Science.gov

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. 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.

  3. Magnetospheric ULF waves with an increasing amplitude induced by solar wind dynamic pressure changes: THEMIS observations

    NASA Astrophysics Data System (ADS)

    Shen, X.; Zong, Q.; Shi, Q.; Tian, A.; Sun, W.; Wang, Y.; Zhou, X.; Fu, S.; Angelopoulos, V.; Pu, Z.; Hartinger, M.

    2014-12-01

    We report the in situ observation of the magnetospheric ultra-low frequency (ULF) waves with an increasing amplitude induced by solar wind dynamic pressure changes. We examine the magnetospheric responses to solar wind dynamic pressure enhancements from April 1, 2007 to December 31, 2012, and find six ULF wave events with slow but clear wave amplitude increase. The amplitudes of ion velocities and magnetic field of these waves continuously increase by 2.1 ˜ 4.4 times during three to six wave cycles. We choose two typical cases to further investigate the cause of this wave amplitude increase. We find that the wave amplitude growth is mainly contributed by the toroidal mode wave. Interestingly, toroidal mode waves are standing, while compressional and poloidal mode waves are not. Thus, we suspect that the wave amplitude increase may be caused by the superposition of two wave sources. One wave source is the standing wave excited by the solar wind dynamic impulse. Additionally, fast mode compressional wave continuously shakes the magnetic field lines. The azimuthal component of this magnetic perturbation is the second wave source. Furthermore, the simple model calculation of superposing two waves match the observations pretty well.

  4. Intravascular pressure augments cerebral arterial constriction by inducing voltage-insensitive Ca2+ waves.

    PubMed

    Mufti, Rania E; Brett, Suzanne E; Tran, Cam Ha T; Abd El-Rahman, Rasha; Anfinogenova, Yana; El-Yazbi, Ahmed; Cole, William C; Jones, Peter P; Chen, S R Wayne; Welsh, Donald G

    2010-10-15

    This study examined whether elevated intravascular pressure stimulates asynchronous Ca(2+) waves in cerebral arterial smooth muscle cells and if their generation contributes to myogenic tone development. The endothelium was removed from rat cerebral arteries, which were then mounted in an arteriograph, pressurized (20-100 mmHg) and examined under a variety of experimental conditions. Diameter and membrane potential (V(M)) were monitored using conventional techniques; Ca(2+) wave generation and myosin light chain (MLC(20))/MYPT1 (myosin phosphatase targeting subunit) phosphorylation were assessed by confocal microscopy and Western blot analysis, respectively. Elevating intravascular pressure increased the proportion of smooth muscle cells firing asynchronous Ca(2+) waves as well as event frequency. Ca(2+) wave augmentation occurred primarily at lower intravascular pressures (<60 mmHg) and ryanodine, a plant alkaloid that depletes the sarcoplasmic reticulum (SR) of Ca(2+), eliminated these events. Ca(2+) wave generation was voltage insensitive as Ca(2+) channel blockade and perturbations in extracellular [K(+)] had little effect on measured parameters. Ryanodine-induced inhibition of Ca(2+) waves attenuated myogenic tone and MLC(20) phosphorylation without altering arterial V(M). Thapsigargin, an SR Ca(2+)-ATPase inhibitor also attenuated Ca(2+) waves, pressure-induced constriction and MLC(20) phosphorylation. The SR-driven component of the myogenic response was proportionally greater at lower intravascular pressures and subsequent MYPT1 phosphorylation measures revealed that SR Ca(2+) waves facilitated pressure-induced MLC(20) phosphorylation through mechanisms that include myosin light chain phosphatase inhibition. Cumulatively, our findings show that mechanical stimuli augment Ca(2+) wave generation in arterial smooth muscle and that these transient events facilitate tone development particularly at lower intravascular pressures by providing a proportion of the Ca

  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

    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.

  8. 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.

  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. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

    2016-09-01

    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.

  16. 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.

  17. 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.

  18. Pressure wave: Gun barrel interactions

    NASA Astrophysics Data System (ADS)

    Crowley, A. B.; King, W. P. C.

    1986-01-01

    The interaction of pressure waves generated during the internal ballistics cycle with the vibrations of a tank barrel, and the possible effects on accuracy, are described. The investigation is based on codes simulating the complete internal ballistics cycle, including the venting of gases after shot exit, and the longitudinal and flexural vibration modes of the barrel, both of which were developed at the Royal Military College of Science. The computative effects of pressure waves on both accuracy and structural integrity are discussed for a number of different charge and barrel configurations.

  19. Pressure-induced continuous phase transition of charge-density-wave state in a linear-chain complex

    NASA Astrophysics Data System (ADS)

    Kuroda, Noritaka; Sakai, Masamichi; Nishina, Yuichiro; Sasaki, Kazuo

    1992-05-01

    [Pt(en)2][Pt(en)2Cl2](ClO4)4 (en=ethylenediamine) is found to undergo a novel phase transition from the charge-density-wave (CDW) state to a new phase under hydrostatic pressure. The new phase appears at 3 GPa and coexists with the CDW state up to 6 GPa, at least. The volume ratio between the two coexisting phases measured by Raman scattering spectroscopy changes continuously with pressure. The result is discussed in terms of the theoretical approach to the polymorphic phase transition developed recently by Bassler, Sasaki, and Griffiths. It is suggested that kink solitons play an important role in this phase transition.

  20. 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.

  1. Role of anion ordering and effective pressure in the field-induced spin-density-wave phase of (TMTSF)2X

    NASA Astrophysics Data System (ADS)

    Minamidate, T.; Matsunaga, N.; Nomura, K.; Sasaki, T.

    2016-08-01

    Magnetoresistance and Hall resistance measurements were conducted in the field-induced spin-density-wave (FISDW) phase of (TMTSF)2ReO4 above 1.0 GPa, with an anion ordering specified by Q_\\text{AO}=(0, 1/2, 1/2) . The quantized Hall resistance shows the sequence N = 0, 1, 2, -2, 4, -4, -6, -8, \\cdots , with decreasing field that is successfully explained by the “extended standard model”. Consequently, we demonstrate that the difference between the chemical and hydrostatic pressures is linked to the appearance of the peculiar FISDW phase of the TMTSF salts with Q_\\text{AO}=(0, 1/2, *) .

  2. Supratentorial pressures. Part II: Intracerebral pulse waves.

    PubMed

    Miller, J D; Peeler, D F; Pattisapu, J; Parent, A D

    1987-09-01

    Intracerebral pulse waves were recorded in cat and monkey while intracranial pressure (ICP) manipulations were performed. The intracerebral pulse waves appeared comparable to cerebrospinal fluid (CSF) pulsations. The wave forms were divided into multiple smaller waves, designated P1 to P4. The P1 component was primarily of arterial origin and was accentuated by increasing ICP unrelated to increased venous pressure, most commonly from a mass lesion. Bilateral carotid occlusion resulted in decreased amplitude of P1. Venous hypertension from jugular venous or sagittal sinus occlusion, on the other hand, accentuated waves P2 and P3 more than P1. This is consistent with a Starling resistor model of the cerebral venous system in which mass lesions may compress low-pressure veins and accentuate the arterial pressure-dependent P1 wave, whereas venous hypertension causes increased prominence of the later P2 and P3 waves. PMID:2891069

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

    PubMed Central

    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.; Wayne Chen, S.R.

    2016-01-01

    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 Ca2+ 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 Ca2+ release and VT. Like racemic carvedilol, R-carvedilol directly reduces the open duration of the cardiac ryanodine receptor (RyR2), suppresses spontaneous Ca2+ oscillations in human embryonic kidney (HEK) 293 cells, Ca2+ 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 Ca2+-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

  4. 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.

  5. 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

  6. 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.

  7. 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)

  8. 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.

  9. 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.

  10. Pressure waves in a supersaturated bubbly magma

    USGS Publications Warehouse

    Kurzon, I.; Lyakhovsky, V.; Navon, O.; Chouet, B.

    2011-01-01

    We study the interaction of acoustic pressure waves with an expanding bubbly magma. The expansion of magma is the result of bubble growth during or following magma decompression and leads to two competing processes that affect pressure waves. On the one hand, growth in vesicularity leads to increased damping and decreased wave amplitudes, and on the other hand, a decrease in the effective bulk modulus of the bubbly mixture reduces wave velocity, which in turn, reduces damping and may lead to wave amplification. The additional acoustic energy originates from the chemical energy released during bubble growth. We examine this phenomenon analytically to identify conditions under which amplification of pressure waves is possible. These conditions are further examined numerically to shed light on the frequency and phase dependencies in relation to the interaction of waves and growing bubbles. Amplification is possible at low frequencies and when the growth rate of bubbles reaches an optimum value for which the wave velocity decreases sufficiently to overcome the increased damping of the vesicular material. We examine two amplification phase-dependent effects: (1) a tensile-phase effect in which the inserted wave adds to the process of bubble growth, utilizing the energy associated with the gas overpressure in the bubble and therefore converting a large proportion of this energy into additional acoustic energy, and (2) a compressive-phase effect in which the pressure wave works against the growing bubbles and a large amount of its acoustic energy is dissipated during the first cycle, but later enough energy is gained to amplify the second cycle. These two effects provide additional new possible mechanisms for the amplification phase seen in Long-Period (LP) and Very-Long-Period (VLP) seismic signals originating in magma-filled cracks.

  11. Transient flows and pressure waves in pipes

    SciTech Connect

    Wang, X.Q.; Sun, J.G.; Sha, W.T.

    1994-06-01

    Transient laminar flows and pressure-wave propagations in pipes connected with components, commonly known as water hammer, are analyzed. The system studied consists of a constant-pressure vessel, a uniform circular pipe, a valve between them, and a receiver vessel. A pressure-wave equation and a linearized velocity equation are derived from the equations of mass and momentum conservation. Waveform distortion due to viscous dissipation and pipe-wall elastic expansion is characterized by a dimensionless transmission number, K. The coefficients of the damping of the pressure waves were found to be related to the roots of the Bessel function J{sub 0}. An exact solution of the pressure-wave equation was obtained numerically. The relationship between the distortion of a traveling wave and the transmission number K was studied. The problem is also calculated with a general-purpose computer code, COMMIX, which solves the exact mass conservation equation and Navier-Stokes equations. The COMMIX calculational results agreed well with the analytical solutions.

  12. 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.

  13. 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.

  14. Reduction of hydraulic line oscillating pressures induced by pump cavitation

    NASA Astrophysics Data System (ADS)

    Druhak, G.; Marino, P.; Bernstein, M.

    1982-05-01

    A Helmholtz resonator cavitation attenuator to reduce oscillating pressure and resulting vibration induced stresses was developed. Its development, the magnitude of reduction it effected in hydraulic line and bracket stresses, and the analytic procedure to calculate the standing pressure wave induced stresses in hydraulic lines are described.

  15. Reflections of pressure waves at tunnel portals

    NASA Astrophysics Data System (ADS)

    Brown, J. M. B.; Vardy, A. E.

    1994-05-01

    Reflections of plane waves from the open ends (portals) of axisymmetric pipes and plane two-dimensional (2-D) channels are investigated analytically, numerically, and experimentally. An analytical approach developed by Rudinger for pressure decay at an axisymmetric, flanged portal is extended to longer times, and equivalent analyses are developed for reflections from unflanged portals - both axisymmetric and plane 2-D. Predictions for the latter case are compared with numerical results from a computer program based on a 2-D method of bicharacteristics. The theoretical results are compared with measurements from a low pressure shock tube, which was used to investigate alternative end configurations including scarfed portals with and without flange plates. These confirm that the rate of pressure decay is much slower in the plane 2-D case and that flange plates further reduce the rate of decay, albeit slightly. Scarfed portals are shown to cause more uniform decay rates than 90 deg portals.

  16. 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.

  17. Laser-induced shock waves effects in materials

    SciTech Connect

    Dingus, R.S.; Shafer, B.P.

    1990-01-01

    A review of the effects of pressure pulses on materials is presented with an orientation toward laser-induced shock wave effects in biological tissue. The behavior is first discussed for small amplitudes, namely sound waves, since many important features in this region are also applicable at large amplitudes. The generation of pressure pulses by lasers is discussed along with amplitudes. The origin and characteristic properties of shock waves are discussed along with the different types of effects they can produce. The hydrodynamic code techniques required for shock wave calculations are discussed along with the necessary empirical data base and methods for generating that data base. 7 refs., 15 figs.

  18. Effect of tube ovalling on pressure wave propagation speed.

    PubMed

    Anderson, A; Johnson, G R

    1990-01-01

    For physiological and other flows it is often assumed that the pressure pulse wave speed is given by the classic Moens-Korteweg expression and this may be used, for example, to assist in the determination of in vivo blood vessel wall incremental Young's modulus. A number of physical factors affecting the value of this wave speed have been reviewed in the literature, but the effect of slight ovalling of the tube cross-section is rarely mentioned. The analysis for a tube of elliptic cross-section shows that even a very small degree of ovalling can cause quite substantial reductions in Young mode wave propagation velocities compared with the classic Moens-Korteweg expression. Bending-induced changes in cross-section shape with internal pressure increase the apparent elasticity of the tube wall. Experimental confirmation is provided by waterhammer wave speed measurements in a copper tube that has been ovalled by coiling. Even though the Young mode is not dominant in this case, as it would be for a physiological case, the measured wave speed is quite clearly less than the Moens-Korteweg theory and it can be shown that the small degree of measured tube ovality explains this.

  19. Measurement of blast wave by a miniature fiber optic pressure transducer in the rat brain.

    PubMed

    Chavko, Mikulas; Koller, Wayne A; Prusaczyk, W Keith; McCarron, Richard M

    2007-01-30

    Exposure to blast wave that is generated during an explosion may result in brain damage and related neurological impairments. The aim of this study was to investigate pressure changes induced by exposure to blast inside the rat brain. For intracranial pressure measurement we used a miniature optic fiber sensor (o.d. 550 microm) with a computer recording system. The sensor was placed in the third cerebral ventricle of anesthetized rats exposed to 40 kPa blast wave in a pneumatic-pressure driven shock tube. Short pressure waves lasting several ms were detected inside the brain with the magnitude that might result in nervous tissue damage. PMID:16949675

  20. Dynamical coupling of wind and ocean waves through wave-induced air flow.

    PubMed

    Hristov, T S; Miller, S D; Friehe, C A

    2003-03-01

    Understanding the physical mechanisms behind the generation of ocean waves by wind has been a longstanding challenge. Previous studies have assumed that ocean waves induce fluctuations in velocity and pressure of the overlying air that are synchronized with the waves, and numerical models have supported this assumption. In a complex feedback, these fluctuations provide the energy for wave generation. The spatial and temporal structure of the wave-induced airflow therefore holds the key to the physics of wind-wave coupling, but detailed observations have proved difficult. Here we present an analysis of wind velocities and ocean surface elevations observed over the open ocean. We use a linear filter to identify the wave-induced air flow from the measurements and find that its structure is in agreement with 'critical-layer' theory. Considering that the wave-induced momentum flux is then controlled by the wave spectrum and that it varies considerably in vertical direction, a simple parameterization of the total air-sea momentum flux is unlikely to exist.

  1. 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.

  2. On the pressure field of nonlinear standing water waves

    NASA Technical Reports Server (NTRS)

    Schwartz, L. W.

    1980-01-01

    The pressure field produced by two dimensional nonlinear time and space periodic standing waves was calculated as a series expansion in the wave height. The high order series was summed by the use of Pade approximants. Calculations included the pressure variation at great depth, which was considered to be a likely cause of microseismic activity, and the pressure distribution on a vertical barrier or breakwater.

  3. 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.

  4. The impact of wave loads and pore-water pressure generation on initiation of sediment transport

    USGS Publications Warehouse

    Clukey, E.C.; Kulhawy, F.H.; Liu, P.L.-F.; Tate, G.B.

    1985-01-01

    The build-up of pore-water pressure by waves can lead to sediment liquefaction and subsequent transport by traction currents. This process was investigated by measuring pore-water pressures both in a field experiment and laboratory wave tank tests. Liquefaction was observed in the wave tank tests. The results suggest that sand is less susceptible than silts to wave-induced liquefaction because of the tendency to partially dissipate pore-water pressures. However, previous studies have determined that pore-water pressures must approach liquefaction before current velocities necessary to initiate transport are reduced. Once liquefaction has occurred more sediment can be transported. ?? 1985 Springer-Verlag New York Inc.

  5. Plateau Waves of Intracranial Pressure and Multimodal Brain Monitoring.

    PubMed

    Dias, Celeste; Maia, Isabel; Cerejo, Antonio; Smielewski, Peter; Paiva, José-Artur; Czosnyka, Marek

    2016-01-01

    The aim of this study was to describe multimodal brain monitoring characteristics during plateau waves of intracranial pressure (ICP) in patients with head injury, using ICM+ software for continuous recording. Plateau waves consist of an abrupt elevation of ICP above 40 mmHg for 5-20 min. This is a prospective observational study of patients with head injury who were admitted to a neurocritical care unit and who developed plateau waves. We analyzed 59 plateau waves that occurred in 8 of 18 patients (44 %). At the top of plateau waves arterial blood pressure remained almost constant, but cerebral perfusion pressure, cerebral blood flow, brain tissue oxygenation, and cerebral oximetry decreased. After plateau waves, patients with a previously better autoregulation status developed hyperemia, demonstrated by an increase in cerebral blood flow and brain oxygenation. Pressure and oxygen cerebrovascular reactivity indexes (pressure reactivity index and ORxshort) increased significantly during the plateau wave as a sign of disruption of autoregulation. Bedside multimodal brain monitoring is important to characterize increases in ICP and give differential diagnoses of plateau waves, as management of this phenomenon differs from that of regular ICP.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. Nonlinear Pressure Wave Analysis by Concentrated Mass Model

    NASA Astrophysics Data System (ADS)

    Ishikawa, Satoshi; Kondou, Takahiro; Matsuzaki, Kenichiro

    A pressure wave propagating in a tube often changes to a shock wave because of the nonlinear effect of fluid. Analyzing this phenomenon by the finite difference method requires high computational cost. To lessen the computational cost, a concentrated mass model is proposed. This model consists of masses, connecting nonlinear springs, connecting dampers, and base support dampers. The characteristic of a connecting nonlinear spring is derived from the adiabatic change of fluid, and the equivalent mass and equivalent damping coefficient of the base support damper are derived from the equation of motion of fluid in a cylindrical tube. Pressure waves generated in a hydraulic oil tube, a sound tube and a plane-wave tube are analyzed numerically by the proposed model to confirm the validity of the model. All numerical computational results agree very well with the experimental results carried out by Okamura, Saenger and Kamakura. Especially, the numerical analysis reproduces the phenomena that a pressure wave with large amplitude propagating in a sound tube or in a plane tube changes to a shock wave. Therefore, it is concluded that the proposed model is valid for the numerical analysis of nonlinear pressure wave problem.

  11. Standing wave pressure fields generated in an acoustic levitation chamber

    NASA Astrophysics Data System (ADS)

    Hancock, Andrew; Allen, John S.; Kruse, Dustin E.; Dayton, Paul A.; Kargel, Christian M.; Insana, Michael F.

    2001-05-01

    We are developing an acoustic levitation chamber for measuring adhesion force strengths among biological cells. Our research has four phases. Phase I, presented here, is concerned with the design and construction of a chamber for trapping cell-sized microbubbles with known properties in acoustic standing waves, and examines the theory that describes the standing wave field. A cylindrical chamber has been developed to generate a stable acoustic standing wave field. The pressure field was mapped using a 0.4-mm needle hydrophone, and experiments were performed using 100 micron diameter unencapsulated air bubbles, 9 micron diameter isobutane-filled microbubbles, and 3 micron diameter decafluorobutane (C4F10)-filled microbubbles, confirming that the net radiation force from the standing wave pressure field tends to band the microbubbles at pressure antinodes, in accordance with theory.

  12. Radiation-pressure-induced nonlinearity in microdroplets.

    PubMed

    Zhang, Peng; Jung, Sunghwan; Lee, Aram; Xu, Yong

    2015-12-01

    High quality (Q) factor whispering gallery modes (WGMs) can induce nonlinear effects in liquid droplets through mechanisms such as radiation pressure, Kerr nonlinearity, and thermal effects. However, such nonlinear effects, especially those due to radiation pressure, have yet to be thoroughly investigated and compared in the literature. In this study, we present an analytical approach that can exactly calculate the droplet deformation induced by the radiation pressure. The accuracy of the analytical approach is confirmed through numerical analyses based on the boundary element method. We show that the nonlinear optofluidic effect induced by the radiation pressure is stronger than the Kerr effect and the thermal effect under a large variety of realistic conditions. Using liquids with ultralow and experimentally attainable interfacial tension, we further confirm the prediction that it may only take a few photons to produce measurable WGM resonance shift through radiation-pressure-induced droplet deformation. PMID:26764829

  13. Measurement of Strength at High Pressures Using Oblique Shock Waves

    NASA Astrophysics Data System (ADS)

    Stolyar, Victoria; Ravichandran, Guruswami; Alexander, Scott

    2013-06-01

    At high pressures and high strain rates, the measurement of strength is important to many implications including planetary impact and inertial confinement fusion. Understanding how strength depends on pressure allows for the characterization of materials and validation of constitutive models. Slotted barrel guns have traditionally been used in experiments, such as the pressure-shear plate impact technique, to generate longitudinal and shear waves through an oblique impact. A new methodology for measuring material strength using normal impact (1-2 km/s) is described. In this configuration, a composite target is designed with an angled material of interest embedded into a driver material. This driver material is used to generate an oblique shock wave that is followed by a shear wave, due to the angled nature of the target material. Using shock polar analysis, the rear surface of the target is designed to be parallel to the transmitted shock wave in order to mitigate wave interactions at the rear surface. A window is used on the rear surface of the target to measure the in-situ particle velocities at the target-window interface. Using three VISAR measurements, the tangential and longitudinal particle velocities at the rear surface of the target are found from which the shear stress (strength) is inferred as a function of pressure. Results are presented for 6061-T6 Aluminum as well as Tantalum. Hydrocode simulations are used to predict the experimental results as well as characterize the wave interactions in the oblique wedge experiments.

  14. Calculated mean arterial pressure in the posterior tibial and radial artery pressure wave in newborn infants.

    PubMed

    Gevers, M; Hack, M W; van Genderingen, H R; Lafeber, H N; Westerhof, N

    1995-01-01

    Mean arterial pressure (MAP) is the area under the pressure wave averaged over the cardiac cycle, and therefore depends on pressure wave contour. A generally used rule of thumb to estimate MAP of peripheral arteries in adults is adding one-third of the arterial pulse pressure (PP) to diastolic arterial pressure (DAP). As peripheral pressure wave forms in neonates do not resemble adult peripheral wave forms, it may be expected that this rule of thumb does not hold for neonates. Previously, we found that MAP can be calculated by adding 50% PP to DAP in radial artery waves in neonates. In the present study, we investigated in neonates how MAP in the posterior tibial artery depends on systolic and diastolic pressure and we compared these findings to those found in the radial artery. Forty infants admitted for intensive care were studied. We analyzed 5000 invasively and accurately obtained blood pressure waves in the posterior tibial artery of 20 neonates and another 5000 waves similarly obtained from the radial artery in another group of 20 neonates. We found that MAP in posterior tibial artery waves is well approximated by adding 41.5 +/- 2.0% of PP to DAP, whereas MAP in radial artery waves can be calculated by adding 46.7 +/- 1.7% of PP to DAP. These values are significantly different (p < 0.0001). In conclusion, the rule of thumb as used in the adult to find MAP, where 33% PP is added to DAP, does not hold for the newborn. We recommend to calculate MAP in the tibial artery by adding 40% of PP to DAP and in the radial artery by adding 50% of PP to DAP.

  15. 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.

  16. Reduction of Orifice-Induced Pressure Errors

    NASA Technical Reports Server (NTRS)

    Plentovich, Elizabeth B.; Gloss, Blair B.; Eves, John W.; Stack, John P.

    1987-01-01

    Use of porous-plug orifice reduces or eliminates errors, induced by orifice itself, in measuring static pressure on airfoil surface in wind-tunnel experiments. Piece of sintered metal press-fitted into static-pressure orifice so it matches surface contour of model. Porous material reduces orifice-induced pressure error associated with conventional orifice of same or smaller diameter. Also reduces or eliminates additional errors in pressure measurement caused by orifice imperfections. Provides more accurate measurements in regions with very thin boundary layers.

  17. Pressure induced crystallization in amorphous silicon

    NASA Astrophysics Data System (ADS)

    Pandey, K. K.; Garg, Nandini; Shanavas, K. V.; Sharma, Surinder M.; Sikka, S. K.

    2011-06-01

    We have investigated the high pressure behavior of amorphous silicon (a-Si) using x-ray diffraction and Raman scattering techniques. Our experiments show that a-Si undergoes a polyamorphous transition from the low density amorphous to the high density amorphous phase, followed by pressure induced crystallization to the primitive hexagonal (ph) phase. On the release path, the sequence of observed phase transitions depends on whether the pressure is reduced slowly or rapidly. Using the results of our first principles calculations, pressure induced preferential crystallization to the ph phase is explained in terms of a thermodynamic model based on phenomenological random nucleation and the growth process.

  18. 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.

  19. Microwave background anisotropy induced by gravitational waves

    NASA Technical Reports Server (NTRS)

    Linder, Eric V.

    1988-01-01

    A cosmological background of gravitational waves induces redshift perturbations in light transversing it. Calculations of this Sachs-Wolfe effect on the microwave background are presented in an Omega = 1 Friedmann universe as a function of angular scale and gravitational wave spectrum. Blurriness of the last-scattering surface can cause nonnegligible dilution of the anisotropy for wavelengths less than about 100 Mpc. The limit implied for the energy density of the gravitational waves is given. A difficulty in associating a linear scale with an angular anisotropy, due to the clumpiness of the universe, is also pointed out.

  20. Ultrasonic wave based pressure measurement in small diameter pipeline.

    PubMed

    Wang, Dan; Song, Zhengxiang; Wu, Yuan; Jiang, Yuan

    2015-12-01

    An effective non-intrusive method of ultrasound-based technique that allows monitoring liquid pressure in small diameter pipeline (less than 10mm) is presented in this paper. Ultrasonic wave could penetrate medium, through the acquisition of representative information from the echoes, properties of medium can be reflected. This pressure measurement is difficult due to that echoes' information is not easy to obtain in small diameter pipeline. The proposed method is a study on pipeline with Kneser liquid and is based on the principle that the transmission speed of ultrasonic wave in pipeline liquid correlates with liquid pressure and transmission speed of ultrasonic wave in pipeline liquid is reflected through ultrasonic propagation time providing that acoustic distance is fixed. Therefore, variation of ultrasonic propagation time can reflect variation of pressure in pipeline. Ultrasonic propagation time is obtained by electric processing approach and is accurately measured to nanosecond through high resolution time measurement module. We used ultrasonic propagation time difference to reflect actual pressure in this paper to reduce the environmental influences. The corresponding pressure values are finally obtained by acquiring the relationship between variation of ultrasonic propagation time difference and pressure with the use of neural network analysis method, the results show that this method is accurate and can be used in practice.

  1. 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.

  2. 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.

  3. 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.

  4. Numerical study on pressure wave propagation in a mercury loop

    SciTech Connect

    Kogawa, Hiroyuki; Hasegawa, Shoichi; Futakawa, Masatoshi; Riemer, Bernie; Wendel, Mark W; Haines, John R

    2008-01-01

    On-beam tests were carried out at the Los Alamos Neutron Science Center Weapons Neutron Research (LANSCE WNR) facility in June 2005 to investigate pressure wave mitigation in mercury targets for the MW-class spallation neutron sources under international collaboration between US Spallation Neutron Source (SNS) and Japanese Spallation Neutron Source (JSNS). A mercury loop was used for the target, a so-called In-Beam Bubbling Test Loop (IBBTL). The loop consists of the rectangular pipe of 25 mm x 50 mm^2 in cross section, 1.5 mm in wall thickness and 2 m in total length approximately. The SNS team set 8 strain sensors on the pipe wall to measure the strain propagation caused by the pressure wave. The maximum strain appeared at 350 mm apart from the proton-bombarded point at 5.5 ms after the proton bombardment. It is known that the propagation velocity of the pressure wave in mercury is ca. 1500 m/s and that of the stress wave in stainless steel is ca. 5000 m/s. However, the apparent wave propagation velocity in the IBBTL was lower than those velocities and was observed to be 65 m/s. Numerical analysis was carried out to understand the strain propagation in the pipe wall of the IBBTL. Numerical results showed that the maximum strain at 350 mm apart from the beam spot appeared at 5.5 ms after proton bombardment in good agreement with experimental results.

  5. 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.

  6. 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.

  7. Internal wave-turbulence pressure above sloping sea bottoms

    NASA Astrophysics Data System (ADS)

    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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. Pressure measurements of a three wave journal air bearing

    NASA Technical Reports Server (NTRS)

    Dimofte, Florin; Addy, Harold E., Jr.

    1994-01-01

    In order to validate theoretical predictions of a wave journal bearing concept, a bench test rig was assembled at NASA Lewis Research Center to measure the steady-state performance of a journal air bearing. The tester can run up to 30,000 RPM and the spindle has a run out of less than 1 micron. A three wave journal bearing (50 mm diameter and 58 mm length) has been machined at NASA Lewis. The pressures at 16 ports along the bearing circumference at the middle of the bearing length were measured and compared to the theoretical prediction. The bearing ran at speeds up to 15,000 RPM and certain loads. Good agreement was found between the measured and calculated pressures.

  13. 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.

  14. 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.

  15. Intracranial pressure increases during exposure to a shock wave.

    PubMed

    Leonardi, Alessandra Dal Cengio; Bir, Cynthia A; Ritzel, Dave V; VandeVord, Pamela J

    2011-01-01

    Traumatic brain injuries (TBI) caused by improvised explosive devices (IEDs) affect a significant percentage of surviving soldiers wounded in Iraq and Afghanistan. The extent of a blast TBI, especially initially, is difficult to diagnose, as internal injuries are frequently unrecognized and therefore underestimated, yet problems develop over time. Therefore it is paramount to resolve the physical mechanisms by which critical stresses are inflicted on brain tissue from blast wave encounters with the head. This study recorded direct pressure within the brains of male Sprague-Dawley rats during exposure to blast. The goal was to understand pressure wave dynamics through the brain. In addition, we optimized in vivo methods to ensure accurate measurement of intracranial pressure (ICP). Our results demonstrate that proper sealing techniques lead to a significant increase in ICP values, compared to the outside overpressure generated by the blast. Further, the values seem to have a direct relation to a rat's size and age: heavier, older rats had the highest ICP readings. These findings suggest that a global flexure of the skull by the transient shockwave is an important mechanism of pressure transmission inside the brain.

  16. Intracranial pressure increases during exposure to a shock wave.

    PubMed

    Leonardi, Alessandra Dal Cengio; Bir, Cynthia A; Ritzel, Dave V; VandeVord, Pamela J

    2011-01-01

    Traumatic brain injuries (TBI) caused by improvised explosive devices (IEDs) affect a significant percentage of surviving soldiers wounded in Iraq and Afghanistan. The extent of a blast TBI, especially initially, is difficult to diagnose, as internal injuries are frequently unrecognized and therefore underestimated, yet problems develop over time. Therefore it is paramount to resolve the physical mechanisms by which critical stresses are inflicted on brain tissue from blast wave encounters with the head. This study recorded direct pressure within the brains of male Sprague-Dawley rats during exposure to blast. The goal was to understand pressure wave dynamics through the brain. In addition, we optimized in vivo methods to ensure accurate measurement of intracranial pressure (ICP). Our results demonstrate that proper sealing techniques lead to a significant increase in ICP values, compared to the outside overpressure generated by the blast. Further, the values seem to have a direct relation to a rat's size and age: heavier, older rats had the highest ICP readings. These findings suggest that a global flexure of the skull by the transient shockwave is an important mechanism of pressure transmission inside the brain. PMID:21091267

  17. On Pressure Wave Simulations in Liquid Metal Neutron Source Targets

    NASA Astrophysics Data System (ADS)

    Fetzer, Jana R.; Class, Andreas

    2014-11-01

    Sound waves generated by fluid flow at low Mach numbers is associated with separated scales and thus with difficulties to construct efficient numerical methods for their approximation. One method is the Multi Pressure Variables (MPV) approach introduced for aero-acoustic applications. The MPV approach is based on a single time scale multiple space scale asymptotic analysis derived for subsonic flow by an asymptotic series expansion in the Mach-number. Distinguished are the flow and acoustic length scales resulting in three pressure contribution, i.e. thermodynamic, acoustic and dynamic pressure which are discretized on numerical meshes of different resolution. We propose to apply MPV to analyse liquid metal cooled spallation targets with a pulsed proton beams. These targets are operating in high power neutron sources for fundamental research. The nearly instantaneous heating of the liquid metal results in volumetric expansion of inertia confined liquid and thus to high pressure waves, which represent a major lifetime limiting thread. Our development accompanies design activities for the META:LIC (MEgawatt TArget: Lead bIsmuth Cooled) target proposed for the European Spallation Source.

  18. 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.

  19. 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.

  20. 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.

  1. Exercise central (aortic) blood pressure is predominantly driven by forward traveling waves, not wave reflection.

    PubMed

    Schultz, Martin G; Davies, Justin E; Roberts-Thomson, Phillip; Black, J Andrew; Hughes, Alun D; Sharman, James E

    2013-07-01

    Exercise hypertension independently predicts cardiovascular mortality, although little is known about exercise central hemodynamics. This study aimed to determine the contribution of arterial wave travel and aortic reservoir characteristics to central blood pressure (BP) during exercise. We hypothesized that exercise central BP would be principally related to forward wave travel and aortic reservoir function. After routine diagnostic coronary angiography, invasive pressure and flow velocity were recorded in the ascending aorta via sensor-tipped intra-arterial wires in 10 participants (age, 55±10 years; 70% men) free of coronary artery disease with normal left ventricular function. Measures were recorded at baseline and during supine cycle ergometry. Using wave intensity analysis, dominant wave types throughout the cardiac cycle were identified (forward and backward, compression, and decompression), and aortic reservoir and excess pressure were calculated. Central systolic BP increased significantly with exercise (Δ=19±12 mm Hg; P<0.001). This was associated with increases in systolic forward compression waves (Δ=12×10(6)±17×10(6) W·m(-2)·s(-1); P=0.045) and forward decompression waves in late systole (Δ=9×10(6)±6×10(6) W·m(-2)·s(-1); P<0.001). Despite significant augmentation in BP (Δ=9±6 mm Hg; P=0.002), reflected waves did not increase in magnitude (Δ=-1×10(6)±3×10(6) W·m(-2)·s(-1); P=0.2). Excess pressure rose significantly with exercise (Δ=16±9 mm Hg; P<0.001), and reservoir pressure integral fell (Δ=-5×10(5)±5×10(5) Pa·s; P=0.010). Change in reflection coefficient negatively correlated with change in central systolic BP (r=-0.68; P=0.03). We conclude that elevation of exercise central BP is principally because of increases in aortic forward traveling waves generated by left ventricular ejection. These findings have relevance to understanding central BP waveform morphology and pathophysiology of exercise hypertension.

