Electron-ion relaxation in a dense plasma. [supernovae core physics

NASA Technical Reports Server (NTRS)

Littleton, J. E.; Buchler, J.-R.

1974-01-01

The microscopic physics of the thermonuclear runaway in highly degenerate carbon-oxygen cores is investigated to determine if and how a detonation wave is generated. An expression for the electron-ion relaxation time is derived under the assumption of large degeneracy and extreme relativity of the electrons in a two-temperature plasma. Since the nuclear burning time proves to be several orders of magnitude shorter than the relaxation time, it is concluded that in studying the structure of the detonation wave the electrons and ions must be treated as separate fluids.

Pair production rates in mildly relativistic, magnetized plasmas

NASA Technical Reports Server (NTRS)

Burns, M. L.; Harding, A. K.

1984-01-01

Electron-positron pairs may be produced by either one or two photons in the presence of a strong magnetic field. In magnetized plasmas with temperatures kT approximately sq mc, both of these processes may be important and could be competitive. The rates of one-photon and two-photon pair production by photons with Maxwellian, thermal bremsstrahlung, thermal synchrotron and power law spectra are calculated as a function of temperature or power law index and field strength. This allows a comparison of the two rates and a determination of the conditions under which each process may be a significant source of pairs in astrophysical plasmas. It is found that for photon densities n(gamma) or = 10 to the 25th power/cu cm and magnetic field strengths B or = 10 to the 12th power G, one-photon pair production dominates at kT approximately sq mc for a Maxwellian, at kT approximately 2 sq mc for a thermal bremsstrahlung spectrum, at all temperatures for a thermal synchrotron spectrum, and for power law spectra with indices s approximately 4.

Interesting features of nonlinear shock equations in dissipative pair-ion-electron plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masood, W.; National Centre for Physics; Rizvi, H.

2011-09-15

Two dimensional nonlinear electrostatic waves are studied in unmagnetized, dissipative pair-ion-electron plasmas in the presence of weak transverse perturbation. The dissipation in the system is taken into account by incorporating the kinematic viscosity of both positive and negative ions. In the linear case, a biquadratic dispersion relation is obtained, which yields the fast and slow modes in a pair-ion-electron plasma. It is shown that the limiting cases of electron-ion and pair-ion can be retrieved from the general biquadratic dispersion relation, and the differences in the characters of the waves propagating in both the cases are also highlighted. Using the smallmore » amplitude approximation method, the nonlinear Kadomtsev Petviashvili Burgers as well as Burgers-Kadomtsev Petviashvili equations are derived and their applicability for pair-ion-electron plasma is explained in detail. The present study may have relevance to understand the formation of two dimensional electrostatic shocks in laboratory produced pair-ion-electron plasmas.« less

Electrostatic shocks and solitons in pair-ion plasmas in a two-dimensional geometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masood, W.; Mahmood, S.; Imtiaz, N.

2009-12-15

Nonlinear electrostatic waves are studied in unmagnetized, dissipative pair-ion plasmas in the presence of weak transverse perturbations. The dissipation in the system is taken into account by incorporating the kinematic viscosity of both positive and negative ions in plasmas. The Kadomtsev-Petviashvili-Burger equation is derived using the small amplitude expansion method. The Kadomtsev-Petviashvili equation for pair-ion plasmas is also presented by ignoring the dissipative effects. Both compressive and rarefactive shocks and solitary waves are found to exist in pair-ion plasmas. The dependence of compression and rarefaction on the temperature ratios between the ion species is numerically shown. The present study maymore » have relevance to the understanding of the formation of electrostatic shocks and solitons in laboratory produced pair-ion plasmas.« less

New longitudinal mode and compression of pair ions in plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ehsan, Zahida; Imran, Muhammad, E-mail: imransindhu@hotmail.com; Tsintsadze, N. L.

Positive and negative ions forming the so-called pair plasma differing in sign of their charge but asymmetric in mass and temperature support a new acoustic-like mode. The condition for the excitation of ion sound wave through electron beam induced Cherenkov instability is also investigated. This beam can generate a perturbation in the pair ion plasmas in the presence of electrons when there is number density, temperature, and mass difference in the two species of ions. Basic emphasis is on the focusing of ion sound waves, and we show how, in the area of localization of wave energy, the density ofmore » pair particles increases while electrons are pushed away from that region. Further, this localization of wave is dependent on the shape of the pulse. Considering the example of pancake and bullet shaped pulses, we find that only the former leads to compression of pair ions in the supersonic regime of the focusing region. Here, possible existence of regions where pure pair particles can exist may also be speculated which is not only useful from academic point of view but also to mimic the situation of plasma (electron positron asymmetric and symmetric) observed in astrophysical environment.« less

A criterion for pure pair-ion plasmas and the role of quasineutrality in nonlinear dynamics

NASA Astrophysics Data System (ADS)

Saleem, H.

2007-01-01

A criterion is presented to decide whether a produced plasma can be called a pure pair-ion plasma or not. The theory is discussed in the light of recent experiments which claim that a pure pair-ion fullerene (C60±) plasma has been produced. It is also shown that the ion acoustic wave is replaced by the pair ion convective cell (PPCC) mode as the electron density becomes vanishingly small in a magnetized plasma comprised of positive and negative ions. The nonlinear dynamics of pure pair plasmas is described by two coupled equations which have no analog in electron-ion plasmas. In a stationary frame, it becomes similar to the Hasegawa-Mima equation but does not contain drift waves and ion acoustic waves.

Pair Production Induced by Ultrashort and Ultraintense Laser Pulses in Plasmas

NASA Astrophysics Data System (ADS)

Luo, Yue-E.; Wang, Xue-Wen; Wang, Yuan-Sheng; Ji, Shen-Tong; Yu, Hong

2018-06-01

The probability of Schwinger pair production is calculated, which is induced by an ultraintense and ultrashort laser pulse propagating in a plasma. The dependence of the probability on the amplitude of the laser pulse and the frequency of plasmas is analyzed. Particularly, the effect of the pulse duration on the probability is discussed, by introducing a pulse-shape function to describe the temporal shape of the laser pulse. The results show that a laser with shorter pulse is more efficient in pair production. The probability of pair production increases when the order of the duration is comparable to the period of a laser.

Progress towards a laser produced relativistic electron-positron pair plasma

DOE PAGES

Chen, Hui; Bonlie, J.; Cauble, R.; ...

2016-04-01

Here, a set of experiments has been performed exploring unique characteristics of pair jets and plasmas at several energetic short-pulse laser facilities including Titan at Livermore and OMEGA EP in Rochester, as well as the Osaka LFEX and AWE Orion lasers. New results are summarized, including positron beam emittance, scaling of pair production vs. laser energy, and initial results on the pair jet collimation using electromagnetic fields.

Dressed soliton in quantum dusty pair-ion plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatterjee, Prasanta; Muniandy, S. V.; Wong, C. S.

Nonlinear propagation of a quantum ion-acoustic dressed soliton is studied in a dusty pair-ion plasma. The Korteweg-de Vries (KdV) equation is derived using reductive perturbation technique. A higher order inhomogeneous differential equation is obtained for the higher order correction. The expression for a dressed soliton is calculated using a renormalization method. The expressions for higher order correction are determined using a series solution technique developed by Chatterjee et al. [Phys. Plasmas 16, 072102 (2009)].

Mode suppression of a two-dimensional potential relaxation instability in a weakly magnetized discharge plasma

NASA Astrophysics Data System (ADS)

Gyergyek, T.; Čerček, M.; Jelić, N.; Stanojević, M.

1993-05-01

A potential relaxation instability (PRI) is modulated by an external signal using an additional grid to modulate the radial plasma potential profile in a magnetized plasma column in a linear magnetized discharge plasma device. It is observed that the electrode current oscillations follow the van der Pol equation with an external forcing term, and the linear growth rate of the instability is measured.

Gadolinium-based magnetic resonance contrast agents at 7 Tesla: in vitro T1 relaxivities in human blood plasma.

