WorldWideScience

Sample records for beat wave accelerators

  1. Plasma Beat-Wave Acceleration

    Science.gov (United States)

    Clayton, Christopher E.

    2002-04-01

    Among all the advanced accelerator concepts that use lasers as the power source, most of the effort to date has been with the idea of using a laser pulse to excite a accelerating mode in a plasma. Within this area, there are a variety of approaches for creating the accelerating mode, as indicated by the other talks in this session. What is common to these approaches is the physics of how a laser pulse pushes on plasma electrons to organize electron-density perturbations, the sources of the ultra-high (> GeV/M) accelerating gradients. It is the "ponderomotive force", proportional to the local gradient of the of the laser intensity, that pushes plasma electrons forward (on the leading edge of the pulse) and backwards (on the trailing edge) which leads to harmonic motion of the electrons. As the laser pulse moves through the plasma at group velocity Vg c, the oscillating electrons show up macroscopically as a plasma mode or wave with frequency w equal to the plasma frequency and k = w/Vg. For short laser pulses, this is the Laser Wakefield Accelerator (LWFA) concept. Closely related is the Plasma Beat-Wave Acceleration (PBWA) concept. Here, the laser pulse that perturbs the plasma is composed of two closely-spaced frequencies that "beat", i.e., periodically constructively and destructively interfere, forming an electromagnetic beat wave. One can visualize this as a train of short pulses. If this beating frequency is set to the plasma frequency, then each pulse in the train will reinforce the density perturbation caused by the previous pulse. The principal advantage of multiple pulses driving up the plasma wave as opposed to a single pulse is in efficiency, allowing for the production of relatively large diameter (more 1-D like) accelerating modes. In this talk I will discuss past, current and planned PBWA experiments which are taking place at UCLA, RAL in England, and LULI in France.

  2. Possible instabilities in the beat wave accelerator

    International Nuclear Information System (INIS)

    In this article the concept of the beat wave accelerator is studied with emphasis put on the plasma physics. An important effect is the relativistic nature of the electrons oscillating in the electric field of the beat wave. Various instabilities are presented which could limit the overall efficiency of the accelerating process. (author)

  3. Investigation on laser accelerators. Plasma beat wave accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Miura, Akihiko; Miyamoto, Yasuaki; Hagiwara, Masayoshi; Suzuki, Mitsutoshi; Sudo, Osamu [Power Reactor and Nuclear Fuel Development Corp., Tokai, Ibaraki (Japan). Tokai Works

    1998-04-01

    Laser accelerator technology has characteristics of high energy, compact, short pulse and high luminescence{center_dot}low emittance. This means potential many applications in wide ranges of fields as well as high energy and nuclear physics. High power short laser pulses are injected to a plasma in the typical example of laser accelerators. Large electric fields are induced in the plasma. Electrons in the plasma are accelerated with the ponderomotive force of the electric field. The principles of interaction on beat wave, wakefield accelerators, inverse free electron laser and inverse Cherenkov radiation are briefly introduced. The overview of plasma beat wave accelerator study is briefly described on the programs at Chalk River Laboratories(Canada), UCLA(USA), Osaka Univ. (Japan) and Ecole Polytechnique (France). Issues of the plasma beat wave accelerator are discussed from the viewpoint of application. Existing laser technologies of CO{sub 2}, YAG and YFL are available for the present day accelerator technology. An acceleration length of beat wave interaction is limited due to its phase condition. Ideas on multi-staged acceleration using the phasing plasma fiber are introduced. (Y. Tanaka)

  4. Continuing studies of the plasma beat wave accelerator

    International Nuclear Information System (INIS)

    This is a proposal for the release of third year funds for the ''Plasma Beat Wave Accelerator'' program (PBWA) at UCLA under the direction of Professor C. Joshi. This report is also a summary of progress on this project since March 1990; i.e., the date of the last report to the DOE. Once again we note that although the program is for historical reasons called the Plasma Beat Wave Accelerator Program, our group is active in all areas of applications of lasers and plasmas in future high energy accelerators. These are as follows: heat gradient plasma structures; excited by plasma beat wave technique; laser wake field technique; and plasma wake field technique. Development of a photoinjector-driven, 20 MeV linac; and theoretical studies of the plasma lens and use of plasmas at the final focus

  5. Beat-wave accelerator studies at the Rutherford Appleton Laboratory

    International Nuclear Information System (INIS)

    The study carried out in 1982-83 at the Rutherford Appleton Laboratory to examine how one might use the beat-wave principle to construct a useful high energy accelerator is reviewed, and comments are made on later developments. A number of problems are evident to which solutions cannot at present be foreseen. (author)

  6. Ion Acceleration by Beating Electrostatic Waves: Theory, Experiments and Relevance to Spacecraft Propulsion

    Science.gov (United States)

    Choueiri, Edgar

    2007-10-01

    After a brief overview of electrodeless plasma propulsion concepts, we will focus on a recently discovered ion acceleration mechanism, which appears to occur naturally in Earth's ionosphere, holds promise as an effective means to energize ions for applications in thermonuclear fusion and electrodeless space plasma propulsion. Unlike previously known mechanisms for energizing plasmas with electrostatic (ES) waves, and which accelerate only ions whose initial velocities are above a certain threshold (close to the wave's phase velocity), the new acceleration mechanism, involving pairs of beating ES waves, is non-resonant and can accelerate ions with arbitrarily small initial velocities, thus offering a more effective way to couple energy to plasmas. We will discuss the fundamentals of the nonlinear dynamics of a single magnetized ion interacting with a pair of beating ES waves and show that there exist necessary and sufficient conditions for the phenomenon to occur. We will see how these fundamental conditions are derived by analyzing the motion's Hamiltonian using a second-order perturbation technique in conjunction with Lie transformations. The analysis shows that when the Hamiltonian lies outside the energy barrier defined by the location of the elliptic and hyperbolic critical points of the motion, the electric field of the beating waves can accelerate ions regularly from low initial velocities, then stochastically, to high energies. We will then illustrate real plasma effects using Monte Carlo numerical simulation and discuss the recent results from a dedicated experiment in my lab in which laser-induced fluorescence (LIF) measurements of ion energies have provided the first laboratory observation of this acceleration mechanism. The talk will conclude with a few ideas on how the fundamental insight can be applied to develop novel plasma propulsion concepts.

  7. Beat wave development work

    International Nuclear Information System (INIS)

    The first phase of experiments on beat wave acceleration have been completed at UCLA. Here we examined the suitability of a theta pinch as a plasma source. The beatwave was excited to amplitudes providing GeV/m-scale accelerating fields. However, trapped magnetic fields within the theta-pinch plasma hindered the injection of test particles. Optical diagnostics were developed to measure the accelerating gradient-length product which was found to be around 3 MeV. Future plans are also discussed. copyright 1989 American Institute of Physics

  8. Resonant Bloch-wave beatings.

    Science.gov (United States)

    Kartashov, Yaroslav V; Vysloukh, Victor A; Torner, Lluis

    2014-07-01

    We introduce Bloch-wave beatings in arrays of multimode periodically bent waveguides with a transverse refractive index gradient. The new phenomenon manifests itself in the periodic drastic increase of the amplitude of the Bloch oscillations that accompanies resonant conversion of modes guided by the individual waveguides. The Bloch-wave beatings are found to be most pronounced when the length of the resonant mode conversion substantially exceeds the longitudinal period of the Bloch oscillations. The beating frequency decreases when the amplitude of waveguide bending decreases, while the beating amplitude is restricted by the amplitude of the Bloch oscillations that emerge from the second allowed band of the Floquet-Bloch lattice spectrum.

  9. Resonant Bloch-wave beatings

    CERN Document Server

    Kartashov, Yaroslav V; Torner, Lluis

    2014-01-01

    We introduce Bloch-wave beatings in arrays of multimode periodically bent waveguides with a transverse refractive index gradient. The new phenomenon manifests itself in the periodic drastic increase of the amplitude of the Bloch oscillations that accompanies resonant conversion of modes guided by the individual waveguides. The Bloch-wave beatings are found to be most pronounced when the length of the resonant mode conversion substantially exceeds the longitudinal period of the Bloch oscillations. The beating frequency decreases when the amplitude of waveguide bending decreases, while the beating amplitude is restricted by the amplitude of the Bloch oscillations that emerge from the second allowed band of the Floquet-Bloch lattice spectrum.

  10. Optical Beat-Wave Experiment on CTIX

    Science.gov (United States)

    Horton, Robert; Hwang, David; Liu, Fei; Zhu, Ben; Evans, Russell

    2009-11-01

    By launching intense electromagnetic waves at differing frequencies, a wave at the beat (difference) frequency can be created within a region of plasma. The beat wave is efficiently damped, and electron current generated, if the beat frequency is close to local plasma frequency, and if phase velocity is close to electron thermal velocity. Beat-wave acceleration of plasma electrons was previously demonstrated at low plasma density [1]. At the higher densities of the CTIX compact-toroid accelerator, plasma frequencies are such that CO2 lasers (f 30 THz) are a cost-effective driver. An experiment is being prepared to test beat-wave current drive using two TEA CO2 lasers on CTIX. The experiment will test models of wave mixing, quasilinear modification of the velocity distribution, and amplification of seed current by plasma kinetic effects. An application of the methods developed may be standoff current generation in a target plasma. Experimental issues to be addressed include: precisely-timed production of the compressed, target plasma; grating tuning of the CO2 lasers for frequency selection; high-peak-power, simultaneous operation of TEA lasers, design of optics; optical and plasma diagnostics. Initial results will be presented.[4pt] [1] Rogers, J. H. and Hwang, D. Q., Phys. Rev. Lett. v68 p3877 (1992).

  11. Electron acceleration by electron plasma wave excited by beating two cross-focused Cosh-Gaussian laser beams in collisionless plasma

    International Nuclear Information System (INIS)

    This paper presents a scheme for electron acceleration by excitation of an electron plasma wave (EPW) by beating two cross focused Cosh-Gaussian (ChG) laser beams in an underdense plasma where ponderomotive nonlinearity is operative. The ponderomotive nonlinearity depends not only on the intensity of first laser beam but also on that of second laser beam. Therefore, the propagation dynamics of one laser beam affects that of other and hence, cross-focusing of the two laser beams takes place. Virial theorem technique has been invoked to study the propagation dynamics of the laser beams. Due to nonuniform intensity distribution along the wavefronts of the laser beams, the background electron concentration gets modified. The amplitude of EPW, which depends on the background electron concentration, is thus nonlinearly coupled with the laser beams. The effects of ponderomotive nonlinearity and cross-focusing of the laser beams on excitation of EPW have been incorporated. The generated plasma wave produces regions of positive and negative charges and thus establishes an electric field that travels along with the plasma wave. If a charged particle is injected into the plasma at approximately the same velocity as plasma wave, it will stay in phase with the field, absorb energy from the field and accelerate steadily. It has been found that by changing the decentered parameter the peak intensity of ChG laser beam can be shifted in the transverse direction and hence, optimum acceleration of the electrons can be obtained. The plasma based electron accelerators can adieu to the era of gargantuan mega-accelerators. (author)

  12. Investigation of beat-waves generation with high efficiency

    International Nuclear Information System (INIS)

    A method for generating high power beating radio-frequency wave with high conversion efficiency is proposed. Based on Cherenkov radiation, two longitudinal resonant modes are excited simultaneously and interacted with intense electron beam synchronously. An experiment was carried out and beat-waves with an average power of about 2.3 GW, frequencies of 9.29 GHz and 10.31 GHz, and efficiency of about 40% were obtained. Through controlling the electron energy, the amplitude proportions of the two resonant modes are altered, and different beat-wave patterns are formed

  13. Investigation of beat-waves generation with high efficiency

    Science.gov (United States)

    Song, W.; Shi, Y. C.; Deng, Y. Q.; Zhu, X. X.; Zhang, Z. Q.; Hu, X. G.

    2013-10-01

    A method for generating high power beating radio-frequency wave with high conversion efficiency is proposed. Based on Cherenkov radiation, two longitudinal resonant modes are excited simultaneously and interacted with intense electron beam synchronously. An experiment was carried out and beat-waves with an average power of about 2.3 GW, frequencies of 9.29 GHz and 10.31 GHz, and efficiency of about 40% were obtained. Through controlling the electron energy, the amplitude proportions of the two resonant modes are altered, and different beat-wave patterns are formed.

  14. Investigation of beat-waves generation with high efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Song, W.; Shi, Y. C.; Deng, Y. Q.; Zhu, X. X.; Zhang, Z. Q.; Hu, X. G. [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi' an, Shanxi 710024 (China)

    2013-10-21

    A method for generating high power beating radio-frequency wave with high conversion efficiency is proposed. Based on Cherenkov radiation, two longitudinal resonant modes are excited simultaneously and interacted with intense electron beam synchronously. An experiment was carried out and beat-waves with an average power of about 2.3 GW, frequencies of 9.29 GHz and 10.31 GHz, and efficiency of about 40% were obtained. Through controlling the electron energy, the amplitude proportions of the two resonant modes are altered, and different beat-wave patterns are formed.

  15. Cardiac beat-to-beat alternations driven by unusual spiral waves

    OpenAIRE

    Kim, Tae Yun; Woo, Sung-Jae; Hwang, Seong-min; Hong, Jin Hee; Lee, Kyoung J.

    2007-01-01

    Alternans, a beat-to-beat temporal alternation in the sequence of heartbeats, is a known precursor of the development of cardiac fibrillation, leading to sudden cardiac death. The equally important precursor of cardiac arrhythmias is the rotating spiral wave of electro-mechanical activity, or reentry, on the heart tissue. Here, we show that these two seemingly different phenomena can have a remarkable relationship. In well controlled in vitro tissue cultures, isotropic populations of rat vent...

  16. Standing wave linear accelerator

    International Nuclear Information System (INIS)

    Consideration is being given to standing wave linear accelerator containing generator, phase shifter, two accelerating resonator sections, charged particle injector and waveguide bridge. Its first arm is oined up with generator via the phase shifter, the second and the third ones-with accelerating sections and the fourth one - with HF-power absorber. HF-power absorber represents a section of circular diaphragmatic wavequide with transformer with input wave and intrawaveguide output load located between injector and the first accelerating section. The section possesses holes in side walls lying on accelerator axis. The distances between centers of the last cell of the fast accelerating section and the first cell of the second accelerating sectiOn equal (2n+3)lambda/4, where n=1, 2, 3..., lambda - wave length of generator. The suggested system enables to improve by one order spectral characteristics of accelerators as compared to the prototype in which magnetrons are used as generator

  17. Theory of beat wave excitation in an inhomogeneous plasma

    International Nuclear Information System (INIS)

    The theory of beat wave excitation in a slightly inhomogeneous plasma is presented. While the theory is general it applies directly to the experiments performed in Alaska by the ionospheric heating facilities HIPAS [High Power Auroral Simulation, Radio Sci. 25, 1269 (1990)] and HAARP [High Frequency Active Auroral Research Project, Geophys. Res. Lett. 25, 257 (1998)]. A ray tracing (WKB) formalism appropriate for computations is developed. The computational implementation of this formalism and extensive results will be presented in a follow up to this paper. Also the beat wave excitation of upper-hybrid waves is investigated analytically. The complicated trajectories of these waves in the plasma are described. When this beat wave reaches the plasma wave resonance it can, in the HIPAS-HAARP experiments, attain nonlinear amplitude. The electrostatic upper-hybrid waves are trapped around the density maximum of the ionosphere. This trapping is investigated in detail. Beat wave pumping of the trapped modes is possible using HAARP and HIPAS or with split beams from HAARP

  18. Laser-driven Beat-Wave Current Drive in Dense Plasmas with Demo on CTIX

    Science.gov (United States)

    Liu, Fei; Horton, Robert; Hwang, David; Zhu, Ben; Evans, Russell; Hong, Sean; Hsu, Scott

    2010-11-01

    The ability to remotely generate plasma current in dense plasmas hanging freely in vacuum in voluminous amount without obstruction to diagnostics will greatly enhance our ability to study the physics of high energy density plasmas in strong magnetic fields. Plasma current can be generated through nonlinear beat-wave process by launching two intense electromagnetic waves into unmagnetized plasma. Beat-wave acceleration of electrons has been demonstrated in a low-density plasma using microwaves [1]. The proposed PLX experimental facility presently under construction at Los Alamos offers the opportunity to test the method at a density level scalable to the study of HED plasmas. For PLX beat-wave experiments, CO2 lasers will be used as pump waves due to their high power and tunability. For a typical PLX density ne=10^17cm-3, two CO2 lasers can be separately tuned to 9P(28) and 10P(20) to match the 2.84THz plasma frequency. The beat-wave demo experiment will be conducted on CTIX. The laser arrangement is being converted to two independent single lasers. Frequency-tuning methods, optics focusing system and diagnostics system will be discussed. The laser measurements and results of synchronization of two lasers will be presented, and scaling to PLX experiments will be given. [1] Rogers, J. H. and Hwang, D. Q., PRL. v68 p3877 (1992).

  19. CO2 Laser Beat-Wave Experiment in an Unmagnetized Plasma

    Science.gov (United States)

    Liu, Fei; Hwang, David; Horton, Robert; Hong, Sean; Evans, Russell

    2012-10-01

    The ability to remotely generate plasma current in dense plasmas is a basic yet important investigation in experimental plasma physics and fusion energy research. It is even more advantageous if the wave penetration is independent of the electron acceleration process. Plasma current can be generated through beat-wave mixing process by launching two intense electromagnetic waves (φ>>φpe) into plasma. The beat wave formation process can be efficient if the difference frequency of the two pump waves is matched to a local resonant frequency of the medium, i.e. in this case the local plasma frequency. Beat wave can accelerate plasma electrons via quasi-linear Landau process, which has been demonstrated in a low-density plasma using microwaves.footnotetextRogers, J. H. and Hwang, D. Q., Phys. Rev. Lett. v68 p3877 (1992). The CO2 lasers provide the high tunability for the wave-particle interaction experiment at a variety of plasma densities with plasma frequency in THz range. Two sections of Lumonics TEA CO2 lasers have been modified to serve as the two pump wave sources with peak power over 100MW. The development of the tunable CO2 lasers, a high-density plasma target source and diagnostics system will be presented. The initial results of unbalanced beat-wave experiment using one high-power pulsed and one low-power CW CO2 lasers will be presented and discussed using the independent plasma source to control the φpe of the interaction region. This work is supported by U.S. DOE under Contract No. DE-FG02-10ER55083.

  20. Superconducting traveling wave accelerators

    International Nuclear Information System (INIS)

    This note considers the applicability of superconductivity to traveling wave accelerators. Unlike CW operation of a superconducting standing wave or circulating wave accelerator section, which requires improvement factors (superconductor conductivity divided by copper conductivity) of about 106 in order to be of practical use, a SUperconducting TRaveling wave Accelerator, SUTRA, operating in the pulsed mode requires improvement factors as low as about 103, which are attainable with niobium or lead at 4.2K, the temperature of liquid helium at atmospheric pressure. Changing from a copper traveling wave accelerator to SUTRA achieves the following. (1) For a given gradient SUTRA reduces the peak and average power requirements typically by a factor of 2. (2) SUTRA reduces the peak power still further because it enables us to increase the filling time and thus trade pulse width for gradient. (3) SUTRA makes possible a reasonably long section at higher frequencies. (4) SUTRA makes possible recirculation without additional rf average power. 8 references, 6 figures, 1 table

  1. Terahertz generation by beating two Langmuir waves in a warm and collisional plasma

    International Nuclear Information System (INIS)

    Terahertz (THz) radiation generated by beating of two Langmuir waves in a warm and collisional plasma is discussed theoretically. The critical angle between the two Langmuir waves and the critical wave-length (wave vector) of Langmuir waves for generating THz radiation are obtained analytically. Furthermore, the maximum radiation energy is obtained. We find that the critical angle, the critical wave-length, and the generated radiation energy strongly depend on plasma temperature and wave-length of the Langmuir waves. That is, the THz radiation generated by beating of two Langmuir waves in a warm and collisional plasma can be controlled by adjusting the plasma temperature and the Langmuir wave-length

  2. Observation of Atom-Wave Beats Using a Kerr Modulator for Atom Waves.

    Science.gov (United States)

    Décamps, B; Gillot, J; Vigué, J; Gauguet, A; Büchner, M

    2016-02-01

    A phase modulation puts the atom in a coherent superposition of quantum states with different kinetic energies. We have detected the interference of such modulated waves at the output of our atom interferometer, and we have observed beats at the difference of the modulation frequencies and its harmonics, in good agreement with theory. The phase modulations were produced by a Kerr phase modulator, i.e., by the propagation of the atom wave in a time-dependent electric field. An extension of this technique to electron interferometry should open the way to very high temporal resolution in electron microscopy. PMID:26894710

  3. Observation of Atom-Wave Beats Using a Kerr Modulator for Atom Waves.

    Science.gov (United States)

    Décamps, B; Gillot, J; Vigué, J; Gauguet, A; Büchner, M

    2016-02-01

    A phase modulation puts the atom in a coherent superposition of quantum states with different kinetic energies. We have detected the interference of such modulated waves at the output of our atom interferometer, and we have observed beats at the difference of the modulation frequencies and its harmonics, in good agreement with theory. The phase modulations were produced by a Kerr phase modulator, i.e., by the propagation of the atom wave in a time-dependent electric field. An extension of this technique to electron interferometry should open the way to very high temporal resolution in electron microscopy.

  4. Ponderomotive Acceleration by Relativistic Waves

    CERN Document Server

    Lau, Calvin; Yeh, Po-Chun; Luk, Onnie; McClenaghan, Joseph; Ebisuzaki, Toshikazu; Tajima, Toshiki

    2014-01-01

    In the extreme high intensity regime of electromagnetic (EM) waves in plasma, the acceleration process is found to be dominated by the ponderomotive acceleration (PA). While the wakefields driven by the ponderomotive force of the relativistic intensity EM waves are important, they may be overtaken by the PA itself in the extreme high intensity regime when the dimensionless vector potential $a_0$ of the EM waves far exceeds unity. The energy gain by this regime (in 1D) is shown to be (approximately) proportional to $a_0^2$. Before reaching this extreme regime, the coexistence of the PA and the wakefield acceleration (WA) is observed where the wave structures driven by the wakefields show the phenomenon of multiple and folded wave-breakings. Investigated are various signatures of the acceleration processes such as the dependence on the mass ratio for the energy gain as well as the energy spectral features. The relevance to high energy cosmic ray acceleration and to the relativistic laser acceleration is conside...

  5. On the Interaction of Two Beating Electrostatic Waves with Plasma Electrons

    Science.gov (United States)

    Malá, Z.

    2002-01-01

    This paper is devoted to the study of the interaction of particles with two beating plasma waves. We follow the instructional article by Ott and Dum. According to them, the sum of wave actions during the interaction is constant, supposing the effect of trapped particles on the beat can be neglected. In the present paper, this problem is solved more generally, just for the case of trapped and also untrapped particles in the wave. Our study shows that the sum of wave actions is constant also in the case when the influence of the trapped particles on the amplitudes of two waves was considered. On the contrary this conclusion is not valid if it is supposed that two original waves are amplitude modulated e.g. by the influence of the interaction of the beat with particles.

  6. Observation of Quantum Beat in Rb by Parametric Four-Wave Mixing

    Institute of Scientific and Technical Information of China (English)

    ZHU Chang-Jun; HE Jun-Fang; XUE Bing; ZHAI Xue-Jun

    2007-01-01

    @@ Two coupled parametric four-wave-mixing processes in Rb atoms are studied using perturbation theory, which reveals clear evidence of the appearance of quantum beat at 608cm-1, corresponding to the energy difference of the 7s - 5d states of Rb atoms, in the parametric four-wave-mixing signals. A pump-probe technique is utilized to observe the quantum beat. Time-varying characteristics of the quantum beat are investigated using time-dependent Fourier transform. The results show that the time-varying characteristics of the quantum beat not only offers a sensitive detecting method for observing the decay of atomic wave packets, but also provides a potential tool for monitoring the dissociation of molecules.

  7. Sequentially pulsed traveling wave accelerator

    Science.gov (United States)

    Caporaso, George J.; Nelson, Scott D.; Poole, Brian R.

    2009-08-18

    A sequentially pulsed traveling wave compact accelerator having two or more pulse forming lines each with a switch for producing a short acceleration pulse along a short length of a beam tube, and a trigger mechanism for sequentially triggering the switches so that a traveling axial electric field is produced along the beam tube in synchronism with an axially traversing pulsed beam of charged particles to serially impart energy to the particle beam.

  8. Wave Detection in Acceleration Plethysmogram

    OpenAIRE

    Ahn, Jae Mok

    2015-01-01

    Objectives Acceleration plethysmogram (APG) obtained from the second derivative of photoplethysmography (PPG) is used to predict risk factors for atherosclerosis with age. This technique is promising for early screening of atherosclerotic pathologies. However, extraction of the wave indices of APG signals measured from the fingertip is challenging. In this paper, the development of a wave detection algorithm including a preamplifier based on a microcontroller that can detect the a, b, c, and ...

  9. Nonlinear Spatial Landau Damping of Plasma Waves Beating at Plasma Angular Velocity

    Science.gov (United States)

    Kabantsev, A. A.; Driscoll, C. F.

    2014-10-01

    Experiments on pure electron plasmas characterize the nonlinear beat between two counter-propagating plasma waves, and the spatial Landau damping of the beat wave at the wave/rotation critical radius. The two plasma waves are (mθ = 1 ,kz = 1 , ω =ω* +/-ω1) , giving the beat wave with (mθ = 2 , ω = 2ω*) . The beat wave is resonant with the plasma rotation Ω (r) at radius r* where Ω (r*) =ω* . The net effect of this resonance is an energy exchange through wave-particle interaction between the two primary plasma waves and the background plasma rotation. Initial excitation of only one of the waves leads first to its fast sharing of energy with the other wave, and then followed by a slower combined decay of both waves. In contrast, initial excitation of both waves to (approximately) the same amplitude leads to three alternative scenarios: 1) both plasma waves may show the slow and synchronous decay evolution; 2) one of the waves may decay faster, with temporarily arrested decay of the other; 3) it may switch back and forth (seemingly randomly) between the first two types of evolution. Interestingly, wave/particle energy flow can be reversed when the plasma density profile is made to have a positive density gradient at r*. In this case, spontaneous excitation (instability) of both ω =ω* +/-ω1 plasma waves is observed. Supported by NSF/DoE Partnership Grants PHY-0903877 and DE-SC000245, and DOE/HEDLP Grant DE-SC0008693.

  10. Wavelength of ocean waves and surf beat at duck from array measurements

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, A.A.; Menon, H.B.; Sarma, Y.V.B.; Jog, P.D.; Almeida, A.M.

    Wavelength of ocean waves and surf beat (infra gravity waves) has for the first time been computed as a function of frequency from different combinations of non-collinear 3-gauge arrays. Data at the 15-gauge polygonal array at 8 m depth at Duck...

  11. Cosmological Acceleration from Gravitational Waves

    CERN Document Server

    Marochnik, Leonid

    2015-01-01

    It is shown that the classical gravitational waves of super-horizon wavelengths are able to form the de Sitter accelerated expansion of the empty (with no matter fields) Universe. The contemporary Universe is about 70% empty and asymptotically is going to become completely empty, so the effect caused by emptiness should be already very noticeable. It could manifest itself as the dark energy.

  12. Free-electron laser from wave-mechanical beats of 2 electron beams

    Science.gov (United States)

    Lichtenstein, R. M.

    1982-01-01

    It is possible, though technically difficult, to produce beams of free electrons that exhibit beats of a quantum mechanical nature. (1) the generation of electromagnetic radiation, e.g., light, based on the fact that the beats give rise to alternating charge and current densities; and a frequency shifter, based on the fact that a beam with beats constitutes a moving grating. When such a grating is exposed to external radiation of suitable frequency and direction, the reflected rediation will be shifted in frequency, since the grating is moving. A twofold increase of the frequency is readily attainable. It is shown that it is impossible to generate radiation, because the alternating electromagnetic fields that accompany the beats cannot reform themselves into freely propagating waves. The frequency shifter is useless as a practical device, because its reflectance is extremely low for realizable beams.

  13. Beat-type Langmuir wave emissions associated with a type III solar radio burst: Evidence of parametric decay

    Science.gov (United States)

    Hospodarsky, G. B.; Gurnett, D. A.

    1995-01-01

    Recent measurements from the plasma wave instrument on the Galileo spacecraft have shown that Langmuir waves observed in conjunction with a type III solar radio burst contain many beat-type waveforms, with beat frequencies ranging from about 150 to 650 Hz. Strong evidence exists that the beat pattern is produced by two closely spaced narrowband components. The most likely candidates for these two waves are a beam-generated Langmuir wave and an oppositely propagating Langmuir wave produced by parametric decay. In the parametric decay process, nonlinear interactions cause the beam-driven Langmuir wave to decay into a Langmuir wave and a low-frequency ion sound wave. Comparisons of the observed beat frequency are in good agreement with theoretical predictions for a three-wave parametric decay process. Weak low-frequency emissions are also sometimes observed at the predicted frequency of the ion sound wave.

  14. Stimulated Brillouin side-scattering of the beat wave excited by two counter-propagating X-mode lasers in magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Kanika; Sajal, Vivek, E-mail: vsajal@rediffmail.com; Kumar, Ravindra; Sharma, Navneet K. [Department of Physics and Materials Science and Engineering, Jaypee Institute of Information Technology, Noida 201307, Uttar Pradesh (India); Baliyan, Sweta [Department of Physics, Maitreyi College, University of Delhi, New Delhi 110021 (India)

    2015-06-15

    The stimulated Brillouin scattering (SBS) of nonresonant beat mode in the presence of static magnetic field is investigated in a plasma. Two counter-propagating lasers of frequencies (ω{sub 1} and ω{sub 2}) and wave vectors (k{sub 1} and k{sub 2}) drive a nonresonant space charge beat mode at the phase matching condition of frequency ω{sub 0}≈ω{sub 1}∼ω{sub 2} and wave number k{sup →}{sub 0}≈k{sup →}{sub 1}+k{sup →}{sub 2}. The driver wave parametrically excites a pair of ion acoustic wave (ω,k{sup →}) and a sideband electromagnetic wave (ω{sub 3},k{sup →}{sub 3}). The beat wave couples with the sideband electromagnetic wave to exert a nonlinear ponderomotive force at the frequency of ion acoustic wave. Density perturbations due to ion acoustic wave and ponderomotive force couple with the oscillatory motion of plasma electron due to velocity of beat wave to give rise to a nonlinear current (by feedback mechanism) responsible for the growth of sideband wave at resonance. The growth rate of SBS was reduced (from ∼10{sup 12}s{sup −1} to 10{sup 10}s{sup −1}) by applying a transverse static magnetic field ∼90 T. The present study can be useful for the excitation of fast plasma waves (for the purpose of electron acceleration) by two counter-propagating laser beams.

  15. Collective acceleration of protons by the plasma waves in a counterstreaming electron beam

    International Nuclear Information System (INIS)

    A novel advanced accelerator is proposed. The counterstreaming electron beam accelerator relies on the same physical mechanism as that of the plasma accelerator but replaces the stationary plasma in the plasma accelerator by a magnetized relativistic electron beam, drifting antiparallel to the driving source and the driven particles, as the wave supporting medium. The plasma wave in a counterstreaming electron beam can be excited either by a density-ramped driving electron beam or by properly beating two laser beams. The fundamental advantages of the counterstreaming electron beam accelerator over the plasma accelerator are a longer and tunable plasma wavelength, a longer pump depletion length or a larger transformer ratio, and easier pulse shaping for the driving source and the driven beam. Thus the energy gain of the driven particles can be greatly enhanced whereas the trapping threshold can be dramatically reduced so as to admit the possibility for proton acceleration

  16. Efficiency of dispersive wave generation from a dual-frequency beat signal

    CERN Document Server

    Webb, K E; Xu, Y Q; Genty, G; Murdoch, S G

    2016-01-01

    The emission of dispersive waves (DWs) by temporal solitons can be described as a cascaded four-wave mixing process triggered by a pair of monochromatic continuous waves (CWs). We report experimental and numerical results demonstrating that the efficiency of this process is strongly and non-trivially affected by the frequency detuning of the CW pump lasers. We explain our results by showing that individual cycles of the input dual-frequency beat signal can evolve as higher-order solitons whose temporal compression and soliton fission govern the DW efficiency. Analytical predictions based on the detuning dependence of the soliton order are shown to be in excellent agreement with experimental and numerical observations.

  17. Observation of Quantum Beating from Two Coupled Parametric Six-Wave Mixing Signals in Rb

    Institute of Scientific and Technical Information of China (English)

    ZHU Chang-Jun; HE Jun-Fang; ZHAI Xue-Jun; XUE Bing

    2008-01-01

    Two processes of coupled difference-frequency axially phase-matched parametric six-wave mixing are carried out in Rb vapour by two-photon excitation using fs laser pulses, and parametric six-wave mixing signals in the infrared and near infrared regime are detected. The infrared parametric six-wave mixing signals are up-converted into the visible spectral range by sum-frequency mixing with the pump laser in a LiI03 crystal. Moreover, quantum beating at 608cm-1, corresponding to the 7s - 5d energy difference in Rb, is observed from the sum-frequency signal at 495 nm. As a result, we obtain modulated light signals in the visible, near infrared and infrared spectral ranges, and study the interference between 7s and 5d states of Rb.

  18. Laser beat wave resonant terahertz generation in a magnetized plasma channel

    Energy Technology Data Exchange (ETDEWEB)

    Bhasin, Lalita; Tripathi, V. K. [Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India); Kumar, Pawan, E-mail: kumarpawan-30@yahoo.co.in [Department of Physics, Raj Kumar Goel Institute of Technology, Ghaziabad, Uttar Pradesh 201003 (India)

    2016-02-15

    Resonant excitation of terahertz (THz) radiation by nonlinear mixing of two lasers in a ripple-free self created plasma channel is investigated. The channel has a transverse static magnetic field and supports a THz X-mode with phase velocity close to the speed of light in vacuum when the frequency of the mode is close to plasma frequency on the channel axis and its value decreases with the intensity of lasers. The THz is resonantly driven by the laser beat wave ponderomotive force. The THz amplitude scales almost three half power of the intensity of lasers as the width of the THz eigen mode shrinks with laser intensity.

  19. Traveling Wave Accelerating Structure for a Superconducting Accelerator

    CERN Document Server

    Kanareykin, Alex; Solyak, Nikolay

    2005-01-01

    We are presenting a superconducting traveling wave accelerating structure (STWA) concept, which may prove to be of crucial importance to the International Linear Collider. Compared to the existing design of a TESLA cavity, the traveling wave structure can provide ~20-40% higher accelerating gradient for the same aperture and the same peak surface magnetic RF field. The recently achieved SC structure gradient of 35 MV/m can be increased up to ~50 MV/m with the new STWA structure design. The STWA structure is supposed to be installed into the superconducting resonance ring and is fed by the two couplers with appropriate phase advance to excite a traveling wave inside the structure. The system requires two independent tuners to be able to adjust the cavity and feedback waveguide frequencies and hence to reduce the unwanted backward wave. In this presentation we discuss the structure design, optimization of the parameters, tuning requirements and plans for further development.

  20. Beat wave excitation of electron plasma wave by relativistic cross focusing of cosh-Gaussian laser beams in plasma

    Science.gov (United States)

    Singh, Arvinder; Gupta, Naveen

    2015-06-01

    A scheme for beat wave excitation of electron plasma wave (EPW) is proposed by relativistic cross-focusing of two coaxial Cosh-Gaussian (ChG) laser beams in an under dense plasma. The plasma wave is generated on account of beating of two coaxial laser beams of frequencies ω1 and ω2 . The mechanism for laser produced nonlinearity is assumed to be relativistic nonlinearity in electron mass. Following moment theory approach in Wentzel Kramers Brillouin (W.K.B) approximation, the coupled differential equations governing the evolution of spot size of laser beams with distance of propagation have been derived. The relativistic nonlinearity depends not only on the intensity of first laser beam but also on the intensity of second laser beam. Therefore, propagation dynamics of one laser beam affect that of second beam and hence cross-focusing of the two laser beams takes place. Due to non uniform intensity distribution of pump laser beams, the background electron concentration gets modified. The amplitude of EPW, which depends on the background electron concentration, thus gets nonlinearly coupled with the laser beams. The effects of relativistic electron mass nonlinearity and the cross-focusing of pump beams on excitation of EPW have been incorporated. Numerical simulations have been carried out to investigate the effect of laser as well as plasma parameters on cross-focusing of laser beams and further its effect on power of excited EPW.

  1. Velocity bunching in travelling wave accelerator with low acceleration gradient

    CERN Document Server

    Huang, Rui-Xuan; Li, Wei-Wei; Jia, Qi-Ka

    2013-01-01

    We present the analytical and simulated results concerning the influences of the acceleration gradient in the velocity bunching process, which is a bunch compression scheme that uses a traveling wave accelerating structure as a compressor. Our study shows that the bunch compression application with low acceleration gradient is more tolerant to phase jitter and more successful to obtain compressed electron beam with symmetrical longitudinal distribution and low energy spread. We also present a transverse emittance compensation scheme to compensate the emittance growth caused by the increasing of the space charge force in the compressing process that is easy to be adjusted for different compressing factors.

  2. Estimation of beat-to-beat changes in stroke volume from arterial pressure: A comparison of two pressure wave analysis techniques during head- up tilt testing in young, healthy men

    NARCIS (Netherlands)

    Jellema, W.T.; Imholz, B.P.M.; Oosting, H.; Wesseling, K.H.; Lieshout, J.J. van

    1999-01-01

    Objective: The aim of this study was to compare beat-to-beat changes in stroke volume (SV) estimated by two different pressure wave analysis techniques during orthostatic stress testing: pulse contour analysis and Modelflow, ie, simulation of a three-element model of aortic input impedance. Methods:

  3. First in vivo traveling wave magnetic particle imaging of a beating mouse heart

    Science.gov (United States)

    Vogel, P.; Rückert, M. A.; Klauer, P.; Kullmann, W. H.; Jakob, P. M.; Behr, V. C.

    2016-09-01

    Magnetic particle imaging (MPI) is a non-invasive imaging modality for direct detection of superparamagnetic iron-oxide nanoparticles based on the nonlinear magnetization response of magnetic materials to alternating magnetic fields. This highly sensitive and rapid method allows both a quantitative and a qualitative analysis of the measured signal. Since the first publication of MPI in 2005 several different scanner concepts have been presented and in 2009 the first in vivo imaging results of a beating mouse heart were shown. However, since the field of view (FOV) of the first MPI-scanner only covers a small region several approaches and hardware enhancements were presented to overcome this issue and could increase the FOV on cost of acquisition speed. In 2014 an alternative scanner concept, the traveling wave MPI (TWMPI), was presented, which allows scanning an entire mouse-sized volume at once. In this paper the first in vivo imaging results using the TWMPI system are presented. By optimizing the trajectory the temporal resolution is sufficiently high to resolve the dynamic of a beating mouse heart.

  4. Thermal gravitational waves in accelerating universe

    Directory of Open Access Journals (Sweden)

    B Ghayour

    2013-10-01

    Full Text Available Gravitational waves are considered in thermal vacuum state. The amplitude and spectral energy density of gravitational waves are found enhanced in thermal vacuum state compared to its zero temperature counterpart. Therefore, the allowed amount of enhancement depends on the upper bound of WMAP-5 and WMAP-7 for the amplitude and spectral energy density of gravitational waves. The enhancement of amplitude and spectral energy density of the waves in thermal vacuum state is consistent with current accelerating phase of the universe. The enhancement feature of amplitude and spectral energy density of the waves is independent of the expansion model of the universe and hence the thermal effect accounts for it. Therefore, existence of thermal gravitational waves is not ruled out

  5. High-gain X-ray free electron laser by beat-wave terahertz undulator

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Chao; Hei, DongWei [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi' an City 710024 (China); Institute of Energy, Tsinghua University, Beijing 100084 (China); Pellegrin, Claudio; Tantawi, Sami [SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94309 (United States)

    2013-12-15

    The THz undulator has a higher gain to realize a much brighter X-ray at saturation, compared with the optical undulator under the same undulator strength and beam quality. In order to fill the high-power THz gap and realize the THz undulator, two superimposed laser pulses at normal incidence to the electron-beam moving direction form an equivalent high-field THz undulator by the frequency difference to realize the high-gain X-ray Free electron laser. The pulse front tilt of lateral fed lasers is used to realize the electron-laser synchronic interaction. By PIC simulation, a higher gain and a larger X-ray radiation power by the beat wave THz undulator could be realized, compared with the optical undulator for the same electron beam parameters.

  6. Features of amplitude and Doppler frequency variation of ELF/VLF waves generated by "beat-wave" HF heating at high latitudes

    Science.gov (United States)

    Tereshchenko, E. D.; Shumilov, O. I.; Kasatkina, E. A.; Gomonov, A. D.

    2014-07-01

    Observations of extremely low frequency (ELF, 3-3000 Hz) radio waves generated by a "beat-wave" (BW) high frequency (~ 4.04-4.9 MHz) ionospheric heating are presented. ELF waves were registered with the ELF receiver located at Lovozero (68°N, 35°E), 660 km east from the European Incoherent Scatter Tromso heating facility (69.6°N, 19.2°E). Frequency shifts between the generated beat-wave and received ELF waves were detected in all sessions. It is shown that the amplitudes of ELF waves depend on the auroral electrojet current strength. Our results showing a strong dependence of ELF signal intensities on the substorm development seem to support the conclusion that electrojet currents may affect the BW generation of ELF/VLF waves.

  7. Measurement of optical-beat frequency in a photoconductive terahertz-wave generator using microwave higher harmonics

    Science.gov (United States)

    Murasawa, Kengo; Sato, Koki; Hidaka, Takehiko

    2011-05-01

    A new method for measuring optical-beat frequencies in the terahertz (THz) region using microwave higher harmonics is presented. A microwave signal was applied to the antenna gap of a photoconductive (PC) device emitting a continuous electromagnetic wave at about 1 THz by the photomixing technique. The microwave higher harmonics with THz frequencies are generated in the PC device owing to the nonlinearity of the biased photoconductance, which is briefly described in this article. Thirteen nearly periodic peaks in the photocurrent were observed when the microwave was swept from 16 to 20 GHz at a power of -48 dBm. The nearly periodic peaks are generated by the homodyne detection of the optical beat with the microwave higher harmonics when the frequency of the harmonics coincides with the optical-beat frequency. Each peak frequency and its peak width were determined by fitting a Gaussian function, and the order of microwave harmonics was determined using a coarse (i.e., lower resolution) measurement of the optical-beat frequency. By applying the Kalman algorithm to the peak frequencies of the higher harmonics and their standard deviations, the optical-beat frequency near 1 THz was estimated to be 1029.81 GHz with the standard deviation of 0.82 GHz. The proposed method is applicable to a conventional THz-wave generator with a photomixer.

  8. Beat-Wave Experiments in the Micro Wave Range : Pump Depletion

    OpenAIRE

    Andreev, N.; Campos, E; Cros, B.; Godiot, J.; Gorbunov, L.; Matthieussent, G.

    1995-01-01

    Excitation of electron plasma waves by the mixing of two microwave beams is studied in a laboratory plasma. The first experimental observation of pump wave depletion is presented. The numerical calculations, based on one-dimensional model, describing space-time evolution of eight interacting waves, are in good agreement with experimental data. Estimation of the depletion on the basis of conservation laws is also discussed.

  9. Oscillator and system development on the VULCAN glass laser system for the plasma beat-wave program

    International Nuclear Information System (INIS)

    This thesis describes the oscillator and system development on the VULCAN glass laser undertaken in support of the RAL Plasma Beat-wave experiments. This program seeks to evaluate advanced particle acceleration schemes for a new generation of machines for fundamental research in high energy physics. The experiments required two synchronised high power laser pulses of slightly different wavelength. These pulses were generated using two different laser media; Nd:YAG and Nd:YLF operating at 1.064 and 1.053 microns respectively. The first oscillator system developed operated with both lasing media housed in the same laser cavity. Problems with the stability of the optical output required the development of a second system which housed the two lasing media in separate cavities. The second aspect of the development work, described in this thesis, was the reconfiguration of the VULCAN glass laser system to amplify the two laser pulses to power levels of 0.5 TW per pulse. The first scheduled experiment required the two pulses to be propagated co-linearly. To amplify the pulses to the high output powers required two amplifying media to be used which preferentially amplify the two lasing wavelengths. For the later experiments the two laser pulses were amplified in separate amplifier chains which required the design of an efficient beam combiner. (author)

  10. Soliton radiation beat analysis of optical pulses generated from two continuous-wave lasers

    International Nuclear Information System (INIS)

    We propose a fibre-based approach for generation of optical frequency combs (OFCs) with the aim of calibration of astronomical spectrographs in the low and medium-resolution range. This approach includes two steps: in the first step, an appropriate state of optical pulses is generated and subsequently moulded in the second step delivering the desired OFC. More precisely, the first step is realised by injection of two continuous-wave (CW) lasers into a conventional single-mode fibre, whereas the second step generates a broad OFC by using the optical solitons generated in step one as initial condition. We investigate the conversion of a bichromatic input wave produced by two initial CW lasers into a train of optical solitons, which happens in the fibre used as step one. Especially, we are interested in the soliton content of the pulses created in this fibre. For that, we study different initial conditions (a single cosine-hump, an Akhmediev breather, and a deeply modulated bichromatic wave) by means of soliton radiation beat analysis and compare the results to draw conclusion about the soliton content of the state generated in the first step. In case of a deeply modulated bichromatic wave, we observed the formation of a collective soliton crystal for low input powers and the appearance of separated solitons for high input powers. An intermediate state showing the features of both, the soliton crystal and the separated solitons, turned out to be most suitable for the generation of OFC for the purpose of calibration of astronomical spectrographs

  11. Soliton radiation beat analysis of optical pulses generated from two continuous-wave lasers

    Energy Technology Data Exchange (ETDEWEB)

    Zajnulina, M.; Giannone, D.; Haynes, R.; Roth, M. M. [innoFSPEC-VKS, Leibniz Institute for Astrophysics, An der Sternwarte 16, 14482 Potsdam (Germany); Böhm, M. [innoFSPEC-InFaSe, University of Potsdam, Am Mühlenberg 3, 14476 Golm (Germany); Blow, K. [Aston Institute of Photonic Technologies, Aston Triangle, Birmingham B4 7ET (United Kingdom); Rieznik, A. A. [Instituto Tecnologico de Buenos Aires and CONICET, Buenos Aires (Argentina)

    2015-10-15

    We propose a fibre-based approach for generation of optical frequency combs (OFCs) with the aim of calibration of astronomical spectrographs in the low and medium-resolution range. This approach includes two steps: in the first step, an appropriate state of optical pulses is generated and subsequently moulded in the second step delivering the desired OFC. More precisely, the first step is realised by injection of two continuous-wave (CW) lasers into a conventional single-mode fibre, whereas the second step generates a broad OFC by using the optical solitons generated in step one as initial condition. We investigate the conversion of a bichromatic input wave produced by two initial CW lasers into a train of optical solitons, which happens in the fibre used as step one. Especially, we are interested in the soliton content of the pulses created in this fibre. For that, we study different initial conditions (a single cosine-hump, an Akhmediev breather, and a deeply modulated bichromatic wave) by means of soliton radiation beat analysis and compare the results to draw conclusion about the soliton content of the state generated in the first step. In case of a deeply modulated bichromatic wave, we observed the formation of a collective soliton crystal for low input powers and the appearance of separated solitons for high input powers. An intermediate state showing the features of both, the soliton crystal and the separated solitons, turned out to be most suitable for the generation of OFC for the purpose of calibration of astronomical spectrographs.

  12. Beat-the-wave evacuation mapping for tsunami hazards in Seaside, Oregon, USA

    Science.gov (United States)

    Priest, George R.; Stimely, Laura; Wood, Nathan J.; Madin, Ian; Watzig, Rudie

    2016-01-01

    Previous pedestrian evacuation modeling for tsunamis has not considered variable wave arrival times or critical junctures (e.g., bridges), nor does it effectively communicate multiple evacuee travel speeds. We summarize an approach that identifies evacuation corridors, recognizes variable wave arrival times, and produces a map of minimum pedestrian travel speeds to reach safety, termed a “beat-the-wave” (BTW) evacuation analysis. We demonstrate the improved approach by evaluating difficulty of pedestrian evacuation of Seaside, Oregon, for a local tsunami generated by a Cascadia subduction zone earthquake. We establish evacuation paths by calculating the least cost distance (LCD) to safety for every grid cell in a tsunami-hazard zone using geospatial, anisotropic path distance algorithms. Minimum BTW speed to safety on LCD paths is calculated for every grid cell by dividing surface distance from that cell to safety by the tsunami arrival time at safety. We evaluated three scenarios of evacuation difficulty: (1) all bridges are intact with a 5-minute evacuation delay from the start of earthquake, (2) only retrofitted bridges are considered intact with a 5-minute delay, and (3) only retrofitted bridges are considered intact with a 10-minute delay. BTW maps also take into account critical evacuation points along complex shorelines (e.g., peninsulas, bridges over shore-parallel estuaries) where evacuees could be caught by tsunami waves. The BTW map is able to communicate multiple pedestrian travel speeds, which are typically visualized by multiple maps with current LCD-based mapping practices. Results demonstrate that evacuation of Seaside is problematic seaward of the shore-parallel waterways for those with any limitations on mobility. Tsunami vertical-evacuation refuges or additional pedestrian bridges may be effective ways of reducing loss of life seaward of these waterways.

  13. Diffusive Shock Acceleration at Cosmological Shock Waves

    OpenAIRE

    Kang, Hyesung; Ryu, Dongsu

    2012-01-01

    We reexamine nonlinear diffusive shock acceleration (DSA) at cosmological shocks in the large scale structure of the Universe, incorporating wave-particle interactions that are expected to operate in collisionless shocks. Adopting simple phenomenological models for magnetic field amplification (MFA) by cosmic-ray (CR) streaming instabilities and Alfv'enic drift, we perform kinetic DSA simulations for a wide range of sonic and Alfv'enic Mach numbers and evaluate the CR injection fraction and a...

  14. Suppression of stimulated Brillouin instability of a beat-wave of two lasers in multiple-ion-species plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Yadav, Pinki; Gupta, D. N., E-mail: dngupta@physics.du.ac.in; Avinash, K. [Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India)

    2016-01-15

    Stimulated Brillouin instability of a beat-wave of two lasers in plasmas with multiple-ion-species (negative-ions) was studied. The inclusion of negative-ions affects the growth of ion-acoustic wave in Brillouin scattering. Thus, the growth rate of instability is suppressed significantly by the density of negative-ions. To obey the phase-matching condition, the growth rate of the instability attains a maxima for an appropriate scattering angle (angle between the pump and scattered sideband waves). This study would be technologically important to have diagnostics in low-temperature plasmas.

  15. Channeled particle acceleration by plasma waves in metals

    International Nuclear Information System (INIS)

    A solid state accelerator concept utilizing particle acceleration along crystal channels by longitudinal electron plasma waves in a metal is presented. Acceleration gradients of order 100 GV/cm are theoretically possible. Particle dechanneling due to electron multiple scattering can be eliminated with a sufficiently high acceleration gradient. Plasma wave dissipation and generation in metals are also discussed

  16. High-Gradient, Millimeter Wave Accelerating Structure

    CERN Document Server

    Kuzikov, S V; Peskov, N Yu

    2015-01-01

    The millimeter wave all-metallic accelerating structure, aimed to provide more than 100 MeV/m gradient and fed by feeding RF pulses of 20-30 ns duration, is proposed. The structure is based on a waveguide with small helical corrugation. Each section of 10-20 wavelengths long has big circular cross-section aperture comparable with wavelength. Because short wavelength structures are expected to be critical to wakefields excitation and emittance growth, we suggest to combine in one structure properties of a linear accelerator and a cooling damping ring simultaneously. It provides acceleration of straight on-axis beam as well as cooling of this beam due to the synchrotron radiation of particles in strong non-synchronous transverse fields. These properties are provided by specific slow eigen mode which consists of two partial waves, TM01 and TM11. Simulations show that shunt impedance can be as high as 100 MOhm/m. Results of the first low-power tests with 30 GHz accelerating section are analyzed.

  17. Langmuir Waves and Electron Acceleration at Heliospheric Shocks

    OpenAIRE

    Pulupa, Marc Peter

    2010-01-01

    Radio waves at the local plasma frequency and its harmonic are generated upstream of collisionless shocks in foreshock regions which are magnetically connected to the shock. The radio waves are created in a multi-step process which involves the acceleration of electrons at the shock front, growth of electrostatic Langmuir waves driven by the accelerated electron beam, and conversion of the Langmuir waves into radio waves.These radio waves can be used to remotely determine properties of the s...

  18. Detection of c, d, and e waves in the acceleration photoplethysmogram.

    Science.gov (United States)

    Elgendi, Mohamed

    2014-11-01

    Analyzing the acceleration photoplethysmogram (APG) is becoming increasingly important for diagnosis. However, processing an APG signal is challenging, especially if the goal is to detect its small components (c, d, and e waves). Accurate detection of c, d, and e waves is an important first step for any clinical analysis of APG signals. In this paper, a novel algorithm that can detect c, d, and e waves simultaneously in APG signals of healthy subjects that have low amplitude waves, contain fast rhythm heart beats, and suffer from non-stationary effects was developed. The performance of the proposed method was tested on 27 records collected during rest, resulting in 97.39% sensitivity and 99.82% positive predictivity. PMID:25176597

  19. Gravitational waves generated by laser accelerated relativistic ions

    OpenAIRE

    Gelfer, Evgeny; Kadlecová, Hedvika; Klimo, Ondřej; Weber, Stefan; Korn, Georg

    2015-01-01

    The generation of gravitational waves by laser accelerated relativistic ions is investigated. The piston and light sail models of laser plasma acceleration are considered and analytical expressions for space-time metric perturbation are derived. For both models the dependence of gravitational waves amplitude on the laser and plasma parameters as well as gravitational waves spectrum and angular distribution are examined

  20. Acceleration of cosmic rays by shock waves

    International Nuclear Information System (INIS)

    In recent years there has been renewed interest in the possibility that the acceleration of cosmic rays should occur, not in discrete sources, but in the diffuse interstellar medium, as a consequence of shock waves associated with supernova remnants. Since the supernova remnants concerned are rather large and indeed tend to dominate the whole interstellar medium it is becoming clear that the problems of acceleration and propagation of cosmic rays cannot be so easily separated. A further difficulty is concerned with the escape of cosmic rays from the galaxy which may be associated with a galactic wind which is partly driven by cosmic ray pressure and therefore not an independent process. These complexities give added interest and significance to the role of cosmic rays in the dynamics of the interstellar medium but of course also make the traditional problems of cosmic ray physics much more difficult to treat. We attempt here to review the current status of investigations into various aspects of the problem of shock acceleration of cosmic rays

  1. High-power, mid-infrared, picosecond pulses generated by compression of a CO2 laser beat-wave in GaAs

    CERN Document Server

    Pigeon, J J; Joshi, C

    2015-01-01

    We report on the generation of a train of ~ 2 ps, 10 um laser pulses via multiple four-wave mixing and compression of an infrared laser beat-wave propagating in the negative group velocity dispersion region of bulk GaAs and a combination of GaAs and NaCl. The use of a 200 ps, 106 GHz beat-wave, produced by combining laser pulses amplified on the 10P(20) and 10P(16) transition of a CO2 laser, provides a novel method for generating high-power, picosecond, mid-IR laser pulses at a high repetition rate. By using 165 and 882 GHz beat-waves we show that cascaded phase-mismatched difference frequency generation plays a significant role in the four-wave mixing process in GaAs.

  2. Superconducting travelling wave ring with high gradient accelerating section

    Energy Technology Data Exchange (ETDEWEB)

    Avrakhov, P.; Solyak, N.; /Fermilab

    2007-06-01

    Use of a superconducting traveling wave accelerating (STWA) structure instead of a standing wave cavity has major advantages in increasing the accelerating gradient in the ILC. In contrast with standing wave cavity STWA requires feedback loop, which sends wave from the structure output to input, making a superconducting traveling wave ring (STWR). One or few input couplers need to excite STWR and compensate power dissipations due to beam loading. To control traveling wave regime in the structure two independent knobs can be used for tuning both resonant ring frequency and backward wave. We discuss two variants of the STWR with one and two feed couplers.

  3. An introduction to acceleration mechanisms

    International Nuclear Information System (INIS)

    This paper discusses the acceleration of charged particles by electromagnetic fields, i.e., by fields that are produced by the motion of other charged particles driven by some power source. The mechanisms that are discussed include: Ponderamotive Forces, Acceleration, Plasma Beat Wave Acceleration, Inverse Free Electron Laser Acceleration, Inverse Cerenkov Acceleration, Gravity Acceleration, 2D Linac Acceleration and Conventional Iris Loaded Linac Structure Acceleration

  4. Study of beat phenomenon on a pile-supported pipeline system subjected to wave loading

    Institute of Scientific and Technical Information of China (English)

    Meng Xun; Huang Weiping; Li Huajun

    2007-01-01

    Classical beat phenomenon has been observed in most combined systems. The focus of this paper is to provide a better understanding of this phenomenon in an offshore pile-supported pipeline system. The beat phenomeon is caused by the coupling movement of the pipeline and its vertical pile support under certain conditions. It can induce excessive vibration and cause fatigue failure at pipe elbow. However, in some circumstances it does not exist. Numerical results in both frequency and time domains are presented to elucidate this phenomenon in a combined pipeline system. The conclusions of this paper could give constructive guidance to future design of simply supported pipeline systems.

  5. Coupler tuning for constant gradient travelling wave accelerating structures

    International Nuclear Information System (INIS)

    The method of the coupler tuning for the constant gradient traveling wave accelerating structure was described and the formula of coupling coefficient p was deduced on the basis of analyzing the existing methods for the constant impedance traveling wave accelerating structures and coupling-cavity chain equivalent circuits. The method and formula were validated by the simulation result by CST and experiment data. (authors)

  6. Protons Surfatron acceleration by electromagnetic wave in space plasma

    International Nuclear Information System (INIS)

    In this work fundamental interactions of type wave-particles are discussed. Main object of the investigation is Surfatron accelerations of the protons by single electromagnetic wave. The Surfatron effect of protons acceleration is investigated through numerical simulations, on the basis of nonlinear, nonstationary, second order differential equation for the wave phase at the charged particle’s trajectory. The temporal dynamics of protons Surfatron acceleration for different variants of the initial parameters are studied. The optimal conditions for maximum ultrarelativistic particles Surfatron acceleration by the electromagnetic wave in space plasma are considered. An analytical approximation for protons energy strong growth was done. Key words: Surfatron acceleration, space plasmas, electromagnetic wave, proton, charge trapping

  7. Beat-to-Beat Blood Pressure Monitor

    Science.gov (United States)

    Lee, Yong Jin

    2012-01-01

    This device provides non-invasive beat-to-beat blood pressure measurements and can be worn over the upper arm for prolonged durations. Phase and waveform analyses are performed on filtered proximal and distal photoplethysmographic (PPG) waveforms obtained from the brachial artery. The phase analysis is used primarily for the computation of the mean arterial pressure, while the waveform analysis is used primarily to obtain the pulse pressure. Real-time compliance estimate is used to refine both the mean arterial and pulse pressures to provide the beat-to-beat blood pressure measurement. This wearable physiological monitor can be used to continuously observe the beat-to-beat blood pressure (B3P). It can be used to monitor the effect of prolonged exposures to reduced gravitational environments and the effectiveness of various countermeasures. A number of researchers have used pulse wave velocity (PWV) of blood in the arteries to infer the beat-to-beat blood pressure. There has been documentation of relative success, but a device that is able to provide the required accuracy and repeatability has not yet been developed. It has been demonstrated that an accurate and repeatable blood pressure measurement can be obtained by measuring the phase change (e.g., phase velocity), amplitude change, and distortion of the PPG waveforms along the brachial artery. The approach is based on comparing the full PPG waveform between two points along the artery rather than measuring the time-of-flight. Minimizing the measurement separation and confining the measurement area to a single, well-defined artery allows the waveform to retain the general shape between the two measurement points. This allows signal processing of waveforms to determine the phase and amplitude changes. Photoplethysmography, which measures changes in arterial blood volume, is commonly used to obtain heart rate and blood oxygen saturation. The digitized PPG signals are used as inputs into the beat-to-beat blood

  8. Particle acceleration in tangential discontinuities by lower hybrid waves

    Directory of Open Access Journals (Sweden)

    D. Spicer

    2002-01-01

    Full Text Available We consider the role that the lower-hybrid wave turbulence plays in providing the necessary resistivity at collisionless reconnection sights. The mechanism for generating the waves is considered to be the lower-hybrid drift instability. We find that the level of the wave amplitude is sufficient enough to heat and accelerate both electrons and ions.

  9. Advanced accelerator and mm-wave structure research at LANL

    Energy Technology Data Exchange (ETDEWEB)

    Simakov, Evgenya Ivanovna [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-06-22

    This document outlines acceleration projects and mm-wave structure research performed at LANL. The motivation for PBG research is described first, with reference to couplers for superconducting accelerators and structures for room-temperature accelerators and W-band TWTs. These topics are then taken up in greater detail: PBG structures and the MIT PBG accelerator; SRF PBG cavities at LANL; X-band PBG cavities at LANL; and W-band PBG TWT at LANL. The presentation concludes by describing other advanced accelerator projects: beam shaping with an Emittance Exchanger, diamond field emitter array cathodes, and additive manufacturing of novel accelerator structures.

  10. Inter-beat intervals of cardiac-cell aggregates during exposure to 2.45 GHz CW, pulsed, and square-wave-modulated microwaves.

    Science.gov (United States)

    Seaman, R L; DeHaan, R L

    1993-01-01

    Inter-beat intervals of aggregated cardiac cells from chicken embryos were studied during 190 s exposures to 2.45 GHz microwaves in an open-ended coaxial device. Averaged specific-absorption rates (SARs) and modulation conditions were 1.2-86.9 W/kg continuous-wave (CW), 1.2-12.2 W/kg pulse modulation (PW, duty cycle approximately 11%), and 12.0-43.5 W/kg square-wave modulation (duty cycle = 50%). The inter-beat interval decreased during microwave exposures at 42.0 W/kg and higher when CW or square-wave modulation was used, which is consistent with established effects of elevated temperatures. However, increases in the inter-beat interval during CW exposures at 1.2-12.2 W/kg, and decreases in the inter-beat interval after PW exposures at 8.4-12.2 W/kg, are not consistent with simple thermal effects. Analysis of variance indicated that SAR, modulation, and the modulation-SAR interaction were all significant factors in altering the inter-beat interval. The latter two factors indicated that the cardiac cells were affected by athermal as well as thermal effects of microwave exposure.