  2. Narrowed Aortoseptal Angle Is Related to Increased Central Blood Pressure and Aortic Pressure Wave Reflection.

    PubMed

    Olafiranye, Oladipupo; Ibrahim, Mediha; Kamran, Haroon; Venner-Jones, Kinda; McFarlane, Samy I; Salciccioli, Louis; Lazar, Jason M

    2012-08-01

    The left ventricular (LV) aortoseptal angle (ASA) decreases with age, and is associated with basal septal hypertrophy (septal bulge). Enhanced arterial pressure wave reflection is known to impact LV hypertrophy. We assessed whether ASA is related to central blood pressure (BP) and augmentation index (AI), a measure of the reflected pressure wave. We studied 75 subjects (age 62 ± 16 years; 66% female) who were referred for transthoracic echocardiography and had radial artery applanation tonometry within 24 h. Peripheral systolic BP (P-SBP), peripheral diastolic BP (P-DBP), and peripheral pulse pressure (P-PP) were obtained by sphygmomanometry. Central BPs (C-SBP, C-DBP, C-PP) and AI were derived from applanation tonometry. AI was corrected for heart rate (AI75). The basal septal wall thickness (SWT), mid SWT and ASA were measured using the parasternal long axis echocardiographic view. Mean ASA and AI75 were 117 ± 11° and 22 ± 11%, respectively. ASA correlated with AI75 (r = -0.31, p ≤ 0.01), C-SBP (r = -0.24, p = 0.04), C-PP (r = -0.29, p = 0.01), but only showed a trend towards significance with P-SBP (r = -0.2, p = 0.09) and P-PP (r = -0.21, p = 0.08). Interestingly, C-PP was correlated with basal SWT (r = 0.27, p = 0.02) but not with mid SWT (r = 0.19, p = 0.11). On multivariate linear regression analysis, adjusted for age, gender, weight, and mean arterial pressure, AI75 was an independent predictor of ASA (p = 0.02). Our results suggest that a narrowed ASA is related to increased pressure wave reflection and higher central BP. Further studies are needed to determine whether narrowed LV ASA is a cause or consequence of enhanced wave reflection and whether other factors are involved.

  3. 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

  4. 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.

  5. 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

  6. 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

  7. Brane-induced-gravity shock waves.

    PubMed

    Kaloper, Nemanja

    2005-05-13

    We construct exact gravitational field solutions for a relativistic particle localized on a tensional brane in brane-induced gravity. They are a generalization of gravitational shock waves in 4D de Sitter space. We provide the metrics for both the normal branch and the self-inflating branch Dvali-Gabadadze-Porrati brane worlds, and compare them to the 4D Einstein gravity solution and to the case when gravity resides only in the 5D bulk, without any brane-localized curvature terms. At short distances the wave profile looks the same as in four dimensions. The corrections appear only far from the source, where they differ from the long distance corrections in 4D de Sitter space. We also discover a new nonperturbative channel for energy emission into the bulk from the self-inflating [corrected] branch, when gravity is modified at the de Sitter radius.

  8. 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).

  9. Tunable Lattice-Induced Opacity for Matter Wave Transport

    NASA Astrophysics Data System (ADS)

    Zhang, Chen; Greene, Chris H.

    2014-03-01

    We describe the novel phenomena of lattice-induced opacity in the process of matter wave scattering from a two dimensional atomic lattice. As an analogue to the confinement-induced resonance, the two dimensional atomic lattice can be tuned to complete opacity to a normally incident low energy matter wave, by changing the s-wave scattering length between the matter wave and the atoms in the lattice. A scheme for a matter wave transistor is proposed based on the transmission-reflection properties of the matter wave through the atomic lattice. We also propose a matter wave cavity, constructed by two parallel 2D atomic lattices that are both opaque to the matter wave. In higher kinetic energy regimes of the matter wave, the two dimensional atomic lattice is shown to be a matter wave beam splitter and wave plate, with tunable peak intensity into different directions.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. In situ observations of wave-induced sea ice breakup

    NASA Astrophysics Data System (ADS)

    Kohout, A. L.; Williams, M. J. M.; Toyota, T.; Lieser, J.; Hutchings, J.

    2016-09-01

    Ocean waves can propagate hundreds of kilometers into sea ice, leaving behind a wake of broken ice floes. Three floe breakup events were observed during the second Sea Ice Physics and Ecosystem Experiment (SIPEX-2). We show that the three breakup events were likely influenced by ocean waves. We compare the observations to a wave induced floe breakup model which includes an empirical wave attenuation model, and show that the model underestimates the extent of floe breaking for long period waves.

  15. Frequency interpretation of tidal peak in intracranial pressure wave.

    PubMed

    Shahsavari, Sima; McKelvey, Tomas

    2008-01-01

    A new approach to locate different components of ICP signal for each cardiac induced ICP beat is presented. In this method an initial timing map is used to define the appropriate part of the ICP wave which should be searched for the specific component. In parallel a recently proposed method was used to decompose the ICP wave to its different frequency harmonics. This algorithm, which is based on tracking the amplitude of the harmonic components using Kalman filtering, brings both heart rate variability and cardiorespiratory interaction into account and provides good time and frequency resolution. Comparing the results of two methods for seventeen ICP records, each one hour long, it has been observed that the fundamental cardiac component has the most significant contribution in the construction of the tidal peak in ICP and therefore tracking of this harmonic could be informative of the tidal peak evolution over the time.

  16. 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.

  17. Pressure wave attenuation and dispersion in two-phase flow

    SciTech Connect

    Kovarik, F.S.; Bankoff, S.G.

    1987-01-01

    The pressure shock wave propagation behavior in three vapor-liquid systems, steam-water, ethanol-ethanol, and Freon-Freon, has been investigated over a void fraction, ..cap alpha.., range from zero to 30%. Attenuation and dispersion behavior seems relatively insensitive (no order-of-magnitude deviations) to differences in system physical properties. The attenuation coefficient of water, BETA/sub H/2/sub O/ ranged from 0.021 cm/sup -1/ at 5% void to 0.072 cm/sup -1/ at 30% void fraction. BETA/sub F113/ was as much as 40% lower than BETA/sub ETOH/ or BETA/sub H/2/sub O/ for void fractions less than 20% where the initial wave amplitude, ..delta..P/sub o/ was 2.90 bar. Larger amplitude waves (4.14 bar) demonstrated a greater rate of attenuation throughout the void fraction range, more pronounced in the lower regions: 80% greater for 5% steam-water and 120% greater for 5% Freon-113. The attenuation data from the present investigation tend to lie between one- and two-component acoustic attenuation theories and data. However, near the resonant bubble frequency, the two component results approach the one-component region. As the void fraction is decreased, the one- and two-component acoustic theories and data (small and finite amplitude, including the present experimentation) smoothly converge.

  18. Genesis of the characteristic pulmonary venous pressure waveform as described by the reservoir-wave model

    PubMed Central

    Bouwmeester, J Christopher; Belenkie, Israel; Shrive, Nigel G; Tyberg, John V

    2014-01-01

    Conventional haemodynamic analysis of pulmonary venous and left atrial (LA) pressure waveforms yields substantial forward and backward waves throughout the cardiac cycle; the reservoir wave model provides an alternative analysis with minimal waves during diastole. Pressure and flow in a single pulmonary vein (PV) and the main pulmonary artery (PA) were measured in anaesthetized dogs and the effects of hypoxia and nitric oxide, volume loading, and positive-end expiratory pressure (PEEP) were observed. The reservoir wave model was used to determine the reservoir contribution to PV pressure and flow. Subtracting reservoir pressure and flow resulted in ‘excess’ quantities which were treated as wave-related. Wave intensity analysis of excess pressure and flow quantified the contributions of waves originating upstream (from the PA) and downstream (from the LA and/or left ventricle (LV)). Major features of the characteristic PV waveform are caused by sequential LA and LV contraction and relaxation creating backward compression (i.e. pressure-increasing) waves followed by decompression (i.e. pressure-decreasing) waves. Mitral valve opening is linked to a backwards decompression wave (i.e. diastolic suction). During late systole and early diastole, forward waves originating in the PA are significant. These waves were attenuated less with volume loading and delayed with PEEP. The reservoir wave model shows that the forward and backward waves are negligible during LV diastasis and that the changes in pressure and flow can be accounted for by the discharge of upstream reservoirs. In sharp contrast, conventional analysis posits forward and backward waves such that much of the energy of the forward wave is opposed by the backward wave. PMID:25015922

  19. Genesis of the characteristic pulmonary venous pressure waveform as described by the reservoir-wave model.

    PubMed

    Bouwmeester, J Christopher; Belenkie, Israel; Shrive, Nigel G; Tyberg, John V

    2014-09-01

    Conventional haemodynamic analysis of pulmonary venous and left atrial (LA) pressure waveforms yields substantial forward and backward waves throughout the cardiac cycle; the reservoir wave model provides an alternative analysis with minimal waves during diastole. Pressure and flow in a single pulmonary vein (PV) and the main pulmonary artery (PA) were measured in anaesthetized dogs and the effects of hypoxia and nitric oxide, volume loading, and positive-end expiratory pressure (PEEP) were observed. The reservoir wave model was used to determine the reservoir contribution to PV pressure and flow. Subtracting reservoir pressure and flow resulted in 'excess' quantities which were treated as wave-related.Wave intensity analysis of excess pressure and flow quantified the contributions of waves originating upstream (from the PA) and downstream (from the LA and/or left ventricle (LV)).Major features of the characteristic PV waveform are caused by sequential LA and LV contraction and relaxation creating backward compression (i.e.pressure-increasing) waves followed by decompression (i.e. pressure-decreasing) waves. Mitral valve opening is linked to a backwards decompression wave (i.e. diastolic suction). During late systole and early diastole, forward waves originating in the PA are significant. These waves were attenuated less with volume loading and delayed with PEEP. The reservoir wave model shows that the forward and backward waves are negligible during LV diastasis and that the changes in pressure and flow can be accounted for by the discharge of upstream reservoirs. In sharp contrast, conventional analysis posits forward and backward waves such that much of the energy of the forward wave is opposed by the backward wave.

  20. 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.

  1. 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.

  2. Doping-induced Charge-Density-Wave

    NASA Astrophysics Data System (ADS)

    Nomura, Atsushi; Yamaya, Kazuhiko; Takayanagi, Shigeru; Ichimura, Koichi; Matsuura, Toru; Tanda, Satoshi; Hokkaido University Team

    Doping is a useful method for searching new characters in solids, as we can see in the discoveries of impurity semiconductors and high-temperature superconductors. If a Charge-Density-Wave (CDW) is induced in materials which do not exhibit a CDW, new CDW properties might be brought there. TaSe3 exhibits no CDW transition but a superconductivity transition at about 2 K while it has a quasi-one-dimensional chain structure as well as typical CDW conductors, NbSe3, TaS3, and NbS3. Therefore, TaSe3 is one of the suitable materials for the induction of a CDW by doping, and we tried to induce a CDW in TaSe3 by doping Cu. Cu concentration was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The high Cu concentration was consistent with the high value of residual resistance (R (4 . 5 K) / (R (280 K) - R (4 . 5 K))). Single-crystal X-ray diffraction pattern (XRD) showed an expansion of the c-axis in Cu-doped TaSe3. The temperature dependence of the resistivity showed the anomaly at 80-100 K in Cu-doped TaSe3, which was never observed in pure TaSe3. These results suggest that the Cu-doping induces a CDW. We will discuss the relation between the resistivity anomaly and superconductivity.

  3. 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.

  4. Effect of focusing conditions on laser-induced shock waves at titanium-water interface.

    PubMed

    Nath, Arpita; Khare, Alika

    2011-07-01

    The spatial and temporal evolution of laser-induced shock waves at a titanium-water interface was analyzed using a beam deflection setup. The focusing conditions of the source laser were varied, and its effect onto the dynamics of shock waves was elucidated. For a tightly focused condition, the speed of the shock wave was ~6.4 Km/s, whereas for a defocused condition the velocities reduced to <3 km/s at the vicinity of the titanium-water interface. When the laser is focused a few millimeters above the target, i.e., within the water, the emission of dual shock waves was observed toward the rear side of the focal volume. These shock waves originate from the titanium-water interface as well as from the pure water breakdown region, respectively. The shock wave pressure is estimated from the shock wave velocity using the Newton's second law across a shock wave discontinuity. The shock wave pressure for a tightly focused condition was 18 GPa, whereas under a defocused condition the pressure experienced was ≤1 GPa in the proximity of target.

  5. Effect of focusing conditions on laser-induced shock waves at titanium-water interface

    SciTech Connect

    Nath, Arpita; Khare, Alika

    2011-07-01

    The spatial and temporal evolution of laser-induced shock waves at a titanium-water interface was analyzed using a beam deflection setup. The focusing conditions of the source laser were varied, and its effect onto the dynamics of shock waves was elucidated. For a tightly focused condition, the speed of the shock wave was {approx}6.4 Km/s, whereas for a defocused condition the velocities reduced to <3 km/s at the vicinity of the titanium-water interface. When the laser is focused a few millimeters above the target, i.e., within the water, the emission of dual shock waves was observed toward the rear side of the focal volume. These shock waves originate from the titanium-water interface as well as from the pure water breakdown region, respectively. The shock wave pressure is estimated from the shock wave velocity using the Newton's second law across a shock wave discontinuity. The shock wave pressure for a tightly focused condition was 18 GPa, whereas under a defocused condition the pressure experienced was {<=}1 GPa in the proximity of target.

  6. Non-gyrotropic pressure anisotropy induced by velocity shear.

    NASA Astrophysics Data System (ADS)

    Tenerani, A.; Del Sarto, D.; Pegoraro, F.; Califano, F.

    2015-12-01

    We discuss how, in a collisionless magnetized plasma, a sheared velocity field may lead to the anisotropization of an initial Maxwellian state. By including the full pressure tensor dynamics in a fluid plasma model, we show, analytically and numerically, that a sheared velocity field makes an initial isotropic state anisotropic and non-gyrotropic [1], i.e., makes the plasma pressure tensor anisotropic also in the plane perpendicular to the magnetic field. The propagation of transverse magneto-elastic waves in the anisotropic plasma affects the process of formation of a non-gyrotropic pressure and can lead to its spatial filamentation. This plasma dynamics implies in particular that isotropic MHD equilibria cease to be equilibria in presence of a stationary sheared flow. Similarly, in the case of turbulence, where small-scale spatial inhomogeneities are naturally developed during the direct cascade, we may expect that isotropic turbulent states are not likely to exist whenever a full pressure tensor evolution is accounted for. These results may be relevant to understanding the agyrotropic pressure configurations which are well documented in solar wind measurements and possibly correlated to plasma flows (see e.g. Refs.[2,3]), and which have also been measured in Vlasov simulations of Alfvenic turbulence [4]. [1] D. Del Sarto, F. Pegoraro, F. Califano, "Pressure anisotropy and small spatial scales induced by a velocity shear", http://arxiv.org/abs/1507.04895 [2] H.F. Astudillo, E. Marsch, S. Livi, H. Rosenbauer, "TAUS measurements of non-gyrotropic distribution functions of solar wind alpha particles", AIP Conf. Proc. 328, 289 (1996). [3] A. Posner, M.W. Liemhon, T.H. Zurbuchen, "Upstream magnetospheric ion flux tube within a magnetic cloud: Wind/STICS", Geophys. Res. Lett. 30, (2003). [4] S. Servidio, F. Valentini, F. Califano, P. Veltri, "Local kinetic effects in Two-Dimensional Plasma Turbulence", Phys. Rev. Lett. 108, 045001 (2012).

  7. 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.

  8. Energetic electron response to ULF waves induced by interplanetary shocks in the outer radiation belt

    NASA Astrophysics Data System (ADS)

    Zong, Q.-G.; Zhou, X.-Z.; Wang, Y. F.; Li, X.; Song, P.; Baker, D. N.; Fritz, T. A.; Daly, P. W.; Dunlop, M.; Pedersen, A.

    2009-10-01

    Strong interplanetary shock interactions with the Earth's magnetosphere have great impacts on energetic particle dynamics in the magnetosphere. An interplanetary shock on 7 November 2004 (with the maximum solar wind dynamic pressure of ˜70 nPa) was observed by the Cluster constellation to induce significant ULF waves in the plasmasphere boundary, and energetic electrons (up to 2 MeV) were almost simultaneously accelerated when the interplanetary shock impinged upon the magnetosphere. In this paper, the relationship between the energetic electron bursts and the large shock-induced ULF waves is studied. It is shown that the energetic electrons could be accelerated and decelerated by the observed ULF wave electric fields, and the distinct wave number of the poloidal and toroidal waves at different locations also indicates the different energy ranges of electrons resonating with these waves. For comparison, a rather weak interplanetary shock on 30 August 2001 (dynamic pressure ˜2.7 nPa) is also investigated. It is found that interplanetary shocks or solar wind pressure pulses with even small dynamic pressure change can have a nonnegligible role in the radiation belt dynamics.

  9. Electron Density in Atmospheric Pressure Microwave Surface Wave Discharges

    NASA Astrophysics Data System (ADS)

    Jasinski, M.; Zakrzewski, Z.; Mizeraczyk, J.

    2008-03-01

    In this paper, we present results of the spectroscopic measurements of the electron density in a microwave surface wave sustained discharges in Ar and Ne at atmospheric pressure. The discharge in the form of a plasma column was generated inside a quartz tube cooled with a dielectric liquid. The microwave power delivered to the discharge via rectangular waveguide was applied in the range of 200-1500 W. In all investigations presented in this paper, the gas flow rate was relatively low (0.5 l/min), so the plasma column was generated in the form of a single filament, and the lengths of the upstream and downstream plasma columns were almost the same. The electron density in the plasma columns was determined using the method based on the Stark broadening of Hβ spectral line, including plasma region inside the waveguide which was not investigated earlier.

  10. Electron Density in Atmospheric Pressure Microwave Surface Wave Discharges

    SciTech Connect

    Jasinski, M.; Zakrzewski, Z.; Mizeraczyk, J.

    2008-03-19

    In this paper, we present results of the spectroscopic measurements of the electron density in a microwave surface wave sustained discharges in Ar and Ne at atmospheric pressure. The discharge in the form of a plasma column was generated inside a quartz tube cooled with a dielectric liquid. The microwave power delivered to the discharge via rectangular waveguide was applied in the range of 200-1500 W. In all investigations presented in this paper, the gas flow rate was relatively low (0.5 l/min), so the plasma column was generated in the form of a single filament, and the lengths of the upstream and downstream plasma columns were almost the same. The electron density in the plasma columns was determined using the method based on the Stark broadening of H{sub {beta}} spectral line, including plasma region inside the waveguide which was not investigated earlier.

  11. Experimental study of Richtmyer-Meshkov instability induced by cylindrical shock waves

    NASA Astrophysics Data System (ADS)

    Hosseini, S. H. R.; Takayama, K.

    2005-08-01

    The paper describes the results of holographic interferometric flow visualization of the Richtmyer-Meshkov instability induced by cylindrical shock waves propagating across cylindrical interfaces. Experiments were conducted in an annular coaxial vertical diaphragmless shock tube, which can produce converging cylindrical shock waves with minimum disturbances. The shock wave converged and interacted with a cylindrical soap bubble filled with He, Ne, air, Ar, Kr, Xe, or SF6. The soap bubble was placed coaxially in the test section. The effects of density variation on the Richtmyer-Meshkov instability for a wide range of Atwood numbers were determined. Pressure histories at different radii during the shock wave implosion and reflection from the center were measured. Double-exposure holographic interferometry was used and the motion of the converging shock wave and its interaction with the gaseous interface were visualized. The variation of the pressure at the center with interface Atwood number for constant incident shock Mach number was studied. It is found that the dominant mechanism limiting the maximum pressure at the center of convergence is related to the instability of the converging shock wave induced by its interaction with the interface. A short time after the impulsive acceleration, the interface started deforming, and the growth of these perturbations is described. The results show that after diverging shock wave interaction, the reshocked cylindrical interfaces have a higher growth rate of the turbulent mixing zone than that of the reshocked interface in a plane geometry reported by previous works.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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

  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. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Stochastic sensitivity analysis for timing and amplitude of pressure waves in the arterial system.

    PubMed

    Eck, V G; Feinberg, J; Langtangen, H P; Hellevik, L R

    2015-04-01

    In the field of computational hemodynamics, sensitivity quantification of pressure and flow wave dynamics has received little attention. This work presents a novel study of the sensitivity of pressure-wave timing and amplitude in the arterial system with respect to arterial stiffness. Arterial pressure and flow waves were simulated with a one-dimensional distributed wave propagation model for compliant arterial networks. Sensitivity analysis of this model was based on a generalized polynomial chaos expansion evaluated by a stochastic collocation method. First-order statistical sensitivity indices were formulated to assess the effect of arterial stiffening on timing and amplitude of the pressure wave and backward-propagating pressure wave in the ascending aorta, at the maximum pressure and inflection point in the systolic phase. Only the stiffness of aortic arteries was found to significantly influence timing and amplitude of the backward-propagating pressure wave, whereas other large arteries in the systemic tree showed marginal impact. Furthermore, the ascending aorta, aortic arch, thoracic aorta, and infrarenal abdominal aorta had the largest influence on amplitude, whereas only the thoracic aorta influenced timing. Our results showed that the non-intrusive polynomial chaos expansion is an efficient method to compute statistical sensitivity measures for wave propagation models. These sensitivities provide new knowledge in the relative importance of arterial stiffness at various locations in the arterial network. Moreover, they will significantly influence clinical data collection and effective composition of the arterial tree for in-silico clinical studies.

  7. 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.

  8. Shock induced porous barrier flows, with underlying wall pressure amplification

    NASA Astrophysics Data System (ADS)

    Skews, B. W.; Bugarin, S.

    The flow field resulting from the impact of a shock wave on a variety of sheets of permeable material is studied. Earlier studies examined the flow through stationary sheets. It has, however, been found that if the sheet is placed a short distance in front of a surface, and can move under the shock loading, the pressure on the surface is amplified following shock impact, compared to the pressures that would be experienced with no covering. An important application to consider is the effect that textile clothing may have on a persons body when exposed to a blast environment. Single and multiple layers of a range of textiles have been tested. It was established that the heavier, more impermeable textiles such as Kevlar can amplify the shock wave pressure by as much as 400%. Experiments were also done with the textiles placed at an angle to the incoming shock wave and the mechanism for the amplification established through schlieren photography and pressure measurements.

  9. On tidal variability induced by nonlinear interaction with planetary waves

    SciTech Connect

    Teitelbaum, H.; Vial, F. )

    1991-08-01

    Short-time variability of the atmospheric tides is frequently observed in the meteor region but is not yet fully explained in terms of production mechanisms. This is probably due to the existence of several such mechanisms acting together or separately. In this paper the authors show that many observations can be explained by nonlinear interactions between tides and planetary waves having periods corresponding to those of the observed tidal amplitude modulations. These nonlinear interactions generate two secondary waves whose frequencies are the sum and difference of frequencies of the primary waves. These two waves beat with the tide, modulating its amplitude with the planetary wave period. A numerical model is used to demonstrate that with primary waves of reasonable amplitudes the nonlinear interactions can be quite large. This is because the importance of nonlinearity depends essentially on the amplitude of the induced fluid velocity in the direction of wave propagation compared to the wave propagation velocity. When two waves propagate simultaneously, the fluid velocity can have a large component in the direction of propagation of one of the waves, and advective (nonlinear) terms can be large. This point is further illustrated in the case of two gravity waves interacting together. Finally, some observational campaigns carried out above Garchy (45{degree}N) are analyzed using a nonparametric method. The results indicate that nonlinear interactions between tides and planetary waves really take place in the upper mesosphere and lower thermosphere.

  10. 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

  11. Topography and measurement of pyloric pressure waves and tone in humans.

    PubMed

    Heddle, R; Dent, J; Toouli, J; Read, N W

    1988-10-01

    The topography of human pyloric pressure is ill defined, and previous studies of pyloric motility in humans have given conflicting results. A detailed profile of pyloric pressure has been recorded in seven healthy volunteers using a manometric assembly with 13 side holes spaced at 3-mm intervals on reverse aspect of a 3.5-cm long sleeve sensor. After a fasting control period of 40 min, recordings were made for 40 min during intraduodenal infusion of a lipid emulsion. Two major patterns of pressure waves were seen during the fasting control period, namely pressure waves confined to a narrow pyloric zone (isolated pyloric pressure waves) and pressure waves that were less localized and involved the antrum and/or duodenum. During lipid infusion the motility pattern was dominated by isolated pyloric pressure waves and localized pyloric tone. Ninety-two percent of the isolated pyloric pressure waves recorded by the sleeve were recorded by only one or two side holes, consistent with a phasically active zone less than 9 mm in length. Pyloric tone was confined to an even narrower zone and was most often recorded by only one side hole. When both tone and isolated pyloric pressure waves occurred together, they were recorded by the same side holes. By comparison with the side holes, the sleeve recorded 89% of isolated pyloric pressure waves and 98% of nonlocalized waves and recorded pyloric tone with a moderate sensitivity but high specificity. The technical challenge of recording localized pyloric contraction is considerable, and much of the conflict between previous studies of the human pylorus is explicable on methodological grounds.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. 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

  13. 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

  14. 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

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

    PubMed Central

    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

  16. 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

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

    PubMed

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

    2016-08-05

    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.

  18. High speed interference heating loads and pressure distributions resulting from elevon deflections. [shock wave interaction effects on hypersonic aircraft surfaces

    NASA Technical Reports Server (NTRS)

    Johnson, C. B.; Kaufman, L. G., III

    1979-01-01

    Effects of elevon-induced three-dimensional shock-wave turbulent boundary-layer interactions on hypersonic aircraft surfaces are analyzed. Detailed surface pressure and heating rate distributions obtained on wing-elevon-fuselage models representative of aft portions of hypersonic aircraft are compared with analytical and experimental results from other sources. Examples are presented that may be used to evaluate the adequacy of current theoretical methods for estimating the effects of three-dimensional shock-wave turbulent boundary-layer interactions on hypersonic aircraft surfaces.

  19. Seismically induced pressure transients at geothermal reservoirs in the eastern Marmara region

    NASA Astrophysics Data System (ADS)

    Woith, Heiko; Wang, Rongjiang; Caka, Deniz; Irmak, T. Serkan; Tunc, Berna; Luehr, Birger-G.; Baris, Serif

    2014-05-01

    The potential role of fluids in processes related to the triggering of earthquakes and volcanic eruptions is frequently emphasized. Here, we focus on the response of hydrogeological systems to earthquakes, specifically on seismically induced pore-pressure variations in geothermal areas located in the eastern Marmara region. At a 500 m deep artesian geothermal well the pressure is continuously being monitored at a sampling rate of 100 Hz. A seismometer is co-located close to the well-head and the data are recorded by the same digitizer. Hydro-seismograms were recorded in relation to local and distant earthquakes. The ML=5.2 Manyas earthquake which occurred on 20 October 2006 at a distance of 77 km led to a dynamic response of the pore pressure of the order of 4 mbar triggered upon the arrival of the S-wave. Four days later, the ML=5.2 Gemlik earthquake at a distance of 20 km led to a dynamic pore pressure response of the order of 15 mbar triggered upon the arrival of the P-wave. In both cases the peak amplitude of the ground velocity was about 2 mm/s. Weak oscillations of the pore pressure were observed during the passage of surface waves generated by remote earthquakes at distances of up to 9,000 km. Additionally to the dynamic response, a small persistent pressure increase of 1 and 2 mbar had been recorded after both local earthquakes. According to preliminary results, the observed pressure increase is opposite to the static pressure decrease predicted by Okada's model. At the present stage we conclude that the response of the Armutlu geothermal system to earthquakes is likely caused by a dynamic interaction of passing seismic waves (P-, S-, and surface waves) with the fluid reservoir in case a threshold of the ground shaking is exceeded.

  20. 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.

  1. Pressure-induced decomposition of indium hydroxide.

    PubMed

    Gurlo, Aleksander; Dzivenko, Dmytro; Andrade, Miria; Riedel, Ralf; Lauterbach, Stefan; Kleebe, Hans-Joachim

    2010-09-15

    A static pressure-induced decomposition of indium hydroxide into metallic indium that takes place at ambient temperature is reported. The lattice parameter of c-In(OH)(3) decreased upon compression from 7.977(2) to approximately 7.45 A at 34 GPa, corresponding to a decrease in specific volume of approximately 18%. Fitting the second-order Birch-Murnaghan equation of state to the obtained compression data gave a bulk modulus of 99 +/- 3 GPa for c-In(OH)(3). The c-In(OH)(3) crystals with a size of approximately 100 nm are comminuted upon compression, as indicated by the grain-size reduction reflected in broadening of the diffraction reflections and the appearance of smaller (approximately 5 nm) incoherently oriented domains in TEM. The rapid decompression of compressed c-In(OH)(3) leads to partial decomposition of indium hydroxide into metallic indium, mainly as a result of localized stress gradients caused by relaxation of the highly disordered indium sublattice in indium hydroxide. This partial decomposition of indium hydroxide into metallic indium is irreversible, as confirmed by angle-dispersive X-ray diffraction, transmission electron microscopy imaging, Raman scattering, and FTIR spectroscopy. Recovered c-In(OH)(3) samples become completely black and nontransparent and show typical features of metals, i.e., a falling absorption in the 100-250 cm(-1) region accompanied by a featureless spectrum in the 250-2500 cm(-1) region in the Raman spectrum and Drude-like absorption of free electrons in the region of 4000-8000 cm(-1) in the FTIR spectrum. These features were not observed in the initial c-In(OH)(3), which is a typical white wide-band-gap semiconductor.

  2. Necessary condition for solitary wave induced in a water wave field

    NASA Astrophysics Data System (ADS)

    Nakamura, Shigehisa

    2014-05-01

    This work concerns to a problem on monitoring of nonlinear waves on water surface where a water surface wave field is existing. As for solitary wave as a nonlinear wave, there has been developed after formulation and reduction under some given specific condition of a uniform bathymetry. It is well known that this solitary wave can be reduced after a formulation as layleigh noted (which is found in "Hydrodynamics" written by Lamb inn 1879). This can be found in the Lamb's version of 1932. Lamb noted about height of solitary wave is expresssed by a hyperbolic function of water depth with a uniform bathymetry on a horizontal flat. The author has had to work for reproducing this kind of solitary wave in a water basin where a periodical water surface wave field can be generated even the water in the basin is a viscous fluid. What is the point in this work, is that a solitary wave can be reproduced even in a viscous water of an existing water wave field when several conditions are exactly established. That is, the interested water basin has a very gentle sloping of the bed. The water surface wave field is formed to crossing a couple of boundary with slit. The first slit acts to induce a Fresnel-like diffraction of the wave train. The second slit acts to relese wave energy behind the second barrier parallel to the first first barrier. A coupleof solid boundary arranged normal to the second boundary to locateing a symmetric position on both sidess of the slit. At each of the corners formed in front of the second barrier, the incident wave acts to grow its wave height as if it is following to Green's law for a linear simple harmonic wave. These waves on both sides of the corners are established by the incident wave and the refracted wave and start to form a coupled translational motion along the second boundary between the two corners to form a couple of solitary wave train just in front of the second boundary. The couple of solitary wave train has been identified them to

  3. Effects of an acoustic diode on the pressure waveform and cavitation bubble dynamics produced by a piezoelectric shock wave generator

    NASA Astrophysics Data System (ADS)

    Zhu, Songlin; Zhong, Pei

    2003-10-01

    High-speed schlieren imaging, combined with fiber optical probe hydrophone (FOPH) and passive cavitation detection (PCD) were used to access the effects of an acoustic diode (AD) on the pressure waveform and associated cavitation activities produced by a piezoelectric shock wave (PSW) generator. Without the AD, a typical pressure waveform at the focus of the PSW generator consists of a leading shock wave, followed by a tensile wave and several oscillation waves (OWs) of gradually reduced amplitudes. When the AD was placed 30 mm in front of the focus, the amplitude of the tensile wave was reduced and the subsequent OWs were removed. The pulse intensity integral of the tensile wave was reduced by 58%, and subsequently, PSW-induced bubble dynamics were altered significantly. Based on PCD data, the collapse time of cavitation bubble(s) was reduced by about 11%. Although intensive collapse of microbubbles was observed in about 10 μs following the shock front of the original PSW, the forced collapse of microbubbles was not observed when the AD was used, presumably due to the removal of the OWs. Theoretical calculation based on the Gilmore model confirmed these experimental observations. [Work supported by the Whitaker Foundation and NIH.