PubMed

Noebauer-Huhmann, Iris M; Szomolanyi, Pavol; Juras, Vladimír; Kraff, Oliver; Ladd, Mark E; Trattnig, Siegfried

2010-09-01

PURPOSE/INTRODUCTION: The aim of this study was to determine the T1 relaxivities (r1) of 8 gadolinium (Gd)-based MR contrast agents in human blood plasma at 7 Tesla, compared with 3 Tesla. Eight commercially available Gd-based MR contrast agents were diluted in human blood plasma to concentrations of 0, 0.25, 0.5, 1, and 2 mmol/L. In vitro measurements were performed at 37 degrees C, on a 7 Tesla and on a 3 Tesla whole-body magnetic resonance imaging scanner. For the determination of T1 relaxation times, Inversion Recovery Sequences with inversion times from 0 to 3500 ms were used. The relaxivities were calculated. The r1 relaxivities of all agents, diluted in human blood plasma at body temperature, were lower at 7 Tesla than at 3 Tesla. The values at 3 Tesla were comparable to those published earlier. Notably, in some agents, a minor negative correlation of r1 with a concentration of up to 2 mmol/L could be observed. This was most pronounced in the agents with the highest protein-binding capacity. At 7 Tesla, the in vitro r1 relaxivities of Gd-based contrast agents in human blood plasma are lower than those at 3 Tesla. This work may serve as a basis for the application of Gd-based MR contrast agents at 7 Tesla. Further studies are required to optimize the contrast agent dose in vivo.

Weak nanoscale chaos and anomalous relaxation in DNA

NASA Astrophysics Data System (ADS)

Mazur, Alexey K.

2017-06-01

Anomalous nonexponential relaxation in hydrated biomolecules is commonly attributed to the complexity of the free-energy landscapes, similarly to polymers and glasses. It was found recently that the hydrogen-bond breathing of terminal DNA base pairs exhibits a slow power-law relaxation attributable to weak Hamiltonian chaos, with parameters similar to experimental data. Here, the relationship is studied between this motion and spectroscopic signals measured in DNA with a small molecular photoprobe inserted into the base-pair stack. To this end, the earlier computational approach in combination with an analytical theory is applied to the experimental DNA fragment. It is found that the intensity of breathing dynamics is strongly increased in the internal base pairs that flank the photoprobe, with anomalous relaxation quantitatively close to that in terminal base pairs. A physical mechanism is proposed to explain the coupling between the relaxation of base-pair breathing and the experimental response signal. It is concluded that the algebraic relaxation observed experimentally is very likely a manifestation of weakly chaotic dynamics of hydrogen-bond breathing in the base pairs stacked to the photoprobe and that the weak nanoscale chaos can represent an ubiquitous hidden source of nonexponential relaxation in ultrafast spectroscopy.

Weak nanoscale chaos and anomalous relaxation in DNA.

PubMed

Mazur, Alexey K

2017-06-01

Anomalous nonexponential relaxation in hydrated biomolecules is commonly attributed to the complexity of the free-energy landscapes, similarly to polymers and glasses. It was found recently that the hydrogen-bond breathing of terminal DNA base pairs exhibits a slow power-law relaxation attributable to weak Hamiltonian chaos, with parameters similar to experimental data. Here, the relationship is studied between this motion and spectroscopic signals measured in DNA with a small molecular photoprobe inserted into the base-pair stack. To this end, the earlier computational approach in combination with an analytical theory is applied to the experimental DNA fragment. It is found that the intensity of breathing dynamics is strongly increased in the internal base pairs that flank the photoprobe, with anomalous relaxation quantitatively close to that in terminal base pairs. A physical mechanism is proposed to explain the coupling between the relaxation of base-pair breathing and the experimental response signal. It is concluded that the algebraic relaxation observed experimentally is very likely a manifestation of weakly chaotic dynamics of hydrogen-bond breathing in the base pairs stacked to the photoprobe and that the weak nanoscale chaos can represent an ubiquitous hidden source of nonexponential relaxation in ultrafast spectroscopy.

QM and QM/MM Studies on Excited-State Relaxation Mechanisms of Unnatural Bases in Vacuo and Base Pairs in DNA.

PubMed

Wang, Qian; Xie, Xiao-Ying; Han, Juan; Cui, Ganglong

2017-11-22

Semisynthetic alphabet can potentially increase the genetic information stored in DNA through the formation of unusual base pairs such as d5SICS:dNaM. However, recent experiments show that near-visible-light irradiation on the d5SICS and dNaM chromophores could lead to genetic mutations and damages. Until now, their photophysical mechanisms remain elusive. Herein, we have employed MS-CASPT2//CASSCF and QM(MS-CASPT2//CASSCF)/MM methods to explore the spectroscopic properties and excited-state relaxation mechanisms of d5SICS, dNaM, and d5SICS:dNaM in DNA. We have found that (1) the S 2 state of d5SICS, the S 1 state of dNaM, and the S 2 state of d5SICS:dNaM are initially populated upon near-visible-light irradiation and (2) for d5SICS and d5SICS:dNaM, there are several parallel relaxation pathways to populate the lowest triplet state, but for dNaM, a main relaxation pathway is uncovered. Moreover, we have found that the excited-state relaxation mechanism of d5SICS:dNaM in DNA is similar to that of the isolated d5SICS chromophore. These mechanistic insights contribute to the understanding of photophysics and photochemistry of unusual base pairs and to the design of better semisynthetic genetic alphabet.

Temporal-spatial measurement of electron relaxation time in femtosecond laser induced plasma using two-color pump-probe imaging technique

NASA Astrophysics Data System (ADS)

Pan, Changji; Jiang, Lan; Wang, Qingsong; Sun, Jingya; Wang, Guoyan; Lu, Yongfeng

2018-05-01

The femtosecond (fs) laser is a powerful tool to study ultrafast plasma dynamics, especially electron relaxation in strong ionization of dielectrics. Herein, temporal-spatial evolution of femtosecond laser induced plasma in fused silica was investigated using a two-color pump-probe technique (i.e., 400 nm and 800 nm, respectively). We demonstrated that when ionized electron density is lower than the critical density, free electron relaxation time is inversely proportional to electron density, which can be explained by the electron-ion scattering regime. In addition, electron density evolution within plasma was analyzed in an early stage (first 800 fs) of the laser-material interaction.

Plasma Relaxation and Topological Aspects in Electron Magnetohydrodynamics

NASA Astrophysics Data System (ADS)

Shivamoggi, Bhimsen

2016-10-01

Parker's formulation of isotopological plasma relaxation process toward minimum magnetics energy states in magnetohydrodynamics (MHD) is extended to electron MHD (EMHD). The lower bound on magnetic energy in EMHD is determined by both the magnetic field and the electron vorticity field topologies, and is shown to be reduced further in EMHD by an amount proportional to the sum of total electron-flow kinetic energy and total electron-flow enstrophy. The EMHD Beltrami condition becomes equivalent to the potential vorticity conservation equation in two-dimensional (2D) hydrodynamics, and the torsion coefficient and turns out to be proportional to potential vorticity. The winding pattern of the magnetic field lines appears to evolve therefore in the same way as potential vorticity lines in 2D hydrodynamics.

Plasma relaxation and topological aspects in electron magnetohydrodynamics

NASA Astrophysics Data System (ADS)

Shivamoggi, B. K.

2016-07-01

Parker's formulation of isotopological plasma relaxation process toward minimum magnetics energy states in magnetohydrodynamics (MHD) is extended to electron MHD (EMHD). The lower bound on magnetic energy in EMHD is determined by both the magnetic field and the electron vorticity field topologies, and is shown to be reduced further in EMHD by an amount proportional to the sum of total electron-flow kinetic energy and total electron-flow enstrophy. The EMHD Beltrami condition becomes equivalent to the potential vorticity conservation equation in two-dimensional (2D) hydrodynamics, and the torsion coefficient α turns out to be proportional to potential vorticity. The winding pattern of the magnetic field lines appears to evolve, therefore, in the same way as potential vorticity lines in 2D hydrodynamics.