  11. Beat-to-Beat Blood Pressure Monitor

    Science.gov (United States)

    Lee, Yong Jin

    2012-01-01

    This device provides non-invasive beat-to-beat blood pressure measurements and can be worn over the upper arm for prolonged durations. Phase and waveform analyses are performed on filtered proximal and distal photoplethysmographic (PPG) waveforms obtained from the brachial artery. The phase analysis is used primarily for the computation of the mean arterial pressure, while the waveform analysis is used primarily to obtain the pulse pressure. Real-time compliance estimate is used to refine both the mean arterial and pulse pressures to provide the beat-to-beat blood pressure measurement. This wearable physiological monitor can be used to continuously observe the beat-to-beat blood pressure (B3P). It can be used to monitor the effect of prolonged exposures to reduced gravitational environments and the effectiveness of various countermeasures. A number of researchers have used pulse wave velocity (PWV) of blood in the arteries to infer the beat-to-beat blood pressure. There has been documentation of relative success, but a device that is able to provide the required accuracy and repeatability has not yet been developed. It has been demonstrated that an accurate and repeatable blood pressure measurement can be obtained by measuring the phase change (e.g., phase velocity), amplitude change, and distortion of the PPG waveforms along the brachial artery. The approach is based on comparing the full PPG waveform between two points along the artery rather than measuring the time-of-flight. Minimizing the measurement separation and confining the measurement area to a single, well-defined artery allows the waveform to retain the general shape between the two measurement points. This allows signal processing of waveforms to determine the phase and amplitude changes.

  12. Detection of a and b waves in the acceleration photoplethysmogram

    OpenAIRE

    Elgendi, Mohamed; Norton, Ian; Brearley, Matt; Abbott, Derek; Schuurmans, Dale

    2014-01-01

    Background Analyzing acceleration photoplethysmogram (APG) signals measured after exercise is challenging. In this paper, a novel algorithm that can detect a waves and consequently b waves under these conditions is proposed. Accurate a and b wave detection is an important first step for the assessment of arterial stiffness and other cardiovascular parameters. Methods Nine algorithms based on fixed thresholding are compared, and a new algorithm is introduced to improve the detection rate using...

  13. Electronic excitation by short X-ray pulses: From quantum beats to wave packet revivals

    CERN Document Server

    Riviere, Paula; Rost, Jan M

    2011-01-01

    We propose a simple way to determine the periodicities of wave packets in quantum systems directly from the energy differences of the states involved. The resulting classical periods and revival times are more accurate than those obtained with the traditional expansion of the energies about the central quantum number n, especially when n is low. The latter type of wave packet motion occurs upon excitation of highly charged ions with short XUV or X-ray pulses. Moreover, we formulate the wave packet dynamics in such a form that it directly reveals the origin of phase shifts in the maxima of the autocorrelation function. This phenomenon, so far poorly understood since it is not prominent in the high n regime, becomes a dominant feature in low n wave packet dynamics.

  14. Cosmic Rays Accelerated at Cosmological Shock Waves

    Indian Academy of Sciences (India)

    Renyi Ma; Dongsu Ryu; Hyesung Kang

    2011-03-01

    Based on hydrodynamic numerical simulations and diffusive shock acceleration model, we calculated the ratio of cosmic ray (CR) to thermal energy. We found that the CR fraction can be less than ∼ 0.1 in the intracluster medium, while it would be of order unity in the warm-hot intergalactic medium.

  15. Materials for acceleration by surface electromagnetic waves

    International Nuclear Information System (INIS)

    Recommendation to the choice of materials for accelerating dielectric resonator are elaborated on the basis of a great number of studied literature on optical resistance. A catalog of properties of material perspective for the use in this purpose is made up (CsI, Ge, LiF, SrTiO3 and etc, in particular)

  16. Breakdown of Acceleration Waves in Radiative Magneto-fluids

    Directory of Open Access Journals (Sweden)

    Arisudan Rai

    2003-10-01

    Full Text Available The problem of propagation of acceleration waves in an optically thick medium of electrically conducting fluid has been dealt with. During propagation of the waves, the effects of radiation pressure, radiation energy density, and heat transfer through thermal radiation and thermal conduction have been taken into account. The growth equation for the variation of amplitude of the wave has been derived and solved. It has been concluded that all the compressive waves with initial amplitudes greater than a critical value will grow and terminate into a shock wave due to nonlinear steepening, while all expansion waves will decay out. Acritical stage, when the compressive wave will either grow or decay, has also been discussed. The effects of radiation pressure and radiative heat transfer on the shock formation have been discussed and analysed.

  17. Plasma production for electron acceleration by resonant plasma wave

    Science.gov (United States)

    Anania, M. P.; Biagioni, A.; Chiadroni, E.; Cianchi, A.; Croia, M.; Curcio, A.; Di Giovenale, D.; Di Pirro, G. P.; Filippi, F.; Ghigo, A.; Lollo, V.; Pella, S.; Pompili, R.; Romeo, S.; Ferrario, M.

    2016-09-01

    Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to provide very high accelerating fields (10-100 GV/m), enabling acceleration of electrons to GeV energy in few centimeter. However, the quality of the electron bunches accelerated with this technique is still not comparable with that of conventional accelerators (large energy spread, low repetition rate, and large emittance); radiofrequency-based accelerators, in fact, are limited in accelerating field (10-100 MV/m) requiring therefore hundred of meters of distances to reach the GeV energies, but can provide very bright electron bunches. To combine high brightness electron bunches from conventional accelerators and high accelerating fields reachable with plasmas could be a good compromise allowing to further accelerate high brightness electron bunches coming from LINAC while preserving electron beam quality. Following the idea of plasma wave resonant excitation driven by a train of short bunches, we have started to study the requirements in terms of plasma for SPARC_LAB (Ferrario et al., 2013 [1]). In particular here we focus on hydrogen plasma discharge, and in particular on the theoretical and numerical estimates of the ionization process which are very useful to design the discharge circuit and to evaluate the current needed to be supplied to the gas in order to have full ionization. Eventually, the current supplied to the gas simulated will be compared to that measured experimentally.

  18. The acceleration of cosmic rays by shock waves

    International Nuclear Information System (INIS)

    The direct transfer of energy to cosmic rays from supersonic motions of the background medium via shock waves, by means of an efficient first order Fermi mechanism, is considered. The acceleration of cosmic rays by shock waves is most effective in the dilute and hot, 1,000,000-K component of the interstellar medium. There is no limit to the energy that can be achieved by shock acceleration, if enough time is available and the particles can be contained in the vicinity of the shock. The two basic first order Fermi mechanisms contributing to the overall process of shock acceleration of cosmic rays are reflection at, or transmission through, the magnetic field jump associated with the shock, and multiple reflection between the media upstream and downstream of the shock, due to the presence of waves that scatter the particles in pitch angle

  19. Traveling wave linear accelerator with RF power flow outside of accelerating cavities

    Energy Technology Data Exchange (ETDEWEB)

    Dolgashev, Valery A.

    2016-06-28

    A high power RF traveling wave accelerator structure includes a symmetric RF feed, an input matching cell coupled to the symmetric RF feed, a sequence of regular accelerating cavities coupled to the input matching cell at an input beam pipe end of the sequence, one or more waveguides parallel to and coupled to the sequence of regular accelerating cavities, an output matching cell coupled to the sequence of regular accelerating cavities at an output beam pipe end of the sequence, and output waveguide circuit or RF loads coupled to the output matching cell. Each of the regular accelerating cavities has a nose cone that cuts off field propagating into the beam pipe and therefore all power flows in a traveling wave along the structure in the waveguide.

  20. Observation of autoionization dynamics and sub-cycle quantum beating in electronic molecular wave packets

    Science.gov (United States)

    Reduzzi, M.; Chu, W.-C.; Feng, C.; Dubrouil, A.; Hummert, J.; Calegari, F.; Frassetto, F.; Poletto, L.; Kornilov, O.; Nisoli, M.; Lin, C.-D.; Sansone, G.

    2016-03-01

    The coherent interaction with ultrashort light pulses is a powerful strategy for monitoring and controlling the dynamics of wave packets in all states of matter. As light presents an oscillation period of a few femtoseconds (T = 2.6 fs in the near infrared spectral range), an external optical field can induce changes in a medium on the sub-cycle timescale, i.e. in a few hundred attoseconds. In this work, we resolve the dynamics of autoionizing states on the femtosecond timescale and observe the sub-cycle evolution of a coherent electronic wave packet in a diatomic molecule, exploiting a tunable ultrashort extreme ultraviolet pulse and a synchronized infrared field. The experimental observations are based on measuring the variations of the extreme ultraviolet radiation transmitted through the molecular gas. The different mechanisms contributing to the wave packet dynamics are investigated through theoretical simulations and a simple three level model. The method is general and can be extended to the investigation of more complex systems.

  1. Beating the spin-down limit on gravitational wave emission from the Vela pulsar

    CERN Document Server

    Abadie, J; Abbott, R; Abernathy, M; Accadia, T; Acernese, F; Adams, C; Adhikari, R; Affeldt, C; Allen, B; Allen, G S; Ceron, E Amador; Amariutei, D; Amin, R S; Anderson, S B; Anderson, W G; Antonucci, F; Arai, K; Arain, M A; Araya, M C; Aston, S M; Astone, P; Atkinson, D; Aufmuth, P; Aulbert, C; Aylott, B E; Babak, S; Baker, P; Ballardin, G; Ballmer, S; Barker, D; Barnum, S; Barone, F; Barr, B; Barriga, P; Barsotti, L; Barsuglia, M; Barton, M A; Bartos, I; Bassiri, R; Bastarrika, M; Basti, A; Bauchrowitz, J; Bauer, Th S; Behnke, B; Beker, M BejgerM G; Bell, A S; Belletoile, A; Belopolski, I; Benacquista, M; Bertolini, A; Betzwieser, J; Beveridge, N; Beyersdorf, P T; Bilenko, I A; Billingsley, G; Birch, J; Birindelli, S; Biswas, R; Bitossi, M; Bizouard, M A; Black, E; Blackburn, J K; Blackburn, L; Blair, D; Bland, B; Blom, M; Bock, O; Bodiya, T P; Bogan, C; Bondarescu, R; Bondu, F; Bonelli, L; Bonnand, R; Bork, R; Born, M; Boschi, V; Bose, S; Bosi, L; Bouhou, B; Boyle, M; Braccini, S; Bradaschia, C; Brady, P R; Braginsky, V B; Brau, J E; Breyer, J; Bridges, D O; Brillet, A; Brinkmann, M; Brisson, V; Britzger, M; Brooks, A F; Brown, D A; Brummit, A; Budzyński, R; Bulik, T; Bulten, H J; Buonanno, A; Burguet--Castell, J; Burmeister, O; Buskulic, D; Buy, C; Byer, R L; Cadonati, L; Cagnoli, G; Cain, J; Calloni, E; Camp, J B; Campagna, E; Campsie, P; Cannizzo, J; Cannon, K; Canuel, B; Cao, J; Capano, C; Carbognani, F; Caride, S; Caudill, S; Cavaglià, M; Cavalier, F; Cavalieri, R; Cella, G; Cepeda, C; Cesarini, E; Chaibi, O; Chalermsongsak, T; Chalkley, E; Charlton, P; Chassande-Mottin, E; Chelkowski, S; Chen, Y; Chincarini, A; Christensen, N; Chua, S S Y; Chung, C T Y; Chung, S; Clara, F; Clark, D; Clark, J; Clayton, J H; Cleva, F; Coccia, E; Colacino, C N; Colas, J; Colla, A; Colombini, M; Conte, R; Cook, D; Corbitt, T R; Cornish, N; Corsi, A; Costa, C A; Coughlin, M; Coulon, J -P; Coward, D M; Coyne, D C; Creighton, J D E; Creighton, T D; Cruise, A M; Culter, R M; Cumming, A; Cunningham, L; Cuoco, E; Dahl, K; Danilishin, S L; Dannenberg, R; D'Antonio, S; Danzmann, K; Das, K; Dattilo, V; Daudert, B; Daveloza, H; Davier, M; Davies, G; Daw, E J; Day, R; Dayanga, T; De Rosa, R; DeBra, D; Debreczeni, G; Degallaix, J; del Prete, M; Dent, T; Dergachev, V; DeRosa, R; DeSalvo, R; Dhurandhar, S; Di Fiore, L; Di Lieto, A; Di Palma, I; Emilio, M Di Paolo; Di Virgilio, A; Díaz, M; Dietz, A; Donovan, F; Dooley, K L; Dorsher, S; Douglas, E S D; Drago, M; Drever, R W P; Driggers, J C; Dumas, J -C; Dwyer, S; Eberle, T; Edgar, M; Edwards, M; Effler, A; Ehrens, P; Engel, R; Etzel, T; Evans, M; Evans, T; Factourovich, M; Fafone, V; Fairhurst, S; Fan, Y; Farr, B F; Fazi, D; Fehrmann, H; Feldbaum, D; Ferrante, I; Fidecaro, F; Finn, L S; Fiori, I; Flaminio, R; Flanigan, M; Foley, S; Forsi, E; Forte, L A; Fotopoulos, N; Fournier, J -D; Franc, J; Frasca, S; Frasconi, F; Frede, M; Frei, M; Frei, Z; Freise, A; Frey, R; Fricke, T T; Friedrich, D; Fritschel, P; Frolov, V V; Fulda, P; Fyffe, M; Galimberti, M; Gammaitoni, L; Garcia, J; Garofoli, J A; Garufi, F; Gáspár, M E; Gemme, G; Genin, E; Gennai, A; Ghosh, S; Giaime, J A; Giampanis, S; Giardina, K D; Giazotto, A; Gill, C; Goetz, E; Goggin, L M; González, G; Gorodetsky, M L; Goßler, S; Gouaty, R; Graef, C; Granata, M; Grant, A; Gras, S; Gray, C; Greenhalgh, R J S; Gretarsson, A M; Greverie, C; Grosso, R; Grote, H; Grunewald, S; Guidi, G M; Guido, C; Gupta, R; Gustafson, E K; Gustafson, R; Hage, B; Hallam, J M; Hammer, D; Hammond, G; Hanks, J; Hanna, C; Hanson, J; Harms, J; Harry, G M; Harry, I W; Harstad, E D; Hartman, M T; Haughian, K; Hayama, K; Hayau, J -F; Hayler, T; Heefner, J; Heitmann, H; Hello, P; Hendry, M A; Heng, I S; Heptonstall, A W; Herrera, V; Hewitson, M; Hild, S; Hoak, D; Hodge, K A; Holt, K; Hong, T; Hooper, S; Hosken, D J; Hough, J; Howell, E J; Huet, D; Hughey, B; Husa, S; Huttner, S H; Ingram, D R; Inta, R; Isogai, T; Ivanov, A; Jaranowski, P; Johnson, W W; Jones, D I; Jones, G; Jones, R; Ju, L; Kalmus, P; Kalogera, V; Kandhasamy, S; Kanner, J B; Katsavounidis, E; Katzman, W; Kawabe, K; Kawamura, S; Kawazoe, F; Kells, W; Kelner, M; Keppel, D G; Khalaidovski, A; Khalili, F Y; Khazanov, E A; Kim, H; Kim, N; King, P J; Kinzel, D L; Kissel, J S; Klimenko, S; Kondrashov, V; Kopparapu, R; Koranda, S; Korth, W Z; Kowalska, I; Kozak, D; Kringel, V; Krishnamurthy, S; Krishnan, B; Królak, A; Kuehn, G; Kumar, R; Kwee, P; Landry, M; Lantz, B; Lastzka, N; Lazzarini, A; Leaci, P; Leong, J; Leonor, I; Leroy, N; Letendre, N; Li, J; Li, T G F; Liguori, N; Lindquist, P E; Lockerbie, N A; Lodhia, D; Lorenzini, M; Loriette, V; Lormand, M; Losurdo, G; Lu, P; Luan, J; Lubinski, M; Lück, H; Lundgren, A P; Macdonald, E; Machenschalk, B; MacInnis, M; Mageswaran, M; Mailand, K; Majorana, E; Maksimovic, I; Man, N; Mandel, I; Mandic, V; Mantovani, M; Marandi, A; Marchesoni, F

    2011-01-01

    We present direct upper limits on continuous gravitational wave emission from the Vela pulsar using data from the Virgo detector's second science run. These upper limits have been obtained using three independent methods that assume the gravitational wave emission follows the radio timing. Two of the methods produce frequentist upper limits for an assumed known orientation of the star's spin axis and value of the wave polarization angle of, respectively, $1.9\\ee{-24}$ and $2.2\\ee{-24}$, with 95% confidence. The third method, under the same hypothesis, produces a Bayesian upper limit of $2.1\\ee{-24}$, with 95% degree of belief. These limits are below the indirect {\\it spin-down limit} of $3.3\\ee{-24}$ for the Vela pulsar, defined by the energy loss rate inferred from observed decrease in Vela's spin frequency, and correspond to a limit on the star ellipticity of $\\sim 10^{-3}$. Slightly less stringent results, but still well below the spin-down limit, are obtained assuming the star's spin axis inclination and ...

  2. High frequency single mode traveling wave structure for particle acceleration

    Science.gov (United States)

    Ivanyan, M. I.; Danielyan, V. A.; Grigoryan, B. A.; Grigoryan, A. H.; Tsakanian, A. V.; Tsakanov, V. M.; Vardanyan, A. S.; Zakaryan, S. V.

    2016-09-01

    The development of the new high frequency slow traveling wave structures is one of the promising directions in accomplishment of charged particles high acceleration gradient. The disc and dielectric loaded structures are the most known structures with slowly propagating modes. In this paper a large aperture high frequency metallic two-layer accelerating structure is studied. The electrodynamical properties of the slowly propagating TM01 mode in a metallic tube with internally coated low conductive thin layer are examined.

  3. Electronic excitation by short x-ray pulses: from quantum beats to wave packet revivals

    Science.gov (United States)

    Rivière, P.; Iqbal, S.; Rost, J. M.

    2014-06-01

    We propose a simple way to determine the periodicities of wave packets (WPs) in quantum systems directly from the energy differences of the states involved. The resulting classical periods and revival times are more accurate than those obtained with the traditional expansion of the energies about the central quantum number \\overline{n}, especially when \\overline{n} is low. The latter type of WP motion occurs upon excitation of highly charged ions with short XUV or x-ray pulses. Moreover, we formulate the WP dynamics in such a form that it directly reveals the origin of phase shifts in the maxima of the autocorrelation function, a phenomenon most prominent in the low \\overline{n} WP dynamics.

  4. Numeric Spectrum of Relic Gravitational Waves in Accelerating Universe

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yang; ZHAO Wen; YUAN Ye-Fei; XIA Tian-Yang

    2005-01-01

    @@ The accelerating expansion of the Universe in the present stage is a process that will change the spectrum of relic gravitational waves. Here we present a numerical calculation for the power spectrum of relic gravitational waves in the accelerating Universe. The results show that although the overall features of the power spectrum are similar to those in the non-accelerating models, the amplitude is smaller in order of 10-1. We also find that the spectrum is very sensitive to the index β of the inflationary expansion with the scale factor a(τ) ∝ |τ|1+β. With increase of β, the resulting spectrum tends to be flatter with more power on high frequencies, and the sensitivity of the second science run of the LIGO detectors puts a restriction on the parameterβ< -1.8. The influence of reheating followed by the inflation has been examined.

  5. Thomson scattering and ponderomotive intermodulation within standing laser beat waves in plasma

    International Nuclear Information System (INIS)

    Electrons in a standing electromagnetic wave--an optical lattice--tend to oscillate due to the quiver and ponderomotive potentials. For sufficiently intense laser fields (Iλ2 17 W cm-2 μm2) and in plasmas with sufficiently low electron densities (n 18 cm-3), these oscillations can occur faster than the plasma can respond. This paper shows that these oscillations result in Thomson scattering of light at both the laser and ponderomotive bounce frequencies and their harmonics as well as at mixtures of these frequencies. We term this mixing ponderomotive intermodulation. Here, the case of counterpropagating laser beams creating a one-dimensional (1D) optical lattice is analyzed. The near-equilibrium electron orbits and subsequent Thomson scattering patterns are computed in the single-particle limit. Scaling laws are derived to quantify the range of validity of this approach. Finally, collective plasma and laser focusing effects are included by using particle-in-cell (PIC) techniques. This effect resulting in light-frequency conversion has applications both as an infrared light source and as a means to diagnose high laser intensities inside dense plasmas

  6. Stochastic electron acceleration during turbulent reconnection in strong shock waves

    Science.gov (United States)

    Matsumoto, Yosuke

    2016-04-01

    Acceleration of charged particles is a fundamental topic in astrophysical, space and laboratory plasmas. Very high energy particles are commonly found in the astrophysical and planetary shocks, and in the energy releases of solar flares and terrestrial substorms. Evidence for relativistic particle production during such phenomena has attracted much attention concerning collisionless shock waves and magnetic reconnection, respectively, as ultimate plasma energization mechanisms. While the energy conversion proceeds macroscopically, and therefore the energy mostly flows to ions, plasma kinetic instabilities excited in a localized region have been considered to be the main electron heating and acceleration mechanisms. We present that efficient electron energization can occur in a much larger area during turbulent magnetic reconnection from the intrinsic nature of a strong collisionless shock wave. Supercomputer simulations have revealed a multiscale shock structure comprising current sheets created via an ion-scale Weibel instability and resulting energy dissipation through magnetic reconnection. A part of the upstream electrons undergoes first-order Fermi acceleration by colliding with reconnection jets and magnetic islands, giving rise to a nonthermal relativistic population downstream. The dynamics has shed new light on magnetic reconnection as an agent of energy dissipation and particle acceleration in strong shock waves.

  7. Characterising the acceleration phase of blast wave formation

    International Nuclear Information System (INIS)

    Intensely heated, localised regions in uniform fluids will rapidly expand and generate an outwardly propagating blast wave. The Sedov-Taylor self-similar solution for such blast waves has long been studied and applied to a variety of scenarios. A characteristic time for their formation has also long been identified using dimensional analysis, which by its very nature, can offer several interpretations. We propose that, rather than simply being a characteristic time, it may be interpreted as the definitive time taken for a blast wave resulting from an intense explosion in a uniform media to contain its maximum kinetic energy. A scaling relation for this measure of the acceleration phase, preceding the establishment of the blast wave, is presented and confirmed using a 1D planar hydrodynamic model

  8. Heat wave beats green wave: the effect of a climate extreme on alpine grassland phenology as seen by phenocams

    Science.gov (United States)

    Cremonese, Edoardo; Filippa, Gianluca; Migliavacca, Mirco; Siniscalco, Consolata; Oddi, Ludovica; Galvagno, Marta

    2016-04-01

    The year 2015 has been one of the warmest on record for many regions of the world. The record-breaking temperatures did not spare the European Alps, where the summer anomaly reached +4°C. This heat wave caused important impacts on the seasonal development and structural properties of alpine grasslands that deserve investigations. Phenocams are useful tools to describe canopy greenness seasonal dynamics and many recent studies demonstrated that the major phenological events (e.g. budbrust, senescence, …) can be extracted from greenness trajectories. In contrast, little is know about their capabilities to describe the impact of extreme climate events on a fully developed canopy. Moreover the relation between quantitative structural and functional vegetation properties (e.g. biomass, LAI, …) and phenocam data remains poorly investigated. In this study we examine the impact of the 2015 summer heat wave on a subalpine grassland by jointly analyzing phenocam greenness trajectories, proximal sensing and flux data together with field measures of vegetation structural properties. The effect of different environmental drivers on greenness seasonal development was further evaluated by a modeling approach (GSI model). Phenocam tracked the impact of heatwave 2015 that caused a lower canopy development and an anticipation of yellowing by more than 2 months. The same pattern was observed for CO2 fluxes, NDVI and field measures. GSI model results show that during the heatwave, a combination of moisture and high temperature limitation was responsible for the observed reduction of the canopy development. Moreover, spatially explicit analysis of digital images allowed to highlight the differential response of specific plant functional types to the extreme event.

  9. Dynamics of electron acceleration in laser-driven wakefields. Acceleration limits and asymmetric plasma waves

    Energy Technology Data Exchange (ETDEWEB)

    Popp, Antonia

    2011-12-16

    The experiments presented in this thesis study several aspects of electron acceleration in a laser-driven plasma wave. High-intensity lasers can efficiently drive a plasma wave that sustains electric fields on the order of 100 GV/m. Electrons that are trapped in this plasma wave can be accelerated to GeV-scale energies. As the accelerating fields in this scheme are 3-4 orders of magnitude higher than in conventional radio-frequency accelerators, the necessary acceleration distance can be reduced by the same factor, turning laser-wakefield acceleration (LWFA) into a promising compact, and potentially cheaper, alternative. However, laser-accelerated electron bunches have not yet reached the parameter standards of conventional accelerators. This work will help to gain better insight into the acceleration process and to optimize the electron bunch properties. The 25 fs, 1.8 J-pulses of the ATLAS laser at the Max-Planck-Institute of Quantum Optics were focused into a steady-state flow gas cell. This very reproducible and turbulence-free gas target allows for stable acceleration of electron bunches. Thus the sensitivity of electron parameters to subtle changes of the experimental setup could be determined with meaningful statistics. At optimized experimental parameters, electron bunches of {approx}50 pC total charge were accelerated to energies up to 450 MeV with a divergence of {approx}2 mrad FWHM. As, in a new design of the gas cell, its length can be varied from 2 to 14 mm, the electron bunch energy could be evaluated after different acceleration distances, at two different electron densities. From this evolution important acceleration parameters could be extracted. At an electron density of 6.43. 10{sup 18} cm{sup -3} the maximum electric field strength in the plasma wave was determined to be {approx}160 GV/m. The length after which the relativistic electrons outrun the accelerating phase of the electric field and are decelerated again, the so-called dephasing length

  10. Dynamics of electron acceleration in laser-driven wakefields. Acceleration limits and asymmetric plasma waves

    International Nuclear Information System (INIS)

    The experiments presented in this thesis study several aspects of electron acceleration in a laser-driven plasma wave. High-intensity lasers can efficiently drive a plasma wave that sustains electric fields on the order of 100 GV/m. Electrons that are trapped in this plasma wave can be accelerated to GeV-scale energies. As the accelerating fields in this scheme are 3-4 orders of magnitude higher than in conventional radio-frequency accelerators, the necessary acceleration distance can be reduced by the same factor, turning laser-wakefield acceleration (LWFA) into a promising compact, and potentially cheaper, alternative. However, laser-accelerated electron bunches have not yet reached the parameter standards of conventional accelerators. This work will help to gain better insight into the acceleration process and to optimize the electron bunch properties. The 25 fs, 1.8 J-pulses of the ATLAS laser at the Max-Planck-Institute of Quantum Optics were focused into a steady-state flow gas cell. This very reproducible and turbulence-free gas target allows for stable acceleration of electron bunches. Thus the sensitivity of electron parameters to subtle changes of the experimental setup could be determined with meaningful statistics. At optimized experimental parameters, electron bunches of ∼50 pC total charge were accelerated to energies up to 450 MeV with a divergence of ∼2 mrad FWHM. As, in a new design of the gas cell, its length can be varied from 2 to 14 mm, the electron bunch energy could be evaluated after different acceleration distances, at two different electron densities. From this evolution important acceleration parameters could be extracted. At an electron density of 6.43. 1018 cm-3 the maximum electric field strength in the plasma wave was determined to be ∼160 GV/m. The length after which the relativistic electrons outrun the accelerating phase of the electric field and are decelerated again, the so-called dephasing length, was found to be 4.9 mm

  11. 铷原子中参量六波混频和量子拍的研究%Parametric Six-Wave Mixing and Quantum Beatings in Rb

    Institute of Scientific and Technical Information of China (English)

    朱长军; 薛兵; 翟学军; 贺俊芳

    2009-01-01

    在铷原子中实现了轴向相位匹配的参量六波混频,并探测到位于红外光谱区的六波混频信号.六波混频信号与泵浦激光进行和频,产生了位于可见光范围内的可调谐的和频信号,并从和频信号中观察到频率为608 cm-1的量子拍.结果表明,六波混频信号中的量子拍能够用于研究原子和分子的相干特性.%Axially phase-matched parametric six-wave mixing was achieved in Rb and the parametric six-wave mixing signals in the infrared range were detected. Tunable signals in the visible range were produced by sum-frequency mixing of the pump laser and the parametric six-wave mixing signals in the infrared range. And, quantum beating at a frequency of 608 cm-1 was observed from the sum-frequency signal, indicating that the coherent properties of atoms and molecules can be studied by means of quantum beating recovered from parametric six-wave mixing signals.

  12. Chirped standing wave acceleration of ions with intense lasers

    CERN Document Server

    Mackenroth, Felix; Marklund, Mattias

    2016-01-01

    We propose a novel mechanism for ion acceleration based on the guided motion of electrons from a thin target. The electron motion is locked to the moving nodes of a standing wave formed by a chirped laser pulse reflected from a mirror behind the target. This provides a stable longitudinal field of charge separation, thus giving rise to chirped standing wave acceleration (CSWA) of the residual ions of the layer. We demonstrate, both analytically and numerically, that quasi-monoenergetic ion beams with energies of the order 100 MeV are feasible for realistic pulse energies of 10 J. Moreover, a scaling law for higher laser intensities and layer densities is presented, indicating stable GeV-level energy gains of dense ion bunches, for soon-to-be available laser intensities.

  13. Demonstrations that the Solar Wind Is Not Accelerated by Waves

    Science.gov (United States)

    Roberts, Aaron

    2008-01-01

    The present work uses both observations and theoretical considerations to show that hydromagnetic waves cannot produce the acceleration of the fast solar wind and the related heating of the open solar corona. Waves do exist, and can play a role in the differential heating and acceleration of minor ions, but their amplitudes are not sufficient to power the wind, as demonstrated by extrapolation of magnetic spectra from Helios and Ulysses observations. Dissipation mechanisms invoked to circumvent this conclusion cannot be effective for a variety of reasons. In particular, turbulence does not play a strong role in the corona as shown by both observations of coronal striations and theoretical considerations of line-tying to a nonturbulent photosphere, nonlocality of interactions, and the nature of the kinetic dissipation. In the absence of wave heating and acceleration, the chromosphere and transition region become the natural source of open coronal energization. We suggest a variant of the 'velocity filtration' approach in which the emergence and complex churning of the magnetic flux in the chromosphere and transition region continuously and ubiquitously produces the nonthermal distributions required. These particles are then released by magnetic carpet reconnection at a wide range of scales and produce the wind as described in kinetic approaches. Since the carpet reconnection is not the main source of the energization of the plasma, there is no expectation of an observable release of energy in nanoflares.

  14. Solid-particle jet formation under shock-wave acceleration.

    Science.gov (United States)

    Rodriguez, V; Saurel, R; Jourdan, G; Houas, L

    2013-12-01

    When solid particles are impulsively dispersed by a shock wave, they develop a spatial distribution which takes the form of particle jets whose selection mechanism is still unidentified. The aim of the present experimental work is to study particle dispersal with fingering effects in an original quasi-two-dimensional experiment facility in order to accurately extract information. Shock and blast waves are generated in the carrier gas at the center of a granular medium ring initially confined inside a Hele-Shaw cell and impulsively accelerated. With the present experimental setup, the particle jet formation is clearly observed. From fast flow visualizations, we notice, in all instances, that the jets are initially generated inside the particle ring and thereafter expelled outward. This point has not been observed in three-dimensional experiments. We highlight that the number of jets is unsteady and decreases with time. For a fixed configuration, considering the very early times following the initial acceleration, the jet size selection is independent of the particle diameter. Moreover, the influence of the initial overpressure and the material density on the particle jet formation have been studied. It is shown that the wave number of particle jets increases with the overpressure and with the decrease of the material density. The normalized number of jets as a function of the initial ring acceleration shows a power law valid for all studied configurations involving various initial pressure ratios, particle sizes, and particle materials. PMID:24483561

  15. Resonance control for a cw [continuous wave] accelerator

    International Nuclear Information System (INIS)

    A resonance-control technique is described that has been successfully applied to several cw accelerating structures built by the Los Alamos National Laboratory for the National Bureau of Standards and for the University of Illinois. The technique involves sensing the rf fields in an accelerating structure as well as the rf power feeding into the cavity and, then, using the measurement to control the resonant frequency of the structure by altering the temperature of the structure. The temperature of the structure is altered by adjusting the temperature of the circulating cooling water. The technique has been applied to continuous wave (cw) side-coupled cavities only but should have applications with most high-average-power accelerator structures. Some additional effort would be required for pulsed systems

  16. Accelerated electron populations formed by Langmuir wave-caviton interactions

    CERN Document Server

    Sircombe, N J; Dendy, R O

    2004-01-01

    Direct numerical simulations of electron dynamics in externally driven electrostatic waves have been carried out using a relativistic two-fluid one-dimensional Vlasov-Poisson code. When the driver wave has sufficiently large amplitude, ion density holes (cavitons) form. The interaction between these cavitons and other incoming Langmuir waves gives rise to substantial local acceleration of groups of electrons, and fine jet-like structures arise in electron phase space. We show that these jets are caused by wave-breaking when finite amplitude Langmuir waves experience the ion density gradient at the leading edge of the holes, and are not caused by caviton burn-out. An analytical two-fluid model gives the critical density gradient and caviton depth for which this process can occur. In particular, the density gradient critically affects the rate at which a Langmuir wave, moving into the caviton, undergoes Landau damping. This treatment also enables us to derive analytical estimates for the maximum energy of accel...

  17. Improved ion acceleration via laser surface plasma waves excitation

    Energy Technology Data Exchange (ETDEWEB)

    Bigongiari, A. [CEA/DSM/LSI, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France); TIPS/LULI, Université Paris 6, CNRS, CEA, Ecole Polytechnique, 3, rue Galilée, 94200 Ivry-sur-Seine (France); Raynaud, M. [CEA/DSM/LSI, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France); Riconda, C. [TIPS/LULI, Université Paris 6, CNRS, CEA, Ecole Polytechnique, 3, rue Galilée, 94200 Ivry-sur-Seine (France); Héron, A. [CPHT, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France)

    2013-05-15

    The possibility of enhancing the emission of the ions accelerated in the interaction of a high intensity ultra-short (<100 fs) laser pulse with a thin target (<10λ{sub 0}), via surface plasma wave excitation is investigated. Two-dimensional particle-in-cell simulations are performed for laser intensities ranging from 10{sup 19} to 10{sup 20} Wcm{sup −2}μm{sup 2}. The surface wave is resonantly excited by the laser via the coupling with a modulation at the target surface. In the cases where the surface wave is excited, we find an enhancement of the maximum ion energy of a factor ∼2 compared to the cases where the target surface is flat.

  18. Low power RF measurements of travelling wave type linear accelerator

    International Nuclear Information System (INIS)

    RRCAT is engaged in the development of travelling wave (TW) type linear accelerator for irradiation of industrial and agricultural products. TW accelerator designed for 2π/3 mode to operate at frequency of 2856 MHz. It consists of input coupler, buncher cells, regular cells and output coupler. Low power measurement of this structure includes measurement of resonant frequency of the cells for different resonant modes and quality factor, tuning of input-output coupler and measurement of phase advance per cell and electric field in the structure. Steele's non-resonant perturbation technique has been used for measurement of phase advance per cell and electric field in the structure. Kyhl's method has been used for the tuning of input-output coupler. Computer based automated bead pull set-up has been developed for measurement of phase advance per cell and electric field profile in the structure. All the codes are written in Python for interfacing of Vector Network Analyzer (VNA) , stepper motor with computer. These codes also automate the measurement process. This paper describes the test set- up for measurement and results of measurement of travelling wave type linear accelerating structure. (author)

  19. Particle Acceleration at Relativistic and Ultra-Relativistic Shock Waves

    Science.gov (United States)

    Meli, A.

    We perform Monte Carlo simulations using diffusive shock acceleration at relativistic and ultra-relativistic shock waves. High upstream flow gamma factors are used, Γ=(1-uup2/c2)-0.5, which are relevant to models of ultra-relativistic particle shock acceleration in the central engines and relativistic jets of Active Galactic Nuclei (AGN) and in Gamma-Ray Burst (GRB) fireballs. Numerical investigations are carried out on acceleration properties in the relativistic and ultra-relativistic flow regime (Γ ˜ 10-1000) concerning angular distributions, acceleration time scales, particle energy gain versus number of crossings and spectral shapes. We perform calculations for both parallel and oblique sub-luminal and super-luminal shocks. For parallel and oblique sub-luminal shocks, the spectra depend on whether or not the scattering is represented by pitch angle diffusion or by large angle scattering. The large angle case exhibits a distinctive structure in the basic power-law spectrum not nearly so obvious for small angle scattering. However, both cases yield a significant 'speed-up' of acceleration rate when compared with the conventional, non-relativistic expression, tacc=[c/(uup-udown)] (λup/uup+λdown/udown). An energization by a factor Γ2 for the first crossing cycle and a large energy gains for subsequent crossings as well as the high 'speed-up' factors found, are important in supporting past works, especially the models developed by Vietri and Waxman on ultra-high energy cosmic ray, neutrino and gamma-ray production in GRB. For oblique super-luminal shocks, we calculate the energy gain and spectral shape for a number of different inclinations. For this case the acceleration of particles is 'pictured' by a shock drift mechanism. We use high gamma flows with Lorentz factors in the range 10-40 which are relevant to ultra-relativistic shocks in AGN accretion disks and jets. In all investigations we closely follow the particle's trajectory along the magnetic field

  20. A tuning method for nonuniform traveling-wave accelerating structures

    International Nuclear Information System (INIS)

    The tuning method of uniform traveling-wave structures based on non-resonant perturbation field distribution measurement has been widely used in tuning both constant-impedance and constant-gradient structures. In this paper, the method of tuning nonuniform structures is proposed on the basis of the above theory. The internal reflection coefficient of each cell is obtained from analyzing the normalized voltage distribution. A numerical simulation of tuning process according to the coupled cavity chain theory has been done and the result shows each cell is in right phase advance after tuning. The method will be used in the tuning of a disk-loaded traveling-wave structure being developed at the Accelerator Laboratory, Tsinghua University. (authors)

  1. Fast acceleration of 2D wave propagation simulations using modern computational accelerators.

    Directory of Open Access Journals (Sweden)

    Wei Wang

    Full Text Available Recent developments in modern computational accelerators like Graphics Processing Units (GPUs and coprocessors provide great opportunities for making scientific applications run faster than ever before. However, efficient parallelization of scientific code using new programming tools like CUDA requires a high level of expertise that is not available to many scientists. This, plus the fact that parallelized code is usually not portable to different architectures, creates major challenges for exploiting the full capabilities of modern computational accelerators. In this work, we sought to overcome these challenges by studying how to achieve both automated parallelization using OpenACC and enhanced portability using OpenCL. We applied our parallelization schemes using GPUs as well as Intel Many Integrated Core (MIC coprocessor to reduce the run time of wave propagation simulations. We used a well-established 2D cardiac action potential model as a specific case-study. To the best of our knowledge, we are the first to study auto-parallelization of 2D cardiac wave propagation simulations using OpenACC. Our results identify several approaches that provide substantial speedups. The OpenACC-generated GPU code achieved more than 150x speedup above the sequential implementation and required the addition of only a few OpenACC pragmas to the code. An OpenCL implementation provided speedups on GPUs of at least 200x faster than the sequential implementation and 30x faster than a parallelized OpenMP implementation. An implementation of OpenMP on Intel MIC coprocessor provided speedups of 120x with only a few code changes to the sequential implementation. We highlight that OpenACC provides an automatic, efficient, and portable approach to achieve parallelization of 2D cardiac wave simulations on GPUs. Our approach of using OpenACC, OpenCL, and OpenMP to parallelize this particular model on modern computational accelerators should be applicable to other

  2. Birefringence-induced frequency beating in high-finesse cavities by continuous-wave cavity ring-down spectroscopy

    Science.gov (United States)

    Dupré, Patrick

    2015-11-01

    By analyzing the decaying intensity, leaking out a high-finesse cavity previously "filled" by a cw laser source (using the cavity ring-down spectroscopy technique), we observed frequency beating between what we think are two orthogonal eigenpolarization states of the intracavity electromagnetic field. The time decay (ring down) is analyzed by varying the angle of the polarization analyzer located in front of the detector. A full modeling of the observed signal is proposed. It is based on the Jones matrix formalism required for modeling the cavity behavior following a rotated phase shifter. The full transfer function is first established in the frequency domain, and then Fourier transformed to recover the temporal response. The same optical cavity, i.e., constituted of the same set of mirrors, is used at two different wavelengths (˜800 and ˜880 nm). It demonstrates the differences in behavior between a high-finesse cavity (˜400 000 ) and a lower finesse cavity (˜50 000 ). Beating frequency, characteristics time, and beat amplitude are mainly discussed versus the analyzer angle. A cavity birefringence of ˜1.6 ×10-5 rad, resulting from the mirror birefringence is suggested. If the current analysis is in agreement with pulsed CRDS experiments (polarimetry) obtained in an isotropic moderate-finesse cavity, it differs from a recent work report on a high-finesse cavity associated with a source mode locking [Phys. Rev. A 85, 013837 (2012), 10.1103/PhysRevA.85.013837].

  3. LIGA-fabricated compact mm-wave linear accelerator cavities.

    Energy Technology Data Exchange (ETDEWEB)

    Song, J.J.; Bajikar, S.S.; DeCarlo, F.; Kang, Y.W.; Kustom, R.L.; Mancini, D.C.; Nassiri, A.; Lai, B.; Feinerman, A.D.; White, V.

    1998-03-23

    Millimeter-wave rf cavities for use in linear accelerators, free-electron lasers, and mm-wave undulatory are under development at Argonne National Laboratory. Typical cavity dimensions are in the 1000 mm range, and the overall length of the accelerator structure, which consists of 30-100 cavities, is about 50-100 mm. An accuracy of 0.2% in the cavity dimensions is necessary in order to achieve a high Q-factor of the cavity. To achieve this these structures are being fabricated using deep X-ray lithography, electroforming, and assembly (LIGA). The first prototype cavity structures are designed for 108 GHz and 2p/3-mode operation. Input and output couplers are integrated with the cavity structures. The cavities are fabricated on copper substrates by electroforming copper into 1-mm-thick PMMA resists patterned by deep x-ray lithography and polishing the copper down to the desired thickness. These are fabricated separately and subsequently assembled with precision spacing and alignment using microspheres, optical fibers, or microfabricated spacers/alignment pieces. Details of the fabrication process, alignment, and assembly work are presented in here.

  4. Cosmic ray acceleration at blast waves from type Ia supernovae

    CERN Document Server

    Kang, H

    2007-01-01

    We have calculated the cosmic ray (CR) acceleration at young remnants from Type Ia supernovae expanding into a uniform interstellar medium (ISM). Adopting quasi-parallel magnetic fields, gasdynamic equations and the diffusion convection equation for the particle distribution function are solved in a comoving spherical grid which expands with the shock. Bohm-type diffusion due to self-excited Alfven waves, drift and dissipation of these waves in the precursor and thermal leakage injection were included. With magnetic fields amplified by the CR streaming instability, the particle energy can reach up to 10^{16}Z eV at young supernova remnants (SNRs) of several thousand years old. The fraction of the explosion energy transferred to the CR component asymptotes to 40-50 % by that time. For a typical SNR in a warm ISM, the accelerated CR energy spectrum should exhibit a concave curvature with the power-law slope flattening from 2 to 1.6 at E>0.1 TeV.

  5. Beat Dreams?

    DEFF Research Database (Denmark)

    Sørensen, Bent

    2009-01-01

    Two of the founding members of the Beat Generation of the 1950s wrote dream books with almost identical titles: Jack Kerouac's Book of Dreams (1961) and William Burroughs' My Education: A Book of Dreams (1995). This paper queries the function of such dream books, both from a perspective of seeing...... dream writing as a confessional genre, and from the perspective of didacticism implicit in sharing one's dream life with one's readers. What role does memory, politics, fantasies and reality play in communicating with and via dreams?...

  6. Shock drift acceleration in the presence of waves

    Science.gov (United States)

    Decker, R. B.; Vlahos, L.

    1985-01-01

    Attention is given to the initial results of a model designed to study the modification of the scatter-free, shock drift acceleration of energetic test particles by wave activity in the vicinity of a quasi-perpendicular, fast-mode MHD shock. It is emphasized that the concept of magnetic moment conservation is a valid approximation only in the perpendicular and nearly perpendicular regimes, when the angle theta-Bn between the shock normal and the upstream magnetic field vector is in the range from 70 deg to 90 deg. The present investigation is concerned with one step in a program which is being developed to combine the shock drift and diffusive processes at a shock of arbitrary theta-Bn.

  7. MHD dissipative flow and heat transfer of Casson fluids due to metachronal wave propulsion of beating cilia with thermal and velocity slip effects under an oblique magnetic field

    Science.gov (United States)

    Akbar, Noreen Sher; Tripathi, D.; Bég, O. Anwar; Khan, Z. H.

    2016-11-01

    A theoretical investigation of magnetohydrodynamic (MHD) flow and heat transfer of electrically-conducting viscoplastic fluids through a channel is conducted. The robust Casson model is implemented to simulate viscoplastic behavior of fluids. The external magnetic field is oblique to the fluid flow direction. Viscous dissipation effects are included. The flow is controlled by the metachronal wave propagation generated by cilia beating on the inner walls of the channel. The mathematical formulation is based on deformation in longitudinal and transverse velocity components induced by the ciliary beating phenomenon with cilia assumed to follow elliptic trajectories. The model also features velocity and thermal slip boundary conditions. Closed-form solutions to the non-dimensional boundary value problem are obtained under physiological limitations of low Reynolds number and large wavelength. The influence of key hydrodynamic and thermo-physical parameters i.e. Hartmann (magnetic) number, Casson (viscoplastic) fluid parameter, thermal slip parameter and velocity slip parameter on flow characteristics are investigated. A comparative study is also made with Newtonian fluids (corresponding to massive values of plastic viscosity). Stream lines are plotted to visualize trapping phenomenon. The computations reveal that velocity increases with increasing the magnitude of Hartmann number near the channel walls whereas in the core flow region (center of the channel) significant deceleration is observed. Temperature is elevated with greater Casson parameter, Hartmann number, velocity slip, eccentricity parameter, thermal slip and also Brinkmann (dissipation) number. Furthermore greater Casson parameter is found to elevate the quantity and size of the trapped bolus. In the pumping region, the pressure rise is reduced with greater Hartmann number, velocity slip, and wave number whereas it is enhanced with greater cilia length.

  8. Electrostatic Wave Generation and Transverse Ion Acceleration by Alfvenic Wave Components of BBELF Turbulence

    Science.gov (United States)

    Singh, Nagendra; Khazanov, George; Mukhter, Ali

    2007-01-01

    We present results here from 2.5-D particle-in-cell simulations showing that the electrostatic (ES) components of broadband extremely low frequency (BBELF) waves could possibly be generated by cross-field plasma instabilities driven by the relative drifts between the heavy and light ion species in the electromagnetic (EM) Alfvenic component of the BBELF waves in a multi-ion plasma. The ES components consist of ion cyclotron as well as lower hybrid modes. We also demonstrate that the ES wave generation is directly involved in the transverse acceleration of ions (TAI) as commonly measured with the BBELF wave events. The heating is affected by ion cyclotron resonance in the cyclotron modes and Landau resonance in the lower hybrid waves. In the simulation we drive the plasma by the transverse electric field, E(sub y), of the EM waves; the frequency of E(sub y), omega(sub d), is varied from a frequency below the heavy ion cyclotron frequency, OMEGA(sub h), to below the light ion cyclotron frequency, OMEGA(sub i). We have also performed simulations for E(sub y) having a continuous spectrum given by a power law, namely, |Ey| approx. omega(sub d) (exp -alpha), where the exponent alpha = _, 1, and 2 in three different simulations. The driving electric field generates polarization and ExB drifts of the ions and electrons. When the interspecies relative drifts are sufficiently large, they drive electrostatic waves, which cause perpendicular heating of both light and heavy ions. The transverse ion heating found here is discussed in relation to observations from Cluster, FAST and Freja.

  9. Ion acceleration in a solitary wave by an intense picosecond laser pulse.

    Science.gov (United States)

    Zhidkov, A; Uesaka, M; Sasaki, A; Daido, H

    2002-11-18

    Acceleration of ions in a solitary wave produced by shock-wave decay in a plasma slab irradiated by an intense picosecond laser pulse is studied via particle-in-cell simulation. Instead of exponential distribution as in known mechanisms of ion acceleration from the target surface, these ions accelerated forwardly form a bunch with relatively low energy spread. The bunch is shown to be a solitary wave moving over expanding plasma; its velocity can exceed the maximal velocity of ions accelerated forward from the rear side of the target.

  10. Acceleration of charged particles in ion excitation waves in the solar corona

    International Nuclear Information System (INIS)

    A possibility of charged particle acceleration in a shock wave of isothermal compression in the transition region between the lower corona and the upper chromosphere is considered. The shock wave motion is accompanied with emission in spectral lines of multicharged ions and helium. It follows from the results of the paper that in the bursts conditioned by the motion of shock wave fronts electrons and protons are accelerated with an equal probability approximately. The times of acceleration and particle output from the region behind the front are of the same order and independent of the particle energy, but depend only on characteristic lengths of inhomogeneities in the wave front and on its velocity

  11. Continuous Wavelet Transform Analysis of Acceleration Signals Measured from a Wave Buoy

    OpenAIRE

    Laurence Zsu-Hsin Chuang; Jong-Hao Wang; Li-Chung Wu

    2013-01-01

    Accelerometers, which can be installed inside a floating platform on the sea, are among the most commonly used sensors for operational ocean wave measurements. To examine the non-stationary features of ocean waves, this study was conducted to derive a wavelet spectrum of ocean waves and to synthesize sea surface elevations from vertical acceleration signals of a wave buoy through the continuous wavelet transform theory. The short-time wave features can be revealed by simultaneously examining ...

  12. A traveling-wave forward coupler design for a new accelerating mode in a silicon woodpile accelerator

    International Nuclear Information System (INIS)

    Silicon woodpile photonic crystals provide a base structure that can be used to build a three-dimensional dielectric waveguide system for high-gradient laser driven acceleration. A new woodpile waveguide design that hosts a phase synchronous, centrally confined accelerating mode is proposed. Comparing with previously discovered silicon woodpile accelerating modes, this mode shows advantages in terms of better electron beam loading and higher achievable acceleration gradient. Several traveling-wave coupler design schemes developed for multi-cell RF cavity accelerators are adapted to the woodpile power coupler design for this new accelerating mode. Design of a forward coupled, highly efficient silicon woodpile accelerator is achieved. Simulation shows high efficiency of over 75% of the drive laser power coupled to this fundamental accelerating mode, with less than 15% backward wave scattering. The estimated acceleration gradient, when the coupler structure is driven at the damage threshold fluence of silicon at its operating 1.506 μm wavelength, can reach 185 MV/m. Lastly, a 17-layer woodpile waveguide structure was successfully fabricated, and the measured bandgap is in excellent agreement with simulation

  13. The observation of theta wave modulation on brain training by 5 Hz-binaural beat stimulation in seven days.

    Science.gov (United States)

    Yamsa-Ard, Traisak; Wongsawat, Yodchanan

    2015-08-01

    Traditional buddhist meditation method maybe easy for someone with high experience. However, for the beginner, it is very difficult to keep mental concentration with the tradition way for more than 5 minutes. This research aims to observe effect of the new method for meditation in various analysis methods. A piano music mixed with a 5 Hz (theta band enhancement) binaural beat frequency was used to modulate the brain signals continuously for 7 days. Male of the average age of 33.5±3.84 and female of the average age of 28.6±2.49 were participated. All participants were acquired EEGs twice, before the experiment and seven days after the experiment. We also proposed the observations on the changes of absolute powers, relative powers and brain connectivity (coherence) of the participants. After seven days of training, the absolute power, relative power, and coherence were clearly closer to the normative database. We can initially say that the recommended meditation method can efficiently mimic the effect of having the traditional buddhist meditation on enhancing the delta and theta powers in the brain. PMID:26737822

  14. Simple Scalings for Various Regimes of Electron Acceleration in Surface Plasma Waves

    OpenAIRE

    Riconda, C; Raynaud, M.; Vialis, T.; Grech, M.

    2015-01-01

    International audience Different electron acceleration regimes in the evanescent field of a surface plasma wave are studied by considering the interaction of a test electron with the high-frequency electromagnetic field of a surface wave. The non-relativistic and relativistic limits are investigated. Simple scalings are founddemonstrating the possibility to achieve an efficient conversion of the surface wave field energy into electron kinetic energy. This mechanism of electron acceleration...

  15. Theory for resonant ion acceleration by nonlinear magnetosonic fast and slow waves in finite beta plasmas

    International Nuclear Information System (INIS)

    A Korteweg--de Vries equation that is applicable to both the nonlinear magnetosonic fast and slow waves is derived from a two-fluid model with finite ion and electron pressures. As in the cold plasma theory, the fast wave has a critical angle theta/sub c/. For propagation angles greater than theta/sub c/ (quasiperpendicular propagation), the fast wave has a positive soliton, whereas for angles smaller than theta/sub c/, it has a negative soliton. Finite β effects decrease the value of theta/sub c/. The slow wave has a positive soliton for all angles of propagation. The magnitude of resonant ion acceleration (the v/sub p/ x B acceleration) by the nonlinear fast and slow waves is evaluated. In the fast wave, the electron pressure makes the acceleration stronger for all propagation angles. The decrease in theta/sub c/ resulting from finite β effects results in broadening of the region of strong acceleration. It is also found that fairly strong ion acceleration can occur in the nonlinear slow wave in high β plasmas. The possibility of unlimited acceleration of ions by quasiperpendicular magnetosonic fast waves is discussed

  16. THEORETICAL ANALYSIS AND EXPERIMENTAL VERIFICATION ON TERNARY-WAVES METHOD TO COMPILE ACCELERATED SPECTRA

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The equivalent damage calculation formulae of fatigue crack formation and growth are established. In order tocompile the fatigue crack formation and growth accelerated load spectra, the main wave shapes and load sequence of theactual load spectrum are kept constant, and the carrier waves are cut off. And secondary waves are put together into newsecondary waves to shorten the test time according to the equivalent damage calculation formulae respectively. Then bythe fatigue cumulative damage calculation of the fatigue crack formation and growth accelerated load spectra, the onecorresponding to the bigger damage is determined as the fatigue accelerated test load spectrum. Therefore in the test pro-cess, the fatigue accelerated test spectrum may be applied till fatigue failure, the engineering fatigue crack length of full-scale structure need not be inspected, and the fatigue crack formation accelerated load spectrum need not be transferredinto the fatigue crack growth accelerated load spectrum. Finally, it is verified by tests of two kinds of specimens that thedamages of the specimens caused by the accelerated load spectra are near to those by the actual load spectra; namely, thetested life of actual load spectra is similar to that of accelerated load spectra. But the test time of accelerated load spectrais shortened by about three-quarters that of actual load spectra. From these tests, it is also found that the fatigue accelerat-ed test spectrum has an advantage over FALSTAFF spectra.

  17. Enhancement of wave and acceleration of electron in plasma in the external field

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    This paper investigates the enhancement of Langmuir and ion-acoustic wave and the acceleration of the electron in collisionless plasma.in the presence of an external transverse field.Based on hydrodynamic equations,an equation formulizing the parametric instability was derived.Furthermore,the formula for ponderomotive force and the expression that describes the electron acceleration were obtained.The results show that Langmuir and ion-acoustic wave are enhanced and the charged particles can be accelerated by the coupling of wave-wave.In addition,it can be concluded that ponderomotive force,due to the coupling of the external field(pump)to the Langmuir wave(ion-acoustic wave),is the driving force to excite the parametric instability and comprises the high- and low-frequency components.

  18. Continuous wavelet transform analysis of acceleration signals measured from a wave buoy.

    Science.gov (United States)

    Chuang, Laurence Zsu-Hsin; Wu, Li-Chung; Wang, Jong-Hao

    2013-01-01

    Accelerometers, which can be installed inside a floating platform on the sea, are among the most commonly used sensors for operational ocean wave measurements. To examine the non-stationary features of ocean waves, this study was conducted to derive a wavelet spectrum of ocean waves and to synthesize sea surface elevations from vertical acceleration signals of a wave buoy through the continuous wavelet transform theory. The short-time wave features can be revealed by simultaneously examining the wavelet spectrum and the synthetic sea surface elevations. The in situ wave signals were applied to verify the practicality of the wavelet-based algorithm. We confirm that the spectral leakage and the noise at very-low-frequency bins influenced the accuracies of the estimated wavelet spectrum and the synthetic sea surface elevations. The appropriate thresholds of these two factors were explored. To study the short-time wave features from the wave records, the acceleration signals recorded from an accelerometer inside a discus wave buoy are analysed. The results from the wavelet spectrum show the evidence of short-time nonlinear wave events. Our study also reveals that more surface profiles with higher vertical asymmetry can be found from short-time nonlinear wave with stronger harmonic spectral peak. Finally, we conclude that the algorithms of continuous wavelet transform are practical for revealing the short-time wave features of the buoy acceleration signals. PMID:23966188

  19. Continuous Wavelet Transform Analysis of Acceleration Signals Measured from a Wave Buoy

    Directory of Open Access Journals (Sweden)

    Laurence Zsu-Hsin Chuang

    2013-08-01

    Full Text Available Accelerometers, which can be installed inside a floating platform on the sea, are among the most commonly used sensors for operational ocean wave measurements. To examine the non-stationary features of ocean waves, this study was conducted to derive a wavelet spectrum of ocean waves and to synthesize sea surface elevations from vertical acceleration signals of a wave buoy through the continuous wavelet transform theory. The short-time wave features can be revealed by simultaneously examining the wavelet spectrum and the synthetic sea surface elevations. The in situ wave signals were applied to verify the practicality of the wavelet-based algorithm. We confirm that the spectral leakage and the noise at very-low-frequency bins influenced the accuracies of the estimated wavelet spectrum and the synthetic sea surface elevations. The appropriate thresholds of these two factors were explored. To study the short-time wave features from the wave records, the acceleration signals recorded from an accelerometer inside a discus wave buoy are analysed. The results from the wavelet spectrum show the evidence of short-time nonlinear wave events. Our study also reveals that more surface profiles with higher vertical asymmetry can be found from short-time nonlinear wave with stronger harmonic spectral peak. Finally, we conclude that the algorithms of continuous wavelet transform are practical for revealing the short-time wave features of the buoy acceleration signals.

  20. Multi-input multi-output frequency-modulated continuous wave synthetic aperture radar system using beat-frequency division waveforms

    International Nuclear Information System (INIS)

    Attention has been paid to lightweight, cost-effective frequency-modulated continuous wave (FMCW) synthetic aperture radar (SAR) in recent years. Though FMCW SAR can operate at high altitude, it is still impracticable for wide swath or high Doppler bandwidth remote sensing because of the dramatic losses of range resolution and processing gain. Moreover, the system sampling rate is too high for real-time processing. All these restrictions caused by the bandwidth loss of the dechirp operation can be relieved by expanding the system sweep cycle. However, the broadening of the sweep cycle decreases the system pulse repetition frequency with azimuth ambiguity, which can be suppressed by exploiting the spatial diversity of multi-input multi-output (MIMO) systems. This paper reports a MIMO-FMCW SAR system using beat-frequency division waveforms. There is a small frequency interval and a large overlap (in frequency) between the orthogonal waveforms. As the frequency interval is much smaller than the signal bandwidth, the echoes that come from different transmitters can be separated by bandpass filtering with little intrapulse interference. Consequently, the applications of FMCW SAR systems can be extended for wider swath or higher Doppler bandwidth remote sensing. Theoretical analysis and simulation results illustrate the feasibility of this system. (paper)

  1. Multi-input multi-output frequency-modulated continuous wave synthetic aperture radar system using beat-frequency division waveforms

    Science.gov (United States)

    Wang, Jie; Chen, Long-yong; Liang, Xing-dong; Ding, Chi-biao; Hong, Wen; Zhou, Liang-jiang; Dong, Yong-wei; Li, Kun

    2013-07-01

    Attention has been paid to lightweight, cost-effective frequency-modulated continuous wave (FMCW) synthetic aperture radar (SAR) in recent years. Though FMCW SAR can operate at high altitude, it is still impracticable for wide swath or high Doppler bandwidth remote sensing because of the dramatic losses of range resolution and processing gain. Moreover, the system sampling rate is too high for real-time processing. All these restrictions caused by the bandwidth loss of the dechirp operation can be relieved by expanding the system sweep cycle. However, the broadening of the sweep cycle decreases the system pulse repetition frequency with azimuth ambiguity, which can be suppressed by exploiting the spatial diversity of multi-input multi-output (MIMO) systems. This paper reports a MIMO-FMCW SAR system using beat-frequency division waveforms. There is a small frequency interval and a large overlap (in frequency) between the orthogonal waveforms. As the frequency interval is much smaller than the signal bandwidth, the echoes that come from different transmitters can be separated by bandpass filtering with little intrapulse interference. Consequently, the applications of FMCW SAR systems can be extended for wider swath or higher Doppler bandwidth remote sensing. Theoretical analysis and simulation results illustrate the feasibility of this system.