  4. Numerical study on wave dynamics and wave-induced bed erosion characteristics in Potter Cove, Antarctica

    NASA Astrophysics Data System (ADS)

    Lim, Chai Heng; Lettmann, Karsten; Wolff, Jörg-Olaf

    2013-12-01

    Wave generation, propagation, and transformation from deep ocean over complex bathymetric terrains to coastal waters around Potter Cove (King George Island, South Shetland Islands, Antarctica) have been simulated for an austral summer month using the Simulating Waves Nearshore (SWAN) wave model. This study aims to examine and understand the wave patterns, energy fluxes, and dissipations in Potter Cove. Bed shear stress due to waves is also calculated to provide a general insight on the bed sediment erosion characteristics in Potter Cove.A nesting approach has been implemented from an oceanic scale to a high-resolution coastal scale around Potter Cove. The results of the simulations were compared with buoy observations obtained from the National Data Buoy Center, the WAVEWATCH III model results, and GlobWave altimeter data. The quality of the modelling results has been assessed using two statistical parameters, namely the Willmott's index of agreement D and the bias index. Under various wave conditions, the significant wave heights at the inner cove were found to be about 40-50 % smaller than the ones near the mouth of Potter Cove. The wave power in Potter Cove is generally low. The spatial distributions of the wave-induced bed shear stress and active energy dissipation were found to be following the pattern of the bathymetry, and waves were identified as a potential major driving force for bed sediment erosion in Potter Cove, especially in shallow water regions. This study also gives some results on global ocean applications of SWAN.

  5. 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.

  6. Bioluminescence imaging of wave-induced turbulence

    NASA Astrophysics Data System (ADS)

    Stokes, M. Dale; Deane, Grant B.; Latz, Michael I.; Rohr, Jim

    2004-01-01

    The ability to measure turbulent processes on small spatial and temporal scales is a long standing problem in physical oceanography. Here we explore a novel means of measuring fluid shear stress using the cell flashing behavior of bioluminescent dinoflagellates. To illustrate this technique, we present estimates of the heterogeneous, time-varying shear stress inside a breaking wave crest. These results have implications for a better understanding of upper ocean wave physics, air-sea gas transfer, and the biology of planktonic near-surface organisms as well as providing a new quantitative fluid visualization tool.

  7. Harmonics tracking of intracranial and arterial blood pressure waves.

    PubMed

    Shahsavari, Sima; McKelvey, Tomas

    2008-01-01

    Considering cardiorespiratory interaction and heart rate variability, a new approach is proposed to decompose intracranial pressure and arterial blood pressure to their different harmonics. The method is based on tracking the amplitudes of the harmonics by a Kalman filter based tracking algorithm. The algorithm takes benefit of combined frequency estimation technique which uses both Fast Fourier Transform and RR-interval detection. The result would be of use in intracranial pressure and arterial blood pressure waveform analysis as well as other investigations which need to estimate contribution of specific harmonic in above mentioned signals such as Pressure-Volume Compensatory Reserve assessment.

  8. 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.

  9. Observed high-altitude pressure waves from an underground and a surface explosion

    SciTech Connect

    Banister, J.R.; Hereford, W.V. )

    1991-03-20

    Measurements of high-altitude pressure waves from underground and surface explosions are of interest, as these waves can affect ionospheric electron density and be a source of infrasonic signals. Canisters, equipped with parachutes, were dropped from aircraft to determine time histories of pressure waves radiated by the ground surface above an underground nuclear explosion and a surface chemical explosion. These canisters contained transducers to document pressure and acceleration histories as well as a transmitter to relay information to ground receiver stations. The authors found observed pressure histories from the underground explosion to be consistent with histories calculated from surface ground motion records. The peak blast wave overpressures from the chemical explosion agreed with predicted scaled values. Observed time histories, however, had shorter positive phase duration than predicted with scaling.

  10. Observed high-altitude pressure waves from an underground and a surface explosion

    NASA Astrophysics Data System (ADS)

    Banister, John R.; Hereford, William V.

    1991-03-01

    Measurements of high-altitude pressure waves from underground and surface explosions are of interest, as these waves can affect ionospheric electron density and be a source of infrasonic signals. Canisters, equipped with parachutes, were dropped from aircraft to determine time histories of pressure waves radiated by the ground surface above an underground nuclear explosion and a surface chemical explosion. These canisters contained transducers to document pressure and acceleration histories as well as a transmitter to relay information to ground receiver stations. We found observed pressure histories from the underground explosion to be consistent with histories calculated from surface ground motion records. The peak blast wave overpressures from the chemical explosion agreed with predicted scaled values. Observed time histories, however, had shorter positive phase duration than predicted with scaling.

  11. Pressure-induced structural changes of HBr

    NASA Astrophysics Data System (ADS)

    Ikeda, Takashi; Sprik, Michiel; Terakura, Kiyoyuki; Parrinello, Michele

    1999-04-01

    First-principles molecular dynamics simulation of solid HBr under pressure has been performed using the Car-Parrinello method. A detailed study of the pressure response of the vibrational and proton-transfer dynamics showed that the phase I can be described as a rotator phase with fluctuating hydrogen bonds up to ∼10 GPa. We reproduced the shoulder-like structure seen in the infrared spectra of the H-Br stretching mode in the disordered phase.

  12. Light-shift-induced spatial structures: Application to degenerate four-wave mixing

    NASA Astrophysics Data System (ADS)

    Schiffer, M.; Cruse, E.; Lange, W.

    1994-05-01

    Degenerate four-wave mixing in dense sodium vapor under conditions of strong pressure-induced Zeeman pumping is investigated. Thermal diffusion and its interplay with the Zeeman light shift are found to be responsible for the generation of a grating mechanism that is not sensitive to thermal washout. The effect can be observed experimentally after eliminating the influence of radiation trapping by the use of nitrogen as a buffer gas. Under these conditions large nonlinearities are produced which also influence the propagation of the signal wave via collision-aided circular birefringence.

  13. 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.

  14. Experimental and theoretical investigations on shock wave induced phase transitions

    NASA Astrophysics Data System (ADS)

    Gupta, Satish C.; Sikka, S. K.

    2001-06-01

    Shock wave loading of a material can cause variety of phase transitions, like polymorphism, amorphization, metallization and molecular dissociations. As the shocked state lasts only for a very short duration (about a few microseconds or less), in-situ microscopic measurements are very difficult. Although such studies are beginning to be possible, most of the shock-induced phase transitions are detected using macroscopic measurements. The microscopic nature of the transition is then inferred from comparison with static pressure data or interpreted by theoretical methods. For irreversible phase transitions, microscopic measurements on recovered samples, together with orientation relations determined from selected area electron diffraction and examination of the morphology of growth of the new phase can provide insight into mechanism of phase transitions. On theoretical side, the current ab initio band structure techniques based on density functional formalism provide capability for accurate computation of the small energy differences (a few mRy or smaller) between different plausible structures. Total energy calculation along the path of a phase transition can furnish estimates of activation barrier, which has implications for understanding kinetics of phase transitions. Molecular dynamics calculations, where the new structure evolves naturally, are becoming increasingly popular especially for understanding crystal to amorphous phase transitions. Illustrations from work at our laboratory will be presented.

  15. Arterial blood pressure wave forms in radial and posterior tibial arteries in critically ill newborn infants.

    PubMed

    Gevers, M; Hack, W W; Ree, E F; Lafeber, H N; Westerhof, N

    1993-04-01

    The aim of this study was to document arterial blood pressure wave forms at two sites along the arterial tree of the neonate: in the radial and posterior tibial arteries. Using a high-fidelity catheter tip-transducer system, peripheral arterial blood pressure wave forms in 26 critically newborn infants were studied. In 14 infants the radial artery and in 12 infants the posterior tibial artery was cannulated. Radial artery blood pressure waves resembled those of proximal aortic rather than those of the radial artery in adults. Quantitative analysis of the waves was performed to reassure this finding. Blood pressure waves obtained from posterior tibial artery resembled those of femoral artery rather than those of posterior tibial artery waves in adults. We conclude that radial and posterior tibial artery wave forms in neonates appear to have a central appearance. This phenomenon might be explained by the close proximity of the radial and posterior tibial artery to the central aorta and femoral artery respectively, due to the small and short limbs of the neonate. The finding allows an "easy central pressure look" at both ends of the neonatal aorta.

  16. 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.

  17. [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

  18. Quantification of abnormal intracranial pressure waves and isotope cisternography for diagnosis of occult communicating hydrocephalus

    SciTech Connect

    Cardoso, E.R.; Piatek, D.; Del Bigio, M.R.; Stambrook, M.; Sutherland, J.B.

    1989-01-01

    Nineteen consecutive patients with suspected occult communicating hydrocephalus were investigated by means of clinical evaluation, neuropsychological testing, isotope cisternography, computed tomography scanning, and continuous intracranial pressure monitoring. Semi-quantitative grading systems were used in the evaluation of the clinical, neuropsychological, and cisternographic assessments. Clinical examination, neuropsychological testing, and computed tomography scanning were repeated 3 months after ventriculoperitoneal shunting. All patients showed abnormal intracranial pressure waves and all improved after shunting. There was close correlation between number, peak, and pulse pressures of B waves and the mean intracranial pressure. However, quantification of B waves by means of number, frequency, and amplitude did not help in predicting the degree of clinical improvement postshunting. The most sensitive predictor of favorable response to shunting was enlargement of the temporal horns on computed tomography scan. Furthermore, the size of temporal horns correlated with mean intracranial pressure. There was no correlation between abnormalities on isotope cisternography and clinical improvement.

  19. 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.

  20. Medium characterization from interface-wave impedance and ellipticity using simultaneous displacement and pressure measurements.

    PubMed

    van Dalen, K N; Drijkoningen, G G; Smeulders, D M J; Heller, H K J; Glorieux, C; Sarens, B; Verstraeten, B

    2011-09-01

    The interface-wave impedance and ellipticity are wave attributes that interrelate the full waveforms as observed in different components. For each of the fluid/elastic-solid interface waves, i.e., the pseudo-Rayleigh (pR) and Stoneley (St) waves, the impedance and ellipticity are found to have different functional dependencies on Young's modulus and Poisson's ratio. By combining the attributes in a cost function, unique and stable estimates of these parameters can be obtained, particularly when using the St wave. In a validation experiment, the impedance of the laser-excited pR wave is successfully extracted from simultaneous measurements of the normal particle displacement and the fluid pressure at a water/aluminum interface. The displacement is measured using a laser Doppler vibrometer (LDV) and the pressure with a needle hydrophone. Any LDV measurement is perturbed by refractive-index changes along the LDV beam once acoustic waves interfere with the beam. Using a model that accounts for these perturbations, an impedance decrease of 28% with respect to the plane wave impedance of the pR wave is predicted for the water/aluminum configuration. Although this deviation is different for the experimentally extracted impedance, there is excellent agreement between the observed and predicted pR waveforms in both the particle displacement and fluid pressure.

  1. 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.

  2. 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.

  3. High sea-floor stress induced by extreme hurricane waves

    NASA Astrophysics Data System (ADS)

    Wijesekera, Hemantha W.; Wang, David W.; Teague, William J.; Jarosz, Ewa

    2010-06-01

    Strong surface waves and currents generated by major hurricanes can produce extreme forces at the seabed that scour the seafloor and cause massive underwater mudslides. Our understanding of these forces is poor due to lack of concurrent measurements of waves and currents under these storms. Using unique observations collected during the passage of a category-4 hurricane, Ivan, bottom stress due to currents and waves over the outer continental shelf in the Gulf of Mexico was examined. During the passage of Ivan, the bottom stress was highly correlated with the wind with a maximum of about 40% of the wind stress. The bottom stress was dominated by the wave-induced stresses, and exceeded critical levels at depths as large as 90 m. Surprisingly, the bottom damaging stress persisted after the passage of Ivan for about a week, and was modulated by near-inertial waves.

  4. 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

  5. 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.

  6. 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

  7. Pressure mediated reduction of ultrasonically-induced cell lysis

    SciTech Connect

    Ciaravino, V.; Miller, M.W.; Carstensen, E.L.

    1981-01-01

    Chinese hamster V-79 cells, exposed in polystyrene tubes for 5 min to 1 MHz continous wave ultrasound, were lysed more by a 10W/cm/sup 2/ than a 5W/cm/sup 2/ intensity. Higher atmospheric pressure was needed to eliminate lysis with the former relative to the latter intensity, but lysis by 10W/cm/sup 2/ was completely eliminated with 2 atmospheres of hydrostatic pressure. The reduction in lysis per unit increase in atomspheric pressure was comparable for both ultrasound intensities.

  8. 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

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. Temporal Behavior of Radiation-Pressure-Induced Vibrations of an Optical Microcavity Phonon Mode

    NASA Astrophysics Data System (ADS)

    Carmon, Tal; Rokhsari, Hossein; Yang, Lan; Kippenberg, Tobias J.; Vahala, Kerry J.

    2005-06-01

    We analyze experimentally and theoretically mechanical oscillation within an optical cavity stimulated by the pressure of circulating optical radiation. The resulting radio frequency cavity vibrations (phonon mode) cause modulation of the incident, continuous-wave (cw) input pump beam. Furthermore, with increasing cw pump power, an evolution from sinusoidal modulation to random oscillations is observed in the pump power coupled from the resonator. The temporal evolution with pump power is studied, and agreement was found with theory. In addition to applications in quantum optomechanics, the present work suggests that radiation-pressure-induced effects can establish a practical limit for the miniaturization of optical silica microcavities.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

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

    DOE PAGES

    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.

  19. 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.

  20. 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.

  1. 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).

  2. 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.

  3. Cells under pressure - treatment of eukaryotic cells with high hydrostatic pressure, from physiologic aspects to pressure induced cell death.

    PubMed

    Frey, Benjamin; Janko, Christina; Ebel, Nina; Meister, Silke; Schlücker, Eberhard; Meyer-Pittroff, Roland; Fietkau, Rainer; Herrmann, Martin; Gaipl, Udo S

    2008-01-01

    The research on high hydrostatic pressure in medicine and life sciences is multifaceted. According to the used pressure head the research has to be divided into two different parts. To study physiological aspects of pressure on eukaryotic cells physiological pressure (pHHP; < 100 MPa) is used. pHHP induces morphological alterations in the cellular organelles and evokes a reversible stress response similar to the well known heat shock response. pHHP induces highly reversible alterations and normally does not affect cellular viability. The treatment of eukaryotic cells with non-physiological pressure (HHP; > or = 100 MPa) reveals different outcomes. Treatment with HHP < 150 MPa does not markedly affect viability of human cells, but induces apoptosis in murine cells. In human cells apoptosis is observed after treatment with > or = 200 MPa. Moreover, HHP treatment with > 300 MPa leads to necrosis. Therefore, HHP plays a role for the sterilisation of human transplants, of food stuff, and pharmaceuticals. Human tumour cells subjected to HHP > 300 MPa display a necrotic phenotype along with a gelificated cytoplasm, preserve their shape, and retain their immunogenicity. These observations favour the use of HHP to produce whole cell based tumour vaccines. Further experiments revealed that the increment of pressure as well as the pressure holding time influences the cell death of tumour cells. We conclude that high hydrostatic pressure offers both, an economic, easy to apply, clean, and fast technique for the generation of vaccines, and a promising tool to study physiological aspects.

  4. Barocaloric effect and the pressure induced solid state refrigerator

    NASA Astrophysics Data System (ADS)

    de Oliveira, N. A.

    2011-03-01

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

  5. 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.

  6. 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.

  7. Shear flow induced wave couplings in the solar wind

    SciTech Connect

    Poedts, S.; Rogava, A.D. |; Mahajan, S.M. |

    1998-01-01

    A sheared background flow in a plasma induces coupling between different MHD wave modes, resulting in their mutual transformations with corresponding energy redistributing between the modes. In this way, the energy can be transfered from one wave mode to the other, but energy can also be added to or extracted from the background flow. In the present paper it is investigated whether the wave coupling and energy transfer mechanisms can operate under solar wind conditions. It is shown that this is indeed the case. Hence, the long-period waves observed in the solar wind at r > 0.3 AU might be generated by much faster periodic oscillations in the photosphere of the Sun. Other possible consequences for observable beat phenomena in the wind and the acceleration of the solar wind particles are also discussed.

  8. Wave reflection augments central systolic and pulse pressures during facial cooling.

    PubMed

    Edwards, David G; Roy, Matthew S; Prasad, Raju Y

    2008-06-01

    Cardiovascular events are more common in the winter months, possibly because of hemodynamic alterations in response to cold exposure. The purpose of this study was to determine the effect of acute facial cooling on central aortic pressure, arterial stiffness, and wave reflection. Twelve healthy subjects (age 23 +/- 3 yr; 6 men, 6 women) underwent supine measurements of carotid-femoral pulse wave velocity (PWV), brachial artery blood pressure, and central aortic pressure (via the synthesis of a central aortic pressure waveform by radial artery applanation tonometry and generalized transfer function) during a control trial (supine rest) and a facial cooling trial (0 degrees C gel pack). Aortic augmentation index (AI), an index of wave reflection, was calculated from the aortic pressure waveform. Measurements were made at baseline, 2 min, and 7 min during each trial. Facial cooling increased (P < 0.05) peripheral and central diastolic and systolic pressures. Central systolic pressure increased more than peripheral systolic pressure (22 +/- 3 vs. 15 +/- 2 mmHg; P < 0.05), resulting in decreased pulse pressure amplification ratio. Facial cooling resulted in a robust increase in AI and a modest increase in PWV (AI: -1.4 +/- 3.8 vs. 21.2 +/- 3.0 and 19.9 +/- 3.6%; PWV: 5.6 +/- 0.2 vs. 6.5 +/- 0.3 and 6.2 +/- 0.2 m/s; P < 0.05). Change in mean arterial pressure but not PWV predicted the change in AI, suggesting that facial cooling may increase AI independent of aortic PWV. Facial cooling and the resulting peripheral vasoconstriction are associated with an increase in wave reflection and augmentation of central systolic pressure, potentially explaining ischemia and cardiovascular events in the cold.

  9. 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.

  10. Atmospheric Pressure Oscillations Forced by Surface Waves From the 2003 Tokachi-Oki Earthquake

    NASA Astrophysics Data System (ADS)

    Watada, S.; Nishida, K.; Sekiguchi, S.

    2004-12-01

    Clear atmospheric pressure changes associated with the 2003 Tokachi-Oki Earthquake with M 8.3 were recorded by 8 microbarographs along Japan. The maximum oscillatory pressure change is about 2 Pascal with dominant period is about 15-20 second, and lasted for more than 30 minutes. Comparing the pressure change with broadband seismic records observed near or at the microbarogram, the pressure change starts at the arrival of seismic waves and reaches its maximum amplitude at the arrival of Rayleigh waves. Four microbarographs, co-located with STS-1 broadband seismographs and suffering less atmospheric wind noise, show that peaks in vertical ground velocity records correspond to the peaks of atmospheric pressure records. Similar pressure changes were observed during the largest aftershock (M 7.4). All ground motion analyzed in this paper were recorded by STS-1 broadband sensors. Spectrum analysis in the frequency domain supports that the vertical ground velocity and the pressure change has the same phase and the amplitude ratio is constant up to a period of about 50 second. The constant amplitude ratio is about (atmospheric density) times (sound velocity in the atmosphere), indicating that the surface ground in vertical ground motion compresses or inflates the air above the ground locally and low-frequency sound waves are generated. Pressure change recorded after the passage of Rayleigh waves does not well correlate with the ground velocity. Through the precise atmospheric pressure and ground motion measurement at the same sites, we witnessed the process of low-frequency sound generation by the vertical ground surface motion acted as a vibrating plate of a speaker. The radiated low-frequency sound waves propagates upward and reaches to the ionosphere with large amplitude because of the energy conservation. The ionospheric turbulence reported in the past researches were originated from this low-frequency sound at the ground surface.

  11. 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.

  12. The relationship between pore-pressure and the elastic-wave velocities of TCDP-cores

    NASA Astrophysics Data System (ADS)

    Kitamura, K.; Takahashi, M.; Masuda, K.; Ito, H.; Song, S.; Wang, C.

    2005-12-01

    The elastic-wave velocities and the permeability of fault-related rocks are essential keys to reveal the earthquake process. We measured these parameters of boring-cores of the Chelungpu-fault (TCDP-cores) that is the earthquake-source fault of the 1999 Chi-Chi earthquake in Taiwan under high-pressure conditions. Experimental apparatus we used is the gas-medium, high-pressure and high-temperature deformation apparatus at the AIST Japan. We measured elastic-wave velocities and permeability simultaneously with decreasing pore-pressure (Pp) from 20 to 0 MPa under the constant confining-pressure and temperature condition (30 MPa and 25C). We measured compressional-wave velocities (Vp) and shear-wave velocities (Vs) at once. We adopted the oscillation method to measure the permeability because this method can measure the low-permeability with relatively short time, under high pore pressure conditions. We obtained 18 experimental cylindrical specimens sized 20 mm in diameter and 20 mm long, sampled from 482 m to 1316 m depth of the TCDP-core archives (mainly silty-sandstone and sandstone). It would be the first report to refer a relation between these physical properties of porous sediments. The results of our elastic-wave velocities measurement indicate the strong effect of pore-pressure on elastic-wave velocities. They increased rapidly with decreasing Pp down to 10 MPa. The elastic-wave velocities didn_ft change with decreasing Pp from 10 to 0 MPa. All samples showed similar pore pressure- velocity curves but different ratios of dV/dPp. It is considered that the volume of pores and crack decreased with decrease of pore-pressure. It can be said the pressurization effect on the elastic wave velocity would reflect significantly on the bulk density of sedimentary rocks. The Vp- and Vs-values decreased successively from silty-sandstone to sandstone at low-Pp condition (10-0 MPa). These results indicate that the Vp- and Vs-values are controlled by lithology under low

  13. 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

  14. 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

  15. 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.

  16. Molecular dynamics study of accelerated ion-induced shock waves in biological media

    NASA Astrophysics Data System (ADS)

    de Vera, Pablo; Mason, Nigel J.; Currell, Fred J.; Solov'yov, Andrey V.

    2016-09-01

    We present a molecular dynamics study of the effects of carbon- and iron-ion induced shock waves in DNA duplexes in liquid water. We use the CHARMM force field implemented within the MBN Explorer simulation package to optimize and equilibrate DNA duplexes in liquid water boxes of different sizes and shapes. The translational and vibrational degrees of freedom of water molecules are excited according to the energy deposited by the ions and the subsequent shock waves in liquid water are simulated. The pressure waves generated are studied and compared with an analytical hydrodynamics model which serves as a benchmark for evaluating the suitability of the simulation boxes. The energy deposition in the DNA backbone bonds is also monitored as an estimation of biological damage, something which is not possible with the analytical model. Contribution to the Topical Issue "Atomic Cluster Collisions (7th International Symposium)", edited by Gerardo Delgado Barrio, Andrey V. Solov'yov, Pablo Villarreal, Rita Prosmiti.

  17. Molecular dynamics study of accelerated ion-induced shock waves in biological media

    NASA Astrophysics Data System (ADS)

    de Vera, Pablo; Mason, Nigel J.; Currell, Fred J.; Solov'yov, Andrey V.

    2016-09-01

    We present a molecular dynamics study of the effects of carbon- and iron-ion induced shock waves in DNA duplexes in liquid water. We use the CHARMM force field implemented within the MBN Explorer simulation package to optimize and equilibrate DNA duplexes in liquid water boxes of different sizes and shapes. The translational and vibrational degrees of freedom of water molecules are excited according to the energy deposited by the ions and the subsequent shock waves in liquid water are simulated. The pressure waves generated are studied and compared with an analytical hydrodynamics model which serves as a benchmark for evaluating the suitability of the simulation boxes. The energy deposition in the DNA backbone bonds is also monitored as an estimation of biological damage, something which is not possible with the analytical model.

  18. 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.

  19. 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

  20. The acute effects of smokeless tobacco on central aortic blood pressure and wave reflection characteristics.

    PubMed

    Martin, Jeffrey S; Beck, Darren T; Gurovich, Alvaro N; Braith, Randy W

    2010-10-01

    The main objectives of this study were to examine the acute effect of a single dose of smokeless tobacco (ST) on central aortic blood pressure and wave reflection characteristics. Fifteen apparently healthy male subjects (aged 30.6 ± 6.2 y) were given a 2.5 g oral dose of ST after baseline measurements were recorded. Pulse wave analysis using radial artery applanation tonometry was performed in triplicate at baseline (0 min) and at 10-min intervals during (10, 20 and 30 min) and after (40, 50 and 60 min) ST use. An acute dose of ST was associated with a significant increase in heart rate (HR), central aortic systolic and diastolic blood pressure, peripheral brachial systolic and diastolic blood pressure, and aortic augmentation index normalized to a fixed heart rate of 75 bpm (AIx@75). Furthermore, ejection duration and round trip travel time of the reflected pressure wave (Δt(p)) were significantly decreased as a result of one time ST use. As a result of changes in aortic pressure wave reflection characteristics, there was a significant increase in wasted left ventricular pressure energy (LVE(w)) and the tension-time index (TTI) as a result of ST use. In conclusion, one time use of ST elicits significant transient increases in HR, central aortic pressures, AIx@75, the TTI and LVE(w). Chronic users subjected to decades of elevated central pressures and left ventricular work may have an increased cardiovascular risk as central aortic pressures are even more strongly related to cardiovascular outcomes than peripheral blood pressures.

  1. 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.

  2. 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.

  3. Change in Pulsatile Cerebral Arterial Pressure and Flow Waves as a Therapeutic Strategy?

    PubMed

    Kim, Mi Ok; Adji, Audrey; O'Rourke, Michael F; Avolio, Alberto P; Smielewski, Peter; Pickard, John D; Czosnyka, Marek

    2016-01-01

    While intracranial pressure (ICP), arterial pressure and transcranial middle cerebral artery flow velocity (MCAFV) are often monitored in unconscious patients following stroke or head injury, the value of waveform indices has not been fully established. We retrospectively analysed the data of eight adults (aged 19-36 years) with closed head injury who had spontaneous and repeated episodes of elevated ICP (i.e. "plateau waves"). MCAFV was measured using transcranial Doppler, ICP using a Codman catheter and radial artery pressure using cannulation. Ascending aortic pressure (AAP) was generated from the radial artery using SphygmoCor(TM). Cerebral perfusion pressure (CPP) was calculated as AAP - ICP in the time domain.During the period of increased ICP, ICP and cerebral flow velocity amplitude increased significantly compared with the basal condition, while cerebral mean flow decreased. Amplitude of the secondary peak in ICP, AAP and MCAFV waveform became apparent.An increase in the amplitude of ICP, AAP and MCAFV waves can be attributed to the greater prominence of reflected waves from the lower body, which was apparent in pulse waveform analysis. Arterial vasodilators such as nitrates reduce reflected pressure waves from the lower body and, by decreasing the amplitude of AAP, ICP and MCAFV, may be as beneficial for the cerebral circulation as they are for the left ventricle of the heart.

  4. Relationship between radial and central arterial pulse wave and evaluation of central aortic pressure using the radial arterial pulse wave.

    PubMed

    Takazawa, Kenji; Kobayashi, Hideyuki; Shindo, Naohisa; Tanaka, Nobuhiro; Yamashina, Akira

    2007-03-01

    Since a decrease of central aortic pressure contributes to the prevention of cardiovascular events, simple measurement of not only brachial blood pressure but also central aortic pressure may be useful in the prevention and treatment of cardiovascular diseases. In this study, we simultaneously measured radial artery pulse waves non-invasively and ascending aortic pressure invasively, before and after the administration of nicorandil. We then compared changes in central aortic pressure and radial arterial blood pressure calibrated with brachial blood pressure in addition to calculating the augmentation index (AI) at the aorta and radial artery. After nicorandil administration, the reduction in maximal systolic blood pressure in the aorta (Deltaa-SBP) was -14+/-15 mmHg, significantly larger than that in early systolic pressure in the radial artery (Deltar-SBP) (-9+/-12 mmHg). The reduction in late systolic blood pressure in the radial artery (Deltar-SBP2) was -15+/-14 mmHg, significantly larger than Deltar-SBP, but not significantly different from Deltaa-SBP. There were significant relationships between Deltaa-SBP and Deltar-SBP (r=0.81, p<0.001), and between Deltaa-SBP and Deltar-SBP2 (r=0.91, p<0.001). The slope of the correlation regression line with Deltar-SBP2 (0.83) was larger and closer to 1 than that with Deltar-SBP (0.63), showing that the relationship was close to 1:1. Significant correlations were obtained between aortic AI (a-AI) and radial AI (r-AI) (before nicorandil administration: r=0.91, p<0.001; after administration: r=0.70, p<0.001). These data suggest that the measurement of radial artery pulse wave and observation of changes in the late systolic blood pressure in the radial artery (r-SBP2) in addition to the ordinary measurement of brachial blood pressure may enable a more accurate evaluation of changes in maximal systolic blood pressure in the aorta (a-SBP).

  5. 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.

  6. 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

  7. Modeling of depth-induced wave breaking under finite depth wave growth conditions

    NASA Astrophysics Data System (ADS)

    van der Westhuysen, André J.

    2010-01-01

    Recent studies have shown that the spectral wind wave model SWAN (Simulating Waves Nearshore) underestimates wave heights and periods in situations of finite depth wave growth. In this study, this inaccuracy is addressed through a rescaling of the Battjes and Janssen (1978) bore-based model for depth-induced breaking, considering both sloping bed surf zone situations and finite depth wave growth conditions. It is found that the variation of the model error with the breaker index γBJ in this formulation differs significantly between the two types of conditions. For surf zones, clear optimal values are found for the breaker index. By contrast, under finite depth wave growth conditions, model errors asymptotically decrease with increasing values of the breaker index (weaker dissipation). Under both the surf zone and finite depth wave growth conditions, optimal calibration settings of γBJ were found to correlate with the dimensionless depth kpd (where kp is the spectral peak wave number and d is the water depth) and the local mean wave steepness. Subsequently, a new breaker index, based on the local shallow water nonlinearity, expressed in terms of the biphase of the self-interactions of the spectral peak, is proposed. Implemented in the bore-based breaker model of Thornton and Guza (1983), this breaker index accurately predicts the large difference in dissipation magnitudes found between surf zone conditions and finite depth growth situations. Hence, the proposed expression yields a significant improvement in model accuracy over the default Battjes and Janssen (1978) model for finite depth growth situations, while retaining good performance for sloping bed surf zones.

  8. Pressure Dependence of the Charge-Density-Wave Gap in Rare-Earth Tri-Tellurides

    SciTech Connect

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

    2009-12-14

    We investigate the pressure dependence of the optical properties of CeTe{sub 3}, which exhibits an incommensurate charge-density-wave (CDW) state already at 300 K. Our data are collected in the mid-infrared 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 RTe{sub 3}.

  9. 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.

  10. 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.

  11. 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.

  12. 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).

  13. Shock wave induced sonoporation and gene transfer

    NASA Astrophysics Data System (ADS)

    Miller, Douglas L.

    2003-10-01

    During shockwave (SW) treatment, cavitation activity can be applied for cell killing. A bonus is that some surviving cells appear to be briefly permeabilized, or sonoporated, allowing them to take up large molecules including DNA. In vitro research has indicated that as the number of SW increased, survival declined exponentially but the number of sonoporated cells increased to better than 50% of survivors for 1000 SW. In vivo tests have demonstrated SW-induced tumor ablation could indeed be accompanied by the transfection of marker plasmids into mouse B16 melanoma tumors in vivo. With intratumor injection of plasmid DNA and air bubbles, significant results were obtained for only 400 SW. In a trial of cancer therapy, the effects of 500 SW combined with interleukin-12 immuno-gene therapy was observed on the progression of two mouse tumors, B16 melanoma and RENCA renal carcinoma. The combination of SW and IL-12 plasmid injection provided a statistically significant inhibition of tumor growth relative to SW alone for both tumor models, demonstrating feasibility for this treatment method. In the future, the development of intravenous gene delivery and improved transfection, together with image-guided ultrasound treatment, should lead to the clinical application of ultrasound enhanced gene therapy. [Work supported by NIH Grant No. EB002782.

  14. Scaling Law of Impact Induced Shock Pressure in Planetary Mantle

    NASA Astrophysics Data System (ADS)

    Monteux, Julien; Arkani-Hamed, Jafar

    2015-04-01

    While hydrocode simulation of impact induced shock pressure inside planetary mantle is more accurate, it is not suitable for studying several hundreds of impacts occurring during the accretion of a planet. Not only simulation of each impact takes over two orders of magnitude longer computer time than that of a scaling law simulation [1], but also it is cumbersome to apply for growing proto-planets where size of a proto-planet and impact velocities of the accreting bodies increase significantly. This is compounded by the formation of the iron core during the accretion with increasing size. Major impacting bodies during accretion of a Mars type planet have very low velocities. We use iSale hydrocode simulations and adopt physical properties of dunite for the mantle to calculate shock pressure and particle velocity in a Mars type body for 11 impact velocities ranging from 4 to 60 km/s. Large impactors of 100 to 1000 km in diameter, comparable to those impacted on Mars and created giant impact basins, are examined. The results are in good agreement with those of Pierazzo et al. [2] which were calculated for impact velocities higher than 10 km/s and impactor of 0.2 to 10 km in diameter. The internal consistency of our models indicates that our scaling laws are also accurate for lower impact velocities. We found no distinct isobaric region, rather the peak shock pressure changes relatively slowly versus distance from the impact site in the near field zone, within ~ 3 times the impactor radius, compare to that in the far field zone as also suggested by Ahrens and O'Keefe [3]. Hence we propose two distinct scaling laws, the power law distribution of shock pressure P as a function of distance R from the impact site at the surface, one for the near field zone and the other for the far field zone: Log P = a + n Log (R/Rimp) With n = 1.72 - 2.44 Log(Vimp) for R < ~3 Rimp, and n = -0.84 -0.51 Log(Vimp) for R > ~3 Rimp where a is a constant, Rimp is the impactor radius, and Vimp

  15. Shear wave induced resonance elastography of spherical masses with polarized torsional waves

    NASA Astrophysics Data System (ADS)

    Hadj Henni, Anis; Schmitt, Cédric; Trop, Isabelle; Cloutier, Guy

    2012-03-01

    Shear wave induced resonance (SWIR) is a technique for dynamic ultrasound elastography of confined mechanical inclusions. It was developed for breast tumor imaging and tissue characterization. This method relies on the polarization of torsional shear waves modeled with the Helmholtz equation in spherical coordinates. To validate modeling, an invitro set-up was used to measure and image the first three eigenfrequencies and eigenmodes of a soft sphere. A preliminary invivo SWIR measurement on a breast fibroadenoma is also reported. Results revealed the potential of SWIR elastography to detect and mechanically characterize breast lesions for early cancer detection.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Pressure induced mechanical properties of boron based pnictides

    NASA Astrophysics Data System (ADS)

    Varshney, Dinesh; Joshi, G.; Varshney, Meenu; Shriya, Swarna

    2010-05-01

    The elastic and thermodynamical properties of the III-V semiconductors as BY (Y = N, P, As) are calculated in zincblende and NaCl phases by formulating an effective interionic interaction potential. This potential consists of the long-range Coulomb, the Hafemeister and Flygare type short-range overlap repulsion extended up to the second neighbour ions and the van der Waals (vdW) interaction. The variations of elastic constants with pressure follow a systematic trend identical to that observed in other compounds of ZnS type structure family and the Born relative stability criteria is valid in boron monopnictides. From the elastic constants the Poisson's ratio ν, the ratio R S/ B of S (Voigt averaged shear modulus) over B (bulk modulus), elastic wave velocity, average wave velocity and thermodynamical property Debye temperature are calculated. By analyzing the Poisson's ratio ν and the ratio R S/ B we conclude that at low pressures the boron monopnictides are brittle in nature in ZnS phase and ductile nature at high pressures in both ZnS and NaCl phases. To our knowledge this is the first quantitative theoretical prediction of the pressure dependence of ductile (brittle) nature of BY compounds.

