rates, without appearing to affect the CCP. This approach could be beneficial for the economic removal of microalgae from solution for the production of both biofuels and biomedical compounds without the addition of non-environmentally friendly chemicals. PMID:26574522

  19. Atomistic pathways of the pressure-induced densification of quartz

    NASA Astrophysics Data System (ADS)

    Liang, Yunfeng; Miranda, Caetano R.; Scandolo, Sandro

    2015-10-01

    When quartz is compressed at room temperature it retains its crystal structure at pressures well above its stability domain (0-2 GPa), and collapses into denser structures only when pressure reaches 20 GPa. Depending on the experimental conditions, pressure-induced densification can be accompanied by amorphization; by the formation of crystalline, metastable polymorphs; and can be preceded by the appearance of an intermediate phase, quartz II, with unknown structure. Based on molecular dynamic simulations, we show that this rich phenomenology can be rationalized through a unified theoretical framework of the atomistic pathways leading to densification. The model emphasizes the role played by the oxygen sublattice, which transforms from a bcc-like order in quartz into close-packed arrangements in the denser structures, through a ferroelastic instability of martensitic nature.

  20. Pressure-induced phase transition in CrO2.

    PubMed

    Alptekin, Sebahaddin

    2015-12-01

    The ab initio constant pressure molecular dynamics technique and density functional theory with generalized gradient approximation (GGA) was used to study the pressure-induced phase transition of CrO2. The phase transition of the rutile (P42/mnm) to the orthorhombic CaCl2 (Pnnm) structure at 30 GPa was determined successfully in a constant pressure simulation. This phase transition was analyzed from total energy calculations and, from the enthalpy calculation, occurred at around 17 GPa. Structural properties such as bulk modules, lattice parameters and phase transition were compared with experimental results. The phase transition at 12 ± 3 GPa was in good agreement with experimental results, as was the phase transition from the orthorhombic CaCl2 (Pnnm) to the monoclinic (P21/c) structure also found at 35 GPa. PMID:26541468

  1. Studies of wave phenomena using HF-induced scatter target

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaya, N.; Borisova, T.; Kornienko, V.; Rietveld, M.; Frolov, V.; Uryadov, V.; Kagan, L.; Yampolski, Y.; Vertogradov, G.; Kelley, M.

    Experimental results from Tromso and Sura heating experiments at high and mid-latitudes are examined It was shown that the combination of HF-induced target and bi-static HF Doppler radio scatter observations is a profitable method for the identification and studies of wave phenomena of different origin We analysed the ULF activity in the Pc 3-4 range and the medium-scale traveling ionospheric disturbances TIDs at high and mid-latitudes Bi-static HF Doppler radio scatter observations were carried out on the London-Tromso-St Petersburg path in the course of Tromso heating experiments During Sura heating experiments multi-position bi-static HF Doppler radio scatter observations were simultaneously performed at three reception points including St Petersburg Kharkov and Rostov-on-Don Ray tracing and Doppler shift simulations were made for all experiments Parameters of ULF waves were found The interesting feature detected from Sura heating experiment was the dependence of the ULF wave parameters from the effective radiated power of the heating facility Medium-scale TIDs were observed in the evening and pre-midnight hours TIDs in the auroral E region with periods of 20-25 min were traveling southward at speeds from 190-250 m s TIDs in the mid-latitudinal F region with periods from 15 to 45 min were at speeds between 40 and 120 m s During quiet magnetic conditions the waves were traveling in the north-east direction In disturbed conditions the waves were moving in the south-west direction with higher speeds as compared with quiet conditions Possible mechanisms

  2. Pressure-induced exotic states in rare earth hexaborides.

    PubMed

    Sun, Liling; Wu, Qi

    2016-08-01

    Finding the exotic phenomena in strongly correlated electron systems (SCESs) and understanding the corresponding microphysics have long been the research frontiers of condensed matter physics. The remarkable examples for the intriguing phenomena discovered in past years include unconventional superconductivity, heavy Fermion behaviors, giant magneto-resistance and so on. A fascinating type of rare earth hexaboride RB6 (R  =  Sm, Yb, Eu and Ce) belongs to a strongly correlated electron system (SCES), but shows unusual ambient-pressure and high-pressure behaviors beyond the phenomena mentioned above. Particularly, the recent discovery of the coexistence of an unusual metallic surface state and an insulating bulk state in SmB6, known to be a Kondo insulator decades ago, by theoretical calculations and many experimental measurements creates new interest for the investigation of the RB6. This significant progress encourages people to revisit the RB6 with an attempt to establish a new physics that links the SCES and the unusual metallic surface state which is a common feature of a topological insulator (TI). It is well known that pressure has the capability of tuning the electronic structure and modifying the ground state of solids, or even inducing a quantum phase transition which is one of the kernel issues in studies of SCESs. In this brief review, we will describe the progress in high pressure studies on the RB6 based on our knowledge and research interests, mainly focusing on the pressure-induced phenomena in YbB6 and SmB6, especially on the quantum phase transitions and their connections with the valence state of the rare earth ions. Moreover, some related high-pressure results obtained from CeB6 and EuB6 are also included. Finally, a summary is given in the conclusions and perspectives section. PMID:27376406

  3. Pressure-induced exotic states in rare earth hexaborides

    NASA Astrophysics Data System (ADS)

    Sun, Liling; Wu, Qi

    2016-08-01

    Finding the exotic phenomena in strongly correlated electron systems (SCESs) and understanding the corresponding microphysics have long been the research frontiers of condensed matter physics. The remarkable examples for the intriguing phenomena discovered in past years include unconventional superconductivity, heavy Fermion behaviors, giant magneto-resistance and so on. A fascinating type of rare earth hexaboride RB6 (R  =  Sm, Yb, Eu and Ce) belongs to a strongly correlated electron system (SCES), but shows unusual ambient-pressure and high-pressure behaviors beyond the phenomena mentioned above. Particularly, the recent discovery of the coexistence of an unusual metallic surface state and an insulating bulk state in SmB6, known to be a Kondo insulator decades ago, by theoretical calculations and many experimental measurements creates new interest for the investigation of the RB6. This significant progress encourages people to revisit the RB6 with an attempt to establish a new physics that links the SCES and the unusual metallic surface state which is a common feature of a topological insulator (TI). It is well known that pressure has the capability of tuning the electronic structure and modifying the ground state of solids, or even inducing a quantum phase transition which is one of the kernel issues in studies of SCESs. In this brief review, we will describe the progress in high pressure studies on the RB6 based on our knowledge and research interests, mainly focusing on the pressure-induced phenomena in YbB6 and SmB6, especially on the quantum phase transitions and their connections with the valence state of the rare earth ions. Moreover, some related high-pressure results obtained from CeB6 and EuB6 are also included. Finally, a summary is given in the conclusions and perspectives section.

  4. Tracking Ocean Gravity Waves in Real-time: Highlights of Bottom Pressure Data Recorded on Ocean Networks Canada's NEPTUNE observatory

    NASA Astrophysics Data System (ADS)

    Heesemann, Martin; Mihaly, Steve; Gemmrich, Johannes; Davis, Earl; Thomson, Richard; Dewey, Richard

    2016-04-01

    Ocean Networks Canada operates two cabled ocean observatories off Vancouver Island on Canada's west coast. The regional NEPTUNE observatory spans the entire Juan de Fuca tectonic plate from the coast across the subduction zone to the hydrothermally active Endeavour Segment of the Juan de Fuca Ridge Segment while the VENUS observatory focuses on coastal processes. Both observatories collect data on physical, chemical, biological, and geological aspects of the ocean over long time periods, supporting research on complex earth processes. High-precision bottom pressure recorders (BPR) deployed on the NEPTUNE observatory are capable of detecting a wide range of phenomena related to sea level variations. The observatory BPRs provide observations of nano-resolution (with respect to full scale of the instrument) pressure variations which correspond to sub-millimeter scale surface water displacements in several kilometers of water. Detected signals include tides, tsunamis, infragravity waves, swell, wave-induced microseisms, storm surge, and seismic signals. Spectral analysis reveals many of these phenomena with periods ranging from a few seconds to many hours. Dispersion patterns from distant swells are prominent in the swell and microseism bands. By comparing the difference of arrival times between longer period waves, which arrive first, and shorter period waves we can estimate the distance the swells travelled since they were generated. Using this information, swell can be tracked back to specific storms across the Pacific. The presentation will high-light some examples of the mentioned phenomena in the continuous time-series that in some instances are more than seven years long.

  5. Characterization of a Setup to test the Impact of High-Amplitude Pressure Waves on Living Cells

    NASA Astrophysics Data System (ADS)

    Schmidt, Mischa; Kahlert, Ulf; Wessolleck, Johanna; Maciaczyk, Donata; Merkt, Benjamin; Maciaczyk, Jaroslaw; Osterholz, Jens; Nikkhah, Guido; Steinhauser, Martin O.

    2014-01-01

    The impact of pressure waves on cells may provide several possible applications in biology and medicine including the direct killing of tumors, drug delivery or gene transfection. In this study we characterize the physical properties of mechanical pressure waves generated by a nanosecond laser pulse in a setup with well-defined cell culture conditions. To systematically characterize the system on the relevant length and time scales (micrometers and nanoseconds) we use photon Doppler velocimetry (PDV) and obtain velocity profiles of the cell culture vessel at the passage of the pressure wave. These profiles serve as input for numerical pressure wave simulations that help to further quantify the pressure conditions on the cellular length scale. On the biological level we demonstrate killing of glioblastoma cells and quantify experimentally the pressure threshold for cell destruction.

  6. Characterization of a Setup to test the Impact of High-Amplitude Pressure Waves on Living Cells

    PubMed Central

    Schmidt, Mischa; Kahlert, Ulf; Wessolleck, Johanna; Maciaczyk, Donata; Merkt, Benjamin; Maciaczyk, Jaroslaw; Osterholz, Jens; Nikkhah, Guido; Steinhauser, Martin O.

    2014-01-01

    The impact of pressure waves on cells may provide several possible applications in biology and medicine including the direct killing of tumors, drug delivery or gene transfection. In this study we characterize the physical properties of mechanical pressure waves generated by a nanosecond laser pulse in a setup with well-defined cell culture conditions. To systematically characterize the system on the relevant length and time scales (micrometers and nanoseconds) we use photon Doppler velocimetry (PDV) and obtain velocity profiles of the cell culture vessel at the passage of the pressure wave. These profiles serve as input for numerical pressure wave simulations that help to further quantify the pressure conditions on the cellular length scale. On the biological level we demonstrate killing of glioblastoma cells and quantify experimentally the pressure threshold for cell destruction. PMID:24458018

  7. Influence of equivalence ratio on the mechanism of pressure wave generation during knocking combustion

    NASA Astrophysics Data System (ADS)

    Terashima, Hiroshi; Koshi, Mitsuo

    2015-11-01

    Knocking in spark-assisted engines is known as a severe pressure oscillation mainly caused by hot-spot autoignition in end-gas regions. In this study, knocking combustion of n-heptane/air mixtures modeled in a one-dimensional constant volume reactor is simulated with particular emphasis on the effects of equivalence ratio (0.6 to 2.0) on the mechanism of pressure wave generation. An efficient compressible flow solver with detailed chemical kinetics of n-heptane (373 species and 1071 reactions) is applied. The results demonstrate that the presence of negative temperature coefficient region significantly influence the knocking timing and knocking intensity, i.e., pressure wave amplitude in end-gas regions. The condition with equivalence ratios lower than 1.0 mostly leads to the reduction of the knocking intensity because of slower heat release rates of end-gas autoignition. On the other hand, the results with higher equivalence ratios of 1.2 to 2.0 indicate that a significant peak in the knocking intensity is produced at an equivalence ratio, which varies with initial temperature conditions. The final presentation will address the relationship between the knocking intensity and equivalence ratio with the discussion on detailed physics of pressure wave generation.

  8. Propagation of impact-induced shock waves in porous sandstone using mesoscale modeling

    NASA Astrophysics Data System (ADS)