  2. Advanced accelerators

    International Nuclear Information System (INIS)

    This report discusses the suitability of four novel particle acceleration technologies for multi-TeV particle physics machines: laser driven linear accelerators (linac), plasma beat-wave devices, plasma wakefield devices, and switched power and cavity wakefield linacs. The report begins with the derivation of beam parameters practical for multi-TeV devices. Electromagnetic field breakdown of materials is reviewed. The two-beam accelerator scheme for using a free electron laser as the driver is discussed. The options recommended and the conclusions reached reflect the importance of cost. We recommend that more effort be invested in achieving a self-consistent range of TeV accelerator design parameters. Beat-wave devices have promise for 1-100 GeV applications and, while not directly scalable to TeV designs, the current generation of ideas are encouraging for the TeV regime. In particular, surfatrons, finite-angle optical mixing devices, plasma grating accelerator, and the Raman forward cascade schemes all deserve more complete analysis. The exploitation of standard linac geometry operated in an unconventional mode is in a phase of rapid evolution. While conceptual projects abound, there are no complete designs. We recommend that a fraction of sponsored research be devoted to this approach. Wakefield devices offer a great deal of potential; trades among their benefits and constraints are derived and discussed herein. The study of field limitation processes has received inadequate attention; this limits experiment designers. The costs of future experiments are such that investment in understanding these processes is prudent. 34 refs., 12 figs., 3 tabs

  3. Phase speed of electrostatic waves: The critical parameter for efficient electron surfing acceleration

    CERN Document Server

    Dieckmann, M E; Parviainen, M; Shukla, P K; Sircombe, N J

    2006-01-01

    Particle acceleration by means of non-linear plasma wave interactions is of great topical interest. Accordingly, in this paper we focus on the electron surfing process. Self-consistent kinetic simulations, using both relativistic Vlasov and PIC (Particle In Cell) approaches, show here that electrons can be accelerated to highly relativistic energies (up to 100 m_e c^2) if the phase speed of the electrostatic wave is mildly relativistic (0.6c to 0.9c for the magnetic field strengths considered). The acceleration is strong because of relativistic stabilisation of the nonlinearly saturated electrostatic wave, seen in both relativistic Vlasov and PIC simulations. An inverse power law momentum distribution can arise for the most strongly accelerated electrons. These results are of relevance to observed rapid changes in the radio synchrotron emission intensities from microquasars, gamma ray bursts and other astrophysical objects that require rapid acceleration mechanisms for electrons.

  4. Phase speed of electrostatic waves: the critical parameter for efficient electron surfing acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Dieckmann, M E [Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, 44780 Bochum (Germany); Sircombe, N J [Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, 44780 Bochum (Germany); Parviainen, M [Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, 44780 Bochum (Germany); Shukla, P K [Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, 44780 Bochum (Germany); Dendy, R O [UKAEA Culham Division, Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB (United Kingdom); Physics Department, University of Warwick, Coventry CV4 7AL (United Kingdom)

    2006-04-15

    Particle acceleration by means of nonlinear plasma wave interactions is of great topical interest. Accordingly, in this paper we focus on the electron surfing process. Self-consistent kinetic simulations, using both relativistic Vlasov and particle-in-cell (PIC) approaches, show here that electrons can be accelerated to highly relativistic energies (up to 100m{sub e}c{sup 2}) if the phase speed of the electrostatic wave is mildly relativistic (0.6c to 0.9c for the magnetic field strengths considered). The acceleration is strong because of relativistic stabilization of the nonlinearly saturated electrostatic wave, seen in both relativistic Vlasov and PIC simulations. An inverse power law momentum distribution can arise for the most strongly accelerated electrons. These results are of relevance to observed rapid changes in the radio synchrotron emission intensities from microquasars, gamma ray bursts and other astrophysical objects that require rapid acceleration mechanisms for electrons.

  5. Electron trapping and acceleration by kinetic Alfvén waves in solar flares

    Science.gov (United States)

    Artemyev, A. V.; Zimovets, I. V.; Rankin, R.

    2016-05-01

    Context. Theoretical models and spacecraft observations of solar flares highlight the role of wave-particle interaction for non-local electron acceleration. In one scenario, the acceleration of a large electron population up to high energies is due to the transport of electromagnetic energy from the loop-top region down to the footpoints, which is then followed by the energy being released in dense plasma in the lower atmosphere. Aims: We consider one particular mechanism of non-linear electron acceleration by kinetic Alfvén waves. Here, waves are generated by plasma flows in the energy release region near the loop top. We estimate the efficiency of this mechanism and the energies of accelerated electrons. Methods: We use analytical estimates and test-particle modelling to investigate the effects of electron trapping and acceleration by kinetic Alfvén waves in the inhomogeneous plasma of the solar corona. Results: We demonstrate that, for realistic wave amplitudes, electrons can be accelerated up to 10-1000 keV during their propagation along magnetic field lines. Here the electric field that is parallel to the direction of the background magnetic field is about 10 to 103 times the amplitude of the Dreicer electric field. The acceleration mechanism strongly depends on electron scattering which is due to collisions that only take place near the loop footpoints. Conclusions: The non-linear wave-particle interaction can play an important role in the generation of relativistic electrons within flare loops. Electron trapping and coherent acceleration by kinetic Alfvén waves represent the energy cascade from large-scale plasma flows that originate at the loop-top region down to the electron scale. The non-diffusive character of the non-linear electron acceleration may be responsible for the fast generation of high-energy particles.

  6. Quantum-beat Auger spectroscopy

    CERN Document Server

    Zhang, Song Bin

    2015-01-01

    The concept of nonlinear quantum-beat pump-probe Auger spectroscopy is introduced by discussing a relatively simple four-level model system. We consider a coherent wave packet involving two low-lying states that was prepared by an appropriate pump pulse. This wave packet is subsequently probed by a weak, time-delayed probe pulse with nearly resonant coupling to a core-excited state of the atomic or molecular system. The resonant Auger spectra are then studied as a function of the duration of the probe pulse and the time delay. With a bandwidth of the probe pulse approaching the energy spread of the wave packet, the Auger yields and spectra show quantum beats as a function of pump-probe delay. An analytic theory for the quantum-beat Auger spectroscopy will be presented, which allows for the reconstruction of the wave packet by analyzing the delaydependent Auger spectra. The possibility of extending this method to a more complex manifold of electronic and vibrational energy levels is also discussed.

  7. Simple Scalings for Various Regimes of Electron Acceleration in Surface Plasma Waves

    CERN Document Server

    Riconda, C; Vialis, T; Grech, M

    2015-01-01

    Different electron acceleration regimes in the evanescent field of a surface plasma wave are studied by considering the interaction of a test electron with the high-frequency electromagnetic field of a surface wave. The non-relativistic and relativistic limits are investigated. Simple scalings are found demonstrating the possibility to achieve an efficient conversion of the surface wave field energy into electron kinetic energy. This mechanism of electron acceleration can provide a high-frequency pulsed source of relativistic electrons with a well defined energy. In the relativistic limit, the most energetic electrons are obtained in the so-called electromagnetic regime for surface waves. In this regime the particles are accelerated to velocities larger than the wave phase velocity, mainly in the direction parallel to the plasma-vacuum interface.

  8. Plasma acceleration by the interaction of parallel propagating Alfv\\'en waves

    CERN Document Server

    Mottez, Fabrice

    2014-01-01

    It is shown that two circularly polarised Alfv\\'en waves that propagate along the ambient magnetic field in an uniform plasma trigger non oscillating electromagnetic field components when they cross each other. The non-oscilliating field components can accelerate ions and electrons with great efficiency. This work is based on particle-in-cell (PIC) numerical simulations and on analytical non-linear computations. The analytical computations are done for two counter-propagating monochromatic waves. The simulations are done with monochromatic waves and with wave packets. The simulations show parallel electromagnetic fields consistent with the theory, and they show that the particle acceleration result in plasma cavities and, if the waves amplitudes are high enough, in ion beams. These acceleration processes could be relevant in space plasmas. For instance, they could be at work in the auroral zone and in the radiation belts of the Earth magnetosphere. In particular, they may explain the origin of the deep plasma...

  9. Simple scalings for various regimes of electron acceleration in surface plasma waves

    Energy Technology Data Exchange (ETDEWEB)

    Riconda, C.; Vialis, T. [LULI, Sorbonne Université, Université Pierre et Marie Curie, Ecole Polytechnique, CNRS UMR 7605, CEA, Paris 75005 (France); Raynaud, M. [Laboratoire des Solides Irradiés, CNRS UMR 7642, CEA-DSM-IRAMIS, Ecole Polytechnique, Université Paris-Saclay, 91128 Palaiseau (France); Grech, M. [LULI, CNRS UMR 7605, Université Pierre et Marie Curie, Ecole Polytechnique, CEA, 91128 Palaiseau (France)

    2015-07-15

    Different electron acceleration regimes in the evanescent field of a surface plasma wave are studied by considering the interaction of a test electron with the high-frequency electromagnetic field of a surface wave. The non-relativistic and relativistic limits are investigated. Simple scalings are found demonstrating the possibility to achieve an efficient conversion of the surface wave field energy into electron kinetic energy. This mechanism of electron acceleration can provide a high-frequency pulsed source of relativistic electrons with a well defined energy. In the relativistic limit, the most energetic electrons are obtained in the so-called electromagnetic regime for surface waves. In this regime, the particles are accelerated to velocities larger than the wave phase velocity, mainly in the direction parallel to the plasma-vacuum interface.

  10. Nonlinear theory of diffusive acceleration of particles by shock waves

    International Nuclear Information System (INIS)

    Among the various acceleration mechanisms which have been suggested as responsible for the nonthermal particle spectra and associated radiation observed in many astrophysical and space physics environments, diffusive shock acceleration appears to be the most successful. We review the current theoretical understanding of this process, from the basic ideas of how a shock energizes a few reactionless particles to the advanced nonlinear approaches treating the shock and accelerated particles as a symbiotic self-organizing system. By means of direct solution of the nonlinear problem we set the limit to the test-particle approximation and demonstrate the fundamental role of nonlinearity in shocks of astrophysical size and lifetime. We study the bifurcation of this system, proceeding from the hydrodynamic to kinetic description under a realistic condition of Bohm diffusivity. We emphasize the importance of collective plasma phenomena for the global flow structure and acceleration efficiency by considering the injection process, an initial stage of acceleration and, the related aspects of the physics of collisionless shocks. We calculate the injection rate for different shock parameters and different species. This, together with differential acceleration resulting from nonlinear large-scale modification, determines the chemical composition of accelerated particles. The review concentrates on theoretical and analytical aspects but our strategic goal is to link the fundamental theoretical ideas with the rapidly growing wealth of observational data. (author)

  11. Travelling wave accelerating structure design for TESLA positron injector linac

    CERN Document Server

    Jin, K; Zhou, F; Flöttmann, K

    2000-01-01

    A modified cup-like TW accelerating structure for TESLA Positron Pre-Accelerator (PPA) is designed by optimizing the structure geometry and by changing the iris thickness cell by cell in a section . This structure has high shunt-impedance and a large iris radius to meet with the requirements of high gradient and large transverse acceptance. The beam dynamics in the structure with the optimum solenoid focus field are studied. A satisfactory positron beam transmission and the beam performance at the PPA output have been obtained. In this paper the accelerating structure design is described in detail and the results are presented.

  12. dc acceleration of charged particles by an electrostatic wave propagating obliquely to a magnetic field

    International Nuclear Information System (INIS)

    A charged particle trapped in an electrostatic wave is accelerated in the plane perpendicular to the wave vector k. It is found that there is an optimum angle theta = theta/sub m/ at which the particle gains a maximum energy which is about four times larger than that at theta = π/2, theta being the angle between k and the magnetic field

  13. Experimental, theoretical, and computational studies of the plasma beat wave accelerator concept. Final report, May 1, 1989--June 30, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, C.

    1994-12-31

    As can be seen this was an extremely productive period with the PI and his team completing all the tasks in the original proposal. The following six pages list the work statement as it appeared in the initial proposal. Next to it is a summary of what the actual performance was. A check mark means the accomplishment was exactly as planned in the work statement. A list of key publications under each main subtask in the work statement are also listed.

  14. Acceleration of cosmic rays in SNR shock waves

    International Nuclear Information System (INIS)

    The time dependence of the energy density of cosmic rays accelerated in the outer shock of a supernova is studied in simple nonlinear models. The solutions are classified in their dependence on the parameters of the system. (orig.)

  15. Visualizing acoustical beats with a smartphones

    CERN Document Server

    Giménez, Marcos H; Castro-Palacio, Juan C; Gómez-Tejedor, José A; Monsoriu, Juan A

    2016-01-01

    In this work, a new Physics laboratory experiment on Acoustics beats is presented. We have designed a simple experimental setup to study superposition of sound waves of slightly different frequencies (acoustic beat). The microphone of a smartphone is used to capture the sound waves emitted by two equidistant speakers from the mobile which are at the same time connected to two AC generators. The smartphone is used as a measuring instrument. By means of a simple and free AndroidTM application, the sound level (in dB) as a function of time is measured and exported to a .csv format file. Applying common graphing analysis and a fitting procedure, the frequency of the beat is obtained. The beat frequencies as obtained from the smartphone data are compared with the difference of the frequencies set at the AC generator. A very good agreement is obtained being the percentage discrepancies within 1 %.

  16. Acceleration of the Fast Solar Wind by Solitary Waves in Coronal Holes

    Science.gov (United States)

    Ofman, Leon

    2001-01-01

    The purpose of this investigation is to develop a new model for the acceleration of the fast solar wind by nonlinear. time-dependent multidimensional MHD simulations of waves in solar coronal holes. Preliminary computational studies indicate that nonlinear waves are generated in coronal holes by torsional Alfv\\'{e}n waves. These waves in addition to thermal conduction may contribute considerably to the accelerate the solar wind. Specific goals of this proposal are to investigate the generation of nonlinear solitary-like waves and their effect on solar wind acceleration by numerical 2.5D MHD simulation of coronal holes with a broad range of plasma and wave parameters; to study the effect of random disturbances at the base of a solar coronal hole on the fast solar wind acceleration with a more advanced 2.5D MHD model and to compare the results with the available observations; to extend the study to a full 3D MHD simulation of fast solar wind acceleration with a more realistic model of a coronal hole and solar boundary conditions. The ultimate goal of the three year study is to model the, fast solar wind in a coronal hole, based on realistic boundary conditions in a coronal hole near the Sun, and the coronal hole structure (i.e., density, temperature. and magnetic field geometry,) that will become available from the recently launched SOHO spacecraft.

  17. Measuring test mass acceleration noise in space-based gravitational wave astronomy

    CERN Document Server

    Congedo, Giuseppe

    2014-01-01

    The basic constituent of interferometric gravitational wave detectors -- the test mass to test mass interferometric link -- behaves as a differential dynamometer measuring effective differential forces, comprising an integrated measure of gravity curvature, inertial effects, as well as non-gravitational spurious forces. This last contribution is going to be characterised by the LISA Pathfinder mission, a technology precursor of future space-borne detectors like eLISA. Changing the perspective from displacement to acceleration can benefit the data analysis of LISA Pathfinder and future detectors. The response in differential acceleration to gravitational waves is derived for a space-based detector's interferometric link. The acceleration formalism can also be integrated into time delay interferometry by building up the unequal-arm Michelson differential acceleration combination. The differential acceleration is nominally insensitive to the system free evolution dominating the slow displacement dynamics of low-...

  18. Heavy ion acceleration by nonlinear magnetosonic waves in a two-ion-species plasma

    International Nuclear Information System (INIS)

    The ion dynamics in perpendicular nonlinear magnetosonic waves in a plasma containing two ion species is studied through theory and simulation using a one dimension, electromagnetic particle code with full ion and electron dynamics; in the simulations the density of heavier ions was set to be 10% of that of lighter ions. As in a single-ion-species plasma, some of the light ions can be accelerated by the longitudinal electric field formed in a wave. It is found that the bulk of heavy ions are accelerated by the transverse electric field. For a large-amplitude wave, the maximum speed of heavy ions is about the wave propagation speed, which exceeds the Alfven speed. Theoretical estimates of maximum speeds are given for small- and large- amplitude waves. They are in good agreement with the simulation results. (author)

  19. Shock-wave proton acceleration from a hydrogen gas jet

    Science.gov (United States)

    Cook, Nathan; Pogorelsky, Igor; Polyanskiy, Mikhail; Babzien, Marcus; Tresca, Olivier; Maharjan, Chakra; Shkolnikov, Peter; Yakimenko, Vitaly

    2013-04-01

    Typical laser acceleration experiments probe the interaction of intense linearly-polarized solid state laser pulses with dense metal targets. This interaction generates strong electric fields via Transverse Normal Sheath Acceleration and can accelerate protons to high peak energies but with a large thermal spectrum. Recently, the advancement of high pressure amplified CO2 laser technology has allowed for the creation of intense (10^16 Wcm^2) pulses at λ˜10 μm. These pulses may interact with reproducible, high rep. rate gas jet targets and still produce plasmas of critical density (nc˜10^19 cm-3), leading to the transference of laser energy via radiation pressure. This acceleration mode has the advantage of producing narrow energy spectra while scaling well with pulse intensity. We observe the interaction of an intense CO2 laser pulse with an overdense hydrogen gas jet. Using two pulse optical probing in conjunction with interferometry, we are able to obtain density profiles of the plasma. Proton energy spectra are obtained using a magnetic spectrometer and scintillating screen.

  20. Plasma-based and novel accelerators

    International Nuclear Information System (INIS)

    This publication is a collection of papers presented at Workshop on Plasma-Based and Novel Accelerators held at National Institute for Fusion Science, Nagoya, on December 19-20, 1991. Plasma-based accelerators are attracting considerable attention in these days a new, exciting field of plasma applications. The study gives rise to and spurs study of other unique accelerators like laser-based accelerators. The talks in the Workshop encompassed beat-wave accelerator (BWA), plasma wake field accelerator (PWFA), Vp x B accelerator, laser-based accelerators and some novel methods of acceleration. They also covered the topics such as FEL, cluster acceleration and plasma lens. Small scale experiments as those in universities have exhibited brilliant results while larger scale experiments like BWA in Institute of Laser Engineering, Osaka University, and PWFA in KEK start showing significant results as well. (J.P.N.)

  1. Ionizing wave via high-power HF acceleration

    CERN Document Server

    Mishin, Evgeny

    2010-01-01

    Recent ionospheric modification experiments with the 3.6 MW transmitter at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska led to discovery of artificial ionization descending from the nominal interaction altitude in the background F-region ionosphere by ~60 km. This paper presents a physical model of an ionizing wavefront created by suprathermal electrons accelerated by the HF-excited plasma turbulence.

  2. Simulation and analysis of TE wave propagation for measurement of electron cloud densities in particle accelerators

    International Nuclear Information System (INIS)

    The use of transverse electric (TE) waves has proved to be a powerful, noninvasive method for estimating the densities of electron clouds formed in particle accelerators. Results from the plasma simulation program VSim have served as a useful guide for experimental studies related to this method, which have been performed at various accelerator facilities. This paper provides results of the simulation and modeling work done in conjunction with experimental efforts carried out at the Cornell electron storage ring “Test Accelerator” (CESRTA). This paper begins with a discussion of the phase shift induced by electron clouds in the transmission of RF waves, followed by the effect of reflections along the beam pipe, simulation of the resonant standing wave frequency shifts and finally the effects of external magnetic fields, namely dipoles and wigglers. A derivation of the dispersion relationship of wave propagation for arbitrary geometries in field free regions with a cold, uniform cloud density is also provided

  3. Simulation and Analysis of TE Wave Propagation as a Probe for Electron Clouds in Particle Accelerators

    CERN Document Server

    Sonnad, Kiran G; Schwartz, Robert; Veitzer, Seth

    2013-01-01

    The use of transverse electric (TE) waves has proved to be a powerful, noninvasive method for estimating the densities of electron clouds formed in particle accelerators. Results from the plasma simulation program VORPAL have been a useful guide for experimental studies related to this method, which have been performed at various accelerator facilities. This paper provides results of the simulation and modeling work done in conjunction with experimental efforts carried out at CesrTA. The discussion starts from the phase shift induced by electron clouds in the transmission of the wave, followed by the effect of reflections along the beam-pipe, the simulation of the resonant wave method and the effects of external magnetic fields, namely dipoles and wigglers. A derivation of the dispersion relationship of wave propagation for arbitrary geometries in field free regions with a uniform cloud density is also provided.

  4. An electromagnetic railgun accelerator: a generator of strong shock waves in channels

    Science.gov (United States)

    Bobashev, S. V.; Zhukov, B. G.; Kurakin, R. O.; Ponyaev, S. A.; Reznikov, B. I.

    2014-11-01

    Processes that accompany the generation of strong shock waves during the acceleration of a free plasma piston (PP) in the electromagnetic railgun channel have been experimentally studied. The formation of shock waves in the railgun channel and the motion of a shock-wave-compressed layer proceed (in contrast to the case of a classical shock tube) in a rather strong electric field (up to 300 V/cm). The experiments were performed at the initial gas pressures in the channel ranging from 25 to 500 Torr. At 25 Torr, the shock-wave Mach numbers reached 32 in argon and 16 in helium. At high concentrations of charged particles behind the shock wave, the electric field causes the passage of a part of the discharge current through the volume of the shock-wave-compressed layer, which induces intense glow comparable with that of the PP glow.

  5. Electron acceleration by young supernova remnant blast waves

    Science.gov (United States)

    Blandford, R. D.

    1992-01-01

    Some general considerations regarding relativistic particle acceleration by young supernova remnants are reviewed. Recent radio observations of supernova remnants apparently locate the bounding shock and exhibit large electron density gradients which verify the presence of strong particle scattering. The radio 'rim' in Tycho's remnant has been found to contain a predominantly radial magnetic field. This may be attributable to an instability of the shock surface and a progress report on an investigation of the stability of strong shocks in partially ionized media is presented.

  6. Transient beam loading compensation in traveling wave linear accelerators

    International Nuclear Information System (INIS)

    For normal conducting linear colliders the transient beam loading in the accelerating structures is typically of the order of 20-30%. This results in a multibunch energy spread of the same magnitude if no remedy is taken into account. On the other hand, in a linear collider the transient energy spread has to be controlled down to a few tenth of a percent. Two possible methods, assuming two different setups, e.g. klystron plus structure and klystron plus SLED cavity plus structure, are investigated. A description of the whole rf system and the resulting energy spread is presented especially for the case of the S-Band linear collider study. (orig.)

  7. Electron acceleration at Jupiter: input from cyclotron-resonant interaction with whistler-mode chorus waves

    Directory of Open Access Journals (Sweden)

    E. E. Woodfield

    2013-10-01

    Full Text Available Jupiter has the most intense radiation belts of all the outer planets. It is not yet known how electrons can be accelerated to energies of 10 MeV or more. It has been suggested that cyclotron-resonant wave-particle interactions by chorus waves could accelerate electrons to a few MeV near the orbit of Io. Here we use the chorus wave intensities observed by the Galileo spacecraft to calculate the changes in electron flux as a result of pitch angle and energy diffusion. We show that, when the bandwidth of the waves and its variation with L are taken into account, pitch angle and energy diffusion due to chorus waves is a factor of 8 larger at L-shells greater than 10 than previously shown. We have used the latitudinal wave intensity profile from Galileo data to model the time evolution of the electron flux using the British Antarctic Survey Radiation Belt (BAS model. This profile confines intense chorus waves near the magnetic equator with a peak intensity at ∼5° latitude. Electron fluxes in the BAS model increase by an order of magnitude for energies around 3 MeV. Extending our results to L = 14 shows that cyclotron-resonant interactions with chorus waves are equally important for electron acceleration beyond L = 10. These results suggest that there is significant electron acceleration by cyclotron-resonant interactions at Jupiter contributing to the creation of Jupiter's radiation belts and also increasing the range of L-shells over which this mechanism should be considered.

  8. Particle acceleration in ultra-relativistic parallel shock waves

    CERN Document Server

    Meli, A

    2003-01-01

    Monte-Carlo computations for highly relativistic parallel shock particle acceleration are presented for upstream flow gamma factors, $\\Gamma=(1-V_{1}^{2}/c^{2})^{-0.5}$ with values between 5 and $10^{3}$. The results show that the spectral shape at the shock depends on whether or not the particle scattering is small angle with $\\delta \\theta 2r_{g} \\Gamma^{2}$ where $\\lambda$ is the scattering mean free path along the field line and $r_{g}$ the gyroradius, these quantities being measured in the plasma flow frame. The large angle scattering case exhibits distinctive structure superimposed on the basic power-law spectrum, largely absent in the pitch angle case. Also, both cases yield an acceleration rate faster than estimated by the conventional, non-relativistic expression, $t_{acc}=[c/(V_{1}-V_{2})] [\\lambda_{1}/V_{1}+\\lambda_{2}/V_{2}]$ where '1' and '2' refer to upstream and downstream and $\\lambda$ is the mean free path. A $\\Gamma^{2}$ energy enhancement factor in the first shock crossing cycle and a sign...

  9. Electromagnetic waves and bursty electron acceleration: implications from Freja

    Directory of Open Access Journals (Sweden)

    L. Andersson

    Full Text Available Dispersive Alfvén wave activity is identified in four dayside auroral oval events measured by the Freja satellite. The events are characterized by ion injection, bursty electron precipitation below about 1 keV, transverse ion heating and broadband extremely low frequency (ELF emissions below the lower hybrid cutoff frequency (a few kHz. Large-scale density depletions/cavities, as determined by the Langmuir probe measurements, and strong electrostatic emissions are often observed simultaneously. A correlation study has been carried out between the E and B field fluctuations below 64 Hz and 10 Hz, respectively, (the DC instruments upper threshold and the characteristics of the precipitating electrons. This study revealed that the energisation of electrons is indeed related to the broadband ELF emissions and that the electrostatic component plays a predominant role during very active magnetospheric conditions. Furthermore, the effect of the ELF electromagnetic emissions on the larger scale field-aligned current systems has been investigated, and it is found that such an effect cannot be detected. Instead, the Alfvénic activity creates a local region of field-aligned currents. It is suggested that dispersive Alfvén waves set up these local field-aligned current regions and, in turn, trigger more electrostatic emissions during certain conditions. In these regions, ions are transversely heated, and large-scale density depletions/cavities may be created during especially active periods.

    Key words. Ionosphere (particle acceleraton; wave-particle interactions Magnetospheric physics (auroral phenomena

  10. Modification of the beam transfer model of travelling wave accelerator structures at SACLA

    International Nuclear Information System (INIS)

    In order to perform efficient beam tuning at SACLA, we had developed a beam transfer model to calculate the beam transverse envelope in a linear accelerator using linear symplectic matrices. However the measured beam orbit responses were not consistent with the calculated orbit. In order to investigate the error source, we modify the transfer matrix of an accelerator structure so that the matrix model reproduces the measured orbit response. In this paper, we report detail of the error source and how the beam transfer model of a travelling wave accelerator structure is modified. (author)

  11. Cold test results of a side-coupled standing-wave electron-accelerating structure

    Science.gov (United States)

    Song, Ki Baek; Li, Yonggui; Lee, Sanghyun; Lee, Byeong-No; Park, Hyung Dal; Cha, Sung-Su; Lee, Byung Cheol

    2013-07-01

    The radio-frequency (RF) cavity for the dual-energy S-band electron linear accelerator (LINAC) is designed for a cargo inspection system (CIS) at the Korea Atomic Energy Research Institute (KAERI). The cold test results of the electron accelerator structure, which has a side-coupled standing-wave interlaced-pulse dual-energy mode, are described. The design concept, basic structure, microwave-tuning method, and cold-test procedure are described as well. The measured dispersion curve, spectrum characteristics, ρ-f relation of the power coupler, and axial field distribution of the accelerating gradient are provided.

  12. Relationship between Alfvén Wave and Quasi-Static Acceleration in Earth's Auroral Zone

    Science.gov (United States)

    Mottez, Fabrice

    2016-02-01

    There are two main categories of acceleration processes in the Earth's auroral zone: those based on quasi-static structures, and those based on Alfvén wave (AW). AWs play a nonnegligible role in the global energy budget of the plasma surrounding the Earth because they participate in auroral acceleration, and because auroral acceleration conveys a large portion of the energy flux across the magnetosphere. Acceleration events by double layers (DLs) and by AW have mostly been investigated separately, but many studies cited in this chapter show that they are not independent: these processes can occur simultaneously, and one process can be the cause of the other. The quasi-simultaneous occurrences of acceleration by AW and by quasi-static structures have been observed predominantly at the polar cap boundary of auroral arc systems, where often new bright arcs develop or intensify.

  13. Model for the heart beat-to-beat time series during meditation

    Science.gov (United States)

    Capurro, A.; Diambra, L.; Malta, C. P.

    2003-09-01

    We present a model for the respiratory modulation of the heart beat-to-beat interval series. The model consists of a pacemaker, that simulates the membrane potential of the sinoatrial node, modulated by a periodic input signal plus correlated noise that simulates the respiratory input. The model was used to assess the waveshape of the respiratory signals needed to reproduce in the phase space the trajectory of experimental heart beat-to-beat interval data. The data sets were recorded during meditation practices of the Chi and Kundalini Yoga techniques. Our study indicates that in the first case the respiratory signal has the shape of a smoothed square wave, and in the second case it has the shape of a smoothed triangular wave.

  14. Accelerating Wave Function Convergence in Interactive Quantum Chemical Reactivity Studies

    CERN Document Server

    Mühlbach, Adrian H; Reiher, Markus

    2015-01-01

    The inherently high computational cost of iterative self-consistent-field (SCF) methods proves to be a critical issue delaying visual and haptic feedback in real-time quantum chemistry. In this work, we introduce two schemes for SCF acceleration. They provide a guess for the initial density matrix of the SCF procedure generated by extrapolation techniques. SCF optimizations then converge in fewer iterations, which decreases the execution time of the SCF optimization procedure. To benchmark the proposed propagation schemes, we developed a test bed for performing quantum chemical calculations on sequences of molecular structures mimicking real-time quantum chemical explorations. Explorations of a set of six model reactions employing the semi-empirical methods PM6 and DFTB3 in this testing environment showed that the proposed propagation schemes achieved speedups of up to thirty percent as a consequence of a reduced number of SCF iterations.

  15. Prospects for all-optical ultrafast muon acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Peano, F; Vieira, J; Silva, L O [GoLP/Institudo de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, 1049-001 Lisboa (Portugal); Mulas, R; Coppa, G [Dipartimento di Energetica, Politecnico di Torino, 10129 Torino (Italy); Bingham, R [Space Science and Technology Department, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxon, OX11 0QX (United Kingdom)], E-mail: fabio.peano@ist.utl.pt, E-mail: luis.silva@ist.utl.pt

    2009-02-15

    A scheme for fast, compact and controllable acceleration of heavy particles in vacuum has been recently proposed (Peano F et al 2008 New J. Phys. 10 033028), wherein two counterpropagating laser beams with variable frequencies drive a beat-wave structure with variable phase velocity, leading to particle trapping and acceleration. The technique allows for fine control over the energy distribution and the total charge of the accelerated beam to be obtained via tuning of the frequency variation. Here, the theoretical bases of the acceleration scheme are described, and the possibility of applications to ultrafast muon acceleration and to the prompt extraction of cold-muon beams is discussed.

  16. Prospects for all-optical ultrafast muon acceleration

    CERN Document Server

    Peano, F; Mulas, R; Coppa, G; Bingham, R; Silva, L O

    2008-01-01

    A scheme for fast, compact, and controllable acceleration of heavy particles in vacuum has been recently proposed [F. Peano et al., New J. Phys. 10 033028 (2008)], wherein two counterpropagating laser beams with variable frequencies drive a beat-wave structure with variable phase velocity, leading to particle trapping and acceleration. The technique allows for fine control over the energy distribution and the total charge of the accelerated beam, to be obtained via tuning of the frequency variation. Here, the theoretical bases of the acceleration scheme are described, and the possibility of applications to ultrafast muon acceleration and to the prompt extraction of cold-muon beams is discussed.

  17. Acceleration and heating of two-fluid solar wind by Alfven waves

    Science.gov (United States)

    Sandbaek, Ornulf; Leer, Egil

    1994-01-01

    Earlier model studies of solar wind driven by thermal pressure and Alfven waves have shown that wave amplitudes of 20-30 km/s at the coronal base are sufficient to accelerate the flow to the high speeds observed in quasi-steady streams emanating from large coronal holes. We focus on the energy balance in the proton gas and show that heat conduction from the region where the waves are dissipated may play an important role in determining the proton temperature at the orbit of Earth. In models with 'classical' heat conduction we find a correlation between high flow speed, high proton temperature, and low electron temperature at 1 AU. The effect of wave heating on the development of anisotropies in the solar wind proton gas pressure is also investigated in this study.

  18. Model for the respiratory modulation of the heart beat-to-beat time interval series

    Science.gov (United States)

    Capurro, Alberto; Diambra, Luis; Malta, C. P.

    2005-09-01

    In this study we present a model for the respiratory modulation of the heart beat-to-beat interval series. The model consists of a set of differential equations used to simulate the membrane potential of a single rabbit sinoatrial node cell, excited with a periodic input signal with added correlated noise. This signal, which simulates the input from the autonomous nervous system to the sinoatrial node, was included in the pacemaker equations as a modulation of the iNaK current pump and the potassium current iK. We focus at modeling the heart beat-to-beat time interval series from normal subjects during meditation of the Kundalini Yoga and Chi techniques. The analysis of the experimental data indicates that while the embedding of pre-meditation and control cases have a roughly circular shape, it acquires a polygonal shape during meditation, triangular for the Kundalini Yoga data and quadrangular in the case of Chi data. The model was used to assess the waveshape of the respiratory signals needed to reproduce the trajectory of the experimental data in the phase space. The embedding of the Chi data could be reproduced using a periodic signal obtained by smoothing a square wave. In the case of Kundalini Yoga data, the embedding was reproduced with a periodic signal obtained by smoothing a triangular wave having a rising branch of longer duration than the decreasing branch. Our study provides an estimation of the respiratory signal using only the heart beat-to-beat time interval series.

  19. Electron acceleration in an ion channel by a magnetized plasma wave

    Directory of Open Access Journals (Sweden)

    A. Kargarian

    2014-04-01

    Full Text Available In this paper, the acceleration of an electron in the interaction with a plasma wave and a magnetized ion-channel is analyzed. The electron dynamics is studied treated employing complete three-dimensional Lorentz force equations. A relativistic three dimensional single particle code is used to obtain the electron-trajectories. The results of numerical calculation show that the electrons can be accelerated in the magnetized channel. Furthermore, the electron energy gain with axial magnetic field is compared to that without axial magnetic field.

  20. Spectral-element Seismic Wave Propagation on CUDA/OpenCL Hardware Accelerators

    Science.gov (United States)

    Peter, D. B.; Videau, B.; Pouget, K.; Komatitsch, D.

    2015-12-01

    Seismic wave propagation codes are essential tools to investigate a variety of wave phenomena in the Earth. Furthermore, they can now be used for seismic full-waveform inversions in regional- and global-scale adjoint tomography. Although these seismic wave propagation solvers are crucial ingredients to improve the resolution of tomographic images to answer important questions about the nature of Earth's internal processes and subsurface structure, their practical application is often limited due to high computational costs. They thus need high-performance computing (HPC) facilities to improving the current state of knowledge. At present, numerous large HPC systems embed many-core architectures such as graphics processing units (GPUs) to enhance numerical performance. Such hardware accelerators can be programmed using either the CUDA programming environment or the OpenCL language standard. CUDA software development targets NVIDIA graphic cards while OpenCL was adopted by additional hardware accelerators, like e.g. AMD graphic cards, ARM-based processors as well as Intel Xeon Phi coprocessors. For seismic wave propagation simulations using the open-source spectral-element code package SPECFEM3D_GLOBE, we incorporated an automatic source-to-source code generation tool (BOAST) which allows us to use meta-programming of all computational kernels for forward and adjoint runs. Using our BOAST kernels, we generate optimized source code for both CUDA and OpenCL languages within the source code package. Thus, seismic wave simulations are able now to fully utilize CUDA and OpenCL hardware accelerators. We show benchmarks of forward seismic wave propagation simulations using SPECFEM3D_GLOBE on CUDA/OpenCL GPUs, validating results and comparing performances for different simulations and hardware usages.

  1. On the physics of waves in the solar atmosphere: Wave heating and wind acceleration

    Science.gov (United States)

    Musielak, Z. E.

    1994-01-01

    New calculations of the acoustic wave energy fluxes generated in the solar convective zone have been performed. The treatment of convective turbulence in the sun and solar-like stars, in particular, the precise nature of the turbulent power spectrum has been recognized as one of the most important issues in the wave generation problem. Several different functional forms for spatial and temporal spectra have been considered in the literature and differences between the energy fluxes obtained for different forms often exceed two orders of magnitude. The basic criterion for choosing the appropriate spectrum was the maximal efficiency of the wave generation. We have used a different approach based on physical and empirical arguments as well as on some results from numerical simulation of turbulent convection.

  2. Time-domain analysis of beat-to-beat variability of repolarization morphology in patients with ischemic cardiomyopathy.

    Science.gov (United States)

    Burattini, L; Zareba, W

    1999-01-01

    There is growing evidence that beat-to-beat changes in ventricular repolarization contribute to increased vulnerability to ventricular arrhythmias. Beat-to-beat repolarization variability is usually measured in the electrocardiogram (ECG) by tracking consecutive QT or RT intervals. However, these measurements strongly depend on the accurate identification of T-wave endpoints, and they do not reflect changes in repolarization morphology. In this article, we propose a new computerized time-domain method to measure beat-to-beat variability of repolarization morphology without the need to identify T-wave endpoints. The repolarization correlation index (RCI) is computed for each beat to determine the difference between the morphology of repolarization within a heart-rate dependent repolarization window compared to a template (median) repolarization morphology. The repolarization variability index (RVI) describes the mean value of repolarization correlation in a studied ECG recording. To validate our method, we analyzed repolarization variability in 128-beat segments from Holter ECG recordings of 42 ischemic cardiomyopathy (ICM) patients compared to 36 healthy subjects. The ICM patients had significantly higher values of RVI than healthy subjects (in lead X: 0.045 +/- 0.035 vs. 0.024 +/- 0.010, respectively; P 0.044). No significant correlation was found between the RVI values and the magnitude of heart rate, heart rate variability, QTc interval duration, or ejection fraction in studied ICM patients. In conclusion, our time-domain method, based on computation of repolarization correlation indices for consecutive beats, provides a new approach to quantify beat-to-beat variability of repolarization morphology without the need to identify T-wave endpoints. PMID:10688321

  3. Wave packet analysis and break-up length calculations for an accelerating planar liquid jet

    International Nuclear Information System (INIS)

    This paper examines the process of transition to turbulence within an accelerating planar liquid jet. By calculating the propagation and spatial evolution of disturbance wave packets generated at a nozzle where the jet emerges, we are able to estimate break-up lengths and break-up times for different magnitudes of acceleration and different liquid to air density ratios. This study uses a basic jet velocity profile that has shear layers in both air and the liquid either side of the fluid interface. The shear layers are constructed as functions of velocity which behave in line with our CFD simulations of injecting diesel jets. The non-dimensional velocity of the jet along the jet centre-line axis is assumed to take the form V (t) = tanh(at), where the parameter a determines the magnitude of the acceleration. We compare the fully unsteady results obtained by solving the unsteady Rayleigh equation to those of a quasi-steady jet to determine when the unsteady effects are significant and whether the jet can be regarded as quasi-steady in typical operating conditions for diesel engines. For a heavy fluid injecting into a lighter fluid (density ratio ρair/ρjet = q < 1), it is found that unsteady effects are mainly significant at early injection times where the jet velocity profile is changing fastest. When the shear layers in the jet thin with time, the unsteady effects cause the growth rate of the wave packet to be smaller than the corresponding quasi-steady jet, whereas for thickening shear layers the unsteady growth rate is larger than that of the quasi-steady jet. For large accelerations (large a), the unsteady effect remains at later times but its effect on the growth rate of the wave packet decreases as the time after injection increases. As the rate of acceleration is reduced, the range of velocity values for which the jet can be considered as quasi-steady increases until eventually the whole jet can be considered quasi-steady. For a homogeneous jet (q = 1), the

  4. Forward and adjoint spectral-element simulations of seismic wave propagation using hardware accelerators

    Science.gov (United States)

    Peter, Daniel; Videau, Brice; Pouget, Kevin; Komatitsch, Dimitri

    2015-04-01

    Improving the resolution of tomographic images is crucial to answer important questions on the nature of Earth's subsurface structure and internal processes. Seismic tomography is the most prominent approach where seismic signals from ground-motion records are used to infer physical properties of internal structures such as compressional- and shear-wave speeds, anisotropy and attenuation. Recent advances in regional- and global-scale seismic inversions move towards full-waveform inversions which require accurate simulations of seismic wave propagation in complex 3D media, providing access to the full 3D seismic wavefields. However, these numerical simulations are computationally very expensive and need high-performance computing (HPC) facilities for further improving the current state of knowledge. During recent years, many-core architectures such as graphics processing units (GPUs) have been added to available large HPC systems. Such GPU-accelerated computing together with advances in multi-core central processing units (CPUs) can greatly accelerate scientific applications. There are mainly two possible choices of language support for GPU cards, the CUDA programming environment and OpenCL language standard. CUDA software development targets NVIDIA graphic cards while OpenCL was adopted mainly by AMD graphic cards. In order to employ such hardware accelerators for seismic wave propagation simulations, we incorporated a code generation tool BOAST into an existing spectral-element code package SPECFEM3D_GLOBE. This allows us to use meta-programming of computational kernels and generate optimized source code for both CUDA and OpenCL languages, running simulations on either CUDA or OpenCL hardware accelerators. We show here applications of forward and adjoint seismic wave propagation on CUDA/OpenCL GPUs, validating results and comparing performances for different simulations and hardware usages.

  5. Observational and Theoretical Challenges to Wave or Turbulence Accelerations of the Fast Solar Wind

    Science.gov (United States)

    Roberts, D. Aaron

    2008-01-01

    We use both observations and theoretical considerations to show that hydromagnetic waves or turbulence cannot produce the acceleration of the fast solar wind and the related heating of the open solar corona. Waves do exist as shown by Hinode and other observations, and can play a role in the differential heating and acceleration of minor ions but their amplitudes are not sufficient to power the wind, as demonstrated by extrapolation of magnetic spectra from Helios and Ulysses observations. Dissipation mechanisms invoked to circumvent this conclusion cannot be effective for a variety of reasons. In particular, turbulence does not play a strong role in the corona as shown by both eclipse observations of coronal striations and theoretical considerations of line-tying to a nonturbulent photosphere, nonlocality of interactions, and the nature of kinetic dissipation. In the absence of wave heating and acceleration, the chromosphere and transition region become the natural source of open coronal energization. We suggest a variant of the velocity filtration approach in which the emergence and complex churning of the magnetic flux in the chromosphere and transition region continuously and ubiquitously produces the nonthermal distributions required. These particles are then released by magnetic carpet reconnection at a wide range of scales and produce the wind as described in kinetic approaches. Since the carpet reconnection is not the main source of the energization of the plasma, there is no expectation of an observable release of energy in nanoflares.

  6. Demonstrations that the Solar Wind is Not Accelerated by Waves or Turbulence

    Science.gov (United States)

    Roberts, D. Aaron

    2010-01-01

    The present work uses observations and theoretical considerations to provide both qualitative and quantitative arguments that hydromagnetic waves, whether turbulent or not, cannot produce the acceleration of the fast solar wind and the related heating of the open solar corona. Waves do exist, and can play a role in the differential heating and acceleration of minor ions, but their amplitudes are not sufficient to power the wind, as demonstrated by extrapolation of magnetic spectra from Helios and Ulysses observations. Dissipation mechanisms invoked to circumvent this conclusion cannot be effective for a variety of reasons. In particular, turbulence does not play a strong role in the corona as shown both by observations of coronal striations and other features, and by theoretical considerations of line-tying to a nonturbulent photosphere, nonlocality of interactions, and the nature of the kinetic dissipation. We consider possible "ways out" of the arguments presented, and suggest that in the absence of wave or turbulent heating and acceleration, the chromosphere and transition region become the natural source, if yet unproven, of open coronal energization through the production of nonthermal particle distributions.

  7. Electron acceleration to high energies at quasi-parallel shock waves in the solar corona

    Science.gov (United States)

    Mann, G.; Classen, H.-T.

    1995-01-01

    In the solar corona shock waves are generated by flares and/or coronal mass ejections. They manifest themselves in solar type 2 radio bursts appearing as emission stripes with a slow drift from high to low frequencies in dynamic radio spectra. Their nonthermal radio emission indicates that electrons are accelerated to suprathermal and/or relativistic velocities at these shocks. As well known by extraterrestrial in-situ measurements supercritical, quasi-parallel, collisionless shocks are accompanied by so-called SLAMS (short large amplitude magnetic field structures). These SLAMS can act as strong magnetic mirrors, at which charged particles can be reflected and accelerated. Thus, thermal electrons gain energy due to multiple reflections between two SLAMS and reach suprathermal and relativistic velocities. This mechanism of accelerating electrons is discussed for circumstances in the solar corona and may be responsible for the so-called 'herringbones' observed in solar type 2 radio bursts.

  8. Untangling the Effect of Head Acceleration on Brain Responses to Blast Waves.

    Science.gov (United States)

    Mao, Haojie; Unnikrishnan, Ginu; Rakesh, Vineet; Reifman, Jaques

    2015-12-01

    Multiple injury-causing mechanisms, such as wave propagation, skull flexure, cavitation, and head acceleration, have been proposed to explain blast-induced traumatic brain injury (bTBI). An accurate, quantitative description of the individual contribution of each of these mechanisms may be necessary to develop preventive strategies against bTBI. However, to date, despite numerous experimental and computational studies of bTBI, this question remains elusive. In this study, using a two-dimensional (2D) rat head model, we quantified the contribution of head acceleration to the biomechanical response of brain tissues when exposed to blast waves in a shock tube. We compared brain pressure at the coup, middle, and contre-coup regions between a 2D rat head model capable of simulating all mechanisms (i.e., the all-effects model) and an acceleration-only model. From our simulations, we determined that head acceleration contributed 36-45% of the maximum brain pressure at the coup region, had a negligible effect on the pressure at the middle region, and was responsible for the low pressure at the contre-coup region. Our findings also demonstrate that the current practice of measuring rat brain pressures close to the center of the brain would record only two-thirds of the maximum pressure observed at the coup region. Therefore, to accurately capture the effects of acceleration in experiments, we recommend placing a pressure sensor near the coup region, especially when investigating the acceleration mechanism using different experimental setups. PMID:26458125

  9. A 3D MPI-Parallel GPU-accelerated framework for simulating ocean wave energy converters

    Science.gov (United States)

    Pathak, Ashish; Raessi, Mehdi

    2015-11-01

    We present an MPI-parallel GPU-accelerated computational framework for studying the interaction between ocean waves and wave energy converters (WECs). The computational framework captures the viscous effects, nonlinear fluid-structure interaction (FSI), and breaking of waves around the structure, which cannot be captured in many potential flow solvers commonly used for WEC simulations. The full Navier-Stokes equations are solved using the two-step projection method, which is accelerated by porting the pressure Poisson equation to GPUs. The FSI is captured using the numerically stable fictitious domain method. A novel three-phase interface reconstruction algorithm is used to resolve three phases in a VOF-PLIC context. A consistent mass and momentum transport approach enables simulations at high density ratios. The accuracy of the overall framework is demonstrated via an array of test cases. Numerical simulations of the interaction between ocean waves and WECs are presented. Funding from the National Science Foundation CBET-1236462 grant is gratefully acknowledged.

  10. Shock wave acceleration of protons in inhomogeneous plasma interacting with ultrashort intense laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Lecz, Zs. [ELI-ALPS, ELI-HU Nkft., Szeged (Hungary); Andreev, A. [ELI-ALPS, ELI-HU Nkft., Szeged (Hungary); Max-Born Institute, Berlin (Germany)

    2015-04-15

    The acceleration of protons, triggered by solitary waves in expanded solid targets is investigated using particle-in-cell simulations. The near-critical density plasma is irradiated by ultrashort high power laser pulses, which generate the solitary wave. The transformation of this soliton into a shock wave during propagation in plasma with exponentially decreasing density profile is described analytically, which allows to obtain a scaling law for the proton energy. The high quality proton bunch with small energy spread is produced by reflection from the shock-front. According to the 2D simulations, the mechanism is stable only if the laser pulse duration is shorter than the characteristic development time of the parasitic Weibel instability.

  11. Reformed Solitary Kinetic Alfvén Waves due to Dissipations and Auroral Electron Acceleration

    Institute of Scientific and Technical Information of China (English)

    WU De-Jin; CHAO Jih-Kwin; LEE Luo-Chuan; FENG Xue-Shang

    2001-01-01

    The physical nature of the auroral electron acceleration has been an outstanding problem in space physics for decades.Some recent observations from the auroral orbit satellites,FREJA and FAST,showed that large amplitude solitary kinetic Alfvén waves (SKAWs) are a common electromagnetic active phenomenon in the auroral magnetosphere. In a Iow-ββ/2 (i.e.,β/2 < me/mi < 1) plasma,the drift velocity of electrons relative to ions within SKAWs is much larger than thermal velocities of both electrons and ions.This leads to instabilities and causes dissipations of SKAWs.In the present work,based on the analogy of classical particle motion in a potential well,it is shown that a shock-like structure can be formed from SKAWs if dissipation effects are included.The reformed SKAWs with a shock-like structure have a local density jump and a net field-aligned electric potential drop of order of mev2A/e over a characteristic width of several )e.As a consequence,the reformed SKAWs can efficiently accelerate electrons field-aligned to the order of the local Alfvén velocity.In particular,we argue that this electron acceleration mechanism by reformed SKAWs can play an important role in the auroral electron acceleration problem.The result shows that not only the location of acceleration regions predicted by this model is well consistent with the observed auroral electron acceleration region of I 2 RE above the auroral ionosphere,but also the accelerated electrons from this region can obtain an energy of several keV and carry a field-aligned current of several/A/m2 which are comparable to the observations of auroral electrons.

  12. Electron acceleration during the decay of nonlinear Whistler waves in low-beta electron-ion plasma

    Energy Technology Data Exchange (ETDEWEB)

    Umeda, Takayuki; Saito, Shinji [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya City, Aichi 464-8601 (Japan); Nariyuki, Yasuhiro, E-mail: umeda@stelab.nagoya-u.ac.jp, E-mail: saito@stelab.nagoya-u.ac.jp, E-mail: nariyuki@edu.u-toyama.ac.jp [Faculty of Human Development, University of Toyama, Toyama City, Toyama 930-8555 (Japan)

    2014-10-10

    Relativistic electron acceleration through dissipation of a nonlinear, short-wavelength, and monochromatic electromagnetic whistler wave in low-beta plasma is investigated by utilizing a one-dimensional fully relativistic electromagnetic particle-in-cell code. The nonlinear (large-amplitude) parent whistler wave decays through the parametric instability which enhances electrostatic ion acoustic waves and electromagnetic whistler waves. These waves satisfy the condition of three-wave coupling. Through the decay instability, the energy of electron bulk velocity supporting the parent wave is converted to the thermal energy perpendicular to the background magnetic field. Increase of the perpendicular temperature triggers the electron temperature anisotropy instability which generates broadband whistler waves and heats electrons in the parallel direction. The broadband whistler waves are inverse-cascaded during the relaxation of the electron temperature anisotropy. In lower-beta conditions, electrons with a pitch angle of about 90° are successively accelerated by inverse-cascaded whistler waves, and selected electrons are accelerated to over a Lorentz factor of 10. The result implies that the nonlinear dissipation of a finite-amplitude and short-wavelength whistler wave plays an important role in producing relativistic nonthermal electrons over a few MeV especially at lower beta plasmas.

  13. Wearable Beat to Beat Blood Pressure Monitor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A key component of NASA's human exploration programs is a system that monitors the health of the crew during space missions. The wearable beat-to-beat blood...

  14. Ultrarelativistic electron butterfly distributions created by parallel acceleration due to magnetosonic waves

    Science.gov (United States)

    Li, Jinxing; Bortnik, Jacob; Thorne, Richard M.; Li, Wen; Ma, Qianli; Baker, Daniel N.; Reeves, Geoffrey D.; Fennell, Joseph F.; Spence, Harlan E.; Kletzing, Craig A.; Kurth, William S.; Hospodarsky, George B.; Angelopoulos, Vassilis; Blake, J. Bernard.

    2016-04-01

    The Van Allen Probe observations during the recovery phase of a large storm that occurred on 17 March 2015 showed that the ultrarelativistic electrons at the inner boundary of the outer radiation belt (L* = 2.6-3.7) exhibited butterfly pitch angle distributions, while the inner belt and the slot region also showed evidence of sub-MeV electron butterfly distributions. Strong magnetosonic waves were observed in the same regions and at the same time periods as these butterfly distributions. Moreover, when these magnetosonic waves extended to higher altitudes (L* = 4.1), the butterfly distributions also extended to the same region. Combining test particle calculations and Fokker-Planck diffusion simulations, we successfully reproduced the formation of the ultrarelativistic electron butterfly distributions, which primarily result from parallel acceleration caused by Landau resonance with magnetosonic waves. The coexistence of ultrarelativistic electron butterfly distributions with magnetosonic waves was also observed in the 24 June 2015 storm, providing further support that the magnetosonic waves play a key role in forming butterfly distributions.

  15. Ultra-high-energy cosmic ray acceleration by relativistic blast waves

    Science.gov (United States)

    Gallant, Yves A.; Achterberg, Abraham

    1999-05-01

    We consider the acceleration of charged particles at the ultrarelativistic shocks, with Lorentz factors Gamma_s>>1 relative to the upstream medium, arising in relativistic fireball models of gamma-ray bursts (GRBs). We show that for Fermi-type shock acceleration, particles initially isotropic in the upstream medium can gain a factor of order Gamma_s^2 in energy in the first shock-crossing cycle, but that the energy gain factor for subsequent shock-crossing cycles is only of order 2, because for realistic deflection processes particles do not have time to become isotropic upstream before recrossing the shock. We evaluate the maximum energy attainable and the efficiency of this process, and show that for a GRB fireball expanding into a typical interstellar medium, these exclude the production of ultra-high-energy cosmic rays (UHECRs), with energies in the range 10^18.5-10^20.5 eV, by the blast wave. However, we propose that in the context of neutron-star binaries as the progenitors of GRBs, relativistic ions from the pulsar-wind bubbles produced by these systems could be accelerated by the blast wave. We show that if the known binary pulsars are typical, the maximum energy, efficiency, and spectrum in this case can account for the observed population of UHECRs.

  16. Nonlinear ghost waves accelerate the progression of high-grade brain tumors

    Science.gov (United States)

    Pardo, Rosa; Martínez-González, Alicia; Pérez-García, Víctor M.

    2016-10-01

    We study a reduced continuous model describing the evolution of high grade gliomas in response to hypoxic events through the interplay of different cellular phenotypes. We show that hypoxic events, even when sporadic and/or limited in space, may have a crucial role on the acceleration of high grade gliomas growth. Our modeling approach is based on two cellular phenotypes. One of them is more migratory and a second one is more proliferative. Transitions between both phenotypes are driven by the local oxygen values, assumed in this simple model to be uniform. Surprisingly, even very localized in time hypoxia events leading to transient migratory populations have the potential to accelerate the tumor's invasion speed up to speeds close to those of the migratory phenotype. The high invasion speed persists for times much longer than the lifetime of the hypoxic event. Moreover, the phenomenon is observed both when the migratory cells form a persistent wave of cells located on the invasion front and when they form a evanescent "ghost" wave disappearing after a short time by decay to the more proliferative phenotype. Our findings are obtained through numerical simulations of the model equations both in 1D and higher dimensional scenarios. We also provide a deeper mathematical analysis of some aspects of the problem such as the conditions for the existence of persistent waves of cells with a more migratory phenotype.

  17. Off beat: pluralizing rhythm

    NARCIS (Netherlands)

    J.H. Hoogstad; B. Stougaard Pedersen

    2013-01-01

    Off Beat: Pluralizing Rhythm draws attention to rhythm as a tool for analyzing various cultural objects. In fields as diverse as music, culture, nature, and economy, rhythm can be seen as a phenomenon that both connects and divides. It suggests a certain measure with which people, practices, and cul

  18. Accelerator

    International Nuclear Information System (INIS)

    The invention claims equipment for stabilizing the position of the front covers of the accelerator chamber in cyclic accelerators which significantly increases accelerator reliability. For stabilizing, it uses hydraulic cushions placed between the electromagnet pole pieces and the front chamber covers. The top and the bottom cushions are hydraulically connected. The cushions are disconnected and removed from the hydraulic line using valves. (J.P.)

  19. Experimental Validation of a Branched Solution Model for Magnetosonic Ionization Waves in Plasma Accelerators

    Science.gov (United States)

    Underwood, Thomas; Loebner, Keith; Cappelli, Mark

    2015-11-01

    Detailed measurements of the thermodynamic and electrodynamic plasma state variables within the plume of a pulsed plasma accelerator are presented. A quadruple Langmuir probe operating in current-saturation mode is used to obtain time resolved measurements of the plasma density, temperature, potential, and velocity along the central axis of the accelerator. This data is used in conjunction with a fast-framing, intensified CCD camera to develop and validate a model predicting the existence of two distinct types of ionization waves corresponding to the upper and lower solution branches of the Hugoniot curve. A deviation of less than 8% is observed between the quasi-steady, one-dimensional theoretical model and the experimentally measured plume velocity. This work is supported by the U.S. Department of Energy Stewardship Science Academic Program in addition to the National Defense Science Engineering Graduate Fellowship.

  20. Beam characterization of a new continuous wave radio frequency quadrupole accelerator

    International Nuclear Information System (INIS)

    A new Continuous Wave (CW) Radio Frequency Quadrupole (RFQ) for the ATLAS (Argonne Tandem Linac Accelerator System) Intensity Upgrade was developed, built and tested at Argonne National Laboratory. We present here a characterization of the RFQ output beam in the longitudinal phase space, as well as a measurement of the transverse beam halo. Measurement results are compared to simulations performed using the beam dynamics code TRACK. -- Highlights: • Beam commissioning of a new CW RFQ has been performed at Argonne National Laboratory. • Energy spread and bunch shape measurements were conducted. • The formation of a beam halo in the transverse phase space was studied

  1. A direct current rectification scheme for microwave space power conversion using traveling wave electron acceleration

    Science.gov (United States)

    Manning, Robert M.

    1993-01-01

    The formation of the Vision-21 conference held three years ago allowed the present author to reflect and speculate on the problem of converting electromagnetic energy to a direct current by essentially reversing the process used in traveling wave tubes that converts energy in the form of a direct current to electromagnetic energy. The idea was to use the electric field of the electromagnetic wave to produce electrons through the field emission process and accelerate these electrons by the same field to produce an electric current across a large potential difference. The acceleration process was that of cyclotron auto-resonance. Since that time, this rather speculative ideas has been developed into a method that shows great promise and for which a patent is pending and a prototype design will be demonstrated in a potential laser power beaming application. From the point of view of the author, a forum such as Vision-21 is becoming an essential component in the rather conservative climate in which our initiatives for space exploration are presently formed. Exchanges such as Vision-21 not only allows us to deviate from the 'by-the-book' approach and rediscover the ability and power in imagination, but provides for the discussion of ideas hitherto considered 'crazy' so that they may be given the change to transcend from the level of eccentricity to applicability.

  2. Accelerated dynamics of blast wave driven Rayleigh-Taylor instabilities in high energy density plasmas

    Science.gov (United States)

    Swisher, N.; Kuranz, C.; Drake, R. P.; Abarzhi, S. I.

    2014-10-01

    We report the systematic analysis of experimental data describing the late time evolution of the high Mach number and high Reynolds number Rayleigh-Taylor instability which is driven by a blast wave. The parameter regime is relevant to high energy density plasmas and astrophysics. The experiments have been conducted at the Omega laser facility. By processing the experimental x-ray images, we quantified the delicate features of RT dynamics, including the measurements of the curvature of the transmitted shock and the interface envelopes, the positions of RT bubbles and spikes, and the quantification of statistics of RT mixing. The measurements were performed at four time steps and for three different initial perturbations of the target (single mode and two two-mode). We found that within the noise level the curvatures of the shock and interface envelope evolve steadily and are an imprint of laser imperfections. At late times, the bubble merge does not occur, and the flow keeps significant degree of order. Yet, the blast-wave-driven RT spikes do accelerate with the power-law exponent smaller than that in case of sustained acceleration. We compared the experimental results with the momentum model of RT mixing and stochastic model achieving good agreement. The work is supported by the US National Science Foundation.

  3. beat a dead horse

    Institute of Scientific and Technical Information of China (English)

    吕浙

    2005-01-01

    beat a dead horse的字面意思为“鞭打死马”。“鞭打死马”有什么作用?毫无疑问,一点意义也没有。因此,该习语的意思相当于中文的“徒劳,白费力气,白费口舌”。如:

  4. RF-thermal-structural-RF coupled analysis on a travelling wave disk-loaded accelerating structure

    International Nuclear Information System (INIS)

    The travelling wave (TW) disk-loaded accelerating structure is one of the key components in normal conducting (NC) linear accelerators, and has been studied for many years. In the design process, usually after the dimensions of each cell and the two couplers are finalized, the structure is fabricated and tuned, and then the whole structure RF characteristics are measured by using a vector network analyzer. Before fabrication, the whole structure characteristics (including RF, thermal and structural ones) are less simulated due to the limited capability of currently available computers. In this paper, we described a method for performing RF-thermal-structural-RF coupled analysis on a TW disk-loaded structure using only one PC. In order to validate our method, we first analyzed and compared our RF simulation results on the 3 m long BEPC Ⅱ structure with the corresponding experimental results, which shows very good consistency. Finally, the RF-thermal-structure-RF coupled analysis results on the 1.35 m long NSC KIPT linac accelerating structure are presented. (authors)

  5. Particle acceleration and wave excitation in quasi-parallel high-Mach-number collisionless shocks: Particle-in-cell simulation

    CERN Document Server

    Kato, Tsunehiko N

    2014-01-01

    We herein investigate shock formation and particle acceleration processes for both protons and electrons in a quasi-parallel high-Mach-number collisionless shock through a long-term, large-scale particle-in-cell simulation. We show that both protons and electrons are accelerated in the shock and that these accelerated particles generate large-amplitude Alfv\\'{e}nic waves in the upstream region of the shock. After the upstream waves have grown sufficiently, the local structure of the collisionless shock becomes substantially similar to that of a quasi-perpendicular shock due to the large transverse magnetic field of the waves. A fraction of protons are accelerated in the shock with a power-law-like energy distribution. The rate of proton injection to the acceleration process is approximately constant, and in the injection process, the phase-trapping mechanism for the protons by the upstream waves can play an important role. The dominant acceleration process is a Fermi-like process through repeated shock crossi...

  6. Stochastic Acceleration of $^3$He and $^4$He in Solar Flares by Parallel Propagating Plasma Waves: General Results

    CERN Document Server

    Liu, S; Mason, G M; Liu, Siming; Petrosian, Vah\\'{e}; Mason, Glenn M.