  2. 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.

  3. 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.

  4. 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.

  5. Spin-transfer torque induced spin waves in antiferromagnetic insulators

    NASA Astrophysics Data System (ADS)

    Daniels, Matthew; Guo, Wei; Stocks, G. Malcolm; Xiao, Di; Xiao, Jiang

    2015-03-01

    We explore the possibility of exciting spin waves in insulating antiferromagnetic films by injecting spin current at the surface. We analyze both magnetically compensated and uncompensated interfaces. We find that the spin current induced spin-transfer torque can excite spin waves in insulating antiferromagnetic materials and that the chirality of the excited spin wave is determined by the polarization of the injected spin current. Furthermore, the presence of magnetic surface anisotropy can greatly increase the accessibility of these excitations. Supported by NSF EFRI-1433496 (M.W.D), U.S. DOE Office of Basic Energy Sciences, Materials Sciences and Engineering (D.X. & G.M.S.), Major State Basic Research Project of China and National Natural Science Foundation of China (W.G. and J.X.).

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    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.

  8. 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. __________________________________________________

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

    George, Atanasiu Catalin; 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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

  4. Probing and Modeling of Pressure-induced Structural Transformation in Oxide Melts at High Pressure

    NASA Astrophysics Data System (ADS)

    Cody, G.; Lee, S.; Mysen, B.; Fei, Y.; Eng, P.

    2008-12-01

    Pressure-induced bonding transitions in oxide melts give improved prospects for the non-linear pressure dependence of their macroscopic transport properties in the earth's interior. The inherent difficulties of current experimental technologies, however, pose major challenges for probing structural changes of prototypical model oxide melts at high pressure, making it one of the unsolved problems in geophysics. Recent advances in element specific experimental probe of local structures, such as high resolution solid- state NMR and x-ray Raman scattering unveils new structural insights into the pressure-induced changes in the bonding nature (either gradual or abrupt) of the archetypal oxides melts (e.g. Lee SK et al. Proc. Nat. Aca. Sci. 2008, 105, 7925; Lee SK et al. J. Phys. Chem. B. 2008 in press). Here, we report recent progress that we have made using these techniques. Non-random spatial distribution of aluminum in oxide glasses were for the first time revealed via through-space correlation NMR spectroscopy: four, five, six coordinated aluminums have differential proximity among each other but favoring the formation of clusters mainly composed of six coordinated Al. While silicate glasses studied here exhibit a general trend of decreasing non-bridging oxygen fraction with pressure, the details of their pressure dependence is significantly affected by the composition of melts, such as Na/Si, Si/Al ratio as well as types of network modifying cations. We account for these differences with a conceptual model that utilizes pressure flexibility (the resistance to structural changes with increased pressurization). An oxide melts with a large pressure flexibility, thus, may undergo a gradual structural transformation. In contrast, a melts with the opposite behavior undergoes an abrupt coordination transformation. The observed information of connectivity among network forming cations was used to calculate the crystal-melt partitioning coefficient and activity of silica in

  5. 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.

  6. 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)

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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

  12. Pressure-induced transformation plasticity of H(2)O ice.

    PubMed

    Dunand, D C; Schuh, C; Goldsby, D L

    2001-01-22

    Transformation plasticity is a deformation mechanism which occurs during phase transformation of an externally stressed material. Pressure-induced transformation plasticity of ice could be relevant to the geology of the moons of the outer solar system, and has long been postulated to occur in olivine in the earth's interior. In the present work, ice specimens were subjected to isostatic pressure cycling between 0 and 300 MPa to induce reversible polymorphic transformation between ice I and II at 230 K. When a small uniaxial compressive stress was applied during cycling, the specimens exhibited a compressive strain (as large as 18.5% after a single cycle) proportional to the applied stress, in agreement with observations and theory for transformation plasticity of metals induced by polymorphic thermal cycling. PMID:11177908

  13. Determination of aortic pulse wave velocity from waveform decomposition of the central aortic pressure pulse.

    PubMed

    Qasem, Ahmed; Avolio, Alberto

    2008-02-01

    Aortic pulse wave velocity (PWV), calculated from pulse transit time (PTT) using 2 separate pulse recordings over a known distance, is a significant biomarker of cardiovascular risk. This study evaluates a novel method of determining PTT from waveform decomposition of central aortic pressure using a single pulse measurement. Aortic pressure was estimated from a transformed radial pulse and decomposed into forward and backward waves using a triangular flow wave. Pulse transit time was determined from cross-correlation of forward and backward waves. Pulse transit time, representing twice the PTT between 2 specific sites, was compared with independent measurements of carotid-femoral PTT in a cohort of 46 subjects (23 females; age 57+/-14 years). Linear regression between measured PTT (y; milliseconds) and calculated PTT (x; milliseconds) was y=1.05x-2.1 (r=0.67; P<0.001). This model was tested in a separate group of 44 subjects (21 females; age 55+/-14 years) by comparing measured carotid-femoral PWV (y; meters per second) and PWV calculated using the estimated value of PTT (eTR/2) and carotid femoral distance (x; meters per second; y=1.21x-2.5; r=0.82; P<0.001). Findings indicate that the time lag between the forward and backward waves obtained from the decomposition of aortic pressure wave can be used to determine PWV along the aortic trunk and shows good agreement with carotid-femoral PWV. This technique can be used as a noninvasive and nonintrusive method for measurement of aortic PWV using a single pressure recording.

  14. 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.

  15. 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.

  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. Superconductivity and magnetic field induced spin density waves in the (TMTTF)2X family

    NASA Astrophysics Data System (ADS)

    Balicas, L.; Behnia, K.; Kang, W.; Canadell, E.; Auban-Senzier, P.; Jérome, D.; Ribault, M.; Fabre, J. M.

    1994-10-01

    We report magnetotransport measurements in the quasi one dimensional (Q-1-D) organic conductor (TMTTF)2Br at pressures up to 26 kbar, clown to 0.45 K in magnetic fields up to 19 T along the c^{ast} direction. It is found that a superconducting ground state is stabilized under 26 kbar at T_C = 0.8 K. No magnetic field induced spin density wave (FISDW) transitions are observed below 19T unlike other Q-1-D superconductors pertaining to the selenium series. The computed amplitude of the interchain coupling along transverse directions is unable to explain the missing; FISDW instability.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    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-3 from the quantum atom, where Q denotes the distance between the two walls, whereas it acquires an additional force proportional to Q-2 from the BEC due to the atom-atom interaction in the BEC. These forces can be understood as the matter-wave pressure.

  1. 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.

  2. Brachial vs. central systolic pressure and pulse wave transmission indicators: a critical analysis.

    PubMed

    Izzo, Joseph L

    2014-12-01

    This critique is intended to provide background for the reader to evaluate the relative clinical utilities of brachial cuff systolic blood pressure (SBP) and its derivatives, including pulse pressure, central systolic pressure, central augmentation index (AI), and pulse pressure amplification (PPA). The critical question is whether the newer indicators add sufficient information to justify replacing or augmenting brachial cuff blood pressure (BP) data in research and patient care. Historical context, pathophysiology of variations in pulse wave transmission and reflection, issues related to measurement and model errors, statistical limitations, and clinical correlations are presented, along with new comparative data. Based on this overview, there is no compelling scientific or practical reason to replace cuff SBP with any of the newer indicators in the vast majority of clinical situations. Supplemental value for central SBP may exist in defining patients with exaggerated PPA ("spurious systolic hypertension"), managing cardiac and aortic diseases, and in studies of cardiovascular drugs, but there are no current standards for these possibilities.

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

    USGS Publications Warehouse

    ,

    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.

  4. 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

  5. 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)

  6. 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.

  7. 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.

  8. 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).

  9. 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.

  10. Investigations of pressure induced structural phase transformations in pentaerythritol

    NASA Astrophysics Data System (ADS)

    Garg, Nandini; Sharma, Surinder M.; Sikka, S. K.

    2005-10-01

    We have investigated the pressure induced structural changes in pentaerythritol {2,2-bis-(hydroxymethyl)-1,3-propanediol} with the help of X-ray diffraction studies. Our results show that this compound undergoes transformations to a lower symmetry phase between 5.2-5.9 GPa. It further undergoes phase transformations at ˜8.5 and ˜11 GPa; eventually evolving to a disordered phase beyond 14-15 GPa in agreement with our earlier Raman studies. On release of pressure from 18.5 GPa, the compound transforms back to the initial tetragonal phase.

  11. Oleanolic acid alleviated pressure overload-induced cardiac remodeling.

    PubMed

    Liao, Hai-Han; Zhang, Nan; Feng, Hong; Zhang, Ning; Ma, Zhen-Guo; Yang, Zheng; Yuan, Yuan; Bian, Zhou-Yan; Tang, Qi-Zhu

    2015-11-01

    Previous study has demonstrated that oleanolic acid (OA) possessing the anti-inflammatory and anti-oxidant properties blunted high-glucose-induced diabetic cardiomyopathy and ameliorated experimental autoimmune myocarditis in mice. However, little is known about its effects on pressure overload-induced cardiac remodeling. Herein, we investigated the effect of OA on cardiac remodeling and underlying mechanism. Mice, subjected to aortic banding (AB), were randomly assigned into control group and experimental group. OA premixed in diets was administered to mice after 3 days of AB. Echocardiography and catheter-based measurements of hemodynamic parameters were performed after 8 weeks' treatment of OA. Histologic examination and molecular analyses were used to assess cardiac hypertrophy and tissue fibrosis. In addition, the inhibitory effects of OA on H9c2 cardiomyocytes and cardiac primary fibroblast responded to the stimulation of AngII were also investigated. OA ameliorated the systolic and diastolic dysfunction induced by pressure overload evidenced by echocardiography and catheter-based measurements. OA also decreased the mRNA expression of cardiac hypertrophy and fibrosis markers evidenced by RT-PCR. It has been shown in our study that pressure overload activated the phosphorylations of Akt, mTOR, p70s6k, S6, GSK3β, and FoxO3a, and treatment of OA attenuated the phosphorylation of these proteins. In addition, hypertrophy of cardiomyocytes and fibrosis markers induced by AngII was inhibited by OA in vitro. Our findings uncover that OA suppressed AB-induced cardiac hypertrophy, partly by inhibiting the activity of Akt/mTOR pathway, and suggest that treatment of OA may have a benefit on retarding the progress of cardiac remodeling under long terms of pressure overload. PMID:26215454

  12. Dominance of the forward compression wave in determining pulsatile components of blood pressure: similarities between inotropic stimulation and essential hypertension.

    PubMed

    Fok, Henry; Guilcher, Antoine; Brett, Sally; Jiang, Benyu; Li, Ye; Epstein, Sally; Alastruey, Jordi; Clapp, Brian; Chowienczyk, Phil

    2014-11-01

    Pulsatile components of blood pressure may arise from forward (ventricular generated) or backward wave travel in the arterial tree. The objective of this study was to determine the relative contributions of forward and backward waves to pulsatility. We used wave intensity and wave separation analysis to determine pulsatile components of blood pressure during inotropic and vasopressor stimulation by dobutamine and norepinephrine in normotensive subjects and compared pulse pressure components in hypertensive (mean±SD, 48.8±11.3 years; 165±26.6/99±14.2 mm Hg) and normotensive subjects (52.2±12.6 years; 120±14.2/71±8.2 mm Hg). Dobutamine (7.5 μg/kg per minute) increased the forward compression wave generated by the ventricle and increased pulse pressure from 36.8±3.7 to 59.0±3.4 mm Hg (mean±SE) but had no significant effect on mean arterial pressure or the midsystolic backward compression wave. By contrast, norepinephrine (50 ng/kg per minute) had no significant effect on the forward compression wave but increased the midsystolic backward compression wave. Despite this increase in the backward compression wave, and an increase in mean arterial pressure, norepinephrine increased central pulse pressure less than dobutamine (increases of 22.1±3.8 and 7.2±2.8 mm Hg for dobutamine and norepinephrine, respectively; P<0.02). An elevated forward wave component (mean±SE, 50.4±3.4 versus 35.2±1.8 mm Hg, in hypertensive and normotensive subjects, respectively; P<0.001) accounted for approximately two thirds of the total difference in central pulse pressures between hypertensive and normotensive subjects. Increased central pulse pressure during inotropic stimulation and in essential hypertension results primarily from the forward compression wave.

  13. 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.

  14. Kinetic model of ionization waves in a positive column at intermediate pressures in inert gases

    NASA Astrophysics Data System (ADS)

    Golubovskii, Yu. B.; Maiorov, V. A.; Nekutchaev, V. O.; Behnke, J.; Behnke, J. F.

    2001-03-01

    A kinetic model of ionization waves in the inert gas discharge is constructed, which is based on the simultaneous solution of the kinetic equation for electrons and the continuity equations for ions and excited atoms. The model corresponds to a range of intermediate pressures and small currents, when elastic collisions dominate in the electron energy balance and electron-electron collisions are negligibly small. A linear theory of ionization waves is constructed, growth rates and frequencies of wave disturbances able to propagate in plasma are found. It is shown that there is an upper bound to the existence of striations by pressure, as well as the lower bound by current. The self-consistent solution of the source system of equations is obtained, which describes a nonlinear wave. The profile of electric field and the electron distribution function in this field are calculated. The results of calculations are compared with the experimental data. The wavelengths obtained are essentially larger than the electron energy relaxation length. Such waves cannot be described within the limits of fluid models.

  15. 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

  16. Pressure-induced activity loss in solid state catalase.

    PubMed

    Wurster, D E; Ternik, R L

    1995-02-01

    The pressure-induced reductions in the activities of a number of enzymes in the solution state, and more recently in the solid state, have been reported. To further investigate the effect of pressure on proteins in the solid state, the enzyme catalase was used as a model. Compacts containing 150.0 +/- 0.2 mg of catalase powder were prepared on instrumented laboratory presses using various compaction pressures between 0 and 669 MPa. After compaction, a spectrophotometric assay was utilized to determine the pseudo-first-order rate constants for the catalase-catalyzed decomposition of hydrogen peroxide. These rate constants were used to calculate the change in catalase activity. Results indicated a loss in catalase activity of up to 30% at compaction pressures of 251 MPa or greater. While the mechanism which produces the loss of enzyme activity is not clear, a strong linear correlation between enzyme activity and compaction pressure was seen over the range of pressures (0-251 MPa) where the decrease in activity occurred. In addition, compact densities were calculated and correlated to enzyme activity values. This correlation did not appear to be as strong. PMID:7738799

  17. Ventricular size and isotope cisternography in patients with acute transient rises of intracranial pressure (plateau waves)

    SciTech Connect

    Hayashi, M.; Kobayashi, H.; Fujii, H.; Yamamoto, S.

    1982-12-01

    The size of the ventricular system and cerebrospinal fluid (CSF) flow were determined in 17 patients with plateau waves, using computerized tomography (CT) and isotope cisternography. Some patients had increased intracranial pressure (ICP) resulting from space-occupying lesions and other causes, and some had normal ICP observed in normal-pressure hydrocephalus. The size and shape of the ventricular system during plateau wave phases as ascertained by CT showed little or no change as compared with its size and shape during the interval phases between two waves. It was also noticed that, in patients with supratentorial masses, the midline shift showed no difference in degree between the two phases. These findings suggest that there is little change in the intracranial CSF volume between the two phases, that is, there is little compensatory outflow of the intracranial CSF for the ICP variations. These results may also support the assumption that the plateau waves are not caused by an intermittent obstruction of the CSF pathways. Isotope cisternography showed a marked delay of clearance of radioactivity from the intracranial CSF in 15 patients. The cisternographic pattern in patients with increased ICP and the absence of ventricular dilatation demonstrated an abnormally large accumulation of radioactivity over the cerebral convexities, and the pattern in patients with normal-pressure hydrocephalus showed complete obstruction of the subarachnoid space over both cerebral convexities. These observations suggest that, in patients with plateau waves, there is a marked delay in CSF absorption. The authors postulate that the reduction of CSF absorption may create a critically tight condition within the cranial cavity and act as a contributory factor in the development of the plateau waves.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. Pressure wave measurements from thermal cook-off of an HMX based high explosive

    SciTech Connect

    Forbes, J W; Tarver, C M; Urtiew, P A; Garcia, F; Greenwood, D W; Vandersall, K S

    2000-10-10

    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 pressure wave and how this wave propagates in this adjacent material. The output pulse from the thermal cook-off explosive containing fixture is of obvious interest for assessing many scenarios.

  4. Pressure Wave Measurements from Thermal Cook-off of an HMX Based Explosive

    SciTech Connect

    Forbes, J W; Tarver, C M; Urtiew, P A; Garcia, F; Greenwood, D W; Vandersall, K S

    2001-05-09

    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 pressure wave and how this wave propagates in this adjacent material. The output pulse from the thermal cook-off explosive containing fixture is of obvious interest for assessing many scenarios.

  5. Pressure Wave Measurements from Thermal Cook-Off of an HMX Based High Explosive PBX 9501

    SciTech Connect

    Garcia, F; Forbes, J W; Tarver, C M; Urtiew, P A; Greenwood, D W; Vandersall, K S

    2001-05-31

    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 pressure wave and how this wave propagates in this adjacent material. The output pulse from the thermal cook-off explosive containing fixture is of obvious interest for assessing many scenarios.

  6. Wave propagation with different pressure signals: an experimental study on the latex tube.

    PubMed

    Ursino, M; Artioli, E; Gallerani, M

    1993-07-01

    To have deeper insight into the main factors affecting wave propagation in real hydraulic lines, we measured the true propagation coefficient in two latex rubber tubes via the three-point pressure method. The measurements were performed using both sinusoidal pressure signals of different amplitudes and periodic square waves as well as aperiodic pressure 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 pressure 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 wave attenuation. Finally, increasing the amplitude of pressure changes significantly affects the measured value of the propagation coefficient, especially at those frequencies for which direct and reflected waves 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.

  7. Wave propagation with different pressure signals: an experimental study on the latex tube.

    PubMed

    Ursino, M; Artioli, E; Gallerani, M

    1993-07-01

    To have deeper insight into the main factors affecting wave propagation in real hydraulic lines, we measured the true propagation coefficient in two latex rubber tubes via the three-point pressure method. The measurements were performed using both sinusoidal pressure signals of different amplitudes and periodic square waves as well as aperiodic pressure 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 pressure 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 wave attenuation. Finally, increasing the amplitude of pressure changes significantly affects the measured value of the propagation coefficient, especially at those frequencies for which direct and reflected waves 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

  8. Radial energy transport by magnetospheric ULF waves: Effects of magnetic curvature and plasma pressure

    NASA Technical Reports Server (NTRS)

    Kouznetsov, Igor; Lotko, William

    1995-01-01

    The 'radial' transport of energy by internal ULF waves, 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 pressure. The radial mode structure of the coupled fast and intermediate MHD waves is determined by numerical solution of the inhomogeneous wave equation; the parallel mode structure is characterized by a Wentzel-Kramer-Brillouin (WKB) approximation. Ionospheric dissipation is modeled by allowing the parallel wave 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 pressure 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 wave 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 wave, 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 wave occurs between the location of its (field line) resonance and that of the