    GÜLdemeister, Nicole; WÜNnemann, Kai; Durr, Nathanael; Hiermaier, Stefan

    2013-01-01

    Abstract-Generation and propagation of shock <span class="hlt">waves</span> by meteorite impact is significantly affected by material properties such as porosity, water content, and strength. The objective of this work was to quantify processes related to the shock-<span class="hlt">induced</span> compaction of pore space by numerical modeling, and compare the results with data obtained in the framework of the Multidisciplinary Experimental and Modeling Impact Research Network (MEMIN) impact experiments. We use mesoscale models resolving the collapse of individual pores to validate macroscopic (homogenized) approaches describing the bulk behavior of porous and water-saturated materials in large-scale models of crater formation, and to quantify localized shock amplification as a result of pore space crushing. We carried out a suite of numerical models of planar shock <span class="hlt">wave</span> propagation through a well-defined area (the "sample") of porous and/or water-saturated material. The porous sample is either represented by a homogeneous unit where porosity is treated as a state variable (macroscale model) and water content by an equation of state for mixed material (ANEOS) or by a defined number of individually resolved pores (mesoscale model). We varied porosity and water content and measured thermodynamic parameters such as shock <span class="hlt">wave</span> velocity and particle velocity on meso- and macroscales in separate simulations. The mesoscale models provide additional data on the heterogeneous distribution of peak shock <span class="hlt">pressures</span> as a consequence of the complex superposition of reflecting rarefaction <span class="hlt">waves</span> and shock <span class="hlt">waves</span> originating from the crushing of pores. We quantify the bulk effect of porosity, the reduction in shock <span class="hlt">pressure</span>, in terms of Hugoniot data as a function of porosity, water content, and strength of a quartzite matrix. We find a good agreement between meso-, macroscale models and Hugoniot data from shock experiments. We also propose a combination of a porosity compaction model (ɛ-α model) that was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4291638','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4291638"><span id="translatedtitle">Transdermal deferoxamine prevents <span class="hlt">pressure-induced</span> diabetic ulcers</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Duscher, Dominik; Neofytou, Evgenios; Wong, Victor W.; Maan, Zeshaan N.; Rennert, Robert C.; Januszyk, Michael; Rodrigues, Melanie; Malkovskiy, Andrey V.; Whitmore, Arnetha J.; Galvez, Michael G.; Whittam, Alexander J.; Brownlee, Michael; Rajadas, Jayakumar; Gurtner, Geoffrey C.</p> <p>2015-01-01</p> <p>There is a high mortality in patients with diabetes and severe <span class="hlt">pressure</span> ulcers. For example, chronic <span class="hlt">pressure</span> sores of the heels often lead to limb loss in diabetic patients. A major factor underlying this is reduced neovascularization caused by impaired activity of the transcription factor hypoxia <span class="hlt">inducible</span> factor-1 alpha (HIF-1α). In diabetes, HIF-1α function is compromised by a high glucose-<span class="hlt">induced</span> and reactive oxygen species-mediated modification of its coactivator p300, leading to impaired HIF-1α transactivation. We examined whether local enhancement of HIF-1α activity would improve diabetic wound healing and minimize the severity of diabetic ulcers. To improve HIF-1α activity we designed a transdermal drug delivery system (TDDS) containing the FDA-approved small molecule deferoxamine (DFO), an iron chelator that increases HIF-1α transactivation in diabetes by preventing iron-catalyzed reactive oxygen stress. Applying this TDDS to a <span class="hlt">pressure-induced</span> ulcer model in diabetic mice, we found that transdermal delivery of DFO significantly improved wound healing. Unexpectedly, prophylactic application of this transdermal delivery system also prevented diabetic ulcer formation. DFO-treated wounds demonstrated increased collagen density, improved neovascularization, and reduction of free radical formation, leading to decreased cell death. These findings suggest that transdermal delivery of DFO provides a targeted means to both prevent ulcer formation and accelerate diabetic wound healing with the potential for rapid clinical translation. PMID:25535360</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3197099','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3197099"><span id="translatedtitle"><span class="hlt">Pressure</span> Controlled Ventilation to <span class="hlt">Induce</span> Acute Lung Injury in Mice</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Koeppen, Michael; Eckle, Tobias; Eltzschig, Holger K.</p> <p>2011-01-01</p> <p>Murine models are extensively used to investigate acute injuries of different organs systems (1-34). Acute lung injury (ALI), which occurs with prolonged mechanical ventilation, contributes to morbidity and mortality of critical illness, and studies on novel genetic or pharmacological targets are areas of intense investigation (1-3, 5, 8, 26, 30, 33-36). ALI is defined by the acute onset of the disease, which leads to non-cardiac pulmonary edema and subsequent impairment of pulmonary gas exchange (36). We have developed a murine model of ALI by using a <span class="hlt">pressure</span>-controlled ventilation to <span class="hlt">induce</span> ventilator-<span class="hlt">induced</span> lung injury (2). For this purpose, C57BL/6 mice are anesthetized and a tracheotomy is performed followed by induction of ALI via mechanical ventilation. Mice are ventilated in a <span class="hlt">pressure</span>-controlled setting with an inspiratory peak <span class="hlt">pressure</span> of 45 mbar over 1 - 3 hours. As outcome parameters, pulmonary edema (wet-to-dry ratio), bronchoalveolar fluid albumin content, bronchoalveolar fluid and pulmonary tissue myeloperoxidase content and pulmonary gas exchange are assessed (2). Using this technique we could show that it sufficiently <span class="hlt">induces</span> acute lung inflammation and can distinguish between different treatment groups or genotypes (1-3, 5). Therefore this technique may be helpful for researchers who pursue molecular mechanisms involved in ALI using a genetic approach in mice with gene-targeted deletion. PMID:21587159</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15003268','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15003268"><span id="translatedtitle"><span class="hlt">Pressure</span> <span class="hlt">wave</span> measurements from thermal cook-off of an HMX based high explosive</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Forbes, J W; Tarver, C M; Urtiew, P A; Garcia, F; Greenwood, D W; Vandersall, K S</p> <p>2000-10-10</p> <p>A better understanding of thermal cook-off is important for safe handling and storing explosive devices. A number of safety issues exist about what occurs when a cased explosive thermally cooks off. For example, violence of the events as a function of confinement are important for predictions of collateral damage. This paper demonstrates how adjacent materials can be gauged to measure the resulting <span class="hlt">pressure</span> <span class="hlt">wave</span> and how this <span class="hlt">wave</span> propagates in this adjacent material. The output pulse from the thermal cook-off explosive containing fixture is of obvious interest for assessing many scenarios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15005663','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15005663"><span id="translatedtitle"><span class="hlt">Pressure</span> <span class="hlt">Wave</span> Measurements from Thermal Cook-Off of an HMX Based High Explosive PBX 9501</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Garcia, F; Forbes, J W; Tarver, C M; Urtiew, P A; Greenwood, D W; Vandersall, K S</p> <p>2001-05-31</p> <p>A better understanding of thermal cook-off is important for safe handling and storing explosive devices. A number of safety issues exist about what occurs when a cased explosive thermally cooks off. For example, violence of the events as a function of confinement are important for predictions of collateral damage. This paper demonstrates how adjacent materials can be gauged to measure the resulting <span class="hlt">pressure</span> <span class="hlt">wave</span> and how this <span class="hlt">wave</span> propagates in this adjacent material. The output pulse from the thermal cook-off explosive containing fixture is of obvious interest for assessing many scenarios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15004116','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15004116"><span id="translatedtitle"><span class="hlt">Pressure</span> <span class="hlt">Wave</span> Measurements from Thermal Cook-off of an HMX Based Explosive</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Forbes, J W; Tarver, C M; Urtiew, P A; Garcia, F; Greenwood, D W; Vandersall, K S</p> <p>2001-05-09</p> <p>A better understanding of thermal cook-off is important for safe handling and storing explosive devices. A number of safety issues exist about what occurs when a cased explosive thermally cooks off. For example, violence of the events as a function of confinement are important for predictions of collateral damage. This paper demonstrates how adjacent materials can be gauged to measure the resulting <span class="hlt">pressure</span> <span class="hlt">wave</span> and how this <span class="hlt">wave</span> propagates in this adjacent material. The output pulse from the thermal cook-off explosive containing fixture is of obvious interest for assessing many scenarios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014FlDyR..46b5504S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014FlDyR..46b5504S"><span id="translatedtitle">Solitary and transitional <span class="hlt">waves</span> in <span class="hlt">pressure</span>-driven two-layer microchannel flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sisoev, G. M.; Bennett, C. J.</p> <p>2014-04-01</p> <p>Similar to the case of the gravity-driven flow (Sisoev and Bennett 2013 Fluid Dyn. Res. 45 015503) we use the integral method to derive evolution equations modeling a <span class="hlt">pressure</span>-driven two-layer flow of immiscible viscous fluids in a plane microchannel. It is shown that the system possesses a vast set of steady-traveling solitary and transitional <span class="hlt">waves</span>. Analysis of the phase trajectories of the relevant dynamical system indicates the existence of families of steady-traveling periodic <span class="hlt">waves</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/8231298','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/8231298"><span id="translatedtitle"><span class="hlt">Wave</span> propagation with different <span class="hlt">pressure</span> signals: an experimental study on the latex tube.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ursino, M; Artioli, E; Gallerani, M</p> <p>1993-07-01</p> <p>To have deeper insight into the main factors affecting <span class="hlt">wave</span> propagation in real hydraulic lines, we measured the true propagation coefficient in two latex rubber tubes via the three-point <span class="hlt">pressure</span> method. The measurements were performed using both sinusoidal <span class="hlt">pressure</span> signals of different amplitudes and periodic square <span class="hlt">waves</span> as well as aperiodic <span class="hlt">pressure</span> impulses. The results obtained were then compared with those predicted by a classic linear model valuable for a purely elastic maximally tethered tube. Our measurements demonstrate that the three-point <span class="hlt">pressure</span> method may introduce significant errors at low frequencies (below 1 Hz in the present experiments) when the distance between two consecutive transducers becomes much lower than the wavelength. The pattern of phase velocity in the range 2-20 Hz turns out to be about 10 per cent higher than the theoretical one computed using the static value of the Young modulus. This result supports the idea that the dynamic Young modulus of the material is slightly higher than that measured in static conditions. The experimental attenuation per wavelength is significantly higher than the theoretical one over most of the frequencies examined, and settles at a constant value as frequency increases. Introduction of wall viscoelasticity in the theoretical model can explain only a portion of the observed high frequency damping and <span class="hlt">wave</span> attenuation. Finally, increasing the amplitude of <span class="hlt">pressure</span> changes significantly affects the measured value of the propagation coefficient, especially at those frequencies for which direct and reflected <span class="hlt">waves</span> sum together in a positive fashion. In these conditions we observed a moderate increase in phase velocity and a much more evident increase in attenuation per wavelength. PMID:8231298</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950058892&hterms=short+term+effects&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dshort%2Bterm%2Beffects','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950058892&hterms=short+term+effects&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dshort%2Bterm%2Beffects"><span id="translatedtitle">Radial energy transport by magnetospheric ULF <span class="hlt">waves</span>: Effects of magnetic curvature and plasma <span class="hlt">pressure</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kouznetsov, Igor; Lotko, William</p> <p>1995-01-01</p> <p>The 'radial' transport of energy by internal ULF <span class="hlt">waves</span>, stimulated by dayside magnetospheric boundary oscillations, is analyzed in the framework of one-fluid magnetohydrodynamics. (the term radial is used here to denote the direction orthogonal to geomagnetic flux surfaces.) The model for the inhomogeneous magnetospheric plasma and background magnetic field is axisymmetric and includes radial and parallel variations in the magnetic field, magnetic curvature, plasma density, and low but finite plasma <span class="hlt">pressure</span>. The radial mode structure of the coupled fast and intermediate MHD <span class="hlt">waves</span> is determined by numerical solution of the inhomogeneous <span class="hlt">wave</span> equation; the parallel mode structure is characterized by a Wentzel-Kramer-Brillouin (WKB) approximation. Ionospheric dissipation is modeled by allowing the parallel <span class="hlt">wave</span> number to be complex. For boudnary oscillations with frequencies in the range from 10 to 48 mHz, and using a dipole model for the background magnetic field, the combined effects of magnetic curvature and finite plasma <span class="hlt">pressure</span> are shown to (1) enhance the amplitude of field line resonances by as much as a factor of 2 relative to values obtained in a cold plasma or box-model approximation for the dayside magnetosphere; (2) increase the energy flux delivered to a given resonance by a factor of 2-4; and (3) broaden the spectral width of the resonance by a factor of 2-3. The effects are attributed to the existence of an 'Alfven buoyancy oscillation,' which approaches the usual shear mode Alfven <span class="hlt">wave</span> at resonance, but unlike the shear Alfven mode, it is dispersive at short perpendicular wavelengths. The form of dispersion is analogous to that of an internal atmospheric gravity <span class="hlt">wave</span>, with the magnetic tension of the curved background field providing the restoring force and allowing radial propagation of the mode. For nominal dayside parameters, the propagation band of the Alfven buoyancy <span class="hlt">wave</span> occurs between the location of its (field line) resonance and that of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JaJAP..43.2080H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JaJAP..43.2080H"><span id="translatedtitle">Generation of Radiation <span class="hlt">Pressure</span> in Thermally <span class="hlt">Induced</span> Ultrasonic Emitter Based on Nanocrystalline Silicon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hirota, Jun; Shinoda, Hiroyuki; Koshida, Nobuyoshi</p> <p>2004-04-01</p> <p>To confirm the applicability of thermally <span class="hlt">induced</span> ultrasonic emission from nanocrystalline silicon (nc-Si) devices as radiation <span class="hlt">pressure</span> generators, the dynamic response has been investigated under a pulse operation mode. The nc-Si emitter is fabricated on a p-type Si wafer by conventional electrochemical anodization with subsequent formation of the surface electrode. Due to the flat nature of the frequency response of this emitter, the device emits an acoustic <span class="hlt">wave</span> with little distortion under the pulse-drive condition. It is shown that a significant radiation <span class="hlt">pressure</span> of 34.5 Pa is generated by a concentrated burst-like electrical input, and that a beam located at a distance can be levitated as a result of the mechanical loading effect. This silicon-based emitter is attractive for applications to integrated nano- or micro-electromechanical systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3312616','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3312616"><span id="translatedtitle">Over-<span class="hlt">Pressure</span> Suppresses Ultrasonic-<span class="hlt">Induced</span> Drug Uptake</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Stringham, S. Briant; Viskovska, Maria A.; Richardson, Eric S.; Ohmine, Seiga; Husseini, Ghaleb A.; Murray, Byron K.; Pitt, William G.</p> <p>2012-01-01</p> <p>Ultrasound (US) is used to enhance and target delivery of drugs and genes to cancer tissues. The present study further examines the role of acoustic cavitation in US-<span class="hlt">induced</span> permeabilization of cell membranes and subsequent drug or gene uptake by the cell. Rat colon cancer cells were exposed to ultrasound at various static <span class="hlt">pressures</span> to examine the hypothesis that oscillating bubbles, also known as cavitating bubbles, permeabilize cells. Increasing <span class="hlt">pressure</span> suppresses bubble cavitation activity; thus if applied <span class="hlt">pressure</span> were to reduce drug uptake, cell permeabilization would be strongly linked to bubble cavitation activity. Cells were exposed to 476 kHz pulsed ultrasound at average intensities of 2.75 W/cm2 and 5.5 W/cm2 at various <span class="hlt">pressures</span> and times in an isothermal chamber. Cell fractions with reversible membrane damage (calcein uptake) and irreversible damage (propidium iodide uptake) were analyzed by flow cytometry. <span class="hlt">Pressurization</span> to 3 atm nearly eliminated the biological effect of US in promoting calcein uptake. Data also showed a linear increase in membrane permeability based upon increased time and intensity. This research shows that US-mediated cell membrane permeability is likely linked to cavitation bubble activity. PMID:19056161</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21504017','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21504017"><span id="translatedtitle"><span class="hlt">Pressure</span> <span class="hlt">induced</span> reactions amongst calcium aluminate hydrate phases</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Moon, Ju-hyuk; Oh, Jae Eun; Balonis, Magdalena; Glasser, Fredrik P.; Clark, Simon M.; Monteiro, Paulo J.M.</p> <p>2011-06-15</p> <p>The compressibilities of two AFm phases (straetlingite and calcium hemicarboaluminate hydrate) and hydrogarnet were obtained up to 5 GPa by using synchrotron high-<span class="hlt">pressure</span> X-ray powder diffraction with a diamond anvil cell. The AFm phases show abrupt volume contraction regardless of the molecular size of the <span class="hlt">pressure</span>-transmitting media. This volume discontinuity could be associated to a structural transition or to the movement of the weakly bound interlayer water molecules in the AFm structure. The experimental results seem to indicate that the <span class="hlt">pressure-induced</span> dehydration is the dominant mechanism especially with hygroscopic <span class="hlt">pressure</span> medium. The Birch-Murnaghan equation of state was used to compute the bulk modulus of the minerals. Due to the discontinuity in the <span class="hlt">pressure</span>-volume diagram, a two stage bulk modulus of each AFm phase was calculated. The abnormal volume compressibility for the AFm phases caused a significant change to their bulk modulus. The reliability of this experiment is verified by comparing the bulk modulus of hydrogarnet with previous studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1815523B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1815523B"><span id="translatedtitle">Eruptive Source Parameters from Near-Source Gravity <span class="hlt">Waves</span> <span class="hlt">Induced</span> by Large Vulcanian eruptions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barfucci, Giulia; Ripepe, Maurizio; De Angelis, Silvio; Lacanna, Giorgio; Marchetti, Emanuele</p> <p>2016-04-01</p> <p>The sudden ejection of hot material from volcanic vent perturbs the atmosphere generating a broad spectrum of <span class="hlt">pressure</span> oscillations from acoustic infrasound (<10 Hz) to gravity <span class="hlt">waves</span> (<0.03 Hz). However observations of gravity <span class="hlt">waves</span> excited by volcanic eruptions are still rare, mostly limited to large sub-plinian eruptions and frequently at large distance from the source (>100 km). Atmospheric Gravity <span class="hlt">waves</span> are <span class="hlt">induced</span> by perturbations of the hydrostatic equilibrium of the atmosphere and propagate within a medium with internal density stratification. They are initiated by mechanisms that cause the atmosphere to be displaced as for the injection of volcanic ash plume during an eruption. We use gravity <span class="hlt">waves</span> to infer eruptive source parameters, such as mass eruption rate (MER) and duration of the eruption, which may be used as inputs in the volcanic ash transport and dispersion models. We present the analysis of near-field observations (<7 km) of atmospheric gravity <span class="hlt">waves</span>, with frequencies of 0.97 and 1.15 mHz, recorded by a <span class="hlt">pressure</span> sensors network during two explosions in July and December 2008 at Soufrière Hills Volcano, Montserrat. We show that gravity <span class="hlt">waves</span> at Soufrière Hills Volcano originate above the volcanic dome and propagate with an apparent horizontal velocities of 8-10 m/s. Assuming a single mass injection point source model, we constrain the source location at ~3.5 km a.s.l., above the vent, duration of the gas thrust < 140 s and MERs of 2.6 and 5.4 x10E7 kg/s, for the two eruptive events. Source duration and MER derived by modeling Gravity <span class="hlt">Waves</span> are fully compatible with others independent estimates from field observations. Our work strongly supports the use of gravity <span class="hlt">waves</span> to model eruption source parameters and can have a strong impact on our ability to monitor volcanic eruption at a large distance and may have future application in assessing the relative magnitude of volcanic explosions.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1295510-negative-pressures-spallation-water-drops-subjected-nanosecond-shock-waves','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1295510-negative-pressures-spallation-water-drops-subjected-nanosecond-shock-waves"><span id="translatedtitle">Negative <span class="hlt">pressures</span> and spallation in water drops subjected to nanosecond shock <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Stan, Claudiu A.; Willmott, Philip R.; Stone, Howard A.; Koglin, Jason E.; Liang, Mengning; Aquila, Andrew L.; Robinson, Joseph S.; Gumerlock, Karl L.; Blaj, Gabriel; Sierra, Raymond G.; et al</p> <p>2016-05-16</p> <p>Most experimental studies of cavitation in liquid water at negative <span class="hlt">pressures</span> reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock <span class="hlt">waves</span>, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative <span class="hlt">pressures</span> below –100 MPamore » were reached in the drops. As a result, we model the negative <span class="hlt">pressures</span> from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation <span class="hlt">pressures</span>.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JPhCS.705a2029A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JPhCS.705a2029A&link_type=ABSTRACT"><span id="translatedtitle">Arterial pulse <span class="hlt">pressure</span> amplification described by means of a nonlinear <span class="hlt">wave</span> model: characterization of human aging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alfonso, M.; Cymberknop, L.; Armentano, R.; Pessana, F.; Wray, S.; Legnani, W.</p> <p>2016-04-01</p> <p>The representation of blood <span class="hlt">pressure</span> pulse as a combination of solitons captures many of the phenomena observed during its propagation along the systemic circulation. The aim of this work is to analyze the applicability of a compartmental model for propagation regarding the <span class="hlt">pressure</span> pulse amplification associated with arterial aging. The model was applied to blood <span class="hlt">pressure</span> waveforms that were synthesized using solitons, and then validated by waveforms obtained from individuals from differentiated age groups. Morphological changes were verified in the blood <span class="hlt">pressure</span> waveform as a consequence of the aging process (i.e. due to the increase in arterial stiffness). These changes are the result of both a nonlinear interaction and the phenomena present in the propagation of nonlinear mechanic <span class="hlt">waves</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27182751','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27182751"><span id="translatedtitle">Negative <span class="hlt">Pressures</span> and Spallation in Water Drops Subjected to Nanosecond Shock <span class="hlt">Waves</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stan, Claudiu A; Willmott, Philip R; Stone, Howard A; Koglin, Jason E; Liang, Mengning; Aquila, Andrew L; Robinson, Joseph S; Gumerlock, Karl L; Blaj, Gabriel; Sierra, Raymond G; Boutet, Sébastien; Guillet, Serge A H; Curtis, Robin H; Vetter, Sharon L; Loos, Henrik; Turner, James L; Decker, Franz-Josef</p> <p>2016-06-01</p> <p>Most experimental studies of cavitation in liquid water at negative <span class="hlt">pressures</span> reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock <span class="hlt">waves</span>, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative <span class="hlt">pressures</span> below -100 MPa were reached in the drops. We model the negative <span class="hlt">pressures</span> from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation <span class="hlt">pressures</span>. PMID:27182751</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21236018','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21236018"><span id="translatedtitle">Influence of autoignition delay time characteristics of different fuels on <span class="hlt">pressure</span> <span class="hlt">waves</span> and knock in reciprocating engines</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bradley, D.; Kalghatgi, G.T.</p> <p>2009-12-15</p> <p>The functional relationship of autoignition delay time with temperature and <span class="hlt">pressure</span> is employed to derive the propagation velocities of autoignitive reaction fronts for particular reactivity gradients, once autoignition has been initiated. In the present study of a variety of premixtures, with different functional relationships, such gradients comprise fixed initial temperature gradients. The smaller is the ratio of the acoustic speed through the mixture to the localised velocity of the autoignitive front, the greater are the amplitude and frequency of the <span class="hlt">induced</span> <span class="hlt">pressure</span> <span class="hlt">wave</span>. This might lead to damaging engine knock. At higher values of the ratio, the autoignition can be benign with only small over-<span class="hlt">pressures</span>. This approach to the effects of autoignition is confirmed by its application to a variety of experimental studies involving: (i)Imposed temperature gradients in a rapid compression and expansion machine. (ii)Onset of knock in an engine with advancing spark timing. (iii)Development of autoignition at a single hot spot in an engine. (iv)Autoignition fronts initiated by several hot spots. There is much diversity in the effects that can be produced by different fuels in different ranges of temperature and <span class="hlt">pressure</span>. Higher values of autoignitive propagation speeds lead to increasingly severe engine knock. Such effects cannot always be predicted from the Research and Motor octane numbers. (author)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/969240','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/969240"><span id="translatedtitle"><span class="hlt">Pressure</span> dependence of the optical properties of the charge-density-<span class="hlt">wave</span> compound LaTe2</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lavagnini, M.; Sacchetti, A.; Degiorgi, L.; Arcangeletti, E.; Baldassarre, L.; Postorino, P.; Lupi, S.; Perucchi, A.; Shin, K.Y.; Fisher, I.R.; /Stanford U., Geballe Lab.</p> <p>2009-12-14</p> <p>We report the <span class="hlt">pressure</span> dependence of the optical response of LaTe{sub 2}, which is deep in the charge-density-<span class="hlt">wave</span> (CDW) ground state even at 300 K. The reflectivity spectrum is collected in the mid-infrared spectral range at room temperature and at <span class="hlt">pressures</span> between 0 and 7 GPa. We extract the energy scale due to the single particle excitation across the CDW gap and the Drude weight. We establish that the gap decreases upon compressing the lattice, while the Drude weight increases. This signals a reduction in the quality of nesting upon applying <span class="hlt">pressure</span>, therefore <span class="hlt">inducing</span> a lesser impact of the CDW condensate on the electronic properties of LaTe{sub 2}. The consequent suppression of the CDW gap leads to a release of additional charge carriers, manifested by the shift of weight from the gap feature into the metallic component of the optical response. On the contrary, the power-law behavior, seen in the optical conductivity at energies above the gap excitation and indicating a weakly interacting limit within the Tomonaga-Luttinger liquid scenario, seems to be only moderately dependent on <span class="hlt">pressure</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011RScI...82b3906K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011RScI...82b3906K"><span id="translatedtitle">Combined ultrasonic elastic <span class="hlt">wave</span> velocity and microtomography measurements at high <span class="hlt">pressures</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kono, Yoshio; Yamada, Akihiro; Wang, Yanbin; Yu, Tony; Inoue, Toru</p> <p>2011-02-01</p> <p>Combined ultrasonic and microtomographic measurements were conducted for simultaneous determination of elastic property and density of noncrystalline materials at high <span class="hlt">pressures</span>. A Paris-Edinburgh anvil cell was placed in a rotation apparatus, which enabled us to take a series of x-ray radiography images under <span class="hlt">pressure</span> over a 180° angle range and construct accurately the three-dimensional sample volume using microtomography. In addition, ultrasonic elastic <span class="hlt">wave</span> velocity measurements were carried out simultaneously using the pulse reflection method with a 10° Y-cut LiNbO3 transducer attached to the end of the lower anvil. Combined ultrasonic and microtomographic measurements were carried out for SiO2 glass up to 2.6 GPa and room temperature. A decrease in elastic <span class="hlt">wave</span> velocities of the SiO2 glass was observed with increasing <span class="hlt">pressure</span>, in agreement with previous studies. The simultaneous measurements on elastic <span class="hlt">wave</span> velocities and density allowed us to derive bulk (Ks) and shear (G) moduli as a function of <span class="hlt">pressure</span>. Ks and G of the SiO2 glass also decreased with increasing <span class="hlt">pressure</span>. The negative <span class="hlt">pressure</span> dependence of Ks is stronger than that of G, and as a result the value of Ks became similar to G at 2.0-2.6 GPa. There is no reason why we cannot apply this new technique to high temperatures as well. Hence the results demonstrate that the combined ultrasonic and microtomography technique is a powerful tool to derive advanced (accurate) P-V-Ks-G-(T) equations of state for noncrystalline materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1021788','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1021788"><span id="translatedtitle">Combined ultrasonic elastic <span class="hlt">wave</span> velocity and microtomography measurements at high <span class="hlt">pressures</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kono, Yoshio; Yamada, Akihiro; Wang, Yanbin; Yu, Tony; Inoue, Toru</p> <p>2011-09-16</p> <p>Combined ultrasonic and microtomographic measurements were conducted for simultaneous determination of elastic property and density of noncrystalline materials at high <span class="hlt">pressures</span>. A Paris-Edinburgh anvil cell was placed in a rotation apparatus, which enabled us to take a series of x-ray radiography images under <span class="hlt">pressure</span> over a 180{sup o} angle range and construct accurately the three-dimensional sample volume using microtomography. In addition, ultrasonic elastic <span class="hlt">wave</span> velocity measurements were carried out simultaneously using the pulse reflection method with a 10{sup o} Y-cut LiNbO{sub 3} transducer attached to the end of the lower anvil. Combined ultrasonic and microtomographic measurements were carried out for SiO{sub 2} glass up to 2.6 GPa and room temperature. A decrease in elastic <span class="hlt">wave</span> velocities of the SiO{sub 2} glass was observed with increasing <span class="hlt">pressure</span>, in agreement with previous studies. The simultaneous measurements on elastic <span class="hlt">wave</span> velocities and density allowed us to derive bulk (K{sub s}) and shear (G) moduli as a function of <span class="hlt">pressure</span>. K{sub s} and G of the SiO{sub 2} glass also decreased with increasing <span class="hlt">pressure</span>. The negative <span class="hlt">pressure</span> dependence of K{sub s} is stronger than that of G, and as a result the value of K{sub s} became similar to G at 2.0-2.6 GPa. There is no reason why we cannot apply this new technique to high temperatures as well. Hence the results demonstrate that the combined ultrasonic and microtomography technique is a powerful tool to derive advanced (accurate) P-V-Ks-G-(T) equations of state for noncrystalline materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22062255','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22062255"><span id="translatedtitle">Combined ultrasonic elastic <span class="hlt">wave</span> velocity and microtomography measurements at high <span class="hlt">pressures</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kono, Yoshio; Yamada, Akihiro; Inoue, Toru; Wang Yanbin; Yu, Tony</p> <p>2011-02-15</p> <p>Combined ultrasonic and microtomographic measurements were conducted for simultaneous determination of elastic property and density of noncrystalline materials at high <span class="hlt">pressures</span>. A Paris-Edinburgh anvil cell was placed in a rotation apparatus, which enabled us to take a series of x-ray radiography images under <span class="hlt">pressure</span> over a 180 deg. angle range and construct accurately the three-dimensional sample volume using microtomography. In addition, ultrasonic elastic <span class="hlt">wave</span> velocity measurements were carried out simultaneously using the pulse reflection method with a 10 deg. Y-cut LiNbO{sub 3} transducer attached to the end of the lower anvil. Combined ultrasonic and microtomographic measurements were carried out for SiO{sub 2} glass up to 2.6 GPa and room temperature. A decrease in elastic <span class="hlt">wave</span> velocities of the SiO{sub 2} glass was observed with increasing <span class="hlt">pressure</span>, in agreement with previous studies. The simultaneous measurements on elastic <span class="hlt">wave</span> velocities and density allowed us to derive bulk (K{sub s}) and shear (G) moduli as a function of <span class="hlt">pressure</span>. K{sub s} and G of the SiO{sub 2} glass also decreased with increasing <span class="hlt">pressure</span>. The negative <span class="hlt">pressure</span> dependence of K{sub s} is stronger than that of G, and as a result the value of K{sub s} became similar to G at 2.0-2.6 GPa. There is no reason why we cannot apply this new technique to high temperatures as well. Hence the results demonstrate that the combined ultrasonic and microtomography technique is a powerful tool to derive advanced (accurate) P-V-K{sub s}-G-(T) equations of state for noncrystalline materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhaTr..85..708W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhaTr..85..708W"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> phase transition and structural properties of CrO2</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, H. Y.; Chen, Y. H.; Deng, C. R.; Su, X. F.</p> <p>2012-08-01</p> <p>The structural properties and <span class="hlt">pressure-induced</span> phase transitions of CrO2 have been investigated using the pseudopotential plane-<span class="hlt">wave</span> method based on the density functional theory (DFT). The rutile-type (P42/mnm), CaCl2-type (Pnnm), pyrite-type (Pā3), and CaF2-type (Fm-3m) phases of CrO2 have been considered. The structural properties such as lattice parameters, bulk moduli and its <span class="hlt">pressure</span> derivative are consistent with the available experimental data. The second-order phase-transition <span class="hlt">pressure</span> of CrO2 from the rutile phase to CaCl2 phase is 10.9 GPa, which is in good agreement with the experimental result. The sequence of these phases is rutile-type → CaCl2-type → pyrite-type → CaF2-type with the phase-transition <span class="hlt">pressures</span> 10.9, 23.9, and 144.5 GPa, respectively. The equation of state of different phases has also been presented. It is more difficult to compress with the increase of <span class="hlt">pressure</span> for different phases of CrO2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhRvL.111e2001B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhRvL.111e2001B"><span id="translatedtitle">Medium-<span class="hlt">Induced</span> QCD Cascade: Democratic Branching and <span class="hlt">Wave</span> Turbulence</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Blaizot, J.-P.; Iancu, E.; Mehtar-Tani, Y.</p> <p>2013-08-01</p> <p>We study the average properties of the gluon cascade generated by an energetic parton propagating through a quark-gluon plasma. We focus on the soft, medium-<span class="hlt">induced</span> emissions which control the energy transport at large angles with respect to the leading parton. We show that the effect of multiple branchings is important. In contrast with what happens in a usual QCD cascade in vacuum, medium-<span class="hlt">induced</span> branchings are quasidemocratic, with offspring gluons carrying sizable fractions of the energy of their parent gluon. This results in an efficient mechanism for the transport of energy toward the medium, which is akin to <span class="hlt">wave</span> turbulence with a scaling spectrum ˜1/ω. We argue that the turbulent flow may be responsible for the excess energy carried by very soft quanta, as revealed by the analysis of the dijet asymmetry observed in Pb-Pb collisions at the LHC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23952386','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23952386"><span id="translatedtitle">Medium-<span class="hlt">induced</span> QCD cascade: democratic branching and <span class="hlt">wave</span> turbulence.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Blaizot, J-P; Iancu, E; Mehtar-Tani, Y</p> <p>2013-08-01</p> <p>We study the average properties of the gluon cascade generated by an energetic parton propagating through a quark-gluon plasma. We focus on the soft, medium-<span class="hlt">induced</span> emissions which control the energy transport at large angles with respect to the leading parton. We show that the effect of multiple branchings is important. In contrast with what happens in a usual QCD cascade in vacuum, medium-<span class="hlt">induced</span> branchings are quasidemocratic, with offspring gluons carrying sizable fractions of the energy of their parent gluon. This results in an efficient mechanism for the transport of energy toward the medium, which is akin to <span class="hlt">wave</span> turbulence with a scaling spectrum ~1/sqrt[ω]. We argue that the turbulent flow may be responsible for the excess energy carried by very soft quanta, as revealed by the analysis of the dijet asymmetry observed in Pb-Pb collisions at the LHC. PMID:23952386</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRC..121.1881X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRC..121.1881X"><span id="translatedtitle">Poleward propagation of parametric subharmonic instability-<span class="hlt">induced</span> inertial <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xie, Xiaohui; Liu, Qian; Shang, Xiaodong; Chen, Guiying; Wang, Dongxiao</p> <p>2016-03-01</p> <p>This study presents two sets of current records obtained from the South China Sea and satellite altimeter data, and it suggests that near-inertial <span class="hlt">waves</span> <span class="hlt">induced</span> by parametric subharmonic instability (PSI) associated with internal tides can be transported poleward beyond their critical latitude φc by background geostrophic flow (BGF). The two mooring locations were poleward of φc (≈14°N) for diurnal subharmonics (0.5D1; half diurnal frequency D1); however, both of the current records revealed clear signals at 0.5D1. The enhanced subinertial motion at 0.5D1 exhibited a fortnightly spring-neap cycle but did not agree with that of D1, indicating that it may not be generated via PSI associated with the local D1. Observations from the altimeter data and a ray-tracing simulation suggested that these nonlocally generated 0.5D1 <span class="hlt">waves</span> may be excited near their φc, after which they propagated poleward under the role of the BGF to the observation site with a latitude higher than φc. The poleward propagation of near-inertial <span class="hlt">waves</span> can produce elevated vertical shears; thus, it may play an important role in enhancing the local turbulent mixing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013JMiMi..23h5018K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013JMiMi..23h5018K&link_type=ABSTRACT"><span id="translatedtitle">CMOS-compatible ruggedized high-temperature Lamb <span class="hlt">wave</span> <span class="hlt">pressure</span> sensor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kropelnicki, P.; Muckensturm, K.-M.; Mu, X. J.; Randles, A. B.; Cai, H.; Ang, W. C.; Tsai, J. M.; Vogt, H.</p> <p>2013-08-01</p> <p>This paper describes the development of a novel ruggedized high-temperature <span class="hlt">pressure</span> sensor operating in lateral field exited (LFE) Lamb <span class="hlt">wave</span> mode. The comb-like structure electrodes on top of aluminum nitride (AlN) were used to generate the <span class="hlt">wave</span>. A membrane was fabricated on SOI wafer with a 10 µm thick device layer. The sensor chip was mounted on a <span class="hlt">pressure</span> test package and <span class="hlt">pressure</span> was applied to the backside of the membrane, with a range of 20-100 psi. The temperature coefficient of frequency (TCF) was experimentally measured in the temperature range of -50 °C to 300 °C. By using the modified Butterworth-van Dyke model, coupling coefficients and quality factor were extracted. Temperature-dependent Young's modulus of composite structure was determined using resonance frequency and sensor interdigital transducer (IDT) wavelength which is mainly dominated by an AlN layer. Absolute sensor phase noise was measured at resonance to estimate the sensor <span class="hlt">pressure</span> and temperature sensitivity. This paper demonstrates an AlN-based <span class="hlt">pressure</span> sensor which can operate in harsh environment such as oil and gas exploration, automobile and aeronautic applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5056123','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5056123"><span id="translatedtitle">Bromoform (CHBr sub 3 ) -- A very high-<span class="hlt">pressure</span> shock-<span class="hlt">wave</span> analyzer</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>McQueen, R.G.; Isaak, D.G.</p> <p>1989-01-01</p> <p>Bromoform, CHBr{sub 3}, appears to radiate like a black body. This means that the amount of radiation emitted from the shock front is extremely sensitive to temperature and hence even more sensitive to <span class="hlt">pressure</span>. This feature has been exploited to locate overtake <span class="hlt">waves</span> in impact experiments. Heretofore, Bromoform was used only for making timing measurements. However, if its P, V, E, and T EOS are known it could be used as high-<span class="hlt">pressure</span> analyzer. Measurements to determine the Hugoniot, the Grueneisen parameter, {gamma}, and its optical radiation characterization are described, and preliminary data are presented. 8 refs., 7 figs., 1 tab.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.5062S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.5062S"><span id="translatedtitle">Mountain <span class="hlt">Wave-Induced</span> Turbulence - "Lower Turbulent Zones" Revisited</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Strauss, Lukas; Grubišić, Vanda; Serafin, Stefano; Mühlgassner, Rita</p> <p>2014-05-01</p> <p>In their seminal 1974 paper on "Lower Turbulent Zones Associated with Mountain Lee <span class="hlt">Waves</span>" P. F. Lester and W. A. Fingerhut attempted to characterize regions of low-level turbulence in the lee of mountain ranges that are commonly associated with large-amplitude mountain <span class="hlt">waves</span> aloft. For their study, they made extensive use of airborne measurements with small research aircraft that penetrated into the "lower turbulent zone" (LTZ). The Lester and Fingerhut study complemented previous work on <span class="hlt">wave-induced</span> LTZs by J. P. Kuettner and others in the 1950s who were among the first to employ sailplanes as scientific measurement platforms. Given the limitations of scientific instrumentation on research aircraft in the 1970s (e.g., no GPS) and, in particular, on sailplanes in the 1950s, credit has to be given to these authors for their remarkably detailed account and classification of LTZs. Ever since then, scientists have been trying to refine the conceptual model of the LTZ and shed more light on the origin of turbulence therein. The Terrain-<span class="hlt">Induced</span> Rotor Experiment (T-REX, Sierra Nevada, California, 2006) is the most recent, major effort organized to investigate the characteristics of LTZs by studying the coupled mountain-<span class="hlt">wave</span>, rotor, and boundary-layer system. During T-REX, comprehensive ground-based and airborne, in situ and remote sensing measurements were collected during 15 Intensive Observation Periods (IOPs). In this study, we make use of the extensive T-REX datasets to revisit the LTZ concept. During T-REX IOPs, the University of Wyoming King Air (UWKA) research aircraft flew straight-and-level legs aligned with the mean wind direction to document the variation of flow and turbulence over and downwind of the Sierra Nevada. In order to characterize the structure and intensity of turbulence within the LTZ, turbulent kinetic energy (TKE) and eddy-dissipation rate (EDR) were computed from UWKA research flights. In contrast to the rough average values of TKE and EDR</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/3532981','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/3532981"><span id="translatedtitle">Changes in intrathoracic <span class="hlt">pressures</span> <span class="hlt">induced</span> by positive end-expiratory <span class="hlt">pressure</span> ventilation after cardiac surgical procedures.