    2005-01-01

    We study the acceleration in solar flares of $^3$He and $^4$He from a thermal background by parallel propagating plasma waves with a general broken power-law spectrum that takes into account the turbulence generation processes at large scales and the thermal damping effects at small scales. The exact dispersion relation for a cold plasma is used to describe the relevant wave modes. Because low-energy $\\alpha$-particles only interact with small scale waves in the $^4$He-cyclotron branch, where the wave frequencies are below the $\\alpha$-particle gyro-frequency, their pitch angle averaged acceleration time is at least one order of magnitude longer than that of $^3$He ions, which mostly resonate with relatively higher frequency waves in the proton-cyclotron (PC) branch. The $\\alpha$-particle acceleration rate starts to approach that of $^3$He beyond a few tens of keV nucleon$^{-1}$, where $\\alpha$-particles can also interact with long wavelength waves in the PC branch. However, the $^4$He acceleration rate is al...

  7. Accelerated rogue waves generated by soliton fusion at the advanced stage of supercontinuum formation in photonic crystal fibers

    CERN Document Server

    Driben, Rodislav

    2012-01-01

    Soliton fusion is a fascinating and delicate phenomenon that manifests itself in optical fibers in case of interaction between co-propagating solitons with small temporal and wavelengths separation. We show that the mechanism of acceleration of trailing soliton by dispersive waves radiated from the preceding one provides necessary conditions for soliton fusion at the advanced stage of supercontinuum generation in photonic crystal fibers. As a result of fusion large intensity robust light structures arise and propagate over significant distances. In presence of small random noise the delicate condition for the effective fusion between solitons can easily be broken, making the fusion induced giant waves a rare statistical event. Thus oblong-shaped giant accelerated waves become excellent candidates for optical rogue waves.

  8. Analysis of the dependence of surfatron acceleration of electrons by an electromagnetic wave in space plasma on the particle momentum along the wave front

    Energy Technology Data Exchange (ETDEWEB)

    Erokhin, A. N., E-mail: nerokhin@mx.iki.rssi.ru [People’s Friendship University of Russia (Russian Federation); Zol’nikova, N. N. [Russian Academy of Sciences, Space Research Institute (Russian Federation); Erokhin, N. S. [People’s Friendship University of Russia (Russian Federation)

    2016-01-15

    Based on the numerical solution of the nonlinear nonstationary second-order equation for the wave phase on the particle trajectory, the dynamics of surfatron acceleration of electrons by an electromagnetic wave propagating across the external magnetic field in space plasma is analyzed as a function of the electron momentum along the wave front. Numerical calculations show that, for strongly relativistic initial values of the electron momentum component along the wave front g{sub y}(0) (the other parameters of the problem being the same), electrons are trapped into the regime of ultrarelativistic surfatron acceleration within a certain interval of the initial wave phase Ψ(0) on the particle trajectory. It is assumed in the calculations that vertical bar Ψ(0) vertical bar ≤ π. For strongly relativistic values of g{sub y}(0), electrons are immediately trapped by the wave for 19% of the initial values of the phase Ψ(0) (favorable phases). For the rest of the values of Ψ(0), trapping does not occur even at long times. This circumstance substantially simplifies estimations of the wave damping due to particle acceleration in subsequent calculations. The dynamics of the relativistic factor and the components of the electron velocity and momentum under surfatron acceleration is also analyzed. The obtained results are of interest for the development of modern concepts of possible mechanisms of generation of ultrarelativistic particle fluxes in relatively calm space plasma, as well as for correct interpretation of observational data on the fluxes of such particles and explanation of possible reasons for the deviation of ultrarelativistic particle spectra detected in the heliosphere from the standard power-law scalings and the relation of these variations to space weather and large-scale atmospheric processes similar to tropical cyclones.

  9. Modeling of Nonlinear Beat Signals of TAE's

    Science.gov (United States)

    Zhang, Bo; Berk, Herbert; Breizman, Boris; Zheng, Linjin

    2012-03-01

    Experiments on Alcator C-Mod reveal Toroidal Alfven Eigenmodes (TAE) together with signals at various beat frequencies, including those at twice the mode frequency. The beat frequencies are sidebands driven by quadratic nonlinear terms in the MHD equations. These nonlinear sidebands have not yet been quantified by any existing codes. We extend the AEGIS code to capture nonlinear effects by treating the nonlinear terms as a driving source in the linear MHD solver. Our goal is to compute the spatial structure of the sidebands for realistic geometry and q-profile, which can be directly compared with experiment in order to interpret the phase contrast imaging diagnostic measurements and to enable the quantitative determination of the Alfven wave amplitude in the plasma core

  10. Structure of a strong supernova shock wave and rapid electron acceleration confined in its transition region

    CERN Document Server

    Shimada, Nobue; Amano, Takanobu; 10.1063/1.3322828

    2010-01-01

    A new rapid energization process within a supernova shock transition region (STR) is reported by utilizing numerical simulation. Although the scale of a STR as a main dissipation region is only several hundreds of thousands km, several interesting structures are found relating to generation of a root of the energetic particles. The nonlinear evolution of plasma instabilities lead to a dynamical change in the ion phase space distribution which associates with change of the field properties. As a result, different types of large-amplitude field structures appear. One is the leading wave packet and another is a series of magnetic solitary humps. Each field structure has a microscopic scale (~ the ion inertia length). Through the multiple nonlinear scattering between these large-amplitude field structures, electrons are accelerated directly. Within a STR, quick thermalization realizes energy equipartition between the ion and electron, hot electrons play an important role in keeping these large-amplitude field str...

  11. Particle Diffusion and Acceleration by Shock Wave in Magnetized Filamentary Turbulence

    CERN Document Server

    Honda, M; Honda, Mitsuru; Honda, Yasuko S.

    2005-01-01

    We expand the off-resonant scattering theory for particle diffusion in magnetized current filaments that can be typically compared to astrophysical jets, including active galactic nucleus jets. In a high plasma beta region where the directional bulk flow is a free-energy source for establishing turbulent magnetic fields via current filamentation instabilities, a novel version of quasi-linear theory to describe the diffusion of test particles is proposed. The theory relies on the proviso that the injected energetic particles are not trapped in the small-scale structure of magnetic fields wrapping around and permeating a filament but deflected by the filaments, to open a new regime of the energy hierarchy mediated by a transition compared to the particle injection. The diffusion coefficient derived from a quasi-linear type equation is applied to estimating the timescale for the stochastic acceleration of particles by the shock wave propagating through the jet. The generic scalings of the achievable highest ener...

  12. PROPERTIES OF A CORONAL SHOCK WAVE AS A DRIVER OF EARLY SEP ACCELERATION

    Energy Technology Data Exchange (ETDEWEB)

    Kozarev, K. A. [Smithsonian Astrophysical Observatory, Cambridge, MA 02138 (United States); Raymond, J. C. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Lobzin, V. V. [Learmonth Solar Observatory, Exmouth, WA 6707 (Australia); Hammer, M., E-mail: kkozarev@cfa.harvard.edu [Department of Physics, Cornell University, 109 Clark Hall, Ithaca, NY 14853 (United States)

    2015-02-01

    Coronal mass ejectmons (CMEs) are thought to drive collisionless shocks in the solar corona, which in turn have been shown to be capable of accelerating solar energetic particles (SEPs) in minutes. It has been notoriously difficult to extract information about energetic particle spectra in the corona, owing to a lack of in situ measurements. It is possible, however, to combine remote observations with data-driven models in order to deduce coronal shock properties relevant to the local acceleration of SEPs and their heliospheric connectivity to near-Earth space. We present such novel analysis applied to the 2011 May 11 CME event on the western solar limb, focusing on the evolution of the eruption-driven, dome-like shock wave observed by the Atmospheric Imaging Assembly (AIA) EUV telescopes on board the Solar Dynamics Observatory spacecraft. We analyze the shock evolution and estimate its strength using emission measure modeling. We apply a new method combining a geometric model of the shock front with a potential field source surface model to estimate time-dependent field-to-shock angles and heliospheric connectivity during shock passage in the low corona. We find that the shock was weak, with an initial speed of ∼450 km s{sup –1}. It was initially mostly quasi-parallel, but a significant portion of it turned quasi-perpendicular later in the event. There was good magnetic connectivity to near-Earth space toward the end of the event as observed by the AIA instrument. The methods used in this analysis hold a significant potential for early characterization of coronal shock waves and forecasting of SEP spectra based on remote observations.

  13. Ultra-high-energy cosmic ray acceleration by relativistic blast waves

    CERN Document Server

    Gallant, Y A; Gallant, Yves A.; Achterberg, Abraham

    1999-01-01

    We consider the acceleration of charged particles at the ultra-relativistic shocks, with Lorentz factors \\Gamma_s >> 1 relative to the upstream medium, arising in relativistic fireball models of gamma-ray bursts (GRBs). We show that for Fermi-type shock acceleration, particles initially isotropic in the upstream medium can gain a factor of order \\Gamma_s^2 in energy in the first shock crossing cycle, but that the energy gain factor for subsequent shock crossing cycles is only of order 2, because for realistic deflection processes particles do not have time to re-isotropise upstream before recrossing the shock. We evaluate the maximum energy attainable and the efficiency of this process, and show that for a GRB fireball expanding into a typical interstellar medium, these exclude the production of ultra-high-energy cosmic rays (UHECRs), with energies in the range 10^{18.5} - 10^{20.5} eV, by the blast wave. We propose, however, that in the context of neutron star binaries as the progenitors of GRBs, relativisti...

  14. Shock Waves and Cosmic Ray Acceleration in the Outskirts of Galaxy Clusters

    CERN Document Server

    Hong, Sungwook E; Kang, Hyesung; Cen, Renyue

    2014-01-01

    The outskirts of galaxy clusters are continuously disturbed by mergers and gas infall along filaments, which in turn induce turbulent flow motions and shock waves. We examine the properties of shocks that form within $r_{200}$ in sample galaxy clusters from structure formation simulations. While most of these shocks are weak and inefficient accelerators of cosmic rays (CRs), there are a number of strong, energetic shocks which can produce large amounts of CR protons via diffusive shock acceleration. We show that the energetic shocks reside mostly in the outskirts and a substantial fraction of them are induced by infall of the warm-hot intergalactic medium from filaments. As a result, the radial profile of the CR pressure in the intracluster medium is expected to be broad, dropping off more slowly than that of the gas pressure, and might be even temporarily inverted, peaking in the outskirts. The volume-integrated momentum spectrum of CR protons inside $r_{200}$ has the power-law slope of $4.25 - 4.5$, indicat...

  15. Modulation of attosecond beating in resonant two-photon ionization

    CERN Document Server

    Galán, Álvaro J; Martín, Fernando

    2014-01-01

    We present a theoretical study of the photoelectron attosecond beating at the basis of RABBIT (Reconstruction of Attosecond Beating By Interference of Two-photon transitions) in the presence of autoionizing states. We show that, as a harmonic traverses a resonance, its sidebands exhibit a peaked phase shift as well as a modulation of the beating frequency itself. Furthermore, the beating between two resonant paths persists even when the pump and the probe pulses do not overlap, thus providing a sensitive non-holographic interferometric means to reconstruct coherent metastable wave packets. We characterize these phenomena quantitatively with a general finite-pulse analytical model that accounts for the effect of both intermediate and final resonances on two-photon processes, at a negligible computational cost. The model predictions are in excellent agreement with those of accurate ab initio calculations for the helium atom in the region of the N=2 doubly excited states.

  16. Jacobian-free Newton-Krylov methods with GPU acceleration for computing nonlinear ship wave patterns

    CERN Document Server

    Pethiyagoda, Ravindra; Moroney, Timothy J; Back, Julian M

    2014-01-01

    The nonlinear problem of steady free-surface flow past a submerged source is considered as a case study for three-dimensional ship wave problems. Of particular interest is the distinctive wedge-shaped wave pattern that forms on the surface of the fluid. By reformulating the governing equations with a standard boundary-integral method, we derive a system of nonlinear algebraic equations that enforce a singular integro-differential equation at each midpoint on a two-dimensional mesh. Our contribution is to solve the system of equations with a Jacobian-free Newton-Krylov method together with a banded preconditioner that is carefully constructed with entries taken from the Jacobian of the linearised problem. Further, we are able to utilise graphics processing unit acceleration to significantly increase the grid refinement and decrease the run-time of our solutions in comparison to schemes that are presently employed in the literature. Our approach provides opportunities to explore the nonlinear features of three-...

  17. Bounded Acceleration Capacity Drop in a Lagrangian Formulation of the Kinematic Wave Model with Vehicle Characteristics and Unconstrained Overtaking

    NARCIS (Netherlands)

    Calvert, S.C.; Snelder, M.; Taale, H.; Wageningen-Kessels, F.L.M. van; Hoogendoorn, S.P.

    2015-01-01

    In this contribution a model-based analysis of the application of bounded acceleration in traffic flow is considered as a cause for the capacity drop. This is performed in a Lagrangian formulation of the kinematic wave model with general vehicle specific characteristics. Unconstrained overtaking is

  18. Nonlinear local parallel acceleration of electrons through Landau trapping by oblique whistler mode waves in the outer radiation belt

    Science.gov (United States)

    Agapitov, Oleksiy; Artemyev, Anton; Mourenas, Didier; Mozer, Forrest; Krasnoselskikh, Vladimir

    2016-04-01

    Simultaneous observations of electron velocity distributions and chorus waves by the Van Allen Probe B are analyzed to identify long-lasting (more than 6 h) signatures of electron Landau resonant interactions with oblique chorus waves in the outer radiation belt. Such Landau resonant interactions result in the trapping of ˜1-10 keV electrons and their acceleration up to 100-300 keV. This kind of process becomes important for oblique whistler mode waves having a significant electric field component along the background magnetic field. In the inhomogeneous geomagnetic field, such resonant interactions then lead to the formation of a plateau in the parallel (with respect to the geomagnetic field) velocity distribution due to trapping of electrons into the wave effective potential. We demonstrate that the electron energy corresponding to the observed plateau remains in very good agreement with the energy required for Landau resonant interaction with the simultaneously measured oblique chorus waves over 6 h and a wide range of L shells (from 4 to 6) in the outer belt. The efficient parallel acceleration modifies electron pitch angle distributions at energies ˜50-200 keV, allowing us to distinguish the energized population. The observed energy range and the density of accelerated electrons are in reasonable agreement with test particle numerical simulations.

  19. Masses for Galactic Beat Cepheids

    Science.gov (United States)

    D'Cruz, Noella L.; Morgan, Siobahn M.; Böhm-Vitense, Erika

    2000-08-01

    Accurate mass determinations for Cepheids may be used to determine the degree of excess mixing in the interiors of their main-sequence progenitors: the larger the excess mixing, the larger the luminosity of the Cepheid of a given mass, or the smaller the mass of a Cepheid with given luminosity. Dynamical masses determined recently for a few Cepheid binaries indicate excess mixing somewhat stronger than that corresponding to the convective overshoot models by Schaller et al. Beat Cepheids can be used similarly to test main-sequence mixing in stellar interiors. The period ratios for beat Cepheids depend on luminosity, Teff, heavy element abundance, and mass. By comparing pulsational models and the observationally derived luminosity, Teff, metallicities, and period ratios it is possible to obtain masses for these stars, the so-called beat masses. With the old opacities masses much smaller than the evolutionary masses were obtained. With the new OPAL opacities a beat mass close to the dynamical mass was obtained for the binary beat Cepheid Y Carinae, showing that it is now possible to obtain reliable beat masses. In this paper, we determine beat masses for seven Galactic beat Cepheids for which photometric and spectroscopic data are available. We find an average mass around 4.2+/-0.3 Msolar for these stars, though the actual error limits for each star may be larger mainly because of uncertainties in E(B-V) and the heavy element abundances. (As derived spectroscopically, beat Cepheids are in general metal-poor, with -0.4relation between the derived beat masses and the luminosities again indicates excess mixing that is somewhat larger than that corresponding to the models by Schaller et al.

  20. Accelerating Simulation of Seismic Wave Propagation by Multi-GPUs (Invited)

    Science.gov (United States)

    Okamoto, T.; Takenaka, H.; Nakamura, T.; Aoki, T.

    2010-12-01

    Simulation of seismic wave propagation is essential in modern seismology: the effects of irregular topography of the surface, internal discontinuities and heterogeneity on the seismic waveforms must be precisely modeled in order to probe the Earth's and other planets' interiors, to study the earthquake sources, and to evaluate the strong ground motions due to earthquakes. Devices with high computing performance are necessary because in large scale simulations more than one billion of grid points are required. GPU (Graphics Processing Unit) is a remarkable device for its many core architecture with more-than-one-hundred processing units, and its high memory bandwidth. Now GPU delivers extremely high computing performance (more than one tera-flops in single-precision arithmetic) at a reduced power and cost compared to conventional CPUs. The simulation of seismic wave propagation is a memory intensive problem which involves large amount of data transfer between the memory and the arithmetic units while the number of arithmetic calculations is relatively small. Therefore the simulation should benefit from the high memory bandwidth of the GPU. Thus several approaches to adopt GPU to the simulation of seismic wave propagation have been emerging (e.g., Komatitsch et al., 2009; Micikevicius, 2009; Michea and Komatitsch, 2010; Aoi et al., SSJ 2009, JPGU 2010; Okamoto et al., SSJ 2009, SACSIS 2010). In this paper we describe our approach to accelerate the simulation of seismic wave propagation based on the finite-difference method (FDM) by adopting multi-GPU computing. The finite-difference scheme we use is the three-dimensional, velocity-stress staggered grid scheme (e.g., Grave 1996; Moczo et al., 2007) for heterogeneous medium with perfect elasticity (incorporation of an-elasticity is underway). We use the GPUs (NVIDIA S1070, 1.44 GHz) installed in the TSUBAME grid cluster in the Global Scientific Information and Computing Center, Tokyo Institute of Technology and NVIDIA

  1. Electromagnetic and beam dynamics design of a 5 MeV, 3 kW travelling wave electron linear accelerator

    International Nuclear Information System (INIS)

    An S-band (2856 MHz) 5 MeV, 3 kW traveling wave linear accelerator is currently under design and development at Raja Ramanna Centre for Advanced Technology, Indore. The accelerating structure is a 2π/3 mode constant impedance traveling wave structure, designed to accelerates the 50 keV electron beam from the electron gun to 5 MeV. It comprises of traveling wave buncher cells followed by regular accelerating cells. This paper presents the details of electromagnetic design simulations to fix the mechanical dimensions and tolerances, as well as heat loss calculations in the structure. Comparison of the results obtained from detailed numerical simulations with those obtained from approximate analytical calculations is described in the paper. The beam dynamics simulation from beginning to end of the linac is also performed and the required magnetic field profile for keeping the beam focused in the linac has been evaluated. The aim has been to maximize the capture efficiency with reduced energy spread in a short and compact structure. (author)

  2. Generation of the cosmic rays flux variations due to surfatron acceleration of charges by electromagnetic waves in space plasma

    Science.gov (United States)

    Erokhin, Nikolay; Loznikov, Vladimir; Shkevov, Rumen; Zolnikova, Nadezhda; Mikhailovskaya, Ludmila

    2016-07-01

    The analysis of experimental data on the spectra of cosmic rays (CR) has shown their variability on time scales of a few years, in particular, CR variations observed in E / Z range from TeV to 10000 TeV, where E is the energy of the particle, Z is its charge number. Consequently, the source of these variations must be located at a distance of no more than 1 parsec from the sun in the closest local interstellar clouds. As a mechanism of such variations appearance it is considered the surfatron acceleration of CR particles by electromagnetic wave in a relatively quiet space plasma. On the basis of developed model the numerical calculations were performed for particle capture dynamics (electrons, protons, helium and iron nuclei) in the wave effective potential well with a following growth their energy by 3-6 orders of magnitude. Optimal conditions for the implementation of charged particles surfatron acceleration in space plasma, the rate of trapped particles energy growth, the dynamics of wave phase on the captured particle trajectory, a temporal dynamics of components for charge impulse momentum and speed were studied. It is indicated that the capture of a small fraction of particles by wave for energies about TeV and less followed by their surfatron acceleration to an energy of about 10000 TeV will lead to a significant increase in the CR flux at such high energies. Thus CL flow variations are conditioned by changes in the space weather parameters

  3. Diffusive cosmic ray acceleration at relativistic shock waves with magnetostatic turbulence

    CERN Document Server

    Schlickeiser, Reinhard

    2015-01-01

    The analytical theory of diffusive cosmic ray acceleration at parallel stationary shock waves with magnetostatic turbulence is generalized to arbitrary shock speeds $V_s=\\beta_1c$, including in particular relativistic speeds. This is achieved by applying the diffusion approximation to the relevant Fokker-Planck particle transport equation formulated in the mixed comoving coordinate system. In this coordinate system the particle's momentum coordinates $p$ and $\\mu =p_{\\parallel }/p$ are taken in the rest frame of the streaming plasma, whereas the time and space coordinates are taken in the observer's system. For magnetostatic slab turbulence the diffusion-convection transport equation for the isotropic (in the rest frame of the streaming plasma) part of the particle's phase space density is derived. For a step-wise shock velocity profile the steady-state diffusion-convection transport equation is solved. For a symmetric pitch-angle scattering Fokker-Planck coefficient $D_{\\mu \\mu }(-\\mu )=D_{\\mu \\mu }(\\mu )$ t...

  4. Acceleration of low-energy protons and alpha particles at interplanetary shock waves

    Science.gov (United States)

    Scholer, M.; Hovestadt, D.; Ipavich, F. M.; Gloeckler, G.

    1983-01-01

    The low-energy protons and alpha particles in the energy range 30 keV/charge to 150 keV/charge associated with three different interplanetary shock waves in the immediate preshock and postshock region are studied using data obtained by the ISEE 3. The spatial distributions in the preshock and postshock medium are presented, and the dependence of the phase space density at different energies on the distance from the shock and on the form of the distribution function of both species immediately at the shock is examined. It is found that in the preshock region the particles are flowing in the solar wind frame of reference away from the shock and in the postshock medium the distribution is more or less isotropic in this frame of reference. The distribution function in the postshock region can be represented by a power law in energy which has the same spectral exponent for both protons and alpha particles. It is concluded that the first-order Fermi acceleration process can consistently explain the data, although the spectra of diffuse bow shock associated particles are different from the spectra of the interplanetary shock-associated particles in the immediate vicinity of the shock. In addition, the mean free path of the low energy ions in the preshock medium is found to be considerably smaller than the mean free path determined by the turbulence of the background interplanetary medium.

  5. Stochastic acceleration of electrons by fast magnetosonic waves in solar flares: the effects of anisotropy in velocity and wavenumber space

    Energy Technology Data Exchange (ETDEWEB)

    Pongkitiwanichakul, Peera [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Chandran, Benjamin D. G., E-mail: peera@oddjob.uchicago.edu [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States)

    2014-11-20

    We develop a model for stochastic acceleration of electrons in solar flares. As in several previous models, the electrons are accelerated by turbulent fast magnetosonic waves ({sup f}ast waves{sup )} via transit-time-damping (TTD) interactions. (In TTD interactions, fast waves act like moving magnetic mirrors that push the electrons parallel or anti-parallel to the magnetic field). We also include the effects of Coulomb collisions and the waves' parallel electric fields. Unlike previous models, our model is two-dimensional in both momentum space and wavenumber space and takes into account the anisotropy of the wave power spectrum F{sub k} and electron distribution function f {sub e}. We use weak turbulence theory and quasilinear theory to obtain a set of equations that describes the coupled evolution of F{sub k} and f {sub e}. We solve these equations numerically and find that the electron distribution function develops a power-law-like non-thermal tail within a restricted range of energies E in (E {sub nt}, E {sub max}). We obtain approximate analytic expressions for E {sub nt} and E {sub max}, which describe how these minimum and maximum energies depend upon parameters such as the electron number density and the rate at which fast-wave energy is injected into the acceleration region at large scales. We contrast our results with previous studies that assume that F{sub k} and f {sub e} are isotropic, and we compare one of our numerical calculations with the time-dependent hard-X-ray spectrum observed during the 1980 June 27 flare. In our numerical calculations, the electron energy spectra are softer (steeper) than in models with isotropic F{sub k} and f {sub e} and closer to the values inferred from observations of solar flares.

  6. Numerical modeling of surf beat generated by moving breakpoint

    Institute of Scientific and Technical Information of China (English)

    DONG GuoHai; MA XiaoZhou; TENG Bin

    2009-01-01

    As an important hydrodynamic phenomenon in the nearshore zone, the cross-shore surf beat is nu-merically studied in this paper with a fully nonlinear Boussinesq-type model, which resolves the pri-mary wave motion as well as the long waves. Compared with the classical Boussinesq equations, the equations adopted here allow for improved linear dispersion characteristics. Wave breaking and run-up in the swash zone are included in the numerical model. Mutual interactions between short waves and long waves are inherent in the model. The numerical study of long waves is based on bichromatic wave groups with a wide range of mean frequencies, group frequencies and modulation rates. The cross-shore variation in the amplitudes of short waves and long waves is investigated. The model results are compared with laboratory experiments from the literature and good agreement is found.

  7. Numerical modeling of surf beat generated by moving breakpoint

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    As an important hydrodynamic phenomenon in the nearshore zone, the cross-shore surf beat is numerically studied in this paper with a fully nonlinear Boussinesq-type model, which resolves the primary wave motion as well as the long waves. Compared with the classical Boussinesq equations, the equations adopted here allow for improved linear dispersion characteristics. Wave breaking and run-up in the swash zone are included in the numerical model. Mutual interactions between short waves and long waves are inherent in the model. The numerical study of long waves is based on bichromatic wave groups with a wide range of mean frequencies, group frequencies and modulation rates. The cross-shore variation in the amplitudes of short waves and long waves is investigated. The model results are compared with laboratory experiments from the literature and good agreement is found.

  8. Electron acceleration by an obliquely propagating electromagnetic wave in the regime of validity of the Fokker-Planck-Kolmogorov approach

    Science.gov (United States)

    Hizanidis, Kyriakos; Vlahos, L.; Polymilis, C.

    1989-01-01

    The relativistic motion of an ensemble of electrons in an intense monochromatic electromagnetic wave propagating obliquely in a uniform external magnetic field is studied. The problem is formulated from the viewpoint of Hamiltonian theory and the Fokker-Planck-Kolmogorov approach analyzed by Hizanidis (1989), leading to a one-dimensional diffusive acceleration along paths of constant zeroth-order generalized Hamiltonian. For values of the wave amplitude and the propagating angle inside the analytically predicted stochastic region, the numerical results suggest that the diffusion probes proceeds in stages. In the first stage, the electrons are accelerated to relatively high energies by sampling the first few overlapping resonances one by one. During that stage, the ensemble-average square deviation of the variable involved scales quadratically with time. During the second stage, they scale linearly with time. For much longer times, deviation from linear scaling slowly sets in.

  9. A Focused Transport Approach to SEP acceleration at a Fast Parallel Shock in the Corona Including Self-excitation of Alfvén Waves

    Science.gov (United States)

    le Roux, J. A.

    2012-12-01

    It has been argued that the acceleration of SEPS at a quasi-parallel CME-driven shock to GeV energies in the corona only occurs if strong wave-excitation by SEPs ahead of the shock reduces the parallel mean free path upstream, thus boosting the rate of diffusive shock acceleration. To investigate this issue, we modeled SEP acceleration at a fast parallel traveling shock in the corona with an existing time-dependent focused transport model. The model has been expanded recently to also feature time-dependent self-excitation and damping of Alfvén waves by SEP anisotropies ahead of the shock based on standard quasi-linear theory. Alfvén wave propagation near the traveling shock is modeled based on standard theory for wave transport in a slowly varying non-uniform plasma medium. Preliminary results will be shown to illustrate the increase in wave power driven by SEP anisotropies upstream, the effect of the shock wave in shortening the wave length and increasing the wave amplitude of Alfvén waves, and the associated acceleration of SEPs by 1st order Fermi acceleration to high energies. The role of the acceleration of the cross-shock solar wind flow, which was found to create a downstream population of shock pre-heated particles which forms an additional source for injection into 1st order Fermi acceleration, will be discussed in terms of how it affects self-excitation of Alfvén waves and the formation of high-energy SEPs by 1st order Fermi acceleration.

  10. Pump depletion limited evolution of the relativistic plasma wave-front in a forced laser-wakefield accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Fang, F; Clayton, C E; Marsh, K A; Pak, A E; Ralph, J E; Joshi, C [Department of Electrical Engineering, University of California, Los Angeles, CA 90095 (United States); Lopes, N C [Grupo de Lasers e Plasmas, Instituto Superior Tecnico, Lisbon (Portugal)], E-mail: cclayton@ucla.edu

    2009-02-15

    In a forced laser-wakefield accelerator experiment (Malka et al 2002 Science 298 1596) where the length of the pump laser pulse is a few plasma periods long, the leading edge of the laser pulse undergoes frequency downshifting and head erosion as the laser energy is transferred to the wake. Therefore, after some propagation distance, the group velocity of the leading edge of the pump pulse-and thus of the driven electron plasma wave-will slow down. This can have implications for the dephasing length of the accelerated electrons and therefore needs to be understood experimentally. We have carried out an experimental investigation where we have measured the velocity v{sub f} of the 'wave-front' of the plasma wave driven by a nominally 50 fs (full width half maximum), intense (a{sub 0} {approx_equal} 1), 0.815 {mu}m laser pulse. To determine the speed of the wave front, time- and space-resolved refractometry, interferometry and Thomson scattering were used. Although a laser pulse propagating through a relatively low-density plasma (n{sub e} = 1.3 x 10{sup 19} cm{sup -3}) showed no measurable changes in v{sub f} over 1.3 mm (and no accelerated electrons), a high-density plasma (n{sub e} = 5 x 10{sup 19} cm{sup -3}) generated accelerated electrons and showed a continuous change in v{sub f} as the laser pulse propagated through the plasma. Possible causes and consequences of the observed v{sub f} evolution are discussed.

  11. The load-response of the flagellar beat

    CERN Document Server

    Klindt, Gary S; Wanger, Christian; Friedrich, Benjamin M

    2016-01-01

    Cilia and flagella exhibit regular bending waves that perform mechanical work on the surrounding fluid, to propel cellular swimmers and pump fluids inside organisms. Here, we quantify a force-velocity relationship of the beating flagellum, by exposing flagellated \\emph{Chlamydomonas} cells to controlled microfluidic flows. A simple theory of flagellar limit-cycle oscillations, calibrated by measurements in the absence of flow, reproduces this relationship quantitatively. We derive a link between the chemo-mechanical efficiency of the flagellar beat and its ability to synchronize to oscillatory flows.

  12. Acceleration and deceleration of neutrons: From the phase modulation of a neutron wave to a neutron turbine with refracting prisms

    International Nuclear Information System (INIS)

    The possibility of the acceleration and deceleration of neutrons undergoing diffraction at a moving grating is discussed. It is shown that, in contrast to phase π gratings used at the present time, which form a discrete spectrum featuring a large number of lines, a grating that has a special profile may shift, under certain conditions, the entire spectrum of diffracted neutrons. A blazing grating of this type may be used in efficiently accelerating and decelerating neutrons. As the scale of the structure becomes larger, a description based on the idea of neutron-wave refraction at its elements becomes valid, a system of moving prims forming a “neutron turbine,” which is also able to accelerate or decelerate neutrons, being a classical limit of this enlargement.

  13. Psychophysiological reactivity to auditory Binaural Beats stimulation in the alpha and theta EEG brain-wave frequency bands: A randomized, double–blind and placebo–controlled study in human healthy young adult subjects

    OpenAIRE

    Pfaff, Hans Uwe

    2014-01-01

    Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Psicología, Departamento de Psicología Biológica y de la Salud. Fecha de lectura: 25-06-2014 Binaural beats are an acoustical illusion of the perception of a “virtual” third tone, fluctuating (i.e. beating) in its volume evoked by two carrier–sinusoids of same amplitudes, but slightly different frequencies f1 and f2, presented by stereo-headphones. Although this illusion was discovered as early as 1839 ...

  14. Electromagnetic wave activity detected by MMS at the vicinity of the magnetopause and its relation to heating and acceleration of particles

    Science.gov (United States)

    Le Contel, Olivier; Retino, Alessandro; Breuillard, Hugo; Berthomier, Matthieu; Mirioni, Laurent; Sahraoui, Fouad; Chust, Thomas; Chasapis, Alexandros; Aunai, Nicolas; Lavraud, Benoit; Lindqvist, Per-Arne; Khotyaintsev, Yuri; Vaivads, Andris; Marklund, Goran; Ergun, Robert E.; Goodrich, Katherine; Wilder, Frederick D.; Argall, Matthew; Burch, Jim L.; Torbert, Roy B.

    2016-04-01

    In the present study, we analyze different dayside magnetopause crossings detected by the MMS mission in order to investigate the relation between the electromagnetic wave activity and particle heating/acceleration. In particular, our study is focused on two different frequency ranges: (1) 1-10 Hz range which corresponds to the frequency domain of kinetic Alfvén and lower-hybrid waves, (2) 10 Hz-1kHz which corresponds mainly to the whistler mode wave frequency domain. After characterizing the different types of waves, we estimate their respective energy content as well as their possible role for heating and accelerating the plasma.

  15. Alfvén wave interaction with inhomogeneous plasmas: acceleration and energy cascade towards small-scales

    Directory of Open Access Journals (Sweden)

    V. Génot

    2004-06-01

    Full Text Available Investigating the process of electron acceleration in auroral regions, we present a study of the temporal evolution of the interaction of Alfvén waves (AW with a plasma inhomogeneous in a direction transverse to the static magnetic field. This type of inhomogeneity is typical of the density cavities extended along the magnetic field in auroral acceleration regions. We use self-consistent Particle In Cell (PIC simulations which are able to reproduce the full nonlinear evolution of the electromagnetic waves, as well as the trajectories of ions and electrons in phase space. Physical processes are studied down to the ion Larmor radius and electron skin depth scales. We show that the AW propagation on sharp density gradients leads to the formation of a significant parallel (to the magnetic field electric field (E-field. It results from an electric charge separation generated on the density gradients by the polarization drift associated with the time varying AW E-field. Its amplitude may reach a few percents of the AW E-field. This parallel component accelerates electrons up to keV energies over a distance of a few hundred Debye lengths, and induces the formation of electron beams. These beams trigger electrostatic plasma instabilities which evolve toward the formation of nonlinear electrostatic structures (identified as electron holes and double layers. When the electrostatic turbulence is fully developed we show that it reduces the further wave/particle exchange. This sequence of mechanisms is analyzed with the program WHAMP, to identify the instabilities at work and wavelet analysis techniques are used to characterize the regime of energy conversions (from electromagnetic to electrostatic structures, from large to small length scales. This study elucidates a possible scenario to account for the particle acceleration and the wave dissipation in inhomogeneous plasmas. It would consist of successive phases of acceleration along the magnetic field

  16. Early repolarization as a predictor of premature ventricular beats.

    Science.gov (United States)

    Matoshvili, Z T; Petriashvili, Sh G; Archadze, A T; Azaladze, I G

    2015-02-01

    Early repolarization pattern (ERP) is a common ECG variant, characterized by J point elevation manifested either as terminal QRS slurring (the transition from the QRS segment to the ST segment) or notching (a positive deflection inscribed on terminal QRS complex) associated with concave upward ST-segment elevation and prominent T waves in at least two contiguous leads. Aim of this observational study was to compare number of premature ventricular beats in the different groups of patients with early repolarization. The result of this observational study shows that there are: 1,74 fold higher number of premature ventricular beats in 41-74 year subgroup VS 19-40 year subgroup; 1,31 fold higher number of premature ventricular beats in male subgroup VS female subgroup (But this difference is not statistically significant, because t=1,49, p=0,141); 2,85 fold higher number of premature ventricular beats in CAD+ERP subgroup VS ERP without CAD subgroup; 1,74 fold higher number of premature ventricular beats in HF+ERP subgroup VS ERP without HF subgroup; 1,81 fold higher number of premature ventricular beats in CAD+ERP subgroup VS CAD without ERP subgroup; 1,58 fold higher number of premature ventricular beats in HF+ERP subgroup VS HF without ERP subgroup; So, CAD+ERP is very arrhythmogenic condition, after this is HF+ERP, Then Age. This study shows that ERP independently increase number of PVB in different groups (CAD, HF). This is principally new and very important result. Also the number of patients is enough to make this conclusion.

  17. Beat Subterranean: Tactics of Assemblage and Worldmaking in Beat Generation Writing

    OpenAIRE

    Fazzino, Jimmy Michael

    2012-01-01

    My dissertation argues that the core beat trope of the subterranean can be developed as a productive means of literary analysis. I show that beat writers conceive of themselves and their work as existing within vast "underground" networks of radical and avant-garde art and literature, and by locating the beats within such assemblages, the subterranean offers, above all, a model for reconceptualizing beat geography. While the Beat Generation has been regarded as quintessentially American, beat...

  18. Increased Short-Term Beat-To-Beat Variability of QT Interval in Patients with Acromegaly.

    Directory of Open Access Journals (Sweden)

    Andrea Orosz

    Full Text Available Cardiovascular diseases, including ventricular arrhythmias are responsible for increased mortality in patients with acromegaly. Acromegaly may cause repolarization abnormalities such as QT prolongation and impairment of repolarization reserve enhancing liability to arrhythmia. The aim of this study was to determine the short-term beat-to-beat QT variability in patients with acromegaly. Thirty acromegalic patients (23 women and 7 men, mean age±SD: 55.7±10.4 years were compared with age- and sex-matched volunteers (mean age 51.3±7.6 years. Cardiac repolarization parameters including frequency corrected QT interval, PQ and QRS intervals, duration of terminal part of T waves (Tpeak-Tend and short-term variability of QT interval were evaluated. All acromegalic patients and controls underwent transthoracic echocardiographic examination. Autonomic function was assessed by means of five standard cardiovascular reflex tests. Comparison of the two groups revealed no significant differences in the conventional ECG parameters of repolarization (QT: 401.1±30.6 ms vs 389.3±16.5 ms, corrected QT interval: 430.1±18.6 ms vs 425.6±17.3 ms, QT dispersion: 38.2±13.2 ms vs 36.6±10.2 ms; acromegaly vs control, respectively. However, short-term beat-to-beat QT variability was significantly increased in acromegalic patients (4.23±1.03 ms vs 3.02±0.80, P<0.0001. There were significant differences between the two groups in the echocardiographic dimensions (left ventricular end diastolic diameter: 52.6±5.4 mm vs 48.0±3.9 mm, left ventricular end systolic diameter: 32.3±5.2 mm vs 29.1±4.4 mm, interventricular septum: 11.1±2.2 mm vs 8.8±0.7 mm, posterior wall of left ventricle: 10.8±1.4 mm vs 8.9±0.7 mm, P<0.05, respectively. Short-term beat-to-beat QT variability was elevated in patients with acromegaly in spite of unchanged conventional parameters of ventricular repolarization. This enhanced temporal QT variability may be an early indicator of increased

  19. Acceleration of relativistic electrons due to resonant interaction with oblique monochromatic whistler-mode waves generated in the ionosphere.

    Science.gov (United States)

    Kuzichev, Ilya; Shklyar, David

    2016-04-01

    One of the most challenging problems of the radiation belt studies is the problem of particles energization. Being related to the process of particle precipitation and posing a threat to scientific instruments on satellites, the problem of highly energetic particles in the radiation belts turns out to be very important. A lot of progress has been made in this field, but still some aspects of the energization process remain open. The main mechanism of particle energization in the radiation belts is the resonant interaction with different waves, mainly, in whistler frequency range. The problem of special interest is the resonant wave-particle interaction of the electrons of relativistic energies. Relativistic resonance condition provides some important features such as the so-called relativistic turning acceleration discovered by Omura et al. [1, 2]. This process appears to be a very efficient mechanism of acceleration in the case of interaction with the whistler-mode waves propagating along geomagnetic field lines. But some whistler-mode waves propagate obliquely to the magnetic field lines, and the efficiency of relativistic turning acceleration in this case is to be studied. In this report, we present the Hamiltonian theory of the resonant interaction of relativistic electrons with oblique monochromatic whistler-mode waves. We have shown that the presence of turning point requires a special treatment when one aims to derive the resonant Hamiltonian, and we have obtained two different resonant Hamiltonians: one to be applied far enough from the turning point, while another is valid in the vicinity of the turning point. We have performed numerical simulation of relativistic electron interaction with whistler-mode waves generated in the ionosphere by a monochromatic source. It could be, for example, a low-frequency transmitter. The wave-field distribution along unperturbed particle trajectory is calculated by means of geometrical optics. We show that the obliquity of

  20. J point elevation as a predictor of premature ventricular beats.

    Science.gov (United States)

    Matoshvili, Z; Petriashvili, Sh; Archvadze, A; Azaladze, I

    2014-01-01

    Early repolarization pattern (ERP) is a common ECG variant, characterized by J point elevation manifested either as terminal QRS slurring (the transition from the QRS segment to the ST segment) or notching (a positive deflection inscribed on terminal QRS complex) associated with concave upward ST-segment elevation and prominent T waves in at least two contiguous leads. 36 patients were included in this observation. There are 36 patients (19-68 years old) with early repolarization ECG patterns. All this 36 patients were divided into two groups according to their level of J point elevation. First group consisted of 12 patients with J point elevation ≥0,15 mV; second group - of 24 patients with J point elevation premature ventricular beat during 24 h. Before and during this monitoring patients don't take any antyarrhythmic drugs. In the first group (J point elevation ≥0,15 mV) sum of premature ventricular beats were 27432, in the second group (J point elevation premature ventricular beats were 31 896. The results of this observational study shows that there is 1,72 fold higher number of premature ventricular beats in first group. So, J point elevation equal or more then 0,15 mV, is more arrhythmogenic and induces premature ventricular beats. This is principally new and very important result.

  1. Increased Short-Term Beat-To-Beat Variability of QT Interval in Patients with Acromegaly.

    Science.gov (United States)

    Orosz, Andrea; Csajbók, Éva; Czékus, Csilla; Gavallér, Henriette; Magony, Sándor; Valkusz, Zsuzsanna; Várkonyi, Tamás T; Nemes, Attila; Baczkó, István; Forster, Tamás; Wittmann, Tibor; Papp, Julius Gy; Varró, András; Lengyel, Csaba

    2015-01-01

    Cardiovascular diseases, including ventricular arrhythmias are responsible for increased mortality in patients with acromegaly. Acromegaly may cause repolarization abnormalities such as QT prolongation and impairment of repolarization reserve enhancing liability to arrhythmia. The aim of this study was to determine the short-term beat-to-beat QT variability in patients with acromegaly. Thirty acromegalic patients (23 women and 7 men, mean age±SD: 55.7±10.4 years) were compared with age- and sex-matched volunteers (mean age 51.3±7.6 years). Cardiac repolarization parameters including frequency corrected QT interval, PQ and QRS intervals, duration of terminal part of T waves (Tpeak-Tend) and short-term variability of QT interval were evaluated. All acromegalic patients and controls underwent transthoracic echocardiographic examination. Autonomic function was assessed by means of five standard cardiovascular reflex tests. Comparison of the two groups revealed no significant differences in the conventional ECG parameters of repolarization (QT: 401.1±30.6 ms vs 389.3±16.5 ms, corrected QT interval: 430.1±18.6 ms vs 425.6±17.3 ms, QT dispersion: 38.2±13.2 ms vs 36.6±10.2 ms; acromegaly vs control, respectively). However, short-term beat-to-beat QT variability was significantly increased in acromegalic patients (4.23±1.03 ms vs 3.02±0.80, Pacromegaly in spite of unchanged conventional parameters of ventricular repolarization. This enhanced temporal QT variability may be an early indicator of increased liability to arrhythmia.

  2. The Rhodotron, a new 10 MeV, 100 kW, cw metric wave electron accelerator

    International Nuclear Information System (INIS)

    New applications for high energy, high current electron beam processing are continually expanding. Today, however, 10 MeV rf electron linacs are frequently limited to an average beam power of only 20 or 30 kW. To achieve higher beam power, CW operation and the use of lower frequencies are necessary. In the last years, the principle for a new kind of electron accelerator was developed by the Atomic Energy Agency (CEA) in France. This accelerator is based on the principle of recirculating a beam throughout a single coaxial cavity resonating in metric waves. A 3.3 MeV, 4 mA prototype has been built and successfully tested. The industrial accelerator developed by IBA in collaboration with the CEA is a 10 MeV, 100 kW beam power unit with an additional beam exit at 5 MeV. The cavity, made of copper-plated steel, will resonate at 107.5 MHz. A rf power of 100 kW is needed to produce an electric field allowing an energy gain of 1 MeV per crossing. In addition, 100 kW of power is needed for acceleration. The 200 kW output amplifier uses a 100 kW plate dissipation tetrode (TH 681 from Thomson-CSF) in a grounded grid configuration. In this paper, the design of the new model as well as the prototype manufacturing schedule are presented in more detail. (orig.)

  3. Effects of density profile and multi-species target on laser-heated thermal-pressure-driven shock wave acceleration

    International Nuclear Information System (INIS)

    The shock wave acceleration of ions driven by laser-heated thermal pressure is studied through one-dimensional particle-in-cell simulation and analysis. The generation of high-energy mono-energetic protons in recent experiments (D. Haberberger et al., 2012 Nat. Phys. 8 95) is attributed to the use of exponentially decaying density profile of the plasma target. It does not only keep the shock velocity stable but also suppresses the normal target normal sheath acceleration. The effects of target composition are also examined, where a similar collective velocity of all ion species is demonstrated. The results also give some reference to future experiments of producing energetic heavy ions. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  4. Direct visualization of mechanical beats by means of an oscillating smartphone

    CERN Document Server

    Giménez, Marcos H; Monsoriu, Juan A

    2016-01-01

    The resonance phenomenon is widely known from Physics courses. Qualitatively speaking, it takes place in a driven oscillating system whenever the driven frequency approaches the natural frequency. It is when the amplitude of the oscillations become maximal. Very closely related to this phenomenon, there is another which is very surprising too. It takes place when the driven and natural frequencies of the system are slightly different and interfere constructively and destructively, forming the so called beats. The frequency of the beats is just the difference of the interfering waves frequencies. Beats are very noticeable in acoustic systems. We all have probably perceived them in the form of periodic ups and downs in the sound intensity volume. There are several works in this journal on visualizing the beats in acoustic systems. For instance, the microphone and the speaker of two mobile devices were used in previous work to analyze the acoustic beat produced by two signals of close frequencies. The formation ...

  5. Doppler Beats or Interference Fringes?

    Science.gov (United States)

    Kelly, Paul S.

    1979-01-01

    Discusses the following: another version of Doppler beats; alternate proof of spin-1 sin-1/2 problems; some mechanisms related to Dirac's strings; Doppler redshift in oblique approach of source and observer; undergraduate experiment on noise thermometry; use of the time evolution operator; resolution of an entropy maximization controversy;…

  6. Numerical modeling of gravitational wave sources accelerated by OpenCL

    OpenAIRE

    Khanna, Gaurav; McKennon, Justin

    2010-01-01

    In this work, we make use of the OpenCL framework to accelerate an EMRI modeling application using the hardware accelerators -- Cell BE and Tesla CUDA GPU. We describe these compute technologies and our parallelization approach in detail, present our performance results, and then compare them with those from our previous implementations based on the native CUDA and Cell SDKs. The OpenCL framework allows us to execute identical source-code on both architectures and yet obtain strong performanc...

  7. Accelerated binding kinetics by surface acoustic waves (SAW) micromixing in surface plasmon resonance (SPR) system for biodetection

    Science.gov (United States)

    Renaudin, Alan; Chabot, Vincent; Grondin, Etienne; Aimez, Vincent; Charette, Paul G.

    2011-02-01

    A design incorporating surface plasmon resonance (SPR) biosensing and surface acoustic wave (SAW) active microfluidic mixing, integrated on a single LiNbO3 piezoelectric substrate, is presented. Validation experiments show that SAW-mixing (microstreaming) results in accelerated binding kinetics (time-to-saturation) for a standard assay with appropriate SAW excitation parameters. Since both SPR sensors and SAW transducers can be fabricated simultaneously using low-cost microfabrication methods, the proposed design should contribute to improved lab-on-chip devices for detecting and identifying biomolecules of interest with greater accuracy and speed across multiple applications.

  8. Nonlinear amplitude dynamics in flagellar beating

    CERN Document Server

    Oriola, David; Casademunt, Jaume

    2016-01-01

    The physical basis of flagellar and ciliary beating is a major problem in biology which is still far from completely understood. The fundamental cytoskeleton structure of cilia and flagella is the axoneme, a cylindrical array of microtubule doublets connected by passive crosslinkers and dynein motor proteins. The complex interplay of these elements leads to the generation of self-organized bending waves. Although many mathematical models have been proposed to understand this process, few attempts have been made to assess the role of dyneins on the nonlinear nature of the axoneme. Here, we investigate the nonlinear dynamics of flagella by considering an axonemal sliding control mechanism for dynein activity. This approach unveils the nonlinear selection of the oscillation amplitudes, which are typically either missed or prescribed in mathematical models. The explicit set of nonlinear equations are derived and solved numerically. Our analysis reveals the spatiotemporal dynamics of dynein populations and flagell...

  9. The role of waves and DC electric fields for electron heating and acceleration in the diffusion region

    Science.gov (United States)

    Graham, Daniel; Khotyaintsev, Yuri; Vaivads, Andris; Norgren, Cecilia; Andre, Mats; Lindqvist, Per-Arne; Le Contel, Olivier; Ergun, Robert; Goodrich, Katherine; Torbert, Roy; Burch, James; Russell, Christopher; Magnes, Werner; Giles, Barbara; Pollock, Craig; Mauk, Barry; Fuselier, Stephen

    2016-04-01

    Magnetic reconnection is a fundamental process in solar and astrophysical plasmas. The processes operating at electron spatial-scales, which enable magnetic field lines to reconnect, are generally difficult to resolve and identify. However, the recently launched Magnetospheric Multiscale (MMS) mission is specifically designed to resolve electron spatial scales. We use the MMS spacecraft to investigate the process operating within the diffusion region to determine the causes of electron heating and acceleration. In particular, we investigate the type of electrostatic and electromagnetic waves that develop and how they affect the electron distributions. We also compare the roles of wave-particle interactions with DC electric fields to determine which is responsible for the electron heating observed in diffusion regions.

  10. Nonlinear Alfvén waves, discontinuities, proton perpendicular acceleration, and magnetic holes/decreases in interplanetary space and the magnetosphere: intermediate shocks?

    Directory of Open Access Journals (Sweden)

    B. T. Tsurutani

    2005-01-01

    Full Text Available Alfvén waves, discontinuities, proton perpendicular acceleration and magnetic decreases (MDs in interplanetary space are shown to be interrelated. Discontinuities are the phase-steepened edges of Alfvén waves. Magnetic decreases are caused by a diamagnetic effect from perpendicularly accelerated (to the magnetic field protons. The ion acceleration is associated with the dissipation of phase-steepened Alfvén waves, presumably through the Ponderomotive Force. Proton perpendicular heating, through instabilities, lead to the generation of both proton cyclotron waves and mirror mode structures. Electromagnetic and electrostatic electron waves are detected as well. The Alfvén waves are thus found to be both dispersive and dissipative, conditions indicting that they may be intermediate shocks. The resultant 'turbulence' created by the Alfvén wave dissipation is quite complex. There are both propagating (waves and nonpropagating (mirror mode structures and MDs byproducts. Arguments are presented to indicate that similar processes associated with Alfvén waves are occurring in the magnetosphere. In the magnetosphere, the 'turbulence' is even further complicated by the damping of obliquely propagating proton cyclotron waves and the formation of electron holes, a form of solitary waves. Interplanetary Alfvén waves are shown to rapidly phase-steepen at a distance of 1AU from the Sun. A steepening rate of ~35 times per wavelength is indicated by Cluster-ACE measurements. Interplanetary (reverse shock compression of Alfvén waves is noted to cause the rapid formation of MDs on the sunward side of corotating interaction regions (CIRs. Although much has been learned about the Alfvén wave phase-steepening processfrom space plasma observations, many facets are still not understood. Several of these topics are discussed for the interested researcher. Computer simulations and theoretical developments will be particularly useful in making further progress in

  11. Musicians' Perception of Beat in Monotonic Stimuli.

    Science.gov (United States)

    Duke, Robert A.

    1989-01-01

    Assesses musicians' perceptions of beat in monotonic stimuli and attempts to define empirically the range of perceived beat tempo in music. Subjects performed a metric pulse in response to periodic stimulus tones. Results indicate a relatively narrow range within which beats are perceived by trained musicians. (LS)

  12. Ultra-high-energy cosmic ray acceleration by relativistic blast waves

    OpenAIRE

    Gallant, Yves A.; Achterberg, Abraham

    1998-01-01

    We consider the acceleration of charged particles at the ultra-relativistic shocks, with Lorentz factors \\Gamma_s >> 1 relative to the upstream medium, arising in relativistic fireball models of gamma-ray bursts (GRBs). We show that for Fermi-type shock acceleration, particles initially isotropic in the upstream medium can gain a factor of order \\Gamma_s^2 in energy in the first shock crossing cycle, but that the energy gain factor for subsequent shock crossing cycles is only of order 2, beca...

  13. Numerical modeling of gravitational wave sources accelerated by OpenCL

    CERN Document Server

    Khanna, Gaurav

    2010-01-01

    In this work, we make use of the OpenCL framework to accelerate an EMRI modeling application using the hardware accelerators -- Cell BE and Tesla CUDA GPU. We describe these compute technologies and our parallelization approach in detail, present our performance results, and then compare them with those from our previous implementations based on the native CUDA and Cell SDKs. The OpenCL framework allows us to execute identical source-code on both architectures and yet obtain strong performance gains that are comparable to what can be derived from the native SDKs.

  14. Beatwave acceleration in a plasma metamaterial

    Science.gov (United States)

    Lopes, A.; Alves, E. P.; Fonseca, R. A.; Silva, L. O.

    2015-11-01

    These media can be engineered to produce negative indices of refraction, which support the propagation of unusual light waves. In addition, the interaction of these unusual light waves with charged particles in the medium can lead to unusual features like negative radiation pressure. It is well known that two counter propagating chirped lasers in a positive response medium can lead to energy transfer from the waves to the particles leading to its acceleration. In this work, we explore the combination of two co-propagating EM pulses which, under the right conditions, achieve the same results as the previous scheme, but now in a plasma metamaterial. Depending on the chosen frequency, one of the pulses can experience a positive response medium (n>0) and the other a negative one (n<0), leading to anti-parallel phase velocities. This setup is capable of creating a beat wave which enables the acceleration of charged particles via the radiation tension. Our results are supported by numerical simulations using meta-OSIRIS, which combines a solver to deal with dielectric and magnetic materials with arbitrary EM linear properties with the standard PIC algorithm. Our simulations addressing this new setup provide results consistent with the theoretical predictions. Work supported by the European Research Council (Accelerates ERC-2010-AdG 267841).

  15. Quantum beats in the field ionization of Rydberg atoms in the presence of magnetic fields

    Science.gov (United States)

    Gregoric, Vincent C.; Hastings, Hannah; Carroll, Thomas J.; Noel, Michael W.

    2016-05-01

    By exciting a coherent superposition and varying its phase evolution, quantum beats in the selective field ionization of Rydberg atoms have been observed. Here, we present a study exploring the effect of electric and magnetic fields on quantum beats. Beginning with a single excited state, a coherent superposition is created by a short electric field pulse in the presence of a static magnetic field. The resulting quantum beats are then observed in the field ionization spectrum. Additionally, millimeter-wave spectroscopy is used to probe the state populations in this superposition. This work is supported by the National Science Foundation under Grants No. 1205895 and No. 1205897.

  16. Development of an Efficient GPU-Accelerated Model for Fully Nonlinear Water Waves

    DEFF Research Database (Denmark)

    of an optimized sequential single-CPU algorithm based on a flexible-order Finite Difference Method. High performance is pursued by utilizing many-core processing in the model focusing on GPUs for acceleration of code execution. This involves combining analytical methods with an algorithm redesign of...

  17. Development of a GPU-accelerated MIKE 21 Solver for Water Wave Dynamics

    DEFF Research Database (Denmark)

    Aackermann, Peter Edward; Pedersen, Peter Juhler Dinesen; Engsig-Karup, Allan Peter;

    2013-01-01

    With encouragement by the company DHI are the aim of this B.Sc. thesis1 to investigate, whether if it is possible to accelerate the simulation speed of DHIs commercial product MIKE 21 HD, by formulating a parallel solution scheme and implementing it to be executed on a CUDA-enabled GPU (massive...

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

    Science.gov (United States)

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

    2016-09-01

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

  19. Acceleration of cometary H2O group pickup ions by obliquely propagating nonlinear magnetosonic waves

    Science.gov (United States)

    Srivastava, Krishna M.; Tsurutani, Bruce T.; Goldstein, Bruce E.; Sharma, V.; Okada, M.

    1993-01-01

    The observations made during the encounter with comet Giacobini Zinner show that the character of MHD turbulence is governed by the magnetosonic (MS) waves generated by the pickup ions via a resonant cyclotron instability. The interaction of cometary ions in the mass loaded solar wind with MS waves propagating away from the comet and oblique to the interplanetary magnetic field (IMF) is investigated using the test particle approach. Ion trajectories, distribution functions, widths of pitch angle scattering and energy diffusion are obtained. We have also investigated the relationship between pitch angle scattering and the three parameters, namely, alpha, the angle between the solar wind flow direction and the ambient magnetic field, theta(sub BK), the angle between the ambient magnetic field and the wave propagation vector, and the ion injection velocity.

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

    CERN Document Server

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

    2016-01-01

    We present a molecular dynamics study of the effects of carbon- and iron-ion induced shock waves in DNA duplexes in liquid water. We use the CHARMM force field implemented within the MBN Explorer simulation package to optimize and equilibrate DNA duplexes in liquid water boxes of different sizes and shapes. The translational and vibrational degrees of freedom of water molecules are excited according to the energy deposited by the ions and the subsequent shock waves in liquid water are simulated. The pressure waves generated are studied and compared with an analytical hydrodynamics model which serves as a benchmark for evaluating the suitability of the simulation boxes. The energy deposition in the DNA backbone bonds is also monitored as an estimation of biological damage, something which lies beyond the possibilities of the analytical model.

  1. Abstract Possible: The Birmingham Beat

    OpenAIRE

    Bergman, Aeron; Salinas, Alejandra

    2013-01-01

    Gruppeutstilling. Samarbeidspartner: Alejandra Salinas. ABSTRACT YOUR SHIT IS Video loop and billboard. Eastside Projects, Birmingham UK Abstract Possible: The Birmingham Beat Curated by Maria Lind 6 October - 1 December 2012. Invited artists: José León Cerrillo, Zachary Formwalt, Goldin+Senneby, Wade Guyton, Yelena Popova, Alejandra Salinas and Aeron Bergman. Visningssted: Eastside Projects, Birmingham, UK. Se også: http://eastsideprojects.org/past/abstract-possible

  2. Beating phantasies: Mourned and unmourned.

    Science.gov (United States)

    Antinucci, Giuseppina

    2016-06-01

    This paper intends to explore the organizing function and fate of sado-masochistic phantasies in their fixed form, in the psychic life of patients who have suffered early traumas, due to environmental vicissitudes and maternal psychopathology. The theoretical starting point is provided by the Novicks' research into transitory and permanent beating phantasies in adult and child patients, their onset and their psychic function, based on an examination of Freud's paper 'A child is being beaten'. In this text Freud achieves an unprecedented syncretism, locating the phantasy at the intersection between the oedipal complex, which is a vertical structure organizing sexual and generational differences, and the fraternal dimension, which is horizontal and organizes the lateral relationship with that similar but different other who is the sibling. Reporting in some detail material from the analyses of two young women, whose clinical presentation and early traumas show some similarities, the author puts in the context of the analytic work the emerging of the sado-masochistic phantasies, emphasizing their use and function in the transference-countertransference interplay. The beating phantasies shore up a precarious sense of self, threatened with psychic depletion and death, in identification with the absent mother of early infancy. An overly close relationship with a sibling, experienced as a narcissistic double, compounds the clinical picture, to establish the triangle formed by the parent(s) and two children which features in the beating phantasy. Finally, the author explores the contribution of ameliorating factors, such as alternative identificatory figures, constitutional endowment and capacity for sublimation, to account for the different fate of the fixed beating phantasies. PMID:26602362

  3. Simultaneous beat-by-beat investigation of the effects of the Valsalva maneuver on left and right ventricular filling and the possible mechanism.

    Directory of Open Access Journals (Sweden)

    Zhen Wang

    Full Text Available Although the influence of the Valsalva maneuver on the heart and circulatory system has been investigated, the mechanism of intrathoracic pressure influencing cardiovascular function is unclear. To test our hypothesis that the interaction between the anatomy-determined partially-intrathoracic system and the fully-intrathoracic system might explain those issues and help to disclose the mechanism, we used the Hitachi dual pulse wave Doppler echocardiographic apparatus to investigate simultaneously the beat-by-beat influence of 40-mmHg Valsalva maneuver on left and right cardiac ventricular filling in 30 male adult volunteers. The mitral and tricuspid blood inflow velocity spectra during the Valsalva maneuver were recorded simultaneously. The peak velocity (PV, velocity-time integral (VTI and inflow volume (IV of each cycle were measured or calculated. The PV, VTI and IV of the left heart remained unchanged at the first beat after the Valsalva maneuver onset (compared with those at rest, p>0.1 and then decreased gradually to the lowest at the 11±1.2th beat (range, 9th to 12th beat. Simultaneously, the PV, VTI and IV of the right heart decreased significantly (p<0.05 at the first cycle, decreased rapidly to the lowest at the 6±0.8th beat (range, 4th to 7th beat and then increased gradually to the 9±1.3th beat (range, 8th to 10th beat. These results suggest that the left heart and right heart have different physiological responses to the Valsalva maneuver. These could be explained by our hypothesis, the interaction between the partially-intrathoracic system and the fully-intrathoracic system, which might help to disclose the mechanism of how intrathoracic pressure influences the heart and circulatory system.

  4. A Fast GPU-accelerated Mixed-precision Strategy for Fully NonlinearWater Wave Computations

    DEFF Research Database (Denmark)

    Glimberg, Stefan Lemvig; Engsig-Karup, Allan Peter; Madsen, Morten G.