  9. 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('https://www.ncbi.nlm.nih.gov/pubmed/26541468','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26541468"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> phase transition in CrO2.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Alptekin, Sebahaddin</p> <p>2015-12-01</p> <p>The ab initio constant <span class="hlt">pressure</span> molecular dynamics technique and density functional theory with generalized gradient approximation (GGA) was used to study the <span class="hlt">pressure-induced</span> 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 <span class="hlt">pressure</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26574522','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26574522"><span id="translatedtitle">Carbon dioxide <span class="hlt">pressure-induced</span> coagulation of microalgae.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, Roland; Jessop, Philip G; Champagne, Pascale</p> <p>2015-12-28</p> <p>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-<span class="hlt">pressure</span> gas without the addition of coagulants. Coagulation of microalgae under high-<span class="hlt">pressure</span> gas was found to be an efficient method to separate algae from suspension. The critical coagulation <span class="hlt">pressures</span> (CCPs) for H(2) and CO(2) were determined to be 6.1 and 6.2 MPa, respectively. The CO(2)-<span class="hlt">induced</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26574522','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26574522"><span id="translatedtitle">Carbon dioxide <span class="hlt">pressure-induced</span> coagulation of microalgae.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, Roland; Jessop, Philip G; Champagne, Pascale</p> <p>2015-12-28</p> <p>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-<span class="hlt">pressure</span> gas without the addition of coagulants. Coagulation of microalgae under high-<span class="hlt">pressure</span> gas was found to be an efficient method to separate algae from suspension. The critical coagulation <span class="hlt">pressures</span> (CCPs) for H(2) and CO(2) were determined to be 6.1 and 6.2 MPa, respectively. The CO(2)-<span class="hlt">induced</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27376406','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27376406"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> exotic states in rare earth hexaborides.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sun, Liling; Wu, Qi</p> <p>2016-08-01</p> <p>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-<span class="hlt">pressure</span> and high-<span class="hlt">pressure</span> 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 <span class="hlt">pressure</span> has the capability of tuning the electronic structure and modifying the ground state of solids, or even <span class="hlt">inducing</span> 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 <span class="hlt">pressure</span> studies on the RB6 based on our knowledge and research interests, mainly focusing on the <span class="hlt">pressure-induced</span> 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-<span class="hlt">pressure</span> results obtained from CeB6 and EuB6 are also included. Finally, a summary is given in the conclusions and perspectives section. PMID:27376406</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JChPh.138i4506T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JChPh.138i4506T"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> phase transition and polymerization of tetracyanoethylene (TCNE)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tomasino, Dane; Chen, Jing-Yin; Kim, Minesob; Yoo, Choong-Shik</p> <p>2013-03-01</p> <p>We have studied the <span class="hlt">pressure-induced</span> physical and chemical transformations of tetracyanoethylene (TCNE or C6N4) in diamond anvil cells using micro-Raman spectroscopy, laser-heating, emission spectroscopy, and synchrotron x-ray diffraction. The results indicate that TCNE in a quasi-hydrostatic condition undergoes a shear-<span class="hlt">induced</span> phase transition at 10 GPa and then a chemical change to two-dimensional (2D) C=N polymers above 14 GPa. These phase and chemical transformations depend strongly on the state of stress in the sample and occur sluggishly in non-hydrostatic conditions over a large <span class="hlt">pressure</span> range between 7 and 14 GPa. The x-ray diffraction data indicate that the phase transition occurs isostructurally within the monoclinic structure (P21/c) without any apparent volume discontinuity and the C=N polymer is highly disordered but remains stable to 60 GPa—the maximum <span class="hlt">pressure</span> studied. On the other hand, laser-heating of the C=N polymer above 25 GPa further converts to a theoretically predicted 3D C-N network structure, evident from an emergence of new Raman νs(C-N) at 1404 cm-1 at 25 GPa and the visual appearance of translucent solid. The C-N product is, however, unstable upon <span class="hlt">pressure</span> unloading below 10 GPa, resulting in a grayish powder that can be considered as nano-diamonds with high-nitrogen content at ambient <span class="hlt">pressure</span>. The C-N product shows a strong emission line centered at 640 nm at 30 GPa, which linearly shifts toward shorter wavelength at the rate of -1.38 nm/GPa. We conjecture that the observed red shift upon unloading <span class="hlt">pressure</span> is due to increase of defects in the C-N product and thereby weakening of C-N bonds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016RPPh...79h4503S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016RPPh...79h4503S"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> exotic states in rare earth hexaborides</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Liling; Wu, Qi</p> <p>2016-08-01</p> <p>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-<span class="hlt">pressure</span> and high-<span class="hlt">pressure</span> 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 <span class="hlt">pressure</span> has the capability of tuning the electronic structure and modifying the ground state of solids, or even <span class="hlt">inducing</span> 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 <span class="hlt">pressure</span> studies on the RB6 based on our knowledge and research interests, mainly focusing on the <span class="hlt">pressure-induced</span> 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-<span class="hlt">pressure</span> results obtained from CeB6 and EuB6 are also included. Finally, a summary is given in the conclusions and perspectives section.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25535360','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25535360"><span id="translatedtitle">Transdermal deferoxamine prevents <span class="hlt">pressure-induced</span> diabetic ulcers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Duscher, Dominik; Neofytou, Evgenios; Wong, Victor W; Maan, Zeshaan N; Rennert, Robert C; Inayathullah, Mohammed; Januszyk, Michael; Rodrigues, Melanie; Malkovskiy, Andrey V; Whitmore, Arnetha J; Walmsley, Graham G; 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4291638','PMC'); return false;" href="https://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.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 PAGES</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/abs/2016JPhCS.705a2029A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.705a2029A"><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="https://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> </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_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" 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_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> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27182751','PUBMED'); return false;" href="https://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="https://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>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18378271','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18378271"><span id="translatedtitle">Shock <span class="hlt">wave</span> emission from laser-<span class="hlt">induced</span> cavitation bubbles in polymer solutions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brujan, Emil-Alexandru</p> <p>2008-09-01</p> <p>The role of extensional viscosity on the acoustic emission from laser-<span class="hlt">induced</span> cavitation bubbles in polymer solutions and near a rigid boundary is investigated by acoustic measurements. The polymer solutions consist of a 0.5% polyacrylamide (PAM) aqueous solution with a strong elastic component and a 0.5% carboxymethylcellulose (CMC) aqueous solution with a weak elastic component. A reduction of the maximum amplitude of the shock <span class="hlt">wave</span> <span class="hlt">pressure</span> and a prolongation of the oscillation period of the bubble were found in the elastic PAM solution. It might be caused by an increased resistance to extensional flow which is conferred upon the liquid by the polymer additive. In both polymer solutions, however, the shock <span class="hlt">pressure</span> decays proportionally to r(-1) with increasing distance r from the emission centre.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JTST...20..866K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JTST...20..866K"><span id="translatedtitle">Shock-<span class="hlt">Wave-Induced</span> Spraying: Modeling and Physics of a New Spray Process</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karimi, Mo; Jodoin, Bertrand; Rankin, Gary</p> <p>2011-06-01</p> <p>A two-dimensional axisymmetric transient model for the shock-<span class="hlt">wave-induced</span> spraying process (SISP) is developed. SISP is a new cold spray process used to apply coatings of various metallic materials onto a wide range of different substrates. The model is validated with reference to a simplified one-dimensional approximation of the flow field. The model solves equations for mass, momentum, energy, ideal-gas law, as well as turbulence. The valve is represented as a ball-seat-type valve. The results are presented as contours of flow variables in a space-time domain. Values of <span class="hlt">pressure</span>, axial velocity, Mach number, as well as static and total temperature are examined. The effects of varying supply <span class="hlt">pressure</span> and temperature on these flow variables are investigated in detail. Additionally, air and helium are compared as the driving gas.</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://adsabs.harvard.edu/abs/2013JMiMi..23h5018K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JMiMi..23h5018K"><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://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://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.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('https://www.ncbi.nlm.nih.gov/pubmed/23232414','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23232414"><span id="translatedtitle">Shear <span class="hlt">wave</span> <span class="hlt">induced</span> resonance elastography of venous thrombi: a proof-of-concept.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schmitt, Cédric; Montagnon, Emmanuel; Henni, Anis Hadj; Qi, Shijie; Cloutier, Guy</p> <p>2013-03-01</p> <p>Shear <span class="hlt">wave</span> <span class="hlt">induced</span> resonance elastography (SWIRE) is proposed for deep venous thrombosis (DVT) elasticity assessment. This new imaging technique takes advantage of properly polarized shear <span class="hlt">waves</span> to <span class="hlt">induce</span> resonance of a confined mechanical heterogeneity. Realistic phantoms (n = 9) of DVT total and partial clot occlusions with elasticities from 406 to 3561 Pa were built for in vitro experiments. An ex vivo study was also performed to evaluate the elasticity of two fresh porcine venous thrombi in a pig model. Transient shear <span class="hlt">waves</span> at 45-205 Hz were generated by the vibration of a rigid plate (plane wavefront) or by a needle to simulate a radiation <span class="hlt">pressure</span> on a line segment (cylindrical wavefront). <span class="hlt">Induced</span> propagation of shear <span class="hlt">waves</span> was imaged with an ultrafast ultrasound scanner and a finite element method was developed to simulate tested experimental conditions. An inverse problem was then formulated considering the first resonance frequency of the DVT inclusion. Elasticity agreements between SWIRE and a reference spectroscopy instrument (RheoSpectris) were found in vitro for total clots either in plane (r(2) = 0.989) or cylindrical (r(2) = 0.986) wavefront configurations. For total and partial clots, elasticity estimation errors were 9.0 ±4.6% and 9.3 ±11.3%, respectively. Ex vivo, the blood clot elasticity was 498 ±58 Pa within the inferior vena cava and 436 ±45 Pa in the right common iliac vein (p = 0.22). To conclude, the SWIRE technique seems feasible to quantitatively assess blood clot elasticity in the context of DVT ultrasound imaging.</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://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="https://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/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/abs/2008AIPC..975.1492C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AIPC..975.1492C"><span id="translatedtitle">Ultrasonic Guided <span class="hlt">Waves</span> for Health Monitoring of High <span class="hlt">Pressure</span> Composite Tanks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Castaings, M.; Hosten, B.</p> <p>2008-02-01</p> <p>Ultrasonic guided <span class="hlt">wave</span> modes are proposed to control the integrity of high-<span class="hlt">pressure</span> composite tanks produced by EADS—ASTRIUM, France. The purpose is to demonstrate the potentiality of air-coupled transducers to set-up a contact-less, single-sided technique for testing the moisture content and/or the micro-cracking of carbon epoxy composite wound around a Titanium liner.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19720026553&hterms=types+waves&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dtypes%2Bwaves','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19720026553&hterms=types+waves&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dtypes%2Bwaves"><span id="translatedtitle">The vibration of a box-type structure. II - Response to a travelling <span class="hlt">pressure</span> <span class="hlt">wave</span>.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Popplewell, N.</p> <p>1971-01-01</p> <p>A finite element method is formulated for determining the transient response of a box-type structure to a traveling, arbitrarily shaped <span class="hlt">pressure</span> <span class="hlt">wave</span>. The method is illustrated by considering an example of practical concern - the sonic boom. The acceleration-time histories of a closed box are compared with those obtained experimentally from a simulated boom. Satisfactory agreement is obtained with only four rectangular elements per individual face and a simplified loading of the box.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21466521','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21466521"><span id="translatedtitle">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://www.osti.gov/scitech">SciTech Connect</a></p> <p>Guzatov, D V; Gaida, L S; Afanas'ev, Anatolii A</p> <p>2008-12-31</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>. (light <span class="hlt">pressure</span>)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25658240','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25658240"><span id="translatedtitle">Black tea lowers blood <span class="hlt">pressure</span> and <span class="hlt">wave</span> reflections in fasted and postprandial conditions in hypertensive patients: a randomised study.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Grassi, Davide; Draijer, Richard; Desideri, Giovambattista; Mulder, Theo; Ferri, Claudio</p> <p>2015-02-04</p> <p>Hypertension and arterial stiffening are independent predictors of cardiovascular mortality. Flavonoids may exert some vascular protection. We investigated the effects of black tea on blood <span class="hlt">pressure</span> (BP) and <span class="hlt">wave</span> reflections before and after fat load in hypertensives. According to a randomized, double-blind, controlled, cross-over design, 19 patients were assigned to consume black tea (129 mg flavonoids) or placebo twice a day for eight days (13 day wash-out period). Digital volume pulse and BP were measured before and 1, 2, 3 and 4 h after tea consumption. Measurements were performed in a fasted state and after a fat load. Compared to placebo, reflection index and stiffness index decreased after tea consumption (p<0.0001). Fat challenge increased <span class="hlt">wave</span> reflection, which was counteracted by tea consumption (p<0.0001). Black tea decreased systolic and diastolic BP (-3.2 mmHg, p<0.005 and -2.6 mmHg, p<0.0001; respectively) and prevented BP increase after a fat load (p<0.0001). Black tea consumption lowers <span class="hlt">wave</span> reflections and BP in the fasting state, and during the challenging haemodynamic conditions after a fat load in hypertensives. Considering lipemia-<span class="hlt">induced</span> impairment of arterial function may occur frequently during the day, our findings suggest regular consumption of black tea may be relevant for cardiovascular protection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25322237','PUBMED'); return false;" href="https://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="https://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.</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="https://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> </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.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="https://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.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="https://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.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="https://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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4286758','PMC'); return false;" href="https://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('https://www.ncbi.nlm.nih.gov/pubmed/25567430','PUBMED'); return false;" href="https://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="https://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.</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://adsabs.harvard.edu/abs/2000JPCM...12.4417S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000JPCM...12.4417S"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> amorphization and orientational disorder in potash alum</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sakuntala, T.; Arora, Akhilesh K.; Shekar, N. V. Chandra; Sahu, P. Ch</p> <p>2000-05-01</p> <p><span class="hlt">Pressure-induced</span> amorphization in potassium aluminium sulphate dodecahydrate (potash alum) has been studied using Raman spectroscopy in a diamond anvil cell up to a <span class="hlt">pressure</span> of 15 GPa. In potash alum, some of the sulphate ions are misoriented with their S-O bond pointing towards potassium rather than aluminium, leading to an `orientational disorder' which ranges from 10 to 24% at ambient conditions. The disorder is quantified from the intensities of the Raman lines characteristic of the two orientations. The samples with low initial disorder exhibit a sequence of two structural phase transitions occurring at 1.5 and 9 GPa respectively. The phase above 1.5 GPa, which could be <span class="hlt">pressure</span> quenched to ambient conditions, is found to be free from orientational disorder. On the other hand, in the samples with high initial disorder, the disorder is found to grow as a function of <span class="hlt">pressure</span> and beyond a critical value the system turns amorphous, which is confirmed from the disappearance of sharp diffraction peaks. In view of these results it is apparent that the orientational disorder is the driving mechanism of amorphization in potash alum. The different initial disorders in different samples are believed to arise from a combination of a dynamic disorder (equilibrium) and a static disorder arising from the defects. This defect could possibly be a missing molecule in the water octahedra around the potassium ion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3341048','PMC'); return false;" href="https://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('https://www.ncbi.nlm.nih.gov/pubmed/26736997','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26736997"><span id="translatedtitle">A new approach to generate arbitrary pulsatile <span class="hlt">pressure</span> <span class="hlt">wave</span> forms in mechanical circulatory support systems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Aghababaei, Amin; Hexamer, Martin</p> <p>2015-01-01</p> <p>Pulsatile <span class="hlt">pressure</span>/flow <span class="hlt">wave</span> forms reproduction of blood in mechanical circulatory systems are still an open topic. Regarding the periodic behavior of pulsatile hemodynamics, a repetitive control algorithm was adopted as a potential methodology for rotary blood pumps. The developed algorithm was tested on a mock system including an oxygenator, a resistance, and a compliance. The post-oxygenator <span class="hlt">pressure</span> served as the feedback of the control system. Initially, a model of the whole system was developed in order to use repetitive control algorithm. Then the performance of the developed algorithm was evaluated in three different scenarios. The experimental results indicated that the proposed method was able to accurately reproduce any pattern of pulsatile <span class="hlt">pressure</span>. Moreover, it demonstrated an acceptable robustness in terms of model uncertainty and nonlinearity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15002349','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15002349"><span id="translatedtitle"><span class="hlt">Pressure</span> <span class="hlt">Wave</span> Measurements During Thermal Explosion of HMX-Based High Explosives</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Forbes, J W; Garcia, F; Tarver, C M; Urtiew, P A; Greenwood, D W; Vandersall, K S</p> <p>2002-06-27</p> <p>Five different experiments on thermal heating of explosive materials have been performed. Three experiments thermally exploded PBX 9501 (HMX/Estane/BDNPA-F; 9512.512.5 wt %) donor charges while two others thermally exploded LX-04 (HMX/Viton A; 85/15 wt %). These donor charges were encased in 304 stainless steel. The transmitted two-dimensional <span class="hlt">pressure</span> <span class="hlt">waves</span> were measured by gauges in acceptor cylinders of Teflon, PBX 9501, or LX-04 that were in contact with the donors' steel case. A fifth experiment measured the <span class="hlt">pressure</span> in an acceptor charge of PBX 9501 that had a 100 mm stand-off from the top of the steel case of the thermally cooked off PBX 9501 donor charge. Reactive flow hydrodynamic modeling using a rapid deflagration velocity of approximately 500 m/s was able to reproduce the <span class="hlt">pressure</span> gauge records for both the in contact and stand off experiments that used PBX 9501 donors and acceptors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4974634','PMC'); return false;" href="https://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/2016NatSR...630856D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...630856D"><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="https://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=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> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMNH23B1623S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMNH23B1623S"><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://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('https://www.ncbi.nlm.nih.gov/pubmed/8798264','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8798264"><span id="translatedtitle">Bisferiens peaks in the radial artery <span class="hlt">pressure</span> <span class="hlt">wave</span> during patent ductus arteriosus in newborn infants: relationship with ascending aortic flow.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gevers, M; van der Mooren, K; Stergiopulos, N; Van Genderingen, H R; Lafeber, H N; Hack, W W; Westerhof, N</p> <p>1996-07-01</p> <p>Previously, we found evidence that bisferiens peaks in the radial artery <span class="hlt">pressure</span> <span class="hlt">wave</span> in the newborn infant may suggest the presence of a left-to-right shunt through a patent ductus arteriosus (PDA). The purpose of the present study was to analyze the origin of this pulsus bisferiens. Starting from the assumption that the radial artery <span class="hlt">pressure</span> <span class="hlt">wave</span> form is similar to the aortic <span class="hlt">pressure</span> <span class="hlt">wave</span> form, as described previously, we attempted to explain the bisferiens peaks on the basis of echocardiographically obtained ascending aortic flow. We studied 11 preterm mechanically ventilated infants with a left-to-right shunt through a PDA and 7 without. Aortic volume flow was established echocardiographically, and radial artery blood <span class="hlt">pressure</span> measurement was performed with a high fidelity cathetermanometer system. Ascending aortic peak flow during PDA was significantly higher in the case of PDA, compared with the case without PDA. An augmented peak flow with an abrupt decline after the high peak in PDA, resulting in a sharp <span class="hlt">pressure</span> peak with a steep decline after the peak, was thought to explain the first sharp peak of pulsus bisferiens. An abrupt decline of flow after peak flow is thought to be due to the fast runoff of blood through the ductus. According to the pulsatile <span class="hlt">pressure</span> dynamics theories, which state that <span class="hlt">pressure</span> <span class="hlt">wave</span> forms consist of forward and backward <span class="hlt">wave</span> forms, the second peak of the pulsus bisferiens can be explained by the return of the reflected (backward) <span class="hlt">wave</span> form when the forward <span class="hlt">wave</span> form has already considerably decreased. We conclude that the bisferiens peaks found in PDA result from a combination of large stroke volume (augmented first peak) and large runoff (quick decline of the forward <span class="hlt">wave</span>) before the return of the reflected <span class="hlt">wave</span>.</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://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://adsabs.harvard.edu/abs/2015ExFl...56...93Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ExFl...56...93Y"><span id="translatedtitle">Application of background-oriented schlieren (BOS) technique to a laser-<span class="hlt">induced</span> underwater 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>Yamamoto, Shota; Tagawa, Yoshiyuki; Kameda, Masaharu</p> <p>2015-05-01</p> <p>An ultra-high-speed imaging system based on the background-oriented schlieren (BOS) technique has been built in order to capture a laser-<span class="hlt">induced</span> underwater shock <span class="hlt">wave</span>. This BOS technique is able to provide two-dimensional density-gradient field of fluid and requires a simple setup. The imaging system consists of an ultra-high-speed video camera, a laser stroboscope, and a patterned background. This system takes images every . Furthermore, since the density change of water disturbed by the shock is exceedingly small, the system has high spatial resolution . Using this BOS system, temporal position of a shock <span class="hlt">wave</span> is examined. The position agrees well with that measured by conventional shadowgraph, which indicates that the high-speed imaging system can successfully capture the instantaneous position of the underwater shock <span class="hlt">wave</span> that propagates with the speed of about 1500 m/s. The local density gradient can be determined up to , which is confirmed by the gradient estimated from the <span class="hlt">pressure</span> time history measured by a hydrophone.</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('https://www.ncbi.nlm.nih.gov/pubmed/24812515','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24812515"><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="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</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/m(2), 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24812515','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24812515"><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="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</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/m(2), 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/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://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://www.ncbi.nlm.nih.gov/pubmed/27369159','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27369159"><span id="translatedtitle">Analytical analysis of slow and fast <span class="hlt">pressure</span> <span class="hlt">waves</span> in a two-dimensional cellular solid with fluid-filled cells.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dorodnitsyn, Vladimir; Van Damme, Bart</p> <p>2016-06-01</p> <p><span class="hlt">Wave</span> propagation in cellular and porous media is widely studied due to its abundance in nature and industrial applications. Biot's theory for open-cell media predicts the existence of two simultaneous <span class="hlt">pressure</span> <span class="hlt">waves</span>, distinguished by its velocity. A fast <span class="hlt">wave</span> travels through the solid matrix, whereas a much slower <span class="hlt">wave</span> is carried by fluid channels. In closed-cell materials, the slow <span class="hlt">wave</span> disappears due to a lack of a continuous fluid path. However, recent finite element (FE) simulations done by the authors of this paper also predict the presence of slow <span class="hlt">pressure</span> <span class="hlt">waves</span> in saturated closed-cell materials. The nature of the slow <span class="hlt">wave</span> is not clear. In this paper, an equivalent unit cell of a medium with square cells is proposed to permit an analytical description of the dynamics of such a material. A simplified FE model suggests that the fluid-structure interaction can be fully captured using a wavenumber-dependent spring support of the vibrating cell walls. Using this approach, the <span class="hlt">pressure</span> <span class="hlt">wave</span> behavior can be calculated with high accuracy, but with less numerical effort. Finally, Rayleigh's energy method is used to investigate the coexistence of two <span class="hlt">waves</span> with different velocities. PMID:27369159</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22505642','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22505642"><span id="translatedtitle">Cyclooxygenase inhibition augments central blood <span class="hlt">pressure</span> and aortic <span class="hlt">wave</span> reflection in aging humans.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Barnes, Jill N; Casey, Darren P; Hines, Casey N; Nicholson, Wayne T; Joyner, Michael J</p> <p>2012-06-15</p> <p>The augmentation index and central blood <span class="hlt">pressure</span> increase with normal aging. Recently, cyclooxygenase (COX) inhibitors, commonly used for the treatment of pain, have been associated with transient increases in the risk of cardiovascular events. We examined the effects of the COX inhibitor indomethacin (Indo) on central arterial hemodynamics and <span class="hlt">wave</span> reflection characteristics in young and old healthy adults. High-fidelity radial arterial <span class="hlt">pressure</span> waveforms were measured noninvasively by applanation tonometry before (control) and after Indo treatment in young (25 ± 5 yr, 7 men and 6 women) and old (64 ± 6 yr, 5 men and 6 women) subjects. Aortic systolic (control: 115 ± 3 mmHg vs. Indo: 125 ± 5 mmHg, P < 0.05) and diastolic (control: 74 ± 2 mmHg vs. Indo: 79 ± 3 mmHg, P < 0.05) <span class="hlt">pressures</span> were elevated after Indo treatment in older subjects, whereas only diastolic <span class="hlt">pressure</span> was elevated in young subjects (control: 71 ± 2 mmHg vs. Indo: 76 ± 1 mmHg, P < 0.05). Mean arterial <span class="hlt">pressure</span> increased in both young and old adults after Indo treatment (P < 0.05). The aortic augmentation index and augmented <span class="hlt">pressure</span> were elevated after Indo treatment in older subjects (control: 30 ± 5% vs. Indo 36 ± 6% and control 12 ± 1 mmHg vs. Indo: 18 ± 2 mmHg, respectively, P < 0.05), whereas pulse <span class="hlt">pressure</span> amplification decreased (change: 8 ± 3%, P < 0.05). In addition, older subjects had a 61 ± 11% increase in wasted left ventricular energy after Indo treatment (P < 0.05). In contrast, young subjects showed no significant changes in any of the variables of interest. Taken together, these results demonstrate that COX inhibition with Indo unfavorably increases central <span class="hlt">wave</span> reflection and augments aortic <span class="hlt">pressure</span> in old but not young subjects. Our results suggest that aging individuals have a limited ability to compensate for the acute hemodynamic changes caused by systemic COX inhibition.</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('https://www.ncbi.nlm.nih.gov/pubmed/18835205','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18835205"><span id="translatedtitle">Continuous-<span class="hlt">wave</span> far-infrared ESR spectrometer for high-<span class="hlt">pressure</span> measurements.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Náfrádi, Bálint; Gaál, Richárd; Sienkiewicz, Andrzej; Fehér, Titusz; Forró, László</p> <p>2008-12-01</p> <p>We present a newly-developed microwave probe for performing sensitive high-field/multi-frequency electron spin resonance (ESR) measurements under high hydrostatic <span class="hlt">pressures</span>. The system consists of a BeCu-made <span class="hlt">pressure</span>-resistant vessel, which accommodates the investigated sample and a diamond microwave coupling window. The probe's interior is completely filled with a <span class="hlt">pressure</span>-transmitting fluid. The setup operates in reflection mode and can easily be assembled with a standard oversized microwave circuitry. The probe-head withstands hydrostatic <span class="hlt">pressures</span> up to 1.6 GPa and interfaces with our home-built quasi-optical high-field ESR facility, operating in a millimeter/submillimeter frequency range of 105-420 GHz and in magnetic fields up to 16 T. The overall performance of the probe was tested, while studying the <span class="hlt">pressure-induced</span> changes in the spin-relaxation mechanisms of a quasi-1D conducting polymer, KC(60). The preliminary measurements revealed that the probe yields similar signal-to-noise ratio to that of commercially available low-frequency ESR spectrometers. Moreover, by observing the conduction electron spin resonance (CESR) linewidth broadening for KC(60) in an unprecedented microwave frequency range of 210-420 GHz and in the <span class="hlt">pressure</span> range of up to 1.6 GPa, we demonstrate that a combination of high-<span class="hlt">pressure</span> ESR probe and high-field/multi-frequency spectrometer allows us to measure the spin relaxation rates in conducting spin systems, like the quasi-1D conductor, KC(60).</p> </li> <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="https://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('https://www.ncbi.nlm.nih.gov/pubmed/26302781','PUBMED'); return false;" href="https://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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4548189','PMC'); return false;" href="https://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://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://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/1984spte.symp.1625Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1984spte.symp.1625Y"><span id="translatedtitle">Deformation of drop due to radiation <span class="hlt">pressure</span> of acoustic standing <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>Yamanaka, T.; Saito, M.; Kamimura, H.</p> <p></p> <p>To investigate the deformation of a liquid drop due to radiation <span class="hlt">pressure</span> of acoustic standing <span class="hlt">waves</span>, an analytical and experimental study was carried out. An approximate axisymmetric figure of equilibrium is obtained. The experimental study was carried out in the laboratory by using a triaxial acoustic chamber. An injection syringe was placed at the center of the triaxial acoustic resonance chamber. Holding a small liquid drop at the pointed end of the syringe, deformations of the liquid drop were measured. Assuming an oblate spheroid for the deformation, the experimental results were compared with theory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996ChJOL..14...91L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996ChJOL..14...91L"><span id="translatedtitle">The <span class="hlt">wave</span> grouping effect on <span class="hlt">wave</span> forces on a vertical breakwater</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Wei-Qi; Huang, Pei-Ji</p> <p>1996-03-01</p> <p>Linear <span class="hlt">wave</span> theory and Longuet-Higgins and Steward's (1964) group-<span class="hlt">induced</span> second-order long <span class="hlt">wave</span> (GSLW) theory were used in this study on the grouping effect on <span class="hlt">wave</span> forces acting on a vertical breakwater. The calculated variance of total <span class="hlt">wave</span> <span class="hlt">pressure</span> on the vertical breakwater was closer to the measured value if the <span class="hlt">wave</span> grouping effect was considered.</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/abs/2016JPSJ...85d4703S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPSJ...85d4703S"><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://ntrs.nasa.gov/search.jsp?R=19880032560&hterms=plane+wave+spectrum&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dplane%2Bwave%2Bspectrum','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19880032560&hterms=plane+wave+spectrum&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dplane%2Bwave%2Bspectrum"><span id="translatedtitle">Vacillations <span class="hlt">induced</span> by interference of stationary and traveling planetary <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>Salby, Murry L.; Garcia, Rolando R.</p> <p>1987-01-01</p> <p>The interference pattern produced when a traveling planetary <span class="hlt">wave</span> propagates over a stationary forced <span class="hlt">wave</span> is explored, examining the interference signature in a variety of diagnostics. The <span class="hlt">wave</span> field is first restricted to a diatomic spectrum consisting of two components: a single stationary <span class="hlt">wave</span> and a single monochromatic traveling <span class="hlt">wave</span>. A simple barotropic normal mode propagating over a simple stationary plane <span class="hlt">wave</span> is considered, and closed form solutions are obtained. The <span class="hlt">wave</span> fields are then restricted spatially, providing more realistic structures without sacrificing the advantages of an analytical solution. Both stationary and traveling <span class="hlt">wave</span> fields are calculated numerically with the linearized Primitive Equations in a realistic basic state. The mean flow reaction to the fluctuating eddy forcing which results from interference is derived. Synoptic geopotential behavior corresponding to the combined <span class="hlt">wave</span> and mean flow fields is presented, and the synoptic signature in potential vorticity on isentropic surfaces is examined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ShWav..22..567H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ShWav..22..567H"><span id="translatedtitle">Numerical studies of shock focusing <span class="hlt">induced</span> by reflection of detonation <span class="hlt">waves</span> within a hemispherical implosion chamber</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hatanaka, K.; Saito, T.; Takayama, K.</p> <p>2012-11-01</p> <p>The initiation and the propagation of detonation <span class="hlt">waves</span> in a hemispherical chamber and the imploding shock <span class="hlt">waves</span> that are the reflected detonation <span class="hlt">waves</span> at the chamber wall are numerically investigated. The effects of the boundary layer and the non-uniformity of the flow field <span class="hlt">induced</span> by the detonation <span class="hlt">wave</span> on the imploding shock stability are examined. It is found that the effect of the boundary layer separation on the chamber wall has the strongest effect on the implosion focus.</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/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/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://eric.ed.gov/?q=wave+AND+interference&pg=3&id=EJ730123','ERIC'); return false;" href="http://eric.ed.gov/?q=wave+AND+interference&pg=3&id=EJ730123"><span id="translatedtitle">The Loss Spiral of Work <span class="hlt">Pressure</span>, Work-Home Interference and Exhaustion: Reciprocal Relations in a Three-<span class="hlt">Wave</span> Study</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Demerouti, Evangelia; Bakker, Arnold B.; Bulters, Annemieke J.</p> <p>2004-01-01</p> <p>This study tested the "loss spiral" hypothesis of work-home interference (WHI). Accordingly, work <span class="hlt">pressure</span> was expected to lead to WHI and exhaustion, and, vice versa, exhaustion was expected to result in more WHI and work <span class="hlt">pressure</span> over time. Results of SEM-analyses using three <span class="hlt">waves</span> of data obtained from 335 employees of an employment agency…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.8206D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.8206D"><span id="translatedtitle">Laboratory Experiment on the Non-Breaking Surface-<span class="hlt">Wave-Induced</span> Mixing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dai, Dejun; Qiao, Fangli</p> <p>2015-04-01</p> <p>Mixing <span class="hlt">induced</span> by non-breaking surface <span class="hlt">waves</span> was investigated in a <span class="hlt">wave</span> tank by measuring the thermal destratification rate of water column. One experiment without <span class="hlt">waves</span> and four experiments with <span class="hlt">waves</span> of amplitude ranging from 1.0 to 1.5 cm and wavelength from 30 to 75 cm were conducted. Water temperature variations at distances from 4 down to 12 cm were measured. In the layer from 4 to 7 cm, the originally dense isothermal lines disperse soon after the <span class="hlt">waves</span> are generated, while the vertical gradient from 9 to 12 cm is maintained for a relatively long time. The time span during which the water temperature becomes well-mixed changes from about 20 hours without the <span class="hlt">waves</span> to tens of minutes with the <span class="hlt">waves</span>, and it decreases with increasing <span class="hlt">wave</span> amplitude and wavelength. One-dimensional diffusion model with <span class="hlt">wave-induced</span> mixing parameterization shows consistent results with the measurement. The study demonstrates that the mixing <span class="hlt">induced</span> by non-breaking <span class="hlt">waves</span> may add an important contribution to the vertical mixing process in the upper ocean and suggests a way to parameterize <span class="hlt">wave-induced</span> mixing in numerical ocean models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.727a2001A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.727a2001A"><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/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://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> <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://ntrs.nasa.gov/search.jsp?R=19900054827&hterms=chromosphere&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dchromosphere','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900054827&hterms=chromosphere&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dchromosphere"><span id="translatedtitle">Lower solar chromosphere-corona transition region. II - <span class="hlt">Wave</span> <span class="hlt">pressure</span> effects for a specific form of the heating function</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Woods, D. Tod; Holzer, Thomas E.; Macgregor, Keith B.</p> <p>1990-01-01</p> <p>Lower transition region models with a balance between mechanical heating and radiative losses are expanded to include <span class="hlt">wave</span> <span class="hlt">pressure</span> effects. The models are used to study the simple damping length form of the heating function. The results are compared to the results obtained by Woods et al. (1990) for solutions in the lower transition region. The results suggest that a mixture of fast-mode and slow-mode <span class="hlt">waves</span> may provide the appropriate heating mechanism in the lower transition region, with the decline in effective vertical <span class="hlt">wave</span> speed caused by the refraction and eventual total reflection of the fast-mode <span class="hlt">wave</span> resulting from the decreasing atmospheric density.</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('https://www.ncbi.nlm.nih.gov/pubmed/24116702','PUBMED'); return false;" href="https://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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhL.109f1108X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhL.109f1108X"><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/abs/2007AIPC..955.1186O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AIPC..955.1186O"><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://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Orlikowski, Daniel; Nguyen, Jeffrey H.; Patterson, J. Reed; Minich, Roger; Martin, L. Peter; Holmes, Neil C.