Collisional relaxation of an isotopic, strongly magnetized pure ion plasma and topics in resonant wave-particle interaction of plasmas

NASA Astrophysics Data System (ADS)

Chim, Chi Yung

First in Chapter 2, we discuss the collisional relaxation of a strongly magnetized pure ion plasma that is composed of two species with slightly different masses, but both with singly-ionized atoms. In a limit of high cyclotron frequencies O j, the total cyclotron action Ij for the two species are adiabatic invariants. In a few collisions, maximizing entropy yields a modified Gibbs distribution of the form exp[-H/T ∥-alpha1 I 1-alpha2I2]. Here, H is the total Hamiltonian and alphaj's are related to parallel and perpendicular temperatures through T ⊥j=(1/T∥ +alphaj/Oj) -1. On a longer timescale, the two species share action so that alpha 1 and alpha2 relax to a common value alpha. On an even longer timescale, the total action ceases to be a constant of the motion and alpha relaxes to zero. Next, weak transport produces a low density halo of electrons moving radially outward from the pure electron plasma core, and the m = 1 mode begins to damp algebraically when the halo reaches the wall. The damping rate is proportional to the particle flux through the resonant layer at the wall. Chapter 3 explains analytically the new algebraic damping due to both mobility and diffusion transport. Electrons swept around the resonant "cat's eye" orbits form a dipole (m = 1) density distribution, setting up a field that produces ExB-drift of the core back to the axis, that is, damps the mode. Finally, Chapter 4 provides a simple mechanistic interpretation of the resonant wave-particle interaction of Landau. For the simple case of a Vlasov plasma oscillation, the non-resonant electrons are driven resonantly by the bare electric field from the resonant electrons, and this complex driver field is of a phase to reduce the oscillation amplitude. The wave-particle resonant interaction also occurs in 2D ExB-drift waves, such as a diocotron wave. In this case, the bare electric field from the resonant electrons causes ExB-drift motion back in the core plasma, thus damping the wave.

Transient slowing down relaxation dynamics of the supercooled dusty plasma liquid after quenching.

PubMed

Su, Yen-Shuo; Io, Chong-Wai; I, Lin

2012-07-01

The spatiotemporal evolutions of microstructure and motion in the transient relaxation toward the steady supercooled liquid state after quenching a dusty plasma Wigner liquid, formed by charged dust particles suspended in a low pressure discharge, are experimentally investigated through direct optical microscopy. It is found that the quenched liquid slowly evolves to a colder state with more heterogeneities in structure and motion. Hopping particles and defects appear in the form of clusters with multiscale cluster size distributions. Via the structure rearrangement induced by the reduced thermal agitation from the cold thermal bath after quenching, the temporarily stored strain energy can be cascaded through the network to different newly distorted regions and dissipated after transferring to nonlinearly coupled motions with different scales. It leads to the observed self-similar multiscale slowing down relaxation with power law increases of structural order and structural relaxation time, the similar power law decreases of particle motions at different time scales, and the stronger and slower fluctuations with increasing waiting time toward the new steady state.

Dense GeV electron–positron pairs generated by lasers in near-critical-density plasmas

PubMed Central

Zhu, Xing-Long; Yu, Tong-Pu; Sheng, Zheng-Ming; Yin, Yan; Turcu, Ion Cristian Edmond; Pukhov, Alexander

2016-01-01

Pair production can be triggered by high-intensity lasers via the Breit–Wheeler process. However, the straightforward laser–laser colliding for copious numbers of pair creation requires light intensities several orders of magnitude higher than possible with the ongoing laser facilities. Despite the numerous proposed approaches, creating high-energy-density pair plasmas in laboratories is still challenging. Here we present an all-optical scheme for overdense pair production by two counter-propagating lasers irradiating near-critical-density plasmas at only ∼1022 W cm−2. In this scheme, bright γ-rays are generated by radiation-trapped electrons oscillating in the laser fields. The dense γ-photons then collide with the focused counter-propagating lasers to initiate the multi-photon Breit–Wheeler process. Particle-in-cell simulations indicate that one may generate a high-yield (1.05 × 1011) overdense (4 × 1022 cm−3) GeV positron beam using 10 PW scale lasers. Such a bright pair source has many practical applications and could be basis for future compact high-luminosity electron–positron colliders. PMID:27966530

Infant transmitted/founder HIV-1 viruses from peripartum transmission are neutralization resistant to paired maternal plasma

PubMed Central

Kumar, Amit; Smith, Claire E. P.; Giorgi, Elena E.; Martinez, David R.; Yusim, Karina; Stamper, Lisa; McGuire, Erin; Montefiori, David C.

2018-01-01

Despite extensive genetic diversity of HIV-1 in chronic infection, a single or few maternal virus variants become the founders of an infant’s infection. These transmitted/founder (T/F) variants are of particular interest, as a maternal or infant HIV vaccine should raise envelope (Env) specific IgG responses capable of blocking this group of viruses. However, the maternal or infant factors that contribute to selection of infant T/F viruses are not well understood. In this study, we amplified HIV-1 env genes by single genome amplification from 16 mother-infant transmitting pairs from the U.S. pre-antiretroviral era Women Infant Transmission Study (WITS). Infant T/F and representative maternal non-transmitted Env variants from plasma were identified and used to generate pseudoviruses for paired maternal plasma neutralization sensitivity analysis. Eighteen out of 21 (85%) infant T/F Env pseudoviruses were neutralization resistant to paired maternal plasma. Yet, all infant T/F viruses were neutralization sensitive to a panel of HIV-1 broadly neutralizing antibodies and variably sensitive to heterologous plasma neutralizing antibodies. Also, these infant T/F pseudoviruses were overall more neutralization resistant to paired maternal plasma in comparison to pseudoviruses from maternal non-transmitted variants (p = 0.012). Altogether, our findings suggest that autologous neutralization of circulating viruses by maternal plasma antibodies select for neutralization-resistant viruses that initiate peripartum transmission, raising the speculation that enhancement of this response at the end of pregnancy could further reduce infant HIV-1 infection risk. PMID:29672607

Effects of the plasma profiles on photon and pair production in ultrahigh intensity laser solid interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Y. X.; Jin, X. L., E-mail: jinxiaolin@uestc.edu.cn; Yan, W. Z.

The model of photon and pair production in strong field quantum electrodynamics is implemented into our 1D3V particle-in-cell code with Monte Carlo algorithm. Using this code, the evolution of the particles in ultrahigh intensity laser (∼10{sup 23} W/cm{sup 2}) interaction with aluminum foil target is observed. Four different initial plasma profiles are considered in the simulations. The effects of initial plasma profiles on photon and pair production, energy spectra, and energy evolution are analyzed. The results imply that one can set an optimal initial plasma profile to obtain the desired photon distributions.

Dynamics in a one-dimensional ferrogel model: relaxation, pairing, shock-wave propagation.

PubMed

Goh, Segun; Menzel, Andreas M; Löwen, Hartmut

2018-05-23

Ferrogels are smart soft materials, consisting of a polymeric network and embedded magnetic particles. Novel phenomena, such as the variation of the overall mechanical properties by external magnetic fields, emerge consequently. However, the dynamic behavior of ferrogels remains largely unveiled. In this paper, we consider a one-dimensional chain consisting of magnetic dipoles and elastic springs between them as a simple model for ferrogels. The model is evaluated by corresponding simulations. To probe the dynamics theoretically, we investigate a continuum limit of the energy governing the system and the corresponding equation of motion. We provide general classification scenarios for the dynamics, elucidating the touching/detachment dynamics of the magnetic particles along the chain. In particular, it is verified in certain cases that the long-time relaxation corresponds to solutions of shock-wave propagation, while formations of particle pairs underlie the initial stage of the dynamics. We expect that these results will provide insight into the understanding of the dynamics of more realistic models with randomness in parameters and time-dependent magnetic fields.

Ion acoustic waves in pair-ion plasma: Linear and nonlinear analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saeed, R.; Mushtaq, A.

2009-03-15

Linear and nonlinear properties of low frequency ion acoustic wave (IAW) in pair-ion plasma in the presence of electrons are investigated. The dispersion relation and Kadomtsev-Petviashvili equation for linear/nonlinear IAW are derived from sets of hydrodynamic equations where the ion pairs are inertial while electrons are Boltzmannian. The dispersion curves for various concentrations of electrons are discussed and compared with experimental results. The predicted linear IAW propagates at the same frequencies as those of the experimentally observed IAW if n{sub e0}{approx}10{sup 4} cm{sup -3}. It is found that nonlinear profile of the ion acoustic solitary waves is significantly affected bymore » the percentage ratio of electron number density and temperature. It is also determined that rarefactive solitary waves can propagate in this system. It is hoped that the results presented in this study would be helpful in understanding the salient features of the finite amplitude localized ion acoustic solitary pulses in a laboratory fullerene plasma.« less

Bimodal dielectric relaxation of electrolyte solutions in weakly polar solvents.