    2011-01-01

    -preconditioned defect correction method. The improved strategy improves the performance by exploiting architectural features of modern GPUs for mixed precision computations and is tested in a recently developed generic library for fast prototyping of PDE solvers. The new wave tool is applicable to solve and analyze...

  5. Heating and Acceleration of the Fast Solar Wind by Alfv\\'{e}n Wave Turbulence

    CERN Document Server

    van Ballegooijen, A A

    2016-01-01

    We present numerical simulations of reduced magnetohydrodynamic (RMHD) turbulence in a magnetic flux tube at the center of a polar coronal hole. The model for the background atmosphere is a solution of the momentum equation, and includes the effects of wave pressure on the solar wind outflow. Alfv\\'{e}n waves are launched at the coronal base, and reflect at various heights due to variations in Alfv\\'{e}n speed and outflow velocity. The turbulence is driven by nonlinear interactions between the counter-propagating Alfv\\'{e}n waves. Results are presented for two models of the background atmosphere. In the first model the plasma density and Alfv\\'{e}n speed vary smoothly with height, resulting in minimal wave reflections and low energy dissipation rates. We find that the dissipation rate is insufficient to maintain the temperature of the background atmosphere. The standard phenomenological formula for the dissipation rate significantly overestimates the rate derived from our RMHD simulations, and a revised formu...

  6. A review of beat-to-beat vectorcardiographic (VCG) parameters for analyzing repolarization variability in ECG signals.

    Science.gov (United States)

    Hasan, Muhammad A; Abbott, Derek

    2016-02-01

    Elevated ventricular repolarization lability is believed to be linked to the risk of ventricular tachycardia/ventricular fibrillation. However, ventricular repolarization is a complex electrical phenomenon, and abnormalities in ventricular repolarization are not completely understood. To evaluate repolarization lability, vectorcardiography (VCG) is an alternative approach where the electrocardiographic (ECG) signal can be considered as possessing both magnitude and direction. Recent research has shown that VCG is advantageous over ECG signal analysis for identification of repolarization abnormality. One of the key reasons is that the VCG approach does not rely on exact identification of the T-wave offset, which improves the reproducibility of the VCG technique. However, beat-to-beat variability in VCG is an emerging area for the investigation of repolarization abnormality though not yet fully realized. Therefore, the purpose of this review is to explore the techniques, findings, and efficacy of beat-to-beat VCG parameters for analyzing repolarization lability, which may have potential utility for further study. PMID:25992510

  7. Losing the beat: deficits in temporal coordination

    Science.gov (United States)

    Palmer, Caroline; Lidji, Pascale; Peretz, Isabelle

    2014-01-01

    Tapping or clapping to an auditory beat, an easy task for most individuals, reveals precise temporal synchronization with auditory patterns such as music, even in the presence of temporal fluctuations. Most models of beat-tracking rely on the theoretical concept of pulse: a perceived regular beat generated by an internal oscillation that forms the foundation of entrainment abilities. Although tapping to the beat is a natural sensorimotor activity for most individuals, not everyone can track an auditory beat. Recently, the case of Mathieu was documented (Phillips-Silver et al. 2011 Neuropsychologia 49, 961–969. (doi:10.1016/j.neuropsychologia.2011.02.002)). Mathieu presented himself as having difficulty following a beat and exhibited synchronization failures. We examined beat-tracking in normal control participants, Mathieu, and a second beat-deaf individual, who tapped with an auditory metronome in which unpredictable perturbations were introduced to disrupt entrainment. Both beat-deaf cases exhibited failures in error correction in response to the perturbation task while exhibiting normal spontaneous motor tempi (in the absence of an auditory stimulus), supporting a deficit specific to perception–action coupling. A damped harmonic oscillator model was applied to the temporal adaptation responses; the model's parameters of relaxation time and endogenous frequency accounted for differences between the beat-deaf cases as well as the control group individuals. PMID:25385783

  8. Accelerated two-wave mixing response in erbium-doped fibers with saturable optical absorption

    Science.gov (United States)

    Hernandez, Eliseo; Stepanov, Serguei; Plata Sanchez, Marcos

    2016-08-01

    The contribution of the spatially uniform variation of average optical absorption to the dynamics of the transient two-wave mixing (TWM) response is considered. It is shown theoretically and confirmed experimentally that this transient effect, via dynamic population gratings in erbium-doped fibers (EDFs) can ensure a response nearly two times faster in such gratings as compared to the growth rate of fluorescence uniformly excited under similar conditions, and can also result in an additional overshot in the tail of the TWM response. This additional ‘accelerating’ contribution is of even type, and does not influence the odd transient TWM response for the refractive index component of such gratings in the EDFs reported earlier. It is also shown that this effect can be utilized to monitor the formation of the dynamic grating with an auxiliary probe wave of the essentially different non-Bragg wavelength.

  9. Nonlinear electron acceleration by oblique whistler waves: Landau resonance vs. cyclotron resonance

    OpenAIRE

    Artemyev, A. V.; A. A. Vasiliev; Mourenas, Didier; Agapitov, O. V.; V. V. Krasnoselskikh

    2013-01-01

    This paper is devoted to the study of the nonlinear interaction of relativistic electrons and highamplitude strongly oblique whistler waves in the Earth’s radiation belts. We consider electrontrapping into Landau and fundamental cyclotron resonances in a simplified model of dipolarmagnetic field. Trapping into the Landau resonance corresponds to a decrease of electronequatorial pitch-angles, while trapping into the first cyclotron resonance increases electronequatorial pitch-angles. For 100 k...

  10. Accelerated stationary iterative methods for the numerical solution of electromagnetic wave scattering problems

    OpenAIRE

    Mullen, Marie

    2010-01-01

    The main focus of this work is to contribute to the development of iterative solvers applied to the method of moments solution of electromagnetic wave scattering problems. In recent years there has been much focus on current marching iterative methods, such as Gauss-Seidel and others. These methods attempt to march a solution for the unknown basis function amplitudes in a manner that mimics the physical processes which create the current. In particular the forward backwar...

  11. Comparison of the Effects of Wave-Particle Interactions and the Kinetic Suprathermal Electron Population on the Acceleration of the Solar Wind

    Science.gov (United States)

    Tam, S. W. Y.; Chang, T.

    2002-01-01

    Kinetic effects due to wave-particle interactions and suprathermal electrons have been suggested in the literature as possible solar wind acceleration mechanisms. Ion cyclotron resonant heating, in particular, has been associated with some qualitative features observed in the solar wind. In terms of solar wind acceleration, however, it is interesting to compare the kinetic effects of suprathermal electrons with those due to the wave-particle interactions. The combined effects of the two acceleration mechanisms on the fast solar wind have been studied by Tam and Chang (1999a,b). In this study. we investigate the role of the suprathermal electron population in the acceleration of the solar wind. Our model follows the global kinetic evolution of the fast solar wind under the influence of ion cyclotron resonant heating, while taking into account Coulomb collisions, and the ambipolar electric field that is consistent with the particle distributions themselves. The kinetic effects due to the suprathermal electrons, which we define to be the tail of the electron distributions, can be included in the model as an option. By comparing the results with and without the inclusion of the suprathermal electron effects, we determine the relative importance of suprathermal electrons and wave-particle interactions in driving the solar wind. We find that although suprathermal electrons enhance the ambipolar electric potential in the solar wind considerably, their overall influence as an acceleration mechanism is relatively insignificant in a wave-driven solar wind.

  12. Generation of quasi-monoenergetic heavy ion beams via staged shock wave acceleration driven by intense laser pulses in near-critical plasmas

    Science.gov (United States)

    Zhang, W. L.; Qiao, B.; Shen, X. F.; You, W. Y.; Huang, T. W.; Yan, X. Q.; Wu, S. Z.; Zhou, C. T.; He, X. T.

    2016-09-01

    Laser-driven ion acceleration potentially offers a compact, cost-effective alternative to conventional accelerators for scientific, technological, and health-care applications. A novel scheme for heavy ion acceleration in near-critical plasmas via staged shock waves driven by intense laser pulses is proposed, where, in front of the heavy ion target, a light ion layer is used for launching a high-speed electrostatic shock wave. This shock is enhanced at the interface before it is transmitted into the heavy ion plasmas. Monoenergetic heavy ion beam with much higher energy can be generated by the transmitted shock, comparing to the shock wave acceleration in pure heavy ion target. Two-dimensional particle-in-cell simulations show that quasi-monoenergetic {{{C}}}6+ ion beams with peak energy 168 MeV and considerable particle number 2.1 × {10}11 are obtained by laser pulses at intensity of 1.66 × {10}20 {{W}} {{cm}}-2 in such staged shock wave acceleration scheme. Similarly a high-quality {{Al}}10+ ion beam with a well-defined peak with energy 250 MeV and spread δ E/{E}0=30 % can also be obtained in this scheme.

  13. Beat-to-beat analysis method for magnetocardiographic recordings during interventions

    International Nuclear Information System (INIS)

    Multichannel magnetocardiography (MCG) during exercise testing has been shown to detect myocardial ischaemia in patients with coronary artery disease. Previous studies on exercise MCG have focused on one or few time intervals during the recovery period and only a fragment of the data available has been utilized. We present a method for beat-to-beat analysis and parametrization of the MCG signal. The method can be used for studying and quantifying the changes induced in the MCG by interventions. We test the method with data recorded in bicycle exercise testing in healthy volunteers and patients with coronary artery disease. Information in all cardiac cycles recorded during the recovery period of exercise MCG testing is, for the first time, utilized in the signal analysis. Exercise-induced myocardial ischaemia was detected by heart rate adjustment of change in magnetic field map orientation. In addition to the ST segment, the T wave in the MCG was also found to provide information related to myocardial ischaemia. The method of analysis efficiently utilizes the spatial and temporal properties of multichannel MCG mapping, providing a new tool for detecting and quantifying fast phenomena during interventional MCG studies. The method can also be applied to an on-line analysis of MCG data. (author)

  14. Evidence of resonant surface wave excitation in the relativistic regime through measurements of proton acceleration from grating targets

    CERN Document Server

    Ceccotti, T; Sgattoni, A; Bigongiari, A; Raynaud, M; Riconda, C; Heron, A; Baffigi, F; Labate, L; Gizzi, L A; Vassura, L; Fuchs, J; Passoni, M; Kveton, M; Novotny, F; Possolt, M; Prokupek, J; Proska, J; Psikal, J; Stolcova, L; Velyhan, A; Bougeard, M; D'Oliveira, P; Tcherbakoff, O; Reau, F; Martin, P; Macchi, A

    2013-01-01

    The interaction of laser pulses with thin grating targets, having a periodic groove at the irradiated surface, has been experimentally investigated. Ultrahigh contrast ($\\sim 10^{12}$) pulses allowed to demonstrate an enhanced laser-target coupling for the first time in the relativistic regime of ultra-high intensity $>10^{19} \\mbox{W/cm}^{2}$. A maximum increase by a factor of 2.5 of the cut-off energy of protons produced by Target Normal Sheath Acceleration has been observed with respect to plane targets, around the incidence angle expected for resonant excitation of surface waves. A significant enhancement is also observed for small angles of incidence, out of resonance.

  15. Bondage fantasies and beating fantasies.

    Science.gov (United States)

    Weiss, J

    1998-10-01

    Two male patients had masochistic sexual fantasies: one had bondage fantasies, the other beating fantasies. Each patient had been traumatized in childhood by his experiences with a martyr mother. Each had developed the belief that in an intimate sexual relationship with a woman he would hurt her. As a consequence, each tended to suppress his sexuality. Each used masochistic fantasies to reassure himself that he was not hurting his fantasied or real partner. The reassurance made it safe to experience his sexual feelings. The two patients' use of their masochistic fantasies is compared to the fetishist's use of his fetish, as described by Freud. PMID:9820894

  16. Plasma heating and acceleration by strong magnetosonic waves propagating obliquely to a magnetostatic field

    International Nuclear Information System (INIS)

    The behavior of strong magnetosonic waves with ω>ω/sub c/i (ω/sub c/i = q/sub i/B/m/sub i/c) is investigated in oblique propagation with particle simulation. Strong ion and electron heatings versus the angle [theta = (k,B0)] are found for theta0. Ion heating peaks at a particular angle but disappears below a critical angle theta/sub t//sub i/; electron heating sets in below a second critical angle theta/sub t//sub e/. The phenomena exhibit unexpected structure with theta

  17. Acceleration of Magnetospheric Relativistic Electrons by Ultra-Low Frequency Waves: A Comparison between Two Cases Observed by Cluster and LANL Satellites

    Science.gov (United States)

    Shao, X.; Fung, S. F.; Tan, L. C.; Sharma, A. S.

    2010-01-01

    Understanding the origin and acceleration of magnetospheric relativistic electrons (MREs) in the Earth's radiation belt during geomagnetic storms is an important subject and yet one of outstanding questions in space physics. It has been statistically suggested that during geomagnetic storms, ultra-low-frequency (ULF) Pc-5 wave activities in the magnetosphere are correlated with order of magnitude increase of MRE fluxes in the outer radiation belt. Yet, physical and observational understandings of resonant interactions between ULF waves and MREs remain minimum. In this paper, we show two events during storms on September 25, 2001 and November 25, 2001, the solar wind speeds in both cases were > 500 km/s while Cluster observations indicate presence of strong ULF waves in the magnetosphere at noon and dusk, respectively, during a approx. 3-hour period. MRE observations by the Los Alamos (LANL) spacecraft show a quadrupling of 1.1-1.5 MeV electron fluxes in the September 25, 2001 event, but only a negligible increase in the November 2.5, 2001 event. We present a detailed comparison between these two events. Our results suggest that the effectiveness of MRE acceleration during the September 25, 2001 event can be attributed to the compressional wave mode with strong ULF wave activities and the physical origin of MRE acceleration depends more on the distribution of toroidal and poloidal ULF waves in the outer radiation belt.

  18. The generation of high fields for particle acceleration to very high energies

    International Nuclear Information System (INIS)

    A Workshop organised by the CERN Accelerator School, the European Committee for Future Accelerators and the Istituto Nazionale di Fisica Nucleare was held at the Frascati laboratory of INFN during the last week of September 1984. Its purpose was to bring together an inter-disciplinary group of physicists to review ideas for the acceleration of particles to energies beyond those attainable in machines whose construction is underway, or is currently contemplated. These proceedings contain some of the material presented and discussed at the Workshop, comprising papers on topics such as: the free-electron-laser, the lasertron, wakefield accelerators, the laser excitation of droplet arrays, a switched-power linac, plasma beat-wave accelerators and the choice of basic parameters for linear colliders intended for the TeV energy region. (orig.)

  19. Electron acceleration in preformed plasma channels with terawatt CO{sub 2} laser

    Energy Technology Data Exchange (ETDEWEB)

    Pogorelsky, I.V.

    1995-02-01

    Extended cylindrical plasma channels produced under gas breakdown by axicon-focused laser beams may be used as optical waveguides in laser-driven electron accelerators. Plasma channeling of the laser beams will help to maintain a high acceleration gradient over many Rayleigh lengths. In addition, the rarefied gas density channel produced after the optical gas breakdown, and followed by a plasma column expansion, reduces multiple scattering of the electron beam. A high-power picosecond C0{sub 2}laser operational at the ATF and being further upgraded to the 1 TW level is considered as the source for a plasma channel formation and as the laser accelerator driver. We show how various laser accelerator schemes including beat wave, wake field, and Inverse Cherenkov accelerator benefit from using a channeled short-pulse C0{sub 2}laser as a driver.

  20. All-optical trapping and acceleration of heavy particles

    CERN Document Server

    Peano, F; Silva, L O; Mulas, R; Coppa, G

    2008-01-01

    A scheme for fast, compact, and controllable acceleration of heavy particles in vacuum is proposed, in which two counterpropagating lasers with variable frequencies drive a beat-wave structure with variable phase velocity, thus allowing for trapping and acceleration of heavy particles, such as ions or muons. Fine control over the energy distribution and the total charge of the beam is obtained via tuning of the frequency variation. The acceleration scheme is described with a one-dimensional theory, providing the general conditions for trapping and scaling laws for the relevant features of the particle beam. Two-dimensional, electromagnetic particle-in-cell simulations confirm the validity and the robustness of the physical mechanism.

  1. GPU acceleration of a nonhydrostatic model for the internal solitary waves simulation

    Institute of Scientific and Technical Information of China (English)

    CHEN Tong-qing; ZHANG Qing-he

    2013-01-01

    The parallel computing algorithm for a nonhydrostatic model on one or multiple Graphic Processing Units (GPUs) for the simulation of internal solitary waves is presented and discussed.The computational efficiency of the GPU scheme is analyzed by a series of numerical experiments,including an ideal case and the field scale simulations,performed on the workstation and the supercomputer system.The calculated results show that the speedup of the developed GPU-based parallel computing scheme,compared to the implementation on a single CPU core,increases with the number of computational grid cells,and the speedup can increase quasilinearly with respect to the number of involved GPUs for the problem with relatively large number of grid cells within 32 GPUs.

  2. Backward-propagating MeV electrons in ultra-intense laser interactions: Standing wave acceleration and coupling to the reflected laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Orban, Chris, E-mail: orban@physics.osu.edu; Feister, Scott [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Innovative Scientific Solutions, Inc., Dayton, Ohio 45459 (United States); Morrison, John T. [National Research Council, Washington, DC 20001 (United States); Intense Energy Solutions, LLC, Plain City, Ohio 43064 (United States); Chowdhury, Enam A. [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Center for Ultra-Fast Optical Science, University of Michigan, Ann Arbor, Michigan 48109 (United States); Nees, John A. [Innovative Scientific Solutions, Inc., Dayton, Ohio 45459 (United States); Intense Energy Solutions, LLC, Plain City, Ohio 43064 (United States); Frische, Kyle [Innovative Scientific Solutions, Inc., Dayton, Ohio 45459 (United States); Roquemore, W. M. [Air Force Research Laboratory, Dayton, Ohio 45433 (United States)

    2015-02-15

    Laser-accelerated electron beams have been created at a kHz repetition rate from the reflection of intense (∼10{sup 18 }W/cm{sup 2}), ∼40 fs laser pulses focused on a continuous water-jet in an experiment at the Air Force Research Laboratory. This paper investigates Particle-in-Cell simulations of the laser-target interaction to identify the physical mechanisms of electron acceleration in this experiment. We find that the standing-wave pattern created by the overlap of the incident and reflected laser is particularly important because this standing wave can “inject” electrons into the reflected laser pulse where the electrons are further accelerated. We identify two regimes of standing wave acceleration: a highly relativistic case (a{sub 0} ≥ 1), and a moderately relativistic case (a{sub 0} ∼ 0.5) which operates over a larger fraction of the laser period. In previous studies, other groups have investigated the highly relativistic case for its usefulness in launching electrons in the forward direction. We extend this by investigating electron acceleration in the specular (back reflection) direction and over a wide range of intensities (10{sup 17}–10{sup 19 }W cm{sup −2})

  3. Accelerating waves in polar coronal holes as seen by EIS and SUMER

    CERN Document Server

    Gupta, G R; Teriaca, L; Imada, S; Solanki, S

    2010-01-01

    We present EIS/Hinode & SUMER/SoHO joint observations allowing the first spectroscopic detection of accelerating disturbances as recorded with coronal lines in inter-plume and plume regions of a polar coronal hole. From time-distance radiance maps, we detect the presence of propagating disturbances in a polar inter-plume region with a period of 15 to 20 min and a propagation speed increasing from 130+/-14 km/s just above the limb, to 330+/-140 km/s around 160" above the limb. These disturbances can also be traced to originate from a bright region of the on-disk part of the coronal hole where the propagation speed was found to be in the range of 25+/-1.3 to 38+/-4.5 km/s, with the same periodicity. These on-disk bright regions can be visualized as the base of the coronal funnels. The adjacent plume region also shows the presence of propagating disturbance with the same range of period but with propagation speeds in the range of 135+/-18 to 165+/-43 km/s only. To our knowledge, this result provides first sp...

  4. Elastic interactions synchronize beating in cardiomyocytes.

    Science.gov (United States)

    Cohen, Ohad; Safran, Samuel A

    2016-07-13

    Motivated by recent experimental results, we study theoretically the synchronization of the beating phase and frequency of two nearby cardiomyocyte cells. Each cell is represented as an oscillating force dipole in an infinite, viscoelastic medium and the propagation of the elastic signal within the medium is predicted. We examine the steady-state beating of two nearby cells, and show that elastic interactions result in forces that synchronize the phase and frequency of beating in a manner that depends on their mutual orientation. The theory predicts both in-phase and anti-phase steady-state beating depending on the relative cell orientations, as well as how synchronized beating varies with substrate elasticity and the inter-cell distance. These results suggest how mechanics plays a role in cardiac efficiency, and may be relevant for the design of cardiomyocyte based micro devices and other biomedical applications. PMID:27352146

  5. The Clinical Sigfificance of QRS-T Waves in Ventricular Premature Beat by Fuzzy Differentiation%模糊差异鉴别对室性早搏QRS-T波形态的临床意义

    Institute of Scientific and Technical Information of China (English)

    吴达; 俞致远; 祝健

    2000-01-01

    Electrocardiograms (ECG)were collected in 895 cases of simple ventricular prematurebeat(VP3) and 18 cases of ventricuiar premature beat with ventricular tachycardia (VT); QRS-Twaves in ECG were measured and then handled by fuzzy set theory and fuzzy differentiationmethod. It was found that a widened QRS complex, especially with the duration of ≥ 0.16 s.indicated a greater possibility of myocardial damage. This finding is in accord with the resultsderived from classical statistical analysis, but shows some differences with the authoriativetraditional differentiation method suggested by Schamroth in the early 1980 s.%根据模糊集理论和模糊差异鉴别方法,对895例单纯室性早搏和18例室性早搏伴室性心动过速心电图的QRS-T波进行测量并作模糊数据处理,发现QRS波增宽,尤其是当时限≥0.16 s时,存在心肌损害的可能性越大.这一结论与用经典数理统计方法处理所得结论一致,但与80年代初由Schamroth所提出的权威的传统鉴别方法的结论有差异.

  6. Backward-Propagating MeV Electrons in Ultra-Intense Laser Interactions: Standing Wave Acceleration and Coupling to the Reflected Laser Pulse

    CERN Document Server

    Orban, Chris; Chowdhury, Enam D; Nees, John A; Frische, Kyle; Roquemore, W Melvyn

    2014-01-01

    Laser-accelerated electron beams have been created at a kHz repetition rate from the reflection of intense ($\\sim10^{18}$ W/cm$^2$), 30 fs laser pulses focused on a continuous water-jet in an experiment at the Air Force Research Laboratory. This paper investigates Particle-In-Cell (PIC) simulations of the laser-target interaction to identify the physical mechanisms of electron acceleration in this experiment. We find that the standing-wave pattern created by the overlap of the incident and reflected laser is particularly important because this standing wave "injects" electrons into the reflected laser pulse where the electrons are further accelerated. We identify two regimes of standing wave acceleration: a highly relativistic case ($a_0~\\geq~1$), and a moderately relativistic case ($a_0~\\sim~0.5$) which operates over a larger fraction of the laser period. Previous work by other groups investigated the highly relativistic case for its usefulness in launching electrons in the forward direction. We extend this ...

  7. Accelerated adhesion of grafted skin by laser-induced stress wave-based gene transfer of hepatocyte growth factor

    Science.gov (United States)

    Aizawa, Kazuya; Sato, Shunichi; Terakawa, Mitsuhiro; Saitoh, Daizoh; Tsuda, Hitoshi; Ashida, Hiroshi; Obara, Minoru

    2009-11-01

    Gene therapy using wound healing-associated growth factor gene has received much attention as a new strategy for improving the outcome of tissue transplantation. We delivered plasmid DNA coding for human hepatocyte growth factor (hHGF) to rat free skin grafts by the use of laser-induced stress waves (LISWs); autografting was performed with the grafts. Systematic analysis was conducted to evaluate the adhesion properties of the grafted tissue; angiogenesis, cell proliferation, and reepithelialization were assessed by immunohistochemistry, and reperfusion was measured by laser Doppler imaging as a function of time after grafting. Both the level of angiogenesis on day 3 after grafting and the increased ratio of blood flow on day 4 to that on day 3 were significantly higher than those in five control groups: grafting with hHGF gene injection alone, grafting with control plasmid vector injection alone, grafting with LISW application alone, grafting with LISW application after control plasmid vector injection, and normal grafting. Reepithelialization was almost completed on day 7 even at the center of the graft with LISW application after hHGF gene injection, while it was not for the grafts of the five control groups. These findings demonstrate the validity of our LISW-based HGF gene transfection to accelerate the adhesion of grafted skins.

  8. Electrical Brain Responses to Beat Irregularities in Two Cases of Beat Deafness.

    Science.gov (United States)

    Mathias, Brian; Lidji, Pascale; Honing, Henkjan; Palmer, Caroline; Peretz, Isabelle

    2016-01-01

    Beat deafness, a recently documented form of congenital amusia, provides a unique window into functional specialization of neural circuitry for the processing of musical stimuli: Beat-deaf individuals exhibit deficits that are specific to the detection of a regular beat in music and the ability to move along with a beat. Studies on the neural underpinnings of beat processing in the general population suggest that the auditory system is capable of pre-attentively generating a predictive model of upcoming sounds in a rhythmic pattern, subserved largely within auditory cortex and reflected in mismatch negativity (MMN) and P3 event-related potential (ERP) components. The current study examined these neural correlates of beat perception in two beat-deaf individuals, Mathieu and Marjorie, and a group of control participants under conditions in which auditory stimuli were either attended or ignored. Compared to control participants, Mathieu demonstrated reduced behavioral sensitivity to beat omissions in metrical patterns, and Marjorie showed a bias to identify irregular patterns as regular. ERP responses to beat omissions reveal an intact pre-attentive system for processing beat irregularities in cases of beat deafness, reflected in the MMN component, and provide partial support for abnormalities in later cognitive stages of beat processing, reflected in an unreliable P3b component exhibited by Mathieu-but not Marjorie-compared to control participants. P3 abnormalities observed in the current study resemble P3 abnormalities exhibited by individuals with pitch-based amusia, and are consistent with attention or auditory-motor coupling accounts of deficits in beat perception. PMID:26941591

  9. Electrical Brain Responses to Beat Irregularities in Two Cases of Beat Deafness.

    Science.gov (United States)

    Mathias, Brian; Lidji, Pascale; Honing, Henkjan; Palmer, Caroline; Peretz, Isabelle

    2016-01-01

    Beat deafness, a recently documented form of congenital amusia, provides a unique window into functional specialization of neural circuitry for the processing of musical stimuli: Beat-deaf individuals exhibit deficits that are specific to the detection of a regular beat in music and the ability to move along with a beat. Studies on the neural underpinnings of beat processing in the general population suggest that the auditory system is capable of pre-attentively generating a predictive model of upcoming sounds in a rhythmic pattern, subserved largely within auditory cortex and reflected in mismatch negativity (MMN) and P3 event-related potential (ERP) components. The current study examined these neural correlates of beat perception in two beat-deaf individuals, Mathieu and Marjorie, and a group of control participants under conditions in which auditory stimuli were either attended or ignored. Compared to control participants, Mathieu demonstrated reduced behavioral sensitivity to beat omissions in metrical patterns, and Marjorie showed a bias to identify irregular patterns as regular. ERP responses to beat omissions reveal an intact pre-attentive system for processing beat irregularities in cases of beat deafness, reflected in the MMN component, and provide partial support for abnormalities in later cognitive stages of beat processing, reflected in an unreliable P3b component exhibited by Mathieu-but not Marjorie-compared to control participants. P3 abnormalities observed in the current study resemble P3 abnormalities exhibited by individuals with pitch-based amusia, and are consistent with attention or auditory-motor coupling accounts of deficits in beat perception.

  10. Electrical brain responses to beat irregularities in two cases of beat deafness

    Directory of Open Access Journals (Sweden)

    Brian eMathias

    2016-02-01

    Full Text Available Beat deafness, a recently documented form of congenital amusia, provides a unique window into functional specialization of neural circuitry for the processing of musical stimuli: Beat-deaf individuals exhibit deficits that are specific to the detection of a regular beat in music and the ability to move along with a beat. Studies on the neural underpinnings of beat processing in the general population suggest that the auditory system is capable of pre-attentively generating a predictive model of upcoming sounds in a rhythmic pattern, subserved largely within auditory cortex and reflected in mismatch negativity (MMN and P3 event-related potential (ERP components. The current study examined these neural correlates of beat perception in two beat-deaf individuals, Mathieu and Marjorie, and a group of control participants under conditions in which auditory stimuli were either attended or ignored. Compared to control participants, Mathieu demonstrated reduced behavioral sensitivity to beat omissions in metrical patterns, and Marjorie showed a bias to identify irregular patterns as regular. ERP responses to beat omissions reveal an intact pre-attentive system for processing beat irregularities in cases of beat deafness, reflected in the MMN component, and provide partial support for abnormalities in later cognitive stages of beat processing, reflected in an unreliable P3b component exhibited by Mathieu – but not Marjorie – compared to control participants. P3 abnormalities observed in the current study resemble P3 abnormalities exhibited by individuals with pitch-based amusia, and are consistent with attention or auditory-motor coupling accounts of deficits in beat perception.

  11. Dynamic focusing in the zebrafish beating heart

    Science.gov (United States)

    Andrés-Delgado, L.; Peralta, M.; Mercader, N.; Ripoll, J.

    2016-03-01

    Of the large amount of the animal models available for cardiac research, the zebrafish is extremely valuable due to its transparency during early stages of development. In this work a dual illumination laser sheet microscope with simultaneous dual camera imaging is used to image the beating heart at 200 fps, dynamically and selectively focusing inside the beating heart through the use of a tunable lens. This dual color dynamic focusing enables imaging with cellular resolution at unprecedented high frame rates, allowing 3D imaging of the whole beating heart of embryonic zebrafish.

  12. On the beating of reinforcement pulp

    OpenAIRE

    Hiltunen, Eero

    2003-01-01

    The aim of this work was to gain a better understanding of the effect of reinforcement pulp beating on the strength of mechanical pulp-dominated paper. The main purpose of reinforcement pulp beating is to improve the runnability of paper. The first objective of this study was to maximize the runnability related strength properties by beating. It was assumed that the flaw-resisting ability of paper correlates with the runnability of the dry paper web. In-plane fracture properties were assumed ...

  13. Low-Frequency Wave Activity Detected by MMS during Dusk Magnetopause Crossings and its Relation to Heating and Acceleration of Particles

    Science.gov (United States)

    Le Contel, O.; Roux, A.; Retino, A.; Mirioni, L.; Sahraoui, F.; Chust, T.; Berthomier, M.; Chasapis, A.; Aunai, N.; Leroy, P.; Alison, D.; Lavraud, B.; Lindqvist, P. A.; Khotyaintsev, Y. V.; Vaivads, A.; Marklund, G. T.; Burch, J. L.; Torbert, R. B.; Moore, T.; Ergun, R. E.; Needell, J.; Chutter, M.; Rau, D.; Dors, I.; Macri, J.; Russell, C. T.; Magnes, W.; Strangeway, R. J.; Bromund, K. R.; Plaschke, F.; Fischer, D.; Leinweber, H. K.; Anderson, B. J.; Nakamura, R.; Argall, M. R.; Le, G.; Slavin, J. A.; Kepko, L.; Baumjohann, W.; Pollock, C. J.; Mauk, B.; Fuselier, S. A.; Goodrich, K.; Wilder, F. D.

    2015-12-01

    Since the 9th of July, the MMS fleet of four satellites have evolved into a tetrahedral configuration with an average inter-satellite distance of 160 km and an apogee of 12 earth radii on the dusk side. In this study we report on ultra-low (1 mHz to ~10 Hz) and very-low (10 Hz to ~ 4 kHz) frequency wave activity measured by the four satellites during several crossings of the dusk equatorial magnetopause. Since the Larmor radius of magnetosheath protons is of the order of 50 km, this inter-satellite distance allows us to investigate in detail the physics of the magnetopause at proton scales including current structures related to Kelvin-Helmholtz instability as well as other energy transfer processes. From wave polarization analysis, we characterize the different types of emissions and discuss different mechanisms of heating and acceleration of particles. In particular, we focus on the electron heating by kinetic Alfvén waves and lower hybrid waves and the electron acceleration by oblique whistler mode waves, which have been suggested as possible mechanisms from previous Cluster and THEMIS measurements.

  14. Stochastic Acceleration of Electrons by Fast Magnetosonic Waves in Solar Flares: the Effects of Anisotropy in Velocity andWavenumber Space

    CERN Document Server

    Pongkitiwanichakul, Peera

    2014-01-01

    We develop a model for stochastic acceleration of electrons in solar flares. As in several previous models, the electrons are accelerated by turbulent fast magnetosonic waves ("fast waves") via transit-time-damping (TTD) interactions. (In TTD interactions, fast waves act like moving magnetic mirrors that push the electrons parallel or anti-parallel to the magnetic field). We also include the effects of Coulomb collisions and the waves' parallel electric fields. Unlike previous models, our model is two-dimensional in both momentum space and wavenumber space and takes into account the anisotropy of the wave power spectrum $F_k$ and electron distribution function $f_{\\rm e}$. We use weak turbulence theory and quasilinear theory to obtain a set of equations that describes the coupled evolution of $F_k$ and $f_{\\rm e}$. We solve these equations numerically and find that the electron distribution function develops a power-law-like non-thermal tail within a restricted range of energies $E\\in (E_{\\rm nt}, E_{\\rm max}...

  15. The effect of plasma inhomogeneities on (i) radio emission generation by non-gyrotropic electron beams and (ii) particle acceleration by Langmuir waves

    Science.gov (United States)

    Tsiklauri, David

    2015-04-01

    Extensive particle-in-cell simulations of fast electron beams injected in a background magnetised plasma with a decreasing density profile were carried out. These simulations were intended to further shed light on a newly proposed mechanism for the generation of electromagnetic waves in type III solar radio bursts [1]. Here recent progress in an alternative to the plasma emission model using Particle-In-Cell, self-consistent electromagnetic wave emission simulations of solar type III radio bursts will be presented. In particular, (i) Fourier space drift (refraction) of non-gyrotropic electron beam-generated wave packets, caused by the density gradient [1,2], (ii) parameter space investigation of numerical runs [3], (iii) concurrent generation of whistler waves [4] and a separate problem of (iv) electron acceleration by Langmuir waves in a background magnetised plasma with an increasing density profile [5] will be discussed. In all considered cases the density inhomogeneity-induced wave refraction plays a crucial role. In the case of non-gyrotropic electron beam, the wave refraction transforms the generated wave packets from standing into freely escaping EM radiation. In the case of electron acceleration by Langmuir waves, a positive density gradient in the direction of wave propagation causes a decrease in the wavenumber, and hence a higher phase velocity vph = ω/k. The k-shifted wave is then subject to absorption by a faster electron by wave-particle interaction. The overall effect is an increased number of high energy electrons in the energy spectrum. [1] D. Tsiklauri, Phys. Plasmas 18, 052903 (2011); http://dx.doi.org/10.1063/1.3590928 [2] H. Schmitz, D. Tsiklauri, Phys. Plasmas 20, 062903 (2013); http://dx.doi.org/10.1063/1.4812453 [3] R. Pechhacker, D. Tsiklauri, Phys. Plasmas 19, 112903 (2012); http://dx.doi.org/10.1063/1.4768429 [4] M. Skender, D. Tsiklauri, Phys. Plasmas 21, 042904 (2014); http://dx.doi.org/10.1063/1.4871723 [5] R. Pechhacker, D. Tsiklauri

  16. Beating Depression …Help Is Available

    Science.gov (United States)

    ... Navigation Bar Home Current Issue Past Issues Beating Depression …Help Is Available Past Issues / Summer 2007 Table ... treatments are available from your physician. Types of Depression Just like other illnesses, such as heart disease, ...

  17. High Blood Pressure: Keep the Beat Recipes

    Science.gov (United States)

    ... this page please turn Javascript on. Feature: High Blood Pressure Keep the Beat Recipes Past Issues / Fall 2011 ... National Heart, Lung, and Blood Institute To Improve Blood Pressure, Try the DASH Diet If you're one ...

  18. Shear flow induced wave couplings in the solar wind

    Energy Technology Data Exchange (ETDEWEB)

    Poedts, S. [KULeuven, Heverlee (Belgium). Centre for Plasma Astrophysics; Rogava, A.D. [Tbilisi State Univ. (Georgia). Dept. of Physics]|[International Centre for Theoretical Physics, Trieste (Italy); Mahajan, S.M. [Univ. of Texas, Austin, TX (United States). Institute for Fusion Studies]|[International Centre for Theoretical Physics, Trieste (Italy)

    1998-01-01

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

  19. Heart Beat Classification Using Particle Swarm Optimization

    OpenAIRE

    Ali Khazaee

    2013-01-01

    This paper proposes a novel system to classify three types of electrocardiogram beats, namely normal beats and two manifestations of heart arrhythmia. This system includes three main modules: a feature extraction module, a classifier module, and an optimization module. In the feature extraction module, a proper set combining the shape features and timing features is proposed as the efficient characteristic of the patterns. In the classifier module, a multi-class support vector machine (SVM)-b...

  20. Direct Acceleration of Ions With Variable-frequency Lasers

    CERN Document Server

    Peano, F; Fonseca, R A; Mulas, R; Coppa, G; Silva, L O

    2008-01-01

    A method is proposed for producing monoergetic, high-quality ion beams in vacuum, via direct acceleration by the electromagnetic field of two counterpropagating, variable-frequency lasers: ions are trapped and accelerated by a beat-wave structure with variable phase velocity, allowing for fine control over the energy and the charge of the beam via tuning of the frequency variation. The physical mechanism is described with a one-dimensional theory, providing the general conditions for trapping and scaling laws for the relevant features of the ion beam. Two-dimensional, electromagnetic particle-in-cell simulations, in which hydrogen gas is considered as an ion source, confirm the validity and the robustness of the method.

  1. A Solid state accelerator

    International Nuclear Information System (INIS)

    We present a solid state accelerator concept utilizing particle acceleration along crystal channels by longitudinal electron plasma waves in a metal. Acceleration gradients of order 100 GV/cm are theoretically possible, but channeling radiation limits the maximum attainable energy to 105 TeV for protons. Beam dechanneling due to multiple scattering is substantially reduced by the high acceleration gradient. Plasma wave dissipation and generation in metals are also discussed

  2. The impact of binaural beats on creativity

    Directory of Open Access Journals (Sweden)

    Susan A. Reedijk

    2013-11-01

    Full Text Available Human creativity relies on a multitude of cognitive processes, some of which are influenced by the neurotransmitter dopamine. This suggests that creativity could be enhanced by interventions that either modulate the production or transmission of dopamine directly, or affect dopamine-driven processes. In the current study we hypothesized that creativity can be influenced by means of binaural beats, an auditory illusion that is considered a form of cognitive entrainment that operates through stimulating neuronal phase locking. We aimed to investigate whether binaural beats affect creative performance at all, whether they affect divergent thinking, convergent thinking, or both, and whether possible effects may be mediated by the individual striatal dopamine level. Binaural beats were presented at alpha and gamma frequency. Participants completed a divergent and a convergent thinking task to assess two important functions of creativity, and filled out the Positive And Negative Affect Scale – mood State questionnaire (PANAS-S and affect grid to measure current mood. Dopamine levels in the striatum were estimated using spontaneous eye blink rates (EBRs. Results showed that binaural beats, regardless of the presented frequency, can affect divergent but not convergent thinking. Individuals with low EBRs mostly benefitted from alpha binaural beat stimulation, while individuals with high EBR were unaffected or even impaired by both alpha and gamma binaural beats. This suggests that binaural beats, and possibly other forms of cognitive entrainment, are not suited for a one-size-fits-all approach, and that individual cognitive-control systems need to be taken into account when studying cognitive enhancement methods.

  3. Short-term beat-to-beat variability of the QT interval is increased and correlates with parameters of left ventricular hypertrophy in patients with hypertrophic cardiomyopathy.

    Science.gov (United States)

    Orosz, Andrea; Baczkó, István; Nagy, Viktória; Gavallér, Henriette; Csanády, Miklós; Forster, Tamás; Papp, Julius Gy; Varró, András; Lengyel, Csaba; Sepp, Róbert

    2015-09-01

    Stratification models for the prediction of sudden cardiac death (SCD) are inappropriate in patients with hypertrophic cardiomyopathy (HCM). We investigated conventional electrocardiogram (ECG) repolarization parameters and the beat-to-beat short-term QT interval variability (QT-STV), a new parameter of proarrhythmic risk, in 37 patients with HCM (21 males, average age 48 ± 15 years). Resting ECGs were recorded for 5 min and the frequency corrected QT interval (QTc), QT dispersion (QTd), beat-to-beat short-term variability of QT interval (QT-STV), and the duration of terminal part of T waves (Tpeak-Tend) were calculated. While all repolarization parameters were significantly increased in patients with HCM compared with the controls (QTc, 488 ± 61 vs. 434 ± 23 ms, p < 0.0001; QT-STV, 4.5 ± 2 vs. 3.2 ± 1 ms, p = 0.0002; Tpeak-Tend duration, 107 ± 27 vs. 91 ± 10 ms, p = 0.0015; QTd, 47 ± 17 vs. 34 ± 9 ms, p = 0.0002), QT-STV had the highest relative increase (+41%). QT-STV also showed the best correlation with indices of left ventricular (LV) hypertrophy, i.e., maximal LV wall thickness normalized for body surface area (BSA; r = 0.461, p = 0.004) or LV mass (determined by cardiac magnetic resonance imaging) normalized for BSA (r = 0.455, p = 0.015). In summary, beat-to-beat QT-STV showed the most marked increase in patients with HCM and may represent a novel marker that merits further testing for increased SCD risk in HCM. PMID:26313025

  4. Proarrhythmic electrical remodelling is associated with increased beat-to-beat variability of repolarisation

    DEFF Research Database (Denmark)

    Thomsen, Morten Bækgaard; Oros, Avram; Schoenmakers, Marieke;

    2007-01-01

    Acquired long-QT syndrome in combination with increased beat-to-beat variability of repolarisation duration (BVR) is associated with lethal torsades de pointes arrhythmias (TdP) in dogs with remodelled heart after atrioventricular block (AVB). We evaluated the relative contributions of bradycardia...

  5. SPS accelerating cavity

    CERN Multimedia

    1983-01-01

    See photo 8202397: View towards the downstream end of one of the SPS accelerating cavities (200 MHz, travelling wave structure). See 7603195 and 8011289 for more details, 7411032 for the travelling wave structure, and also 8104138.

  6. SPS accelerating cavity

    CERN Multimedia

    1983-01-01

    View towards the downstream end of one of the SPS accelerating cavities (200 MHz, travelling wave structure). See 7603195 and 8011289 for more details, 7411032 for the travelling wave structure, and also 8104138.

  7. Probing an Excited-State Atomic Transition Using Hyperfine Quantum Beat Spectroscopy

    CERN Document Server

    Wade, Christopher G; Keaveney, James; Adams, Charles S; Weatherill, Kevin J

    2014-01-01

    We describe a method to observe the dynamics of an excited-state transition in a room temperature atomic vapor using hyperfine quantum beats. Our experiment using cesium atoms consists of a pulsed excitation of the D2 transition, and continuous-wave driving of an excited-state transition from the 6P$_{3/2}$ state to the 7S$_{1/2}$ state. We observe quantum beats in the fluorescence from the 6P$_{3/2}$ state which are modified by the driving of the excited-state transition. The Fourier spectrum of the beat signal yields evidence of Autler-Townes splitting of the 6P$_{3/2}$, F = 5 hyperfine level and Rabi oscillations on the excited-state transition. A detailed model provides qualitative agreement with the data, giving insight to the physical processes involved.

  8. Microwave radiation and heart-beat rate of rabbits.

    Science.gov (United States)

    Chou, C K; Han, L F; Guy, A W

    1980-06-01

    Each of three adult New Zealand rabbits, 2 male and 1 female albinos, was exposed dorsally or ventrally, to 2450-MHz plane waves for 20 min under each of several field conditions: 1) to continuous waves (CW) at 5 mW/cm2; 2) to pulsed waves (PW) of 1-microsecond width that recurred 700 pps at an average of 5 mW/cm2 and at a peak of 7.1 W/cm2; 3) to PW of 10-microseconds width at a peak of 13.7 W/cm2 that were synchronized with and triggered by the R wave of the electrocardiogram (EKG) at various delay times (0, 100, and 200 ms; and 4) to CW at 80 mW/cm2. Carbon-loaded Teflon electrodes were used to record the EKG from forelimbs of an animal before, during, and after irradiation whilst it was maintained in a constant exposure geometry in a wooden squeeze box. Field induced changes in the heart-beat rate were observed at 80 mW/cm2 but not a lower average power densities, although a peak positive chronotropic effect might have been occasioned by PM introduced at 100 and 200 ms after the R wave peak. No cumulative effect was observed over a period of four months. Thermographic analysis revealed relatively little absorption of microwave energy by the myocardium irrespective of anatomical aspect of exposure.

  9. Multi-component based cross correlation beat detection in electrocardiogram analysis

    Directory of Open Access Journals (Sweden)

    Owens Frank J

    2004-07-01

    Full Text Available Abstract Background The first stage in computerised processing of the electrocardiogram is beat detection. This involves identifying all cardiac cycles and locating the position of the beginning and end of each of the identifiable waveform components. The accuracy at which beat detection is performed has significant impact on the overall classification performance, hence efforts are still being made to improve this process. Methods A new beat detection approach is proposed based on the fundamentals of cross correlation and compared with two benchmarking approaches of non-syntactic and cross correlation beat detection. The new approach can be considered to be a multi-component based variant of traditional cross correlation where each of the individual inter-wave components are sought in isolation as opposed to being sought in one complete process. Each of three techniques were compared based on their performance in detecting the P wave, QRS complex and T wave in addition to onset and offset markers for 3000 cardiac cycles. Results Results indicated that the approach of multi-component based cross correlation exceeded the performance of the two benchmarking techniques by firstly correctly detecting more cardiac cycles and secondly provided the most accurate marker insertion in 7 out of the 8 categories tested. Conclusion The main benefit of the multi-component based cross correlation algorithm is seen to be firstly its ability to successfully detect cardiac cycles and secondly the accurate insertion of the beat markers based on pre-defined values as opposed to performing individual gradient searches for wave onsets and offsets following fiducial point location.

  10. Intermode beat stabilized laser with frequency pulling.

    Science.gov (United States)

    Yokoyama, S; Araki, T; Suzuki, N

    1994-01-20

    A frequency-stabilized two-mode He-Ne laser has been developed. The intermode beat frequency of the experimental laser was approximately 600 MHz for a 25-cm cavity. The laser frequency in which the mode stands is pulled to the center of the gain curve (frequency pulling). The degree of pulling depends on where the longitudinal modes stand in the broadened gain curve. Beat frequency is thereby changed periodically of the order of hundreds of kilohertz with respect to cavity expansion. The frequency pulling was effectively used for frequency stabilization of the laser. The standing position of the longitudinal mode lights was locked in the gain curve by controlling the change of intermode beat frequency. A microwave mixer was applied to extract the frequency change of the intermode beat. Excellent frequency stability (10(10) for the laser oscillation and 10(6) for the beat frequency) was attained. The polarization orthogonality of the proposed laser was superior to that of Zeeman lasers.

  11. Independent Control of the Static and Dynamic Components of the Chlamydomonas Flagellar Beat.

    Science.gov (United States)

    Geyer, Veikko F; Sartori, Pablo; Friedrich, Benjamin M; Jülicher, Frank; Howard, Jonathon

    2016-04-25

    When the green alga Chlamydomonas reinhardtii swims, it uses the breaststroke beat of its two flagella to pull itself forward [1]. The flagellar waveform can be decomposed into a static component, corresponding to an asymmetric time-averaged shape, and a dynamic component, corresponding to the time-varying wave [2]. Extreme lightening conditions photoshock the cell, converting the breaststroke beat into a symmetric sperm-like beat, which causes a reversal of the direction of swimming [3]. Waveform conversion is achieved by a reduction in magnitude of the static component, whereas the dynamic component remains unchanged [2]. The coupling between static and dynamic components, however, is poorly understood, and it is not known whether the static component requires the dynamic component or whether it can exist independently. We used isolated and reactivated axonemes [4] to investigate the relation between the two beat components. We discovered that, when reactivated in the presence of low ATP concentrations, axonemes displayed the static beat component in absence of the dynamic component. Furthermore, we found that the amplitudes of the two components depend on ATP in qualitatively different ways. These results show that the decomposition into static and dynamic components is not just a mathematical concept but that the two components can independently control different aspects of cell motility: the static component controls swimming direction, whereas the dynamic component provides propulsion. PMID:27040779

  12. Fully nonlinear time-domain simulation of a backward bent duct buoy floating wave energy converter using an acceleration potential method

    Science.gov (United States)

    Lee, Kyoung-Rok; Koo, Weoncheol; Kim, Moo-Hyun

    2013-12-01

    A floating Oscillating Water Column (OWC) wave energy converter, a Backward Bent Duct Buoy (BBDB), was simulated using a state-of-the-art, two-dimensional, fully-nonlinear Numerical Wave Tank (NWT) technique. The hydrodynamic performance of the floating OWC device was evaluated in the time domain. The acceleration potential method, with a full-updated kernel matrix calculation associated with a mode decomposition scheme, was implemented to obtain accurate estimates of the hydrodynamic force and displacement of a freely floating BBDB. The developed NWT was based on the potential theory and the boundary element method with constant panels on the boundaries. The mixed Eulerian-Lagrangian (MEL) approach was employed to capture the nonlinear free surfaces inside the chamber that interacted with a pneumatic pressure, induced by the time-varying airflow velocity at the air duct. A special viscous damping was applied to the chamber free surface to represent the viscous energy loss due to the BBDB's shape and motions. The viscous damping coefficient was properly selected using a comparison of the experimental data. The calculated surface elevation, inside and outside the chamber, with a tuned viscous damping correlated reasonably well with the experimental data for various incident wave conditions. The conservation of the total wave energy in the computational domain was confirmed over the entire range of wave frequencies.

  13. Self-consistent plasma heating and acceleration by strong magnetosonic waves for theta = 90 0. Part I: Basic mechanisms

    International Nuclear Information System (INIS)

    The behavior of strong magnetosonic waves propagating perpendicular to a static field B0 is investigated within the frequency range ω/sub c/i0 results; the electrons exhibit only poor heating associated with their adiabatic compression. The dynamics of both particle species, the consequences of the wave--particle energy transfer and the particle viscosities, are studied in detail. Competitive and self-consistent effects such as space-charge effects, wave overtaking, ion trapping, and wave damping are investigated and compared with previous models; the mechanisms by which these various phenomena interact on each other are analyzed. Characteristics of nonstochastic and stochastic ion heating are also discussed. Our computations show that if sufficient intensity is reached, one is not constrained to use lower-hybrid waves or cyclotron harmonic waves to heat a plasma efficiently and that any frequency below ω/sub lh/ can be used

  14. Active Affective Learning for Accelerated Schools.

    Science.gov (United States)

    Richardson, Robert B.

    This paper provides the groundwork for Active Affective Learning and teaching adapted to the needs of the disadvantaged, at-risk students served by the Accelerated Schools Movement. One of the "golden rules" for the practice of Accelerated Learning, according to psychiatrist Georgi Lozanov, has been to maintain an "up-beat" classroom presentation…

  15. Beat that Word: How Listeners Integrate Beat Gesture and Focus in Multimodal Speech Discourse.

    Science.gov (United States)

    Dimitrova, Diana; Chu, Mingyuan; Wang, Lin; Özyürek, Asli; Hagoort, Peter

    2016-09-01

    Communication is facilitated when listeners allocate their attention to important information (focus) in the message, a process called "information structure." Linguistic cues like the preceding context and pitch accent help listeners to identify focused information. In multimodal communication, relevant information can be emphasized by nonverbal cues like beat gestures, which represent rhythmic nonmeaningful hand movements. Recent studies have found that linguistic and nonverbal attention cues are integrated independently in single sentences. However, it is possible that these two cues interact when information is embedded in context, because context allows listeners to predict what information is important. In an ERP study, we tested this hypothesis and asked listeners to view videos capturing a dialogue. In the critical sentence, focused and nonfocused words were accompanied by beat gestures, grooming hand movements, or no gestures. ERP results showed that focused words are processed more attentively than nonfocused words as reflected in an N1 and P300 component. Hand movements also captured attention and elicited a P300 component. Importantly, beat gesture and focus interacted in a late time window of 600-900 msec relative to target word onset, giving rise to a late positivity when nonfocused words were accompanied by beat gestures. Our results show that listeners integrate beat gesture with the focus of the message and that integration costs arise when beat gesture falls on nonfocused information. This suggests that beat gestures fulfill a unique focusing function in multimodal discourse processing and that they have to be integrated with the information structure of the message.

  16. Large Amplitude Whistler Waves and Electron Acceleration in the Earth's Radiation Belts: A Review of STEREO and Wind Observations

    Science.gov (United States)

    Cattell, Cynthia; Breneman, A.; Goetz, K.; Kellogg, P.; Kersten, K.; Wygant, J.; Wilson, L. B., III; Looper, Mark D.; Blake, J. Bernard; Roth, I.

    2012-01-01

    One of the critical problems for understanding the dynamics of Earth's radiation belts is determining the physical processes that energize and scatter relativistic electrons. We review measurements from the Wind/Waves and STEREO S/Waves waveform capture instruments of large amplitude whistler-mode waves. These observations have provided strong evidence that large amplitude (100s mV/m) whistler-mode waves are common during magnetically active periods. The large amplitude whistlers have characteristics that are different from typical chorus. They are usually nondispersive and obliquely propagating, with a large longitudinal electric field and significant parallel electric field. We will also review comparisons of STEREO and Wind wave observations with SAMPEX observations of electron microbursts. Simulations show that the waves can result in energization by many MeV and/or scattering by large angles during a single wave packet encounter due to coherent, nonlinear processes including trapping. The experimental observations combined with simulations suggest that quasilinear theoretical models of electron energization and scattering via small-amplitude waves, with timescales of hours to days, may be inadequate for understanding radiation belt dynamics.

  17. SIMULATION OF ENERGETIC PARTICLE TRANSPORT AND ACCELERATION AT SHOCK WAVES IN A FOCUSED TRANSPORT MODEL: IMPLICATIONS FOR MIXED SOLAR PARTICLE EVENTS

    Energy Technology Data Exchange (ETDEWEB)

    Kartavykh, Y. Y.; Dröge, W. [Institut für Theoretische Physik und Astrophysik, Universität Würzburg, D-97074 Würzburg (Germany); Gedalin, M. [Department of Physics, Ben-Gurion Unversity of the Negev, Beer-Sheva (Israel)

    2016-03-20

    We use numerical solutions of the focused transport equation obtained by an implicit stochastic differential equation scheme to study the evolution of the pitch-angle dependent distribution function of protons in the vicinity of shock waves. For a planar stationary parallel shock, the effects of anisotropic distribution functions, pitch-angle dependent spatial diffusion, and first-order Fermi acceleration at the shock are examined, including the timescales on which the energy spectrum approaches the predictions of diffusive shock acceleration theory. We then consider the case that a flare-accelerated population of ions is released close to the Sun simultaneously with a traveling interplanetary shock for which we assume a simplified geometry. We investigate the consequences of adiabatic focusing in the diverging magnetic field on the particle transport at the shock, and of the competing effects of acceleration at the shock and adiabatic energy losses in the expanding solar wind. We analyze the resulting intensities, anisotropies, and energy spectra as a function of time and find that our simulations can naturally reproduce the morphologies of so-called mixed particle events in which sometimes the prompt and sometimes the shock component is more prominent, by assuming parameter values which are typically observed for scattering mean free paths of ions in the inner heliosphere and energy spectra of the flare particles which are injected simultaneously with the release of the shock.

  18. Simulation of Energetic Particle Transport and Acceleration at Shock Waves in a Focused Transport Model: Implications for Mixed Solar Particle Events

    Science.gov (United States)

    Kartavykh, Y. Y.; Dröge, W.; Gedalin, M.

    2016-03-01

    We use numerical solutions of the focused transport equation obtained by an implicit stochastic differential equation scheme to study the evolution of the pitch-angle dependent distribution function of protons in the vicinity of shock waves. For a planar stationary parallel shock, the effects of anisotropic distribution functions, pitch-angle dependent spatial diffusion, and first-order Fermi acceleration at the shock are examined, including the timescales on which the energy spectrum approaches the predictions of diffusive shock acceleration theory. We then consider the case that a flare-accelerated population of ions is released close to the Sun simultaneously with a traveling interplanetary shock for which we assume a simplified geometry. We investigate the consequences of adiabatic focusing in the diverging magnetic field on the particle transport at the shock, and of the competing effects of acceleration at the shock and adiabatic energy losses in the expanding solar wind. We analyze the resulting intensities, anisotropies, and energy spectra as a function of time and find that our simulations can naturally reproduce the morphologies of so-called mixed particle events in which sometimes the prompt and sometimes the shock component is more prominent, by assuming parameter values which are typically observed for scattering mean free paths of ions in the inner heliosphere and energy spectra of the flare particles which are injected simultaneously with the release of the shock.

  19. Accelerating field waves transmission of dielectric wall accelerator%介质壁加速器加速场建立过程中波传输分析

    Institute of Scientific and Technical Information of China (English)

    赵全堂; 袁平; 张子民; 曹树春; 申晓康; 赵红卫

    2011-01-01

    介绍了介质壁加速器(DWA)的原理和几种可能实现的结构.通过对多层介质圆柱的平面波电磁散射的研究,用FORTRAN语言编写程序计算和分析了DWA加速管三层介质柱体结构的平面波电磁散射的散射宽度与几何结构参数、材料参数的关系,用以优化设计介质壁加速管结构.计算结果表明:当加速管材料和等势环介电常数一定时,平面波电磁散射宽度随半径增大而增大;当加速管内外径一定时,加速管材料和等势环介电常数增大时散射宽度变化不明显,但最小散射宽度显著减小.当加速管半径和材料一定时,总能找到使散射宽度达到最小的等势环介质厚度.%The paper introduces the principle and some feasible structures of dielectric wall acceleratorDWA). By the study of electromagnetic scattering of multilayer dielectric cylinders, the relation of scattering width , parameters of materials and structure of beam pipe of DWA is investigated with FORTRAN program, for designing the accelerating beam pipe of DWA with high accelerating gradient and high energy coupling efficiency. The results confirm that, with permittivities of dielectric cylinders fixed, the scattering width becomes larger when the radiuses get larger. With radiuses of dielectric cylinders fixed, the scattering width shows no obvious change when the permittivities become larger, but the minimal scattering width becomes smaller. When the radiuses and permittivities of the first and the second layers are given,there is always a third layer thickness at which the scattering width is minimum.

  20. A 50-MeV mm-wave electron linear accelerator system for production of tunable short wavelength synchrotron radiation

    International Nuclear Information System (INIS)

    The Advanced Photon Source (APS) at Argonne in collaboration with the University of Illinois at Chicago and the University of Wisconsin at Madison is developing a new millimeter wavelength, 50-MeV electron linear accelerator system for production of coherent tunable wavelength synchrotron radiation. Modern micromachining techniques based on deep etch x-ray lithography, LIGA (Lithografie, Galvanoformung, Abformung), capable of producing high-aspect ratio structures are being considered for the fabrication of the accelerating components

  1. Induced emission of Alfvén waves in inhomogeneous streaming plasma: implications for solar corona heating and solar wind acceleration.

    Science.gov (United States)

    Galinsky, V L; Shevchenko, V I

    2013-07-01

    The results of a self-consistent kinetic model of heating the solar corona and accelerating the fast solar wind are presented for plasma flowing in a nonuniform magnetic field configuration of near-Sun conditions. The model is based on a scale separation between the large transit or inhomogeneity scales and the small dissipation scales. The macroscale instability of the marginally stable particle distribution function compliments the resonant frequency sweeping dissipation of transient Alfvén waves by their induced emission in inhomogeneous streaming plasma that provides enough energy for keeping the plasma temperature decaying not faster than r(-1) in close agreement with in situ heliospheric observations.

  2. Wave

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo

    2008-01-01

    Estimates for the amount of potential wave energy in the world range from 1-10 TW. The World Energy Council estimates that a potential 2TW of energy is available from the world’s oceans, which is the equivalent of twice the world’s electricity production. Whilst the recoverable resource is many...... times smaller it remains very high. For example, whilst there is enough potential wave power off the UK to supply the electricity demands several times over, the economically recoverable resource for the UK is estimated at 25% of current demand; a lot less, but a very substantial amount nonetheless....

  3. Waves and particles in the Fermi accelerator model. Numerical simulation; Ondes et particules dans le modele de l`accelerateur de Fermi. Simulation numerique

    Energy Technology Data Exchange (ETDEWEB)

    Meplan, O.

    1996-01-01

    This thesis is devoted to a numerical study of the quantum dynamics of the Fermi accelerator which is classically chaotic: it is particle in a one dimensional box with a oscillating wall. First, we study the classical dynamics: we show that the time of impact of the particle with the moving wall and its energy in the wall frame are conjugated variables and that Poincare surface of sections in these variables are more understandable than the usual stroboscopic sections. Then, the quantum dynamics of this systems is studied by the means of two numerical methods. The first one is a generalization of the KKR method in the space-time; it is enough to solve an integral equation on the boundary of a space-time billiard. The second method is faster and is based on successive free propagations and kicks of potential. This allows us to obtain Floquet states which we can on one hand, compare to the classical dynamics with the help of Husimi distributions and on the other hand, study as a function of parameters of the system. This study leads us to nice illustrations of phenomenons such as spatial localizations of a wave packet in a vibrating well or tunnel effects. In the adiabatic situation, we give a formula for quasi-energies which exhibits a phase term independent of states. In this regime, there exist some particular situations where the quasi-energy spectrum presents a total quasi-degeneracy. Then, the wave packet energy can increase significantly. This phenomenon is quite surprising for smooth motion of the wall. The third part deals with the evolution of a classical wave in the Fermi accelerator. Using generalized KKR method, we show a surprising phenomenon: in most of situations (so long as the wall motion is periodic), a wave is localized exponentially in the well and its energy increases in a geometric way. (author). 107 refs., 66 figs., 5 tabs. 2 appends.

