WorldWideScience

Sample records for high amplitude shock

  1. Evaluation of a Hopkinson bar fly-away technique for high amplitude shock accelerometer calibration

    Energy Technology Data Exchange (ETDEWEB)

    Togami, T.C.; Bateman, V.I.; Brown, F.A.

    1997-11-01

    A split Hopkinson bar technique has been developed to evaluate the performance of accelerometers that measure large amplitude pulses. An evaluation of this technique has been conducted in the Mechanical Shock Laboratory at Sandia National Laboratories (SNL) to determine its use in the practical calibration of accelerometers. This evaluation consisted of three tasks. First, the quartz crystal was evaluated in a split Hopkinson bar configuration to evaluate the quartz gage`s sensitivity and frequency response at force levels of 18,000, 35,000 and 53,000 N at ambient temperature, {minus}48 C and +74 C. Secondly, the fly away technique was evaluated at shock amplitudes of 50,000, 100,000, 150,000 and 200,000 G (1 G = 9.81 m/s{sup 2}) at ambient temperature, {minus}48 C and +74 C. Lastly, the technique was performed using a NIST calibrated reference accelerometer. Comparisons of accelerations calculated from the quartz gage data and the measured acceleration data have shown very good agreement. Based on this evaluation, the authors expect this split Hopkinson fly away technique to be certified by the SNL Primary Standards Laboratory.

  2. LOW AMPLITUDE SINGLE AND MULTIPLE SHOCK INITIATION EXPERIMENTS AND MODELING OF LX-04

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-06-27

    Shock initiation experiments were performed on the plastic bonded explosive (PBX) LX-04 (85% HMX, 15% Viton binder) using single and multiple low amplitude shocks to obtain pressure history data for use in Ignition and Growth reactive flow modeling parameterization. A 100 mm diameter propellant driven gas gun was utilized to initiate the LX-04 explosive charges containing manganin piezoresistive pressure gauge packages placed between explosive discs. In the single shock experiments, the run distances to detonation at three shock pressures showed agreement with previously published data above 3 GPa. Even longer run distances to detonation were measured using 80 mm long by 145 mm diameter LX-04 charges impacted by low velocity projectiles from a 155 mm diameter gun. The minimum shock pressure required to cause low levels of exothermic reaction were determined for these large LX-04 charge dimensions. Multiple shocks were generated as double shocks by using a flyer plate with two materials and as reflected shocks by placing a high impedance material at the rear of the explosive charge. In both cases, the first shock pressure was not high enough to cause detonation of LX-04, and the second shock pressure, which would have been sufficient to cause detonation if generated by a single shock, failed to cause detonation. Thus LX-04 exhibited shock desensitization over a range of 0.6 to 1.4 GPa. The higher shock pressure LX-04 model was extended to accurately simulate these lower pressure and multiple shock gauge records. The shock desensitization effects observed with multiple shock compressions were partially accounted for in the model by using a critical compression corresponding to a shock pressure of 1.2 GPa. This shock desensitization effect occurs at higher pressures than those of other HMX-based PBX's containing higher HMX percentages.

  3. High Amplitude Secondary Mass Drive

    Energy Technology Data Exchange (ETDEWEB)

    DYCK,CHRISTOPHER WILLIAM; ALLEN,JAMES J.; HUBER,ROBERT JOHN; SNIEGOWSKI,JEFFRY J.

    2000-07-06

    In this paper we describe a high amplitude electrostatic drive for surface micromachined mechanical oscillators that may be suitable for vibratory gyroscopes. It is an advanced design of a previously reported dual mass oscillator (Dyck, et. al., 1999). The structure is a 2 degree-of-freedom, parallel-plate driven motion amplifier, termed the secondary mass drive oscillator (SMD oscillator). During each cycle the device contacts the drive plates, generating large electrostatic forces. Peak-to-peak amplitudes of 54 {micro}m have been obtained by operating the structure in air with an applied voltage of 11 V. We describe the structure, present the analysis and design equations, and show recent results that have been obtained, including frequency response data, power dissipation, and out-of- plane motion.

  4. Effect of initial perturbation amplitude on Richtmyer-Meshkov flows induced by strong shocks

    Energy Technology Data Exchange (ETDEWEB)

    Dell, Z.; Abarzhi, S. I., E-mail: snezhana.abarzhi@gmail.com, E-mail: sabarji@andrew.cmu.edu [Mellon College of Science and Carnegie Mellon University – Qatar, Carnegie Mellon University, Pittsburgh, Pennsylvania 15231 (United States); Stellingwerf, R. F. [Stellingwerf Consulting, Huntsville, Alabama 35803 (United States)

    2015-09-15

    We systematically study the effect of the initial perturbation on Richtmyer-Meshkov (RM) flows induced by strong shocks in fluids with contrasting densities. Smooth Particle Hydrodynamics simulations are employed. A broad range of shock strengths and density ratios is considered. The amplitude of the initial single mode sinusoidal perturbation of the interface varies from 0% to 100% of its wavelength. The simulations results are compared, wherever possible, with four rigorous theories, and with other experiments and simulations, achieving good quantitative and qualitative agreement. Our study is focused on early time dynamics of the Richtmyer-Meshkov instability (RMI). We analyze the initial growth-rate of RMI immediately after the shock passage, when the perturbation amplitude increases linearly with time. For the first time, to the authors' knowledge, we find that the initial growth-rate of RMI is a non-monotone function of the initial perturbation amplitude, thus restraining the amount of energy that can be deposited by the shock at the interface. The maximum value of the initial growth-rate depends on the shock strength and the density ratio, whereas the corresponding value of the initial perturbation amplitude depends only slightly on the shock strength and density ratio.

  5. Large-Amplitude Electrostatic Waves Observed at a Supercritical Interplanetary Shock

    Science.gov (United States)

    Wilson, L. B., III; Cattell, C. A.; Kellogg, P. J.; Goetz, K.; Kersten, K.; Kasper, J. C.; Szabo, A.; Wilber, M.

    2010-01-01

    We present the first observations at an interplanetary shock of large-amplitude (> 100 mV/m pk-pk) solitary waves and large-amplitude (approx.30 mV/m pk-pk) waves exhibiting characteristics consistent with electron Bernstein waves. The Bernstein-like waves show enhanced power at integer and half-integer harmonics of the cyclotron frequency with a broadened power spectrum at higher frequencies, consistent with the electron cyclotron drift instability. The Bernstein-like waves are obliquely polarized with respect to the magnetic field but parallel to the shock normal direction. Strong particle heating is observed in both the electrons and ions. The observed heating and waveforms are likely due to instabilities driven by the free energy provided by reflected ions at this supercritical interplanetary shock. These results offer new insights into collisionless shock dissipation and wave-particle interactions in the solar wind.

  6. Quasiperpendicular high Mach number Shocks

    CERN Document Server

    Sulaiman, A H; Dougherty, M K; Burgess, D; Fujimoto, M; Hospodarsky, G B

    2015-01-01

    Shock waves exist throughout the universe and are fundamental to understanding the nature of collisionless plasmas. Reformation is a process, driven by microphysics, which typically occurs at high Mach number supercritical shocks. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. In this letter we present a study of very high Mach number shocks in a parameter space that has been poorly explored and we identify reformation using in situ magnetic field observations from the Cassini spacecraft at 10 AU. This has given us an insight into quasi-perpendicular shocks across two orders of magnitude in Alfven Mach number (MA) which could potentially bridge the gap between modest terrestrial shocks and more exotic astrophysical shocks. For the first time, we show evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted timescale of ~0.3 {\\tau}c, where {\\tau}c is the ion gyroperio...

  7. Arbitrary amplitude magnetosonic solitary and shock structures in spin quantum plasma

    Energy Technology Data Exchange (ETDEWEB)

    Sahu, Biswajit [Department of Mathematics, West Bengal State University, Barasat, Kolkata-700126 (India); Sinha, Anjana; Roychoudhury, Rajkumar; Khan, Manoranjan [Department of Instrumentation Science, Jadavpur University, Kolkata-700 032 (India)

    2013-11-15

    A nonlinear analysis is carried out for the arbitrary amplitude magnetosonic solitary and shock structures in spin quantum plasmas. A quantum magnetohydrodynamic model is used to describe the magnetosonic quantum plasma with the Bohm potential and the pressure like spin force for electrons. Analytical calculations are used to simplify the basic equations, which are then studied numerically. It is shown that the magnetic diffusivity is responsible for dissipation, which causes the shock-like structures rather than the soliton structures. Additionally, wave speed, Zeeman energy, and Bohm potential are found to have significant impact on the shock wave structures.

  8. Quasiperpendicular High Mach Number Shocks

    Science.gov (United States)

    Sulaiman, A. H.; Masters, A.; Dougherty, M. K.; Burgess, D.; Fujimoto, M.; Hospodarsky, G. B.

    2015-09-01

    Shock waves exist throughout the Universe and are fundamental to understanding the nature of collisionless plasmas. Reformation is a process, driven by microphysics, which typically occurs at high Mach number supercritical shocks. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. In this Letter we present a study of very high Mach number shocks in a parameter space that has been poorly explored and we identify reformation using in situ magnetic field observations from the Cassini spacecraft at 10 AU. This has given us an insight into quasiperpendicular shocks across 2 orders of magnitude in Alfvén Mach number (MA ) which could potentially bridge the gap between modest terrestrial shocks and more exotic astrophysical shocks. For the first time, we show evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted time scale of ˜0.3 τc , where τc is the ion gyroperiod. In addition, we experimentally reveal the relationship between reformation and MA and focus on the magnetic structure of such shocks to further show that for the same MA , a reforming shock exhibits stronger magnetic field amplification than a shock that is not reforming.

  9. The influence of fluid properties and pulse amplitude on bubble dynamics in the field of a shock wave lithotripter.

    Science.gov (United States)

    Choi, M J; Coleman, A J; Saunders, J E

    1993-11-01

    This study concerns the radial dynamics of a bubble driven by pulsed ultrasound of the type generated during extracorporeal shock wave lithotripsy. In particular, a numerical model has been used to examine the sensitivity of the bubble oscillations to changes in both the amplitude of the driving field and the physical conditions of the fluid surrounding the bubble: viscosity, surface tension, temperature and gas content. It is shown that, at high negative pressures (p- = 10 MPa) as in lithotripsy, the timing and amplitude of bubble collapses have a considerably reduced sensitivity to the initial bubble size and all fluid parameters, except gas content, compared with those expected in lower-amplitude fields (p- = 0.2 MPa). This study indicates that, in the lithotripsy fields, the differences in the viscosity, surface tension and temperature of body fluids and the initial bubble size will have little effect on bubble dynamics compared with those expected in water.

  10. Arbitrary amplitude solitary and shock waves in an unmagnetized quantum dusty electron-positron-ion plasma

    Energy Technology Data Exchange (ETDEWEB)

    Rouhani, M. R.; Akbarian, A.; Mohammadi, Z. [Department of Physics, Alzahra University, P. O. Box 1993891176, Tehran (Iran, Islamic Republic of)

    2013-08-15

    The behavior of quantum dust ion acoustic soliton and shocks in a plasma including inertialess quantum electrons and positrons, classical cold ions, and stationary negative dust grains are studied, using arbitrary amplitude approach. The effect of dissipation due to viscosity of ions is taken into account. The numerical analysis of Sagdeev potential for small value of quantum diffraction parameter (H) shows that for chosen plasma, only compressive solitons can exist and the existence domain of this type of solitons is decreased by increasing dust density (d). Additionally, the possibility of propagation of both subsonic and supersonic compressive solitons is investigated. It is shown that there is a critical dust density above which only supersonic solitons are observed. Moreover, increasing d leads to a reduction in the existence domain of compressive solitons and the possibility of propagation of rarefactive soliton is provided. So, rarefactive solitons are observed only due to the presence of dust particles in this model quantum plasma. Furthermore, numerical solution of governed equations for arbitrary amplitude shock waves has been investigated. It is shown that only compressive large amplitude shocks can propagate. Finally, the effects of plasma parameters on these structures are investigated. This research will be helpful in understanding the properties of dense astrophysical (i.e., white dwarfs and neutron stars) and laboratory dusty plasmas.

  11. High initial amplitude and high Mach number effects on the evolution of the single-mode Richtmyer-Meshkov instability.

    Science.gov (United States)

    Rikanati, A; Oron, D; Sadot, O; Shvarts, D

    2003-02-01

    Effects of high-Mach numbers and high initial amplitudes on the evolution of the single-mode Richtmyer-Meshkov shock-wave induced hydrodynamic instability are studied using theoretical models, experiments, and numerical simulations. Two regimes in which there is a significant deviation from the linear dependence of the initial velocity on the initial perturbation amplitude are defined and characterized. In one, the observed reduction of the initial velocity is primarily due to large initial amplitudes. This effect is accurately modeled by a vorticity deposition model, quantifying both the effect of the initial perturbation amplitude and the exact shape of the interface. In the other, the reduction is dominated by the proximity of the shock wave to the interface. This effect is modeled by a modified incompressible model where the shock wave is mimicked by a moving bounding wall. These results are supplemented with high initial amplitude Mach 1.2 shock-tube experiments, enabling separation of the two effects. It is shown that in most of the previous experiments, the observed reduction is predominantly due to the effect of high initial amplitudes.

  12. Combining Amplitude Spectrum Area with Previous Shock Information Using Neural Networks Improves Prediction Performance of Defibrillation Outcome for Subsequent Shocks in Out-Of-Hospital Cardiac Arrest Patients.

    Directory of Open Access Journals (Sweden)

    Mi He

    Full Text Available Quantitative ventricular fibrillation (VF waveform analysis is a potentially powerful tool to optimize defibrillation. However, whether combining VF features with additional attributes that related to the previous shock could enhance the prediction performance for subsequent shocks is still uncertain.A total of 528 defibrillation shocks from 199 patients experienced out-of-hospital cardiac arrest were analyzed in this study. VF waveform was quantified using amplitude spectrum area (AMSA from defibrillator's ECG recordings prior to each shock. Combinations of AMSA with previous shock index (PSI or/and change of AMSA (ΔAMSA between successive shocks were exercised through a training dataset including 255shocks from 99patientswith neural networks. Performance of the combination methods were compared with AMSA based single feature prediction by area under receiver operating characteristic curve(AUC, sensitivity, positive predictive value (PPV, negative predictive value (NPV and prediction accuracy (PA through a validation dataset that was consisted of 273 shocks from 100patients.A total of61 (61.0% patients required subsequent shocks (N = 173 in the validation dataset. Combining AMSA with PSI and ΔAMSA obtained highest AUC (0.904 vs. 0.819, p<0.001 among different combination approaches for subsequent shocks. Sensitivity (76.5% vs. 35.3%, p<0.001, NPV (90.2% vs. 76.9%, p = 0.007 and PA (86.1% vs. 74.0%, p = 0.005were greatly improved compared with AMSA based single feature prediction with a threshold of 90% specificity.In this retrospective study, combining AMSA with previous shock information using neural networks greatly improves prediction performance of defibrillation outcome for subsequent shocks.

  13. Shock compaction of high- Tc superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Weir, S.T.; Nellis, W.J.; McCandless, P.C.; Brocious, W.F. (Lawrence Livermore National Lab., CA (USA)); Seaman, C.L.; Early, E.A.; Maple, M.B. (California Univ., San Diego, La Jolla, CA (USA). Dept. of Physics); Kramer, M.J. (Ames Lab., IA (USA)); Syono, Y.; Kikuchi, M. (Tohoku Univ., Sendai (Japan))

    1990-09-01

    We present the results of shock compaction experiments on high-{Tc} superconductors and describe the way in which shock consolidation addresses critical problems concerning the fabrication of high J{sub c} bulk superconductors. In particular, shock compaction experiments on YBa{sub 2}Cu{sub 3}O{sub 7} show that shock-induced defects can greatly increase intragranular critical current densities. The fabrication of crystallographically aligned Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} samples by shock-compaction is also described. These experiments demonstrate the potential of the shock consolidation method as a means for fabricating bulk high-{Tc} superconductors having high critical current densities.

  14. A miniature high repetition rate shock tube.

    Science.gov (United States)

    Tranter, R S; Lynch, P T

    2013-09-01

    A miniature high repetition rate shock tube with excellent reproducibility has been constructed to facilitate high temperature, high pressure, gas phase experiments at facilities such as synchrotron light sources where space is limited and many experiments need to be averaged to obtain adequate signal levels. The shock tube is designed to generate reaction conditions of T > 600 K, P shock waves with predictable characteristics are created, repeatably. Two synchrotron-based experiments using this apparatus are also briefly described here, demonstrating the potential of the shock tube for research at synchrotron light sources.

  15. High Frequency Amplitude Detector for GMI Magnetic Sensors

    Directory of Open Access Journals (Sweden)

    Aktham Asfour

    2014-12-01

    Full Text Available A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted.

  16. Low Pressure Evidence of High Pressure Shock: Thermal Histories and Annealing in Shocked Meteorites

    Science.gov (United States)

    Sharp, T. G.; Hu, J.

    2016-08-01

    In this study we look at the mineralogy associated with shock veins in several highly shocked L chondrites to better understand shock conditions and the importance of thermal history in creating and destroying high-pressure minerals.

  17. Subharmonic and fundamental high amplitude excitation of an axisymmetric jet

    Science.gov (United States)

    Raman, Ganesh; Rice, Edward J.

    1989-01-01

    The effect of simultaneous excitation at the fundamental and subharmonic frequencies on the behavior of a circular jet shear layer is studied. Attention is given to the effect of the initial phase difference, the Strouhal number pair, and amplitudes of the fundamental and subharmonic tones. High-amplitude excitation devices which can provide a wide range of forcing conditions when used in conjunction with equipment that produces complex waveforms are used.

  18. High Amplitude (delta)-Scutis in the Large Magellanic Cloud

    Energy Technology Data Exchange (ETDEWEB)

    Garg, A; Cook, K H; Nikolaev, S; Huber, M E; Rest, A; Becker, A C; Challis, P; Clocchiatti, A; Miknaitis, G; Minniti, D; Morelli, L; Olsen, K; Prieto, J L; Suntzeff, N B; Welch, D L; Wood-Vasey, W M

    2010-01-25

    The authors present 2323 High-Amplitude {delta}-Scutis (HADS) candidates discovered in the Large Magellanic Cloud (LMC) by the SuperMACHO survey (Rest et al. 2005). Frequency analyses of these candidates reveal that several are multimode pulsators, including 119 whose largest amplitude of pulsation is in the fundamental (F) mode and 19 whose largest amplitude of pulsation is in the first overtone (FO) mode. Using Fourier decomposition of the HADS light curves, they find that the period-luminosity (PL) relation defined by the FO pulsators does not show a clear separation from the PL-relation defined by the F pulsators. This differs from other instability strip pulsators such as type c RR Lyrae. They also present evidence for a larger amplitude, subluminous population of HADS similar to that observed in Fornax (Poretti et al. 2008).

  19. High Amplitude \\delta-Scutis in the Large Magellanic Cloud

    CERN Document Server

    Garg, A; Nikolaev, S; Huber, M E; Rest, A; Becker, A C; Challis, P; Clocchiatti, A; Miknaitis, G; Minniti, D; Morelli, L; Olsen, K; Prieto, J L; Suntzeff, N B; Welch, D L; Wood-Vasey, W M

    2010-01-01

    We present 2323 High-Amplitude \\delta-Scuti (HADS) candidates discovered in the Large Magellanic Cloud (LMC) by the SuperMACHO survey (Rest et al. 2005). Frequency analyses of these candidates reveal that several are multimode pulsators, including 119 whose largest amplitude of pulsation is in the fundamental (F) mode and 19 whose largest amplitude of pulsation is in the first overtone (FO) mode. Using Fourier decomposition of the HADS light curves, we find that the period-luminosity (PL) relation defined by the FO pulsators does not show a clear separation from the PL-relation defined by the F pulsators. This differs from other instability strip pulsators such as type c RR Lyrae. We also present evidence for a larger amplitude, subluminous population of HADS similar to that observed in Fornax (Poretti et al. 2008).

  20. High amplitude nonlinear acoustic wave driven flow fields in cylindrical and conical resonators.

    Science.gov (United States)

    Antao, Dion Savio; Farouk, Bakhtier

    2013-08-01

    A high fidelity computational fluid dynamic model is used to simulate the flow, pressure, and density fields generated in a cylindrical and a conical resonator by a vibrating end wall/piston producing high-amplitude standing waves. The waves in the conical resonator are found to be shock-less and can generate peak acoustic overpressures that exceed the initial undisturbed pressure by two to three times. A cylindrical (consonant) acoustic resonator has limitations to the output response observed at one end when the opposite end is acoustically excited. In the conical geometry (dissonant acoustic resonator) the linear acoustic input is converted to high energy un-shocked nonlinear acoustic output. The model is validated using past numerical results of standing waves in cylindrical resonators. The nonlinear nature of the harmonic response in the conical resonator system is further investigated for two different working fluids (carbon dioxide and argon) operating at various values of piston amplitude. The high amplitude nonlinear oscillations observed in the conical resonator can potentially enhance the performance of pulse tube thermoacoustic refrigerators and these conical resonators can be used as efficient mixers.

  1. Non-Linear High Amplitude Oscillations in Wave-shaped Resonators

    Science.gov (United States)

    Antao, Dion; Farouk, Bakhtier

    2011-11-01

    A numerical and experimental study of non-linear, high amplitude standing waves in ``wave-shaped'' resonators is reported here. These waves are shock-less and can generate peak acoustic overpressures that can exceed the ambient pressure by three/four times its nominal value. A high fidelity compressible axisymmetric computational fluid dynamic model is used to simulate the phenomena in cylindrical and arbitrarily shaped axisymmetric resonators. Working fluids (Helium, Nitrogen and R-134a) at various operating pressures are studied. The experiments are performed in a constant cross-section cylindrical resonator in atmospheric pressure nitrogen and helium to provide model validation. The high amplitude non-linear oscillations demonstrated can be used as a prime mover in a variety of applications including thermoacoustic cryocooling. The work reported is supported by the US National Science Foundation under grant CBET-0853959.

  2. Radial convection of finite ion temperature, high amplitude plasma blobs

    DEFF Research Database (Denmark)

    Wiesenberger, M.; Madsen, Jens; Kendl, Alexander

    2014-01-01

    We present results from simulations of seeded blob convection in the scrape-off-layer of magnetically confined fusion plasmas. We consistently incorporate high fluctuation amplitude levels and finite Larmor radius (FLR) effects using a fully nonlinear global gyrofluid model. This is in line...... with conditions found in tokamak scrape-off-layers (SOL) regions. Varying the ion temperature, the initial blob width, and the initial amplitude, we found an FLR dominated regime where the blob behavior is significantly different from what is predicted by cold-ion models. The transition to this regime is very...

  3. Simulation of transients of high amplitude in pipe systems

    NARCIS (Netherlands)

    Boersma, J.M.; Looijmans, K.N.H.

    1999-01-01

    Fast high-amplitude transients ask for a non-linear modelling approach in which large density variations and heat exchange can be considered. Operation of safety-valves, relief valves, the occurrence of valve failure and the start-up or shutdown of rotating equipment in industrial pipe systems can l

  4. A transport equation for the evolution of shock amplitudes along rays

    Directory of Open Access Journals (Sweden)

    Giovanni Russo

    1991-05-01

    Full Text Available A new asymptotic method is derived for the study of the evolution of weak shocks in several dimension. The method is based on the Generalized Wavefront Expansion derived in [1]. In that paper the propagation of a shock into a known background was studied under the assumption that shock is weak, i.e. Mach Number =1+O(ε, ε ≪ 1, and that the perturbation of the field varies over a length scale O(ε. To the lowest order, the shock surface evolves along the rays associated with the unperturbed state. An infinite system of compatibility relations was derived for the jump in the field and its normal derivatives along the shock, but no valid criterion was found for a truncation of the system. Here we show that the infinite hierarchy is equivalent to a single equation that describes the evolution of the shock along the rays. We show that this method gives equivalent results to those obtained by Weakly Nonlinear Geometrical Optics [2].

  5. Small-amplitude shock waves and double layers in dusty plasmas with opposite polarity charged dust grains

    Science.gov (United States)

    Amina, M.; Ema, S. A.; Mamun, A. A.

    2017-06-01

    Theoretical investigation is carried out for understanding the properties of nonlinear dust-acoustic (DA) waves in an unmagnetized dusty plasma whose constituents are massive, micron-sized, positive and negatively charged inertial dust grains along with q (nonextensive) distributed electrons and ions. The reductive perturbation method is employed in order to derive two types of nonlinear dynamical equations, namely, Burgers equation and modified Gardner equation (Gardner equation with dissipative term). They are also numerically analyzed to investigate the basic features (viz., polarity, amplitude, width, etc.) of shock waves and double layers. It has been observed that the effects of nonextensivity, opposite polarity charged dust grains, and different dusty plasma parameters have significantly modified the fundamental properties of shock waves and double layers. The results of this investigation may be used for researches of the nonlinear wave propagation in laboratory and space plasmas.

  6. Radial convection of finite ion temperature, high amplitude plasma blobs

    CERN Document Server

    Wiesenberger, M; Kendl, A

    2014-01-01

    We present results from simulations of seeded blob convection in the scrape-off-layer of magnetically confined fusion plasmas. We consistently incorporate high fluctuation amplitude levels and finite Larmor radius (FLR) effects using a fully nonlinear global gyrofluid model. This is in line with conditions found in tokamak scrape-off-layers (SOL) regions. Varying the ion temperature, the initial blob width and the initial amplitude, we found an FLR dominated regime where the blob behavior is significantly different from what is predicted by cold-ion models. The transition to this regime is very well described by the ratio of the ion gyroradius to the characteristic gradient scale length of the blob. We compare the global gyrofluid model with a partly linearized local model. For low ion temperatures we find that simulations of the global model show more coherent blobs with an increased cross-field transport compared to blobs simulated with the local model. The maximal blob amplitude is significantly higher in ...

  7. Electron acceleration in a nonrelativistic shock with very high Alfv\\'en Mach number

    CERN Document Server

    Matsumoto, Y; Hoshino, M

    2013-01-01

    Electron acceleration associated with various plasma kinetic instabilities in a nonrelativistic, very-high-Alfv\\'en Mach-number ($M_A \\sim 45$) shock is revealed by means of a two-dimensional fully kinetic PIC simulation. Electromagnetic (ion Weibel) and electrostatic (ion-acoustic and Buneman) instabilities are strongly activated at the same time in different regions of the two-dimensional shock structure. Relativistic electrons are quickly produced predominantly by the shock surfing mechanism with the Buneman instability at the leading edge of the foot. The energy spectrum has a high-energy tail exceeding the upstream ion kinetic energy accompanying the main thermal population. This gives a favorable condition for the ion acoustic instability at the shock front, which in turn results in additional energization. The large-amplitude ion Weibel instability generates current sheets in the foot, implying another dissipation mechanism via magnetic reconnection in a three-dimensional shock structure in the very-hi...

  8. High-pressure minerals in shocked meteorites

    Science.gov (United States)

    Tomioka, Naotaka; Miyahara, Masaaki

    2017-09-01

    Heavily shocked meteorites contain various types of high-pressure polymorphs of major minerals (olivine, pyroxene, feldspar, and quartz) and accessory minerals (chromite and Ca phosphate). These high-pressure minerals are micron to submicron sized and occur within and in the vicinity of shock-induced melt veins and melt pockets in chondrites and lunar, howardite-eucrite-diogenite (HED), and Martian meteorites. Their occurrence suggests two types of formation mechanisms (1) solid-state high-pressure transformation of the host-rock minerals into monomineralic polycrystalline aggregates, and (2) crystallization of chondritic or monomineralic melts under high pressure. Based on experimentally determined phase relations, their formation pressures are limited to the pressure range up to 25 GPa. Textural, crystallographic, and chemical characteristics of high-pressure minerals provide clues about the impact events of meteorite parent bodies, including their size and mutual collision velocities and about the mineralogy of deep planetary interiors. The aim of this article is to review and summarize the findings on natural high-pressure minerals in shocked meteorites that have been reported over the past 50 years.

  9. Frequencies and amplitudes of high-degree solar oscillations

    Science.gov (United States)

    Kaufman, James Morris

    Measurements of some of the properties of high-degree solar p- and f-mode oscillations are presented. Using high-resolution velocity images from Big Bear Solar Observatory, we have measured mode frequencies, which provide information about the composition and internal structure of the Sun, and mode velocity amplitudes (corrected for the effects of atmospheric seeing), which tell us about the oscillation excitation and damping mechanisms. We present a new and more accurate table of the Sun's acoustic vibration frequencies, nunl, as a function of radial order n and spherical harmonic degree l. These frequencies are averages over azimuthal order m and approximate the normal mode frequencies of a nonrotating spherically symmetric Sun near solar minimum. The frequencies presented here are for solar p- and f-modes with 180 less than or = l less than or = 1920, 0 less than or = n less than or = 8, and 1.7 mHz less than or = nunl less than or = 5.3 mHz. The uncertainties, sigmanl, in the frequencies areas are as low as 3.1 micro-Hz. The theoretically expected f-mode frequencies are given by omega squared = gkh approx. = gl/R, where g is the gravitational acceleration at the surface, kh is the horizontal component of the wave vector, and R is the radius of the Sun. We find that the observed frequencies are significantly less than expected for l greater than 1000, for which we have no explanation. Observations of high-degree oscillations, which have very small spatial features, suffer from the effects of atmospheric image blurring and image motion (or 'seeing'), thereby reducing the amplitudes of their spatial-frequency components. In an attempt to correct the velocity amplitudes for these effects, we simultaneously measured the atmospheric modulation transfer function (MTF) by looking at the effects of seeing on the solar limb. We are able to correct the velocity amplitudes using the MTF out to l approx. = 1200. We find that the frequency of the peak velocity power (as a

  10. High Temperature Phenomena in Shock Waves

    CERN Document Server

    2012-01-01

    The high temperatures generated in gases by shock waves give rise to physical and chemical phenomena such as molecular vibrational excitation, dissociation, ionization, chemical reactions and inherently related radiation. In continuum regime, these processes start from the wave front, so that generally the gaseous media behind shock waves may be in a thermodynamic and chemical non-equilibrium state. This book presents the state of knowledge of these phenomena. Thus, the thermodynamic properties of high temperature gases, including the plasma state are described, as well as the kinetics of the various chemical phenomena cited above. Numerous results of measurement and computation of vibrational relaxation times, dissociation and reaction rate constants are given, and various ionization and radiative mechanisms and processes are presented. The coupling between these different phenomena is taken into account as well as their interaction with the flow-field. Particular points such as the case of rarefied flows an...

  11. Large-amplitude ULF waves at high latitudes

    Science.gov (United States)

    Guido, T.; Tulegenov, B.; Streltsov, A. V.

    2014-11-01

    We present results from the statistical study of ULF waves detected by the fluxgate magnetometer in Gakona, Alaska during several experimental campaigns conducted at the High Frequency Active Auroral Research Program (HAARP) facility in years 2011-2013. We analyzed frequencies of ULF waves recorded during 26 strongly disturbed geomagnetic events (substorms) and compared them with frequencies of ULF waves detected during magnetically quiet times. Our analysis demonstrates that the frequency of the waves carrying most of the power in almost all these events is less than 1 mHz. We also analyzed data from the ACE satellite, measuring parameters of the solar wind in the L1 Lagrangian point between Earth and Sun, and found that in several occasions there is a strong correlation between oscillations of the magnetic field in the solar wind and oscillations detected on the ground. We also found several cases when there is no correlation between signals detected on ACE and on the ground. This finding suggests that these frequencies correspond to the fundamental eigenfrequency of the coupled magnetosphere-ionosphere system, and the amplitude of these waves can reach significant magnitude when the system is driven by the external driver (for example, the solar wind) with this particular frequency. When the frequency of the driver does not match the frequency of the system, the waves still are observed, but their amplitudes are much smaller.

  12. Universal High Order Subroutine with New Shock Detector for Shock Boundary Layer Interaction

    CERN Document Server

    Oliveria, M; Liu, X; Liu, C

    2014-01-01

    The goal of this work is to develop a new universal high order subroutine for shock boundary layer interaction. First, an effective shock/discontinuity detector has been developed.The detector has two steps.The first step is to check the ratio of the truncation errors on the coarse and fine grids and the second step is to check the local ratio of the left and right slopes. The currently popular shock/discontinuity detectors can detect shock, but mistake high frequency waves and critical points as shock and then damp the physically important high frequency waves.Preliminary results show the new shock/discontinuity detector is very delicate and can detect all shocks including strong, weak and oblique shocks or discontinuity in function and the first, second, and third order derivatives without artificial constants, but never mistake high frequency waves and critical points, expansion waves as shock. This will overcome the bottle neck problem with numerical simulation for the shock-boundary layer interaction, sh...

  13. Injection coupling with high amplitude transverse modes: Experimentation and simulation

    Science.gov (United States)

    Mery, Yoann; Ducruix, Sébastien; Scouflaire, Philippe; Candel, Sébastien

    2009-06-01

    High frequency combustion instabilities have technical importance in the design of liquid rocket engines. These phenomena involve a strong coupling between transverse acoustic modes and combustion. They are currently being investigated by combining experimentation and numerical simulations. On the experimental level, the coupling is examined in a model scale system featuring a multiple injector combustor (MIC) comprising five coaxial injectors fed with liquid oxygen and gaseous methane. This system is equipped with a novel VHAM actuator (Very High Amplitude Modulator) which comprises two nozzles and a rotating toothed wheel blocking the nozzles in an alternate fashion. This device was designed to obtain the highest possible levels of transverse oscillation in the MIC. After a brief review of the VHAM, this article reports cold flow experiments using this modulator. Velocity maps obtained under resonant conditions using the VHAM are examined at different instants during a cycle of oscillation. Experimental data are compared with numerical pressure and velocity fields obtained from an acoustic solver. The good agreement observed in the nozzle vicinity indicates that numerical simulations can be used to analyze the complex flow field generated by the VHAM. To cite this article: Y. Mery et al., C. R. Mecanique 337 (2009).

  14. Shock Mechanism Analysis and Simulation of High-Power Hydraulic Shock Wave Simulator

    Directory of Open Access Journals (Sweden)

    Xiaoqiu Xu

    2017-01-01

    Full Text Available The simulation of regular shock wave (e.g., half-sine can be achieved by the traditional rubber shock simulator, but the practical high-power shock wave characterized by steep prepeak and gentle postpeak is hard to be realized by the same. To tackle this disadvantage, a novel high-power hydraulic shock wave simulator based on the live firing muzzle shock principle was proposed in the current work. The influence of the typical shock characteristic parameters on the shock force wave was investigated via both theoretical deduction and software simulation. According to the obtained data compared with the results, in fact, it can be concluded that the developed hydraulic shock wave simulator can be applied to simulate the real condition of the shocking system. Further, the similarity evaluation of shock wave simulation was achieved based on the curvature distance, and the results stated that the simulation method was reasonable and the structural optimization based on software simulation is also beneficial to the increase of efficiency. Finally, the combination of theoretical analysis and simulation for the development of artillery recoil tester is a comprehensive approach in the design and structure optimization of the recoil system.

  15. High Amplitude (delta)-Scutis in the Large Magellanic Cloud

    National Research Council Canada - National Science Library

    Garg, A; Cook, K H; Nikolaev, S; Huber, M E; Rest, A; Becker, A C; Challis, P; Clocchiatti, A; Miknaitis, G; Minniti, D; Morelli, L; Olsen, K; Prieto, J L; Suntzeff, N B; Welch, D L; Wood-Vasey, W M

    2010-01-01

    ... (LMC) by the SuperMACHO survey (Rest et al. 2005). Frequency analyses of these candidates reveal that several are multimode pulsators, including 119 whose largest amplitude of pulsation is in the fundamental (F...

  16. The High Amplitude delta Scuti Star AD Canis Minoris

    Science.gov (United States)

    Axelsen, R. A.; Napier-Munn, T.

    2016-12-01

    The high amplitude delta Scuti star AD Canis Minoris was studied by photoelectric photometry (PEP) during one night in in February 2011 and by digital single lens reflex (DSLR) photometry during seven nights in January and February 2016. Nine light curve peaks were captured, eight of them by DSLR photometry. A review of the literature enabled us to tabulate 109 times of maximum since 1959, to which we added 9 times of maximum from our data, thus creating the largest dataset to date for this star. Assuming a linear ephemeris, the period of AD CMi was calculated to be 0.122974511 (+/- 0.000000004) d, almost identical to that quoted in earlier literature. We constructed an observed minus computed (O-C) diagram which exhibited a quasi-sinusoidal shape, and fitted a weighted model characterised by combined quadratic and trigonometric functions. The fit indicates that the shape of the O-C diagram is attributable to the effects of a slow increase in the pulsation period of AD CMi at a constant rate, and the light time effect of a binary pair, confirming the results from previous authors, and updating most of the coefficients of the equation for the fitted model. The values of all of the coefficients in the function are statistically significant. The rate of increase in the pulsation period of AD CMi was calculated from the entire dataset to be dP/dt = 6.17 (+/- 0.75) x 10-9 d yr-1 or dP/Pdt = 5.01 (+/- 0.61) x 10-8 yr-1.

  17. Controlled tissue emulsification produced by high intensity focused ultrasound shock waves and millisecond boiling.

    Science.gov (United States)

    Khokhlova, Tatiana D; Canney, Michael S; Khokhlova, Vera A; Sapozhnikov, Oleg A; Crum, Lawrence A; Bailey, Michael R

    2011-11-01

    In high intensity focused ultrasound (HIFU) applications, tissue may be thermally necrosed by heating, emulsified by cavitation, or, as was recently discovered, emulsified using repetitive millisecond boiling caused by shock wave heating. Here, this last approach was further investigated. Experiments were performed in transparent gels and ex vivo bovine heart tissue using 1, 2, and 3 MHz focused transducers and different pulsing schemes in which the pressure, duty factor, and pulse duration were varied. A previously developed derating procedure to determine in situ shock amplitudes and the time-to-boil was refined. Treatments were monitored using B-mode ultrasound. Both inertial cavitation and boiling were observed during exposures, but emulsification occurred only when shocks and boiling were present. Emulsified lesions without thermal denaturation were produced with shock amplitudes sufficient to induce boiling in less than 20 ms, duty factors of less than 0.02, and pulse lengths shorter than 30 ms. Higher duty factors or longer pulses produced varying degrees of thermal denaturation combined with mechanical emulsification. Larger lesions were obtained using lower ultrasound frequencies. The results show that shock wave heating and millisecond boiling is an effective and reliable way to emulsify tissue while monitoring the treatment with ultrasound.

  18. Design, Simulation and Fabrication of Triaxial MEMS High Shock Accelerometer.

    Science.gov (United States)

    Zhang, Zhenhai; Shi, Zhiguo; Yang, Zhan; Xie, Zhihong; Zhang, Donghong; Cai, De; Li, Kejie; Shen, Yajing

    2015-04-01

    On the basis of analyzing the disadvantage of other structural accelerometer, three-axis high g MEMS piezoresistive accelerometer was put forward in order to apply to the high-shock test field. The accelerometer's structure and working principle were discussed in details. The simulation results show that three-axis high shock MEMS accelerometer can bear high shock. After bearing high shock impact in high-shock shooting test, three-axis high shock MEMS accelerometer can obtain the intact metrical information of the penetration process and still guarantee the accurate precision of measurement in high shock load range, so we can not only analyze the law of stress wave spreading and the penetration rule of the penetration process of the body of the missile, but also furnish the testing technology of the burst point controlling. The accelerometer has far-ranging application in recording the typical data that projectile penetrating hard target and furnish both technology guarantees for penetration rule and defend engineering.

  19. Research on High Frequency Amplitude Attenuation of Electric Fast Transient Generator

    Directory of Open Access Journals (Sweden)

    Huafu Zhang

    2013-01-01

    Full Text Available In order to solve the amplitude attenuation of electric fast transient (EFT generator operating in high frequency, the charging and discharging process of energy storage capacitor in EFT generator are analyzed, the main circuit voltage variation mathematical model is established, the parameters of main loop circuit and the parameters of switch driving waveform which affect burst amplitude are discussed. Through the simulation, this paper puts forward effective methods to overcome burst amplitude attenuation in high frequency. The simulation results show that when the frequency is low, the duty ratio of drive signal have little effect on energy storage capacitor voltage amplitude attenuation. when the charging resistance is less than 500 Ω, the duty ratio of drive signal is less than 0.125, the repetition frequency of burst reaches 1.2 MHz, the amplitude attenuation of energy storage capacitor voltage is less than 9%, the amplitude of burst satisfies IEC61000-4-4 standards.

  20. DESIGN NOTE: A fast high-voltage pulse generator with variable amplitude and duration

    Science.gov (United States)

    Upadhyay, Jankee; Navathe, C. P.

    2006-07-01

    A high-voltage pulse generator based on a self-matched transmission line with variable pulse amplitude and duration is developed. Two avalanche transistor stacks are used as switches. The pulse width is varied by adjusting the delay in triggering two switches whereas amplitude is adjusted by adjusting load resistance. A pulse with amplitude of 800 V to 3.8 kV and width of 5 ns to 38 ns can be obtained using this circuit.

  1. External Drive to Inhibitory Cells Induces Alternating Episodes of High- and Low-Amplitude Oscillations

    NARCIS (Netherlands)

    Gonzalez, Oscar J. Avella; van Aerde, Karlijn I.; van Elburg, Ronald A. J.; Poil, Simon-Shlomo; Mansvelder, Huibert D.; Linkenkaer-Hansen, Klaus; van Pelt, Jaap; van Ooyen, Arjen

    2012-01-01

    Electrical oscillations in neuronal network activity are ubiquitous in the brain and have been associated with cognition and behavior. Intriguingly, the amplitude of ongoing oscillations, such as measured in EEG recordings, fluctuates irregularly, with episodes of high amplitude alternating with epi

  2. Brh V128 is a Double-Mode High-Amplitude delta Scuti Star

    Science.gov (United States)

    Bernhard, K.; Pejcha, O.; Proksch, W.; Quester, W.; van Cauteren, P.; Wils, P.

    2004-08-01

    CCD-V and unfiltered photometric data show that Brh V128 = GSC 1893-89 is a new high-amplitude double-mode Delta Scuti variable with a fundamental period of 0.1534 days and a period ratio of 0.767. The amplitude of the first overtone pulsation is slightly larger than that of the fundamental mode.

  3. MAGNETIC METHOD FOR PRODUCING HIGH VELOCITY SHOCK WAVES IN GASES

    Science.gov (United States)

    Josephson, V.

    1960-01-26

    A device is described for producing high-energy plasmas comprising a tapered shock tube of dielectric material and having a closed small end, an exceedingly low-inductance coll supported about and axially aligned with the small end of the tapered tube. an elongated multiturn coil supported upon the remninder of the exterior wall of the shock tube. a potential source and switch connected in series with the low-inductance coil, a potential source and switch connected in series with the elongated coil, means for hermetically sealing the large end of the tube, means for purging the tube of gases, and means for admitting a selected gas into the shock tube.

  4. Off-shell helicity amplitudes in high-energy factorization

    CERN Document Server

    van Hameren, Andreas; Kutak, Krzysztof

    2013-01-01

    In the Catani-Ciafaloni-Hautmann high-energy factorization approach a cross section is expressed as a convolution of unintegrated gluon densities and a gauge-invariant hard process, in which two incoming gluons are off-shell with momenta satisfying certain high-energy kinematics. We present two methods of evaluating the tree-level hard process with multiple final states. The first one assumes that only one of the gluons is off-shell and relies on the Slavnov-Taylor identities. Such asymmetric configuration of incoming gluons is phenomenologically important in small x probing by forward processes. The second method deals also with two off-shell gluons and is based on the analytic continuation of the off-shell gluons momenta to the complex space. The methods were implemented into Monte Carlo computer programs and used in phenomenological applications. The results of both methods are straightforwardly related to Lipatov's effective vertices in quasi-multi-regge kinematics.

  5. High extinction amplitude modulation in ultrashort pulse shaping

    CERN Document Server

    Lin, Yen-Wei

    2016-01-01

    We explored the issues related to the resolution and the modulation extinction when filtering the spectrum of a UV femtosecond laser with a standard ultrashort pulse shaper. We have learned that a higher pulse shaping resolution often requires a larger working beam size or a higher density grating for greater dispersion. However, these approaches also introduce more optical errors and degrade the extinction. In this work, we examined specifics of each component to determine the best configuration of our spectral filtering setup. As a proof-of-concept demonstration, we utilized elements available as standard products and achieved 100 GHz filtering resolution with high extinction at the UV-A wavelength, which is superb in this wavelength range. The high extinction spectral filtering is especially important while modifying a broadband laser for the optical control of molecule's internal state.

  6. Freeform high-speed large-amplitude deformable Piezo Mirrors

    CERN Document Server

    Wapler, Matthias C; Wallrabe, Ulrike

    2013-01-01

    We present a new type of tunable mirror with sharply-featured freeform displacement profiles, large displacements of several 100\\mu m and high operating frequencies close to the kHz range at 15mm diameter. The actuation principle is based on a recently explored "topological" displacement mode of piezo sheets. The prototypes presented here include a rotationally symmetric axicon, a hyperbolic sech-icon and a non-symmetric pyram-icon and are scalable to smaller dimensions. The fabrication process is economic and cleanroom-free, and the optical quality is sufficient to demonstrate the diffraction patterns of the optical elements.

  7. Vacuum high harmonic generation in the shock regime

    CERN Document Server

    Böhl, P; Ruhl, H

    2015-01-01

    Electrodynamics becomes nonlinear and permits the self-interaction of fields when the quantised nature of vacuum states is taken into account. The effect on a plane probe pulse propagating through a stronger constant crossed background is calculated using numerical simulation and by analytically solving the corresponding wave equation. The electromagnetic shock resulting from vacuum high harmonic generation is investigated and a nonlinear shock parameter identified.

  8. High-Energy String Scattering Amplitudes and Signless Stirling Number Identity

    Directory of Open Access Journals (Sweden)

    Jen-Chi Lee

    2012-07-01

    Full Text Available We give a complete proof of a set of identities (7 proposed recently from calculation of high-energy string scattering amplitudes. These identities allow one to extract ratios among high-energy string scattering amplitudes in the fixed angle regime from high-energy amplitudes in the Regge regime. The proof is based on a signless Stirling number identity in combinatorial theory. The results are valid for arbitrary real values L rather than only for L=0,1 proved previously. The identities for non-integer real value L were recently shown to be realized in high-energy compactified string scattering amplitudes [He S., Lee J.C., Yang Y., arXiv:1012.3158]. The parameter L is related to the mass level of an excited string state and can take non-integer values for Kaluza-Klein modes.

  9. High-power laser experiments to study collisionless shock generation

    Science.gov (United States)

    Sakawa, Y.; Kuramitsu, Y.; Morita, T.; Kato, T.; Tanji, H.; Ide, T.; Nishio, K.; Kuwada, M.; Tsubouchi, T.; Ide, H.; Norimatsu, T.; Gregory, C.; Woolsey, N.; Schaar, K.; Murphy, C.; Gregori, G.; Diziere, A.; Pelka, A.; Koenig, M.; Wang, S.; Dong, Q.; Li, Y.; Park, H.-S.; Ross, S.; Kugland, N.; Ryutov, D.; Remington, B.; Spitkovsky, A.; Froula, D.; Takabe, H.

    2013-11-01

    A collisionless Weibel-instability mediated shock in a self-generated magnetic field is studied using two-dimensional particle-in-cell simulation [Kato and Takabe, Astophys. J. Lett. 681, L93 (2008)]. It is predicted that the generation of the Weibel shock requires to use NIF-class high-power laser system. Collisionless electrostatic shocks are produced in counter-streaming plasmas using Gekko XII laser system [Kuramitsu et al., Phys. Rev. Lett. 106, 175002 (2011)]. A NIF facility time proposal is approved to study the formation of the collisionless Weibel shock. OMEGA and OMEGA EP experiments have been started to study the plasma conditions of counter-streaming plasmas required for the NIF experiment using Thomson scattering and to develop proton radiography diagnostics.

  10. Equation of State for Shock Compression of High Distension Solids

    Science.gov (United States)

    Grady, Dennis

    2013-06-01

    Shock Hugoniot data for full-density and porous compounds of boron carbide, silicon dioxide, tantalum pentoxide, uranium dioxide and playa alluvium are investigated for the purpose of equation-of-state representation of intense shock compression. Complications of multivalued Hugoniot behavior characteristic of highly distended solids are addressed through the application of enthalpy-based equations of state of the form originally proposed by Rice and Walsh in the late 1950's. Additivity of cold and thermal pressure intrinsic to the Mie-Gruneisen EOS framework is replaced by isobaric additive functions of the cold and thermal specific volume components in the enthalpy-based formulation. Additionally, experimental evidence supports acceleration of shock-induced phase transformation on the Hugoniot with increasing levels of initial distention for silicon dioxide, uranium dioxide and possibly boron carbide. Methods for addressing this experimentally observed facet of the shock compression are introduced into the EOS model.

  11. High-power laser experiments to study collisionless shock generation

    Directory of Open Access Journals (Sweden)

    Sakawa Y.

    2013-11-01

    Full Text Available A collisionless Weibel-instability mediated shock in a self-generated magnetic field is studied using two-dimensional particle-in-cell simulation [Kato and Takabe, Astophys. J. Lett. 681, L93 (2008]. It is predicted that the generation of the Weibel shock requires to use NIF-class high-power laser system. Collisionless electrostatic shocks are produced in counter-streaming plasmas using Gekko XII laser system [Kuramitsu et al., Phys. Rev. Lett. 106, 175002 (2011]. A NIF facility time proposal is approved to study the formation of the collisionless Weibel shock. OMEGA and OMEGA EP experiments have been started to study the plasma conditions of counter-streaming plasmas required for the NIF experiment using Thomson scattering and to develop proton radiography diagnostics.

  12. Rapid high-amplitude circumferential slow wave propagation during normal gastric pacemaking and dysrhythmias.

    Science.gov (United States)

    O'Grady, G; Du, P; Paskaranandavadivel, N; Angeli, T R; Lammers, W J E P; Asirvatham, S J; Windsor, J A; Farrugia, G; Pullan, A J; Cheng, L K

    2012-07-01

    Gastric slow waves propagate aborally as rings of excitation. Circumferential propagation does not normally occur, except at the pacemaker region. We hypothesized that (i) the unexplained high-velocity, high-amplitude activity associated with the pacemaker region is a consequence of circumferential propagation; (ii) rapid, high-amplitude circumferential propagation emerges during gastric dysrhythmias; (iii) the driving network conductance might switch between interstitial cells of Cajal myenteric plexus (ICC-MP) and circular interstitial cells of Cajal intramuscular (ICC-IM) during circumferential propagation; and (iv) extracellular amplitudes and velocities are correlated. An experimental-theoretical study was performed. High-resolution gastric mapping was performed in pigs during normal activation, pacing, and dysrhythmia. Activation profiles, velocities, and amplitudes were quantified. ICC pathways were theoretically evaluated in a bidomain model. Extracellular potentials were modeled as a function of membrane potentials. High-velocity, high-amplitude activation was only recorded in the pacemaker region when circumferential conduction occurred. Circumferential propagation accompanied dysrhythmia in 8/8 experiments was faster than longitudinal propagation (8.9 vs 6.9 mm s(-1) ; P = 0.004) and of higher amplitude (739 vs 528 μV; P = 0.007). Simulations predicted that ICC-MP could be the driving network during longitudinal propagation, whereas during ectopic pacemaking, ICC-IM could outpace and activate ICC-MP in the circumferential axis. Experimental and modeling data demonstrated a linear relationship between velocities and amplitudes (P propagation. Rapid circumferential propagation also emerges during a range of gastric dysrhythmias, elevating extracellular amplitudes and organizing transverse wavefronts. One possible explanation for these findings is bidirectional coupling between ICC-MP and circular ICC-IM networks. © 2012 Blackwell Publishing Ltd.

  13. Shock

    Science.gov (United States)

    Shock can be caused by any condition that reduces blood flow, including: Heart problems (such as heart attack or heart failure ) Low blood volume (as with heavy bleeding or dehydration ) Changes in blood vessels (as with infection ...

  14. Dispersive nature of high mach number collisionless plasma shocks: Poynting flux of oblique whistler waves.

    Science.gov (United States)

    Sundkvist, David; Krasnoselskikh, V; Bale, S D; Schwartz, S J; Soucek, J; Mozer, F

    2012-01-13

    Whistler wave trains are observed in the foot region of high Mach number quasiperpendicular shocks. The waves are oblique with respect to the ambient magnetic field as well as the shock normal. The Poynting flux of the waves is directed upstream in the shock normal frame starting from the ramp of the shock. This suggests that the waves are an integral part of the shock structure with the dispersive shock as the source of the waves. These observations lead to the conclusion that the shock ramp structure of supercritical high Mach number shocks is formed as a balance of dispersion and nonlinearity.

  15. VizieR Online Data Catalog: VVV high amplitude NIR variable stars (Contreras Pena+, 2017)

    Science.gov (United States)

    Contreras Pena, C.; Lucas, P. W.; Minniti, D.; Kurtev, R.; Stimson, W.; Navarro Molina, C.; Borissova, J.; Kumar, M. S. N.; Thompson, M. A.; Gledhill, T.; Terzi, R.; Froebrich, D.; Caratti o Garatti, A.

    2017-08-01

    We present the single epoch ZYJHKs photometry obtained from VVV catalogues for 816 high-amplitude variables. We also present the amplitude of the Ks light curve of the objects derived from 2010-2015 photometry. For each object we also provide a provisional classification derived from the shape of the light curve. For objects found to be likely associated with SFRs we present an spectral index derived from the object's spectral energy distribution. (2 data files).

  16. Kepler observations of the high-amplitude δ Scuti star V2367 Cyg

    DEFF Research Database (Denmark)

    Balona, L. A.; Lenz, P.; Antoci, V.

    2012-01-01

    We analyse Kepler observations of the high-amplitude δ Scuti (HADS) star V2367 Cyg (KIC 9408694). The variations are dominated by a mode with frequency f1= 5.6611 d−1. Two other independent modes with f2= 7.1490 d−1 and f3= 7.7756 d−1 have amplitudes an order of magnitude smaller than f1. Nearly ...

  17. Development of high-voltage pulse generator with variable amplitude and duration

    Science.gov (United States)

    Upadhyay, J.; Sharma, M. L.; Ahuja, Aakash B.; Navathe, C. P.

    2014-06-01

    A high voltage pulse generator with variable amplitude (100-3000 V) and duration (100-2000 μs) has been designed and developed. The variable duration pulse has been generated by adopting a simple and novel technique of varying the turn off delay time of a high voltage Metal Oxide Semiconductor Field Effect Transistor (MOSFET) based switch by varying external gate resistance. The pulse amplitude is made variable by adjusting biasing supply of the high voltage switch. The high voltage switch has been developed using a MOSFET based stack of 3 kV rating with switching time of 7 ns.

  18. Electrostatic Instabilities at High Frequency in a Plasma Shock Front

    Institute of Scientific and Technical Information of China (English)

    LV Jian-Hong; HE Yong; HU Xi-Wei

    2007-01-01

    New electrostatic instabilities in the plasma shock front are reported.These instabilities are driven by the electrostatic field which is caused by charge separation and the parameter gradients in a plasma shock front.The linear analysis to the high frequency branch of electrostatic instabilities has been carried out and the dispersion relations are obtained numerically.There are unstable disturbing waves in both the parallel and perpendicular directions of shock propagation.The real frequencies of both unstable waves are similar to the electron electrostatic wave,and the unstable growth rate in the parallel direction is much greater than the one in the perpendicular direction.The dependence of growth rates on the electric field and parameter gradients is also presented.

  19. Heat shock response and mammal adaptation to high elevation (hypoxia)

    Institute of Scientific and Technical Information of China (English)

    WANG Xiaolin; XU Cunshuan; WANG Xiujie; WANG Dongjie; WANG Qingshang; ZHANG Baochen

    2006-01-01

    The mammal's high elevation (hypoxia) adaptation was studied by using the immunological and the molecular biological methods to understand the significance of Hsp (hypoxia) adaptation in the organic high elevation, through the mammal heat shock response. (1) From high elevation to low elevation (natural hypoxia): Western blot and conventional RT-PCR and real-time fluorescence quota PCR were adopted. Expression difference of heat shock protein of 70 (Hsp70) and natural expression of brain tissue of Hsp70 gene was determined in the cardiac muscle tissue among the different elevation mammals (yak). (2)From low elevation to high elevation (hypoxia induction):The mammals (domestic rabbits) from the low elevation were sent directly to the areas with different high elevations like 2300, 3300 and 5000 m above sea level to be raised for a period of 3 weeks before being slaughtered and the genetic inductive expression of the brain tissue of Hsp70 was determined with RT-PCR. The result indicated that all of the mammals at different elevations possessed their heat shock response gene. Hsp70 of the high elevation mammal rose abruptly under stress and might be induced to come into being by high elevation (hypoxia). The speedy synthesis of Hsp70 in the process of heat shock response is suitable to maintain the cells' normal physiological functions under stress. The Hsp70 has its threshold value. The altitude of 5000 m above sea level is the best condition for the heat shock response, and it starts to reduce when the altitude is over 6000 m above sea level. The Hsp70 production quantity and the cell hypoxia bearing capacity have their direct ratio.

  20. Simple method for measuring vibration amplitude of high power airborne ultrasonic transducer: using thermo-couple.

    Science.gov (United States)

    Saffar, Saber; Abdullah, Amir

    2014-03-01

    Vibration amplitude of transducer's elements is the influential parameters in the performance of high power airborne ultrasonic transducers to control the optimum vibration without material yielding. The vibration amplitude of elements of provided high power airborne transducer was determined by measuring temperature of the provided high power airborne transducer transducer's elements. The results showed that simple thermocouples can be used both to measure the vibration amplitude of transducer's element and an indicator to power transmission to the air. To verify our approach, the power transmission to the air has been investigated by other common method experimentally. The experimental results displayed good agreement with presented approach. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. Internal friction mechanism of Fe-19Mn alloy at low and high strain amplitude

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Shuke, E-mail: huangshuke@163.com [Institute of Machinery Manufacturing Technology, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Huang, Wenrong; Liu, Jianhui [Institute of Machinery Manufacturing Technology, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Teng, Jin; Li, Ning; Wen, Yuhua [School of Manufacturing Science and Engineering, Sichuan University, Chengdu, Sichuan 610065 (China)

    2013-01-10

    Fe-Mn damping alloy, which can decrease the vibrating and noise effectively, will be widely applied to household appliances, automobiles, industrial facilities, etc. In this paper, the internal friction mechanism of Fe-19Mn alloy at low strain amplitude (10{sup -5} range) and high strain amplitude (10{sup -4} range) was investigated. The internal friction was measured using multifunction internal friction equipment and reversal torsion pendulum. The microstructure was observed using scanning electron microscopy. The phase transformation temperatures were determined using differential scanning calorimetry. The results indicated that the internal friction of Fe-19Mn alloy after solution treating was related to strain amplitude. The internal friction mechanism was believed to the movements of four damping sources ({epsilon}-martensite variant boundaries, stacking fault boundaries in {epsilon}-martensite and {gamma}-austenite, {gamma}/{epsilon} interfaces), which could be explained using the interactive movements of Shockley partial dislocations and point defects. At low strain amplitude (10{sup -5} range), the bowing out movements of Shockley partial dislocations are the main moving mode of generating internal friction. At high strain amplitude (10{sup -4} range), however, the breaking away movements of Shockley partial dislocations are the high internal friction mechanism of Fe-19Mn alloy.

  2. The analysis of high amplitude of potential oscillations near the hollow cathode of ion thruster

    Science.gov (United States)

    Qin, Yu; Xie, Kan; Guo, Ning; Zhang, Zun; Zhang, Cen; Gu, Zengjie; Zhang, Yu; Jiang, Zhaorui; Ouyang, Jiting

    2017-05-01

    The influence of gas flow, current level, and different shapes of anode on the oscillation amplitude and the characteristics of the hollow cathode discharge were investigated. The average plasma potential, temporal measurements of plasma potential, ion density, the electron temperature, as well as waveforms of plasma potential for test conditions were measured. At the same time, the time-resolved images of the plasma plume were also recorded. The results show that the potential oscillations appear at high discharge current or low flow rate. The potential oscillation boundaries, the position of maximum amplitude of plasma potential, and the position where the highest ion density was observed, were found. Both of the positions are affected by different shapes of anode configurations. This high amplitude of potential oscillations is ionization-like instabilities. The xenon ions ionized in space was analyzed for the fast potential rise and spatial dissipation of the space xenon ions was the reason for the gradual potential delay.

  3. High-pressure phases in shock-induced melt of the unique highly shocked LL6 chondrite Northwest Africa 757

    Science.gov (United States)

    Hu, Jinping; Sharp, Thomas G.

    2016-07-01

    Northwest Africa 757 is unique in the LL chondrite group because of its abundant shock-induced melt and high-pressure minerals. Olivine fragments entrained in the melt transform partially and completely into ringwoodite. Plagioclase and Ca-phosphate transform to maskelynite, lingunite, and tuite. Two distinct shock-melt crystallization assemblages were studied by FIB-TEM analysis. The first melt assemblage, which includes majoritic garnet, ringwoodite plus magnetite-magnesiowüstite, crystallized at pressures of 20-25 GPa. The other melt assemblage, which consists of clinopyroxene and wadsleyite, solidified at ~15 GPa, suggesting a second veining event under lower pressure conditions. These shock features are similar to those in S6 L chondrites and indicate that NWA 757 experienced an intense impact event, comparable to the impact event that disrupted the L chondrite parent body at 470 Ma.

  4. High performance single-error-correcting quantum codes for amplitude damping

    CERN Document Server

    Shor, Peter W; Smolin, John A; Zeng, Bei

    2009-01-01

    We construct families of high performance quantum amplitude damping codes. All of our codes are nonadditive and most modestly outperform the best possible additive codes in terms of encoded dimension. One family is built from nonlinear error-correcting codes for classical asymmetric channels, with which we systematically construct quantum amplitude damping codes with parameters better than any prior construction known for any block length n > 7 except n=2^r-1. We generalize this construction to employ classical codes over GF(3) with which we numerically obtain better performing codes up to length 14. Because the resulting codes are of the codeword stabilized (CWS) type, easy encoding and decoding circuits are available.

  5. Multiband carrierless amplitude/phase modulation for ultra-wideband high data rate wireless communications

    DEFF Research Database (Denmark)

    Puerta Ramírez, Rafael; Rommel, Simon; Altabas, Jose A.

    2016-01-01

    We report on the first experimental demonstration of carrierless amplitude/phase modulation in a flexible multiband approach for ultrawideband high-data-rate wireless communications. An effective bitrate of 2 GB/s is achieved while complying with the restrictions on the effective radiated power e...

  6. In search of objective manometric criteria for colonic high-amplitude propagated pressure waves

    NARCIS (Netherlands)

    De Schryver, AMP; Samsom, M; Smout, AJPM

    2002-01-01

    The aims of this study were to explore all characteristics of high-amplitude propagated contractions (HAPCs) that would allow them to be distinguished from nonHAPC colonic pressure waves, and to develop computer algorithms for automated HAPC detection. Colonic manometry recordings obtained from 24 h

  7. Numerical modeling of dune progression in a high amplitude meandering channel

    Science.gov (United States)

    Laboratory experiments carried out by Abad and Garcia (2009) in a high-amplitude Kinoshita meandering channel show bed morphodynamics to comprise steady (local scour and deposition) and unsteady (migrating bedforms) components. The experiments are replicated with a numerical model. The sediment tran...

  8. A diaphragmless shock tube for high temperature kinetic studies.

    Science.gov (United States)

    Tranter, Robert S; Giri, Binod R

    2008-09-01

    A novel, diaphragmless shock tube (DFST) has been developed for use in high temperature chemical kinetic studies. The design of the apparatus is presented along with performance data that demonstrate the range and reproducibility of reaction conditions that can be generated. The ability to obtain data in the fall off region, confined to much narrower pressure ranges than can be obtained with a conventional shock tube is shown, and results from laser schlieren densitometry experiments on the unimolecular dissociation of phenyl iodide (P(2)=57+/-9 and 122+/-7 torr, T(2)=1250-1804 K) are presented. These are compared with results similar to those that would be obtained from a classical shock tube and the implications for extrapolation by theoretical methods are discussed. Finally, the use of the DFST with an online mass spectrometer to create reproducible experiments that can be signal averaged to improve signal/noise and the quality of mass peaks is demonstrated; something that is not possible with a conventional shock tube where each experiment has to be considered unique.

  9. High dose insulin in toxic cardiogenic shock.

    Science.gov (United States)

    Holger, Joel S; Engebretsen, Kristin M; Marini, John J

    2009-04-01

    To report the successful use of high dose insulin (HDI) in previously unreported insulin dosing ranges in a patient with severe myocardial toxicity due to an amitriptyline and citalopram overdose. A 65-year-old female presented in respiratory arrest, which was followed by bradycardic pulseless electrical activity after ingesting multiple medications. After a prolonged resuscitation, the patient was maintained only on infusions of norepinephrine (40 mcg/min), vasopressin (4 units/h), insulin (80 units/h), and sodium bicarbonate. Due to a deteriorating clinical condition and limited prognosis, the insulin infusion was titrated incrementally upwards to 600 units/h (6 units/kg/h) over a 5 h time period while simultaneously completely weaning off both vasopressors. She developed brisk pulses and warm extremities, and her cardiac output nearly tripled. After 2 days of stabilization the insulin was slowly tapered, and the patient recovered. HDI as a single cardiovascular agent significantly improved clinical and cardiovascular parameters after the failure of vasopressor therapy in severe cardiovascular toxicity. Higher doses of insulin than previously recommended may be needed in toxic poisonings when severe myocardial depression is present.

  10. On high explosive launching of projectiles for shock physics experiments.

    Science.gov (United States)

    Swift, Damian C; Forest, Charles A; Clark, David A; Buttler, William T; Marr-Lyon, Mark; Rightley, Paul

    2007-06-01

    The hydrodynamic operation of the "Forest Flyer" type of explosive launching system for shock physics projectiles was investigated in detail using one and two dimensional continuum dynamics simulations. The simulations were numerically converged and insensitive to uncertainties in the material properties; they reproduced the speed of the projectile and the shape of its rear surface. The most commonly used variant, with an Al alloy case, was predicted to produce a slightly curved projectile, subjected to some shock heating and likely exhibiting some porosity from tensile damage. The curvature is caused by a shock reflected from the case; tensile damage is caused by the interaction of the Taylor wave pressure profile from the detonation wave with the free surface of the projectile. The simulations gave only an indication of tensile damage in the projectile, as damage is not understood well enough for predictions in this loading regime. The flatness can be improved by using a case of lower shock impedance, such as polymethyl methacrylate. High-impedance cases, including Al alloys but with denser materials improving the launching efficiency, can be used if designed according to the physics of oblique shock reflection, which indicates an appropriate case taper for any combination of explosive and case material. The tensile stress induced in the projectile depends on the relative thickness of the explosive, expansion gap, and projectile. The thinner the projectile with respect to the explosive, the smaller the tensile stress. Thus if the explosive is initiated with a plane wave lens, the tensile stress is lower than that for initiation with multiple detonators over a plane. The previous plane wave lens designs did, however, induce a tensile stress close to the spall strength of the projectile. The tensile stress can be reduced by changes in the component thicknesses. Experiments verifying the operation of explosively launched projectiles should attempt to measure

  11. Nonlinear reflection of high-amplitude laser pulses from relativistic electron mirrors

    Science.gov (United States)

    Kulagin, V. V.; Kornienko, V. N.; Cherepenin, V. A.

    2016-04-01

    A coherent X-ray pulse of attosecond duration can be formed in the reflection of a counterpropagating laser pulse from a relativistic electron mirror. The reflection of a high-amplitude laser pulse from the relativistic electron mirror located in the field of an accelerating laser pulse is investigated by means of two-dimensional (2D) numerical simulation. It is shown that provided the amplitude of the counterpropagating laser pulse is several times greater than the amplitude of the accelerating laser pulse, the reflection process is highly nonlinear, which causes a significant change in the X-ray pulse shape and its shortening up to generation of quasi-unipolar pulses and single-cycle pulses. A physical mechanism responsible for this nonlinearity of the reflection process is explained, and the parameters of the reflected X-ray pulses are determined. It is shown that the duration of these pulses may constitute 50 - 60 as, while their amplitude may be sub-relativistic.

  12. Development of a shock noise prediction code for high-speed helicopters - The subsonically moving shock

    Science.gov (United States)

    Tadghighi, H.; Holz, R.; Farassat, F.; Lee, Yung-Jang

    1991-01-01

    A previously defined airfoil subsonic shock-noise prediction formula whose result depends on a mapping of the time-dependent shock surface to a time-independent computational domain is presently coded and incorporated in the NASA-Langley rotor-noise prediction code, WOPWOP. The structure and algorithms used in the shock-noise prediction code are presented; special care has been taken to reduce computation time while maintaining accuracy. Numerical examples of shock-noise prediction are presented for hover and forward flight. It is confirmed that shock noise is an important component of the quadrupole source.

  13. Novel method of high-accuracy wavefront-phase and amplitude correction for coronagraphy

    Science.gov (United States)

    Bowers, Charles W.; Woodgate, Bruce E.; Lyon, Richard G.

    2003-11-01

    Detection of extra-solar, and especially terrestrial-like planets, using coronagraphy requires an extremely high level of wavefront correction. For example, the study of Woodruff et al. (2002) has shown that phase uniformity of order 10-4λ(rms) must be achieved over the critical range of spatial frequencies to produce the ~1010 contrast needed for the Terrestrial Planet Finder (TPF) mission. Correction of wavefront phase errors to this level may be accomplished by using a very high precision deformable mirror (DM). However, not only phase but also amplitude uniformity of the same scale (~10-4) and over the same spatial frequency range must be simultaneously obtained to remove all residual speckle in the image plane. We present a design for producing simultaneous wavefront phase and amplitude uniformity to high levels from an input wavefront of lower quality. The design uses a dual Michelson interferometer arrangement incorporating two DM and a single, fixed mirror (all at pupils) and two beamsplitters: one with unequal (asymmetric) beam splitting and one with symmetric beam splitting. This design allows high precision correction of both phase and amplitude using DM with relatively coarse steps and permits a simple correction algorithm.

  14. Dynamics of self-generated, large amplitude magnetic fields following high-intensity laser matter interaction

    CERN Document Server

    Sarri, G; Cecchetti, C A; Kar, S; Liseykina, T V; Yang, X H; Dieckmann, M E; Fuchs, J; Galimberti, M; Gizzi, L A; Jung, R; Kourakis, I; Osterholz, J; Pegoraro, F; Robinson, A P L; Romagnani, L; Willi, O; Borghesi, M

    2012-01-01

    The dynamics of magnetic fields with amplitude of several tens of Megagauss, generated at both sides of a solid target irradiated with a high intensity (? 1019W/cm2) picosecond laser pulse, has been spatially and temporally resolved using a proton imaging technique. The amplitude of the magnetic fields is sufficiently large to have a constraining effect on the radial expansion of the plasma sheath at the target surfaces. These results, supported by numerical simulations and simple analytical modeling, may have implications for ion acceleration driven by the plasma sheath at the rear side of the target as well as for the laboratory study of self-collimated high-energy plasma jets.