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bonnet, F; Fischler, M; Dubois, C L; Brodaty, D; Pluskwa, F; Guilmet, D; Vourc'h, G</p> <p>1986-10-01</p> <p>The consequences of controlled ventilation with positive end-expiratory <span class="hlt">pressure</span> (PEEP) were studied, after cardiac surgical procedures, in two groups of patients supposed to have different lung and chest wall mechanical properties. The first group included 6 patients who had undergone coronary artery graft surgical procedures (CGS). The second group included 5 patients who had undergone a mitral valve replacement (MVR). Postoperatively, static lung and chest wall compliance was measured by stepwise inflation and deflation of the thorax. Esophageal, pericardial, and pleural <span class="hlt">pressures</span> were then measured, and cardiac output was determined while PEEP was increased from 0 to 20 cm H2O. Lung and chest wall compliance values sharply decreased in MVR patients. This accounts for the lower values for pleural and pericardial <span class="hlt">pressures</span> in this group than in the CGS patient group, but the transmission of airway <span class="hlt">pressure</span> was identical in the two groups when PEEP was increased. The decrease in cardiac output <span class="hlt">induced</span> by PEEP was similar in the two groups. The results suggest that the opposing influences of lung and chest wall compliance on airway <span class="hlt">pressure</span> transmission could at least partly explain the hemodynamic effects of PEEP in patients in whom the mechanical properties of the lung and thorax are impaired. PEEP ventilation should be used cautiously in patients suspected of having thoracic rigidity. PMID:3532981</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/921152','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/921152"><span id="translatedtitle">New experimental capabilities and theoretical insights of high <span class="hlt">pressure</span> compression <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Orlikowski, D; Nguyen, J; Patterson, J R; Minich, R; Martin, L P; Holmes, N</p> <p>2007-07-20</p> <p>Currently there are three platforms that offer quasi-isentropic compression or ramp-<span class="hlt">wave</span> compression (RWC): light-gas gun, magnetic flux (Z-pinch), and laser. We focus here on the light-gas gun technique and on some current theoretical insights from experimental data. A gradient impedance through the length of the impactor provides the <span class="hlt">pressure</span> pulse upon impactor to the subject material. Applications and results are given concerning high-<span class="hlt">pressure</span> strength and liquid to solid, phase transition of water plus its associated phase fraction history. We also introduce the Korteweg-deVries-Burgers equation as a means to understand the evolution these RWC <span class="hlt">waves</span> that propagate through the thickness of the subject material. This equation has the necessary competition between non-linear, dispersion, and dissipation processes, which is shown through observed structures that are manifested in the experimental particle velocity histories. Such methodology points towards a possible quantifiable dissipation, through which RWC experiments may be analyzed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/866800','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/866800"><span id="translatedtitle">Instantaneous and efficient surface <span class="hlt">wave</span> excitation of a low <span class="hlt">pressure</span> gas or gases</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Levy, Donald J.; Berman, Samuel M.</p> <p>1988-01-01</p> <p>A system for instantaneously ionizing and continuously delivering energy in the form of surface <span class="hlt">waves</span> to a low <span class="hlt">pressure</span> gas or mixture of low <span class="hlt">pressure</span> gases, comprising a source of rf energy, a discharge container, (such as a fluorescent lamp discharge tube), an rf shield, and a coupling device responsive to rf energy from the source to couple rf energy directly and efficiently to the gas or mixture of gases to ionize at least a portion of the gas or gases and to provide energy to the gas or gases in the form of surface <span class="hlt">waves</span>. The majority of the rf power is transferred to the gas or gases near the inner surface of the discharge container to efficiently transfer rf energy as excitation energy for at least one of the gases. The most important use of the invention is to provide more efficient fluorescent and/or ultraviolet lamps.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005JQSRT..95..221Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005JQSRT..95..221Y&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Pressure</span> broadening measurement of submillimeter-<span class="hlt">wave</span> lines of O3</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamada, M. M.; Amano, T.</p> <p>2005-10-01</p> <p>The <span class="hlt">pressure</span> broadening coefficients and their temperature dependences for two submillimeter-<span class="hlt">wave</span> transitions of ozone, one being monitored with Odin and the other to be monitored with JEM/SMILES and EOS-MLS, have been determined by using a BWO based submillimeter-<span class="hlt">wave</span> spectrometer. The measurements have also been extended to one of the symmetric isotopic species, 16O18O16O. The isotopic species is observed in natural abundance and as a consequence the temperature dependence is not determined due to weak signal intensity. The <span class="hlt">pressure</span> broadening parameters are determined with better than 1% accuracy, while the temperature dependence exponents are obtained within 1.5 3% accuracy for the normal species transitions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22561301','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22561301"><span id="translatedtitle">Increasing pulse <span class="hlt">wave</span> velocity in a realistic cardiovascular model does not increase pulse <span class="hlt">pressure</span> with age.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mohiuddin, Mohammad W; Rihani, Ryan J; Laine, Glen A; Quick, Christopher M</p> <p>2012-07-01</p> <p>The mechanism of the well-documented increase in aortic pulse <span class="hlt">pressure</span> (PP) with age is disputed. Investigators assuming a classical windkessel model believe that increases in PP arise from decreases in total arterial compliance (C(tot)) and increases in total peripheral resistance (R(tot)) with age. Investigators assuming a more sophisticated pulse transmission model believe PP rises because increases in pulse <span class="hlt">wave</span> velocity (c(ph)) make the reflected <span class="hlt">pressure</span> <span class="hlt">wave</span> arrive earlier, augmenting systolic <span class="hlt">pressure</span>. It has recently been shown, however, that increases in c(ph) do not have a commensurate effect on the timing of the reflected <span class="hlt">wave</span>. We therefore used a validated, large-scale, human arterial system model that includes realistic pulse <span class="hlt">wave</span> transmission to determine whether increases in c(ph) cause increased PP with age. First, we made the realistic arterial system model age dependent by altering cardiac output (CO), R(tot), C(tot), and c(ph) to mimic the reported changes in these parameters from age 30 to 70. Then, c(ph) was theoretically maintained constant, while C(tot), R(tot), and CO were altered. The predicted increase in PP with age was similar to the observed increase in PP. In a complementary approach, C(tot), R(tot), and CO were theoretically maintained constant, and c(ph) was increased. The predicted increase in PP was negligible. We found that increases in c(ph) have a limited effect on the timing of the reflected <span class="hlt">wave</span> but cause the system to degenerate into a windkessel. Changes in PP can therefore be attributed to a decrease in C(tot). PMID:22561301</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4199901','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4199901"><span id="translatedtitle">Cross-Sectional Relations of Arterial Stiffness, <span class="hlt">Pressure</span> Pulsatility, <span class="hlt">Wave</span> Reflection and Arterial Calcification</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Tsao, Connie W.; Pencina, Karol M.; Massaro, Joseph M.; Benjamin, Emelia J.; Levy, Daniel; Vasan, Ramachandran S.; Hoffmann, Udo; O’Donnell, Christopher J.; Mitchell, Gary F.</p> <p>2014-01-01</p> <p>Objective Arterial hemodynamics and vascular calcification are associated with increased risk for CVD, but their inter-relations remain unclear. We sought to examine the associations of arterial stiffness, <span class="hlt">pressure</span> pulsatility, and <span class="hlt">wave</span> reflection with arterial calcification in individuals free of prevalent cardiovascular disease (CVD). Approach and Results Framingham Heart Study Third Generation and Offspring Cohort participants free of CVD underwent applanation tonometry to measure arterial stiffness, <span class="hlt">pressure</span> pulsatility, and <span class="hlt">wave</span> reflection, including carotid-femoral pulse <span class="hlt">wave</span> velocity (CFPWV), central pulse <span class="hlt">pressure</span> (CPP), forward <span class="hlt">wave</span> amplitude, and augmentation index (AI). Participants in each cohort (n=1905, 45±6 years and n=1015, 65±9 years, respectively) underwent multi-detector computed tomography to assess presence and quantity of thoracic (TAC) and abdominal (AAC) aortic calcification and coronary artery calcification (CAC). In multivariable-adjusted models, both higher CFPWV and CPP were associated with greater TAC and AAC, whereas higher AI was associated with AAC. Among the tonometry measures, CFPWV was the strongest correlate of all calcification measures in multivariable-adjusted models (odds ratio [OR] per SD for TAC 2.69 (95%CI 2.17-3.35), AAC 1.47 (95%CI 1.26-1.73), and CAC 1.48 (95%CI 1.28-1.72), all p<0.001, respectively). We observed stronger relations of CFPWV, CPP, and forward <span class="hlt">wave</span> amplitude with nearly all continuous calcification measures in the younger Third Generation Cohort as compared with the Offspring Cohort. Conclusions In community-dwelling individuals without prevalent CVD, abnormal central arterial hemodynamics were positively associated with vascular calcification, and were observed at younger ages than previously recognized. The mechanisms of these associations may be bidirectional and deserve further study. PMID:25169933</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/7107227','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/7107227"><span id="translatedtitle">Combustion and <span class="hlt">pressure</span> <span class="hlt">wave</span> interaction in enclosed mixtures initiated by temperature nonuniformities</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Weber, H.J.; Mack, A.; Roth, P. . Inst. fuer Verbrennung und Gasdynamik)</p> <p>1994-06-01</p> <p>The dynamics of one-dimensional combustion <span class="hlt">waves</span> originating from hot-spot ignition was studied numerically by solving the corresponding conservation equations for mass, species, energy, and momentum. The mathematical model included a multispecies transport model and a detailed reaction mechanism. The numerical solution of the time-dependent conservation equations was based on the method of lines and on a dynamic adaptive grid technique. Due to the stiffness of the resulting system of ordinary differential equations, the BDF-code DASSL was used to integrate the equations. The results of the simulations show that the interaction of combustion and <span class="hlt">pressure</span> <span class="hlt">wave</span> can lead to deflagration to detonation transition. Depending on the temperature levels and the shape of the temperature nonuniformity, ordinary flame propagation, deflagration to detonation transition or to deflagration <span class="hlt">waves</span>, depending on the initial conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26737694','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26737694"><span id="translatedtitle">Heart rate variability during plateau <span class="hlt">waves</span> of intracranial <span class="hlt">pressure</span>: A pilot descriptive study.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Luís, A; Santos, A S; Dias, C; Almeida, R; Rocha, A P</p> <p>2015-01-01</p> <p>This study aims to describe heart rate variability during the first episode of plateau <span class="hlt">waves</span> of intracranial <span class="hlt">pressure</span> (ICP) in Traumatic Brain Injury (TBI) in order to characterize and identify at bedside this cerebrovascular phenomenon. The general behavior of the heart rate variability (HRV) spectral measures expressed in the medians across patients is concordant with an increased HRV in the latter part of the baseline and plateau <span class="hlt">wave</span>, followed by a decrease after the event and a new increase during the recovery. In low and high frequency bands the same increase is more marked in the parametric analysis. Interpretation of HRV may help clinicians to better identify the plateau <span class="hlt">waves</span> and allow earlier management. PMID:26737694</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014APS..DFDR17011R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014APS..DFDR17011R"><span id="translatedtitle">Bottom shear stress and <span class="hlt">pressure</span> perturbations under an internal solitary <span class="hlt">wave</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rivera, Gustavo; Diamessis, Peter</p> <p>2014-11-01</p> <p>The bottom boundary layer (BBL) under a mode-1 internal solitary <span class="hlt">wave</span> (ISW) of depression propagating against an oncoming model barotropic current is examined using 2-D direct numerical simulation based on a spectral multidomain penalty method model. Use of a postprocessing projection onto a modified set of divergence-free basis functions enables investigation of <span class="hlt">wave</span>-based Reynolds numbers within the range [105 ,106 ] . At sufficiently high ISW amplitude, the BBL undergoes a global instability which produces intermittent vortex shedding from within the separation bubble in the lee of the <span class="hlt">wave</span>. The interplay between the bottom shear stress field and <span class="hlt">pressure</span> perturbations during vortex ejection events and the subsequent evolution of the vortices is the focus of this presentation. Implications for resuspension of bottom particulate matter are discussed in the context of specific sediment transport models. Support from the Cornell Sloan Diversity Fellowship program is gratefully acknowledged.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.3289W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.3289W"><span id="translatedtitle">Elastic <span class="hlt">wave</span> velocities of peridotite KLB-1 at mantle <span class="hlt">pressures</span> and implications for mantle velocity modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Xuebing; Chen, Ting; Zou, Yongtao; Liebermann, Robert C.; Li, Baosheng</p> <p>2015-05-01</p> <p>Compressional (VP) and shear (VS) <span class="hlt">wave</span> velocities of a synthetic KLB-1 peridotite were measured for the first time up to 10 GPa using ultrasonic interferometry. Analysis of the P and S <span class="hlt">wave</span> velocities yielded K0 = 123(1) GPa, K0' = 5.1(2), G0 = 75(1) GPa, and G0'= 1.3(1) for the bulk and shear moduli and their <span class="hlt">pressure</span> derivatives. Comparison with Voigt-Reuss-Hill (VRH) calculations based on literature elasticity data for its constituent minerals indicates that the experimentally measured P and S <span class="hlt">wave</span> velocities, densities, bulk sound velocities, and VP/VS ratios fall close to the lower limit of VRH averages associated with the uncertainties of the mineral elasticity data. A comparison with previous modeling of mantle compositions implies that the velocities for an aggregate with the pyrolitic composition of KLB-1 are in close agreement with seismic data at the depths of the Earth's upper mantle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4286758','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4286758"><span id="translatedtitle">Artificial magnetic field <span class="hlt">induced</span> by an evanescent <span class="hlt">wave</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Mochol, Małgorzata; Sacha, Krzysztof</p> <p>2015-01-01</p> <p>Cold atomic gases are perfect laboratories for realization of quantum simulators. In order to simulate solid state systems in the presence of magnetic fields special effort has to be made because atoms are charge neutral. There are different methods for realization of artificial magnetic fields, that is the creation of specific conditions so that the motion of neutral particles mimics the dynamics of charged particles in an effective magnetic field. Here, we consider adiabatic motion of atoms in the presence of an evanescent <span class="hlt">wave</span>. Theoretical description of the adiabatic motion involves artificial vector and scalar potentials related to the Berry phases. Due to the large gradient of the evanescent field amplitude, the potentials can be strong enough to <span class="hlt">induce</span> measurable effects in cold atomic gases. We show that the resulting artificial magnetic field is able to <span class="hlt">induce</span> vortices in a Bose-Einstein condensate trapped close to a surface of a prism where the evanescent <span class="hlt">wave</span> is created. We also analyze motion of an atomic cloud released from a magneto-optical trap that falls down on the surface of the prism. The artificial magnetic field is able to reflect falling atoms that can be observed experimentally. PMID:25567430</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25567430','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25567430"><span id="translatedtitle">Artificial magnetic field <span class="hlt">induced</span> by an evanescent <span class="hlt">wave</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mochol, Małgorzata; Sacha, Krzysztof</p> <p>2015-01-01</p> <p>Cold atomic gases are perfect laboratories for realization of quantum simulators. In order to simulate solid state systems in the presence of magnetic fields special effort has to be made because atoms are charge neutral. There are different methods for realization of artificial magnetic fields, that is the creation of specific conditions so that the motion of neutral particles mimics the dynamics of charged particles in an effective magnetic field. Here, we consider adiabatic motion of atoms in the presence of an evanescent <span class="hlt">wave</span>. Theoretical description of the adiabatic motion involves artificial vector and scalar potentials related to the Berry phases. Due to the large gradient of the evanescent field amplitude, the potentials can be strong enough to <span class="hlt">induce</span> measurable effects in cold atomic gases. We show that the resulting artificial magnetic field is able to <span class="hlt">induce</span> vortices in a Bose-Einstein condensate trapped close to a surface of a prism where the evanescent <span class="hlt">wave</span> is created. We also analyze motion of an atomic cloud released from a magneto-optical trap that falls down on the surface of the prism. The artificial magnetic field is able to reflect falling atoms that can be observed experimentally. PMID:25567430</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997PNAS...94.7621P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997PNAS...94.7621P"><span id="translatedtitle">Visual Stimuli <span class="hlt">Induce</span> <span class="hlt">Waves</span> of Electrical Activity in Turtle Cortex</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prechtl, J. C.; Cohen, L. B.; Pesaran, B.; Mitra, P. P.; Kleinfeld, D.</p> <p>1997-07-01</p> <p>The computations involved in the processing of a visual scene invariably involve the interactions among neurons throughout all of visual cortex. One hypothesis is that the timing of neuronal activity, as well as the amplitude of activity, provides a means to encode features of objects. The experimental data from studies on cat [Gray, C. M., Konig, P., Engel, A. K. & Singer, W. (1989) Nature (London) 338, 334-337] support a view in which only synchronous (no phase lags) activity carries information about the visual scene. In contrast, theoretical studies suggest, on the one hand, the utility of multiple phases within a population of neurons as a means to encode independent visual features and, on the other hand, the likely existence of timing differences solely on the basis of network dynamics. Here we use widefield imaging in conjunction with voltage-sensitive dyes to record electrical activity from the virtually intact, unanesthetized turtle brain. Our data consist of single-trial measurements. We analyze our data in the frequency domain to isolate coherent events that lie in different frequency bands. Low frequency oscillations (<5 Hz) are seen in both ongoing activity and activity <span class="hlt">induced</span> by visual stimuli. These oscillations propagate parallel to the afferent input. Higher frequency activity, with spectral peaks near 10 and 20 Hz, is seen solely in response to stimulation. This activity consists of plane <span class="hlt">waves</span> and spiral-like <span class="hlt">waves</span>, as well as more complex patterns. The plane <span class="hlt">waves</span> have an average phase gradient of ≈ π /2 radians/mm and propagate orthogonally to the low frequency <span class="hlt">waves</span>. Our results show that large-scale differences in neuronal timing are present and persistent during visual processing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25322237','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25322237"><span id="translatedtitle">Underwater blast <span class="hlt">wave</span> <span class="hlt">pressure</span> sensor based on polymer film fiber Fabry-Perot cavity.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Junjie; Wang, Meng; Xu, Jian; Peng, Li; Yang, Minghong; Xia, Minghe; Jiang, Desheng</p> <p>2014-10-01</p> <p>This paper describes the theoretical and experimental aspects of an optical underwater shock <span class="hlt">wave</span> sensor based on a polymer film optical fiber Fabry-Perot cavity manufactured by vacuum deposition technology. The transduction mechanism of the sensor involves a normally incident acoustic stress <span class="hlt">wave</span> that changes the thickness of the polymer film, thereby giving rise to a phase shift. This transient interferometric phase is interrogated by a three-phase-step algorithm. Theoretically, the sensor-acoustic-field interaction principle is analyzed, and the phase modulation sensitivity based on the theory of <span class="hlt">waves</span> in the layered media is calculated. Experimentally, a static calibration test and a dynamic calibration test are conducted using a piston-type <span class="hlt">pressure</span> calibration machine and a focusing-type electromagnetic shock <span class="hlt">wave</span>. Results indicate that the repeatability, hysteresis, nonlinearity, and the overall measurement accuracy of the sensor within the full <span class="hlt">pressure</span> range of 55 MPa are 1.82%, 0.86%, 1.81%, and 4.49%, respectively. The dynamic response time is less than 0.767 μs. Finally, three aspects that need further study for practical use are pointed out. PMID:25322237</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.3694M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.3694M"><span id="translatedtitle">Temporal pore <span class="hlt">pressure</span> <span class="hlt">induced</span> stress changes during injection and depletion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Müller, Birgit; Heidbach, Oliver; Schilling, Frank; Fuchs, Karl; Röckel, Thomas</p> <p>2016-04-01</p> <p><span class="hlt">Induced</span> seismicity is observed during injection of fluids in oil, gas or geothermal wells as a rather immediate response close to the injection wells due to the often high-rate <span class="hlt">pressurization</span>. It was recognized even earlier in connection with more moderate rate injection of fluid waste on a longer time frame but higher <span class="hlt">induced</span> event magnitudes. Today, injection-related <span class="hlt">induced</span> seismicity significantly increased the number of events with M>3 in the Mid U.S. However, <span class="hlt">induced</span> seismicity is also observed during production of fluids and gas, even years after the onset of production. E.g. in the Groningen gas field production was required to be reduced due to the increase in felt and damaging seismicity after more than 50 years of exploitation of that field. Thus, injection and production <span class="hlt">induced</span> seismicity can cause severe impact in terms of hazard but also on economic measures. In order to understand the different onset times of <span class="hlt">induced</span> seismicity we built a generic model to quantify the role of poro-elasticity processes with special emphasis on the factors time, regional crustal stress conditions and fault parameters for three case studies (injection into a low permeable crystalline rock, hydrothermal circulation and production of fluids). With this approach we consider the spatial and temporal variation of reservoir stress paths, the "early" injection-related <span class="hlt">induced</span> events during stimulation and the "late" production <span class="hlt">induced</span> ones. Furthermore, in dependence of the undisturbed in situ stress field conditions the stress tensor can change significantly due to injection and long-term production with changes of the tectonic stress regime in which previously not critically stressed faults could turn to be optimally oriented for fault reactivation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22947434','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22947434"><span id="translatedtitle">Head orientation affects the intracranial <span class="hlt">pressure</span> response resulting from shock <span class="hlt">wave</span> loading in the rat.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dal Cengio Leonardi, Alessandra; Keane, Nickolas J; Bir, Cynthia A; Ryan, Anne G; Xu, Liaosa; Vandevord, Pamela J</p> <p>2012-10-11</p> <p>Since an increasing number of returning military personnel are presenting with neurological manifestations of traumatic brain injury (TBI), there has been a great focus on the effects resulting from blast exposure. It is paramount to resolve the physical mechanism by which the critical stress is being inflicted on brain tissue from blast <span class="hlt">wave</span> encounters with the head. This study quantitatively measured the effect of head orientation on intracranial <span class="hlt">pressure</span> (ICP) of rats exposed to a shock <span class="hlt">wave</span>. Furthermore, the study examined how skull maturity affects ICP response of animals exposed to shock <span class="hlt">waves</span> at various orientations. Results showed a significant increase in ICP values in larger rats at any orientation. Furthermore, when side-ICP values were compared to the other orientations, the peak <span class="hlt">pressures</span> were significantly lower suggesting a relation between ICP and orientation of the head due to geometry of the skull and location of sutures. This finding accentuates the importance of skull dynamics in explaining possible injury mechanisms during blast. Also, the rate of <span class="hlt">pressure</span> change was measured and indicated that the rate was significantly higher when the top of the head was facing the shock front. The results confirm that the biomechanical response of the superior rat skull is distinctive compared to other areas of the skull, suggesting a skull flexure mechanism. These results not only present insights into the mechanism of brain injury, but also provide information which can be used for designing more effective protective head gear. PMID:22947434</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4005495','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4005495"><span id="translatedtitle">Non-invasive measurement of local pulse <span class="hlt">pressure</span> by pulse <span class="hlt">wave</span>-based ultrasound manometry (PWUM)</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Vappou, J; Luo, J; Okajima, K; Di Tullio, M; Konofagou, E E</p> <p>2014-01-01</p> <p>The central Blood <span class="hlt">Pressure</span> (CBP) has been established as a relevant indicator of cardiovascular disease. Despite its significance, CBP remains particularly challenging to measure in standard clinical practice. The objective of this study is to introduce Pulse <span class="hlt">Wave</span>-based Ultrasound Manometry (PWUM) as a simple-touse, non-invasive ultrasound-based method for quantitative measurement of the central pulse <span class="hlt">pressure</span>. Arterial wall displacements are estimated using radiofrequency (RF) ultrasound signals acquired at high frame rates and the pulse <span class="hlt">pressure</span> waveform is estimated using both the distension waveform and the local Pulse <span class="hlt">Wave</span> Velocity (PWV). The method was tested on the abdominal aorta of 11 healthy subjects (age 35.7± 16 y.o.). PWUM pulse <span class="hlt">pressure</span> measurements were compared to those obtained by radial applanation tonometry using a commercial system. The average intra-subject variability of the pulse <span class="hlt">pressure</span> amplitude was found to be equal to 4.2 mmHg, demonstrating good reproducibility of the method. Excellent correlation was found between the waveforms obtained by PWUM and those obtained by tonometry in all subjects (0.94 <r < 0.98). A significant bias of 4.7 mmHg was found between PWUM and tonometry. PWUM is a highly translational method that can be easily integrated in clinical ultrasound imaging systems. It provides an estimate of the pulse <span class="hlt">pressure</span> waveform at the imaged location, and may offer therefore the possibility to estimate the pulse <span class="hlt">pressure</span> at different arterial sites. Future developments include the validation of the method against invasive estimates on patients, as well as its application to other large arteries. PMID:21904023</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20974634','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20974634"><span id="translatedtitle">Squeezed-state source using radiation-<span class="hlt">pressure-induced</span> rigidity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Corbitt, Thomas; Ottaway, David; Mavalvala, Nergis; Chen Yanbei; Khalili, Farid; Vyatchanin, Sergey; Whitcomb, Stan</p> <p>2006-02-15</p> <p>We propose an experiment to extract ponderomotive squeezing from an interferometer with high circulating power and low mass mirrors. In this interferometer, optical resonances of the arm cavities are detuned from the laser frequency, creating a mechanical rigidity that dramatically suppresses displacement noises. After taking into account imperfection of optical elements, laser noise, and other technical noise consistent with existing laser and optical technologies and typical laboratory environments, we expect the output light from the interferometer to have measurable squeezing of 5 dB, with a frequency-independent squeeze angle for frequencies below 1 kHz. This squeeze source is well suited for injection into a gravitational-<span class="hlt">wave</span> interferometer, leading to improved sensitivity from reduction in the quantum noise. Furthermore, this design provides an experimental test of quantum-limited radiation <span class="hlt">pressure</span> effects, which have not previously been tested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3341048','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3341048"><span id="translatedtitle">Buckling-<span class="hlt">induced</span> encapsulation of structured elastic shells under <span class="hlt">pressure</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Shim, Jongmin; Perdigou, Claude; Chen, Elizabeth R.; Bertoldi, Katia; Reis, Pedro M.</p> <p>2012-01-01</p> <p>We introduce a class of continuum shell structures, the Buckliball, which undergoes a structural transformation <span class="hlt">induced</span> by buckling under <span class="hlt">pressure</span> loading. The geometry of the Buckliball comprises a spherical shell patterned with a regular array of circular voids. In order for the pattern transformation to be <span class="hlt">induced</span> by buckling, the possible number and arrangement of these voids are found to be restricted to five specific configurations. Below a critical internal <span class="hlt">pressure</span>, the narrow ligaments between the voids buckle, leading to a cooperative buckling cascade of the skeleton of the ball. This ligament buckling leads to closure of the voids and a reduction of the total volume of the shell by up to 54%, while remaining spherical, thereby opening the possibility of encapsulation. We use a combination of precision desktop-scale experiments, finite element simulations, and scaling analyses to explore the underlying mechanics of these foldable structures, finding excellent qualitative and quantitative agreement. Given that this folding mechanism is <span class="hlt">induced</span> by a mechanical instability, our Buckliball opens the possibility for reversible encapsulation, over a wide range of length scales. PMID:22451901</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Tectp.651..232Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Tectp.651..232Z"><span id="translatedtitle">Coseismic water-level changes in a well <span class="hlt">induced</span> by teleseismic <span class="hlt">waves</span> from three large earthquakes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Yan; Fu, Li-Yun; Huang, Fuqiong; Chen, Xuezhong</p> <p>2015-05-01</p> <p>Three large earthquakes (the 2007 Mw 8.4 Sumatra, the 2008 Mw 7.9 Wenchuan, and the 2011 Mw 9.0 Tohoku) <span class="hlt">induce</span> coseismic water-level increment at far fields (epicentral distances > 1000 km) in the Fuxin well located in the Fuxin City, northeastern China (the well with the observation of both water levels and volume strains). A comprehensive analysis for the mechanism of far-field coseismic water-level changes is performed by analyzing the in-situ permeability, Skempton's coefficient B, and with the broadband seismograms from a nearby station. We observe an undrained compaction with a decreasing permeability <span class="hlt">induced</span> by the shaking of teleseismic <span class="hlt">waves</span> in the far field. Shaking by teleseismic <span class="hlt">waves</span> can <span class="hlt">induce</span> compaction or dilatation in the aquifer of Fuxin well; is able to enhance permeability and thus build a new pore-<span class="hlt">pressure</span> equilibrium system between the Fuxin well and the nearby Sihe reservoir (150 m away from the Fuxin well). The resulting interstitial fluid flow across the region increases coseismic water levels in the aquifer of Fuxin well.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatSR...630856D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatSR...630856D&link_type=ABSTRACT"><span id="translatedtitle">The <span class="hlt">Pressure</span> <span class="hlt">induced</span> by salt crystallization in confinement</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Desarnaud, J.; Bonn, D.; Shahidzadeh, N.</p> <p>2016-08-01</p> <p>Salt crystallization is a major cause of weathering of rocks, artworks and monuments. Damage can only occur if crystals continue to grow in confinement, i.e. within the pore space of these materials, thus generating mechanical stress. We report the direct measurement, at the microscale, of the force exerted by growing alkali halide salt crystals while visualizing their spontaneous nucleation and growth. The experiments reveal the crucial role of the wetting films between the growing crystal and the confining walls for the development of the <span class="hlt">pressure</span>. Our results suggest that the measured force originates from repulsion between the similarly charged confining wall and the salt crystal separated by a ~1.5 nm liquid film. Indeed, if the walls are made hydrophobic, no film is observed and no repulsive forces are detected. We also show that the magnitude of the <span class="hlt">induced</span> <span class="hlt">pressure</span> is system specific explaining why different salts lead to different amounts of damage to porous materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27493020','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27493020"><span id="translatedtitle">The <span class="hlt">Pressure</span> <span class="hlt">induced</span> by salt crystallization in confinement.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Desarnaud, J; Bonn, D; Shahidzadeh, N</p> <p>2016-01-01</p> <p>Salt crystallization is a major cause of weathering of rocks, artworks and monuments. Damage can only occur if crystals continue to grow in confinement, i.e. within the pore space of these materials, thus generating mechanical stress. We report the direct measurement, at the microscale, of the force exerted by growing alkali halide salt crystals while visualizing their spontaneous nucleation and growth. The experiments reveal the crucial role of the wetting films between the growing crystal and the confining walls for the development of the <span class="hlt">pressure</span>. Our results suggest that the measured force originates from repulsion between the similarly charged confining wall and the salt crystal separated by a ~1.5 nm liquid film. Indeed, if the walls are made hydrophobic, no film is observed and no repulsive forces are detected. We also show that the magnitude of the <span class="hlt">induced</span> <span class="hlt">pressure</span> is system specific explaining why different salts lead to different amounts of damage to porous materials. PMID:27493020</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4974634','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4974634"><span id="translatedtitle">The <span class="hlt">Pressure</span> <span class="hlt">induced</span> by salt crystallization in confinement</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Desarnaud, J.; Bonn, D.; Shahidzadeh, N.</p> <p>2016-01-01</p> <p>Salt crystallization is a major cause of weathering of rocks, artworks and monuments. Damage can only occur if crystals continue to grow in confinement, i.e. within the pore space of these materials, thus generating mechanical stress. We report the direct measurement, at the microscale, of the force exerted by growing alkali halide salt crystals while visualizing their spontaneous nucleation and growth. The experiments reveal the crucial role of the wetting films between the growing crystal and the confining walls for the development of the <span class="hlt">pressure</span>. Our results suggest that the measured force originates from repulsion between the similarly charged confining wall and the salt crystal separated by a ~1.5 nm liquid film. Indeed, if the walls are made hydrophobic, no film is observed and no repulsive forces are detected. We also show that the magnitude of the <span class="hlt">induced</span> <span class="hlt">pressure</span> is system specific explaining why different salts lead to different amounts of damage to porous materials. PMID:27493020</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFMMR31A0115H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFMMR31A0115H"><span id="translatedtitle">Elastic <span class="hlt">wave</span> velocities of Fe-bearing ringwoodite under <span class="hlt">pressure</span> and temperature conditions of the mantle transition region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Higo, Y.; Inoue, T.; Irifune, T.; Li, B.; Liebermann, R. C.</p> <p>2005-12-01</p> <p>Ringwoodite (high <span class="hlt">pressure</span> polymorph of olivine) is considered to be the most abundant mineral at depths between 520km and 660km in the mantle transition region, and it is important to accurately determine the elastic <span class="hlt">wave</span> velocities in order to discuss the mineralogy and composition of the mantle transition region. In this study, We have developed ultrasonic interferometry conjunction with in situ X-radiation techniques (X-ray diffraction and X-radiography) in a DIA-type cubic anvil high-<span class="hlt">pressure</span> apparatus, in order to obtain high-quality elastic <span class="hlt">wave</span> velocity data under the conditions of the mantle transition region and measured the elastic <span class="hlt">wave</span> velocity of iron-bearing ringwoodite under high temperature and high <span class="hlt">pressure</span>. The specimen was hot-pressed at 19GPa and 1473K in a 3000-ton high <span class="hlt">pressure</span> apparatus (ORANGE-3000: GRC at ehime university). High-<span class="hlt">pressure</span> ultrasonic experiments were performed using Kawai-type high-<span class="hlt">pressure</span> apparatus SPEED-1500 at BL04B1. The unit cell constants of <span class="hlt">pressure</span> marker (NaCl, Au) and sample (ringwoodite) were measured for estimation of <span class="hlt">pressure</span> and sample length. Also, X-radiography was used in this study for direct measurement of sample length at high <span class="hlt">pressure</span> and high temperature. The ultrasonic signals were generated and received by a LiNbO3 transducer (10° Y-cut), which can produce both longitudinal and shear <span class="hlt">waves</span> at the same time. The waveforms were very clear and the each echoes both P-<span class="hlt">wave</span> and S-<span class="hlt">wave</span> were identifiable at high temperature and high <span class="hlt">pressure</span>. P-<span class="hlt">wave</span> and S-<span class="hlt">wave</span> velocities increasing with increasing <span class="hlt">pressure</span>. And P-<span class="hlt">wave</span> and S-<span class="hlt">wave</span> velocities decrease with increasing temperature. Especially, S-<span class="hlt">wave</span> velocity has large temperature dependence, which velocity (at 18 GPa, 1673 K) slower than those of ambient condition. The results of our high-<span class="hlt">pressure</span> experiment, including the elastic moduli and their <span class="hlt">pressure</span> dependence, effect of iron on the elastic moduli, as well as their implication for the mantle transition</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3409693','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3409693"><span id="translatedtitle">CXCR4 gene transfer prevents <span class="hlt">pressure</span> overload <span class="hlt">induced</span> heart failure</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>LaRocca, Thomas J.; Jeong, Dongtak; Kohlbrenner, Erik; Lee, Ahyoung; Chen, JiQiu; Hajjar, Roger J.; Tarzami, Sima T.</p> <p>2012-01-01</p> <p>Stem cell and gene therapies are being pursued as strategies for repairing damaged cardiac tissue following myocardial infarction in an attempt to prevent heart failure. The chemokine receptor-4 (CXCR4) and its ligand, CXCL12, play a critical role in stem cell recruitment post-acute myocardial infarction. Whereas progenitor cell migration via the CXCL12/CXCR4 axis is well characterized, little is known about the molecular mechanisms of CXCR4 mediated modulation of cardiac hypertrophy and failure. We used gene therapy to test the effects of CXCR4 gene delivery on adverse ventricular remodeling due to <span class="hlt">pressure</span> overload. We assessed the effect of cardiac overexpression of CXCR4 during trans-aortic constriction (TAC) using a cardiotropic adeno-associated viral vector (AAV9) carrying the CXCR4 gene. Cardiac overexpression of CXCR4 in mice with <span class="hlt">pressure</span> overload prevented ventricular remodeling, preserved capillary density and maintained function as determined by echocardiography and in vivo hemodynamics. In isolated adult rat cardiac myocytes, CXCL12 treatment prevented isoproterenol <span class="hlt">induced</span> hypertrophy and interrupted the calcineurin/NFAT pathway. Finally, a complex involving the L-type calcium channel, β2-adenoreceptor, and CXCR4 (Cav1.2/β2AR/CXCR4) was identified in healthy cardiac myocytes and was shown to dissociate as a consequence of heart failure. CXCR4 administered to the heart via gene transfer prevents <span class="hlt">pressure</span> overload <span class="hlt">induced</span> heart failure. The identification of CXCR4 participation in a Cav1.2-β2AR regulatory complex provides further insight into the mechanism by which CXCR4 modulates calcium homeostasis and chronic <span class="hlt">pressure</span> overload responses in the cardiac myocyte. Together these results suggest AAV9.CXCR4 gene therapy is a potential therapeutic approach for congestive heart failure. PMID:22668785</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002ASAJ..112.2240T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002ASAJ..112.2240T"><span id="translatedtitle">Radiation <span class="hlt">pressure</span> of standing <span class="hlt">waves</span> on liquid columns and small diffusion flames</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thiessen, David B.; Marr-Lyon, Mark J.; Wei, Wei; Marston, Philip L.</p> <p>2002-11-01</p> <p>The radiation <span class="hlt">pressure</span> of standing ultrasonic <span class="hlt">waves</span> in air is demonstrated in this investigation to influence the dynamics of liquid columns and small flames. With the appropriate choice of the acoustic amplitude and wavelength, the natural tendency of long columns to break because of surface tension was suppressed in reduced gravity [M. J. Marr-Lyon, D. B. Thiessen, and P. L. Marston, Phys. Rev. Lett. 86, 2293-2296 (2001); 87(20), 9001(E) (2001)]. Evaluation of the radiation force shows that narrow liquid columns are attracted to velocity antinodes. The response of a small vertical diffusion flame to ultrasonic radiation <span class="hlt">pressure</span> in a horizontal standing <span class="hlt">wave</span> was observed in normal gravity. In agreement with our predictions of the distribution of ultrasonic radiation stress on the flame, the flame is attracted to a <span class="hlt">pressure</span> antinode and becomes slightly elliptical with the major axis in the plane of the antinode. The radiation <span class="hlt">pressure</span> distribution and the direction of the radiation force follow from the dominance of the dipole scattering for small flames. Understanding radiation stress on flames is relevant to the control of hot fluid objects. [Work supported by NASA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvB..93l5102H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvB..93l5102H"><span id="translatedtitle">Evolution of the charge density <span class="hlt">wave</span> superstructure in ZrTe3 under <span class="hlt">pressure</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoesch, Moritz; Garbarino, Gaston; Battaglia, Corsin; Aebi, Philipp; Berger, Helmuth</p> <p>2016-03-01</p> <p>The material ZrTe3 is a well-known example of an incommensurate periodic lattice distortion (PLD) at low temperatures due to a charge density <span class="hlt">wave</span> (CDW). Previous studies have found a sharp boundary as a function of <span class="hlt">pressure</span> between CDW below 5 GPa and bulk superconductivity above this value. We present a study of low-temperature-high-<span class="hlt">pressure</span> single crystal x-ray diffraction along with ab initio density functional theory calculations. The modulation vector qCDW is found to change smoothly with <span class="hlt">pressure</span> until the PLD is lost. Fermi surface calculations reproduce these changes, but neither these nor the experimental crystal lattice structure show a particular step change at 5 GPa, thus leading to the conclusion that the CDW is lost accidentally by tipping the balance of CDW formation in the Fermi surface nesting that stabilizes it.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EPJD...68...46H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EPJD...68...46H"><span id="translatedtitle">Plasmid DNA damage <span class="hlt">induced</span> by helium atmospheric <span class="hlt">pressure</span> plasma jet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Han, Xu; Cantrell, William A.; Escobar, Erika E.; Ptasinska, Sylwia</p> <p>2014-03-01</p> <p>A helium atmospheric <span class="hlt">pressure</span> plasma jet (APPJ) is applied to <span class="hlt">induce</span> damage to aqueous plasmid DNA. The resulting fractions of the DNA conformers, which indicate intact molecules or DNA with single- or double-strand breaks, are determined using agarose gel electrophoresis. The DNA strand breaks increase with a decrease in the distance between the APPJ and DNA samples under two working conditions of the plasma source with different parameters of applied electric pulses. The damage level <span class="hlt">induced</span> in the plasmid DNA is also enhanced with increased plasma irradiation time. The reactive species generated in the APPJ are characterized by optical emission spectra, and their roles in possible DNA damage processes occurring in an aqueous environment are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=481918','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=481918"><span id="translatedtitle">Aortic stenosis in adults. Non-invasive estimation of <span class="hlt">pressure</span> differences by continuous <span class="hlt">wave</span> Doppler echocardiography.