  4. Fifth-order attosecond polarization beats using twin color-locked noisy lights in cascade three-level system with Doppler-free approach

    Institute of Scientific and Technical Information of China (English)

    Jianping Song; Xiangchen Zhang; Yanpeng Zhang; Keqing Lu; Yu Feng; Chenli Gan; Long Li; Yuanyuan Li; Xiaojun Yu; Hao Ge; Ruiqiong Ma; Chuangshe Li

    2005-01-01

    Fifth-order attosecond sum-frequency polarization beat (FASPB) is studied in a cascade three level system with the phase-conjugation fourth-order coherence function theory. An improved schematic diagram of geometry, which is different from that inducing fifth-order femtosecond different-frequency polarization beat(FFDPB), is used to obtain FASPB. By analyzing the cases that pump beams have either narrow or broad bandwidth, it is found that the temporal behavior of the sum-frequency polarization beat signal depends on the properties of the lasers and transverse relaxation rate of the atomic energy-level system. Finally,the cascaded four-wave mixing (FWM) processes and the difference between attosecond and femtosecond polarization beats have been discussed, it is found that cascaded or sequential lower processes can often obscure the direct fifth-order polarization beat processes.

  5. Beat Noise Limitation in Coherent Time-Spreading OCDMA Network

    Institute of Scientific and Technical Information of China (English)

    Ken-ichi; Kitayama; Koji; Mutsushima

    2003-01-01

    The BER performance of the coherent time-spreading OCDMA network is analyzed by considering the MAI and beat noises as well as the other additive noises. The influence and solution for the beat noise issue are discussed.

  6. Heat Beats Cold for Treating Jellyfish Stings

    Science.gov (United States)

    ... page: https://medlineplus.gov/news/fullstory_158584.html Heat Beats Cold for Treating Jellyfish Stings Evidence favors hot water or hot packs to ease pain ... 29, 2016 (HealthDay News) -- If you're unlucky enough to suffer a jellyfish sting, new research says that heat is better than cold for easing the pain. ...

  7. Beat the Instructor: An Introductory Forecasting Game

    Science.gov (United States)

    Snider, Brent R.; Eliasson, Janice B.

    2013-01-01

    This teaching brief describes a 30-minute game where student groups compete in-class in an introductory time-series forecasting exercise. The students are challenged to "beat the instructor" who competes using forecasting techniques that will be subsequently taught. All forecasts are graphed prior to revealing the randomly generated…

  8. Quantum beats of the rigid rotor

    OpenAIRE

    Kowalski, K.; Rembieliński, J.

    2013-01-01

    The dynamics is investigated of a free particle on a sphere (rigid rotor or rotator) that is initially in a coherent state. The instability of coherent states with respect to the free evolution leads to nontrivial time-development of averages of observables representing the position of a particle on a sphere that can be interpreted as quantum beats.

  9. Mechanical communication in cardiac cell synchronized beating

    Science.gov (United States)

    Nitsan, Ido; Drori, Stavit; Lewis, Yair E.; Cohen, Shlomi; Tzlil, Shelly

    2016-05-01

    Cell-cell communication, which enables cells to coordinate their activity and is essential for growth, development and function, is usually ascribed a chemical or electrical origin. However, cells can exert forces and respond to environment elasticity and to mechanical deformations created by their neighbours. The extent to which this mechanosensing ability facilitates intercellular communication remains unclear. Here we demonstrate mechanical communication between cells directly for the first time, providing evidence for a long-range interaction that induces long-lasting alterations in interacting cells. We show that an isolated cardiac cell can be trained to beat at a given frequency by mechanically stimulating the underlying substrate. Deformations are induced using an oscillatory mechanical probe that mimics the deformations generated by a beating neighbouring cardiac cell. Unlike electrical field stimulation, the probe-induced beating rate is maintained by the cell for an hour after the stimulation stops, implying that long-term modifications occur within the cell. These long-term alterations provide a mechanism for cells that communicate mechanically to be less variable in their electromechanical delay. Mechanical coupling between cells therefore ensures that the final outcome of action potential pacing is synchronized beating. We further show that the contractile machinery is essential for mechanical communication.

  10. Left ventricular beat to beat performance in atrial fibrillation: dependence on contractility, preload, and afterload

    OpenAIRE

    Muntinga, H; Gosselink, A; Blanksma, P; De Kam, P J; van der Wall, E; Crijns, H.

    1999-01-01

    OBJECTIVE—To assess independent determinants of beat to beat variation in left ventricular performance during atrial fibrillation.
DESIGN—Prospective study.
SETTING—University hospital.
PATIENTS—Seven patients with chronic non-valvar atrial fibrillation.
INTERVENTIONS—Invasive and non-invasive haemodynamic variables were assessed using a non-imaging computerised nuclear probe, a balloon tipped flow directed catheter, and a non-invasive fingertip blood pressure measurement system linked to a p...

  11. In time with rhythms : beat perception and sensorimotor synchronisation

    NARCIS (Netherlands)

    Schlichting, Nadine

    2015-01-01

    Music and beat perception are strongly connected to movement, a phenomenon known as sensorimotor synchronisation. Neurophysiologically, simple metronome-like beat sounds entrain neural oscillations, so that the brain oscillates with the same frequency as the beat frequency. The usefulness of being e

  12. Finger beat-to-beat blood pressure responses to successive hand elevations.

    Science.gov (United States)

    Raamat, R; Jagomägi, K; Talts, J; Mäger, I

    2009-06-01

    We investigated finger beat-to-beat blood pressure responses to a series of successive hand elevations in 14 normal volunteers. By passive elevation of the hand by 40 cm and lowering it again after a minute, calibrated hydrostatic pressure changes were induced in the finger arteries of the subjects. Three successive procedures with a 2-min interval between them were performed. Transitions between positions were completed smoothly over a 10-s period. Non-invasive beat-to-beat mean arterial pressure (MAP) in the finger arteries was measured by applying the servo-oscillometric physiograph (University of Tartu, Estonia). A good agreement between the evoked MAP changes during all the three hand elevations (-31.2, -30.4 and -30.0 mmHg, respectively) and the calculated hydrostatic pressure change (-31.0 mmHg) was obtained. The height difference of approximately 40 cm and rate of 4-5 cm/s can be recommended for the hand elevation test, greater postural changes and higher rates may diminish agreement between the measured blood pressure response and the corresponding hydrostatic pressure change. The applied hydrostatic test may be helpful for assessing the accuracy of beat-to-beat finger blood pressure measurement. PMID:19027338

  13. Far field acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Fernow, R.C.

    1995-07-01

    Far fields are propagating electromagnetic waves far from their source, boundary surfaces, and free charges. The general principles governing the acceleration of charged particles by far fields are reviewed. A survey of proposed field configurations is given. The two most important schemes, Inverse Cerenkov acceleration and Inverse free electron laser acceleration, are discussed in detail.

  14. Different Alfvén wave acceleration processes of electrons in substorms at ~4-5 RE and 2-3 RE radial distance

    Directory of Open Access Journals (Sweden)

    J. C. Samson

    2004-06-01

    Full Text Available Recent statistical studies show the existence of an island of cavities and enhanced electric field structures at 4-5RE radial distance in the evening and midnight magnetic local time (MLT sectors in the auroral region during disturbed conditions, as well as ion beam occurrence frequency changes at the same altitude. We study the possibility that the mechanism involved is electron Landau resonance with incoming Alfvén waves and study the feasibility of the idea further with Polar electric field, magnetic field, spacecraft potential and electron data in an event where Polar maps to a substorm over the CANOPUS magnetometer array. Recently, a new type of auroral kilometric radiation (AKR emission originating from ~2-3RE radial distance, the so-called dot-AKR emission, has been reported to occur during substorm onsets and suggested to also be an effect of Alfvénic wave acceleration in a pre-existing auroral cavity. We improve the analysis of the dot-AKR, giving it a unified theoretical handling with the high-altitude Landau resonance phenomena. The purpose of the paper is to study the two types of Alfvénic electron acceleration, acknowledging that they have different physical mechanisms, altitudes and roles in substorm-related auroral processes.

  15. Stochastic gyroresonant electron acceleration in a low-beta plasma. I - Interaction with parallel transverse cold plasma waves

    Science.gov (United States)

    Steinacker, Juergen; Miller, James A.

    1992-01-01

    The gyroresonance of electrons with parallel transverse cold plasma waves is considered, and the Fokker-Planck equation describing the evolution of the electron distribution function in the presence of a spectrum of turbulence is derived. A new resonance which produces a divergence in the Fokker-Planck coefficients is identified; it results when the electron is in gyroresonance with a wave that has a group velocity equal to the velocity of the electron along the magnetic field. Under the assumption of a power-law spectral density, the Fokker-Planck coefficients are calculated numerically, and their complicated momentum and pitch-angle dependence, as well as the influence of various approximations to the dispersion relation, gyroresonance condition, and spectral density are discussed. It is found that there is no resonance gap at any pitch angle as long as the full gyroresonance condition is used and waves propagating on both directions are present.

  16. Beat that Word: How Listeners Integrate Beat Gesture and Focus in Multimodal Speech Discourse.

    Science.gov (United States)

    Dimitrova, Diana; Chu, Mingyuan; Wang, Lin; Özyürek, Asli; Hagoort, Peter

    2016-09-01

    Communication is facilitated when listeners allocate their attention to important information (focus) in the message, a process called "information structure." Linguistic cues like the preceding context and pitch accent help listeners to identify focused information. In multimodal communication, relevant information can be emphasized by nonverbal cues like beat gestures, which represent rhythmic nonmeaningful hand movements. Recent studies have found that linguistic and nonverbal attention cues are integrated independently in single sentences. However, it is possible that these two cues interact when information is embedded in context, because context allows listeners to predict what information is important. In an ERP study, we tested this hypothesis and asked listeners to view videos capturing a dialogue. In the critical sentence, focused and nonfocused words were accompanied by beat gestures, grooming hand movements, or no gestures. ERP results showed that focused words are processed more attentively than nonfocused words as reflected in an N1 and P300 component. Hand movements also captured attention and elicited a P300 component. Importantly, beat gesture and focus interacted in a late time window of 600-900 msec relative to target word onset, giving rise to a late positivity when nonfocused words were accompanied by beat gestures. Our results show that listeners integrate beat gesture with the focus of the message and that integration costs arise when beat gesture falls on nonfocused information. This suggests that beat gestures fulfill a unique focusing function in multimodal discourse processing and that they have to be integrated with the information structure of the message. PMID:27027421

  17. On the phase velocity of plasma waves in a self-modulated laser wake-field accelerator

    NARCIS (Netherlands)

    Andreev, N. E.; Kirsanov, V. I.; Sakharov, A. S.; van Amersfoort, P. W.; Goloviznin, V. V.

    1996-01-01

    The properties of the wake field excited by a flattop laser pulse with a sharp leading edge and a power below the critical one for relativistic self-focusing are studied analytically and numerically with emphasis on the phase velocity of the plasma wave. The paraxial model describing modulation of t

  18. Newborn infants detect the beat in music.

    Science.gov (United States)

    Winkler, István; Háden, Gábor P; Ladinig, Olivia; Sziller, István; Honing, Henkjan

    2009-02-17

    To shed light on how humans can learn to understand music, we need to discover what the perceptual capabilities with which infants are born. Beat induction, the detection of a regular pulse in an auditory signal, is considered a fundamental human trait that, arguably, played a decisive role in the origin of music. Theorists are divided on the issue whether this ability is innate or learned. We show that newborn infants develop expectation for the onset of rhythmic cycles (the downbeat), even when it is not marked by stress or other distinguishing spectral features. Omitting the downbeat elicits brain activity associated with violating sensory expectations. Thus, our results strongly support the view that beat perception is innate.

  19. Heart Beat Classification Using Particle Swarm Optimization

    Directory of Open Access Journals (Sweden)

    Ali Khazaee

    2013-05-01

    Full Text Available This paper proposes a novel system to classify three types of electrocardiogram beats, namely normal beats and two manifestations of heart arrhythmia. This system includes three main modules: a feature extraction module, a classifier module, and an optimization module. In the feature extraction module, a proper set combining the shape features and timing features is proposed as the efficient characteristic of the patterns. In the classifier module, a multi-class support vector machine (SVM-based classifier is proposed. For the optimization module, a particle swarm optimization algorithm is proposed to search for the best value of the SVM parameters and upstream by looking for the best subset of features that feed the classifier. Simulation results show that the proposed algorithm has very high recognition accuracy. This high efficiency is achieved with only little features, which have been selected using particle swarm optimizer.

  20. Robotic Catheters for Beating Heart Surgery

    OpenAIRE

    Kesner, Samuel Benjamin

    2011-01-01

    Compliant and flexible cardiac catheters provide direct access to the inside of the heart via the vascular system without requiring clinicians to stop the heart or open the chest. However, the fast motion of the intracardiac structures makes it difficult to modify and repair the cardiac tissue in a controlled and safe manner. In addition, rigid robotic tools for beating heart surgery require the chest to be opened and the heart exposed, making the procedures highly invasive. The novel robot...

  1. Beat-to-beat left ventricular performance in atrial fibrillation: radionuclide assessment with the computerized nuclear probe

    International Nuclear Information System (INIS)

    There is wide beat-to-beat variability in cycle length and left ventricular performance in patients with atrial fibrillation. In this study, left ventricular ejection fraction and relative left ventricular volumes were evaluated on a beat-to-beat basis with the computerized nuclear probe, an instrument with sufficiently high sensitivity to allow continuous evaluation of the radionuclide time-activity curve. Of 18 patients with atrial fibrillation, 5 had mitral stenosis, 6 had mitral regurgitation, and 7 had coronary artery disease. Fifty consecutive beats were analyzed in each patient. The mean left ventricular ejection fraction ranged from 17 to 51%. There was substantial beat-to-beat variation in cycle length and left ventricular ejection fraction in all patients, including those with marked left ventricular dysfunction. In 14 patients who also underwent multiple gated cardiac blood pool imaging, there was an excellent correlation between mean ejection fraction derived from the nuclear probe and gated ejection fraction obtained by gamma camera imaging (r . 0.90). Based on beat-to-beat analysis, left ventricular function was dependent on relative end-diastolic volume and multiple preceding cycle lengths, but not preceding end-systolic volumes. This study demonstrates that a single value for left ventricular ejection fraction does not adequately characterize left ventricular function in patients with atrial fibrillation. Furthermore, both the mean beat-to-beat and the gated ejection fraction may underestimate left ventricular performance at rest in such patients

  2. Controlled Electron Injection into Plasma Accelerators and Space Charge Estimates

    International Nuclear Information System (INIS)

    Plasma based accelerators are capable of producing electron sources which are ultra-compact (a few microns) and high energies (up to hundreds of MeVs) in much shorter distances than conventional accelerators. This is due to the large longitudinal electric field that can be excited without the limitation of breakdown as in RF structures.The characteristic scale length of the accelerating field is the plasma wavelength and for typical densities ranging from 1018 - 1019 cm-3, the accelerating fields and scale length can hence be on the order of 10-100GV/m and 10-40 mu m, respectively. The production of quasimonoenergetic beams was recently obtained in a regime relying on self-trapping of background plasma electrons, using a single laser pulse for wakefield generation. In this dissertation, we study the controlled injection via the beating of two lasers (the pump laser pulse creating the plasma wave and a second beam being propagated in opposite direction) which induce a localized injection of background plasma electrons. The aim of this dissertation is to describe in detail the physics of optical injection using two lasers, the characteristics of the electron beams produced (the micrometer scale plasma wavelength can result in femtosecond and even attosecond bunches) as well as a concise estimate of the effects of space charge on the dynamics of an ultra-dense electron bunch with a large energy spread

  3. Interpretive selection of waves with an accelerated construction of dynamic deep layers by the method of controlled-direction pickup

    Energy Technology Data Exchange (ETDEWEB)

    Zavalishin, B.R.; Konopliantsev, M.A.; Voskresenskii, Iu.N.

    1982-01-01

    With the construction of a dynamic deep layer by the method of controlled-direction pickup, there is a possibility of having interpretive selection of useful waves, increasing the geological effectiveness of seismic prospecting. This possibility is realized by the system of programs called CDP-B. In order to increase the profitability of the construction of the layer, it is suggested that the controlled-direction pickup be carried out after the accumulation of information exclude the possibility of the selection of useful waves, it is carried out by a method differing from the accumulation accoring to OGT. Examination is made of the conditions of the applicability of the proposed procedures of interpreting and processing for the construction of nonhorizontally placed reflecting boundaries.

  4. Beat note stabilization of a 10-60 GHz dual-polarization microlaser through optical down conversion.

    Science.gov (United States)

    Rolland, A; Brunel, M; Loas, G; Frein, L; Vallet, M; Alouini, M

    2011-02-28

    Down-conversion of a high-frequency beat note to an intermediate frequency is realized by a Mach-Zehnder intensity modulator. Optically-carried microwave signals in the 10-60 GHz range are synthesized by using a two-frequency solid-state microchip laser as a voltage-controlled oscillator inside a digital phase-locked loop. We report an in-loop relative frequency stability better than 2.5×10⁻¹¹. The principle is applicable to beat notes in the millimeter-wave range.

  5. The Harvard Beat Assessment Test (H-BAT): a battery for assessing beat perception and production and their dissociation.

    Science.gov (United States)

    Fujii, Shinya; Schlaug, Gottfried

    2013-01-01

    Humans have the abilities to perceive, produce, and synchronize with a musical beat, yet there are widespread individual differences. To investigate these abilities and to determine if a dissociation between beat perception and production exists, we developed the Harvard Beat Assessment Test (H-BAT), a new battery that assesses beat perception and production abilities. H-BAT consists of four subtests: (1) music tapping test (MTT), (2) beat saliency test (BST), (3) beat interval test (BIT), and (4) beat finding and interval test (BFIT). MTT measures the degree of tapping synchronization with the beat of music, whereas BST, BIT, and BFIT measure perception and production thresholds via psychophysical adaptive stair-case methods. We administered the H-BAT on thirty individuals and investigated the performance distribution across these individuals in each subtest. There was a wide distribution in individual abilities to tap in synchrony with the beat of music during the MTT. The degree of synchronization consistency was negatively correlated with thresholds in the BST, BIT, and BFIT: a lower degree of synchronization was associated with higher perception and production thresholds. H-BAT can be a useful tool in determining an individual's ability to perceive and produce a beat within a single session.

  6. The Harvard Beat Assessment Test (H-BAT): a battery for assessing beat perception and production and their dissociation

    Science.gov (United States)

    Fujii, Shinya; Schlaug, Gottfried

    2013-01-01

    Humans have the abilities to perceive, produce, and synchronize with a musical beat, yet there are widespread individual differences. To investigate these abilities and to determine if a dissociation between beat perception and production exists, we developed the Harvard Beat Assessment Test (H-BAT), a new battery that assesses beat perception and production abilities. H-BAT consists of four subtests: (1) music tapping test (MTT), (2) beat saliency test (BST), (3) beat interval test (BIT), and (4) beat finding and interval test (BFIT). MTT measures the degree of tapping synchronization with the beat of music, whereas BST, BIT, and BFIT measure perception and production thresholds via psychophysical adaptive stair-case methods. We administered the H-BAT on thirty individuals and investigated the performance distribution across these individuals in each subtest. There was a wide distribution in individual abilities to tap in synchrony with the beat of music during the MTT. The degree of synchronization consistency was negatively correlated with thresholds in the BST, BIT, and BFIT: a lower degree of synchronization was associated with higher perception and production thresholds. H-BAT can be a useful tool in determining an individual's ability to perceive and produce a beat within a single session. PMID:24324421

  7. Attosecond Quantum-Beat Spectroscopy in Helium

    CERN Document Server

    Shivaram, Niranjan; Timmers, Henry; Sandhu, Arvinder

    2015-01-01

    The evolution of electron wavepackets determines the course of many physical and chemical phenomena and attosecond spectroscopy aims to measure and control such dynamics in real-time. Here, we investigate radial electron wavepacket motion in Helium by using an XUV attosecond pulse train to prepare a coherent superposition of excited states and a delayed femtosecond IR pulse to ionize them. Quantum beat signals observed in the high resolution photoelectron spectrogram allow us to follow the field-free evolution of the bound electron wavepacket and determine the time-dependent ionization dynamics of the low-lying 2p state.

  8. High-order absorbing boundary conditions with corner/edge compatibility for GPU-accelerated discontinuous Galerkin wave simulations

    CERN Document Server

    Modave, Axel; Chan, Jesse; Warburton, Tim

    2016-01-01

    Discontinuous Galerkin finite element schemes exhibit attractive features for accurate large-scale wave-propagation simulations on modern parallel architectures. For many applications, these schemes must be coupled with non-reflective boundary treatments to limit the size of the computational domain without losing accuracy or computational efficiency, which remains a challenging task. In this paper, we present a combination of high-order absorbing boundary conditions (HABCs) with a nodal discontinuous Galerkin method for cuboidal computational domains. Compatibility conditions are derived for HABCs intersecting at the edges and the corners of a cuboidal domain. We propose a GPU implementation of the computational procedure, which results in a multidimensional solver with equations to be solved on 0D, 1D, 2D and 3D spatial regions. Numerical results demonstrate both the accuracy and the computational efficiency of our approach. We have considered academic benchmarks, as well as a realistic benchmark based on t...

  9. Beats on the Table: Beat Writing in the Chicago Review and Big Table

    Directory of Open Access Journals (Sweden)

    Jaap van der Bent

    2012-07-01

    Full Text Available Normal 0 21 false false false NL X-NONE X-NONE MicrosoftInternetExplorer4 Kleine literaire tijdschriften, zogenaamde little magazines, hebben een belangrijke rol gespeeld bij de doorbraak, in de loop van de jaren vijftig, van de Amerikaanse Beat Generation. Aangezien grotere uitgeverijen en de gevestigde tijdschriften lange tijd terugschrokken voor de zowel inhoudelijk als formeel van de norm afwijkende uitingen van de Beats, verscheen hun werk aanvankelijk vooral in kleinere tijdschriften als de twee waaraan in dit artikel aandacht wordt besteed: de Chicago Review en Big Table. Aan de hand van een beschrijving van de inhoud van deze twee tijdschriften wordt geprobeerd duidelijk te maken hoe het werk van de Beat Generation zich in deze tijdschriften gaandeweg een eigen plaats verwierf. Speciale aandacht wordt besteed aan de rol van de redacteuren Irving Rosenthal en Paul Carroll; door zijn uitgekiende strategie om voor het omstreden werk van Beat-auteur William S. Burroughs geleidelijk een steeds grotere plaats in te ruimen, bepaalde vooral Rosenthal het veranderende karakter van de Chicago Review. De veranderingen bij dat tijdschrift verliepen niet zonder slag of stoot en waren voor de eigenaar ervan, de University of Chicago, op een gegeven moment aanleiding om de Chicago Review aan censuur te onderwerpen. Ook deze censuur en de reactie erop, de oprichting van Big Table, worden in het artikel belicht.

  10. The chemical composition of Galactic beat Cepheids

    Science.gov (United States)

    Kovtyukh, V.; Lemasle, B.; Chekhonadskikh, F.; Bono, G.; Matsunaga, N.; Yushchenko, A.; Anderson, R. I.; Belik, S.; da Silva, R.; Inno, L.

    2016-08-01

    We determine the metallicity and detailed chemical abundances (α, iron-peak and neutron-capture elements) for the almost complete (18/24) sample of Galactic double mode Cepheids (also called beat Cepheids). Double mode Cepheids are Cepheids that pulsate in two modes simultaneously. We calibrate a new relation between their metallicity and their period ratio P1/P0. This linear relation allows to determine the metallicity of bimodal Cepheids with an accuracy of 0.03 dex in the range of [Fe/H] from +0.2 to -0.5 dex. By extrapolating the relation to Magellanic Clouds beat Cepheids, we provide their metallicity distribution function. Moreover, by using this relation, we also provide the first metallicity estimate for two double-mode F/1O Cepheids located in and beyond the Galactic bulge. Finally, we report the discovery of a super-Lithium rich double mode Cepheid V371 Per which has a Lithium abundance of logA(Li) = 3.54 ± 0.09 dex. Along with V1033 Cyg (which is an ordinary classical Cepheid), it is the second known Cepheid of such type in the Galaxy.

  11. Collective ion acceleration

    International Nuclear Information System (INIS)

    Progress achieved in the understanding and development of collective ion acceleration is presented. Extensive analytic and computational studies of slow cyclotron wave growth on an electron beam in a helix amplifier were performed. Research included precise determination of linear coupling between beam and helix, suppression of undesired transients and end effects, and two-dimensional simulations of wave growth in physically realizable systems. Electrostatic well depths produced exceed requirements for the Autoresonant Ion Acceleration feasibility experiment. Acceleration of test ions to modest energies in the troughs of such waves was also demonstrated. Smaller efforts were devoted to alternative acceleration mechanisms. Langmuir wave phase velocity in Converging Guide Acceleration was calculated as a function of the ratio of electron beam current to space-charge limiting current. A new collective acceleration approach, in which cyclotron wave phase velocity is varied by modulation of electron beam voltage, is proposed. Acceleration by traveling Virtual Cathode or Localized Pinch was considered, but appears less promising. In support of this research, fundamental investigations of beam propagation in evacuated waveguides, of nonneutral beam linear eigenmodes, and of beam stability were carried out. Several computer programs were developed or enhanced. Plans for future work are discussed

  12. Acupuncture Treatment for 98 Cases of Ventricular Premature Beat

    Institute of Scientific and Technical Information of China (English)

    Han Baojie; Wang Feng; Wang Xinzhong

    2008-01-01

    @@ Ventricular premature beat is a commonly encountered arrhythmia,which can occur in patients with and without cardiac diseases.In TCM.ventricular premature beat fall into the category of palpitation and obstruction of qi in the chest.The authors treated it with acupuncture and obtained satisfactory thera-peutic effects.A summary follows.

  13. SPS accelerating cavity

    CERN Multimedia

    1983-01-01

    See photo 8302397: View from the downstream end of one of the SPS accelerating cavities (200 MHz, travelling wave structure). See 7603195 and 8011289 for more details, 7411032 for the travelling wave structure, and also 8104138. Giacomo Primadei stands on the left.

  14. SPS accelerating cavity

    CERN Multimedia

    1980-01-01

    One of the SPS acceleration cavities (200 MHz, travelling wave structure). On the ceiling one sees the coaxial transmission line which feeds the power from the amplifier, located in a surface building above, to the upstream end of the cavity. See 7603195 for more details, 7411032 for the travelling wave structure, and also 8104138, 8302397.

  15. SPS accelerating cavity

    CERN Multimedia

    CERN PhotoLab

    1981-01-01

    One of the SPS accelerating cavities (200 MHz, travelling wave structure). The power that is fed into the upstream end of the cavity is extracted at the downstream end and sent into a dump load. See 7603195 for more details, 7411032 for the travelling wave structure, and also 8011289, 8302397.

  16. Coordinated Beating of Algal Flagella is Mediated by Basal Coupling

    Science.gov (United States)

    Wan, Kirsty; Goldstein, Raymond

    Cilia or flagella often exhibit synchronized behavior. This includes phase-locking, as seen in Chlamydomonas, and metachronal wave formation in the respiratory cilia of higher organisms. Since the observations by Gray and Rothschild of phase synchrony of nearby swimming spermatozoa, it has been a working hypothesis that synchrony arises from hydrodynamic interactions between beating filaments. Recent work on the dynamics of physically separated pairs of flagella isolated from the multicellular alga Volvox has shown that hydrodynamic coupling alone is sufficient for synchrony. However, the situation is more complex when considering multiple flagella on a single cell. We suggest that a mechanism, internal to the cell, provides an additional flagellar coupling. For instance, flagella of Chlamydomonas mutants deficient in filamentary connections between basal bodies are found to display markedly different synchronization from the wildtype. Diverse flagellar coordination strategies found in quadri-, octo- and hexadecaflagellates reveal further evidence that intracellular couplings between flagellar basal bodies compete with hydrodynamic interactions to determine the precise form of flagellar synchronization in unicellular algae.

  17. Beat Perception and Sociability: Evidence from Williams Syndrome

    Science.gov (United States)

    Lense, Miriam D.; Dykens, Elisabeth M.

    2016-01-01

    Beat perception in music has been proposed to be a human universal that may have its origins in adaptive processes involving temporal entrainment such as social communication and interaction. We examined beat perception skills in individuals with Williams syndrome (WS), a genetic, neurodevelopmental disorder. Musical interest and hypersociability are two prominent aspects of the WS phenotype although actual musical and social skills are variable. On a group level, beat and meter perception skills were poorer in WS than in age-matched peers though there was significant individual variability. Cognitive ability, sound processing style, and musical training predicted beat and meter perception performance in WS. Moreover, we found significant relationships between beat and meter perception and adaptive communication and socialization skills in WS. Results have implications for understanding the role of predictive timing in both music and social interactions in the general population, and suggest music as a promising avenue for addressing social communication difficulties in WS. PMID:27378982

  18. Beat Perception and Sociability: Evidence from Williams Syndrome.

    Science.gov (United States)

    Lense, Miriam D; Dykens, Elisabeth M

    2016-01-01

    Beat perception in music has been proposed to be a human universal that may have its origins in adaptive processes involving temporal entrainment such as social communication and interaction. We examined beat perception skills in individuals with Williams syndrome (WS), a genetic, neurodevelopmental disorder. Musical interest and hypersociability are two prominent aspects of the WS phenotype although actual musical and social skills are variable. On a group level, beat and meter perception skills were poorer in WS than in age-matched peers though there was significant individual variability. Cognitive ability, sound processing style, and musical training predicted beat and meter perception performance in WS. Moreover, we found significant relationships between beat and meter perception and adaptive communication and socialization skills in WS. Results have implications for understanding the role of predictive timing in both music and social interactions in the general population, and suggest music as a promising avenue for addressing social communication difficulties in WS. PMID:27378982

  19. Computer Simulation of the Beating Human Heart

    Science.gov (United States)

    Peskin, Charles S.; McQueen, David M.

    2001-06-01

    The mechanical function of the human heart couples together the fluid mechanics of blood and the soft tissue mechanics of the muscular heart walls and flexible heart valve leaflets. We discuss a unified mathematical formulation of this problem in which the soft tissue looks like a specialized part of the fluid in which additional forces are applied. This leads to a computational scheme known as the Immersed Boundary (IB) method for solving the coupled equations of motion of the whole system. The IB method is used to construct a three-dimensional Virtual Heart, including representations of all four chambers of the heart and all four valves, in addition to the large arteries and veins that connect the heart to the rest of the circulation. The chambers, valves, and vessels are all modeled as collections of elastic (and where appropriate, actively contractile) fibers immersed in viscous incompressible fluid. Results are shown as a computer-generated video animation of the beating heart.

  20. Evaluation of the beat-to-beat detection accuracy of PulseOn wearable optical heart rate monitor.

    Science.gov (United States)

    Parak, Jakub; Tarniceriu, Adrian; Renevey, Philippe; Bertschi, Mattia; Delgado-Gonzalo, Ricard; Korhonen, Ilkka

    2015-08-01

    Heart rate variability (HRV) provides significant information about the health status of an individual. Optical heart rate monitoring is a comfortable alternative to ECG based heart rate monitoring. However, most available optical heart rate monitoring devices do not supply beat-to-beat detection accuracy required by proper HRV analysis. We evaluate the beat-to-beat detection accuracy of a recent wrist-worn optical heart rate monitoring device, PulseOn (PO). Ten subjects (8 male and 2 female; 35.9±10.3 years old) participated in the study. HRV was recorded with PO and Firstbeat Bodyguard 2 (BG2) device, which was used as an ECG based reference. HRV was recorded during sleep. As compared to BG2, PO detected on average 99.57% of the heartbeats (0.43% of beats missed) and had 0.72% extra beat detection rate, with 5.94 ms mean absolute error (MAE) in beat-to-beat intervals (RRI) as compared to the ECG based RRI BG2. Mean RMSSD difference between PO and BG2 derived HRV was 3.1 ms. Therefore, PO provides an accurate method for long term HRV monitoring during sleep. PMID:26738173

  1. Mode beating and heterodyning of monolithically integrated semiconductor ring lasers

    Science.gov (United States)

    Liu, Chiyu

    Monolithically integrated semiconductor ring lasers (SRLs) are attractive optical sources for optoelectronic integrated circuits (OEICs) because they do not require any feedback elements, do not have parts exposed to external ambient, and can operate in a traveling-wave mode. They are promising candidates for wavelength filtering, unidirectional traveling-wave operation, and multiplexing/demultiplexing applications. Ring lasers can also be used as ultrashort pulse generators using various mode-locking schemes and as active gyro components. However, the SRL is a very complicated dynamic system, which requires more investigations to understand the performance regarding details of the design and fabrication. As a part of NASA-supported project "Monolithically Integrated Semiconductor Ring Laser Gyro for Space Applications", this dissertation research was focused on design and characterization of a novel monolithically integrated rotation sensor based on two large-size independent SRLs. Numerical modeling based on the beam propagation method (BPM) was used to design the fabrication parameters for the single-mode ridge-waveguide ring cavity and directional coupler waveguides. The mode internal coupling in single lateral-mode laser diodes with InGaAs/GaAs material system was investigated by optical experiments and numerical modeling. To gain the understanding of the SRL performance, optical and electrical characterization was performed on fabricated SRLs. Particular emphasis was placed on the study of optical and radio frequency (RF) beating spectra of longitudinal modes of ring lasers. RF measurements provide high accuracy in the diagnosis of laser oscillation parameters by purely electronic means, particularly in the measurement of the group index and its dependence on current and temperature. Theoretical analysis based on the effective index method provides good agreement between the experimental data and numerical calculations. Finally, optical heterodyning spectra

  2. Gimme the beat: assessment of low frequency beat noise for drilling rig

    Energy Technology Data Exchange (ETDEWEB)

    Bilawchuk, Steven; Froment, Patrick [aci Acoustical Consultants Inc. (Canada)], email: stevenb@aciacoustical.com, email: patrickf@aciacoustical.com

    2011-07-01

    The concern of an Alberta resident over the noise level from a drilling rig led to a low frequency noise impact assessment being done by an acoustic consulting firm. This paper describes the investigation that was conducted to determine the low frequency noise source, evaluate its sound emission levels and spectra, and propose mitigation options. Noise measurements were made over several days, with a sound level meter and additionally, a weather monitoring station was also used. Analysis showed low frequency tonal noise at the residential location, resulting in an overall sound level exceeding the permissible sound level imposed by the Alberta noise regulating bodies. Moreover, a beat phenomenon was observed, and after detailed investigation of possible sources, it was established that shale shakers were responsible for the low frequency noise and the beat phenomenon, a fact verified by beat theory. Due to the temporary nature of the drilling rig's operation, no thorough mitigation options could be proposed but a simple stop gap solution for the shale shakers allowed the reduction of low frequency tonal noise.

  3. Terahertz beat freuquency generation from two-mode lasing operation of coupled microdisk laser

    CERN Document Server

    Ryu, Jung-Wan; Kim, Chil-Min; Shinohara, Susumu; Kim, Sang Wook

    2012-01-01

    We propose a coupled microdisk laser as a compact and tunable laser source for the generation of a coherent continuous wave THz radiation by photomixing. Using the Schr\\"odinger-Bloch model including the nonlinear effect of active medium, we find single mode and two mode lasings depending on the pumping strength. We explain the transitions of lasing modes in terms of resonant modes which are the solutions of the Schr\\"odinger-Bloch model without active medium and nonlinear interaction. In particular, a two mode lasing is shown to generate THz oscillating frequency originating from the light beating of two nearly degenerated resonant modes with different symmetries.

  4. Conditional control of quantum beats in a cavity QED system

    CERN Document Server

    Norris, D G; Orozco, L A; 10.1088/1742-6596/274/1/012143

    2011-01-01

    We probe a ground-state superposition that produces a quantum beat in the intensity correlation of a two-mode cavity QED system. We mix drive with scattered light from an atomic beam traversing the cavity, and effectively measure the interference between the drive and the light from the atom. When a photon escapes the cavity, and upon detection, it triggers our feedback which modulates the drive at the same beat frequency but opposite phase for a given time window. This results in a partial interruption of the beat oscillation in the correlation function, that then returns to oscillate.

  5. Beliefs about wife beating: an exploratory study with Lebanese students.

    Science.gov (United States)

    Obeid, Nadine; Chang, Doris F; Ginges, Jeremy

    2010-06-01

    In recent years, there has been a growing interest in understanding the sociocultural contexts and risk factors for domestic violence in the Arab world. This study provides an analysis of the religious, legal, and familial contexts of domestic violence in Lebanon and assesses contemporary attitudes toward women and wife beating in a sample of 206 Lebanese university students. Gender, patriarchal attitudes, religion, childhood experiences with family violence, and mother's employment status were investigated as predictors of attitudes toward wife beating. Consistent with feminist theories of wife abuse, gender and attitudes toward women's roles emerged as the strongest predictors of beliefs about wife beating. PMID:20445079

  6. "'Jackin’ for Beats'": DJing for Citation Critique

    Directory of Open Access Journals (Sweden)

    Todd Craig

    2013-10-01

    Full Text Available A challenge in teaching English composition is helping students envision plagiarism as “borrowing” – showing love to author(s and/or text(s that further their argument(s, versus “stealing” – biting someone’s style and words. Alastair Pennycook (1996 and Sarah Wakefield (2006 have contributed pieces to the elaborate plagiarism/citation puzzle, while Houston Baker situated the hip-hop DJ in seminal text Black Studies, Rap and the Academy (1993. Merging these moments introduces critical questions: Did Diddy invent “the remix” or become the illest beat-biter ever? How did DJ/Producers Pete Rock and Large Professor pay homage to previous musical genres to further hip-hop remix production without just taking 4-8 bar samples, copying sources and claiming unethical ownership? And how can this discussion provide students a window into citation conversations? This article will remix these “texts” to introduce the idea of DJ Rhetoric to discuss plagiarism. Through the lens of the hip-hop DJ in writing classrooms, one can foster an appreciation of the difference between “love and theft” in student citation. This article will couple examples from hip-hop music/culture while simultaneously remixing interviews from various hip-hop DJ/producers to help answer these difficult questions.

  7. Selective particle capture by asynchronously beating cilia

    Science.gov (United States)

    Ding, Yang; Kanso, Eva

    2015-12-01

    Selective particle filtration is fundamental in many engineering and biological systems. For example, many aquatic microorganisms use filter feeding to capture food particles from the surrounding fluid, using motile cilia. One of the capture strategies is to use the same cilia to generate feeding currents and to intercept particles when the particles are on the downstream side of the cilia. Here, we develop a 3D computational model of ciliary bands interacting with flow suspended particles and calculate particle trajectories for a range of particle sizes. Consistent with experimental observations, we find optimal particle sizes that maximize capture rate. The optimal size depends nonlinearly on cilia spacing and cilia coordination, synchronous vs. asynchronous. These parameters affect the cilia-generated flow field, which in turn affects particle trajectories. The low capture rate of smaller particles is due to the particles' inability to cross the flow streamlines of neighboring cilia. Meanwhile, large particles have difficulty entering the sub-ciliary region once advected downstream, also resulting in low capture rates. The optimal range of particle sizes is enhanced when cilia beat asynchronously. These findings have potentially important implications on the design and use of biomimetic cilia in processes such as particle sorting in microfluidic devices.

  8. Feathering collisions in beating reed simulation

    Science.gov (United States)

    Smyth, Tamara; Abel, Jonathan S.; Smith, Julius O.

    2003-10-01

    Pressure controlled valves are the primary sound production mechanisms for woodwind and brass musical instruments, as well as for many bioacoustic vocal systems such as the larynx and syrinx (the vocal organ in birds). During sound production, air flow sets a reed or membrane into motion creating a variable height in the valve channel and, potentially, periodically closing the channel completely. Depending on how this event is handled, an abrupt termination of air flow between open and closed states can cause undesirable discontinuities and inaccuracies in a discrete-time simulation-particularly at relatively low audio sampling rates. A solution was developed by re-examining the behavior of the differential equation governing volume flow through a pressure-controlled valve, paying particular attention to this rather troublesome transition. A closed-form solution for the time evolution of volume flow is given and used to derive an update for volume flow. The result is a smoother, more accurate, and nearly alias-free transition from open to closed. ``Feathered collisions'' of this nature can refine the sound quality produced by the numerical simulation of beating reeds, such as in clarinets, at typical audio sampling rates.

  9. Mercury Beating Heart: Modifications to the Classical Demonstration

    Science.gov (United States)

    Najdoski, Metodija; Mirceski, Valentin; Petrusevski, Vladimir M.; Demiri, Sani

    2007-01-01

    The mercury beating heart (MBH) is a commonly performed experiment, which is based on varying oxidizing agents and substituting other metals for iron. Various modified versions of the classical demonstration of the experiment are presented.

  10. "Keep the Beat": Healthy Blood Pressure Helps Prevent Heart Disease

    Science.gov (United States)

    ... Keep the Beat": Healthy Blood Pressure Helps Prevent Heart Disease Past Issues / Winter 2010 Table of Contents Your ... a condition that also increases the chance of heart disease and stroke. High blood pressure is especially common ...

  11. Botox Beats Implant for Urinary Incontinence in Women

    Science.gov (United States)

    ... html Botox Beats Implant for Urinary Incontinence in Women But both have side effects that may affect ... 2016 TUESDAY, Oct. 4, 2016 (HealthDay News) -- For women with bladder incontinence who haven't been helped ...

  12. Taming microwave plasma to beat thermodynamics in CO2 dissociation

    NARCIS (Netherlands)

    van Rooij, G.; van den Bekerom, D.; N. den Harder,; Minea, T.; G. Berden,; Bongers, W.; Engeln, R.; Graswinckel, M.; Zoethout, E.; M. C. M. van de Sanden,

    2015-01-01

    The strong non-equilibrium conditions provided by the plasma phase offer the opportunity to beat traditional thermal process energy efficiencies via preferential excitation of molecular vibrations. Simple molecular physics considerations are presented to explain potential dissociation pathways in a

  13. Switched Matrix Accelerator

    International Nuclear Information System (INIS)

    We describe a new concept for a microwave circuit functioning as a charged-particle accelerator at mm-wavelengths, permitting an accelerating gradient higher than conventional passive circuits can withstand consistent with cyclic fatigue. The device provides acceleration for multiple bunches in parallel channels, and permits a short exposure time for the conducting surface of the accelerating cavities. Our analysis includes scalings based on a smooth transmission line model and a complementary treatment with a coupled-cavity simulation. We provide also an electromagnetic design for the accelerating structure, arriving at rough dimensions for a seven-cell accelerator matched to standard waveguide and suitable for bench tests at low power in air at 91.392. GHz. A critical element in the concept is a fast mm-wave switch suitable for operation at high-power, and we present the considerations for implementation in an H-plane tee. We discuss the use of diamond as the photoconductor switch medium

  14. Towards T1-limited magnetic resonance imaging using Rabi beats

    CERN Document Server

    Fedder, H; Rempp, F; Wolf, T; Hemmer, P; Jelezko, F; Wrachtrup, J

    2010-01-01

    Two proof-of-principle experiments towards T1-limited magnetic resonance imaging with NV centers in diamond are demonstrated. First, a large number of Rabi oscillations is measured and it is demonstrated that the hyperfine interaction due to the NV's 14N can be extracted from the beating oscillations. Second, the Rabi beats under V-type microwave excitation of the three hyperfine manifolds is studied experimentally and described theoretically.

  15. Towards T 1-limited magnetic resonance imaging using Rabi beats

    Science.gov (United States)

    Fedder, H.; Dolde, F.; Rempp, F.; Wolf, T.; Hemmer, P.; Jelezko, F.; Wrachtrup, J.

    2011-03-01

    Two proof-of-principle experiments toward T 1-limited magnetic resonance imaging with NV centers in diamond are demonstrated. First, a large number of Rabi oscillations is measured and it is demonstrated that the hyperfine interaction due to the NV's 14N can be extracted from the beating oscillations. Second, the Rabi beats under V-type microwave excitation of the three hyperfine manifolds is studied experimentally and described theoretically.

  16. Fast beating null strip during the reflection of pulsed Gaussian beams incident at the Rayleigh angle.

    Science.gov (United States)

    Declercq, Nico F

    2006-12-22

    It is well known that harmonic bounded Gaussian beams undergo a transformation into two bounded beams upon reflection on a solid immersed in a liquid. The effect is known as the Schoch effect and can be found at the Rayleigh angle for thick plates and at the different Lamb angles for thin plates. Here, a study is made on the effect of pulsed Gaussian beams reflected on solids. It is found experimentally that the Rayleigh wave phenomenon still generates two reflected bounded beams, whereas Lamb wave phenomena do not generate this effect. This fact may be explained intuitively by realizing that the Rayleigh phenomenon is a coincidental phenomenon that is generated in situ, whereas the Lamb wave phenomenon is a non-coincidental phenomenon that is generated only after incident sound is influenced by both sides of a thin plate. Another explanation is the fact that Rayleigh waves are not dispersive, whereas stimulation and propagation of Lamb waves is frequency dependent. A pulse contains many frequencies and therefore only a fraction of the incident pulse is transformed into a Lamb wave. In this paper, numerical simulations are performed that show that actually the Schoch effect does occur neither for Rayleigh waves, nor for Lamb waves. As a matter of fact, a pulse, incident at the Rayleigh angle, generates two reflected lobes with a null zone of a different kind. The null zone is beating several times during the passage of each pulse. This results in a 'null zone' having a lower mean intensity than any of the two lobes, still less outspoken than for the case of harmonic incident bounded beams. This effect does only occur for Rayleigh wave generation and is much less outspoken for Lamb wave generation. PMID:16815510

  17. Vortices in brain waves

    OpenAIRE

    Freeman, Walter J III; Vitiello, Giuseppe

    2008-01-01

    Interactions by mutual excitation in neural populations in human and animal brains cre- ate a mesoscopic order parameter that is recorded in brain waves (electroencephalogram, EEG). Spatially and spectrally distributed oscillations are imposed on the background activity by inhibitory feedback in the gamma range (30–80 Hz). Beats recur at theta rates (3–7 Hz), at which the order parameter transiently approaches zero and micro- scopic activity becomes disordered. After these null spikes, the or...

  18. Controlled Electron Injection into Plasma Accelerators and SpaceCharge Estimates

    Energy Technology Data Exchange (ETDEWEB)

    Fubiani, Gwenael J.

    2005-09-01

    Plasma based accelerators are capable of producing electron sources which are ultra-compact (a few microns) and high energies (up to hundreds of MeVs) in much shorter distances than conventional accelerators. This is due to the large longitudinal electric field that can be excited without the limitation of breakdown as in RF structures.The characteristic scale length of the accelerating field is the plasma wavelength and for typical densities ranging from 1018 - 1019 cm-3, the accelerating fields and scale length can hence be on the order of 10-100GV/m and 10-40 mu m, respectively. The production of quasimonoenergetic beams was recently obtained in a regime relying on self-trapping of background plasma electrons, using a single laser pulse for wakefield generation. In this dissertation, we study the controlled injection via the beating of two lasers (the pump laser pulse creating the plasma wave and a second beam being propagated in opposite direction) which induce a localized injection of background plasma electrons. The aim of this dissertation is to describe in detail the physics of optical injection using two lasers, the characteristics of the electron beams produced (the micrometer scale plasma wavelength can result in femtosecond and even attosecond bunches) as well as a concise estimate of the effects of space charge on the dynamics of an ultra-dense electron bunch with a large energy spread.

  19. Controlled Electron Injection into Plasma Accelerators and SpaceCharge Estimates

    Energy Technology Data Exchange (ETDEWEB)

    Fubiani, Gwenael G.J. [Univ. of California, Berkeley, CA (United States)

    2005-09-01

    Plasma based accelerators are capable of producing electron sources which are ultra-compact (a few microns) and high energies (up to hundreds of MeVs) in much shorter distances than conventional accelerators. This is due to the large longitudinal electric field that can be excited without the limitation of breakdown as in RF structures.The characteristic scale length of the accelerating field is the plasma wavelength and for typical densities ranging from 1018 - 1019 cm-3, the accelerating fields and scale length can hence be on the order of 10-100GV/m and 10-40 μm, respectively. The production of quasimonoenergetic beams was recently obtained in a regime relying on self-trapping of background plasma electrons, using a single laser pulse for wakefield generation. In this dissertation, we study the controlled injection via the beating of two lasers (the pump laser pulse creating the plasma wave and a second beam being propagated in opposite direction) which induce a localized injection of background plasma electrons. The aim of this dissertation is to describe in detail the physics of optical injection using two lasers, the characteristics of the electron beams produced (the micrometer scale plasma wavelength can result in femtosecond and even attosecond bunches) as well as a concise estimate of the effects of space charge on the dynamics of an ultra-dense electron bunch with a large energy spread.

  20. Sudden cardiac death in dogs with remodeled hearts is associated with larger beat-to-beat variability of repolarization

    DEFF Research Database (Denmark)

    Thomsen, Morten Bækgaard; Truin, Michiel; van Opstal, Jurren M;

    2005-01-01

    Increased proarrhythmia in dogs with chronic AV block (AVB) has been explained by ventricular remodeling causing a decrease in repolarization reserve. Beat-to-beat variability of repolarization (BVR) has been suggested to reflect repolarization reserve, in which high variability represents...... diminished reserve and larger propensity for repolarization-dependent ventricular arrhythmia. A subset of chronic AVB dogs (10%) suffers sudden cardiac death (SCD). With the assumption that repolarization defects constitute a potentially lethal proarrhythmic substrate, we hypothesized that BVR in SCD dogs....... In comparison, dogs with acute AVB had low variability (1.3 +/- 0.3 ms; n = 9; P Cardiac electrical remodeling after AVB is associated with an increase in beat-to-beat variability of repolarization. Chronic AVB dogs displaying further elevated variability of repolarization are prone...

  1. Beat-to-beat assessment of left ventricular ejection in atrial fibrillation

    International Nuclear Information System (INIS)

    Beat-to-beat left ventricular ejection was evaluated in a group of 20 patients with chronic atrial fibrillation using a computerized single probe detector. The reference group consisted of 10 patients with sinus rhythm. For each patient 30 successive cardiac cycles were analyzed and the relative variations of four parameters were assessed: R-R interval, diastolic and systolic time intervals, and ejection amplitude, corresponding to the left ventricular stroke volume. The mean variations were respectively 3.4%, 10.4%, 8.4%, and 11.8% in patients with sinus rhythm, and 21.9%, 37.9%, 10.6% and 30.5% in patients with artrial fibrillation. This demonstrates that changes in ejection are mainly related to the duration of the filling phase, with nearly constant systolic times. Correlations between R-R intervals and systolic ejection amplitudes were highly significant (P<0.001) in patients with atrial fibrillation in 85% of cases. This information complements the average ejection fraction obtained from multiple cycle superimposition. (orig.)

  2. [Non-heart-beating donors are ineligible].

    Science.gov (United States)

    Heide, W

    2016-02-01

    The death of the donor is a mandatory prerequisite for organ transplantation (dead donor rule) worldwide. It is a medical, legal and ethical consensus to accept the concept of brain death, as first proposed in 1968 by the ad hoc committee of the Harvard Medical School, as a certain criterion of death. In isolated cases where the diagnosis of brain death was claimed to be wrong, it could be demonstrated that the diagnostic procedure for brain death had not been correctly performed. In March 2014 a joint statement by the German neuromedical societies emphasized that 1) the diagnosis of brain death is one of the safest diagnoses in medicine if performed according to accepted medical standards and criteria and 2) the concept of non-heart-beating donors (NHBD, i. e. organ donation after an arbitrarily defined duration of circulatory and cardiac arrest) practiced in some European countries must be absolutely rejected because it implicates a high risk of diagnostic error. According to the current literature it is unclear at what time cardiac and circulatory arrest is irreversible and leads to irreversible cessation of all functions of the entire brain including the brainstem, even though clinical signs of cessation of brain functions are always found after 10 min. Furthermore, is it often an arbitrary decision to exactly define the duration of cardiac arrest if continuous echocardiographic monitoring has not been carried out from the very beginning. Last but not least there are ethical concerns against the concept of NHBD because it might influence therapeutic efforts to resuscitate a patient with cardiac arrest. Therefore, the German Medical Council (BÄK) has repeatedly rejected the concept of NHBD for organ transplantation since 1995. PMID:26830897

  3. The acceleration of galactic cosmic rays

    International Nuclear Information System (INIS)

    A number of acceleration mechanisms are discussed including stochastic acceleration, shock acceleration, laminar shock acceleration and acceleration by shocks in scattering media. The self-consistent problem is analysed and it is concluded that provided the cosmic rays are scattered effectively and provided energy losses are not too severe, they can be very efficiently accelerated by shock waves in the interstellar medium. (C.F.)

  4. Beat-rate dependent mitral flow patterns for in vitro hemodynamic applications.

    Science.gov (United States)

    Vismara, Riccardo; Fiore, Gianfranco B

    2010-12-01

    The conservative surgery approach for restoring the functionality of heart valves has predominated during the last two decades, particularly for the mitral valve. In vitro pulsatile testing is a key methodology for the investigation of heart valve hemodynamics, and particularly for the ideation, validation and optimization of novel techniques in heart valve surgery. Traditionally, however, pulsatile mock loops have been developed for the study of aortic valve substitutes, and scarce attention has been paid in replicating the mitral flow patterns with due hemodynamic fidelity. In this work we provide detailed analytical expressions to produce beat-rate dependent, physiologic-like mitral flow patterns for in vitro applications. The approach we propose is based on a biomechanical analysis of the factors which govern hemodynamic changes in the mitral flow pattern, namely in terms of E and A wave contours and E/A peaks ratio, when switching from rest to mild exercise conditions. The patterns from the model we obtained were in good agreement with clinical literature data in terms of i) gradual superimposition of the E and A wave, which yielded a single peak at 96 bpm; ii) decrease in the E/A ratio with increasing heart rate; iii) amount of flow delivered by each of the two waves. The proposed method provides a physiologically representative, beat-rate dependent analytical expression of the mitral flow pattern, which can be used in in vitro hydrodynamic investigations to accurately replicate the changes that the flow waves experience when the heart rate shifts from rest to mild exercise conditions.

  5. Beating of wives: a cross-cultural perspective.

    Science.gov (United States)

    Campbell, J C

    1985-01-01

    This paper reports a more in-depth analysis of wife beating from a cross-cultural perspective. As background for the analysis, the methodological, operationalization, and measurement in previous cross-cultural research on wife beating is examined. Subsequently, a review of findings from these studies and the theoretical explanations from selected disciplines are presented as the basis of selection of variables expected to affect the presence and severity of wife abuse in a given culture. These variables are then examined with evidence from female perspective ethnographies on eleven different societies. This cross-cultural analysis of wife beating has illuminated more issues of methodology and variations of patterns than it has answered any questions about what may increase the frequency and severity of wife-beating in a given culture. It is possible that the beating of wives is a personal expression of hostility against women that may be expressed in addition to, or instead of, institutionalized aggression toward women in that culture. As such, wife beating can take many forms. It can be an indication of manhood, a means of personal control, a reflection of personal animosity, and an expression of sexual jealousy. These personal forms would be paralleled by societal expression such as gang rape, control of women by exclusion from the public sphere, general hostility between sexes, and the virtue of women becoming an issue of extended family and community honor. In conclusion, the importance of the variables is summarized and directions for future cross-cultural research on wife beating are suggested.

  6. Revivals of Quantum Wave Packets

    CERN Document Server

    Bluhm, R; Porter, J; Tudose, B; Bluhm, Robert; Kostelecky, Alan; Porter, James; Tudose, Bogdan

    1997-01-01

    We present a generic treatment of wave-packet revivals for quantum-mechanical systems. This treatment permits a classification of certain ideal revival types. For example, wave packets for a particle in a one-dimensional box are shown to exhibit perfect revivals. We also examine the revival structure of wave packets for quantum systems with energies that depend on two quantum numbers. Wave packets in these systems exhibit quantum beats in the initial motion as well as new types of long-term revivals. As an example, we consider the revival structure of a particle in a two-dimensional box.

  7. Cluster observations of particle acceleration up to supra-thermal energies in the cusp region related to low-frequency wave activity – possible implications for the substorm initiation process

    Directory of Open Access Journals (Sweden)

    T. A. Fritz

    2008-03-01

    Full Text Available The purpose of our study is to investigate the way particles are accelerated up to supra-thermal energies in the cusp diamagnetic cavities. For this reason we have examined a number of Cluster cusp crossings, originally identified by Zhang et al. (2005, for the years 2001 and 2002 using data from RAPID, STAFF, EFW, CIS, PEACE, and FGM experiments. In the present study we focus on two particular cusp crossings on 25 March 2002 and on 10 April 2002 which demonstrate in a clear way the general characteristics of the events in our survey. Both events exhibit very sharp spatial boundaries seen both in CNO (primarily single-charged oxygen of ionospheric origin based on CIS observations and H+ flux increases within the RAPID energy range with the magnetic field intensity being anti-correlated. Unlike the first event, the second one shows also a moderate electron flux increase. The fact that the duskward electric field Ey has relatively low values <5 mV/m while the local wave activity is very intense provides a strong indication that particle energization is caused primarily by wave-particle interactions. The wave power spectra and propagation parameters during these cusp events are examined in detail. It is concluded that the high ion fluxes and at the same time the presence or absence of any sign of energization in the electrons clearly shows that the particle acceleration depends on the wave power near the local particle gyrofrequency and on the persistence of the wave-particle interaction process before particles escape from cusp region. Furthermore, the continuous existence of energetic O+ ions suggests that energetic O+ populations are of spatial nature at least for the eight events that we have studied so far.

  8. Linear Accelerators

    CERN Document Server

    Vretenar, M

    2014-01-01

    The main features of radio-frequency linear accelerators are introduced, reviewing the different types of accelerating structures and presenting the main characteristics aspects of linac beam dynamics.

  9. ALGORITHM FOR AUTOMATIC DETECTION OF ECG WAVES

    OpenAIRE

    Dib, Nabil; Bereksi-Reguig, Fethi

    2011-01-01

    An accurate measurement of the different electrocardiogram (ECG) intervals is dependent on the accurate identification of the beginning and the end of the P, QRS, and T waves. Available commercial systems provide a good QRS detection accuracy. However, the detection of the P and T waves remains a serious challenge due to their widely differing morphologies in normal and abnormal beats. In this paper, a new algorithm for the detection of the QRS complex as well as for P and T waves identificat...

  10. Prevention of adenosine A2A receptor activation diminishes beat-to-beat alternation in human atrial myocytes.

    Science.gov (United States)

    Molina, Cristina E; Llach, Anna; Herraiz-Martínez, Adela; Tarifa, Carmen; Barriga, Montserrat; Wiegerinck, Rob F; Fernandes, Jacqueline; Cabello, Nuria; Vallmitjana, Alex; Benitéz, Raúl; Montiel, José; Cinca, Juan; Hove-Madsen, Leif

    2016-01-01

    Atrial fibrillation (AF) has been associated with increased spontaneous calcium release from the sarcoplasmic reticulum and linked to increased adenosine A2A receptor (A2AR) expression and activation. Here we tested whether this may favor atrial arrhythmogenesis by promoting beat-to-beat alternation and irregularity. Patch-clamp and confocal calcium imaging was used to measure the beat-to-beat response of the calcium current and transient in human atrial myocytes. Responses were classified as uniform, alternating or irregular and stimulation of Gs-protein coupled receptors decreased the frequency where a uniform response could be maintained from 1.0 ± 0.1 to 0.6 ± 0.1 Hz; p < 0.01 for beta-adrenergic receptors and from 1.4 ± 0.1 to 0.5 ± 0.1 Hz; p < 0.05 for A2ARs. The latter was linked to increased spontaneous calcium release and after-depolarizations. Moreover, A2AR activation increased the fraction of non-uniformly responding cells in HL-1 myocyte cultures from 19 ± 3 to 51 ± 9 %; p < 0.02, and electrical mapping in perfused porcine atria revealed that adenosine induced electrical alternans at longer cycle lengths, doubled the fraction of electrodes showing alternation, and increased the amplitude of alternations. Importantly, protein kinase A inhibition increased the highest frequency where uniform responses could be maintained from 0.84 ± 0.12 to 1.86 ± 0.11 Hz; p < 0.001 and prevention of A2AR-activation with exogenous adenosine deaminase selectively increased the threshold from 0.8 ± 0.1 to 1.2 ± 0.1 Hz; p = 0.001 in myocytes from patients with AF. In conclusion, A2AR-activation promotes beat-to-beat irregularities in the calcium transient in human atrial myocytes, and prevention of A2AR activation may be a novel means to maintain uniform beat-to-beat responses at higher beating frequencies in patients with atrial fibrillation.

  11. Beat & beyond : memoir, myth and visual arts in women of the beat generation = Más allá del "Beat": memoria, mito y arte visual en las mujeres de la generación beat

    OpenAIRE

    Encarnación Pinedo, Estíbaliz

    2016-01-01

    El objetivo de esta tesis doctoral es revaluar el trabajo de las mujeres de la Generación Beat dentro de un discurso artístico y literario post(Beat) o más allá de lo “Beat.” El capítulo dos, en el que se analizan once memorias, se centra en el dilema entre lo personal y lo literario y sirve para delinear el contexto socio-político y artístico en el que las autoras escribieron. A través del análisis de temas comunes a las distintas memorias (la escritura, los roles de género, y la conexión co...

  12. Robotic force stabilization for beating heart intracardiac surgery.

    Science.gov (United States)

    Yuen, Shelten G; Yip, Michael C; Vasilyev, Nikolay V; Perrin, Douglas P; del Nido, Pedro J; Howe, Robert D

    2009-01-01

    The manipulation of fast moving, delicate tissues in beating heart procedures presents a considerable challenge to surgeons. We present a new robotic force stabilization system that assists surgeons by maintaining a constant contact force with the beating heart. The system incorporates a novel, miniature uniaxial force sensor that is mounted to surgical instrumentation to measure contact forces during surgical manipulation. Using this sensor in conjunction with real-time tissue motion information derived from 3D ultrasound, we show that a force controller with feed-forward motion terms can provide safe and accurate force stabilization in an in vivo contact task against the beating mitral valve annulus. This confers a 50% reduction in force fluctuations when compared to a standard force controller and a 75% reduction in fluctuations when compared to manual attempts to maintain the same force. PMID:20425967

  13. Superresolution measurement of nanofiber diameter by modes beating

    Science.gov (United States)

    Fenton, E. F.; Solano, P.; Hoffman, J. E.; Orozco, L. A.; Rolston, S. L.; Fatemi, F. K.