  15. Analysis of the Petersen Diagram of Double-Mode High-Amplitude {\\delta} Scuti Stars

    CERN Document Server

    Furgoni, Riccardo

    2016-01-01

    I created the Petersen diagram relative to all the Double Mode High Amplitude {\\delta} Scuti stars listed in the AAVSO's International Variable Star Index up to date December 29, 2015. For the first time I noticed that the ratio between the two periods P1/P0 seems in evident linear relation with the duration of the period P0, a finding never explicitly described in literature regarding this topic.

  16. Variable amplitude corrosion fatigue and fracture mechanics of weldable high strength jack-up steels

    OpenAIRE

    Etube, L. S.

    1998-01-01

    The tubular welded joints used in the construction of Offshore structures can experience millions of variable amplitude wave induced stress cycles during their operational life. Fatigue has been identified as the main cause of degradation of structural integrity in these structures. As a result, fatigue is an important consideration in their design. Jack-up legs are made from a range of high strength steels with yield strengths up to 70OMPa. These steels are thought to exhib...

  17. High-resolution, high-reflectivity operation of lamellar multilayer amplitude gratings: identification of the single-order regime

    NARCIS (Netherlands)

    Kozhevnikov, I. V.; van der Meer, R.; Bastiaens, H. M. J.; Boller, K. J.; F. Bijkerk,

    2010-01-01

    High resolution while maintaining high peak reflectivities can be achieved for Lamellar Multilayer Amplitude Gratings (LMAG) in the soft-x-ray (SXR) region. Using the coupled waves approach (CWA), it is derived that for small lamellar widths only the zeroth diffraction order needs to be considered f

  18. A high-stability non-contact dilatometer for low-amplitude temperature-modulated measurements

    Science.gov (United States)

    Luckabauer, Martin; Sprengel, Wolfgang; Würschum, Roland

    2016-07-01

    Temperature modulated thermophysical measurements can deliver valuable insights into the phase transformation behavior of many different materials. While especially for non-metallic systems at low temperatures numerous powerful methods exist, no high-temperature device suitable for modulated measurements of bulk metallic alloy samples is available for routine use. In this work a dilatometer for temperature modulated isothermal and non-isothermal measurements in the temperature range from room temperature to 1300 K is presented. The length measuring system is based on a two-beam Michelson laser interferometer with an incremental resolution of 20 pm. The non-contact measurement principle allows for resolving sinusoidal length change signals with amplitudes in the sub-500 nm range and physically decouples the length measuring system from the temperature modulation and heating control. To demonstrate the low-amplitude capabilities, results for the thermal expansion of nickel for two different modulation frequencies are presented. These results prove that the novel method can be used to routinely resolve length-change signals of metallic samples with temperature amplitudes well below 1 K. This high resolution in combination with the non-contact measurement principle significantly extends the application range of modulated dilatometry towards high-stability phase transformation measurements on complex alloys.

  19. Facilitation of epileptic activity during sleep is mediated by high amplitude slow waves.

    Science.gov (United States)

    Frauscher, Birgit; von Ellenrieder, Nicolás; Ferrari-Marinho, Taissa; Avoli, Massimo; Dubeau, François; Gotman, Jean

    2015-06-01

    Epileptic discharges in focal epilepsy are frequently activated during non-rapid eye movement sleep. Sleep slow waves are present during this stage and have been shown to include a deactivated ('down', hyperpolarized) and an activated state ('up', depolarized). The 'up' state enhances physiological rhythms, and we hypothesize that sleep slow waves and particularly the 'up' state are the specific components of non-rapid eye movement sleep that mediate the activation of epileptic activity. We investigated eight patients with pharmaco-resistant focal epilepsies who underwent combined scalp-intracerebral electroencephalography for diagnostic evaluation. We analysed 259 frontal electroencephalographic channels, and manually marked 442 epileptic spikes and 8487 high frequency oscillations during high amplitude widespread slow waves, and during matched control segments with low amplitude widespread slow waves, non-widespread slow waves or no slow waves selected during the same sleep stages (total duration of slow wave and control segments: 49 min each). During the slow waves, spikes and high frequency oscillations were more frequent than during control segments (79% of spikes during slow waves and 65% of high frequency oscillations, both P ∼ 0). The spike and high frequency oscillation density also increased for higher amplitude slow waves. We compared the density of spikes and high frequency oscillations between the 'up' and 'down' states. Spike and high frequency oscillation density was highest during the transition from the 'up' to the 'down' state. Interestingly, high frequency oscillations in channels with normal activity expressed a different peak at the transition from the 'down' to the 'up' state. These results show that the apparent activation of epileptic discharges by non-rapid eye movement sleep is not a state-dependent phenomenon but is predominantly associated with specific events, the high amplitude widespread slow waves that are frequent, but not

  20. WEATHER ON OTHER WORLDS. III. A SURVEY FOR T DWARFS WITH HIGH-AMPLITUDE OPTICAL VARIABILITY

    Energy Technology Data Exchange (ETDEWEB)

    Heinze, Aren N.; Metchev, Stanimir [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Kellogg, Kendra, E-mail: aren.heinze@stonybrook.edu, E-mail: smetchev@uwo.ca [Department of Physics and Astronomy, The University of Western Ontario, 1151 Richmond St, London, ON N6A 3K7 (Canada)

    2015-03-10

    We have monitored 12 T dwarfs with the Kitt Peak 2.1 m telescope using an F814W filter (0.7-0.95 μm) to place in context the remarkable 10%-20% variability exhibited by the nearby T dwarf Luhman 16B in this wavelength regime. The motivation was the poorly known red optical behavior of T dwarfs, which have been monitored almost exclusively at infrared wavelengths, where variability amplitudes greater than 10% have been found to be very rare. We detect highly significant variability in two T dwarfs. The T2.5 dwarf 2MASS 13243559+6358284 shows consistent ∼17% variability on two consecutive nights. The T2 dwarf 2MASS J16291840+0335371 exhibits ∼10% variability that may evolve from night to night, similarly to Luhman 16B. Both objects were previously known to be variable in the infrared, but with considerably lower amplitudes. We also find evidence for variability in the T6 dwarf J162414.37+002915.6, but since it has lower significance, we conservatively refrain from claiming this object as a variable. We explore and rule out various telluric effects, demonstrating that the variations we detect are astrophysically real. We suggest that high-amplitude photometric variability for T dwarfs is likely more common in the red optical than at longer wavelengths. The two new members of the growing class of high-amplitude variable T dwarfs offer excellent prospects for further study of cloud structures and their evolution.

  1. [High-frequency ventilation. I. Distribution of alveolar pressure amplitudes during high frequency oscillation in the lung model].

    Science.gov (United States)

    Theissen, J; Lunkenheimer, P P; Niederer, P; Bush, E; Frieling, G; Lawin, P

    1987-09-01

    The pattern of intrapulmonary pressure distribution was studied during high-frequency ventilation in order to explain the inconsistent results reported in the literature. Methods. Pressure and flow velocity (hot-wire anemometry) were measured in different lung compartments: 1. In transalveolar chambers sealed to the perforated pleural surfaces of dried pig lungs; 2. In emphysema-simulating airbags sealed to the isolated bronchial trees of dried pig lungs; and 3. In transalveolar chambers sealed to the perforated pleural surfaces of freshly excised pig lungs. Results. 1. The pressure amplitudes change from one area to another and depending on the exciting frequency. 2. High-frequency oscillation is associated with an increase in pressure amplitude when the exciting frequency rises, whereas with conventional high-frequency jet ventilation the pressure amplitude is more likely to decrease with frequency. 3. During high-frequency jet ventilation the local pressure amplitude changes with the position of the tube in the trachea rather than with the exciting frequency. 4. When the volume of the measuring chamber is doubled the resulting pressure amplitude falls to half the control value. 5. The pressure amplitude and mean pressure measured in the transalveolar chamber vary more or less independently from the peak flow velocity. High-frequency ventilation is thus seen to be a frequency-dependant, inhomogeneous mode of ventilation that can essentially be homogenized by systematically changing the exciting frequency. The frequency-dependant response to different lung areas to excitation is likely to result from an intrabronchially-localized aerodynamic effect rather than the mechanical properties of the lung parenchyma.

  2. Speckle interferometric sensor to measure low-amplitude high frequency Ocular Microtremor (OMT)

    Science.gov (United States)

    Ryle, James P.; Al-Kalbani, Mohammed; Gopinathan, Unnikrishnan; Boyle, Gerard; Coakley, Davis; Sheridan, John T.

    2009-08-01

    Ocular microtremor (OMT) is a physiological high frequency (up to 150Hz) low amplitude (150-2500nm) involuntary tremor of the human eye. It is one of the three fixational ocular motions described by Adler and Fliegelman in 1934 as well as microsaccades and drift. Clinical OMT investigations to date have used eye-contacting piezoelectric probes or piezoelectric strain gauges. Before contact can be made, the eye must first be anaesthetised. In some cases, this induces eyelid spasms (blepharospasm) making it impossible to measure OMT. Using the contact probe method, the eye motion is mechanically damped. In addition to this, it is not possible to obtain exact information about the displacement. Results from clinical studies to date have given electrical signal amplitudes from the probe. Recent studies suggest a number of clinical applications for OMT, these include monitoring the depth of anaesthesia of a patient in surgery, prediction of outcome in coma, diagnosis of brainstem death. In addition to this, abnormal OMT frequency content is present in patients with neurological disorders such as Multiple sclerosis and Parkinson's disease. However for ongoing clinical investigations the contact probe method falls short of a non-contact accurate measurement solution. In this paper, we design a compact non contact phase modulating optical fiber speckle interferometer to measure eye motions. We present our calibration results using a calibrated piezoelectric vibration simulator. Digital signal processing is then performed to extract the low amplitude high frequency displacement information.

  3. Tip radius preservation for high resolution imaging in amplitude modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, Jorge R., E-mail: jorge.rr@cea.cu [Instituto de Ciencia de Materiales de Madrid, Sor Juana Inés de la Cruz 3, Canto Blanco, 28049 Madrid, España (Spain)

    2014-07-28

    The acquisition of high resolution images in atomic force microscopy (AFM) is correlated to the cantilever's tip shape, size, and imaging conditions. In this work, relative tip wear is quantified based on the evolution of a direct experimental observable in amplitude modulation atomic force microscopy, i.e., the critical amplitude. We further show that the scanning parameters required to guarantee a maximum compressive stress that is lower than the yield/fracture stress of the tip can be estimated via experimental observables. In both counts, the optimized parameters to acquire AFM images while preserving the tip are discussed. The results are validated experimentally by employing IgG antibodies as a model system.

  4. High CW power, phase and amplitude modulatorrealized with fast ferrite phase-shifters

    CERN Document Server

    Valuch, D

    2004-01-01

    Superconducting cavity resonators are suffering from detuning effects caused by high internal electromagnetic fields (Lorentz force detuning). For classical resonators working with continuous wave signals, this detuning is static and compensated by the slow mechanical tuning system. However, pulsing of superconducting cavities, an operational mode only recently considered, results in dynamic detuning effects. New ways to handle this effect have to be found and worked out. A way to supply several superconducting cavities in the particle accelerator by one large transmitter while keeping the possibility of controlling the field in each individual cavity is shown. By introducing a fast phase and amplitude modulator into each cavity feeder line, the individual deviations of each cavity with respect to the average can be compensated in order to equalize their behaviour for the main control loop, which will compensate the global detuning of all cavities. Several types of phase and amplitude modulators suitable for ...

  5. Shock initiation studies on high concentration hydrogen peroxide

    Energy Technology Data Exchange (ETDEWEB)

    Sheffield, Stephen A [Los Alamos National Laboratory; Dattelbaum, Dana M [Los Alamos National Laboratory; Stahl, David B [Los Alamos National Laboratory; Gibson, L. Lee [Los Alamos National Laboratory; Bartram, Brian D. [Los Alamos National Laboratory

    2009-01-01

    Concentrated hydrogen peroxide (H{sub 2}O{sub 2}) has been known to detonate for many years. However, because of its reactivity and the difficulty in handling and confining it, along with the large critical diameter, few studies providing basic information about the initiation and detonation properties have been published. We are conducting a study to understand and quantify the initiation and detonation properties of highly concentrated H{sub 2}O{sub 2} using a gas-driven two-stage gun to produce well defined shock inputs. Multiple magnetic gauges are used to make in-situ measurements of the growth of reaction and subsequent detonation in the liquid. These experiments are designed to be one-dimensional to eliminate any difficulties that might be encountered with large critical diameters. Because of the concern of the reactivity of the H{sub 2}O{sub 2} with the confining materials, a remote loading system has been developed. The gun is pressurized, then the cell is filled and the experiment shot within less than three minutes. TV cameras are attached to the target so the cell filling can be monitored. Several experiments have been completed on {approx}98 wt % H{sub 2}O{sub 2}/H{sub 2}O mixtures; initiation has been observed in some experiments that shows homogeneous shock initiation behavior. The initial shock pressurizes and heats the mixture. After an induction time, a thermal explosion type reaction produces an evolving reactive wave that strengthens and eventually overdrives the first wave producing a detonation. From these measurements, we have determined unreacted Hugoniot information, times (distances) to detonation (Pop-plot points) that indicate low sensitivity, and detonation velocities of high concentration H{sub 2}O{sub 2}/H{sub 2}O solutions that agree with earlier estimates.

  6. Shock initiation studies on high concentration hydrogen peroxide

    Energy Technology Data Exchange (ETDEWEB)

    Sheffield, Stephen A [Los Alamos National Laboratory; Dattelbaum, Dana M [Los Alamos National Laboratory; Stahl, David B [Los Alamos National Laboratory; Gibson, L. Lee [Los Alamos National Laboratory; Bartram, Brian D. [Los Alamos National Laboratory

    2009-01-01

    Concentrated hydrogen peroxide (H{sub 2}O{sub 2}) has been known to detonate for many years. However, because of its reactivity and the difficulty in handling and confining it, along with the large critical diameter, few studies providing basic information about the initiation and detonation properties have been published. We are conducting a study to understand and quantify the initiation and detonation properties of highly concentrated H{sub 2}O{sub 2} using a gas-driven two-stage gun to produce well defined shock inputs. Multiple magnetic gauges are used to make in-situ measurements of the growth of reaction and subsequent detonation in the liquid. These experiments are designed to be one-dimensional to eliminate any difficulties that might be encountered with large critical diameters. Because of the concern of the reactivity of the H{sub 2}O{sub 2} with the confining materials, a remote loading system has been developed. The gun is pressurized, then the cell is filled and the experiment shot within less than three minutes. TV cameras are attached to the target so the cell filling can be monitored. Several experiments have been completed on {approx}98 wt % H{sub 2}O{sub 2}/H{sub 2}O mixtures; initiation has been observed in some experiments that shows homogeneous shock initiation behavior. The initial shock pressurizes and heats the mixture. After an induction time, a thermal explosion type reaction produces an evolving reactive wave that strengthens and eventually overdrives the first wave producing a detonation. From these measurements, we have determined unreacted Hugoniot information, times (distances) to detonation (Pop-plot points) that indicate low sensitivity, and detonation velocities of high concentration H{sub 2}O{sub 2}/H{sub 2}O solutions that agree with earlier estimates.

  7. High-speed helicopter rotor noise - Shock waves as a potent source of sound

    Science.gov (United States)

    Farassat, F.; Lee, Yung-Jang; Tadghighi, H.; Holz, R.

    1991-01-01

    In this paper we discuss the problem of high speed rotor noise prediction. In particular, we propose that from the point of view of the acoustic analogy, shocks around rotating blades are sources of sound. We show that, although for a wing at uniform steady rectilinear motion with shocks the volume quadrupole and shock sources cancel in the far field to the order of 1/r, this cannot happen for rotating blades. In this case, some cancellation between volume quadrupoles and shock sources occurs, yet the remaining shock noise contribution is still potent. A formula for shock noise prediction is presented based on mapping the deformable shock surface to a time independent region. The resulting equation is similar to Formulation 1A of Langley. Shock noise prediction for a hovering model rotor for which experimental noise data exist is presented. The comparison of measured and predicted acoustic data shows good agreement.

  8. Effects of thrust amplitude and duration of high velocity low amplitude spinal manipulation on lumbar muscle spindle responses to vertebral position and movement

    Science.gov (United States)

    Cao, Dong-Yuan; Reed, William R.; Long, Cynthia R.; Kawchuk, Gregory N.; Pickar, Joel G.

    2013-01-01

    OBJECTIVE Mechanical characteristics of high velocity low amplitude spinal manipulations (HVLA-SM) can be variable. Sustained changes in peripheral neuronal signaling due to altered load transmission to a sensory receptor’s local mechanical environment are often considered a mechanism contributing to the therapeutic effects of spinal manipulation. The purpose of this study was to determine whether an HVLA-SM’s thrust amplitude or duration altered neural responsiveness of lumbar muscle spindles to either vertebral movement or position. METHODS Anesthetized cats (n=112) received L6 HVLA-SMs delivered to the spinous process. Cats were divided into 6 cohorts depending upon the peak thrust force (25%, 55%, 85% body weight) or thrust displacement (1, 2, 3mm) they received. Cats in each cohort received 8 thrust durations (0–250ms). Afferent discharge from 112 spindles was recorded in response to ramp and hold vertebral movement before and after the manipulation. Changes in mean instantaneous frequency (MIF) during the baseline period preceding the ramps (ΔMIFresting), during ramp movements (ΔMIFmovement), and with the vertebra held in the new position (ΔMIFposition) were compared. RESULTS Thrust duration had a small but statistically significant effect on ΔMIFresting at all six thrust amplitudes compared to control (0ms thrust duration). The lowest amplitude thrust displacement (1mm) increased ΔMIFresting at all thrust durations. For all the other thrust displacements and forces, the direction of change in ΔMIFresting was not consistent and the pattern of change was not systematically related to thrust duration. Regardless of thrust force, displacement, or duration, ΔMIFmovement and ΔMIFposition were not significantly different from control. Conclusion Relatively low amplitude thrust displacements applied during an HVLA-SM produced sustained increases in the resting discharge of paraspinal muscle spindles regardless of the duration over which the thrust was

  9. Effects of thrust amplitude and duration of high-velocity, low-amplitude spinal manipulation on lumbar muscle spindle responses to vertebral position and movement.

    Science.gov (United States)

    Cao, Dong-Yuan; Reed, William R; Long, Cynthia R; Kawchuk, Gregory N; Pickar, Joel G

    2013-02-01

    Mechanical characteristics of high-velocity, low-amplitude spinal manipulations (HVLA-SMs) can vary. Sustained changes in peripheral neuronal signaling due to altered load transmission to a sensory receptor's local mechanical environment are often considered a mechanism contributing to the therapeutic effects of spinal manipulation. The purpose of this study was to determine whether variation in an HVLA-SM's thrust amplitude and duration alters the neural responsiveness of lumbar muscle spindles to either vertebral movement or position. Anesthetized cats (n = 112) received L6 HVLA-SMs delivered to the spinous process. Cats were divided into 6 cohorts depending upon the peak thrust force (25%, 55%, 85% body weight) or thrust displacement (1, 2, 3 mm) they received. Cats in each cohort received 8 thrust durations (0-250 milliseconds). Afferent discharge from 112 spindles was recorded in response to ramp and hold vertebral movement before and after the manipulation. Changes in mean instantaneous frequency (∆MIF) during the baseline period preceding the ramps (∆MIFresting), during ramp movement (∆MIFmovement), and with the vertebra held in the new position (∆MIFposition) were compared. Thrust duration had a small but statistically significant effect on ∆MIFresting at all 6 thrust amplitudes compared with control (0-millisecond thrust duration). The lowest amplitude thrust displacement (1 mm) increased ∆MIFresting at all thrust durations. For all the other thrust displacements and forces, the direction of change in ∆MIFresting was not consistent, and the pattern of change was not systematically related to thrust duration. Regardless of thrust force, displacement, or duration, ∆MIFmovement and ∆MIFposition were not significantly different from control. Relatively low-amplitude thrust displacements applied during an HVLA-SM produced sustained increases in the resting discharge of paraspinal muscle spindles regardless of the duration over which the thrust

  10. Shock-induced heating and millisecond boiling in gels and tissue due to high intensity focused ultrasound.

    Science.gov (United States)

    Canney, Michael S; Khokhlova, Vera A; Bessonova, Olga V; Bailey, Michael R; Crum, Lawrence A

    2010-02-01

    Nonlinear propagation causes high-intensity ultrasound waves to distort and generate higher harmonics, which are more readily absorbed and converted to heat than the fundamental frequency. Although such nonlinear effects have been investigated previously and found to not significantly alter high-intensity focused ultrasound (HIFU) treatments, two results reported here change this paradigm. One is that at clinically relevant intensity levels, HIFU waves not only become distorted but form shock waves in tissue. The other is that the generated shock waves heat the tissue to boiling in much less time than predicted for undistorted or weakly distorted waves. In this study, a 2-MHz HIFU source operating at peak intensities up to 25,000 W/cm(2) was used to heat transparent tissue-mimicking phantoms and ex vivo bovine liver samples. Initiation of boiling was detected using high-speed photography, a 20-MHz passive cavitation detector and fluctuation of the drive voltage at the HIFU source. The time to boil obtained experimentally was used to quantify heating rates and was compared with calculations using weak shock theory and the shock amplitudes obtained from nonlinear modeling and measurements with a fiber optic hydrophone. As observed experimentally and predicted by calculations, shocked focal waveforms produced boiling in as little as 3 ms and the time to initiate boiling was sensitive to small changes in HIFU output. Nonlinear heating as a result of shock waves is therefore important to HIFU, and clinicians should be aware of the potential for very rapid boiling because it alters treatments.

  11. First Results with a Fast Phase and Amplitude Modulator for High Power RF Application

    CERN Document Server

    Frischholz, Hans; Valuch, D; Weil, C

    2004-01-01

    In a high energy and high power superconducting proton linac, it is more economical to drive several cavities with a single high power transmitter rather than to use one transmitter per cavity. However, this option has the disadvantage of not permitting individual control for each cavity, which potentially leads to instabilities. Provided that it can be built at a reasonable cost, a fast phase and amplitude modulator inserted into each cavity feeder line can provide the necessary control capability. A prototype of such a device has been built, based on two fast and compact high power RF phase-shifters, magnetically biased by external coils. The design is described, together with the results obtained at high and low power levels.

  12. Semi-blind Adaptive Beamforming for High-throughput Quadrature Amplitude Modulation Systems

    Institute of Scientific and Technical Information of China (English)

    Sheng Chen; Wang Yao; Lajos Hanzo

    2010-01-01

    A semi-blind adaptive beamforming scheme is proposed for wireless systems that employ high-throughput quadrature amplitude modulation signalling. A minimum number of training symbols, equal to the number of receiver antenna array's elements, are first utilised to provide a rough initial least squares estimate of the beamformer's weight vector. A concurrent constant modulus algorithm and soft decision-directed scheme is then applied to adapt the beamformer. This semi-blind adaptive beamforming scheme is capable of converging fast to the minimum mean-square-error beamforming solution, as demonstrated in our simulation study.

  13. Interaction of a highly radiative shock with a solid obstacle

    Science.gov (United States)

    Koenig, M.; Michel, Th.; Yurchak, R.; Michaut, C.; Albertazzi, B.; Laffite, S.; Falize, E.; Van Box Som, L.; Sakawa, Y.; Sano, T.; Hara, Y.; Morita, T.; Kuramitsu, Y.; Barroso, P.; Pelka, A.; Gregori, G.; Kodama, R.; Ozaki, N.; Lamb, D.; Tzeferacos, P.

    2017-08-01

    In this paper, we present the recent results obtained regarding highly radiative shocks (RSs) generated in a low-density gas filled cell on the GEKKO XII laser facility. The RS was generated by using an ablator-pusher two-layer target (CH/Sn) and a propagation medium (Xe). High velocity RSs have been generated (100-140 km/s), while limiting as much as possible the preheating produced by the corona emission. Both self-emission and visible probe diagnostics highlighted a strong emission in the shock and an electron density in the downstream gas. The RS characteristics that depend on the initial conditions are described here as well as its precursor interaction with an aluminium foil used as an obstacle. The obtained results are discussed which show a strong extension of the radiative precursor (1 mm) leading to an expansion velocity of the obstacle up to ≈30 km/s compatible to a 20 eV temperature.

  14. Real-time, high frequency QRS electrocardiograph with reduced amplitude zone detection

    Science.gov (United States)

    Schlegel, Todd T. (Inventor); DePalma, Jude L. (Inventor); Moradi, Saeed (Inventor)

    2009-01-01

    Real time cardiac electrical data are received from a patient, manipulated to determine various useful aspects of the ECG signal, and displayed in real time in a useful form on a computer screen or monitor. The monitor displays the high frequency data from the QRS complex in units of microvolts, juxtaposed with a display of conventional ECG data in units of millivolts or microvolts. The high frequency data are analyzed for their root mean square (RMS) voltage values and the discrete RMS values and related parameters are displayed in real time. The high frequency data from the QRS complex are analyzed with imbedded algorithms to determine the presence or absence of reduced amplitude zones, referred to herein as ''RAZs''. RAZs are displayed as ''go, no-go'' signals on the computer monitor. The RMS and related values of the high frequency components are displayed as time varying signals, and the presence or absence of RAZs may be similarly displayed over time.

  15. Coronal Heating and Acceleration of the High/Low-Speed Solar Wind by Fast/Slow MHD Shock Trains

    CERN Document Server

    Suzuki, T K

    2004-01-01

    We investigate coronal heating and acceleration of the high- and low-speed solar wind in the open field region by dissipation of fast and slow magnetohydrodynamical (MHD) waves through MHD shocks. Linearly polarized \\Alfven (fast MHD) waves and acoustic (slow MHD) waves travelling upwardly along with a magnetic field line eventually form fast switch-on shock trains and hydrodynamical shock trains (N-waves) respectively to heat and accelerate the plasma. We determine one dimensional structure of the corona from the bottom of the transition region (TR) to 1AU under the steady-state condition by solving evolutionary equations for the shock amplitudes simultaneously with the momentum and proton/electron energy equations. Our model reproduces the overall trend of the high-speed wind from the polar holes and the low-speed wind from the mid- to low-latitude streamer except the observed hot corona in the streamer. The heating from the slow waves is effective in the low corona to increase the density there, and plays ...

  16. Sensitivity of once-shocked, weathered high explosives

    Energy Technology Data Exchange (ETDEWEB)

    Williams, K.L.; Harris, B.W.

    1998-07-01

    Effects caused by stimulating once-shocked, weathered high explosives (OSW-HE) are investigated. The sensitivity of OSW-HE to mechanical stimuli was determined using standard industry tests. Some initial results are given. Pieces of OSW-HE were collected from active and inactive firing sites and from an area surrounding a drop tower at Los Alamos where skid and spigot tests were done. Samples evaluated were cast explosives or plastic bonded explosive (PBX) formulations containing cyclotrimethylenetrinitramine (RDX), cyclotetramethylene tetranitramine (HMX), 2,4,6-trinitrotoluene (TNT), mock or inert HE [tris(beta-chloroethyl)phosphate (CEF)], barium nitrate, cyanuric acid, talc, and Kel-F. Once-shocked, weathered LX-10 Livermore explosive [HMX/Viton A, (95/5 wt %)], PBX 9011 [HMX/Estane, (90/10 wt %)], PBX 9404 [HMX/nitrocellulose, tris(beta-chloroethyl) phosphate, (94/3/3 wt %)], Composition B or cyclotol (TNT/RDX explosives), and PBX 9007 (90% RDX, 9.1% styrene, 0.5% dioctyl phthalate, and 0.45 resin) were subjected to the hammer test, the drop-weight impact sensitivity test, differential thermal analysis (DTA), the spark test, the Henkin`s critical temperature test, and the flame test. Samples were subjected to remote, wet cutting and drilling; remote, liquid-nitrogen-cooled grinding and crushing; and scanning electron microscope (SEM) surface analyses for morphological changes.

  17. High Frequency Measurements in Shock-Wave/Turbulent Boundary-Layer Interaction at Duplicated Flight Conditions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Large amplitude, unsteady heating loads and steep flow gradients produced in regions of shock-wave/turbulent boundary-layer interaction (SWTBLI) pose a serious and...

  18. High Frequency Measurements in Shock-Wave/Turbulent Boundary-Layer Interaction at Duplicated Flight Conditions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Large amplitude, unsteady heating loads and steep flow gradients produced in regions of shock-wave/turbulent boundary-layer interaction (SWTBLI) pose a serious and...

  19. Role of the Ionosphere in the Generation of Large-Amplitude Ulf Waves at High Latitudes

    Science.gov (United States)

    Tulegenov, B.; Guido, T.; Streltsov, A. V.

    2014-12-01

    We present results from the statistical study of ULF waves detected by the fluxgate magnetometer in Gakona, Alaska during several experimental campaigns conducted at the High Frequency Active Auroral Research Program (HAARP) facility in years 2011-2013. We analyzed frequencies of ULF waves recorded during 26 strongly disturbed geomagnetic events (substorms) and compared them with frequencies of ULF waves detected during magnetically quite times. Our analysis demonstrates that the frequency of the waves carrying most of the power almost in all these events is less than 1 mHz. We also analyzed data from the ACE satellite, measuring parameters of the solar wind in the L1 Lagrangian point between Earth and Sun, and found that in several occasions there is a strong correlation between oscillations of the magnetic field in the solar wind and oscillations detected on the ground. We also found several cases when there is no correlation between signals detected on ACE and on the ground. This finding suggests that these frequencies correspond to the fundamental eigenfrequency of the coupled magnetosphere-ionosphere system. The low frequency of the oscillations is explained by the effect of the ionosphere, where the current is carried by ions through highly collisional media. The amplitude of these waves can reach significant magnitude when the system is driven by the external driver (for example, the solar wind) with this particular frequency. When the frequency of the driver does not match the frequency of the system, the waves still are observed, but their amplitudes are much smaller.

  20. Adhesive bond strength evaluation in composite materials by laser-generated high amplitude ultrasound

    Science.gov (United States)

    Perton, M.; Blouin, A.; Monchalin, J.-P.

    2011-01-01

    Adhesive bonding of composites laminates is highly efficient but is not used for joining primary aircraft structures, since there is presently no nondestructive inspection technique to ensure the quality of the bond. We are developing a technique based on the propagation of high amplitude ultrasonic waves to evaluate the adhesive bond strength. Large amplitude compression waves are generated by a short pulse powerful laser under water confinement and are converted after reflection by the assembly back surface into tensile waves. The resulting tensile stresses can cause a delamination inside the laminates or at the bond interfaces. The adhesion strength is evaluated by increasing the laser pulse energy until disbond. A good bond is unaffected by a certain level of stress whereas a weaker one is damaged. The method is shown completely non invasive throughout the whole composite assembly. The sample back surface velocity is measured by an optical interferometer and used to estimate stress history inside the sample. The depth and size of the disbonds are revealed by a post-test inspection by the well established laser-ultrasonic technique. Experimental results show that the proposed method is able to differentiate weak bond from strong bonds and to estimate quantitatively their bond strength.

  1. Shock response of the commercial high explosive Detasheet

    Science.gov (United States)

    Asay, B. W.; Ramsay, J. B.; Anderson, M. U.; Graham, R. A.

    1994-12-01

    The mechanical and chemical response of the flexible commercial high explosive DetasheetR is studied under controlled impact and plane-wave, high explosive loading. Results on nonreactive material behavior, sound speed, shock-initiation sensitivity and detonation pressure are presented. The material is found to respond in a viscous manner reminiscent of viscoelastic response of polymeric materials. Time-resolved pressure and pressure-rate measurements with PVDF piezoelectric polymer gauges are presented along with Manganin pressure and plate-dent test measurements of detonation pressure. Detonation pressures of 18GPa are indicated. Pressure measurements show initiation of reaction between 3 and 8 mm for an impact stress of 3.1 GPa. Plane wave loading wedge tests show run distances to detonation consistent with the pressure measurements, and with behavior like that of XTX8003 (80 % PETN/20 % Sylgard 182R).

  2. Highly trabeculated structure of the human endocardium underlies asymmetrical response to low-energy monophasic shocks

    Science.gov (United States)

    Connolly, Adam; Robson, Matthew D.; Schneider, Jürgen; Burton, Rebecca; Plank, Gernot; Bishop, Martin J.

    2017-09-01

    Novel low-energy defibrillation therapies are thought to be driven by virtual-electrodes (VEs), due to the interaction of applied monophasic electric shocks with fine-scale anatomical structures within the heart. Significant inter-species differences in the cardiac (micro)-anatomy exist, however, particularly with respect to the degree of endocardial trabeculations, which may underlie important differences in response to low-energy defibrillation protocols. Understanding the interaction of monophasic electric fields with the specific human micro-anatomy is therefore imperative in facilitating the translation and optimisation of these promising experimental therapies to the clinic. In this study, we sought to investigate how electric fields from implanted devices interact with the highly trabeculated human endocardial surface to better understand shock success in order to help optimise future clinical protocols. A bi-ventricular human computational model was constructed from high resolution (350 μm) ex-vivo MR data, including anatomically accurate endocardial structures. Monophasic shocks were applied between a basal right ventricular catheter and an exterior ground. Shocks of varying strengths were applied with both anodal [positive right ventricle (RV) electrode] and cathodal (negative RV electrode) polarities at different states of tissue refractoriness and during induced arrhythmias. Anodal shocks induced isolated positive VEs at the distal side of "detached" trabeculations, which rapidly spread into hyperpolarised tissue on the surrounding endocardial surfaces following the shock. Anodal shocks thus depolarised more tissue 10 ms after the shock than cathodal shocks where the propagation of activation from VEs induced on the proximal side of "detached" trabeculations was prevented due to refractory endocardium. Anodal shocks increased arrhythmia complexity more than cathodal shocks during failed anti-arrhythmia shocks. In conclusion, multiple detached

  3. Shock propagation and attenuation in high-power excimer lasers

    Science.gov (United States)

    Holzwarth, Achim; Berger, Peter; Huegel, Helmut

    1993-05-01

    Theoretical and experimental investigations on the propagation, reflection, and attenuation of shock waves as they occur in excimer lasers have been performed. The numerical simulations have been carried out using a two-dimensional, unsteady finite difference scheme. The experimental setup is a piston driven shock tube with a rectangular cross section working in air at atmospheric pressure. The shocks were detected interferometrically as well as by means of pressure transducers. This shock tube allows us to investigate basic phenomena of shock diffraction which can be used to confirm the computational results in the range of weak shock waves. In particular, the influence of the shape of the wall contour on the reflection of shock waves has been investigated theoretically. The decay time of pressure and density perturbations differs for various wall configurations in such a way that short electrodes accelerate the attenuation as well as does a strong area increase in the vicinity of them. After each laser pulse there is a shock travelling into the laser channel. Experiments have been carried out on the reflection of this shock at a specially formed bend that is able to focus the shock into a muffling element.

  4. Resonance of a Metal Drop under the Effect of Amplitude-Modulated High Frequency Magnetic Field

    Science.gov (United States)

    Guo, Jiahong; Lei, Zuosheng; Zhu, Hongda; Zhang, Lijie; Magnetic Hydrodynamics(Siamm) Team; Magnetic Mechanics; Engineering(Smse) Team

    2016-11-01

    The resonance of a sessile and a levitated drop under the effect of high frequency amplitude-modulated magnetic field (AMMF) is investigated experimentally and numerically. It is a new method to excite resonance of a metal drop, which is different from the case in the presence of a low-frequency magnetic field. The transient contour of the drop is obtained in the experiment and the simulation. The numerical results agree with the experimental results fairly well. At a given frequency and magnetic flux density of the high frequency AMMF, the edge deformations of the drop with an azimuthal wave numbers were excited. A stability diagram of the shape oscillation of the drop and its resonance frequency spectrum are obtained by analysis of the experimental and the numerical data. The results show that the resonance of the drop has a typical character of parametric resonance. The National Natural Science Foundation of China (No. 51274237 and 11372174).

  5. Thermal effects on seeded finite ion temperature, high amplitude plasma blobs

    CERN Document Server

    Held, M; Madsen, J; Kendl, A

    2016-01-01

    Thermal effects on the perpendicular convection of seeded pressure blobs in the scrape-off layer of magnetised fusion plasmas are investigated. Our numerical study is based on a four field full-F gyrofluid model, which entails the consistent description of high fluctuation amplitudes and dynamic finite Larmor radius effects. We find that a temperature perturbation increases the maximal blob velocity and that a finite Larmor radius contributes to highly compact blob structures with finite poloidal motion. An extensive parameter study reveals that a smooth transition to this compact blob regime occurs when the finite Larmor radius effect strength, defined by the ratio of the ion diamagnetic to the perpendicular vorticity, exceeds unity. The maximal blob velocities excellently agree with the inertial velocity scaling law over more than an order of magnitude. We show that the finite Larmor radius effect strength affects the radial transport and verify the here presented empirical scaling law for the maximal radia...

  6. High and low strength nonsynchronized shocks given during canine ventricular tachycardia.

    Science.gov (United States)

    McClelland, J H; Daubert, J P; Kavanagh, K M; Harrell, F E; Ideker, R E

    1992-07-01

    Cardioversion shocks given during ventricular tachycardia may cause ventricular fibrillation or acceleration of ventricular tachycardia, or arrest the tachycardia. A recently proposed theory may explain why the former two phenomena may occur. Briefly, this theory states that potential gradient shock fields of a critical strength delivered to tissue with a critical degree of refractoriness will cause circulating wave fronts of ventricular activation ("rotors") manifest as ventricular arrhythmia. We tested this theory by delivering nonsynchronized shocks 50% higher than defibrillation threshold or 50% lower than defibrillation threshold during 275 episodes of ventricular tachycardia in eight dogs with 5- to 7-day-old myocardial infarcts. Shocks stronger than the defibrillation threshold are likely to create shock fields in the ventricles everywhere stronger than this critical value, and therefore would not generate rotors. Shocks less strong than the defibrillation threshold may create shock fields within the ventricles that include the critical value, and therefore cause rotors if given when critically refractory tissue is present. Nonsynchronized shocks were used to increase the likelihood of encountering tissue with a critical degree of refractoriness. Ventricular fibrillation or acceleration of ventricular tachycardia occurred following 83 of 138 (60%) low strength shocks and following 20 of 137 (14.6%) high strength shocks. The pooled odds ratio for induction of ventricular fibrillation or accelerated ventricular tachycardia after low strength shocks as compared to high strength shocks was 8.9. when given during ventricular tachycardia, low strength shocks are much more likely to cause ventricular fibrillation or accelerated ventricular tachycardia than are high strength shocks (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

  7. An output amplitude configurable wideband automatic gain control with high gain step accuracy

    Institute of Scientific and Technical Information of China (English)

    何晓丰; 莫太山; 马成炎; 叶甜春

    2012-01-01

    An output amplitude configurable wideband automatic gain control (AGC) with high gain step accuracy for the GNSS receiver is presented.The amplitude of an AGC is configurable in order to cooperate with baseband chips to achieve interference suppression and be compatible with different full range ADCs.And what's more,the gain-boosting technology is introduced and the circuit is improved to increase the step accuracy.A zero,which is composed by the source feedback resistance and the source capacity,is introduced to compensate for the pole.The AGC is fabricated in a 0.18 μm CMOS process.The AGC shows a 62 dB gain control range by 1 dB each step with a gain error of less than 0.2 dB.The AGC provides 3 dB bandwidth larger than 80 MHz and the overall power consumption is less than 1.8 mA,and the die area is 800 × 300μm2.

  8. Relativistic electron scattering by magnetosonic waves: Effects of discrete wave emission and high wave amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Artemyev, A. V., E-mail: ante0226@gmail.com [Space Research Institute, RAS, Moscow (Russian Federation); Mourenas, D.; Krasnoselskikh, V. V. [LPC2E/CNRS - University of Orleans, Orleans (France); Agapitov, O. V. [Space Sciences Laboratory, University of California, Berkeley, California 94720 (United States)

    2015-06-15

    In this paper, we study relativistic electron scattering by fast magnetosonic waves. We compare results of test particle simulations and the quasi-linear theory for different spectra of waves to investigate how a fine structure of the wave emission can influence electron resonant scattering. We show that for a realistically wide distribution of wave normal angles θ (i.e., when the dispersion δθ≥0.5{sup °}), relativistic electron scattering is similar for a wide wave spectrum and for a spectrum consisting in well-separated ion cyclotron harmonics. Comparisons of test particle simulations with quasi-linear theory show that for δθ>0.5{sup °}, the quasi-linear approximation describes resonant scattering correctly for a large enough plasma frequency. For a very narrow θ distribution (when δθ∼0.05{sup °}), however, the effect of a fine structure in the wave spectrum becomes important. In this case, quasi-linear theory clearly fails in describing accurately electron scattering by fast magnetosonic waves. We also study the effect of high wave amplitudes on relativistic electron scattering. For typical conditions in the earth's radiation belts, the quasi-linear approximation cannot accurately describe electron scattering for waves with averaged amplitudes >300 pT. We discuss various applications of the obtained results for modeling electron dynamics in the radiation belts and in the Earth's magnetotail.

  9. Squeeze Film Dampers Executing Small Amplitude Circular-Centered Orbits in High-Speed Turbomachinery

    Directory of Open Access Journals (Sweden)

    Sina Hamzehlouia

    2016-01-01

    Full Text Available This work represents a pressure distribution model for finite length squeeze film dampers (SFDs executing small amplitude circular-centered orbits (CCOs with application in high-speed turbomachinery design. The proposed pressure distribution model only accounts for unsteady (temporal inertia terms, since based on order of magnitude analysis, for small amplitude motions of the journal center, the effect of convective inertia is negligible relative to unsteady (temporal inertia. In this work, the continuity equation and the momentum transport equations for incompressible lubricants are reduced by assuming that the shapes of the fluid velocity profiles are not strongly influenced by the inertia forces, obtaining an extended form of Reynolds equation for the hydrodynamic pressure distribution that accounts for fluid inertia effects. Furthermore, a numerical procedure is represented to discretize the model equations by applying finite difference approximation (FDA and to numerically determine the pressure distribution and fluid film reaction forces in SFDs with significant accuracy. Finally, the proposed model is incorporated into a simulation model and the results are compared against existing SFD models. Based on the simulation results, the pressure distribution and fluid film reaction forces are significantly influenced by fluid inertia effects even at small and moderate Reynolds numbers.

  10. High-order shock-fitted detonation propagation in high explosives

    Science.gov (United States)

    Romick, Christopher M.; Aslam, Tariq D.

    2017-03-01

    A highly accurate numerical shock and material interface fitting scheme composed of fifth-order spatial and third- or fifth-order temporal discretizations is applied to the two-dimensional reactive Euler equations in both slab and axisymmetric geometries. High rates of convergence are not typically possible with shock-capturing methods as the Taylor series analysis breaks down in the vicinity of discontinuities. Furthermore, for typical high explosive (HE) simulations, the effects of material interfaces at the charge boundary can also cause significant computational errors. Fitting a computational boundary to both the shock front and material interface (i.e. streamline) alleviates the computational errors associated with captured shocks and thus opens up the possibility of high rates of convergence for multi-dimensional shock and detonation flows. Several verification tests, including a Sedov blast wave, a Zel'dovich-von Neumann-Döring (ZND) detonation wave, and Taylor-Maccoll supersonic flow over a cone, are utilized to demonstrate high rates of convergence to nontrivial shock and reaction flows. Comparisons to previously published shock-capturing multi-dimensional detonations in a polytropic fluid with a constant adiabatic exponent (PF-CAE) are made, demonstrating significantly lower computational error for the present shock and material interface fitting method. For an error on the order of 10 m /s, which is similar to that observed in experiments, shock-fitting offers a computational savings on the order of 1000. In addition, the behavior of the detonation phase speed is examined for several slab widths to evaluate the detonation performance of PBX 9501 while utilizing the Wescott-Stewart-Davis (WSD) model, which is commonly used in HE modeling. It is found that the thickness effect curve resulting from this equation of state and reaction model using published values is dramatically more steep than observed in recent experiments. Utilizing the present fitting

  11. The Dynamics of Very High Alfvén Mach Number Shocks in Space Plasmas

    Science.gov (United States)

    Sundberg, Torbjörn; Burgess, David; Scholer, Manfred; Masters, Adam; Sulaiman, Ali H.

    2017-02-01

    Astrophysical shocks, such as planetary bow shocks or supernova remnant shocks, are often in the high or very-high Mach number regime, and the structure of such shocks is crucial for understanding particle acceleration and plasma heating, as well inherently interesting. Recent magnetic field observations at Saturn’s bow shock, for Alfvén Mach numbers greater than about 25, have provided evidence for periodic non-stationarity, although the details of the ion- and electron-scale processes remain unclear due to limited plasma data. High-resolution, multi-spacecraft data are available for the terrestrial bow shock, but here the very high Mach number regime is only attained on extremely rare occasions. Here we present magnetic field and particle data from three such quasi-perpendicular shock crossings observed by the four-spacecraft Cluster mission. Although both ion reflection and the shock profile are modulated at the upstream ion gyroperiod timescale, the dominant wave growth in the foot takes place at sub-proton length scales and is consistent with being driven by the ion Weibel instability. The observed large-scale behavior depends strongly on cross-scale coupling between ion and electron processes, with ion reflection never fully suppressed, and this suggests a model of the shock dynamics that is in conflict with previous models of non-stationarity. Thus, the observations offer insight into the conditions prevalent in many inaccessible astrophysical environments, and provide important constraints for acceleration processes at such shocks.

  12. Shock Wave-Boundary Layer Interaction in Forced Shock Oscillations

    Institute of Scientific and Technical Information of China (English)

    Piotr Doerffer; Oskar Szulc; Franco Magagnato

    2003-01-01

    The flow in transonic diffusers as well as in supersonic air intakes becomes often unsteady due to shock wave boundary layer interaction. The oscillations may be induced by natural separation unsteadiness or may be forced by boundary conditions. Significant improvement of CFD tools, increase of computer resources as well as development of experimental methods have again.drawn the attention of researchers to this topic.To investigate the problem forced oscillations of transonic turbulent flow in asymmetric two-dimensional Laval nozzle were considered. A viscous, perfect gas flow, was numerically simulated using the Reynolds-averaged compressible Navier-Stokes solver SPARC, employing a two-equation, eddy viscosity, turbulence closure in the URANS approach.For time-dependent and stationary flow simulations, Mach numbers upstream of the shock between 1.2 and 1.4 were considered. Comparison of computed and experimental data for steady states generally gave acceptable agreement. In the case of forced oscillations, a harmonic pressure variation was prescribed at the exit plane resulting in shock wave motion. Excitation frequencies between 0 Hz and 1024 Hz were investigated at the same pressure amplitude.The main result of the work carried out is the relation between the amplitude of the shock wave motion and the excitation frequency in the investigated range. Increasing excitation frequency resulted in decreasing amplitude of the shock movement. At high frequencies a natural mode of shock oscillation (of small amplitude) was observed which is not sensitive to forced excitement.

  13. [Transient high frequency nodal rhythm after a high voltage electric shock. Report of one case].

    Science.gov (United States)

    Supervía, August; Del Baño, Francisco; Aguirre, Alfons; Membrilla, Estela

    2013-09-01

    Electrical shock can cause a direct myocardial damage and different types of arrhythmias, which are uncommon and occur more often when there is a high voltage exposure. We report a 19-year-old male that received a high voltage shock, falling thereafter from an altitude of four meters. On admission to the emergency room, he had second and third degree burns in the right hand and the left thigh. The electrocardiogram showed a nodal rhythm of 72 beats per minute. After four hours of monitoring, sinus rhythm returned spontaneously.

  14. Variable amplitude corrosion fatigue and fracture mechanics of weldable high strength jack-up steels

    Science.gov (United States)

    Etube, Linus Sone

    The tubular welded joints used in the construction of Offshore structures can experience millions of variable amplitude wave induced stress cycles during their operational life. Fatigue has been identified as the main cause of degradation of structural integrity in these structures. As a result, fatigue is an important consideration in their design. Jack-up legs are made from a range of high strength steels with yield strengths up to TOOMPa. These steels are thought to exhibit fatigue resistance properties which are different when compared with conventional fixed platform steels such as BS 4360 50D and BS 7191 355D. The difference in their behaviour was heightened by the discovery, in the late 80s and early 90s, of extensive cracking around the spud can regions of several Jack-ups operating in the North Sea. It was thought that these steels may be more susceptible to hydrogen cracking and embrittlement. There was the additional requirement to study their behaviour under realistic loading conditions typical of the North Sea environment. This thesis contains results of an investigation undertaken to assess the performance of a typical high strength weldable Jack-up steel under realistic loading and environmental conditions. Details of the methodology employed to develop a typical Jack-up Offshore Standard load History (JOSH) are presented. The factors which influence fatigue resistance of structural steels used in the construction of Jack-up structures are highlighted. The methods used to model the relevant factors for inclusion in JOSH are presented with particular emphasis on loading and structural response interaction. Results and details of experimental variable amplitude corrosion fatigue (VACF) tests conducted using JOSH are reported and discussed with respect to crack growth mechanisms in high strength weldable Jack-up steels. Different fracture mechanics models for VACF crack growth prediction are compared and an improved generalised methodology for fast

  15. Giant-amplitude, high-work density microactuators with phase transition activated nanolayer bimorphs.

    Science.gov (United States)

    Liu, Kai; Cheng, Chun; Cheng, Zhenting; Wang, Kevin; Ramesh, Ramamoorthy; Wu, Junqiao

    2012-12-12

    Various mechanisms are currently exploited to transduce a wide range of stimulating sources into mechanical motion. At the microscale, simultaneously high amplitude, high work output, and high speed in actuation are hindered by limitations of these actuation mechanisms. Here we demonstrate a set of microactuators fabricated by a simple microfabrication process, showing simultaneously high performance by these metrics, operated on the structural phase transition in vanadium dioxide responding to diverse stimuli of heat, electric current, and light. In both ambient and aqueous conditions, the actuators bend with exceedingly high displacement-to-length ratios up to 1 in the sub-100 μm length scale, work densities over 0.63 J/cm(3), and at frequencies up to 6 kHz. The functionalities of actuation can be further enriched with integrated designs of planar as well as three-dimensional geometries. Combining the superior performance, high durability, diversity in responsive stimuli, versatile working environments, and microscale manufacturability, these actuators offer potential applications in microelectromechanical systems, microfluidics, robotics, drug delivery, and artificial muscles.

  16. High efficiency processing for reduced amplitude zones detection in the HRECG signal

    Science.gov (United States)

    Dugarte, N.; Álvarez, A.; Balacco, J.; Mercado, G.; Gonzalez, A.; Dugarte, E.; Olivares, A.

    2016-04-01

    Summary - This article presents part of a more detailed research proposed in the medium to long term, with the intention of establishing a new philosophy of electrocardiogram surface analysis. This research aims to find indicators of cardiovascular disease in its early stage that may go unnoticed with conventional electrocardiography. This paper reports the development of a software processing which collect some existing techniques and incorporates novel methods for detection of reduced amplitude zones (RAZ) in high resolution electrocardiographic signal (HRECG).The algorithm consists of three stages, an efficient processing for QRS detection, averaging filter using correlation techniques and a step for RAZ detecting. Preliminary results show the efficiency of system and point to incorporation of techniques new using signal analysis with involving 12 leads.

  17. High Capacity Phase/Amplitude Modulated Optical Communication Systems and Nonlinear Inter-Channel Impairments

    Science.gov (United States)

    Tavassoli, Vahid

    This thesis studies and mathematically models nonlinear interactions among channels of modern high bit rate (amplitude/) phase modulated optical systems. First, phase modulated analogue systems are studied and a differential receiving method is suggested with experimental validation. The main focus of the rest of the thesis is on digital advanced modulation format systems. Cross-talk due to fiber Kerr nonlinearity in two-format hybrid systems as well as 16-QAM systems is mathematically modelled and verified by simulation for different system parameters. A comparative study of differential receivers and coherent receivers is also given for hybrid systems. The model is based on mathematically proven assumptions and provides an intuitive analytical understanding of nonlinear cross-talk in such systems.

  18. Pulsation analysis of the high amplitude δ Scuti star CW Serpentis

    Science.gov (United States)

    Niu, Jia-Shu; Fu, Jian-Ning; Zong, Wei-Kai

    2013-10-01

    Time-series photometric observations were made for the high amplitude δ Scuti star CW Ser between 2011 and 2012 at the Xinglong Station of National Astronomical Observatories, Chinese Academy of Sciences. After performing the frequency analysis of the light curves, we confirmed the fundamental frequency of f = 5.28677 c d-1, together with seven harmonics of the fundamental frequency, which are newly detected. No additional frequencies were detected. The O — C diagram, produced with the 21 newly determined times of maximum light combined with those provided in the literature, helps to obtain a new ephemeris formula of the times of maximum light with the pulsation period of 0.189150355 ± 0.000000003 d.

  19. Generation of high pressure shocks relevant to the shock-ignition intensity regime

    Science.gov (United States)

    Batani, D.; Antonelli, L.; Atzeni, S.; Badziak, J.; Baffigi, F.; Chodukowski, T.; Consoli, F.; Cristoforetti, G.; De Angelis, R.; Dudzak, R.; Folpini, G.; Giuffrida, L.; Gizzi, L. A.; Kalinowska, Z.; Koester, P.; Krousky, E.; Krus, M.; Labate, L.; Levato, T.; Maheut, Y.; Malka, G.; Margarone, D.; Marocchino, A.; Nejdl, J.; Nicolai, Ph.; O'Dell, T.; Pisarczyk, T.; Renner, O.; Rhee, Y. J.; Ribeyre, X.; Richetta, M.; Rosinski, M.; Sawicka, M.; Schiavi, A.; Skala, J.; Smid, M.; Spindloe, Ch.; Ullschmied, J.; Velyhan, A.; Vinci, T.

    2014-03-01

    An experiment was performed using the PALS laser to study laser-target coupling and laser-plasma interaction in an intensity regime ≤1016 W/cm2, relevant for the "shock ignition" approach to Inertial Confinement Fusion. A first beam at low intensity was used to create an extended preformed plasma, and a second one to create a strong shock. Pressures up to 90 Megabars were inferred. Our results show the importance of the details of energy transport in the overdense region.

  20. Generation of high pressure shocks relevant to the shock-ignition intensity regime

    Energy Technology Data Exchange (ETDEWEB)

    Batani, D.; Folpini, G.; Giuffrida, L.; Maheut, Y.; Malka, G.; Nicolai, Ph.; Ribeyre, X. [Université Bordeaux, CNRS, CEA, CELIA (Centre Lasers Intenses et Applications), UMR 5107, F-33405 Talence (France); Antonelli, L. [Université Bordeaux, CNRS, CEA, CELIA (Centre Lasers Intenses et Applications), UMR 5107, F-33405 Talence (France); Università di Roma “Tor Vergata,” Roma (Italy); Atzeni, S.; Marocchino, A.; Schiavi, A. [Dipartimento SBAI, Université di Roma “La Sapienza” and CNISM, Roma (Italy); Badziak, J.; Chodukowski, T.; Kalinowska, Z.; Pisarczyk, T.; Rosinski, M. [Institute of Plasma Physics and Laser Microfusion, Warsaw (Poland); Baffigi, F.; Cristoforetti, G.; Gizzi, L. A.; Koester, P. [Intense Laser Irradiation Laboratory, INO-CNR, Pisa (Italy); and others

    2014-03-15

    An experiment was performed using the PALS laser to study laser-target coupling and laser-plasma interaction in an intensity regime ≤10{sup 16} W/cm{sup 2}, relevant for the “shock ignition” approach to Inertial Confinement Fusion. A first beam at low intensity was used to create an extended preformed plasma, and a second one to create a strong shock. Pressures up to 90 Megabars were inferred. Our results show the importance of the details of energy transport in the overdense region.

  1. Noninvasive respiratory support of juvenile rabbits by high-amplitude bubble continuous positive airway pressure.

    Science.gov (United States)

    Diblasi, Robert M; Zignego, Jay C; Tang, Dennis M; Hildebrandt, Jack; Smith, Charles V; Hansen, Thomas N; Richardson, C Peter

    2010-06-01

    Bubble continuous positive airway pressure (B-CPAP) applies small-amplitude, high-frequency oscillations in airway pressure (DeltaPaw) that may improve gas exchange in infants with respiratory disease. We developed a device, high-amplitude B-CPAP (HAB-CPAP), which provides greater DeltaPaw than B-CPAP provides. We studied the effects of different operational parameters on DeltaPaw and volumes of gas delivered to a mechanical infant lung model. In vivo studies tested the hypothesis that HAB-CPAP provides noninvasive respiratory support greater than that provided by B-CPAP. Lavaged juvenile rabbits were stabilized on ventilator nasal CPAP. The animals were then supported at the same mean airway pressure, bias flow, and fraction of inspired oxygen (FiO2) required for stabilization, whereas the bubbler angle was varied in a randomized crossover design at exit angles, relative to vertical, of 0 (HAB-CPAP0; equivalent to conventional B-CPAP), 90 (HAB-CPAP90), and 135 degrees (HAB-CPAP135). Arterial blood gases and pressure-rate product (PRP) were measured after 15 min at each bubbler angle. Pao2 levels were higher (p<0.007) with HAB-CPAP135 than with conventional B-CPAP. PaCO2 levels did not differ (p=0.073) among the three bubbler configurations. PRP with HAB-CPAP135 were half of the PRP with HAB-CPAP0 or HAB-CPAP90 (p=0.001). These results indicate that HAB-CPAP135 provides greater respiratory support than conventional B-CPAP does.

  2. Measuring the Energy Release of Low Amplitude Impact of High Explosive Events

    Science.gov (United States)

    Straight, J. W.; Idar, D. J.; Smith, L.; Osborn, M. A.; Viramontes, L. E.; Chavez, P. J.

    2004-07-01

    Predicting the degree of violence of high explosive (HE) reactions for a given event is desirable for risk assessments and a goal for computational models. Historically, different types of low amplitude impact tests on HE specimens have been performed to determine the critical impact-velocity threshold for high explosive violent reactions (HEVR). Additionally, the energy release relative to a steady-state detonation is also desirable for assessing the potential outcome of an accidental event. Traditionally, blast gauge measurements have been used to measure the overpressure of the HEVR event at a defined distance. This paper summarizes the use of this active technique coupled with a passive technique to derive average energy release curves for Modified Steven tests. A classic ballistic pendulum design was employed with the traditional blast gauge method. Calibration of the ballistic pendulum involved three elements. First, two mechanical measurements were related to the actual peak swing of the pendulum. Second, the general nature of the swing versus energy release curve was estimated. Two different approaches were used to estimate the momenta as a function of HE energy release using the Gurney relationships for an unsymmetrical sandwich. Finally, both techniques were simultaneously benchmarked with PBX 9501 calibration charges. Test results demonstrate the utility of using coupled diagnostic methods for low amplitude insult testing. Each set of data was fit to derive a working curve for the determination of the average energy release for HEVR event based on mass relative to a steady-state detonation. These tests results and working curve derivations are presented.

  3. A compact, low jitter, nanosecond rise time, high voltage pulse generator with variable amplitude

    Science.gov (United States)

    Mao, Jiubing; Wang, Xin; Tang, Dan; Lv, Huayi; Li, Chengxin; Shao, Yanhua; Qin, Lan

    2012-07-01

    In this paper, a compact, low jitter, nanosecond rise time, command triggered, high peak power, gas-switch pulse generator system is developed for high energy physics experiment. The main components of the system are a high voltage capacitor, the spark gap switch and R = 50 Ω load resistance built into a structure to obtain a fast high power pulse. The pulse drive unit, comprised of a vacuum planar triode and a stack of avalanche transistors, is command triggered by a single or multiple TTL (transistor-transistor logic) level pulses generated by a trigger pulse control unit implemented using the 555 timer circuit. The control unit also accepts user input TTL trigger signal. The vacuum planar triode in the pulse driving unit that close the first stage switches is applied to drive the spark gap reducing jitter. By adjusting the charge voltage of a high voltage capacitor charging power supply, the pulse amplitude varies from 5 kV to 10 kV, with a rise time of gas-switch and available capacitor recovery time.

  4. SONIC SPEED AND SHOCK WAVE IN HIGH VELOCITY AERATED FLOWS FROM HIGH HEAD DISCHARGE STRUCTURES

    Institute of Scientific and Technical Information of China (English)

    Dong Zhi-yong

    2003-01-01

    The compressible characteristics in aerated flows at the high velocity of about 50m/s were analyzed. Based on the theory of compressible the relations between the sonic speed and shock wave in high-velocity aerated flow were theoretically deduced. And comparisons with measured data were made. The theoretical and experimental results show the sonic speed in aerated flow is merely of the order of several-dozen meters per second, and its minimum value is only 20m/s, which is far much less than that in water or air alone. So high subsonic flow, supersonic flow and transonic flow as well as compression wave, shock wave and expansion wave similarly to aerodnamics may be produced in high velocity aerated flow at the speed of the order of 50m/s. Hence the influences of these compressible characteristics on high head discharge structures can not be neglected, especially on super high dams over 200m high.

  5. Detecting phase-amplitude coupling with high frequency resolution using adaptive decompositions.

    Science.gov (United States)

    Pittman-Polletta, Benjamin; Hsieh, Wan-Hsin; Kaur, Satvinder; Lo, Men-Tzung; Hu, Kun

    2014-04-15

    Phase-amplitude coupling (PAC)--the dependence of the amplitude of one rhythm on the phase of another, lower-frequency rhythm - has recently been used to illuminate cross-frequency coordination in neurophysiological activity. An essential step in measuring PAC is decomposing data to obtain rhythmic components of interest. Current methods of PAC assessment employ narrowband Fourier-based filters, which assume that biological rhythms are stationary, harmonic oscillations. However, biological signals frequently contain irregular and nonstationary features, which may contaminate rhythms of interest and complicate comodulogram interpretation, especially when frequency resolution is limited by short data segments. To better account for nonstationarities while maintaining sharp frequency resolution in PAC measurement, even for short data segments, we introduce a new method of PAC assessment which utilizes adaptive and more generally broadband decomposition techniques - such as the empirical mode decomposition (EMD). To obtain high frequency resolution PAC measurements, our method distributes the PAC associated with pairs of broadband oscillations over frequency space according to the time-local frequencies of these oscillations. We compare our novel adaptive approach to a narrowband comodulogram approach on a variety of simulated signals of short duration, studying systematically how different types of nonstationarities affect these methods, as well as on EEG data. Our results show: (1) narrowband filtering can lead to poor PAC frequency resolution, and inaccuracy and false negatives in PAC assessment; (2) our adaptive approach attains better PAC frequency resolution and is more resistant to nonstationarities and artifacts than traditional comodulograms. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Diffusive Shock Acceleration of High Energy Cosmic Rays

    CERN Document Server

    Baring, M G

    2004-01-01

    The process of diffusive acceleration of charged particles in shocked plasmas is widely invoked in astrophysics to account for the ubiquitous presence of signatures of non-thermal relativistic electrons and ions in the universe. A key characteristic of this statistical energization mechanism is the absence of a momentum scale; astrophysical systems generally only impose scales at the injection (low energy) and loss (high energy) ends of the particle spectrum. The existence of structure in the cosmic ray spectrum (the "knee") at around 3000 TeV has promoted contentions that there are at least two origins for cosmic rays, a galactic one supplying those up to the knee, and even beyond, and perhaps an extragalactic one that can explain even the ultra-high energy cosmic rays (UHECRs) seen at 1-300 EeV. Accounting for the UHECRs with familiar astrophysical sites of acceleration has historically proven difficult due to the need to assume high magnetic fields in order to reduce the shortest diffusive acceleration tim...

  7. Note: A high Mach number arc-driven shock tube for turbulence studies.

    Science.gov (United States)

    Titus, J B; Alexander, A B; Johnson, J A

    2013-04-01

    A high Mach arc-driven shock tube has been built at the Center for Plasma Science and Technology of Florida A&M University to study shock waves. A larger apparatus with higher voltage was built to study more stable shock waves and subsequent plasmas. Initial measurements of the apparatus conclude that the desired Mach numbers can be reached using only two-thirds the maximum possible energy that the circuit can provide.

  8. Efficient Ultra-High Speed Communication with Simultaneous Phase and Amplitude Regenerative Sampling (SPARS)

    Science.gov (United States)

    Carlowitz, Christian; Girg, Thomas; Ghaleb, Hatem; Du, Xuan-Quang

    2017-08-01

    For ultra-high speed communication systems at high center frequencies above 100 GHz, we propose a disruptive change in system architecture to address major issues regarding amplifier chains with a large number of amplifier stages. They cause a high noise figure and high power consumption when operating close to the frequency limits of the underlying semiconductor technologies. Instead of scaling a classic homodyne transceiver system, we employ repeated amplification in single-stage amplifiers through positive feedback as well as synthesizer-free self-mixing demodulation at the receiver to simplify the system architecture notably. Since the amplitude and phase information for the emerging oscillation is defined by the input signal and the oscillator is only turned on for a very short time, it can be left unstabilized and thus come without a PLL. As soon as gain is no longer the most prominent issue, relaxed requirements for all the other major components allow reconsidering their implementation concepts to achieve further improvements compared to classic systems. This paper provides the first comprehensive overview of all major design aspects that need to be addressed upon realizing a SPARS-based transceiver. At system level, we show how to achieve high data rates and a noise performance comparable to classic systems, backed by scaled demonstrator experiments. Regarding the transmitter, design considerations for efficient quadrature modulation are discussed. For the frontend components that replace PA and LNA amplifier chains, implementation techniques for regenerative sampling circuits based on super-regenerative oscillators are presented. Finally, an analog-to-digital converter with outstanding performance and complete interfaces both to the analog baseband as well as to the digital side completes the set of building blocks for efficient ultra-high speed communication.

  9. Multichannel emission spectrometer for high dynamic range optical pyrometry of shock-driven materials

    Science.gov (United States)

    Bassett, Will P.; Dlott, Dana D.

    2016-10-01

    An emission spectrometer (450-850 nm) using a high-throughput, high numerical aperture (N.A. = 0.3) prism spectrograph with stepped fiberoptic coupling, 32 fast photomultipliers and thirty-two 1.25 GHz digitizers is described. The spectrometer can capture single-shot events with a high dynamic range in amplitude and time (nanoseconds to milliseconds or longer). Methods to calibrate the spectrometer and verify its performance and accuracy are described. When a reference thermal source is used for calibration, the spectrometer can function as a fast optical pyrometer. Applications of the spectrometer are illustrated by using it to capture single-shot emission transients from energetic materials or reactive materials initiated by kmṡs-1 impacts with laser-driven flyer plates. A log (time) data analysis method is used to visualize multiple kinetic processes resulting from impact initiation of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) or a Zr/CuO nanolaminate thermite. Using a gray body algorithm to interpret the spectral radiance from shocked HMX, a time history of temperature and emissivity was obtained, which could be used to investigate HMX hot spot dynamics. Finally, two examples are presented showing how the spectrometer can avoid temperature determination errors in systems where thermal emission is accompanied by atomic or molecular emission lines.

  10. High-speed imaging of dynamic shock wave reflection phenomena

    CSIR Research Space (South Africa)

    Naidoo, K

    2010-09-01

    Full Text Available Dynamic shock wave reflection generated by a rapidly pitching wedge in a steady supersonic free stream has been studied with numerical simulation previously. An experimental facility was developed for the investigation of these dynamic phenomena...

  11. Mechanisms of shock-induced reactions in high explosives

    Science.gov (United States)

    Kay, Jeffrey J.

    2017-01-01

    Understanding the mechanisms by which shock waves initiate chemical reactions in explosives is key to understanding their unique and defining property: the ability to undergo rapid explosive decomposition in response to mechanical stimulus. Although shock-induced reactions in explosives have been studied experimentally and computationally for decades, the nature of even the first chemical reactions that occur in response to shock remain elusive. To predictively understand how explosives respond to shock, the detailed sequence of events that occurs - mechanical deformation, energy transfer, bond breakage, and first chemical reactions - must be understood at the quantum-mechanical level. This paper reviews recent work in this field and ongoing experimental and theoretical work at Sandia National Laboratories in this important area of explosive science.

  12. A study of daily variation in cosmic ray intensity during high/low amplitude days

    Indian Academy of Sciences (India)

    Rajesh K Mishra; Rekha Agarwal Mishra

    2007-03-01

    A detailed study has been conducted on the long-term changes in the diurnal, semi-diurnal and tri-diurnal anisotropies of cosmic rays in terms of the high/low amplitude anisotropic wave train events (HAE/LAE) during the period 1981-94 using the neutron monitor data from Deep River Neutron Monitoring Station. In all, 38 HAE and 28 LAE cases have been studied. An inter-comparison of the first three harmonics during these events has been made so as to understand the basic reason for the occurrence of these types of events. It has been observed that the phase of diurnal anisotropy shifts towards earlier hours for HAEs and it shifts towards earlier hour as compared to 18-h direction for LAEs. For semi-diurnal anisotropy, phase remains statistically the same for both HAE and LAE. In the case of tri-diurnal anisotropy, phase is evenly distributed for both types of events. The interplanetary magnetic field (IMF) and solar wind plasma (SWP) parameters during these events are also investigated. It has also been observed that HAE/LAEs are weakly dependent on high-speed solar wind velocity. The two types of solar wind streams (corotating streams and flare-generated streams) produce significant deviations in cosmic ray intensity during HAE/LAE.

  13. Spline-based high-accuracy piecewise-polynomial phase-to-sinusoid amplitude converters.

    Science.gov (United States)

    Petrinović, Davor; Brezović, Marko

    2011-04-01

    We propose a method for direct digital frequency synthesis (DDS) using a cubic spline piecewise-polynomial model for a phase-to-sinusoid amplitude converter (PSAC). This method offers maximum smoothness of the output signal. Closed-form expressions for the cubic polynomial coefficients are derived in the spectral domain and the performance analysis of the model is given in the time and frequency domains. We derive the closed-form performance bounds of such DDS using conventional metrics: rms and maximum absolute errors (MAE) and maximum spurious free dynamic range (SFDR) measured in the discrete time domain. The main advantages of the proposed PSAC are its simplicity, analytical tractability, and inherent numerical stability for high table resolutions. Detailed guidelines for a fixed-point implementation are given, based on the algebraic analysis of all quantization effects. The results are verified on 81 PSAC configurations with the output resolutions from 5 to 41 bits by using a bit-exact simulation. The VHDL implementation of a high-accuracy DDS based on the proposed PSAC with 28-bit input phase word and 32-bit output value achieves SFDR of its digital output signal between 180 and 207 dB, with a signal-to-noise ratio of 192 dB. Its implementation requires only one 18 kB block RAM and three 18-bit embedded multipliers in a typical field-programmable gate array (FPGA) device.