PubMed

Yamaguchi, Tsuyoshi; Koda, Shinobu

2014-12-28

The dielectric relaxation spectra of dilute electrolyte solutions in solvents of small dielectric constants are investigated both theoretically and experimentally. The theoretical calculation in our previous work [T. Yamaguchi, T. Matsuoka, and S. Koda, J. Chem. Phys. 135, 164511 (2011)] is reanalyzed, and it is shown that the dielectric relaxation spectra are composed of three components, namely, the relaxation of ionic atmosphere, the reorientational relaxation of ion pairs, and the collision between ions. The relaxation frequency of the slowest one increases with increasing the concentration, and the slower two relaxations, those of ionic atmosphere and ion pairs, merge into one at the concentration where the Debye length is comparable to the size of ions. Experimentally, the dielectric relaxation spectra of some electrolytes in two solvents, tetrahydrofuran and tetraglyme, are determined at frequencies from 300 kHz to 200 MHz, and the presence of the slower two relaxations was confirmed. The concentration dependence of the relaxation frequency is also in harmony with the theoretical calculation. The relationship between the dielectric relaxation spectra and the concentration dependence of the ionic conductivity is discussed.

Bimodal dielectric relaxation of electrolyte solutions in weakly polar solvents

NASA Astrophysics Data System (ADS)

Yamaguchi, Tsuyoshi; Koda, Shinobu

2014-12-01

The dielectric relaxation spectra of dilute electrolyte solutions in solvents of small dielectric constants are investigated both theoretically and experimentally. The theoretical calculation in our previous work [T. Yamaguchi, T. Matsuoka, and S. Koda, J. Chem. Phys. 135, 164511 (2011)] is reanalyzed, and it is shown that the dielectric relaxation spectra are composed of three components, namely, the relaxation of ionic atmosphere, the reorientational relaxation of ion pairs, and the collision between ions. The relaxation frequency of the slowest one increases with increasing the concentration, and the slower two relaxations, those of ionic atmosphere and ion pairs, merge into one at the concentration where the Debye length is comparable to the size of ions. Experimentally, the dielectric relaxation spectra of some electrolytes in two solvents, tetrahydrofuran and tetraglyme, are determined at frequencies from 300 kHz to 200 MHz, and the presence of the slower two relaxations was confirmed. The concentration dependence of the relaxation frequency is also in harmony with the theoretical calculation. The relationship between the dielectric relaxation spectra and the concentration dependence of the ionic conductivity is discussed.

Extended MHD Modeling of Tearing-Driven Magnetic Relaxation

NASA Astrophysics Data System (ADS)

Sauppe, Joshua

2016-10-01

Driven plasma pinch configurations are characterized by the gradual accumulation and episodic release of free energy in discrete relaxation events. The hallmark of this relaxation in a reversed-field pinch (RFP) plasma is flattening of the parallel current density profile effected by a fluctuation-induced dynamo emf in Ohm's law. Nonlinear two-fluid modeling of macroscopic RFP dynamics has shown appreciable coupling of magnetic relaxation and the evolution of plasma flow. Accurate modeling of RFP dynamics requires the Hall effect in Ohm's law as well as first order ion finite Larmor radius (FLR) effects, represented by the Braginskii ion gyroviscous stress tensor. New results find that the Hall dynamo effect from < J × B > / ne can counter the MHD effect from - < V × B > in some of the relaxation events. The MHD effect dominates these events and relaxes the current profile toward the Taylor state, but the opposition of the two dynamos generates plasma flow in the direction of equilibrium current density, consistent with experimental measurements. Detailed experimental measurements of the MHD and Hall emf terms are compared to these extended MHD predictions. Tracking the evolution of magnetic energy, helicity, and hybrid helicity during relaxation identifies the most important contributions in single-fluid and two-fluid models. Magnetic helicity is well conserved relative to the magnetic energy during relaxation. The hybrid helicity is dominated by magnetic helicity in realistic low-beta pinch conditions and is also well conserved. Differences of less than 1 % between magnetic helicity and hybrid helicity are observed with two-fluid modeling and result from cross helicity evolution through ion FLR effects, which have not been included in contemporary relaxation theories. The kinetic energy driven by relaxation in the computations is dominated by velocity components perpendicular to the magnetic field, an effect that had not been predicted. Work performed at

The effect of dissolved oxygen on the relaxation rates of blood plasma: Implications for hyperoxia calibrated BOLD.

PubMed

Ma, Yuhan; Berman, Avery J L; Pike, G Bruce

2016-12-01

To determine the contribution of paramagnetic dissolved oxygen in blood plasma to blood-oxygenation-level-dependent (BOLD) signal changes in hyperoxic calibrated BOLD studies. Bovine blood plasma samples were prepared with partial pressures of oxygen (pO 2 ) ranging from 110 to 600 mmHg. R 1 , R 2 , and R 2 * of the plasma with dissolved oxygen were measured using quantitative MRI sequences at 3 Tesla. Simulations were performed to predict the relative effects of dissolved oxygen and deoxyhemoglobin changes in hyperoxia calibrated BOLD. The relaxivities of dissolved oxygen in plasma were found to be r 1, O2 =1.97 ± 0.09 ×10 -4 s -1 mmHg -1 , r 2, O2 =2.3 ± 0.7 ×10 -4 s -1 mmHg -1 , and r 2, O2 * = 2.3 ± 0.7 ×10 -4 s -1 mmHg -1 . Simulations predict that neither the transverse nor longitudinal relaxation rates of dissolved oxygen contribute significantly to the BOLD signal during hyperoxia. During hyperoxia, the increases in R 2 and R 2 * of blood from dissolved oxygen in plasma are considerably less than the decreases in R 2 and R 2 * from venous deoxyhemoglobin. R 1 effects due to dissolved oxygen are also predicted to be negligible. As a result, dissolved oxygen in arteries should not contribute significantly to the hyperoxic calibrated BOLD signal. Magn Reson Med 76:1905-1911, 2016. © 2015 International Society for Magnetic Resonance in Medicine. © 2015 International Society for Magnetic Resonance in Medicine.

Two dimensional nonplanar evolution of electrostatic shock waves in pair-ion plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masood, W.; Rizvi, H.

2012-01-15

Electrostatic waves in a two dimensional nonplanar geometry are studied in an unmagnetized, dissipative pair-ion plasma in the presence of weak transverse perturbations. The dissipation in the system is taken into account by incorporating the kinematic viscosity of both positive and negative ions in plasmas. The nonplanar Kadomtsev-Petviashvili-Burgers (KPB) as well as the Burgers Kadomtsev-Petviashvili (Burgers KP) equations are derived using the small amplitude expansion method and the range of applicability of both the equations are discussed. The system under consideration is observed to admit compressive rarefactive shocks. The present study may have relevance to understand the formation of twomore » dimensional nonplanar electrostatic shocks in laboratory plasmas.« less

MHD simulation of relaxation transition to a flipped relaxed state in spherical torus

NASA Astrophysics Data System (ADS)

Kanki, Takashi; Nagata, Masayoshi; Kagei, Yasuhiro

2008-11-01

Recently, it has been demonstrated in the HIST device that in spite of the violation of the Kruskal-Shafranov stability condition, a normal spherical torus (ST) plasma has relaxed to a flipped ST state through a transient reversed-field pinch-like state when the vacuum toroidal field is decreased and its direction is reversed [1]. It has been also observed during this relaxation transition process that not only the toroidal field but also the poloidal field reverses polarity spontaneously and that the ion flow velocity is strongly fluctuated and abruptly increased up to > 50 km/s. The purpose of the present study is to investigate the plasma flows and the relevant MHD relaxation phenomena to elucidate this transition mechanism by using three-dimensional MHD simulations [2]. It is found from the numerical results that the magnetic reconnection between the open and closed field lines occurs due to the non-linear growth of the n=1 kink instability of the central open flux, generating the toroidal flow ˜ 60 km/s in the direction of the toroidal current. The n=1 kink instability and the plasma flows driven by the magnetic reconnection are consider to be responsible for the self-reversal of the magnetic fields. [1] M. Nagata el al., Phys. Rev. Lett. 90, 225001 (2003). [2] Y. Kagei el al., Plasma. Phys. Control. Fusion 45, L17 (2003).

Generation of neutral and high-density electron-positron pair plasmas in the laboratory.