    2016-05-01

    Nanofibers are becoming an important tool in quantum information technologies for coupling photonics systems to atomic systems. Nondestructive techniques for characterizing these nanofibers prior to integration into an apparatus are desirable. In this work, we probe the light propagating in a fused silica optical nanofiber (750-nm-diameter) by coupling it evanescently to a 6- μm-diameter microfiber that is scanned along the nanofiber length. This technique is capable of observing all possible beat lengths among different propagating modes. The beat lengths are strongly dependent on the nanofiber diameter and refractive index of the fiber. The steep dependence has enabled measurements of the fiber diameter with sub-Angstrom sensitivity. The diameter extracted from the beat length measurements agrees with a measurement made using scanning electron microscopy. Work supported by NSF.

  14. On readout of vibrational qubits using quantum beats

    International Nuclear Information System (INIS)

    Readout of the final states of qubits is a crucial step towards implementing quantum computation in experiment. Although not scalable to large numbers of qubits per molecule, computational studies show that molecular vibrations could provide a significant (factor 2–5 in the literature) increase in the number of qubits compared to two-level systems. In this theoretical work, we explore the process of readout from vibrational qubits in thiophosgene molecule, SCCl2, using quantum beat oscillations. The quantum beats are measured by first exciting the superposition of the qubit-encoding vibrational states to the electronically excited readout state with variable time-delay pulses. The resulting oscillation of population of the readout state is then detected as a function of time delay. In principle, fitting the quantum beat signal by an analytical expression should allow extracting the values of probability amplitudes and the relative phases of the vibrational qubit states. However, we found that if this procedure is implemented using the standard analytic expression for quantum beats, a non-negligible phase error is obtained. We discuss the origin and properties of this phase error, and propose a new analytical expression to correct the phase error. The corrected expression fits the quantum beat signal very accurately, which may permit reading out the final state of vibrational qubits in experiments by combining the analytic fitting expression with numerical modelling of the readout process. The new expression is also useful as a simple model for fitting any quantum beat experiments where more accurate phase information is desired

  15. Can We Learn to Beat the Best Stock

    CERN Document Server

    Borodin, A; Gogan, V; 10.1613/jair.1336

    2011-01-01

    A novel algorithm for actively trading stocks is presented. While traditional expert advice and "universal" algorithms (as well as standard technical trading heuristics) attempt to predict winners or trends, our approach relies on predictable statistical relations between all pairs of stocks in the market. Our empirical results on historical markets provide strong evidence that this type of technical trading can "beat the market" and moreover, can beat the best stock in the market. In doing so we utilize a new idea for smoothing critical parameters in the context of expert learning.

  16. PROTON ACCELERATION AT OBLIQUE SHOCKS

    International Nuclear Information System (INIS)

    Acceleration at the shock waves propagating oblique to the magnetic field is studied using a recently developed theoretical/numerical model. The model assumes that resonant hydromagnetic wave-particle interaction is the most important physical mechanism relevant to motion and acceleration of particles as well as to excitation and damping of waves. The treatment of plasma and waves is self-consistent and time dependent. The model uses conservation laws and resonance conditions to find where waves will be generated or damped, and hence particles will be pitch-angle-scattered. The total distribution is included in the model and neither introduction of separate population of seed particles nor some ad hoc escape rate of accelerated particles is needed. Results of the study show agreement with diffusive shock acceleration models in the prediction of power spectra for accelerated particles in the upstream region. However, they also reveal the presence of spectral break in the high-energy part of the spectra. The role of the second-order Fermi-like acceleration at the initial stage of the acceleration is discussed. The test case used in the paper is based on ISEE-3 data collected for the shock of 1978 November 12.

  17. Proton Acceleration at Oblique Shocks

    Science.gov (United States)

    Galinsky, V. L.; Shevchenko, V. I.

    2011-06-01

    Acceleration at the shock waves propagating oblique to the magnetic field is studied using a recently developed theoretical/numerical model. The model assumes that resonant hydromagnetic wave-particle interaction is the most important physical mechanism relevant to motion and acceleration of particles as well as to excitation and damping of waves. The treatment of plasma and waves is self-consistent and time dependent. The model uses conservation laws and resonance conditions to find where waves will be generated or damped, and hence particles will be pitch-angle-scattered. The total distribution is included in the model and neither introduction of separate population of seed particles nor some ad hoc escape rate of accelerated particles is needed. Results of the study show agreement with diffusive shock acceleration models in the prediction of power spectra for accelerated particles in the upstream region. However, they also reveal the presence of spectral break in the high-energy part of the spectra. The role of the second-order Fermi-like acceleration at the initial stage of the acceleration is discussed. The test case used in the paper is based on ISEE-3 data collected for the shock of 1978 November 12.

  18. Interpretation of Normal and Pathological ECG Beats using Multiresolution Wavelet Analysis

    Directory of Open Access Journals (Sweden)

    Shubhada S.Ardhapurkar

    2012-12-01

    Full Text Available The Discrete wavelet transform has great capability to analyse the temporal and spectral properties of non stationary signal like ECG. In this paper, we have developed and evaluated a robust algorithm using multiresolution analysis based on the discrete wavelet transform (DWT for twelve-lead electrocardiogram (ECG temporal feature extraction. In the first step, ECG was denoised considerably by employing kernel density estimation on subband coefficients then QRS complexes were detected. Further, by selecting appropriate coefficients and applying wave segmentation strategy P and T wave peaks were detected. Finally, the determination of P and T wave onsets and ends was performed. The novelty of this approach lies in detection of different morphologies in ECG wave with few decision rules. We have evaluated the algorithm on normal and abnormal beats from various manually annotated databases from physiobank having different sampling frequencies. The QRS detector obtained a sensitivity of 99.5% and a positive predictivity of 98.9% over the first lead of the MIT-BIH Arrhythmia Database.

  19. Superposed-laser electron acceleration

    International Nuclear Information System (INIS)

    A new mechanism is proposed for electron acceleration by using two superposed laser beams in vacuum. In this mechanism, an electron is accelerated by the longitudinal component of the wave electric field in the overlapped region of two laser beams. Single-particle computations and analytical works are performed in order to demonstrate the viability. These results show that the electron can be accelerated well in this proposed mechanism. (author)

  20. Analysis of ependymal ciliary beat pattern and beat frequency using high speed imaging: comparison with the photomultiplier and photodiode methods

    Directory of Open Access Journals (Sweden)

    O'Callaghan Chris

    2012-06-01

    Full Text Available Abstract Background The aim of this study was to compare beat frequency measurements of ependymal cilia made by digital high speed imaging to those obtained using the photomultiplier and modified photodiode techniques. Using high speed video analysis the relationship of the power and recover strokes was also determined. Methods Ciliated strips of ependyma attached to slices from the brain of Wistar rats were incubated at 30°C and observed using a ×50 water immersion lens. Ciliary beat frequency was measured using each of the three techniques: the high speed video, photodiode and photomultiplier. Readings were repeated after 30 minutes incubation at 37°C. Ependymal cilia were observed in slow motion and the precise movement of cilia during the recovery stroke relative to the path travelled during the power stroke was measured. Results The mean (95% confidence intervals beat frequencies determined by the high speed video, photomultiplier and photodiode at 30°C were 27.7 (26.6 to 28.8, 25.5 (24.4 to 26.6 and 20.8 (20.4 to 21.3 Hz, respectively. The mean (95% confidence intervals beat frequencies determined by the high speed video, photomultiplier and photodiode at 37°C were 36.4 (34 to 39.5, 38.4 (36.8 to 39.9 and 18.8 (16.9 to 20.5 Hz. The inter and intra observer reliability for measurement of ciliary beat frequency was 3.8% and 1%, respectively. Ependymal cilia were observed to move in a planar fashion during the power and recovery strokes with a maximum deviation to the right of the midline of 12.1(11.8 to 13.0° during the power stroke and 12.6(11.6 to 13.6° to the left of the midline during the recovery stroke. Conclusion The photodiode technique greatly underestimates ciliary beat frequency and should not be used to measure ependymal ciliary beat frequency at the temperatures studied. Ciliary beat frequency from the high speed video and photomultiplier techniques cannot be used interchangeably. Ependymal cilia had minimal deviation to

  1. Respiratory sinus arrhythmia during anaesthesia: assessment of respiration related beat-to-beat heart rate variability analysis methods.

    Science.gov (United States)

    Loula, P; Jäntti, V; Yli-Hankala, A

    1997-11-01

    Beat-to-beat heart rate variability analysis is a powerful tool for the diagnosis of neuropathy. Respiration-related heart rate variability (respiratory sinus arrhythmia, RSA) reflects the function of parasympathetic nervous system during spontaneous ventilation while awake. RSA is also claimed to monitor the depth of anaesthesia. Power spectrum analysis or various averaging techniques of the heart rate variability are usually applied. The current literature, however, does not usually interpret the ground rules and limitations of the method used, and this may sometimes lead to erroneous conclusions on the data. The aim of our study was to compare and analyse critically the performance of different methods of evaluating RSA during anaesthesia and positive pressure ventilation. Power spectrum analysis, the root mean square of the successive RR-interval difference (RMSSD), and two respiration related methods, RSA index and average phase RSA, were included in the comparison. To test these methods, 11 patients were anaesthetised with isoflurane and their lungs were ventilated mechanically with a frequency of 6 cycles min-1. Each patient received a bolus dose of atropine (20 micrograms kg-1) during the trial. Electrocardiogram, electroencephalogram and tracheal pressure signal from respirator were recorded and analyses were performed off-line. We demonstrated that general indices, such as RMSSD, may be strongly affected by heart rate level and other non-respiration related variations in heart rate. We also showed that the effect of unwanted fluctuations on RSA can be reduced with respiration dependent beat-to-beat methods. Furthermore we confirmed that in addition to the amplitude, also the pattern of respiratory sinus arrhythmia is of interest: the pattern is reversed in phase compared to spontaneous breathing while awake, as we have shown earlier. To analyse RSA during anaesthesia, we recommend the use of an average phase RSA method based on beat-to-beat variability

  2. Superconducting linear accelerator system for NSC

    Indian Academy of Sciences (India)

    P N Prakash; T S Datta; B P Ajith Kumar; J Antony; P Barua; J Chacko; A Choudhury; G K Chadhari; S Ghosh; S Kar; S A Krishnan; Manoj Kumar; Rajesh Kumar; A Mandal; D S Mathuria; R S Meena; R Mehta; K K Mistri; A Pandey; M V Suresh Babu; B K Sahu; A Sarkar; S S K Sonti; A Rai; S Venkatramanan; J Zacharias; R K Bhowmik; A Roy

    2002-11-01

    This paper reports the construction of a superconducting linear accelerator as a booster to the 15 UD Pelletron accelerator at Nuclear Science Centre, New Delhi. The LINAC will use superconducting niobium quarter wave resonators as the accelerating element. Construction of the linear accelerator has progressed sufficiently. Details of the entire accelerator system including the cryogenics facility, RF electronics development, facilities for fabricating niobium resonators indigenously, and present status of the project are presented.

  3. Comparison of standing-wave and traveling-wave structures

    International Nuclear Information System (INIS)

    The controversy over the relative advantages of standing-wave and traveling-wave linear accelerators is now in its fourth decade. It has been fed by a considerable body of misinformation. The author hopes in this paper to shed some light on the subject, and expose some of the falsehoods. The discussion is directed toward the question of which structure to use for short pulse high field electron accelerators since it is almost universally accepted that standing-wave structures are appropriate for CW and long pulse accelerators. Three arguments against standing-wave accelerators are discussed and shown to be invalid

  4. Comparison of standing-wave and traveling-wave structures

    Energy Technology Data Exchange (ETDEWEB)

    Miller, R.H.

    1986-04-01

    The controversy over the relative advantages of standing-wave and traveling-wave linear accelerators is now in its fourth decade. It has been fed by a considerable body of misinformation. The author hopes in this paper to shed some light on the subject, and expose some of the falsehoods. The discussion is directed toward the question of which structure to use for short pulse high field electron accelerators since it is almost universally accepted that standing-wave structures are appropriate for CW and long pulse accelerators. Three arguments against standing-wave accelerators are discussed and shown to be invalid.

  5. Using Science and Much More to Beat the Flood

    Science.gov (United States)

    Seeley, Claire

    2014-01-01

    The Beat the Flood challenge involves designing and building a model flood-proof home, which is then tested in "flood" conditions. It is set on the fictitious Watu Island. The children form teams, with each team member being assigned a responsibility for the duration of the task--team leader, chief recorder, and resource manager. This…

  6. Perceptions of Conducting: Accuracy in Detecting Modulated Beat.

    Science.gov (United States)

    Brittin, Ruth V.

    1992-01-01

    Presents findings of a study of viewers' ability to detect changes in conducting beat patterns. Reports that music education majors were significantly better able to detect tempo decreases than increases and better able than nonmajors to detect decreases. Indicates that nonmajors were better able than majors to identify tempo increases. (SG)

  7. Efficiency of brainwave entrainment by binaural beats in reducing anxiety

    Directory of Open Access Journals (Sweden)

    Ahmad Alipoor

    2014-04-01

    Full Text Available Background: Anxiety is a fundamental phenomenon that is a common symptom in all mental disorders. The aim of the present study was to assess the effect of brainwave entrainment on anxiety reduction using binaural beats. Methods: In this experimental double-blind study, 30 employees were selected from an engineering research firm through random sampling and replacement and divided into two groups: control group and experimental group. All participants completed the Spielberger’s State-Trait Anxiety Inventory (STAI. Then, the experimental group listened to binaural beats which was recorded on a non-vocal piece of music for 4 weeks, 3 sessions each week. Each session lasted about 20 minutes. At the same time, the control group listened to the background music without any entrainment sound. At the end, both groups completed the anxiety questionnaire and the anxiety scores of both groups obtained before and after intervention were analyzed by ANCOVA. Results: The findings showed that the brainwave entrainment using binaural beats led to the significant reduction of state anxiety (P<0.001 and trait anxiety (P<0.018. Conclusion: Brainwave entrainment using binaural beats is an effective factor in decreasing state and trait anxiety; so, it can be used to reduce anxiety in mental health centers.

  8. Reduced Order Dead-Beat Observers for a Bioreactor

    CERN Document Server

    Karafyllis, Iasson

    2010-01-01

    This paper studies the strong observability property and the reduced-order dead-beat observer design problem for a continuous bioreactor. New relationships between coexistence and strong observability, and checkable sufficient conditions for strong observability, are established for a chemostat with two competing microbial species. Furthermore, the dynamic output feedback stabilization problem is solved for the case of one species.

  9. Subdividing the beat: auditory and motor contributions to synchronization

    NARCIS (Netherlands)

    Loehr, J.D.; Palmer, C.

    2009-01-01

    THE CURRENT STUDY EXAMINED HOW AUDITORY AND kinematic information influenced pianists' ability to synchronize musical sequences with a metronome. Pianists performed melodies in which quarter-note beats were subdivided by intervening eighth notes that resulted from auditory information (heard tones),

  10. Statistics of quantum beats in the time dependence of the neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Prokopets, G.A.; Prokopets, A.G. [National University of Kyiv-Mohyla Academy, Physics and Mathematics Department, Kyiv (Ukraine)

    2011-12-15

    The numerical calculations of the delay time distributions for the neutron scattering have been carried out. The scattering of the short wave packet of neutrons with the broad energy interval 500-800 keV by {sup 58}Ni nuclei has been studied. The decay curves and average times of the compound scattering were found as for the forward scattering as for the specific spin-parity states. The time oscillations of the decay curves were identified as quantum beats that were caused by the interference of the excited resonance set. The statistical analysis of the frequency spectra of the decay curves oscillations has been carried out. The behavior of the examined statistical observables turns out to be close to the Poisson law. (orig.)

  11. Statistics of quantum beats in the time dependence of the neutron scattering

    International Nuclear Information System (INIS)

    The numerical calculations of the delay time distributions for the neutron scattering have been carried out. The scattering of the short wave packet of neutrons with the broad energy interval 500-800 keV by 58Ni nuclei has been studied. The decay curves and average times of the compound scattering were found as for the forward scattering as for the specific spin-parity states. The time oscillations of the decay curves were identified as quantum beats that were caused by the interference of the excited resonance set. The statistical analysis of the frequency spectra of the decay curves oscillations has been carried out. The behavior of the examined statistical observables turns out to be close to the Poisson law. (orig.)

  12. Factors associated with wife beating in Egypt: Analysis of two surveys (1995 and 2005)

    OpenAIRE

    Dhaher Enas; Labeeb Shokria; Mikolajczyk Rafael T; Akmatov Manas K; Khan Md Mobarak

    2008-01-01

    Abstract Background Wife beating is an important public health problem in many developing countries. We assessed the rates of wife beating and examined factors associated with wife beating in 1995 and 2005 in Egypt. Methods We used data from two Demographic and Health Surveys (DHS) conducted in Egypt in 1995 and 2005 using multistage household sampling. Data related to wife beating included information from 7122 women in 1995 and 5612 women in 2005. Logistic regression was used to analyze fac...

  13. Finding the beat: a neural perspective across humans and non-human primates

    OpenAIRE

    Merchant, Hugo; Grahn, Jessica; Trainor, Laurel; Rohrmeier, Martin; Fitch, W. Tecumseh

    2015-01-01

    Humans possess an ability to perceive and synchronize movements to the beat in music (‘beat perception and synchronization’), and recent neuroscientific data have offered new insights into this beat-finding capacity at multiple neural levels. Here, we review and compare behavioural and neural data on temporal and sequential processing during beat perception and entrainment tasks in macaques (including direct neural recording and local field potential (LFP)) and humans (including fMRI, EEG and...

  14. An FMM-FFT accelerated integral equation solver for characterizing electromagnetic wave propagation in mine tunnels and galleries loaded with conductors

    KAUST Repository

    Yücel, Abdulkadir C.

    2014-07-01

    Reliable wireless communication and tracking systems in underground mines are of paramount importance to increase miners\\' productivity while monitoring the environmental conditions and increasing the effectiveness of rescue operations. Key to the design and optimization of such systems are electromagnetic (EM) simulation tools capable of analyzing wave propagation in electromagnetically large mine tunnels and galleries loaded with conducting cables (power, telephone) and mining equipment (trolleys, rails, carts), and potentially partially obstructed by debris from a cave-in. Current tools for simulating EM propagation in mine environments leverage (multi-) modal decompositions (Emslie et. al., IEEE Trans. Antennas Propag., 23, 192-205, 1975; Sun and Akyildiz, IEEE Trans. Commun., 58, 1758-1768, 2010), ray-tracing techniques (Zhang, IEEE Tran. Vehic. Tech., 5, 1308-1314, 2003), or full wave methods. Modal approaches and ray-tracing techniques cannot accurately account for the presence of conductors, intricate details of transmitters/receivers, wall roughness, or unstructured debris from a cave-in. Classical full-wave methods do not suffer from such restrictions. However, they require prohibitively large computational resources when applied to the analysis of electromagnetically large tunnels loaded with conductors. Recently, an efficient hybrid method of moment and transmission line solver has been developed to analyze the EM wave propagation inside tunnels loaded with conductors (Brocker et. al., in Proc IEEE AP-S Symp, pp.1,2, 2012). However, the applicability of the solver is limited to the characterization of EM wave propagation at medium frequency band.

  15. Janus Waves

    CERN Document Server

    Papazoglou, Dimitris G; Tzortzakis, Stelios

    2016-01-01

    We show the existence of a family of waves that share a common interesting property affecting the way they propagate and focus. These waves are a superposition of twin waves, which are conjugate to each other under inversion of the propagation direction. In analogy to holography, these twin "real" and "virtual" waves are related respectively to the converging and the diverging part of the beam and can be clearly visualized in real space at two distinct foci under the action of a focusing lens. Analytic formulas for the intensity distribution after focusing are derived, while numerical and experimental demonstrations are given for some of the most interesting members of this family, the accelerating Airy and ring-Airy beams.

  16. Future accelerators (?)

    Energy Technology Data Exchange (ETDEWEB)

    John Womersley

    2003-08-21

    I describe the future accelerator facilities that are currently foreseen for electroweak scale physics, neutrino physics, and nuclear structure. I will explore the physics justification for these machines, and suggest how the case for future accelerators can be made.

  17. The effect of s-wave scattering length on self-trapping and tunneling phenomena of Fermi gases in one-dimensional accelerating optical lattices

    Institute of Scientific and Technical Information of China (English)

    贾伟; 豆福全; 孙建安; 段文山

    2015-01-01

    We investigate the tunneling dynamics of the Fermi gases in an optical lattice in the Bose–Einstein condensation (BEC) regime. The three critical scattering lengths and the system energies are found in different cases of Josephson os-cillation (JO), oscillating-phase-type self-trapping (OPTST), running-phase-type self-trapping (RPTST), and self-trapping (ST). It is found that the s-wave scattering lengths have a crucial role on the tunneling dynamics. By adjusting the scattering length in the adiabatic condition, the transition probability changes with the adiabatic periodicity and a rectangular periodic pattern emerges. The periodicity of the rectangular wave depends on the system parameters such as the periodicity of the adjustable parameter, the s-wave scattering length.

  18. Ambulatory instrument for monitoring indirect beat-to-beat blood pressure in superficial temporal artery using volume-compensation method.

    Science.gov (United States)

    Tanaka, S; Yamakoshi, K

    1996-11-01

    A portable instrument, based on a volume-compensation technique, is designed for ambulatory monitoring of indirect beat-to-beat blood pressure (BP) in the superficial temporal artery. The instrument consists of a small disc-type cuff and a portable unit carried by the subject. Several components are integrated in the cuff for applying counter-pressure to the artery, i.e. a reflectance-type photo-plethysmographic sensor for arterial volume detection, a pressure sensor for cuff pressure Pc measurement and a nozzle flapper-type- electro-pneumatic convertor for controlling Pc. The portable unit includes volume servo control circuitry and a microprocessor-based signal-processing and recording unit. This automatically performs all the necessary measurement procedures and stores into a memory IC element the processed systolic, mean and diastolic blood pressure data, together with pulse intervals on a beat-to-beat basis from the servo-controlled Pc (indirectly measured BP waveform). With this instrument, momentary changes in BP during ambulatory situations such as bicycle ergometer exercise and daily activities including motorway driving are successfully recorded. From the results of simultaneous measurement of the subject's posture changes, the effect of posture change on blood pressure, e.g. baroreceptor-cardiac reflex, is also clearly demonstrated.

  19. Use of seismocardiogram for the beat-to-beat assessment of the Pulse Transit Time: A pilot study.

    Science.gov (United States)

    Di Rienzo, Marco; Vaini, Emanuele; Lombardi, Prospero

    2015-08-01

    We propose a new methodology for the estimation of Pulse Transit Time, PTT, based on the use of the seismocardiogram for the identification of the aortic valve opening, AO. This method has been implemented to obtain a first description of the AO-derived PTT beat-to-beat variability at rest and during the recovery after a cycloergometer exercise at 25W and 100W, its relation with systolic blood pressure, S(BP), and its difference with respect to variability of the Pulse Arrival Time, PAT (i.e. the BP transit time estimated by considering the ECG R peak instead of AO as proximal site). Our preliminary data indicate that 1) the fast components of the PTT variability are only marginally influenced by respiration; 2) only the slower components of the PTT variability are correlated with systolic BP; 3) major differences exist in the dynamics of PTT and PAT, being PAT variability significantly larger and importantly influenced by the beat-to-beat changes occurring in the Pre Ejection Period. PMID:26737949

  20. Shock accelerated vortex ring

    CERN Document Server

    Haehn, N; Oakley, J; Anderson, M; Rothamer, D; Bonazza, R

    2009-01-01

    The interaction of a shock wave with a spherical density inhomogeneity leads to the development of a vortex ring through the impulsive deposition of baroclinic vorticity. The present fluid dynamics videos display this phenomenon and were experimentally investigated at the Wisconsin Shock Tube Laboratory's (WiSTL) 9.2 m, downward firing shock tube. The tube has a square internal cross-section (0.25 m x 0.25 m) with multiple fused silica windows for optical access. The spherical soap bubble is generated by means of a pneumatically retracted injector and released into free-fall 200 ms prior to initial shock acceleration. The downward moving, M = 2.07 shock wave impulsively accelerates the bubble and reflects off the tube end wall. The reflected shock wave re-accelerates the bubble (reshock), which has now developed into a vortex ring, depositing additional vorticity. In the absence of any flow disturbances, the flow behind the reflected shock wave is stationary. As a result, any observed motion of the vortex rin...

  1. Beat-to-beat systolic time-interval measurement from heart sounds and ECG

    International Nuclear Information System (INIS)

    Systolic time intervals are highly correlated to fundamental cardiac functions. Several studies have shown that these measurements have significant diagnostic and prognostic value in heart failure condition and are adequate for long-term patient follow-up and disease management. In this paper, we investigate the feasibility of using heart sound (HS) to accurately measure the opening and closing moments of the aortic heart valve. These moments are crucial to define the main systolic timings of the heart cycle, i.e. pre-ejection period (PEP) and left ventricular ejection time (LVET). We introduce an algorithm for automatic extraction of PEP and LVET using HS and electrocardiogram. PEP is estimated with a Bayesian approach using the signal's instantaneous amplitude and patient-specific time intervals between atrio-ventricular valve closure and aortic valve opening. As for LVET, since the aortic valve closure corresponds to the start of the S2 HS component, we base LVET estimation on the detection of the S2 onset. A comparative assessment of the main systolic time intervals is performed using synchronous signal acquisitions of the current gold standard in cardiac time-interval measurement, i.e. echocardiography, and HS. The algorithms were evaluated on a healthy population, as well as on a group of subjects with different cardiovascular diseases (CVD). In the healthy group, from a set of 942 heartbeats, the proposed algorithm achieved 7.66 ± 5.92 ms absolute PEP estimation error. For LVET, the absolute estimation error was 11.39 ± 8.98 ms. For the CVD population, 404 beats were used, leading to 11.86 ± 8.30 and 17.51 ± 17.21 ms absolute PEP and LVET errors, respectively. The results achieved in this study suggest that HS can be used to accurately estimate LVET and PEP. (paper)

  2. Time Reversal in Subwavelength-Scaled Resonant Media: Beating the Diffraction Limit

    Directory of Open Access Journals (Sweden)

    Fabrice Lemoult

    2011-01-01

    Full Text Available Time reversal is a physical concept that can focus waves both spatially and temporally regardless of the complexity of the propagation medium. Time reversal mirrors have been demonstrated first in acoustics, then with electromagnetic waves, and are being intensively studied in many fields ranging from underwater communications to sensing. In this paper, we will review the principles of time reversal and in particular its ability to focus waves in complex media. We will show that this focusing effect depends on the complexity of the propagation medium rather than on the time reversal mirror itself. A modal approach will be utilized to explain the physical mechanism underlying the concept. A particular focus will be given on the possibility to break the diffraction barrier from the far field using time reversal. We will show that finite size media made out of coupled subwavelength resonators support modes which can radiate efficiently in the far field spatial information of the near field of a source. We will show through various examples that such a process, due to reversibility, permits to beat the diffraction limit using far field time reversal, and especially that this result occurs owing to the broadband inherent nature of time reversal.

  3. Generation and detection of whistler wave induced space plasma turbulence at Gakona, Alaska

    International Nuclear Information System (INIS)

    We report on high-frequency wave injection experiments using the beat wave technique to study the generation of very-low-frequency (VLF) whistler waves in the ionosphere above Gakona, Alaska. This work is aimed at investigating whistler wave interactions with ionospheric plasmas and radiation belts. The beat wave technique involves injecting two X-mode waves at a difference frequency in the VLF range using the High-frequency Active Auroral Research Program (HAARP) heating facility. A sequence of beat wave-generated whistler waves at 2, 6.5, 7.5, 8.5, 9.5, 11.5, 15.5, 22.5, 28.5 and 40.5 kHz were detected in our 2011 experiments. We present Modular Ultra-high-frequency Ionospheric Radar (MUIR) (446 MHz) measurements of ion lines as the primary diagnosis of ionospheric plasma effects caused by beat wave-generated whistler waves. A magnetometer and digisonde were used to monitor the background ionospheric plasma conditions throughout the experiments. Our theoretical and data analyses show that VLF whistler waves can effectively interact with ionospheric plasmas via two different four-wave interaction processes leading to energization of electrons and ions. These preliminary results support our Arecibo experiments to study NAU-launched 40.75 kHz whistler wave interactions with space plasmas. (paper)

  4. Generation and detection of whistler wave induced space plasma turbulence at Gakona, Alaska

    Science.gov (United States)

    Rooker, L. A.; Lee, M. C.; Pradipta, R.; Watkins, B. J.

    2013-07-01

    We report on high-frequency wave injection experiments using the beat wave technique to study the generation of very-low-frequency (VLF) whistler waves in the ionosphere above Gakona, Alaska. This work is aimed at investigating whistler wave interactions with ionospheric plasmas and radiation belts. The beat wave technique involves injecting two X-mode waves at a difference frequency in the VLF range using the High-frequency Active Auroral Research Program (HAARP) heating facility. A sequence of beat wave-generated whistler waves at 2, 6.5, 7.5, 8.5, 9.5, 11.5, 15.5, 22.5, 28.5 and 40.5 kHz were detected in our 2011 experiments. We present Modular Ultra-high-frequency Ionospheric Radar (MUIR) (446 MHz) measurements of ion lines as the primary diagnosis of ionospheric plasma effects caused by beat wave-generated whistler waves. A magnetometer and digisonde were used to monitor the background ionospheric plasma conditions throughout the experiments. Our theoretical and data analyses show that VLF whistler waves can effectively interact with ionospheric plasmas via two different four-wave interaction processes leading to energization of electrons and ions. These preliminary results support our Arecibo experiments to study NAU-launched 40.75 kHz whistler wave interactions with space plasmas.

  5. ECG Case of the Month: ECG in a 20-Year-Old Woman with Dyspnea. Sinus tachycardia (104 beats/minute), slight right axis deviation of the QRS (+92°), an R/S ratio greater than 1 in lead V1 with ST depression and T wave inversion in leads V1 - V4, and a prominent S wave in lead I, Q wave in lead III, and inverted T wave in lead III(S1 Q3 T3). These findings suggest right ventricular hypertrophy or strain and are consistent with pulmonary emboli.

    Science.gov (United States)

    Lathia, Viral N; Haas, John R; Jaligam, Vijayendra R; Mickman, Carl T; Lo, Betty P; Glancy, D Luke

    2015-01-01

    A 20-year-old Hispanic woman presented to the emergency department complaining of six months of progressive dyspnea on exertion associated with intermittent palpitations. Her only past medical history was a stillbirth at 32 weeks gestation about two years ago. Her vital signs in the emergency department were a heart rate of 120 beats/minute, a blood pressure of 145/86 mmHg, and an arterial oxygen saturation of 98 percent with her breathing air. Significant laboratory values included a blood hemoglobin of 14.5 gm/dL, a hematocrit of 49 percent, a brain naturetic peptide (BNP) level of 177 pg/mL, a D-dimer level of 330 ng/ml, a prothrombin time of 12.85 s with an INR of 1.2, and a partial thromboplastin time of 45.7s. Urine pregnancy test was positive, and serum beta-human chorionic gonadotropin level was 81 MIU/mL consistent with a fetus of 3-4 weeks gestational age. An electrocardiogram was recorded. PMID:25978754

  6. Developing de Broglie Wave

    Directory of Open Access Journals (Sweden)

    Zheng-Johansson J. X.

    2006-10-01

    Full Text Available The electromagnetic component waves, comprising together with their generating oscillatory massless charge a material particle, will be Doppler shifted when the charge hence particle is in motion, with a velocity v, as a mere mechanical consequence of the source motion. We illustrate here that two such component waves generated in opposite directions and propagating at speed c between walls in a one-dimensional box, superpose into a traveling beat wave of wavelength Λd=vcΛ and phase velocity c2/v+v which resembles directly L. de Broglie’s hypothetic phase wave. This phase wave in terms of transmitting the particle mass at the speed v and angular frequency Ωd= 2πv/Λd, with Λd and Ωd obeying the de Broglie relations, represents a de Broglie wave. The standing-wave function of the de Broglie (phase wave and its variables for particle dynamics in small geometries are equivalent to the eigen-state solutions to Schrödinger equation of an identical system.

  7. An efficient method for ectopic beats cancellation based on radial basis function.

    Science.gov (United States)

    Mateo, Jorge; Torres, Ana; Rieta, José J

    2011-01-01

    The analysis of the surface Electrocardiogram (ECG) is the most extended noninvasive technique in cardiological diagnosis. In order to properly use the ECG, we need to cancel out ectopic beats. These beats may occur in both normal subjects and patients with heart disease, and their presence represents an important source of error which must be handled before any other analysis. This paper presents a method for electrocardiogram ectopic beat cancellation based on Radial Basis Function Neural Network (RBFNN). A train-able neural network ensemble approach to develop customized electrocardiogram beat classifier in an effort to further improve the performance of ECG processing and to offer individualized health care is presented. Six types of beats including: Normal Beats (NB); Premature Ventricular Contractions (PVC); Left Bundle Branch Blocks (LBBB); Right Bundle Branch Blocks (RBBB); Paced Beats (PB) and Ectopic Beats (EB) are obtained from the MIT-BIH arrhythmia database. Four morphological features are extracted from each beat after the preprocessing of the selected records. Average Results for the RBFNN based method provided an ectopic beat reduction (EBR) of (mean ± std) EBR = 7, 23 ± 2.18 in contrast to traditional compared methods that, for the best case, yielded EBR = 4.05 ± 2.13. The results prove that RBFNN based methods are able to obtain a very accurate reduction of ectopic beats together with low distortion of the QRST complex.

  8. Accelerating Value Creation with Accelerators

    DEFF Research Database (Denmark)

    Jonsson, Eythor Ivar

    2015-01-01

    accelerator programs. Microsoft runs accelerators in seven different countries. Accelerators have grown out of the infancy stage and are now an accepted approach to develop new ventures based on cutting-edge technology like the internet of things, mobile technology, big data and virtual reality. It is also...... with the traditional audit and legal universes and industries are examples of emerging potentials both from a research and business point of view to exploit and explore further. The accelerator approach may therefore be an Idea Watch to consider, no matter which industry you are in, because in essence accelerators...

  9. First Beta-Beating Measurement in the LHC

    CERN Document Server

    Aiba, M; Franchi, A; Giovannozzi, M; Kain, V; Morita, A; Tomás, R; Vanbavinckhove, G; Wenninger, J

    2009-01-01

    This note reports on the first LHC beta-beating and coupling measurements. Thanks to an excellent functioning of the BPM system and the related software, injection oscillations were recorded for the first 90 turns at all BPMs of Beam 2. Three different algorithms are used to measure the optics parameters from the BPM data. All algorithms show consistent measurements but feature different accuracy. The Singular Value Decomposition (SVD) approach shows a high resolution despite the limited number of turns. The vertical beta-beating is observed to be about a factor of two larger than in the horizontal plane. This asymetry is partly due to sextupoles misalignments but also suggests the possible existance of focusing errors at defocussing locations. Rather large coupling is observed since no skew quadrupole was excited at the time of the data acquisition. We also report a list of suspected malfunctioning BPMs identified through various analyses.

  10. Emergence of Synchronized Beating during the Regrowth of Eukaryotic Flagella

    Science.gov (United States)

    Goldstein, Raymond E.; Polin, Marco; Tuval, Idan

    2011-09-01

    A fundamental issue in the biology of eukaryotic flagella is the origin of synchronized beating observed in tissues and organisms containing multiple flagella. Recent studies of the biflagellate unicellular alga Chlamydomonas reinhardtii provided the first evidence that the interflagellar coupling responsible for synchronization is of hydrodynamic origin. To investigate this mechanism in detail, we study here synchronization in Chlamydomonas as its flagella slowly regrow after mechanically induced self-scission. The duration of synchronized intervals is found to be strongly dependent on flagellar length. Analysis within a stochastic model of coupled phase oscillators is used to extract the length dependence of the interflagellar coupling and the intrinsic beat frequencies of the two flagella. Physical and biological considerations that may explain these results are proposed.

  11. A waveguide polarization toolset design based on mode beating

    OpenAIRE

    Hutchings, D.C.; Holmes, B.M.

    2011-01-01

    A toolset of waveguide elements is examined, which can be combined to produce polarization functional devices in a single contiguous waveguide. In particular, waveguide implementations of an optical isolator and a polarization modulator are discussed. The waveguide elements, i.e., quasi-phase-matched nonreciprocal polarization mode converter, reciprocal polarization mode converter (R-PMC), and a differential phase shifter, are all based on mode beating. A universal 3-dB R-PMC specification is...

  12. Robotic Motion Compensation for Beating Heart Intracardiac Surgery

    OpenAIRE

    Howe, Robert D.; Yuen, Shelten G.; Kettler, Daniel T.; Notovny, Paul M.; Plowes, Richard D.

    2009-01-01

    3D ultrasound imaging has enabled minimally invasive, beating heart intracardiac procedures. However, rapid heart motion poses a serious challenge to the surgeon that is compounded by significant time delays and noise in 3D ultrasound. This paper investigates the concept of using a one-degree-of-freedom motion compensation system to synchronize with tissue motions that may be approximated by 1D motion models. We characterize the motion of the mitral valve annulus and show that it is well appr...

  13. Observation of chaotic beats in a driven memristive Chua's circuit

    OpenAIRE

    Ahamed, A. Ishaq; Srinivasan, K.; Murali, K.; Lakshmanan, M.

    2010-01-01

    In this paper, a time varying resistive circuit realising the action of an active three segment piecewise linear flux controlled memristor is proposed. Using this as the nonlinearity, a driven Chua's circuit is implemented. The phenomenon of chaotic beats in this circuit is observed for a suitable choice of parameters. The memristor acts as a chaotically time varying resistor (CTVR), switching between a less conductive OFF state and a more conductive ON state. This chaotic switching is govern...

  14. Measuring Cosmic Distances with Stellar Heart Beats

    Science.gov (United States)

    2004-10-01

    this particular type and bright enough to be easily seen with the unaided eye. In 1912, American astronomer Henrietta Leavitt observed 20 variable stars of the Cepheid-type in the Small Magellanic Cloud (SMC), one of the closest galaxies to the Milky Way. For all purposes, these stars are all at the same distance (the size of the SMC is negligible compared to its much larger distance from us). Apparently brighter stars in this group are thus also intrinsically brighter (more luminous). Henrietta Leavitt discovered a basic relation between the intrinsic brightness and the pulsation period of Cepheid variable stars in the SMC and showed that intrinsically brighter Cepheids have longer periods. This relation is now known as the "Period-Luminosity relation" and is an important way to derive the distance to stars of this type. By measuring the period of a Cepheid star, its intrinsic brightness can be deduced and from the observed apparent brightness, the distance may then be calculated. In this way, Cepheid stars are used by astronomers as one of the "standard candles" in the Universe. They act either as distance indicators themselves or are used to calibrate other distance indicators. The Cepheid stars have taken on an even more important role since the Hubble Space Telescope Key Project on the extragalactic distance scale relies completely on them for the calibration of distance indicators to reach cosmologically large distances. In other words, if the calibration of the Cepheid Period-Luminosity relation were wrong, the entire extragalactic distance scale and with it, the rate of cosmic expansion and the related acceleration, as well as the estimated age of the Universe, would also be off. A main problem is thus to calibrate as accurately as possible the Period-Luminosity relation for nearby Cepheids. This requires measuring their distances with the utmost precision, a truly daunting task. And this is where interferometry now enters the picture. The Baade

  15. Moving to the beat and singing are linked in humans

    Directory of Open Access Journals (Sweden)

    Simone eDalla Bella

    2015-12-01

    Full Text Available The abilities to sing and to move to the beat of a rhythmic auditory stimulus emerge early during development, and both engage perceptual, motor, and sensorimotor processes. These similarities between singing and synchronization to a beat may be rooted in biology. Patel (2008 has suggested that motor synchronization to auditory rhythms may have emerged during evolution as a byproduct of selection for vocal learning (vocal learning and synchronization hypothesis. This view predicts a strong link between vocal performance and synchronization skills in humans. Here we tested this prediction by asking occasional singers to tap along with auditory pulse trains and to imitate familiar melodies. Both vocal imitation and synchronization skills were measured in terms of accuracy and precision or consistency. Accurate and precise singers tapped more in the vicinity of the pacing stimuli (i.e., they were more accurate than inaccurate and imprecise singers. Moreover, accurate singers were more consistent when tapping to the beat. These differences cannot be ascribed to basic motor skills or to motivational factors. Individual differences in terms of singing proficiency and synchronization skills may reflect the variability of a shared sensorimotor translation mechanism.

  16. Elastic Beating Pump Using Induced-Charge Electro-osmosis

    Science.gov (United States)

    Sugioka, Hideyuki

    2016-10-01

    Pumping a viscous liquid in a confined space is essential in microfluidic systems because the pressure-driven flow rate through small channels decreases with the third or fourth power of the channel size. Hence, inspired by a cilium's pumping ability in a confined space, we propose an elastic beating pump using a hydrodynamic force due to induced-charge electro-osmosis (ICEO) and numerically examine the pumping performance. By the multiphysics coupled simulation technique based on the boundary element method along with the thin double-layer approximation, we find that by selecting the optimum rigidity of the elastic beam, the ICEO elastic beating pump functions effectively at high frequencies with low applied voltages and shows a large average flow velocity with a remarkably large peak velocity that may be useful to flow a liquid with unexpectedly high viscosity. Furthermore, we propose a simple model that explains the characteristics of the time response behavior of the ICEO elastic beating pump tosome extent. By this analysis, we can considerably contribute to developments in studies on the artificial cilia having versatile functions.

  17. Laser accelerator

    OpenAIRE

    Vigil, Ricardo

    2014-01-01

    Approved for public release; distribution is unlimited In 1979,W. B. Colson and S. K. Ride proposed a new kind of electron accelerator using a uniform magnetic field in combination with a circularly-polarized laser field. A key concept is to couple the oscillating electric field to the electron’s motion so that acceleration is sustained. This dissertation investigates the performance of the proposed laser accelerator using modern high powered lasers and mag-netic fields that are significan...

  18. Charged particle acceleration by electron beam in corrugated plasma waveguide

    International Nuclear Information System (INIS)

    A two-beam charged particle acceleration scheme in a plasma waveguide with corrugated conducting walls is considered. The guiding heavy-current relativistic electron beam is in synchronism with the first plasma wave space harmonics and the accelerated beam is synchronism with a quicker plasma wave. In this case under weak corrugation of the wall the accelerating resonance field effecting the accelerated particles notably increases the field braking the guiding beam. The process of plasma wave excitation with regard to the guiding beam space charge and the relativistic particle acceleration dynamics are investigated by numeric methods. Optimal acceleration modes are found. 19 refs.; 12 figs

  19. Medically treated anorexia nervosa is associated with normal P wave parameters.

    Science.gov (United States)

    Nussinovitch, Moshe; Gur, Eitan; Nussinovitch, Naomi; Kaminer, Keren; Volovitz, Benjamin; Nussinovitch, Udi

    2012-07-30

    Anorexia nervosa (AN) is an increasingly common medical condition. Some studies have demonstrated an increased prevalence of atrial premature contractions and anatomical changes in AN patients. Our aim was to investigate P wave parameters and P wave dispersion, an electrocardiographic marker for supraventricular arrhythmias, and its effect on AN. The study group included 48 patients with AN, most hospitalized for a few weeks, and a matched control group. All participants underwent 12-lead electrocardiography (ECG) under strict standards. P wave length and P wave dispersion in each patient were computed from a randomly selected beat and an averaged beat, constructed from 7 to 12 beats, included in a 10-s ECG. There were no statistically significant differences found between the groups for minimal, maximal, average P wave duration and P wave dispersion, calculated either from a random beat or averaged beats. In conclusion, medically treated AN patients who have gained weight have normal P wave parameters, and therefore do not appear to have an increased electrocardiographic risk for atrial fibrillation compared with healthy controls. Further studies are required to evaluate the influence of different disease stages, electrolyte imbalance and other medical complications on P wave parameters and risk for supraventricular arrhythmias in AN patients. PMID:22421068

  20. Double layers are not particle accelerators

    International Nuclear Information System (INIS)

    It is pointed out that the continuing advocacy of electrostatic double layers as particle accelerators in the aurora and other space and astrophysical plasmas is fundamentally unsound. It is suggested furthermore that there is little reason to invoke static or quasi-static electric fields as the cause of auroral electron acceleration. Stochastic acceleration by electrostatic wave turbulence appears to present a natural explanation for this and for electron acceleration in other space and astrophysical plasmas. (author)

  1. Measurement of Terahertz Optical-Beat Frequency Using High-Order Harmonics of Microwave in a Photoconductive Device

    Directory of Open Access Journals (Sweden)

    Kengo Murasawa

    2011-01-01

    Full Text Available A method for measuring frequencies of the terahertz (THz radiation emitted by the antenna mounted on the photoconductive (PC device is presented. Two laser beams with slightly different frequencies irradiate the PC device, producing a beat current of 1 THz in the photocurrent. A microwave signal is applied to the antenna electrode. The frequency of the THz wave is measured using the homodyne detection of the optical beat with the high-order harmonics of the microwave. It is being investigated that the high-order harmonics are produced by the PC device owing to its nonlinearity. Periodic peaks generated by the homodyne detection were observed in the photocurrent, as the microwave was swept from 16 to 20 GHz with a power of −40 dBm. Using the peak frequencies, the THz-wave frequency was determined to be 1030.3±3.73 GHz. The measurement error is estimated to be less than 0.43 GHz. The proposed method realizes a compact frequency meter in the THz region.

  2. LIBO accelerates

    CERN Multimedia

    2002-01-01

    The prototype module of LIBO, a linear accelerator project designed for cancer therapy, has passed its first proton-beam acceleration test. In parallel a new version - LIBO-30 - is being developed, which promises to open up even more interesting avenues.

  3. Relativistic shocks and particle acceleration

    International Nuclear Information System (INIS)

    In this paper, we investigate the fluid dynamics of relativistic shock waves, and use the results to calculate the spectral index of particles accelerated by the Fermi process in such shocks. We have calculated the distributions of Fermi-accelerated particles at shocks propagating into cold proton-electron plasma and also cold electron-positron plasma. We have considered two different power spectra for the scattering waves, and find, in contrast to the non-relativistic case, that the spectral index of the accelerated particles depends on the wave power spectrum. On the assumption of thermal equilibrium both upstream and downstream, we present some useful fits for the compression ratio of shocks propagating at arbitrary speeds into gas of any temperature. (author)

  4. Fresnel diffraction patterns as accelerating beams

    CERN Document Server

    Zhang, Yiqi; Zheng, Huaibin; Wu, Zhenkun; Li, Yuanyuan; Lu, Keqing; Zhang, Yanpeng

    2013-01-01

    We demonstrate that beams originating from Fresnel diffraction patterns are self-accelerating in free space. In addition to accelerating and self-healing, they also exhibit parabolic deceleration property, which is in stark contrast to other accelerating beams. We find that the trajectory of Fresnel paraxial accelerating beams is similar to that of nonparaxial Weber beams. Decelerating and accelerating regions are separated by a critical propagation distance, at which no acceleration is present. During deceleration, the Fresnel diffraction beams undergo self-smoothing, in which oscillations of the diffracted waves gradually focus and smooth out at the critical distance.

  5. Particle acceleration in space and laboratory plasmas

    International Nuclear Information System (INIS)

    The general principle of charged particle acceleration in space and laboratory plasmas is illustrated by a discussion of particular types of acceleration mechanisms which can be classified as either deterministic processes or stochastic processes. Acceleration by parallel electric fields, produced in double layers is an example of a deterministic process. Fermi acceleration and acceleration by turbulent wave fields are examples of stochastic processes. The physical acceleration mechanism involved in each type of process is discussed and examples given for space and laboratory plasmas. (author)

  6. A 71 dB Gain, High Efficiency Relativistic Klystron using a High Current Linear Accelerator Traveling Wave Buncher Output Structure

    International Nuclear Information System (INIS)

    After five years of operation, the 17 GHz MKII relativistic klystron in service at the MIT Plasma Science and Fusion Center was upgraded with a new output structure to provide a common source of high peak power for continuing operation of the 17 GHz linac, for RF gun testing and for energizing a recently developed circularly polarized beam deflection RF system to evaluate the ultra short electron bunch performance of the linac. The salient features of the impedance and phase velocity tapered new traveling wave output structure designed for high gain and stability are described; and initial high power test results of the 17 GHz relativistic klystron are presented. The output structure was designed as a beam driven bunching and phase shifting 2π/3 mode circuit using codes that were developed over a 40 year period designing, fabricating and testing high current traveling wave linac bunchers. The electrical length of the new (MKIII) output circuit was extended to 1200 degrees using a group to phase velocity harmonic mean ratio of 0.124 to provide total skin losses of less than 5 percent and a phase/frequency sensitivity of only 0.6 degree/MHz. A dual feed racetrack shaped output cavity having a decelerating gradient of 150 kV/cm and beam apertures substantially larger than λ0/2, to allow reduction of space charge debunching forces, are added advantages of this 25 MW, 71 dB gain RF amplifier

  7. Spontaneous waves in muscle fibres

    CERN Document Server

    Gunther, Stefan; 10.1088/1367-2630/9/11/417

    2009-01-01

    Mechanical oscillations are important for many cellular processes, e.g. the beating of cilia and flagella or the sensation of sound by hair cells. These dynamic states originate from spontaneous oscillations of molecular motors. A particularly clear example of such oscillations has been observed in muscle fibers under non-physiological conditions. In that case, motor oscillations lead to contraction waves along the fiber. By a macroscopic analysis of muscle fiber dynamics we find that the spontaneous waves involve non-hydrodynamic modes. A simple microscopic model of sarcomere dynamics highlights mechanical aspects of the motor dynamics and fits with the experimental observations.

  8. Doppler-cancelled response to VLF gravitational waves

    Science.gov (United States)

    Caporali, A.

    1981-01-01

    The interaction of long periodic gravitational waves with a three link microwave system known as the Doppler Cancelling System is discussed. This system, which was developed for a gravitational redshift experiment, uses one-way and two-way Doppler informatin to construct the beat signal of two reference oscillators moving with respect to each other. The geometric optics approximation is used to derive the frequency shift produced on a light signal propagating in a gravitational wave space-time. The signature left on the Doppler-cancelled beat by burst and continuous gravitational waves is analyzed. A comparison is made between the response to gravitational waves of the Doppler Cancelling System and that of a Doppler tracking system which employs two-way, round-trip radio waves. A three-fold repetition of the gravitational wave form is found to be a common feature of the response functions of both systems. These two functions otherwise exhibit interesting differences.

  9. Multi-channel System for Beat to Beat QT Interval Variability and its Use in Screening for Coronary Artery Disease and Cardiomyopathy

    Science.gov (United States)

    Starc, V.; Schlegel, T. T.; Arenare, B.; Greco, E. C.; DePalma, J. L.; Nunez, T.; Medina, R.; Jugo, D.; Rahman, M. A.; Delgado, R.

    2007-01-01

    We investigated the ability of beat-to-beat QT interval variability (QTV) and related parameters to differentiate healthy individuals from patients with obstructive coronary artery disease (CAD) and cardiomyopathy (CM). For this purpose we developed a PC-based ECG software program that in real time, acquires, analyzes and displays QTV in each of the eight independent channels that constitute the 12-lead conventional ECG. The system also analyzes and displays the QTV from QT interval signals that are derived from multiple channels and from singular value decomposition (SVD) to substantially reduce the effect of noise and other artifacts on the QTV results. It also provides other useful SVD-related parameters such as the normalized 3-dimensional volume of the T wave (nTV) = 100*(rho(sub 2)*rho(sub 3)rho(sub 1^2). Advanced high-fidelity 12-lead ECG tests (approx. 5-min supine) were first performed on a "training set" of 99 individuals: 33 with ischemic or dilated CM and low ejection fraction (EF less than 40%); 33 with catheterization-proven obstructive CAD but normal EF; and 33 age-/gender-matched healthy controls. All QTV parameters that were studied for their accuracy in detecting CM and CAD significantly differentiated both CM and CAD from controls (p less than 0.0001). Retrospective areas under the ROC curve (AUC) of SDNN-QTV, rmsSD-QTV, and QTV Index (QTVI) for CM vs. controls in the lead V5 were 0.85, 0.90, and 0.99, respectively, and those for CAD vs. controls in the lead II were 0.82, 0.82, and 0.89. Other advanced ECG parameters, such as HFQRS RAZ score, LF Lomb of RRV or QRS-T angle, differentiated both CM and CAD from controls less significantly, with the respective AUC values of 0.89, 0.88 and 0.98 for CM vs. controls, and 0.73, 0.71 and 0.80 for CAD vs. controls. QTV parameters (especially QTVI, which is QTV as indexed to RRV) were, diagnostically speaking, amongst the best performing of the advanced ECG techniques studied thus far.

  10. Method for charged particle beam acceleration

    International Nuclear Information System (INIS)

    The method of charged particle beam acceleration based on its resonance interaction with electromagnetic field of travelling wave is suggested. The electron beam is injected into waveguide in which longitudinal magnetic field and electromagnetic wave are excited. With the purpose of reducing HF-power losses in the waveguide walls, the azimuthal particle motion is synchronized with azimuthal change of longitudinal component of electric field of the accelerating electromagnetic wave. The suggested method permits to increase the efficiency and shunting resistance of the accelerating waveguide by reducing its boundary surface

  11. Stochastic Particle Acceleration in Blazar Jets

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The bulk kinetic energy of jets can be dissipated via generating tur bulent plasma waves. We examine stochastic particle acceleration in blazar jets to explain the emissions of all blazars. We show that acceleration of electrons by plasma turbulence waves with a spectrum W(k) ~ k-4/3 produces a nonthermal population of relativistic electrons whose peak frequency of synchrotron emission can fit the observational trends in the spectral energy distribution of all blazars.The plasma nonlinear processes responsible for the formation of turbulent spectrum are investigated. Increases in the interaction time of turbulent waves can produce a flatter speckrum leading to efficient particle acceleration.

  12. Laser-Neuron Interaction with Femtosecond Beat-Modulated 800-1200 nm Photon Beams, as the Treatment of Brain Cancer Tissue. Laser Neurophysics

    Science.gov (United States)

    Stefan, V. Alexander

    2011-03-01

    I propose a novel mechanism for the brain cancer tissue treatment: nonlinear interaction of ultrashort pulses of beat-photon, (ω1 -- ω2) , or double-photon, (ω1 +ω2) , beams with the cancer tissue. The multiphoton scattering is described via photon diffusion equation. The open-scull cerebral tissue can be irradiated with the beat-modulated photon pulses with the laser irradiances in the range of a few mW/cm2 , and repetition rate of a few 100s Hz generated in the beat-wave driven free electron laser. V. Stefan, B. I. Cohen, and C. Joshi, Nonlinear Mixing of Electromagnetic Waves in PlasmasScience 27 January 1989: V. Alexander Stefan, Genomic Medical Physics: A New Physics in the Making, (S-U-Press, 2008).} This highly accurate cancer tissue ablation removal may prove to be an efficient method for the treatment of brain cancer. Work supported in part by Nikola Tesla Laboratories (Stefan University), La Jolla, CA.

  13. Dynamic curvature regulation accounts for the symmetric and asymmetric beats of Chlamydomonas flagella

    CERN Document Server

    Sartori, Pablo; Scholich, Andre; Jülicher, Frank; Howard, Jonathon

    2015-01-01

    Axonemal dyneins are the molecular motors responsible for the beating of cilia and flagella. These motors generate sliding forces between adjacent microtubule doublets within the axoneme, the motile cytoskeletal structure inside the flagellum. To create regular, oscillatory beating patterns, the activities of the axonemal dyneins must be coordinated both spatially and temporally. It is thought that coordination is mediated by stresses or strains that build up within the moving axoneme, but it is not known which components of stress or strain are involved, nor how they feed back on the dyneins. To answer this question, we used isolated, reactivate axonemes of the unicellular alga Chlamydomonas as a model system. We derived a theory for beat regulation in a two-dimensional model of the axoneme. We then tested the theory by measuring the beat waveforms of wild type axonemes, which have asymmetric beats, and mutant axonemes, in which the beat is nearly symmetric, using high-precision spatial and temporal imaging....

  14. Coherent Control of Four-Wave Mixing

    CERN Document Server

    Zhang, Yanpeng; Xiao, Min

    2011-01-01

    "Coherent Control of Four-Wave Mixing" discusses the frequency, temporal and spatial domain interplays of four-wave mixing (FWM) processes induced by atomic coherence in multi-level atomic systems. It covers topics in five major areas: the ultrafast FWM polarization beats due to interactions between multi-color laser beams and multi-level media; coexisting Raman-Rayleigh-Brillouin-enhanced polarization beats due to color-locking noisy field correlations; FWM processes with different kinds of dual-dressed schemes in ultra-thin, micrometer and long atomic cells; temporal and spatial interference between FWM and six-wave mixing (SWM) signals in multi-level electromagnetically induced transparency (EIT) media; spatial displacements and splitting of the probe and generated FWM beams, as well as the observations of gap soliton trains, vortex solitons, and stable multicomponent vector solitons in the FWM signals. The book is intended for scientists, researchers, advanced undergraduate and graduate students in Nonlin...

  15. Intermixing between four-wave mixing and six-wave mixing in a four-level atomic system

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yanpeng; Brown, Andy W; Gan Chenli; Xiao Min [Department of Physics, University of Arkansas, Fayetteville, AR 72701 (United States)

    2007-09-14

    We investigate the interplay between six-wave mixing (SWM) and four-wave mixing (FWM) resulting from atomic coherence and polarization beat in a four-level atomic system. The dressed FWM evolution and competition pathways can be controlled by the coupling field to exhibit two FWM and SWM turning points, FWM+SWM, and FWM+FWM interference regions. Quantum interference between two FWM or one FWM and one SWM channels leads to nonlinear signal enhancement and suppression under different conditions. The fifth-order nonlinear response can be obtained by the phase control of the polarization beat between the FWM and SWM signals.

  16. Application of Plasma Waveguides to High Energy Accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Milchberg, Howard [Univ. of Maryland, College Park, MD (United States)

    2016-07-01

    This grant supported basic experimental, theoretical and computer simulation research into developing a compact, high pulse repetition rate laser accelerator using the direct laser acceleration mechanism in plasma-based slow wave structures.

  17. Individual differences in beat perception affect gait responses to low- and high-groove music.

    Science.gov (United States)

    Leow, Li-Ann; Parrott, Taylor; Grahn, Jessica A

    2014-01-01

    Slowed gait in patients with Parkinson's disease (PD) can be improved when patients synchronize footsteps to isochronous metronome cues, but limited retention of such improvements suggest that permanent cueing regimes are needed for long-term improvements. If so, music might make permanent cueing regimes more pleasant, improving adherence; however, music cueing requires patients to synchronize movements to the "beat," which might be difficult for patients with PD who tend to show weak beat perception. One solution may be to use high-groove music, which has high beat salience that may facilitate synchronization, and affective properties, which may improve motivation to move. As a first step to understanding how beat perception affects gait in complex neurological disorders, we examined how beat perception ability affected gait in neurotypical adults. Synchronization performance and gait parameters were assessed as healthy young adults with strong or weak beat perception synchronized to low-groove music, high-groove music, and metronome cues. High-groove music was predicted to elicit better synchronization than low-groove music, due to its higher beat salience. Two musical tempi, or rates, were used: (1) preferred tempo: beat rate matched to preferred step rate and (2) faster tempo: beat rate adjusted to 22.5% faster than preferred step rate. For both strong and weak beat-perceivers, synchronization performance was best with metronome cues, followed by high-groove music, and worst with low-groove music. In addition, high-groove music elicited longer and faster steps than low-groove music, both at preferred tempo and at faster tempo. Low-groove music was particularly detrimental to gait in weak beat-perceivers, who showed slower and shorter steps compared to uncued walking. The findings show that individual differences in beat perception affect gait when synchronizing footsteps to music, and have implications for using music in gait rehabilitation. PMID:25374521

  18. Matrix Organisation : The design of cross-beat teamwork in newsrooms

    OpenAIRE

    Grubenmann, Stephanie

    2016-01-01

    Confronted by increased internal and external complexity, traditional forms of newswork have reached their limits. Journalistic start-ups, such as Quartz and NZZ.at, form emerging editorial teams around "obsessions" or "phenomena" to gain cross-beat perspectives of complex issues such as climate change, the financial crisis or the refugee crisis. Legacy media experimenting with cross-beat newswork see themselves confronted by challenges arising predominantly from beat structures. Consequently...

  19. Individual differences in beat perception affect gait responses to low- and high-groove music.

    Directory of Open Access Journals (Sweden)

    Li-Ann eLeow

    2014-10-01

    Full Text Available Slowed gait in Parkinson’s disease (PD patients can be improved when patients synchronize footsteps to isochronous metronome cues, but limited retention of such improvements suggest that permanent cueing regimes are needed for long-term improvements. If so, music might make permanent cueing regimes more pleasant, improving adherence; however, music cueing requires patients to synchronize movements to the beat, which might be difficult for PD patients who tend to show weak beat perception. One solution may be to use high groove music, which has high beat salience that may facilitate synchronization, and affective properties which may improve motivation to move. As a first step in understanding how beat perception affects gait in complex neurological disorders, we examined how beat perception ability affected gait in neurotypical adults. Synchronization performance and gait parameters were assessed as healthy young adults with strong or weak beat perception synchronized to low groove music, high groove music, and metronome cues. High groove music was predicted to elicit better synchronization than low groove music, due to its higher beat salience. Two musical tempi, or rates, were used: (1 preferred tempo: beat rate matched to preferred step rate and (2 faster tempo: beat rate adjusted to 22.5% faster than preferred step rate. For both strong and weak beat-perceivers, synchronization performance was best with metronome cues, followed by high groove music, and worst with low groove music. In addition, high groove music elicited longer and faster steps than low groove music, both at preferred tempo and at faster tempo. Low groove music was particularly detrimental to gait in weak beat-perceivers, who showed slower and shorter steps compared to uncued walking. The findings show that individual differences in beat perception affect gait when synchronizing footsteps to music, and have implications for using music in gait rehabilitation.