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hegrenaes, L; Hatle, L</p> <p>1985-01-01</p> <p>The peak and mean aortic transvalvar <span class="hlt">pressure</span> differences measured invasively and non-invasively by continuous <span class="hlt">wave</span> Doppler echocardiography were compared in 87 consecutive patients with aortic stenosis. The mean values were calculated from the maximal velocities of the aortic jet recorded with a spectral display of the Doppler frequency shifts and by applying a modified Bernoulli equation. Technically satisfactory velocity curves for estimating the mean <span class="hlt">pressure</span> differences could not be obtained in three patients and invasive measurements were not obtained in two. In all patients the peak transvalvar <span class="hlt">pressure</span> difference was calculated since the aortic jet was identified non-invasively. The peak and mean <span class="hlt">pressure</span> differences measured invasively and non-invasively correlated well--with only minor underestimation of the <span class="hlt">pressure</span> differences measured with the Doppler technique--regardless of age, sex, and the presence or absence of aortic valvar regurgitation, or other valvar lesions. With a systematic search for the highest velocities in the aortic jet and with on line spectral analysis of the Doppler frequencies the peak and the mean aortic <span class="hlt">pressure</span> differences can be determined non-invasively with a high degree of precision in almost all patients. Images PMID:4052281</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980223577','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980223577"><span id="translatedtitle">Analytic Study of <span class="hlt">Induced</span> <span class="hlt">Pressure</span> on Long Bodies of Revolution with Varying Nose Bluntness at Hypersonic Speeds</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>VanHise, Vernon</p> <p>1961-01-01</p> <p><span class="hlt">Pressure</span> distributions and shock shapes for a series of cylindrical afterbodies having nose fineness ratios from 0.4 to 4 have been calculated by using the method of characteristics for a perfect gas. The fluid mediums investigated were air and helium and the Mach number range was from 5 to 40. Flow parameters obtained from blast-<span class="hlt">wave</span> analogy gave good correlations of blunt-nose <span class="hlt">induced</span> <span class="hlt">pressures</span> and shock shapes. Experimental results are found to be in good agreement with the characteristic calculations. The concept of hypersonic similitude enables good correlation of the results with respect to body shape, Mach number, and ratio of specific heats.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IJCMS...450015V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IJCMS...450015V"><span id="translatedtitle"><span class="hlt">Pressure</span> <span class="hlt">induced</span> stiffening, thermal softening of bulk modulus and brittle nature of mercury chalcogenides</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Varshney, Dinesh; Shriya, Swarna; Sapkale, Raju; Varshney, Meenu; Ameri, M.</p> <p>2015-07-01</p> <p>The <span class="hlt">pressure</span> and temperature dependent elastic properties of mercury chalcogenides (HgX; X = S, Se and Te) with <span class="hlt">pressure</span> <span class="hlt">induced</span> structural transition from ZnS-type (B3) to NaCl-type (B1) structure have been analyzed within the framework of a model interionic interaction potential with long-range Coulomb and charge transfer interactions, short-range overlap repulsion and van der Waals (vdW) interactions as well as zero point energy effects. Emphasis is on the evaluation of the Bulk modulus with <span class="hlt">pressure</span> and temperature dependency to yield the Poisson's ratio ν, the Pugh ratio ϕ, anisotropy parameter, Shear and Young's modulus, Lamé's constant, Klein man parameter, elastic <span class="hlt">wave</span> velocity and Debye temperature. The Poisson's ratio behavior infers that HgX are brittle in nature. To our knowledge this is the first quantitative theoretical prediction of the <span class="hlt">pressure</span> dependence of elastic and thermodynamical properties explicitly the ductile (brittle) nature of HgX and still awaits experimental confirmations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ShWav..25..415G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ShWav..25..415G"><span id="translatedtitle">Laser-<span class="hlt">induced</span> blast <span class="hlt">waves</span> in air and their effect on monodisperse droplet chains of ethanol and kerosene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gebel, G. C.; Mosbach, T.; Meier, W.; Aigner, M.</p> <p>2015-07-01</p> <p>Weak spherical blast <span class="hlt">waves</span> in static air and their breakup of ethanol and Jet A-1 kerosene droplets were investigated. The blast <span class="hlt">waves</span> were created by laser-<span class="hlt">induced</span> air breakdowns at ambient temperature and <span class="hlt">pressure</span>. In the first part of this study, they were visualized with schlieren imaging, and their trajectories were tracked with high temporal resolution. The laser pulse energy was varied to create blast <span class="hlt">waves</span> of different strengths. Their initial energies were determined by the application of a numerical and a semi-empirical blast <span class="hlt">wave</span> model. In the second part, monodisperse ethanol and kerosene droplet chains were injected. Their interaction with the blast <span class="hlt">waves</span> was visualized by the application of shadowgraph imaging. The perpendicular distance of the breakdown origin toward the droplet chains was varied to study the effect on the fuel droplets as a function of the distance. Droplets within a few millimeters around the breakdown origin were disintegrated into two to three secondary droplets. The blast-<span class="hlt">induced</span> flow velocities on the post-shock side and the corresponding Weber numbers were calculated from the data of a non-dimensional numerical simulation, and a close look was taken at the breakup process of the droplets. The analysis showed that the aerodynamic force of the blast-<span class="hlt">induced</span> flow was sufficient to deform the droplets into disk-like shapes, but diminished too fast to accomplish breakup. Due to the release of strain energy, the deformed droplets relaxed, stretched into filaments and finally disintegrated by capillary pinching.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AGUFMNH23B1623S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AGUFMNH23B1623S&link_type=ABSTRACT"><span id="translatedtitle">Numerical Analysis of Secondary Undulations in Urauchi Bay Caused by an Eastward <span class="hlt">Pressure</span> <span class="hlt">Wave</span> over the East China Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saita, T.; Asano, T.</p> <p>2012-12-01</p> <p>Background and Methods Seiches, called abiki in Japanese, are frequently observed along the west coast of Kyushu Island, Japan. In 2009, an abiki of almost 3 m in total height occurred in Urauchi Bay at the Koshiki Islands located off Kyushu Island. The Seiches in the bay have been attributed to a meteorological disturbance over the East China Sea. Here, the response of the East China Sea to propagating <span class="hlt">pressure</span> <span class="hlt">waves</span> and the resulting oscillations in Urauchi Bay are evaluated by numerical analysis. The computational domains are the East China Sea (Domain I) and Urauchi Bay (Domain II). The primitive equations are a continuity equation and nonlinear shallow-water equations, taking into account the effect of an atmospheric <span class="hlt">pressure</span> gradient at the sea surface. Results (1) Development of long-period <span class="hlt">waves</span> in the East China Sea The water surface undulations generated by <span class="hlt">pressure</span> <span class="hlt">waves</span> propagating eastward over the East China Sea are evaluated. In the calculations, the shapes of <span class="hlt">pressure</span> <span class="hlt">waves</span> are simplified such that barometric <span class="hlt">pressure</span> changes along the east-west direction only. The <span class="hlt">pressure</span> is constant along the meridional direction. The <span class="hlt">pressure</span> <span class="hlt">waves</span> move from west to east in Domain I at a constant speed. Calculations are executed under 891 conditions where the <span class="hlt">wave</span> lengths L, amplitude Pmax, and phase velocity Cp of the <span class="hlt">pressure</span> <span class="hlt">waves</span> are changed in the ranges of 10-140 km, 1-3 hPa, and 60-210 km/h, respectively. Eastward <span class="hlt">pressure</span> <span class="hlt">waves</span> over the East China Sea generate water level fluctuations of sufficient duration to put Urauchi Bay into resonance. For Cp of 80-140 km/h, surface <span class="hlt">wave</span> heights become especially large. The increase in <span class="hlt">wave</span> height is attributed to Proudman resonance because Cp is close to 88.3 km/h which is the propagation speed of a surface <span class="hlt">wave</span> estimated for the mean water depth in the western area of the Okinawa Trough. A smaller L increases the amplitude of water level fluctuations and shortens their period. L of 10-40 km leads to fluctuations</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/836673','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/836673"><span id="translatedtitle">Seismic attenuation due to <span class="hlt">wave-induced</span> flow</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pride, S.R.; Berryman, J.G.; Harris, J.M.</p> <p>2003-10-09</p> <p>Analytical expressions for three P-<span class="hlt">wave</span> attenuation mechanisms in sedimentary rocks are given a unified theoretical framework. Two of the models concern <span class="hlt">wave-induced</span> flow due to heterogeneity in the elastic moduli at mesoscopic scales (scales greater than grain sizes but smaller than wavelengths). In the first model, the heterogeneity is due to lithological variations (e.g., mixtures of sands and clays) with a single fluid saturating all the pores. In the second model, a single uniform lithology is saturated in mesoscopic ''patches'' by two immiscible fluids (e.g., air and water). In the third model, the heterogeneity is at ''microscopic'' grain scales (broken grain contacts and/or micro-cracks in the grains) and the associated fluid response corresponds to ''squirt flow''. The model of squirt flow derived here reduces to proper limits as any of the fluid bulk modulus, crack porosity, and/or frequency is reduced to zero. It is shown that squirt flow is incapable of explaining the measured level of loss (10{sup -2} < Q{sup -1} < 10{sup -1}) within the seismic band of frequencies (1 to 10{sup 4} Hz); however, either of the two mesoscopic scale models easily produce enough attenuation to explain the field data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16799688','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16799688"><span id="translatedtitle">Underwater light polarization and radiance fluctuations <span class="hlt">induced</span> by surface <span class="hlt">waves</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sabbah, Shai; Shashar, Nadav</p> <p>2006-07-01</p> <p>The underwater light field is an ever-changing environment. Surface <span class="hlt">waves</span> <span class="hlt">induce</span> variability in the radiance and the light's polarization. We examined the dependence of the polarization fluctuations associated with diffuse light (not including contribution from direct skylight) on the viewing zenith angle (30 degrees, 70 degrees, and 90 degrees), solar zenith angle (23 degrees -72 degrees), depth of 0.5-3 m, and light wavelength (380-650 nm) while observing within the azimuthal plane in the wind-<span class="hlt">wave</span> direction. Polarization and radiance fluctuated with time. Light variability (presented by the coefficient of variation calculated over a series of fluctuations in the radiance and percent polarization, and by the standard deviation calculated over a series of fluctuations in the e-vector orientation) was highest at a viewing zenith angle of 70 degrees , depended positively on the solar zenith angle, and decreased with depth at viewing zenith angles of 30 degrees and 70 degrees . Additionally, the variability of the percent polarization was significantly higher than that of the radiance. The temporal light fluctuations offer possibilities, such as enhancing the detection of transparent and reflecting objects; however, they set constraints on the optimal underwater polarization vision by both animals and by the use of instruments. PMID:16799688</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15013612','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15013612"><span id="translatedtitle">Seismic attenuation due to <span class="hlt">wave-induced</span> flow</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pride, S; Berryman, J; Harris, J</p> <p>2003-10-17</p> <p>Analytical expressions for three P-<span class="hlt">wave</span> attenuation mechanisms in sedimentary rocks are given a unified theoretical framework. Two of the models concern <span class="hlt">wave-induced</span> flow due to heterogeneity in the elastic moduli at ''mesoscopic'' scales (scales greater than grain sizes but smaller than wavelengths). In the first model, the heterogeneity is due to lithological variations (e.g., mixtures of sands and clays) with a single fluid saturating all the pores. In the second model, a single uniform lithology is saturated in mesoscopic ''patches'' by two immiscible fluids (e.g., air and water). In the third model, the heterogeneity is at ''microscopic'' grain scales (broken grain contacts and/or micro-cracks in the grains) and the associated fluid response corresponds to ''squirt flow''. The model of squirt flow derived here reduces to proper limits as any of the fluid bulk modulus, crack porosity, and/or frequency is reduced to zero. It is shown that squirt flow is incapable of explaining the measured level of loss (10{sup -2} < Q{sup -1} < 10{sup -1}) within the seismic band of frequencies (1 to 10{sup 4} Hz); however, either of the two mesoscopic scale models easily produce enough attenuation to explain field data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSA43A2128E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSA43A2128E"><span id="translatedtitle">Observations of dayside subauroral proton arcs and EMIC <span class="hlt">waves</span> associated with increases in solar wind <span class="hlt">pressure</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Engebretson, M. J.; Dasrath, D. K.; Frey, H. U.; Yeoman, T. K.; Lessard, M.</p> <p>2013-12-01</p> <p>We present three examples of simultaneous subauroral proton arcs in the southern hemisphere near local noon recorded by the Far Ultraviolet (FUV) instrument on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft and associated Pc1 <span class="hlt">waves</span> recorded by ground based magnetometers at high latitude stations in Antarctica. Each event appeared to be triggered by a large increase in solar wind dynamic <span class="hlt">pressure</span> during otherwise quiet geomagnetic conditions. The resulting compression of the dayside magnetosphere triggered ~0.5 Hz EMIC <span class="hlt">waves</span> which were observed by search coil magnetometers at Halley and South Pole Station, Antarctica. These <span class="hlt">waves</span> in turn caused energetic protons to precipitate into the southern high latitude ionosphere where they caused the appearance of an aurora several degrees of latitude equatorward of the steady southern auroral oval, and generated plasma irregularities which were detected by the Halley SuperDARN radar. Two additional proton arcs at similar latitude but in the dusk sector occurred shortly after the main phase of minor geomagnetic storms, and were not associated with solar wind <span class="hlt">pressure</span> increases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PEPS....3...18O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PEPS....3...18O"><span id="translatedtitle">Ultrahigh-<span class="hlt">pressure</span> acoustic <span class="hlt">wave</span> velocities of SiO2-Al2O3 glasses up to 200 GPa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ohira, Itaru; Murakami, Motohiko; Kohara, Shinji; Ohara, Koji; Ohtani, Eiji</p> <p>2016-12-01</p> <p>Extensive experimental studies on the structure and density of silicate glasses as laboratory analogs of natural silicate melts have attempted to address the nature of dense silicate melts that may be present at the base of the mantle. Previous ultrahigh-<span class="hlt">pressure</span> experiments, however, have been performed on simple systems such as SiO2 or MgSiO3, and experiments in more complex system have been conducted under relatively low-<span class="hlt">pressure</span> conditions below 60 GPa. The effect of other metal cations on structural changes that occur in dense silicate glasses under ultrahigh <span class="hlt">pressures</span> has been poorly understood. Here, we used a Brillouin scattering spectroscopic method up to <span class="hlt">pressures</span> of 196.9 GPa to conduct in situ high-<span class="hlt">pressure</span> acoustic <span class="hlt">wave</span> velocity measurements of SiO2-Al2O3 glasses in order to understand the effect of Al2O3 on <span class="hlt">pressure-induced</span> structural changes in the glasses as analogs of aluminosilicate melts. From 10 to 40 GPa, the transverse acoustic <span class="hlt">wave</span> velocity ( V S ) of Al2O3-rich glass (SiO2 + 20.5 mol% Al2O3) was greater than that of Al2O3-poor glass (SiO2 + 3.9 mol% Al2O3). This result suggests that SiO2-Al2O3 glasses with higher proportions of Al ions with large oxygen coordination numbers (5 and 6) become elastically stiffer up to 40 GPa, depending on the Al2O3 content, but then soften above 40 GPa. At <span class="hlt">pressures</span> from 40 to ~100 GPa, the increase in V S with increasing <span class="hlt">pressure</span> became less steep than below 40 GPa. Above ~100 GPa, there were abrupt increases in the P-V S gradients ( dV S /dP) at 130 GPa in Al2O3-poor glass and at 116 GPa in Al2O3-rich glass. These changes resemble previous experimental results on SiO2 glass and MgSiO3 glass. Given that changes of dV S / dP have commonly been related to changes in the Si-O coordination states in the glasses, our results, therefore, may indicate a drastic structural transformation in SiO2-Al2O3 glasses above 116 GPa, possibly associated with an average Si-O coordination number change to higher than 6. Compared</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016APS..MARY21013N&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016APS..MARY21013N&link_type=ABSTRACT"><span id="translatedtitle">Nature of <span class="hlt">Pressure-induced</span> Insulating States in Simple Metals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Naumov, Ivan; Hemley, Russell</p> <p></p> <p>As experimentally established, all the alkali metals and heavy alkaline earth metals (Ca, Sr and Ba) become progressively less conductive on compression, at least up to some critical limit over a broad <span class="hlt">pressure</span> range. Of these metals, Li and Na clearly undergo <span class="hlt">pressure-induced</span> metal-insulator transitions, which may also be called reverse Mott transitions. Here, using group theory arguments and first-principles calculations, we show that such transitions can be understood in terms of band representations introduced by Zak. The valence bands in the insulating states are described by simple and composite band representations constructed from localized Wannier functions centered on points unoccupied by atoms. The character of the Wannier functions is closely related to the degree of s-p(-d) hybridization and reflects multi-center chemical bonding in these insulating states. The conditions under which an insulating state is allowed for structures having an integer number of atoms per primitive unit cell as well as re-entrant (i.e., metal-insulator-metal) transition sequences are detailed, resulting in predictions of semimetallic phases with flat surface states. The general principles developed are tested and applied to the alkali and alkaline earth metals, including elements where high-<span class="hlt">pressure</span> insulating phases have been identified or reported (e.g., Li, Na, and Ca). This research was supported by EFree, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award DESC0001057.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvB..91j4110B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvB..91j4110B"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> phase transitions and metallization in VO2</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bai, Ligang; Li, Quan; Corr, Serena A.; Meng, Yue; Park, Changyong; Sinogeikin, Stanislav V.; Ko, Changhyun; Wu, Junqiao; Shen, Guoyin</p> <p>2015-03-01</p> <p>We report the results of <span class="hlt">pressure-induced</span> phase transitions and metallization in VO2 based on synchrotron x-ray diffraction, electrical resistivity, and Raman spectroscopy. Our isothermal compression experiments at room temperature and 383 K show that the room temperature monoclinic phase (M 1 ,P 21/c ) and the high-temperature rutile phase (R ,P 42/m n m ) of VO2 undergo phase transitions to a distorted M 1 monoclinic phase (M 1' ,P 21/c ) above 13.0 GPa and to an orthorhombic phase (CaCl2-like, P n n m ) above 13.7 GPa, respectively. Upon further compression, both high-<span class="hlt">pressure</span> phases transform into a new phase (phase X ) above 34.3 and 38.3 GPa at room temperature and 383 K, respectively. The room temperature M 1 -M 1' phase transition structurally resembles the R -CaCl2 phase transition at 383 K, suggesting a second-order displacive type of transition. Contrary to previous studies, our electrical resistivity results, Raman measurements, as well as ab initio calculations indicate that the new phase X , rather than the M 1' phase, is responsible for the metallization under <span class="hlt">pressure</span>. The metallization mechanism is discussed based on the proposed crystal structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19840025864&hterms=Flowers&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DFlowers','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19840025864&hterms=Flowers&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DFlowers"><span id="translatedtitle">Experimental validation of a millimeter <span class="hlt">wave</span> radar technique to remotely sense atmospheric <span class="hlt">pressure</span> at the Earth's surface</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Flower, D. A.; Peckham, G. E.; Bradford, W. J.</p> <p>1984-01-01</p> <p>Experiments with a millimeter <span class="hlt">wave</span> radar operating on the NASA CV-990 aircraft which validate the technique for remotely sensing atmospheric <span class="hlt">pressure</span> at the Earth's surface are described. Measurements show that the precise millimeter <span class="hlt">wave</span> observations needed to deduce <span class="hlt">pressure</span> from space with an accuracy of 1 mb are possible, that sea surface reflection properties agree with theory and that the measured variation of differential absorption with altitude corresponds to that expected from spectroscopic models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005shwa.book..979Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005shwa.book..979Y"><span id="translatedtitle">Impulse characteristics of laser-<span class="hlt">induced</span> blast <span class="hlt">wave</span> in monoatomic gases</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, X. L.; Ohtani, T.; Sasoh, A.; Kim, S.; Urabe, N.; Jeung, I.-S.</p> <p></p> <p>The paper focuses on physical gas-dynamic characteristics of impulse generation by laser <span class="hlt">Induced</span> blast <span class="hlt">wave</span> (LIBW) in a laser-driven in tube accelerator (LITA). Propagation, reflection of blast <span class="hlt">wave</span> and <span class="hlt">wave</span> structure were intensively studied by using an ICCD camera system through shadowgraph.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993SPIE.1893...74T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993SPIE.1893...74T"><span id="translatedtitle">Tissue differentiation using laser-<span class="hlt">induced</span> shock <span class="hlt">waves</span> by detection of acoustic transients through an optical <span class="hlt">wave</span>-guide</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tschepe, Johannes; Ahrens, Thomas; Helfmann, Juergen; Mueller, Gerhard J.; Gapontsev, Valentin P.</p> <p>1993-05-01</p> <p>Some physical phenomena which occur during the fragmentation of calculi by laser <span class="hlt">induced</span> optical break down are presented. With in vitro experiments it could be shown that the energy of the laser <span class="hlt">induced</span> plasma and of the cavitation bubble (<span class="hlt">induced</span> by the plasma) depends by the nature of the tissue. The laser <span class="hlt">induced</span> plasma and the cavitation bubble generate shock <span class="hlt">waves</span>. These sound <span class="hlt">waves</span> are transferred via the laser fiber and detected with a piezo- electrical sensor at the proximal end. The acoustic signal contains information on the potential energy of the bubble, which depends on the energy of the plasma. The possibility of measuring the energy dependent acoustic transients allows to distinguish between hard and soft tissue and by this it is suitable for controlling the laser lithotripsy process. The transmission of acoustic transients through silica glass fibers is investigated by theoretical calculations. It shows the feasibility of silica glass fibers as an acoustic <span class="hlt">wave</span> guide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4011902','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4011902"><span id="translatedtitle">The 24-hour pulse <span class="hlt">wave</span> velocity, aortic augmentation index, and central blood <span class="hlt">pressure</span> in normotensive volunteers</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kuznetsova, Tatyana Y; Korneva, Viktoria A; Bryantseva, Evgeniya N; Barkan, Vitaliy S; Orlov, Artemy V; Posokhov, Igor N; Rogoza, Anatoly N</p> <p>2014-01-01</p> <p>The purpose of this study was to examine the pulse <span class="hlt">wave</span> velocity, aortic augmentation index corrected for heart rate 75 (AIx@75), and central systolic and diastolic blood <span class="hlt">pressure</span> during 24-hour monitoring in normotensive volunteers. Overall, 467 subjects (206 men and 261 women) were recruited in this study. Participants were excluded from the study if they were less than 19 years of age, had blood test abnormalities, had a body mass index greater than 2 7.5 kg/m2, had impaired glucose tolerance, or had hypotension or hypertension. Ambulatory blood <span class="hlt">pressure</span> monitoring (ABPM) with the BPLab® device was performed in each subject. ABPM waveforms were analyzed using the special automatic Vasotens® algorithm, which allows the calculation of pulse <span class="hlt">wave</span> velocity, AIx@75, central systolic and diastolic blood <span class="hlt">pressure</span> for “24-hour”, “awake”, and “asleep” periods. Circadian rhythms and sex differences in these indexes were identified. Pending further validation in prospective outcome-based studies, our data may be used as preliminary diagnostic values for the BPLab ABPM additional index in adult subjects. PMID:24812515</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JChPh.139r4504C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JChPh.139r4504C"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> transformations in computer simulations of glassy water</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chiu, Janet; Starr, Francis W.; Giovambattista, Nicolas</p> <p>2013-11-01</p> <p>Glassy water occurs in at least two broad categories: low-density amorphous (LDA) and high-density amorphous (HDA) solid water. We perform out-of-equilibrium molecular dynamics simulations to study the transformations of glassy water using the ST2 model. Specifically, we study the known (i) compression-<span class="hlt">induced</span> LDA-to-HDA, (ii) decompression-<span class="hlt">induced</span> HDA-to-LDA, and (iii) compression-<span class="hlt">induced</span> hexagonal ice-to-HDA transformations. We study each transformation for a broad range of compression/decompression temperatures, enabling us to construct a "P-T phase diagram" for glassy water. The resulting phase diagram shows the same qualitative features reported from experiments. While many simulations have probed the liquid-state phase behavior, comparatively little work has examined the transitions of glassy water. We examine how the glass transformations relate to the (first-order) liquid-liquid phase transition previously reported for this model. Specifically, our results support the hypothesis that the liquid-liquid spinodal lines, between a low-density and high-density liquid, are extensions of the LDA-HDA transformation lines in the limit of slow compression. Extending decompression runs to negative <span class="hlt">pressures</span>, we locate the sublimation lines for both LDA and hyperquenched glassy water (HGW), and find that HGW is relatively more stable to the vapor. Additionally, we observe spontaneous crystallization of HDA at high <span class="hlt">pressure</span> to ice VII. Experiments have also seen crystallization of HDA, but to ice XII. Finally, we contrast the structure of LDA and HDA for the ST2 model with experiments. We find that while the radial distribution functions (RDFs) of LDA are similar to those observed in experiments, considerable differences exist between the HDA RDFs of ST2 water and experiment. The differences in HDA structure, as well as the formation of ice VII (a tetrahedral crystal), are a consequence of ST2 overemphasizing the tetrahedral character of water.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24320281','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24320281"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> transformations in computer simulations of glassy water.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chiu, Janet; Starr, Francis W; Giovambattista, Nicolas</p> <p>2013-11-14</p> <p>Glassy water occurs in at least two broad categories: low-density amorphous (LDA) and high-density amorphous (HDA) solid water. We perform out-of-equilibrium molecular dynamics simulations to study the transformations of glassy water using the ST2 model. Specifically, we study the known (i) compression-<span class="hlt">induced</span> LDA-to-HDA, (ii) decompression-<span class="hlt">induced</span> HDA-to-LDA, and (iii) compression-<span class="hlt">induced</span> hexagonal ice-to-HDA transformations. We study each transformation for a broad range of compression/decompression temperatures, enabling us to construct a "P-T phase diagram" for glassy water. The resulting phase diagram shows the same qualitative features reported from experiments. While many simulations have probed the liquid-state phase behavior, comparatively little work has examined the transitions of glassy water. We examine how the glass transformations relate to the (first-order) liquid-liquid phase transition previously reported for this model. Specifically, our results support the hypothesis that the liquid-liquid spinodal lines, between a low-density and high-density liquid, are extensions of the LDA-HDA transformation lines in the limit of slow compression. Extending decompression runs to negative <span class="hlt">pressures</span>, we locate the sublimation lines for both LDA and hyperquenched glassy water (HGW), and find that HGW is relatively more stable to the vapor. Additionally, we observe spontaneous crystallization of HDA at high <span class="hlt">pressure</span> to ice VII. Experiments have also seen crystallization of HDA, but to ice XII. Finally, we contrast the structure of LDA and HDA for the ST2 model with experiments. We find that while the radial distribution functions (RDFs) of LDA are similar to those observed in experiments, considerable differences exist between the HDA RDFs of ST2 water and experiment. The differences in HDA structure, as well as the formation of ice VII (a tetrahedral crystal), are a consequence of ST2 overemphasizing the tetrahedral character of water. PMID:24320281</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110022626','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110022626"><span id="translatedtitle">A Study of Standing <span class="hlt">Pressure</span> <span class="hlt">Waves</span> Within Open and Closed Acoustic Resonators</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Daniels, C.; Steinetz, B.; Finkbeiner, J.; Raman, G.; Li, X.</p> <p>2002-01-01</p> <p>The first section of the results presented herein was conducted on an axisymmetric resonator configured with open ventilation ports on either end of the resonator, but otherwise closed and free from obstruction. The remaining section presents the results of a similar resonator shape that was closed, but contained an axisymmetric blockage centrally located through the axis of the resonator. Ambient air was used as the working fluid. In each of the studies, the resonator was oscillated at the resonant frequency of the fluid contained within the cavity while the dynamic <span class="hlt">pressure</span>, static <span class="hlt">pressure</span>, and temperature of the fluid were recorded at both ends of the resonator. The baseline results showed a marked reduction in the amplitude of the dynamic <span class="hlt">pressure</span> waveforms over previous studies due to the use of air instead of refrigerant as the working fluid. A sharp reduction in the amplitude of the acoustic <span class="hlt">pressure</span> <span class="hlt">waves</span> was expected and recorded when the configuration of the resonators was modified from closed to open. A change in the resonant frequency was recorded when blockages of differing geometries were used in the closed resonator, while acoustic <span class="hlt">pressure</span> amplitudes varied little from baseline measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JFST....5..235A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JFST....5..235A"><span id="translatedtitle"><span class="hlt">Pressure</span> Generation from Micro-Bubble Collapse at Shock <span class="hlt">Wave</span> Loading</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abe, Akihisa; Ohtani, Kiyonobu; Takayama, Kazuyoshi; Nishio, Shigeru; Mimura, Haruo; Takeda, Minoru</p> <p></p> <p>This paper reports the result of a primary experimental and analytical study used to explore a reliable technology that is potentially applicable to the inactivation of micro-creatures contained in ship ballast water. A shock <span class="hlt">wave</span> generated by the micro-explosion of a 10mg silver azide pellet in a 10mm wide parallel test section was used to interact with a bubble cloud consisting of bubbles with average diameter 10µm produced by a swirling flow type micro-bubble generator. Observations were carried out with a high-speed camera, IMACON200, and the corresponding rebound <span class="hlt">pressures</span> of the collapsing bubbles were measured with a fiber optic probe <span class="hlt">pressure</span> transducer that provides high spatial and temporal resolutions. We found that micro-bubbles collapse in several hundred nanoseconds after the shock exposure and the resulting peak <span class="hlt">pressure</span> pulses that repeatedly occurred exceeded well over 200MPa measured at the 20mm distance from the explosion center. These continued for well over 20µs. The experimental <span class="hlt">pressure</span> responses were explained by solving the one-dimensional bubble Rayleigh-Plesset equation. Such high peak <span class="hlt">pressures</span> could be used effectively for the inactivation of micro-creatures contained in ship ballast water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013OptLT..45..540F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013OptLT..45..540F"><span id="translatedtitle">Effects of the air <span class="hlt">pressure</span> on the <span class="hlt">wave</span>-packet dynamics of gaseous iodine molecules at room temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fan, Rongwei; He, Ping; Chen, Deying; Xia, Yuanqin; Yu, Xin; Wang, Jialing; Jiang, Yugang</p> <p>2013-02-01</p> <p>Based on ultrafast laser pulses, time-resolved resonance enhancement coherent anti-Stokes Raman scattering (RE-CARS) is applied to investigate <span class="hlt">wave</span>-packet dynamics in gaseous iodine. The effects of air <span class="hlt">pressure</span> on the <span class="hlt">wave</span>-packet dynamics of iodine molecules are studied at <span class="hlt">pressures</span> ranging from 1.5 Torr to 750 Torr. The RE-CARS signals are recorded in a gas cell filled with a mixture of about 0.3 Torr iodine in air buffer gas at room temperature. The revivals and fractional revival structures in the <span class="hlt">wave</span>-packet signal are found to gradually disappear with rising air <span class="hlt">pressure</span> up to 750 Torr, and the decay behaviors of the excited B-state and ground X-state become faster with increasing air <span class="hlt">pressure</span>, which is due to the collision effects of the molecules and the growing complexity of the spectra at high <span class="hlt">pressures</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11969832','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11969832"><span id="translatedtitle">Self-consistent axial modeling of surface-<span class="hlt">wave</span>-produced discharges at low and intermediate <span class="hlt">pressures</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Petrova, T; Benova, E; Petrov, G; Zhelyazkov, I</p> <p>1999-07-01</p> <p>A model for description of the axial structure of a surface-<span class="hlt">wave</span>-produced and -sustained plasma based on numerical calculation of a complete set of electrodynamic and kinetic equations is presented. The model includes a self-consistent solution to the electron Boltzmann equation, a set of particle balance equations for electrons, excited atoms, atomic and molecular ions, as well as Maxwell's equations with appropriate boundary conditions. A gas thermal balance equation is used to predict the neutral gas temperature self-consistently. Precise calculations of discharge characteristics of an argon plasma column sustained by an azimuthally symmetric surface <span class="hlt">wave</span> at low and intermediate gas <span class="hlt">pressures</span> have been performed. A comparison with available experimental data is done in order to test the validity of the model. PMID:11969832</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.9546Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.9546Z"><span id="translatedtitle">Unusual properties of high-compliance porosity extracted from measurements of <span class="hlt">pressure</span>-dependent <span class="hlt">wave</span> velocities in rocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zaitsev, Vladimir Y.; Radostin, Andrey V.; Pasternak, Elena; Dyskin, Arcady</p> <p>2016-04-01</p> <p>Conventionally the interpretation of <span class="hlt">wave</span> velocities and their variations under load is conducted assuming that closable cracks have simple planar shapes, like the popular model of penny-shape cracks. For such cracks, the proportion between complementary variations in different elastic parameters of rocks (such as S- and P-<span class="hlt">wave</span> velocities) is strictly pre-determined, in particular, it is independent of the crack aspect ratio and rather weakly dependent on the Poisson's ratio of the intact rock. Real rocks, however, contain multitude of cracks of different geometry. Faces of such cracks can exhibit complex modes of interaction when closed by external load, which may result in very different ratios between normal- and shear compliances of such defects. In order to describe the reduction of different elastic moduli, we propose a model in which the compliances of crack-like defects are explicitly decoupled and are not predetermined, so that the ratio q between total normal- and shear- compliances imparted to the rock mass (as well as individual values of these compliances) can be estimated from experimental data on reduction of different elastic moduli (e.g., <span class="hlt">pressure</span> dependences of P- and S-<span class="hlt">wave</span> velocities). Physically, the so-extracted ratio q can be interpreted as intrinsic property of individual crack-like defects similar to each other, or as a characteristic of proportion between concentrations of pure normal cracks with very large q and pure shear cracks with q→0. The latter case can correspond, e.g., to saturated cracks in which weakly-compressible liquid prevents crack closing under normal loading. It can be shown that for conventional dry planar cracks, the compliance ratio is q ˜2. The developed model applied to the data on <span class="hlt">wave</span>-velocity variations with external <span class="hlt">pressure</span> indicates that elastic properties of the real crack-like defects in rocks can differ considerably from the usually assumed ones. Comparison with experimental data on variations P- and S-<span class="hlt">wave</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4548189','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4548189"><span id="translatedtitle"><span class="hlt">Wave</span> trains <span class="hlt">induced</span> by circularly polarized electric fields in cardiac tissues</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Feng, Xia; Gao, Xiang; Tang, Juan-Mei; Pan, Jun-Ting; Zhang, Hong</p> <p>2015-01-01</p> <p>Clinically, cardiac fibrillation caused by spiral and turbulent <span class="hlt">waves</span> can be terminated by globally resetting electric activity in cardiac tissues with a single high-voltage electric shock, but it is usually associated with severe side effects. Presently, a promising alternative uses <span class="hlt">wave</span> emission from heterogeneities <span class="hlt">induced</span> by a sequence of low-voltage uniform electric field pulses. Nevertheless, this method can only emit <span class="hlt">waves</span> locally near obstacles in turbulent <span class="hlt">waves</span> and thereby requires multiple obstacles to globally synchronize myocardium and thus to terminate fibrillation. Here we propose a new approach using <span class="hlt">wave</span> emission from heterogeneities <span class="hlt">induced</span> by a low-voltage circularly polarized electric field (i.e., a rotating uniform electric field). We find that, this approach can generate circular <span class="hlt">wave</span> trains near obstacles and they propagate outwardly. We study the characteristics of such circular <span class="hlt">wave</span> trains and further find that, the higher-frequency circular <span class="hlt">wave</span> trains can effectively suppress spiral turbulence. PMID:26302781</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26302781','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26302781"><span id="translatedtitle"><span class="hlt">Wave</span> trains <span class="hlt">induced</span> by circularly polarized electric fields in cardiac tissues.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Feng, Xia; Gao, Xiang; Tang, Juan-Mei; Pan, Jun-Ting; Zhang, Hong</p> <p>2015-01-01</p> <p>Clinically, cardiac fibrillation caused by spiral and turbulent <span class="hlt">waves</span> can be terminated by globally resetting electric activity in cardiac tissues with a single high-voltage electric shock, but it is usually associated with severe side effects. Presently, a promising alternative uses <span class="hlt">wave</span> emission from heterogeneities <span class="hlt">induced</span> by a sequence of low-voltage uniform electric field pulses. Nevertheless, this method can only emit <span class="hlt">waves</span> locally near obstacles in turbulent <span class="hlt">waves</span> and thereby requires multiple obstacles to globally synchronize myocardium and thus to terminate fibrillation. Here we propose a new approach using <span class="hlt">wave</span> emission from heterogeneities <span class="hlt">induced</span> by a low-voltage circularly polarized electric field (i.e., a rotating uniform electric field). We find that, this approach can generate circular <span class="hlt">wave</span> trains near obstacles and they propagate outwardly. We study the characteristics of such circular <span class="hlt">wave</span> trains and further find that, the higher-frequency circular <span class="hlt">wave</span> trains can effectively suppress spiral turbulence. PMID:26302781</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DPPUP2052J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DPPUP2052J"><span id="translatedtitle">Flow <span class="hlt">induced</span> dust acoustic shock <span class="hlt">waves</span> in a complex plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jaiswal, Surabhi; Bandyopadhyay, Pintu; Sen, Abhijit</p> <p>2015-11-01</p> <p>We report on experimental observations of particle flow <span class="hlt">induced</span> large amplitude shock <span class="hlt">waves</span> in a dusty plasma. These dust acoustic shocks (DAS) are observed for strongly supersonic flows and have been studied in a U-shaped Dusty Plasma Experimental (DPEx) device for charged kaolin dust in a background of Argon plasma. The strong flow of the dust fluid is <span class="hlt">induced</span> by adjusting the pumping speed and neutral gas flow into the device. An isolated copper wire mounted on the cathode acts as a potential barrier to the flow of dust particles. A sudden change of the dust density near the potential hill is used to trigger the onset of high velocity dust acoustic shocks. The dynamics of the shocks are captured by fast video pictures of the structures that are illuminated by a laser sheet beam. The physical characteristics of the shock are delineated from a parametric scan of their dynamical properties over a range of plasma parameters and flow speeds. Details of these observations and a physical explanation based on model calculations will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JPSJ...85d4703S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JPSJ...85d4703S&link_type=ABSTRACT"><span id="translatedtitle">Charge Order <span class="hlt">Induced</span> in an Orbital Density-<span class="hlt">Wave</span> State</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Singh, Dheeraj Kumar; Takimoto, Tetsuya</p> <p>2016-04-01</p> <p>Motivated by recent angle resolved photoemission measurements [D. V. Evtushinsky et al., Phys. Rev. Lett. 105, 147201 (2010)] and evidence of the density-<span class="hlt">wave</span> state for the charge and orbital ordering [J. García et al., Phys. Rev. Lett. 109, 107202 (2012)] in La0.5Sr1.5MnO4, the issue of charge and orbital ordering in a two-orbital tight-binding model for layered manganite near half doping is revisited. We find that the charge order with the ordering wavevector 2{Q} = (π ,π ) is <span class="hlt">induced</span> by the orbital order of d-/d+-type having B1g representation with a different ordering wavevector Q, where the orbital order as the primary order results from the strong Fermi-surface nesting. It is shown that the <span class="hlt">induced</span> charge order parameter develops according to TCO - T by decreasing the temperature below the orbital ordering temperature TCO, in addition to the usual mean-field behavior of the orbital order parameter. Moreover, the same orbital order is found to stabilize the CE-type spin arrangement observed experimentally below TCE < TCO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27432864','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27432864"><span id="translatedtitle">Renal Nerve Stimulation-<span class="hlt">Induced</span> Blood <span class="hlt">Pressure</span> Changes Predict Ambulatory Blood <span class="hlt">Pressure</span> Response After Renal Denervation.