  14. Short-lived high-amplitude cooling on Svalbard during the Dark Ages

    Science.gov (United States)

    van der Bilt, Willem; D`Andrea, William; Bakke, Jostein; Balascio, Nicholas; Werner, Johannes; Hoek, Wim

    2016-04-01

    As the paradigm of a stable Holocene climate has shifted, an increasing number of high-resolution proxy timeseries reveal dynamic conditions, characterized by high-amplitude climate shifts. Some of these events occurred during historical times and allow us to study the interaction between environmental and cultural change, providing valuable lessons for the near future. These include the Dark Ages Cold Period (DACP) between 300 and 800 AD, a period marked by political upheaval and climate instability that remains poorly investigated. Here, we present two temperature reconstructions from the High Arctic Svalbard Archipelago. To this end, we applied the established alkenone-based UK37 paleothermometer on sediments from two lakes on western Spitsbergen, Lake Hajeren and Lake Hakluyt. The Arctic is presently warming twice as fast as the global average and proxy data as well as model simulations suggest that this amplified response is characteristic for regional climate. The Arctic therefore provides a uniquely sensitive environment to study relatively modest climate shifts, like the DACP, that may not be adequately captured at lower-latitude sites. Owing to undisturbed sediments, a high sampling resolution and robust chronological control, the presented reconstructions resolve the attendant sub-centennial-scale climate shifts. Our findings suggest that the DACP marks a cold spell within the cool Neoglacial period, which started some 4 ka BP on Svalbard. Close investigation reveals a distinct temperature minimum around 500 AD that is reproduced in another alkenone-based temperature reconstruction from a nearby lake. At ± 1.75 °C, cooling underlines the sensitivity of Arctic climate as well as the magnitude of the DACP.

  15. Vacuum high-harmonic generation and electromagnetic shock

    Science.gov (United States)

    Böhl, P.; King, B.; Ruhl, H.

    2016-04-01

    > When one takes into account the presence of virtual charged states in the quantum vacuum, a nonlinear self-interaction can arise in the propagation of electromagnetic fields. This self-interaction is often referred to as `real photon-photon scattering'. When the centre-of-mass energy of colliding photons is much lower than the rest energy of an electron-positron pair, this quantum effect can be included in the classical field equations of motion as a vacuum current and charge density using the Heisenberg-Euler Lagrangian. Using analytical and numerical methods for subcritical fields, the intrinsic solution to Maxwell's equations has been found for counterpropagating probe and pump plane waves in the presence of vacuum four- and six-wave mixing. In the corresponding all-order solution for the scattered probe, a route to vacuum high-harmonic generation is identified in which a long phase length can compensate for the weakness of interacting fields. The resulting shocks in the probe carrier wave and envelope are studied for different parameter regimes and polarisation set-ups. In this special issue, we study two additional set-ups: that of a slowly varying single-cycle background to highlight the effect of an oscillating background on the probe harmonic spectrum, and that of a few-cycle probe to highlight the smoothing of the harmonic peaks produced by a wider spectrum of probe photons. We also correct sign errors in an earlier publication.

  16. High-amplitude electrical stimulation can reduce elicited neuronal activity in visual prosthesis

    Science.gov (United States)

    Barriga-Rivera, Alejandro; Guo, Tianruo; Yang, Chih-Yu; Abed, Amr Al; Dokos, Socrates; Lovell, Nigel H.; Morley, John W.; Suaning, Gregg J.

    2017-01-01

    Retinal electrostimulation is promising a successful therapy to restore functional vision. However, a narrow stimulating current range exists between retinal neuron excitation and inhibition which may lead to misperformance of visual prostheses. As the conveyance of representation of complex visual scenes may require neighbouring electrodes to be activated simultaneously, electric field summation may contribute to reach this inhibitory threshold. This study used three approaches to assess the implications of relatively high stimulating conditions in visual prostheses: (1) in vivo, using a suprachoroidal prosthesis implanted in a feline model, (2) in vitro through electrostimulation of murine retinal preparations, and (3) in silico by computing the response of a population of retinal ganglion cells. Inhibitory stimulating conditions led to diminished cortical activity in the cat. Stimulus-response relationships showed non-monotonic profiles to increasing stimulating current. This was observed in vitro and in silico as the combined response of groups of neurons (close to the stimulating electrode) being inhibited at certain stimulating amplitudes, whilst other groups (far from the stimulating electrode) being recruited. These findings may explain the halo-like phosphene shapes reported in clinical trials and suggest that simultaneous stimulation in retinal prostheses is limited by the inhibitory threshold of the retinal ganglion cells. PMID:28209965

  17. High amplitude theta wave bursts: a novel electroencephalographic feature of rem sleep and cataplexy.

    Science.gov (United States)

    Lo Martire, Viviana Carmen; Bastianini, Stefano; Berteotti, Chiara; Silvani, Alessandro; Zoccoli, Giovanna

    2015-01-01

    High amplitude theta wave bursts (HATs) were originally described during REMS and cataplexy in ORX-deficient mice as a novel neurophysiological correlate of narcolepsy (Bastianini et al., 2012). This finding was replicated the following year by Vassalli et al. in both ORX-deficient narcoleptic mice and narcoleptic children during cataplexy episodes (Vassalli et al., 2013). The relationship between HATs and narcolepsy-cataplexy in mice and patients indicates that the lack of ORX peptides is responsible for this abnormal EEG activity, the physiological meaning of which is still unknown. This review aimed to explore different phasic EEG events previously described in the published literature in order to find analogies and differences with HATs observed in narcoleptic mice and patients. We found similarities in terms of morphology, frequency and duration between HATs and several physiological (mu and wicket rhythms, sleep spindles, saw-tooth waves) or pathological (SWDs, HVSs, bursts of polyphasic complexes EEG complexes reported in a mouse model of CJD, and BSEs) EEG events. However, each of these events also shows significant differences from HATs, and thus cannot be equaled to them. The available evidence thus suggests that HATs are a novel neurophysiological phenomenon. Further investigations on HATs are required in order to investigate their physiological meaning, to individuate their brain structure(s) of origin, and to clarify the neural circuits involved in their manifestation.

  18. Skeletal bone morphology is resistant to the high amplitude seasonal leptin cycle in the Siberian hamster.

    Science.gov (United States)

    Rousseau, K; Atcha, Z; Denton, J; Cagampang, F R A; Ennos, A R; Freemont, A J; Loudon, A S I

    2005-09-01

    Recent studies have suggested that the adipocyte-derived hormone, leptin, plays a role in the regulation of metabolism. Here, we tested this hypothesis in the seasonally breeding Siberian hamster, as this species exhibits profound seasonal changes in adiposity and circulating leptin concentrations driven by the annual photoperiodic cycle. Male hamsters were kept in either long (LD) or short (SD) photoperiods. Following exposure to short photoperiods for 8 weeks animals exhibited a significant weight-loss and a 16-fold reduction of serum leptin concentrations. At Week 9, animals in both photoperiods were infused with leptin or PBS via osmotic mini-pump for 14 days. Chronic leptin infusion mimicked LD-like concentrations in SD-housed animals and caused a further decline in body weight and adipose tissue. In LD-housed animals, leptin infusion resulted in a significant elevation of serum concentrations above natural LD-like levels, but had no discernable effect on body weight or overall adiposity. Both bending and compression characteristics and histomorphometric measurements of trabecular bone mass were unaltered by leptin treatment or photoperiod. Our data therefore show that despite a high natural amplitude cycle of leptin, this hormone has no apparent role in the regulation of bone metabolism, and therefore do not support recent propositions that this hormone is an important component in the metabolism of bone tissue.

  19. High amplitude phase resetting in rev-erbalpha/per1 double mutant mice.

    Directory of Open Access Journals (Sweden)

    Corinne Jud

    Full Text Available Over time, organisms developed various strategies to adapt to their environment. Circadian clocks are thought to have evolved to adjust to the predictable rhythms of the light-dark cycle caused by the rotation of the Earth around its own axis. The rhythms these clocks generate persist even in the absence of environmental cues with a period of about 24 hours. To tick in time, they continuously synchronize themselves to the prevailing photoperiod by appropriate phase shifts. In this study, we disrupted two molecular components of the mammalian circadian oscillator, Rev-Erbalpha and Period1 (Per1. We found that mice lacking these genes displayed robust circadian rhythms with significantly shorter periods under constant darkness conditions. Strikingly, they showed high amplitude resetting in response to a brief light pulse at the end of their subjective night phase, which is rare in mammals. Surprisingly, Cry1, a clock component not inducible by light in mammals, became slightly inducible in these mice. Taken together, Rev-Erbalpha and Per1 may be part of a mechanism preventing drastic phase shifts in mammals.

  20. The Spectral Amplitude of Stellar Convection and Its Scaling in the High-Rayleigh-number Regime

    Science.gov (United States)

    Featherstone, Nicholas A.; Hindman, Bradley W.

    2016-02-01

    Convection plays a central role in the dynamics of any stellar interior, and yet its operation remains largely hidden from direct observation. As a result, much of our understanding concerning stellar convection necessarily derives from theoretical and computational models. The Sun is, however, exceptional in that regard. The wealth of observational data afforded by its proximity provides a unique test bed for comparing convection models against observations. When such comparisons are carried out, surprising inconsistencies between those models and observations become apparent. Both photospheric and helioseismic measurements suggest that convection simulations may overestimate convective flow speeds on large spatial scales. Moreover, many solar convection simulations have difficulty reproducing the observed solar differential rotation owing to this apparent overestimation. We present a series of three-dimensional stellar convection simulations designed to examine how the amplitude and spectral distribution of convective flows are established within a star’s interior. While these simulations are nonmagnetic and nonrotating in nature, they demonstrate two robust phenomena. When run with sufficiently high Rayleigh number, the integrated kinetic energy of the convection becomes effectively independent of thermal diffusion, but the spectral distribution of that kinetic energy remains sensitive to both of these quantities. A simulation that has converged to a diffusion-independent value of kinetic energy will divide that energy between spatial scales such that low-wavenumber power is overestimated and high-wavenumber power is underestimated relative to a comparable system possessing higher Rayleigh number. We discuss the implications of these results in light of the current inconsistencies between models and observations.

  1. Pulse shaping techniques for a high-g shock tester based on collision principle

    Science.gov (United States)

    Duan, Zhengyong; Tang, Chuansheng; Li, Yang; Han, Junliang; Wu, Guoxiong

    2016-09-01

    Pulse shaping techniques are discussed in this paper for the practicability of a developed high-g shock tester. The tester is based on collision principle where there is a one-level velocity amplifier. A theoretical and experimental study of pulse shaping techniques is presented. A model was built and theoretical formulae were deduced for the shock peak acceleration and its duration. Then theoretical analysis and some experiments were conducted. The test results verify the validity of theoretical model and show that the shock tester can generate the expected high-g shock pulses by integrated usage of different impact velocities and pulse shapers made from different materials. This is important in practical applications where the items under test can be shown to excite specific resonances at predetermined acceleration levels using the shock tester.

  2. Biological implications of high-energy cosmic ray induced muon flux in the extragalactic shock model

    CERN Document Server

    Atri, Dimitra

    2011-01-01

    A ~ 62 My periodicity in fossil biodiversity has been observed in independent studies of paleobiology databases going back 542 My. The period and phase of this biodiversity cycle coincides with the motion of our solar system in the galactic disk that oscillates perpendicular to the galactic plane with an amplitude of about 70 parsecs and a period of 63.6 My. Our Galaxy is falling toward the Virgo cluster due to its gravitational pull, forming a galactic shock at the north end of our galaxy due to this motion, capable of accelerating particles and exposing our galaxy's northern side to a higher flux of cosmic rays. These high-energy particles strike the Earth's atmosphere initiating extensive air showers, ionizing the atmosphere by producing charged secondary particles. Secondary particles such as muons produced as a result of nuclear interactions are able to reach the ground, enhancing the biological radiation dose, causing DNA damage and increasing mutation rates, which can have serious biological implicatio...

  3. Quantifying the high-velocity, low-amplitude spinal manipulative thrust: a systematic review.

    Science.gov (United States)

    Downie, Aron S; Vemulpad, Subramanyam; Bull, Peter W

    2010-09-01

    The purpose of this study was to systematically review studies that quantify the high-velocity, low-amplitude (HVLA) spinal thrust, to qualitatively compare the apparatus used and the force-time profiles generated, and to critically appraise studies involving the quantification of thrust as an augmented feedback tool in psychomotor learning. A search of the literature was conducted to identify the sources that reported quantification of the HVLA spinal thrust. MEDLINE-OVID (1966-present), MANTIS-OVID (1950-present), and CINAHL-EBSCO host (1981-present) were searched. Eligibility criteria included that thrust subjects were human, animal, or manikin and that the thrust type was a hand-delivered HVLA spinal thrust. Data recorded were single force, force-time, or displacement-time histories. Publications were in English language and after 1980. The relatively small number of studies, combined with the diversity of method and data interpretation, did not enable meta-analysis. Twenty-seven studies met eligibility criteria: 17 studies measured thrust as a primary outcome (13 human, 2 cadaver, and 2 porcine). Ten studies demonstrated changes in psychomotor learning related to quantified thrust data on human, manikin, or other device. Quantifiable parameters of the HVLA spinal thrust exist and have been described. There remain a number of variables in recording that prevent a standardized kinematic description of HVLA spinal manipulative therapy. Despite differences in data between studies, a relationship between preload, peak force, and thrust duration was evident. Psychomotor learning outcomes were enhanced by the application of thrust data as an augmented feedback tool. Copyright © 2010 National University of Health Sciences. Published by Mosby, Inc. All rights reserved.

  4. The shock tube as a device for testing transonic airfoils at high Reynolds numbers

    Science.gov (United States)

    Cook, W. J.; Presley, L. L.; Chapman, G. T.

    1978-01-01

    A performance analysis of gas-driven shock tubes shows that transonic airfoil flows with chord Reynolds numbers in the range of 100 million can be generated behind the primary shock in a large shock tube. A study of flow over simple airfoils has been carried out at low and intermediate Reynolds numbers to assess the testing technique. Results obtained from schlieren photos and airfoil pressure measurements show that steady transonic flows similar to those observed for the airfoils in wind tunnels can be generated within the available testing time in a shock tube with either properly-contoured test section walls or a properly-designed slotted-wall test section. The study indicates that the shock tube is a useful facility for studying two-dimensional high Reynolds number transonic airfoil flows.

  5. Amplitude-integrated electroencephalographic activity is suppressed in preterm infants with high scores on illness severity

    NARCIS (Netherlands)

    ter Horst, Hendrik J.; Jongbloed-Pereboom, Marjolein; van Eykern, Leo A.; Bos, Arend F.

    2011-01-01

    Background: The neonatal acute physiology score. SNAP-II, reflects the severity of illness in newborns. In term newborns, amplitude integrated EEG (aEEG), is depressed following asphyxia. In preterm infants aEEG is discontinuous, and therefore more difficult to assess compared to term infants. Aims:

  6. Characterization of a High Temporal Resolution TDLAS System for Measurements in a Shock Tube Facility

    Science.gov (United States)

    Förster, F.; O'Byrne, Sean; Kleine, H.; Weigand, B.

    Transient heating and pressurization of a gas by shock waves can be useful for a variety of purposes, particularly for configurations involving shock wave focussing. Unless the geometry is particularly simple, the time history of temperature can be difficult to predict accurately. Hence, a non-intrusive measurement technique with high temporal resolution is required to record the time history of the very rapidly changing temperature of a shock-heated flow. One promising measurement techniques for these high-speed flows is Tunable Diode Laser Absorption Spectroscopy (TDLAS)

  7. Comparison Between Surf and Multi-Shock Forest Fire High Explosive Burn Models

    Energy Technology Data Exchange (ETDEWEB)

    Greenfield, Nicholas Alexander [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-07-18

    PAGOSA1 has several different burn models used to model high explosive detonation. Two of these, Multi-Shock Forest Fire and Surf, are capable of modeling shock initiation. Accurately calculating shock initiation of a high explosive is important because it is a mechanism for detonation in many accident scenarios (i.e. fragment impact). Comparing the models to pop-plot data give confidence that the models are accurately calculating detonation or lack thereof. To compare the performance of these models, pop-plots2 were created from simulations where one two cm block of PBX 9502 collides with another block of PBX 9502.

  8. Influence of shock wave pressure amplitude and pulse repetition frequency on the lifespan, size and number of transient cavities in the field of an electromagnetic lithotripter

    Science.gov (United States)

    Huber, Peter; Jöchle, Knut; Debus, Jürgen

    1998-10-01

    Monitoring the generation of cavitation is of great interest for diagnostic and therapeutic use of ultrasound in medicine, since cavitation is considered to play a major role in nonthermal ultrasound interactions with tissue. Important parameters are the number of cavitation events and the energy released during the bubble collapse. This energy is correlated to the maximum bubble radius which is related to the cavitation lifespan. The aim of this study was therefore to investigate the influence of the acoustic pressure amplitude and the pulse repetition frequency (PRF) in the field of a lithotripter (Lithostar, Siemens) on the number, size and lifespan of transient cavitation bubbles in water. We used scattered laser light recorded by a photodiode and stroboscopic photographs to monitor the cavitation activity. We found that PRF (range 0.5-5 Hz) had no influence on the cavitation bubble lifespan and size, whereas lifespan and size increased with the acoustic pressure amplitude. In contrast, the number of cavitation events strongly increased with PRF, whereas the pressure amplitude had no significant influence on the number of cavitation events. Thus, by varying the pressure amplitude and PRF, it might be possible to deliver a defined relative number of cavitations at a defined relative energy level in a defined volume. This seems to be relevant to further studies that address the biological effects of transient cavitation occurring in the fields of lithotripters.

  9. Studying astrophysical collisionless shocks with counterstreaming plasmas from high power lasers

    Science.gov (United States)

    Park, Hye-Sook; Ryutov, D. D.; Ross, J. S.; Kugland, N. L.; Glenzer, S. H.; Plechaty, C.; Pollaine, S. M.; Remington, B. A.; Spitkovsky, A.; Gargate, L.; Gregori, G.; Bell, A.; Murphy, C.; Sakawa, Y.; Kuramitsu, Y.; Morita, T.; Takabe, H.; Froula, D. H.; Fiksel, G.; Miniati, F.; Koenig, M.; Ravasio, A.; Pelka, A.; Liang, E.; Woolsey, N.; Kuranz, C. C.; Drake, R. P.; Grosskopf, M. J.

    2012-03-01

    Collisions of high Mach number flows occur frequently in astrophysics, and the resulting shock waves are responsible for the properties of many astrophysical phenomena, such as supernova remnants, Gamma Ray Bursts and jets from Active Galactic Nuclei. Because of the low density of astrophysical plasmas, the mean free path due to Coulomb collisions is typically very large. Therefore, most shock waves in astrophysics are "collisionless", since they form due to plasma instabilities and self-generated magnetic fields. Laboratory experiments at the laser facilities can achieve the conditions necessary for the formation of collisionless shocks, and will provide a unique avenue for studying the nonlinear physics of collisionless shock waves. We are performing a series of experiments at the Omega and Omega-EP lasers, in Rochester, NY, with the goal of generating collisionless shock conditions by the collision of two high-speed plasma flows resulting from laser ablation of solid targets using ˜1016 W/cm2 laser irradiation. The experiments will aim to answer several questions of relevance to collisionless shock physics: the importance of the electromagnetic filamentation (Weibel) instabilities in shock formation, the self-generation of magnetic fields in shocks, the influence of external magnetic fields on shock formation, and the signatures of particle acceleration in shocks. Our first experiments using Thomson scattering diagnostics studied the plasma state from a single foil and from double foils whose flows collide "head-on". Our data showed that the flow velocity and electron density were 108 cm/s and 1019 cm-3, respectively, where the Coulomb mean free path is much larger than the size of the interaction region. Simulations of our experimental conditions show that weak Weibel mediated current filamentation and magnetic field generation were likely starting to occur. This paper presents the results from these first Omega experiments.

  10. A novel smart rotor support with shape memory alloy metal rubber for high temperatures and variable amplitude vibrations

    Science.gov (United States)

    Ma, Yanhong; Zhang, Qicheng; Zhang, Dayi; Scarpa, Fabrizio; Liu, Baolong; Hong, Jie

    2014-12-01

    The work describes the design, manufacturing and testing of a smart rotor support with shape memory alloy metal rubber (SMA-MR) elements, able to provide variable stiffness and damping characteristics with temperature, motion amplitude and excitation frequency. Differences in damping behavior and nonlinear stiffness between SMA-MR and more traditional metal rubber supports are discussed. The mechanical performance shown by the prototype demonstrates the feasibility of using the SMA-MR concept for active vibration control in rotordynamics, in particular at high temperatures and large amplitude vibrations.

  11. The influence of temperature dynamics and dynamic finite ion Larmor radius effects on seeded high amplitude plasma blobs

    DEFF Research Database (Denmark)

    Held, Magnus; Wiesenberger, M.; Madsen, Jens

    2016-01-01

    Thermal effects on the perpendicular convection of seeded pressure blobs in the scrape-off layer of magnetised fusion plasmas are investigated. Our numerical study is based on a four field full-F gyrofluid model, which entails the consistent description of high fluctuation amplitudes and dynamic...

  12. A single high dose of escitalopram increases mismatch negativity without affecting processing negativity or P300 amplitude in healthy volunteers

    DEFF Research Database (Denmark)

    Wienberg, M; Glenthøj, Birte Yding; Jensen, K S

    2009-01-01

    processing. The present study was designed to replicate and further extent the results of our initial study on the effects of a low dose of escitalopram (10 mg) on MMN, PN and P300 amplitude. In a randomised, double-blind, cross-over experiment, 20 healthy male volunteers received either a single, orally...... administered dose of 15 mg escitalopram (a highly selective serotonin reuptake inhibitor (SSRI)) or placebo, after which their PN, MMN and P300 amplitude were assessed. Similar to our initial study with 10 mg escitalopram, 15 mg escitalopram significantly increased MMN, while it did not affect P300 amplitude....... In contrast to our initial study, however, the currently higher dose of escitalopram did not increase PN. Results support the view that a broad range of increased serotonergic activity enhances MMN, while the relationship between serotonin and PN seems more complex. The current study does not support...

  13. The effect of high energy shock waves focused on cortical bone: an in vitro study.

    Science.gov (United States)

    Kaulesar Sukul, D M; Johannes, E J; Pierik, E G; van Eijck, G J; Kristelijn, M J

    1993-01-01

    Extracorporeal shock wave lithotripsy has become an accepted alternative for the management of nephrolithiasis and cholelithiasis. Direct impact of shock waves cause tear and shear forces at transition sites between tissues with divergent acoustic impedances leading to stone fragmentation. The aim of this study was to determine whether shock waves can cause cortical bone damage at all and, if so, what the relationship is, if any, between the energy density of the shock waves, the number of shock waves applied, and the resulting cortical bone damage. With the Siemens Lithostar Plus with overhead module, electromagnetic shock waves, generated under water with energy densities of 0.23, 0.33, 0.42, or 0.54 mJ/mm2, corresponding with power settings 2, 4, 6, and 8, were applied to bone specimens, i.e., of rabbit femurs and tibiae. Prior to exposure to the shock waves, the bones were mounted on a specially constructed perspex holder which could be placed in a water-filled test basin with an elastic membrane in the front through which the shock waves propagate without loss of energy. This setup made it possible not only to induce complete fractures, but also to detect the existence of a linear relationship with a Spearman rank correlation coefficient of -0.72 (P < or = 0.01) between the energy level of the shock waves and the severity of the cortical bone defects. The latter findings are especially of great importance because this means that the process can be controlled and that the cortical effects will be predictable and reproducible. This study should be considered a preliminary test concerning the effects of high energy shock wave on bone.(ABSTRACT TRUNCATED AT 250 WORDS)

  14. An unusual very low-mass high-amplitude pre-main sequence periodic variable

    CERN Document Server

    Rodriguez-Ledesma, Maria V; Ibrahimov, Mansur; Messina, Sergio; Parihar, Padmakar; Hessman, Frederic; de Oliveira, Catarina Alves; Herbst, William

    2012-01-01

    We have investigated the nature of the variability of CHS7797, an unusual periodic variable in the Orion Nebula Cluster. An extensive I-band photometric data set of CHS7797 was compiled between 2004-2010 using various telescopes. Further optical data have been collected in R and z' bands. In addition, simultaneous observations of the ONC region including CHS7797 were performed in the I, J, Ks and IRAC [3.6] and [4.5] bands over a time interval of about 40d. CHS7797 shows an unusual large-amplitude variation of about 1.7 mag in the R, I, and z' bands with a period 17.786. The amplitude of the brightness modulation decreases only slightly at longer wavelengths. The star is faint during 2/3 of the period and the shape of the phased light-curves for seven different observing seasons shows minor changes and small-amplitude variations. Interestingly, there are no significant colour-flux correlations for wavelengths smaller than 2microns, while the object becomes redder when fainter at longer wavelengths. CHS7797 ha...

  15. High-Energy Molecular Beam Source Using a Non-Diaphragm Type Small Shock Tube

    Science.gov (United States)

    Yoshimoto, Yuta; Miyoshi, Nobuya; Kinefuchi, Ikuya; Shimizu, Kazuya; Takagi, Shu; Matsumoto, Yoichiro

    2010-11-01

    The molecular beam technique is one of the powerful tools to analyze gas-surface interactions. In order to generate high-energy molecular beam in a range of 1 - 5 eV, which corresponds to the typical activation energy of surface reactions, we are developing a beam source using a non-diaphragm type shock tube, which can operate at a repetition rate high enough for efficient data acquisition. We made the volume of a tube much smaller than that of conventional ones so that the evacuation time between each shot becomes as short as possible. Our measurement of shock Mach numbers showed that even small diameter (2 or 4 mm) tubes, in which the wall boundary layer has a large influence on the propagation of shock waves, could generate molecular beam with the translational energy of more than 1 eV. This is because the reduction of shock formation distance by rapid opening of the valve, which separates a high pressure room from a low pressure room, weakened the effect of viscous damping on the accelerating shock wave. In addition, the convergent shock tubes of which diameters linearly decrease from 4 to 2 mm exhibited higher Mach numbers than straight ones. This indicates that the application of the convergent tube with the optimized geometry would be promising for generating high-energy molecular beam.

  16. Operation of High-Voltage Transverse Shock Wave Ferromagnetic Generator in the Open Circuit and Charging Modes

    Science.gov (United States)

    2005-06-01

    FMGs are based on the transverse (when the shock wave propagates across the magnetization vector M) shock demagnetization of Nd2Fe14B hard...generators based on the transverse (when the shock wave propagates across the magnetization vector M) shock wave demagnetization of Nd2Fe14B hard...and photo of a high-voltage transverse FMG are shown in Fig. 1. It contains a hollow hard ferromagnetic cylindrical Nd2Fe14B energy-carrying

  17. Collisionless shock waves in space - A very high beta structure. [solar wind measurements

    Science.gov (United States)

    Formisano, V.; Russell, C. T.; Means, J. D.; Greenstadt, E. W.; Scarf, F. L.; Neugebauter, M.

    1975-01-01

    Measurements from six OGO-5 particle and field experiments are used to examine the structure of the earth's bow shock during a period of extremely high beta (the ratio of plasma thermal to magnetic energy density), as determined from simultaneous measurements of the upstream plasma on board the HEOS satellite. Even though the interplanetary field is nearly perpendicular to the shock normal, the shock is extremely turbulent. Large field increases are observed up to a factor of 20 above the upstream values. Ahead of these large enhancements, smaller magnetic effects accompanied by electrostatic noise, electron heating, and ion deflection are observed for several minutes. These observations suggest that a steady-state shock may not be able to form at very high beta. Further, they show that while the magnetic energy density may be relatively unimportant in the upstream flow, it can become very significant within the shock structure, and hence the magnetic field should not be ignored in theoretical treatments of very high beta shocks.

  18. High Performance of Space Vector Modulation Direct Torque Control SVM-DTC Based on Amplitude Voltage and Stator Flux Angle

    Directory of Open Access Journals (Sweden)

    Hassan Farhan Rashag

    2013-04-01

    Full Text Available Various aspects related to controlling induction motor are investigated. Direct torque control is an original high performance control strategy in the field of AC drive. In this proposed method, the control system is based on Space Vector Modulation (SVM, amplitude of voltage in direct- quadrature reference frame (d-q reference and angle of stator flux. Amplitude of stator voltage is controlled by PI torque and PI flux controller. The stator flux angle is adjusted by rotor angular frequency and slip angular frequency. Then, the reference torque and the estimated torque is applied to the input of PI torque controller and the control quadrature axis voltage is determined. The control d-axis voltage is determined from the flux calculator. These q and d axis voltage are converted into amplitude voltage. By applying polar to Cartesian on amplitude voltage and stator flux angle, direct voltage and quadratures voltage are generated. The reference stator voltages in d-q are calculated based on forcing the stator voltage error to zero at next sampling period. By applying inverse park transformation on d-q voltages, the stator voltages in &alpha and &beta frame are generated and apply to SVM. From the output of SVM, the motor control signal is generated and the speed of the induction motor regulated toward the rated speed. The simulation Results have demonstrated exceptional performance in steady and transient states and shows that decrease of torque and flux ripples is achieved in a complete speed range.

  19. Implications of high amplitude atmospheric CO2 fluctuations on past millennium climate change

    Science.gov (United States)

    van Hoof, Thomas; Kouwenberg, Lenny; Wagner-Cremer, Friederike; Visscher, Henk

    2010-05-01

    Stomatal frequency analysis of leaves of land plants preserved in peat and lake deposits can provide a proxy record of pre-industrial atmospheric CO2 concentration complementary to measurements in Antarctic ice cores. Stomatal frequency based CO2 trends from the USA and NW European support the presence of significant CO2 variability during the first half of the last millennium (Kouwenberg et al., 2005; Wagner et al., 2004; van Hoof et al., 2008). The timing of the most significant perturbation in the stomata records (1200 AD) is in agreement with an observed CO2 fluctuation in the D47 Antarctic ice-core record (Barnola et al., 1995; van Hoof et al., 2005). The amplitude of the stomatal frequency based CO2 changes (> 34ppmv) exceeds the maximum amplitude of CO2 variability in the D47 ice core (Proceedings of the National Academy of Sciences of the USA, v. 105, no. 41, pp. 15815-15818 Wagner F., L.L.R. Kouwenberg, T.B. van Hoof and H. Visscher 2004. Reproducibility of Holocene atmospheric CO2 records based on stomatal frequency. Quartenary Science Reviews. V. 23, pp. 1947-1954

  20. Collisionless Weibel shocks: Full formation mechanism and timing

    Energy Technology Data Exchange (ETDEWEB)

    Bret, A. [ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain); Instituto de Investigaciones Energéticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071 Ciudad Real (Spain); Stockem, A. [GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisbon (Portugal); Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Narayan, R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51 Cambridge, Massachusetts 02138 (United States); Silva, L. O. [GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisbon (Portugal)

    2014-07-15

    Collisionless shocks in plasmas play an important role in space physics (Earth's bow shock) and astrophysics (supernova remnants, relativistic jets, gamma-ray bursts, high energy cosmic rays). While the formation of a fluid shock through the steepening of a large amplitude sound wave has been understood for long, there is currently no detailed picture of the mechanism responsible for the formation of a collisionless shock. We unravel the physical mechanism at work and show that an electromagnetic Weibel shock always forms when two relativistic collisionless, initially unmagnetized, plasma shells encounter. The predicted shock formation time is in good agreement with 2D and 3D particle-in-cell simulations of counterstreaming pair plasmas. By predicting the shock formation time, experimental setups aiming at producing such shocks can be optimised to favourable conditions.

  1. 32-channel pyrometer with high dynamic range for studies of shocked nanothermites

    Science.gov (United States)

    Bassett, Will P.; Dlott, Dana D.

    2017-01-01

    A 32-channel optical pyrometer has been developed for studying temperature dynamics of shock-initiated reactive materials with one nanosecond time resolution and high dynamic range. The pyrometer consists of a prism spectrograph which directs the spectrally-resolved emission to 32 fiber optics and 32 photomultiplier tubes and digitizers. Preliminary results show shock-initiated reactions of a nanothermite composite, nano CuO/Al in nitrocellulose binder, consists of three stages. The first stage occurred at 30 ns, right after the shock unloaded, the second stage at 100 ns and the third at 1 μs, and the temperatures ranged from 2100K to 3000K. Time-resolved emission spectra suggest hot spots formed during shock unloading, which initiated the bulk thermite/nitrocellulose reaction.

  2. In-situ Raman spectroscopy and high-speed photography of a shocked triaminotrinitrobenzene based explosive

    Science.gov (United States)

    Saint-Amans, C.; Hébert, P.; Doucet, M.; de Resseguier, T.

    2015-01-01

    We have developed a single-shot Raman spectroscopy experiment to study at the molecular level the initiation mechanisms that can lead to sustained detonation of a triaminotrinitrobenzene-based explosive. Shocks up to 30 GPa were generated using a two-stage laser-driven flyer plate generator. The samples were confined by an optical window and shock pressure was maintained for at least 30 ns. Photon Doppler Velocimetry measurements were performed at the explosive/window interface to determine the shock pressure profile. Raman spectra were recorded as a function of shock pressure and the shifts of the principal modes were compared to static high-pressure measurements performed in a diamond anvil cell. Our shock data indicate the role of temperature effects. Our Raman spectra also show a progressive extinction of the signal which disappears around 9 GPa. High-speed photography images reveal a simultaneous progressive darkening of the sample surface up to total opacity at 9 GPa. Reflectivity measurements under shock compression show that this opacity is due to a broadening of the absorption spectrum over the entire visible region.

  3. High-Pressure Minerals in Meteorites: Constraints on Shock Conditions and Duration

    Science.gov (United States)

    Sharp, Thomas G.

    2004-01-01

    The objective of this research was to better understand the conditions and duration of shock metamorphism in meteorites through microstructural and microanalytical characterization of high-pressure minerals. A) Continue to investigate the mineralogy and microstructures of melt-veins in a suite of chondritic samples ranging from shock grades S3 through S6 to determine how the mineral assemblages that crystallize at high-pressure and are related to shock grade. B) Investigate the chemical, mineralogical, and microstructural heterogeneities that occur across melt veins to interpret crystallization histories. C) Use static high-pressure experiments to simulate crystallization of melt veins for mineralogical and textural comparisons with the melt veins of naturally shocked samples. D) Characterize the compositions and defect microstructures of polycrystalline ringwoodite, wadsleyite, majorite, (Mg,Fe)Si03-ilmenite and (Mg,Fe)SiO3-perovskite in S6 samples to understand the mechanisms of phase transformations that occur during shock. These results will combined with kinetic data to constrain the time scales of kinetic processes. E) Investigate the transformations of metastable high-pressure minerals back to low- pressure forms to constrain post-shock temperatures and estimates of the peak shock pressure. Of these objectives, we have obtained publishable data on A, B and D. I am currently doing difficult high-pressure melting and quench experiments on an L chondrite known as Mbale. These experiments will provide additional constraints on the mineral assemblages that are produced during rapid quench of an L chondrite at pressures of 16 to 25 GPa. Results from published or nearly published research is presented below. Lists of theses, dissertations and publications are given below.

  4. Short duration high amplitude flares detected on the M dwarf star KIC 5474065

    CERN Document Server

    Ramsay, Gavin; Hakala, Pasi; Garcia-Alvarez, David; Brooks, Adam; Barclay, Thomas; Still, Martin

    2013-01-01

    Using data obtained during the RATS-Kepler project we identified one short duration flare in a 1 hour sequence of ground based photometry of the dwarf star KIC 5474065. Observations made using GTC show it is a star with a M4 V spectral type. Kepler observations made using 1 min sampling show that KIC 5474065 exhibits large amplitude (deltaF/F>0.4) optical flares which have a duration as short as 10 mins. We compare the energy distribution of flares from KIC 5474065 with that of KIC 9726699, which has also been observed using 1 min sampling, and ground based observations of other M dwarf stars in the literature. We discuss the possible implications of these short duration, relatively low energy flares would have on the atmosphere of exo-planets orbiting in the habitable zone of these flare stars.

  5. Multiband Carrierless Amplitude Phase Modulation for High Capacity Optical Data Links

    DEFF Research Database (Denmark)

    Iglesias Olmedo, Miguel; Zuo, Tianjian; Jensen, Jesper Bevensee

    2014-01-01

    packaging. Therefore, increasing effort is now put into the possibility of exploiting higher order modulation formats with increased spectral efficiency and reduced optical transceiver complexity. As these type of links are based on intensity modulation and direct detection, modulation formats relying...... on optical coherent detection can not be straight forwardly employed. As an alternative and more viable solution, this paper proposes the use of carrierless amplitude phase (CAP) in a novel multiband approach (MultiCAP) that achieves record spectral efficiency, increases tolerance towards dispersion......Short range optical data links are experiencing bandwidth limitations making it very challenging to cope with the growing data transmission capacity demands. Parallel optics appears as a valid short-term solution. It is, however, not a viable solution in the long-term because of its complex optical...

  6. Using domain walls to perform non-local measurements with high spin signal amplitudes

    Science.gov (United States)

    Savero Torres, W.; Pham, V.-T.; Zahnd, G.; Laczkowski, P.; Nguyen, V.-D.; Beigné, C.; Notin, L.; Jamet, M.; Marty, A.; Vila, L.; Attané, J.-P.

    2016-07-01

    Standard non-local measurements require lateral spin-valves with two different ferromagnetic electrodes, to create and to detect the spin accumulation. Here we show that non-local measurements can also be performed in a cross-shaped nanostructure, made of a single ferromagnetic wire connected to an orthogonal non-magnetic wire. A magnetic domain wall located underneath the ferromagnetic/non-magnetic interface is used to control the magnetizations of the injection and detection zones. As these zones can be very close, our results display spin signals possessing amplitudes larger than those obtained in conventional non-local measurements. We also show that this method can be used as a domain wall detection technique.

  7. The Spectral Amplitude of Stellar Convection and its Scaling in the High-Rayleigh-Number Regime

    CERN Document Server

    Featherstone, Nicholas A

    2015-01-01

    Convection plays a central role in the dynamics of any stellar interior, and yet its operation remains largely-hidden from direct observation. As a result, much of our understanding concerning stellar convection necessarily derives from theoretical and computational models. The Sun is, however, exceptional in that regard. The wealth of observational data afforded by its proximity provides a unique testbed for comparing convection models against observations. When such comparisons are carried out, surprising inconsistencies between those models and observations become apparent. Both photospheric and helioseismic measurements suggest that convection simulations may overestimate convective flow speeds on large spatial scales. Moreover, many solar convection simulations have difficulty reproducing the observed solar differential rotation due to this apparent overestimation. We present a series of 3-dimensional (3-D) stellar convection simulations designed to examine how the amplitude and spectral distribution of ...

  8. Shock Ignition: A New Approach to High Gain Targets for the National Ignition Facility

    Science.gov (United States)

    Perkins, L. John; Lafortune, Kai; Divol, Laurent; Betti, Riccardo

    2008-11-01

    Shock-ignition is being studied as a future option for achieving high target gains on NIF, offering the potential for testing high yield (200MJ), reactor-relevant targets for inertial fusion energy and targets with appreciable gains at drive energies much less than 1MJ. In contrast to conventional hotspot ignition, the assembly and ignition phases are separated by imploding a high mass shell at low velocity. The assembled fuel is then separately ignited by a strong, spherical shock driven by a high intensity spike at the end of the pulse and timed to reach the center as the main fuel is stagnating. Because the implosion velocity is significantly less than that required for hotspot ignition, considerably more fuel mass can be assembled and burned for the same kinetic energy in the shell. Like fast ignition, shock ignition could achieve high gains at low drive energy, but has the advantages of requiring only a single laser with less demanding timing and spatial focusing requirements. We will discuss gain curves for shock-ignited NIF targets in both UV and green light and examine the feasibility of designs that employ indirect drive fuel assembly with direct drive shock ignition

  9. The effects of photobiomodulation and low-amplitude high-frequency vibration on bone healing process: a comparative study.

    Science.gov (United States)

    Rajaei Jafarabadi, M; Rouhi, G; Kaka, G; Sadraie, S H; Arum, J

    2016-12-01

    This study aimed at investigating the effects of photobiomodulation (PBM) and low-amplitude high-frequency (LAHF) whole body mechanical vibration on bone fracture healing process when metallic plates are implanted in rats' femurs. Forty male rats weighing between 250 and 350 g, 12 weeks old, were employed in this study. A transverse critical size defect (CSD) was made in their right femurs that were fixed by stainless steel plates. After the surgery, the rats were divided equally into four groups: low-level laser therapy group (GaAlAs laser, 830 nm, 40 mW, 4 J/cm(2), 0.35 cm beam diameter, LLLT), whole body vibration group (60 Hz, 0.1 mm amplitude, 1.5 g, WBV), a combination of laser and vibration group (LV), and the control group (C). Each group was divided into two subgroups based on sacrifice dates. The rats were sacrificed at intervals of 3 and 6 weeks after the surgery to extract their right femurs for radiography and biomechanical and histological analyses, and the results were analyzed using standard statistical methods. Radiographic analyses showed greater callus formation in the LLLT and WBV groups than in control group at both 3 (P low-amplitude high-frequency WBV both had a positive impact on bone healing process, for critical size defects in the presence of a stainless steel implant. But their combination, i.e., low-level laser therapy and low-amplitude high-frequency whole body vibration (LV), interestingly did not accelerate the fractured bone healing process.

  10. Modeling of energy transfer in hypersonic shocks using high fidelity models

    Science.gov (United States)

    Zhu, Tong

    The spectra of high-temperature, chemically reacting hypersonic flows provides the most powerful diagnostic available for testing thermochemically nonequilibrium models in re-entry conditions. Several shock tube experiments have revealed that conventional phenomenological approach can not accurately predict the internal temperature of the gas and also the corresponding radiation. In particular, large rotational nonequilibrium in strong shocks has been observed in several experiments with high peak translational temperatures. The Direct Simulation Monte Carlo (DSMC) method is a particlebased simulation method that is capable of properly simulating flows with large nonequilibrium. In the experiments above, one dimensional shocks are most widely studied but they are challenging to simulate using the DSMC method due to the unsteady nature of the flows and especially for hypersonic flows with chemical reactions taking place. Therefore, efficient approaches for simulating one-dimensional shocks are developed for use in DSMC simulations. Both a shock stabilization technique and a modified DSMC unsteady sampling approach are used in simulating one dimensional, unsteady shocks. In the latter approach, a moving sampling region is used to obtain an accurate profile of the reflected shock in air. The shock number density and temperature profiles are obtained and used to calculate excitation and radiation. The Quasi-Steady-State (QSS) assumption is made in the excitation calculation where both electron impact and heavy particle impact excitation for the NO(A2sum +) and the N+2 (B2sum +u ) states are studied. The calculated NOradiation in the wavelength range o lambda = 235 +/- 7 nm for shock speeds below 7 km/s are in good agreement with the experiment, but, the predicted radiation is lower than the experiment for shock speeds above 7 km/s. In addition, the N+2 radiation in the wavelength range of lambda = 391.4 +/- 0.2 nm are in good agreement with the experimental data for

  11. High strength and high ductility behavior of 6061-T6 alloy after laser shock processing

    Science.gov (United States)

    Gencalp Irizalp, Simge; Saklakoglu, Nursen

    2016-02-01

    The plastic deformation behavior of 6061-T6 alloy which was subjected to severe plastic deformation (SPD) at high strain rates during laser shock processing (LSP) was researched. In LSP-treated materials, the near surface microstructural change was examined by TEM and fracture surfaces after tensile testing were examined by SEM. An increase in strength of metallic materials brings about the decrease in ductility. In this study, the results showed that LSP-treated 6061-T6 alloy exhibited both high strength and high ductility. TEM observation showed that stacking fault (SF) ribbon enlarged, deformation twins formed and twin boundary increased in LSP-treated 6061-T6 alloy. This observation was an indication of stacking fault energy (SFE) decrease. Work hardening capability was recovered after LSP impacts.

  12. The MACHO Project Sample of Galactic Bulge High-Amplitude Scuti Stars: Pulsation Behavior and Stellar Properties

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, D.P.; Cook, K.H.; Freeman, K.C.; Geha, M.; Griest, K.; Lehner, M.J.; Marshall, S.L.; McNamara, B.J.; Minniti, D.; Nelson, C.; Peterson, B.A.; Popowski, P.; Pratt, M.R.; Quinn, P.J.; Rodgers, A.W.; Sutherland, W.; Templeton, M.R.; Vandehei, T.; Welch, D.L.

    1999-11-16

    We have detected 90 objects with periods and lightcurve structure similar to those of field {delta} Scuti stars, using the Massive Compact Halo Object (MACHO) Project database of Galactic bulge photometry. If we assume similar extinction values for all candidates and absolute magnitudes similar to those of other field high-amplitude {delta} Scuti stars (HADS), the majority of these objects lie in or near the Galactic bulge. At least two of these objects are likely foreground {delta} Scuti stars, one of which may be an evolved nonradial pulsator, similar to other evolved, disk-population {delta} Scuti stars. We have analyzed the light curves of these objects and find that they are similar to the light curves of field {delta} Scuti stars and the {delta} Scuti stars found by the Optical Gravitational Lens Experiment (OGLE). However, the amplitude distribution of these sources lies between those of low- and high-amplitude {delta} Scuti stars, which suggests that they may be an intermediate population. We have found nine double-mode HADS with frequency ratios ranging from 0.75 to 0.79, four probable double- and multiple-mode objects, and another four objects with marginal detections of secondary modes. The low frequencies (5-14 cycles d{sup -1}) and the observed period ratios of {approx}0.77 suggest that the majority of these objects are evolved stars pulsating in fundamental or first overtone radial modes.

  13. Stability analysis of amplitude death in delay-coupled high-dimensional map networks and their design procedure

    Science.gov (United States)

    Watanabe, Tomohiko; Sugitani, Yoshiki; Konishi, Keiji; Hara, Naoyuki

    2017-01-01

    The present paper studies amplitude death in high-dimensional maps coupled by time-delay connections. A linear stability analysis provides several sufficient conditions for an amplitude death state to be unstable, i.e., an odd number property and its extended properties. Furthermore, necessary conditions for stability are provided. These conditions, which reduce trial-and-error tasks for design, and the convex direction, which is a popular concept in the field of robust control, allow us to propose a design procedure for system parameters, such as coupling strength, connection delay, and input-output matrices, for a given network topology. These analytical results are confirmed numerically using delayed logistic maps, generalized Henon maps, and piecewise linear maps.

  14. Antiknock Performance of Interlayered High-Damping-Rubber Blast Door under Thermobaric Shock Wave

    Directory of Open Access Journals (Sweden)

    Xiudi Li

    2016-01-01

    Full Text Available The long duration and high impulse shock wave of thermobaric bomb threatens the security of underground structures. To obtain high resistance blast door against thermobaric shock wave, firstly, the dynamic mechanic property of high damping rubber was studied by split Hopkinson pressure bar (SHPB equipment and the stress-strain relationship of high damping rubber under average strain rate of 5200/s was obtained. Secondly, the numerical model of interlayered high-damping-rubber blast door was established with ANSYS/LS-DYNA code based on test results, and the antiknock performance of interlayered high-damping-rubber blast door under thermobaric shock wave was analyzed by contrast with ordinary blast door. The results showed that the midspan displacement of the blast door decreased firstly and then increased with the increase of thickness of the high-damping-rubber interlayer, and the optimal thickness of the high-damping-rubber interlayer for energy consuming was 150 mm in the calculation condition of this paper. With the increase of the distance between the interlayer and the front surface of the door, the midspan displacement of the blast door decreased continually. The midspan maximum displacement of interlayered high-damping-rubber blast door decreased 74.5% in comparison to ordinary blast door. It showed that the high-damping-rubber structure can effectively improve the antiknock performance of blast door under thermobaric shock wave.

  15. Acoustic minor losses in high amplitude resonators with single-sided junctions

    Science.gov (United States)

    Doller, Andrew J.

    Steady flow engineering handbooks like Idelchik20 do not exist for investigators interested in acoustic (oscillating) fluid flows in complex resonators. Measurements of acoustic minor loss coefficients are presented in this dissertation for a limited number of resonator configurations having single-sided junctions. While these results may be useful, the greater purpose of this work is to provide a set of controlled measurements that can be used to benchmark computational models of acoustic flows used for more complicated resonator structures. The experiments are designed around a driver operating at 150 Hz enabling acoustic pressures in excess of 10k Pa in liquid cooled, temperature controlled resonators with 90°, 45° and 25° junctions. These junctions join a common 109 cm long 4.7 cm diameter section to a section of 8.4 mm diameter tube making two sets of resonators: one set with a small diameter length approximately a quarter-wavelength (45 cm), the other approximately a half-wavelength (112 cm). The long resonators have a velocity node at the junction; the short resonators have a velocity anti-node generating the greatest minor losses. Input power is measured by an accelerometer and a pressure transducer at the driver. A pressure sensor at the rigid termination measures radiation pressure from the driver and static junction pressure, as well as the acoustic pressure used to calculate linear thermal and viscous resonator wall losses. At the largest amplitudes, the 90° junction was found to dissipate as much as 0.3 Watt, 1/3 the power of linear losses alone. For each junction, the power dissipation depends on acoustic pressure differently: pressure cubed for the 90°, pressure to the 3.76 for the 45° and pressure to the 4.48 for the 25°. Common among all resonators, blowing acoustic half-cycle minor losses (KB) are excited at lower amplitudes than the suction half-cycle (KS) minor losses. Data collected for the 90° junction shows KB reaches an asymptotic

  16. High-energy synchrotron X-ray radiography of shock-compressed materials

    Science.gov (United States)

    Rutherford, Michael E.; Chapman, David J.; Collinson, Mark A.; Jones, David R.; Music, Jasmina; Stafford, Samuel J. P.; Tear, Gareth R.; White, Thomas G.; Winters, John B. R.; Drakopoulos, Michael; Eakins, Daniel E.

    2015-06-01

    This presentation will discuss the development and application of a high-energy (50 to 250 keV) synchrotron X-ray imaging method to study shock-compressed, high-Z samples at Beamline I12 at the Diamond Light Source synchrotron (Rutherford-Appleton Laboratory, UK). Shock waves are driven into materials using a portable, single-stage gas gun designed by the Institute of Shock Physics. Following plate impact, material deformation is probed in-situ by white-beam X-ray radiography and complimentary velocimetry diagnostics. The high energies, large beam size (13 x 13 mm), and appreciable sample volumes (~ 1 cm3) viable for study at Beamline I12 compliment existing in-house pulsed X-ray capabilities and studies at the Dynamic Compression Sector. The authors gratefully acknowledge the ongoing support of Imperial College London, EPSRC, STFC and the Diamond Light Source, and AWE Plc.

  17. High sensitivity phonon-mediated kinetic inductance detector with combined amplitude and phase read-out

    Science.gov (United States)

    Cardani, L.; Casali, N.; Colantoni, I.; Cruciani, A.; Bellini, F.; Castellano, M. G.; Cosmelli, C.; D'Addabbo, A.; Di Domizio, S.; Martinez, M.; Tomei, C.; Vignati, M.

    2017-01-01

    Developing wide-area cryogenic light detectors with baseline resolution better than 20 eV is one of the priorities of next generation bolometric experiments searching for rare interactions, as the simultaneous read-out of the light and heat signals enables background suppression through particle identification. Among the proposed technological approaches for the phonon sensor, the naturally multiplexed Kinetic Inductance Detectors (KIDs) stand out for their excellent intrinsic energy resolution and reproducibility. The potential of this technique was proved by the CALDER project that reached a baseline resolution of 154 ± 7 eV RMS by sampling a 2 × 2 cm2 Silicon substrate with 4 Aluminum KIDs. In this paper, we present a prototype of Aluminum KID with improved geometry and quality factor. The design improvement, as well as the combined analysis of amplitude and phase signals, allowed to reach a baseline resolution of 82 ± 4 eV by sampling the same substrate with a single Aluminum KID.

  18. Resolving longitudinal amplitude and phase information of two continuous data streams for high-speed and real-time processing

    Directory of Open Access Journals (Sweden)

    A. Guntoro

    2009-05-01

    Full Text Available Although there is an increase of performance in DSPs, due to its nature of execution a DSP could not perform high-speed data processing on a continuous data stream. In this paper we discuss the hardware implementation of the amplitude and phase detector and the validation block on a FPGA. Contrary to the software implementation which can only process data stream as high as 1.5 MHz, the hardware approach is 225 times faster and introduces much less latency.

  19. Surrogate data modeling the relationship between high frequency amplitudes and Higuchi fractal dimension of EEG signals in anesthetized rats.

    Science.gov (United States)

    Spasic, Sladjana; Kalauzi, Aleksandar; Kesic, Srdjan; Obradovic, Milica; Saponjic, Jasna

    2011-11-21

    We used spectral analysis and Higuchi fractal dimension (FD) to correlate the EEG spectral characteristics of the sensorimotor cortex, hippocampus, and pons with their corresponding EEG signal complexities in anesthetized rats. We have explored the quantitative relationship between the mean FDs and EEG wide range high frequency (8-50 Hz) activity during ketamine/xylazine versus nembutal anesthesia at surgical plane. Using FD we detected distinct inter-structure complexity pattern and uncovered for the first time that the polygraphically and behaviorally defined anesthetized state at surgical plane as equal during experiment in two anesthetic regimens, is not the same with respect to the degree of neuronal activity (degree of generalized neuronal inhibition achieved) at different brain levels. Using the correlation of certain brain structure EEG spectral characteristics with their corresponding FDs, and the surrogate data modeling, we determined what particular frequency band contributes to EEG complexities in ketamine/xylazine versus nembutal anesthesia. In this study we have shown that the quantitative relationship between higher frequency EEG amplitude and EEG complexity is the best-modeled by surrogate data as a 3rd order polynomial. On the base of our EEG amplitude/EEG complexity relationship model, and the evidenced spectral differences in ketamine versus nembutal anesthesia we have proved that higher amplitudes of sigma, beta, and gamma frequency in ketamine anesthesia yields to higher FDs.

  20. Robust and Accurate Shock Capturing Method for High-Order Discontinuous Galerkin Methods

    Science.gov (United States)

    Atkins, Harold L.; Pampell, Alyssa

    2011-01-01

    A simple yet robust and accurate approach for capturing shock waves using a high-order discontinuous Galerkin (DG) method is presented. The method uses the physical viscous terms of the Navier-Stokes equations as suggested by others; however, the proposed formulation of the numerical viscosity is continuous and compact by construction, and does not require the solution of an auxiliary diffusion equation. This work also presents two analyses that guided the formulation of the numerical viscosity and certain aspects of the DG implementation. A local eigenvalue analysis of the DG discretization applied to a shock containing element is used to evaluate the robustness of several Riemann flux functions, and to evaluate algorithm choices that exist within the underlying DG discretization. A second analysis examines exact solutions to the DG discretization in a shock containing element, and identifies a "model" instability that will inevitably arise when solving the Euler equations using the DG method. This analysis identifies the minimum viscosity required for stability. The shock capturing method is demonstrated for high-speed flow over an inviscid cylinder and for an unsteady disturbance in a hypersonic boundary layer. Numerical tests are presented that evaluate several aspects of the shock detection terms. The sensitivity of the results to model parameters is examined with grid and order refinement studies.

  1. Prompt high-energy emission from gamma-ray bursts in the internal shock model

    CERN Document Server

    Bosnjak, Z; Dubus, G

    2008-01-01

    The prompt GRB emission is thought to arise from electrons accelerated in internal shocks propagating within a highly relativistic outflow. The launch of Fermi offers the prospect of observations with unprecedented sensitivity in high-energy (>100 MeV) gamma-rays. The aim is to explore the predictions for HE emission from internal shocks, taking into account both dynamical and radiative aspects, and to deduce how HE observations constrain the properties of the relativistic outflow. The emission is modeled by combining a time-dependent radiative code with a dynamical code giving the evolution of the physical conditions in the shocked regions.Synthetic lightcurves and spectra are compared to observations. The HE emission deviates significantly from analytical estimates, which tend to overpredict the IC component, when the time dependence and full cross-sections are included. The exploration of the parameter space favors the case where the dominant process in the BATSE range is synchrotron emission. The HE compo...

  2. [Cardiogenic shock].

    Science.gov (United States)

    Houegnifioh, Komlanvi Kafui; Gfeller, Etienne; Garcia, Wenceslao; Ribordy, Vincent

    2014-08-13

    Cardiogenic shock, especially when it complicates a myocardial infarction, is still associated with high mortality rate. Emergency department or first care physicians are often the first providers to assess the cardiogenic shock patient, and plays thereby a key role in achieving a timely diagnosis and treatment. This review will detail the actual physiopathology understanding of the cardiogenic shock, its diagnosis and management focusing on the care within the emergency department.

  3. High Energy Asymptotics of the Scattering Amplitude for the Schrödinger Equation

    Indian Academy of Sciences (India)

    D Yafaev

    2002-02-01

    We find an explicit function approximating at high energies the kernel of the scattering matrix with arbitrary accuracy. Moreover, the same function gives all diagonal singularities of the kernel of the scattering matrix in the angular variables.

  4. Study of High and Low Amplitude Wave Trains of Cosmic Ray Diurnal Variation during Solar Cycle 23

    Indian Academy of Sciences (India)

    Ambika Singh; Anil Kumar Tiwari; S. P. Agrawal

    2010-06-01

    A detailed study has been conducted on the long-term changes in the diurnal variation of cosmic rays in terms of high and low amplitude wave trains event (HAEs/LAEs) during the period 1996–2008 (solar cycle 23), using the neutron monitor data from Kiel neutron monitoring station. As such, 17 HAE and 48 LAE cases have been detected and analyzed. These HAEs appear quite dominantly during the declining phase as well as near the maximum of the solar activity cycle 23. In contrast, the low amplitude events (LAEs) are inversely correlated with solar activity cycle. In fact, LAEs appear quite dominantly during the minimum phase of the solar activity. When we compare our results for diurnal phase with that observed on an annual average basis, we notice no significant diurnal phase shift for HAEs as well as for LAEs. Moreover, we find that the high-speed solar wind streams (HSSWS) do not play any significant role in causing these variations. These results are discussed on the basis of that observed in earlier cycles.

  5. Influence of high flux hydrogen-plasma exposure on the thermal shock induced crack formation in tungsten

    NARCIS (Netherlands)

    Wirtz, M.; Linke, J.; Pintsuk, G.; Rapp, J.; Wright, G. M.

    2012-01-01

    The influence of high flux hydrogen-plasma on the thermal shock behaviour of tungsten was investigated in a combined experiment using the linear plasma device Pilot-PSI and the electron beam facility JUDITH 1. Tungsten targets were exposed to high flux hydrogen plasma, cyclic thermal shock tests and

  6. Standardized Laboratory Test Requirements for Hardening Equipment to Withstand Wave Impact Shock in Small High Speed Craft

    Science.gov (United States)

    2017-02-06

    penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR...the risk of equipment malfunction or failure due to shock forces caused by wave impacts in high-speed craft. The engineering rationale, assumptions...procurement documents are presented. 15. SUBJECT TERMS Shock Wave slam shock test equipment operability risk reduction 16. SECURITY

  7. High amplitude vortex-induced pulsations in a gas transport system

    NARCIS (Netherlands)

    Kriesels, P.C.; Peters, M.C.A.M.; Hirschberg, A.; Wijnands, A.P.J.; Iafrati, A.; Riccardi, G.; Piva, R.; Bruggeman, J.C.

    1995-01-01

    High Reynolds number, low Mach number gas flows in pipe systems with closed side branches exhibit spectacular low frequency self-sustained pulsations driven by periodic vortex shedding at specific values of the Strouhal number. A detailed study is presented of the behaviour of the flow in a system w

  8. Interaction of cylindrically converging diffracted shock with uniform interface

    Science.gov (United States)

    Liang, Yu; Ding, Juchun; Zhai, Zhigang; Si, Ting; Luo, Xisheng

    2017-08-01

    The Richtmyer-Meshkov instability of an unperturbed air/SF6 interface subjected to a diffracted shock is experimentally studied by high-speed schlieren photography under cylindrical circumstances. The cylindrically converging diffracted shock (CCDS) is produced by a cylindrically uniform shock diffracting around a rigid cylinder(s), and the unperturbed interface is created by a soap film technique. The effects of coupling of multiple rigid cylinders and diverse spacings from the cylinder to interface on a flow field are highlighted. Schlieren images indicate that the amplitude of disturbances on the CCDS increases compared with the local shock radius. After the CCDS impact, a bulge is derived from the interface due to the shock-shock interaction inside the interface, and the number of bulges depends upon the number of cylinders. As the number of cylinders increases, the bulge becomes less pronounced, which is ascribed to additional shock-shock interactions inside the volume. As the distance between the cylinder and interface increases, an air cavity is first observed before the formation of a bulge. The amplitude of perturbation on the interface is found to reduce before the central reflected shock arrival because of the Rayleigh-Taylor stabilization effect. Through equating the pre-interface disturbance of the CCDS to the pre-shock perturbation of the perturbed interface, the initially linear growth rate is theoretically computed based on the impulsive model considering the Bell-Plesset effect. The theoretical results are found to deviate greatly from the experimental counterparts. Instead, taking the post-shock interface amplitude as an initial interface amplitude, the model works well. Therefore, the interface perturbations produced are notably smaller than the disturbances causing them. Moreover, the nonlinear behavior of perturbation growth is estimated by the model considering the Rayleigh-Taylor effect.

  9. Thermal shock behaviour of tungsten after high flux H-plasma loading

    Science.gov (United States)

    Wirtz, M.; Linke, J.; Pintsuk, G.; De Temmerman, G.; Wright, G. M.

    2013-11-01

    Previous studies have shown that transient thermal shock loads induce crack networks on tungsten samples especially at low base temperatures. To achieve test conditions which are more relevant for the performance of tungsten-armoured plasma facing components in next step thermonuclear fusion devices tungsten tiles were exposed to high flux hydrogen-plasma in the linear plasma generator Pilot-PSI and the high heat flux ion beam test facility MARION. Subsequently, the cyclic transient heat load tests were done in the electron beam facility JUDITH 1. The induced damages after these combined tests were examined by microscopically means, profilometry and metallography. The comparison of the obtained results and damage characteristics with those obtained after thermal shock loading show that the preloading of tungsten targets with high flux hydrogen-plasma has significant influence on the thermal shock behaviour of tungsten in terms of crack distance, width, and depth as well as cracked area. Furthermore the plasma parameters, in particular pulse duration and sample temperature during loading, have strong impact on the damage pattern after thermal shock loading.

  10. Shock Melting Temperature of Initially Porous Iron and Indication for Melting Curve of Iron at High Pressures

    Institute of Scientific and Technical Information of China (English)

    LI Xi-Jun; ZHANG Dai-Yu; LIU Fu-Sheng; JING Fu-Qian

    2004-01-01

    The melting curve ofiron is crucial for modelling of the earth's internal heat structures and to understand melting of solids at high pressures. However, the measured melting temperatures of iron at high pressures are disparate so far. We measured the shocked interface (porous iron/sapphire window) temperatures of a kind of porous iron. By using a model for shock temperature measurement [High Pressures Res. 2 (1990) 159] and the previous results of sound velocity measurements [Chin. Phys. Lett. 18 (2001) 852], we determine the melting temperatures of iron at shock compression high pressures of 145 and 171 Gpa. They are consistent with the results reported by other shock compression experiments. Based on the possible different melting mechanisms of iron in diamond anvil cell and in shock compression, the corrected melting temperatures of iron at high pressures become more consistent.

  11. Amplitude limits and nonlinear damping of shear-Alfvén waves in high-beta low-collisionality plasmas

    Science.gov (United States)

    Squire, J.; Schekochihin, A. A.; Quataert, E.

    2017-05-01

    This work, which extends Squire et al (Astrophys. J. Lett. 2016 830 L25), explores the effect of self-generated pressure anisotropy on linearly polarized shear-Alfvén fluctuations in low-collisionality plasmas. Such anisotropies lead to stringent limits on the amplitude of magnetic perturbations in high-β plasmas, above which a fluctuation can destabilize itself through the parallel firehose instability. This causes the wave frequency to approach zero, ‘interrupting’ the wave and stopping its oscillation. These effects are explored in detail in the collisionless and weakly collisional ‘Braginskii’ regime, for both standing and traveling waves. The focus is on simplified models in one dimension, on scales much larger than the ion gyroradius. The effect has interesting implications for the physics of magnetized turbulence in the high-β conditions that are prevalent in many astrophysical plasmas.

  12. Half a century of continuous shock interaction investigations in the Joint Institute for High Temperatures of Russian Academy of Sciences

    Science.gov (United States)

    Bazhenova, T. V.; Golub, V. V.; Gvozdeva, L. G.; Kotelnikov, A. L.

    2014-07-01

    This article describes the history of the investigations of shock wave interactions at the Physical Gasdynamic Department, starting from the early 50s of the last century, when the first research related to missile reentry was made. The review focuses on a number of topics studied over more than 50 years and includes the study of strong shock waves, where it is necessary to take into account the physicochemical transformations in gases, shock wave reflection, diffraction, interaction with the boundary layer and with the nozzle, as well as detonation wave formation and interactions. The investigation of shock wave interactions is a current topic at the Joint Institute for High Temperatures of the Russian Academy of Sciences. Some new results are observed: the formation of impulse jets and the self-ignition of a cold hydrogen jet, diffraction of 3D shock waves, and the effect of an impulse jet and diffracted shock wave on an obstacle.

  13. Specularly reflected He sup 2+ at high Mach number quasi-parallel shocks

    Energy Technology Data Exchange (ETDEWEB)

    Fuselier, S.A.; Lennartsson, O.W. (Lockheed Palo Alto Research Lab., CA (United States)); Thomsen, M.F. (Los Alamos National Lab., NM (United States)); Russell, C.T. (Univ. of California, Los Angeles (United States))

    1990-04-01

    Upstream from the Earth's quasi-parallel bow shock, the Lockheed Plasma Composition Experiment on ISEE 1 often observes two types of suprathermal He{sup 2+} distributions. Always present to some degree is an energetic (several keV/eto 17.4 keV/e, the maximum energy of the detector) diffuse He{sup 2+} distribution. Sometimes, apparently when the Alfven Mach number, M{sub A}, is high enough and the spacecraft is near the shock (within a few minutes of a crossing), a second type of suprathermal He{sup 2+} distribution is also observed. This nongyrotropic, gyrating He{sup 2+} distribution has velocity components parallel and perpendicular to the magnetic field that are consistent with near-specular reflection of a portion of the incident solar wind He{sup 2+} distribution off the shock. Specularly reflected and diffuse proton distributions are associated with these gyrating He{sup 2+} distributions. The presence of these gyrating He{sup 2+} distributions suggests that specular reflection is controlled primarily by magnetic forces in high Mach number quasi-parallel shocks and that these distributions may be a seed population for more energetic diffuse He{sup 2+} distributions.

  14. Shock tube/time-of-flight mass spectrometer for high temperature kinetic studies.

    Science.gov (United States)

    Tranter, Robert S; Giri, Binod R; Kiefer, John H

    2007-03-01

    A shock tube (ST) with online, time-of-flight mass spectrometric (TOF-MS) detection has been constructed for the study of elementary reactions at high temperature. The ST and TOF-MS are coupled by a differentially pumped molecular beam sampling interface, which ensures that the samples entering the TOF-MS are not contaminated by gases drawn from the cold end wall thermal boundary layer in the ST. Additionally, the interface allows a large range of postshock pressures to be used in the shock tube while maintaining high vacuum in the TOF-MS. The apparatus and the details of the sampling system are described along with an analysis in which cooling of the sampled gases and minimization of thermal boundary layer effects are discussed. The accuracy of kinetic measurements made with the apparatus has been tested by investigating the thermal unimolecular dissociation of cyclohexene to ethylene and 1,3-butadiene, a well characterized reaction for which considerable literature data that are in good agreement exist. The experiments were performed at nominal reflected shock wave pressures of 600 and 1300 Torr, and temperatures ranging from 1260 to 1430 K. The rate coefficients obtained are compared with the earlier shock tube studies and are found to be in very good agreement. As expected no significant difference is observed in the rate constant between pressures of 600 and 1300 Torr.

  15. NUMERICAL SIMULATION FOR DYNAMIC INITIAL SHOCK PARAMETERS OF COUPLING CHARGE ON BOREHOLE WALL UNDER THE ACTION OF HIGH EXPLOSIVES

    Institute of Scientific and Technical Information of China (English)

    倪芝芳; 李玉民

    1996-01-01

    According to detonation theory and hydrodynamic principle, a physical model has been set up in this paper. Based on the model a methodology for calculating dynamic initial shock parameters such as shock pressure p,,, shock wave velosity Dm etc. of coupling charge on borehole wall has ben developed. The shock parameters have been calculated when high explosives works on granite, limestone and marble respectively. The magnitude of every parameter on borehole wall has been obtained from ignited dot to the end of borehole along axial direction. Some important conclusions are also gained.

  16. Large-amplitude jumps and non-Gaussian dynamics in highly concentrated hard sphere fluids.

    Science.gov (United States)

    Saltzman, Erica J; Schweizer, Kenneth S

    2008-05-01

    Our microscopic stochastic nonlinear Langevin equation theory of activated dynamics has been employed to study the real-space van Hove function of dense hard sphere fluids and suspensions. At very short times, the van Hove function is a narrow Gaussian. At sufficiently high volume fractions, such that the entropic barrier to relaxation is greater than the thermal energy, its functional form evolves with time to include a rapidly decaying component at small displacements and a long-range exponential tail. The "jump" or decay length scale associated with the tail increases with time (or particle root-mean-square displacement) at fixed volume fraction, and with volume fraction at the mean alpha relaxation time. The jump length at the alpha relaxation time is predicted to be proportional to a measure of the decoupling of self-diffusion and structural relaxation. At long times corresponding to mean displacements of order a particle diameter, the volume fraction dependence of the decay length disappears. A good superposition of the exponential tail feature based on the jump length as a scaling variable is predicted at high volume fractions. Overall, the theoretical results are in good accord with recent simulations and experiments. The basic aspects of the theory are also compared with a classic jump model and a dynamically facilitated continuous time random-walk model. Decoupling of the time scales of different parts of the relaxation process predicted by the theory is qualitatively similar to facilitated dynamics models based on the concept of persistence and exchange times if the elementary event is assumed to be associated with transport on a length scale significantly smaller than the particle size.

  17. A planar shock isolation system with high-static-low-dynamic-stiffness characteristic based on cables

    Science.gov (United States)

    Ma, Yanhui; He, Minghua; Shen, Wenhou; Ren, Gexue

    2015-12-01

    In this paper, a simple and designable shock isolation system with ideal high-static-low-dynamic-stiffness (HSLDS) is proposed, which is intended for the horizontal plane shock isolation application. In this system, the isolated object is suspended by several bearing cables and constrained by a number of uniformly distributed pretensioned cables in the horizontal plane, where the low dynamic stiffness of the system is main controlled by the pretension of the planar cables, whilst the high static stiffness is determined by the axial stiffness of the planar cables and their geometric settings. To obtain the HSLDS characteristic of the system, a brief theoretical description of the relationship between the restoring force and displacement is derived. By obtaining the three-order Taylor expansion with sufficient accuracy of the restoring force, influence of planar cable parameters on the low dynamic and high static stiffness is thus given, therefore, the required HSLDS isolator can be easily designed by adjusting the planar cable length, pretension and tensile stiffness. Finally, the isotropy characteristic of the restoring force of the system with different numbers of planar cables is investigated. To evaluate the performance of the system, a rigid isolated object and flexible cables coupling simulation model considering the contacts of the system is established by using multibody dynamics approach. In this model, flexible cables are simulated by 3-node cable element based on the absolute nodal coordinate formulation; the contact between cable and isolated object is simulated based on Hertz contact theory. Finally, the time-domain shock excitation is converted from the design shock spectrum on the basis of BV043/85 criterion. The design procedure of this isolator and some useful guidelines for choosing cable parameters are presented. In addition, a summary about the performance of the isolators with different numbers of cables shocking in an arbitrary direction is

  18. Flare vs. Shock Acceleration of High-energy Protons in Solar Energetic Particle Events

    Science.gov (United States)

    Cliver, E. W.