PubMed

Sarri, G; Poder, K; Cole, J M; Schumaker, W; Di Piazza, A; Reville, B; Dzelzainis, T; Doria, D; Gizzi, L A; Grittani, G; Kar, S; Keitel, C H; Krushelnick, K; Kuschel, S; Mangles, S P D; Najmudin, Z; Shukla, N; Silva, L O; Symes, D; Thomas, A G R; Vargas, M; Vieira, J; Zepf, M

2015-04-23

Electron-positron pair plasmas represent a unique state of matter, whereby there exists an intrinsic and complete symmetry between negatively charged (matter) and positively charged (antimatter) particles. These plasmas play a fundamental role in the dynamics of ultra-massive astrophysical objects and are believed to be associated with the emission of ultra-bright gamma-ray bursts. Despite extensive theoretical modelling, our knowledge of this state of matter is still speculative, owing to the extreme difficulty in recreating neutral matter-antimatter plasmas in the laboratory. Here we show that, by using a compact laser-driven setup, ion-free electron-positron plasmas with unique characteristics can be produced. Their charge neutrality (same amount of matter and antimatter), high-density and small divergence finally open up the possibility of studying electron-positron plasmas in controlled laboratory experiments.

NMR scalar couplings across Watson–Crick base pair hydrogen bonds in DNA observed by transverse relaxation-optimized spectroscopy

PubMed Central

Pervushin, Konstantin; Ono, Akira; Fernández, César; Szyperski, Thomas; Kainosho, Masatsune; Wüthrich, Kurt

1998-01-01

This paper describes the NMR observation of 15N—15N and 1H—15N scalar couplings across the hydrogen bonds in Watson–Crick base pairs in a DNA duplex, hJNN and hJHN. These couplings represent new parameters of interest for both structural studies of DNA and theoretical investigations into the nature of the hydrogen bonds. Two dimensional [15N,1H]-transverse relaxation-optimized spectroscopy (TROSY) with a 15N-labeled 14-mer DNA duplex was used to measure hJNN, which is in the range 6–7 Hz, and the two-dimensional hJNN-correlation-[15N,1H]-TROSY experiment was used to correlate the chemical shifts of pairs of hydrogen bond-related 15N spins and to observe, for the first time, hJHN scalar couplings, with values in the range 2–3.6 Hz. TROSY-based studies of scalar couplings across hydrogen bonds should be applicable for large molecular sizes, including protein-bound nucleic acids. PMID:9826668

Erratum: A Simple, Analytical Model of Collisionless Magnetic Reconnection in a Pair Plasma

NASA Technical Reports Server (NTRS)

Hesse, Michael; Zenitani, Seiji; Kuznetsova, Masha; Klimas, Alex

2011-01-01

The following describes a list of errata in our paper, "A simple, analytical model of collisionless magnetic reconnection in a pair plasma." It supersedes an earlier erratum. We recently discovered an error in the derivation of the outflow-to-inflow density ratio.

Generation of neutral and high-density electron–positron pair plasmas in the laboratory

PubMed Central

Sarri, G.; Poder, K.; Cole, J. M.; Schumaker, W.; Di Piazza, A.; Reville, B.; Dzelzainis, T.; Doria, D.; Gizzi, L. A.; Grittani, G.; Kar, S.; Keitel, C. H.; Krushelnick, K.; Kuschel, S.; Mangles, S. P. D.; Najmudin, Z.; Shukla, N.; Silva, L. O.; Symes, D.; Thomas, A. G. R.; Vargas, M.; Vieira, J.; Zepf, M.

2015-01-01

Electron–positron pair plasmas represent a unique state of matter, whereby there exists an intrinsic and complete symmetry between negatively charged (matter) and positively charged (antimatter) particles. These plasmas play a fundamental role in the dynamics of ultra-massive astrophysical objects and are believed to be associated with the emission of ultra-bright gamma-ray bursts. Despite extensive theoretical modelling, our knowledge of this state of matter is still speculative, owing to the extreme difficulty in recreating neutral matter–antimatter plasmas in the laboratory. Here we show that, by using a compact laser-driven setup, ion-free electron–positron plasmas with unique characteristics can be produced. Their charge neutrality (same amount of matter and antimatter), high-density and small divergence finally open up the possibility of studying electron–positron plasmas in controlled laboratory experiments. PMID:25903920

Exact solution of CKP equation and formation and interaction of two solitons in pair-ion-electron plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Batool, Nazia; Jahangir, R.; National Center of Physics

In the present investigation, cylindrical Kadomstev-Petviashvili (CKP) equation is derived in pair-ion-electron plasmas to study the propagation and interaction of two solitons. Using a novel gauge transformation, two soliton solutions of CKP equation are found analytically by using Hirota's method and to the best of our knowledge have been used in plasma physics for the first time. Interestingly, it is observed that unlike the planar Kadomstev-Petviashvili (KP) equation, the CKP equation admits horseshoe-like solitary structures. Another non-trivial feature of CKP solitary solution is that the interaction parameter gets modified by the plasma parameters contrary to the one obtained for Korteweg–demore » Vries equation. The importance of the present investigation to understand the formation and interaction of solitons in laboratory produced pair plasmas is also highlighted.« less

Current-driven ion-acoustic and potential-relaxation instabilities excited in plasma plume during electron beam welding

NASA Astrophysics Data System (ADS)

Trushnikov, D. N.; Mladenov, G. M.; Belenkiy, V. Ya.; Koleva, E. G.; Varushkin, S. V.

2014-04-01

Many papers have sought correlations between the parameters of secondary particles generated above the beam/work piece interaction zone, dynamics of processes in the keyhole, and technological processes. Low- and high-frequency oscillations of the current, collected by plasma have been observed above the welding zone during electron beam welding. Low-frequency oscillations of secondary signals are related to capillary instabilities of the keyhole, however; the physical mechanisms responsible for the high-frequency oscillations (>10 kHz) of the collected current are not fully understood. This paper shows that peak frequencies in the spectra of the collected high-frequency signal are dependent on the reciprocal distance between the welding zone and collector electrode. From the relationship between current harmonics frequency and distance of the collector/welding zone, it can be estimated that the draft velocity of electrons or phase velocity of excited waves is about 1600 m/s. The dispersion relation with the properties of ion-acoustic waves is related to electron temperature 10 000 K, ion temperature 2 400 K and plasma density 1016 m-3, which is analogues to the parameters of potential-relaxation instabilities, observed in similar conditions. The estimated critical density of the transported current for creating the anomalous resistance state of plasma is of the order of 3 A.m-2, i.e. 8 mA for a 3-10 cm2 collector electrode. Thus, it is assumed that the observed high-frequency oscillations of the current collected by the positive collector electrode are caused by relaxation processes in the plasma plume above the welding zone, and not a direct demonstration of oscillations in the keyhole.

Water-separated ion pairs cause the slow dielectric mode of magnesium sulfate solutions

NASA Astrophysics Data System (ADS)

Mamatkulov, Shavkat I.; Rinne, Klaus F.; Buchner, Richard; Netz, Roland R.; Bonthuis, Douwe Jan

2018-06-01

We compare the dielectric spectra of aqueous MgSO4 and Na2SO4 solutions calculated from classical molecular dynamics simulations with experimental data, using an optimized thermodynamically consistent sulfate force field. Both the concentration-dependent shift of the static dielectric constant and the spectral shape match the experimental results very well for Na2SO4 solutions. For MgSO4 solutions, the simulations qualitatively reproduce the experimental observation of a slow mode, the origin of which we trace back to the ion-pair relaxation contribution via spectral decomposition. The radial distribution functions show that Mg2+ and SO42 - ions form extensive water-separated—and thus strongly dipolar—ion pairs, the orientational relaxation of which provides a simple physical explanation for the prominent slow dielectric mode in MgSO4 solutions. Remarkably, the Mg2+-SO42 - ion-pair relaxation extends all the way into the THz range, which we rationalize by the vibrational relaxation of tightly bound water-separated ion pairs. Thus, the relaxation of divalent ion pairs can give rise to widely separated orientational and vibrational spectroscopic features.

An electromyographic study of muscle relaxants in man.