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>de Jong, Mark R; Adiyaman, Ahmet; Gal, Pim; Smit, Jaap Jan J; Delnoy, Peter Paul H M; Heeg, Jan-Evert; van Hasselt, Boudewijn A A M; Lau, Elizabeth O Y; Persu, Alexandre; Staessen, Jan A; Ramdat Misier, Anand R; Steinberg, Jonathan S; Elvan, Arif</p> <p>2016-09-01</p> <p>Blood <span class="hlt">pressure</span> (BP) response to renal denervation (RDN) is highly variable and its effectiveness debated. A procedural end point for RDN may improve consistency of response. The objective of the current analysis was to look for the association between renal nerve stimulation (RNS)-<span class="hlt">induced</span> BP increase before and after RDN and changes in ambulatory BP monitoring (ABPM) after RDN. Fourteen patients with drug-resistant hypertension referred for RDN were included. RNS was performed under general anesthesia at 4 sites in the right and left renal arteries, both before and immediately after RDN. RNS-<span class="hlt">induced</span> BP changes were monitored and correlated to changes in ambulatory BP at a follow-up of 3 to 6 months after RDN. RNS resulted in a systolic BP increase of 50±27 mm Hg before RDN and systolic BP increase of 13±16 mm Hg after RDN (P<0.001). Average systolic ABPM was 153±11 mm Hg before RDN and decreased to 137±10 mm Hg at 3- to 6-month follow-up (P=0.003). Changes in RNS-<span class="hlt">induced</span> BP increase before versus immediately after RDN and changes in ABPM before versus 3 to 6 months after RDN were correlated, both for systolic BP (R=0.77, P=0.001) and diastolic BP (R=0.79, P=0.001). RNS-<span class="hlt">induced</span> maximum BP increase before RDN had a correlation of R=0.61 (P=0.020) for systolic and R=0.71 (P=0.004) for diastolic ABPM changes. RNS-<span class="hlt">induced</span> BP changes before versus after RDN were correlated with changes in 24-hour ABPM 3 to 6 months after RDN. RNS should be tested as an acute end point to assess the efficacy of RDN and predict BP response to RDN. PMID:27432864</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930083553','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930083553"><span id="translatedtitle">Study of the <span class="hlt">Pressure</span> Rise Across Shock <span class="hlt">Waves</span> Required to Separate Laminar and Turbulent Boundary Layers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Donaldson, Coleman Dup; Lange, Roy H</p> <p>1952-01-01</p> <p>Results are presented of a dimensional study and an experimental investigation of the <span class="hlt">pressure</span> rise across a shock <span class="hlt">wave</span> which causes separation of the boundary layer on a flat plate. The experimental part of the investigation was conducted at a Mach number of 3.03 for a Reynolds number range of 2 x 10 (sup) 6 to 19 x 10 (sup) 6. The available experimental data are compared with the predictions of the present study, and the significance of the results obtained is discussed relative to certain practical design problems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhyB..404..373M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhyB..404..373M"><span id="translatedtitle">Fluctuation of the charge density <span class="hlt">wave</span> in TTF-TCNQ under high <span class="hlt">pressure</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murata, Keizo; Weng, Yufeng; Seno, Yuki; Rani Tamilselvan, Natarajan; Kobayashi, Kensuke; Arumugam, Sonachalam; Takashima, Yusaku; Yoshino, Harukazu; Kato, Reizo</p> <p>2009-03-01</p> <p>Temperature dependence of the resistivity of TTF-TCNQ along the b-(1D)- and a-axes was studied under hydrostatic <span class="hlt">pressure</span> up to 8 GPa. A striking contrast was seen between the b-(1D)- and a-axes in the power-law dependence of resistivity ρ=ρ0Tα in the metallic region as well as the activation energy in the charge density <span class="hlt">wave</span> (CDW) insulating state. We note that the careful terminal configuration is essentially important to obtain these properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AIPC.1434.1226J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AIPC.1434.1226J"><span id="translatedtitle">Evaluation of mechanical losses in a linear motor <span class="hlt">pressure</span> <span class="hlt">wave</span> generator</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jacob, Subhash; Rangasamy, Karunanithi; Jonnalagadda, Kranthi Kumar; Chakkala, Damu; Achanur, Mallappa; Govindswamy, Jagadish; Gour, Abhay Singh</p> <p>2012-06-01</p> <p>A moving magnet linear motor compressor or <span class="hlt">pressure</span> <span class="hlt">wave</span> generator (PWG) of 2 cc swept volume with dual opposed piston configuration has been developed to operate miniature pulse tube coolers. Prelimnary experiments yielded only a no-load cold end temperature of 180 K. Auxiliary tests and the interpretation of detailed modeling of a PWG suggest that much of the PV power has been lost in the form of blow-by at piston seals due to large and non-optimum clearance seal gap between piston and cylinder. The results of experimental parameters simulated using Sage provide the optimum seal gap value for maximizing the delivered PV power.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24892591','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24892591"><span id="translatedtitle">High-<span class="hlt">pressure-induced</span> structural changes, amorphization and molecule penetration in MFI microporous materials: a review.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vezzalini, Giovanna; Arletti, Rossella; Quartieri, Simona</p> <p>2014-06-01</p> <p>This is a comparative study on the high-<span class="hlt">pressure</span> behavior of microporous materials with an MFI framework type (i.e. natural mutinaite, ZSM-5 and the all-silica phase silicalite-1), based on in-situ experiments in which penetrating and non-penetrating <span class="hlt">pressure</span>-transmitting media were used. Different <span class="hlt">pressure-induced</span> phenomena and deformation mechanisms (e.g. <span class="hlt">pressure-induced</span> over-hydration, <span class="hlt">pressure-induced</span> amorphization) are discussed. The influence of framework and extra-framework composition and of the presence of silanol defects on the response to the high <span class="hlt">pressure</span> of MFI-type zeolites is discussed. PMID:24892591</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AIPC.1573..386J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AIPC.1573..386J"><span id="translatedtitle">Studies on an improved indigenous <span class="hlt">pressure</span> <span class="hlt">wave</span> generator and its testing with a pulse tube cooler</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jacob, S.; Karunanithi, R.; Narsimham, G. S. V. L.; Kranthi, J. Kumar; Damu, C.; Praveen, T.; Samir, M.; Mallappa, A.</p> <p>2014-01-01</p> <p>Earlier version of an indigenously developed <span class="hlt">Pressure</span> <span class="hlt">Wave</span> Generator (PWG) could not develop the necessary <span class="hlt">pressure</span> ratio to satisfactorily operate a pulse tube cooler, largely due to high blow by losses in the piston cylinder seal gap and due to a few design deficiencies. Effect of different parameters like seal gap, piston diameter, piston stroke, moving mass and the piston back volume on the performance is studied analytically. Modifications were done to the PWG based on analysis and the performance is experimentally measured. A significant improvement in PWG performance is seen as a result of the modifications. The improved PWG is tested with the same pulse tube cooler but with different inertance tube configurations. A no load temperature of 130 K is achieved with an inertance tube configuration designed using Sage software. The delivered PV power is estimated to be 28.4 W which can produce a refrigeration of about 1 W at 80 K.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26091643','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26091643"><span id="translatedtitle">High Definition Oscillometry: Non-invasive Blood <span class="hlt">Pressure</span> Measurement and Pulse <span class="hlt">Wave</span> Analysis.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Egner, Beate</p> <p>2015-01-01</p> <p>Non-invasive monitoring of blood <span class="hlt">pressure</span> has become increasingly important in research. High-Definition Oscillometry (HDO) delivers not only accurate, reproducible and thus reliable blood <span class="hlt">pressure</span> but also visualises the pulse <span class="hlt">waves</span> on screen. This allows for on-screen feedback in real time on data validity but even more on additional parameters like systemic vascular resistance (SVR), stroke volume (SV), stroke volume variances (SVV), rhythm and dysrhythmia. Since complex information on drug effects are delivered within a short period of time, almost stress-free and visible in real time, it makes HDO a valuable technology in safety pharmacology and toxicology within a variety of fields like but not limited to cardiovascular, renal or metabolic research. PMID:26091643</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014NatCo...5E5247C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014NatCo...5E5247C&link_type=ABSTRACT"><span id="translatedtitle">Enhanced acoustic sensing through <span class="hlt">wave</span> compression and <span class="hlt">pressure</span> amplification in anisotropic metamaterials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Yongyao; Liu, Haijun; Reilly, Michael; Bae, Hyungdae; Yu, Miao</p> <p>2014-10-01</p> <p>Acoustic sensors play an important role in many areas, such as homeland security, navigation, communication, health care and industry. However, the fundamental <span class="hlt">pressure</span> detection limit hinders the performance of current acoustic sensing technologies. Here, through analytical, numerical and experimental studies, we show that anisotropic acoustic metamaterials can be designed to have strong <span class="hlt">wave</span> compression effect that renders direct amplification of <span class="hlt">pressure</span> fields in metamaterials. This enables a sensing mechanism that can help overcome the detection limit of conventional acoustic sensing systems. We further demonstrate a metamaterial-enhanced acoustic sensing system that achieves more than 20 dB signal-to-noise enhancement (over an order of magnitude enhancement in detection limit). With this system, weak acoustic pulse signals overwhelmed by the noise are successfully recovered. This work opens up new vistas for the development of metamaterial-based acoustic sensors with improved performance and functionalities that are highly desirable for many applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JMiMi..17.1334P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JMiMi..17.1334P"><span id="translatedtitle">Design and fabrication of dielectric diaphragm <span class="hlt">pressure</span> sensors for applications to shock <span class="hlt">wave</span> measurement in air</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parkes, W.; Djakov, V.; Barton, J. S.; Watson, S.; MacPherson, W. N.; Stevenson, J. T. M.; Dunare, C. C.</p> <p>2007-07-01</p> <p>Optical fibre <span class="hlt">pressure</span> sensors have potential performance advantages over electrical sensors in measuring rapid transients such as shock <span class="hlt">waves</span> from explosive blasts. We report the development of micromachined optical fibre Fabry-Pérot <span class="hlt">pressure</span> sensors using a silicon dioxide or nitride diaphragm and detail the fabrication stages of the sensor body and diaphragm. The planar technology used is based on silicon deep etching and direct fusion bonding of silicon wafers. Test results for both types of diaphragm are presented. Sensors with rise times better than 3 µs, range 0.1 to 1 MPa and resolution ~500 Pa have been demonstrated in explosives trials. Despite the difference in the sign of stress for the two diaphragm types, both demonstrated excellent high-speed response to explosively generated air shocks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20853011','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20853011"><span id="translatedtitle">Measurement of radiation-<span class="hlt">pressure-induced</span> optomechanical dynamics in a suspended Fabry-Perot cavity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Corbitt, Thomas; Ottaway, David; Innerhofer, Edith; Pelc, Jason; Mavalvala, Nergis</p> <p>2006-08-15</p> <p>We report on experimental observation of radiation-<span class="hlt">pressure</span> <span class="hlt">induced</span> effects in a high-power optical cavity. These effects play an important role in next-generation gravitational <span class="hlt">wave</span> detectors, as well as in quantum nondemolition interferometers. We measure the properties of an optical spring, created by coupling of an intense laser field to the pendulum mode of a suspended mirror, and also the parametric instability (PI) that arises from the coupling between acoustic modes of the cavity mirrors and the cavity optical mode. We measure an unprecedented optical rigidity of K=(3.08{+-}0.09)x10{sup 4} N/m, corresponding to an optical rigidity that is 6000 times stiffer than the mechanical stiffness, and PI strength R{approx_equal}3. We measure the unstable nature of the optical spring resonance, and demonstrate that the PI can be stabilized by feedback to the frequency of the laser source.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1214583L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1214583L"><span id="translatedtitle">Siderite breakdown and <span class="hlt">pressure</span> <span class="hlt">induced</span> Fe-C redox reactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lavina, Barbara; Dera, Przemyslaw; Kim, Eunja; Downs, Robert T.</p> <p>2010-05-01</p> <p>Siderite, FeCO3, was investigated at high <span class="hlt">pressure</span> (up to ~ 40 GPa) and high temperature (up to about 2400K) using a laser heated diamond anvil cell. The structure of the sample was probed with a synchrotron monochromatic beam; powder, multigrain and single crystaldiffraction techniques were used according to changing size of the crystallites in the course of the experiment. At about 35 GPa we observed the breakdown of the carbonate into h-Fe3O4 (the orthorhombic high <span class="hlt">pressure</span> phase of Fe3O4[1]) and undetected carbon phases. We suggest the breakdown was achieved through a redox reaction where the iron formal valence is increased at the expense of the carbon reduction. This observation is in agreement with results of shock experiments on siderite [2-4] in which however the presence of hematite in the starting material prevented to discriminate among possible reactions determining the synthesis of Fe3O4. Oxygen fugacity and the crystal chemistry of deep Earth mineral assemblages exert a major control on ionic speciation, therefore experimental confirmation are necessary to determine the actual redox equilibrium between iron and carbon in the mantle. Remarkably, perovskite strongly favor the partitioning of Fe3+ [5] and so it might favor the C reduction. If the <span class="hlt">pressure</span> effect on Fe-C redox equilibrium found in this experiment is active in the deep Earth, the speciation of carbon would be strongly affected, in particular, the stability of carbonates and CO2 might be controlled by <span class="hlt">pressure</span> <span class="hlt">induced</span> reductions rather than by the stability of the pure phases. Carbon reduction at <span class="hlt">pressure</span> might account for the greater subduction of carbon with respect to hydrogen [6]. On the other hand uplifting of reduced carbon assembly might release C-O fluids through reduction of Fe3+. Our results suggest that Fe-C redox reactions might have a crucial role on the carbon speciation which has a major importance on deep Earth processes. References [1] Haavik, et al. (2000) American</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015APS..GECLW1060S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015APS..GECLW1060S&link_type=ABSTRACT"><span id="translatedtitle">PIC-DSMC analysis on interaction of a laser <span class="hlt">induced</span> discharge and shock <span class="hlt">wave</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shimamura, Kohei</p> <p>2015-09-01</p> <p>Laser <span class="hlt">induced</span> discharge and the shock <span class="hlt">wave</span> have attracted great interest for use in the electrical engineering. When the high intensity laser (10 GW >) is focused in the atmosphere, the breakdown occurs and the discharge <span class="hlt">wave</span> propagates toward to the laser irradiation. The shock <span class="hlt">wave</span> is generated around the discharge <span class="hlt">wave</span>, which is called as the laser supported detonation <span class="hlt">wave</span>. After breakdown occurred, the initial electron of the avalanche ionization is produced by the photoionization due to the plasma radiation. It is well recognized that the radiation of the laser plasma affects the propagation mechanism of the laser <span class="hlt">induced</span> discharge <span class="hlt">wave</span> after the initiation of the breakdown. However, it is difficult to observe the interaction between the plasma radiation and the electron avalanche in the ionization-<span class="hlt">wave</span> front in experimentally except in the high intensity laser. In the numerical calculation of the laser-<span class="hlt">induced</span> discharge, the fluid dynamics based on the Navier-Stokes equation have been widely used. However, it is difficult to investigate the avalanche ionization at the <span class="hlt">wave</span> front using the fluid dynamics simulation. To investigate the interaction of the ionization-<span class="hlt">wave</span> front and the shock <span class="hlt">wave</span>, it is appropriate to utilize the PIC-DSMC method. The present study showed the propagation of the ionization front of the discharge <span class="hlt">wave</span> and the shock <span class="hlt">wave</span> using the particle simulation. This work was supported by Kato Foundation for Promotion of Science and Japan Power Academy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760006623','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760006623"><span id="translatedtitle">Theoretical monochromatic-<span class="hlt">wave-induced</span> currents in intermediate water with viscosity and nonzero mass transport</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Talay, T. A.</p> <p>1975-01-01</p> <p><span class="hlt">Wave-induced</span> mass-transport current theories with both zero and nonzero net mass (or volume) transport of the water column are reviewed. A relationship based on the Longuet-Higgens theory is derived for <span class="hlt">wave-induced</span>, nonzero mass-transport currents in intermediate water depths for a viscous fluid. The relationship is in a form useful for experimental applications; therefore, some design criteria for experimental <span class="hlt">wave</span>-tank tests are also presented. Sample parametric cases for typical <span class="hlt">wave</span>-tank conditions and a typical ocean swell were assessed by using the relation in conjunction with an equation developed by Unluata and Mei for the maximum <span class="hlt">wave-induced</span> volume transport. Calculations indicate that substantial changes in the <span class="hlt">wave-induced</span> mass-transport current profiles may exist dependent upon the assumed net volume transport. A maximum volume transport, corresponding to an infinite channel or idealized ocean condition, produces the largest <span class="hlt">wave-induced</span> mass-transport currents. These calculations suggest that <span class="hlt">wave-induced</span> mass-transport currents may have considerable effects on pollution and suspended-sediments transport as well as buoy drift, the surface and midlayer water-column currents caused by <span class="hlt">waves</span> increasing with increasing net volume transports. Some of these effects are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ApPhL.109f1108X&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ApPhL.109f1108X&link_type=ABSTRACT"><span id="translatedtitle">Radiation <span class="hlt">pressure</span> <span class="hlt">induced</span> difference-sideband generation beyond linearized description</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiong, Hao; Fan, Yu-Wan; Yang, Xiaoxue; Wu, Ying</p> <p>2016-08-01</p> <p>We investigate radiation-<span class="hlt">pressure</span> <span class="hlt">induced</span> generation of the frequency components at the difference-sideband in an optomechanical system, which beyond the conventional linearized description of optomechanical interactions between cavity fields and the mechanical oscillation. We analytically calculate amplitudes of these signals, and identify a simple square-root law for both the upper and lower difference-sideband generation which can describe the dependence of the intensities of these signals on the pump power. Further calculation shows that difference-sideband generation can be greatly enhanced via achieving the matching conditions. The effect of difference-sideband generation, which may have potential application for manipulation of light, is especially suited for on-chip optomechanical devices, where nonlinear optomechanical interaction in the weak coupling regime is within current experimental reach.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JPhCS.727a2001A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JPhCS.727a2001A&link_type=ABSTRACT"><span id="translatedtitle">On the influence of the hysteretic behavior of the capillary <span class="hlt">pressure</span> on the <span class="hlt">wave</span> propagation in partially saturated soils</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Albers, Bettina</p> <p>2016-06-01</p> <p>It is well known that the capillary <span class="hlt">pressure</span> curve of partially saturated soils exhibits a hysteresis. For the same degree of saturation it has different values depending on the initial state of the soil, thus for drying of a wet soil or wetting of a dry soil. The influence of these different values of the capillary <span class="hlt">pressure</span> on the propagation of sound <span class="hlt">waves</span> is studied by use of a linear hyperbolic model. Even if the model does not contain a hysteresis operator, the effect of hysteresis in the capillary <span class="hlt">pressure</span> curve is accounted for. In order to obtain the limits of phase speeds and attenuations for the two processes the correspondent values for main drying and main wetting are inserted into the model separately. This is done for two examples of soils, namely for Del Monte sand and for a silt loam both filled by an air-water mixture. The <span class="hlt">wave</span> analysis reveals four <span class="hlt">waves</span>: one transversal <span class="hlt">wave</span> and three longitudinal <span class="hlt">waves</span>. The <span class="hlt">waves</span> which are driven by the immiscible pore fluids are influenced by the hysteresis in the capillary <span class="hlt">pressure</span> curve while the <span class="hlt">waves</span> which are mainly driven by the solid are not.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApSS..357..678Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApSS..357..678Y"><span id="translatedtitle">Fabricating micro embossments on the metal surface through spatially modulating laser-<span class="hlt">induced</span> shock <span class="hlt">wave</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ye, Y. X.; Xuan, T.; Lian, Z. C.; Hua, X. J.; Fu, Y. H.</p> <p>2015-12-01</p> <p>In this paper, we propose one improved method to fabricate micro embossments on the metal surface through laser shock processing. One mapping layer with holes must be actively designed and produced on the metal surface, with which, laser-<span class="hlt">induced</span> shock <span class="hlt">wave</span> will be spatially modulated. Laser shock experiments were conducted. Then the surface morphologies, and metallographic microstructures were characterized. The forming process of the micro embossments was simulated with ABAQUS. The results show that under the spatially modulated shock loading, the surface material flows from the high-<span class="hlt">pressure</span> zone to the low-<span class="hlt">pressure</span> zone, which is responsible for forming the micro embossments. The shapes, sizes and arrangements of the micro embossments conform to those of the mapping holes. The hardnesses on the entire laser-shocked zones improve remarkably due to the plastic deformation at a high strain rate. The influences of the laser energy and mask pattern on the embossed structures are presented. Within certain limits, increasing laser energy is beneficial for making the embossment more convex. However, further excessively increasing the laser energy, the embossment will exhibit the height saturation due to the <span class="hlt">pressure</span> rise within the closed mapping hole. The transverse sizes of the mapping holes also can influence the embossment heights significantly. Process parameters need to be chosen carefully to suppress the severe adiabatic compression of the gas within the mapping holes, and then avoid weakening the mechanical properties of the micro embossments. This method has a potential application in manufacturing protruded structures on the metal surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24116702','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24116702"><span id="translatedtitle">Ambient <span class="hlt">pressure</span> laser desorption and laser-<span class="hlt">induced</span> acoustic desorption ion mobility spectrometry detection of explosives.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ehlert, Sven; Walte, Andreas; Zimmermann, Ralf</p> <p>2013-11-19</p> <p>The development of fast, mobile, and sensitive detection systems for security-relevant substances is of enormous importance. Because of the low vapor <span class="hlt">pressures</span> of explosives and improvised explosive devices, adequate sampling procedures are crucial. Ion mobility spectrometers (IMSs) are fast and sensitive instruments that are used as detection systems for explosives. Ambient <span class="hlt">pressure</span> laser desorption (APLD) and ambient <span class="hlt">pressure</span> laser-<span class="hlt">induced</span> acoustic desorption (AP-LIAD) are new tools suitable to evaporate explosives in order to detect them in the vapor phase. Indeed, the most important advantage of APLD or AP-LIAD is the capability to sample directly from the surface of interest without any transfer of the analyte to other surfaces such as wipe pads. A much more gentle desorption, compared to classical thermal-based desorption, is possible with laser-based desorption using very short laser pulses. With this approach the analyte molecules are evaporated in a very fast process, comparable to a shock <span class="hlt">wave</span>. The thermal intake is reduced considerably. The functionality of APLD and AP-LIAD techniques combined with a hand-held IMS system is shown for a wide range of common explosives such as EGDN (ethylene glycol dinitrate), urea nitrate, PETN (pentaerythritol tetranitrate), HMTD (hexamethylene triperoxide diamine), RDX (hexogen), tetryl (2,4,6-trinitrophenylmethylnitramine), and TNT (trinitrotoluene). Detection limits down to the low nanogram range are obtained. The successful combination of IMS detection and APLD/AP-LIAD sampling is shown. PMID:24116702</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3774482','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3774482"><span id="translatedtitle">Critical closing <span class="hlt">pressure</span> during midazolam-<span class="hlt">induced</span> sleep</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Eckert, Danny J.; Gregorio, Marcelo G.; Danzi, Naury J.; Moriya, Henrique T.; Malhotra, Atul; Lorenzi-Filho, Geraldo</p> <p>2011-01-01</p> <p>The critical closing <span class="hlt">pressure</span> (Pcrit) is the airway <span class="hlt">pressure</span> at which the airway collapses and reflects the anatomical contribution to the genesis of obstructive sleep apnea. Pcrit is usually determined during non-rapid eye movement sleep at night, but has been determined under midazolam sedation during the day in the absence of sleep stage monitoring. Indeed, little is known about the effects of midazolam on sleep architecture. Moreover, deeper sedation with midazolam can decrease upper airway muscle activity and increase collapsibility compared with natural sleep. Pcrit under sedation has not been systematically compared with the usual method performed during natural sleep. Therefore, this study aimed to test the hypothesis that Pcrit following low doses of midazolam during the day would be comparable to Pcrit measured during natural sleep in the same patient. Fifteen men (age 54 ± 10 yr, body mass index 30 ± 4 kg/m2) with obstructive sleep apnea underwent a baseline standard overnight polysomnogram (apnea-hypopnea index 38 ± 22 events/h, range: 8–66 events/h), and Pcrit was determined during natural sleep and following midazolam. Sleep induction was obtained with low doses of midazolam (2.4 mg, range 2.0–4.4 mg), and sleep architecture was comparable to natural sleep. Natural sleep and <span class="hlt">induced</span> sleep Pcrit were similar (−0.82 ± −3.44 and −0.97 ± 3.21 cmH2O, P = 0.663) and closely associated (intraclass correlation coefficient = 0.92; 95% confidence interval, 0.78–0.97, P < 0.001). Natural and midazolam-<span class="hlt">induced</span> Pcrit correlated with obstructive sleep apnea severity, indicating that both Pcrit measures provided meaningful physiological information. Pcrit determined during the day with sleep induction is similar to natural overnight sleep and is a valid alternative approach in which to determine Pcrit. PMID:21852408</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20020039729&hterms=Cuff&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DCuff','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020039729&hterms=Cuff&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DCuff"><span id="translatedtitle">Cerebrovascular Responses During Lower Body Negative <span class="hlt">Pressure-Induced</span> Presyncope</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kuriyama, Kana; Watenpaugh, D. E.; Hargens, Alan R.; Ueno, T.; Ballard, R. E.; Fortney, S. M.</p> <p>1996-01-01</p> <p>Reduced orthostatic tolerance is commonly observed after space flight, occasionally causing presyncopal conditions. Although the cerebrovascular system may play an important role in presyncope, there have been few reports concerning cerebral hemodynamics during presyncope. The purpose of this study was to investigate cerebrovascular responses during presyncope <span class="hlt">induced</span> by lower body negative <span class="hlt">pressure</span> (LBNP). Seven healthy male volunteers were exposed to LBNP in steps of -10 mmHg every 3 min until presyncopal symptoms were detected. Blood <span class="hlt">pressure</span> (BP) and heart rate (HR) were measured with a finger cuff. Cerebral tissue oxy- and deoxy- hemoglobin (Hb) concentrations were estimated using near infrared spectroscopy (NIRS). Cerebral blood flow (CBF) velocity at the middle cerebral artery was measured with Transcranial Doppler Sonography (TCD). We focused on the data during the 2 min before endpoint. BP marked a gradual decrease (91 to 86 mmHg from 2 min to 30 sec before endpoint), which was accelerated along with HR decrease during the final 30 sec (86 to 71 mmHg). Cerebral oxy-Hb concentration decreases as presyncope is approached while total-Hb concentration remains fairly constant. TCD reveals a decrease in the CBF velocity. The TCD and NIRS results suggest that CBF decreases along with the BP decrease. Cerebrovascular responses during presyncope are closely related to cardiovascular responses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008APS..DFD.HU003D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008APS..DFD.HU003D"><span id="translatedtitle">An Experimental Investigation of the Free Surface Profiles Generated by a Moving <span class="hlt">Pressure</span> Source: Solitary Capillary-Gravity <span class="hlt">Waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Diorio, J. D.; Watkins, N.; Zuech, J.; Duncan, J. H.</p> <p>2008-11-01</p> <p>There have been several recent numerical investigations that have shown the existence of three-dimensional nonlinear solitary surface <span class="hlt">wave</span> patterns that propagate with speeds less than the minimum <span class="hlt">wave</span> phase speed prescribed by linear theory (23 cm/s for clean water). In the present study, <span class="hlt">wave</span> patterns were generated by translating a small-diameter region of high <span class="hlt">pressure</span> across a water surface. The high-<span class="hlt">pressure</span> region was created by forcing air through a small-diameter vertically oriented tube attached to a carriage that propelled it horizontally at speeds near 23 cm/s. The <span class="hlt">wave</span> pattern was measured with a cinematic LIF technique. It was found that a steady solitary <span class="hlt">wave</span> pattern can exist at speeds below the linear-theory minimum phase speed, while for speeds above the minimum, a pattern of gravity-capillary <span class="hlt">waves</span> was produced. The solitary <span class="hlt">wave</span> pattern, which only appeared when the <span class="hlt">pressure</span> forcing was large, dissipated rapidly when the forcing was turned off. The streamwise dimension of the solitary <span class="hlt">wave</span> was much smaller than the transverse dimension.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22490925','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22490925"><span id="translatedtitle">Effect of anisotropic dust <span class="hlt">pressure</span> and superthermal electrons on propagation and stability of dust acoustic solitary <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bashir, M. F.; Behery, E. E.; El-Taibany, W. F.</p> <p>2015-06-15</p> <p>Employing the reductive perturbation technique, Zakharov–Kuznetzov (ZK) equation is derived for dust acoustic (DA) solitary <span class="hlt">waves</span> in a magnetized plasma which consists the effects of dust anisotropic <span class="hlt">pressure</span>, arbitrary charged dust particles, Boltzmann distributed ions, and Kappa distributed superthermal electrons. The ZK solitary <span class="hlt">wave</span> solution is obtained. Using the small-k expansion method, the stability analysis for DA solitary <span class="hlt">waves</span> is also discussed. The effects of the dust <span class="hlt">pressure</span> anisotropy and the electron superthermality on the basic characteristics of DA <span class="hlt">waves</span> as well as on the three-dimensional instability criterion are highlighted. It is found that the DA solitary <span class="hlt">wave</span> is rarefactive (compressive) for negative (positive) dust. In addition, the growth rate of instability increases rapidly as the superthermal spectral index of electrons increases with either positive or negative dust grains. A brief discussion for possible applications is included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014APS..DFDG29003T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014APS..DFDG29003T"><span id="translatedtitle">Spatiotemporal evolution of a laser-<span class="hlt">induced</span> shock <span class="hlt">wave</span> measured by the background-oriented schlieren technique</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tagawa, Yoshiyuki; Yamamoto, Shota; Kameda, Masaharu</p> <p>2014-11-01</p> <p>We investigate the spatiotemporal evolution of a laser-<span class="hlt">induced</span> shock <span class="hlt">wave</span> in a liquid filled thin tube. In order to measure <span class="hlt">pressure</span> distribution at shock front, we adopt the background-oriented schlieren (BOS) technique. This technique provides two- or three-dimensional <span class="hlt">pressure</span> field in a small region with a simple setup. With an ultra high-speed video camera and a laser stroboscope, we successfully capture the spatial evolution of the shock every 0.2 μs. We find an angular variation of the <span class="hlt">pressure</span> at the shock front. The maximum <span class="hlt">pressure</span> is in the direction of the laser shot while the minimum value is in the perpendicular direction. We compare the temporal evolution of the <span class="hlt">pressure</span> measured by BOS technique with those obtained by another method, i.e. <span class="hlt">pressure</span> estimation from the shock front position. Overall trend from both methods show a good agreement. The <span class="hlt">pressure</span> from the shock front position exists between the maximum and minimum values from BOS technique. It indicates that our quantification method can measure more detailed <span class="hlt">pressure</span> field in two- or three-dimensions. Our results might be used for the efficient generation systems for the microjet, which can be applicable for needle free injection devices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012APS..DFDG28007M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012APS..DFDG28007M"><span id="translatedtitle">On the unsteady free surface <span class="hlt">wave</span> pattern found behind a localized <span class="hlt">pressure</span> distribution moving at speeds just below the minimum phase speed of linear gravity capillary <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Masnadi, N.; Duncan, J. H.</p> <p>2012-11-01</p> <p>The non-linear response of a water free surface to a localized <span class="hlt">pressure</span> distribution moving at constant speed just below the minimum phase speed (Cmin ~ 23 cm/s) of gravity-capillary <span class="hlt">waves</span> is studied experimentally in a long tank. The <span class="hlt">pressure</span> distribution is generated by blowing air onto the water surface via a vertically oriented 2-mm-ID tube that is mounted on an instrument carriage that is in turn set to move along the tank at constant speeds between 20 and 23 cm/s. A cinematic light refraction method is used to obtain quantitative measurements of the surface deformation pattern behind the air jet. At towing speeds just below Cmin, an unsteady V-shaped <span class="hlt">wave</span> pattern appears behind the <span class="hlt">pressure</span> source. From observations of the <span class="hlt">wave</span> pattern evolution, it is found that localized depressions are generated near the <span class="hlt">pressure</span> source and propagate in pairs along the two arms of the V-shaped pattern. These are eventually shed from the tips of the pattern and rapidly decay. Measurements of the evolution of the speed of these localized depression patterns are compared to existing measurements of the speeds of steady three-dimensional solitary gravity-capillary <span class="hlt">waves</span> (lumps) that appear behind the <span class="hlt">pressure</span> source at even lower towing speeds. Supported by the National Science Foundation Division of Ocean Sciences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/9039074','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/9039074"><span id="translatedtitle">Senescent heart compared with <span class="hlt">pressure</span> overload-<span class="hlt">induced</span> hypertrophy.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Assayag, P; Charlemagne, D; de Leiris, J; Boucher, F; Valère, P E; Lortet, S; Swynghedauw, B; Besse, S</p> <p>1997-01-01</p> <p>Although systolic left ventricular (LV) function is normal in the elderly, aging is associated in rat papillary muscle with mechanical and sarcoplasmic reticulum Ca2+ ATPase alterations similar to those observed in the hypertrophied heart. However, alterations in the other calcium-regulating proteins implicated in contraction and relaxation are still unknown. To investigate alterations in LV function and calcium-regulating proteins, we measured hemodynamics and Na(+)-Ca2+ exchanger (NCx), ryanodine receptor (RyR2), and sarcoplasmic reticular Ca2+ ATPase (SERCA2) mRNA levels (expressed in densitometric scores normalized to that of poly(A+) mRNA) in left ventricle from 4-month-old (adult, n = 13) and 24-month-old (senescent, n = 15) rats. For ex vivo contractile function, active tension was measured during isolated heart perfusion in adult (n = 11) and senescent (n = 11) rats. For comparison of age-dependent effects of moderate hypertension on both hemodynamics and calcium proteins, renovascular hypertension was <span class="hlt">induced</span> or a sham operation performed at 2 (n = 11 and n = 6) and 22 (n = 26 and n = 5) months of age. In senescent rats, LV systolic <span class="hlt">pressure</span> and maximal rates of <span class="hlt">pressure</span> development were unaltered, although active tension was depressed (4.7 +/- 0.4 versus 8.3 +/- 0.7 g/g heart weight in adults, P < .0001). SERCA2 mRNA levels were decreased in senescent left ventricle (0.98 +/- 0.05 versus 1.18 +/- 0.05 in adults, P < .01), without changes in NCx and RyR2 mRNA accumulation. Renovascular hypertension resulted in 100% mortality in aged rats; in adults, renovascular hypertension resulted, 2 months later, in an increase of LV systolic <span class="hlt">pressure</span> (170 +/- 7 versus 145 +/- 3 mm Hg in sham-operated rats, P < .05) and in mild LV hypertrophy (+18%, P < .01) associated with a decrease in SERCA2 mRNA levels (1.02 +/- 0.03 versus 1.18 +/- 0.03 in sham-operated rats, P < .001). Contractile dysfunction in senescent isolated heart and decreased SERCA2 mRNA levels were</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3711703','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3711703"><span id="translatedtitle">Vibration and <span class="hlt">pressure</span> <span class="hlt">wave</span> therapy for calf strains: a proposed treatment</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Saxena, Amol; St. Louis, Marie; Fournier, Magali</p> <p>2013-01-01</p> <p>Summary Calf (lower leg) strains have a variety of treatment regimens with variable outcomes and return to activity (RTA) time frames. These injuries involve disruption of portions or the entire gastrocnemius-soleus myo-tendinous complex. Conservative treatment initially consists of rest, ice, compression, elevation (RICE). Immediately following calf injury, patients can utilize cryotherapy, massage, passive range of motion, and progressive exercise. In general, Grade I through Grade III calf strains can take up to 6 weeks before the athlete can return to training. It can also involve the loss of more than 50% of muscle integrity. Recently, vibration therapy and radial <span class="hlt">pressure</span> <span class="hlt">waves</span> have been utilized to treat muscular strains and other myo-tendinous injuries that involve trigger points. Studies have suggested vibration therapy with rehabilitation can increase muscle strength and flexibility in patients. Segmental vibration therapy (SVT) is treatment to a more focal area. Vibration therapy (VT) is applied directly to the area of injury. VT is a mechanical stimulus that is thought to stimulate the sensory receptors, as well as decrease inflammatory cells and receptors. Therefore, VT could be a valuable tool in treating athlete effectively and decreasing their recovery time. The purpose of this paper is to give the reader baseline knowledge of VT and propose a treatment protocol for calf strains using this technology along with radial <span class="hlt">pressure</span> <span class="hlt">waves</span>. PMID:23888287</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22257006','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22257006"><span id="translatedtitle">Experimental determination of radiated internal <span class="hlt">wave</span> power without <span class="hlt">pressure</span> field data</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lee, Frank M.; Morrison, P. J.; Paoletti, M. S.; Swinney, Harry L.</p> <p>2014-04-15</p> <p>We present a method to determine, using only velocity field data, the time-averaged energy flux (J) and total radiated power P for two-dimensional internal gravity <span class="hlt">waves</span>. Both (J) and P are determined from expressions involving only a scalar function, the stream function ψ. We test the method using data from a direct numerical simulation for tidal flow of a stratified fluid past a knife edge. The results for the radiated internal <span class="hlt">wave</span> power given by the stream function method agree to within 0.5% with results obtained using <span class="hlt">pressure</span> and velocity data from the numerical simulation. The results for the radiated power computed from the stream function agree well with power computed from the velocity and <span class="hlt">pressure</span> if the starting point for the stream function computation is on a solid boundary, but if a boundary point is not available, care must be taken to choose an appropriate starting point. We also test the stream function method by applying it to laboratory data for tidal flow past a knife edge, and the results are found to agree with the direct numerical simulation. The supplementary material includes a Matlab code with a graphical user interface that can be used to compute the energy flux and power from two-dimensional velocity field data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3462261','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3462261"><span id="translatedtitle">Stone Comminution Correlates with the Average Peak <span class="hlt">Pressure</span> Incident on a Stone during Shock <span class="hlt">Wave</span> Lithotripsy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Smith, N.; Zhong, P.</p> <p>2012-01-01</p> <p>To investigate the roles of lithotripter shock <span class="hlt">wave</span> (LSW) parameters and cavitation in stone comminution, a series of in vitro fragmentation experiments have been conducted in water and 1,3-butanediol (a cavitation-suppressive fluid) at a variety of acoustic field positions of an electromagnetic shock <span class="hlt">wave</span> lithotripter. Using field mapping data and integrated parameters averaged over a circular stone holder area (Rh = 7 mm), close logarithmic correlations between the average peak <span class="hlt">pressure</span> (P+(avg)) incident on the stone (D = 10 mm BegoStone) and comminution efficiency after 500 and 1,000 shocks have been identified. Moreover, the correlations have demonstrated distinctive thresholds in P+(avg) (5.3 MPa and 7.6 MPa for soft and hard stones, respectively), that are required to initiate stone fragmentation independent of surrounding fluid medium and LSW dose. These observations, should they be confirmed using other shock <span class="hlt">wave</span> lithotripters, may provide an important field parameter (i.e., P+(avg)) to guide appropriate application of SWL in clinics, and facilitate device comparison and design improvements in future lithotripters. PMID:22935690</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007APS..DFD.EB001V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007APS..DFD.EB001V"><span id="translatedtitle">Nonlinear <span class="hlt">wave</span> evolution in <span class="hlt">pressure</span>-driven stratified flow of Newtonian and Herschel-Bulkley fluids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Valluri, Prashant; Sahu, Kirti; Ding, Hang; Spelt, Peter; Matar, Omar; Lawrence, Chris</p> <p>2007-11-01</p> <p><span class="hlt">Pressure</span>-driven stratified channel flow of a Newtonian fluid flowing over a Herschel-Bulkley (HB) fluid is considered. The effects of yield stress and shear-thinning rheology on the nonlinear <span class="hlt">wave</span> evolution are studied using numerical simulations; the HB rheology is regularized at low shear rates using a bi-viscosity formulation. Two different numerical methods were used to carry out the computations: a level-set method (based on that by Spelt, J. Comput. Phys. 2005) and a diffuse-interface method (based on that by Ding et al., J. Comput. Phys., in press). The simulations, which account for fluid inertia, surface tension and gravity are validated against linear theory predictions at early times. The results at later times show the spatio-temporal evolution into the nonlinear regime wherein <span class="hlt">waves</span> are strongly deformed, leading to the onset of drop entrainment. It is shown that the apparent viscosity in the region of the HB fluid directly involved in the onset of entrainment is almost constant; unyielded regions are confined to <span class="hlt">wave</span> troughs at late stages of the nonlinear evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014EGUGA..1614104Z&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014EGUGA..1614104Z&link_type=ABSTRACT"><span id="translatedtitle">External and internal <span class="hlt">waves</span> in stream-potential <span class="hlt">pressure</span>-coordinate dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zirk, Marko; Rõõm, Rein</p> <p>2014-05-01</p> <p>In stream-potential dynamics <span class="hlt">pressure</span> coordinate velocity -→v = {dx/dt,dy/dt,dp/dt} = {vx,vy,vp} = {u,v,ω } is presented in terms of 4D stream-potential {ψ0,ψx,ψy,ψp} -→v = downtriangleψ0 + downtriangle× -→ψ leftrightarrow vi = Giαδαψ0 + ɛαβγδβψγ, with diagonal metric tensor with main elements G11 = G22 = 1, G33 = p2/H2 (H = RT/g is the height scale). Vector potential -→ ψ is further expressed via horizontal curl and divergence of the stream function ω = δxψy - δyψx ≠¡ dp/dt, Ξ = δxψx + δyψy. The <span class="hlt">wave</span>-vector components in linearized stream-potential dynamics are the scalar flow potential ψ0, surface <span class="hlt">pressure</span> fluctuation p's, horizontal divergence Ξ and curl ω of the fluctuative part -→ψ' of complete vector potential -→ψ = -→ψ + -→ψ' . Equations for ψ0 and p's form the external <span class="hlt">wave</span> subsystem δp' δ« ps dξ0 - -→- p2 δ2 -s+ downtriangle2 ψ0dp = 0, -+gH downtriangle2(p's/ps) = A0(ψ ,ω,Ξ), L0ψ0 = ξ0, L0 =-2 -2+downtriangle2, δt 0 dt H δp (1) while the equations for Ξ, ω and temperature fluctuation T' form the internal <span class="hlt">wave</span> subsystem d-→ξ -→ -→- dT ' Tiω ( ) ( p2 δ2 ) p2 -dt = A (ψ,ω,Ξ), -dt = -p-+Q, L0Ξ = δp p2ξp/H2 , H2- δp2 + downtriangle2 ω = H2-(δyξx - δxξy) (2) with Ti = (R/cp)T - pδpT. In these equations 0 -→ α -→ -→ i iαβ ξ = downtriangle · v = δαv , ξ = downtriangle ×v leftrightarrow ξ = ɛ δαvβ are the 3D divergence and curl of velocity. In the presentation equation systems (1) and (2) are solved both analytically and numerically. Interaction of external <span class="hlt">waves</span> with stationary internal orographic <span class="hlt">waves</span> is investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4713536','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4713536"><span id="translatedtitle">Cinnamaldehyde attenuates <span class="hlt">pressure</span> overload-<span class="hlt">induced</span> cardiac hypertrophy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Yang, Liu; Wu, Qing-Qing; Liu, Yuan; Hu, Zhe-Fu; Bian, Zhou-Yan; Tang, Qi-Zhu</p> <p>2015-01-01</p> <p>Background: Cinnamaldehyde is a major bioactive compound isolated from the leaves of Cinnamomum osmophloeum. Studies have demonstrated that cinnamaldehyde has anti-bacterial activity, anti-tumorigenic effect, immunomodulatory effect, anti-fungal activity, anti-oxidative effect, anti-inflammatory and anti-diabetic effect. It has been proven that Cinnamaldehyde improves ischemia/reperfusion injury of pre-treatment. However, little is known about the effect of cinnamaldehyde on cardiac hypertrophy. Methods: Aortic banding (AB) was performed to <span class="hlt">induce</span> cardiac hypertrophy in mice. Cinnamaldehyde premixed in diets was administered to mice after one week of AB. Echocardiography and catheter-based measurements of hemodynamic parameters were performed at week 7 after starting cinnamaldehyde (8 weeks after surgery). The extent of cardiac hypertrophy was evaluated by pathological and molecular analyses of heart samples. Meanwhile, the effect of cinnamaldehyde on myocardial hypertrophy, fibrosis and dysfunction <span class="hlt">induced</span> by AB was investigated, as was assessed by heart weigh/body weight, lung weight/body weight, heart weight/tibia length, echocardiographic and haemodynamic parameters, histological analysis, and gene expression of hypertrophic and fibrotic markers. Results: Our data demonstrated that echocardiography and catheter-based measurements of hemodynamic parameters at week 7 revealed the amelioration of systolic and diastolic abnormalities by cinnamaldehyde intervention. Cardiac fibrosis in AB mice was also decreased by cinnamaldehyde. Moreover, the beneficial effect of cinnamaldehyde was associated with the normalization in gene expression of hypertrophic and fibrotic markers. Further studies showed that <span class="hlt">pressure</span> overload significantly <span class="hlt">induced</span> the activation of extracellular signal-regulated kinase (ERK) signaling pathway, which was blocked by cinnamaldehyde. Conclusion: Cinnamaldehyde may be able to retard the progression of cardiac hypertrophy and fibrosis, probably</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRC..118.1955L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRC..118.1955L"><span id="translatedtitle">Field observations of <span class="hlt">wave-induced</span> streaming through a submerged seagrass (Posidonia oceanica) meadow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Luhar, Mitul; Infantes, Eduardo; Orfila, Alejandro; Terrados, Jorge; Nepf, Heidi M.