</p> <p>2007-12-01</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. An impedance gradient through the length of the impactor provides the <span class="hlt">pressure</span> pulse upon impact to the subject material. Applications and results are given concerning high-<span class="hlt">pressure</span> strength and the liquid-to-solid, phase transition of water giving its first associated phase fraction history. We also introduce the Korteweg-deVries-Burgers equation as a means to understand the evolution of these RWC <span class="hlt">waves</span> as they propagate through the thickness of the subject material. This model 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 possibility of quantifying dissipation, through which RWC experiments may be analyzed.</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=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://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://ntrs.nasa.gov/search.jsp?R=20020039729&hterms=Hemoglobin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DHemoglobin','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020039729&hterms=Hemoglobin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DHemoglobin"><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/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> </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/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="https://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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5053542','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5053542"><span id="translatedtitle">Intraocular <span class="hlt">Pressure</span> <span class="hlt">Induced</span> Retinal Changes Identified Using Synchrotron Infrared Microscopy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Chow, Seong Hoong; Wang, Jiang-Hui; He, Zheng; Nguyen, Christine; Lin, Tsung-Wu; Bui, Bang V.</p> <p>2016-01-01</p> <p>Infrared (IR) spectroscopy has been used to quantify chemical and structural characteristics of a wide range of materials including biological tissues. In this study, we examined spatial changes in the chemical characteristics of rat retina in response to intraocular <span class="hlt">pressure</span> (IOP) elevation using synchrotron infrared microscopy (SIRM), a non-destructive imaging approach. IOP elevation was <span class="hlt">induced</span> by placing a suture around the eye of anaesthetised rats. Retinal sections were collected onto transparent CaF2 slides 10 days following IOP elevation. Using combined SIRM spectra and chemical mapping approaches it was possible to quantify IOP <span class="hlt">induced</span> changes in protein conformation and chemical distribution in various layers of the rat retina. We showed that 10 days following IOP elevation there was an increase in lipid and protein levels in the inner nuclear layer (INL) and ganglion cell layer (GCL). IOP elevation also resulted in an increase in nucleic acids in the INL. Analysis of SIRM spectra revealed a shift in amide peaks to lower vibrational frequencies with a more prominent second shoulder, which is consistent with the presence of cell death in specific layers of the retina. These changes were more substantial in the INL and GCL layers compared with those occurring in the outer nuclear layer. These outcomes demonstrate the utility of SIRM to quantify the effect of IOP elevation on specific layers of the retina. Thus SIRM may be a useful tool for the study of localised tissue changes in glaucoma and other eye diseases. PMID:27711151</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="https://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/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://www.ncbi.nlm.nih.gov/pubmed/26648261','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26648261"><span id="translatedtitle">Shensongyangxin protects against <span class="hlt">pressure</span> overload‑<span class="hlt">induced</span> cardiac hypertrophy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shen, Di-Fei; Wu, Qing-Qing; Ni, Jian; Deng, Wei; Wei, Cong; Jia, Zhen-Hua; Zhou, Heng; Zhou, Meng-Qiao; Bian, Zhou-Yan; Tang, Qi-Zhu</p> <p>2016-01-01</p> <p>Shensongyangxin (SSYX) is a medicinal herb, which has long been used in traditional Chinese medicine. Various pharmacological activities of SSYX have been identified. However, the role of SSYX in cardiac hypertrophy remains to be fully elucidated. In present study, aortic banding (AB) was performed to <span class="hlt">induce</span> cardiac hypertrophy in mice. SSYX (520 mg/kg) was administered by daily gavage between 1 and 8 weeks following surgery. The extent of cardiac hypertrophy was then evaluated by pathological and molecular analyses of heart tissue samples. In addition, in vitro experiments were performed to confirm the in vivo results. The data of the present study demonstrated that SSYX prevented the cardiac hypertrophy and fibrosis <span class="hlt">induced</span> by AB, as assessed by measurements of heart weight and gross heart size, hematoxylin and eosin staining, cross‑sectional cardiomyocyte area and the mRNA expression levels of hypertrophic markers. SSYX also inhibited collagen deposition and suppressed the expression of transforming growth factor β (TGFβ), connective tissue growth factor, fibronectin, collagen Ⅰα and collagen Ⅲα, which was mediated by the inhibition of the TGFβ/small mothers against decapentaplegic (Smad) signaling pathway. The inhibitory action of SSYX on cardiac hypertrophy was mediated by the inhibition of Akt signaling. In vitro investigations in the rat H9c2 cardiac cells also demonstrated that SSYX attenuated angiotensin II‑<span class="hlt">induced</span> cardiomyocyte hypertrophy. These findings suggested that SSYX attenuated cardiac hypertrophy and fibrosis in the <span class="hlt">pressure</span> overloaded mouse heart. Therefore, the cardioprotective effect of SSYX is associated with inhibition of the Akt and TGFβ/Smad signaling pathways. PMID:26648261</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AIPC..880.1156F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AIPC..880.1156F"><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://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fontana, Giorgio; Baker, Robert M. L.</p> <p>2007-01-01</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://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('https://www.ncbi.nlm.nih.gov/pubmed/7651767','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/7651767"><span id="translatedtitle">Bisferiens peaks in the radial artery <span class="hlt">pressure</span> <span class="hlt">wave</span> in newborn infants: a sign of patent ductus arteriosus.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gevers, M; Van Genderingen, H R; Van der Mooren, K; Lafeber, H N; Hack, W W; Westerhof, N</p> <p>1995-06-01</p> <p>Previously, we found evidence that radial artery <span class="hlt">pressure</span> <span class="hlt">wave</span> forms in newborns represent central aortic <span class="hlt">wave</span> forms, provided that <span class="hlt">pressure</span> is measured with adequate accuracy. Therefore, we postulated that the neonatal radial artery <span class="hlt">wave</span> form, like the adult aortic <span class="hlt">wave</span> form, may contribute to cardiovascular diagnosis. We investigated whether radial artery <span class="hlt">wave</span> forms in infants suffering from patent ductus arteriosus (PDA) are different from the <span class="hlt">wave</span> forms as seen without the presence of PDA. We studied 34 newborn infants with a radial artery line and with the possible clinical diagnosis of PDA with left-to-right shunt. On the basis of echocardiographic examination to assess PDA, these infants were divided in two groups: infants with PDA (n = 24) and without PDA (n = 10). In 15 out of 24 infants with PDA, recordings were repeated after ductal closure. Blood <span class="hlt">pressure</span> measurement was performed with a high fidelity cathetermanometer system using a tip-transducer (natural frequency 95 Hz, damping coefficient 0.15). Contour analysis was performed by describing morphology of the <span class="hlt">waves</span> during PDA and without PDA. In 23 out of 24 infants with PDA, a pulsus bisferiens was present: two peaks separated by a deep cleft. The average <span class="hlt">pressure</span> difference between the first <span class="hlt">pressure</span> peak and the cleft [delta Ppeak1] was 0.35 +/- 0.19 kPa, and the average difference between the cleft and the second <span class="hlt">pressure</span> peak [delta Ppeak2] was 0.44 +/- 0.23 kPa. the ratio of mean magnitude of delta Ppeak1 and delta Ppeak2 was 0.81 +/- 0.26. None of the 10 infants without PDA showed pulsus bisferiens.(ABSTRACT TRUNCATED AT 250 WORDS)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IzAOP..51...42K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IzAOP..51...42K"><span id="translatedtitle">Effects that internal gravity <span class="hlt">waves</span> from convective clouds have on atmospheric <span class="hlt">pressure</span> and spatial temperature-disturbance distribution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kshevetskii, S. P.; Kulichkov, S. N.</p> <p>2015-01-01</p> <p>Experimental data on variations in atmospheric surface <span class="hlt">pressure</span> in the region of thunderstorm phenomena are analyzed. A relationship between variations in atmospheric <span class="hlt">pressure</span> at the land surface and those in tropospheric temperature has been found, and the relation between the vertical distribution of tropospheric temperature and variations in atmospheric <span class="hlt">pressure</span> at the land surface is studied. The propagation of internal gravity <span class="hlt">waves</span> caused by atmospheric heating due to water-vapor condensation during the formation of a convective cloud is simulated. The results of calculations show that the lifetime of these internal gravity <span class="hlt">waves</span> may significantly exceed the lifetime of this cloud. It is shown that the form of the disturbance of atmospheric <span class="hlt">pressure</span> under such a convective cloud is a sequence of minimum and maximum <span class="hlt">pressure</span> variations and the amplitude of maxima may exceed that of minima.</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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4473736','PMC'); return false;" href="https://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="https://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('https://www.ncbi.nlm.nih.gov/pubmed/26647962','PUBMED'); return false;" href="https://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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4673455','PMC'); return false;" href="https://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/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://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/2016SuMi...98..423G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SuMi...98..423G"><span id="translatedtitle">Effect of hydrostatic <span class="hlt">pressure</span> and magnetic field on electromagnetically <span class="hlt">induced</span> transparency based nonlinear frequency conversion in quantum ring</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gumber, Sukirti; Gambhir, Monica; Jha, Pradip Kumar; Mohan, Man</p> <p>2016-10-01</p> <p>We study the combined effect of hydrostatic <span class="hlt">pressure</span> and magnetic field on electromagnetically <span class="hlt">induced</span> transparency in quantum ring. The high flexibility in size and shape of ring makes it possible to fabricate a nearly perfect two-dimensional quantum structure. We also explore the dependence of frequency conversion, measured in terms of third order nonlinear susceptibility χ(3) , on coupling field, hydrostatic <span class="hlt">pressure</span> and magnetic field. Although, a dip in χ(3) is observed with the introduction of strong coupling field, it renders the ring structure transparent to generated <span class="hlt">wave</span> thus effectively enhancing the output of nonlinear frequency conversion process. At a fixed coupling strength, the output can be further enhanced by increasing the magnetic field while it shows an inverse relationship with <span class="hlt">pressure</span>. These parameters, being externally controlled, provide an easy handle to control the output of quantum ring which can be used as frequency converter in communication networks.</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/2004SPIE.5319..155S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004SPIE.5319..155S"><span id="translatedtitle">Study for prevention of proliferation of smooth muscle cells after balloon angioplasty using Ho:YAG laser-<span class="hlt">induced</span> acoustic <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>Suga, Eriko; Yamashita, Erika; Futami, Hikaru; Arai, Tsunenori</p> <p>2004-07-01</p> <p>We designed the method for prevention of restenosis after balloon angioplasty using laser-<span class="hlt">induced</span> bubble-collapse acoustic <span class="hlt">wave</span>. This study was performed to evaluate the effect on smooth muscle cells (SMCs) by Ho:YAG laser (λ=2.10μm)-<span class="hlt">induced</span> acoustic <span class="hlt">wave</span>, in vitro and in vivo. The laser energy was delivered by a silica glass fiber into water. Sound <span class="hlt">pressure</span> was measured with a hydrophone changing the laser energy. The laser-<span class="hlt">induced</span> acoustic <span class="hlt">wave</span> was loaded to SMCs in vitro. This acoustic effect on SMCs was measured by MTT assay. The acoustic <span class="hlt">wave</span> loaded SMCs were controllably injured with the laser energy and laser shots. The balloon denudated rabbit aorta was used to evaluate in vivo effect. The laser-<span class="hlt">induced</span> acoustic <span class="hlt">wave</span> loaded aorta was extracted at 42 days after the laser irradiation, and was examined by Hematoxylin-Eosin staining. We found that the laser irradiation of 20 pulses with 60mJ/pulse prevented SMCs proliferation. We think the mechanism of this effect might be same as brachytherapy. We demonstrated the applicability of Ho:YAG laser-<span class="hlt">induced</span> acoustic <span class="hlt">wave</span> against vascular restenosis after balloon angioplasty.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/7368750','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/7368750"><span id="translatedtitle">Free energy in plasmas under <span class="hlt">wave-induced</span> diffusion</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fisch, N.J. . Plasma Physics Lab.); Rax, J.M. )</p> <p>1993-05-01</p> <p>When <span class="hlt">waves</span> propagate through a bounded plasma, the <span class="hlt">wave</span> may be amplified or damped at the expense of the plasma kinetic energy. In many cases of interest, the primary effect of the <span class="hlt">wave</span> is to cause plasma diffusion in velocity and configuration space. In the absence of collisions, the rearrangement of the plasma conserves entropy, as large-grain structures are mixed and fine-grain structures emerge. The maximum extractable energy by <span class="hlt">waves</span> so diffusing the plasma is a quantity of fundamental interest; it can be defined, but it is difficult to calculate. Through the consideration of specific examples, certain strategies for maximizing energy extraction are identified.</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://ntrs.nasa.gov/search.jsp?R=19860018284&hterms=wave+interference&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dwave%2Binterference','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19860018284&hterms=wave+interference&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dwave%2Binterference"><span id="translatedtitle">Vacillations <span class="hlt">induced</span> by interference of stationary and traveling <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>Salby, M. L.; Garcia, R. R.</p> <p>1985-01-01</p> <p>It was shown that there exists a correspondence between interference of the 16-day <span class="hlt">wave</span> with the stationary planetary <span class="hlt">wave</span> and vacillations in eddy heat and momentum fluxes. There has been speculation on the role such interference may play in stratospheric warmings. The appearance of higher-order normal modes, e.g., the 16-day <span class="hlt">wave</span>, prior to disturbances in the stratospheric vortex has also been noted. Since amplitudes of the 16-day <span class="hlt">wave</span> are compared to those of the stationary component, it can significantly alter the instantaneous total <span class="hlt">wave</span> field. The behavior of the <span class="hlt">wave</span> number 1 height field at 60 deg N during January 1979 is shown when a large amplitude disturbance retrogressed barotropically around the globe over much of the troposphere and stratosphere. This transient disturbance has been identified with the 16-day <span class="hlt">wave</span>. More generally, the presence of fluctuating planetary <span class="hlt">wave</span> activity can, through combined interference, alter the instantaneous planetary <span class="hlt">wave</span> field as well as the transports it produces. The implications of such interference in a quasi-geostrophic framework has been explored, using the Eliassen-Palm (EP) flux as a diagnostic.</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/2015APS..SHK.C2002C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..SHK.C2002C"><span id="translatedtitle">Shock <span class="hlt">wave</span> equation of state experiments at multi-TPa <span class="hlt">pressures</span> on NIF</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Celliers, P. M.; Fratanduono, D. E.; Peterson, J. L.; Meezan, N. B.; MacKinnon, A. J.; Braun, D. G.; Millot, M.; Fry, J.; Boehm, K. J.; Collins, G. W.; Nikroo, A.; Fitzsimmons, P.</p> <p>2015-06-01</p> <p>The National Ignition Facility provides an unprecedented capability to generate steady, planar, ultra-high <span class="hlt">pressure</span> shock <span class="hlt">waves</span> (around 10 TPa) in solid samples. Building on successful laser shock equation of state experiments performed on a variety of other laser facilities, we have designed and fielded experiments to perform impedance match experiments on samples of C, Be, quartz and CH, in the range of 3 to 7 TPa. The experiments use a line-imaging VISAR as the primary diagnostic to measure the shock velocity in an Al reference standard and in an array of the four samples. Initial tests with the line-imaging VISAR show that the NIF is capable of driving shocks that are steady for several ns, with smooth planar breakout patterns over a 2 mm diameter spot. Initial results will be discussed. Prepared by LLNL under Contract DE-AC52-07NA27344.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21643336','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21643336"><span id="translatedtitle">Low-cost rapid miniature optical <span class="hlt">pressure</span> sensors for blast <span class="hlt">wave</span> measurements.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wu, Nan; Wang, Wenhui; Tian, Ye; Zou, Xiaotian; Maffeo, Michael; Niezrecki, Christopher; Chen, Julie; Wang, Xingwei</p> <p>2011-05-23</p> <p>This paper presents an optical <span class="hlt">pressure</span> sensor based on a Fabry-Perot (FP) interferometer formed by a 45° angle polished single mode fiber and an external silicon nitride diaphragm. The sensor is comprised of two V-shape grooves with different widths on a silicon chip, a silicon nitride diaphragm released on the surface of the wider V-groove, and a 45° angle polished single mode fiber. The sensor is especially suitable for blast <span class="hlt">wave</span> measurements: its compact structure ensures a high spatial resolution; its thin diaphragm based design and the optical demodulation scheme allow a fast response to the rapid changing signals experienced during blast events. The sensor shows linearity with the correlation coefficient of 0.9999 as well as a hysteresis of less than 0.3%. The shock tube test demonstrated that the sensor has a rise time of less than 2 µs from 0 kPa to 140 kPa. PMID:21643336</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18079263','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18079263"><span id="translatedtitle"><span class="hlt">Wave</span> reflection and central aortic <span class="hlt">pressure</span> are increased in response to static and dynamic muscle contraction at comparable workloads.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Edwards, David G; Mastin, Corey R; Kenefick, Robert W</p> <p>2008-02-01</p> <p>We determined the effects of static and dynamic muscle contraction at equivalent workloads on central aortic <span class="hlt">pressure</span> and <span class="hlt">wave</span> reflection. At random, 14 healthy men and women (23 +/- 5 yr of age) performed a static handgrip forearm contraction [90 s at 30% of maximal voluntary contraction (MVC)], dynamic handgrip contractions (1 contraction/s for 180 s at 30% MVC), and a control trial. During static and dynamic trials, tension-time index was controlled by holding peak tension constant. Measurements of brachial artery blood <span class="hlt">pressure</span> and the synthesis of a central aortic <span class="hlt">pressure</span> waveform (by radial artery applanation tonometry and generalized transfer function) were conducted at baseline, during each trial, and during 1 min of postexercise ischemia (PEI). Aortic augmentation index (AI), an index of <span class="hlt">wave</span> reflection, was calculated from the aortic <span class="hlt">pressure</span> waveform. AI increased during both static and dynamic trials (static, 5.2 +/- 3.1 to 11.8 +/- 3.4%; dynamic, 5.8 +/- 3.0 to 13.3 +/- 3.4%; P < 0.05) and further increased during PEI (static, 18.5 +/- 3.1%; dynamic, 18.6 +/- 2.9%; P < 0.05). Peripheral and central systolic and diastolic <span class="hlt">pressures</span> increased (P < 0.05) during both static and dynamic trials and remained elevated during PEI. AI and <span class="hlt">pressure</span> responses did not differ between static and dynamic trials. Peripheral and central <span class="hlt">pressures</span> increased similarly during static and dynamic contraction; however, the rise in central systolic <span class="hlt">pressure</span> during both conditions was augmented by increased <span class="hlt">wave</span> reflection. The present data suggest that <span class="hlt">wave</span> reflection is an important determinant of the central blood <span class="hlt">pressure</span> response during forearm muscle contractions.</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('https://www.ncbi.nlm.nih.gov/pubmed/22733475','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22733475"><span id="translatedtitle">Blood <span class="hlt">pressure</span> and obesity exert independent influences on pulse <span class="hlt">wave</span> velocity in youth.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lurbe, Empar; Torro, Isabel; Garcia-Vicent, Consuelo; Alvarez, Julio; Fernández-Fornoso, José Antonio; Redon, Josep</p> <p>2012-08-01</p> <p>The objective was to analyze pulse <span class="hlt">wave</span> velocity (PWV) in normotensive, high-normal, and hypertensive youths by using aortic-derived parameters from peripheral recordings. The impact of obesity on vascular phenotypes was also analyzed. A total of 501 whites from 8 to 18 years of age were included. The subjects were divided according to BP criteria: 424 (85%) were normotensive, 56 (11%) high-normal, and 21 (4%) hypertensive. Obesity was present in 284 (56%) and overweight in 138 (28%). Pulse <span class="hlt">wave</span> analysis using a SphygmoCor device was performed to determine central blood <span class="hlt">pressure</span> (BP), augmentation index, and measurement of PWV. Among the BP groups, differences appeared in age, sex, and height but not in body mass index. Significant differences in peripheral and central systolic and diastolic BPs and pulse <span class="hlt">pressures</span> were observed within groups. A graded increase in PWV was present across the BP strata without differences in augmentation index. Using a multiple regression analysis, age, BP groups, and obesity status were independently associated with PWV. Older and hypertensive subjects had the highest PWV, whereas, from normal weight status to obesity, PWV decreased. Likewise, PWV was positively related to peripheral or central systolic BP and negatively related to body mass index z score. For 1 SD of peripheral systolic BP, PWV increased 0.329 m/s, and for 1 SD of body mass index z score PWV decreased 0.129 m/s. In conclusion, PWV is increased in hypertensive and even in high-normal children and adolescents. Furthermore, obesity, the factor most frequently related to essential hypertension in adolescents, blunted the expected increment in PWV of hypertensive and high-normal subjects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JMEP...20.1144G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JMEP...20.1144G"><span id="translatedtitle">Multi-Length Scale Modeling of High-<span class="hlt">Pressure-Induced</span> Phase Transformations in Soda-Lime Glass</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grujicic, M.; Bell, W. C.; Glomski, P. S.; Pandurangan, B.; Cheeseman, B. A.; Fountzoulas, C.; Patel, P.</p> <p>2011-10-01</p> <p>Molecular-level modeling and simulations are employed to study room-temperature micro-structural and mechanical response of soda-lime glass when subjected to high (i.e., several giga-Pascal) uniaxial-strain stresses/<span class="hlt">pressure</span>. The results obtained revealed the occurrence of an irreversible phase-transformation at ca. 4 GPa which was associated with a (permanent) 3-7% volume reduction. Close examination of molecular-level topology revealed that the <span class="hlt">pressure-induced</span> phase transformation in question is associated with an increase in the average coordination number of the silicon atoms, and the creation of two- to fourfold (smaller, high packing-density) Si-O rings. The associated loading and unloading axial-stress versus specific-volume isotherms were next converted into the corresponding loading Hugoniot and unloading isentrope axial-stress versus specific-volume relations. These were subsequently used to analyze the role of the <span class="hlt">pressure-induced</span> phase-transformation/irreversible-densification in mitigating the effects of blast and ballistic impact loading onto a prototypical glass plate used in monolithic and laminated transparent armor applications. The results of this part of the study revealed that <span class="hlt">pressure-induced</span> phase-transformation can provide several beneficial effects such as lowering of the loading/unloading stress-rates and stresses, shock/release-<span class="hlt">wave</span> dispersion, and energy absorption associated with the study of phase-transformation.</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('https://www.ncbi.nlm.nih.gov/pubmed/23556559','PUBMED'); return false;" href="https://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="https://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.</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="https://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..1413327S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1413327S"><span id="translatedtitle"><span class="hlt">Wave-induced</span> boundary-layer separation: A case study comparing airborne observations and results from a mesoscale model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Strauss, L.; Serafin, S.; Grubišić, V.</p> <p>2012-04-01</p> <p><span class="hlt">Wave-induced</span> boundary-layer separation (BLS) results from the adverse-<span class="hlt">pressure</span> gradient forces that are exerted on the atmospheric boundary-layer by internal gravity <span class="hlt">waves</span> in flow over orography. BLS has received significant attention in recent years, particularly so, because it is a key ingredient in the formation of atmospheric rotors. Traditionally depicted as horizontal eddies in the lee of mountain ranges, rotors originate from the interaction between internal gravity <span class="hlt">waves</span> and the atmospheric boundary-layer. Our study focuses on the first observationally documented case of <span class="hlt">wave-induced</span> BLS, which occurred on 26 Jan 2006 in the lee of the Medicine Bow Mountains in SE Wyoming (USA). Observations from the University of Wyoming King Air (UWKA) aircraft, in particular, the remote sensing measurements with the Wyoming Cloud Radar (WCR), reveal strong <span class="hlt">wave</span> activity, downslope winds in excess of 30 m/s, and near-surface flow reversal in the lee of the mountain range. The fine resolution of WCR data (on the order of 40x40 m2 for two-dimensional velocity fields) exhibits fine-scale vortical structures ("subrotors") which are embedded within the main rotor zone. Our case study intends to complete the characterisation of the observed boundary-layer separation event. Modelling of the event with the mesoscale Weather Research and Forecast Model (WRF) provides insight into the mesoscale triggers of <span class="hlt">wave-induced</span> BLS and turbulence generation. Indeed, the mesoscale model underpins the expected concurrence of the essential processes (gravity <span class="hlt">waves</span>, <span class="hlt">wave</span> breaking, downslope windstorms, etc.) leading to BLS. To exploit the recorded in situ and radar data to their full extent, a quantitative evaluation of the structure and intensity of turbulence is conducted by means of a power spectral analysis of the vertical wind component, measured along the flight track. An intercomparison of observational and modelling results serves the purpose of model verification and can shed some more</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19696859','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19696859"><span id="translatedtitle">Dynamic index modulation mechanism in polarization-maintained fiber Bragg gratings <span class="hlt">induced</span> by transverse acoustic <span class="hlt">waves</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Miao, Ren; Zhang, Wei; Feng, Xue; Zhao, Jianhui; Liu, Xiaoming</p> <p>2009-08-20</p> <p>A novel index modulation mechanism of polarization-maintained fiber Bragg gratings based on the microbend of stress members <span class="hlt">induced</span> by a transverse acoustic <span class="hlt">wave</span> is proposed and investigated experimentally. The index modulation leads to a series of ghost gratings with specific polarization, whose wavelengths can be tuned by the acoustic <span class="hlt">wave</span> frequency and whose intensities depend on the vibration direction of the transverse acoustic <span class="hlt">wave</span>. Our method provides a novel way to achieve polarization-dependent narrowband acousto-optic tunable filters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4746592','PMC'); return false;" href="https://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> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26857266','PUBMED'); return false;" href="https://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="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pinsker, Florian</p> <p>2016-02-09</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>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25968379','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25968379"><span id="translatedtitle">Optical beam distortions <span class="hlt">induced</span> by a shock <span class="hlt">wave</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Banakh, V A; Sukharev, A A; Falits, A V</p> <p>2015-03-10</p> <p>The mean intensity and the displacement from the initially given propagation direction of the optical beam passed through the shock <span class="hlt">wave</span> have been calculated. It has been shown that the spatial inhomogeneity of the refractive index of air caused by the shock <span class="hlt">wave</span> arising in supersonic flow flowing a conical body can cause the focusing of the beam and strong anisotropic distortions of the intensity distribution in its cross section. The angular displacement of the optical beam from the initially given propagation direction owing to the shock <span class="hlt">wave</span> depends only on the height above the Earth's surface at which the shock <span class="hlt">wave</span> is formed. As the height increases, the influence of the shock <span class="hlt">wave</span> on the optical beam propagating through it decreases.</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="https://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/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://pubs.er.usgs.gov/publication/70028026','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70028026"><span id="translatedtitle">Nearshore <span class="hlt">wave-induced</span> cyclical flexing of sea cliffs</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Adams, P.N.; Storlazzi, C.D.; Anderson, R. Scott</p> <p>2005-01-01</p> <p>[1] Evolution of a tectonically active coast is driven by geomorphically destructive energy supplied by ocean <span class="hlt">waves</span>. <span class="hlt">Wave</span> energy is episodic and concentrated; sea cliffs are battered by the geomorphic wrecking ball every 4-25 s. We measure the response of sea cliffs to <span class="hlt">wave</span> assault by sensing the ground motion using near-coastal seismometers. Sea cliffs respond to <span class="hlt">waves</span> in two distinct styles. High-frequency motion (20 Hz) reflects the natural frequency of the sea cliff as it rings in response to direct <span class="hlt">wave</span> impact. Low-frequency motion in the 0.1-0.05 Hz (10-20 s) band consistently agrees with the dominant nearshore <span class="hlt">wave</span> period. Integrating microseismic velocities suggests 50 ??m and 10 ??m displacements in horizontal and vertical directions, respectively. Displacement ellipsoids exhibit simultaneous downward and seaward sea cliff motion with each <span class="hlt">wave</span>. Video footage corroborates the downward sea cliff flex in response to the imposed water load on the <span class="hlt">wave</span> cut platform. Gradients in displacement amplitudes documented using multiple seismometers suggest longitudinal and shear strain of the flexing sea cliff on the order of 0.5-4 ?? strains during each <span class="hlt">wave</span> loading cycle. As this sea cliff flexure occurs approximately 3 million times annually, it has the potential to fatigue the rock through cyclical loading. Local sea cliff retreat rates of 10 cm/yr imply that a given parcel of rock is flexed through roughly 109 cycles of increasing amplitude before exposure to direct <span class="hlt">wave</span> attack at the cliff face. Copyright 2005 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14242019','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14242019"><span id="translatedtitle"><span class="hlt">PRESSURE-INDUCED</span> COLOR MUTATION OF EUGLENA GRACILIS.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>GROSS, J A</p> <p>1965-02-12</p> <p>Photosynthetic cultures of Euglena gracilis Z which were illuminated during growth were more resistant to the lethal effect of high hydrostatic <span class="hlt">pressures</span> than nonphotosynthetic cultures grown in the dark. A high percentage of mutants permanently lacking chlorophyll and with altered carotenoids was obtained after subjecting cultures to high <span class="hlt">pressure</span>. A minimum <span class="hlt">pressure</span> of 500 atmospheres was critical for color mutation and morphological change. The highest effective <span class="hlt">pressure</span> used was 1000 atmospheres.</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://ntrs.nasa.gov/search.jsp?R=19900053323&hterms=superconductor&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dsuperconductor','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900053323&hterms=superconductor&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dsuperconductor"><span id="translatedtitle">The electric field <span class="hlt">induced</span> by a gravitational <span class="hlt">wave</span> in a superconductor - A principle for a new gravitational <span class="hlt">wave</span> antenna</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Peng, Huei; Torr, Douglas G.</p> <p>1990-01-01</p> <p>This paper investigates the effect of gravitational <span class="hlt">waves</span> on a superconductor. It is found that the key properties of a superconductor, namely zero resistance and perfect diamagnetism, give rise to an important new effect, the presence of an <span class="hlt">induced</span> electric field E in the interior of the superconductor. The E field reacts with the ions and superelectrons. It is argued that the <span class="hlt">induced</span> E field might provide a significantly more sensitive means of detecting gravitational <span class="hlt">waves</span>. It appears likely that existing resonant-mass superconducting antennas with L about 3m, Q about 10 to the 8th could be readily modified to detect E fields <span class="hlt">induced</span> by GWs of dimensionless amplitude h about 10 to the -24th.</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/2015EGUGA..1714118P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1714118P"><span id="translatedtitle">Non-Lithostatic <span class="hlt">Pressure</span> and Transformation-<span class="hlt">Induced</span> Boudinage</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Podladchikov, Yury; Dabrowski, Marcin</p> <p>2015-04-01</p> <p>(Ultra) high <span class="hlt">pressure</span> rocks often found as competent boudanes within lower <span class="hlt">pressure</span> less competent rocks. Competent layer parallel extension would cause underpressure. We explore densification as the reason for boudinage, monitor related evolution of the <span class="hlt">pressure</span> field and discuss its geodynamic implications.</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('https://www.ncbi.nlm.nih.gov/pubmed/27388527','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27388527"><span id="translatedtitle">Changes in Central Aortic <span class="hlt">Pressure</span> Levels, <span class="hlt">Wave</span> Components and Determinants Associated with High Peripheral Blood <span class="hlt">Pressure</span> States in Childhood: Analysis of Hypertensive Phenotype.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>García-Espinosa, Victoria; Curcio, Santiago; Marotta, Marco; Castro, Juan M; Arana, Maite; Peluso, Gonzalo; Chiesa, Pedro; Giachetto, Gustavo; Bia, Daniel; Zócalo, Yanina</p> <p>2016-10-01</p> <p>The aims were to determine whether children's high peripheral blood <span class="hlt">pressure</span> states (HBP) are associated with increased central aortic blood <span class="hlt">pressure</span> (BP) and to characterize hemodynamic and vascular changes associated with HBP in terms of changes in cardiac output (stroke volume, SV), arterial stiffness (aortic pulse <span class="hlt">wave</span> velocity, PWV), peripheral vascular resistances (PVR) and net and relative contributions of reflected <span class="hlt">waves</span> to the aortic pulse amplitude. We included 154 subjects (mean age 11; range 4-16 years) assigned to one of two groups: normal peripheral BP (NBP, n = 101), defined as systolic and diastolic BP < 90th percentile, or high BP (HBP, n = 53), defined as average systolic and/or diastolic BP levels ≥90th percentile (curves for sex, age and body height). The HBP group included children with hypertensive and pre-hypertensive BP levels. After a first analysis, groups were compared excluding obese and dyslipidemic children. Peripheral and central aortic BP, PWV and pulse <span class="hlt">wave</span>-derived parameters (augmentation index, forward and backward <span class="hlt">wave</span> components' amplitude) were measured using gold-standard techniques, applanation tonometry (SphygmoCor) and oscillometry (Mobil-O-Graph). Independent of the presence of dyslipidemia and/or obesity, aortic systolic and pulse BP were higher in HBP than in NBP children. The increase in central BP could not be explained by an increase in the relative contribution of reflections to the aortic <span class="hlt">pressure</span> <span class="hlt">wave</span>, higher PVR or by an augmented peripheral reflection coefficient. Instead, the rise in central BP would be explained by an increase in the amplitude of both incident and reflected <span class="hlt">wave</span> components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013APS..DFDH28008M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..DFDH28008M"><span id="translatedtitle">On the unsteady gravity-capillary <span class="hlt">wave</span> pattern found behind a slow moving localized <span class="hlt">pressure</span> distribution</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>2013-11-01</p> <p>The non-linear response of a water surface to a slow-moving <span class="hlt">pressure</span> distribution is studied experimentally using a vertically oriented carriage-mounted air-jet tube that is set to translate over the water surface in a long tank. The free surface deformation pattern is measured with a full-field refraction-based method that utilizes a vertically oriented digital movie camera (under the tank) and a random dot pattern (above the water surface). At towing speeds just below the minimum phase speed of gravity-capillary <span class="hlt">waves</span> (cmin ~ 23 cm/s), an unsteady V-shaped pattern is formed behind the <span class="hlt">pressure</span> source. Localized depressions are generated near the source and propagate in pairs along the two arms of the V-shaped pattern. These depressions are eventually shed from the tips of the pattern at a frequency of about 1 Hz. It is found that the shape and phase speeds of the first depressions shed in each run are quantitatively similar to the freely-propagating gravity-capillary lumps from potential flow calculations. In the experiments, the amplitudes of the depressions decrease by approximately 60 percent while travelling 12 wavelengths. The depressions shed later in each run behave in a less consistent manner, probably due to their interaction with neighboring depressions.</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://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://adsabs.harvard.edu/abs/2014PhFl...26j6601V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhFl...26j6601V"><span id="translatedtitle">The mean flow and long <span class="hlt">waves</span> <span class="hlt">induced</span> by two-dimensional internal gravity wavepackets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van den Bremer, T. S.; Sutherland, B. R.</p> <p>2014-10-01</p> <p>Through theory supported by numerical simulations, we examine the <span class="hlt">induced</span> local and long range response flows resulting from the momentum flux divergence associated with with a two-dimensional Boussinesq internal gravity wavepacket in a uniformly stratified ambient. Our theoretical approach performs a perturbation analysis that takes advantage of the separation of scales between <span class="hlt">waves</span> and the amplitude envelope of a quasi-monochromatic wavepacket. We first illustrate our approach by applying it to the well-studied case of deep water surface gravity <span class="hlt">waves</span>, showing that the <span class="hlt">induced</span> flow, UDF, resulting from the divergence of the horizontal momentum flux is equal to the Stokes drift. For a localized surface wavepacket, UDF is itself a divergent flow and so there is the well-known non-local response manifest in the form of a deep return flow beneath the wavepacket. For horizontally periodic and vertically localized internal wavepackets, the divergent-flux <span class="hlt">induced</span> flow, uDF, is found from consideration of the vertical gradient of the vertical flux of horizontal momentum associated with the <span class="hlt">waves</span>. Because uDF is itself a non-divergent flow field, this accounts entirely for the <span class="hlt">wave-induced</span> flow; there is no response flow. Our focus is upon internal wavepackets that are localized in the horizontal and vertical. We derive a formula for the divergent-flux <span class="hlt">induced</span> flow that, as in this case of surface wavepackets, is itself a divergent flow. We show that the response is a horizontally long internal <span class="hlt">wave</span> that translates vertically with the wavepacket at its group velocity. Scaling relationships are used to estimate the wavenumber, horizontal extent, and amplitude of this <span class="hlt">induced</span> long <span class="hlt">wave</span>. At higher order in perturbation theory we derive an explicit integral formula for the <span class="hlt">induced</span> long <span class="hlt">wave</span>. Thus, we provide validation of Bretherton's analysis of flows <span class="hlt">induced</span> by two-dimensional internal wavepackets [F. P. Bretherton, "On the mean motion <span class="hlt">induced</span> by gravity <span class="hlt">waves</span>," J. Fluid</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://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://www.ncbi.nlm.nih.gov/pubmed/19806456','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19806456"><span id="translatedtitle">Biomechanical assessment of brain dynamic responses due to blast <span class="hlt">pressure</span> <span class="hlt">waves</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chafi, M S; Karami, G; Ziejewski, M</p> <p>2010-02-01</p> <p>A mechanized and integrated computational scheme is introduced to determine the human brain responses in an environment where the human head is exposed to explosions from trinitrotoluene (TNT), or other high-yield explosives, in military applications. The procedure is based on a three-dimensional (3-D) non-linear finite element method (FEM) that implements a simultaneous conduction of explosive detonation, shock <span class="hlt">wave</span> propagation, blast-head interactions, and the confronting human head. The processes of blast propagation in the air and blast interaction with the head are modeled by an Arbitrary Lagrangian-Eulerian (ALE) multi-material FEM formulation, together with a penalty-based fluid/structure interaction (FSI) algorithm. Such a model has already been successfully validated against experimental data regarding air-free blast and plate-blast interactions. The human head model is a 3-D geometrically realistic configuration that has been previously validated against the brain intracranial <span class="hlt">pressure</span> (ICP), as well as shear and principal strains under different impact loadings of cadaveric experimental tests of Hardy et al. [Hardy W. N., C. Foster, M. Mason, S. Chirag, J. Bishop, M. Bey, W. Anderst, and S. Tashman. A study of the response of the human cadaver head to impact. Proc. 51 ( st ) Stapp. Car Crash J. 17-80, 2007]. Different scenarios have been assumed to capture an appropriate picture of the brain response at a constant stand-off distance of nearly 80 cm from the core of the explosion, but exposed to different amounts of a highly explosive (HE) material such as TNT. The over-<span class="hlt">pressures</span> at the vicinity of the head are in the range of about 2.4-8.7 atmosphere (atm), considering the reflected <span class="hlt">pressure</span> from the head. The methodology provides brain ICP, maximum shear stresses and maximum principal strain within the milli-scale time frame of this highly dynamic phenomenon. While focusing on the two mechanical parameters of <span class="hlt">pressure</span>, and also on the maximum shear</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://adsabs.harvard.edu/abs/2016OptLE..79...61B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OptLE..79...61B"><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://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="https://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('https://www.ncbi.nlm.nih.gov/pubmed/24116532','PUBMED'); return false;" href="https://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="https://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.