PubMed

Suzuki, H; Kanayama, T; Nakagawa, H; Yazaki, S; Shiratsuchi, T

1975-05-01

Supramaximal paired stimuli were applied to the ulnar nerve, and the amplitude of the muscle action potential evoked in the abductor digiti minimi by the second member of the stimulus pair (test response) was compared with that evoked by the first component (conditioning response). The interval between the two components of the stimulus pair (the pair interval) was increased stepwise from 7 to 100 msec and a curve (recovery curve) was obtained by relating the changes in pair interval to the difference in amplitude of the test and conditioning responses. Alterations of the recovery curve (RC) during partial paralysis by muscle relaxants were investigated in healthy adult patients under the lightest plane of general anaesthesia. The control curve obtained in 32 subjects before the administration of a muscle relaxant drug was characterized by slight depressions at very short intervals of paired stimuli, followed by a slight potentiation at 20-100 msec. With non-depolarizing relaxants, RC altered to the characteristic pattern of potentiation at very short intervals of stimuli, followed by a notable depression at longer intervals. In depolarizing blocks with small doses of suxamethonium, the depression of RC at short intervals in the control was enhanced and the pattern of RC was different from that of non-depolarizing agents. When desensitization blocks were instigated by the i.v. administration of suxamethonium, the RC patterns were similar to those of competitive agents.

Ideal relaxation of the Hopf fibration

NASA Astrophysics Data System (ADS)

Smiet, Christopher Berg; Candelaresi, Simon; Bouwmeester, Dirk

2017-07-01

Ideal magnetohydrodynamics relaxation is the topology-conserving reconfiguration of a magnetic field into a lower energy state where the net force is zero. This is achieved by modeling the plasma as perfectly conducting viscous fluid. It is an important tool for investigating plasma equilibria and is often used to study the magnetic configurations in fusion devices and astrophysical plasmas. We study the equilibrium reached by a localized magnetic field through the topology conserving relaxation of a magnetic field based on the Hopf fibration in which magnetic field lines are closed circles that are all linked with one another. Magnetic fields with this topology have recently been shown to occur in non-ideal numerical simulations. Our results show that any localized field can only attain equilibrium if there is a finite external pressure, and that for such a field a Taylor state is unattainable. We find an equilibrium plasma configuration that is characterized by a lowered pressure in a toroidal region, with field lines lying on surfaces of constant pressure. Therefore, the field is in a Grad-Shafranov equilibrium. Localized helical magnetic fields are found when plasma is ejected from astrophysical bodies and subsequently relaxes against the background plasma, as well as on earth in plasmoids generated by, e.g., a Marshall gun. This work shows under which conditions an equilibrium can be reached and identifies a toroidal depression as the characteristic feature of such a configuration.

Spontaneous pairing and cooperative movements of micro-particles in a two dimensional plasma crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhdanov, S. K.; Couëdel, L., E-mail: lenaic.couedel@univ-amu.fr; Nosenko, V.

2015-05-15

In an argon plasma of 20 W rf discharge at a pressure of 1.38 Pa, a stable highly ordered monolayer of microparticles is suspended. We observe spontaneous particle pairing when suddenly reducing the gas pressure. Special types of dynamical activity, in particular, entanglement and cooperative movements of coupled particles have been registered. In the course of the experiment first appeared single vertical pairs of particles, in further they gradually accumulated causing melting of the entire crystal. To record pairing events, the particle suspension is side-view imaged using a vertically extended laser sheet. The long-lasting pre-melting phase assured the credible recording and identificationmore » of isolated particle pairs. The high monolayer charge density is crucial to explain the spontaneous pairing events observed in our experiments as the mutual repulsion between the particles comprising the monolayer make its vertical extend thicker.« less

Relaxivity of Ferumoxytol at 1.5 T and 3.0 T.

PubMed

Knobloch, Gesine; Colgan, Timothy; Wiens, Curtis N; Wang, Xiaoke; Schubert, Tilman; Hernando, Diego; Sharma, Samir D; Reeder, Scott B

2018-05-01

The aim of this study was to determine the relaxation properties of ferumoxytol, an off-label alternative to gadolinium-based contrast agents, under physiological conditions at 1.5 T and 3.0 T. Ferumoxytol was diluted in gradually increasing concentrations (0.26-4.2 mM) in saline, human plasma, and human whole blood. Magnetic resonance relaxometry was performed at 37°C at 1.5 T and 3.0 T. Longitudinal and transverse relaxation rate constants (R1, R2, R2*) were measured as a function of ferumoxytol concentration, and relaxivities (r1, r2, r2*) were calculated. A linear dependence of R1, R2, and R2* on ferumoxytol concentration was found in saline and plasma with lower R1 values at 3.0 T and similar R2 and R2* values at 1.5 T and 3.0 T (1.5 T: r1saline = 19.9 ± 2.3 smM; r1plasma = 19.0 ± 1.7 smM; r2saline = 60.8 ± 3.8 smM; r2plasma = 64.9 ± 1.8 smM; r2*saline = 60.4 ± 4.7 smM; r2*plasma = 64.4 ± 2.5 smM; 3.0 T: r1saline = 10.0 ± 0.3 smM; r1plasma = 9.5 ± 0.2 smM; r2saline = 62.3 ± 3.7 smM; r2plasma = 65.2 ± 1.8 smM; r2*saline = 57.0 ± 4.7 smM; r2*plasma = 55.7 ± 4.4 smM). The dependence of relaxation rates on concentration in blood was nonlinear. Formulas from second-order polynomial fittings of the relaxation rates were calculated to characterize the relationship between R1blood and R2 blood with ferumoxytol. Ferumoxytol demonstrates strong longitudinal and transverse relaxivities. Awareness of the nonlinear relaxation behavior of ferumoxytol in blood is important for ferumoxytol-enhanced magnetic resonance imaging applications and for protocol optimization.

Current-driven ion-acoustic and potential-relaxation instabilities excited in plasma plume during electron beam welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trushnikov, D. N., E-mail: trdimitr@yandex.ru; Mladenov, G. M., E-mail: gmmladenov@abv.bg; Koleva, E. G., E-mail: eligeorg@abv.bg

Many papers have sought correlations between the parameters of secondary particles generated above the beam/work piece interaction zone, dynamics of processes in the keyhole, and technological processes. Low- and high-frequency oscillations of the current, collected by plasma have been observed above the welding zone during electron beam welding. Low-frequency oscillations of secondary signals are related to capillary instabilities of the keyhole, however; the physical mechanisms responsible for the high-frequency oscillations (>10 kHz) of the collected current are not fully understood. This paper shows that peak frequencies in the spectra of the collected high-frequency signal are dependent on the reciprocal distancemore » between the welding zone and collector electrode. From the relationship between current harmonics frequency and distance of the collector/welding zone, it can be estimated that the draft velocity of electrons or phase velocity of excited waves is about 1600 m/s. The dispersion relation with the properties of ion-acoustic waves is related to electron temperature 10 000 K, ion temperature 2 400 K and plasma density 10{sup 16} m{sup −3}, which is analogues to the parameters of potential-relaxation instabilities, observed in similar conditions. The estimated critical density of the transported current for creating the anomalous resistance state of plasma is of the order of 3 A·m{sup −2}, i.e. 8 mA for a 3–10 cm{sup 2} collector electrode. Thus, it is assumed that the observed high-frequency oscillations of the current collected by the positive collector electrode are caused by relaxation processes in the plasma plume above the welding zone, and not a direct demonstration of oscillations in the keyhole.« less

A Simple, Analytical Model of Collisionless Magnetic Reconnection in a Pair Plasma

NASA Technical Reports Server (NTRS)

Hesse, Michael; Zenitani, Seiji; Kuznetova, Masha; Klimas, Alex

2011-01-01

A set of conservation equations is utilized to derive balance equations in the reconnection diffusion region of a symmetric pair plasma. The reconnection electric field is assumed to have the function to maintain the current density in the diffusion region, and to impart thermal energy to the plasma by means of quasi-viscous dissipation. Using these assumptions it is possible to derive a simple set of equations for diffusion region parameters in dependence on inflow conditions and on plasma compressibility. These equations are solved by means of a simple, iterative, procedure. The solutions show expected features such as dominance of enthalpy flux in the reconnection outflow, as well as combination of adiabatic and quasi-viscous heating. Furthermore, the model predicts a maximum reconnection electric field of E(sup *)=0.4, normalized to the parameters at the inflow edge of the diffusion region.