    2016-12-01

    Recent studies have presented evidence for a significant to dominant role for a flare-resident acceleration process for high-energy protons in large (“gradual”) solar energetic particle (SEP) events, contrary to the more generally held view that such protons are primarily accelerated at shock waves driven by coronal mass ejections (CMEs). The new support for this flare-centric view is provided by correlations between the sizes of X-ray and/or microwave bursts and associated SEP events. For one such study that considered >100 MeV proton events, we present evidence based on CME speeds and widths, shock associations, and electron-to-proton ratios that indicates that events omitted from that investigation’s analysis should have been included. Inclusion of these outlying events reverses the study’s qualitative result and supports shock acceleration of >100 MeV protons. Examination of the ratios of 0.5 MeV electron intensities to >100 MeV proton intensities for the Grechnev et al. event sample provides additional support for shock acceleration of high-energy protons. Simply scaling up a classic “impulsive” SEP event to produce a large >100 MeV proton event implies the existence of prompt 0.5 MeV electron events that are approximately two orders of magnitude larger than are observed. While classic “impulsive” SEP events attributed to flares have high electron-to-proton ratios (≳5 × 105) due to a near absence of >100 MeV protons, large poorly connected (≥W120) gradual SEP events, attributed to widespread shock acceleration, have electron-to-proton ratios of ˜2 × 103, similar to those of comparably sized well-connected (W20-W90) SEP events.

  19. Low amplitude insult project: PBX 9501 high explosive violent reaction experiments

    Energy Technology Data Exchange (ETDEWEB)

    Idar, D.J.; Lucht, R.A.; Straight, J.W.; Scammon, R.J.; Browning, R.V.; Middleditch, J.; Dienes, J.K.; Skidmore, C.B.; Buntain, G.A.

    1998-12-31

    The Modified Steven test geometry has been used with several different target designs to investigate the mechanical loading behavior of PBX 9501 to a low velocity impact. A 2 kg. mild steel spigot projectile is launched via a new powder driven gun design, from {approximately} 20 to 105 m/s, at lightly confined, steel targets. Brief descriptions of the gun design and operation are given. The threshold velocity to reaction for various target designs, different PBX 9501 lots, and different high explosive (HE) thicknesses are reported and compared. Various diagnostics have been employed to evaluate the pressure profile and timing, and target strain behavior relative to projectile impact. The violence of reaction, as measured by both passive and active techniques, is reported relative to a steady state detonation in PBX 9501. Experimental results suggest slightly different ignition mechanisms dominate based on (HE) thickness, resulting in delayed reactions from {approximately} 0.2- to 2.8-ms after impact. Post-test analyses of the PBX 9501 are briefly summarized.

  20. Low amplitude insult project: PBX 9501 high explosive violent reaction experiments

    Energy Technology Data Exchange (ETDEWEB)

    Idar, D.J.; Lucht, R.A.; Straight, J.W.; Scammon, R.J.; Browning, R.V.; Middleditch, J.; Dienes, J.K.; Skidmore, C.B.; Buntain, G.A.

    1998-12-31

    The Modified Steven test geometry has been used with several different target designs to investigate the mechanical loading behavior of PBX 9501 to a low velocity impact. A 2 kg. mild steel spigot projectile is launched via a new powder driven gun design, from {approximately} 20 to 105 m/s, at lightly confined, steel targets. Brief descriptions of the gun design and operation are given. The threshold velocity to reaction for various target designs, different PBX 9501 lots, and different high explosive (HE) thicknesses are reported and compared. Various diagnostics have been employed to evaluate the pressure profile and timing, and target strain behavior relative to projectile impact. The violence of reaction, as measured by both passive and active techniques, is reported relative to a steady state detonation in PBX 9501. Experimental results suggest slightly different ignition mechanisms dominate based on (HE) thickness, resulting in delayed reactions from {approximately} 0.2- to 2.8-ms after impact. Post-test analyses of the PBX 9501 are briefly summarized.

  1. Ultra-high-speed studies of shock phenomena in a miniaturized system: A preliminary evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Trott, W.M.; Erickson, K.L.

    1997-09-01

    A laboratory-scale experimental test system for small-scale of shock phenomena has been assembled. This system uses a variety of miniature test platforms in which shock loading is provided by laser-driven flyer impact. Acceptor materials include thin-film explosives and high-density metal foils. Optical access is provided for high-speed optical diagnostics such as optically recording velocity interferometry and single-pulse Raman spectroscopy. The experimental assembly for Raman studies features a common laser source for both flyer generation and excitation of Raman scattering (to achieve high timing precision) and a detection scheme that uses the coupling fiber for the excitation source to collect with high efficiency backscattered Raman light. Preliminary system evaluation experiments indicate that detailed particle velocity studies of the dynamic material properties of high-density metals under short-pulse, high-strain-rate loading can be performed in a miniaturized test configuration. Single-pulse Raman studies on shock compressed thin film explosives also appear feasible if the thickness and grain structure of these films can be tailored to enhance the Raman scattering signal sufficiently. Possible improvements in the experimental design and a number of likely applications of these techniques are also discussed.

  2. Formation of Cosmic Crystals in Highly-Supersaturated Silicate Vapor Produced by Planetesimal Bow Shocks

    CERN Document Server

    Miura, H; Yamamoto, T; Nakamoto, T; Yamada, J; Tsukamoto, K; Nozawa, J

    2010-01-01

    Several lines of evidence suggest that fine silicate crystals observed in primitive meteorite and interplanetary dust particles (IDPs) nucleated in a supersaturated silicate vapor followed by crystalline growth. We investigated evaporation of $\\mu$m-sized silicate particles heated by a bow shock produced by a planetesimal orbiting in the gas in the early solar nebula and condensation of crystalline silicate from the vapor thus produced. Our numerical simulation of shock-wave heating showed that these {\\mu}m-sized particles evaporated almost completely when the bow shock is strong enough to cause melting of chondrule precursor dust particles. We found that the silicate vapor cools very rapidly with expansion into the ambient unshocked nebular region; the cooling rate is estimated, for instance, to be as high as 2000 K s$^{-1}$ for a vapor heated by a bow shock associated with a planetesimal of radius 1 km. The rapid cooling of the vapor leads to nonequilibrium gas-phase condensation of dust at temperatures muc...

  3. Early Fluid Resuscitation and High Volume Hemofiltration Decrease Septic Shock Progression in Swine.

    Science.gov (United States)

    Zhao, Ping; Zheng, Ruiqiang; Xue, Lu; Zhang, Min; Wu, Xiaoyan

    2015-01-01

    This study aimed to assess the effects of early fluid resuscitation (EFR) combined with high volume hemofiltration (HVHF) on the cardiopulmonary function and removal of inflammatory mediators in a septic shock swine model. Eighteen swine were randomized into three groups: control (n = 6) (extracorporeal circulating blood only), continuous renal replacement therapy (CRRT) (n = 6; ultrafiltration volume = 25 mL/Kg/h), and HVHF (n = 6; ultrafiltration volume = 85 mL/Kg/h). The septic shock model was established by intravenous infusion of lipopolysaccharides (50 µg/kg/h). Hemodynamic parameters (arterial pressure, heart rate, cardiac output, stroke volume variability, left ventricular contractility, systemic vascular resistance, and central venous pressure), vasoactive drug parameters (dose and time of norepinephrine and hourly fluid intake), pulmonary function (partial oxygen pressure and vascular permeability), and cytokines (interleukin-6 and interleukin-10) were observed. Treatment resulted in significant changes at 4-6 h. HVHF was beneficial, as shown by the dose of vasoactive drugs, fluid intake volume, left ventricular contractility index, and partial oxygen pressure. Both CRRT and HVHF groups showed improved removal of inflammatory mediators compared with controls. In conclusion, EFR combined with HVHF improved septic shock in this swine model. The combination decreased shock progression, reduced the need for vasoactive drugs, and alleviated the damage to cardiopulmonary functions.

  4. Generation and Evolution of High-Mach Number, Laser-Driven Magnetized Collisionless Shocks in the Laboratory

    CERN Document Server

    Schaeffer, Derek; Haberberger, Dan; Fiksel, Gennady; Bhattacharjee, Amitava; Barnak, Daniel; Hu, Suxing; Germaschewski, Kai

    2016-01-01

    Shocks act to convert incoming supersonic flows to heat, and in collisionless plasmas the shock layer forms on kinetic plasma scales through collective electromagnetic effects. These collisionless shocks have been observed in many space and astrophysical systems [Smith 1975, Smith 1980, Burlaga 2008, Sulaiman 2015], and are believed to accelerate particles, including cosmic rays, to extremely high energies [Kazanas 1986, Loeb 2000, Bamba 2003, Masters 2013, Ackermann 2013]. Of particular importance are the class of high-Mach number, supercritical shocks [Balogh 2013] ($M_A\\gtrsim4$), which must reflect significant numbers of particles back into the upstream to accommodate entropy production, and in doing so seed proposed particle acceleration mechanisms [Blandford 1978, McClements 2001, Caprioli 2014, Matsumoto 2015]. Here we present the first laboratory generation of high-Mach number magnetized collisionless shocks created through the interaction of an expanding laser-driven plasma with a magnetized ambient ...

  5. High-amplitude THz and GHz strain waves, generated by ultrafast screening of piezoelectric fields in InGaN/GaN multiple quantum wells

    DEFF Research Database (Denmark)

    Porte, Henrik; van Capel, P.J.S.; Turchinovich, Dmitry

    2010-01-01

    Screening of large built-in piezoelectric fields in InGaN/GaN quantum wells leads to high-amplitude acoustic emission. We will compare acoustic emission by quantum wells with different thicknesses with photoluminescence; indicating screening.......Screening of large built-in piezoelectric fields in InGaN/GaN quantum wells leads to high-amplitude acoustic emission. We will compare acoustic emission by quantum wells with different thicknesses with photoluminescence; indicating screening....

  6. Shock-Ignited High Gain/Yield Targets for the National Ignition Facility

    Science.gov (United States)

    Perkins, L. J.; Lafortune, K. N.; Bedrosiian, P.; Tabak, M.; Miles, A.; Dixit, S.; Betti, R.; Anderson, K.; Zhou, C.

    2006-10-01

    Shock-ignition, a new concept for ICF ignition [C.Zhou, R.Betti Bull APS, v50, 2005], is being studied as a future option for efficiently achieving high gains in large laser facilities such as NIF. Accordingly, this offers the potential for testing: (1)High yield (up to 200MJ), reactor-relevant targets for inertial fusion energy (2)High fusion yield targets for DOE NNSA stockpile application (3)Targets with appreciable gain at low laser drive energies (gains of 10's at 150kJ) (4)Ignition of simple, non-cryo (room temperature) single shell gas targets at (unity gain). By contrast to conventional hotspot ignition, we separate the assembly and ignition phases by initially imploding a massive cryogenic shell on a low adiabat (alpha 0.7) at low velocity (less than 2e7cm/s) using a direct drive pulse of modest total energy. The assembled fuel is then separately ignited by a strong, spherically convergent shock driven by a high intensity spike at the end of the pulse and timed to reach the center as the main fuel is stagnating and starting to rebound. Like fast ignition, shock ignition can achieve high gains with low drive energy, but has the advantages of requiring only a single laser with less demanding timing and spatial focusing requirements.

  7. Amplitude differences in high-frequency fMRI signals between eyes open and eyes closed resting states.

    Science.gov (United States)

    Yuan, Bin-Ke; Wang, Jue; Zang, Yu-Feng; Liu, Dong-Qiang

    2014-01-01

    Recent studies employing rapid sampling techniques have demonstrated that the resting state fMRI (rs-fMRI) signal exhibits synchronized activities at frequencies much higher than the conventional frequency range (high-frequency fluctuations between different resting states. Here, we acquired rs-fMRI data at a high sampling rate (TR = 400 ms) from subjects with both eyes open (EO) and eyes closed (EC), and compared the amplitude of fluctuation (AF) between EO and EC for both the low- and high-frequency components. In addition to robust AF differences in the conventional low frequency band (high-frequency (primarily in 0.1-0.35 Hz) differences. The high-frequency results without covariates regression exhibited noisy patterns. For the data with nuisance covariates regression, we found a significant and reproducible reduction in high-frequency AF between EO and EC in the bilateral PSMC and the supplementary motor area (SMA), and an increase in high-frequency AF in the left middle occipital gyrus (MOG). Furthermore, we investigated the effect of sampling rate by down-sampling the data to effective TR = 2 s. Briefly, by using the rapid sampling rate, we were able to detect more regions with significant differences while identifying fewer artifactual differences in the high-frequency bands as compared to the down-sampled dataset. We concluded that (1) high-frequency fluctuations of rs-fMRI signals can be modulated by different resting states and thus may be of physiological importance; and (2) the regression of covariates and the use of fast sampling rates are superior for revealing high-frequency differences in rs-fMRI signals.

  8. Effects of high shock pressures and pore morphology on hot spot mechanisms in HMX

    Science.gov (United States)

    Springer, H. K.; Tarver, C. M.; Bastea, S.

    2017-01-01

    The shock initiation and detonation behavior of heterogeneous solid explosives is governed by its microstructure and reactive properties. New additive manufacturing techniques offer unprecedented control of explosive microstructures previously impossible, enabling us to develop novel explosives with tailored shock sensitivity and detonation properties. Since microstructure-performance relationships are not well established for explosives, there is little material design guidance for these manufacturing techniques. In this study, we explore the effects of high shock pressures (15-38 GPa) with long shock durations and different pore morphologies on hot spot mechanisms in HMX. HMX is chosen as the model material because we have experimental data on many of the chemical-thermal-mechanical properties required for pore collapse simulations. Our simulations are performed using the multi-physics arbitrary Lagrangian Eulerian finite element hydrocode, ALE3D, with Cheetah-based models for the unreacted and the product equation-of-states. We use a temperature-dependent specific heat with the unreacted equation-of-state and a temperature-dependent viscosity model to ensure accurate shock temperatures for subsequent chemistry. The Lindemann Law model is used for shock melting in HMX. In contrast to previous pore collapse studies at lower shock pressures (≤10 GPa) in HMX and shorter post-collapse burning times, our calculations show that shock melting occurs above 15 GPa due to higher bulk heating and a prominent elongated ("jet-like") hot spot region forms at later times. The combination of the elongated, post-collapse hot spot region and the higher bulk heating with increasing pressure dramatically increases the growth rate of reaction. Our calculations show that the reaction rate, dF/dt, increases with increasing shock pressure. We decompose the reaction rate into ignition ((dF/dt)ig) and growth ((dF/dt)gr) phases to better analyze our results. We define the ignition phase

  9. Shock Formation in Lovelock Theories

    CERN Document Server

    Reall, Harvey S; Way, Benson

    2014-01-01

    We argue that Lovelock theories of gravity suffer from shock formation, unlike General Relativity. We consider the propagation of (i) a discontinuity in curvature, and (ii) weak, high frequency, gravitational waves. Such disturbances propagate along characteristic hypersurfaces of a "background" spacetime and their amplitude is governed by a transport equation. In GR the transport equation is linear. In Lovelock theories, it is nonlinear and its solutions can blow up, corresponding to the formation of a shock. We show that this effect is absent in some simple cases e.g. a flat background spacetime, and demonstrate its presence for a plane wave background. We comment on weak cosmic censorship, the evolution of shocks, and the nonlinear stability of Minkowski spacetime, in Lovelock theories.

  10. Whistler Waves Associated with Weak Interplanetary Shocks

    Science.gov (United States)

    Velez, J. C. Ramirez; Blanco-Cano, X.; Aguilar-Rodriguez, E.; Russell, C. T.; Kajdic, P.; Jian,, L. K.; Luhmann, J. G.

    2012-01-01

    We analyze the properties of 98 weak interplanetary shocks measured by the dual STEREO spacecraft over approximately 3 years during the past solar minimum. We study the occurrence of whistler waves associated with these shocks, which on average are high beta shocks (0.2 whistler waves can extend up to 100,000 km in the upstream region but in most cases (88%) are contained in a distance within 30,000 km from the shock. This corresponds to a larger region with upstream whistlers associated with IP shocks than previously reported in the literature. The maximum amplitudes of the waves are observed next to the shock interface, and they decrease as the distance to the shock increases. In most cases the wave propagation direction becomes more aligned with the magnetic field as the distance to the shock increases. These two facts suggest that most of the waves in the upstream region are Landau damping as they move away from the shock. From the analysis we also conclude that it is likely that the generation mechanism of the upstream whistler waves is taking place at the shock interface. In the downstream region, the waves are irregularly polarized, and the fluctuations are very compressive; that is, the compressive component of the wave clearly dominates over the transverse one. The majority of waves in the downstream region (95%) propagate at oblique angles with respect to the ambient magnetic field (>60 deg.). The wave propagation with respect to the shock-normal direction has no preferred direction and varies similarly to the upstream case. It is possible that downstream fluctuations are generated by ion relaxation as suggested in previous hybrid simulation shocks.

  11. Generation and Evolution of High-Mach-Number Laser-Driven Magnetized Collisionless Shocks in the Laboratory

    Science.gov (United States)

    Schaeffer, D. B.; Fox, W.; Haberberger, D.; Fiksel, G.; Bhattacharjee, A.; Barnak, D. H.; Hu, S. X.; Germaschewski, K.

    2017-07-01

    We present the first laboratory generation of high-Mach-number magnetized collisionless shocks created through the interaction of an expanding laser-driven plasma with a magnetized ambient plasma. Time-resolved, two-dimensional imaging of plasma density and magnetic fields shows the formation and evolution of a supercritical shock propagating at magnetosonic Mach number Mms≈12 . Particle-in-cell simulations constrained by experimental data further detail the shock formation and separate dynamics of the multi-ion-species ambient plasma. The results show that the shocks form on time scales as fast as one gyroperiod, aided by the efficient coupling of energy, and the generation of a magnetic barrier between the piston and ambient ions. The development of this experimental platform complements present remote sensing and spacecraft observations, and opens the way for controlled laboratory investigations of high-Mach number collisionless shocks, including the mechanisms and efficiency of particle acceleration.

  12. Study on the shock absorbing technique of high speed railway bridges

    Institute of Scientific and Technical Information of China (English)

    Li Chenggen; Gao Ri

    2011-01-01

    Based on the idea of "bearing function separation", a structural member called shock absorber that makes use of its plastic deformation is presented for reducing the seismic response of the bridge. The design criterion for matching material stress, strain and earthquake fortification aim, is also given. The analysis results show that the high speed railway box girder with the absorber in this paper has great reduction effect in seismic response of the bridge piers.

  13. Modeling Hot-Spot Contributions in Shocked High Explosives at the Mesoscale

    Energy Technology Data Exchange (ETDEWEB)

    Harrier, Danielle [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-08-12

    When looking at performance of high explosives, the defects within the explosive become very important. Plastic bonded explosives, or PBXs, contain voids of air and bonder between the particles of explosive material that aid in the ignition of the explosive. These voids collapse in high pressure shock conditions, which leads to the formation of hot spots. Hot spots are localized high temperature and high pressure regions that cause significant changes in the way the explosive material detonates. Previously hot spots have been overlooked with modeling, but now scientists are realizing their importance and new modeling systems that can accurately model hot spots are underway.

  14. High energy neutrino and gamma ray transients from relativistic supernova shock breakouts

    CERN Document Server

    Kashiyama, Kazumi; Horiuchi, Shunsaku; Gao, Shan; Mészáros, Peter

    2013-01-01

    Relativistic shocks that accompany supernovae (SNe) produce X-ray burst emissions as they break out in the dense circumstellar medium around the progenitors. This phenomenon is sometimes associated with peculiar low-luminosity gamma-ray bursts (LL GRBs). Here, we investigate the high energy neutrino and gamma-ray counterparts of such a class of SNe. Just beyond the shock breakout radius, particle acceleration in the collisionless shock starts to operate in the presence of breakout photons. We show that protons may be accelerated to sufficiently high energies and produce high energy neutrinos and gamma rays via the photomeson interaction. These neutrinos and gamma rays may be detectable from 10 Mpc away by IceCube/KM3Net as multi-TeV transients almost simultaneously with the X-ray burst emission, and even from 100 Mpc away with follow-up observations by CTA using a wide-field sky monitor like Swift as a trigger. A statistical technique using a stacking approach could also be possible for the detection, with th...

  15. High-pressure shock behavior of WC and Ta2O5 powders.

    Energy Technology Data Exchange (ETDEWEB)

    Knudson, Marcus D. (Sandia National Laboratories, Albuquerque, NM); Reinhart, William Dodd (Sandia National Laboratories, Albuquerque, NM); Vogler, Tracy John; Root, Seth (Sandia National Laboratories, Albuquerque, NM)

    2011-10-01

    Planar shock experiments were conducted on granular tungsten carbide (WC) and tantalum oxide (Ta{sub 2}O{sub 5}) using the Z machine and a 2-stage gas gun. Additional shock experiments were also conducted on a nearly fully dense form of Ta{sub 2}O{sub 5}. The experiments on WC yield some of the highest pressure results for granular materials obtained to date. Because of the high distention of Ta{sub 2}O{sub 5}, the pressures obtained were significantly lower, but the very high temperatures generated led to large contributions of thermal energy to the material response. These experiments demonstrate that the Z machine can be used to obtain accurate shock data on granular materials. The data on Ta{sub 2}O{sub 5} were utilized in making improvements to the P-{lambda} model for high pressures; the model is found to capture the results not only of the Z and gas gun experiments but also those from laser experiments on low density aerogels. The results are also used to illustrate an approach for generating an equation of state using only the limited data coming from nanoindentation. Although the EOS generated in this manner is rather simplistic, for this material it gives reasonably good results.

  16. Blast-Induced Acceleration in a Shock Tube: Distinguishing Primary and Tertiary Blast Injury

    Science.gov (United States)

    2014-10-01

    Annual, Year 2 3. DATES COVERED 4. TITLE AND SUBTITLE Blast-Induced Acceleration in a Shock Tube : Distinguishing Primary and Tertiary 5a...Using a highly characterized shock tube simulation of blast, rats will be exposed to BOP with varied peak amplitudes and impulse in association...understanding of the relation of the former to the latter. As the use of shock tubes has greatly expanded in recent years for biomedical research

  17. Nano-structural characteristics of carbon nanotube-polymer composite films for high-amplitude optoacoustic generation

    Science.gov (United States)

    Baac, Hyoung Won; Ok, Jong G.; Lee, Taehwa; Jay Guo, L.

    2015-08-01

    We demonstrate nano-structural characteristics of carbon nanotube (CNT)-polydimethylsiloxane (PDMS) composite films that can be used as highly efficient and robust ultrasound transmitters for diagnostic and therapeutic applications. An inherent architecture of the nano-composite provides unique thermal, optical, and mechanical properties that are accommodated not just for efficient energy conversion but also for extraordinary robustness against pulsed laser ablation. First, we explain a thermoacoustic transfer mechanism within the nano-composite. CNT morphologies are examined to determine a suitable arrangement for heat transfer to the surrounding PDMS. Next, we introduce an approach to enhance optical extinction of the composite films, which uses shadowed deposition of a thin Au layer through an as-grown CNT network. Finally, the transmitter robustness is quantified in terms of laser-induced damage threshold. This reveals that the CNT-PDMS films can withstand an order-of-magnitude higher optical fluence (and extinction) than a Cr film used as a reference. Such robustness is crucial to increase the maximum-available optical energy for optoacoustic excitation and pressure generation. All of these structure-originated characteristics manifest the CNT-PDMS composite films as excellent optoacoustic transmitters for high-amplitude and high-frequency ultrasound generation.

  18. Multi-fluid approach to high-frequency waves in plasmas: I. Small-amplitude regime in fully ionized medium

    CERN Document Server

    Martínez-Gómez, David; Terradas, Jaume

    2016-01-01

    Ideal MHD provides an accurate description of low-frequency Alfv\\'en waves in fully ionized plasmas. However, higher frequency waves in many plasmas of the solar atmosphere cannot be correctly described by ideal MHD and a more accurate model is required. Here, we study the properties of small-amplitude incompressible perturbations in both the low and the high frequency ranges in plasmas composed of several ionized species. We use a multi-fluid approach and take into account the effects of collisions between ions and the inclusion of Hall's term in the induction equation. Through the analysis of the corresponding dispersion relations and numerical simulations we check that at high frequencies ions of different species are not as strongly coupled as in the low frequency limit. Hence, they cannot be treated as a single fluid. In addition, elastic collisions between the distinct ionized species are not negligible for high frequency waves since an appreciable damping is obtained. Furthermore, Coulomb collisions be...

  19. Nano-structural characteristics of carbon nanotube-polymer composite films for high-amplitude optoacoustic generation.

    Science.gov (United States)

    Baac, Hyoung Won; Ok, Jong G; Lee, Taehwa; Guo, L Jay

    2015-09-14

    We demonstrate nano-structural characteristics of carbon nanotube (CNT)-polydimethylsiloxane (PDMS) composite films that can be used as highly efficient and robust ultrasound transmitters for diagnostic and therapeutic applications. An inherent architecture of the nano-composite provides unique thermal, optical, and mechanical properties that are accommodated not just for efficient energy conversion but also for extraordinary robustness against pulsed laser ablation. First, we explain a thermoacoustic transfer mechanism within the nano-composite. CNT morphologies are examined to determine a suitable arrangement for heat transfer to the surrounding PDMS. Next, we introduce an approach to enhance optical extinction of the composite films, which uses shadowed deposition of a thin Au layer through an as-grown CNT network. Finally, the transmitter robustness is quantified in terms of laser-induced damage threshold. This reveals that the CNT-PDMS films can withstand an order-of-magnitude higher optical fluence (and extinction) than a Cr film used as a reference. Such robustness is crucial to increase the maximum-available optical energy for optoacoustic excitation and pressure generation. All of these structure-originated characteristics manifest the CNT-PDMS composite films as excellent optoacoustic transmitters for high-amplitude and high-frequency ultrasound generation.

  20. Elastic moduli, damping and modulus of rupture changes in a high alumina refractory castable due to different types of thermal shock

    Directory of Open Access Journals (Sweden)

    Pereira, A. H. A.

    2012-06-01

    Full Text Available The work herein verifies the changes of the elastic moduli, damping and modulus of rupture (MOR of a high alumina refractory castable due to heating, cooling and heating-cooling thermal shock damage. Twelve prismatic specimens were prepared for the tests and divided into four groups. The thermal shocks were performed on three groups, each containing three specimens having abrupt temperature changes of 1100°C during heating in the first group, during cooling in the second and during heating followed by cooling in the third group. The fourth group, which was taken as a reference did not receive any thermal shock. The elastic moduli were measured after each thermal shock cycle. After 10 cycles, the MOR, the damping and the damping dependence on excitation amplitude were measured at room temperature for all specimens. The elastic moduli showed a similar decrease and the damping a similar increase due to the cooling and heating-cooling thermal shocks. The heating thermal shocks caused no significant changes on the elastic moduli and damping. However, the MOR appeared to be sensitive to the heating thermal shock. This work also shows that the damping for the studied refractory castable is non-linear (i.e., amplitude of excitation sensitive and that this non-linearity increases when the damage level rises.

    En este trabajo se investigaron las alteraciones de los módulos elásticos dinámicos, del amortiguamiento y del módulo de rotura (MOR de un material refractario moldeable de alta alúmina después de recibir choques térmicos de calentamiento, enfriamiento y calentamiento seguido de enfriamiento (calentamiento-enfriamiento. Para ello se prepararon doce cuerpos prismáticos dividiéndolos en cuatro grupos. Los choques térmicos se le aplicaron a sólo tres grupos, cada uno con tres muestras. Al primer grupo se le aplicó un cambio brusco de temperatura de 1100 °C en calentamiento, en enfriamiento al segundo grupo y calentamiento seguido

  1. Collimated Propagation of Fast Electron Beams Accelerated by High-Contrast Laser Pulses in Highly Resistive Shocked Carbon

    Science.gov (United States)

    Vaisseau, X.; Morace, A.; Touati, M.; Nakatsutsumi, M.; Baton, S. D.; Hulin, S.; Nicolaï, Ph.; Nuter, R.; Batani, D.; Beg, F. N.; Breil, J.; Fedosejevs, R.; Feugeas, J.-L.; Forestier-Colleoni, P.; Fourment, C.; Fujioka, S.; Giuffrida, L.; Kerr, S.; McLean, H. S.; Sawada, H.; Tikhonchuk, V. T.; Santos, J. J.

    2017-05-01

    Collimated transport of ultrahigh intensity electron current was observed in cold and in laser-shocked vitreous carbon, in agreement with simulation predictions. The fast electron beams were created by coupling high-intensity and high-contrast laser pulses onto copper-coated cones drilled into the carbon samples. The guiding mechanism—observed only for times before the shock breakout at the inner cone tip—is due to self-generated resistive magnetic fields of ˜0.5 - 1 kT arising from the intense currents of fast electrons in vitreous carbon, by virtue of its specific high resistivity over the range of explored background temperatures. The spatial distribution of the electron beams, injected through the samples at different stages of compression, was characterized by side-on imaging of hard x-ray fluorescence.

  2. The use of percutaneous left ventricular assist device in high-risk percutaneous coronary intervention and cardiogenic shock.

    Science.gov (United States)

    Akhondi, Andre Babak; Lee, Michael S

    2013-01-01

    Patients with high-risk coronary lesions may be denied coronary artery bypass grafting due to excessive comorbidities. Percutaneous coronary intervention (PCI) may be a feasible revascularization strategy in high-risk patients who present with ST-elevation myocardial infarction and cardiogenic shock. Historically, the use if intra-aortic balloon pump (IABP) has been used in high-risk PCI and cardiogenic shock. However, recent data has shown that elective IABP insertion did not reduce the incidence of major cardiovascular events following PCI. The use of a left ventricular assist device is a reasonable and safe alternative compared with IABP counterpulsation, giving greater cardiac output and hemodynamic support in patients undergoing high-risk PCI and in those with severe cardiogenic shock. This review outlines a case of severe cardiogenic shock and hemodynamic instability where high-risk PCI is a reasonable option.

  3. High Energy Neutrino Emission Induced by Ultrahigh Energy Nuclei in Cluster Accretion Shocks

    Science.gov (United States)

    Fang, Ke; Olinto, Angela

    2014-03-01

    Accretion shocks in clusters of galaxies can potentially accelerate protons to above 1017 eV and nuclei to ultrahigh energies. High energy neutrinos are produced when these cosmic rays interact with baryons of the massive cluster, or with CMB photons during their extragalactic propagation. In light of the recent IceCube discovery of TeV-PeV neutrinos, we calculate the neutrino emissions from accretion shocks, using a complete numerical propagation method and calibrated based on precision ΛCDM simulation. We pin down the uncertainty and degeneracy in source parameters by taking into account the cosmological evolution of cluster mass, density profiles, velocity dispersions, along with the gravitational gas accretion rates. We find that the neutrino spectrum is distinct from E-2 after considering the cluster mass function which impact both maximum energy and luminosity of the accelerated cosmic rays. We compare the cumulative neutrino flux to sensitivities of the existing and future high energy neutrino observatories. We also discuss the implication of our results on the scenario of cluster accretion shocks being the sources of ultrahigh energy cosmic rays.

  4. The influence of temperature dynamics and dynamic finite ion Larmor radius effects on seeded high amplitude plasma blobs

    Science.gov (United States)

    Held, M.; Wiesenberger, M.; Madsen, J.; Kendl, A.

    2016-12-01

    Thermal effects on the perpendicular convection of seeded pressure blobs in the scrape-off layer of magnetised fusion plasmas are investigated. Our numerical study is based on a four field full-F gyrofluid model, which entails the consistent description of high fluctuation amplitudes and dynamic finite Larmor radius effects. We find that the maximal radial blob velocity increases with the square root of the initial pressure perturbation and that a finite Larmor radius contributes to highly compact blob structures that propagate in the poloidal direction. An extensive parameter study reveals that a smooth transition to this compact blob regime occurs when the finite Larmor radius effect strength, defined by the ratio of the magnetic field aligned component of the ion diamagnetic to the \\boldsymbol{E}× \\boldsymbol{B} vorticity, exceeds unity. The maximal radial blob velocities agree excellently with the inertial velocity scaling law over more than an order of magnitude. We show that the finite Larmor radius effect strength affects the poloidal and total particle transport and present an empirical scaling law for the poloidal and total blob velocities. Distinctions to the blob behaviour in the isothermal limit with constant finite Larmor radius effects are highlighted.

  5. Electron Scattering by High-Frequency Whistler Waves at Earth's Bow Shock

    Science.gov (United States)

    Oka, M.; Wilson, L. B., III; Phan, T. D.; Hull, A. J.; Amano, T.; Hoshino, M.; Argall, M. R.; Le Contel, O.; Agapitov, O.; Gersham, D. J.; hide

    2017-01-01

    Electrons are accelerated to non-thermal energies at shocks in space and astrophysical environments. While different mechanisms of electron acceleration have been proposed, it remains unclear how non-thermal electrons are produced out of the thermal plasma pool. Here, we report in situ evidence of pitch-angle scattering of non-thermal electrons by whistler waves at Earths bow shock. On 2015 November 4, the Magnetospheric Multiscale (MMS) mission crossed the bow shock with an Alfvn Mach number is approximately 11 and a shock angle of approximately 84deg. In the ramp and overshoot regions, MMS revealed bursty enhancements of non-thermal (0.52 keV) electron flux, correlated with high-frequency (0.2 - 0.4 Omega(sub ce), where Omega(sub ce) is the cyclotron frequency) parallel-propagating whistler waves. The electron velocity distribution (measured at 30 ms cadence) showed an enhanced gradient of phase-space density at and around the region where the electron velocity component parallel to the magnetic field matched the resonant energy inferred from the wave frequency range. The flux of 0.5 keV electrons (measured at 1ms cadence) showed fluctuations with the same frequency. These features indicate that non-thermal electrons were pitch-angle scattered by cyclotron resonance with the high-frequency whistler waves. However, the precise role of the pitch-angle scattering by the higher-frequency whistler waves and possible nonlinear effects in the electron acceleration process remains unclear.

  6. High-speed flow visualization in hypersonic, transonic, and shock tube flows

    Science.gov (United States)

    Kleine, H.; Olivier, H.

    2017-02-01

    High-speed flow visualisation has played an important role in the investigations conducted at the Stoßwellenlabor of the RWTH Aachen University for many decades. In addition to applying the techniques of high-speed imaging, this laboratory has been actively developing new or enhanced visualisation techniques and approaches such as various schlieren methods or time-resolved Mach-Zehnder interferometry. The investigated high-speed flows are inherently highly transient, with flow Mach numbers ranging from about M = 0.7 to M = 8. The availability of modern high-speed cameras has allowed us to expand the investigations into problems where reduced reproducibility had so far limited the amount of information that could be extracted from a limited number of flow visualisation records. Following a brief historical overview, some examples of recent studies are given, which represent the breadth of applications in which high-speed imaging has been an essential diagnostic tool to uncover the physics of high-speed flows. Applications include the stability of hypersonic corner flows, the establishment of shock wave systems in transonic airfoil flow, and the complexities of the interactions of shock waves with obstacles of various shapes.

  7. Shock conditions for hypoelastic materials

    Science.gov (United States)

    Renardy, Michael; Rogers, Robert C.

    1993-10-01

    The equations governing the motion of hypoelastic materials (and related models of non-Newtonian fluids) are not in conservation form. Hence there is no obvious formulation of Rankine-Hugoniot jump conditions across a shock. In this paper we demonstrate that a viscosity criterion can be used to obtain meaningful shock conditions. In particular, we discuss shocks of small amplitude. The shock conditions obtained will in general depend on the form of the viscosity term.

  8. Pulsation and Long-Term Variability of the High-Amplitude δ Scuti Star AD Canis Minoris

    Institute of Scientific and Technical Information of China (English)

    Pongsak Khokhuntod; Jian-Ning Fu; Chayan Boonyarak; Kanokwan Marak; Li Chen; Shi-Yang Jiang

    2007-01-01

    Time-series photometry was made for the large-amplitude δ Scuti star AD CMi in 2005 and 2006.High-quality photometric data provided in the literature were used to analyze the pulsation of the star,with the derived multiple frequencies fitted to our new data.Besides the dominant frequency and its harmonics,one low frequency(2.27402 cd-1)is discovered,which provides a reasonable interpretation for the long-noticed luminosity variation at the maximum and minimum light.Combining the nine new times of light maxima determined from the new data with the 64 times collected from the literature.we analyzed the long-term variability of AD CMi with the O-C technique.The results provide the updated value of period of 0.122974478 days.and seem to be in favor of the model of combination of the evolutionary effect and light-time effect of a binary system.of which some parameters are hereby deduced.

  9. Teaching and Assessment of High-Velocity, Low-Amplitude Techniques for the Spine in Predoctoral Medical Education.

    Science.gov (United States)

    Channell, Millicent King

    2016-09-01

    Although national didactic criteria have been set for predoctoral education and assessment in osteopathic manipulative treatment, there is no criterion standard for teaching methods and assessments of osteopathic manipulative treatment competence in colleges of osteopathic medicine. This issue is more pressing with the creation of the single graduate medical education accreditation system by the American Osteopathic Association and Accreditation Council for Graduate Medical Education, which introduced the creation of "osteopathic recognition" for residencies that want to incorporate osteopathic principles and practice into their programs. Residencies with osteopathic recognition may include both osteopathic and allopathic graduates. Increased standardization at the predoctoral level, however, is recommended as osteopathic principles and practice training applications are expanded. The objectives of this article are to review the standards for teaching osteopathic medical students high-velocity, low-amplitude (HVLA) techniques for the spine; to review and discuss the methods used to assess medical students' proficiency in using HVLA; and to propose baseline standards for teaching and assessing HVLA techniques among medical students.

  10. Pulsation and Long-Term Variability of the High-Amplitude δ Scuti Star AD Canis Minoris

    Science.gov (United States)

    Khokhuntod, Pongsak; Fu, Jian-Ning; Boonyarak, Chayan; Marak, Kanokwan; Chen, Li; Jiang, Shi-Yang

    2007-06-01

    Time-series photometry was made for the large-amplitude δ Scuti star AD CMi in 2005 and 2006. High-quality photometric data provided in the literature were used to analyze the pulsation of the star, with the derived multiple frequencies fitted to our new data. Besides the dominant frequency and its harmonics, one low frequency (2.27402 c d-1) is discovered, which provides a reasonable interpretation for the long-noticed luminosity variation at the maximum and minimum light. Combining the nine new times of light maxima determined from the new data with the 64 times collected from the literature, we analyzed the long-term variability of AD CMi with the O-C technique. The results provide the updated value of period of 0.122974478 days, and seem to be in favor of the model of combination of the evolutionary effect and light-time effect of a binary system, of which some parameters are hereby deduced.

  11. The Kep-Cont Mission: Continuing the observation of high-amplitude variable stars in the Kepler field of view

    CERN Document Server

    Molnár, L; Kolenberg, K; Borkovits, T; Antoci, V; Vida, K; Ngeow, C C; Guzik, J A; Plachy, E; Castanheira, B

    2013-01-01

    As a response to the Kepler white paper call, we propose to keep Kepler pointing to its current field of view and continue observing thousands of large amplitude variables (Cepheid, RR Lyrae and delta Scuti stars among others) with high cadence in the Kep-Cont Mission. The degraded pointing stability will still allow observation of these stars with reasonable (better than millimag) precision. The Kep-Cont mission will allow studying the nonradial modes in Blazhko-modulated and first overtone RR Lyrae stars and will give a better view on the period jitter of the only Kepler Cepheid in the field. With continued continuous observation of the Kepler RR Lyrae sample we may get closer to the origin of the century-old Blazhko problem. Longer time-span may also uncover new dynamical effects like apsidal motion in eclipsing binaries. A continued mission will have the advantage of providing unprecedented, many-years-long homogeneous and continuous photometric data of the same targets. We investigate the pragmatic detai...

  12. Patient-centered outcomes of high-velocity, low-amplitude spinal manipulation for low back pain: a systematic review.

    Science.gov (United States)

    Goertz, C M; Pohlman, K A; Vining, R D; Brantingham, J W; Long, C R

    2012-10-01

    Low back pain (LBP) is a well-recognized public health problem with no clear gold standard medical approach to treatment. Thus, those with LBP frequently turn to treatments such as spinal manipulation (SM). Many clinical trials have been conducted to evaluate the efficacy or effectiveness of SM for LBP. The primary objective of this paper was to describe the current literature on patient-centered outcomes following a specific type of commonly used SM, high-velocity low-amplitude (HVLA), in patients with LBP. A systematic search strategy was used to capture all LBP clinical trials of HVLA using our predefined patient-centered outcomes: visual analogue scale, numerical pain rating scale, Roland-Morris Disability Questionnaire, and the Oswestry Low Back Pain Disability Index. Of the 1294 articles identified by our search, 38 met our eligibility criteria. Like previous SM for LBP systematic reviews, this review shows a small but consistent treatment effect at least as large as that seen in other conservative methods of care. The heterogeneity and inconsistency in reporting within the studies reviewed makes it difficult to draw definitive conclusions. Future SM studies for LBP would benefit if some of these issues were addressed by the scientific community before further research in this area is conducted.

  13. Asteroseismology of KIC\\,11754974: a high-amplitude SX\\,Phe pulsator in a 343-day binary system

    CERN Document Server

    Murphy, S J; Kurtz, D W; Suarez, J C; Handler, G; Balona, L A; Smalley, B; Uytterhoeven, K; Szabo, R; Thygesen, A O; Elkin, V; Breger, M; Grigahcene, A; Guzik, J A; Nemec, J M; Southworth, J

    2013-01-01

    The candidate SX Phe star KIC 11754974 shows a remarkably high number of combination frequencies in the Fourier amplitude spectrum: 123 of the 166 frequencies in our multi-frequency fit are linear combinations of independent modes. Predictable patterns in frequency spacings are seen in the Fourier transform of the light curve. We present an analysis of 180 d of short-cadence Kepler photometry and of new spectroscopic data for this evolved, late A-type star. We infer from the 1150-d, long-cadence light curve, and in two different ways, that our target is the primary of a 343-d, non-eclipsing binary system. According to both methods, the mass function is similar, f(M)=0.0207 +/- 0.0003 Msun. The observed pulsations are modelled extensively, using separate, state-of-the-art, time-dependent convection (TDC) and rotating models. The models match the observed temperature and low metallicity, finding a mass of 1.50-1.56 Msun. The models suggest the whole star is metal-poor, and that the low metallicity is not just a...

  14. A novel high amplitude piezoceramic actuator for applications in magnetic resonance elastography: a compliant mechanical amplifier approach

    Science.gov (United States)

    Arani, Arvin; Eskandari, Amiraslan; Ouyang, Puren; Chopra, Rajiv

    2017-08-01

    Piezoceramic actuators are capable of precise positioning with high force, but suffer from limited displacement range, which has hindered their application in the field of magnetic resonance elastography (MRE). The objective of this study was to investigate the feasibility of using a mechanical amplifier in combination with a piezoceramic actuator for the application of endorectal prostate MRE. A five-bar symmetric structure was designed in ANSYS® and manufactured out of brass. Laser vibrometer measurements were used to characterize the amplitude of the CMA actuator while attached to masses in the 0-325 g range and over operating frequencies of 90-500 Hz. The response of the CMA was investigated while mechanically coupled to a balloon type endorectal coil. The resonant frequency of the prototype CMA actuator was predicted within 10% error using ANSYS simulations. The amplification ratio of the CMA actuator was measured to be 10 with the laser vibrometer and 7.6 ± 1.7 (max: 9.2, min: 6.5) using MRE, at a vibration frequency of 200 Hz. Laser vibrometer data also showed that the CMA actuator’s performance did not change whether it was connected to an empty or inflated endorectal. The feasibility of performing endorectal prostate MRE with a CMA actuator was successfully demonstrated in a human volunteer.

  15. A photometric monitoring of bright high-amplitude delta Scuti stars. II. Period updates for seven stars

    CERN Document Server

    Derekas, A; Székely, P; Alfaro, E J; Csák, B; Mészáros, S; Rodríguez, E; Rolland, A; Sarneczky, K; Szabó, G M; Szatmary, K; Varadi, M; Kiss, C; Meszaros, Sz.; Szabo, Gy.M.; Kiss, Cs.

    2003-01-01

    We present new photometric data for seven high-amplitude delta Scuti stars. The observations were acquired between 1996 and 2002, mostly in the Johnson photometric system. For one star (GW UMa), our observations are the first since the discovery of its pulsational nature from the Hipparcos data.The primary goal of this project was to update our knowledge on the period variations of the target stars. For this, we have collected all available photometric observations from the literature and constructed decades-long O-C diagrams of the stars. This traditional method is useful because of the single-periodic nature of the light variations. Text-book examples of slow period evolution (XX Cyg, DY Her, DY Peg) and cyclic period changes due to light-time effect (LITE) in a binary system (SZ Lyn) are updated with the new observations. For YZ Boo, we find a period decrease instead of increase. The previously suggested LITE-solution of BE Lyn (Kiss & Szatmary 1995) is not supported with the new O-C diagram. Instead o...

  16. High-volume hemofiltration reduces the expression of myocardial tumor necrosis factor-alpha in septic shock pigs.

    Science.gov (United States)

    Li, Chunmei; Zhang, Ping; Cheng, Xiuju; Chen, Jianghua

    2013-02-01

    Increasing evidence indicates that the expression of tumor necrosis factor-α (TNF-α) in myocardium correlates with the severity of cardiac dysfunction in septic shock. The aim of this study was to investigate the impact of high-volume hemofiltration (HVHF) on the expression of TNF-α in myocardium in septic shock pigs. Sixteen male Landrace pigs weighing 31 ± 5 kg were randomly assigned to control group (n = 4), septic shock group (n = 6), and HVHF group (septic shock + HVHF, n = 6). All animals were anesthetized and mechanically ventilated. After baseline examinations, septic shock group and HVHF group underwent induction of peritonitis. One hour later, the animals in HVHF group received treatment with HVHF and the treatment was continued for 12 h. As the control of HVHF group, the animals in septic shock group received the same support but hemofiltration. Twelve hours after HVHF therapy, all the animals were sacrificed. TNF-α and nitric oxide (NO) levels in both circulation and myocardium were measured. Compared with those of septic shock animals, the levels of cardiac output, stroke volume, and mean arterial pressure were better maintained in HVHF group. The expression of TNF-α in myocardium in HVHF group was lower than that in septic shock group (44.17 ± 18.70 vs. 92.50 ± 33.89 pg/mg protein, P = 0.015). The difference of TNF-α in circulation between HVHF group and septic shock group was no significance at different time. However, circulating NO in HVHF group was lower than that in septic shock group. These results suggest that HVHF improves hemodynamics and heart dysfunction in septic shock pigs, which may be attributed to reduction of TNF-α in myocardium but not in circulation.

  17. Protostring scattering amplitudes

    Science.gov (United States)

    Thorn, Charles B.

    2016-11-01

    We calculate some tree-level scattering amplitudes for a generalization of the protostring, which is a novel string model implied by the simplest string bit models. These bit models produce a light-cone world sheet which supports s integer moded Grassmann fields. In the generalization we supplement this Grassmann world-sheet system with d =24 -s transverse coordinate world-sheet fields. The protostring corresponds to s =24 and the bosonic string to s =0 . The interaction vertex is a simple overlap with no operator insertions at the break/join point. Assuming that s is even we calculate the multistring scattering amplitudes by bosonizing the Grassmann fields, each pair equivalent to one compactified bosonic field, and applying Mandelstam's interacting string formalism to a system of s /2 compactified and d uncompactified bosonic world-sheet fields. We obtain all amplitudes for open strings with no oscillator excitations and for closed strings with no oscillator excitations and zero winding number. We then study in detail some simple special cases. Multistring processes with maximal helicity violation have much simpler amplitudes. We also specialize to general four-string amplitudes and discuss their high energy behavior. Most of these models are not covariant under the full Lorentz group O (d +1 ,1 ). The exceptions are the bosonic string whose Lorentz group is O (25 ,1 ) and the protostring whose Lorentz group is O (1 ,1 ). The models in between only enjoy an O (1 ,1 )×O (d ) spacetime symmetry.

  18. High Power Proton Beam Shocks and Magnetohydrodynamics in a Mercury Jet Target for a Neutrino Factory

    CERN Document Server

    Fabich, A; Fabjan, Christian

    2002-01-01

    The feasibility of liquid metal jet targets for secondary particle production with high power proton beams has been studied. The main aspects of the thesis were benchmark experiments covering the behaviour of liquid targets under thermal shock waves induced by high power proton beams, and also magnetohydrodynamic effects. Severe challenges were imposed by safety issues and the restricted beam time to the tests in ISOLDE at CERN and at the High Magnetic Field Laboratory at Grenoble. Restricted access times in high radiation level areas were of the order of minutes and in this short time span, the complete experimental setup had to be performed and verified. The involvement of mercury as liquid target material and its activation during beam tests demanded special confinement precautions. The setup for both experiments was based on the use of a high speed camera system for observation of the mercury target. The presence of high radiation or high magnetic field required the installation of the sensitive camera sy...

  19. Cloud Atlas: Discovery of Patchy Clouds and High-amplitude Rotational Modulations in a Young, Extremely Red L-type Brown Dwarf

    Science.gov (United States)

    Lew, Ben W. P.; Apai, Daniel; Zhou, Yifan; Schneider, Glenn; Burgasser, Adam J.; Karalidi, Theodora; Yang, Hao; Marley, Mark S.; Cowan, Nicolas B.; Bedin, Luigi R.; Metchev, Stanimir A.; Radigan, Jacqueline; Lowrance, Patrick J.

    2016-10-01

    Condensate clouds fundamentally impact the atmospheric structure and spectra of exoplanets and brown dwarfs, but the connections between surface gravity, cloud structure, dust in the upper atmosphere, and the red colors of some brown dwarfs remain poorly understood. Rotational modulations enable the study of different clouds in the same atmosphere, thereby providing a method to isolate the effects of clouds. Here, we present the discovery of high peak-to-peak amplitude (8%) rotational modulations in a low-gravity, extremely red (J-K s = 2.55) L6 dwarf WISEP J004701.06+680352.1 (W0047). Using the Hubble Space Telescope (HST) time-resolved grism spectroscopy, we find a best-fit rotational period (13.20 ± 0.14 hr) with a larger amplitude at 1.1 μm than at 1.7 μm. This is the third-largest near-infrared variability amplitude measured in a brown dwarf, demonstrating that large-amplitude variations are not limited to the L/T transition but are present in some extremely red L-type dwarfs. We report a tentative trend between the wavelength dependence of relative amplitude, possibly proxy for small dust grains lofted in the upper atmosphere, and the likelihood of large-amplitude variability. By assuming forsterite as a haze particle, we successfully explain the wavelength-dependent amplitude with submicron-sized haze particle sizes of around 0.4 μm. W0047 links the earlier spectral and later spectral type brown dwarfs in which rotational modulations have been observed; the large amplitude variations in this object make this a benchmark brown dwarf for the study of cloud properties close to the L/T transition.

  20. Low-amplitude, high-frequency electromagnetic field exposure causes delayed and reduced growth in Rosa hybrida.

    Science.gov (United States)

    Grémiaux, Alexandre; Girard, Sébastien; Guérin, Vincent; Lothier, Jérémy; Baluška, František; Davies, Eric; Bonnet, Pierre; Vian, Alain

    2016-01-15

    It is now accepted that plants perceive high-frequency electromagnetic field (HF-EMF). We wondered if the HF-EMF signal is integrated further in planta as a chain of reactions leading to a modification of plant growth. We exposed whole small ligneous plants (rose bush) whose growth could be studied for several weeks. We performed exposures at two different development stages (rooted cuttings bearing an axillary bud and 5-leaf stage plants), using two high frequency (900MHz) field amplitudes (5 and 200Vm(-1)). We achieved a tight control on the experimental conditions using a state-of-the-art stimulation device (Mode Stirred Reverberation Chamber) and specialized culture-chambers. After the exposure, we followed the shoot growth for over a one-month period. We observed no growth modification whatsoever exposure was performed on the 5-leaf stage plants. When the exposure was performed on the rooted cuttings, no growth modification was observed on Axis I (produced from the elongation of the axillary bud). Likewise, no significant modification was noted on Axis II produced at the base of Axis I, that came from pre-formed secondary axillary buds. In contrast, Axis II produced at the top of Axis I, that came from post-formed secondary buds consistently displayed a delayed and significant reduced growth (45%). The measurements of plant energy uptake from HF-EMF in this exposure condition (SAR of 7.2 10(-4)Wkg(-1)) indicated that this biological response is likely not due to thermal effect. These results suggest that exposure to electromagnetic field only affected development of post-formed organs.

  1. High Shock, High Frequency Characteristics of a Mechanical Isolator for a Piezoresistive Accelerometer, the ENDEVCO 7270AM6*

    Energy Technology Data Exchange (ETDEWEB)

    BATEMAN,VESTA I.; BROWN,FREDERICK A.; NUSSER,MICHAEL A.

    2000-07-01

    A mechanical isolator has been developed for a piezoresistive accelerometer. The purpose of the isolator is to mitigate high frequency shocks before they reach the accelerometer because the high frequency shocks may cause the accelerometer to resonate. Since the accelerometer is undamped, it often breaks when it resonates. The mechanical isolator was developed in response to impact test requirements for a variety of structures at Sandia National Laboratories (SNL). An Extended Technical Assistance Program (ETAP) with the accelerometer manufacturer has resulted in a commercial mechanically isolated accelerometer that is available to the general public, the ENDEVCO 7270AM6*, for three shock acceleration ranges of 6,000 g, 20,000 g, and 60,000 g. The in-axis response shown in this report has acceptable frequency domain performance from DC to 10 kHz and 10(XO)over a temperature range of {minus}65 F to +185 F. Comparisons with other isolated accelerometers show that the ENDEVCO 7270AM6 has ten times the bandwidth of any other commercial isolator. ENDEVCO 7270AM6 cross-axis response is shown in this report.

  2. A high-density ERP study reveals latency, amplitude, and topographical differences in multiple sclerosis patients versus controls.

    LENUS (Irish Health Repository)

    Whelan, R

    2012-02-01

    OBJECTIVE: To quantify latency, amplitude and topographical differences in event-related potential (ERP) components between multiple sclerosis (MS) patients and controls and to compare ERP findings with results from the paced auditory serial addition test (PASAT). METHODS: Fifty-four subjects (17 relapsing remitting (RRMS) patients, 16 secondary progressive (SPMS) patients, and 21 controls) completed visual and auditory oddball tasks while data were recorded from 134 EEG channels. Latency and amplitude differences, calculated using composite mean amplitude measures, were tested using an ANOVA. Topographical differences were tested using statistical parametric mapping (SPM). RESULTS: In the visual modality, P2, P3 amplitudes and N2 latency were significantly different across groups. In the auditory modality, P2, N2, and P3 latencies and N1 amplitude were significantly different across groups. There were no significant differences between RRMS and SPMS patients on any ERP component. There were topographical differences between MS patients and controls for both early and late components for the visual modality, but only in the early components for the auditory modality. PASAT score correlated significantly with auditory P3 latency for MS patients. CONCLUSIONS: There were significant ERP differences between MS patients and controls. SIGNIFICANCE: The present study indicated that both early sensory and later cognitive ERP components are impaired in MS patients relative to controls.

  3. Impact of an Elevated Temperature Environment on Sn-Ag-Cu Interconnect Board Level High-G Mechanical Shock Performance

    Science.gov (United States)

    Lee, Tae-Kyu; Chen, Zhiqiang; Baty, Greg; Bieler, Thomas R.; Kim, Choong-Un

    2016-12-01

    The mechanical stability of Sn-Ag-Cu interconnects with low and high silver content against mechanical shock at room and elevated temperatures was investigated. With a heating element-embedded printed circuit board design, a test temperature from room temperature to 80°C was established. High impact shock tests were applied to isothermally pre-conditioned ball-grid array interconnects. Under cyclic shock testing, degradation and improved shock performances were identified associated with test temperature variation and non-solder mask defined and solder-mask defined pad design configuration differences. Different crack propagation paths were observed, induced by the effect of the elevated temperature test conditions and isothermal aging pre-conditions.

  4. Shocks and Cool Cores: An ALMA View of Massive Galaxy Cluster Formation at High Redshifts

    Science.gov (United States)

    Basu, Kaustuv

    2017-07-01

    These slides present some recent results on the Sunyaev-Zel'dovich (SZ) effect imaging of galaxy cluster substructures. The advantage of SZ imaging at high redshifts or in the low density cluster outskirts is already well-known. Now with ALMA a combination of superior angular resolution and high sensitivity is available. One example is the first ALMA measurement of a merger shock at z=0.9 in the famous El Gordo galaxy cluster. Here comparison between SZ, X-ray and radio data enabled us to put constraints on the shock Mach number and magnetic field strength for a high-z radio relic. Second example is the ALMA SZ imaging of the core region of z=1.4 galaxy cluster XMMU J2235.2-2557. Here ALMA data provide an accurate measurement of the thermal pressure near the cluster center, and from a joint SZ/X-ray analysis we find clear evidence for a reduced core temperature. This result indicate that a cool core establishes itself early enough in the cluster formation history while the gas accumulation is still continuing. The above two ALMA measurements are among several other recent SZ results that shed light on the formation process of massive clusters at high redshifts.

  5. Unsteadiness of Shock Wave/Boundary Layer Interaction in Supersonic Cascade

    Institute of Scientific and Technical Information of China (English)

    Hong-JuanWang; Ke-JunCai; 等

    1996-01-01

    An investigation of the passive control of shock wave/boundary layer interaction for reducing the amplitude of the shock oscillation was conducted on the circular arc-wedge(CW) profile cascade in a 220290mm transonic compressor cascade wind tunnel.A perforated surface with a cavity beneath it was positioned on the suction surface of the blade at the location of shock impingement.The Schlieren and high-speed photographs for flow over pervorated blade are presented and compared with the results for solid blades,With the perforated surface,the high-speen photographs indicated an significant suppression of shock osciation.

  6. Neural responses to the mechanical parameters of a high velocity, low amplitude spinal manipulation: effect of preload parameters

    Science.gov (United States)

    Reed, William. R.; Long, Cynthia R.; Kawchuk, Gregory N.; Pickar, Joel G.

    2014-01-01

    Objective The purpose of this study was to determine how the preload that precedes a high velocity low amplitude spinal manipulation (HVLA-SM) affects muscle spindle input from lumbar paraspinal muscles both during and after the HVLA-SM. Methods Primary afferent activity from muscle spindles in lumbar paraspinal muscles were recorded from the L6 dorsal root in anesthetized cats. HVLA-SM of the L6 vertebra was preceded either by no preload or by systematic changes in the preload magnitude, duration, and the presence or absence of a downward incisural point (DIP). Immediate effects of preload on muscle spindle responses to the HVLA-SM were determined by comparing mean instantaneous discharge frequencies (MIF) during the HVLA-SM’s thrust phase with baseline. Longer lasting effects of preload on spindle responses to the HVLA-SM were determined by comparing MIF during slow ramp and hold movement of the L6 vertebra before and following the HVLA-SM. Results The smaller compared to the larger preload magnitude and the longer compared to the shorter preload duration significantly increased (P=0.02 and P=0.04) respectively) muscle spindle responses during the HVLA-SM thrust. The absence of preload had the greatest effect on the change in MIF. Interactions between preload magnitude, duration and DIP often produced statistically significant but arguably physiologically modest changes in the passive signaling properties of the muscle spindle following the manipulation. Conclusion Because preload parameters in this animal model were shown to affect neural responses to an HVLA-SM, preload characteristics should be taken into consideration when judging this intervention’s therapeutic benefit in both clinical efficacy studies and in clinical practice. PMID:24387888

  7. High temperature shock tube experiments and kinetic modeling study of diisopropyl ketone ignition and pyrolysis

    KAUST Repository

    Barari, Ghazal

    2017-03-10

    Diisopropyl ketone (DIPK) is a promising biofuel candidate, which is produced using endophytic fungal conversion. In this work, a high temperature detailed combustion kinetic model for DIPK was developed using the reaction class approach. DIPK ignition and pyrolysis experiments were performed using the UCF shock tube. The shock tube oxidation experiments were conducted between 1093K and 1630K for different reactant compositions, equivalence ratios (φ=0.5–2.0), and pressures (1–6atm). In addition, methane concentration time-histories were measured during 2% DIPK pyrolysis in argon using cw laser absorption near 3400nm at temperatures between 1300 and 1400K near 1atm. To the best of our knowledge, current ignition delay times (above 1050K) and methane time histories are the first such experiments performed in DIPK at high temperatures. Present data were used as validation targets for the new kinetic model and simulation results showed fair agreement compared to the experiments. The reaction rates corresponding to the main consumption pathways of DIPK were found to have high sensitivity in controlling the reactivity, so these were adjusted to attain better agreement between the simulation and experimental data. A correlation was developed based on the experimental data to predict the ignition delay times using the temperature, pressure, fuel concentration and oxygen concentration.

  8. The strengthening mechanism of a nickel-based alloy after laser shock processing at high temperatures

    Directory of Open Access Journals (Sweden)

    Yinghong Li, Liucheng Zhou, Weifeng He, Guangyu He, Xuede Wang, Xiangfan Nie, Bo Wang, Sihai Luo and Yuqin Li

    2013-01-01

    Full Text Available We investigated the strengthening mechanism of laser shock processing (LSP at high temperatures in the K417 nickel-based alloy. Using a laser-induced shock wave, residual compressive stresses and nanocrystals with a length of 30–200 nm and a thickness of 1 μm are produced on the surface of the nickel-based alloy K417. When the K417 alloy is subjected to heat treatment at 900 °C after LSP, most of the residual compressive stress relaxes while the microhardness retains good thermal stability; the nanocrystalline surface has not obviously grown after the 900 °C per 10 h heat treatment, which shows a comparatively good thermal stability. There are several reasons for the good thermal stability of the nanocrystalline surface, such as the low value of cold hardening of LSP, extreme high-density defects and the grain boundary pinning of an impure element. The results of the vibration fatigue experiments show that the fatigue strength of K417 alloy is enhanced and improved from 110 to 285 MPa after LSP. After the 900 °C per 10 h heat treatment, the fatigue strength is 225 MPa; the heat treatment has not significantly reduced the reinforcement effect. The feature of the LSP strengthening mechanism of nickel-based alloy at a high temperature is the co-working effect of the nanocrystalline surface and the residual compressive stress after thermal relaxation.

  9. Proline content and protein patterns in Eucalyptus grandis shoots submitted to high and low temperature shocks

    Directory of Open Access Journals (Sweden)

    Gustavo M. Souza

    2004-07-01

    Full Text Available Proline content and protein patterns changes in response to temperature shocks of both acclimated and non acclimated E. grandis shoots cultivated in vitro were investigated. Analysis of soluble proteins through SDS-PAGE and proline were carried out after 12h at 12ºC (cold acclimation or 33ºC (heat acclimation, and immediately after temperature shocks at 41ºC and 0ºC. Analyses were also performed 24h after the temperature shocks (recovery period. Temperature treatment at 0ºC did not change soluble protein patterns both in acclimatized and non acclimatized plants, whereas cold temperature induced high proline levels, which kept relatively high after recovery period. Three novel, probably HSPs, proteins (90.5, 75 and 39 kDa were observed in both acclimated and non acclimated plants submitted to high temperatures. Plants exposed at 41ºC were able to recover from heat shocks after 24h, whereas they did not recover completely from cold shocks. The effect of the acclimation period on the recovering (homeostasis varied depending on the parameter evaluated, and type and duration of the temperature shock.As respostas às mudanças de temperatura de plantas aclimatadas e não aclimatadas de E. grandis cultivadas in vitro foram avaliadas considerando alterações dos níveis de prolina e proteínas solúveis totais. Análises de proteínas solúveis através de SDS-PAGE e prolina foram realizadas após 12h a 12ºC (aclimatação ao frio ou a 33ºC (aclimatação ao calor, e imediatamente depois dos choques térmicos a 41ºC e 0ºC. Análises também foram realizadas após um período de 24h depois dos choques térmicos (período de recuperação. O tratamento de temperatura a 0ºC não alterou o padrão de proteínas nas plantas aclimatadas e não aclimatadas, entretanto a temperatura baixa induziu altos níveis de prolina, que se mantiveram relativamente altos após o período de recuperação. Três novas proteínas (90,5, 75 e 39 kDa, provavelmente

  10. Thermal Shock Behavior of Single Crystal Oxide Refractive Concentrators for High Temperatures Solar Thermal Propulsion

    Science.gov (United States)

    Zhu, Dongming; Choi, Sung R.; Jacobson, Nathan S.; Miller, Robert A.

    1999-01-01

    Single crystal oxides such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium-aluminum-garnet (Y3Al5O12, or YAG), magnesium oxide (MgO) and sapphire (Al2O3) have been considered as refractive secondary concentrator materials for high temperature solar propulsion applications. However, thermal mechanical reliability of the oxide components in severe thermal environments during space mission sun/shade transitions is of great concern. In this paper, critical mechanical properties of these oxide crystals are determined by the indentation technique. Thermal shock resistance of the oxides is evaluated using a high power CO, laser under high temperature-high thermal gradients. Thermal stress fracture behavior and failure mechanisms of these oxide materials are investigated under various temperature and heating conditions.

  11. High interindividual variability in dose-dependent reduction in speed of movement after exposing C. elegans to shock waves.

    Science.gov (United States)

    Angstman, Nicholas B; Kiessling, Maren C; Frank, Hans-Georg; Schmitz, Christoph

    2015-01-01

    In blast-related mild traumatic brain injury (br-mTBI) little is known about the connections between initial trauma and expression of individual clinical symptoms. Partly due to limitations of current in vitro and in vivo models of br-mTBI, reliable prediction of individual short- and long-term symptoms based on known blast input has not yet been possible. Here we demonstrate a dose-dependent effect of shock wave exposure on C. elegans using shock waves that share physical characteristics with those hypothesized to induce br-mTBI in humans. Increased exposure to shock waves resulted in decreased mean speed of movement while increasing the proportion of worms rendered paralyzed. Recovery of these two behavioral symptoms was observed during increasing post-traumatic waiting periods. Although effects were observed on a population-wide basis, large interindividual variability was present between organisms exposed to the same highly controlled conditions. Reduction of cavitation by exposing worms to shock waves in polyvinyl alcohol resulted in reduced effect, implicating primary blast effects as damaging components in shock wave induced trauma. Growing worms on NGM agar plates led to the same general results in initial shock wave effect in a standard medium, namely dose-dependence and high interindividual variability, as raising worms in liquid cultures. Taken together, these data indicate that reliable prediction of individual clinical symptoms based on known blast input as well as drawing conclusions on blast input from individual clinical symptoms is not feasible in br-mTBI.

  12. Shock adhesion test for composite bonded assembly using a high pulsed power generator

    Science.gov (United States)

    Gay, E.; Berthe, L.; Buzaud, E.; Boustie, M.; Arrigoni, M.

    2013-07-01

    In a context of the rising use of composite assemblies in aeronautic or defense fields, the assessment of their strength is a key issue. The method developed in this study attempts to provide solutions. A shock adhesion test based on short compressive loads, obtained by a high pulsed power generator, is proposed as a proof test to ensure the quality of composite bonded assemblies. A calibrated load induces a local tensile stress able to damage the bond interface. The high pulsed power source is the GEnerateur de Pression Isentropique device (Isentropic Pressure Generator), used to generate the required stresses, with a 450 ns pulse duration to test assemblies above the mm thickness range. The understanding of the mechanisms of wave propagation and tensile stress generation within these multilayer assemblies are scientific challenges. The ability of the technique to induce a tensile stress able to disbond the laminates and the assemblies is demonstrated. This paper details the response of carbon epoxy laminates and their bonded assemblies to a shock loading near the damage threshold.

  13. Critical parameters and universal amplitude ratios of two-dimensional spin-S Ising models using high- and low-temperature expansions

    CERN Document Server

    Butera, P

    2003-01-01

    For the study of Ising models of general spin S on the square lattice, we have combined our recently extended high-temperature expansions with the low-temperature expansions derived some time ago by Enting, Guttmann and Jensen. We have computed for the first time various critical parameters and improved the estimates of others. Moreover the properties of hyperscaling and of universality (spin S independence) of exponents and of various dimensionless amplitude combinations have been verified accurately. Assuming the validity of the lattice-lattice scaling, from our estimates of critical amplitudes for the square lattice we have also obtained estimates of the corresponding amplitudes for the spin S Ising model on the triangular, honeycomb, and kagome` lattices.

  14. Large-amplitude Fourier transformed high-harmonic alternating current cyclic voltammetry: kinetic discrimination of interfering Faradaic processes at glassy carbon and at boron-doped diamond electrodes.

    Science.gov (United States)

    Zhang, Jie; Guo, Si-Xuan; Bond, Alan M; Marken, Frank

    2004-07-01

    Significant advantages of Fourier transformed large-amplitude ac higher (second to eighth) harmonics relative to responses obtained with conventional small-amplitude ac or dc cyclic voltammetric methods have been demonstrated with respect to (i) the suppression of capacitive background currents, (ii) the separation of the reversible reduction of [Ru(NH(3))(6)](3+) from the overlapping irreversible oxygen reduction process under conditions where aerobic oxygen remains present in the electrochemical cell, and (iii) the kinetic resolution of the reversible [Ru(NH(3))(6)](3+/2+) process in mixtures of [Fe(CN)(6)](3-) and [Ru(NH(3))(6)](3+) at appropriately treated boron-doped diamond electrodes, even when highly unfavorable [Fe(CN)(6)](3-) to [Ru(NH(3))(6)](3+) concentration ratios are employed. Theoretical support for the basis of kinetic discrimination in large-amplitude higher harmonic ac cyclic voltammetry is provided.

  15. Amplitude dependent closest tune approach

    CERN Document Server

    Tomas Garcia, Rogelio; Franchi, Andrea; Maclean, Ewen Hamish; CERN. Geneva. ATS Department

    2016-01-01

    Recent observations in the LHC point to the existence of an amplitude dependent closest tune approach. However this dynamical behavior and its underlying mechanism remain unknown. This effect is highly relevant for the LHC as an unexpectedly closest tune approach varying with amplitude modifies the frequency content of the beam and, hence, the Landau damping. Furthermore the single particle stability would also be affected by this effect as it would modify how particles with varying amplitudes approach and cross resonances. We present analytic derivations that lead to a mechanism generating an amplitude dependent closest tune approach.

  16. Level set methods for detonation shock dynamics using high-order finite elements

    Energy Technology Data Exchange (ETDEWEB)

    Dobrev, V. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Grogan, F. C. [Univ. of California, San Diego, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kolev, T. V. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Rieben, R [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Tomov, V. Z. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-05-26

    Level set methods are a popular approach to modeling evolving interfaces. We present a level set ad- vection solver in two and three dimensions using the discontinuous Galerkin method with high-order nite elements. During evolution, the level set function is reinitialized to a signed distance function to maintain ac- curacy. Our approach leads to stable front propagation and convergence on high-order, curved, unstructured meshes. The ability of the solver to implicitly track moving fronts lends itself to a number of applications; in particular, we highlight applications to high-explosive (HE) burn and detonation shock dynamics (DSD). We provide results for two- and three-dimensional benchmark problems as well as applications to DSD.