</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/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/2011ShWav..21...63K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ShWav..21...63K"><span id="translatedtitle">A computer simulation of grain orientation and aspect ratio that promotes the reflection of a <span class="hlt">pressure</span> <span class="hlt">wave</span> by elastic rotational stress</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kennefick, C. M.; Patillo, C. E.; Kupoluyi, T.; Gomes, C. A.</p> <p>2011-02-01</p> <p>Optimal orientation angles and aspect ratios of a grain are presented for the attenuation of a longitudinal <span class="hlt">pressure</span> <span class="hlt">wave</span> by elastic stresses that arise from the rotation of a grain. A computer program in C++ allows the grain to be a two-dimensional ellipse of several orientations with respect to the incoming load. The program also varies the aspect ratio of the grain. The <span class="hlt">induced</span> elastic stresses from the rotation of the grain are calculated with complex variable methods that do not require meshes and elements. Low aspect ratios of 5/3, 10/7 and 5/4 were particularly effective in halting the stress from the <span class="hlt">pressure</span> <span class="hlt">wave</span> when the major axis of the grain was tilted between 15° and 45° and again above 70° with respect to the line of the incoming load. Attenuation was found to be more sensitive to grain orientation than to aspect ratio. The conclusion is supported by numerous switches in the extent of <span class="hlt">wave</span> blockage over small angular variations in the orientation of the grain.</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://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://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.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.osti.gov/scitech/biblio/21251579','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21251579"><span id="translatedtitle">Using line broadening to determine the electron density in an argon surface-<span class="hlt">wave</span> discharge at atmospheric <span class="hlt">pressure</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Christova, M.; Christov, L.; Castanos-Martinez, E.; Moisan, M.; Dimitrijevic, M. S.</p> <p>2008-10-22</p> <p>Broadening due to collisions with charged particles (Stark broadening ) and neutral atoms, was determined for Ar I 522.1, 549.6 and 603.2 nm spectral lines from the spectral series 3p{sup 5}nd-3p{sup 5}4p, in order to evaluate the electron density in a surface-<span class="hlt">wave</span> discharge at atmospheric <span class="hlt">pressure</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/1171523','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/1171523"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> depolymerization of brain microtubules in vitro.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Salmon, E D</p> <p>1975-09-12</p> <p>Microtubules, assembled in vitro from tubulin extracted from rabbit brain, were subjected to changes in hydrostatic <span class="hlt">pressure</span> (200 to 10,000 pounds per square inch) and temperature (37 degrees to 0 degrees C). Increased <span class="hlt">pressure</span>, like cooling, reversibly depolymerizes microtubules, as measured by changes in either turbidity, birefringence, or the number of microtubules seen in electron micrographs. The characteristic response of brain microtubules in vitro to <span class="hlt">pressure</span> is similar to that of mitotic spindle microtubules in vivo.</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://adsabs.harvard.edu/abs/2015ChJOL..33..233W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ChJOL..33..233W"><span id="translatedtitle">Effect of <span class="hlt">wave-induced</span> Stokes drift on the dynamics of ocean mixed layer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Zhifeng; Wu, Kejian; Dong, Sheng; Deng, Zeng'an; Zhang, Xiaoshuang</p> <p>2015-01-01</p> <p>The <span class="hlt">wave</span>-forcing `Coriolis-Stokes forcing' and `Stokes-vortex force' <span class="hlt">induced</span> by Stokes drift affect the upper ocean jointly. To study the effect of the <span class="hlt">wave-induced</span> Stokes drift on the dynamics of the ocean mixed layer, a new three-dimensional (3D) numerical model is derived using the primitive basic equations and Eulerian <span class="hlt">wave</span> averaging. The Princeton Ocean Model (POM), a 3D primitive equation ocean model is used with the upper <span class="hlt">wave</span>-averaged basic equations. The global ocean circulation is simulated using the POM model, and the Stokes drift is evaluated based on the <span class="hlt">wave</span> data generated by WAVEWATCH III. We compared simulations with and without the Stokes drift. The results show that the magnitude of the Stokes drift is comparable with the Eulerian mean current. Including the Stokes drift in the ocean model affects both the Eulerian current and the Lagranian drift and causes the vertical mixing coefficients to increase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26367523','PUBMED'); return false;" href="https://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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16803082','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16803082"><span id="translatedtitle">Generation of sub-Mbar <span class="hlt">pressure</span> by converging shock <span class="hlt">waves</span> produced by the underwater electrical explosion of a wire array.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Krasik, Ya E; Grinenko, A; Sayapin, A; Gurovich, V Tz; Schnitzer, I</p> <p>2006-05-01</p> <p>We report a demonstration of a generation of sub-Mbar <span class="hlt">pressure</span> on the axis of the implosion <span class="hlt">wave</span> produced by an underwater electrical explosion of a cylindrical wire array. The array was exploded by microsecond time scale discharge of a capacitor bank having a stored energy of 4.5 kJ and discharge current amplitude of up to 90 kA. Optical diagnostics were used to determine the time of flight and the trajectory of the converging shock <span class="hlt">wave</span>. This data were applied for a calculation of the water flow parameters using one-dimensional (1D) and 2D hydrodynamic calculations and the Whitham method. All three methods have shown that the shock <span class="hlt">wave</span> <span class="hlt">pressure</span> at 0.1 mm from the axis reaches . PMID:16803082</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3412201','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3412201"><span id="translatedtitle">Effects of Heat <span class="hlt">Wave</span> on Body Temperature and Blood <span class="hlt">Pressure</span> in the Poor and Elderly</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kim, Soyeon; Cheong, Hae-Kwan; Ahn, Byungok; Choi, Kyusik</p> <p>2012-01-01</p> <p>Objectives We aimed to investigate the acute effects of heat stress on body temperature and blood <span class="hlt">pressure</span> of elderly individuals living in poor housing conditions. Methods Repeated measurements of the indoor temperature, relative humidity, body temperature, and blood <span class="hlt">pressure</span> were conducted for 20 elderly individuals living in low-cost dosshouses in Seoul during hot summer days in 2010. Changes in the body temperature, systolic blood <span class="hlt">pressure</span> (SBP) and diastolic blood <span class="hlt">pressure</span> (DBP) according to variations in the indoor and outdoor temperature and humidity were analyzed using a repeated-measures ANOVA controlling for age, sex, alcohol, and smoking. Results Average indoor and outdoor temperatures were 31.47℃ (standard deviation [SD], 0.97℃) and 28.15℃ (SD, 2.03℃), respectively. Body temperature increased by 0.21℃ (95% confidence interval [CI], 0.16 to 0.26℃) and 0.07℃ (95% CI, 0.04 to 0.10℃) with an increase in the indoor and outdoor temperature of 1℃. DBP decreased by 2.05 mmHg (95% CI, 0.05 to 4.05 mmHg), showing a statistical significance, as the indoor temperature increased by 1℃, while it increased by 0.20 mmHg (95% CI, -0.83 to 1.22 mmHg) as outdoor temperature increased by 1℃. SBP decreased by 1.75 mmHg (95% CI, -1.11 to 4.61 mmHg) and 0.35 mmHg (95% CI, -1.04 to 1.73 mmHg), as the indoor and outdoor temperature increased by 1℃, respectively. The effects of relative humidity on SBP and DBP were not statistically significant for both indoor and outdoor. Conclusions The poor and elderly are directly exposed to heat <span class="hlt">waves</span>, while their vital signs respond sensitively to increase in temperature. Careful adaptation strategies to climate change considering socioeconomic status are therefore necessary. PMID:22888472</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995QuEle..25..153W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995QuEle..25..153W"><span id="translatedtitle">EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Measurements of laser-<span class="hlt">induced</span> shock <span class="hlt">waves</span> in aluminium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Werdiger, M.; Arad, B.; Moshe, E.; Eliezer, S.</p> <p>1995-02-01</p> <p>A simple optical method for measurements of high-irradiance (3×1013 W cm-2) laser-<span class="hlt">induced</span> shock <span class="hlt">waves</span> is described. The shock <span class="hlt">wave</span> velocity (~13 km s-1) was measured with an error not exceeding 5%. The laser-<span class="hlt">induced</span> one-to-two-dimensional (1D-to-2D) shock <span class="hlt">wave</span> transition was studied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.6754J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.6754J"><span id="translatedtitle">Modelling <span class="hlt">wave-induced</span> resuspension in the Fitzroy Estuary and Keppel Bay, Australia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Joehnk, Klaus</p> <p>2013-04-01</p> <p>Sediment transport is an essential component of nutrient cycles in many aquatic systems. Accurate simulation of sediment resuspension and transport is essential for successful prediction of changes in water quality and aquatic habitats. This has repeatedly proven to be a problematic component of modelling efforts. Often, turbulence and resuspension is dominated by the effects of wind-<span class="hlt">induced</span> <span class="hlt">waves</span>. Although several models exist to describe the impact of wind-<span class="hlt">induced</span> <span class="hlt">wave</span> dynamics and <span class="hlt">wave</span>-current interactions on sediment resuspension and transport, examples of their integration into complete hydrodynamic models are rare. Such an integration of a hydrodynamic model with a <span class="hlt">wave</span> model has the ability to directly simulate effects of <span class="hlt">wave</span> dynamics on turbulence production in the ocean and water level variation and current effects on <span class="hlt">wave</span> development. Here, we demonstrate the application of a loosely coupled simulation tool running the third generation <span class="hlt">wave</span> model SWAN (Simulating <span class="hlt">WAves</span> Nearshore) together with the CSIRO hydrodynamic model SHOC (Sparse Hydrodynamic Ocean Code). This tool is applied to the well-studied Fitzroy Estuary and Keppel Bay, Queensland, Australia using a fine grid with a resolution down to 200 m nested into a coupled model for the entire Great Barrier Reef (GBR) lagoon on a 4 km grid. SHOC has been previously applied to this system without a <span class="hlt">wave</span> model, but results for suspended sediments have been unsatisfactory. The novel model is able to quantify annual <span class="hlt">wave-induced</span> resuspension versus tidal <span class="hlt">induced</span> resuspension and sediment input by short-term floods. It is intended to improve the capacity for prediction of sediment transport dynamics in other estuaries and bays of the GBR lagoon during flood periods as well as for the dry season (low flood), and provide an operational tool to inform catchment management strategies around Australia. This model is integral part of the eReefs marine modelling project aiming for an operational real time model</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JGRC..116.5021S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JGRC..116.5021S"><span id="translatedtitle">Three-dimensional simulation of <span class="hlt">wave-induced</span> circulation: Comparison of three radiation stress formulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sheng, Y. Peter; Liu, Tianyi</p> <p>2011-05-01</p> <p>A three-dimensional current-<span class="hlt">wave</span> modeling system, Curvilinear-grid Hydrodynamics 3D (CH3D)-Simulating <span class="hlt">Waves</span> Nearshore (SWAN), has been used to simulate <span class="hlt">wave-induced</span> circulation and compare the performances of three radiation stress (RS) formulations: two depth-dependent formulations (M08 by Mellor (2008) and X04 by Xia et al. (2004)) and one depth-independent formulation (LHS by Longuet-Higgins and Stewart (1964)). While all are based on linear <span class="hlt">wave</span> theory, LHS uses the vertically integrated equations of motion, and M08 and X04 consider the three-dimensional equations of motion. Results of CH3D-SWAN with three RS formulations are compared with steady state <span class="hlt">wave</span> setup, observed data in an undertow experiment by Ting and Kirby (1994) (TK94), and observed data in a laboratory fringing reef. All three RS formulations reproduce the analytical solution of <span class="hlt">wave</span> setup very well. Simulated <span class="hlt">wave-induced</span> currents and turbulence for TK94 are the best when M08 is used and worst when X04 is used, apparently due to the errors in the X04 formulation. All three RS formulations give good simulation of <span class="hlt">wave</span> setup in the fringing reef. <span class="hlt">Wave-induced</span> currents in the fringing reef simulated by the three RS formulations are quite different: M08 produces a single large clockwise gyre in the x-z plane, LHS produces a weaker gyre, and X04 produces a clockwise gyre plus a counterclockwise gyre inside the surf zone. Using the CH3D-Storm Surge Modeling System and M08, storm surge and currents in the Outer Banks and Chesapeake Bay during Hurricane Isabel are simulated. Compared to the earlier simulation obtained with the LHS, M08 produces similar storm surge but slightly improved the <span class="hlt">wave-induced</span> currents.</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="https://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('https://www.ncbi.nlm.nih.gov/pubmed/12907428','PUBMED'); return false;" href="https://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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4851087','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4851087"><span id="translatedtitle">Signal Analysis and Waveform Reconstruction of Shock <span class="hlt">Waves</span> Generated by Underwater Electrical Wire Explosions with Piezoelectric <span class="hlt">Pressure</span> Probes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhou, Haibin; Zhang, Yongmin; Han, Ruoyu; Jing, Yan; Wu, Jiawei; Liu, Qiaojue; Ding, Weidong; Qiu, Aici</p> <p>2016-01-01</p> <p>Underwater shock <span class="hlt">waves</span> (SWs) generated by underwater electrical wire explosions (UEWEs) have been widely studied and applied. Precise measurement of this kind of SWs is important, but very difficult to accomplish due to their high peak <span class="hlt">pressure</span>, steep rising edge and very short pulse width (on the order of tens of μs). This paper aims to analyze the signals obtained by two kinds of commercial piezoelectric <span class="hlt">pressure</span> probes, and reconstruct the correct <span class="hlt">pressure</span> waveform from the distorted one measured by the <span class="hlt">pressure</span> probes. It is found that both PCB138 and Müller-plate probes can be used to measure the relative SW <span class="hlt">pressure</span> value because of their good uniformities and linearities, but none of them can obtain precise SW waveforms. In order to approach to the real SW signal better, we propose a new multi-exponential <span class="hlt">pressure</span> waveform model, which has considered the faster <span class="hlt">pressure</span> decay at the early stage and the slower <span class="hlt">pressure</span> decay in longer times. Based on this model and the energy conservation law, the <span class="hlt">pressure</span> waveform obtained by the PCB138 probe has been reconstructed, and the reconstruction accuracy has been verified by the signals obtained by the Müller-plate probe. Reconstruction results show that the measured SW peak <span class="hlt">pressures</span> are smaller than the real signal. The waveform reconstruction method is both reasonable and reliable. PMID:27110789</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27110789','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27110789"><span id="translatedtitle">Signal Analysis and Waveform Reconstruction of Shock <span class="hlt">Waves</span> Generated by Underwater Electrical Wire Explosions with Piezoelectric <span class="hlt">Pressure</span> Probes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhou, Haibin; Zhang, Yongmin; Han, Ruoyu; Jing, Yan; Wu, Jiawei; Liu, Qiaojue; Ding, Weidong; Qiu, Aici</p> <p>2016-01-01</p> <p>Underwater shock <span class="hlt">waves</span> (SWs) generated by underwater electrical wire explosions (UEWEs) have been widely studied and applied. Precise measurement of this kind of SWs is important, but very difficult to accomplish due to their high peak <span class="hlt">pressure</span>, steep rising edge and very short pulse width (on the order of tens of μs). This paper aims to analyze the signals obtained by two kinds of commercial piezoelectric <span class="hlt">pressure</span> probes, and reconstruct the correct <span class="hlt">pressure</span> waveform from the distorted one measured by the <span class="hlt">pressure</span> probes. It is found that both PCB138 and Müller-plate probes can be used to measure the relative SW <span class="hlt">pressure</span> value because of their good uniformities and linearities, but none of them can obtain precise SW waveforms. In order to approach to the real SW signal better, we propose a new multi-exponential <span class="hlt">pressure</span> waveform model, which has considered the faster <span class="hlt">pressure</span> decay at the early stage and the slower <span class="hlt">pressure</span> decay in longer times. Based on this model and the energy conservation law, the <span class="hlt">pressure</span> waveform obtained by the PCB138 probe has been reconstructed, and the reconstruction accuracy has been verified by the signals obtained by the Müller-plate probe. Reconstruction results show that the measured SW peak <span class="hlt">pressures</span> are smaller than the real signal. The waveform reconstruction method is both reasonable and reliable. PMID:27110789</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://www.osti.gov/scitech/biblio/22311311','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22311311"><span id="translatedtitle">Rotation-<span class="hlt">induced</span> nonlinear wavepackets in internal <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Whitfield, A. J. Johnson, E. R.</p> <p>2014-05-15</p> <p>The long time effect of weak rotation on an internal solitary <span class="hlt">wave</span> is the decay into inertia-gravity <span class="hlt">waves</span> and the eventual formation of a localised wavepacket. Here this initial value problem is considered within the context of the Ostrovsky, or the rotation-modified Korteweg-de Vries (KdV), equation and a numerical method for obtaining accurate wavepacket solutions is presented. The flow evolutions are described in the regimes of relatively-strong and relatively-weak rotational effects. When rotational effects are relatively strong a second-order soliton solution of the nonlinear Schrödinger equation accurately predicts the shape, and phase and group velocities of the numerically determined wavepackets. It is suggested that these solitons may form from a local Benjamin-Feir instability in the inertia-gravity <span class="hlt">wave</span>-train radiated when a KdV solitary <span class="hlt">wave</span> rapidly adjusts to the presence of strong rotation. When rotational effects are relatively weak the initial KdV solitary <span class="hlt">wave</span> remains coherent longer, decaying only slowly due to weak radiation and modulational instability is no longer relevant. Wavepacket solutions in this regime appear to consist of a modulated KdV soliton wavetrain propagating on a slowly varying background of finite extent.</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://ntrs.nasa.gov/search.jsp?R=19850037158&hterms=plane+wave+spectrum&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dplane%2Bwave%2Bspectrum','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19850037158&hterms=plane+wave+spectrum&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dplane%2Bwave%2Bspectrum"><span id="translatedtitle">A further study of gravity <span class="hlt">wave</span> <span class="hlt">induced</span> drag and diffusion in the mesosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Holton, J. R.; Zhu, X.</p> <p>1984-01-01</p> <p>Lindzen's (1967) parameterization for the drag and eddy diffusion produced by breaking internal gravity <span class="hlt">waves</span> in the mesosphere and lower thermosphere is applied to a modified version of the beta-plane channel model of Holton (1982) in which an isotropic source spectrum of <span class="hlt">waves</span> is specified similar to that given in 1982 by Matsuno (1982). The transmission for each <span class="hlt">wave</span> component is influenced by Newtonian cooling and by eddy diffusion <span class="hlt">induced</span> by the breaking of other <span class="hlt">wave</span> components. In general the <span class="hlt">waves</span> with smallest Doppler-shifted phase speeds break first and produce sufficient eddy diffusion to significantly raise the breaking heights for the higher speed components. Thus, the <span class="hlt">wave</span> drag and diffusion is spread through a deep layer and the resulting mean wind profiles for both summer and winter solstice conditions are more realistic than those computed previously by Holton.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26371910','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26371910"><span id="translatedtitle">Dispersive <span class="hlt">waves</span> <span class="hlt">induced</span> by self-defocusing temporal solitons in a beta-barium-borate crystal.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhou, Binbin; Bache, Morten</p> <p>2015-09-15</p> <p>We experimentally observe dispersive <span class="hlt">waves</span> in the anomalous dispersion regime of a beta-barium-borate (BBO) crystal, <span class="hlt">induced</span> by a self-defocusing few-cycle temporal soliton. Together the soliton and dispersive <span class="hlt">waves</span> form an energetic octave-spanning supercontinuum. The soliton was excited in the normal dispersion regime of BBO through a negative cascaded quadratic nonlinearity. Using pump wavelengths from 1.24 to 1.4 μm, dispersive <span class="hlt">waves</span> are found from 1.9 to 2.2 μm, agreeing well with calculated resonant phase-matching wavelengths due to degenerate four-<span class="hlt">wave</span> mixing to the soliton. We also observe resonant radiation from nondegenerate four-<span class="hlt">wave</span> mixing between the soliton and a probe <span class="hlt">wave</span>, which was formed by leaking part of the pump spectrum into the anomalous dispersion regime. We confirm the experimental results through simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.5944S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.5944S"><span id="translatedtitle">Magnetospheric ULF <span class="hlt">Waves</span> with an Increasing Amplitude as a Superposition of Two <span class="hlt">Wave</span> Modes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shen, Xiaochen; Zong, Qiugang; Shi, Quanqi; Tian, Anmin; Sun, Weijie; Wang, Yongfu; Zhou, Xuzhi; Fu, Suiyan; Hartinger, Michael; Angelopoulos, Vassilis</p> <p>2015-04-01</p> <p>Ultra-low frequency (ULF) <span class="hlt">waves</span> play an important role in transferring energy by buffeting the magnetosphere with solar wind <span class="hlt">pressure</span> impulses. The amplitudes of magnetospheric ULF <span class="hlt">waves</span>, which are <span class="hlt">induced</span> by solar wind dynamic <span class="hlt">pressure</span> enhancements or shocks, are thought to damp in half or one <span class="hlt">wave</span> cycle. We report on in situ observations of the solar wind dynamic <span class="hlt">pressure</span> impulses-<span class="hlt">induced</span> magnetospheric ULF <span class="hlt">waves</span> with increasing amplitudes. We have found six ULF <span class="hlt">wave</span> events, which were <span class="hlt">induced</span> by solar wind dynamic <span class="hlt">pressure</span> enhancements, with slow but clear <span class="hlt">wave</span> amplitude increase. During three or four <span class="hlt">wave</span> cycles, the amplitudes of ion velocities and electric field of these <span class="hlt">waves</span> increased continuously by 1.3 ~4.4 times. Two significant events were selected to further study the characteristics of these ULF <span class="hlt">waves</span>. We have found that the <span class="hlt">wave</span> amplitude growth is mainly contributed by the toroidal mode <span class="hlt">wave</span>. We suggest that the <span class="hlt">wave</span> amplitude increase in the radial electric field is caused by the superposition of two <span class="hlt">wave</span> modes, a standing <span class="hlt">wave</span> excited by the solar wind dynamic impulse and a propagating compressional <span class="hlt">wave</span>. When superposed, the two <span class="hlt">wave</span> modes fit observations as does a calculation that superposes electric fields from two <span class="hlt">wave</span> sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1719c0052A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1719c0052A"><span id="translatedtitle">The use of laser-<span class="hlt">induced</span> shock <span class="hlt">wave</span> plasma spectroscopy (LISPS) for examining physical characteristics of pharmaceutical products</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abdulmadjid, Syahrun Nur; Lahna, Kurnia; Desiyana, Lydia Septa</p> <p>2016-03-01</p> <p>An experimental study has been performed to examine the physical characteristics of pharmaceutical products, such as tablet, by employing an emission plasma <span class="hlt">induced</span> by Nd-YAG laser at a low <span class="hlt">pressure</span> of Helium gas. The hardness of tablet is one of the parameters that examined during the production process for standard quality of pharmaceutical products. In the Laser-<span class="hlt">Induced</span> Shock <span class="hlt">Wave</span> Plasma Spectroscopy (LISPS), the shock <span class="hlt">wave</span> has a significant role in <span class="hlt">inducing</span> atomic excitation. It was known that, the speed of the shock wavefront depends on the hardness of the sample, and it correlates with the ionization rate of the ablated atoms. The hardness of the tablet is examined using the intensity ratio between the ion of Mg (II) 275.2 nm and the neutral of Mg (I) 285.2 nm emission lines detected from the laser-<span class="hlt">induced</span> plasma. It was observed that the ratio changes with respect to the change in the tablet hardness, namely the ratio is higher for the hard tablet. Besides the ratio measurements, we also measured the depth profile of a tablet by focusing 60 shots of irradiation of laser light at a fixed position on the surface of the tablet. It was found that the depth profile varies differently with the hardness of the tablet. These experiment results show that the technique of LISPS can be applied to examine the quality of pharmaceutical products.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003PhDT.......152P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003PhDT.......152P"><span id="translatedtitle">A nonlinear solid shell element formulation for analysis of composite panels under blast <span class="hlt">wave</span> <span class="hlt">pressure</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>Park, Hun</p> <p></p> <p>A comprehensive methodology to accurately predict the dynamic response of composite panels under blast <span class="hlt">wave</span> <span class="hlt">pressure</span> loading has been successfully developed for the first time. It includes the modeling of geometrically nonlinear dynamic effect, progressive failure and strain-rate effect on constitutive equation and strength. For dynamic analysis, a nonlinear solid shell element formulation is combined with the trapezoidal rule for numerical integration in time. The progressive damage incorporates the effect of the material failure, such as fiber failure, matrix cracking and fiber-matrix shearing failure on the stiffness and strength. Material degradation models based on the rule of mixtures are proposed for each failure mode. To implement the strain-rate effect on the constitutive equation of the material, a viscoplastic model is adopted. In this model, three material parameters are determined by conducting uniaxial tension tests on off-axis specimen. The effect of strain rates on material strength is implemented via the linear least square fit of the test data. A key ingredient of the analysis is a geometrically nonlinear solid shell element based on the assumed strain formulation to alleviate element locking. In this approach, the composite shell is treated as a three-dimensional solid. Accordingly, the change of shell thickness is allowed and the kinematics of deformation is described by six vector components at a point on the shell midsurface. The mass matrix always remains constant during the analysis. Example problems under static and dynamic loadings are solved to investigate the behavior of composite panels undergoing large deformation while experiencing material damage. The analysis results are compared with the test data available. Results of the numerical analysis show that the effect of the progressive failure and strain-rates on structural responses are considerable. For a composite plate under static <span class="hlt">pressure</span> loadings, maximum displacement and</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> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25771332','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25771332"><span id="translatedtitle">Influences of non-uniform <span class="hlt">pressure</span> field outside bubbles on the propagation of acoustic <span class="hlt">waves</span> in dilute bubbly liquids.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Yuning; Du, Xiaoze</p> <p>2015-09-01</p> <p>Predictions of the propagation of the acoustic <span class="hlt">waves</span> in bubbly liquids is of great importance for bubble dynamics and related applications (e.g. sonochemistry, sonochemical reactor design, biomedical engineering). In the present paper, an approach for modeling the propagation of the acoustic <span class="hlt">waves</span> in dilute bubbly liquids is proposed through considering the non-uniform <span class="hlt">pressure</span> field outside the bubbles. This approach is validated through comparing with available experimental data in the literature. Comparing with the previous models, our approach mainly improves the predictions of the attenuation of acoustic <span class="hlt">waves</span> in the regions with large kR0 (k is the <span class="hlt">wave</span> number and R0 is the equilibrium bubble radius). Stability of the oscillating bubbles under acoustic excitation are also quantitatively discussed based on the analytical solution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMOS23B1184B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMOS23B1184B"><span id="translatedtitle">Surface-<span class="hlt">Induced</span> Turbulence and Resulting Sand Suspension Beneath Breaking <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>Brinkkemper, J.; Ruessink, G.</p> <p>2014-12-01</p> <p>Breaking <span class="hlt">waves</span> and bores inject large amounts of turbulence into the water column as vortices, which can travel downward and entrain sand from the bed. Coastal evolution models rarely include the effect of this surface-<span class="hlt">induced</span> turbulence on sand suspension and subsequent transport to predict surf-zone morphodynamics. Here, we analyze turbulence and suspension measurements beneath non-breaking <span class="hlt">waves</span> and plunging breakers, collected during the field-scale BARDEXII laboratory experiment using a vertical array of 3 ADVs and 7 OBSs. The array was positioned at a single cross-shore location, but, because of changes in <span class="hlt">wave</span> conditions and water levels, experienced different degrees of <span class="hlt">wave</span> breaking. Results show a phase-coupling for both turbulence kinetic energy and sand concentration with the short-<span class="hlt">wave</span> orbital motion during all conditions, with the highest values when the cross-shore velocity is onshore directed. The vertical turbulence flux under plunging breakers also depends on <span class="hlt">wave</span> phase, with a downward and upward flux during offshore and onshore directed <span class="hlt">wave</span> orbital motion, respectively. The plunging jet hits the water surface in the <span class="hlt">wave</span> trough, resulting in a downward turbulence flux during the offshore directed <span class="hlt">wave</span> orbital motion. The upward flux during the onshore directed <span class="hlt">wave</span> orbital motion might represent the injected air bubbles rising to the water surface. This upward flux coincides with the peak in suspension, which, accordingly, reaches higher in the water column than beneath non-breaking <span class="hlt">waves</span>. Besides a phase-coupling with the short-<span class="hlt">wave</span> orbital motion, turbulence kinetic energy and sand concentration were also modulated on an infragravity timescale, with high values during the offshore directed infragravity flow. The effect of surface-generated turbulence on the direction and magnitude of short- and infragravity-<span class="hlt">induced</span> cross-shore sand fluxes will also be discussed. This research is supported by the Dutch Technology Foundation STW, which is part</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JPhD...41t5203D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JPhD...41t5203D"><span id="translatedtitle">Polydiagnostic calibration performed on a low <span class="hlt">pressure</span> surface <span class="hlt">wave</span> sustained argon plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Vries, N.; Palomares, J. M.; Iordanova, E. I.; van Veldhuizen, E. M.; van der Mullen, J. J. A. M.</p> <p>2008-10-01</p> <p>The electron density and electron temperature of a low <span class="hlt">pressure</span> surface <span class="hlt">wave</span> sustained argon plasma have been determined using passive and active (laser) spectroscopic methods simultaneously. In this way the validity of the various techniques is established while the plasma properties are determined more precisely. The electron density, ne, is determined with Thomson scattering (TS), absolute continuum measurements, Stark broadening and an extrapolation of the atomic state distribution function (ASDF). The electron temperature, Te, is obtained using TS and absolute line intensity (ALI) measurements combined with a collisional-radiative (CR) model for argon. At an argon <span class="hlt">pressure</span> of 15 mbar, the ne values obtained with TS and Stark broadening agree with each other within the error bars and are equal to (4 ± 0.5) × 1019 m-3, whereas the ne value (2 ± 0.5) × 1019 m-3 obtained from the continuum is about 30% lower. This suggests that the used formula and cross-section values for the continuum method have to be reconsidered. The electron density determined by means of extrapolation of the ASDF to the continuum is too high (~1020 m-3). This is most probably related to the fact that the plasma is strongly ionizing so that the extrapolation method is not justified. At 15 mbar, the Te values obtained with TS are equal to 13 400 ± 1100 K while the ALI/CR-model yields an electron temperature that is about 10% lower. It can be concluded that the passive results are in good or fair agreement with the active results. Therefore, the calibrated passive methods can be applied to other plasmas in a similar regime for which active diagnostic techniques cannot be used.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhRvL.111h7001K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhRvL.111h7001K"><span id="translatedtitle"><span class="hlt">Pressure-Induced</span> Unconventional Superconducting Phase in the Topological Insulator Bi2Se3</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kirshenbaum, Kevin; Syers, P. S.; Hope, A. P.; Butch, N. P.; Jeffries, J. R.; Weir, S. T.; Hamlin, J. J.; Maple, M. B.; Vohra, Y. K.; Paglione, J.</p> <p>2013-08-01</p> <p>Simultaneous low-temperature electrical resistivity and Hall effect measurements were performed on single-crystalline Bi2Se3 under applied <span class="hlt">pressures</span> up to 50 GPa. As a function of <span class="hlt">pressure</span>, superconductivity is observed to onset above 11 GPa with a transition temperature Tc and upper critical field Hc2 that both increase with <span class="hlt">pressure</span> up to 30 GPa, where they reach maximum values of 7 K and 4 T, respectively. Upon further <span class="hlt">pressure</span> increase, Tc remains anomalously constant up to the highest achieved <span class="hlt">pressure</span>. Conversely, the carrier concentration increases continuously with <span class="hlt">pressure</span>, including a tenfold increase over the <span class="hlt">pressure</span> range where Tc remains constant. Together with a quasilinear temperature dependence of Hc2 that exceeds the orbital and Pauli limits, the anomalously stagnant <span class="hlt">pressure</span> dependence of Tc points to an unconventional <span class="hlt">pressure-induced</span> pairing state in Bi2Se3 that is unique among the superconducting topological insulators.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910006217','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910006217"><span id="translatedtitle">Simultaneous measurements of velocity, temperature, and <span class="hlt">pressure</span> using rapid CW wavelength-modulation laser-<span class="hlt">induced</span> fluorescence of OH</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chang, A. Y.; Battles, B. E.; Hanson, R. K.</p> <p>1990-01-01</p> <p>In high speed flows, laser <span class="hlt">induced</span> fluorescence (LIF) on Doppler shifted transitions is an attractive technique for velocity measurement. LIF velocimetry was applied to combined single-point measurements of velocity, temperature, and <span class="hlt">pressure</span> and 2-D imaging of velocity and <span class="hlt">pressure</span>. Prior to recent research using NO, LIF velocimetry in combustion related flows relied largely on the use of seed molecules. Simultaneous, single-point LIF measurements is reported of velocity, temperature, and <span class="hlt">pressure</span> using the naturally occurring combustion species OH. This experiment is an extension of earlier research in which a modified ring dye laser was used to make time resolved temperature measurements behind reflected shock <span class="hlt">waves</span> by using OH absorption an in postflame gases by using OH LIF. A pair of fused-silica rhombs mounted on a single galvanonmeter in an intracavity-doubled Spectra-Physics 380 ring laser permit the UV output to be swept continuously over a few <span class="hlt">wave</span> numbers at an effective frequency of 3kHz.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhDT........58R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhDT........58R"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> phase transitions of indium selenide</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rasmussen, Anya Marie</p> <p></p> <p>In2Se3 has potential as a phase-change material for memory applications. Understanding its phase diagram is important to achieve controlled switching between phases. <span class="hlt">Pressure</span>-dependent phase transitions of In2Se3 bulk powders and nanowire samples were studied at room temperature and at elevated temperatures using synchrotron x-ray diffraction and diamond-anvil cells (DACs). alpha-In2Se3 transforms into the beta phase at 0.7 GPa, an order of magnitude lower than phase-transition critical <span class="hlt">pressures</span> in typical semiconductors. The bulk moduli are reported and the c/a ratio for the beta phase is shown to have a highly nonlinear dependence on <span class="hlt">pressure</span>. gamma-In2Se3, metastable under ambient conditions, transforms into to the high-<span class="hlt">pressure</span> beta phase between 2.8 GPa and 3.2 GPa in bulk powder samples and at slightly higher <span class="hlt">pressures</span>, between 3.2 GPa and 3.7 GPa in nanowire samples. While the gamma phase bulk modulus is similar to that of the beta phase, the decrease due to <span class="hlt">pressure</span> in the unit cell parameter ratio, c/a, is less than half the decrease seen in the beta phase. Using high-temperature DACs, we investigated how elevated temperatures and <span class="hlt">pressures</span> affect the crystal structure of In 2Se3. From these measurements, the high-<span class="hlt">pressure</span> beta phase was found to be metastable. The high-<span class="hlt">pressure</span> beta phase transitions into the high-temperature beta phase at temperatures above 380 °C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/980370','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/980370"><span id="translatedtitle">Novel <span class="hlt">Pressure-Induced</span> Interactions in Silane-Hydrogen</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Strobel, T.; Somayazulu, M; Hemley, R</p> <p>2009-01-01</p> <p>We report novel molecular compound formation from silane-hydrogen mixtures with intermolecular interactions unprecedented for hydrogen-rich solids. A complex H2 vibron spectrum with anticorrelated <span class="hlt">pressure</span>-frequency dependencies and a striking H-D exchange below 10 GPa reveal strong and unusual attractive interactions between SiH4 and H2 and molecular bond destabilization at remarkably low <span class="hlt">pressure</span>. The unique features of the observed SiH4(H2)2 compound suggest a new range of accessible <span class="hlt">pressure</span>-driven intermolecular interactions for hydrogen-bearing simple molecular systems and a new approach to perturb the hydrogen covalent bond.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007PhRvB..76q4106D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007PhRvB..76q4106D"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> enhancement of ferroelectricity in multiferroic RMn2O5 (R=Tb,Dy,Ho)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dela Cruz, C. R.; Lorenz, B.; Sun, Y. Y.; Wang, Y.; Park, S.; Cheong, S.-W.; Gospodinov, M. M.; Chu, C. W.</p> <p>2007-11-01</p> <p>Measurements of ferroelectric polarization and dielectric constant were done on RMn2O5 (R=Tb,Dy,Ho) with applied hydrostatic <span class="hlt">pressures</span> of up to 18kbar . At ambient <span class="hlt">pressure</span>, distinctive anomalies were observed in the temperature profile of both physical properties at critical temperatures marking the onset of long range antiferromegnetic order (TN1) and ferroelectricity (TC1) , as well as at temperatures when anomalous changes in the polarization, dielectric constant, and spin <span class="hlt">wave</span> commensurability have been previously reported. In particular, the step in the dielectric constant at low temperatures (TC2) , associated with both a drop in the ferroelectric polarization and an incommensurate magnetic structure, was shown to be suddenly quenched upon passing an R -dependent critical <span class="hlt">pressure</span>. This was shown to correlate with the stabilization of the high ferroelectric polarization state, which is coincident with the commensurate magnetic structure. The observation is suggested to be due to a <span class="hlt">pressure-induced</span> phase transition into a commensurate magnetic structure, as exemplified by the <span class="hlt">pressure</span>-temperature (p-T) phase diagrams constructed in this work. The p-T phase diagrams are determined for all three compounds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/10550528','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/10550528"><span id="translatedtitle">Reduction of high-energy shock-<span class="hlt">wave-induced</span> renal tubular injury by selenium.