Evolution of the plasma-sprayed microstructure in 7 wt% yttria-stabilized zirconia thermal barrier coatings during uniaxial stress relaxation and the concomitant changes in material properties

NASA Astrophysics Data System (ADS)

Petorak, Christopher

The understanding of failure mechanisms in plasma sprayed 7 wt% yttria stabilized zirconia (YSZ) is a key step toward optimizing thermal barrier coating (TBC) usage, design, and life prediction. The purpose of the present work is to characterize and understand the stress relaxation behavior occurring in plasma-sprayed YSZ coatings, so that the correlating magnitude of unfavorable tensile stress, which coatings experienced upon cooling, may be reduced through microstructural design. The microstructure and properties of as-sprayed coatings changes immensely during service at high temperature, and therefore the effects of long heat-treatment times, and the concomitant change within the microstructure, on the time-dependent mechanical behavior of stand-alone YSZ coatings was studied in parallel with the as-sprayed coating condition. Aside from influencing the mechanical properties, stress relaxation also affects the insulating efficiency of plasma-sprayed 7wt% YSZ coatings. Directionally dependent changes in microstructure due to stress relaxation of a uniaxially applied stress at 1200°C were observed in plasma-sprayed coatings. Small angle neutron scattering (SANS) investigation of coatings after stress relaxation displayed a 46% reduction in the specific surface area connected to the load-orientation dependent closure of void surface area perpendicular to the applied load when compared to coatings sintered in air, i.e. no applied load. These anisotropic microstructural changes were linked to the thermal properties of the coating. For example, a coating stress relaxed from 60 MPa for 5-min at 1200°C exhibited a thermal conductivity of 2.1 W/m-K. A coating that was only heat-treated for 5-min at 1200°C (i.e. no stress applied) exhibited a thermal conductivity of 1.7 W/m·K. In the current study, uniaxial stress relaxation in plasma-sprayed 7wt% YSZ coatings was determined the result of: (1) A more uniform distribution of the applied load with time, (2) A reduction

High-throughput and simultaneous analysis of eight central-acting muscle relaxants in human plasma by ultra-performance liquid chromatography-tandem mass spectrometry in the positive and negative ionization modes.

PubMed

Ogawa, Tadashi; Hattori, Hideki; Kaneko, Rina; Ito, Kenjiro; Iwai, Masae; Mizutani, Yoko; Arinobu, Tetsuya; Ishii, Akira; Seno, Hiroshi

2011-06-01

In this report, a high-throughput and sensitive method for analysis of eight central-acting muscle relaxants in human plasma by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) in the positive and negative ionization modes using tolbutamide as internal standard is presented. After pretreatment of a plasma sample by solid-phase extraction with an Oasis HLB cartridge, muscle relaxants were analyzed by UPLC with Acquity UPLC BEH C(18) column and Acquity TQD tandem quadrupole mass spectrometer equipped with an electrospray ionization interface. The calibration curves for muscle relaxants spiked into human plasma equally showed good linearities in the nanogram per milliliter order range. The detection limits (signal-to-noise ratio = 3) was as low as 0.1-2 ng/mL. The method gave satisfactory recovery rates, accuracy, and precision for quality control samples spiked with muscle relaxants. To further validate the present method, 250 mg of chlorphenesin carbamate was orally administered to a healthy male volunteer, and the concentrations of chlorphenesin carbamate in plasma were measured 0.5, 1, 2, 4, 6, and 8 h after dosing; their concentrations in human plasma were between 0.62 and 2.44 μg/mL. To our knowledge, this is the first report describing simultaneous analysis of over more than two central-acting muscle relaxants by liquid chromatography-tandem mass spectrometry. This has been realized by the capability of our instrument for simultaneous multiple reaction monitoring of the target compounds in both positive and negative ionization modes. Therefore, the present method seems very useful in forensic and clinical toxicology and pharmacokinetic studies.

A simple, analytical model of collisionless magnetic reconnection in a pair plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hesse, Michael; Zenitani, Seiji; Kuznetsova, Masha

2009-10-15

A set of conservation equations is utilized to derive balance equations in the reconnection diffusion region of a symmetric pair plasma. The reconnection electric field is assumed to have the function to maintain the current density in the diffusion region and to impart thermal energy to the plasma by means of quasiviscous dissipation. Using these assumptions it is possible to derive a simple set of equations for diffusion region parameters in dependence on inflow conditions and on plasma compressibility. These equations are solved by means of a simple, iterative procedure. The solutions show expected features such as dominance of enthalpymore » flux in the reconnection outflow, as well as combination of adiabatic and quasiviscous heating. Furthermore, the model predicts a maximum reconnection electric field of E{sup *}=0.4, normalized to the parameters at the inflow edge of the diffusion region.« less

Solitary Ring Pairs and Non-Thermal Regimes in Plasmas Connected with Black Holes*

NASA Astrophysics Data System (ADS)

Coppi, Bruno

2011-10-01

The two-dimensional plasma and field configurations that can be associated with compact objects such as black holes are described, (in the limit where assuming a scalar pressure can be justified), by two characteristic non-linear equations: i) one that connects the plasma density profile to that of the relevant magnetic surfaces and is called the ``master equation'': ii) the other, the ``vertical equilibrium equation,'' connects the plasma pressure to the density and the magnetic surfaces and is closely related to the G-S equation for magnetically confined laboratory plasmas. Two kinds of solutions are found that consist of: i) a periodic sequence of plasma rings; ii) solitary pairs of rings. Experimental observations support the presence of rings around collapsed objects. Tridimensional configuration are found in the linear approximation as consisting of trailing spirals. Observations of High Frequency Quasi-Periodic oscillations implies that they originate from 3-dimentional structures. The existing theory is extended to involve non-thermal particle distributions in order to comply with relevant experimental observations. *Sponsored in part by the U.S. DOE.

Particle acceleration during magnetic reconnection in a low-beta pair plasma

DOE PAGES

Guo, Fan; Li, Hui; Daughton, William; ...

2016-04-29

Plasma energization through magnetic reconnection in the magnetically dominated regime featured by low plasma beta (β=8πnkT0/B 2 <<1) and/or high magnetization (σ=B 2/(4πnmc 2)>>1) is important in a series of astrophysical systems such as solar flares, pulsar wind nebula, and relativistic jets from black holes. In this paper, we review the recent progress on kinetic simulations of this process and further discuss plasma dynamics and particle acceleration in a low-β reconnection layer that consists of electron–positron pairs. We also examine the effect of different initial thermal temperatures on the resulting particle energy spectra. While earlier papers have concluded that themore » spectral index is smaller for higher σ, our simulations show that the spectral index approaches p = 1 for sufficiently low plasma β, even if σ~1. Since this predicted spectral index in the idealized limit is harder than most observations, it is important to consider effects that can lead to a softer spectrum such as open boundary simulations. Here, we also remark that the effects of three-dimensional reconnection physics and turbulence on reconnection need to be addressed in the future.« less

Particle acceleration during magnetic reconnection in a low-beta pair plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Fan; Li, Hui; Daughton, William

Plasma energization through magnetic reconnection in the magnetically dominated regime featured by low plasma beta (β=8πnkT0/B 2 <<1) and/or high magnetization (σ=B 2/(4πnmc 2)>>1) is important in a series of astrophysical systems such as solar flares, pulsar wind nebula, and relativistic jets from black holes. In this paper, we review the recent progress on kinetic simulations of this process and further discuss plasma dynamics and particle acceleration in a low-β reconnection layer that consists of electron–positron pairs. We also examine the effect of different initial thermal temperatures on the resulting particle energy spectra. While earlier papers have concluded that themore » spectral index is smaller for higher σ, our simulations show that the spectral index approaches p = 1 for sufficiently low plasma β, even if σ~1. Since this predicted spectral index in the idealized limit is harder than most observations, it is important to consider effects that can lead to a softer spectrum such as open boundary simulations. Here, we also remark that the effects of three-dimensional reconnection physics and turbulence on reconnection need to be addressed in the future.« less

Accumulation of flame retardants in paired eggs and plasma of bald eagles.