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

    Science.gov (United States)

    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.

  18. Electromagnetic Structure and Electron Acceleration in Shock–Shock Interaction

    Science.gov (United States)

    Nakanotani, Masaru; Matsukiyo, Shuichi; Hada, Tohru; Mazelle, Christian X.

    2017-09-01

    A shock–shock interaction is investigated by using a one-dimensional full particle-in-cell simulation. The simulation reproduces the collision of two symmetrical high Mach number quasi-perpendicular shocks. The basic structure of the shocks and ion dynamics is similar to that obtained by previous hybrid simulations. The new aspects obtained here are as follows. Electrons are already strongly accelerated before the two shocks collide through multiple reflection. The reflected electrons self-generate waves upstream between the two shocks before they collide. The waves far upstream are generated through the right-hand resonant instability with the anomalous Doppler effect. The waves generated near the shock are due to firehose instability and have much larger amplitudes than those due to the resonant instability. The high-energy electrons are efficiently scattered by the waves so that some of them gain large pitch angles. Those electrons can be easily reflected at the shock of the other side. The accelerated electrons form a power-law energy spectrum. Due to the accelerated electrons, the pressure of upstream electrons increases with time. This appears to cause the deceleration of the approaching shock speed. The accelerated electrons having sufficiently large Larmor radii are further accelerated through the similar mechanism working for ions when the two shocks are colliding.

  19. High Order Numerical Methods for LES of Turbulent Flows with Shocks

    Science.gov (United States)

    Kotov, D. V.; Yee, H. C.; Hadjadj, A.; Wray, A.; Sjögreen, B.

    2014-01-01

    Simulation of turbulent flows with shocks employing explicit subgrid-scale (SGS) filtering may encounter a loss of accuracy in the vicinity of a shock. In this work we perform a comparative study of different approaches to reduce this loss of accuracy within the framework of the dynamic Germano SGS model. One of the possible approaches is to apply Harten's subcell resolution procedure to locate and sharpen the shock, and to use a one-sided test filter at the grid points adjacent to the exact shock location. The other considered approach is local disabling of the SGS terms in the vicinity of the shock location. In this study we use a canonical shock-turbulence interaction problem for comparison of the considered modifications of the SGS filtering procedure. For the considered test case both approaches show a similar improvement in the accuracy near the shock.

  20. A new delirium phenotype with rapid high amplitude onset and nearly as rapid reversal: Central Coast Australia Delirium Intervention Study

    Directory of Open Access Journals (Sweden)

    Regal PJ

    2015-02-01

    , and 45%/80% for the Delirium Index. General medicine and geriatric medicine groups had similar outcomes.Conclusion: This delirium phenotype selects for a rapid high amplitude critical decline in attention, executive function, IADL, and apathy that recovers almost as rapidly.Keywords: delirium, inattention, executive function, dementia

  1. Theoretical Research on Thermal Shock Resistance of Ultra-High Temperature Ceramics Focusing on the Adjustment of Stress Reduction Factor

    Directory of Open Access Journals (Sweden)

    Daining Fang

    2013-02-01

    Full Text Available The thermal shock resistance of ceramics depends on not only the mechanical and thermal properties of materials, but also the external constraint and thermal condition. So, in order to study the actual situation in its service process, a temperature-dependent thermal shock resistance model for ultra-high temperature ceramics considering the effects of the thermal environment and external constraint was established based on the existing theory. The present work mainly focused on the adjustment of the stress reduction factor according to different thermal shock situations. The influences of external constraint on both critical rupture temperature difference and the second thermal shock resistance parameter in either case of rapid heating or cooling conditions had been studied based on this model. The results show the necessity of adjustment of the stress reduction factor in different thermal shock situations and the limitations of the applicable range of the second thermal shock resistance parameter. Furthermore, the model was validated by the finite element method.

  2. High-power laser shock-induced dynamic fracture of aluminum and microscopic observation of samples

    Directory of Open Access Journals (Sweden)

    Fan Zhang

    2015-01-01

    Full Text Available High-power laser induced shocks generated by “ShenGuang II” laser facility has been used to study spall fracture of polycrystalline aluminum at strain rates more than 106/s. The free surface velocity histories of shock-loaded samples, 150 μm thick and with initial temperature from 293 K to 873 K, have been recorded using velocity interferometer system for any reflector (VISAR. From the free surface velocity profile, spall strength and yield stress are calculated, it demonstrates that spall strength will decline and yield strength increase with initial temperature. The loaded samples are recovered to obtain samples' section and free surface metallographic pictures through Laser Scanning Confocal Microscopy. It is found that there are more micro-voids and more opportunity to appear bigger voids near the spall plane and the grain size increases with temperature slowly but smoothly except the sharply change at 893 K (near melting point. Besides, the fracture mechanisms change from mainly intergranular fracture to transgranular fracture with the increase of initial temperature.

  3. Highly Excited H2 in Herbig-Haro 7: Formation Pumping in Shocked Molecular Gas?

    CERN Document Server

    Pike, R E; Burton, M G; Chrysostomou, A

    2016-01-01

    We have obtained K-band spectra at R~5,000 and angular resolution 0.3" of a section of the Herbig-Haro 7 (HH7) bow shock, using the Near-Infrared Integral Field Spectrograph at Gemini North. Present in the portion of the data cube corresponding to the brightest part of the bow shock are emission lines of H2 with upper state energies ranging from ~6,000 K up to the dissociation energy of H2, ~50,000 K. Because of low signal-to-noise ratios, the highest excitation lines cannot be easily seen elsewhere in the observed region. However, excitation temperatures, measured throughout much of the observed region using lines from levels as high as 25,000 K, are a strong function of upper level energy, indicating that the very highest levels are populated throughout. The level populations in the brightest region are well fit by a two-temperature model, with 98.5% of the emitting gas at T=1800 K and 1.5% at T=5200 K. The bulk of the H2 line emission in HH7, from the 1,800 K gas, has previously been well modeled by a cont...

  4. Effect of high repetition laser shock peening on biocompatibility and corrosion resistance of magnesium

    Science.gov (United States)

    Caralapatti, Vinodh Krishna; Narayanswamy, Sivakumar

    2017-02-01

    Magnesium, as a biomaterial has the potential to replace conventional implant materials owing to its numerous advantages. However, high corrosion rate is a major obstacle that has to be addressed for its implementation as implants. This study aims to evaluate the feasibility and effects of High Repetition Laser Shock Peening (HRLSP) on biocompatibility and corrosion resistance of Mg samples and as well as to analyze the effect of operational parameters such as peening with overlap on corrosion rate. From the results obtained using hydrogen evolution and mass loss methods, it was found that corrosion rates of both 0% overlap and 66% overlap peened samples reduced by more than 50% compared to that of unpeened sample and sample peened with 66% overlap exhibited least corrosion. The biocompatibility of peened Mg samples was also enhanced as there was neither rapid pH variation nor large hydrogen bubble formation around samples.

  5. Ion acoustic shock and solitary waves in highly relativistic plasmas with nonextensive electrons and positrons

    Science.gov (United States)

    Hafez, M. G.; Talukder, M. R.; Hossain Ali, M.

    2016-01-01

    The Korteweg-de Vries Burgers (KdVB) -like equation is derived to study the characteristics of nonlinear propagation of ion acoustic solitions in a highly relativistic plasma containing relativistic ions and nonextensive distribution of electrons and positrons using the well known reductive perturbation technique. The KdVB-like equation is solved employing the Bernoulli's equation method taking unperturbed positron to electron concentration ratio, electron to positron temperature ratio, strength of nonextensivity, ion kinematic viscosity, and highly relativistic streaming factor. It is found that these parameters significantly modify the structures of the solitonic excitation. The ion acoustic shock profiles are observed due to the influence of ion kinematic viscosity. In the absence of dissipative term to the KdVB equation, compressive and rarefactive solitons are observed in case of superthermality, but only compressive solitons are found for the case of subthermality.

  6. Distributive shock due to systemic capillary leak syndrome treated with high-dose immunosuppression.

    Science.gov (United States)

    Sheehan, James Robert; Keating, Liza; Chan, Antoni; Walden, Andrew

    2013-04-09

    A female patient in her 60s presented with a history of malaise, chills, headache and vomiting. She was in shock on presentation with a high haematocrit and a low albumin with evidence of rhabdomyolysis. Severe limb and truncal oedema developed with worsening hypotension leading to intensive care unit admission for multiple organ support. Extensive radiological, microbiological and immunological work up was negative with the exception of a monoclonal gammopathy. A review of patient investigations led to a diagnosis of Clarkson's disease. Treatment with high-dose methylprednisolone and intravenous immunoglobulins led to a rapid decline in the creatine kinase (CK) level and vasopressor requirements. The patient was discharged home on long-term terbutaline and has made a good recovery.

  7. The chemical shock tube as a tool for studying high-temperature chemical kinetics

    Science.gov (United States)

    Brabbs, Theodore A.

    1986-01-01

    Although the combustion of hydrocarbons is our primary source of energy today, the chemical reactions, or pathway, by which even the simplest hydro-carbon reacts with atmospheric oxygen to form CO2 and water may not always be known. Furthermore, even when the reaction pathway is known, the reaction rates are always under discussion. The shock tube has been an important and unique tool for building a data base of reaction rates important in the combustion of hydrocarbon fuels. The ability of a shock wave to bring the gas sample to reaction conditions rapidly and homogeneously makes shock-tube studies of reaction kinetics extremely attractive. In addition to the control and uniformity of reaction conditions achieved with shock-wave methods, shock compression can produce gas temperatures far in excess of those in conventional reactors. Argon can be heated to well over 10 000 K, and temperatures around 5000 K are easily obtained with conventional shock-tube techniques. Experiments have proven the validity of shock-wave theory; thus, reaction temperatures and pressures can be calculated from a measurement of the incident shock velocity. A description is given of the chemical shock tube and auxiliary equipment and of two examples of kinetic experiments conducted in a shock tube.

  8. Measurement of high-pressure shock waves in cryogenic deuterium-tritium ice layered capsule implosions on NIF.

    Science.gov (United States)

    Robey, H F; Moody, J D; Celliers, P M; Ross, J S; Ralph, J; Le Pape, S; Berzak Hopkins, L; Parham, T; Sater, J; Mapoles, E R; Holunga, D M; Walters, C F; Haid, B J; Kozioziemski, B J; Dylla-Spears, R J; Krauter, K G; Frieders, G; Ross, G; Bowers, M W; Strozzi, D J; Yoxall, B E; Hamza, A V; Dzenitis, B; Bhandarkar, S D; Young, B; Van Wonterghem, B M; Atherton, L J; Landen, O L; Edwards, M J; Boehly, T R

    2013-08-09

    The first measurements of multiple, high-pressure shock waves in cryogenic deuterium-tritium (DT) ice layered capsule implosions on the National Ignition Facility have been performed. The strength and relative timing of these shocks must be adjusted to very high precision in order to keep the DT fuel entropy low and compressibility high. All previous measurements of shock timing in inertial confinement fusion implosions [T. R. Boehly et al., Phys. Rev. Lett. 106, 195005 (2011), H. F. Robey et al., Phys. Rev. Lett. 108, 215004 (2012)] have been performed in surrogate targets, where the solid DT ice shell and central DT gas regions were replaced with a continuous liquid deuterium (D2) fill. This report presents the first experimental validation of the assumptions underlying this surrogate technique.

  9. Challenging shock models with SOFIA OH observations in the high-mass star-forming region Cepheus A

    Science.gov (United States)

    Gusdorf, A.; Güsten, R.; Menten, K. M.; Flower, D. R.; Pineau des Forêts, G.; Codella, C.; Csengeri, T.; Gómez-Ruiz, A. I.; Heyminck, S.; Jacobs, K.; Kristensen, L. E.; Leurini, S.; Requena-Torres, M. A.; Wampfler, S. F.; Wiesemeyer, H.; Wyrowski, F.

    2016-01-01

    Context. OH is a key molecule in H2O chemistry, a valuable tool for probing physical conditions, and an important contributor to the cooling of shock regions around high-mass protostars. OH participates in the re-distribution of energy from the protostar towards the surrounding Interstellar Medium. Aims: Our aim is to assess the origin of the OH emission from the Cepheus A massive star-forming region and to constrain the physical conditions prevailing in the emitting gas. We thus want to probe the processes at work during the formation of massive stars. Methods: We present spectrally resolved observations of OH towards the protostellar outflows region of Cepheus A with the GREAT spectrometer onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) telescope. Three triplets were observed at 1834.7 GHz, 1837.8 GHz, and 2514.3 GHz (163.4 μm, 163.1 μm between the 2Π1/2 J = 1/2 states, and 119.2 μm, a ground transition between the 2Π3/2 J = 3/2 states), at angular resolutions of 16.̋3, 16.̋3, and 11.̋9, respectively. We also present the CO (16-15) spectrum at the same position. We compared the integrated intensities in the redshifted wings to the results of shock models. Results: The two OH triplets near 163 μm are detected in emission, but with blending hyperfine structure unresolved. Their profiles and that of CO (16-15) can be fitted by a combination of two or three Gaussians. The observed 119.2 μm triplet is seen in absorption, since its blending hyperfine structure is unresolved, but with three line-of-sight components and a blueshifted emission wing consistent with that of the other lines. The OH line wings are similar to those of CO, suggesting that they emanate from the same shocked structure. Conclusions: Under this common origin assumption, the observations fall within the model predictions and within the range of use of our model only if we consider that four shock structures are caught in our beam. Overall, our comparisons suggest that

  10. On the Fielding of a High Gain, Shock-Ignited Target on the National Ignitiion Facility in the Near Term

    Energy Technology Data Exchange (ETDEWEB)

    Perkins, L J; Betti, R; Schurtz, G P; Craxton, R S; Dunne, A M; LaFortune, K N; Schmitt, A J; McKenty, P W; Bailey, D S; Lambert, M A; Ribeyre, X; Theobald, W R; Strozzi, D J; Harding, D R; Casner, A; Atzemi, S; Erbert, G V; Andersen, K S; Murakami, M; Comley, A J; Cook, R C; Stephens, R B

    2010-04-12

    Shock ignition, a new concept for igniting thermonuclear fuel, offers the possibility for a near-term ({approx}3-4 years) test of high gain inertial confinement fusion on the National Ignition Facility at less than 1MJ drive energy and without the need for new laser hardware. In shock ignition, compressed fusion fuel is separately ignited by a strong spherically converging shock and, because capsule implosion velocities are significantly lower than those required for conventional hotpot ignition, fusion energy gains of {approx}60 may be achievable on NIF at laser drive energies around {approx}0.5MJ. Because of the simple all-DT target design, its in-flight robustness, the potential need for only 1D SSD beam smoothing, minimal early time LPI preheat, and use of present (indirect drive) laser hardware, this target may be easier to field on NIF than a conventional (polar) direct drive hotspot ignition target. Like fast ignition, shock ignition has the potential for high fusion yields at low drive energy, but requires only a single laser with less demanding timing and spatial focusing requirements. Of course, conventional symmetry and stability constraints still apply. In this paper we present initial target performance simulations, delineate the critical issues and describe the immediate-term R&D program that must be performed in order to test the potential of a high gain shock ignition target on NIF in the near term.

  11. High-Pressure Shock Compression of Solids VIII The Science and Technology of High-Velocity Impact

    CERN Document Server

    Chhabildas, Lalit C; Horie, Yasuyuki

    2005-01-01

    Research in the field of shock physics and ballistic impact has always been intimately tied to progress in development of facilities for accelerating projectiles to high velocity and instrumentation for recording impact phenomena. The chapters of this book, written by leading US and European experts, cover a broad range of topics and address researchers concerned with questions of material behaviour under impulsive loading and the equations of state of matter, as well as the design of suitable instrumentation such as gas guns and high-speed diagnostics. Applications include high-speed impact dynamics, the inner composition of planets, syntheses of new materials and materials processing. Among the more technologically-oriented applications treated is the testing of the flight characteristics of aeroballistic models and the assessment of impacts in the aerospace industry.

  12. Cloud Atlas: Discovery of Patchy Clouds and High-amplitude Rotational Modulations In a Young, Extremely Red L-type Brown Dwarf

    CERN Document Server

    Lew, Ben W P; Zhou, Yifan; Schneider, Glenn; Burgasser, Adam J; Karalidi, Theodora; Yang, Hao; Marley, Mark S; Cowan, N B; Bedin,; R., L; Metchev, Stanimir A; Radigan, Jacqueline; Lowrance, Patrick J

    2016-01-01

    Condensate clouds fundamentally impact the atmospheric structure and spectra of exoplanets and brown dwarfs but the connections between surface gravity, cloud structure, dust in the upper atmosphere, and the red colors of some brown dwarfs remain poorly understood. Rotational modulations enable the study of different clouds in the same atmosphere, thereby providing a method to isolate the effects of clouds. Here we present the discovery of high peak-to-peak amplitude (8%) rotational modulations in a low-gravity, extremely red (J-Ks=2.55) L6 dwarf WISEP J004701.06+680352.1 (W0047). Using the Hubble Space Telescope (HST) time-resolved grism spectroscopy we find a best-fit rotational period (13.20$\\pm$0.14 hours) with a larger amplitude at 1.1 micron than at 1.7 micron. This is the third largest near-infrared variability amplitude measured in a brown dwarf, demonstrating that large-amplitude variations are not limited to the L/T transition but are present in some extremely red L-type dwarfs. We report a tentativ...

  13. Collisionless shocks driven by 800 nm laser pulses generate high-energy carbon ions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H.; Shen, B. F., E-mail: bfshen@mail.shcnc.ac.cn; Wang, W. P.; Xu, Y.; Liu, Y. Q.; Liang, X. Y.; Leng, Y. X.; Li, R. X., E-mail: ruxinli@mail.shcnc.ac.cn; Xu, Z. Z. [State Key Laboratory of High Filed Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Yan, X. Q.; Chen, J. E. [State Key Laboratory of Nuclear Physics and Technology, Institute of Heavy Ion Physics, Peking University, Beijing 100871 (China)

    2015-01-15

    We present experimental studies on ion acceleration from diamond-like carbon (DLC) foils irradiated by 800 nm, linearly polarized laser pulses with peak intensity of 1.7 × 10{sup 19 }W/cm{sup 2} to 3.5 × 10{sup 19 }W/cm{sup 2} at oblique incidence. Diamond-like carbon foils are heated by the prepulse of a high-contrast laser pulse and expand to form plasmas of near-critical density caused by thermal effect before the arrival of the main pulse. It is demonstrated that carbon ions are accelerated by a collisionless shock wave in slightly overdense plasma excited by forward-moving hot electrons generated by the main pulse.

  14. Analyzing the effect of high repetition laser shock peening on dynamic corrosion rate of magnesium

    Science.gov (United States)

    Caralapatti, Vinodh Krishna; Narayanswamy, Sivakumar

    2017-08-01

    Magnesium as implant material is being investigated extensively due to its superior suitability. With corrosion rate being the major obstacle, this paper aims to determine the effects of high repetition laser shock peening (HRLSP) on the dynamic corrosion rate of magnesium. While there is lot of research on corrosion of magnesium, in this work, a specially designed test bench was used for characterization of dynamic corrosion to mimic the physiological conditions experienced by the implant inside human body. From the results, it can be inferred that corrosion rate of peened samples reduced by at least 6 times compared to unpeened sample and sample peened with 66% overlap 1 scans exhibited the least corrosion. The wettability of the samples was also determined as a measure to analyze the effects of HRLSP on biocompatibility. In addition, peening is seen to induce surface corrosion, which minimizes the risks of implant failure.

  15. Oblique propagation of ion acoustic shock waves in weakly and highly relativistic plasmas with nonthermal electrons and positrons

    Science.gov (United States)

    Hafez, M. G.; Roy, N. C.; Talukder, M. R.; Hossain Ali, M.

    2016-09-01

    This work investigates the oblique nonlinear propagation of ion acoustic (IA) shock waves for both weakly and highly relativistic plasmas composed of nonthermal electrons and positrons with relativistic thermal ions. The KdVB-like equation, involving dispersive, weakly transverse dispersive, nonlinearity and dissipative coefficients, is derived employing the well known reductive perturbation method. The integration of this equation is carried out by the {tanh} method taking the stable shock formation condition into account. The effects of nonthermal electrons and positrons, nonthermal electrons with isothermal positrons, isothermal electrons with nonthermal positrons, and isothermal electrons and positrons on oblique propagation of IA shock waves in weakly relativistic regime are described. Furthermore, the effects of plasma parameters on oblique propagation of IA shock waves in highly relativistic regime are discussed and compared with weakly relativistic case. It is seen that the plasma parameters within certain limits significantly modify the structures of the IA shock waves in both cases. The results may be useful for better understanding of the interactions of charged particles with extra-galactic jets as well as astrophysical compact objects.

  16. Streptococcal toxic shock syndrome

    OpenAIRE

    Gvozdenović Ljiljana; Pasternak Janko; Milovanović Stanislav; Ivanov Dejan; Milić Saša

    2010-01-01

    Introduction. Streptococcal toxic shock syndrome is now recognized as a toxin-mediated, multisystem illness. It is characterized by an early onset of shock with multiorgan failure and continues to be associated with high morbidity and mortality, caused by group A Streptococcus pyogenes. The symptoms for staphylococcal and streptococcal toxic shock syndrome are similar. Streptococcal toxic shock syndrome was not well described until 1993, when children who had suffered from varicella pre...

  17. Hidden focal EEG seizures during prolonged suppressions and high-amplitude bursts in early infantile epileptic encephalopathy.

    Science.gov (United States)

    Al-Futaisi, Amna; Banwell, Brenda; Ochi, Ayako; Hew, Justine; Chu, Bill; Oishi, Makoto; Otsubo, Hiroshi

    2005-05-01

    We report on a 27-month-old female with atypical early infantile epileptic encephalopathy (EIEE), who developed tonic spasms, partial seizures and myoclonic jerks along with episodic bradycardia at 5 days. We recorded digital electroencephalography (EEG) using either an 11-channel neonatal montage or 19 channel scalp electrodes, at 200 Hz sampling rate, and a single reference for a minimum of 30 min. At 18 days EEG showed suppression-burst (SB) patterns during wakefulness and sleep. Tonic spasms concomitant with bursts recorded as brief, low-amplitude fast waves. EEG at 8 months showed increased amplitude of bursts to 1 mV and extension of suppression periods to 65 s. By increasing recording sensitivity, we detected focal epileptiform discharges of slow rhythmic sharp and slow waves building to 30 microV during suppression periods. Status epilepticus occurred at 16 months. EEG at 27 months returned to the previous SB pattern with rare partial seizures. This report is the first to demonstrate clinically silent focal EEG seizures during prolonged suppression periods in atypical EIEE by off-line digital EEG. Digital EEG sensitivity can reveal covert electrical activity during suppression periods in epileptic neonates and infants.

  18. Relationships among physical properties as indicators of high temperature deformation or post-shock thermal annealing in ordinary chondrites

    Science.gov (United States)

    Friedrich, Jon M.; Ruzicka, Alex; Macke, Robert J.; Thostenson, James O.; Rudolph, Rebecca A.; Rivers, Mark L.; Ebel, Denton S.

    2017-04-01

    Collisions and attendant shock compaction must have been important for the accretion and lithification of planetesimals, including the parent bodies of chondrites, but the conditions under which these occurred are not well constrained. A simple model for the compaction of chondrites predicts that shock intensity as recorded by shock stage should be related to porosity and grain fabric. To test this model, we studied sixteen ordinary chondrites of different groups (H, L, LL) using X-ray computed microtomography (μCT) to measure porosity and metal fabric, ideal gas pycnometry and 3D laser scanning to determine porosity, and optical microscopy (OM) to determine shock stage. These included a subsample of six chondrites previously studied using transmission electron microscopy (TEM) to characterize microstructures in olivine. Combining with previous data, results support the simple model in general, but not for chondrites with low shock-porosity-foliation (low-SPF chondrites). These include Kernouvé (H6), Portales Valley (H6/7), Butsura (H6), Park (L6), GRO 85209 (L6), Estacado (H6), MIL 99301 (LL6), Spade (H6), and Queen's Mercy (H6), among others. The data for these meteorites are best explained by high ambient heat during or after shock. Low-SPF chondrites tend to have older 40Ar/39Ar ages (∼4435-4526 Ma) than other, non-low-SPF type 6 chondrites in this study. We conclude that the H, L, and LL asteroids all were shock-compacted at an early stage while warm, with collisions occurring during metamorphic heating of the parent bodies. Results ultimately bear on whether chondrite parent bodies have internal structures more akin to a metamorphosed onion shell or metamorphosed rubble pile, and on the nature of accretion and lithification processes for planetesimals.

  19. Relationships among physical properties as indicators of high temperature deformation or post-shock thermal annealing in ordinary chondrites

    Energy Technology Data Exchange (ETDEWEB)

    Friedrich, Jon M.; Ruzicka, Alex; Macke, Robert J.; Thostenson, James O.; Rudolph, Rebecca A.; Rivers, Mark L.; Ebel, Denton S.

    2017-04-01

    Collisions and attendant shock compaction must have been important for the accretion and lithification of planetesimals, including the parent bodies of chondrites, but the conditions under which these occurred are not well constrained. A simple model for the compaction of chondrites predicts that shock intensity as recorded by shock stage should be related to porosity and grain fabric. To test this model, we studied sixteen ordinary chondrites of different groups (H, L, LL) using X-ray computed microtomography (μCT) to measure porosity and metal fabric, ideal gas pycnometry and 3D laser scanning to determine porosity, and optical microscopy (OM) to determine shock stage. These included a subsample of six chondrites previously studied using transmission electron microscopy (TEM) to characterize microstructures in olivine. Combining with previous data, results support the simple model in general, but not for chondrites with low shock-porosity-foliation (low-SPF chondrites). These include Kernouvé (H6), Portales Valley (H6/7), Butsura (H6), Park (L6), GRO 85209 (L6), Estacado (H6), MIL 99301 (LL6), Spade (H6), and Queen’s Mercy (H6), among others. The data for these meteorites are best explained by high ambient heat during or after shock. Low-SPF chondrites tend to have older 40Ar/39Ar ages (~4435–4526 Ma) than other, non-low-SPF type 6 chondrites in this study. We conclude that the H, L, and LL asteroids all were shock-compacted at an early stage while warm, with collisions occurring during metamorphic heating of the parent bodies. Results ultimately bear on whether chondrite parent bodies have internal structures more akin to a metamorphosed onion shell or metamorphosed rubble pile, and on the nature of accretion and lithification processes for planetesimals.

  20. A review of crustacean sensitivity to high amplitude underwater noise: Data needs for effective risk assessment in relation to UK commercial species.

    Science.gov (United States)

    Edmonds, Nathan J; Firmin, Christopher J; Goldsmith, Denise; Faulkner, Rebecca C; Wood, Daniel T

    2016-07-15

    High amplitude anthropogenic noise is associated with adverse impacts among a variety of organisms but detailed species-specific knowledge is lacking in relation to effects upon crustaceans. Brown crab (Cancer pagurus), European lobster (Homarus gammarus) and Norway lobster (Nephrops norvegicus) together represent the most valuable commercial fishery in the UK (Defra, 2014). Critical evaluation of literature reveals physiological sensitivity to underwater noise among N. norvegicus and closely related crustacean species, including juvenile stages. Current evidence supports physiological sensitivity to local, particle motion effects of sound production in particular. Derivation of correlative relationships between the introduction of high amplitude impulsive noise and crustacean distribution/abundance is hindered by the coarse resolution of available data at the present time. Future priorities for research are identified and argument for enhanced monitoring under current legislative frameworks outlined. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

  1. Finite difference solutions to shocked acoustic waves

    Science.gov (United States)

    Walkington, N. J.; Eversman, W.

    1983-01-01

    The MacCormack, Lambda and split flux finite differencing schemes are used to solve a one dimensional acoustics problem. Two duct configurations were considered, a uniform duct and a converging-diverging nozzle. Asymptotic solutions for these two ducts are compared with the numerical solutions. When the acoustic amplitude and frequency are sufficiently high the acoustic signal shocks. This condition leads to a deterioration of the numerical solutions since viscous terms may be required if the shock is to be resolved. A continuous uniform duct solution is considered to demonstrate how the viscous terms modify the solution. These results are then compared with a shocked solution with and without viscous terms. Generally it is found that the most accurate solutions are those obtained using the minimum possible viscosity coefficients. All of the schemes considered give results accurate enough for acoustic power calculations with no one scheme performing significantly better than the others.

  2. Resolving the shocked gas in HH54 with Herschel: CO line mapping at high spatial and spectral resolution

    CERN Document Server

    Bjerkeli, P; Brinch, C; Olofsson, G; Santangelo, G; Cabrit, S; Benedettini, M; Black, J H; Herczeg, G; Justtanont, K; Kristensen, L E; Larsson, B; Nisini, B; Tafalla, M

    2014-01-01

    The HH54 shock is a Herbig-Haro object, located in the nearby Chamaeleon II cloud. Observed CO line profiles are due to a complex distribution in density, temperature, velocity, and geometry. Resolving the HH54 shock wave in the far-infrared cooling lines of CO constrain the kinematics, morphology, and physical conditions of the shocked region. We used the PACS and SPIRE instruments on board the Herschel space observatory to map the full FIR spectrum in a region covering the HH54 shock wave. Complementary Herschel-HIFI, APEX, and Spitzer data are used in the analysis as well. The observed features in the line profiles are reproduced using a 3D radiative transfer model of a bow-shock, constructed with the Line Modeling Engine code (LIME). The FIR emission is confined to the HH54 region and a coherent displacement of the location of the emission maximum of CO with increasing J is observed. The peak positions of the high-J CO lines are shifted upstream from the lower J CO lines and coincide with the position of ...

  3. Cardiac thrombus developing after an accidental high-voltage electric shock in a child.

    Science.gov (United States)

    Akın, Alper; Bilici, Meki; Demir, Fikri; Gözü Pirinççioğlu, Ayfer; Yavuz, Celal

    2015-01-01

    Electric shock is a condition that may affect various organ systems and potentially cause death. Cardiac findings vary from asymptomatic mild injury to fatal myocardial involvement. Herein we present a five-year-old boy with a cardiac thrombus developing after an accidental electrical shock. Cardiac arrhythmias and evidence of ischemia have been reported after electric shock; we were, however, unable to identify an earlier case report of intracardiac thrombosis related to electric shock. Findings such as elevated cardiac enzymes and systolic dysfunction, which indicate myocardial damage following electric shock, were present in our patient. We think that the cardiac thrombus might have resulted from the myocardial damage and the slowed intracardiac blood flow related to systolic dysfunction. As the thrombus was thought to have been formed through known mechanisms, it was treated traditionally. However, further data regarding the etiology and management of such thrombi is needed.

  4. Ultra-high Energy Cosmic Rays and Neutrinos from Gamma-Ray Bursts, Hypernovae and Galactic Shocks

    CERN Document Server

    Mészáros, P

    2014-01-01

    I review gamma-ray burst models (GRBs) and observations, and discuss the possible production of ultra-high energy cosmic rays and neutrinos in both the standard internal shock models and the newer generation of photospheric and hadronic GRB models, in the light of current constraints imposed by IceCube, Auger and TA observations. I then discuss models that have been proposed to explain the recent astrophysical PeV neutrino observations, including star-forming and star-burst galaxies, hypernovae and galaxy accretion and merger shocks.

  5. Equations of state and melting curve of boron carbide in the high-pressure range of shock compression

    Energy Technology Data Exchange (ETDEWEB)

    Molodets, A. M., E-mail: molodets@icp.ac.ru; Golyshev, A. A.; Shakhrai, D. V. [Russian Academy of Sciences, Institute for Problems in Chemical Physics (Russian Federation)

    2017-03-15

    We have constructed the equations of state for crystalline boron carbide B{sub 11}C (C–B–C) and its melt under high dynamic and static pressures. A kink on the shock adiabat for boron carbide has been revealed in the pressure range near 100 GPa, and the melting curve with negative curvature in the pressure range 0–120 GPa has been calculated. The results have been used for interpreting the kinks on the shock adiabat for boron carbide in the pressure range of 0–400 GPa.

  6. Hot electron generation and energy coupling in planar experiments with shock ignition high intensity lasers

    Science.gov (United States)

    Wei, M. S.; Krauland, C.; Alexander, N.; Zhang, S.; Peebles, J.; Beg, F. N.; Theobald, W.; Borwick, E.; Ren, C.; Yan, R.; Haberberger, D.; Betti, R.; Campbell, E. M.

    2016-10-01

    Hot electrons produced in nonlinear laser plasma interactions are critical issues for shock ignition (SI) laser fusion. We conducted planar target experiments to characterize hot electron and energy coupling using the high energy OMEGA EP laser system at SI high intensities. Targets were multilayered foils consisting of an ablator (either plastic or lithium) and a Cu layer to facilitate hot electron detection via fluorescence and bremsstrahlung measurements. The target was first irradiated by multi-kJ, low-intensity UV beams to produce a SI-relevant mm-scale hot ( 1 keV) preformed plasma. The main interaction pulse, either a kJ 1-ns UV pulse with intensity 1.6x1016 Wcm-2 or a kJ 0.1-ns IR pulse with intensity up to 2x1017 Wcm-2was injected at varied timing delays. The high intensity IR beam was found to strongly interact with underdense plasmas breaking into many filaments near the quarter critical density region followed by propagation of those filaments to critical density, producing hot electrons with Thot 70 keV in a well-contained beam. While the high intensity UV beam showed poor energy coupling. Details of the experiments and the complementary PIC modeling results will be presented. Work supported by U.S. DOE under contracts DE-NA0002730 (NLUF) and DE-SC0014666 (HEDLP).

  7. High-dose insulin: a consecutive case series in toxin-induced cardiogenic shock.

    Science.gov (United States)

    Holger, Joel S; Stellpflug, Samuel J; Cole, Jon B; Harris, Carson R; Engebretsen, Kristin M

    2011-08-01

    Cardiovascular medication overdoses can be difficult to treat. Various treatment modalities are currently recommended. To describe patient outcomes and adverse events of high-dose insulin therapy in consecutive overdose patients in cardiogenic shock after implementation of a high-dose insulin protocol (1-10 U/kg/h, while avoiding or tapering off vasopressors). This is an observational consecutive case series of patients identified from a registry. Data were collected by retrospective chart review of patients treated by our toxicology service with this protocol from February 2007 until March 2010. Twelve patients were treated with high-dose insulin. The mean age was 36.5 years (SD 11.7). Seven patients had pre-existing vasopressor therapy, and all were tapered off vasopressors while on insulin. Two patients experienced pulseless electrical activity cardiac arrest prior to high-dose insulin therapy. Intravenous fat emulsion was given to two patients. The mean maximum insulin infusion rate was 8.35 U/kg/h (mean = 8.35, SD 6.34). The mean duration of insulin infusion was 23.5 h (SD 19.7). The mean duration of glucose infusion post-insulin was 25.2 h (SD 17.7). The primary toxins were β-blocker in five, calcium channel blocker in two, combined β-blocker/calcium channel blocker in two, tricyclic antidepressant in one, and polydrug in 2. CLINICAL OUTCOMES: Eleven of 12 patients survived. One patient expired 9 h into insulin therapy from cardiac arrest shortly after the insulin was stopped and a vasopressor re-initiated (protocol deviation). Six patients experienced a total of 19 hypoglycemic events. Hypokalemia (defined as insulin therapy. One patient was discharged with mild anoxic injury thought due to pulseless electrical activity arrest prior to insulin therapy. Three of these 12 patients have been previously described in published case reports. High-dose insulin therapy based on a 1-10 U/kg/h dosing guideline and recommending avoidance of vasopressors appears to be

  8. Numerical Simulation for Thermal Shock Resistance of Ultra-High Temperature Ceramics Considering the Effects of Initial Stress Field

    Directory of Open Access Journals (Sweden)

    Weiguo Li

    2011-01-01

    Full Text Available Taking the hafnium diboride ceramic as an example, the effects of heating rate, cooling rate, thermal shock initial temperature, and external constraint on the thermal shock resistance (TSR of ultra-high temperature ceramics (UHTCs were studied through numerical simulation in this paper. The results show that the external constraint has an approximately linear influence on the critical rupture temperature difference of UHTCs. The external constraint prepares a compressive stress field in the structure because of the predefined temperature field, and this compressive stress field relieves the tension stress in the structure when it is cooled down and then it improves the TSR of UHTCs. As the thermal shock initial temperature, a danger heating rate (or cooling rate exists where the critical temperature difference is the lowest.

  9. Quantum-statistical equation-of-state models of dense plasmas: high-pressure Hugoniot shock adiabats

    CERN Document Server

    Pain, Jean-Christophe

    2007-01-01

    We present a detailed comparison of two self-consistent equation-of-state models which differ from their electronic contribution: the atom in a spherical cell and the atom in a jellium of charges. It is shown that both models are well suited for the calculation of Hugoniot shock adiabats in the high pressure range (1 Mbar-10 Gbar), and that the atom-in-a-jellium model provides a better treatment of pressure ionization. Comparisons with experimental data are also presented. Shell effects on shock adiabats are reviewed in the light of these models. They lead to additional features not only in the variations of pressure versus density, but also in the variations of shock velocity versus particle velocity. Moreover, such effects are found to be responsible for enhancement of the electronic specific heat.

  10. Protein synthesis is not required for acquisition, consolidation, and extinction of high foot-shock active avoidance training.

    Science.gov (United States)

    González-Salinas, Sofía; Medina, Andrea C; Marín-Vignando, Vera; Ruiz-López, Clyo X; Quirarte, Gina L; Prado-Alcalá, Roberto A

    2015-01-01

    Long-term memory of active avoidance in mice is not disturbed by administration of protein synthesis inhibitors (PSIs) when relatively high levels of training are used, whereas a detrimental effect is produced with lower levels of training. PSIs also disrupt extinction of avoidance behaviors in rodents, but it is not clear whether PSIs also affect this form of learning when the behavior to be extinguished was produced by a high level of training. Experiment 1 demonstrated that rats treated with the PSI cycloheximide (CXM) 30 min before training developed normal acquisition after training with either high or low foot-shock stimulation, but that memory consolidation was hindered only after low foot-shock training. Experiment 2 demonstrated that CXM disrupted extinction when administered before the first of a series of extinction sessions when low foot-shock intensity was used during training; in contrast, after training with a higher foot-shock, the PSI treatment only interfered transiently with extinction. These results indicate that acquisition, consolidation, and extinction of active avoidance learning produced by high aversive stimulation are not dependent on protein synthesis and that these processes are governed by mechanisms different from those underlying moderate forms of learning.

  11. High interindividual variability in dose-dependent reduction in speed of movement after exposing C. elegans to shock waves

    Directory of Open Access Journals (Sweden)

    Nicholas Baker Angstman

    2015-02-01

    Full Text Available In blast-related mild traumatic brain injury (br-mTBI little is known about the connections between initial trauma and expression of individual clinical symptoms. Partly due to limitations of current in vitro and in vivo models of br-mTBI, reliable prediction of individual short- and long-term symptoms based on known blast input has not yet been possible. Here we demonstrate a dose-dependent effect of shock wave exposure on C. elegans using shock waves that share physical characteristics with those hypothesized to induce br-mTBI in humans. Increased exposure to shock waves resulted in decreased mean speed of movement while increasing the proportion of worms rendered paralyzed. Recovery of these two behavioral symptoms was observed during increasing post-traumatic waiting periods. Although effects were observed on a population-wide basis, large interindividual variability was present between organisms exposed to the same highly controlled conditions. Reduction of cavitation by exposing worms to shock waves in polyvinyl alcohol resulted in reduced effect, implicating primary blast effects as damaging components in shock wave induced trauma. Growing worms on NGM agar plates led to the same general results in initial shock wave effect in a standard medium, namely dose-dependence and high interindividual variability, as raising worms in liquid cultures. Taken together, these data indicate that reliable prediction of individual clinical symptoms based on known blast input as well as drawing conclusions on blast input from individual clinical symptoms is not feasible in br-mTBI.

  12. Laser shocks: A tool for experimental simulation of damage into materials

    Energy Technology Data Exchange (ETDEWEB)

    Boustie, M.; Cuq Lelandais, J. P.; Berthe, L.; Ecault, R. [Institut PPRIME, Departement Physique et Mecanique des Materiaux, CNRS-ENSMA-Universite de Poitiers, 1 av Clement Ader, 86961 FUTUROSCOPE Cedex (France); CEA-DAM Valduc, 21120 Is-sur-Tille (France); Laboratoire Procedes et Ingenierie en Mecanique et Materiaux (CNRS), Arts et Metiers ParisTech, 151 bd de l' Hopital, 75013 PARIS (France); Institut PPRIME, Departement Physique et Mecanique des Materiaux, CNRS-ENSMA-Universite de Poitiers, 1 av Clement Ader, 86961 FUTUROSCOPE Cedex (France)

    2012-07-30

    High power laser irradiation of solids results in a strong shock wave propagation, driving very high amplitude pressure loadings with very short durations. These particular characteristics offer the possibility to study the behaviour of matter under extreme dynamic conditions in continuity with what is possible with the conventional generators of shock (launchers of projectiles, explosives). An advantage of laser shocks is a possible recovery of the shocked samples presenting the metallurgical effects of the shock in most cases. We introduce the principle of the laser shock generation, the characterization of these shocks, the principal mechanisms and effects associated with their propagation in the solids. We show how laser shocks can be a laboratory tool for simulating shock effects at ultra high strain rate, providing a high in information experimental layout for validation of damage modelling on an extended strain rate range compared to conventional shock generators. New data have been obtained with ultra short femtosecond range irradiation. Experimental data gathered through post mortem observation, time resolved velocity measurement are shown along with numerical associated simulations, showing the possibility to predict the damage behaviour of metallic targets under extreme strain rate up to 10{sup 8} s{sup -1}.

  13. Effects and Sustainability of a 13-Day High-Intensity Shock Microcycle in Soccer

    Directory of Open Access Journals (Sweden)

    Patrick Wahl

    2014-06-01

    Full Text Available The preseason in soccer is a short period of 6-8 weeks where conditional abilities, technical and tactical elements need to be trained. Therefore, time is lacking to perform long term preparation periods for different abilities, especially endurance training. There is evidence that the implementation of high-intensity shock microcycles in preseason training could be one way to improve physical performance in a short period of time. Therefore, the purpose of the present study was to examine the effects and the sustainability of a high-intensity shock microcycle on soccer specific performance. Over 2 weeks, 12 male soccer players (26.1 ± 4.5 years performed 12 high-intensity training (HIT sessions in addition to their usual training. Before (pre, 6 days (6d and 25 days (25d after training, subjects performed Counter Movement Jump (CMJ, Repeated-Sprint Ability (RSA test and Yo-Yo Intermittent Recovery Test Level 2 (YYIR2. Mean sprint time (RSAMean (cohen’s d = -1.15, percentage decrement score (RSAIndex (cohen’s d = -1.99 and YYIR2 (cohen’s d = +1.92 improved significantly from pre to 6d. 25d after, values showed a significant reduction for YYIR2 (cohen’s d = -0.81 and small to moderate but not significant increase for RSAMean (cohen’s d = +0.37 and RSAIndex (cohen’s d = +0.7 compared to 6d values. Small but no significant increases were found for CMJ (cohen’s d = +0.33 and no significant and substantial changes were found for RSABest (cohen’s d = -0.07 from pre to 6d. For competitive soccer players, block periodization of HIT offers a promising way to largely improve RSA and YYIR2 in a short period of time. Despite moderate to large decreases in RSAIndex and YYIR2 performance in the 19 day period without HIT, values still remained significantly higher 25d after the last HIT session compared to pre-values. However, it might be necessary to include isolated high-intensity sessions after a HIT training block in order to maintain the

  14. Experimental investigation of shock wave - bubble interaction

    Energy Technology Data Exchange (ETDEWEB)

    Alizadeh, Mohsen

    2010-04-09

    In this work, the dynamics of laser-generated single cavitation bubbles exposed to lithotripter shock waves has been investigated experimentally. The energy of the impinging shock wave is varied in several steps. High-speed photography and pressure field measurements simultaneously with image acquisition provide the possibility of capturing the fast bubble dynamics under the effect of the shock wave impact. The pressure measurement is performed using a fiber optic probe hydrophone (FOPH) which operates based on optical diagnostics of the shock wave propagating medium. After a short introduction in chapter 1 an overview of the previous studies in chapter 2 is presented. The reported literatures include theoretical and experimental investigations of several configurations of physical problems in the field of bubble dynamics. In chapter 3 a theoretical description of propagation of a shock wave in a liquid like water has been discussed. Different kinds of reflection of a shock wave at an interface are taken into account. Undisturbed bubble dynamics as well as interaction between a planar shock wave and an initially spherical bubble are explored theoretically. Some physical parameters which are important in this issue such as the velocity of the shock-induced liquid jet, Kelvin impulse and kinetic energy are explained. The shock waves are generated in a water filled container by a focusing piezoelectric generator. The shock wave profile has a positive part with pulse duration of ∼1 μs followed by a longer tension tail (i.e. ∼3 μs). In chapter 4 high-speed images depict the propagation of a shock wave in the water filled tank. The maximum pressure is also derived for different intensity levels of the shock wave generator. The measurement is performed in the free field (i.e. in the absence of laser-generated single bubbles). In chapter 5 the interaction between lithotripter shock waves and laserinduced single cavitation bubbles is investigated experimentally. An

  15. Experimental investigation of shock wave - bubble interaction

    Energy Technology Data Exchange (ETDEWEB)

    Alizadeh, Mohsen

    2010-04-09

    In this work, the dynamics of laser-generated single cavitation bubbles exposed to lithotripter shock waves has been investigated experimentally. The energy of the impinging shock wave is varied in several steps. High-speed photography and pressure field measurements simultaneously with image acquisition provide the possibility of capturing the fast bubble dynamics under the effect of the shock wave impact. The pressure measurement is performed using a fiber optic probe hydrophone (FOPH) which operates based on optical diagnostics of the shock wave propagating medium. After a short introduction in chapter 1 an overview of the previous studies in chapter 2 is presented. The reported literatures include theoretical and experimental investigations of several configurations of physical problems in the field of bubble dynamics. In chapter 3 a theoretical description of propagation of a shock wave in a liquid like water has been discussed. Different kinds of reflection of a shock wave at an interface are taken into account. Undisturbed bubble dynamics as well as interaction between a planar shock wave and an initially spherical bubble are explored theoretically. Some physical parameters which are important in this issue such as the velocity of the shock-induced liquid jet, Kelvin impulse and kinetic energy are explained. The shock waves are generated in a water filled container by a focusing piezoelectric generator. The shock wave profile has a positive part with pulse duration of ∼1 μs followed by a longer tension tail (i.e. ∼3 μs). In chapter 4 high-speed images depict the propagation of a shock wave in the water filled tank. The maximum pressure is also derived for different intensity levels of the shock wave generator. The measurement is performed in the free field (i.e. in the absence of laser-generated single bubbles). In chapter 5 the interaction between lithotripter shock waves and laserinduced single cavitation bubbles is investigated experimentally. An

  16. Eliminating the effect of phase shift between injection current and amplitude modulation in DFB-LD WMS for high-precision measurement.

    Science.gov (United States)

    Wei, Wei; Chang, Jun; Liu, Yuanyuan; Chen, Xi; Liu, Zhaojun; Qin, Zengguang; Wang, Qiang

    2016-05-01

    Phase shift between the injection current and amplitude modulation due to the characteristics of diode lasers is discussed in this paper. Phase shift has no apparent regularity, but it has an obvious effect on measurement results, especially for high-precision measurement. A new method is proposed to suppress the influence of this phase shift. Water vapor is chosen as the target gas for experiment in this paper. A new detection system with the new method applied is presented and shows much better performance than the traditional wavelength modulation spectroscopy detection system. Phase shift fluctuation between the injection current and amplitude modulation is suppressed from 0.72 deg to 0.07 deg; accuracy is improved from 0.88 ppm to 0.16 ppm.

  17. Shock Tube Measurement of the High-Temperature Rate Constant for OH + CH3 → Products.

    Science.gov (United States)

    Wang, Shengkai; Li, Sijie; Davidson, David F; Hanson, Ronald K

    2015-08-20

    The reaction between hydroxyl (OH) and methyl radicals (CH3) is critical to hydrocarbon oxidation. Motivated by the sparseness of its high-temperature rate constant data and the large uncertainties in the existing literature values, the current study has remeasured the overall rate constant of the OH + CH3 reaction and extended the measurement temperature range to 1214-1933 K, using simultaneous laser absorption diagnostics for OH and CH3 radicals behind incident and reflected shock waves. tert-Butyl hydroperoxide and azomethane were used as pyrolytic sources for the OH and CH3 radicals, respectively. The current study bridged the temperature ranges of existing experimental data, and good agreement is seen between the current measurement and some previous experimental and theoretical high-temperature studies. A recommendation for the rate constant expression of the title reaction, based on the weighted average of the high-temperature data from selected studies, is given by k1 = 4.19 × 10(1)(T/K)(3.15) exp(5270 K/T) cm(3) mol(-1) s(-1) ±30%, which is valid over 1000-2500 K.

  18. Numerical Simulation on Seismic Response of the Filled Joint under High Amplitude Stress Waves Using Finite-Discrete Element Method (FDEM

    Directory of Open Access Journals (Sweden)

    Xiaolin Huang

    2016-12-01

    Full Text Available This paper numerically investigates the seismic response of the filled joint under high amplitude stress waves using the combined finite-discrete element method (FDEM. A thin layer of independent polygonal particles are used to simulate the joint fillings. Each particle is meshed using the Delaunay triangulation scheme and can be crushed when the load exceeds its strength. The propagation of the 1D longitude wave through a single filled joint is studied, considering the influences of the joint thickness and the characteristics of the incident wave, such as the amplitude and frequency. The results show that the filled particles under high amplitude stress waves mainly experience three deformation stages: (i initial compaction stage; (ii crushing stage; and (iii crushing and compaction stage. In the initial compaction stage and crushing and compaction stage, compaction dominates the mechanical behavior of the joint, and the particle area distribution curve varies little. In these stages, the transmission coefficient increases with the increase of the amplitude, i.e., peak particle velocity (PPV, of the incident wave. On the other hand, in the crushing stage, particle crushing plays the dominant role. The particle size distribution curve changes abruptly with the PPV due to the fragments created by the crushing process. This process consumes part of wave energy and reduces the stiffness of the filled joint. The transmission coefficient decreases with increasing PPV in this stage because of the increased amount of energy consumed by crushing. Moreover, with the increase of the frequency of the incident wave, the transmission coefficient decreases and fewer particles can be crushed. Under the same incident wave, the transmission coefficient decreases when the filled thickness increases and the filled particles become more difficult to be crushed.

  19. Comparison between holographic interferometry and high-speed videography techniques in the study of the reflection of plane shock waves

    Science.gov (United States)

    Barbosa, Filipe J.; Skews, Beric W.

    1997-05-01

    Double exposure holographic interferometry and high speed laser shadowgraph photography and videography are used to investigate the mutual reflection of two plane shock waves. Normally research on the transition from regular to Mach reflection is undertaken by allowing a plane shock wave to impinge on a wedge. However due to the boundary layer growth on the wedge, regular reflection persists at wedge angles higher than that allowed for by inviscid shock wave theory. Several bifurcated shock tubes have been constructed, wherein an initially planar shock wave is split symmetrically into two and then recombined at the trailing edge of a wedge. The plane of symmetry acts as an ideal rigid wall eliminating thermal and viscous boundary layer effects. The flow visualization system used needs to provide high resolution information on the shockwave, slipstream, triple point and vortex positions and angles. Initially shadowgraph and schlieren methods, with a Xenon light source, were used. These results, while proving useful, are not of a sufficient resolution to measure the Mach stem and slipstream lengths accurately enough in order to determine the transition point between regular and Mach reflection. To obtain the required image resolution a 2 joule double pulse ruby laser, with a 30 ns pulse duration, was used to make holographic interferograms. The combined advantages of holographic interferometry and the 30 ns pulse laser allows one to obtain much sharper definition, and more qualitative as well as quantitative information on the flow field. The disadvantages of this system are: the long time taken to develop holograms, the difficulty of aligning the pulse laser and the fact that only one image per test is obtained. Direct contact shadowgraphs were also obtained using the pulse ruby laser to help determine triple point trajectory angles. In order to provide further information a one million frames per second CCD camera, which can take up to 10 superimposed images, was

  20. Shell-structure effects on high-pressure Rankine-Hugoniot shock adiabats

    CERN Document Server

    Pain, J C

    2007-01-01

    Rankine-Hugoniot shock adiabats are calculated in the pressure range 1 Mbar-10 Gbar with two atomic-structure models: the atom in a spherical cell and the atom in a jellium of charges. These quantum self-consistent-field models include shell effects, which have a strong impact on pressure and shock velocity along the shock adiabat. Comparisons with experimental data are presented and quantum effects are interpreted in terms of electronic specific heat. A simple analytical estimate for the maximum compression is proposed, depending on initial density, atomic weight and atomic number.

  1. Multi-fluid Approach to High-frequency Waves in Plasmas. II. Small-amplitude Regime in Partially Ionized Media

    Science.gov (United States)

    Martínez-Gómez, David; Soler, Roberto; Terradas, Jaume

    2017-03-01

    The presence of neutral species in a plasma has been shown to greatly affect the properties of magnetohydrodynamic waves. For instance, the interaction between ions and neutrals through momentum transfer collisions causes the damping of Alfvén waves and alters their oscillation frequency and phase speed. When the collision frequencies are larger than the frequency of the waves, single-fluid magnetohydrodynamic approximations can accurately describe the effects of partial ionization, since there is a strong coupling between the various species. However, at higher frequencies, the single-fluid models are not applicable and more complex approaches are required. Here, we use a five-fluid model with three ionized and two neutral components, which takes into consideration Hall’s current and Ohm’s diffusion in addition to the friction due to collisions between different species. We apply our model to plasmas composed of hydrogen and helium, and allow the ionization degree to be arbitrary. By analyzing the corresponding dispersion relation and numerical simulations, we study the properties of small-amplitude perturbations. We discuss the effect of momentum transfer collisions on the ion-cyclotron resonances and compare the importance of magnetic resistivity, and ion–neutral and ion–ion collisions on the wave damping at various frequency ranges. Applications to partially ionized plasmas of the solar atmosphere are performed.

  2. Observation and analysis of emergent coherent structures in a high-energy-density shock-driven planar mixing layer experiment

    Science.gov (United States)

    Doss, F. W.; Flippo, K. A.; Merritt, E. C.

    2016-08-01

    Coherent emergent structures have been observed in a high-energy-density supersonic mixing layer experiment. A millimeter-scale shock tube uses lasers to drive Mbar shocks into the tube volume. The shocks are driven into initially solid foam (60 mg /cm3 ) hemicylinders separated by an Al or Ti metal tracer strip; the components are vaporized by the drive. Before the experiment disassembles, the shocks cross at the tube center, creating a very fast (Δ U > 200 km/s) shear-unstable zone. After several nanoseconds, an expanding mixing layer is measured, and after 10+ ns we observe the appearance of streamwise-periodic, spanwise-aligned rollers associated with the primary Kelvin-Helmholtz instability of mixing layers. We additionally image roller pairing and spanwise-periodic streamwise-aligned filaments associated with secondary instabilities. New closures are derived to connect length scales of these structures to estimates of fluctuating velocity data otherwise unobtainable in the high-energy-density environment. This analysis indicates shear-induced specific turbulent energies 103-104 times higher than the nearest conventional experiments. Because of difficulties in continuously driving systems under these conditions and the harshness of the experimental environment limiting the usable diagnostics, clear evidence of these developing structures has never before been observed in this regime.

  3. Electrostatic Assembly Preparation of High-Toughness Zirconium Diboride-Based Ceramic Composites with Enhanced Thermal Shock Resistance Performance.

    Science.gov (United States)

    Zhang, Baoxi; Zhang, Xinghong; Hong, Changqing; Qiu, Yunfeng; Zhang, Jia; Han, Jiecai; Hu, PingAn

    2016-05-11

    The central problem of using ceramic as a structural material is its brittleness, which associated with rigid covalent or ionic bonds. Whiskers or fibers of strong ceramics such as silicon carbide (SiC) or silicon nitride (Si3N4) are widely embedded in a ceramic matrix to improve the strength and toughness. The incorporation of these insulating fillers can impede the thermal flow in ceramic matrix, thus decrease its thermal shock resistance that is required in some practical applications. Here we demonstrate that the toughness and thermal shock resistance of zirconium diboride (ZrB2)/SiC composites can be improved simultaneously by introducing graphene into composites via electrostatic assembly and subsequent sintering treatment. The incorporated graphene creates weak interfaces of grain boundaries (GBs) and optimal thermal conductance paths inside composites. In comparison to pristine ZrB2-SiC composites, the toughness of (2.0%) ZrB2-SiC/graphene composites exhibited a 61% increasing (from 4.3 to 6.93 MPa·m(1/2)) after spark plasma sintering (SPS); the retained strength after thermal shock increased as high as 74.8% at 400 °C and 304.4% at 500 °C. Present work presents an important guideline for producing high-toughness ceramic-based composites with enhanced thermal shock properties.

  4. Real-time, high-resolution x-ray diffraction measurements on shocked crystals at a synchrotron facility.

    Science.gov (United States)

    Gupta, Y M; Turneaure, Stefan J; Perkins, K; Zimmerman, K; Arganbright, N; Shen, G; Chow, P

    2012-12-01

    The Advanced Photon Source (APS) at Argonne National Laboratory was used to obtain real-time, high-resolution x-ray diffraction measurements to determine the microscopic response of shock-compressed single crystals. Disk shaped samples were subjected to plane shock wave compression by impacting them with half-inch diameter, flat-faced projectiles. The projectiles were accelerated to velocities ranging between 300 and 1200 m/s using a compact powder gun designed specifically for use at a synchrotron facility. The experiments were designed to keep the sample probed volume under uniaxial strain and constant stress for a duration longer than the 153.4 ns spacing between x-ray bunches. X-rays from a single pulse (crystals at the APS are presented. Analytic developments to determine the effects of crystal substructure and non-ideal geometry on the diffraction pattern position and shape are presented. Representative real-time x-ray diffraction data, indicating shock-induced microstructural changes, are presented for a shock-compressed Al(111) sample. The experimental developments presented here provided, in part, the impetus for the Dynamic Compression Sector (DCS) currently under development at the APS. Both the synchronization∕x-ray detection methods and the analysis equations for high-resolution single crystal x-ray diffraction can be used at the DCS.

  5. Single and double shock initiation modelling for high explosive materials in last three decades

    Science.gov (United States)

    Hussain, T.; Yan, Liu

    2016-08-01

    The explosives materials are normally in an energetically metastable state. These can undergo rapid chemical decomposition only if sufficient energy has first been added to get the process started. Such energy can be provided by shocks. To predict the response of these materials under impacts of shocks of different strengths and durations and at various conditions, mathematical models are used. During the last three decades, a lot of research has been carried out and several shock initiation models have been presented. The models can be divided into continuum based and physics based models. In this study the single and double shock initiation models presented in last three decades have been reviewed and the ranges of their application has been discussed.

  6. High-performance detection and early prediction of septic shock for alcohol-use disorder patients

    Directory of Open Access Journals (Sweden)

    Jacob Calvert

    2016-06-01

    Conclusions: Analysis of the higher order correlations and trends between relevant clinical measurements using the InSight algorithm leads to more accurate detection and prediction of septic shock, even in cases where diagnosis may be confounded by AUD.

  7. Cardiogenic shock

    Science.gov (United States)

    Shock - cardiogenic ... electrical system of the heart (heart block) Cardiogenic shock occurs when the heart is unable to pump ... orthostatic hypotension) Weak (thready) pulse To diagnose cardiogenic shock, a catheter (tube) may be placed in the ...

  8. STEREO interplanetary shocks and foreshocks

    Energy Technology Data Exchange (ETDEWEB)

    Blanco-Cano, X. [Instituto de Geofisica, UNAM, CU, Coyoacan 04510 DF (Mexico); Kajdic, P. [IRAP-University of Toulouse, CNRS, Toulouse (France); Aguilar-Rodriguez, E. [Instituto de Geofisica, UNAM, Morelia (Mexico); Russell, C. T. [ESS and IGPP, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095 (United States); Jian, L. K. [NASA Goddard Space Flight Center, Greenbelt, MD and University of Maryland, College Park, MD (United States); Luhmann, J. G. [SSL, University of California Berkeley (United States)

    2013-06-13

    We use STEREO data to study shocks driven by stream interactions and the waves associated with them. During the years of the extended solar minimum 2007-2010, stream interaction shocks have Mach numbers between 1.1-3.8 and {theta}{sub Bn}{approx}20-86 Degree-Sign . We find a variety of waves, including whistlers and low frequency fluctuations. Upstream whistler waves may be generated at the shock and upstream ultra low frequency (ULF) waves can be driven locally by ion instabilities. The downstream wave spectra can be formed by both, locally generated perturbations, and shock transmitted waves. We find that many quasiperpendicular shocks can be accompanied by ULF wave and ion foreshocks, which is in contrast to Earth's bow shock. Fluctuations downstream of quasi-parallel shocks tend to have larger amplitudes than waves downstream of quasi-perpendicular shocks. Proton foreshocks of shocks driven by stream interactions have extensions dr {<=}0.05 AU. This is smaller than foreshock extensions for ICME driven shocks. The difference in foreshock extensions is related to the fact that ICME driven shocks are formed closer to the Sun and therefore begin to accelerate particles very early in their existence, while stream interaction shocks form at {approx}1 AU and have been producing suprathermal particles for a shorter time.

  9. Perturbations to aquatic photosynthesis due to high-energy cosmic ray induced muon flux in the extragalactic shock model

    CERN Document Server

    Rodriguez, Lien; Rodriguez, Oscar

    2013-01-01

    We modify a mathematical model of photosynthesis to quantify the perturbations that high energy muons could make on aquatic primary productivity. Then we apply this in the context of the extragalactic shock model, according to which Earth receives an enhanced dose of high-energy cosmic rays when it is at the galactic north. We obtain considerable reduction in the photosynthesis rates, consistent with potential drops in biodiversity.

  10. An attempt to reconstruct the lithotriptor shock wave pulse in kidney: possible temperature effects.

    Science.gov (United States)

    Filipczyński, L; Etienne, J; Piechocki, M

    1992-01-01

    Based on measurements carried out in water in two lithotriptor systems, the authors have made an attempt to reconstruct numerically amplitudes and shapes of shock wave pulses penetrating into kidney which differ from those in water. The difference between these pulses and those observed in water was analyzed and was also demonstrated experimentally. The amplitude and the steepness of the reconstructed pulse front were shown to be much lower than in water depending on the distance of the kidney stone from the patient's body surface. For a distance equal to 4 cm, the shock wave pulse amplitude of 40 MPa in water was estimated to decrease in the kidney by a factor of about two and the steepness of the positive shock pulse front to decrease several times. The analysis was carried out by considering the possible changes of absorption and attenuation in tissues which increase in an unknown way with the wave amplitude. It was shown that the temperature elevation caused by the increase of nonlinear high amplitude absorption is limited due to a corresponding increase in attenuation of the shock wave penetrating soft tissues. The temperature elevation was estimated on the basis of this work to be at most 1.8 times that one estimated in the case of two considered lithotripsy systems when assuming small amplitude absorption and attenuation coefficients.

  11. The High Cadence Transient Survey (HiTS) - I. Survey design and supernova shock breakout constraints

    CERN Document Server

    Förster, Francisco; Martín, Jaime San; Hamuy, Mario; Martínez, Jorge; Huijse, Pablo; Cabrera, Guillermo; Galbany, Lluís; de Jaeger, Thomas; González-Gaitán, Santiago; Anderson, Joseph P; Kuncarayakti, Hanindyo; Pignata, Giuliano; Bufano, Filomena; Littín, Jorge; Olivares, Felipe; Medina, Gustavo; Smith, R Chris; Vivas, A Katherina; Estévez, Pablo A; Muñoz, Ricardo; Vera, Eduardo

    2016-01-01

    We present the first results of the High cadence Transient Survey (HiTS), a survey whose objective is to detect and follow up optical transients with characteristic timescales from hours to days, especially the earliest hours of supernova (SN) explosions. HiTS uses the Dark Energy Camera (DECam) and a custom made pipeline for image subtraction, candidate filtering and candidate visualization, which runs in real-time to be able to react rapidly to the new transients. We discuss the survey design, the technical challenges associated with the real-time analysis of these large volumes of data and our first results. In our 2013, 2014 and 2015 campaigns we have detected more than 120 young SN candidates, but we did not find a clear signature from the short-lived SN shock breakouts (SBOs) originating after the core collapse of red supergiant stars, which was the initial science aim of this survey. Using the empirical distribution of limiting-magnitudes from our observational campaigns we measured the expected recove...

  12. A High Order Finite Difference Scheme with Sharp Shock Resolution for the Euler Equations

    Science.gov (United States)

    Gerritsen, Margot; Olsson, Pelle

    1996-01-01

    We derive a high-order finite difference scheme for the Euler equations that satisfies a semi-discrete energy estimate, and present an efficient strategy for the treatment of discontinuities that leads to sharp shock resolution. The formulation of the semi-discrete energy estimate is based on a symmetrization of the Euler equations that preserves the homogeneity of the flux vector, a canonical splitting of the flux derivative vector, and the use of difference operators that satisfy a discrete analogue to the integration by parts procedure used in the continuous energy estimate. Around discontinuities or sharp gradients, refined grids are created on which the discrete equations are solved after adding a newly constructed artificial viscosity. The positioning of the sub-grids and computation of the viscosity are aided by a detection algorithm which is based on a multi-scale wavelet analysis of the pressure grid function. The wavelet theory provides easy to implement mathematical criteria to detect discontinuities, sharp gradients and spurious oscillations quickly and efficiently.

  13. High level compressive residual stresses produced in aluminum alloys by laser shock processing

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Rosas, G. [Centro de Ingenieria y Desarrollo Industrial, CIDESI, Av. Playa Pie de la Cuesta, 702 Desarrollo San Pablo, c.p. 76130 Santiago de Queretaro, Queretaro (Mexico)]. E-mail: ggomez@cidesi.mx; Rubio-Gonzalez, C. [Centro de Ingenieria y Desarrollo Industrial, CIDESI, Av. Playa Pie de la Cuesta, 702 Desarrollo San Pablo, c.p. 76130 Santiago de Queretaro, Queretaro (Mexico); Ocana, J.L [Departamento de Fisica Aplicada a la Ingenieria Industrial, ETSII, Universidad Politecnica de Madrid (Spain); Molpeceres, C. [Departamento de Fisica Aplicada a la Ingenieria Industrial, ETSII, Universidad Politecnica de Madrid (Spain); Porro, J.A. [Departamento de Fisica Aplicada a la Ingenieria Industrial, ETSII, Universidad Politecnica de Madrid (Spain); Chi-Moreno, W. [Instituto Tecnologico de Morelia (Mexico); Morales, M. [Departamento de Fisica Aplicada a la Ingenieria Industrial, ETSII, Universidad Politecnica de Madrid (Spain)

    2005-11-15

    Laser shock processing (LSP) has been proposed as a competitive alternative technology to classical treatments for improving fatigue and wear resistance of metals. We present a configuration and results for metal surface treatments in underwater laser irradiation at 1064 nm. A convergent lens is used to deliver 1.2 J/cm{sup 2} in a 8 ns laser FWHM pulse produced by 10 Hz Q-switched Nd:YAG, two laser spot diameters were used: 0.8 and 1.5 mm. Results using pulse densities of 2500 pulses/cm{sup 2} in 6061-T6 aluminum samples and 5000 pulses/cm{sup 2} in 2024 aluminum samples are presented. High level of compressive residual stresses are produced -1600 MPa for 6061-T6 Al alloy, and -1400 MPa for 2024 Al alloy. It has been shown that surface residual stress level is higher than that achieved by conventional shot peening and with greater depths. This method can be applied to surface treatment of final metal products.

  14. High-Resolution X-ray Imaging of the Colliding Wind Shock in WR147

    CERN Document Server

    Pittard, J M; Williams, P M; Pollock, A M T; Skinner, S L; Corcoran, M F; Moffat, A F J

    2002-01-01

    We analyze new high-resolution Chandra X-ray images of the Wolf-Rayet binary system WR147. This system contains a WN8 star with an early-type companion located 0.6'' to its north, and is the only known early-type binary with a separation on the sky large enough for the wind-wind collision between the stars to currently be resolved at X-ray energies. The 5 ksec Chandra HRC-I image provides the first direct evidence for spatially extended X-ray emission in an early-type binary system. The X-ray emission peaks close to the position of the radio bow shock and north of the WN8 star. A deeper X-ray image is needed to accurately determine the degree of spatial extension, to exactly align the X-ray and optical/radio frames, and to determine whether part of the detected X-ray emission arises in the individual stellar winds. Simulated X-ray images of the wind-wind collision have a FWHM consistent with the data, and maximum likelihood fits suggest that a deeper observation may also constrain the inclination and wind mom...

  15. High sensitivity of diesel soot morphological and optical properties to combustion temperature in a shock tube.

    Science.gov (United States)

    Qiu, Chong; Khalizov, Alexei F; Hogan, Brian; Petersen, Eric L; Zhang, Renyi

    2014-06-03

    Carbonaceous particles produced from combustion of fossil fuels have strong impacts on air quality and climate, yet quantitative relationships between particle characteristics and combustion conditions remain inadequately understood. We have used a shock tube to study the formation and properties of diesel combustion soot, including particle size distributions, effective density, elemental carbon (EC) mass fraction, mass-mobility scaling exponent, hygroscopicity, and light absorption and scattering. These properties are found to be strongly dependent on the combustion temperature and fuel equivalence ratio. Whereas combustion at higher temperatures (∼2000 K) yields fractal particles of a larger size and high EC content (90 wt %), at lower temperatures (∼1400 K) smaller particles of a higher organic content (up to 65 wt %) are produced. Single scattering albedo of soot particles depends largely on their organic content, increasing drastically from 0.3 to 0.8 when the particle EC mass fraction decreases from 0.9 to 0.3. The mass absorption cross-section of diesel soot increases with combustion temperature, being the highest for particles with a higher EC content. Our results reveal that combustion conditions, especially the temperature, may have significant impacts on the direct and indirect climate forcing of atmospheric soot aerosols.

  16. A high-precision finite element method for shock-tube calculations

    Science.gov (United States)

    Hughes, T. J. R.; Mallet, M.

    1985-01-01

    A two-pass explicit scheme is developed in order to exploit some of the capabilities of finite difference modeling (FDM) for finite element modeling (FEM), which offers the opportunity to account for any type of geometry in fluid flow modeling. Features of the first-order upwind and the Lax-Wendroff high precision explicit finite difference algorithms are reviewed. A flux limiter is developed for FEM to serve as an analog for the single limiter function which has been defined for the various FDMs. It is shown that an antidiffusive limiter must be introduced into the weighting function which normally multiplies the time-derivative term in the variational equation. The two-pass scheme which results is demonstrated to be the equivalent of FDMs with five-point support. However, the present scheme is valid only for one-dimensional calculations and linear shape functions for shock tube flow phenomena. Further work is required for its use with nonlinear hyperbolic systems.