</p> <p>2013-04-01</p> <p>paper reports the findings of a 2 week field campaign designed to study <span class="hlt">wave-induced</span> flows within a meadow of Posidonia oceanica at water depth 9 m. Previous laboratory experiments suggest that <span class="hlt">waves</span> <span class="hlt">induce</span> a mean mass drift in the direction of <span class="hlt">wave</span> propagation ("streaming") through submerged canopies of vegetation. This paper provides the first field measurements of this <span class="hlt">wave-induced</span> streaming. During periods of high <span class="hlt">wave</span> activity, streaming flows with magnitudes as high as 20% of the near-bed oscillatory velocity were measured within the meadow. In addition to presenting field measurements of <span class="hlt">wave-induced</span> streaming, this paper also considers the damping of <span class="hlt">wave-induced</span> oscillatory flow within the seagrass meadow. Oscillatory velocities measured within the meadow were reduced by less than 30% relative to those above the meadow over the duration of the study. This is in agreement with previous laboratory and field measurements which show that oscillatory flows are damped less within submerged canopies compared to unidirectional flows. Existing analytical models underpredict the magnitude of the streaming flow and overpredict oscillatory velocity reductions. These discrepancies are thought to arise because the drag generated by flexible seagrasses moving with <span class="hlt">wave-induced</span> flow is not well described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890004471','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890004471"><span id="translatedtitle">Constraints on gravity <span class="hlt">wave</span> <span class="hlt">induced</span> diffusion in the middle atmosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Strobel, Darrell F.</p> <p>1988-01-01</p> <p>A review of the important constraints on gravity <span class="hlt">wave</span> <span class="hlt">induced</span> diffusion of chemical tracers, heat and momentum is given. Ground-based microwave spectroscopy measurements of H2O and CO and rocket-based mass spectrometer measurements of Ar constrain the eddy diffusion coefficient for constituent transport (K sub zz) to be (1-3) x 10 to the 5th sq cm/sec in the upper mesosphere. Atomic oxygen data also limits K sub zz to a comparable value in the mesopause. From the energy balance of the upper mesosphere the eddy diffusion coefficient for heat transport (D sub H) is, at most, 6 x 10 to the 5th sq cm/sec at the mesopause and decreasing substantially with decreasing altitude. The available evidence for mean wind deceleration and the corresponding eddy diffusion coefficient for momentum stresses (D sub M) suggests that it is at least 1 x 10 to the 6th sq cm/sec in the upper mesosphere. Consequently the eddy Prandtl number for macroscopic scale lengths is greater than 3.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21054532','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21054532"><span id="translatedtitle">High-Frequency Gravitational <span class="hlt">Wave</span> <span class="hlt">Induced</span> Nuclear Fusion</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fontana, Giorgio; Baker, Robert M. L. Jr.</p> <p>2007-01-30</p> <p>Nuclear fusion is a process in which nuclei, having a total initial mass, combine to produce a single nucleus, having a final mass less than the total initial mass. Below a given atomic number the process is exothermic; that is, since the final mass is less than the combined initial mass and the mass deficit is converted into energy by the nuclear fusion. On Earth nuclear fusion does not happen spontaneously because electrostatic barriers prevent the phenomenon. To <span class="hlt">induce</span> controlled, industrial scale, nuclear fusion, only a few methods have been discovered that look promising, but net positive energy production is not yet possible because of low overall efficiency of the systems. In this paper we propose that an intense burst of High Frequency Gravitational <span class="hlt">Waves</span> (HFGWs) could be focused or beamed to a target mass composed of appropriate fuel or target material to efficiently rearrange the atomic or nuclear structure of the target material with consequent nuclear fusion. Provided that efficient generation of HFGW can be technically achieved, the proposed fusion reactor could become a viable solution for the energy needs of mankind and alternatively a process for beaming energy to produce a source of fusion energy remotely - even inside solid materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009APS..DPPPP8002P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009APS..DPPPP8002P"><span id="translatedtitle">Lower Hybrid <span class="hlt">Wave</span> <span class="hlt">Induced</span> Rotation on Alcator C-Mod</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parker, Ron; Podpaly, Yuri; Rice, John; Schmidt, Andrea</p> <p>2009-11-01</p> <p>Injection of RF power in the vicinity of the lower hybrid frequency has been observed to cause strong counter current rotation in Alcator C-Mod plasmas [1,2]. The spin-up rate is consistent with the rate at which momentum is injected by the LH <span class="hlt">waves</span>, and also the rate at which fast electron momentum is transferred to the ions. A momentum diffusivity of ˜ 0.1 m^2/s is sufficient to account for the observed steady-state rotation. This value is also comparable with that derived from an analysis of rotation <span class="hlt">induced</span> by RF mode conversion [3]. Radial force balance requires a radial electric field, suggesting a buildup of negative charge in the plasma core. This may be the result of an inward pinch of the LH produced fast electrons, as would be expected for resonant trapped particles. Analysis of the fast-electron-produced bremsstrahlung during LH power modulation experiments yields an inward pinch velocity of ˜ 1 m/s, consistent with the estimated trapped particle pinch velocity. [4pt] [1] A. Ince-Cushman, et.al., Phys. Rev. Lett., 102, 035002 (2009)[0pt] [2] J. E. Rice, et. al., Nucl. Fusion 49, 025004 (2009)[0pt] [3] Y. Lin, et.al., this meeting</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013APS..SHK.M1075B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..SHK.M1075B"><span id="translatedtitle">Cylindrical shock <span class="hlt">waves</span> and dynamic phenomena <span class="hlt">induced</span> in solids by intense proton beams</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bertarelli, Alessandro; Carra, Federico; Dallocchio, Alessandro; Guinchard, Michael; Mariani, Nicola; Peroni, Lorenzo; Redaelli, Stefano; Scapin, Martina</p> <p>2013-06-01</p> <p>The accidental impact of hadron beams on matter can <span class="hlt">induce</span> intense shockwaves along with complex dynamic phenomena (phase transitions, extended density changes, explosions and fragment projections). These events have been successfully modeled resorting to <span class="hlt">wave</span> propagation codes; to produce accurate results, however, these programs require reliable material constitutive models that are often scarce and inaccurate. A complex and innovative experiment was carried out at CERN to benchmark existing material constitutive models and possibly derive new ones. The test setup, aimed at the characterization of six different materials impacted by 440 GeV intense proton pulses, allowed to generate cylindrical shockwaves on material specimens and to observe the effects <span class="hlt">induced</span> by their propagation. This method, a combination between numerical simulations and an experimental technique, permitting to tune the intensity, location and timing of the beam-deposited energy, may allow to study the effects <span class="hlt">induced</span> by internal, quasi-instantaneous loadings in domains well beyond particle physics (accidents in nuclear facilities, internal explosions, high <span class="hlt">pressure</span> blasts etc.), particularly when relatively little explored cylindrical shockwaves are generated. The research leading to these results has received funding from the European Commission under the FP7 Research Infrastructures project EuCARD, grant agreement no. 227579.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23904049','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23904049"><span id="translatedtitle">Methodology and evaluation of intracranial <span class="hlt">pressure</span> response in rats exposed to complex shock <span class="hlt">waves</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dal Cengio Leonardi, Alessandra; Keane, Nickolas J; Hay, Kathryn; Ryan, Anne G; Bir, Cynthia A; VandeVord, Pamela J</p> <p>2013-12-01</p> <p>Studies on blast neurotrauma have focused on investigating the effects of exposure to free-field blast representing the simplest form of blast threat scenario without considering any reflecting surfaces. However, in reality personnel are often located within enclosures or nearby reflecting walls causing a complex blast environment, that is, involving shock reflections and/or compound <span class="hlt">waves</span> from different directions. The purpose of this study was to design a complex <span class="hlt">wave</span> testing system and perform a preliminary investigation of the intracranial <span class="hlt">pressure</span> (ICP) response of rats exposed to a complex blast <span class="hlt">wave</span> environment (CBWE). The effects of head orientation in the same environment were also explored. Furthermore, since it is hypothesized that exposure to a CBWE would be more injurious as compared to a free-field blast <span class="hlt">wave</span> environment (FFBWE), a histological comparison of hippocampal injury (cleaved caspase-3 and glial fibrillary acidic protein (GFAP)) was conducted in both environments. Results demonstrated that, regardless of orientation, peak ICP values were significantly elevated over the peak static air overpressure. Qualitative differences could be noticed compared to the ICP response in rats exposed to simulated FFBWE. In the CBWE scenario, after the initial loading the skull/brain system was not allowed to return to rest and was loaded again reaching high ICP values. Furthermore, results indicated consistent and distinct ICP-time profiles according to orientation, as well as distinctive values of impulse associated with each orientation. Histologically, cleaved caspase-3 positive cells were significantly increased in the CBWE as compared to the FFBWE. Overall, these findings suggest that the geometry of the skull and the way sutures are distributed in the rats are responsible for the difference in the stresses observed. Moreover, this increase stress contributes to correlation of increased injury in the CBWE. PMID:23904049</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvP...4b4013N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvP...4b4013N"><span id="translatedtitle">Implementation of Electromagnetically <span class="hlt">Induced</span> Transparency in a Metamaterial Controlled with Auxiliary <span class="hlt">Waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakanishi, Toshihiro; Kitano, Masao</p> <p>2015-08-01</p> <p>We propose a metamaterial to realize true electromagnetically <span class="hlt">induced</span> transparency (EIT), where the incidence of an auxiliary electromagnetic <span class="hlt">wave</span> called the control <span class="hlt">wave</span> <span class="hlt">induces</span> transparency for a probe <span class="hlt">wave</span>. The analogy to the original EIT effect in an atomic medium is shown through analytical and numerical calculations derived from a circuit model for the metamaterial. We perform experiments to demonstrate the EIT effect of the metamaterial in the microwave region. The width and position of the transparent region can be controlled by the power and frequency of the control <span class="hlt">wave</span>. We also observe asymmetric transmission spectra unique to the Fano resonance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4473736','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4473736"><span id="translatedtitle">Dual shear <span class="hlt">wave</span> <span class="hlt">induced</span> laser speckle contrast signal and the improvement in shear <span class="hlt">wave</span> speed measurement</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Li, Sinan; Cheng, Yi; Eckersley, Robert J; Elson, Daniel S; Tang, Meng-Xing</p> <p>2015-01-01</p> <p>Shear <span class="hlt">wave</span> speed is quantitatively related to tissue viscoelasticity. Previously we reported shear <span class="hlt">wave</span> tracking at centimetre depths in a turbid optical medium using laser speckle contrast detection. Shear <span class="hlt">wave</span> progression modulates displacement of optical scatterers and therefore modulates photon phase and changes the laser speckle patterns. Time-resolved charge-coupled device (CCD)-based speckle contrast analysis was used to track shear <span class="hlt">waves</span> and measure the time-of-flight of shear <span class="hlt">waves</span> for speed measurement. In this manuscript, we report a new observation of the laser speckle contrast difference signal for dual shear <span class="hlt">waves</span>. A modulation of CCD speckle contrast difference was observed and simulation reproduces the modulation pattern, suggesting its origin. Both experimental and simulation results show that the dual shear <span class="hlt">wave</span> approach generates an improved definition of temporal features in the time-of-flight optical signal and an improved signal to noise ratio with a standard deviation less than 50% that of individual shear <span class="hlt">waves</span>. Results also show that dual shear <span class="hlt">waves</span> can correct the bias of shear <span class="hlt">wave</span> speed measurement caused by shear <span class="hlt">wave</span> reflections from elastic boundaries. PMID:26114021</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26647962','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26647962"><span id="translatedtitle">Nonlinear Generation of Electromagnetic <span class="hlt">Waves</span> through <span class="hlt">Induced</span> Scattering by Thermal Plasma.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tejero, E M; Crabtree, C; Blackwell, D D; Amatucci, W E; Mithaiwala, M; Ganguli, G; Rudakov, L</p> <p>2015-01-01</p> <p>We demonstrate the conversion of electrostatic pump <span class="hlt">waves</span> into electromagnetic <span class="hlt">waves</span> through nonlinear <span class="hlt">induced</span> scattering by thermal particles in a laboratory plasma. Electrostatic <span class="hlt">waves</span> in the whistler branch are launched that propagate near the resonance cone. When the amplitude exceeds a threshold ~5 × 10(-6) times the background magnetic field, <span class="hlt">wave</span> power is scattered below the pump frequency with <span class="hlt">wave</span> normal angles (~59°), where the scattered wavelength reaches the limits of the plasma column. The scattered <span class="hlt">wave</span> has a perpendicular wavelength that is an order of magnitude larger than the pump <span class="hlt">wave</span> and longer than the electron skin depth. The amplitude threshold, scattered frequency spectrum, and scattered <span class="hlt">wave</span> normal angles are in good agreement with theory. The results may affect the analysis and interpretation of space observations and lead to a comprehensive understanding of the nature of the Earth's plasma environment. PMID:26647962</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4673455','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4673455"><span id="translatedtitle">Nonlinear Generation of Electromagnetic <span class="hlt">Waves</span> through <span class="hlt">Induced</span> Scattering by Thermal Plasma</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Tejero, E. M.; Crabtree, C.; Blackwell, D. D.; Amatucci, W. E.; Mithaiwala, M.; Ganguli, G.; Rudakov, L.</p> <p>2015-01-01</p> <p>We demonstrate the conversion of electrostatic pump <span class="hlt">waves</span> into electromagnetic <span class="hlt">waves</span> through nonlinear <span class="hlt">induced</span> scattering by thermal particles in a laboratory plasma. Electrostatic <span class="hlt">waves</span> in the whistler branch are launched that propagate near the resonance cone. When the amplitude exceeds a threshold ~5 × 10−6 times the background magnetic field, <span class="hlt">wave</span> power is scattered below the pump frequency with <span class="hlt">wave</span> normal angles (~59°), where the scattered wavelength reaches the limits of the plasma column. The scattered <span class="hlt">wave</span> has a perpendicular wavelength that is an order of magnitude larger than the pump <span class="hlt">wave</span> and longer than the electron skin depth. The amplitude threshold, scattered frequency spectrum, and scattered <span class="hlt">wave</span> normal angles are in good agreement with theory. The results may affect the analysis and interpretation of space observations and lead to a comprehensive understanding of the nature of the Earth’s plasma environment. PMID:26647962</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatSR...517852T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...517852T"><span id="translatedtitle">Nonlinear Generation of Electromagnetic <span class="hlt">Waves</span> through <span class="hlt">Induced</span> Scattering by Thermal Plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tejero, E. M.; Crabtree, C.; Blackwell, D. D.; Amatucci, W. E.; Mithaiwala, M.; Ganguli, G.; Rudakov, L.</p> <p>2015-12-01</p> <p>We demonstrate the conversion of electrostatic pump <span class="hlt">waves</span> into electromagnetic <span class="hlt">waves</span> through nonlinear <span class="hlt">induced</span> scattering by thermal particles in a laboratory plasma. Electrostatic <span class="hlt">waves</span> in the whistler branch are launched that propagate near the resonance cone. When the amplitude exceeds a threshold ~5 × 10-6 times the background magnetic field, <span class="hlt">wave</span> power is scattered below the pump frequency with <span class="hlt">wave</span> normal angles (~59°), where the scattered wavelength reaches the limits of the plasma column. The scattered <span class="hlt">wave</span> has a perpendicular wavelength that is an order of magnitude larger than the pump <span class="hlt">wave</span> and longer than the electron skin depth. The amplitude threshold, scattered frequency spectrum, and scattered <span class="hlt">wave</span> normal angles are in good agreement with theory. The results may affect the analysis and interpretation of space observations and lead to a comprehensive understanding of the nature of the Earth’s plasma environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SPIE.8794E..1CL','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SPIE.8794E..1CL"><span id="translatedtitle">In the trail of a fiber Bragg grating sensor to assess the central arterial <span class="hlt">pressure</span> <span class="hlt">wave</span> profile</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leitão, Cátia; Antunes, Paulo; Bastos, José M.; André, Paulo; Pinto, João. L.</p> <p>2013-05-01</p> <p>Cardiovascular diseases are one of the primary causes of death in the world. Hemodynamics is the study of the blood propagation and the physics aspects concerned to it, relating <span class="hlt">pressure</span>, flow and resistance. One of the most important topics on hemodynamics is the evaluation of arterial <span class="hlt">wave</span> reflections. Recently this physical parameter of the <span class="hlt">pressure</span> <span class="hlt">wave</span> propagation through the arterial tree was considered as a novel strong risk factor for cardiovascular diseases. Arterial <span class="hlt">pressure</span> reflections can be quantified by central <span class="hlt">pressure</span> profile analysis. In this work we study in the trial of an optical fibre Bragg grating based sensor of assess the central <span class="hlt">pressure</span> profile, with the goal of to achieve a superior sensitivity, with a better signal quality than electromechanical probes, measured directly in the carotid artery.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900011479','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900011479"><span id="translatedtitle">Experimental feasibility of investigating acoustic <span class="hlt">waves</span> in Couette flow with entropy and <span class="hlt">pressure</span> gradients</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parrott, Tony L.; Zorumski, William E.; Rawls, John W., Jr.</p> <p>1990-01-01</p> <p>The feasibility is discussed for an experimental program for studying the behavior of acoustic <span class="hlt">wave</span> propagation in the presence of strong gradients of <span class="hlt">pressure</span>, temperature, and flow. Theory suggests that gradients effects can be experimentally observed as resonant frequency shifts and mode shape changes in a waveguide. A convenient experimental geometry for such experiments is the annular region between two co-rotating cylinders. Radial temperature gradients in a spinning annulus can be generated by differentially heating the two cylinders via electromagnetic induction. Radial <span class="hlt">pressure</span> gradients can be controlled by varying the cylinder spin rates. Present technology appears adequate to construct an apparatus to allow independent control of temperature and <span class="hlt">pressure</span> gradients. A complicating feature of a more advanced experiment, involving flow gradients, is the requirement for independently controlled cylinder spin rates. Also, the boundary condition at annulus terminations must be such that flow gradients are minimally disturbed. The design and construction of an advanced apparatus to include flow gradients will require additional technology development.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B22B..05K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B22B..05K"><span id="translatedtitle">The relationship between gas hydrate saturation and P-<span class="hlt">wave</span> velocity of <span class="hlt">pressure</span> cores obtained in the Eastern Nankai Trough</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Konno, Y.; Yoneda, J.; Jin, Y.; Kida, M.; Suzuki, K.; Nakatsuka, Y.; Fujii, T.; Nagao, J.</p> <p>2014-12-01</p> <p>P-<span class="hlt">wave</span> velocity is an important parameter to estimate gas hydrate saturation in sediments. In this study, the relationship between gas hydrate saturation and P-<span class="hlt">wave</span> velocity have been analyzed using natural hydrate-bearing-sediments obtained in the Eastern Nankai Trough, Japan. The sediment samples were collected by the Hybrid <span class="hlt">Pressure</span> Coring System developed by Japan Agency for Marine-Earth Science and Technology during June-July 2012, aboard the deep sea drilling vessel CHIKYU. P-<span class="hlt">wave</span> velocity was measured on board by the <span class="hlt">Pressure</span> Core Analysis and Transfer System developed by Geotek Ltd. The samples were maintained at a near in-situ <span class="hlt">pressure</span> condition during coring and measurement. After the measurement, the samples were stored core storage chambers and transported to MHRC under <span class="hlt">pressure</span>. The samples were manipulated and cut by the <span class="hlt">Pressure</span>-core Non-destructive Analysis Tools or PNATs developed by MHRC. The cutting sections were determined on the basis of P-<span class="hlt">wave</span> velocity and visual observations through an acrylic window equipped in the PNATs. The cut samples were depressurized to measure gas volume for saturation calculations. It was found that P-<span class="hlt">wave</span> velocity correlates well with hydrate saturation and can be reproduced by the hydrate frame component model. Using <span class="hlt">pressure</span> cores and <span class="hlt">pressure</span> core analysis technology, nondestructive and near in-situ correlation between gas hydrate saturation and P-<span class="hlt">wave</span> velocity can be obtained. This study was supported by funding from the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) planned by the Ministry of Economy, Trade and Industry (METI), Japan.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhPl...23c2105R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhPl...23c2105R"><span id="translatedtitle">Particle-in-cell simulations of multi-MeV pulsed X-ray <span class="hlt">induced</span> air plasmas at low <span class="hlt">pressures</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ribière, M.; Cessenat, O.; d'Almeida, T.; de Gaufridy de Dortan, F.; Maulois, M.; Delbos, C.; Garrigues, A.; Azaïs, B.</p> <p>2016-03-01</p> <p>A full kinetic modelling of the charge particles dynamics generated upon the irradiation of an air-filled cavity by a multi-MeV pulsed x-ray is performed. From the calculated radiative source generated by the ASTERIX generator, we calculated the electromagnetic fields generated by x-ray <span class="hlt">induced</span> air plasmas in a metallic cavity at different <span class="hlt">pressures</span>. Simulations are carried out based on a Particle-In-Cell interpolation method which uses 3D Maxwell-Vlasov calculations of the constitutive charged species densities of air plasmas at different <span class="hlt">pressures</span> at equilibrium. The resulting electromagnetic fields within the cavity are calculated for different electron densities up to 4 × 1010 cm-3. For each air <span class="hlt">pressure</span>, we show electronic plasma <span class="hlt">waves</span> formation followed by Landau damping. As electron density increases, the calculations exhibit space-charged neutralization and return current formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.6723M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.6723M"><span id="translatedtitle">Drift <span class="hlt">induced</span> by repeated hydropeaking <span class="hlt">waves</span> in controlled conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maiolini, Bruno; Bruno, M. Cristina; Biffi, Sofia; Cashman, Matthew J.</p> <p>2014-05-01</p> <p>Repeated hydropeaking events characterize most alpine rivers downstream of power plants fed by high elevation reservoirs. The effects of hydropeaking on the benthic communities are well known, and usually each hydropeaking <span class="hlt">wave</span> causes an increase in tractive force and changes in temperature and water quality. Simulations of hydropeaking in artificial system can help to disentangle the direct effects of the modified flow regime from impacts associated with other associated physio-chemical changes, and with the effects of river regulation and land-use changes that often accompany water resource development. In September 2013 we conducted a set of controlled simulations in five steel flumes fed by an Alpine stream (Fersina stream, Adige River catchment, Trentino, Italy), where benthic invertebrates can freely colonize the flumes. One flume was used as control with no change in flow, in the other four flumes we simulated an hydropeaking <span class="hlt">wave</span> lasting six hours, and repeated for five consecutive days. Flow was increased by twice baseflow in two flumes, and three times in the other two. We collected benthic samples before the beginning (morning of day 1) and after the end (afternoon of day 5) of the set of simulations to evaluate changes in the benthic communities due to <span class="hlt">induced</span> drift migration. During each simulation, we collected drifting organisms at short time intervals to assess the responses to: 1) the initial discharge increase, 2) the persistence of high flows for several hours; 3) the decrease of discharge to the baseflow; 4) the change in drift with each successive day. Preliminary results indicate typical strong increases of catastrophic drift on the onset of each simulated hydropeaking, drift responses proportional to the absolute discharge increase, a decrease in the drift responses over successive days. Different taxa responded with different patterns: taxa which resist tractive force increased in drift only during the periods of baseflow that follow the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010SPIE.7562E..0YA','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010SPIE.7562E..0YA"><span id="translatedtitle">Effects of laser parameters on propagation characteristics of laser-<span class="hlt">induced</span> stress <span class="hlt">wave</span> for gene transfer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ando, Takahiro; Sato, Shunichi; Terakawa, Mitsuhiro; Ashida, Hiroshi; Obara, Minoru</p> <p>2010-02-01</p> <p>Laser-based gene delivery is attractive as a new method for topical gene therapy because of the high spatial controllability of laser energy. Previously, we demonstrated that an exogenous gene can be transferred to cells both in vitro and in vivo by applying nanosecond pulsed laser-<span class="hlt">induced</span> stress <span class="hlt">waves</span> (LISWs) or photomechanical <span class="hlt">waves</span> (PMWs). In this study, we investigated effects of laser parameters on the propagation characteristics of LISWs in soft tissue phantoms and depth-dependent properties of gene transfection. Temporal <span class="hlt">pressure</span> profiles of LISWs were measured with a hydrophone, showing that with a larger laser spot diameter, LISWs can be propagated more efficiently in phantoms with keeping flat wavefront. Phantoms with various thicknesses were placed on the rat dorsal skin that had been injected with plasmid DNA coding for reporter gene, and LISWs were applied from the top of the phantom. Efficient gene expression was observed in the rat skin that had interacted with LISWs propagating through a 15-mm-thick phantom. These results would be useful to determine appropriate laser parameters for gene delivery to deep-located tissue by transcutaneous application of LISWs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011APS..SHK.F1011B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011APS..SHK.F1011B"><span id="translatedtitle">Microscopic studies of cellular damage <span class="hlt">induced</span> by compression <span class="hlt">waves</span> in different environments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bo, Chiara; Balzer, Jens; Brown, Katherine A.; Proud, William G.</p> <p>2011-06-01</p> <p>The cellular basis of <span class="hlt">induced</span>-damage in biological samples under dynamic loading conditions is largely uncharacterized. In this study we propose a new approach to investigate the effects of compression <span class="hlt">waves</span> on in-vitro grown Stem cells extracted from BALB/c mice. A modified split Hopkinson <span class="hlt">pressure</span> bar system is used to simulate damage in the biological samples: the cells are inserted in a confinement chamber either in their growing media or on a 3D scaffold, they are subjected to compression <span class="hlt">waves</span> and finally recovered for further analysis. The difference in mechanical impedance between the cells and the hosting environments is believed to be a key point in the generation of damage. To discriminate the effects of the different mechanical supports on cell morphology pre and after compression, membrane and cytoskeletal proteins disruptions are investigated using fluorescence confocal microscopy. Understanding the underlying mechanism of damage at the microscopic scale could set the basis for the development of therapeutic applications at the cellular level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008QuEle..38.1155G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008QuEle..38.1155G"><span id="translatedtitle">LIGHT <span class="hlt">PRESSURE</span>: Theoretical study of the light <span class="hlt">pressure</span> force acting on a spherical dielectric particle of an arbitrary size in the interference field of two plane monochromatic electromagnetic <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guzatov, D. V.; Gaida, L. S.; Afanas'ev, Anatolii A.</p> <p>2008-12-01</p> <p>The light <span class="hlt">pressure</span> force acting on a spherical dielectric particle in the interference field of two plane monochromatic electromagnetic <span class="hlt">waves</span> is studied in detail for different particle radii and angles of incidence of <span class="hlt">waves</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20860789','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20860789"><span id="translatedtitle">Detection of Broadband Terahertz <span class="hlt">Waves</span> with a Laser-<span class="hlt">Induced</span> Plasma in Gases</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dai Jianming; Xie Xu; Zhang, X.-C.</p> <p>2006-09-08</p> <p>We report the experimental results and theoretical analysis of broadband detection of terahertz (THz) <span class="hlt">waves</span> via electric-field-<span class="hlt">induced</span> second-harmonic generation in laser-<span class="hlt">induced</span> air plasma with ultrashort laser pulses. By introducing the second-harmonic component of the white light in the laser-<span class="hlt">induced</span> plasma as a local oscillator, coherent detection of broadband THz <span class="hlt">waves</span> with ambient air is demonstrated for the first time. Our results show that, depending on the probe intensity, detection of THz <span class="hlt">waves</span> in air can be categorized as incoherent, hybrid, and coherent detection. Coherent detection is achieved only when the tunnel ionization process dominates in gases.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.2699J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.2699J"><span id="translatedtitle"><span class="hlt">Wave</span> energies and <span class="hlt">wave-induced</span> longshore currents in an unstructured-grid model - circulation in front of barrier islands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jörg-Olaf Wolff, , Prof. _., Dr.; Grashorn, Sebastian, , Dr.; Lettmann, Karsten A., , Dr.; Badewien, Thomas H., , Dr.; Stanev, Emil V., Prof. _., Dr.</p> <p>2015-04-01</p> <p>An unstructured-grid model (FVCOM) coupled to a <span class="hlt">wave</span> model (FVCOM-SWAVE) is used to investigate the hydrodynamic and <span class="hlt">wave</span> energy conditions during a moderate and a storm situation in the southern North Sea. Two different setups are presented. One setup covers the whole North Sea with moderately increased grid resolution at the coast, whereas the other comprises a very high resolution East Frisian Wadden Sea setup, one-way coupled to the coarser North Sea model. The results of both model setups are validated, compared to each other and analysed with a focus on longshore currents and <span class="hlt">wave</span> energy. The results show that during storm conditions strong <span class="hlt">wave-induced</span> longshore currents occur in front of the barrier islands of the East Frisian Wadden Sea, resulting in total current speeds up to 2 m/s. This effect is especially pronounced in the high-resolution setup. The <span class="hlt">wave</span>-current interaction also influences the sea surface elevation by raising the water level in the tidal basins. Calculated <span class="hlt">wave</span> energies show large differences between moderate wind and storm conditions with time-averaged values up to 200 kW/m. The numerical results indicate that <span class="hlt">wave</span>-current coupling, albeit numerically expensive, cannot be ignored because it plays an important role in almost all near coastal transport phenomena (sediments, contaminants, bacteria, etc.).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4654478','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4654478"><span id="translatedtitle">Tlr4 Deficiency Protects against Cardiac <span class="hlt">Pressure</span> Overload <span class="hlt">Induced</span> Hyperinflammation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Boehm, Olaf; El Aissati, Sakina; Foltz, Fabian; Goelz, Lina; Goertz, David; Kebir, Sied; Weisheit, Christina; Wolf, Michael; Meyer, Rainer; Baumgarten, Georg</p> <p>2015-01-01</p> <p>Transverse aortic constriction provokes a pro-inflammatory reaction and results in cardiac hypertrophy. Endogenous ligands contribute to cardiac hypertrophy via toll-like receptor (TLR)-4 binding. A lack of TLR4 signaling diminishes hypertrophy and inflammation. Wild type mice undergoing aortic constriction respond to a lipopolysaccharide second-hit stimulus with hyperinflammation. The objective of this study was to assess whether other second-hit challenges utilizing TLR ligands provoke a comparable inflammatory reaction, and to find out whether this response is absent in TLR4 deficient mice. Assuming that cardiac stress alters the expression of pattern recognition receptors we analyzed the effects of transverse aortic constriction and second-hit virulence factor treatment on TLR expression, as well as cytokine regulation. Wild type and Tlr4-/- mice were subjected to three days of TAC and subsequently confronted with gram-positive TLR2 ligand lipoteichoic acid (LTA, 15mg/g bodyweight) or synthetic CpG-oligodesoxynucleotide 1668 thioate (20 nmol/kg bodyweight, 30 min after D-galactosamin desensitization) signaling via TLR9. Hemodynamic measurements and organ preservation were performed 6 h after stimulation. Indeed, the study revealed a robust enhancement of LTA <span class="hlt">induced</span> pattern recognition receptor and cytokine mRNA expression and a LTA-dependent reduction of hemodynamic <span class="hlt">pressure</span> in TAC wild type mice. Second-Hit treatment with CpG-ODNs led to similar results. However, second-hit effects were abolished in Tlr4-/- mice. In total, these data indicate for the first time that cardiac stress increases the inflammatory response towards both, gram-negative and gram-positive, TLR ligands as well as bacterial DNA. The decrease of the inflammatory response upon TLR2 and -9 ligand challenge in TAC Tlr4-/- mice demonstrates that a lack of TLR4 signaling does not only prevent left ventricular hypertrophy but also protects the mice from a cardiac stress <span class="hlt">induced</span> hyperinflammatory</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4348918','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4348918"><span id="translatedtitle">Exercise preconditioning attenuates <span class="hlt">pressure</span> overload-<span class="hlt">induced</span> pathological cardiac hypertrophy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Xu, Tongyi; Tang, Hao; Zhang, Ben; Cai, Chengliang; Liu, Xiaohong; Han, Qingqi; Zou, Liangjian</p> <p>2015-01-01</p> <p>Pathological cardiac hypertrophy, a common response of the heart to a variety of cardiovascular diseases, is typically associated with myocytes remodeling and fibrotic replacement, cardiac dysfunction. Exercise preconditioning (EP) increases the myocardial mechanical load and enhances tolerance of cardiac ischemia-reperfusion injury (IRI), however, is less reported in pathological cardiac hypertrophy. To determine the effect of EP in pathological cardiac hypertrophy, Male 10-wk-old Sprague-Dawley rats (n=30) were subjected to 4 weeks of EP followed by 4-8 weeks of <span class="hlt">pressure</span> overload (transverse aortic constriction, TAC) to <span class="hlt">induce</span> pathological remodeling. TAC in untrained controls (n=30) led to pathological cardiac hypertrophy, depressed systolic function. We observed that left ventricular wall thickness in end diastole, heart size, heart weight-to-body weight ratio, heart weight-to-tibia length ratio, cross-sectional area of cardiomyocytes and the reactivation of fetal genes (atrial natriuretic peptide and brain natriuretic peptide) were markedly increased, meanwhile left ventricular internal dimension at end-diastole, systolic function were significantly decreased by TAC at 4 wks after operation (P < 0.01), all of which were effectively inhibited by EP treatment (P < 0.05), but the differences of these parameters were decreased at 8 wks after operation. Furthermore, EP treatment inhibited degradation of IκBα, and decreased NF-κB p65 subunit levels in the nuclear fraction, and then reduced IL2 levels in the myocardium of rats subject to TAC. EP can effectively attenuate pathological cardiac hypertrophic responses <span class="hlt">induced</span> by TAC possibly through inhibition of degradation of IκB and blockade of the NF-κB signaling pathway in the early stage of pathological cardiac hypertrophy. PMID:25755743</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhRvB..88o5137L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhRvB..88o5137L"><span id="translatedtitle">Temperature-<span class="hlt">pressure</span> phase diagram of CeCoSi: <span class="hlt">Pressure-induced</span> high-temperature phase</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lengyel, E.; Nicklas, M.; Caroca-Canales, N.; Geibel, C.</p> <p>2013-10-01</p> <p>We have studied the temperature-<span class="hlt">pressure</span> phase diagram of CeCoSi by electrical-resistivity experiments under <span class="hlt">pressure</span>. Our measurements revealed a very unusual phase diagram. While at low <span class="hlt">pressures</span> no dramatic changes and only a slight shift of the Neél temperature TN (≈10 K) are observed, at about 1.45 GPa a sharp and large anomaly, indicative of the opening of a spin-density <span class="hlt">wave</span> gap, appears at a comparatively high temperature TS≈38 K. With further increasing <span class="hlt">pressure</span>, TS shifts rapidly to low temperatures and disappears at about 2.15 GPa, likely continuously in a quantum critical point, but without evidence for superconductivity. Even more surprisingly, we observed a clear shift of TS to higher temperatures upon applying a magnetic field. We discuss two possible origins for TS: magnetic ordering of Co and a metaorbital type of transition of Ce.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/914041','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/914041"><span id="translatedtitle">Effect of <span class="hlt">Pressure</span> and Chemical Substitutions on the Charge-Density-<span class="hlt">Wave</span> in LaAgSb2</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Budko,S.; Weiner, T.; Ribeiro, R.; Canfield, P.; Lee, Y.; Vogt, T.; Lacerda</p> <p>2006-01-01</p> <p>We present data on the crystal structure and evolution of the electrical resistivity in lightly doped La{sub 1-x}R{sub x}AgSb{sub 2} (R=Gd, Y, Ce, and Nd) at ambient <span class="hlt">pressure</span> and in LaAgSb{sub 2} under hydrostatic <span class="hlt">pressure</span>. The upper charge density <span class="hlt">wave</span> transition is suppressed by both doping and <span class="hlt">pressure</span> with substitution-related disorder being the dominant mechanism for this suppression in the former case and the anisotropic <span class="hlt">pressure</span> dependence of the unit cell dimensions (as seen in the c/a ratio) prevailing in the latter case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JNuM..431..160R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JNuM..431..160R"><span id="translatedtitle">Status of R&D on mitigating the effects of <span class="hlt">pressure</span> <span class="hlt">waves</span> for the Spallation Neutron Source mercury target</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Riemer, Bernard W.; Wendel, Mark W.; Felde, David K.; Abdou, Ashraf A.; McClintock, David A.