  20. Can compressed sensing beat the Nyquist sampling rate?

    CERN Document Server

    Yaroslavsky, L

    2015-01-01

    Data saving capability of "Compressed sensing (sampling)" in signal discretization is disputed and found to be far below the theoretical upper bound defined by the signal sparsity. On a simple and intuitive example, it is demonstrated that, in a realistic scenario for signals that are believed to be sparse, one can achieve a substantially larger saving than compressing sensing can. It is also shown that frequent assertions in the literature that "Compressed sensing" can beat the Nyquist sampling approach are misleading substitution of terms and are rooted in misinterpretation of the sampling theory.

  1. Different Rebellions--The and the Angry Beat Generation Man

    Institute of Scientific and Technical Information of China (English)

    欧国芳

    2012-01-01

    The Beat Generation (BG) and the Angry Man (AYM) both emerged after the Second World War. Thus, the misunderstanding of the two has existed for a long time. Large quantities of people called the BG the American Angry Young Man. Undoubtedly, the two resembled each other to some extent. However, the BG and the AYM can't be treated alike, for their differences far outweighed their similarities. This paper aims to analyze their differences in many aspects like the national environment and their memberships, which consequently led to other differences such as the differences in essences, features, influence and finale.

  2. Enhanced timing abilities in percussionists generalize to rhythms without a musical beat

    Science.gov (United States)

    Cameron, Daniel J.; Grahn, Jessica A.

    2014-01-01

    The ability to entrain movements to music is arguably universal, but it is unclear how specialized training may influence this. Previous research suggests that percussionists have superior temporal precision in perception and production tasks. Such superiority may be limited to temporal sequences that resemble real music or, alternatively, may generalize to musically implausible sequences. To test this, percussionists and nonpercussionists completed two tasks that used rhythmic sequences varying in musical plausibility. In the beat tapping task, participants tapped with the beat of a rhythmic sequence over 3 stages: finding the beat (as an initial sequence played), continuation of the beat (as a second sequence was introduced and played simultaneously), and switching to a second beat (the initial sequence finished, leaving only the second). The meters of the two sequences were either congruent or incongruent, as were their tempi (minimum inter-onset intervals). In the rhythm reproduction task, participants reproduced rhythms of four types, ranging from high to low musical plausibility: Metric simple rhythms induced a strong sense of the beat, metric complex rhythms induced a weaker sense of the beat, nonmetric rhythms had no beat, and jittered nonmetric rhythms also had no beat as well as low temporal predictability. For both tasks, percussionists performed more accurately than nonpercussionists. In addition, both groups were better with musically plausible than implausible conditions. Overall, the percussionists' superior abilities to entrain to, and reproduce, rhythms generalized to musically implausible sequences. PMID:25540617

  3. Distinguishing between overdrive excited and suppressed ventricular beats in guinea pig ventricular myocardium

    Directory of Open Access Journals (Sweden)

    Amara eGreer-Short

    2015-02-01

    Full Text Available Rapid ventricular pacing rates induces two types of beats following pacing cessation: recovery cycle length (RCL prolongation (overdrive suppression and RCL shortening (overdrive excitation. The goals of this study were to compare common experimental protocols for studying triggered activity in whole-heart preparations and differentiate between recovery beats using a new methodology. Post-pacing recovery beat cycle length (RCL and QRS were normalized to pre-paced R-R and QRS intervals and analyzed using a K-means clustering algorithm. Control hearts only produced suppressed beats: RCL ratio increased with rapid pacing (25±4.0%, n=10 without changing QRS duration. Rapid pacing during hypercalcemia + hypothermia (5.5 mM and 34°C produced significantly earlier excited beats (53±14%, n=5 with wider QRS durations (58±6.3%, n=5 than suppressed beats. Digoxin + hypothermia (0.75 M produced the most excited beats with significantly earlier RCL (44±3.2%, n=6 and wider QRS (60±3.1%, n=6 ratios relative to suppressed beats. Increasing pacing further shortened RCL (30±7.8%, n=6. In a prospective study, TTX (100 nM increased RCL ratio (15±6.0%, n=10 without changing the QRS duration of excited beats. The algorithm was compared to a cross-correlation analysis with 93% sensitivity and 94% specificity. This ECG based algorithm distinguishes between triggered and automatic activity.

  4. Enhanced Timing Abilities in Percussionists Generalize to Rhythms Without a Musical Beat

    Directory of Open Access Journals (Sweden)

    Daniel J Cameron

    2014-12-01

    Full Text Available The ability to entrain movements to music is arguably universal, but it is unclear how specialized training may influence this. Previous research suggests that percussionists have superior temporal precision in perception and production tasks. Such superiority may be limited to temporal sequences that resemble real music or, alternatively, may generalize to musically implausible sequences. To test this, percussionists and nonpercussionists completed two tasks that used rhythmic sequences varying in musical plausibility. In the beat tapping task, participants tapped with the beat of a rhythmic sequence over 3 stages: finding the beat (as an initial sequence played, continuation of the beat (as a second sequence was introduced and played simultaneously, and switching to a second beat (the initial sequence finished, leaving only the second. The metres of the two sequences were either congruent or incongruent, as were their tempi (minimum inter-onset intervals. In the rhythm reproduction task, participants reproduced rhythms of four types, ranging from high to low musical plausibility: Metric simple rhythms induced a strong sense of the beat, metric complex rhythms induced a weaker sense of the beat, nonmetric rhythms had no beat, and jittered nonmetric rhythms also had no beat as well as low temporal predictability. For both tasks, percussionists performed more accurately than nonpercussionists. In addition, both groups were better with musically plausible than implausible conditions. Overall, the percussionists’ superior abilities to entrain to, and reproduce, rhythms generalized to musically implausible sequences.

  5. A Steady-State Picture of Solar Wind Acceleration and Charge State Composition Derived from a Global Wave-Driven MHD Model

    CERN Document Server

    Oran, Rona; van der Holst, Bart; Lepri, Susan T; Frazin, Alberto M Vásquez Federico A Nuevo Richard; Manchester, Ward B; Sokolov, Igor V; Gombosi, Tamas I

    2014-01-01

    The higher charge states found in slow ($<$400km s$^{-1}$) solar wind streams compared to fast streams have supported the hypothesis that the slow wind originates in closed coronal loops, and released intermittently through reconnection. Here we examine whether a highly ionized slow wind can also form along steady and open magnetic field lines. We model the steady-state solar atmosphere using AWSoM, a global magnetohydrodynamic model driven by Alfv{\\'e}n waves, and apply an ionization code to calculate the charge state evolution along modeled open field lines. This constitutes the first charge states calculation covering all latitudes in a realistic magnetic field. The ratios $O^{+7}/O^{+6}$ and $C^{+6}/C^{+5}$ are compared to in-situ Ulysses observations, and are found to be higher in the slow wind, as observed; however, they are under-predicted in both wind types. The modeled ion fractions of S, Si, and Fe are used to calculate line-of-sight intensities, which are compared to EIS observations above a cor...

  6. QRS template matching for recognition of ventricular ectopic beats.

    Science.gov (United States)

    Krasteva, Vessela; Jekova, Irena

    2007-12-01

    We propose a quasi real-time method for discrimination of ventricular ectopic beats from both supraventricular and paced beats in the electrocardiogram (ECG). The heartbeat waveforms were evaluated within a fixed-length window around the fiducial points (100 ms before, 450 ms after). Our algorithm was designed to operate with minimal expert intervention and we define that the operator is required only to initially select up to three 'normal' heartbeats (the most frequently seen supraventricular or paced complexes). These were named original QRS templates and their copies were substituted continuously throughout the ECG analysis to capture slight variations in the heartbeat waveforms of the patient's sustained rhythm. The method is based on matching of the evaluated heartbeat with the QRS templates by a complex set of ECG descriptors, including maximal cross-correlation, area difference and frequency spectrum difference. Temporal features were added by analyzing the R-R intervals. The classification criteria were trained by statistical assessment of the ECG descriptors calculated for all heartbeats in MIT-BIH Supraventricular Arrhythmia Database. The performance of the classifiers was tested on the independent MIT-BIH Arrhythmia Database. The achieved unbiased accuracy is represented by sensitivity of 98.4% and specificity of 98.86%, both being competitive to other published studies. The provided computationally efficient techniques enable the fast post-recording analysis of lengthy Holter-monitor ECG recordings, as well as they can serve as a quasi real-time detection method embedded into surface ECG monitors. PMID:17805974

  7. Unraveling the nature of coherent beatings in chlorosomes

    Energy Technology Data Exchange (ETDEWEB)

    Dostál, Jakub [Department of Chemical Physics, Lund University, P.O. Box 124, SE-22100 Lund (Sweden); Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague (Czech Republic); Mančal, Tomáš; Pšenčík, Jakub [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague (Czech Republic); Vácha, František [Faculty of Science, University of South Bohemia, Branišovská 31, 370 05 České Budějovice (Czech Republic); Zigmantas, Donatas, E-mail: donatas.zigmantas@chemphys.lu.se [Department of Chemical Physics, Lund University, P.O. Box 124, SE-22100 Lund (Sweden)

    2014-03-21

    Coherent two-dimensional (2D) spectroscopy at 80 K was used to study chlorosomes isolated from green sulfur bacterium Chlorobaculum tepidum. Two distinct processes in the evolution of the 2D spectrum are observed. The first being exciton diffusion, seen in the change of the spectral shape occurring on a 100-fs timescale, and the second being vibrational coherences, realized through coherent beatings with frequencies of 91 and 145 cm{sup −1} that are dephased during the first 1.2 ps. The distribution of the oscillation amplitude in the 2D spectra is independent of the evolution of the 2D spectral shape. This implies that the diffusion energy transfer process does not transfer coherences within the chlorosome. Remarkably, the oscillatory pattern observed in the negative regions of the 2D spectrum (dominated by the excited state absorption) is a mirror image of the oscillations found in the positive part (originating from the stimulated emission and ground state bleach). This observation is surprising since it is expected that coherences in the electronic ground and excited states are generated with the same probability and the latter dephase faster in the presence of fast diffusion. Moreover, the relative amplitude of coherent beatings is rather high compared to non-oscillatory signal despite the reported low values of the Huang-Rhys factors. The origin of these effects is discussed in terms of the vibronic and Herzberg-Teller couplings.

  8. Efficient heart beat detection using embedded system electronics

    Science.gov (United States)

    Ramasamy, Mouli; Oh, Sechang; Varadan, Vijay K.

    2014-04-01

    The present day bio-technical field concentrates on developing various types of innovative ambulatory and wearable devices to monitor several bio-physical, physio-pathological, bio-electrical and bio-potential factors to assess a human body's health condition without intruding quotidian activities. One of the most important aspects of this evolving technology is monitoring heart beat rate and electrocardiogram (ECG) from which many other subsidiary results can be derived. Conventionally, the devices and systems consumes a lot of power since the acquired signals are always processed on the receiver end. Because of this back end processing, the unprocessed raw data is transmitted resulting in usage of more power, memory and processing time. This paper proposes an innovative technique where the acquired signals are processed by a microcontroller in the front end of the module and just the processed signal is then transmitted wirelessly to the display unit. Therefore, power consumption is considerably reduced and clearer data analysis is performed within the module. This also avoids the need for the user to be educated about usage of the device and signal/system analysis, since only the number of heart beats will displayed at the user end. Additionally, the proposed concept also eradicates the other disadvantages like obtrusiveness, high power consumption and size. To demonstrate the above said factors, a commercial controller board was used to extend the monitoring method by using the saved ECG data from a computer.

  9. In vivo electroporation mediated gene delivery to the beating heart.

    Directory of Open Access Journals (Sweden)

    Erick L Ayuni

    Full Text Available Gene therapy may represent a promising alternative strategy for cardiac muscle regeneration. In vivo electroporation, a physical method of gene transfer, has recently evolved as an efficient method for gene transfer. In the current study, we investigated the efficiency and safety of a protocol involving in vivo electroporation for gene transfer to the beating heart. Adult male rats were anesthetised and the heart exposed through a left thoracotomy. Naked plasmid DNA was injected retrograde into the transiently occluded coronary sinus before the electric pulses were applied. Animals were sacrificed at specific time points and gene expression was detected. Results were compared to the group of animals where no electric pulses were applied. No post-procedure arrhythmia was observed. Left ventricular function was temporarily altered only in the group were high pulses were applied; CK-MB (Creatine kinase and TNT (Troponin T were also altered only in this group. Histology showed no signs of toxicity. Gene expression was highest at day one. Our results provide evidence that in vivo electroporation with an optimized protocol is a safe and effective tool for nonviral gene delivery to the beating heart. This method may be promising for clinical settings especially for perioperative gene delivery.

  10. Robust estimation of the motile cilia beating frequency.

    Science.gov (United States)

    Meste, O; Brau, F; Guyon, A

    2015-10-01

    The estimation of the cilia beating frequency (CBF) is of great interest in understanding how the CBF modulates liquid fluxes and how it is controlled by the ciliated cell intra- and/or extracellular medium composition in physiological processes. Motion artifacts and camera defaults may hinder the computation of the frequency variations during long-lasting experiments. We have developed a new analysis approach consisting of a preliminary corrective step (removal of a grid pattern on the image sequence and shift compensation), followed by a harmonic model of the observed cilia using a maximum likelihood estimator framework. It is shown that a more accurate estimation of the frequency can be obtained by averaging the squared Fourier transform of individual pixels followed by a particular summation over the different frequencies, namely the compressed spectrum. Robustness of the proposed method over traditional approaches is shown by several examples and simulations. The method is then applied to images of samples containing ciliated ependymal cells located in the third cerebral ventricle of mouse brains, showing that even small variations in CBF in response to changes in the amount of oxygenation, pH or glucose were clearly visible in the computed frequencies. As a conclusion, this method reveals a fine metabolic tuning of the cilia beating in ependimocytes lining the third cerebral ventricle. Such regulations are likely to participate in homeostatic mechanisms regulating CSF movements and brain energy supply. PMID:26215519

  11. Interacting cortical and basal ganglia networks underlying finding and tapping to the musical beat.

    Science.gov (United States)

    Kung, Shu-Jen; Chen, Joyce L; Zatorre, Robert J; Penhune, Virginia B

    2013-03-01

    Humans are able to find and tap to the beat of musical rhythms varying in complexity from children's songs to modern jazz. Musical beat has no one-to-one relationship with auditory features-it is an abstract perceptual representation that emerges from the interaction between sensory cues and higher-level cognitive organization. Previous investigations have examined the neural basis of beat processing but have not tested the core phenomenon of finding and tapping to the musical beat. To test this, we used fMRI and had musicians find and tap to the beat of rhythms that varied from metrically simple to metrically complex-thus from a strong to a weak beat. Unlike most previous studies, we measured beat tapping performance during scanning and controlled for possible effects of scanner noise on beat perception. Results showed that beat finding and tapping recruited largely overlapping brain regions, including the superior temporal gyrus (STG), premotor cortex, and ventrolateral PFC (VLPFC). Beat tapping activity in STG and VLPFC was correlated with both perception and performance, suggesting that they are important for retrieving, selecting, and maintaining the musical beat. In contrast BG activity was similar in all conditions and was not correlated with either perception or production, suggesting that it may be involved in detecting auditory temporal regularity or in associating auditory stimuli with a motor response. Importantly, functional connectivity analyses showed that these systems interact, indicating that more basic sensorimotor mechanisms instantiated in the BG work in tandem with higher-order cognitive mechanisms in PFC.

  12. The role of the basal ganglia in beat perception: neuroimaging and neuropsychological investigations.

    Science.gov (United States)

    Grahn, Jessica A

    2009-07-01

    Perception of musical rhythms is culturally universal. Despite this special status, relatively little is known about the neurobiology of rhythm perception, particularly with respect to beat processing. Findings are presented here from a series of studies that have specifically examined the neural basis of beat perception, using functional magnetic resonance imaging (fMRI) and studying patients with Parkinson's disease. fMRI data indicate that novel beat-based sequences robustly activate the basal ganglia when compared to irregular, nonbeat sequences. Furthermore, although most healthy participants find it much easier to discriminate changes in beat-based sequences compared to irregular sequences, Parkinson's disease patients fail to show the same degree of benefit. Taken together, these data suggest that the basal ganglia are performing a crucial function in beat processing. The results of an additional fMRI study indicate that the role of the basal ganglia is strongly linked to internal generation of the beat. Basal ganglia activity is greater when participants listen to rhythms in which internal generation of the beat is required, as opposed to rhythms with strongly externally cued beats. Functional connectivity between part of the basal ganglia (the putamen) and cortical motor areas (premotor and supplementary motor areas) is also higher during perception of beat rhythms compared to nonbeat rhythms. Increased connectivity between cortical motor and auditory areas is found in those with musical training. The findings from these converging methods strongly implicate the basal ganglia in processing a regular beat, particularly when internal generation of the beat is required. PMID:19673753

  13. The Role of Ion Channels to Regulate Airway Ciliary Beat Frequency During Allergic Inflammation.

    Science.gov (United States)

    Joskova, M; Sutovska, M; Durdik, P; Koniar, D; Hargas, L; Banovcin, P; Hrianka, M; Khazaei, V; Pappova, L; Franova, S

    2016-01-01

    Overproduction of mucus is a hallmark of asthma. The aim of this study was to identify potentially effective therapies for removing excess mucus. The role of voltage-gated (Kir 6.1, KCa 1.1) and store-operated ion channels (SOC, CRAC) in respiratory cilia, relating to the tracheal ciliary beat frequency (CBF), was compared under the physiological and allergic airway conditions. Ex vivo experiments were designed to test the local effects of Kir 6.1, KCa 1.1 and CRAC ion channel modulators in a concentration-dependent manner on the CBF. Cilia, obtained with the brushing method, were monitored by a high-speed video camera and analyzed with ciliary analysis software. In natural conditions, a Kir 6.1 opener accelerated CBF, while CRAC blocker slowed it in a concentration-dependent manner. In allergic inflammation, the effect of Kir 6.1 opener was insignificant, with a tendency to decrease CBF. A cilio-inhibitory effect of a CRAC blocker, while gently reduced by allergic inflammation, remained significant. A KCa 1.1 opener turned out to significantly enhance the CBF under the allergic OVA-sensitized conditions. We conclude that optimally attuned concentration of KCa 1.1 openers or special types of bimodal SOC channel blockers, potentially given by inhalation, might benefit asthma. PMID:27369295

  14. Odors pulsed at wing beat frequencies are tracked by primary olfactory networks and enhance odor detection

    Directory of Open Access Journals (Sweden)

    Shreejoy Tripathy

    2010-03-01

    Full Text Available Each down stroke of an insect’s wings accelerates axial airflow over the antennae. Modeling studies suggest that this can greatly enhance penetration of air and air-born odorants through the antennal sensilla thereby periodically increasing odorant-receptor interactions. Do these periodic changes result in entrainment of neural responses in the antenna and antennal lobe (AL? Does this entrainment affect olfactory acuity? To address these questions, we monitored antennal and AL responses in the moth Manduca sexta while odorants were pulsed at frequencies from 10-72 Hz, encompassing the natural wingbeat frequency. Power spectral density (PSD analysis was used to identify entrainment of neural activity. Statistical analysis of PSDs indicates that the antennal nerve tracked pulsed odor up to 30 Hz. Furthermore, at least 50% of AL local field potentials (LFPs and between 7-25% of unitary spiking responses also tracked pulsed odor up to 30 Hz in a frequency-locked manner. Application of bicuculline (200µM abolished pulse tracking in both LFP and unitary responses suggesting that GABAA receptor activation is necessary for pulse tracking within the AL. Finally, psychophysical measures of odor detection establish that detection thresholds are lowered when odor is pulsed at 20 Hz. These results suggest that AL networks can respond to the oscillatory dynamics of stimuli such as those imposed by the wing beat in a manner analogous to mammalian sniffing.

  15. Observation of Laser Wakefield Acceleration of Electrons

    CERN Document Server

    Amiranoff, F; Bernard, D; Cros, B; Descamps, D; Dorchies, F; Jacquet, F; Malka, V; Marqués, J R; Matthieussent, G; Miné, P; Modena, A; Mora, P; Morillo, J; Najmudin, Z

    1998-01-01

    The acceleration of electrons injected in a plasma wave generated by the laser wakefield mechanism has been observed. A maximum energy gain of 1.6~MeV has been measured and the maximum longitudinal electric field is estimated to 1.5~GV/m. The experimental data agree with theoretical predictions when 3D effects are taken into account. The duration of the plasma wave inferred from the number of accelerated electrons is of the order of 1~ps.

  16. Use of beat-to-beat cardiovascular variability data to determine the validity of sham therapy as the placebo control in osteopathic manipulative medicine research.

    Science.gov (United States)

    Henley, Charles E; Wilson, Thad E

    2014-11-01

    Osteopathic manipulative medicine researchers often use sham therapy as the placebo control during clinical trials. Optimally, the sham therapy should be a hands-on procedure that is perceptually indistinguishable from osteopathic manipulative treatment, does not create an effect on its own, and is not a treatment intervention. However, the sham therapy itself may often influence the outcome. The use of cardiovascular variability (eg, beat-to-beat heart rate variability) as a surrogate for the autonomic nervous system is one objective method by which to identify such an effect. By monitoring cardiovascular variability, investigators can assess autonomic nervous system activity as a response to the sham therapy and quickly determine whether or not the selected sham therapy is a true placebo control. The authors provide evidence for assessment of beat-to-beat heart rate variability as one method for assuring objectivity of sham therapy as a placebo control in osteopathic manipulative medicine research.

  17. Particle acceleration by pulsars

    International Nuclear Information System (INIS)

    The evidence that pulsars accelerate relativistic particles is reviewed, with emphasis on the γ-ray observations. The current state of knowledge of acceleration in strong waves is summarized, with emphasis on the inability of consistent theories to accelerate very high energy particles without converting too much energy into high energy photons. The state of viable models for pair creation by pulsars is summarized, with the conclusion that pulsars very likely lose rotational energy in winds instead of in superluminous strong waves. The relation of the pair creation models to γ-ray observations and to soft X-ray observations of pulsars is outlined, with the conclusion that energetically viable models may exist, but none have yet yielded useful agreement with the extant data. Some paths for overcoming present problems are discussed. The relation of the favored models to cosmic rays is discussed. It is pointed out that the pairs made by the models may have observable consequences for observation of positrons in the local cosmic ray flux and for observations of the 511 keV line from the interstellar medium. Another new point is that asymmetry of plasma supply from at least one of the models may qualitatively explain the gross asymmetry of the X-ray emission from the Crab nebula. It is also argued that acceleration of cosmic ray nuclei by pulsars, while energetically possible, can occur only at the boundary of the bubbles blown by the pulsars, if the cosmic ray composition is to be anything like that of the known source spectrum

  18. A Beat Frequency RF Modulator for Generation of Low Repetition Rate Electron Microbunches for the CEBAF Polarized Source

    Energy Technology Data Exchange (ETDEWEB)

    John Musson; Reza Kazimi; Benard Poelker; Joseph Grames; John Hansknecht

    2007-06-25

    Fiber-based drive lasers now produce all of the spin-polarized electron beams at CEBAF/Jefferson Lab. The flexibility of these drive lasers, combined with the existing three-beam CEBAF photoinjector Chopper, provides a means to implement a beat frequency technique to produce long time intervals between individual electron microbunches (tens of nanoseconds) by merely varying the nominal 499 MHz drive laser frequency by < 20%. This submission describes the RF Laser modulator that uses a divider and heterodyne scheme to maintain coherence with the accelerator Master Oscillator (MO), while providing delay resolution in increments of 2ns. Some possible uses for such a beam are discussed as well as intended future development.

  19. Er-doped fiber ring laser gyroscopes operating in continuous waves

    Institute of Scientific and Technical Information of China (English)

    Jingren Qian; Jue Su; Xuxu Wang; Bing Zhu

    2007-01-01

    A direction related polarizer was inserted into a ring laser cavity to eliminate one of the two eigen-modes as well as spatial hole burning of the gain medium in a bidirectional Er-doped fiber ring laser. Thus, a fiber ring laser gyroscope (FRLG) operating in continuous wave was demonstrated. A beat signal of over 30-dB noise was observed and a good inear relation between the beat frequency shift and cavity rotation rate was obtained.

  20. Keeping the Beat: A Large Sample Study of Bouncing and Clapping to Music

    Science.gov (United States)

    Tranchant, Pauline; Vuvan, Dominique T.; Peretz, Isabelle

    2016-01-01

    The vast majority of humans move in time with a musical beat. This behaviour has been mostly studied through finger-tapping synchronization. Here, we evaluate naturalistic synchronization responses to music–bouncing and clapping–in 100 university students. Their ability to match the period of their bounces and claps to those of a metronome and musical clips varying in beat saliency was assessed. In general, clapping was better synchronized with the beat than bouncing, suggesting that the choice of a specific movement type is an important factor to consider in the study of sensorimotor synchronization processes. Performance improved as a function of beat saliency, indicating that beat abstraction plays a significant role in synchronization. Fourteen percent of the population exhibited marked difficulties with matching the beat. Yet, at a group level, poor synchronizers showed similar sensitivity to movement type and beat saliency as normal synchronizers. These results suggest the presence of quantitative rather than qualitative variations when losing the beat. PMID:27471854

  1. Modification of the algorithm for beat tracking of a musical melody

    OpenAIRE

    Khachai, M. Y.; Kobylkin, K. S.; Khachai, D. M.

    2013-01-01

    A new efficient modification of the known heuristic algorithm for real-time beat tracking is proposed. An improved formula for updating the relative frequencies of time intervals between adjacent onsets is used in the modification. The algorithm has shown good performance on the MIREX Beat Tracking test base. © 2013 Pleiades Publishing, Ltd.

  2. Beat processing is pre-attentive for metrically simple rhythms with clear accents: an ERP study.

    Directory of Open Access Journals (Sweden)

    Fleur L Bouwer

    Full Text Available The perception of a regular beat is fundamental to music processing. Here we examine whether the detection of a regular beat is pre-attentive for metrically simple, acoustically varying stimuli using the mismatch negativity (MMN, an ERP response elicited by violations of acoustic regularity irrespective of whether subjects are attending to the stimuli. Both musicians and non-musicians were presented with a varying rhythm with a clear accent structure in which occasionally a sound was omitted. We compared the MMN response to the omission of identical sounds in different metrical positions. Most importantly, we found that omissions in strong metrical positions, on the beat, elicited higher amplitude MMN responses than omissions in weak metrical positions, not on the beat. This suggests that the detection of a beat is pre-attentive when highly beat inducing stimuli are used. No effects of musical expertise were found. Our results suggest that for metrically simple rhythms with clear accents beat processing does not require attention or musical expertise. In addition, we discuss how the use of acoustically varying stimuli may influence ERP results when studying beat processing.

  3. Beat processing is pre-attentive for metrically simple rhythms with clear accents: an ERP study.

    Science.gov (United States)

    Bouwer, Fleur L; Van Zuijen, Titia L; Honing, Henkjan

    2014-01-01

    The perception of a regular beat is fundamental to music processing. Here we examine whether the detection of a regular beat is pre-attentive for metrically simple, acoustically varying stimuli using the mismatch negativity (MMN), an ERP response elicited by violations of acoustic regularity irrespective of whether subjects are attending to the stimuli. Both musicians and non-musicians were presented with a varying rhythm with a clear accent structure in which occasionally a sound was omitted. We compared the MMN response to the omission of identical sounds in different metrical positions. Most importantly, we found that omissions in strong metrical positions, on the beat, elicited higher amplitude MMN responses than omissions in weak metrical positions, not on the beat. This suggests that the detection of a beat is pre-attentive when highly beat inducing stimuli are used. No effects of musical expertise were found. Our results suggest that for metrically simple rhythms with clear accents beat processing does not require attention or musical expertise. In addition, we discuss how the use of acoustically varying stimuli may influence ERP results when studying beat processing.

  4. Beat processing is pre-attentive for metrically simple rhythms with clear accents: an ERP study.

    Science.gov (United States)

    Bouwer, Fleur L; Van Zuijen, Titia L; Honing, Henkjan

    2014-01-01

    The perception of a regular beat is fundamental to music processing. Here we examine whether the detection of a regular beat is pre-attentive for metrically simple, acoustically varying stimuli using the mismatch negativity (MMN), an ERP response elicited by violations of acoustic regularity irrespective of whether subjects are attending to the stimuli. Both musicians and non-musicians were presented with a varying rhythm with a clear accent structure in which occasionally a sound was omitted. We compared the MMN response to the omission of identical sounds in different metrical positions. Most importantly, we found that omissions in strong metrical positions, on the beat, elicited higher amplitude MMN responses than omissions in weak metrical positions, not on the beat. This suggests that the detection of a beat is pre-attentive when highly beat inducing stimuli are used. No effects of musical expertise were found. Our results suggest that for metrically simple rhythms with clear accents beat processing does not require attention or musical expertise. In addition, we discuss how the use of acoustically varying stimuli may influence ERP results when studying beat processing. PMID:24870123

  5. Beat processing is pre-attentive for metrically simple rhythms with clear accents: An ERP study

    NARCIS (Netherlands)

    F.L. Bouwer; T.L. van Zuijen; H. Honing

    2014-01-01

    The perception of a regular beat is fundamental to music processing. Here we examine whether the detection of a regular beat is pre-attentive for metrically simple, acoustically varying stimuli using the mismatch negativity (MMN), an ERP response elicited by violations of acoustic regularity irrespe

  6. Peak misdetection in heart-beat-based security : Characterization and tolerance

    NARCIS (Netherlands)

    Seepers, Robert M; Strydis, Christos; Peris-Lopez, Pedro; Sourdis, Ioannis; De Zeeuw, Chris I

    2014-01-01

    The Inter-Pulse-Interval (IPI) of heart beats has previously been suggested for security in mobile health (mHealth) applications. In IPI-based security, secure communication is facilitated through a security key derived from the time difference between heart beats. However, there currently exists no

  7. Keeping the Beat: A Large Sample Study of Bouncing and Clapping to Music.

    Science.gov (United States)

    Tranchant, Pauline; Vuvan, Dominique T; Peretz, Isabelle

    2016-01-01

    The vast majority of humans move in time with a musical beat. This behaviour has been mostly studied through finger-tapping synchronization. Here, we evaluate naturalistic synchronization responses to music-bouncing and clapping-in 100 university students. Their ability to match the period of their bounces and claps to those of a metronome and musical clips varying in beat saliency was assessed. In general, clapping was better synchronized with the beat than bouncing, suggesting that the choice of a specific movement type is an important factor to consider in the study of sensorimotor synchronization processes. Performance improved as a function of beat saliency, indicating that beat abstraction plays a significant role in synchronization. Fourteen percent of the population exhibited marked difficulties with matching the beat. Yet, at a group level, poor synchronizers showed similar sensitivity to movement type and beat saliency as normal synchronizers. These results suggest the presence of quantitative rather than qualitative variations when losing the beat. PMID:27471854

  8. Algorithm for identifying and separating beats from arterial pulse records

    Directory of Open Access Journals (Sweden)

    Valentinuzzi Max E

    2005-08-01

    Full Text Available Abstract Background This project was designed as an epidemiological aid-selecting tool for a small country health center with the general objective of screening out possible coronary patients. Peripheral artery function can be non-invasively evaluated by impedance plethysmography. Changes in these vessels appear as good predictors of future coronary behavior. Impedance plethysmography detects volume variations after simple occlusive maneuvers that may show indicative modifications in arterial/venous responses. Averaging of a series of pulses is needed and this, in turn, requires proper determination of the beginning and end of each beat. Thus, the objective here is to describe an algorithm to identify and separate out beats from a plethysmographic record. A secondary objective was to compare the output given by human operators against the algorithm. Methods The identification algorithm detected the beat's onset and end on the basis of the maximum rising phase, the choice of possible ventricular systolic starting points considering cardiac frequency, and the adjustment of some tolerance values to optimize the behavior. Out of 800 patients in the study, 40 occlusive records (supradiastolic- subsystolic were randomly selected without any preliminary diagnosis. Radial impedance plethysmographic pulse and standard ECG were recorded digitizing and storing the data. Cardiac frequency was estimated with the Power Density Function and, thereafter, the signal was derived twice, followed by binarization of the first derivative and rectification of the second derivative. The product of the two latter results led to a weighing signal from which the cycles' onsets and ends were established. Weighed and frequency filters are needed along with the pre-establishment of their respective tolerances. Out of the 40 records, 30 seconds strands were randomly chosen to be analyzed by the algorithm and by two operators. Sensitivity and accuracy were calculated by means

  9. Wave-Packet Revivals for Quantum Systems with Nondegenerate Energies

    CERN Document Server

    Bluhm, R; Tudose, B; Bluhm, Robert; Kostelecky, Alan; Tudose, Bogdan

    1996-01-01

    The revival structure of wave packets is examined for quantum systems having energies that depend on two nondegenerate quantum numbers. For such systems, the evolution of the wave packet is controlled by two classical periods and three revival times. These wave packets exhibit quantum beats in the initial motion as well as new types of long-term revivals. The issue of whether fractional revivals can form is addressed. We present an analytical proof showing that at certain times equal to rational fractions of the revival times the wave packet can reform as a sum of subsidiary waves and that both conventional and new types of fractional revivals can occur.

  10. Observation of single- and two-photon beating between independent Raman scattering

    CERN Document Server

    Chen, Li-Qing; Zhang, Guo-Wan; Ou, Z Y; Zhang, Weiping

    2010-01-01

    By using spontaneous Raman processes in the high gain regime, we produce two independent Raman Stokes fields from an atomic ensemble. Temporal beating is observed between the two directly generated Stokes fields in a single realization. The beat frequency is found to be a result of an AC Stark frequency shift effect. However, due to the spontaneous nature of the process, the phases of the two Stokes fields change from one realization to another so that the beat signal disappears after average over many realizations. On the other hand, the beat signal is recovered in a two-photon correlation measurement, showing a two-photon interference effect. The two-photon beat signal enables us to obtain dephasing information in the Raman process. The dephasing effect is found to depend on the temperature of the atomic medium.

  11. Simple non-invasive analysis of embryonic stem cell-derived cardiomyocytes beating in vitro

    Science.gov (United States)

    Radaszkiewicz, Katarzyna Anna; Sýkorová, Dominika; Karas, Pavel; Kudová, Jana; Kohút, Lukáš; Binó, Lucia; Večeřa, Josef; Víteček, Jan; Kubala, Lukáš; Pacherník, Jiří

    2016-02-01

    The analysis of digital video output enables the non-invasive screening of various active biological processes. For the monitoring and computing of the beating parameters of cardiomyocytes in vitro, CB Analyser (cardiomyocyte beating analyser) software was developed. This software is based on image analysis of the video recording of beating cardiomyocytes. CB Analyser was tested using cardiomyocytes derived from mouse embryonic stem cells at different stages of cardiomyogenesis. We observed that during differentiation (from day 18), the beat peak width decreased, which corresponded to the increased speed of an individual pulse. However, the beating frequency did not change. Further, the effects of epinephrine modulating mature cardiomyocyte functions were tested to validate the CB Analyser analysis. In conclusion, data show that CB Analyser is a useful tool for evaluating the functions of both developing and mature cardiomyocytes under various conditions in vitro.

  12. Accelerator operations

    International Nuclear Information System (INIS)

    This section is concerned with the operation of both the tandem-linac system and the Dynamitron, two accelerators that are used for entirely different research. Developmental activities associated with the tandem and the Dynamitron are also treated here, but developmental activities associated with the superconducting linac are covered separately because this work is a program of technology development in its own right

  13. Tidal acceleration of black holes and superradiance

    OpenAIRE

    Cardoso, Vitor; Pani, Paolo

    2012-01-01

    Tidal effects have long ago locked the Moon in synchronous rotation with the Earth and progressively increase the Earth-Moon distance. This "tidal acceleration" hinges on dissipation. Binaries containing black holes may also be tidally accelerated, dissipation being caused by the event horizon - a flexible, viscous one-way membrane. In fact, this process is known for many years under a different guise: superradiance. In General Relativity, tidal acceleration is obscured by gravitational-wave ...

  14. Synchronization using environmental coupling in mercury beating heart oscillators

    Science.gov (United States)

    Singla, Tanu; Montoya, Fernando; Rivera, M.; Tajima, Shunsuke; Nakabayashi, Seiichiro; Parmananda, P.

    2016-06-01

    We report synchronization of Mercury Beating Heart (MBH) oscillators using the environmental coupling mechanism. This mechanism involves interaction of the oscillators with a common medium/environment such that the oscillators do not interact among themselves. In the present work, we chose a modified MBH system as the common environment. In the absence of coupling, this modified system does not exhibit self sustained oscillations. It was observed that, as a result of the coupling of the MBH oscillators with this common environment, the electrical and the mechanical activities of both the oscillators synchronized simultaneously. Experimental results indicate the emergence of both lag and the complete synchronization in the MBH oscillators. Simulations of the phase oscillators were carried out in order to better understand the experimental observations.

  15. The quantum beat principles and applications of atomic clocks

    CERN Document Server

    Major, F

    2007-01-01

    This work attempts to convey a broad understanding of the physical principles underlying the workings of these quantum-based atomic clocks, with introductory chapters placing them in context with the early development of mechanical clocks and the introduction of electronic time-keeping as embodied in the quartz-controlled clocks. While the book makes no pretense at being a history of atomic clocks, it nevertheless takes a historical perspective in its treatment of the subject. Intended for nonspecialists with some knowledge of physics or engineering, The Quantum Beat covers a wide range of salient topics relevant to atomic clocks, treated in a broad intuitive manner with a minimum of mathematical formalism. Detailed descriptions are given of the design principles of the rubidium, cesium, hydrogen maser, and mercury ion standards; the revolutionary changes that the advent of the laser has made possible, such as laser cooling, optical pumping, the formation of "optical molasses," and the cesium "fountain" stand...

  16. Oxidized Cellulose with Different Carboxyl Content: Structure and Properties before and after Beating

    Science.gov (United States)

    Vendula, Hejlová; Miloslav, Milichovský

    Our recent studies concentrated in investigating influence of beating oxidized cellulose, with different carboxyl content, on changing their basic properties (degree of polymerization, WRV - water resistant value and X-ray diffraction). Cellulose samples of oxidized cellulose were beated by toroidal beating machine. Cellulose consists of both amorphous and crystalline regions. Cellulose consists of linear chains of poly[ß-1,4-D- anhydroglucopyranose] (C6nH10n + 2O5n + 1 (n = degree of polymerization of glucose)), which crystallize through hydrogen bonding between the chains and has cellobiose as repeat unit. Oxidized cellulose is preparing by oxidation of cellulose in the C6 position of the glucopyranose units to carboxylic group (-COOH) and polyanhydroglukuronic acid (PAGA) is arised. An other option is oxidation with sodium hypochlorite with catalytic amounts of sodium bromide and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) under various conditions. Beating and refining or mechanical treatment of fibers in water is an important step in using pulps for papermaking. It is an energy intensive process. The purpose of the treatment is to modify fiber properties to obtain the most desirable paper machine runnability and product properties. End of beating pulps was characterized by position, when all beated pulps under mixture passed through of riddle (about sizes mesh of 50). During beating of samples about different ratio of oxidation it was found, that samples with higher contents of COOH groups in starting pulp are characterized by a significantly lower specific beating energy consumption needed to achieving the same sizes of particles. X-ray analyse shows that for non-beated oxidized cellulose was perceptible high share amorphous contents compared with beated oxidized cellulose.

  17. The Effects of Wave Escape on Fast Magnetosonic Wave Turbulence in Solar Flares

    Science.gov (United States)

    Pongkitiwanichakul, Peera; Chandran, Benjamin D. G.; Karpen, Judith T.; DeVore, C. Richard

    2012-01-01

    One of the leading models for electron acceleration in solar flares is stochastic acceleration by weakly turbulent fast magnetosonic waves ("fast waves"). In this model, large-scale flows triggered by magnetic reconnection excite large-wavelength fast waves, and fast-wave energy then cascades from large wavelengths to small wavelengths. Electron acceleration by large-wavelength fast-waves is weak, and so the model relies on the small-wavelength waves produced by the turbulent cascade. In order for the model to work, the energy cascade time for large-wavelength fast waves must be shorter than the time required for the waves to propagate out of the solar-flare acceleration region. To investigate the effects of wave escape, we solve the wave kinetic equation for fast waves in weak turbulence theory, supplemented with a homogeneous wave-loss term.We find that the amplitude of large-wavelength fast waves must exceed a minimum threshold in order for a significant fraction of the wave energy to cascade to small wavelengths before the waves leave the acceleration region.We evaluate this threshold as a function of the dominant wavelength of the fast waves that are initially excited by reconnection outflows.

  18. Diffusive Shock Acceleration and Reconnection Acceleration Processes

    Science.gov (United States)

    Zank, G. P.; Hunana, P.; Mostafavi, P.; Le Roux, J. A.; Li, Gang; Webb, G. M.; Khabarova, O.; Cummings, A.; Stone, E.; Decker, R.

    2015-12-01

    Shock waves, as shown by simulations and observations, can generate high levels of downstream vortical turbulence, including magnetic islands. We consider a combination of diffusive shock acceleration (DSA) and downstream magnetic-island-reconnection-related processes as an energization mechanism for charged particles. Observations of electron and ion distributions downstream of interplanetary shocks and the heliospheric termination shock (HTS) are frequently inconsistent with the predictions of classical DSA. We utilize a recently developed transport theory for charged particles propagating diffusively in a turbulent region filled with contracting and reconnecting plasmoids and small-scale current sheets. Particle energization associated with the anti-reconnection electric field, a consequence of magnetic island merging, and magnetic island contraction, are considered. For the former only, we find that (i) the spectrum is a hard power law in particle speed, and (ii) the downstream solution is constant. For downstream plasmoid contraction only, (i) the accelerated spectrum is a hard power law in particle speed; (ii) the particle intensity for a given energy peaks downstream of the shock, and the distance to the peak location increases with increasing particle energy, and (iii) the particle intensity amplification for a particular particle energy, f(x,c/{c}0)/f(0,c/{c}0), is not 1, as predicted by DSA, but increases with increasing particle energy. The general solution combines both the reconnection-induced electric field and plasmoid contraction. The observed energetic particle intensity profile observed by Voyager 2 downstream of the HTS appears to support a particle acceleration mechanism that combines both DSA and magnetic-island-reconnection-related processes.

  19. Banding and Step-Stair Artifacts on the Cardiac-CT Caused By Pseudo-Ectopic Beats

    OpenAIRE

    Singh, Amolak; Sethi, Yash; Watkins, Sonya; Youtsey, Angela; Thomas, Angie

    2009-01-01

    Step-stair and banding artifacts may result from irregular ventricular rhythm caused by atrial fibrillation or premature ectopic ventricular contractions. In the case reported here, severe banding and misalignment artifacts occurred due to electrocardiographic noise mimicking ectopic beats. Severe EKG noise or pseudo-ectopic beats may cause rare but serious artifacts during cardiac-CT acquisition. Vendor-provided software for correcting ectopic beats can be used to remove pseudo-ectopic beats...

  20. Accelerator structure work for NLC

    Energy Technology Data Exchange (ETDEWEB)

    Miller, R.H.; Adolphsen, C.; Bane, K.L.F.; Deruyter, H.; Farkas, Z.D.; Hoag, H.A.; Holtkamp, N.; Lavine, T.; Loew, G.A.; Nelson, E.M.; Palmer, R.B.; Paterson, J.M.; Ruth, R.D.; Thompson, K.A.; Vlieks, A.; Wang, J.W.; Wilson, P.B. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Gluckstern, R. [Maryland Univ., College Park, MD (United States); Ko, K.; Kroll, N. [Stanford Linear Accelerator Center, Menlo Park, CA (United States)]|[California Univ., San Diego, La Jolla, CA (United States). Dept. of Physics

    1992-07-01

    The NLC design achieves high luminosity with multiple bunches in each RF pulse. Acceleration of a train of bunches without emittance growth requires control of long range dipole wakefields. SLAC is pursuing a structure design which suppresses the effect of wakefields by varying the physical dimensions of successive cells of the disk-loaded traveling wave structure in a manner which spreads the frequencies of the higher mode while retaining the synchronism between the electrons and the accelerating mode. The wakefields of structures incorporating higher mode detuning have been measured at the Accelerator Test Facility at Argonne. Mechanical design and brazing techniques which avoid getting brazing alloy into the interior of the accelerator are being studied. A test facility for high-power testing of these structures is complete and high power testing has begun.

  1. KEKB accelerator

    International Nuclear Information System (INIS)

    KEKB, the B-Factory at High Energy Accelerator Research Organization (KEK) recently achieved the luminosity of 1 x 1034 cm-2s-1. This luminosity is two orders higher than the world's level at 1990 when the design of KEKB started. This unprecedented result was made possible by KEKB's innovative design and technology in three aspects - beam focusing optics, high current storage, and beam - beam interaction. Now KEKB is leading the luminosity frontier of the colliders in the world. (author)

  2. Accelerating networks

    International Nuclear Information System (INIS)

    Evolving out-of-equilibrium networks have been under intense scrutiny recently. In many real-world settings the number of links added per new node is not constant but depends on the time at which the node is introduced in the system. This simple idea gives rise to the concept of accelerating networks, for which we review an existing definition and-after finding it somewhat constrictive-offer a new definition. The new definition provided here views network acceleration as a time dependent property of a given system as opposed to being a property of the specific algorithm applied to grow the network. The definition also covers both unweighted and weighted networks. As time-stamped network data becomes increasingly available, the proposed measures may be easily applied to such empirical datasets. As a simple case study we apply the concepts to study the evolution of three different instances of Wikipedia, namely, those in English, German, and Japanese, and find that the networks undergo different acceleration regimes in their evolution

  3. Real-Time Analysis of Beats in Music for Entertainment Robots

    Directory of Open Access Journals (Sweden)

    Yue-Der Lin

    2012-12-01

    Full Text Available The dancing actions for entertainment robots are usually designed in advance and saved in a database according to the beats and rhythm of the given music. This research is devoted to developing a real-time algorithm that can detect the primary information of the music needed for the actions of entertainment robots. The computation of the proposed algorithm is very efficient and can satisfy the requirement of real-time processing by a digital signal controller. The digitized music signal is first normalized to make the algorithm robust for miscellaneous music volume. Next, the primary features of the beat for the music are extracted. Based on the extracted features, the algorithm will then identify the occurrence of beats in the music through the use of an optimized classifier. From the accumulated information of the timing for the beats, the algorithm can provide the predicted timing information of the next beat through regression analysis. The type and tempo of the given music can also be derived thereafter. The entertainment robot can thus move or dance according to the information derived by the algorithm. A graphical user interface (GUI program in LabVIEW is also utilized to observe and verify the analysis results. In this study, the ratio for correct beat detection is greater than 90%. The prediction ratio for the correct timing of beats is over 80%, and it is 100% correct for both music type and music tempo.

  4. Electron surfing acceleration in a current sheet of flares

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A model of electron acceleration in a current sheet of flares is studied by the analytical approximation solution and the test particle simulation. The electron can be trapped in a potential of propagating electrostatic wave. The trapped electron moving with the phase velocity vp of wave may be effectively accelerated by evc p× Bz force along the outflow direction in the current sheet, if a criterion condition K > 0 for electron surfing acceleration is satisfied. The electron will be accelerated continuously until the electron detrap from the wave potential at the turning point S.

  5. Relativistic particle acceleration in developing Alfv\\'{e}n turbulence

    CERN Document Server

    Matsukiyo, S; 10.1088/0004-637X/692/2/1004

    2009-01-01

    A new particle acceleration process in a developing Alfv\\'{e}n turbulence in the course of successive parametric instabilities of a relativistic pair plasma is investigated by utilyzing one-dimensional electromagnetic full particle code. Coherent wave-particle interactions result in efficient particle acceleration leading to a power-law like energy distribution function. In the simulation high energy particles having large relativistic masses are preferentially accelerated as the turbulence spectrum evolves in time. Main acceleration mechanism is simultaneous relativistic resonance between a particle and two different waves. An analytical expression of maximum attainable energy in such wave-particle interactions is derived.

  6. Plasma Channel Guided Laser Wakefield Accelerator

    CERN Document Server

    Geddes, C G

    2005-01-01

    High quality electron beams (several 109 electrons above 80 MeV energy with percent energy spread and low divergence) have been produced for the first time in a compact, high gradient, all-optical laser accelerator by extending the interaction distance using a pre-formed plasma density channel to guide the drive laser pulse. Laser-driven accelerators, in which particles are accelerated by the electric field of a plasma wave (wake) driven by the radiation pressure of an intense laser, have over the past decade demonstrated accelerating fields thousands of times greater than those achievable in conventional radio-frequency accelerators. This has spurred interest in them as compact next- generation sources of energetic electrons and radiation. To date, however, acceleration distances have been severely limited by the lack of a controllable method for extending the propagation distance of the focused laser pulse. The ensuing short acceleration distance resulted in low-energy beams with 100 percent electron energy...

  7. The evolutionary neuroscience of musical beat perception: the Action Simulation for Auditory Prediction (ASAP hypothesis.

    Directory of Open Access Journals (Sweden)

    Aniruddh D. Patel

    2014-05-01

    Full Text Available Every human culture has some form of music with a beat: a perceived periodic pulse that structures the perception of musical rhythm and which serves as a framework for synchronized movement to music. What are the neural mechanisms of musical beat perception, and how did they evolve? One view, which dates back to Darwin and implicitly informs some current models of beat perception, is that the relevant neural mechanisms are relatively general and are widespread among animal species. On the basis of recent neural and cross-species data on musical beat processing, this paper argues for a different view. Here we argue that beat perception is a complex brain function involving temporally-precise communication between auditory regions and motor planning regions of the cortex (even in the absence of overt movement. More specifically, we propose that simulation of periodic movement in motor planning regions provides a neural signal that helps the auditory system predict the timing of upcoming beats. This action simulation for auditory prediction (ASAP hypothesis leads to testable predictions. We further suggest that ASAP relies on dorsal auditory pathway connections between auditory regions and motor planning regions via the parietal cortex, and suggest that these connections may be stronger in humans than in nonhuman primates due to the evolution of vocal learning in our lineage. This suggestion motivates cross-species research to determine which species are capable of human-like beat perception, i.e., beat perception that involves accurate temporal prediction of beat times across a fairly broad range of tempi.

  8. Disentangling beat perception from sequential learning and examining the influence of attention and musical abilities on ERP responses to rhythm.

    Science.gov (United States)

    Bouwer, Fleur L; Werner, Carola M; Knetemann, Myrthe; Honing, Henkjan

    2016-05-01

    Beat perception is the ability to perceive temporal regularity in musical rhythm. When a beat is perceived, predictions about upcoming events can be generated. These predictions can influence processing of subsequent rhythmic events. However, statistical learning of the order of sounds in a sequence can also affect processing of rhythmic events and must be differentiated from beat perception. In the current study, using EEG, we examined the effects of attention and musical abilities on beat perception. To ensure we measured beat perception and not absolute perception of temporal intervals, we used alternating loud and soft tones to create a rhythm with two hierarchical metrical levels. To control for sequential learning of the order of the different sounds, we used temporally regular (isochronous) and jittered rhythmic sequences. The order of sounds was identical in both conditions, but only the regular condition allowed for the perception of a beat. Unexpected intensity decrements were introduced on the beat and offbeat. In the regular condition, both beat perception and sequential learning were expected to enhance detection of these deviants on the beat. In the jittered condition, only sequential learning was expected to affect processing of the deviants. ERP responses to deviants were larger on the beat than offbeat in both conditions. Importantly, this difference was larger in the regular condition than in the jittered condition, suggesting that beat perception influenced responses to rhythmic events in addition to sequential learning. The influence of beat perception was present both with and without attention directed at the rhythm. Moreover, beat perception as measured with ERPs correlated with musical abilities, but only when attention was directed at the stimuli. Our study shows that beat perception is possible when attention is not directed at a rhythm. In addition, our results suggest that attention may mediate the influence of musical abilities on beat

  9. Selective Acceleration in Impulsive Solar Flares

    Institute of Scientific and Technical Information of China (English)

    王德焴

    2001-01-01

    A plasma acceleration mechanism is proposed to explain the dramatic enhancement in the ratio of 3 He/4He, (enhancement factor 102 - 103) observed in solar 3He-rich flares. Considering that coronal plasma is mainly composed of hydrogen and helium ions, the hydrogen ion-helium ion hybrid waves and quasi-perpendicular waves can be excited by energetic electron beam during the impulsive solarflares. The frequencies of these waves are close to the 3He++ ion gyrofrequency, but far from the 4He++ ion gyrofrequency. Most of these waves are selectively absorbed by 3He ions. These preheated 3He ions can be successively stochastic accelerated by Alfvén turbulence, when their velocities are larger than the local Alfvén velocity. It makes the ratio of 3He/4He dramatically enhanced and the acceleration energy spectrum of 3He ions forms a power-law distribution during the impulsive solar flares.

  10. Colliding Laser Pulses for Laser-Plasma Accelerator Injection Control

    Energy Technology Data Exchange (ETDEWEB)

    Plateau, Guillaume; Geddes, Cameron; Matlis, Nicholas; Cormier-Michel, Estelle; Mittelberger, Daniel; Nakamura, Kei; Schroeder, Carl; Esarey, Eric; Leemans, Wim

    2011-07-19

    Decoupling injection from acceleration is a key challenge to achieve compact, reliable, tunable laser-plasma accelerators (LPA). In colliding pulse injection the beat between multiple laser pulses can be used to control energy, energy spread, and emittance of the electron beam by injecting electrons in momentum and phase into the accelerating phase of the wake trailing the driver laser pulse. At LBNL, using automated control of spatiotemporal overlap of laser pulses, two-pulse experiments showed stable operation and reproducibility over hours of operation. Arrival time of the colliding beam was scanned, and the measured timing window and density of optimal operation agree with simulations. The accelerator length was mapped by scanning the collision point.

  11. Accelerators and the Accelerator Community

    Energy Technology Data Exchange (ETDEWEB)

    Malamud, Ernest; Sessler, Andrew

    2008-06-01

    In this paper, standing back--looking from afar--and adopting a historical perspective, the field of accelerator science is examined. How it grew, what are the forces that made it what it is, where it is now, and what it is likely to be in the future are the subjects explored. Clearly, a great deal of personal opinion is invoked in this process.

  12. accelerating cavity

    CERN Multimedia

    On the inside of the cavitytThere is a layer of niobium. Operating at 4.2 degrees above absolute zero, the niobium is superconducting and carries an accelerating field of 6 million volts per metre with negligible losses. Each cavity has a surface of 6 m2. The niobium layer is only 1.2 microns thick, ten times thinner than a hair. Such a large area had never been coated to such a high accuracy. A speck of dust could ruin the performance of the whole cavity so the work had to be done in an extremely clean environment.

  13. Enhanced particle acceleration via cascade of autoresonance detrappings

    Energy Technology Data Exchange (ETDEWEB)

    Nakach, R. [Association Euratom-CEA, CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Gell, Y. [CET, Tel-Aviv (Israel)

    1997-10-01

    We propose to enhance the acceleration of electrons by repeating consecutively a basic accelerating mechanism. This mechanism consists of trapping the particles in a traveling ponderomotive well, then autoresonance detrapping them allowing for considerable acceleration. The traveling well is generated by two counterpropagating electromagnetic waves along a uniform magnetic field. (author) 8 refs.

  14. Automatic analysis of ciliary beat frequency using optical flow

    Science.gov (United States)

    Figl, Michael; Lechner, Manuel; Werther, Tobias; Horak, Fritz; Hummel, Johann; Birkfellner, Wolfgang

    2012-02-01

    Ciliary beat frequency (CBF) can be a useful parameter for diagnosis of several diseases, as e.g. primary ciliary dyskinesia. (PCD). CBF computation is usually done using manual evaluation of high speed video sequences, a tedious, observer dependent, and not very accurate procedure. We used the OpenCV's pyramidal implementation of the Lukas-Kanade algorithm for optical flow computation and applied this to certain objects to follow the movements. The objects were chosen by their contrast applying the corner detection by Shi and Tomasi. Discrimination between background/noise and cilia by a frequency histogram allowed to compute the CBF. Frequency analysis was done using the Fourier transform in matlab. The correct number of Fourier summands was found by the slope in an approximation curve. The method showed to be usable to distinguish between healthy and diseased samples. However there remain difficulties in automatically identifying the cilia, and also in finding enough high contrast cilia in the image. Furthermore the some of the higher contrast cilia are lost (and sometimes found) by the method, an easy way to distinguish the correct sub-path of a point's path have yet to be found in the case where the slope methods doesn't work.

  15. Non-heart-beating organ donation in Italy.

    Science.gov (United States)

    Geraci, P M; Sepe, V

    2011-06-01

    In 2007 the non-heart-beating organ donation (NHBD) "Programma Alba" (Sunrise Programme) started in Pavia, Italy. The initial plan was to cut down waiting list for kidney transplantation, while its final aim is to shorten organ transplantation waiting lists. When compared to European countries and the USA, the Italian NHBD program has taken longer to get established. Initially Italian physicians were not entirely aware of the NHBD organ viability for transplantation, furthermore ethical issues and the need to regulate medical requirements to Italian law slowed down the NHBD program. In particular, Italian legislation provides for death ascertainment after irreversible cardiac arrest, 20-minute flat electrocardiogram. This no-touch period is longer when compared to worldwide legislation, and organ viability has been a main concern for Italian transplant doctors over the years. However, recent data let up to 40-minute warm ischemia time to preserve organ viability; this has encouraged Pavia's group to establish the NHBD "Programma Alba". It was designed according to Italian legislation from death diagnosis to graft placement, from this perspective must the significant role of the Transplant coordinator be recognized. Since 2007 seven kidneys have been gathered from seven NHBD. Of these, six NHBD kidneys have been transplanted. Currently, four patients are out of dialysis. This report is a detailed description of NHBD "Programma Alba" and its preliminary results. PMID:21617625

  16. Long beating wavelength in the Schwarz-Hora effect

    CERN Document Server

    Morokov, Y N

    1997-01-01

    Thirty years ago, H.Schwarz has attempted to modulate an electron beam with optical frequency. When a 50-keV electron beam crossed a thin crystalline dielectric film illuminated with laser light, electrons produced the electron-diffraction pattern not only at a fluorescent target but also at a nonfluorescent target. In the latter case the pattern was of the same color as the laser light (the Schwarz-Hora effect). This effect was discussed extensively in the early 1970s. However, since 1972 no reports on the results of further attempts to repeat those experiments in other groups have appeared, while the failures of the initial such attempts have been explained by Schwarz. The analysis of the literature shows there are several unresolved up to now contradictions between the theory and the Schwarz experiments. In this work we consider the interpretation of the long-wavelength spatial beating of the Schwarz-Hora radiation. A more accurate expression for the spatial period has been obtained, taking into account th...

  17. Taming microwave plasma to beat thermodynamics in CO2 dissociation.

    Science.gov (United States)

    van Rooij, G J; van den Bekerom, D C M; den Harder, N; Minea, T; Berden, G; Bongers, W A; Engeln, R; Graswinckel, M F; Zoethout, E; van de Sanden, M C M

    2015-01-01

    The strong non-equilibrium conditions provided by the plasma phase offer the opportunity to beat traditional thermal process energy efficiencies via preferential excitation of molecular vibrations. Simple molecular physics considerations are presented to explain potential dissociation pathways in plasma and their effect on energy efficiency. A common microwave reactor approach is evaluated experimentally with Rayleigh scattering and Fourier transform infrared spectroscopy to assess gas temperatures (exceeding 10(4) K) and conversion degrees (up to 30%), respectively. The results are interpreted on a basis of estimates of the plasma dynamics obtained with electron energy distribution functions calculated with a Boltzmann solver. It indicates that the intrinsic electron energies are higher than is favorable for preferential vibrational excitation due to dissociative excitation, which causes thermodynamic equilibrium chemistry to dominate. The highest observed energy efficiencies of 45% indicate that non-equilibrium dynamics had been at play. A novel approach involving additives of low ionization potential to tailor the electron energies to the vibrational excitation regime is proposed.

  18. Pulse Wave Propagation in the Arterial Tree

    Science.gov (United States)

    van de Vosse, Frans N.; Stergiopulos, Nikos

    2011-01-01

    The beating heart creates blood pressure and flow pulsations that propagate as waves through the arterial tree that are reflected at transitions in arterial geometry and elasticity. Waves carry information about the matter in which they propagate. Therefore, modeling of arterial wave propagation extends our knowledge about the functioning of the cardiovascular system and provides a means to diagnose disorders and predict the outcome of medical interventions. In this review we focus on the physical and mathematical modeling of pulse wave propagation, based on general fluid dynamical principles. In addition we present potential applications in cardiovascular research and clinical practice. Models of short- and long-term adaptation of the arterial system and methods that deal with uncertainties in personalized model parameters and boundary conditions are briefly discussed, as they are believed to be major topics for further study and will boost the significance of arterial pulse wave modeling even more.

  19. On kinematics of very steep waves

    Directory of Open Access Journals (Sweden)

    L. Shemer

    2013-08-01

    Full Text Available Experiments on extremely steep deterministic waves generated in a large wave tank by focusing of a broad-banded wave train serve as a motivation for the theoretical analysis of the conditions leading to wave breaking. Particular attention is given to the crest of the steepest wave where both the horizontal velocity and the vertical acceleration attain their maxima. Analysis is carried out up to the third order in wave steepness. The apparent, Eulerian and Lagrangian accelerations are computed for wave parameters observed in experiments. It is demonstrated that for a wave group with a wide spectrum, the crest propagation velocity differs significantly from both the phase and the group velocities of the peak wave. Conclusions are drawn regarding the applicability of various criteria for wave breaking.

  20. Feedback in a cavity QED system for control of quantum beats

    Directory of Open Access Journals (Sweden)

    Cimmarusti A.D.

    2013-08-01

    Full Text Available Conditional measurements on the undriven mode of a two-mode cavity QED system prepare a coherent superposition of ground states which generate quantum beats. The continuous system drive induces decoherence through the phase interruptions from Rayleigh scattering, which manifests as a decrease of the beat amplitude and an increase of the frequency of oscillation. We report recent experiments that implement a simple feedback mechanism to protect the quantum beat. We continuously drive the system until a photon is detected, heralding the presence of a coherent superposition. We then turn off the drive and let the superposition evolve in the dark, protecting it against decoherence. At a later time we reinstate the drive to measure the amplitude, phase, and frequency of the beats. The amplitude can increase by more than fifty percent, while the frequency is unchanged by the feedback.