  17. Scattering amplitudes in gauge theories

    CERN Document Server

    Henn, Johannes M

    2014-01-01

    At the fundamental level, the interactions of elementary particles are described by quantum gauge field theory. The quantitative implications of these interactions are captured by scattering amplitudes, traditionally computed using Feynman diagrams. In the past decade tremendous progress has been made in our understanding of and computational abilities with regard to scattering amplitudes in gauge theories, going beyond the traditional textbook approach. These advances build upon on-shell methods that focus on the analytic structure of the amplitudes, as well as on their recently discovered hidden symmetries. In fact, when expressed in suitable variables the amplitudes are much simpler than anticipated and hidden patterns emerge.   These modern methods are of increasing importance in phenomenological applications arising from the need for high-precision predictions for the experiments carried out at the Large Hadron Collider, as well as in foundational mathematical physics studies on the S-matrix in quantum ...

  18. Passionflower Extract Induces High-amplitude Rhythms without Phase Shifts in the Expression of Several Circadian Clock Genes in Vitro and in Vivo.

    Science.gov (United States)

    Toda, Kazuya; Hitoe, Shoketsu; Takeda, Shogo; Shimizu, Norihito; Shimoda, Hiroshi

    2017-06-01

    Circadian rhythms play key roles in the regulation of physiological and behavioral systems including wake-sleep cycles. We evaluated the effects of passionflower (aerial parts of Passiflora incarnata Linnaeus) extract (PFE) on circadian rhythms using NIH3T3 cells and mice. PFE (100 μg/mL) induced high-amplitude rhythms in the expression of period circadian protein (Per) 2, cryptochrome (Cry) 1, superoxide dismutase (SOD) 1, and glutathione peroxidase (GPx) in vitro from 12 h after a treatment with serum-rich medium. Isovitexin 2"-O-glucoside, isoschaftoside, and homoorientin, which were purified from PFE, also significantly enhanced Per2 mRNA expression at 20 h. An oral treatment with PFE (100 mg/kg/day) at zeitgeber time (ZT) 0 h for 15 days improved sleep latencies and sleeping times in the pentobarbital-induced sleep test in mice, similar to muscimol (0.2 mg/kg, i.p.). PFE induced high-amplitude rhythms without obvious phase shifts in serum corticosterone levels and the expression of Per1, Per2, and Cry1 in the liver as well as NIH3T3 cells. However, in the cerebrum, PFE enhanced the circadian expression of brain-muscle ARNT-like protein (Bmal) 1, circadian locomotor output cycles kaput (Clock), and Per1. Regarding this difference, we suggest the involvement of several neurotransmitters that influence the circadian rhythm. Indeed, PFE significantly increased dopamine levels at ZT 18 h, and then affected the mRNA expression of the synthetic and metabolic enzymes such as monoamine oxidase (MAO), catechol-O-methyltransferase (COMT), and glutamic acid decarboxylase (GAD). The results obtained show that PFE positively modulates circadian rhythms by inducing high-amplitude rhythms in the expression of several circadian clock genes.

  19. Calibration of PCB-132 Sensors in a Shock Tube

    Science.gov (United States)

    Berridge, Dennis C.; Schneider, Steven P.

    2012-01-01

    While PCB-132 sensors have proven useful for measuring second-mode instability waves in many hypersonic wind tunnels, they are currently limited by their calibration. Until now, the factory calibration has been all that was available, which is a single-point calibration at an amplitude three orders of magnitude higher than a second-mode wave. In addition, little information has been available about the frequency response or spatial resolution of the sensors, which is important for measuring high-frequency instability waves. These shortcomings make it difficult to compare measurements at different conditions and between different sensors. If accurate quantitative measurements could be performed, comparisons of the growth and breakdown of instability waves could be made in different facilities, possibly leading to a method of predicting the amplitude at which the waves break down into turbulence, improving transition prediction. A method for calibrating the sensors is proposed using a newly-built shock tube at Purdue University. This shock tube, essentially a half-scale version of the 6-Inch shock tube at the Graduate Aerospace Laboratories at Caltech, has been designed to attain a moderate vacuum in the driven section. Low driven pressures should allow the creation of very weak, yet still relatively thin shock waves. It is expected that static pressure rises within the range of second-mode amplitudes should be possible. The shock tube has been designed to create clean, planar shock waves with a laminar boundary layer to allow for accurate calibrations. Stronger shock waves can be used to identify the frequency response of the sensors out to hundreds of kilohertz.

  20. Design and Implementation of a High-Voltage Generator with Output Voltage Control for Vehicle ER Shock-Absorber Applications

    Directory of Open Access Journals (Sweden)

    Chih-Lung Shen

    2013-01-01

    Full Text Available A self-oscillating high-voltage generator is proposed to supply voltage for a suspension system in order to control the damping force of an electrorheological (ER fluid shock absorber. By controlling the output voltage level of the generator, the damping force in the ER fluid shock absorber can be adjusted immediately. The shock absorber is part of the suspension system. The high-voltage generator drives a power transistor based on self-excited oscillation, which converts dc to ac. A high-frequency transformer with high turns ratio is used to increase the voltage. In addition, the system uses the car battery as dc power supply. By regulating the duty cycle of the main switch in the buck converter, the output voltage of the buck converter can be linearly adjusted so as to obtain a specific high voltage for ER. The driving system is self-excited; that is, no additional external driving circuit is required. Thus, it reduces cost and simplifies system structure. A prototype version of the actual product is studied to measure and evaluate the key waveforms. The feasibility of the proposed system is verified based on experimental results.

  1. Sensitivity optimization of a monolithic high-shock three-axis piezoresistive accelerometer with single sensing element

    Institute of Scientific and Technical Information of China (English)

    SONG Ping; LI QingZhou; LI KeJie

    2009-01-01

    There exist several difficulties in the design of monolithic high-shock three-axis accelerometer, such as high g overload, transverse overload and the cross coupling in three dimensions, etc. It is necessary to optimize the sensitivity to improve the performance of the accelerometer. For the monolithic high-shock three-axis accelerometer, the complexity of the sensitivity optimization is that it should consider not only the sensitivity difference between different axes but also the elimination of cross-coupling outputs, together with the natural frequency, structural integrity and high g overload. In this paper, the optimization process for decreasing the difference of the sensitivities between different axes of a monolithic high-shock three-axis piezoresistive accelerometer with single sensing element is established. The optimization is conducted in the condition of 100000 g acceleration by two methods-the method based on the optimization module of ANSYS and the ACO (ant colony optimiza-tion) method. The comparison between un-optimized and optimized models proves the efficiency of the optimization methods. In addition, the optimization results show that the ACO method combined with the FEA (finite element analysis) is much more efficient than the method based on the optimization module of ANSYS for the structural optimization problem. And the ACO method can be widely used in the optimization problem of the sensing elements with complicated structure.

  2. New approach of determinations of earthquake moment magnitude using near earthquake source duration and maximum displacement amplitude of high frequency energy radiation

    Energy Technology Data Exchange (ETDEWEB)

    Gunawan, H.; Puspito, N. T.; Ibrahim, G.; Harjadi, P. J. P. [ITB, Faculty of Earth Sciences and Tecnology (Indonesia); BMKG (Indonesia)

    2012-06-20

    The new approach method to determine the magnitude by using amplitude displacement relationship (A), epicenter distance ({Delta}) and duration of high frequency radiation (t) has been investigated for Tasikmalaya earthquake, on September 2, 2009, and their aftershock. Moment magnitude scale commonly used seismic surface waves with the teleseismic range of the period is greater than 200 seconds or a moment magnitude of the P wave using teleseismic seismogram data and the range of 10-60 seconds. In this research techniques have been developed a new approach to determine the displacement amplitude and duration of high frequency radiation using near earthquake. Determination of the duration of high frequency using half of period of P waves on the seismograms displacement. This is due tothe very complex rupture process in the near earthquake. Seismic data of the P wave mixing with other wave (S wave) before the duration runs out, so it is difficult to separate or determined the final of P-wave. Application of the 68 earthquakes recorded by station of CISI, Garut West Java, the following relationship is obtained: Mw = 0.78 log (A) + 0.83 log {Delta}+ 0.69 log (t) + 6.46 with: A (m), d (km) and t (second). Moment magnitude of this new approach is quite reliable, time processing faster so useful for early warning.

  3. Lhermitte's sign, electric shock sensations and high dose ecstasy consumption: preliminary findings.

    Science.gov (United States)

    Boland, B; Mitcheson, L; Wolff, K

    2010-02-01

    The objectives of this study were to perform a preliminary investigation into the nature of electric shock-like experiences reported in association with the use of ecstasy tablets thought to contain methylenedioxymethamphetamines (MDMA). This included exploration of reports of electric shock-like experiences from the user's perspectives and identification of other variables that may be associated with their development. Furthermore we aimed to examine whether the well-recognised electric shock-like symptom, Lhermitte's sign (LS), is associated with ecstasy tablet use in some drug users. A single measure, cross-sectional survey was used incorporating mixed qualitative and quantitative methodology. A select group of ecstasy users (n = 35) recruited through a dance, music and lifestyle magazine completed a telephone interview. Lifetime prevalence of LS in the study population was 18% (n = 6). Development of LS was associated with use of more ecstasy tablets before a typical incident. This study indicates a relationship may exist between the use of ecstasy tablets and LS. The relationship may be dose dependent. The majority of the study population used other substances including alcohol when experiencing electrical shock sensations. LS may explain only a proportion of all electrical shock experiences among ecstasy users.

  4. Dynamic behaviour and shock-induced martensite transformation in near-beta Ti-5553 alloy under high strain rate loading

    Directory of Open Access Journals (Sweden)

    Wang Lin

    2015-01-01

    Full Text Available Ti-5553 alloy is a near-beta titanium alloy with high strength and high fracture toughness. In this paper, the dynamic behaviour and shock-induced martensite phase transformation of Ti-5553 alloy with alpha/beta phases were investigated. Split Hopkinson Pressure Bar was employed to investigate the dynamic properties. Microstructure evolutions were characterized by Scanning Electronic Microscopy and Transmission Electron Microscope. The experimental results have demonstrated that Ti-5553 alloy with alpha/beta phases exhibits various strain rate hardening effects, both failure through adiabatic shear band. Ti-5553 alloy with Widmannstatten microstructure exhibit more obvious strain rate hardening effect, lower critical strain rate for ASB nucleation, compared with the alloy with Bimodal microstructures. Under dynamic compression, shock-induced beta to alpha” martensite transformation occurs.

  5. High Mach-number collisionless shock driven by a laser with an external magnetic field

    Directory of Open Access Journals (Sweden)

    Morita T.

    2013-11-01

    Full Text Available Collisionless shocks are produced in counter-streaming plasmas with an external magnetic field. The shocks are generated due to an electrostatic field generated in counter-streaming laser-irradiated plasmas, as reported previously in a series of experiments without an external magnetic field [T. Morita et al., Phys. Plasmas, 17, 122702 (2010, Kuramitsu et al., Phys. Rev. Lett., 106, 175002 (2011] via laser-irradiation of a double-CH-foil target. A magnetic field is applied to the region between two foils by putting an electro-magnet (∼10 T perpendicular to the direction of plasma expansion. The generated shocks show different characteristics later in time (t > 20ns.

  6. Application of shock tubes to transonic airfoil testing at high Reynolds numbers

    Science.gov (United States)

    Cook, W. J.; Chaney, M. J.; Presley, L. L.; Chapman, G. T.

    1978-01-01

    Performance analysis of a gas-driven shock tube shows that transonic airfoil flows with chord Reynolds numbers of the order of 100 million can be produced, with limitations being imposed by the structural integrity of the facility or the model. A study of flow development over a simple circular arc airfoil at zero angle of attack was carried out in a shock tube at low and intermediate Reynolds numbers to assess the testing technique. Results obtained from schlieren photography and airfoil pressure measurements show that steady transonic flows similar to those produced for the same airfoil in a wind tunnel can be generated within the available testing time in a shock tube with properly contoured test section walls.

  7. Amplitude Equalization of 40 Gb/s RZ-DPSK Signals using Saturation of Four-Wave Mixing in a Highly Nonlinear Fiber

    DEFF Research Database (Denmark)

    Geng, Yan; Peucheret, Christophe; Jeppesen, Palle

    2006-01-01

    We report the first experimental demonstration of amplitude equalization of 40 Gb/s RZ-DPSK signals using saturation of FWM in a HNLF. We show effective power penalty reduction after wavelength conversion of an amplitude distorted signal......We report the first experimental demonstration of amplitude equalization of 40 Gb/s RZ-DPSK signals using saturation of FWM in a HNLF. We show effective power penalty reduction after wavelength conversion of an amplitude distorted signal...

  8. Periodic shock-emission from acoustically driven cavitation clouds: a source of the subharmonic signal.

    Science.gov (United States)

    Johnston, Keith; Tapia-Siles, Cecilia; Gerold, Bjoern; Postema, Michiel; Cochran, Sandy; Cuschieri, Alfred; Prentice, Paul

    2014-12-01

    Single clouds of cavitation bubbles, driven by 254kHz focused ultrasound at pressure amplitudes in the range of 0.48-1.22MPa, have been observed via high-speed shadowgraphic imaging at 1×10(6) frames per second. Clouds underwent repetitive growth, oscillation and collapse (GOC) cycles, with shock-waves emitted periodically at the instant of collapse during each cycle. The frequency of cloud collapse, and coincident shock-emission, was primarily dependent on the intensity of the focused ultrasound driving the activity. The lowest peak-to-peak pressure amplitude of 0.48MPa generated shock-waves with an average period of 7.9±0.5μs, corresponding to a frequency of f0/2, half-harmonic to the fundamental driving. Increasing the intensity gave rise to GOC cycles and shock-emission periods of 11.8±0.3, 15.8±0.3, 19.8±0.2μs, at pressure amplitudes of 0.64, 0.92 and 1.22MPa, corresponding to the higher-order subharmonics of f0/3, f0/4 and f0/5, respectively. Parallel passive acoustic detection, filtered for the fundamental driving, revealed features that correlated temporally to the shock-emissions observed via high-speed imaging, p(two-tailed) subharmonic spectral peaks, in the frequency domain. The larger cavitation clouds (>200μm diameter, at maximum inflation), that developed under insonations of peak-to-peak pressure amplitudes >1.0MPa, emitted shock-waves with two or more fronts suggesting non-uniform collapse of the cloud. The observations indicate that periodic shock-emissions from acoustically driven cavitation clouds provide a source for the cavitation subharmonic signal, and that shock structure may be used to study intra-cloud dynamics at sub-microsecond timescales.

  9. High-resolution PIV measurements of a transitional shock wave-boundary layer interaction

    Science.gov (United States)

    Giepman, R. H. M.; Schrijer, F. F. J.; van Oudheusden, B. W.

    2015-06-01

    This study investigates the effects of boundary layer transition on an oblique shock wave reflection. The Mach number was 1.7, the unit Reynolds number was 35 × 106 m-1, and the pressure ratio over the interaction was 1.35. Particle image velocimetry is used as the main flow diagnostics tool, supported by oil-flow and Schlieren visualizations. At these conditions, the thickness of the laminar boundary layer is only 0.2 mm, and seeding proved to be problematic as practically no seeding was recorded in the lower 40 % of the boundary layer. The top 60 % could, however, still be resolved with good accuracy and is found to be in good agreement with the compressible Blasius solution. Due to the effects of turbulent mixing, the near-wall seeding deficiency disappears when the boundary layer transitions to a turbulent state. This allowed the seeding distribution to be used as an indicator for the state of the boundary layer, permitting to obtain an approximate intermittency distribution for the boundary layer transition region. This knowledge was then used for positioning the oblique shock wave in the laminar, transitional (50 % intermittency) or turbulent region of the boundary layer. Separation is only recorded for the laminar and transitional interactions. For the laminar interaction, a large separation bubble is found, with a streamwise length of 96. The incoming boundary layer is lifted over the separation bubble and remains in a laminar state up to the impingement point of the shock wave. After the shock, transition starts and a turbulent profile is reached approximately 80-90 downstream of the shock. Under the same shock conditions, the transitional interaction displays a smaller separation bubble (43), and transition is found to be accelerated over the separation bubble.

  10. Turbulence generation by a shock wave interacting with a random density inhomogeneity field

    Science.gov (United States)

    Huete Ruiz de Lira, C.

    2010-12-01

    When a planar shock wave interacts with a random pattern of pre-shock density non-uniformities, it generates an anisotropic turbulent velocity/vorticity field. This turbulence plays an important role in the early stages of the mixing process in a compressed fluid. This situation emerges naturally in a shock interaction with weakly inhomogeneous deuterium-wicked foam targets in inertial confinement fusion and with density clumps/clouds in astrophysics. We present an exact small-amplitude linear theory describing such an interaction. It is based on the exact theory of time and space evolution of the perturbed quantities behind a corrugated shock front for a single-mode pre-shock non-uniformity. Appropriate mode averaging in two dimensions results in closed analytical expressions for the turbulent kinetic energy, degree of anisotropy of velocity and vorticity fields in the shocked fluid, shock amplification of the density non-uniformity and sonic energy flux radiated downstream. These explicit formulae are further simplified in the important asymptotic limits of weak/strong shocks and highly compressible fluids. A comparison with the related problem of a shock interacting with a pre-shock isotropic vorticity field is also presented.

  11. Molecular dissociation and shock-induced cooling in fluid nitrogen at high densities and temperatures

    Science.gov (United States)

    Radousky, H. B.; Nellis, W. J.; Ross, M.; Hamilton, D. C.; Mitchell, A. C.

    1986-01-01

    Radiative temperatures and electrical conductivities were measured for fluid nitrogen compressed dynamically to pressures of 18-90 GPa, temperatures of 4000-14,000 K, and densities of 2-3 g/cu cm. The data show a continuous phase transition above 30 GPa shock pressure and confirm that (delta-P/delta-T)v is less than 0, as indicated previously by Hugoniot equation-of-state experiments. The first observation of shock-induced cooling is also reported. The data are interpreted in terms of molecular dissociation, and the concentration of dissociated molecules is calculated as a function of density and temperature.

  12. Silicon carbide resonant tuning fork for microsensing applications in high-temperature and high G-shock environments

    Institute of Scientific and Technical Information of China (English)

    David R Myers; Kan Bun Cheng; Babak Jamshidi; Robert G Azevedo; Debbie G Senesky; Li Chen; Mehran Mehregany; Muthu B J Wijesundara; Albert P Pisano

    2012-01-01

    We present the fabrication and testing of a silicon carbide (SiC) balanced mass doublended tuning fork that survives harsh environments without compromising the device strain sensitivity and resolution bandwidth. The device features a material stack that survives corrosive environments and enables high-temperature operation. To perform hightemperature testing, a specialized setup was constructed that allows the tuning fork to be characterized using traditional silicon electronics. The tuning fork has been operated at 600°C in the presence of dry steam for short durations. This tuning fork has also been tested to 64 000 G using a hard-launch, soft-catch shock implemented with a light gas gun. However, the device still has a strain sensitivity of 66 Hz/μe and strain resolution of 0. 045 μe in a 10 kHz bandwidth. As such, this balanced-mass double-ended tuning fork can be used to create a variety of different sensors including strain gauges, accelerometers, gyroscopes, and pressure transducers. Given the adaptable fabrication process flow, this device could be useful to micro-electro-mechanical systems (MEMS) designers creating sensors for a variety of different applications.

  13. ON SHOCKS DRIVEN BY HIGH-MASS PLANETS IN RADIATIVELY INEFFICIENT DISKS. II. THREE-DIMENSIONAL GLOBAL DISK SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Lyra, Wladimir [Department of Physics and Astronomy, California State University Northridge, 18111 Nordhoff St, Northridge, CA 91330 (United States); Richert, Alexander J. W. [Department of Astronomy and Astrophysics, Penn State University, 525 Davey Lab, University Park, PA 16802 (United States); Boley, Aaron [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Turner, Neal; Okuzumi, Satoshi; Flock, Mario [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Mac Low, Mordecai-Mark, E-mail: wlyra@csun.edu, E-mail: neal.j.turner@jpl.nasa.gov, E-mail: mario.flock@jpl.nasa.gov, E-mail: ajr327@psu.edu, E-mail: acboley@phas.ubc.ca, E-mail: mordecai@amnh.org, E-mail: okuzumi@geo.titech.ac.jp [Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024-5192 (United States)

    2016-02-01

    Recent high-resolution, near-infrared images of protoplanetary disks have shown that these disks often present spiral features. Spiral arms are among the structures predicted by models of disk–planet interaction and thus it is tempting to suspect that planetary perturbers are responsible for these signatures. However, such interpretation is not free of problems. The observed spirals have large pitch angles, and in at least one case (HD 100546) it appears effectively unpolarized, implying thermal emission of the order of 1000 K (465 ± 40 K at closer inspection). We have recently shown in two-dimensional models that shock dissipation in the supersonic wake of high-mass planets can lead to significant heating if the disk is sufficiently adiabatic. Here we extend this analysis to three dimensions in thermodynamically evolving disks. We use the Pencil Code in spherical coordinates for our models, with a prescription for thermal cooling based on the optical depth of the local vertical gas column. We use a 5M{sub J} planet, and show that shocks in the region around the planet where the Lindblad resonances occur heat the gas to substantially higher temperatures than the ambient gas. The gas is accelerated vertically away from the midplane to form shock bores, and the gas falling back toward the midplane breaks up into a turbulent surf. This turbulence, although localized, has high α values, reaching 0.05 in the inner Lindblad resonance, and 0.1 in the outer one. We find evidence that the disk regions heated up by the shocks become superadiabatic, generating convection far from the planet’s orbit.

  14. Towards a shock tube method for the dynamic calibration of pressure sensors.

    Science.gov (United States)

    Downes, Stephen; Knott, Andy; Robinson, Ian

    2014-08-28

    In theory, shock tubes provide a pressure change with a very fast rise time and calculable amplitude. This pressure step could provide the basis for the calibration of pressure transducers used in highly dynamic applications. However, conventional metal shock tubes can be expensive, unwieldy and difficult to modify. We describe the development of a 1.4 MPa (maximum pressure) shock tube made from unplasticized polyvinyl chloride pressure tubing which provides a low-cost, light and easily modifiable basis for establishing a method for determining the dynamic characteristics of pressure sensors.

  15. Immediate Dose-Response Effect of High-Energy Versus Low-Energy Extracorporeal Shock Wave Therapy on Cutaneous Microcirculation.

    Science.gov (United States)

    Kraemer, Robert; Sorg, Heiko; Forstmeier, Vinzent; Knobloch, Karsten; Liodaki, Eirini; Stang, Felix Hagen; Mailaender, Peter; Kisch, Tobias

    2016-12-01

    Elucidation of the precise mechanisms and therapeutic options of extracorporeal shock wave therapy (ESWT) is only at the beginning. Although immediate real-time effects of ESWT on cutaneous hemodynamics have recently been described, the dose response to different ESWT energies in cutaneous microcirculation has never been examined. Thirty-nine Sprague-Dawley rats were randomly assigned to three groups that received either focused high-energy shock waves (group A: total of 1000 impulses, 10 J) to the lower leg of the hind limb, focused low-energy shock waves (group B: total of 300 impulses, 1 J) or placebo shock wave treatment (group C: 0 impulses, 0 J) using a multimodality shock wave delivery system (Duolith SD-1 T-Top, Storz Medical, Tägerwilen, Switzerland). Immediate microcirculatory effects were assessed with the O2C (oxygen to see) system (LEA Medizintechnik, Giessen, Germany) before and for 20 min after application of ESWT. Cutaneous tissue oxygen saturation increased significantly higher after high-energy ESWT than after low-energy and placebo ESWT (A: 29.4% vs. B: 17.3% vs. C: 3.3%; p = 0.003). Capillary blood velocity was significantly higher after high-energy ESWT and lower after low-energy ESWT versus placebo ESWT (group A: 17.8% vs. group B: -22.1% vs. group C: -5.0%, p = 0.045). Post-capillary venous filling pressure was significantly enhanced in the high-energy ESWT group in contrast to the low-energy ESWT and placebo groups (group A: 25% vs. group B: 2% vs. group C: -4%, p = 0.001). Both high-energy and low-energy ESWT affect cutaneous hemodynamics in a standard rat model. High-energy ESWT significantly increases parameters of cutaneous microcirculation immediately after application, resulting in higher tissue oxygen saturation, venous filling pressure and blood velocity, which suggests higher tissue perfusion with enhanced oxygen saturation, in contrast to low-energy as well as placebo ESWT. Low-energy ESWT also increased tissue oxygen

  16. Shock interaction with organized structures: Theory and computation

    Science.gov (United States)

    Ding, Zhong

    Unsteady interactions between shocks and turbulence are important phenomena frequently encountered in high-speed flows. In this dissertation the problem of a shock interaction with an entropy spot is studied by means of both theoretical analysis and nonlinear computation. The main objective of the studies is to apply both theoretical and computational approaches to study the physics underlying such shock interaction process. The theoretical analysis is based on the Fourier decomposition of the upstream disturbance, the interaction of each Fourier mode with the shock, and the reconstruction of the downstream disturbance via the inverse Fourier transform. The theory is linear in that it assumes the principle of superposition and that the Rankine-Hugoniot relations are linearized about the mean position of the shock. The numerical simulation is carried out within the framework of the unsteady and compressible Euler equations, coupled with an equation for the shock motion, solved numerically by a sixth-order accurate spatial scheme and a fourth-order Runge-Kutta time-integration method. Analyses of the results are concentrated on the case of a Mach 2.0 shock interaction with an entropy spot that has a Gaussian density distribution. The theoretical analysis and the numerical simulation are verified with each other for small amplitude disturbances. The roles of the evanescent and the non-evanescent waves and the mechanisms for downstream disturbance generations are explored in details. In addition, the quasi three-dimensional interaction between a shock and a vortex ring is investigated computationally within the framework of the axisymmetric Euler equations. The vortex ring, which is based on Lamb's formula, has an upstream circulation Gamma = 0.01 and its aspect ratio R lies in the range 8 ≤ R ≤ 100. The shock Mach number varies in the range 1.1 ≤ M1 ≤ 1.8. The interaction results in the streamwise compression of the vortex core and the generation of a toroidal

  17. Ultrafast ignition with relativistic shock waves induced by high power lasers

    Institute of Scientific and Technical Information of China (English)

    Shalom; Eliezer; Noaz; Nissim; Shirly; Vinikman; Pinhasi; Erez; Raicher; José; Maria; Martinez; Val

    2014-01-01

    In this paper we consider laser intensities greater than 1016 W cm-2where the ablation pressure is negligible in comparison with the radiation pressure.The radiation pressure is caused by the ponderomotive force acting mainly on the electrons that are separated from the ions to create a double layer(DL).This DL is accelerated into the target,like a piston that pushes the matter in such a way that a shock wave is created.Here we discuss two novel ideas.Firstly,the transition domain between the relativistic and non-relativistic laser-induced shock waves.Our solution is based on relativistic hydrodynamics also for the above transition domain.The relativistic shock wave parameters,such as compression,pressure,shock wave and particle flow velocities,sound velocity and rarefaction wave velocity in the compressed target,and temperature are calculated.Secondly,we would like to use this transition domain for shockwave-induced ultrafast ignition of a pre-compressed target.The laser parameters for these purposes are calculated and the main advantages of this scheme are described.If this scheme is successful a new source of energy in large quantities may become feasible.

  18. High-energy emission from non-relativistic radiative shocks: application to gamma-ray novae

    CERN Document Server

    Vurm, Indrek

    2016-01-01

    Multiwavelength radiation from relativistic particles accelerated at shocks in novae and other astrophysical sources carries a wealth of information about the outflow properties and the microphysical processes at work near the shocks. The observation of GeV gamma-rays from novae by Fermi/LAT demonstrates that the shocks in these systems can accelerate particles to energies of at least $\\sim 10$ GeV. The low-energy extension of the same non-thermal particle distribution inevitably gives rise to emission extending into the X-ray band. Above $\\gtrsim 10$ keV this radiation can escape the system without significant absorption/attenuation, and can potentially be detected by NuSTAR. We present theoretical models for hard X-ray and gamma-ray emission from radiative shocks in both leptonic and hadronic scenarios, accounting for the rapid evolution of the downstream properties due to the fast cooling of thermal plasma. Due to strong Coulomb cooling of the mildly relativistic electrons nominally responsible for produci...

  19. European Markets' Reactions to Exogenous Shocks: A High Frequency Data Analysis of the 2005 London Bombings

    National Research Council Canada - National Science Library

    Christos Kollias; Stephanos Papadamou; Costas Siriopoulos

    2013-01-01

    ...) models are employed. This type of data help reveal a more accurate picture of markets' reaction to exogenous shocks, such as a terrorist attack, and thus allow more reliable inferences. Findings reported herein indicate that the volatility of stock market returns is increased in all cases examined.

  20. Thermal shock behaviour of tungsten after high flux H-plasma loading

    NARCIS (Netherlands)

    Wirtz, M.; Linke, J.; Pintsuk, G.; De Temmerman, G.; Wright, G. M.

    2013-01-01

    Previous studies have shown that transient thermal shock loads induce crack networks on tungsten samples especially at low base temperatures. To achieve test conditions which are more relevant for the performance of tungsten-armoured plasma facing components in next step thermonuclear fusion devices

  1. High Energy-Density Materials with Fast Energy Release: Molecular Scale Shock Response of Explosives

    Science.gov (United States)

    2013-05-01

    ORGANIZATION. REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 Public reporting burden for this collection of information...Transient absorption spectroscopy of laser shocked explosives”, presented by S. D. McGrane 2012 LANL Advanced Thermometry Workshop, “Femtosecond...condensed phases using femtosecond stimulated Raman scattering”, presented by Nhan Dang Poster presentations: 2010 LANL Chemistry Capabilities

  2. Developing a 3-shock, low-adiabat drive for high pressure material science experiments on NIF

    Science.gov (United States)

    Wehrenberg, Christopher; Prisbrey, Shon; Graham, Peter; Park, Hye-Sook; Huntington, Channing; Maddox, Brian; Benedetti, Robin; Rudd, Robert; Arsenlis, Tom; Remington, Bruce

    2014-10-01

    We describe a series of experiments for basic materials science on NIF to develop a planar, 3-shock, low-adiabat drive to reach peak pressures of 5 Mbar, while keeping the physics samples well below their melt temperatures. The primary diagnostic is VISAR, which measures the compression waves as they travel through a Ta witness plate. X-ray ablation from an indirect drive launches a strong (>10 Mbar) shock through a precision fabricated ``reservoir,'' consisting of a CH ablator, followed by layers of Al, CH(18.75%I), 350 mg/cc CRF foam, and a final layer of 10-30 mg/cc foam. This reservoir releases as plasma across a 1.5 mm vacuum gap, then stagnates on the 15 micron thick Ta witness plate, which is backed by a LiF or quartz window. The lowest density reservoir layer sets the strength of the leading shock, which needs to be controlled to keep the physics samples solid, and to control the dislocation density created by this leading shock. We will describe an extensive series of experiments done on NIF to develop this drive. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.

  3. Mechanism associated with the Space Shuttle main engine oxidizer valve/duct system anomalous high amplitude discrete acoustical excitation

    Science.gov (United States)

    Schutzenhofer, L. A.; Jones, J. H.; Jewell, R. E.; Ryan, R. S.

    1980-01-01

    Anomalous high frequency pressure fluctuations in the Space Shuttle main engine have been experienced during hot firings. Through diagnostic analysis of hot firing engine data, it was determined that this excitation originated at the main oxidizer valve. The intensity of these fluctuations was such that the main oxidizer valve was partially consumed in fire, experienced fretting, and had seal damage. Delineated in this paper are the associated dynamical phenomena and the methodologies leading toward understanding the excitation mechanism. The results presented demonstrate that the source of the anomalous frequencies was suppressed by a simple fix and all main oxidizer valve damage was terminated.

  4. Frequency and amplitude characteristics of a high-repetition-rate hybrid TEA-CO/sub 2/ laser

    Energy Technology Data Exchange (ETDEWEB)

    Lachambre, J.L.; Lavigne, P.; Verreault, M.; Otis, G.

    1978-02-01

    The envelope and frequency characteristics of the output pulse of a high-repetition-rate hybrid TEA-CO/sub 2/ laser are presented. Both the intrapulse and interpulse laser frequency stability are experimentally determined at repetition rates up to 300 Hz. The recovery of the CW laser signal following the generation of the TEA laser pulse is analyzed theoretically and experimentally. Short term reproducibilities of + or - 2 MHz are observed at a pulse repetition rate of 300 Hz with initial chirp rates of about 1.5 MHz/microsec. Improvements and limits on power and repetition rate are discussed.

  5. Determining the TNT equivalence of gram-sized explosive charges using shock-wave shadowgraphy and high-speed video recording

    Science.gov (United States)

    Hargather, Michael

    2005-11-01

    Explosive materials are routinely characterized by their TNT equivalence. This can be determined by chemical composition calculations, measurements of shock wave overpressure, or measurements of the shock wave position vs. time. However, TNT equivalence is an imperfect criterion because it is only valid at a given radius from the explosion center (H. Kleine et al., Shock Waves 13(2):123-138, 2003). Here we use a large retroreflective shadowgraph system and a high-speed digital video camera to image the shock wave and record its location vs. time. Optical data obtained from different explosions can be combined to determine a characteristic shock wave x-t diagram, from which the overpressure and the TNT equivalent are determined at any radius. This method is applied to gram-sized triacetone triperoxide (TATP) charges. Such small charges can be used inexpensively and safely for explosives research.

  6. Ion acoustic shock and periodic waves through Burgers equation in weakly and highly relativistic plasmas with nonextensivity

    Science.gov (United States)

    M, G. Hafez; N, C. Roy; M, R. Talukder; M Hossain, Ali

    2017-01-01

    A comparative study is carried out for the nonlinear propagation of ion acoustic shock waves both for the weakly and highly relativistic plasmas consisting of relativistic ions and q-distributed electrons and positions. The Burgers equation is derived to reveal the physical phenomena using the well known reductive perturbation technique. The integration of the Burgers equation is performed by the (G\\prime /G)-expansion method. The effects of positron concentration, ion–electron temperature ratio, electron–positron temperature ratio, ion viscosity coefficient, relativistic streaming factor and the strength of the electron and positron nonextensivity on the nonlinear propagation of ion acoustic shock and periodic waves are presented graphically and the relevant physical explanations are provided.

  7. Amplitudes, acquisition and imaging

    Energy Technology Data Exchange (ETDEWEB)

    Bloor, Robert

    1998-12-31

    Accurate seismic amplitude information is important for the successful evaluation of many prospects and the importance of such amplitude information is increasing with the advent of time lapse seismic techniques. It is now widely accepted that the proper treatment of amplitudes requires seismic imaging in the form of either time or depth migration. A key factor in seismic imaging is the spatial sampling of the data and its relationship to the imaging algorithms. This presentation demonstrates that acquisition caused spatial sampling irregularity can affect the seismic imaging and perturb amplitudes. Equalization helps to balance the amplitudes, and the dealing strategy improves the imaging further when there are azimuth variations. Equalization and dealiasing can also help with the acquisition irregularities caused by shot and receiver dislocation or missing traces. 2 refs., 2 figs.

  8. THE A2667 GIANT ARC AT z = 1.03: EVIDENCE FOR LARGE-SCALE SHOCKS AT HIGH REDSHIFT

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, T.-T.; Kewley, L. J. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Swinbank, A. M. [Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham, DH1 3LE (United Kingdom); Richard, J. [CRAL, Observatoire de Lyon, Universite Lyon 1, 9 Avenue Ch. Andre, F-69561 Saint Genis Laval Cedex (France)

    2012-11-01

    We present the spatially resolved emission line ratio properties of a {approx}10{sup 10} M {sub Sun} star-forming galaxy at redshift z = 1.03. This galaxy is gravitationally lensed as a triple-image giant arc behind the massive lensing cluster A2667. The main image of the galaxy has magnification factors of 14 {+-} 2.1 in flux and {approx}2 Multiplication-Sign 7 in area, yielding an intrinsic spatial resolution of 115-405 pc after adaptive optics correction with OSIRIS at KECK II. The Hubble Space Telescope morphology shows a clumpy structure and the H{alpha} kinematics indicates a large velocity dispersion with V {sub max} sin (i)/{sigma} {approx} 0.73, consistent with high-redshift disk galaxies of similar masses. From the [N II]/H{alpha} line ratios, we find that the central 350 pc of the galaxy is dominated by star formation. The [N II]/H{alpha} line ratios are higher in the outer disk than in the central regions. Most noticeably, we find a blueshifted region of strong [N II]/H{alpha} emission in the outer disk. Applying our recent H II region and slow-shock models, we propose that this elevated [N II]/H{alpha} ratio region is contaminated by a significant fraction of shock excitation due to galactic outflows. Our analysis suggests that shocked regions may mimic flat or inverted metallicity gradients at high redshift.

  9. On the high-temperature combustion of n-butanol: Shock tube data and an improved kinetic model

    KAUST Repository

    Vasu, Subith S.

    2013-11-21

    The combustion of n-butanol has received significant interest in recent years, because of its potential use in transportation applications. Researchers have extensively studied its combustion chemistry, using both experimental and theoretical methods; however, additional work is needed under specific conditions to improve our understanding of n-butanol combustion. In this study, we report new OH time-history data during the high-temperature oxidation of n-butanol behind reflected shock waves over the temperature range of 1300-1550 K and at pressures near 2 atm. These data were obtained at Stanford University, using narrow-line-width ring dye laser absorption of the R1(5) line of OH near 306.7 nm. Measured OH time histories were modeled using comprehensive n-butanol literature mechanisms. It was found that n-butanol unimolecular decomposition rate constants commonly used in chemical kinetic models, as well as those determined from theoretical studies, are unable to predict the data presented herein. Therefore, an improved high-temperature mechanism is presented here, which incorporates recently reported rate constants measured in a single pulse shock tube [C. M. Rosado-Reyes and W. Tsang, J. Phys. Chem. A 2012, 116, 9825-9831]. Discussions are presented on the validity of the proposed mechanism against other literature shock tube experiments. © 2013 American Chemical Society.

  10. Hard X-ray and Gamma-ray Emission Induced by Ultra-High Energy Protons in Cluster Accretion Shocks

    CERN Document Server

    Inoue, S; Sugiyama, N; Inoue, Susumu; Aharonian, Felix A.; Sugiyama, Naoshi

    2005-01-01

    All sufficiently massive clusters of galaxies are expected to be surrounded by strong accretion shocks, where protons can be accelerated to $\\sim 10^{18}$-$10^{19}$ eV under plausible conditions. Such protons interact with the cosmic microwave background and efficiently produce very high energy electron-positron pairs, which then radiate synchrotron and inverse Compton emission, peaking respectively at hard X-ray and TeV gamma-ray energies. Characterized by hard spectra (photon indices $\\sim 1.5$) and spatial distribution tracing the accretion shock, these can dominate over other nonthermal components depending on the shock magnetic field. HESS and other Cerenkov telescopes may detect the TeV emission from nearby clusters, notwithstanding its extended nature. The hard X-rays may be observable by future imaging facilities such as NeXT, and possibly also by ASTRO-E2/HXD. Such detections will not only provide a clear signature of ultra-high energy proton acceleration, but also an important probe of the accretion...

  11. A highly purified vegetal fraction able to modulate HMGB1 and to attenuate septic shock in mice.

    Science.gov (United States)

    Apetrei, Natalia Simona; Călugăru, Ana; Kerek, F; Panteli, Minerva; Rasit, I; Cremer, Lidia; Szegli, G; Lupu, Andreea-Roxana

    2011-01-01

    High-mobility group box protein 1 (HMGB1) is an intracellular protein that may be released actively from monocytes and macrophages or passively from necrotic or damaged cells. Its inhibition in animal experiments, even in the late phase of septic shock, significantly enhanced the survival rate of rodents. The aim of our study was to investigate the effect of a vegetal fraction isolated and highly purified from Helleborus purpurascens regarding the modulation of HMGB1 release either from tumor cells or human blood mononuclear cells. Our results showed that the vegetal fraction was able to down-regulate the release of HMGB1 from activated human blood mononuclear cells (PBMCs) and tumor cells. By combining the purified fraction with Cyclophosphamide the release of HMGB1 from tumor cells was strongly decreased. This synergism was not noticed when the ve getal product was associated with Doxorubicin. We also studied the effect of the purified fraction in mice with septic shock induced by cecal ligation and puncture (CLP) method. The tested vegetal product increased significantly the survival rate of animals compared to the mice not treated with it. Our data suggest that the purified vegetal fraction may modulate inflammation by down-regulating the HMGB1, which can also explain its efficacy in septic shock in mice.

  12. Strong S-wave attenuation and actively degassing magma beneath Taal volcano, Philippines, inferred from source location analysis using high-frequency seismic amplitudes

    Science.gov (United States)

    Kumagai, H.; Lacson, R. _Jr., Jr.; Maeda, Y.; Figueroa, M. S., II; Yamashina, T.

    2014-12-01

    Taal volcano, Philippines, is one of the world's most dangerous volcanoes given its history of explosive eruptions and its close proximity to populated areas. A key feature of these eruptions is that the eruption vents were not limited to Main Crater but occurred on the flanks of Volcano Island. This complex eruption history and the fact that thousands of people inhabit the island, which has been declared a permanent danger zone, together imply an enormous potential for disasters. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) constantly monitors Taal, and international collaborations have conducted seismic, geodetic, electromagnetic, and geochemical studies to investigate the volcano's magma system. Realtime broadband seismic, GPS, and magnetic networks were deployed in 2010 to improve monitoring capabilities and to better understand the volcano. The seismic network has recorded volcano-tectonic (VT) events beneath Volcano Island. We located these VT events based on high-frequency seismic amplitudes, and found that some events showed considerable discrepancies between the amplitude source locations and hypocenters determined by using onset arrival times. Our analysis of the source location discrepancies points to the existence of a region of strong S-wave attenuation near the ground surface beneath the east flank of Volcano Island. This region is beneath the active fumarolic area and above sources of pressure contributing inflation and deflation, and it coincides with a region of high electrical conductivity. The high-attenuation region matches that inferred from an active-seismic survey conducted at Taal in 1993. Our results, synthesized with previous results, suggest that this region represents actively degassing magma near the surface, and imply a high risk of future eruptions on the east flank of Volcano Island.

  13. Computations of the Shock Waves at Hypersonic Velocities Taken into Account the Chemical Reactions that Appear in the Air at High Temperatures

    Directory of Open Access Journals (Sweden)

    Mihai Leonida NICULESCU

    2015-09-01

    Full Text Available The temperature in the nose region of a hypersonic vehicle can be extremely high, for example, reaching approximately 11 000 K at a Mach number of 36 (Apollo reentry. The bow shock wave is normal, or nearly normal, in the nose region of a blunt body, and the gas temperature behind this shock wave can be enormous at hypersonic speeds. In this case, the assumption of a calorically perfect nonreacting gas with the ratio of specific heats  of 1.4 gives an unrealistically high value of temperature. Therefore, the proper inclusion of chemically reacting effects is vital to the calculation of an accurate normal shock wave temperature.

  14. Dynamic response of Cu4Zr54 metallic glass to high strain rate shock loading: plasticity, spall and atomic-level structures

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Shengnian [Los Alamos National Laboratory; Arman, Bedri [Los Alamos National Laboratory; Germann, Timothy C [Los Alamos National Laboratory; Cagin, Tahir [TEXAS A& M UNIV

    2009-01-01

    We investigate dynamic response of Cu{sub 46}Zr{sub 54} metallic glass under adiabatic planar shock wave loading (one-dimensional strain) wjth molecular dynamics simulations, including Hugoniot (shock) states, shock-induced plasticity and spallation. The Hugoniot states are obtained up to 60 CPa along with the von Mises shear flow strengths, and the dynamic spall strength, at different strain rates and temperatures. The spall strengths likely represent the limiting values achievable in experiments such as laser ablation. For the steady shock states, a clear elastic-plastic transition is identified (e.g., in the shock velocity-particle velocity curve), and the shear strength shows strain-softening. However, the elastic-plastic transition across the shock front displays transient stress overshoot (hardening) above the Hugoniot elastic limit followed by a relatively sluggish relaxation to the steady shock state, and the plastic shock front steepens with increasing shock strength. The local von Mises shear strain analysis is used to characterize local deformation, and the Voronoi tessellation analysis, the corresponding short-range structures at various stages of shock, release, tension and spallation. The plasticity in this glass is manifested as localized shear transformation zones and of local structure rather than thermal origin, and void nucleation occurs preferentially at the highly shear-deformed regions. The Voronoi and shear strain analyses show that the atoms with different local structures are of different shear resistances that lead to shear localization (e.g., the atoms indexed with (0,0,12,0) are most shear-resistant, and those with (0,2,8,1) are highly prone to shear flow). The dynamic changes in local structures are consistent with the observed deformation dynamics.

  15. High-amplitude supergiant V5112 Sgr: enrichment of the envelope with heavy s-process metals

    CERN Document Server

    Klochkova., V G

    2013-01-01

    High-resolution (R=60000) echelle spectroscopy of the post-AGB supergiant V5112 Sgr performed in 1996-2012 with the 6-m telescope BTA has revealed peculiarities of the star optical spectrum and has allowed the variability of the velocity field in the stellar atmosphere and envelope to be studied in detail. An asymmetry and splitting of strong absorption lines with a low lower-level excitation potential have been detected for the first time. The effect is maximal in BaII lines whose profile is split into three components. The profile shape and positions of the split lines change with time. The blue components of the split absorption lines are shown to be formed in a structured circumstellar envelope, suggesting an efficient dredge-up of the heavy metals produced during the preceding evolution of this star into the envelope. The envelope expansion velocities have been estimated to be 20 and 30 km/s. The mean radial velocity from diffuse bands in the spectrum of V5112 Sgr coincides with that from the short-wavel...

  16. Computational study of shock interaction with a vortex ring

    Science.gov (United States)

    Ding, Z.; Hussaini, M. Y.; Erlebacher, G.; Krothapalli, A.

    2001-10-01

    The problem of shock interaction with a vortex ring is investigated within the framework of axisymmetric Euler equations solved numerically by a shock-fitted sixth-order compact difference scheme. The vortex ring, which is based on Lamb's formula, has an upstream circulation Γ=0.01 and its aspect ratio R lies in the range 8⩽R⩽100. The shock Mach number varies in the range 1.1⩽M1⩽1.8. The vortex ring/shock interaction results in the streamwise compression of the vortex core by a factor proportional to the ratio of the upstream and downstream mean velocity U1/U2, and the generation of a toroidal acoustic wave and entropy disturbances. The toroidal acoustic wave propagates and interacts with itself on the symmetry axis of the vortex ring. This self-interaction engenders high amplitude rarefaction/compression pressure peaks upstream/downstream of the transmitted vortex core. This results in a significant increase in centerline sound pressure levels, especially near the shock (due to the upstream movement of the rarefaction peak) and in the far downstream (due to the downstream movement of the compression peak). The magnitude of the compression peak increases nonlinearly with M1. For a given M1, vortex rings with smaller aspect ratios (R40) generate pressure disturbances whose amplitudes are roughly independent of R.

  17. Effects of high- and low-energy radial shock waves therapy combined with physiotherapy in the treatment of rotator cuff tendinopathy: a retrospective study.

    Science.gov (United States)

    Su, Xiangzheng; Li, Zhongli; Liu, Zhengsheng; Shi, Teng; Xue, Chao

    2017-06-09

    The aim of this study was to investigate the efficacy of high- and low-energy radial shock waves combined with physiotherapy for rotator cuff tendinopathy patients. Data from rotator cuff tendinopathy patients received high- or low-energy radial shock waves combined with physiotherapy or physiotherapy alone were collected. The Constant and Murley score and visual analog scale score were collected to assess the effectiveness of treatment in three groups at 4, 8, 12, and 24 weeks. In total, 94 patients were involved for our retrospective study. All groups showed remarkable improvement in the visual analog scale and Constant and Murley score compared to baseline at 24 weeks. The high-energy radial shock waves group had more marked improvement in the Constant and Murley score compared to the physiotherapy group at 4 and 8 weeks and at 4 weeks when compared with low-energy group. Furthermore, high-energy radial shock waves group had superior results on the visual analog scale at 4, 8, and 12 weeks compared to low-energy and physiotherapy groups. This retrospective study supported the usage of high-energy radial shock waves as a supplementary therapy over physiotherapy alone for rotator cuff tendinopathy by relieving the symptoms rapidly and maintaining symptoms at a satisfactory level for 24 weeks. Implications for Rehabilitation High-energy radial shock waves can be a supplemental therapy to physiotherapy for rotator cuff tendinopathy. We recommend the usage of high-energy radial shock waves during the first 5 weeks, at an interval of 7 days, of physiotherapy treatment. High-energy radial shock waves treatment combined with physiotherapy can benefit rotator cuff tendinopathy by relieving symptoms rapidly and maintain these improvements at a satisfactory level for quite a long time.

  18. Streptococcal toxic shock syndrome

    Directory of Open Access Journals (Sweden)

    Gvozdenović Ljiljana

    2010-01-01

    Full Text Available Introduction. Streptococcal toxic shock syndrome is now recognized as a toxin-mediated, multisystem illness. It is characterized by an early onset of shock with multiorgan failure and continues to be associated with high morbidity and mortality, caused by group A Streptococcus pyogenes. The symptoms for staphylococcal and streptococcal toxic shock syndrome are similar. Streptococcal toxic shock syndrome was not well described until 1993, when children who had suffered from varicella presented roughly 2-4 weeks later with a clinical syndrome highly suggestive of toxic shock syndrome. Characteristics, complications and therapy. It is characterized by a sudden onset of fever, chills, vomiting, diarrhea, muscle aches and rash. It can rapidly progress to severe and intractable hypotension and multisystem dysfunction. Almost every organ system can be involved. Complications of streptococcal toxic shock syndrome may include kidney failure, liver failure and even death. Crystalloids and inotropic agents are used to treat the hypovolemic shock aggressively, with close monitoring of the patient’s mean arterial pressure and central venous pressure. An immediate and aggressive management of hypovolemic shock is essential in streptococcal toxic shock syndrome. Targeted antibiotics are indicated; penicillin or a betalactam antibiotic is used for treating group A streptococci, and clindamycin has emerged as a key portion of the standard treatment.

  19. Three- and Two- Dimensional Simulations of Re-shock Experiments at High Energy Densities at the National Ignition Facility

    Science.gov (United States)

    Wang, Ping; Raman, Kumar; MacLaren, Stephan; Huntington, Channing; Nagel, Sabrina

    2016-10-01

    We present simulations of recent high-energy-density (HED) re-shock experiments on the National Ignition Facility (NIF). The experiments study the Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instability growth that occurs after successive shocks transit a sinusoidally-perturbed interface between materials of different densities. The shock tube is driven at one or both ends using indirect-drive laser cavities or hohlraums. X-ray area-backlit imaging is used to visualize the growth at different times. Our simulations are done with the three-dimensional, radiation hydrodynamics code ARES, developed at LLNL. We show the instabilitygrowth rate, inferred from the experimental radiographs, agrees well with our 2D and 3D simulations. We also discuss some 3D geometrical effects, suggested by our simulations, which could deteriorate the images at late times, unless properly accounted for in the experiment design. Work supported by U.S. Department of Energy under Contract DE- AC52-06NA27279. LLNL-ABS-680789.

  20. Shock waves in disordered media

    CERN Document Server

    Ghofraniha, N; Folli, V; DelRe, E; Conti, C

    2012-01-01

    We experimentally investigate the interplay between spatial shock waves and the degree of disorder during nonlinear optical propagation in a thermal defocusing medium. We characterize the way the shock point is affected by the amount of disorder and scales with wave amplitude. Evidence for the existence of a phase diagram in terms of nonlinearity and amount of randomness is reported. The results are in quantitative agreement with a theoretical approach based on the hydrodynamic approximation.

  1. Mechanical effects induced by shock waves generated by high energy laser pulses

    Science.gov (United States)

    Fournier, J.; Ballard, P.; Merrien, P.; Barralis, J.; Castex, L.; Fabbro, R.

    1991-09-01

    Specimens made of low alloy and non alloyed medium carbon steels were subjected to high energy laser pulses. Direct ablation and confined plasma procedures were both investigated. An optimum impulse momentum transfer to the material is attained with a pulse duration of 30 ns and a power density of 10 GW .cm^2. Fatigue testing shows that the fatigue strengths of the selected materials are significantly increased. This can be related to the fact that laser shock processing generates an appropriate residual compressive stress field in a sufficiently thick layer and does not alter the initial surface roughness. In addition, the use of cumulative laser impacts and of dual treatment combining thermal and mechanical effects of the laser beam have been investigated and shown to result in an enhanced fatigue strength. Des échantillons d'acier éventuellement faiblement allié sont irradiés par un ou plusieurs pulses laser ayant une intensité comprise entre 1 et 100 GW/cm^2 et une durée d'émission laser de 3 ou 30 ns, les deux configurations d'ablation directe ou de plasma confiné étant utilisées. Les contraintes résiduelles résultant du passage de l'onde de choc sont analysées à l'aide de la technique de diffraction de rayons X. D'après cette étude, il apparaît clairement que les valeurs d'intensité et de durée d'émission laser les plus appropriées sont respectivement 10 GW/cm^2 et 30 ns. Ces valeurs correspondent à l'optimum de transfert d'impulsion. De plus, l'influence du nombre d'impacts laser utilisés est discuté et un essai de fatigue montre que ce traitement mécanique de surface augmente de manière significative la limite d'endurance du matériau étudié.

  2. Thoracic compression myelopathy due to the progression of dystrophic scoliosis, the presence of a paraspinal tumor, and high and excessive amplitude movement of the shoulder.

    Science.gov (United States)

    Kurosawa, Takashi; Yurube, Takashi; Kakutani, Kenichiro; Maeno, Koichiro; Uno, Koki; Kurosaka, Masahiro; Nishida, Kotaro

    2017-01-01

    The authors present a case of 45-year-old man with neurofibromatosis type 1 (NF-1) and thoracic scoliosis, previously undergoing fusion surgery, who developed myelopathy. This patient further complained of lightning pain when he extended and horizontally abducted the convex-side shoulder. Radiological examination revealed the progression of dystrophic scoliosis with opened spinal canals and the presence of a neurofibroma behind the spinal cord at the apical levels. Delayed development of spinal instability can occur due to dystrophy even postoperatively in patients with NF-1. After tumor resection, he had rapid recovery from myelopathy and no recurrence of radiating pain despite shoulder movement. These findings provide a speculation that high, intense amplitude movement of the shoulder toward the spinal canal causes the impingement on the neurofibroma, resulting in indirect compression of the exposed spinal cord. This is the first report describing thoracic compression myelopathy associated with paraspinal displacement of the scapula.

  3. Nuclear Jacobi and Poincaré transitions at high spins and temperatures: Account of dynamic effects and large-amplitude motion

    Science.gov (United States)

    Mazurek, K.; Dudek, J.; Maj, A.; Rouvel, D.

    2015-03-01

    We present a theoretical analysis of the competition between the so-called nuclear Jacobi and Poincaré shape transitions as a function of spin at high temperatures. The latter condition implies the method of choice, a realistic version of the nuclear liquid drop model, here the Lublin-Strasbourg drop model. We address specifically the fact that the Jacobi and Poincaré shape transitions are accompanied by the flattening of the total nuclear energy landscape as a function of the relevant deformation parameters, which enforces large-amplitude oscillation modes that need to be taken into account. For that purpose we introduce an approximate form of the collective Schrödinger equation whose solutions are used to calculate the most probable deformations associated with the nuclear Jacobi and Poincaré transitions. We discuss selected aspects of the new description focusing on the critical-spin values for both types of these transitions.

  4. Search for high-amplitude Delta Scuti and RR Lyrae stars in Sloan Digital Sky Survey Stripe 82 using principal component analysis

    CERN Document Server

    Süveges, M; Váradi, M; Mowlavi, N; Becker, A C; Ivezić, Ž; Beck, M; Nienartowicz, K; Rimoldini, L; Dubath, P; Bartholdi, P; Eyer, L

    2012-01-01

    We propose a robust principal component analysis (PCA) framework for the exploitation of multi-band photometric measurements in large surveys. Period search results are improved using the time series of the first principal component due to its optimized signal-to-noise ratio.The presence of correlated excess variations in the multivariate time series enables the detection of weaker variability. Furthermore, the direction of the largest variance differs for certain types of variable stars. This can be used as an efficient attribute for classification. The application of the method to a subsample of Sloan Digital Sky Survey Stripe 82 data yielded 132 high-amplitude Delta Scuti variables. We found also 129 new RR Lyrae variables, complementary to the catalogue of Sesar et al., 2010, extending the halo area mapped by Stripe 82 RR Lyrae stars towards the Galactic bulge. The sample comprises also 25 multiperiodic or Blazhko RR Lyrae stars.

  5. Nuclear Jacobi and Poincar\\'e Transitions at High Spins and Temperatures: Account~of~Dynamic~Effects~and~Large-Amplitude Motion

    CERN Document Server

    Mazurek, K; Maj, A; Rouvel, D

    2013-01-01

    We present a theoretical analysis of the competition between so-called nuclear Jacobi and Poincar\\'e shape transitions in function of spin - at high temperatures. The latter condition implies the method of choice - a realistic version of the nuclear Liquid Drop Model (LDM), here: the Lublin-Strasbourg Drop (LSD) model. We address specifically the fact that the Jacobi and Poincar\\'e shape transitions are accompanied by the flattening of total nuclear energy landscape as function of the relevant deformation parameters what enforces large amplitude oscillation modes that need to be taken into account. For that purpose we introduce an approximate form of the collective Schr\\"odinger equation whose solutions are used to calculate the most probable deformations associated with both types of transitions and discuss the physical consequences in terms of the associated critical-spin values and transitions themselves.

  6. HyCFS, a high-resolution shock capturing code for numerical simulation on hybrid computational clusters

    Science.gov (United States)

    Shershnev, Anton A.; Kudryavtsev, Alexey N.; Kashkovsky, Alexander V.; Khotyanovsky, Dmitry V.

    2016-10-01

    The present paper describes HyCFS code, developed for numerical simulation of compressible high-speed flows on hybrid CPU/GPU (Central Processing Unit / Graphical Processing Unit) computational clusters on the basis of full unsteady Navier-Stokes equations, using modern shock capturing high-order TVD (Total Variation Diminishing) and WENO (Weighted Essentially Non-Oscillatory) schemes on general curvilinear structured grids. We discuss the specific features of hybrid architecture and details of program implementation and present the results of code verification.

  7. Structure of shock compressed model basaltic glass: Insights from O K-edge X-ray Raman scattering and high-resolution 27Al NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sung Keun; Park, Sun Young; Kim, Hyo-Im; Tschauner, Oliver; Asimow, Paul; Bai, Ligang; Xiao, Yuming; Chow, Paul (UNLV); (SNU); (CIT); (CIW)

    2012-05-29

    The detailed atomic structures of shock compressed basaltic glasses are not well understood. Here, we explore the structures of shock compressed silicate glass with a diopside-anorthite eutectic composition (Di{sub 64}An{sub 36}), a common Fe-free model basaltic composition, using oxygen K-edge X-ray Raman scattering and high-resolution {sup 27}Al solid-state NMR spectroscopy and report previously unknown details of shock-induced changes in the atomic configurations. A topologically driven densification of the Di{sub 64}An{sub 36} glass is indicated by the increase in oxygen K-edge energy for the glass upon shock compression. The first experimental evidence of the increase in the fraction of highly coordinated Al in shock compressed glass is found in the {sup 27}Al NMR spectra. This unambiguous evidence of shock-induced changes in Al coordination environments provides atomistic insights into shock compression in basaltic glasses and allows us to microscopically constrain the magnitude of impact events or relevant processes involving natural basalts on Earth and planetary surfaces.

  8. High pressure phases in NWA 8711, a shock melted L6 chondrite from Northwest Africa: a combined Raman and EMPA study.

    Science.gov (United States)

    Moggi Cecchi, V.; Pratesi, G.; Caporali, S.; Zoppi, M.

    We report the occurrence of two coexisting high-pressure assemblages in shock-induced black veins of NWA 8711, an L6 chondrite recently found in Northwest Africa. The main phases of the host rock are olivine, enstatite, diopside, plagioclase, iron-nickel alloy and troilite. The presence of typical shock metamorphic features both in olivine and pyroxene, as well as of maskelynite and melt veins point to a shock stage S6. Two coexisting distinct assemblages were observed in the shock-melted areas: (1) a very fine-grained intergrowth of silicate phases sprinkled with fine-grained metal and troilite blebs and (2) a coarser-grained polycrystalline aggregate consisting of ringwoodite crystals. EMPA analyses were performed on both the chondritic matrix and on individual grains of the shock-melted area to characterize their mineralogical composition. EMPA analyses on the coarse-grained area suggested the presence of shock-generated ringwoodite and low-Ca majorite. These data are confirmed by Micro-Raman point analyses. The analyses performed on the fine-grained portion of the veins allowed to determine the presence of a majorite-pyrope solid solution. According to literature data the majorite-pyrope solid solution suggests a crystallization from a shock-melted chondritic matrix under high pressures and temperatures. Ringwoodite and low-Ca majorite were instead formed by solid state transformation of olivine and low-Ca pyroxene originally present in the meteorite.

  9. Transient cardiogenic shock during a crisis of pheochromocytoma triggered by high-dose exogenous corticosteroids

    OpenAIRE

    Ibrahim, Majd; Banga, Sandeep; Venkatapuram, Suneetha; Mungee, Sudhir

    2015-01-01

    We report a case of a 39-year-old woman who presented to the emergency department (ED) with symptoms of pharyngitis and fever. Diagnosed with streptococcal pharyngitis, she received antibiotics and dexamethasone, and was discharged. Within 24 h she returned to the ED with signs and symptoms of an acute coronary syndrome; she was thus given β-blockers. Her coronary angiogram was normal. She developed cardiogenic shock with an ejection fraction (EF) of 10% and apical ballooning on echocardiogra...

  10. Shock Detector for SURF model

    Energy Technology Data Exchange (ETDEWEB)

    Menikoff, Ralph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-01-11

    SURF and its extension SURFplus are reactive burn models aimed at shock initiation and propagation of detonation waves in high explosives. A distinctive feature of these models is that the burn rate depends on the lead shock pressure. A key part of the models is an algorithm to detect the lead shock. Typically, shock capturing hydro algorithms have small oscillations behind a shock. Here we investigate how well the shock detection algorithm works for a nearly steady propagating detonation wave in one-dimension using the Eulerian xRage code.

  11. Shock Detector for SURF model

    Energy Technology Data Exchange (ETDEWEB)

    Menikoff, Ralph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-01-11

    SURF and its extension SURFplus are reactive burn models aimed at shock initiation and propagation of detonation waves in high explosives. A distinctive feature of these models is that the burn rate depends on the lead shock pressure. A key part of the models is an algorithm to detect the lead shock. Typically, shock capturing hydro algorithms have small oscillations behind a shock. Here we investigate how well the shock detection algorithm works for a nearly steady propagating detonation wave in one-dimension using the Eulerian xRage code.

  12. High Spectral and Spatial Resolution Observations of Shocked Molecular Hydrogen at the Galactic Center

    CERN Document Server

    Yusef-Zadeh, F; Burton, M; Wardle, M; Ashley, M C B

    2001-01-01

    The presence of OH (1720 MHz) masers, and the absence of counterparts at 1665/1667 MHz has proved to be a clear diagnostic of shocked molecular gas associated with Galactic supernova remnants. This suggests that shocked molecular gas should be associated with the OH (1720 MHz) masers that have been detected in the circumnuclear disk (CND) and Sgr A East at the Galactic center. In order to test this hypothesis, we observed the H$_2$ 1--0 S(1) and Br $\\gamma$ lines using NICMOS on the HST and UNSWIRF on the AAT, near the regions where OH (1720 MHz) masers are detected in the CND and Sgr A East. We present the distribution of H$_2$ in the North and South lobes of the CND and in Sgr A East. H$_2$ emission accompanies almost all of the maser spots detected at the Galactic center. In particular, we find a striking filamentary structure near the Northwest of the CND and evidence that shocked molecular gas is associated with the 70 \\kms molecular cloud at the Galactic center. We argue that the emission from the CND c...

  13. Real topological string amplitudes

    Science.gov (United States)

    Narain, K. S.; Piazzalunga, N.; Tanzini, A.

    2017-03-01

    We discuss the physical superstring correlation functions in type I theory (or equivalently type II with orientifold) that compute real topological string amplitudes. We consider the correlator corresponding to holomorphic derivative of the real topological amplitude G_{χ } , at fixed worldsheet Euler characteristic χ. This corresponds in the low-energy effective action to N=2 Weyl multiplet, appropriately reduced to the orientifold invariant part, and raised to the power g' = -χ + 1. We show that the physical string correlator gives precisely the holomorphic derivative of topological amplitude. Finally, we apply this method to the standard closed oriented case as well, and prove a similar statement for the topological amplitude F_g.

  14. DO COROTATING INTERACTION REGION ASSOCIATED SHOCKS SURVIVE WHEN THEY PROPAGATE INTO THE HELIOSHEATH?

    Energy Technology Data Exchange (ETDEWEB)

    Provornikova, E.; Opher, M. [Astronomy Department, Boston University, Boston, MA 02215 (United States); Izmodenov, V. [Department of Air Mechanics and Gas Dynamics, Faculty of Mechanics and Mathematics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Toth, G., E-mail: eprovorn@bu.edu, E-mail: mopher@bu.edu, E-mail: izmod@iki.rssi.ru, E-mail: gtoth@umich.edu [Center for Space Environment Modeling, University of Michigan, Ann Arbor, MI 48109 (United States)

    2012-09-10

    During the solar minimum at the distance of 42-52 AU from the Sun, Voyager 2 observed recurrent sharp, shock-like increases in the solar wind speed that look very much like forward shocks (Lazarus et al.). The shocks were produced by corotating interaction regions (CIRs) that originated near the Sun. After the termination shock (TS) crossing in 2007, Voyager 2 entered the heliosheath and has been observing the plasma emanated during the recent solar minima. Measurements show high variable flow, but there were no shocks detected in the heliosheath. When CIR-driven shocks propagate to the outer heliosphere, their structure changes due to collision and merging processes of CIRs. In this Letter, we explore an effect of the merging of CIRs on the structure of CIR-associated shocks. We use a three-dimensional MHD model to study the outward propagation of the shocks with characteristics similar to those observed by Voyager 2 at {approx}45 AU (Lazarus et al. 1999). We show that due to merging of CIRs (1) reverse shocks disappear, (2) forward shocks become weaker due to interaction with rarefaction regions from preceding CIRs, and (3) forward shocks significantly weaken in the heliosheath. Merged CIRs produce compression regions in the heliosheath with small fluctuations of plasma parameters. Amplitudes of the fluctuations diminish as they propagate deeper in the sheath. We conclude that interaction of shocks and rarefaction regions could be one of the explanations, why shocks produced by CIRs are not observed in the heliosheath by Voyager 2 while they were frequently observed upstream the TS.

  15. Hypovolemic shock

    Science.gov (United States)

    ... thready Tests that may be done include: Blood chemistry, including kidney function tests and those tests looking ... severe shock. Severe hypovolemic shock may lead to death, even with immediate medical attention. Older adults are ...

  16. High-resolution Observations of the Shock Wave Behavior for Sunspot Oscillations with the Interface Region Imaging Spectrograph

    Science.gov (United States)

    Tian, H.; DeLuca, E.; Reeves, K. K.; McKillop, S.; De Pontieu, B.; Martínez-Sykora, J.; Carlsson, M.; Hansteen, V.; Kleint, L.; Cheung, M.; Golub, L.; Saar, S.; Testa, P.; Weber, M.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Kankelborg, C.; Jaeggli, S.; McIntosh, S. W.

    2014-05-01

    We present the first results of sunspot oscillations from observations by the Interface Region Imaging Spectrograph. The strongly nonlinear oscillation is identified in both the slit-jaw images and the spectra of several emission lines formed in the transition region and chromosphere. We first apply a single Gaussian fit to the profiles of the Mg II 2796.35 Å, C II 1335.71 Å, and Si IV 1393.76 Å lines in the sunspot. The intensity change is ~30%. The Doppler shift oscillation reveals a sawtooth pattern with an amplitude of ~10 km s-1 in Si IV. The Si IV oscillation lags those of C II and Mg II by ~3 and ~12 s, respectively. The line width suddenly increases as the Doppler shift changes from redshift to blueshift. However, we demonstrate that this increase is caused by the superposition of two emission components. We then perform detailed analysis of the line profiles at a few selected locations on the slit. The temporal evolution of the line core is dominated by the following behavior: a rapid excursion to the blue side, accompanied by an intensity increase, followed by a linear decrease of the velocity to the red side. The maximum intensity slightly lags the maximum blueshift in Si IV, whereas the intensity enhancement slightly precedes the maximum blueshift in Mg II. We find a positive correlation between the maximum velocity and deceleration, a result that is consistent with numerical simulations of upward propagating magnetoacoustic shock waves.

  17. Simulations and experiments of ejecta generation in twice-shocked metals

    Science.gov (United States)

    Karkhanis, Varad; Ramaprabhu, Praveen; Buttler, William; Hammerberg, James; Cherne, Frank; Andrews, Malcolm

    2016-11-01

    Using continuum hydrodynamics embedded in the FLASH code, we model ejecta generation in recent target experiments, where a metallic surface was loaded by two successive shock waves. The experimental data were obtained from a two-shockwave, high-explosive tool at Los Alamos National Laboratory, capable of generating ejecta from a shocked tin surface in to a vacuum. In both simulations and experiment, linear growth is observed following the first shock event, while the second shock strikes a finite-amplitude interface leading to nonlinear growth. The timing of the second incident shock was varied systematically in our simulations to realize a finite-amplitude re-initialization of the RM instability driving the ejecta. We find the shape of the interface at the event of second shock is critical in determining the amount of ejecta, and thus must be used as an initial condition to evaluate subsequent ejected mass using a source model. In particular, the agreement between simulations, experiments and the mass model is improved when shape effects associated with the interface at second shock are incorporated. This work was supported in part by the (U.S.) Department of Energy (DOE) under Contract No. DE-AC52-06NA2-5396.

  18. Simulating radiative shocks in nozzle shock tubes

    Science.gov (United States)

    van der Holst, B.; Tóth, G.; Sokolov, I. V.; Daldorff, L. K. S.; Powell, K. G.; Drake, R. P.

    2012-06-01

    We use the recently developed Center for Radiative Shock Hydrodynamics (CRASH) code to numerically simulate laser-driven radiative shock experiments. These shocks are launched by an ablated beryllium disk and are driven down xenon-filled plastic tubes. The simulations are initialized by the two-dimensional version of the Lagrangian Hyades code which is used to evaluate the laser energy deposition during the first 1.1 ns. Later times are calculated with the CRASH code. CRASH solves for the multi-material hydrodynamics with separate electron and ion temperatures on an Eulerian block-adaptive-mesh and includes a multi-group flux-limited radiation diffusion and electron thermal heat conduction. The goal of the present paper is to demonstrate the capability to simulate radiative shocks of essentially three-dimensional experimental configurations, such as circular and elliptical nozzles. We show that the compound shock structure of the primary and wall shock is captured and verify that the shock properties are consistent with order-of-magnitude estimates. The synthetic radiographs produced can be used for comparison with future nozzle experiments at high-energy-density laser facilities.