</p> <p>2012-12-01</p> <p>The Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory has been conducting R&D on mitigating the effects of <span class="hlt">pressure</span> <span class="hlt">waves</span> in mercury spallation targets since 2001. More precisely, cavitation damage of the target vessel caused by the short beam pulse threatens to limit its lifetime more severely than radiation damage as well as limit its ultimate power capacity - and hence its neutron intensity performance. The R&D program has moved from verification of the beam-<span class="hlt">induced</span> damage phenomena to study of material and surface treatments for damage resistance to the current emphasis on gas injection techniques for damage mitigation. Two techniques are being worked on: injection of small dispersed gas bubbles that mitigate the <span class="hlt">pressure</span> <span class="hlt">waves</span> volumetrically; and protective gas walls that isolate the vessel from the damaging effects of collapsing cavitation bubbles. The latter has demonstrated good damage mitigation during in-beam testing with limited pulses, and adequate gas wall coverage at the beam entrance window has been demonstrated with the SNS mercury target flow configuration using a full scale mercury test loop. A question on the required area coverage remains which depends on results from SNS target post irradiation examination. The small gas bubble technique has been less effective during past in-beam tests but those results were with un-optimized and un-verified bubble populations. Another round of in-beam tests with small gas bubbles is planned for 2011. The first SNS target was removed from service in mid 2009 and samples were cut from two locations at the target's beam entrance window. Through-wall damage was observed at the innermost mercury vessel wall (not a containment wall). The damage pattern suggested correlation with the local mercury flow condition which is nearly stagnant at the peak damage location. Detailed post irradiation examination of the samples is under way that will assess the erosion and measure irradiation-<span class="hlt">induced</span> changes</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1060243','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1060243"><span id="translatedtitle">Status of R&D on Mitigating the Effects of <span class="hlt">Pressure</span> <span class="hlt">Waves</span> for the Spallation Neutron Source Mercury Target</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Riemer, Bernie; Wendel, Mark W; Felde, David K; Abdou, Ashraf A; McClintock, David A</p> <p>2012-01-01</p> <p>The Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory has been conducting R&D on mitigating the effects of <span class="hlt">pressure</span> <span class="hlt">waves</span> in mercury spallation targets since 2001. More precisely, cavitation damage of the target vessel caused by the short beam pulse threatens to limit its lifetime more severely than radiation damage as well as limit its ultimate power capacity and hence its neutron intensity performance. The R&D program has moved from verification of the beam-<span class="hlt">induced</span> damage phenomena to study of material and surface treatments for damage resistance to the current emphasis on gas injection techniques for damage mitigation. Two techniques are being worked on: injection of small dispersed gas bubbles that mitigate the <span class="hlt">pressure</span> <span class="hlt">waves</span> volumetrically; and protective gas walls that isolate the vessel from the damaging effects of collapsing cavitation bubbles. The latter has demonstrated good damage mitigation during in-beam testing with limited pulses, and adequate gas wall coverage at the beam entrance window has been demonstrated with the SNS mercury target flow configuration using a full scale mercury test loop. A question on the required area coverage remains which depends on results from SNS target post irradiation examination. The small gas bubble technique has been less effective during past in-beam tests but those results were with un-optimized and un-verified bubble populations. Another round of in-beam tests with small gas bubbles is planned for 2011. The first SNS target was removed from service in mid 2009 and samples were cut from two locations at the target s beam entrance window. Through-wall damage was observed at the innermost mercury vessel wall (not a containment wall). The damage pattern suggested correlation with the local mercury flow condition which is nearly stagnant at the peak damage location. Detailed post irradiation examination of the samples is under way that will assess the erosion and measure irradiation-<span class="hlt">induced</span> changes</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvE..93e2221S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvE..93e2221S"><span id="translatedtitle">Noise-<span class="hlt">induced</span> standing <span class="hlt">waves</span> in oscillatory systems with time-delayed feedback</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stich, Michael; Chattopadhyay, Amit K.</p> <p>2016-05-01</p> <p>In oscillatory reaction-diffusion systems, time-delay feedback can lead to the instability of uniform oscillations with respect to formation of standing <span class="hlt">waves</span>. Here, we investigate how the presence of additive, Gaussian white noise can <span class="hlt">induce</span> the appearance of standing <span class="hlt">waves</span>. Combining analytical solutions of the model with spatiotemporal simulations, we find that noise can promote standing <span class="hlt">waves</span> in regimes where the deterministic uniform oscillatory modes are stabilized. As the deterministic phase boundary is approached, the spatiotemporal correlations become stronger, such that even small noise can <span class="hlt">induce</span> standing <span class="hlt">waves</span> in this parameter regime. With larger noise strengths, standing <span class="hlt">waves</span> could be <span class="hlt">induced</span> at finite distances from the (deterministic) phase boundary. The overall dynamics is defined through the interplay of noisy forcing with the inherent reaction-diffusion dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/288870','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/288870"><span id="translatedtitle">Flow-<span class="hlt">induced</span> noise on <span class="hlt">pressure</span> gradient hydrophones</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lauchle, G.C.; McEachern, J.F.; Jones, A.R.; McConnell, J.A.</p> <p>1996-04-01</p> <p>Moored or drifting hydrophones are subject to a variety of potential self-noise sources. Flow-<span class="hlt">induced</span> self noise arises when the sensors are subjected to oceanic currents such as those due to <span class="hlt">wave</span> motion and changing tides. Research at Penn State, in cooperation with the Naval Air Warfare Center (NAWC), has been concerned with the basic mechanisms of flow-<span class="hlt">induced</span> self noise on velocity gradient hydrophones of various shapes and sizes. These sensors are configured as finite-length cylinders in cross flow and as spheres. The sensors are sensitive to acoustic particle velocity, and one of the sensors is sensitive to acoustic intensity. With the diameter of the sensor as the characteristic dimension, and for operational flow velocities in the 0.5 to 2.0 knot range, the Reynolds number range of interest is from values less than 100 (for some miniature sensors) to about 27,000 (for standard-size sonobuoy hydrophones). Experiments are conducted for the higher ranges of Reynolds number by towing the sensors over the given range of speeds in quiet basins of water (9 meter tow tank at Penn State and a flooded quarry at the NAWC). To achieve the lower range of Reynolds numbers over the same range of velocities, but without having in hand actual miniature sensors, some of the experiments are performed in glycerine. Glycerine has a kinematic viscosity some three orders of magnitude greater than that of water; therefore, a large sensor can be subjected to a velocity in the range of interest but yield an operational Reynolds number that is three orders of magnitude smaller. In this paper, we will show the broadband spectral characteristics of finite-length cylindrical sensors in cross flow, as well as spherical-shaped sensors. The Reynolds number of the flow is the independent variable. The threshold of velocity-dependent noise increase is found to correlate with the occurrence of turbulent flow not necessarily in the wake, but on the surface of the body itself.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996AIPC..368..202L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996AIPC..368..202L"><span id="translatedtitle">Flow-<span class="hlt">induced</span> noise on <span class="hlt">pressure</span> gradient hydrophones</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lauchle, G. C.; McEachern, J. F.; Jones, A. R.; McConnell, J. A.</p> <p>1996-04-01</p> <p>Moored or drifting hydrophones are subject to a variety of potential self-noise sources. Flow-<span class="hlt">induced</span> self noise arises when the sensors are subjected to oceanic currents such as those due to <span class="hlt">wave</span> motion and changing tides. Research at Penn State, in cooperation with the Naval Air Warfare Center (NAWC), has been concerned with the basic mechanisms of flow-<span class="hlt">induced</span> self noise on velocity gradient hydrophones of various shapes and sizes. These sensors are configured as finite-length cylinders in cross flow and as spheres. The sensors are sensitive to acoustic particle velocity, and one of the sensors is sensitive to acoustic intensity. With the diameter of the sensor as the characteristic dimension, and for operational flow velocities in the 0.5 to 2.0 knot range, the Reynolds number range of interest is from values less than 100 (for some miniature sensors) to about 27,000 (for standard-size sonobuoy hydrophones). Experiments are conducted for the higher ranges of Reynolds number by towing the sensors over the given range of speeds in quiet basins of water (9 meter tow tank at Penn State and a flooded quarry at the NAWC). To achieve the lower range of Reynolds numbers over the same range of velocities, but without having in hand actual miniature sensors, some of the experiments are performed in glycerine. Glycerine has a kinematic viscosity some three orders of magnitude greater than that of water; therefore, a large sensor can be subjected to a velocity in the range of interest but yield an operational Reynolds number that is three orders of magnitude smaller. In this paper, we will show the broadband spectral characteristics of finite-length cylindrical sensors in cross flow, as well as spherical-shaped sensors. The Reynolds number of the flow is the independent variable. The threshold of velocity-dependent noise increase is found to correlate with the occurrence of turbulent flow not necessarily in the wake, but on the surface of the body itself. The flow field is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950051862&hterms=isothermal+compression&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2528%2Bisothermal%2Bcompression','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950051862&hterms=isothermal+compression&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2528%2Bisothermal%2Bcompression"><span id="translatedtitle">Collapse and fragmentation of molecular cloud cores. 2: Collapse <span class="hlt">induced</span> by stellar shock <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Boss, Alan P.</p> <p>1995-01-01</p> <p>The standard scenario for low-mass star formation involves 'inside-out' collapse of a dense molecular cloud core following loss of magnetic field support through ambipolar diffusion. However, isotopic anomalies in presolar grains and meteoritical inclusions imply that the collapse of the presolar cloud may have been triggered by a stellar shock <span class="hlt">wave</span>. This paper explores 'outside-in' collapse, that is, protostellar collapse initiated directly by the compression of quiescent dense cloud cores impacted by relatively slow stellar shock <span class="hlt">waves</span>. A second-order accurate, gravitational hydrodynamics code has been used to study both the spherically symmetrical and three-dimensional evolution of initially centrally condensed, isothermal, self-gravitating, solar-mass cloud cores that are struck by stellar shock <span class="hlt">waves</span> with velocities up to 25 km/s and postshock temperatures of 10 to 10,000 K. The models show that such mild shock <span class="hlt">waves</span> do not completely shred and destroy the cloud, and that the dynamical ram <span class="hlt">pressure</span> can compress the cloud to the verge of self-gravitational collapse. However, compression caused by a high postshock temperature is a considerably more effective means of <span class="hlt">inducing</span> collapse. Shock-<span class="hlt">induced</span> collapse produces high initial mass accretion rates (greater than 10(exp -4) solar mass/yr in a solar-mass cloud) that decline rapidly to much lower values, depending on the presence (approximately 10(exp -6) solar mass/yr) or absence (approximately 10(exp -8) to 10(exp -7) solar mass/yr) of an infinite reservoir of mass. Stellar mass accretion rates approximately 10(exp -7) solar mass/yr have been previously inferred from the luminosities of T Tauri stars; balanced mass accretion (stellar rate = envelope rate) at approximately 10(exp -7) solar mass/yr could then be possible if accretion occurs from a finite mass reservoir. Fluid tracers are used to determine what fraction of the stellar shock material is incorporated into the resulting protostellar object and disk</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21044889','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21044889"><span id="translatedtitle">Experimental investigation of the unsteady response of premixed flame fronts to acoustic <span class="hlt">pressure</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wangher, Athena; Searby, Geoff; Quinard, Joel</p> <p>2008-07-15</p> <p>Using OH{sup *} chemiluminescence, we measure the experimental unsteady response of a 1-D premixed flame to an acoustic <span class="hlt">pressure</span> <span class="hlt">wave</span> for a range of frequencies below and above the inverse of the flame transit time. We find that the response is positive and, at low frequency, the order of magnitude is comparable with existing theoretical analyses. However, if it is assumed that the chemiluminescence is proportional to the mass consumption rate, despite some uncertainty in the interpretation of the chemiluminescence signal we find that the frequency dependence of the measured response is not compatible with the predictions of the standard flame model for one-step Arrhenius kinetics. A better, but not perfect, correlation is obtained for the heat release rate. We conclude that the standard model does not provide an adequate description of the unsteady response of real flames and that it is necessary to investigate more realistic chemical models. (author)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20702392','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20702392"><span id="translatedtitle">Effects of oxygen radicals in low-<span class="hlt">pressure</span> surface-<span class="hlt">wave</span> plasma on sterilization</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nagatsu, Masaaki; Terashita, Fumie; Nonaka, Hiroyuki; Xu, Lei; Nagata, Toshi; Koide, Yukio</p> <p>2005-05-23</p> <p>The effects of oxygen radicals on sterilization were studied using a 2.45 GHz surface-<span class="hlt">wave</span> oxygen plasma. A population of 1.5x10{sup 6} Bacillus stearothermophilus spores was irradiated for 3 min or more with oxygen plasma, generated at <span class="hlt">pressures</span> between 6 and 14 Pa. The decimal reduction value (D value), a measure of the effectiveness of sterilization, was determined to be about 15-25 s. Using only oxygen radicals, excluding all charged particles, the 1.5x10{sup 6} spores were sterilized with a D value of 30-45 s after 5 min or more of irradiation. On scanning electron microscopy, the length and width of the spores changed significantly due to chemical etching by oxygen radicals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005ApPhL..86u1502N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005ApPhL..86u1502N"><span id="translatedtitle">Effects of oxygen radicals in low-<span class="hlt">pressure</span> surface-<span class="hlt">wave</span> plasma on sterilization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nagatsu, Masaaki; Terashita, Fumie; Nonaka, Hiroyuki; Xu, Lei; Nagata, Toshi; Koide, Yukio</p> <p>2005-05-01</p> <p>The effects of oxygen radicals on sterilization were studied using a 2.45GHz surface-<span class="hlt">wave</span> oxygen plasma. A population of 1.5×106 Bacillus stearothermophilus spores was irradiated for 3min or more with oxygen plasma, generated at <span class="hlt">pressures</span> between 6 and 14Pa. The decimal reduction value (D value), a measure of the effectiveness of sterilization, was determined to be about 15-25s. Using only oxygen radicals, excluding all charged particles, the 1.5×106 spores were sterilized with a D value of 30-45s after 5min or more of irradiation. On scanning electron microscopy, the length and width of the spores changed significantly due to chemical etching by oxygen radicals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3617730','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3617730"><span id="translatedtitle">Sensing the characteristic acoustic impedance of a fluid utilizing acoustic <span class="hlt">pressure</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Antlinger, Hannes; Clara, Stefan; Beigelbeck, Roman; Cerimovic, Samir; Keplinger, Franz; Jakoby, Bernhard</p> <p>2012-01-01</p> <p>Ultrasonic sensors can be used to determine physical fluid parameters like viscosity, density, and speed of sound. In this contribution, we present the concept for an integrated sensor utilizing <span class="hlt">pressure</span> <span class="hlt">waves</span> to sense the characteristic acoustic impedance of a fluid. We note that the basic setup generally allows to determine the longitudinal viscosity and the speed of sound if it is operated in a resonant mode as will be discussed elsewhere. In this contribution, we particularly focus on a modified setup where interferences are suppressed by introducing a wedge reflector. This enables sensing of the liquid's characteristic acoustic impedance, which can serve as parameter in condition monitoring applications. We present a device model, experimental results and their evaluation. PMID:23565036</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23556559','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23556559"><span id="translatedtitle">Spin current-<span class="hlt">induced</span> by a sound <span class="hlt">wave</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lyapilin, Igor I</p> <p>2013-04-01</p> <p>The interaction of conduction electrons with a longitudinal sound <span class="hlt">wave</span> propagating in a crystal in a constant magnetic field is investigated. It is shown that the transverse spin current arises when the longitudinal sound <span class="hlt">wave</span> propagation through the system. The average power absorbed by the spin subsystem of the conduction electrons and the spin-Hall conductivity have a resonant character. PMID:23556559</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.7365L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.7365L"><span id="translatedtitle">The role of precipitation in aerosol-<span class="hlt">induced</span> changes in northern hemisphere wintertime stationary <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lewinschal, A.; Ekman, A. M. L.; Körnich, H.</p> <p>2012-04-01</p> <p>Aerosol particles have a considerable impact on the energy budget of the atmosphere due to their ability to scatter and absorb incoming solar radiation. Persistent particle emissions in certain regions of the world have lead to quasi-permanent aerosol forcing patterns. This spatially varying forcing pattern has the potential to modify temperature gradients that in turn alter <span class="hlt">pressure</span> gradients and the atmospheric circulation. This study focuses on the effect of aerosol direct radiative forcing on northern hemisphere wintertime stationary <span class="hlt">waves</span>. A global general circulation model based on the ECMWF operational forecast model is applied (EC-Earth). Aerosols are prescribed as monthly mean mixing ratios of sulphate, black carbon, organic carbon, dust and sea salt. Only the direct aerosol effect is considered. The climatic change is defined as the difference between model simulations using present-day and pre-industrial concentrations of aerosol particles. Data from 40-year long simulations using a coupled ocean-atmosphere model system are used. In EC-Earth, the high aerosol loading over South Asia leads to a surface cooling, which appears to enhance the South Asian winter monsoon and weaken the Indian Ocean Walker circulation. The anomalous Walker circulation leads to changes in tropical convective precipitation and consequent changes in latent heat release which effectively acts to generate planetary scale <span class="hlt">waves</span> propagating into the extra-tropics. Using a steady-state linear model we verify that the aerosol-<span class="hlt">induced</span> anomalous convective precipitation is a crucial link between the <span class="hlt">wave</span> changes and the direct aerosol radiative forcing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009ApSS..255.9898A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009ApSS..255.9898A"><span id="translatedtitle">Propagation characteristics of laser-<span class="hlt">induced</span> stress <span class="hlt">wave</span> in deep tissue for gene transfer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ando, Takahiro; Sato, Shunichi; Takano, Shinta; Ashida, Hiroshi; Obara, Minoru</p> <p>2009-09-01</p> <p>Propagation characteristics of laser-<span class="hlt">induced</span> stress <span class="hlt">waves</span> (LISWs) in tissue and their correlation with properties of gene transfection were investigated for targeted deep-tissue gene therapy. LISWs were generated by irradiating a laser-absorbing material with 532-nm Q-switched Nd:YAG laser pulses; a transparent plastic sheet was attached on the absorbing material for plasma confinement. Temporal <span class="hlt">pressure</span> profiles of LISWs that were propagated through different thickness tissues were measured with a needle-type hydrophone and propagation of LISWs in water was visualized by shadowgraph technique. The measurements showed that at a laser fluence of 1.2 J/cm 2 with a laser spot diameter of 3 mm, flat wavefront was maintained for up to 5 mm in depth and peak <span class="hlt">pressure</span> P decreased with increasing tissue thickness d; P was proportional to d-0.54. Rat dorsal skin was injected with plasmid DNA coding for reporter gene, on which different numbers of excised skin(s) was/were placed, and LISWs were applied from the top of the skins. Efficient gene expression was observed in the skin under the 3 mm thick stacked skins, suggesting that deep-located tissue such as muscle can be transfected by transcutaneous application of LISWs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PhPl...11.5643I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PhPl...11.5643I"><span id="translatedtitle">Remarks on the discrete Alfvén <span class="hlt">wave</span> spectrum <span class="hlt">induced</span> by the Hall current</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ito, Atsushi; Hirose, Akira; Mahajan, Swadesh M.; Ohsaki, Shuichi</p> <p>2004-12-01</p> <p>It is shown that the discrete Alfvén <span class="hlt">wave</span> <span class="hlt">induced</span> by the Hall current [S. Ohsaki and S. M. Mahajan, Phys. Plasmas 11, 898 (2004)] is equivalent to the kinetic Alfvén <span class="hlt">wave</span> (KAW). The KAW is, thus, accessible in a fluid description. It is further shown that the dispersion relation for the Hall magnetohydrodynamic <span class="hlt">waves</span> can be reproduced from kinetic theory only if the ion temperature is negligible compared with the electron temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4746592','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4746592"><span id="translatedtitle">Multiple scattering <span class="hlt">induced</span> negative refraction of matter <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Pinsker, Florian</p> <p>2016-01-01</p> <p>Starting from fundamental multiple scattering theory it is shown that negative refraction indices are feasible for matter <span class="hlt">waves</span> passing a well-defined ensemble of scatterers. A simple approach to this topic is presented and explicit examples for systems of scatterers in 1D and 3D are stated that imply negative refraction for a generic incoming quantum <span class="hlt">wave</span> packet. Essential features of the effective scattering field, densities and frequency spectrum of scatterers are considered. Additionally it is shown that negative refraction indices allow perfect transmission of the <span class="hlt">wave</span> passing the ensemble of scatterers. Finally the concept of the superlens is discussed, since it is based on negative refraction and can be extended to matter <span class="hlt">waves</span> utilizing the observations presented in this paper which thus paves the way to ‘untouchable’ quantum systems in analogy to cloaking devices for electromagnetic <span class="hlt">waves</span>. PMID:26857266</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19334944','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19334944"><span id="translatedtitle">Laser <span class="hlt">induced</span> thermal-<span class="hlt">wave</span> fields in bilayered spherical solids.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xie, Guangxi; Chen, Zhifeng; Wang, Chinhua; Mandelis, Andreas</p> <p>2009-03-01</p> <p>We present a theoretical model for evaluating solid bilayered spherical samples (surfaces) that are heated by a frequency modulated light beam generating thermal <span class="hlt">waves</span>. The Green's function method is used as it provides a way of evaluating thermal-<span class="hlt">wave</span> fields of bilayered spherical structures with arbitrary intensity distributions of incident laser beams. The specific thermal-<span class="hlt">wave</span> Green's function corresponding to the composite structure has been derived. The characteristics of the thermal-<span class="hlt">wave</span> field with respect to the thermal diffusivity of the material, the diameter of the sample, the size of the incident beam, and the polar angle at which the thermal-<span class="hlt">wave</span> field is measured on the surface are presented. Experimental results obtained with laser infrared photothermal radiometry are fitted to the theory and the thermal diffusivities of steel spheres are deduced. PMID:19334944</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26857266','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26857266"><span id="translatedtitle">Multiple scattering <span class="hlt">induced</span> negative refraction of matter <span class="hlt">waves</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pinsker, Florian</p> <p>2016-01-01</p> <p>Starting from fundamental multiple scattering theory it is shown that negative refraction indices are feasible for matter <span class="hlt">waves</span> passing a well-defined ensemble of scatterers. A simple approach to this topic is presented and explicit examples for systems of scatterers in 1D and 3D are stated that imply negative refraction for a generic incoming quantum <span class="hlt">wave</span> packet. Essential features of the effective scattering field, densities and frequency spectrum of scatterers are considered. Additionally it is shown that negative refraction indices allow perfect transmission of the <span class="hlt">wave</span> passing the ensemble of scatterers. Finally the concept of the superlens is discussed, since it is based on negative refraction and can be extended to matter <span class="hlt">waves</span> utilizing the observations presented in this paper which thus paves the way to 'untouchable' quantum systems in analogy to cloaking devices for electromagnetic <span class="hlt">waves</span>. PMID:26857266</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009ccbh.conf...27D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009ccbh.conf...27D"><span id="translatedtitle">The Role of Compression and Traveling <span class="hlt">Wave</span> <span class="hlt">Pressures</span> in the Transmission of Sound Out of the Gerbil Cochlea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dong, Wei; Olson, Elizabeth S.</p> <p>2009-02-01</p> <p>Cochlear emissions provide a noninvasive probe of cochlear mechanics, but their utility is hindered by incomplete understanding of their relationship to intracochlear activity. In particular, recent work has uncovered a question about the mode by which emissions travel out of the cochlea - whether they emerge via a "fast" compression <span class="hlt">pressure</span> or a "slow" traveling-<span class="hlt">wave</span> <span class="hlt">pressure</span>. We further probed this question with simultaneous measurements of intracochlear distortion products (DPs) at two well-separated locations and DP oto-acoustic emissions (DPOAEs). In the broad frequency range of the local best frequency (BF), the DP responses demonstrate the now well-known forward-traveling-<span class="hlt">wave</span> character. However, at frequencies substantially lower than the BF, comparisons of both DPOAEs to DPs and of DPs at two locations support a reverse-traveling-<span class="hlt">wave</span>. Finally, a compression <span class="hlt">pressure</span> DP was observed when stimulating at high levels (90 dB) with frequencies that were well above the BF. Therefore, the compression / reverse-traveling-<span class="hlt">wave</span> question appears to be a quantitative question of the relative size of these different <span class="hlt">pressure</span> modes. In previous and present results we find that the reverse-traveling-<span class="hlt">wave</span> mode can be dominant both within the cochlea and in the production of DPOAEs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ShWav..24..467W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ShWav..24..467W"><span id="translatedtitle">On the influence of low initial <span class="hlt">pressure</span> and detonation stochastic nature on Mach reflection of gaseous detonation <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, C. J.; Guo, C. M.</p> <p>2014-09-01</p> <p>The two-dimensional, time-dependent and reactive Navier-Stokes equations were solved to obtain an insight into Mach reflection of gaseous detonation in a stoichiometric hydrogen-oxygen mixture diluted by 25 % argon. This mixture generates a mode-7 detonation <span class="hlt">wave</span> under an initial <span class="hlt">pressure</span> of 8.00 kPa. Chemical kinetics was simulated by an eight-species, forty-eight-reaction mechanism. It was found that a Mach reflection mode always occurs for a planar detonation <span class="hlt">wave</span> or planar air shock <span class="hlt">wave</span> sweeping over wedges with apex angles ranging from to . However, for cellular detonation <span class="hlt">waves</span>, regular reflection always occurs first, which then transforms into Mach reflection. This phenomenon is more evident for detonations ignited under low initial <span class="hlt">pressure</span>. Low initial <span class="hlt">pressure</span> may lead to a curved <span class="hlt">wave</span> front, that determines the reflection mode. The stochastic nature of boundary shape and transition distance, during deflagration-to-detonation transition, leads to relative disorder of detonation cell location and cell shape. Consequently, when a detonation <span class="hlt">wave</span> hits the wedge apex, there appears a stochastic variation of triple point origin and variation of the angle between the triple point trajectory and the wedge surface. As the wedge apex angle increases, the distance between the triple point trajectory origin and the wedge apex increases, and the angle between the triple point trajectory and the wedge surface decreases exponentially.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26377030','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26377030"><span id="translatedtitle">Shear stress <span class="hlt">induces</span> a longitudinal Ca(2+) <span class="hlt">wave</span> via autocrine activation of P2Y1 purinergic signalling in rat atrial myocytes.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kim, Joon-Chul; Woo, Sun-Hee</p> <p>2015-12-01</p> <p>Atrial myocytes are exposed to shear stress during the cardiac cycle and haemodynamic disturbance. In response, they generate a longitudinally propagating global Ca(2+) <span class="hlt">wave</span>. Here, we investigated the cellular mechanisms underlying the shear stress-mediated Ca(2+) <span class="hlt">wave</span>, using two-dimensional confocal Ca(2+) imaging combined with a <span class="hlt">pressurized</span> microflow system in single rat atrial myocytes. Shear stress of ∼16 dyn cm(-2) for 8 s <span class="hlt">induced</span> ∼1.2 aperiodic longitudinal Ca(2+) <span class="hlt">waves</span> (∼79 μm s(-1)) with a delay of 0.2-3 s. Pharmacological blockade of ryanodine receptors (RyRs) or inositol 1,4,5-trisphosphate receptors (IP3 Rs) abolished shear stress-<span class="hlt">induced</span> Ca(2+) <span class="hlt">wave</span> generation. Furthermore, in atrial myocytes from type 2 IP3R (IP3R2) knock-out mice, shear stress failed to <span class="hlt">induce</span> longitudinal Ca(2+) <span class="hlt">waves</span>. The phospholipase C (PLC) inhibitor U73122, but not its inactive analogue U73343, abolished the shear-<span class="hlt">induced</span> longitudinal Ca(2+) <span class="hlt">wave</span>. However, pretreating atrial cells with blockers for stretch-activated channels, Na(+)-Ca(2+) exchanger, transient receptor potential melastatin subfamily 4, or nicotinamide adenine dinucleotide phosphate oxidase did not suppress <span class="hlt">wave</span> generation under shear stress. The P2 purinoceptor inhibitor suramin, and the potent P2Y1 receptor antagonist MRS 2179, both suppressed the Ca(2+) <span class="hlt">wave</span>, whereas the P2X receptor antagonist, iso-PPADS, did not alter it. Suppression of gap junction hemichannels permeable to ATP or extracellular application of ATP-metabolizing apyrase inhibited the <span class="hlt">wave</span>. Removal of external Ca(2+) to enhance hemichannel opening facilitated the <span class="hlt">wave</span> generation. Our data suggest that longitudinally propagating, regenerative Ca(2+) release through RyRs is triggered by P2Y1-PLC-IP3R2 signalling that is activated by gap junction hemichannel-mediated ATP release in atrial myocytes under shear stress. PMID:26377030</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvD..91d3531N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvD..91d3531N"><span id="translatedtitle">Future detectability of gravitational-<span class="hlt">wave</span> <span class="hlt">induced</span> lensing from high-sensitivity CMB experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Namikawa, Toshiya; Yamauchi, Daisuke; Taruya, Atsushi</p> <p>2015-02-01</p> <p>We discuss the future detectability of gravitational-<span class="hlt">wave</span> <span class="hlt">induced</span> lensing from high-sensitivity cosmic microwave background (CMB) experiments. Gravitational <span class="hlt">waves</span> can <span class="hlt">induce</span> a rotational component of the weak-lensing deflection angle, usually referred to as the curl mode, which would be imprinted on the CMB maps. Using the technique of reconstructing lensing signals involved in CMB maps, this curl mode can be measured in an unbiased manner, offering an independent confirmation of the gravitational <span class="hlt">waves</span> complementary to B-mode polarization experiments. Based on the Fisher matrix analysis, we first show that with the noise levels necessary to confirm the consistency relation for the primordial gravitational <span class="hlt">waves</span>, the future CMB experiments will be able to detect the gravitational-<span class="hlt">wave</span> <span class="hlt">induced</span> lensing signals. For a tensor-to-scalar ratio of r ≲0.1 , even if the consistency relation is difficult to confirm with a high significance, the gravitational-<span class="hlt">wave</span> <span class="hlt">induced</span> lensing will be detected at more than 3 σ significance level. Further, we point out that high-sensitivity experiments will be also powerful to constrain the gravitational <span class="hlt">waves</span> generated after the recombination epoch. Compared to the B-mode polarization, the curl mode is particularly sensitive to gravitational <span class="hlt">waves</span> generated at low redshifts (z ≲10 ) with a low frequency (k ≲1 0-3 Mpc-1 ), and it could give a much tighter constraint on their energy density ΩGW by more than 3 orders of magnitude.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611123D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611123D"><span id="translatedtitle">Critical role of wind-<span class="hlt">wave</span> <span class="hlt">induced</span> erosion on the morphodynamic evolution of shallow tidal basins</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>D'Alpaos, Andrea; Carniello, Luca; Rinaldo, Andrea</p> <p>2014-05-01</p> <p>Wind-<span class="hlt">wave</span> <span class="hlt">induced</span> erosion processes are among the chief processes which govern the morphodynamic evolution of shallow tidal basins, both in the vertical and in the horizontal plane. Wind-<span class="hlt">wave</span> <span class="hlt">induced</span> bottom shear stresses can promote the disruption of the polymeric microphytobenthic biofilm and lead to the erosion of tidal-flat surfaces and to the increase in suspended sediment concentration which affects the stability of intertidal ecosystems. Moreover, the impact of wind-<span class="hlt">waves</span> on salt-marsh margins can lead to the lateral erosion of marsh boundaries thus promoting the disappearance of salt-marsh ecosystems. Towards the goal of developing a synthetic theoretical framework to represent wind <span class="hlt">wave-induced</span> resuspension events and account for their erosional effects on the long-term biomorphodynamic evolution of tidal systems, we have employed a complete, coupled finite element model accounting for the role of wind <span class="hlt">waves</span> and tidal currents on the hydrodynamic circulation in shallow basins. Our analyses of the characteristics of combined current and <span class="hlt">wave-induced</span> exceedances in bottom shear stress over a given threshold for erosion, suggest that wind <span class="hlt">wave-induced</span> resuspension events can be modeled as a marked Poisson process. The interarrival time of <span class="hlt">wave-induced</span> erosion events is, in fact, an exponentially distributed random variable, as well as the duration and intensity of overthreshold events. Moreover, the analysis of wind-<span class="hlt">wave</span> <span class="hlt">induced</span> resuspension events for different historical configurations of the Venice Lagoon from the 19th to the 21st century, shows that the interarrival times of erosion events have dramatically decreased through the last two centuries, whereas the intensities of erosion events have experienced a surprisingly high increase. This allows us to characterize the threatening erosion and degradation processes that the Venice Lagoon has been experiencing since the beginning of the last century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999JaJAP..38.3076M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999JaJAP..38.3076M"><span id="translatedtitle">Acoustooptic Effects of Nematic Liquid Crystals <span class="hlt">Induced</span> by Elastic <span class="hlt">Wave</span> Propagating in Glass Substrate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moritake, Hiroshi; Seike, Tadaaki; Toda, Kohji</p> <p>1999-05-01</p> <p>An elastic <span class="hlt">wave</span> delay line with a glass plate as a propagation medium is investigated in relations to acoustooptic effects of nematic liquid crystals. A nematic liquid crystal cell is mounted on the central region of a glass plate for elastic <span class="hlt">wave</span> propagation. The elastic <span class="hlt">wave</span> propagating in the glass plate interacts with the liquid crystal in a wide frequency range. Two types of periodical domain structures are observed in the nematic liquid crystal cell under the existence of the elastic <span class="hlt">wave</span>. One exists in both homeotropically and homogeneously aligned cells, and depends not on the kind of liquid crystal but on the carrier frequency of the elastic <span class="hlt">wave</span>. The other is recognized only in homogeneously aligned cells and depends on the layer thickness and the kind of liquid crystal, but not on the carrier frequency of the elastic <span class="hlt">wave</span>. Both periodical domain structures are <span class="hlt">induced</span> by the elastic <span class="hlt">wave</span> propagating in the glass plate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMNH32A..08L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMNH32A..08L"><span id="translatedtitle">Seismic-<span class="hlt">induced</span> water <span class="hlt">waves</span> by the March 2011 Japan earthquake</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, L.; Liang, W.; Liang, M.; Huang, N.</p> <p>2011-12-01</p> <p>On March 11, 2011, the Mw 9.0 Tohoku earthquake caused unusual water <span class="hlt">waves</span> in many harbors. After about 10 minutes, significant changes in sea level were observed in the coastal regions of Taiwan. The event also <span class="hlt">induced</span> seismic surface <span class="hlt">waves</span> of ~7 cm displacement. The effects of earthquake on water bodies were examined in Taiwan, Japan and Russia. Results show the effect is more amplified at the islands than in the continental area. Other dominant features from this analysis are the roughly 20-40 cm amplitude, period of 2-5 minutes oscillations and ~20 cm amplitude of tsunami <span class="hlt">waves</span> at the Orchid island of Taiwan. The superposition of two <span class="hlt">waves</span> estimates the amplitude of roughly 40 cm at the island but has two different source mechanisms. Therefore, the real tsunami is overestimate and the arrival time for tsunami <span class="hlt">wave</span> groups need to be adjusted. This study will focus on the forced <span class="hlt">waves</span> caused by the passing of seismic <span class="hlt">waves</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvE..93e3203D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvE..93e3203D"><span id="translatedtitle"><span class="hlt">Pressure</span> anisotropy and small spatial scales <span class="hlt">induced</span> by velocity shear</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Del Sarto, D.; Pegoraro, F.; Califano, F.</p> <p>2016-05-01</p> <p>By including the full <span class="hlt">pressure</span> tensor dynamics in a fluid plasma model, we show that a sheared velocity field can provide an effective mechanism that makes the initial isotropic <span class="hlt">pressure</span> nongyrotropic. This is distinct from the usual gyrotropic anisotropy related to the fluid compressibility and usually accounted for in double-adiabatic models. We determine the time evolution of the <span class="hlt">pressure</span> agyrotropy and discuss how the propagation of "magnetoelastic perturbations" can affect the <span class="hlt">pressure</span> tensor anisotropization and its spatial filamentation, which are due to the action of both the magnetic field and the flow strain tensor. We support this analysis with a numerical integration of the nonlinear equations describing the <span class="hlt">pressure</span> tensor evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1614605D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1614605D"><span id="translatedtitle"><span class="hlt">Wave</span> <span class="hlt">induced</span> transport and mixing of buoyant particles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drivdal, Magnus; Broström, Göran; Christensen, Kai H.</p> <p>2014-05-01</p> <p>The modeling of <span class="hlt">wave</span>-current and <span class="hlt">wave</span>-turbulence interactions have received much attention during recent years. Both the breaking of surface <span class="hlt">waves</span> and the inclusion of the Stokes shear production have been shown to increase the upper ocean turbulence. Furthermore the Coriolis force acting on the Stokes drift redistributes the momentum in the upper ocean, leading to a deflection of the currents. An important application affected by these processes that still needs to be studied is the mixing and drift of particles. Using an ocean column model, modified to take surface <span class="hlt">wave</span> effects into account, we investigate how the increased mixing by <span class="hlt">wave</span> breaking and Stokes shear production as well as the stronger veering by the Coriolis-Stokes force effects the drift of suspended particles. Here the suspended particles are buoyant tracers that can represent oil droplets or plankton, for example fish eggs and larvae. The energy and momentum fluxes as well as the Stokes drift depend on the directional <span class="hlt">wave</span> spectrum that can be obtained from a <span class="hlt">wave</span> model or from observations. Comparing with classical Ekman theory some physical effects on the system are studied, and as a realistic test case we use the model to study the oil drift after an offshore oil spill that took place outside the western coast of Norway in 2007. During this accident the average net drift of oil was observed to be approximately 0.1% of the wind speed at an angle of about 90-120 degrees to the right, far slower and more deflected away from the wind direction than predicted by both numerical and empirical models. With wind and <span class="hlt">wave</span> forcing from ECMWF reanalysis data, it is shown that the <span class="hlt">wave</span> effects are important for the resultant drift in this case, and has the potential to improve drift forecasting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AnGeo..26.2253Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AnGeo..26.2253Y"><span id="translatedtitle">Bistatic observations of large and small scale ULF <span class="hlt">waves</span> in SPEAR-<span class="hlt">induced</span> HF coherent backscatter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yeoman, T. K.; Baddeley, L. J.; Dhillon, R. S.; Robinson, T. R.; Wright, D. M.</p> <p>2008-08-01</p> <p>HF radar backscatter which has been artificially-<span class="hlt">induced</span> by a high power RF facility has been demonstrated to provide ionospheric electric field data of unprecedented temporal resolution and accuracy. Here such data, <span class="hlt">induced</span> by the SPEAR high power radar on Svalbard, are used to investigate ULF <span class="hlt">wave</span> processes observed by the CUTLASS HF radars. Observations are presented of both <span class="hlt">waves</span> with a large-scale nature, driven externally to the magnetosphere and those with small azimuthal scale lengths, driven by <span class="hlt">wave</span>-particle interactions. For ULF <span class="hlt">wave</span> events with large azimuthal scale lengths an excellent agreement in the observed <span class="hlt">wave</span> polarisation ellipse is found between the radar observations and ground-based magnetometer data. In contrast, for the small scale events, no ground-based magnetic counterpart is observed. Indeed the data from the two CUTLASS radars seem inconsistent, and each radar must be interpreted separately, as the spatial resolution of the radars is sufficient to resolve the <span class="hlt">wave</span> characteristics along the radar beams, but insufficient to resolve the <span class="hlt">wave</span> characteristics across the beams. A high azimuthal <span class="hlt">wave</span> number (m) <span class="hlt">wave</span> with a period of 300 s and m~-60 is observed to occur over Svalbard at ~14:00 magnetic local time. This confirms the existence of <span class="hlt">waves</span> driven by <span class="hlt">wave</span>-particle interactions with trapped particle populations in the outer magnetosphere. A comparison of the observed <span class="hlt">wave</span> characteristics with previous, lower latitude, observations suggests that these high latitude <span class="hlt">waves</span> have a similar azimuthal scale size to those generated in the inner magnetosphere; the azimuthal <span class="hlt">wave</span> number of -60 observed in the present study is comparable to previous values of -20 -50, but suggests an increase of m with latitude. A similar energy source in drifting proton populations is also suggested, but with lower characteristic proton energies of 10 keV implicated at high latitude, compared to the 20 60 keV energies invoked for previous lower latitude</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22489555','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22489555"><span id="translatedtitle">A coupled cluster and Møller-Plesset perturbation theory study of the <span class="hlt">pressure</span> <span class="hlt">induced</span> phase transition in the LiH crystal</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Grüneis, Andreas</p> <p>2015-09-14</p> <p>We employ Hartree–Fock, second-order Møller-Plesset perturbation, coupled cluster singles and doubles (CCSD) as well as CCSD plus perturbative triples (CCSD(T)) theory to study the <span class="hlt">pressure</span> <span class="hlt">induced</span> transition from the rocksalt to the cesium chloride crystal structure in LiH. We show that the calculated transition <span class="hlt">pressure</span> converges rapidly in this series of increasingly accurate many-electron <span class="hlt">wave</span> function based theories. Using CCSD(T) theory, we predict a transition <span class="hlt">pressure</span> for the structural phase transition in the LiH crystal of 340 GPa. Furthermore, we investigate the potential energy surface for this transition in the parameter space of the Buerger path.