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Strohmaier, W L; Lahme, S; Weidenbach, P M; Bichler, K H</p> <p>1999-10-01</p> <p>In shock-<span class="hlt">wave-induced</span> renal injury cavitation-generated free radicals play an important role. Using an in vitro model with Madin-Darby canine kidney (MDCK) cells, we investigated the influence of selenium, a free radical scavenger, in shock-<span class="hlt">wave-induced</span> tubular cell injury. Suspensions of MDCK cells (33 x 10(6) cells/ml) were placed in small containers (volume 1.1 ml) for shock <span class="hlt">wave</span> exposure. Two groups of 12 containers each were examined: (1) control (no medication), (2) selenium (0.4 microg/ml nutrient medium). Six containers in each group were exposed to shock <span class="hlt">waves</span> (impulse rate 256, frequency 60 Hz, generator voltage 18 kV), while the other six containers in each group served as a control. After shock <span class="hlt">wave</span> exposure, the concentration of cellular enzymes such as lactate dehydrogenase (LDH), N-acetyl-beta-glucosaminidase (NAG), glutamate oxaloacetate transaminase (GOT) and glutamate lactate dehydrogenase (GLDH) in the nutrient medium was examined. Following shock <span class="hlt">wave</span> exposure there was a significant rise in LDH, NAG, GOT and GLDH concentrations. Selenium reduced this enzyme leakage significantly. Thus we conclude that selenium protects renal tubular cells against shock-<span class="hlt">wave-induced</span> injury. Since selenium is an essential part of glutathione peroxidase, this effect seems to be mediated by a reduction in reactive oxygen species. PMID:10550528</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DPPCO4013C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DPPCO4013C"><span id="translatedtitle">Shock <span class="hlt">wave</span> equation of state experiments at multi-TPa <span class="hlt">pressures</span> on NIF</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Celliers, P. M.; Fratanduono, D. E.; Peterson, J. L.; Meezan, N. B.; MacKinnon, A. J.; Braun, D. G.; Millot, M.; Fry, J.; Boehm, K. J.; Sterne, P. A.; Collins, G. W.; Nikroo, A.; Fitzsimmons, P.</p> <p>2015-11-01</p> <p>The National Ignition Facility provides an unprecedented capability to generate steady, planar, ultra-high <span class="hlt">pressure</span> shock <span class="hlt">waves</span> (up to 10 TPa or more) in solid samples. Building on successful laser shock equation of state experiments performed on a variety of other laser facilities, we have designed and fielded experiments to perform impedance match experiments on samples of C, Be, SiO2 and CH, in the range of 3 to 7 TPa. The experiments use a line-imaging VISAR as the primary diagnostic to measure the shock velocity in an Al reference standard and in an array of the four samples. Initial tests with the line-imaging VISAR show that the NIF is capable of driving shocks that are steady to better than 2% in velocity for several ns, with smooth planar breakout patterns over a 2 mm diameter spot. Hugoniot data points will be compared to current equation-of-state models for the various materials under study. This work was performed under the auspices of the U.S. Department of Energy by LLNL under contract DE-AC52-07NA27344.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/788205','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/788205"><span id="translatedtitle">On Plasma Rotation <span class="hlt">Induced</span> by Traveling Fast Alfvin <span class="hlt">Waves</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>F.W. Perkins; R.B. White; and V.S. Chan</p> <p>2001-08-09</p> <p>Absorption of fast Alfven <span class="hlt">waves</span> by the minority fundamental ion-cyclotron resonance, coupled with finite banana width physics, generates torque distributions and ultimately rotational shear layers in the bulk plasma, even when the toroidal wavenumber k(subscript ''phi'') = n/R of the fast <span class="hlt">wave</span> vanishes (n=0) and cyclotron absorption introduces no angular momentum nor canonical angular momentum [F.W. Perkins, R.B. White, P.T. Bonoli, and V.S. Chan, Phys. Plasmas 8 (2001) 2181]. The present work extends these results to travelling <span class="hlt">waves</span> with non-zero n where heating directly introduces angular momentum. Since tokamak fast-<span class="hlt">wave</span> antennas have approximately one wavelength per toroidal field coil, the toroidal mode number n lies in the range n = 10-20, independent of machine size. A zero-dimensional analysis shows that the rotation rate arising from direct torque is comparable to that of the rotational shear layer and has the same scaling. Nondimensional rotation profiles for n = (-10, 10) show modest changes from the n = 0 case in the expected direction. For a balanced antenna spectrum, the nondimensional rotational profile (averaged over n = -10, 10) lies quite close to the n = 0 profile.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApPhA.119..405K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApPhA.119..405K"><span id="translatedtitle">Graphitization <span class="hlt">wave</span> in diamond bulk <span class="hlt">induced</span> by ultrashort laser pulses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kononenko, T. V.; Zavedeev, E. V.; Kononenko, V. V.; Ashikkalieva, K. K.; Konov, V. I.</p> <p>2015-05-01</p> <p>Multi-pulse laser irradiation of diamond bulk after the optical breakdown causes extension of continuous graphitized region toward the laser beam that can be described as propagation of a "graphitization <span class="hlt">wave</span>." Velocity of the graphitization <span class="hlt">wave</span> in single-crystal diamond is measured experimentally as a function of local laser fluence for a few numerical apertures (NA = 0.36-0.09), pulsewidths (140 fs-5 ps), and beam orientations (along [110] or [100] diamond axes). The experimental results are used to develop the model of the crack-assisted thermal graphitization of diamond at the boundary of the laser-modified region. Velocity of the graphitization <span class="hlt">wave</span> is determined in general case by diffusion of heat from the light-absorbing modified region. The revealed rise in the graphitization <span class="hlt">wave</span> velocity for the [110] beam orientation can be explained by the local electric field enhancement near the crack tip, which facilitates diamond ionization and plasma-assisted energy absorption. The proposed model predicts a specific internal structure of the laser-modified region: the network of graphitic inclusions with diamond-filled gaps between them.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22306310','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22306310"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> amorphization of La{sub 1/3}TaO{sub 3}</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Noked, O.; Melchior, A.; Shuker, R.; Livneh, T.; Steininger, R.; Kennedy, B.J.; Sterer, E.</p> <p>2013-06-15</p> <p>La{sub 1/3}TaO{sub 3}, an A-site cation deficient perovskite, has been studied under <span class="hlt">pressure</span> by synchrotron X-ray powder diffraction and Raman spectroscopy. It undergoes irreversible <span class="hlt">pressure</span> <span class="hlt">induced</span> amorphization at P=18.5 GPa. An almost linear unit cell volume decrease vs. <span class="hlt">pressure</span> is observed from ambient <span class="hlt">pressure</span> up to the phase transition. The Raman spectroscopy also shows amorphization at the same <span class="hlt">pressure</span>, with positive shifts of all modes as a function of <span class="hlt">pressure</span>. The <span class="hlt">pressure</span> dependence of the E{sub g} and A{sub 1g} Raman modes arising from the octahedral oxygen network is discussed. - Graphical abstract: La{sub 1/3}Tao{sub 3} exhibits linear pressure–volume relation until irreversible <span class="hlt">pressure</span> <span class="hlt">induced</span> amorphization at 18.5 Gpa. - Highlights: • La{sub 1/3}TaO{sub 3} has been studied under <span class="hlt">pressure</span> by synchrotron XRD and Raman spectroscopy. • La{sub 1/3}TaO{sub 3} undergoes irreversible <span class="hlt">pressure</span> <span class="hlt">induced</span> amorphization around 18.5 GPa. • The transition is manifested in both XRD and Raman measurements. • A linear P–V relation is observed from ambient <span class="hlt">pressure</span> up to the phase transition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21251767','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21251767"><span id="translatedtitle">On Current Drive and <span class="hlt">Wave</span> <span class="hlt">Induced</span> Bootstrap Current in Toroidal Plasmas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hellsten, T.; Johnson, T.</p> <p>2008-11-01</p> <p>A comprehensive treatment of <span class="hlt">wave</span>-particle interactions in toroidal plasmas including collisional relaxation, applicable to heating or anomalous <span class="hlt">wave</span> <span class="hlt">induced</span> transport, has been obtained by using Monte Carlo operators satisfying quasi-neutrality. This approach enables a self-consistent treatment of <span class="hlt">wave</span>-particle interactions applicable to the banana regime in the neoclassical theory. It allows an extension into a regime with large temperature and density gradients, losses and transport of particles by <span class="hlt">wave</span>-particle interactions making the method applicable to transport barriers. It is found that at large gradients the relationship between radial electric field, parallel velocity, temperature and density gradient in the neoclassical theory is modified such that coefficient in front of the logarithmic ion temperature gradient, which in the standard neoclassical theory is small and counteracts the electric field caused by the density gradient, now changes sign and contributes to the built up of the radial electric field. The possibility to drive current by absorbing the <span class="hlt">waves</span> on trapped particles has been studied and how the <span class="hlt">wave</span>-particle interactions affect the bootstrap current. Two new current drive mechanisms are studied: current drive by <span class="hlt">wave</span> <span class="hlt">induced</span> bootstrap current and selective detrapping into passing orbits by directed <span class="hlt">waves</span>.</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://adsabs.harvard.edu/abs/2012AGUFMSM41A2208M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMSM41A2208M"><span id="translatedtitle">Propagation of ULF <span class="hlt">waves</span> into mid-latitudes ionosphere directly driven by solar wind dynamic <span class="hlt">pressure</span> variations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matsushita, T.; Seki, K.; Nishitani, N.; Hori, T.; Teramoto, M.; Kikuchi, T.; Miyoshi, Y.; Reme, H.; Singer, H. J.</p> <p>2012-12-01</p> <p>ULF <span class="hlt">waves</span> such as Pc5 in the magnetosphere have been observed using many methods such as ground-based magnetometers, HF radars, and satellites. It is thought that these magnetospheric ULF <span class="hlt">waves</span> are generated either directly on the dayside by solar wind dynamic <span class="hlt">pressure</span> pulses and/or, Kelvin-Helmholtz surface <span class="hlt">waves</span>, or indirectly on the nightside by mechanisms such as substorms. ULF <span class="hlt">waves</span> can play an important role in mass and energy transport within the inner magnetosphere. It is well known that energetic particles in the inner magnetosphere can be significantly affected by ULF <span class="hlt">waves</span> and many studies have suggested their importance in the acceleration of radiation belt electrons. One outstanding problem in ULF studies is to clarify their global characteristics, especially, how energy for the acceleration is transported from the solar wind to the magnetosphere, and finally to the ionosphere. In this study, we report on ULF <span class="hlt">wave</span> events observed globally in the magnetosphere down to 43 degrees MLAT, at mid-latitudes ionosphere, at about 14:40 and 15:30UT January 31, 2008. During the events, the solar wind had a low speed of 350 km/s, a high density of 30 /cc, and large fluctuations in dynamic <span class="hlt">pressure</span> from 6 nPa to 10 nPa. In order to investigate propagation characteristics of the ULF <span class="hlt">waves</span> based on multi-point observations from geospace to the ground, data obtained by multiple satellite observations (Cluster, GOES, and THEMIS), ground-based magnetometer observations (210 MM of nightside and GBO of dayside), and SuperDARN Hokkaido HF radar are used. The power spectra of ULF <span class="hlt">waves</span> observed in the magnetosphere by the satellites are similar to those of dynamic <span class="hlt">pressure</span> fluctuation in the magnetosheath. Time delay of ULF <span class="hlt">waves</span> in the magnetosphere to the dynamic <span class="hlt">pressure</span> fluctuation in the magnetosheath estimated through cross-correlation indicates that the ULF <span class="hlt">waves</span> propagated from dayside to nightside, and propagation speed of about 400 and 1000 km/s estimated through</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22490850','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22490850"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> reversible phase transition in thiourea dioxide crystal</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wang, Qinglei; Yan, Tingting; Zhu, Hongyang; Cui, Qiliang; Zou, Bo E-mail: zoubo@jlu.edu.cn; Wang, Kai E-mail: zoubo@jlu.edu.cn</p> <p>2015-06-28</p> <p>The effect of high <span class="hlt">pressure</span> on the crystal structure of thiourea dioxide has been investigated by Raman spectroscopy and angle-dispersive X-ray diffraction (ADXRD) in a diamond anvil cell up to 10.3 GPa. The marked changes in the Raman spectra at 3.7 GPa strongly indicated a structural phase transition associated with the distortions of hydrogen bonding. There were no further changes up to the maximum <span class="hlt">pressure</span> of 10.3 GPa and the observed transition was completely reversible when the system was brought back to ambient <span class="hlt">pressure</span>. This transition was further confirmed by the changes of ADXRD spectra. The high-<span class="hlt">pressure</span> phase was indexed and refined to an orthorhombic structure with a possible space group Pbam. The results from the first-principles calculations suggested that this phase transition was mainly related to the changes of hydrogen-bonded networks in thiourea dioxide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1728b0481S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1728b0481S"><span id="translatedtitle"><span class="hlt">Pressure</span> and temperature <span class="hlt">induced</span> elastic properties of rare earth chalcogenides</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shriya, S.; Singh, N.; Sapkale, R.; Varshney, M.; Varshney, Dinesh</p> <p>2016-05-01</p> <p>The <span class="hlt">pressure</span> and temperature dependent mechanical properties as Young modulus, Thermal expansion coefficient of rare earth REX (RE = La, Pr, Eu; X = O, S, Se, and Te) chalcogenides are studied. The rare earth chalcogenides showed a structural phase transition (B1-B2). <span class="hlt">Pressure</span> dependence of Young modulus discerns an increase in <span class="hlt">pressure</span> inferring the hardening or stiffening of the lattice as a consequence of bond compression and bond strengthening. Suppressed Young modulus as functions of temperature infers the weakening of the lattice results in bond weakening in REX. Thermal expansion coefficient demonstrates that REX (RE = La, Pr, Eu; X = O, S, Se, and Te) chalcogenides is mechanically stiffened, and thermally softened on applied <span class="hlt">pressure</span> and temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/941082','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/941082"><span id="translatedtitle"><span class="hlt">Pressure</span> <span class="hlt">Induced</span> Superconductivity in CaFe2As2</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Milton S. Torikachvili; Sergey L. Bud'ko; Ni Ni; Paul Canfield</p> <p>2008-08-01</p> <p>CaFe{sub 2}As{sub 2} has been found to be exceptionally sensitive to the application of hydrostatic <span class="hlt">pressure</span> and can be tuned to reveal all the salient features associated with FeAs superconductivity without introducing any disorder. The ambient <span class="hlt">pressure</span>, 170 K, structural/magnetic, first-order phase transition is suppressed to 128 K by 3.5 kbar. At 5.5 kbar a new transition is detected at 104 K, increasing to above 300 K by 19 kbar. A low temperature, superconducting dome (T{sub c} {approx} 12 K) is centered around 5 kbar, extending down to 2.3 kbar and up to 8.6 kbar. This superconducting phase appears to exist when the low <span class="hlt">pressure</span> transition is suppressed sufficiently, but before the high <span class="hlt">pressure</span> transition has reduced the resistivity too dramatically.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JASTP.103..169P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JASTP.103..169P"><span id="translatedtitle">Whistler <span class="hlt">wave-induced</span> ionospheric plasma turbulence: Source mechanisms and remote sensing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pradipta, R.; Rooker, L. A.; Whitehurst, L. N.; Lee, M. C.; Ross, L. M.; Sulzer, M. P.; Gonzalez, S.; Tepley, C.; Aponte, N.; See, B. Z.; Hu, K. P.</p> <p>2013-10-01</p> <p>We report a series of experiments conducted at Arecibo Observatory in the past, aimed at the investigation of 40.75 kHz whistler <span class="hlt">wave</span> interactions with ionospheric plasmas and the inner radiation belts at L=1.35. The whistler <span class="hlt">waves</span> are launched from a Naval transmitter (code-named NAU) operating in Aguadilla, Puerto Rico at the frequency and power of 40.75 kHz and 100 kW, respectively. Arecibo radar, CADI, and optical instruments were used to monitor the background ionospheric conditions and detect the <span class="hlt">induced</span> ionospheric plasma effects. Four-<span class="hlt">wave</span> interaction processes produced by whistler <span class="hlt">waves</span> in the ionosphere can excite lower hybrid <span class="hlt">waves</span>, which can accelerate ionospheric electrons. Furthermore, whistler <span class="hlt">waves</span> propagating into the magnetosphere can trigger precipitation of energetic electrons from the radiation belts. Radar and optical measurements can distinguish <span class="hlt">wave-wave</span> and <span class="hlt">wave</span>-particle interaction processes occurring at different altitudes. Electron acceleration by different mechanisms can be verified from the radar measurements of plasma lines. To facilitate the coupling of NAU-launched 40.75 kHz whistler <span class="hlt">waves</span> into the ionosphere, we can rely on naturally occurring spread F irregularities to serve as ionospheric ducts. We can also use HF <span class="hlt">wave</span>-created ducts/artificial waveguides, as demonstrated in our earlier Arecibo experiments and recent Gakona experiments at HAARP. The newly constructed Arecibo HF heater will be employed in our future experiments, which can extend the study of whistler <span class="hlt">wave</span> interactions with the ionosphere and the magnetosphere/radiation belts as well as the whistler <span class="hlt">wave</span> conjugate propagation between Arecibo and Puerto Madryn, Argentina.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008PhRvB..78e2102H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008PhRvB..78e2102H"><span id="translatedtitle">Elastic stability of β-Ti under <span class="hlt">pressure</span> calculated using a first-principles plane-<span class="hlt">wave</span> pseudopotential method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hu, Qing-Miao; Lu, Song; Yang, Rui</p> <p>2008-08-01</p> <p>The elastic moduli c' and c44 of β-Ti with respect to external <span class="hlt">pressure</span> P (up to about 138 GPa) are calculated with a first-principles plane-<span class="hlt">wave</span> pseudopotential method. The accuracy of the calculations regarding the plane-<span class="hlt">wave</span> cut-off energy, k -point mesh, and transferability of the pseudopotentials is carefully tested. It is found that the critical <span class="hlt">pressure</span> beyond which β-Ti satisfies the elastic stability conditions is about 60 GPa. The Mulliken population analysis shows that both s and p electrons transfer to the d orbitals with increasing <span class="hlt">pressure</span>, however, the number of s electrons starts to increase when the <span class="hlt">pressure</span> exceeds about 70 GPa. The number of d electrons at the critical <span class="hlt">pressure</span> is about 2.96, in perfect agreement with the critical number of d electrons for a stable bcc Ti-V alloy, which demonstrates the correlation between the stability of bcc metals and their d orbital occupation. The bonding charge density calculations show charge accumulation on the d-t2g orbitals under high <span class="hlt">pressure</span>, which may improve the elastic stability of β-Ti .</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AIPC.1592..341C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AIPC.1592..341C"><span id="translatedtitle">Investigation on the generation characteristic of <span class="hlt">pressure</span> pulse <span class="hlt">wave</span> signal during the measurement-while-drilling process</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Changqing, Zhao; Kai, Liu; Tong, Zhao; Takei, Masahiro; Weian, Ren</p> <p>2014-04-01</p> <p>The mud-pulse logging instrument is an advanced measurement-while-drilling (MWD) tool and widely used by the industry in the world. In order to improve the signal transmission rate, ensure the accurate transmission of information and address the issue of the weak signal on the ground of oil and gas wells, the signal generator should send out the strong mud-pulse signals with the maximum amplitude. With the rotary valve pulse generator as the study object, the three-dimensional Reynolds NS equations and standard k - ɛ turbulent model were used as a mathematical model. The speed and <span class="hlt">pressure</span> coupling calculation was done by simple algorithms to get the amplitudes of different rates of flow and axial clearances. Tests were done to verify the characteristics of the <span class="hlt">pressure</span> signals. The <span class="hlt">pressure</span> signal was captured by the standpiece <span class="hlt">pressure</span> monitoring system. The study showed that the axial clearances grew bigger as the <span class="hlt">pressure</span> <span class="hlt">wave</span> amplitude value decreased and caused the weakening of the pulse signal. As the rate of flow got larger, the <span class="hlt">pressure</span> <span class="hlt">wave</span> amplitude would increase and the signal would be enhanced.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/1425683','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/1425683"><span id="translatedtitle">Dissociation of F-actin <span class="hlt">induced</span> by hydrostatic <span class="hlt">pressure</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Garcia, C R; Amaral Júnior, J A; Abrahamsohn, P; Verjovski-Almeida, S</p> <p>1992-11-01</p> <p>F-actin purified from rabbit skeletal muscle undergoes reversible dissociation when subjected to hydrostatic <span class="hlt">pressures</span> up to 240 MPa. Dissociation and reversibility were detected by the following procedures: fluorescence spectral changes observed under <span class="hlt">pressure</span>, when either intrinsic tryptophan or pyrenyl emission of N-(1-pyrenyl)iodoacetamide-labeled actin were monitored; electron microscopy of samples fixed under <span class="hlt">pressure</span>; size-exclusion HPLC of <span class="hlt">pressurized</span> actin. The effect of <span class="hlt">pressure</span> upon F-actin that had been polymerized in the presence of either Mg2+, Ca2+ or K+ was studied. The standard volume changes for the association of actin subunits, calculated from <span class="hlt">pressure</span>/dissociation curves were 74 +/- 14 ml/mol for Mg-F-actin, 79 +/- 12 ml/mol for Ca-F-actin and 328 +/- 63 ml/mol for K-F-actin, indicating that actin subunits are packed differently in the polymer depending on which cation is present. All <span class="hlt">pressure</span>/dissociation data could be fitted by a model for dissociation of a dimer, which suggests that in the F-actin filament there is a predominant intersubunit interaction interface, most likely the head-to-tail intrastrand interaction between two subunits which repeats itself along the polymer. A tenfold change in total protein concentration from 20 micrograms to 200 micrograms/ml Mg-F-actin did not cause a change in the <span class="hlt">pressure</span> required for half-maximal dissociation. This indicates a heterogeneity of free energy of association among actin monomers in the Mg-F-actin polymer, suggesting that, in addition to the predominant intersubunit interaction, the disordered interactions in the filament significantly contribute to the heterogeneity of microenvironments in the interface between the subunits. PMID:1425683</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMMR31A1985I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMMR31A1985I"><span id="translatedtitle">In situ observation of the <span class="hlt">pressure-induced</span> phase transitions of portlandite and influential factors on the <span class="hlt">pressure</span> response</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Iizuka, R.; Komatsu, K.; Kagi, H.; Nakano, S.</p> <p>2010-12-01</p> <p><span class="hlt">Pressure-induced</span> structural changes in portlandite, Ca(OH)2, draw attentions as a model system for understanding the behavior of hydrogen bonding in solids. There still remains a discrepancy in the <span class="hlt">pressure</span> response of portlandite among the previous studies. A crystal-to-crystal phase transition or a <span class="hlt">pressure-induced</span> amorphization occurs at 8-12 GPa at room temperature in powder samples in various <span class="hlt">pressure</span> transmitting media [Meade and Jeanloz. 1990; Catalli et al., 2008 etc.], whereas a single crystal transforms to a high-<span class="hlt">pressure</span> (high-P) form at 6 GPa [Ekbundit et al., 1996]. So far, the relationship between the phase transition mechanism and influential factors as possible driving forces, such as the grain size, the hydrostatic condition and the isotope effect, has not been fully established yet. In this study, <span class="hlt">pressure</span>-responses of synthesized single crystals and powder of portlandite were investigated using diamond anvil cells under quasi-hydrostatic conditions. Powder samples of Ca(OH)2 were synthesized by dissolving CaO in H2O. Single crystal was obtained by recrystallization from the synthesized powder sample with excess H2O on the glass plates in a desiccator. Raman spectra, IR spectra and X-ray diffraction (XRD) measurements were conducted up to 25 GPa using a 4:1 methanol-ethanol mixture or helium was used as a <span class="hlt">pressure</span> medium. Applied <span class="hlt">pressure</span> and the hydrostaticity were estimated by ruby fluorescence. Angle-dispersive powder X-ray diffraction patterns were measured at the beamline 18C, Photon Factory, KEK. Single crystal XRD was measured using a micro focused X-ray diffractometer (MicroMax-007, Rigaku) with confocal multi layer mirrors. Our results show that both the grain size and the hydrostaticity serve independently as influential factors on the phase transition <span class="hlt">pressure</span> and the process toward the subsequent amorphization. We first observed the difference in the phase transition <span class="hlt">pressure</span> between Ca(OH)2 and Ca(OD)2 single crystals in helium</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMGP42A..08G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMGP42A..08G"><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.; Le Goff, M.; de Wit, M.</p> <p>2010-12-01</p> <p>Meteorites and diamonds encounter high-<span class="hlt">pressures</span> during their geologic histories. These materials commonly contain magnetic inclusions of pyrrhotite, and 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 magnetic measurements performed at high-<span class="hlt">pressures</span> on single and multi-domain pyrrhotite. A magnetic hysteresis model based on our observations suggests that multidomain pyrrhotite transforms into single domain-like material, and once in the single domain state, hysteresis loops become progressively squarer and then squatter with increasing <span class="hlt">pressure</span>, until they ultimately collapse approaching the paramagnetic state at the transition. The ratio of the bulk magnetic coercive force to magnetic remanence for pure pyrrhotite is reversible with <span class="hlt">pressure</span> and follows a logarithmic law as a function of <span class="hlt">pressure</span>, which can be used as a magnetic barometer for natural systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1043806','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1043806"><span id="translatedtitle">The AC-Stark Effect in Nitric Oxide <span class="hlt">Induced</span> by Rapidly Swept Continuous <span class="hlt">Wave</span> Quantum Cascade Lasers</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Duxbury, Geoffrey; Kelly, James F.; Blake, Thomas A.; Langford, Nigel</p> <p>2012-05-07</p> <p>A large AC Stark effect has been observed when nitric oxide, at low <span class="hlt">pressure</span> in a long optical path (100 m) Herriot cell, is subjected to infrared radiation from a rapidly swept, continuous <span class="hlt">wave</span> infrared quantum cascade laser. As the frequency sweep rate of the laser is increased, an emission signal <span class="hlt">induced</span> by rapid passage, occurs after the laser frequency has passed through the resonance of a molecular absorption line. At very high sweep rates a laser field-<span class="hlt">induced</span> splitting of the absorptive part of the signal is observed, due to the AC Stark effect. This splitting is related to the Autler-Townes mixing of the hyperfine transitions, which lie within the lambda doublet components of the transition, under the Doppler broadened envelope.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013MPLB...2750221J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013MPLB...2750221J"><span id="translatedtitle">First-Principles Studies of <span class="hlt">Pressure-Induced</span> Structural and Insulator-To Transitions in Alkaline-Earth Dicarbides MC2 (M = Ca, Sr and Ba)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiang, Li-Na</p> <p>2013-12-01</p> <p><span class="hlt">Pressure-induced</span> phase transitions in MC2 (M = Ca, Sr and Ba) are investigated by using the first-principles plane <span class="hlt">wave</span> pseudopotential method within the generalized gradient approximation. The first-order phase transition from tetragonal phase (CaC2-type, space group I4/mmm) to rhombohedral (CsCl-type, space group R/line{3}m) structure is predicted to occur at 22.2, 10.0 and 3.6 GPa, respectively, and transition <span class="hlt">pressure</span> point of BaC2 agrees well with recent theoretical works. Based on the electronic analysis, the ionic Ca-C bond character becomes stronger with increasing <span class="hlt">pressure</span> in both I4/mmm and R/line{3}m phases. In particular, there will occur a transition from insulator to metal with increasing <span class="hlt">pressure</span> due to the reason that the calculated band gap gets narrower and finally closes at some high <span class="hlt">pressure</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......541S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......541S"><span id="translatedtitle">Surfactant Dynamics: Spreading and <span class="hlt">Wave</span> <span class="hlt">Induced</span> Dynamics of a Monolayer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Strickland, Stephen Lee</p> <p></p> <p>Material adsorbed to the surface of a fluid - for instance crude oil in the ocean, biological surfactant on ocular or pulmonary mucous, or emulsions - can form a 2-dimensional mono-molecular layer. These materials, called surfactants, can behave like a compressible viscous 2-dimensional fluid, and can generate surface stresses that influence the sub-fluid's bulk flow. Additionally, the sub-fluid's flow can advect the surfactant and generate gradients in the surfactant distribution and thereby generate gradients in the interfacial properties. Due to the difficulty of non-invasive measurements of the spatial distribution of a molecular monolayer at the surface, little is known about the dynamics that couple the surface motion and the evolving density field. In this dissertation, I will present a novel method for measuring the spatiotemporal dynamics of the surfactant surface density through the fluorescence emission of NBD-tagged phosphatidylcholine, a lipid, and we will compare the surfactant dynamics to the dynamics of the surface morphology.With this method, we will consider the inward and outward spreading of a surfactant on a thin fluid film as well as the advection of a surfactant by linear and non-linear gravity-capillary <span class="hlt">waves</span>. These two types of surfactant coupled fluid flows will allow us to probe well-accepted assumptions about the coupled fluid-surfactant dynamics. In chapter 1, we review the models used for understanding the spreading of a surfactant on a thin fluid film and the motion of surfactant on a linear gravity-capillary <span class="hlt">wave</span>. In chapter 2, we will present the experimental methods used in this dissertation. In chapter 3, we will study the outward spreading of a localized region of surfactant and show that the spreading of a monolayer is considerably different from the spreading of thicker-layered surfactant. In chapter 4, we will investigate the inward spreading of a surfactant into a circular surfactant-free region and show that hole closure and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25515673','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25515673"><span id="translatedtitle"><span class="hlt">Pressure-induced</span> metathesis reaction to sequester Cs.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Im, Junhyuck; Seoung, Donghoon; Lee, Seung Yeop; Blom, Douglas A; Vogt, Thomas; Kao, Chi-Chang; Lee, Yongjae</p> <p>2015-01-01</p> <p>We report here a <span class="hlt">pressure</span>-driven metathesis reaction where Ag-exchanged natrolite (Ag16Al16Si24O80·16H2O, Ag-NAT) is <span class="hlt">pressurized</span> in an aqueous CsI solution, resulting in the exchange of Ag(+) by Cs(+) in the natrolite framework forming Cs16Al16Si24O80·16H2O (Cs-NAT-I) and, above 0.5 GPa, its high-<span class="hlt">pressure</span> polymorph (Cs-NAT-II). During the initial cation exchange, the precipitation of AgI occurs. Additional <span class="hlt">pressure</span> and heat at 2 GPa and 160 °C transforms Cs-NAT-II to a pollucite-related, highly dense, and water-free triclinic phase with nominal composition CsAlSi2O6. At ambient temperature after <span class="hlt">pressure</span> release, the Cs remains sequestered in a now monoclinic pollucite phase at close to 40 wt % and a favorably low Cs leaching rate under back-exchange conditions. This process thus efficiently combines the <span class="hlt">pressure</span>-driven separation of Cs and I at ambient temperature with the subsequent sequestration of Cs under moderate <span class="hlt">pressures</span> and temperatures in its preferred waste form suitable for long-term storage at ambient conditions. The zeolite pollucite CsAlSi2O6·H2O has been identified as a potential host material for nuclear waste remediation of anthropogenic (137)Cs due to its chemical and thermal stability, low leaching rate, and the large amount of Cs it can contain. The new water-free pollucite phase we characterize during our process will not display radiolysis of water during longterm storage while maintaining the Cs content and low leaching rate. PMID:25515673</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19206843','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19206843"><span id="translatedtitle">Mesoscale variations in acoustic signals <span class="hlt">induced</span> by atmospheric gravity <span class="hlt">waves</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chunchuzov, Igor; Kulichkov, Sergey; Perepelkin, Vitaly; Ziemann, Astrid; Arnold, Klaus; Kniffka, Anke</p> <p>2009-02-01</p> <p>The results of acoustic tomographic monitoring of the coherent structures in the lower atmosphere and the effects of these structures on acoustic signal parameters are analyzed in the present study. From the measurements of acoustic travel time fluctuations (periods 1 min-1 h) with distant receivers, the temporal fluctuations of the effective sound speed and wind speed are retrieved along different ray paths connecting an acoustic pulse source and several receivers. By using a coherence analysis of the fluctuations near spatially distanced ray turning points, the internal <span class="hlt">wave</span>-associated fluctuations are filtered and their spatial characteristics (coherences, horizontal phase velocities, and spatial scales) are estimated. The capability of acoustic tomography in estimating wind shear near ground is shown. A possible mechanism describing the temporal modulation of the near-ground wind field by ducted internal <span class="hlt">waves</span> in the troposphere is proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19730029793&hterms=atmospheric+electric+field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Datmospheric%2Belectric%2Bfield','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19730029793&hterms=atmospheric+electric+field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Datmospheric%2Belectric%2Bfield"><span id="translatedtitle">Atmospheric <span class="hlt">wave-induced</span> instability in the nighttime E-region.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Beer, T.; Moorcroft, D. R.</p> <p>1972-01-01</p> <p>Examination of the perturbed continuity equation when the perturbations are the result of an internal atmospheric gravity <span class="hlt">wave</span> in the E region. The transient response of the ionization is interpreted as the gradient instability and the values of the vertical and horizontal <span class="hlt">wave</span> numbers that will <span class="hlt">induce</span> it are plotted for various heights. Only in the presence of westward directed electric fields, which are believed to occur only at night, will the gravity <span class="hlt">waves</span> <span class="hlt">induce</span> the gradient instability. Approximate analytic expressions are obtained for the permitted <span class="hlt">wave</span> numbers as well as for the instability growth times. In the course of this analysis it is shown that in the D region all irregularities, even those that are field-aligned, will tend to move with the ion velocity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19730057101&hterms=diffusion+coefficient&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Ddiffusion%2Bcoefficient','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19730057101&hterms=diffusion+coefficient&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Ddiffusion%2Bcoefficient"><span id="translatedtitle"><span class="hlt">Wave-induced</span> eddy diffusion coefficients in the upper atmosphere of Mars.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Beasley, W. H.; Hodges, R. R., Jr.</p> <p>1973-01-01</p> <p>A theory and method previously used to calculate terrestrial eddy diffusion coefficients due to instabilities in internal gravity <span class="hlt">waves</span> have been extended to obtain <span class="hlt">wave-induced</span> eddy diffusion coefficients in the upper atmosphere of Mars. If the Martian atmosphere is relatively dry (water vapor mixing ratio much less than .001), the effects of radiative damping are minimal for all but the longest-period <span class="hlt">waves</span>. For greater concentrations of water vapor the effects of radiative damping are increased, but in any event it is reasonable to expect <span class="hlt">wave-induced</span> turbulence, with eddy diffusion coefficients of the order of 10 to the 7th sq cm/sec in the Martian upper atmosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21409059','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21409059"><span id="translatedtitle">Constraints on primordial density perturbations from <span class="hlt">induced</span> gravitational <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Assadullahi, Hooshyar; Wands, David</p> <p>2010-01-15</p> <p>We consider the stochastic background of gravitational <span class="hlt">waves</span> produced during the radiation-dominated hot big bang as a constraint on the primordial density perturbation on comoving length scales much smaller than those directly probed by the cosmic microwave background or large-scale structure. We place weak upper bounds on the primordial density perturbation from current data. Future detectors such as BBO and DECIGO will place much stronger constraints on the primordial density perturbation on small scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22107734','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22107734"><span id="translatedtitle">Emission of radiation <span class="hlt">induced</span> by pervading Alfven <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zhao, G. Q.; Wu, C. S.</p> <p>2013-03-15</p> <p>It is shown that under certain conditions, propagating Alfven <span class="hlt">waves</span> can energize electrons so that consequently a new cyclotron maser instability is born. The necessary condition is that the plasma frequency is lower than electron gyrofrequency. This condition implies high Alfven speed, which can pitch-angle scatter electrons effectively and therefore the electrons are able to acquire free energy which are needed for the instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRB..119.5651G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRB..119.5651G"><span id="translatedtitle"><span class="hlt">Induced</span> electromagnetic field by seismic <span class="hlt">waves</span> in Earth's magnetic field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gao, Yongxin; Chen, Xiaofei; Hu, Hengshan; Wen, Jian; Tang, Ji; Fang, Guoqing</p> <p>2014-07-01</p> <p>Studied in this article are the properties of the electromagnetic (EM) fields generated by an earthquake due to the motional induction effect, which arises from the motion of the conducting crust across the Earth's magnetic field. By solving the governing equations that couple the elastodynamic equations with Maxwell equations, we derive the seismoelectromagnetic wavefields excited by a single-point force and a double-couple source in a full space. Two types of EM disturbances can be generated, i.e., the coseismic EM field accompanying the seismic <span class="hlt">wave</span> and the independently propagating EM <span class="hlt">wave</span> which arrives much earlier than the seismic <span class="hlt">wave</span>. Simulation of an Mw6.1 earthquake shows that at a receiving location where the seismic acceleration is on the order of 0.1 m/s2, the coseismic electric and magnetic fields are on the orders of 1 μV/m and 0.1 nT, respectively, agreeing with the EM data observed in 2008 Mw6.1 Qingchuan earthquake, China, and indicating that the motional induction effect is effective enough to generate observable EM signal. We also simulated the EM signals observed by Haines et al. which were called the Lorentz fields and cannot be explained by the electrokinetic effect. The result shows that the EM <span class="hlt">wave</span> generated by a horizontal force can explain the data well, suggesting that the motional induction effect is responsible for the Lorentz fields. The motional induction effect is compared with the electrokinetic effect, showing the overall conclusion that the former dominates the mechanoelectric conversion under low-frequency and high-conductivity conditions while the latter dominates under high-frequency and low-conductivity conditions.</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. Their policies may differ from this site.</small> </div> </center> <div id="footer-wrapper"> <div class="footer-content"> <div id="footerOSTI" class=""> <div class="row"> <div class="col-md-4 text-center col-md-push-4 footer-content-center"><small><a href="http://www.science.gov/disclaimer.html">Privacy and Security</a></small> <div class="visible-sm visible-xs push_footer"></div> </div> <div class="col-md-4 text-center col-md-pull-4 footer-content-left"> <img src="https://www.osti.gov/images/DOE_SC31.png" alt="U.S. Department of Energy" usemap="#doe" height="31" width="177"><map style="display:none;" name="doe" id="doe"><area shape="rect" coords="1,3,107,30" href="http://www.energy.gov" alt="U.S. Deparment of Energy"><area shape="rect" coords="114,3,165,30" href="http://www.science.energy.gov" alt="Office of Science"></map> <a ref="http://www.osti.gov" style="margin-left: 15px;"><img src="https://www.osti.gov/images/footerimages/ostigov53.png" alt="Office of Scientific and Technical Information" height="31" width="53"></a> <div class="visible-sm visible-xs push_footer"></div> </div> <div class="col-md-4 text-center footer-content-right"> <a href="http://www.osti.gov/nle"><img src="https://www.osti.gov/images/footerimages/NLElogo31.png" alt="National Library of Energy" height="31" width="79"></a> <a href="http://www.science.gov"><img src="https://www.osti.gov/images/footerimages/scigov77.png" alt="science.gov" height="31" width="98"></a> <a href="http://worldwidescience.org"><img src="https://www.osti.gov/images/footerimages/wws82.png" alt="WorldWideScience.org" height="31" width="90"></a> </div> </div> </div> </div> </div> <p><br></p> </div><!-- container --> </body> </html>