  19. Spiral shocks and accretion in discs

    Energy Technology Data Exchange (ETDEWEB)

    Spruit, H.C.; Matsuda, T.; Inoue, M.; Sawada, K.

    1987-12-01

    Recent numerical and analytical results on disc-like accretion with shock waves as the only dissipation mechanism are compared. The global properties of the process are similar to those of the viscous (..cap alpha..) disc model, but precise values of the effective ..cap alpha.. value as a function of the accretion rate can be calculated. At low values of the ratio of specific heats (..gamma.. < 1.45) accretion is possible without radiative losses. Such adiabatic accretion can occur in practice at high accretion rates on to low mass objects and may be important in the formation of planets. Following previous authors, it is pointed out that non-axisymmetric perturbations in the outer parts of a disc increase in amplitude as they propagate in and cause spiral shocks more easily in a disc than perturbations originating in the inner parts.

  20. Comparative Study of Electromagnetic Waves at the Bow Shocks of Venus and Earth

    Science.gov (United States)

    Wei, Hanying; Russell, Christopher T.; Strangeway, Robert J.; Schwartz, Steven J.; Zhang, Tielong

    2016-04-01

    Although the solar interactions with Venus and Earth are quite different in many ways, they both have bow shocks formed upstream of the planet where the solar wind decelerates from a super- to sub- magnetosonic flow. In the upstream foreshock region, there is abundant wave activity generated by the shock or by the back-streaming ions and electrons from the shock. In the downstream magnetosheath region, there is also abundant wave activity either locally generated by the heated electrons or ions from the shock or transported from the shock or foreshock regions by the solar wind. The magnetometers of Venus Express and Magnetospheric Multiscale missions both occasionally record 128 Hz data during their shock crossing, which allow us the search for and analyze waves at such high frequencies. We have found short-duration wave bursts around both Venus and Earth bow shocks, with certain similarities. These waves are mostly quasi-perpendicular propagating and have amplitude and occurrence rate decreasing with distance from the bow shock. In this paper we perform statistical and comparative studies on wave properties to understand their generation mechanisms and their effects to the shock or magnetosheath plasmas.

  1. High-order rational harmonic mode-locking and pulse-amplitude equalization of SOAFL via reshaped gain-switching FPLD pulse injection.

    Science.gov (United States)

    Lin, Gong-Ru; Kang, Jung-Jui; Lee, Chao-Kuei

    2010-04-26

    The 40-GHz rational harmonic mode-locking (RHML) and pulse-amplitude equalization of a semiconductor optical amplifier based fiber-ring laser (SOAFL) is demonstrated by the injection of a reshaped 10-GHz gain-switching FPLD pulse. A nonlinearly biased Mach-Zehnder modulator (MZM) is employed to detune the shape of the double-peak pulse before injecting the SOA, such that a pulse-amplitude equalized 4th-order RHML-SOAFL can be achieved by reshaping the SOA gain within one modulation period. An optical injection mode-locking model is constructed to simulate the compensation of uneven amplitudes between adjacent RHML pulse peaks before and after pulse-amplitude equalization. The indirect gain compensation technique greatly suppresses the clock amplitude jitter from 45% to 3.5% when achieving 4th-order RHML, and the amplitude fluctuation of sub-rational harmonic modulating envelope is attenuated by 45 dB. After pulse-amplitude equalization, the pulsewidth of the optical-injection RHML-SOAFL is 8 ps, which still obeys the trend predicted by the inverse square root of repetition rate. The phase noise contributed by the residual ASE noise of the RHML-SOAFL is significantly decreased from -84 to -90 dBc/Hz after initiating the pulse-amplitude equalization, corresponding to the timing jitter reduction from 0.5 to 0.28 ps.

  2. Importance of post-shock streams and sheath region as drivers of intense magnetospheric storms and high-latitude activity

    Directory of Open Access Journals (Sweden)

    K. E. J. Huttunen

    2004-04-01

    Full Text Available Magnetic disturbances in the Earth's magnetosphere can be very different depending on the type of solar wind driver. We have determined the solar wind causes for intense magnetic storms (Dst<-100nT over a 6-year period from the beginning of 1997 to the end of 2002, using observations by the WIND and ACE spacecraft. We have taken into consideration whether the storm was caused by the sheath region or by the following interplanetary coronal mass ejection (ICME. We also divided ICMEs into those having a magnetic cloud structure and those without such a structure. We found that post-shock streams and sheath regions caused the largest fraction of intense magnetic storms. We present four periods of magnetospheric activity in more detail. One of the events was caused by a magnetic cloud (10-11 August 2000 and the rest (13-14 July 2000, 8-9 June 2000 and 17-18 April 2001 by sheath regions and post-shock streams. We have used several magnetic indices to monitor the low- and high-latitude magnetospheric response to these different solar wind structures. Two of the events are interesting examples where at first strong high-latitude activity took place and the low-latitude response followed several hours later. These events demonstrate that low- and high-latitude activity do not always occur concurrently and the level of activity may be very different. According to the examples shown the evolution of the pressure-corrected Dst index was more difficult to model for a sheath region or a post-shock stream driven storm than for a storm caused by a magnetic cloud.

  3. Association among parental substance use disorder, p300 amplitude, and neurobehavioral disinhibition in preteen boys at high risk for substance use disorder.

    Science.gov (United States)

    Habeych, Miguel E; Sclabassi, Robert J; Charles, Prophete J; Kirisci, Levent; Tarter, Ralph E

    2005-06-01

    The P300 amplitude of the event-related potential as a mediator of the association between parental substance use disorder (SUD) and child's neurobehavioral disinhibition was assessed. The P300 amplitude was recorded using an oddball task in sons of fathers having either lifetime SUD (n = 105) or no psychiatric disorder (n = 160). Neurobehavioral disinhibition was assessed using measures of affect regulation, behavior control, and executive cognitive function. Parental SUD and child's P300 amplitude accounted for, respectively, 16.6% and 16.8% of neurobehavioral disinhibition variance. Controlling for parental and child psychopathology, an association between parental SUD and child's P300 amplitude was not observed. It was concluded that the P300 amplitude does not mediate the association between parental SUD and child's neurobehavioral disinhibition.

  4. Interaction between a normal shock wave and a turbulent boundary layer at high transonic speeds. I - Pressure distribution

    Science.gov (United States)

    Messiter, A. F.

    1980-01-01

    Asymptotic solutions are derived for the pressure distribution in the interaction of a weak normal shock wave with a turbulent boundary layer. The undisturbed boundary layer is characterized by the law of the wall and the law of the wake for compressible flow. In the limiting case considered, for 'high' transonic speeds, the sonic line is very close to the wall. Comparisons with experiment are shown, with corrections included for the effect of longitudinal wall curvature and for the boundary-layer displacement effect in a circular pipe.

  5. TRENDS IN THE DEVELOPMENT OF DETONATION ENGINES FOR HIGH-SPEED AEROSPACE AIRCRAFTS AND THE PROBLEM OF TRIPLE CONFIGURATIONS OF SHOCK WAVES. Part II - Research of counterpropagating shock waves and triple shock wave configurations

    Directory of Open Access Journals (Sweden)

    P. V. Bulat

    2016-03-01

    Full Text Available The paper deals with current issues of the interference theory development of gas-dynamic discontinuities as applied to a problem of propulsion refinement for the air-spacecrafts, designed for hypersonic flight speeds. In the first part of the review we have presented the history of detonation study and different concepts of detonation engines, as well as air intakes designed for hypersonic flight speeds. The second part provides an overview of works on the interference theory development for gas-dynamic discontinuities. We report about classification of the gas-dynamic discontinuities, shock wave propagation, shock-wave structures and triple configurations of shock waves. We have shown that many of these processes are accompanied by a hysteresis phenomenon, there are areas of ambiguity; therefore, in the design of engines and air intakes optimal shock-wave structures should be provided and their sustainability should be ensured. Much attention has recently been given to the use of the air intakes in the shock-wave structures with the rereflection of shock waves and the interference of shock waves in the opposite directions. This review provides increased focus on it, contains references to landmark works, the last calculated and experimental results. Unfortunately, foreign surveys missed many landmark works of the Soviet and Russian researchers, as they were not published in English. At the same time, it was the Soviet school of gas dynamics that has formulated the interference theory of gas-dynamic discontinuities in its present form. To fill this gap is one of this review scopes. The review may be recommended for professionals, engineers and scientists working in the field of aerospace engineering.

  6. High-amplitude, centennial-scale climate oscillations during the last glacial in the western Third Pole as recorded in the Guliya ice cap

    Science.gov (United States)

    Thompson, L. G.; Yao, T.; Mosley-Thompson, E.; Wu, G.; Davis, M. E.; Tian, L.; Lin, P. N.

    2015-12-01

    The Guliya ice cap, located in the Kunlun Mountains in the western Third Pole (TP) region near the northern limit of the southwest monsoon influence, may be the only non-polar ice field that provides detailed histories of climate and environment over the last glacial cycle. A continuous climate record from an ice core drilled in 1992 contains Eemian ice, and basal temperatures measured that year confirmed that the record was not being removed from the bottom. The δ18O record throughout Marine Isotope Stage 2 (MIS2) displays the occurrence of high-amplitude (~20‰) episodes of ~200-year periodicity, and the aerosol records suggest snow cover, regional vegetation and fire frequency that vary in synchrony. These oscillations might reflect the movement of the northernmost penetration of the monsoon precipitation through the Late Glacial Stage, which is restricted by the topographic barrier posed by the Kunlun range, and might also reflect solar-driven nonlinearities in the climate system such as sudden shifts in the jet stream. Recent model simulations suggest that glacial cooling over China was significantly amplified by stationary waves, and the Guliya MIS2 oscillations could reflect cyclical variability in these waves. These results are supported by clumped isotope thermometry of carbonates from the Chinese Loess Plateau, which indicate a 6 to 7oC decrease in Last Glacial Maximum summer temperatures. These studies will lead to a better understanding of the mechanisms driving such high-frequency, high-amplitude oscillations. A review of the 2015 Sino-American cooperative ice core drilling program on Guliya is presented. This program will serve as a flagship for the TP Environment Program, an international, multidisciplinary collaboration among professionals and students in 14 countries designed to investigate environmental changes across the TP. The rapidly warming TP contains ~46,000 glaciers that collectively hold one of Earth's largest stores of fresh water that

  7. Preseason Training: The Effects of a 17-Day High-Intensity Shock Microcycle in Elite Tennis Players

    Directory of Open Access Journals (Sweden)

    Jaime Fernandez-Fernandez, David Sanz-Rivas, Jose Manuel Sarabia, Manuel Moya

    2015-12-01

    Full Text Available Preseasons in tennis are normally reduced to 5 to 7 weeks duration, and coaches should use an integrated approach to conditioning and skill-based work. The aim of the present study was to investigate the effects of adding a high-intensity training (HIT shock microcycle to the normal training content in several physical performance indicators in the preseason training of high-level male tennis players. Over 17 days, 12 male tennis players performed 13 HIT sessions in addition to their usual training. Physical performance tests (30:15 intermittent fitness test [VIFT], 20 m sprint, countermovement jump [CMJ], repeated sprint ability [RSA] were conducted before (pre-test and 5 days after the intervention (post-test. After the shock microcycle, results showed a significant increase in the VIFT (p < 0.001; Large ES and a significant decrease in the mean RSA time (RSAm (p = 0.002; Small ES, while there were no significant changes in the other parameters analysed (e.g., 20 m, CMJ, best RSA time [RSAb]; percentage of decrement in the RSA [%Dec]. Moreover, the training load (TL during tennis sessions was significantly higher (p < 0.01; Large ES than the TL during the integrated sessions, except during the first training session. A 17-day shock microcycle (i.e., 13 HIT sessions in addition to the regular tennis training significantly improved parameters that can impact physical performance in tennis. Moreover, additional sessions, including running exercises based on the 30:15ITF and on-court specific exercises, were characterised by significantly lower TL than tennis-training sessions.

  8. Physics of Collisionless Shocks Space Plasma Shock Waves

    CERN Document Server

    Balogh, André

    2013-01-01

    The present book provides a contemporary systematic treatment of shock waves in high-temperature collisionless plasmas as are encountered in near Earth space and in Astrophysics. It consists of two parts. Part I develops the complete theory of shocks in dilute hot plasmas under the assumption of absence of collisions among the charged particles when the interaction is mediated solely by the self-consistent electromagnetic fields. Such shocks are naturally magnetised implying that the magnetic field plays an important role in their evolution and dynamics. This part treats both subcritical shocks, which dissipate flow energy by generating anomalous resistance or viscosity, and supercritical shocks. The main emphasis is, however, on super-critical shocks where the anomalous dissipation is insufficient to retard the upstream flow. These shocks, depending on the direction of the upstream magnetic field, are distinguished as quasi-perpendicular and quasi-parallel shocks which exhibit different behaviours, reflecti...

  9. Protostring Scattering Amplitudes

    CERN Document Server

    Thorn, Charles B

    2016-01-01

    We calculate some tree level scattering amplitudes for a generalization of the protostring, which is a novel string model implied by the simplest string bit models. These bit models produce a lightcone worldsheet which supports $s$ integer moded Grassmann fields. In the generalization we supplement this Grassmann worldsheet system with $d=24-s$ transverse coordinate worldsheet fields. The protostring corresponds to $s=24$ and the bosonic string to $s=0$. The interaction vertex is a simple overlap with no operator insertions at the break/join point. Assuming that $s$ is even we calculate the multi-string scattering amplitudes by bosonizing the Grassmann fields, each pair equivalent to one compactified bosonic field, and applying Mandelstam's interacting string formalism to a system of $s/2$ compactified and $d$ uncompactified bosonic worldsheet fields. We obtain all amplitudes for open strings with no oscillator excitations and for closed strings with no oscillator excitations and zero winding number. We then ...

  10. Scattering amplitudes in gauge theories

    Energy Technology Data Exchange (ETDEWEB)

    Henn, Johannes M. [Institute for Advanced Study, Princeton, NJ (United States). School of Natural Sciences; Plefka, Jan C. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik

    2014-03-01

    First monographical text on this fundamental topic. Course-tested, pedagogical and self-contained exposition. Includes exercises and solutions. At the fundamental level, the interactions of elementary particles are described by quantum gauge field theory. The quantitative implications of these interactions are captured by scattering amplitudes, traditionally computed using Feynman diagrams. In the past decade tremendous progress has been made in our understanding of and computational abilities with regard to scattering amplitudes in gauge theories, going beyond the traditional textbook approach. These advances build upon on-shell methods that focus on the analytic structure of the amplitudes, as well as on their recently discovered hidden symmetries. In fact, when expressed in suitable variables the amplitudes are much simpler than anticipated and hidden patterns emerge. These modern methods are of increasing importance in phenomenological applications arising from the need for high-precision predictions for the experiments carried out at the Large Hadron Collider, as well as in foundational mathematical physics studies on the S-matrix in quantum field theory. Bridging the gap between introductory courses on quantum field theory and state-of-the-art research, these concise yet self-contained and course-tested lecture notes are well-suited for a one-semester graduate level course or as a self-study guide for anyone interested in fundamental aspects of quantum field theory and its applications. The numerous exercises and solutions included will help readers to embrace and apply the material presented in the main text.

  11. Shock tube design for high intensity blast waves for laboratory testing of armor and combat materiel

    Directory of Open Access Journals (Sweden)

    Elijah Courtney

    2014-06-01

    Full Text Available Shock tubes create simulated blast waves which can be directed and measured to study blast wave effects under laboratory conditions. It is desirable to increase available peak pressure from ∼1 MPa to ∼5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors. Three methods are experimentally investigated to increase peak simulated blast pressure produced by an oxy-acetylene driven shock tube while maintaining suitability for laboratory studies. The first method is the addition of a Shchelkin spiral priming section which supports a deflagration to detonation transition. This approach increases the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve (near Friedlander waveform. The second method is a bottleneck between the driving and driven sections. Coupling a 79 mm diameter driving section to a 53 mm driven section increases the peak pressure from 1.17 MPa to 2.25 MPa. A 103 mm driving section is used to increase peak pressure to 2.64 MPa. The third method, adding solid fuel to the driving section with the oxy-acetylene, results in a peak pressure increasing to 1.70 MPa.

  12. Shock tube design for high intensity blast waves for laboratory testing of armor and combat materiel

    Institute of Scientific and Technical Information of China (English)

    Elijah COURTNEY; Amy COURTNEY; Michael COURTNEY

    2014-01-01

    Shock tubes create simulated blast waves which can be directed and measured to study blast wave effects under laboratory conditions. It is desirable to increase available peak pressure from w1 MPa to w5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors. Three methods are experimentally investigated to increase peak simulated blast pressure produced by an oxy-acetylene driven shock tube while maintaining suitability for laboratory studies. The first method is the addition of a Shchelkin spiral prim-ing section which supports a deflagration to detonation transition. This approach increases the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve (near Friedlander waveform). The second method is a bottleneck between the driving and driven sections. Coupling a 79 mm diameter driving section to a 53 mm driven section increases the peak pressure from 1.17 MPa to 2.25 MPa. A 103 mm driving section is used to increase peak pressure to 2.64 MPa. The third method, adding solid fuel to the driving section with the oxy-acetylene, results in a peak pressure increasing to 1.70 MPa.

  13. Improvement of mechanical properties and life extension of high reliability structural components by laser shock processing

    Science.gov (United States)

    Ocaña, J. L.; Morales, M.; Porro, J. A.; Iordachescu, D.; Díaz, M.; Ruiz de Lara, L.; Correa, C.

    2011-05-01

    Profiting by the increasing availability of laser sources delivering intensities above 109 W/cm2 with pulse energies in the range of several Joules and pulse widths in the range of nanoseconds, laser shock processing (LSP) is being consolidating as an effective technology for the improvement of surface mechanical and corrosion resistance properties of metals and is being developed as a practical process amenable to production engineering. The main acknowledged advantage of the laser shock processing technique consists on its capability of inducing a relatively deep compression residual stresses field into metallic alloy pieces allowing an improved mechanical behaviour, explicitly, the life improvement of the treated specimens against wear, crack growth and stress corrosion cracking. Following a short description of the theoretical/computational and experimental methods developed by the authors for the predictive assessment and experimental implementation of LSP treatments, experimental results on the residual stress profiles and associated surface properties modification successfully reached in typical materials (specifically Al and Ti alloys) under different LSP irradiation conditions are presented. In particular, the analysis of the residual stress profiles obtained under different irradiation parameters and the evaluation of the corresponding induced surface properties as roughness and wear resistance are presented.

  14. Shock Tube Design for High Intensity Blast Waves for Laboratory Testing of Armor and Combat Materiel

    CERN Document Server

    Courtney, Elijah; Courtney, Michael

    2015-01-01

    Shock tubes create simulated blast waves which can be directed and measured to study blast wave effects under laboratory conditions. It is desirable to increase available peak pressure from ~1 MPa to ~5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors. Three methods were investigated to increase peak simulated blast pressure produced by an oxy-acetylene driven shock tube while maintaining suitability for laboratory studies. The first method is the addition of a Shchelkin spiral priming section which works by increasing the turbulent flow of the deflagration wave, thus increasing its speed and pressure. This approach increased the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve (Friedlander waveform). The second method is a bottleneck between the driving and driven sections. Coupling a 79 mm diameter driving section to a 53 mm driven section increased the peak pressure from 1.17 MPa to 2.25 MPa. Using a 1...

  15. Low-amplitude high frequency vibration down-regulates myostatin and atrogin-1 expression, two components of the atrophy pathway in muscle cells.

    Science.gov (United States)

    Ceccarelli, Gabriele; Benedetti, Laura; Galli, Daniela; Prè, Deborah; Silvani, Giulia; Crosetto, Nicola; Magenes, Giovanni; Cusella De Angelis, Maria Gabriella

    2014-05-01

    Whole body vibration (WBV) is a very widespread mechanical stimulus used in physical therapy, rehabilitation and fitness centres. It has been demonstrated that vibration induces improvements in muscular strength and performance and increases bone density. We investigated the effects of low-amplitude, high frequency vibration (HFV) at the cellular and tissue levels in muscle. We developed a system to produce vibrations adapted to test several parameters in vitro and in vivo. For in vivo experiments, we used newborn CD1 wild-type mice, for in vitro experiments, we isolated satellite cells from 6-day-old CD1 mice, while for proliferation studies, we used murine cell lines. Animals and cells were treated with high frequency vibration at 30 Hz. We analyzed the effects of mechanical stimulation on muscle hypertrophy/atrophy pathways, fusion enhancement of myoblast cells and modifications in the proliferation rate of cells. Results demonstrated that mechanical vibration strongly down-regulates atrophy genes both in vivo and in vitro. The in vitro experiments indicated that mechanical stimulation promotes fusion of satellite cells treated directly in culture compared to controls. Finally, proliferation experiments indicated that stimulated cells had a decreased growth rate compared to controls. We concluded that vibration treatment at 30 Hz is effective in suppressing the atrophy pathway both in vivo and in vitro and enhances fusion of satellite muscle cells.

  16. Large Amplitude Variations of an L/T Transition Brown Dwarf: Multi-Wavelength Observations of Patchy, High-Contrast Cloud Features

    CERN Document Server

    Radigan, Jacqueline; Lafrenière, David; Artigau, Etienne; Marley, Mark; Saumon, Didier

    2012-01-01

    We present multiple-epoch photometric monitoring in the $J$, $H$, and $K_s$ bands of the T1.5 dwarf 2MASS J21392676+0220226 (2M2139), revealing persistent, periodic ($P=7.72\\pm$0.05 hr) variability with a peak-to-peak amplitude as high as 26% in the $J$-band. The light curve shape varies on a timescale of days, suggesting that evolving atmospheric cloud features are responsible. Using interpolations between model atmospheres with differing cloud thicknesses to represent a heterogeneous surface, we find that the multi-wavelength variations and the near-infrared spectrum of 2M2139 can be reproduced by either (1)cool, thick cloud features sitting above a thinner cloud layer, or (2)warm regions of low condensate opacity in an otherwise cloudy atmosphere, possibly indicating the presence of holes or breaks in the cloud layer. We find that temperature contrasts between thick and thin cloud patches must be greater than 175 K and as high as 425 K. We also consider whether the observed variability could arise from an ...

  17. Preseason Training: The Effects of a 17-Day High-Intensity Shock Microcycle in Elite Tennis Players

    Science.gov (United States)

    Fernandez-Fernandez, Jaime; Sanz-Rivas, David; Sarabia, Jose Manuel; Moya, Manuel

    2015-01-01

    Preseasons in tennis are normally reduced to 5 to 7 weeks duration, and coaches should use an integrated approach to conditioning and skill-based work. The aim of the present study was to investigate the effects of adding a high-intensity training (HIT) shock microcycle to the normal training content in several physical performance indicators in the preseason training of high-level male tennis players. Over 17 days, 12 male tennis players performed 13 HIT sessions in addition to their usual training. Physical performance tests (30:15 intermittent fitness test [VIFT], 20 m sprint, countermovement jump [CMJ], repeated sprint ability [RSA]) were conducted before (pre-test) and 5 days after the intervention (post-test). After the shock microcycle, results showed a significant increase in the VIFT (p < 0.001; Large ES) and a significant decrease in the mean RSA time (RSAm) (p = 0.002; Small ES), while there were no significant changes in the other parameters analysed (e.g., 20 m, CMJ, best RSA time [RSAb]; percentage of decrement in the RSA [%Dec]). Moreover, the training load (TL) during tennis sessions was significantly higher (p < 0.01; Large ES) than the TL during the integrated sessions, except during the first training session. A 17-day shock microcycle (i.e., 13 HIT sessions) in addition to the regular tennis training significantly improved parameters that can impact physical performance in tennis. Moreover, additional sessions, including running exercises based on the 30:15ITF and on-court specific exercises, were characterised by significantly lower TL than tennis-training sessions. Key points HIT shock microcycle increases performance in professional tennis players in a short period of time. The inclusion of additional sessions, with running exercises based on the 30:15ITF and on-court specific exercises, was characterised by a significantly lower TL than tennis-training sessions alone. Coaches should be aware of TL (e.g., RPE) and fatigue-related parameters

  18. Complex Organic Molecules tracing shocks along the outflow cavity in the high-mass protostar IRAS 20126+4104

    Science.gov (United States)

    Palau, Aina; Walsh, Catherine; Sánchez-Monge, Álvaro; Girart, Josep M.; Cesaroni, Riccardo; Jiménez-Serra, Izaskun; Fuente, Asunción; Zapata, Luis A.; Neri, Roberto

    2017-01-01

    We report on subarcsecond observations of complex organic molecules (COMs) in the high-mass protostar IRAS 20126+4104 with the Plateau de Bure Interferometer in its most extended configurations. In addition to the simple molecules SO, HNCO and H_2^{13}CO, we detect emission from CH3CN, CH3OH, HCOOH, HCOOCH3, CH3OCH3, CH3CH2CN, CH3COCH3, NH2CN, and (CH2OH)2. SO and HNCO present a X-shaped morphology consistent with tracing the outflow cavity walls. Most of the COMs have their peak emission at the putative position of the protostar, but also show an extension towards the south(east), coinciding with an H2 knot from the jet at about 800-1000 au from the protostar. This is especially clear in the case of H_2^{13}CO and CH3OCH3. We fitted the spectra at representative positions for the disc and the outflow, and found that the abundances of most COMs are comparable at both positions, suggesting that COMs are enhanced in shocks as a result of the passage of the outflow. By coupling a parametric shock model to a large gas-grain chemical network including COMs, we find that the observed COMs should survive in the gas phase for ˜2000 yr, comparable to the shock lifetime estimated from the water masers at the outflow position. Overall, our data indicate that COMs in IRAS 20126+4104 may arise not only from the disc, but also from dense and hot regions associated with the outflow.

  19. The effect of high-energy extracorporeal shock waves on hyaline cartilage of adult rats in vivo.

    Science.gov (United States)

    Mayer-Wagner, Susanne; Ernst, Judith; Maier, Markus; Chiquet, Matthias; Joos, Helga; Müller, Peter E; Jansson, Volkmar; Sievers, Birte; Hausdorf, Jörg

    2010-08-01

    The aim of this study was to determine if extracorporeal shock wave therapy (ESWT) in vivo affects the structural integrity of articular cartilage. A single bout of ESWT (1500 shock waves of 0.5 mJ/mm(2)) was applied to femoral heads of 18 adult Sprague-Dawley rats. Two sham-treated animals served as controls. Cartilage of each femoral head was harvested at 1, 4, or 10 weeks after ESWT (n = 6 per treatment group) and scored on safranin-O-stained sections. Expression of tenascin-C and chitinase 3-like protein 1 (Chi3L1) was analyzed by immunohistochemistry. Quantitative real-time polymerase chain reaction (PCR) was used to examine collagen (II)alpha(1) (COL2A1) expression and chondrocyte morphology was investigated by transmission electron microscopy no changes in Mankin scores were observed after ESWT. Positive immunostaining for tenascin-C and Chi3L1 was found up to 10 weeks after ESWT in experimental but not in control cartilage. COL2A1 mRNA was increased in samples 1 and 4 weeks after ESWT. Alterations found on the ultrastructural level showed expansion of the rough-surfaced endoplasmatic reticulum, detachment of the cell membrane and necrotic chondrocytes. Extracorporeal shock waves caused alterations of hyaline cartilage on a molecular and ultrastructural level that were distinctly different from control. Similar changes were described before in the very early phase of osteoarthritis (OA). High-energy ESWT might therefore cause degenerative changes in hyaline cartilage as they are found in initial OA. Copyright 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

  20. Astragalus membranaceus reduces free radical-mediated injury to renal tubules in rabbits receiving high-energy shock waves

    Institute of Scientific and Technical Information of China (English)

    SHENG Bin-wu; CHEN Xing-fa; ZHAO Jun; HE Da-lin; NAN Xun-yi

    2005-01-01

    Background Recent studies have revealed the important role of free radicals in renal damage induced by high-energy shock waves (HESW). This study aimed at investigating the effects of Astragalus membranaceus, a traditional Chinese medicinal herb, on free radical-mediated HESW-induced damage to renal tubules in a live rabbit model.Methods Forty-five healthy male New Zealand white rabbits were randomly divided into three groups: control group (n=15), sham group (n=15), and herb-treated group (n=15). Three days prior to HESW application, the controls received verapamil (0.4 mg/kg), the shams received physiological saline (20 ml), and the herb-treated animals received Astragalus membranaceus (2.4 g/kg) intravenously. HESW (1500 shocks, 18kV) was applied to the right kidneys of all anesthetized rabbits. We measured superoxide dismutase (SOD) and malondialdehyde (MDA) levels before and after shock treatment in blood and kidney homogenates. Histopathological changes were also observed.Results MDA levels increased and SOD activity decreased significantly in the sham group (P0.05). SOD values were significantly higher in the controls than in the shams (P<0.05). By contrast, SOD levels recovered rapidly in the rabbits receiving Astragalus membranaceus, reaching a nadir within 24 hours, and returning to baseline more quickly than in control and sham rabbits (P<0.05). Histopathological examinations showed that renal tubular damage in the controls was less severe than in the shams, while damage in the Astragalus membranaceus group was even more mild, with rapid recovery in comparison with the controls.Conclusion This study provides preliminary evidence indicating that Astragalus membranaceus has strong protective effects on free radical-mediated renal tubular damage induced by HESW and that these effects are superior to the effects of verapamil.

  1. A course in amplitudes

    Science.gov (United States)

    Taylor, Tomasz R.

    2017-05-01

    This a pedagogical introduction to scattering amplitudes in gauge theories. It proceeds from Dirac equation and Weyl fermions to the two pivot points of current developments: the recursion relations of Britto, Cachazo, Feng and Witten, and the unitarity cut method pioneered by Bern, Dixon, Dunbar and Kosower. In ten lectures, it covers the basic elements of on-shell methods.

  2. Excitation of high-radial-order Laguerre–Gaussian modes in a solid-state laser using a lower-loss digitally controlled amplitude mask

    Science.gov (United States)

    Bell, T.; Hasnaoui, A.; Ait-Ameur, K.; Ngcobo, S.

    2017-10-01

    In this paper we experimentally demonstrate selective excitation of high-radial-order Laguerre–Gaussian (LG p or LG{}p,0) modes with radial order p = 1–4 and azimuthal order l = 0 using a diode-pump solid-state laser (DPSSL) that is digitally controlled by a spatial light modulator (SLM). We encoded an amplitude mask containing p-absorbing rings, of various incompleteness (segmented) on grey-scale computer-generated digital holograms, and displayed them on an SLM which acted as an end mirror of the diode-pumped solid-state digital laser. The various incomplete (α) p-absorbing rings were digitally encoded to match the zero-intensity nulls of the desired LG p mode. We show that the creation of LG p , for p = 1 to p = 4, only requires an incomplete circular p-absorbing ring that has a completeness of ≈37.5%, giving the DPSSL resonator a lower pump threshold power while maintaining the same laser characteristics (such as beam propagation properties).

  3. Characteristics of Weak Interplanetary Shocks and Shock-like Events

    Science.gov (United States)

    Balogh, A.; Gloag, J. M.

    The variation of magnetic and plasma parameters across the discontinuity of a colli- sionless shock wave are clearly understood and presented in MHD theory. The anal- ysis of 116 shock waves appearing on the Ulysses shock list in the period mid 1996 to the end of 1999 show that in the cases of the stronger shock waves, measured by the ratio of downstream to upstream magnetic field magnitudes, this MHD descrip- tion is adequate. However in the case of many of the weaker shocks there are events which are not clearly characterised in MHD terms and in these cases plasma param- eters are particularly difficult to interpret. To explore the issues associated with these very weak shocks further, a set of shock-like events is considered which have shock characteristics in the high frequency wave data measured by the plasma wave inves- tigation(URAP) but are not considered to be clearly shock waves purely considering magnetic and plasma data. These shock-like events are thought to extend the spectrum of interplanetary shocks at the very weakest end and possibly beyond what should be considered a collisionless shock wave.

  4. High-resolution observations of the shock wave behavior for sunspot oscillations with the interface region imaging spectrograph

    Energy Technology Data Exchange (ETDEWEB)

    Tian, H.; DeLuca, E.; Reeves, K. K.; McKillop, S.; Golub, L.; Saar, S.; Testa, P.; Weber, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); De Pontieu, B.; Martínez-Sykora, J.; Kleint, L.; Cheung, M.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P. [Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover Street, Org. ADBS, Bldg. 252, Palo Alto, CA 94304 (United States); Carlsson, M.; Hansteen, V., E-mail: hui.tian@cfa.harvard.edu [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, NO-0315 Oslo (Norway); and others

    2014-05-10

    We present the first results of sunspot oscillations from observations by the Interface Region Imaging Spectrograph. The strongly nonlinear oscillation is identified in both the slit-jaw images and the spectra of several emission lines formed in the transition region and chromosphere. We first apply a single Gaussian fit to the profiles of the Mg II 2796.35 Å, C II 1335.71 Å, and Si IV 1393.76 Å lines in the sunspot. The intensity change is ∼30%. The Doppler shift oscillation reveals a sawtooth pattern with an amplitude of ∼10 km s{sup –1} in Si IV. The Si IV oscillation lags those of C II and Mg II by ∼6 and ∼25 s, respectively. The line width suddenly increases as the Doppler shift changes from redshift to blueshift. However, we demonstrate that this increase is caused by the superposition of two emission components. We then perform detailed analysis of the line profiles at a few selected locations on the slit. The temporal evolution of the line core is dominated by the following behavior: a rapid excursion to the blue side, accompanied by an intensity increase, followed by a linear decrease of the velocity to the red side. The maximum intensity slightly lags the maximum blueshift in Si IV, whereas the intensity enhancement slightly precedes the maximum blueshift in Mg II. We find a positive correlation between the maximum velocity and deceleration, a result that is consistent with numerical simulations of upward propagating magnetoacoustic shock waves.

  5. Shock-Resistibility of MEMS-Based Inertial Microswitch under Reverse Directional Ultra-High g Acceleration for IoT Applications

    Science.gov (United States)

    Xu, Qiu; Yang, Zhuoqing; Sun, Yunna; Lai, Liyan; Jin, Zhiyu; Ding, Guifu; Zhao, Xiaolin; Yao, Jinyuan; Wang, Jing

    2017-03-01

    This paper presents a novel MEMS-based inertial microswitch design with multi-directional compact constraint structures for improving the shock-resistibility. Its shock-resistibility in the reverse-sensitive direction to ultra-high g acceleration (~hunderds of thousands) is simulated and analyzed. The dynamic response process indicates that in the designed inertial microswitch the proof mass weight G, the whole system’s stiffness k and the gap x2 between the proof mass and reverse constraint blocks have significant effect on the shock-resistibility. The MEMS inertial microswitch micro-fabricated by surface micromachining has been evaluated using the drop hammer test. The maximum allowable reverse acceleration, which does not cause the spurious trigger, is defined as the reverse acceleration threshold (athr). Test results show that athr increases with the decrease of the gap x2, and the proposed microswitch tends to have a better shock-resistibility under smaller gap. The measured responses of the microswitches with and without constraint structure indicates that the device without constraint structure is prone to spurious trigger, while the designed constraint structures can effectively improve the shock-resistibility. In this paper, the method for improving the shock-resistibility and reducing the spurious trigger has been discussed.

  6. Shock-Resistibility of MEMS-Based Inertial Microswitch under Reverse Directional Ultra-High g Acceleration for IoT Applications

    Science.gov (United States)

    Xu, Qiu; Yang, Zhuoqing; Sun, Yunna; Lai, Liyan; Jin, Zhiyu; Ding, Guifu; Zhao, Xiaolin; Yao, Jinyuan; Wang, Jing

    2017-01-01

    This paper presents a novel MEMS-based inertial microswitch design with multi-directional compact constraint structures for improving the shock-resistibility. Its shock-resistibility in the reverse-sensitive direction to ultra-high g acceleration (~hunderds of thousands) is simulated and analyzed. The dynamic response process indicates that in the designed inertial microswitch the proof mass weight G, the whole system’s stiffness k and the gap x2 between the proof mass and reverse constraint blocks have significant effect on the shock-resistibility. The MEMS inertial microswitch micro-fabricated by surface micromachining has been evaluated using the drop hammer test. The maximum allowable reverse acceleration, which does not cause the spurious trigger, is defined as the reverse acceleration threshold (athr). Test results show that athr increases with the decrease of the gap x2, and the proposed microswitch tends to have a better shock-resistibility under smaller gap. The measured responses of the microswitches with and without constraint structure indicates that the device without constraint structure is prone to spurious trigger, while the designed constraint structures can effectively improve the shock-resistibility. In this paper, the method for improving the shock-resistibility and reducing the spurious trigger has been discussed. PMID:28361893

  7. High-Energy Extracorporeal Shock Wave for Early Stage Osteonecrosis of the Femoral Head: A Single-Center Case Series

    Directory of Open Access Journals (Sweden)

    Fuqiang Gao

    2015-01-01

    Full Text Available Our retrospective study assessed the effects of treatment of early stage ONFH with extracorporeal shock wave therapy. 335 patients (528 hips were treated with shockwave therapy in our institution. Each patient underwent two sessions. The hips were divided into two groups according to whether the lateral pillar of the femoral head (LPFH was preserved: LPFH and non-LPFH groups. Patients were followed up at 3, 6, and 12 months after the treatment. Most of the patients (83.9% hips demonstrated pain reduction and improved mobility of the treated joint (visual analogue scale score, P=0.00006; Harris hip score, P=0.00091. During the follow-up period, 16 hips failed following femoral head collapse and required hip arthroplasty (2 hips in LPFH group and 14 hips in non-LPFH group. The lesion size decreased after ESWT. However, the differences were statistically not significant (LPFH group, P=0.091; non-LPFH group, P=0.087. A significant reduction in bone marrow edema was observed after treatment (LPFH group, P=0.007; non-LPFH group, P=0.016. High-energy extracorporeal shock wave therapy resulted in considerable improvement in early stage ONFH, which can effectively relieve pain and improve the function of the hip.

  8. Highly frequent mutations in negative regulators of multiple virulence genes in group A streptococcal toxic shock syndrome isolates.

    Science.gov (United States)

    Ikebe, Tadayoshi; Ato, Manabu; Matsumura, Takayuki; Hasegawa, Hideki; Sata, Tetsutaro; Kobayashi, Kazuo; Watanabe, Haruo

    2010-04-01

    Streptococcal toxic shock syndrome (STSS) is a severe invasive infection characterized by the sudden onset of shock and multiorgan failure; it has a high mortality rate. Although a number of studies have attempted to determine the crucial factors behind the onset of STSS, the responsible genes in group A Streptococcus have not been clarified. We previously reported that mutations of csrS/csrR genes, a two-component negative regulator system for multiple virulence genes of Streptococcus pyogenes, are found among the isolates from STSS patients. In the present study, mutations of another negative regulator, rgg, were also found in clinical isolates of STSS patients. The rgg mutants from STSS clinical isolates enhanced lethality and impaired various organs in the mouse models, similar to the csrS mutants, and precluded their being killed by human neutrophils, mainly due to an overproduction of SLO. When we assessed the mutation frequency of csrS, csrR, and rgg genes among S. pyogenes isolates from STSS (164 isolates) and non-invasive infections (59 isolates), 57.3% of the STSS isolates had mutations of one or more genes among three genes, while isolates from patients with non-invasive disease had significantly fewer mutations in these genes (1.7%). The results of the present study suggest that mutations in the negative regulators csrS/csrR and rgg of S. pyogenes are crucial factors in the pathogenesis of STSS, as they lead to the overproduction of multiple virulence factors.

  9. Observation of Dispersive Shock Waves, Solitons, and Their Interactions in Viscous Fluid Conduits.

    Science.gov (United States)

    Maiden, Michelle D; Lowman, Nicholas K; Anderson, Dalton V; Schubert, Marika E; Hoefer, Mark A

    2016-04-29

    Dispersive shock waves and solitons are fundamental nonlinear excitations in dispersive media, but dispersive shock wave studies to date have been severely constrained. Here, we report on a novel dispersive hydrodynamic test bed: the effectively frictionless dynamics of interfacial waves between two high viscosity contrast, miscible, low Reynolds number Stokes fluids. This scenario is realized by injecting from below a lighter, viscous fluid into a column filled with high viscosity fluid. The injected fluid forms a deformable pipe whose diameter is proportional to the injection rate, enabling precise control over the generation of symmetric interfacial waves. Buoyancy drives nonlinear interfacial self-steepening, while normal stresses give rise to the dispersion of interfacial waves. Extremely slow mass diffusion and mass conservation imply that the interfacial waves are effectively dissipationless. This enables high fidelity observations of large amplitude dispersive shock waves in this spatially extended system, found to agree quantitatively with a nonlinear wave averaging theory. Furthermore, several highly coherent phenomena are investigated including dispersive shock wave backflow, the refraction or absorption of solitons by dispersive shock waves, and the multiphase merging of two dispersive shock waves. The complex, coherent, nonlinear mixing of dispersive shock waves and solitons observed here are universal features of dissipationless, dispersive hydrodynamic flows.

  10. Coping with shocks in rural Ethiopia

    NARCIS (Netherlands)

    Debebe, Z.Y.; Mebratie, A.; Sparrow, R.; Abebaw, D.; Dekker, M.; Alemu, G.; Bedi, A.S.

    2013-01-01

    Based on household survey data and event history interviews undertaken in a highly shock prone country, this paper investigates which shocks trigger which coping responses and why? We find clear differences in terms of coping strategies across shock types. The two relatively covariate shocks, that

  11. The microphysics of collisionless shock waves

    CERN Document Server

    Marcowith, A; Bykov, A; Dieckman, M E; Drury, L O C; Lembege, B; Lemoine, M; Morlino, G; Murphy, G; Pelletier, G; Plotnikov, I; Reville, B; Riquelme, M; Sironi, L; Novo, A Stockem

    2016-01-01

    Collisionless shocks, that is shocks mediated by electromagnetic processes, are customary in space physics and in astrophysics. They are to be found in a great variety of objects and environments: magnetospheric and heliospheric shocks, supernova remnants, pulsar winds and their nebul\\ae, active galactic nuclei, gamma-ray bursts and clusters of galaxies shock waves. Collisionless shock microphysics enters at different stages of shock formation, shock dynamics and particle energization and/or acceleration. It turns out that the shock phenomenon is a multi-scale non-linear problem in time and space. It is complexified by the impact due to high-energy cosmic rays in astrophysical environments. This review adresses the physics of shock formation, shock dynamics and particle acceleration based on a close examination of available multi-wavelength or in-situ observations, analytical and numerical developments. A particular emphasize is made on the different instabilities triggered during the shock formation and in a...

  12. Effect of Sampling Rates on the Quantification of Forces, Durations, and Rates of Loading of Simulated Side Posture High-Velocity, Low-Amplitude Lumbar Spine Manipulation☆

    Science.gov (United States)

    Gudavalli, Maruti Ram; DeVocht, James; Tayh, Ali; Xia, Ting

    2013-01-01

    Objective Quantification of chiropractic high-velocity, low-amplitude spinal manipulation (HVLA-SM) may require biomechanical equipment capable of sampling data at high rates. However, there are few studies reported in the literature regarding the minimal sampling rate required to record the HVLA-SM force-time profile data accurately and precisely. The purpose of this study was to investigate the effect of different sampling rates on the quantification of forces, durations, and rates of loading of simulated side posture lumbar spine HVLA-SM delivered by doctors of chiropractic. Methods Five doctors of chiropractic (DCs) and 5 asymptomatic participants were recruited for this study. Force-time profiles were recorded during (i) 52 simulated HVLA-SM thrusts to a force transducer placed on a force plate by 2 DCs and (ii) 12 lumbar side posture HVLA-SM on 5 participants by 3 DCs. Data sampling rate of the force plate remained the same at 1000 Hz, whereas the sampling rate of the force transducer varied at 50, 100, 200, and 500 Hz. The data were reduced using custom-written MATLAB (Mathworks, Inc, Natick, MA) and MathCad (version 15; Parametric Technologies, Natick, MA) programs and analyzed descriptively. Results The average differences in the computed durations and rates of loading are smaller than 5% between 50 and 1000 Hz sampling rates. The differences in the computed preloads and peak loads are smaller than 3%. Conclusions The small differences observed in the characteristics of force-time profiles of simulated manual HVLA-SM thrusts measured using various sampling rates suggest that a sampling rate as low as 50 to 100 Hz may be sufficient. The results are applicable to the manipulation performed in this study: manual side posture lumbar spine HVLA-SM. PMID:23790603

  13. Effect of sampling rates on the quantification of forces, durations, and rates of loading of simulated side posture high-velocity, low-amplitude lumbar spine manipulation.

    Science.gov (United States)

    Gudavalli, Maruti Ram; DeVocht, James; Tayh, Ali; Xia, Ting

    2013-06-01

    Quantification of chiropractic high-velocity, low-amplitude spinal manipulation (HVLA-SM) may require biomechanical equipment capable of sampling data at high rates. However, there are few studies reported in the literature regarding the minimal sampling rate required to record the HVLA-SM force-time profile data accurately and precisely. The purpose of this study was to investigate the effect of different sampling rates on the quantification of forces, durations, and rates of loading of simulated side posture lumbar spine HVLA-SM delivered by doctors of chiropractic. Five doctors of chiropractic (DCs) and 5 asymptomatic participants were recruited for this study. Force-time profiles were recorded during (i) 52 simulated HVLA-SM thrusts to a force transducer placed on a force plate by 2 DCs and (ii) 12 lumbar side posture HVLA-SM on 5 participants by 3 DCs. Data sampling rate of the force plate remained the same at 1000 Hz, whereas the sampling rate of the force transducer varied at 50, 100, 200, and 500 Hz. The data were reduced using custom-written MATLAB (Mathworks, Inc, Natick, MA) and MathCad (version 15; Parametric Technologies, Natick, MA) programs and analyzed descriptively. The average differences in the computed durations and rates of loading are smaller than 5% between 50 and 1000 Hz sampling rates. The differences in the computed preloads and peak loads are smaller than 3%. The small differences observed in the characteristics of force-time profiles of simulated manual HVLA-SM thrusts measured using various sampling rates suggest that a sampling rate as low as 50 to 100 Hz may be sufficient. The results are applicable to the manipulation performed in this study: manual side posture lumbar spine HVLA-SM. Copyright © 2013 The Authors. Published by Mosby, Inc. All rights reserved.

  14. A high-order WENO-Z finite difference based particle-source-in-cell method for computation of particle-laden flows with shocks

    Science.gov (United States)

    Jacobs, Gustaaf B.; Don, Wai-Sun

    2009-03-01

    A high-order particle-source-in-cell (PSIC) algorithm is presented for the computation of the interaction between shocks, small scale structures, and liquid and/or solid particles in high-speed engineering applications. The improved high-order finite difference weighted essentially non-oscillatory (WENO-Z) method for solution of the hyperbolic conservation laws that govern the shocked carrier gas flow, lies at the heart of the algorithm. Finite sized particles are modeled as points and are traced in the Lagrangian frame. The physical coupling of particles in the Lagrangian frame and the gas in the Eulerian frame through momentum and energy exchange, is numerically treated through high-order interpolation and weighing. The centered high-order interpolation of the fluid properties to the particle location is shown to lead to numerical instability in shocked flow. An essentially non-oscillatory interpolation (ENO) scheme is devised for the coupling that improves stability. The ENO based algorithm is shown to be numerically stable and to accurately capture shocks, small flow features and particle dispersion. Both the carrier gas and the particles are updated in time without splitting with a third-order Runge-Kutta TVD method. One and two-dimensional computations of a shock moving into a particle cloud demonstrates the characteristics of the WENO-Z based PSIC method (PSIC/WENO-Z). The PSIC/WENO-Z computations are not only in excellent agreement with the numerical simulations with a third-order Rusanov based PSIC and physical experiments in [V. Boiko, V.P. Kiselev, S.P. Kiselev, A. Papyrin, S. Poplavsky, V. Fomin, Shock wave interaction with a cloud of particles, Shock Waves, 7 (1997) 275-285], but also show a significant improvement in the resolution of small scale structures. In two-dimensional simulations of the Mach 3 shock moving into forty thousand bronze particles arranged in the shape of a rectangle, the long time accuracy of the high-order method is demonstrated

  15. Shock train generated turbulence inside a nozzle with a small opening angle

    Energy Technology Data Exchange (ETDEWEB)

    Grzona, A.; Olivier, H. [RWTH Aachen University, Shock Wave Laboratory, Aachen (Germany)

    2011-09-15

    The flow inside an over expanding rectangular nozzle with a small opening angle of 1.6 is investigated by means of high-speed schlieren and shadowgraph photography, pressure probes and hot-wire anemometry on the nozzle centre line in order to measure the turbulent fluctuations generated by the occurring shock wave/boundary layer interaction. Additionally, an optical shock capturing tool is deployed to measure the amplitude and frequency of the shock train oscillation. Varying the back pressure, the pre-shock Mach number is changed between Ma{sub 1} = 1.1 and 2.1. Two different modes of turbulence generation and distribution are detected. For a single normal shock and a normal shock train, the normal Reynolds stress u{sup '2} on the channel axis is only slightly increased compared to the free stream value, whereas for the cases of a lambda foot shock train and an x-type shock train, a strong intensification by forming a turbulent mixing zone can be observed. (orig.)

  16. Structure and Dynamics of Shock-Induced Nanobubble Collapse in Water

    Science.gov (United States)

    Vedadi, Mohammad; Choubey, Amit; Nomura, Ken-Ichi; Kalia, Rajiv; Nakano, Aiichiro; Vashishta, Priya; van Duin, Adri

    2011-03-01

    Structure of water under shock and shock-induced collapse of nanobubbles in water are investigated with molecular dynamics simulations based on a reactive force field. Shock induces dramatic structural changes, including an ice-VII-like structural motif at a particle velocity of 1 km/s. The incipient ice VII formation and the calculated Hugoniot curve are in good agreement with experimental results. In the presence of a nanobubble, we observe a focused nanojet at the onset of nanobubble shrinkage and a secondary shock wave upon nanobubble collapse. The secondary shock wave propagates spherically backwards and induces high pressure as it propagates. Both the propagation velocity and the induced pressure are larger than those of the primary shock. We explored effects of nanobubble radius and shock amplitude on nanojet formation. The nanojet size increases by increasing particle velocity but the effect of increasing radius is more significant. The jet length scales linearly with the nanobubble radius, as observed in experiments on micron-to-millimeter size bubbles. Shock-induced collapse of a nanobubble in the vicinity of a cell membrane creates a transient nanopore when the nanojet impacts the membrane. Transient cell poration has potential applications in drug delivery.

  17. Collisionless ion dynamics in the shock front

    Science.gov (United States)

    Gedalin, Michael

    2016-07-01

    In the vicinity of the shock front the dynamics of ions is governed by the macroscopic regular electric and magnetic field of the shock. Upon crossing the shock the thermal ions form a non-gyrotropic distribution. The pressure of these non-gyrotropic ions shapes the downstream magnetic field. High-energy ions behave in the shock front as test particles under the influence on the macroscopic fields. The reflection and transmission coefficients of high-energy ions at an oblique shock front is not sensitive to the shock structure and depends only on the global magnetic field change at the shock.

  18. Weak Boson Production Amplitude Zeros; Equalities of the Helicity Amplitudes

    CERN Document Server

    Mamedov, F

    2002-01-01

    We investigate the radiation amplitude zeros exhibited by many Standard Model amplitudes for triple weak gauge boson production processes. We show that $WZ\\gamma$ production amplitudes have especially rich structure in terms of zeros, these amplitudes have zeros originating from several different sources. It is also shown that TYPE I current null zone is the special case of the equality of the specific helicity amplitudes.

  19. Periods and Superstring Amplitudes

    CERN Document Server

    Stieberger, S

    2016-01-01

    Scattering amplitudes which describe the interaction of physical states play an important role in determining physical observables. In string theory the physical states are given by vibrations of open and closed strings and their interactions are described (at the leading order in perturbation theory) by a world-sheet given by the topology of a disk or sphere, respectively. Formally, for scattering of N strings this leads to N-3-dimensional iterated real integrals along the compactified real axis or N-3-dimensional complex sphere integrals, respectively. As a consequence the physical observables are described by periods on M_{0,N} - the moduli space of Riemann spheres of N ordered marked points. The mathematical structure of these string amplitudes share many recent advances in arithmetic algebraic geometry and number theory like multiple zeta values, single-valued multiple zeta values, Drinfeld, Deligne associators, Hopf algebra and Lie algebra structures related to Grothendiecks Galois theory. We review the...

  20. Light Meson Distribution Amplitudes

    CERN Document Server

    Arthur, R.; Brommel, D.; Donnellan, M.A.; Flynn, J.M.; Juttner, A.; de Lima, H.Pedroso; Rae, T.D.; Sachrajda, C.T.; Samways, B.

    2010-01-01

    We calculated the first two moments of the light-cone distribution amplitudes for the pseudoscalar mesons ($\\pi$ and $K$) and the longitudinally polarised vector mesons ($\\rho$, $K^*$ and $\\phi$) as part of the UKQCD and RBC collaborations' $N_f=2+1$ domain-wall fermion phenomenology programme. These quantities were obtained with a good precision and, in particular, the expected effects of $SU(3)$-flavour symmetry breaking were observed. Operators were renormalised non-perturbatively and extrapolations to the physical point were made, guided by leading order chiral perturbation theory. The main results presented are for two volumes, $16^3\\times 32$ and $24^3\\times 64$, with a common lattice spacing. Preliminary results for a lattice with a finer lattice spacing, $32^3\\times64$, are discussed and a first look is taken at the use of twisted boundary conditions to extract distribution amplitudes.

  1. Quantitative Seismic Amplitude Analysis

    OpenAIRE

    Dey, A. K.

    2011-01-01

    The Seismic Value Chain quantifies the cyclic interaction between seismic acquisition, imaging and reservoir characterization. Modern seismic innovation to address the global imbalance in hydrocarbon supply and demand requires such cyclic interaction of both feed-forward and feed-back processes. Currently, the seismic value chain paradigm is in a feed-forward mode. Modern seismic data now have the potential to yield the best images in terms of spatial resolution, amplitude accuracy, and incre...

  2. Heterotrophic microbial colonization of the interior of impact-shocked rocks from Haughton impact structure, Devon Island, Nunavut, Canadian High Arctic

    Science.gov (United States)

    Fike, David A.; Cockell, Charles; Pearce, David; Lee, Pascal

    2002-10-01

    The polar desert is one of the most extreme environments on Earth. Endolithic organisms can escape or mitigate the hazards of the polar desert by using the resources available in the interior of rocks. We examined endolithic communities within crystalline rocks that have undergone shock metamorphism as a result of an asteroid or comet impact. Specifically, we present a characterization of the heterotrophic endolithic community and its environment in the interior of impact-shocked gneisses and their host polymict breccia from the Haughton impact structure on Devon Island, Nunavut, Canadian High Arctic. Microbiological colonization of impact-shocked rocks is facilitated by impact-induced fissures and cavities, which occur throughout the samples, the walls of which are lined with high abundances of biologically important elements owing to the partial volatilization of minerals within the rock during the impact. 27 heterotrophic bacteria were isolated from these shocked rocks and were identified by 16S rDNA sequencing. The isolates from the shocked gneiss and the host breccia are similar to each other, and to other heterotrophic communities isolated from polar environments, suggesting that the interiors of the rocks are colonized by microorganisms from the surrounding country rocks and soils. Inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis were used to identify the chemical composition of the shocked materials and to document the in situ growth of microbes in their interiors. The identification of these heterotrophic communities within impact-shocked crystalline rocks extends our knowledge of the habitable biosphere on Earth. The colonization of the interiors of these samples has astrobiological applications both for considering terrestrial, microbiological contamination of meteorites from the Antarctic ice sheet and for investigating possible habitats for microbial

  3. High dynamic range emission measurements of shocked energetic materials: Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)

    Science.gov (United States)

    Bassett, Will P.; Dlott, Dana D.

    2016-06-01

    A new emission apparatus with high time resolution and high dynamic range was used to study shock-induced ignition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine in the form of ultrafine powder (4 ± 3 μm particle size), over a range of impact velocities (0.8-4.3 km s-1) and impact durations (2.5-16 ns). A graybody model was used to extract graybody emissivities and time-dependent temperatures from a few ns to 100 μs. The emission transients consisted of three parts: a 6700 K nanosecond burst during the shocks, a 4000-4500 K temperature spike near 0.3 μs followed by a ˜3300 K tail extending out to ˜100 μs. These temperatures varied remarkably little with impact velocity and duration, while the emission intensities and emissivities changed by over an order of magnitude. The emissivity changes were interpreted with a hot spot model, where hot spot temperatures reached a maximum of 6700 K and the hot spot volume fractions increased from 5% to 100% as impact velocity increased from 1 to 3 km s-1. Changing shock durations in the 2.5-16 ns range had noticeable effects on the microsecond emission. The 0.3 μs temperature spike was much smaller or absent with 2.5 ns shocks, but prominent with longer durations. An explanation for these effects was put forth that invoked the formation of carbon-rich clusters during the shock. In this view, cluster formation was minimal with 2.5 ns shocks, but longer-duration shocks produced increasingly larger clusters, and the 0.3 μs temperature spikes represented cluster ignition.

  4. Reentry Shock

    Institute of Scientific and Technical Information of China (English)

    Dorine; Houston

    1998-01-01

    Dear Xiao Lan, You remember the pain of culture and reentry shock; humor me please; let mereview the facts for the sake of the students you are sending here in greater numbers.Culture shock is the emotional pain that people experience when they visit a newcountry and find customs, experiences, smells, and non-verbal communication stylesto be different from their own country.

  5. Effects of Cervical High-Velocity Low-Amplitude Techniques on Range of Motion, Strength Performance, and Cardiovascular Outcomes: A Review.

    Science.gov (United States)

    Galindez-Ibarbengoetxea, Xabier; Setuain, Igor; Andersen, Lars L; Ramírez-Velez, Robinson; González-Izal, Miriam; Jauregi, Andoni; Izquierdo, Mikel

    2017-07-21

    Cervical high-velocity low-amplitude (HVLA) manipulation technique is among the oldest and most frequently used chiropractic manual therapy, but the physiologic and biomechanics effects were not completely clear. This review aims to describe the effects of cervical HVLA manipulation techniques on range of motion, strength, and cardiovascular performance. A systematic search was conducted of the electronic databases from January 2000 to August 2016: PubMed (n = 131), ScienceDirect (n = 101), Scopus (n = 991), PEDro (n = 33), CINAHL (n = 884), and SciELO (n = 5). Two independent reviewers conducted the screening process to determine article eligibility. The intervention that included randomized controlled trials was thrust, or HVLA, manipulative therapy directed to the cervical spine. Methodological quality was assessed using the Cochrane risk-of-bias tool. The initial search rendered 2145 articles. After screening titles and abstracts, 11 articles remained for full-text review. The review shows that cervical HVLA manipulation treatment results in a large effect size (d > 0.80) on increasing cervical range of motion and mouth opening. In patients with lateral epicondylalgia, cervical HVLA manipulation resulted in increased pain-free handgrip strength, with large effect sizes (1.44 and 0.78, respectively). Finally, in subjects with hypertension the blood pressure seemed to decrease after cervical HVLA manipulation. Higher quality studies are needed to develop a stronger evidence-based foundation for HVLA manipulation techniques as a treatment for cervical conditions.

  6. Validation of the cat as a model for the human lumbar spine during simulated high-velocity, low-amplitude spinal manipulation.

    Science.gov (United States)

    Ianuzzi, Allyson; Pickar, Joel G; Khalsa, Partap S

    2010-07-01

    High-velocity, low-amplitude spinal manipulation (HVLA-SM) is an efficacious treatment for low back pain, although the physiological mechanisms underlying its effects remain elusive. The lumbar facet joint capsule (FJC) is innervated with mechanically sensitive neurons and it has been theorized that the neurophysiological benefits of HVLA-SM are partially induced by stimulation of FJC neurons. Biomechanical aspects of this theory have been investigated in humans while neurophysiological aspects have been investigated using cat models. The purpose of this study was to determine the relationship between human and cat lumbar spines during HVLA-SM. Cat lumbar spine specimens were mechanically tested, using a displacement-controlled apparatus, during simulated HVLA-SM applied at L5, L6, and L7 that produced preload forces of approximately 25% bodyweight for 0.5 s and peak forces that rose to 50-100% bodyweight within approximately 125 ms, similar to that delivered clinically. Joint kinematics and FJC strain were measured optically. Human FJC strain and kinematics data were taken from a prior study. Regression models were established for FJC strain magnitudes as functions of factors species, manipulation site, and interactions thereof. During simulated HVLA-SM, joint kinematics in cat spines were greater in magnitude compared with humans. Similar to human spines, site-specific HVLA-SM produced regional cat FJC strains at distant motion segments. Joint motions and FJC strain magnitudes for cat spines were larger than those for human spine specimens. Regression relationships demonstrated that species, HVLA-SM site, and interactions thereof were significantly and moderately well correlated for HVLA-SM that generated tensile strain in the FJC. The relationships established in the current study can be used in future neurophysiological studies conducted in cats to extrapolate how human FJC afferents might respond to HVLA-SM. The data from the current study warrant further

  7. Developing shock-capturing difference methods

    Institute of Scientific and Technical Information of China (English)

    TU Guo-hua; YUAN Xiang-jiang; LU Li-peng

    2007-01-01

    A new shock-capturing method is proposed which is based on upwind schemes and flux-vector splittings. Firstly, original upwind schemes are projected along characteristic directions. Secondly, the amplitudes of the characteristic decompositions are carefully controlled by limiters to prevent non-physical oscillations. Lastly, the schemes are converted into conservative forms, and the oscillation-free shock-capturing schemes are acquired. Two explicit upwind schemes (2nd-order and 3rd-order) and three compact upwind schemes (3rd-order, 5th-order and 7th-order) are modified by the method for hyperbolic systems and the modified schemes are checked on several one-dimensional and two-dimensional test cases. Some numerical solutions of the schemes are compared with those of a WENO scheme and a MP scheme as well as a compact-WENO scheme. The results show that the method with high order accuracy and high resolutions can capture shock waves smoothly.

  8. Oscillations in the hadron scattering amplitude at high energy and small momentum transfer; Oscillations dans l`amplitude de diffusion hadronique a haute energie et petites moments de transfer

    Energy Technology Data Exchange (ETDEWEB)

    Gauron, Pierre; Basarab Nicolescu [Theoretical Physics Division, Inst. de Physique Nucleaire, Paris-11 Univ., 91 - Orsay (France); Selyugin, O.V. [Lab. of Theoretical Physics, Joint Inst. for Nuclear Research, Dubna (Russian Federation)

    1999-10-01

    We show that the high precision dN/dt UA4/2 data at {radical} = 541 GeV are compatible with the presence of Auberson-Kinoshita-Martin (AKM) type of oscillations at very small momentum transfer. These oscillations seem to be periodic in {radical}|t|, the corresponding period being {approx_equal} 2 {center_dot}10{sup -2} GeV. The existence of such visible oscillations suggests a general mechanism of saturation of axiomatic bounds. As an illustration the consequences for extracting the parameter {rho} = ReF/ImF from dN/dt data are also discussed. (authors) 1 ref., 2 figs.

  9. An Efficient High-Resolution Shock-Capturing Scheme for Multi-Dimensional Flows I.Hydrodynamics

    Institute of Scientific and Technical Information of China (English)

    Cong Yu

    2006-01-01

    Many problems at the forefront of theoretical astrophysics require a treatment of dynamical fluid behavior. We present an efficient high-resolution shock-capturing hydrodynamic scheme designed to study such phenomena. We have implemented a weighted, essentially non-oscillatory (WENO) scheme to fifth order accuracy in space. HLLE approximate Riemann solver is used for the flux computation at cell interface, which does not require spectral decomposition into characteristic waves and so is computationally friendly. For time integration we apply a third order total variation diminishing (TVD) Runge-Kutta scheme.Extensive testing and comparison with schemes that require characteristic decomposition are carried out demonstrating the ability of our scheme to address challenging open questions in astrophysics.

  10. A STUDY ON LIMITATION OF HIGH-ENERGY SHOCK WAVE-INDUCED RENAL DAMAGE BY SALVIA MILTIORRHIZAE INJECTION IN RABBIT MODEL

    Institute of Scientific and Technical Information of China (English)

    陈兴发; 盛斌武; 贺大林

    2004-01-01

    Objective To study the protective function of Salvia Miltiorrhizae on high-energy shockwaves (HESW) induced renal damage. Methods Thirty healthy New Zealand adult male white rabbits were randomly divided into Salvia Miltiorrhizae group and control group with 15 in each. Three days before extracorpeal shock wave lithotripsy (ESWL) the two groups were injected Salvia Miltiorrhizae and physiological saline respectively. Plasma endothelin-1 (ET-1), Superoxide dismutase (SOD) and malondialdehyde (MDA) were determined and renal morphology was observed. Results After ESWL, levels of ET-1 and MDA increased significantly, the activity of SOD decreased significantly compared with those before ESWL in control group (P0.05). After shocking, SOD, related to renal protection, in Salvia Miltiorrhizae group was significantly higher than that of controls (P<0.05). Renal morphological injury was slight in Salvia Miltiorrhizae group. Conclusion Salvia Miltiorrhizae injection has protective function on renal toxicity induced by high-energy shock waves.

  11. Impact of Cooling Rate-Induced Recrystallization on High G Mechanical Shock and Thermal Cycling in Sn-Ag-Cu Solder Interconnects

    Science.gov (United States)

    Lee, Tae-Kyu; Bieler, Thomas R.; Kim, Choong-Un

    2016-01-01

    The mechanical stability and thermo-mechanical fatigue performance of solder joints with low silver content Sn-1.0Ag-0.5Cu (wt.%) (SAC105) alloy based on different cooling rates are investigated in high G level shock environment and thermal cycling conditions. The cooling rate-controlled samples ranging from 1°C/min to 75°C/min cooling rate, not only show differences in microstructure, where a fine poly-granular microstructure develops in the case of fast cooling versus normal cooling, but also show various shock performances based on the microstructure changes. The fast cooling rate improves the high G shock performance by over 90% compared to the normal cooled SAC105 alloy air-cooling environment commonly used after assembly reflow. The microstructure effect on thermal cycling performance is also discussed, which is analyzed based on the Sn grain orientation, interconnect stability, and solder joint bulk microstructure.

  12. Amplitude image processing by diffractive optics.

    Science.gov (United States)

    Cagigal, Manuel P; Valle, Pedro J; Canales, V F

    2016-02-22

    In contrast to the standard digital image processing, which operates over the detected image intensity, we propose to perform amplitude image processing. Amplitude processing, like low pass or high pass filtering, is carried out using diffractive optics elements (DOE) since it allows to operate over the field complex amplitude before it has been detected. We show the procedure for designing the DOE that corresponds to each operation. Furthermore, we accomplish an analysis of amplitude image processing performances. In particular, a DOE Laplacian filter is applied to simulated astronomical images for detecting two stars one Airy ring apart. We also check by numerical simulations that the use of a Laplacian amplitude filter produces less noisy images than the standard digital image processing.

  13. Manually operated piston-driven shock tube

    OpenAIRE

    Reddy, KPJ; Sharath, N

    2013-01-01

    A simple hand-operated shock tube capable of producing Mach 2 shock waves is described. Performance of this miniature shock tube using compressed high pressure air created by a manually operated piston in the driver section of the shock tube as driver gas with air at 1 atm pressure as the test gas in the driven tube is presented. The performance of the shock tube is found to match well with the theoretically estimated values using normal shock relations. Applications of this shock tube named ...

  14. NaAlSi3O8-hollandite and other high-pressure minerals in the shock melt veins of the Suizhou meteorite

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The Suizhou L6 chondrite contains a few very thin shock melt veins of 0.02-0.09 mm in width. In spite of small width of the veins, shock-induced high-pressure phases, such as coarse-grained NaAlSi3O8-hollandite, ringwoodite, majorite and fine-grained matrix majorite-pyropess have been discovered in these veins. NaAlSi3O8-hollandite, the high-pressure phase of plagioclase, in Suizhou shock veins occurs as a single phase mineral, no silicate glassy phase, such as albitic glass, was incorporated with it. The presence of above-mentioned high-pressure phases constrains the high pressure (up to 23-24 GPa) and high temperature (up to 1900-2000℃) regime in Suizhou shock veins, and indicates that the duration of high-pressure regime in the veins should be long enough (a few seconds) for phase transformation and crystallization of minerals under pressure. The discovery of the first natural single-phase crystalline NaAlSi3O8- hollan-dite in Suizhou meteorite is of important significance in un-derstanding the Earth's mantle geochemistry.

  15. Pressure Hull Analysis under Shock Loading

    OpenAIRE

    Ya-Jung Lee; Chia-Hao Hsu; Chien-Hua Huang

    2008-01-01

    The hull of high performance submarines must resist underwater shock loading due to exploding torpedoes or depth bombs. An underwater shock involving an initial shock wave and successive bubble pulsating waves is so complex that a theoretical technique for deriving shock pressure distribution is required for improving simulation efficiency. Complete shock loading is obtained theoretically in this work, and responses of a submarine pressure hull are calculated using ABAQUS USA (Underwater Shoc...

  16. Altered spontaneous brain activity pattern in patients with high myopia using amplitude of low-frequency fluctuation: a resting-state fMRI study

    Directory of Open Access Journals (Sweden)

    Huang X

    2016-11-01

    Full Text Available Xin Huang,1,2,* Fu-Qing Zhou,3,* Yu-Xiang Hu,1 Xiao-Xuan Xu,1 Xiong Zhou,4 Yu-Lin Zhong,1 Jun Wang,4 Xiao-Rong Wu1 1Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Nanchang, 2Department of Ophthalmology, The First People’s Hospital of Jiujiang City, Jiujiang, 3Department of Radiology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Medical Imaging Research Institute, 4Second Department of Respiratory Disease, Jiangxi Provincial People’s Hospital, Nanchang, Jiangxi, People’s Republic of China *These authors contributed equally to this work Objective: Many previous reports have demonstrated significant neural anatomy changes in the brain of high myopic (HM patients, whereas the spontaneous brain activity changes in the HM patients at rest are not well studied. Our objective was to use amplitude of low-frequency fluctuation (ALFF method to investigate the changes in spontaneous brain activity in HM patients and their relationships with clinical features. Methods: A total of 38 patients with HM (17 males and 21 females and 38 healthy controls (HCs (17 males and 21 females closely matched in age, sex, and education underwent resting-state functional magnetic resonance imaging scans. The ALFF method was used to assess local features of spontaneous brain activity. The relationship between the mean ALFF signal values in many brain regions and the clinical features in HM patients was calculated by correlation analysis. Results: Compared with HCs, the HM patients had significantly lower ALFF in the right inferior and middle temporal gyrus, left middle temporal gyrus, left inferior frontal gyrus/putamen, right inferior frontal gyrus/putamen/insula, right middle frontal gyrus, and right inferior parietal lobule and higher ALFF values in the bilateral midcingulate cortex, left postcentral gyrus, and left precuneus/inferior parietal lobule. However, no relationship was found between the mean ALFF

  17. Spin rotation and birefringence effect for a particle in a high energy storage ring and measurement of the real part of the coherent elastic zero-angle scattering amplitude, electric and magnetic polarizabilities

    CERN Document Server

    Baryshevsky, V G

    2005-01-01

    In the present paper the equations for the spin evolution of a particle in a storage ring are analyzed considering contributions from the tensor electric and magnetic polarizabilities of the particle. Study of spin rotation and birefringence effect for a particle in a high energy storage ring provides for measurement as the real part of the coherent elastic zero-angle scattering amplitude as well as tensor electric and magnetic polarizabilities. We proposed the method for measurement the real part of the elastic coherent zero-angle scattering amplitude of particles and nuclei in a storage ring by the paramagnetic resonance in the periodical in time nuclear pseudoelectric and pseudomagnetic fields.