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhDT.......293M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhDT.......293M"><span id="translatedtitle">Physics of unsteady cylinder-<span class="hlt">induced</span> transitional shock <span class="hlt">wave</span> boundary layer interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murphree, Zachary Ryan</p> <p></p> <p>The mean flowfield and time-dependent characteristics of a Mach 5 cylinder-<span class="hlt">induced</span> transitional shock-<span class="hlt">wave</span>/boundary-layer interaction have been studied experimentally. The interactions were generated with a right circular cylinder mounted on a flat plate. The Reynolds number based on distance from the leading edge of the plate to the cylinder leading edge ranged from 4.5 x 106 to 6.1 x 106, and the incoming boundary-layer was transitional. The objectives of the study were to: (i) provide a detailed description of the mean flow structure of the interaction, and (ii) characterize the unsteadiness of the interaction based on fluctuating <span class="hlt">pressure</span> measurements. Mean wall-<span class="hlt">pressure</span> measurements coupled with planar laser scattering and surface visualization showed that the transitional interaction exhibits characteristics that are essentially a "composite" of an upstream laminar interaction and a downstream turbulent interaction. In the upstream region there is a laminar separation bubble that is characterized by a weak separation shock, a <span class="hlt">pressure</span> plateau, and low relative mass/heat flux. The separated boundary-layer reattaches downstream of this bubble, about 4 diameters upstream of the cylinder. This reattached flow is characterized by high relative mass/heat flux, an increase in <span class="hlt">pressure</span> and a rapidly thickening boundary-layer. The flow then separates again in a manner very similar to a low Reynolds number turbulent interaction. Statistical analysis of the <span class="hlt">pressure</span> histories suggest that the entire interaction stretches and contracts in concert. Power spectral densities of the <span class="hlt">pressure</span> fluctuations showed unsteadiness throughout the interaction with energy content in one of two frequency bands: one with a sharp peak from 1-2 kHz and the other with a broader peak at 7-10 kHz. The lower frequency is attributed to the interaction motion, whereas the higher frequency is found underneath the reattached boundary-layer. Cross-correlations and coherence functions in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPhD...48y5201O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPhD...48y5201O"><span id="translatedtitle">Diagnostics of surface <span class="hlt">wave</span> driven low <span class="hlt">pressure</span> plasmas based on indium monoiodide-argon system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ögün, C. M.; Kaiser, C.; Kling, R.; Heering, W.</p> <p>2015-06-01</p> <p>Indium monoiodide is proposed as a suitable alternative to hazardous mercury, i.e. the emitting component inside the compact fluorescent lamps (CFL), with comparable luminous efficacy. Indium monoiodide-argon low <span class="hlt">pressure</span> lamps are electrodelessly driven with surface <span class="hlt">waves</span>, which are launched and coupled into the lamp by the ‘surfatron’, a microwave coupler optimized for an efficient operation at a frequency of 2.45 GHz. A non intrusive diagnostic method based on spatially resolved optical emission spectroscopy is employed to characterize the plasma parameters. The line emission coefficients of the plasma are derived by means of Abel’s inversion from the measured spectral radiance data. The characteristic plasma parameters, e.g. electron temperature and density are determined by comparing the experimentally obtained line emission coefficients with simulated ones from a collisional-radiative model. Additionally, a method to determine the absolute plasma efficiency via irradiance measurements without any goniometric setup is presented. In this way, the relationship between the plasma efficiency and the plasma parameters can be investigated systematically for different operating configurations, e.g. electrical input power, buffer gas <span class="hlt">pressure</span> and cold spot temperature. The performance of indium monoiodide-argon plasma is compared with that of conventional CFLs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21331462','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21331462"><span id="translatedtitle">Numerical study of the direct <span class="hlt">pressure</span> effect of acoustic <span class="hlt">waves</span> in planar premixed flames</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schmidt, H.; Jimenez, C.</p> <p>2010-08-15</p> <p>Recently the unsteady response of 1-D premixed flames to acoustic <span class="hlt">pressure</span> <span class="hlt">waves</span> for the range of frequencies below and above the inverse of the flame transit time was investigated experimentally using OH chemiluminescence Wangher (2008). They compared the frequency dependence of the measured response to the prediction of an analytical model proposed by Clavin et al. (1990), derived from the standard flame model (one-step Arrhenius kinetics) and to a similar model proposed by McIntosh (1991). Discrepancies between the experimental results and the model led to the conclusion that the standard model does not provide an adequate description of the unsteady response of real flames and that it is necessary to investigate more realistic chemical models. Here we follow exactly this suggestion and perform numerical studies of the response of lean methane flames using different reaction mechanisms. We find that the global flame response obtained with both detailed chemistry (GRI3.0) and a reduced multi-step model by Peters (1996) lies slightly above the predictions of the analytical model, but is close to experimental results. We additionally used an irreversible one-step Arrhenius reaction model and show the effect of the <span class="hlt">pressure</span> dependence of the global reaction rate in the flame response. Our results suggest first that the current models have to be extended to capture the amplitude and phase results of the detailed mechanisms, and second that the correlation between the heat release and the measured OH* chemiluminescence should be studied deeper. (author)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhPro..67..434K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhPro..67..434K"><span id="translatedtitle">Improved Performance of an Indigenous Stirling Type Pulse Tube Cooler and <span class="hlt">Pressure</span> <span class="hlt">Wave</span> Generator</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kumar, J. Kranthi; Jacob, S.; Karunanithi, R.; Narasimham, G. S. V. L.; Damu, C.; Praveen, T.; Samir, M.</p> <p></p> <p>Sustained efforts have been made in our laboratory to improve the performance of an indigenously developed <span class="hlt">pressure</span> <span class="hlt">wave</span> gen- erator by reducing the mechanical losses and the required input power. An acoustically matching pulse tube cooler, with a design target of 0.5 W at 80 K, was designed using Sage and experience gained from previous studies. The pulse tube cooler was fabri- cated and tested. The effect of regenerator stacking pattern on the cooler performance was studied by filling the regenerator with mesh of the same size #400 and with multi meshes #250, 325, 400. In present experiments, regenerator with #400 mesh at 30 bar filling <span class="hlt">pressure</span> performed better with more energy efficiency. A no load temperature of 74 K was achieved with input power of 59 W corresponding to a cooling power of 0.22 W at 80 K. Parasitic heat load to the cooler was measured be 0.68 W. This heat load is primarily by heat conduction through the regenerator and pulse tube wall. By reducing the wall thickness from 0.30 mm to 0.15 mm, the parasitic loads can be reduced by 50%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012SPIE.8504E..0FS','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012SPIE.8504E..0FS"><span id="translatedtitle">Developing a platform for high-resolution phase contrast imaging of high <span class="hlt">pressure</span> shock <span class="hlt">waves</span> in matter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schropp, Andreas; Patommel, Jens; Seiboth, Frank; Arnold, Brice; Galtier, Eric C.; Lee, Hae Ja; Nagler, Bob; Hastings, Jerome B.; Schroer, Christian G.</p> <p>2012-10-01</p> <p>Current and upcoming X-ray sources, such as the Linac Coherent Light Source (LCLS) at the Stanford Linear Accelerator Center (SLAC, USA), the SPring-8 Angstrom Compact Free Electron Laser (SACLA, Japan), or the X-ray Free Electron Laser (XFEL, Germany) will provide X-ray beams with outstanding properties.1, 2 Short and intense X-ray pulses of about 50 fs time duration and even shorter will push X-ray science to new frontiers such as, e. g., in high-resolution X-ray imaging, high-energy-density physics or in dynamical studies based on pump-probe techniques. Fast processes in matter often require high-resolution imaging capabilities either by magnified imaging in direct space or diffractive imaging in reciprocal space. In both cases highest resolutions require focusing the X-ray beam.3, 4 In order to further develop high-resolution imaging at free-electron laser sources we are planning a platform to carry out high-resolution phase contrast imaging experiments based on Beryllium compound refractive X-ray lenses (Be-CRLs) at the Matter in Extreme Conditions (MEC) endstation of the LCLS. The instrument provides all necessary equipment to <span class="hlt">induce</span> high <span class="hlt">pressure</span> shock <span class="hlt">waves</span> by optical lasers. The propagation of a shock <span class="hlt">wave</span> is then monitored with an X-ray Free Electron Laser (FEL) pulse by magnified phase contrast imaging. With the CRL optics, X-ray beam sizes in the sub-100nm range are expected, leading to a similar spatial resolution in the direct coherent projection image. The experiment combines different state-of-the art scientific techniques that are currently available at the LCLS. In this proceedings paper we describe the technical developments carried out at the LCLS in order to implement magnified X-ray phase contrast imaging at the MEC endstation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910054153&hterms=force+acceleration&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dforce%2Bacceleration','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910054153&hterms=force+acceleration&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dforce%2Bacceleration"><span id="translatedtitle">Flexural <span class="hlt">waves</span> <span class="hlt">induced</span> by electro-impulse deicing forces</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gien, P. H.</p> <p>1990-01-01</p> <p>The generation, reflection and propagation of flexural <span class="hlt">waves</span> created by electroimpulsive deicing forces are demonstrated both experimentally and analytically in a thin circular plate and a thin semicylindrical shell. Analytical prediction of these <span class="hlt">waves</span> with finite element models shows good correlation with acceleration and displacement measurements at discrete points on the structures studied. However, sensitivity to spurious flexural <span class="hlt">waves</span> resulting from the spatial discretization of the structures is shown to be significant. Consideration is also given to composite structures as an extension of these studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.5190G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.5190G"><span id="translatedtitle">A <span class="hlt">pressure-induced</span>, magnetic transition in pyrrhotite: Implications for the formation <span class="hlt">pressure</span> of meteorites and diamonds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gilder, S. A.; Egli, R.; Hochleitner, R.; Roud, S. C.; Volk, M. W. R.; Le Goff, M.; de Wit, M.</p> <p>2012-04-01</p> <p>Meteorites and diamonds encounter high <span class="hlt">pressures</span> during their formation or subsequent evolution. These materials sometimes contain magnetic inclusions of pyrrhotite. Because magnetic properties are sensitive to strain, pyrrhotite can potentially record the shock or formation <span class="hlt">pressures</span> of its host. Moreover, pyrrhotite undergoes a <span class="hlt">pressure-induced</span> phase transition between 1.6 and 6.2 GPa, but the magnetic signature of this transition is poorly known. Here we report room temperature magnetic measurements on multi- and single domain pyrrhotite under non-hydrostatic <span class="hlt">pressure</span> up to 4.5 GPa. We find that the ratio of magnetic coercivity and remanence follows a logarithmic law with respect to <span class="hlt">pressure</span>, which can potentially be used as a geobarometer. Due to the greater thermal expansion of pyrrhotite with respect to diamond, pyrrhotite inclusions in diamond experience a confining <span class="hlt">pressure</span> at the Earth's surface. Applying our experimentally derived magnetic geobarometer to pyrrhotite-bearing diamonds from Botswana and the Central African Republic suggests the <span class="hlt">pressures</span> of the pyrrhotite inclusions in the diamonds range from 1.3 to 2.1 GPa. These overpressures constrain the mantle source <span class="hlt">pressures</span> from 5.4 to 9.5 GPa, depending on which bulk modulus and thermal expansion coefficients of the two phases are used. We are now trying to develop magnetic barometers on other magnetic phases to apply to meteorites, ultimately to constrain the minimum <span class="hlt">pressure</span> in which the meteorite formed and, hence, information regarding the planetesmal's size, and/or depth, in which the meteorite was derived.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24116532','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24116532"><span id="translatedtitle">Reverberation clutter <span class="hlt">induced</span> by nonlinear internal <span class="hlt">waves</span> in shallow water.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Henyey, Frank S; Tang, Dajun</p> <p>2013-10-01</p> <p>Clutter is related to false alarms for active sonar. It is demonstrated that, in shallow water, target-like clutter in reverberation signals can be caused by nonlinear internal <span class="hlt">waves</span>. A nonlinear internal <span class="hlt">wave</span> is modeled using measured stratification on the New Jersey shelf. Reverberation in the presence of the internal <span class="hlt">wave</span> is modeled numerically. Calculations show that acoustic energy propagating near a sound speed minimum is deflected as a high intensity, higher angle beam into the bottom, where it is backscattered along the reciprocal path. The interaction of sound with the internal <span class="hlt">wave</span> is isolated in space, hence resulting in a target-like clutter, which is found to be greater than 10 dB above the mean reverberation level. PMID:24116532</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24229104','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24229104"><span id="translatedtitle">Supratransmission <span class="hlt">induced</span> by <span class="hlt">waves</span> collisions in a discrete electrical lattice.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Togueu Motcheyo, A B; Tchawoua, C; Tchinang Tchameu, J D</p> <p>2013-10-01</p> <p>We numerically performed a way to produce a supratransmission phenomenon in the Salerno equation describing the dynamics of modulated <span class="hlt">waves</span> in a discrete nonlinear transmission lattice. For the natural supratransmission phenomenon, there exists a threshold of amplitude for which energy can flow in the line. We show that gap transmission is possible with driven amplitude below the threshold due to the collision of different plane <span class="hlt">waves</span> coming from both edges of the line. One of the two plane <span class="hlt">waves</span> has a frequency in the forbidden gap, and another has a frequency in the allowed phonon band. During collision, the <span class="hlt">wave</span> in the allowed band is considered as a perturbation of the ones in the forbidden gap. PMID:24229104</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JGRC..11512005L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JGRC..11512005L"><span id="translatedtitle"><span class="hlt">Wave-induced</span> velocities inside a model seagrass bed</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Luhar, Mitul; Coutu, Sylvain; Infantes, Eduardo; Fox, Samantha; Nepf, Heidi</p> <p>2010-12-01</p> <p>Laboratory measurements reveal the flow structure within and above a model seagrass meadow (dynamically similar to Zostera marina) forced by progressive <span class="hlt">waves</span>. Despite being driven by purely oscillatory flow, a mean current in the direction of <span class="hlt">wave</span> propagation is generated within the meadow. This mean current is forced by a nonzero <span class="hlt">wave</span> stress, similar to the streaming observed in <span class="hlt">wave</span> boundary layers. The measured mean current is roughly four times that predicted by laminar boundary layer theory, with magnitudes as high as 38% of the near-bed orbital velocity. A simple theoretical model is developed to predict the magnitude of this mean current based on the energy dissipated within the meadow. Unlike unidirectional flow, which can be significantly damped within a meadow, the in-canopy orbital velocity is not significantly damped. Consistent with previous studies, the reduction of in-canopy velocity is a function of the ratio of orbital excursion and blade spacing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016OptLE..79...61B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016OptLE..79...61B&link_type=ABSTRACT"><span id="translatedtitle">Determination of hydrocarbon levels in water via laser-<span class="hlt">induced</span> acoustics <span class="hlt">wave</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bidin, Noriah; Hossenian, Raheleh; Duralim, Maisarah; Krishnan, Ganesan; Marsin, Faridah Mohd; Nughro, Waskito; Zainal, Jasman</p> <p>2016-04-01</p> <p>Hydrocarbon contamination in water is a major environmental concern in terms of foreseen collapse of the natural ecosystem. Hydrocarbon level in water was determined by generating acoustic <span class="hlt">wave</span> via an innovative laser-<span class="hlt">induced</span> breakdown in conjunction with high-speed photographic coupling with piezoelectric transducer to trace acoustic <span class="hlt">wave</span> propagation. A Q-switched Nd:YAG (40 mJ) was focused in cuvette-filled hydrocarbon solution at various concentrations (0-2000 ppm) to <span class="hlt">induce</span> optical breakdown, shock <span class="hlt">wave</span> generation and later acoustic <span class="hlt">wave</span> propagation. A nitro-dye (ND) laser (10 mJ) was used as a flash to illuminate and frozen the acoustic <span class="hlt">wave</span> propagation. Lasers were synchronised using a digital delay generator. The image of acoustic <span class="hlt">waves</span> was grabbed and recorded via charged couple device (CCD) video camera at the speed of 30 frames/second with the aid of Matrox software version 9. The optical delay (0.8-10.0 μs) between the acoustic <span class="hlt">wave</span> formation and its frozen time is recorded through photodetectors. A piezo-electric transducer (PZT) was used to trace the acoustic <span class="hlt">wave</span> (sound signal), which cascades to a digital oscilloscope. The acoustic speed is calculated from the ratio of acoustic <span class="hlt">wave</span> radius (1-8 mm) and optical time delay. Acoustic <span class="hlt">wave</span> speed is found to linearly increase with hydrocarbon concentrations. The acoustic signal generation at higher hydrocarbon levels in water is attributed to supplementary mass transfer and impact on the probe. Integrated high-speed photography with transducer detection system authenticated that the signals indeed emerged from the laser-<span class="hlt">induced</span> acoustic <span class="hlt">wave</span> instead of photothermal processes. It is established that the acoustic <span class="hlt">wave</span> speed in water is used as a fingerprint to detect the hydrocarbon levels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014IJMPD..2342001P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014IJMPD..2342001P"><span id="translatedtitle">Nanomechanical sensing of gravitational <span class="hlt">wave-induced</span> Casimir force perturbations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pinto, Fabrizio</p> <p>2014-06-01</p> <p>It is shown by means of the optical medium analogy that the static Casimir force between two conducting plates is modulated by gravitational <span class="hlt">waves</span>. The magnitude of the resulting force changes within the range of already existing small force metrology. It is suggested to enhance the effects on a Casimir force oscillator by mechanical parametric amplification driven by periodic illumination of interacting semiconducting boundaries. This represents a novel opportunity for the ground-based laboratory detection of gravitational <span class="hlt">waves</span> on the nanoscale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhL.108o1901P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhL.108o1901P"><span id="translatedtitle">Shock <span class="hlt">wave</span> <span class="hlt">induced</span> martensitic transformations and morphology changes in Fe-Pd ferromagnetic shape memory alloy thin films</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bischoff, A. J.; Arabi-Hashemi, A.; Ehrhardt, M.; Lorenz, P.; Zimmer, K.; Mayr, S. G.</p> <p>2016-04-01</p> <p>Combining experimental methods and classical molecular dynamics (MD) computer simulations, we explore the martensitic transformation in Fe70Pd30 ferromagnetic shape memory alloy thin films <span class="hlt">induced</span> by laser shock peening. X-ray diffraction and scanning electron microscope measurements at shock <span class="hlt">wave</span> <span class="hlt">pressures</span> of up to 2.5 GPa reveal formation of martensitic variants with preferred orientation of the shorter c-axis of the tetragonal unit cell perpendicular to the surface plane. Moreover, consequential merging of growth islands on the film surface is observed. MD simulations unveil the underlying physics that are characterized by an austenite-martensite transformation with a preferential alignment of the c-axis along the propagation direction of the shock <span class="hlt">wave</span>, resulting in flattening and in-plane expansion of surface features.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.V43A3092J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.V43A3092J"><span id="translatedtitle"><span class="hlt">Pressure</span> <span class="hlt">Wave</span> Propagation along the Décollement of the Nankai Accretionary Wedge: Implications for Aseismic Slip Events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Joshi, A.; Appold, M. S.</p> <p>2015-12-01</p> <p>Seismic and hydrologic observations of the Nankai subduction zone made by the Ocean Drilling Program suggest that pore fluid <span class="hlt">pressures</span> within the accretionary wedge décollement are highly overpressured to near lithostatic values below depths of 2 km beneath the sea floor as a result of sediment diagenesis and dehydration of the subducting oceanic plate. This overpressured zone is also observed to discharge pulses of high fluid <span class="hlt">pressure</span> that migrate up-dip along the décollement at rates of 1's of km/day. These high <span class="hlt">pressure</span> pulses along the décollement may cause large enough reductions in the local effective stress to account for aseismic slip events that have been found to propagate also at rates of 1's of km/day. Because elevated fluid <span class="hlt">pressure</span> and correspondingly decreased effective stress can lead to a dilation of porosity, the <span class="hlt">pressure</span> <span class="hlt">waves</span> may become effective agents of fluid transport that can travel more quickly than fluids flowing in the background Darcian flow regime. The purpose of the present study was to seek theoretical confirmation that <span class="hlt">pressure</span> <span class="hlt">waves</span> are able to travel quickly enough to account for the seismic and hydrological observations documented. This confirmation was sought through a transient one-dimensional numerical solution to the differential fluid mass conservation equation for an elastic porous medium. Results of the numerical simulations show that when overpressures at depths greater than 2 km in the décollement exceed lithostatic <span class="hlt">pressure</span> by at least 3%, <span class="hlt">pressure</span> <span class="hlt">waves</span> are formed that migrate up-dip at rates fast enough to account for aseismic slip over a broad range of geologic conditions. <span class="hlt">Pressure</span> <span class="hlt">waves</span> spawned from these depths in the décollement may travel fast enough to account for aseismic slip when overpressures there are as low as 99% of lithostatic <span class="hlt">pressure</span>, but require low specific storage of 3×10-6 m-1, high sensitivity of permeability to effective stress, low permeability no higher than about 10-21 m2 at depths below</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ShWav..23...25B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ShWav..23...25B"><span id="translatedtitle">Macro-mechanical modeling of blast-<span class="hlt">wave</span> mitigation in foams. Part II: reliability of <span class="hlt">pressure</span> measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Britan, A.; Liverts, M.; Shapiro, H.; Ben-Dor, G.</p> <p>2013-02-01</p> <p>A phenomenological study of the process occurring when a plane shock <span class="hlt">wave</span> reflected off an aqueous foam column filling the test section of a vertical shock tube has been undertaken. The experiments were conducted with initial shock <span class="hlt">wave</span> Mach numbers in the range 1.25le {M}_s le 1.7 and foam column heights in the range 100-450 mm. Miniature piezotrone circuit electronic <span class="hlt">pressure</span> transducers were used to record the <span class="hlt">pressure</span> histories upstream and alongside the foam column. The aim of these experiments was to find a simple way to eliminate a spatial averaging as an artifact of the <span class="hlt">pressure</span> history recorded by the side-on transducer. For this purpose, we discuss first the common behaviors of the <span class="hlt">pressure</span> traces in extended time scales. These observations evidently quantify the low frequency variations of the <span class="hlt">pressure</span> field within the different flow domains of the shock tube. Thereafter, we focus on the fronts of the <span class="hlt">pressure</span> signals, which, in turn, characterize the high-frequency response of the foam column to the shock <span class="hlt">wave</span> impact. Since the front shape and the amplitude of the <span class="hlt">pressure</span> signal most likely play a significant role in the foam destruction, phase changes and/or other physical factors, such as high capacity, viscosity, etc., the common practice of the data processing is revised and discussed in detail. Generally, side-on <span class="hlt">pressure</span> measurements must be used with great caution when performed in wet aqueous foams, because the low sound speed is especially prone to this effect. Since the spatial averaged recorded <span class="hlt">pressure</span> signals do not reproduce well the real behaviors of the <span class="hlt">pressure</span> rise, the recorded shape of the shock <span class="hlt">wave</span> front in the foam appears much thicker. It is also found that when a thin liquid film wet the sensing membrane, the transducer sensitivity was changed. As a result, the <span class="hlt">pressure</span> recorded in the foam could exceed the real amplitude of the post-shock <span class="hlt">wave</span> flow. A simple procedure, which allows correcting this imperfection, is discussed in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20860365','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20860365"><span id="translatedtitle">Charging-delay <span class="hlt">induced</span> dust acoustic collisionless shock <span class="hlt">wave</span>: Roles of negative ions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ghosh, Samiran; Bharuthram, R.; Khan, Manoranjan; Gupta, M. R.</p> <p>2006-11-15</p> <p>The effects of charging-delay and negative ions on nonlinear dust acoustic <span class="hlt">waves</span> are investigated. It has been found that the charging-delay <span class="hlt">induced</span> anomalous dissipation causes generation of dust acoustic collisionless shock <span class="hlt">waves</span> in an electronegative dusty plasma. The small but finite amplitude <span class="hlt">wave</span> is governed by a Korteweg-de Vries Burger equation in which the Burger term arises due to the charging-delay. Numerical investigations reveal that the charging-delay <span class="hlt">induced</span> dissipation and shock strength decreases (increases) with the increase of negative ion concentration (temperature)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/15089478','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/15089478"><span id="translatedtitle">Enhanced acceleration of injected electrons in a laser-beat-<span class="hlt">wave-induced</span> plasma channel.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tochitsky, S Ya; Narang, R; Filip, C V; Musumeci, P; Clayton, C E; Yoder, R B; Marsh, K A; Rosenzweig, J B; Pellegrini, C; Joshi, C</p> <p>2004-03-01</p> <p>Enhanced energy gain of externally injected electrons by a approximately 3 cm long, high-gradient relativistic plasma <span class="hlt">wave</span> (RPW) is demonstrated. Using a CO2 laser beat <span class="hlt">wave</span> of duration longer than the ion motion time across the laser spot size, a laser self-guiding process is initiated in a plasma channel. Guiding compensates for ionization-<span class="hlt">induced</span> defocusing (IID) creating a longer plasma, which extends the interaction length between electrons and the RPW. In contrast to a maximum energy gain of 10 MeV when IID is dominant, the electrons gain up to 38 MeV energy in a laser-beat-<span class="hlt">wave-induced</span> plasma channel. PMID:15089478</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760023652','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760023652"><span id="translatedtitle">Pyroxenes and olivines: Structural implications of shock-<span class="hlt">wave</span> data for high <span class="hlt">pressure</span> phases</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jeanloz, R.; Ahrens, T. J.</p> <p>1975-01-01</p> <p>The nature of the shock-<span class="hlt">induced</span>, high-<span class="hlt">pressure</span> phases of olivine and pyroxene rocks is examined in the light of data for the densities of a new class of perovskite-related silicate structures. Also examined are some new Hugoniot and release adiabat data for bronzite. Reexamining available shock data for magnesian pyroxenes and olivines leads to the conclusion that they define a mixed phase (or disequilibrium) region to about the 100 GPa range, related to the kinetics of phase transformation in these silicates. By recognizing this point, certain discrepancies in previous interpretations of shock data can be explained. A set of theoretical Hugonoits for pyroxene and olivine stoichiometry, perovskite-bearing assemblages was constructed based on their properties deduced from high-<span class="hlt">pressure</span> work, showing that the shock data is compatible with transformations to perovskites in the 45-7GPa region. Finally, the shock data indicate very similar properties for olivine and pyroxene at high <span class="hlt">pressures</span> making them both equally likely candidates for the lower mantle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26367523','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26367523"><span id="translatedtitle">The <span class="hlt">Pressure-Induced</span> Polymorphic Transformations in Fluconazole.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gorkovenko, Ekaterina A; Kichanov, Sergey E; Kozlenko, Denis P; Belushkin, Alexandr V; Wąsicki, Jan; Nawrocik, Wojciech; Mielcarek, Jadwiga; Dubrovinsky, Leonid S; Lathe, Christian; Savenko, Boris N</p> <p>2015-12-01</p> <p>The structural properties and Raman spectra of fluconazole have been studied by means of X-ray diffraction and Raman spectroscopy at <span class="hlt">pressures</span> up to 2.5 and 5.5 GPa, respectively. At a <span class="hlt">pressure</span> of 0.8 GPa, a polymorphic phase transition from the initial form I to a new triclinic form VIII has been observed. At higher <span class="hlt">pressure</span> of P = 3.2 GPa, possible transformation into another new polymorphic form IX has been detected. The unit cell parameters and volumes, and vibration modes as functions of <span class="hlt">pressure</span> have been obtained for the different forms of fluconazole. PMID:26367523</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.2564T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.2564T"><span id="translatedtitle">Microseismicity <span class="hlt">Induced</span> by Fluid <span class="hlt">Pressure</span> Drop (Laboratory Study)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Turuntaev, Sergey; Zenchenko, Evgeny; Melchaeva, Olga</p> <p>2013-04-01</p> <p>Pore <span class="hlt">pressure</span> change in saturated porous rocks may result in its fracturing (Maury et Fourmaintraux, 1993) and corresponding microseismic event occurrences. Microseismicity due to fluid injection is considered in numerous papers (Maxwell, 2010, Shapiro et al., 2005). Another type of the porous medium fracturing is related with rapid pore <span class="hlt">pressure</span> drop at some boundary. The mechanism of such fracturing was considered by (Khristianovich, 1985) as a model of sudden coal blowing and by (Alidibirov, Panov, 1998) as a model of volcano eruptions. If the porous saturated medium has a boundary where it directly contacted with fluid under the high <span class="hlt">pressure</span> (in a hydraulic fracture or in a borehole), and the <span class="hlt">pressure</span> at that boundary is dropped, the conditions for tensile cracks can be achieved at some distance from the boundary. In the paper, the results of experimental study of saturated porous sample fracturing due to pore <span class="hlt">pressure</span> rapid drop are discussed. The samples (82 mm high, ∅60 mm) were made of quartz sand, which was cemented by "liquid glass" glue with mass fraction 1%. The sample (porosity 35%, uniaxial unconfined compression strength 2.5 MPa) was placed in a mould and saturated by oil. The upper end of the sample contacted with the mould upper lid, the lower end contacted with fluid. The fluid <span class="hlt">pressure</span> was increased to 10 MPa and then discharged through the bottom nipple. The <span class="hlt">pressure</span> increases/drops were repeated 30-50 times. Pore <span class="hlt">pressure</span> and acoustic emission (AE) were registered by transducers mounted into upper and bottom lids of the mould. It was found, that AE sources (corresponded to microfracturing) were spreading from the open end to the closed end of the sample, and that maximal number of AE events was registered at some distance from the opened end. The number of AE pulses increased with every next <span class="hlt">pressure</span> drop, meanwhile the number of pulses with high amplitudes diminished. It was found that AE maximal rate corresponded to the fluid <span class="hlt">pressure</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1133527','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1133527"><span id="translatedtitle">Small Gas Bubble Experiment for Mitigation of Cavitation Damage and <span class="hlt">Pressure</span> <span class="hlt">Waves</span> in Short-pulse Mercury Spallation Targets</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wendel, Mark W; Felde, David K; Sangrey, Robert L; Abdou, Ashraf A; West, David L; Shea, Thomas J; Hasegawa, Shoichi; Kogawa, Hiroyuki; Naoe, Dr. Takashi; Farny, Dr. Caleb H.; Kaminsky, Andrew L</p> <p>2014-01-01</p> <p>Populations of small helium gas bubbles were introduced into a flowing mercury experiment test loop to evaluate mitigation of beam-pulse <span class="hlt">induced</span> cavitation damage and <span class="hlt">pressure</span> <span class="hlt">waves</span>. The test loop was developed and thoroughly tested at the Spallation Neutron Source (SNS) prior to irradiations at the Los Alamos Neutron Science Center - Weapons Neutron Research Center (LANSCE-WNR) facility. Twelve candidate bubblers were evaluated over a range of mercury flow and gas injection rates by use of a novel optical measurement technique that accurately assessed the generated bubble size distributions. Final selection for irradiation testing included two variations of a swirl bubbler provided by Japan Proton Accelerator Research Complex (J-PARC) collaborators and one orifice bubbler developed at SNS. Bubble populations of interest consisted of sizes up to 150 m in radius with achieved gas void fractions in the 10^-5 to 10^-4 range. The nominal WNR beam pulse used for the experiment created energy deposition in the mercury comparable to SNS pulses operating at 2.5 MW. Nineteen test conditions were completed each with 100 pulses, including variations on mercury flow, gas injection and protons per pulse. The principal measure of cavitation damage mitigation was surface damage assessment on test specimens that were manually replaced for each test condition. Damage assessment was done after radiation decay and decontamination by optical and laser profiling microscopy with damaged area fraction and maximum pit depth being the more valued results. Damage was reduced by flow alone; the best mitigation from bubble injection was between half and a quarter that of flow alone. Other data collected included surface motion tracking by three laser Doppler vibrometers (LDV), loop wall dynamic strain, beam diagnostics for charge and beam profile assessment, embedded hydrophones and <span class="hlt">pressure</span> sensors, and sound measurement by a suite of conventional and contact microphones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22228040','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22228040"><span id="translatedtitle">Mirror force <span class="hlt">induced</span> <span class="hlt">wave</span> dispersion in Alfvén <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Damiano, P. A.; Johnson, J. R.</p> <p>2013-06-15</p> <p>Recent hybrid MHD-kinetic electron simulations of global scale standing shear Alfvén <span class="hlt">waves</span> along the Earth's closed dipolar magnetic field lines show that the upward parallel current region within these <span class="hlt">waves</span> saturates and broadens perpendicular to the ambient magnetic field and that this broadening increases with the electron temperature. Using resistive MHD simulations, with a parallel Ohm's law derived from the linear Knight relation (which expresses the current-voltage relationship along an auroral field line), we explore the nature of this broadening in the context of the increased perpendicular Poynting flux resulting from the increased parallel electric field associated with mirror force effects. This increased Poynting flux facilitates <span class="hlt">wave</span> energy dispersion across field lines which in-turn allows for electron acceleration to carry the field aligned current on adjacent field lines. This mirror force driven dispersion can dominate over that associated with electron inertial effects for global scale <span class="hlt">waves</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/12907428','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/12907428"><span id="translatedtitle">Static filling <span class="hlt">pressure</span> in patients during <span class="hlt">induced</span> ventricular fibrillation.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schipke, J D; Heusch, G; Sanii, A P; Gams, E; Winter, J</p> <p>2003-12-01</p> <p>The static <span class="hlt">pressure</span> resulting after the cessation of flow is thought to reflect the filling of the cardiovascular system. In the past, static filling <span class="hlt">pressures</span> or mean circulatory filling <span class="hlt">pressures</span> have only been reported in experimental animals and in human corpses, respectively. We investigated arterial and central venous <span class="hlt">pressures</span> in supine, anesthetized humans with longer fibrillation/defibrillation sequences (FDSs) during cardioverter/defibrillator implantation. In 82 patients, the average number of FDSs was 4 +/- 2 (mean +/- SD), and their duration was 13 +/- 2 s. In a total of 323 FDSs, arterial blood <span class="hlt">pressure</span> decreased with a time constant of 2.9 +/- 1.0 s from 77.5 +/- 34.4 to 24.2 +/- 5.3 mmHg. Central venous <span class="hlt">pressure</span> increased with a time constant of 3.6 +/- 1.3 s from 7.5 +/- 5.2 to 11.0 +/- 5.4 mmHg (36 points, 141 FDS). The average arteriocentral venous blood <span class="hlt">pressure</span> difference remained at 13.2 +/- 6.2 mmHg. Although it slowly decreased, the <span class="hlt">pressure</span> difference persisted even with FDSs lasting 20 s. Lack of true equilibrium <span class="hlt">pressure</span> could possibly be due to a waterfall mechanism. However, waterfalls were identified neither between the left ventricle and large arteries nor at the level of the diaphragm in supine patients. We therefore suggest that static filling <span class="hlt">pressures</span>/mean circulatory <span class="hlt">pressures</span> can only be directly assessed if the time after termination of cardiac pumping is adequate, i.e., >20 s. For humans, such times are beyond ethical options. PMID:12907428</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014CPL...612..138Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014CPL...612..138Z"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> irreversible phase transitions of the monoclinic GdOOH nanorods at ambient temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Chuanchao; Dai, Rucheng; Sui, Zhilei; Chen, Qiao; Wang, Zhongping; Yuan, Xiaodong; Zhang, Zengming; Ding, Zejun</p> <p>2014-09-01</p> <p>The structural transition of monoclinic GdOOH nanorods was studied by using a diamond anvil cell at room temperature with the probe of Eu3+ ion luminescence under <span class="hlt">pressures</span> up to 21.4 GPa. The changes of luminescence spectra indicated that a <span class="hlt">pressure-induced</span> phase transition from the monoclinic phase to the high <span class="hlt">pressure</span> tetragonal phase occurs at 10.7 GPa for GdOOH nanorods, and the monoclinic GdOOH nanorods are gradually transformed into the tetragonal phase with increasing <span class="hlt">pressure</span>. After releasing of <span class="hlt">pressure</span> to the ambient, the high <span class="hlt">pressure</span> tetragonal phase is retained, and the phase transition of GdOOH nanorods is irreversible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JAP...101j3514W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JAP...101j3514W"><span id="translatedtitle">Two dimensional hydrodynamic simulation of high <span class="hlt">pressures</span> <span class="hlt">induced</span> by high power nanosecond laser-matter interactions under water</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Benxin; Shin, Yung C.</p> <p>2007-05-01</p> <p>In laser shock peening (LSP) under a water-confinement regime, laser-matter interaction near the coating-water interface can <span class="hlt">induce</span> very high <span class="hlt">pressures</span> in the order of gigapascals, which can impart compressive residual stresses into metal workpieces to improve fatigue and corrosion properties. For axisymmetric laser spots with finite size, the <span class="hlt">pressure</span> generation near the water-coating interface is a two dimensional process in nature. This is in particular the case for microscale LSP performed with very small laser spots, which is a very promising technique to improve the reliability performance of microdevices. However, models capable of predicting two dimensional (2D) spatial distributions of the <span class="hlt">induced</span> <span class="hlt">pressures</span> near the coating-water interface in LSP have rarely been reported in literature. In this paper, a predictive 2D axisymmetric model is developed by numerically solving the hydrodynamic equations, supplemented with appropriate equations of state of water and the coating material. The model can produce 2D spatial distributions of material responses near the water-coating interface in LSP, and is verified through comparisons with experimental measurements. The model calculation shows that the effect of radial release <span class="hlt">wave</span> on <span class="hlt">pressure</span> spatial distributions becomes more significant as the laser spot size decreases, indicating the importance of a 2D model, particularly for microscale LSP.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20982886','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20982886"><span id="translatedtitle">Two dimensional hydrodynamic simulation of high <span class="hlt">pressures</span> <span class="hlt">induced</span> by high power nanosecond laser-matter interactions under water</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wu, Benxin; Shin, Yung C.</p> <p>2007-05-15</p> <p>In laser shock peening (LSP) under a water-confinement regime, laser-matter interaction near the coating-water interface can <span class="hlt">induce</span> very high <span class="hlt">pressures</span> in the order of gigapascals, which can impart compressive residual stresses into metal workpieces to improve fatigue and corrosion properties. For axisymmetric laser spots with finite size, the <span class="hlt">pressure</span> generation near the water-coating interface is a two dimensional process in nature. This is in particular the case for microscale LSP performed with very small laser spots, which is a very promising technique to improve the reliability performance of microdevices. However, models capable of predicting two dimensional (2D) spatial distributions of the <span class="hlt">induced</span> <span class="hlt">pressures</span> near the coating-water interface in LSP have rarely been reported in literature. In this paper, a predictive 2D axisymmetric model is developed by numerically solving the hydrodynamic equations, supplemented with appropriate equations of state of water and the coating material. The model can produce 2D spatial distributions of material responses near the water-coating interface in LSP, and is verified through comparisons with experimental measurements. The model calculation shows that the effect of radial release <span class="hlt">wave</span> on <span class="hlt">pressure</span> spatial distributions becomes more significant as the laser spot size decreases, indicating the importance of a 2D model, particularly for microscale LSP.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PCM....38..777I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PCM....38..777I"><span id="translatedtitle"><span class="hlt">Pressure</span> responses of portlandite and H-D isotope effects on <span class="hlt">pressure-induced</span> phase transitions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Iizuka, Riko; Kagi, Hiroyuki; Komatsu, Kazuki; Ushijima, Daichi; Nakano, Satoshi; Sano-Furukawa, Asami; Nagai, Takaya; Yagi, Takehiko</p> <p>2011-12-01</p> <p>The <span class="hlt">pressure</span> responses of portlandite and the isotope effect on the phase transition were investigated at room temperature from single-crystal Raman and IR spectra and from powder X-ray diffraction using diamond anvil cells under quasi-hydrostatic conditions in a helium <span class="hlt">pressure</span>-transmitting medium. Phase transformation and subsequent peak broadening (partial amorphization) observed from the Raman and IR spectra of Ca(OH)2 occurred at lower <span class="hlt">pressures</span> than those of Ca(OD)2. In contrast, no isotope effect was found on the volume and axial compressions observed from powder X-ray diffraction patterns. X-ray diffraction lines attributable to the high-<span class="hlt">pressure</span> phase remained up to 28.5 GPa, suggesting no total amorphization in a helium <span class="hlt">pressure</span> medium within the examined <span class="hlt">pressure</span> region. These results suggest that the H-D isotope effect is engendered in the local environment surrounding H(D) atoms. Moreover, the ratio of sample-to-methanol-ethanol <span class="hlt">pressure</span> medium (i.e., packing density) in the sample chamber had a significant effect on the increase in the half widths of the diffraction lines, even at <span class="hlt">pressures</span> below the hydrostatic limit of the <span class="hlt">pressure</span> medium.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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