  18. Second sound shock waves and critical velocities in liquid helium 2. Ph.D. Thesis

    Science.gov (United States)

    Turner, T. N.

    1979-01-01

    Large amplitude second-sound shock waves were generated and the experimental results compared to the theory of nonlinear second-sound. The structure and thickness of second-sound shock fronts are calculated and compared to experimental data. Theoretically it is shown that at T = 1.88 K, where the nonlinear wave steepening vanishes, the thickness of a very weak shock must diverge. In a region near this temperature, a finite-amplitude shock pulse evolves into an unusual double-shock configuration consisting of a front steepened, temperature raising shock followed by a temperature lowering shock. Double-shocks are experimentally verified. It is experimentally shown that very large second-sound shock waves initiate a breakdown in the superfluidity of helium 2, which is dramatically displayed as a limit to the maximum attainable shock strength. The value of the maximum shock-induced relative velocity represents a significant lower bound to the intrinsic critical velocity of helium 2.

  19. Generation of Focused Shock Waves in Water for Biomedical Applications

    Science.gov (United States)

    Lukeš, Petr; Šunka, Pavel; Hoffer, Petr; Stelmashuk, Vitaliy; Beneš, Jiří; Poučková, Pavla; Zadinová, Marie; Zeman, Jan

    The physical characteristics of focused two-successive (tandem) shock waves (FTSW) in water and their biological effects are presented. FTSW were ­generated by underwater multichannel electrical discharges in a highly conductive saline solution using two porous ceramic-coated cylindrical electrodes of different diameter and surface area. The primary cylindrical pressure wave generated at each composite electrode was focused by a metallic parabolic reflector to a common focal point to form two strong shock waves with a variable time delay between the waves. The pressure field and interaction between the first and the second shock waves at the focus were investigated using schlieren photography and polyvinylidene fluoride (PVDF) shock gauge sensors. The largest interaction was obtained for a time delay of 8-15 μs between the waves, producing an amplitude of the negative pressure phase of the second shock wave down to -80 MPa and a large number of cavitations at the focus. The biological effects of FTSW were demonstrated in vitro on damage to B16 melanoma cells, in vivo on targeted lesions in the thigh muscles of rabbits and on the growth delay of sarcoma tumors in Lewis rats treated in vivo by FTSW, compared to untreated controls.

  20. Shear strength measurements in a shock loaded commercial silastomer

    Science.gov (United States)

    Millett, J. C. F.; Whiteman, G.; Stirk, S. M.; Bourne, N. K.

    2011-05-01

    The shock-induced shear strength of a commercial silastomer, trade name Sylgard 184™, has been determined using laterally mounted manganin stress gauges. Shear strength has been observed to increase with increasing shock amplitude, in common with many other materials. Shear strength has also been observed to increase slightly behind the shock front as well. It is believed that a combination of polymer chain entanglement and cross linking between chains is responsible. Finally, a ramp on the leading edge of the lower amplitude stress traces has been observed. It has been suggested that this is due to shock-induced collapse of free space between the polymer chains. Similar explanations have been used to explain the apparent non-linearity of the shock velocity with particle velocity at low shock amplitudes.

  1. Shear strength measurements in a shock loaded commercial silastomer

    Energy Technology Data Exchange (ETDEWEB)

    Millett, J C F; Whiteman, G; Stirk, S M; Bourne, N K, E-mail: Jeremy.Millett@awe.co.uk [AWE, Aldermaston, Reading, RG7 4PR. UK (United Kingdom)

    2011-05-11

    The shock-induced shear strength of a commercial silastomer, trade name Sylgard 184(TM), has been determined using laterally mounted manganin stress gauges. Shear strength has been observed to increase with increasing shock amplitude, in common with many other materials. Shear strength has also been observed to increase slightly behind the shock front as well. It is believed that a combination of polymer chain entanglement and cross linking between chains is responsible. Finally, a ramp on the leading edge of the lower amplitude stress traces has been observed. It has been suggested that this is due to shock-induced collapse of free space between the polymer chains. Similar explanations have been used to explain the apparent non-linearity of the shock velocity with particle velocity at low shock amplitudes.

  2. Highly frequent mutations in negative regulators of multiple virulence genes in group A streptococcal toxic shock syndrome isolates.

    Directory of Open Access Journals (Sweden)

    Tadayoshi Ikebe

    2010-04-01

    Full Text Available Streptococcal toxic shock syndrome (STSS is a severe invasive infection characterized by the sudden onset of shock and multiorgan failure; it has a high mortality rate. Although a number of studies have attempted to determine the crucial factors behind the onset of STSS, the responsible genes in group A Streptococcus have not been clarified. We previously reported that mutations of csrS/csrR genes, a two-component negative regulator system for multiple virulence genes of Streptococcus pyogenes, are found among the isolates from STSS patients. In the present study, mutations of another negative regulator, rgg, were also found in clinical isolates of STSS patients. The rgg mutants from STSS clinical isolates enhanced lethality and impaired various organs in the mouse models, similar to the csrS mutants, and precluded their being killed by human neutrophils, mainly due to an overproduction of SLO. When we assessed the mutation frequency of csrS, csrR, and rgg genes among S. pyogenes isolates from STSS (164 isolates and non-invasive infections (59 isolates, 57.3% of the STSS isolates had mutations of one or more genes among three genes, while isolates from patients with non-invasive disease had significantly fewer mutations in these genes (1.7%. The results of the present study suggest that mutations in the negative regulators csrS/csrR and rgg of S. pyogenes are crucial factors in the pathogenesis of STSS, as they lead to the overproduction of multiple virulence factors.

  3. Magnetic field fluctuations across the Earth’s bow shock

    Directory of Open Access Journals (Sweden)

    A. Czaykowska

    Full Text Available We present a statistical analysis of 132 dayside (LT 0700-1700 bow shock crossings of the AMPTE/IRM spacecraft. We perform a superposed epoch analysis of low frequency, magnetic power spectra some minutes up-stream and downstream of the bow shock. The events are devided into categories depending on the angle θBn between bow shock normal and interplanetary magnetic field, and on plasma-β. In the foreshock upstream of the quasi-parallel bow shock, the power of the magnetic fluctuations is roughly 1 order of magnitude larger (δB ~ 4 nT for frequencies 0.01–0.04 Hz than upstream of the quasi-perpendicular shock. There is no significant difference in the magnetic power spectra upstream and downstream of the quasi-parallel bow shock; only at the shock itself, is the magnetic power enhanced by a factor of 4. This enhancement may be due to either an amplification of convecting upstream waves or to wave generation at the shock interface. On the contrary, downstream of the quasi-perpendicular shock, the magnetic wave activity is considerably higher than upstream. Down-stream of the quasi-perpendicular low-β bow shock, we find a dominance of the left-hand polarized component at frequencies just below the ion-cyclotron frequency, with amplitudes of about 3 nT. These waves are identified as ion-cyclotron waves, which grow in a low-β regime due to the proton temperature anisotropy. We find a strong correlation of this anisotropy with the intensity of the left-hand polarized component. Downstream of some nearly perpendicular (θBn ≈ 90° high-β crossings, mirror waves are identified. However, there are also cases where the conditions for mirror modes are met downstream of the nearly perpendicular shock, but no mirror waves are observed.

    Key words. Interplanetary physics (plasma waves and turbulence – Magnetospheric physics (magnetosheath; plasma waves and

  4. The microphysics of collisionless shock waves

    DEFF Research Database (Denmark)

    Marcowith, Alexandre; Bret, Antoine; Bykov, Andrei;

    2016-01-01

    Collisionless shocks, that is shocks mediated by electromagnetic processes, are customary in space physics and in astrophysics. They are to be found in a great variety of objects and environments: magnetospheric and heliospheric shocks, supernova remnants, pulsar winds and their nebulæ, active...... galactic nuclei, gamma-ray bursts and clusters of galaxies shock waves. Collisionless shock microphysics enters at different stages of shock formation, shock dynamics and particle energization and/or acceleration. It turns out that the shock phenomenon is a multi-scale non-linear problem in time and space....... It is complexified by the impact due to high-energy cosmic rays in astrophysical environments. This review adresses the physics of shock formation, shock dynamics and particle acceleration based on a close examination of available multi-wavelength or in situ observations, analytical and numerical developments...

  5. TRENDS IN THE DEVELOPMENT OF DETONATION ENGINES FOR HIGH-SPEED AEROSPACE AIRCRAFTS AND THE PROBLEM OF TRIPLE CONFIGURATIONS OF SHOCK WAVES. Part I. Research of detonation engines

    Directory of Open Access Journals (Sweden)

    P. V. Bulat

    2016-01-01

    Full Text Available We consider current problems of improving propulsion systems of highly supersonic air-space vehicles. In the first part, we review historic developments and list the landmark scientific papers. Classification of detonation engines is presented with detailed consideration of rotation detonation engines and continuous detonation engines. Experimental results on detonation, which are of particular importance for the design of detonation engines, are discussed. The second part of the paper provides an overview of the development in detonation theory, mathematical modelling, and numerical simulation. We focus on the interference of shock waves with formation of triple points, regular and irregular reflection of shock waves, existence of multiple solutions and the resulting appearance of hysteresis. The relevance and importance of triple shock wave configurations for the development of new types of air intakes and detonation jet engines is demonstrated.

  6. Radiative effects in radiative shocks in shock tubes

    Science.gov (United States)

    Drake, R. P.; Doss, F. W.; McClarren, R. G.; Adams, M. L.; Amato, N.; Bingham, D.; Chou, C. C.; DiStefano, C.; Fidkowski, K.; Fryxell, B.; Gombosi, T. I.; Grosskopf, M. J.; Holloway, J. P.; van der Holst, B.; Huntington, C. M.; Karni, S.; Krauland, C. M.; Kuranz, C. C.; Larsen, E.; van Leer, B.; Mallick, B.; Marion, D.; Martin, W.; Morel, J. E.; Myra, E. S.; Nair, V.; Powell, K. G.; Rauchwerger, L.; Roe, P.; Rutter, E.; Sokolov, I. V.; Stout, Q.; Torralva, B. R.; Toth, G.; Thornton, K.; Visco, A. J.

    2011-09-01

    Using modern high-energy-density facilities it is straightforward to produce radiative shock waves in which the transfer of energy by radiation controls the hydrodynamic structure of the system. Some of these experiments use shock tubes. This paper discusses such experiments, with an emphasis on the simple physical relations that determine the primary features of such shocks and on the details and impact of radiative energy transfer in such systems. Notable aspects include the creation of high-density shocked layers, the flow of radiative energy toward regions of higher energy density, and the creation of secondary shocks by ablation of the tube walls ahead of the primary shock front. Simulations of one such experimental system are also shown.

  7. Corrugation of relativistic magnetized shock waves

    CERN Document Server

    Lemoine, M; Gremillet, L

    2016-01-01

    As a shock front interacts with turbulence, it develops corrugation which induces outgoing wave modes in the downstream plasma. For a fast shock wave, the incoming wave modes can either be fast magnetosonic waves originating from downstream, outrunning the shock, or eigenmodes of the upstream plasma drifting through the shock. Using linear perturbation theory in relativistic MHD, this paper provides a general analysis of the corrugation of relativistic magnetized fast shock waves resulting from their interaction with small amplitude disturbances. Transfer functions characterizing the linear response for each of the outgoing modes are calculated as a function of the magnetization of the upstream medium and as a function of the nature of the incoming wave. Interestingly, if the latter is an eigenmode of the upstream plasma, we find that there exists a resonance at which the (linear) response of the shock becomes large or even diverges. This result may have profound consequences on the phenomenology of astrophys...

  8. High-energy extracorporeal shock-wave therapy for treating chronic calcific tendinitis of the shoulder: a systematic review.

    Science.gov (United States)

    Bannuru, Raveendhara R; Flavin, Nina E; Vaysbrot, Elizaveta; Harvey, William; McAlindon, Timothy

    2014-04-15

    Calcific and noncalcific tendinitis of the shoulder can be unresponsive to conventional therapies. Extracorporeal shock-wave therapy (ESWT) has been suggested as an alternative treatment. To assess the efficacy of ESWT in patients with calcific and noncalcific tendinitis. MEDLINE, Cochrane Central Register of Controlled Trials, EMBASE, Web of Science, and Google Scholar were searched up to 1 November 2013. Randomized, controlled trials (RCTs) comparing high-energy versus low-energy ESWT or placebo for treatment of calcific or noncalcific tendinitis of the shoulder. Outcome measures included pain (visual analogue scale score), functional assessment (Constant-Murley score), and resolution of calcifications. Three independent reviewers abstracted data and determined eligibility and quality by consensus. Twenty-eight RCTs met the inclusion criteria. Studies were heterogeneous. Twenty RCTs compared ESWT energy levels and placebo and consistently showed that high-energy ESWT was significantly better than placebo in decreasing pain and improving function and resorption of calcifications in calcific tendinitis. No significant difference was found between ESWT and placebo in treatment of noncalcific tendinitis. The number of RCTs was small, and the studies were heterogeneous. High-energy ESWT is effective for improving pain and shoulder function in chronic calcific shoulder tendinitis and can result in complete resolution of calcifications. This therapy may be underutilized for a condition that can be difficult to manage. None.

  9. Existence domains of arbitrary amplitude nonlinear structures in two-electron temperature space plasmas. II. High-frequency electron-acoustic solitons

    Energy Technology Data Exchange (ETDEWEB)

    Maharaj, S. K. [South African National Space Agency (SANSA) Space Science, P.O. Box 32, Hermanus 7200 (South Africa); Bharuthram, R. [University of the Western Cape, Modderdam Road, Bellville 7530 (South Africa); Singh, S. V. [Indian Institute of Geomagnetism, New Panvel (West), Navi Mumbai 410218 (India); School of Chemistry and Physics, University of KwaZulu-Natal, Private Bag X54001, Durban 4000 (South Africa); Lakhina, G. S. [Indian Institute of Geomagnetism, New Panvel (West), Navi Mumbai 410218 (India)

    2012-12-15

    A three-component plasma model composed of ions, cool electrons, and hot electrons is adopted to investigate the existence of large amplitude electron-acoustic solitons not only for the model for which inertia and pressure are retained for all plasma species which are assumed to be adiabatic but also neglecting inertial effects of the hot electrons. Using the Sagdeev potential formalism, the Mach number ranges supporting the existence of large amplitude electron-acoustic solitons are presented. The limitations on the attainable amplitudes of electron-acoustic solitons having negative potentials are attributed to a number of different physical reasons, such as the number density of either the cool electrons or hot electrons ceases to be real valued beyond the upper Mach number limit, or, alternatively, a negative potential double layer occurs. Electron-acoustic solitons having positive potentials are found to be supported only if inertial effects of the hot electrons are retained and these are found to be limited only by positive potential double layers.

  10. Are gauge shocks really shocks?

    CERN Document Server

    Alcubierre, M

    2005-01-01

    The existence of gauge pathologies associated with the Bona-Masso family of generalized harmonic slicing conditions is proven for the case of simple 1+1 relativity. It is shown that these gauge pathologies are true shocks in the sense that the characteristic lines associated with the propagation of the gauge cross, which implies that the name ``gauge shock'' usually given to such pathologies is indeed correct. These gauge shocks are associated with places where the spatial hypersurfaces that determine the foliation of spacetime become non-smooth.

  11. High-Temperature Shock Tube Measurements of Dimethyl Ether Decomposition and the Reaction of Dimethyl Ether with OH

    Science.gov (United States)

    Cook, Robert D.; Davidson, David F.; Hanson, Ronald K.

    2009-08-01

    We measured the first high-temperature rate measurements of two dimethyl ether (DME) reactions, (1) DME + Ar → CH3O + CH3 + Ar and (2) DME + OH → CH3OCH2 + H2O, in a shock tube by monitoring OH radicals. OH was measured with a narrow-line width laser absorption diagnostic using the well-known R1(5) line of the A-X(0,0) transition at 306.7 nm. The rate k1 is in the falloff regime at high temperatures, so it was measured at several pressures from 0.6 to 11.5 atm and temperatures from 1349 to 1790 K. OH radicals were formed by shock-heating mixtures of DME and O2 in Ar. These mixtures take advantage of the rapid decomposition of the product CH3O, forming H-atoms, which react with O2 to form OH. In carefully chosen mixtures, OH concentration is primarily sensitive to k1 and the well-known rate of H + O2 → OH + O. Uncertainty in the k1 measurements was estimated to be ±35%. The rate measurements were then modeled using RRKM theory, which describes the data quite well. Both the rate measurements and the RRKM model were fit from 1000 to 1800 K using the Troe falloff form: k1,∞(T) = (4.38 × 1021)T-1.57 exp(-42 220 K/T) s-1, k1,o = 7.52 × 1015 exp(-21 537 K/T) cm3 mol-1 s-1, and Fcent = 0.454 exp(-T/2510). The rate of k2 was measured at pressures near 1.6 atm and temperatures from 923 to 1423 K. OH radicals were generated by the thermal decomposition of the OH precursor tert-butyl hydroperoxide (TBHP), and k2 was inferred from the observed decay of OH with an estimated uncertainty of ±40%. The high-temperature measurements were compared with several rate evaluations and previous low-temperature measurements. The rate evaluation by Curran et al. of k2 = (6.32 × 106)T2 exp(328 K/T) (cm3 mol-1 s-1) was found to be an excellent fit to both the previous low-temperature measurements and this work.

  12. High-temperature shock tube measurements of dimethyl ether decomposition and the reaction of dimethyl ether with OH.

    Science.gov (United States)

    Cook, Robert D; Davidson, David F; Hanson, Ronald K

    2009-09-17

    We measured the first high-temperature rate measurements of two dimethyl ether (DME) reactions, (1) DME + Ar --> CH3O + CH3 + Ar and (2) DME + OH --> CH3OCH2 + H2O, in a shock tube by monitoring OH radicals. OH was measured with a narrow-line width laser absorption diagnostic using the well-known R1(5) line of the A-X(0,0) transition at 306.7 nm. The rate k1 is in the falloff regime at high temperatures, so it was measured at several pressures from 0.6 to 11.5 atm and temperatures from 1349 to 1790 K. OH radicals were formed by shock-heating mixtures of DME and O2 in Ar. These mixtures take advantage of the rapid decomposition of the product CH3O, forming H-atoms, which react with O2 to form OH. In carefully chosen mixtures, OH concentration is primarily sensitive to k1 and the well-known rate of H + O2 --> OH + O. Uncertainty in the k1 measurements was estimated to be +/-35%. The rate measurements were then modeled using RRKM theory, which describes the data quite well. Both the rate measurements and the RRKM model were fit from 1000 to 1800 K using the Troe falloff form: k(1,infinity)(T) = (4.38 x 10(21))T(-1.57) exp(-42,220 K/T) s(-1), k(1,o) = 7.52 x 10(15) exp(-21,537 K/T) cm3 mol(-1) s(-1), and F(cent) = 0.454 exp(-T/2510). The rate of k2 was measured at pressures near 1.6 atm and temperatures from 923 to 1423 K. OH radicals were generated by the thermal decomposition of the OH precursor tert-butyl hydroperoxide (TBHP), and k2 was inferred from the observed decay of OH with an estimated uncertainty of +/-40%. The high-temperature measurements were compared with several rate evaluations and previous low-temperature measurements. The rate evaluation by Curran et al. of k2 = (6.32 x 10(6))T2 exp(328 K/T) (cm3 mol(-1) s(-1)) was found to be an excellent fit to both the previous low-temperature measurements and this work.

  13. Material ejection from shock-loaded free surfaces of aluminum and lead

    Energy Technology Data Exchange (ETDEWEB)

    Asay, J.R.

    1976-10-01

    A discussion is presented regarding interferometer experiments conducted on free surfaces which are impulsively loaded with high amplitude shock waves. It is shown that material ejection from shocked surfaces can significantly degrade interferometer experiments. In particular, loss of both light intensity and contrast of interferometer signals can result from various scattering and absorption processes occurring in a cloud of ejected material. An experimental technique is presented which allows determination of the mass and velocity of material ejected from free surfaces during shock loading. The technique has been applied to a study of mass ejection occurring naturally from shocked surfaces of two aluminium alloys and from lead. These results show that the total ejected mass ranges from a few ..mu..g/cm/sup 2/ in the aluminum alloys studied to a few mg/cm/sup 2/ in lead, for shock pressures ranging from about 10 to 50 GPa (100 to 500 kbar). Surface defects, such as pits and scratches, are thought to strongly influence mass ejection in aluminum; whereas in lead, localized shock-induced melting and vaporization are thought to be the dominant mechanisms at the higher shock pressures. Experimental results are also presented for aluminum surfaces which contain artificial defects in the form of wedge-shaped cavities. These results show that the maximum ejecta velocities of approximately two to four times the free surface velocity which are observed in these experiments can be correlated with predictions of steady jetting theory.

  14. Particle-in-cell simulation study of a lower-hybrid shock

    Science.gov (United States)

    Dieckmann, M. E.; Sarri, G.; Doria, D.; Ynnerman, A.; Borghesi, M.

    2016-06-01

    The expansion of a magnetized high-pressure plasma into a low-pressure ambient medium is examined with particle-in-cell simulations. The magnetic field points perpendicular to the plasma's expansion direction and binary collisions between particles are absent. The expanding plasma steepens into a quasi-electrostatic shock that is sustained by the lower-hybrid (LH) wave. The ambipolar electric field points in the expansion direction and it induces together with the background magnetic field a fast E cross B drift of electrons. The drifting electrons modify the background magnetic field, resulting in its pile-up by the LH shock. The magnetic pressure gradient force accelerates the ambient ions ahead of the LH shock, reducing the relative velocity between the ambient plasma and the LH shock to about the phase speed of the shocked LH wave, transforming the LH shock into a nonlinear LH wave. The oscillations of the electrostatic potential have a larger amplitude and wavelength in the magnetized plasma than in an unmagnetized one with otherwise identical conditions. The energy loss to the drifting electrons leads to a noticeable slowdown of the LH shock compared to that in an unmagnetized plasma.

  15. On shocks driven by high-mass planets in radiatively inefficient disks. II. Three-dimensional global disk simulations

    CERN Document Server

    Lyra, Wladimir; Boley, Aaron; Turner, Neal; Mac Low, Mordecai-Mark; Okuzumi, Satoshi; Flock, Mario

    2015-01-01

    Recent high-resolution, near-infrared images of protoplanetary disks have shown that these disks often present spiral features. Spiral arms are among the structures predicted decades ago by numerical simulations of disk-planet interaction and thus it is tempting to suspect that planetary perturbers are responsible for the observed signatures. However, such interpretation is not free of problems. The spirals are found to have large pitch angles, and in at least one case the spiral feature appears effectively unpolarized, which implies thermal emission at roughly 1000 K. We have recently shown in two-dimensional models that shock dissipation in the supersonic wake of high-mass planets can lead to significant heating if the disk is sufficiently adiabatic. In this paper we extend this analysis to three dimensions in thermodynamically evolving disks. We use the Pencil Code in spherical coordinates for our models, with a prescription for thermal cooling based on the optical depth of the local vertical gas column. W...

  16. Nonstationarity of a two-dimensional perpendicular shock: Competing mechanisms

    Science.gov (United States)

    Lembège, Bertrand; Savoini, Philippe; Hellinger, Petr; Trávníček, Pavel M.

    2009-03-01

    Two-dimensional particle-in-cell (PIC) simulations are used for analyzing in detail different nonstationary behaviors of a perpendicular supercritical shock. A recent study by Hellinger et al. (2007) has shown that the front of a supercritical shock can be dominated by the emission of large-amplitude whistler waves. These waves inhibit the self-reformation driven by the reflected ions; then, the shock front appears almost ``quasi-stationary.'' The present study stresses new complementary results. First, for a fixed β i value, the whistler waves emission (WWE) persists for high M A above a critical Mach number (i.e., M A >= M A WWE). The quasi-stationarity is only apparent and disappears when considering the full 3-D field profiles. Second, for lower M A , the self-reformation is retrieved and becomes dominant as the amplitude of the whistler waves becomes negligible. Third, there exists a transition regime in M A within which both processes compete each other. Fourth, these results are observed for a strictly perpendicular shock only as B 0 is within the simulation plane. When B 0 is out of the simulation plane, no whistler waves emission is evidenced and only self-reformation is recovered. Fifth, the occurrence and disappearance of the nonlinear whistler waves are well recovered in both 2-D PIC and 2-D hybrid simulations. The impacts on the results of the mass ratio (2-D PIC simulations), of the resistivity and spatial resolution (2-D hybrid simulations), and of the size of the simulation box along the shock front are analyzed in detail.

  17. Early High-Volume Hemofiltration versus Standard Care for Post-Cardiac Surgery Shock. The HEROICS Study

    National Research Council Canada - National Science Library

    Combes, Alain; Bréchot, Nicolas; Amour, Julien; Cozic, Nathalie; Lebreton, Guillaume; Guidon, Catherine; Zogheib, Elie; Thiranos, Jean-Claude; Rigal, Jean-Christophe; Bastien, Olivier; Benhaoua, Hamina; Abry, Bernard; Ouattara, Alexandre; Trouillet, Jean-Louis; Mallet, Alain; Chastre, Jean; Leprince, Pascal; Luyt, Charles-Edouard

    2015-01-01

    ...), followed by standard-volume continuous venovenous hemodiafiltration (CVVHDF) until resolution of shock and recovery of renal function, or conservative standard care, with delayed CVVHDF only for persistent, severe acute kidney injury...

  18. Identifying nonlinear wave interactions in plasmas using two-point measurements a case study of Short Large Amplitude Magnetic Structures (SLAMS)

    CERN Document Server

    Dudok de Wit, T; Dunlop, M; Luehr, H

    1999-01-01

    A framework is described for estimating Linear growth rates and spectral energy transfers in turbulent wave-fields using two-point measurements. This approach, which is based on Volterra series, is applied to dual satellite data gathered in the vicinity of the Earth's bow shock, where Short Large Amplitude Magnetic Structures (SLAMS) supposedly play a leading role. The analysis attests the dynamic evolution of the SLAMS and reveals an energy cascade toward high-frequency waves.

  19. Shock Induced Emission from Sapphire in High-Pressure Phase of Rh2O3 (Ⅱ) Structure

    Institute of Scientific and Technical Information of China (English)

    ZHANG Dai-Yu; LIU Fu-Sheng; HAO Gao-Yu; SUN Yu-Huai

    2007-01-01

    @@ A distinct optical emission from the Rh2 O3 (Ⅱ) structural sapphire is observed under shock compression of 125,132, and 143 Gpa. The emission intensity continuously increases with the thickness of shocked sapphire. The colour temperature is determined to be about 4000K, which is obviously smaller than the reported value of the alpha phase alumina at the pressures below 80 Gpa. The present results suggest that the structural transformation will cause an obvious change of optical property in sapphire.

  20. PULSE AMPLITUDE DISTRIBUTION RECORDER

    Science.gov (United States)

    Cowper, G.

    1958-08-12

    A device is described for automatica1ly recording pulse annplitude distribution received from a counter. The novelty of the device consists of the over-all arrangement of conventional circuit elements to provide an easy to read permanent record of the pulse amplitude distribution during a certain time period. In the device a pulse analyzer separates the pulses according to annplitude into several channels. A scaler in each channel counts the pulses and operates a pen marker positioned over a drivable recorder sheet. Since the scalers in each channel have the sanne capacity, the control circuitry permits counting of the incoming pulses until one scaler reaches capacity, whereupon the input is removed and an internal oscillator supplies the necessary pulses to fill up the other scalers. Movement of the chart sheet is initiated wben the first scaler reaches capacity to thereby give a series of marks at spacings proportional to the time required to fill the remaining scalers, and accessory equipment marks calibration points on the recorder sheet to facilitate direct reading of the number of external pulses supplied to each scaler.

  1. High Strain Rate Characterization of Shock Absorbing Materials for Landmine Protection Concepts

    Directory of Open Access Journals (Sweden)

    Jennifer McArthur

    2003-01-01

    Full Text Available Numerical modelling of footwear to protect against anti-personnel landmines requires dynamic material properties in the appropriate strain rate regime to accurately simulate material response. Several materials (foamed metals, honeycombs and polymers are used in existing protective boots, however published data at high strain rates is limited.

  2. Algorithm Development and Application of High Order Numerical Methods for Shocked and Rapid Changing Solutions

    Science.gov (United States)

    2007-12-06

    high order well-balanced schemes to a class of hyperbolic systems with source terms, Boletin de la Sociedad Espanola de Matematica Aplicada, v34 (2006...schemes to a class of hyperbolic systems with source terms, Boletin de la Sociedad Espanola de Matematica Aplicada, v34 (2006), pp.69-80. 39. Y. Xu and C.-W

  3. Shock Effects and High Pressure Polymorphs in Polymict Eucrite Northwest Africa 10658

    Science.gov (United States)

    Fudge, C.; Wittmann, A.; Garvie, L. A. J.; Sharp, T. G.

    2016-08-01

    We report the presence of coesite in polymict eucrite NWA 10658. High pressure silica phases have previously been described to coexist with silica glass in the Béréba eucrite. We will present data from transmission electron microscope investigations.

  4. Effects of high temperature on life history traits and heat shock protein expression in chlorpyrifos-resistant Laodelphax striatella.

    Science.gov (United States)

    Wang, Lihua; Shan, Dan; Zhang, Yueliang; Liu, Xiangdong; Sun, Yang; Zhang, Zhichun; Fang, Jichao

    2017-03-01

    The resistance of the small brown planthopper (SBPH), Laodelphax striatella, to insecticides has been widely found in China, and has posed serious problems to efforts to control the pest. To determine the costs and benefits of resistance, the life tables of chlorpyrifos-resistant and -susceptible strains were constructed at 24 and 30°C. The results showed the resistant SBPH (YN-CPF) had lower fitness at 24°C, but slightly higher fitness at 30°C compared to the susceptible SBPH. Transcriptomic analysis showed there are five heat shock protein genes changed their expression, and the up-regulated genes are LsHsc70-1 and LsHsc70-2. The deduced amino acid sequences of LsHsc70-1 and LsHsc70-2 include three heat shock protein 70 (HSP70) family signatures, but LsHSC70-1 has the conserved HSP70 carboxyl terminal region of the "EEVD" motif, while LsHSC70-2 has the endoplasmic reticulum (ER) retention signal of the "KDEL" motif. The phylogenetic tree further identified LsHsc70-1 has closer evolutionary distances to cytoplasmic/nuclear HSP70s from human and Drosophila melanogaster, while LsHsc70-2 has closer evolutionary distances to HSP70s localized to ER. After treatment at 30-44°C, the expression of LsHsc70-1 and LsHsc70-2 was slightly increased in YN-CPF. These results suggested that LsHsc70-1 and LsHsc70-2 are members of Hsc70 family, localized to the cytosol/nucleus and ER, respectively. The up-regulated expression of these genes may protect the chlorpyrifos-resistant pest against damage under high temperatures, increasing its relative fitness, but the lower relative fitness of this population under optimal temperature may be the trade-off. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Management of refractory cardiogenic shock.

    Science.gov (United States)

    Reyentovich, Alex; Barghash, Maya H; Hochman, Judith S

    2016-08-01

    Cardiogenic shock is a life-threatening condition that occurs in response to reduced cardiac output in the presence of adequate intravascular volume and results in tissue hypoxia. Cardiogenic shock has several underlying aetiologies, with the most common being acute myocardial infarction (AMI). Refractory cardiogenic shock presents as persistent tissue hypoperfusion despite administration of adequate doses of two vasoactive medications and treatment of the underlying aetiology. Investigators of the SHOCK trial reported a long-term mortality benefit of emergency revascularization for shock complicating AMI. Since the publication of the SHOCK trial and subsequent guideline recommendations, the increase in community-based use of percutaneous coronary intervention for this condition has resulted in a significant decline in mortality. Despite these successes in the past 15 years, mortality still remains exceptionally high, particularly in patients with refractory cardiogenic shock. In this Review, we discuss the aetiology and pathophysiology of cardiogenic shock and summarize the data on the available therapeutics and their limitations. Although new mechanical circulatory support devices have been shown to improve haemodynamic variables in patients with shock complicating AMI, they did not improve clinical outcomes and are associated with high costs and complications.

  6. Investigations of high-frequency induction hardening process for piston rod of shock absorber

    Institute of Scientific and Technical Information of China (English)

    Xianhua Cheng; Qianqian Shangguan

    2005-01-01

    The microhardness of piston rods treated with different induction hardening processes was tested. The experimental results reveal that the depth of the hardened zone is proportional to the ratio of the moving speed of the piston rod to the output power of the induction generator. This result is proved correct through the Finite Element Method (FEM) simulation of the thermal field of induction heating. From tensile and impact tests, an optimized high frequency induction hardening process for piston rods has been obtained, where the output power was 82%×80 kW and the moving speed of workpiece was 5364 mm/min. The piston rods, treated by the optimized high frequency induction hardening process, show the best comprehensive mechanical performance.

  7. High Efficiency Low Cost CO2 Compression Using Supersonic Shock Wave Technology

    Energy Technology Data Exchange (ETDEWEB)

    Williams, J; Aarnio, M; Grosvenor, A; Taylor, D; Bucher, J

    2010-12-31

    Development and testing results from a supersonic compressor are presented. The compressor achieved record pressure ratio for a fully-supersonic stage and successfully demonstrated the technology potential. Several tasks were performed in compliance with the DOE award objectives. A high-pressure ratio compressor was retrofitted to improve rotordynamics behavior and successfully tested. An outside review panel confirmed test results and design approach. A computational fluid dynamics code used to analyze the Ramgen supersonic flowpath was extensively and successfully modified to improve use on high-performance computing platforms. A comprehensive R&D implementation plan was developed and used to lay the groundwork for a future full-scale compressor demonstration. Conceptual design for a CO2 demonstration compressor was developed and reviewed.

  8. Prospects for detection of very high energy emission from GRB in the context of the External Shock model

    CERN Document Server

    Galli, A

    2008-01-01

    The detection of the 100 GeV-TeV emission by a Gamma-Ray Burst (GRB) will provide an unprecedented opportunity to enlighten the nature of the central engine and the interaction between the relativistic flow and the environment of the burst progenitor. In this paper we show that there are exciting prospects of detecting by MAGIC high energy (HE) emission from the burst during the "early" X-ray flaring activity and, later, during the "normal" afterglow phase. We also identify the best observational strategy (trigger conditions and time period of observation). We determine the expected HE emission from the flaring and afterglow phases of GRBs in the context of the External Shock scenario and compare them with the MAGIC threshold. We find that a X-ray flare with the average properties of the class, can be detected in the 100 GeV range by MAGIC provided that z a few cm^{-3}. In this case the MAGIC observation shall extend to about 10-20 ksec. We provide recipes to tailor this prediction to the observational proper...

  9. Combustion of Shock-Dispersed Flake Aluminum - High-Speed Visualization

    Energy Technology Data Exchange (ETDEWEB)

    Neuwald, P; Reichenbach, H; Kuhl, A

    2006-06-19

    Charges of 0.5 g PETN were used to disperse 1 g of flake aluminum in a rectangular test chamber of 4 liter inner volume and inner dimensions of approximately 10 cm x 10 cm x 40 cm. The subsequent combustion of the flake aluminum with the ambient air in the chamber gave rise to a highly luminous flame. The evolution of the luminous region was studied by means of high-speed cinematography. The high-speed camera is responsive to a broad spectral range in the visible and near infra-red. For a number of tests this response range was narrowed down by means of a band-pass filter with a center wavelength of 488 nm and a half-width of 23 nm. The corresponding images were expected to have a stronger temperature dependence than images obtained without the filter, thus providing better capability to highlight hot-spots. Emission in the range of the pass-band of the filter can be due to continuous thermal radiation from hot Al and Al{sub 2}O{sub 3} particles or to molecular band emission from gaseous AlO. A time-resolving spectrometer was improvised to inspect this topic. The results suggest that AlO emission occurs, but that the continuous spectrum is the dominating effect in our experiments.

  10. Free-flight measurement technique in the free-piston high-enthalpy shock tunnel.

    Science.gov (United States)

    Tanno, H; Komuro, T; Sato, K; Fujita, K; Laurence, S J

    2014-04-01

    A novel multi-component force-measurement technique has been developed and implemented at the impulse facility JAXA-HIEST, in which the test model is completely unrestrained during the test and thus experiences free-flight conditions for a period on the order of milliseconds. Advantages over conventional free-flight techniques include the complete absence of aerodynamic interference from a model support system and less variation in model position and attitude during the test itself. A miniature on-board data recorder, which was a key technology for this technique, was also developed in order to acquire and store the measured data. The technique was demonstrated in a HIEST wind-tunnel test campaign in which three-component aerodynamic force measurement was performed on a blunted cone of length 316 mm, total mass 19.75 kg, and moment of inertia 0.152 kgm(2). During the test campaign, axial force, normal forces, and pitching moment coefficients were obtained at angles of attack from 14° to 32° under two conditions: H0 = 4 MJ/kg, P0 = 14 MPa; and H0 = 16 MJ/kg, P0 = 16 MPa. For the first, low-enthalpy condition, the test flow was considered a perfect gas; measurements were thus directly compared with those obtained in a conventional blow-down wind tunnel (JAXA-HWT2) to evaluate the accuracy of the technique. The second test condition was a high-enthalpy condition in which 85% of the oxygen molecules were expected to be dissociated; high-temperature real-gas effects were therefore evaluated by comparison with results obtained in perfect-gas conditions. The precision of the present measurements was evaluated through an uncertainty analysis, which showed the aerodynamic coefficients in the HIEST low enthalpy test agreeing well with those of JAXA-HWT2. The pitching-moment coefficient, however, showed significant differences between low- and high-enthalpy tests. These differences are thought to result from high-temperature real-gas effects.

  11. [Neurogenic shock].

    Science.gov (United States)

    Meister, Rafael; Pasquier, Mathieu; Clerc, David; Carron, Pierre-Nicolas

    2014-08-13

    The neurogenic shock is a common complication of spinal cord injury, especially when localized at the cervical level. Characterized by a vasoplegia (hypotension) and bradycardia, the neurogenic shock is secondary to the damage of the sympathetic nervous system. The clinical presentation often includes tetraplegia, with or without respiratory failure. Early treatment aims to minimize the occurrence of secondary spinal cord lesions resulting from systemic ischemic injuries. Medical management consists in a standardized ABCDE approach, in order to stabilize vital functions and immobilize the spine. The hospital care includes performing imaging, further measures of neuro-resuscitation, and coordinated surgical assessment and treatment of any other injury.

  12. Pressure Hull Analysis under Shock Loading

    Directory of Open Access Journals (Sweden)

    Ya-Jung Lee

    2008-01-01

    Full Text Available The hull of high performance submarines must resist underwater shock loading due to exploding torpedoes or depth bombs. An underwater shock involving an initial shock wave and successive bubble pulsating waves is so complex that a theoretical technique for deriving shock pressure distribution is required for improving simulation efficiency. Complete shock loading is obtained theoretically in this work, and responses of a submarine pressure hull are calculated using ABAQUS USA (Underwater Shock Analysis codes. In the long run, this deflection and stress data will assist in examining the structural arrangement of the submarine pressure hull.

  13. Relativistic Radiation Mediated Shocks

    CERN Document Server

    Budnik, Ran; Sagiv, Amir; Waxman, Eli

    2010-01-01

    The structure of relativistic radiation mediated shocks (RRMS) propagating into a cold electron-proton plasma is calculated and analyzed. A qualitative discussion of the physics of relativistic and non relativistic shocks, including order of magnitude estimates for the relevant temperature and length scales, is presented. Detailed numerical solutions are derived for shock Lorentz factors $\\Gamma_u$ in the range $6\\le\\Gamma_u\\le30$, using a novel iteration technique solving the hydrodynamics and radiation transport equations (the protons, electrons and positrons are argued to be coupled by collective plasma processes and are treated as a fluid). The shock transition (deceleration) region, where the Lorentz factor $ \\Gamma $ drops from $ \\Gamma_u $ to $ \\sim 1 $, is characterized by high plasma temperatures $ T\\sim \\Gamma m_ec^2 $ and highly anisotropic radiation, with characteristic shock-frame energy of upstream and downstream going photons of a few~$\\times\\, m_ec^2$ and $\\sim \\Gamma^2 m_ec^2$, respectively.P...

  14. Radiation damage and thermal shock response of carbon-fiber-reinforced materials to intense high-energy proton beams

    Science.gov (United States)

    Simos, N.; Zhong, Z.; Ghose, S.; Kirk, H. G.; Trung, L.-P.; McDonald, K. T.; Kotsina, Z.; Nocera, P.; Assmann, R.; Redaelli, S.; Bertarelli, A.; Quaranta, E.; Rossi, A.; Zwaska, R.; Ammigan, K.; Hurh, P.; Mokhov, N.

    2016-11-01

    A comprehensive study on the effects of energetic protons on carbon-fiber composites and compounds under consideration for use as low-Z pion production targets in future high-power accelerators and low-impedance collimating elements for intercepting TeV-level protons at the Large Hadron Collider has been undertaken addressing two key areas, namely, thermal shock absorption and resistance to irradiation damage. Carbon-fiber composites of various fiber weaves have been widely used in aerospace industries due to their unique combination of high temperature stability, low density, and high strength. The performance of carbon-carbon composites and compounds under intense proton beams and long-term irradiation have been studied in a series of experiments and compared with the performance of graphite. The 24-GeV proton beam experiments confirmed the inherent ability of a 3D C/C fiber composite to withstand a thermal shock. A series of irradiation damage campaigns explored the response of different C/C structures as a function of the proton fluence and irradiating environment. Radiolytic oxidation resulting from the interaction of oxygen molecules, the result of beam-induced radiolysis encountered during some of the irradiation campaigns, with carbon atoms during irradiation with the presence of a water coolant emerged as a dominant contributor to the observed structural integrity loss at proton fluences ≥5 ×1020 p /cm2 . The carbon-fiber composites were shown to exhibit significant anisotropy in their dimensional stability driven by the fiber weave and the microstructural behavior of the fiber and carbon matrix accompanied by the presence of manufacturing porosity and defects. Carbon-fiber-reinforced molybdenum-graphite compounds (MoGRCF) selected for their impedance properties in the Large Hadron Collider beam collimation exhibited significant decrease in postirradiation load-displacement behavior even after low dose levels (˜5 ×1018 p cm-2 ). In addition, the

  15. Radiation damage and thermal shock response of carbon-fiber-reinforced materials to intense high-energy proton beams

    Directory of Open Access Journals (Sweden)

    N. Simos

    2016-11-01

    Full Text Available A comprehensive study on the effects of energetic protons on carbon-fiber composites and compounds under consideration for use as low-Z pion production targets in future high-power accelerators and low-impedance collimating elements for intercepting TeV-level protons at the Large Hadron Collider has been undertaken addressing two key areas, namely, thermal shock absorption and resistance to irradiation damage. Carbon-fiber composites of various fiber weaves have been widely used in aerospace industries due to their unique combination of high temperature stability, low density, and high strength. The performance of carbon-carbon composites and compounds under intense proton beams and long-term irradiation have been studied in a series of experiments and compared with the performance of graphite. The 24-GeV proton beam experiments confirmed the inherent ability of a 3D C/C fiber composite to withstand a thermal shock. A series of irradiation damage campaigns explored the response of different C/C structures as a function of the proton fluence and irradiating environment. Radiolytic oxidation resulting from the interaction of oxygen molecules, the result of beam-induced radiolysis encountered during some of the irradiation campaigns, with carbon atoms during irradiation with the presence of a water coolant emerged as a dominant contributor to the observed structural integrity loss at proton fluences ≥5×10^{20}  p/cm^{2}. The carbon-fiber composites were shown to exhibit significant anisotropy in their dimensional stability driven by the fiber weave and the microstructural behavior of the fiber and carbon matrix accompanied by the presence of manufacturing porosity and defects. Carbon-fiber-reinforced molybdenum-graphite compounds (MoGRCF selected for their impedance properties in the Large Hadron Collider beam collimation exhibited significant decrease in postirradiation load-displacement behavior even after low dose levels (∼5×10^{18}

  16. Viscosity of aluminum under shock-loading conditions

    Institute of Scientific and Technical Information of China (English)

    Ma Xiao-Juan; Liu Fu-Sheng; Zhang Ming-Jian; Sun Yan-Yun

    2011-01-01

    A reliable data treatment method is critical for viscosity measurements using the disturbance amplitude damping method of shock waves. In this paper the finite difference method is used to obtain the numerical solutions for the disturbance amplitude damping behaviour of the sinusoidal shock front in a flyer-impact experiment. The disturbance amplitude damping curves are used to depict the numerical solutions of viscous flow. By fitting the experimental data to the numerical solutions of different viscosities, we find that the effective shear viscosity coefficients of shocked aluminum at pressures of 42, 78 and 101 GPa are (1500±100) Pa. s, (2800±100) Pa. s and (3500±100) Pa. s respectively. It is clear that the shear viscosity of aluminum increases with an increase in shock pressure, so aluminum does not melt below a shock pressure of 101 GPa. This conclusion is consistent with the sound velocity measurement.

  17. [Anaphylactic shock during the use of high doses of aprotinin in cardiac surgery].

    Science.gov (United States)

    Cottineau, C; Moreau, X; Drouet, M; De Brux, J L; Brenet, O; Delhumeau, A

    1993-01-01

    A 77-year-old man was admitted for mitral valve replacement, 46 days after a failed conservative mitral surgery where he received high-dose aprotinin. Twenty minutes after induction of anaesthesia, 250 UPh E of aprotinin were infused intravenously; before the end of this infusion, bronchospasm, systemic hypotension and generalized rash were noted. Immediate treatment included intravenous adrenaline and methylprednisolone; cardiovascular stability was restored after 10 minutes. Immediate histamine liberation was confirmed by the analysis of the time course of the clinical events, a previous contact and positive skin tests. Aprotinin has the antigenic molecular structure of natural proteins. Since 1987, it is used in cardiac surgery to reduce postoperative blood loss: to prevent serious allergic reactions to aprotinin, it is necessary, in patients known to have had previous aprotinin therapy, to perform skin testing with diluted aprotinin before infusion.

  18. Interpreting Shock Tube Ignition Data

    Science.gov (United States)

    2003-10-01

    times only for high concentrations (of order 1% fuel or greater). The requirements of engine (IC, HCCI , CI and SI) modelers also present a different...Paper 03F-61 Interpreting Shock Tube Ignition Data D. F. Davidson and R. K. Hanson Mechanical Engineering ... Engineering Department Stanford University, Stanford CA 94305 Abstract Chemical kinetic modelers make extensive use of shock tube ignition data

  19. Numerical investigation of Richtmyer-Meshkov instability driven by cylindrical shocks

    Institute of Scientific and Technical Information of China (English)

    Baolin Tian; Dexun FU; Yanwen Ma

    2006-01-01

    In this Paper,a numerical method with high order accuracy and high resolution was developed to simulate the Richtmyer-Meshkov(RM) instability driven by cylindrical shock waves.Compressible Euler equations in cylindrical coordinate were adopted for the cylindrical geometry and a third order accurate group control scheme was adopted to discretize the equations.Moreover,an adaptive grid technique was developed to refine the grid near the moving interface to improve the resolution of numerical solutions.The results of simulation exhibited the evolution process of RM instability,and the effect of Atwood number was studied.The larger the absolute value of Atwood number,the larger the perturbation amplitude.The nonlinear effect manifests more evidently in cylindrical geometry.The shock reflected from the pole center accelerates the interface for the second time,considerably complicating the interface evolution process,and such phenomena of reshock and secondary shock were studied.

  20. CHY formula and MHV amplitudes

    CERN Document Server

    Du, Yi-jian; Wu, Yong-shi

    2016-01-01

    In this paper, we study the relation between the Cachazo-He-Yuan (CHY) formula and the maximal-helicity-violating (MHV) amplitudes of Yang-Mills and gravity in four dimensions. We prove that only one special rational solution of the scattering equations found by Weinzierl support the MHV amplitudes. Namely, localized at this solution, the integrated CHY formula reproduces the Parke-Taylor formula for Yang-Mills amplitudes as well as the Hodges formula for gravitational amplitudes. This is achieved by developing techniques, in a manifestly M\\"obius covariant formalism, to explicitly compute relevant reduced Pfaffians/determinants. We observe and prove two interesting properties (or identities), which facilitate the computations. We also check that all the other $(n-3)!-1$ solutions to the scattering equations do not support the MHV amplitudes, and prove analytically that this is indeed true for the other special rational solution proposed by Weinzierl, that actually supports the anti-MHV amplitudes.

  1. Grassmannian geometry of scattering amplitudes

    CERN Document Server

    Arkani-Hamed, Nima; Cachazo, Freddy; Goncharov, Alexander; Postnikov, Alexander; Trnka, Jaroslav

    2016-01-01

    Outlining a revolutionary reformulation of the foundations of perturbative quantum field theory, this book is a self-contained and authoritative analysis of the application of this new formulation to the case of planar, maximally supersymmetric Yang–Mills theory. The book begins by deriving connections between scattering amplitudes and Grassmannian geometry from first principles before introducing novel physical and mathematical ideas in a systematic manner accessible to both physicists and mathematicians. The principle players in this process are on-shell functions which are closely related to certain sub-strata of Grassmannian manifolds called positroids - in terms of which the classification of on-shell functions and their relations becomes combinatorially manifest. This is an essential introduction to the geometry and combinatorics of the positroid stratification of the Grassmannian and an ideal text for advanced students and researchers working in the areas of field theory, high energy physics, and the...

  2. Shock compression experiments on Lithium Deuteride single crystals.

    Energy Technology Data Exchange (ETDEWEB)

    Knudson, Marcus D.; Desjarlais, Michael Paul; Lemke, Raymond W.

    2014-10-01

    S hock compression exper iments in the few hundred GPa (multi - Mabr) regime were performed on Lithium Deuteride (LiD) single crystals . This study utilized the high velocity flyer plate capability of the Sandia Z Machine to perform impact experiments at flyer plate velocities in the range of 17 - 32 km/s. Measurements included pressure, density, and temperature between %7E200 - 600 GPa along the Principal Hugoniot - the locus of end states achievable through compression by large amplitude shock waves - as well as pressure and density of re - shock states up to %7E900 GPa . The experimental measurements are compared with recent density functional theory calculations as well as a new tabular equation of state developed at Los Alamos National Labs.

  3. Boundary Layer Transition and Trip Effectiveness on an Apollo Capsule in the JAXA High Enthalpy Shock Tunnel (HIEST) Facility

    Science.gov (United States)

    Kirk, Lindsay C.; Lillard, Randolph P.; Olejniczak, Joseph; Tanno, Hideyuki

    2015-01-01

    Computational assessments were performed to size boundary layer trips for a scaled Apollo capsule model in the High Enthalpy Shock Tunnel (HIEST) facility at the JAXA Kakuda Space Center in Japan. For stagnation conditions between 2 MJ/kg and 20 MJ/kg and between 10 MPa and 60 MPa, the appropriate trips were determined to be between 0.2 mm and 1.3 mm high, which provided kappa/delta values on the heatshield from 0.15 to 2.25. The tripped configuration consisted of an insert with a series of diamond shaped trips along the heatshield downstream of the stagnation point. Surface heat flux measurements were obtained on a capsule with a 250 mm diameter, 6.4% scale model, and pressure measurements were taken at axial stations along the nozzle walls. At low enthalpy conditions, the computational predictions agree favorably to the test data along the heatshield centerline. However, agreement becomes less favorable as the enthalpy increases conditions. The measured surface heat flux on the heatshield from the HIEST facility was under-predicted by the computations in these cases. Both smooth and tripped configurations were tested for comparison, and a post-test computational analysis showed that kappa/delta values based on the as-measured stagnation conditions ranged between 0.5 and 1.2. Tripped configurations for both 0.6 mm and 0.8 mm trip heights were able to effectively trip the flow to fully turbulent for a range of freestream conditions.

  4. Imaging the high-frequency energy radiation process of a main shock and its early aftershock sequence: The case of the 2008 Iwate-Miyagi Nairiku earthquake, Japan

    Science.gov (United States)

    Sawazaki, Kaoru; Enescu, Bogdan

    2014-06-01

    To understand the energy release process that operates at the end of the main shock rupture and start of the aftershock activity, we propose an inversion method that uses continuous high-frequency seismogram envelopes of the main shock and early aftershocks (i.e., events that occur at short times after the main shock). In our approach, the aftershock sequence is regarded as a continuous energy release process, rather than a discrete time series of events. To correct for the contribution of coda wave energy excited by multiple scattering, we use the theoretical envelope synthesized on the basis of the radiative transfer theory as a Green's function. The site amplification factors are corrected considering the conservation of energy flux and using the coda normalization method. The inverted temporal energy release rate for the 2008 MW 6.9 Iwate-Miyagi Nairiku earthquake, Japan, decays following t-1.1, at the lapse time t of 40-900 s after the main shock origin time. This exponent of the decay rate is similar to the p value of the modified Omori law. The amount of estimated energy release is consistent with that calculated from the magnitude listed in the aftershock catalog. Although the uncertainty is large, the location of large energy release at the lapse times of 40-900 s approximately overlaps to that of the aftershocks, which surrounds the large energy release area during the main shock faulting. The maxima of the energy release rate normalized by the average decay rate distributes following a power law, similar to the Gutenberg-Richter law.

  5. Graviton amplitudes from collinear limits of gauge amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Stieberger, Stephan, E-mail: stephan.stieberger@mpp.mpg.de [Max-Planck-Institut für Physik, Werner-Heisenberg-Institut, 80805 München (Germany); Taylor, Tomasz R. [Department of Physics, Northeastern University, Boston, MA 02115 (United States)

    2015-05-11

    We express all tree-level graviton amplitudes in Einstein's gravity as the collinear limits of a linear combination of pure Yang–Mills amplitudes in which each graviton is represented by two gauge bosons, each of them carrying exactly one half of graviton's momentum and helicity.

  6. On the Period-Amplitude and Amplitude-Period Relationships

    Science.gov (United States)

    Wilson, Robert M.; Hathaway, David H.

    2008-01-01

    Examined are Period-Amplitude and Amplitude-Period relationships based on the cyclic behavior of the 12-month moving averages of monthly mean sunspot numbers for cycles 0.23, both in terms of Fisher's exact tests for 2x2 contingency tables and linear regression analyses. Concerning the Period-Amplitude relationship (same cycle), because cycle 23's maximum amplitude is known to be 120.8, the inferred regressions (90-percent prediction intervals) suggest that its period will be 131 +/- 24 months (using all cycles) or 131 +/- 18 months (ignoring cycles 2 and 4, which have the extremes of period, 108 and 164 months, respectively). Because cycle 23 has already persisted for 142 months (May 1996 through February 2008), based on the latter prediction, it should end before September 2008. Concerning the Amplitude-Period relationship (following cycle maximum amplitude versus preceding cycle period), because cycle 23's period is known to be at least 142 months, the inferred regressions (90-percent prediction intervals) suggest that cycle 24's maximum amplitude will be about less than or equal to 96.1 +/- 55.0 (using all cycle pairs) or less than or equal to 91.0 +/- 36.7 (ignoring statistical outlier cycle pairs). Hence, cycle 24's maximum amplitude is expected to be less than 151, perhaps even less than 128, unless cycle pair 23/24 proves to be a statistical outlier.

  7. Shock waves in fluid-filled distensible tubes.

    Science.gov (United States)

    Rudinger, G

    1980-02-01

    Flow of a liquid through distensible tubes is of interest primarily in biological systems, and some properties of shock waves in such tubes are discussed. In shock-fixed coordinates, these flows are steady, and the shock is associated with an increase of pressure and cross-sectional area. Shock transition is analyzed for two flow models, namely, immediate flow separation, when the flow enters the shock zone, and no separation. Shock properties are expressed in terms of the speed index (ratio of the velocity of the shock to that of a small-amplitude wave) and dissipation (loss of total pressure). Examples are worked out for the thoracic aorta of an anesthetized dog, a perfectly elastic tube, and a partially collapsed tube. Appreciable differences in shock velocity and dissipation result if either flow separation or no separation is assumed.

  8. Ion Acceleration at the Quasi-Parallel Shock: Injection Unveiled

    CERN Document Server

    Sundberg, Torbjörn; Burgess, David; Mazelle, Christian X

    2015-01-01

    Collisionless shocks are efficient particle accelerators. At Earth, ions with energies exceeding 100 keV are seen upstream of the bow shock when the magnetic geometry is quasi-parallel, and large-scale supernova remnant shocks can accelerate ions into cosmic rays energies. This energization is attributed to diffusive shock acceleration, however, for this process to become active the ions must first be sufficiently energized. How and where this initial acceleration takes place has been one of the key unresolved issues in shock acceleration theory. Using Cluster spacecraft observations, we study the signatures of ion reflection events in the turbulent transition layer upstream of the shock, and with the support of a hybrid simulation of the shock, we show that these reflection signatures are characteristic of the first step in the ion injection process. These reflection events develop in particular in the region where the trailing edge of large-amplitude upstream waves intercept the local shock ramp and the ups...

  9. Interaction between a normal shock wave and a turbulent boundary layer at high transonic speeds. II - Wall shear stress

    Science.gov (United States)

    Liou, M. S.; Adamson, T. C., Jr.

    1980-01-01

    Asymptotic methods are used to calculate the shear stress at the wall for the interaction between a normal shock wave and a turbulent boundary layer on a flat plate. A mixing length model is used for the eddy viscosity. The shock wave is taken to be strong enough that the sonic line is deep in the boundary layer and the upstream influence is thus very small. It is shown that unlike the result found for laminar flow an asymptotic criterion for separation is not found; however, conditions for incipient separation are computed numerically using the derived solution for the shear stress at the wall. Results are compared with available experimental measurements.

  10. Coping with shocks in rural Ethiopia

    NARCIS (Netherlands)

    Z.Y. Debebe (Zelalem); A.D. Mebratie (Anagaw); R.A. Sparrow (Robert); D. Abebaw Ejigie (Degnet); M. Dekker (Marleen); G. Alemu (Getnet ); A.S. Bedi (Arjun Singh)

    2013-01-01

    textabstractBased on household survey data and event history interviews undertaken in a highly shock prone country, this paper investigates which shocks trigger which coping responses and why? We find clear differences in terms of coping strategies across shock types. The two relatively covariate

  11. Comparison of High-Temperature Properties and Thermal Shock Resistance of Austempered Ductile Irons (ADI) with Those of Pearlitic Ductile Cast Irons

    Science.gov (United States)

    Ajabshiri, Mehrdad; Sharafi, Shahriar; Moeini, Alireza

    2012-01-01

    High-temperature strength and thermal shock resistance of austempered ductile iron (ADI) in high temperatures because of instability of ausferrite phase has been less interest. The aim of this study is to investigate the tensile properties of ADI and pearlitic ductile cast iron by using the short-time tensile test in high temperatures. Tensile test was conducted in temperatures of 298 K, 673 K, 873 K, and 1073 K (25 °C, 400 °C, 600 °C, and 800 °C). Thermal shock test also was conducted by using the molten lead bath at 1273 K (1000 °C). In this experiment, samples of pearlitic ductile cast iron and ADI were divided in two groups; that after immersing in the molten lead bath for 25 seconds, one group was cooled in the air and other one was quenched in the water. Results showed that strength and thermal shock resistance of ADI samples are higher than those of the pearlitic ductile cast iron.

  12. Altered Expression of High Molecular Weight Heat Shock Proteins after OCT4B1 Suppression in Human Tumor Cell Lines

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Mirzaei

    2016-02-01

    Full Text Available Objective: OCT4B1, a novel variant of OCT4, is expressed in cancer cell lines and tissues. Based on our previous reports, OCT4B1 appears to have a crucial role in regulating apoptosis as well as stress response [heat shock proteins (HSPs] pathways. The aim of the present study was to determine the effects of OCT4B1 silencing on the expression of high molecular weight HSPs in three different human tumor cell lines. Materials and Methods: In this experimental study, OCT4B1 expression was suppressed in AGS (gastric adenocarcinoma, 5637 (bladder tumor and U-87MG (brain tumor cell lines using RNAi strategy. Real-time polymerase chain reaction (PCR array was employed for expression level analysis and the fold changes were calculated using RT2 Profiler PCR array data analysis software version 3.5. Results: Our data revealed up-regulation of HSPD1 (from HSP60 family as well as HSPA14, HSPA1L, HSPA4, HSPA5 and HSPA8 (from HSP70 family following OCT4B1 knock-down in all three cell lines. In contrast, the expression of HSP90AA1 and HSP- 90AB1 (from HSP90 family as well as HSPA1B and HSPA6 (from HSP70 family was down-regulated under similar conditions. Other stress-related genes showed varying expression pattern in the examined tumor cell lines. Conclusion: Our data suggest a direct or indirect correlation between the expression of OCT4B1 and HSP90 gene family. However, OCT4B1 expression was not strongly correlated with the expression of HSP70 and HSP60 gene families.

  13. Large amplitude oscillatory elongation flow

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.; Laillé, Philippe; Yu, Kaijia

    2008-01-01

    A filament stretching rheometer (FSR) was used for measuring the elongation flow with a large amplitude oscillative elongation imposed upon the flow. The large amplitude oscillation imposed upon the elongational flow as a function of the time t was defined as epsilon(t) =(epsilon) over dot(0)t + ...

  14. Closed string amplitudes as single-valued open string amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Stieberger, Stephan, E-mail: stephan.stieberger@mpp.mpg.de [Max-Planck-Institut für Physik, Werner-Heisenberg-Institut, 80805 München (Germany); Taylor, Tomasz R. [Department of Physics, Northeastern University, Boston, MA 02115 (United States)

    2014-04-15

    We show that the single trace heterotic N-point tree-level gauge amplitude A{sub N}{sup HET} can be obtained from the corresponding type I amplitude A{sub N}{sup I} by the single-valued (sv) projection: A{sub N}{sup HET}=sv(A{sub N}{sup I}). This projection maps multiple zeta values to single-valued multiple zeta values. The latter represent a subclass of multiple zeta values originating from single-valued multiple polylogarithms at unity. Similar relations between open and closed string amplitudes or amplitudes of different string vacua can be established. As a consequence the α{sup ′}-expansion of a closed string amplitude is dictated by that of the corresponding open string amplitude. The combination of single-valued projections, Kawai–Lewellen–Tye relations and Mellin correspondence reveal a unity of all tree-level open and closed superstring amplitudes together with the maximally supersymmetric Yang–Mills and supergravity theories.

  15. TOFPET2: a high-performance ASIC for time and amplitude measurements of SiPM signals in time-of-flight applications

    Science.gov (United States)

    Di Francesco, A.; Bugalho, R.; Oliveira, L.; Pacher, L.; Rivetti, A.; Rolo, M.; Silva, J. C.; Silva, R.; Varela, J.

    2016-03-01

    We present a readout and digitization ASIC featuring low-noise and low-power for time-of flight (TOF) applications using SiPMs. The circuit is designed in standard CMOS 110 nm technology, has 64 independent channels and is optimized for time-of-flight measurement in Positron Emission Tomography (TOF-PET). The input amplifier is a low impedance current conveyor based on a regulated common-gate topology. Each channel has quad-buffered analogue interpolation TDCs (time binning 20 ps) and charge integration ADCs with linear response at full scale (1500 pC). The signal amplitude can also be derived from the measurement of time-over-threshold (ToT). Simulation results show that for a single photo-electron signal with charge 200 (550) fC generated by a SiPM with 320 pF capacitance the circuit has 24 (30) dB SNR, 75(39) ps r.m.s. resolution, and 4(8) mW power consumption. The event rate is 600 kHz per channel, with up to 2 MHz dark counts rejection.

  16. Particle Acceleration at Shocks: Insights from Supernova Remnant Shocks

    Indian Academy of Sciences (India)

    T. W. Jones

    2011-12-01

    I review some basic properties of diffusive shock acceleration (DSA) in the context of young supernova remnants (SNRs). I also point out some key differences with cosmological, cluster-related shocks. DSA seems to be very efficient in strong, young SNR shocks. Provided the magnetic fields exceed some hundreds of Gauss (possibly amplified by CR related dynamics), these shocks can accelerate cosmic ray hadrons to PeV energies in the time available to them. Electron energies, limited by radiative losses, are likely limited to the TeV range. Injection of fresh particles at these shocks is poorly understood, but hadrons are much more easily injected than the more highly magnetized electrons. That seems supported by observational data, as well. So, while CR protons in young SNRs may play very major roles in the SNR evolution, the CR electron populations have minimal such impact, despite their observational importance.

  17. Particle-in-cell simulation study of a lower-hybrid shock

    CERN Document Server

    Dieckmann, Mark Eric; Doria, Domenico; Ynnerman, Anders; Borghesi, Marco

    2016-01-01

    The expansion of a magnetized high-pressure plasma into a low-pressure ambient medium is examined with particle-in-cell (PIC) simulations. The magnetic field points perpendicularly to the plasma's expansion direction and binary collisions between particles are absent. The expanding plasma steepens into a quasi-electrostatic shock that is sustained by the lower-hybrid (LH) wave. The ambipolar electric field points in the expansion direction and it induces together with the background magnetic field a fast E cross B drift of electrons. The drifting electrons modify the background magnetic field, resulting in its pile-up by the LH shock. The magnetic pressure gradient force accelerates the ambient ions ahead of the LH shock, reducing the relative velocity between the ambient plasma and the LH shock to about the phase speed of the shocked LH wave, transforming the LH shock into a nonlinear LH wave. The oscillations of the electrostatic potential have a larger amplitude and wavelength in the magnetized plasma than...

  18. Amplitude Modulations of Acoustic Communication Signals

    Science.gov (United States)

    Turesson, Hjalmar K.

    2011-12-01

    In human speech, amplitude modulations at 3 -- 8 Hz are important for discrimination and detection. Two different neurophysiological theories have been proposed to explain this effect. The first theory proposes that, as a consequence of neocortical synaptic dynamics, signals that are amplitude modulated at 3 -- 8 Hz are propagated better than un-modulated signals, or signals modulated above 8 Hz. This suggests that neural activity elicited by vocalizations modulated at 3 -- 8 Hz is optimally transmitted, and the vocalizations better discriminated and detected. The second theory proposes that 3 -- 8 Hz amplitude modulations interact with spontaneous neocortical oscillations. Specifically, vocalizations modulated at 3 -- 8 Hz entrain local populations of neurons, which in turn, modulate the amplitude of high frequency gamma oscillations. This suggests that vocalizations modulated at 3 -- 8 Hz should induce stronger cross-frequency coupling. Similar to human speech, we found that macaque monkey vocalizations also are amplitude modulated between 3 and 8 Hz. Humans and macaque monkeys share similarities in vocal production, implying that the auditory systems subserving perception of acoustic communication signals also share similarities. Based on the similarities between human speech and macaque monkey vocalizations, we addressed how amplitude modulated vocalizations are processed in the auditory cortex of macaque monkeys, and what behavioral relevance modulations may have. Recording single neuron activity, as well as, the activity of local populations of neurons allowed us to test both of the neurophysiological theories presented above. We found that single neuron responses to vocalizations amplitude modulated at 3 -- 8 Hz resulted in better stimulus discrimination than vocalizations lacking 3 -- 8 Hz modulations, and that the effect most likely was mediated by synaptic dynamics. In contrast, we failed to find support for the oscillation-based model proposing a

  19. New investigations on shock-wave synthesized high-pressure phases in the system Si-Al-O-N

    Science.gov (United States)

    Schlothauer, T.; Greif, A.; Keller, K.; Schwarz, M. R.; Kroke, E.; Heide, G.

    2012-12-01

    The shock-wave synthesis of nanostructured high-pressure phases at a gram-scale permits the analysis of spinel type nitrides with different chemical composition using methods not suitable for microgram amounts of material. Methods with a significant mass loss through the analytical process like TG-MS or FT-IR or bulk methods at the g-scale like 29Si-MAS-NMR or neutron diffraction were used. The synthesis of pure high-pressure modifications (gamma-phases) of different SiAlON-compounds using amorphous H-bearing precursors at pressures of 30-40 GPa is a necessary prerequisite for precise determinations of crystal chemical features. Etching with HF is a well-known method to purify the high-pressure nitrides (Sekine 2002). The etched parts were analyzed by neutron diffraction, TG-MS, and carrier gas hot extraction (CGHE). Volatile elements like H2 and Cl2, as well as non-stoichiometric oxygen and nitrogen, and NOx, H2O are enriched in the disordered rims. This degassing process ends at temperatures of approximately 600°C, while the spinel structure remains well preserved up to 1300°C. Under these conditions the gamma-phases stay unchanged under air, argon and vacuum. Furthermore chlorine, an important impurity of the H-bearing precursors neither influences the synthesized products nor the synthesis process itself. IR-spectroscopy of gamma-Si3(O,N)4 shows that peak shifts of octahedral lattice vibrations (≈ 680 cm-1) and both tetrahedral vibrations (ny3 and ny4) (Jeanloz 1980, Preudhomme & Tarte 1971) to higher frequencies with decreasing oxygen content occur. This effect is also visible in samples contaminated with impurities of low pressure modifications. The more complex structure of gamma-SiAlON and the simultaneously exchange of the cation- and the anion-positions prevents the appearance of this important feature. Yet to be synthesized pure gamma-SiAlON using similar H-bearing precursors is necessary to resolve its structure. Sekine, T., H. He, T. Kobayashi, K

  20. Classification of high-risk with cardiac troponin and shock index in normotensive patients with pulmonary embolism.

    Science.gov (United States)

    Ozsu, Savas; Erbay, Muge; Durmuş, Zerrin Gürel; Ozlu, Tevfik

    2017-02-01

    Accurate risk stratification of normotensive patients with acute pulmonary embolism (PE) require further investigation. We aimed to develop a simple model using clinical (shock index) and laboratory findings (cardiac Troponin, echocardiography) to assess the risk of 30-day mortality in normotensive patients with acute PE. In this retrospective study, 489 normotensive patients with acute PE diagnosed objectively. The primary end-point was defined as a all cause 30-day mortality. Shock index was calculated on admission. The primary end-point occurred in 67 (13.7%, 95% CI 10.7-16.8) patients with acute PE. Predictors of complications included elevated cardiac troponin (OR 1.7, 95% CI 1.3-2.2) and shock index (OR 1.3, 95% CI 1.1-1.5) by multivariable analysis. Risk index point was created based on OR. The model identified stages (stage I: 0-1 point, stage II: 2 points and stage III: 3 point) with 30-day mortality rates of 4.3, 19 and 38.6 %, respectively. The shock index and cardiac troponin can be safely used in combination to determine intermediate risk in patients with PE in emergency departmant. The study provided observations that will require prospective validation before the proposed risk score is adopted in clinical practice.