PubMed

Guo, Jiehong; Simon, Kendall; Romanak, Kevin; Bowerman, William; Venier, Marta

2018-06-01

In this study, we measured the concentrations of 58 flame retardants (and related compounds) in bald eagle (Haliaeetus leucocephalus) egg and plasma samples from the Michigan. These analytes include polybrominated diphenyl ethers (PBDEs), novel flame retardants (nFRs), Dechlorane-related compounds (Decs), and organophosphate esters (OPEs). A total of 24 paired eaglet plasma and egg samples were collected from inland (IN, N = 13) and the Great Lakes (GL, N = 11) breeding areas from 2000 to 2012. PBDEs were the most abundant chemical group with a geometric mean of 181 ng/g wet weight (ww) in egg and 5.31 ng/g ww in plasma. Decs were barely found in plasma samples, but they were frequently found in eggs (geometric mean 23.5 ng/g ww). OPE levels were comparable to those of PBDEs in the plasma but lower than those of PBDEs in eggs. Dec and PBDE concentrations were significantly higher in GL than in IN (p < 0.05). The ratio of egg to plasma concentrations (lipid normalized) varied with chemicals and correlated with the chemical's octanol-water partition coefficient. The lipid normalized bald eagle egg and plasma concentrations from Lake Superior and Huron were one to three orders of magnitude higher than concentrations measured in composite lake trout (Salvelinus namaycush) from the same lake, implying that they biomagnify in the environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Ion Streaming Instabilities in Pair Ion Plasma and Localized Structure with Non-Thermal Electrons

NASA Astrophysics Data System (ADS)

Nasir Khattak, M.; Mushtaq, A.; Qamar, A.

2015-12-01

Pair ion plasma with a fraction of non-thermal electrons is considered. We investigate the effects of the streaming motion of ions on linear and nonlinear properties of unmagnetized, collisionless plasma by using the fluid model. A dispersion relation is derived, and the growth rate of streaming instabilities with effect of streaming motion of ions and non-thermal electrons is calculated. A qausi-potential approach is adopted to study the characteristics of ion acoustic solitons. An energy integral equation involving Sagdeev potential is derived during this process. The presence of the streaming term in the energy integral equation affects the structure of the solitary waves significantly along with non-thermal electrons. Possible application of the work to the space and laboratory plasmas are highlighted.

Nonlinear structure formation in ion-temperature-gradient driven drift waves in pair-ion plasma with nonthermal electron distribution

NASA Astrophysics Data System (ADS)

Razzaq, Javaria; Haque, Q.; Khan, Majid; Bhatti, Adnan Mehmood; Kamran, M.; Mirza, Arshad M.

2018-02-01

Nonlinear structure formation in ion-temperature-gradient (ITG) driven waves is investigated in pair-ion plasma comprising ions and nonthermal electrons (kappa, Cairns). By using the transport equations of the Braginskii model, a new set of nonlinear equations are derived. A linear dispersion relation is obtained and discussed analytically as well as numerically. It is shown that the nonthermal population of electrons affects both the linear and nonlinear characteristics of the ITG mode in pair-ion plasma. This work will be useful in tokamaks and stellarators where non-Maxwellian population of electrons may exist due to resonant frequency heating, electron cyclotron heating, runaway electrons, etc.

Spin relaxation of radicals in cryptochrome and its role in avian magnetoreception

DOE Office of Scientific and Technical Information (OSTI.GOV)

Worster, Susannah; Kattnig, Daniel R.; Hore, P. J., E-mail: peter.hore@chem.ox.ac.uk

2016-07-21

Long-lived spin coherence and rotationally ordered radical pairs have previously been identified as key requirements for the radical pair mechanism of the avian magnetic compass sense. Both criteria are hard to meet in a biological environment, where thermal motion of the radicals creates dynamic disorder and drives efficient spin relaxation. This has long been cited as a major stumbling block of the radical pair hypothesis. Here we combine Redfield relaxation theory with analytical solutions to a rotational diffusion equation to assess the impact of restricted rotational motion of the radicals on the operation of the compass. The effects of suchmore » motions are first investigated generally in small, model systems and are then critically examined in the magnetically sensitive flavin-tryptophan radical pair that is formed photochemically in the proposed magnetoreceptor protein, cryptochrome. We conclude that relaxation is slowest when rotational motion of the radicals within the protein is fast and highly constrained; that in a regime of slow relaxation, the motional averaging of hyperfine interactions has the potential to improve the sensitivity of the compass; and that consideration of motional effects can significantly alter the design criteria for an optimal compass. In addition, we demonstrate that motion of the flavin radical is likely to be compatible with its role as a component of a functioning radical-pair compass, whereas the motion of the tryptophan radical is less ideal, unless it is particularly fast.« less

Evaluation of Turner relaxed state as a model of long-lived ion-trapping structures in plasma focus and Z-pinches

NASA Astrophysics Data System (ADS)

Auluck, S. K. H.

2011-03-01

Relatively long-lived spheroidal structures coincident with the neutron emission phase have been observed in frozen deuterium fiber Z-pinch and some plasma focus devices. Existence of energetic ion-trapping mechanism in plasma focus has also been inferred from experimental data. It has been conjectured that these are related phenomena. This paper applies Turner's theory [L. Turner, IEEE Trans. Plasma Sci. 14, 849 (1986)] of relaxation of a Hall magnetofluid to construct a model of these structures and ion-trapping mechanism. Turner's solution modified for a finite-length plasma is used to obtain expressions for the magnetic field, velocity, and equilibrium pressure fields and is shown to represent an entity which is simultaneously a fluid vortex, a force-free magnetic field, a confined finite-pressure plasma, a charged object, and a trapped energetic ion beam. Characteristic features expected from diagnostic experiments are evaluated and shown to resemble experimental observations.

Nuclear relaxation rate in layered superconductors with unconventional pairing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maleyev, S.V.; Yashenkin, A.G.; Aristov, D.N.

1994-11-01

The cubic temperature dependence of the nuclear relaxation rate (NRR) in layered superconductors with the order parameter having zeros at the Fermi surface (FS) is found to be universal under quite general conditions. The coefficient in the quasi-Korringa term for the NRR appearing at low temperatures due to impurity scattering is estimated. It is shown that an anisotropy of the gap function over the FS leads to the disappearance of the Hebel-Slichter coherence peak close to [ital T][sub [ital c

Coronal plasma development in wire-array z-pinches made of twisted-pairs

NASA Astrophysics Data System (ADS)

Hoyt, C. L.; Greenly, J. B.; Gourdain, P. A.; Knapp, P. F.; Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.; Kusse, B. R.

2009-11-01

We have investigated coronal and core plasma development in wire array z-pinches in which single fine wires are replaced by twisted-pairs (``cable'') on the 1 MA, 100 ns rise time COBRA pulsed power generator. X-ray radiography, employed to investigate dense wire core expansion, showed periodic axial nonuniformity and evidence for shock waves developing where the individual wire plasmas collide. Laser shadowgraphy images indicated that the axial instability properties of the coronal plasma are substantially modified from ordinary wire arrays. Cable mass per unit length, material and the twist wavelength were varied in order to study their effects upon the instability wavelength. Implosion uniformity and bright-spot formation, as well as magnetic topology evolution, have also been investigated using self-emission imaging, x-ray diagnostics and small B-dot probes, respectively. Results from the cable-array z-pinches will be compared with results from ordinary wire-array z-pinches. This research was supported by the SSAA program of the National Nuclear Security Administration under DOE Cooperative agreement DE-FC03-02NA00057.

Plasma cytokine profiling in sibling pairs discordant for autism spectrum disorder

PubMed Central

2013-01-01

Objective Converging lines of evidence point to the existence of immune dysfunction in autism spectrum disorder (ASD), which could directly affect several key neurodevelopmental processes. Previous studies have shown higher cytokine levels in patients with autism compared with matched controls or subjects with other developmental disorders. In the current study, we used plasma-cytokine profiling for 25 discordant sibling pairs to evaluate whether these alterations occur within families with ASD. Methods Plasma-cytokine profiling was conducted using an array-based multiplex sandwich ELISA for simultaneous quantitative measurement of 40 unique targets. We also analyzed the correlations between cytokine levels and clinically relevant quantitative traits (Vineland Adaptive Behavior Scale in Autism (VABS) composite score, Social Responsiveness Scale (SRS) total T score, head circumference, and full intelligence quotient (IQ)). In addition, because of the high phenotypic heterogeneity of ASD, we defined four subgroups of subjects (those who were non-verbal, those with gastrointestinal issues, those with regressive autism, and those with a history of allergies), which encompass common and/or recurrent endophenotypes in ASD, and tested the cytokine levels in each group. Results None of the measured parameters showed significant differences between children with ASD and their related typically developing siblings. However, specific target levels did correlate with quantitative clinical traits, and these were significantly different when the ASD subgroups were analyzed. It is notable that these differences seem to be attributable to a predisposing immunogenetic background, as no other significant differences were noticed between discordant sibling pairs. Interleukin-1β appears to be the cytokine most involved in quantitative traits and clinical subgroups of ASD. Conclusions In the present study, we found a lack of significant differences in plasma-cytokine levels between

Radiation-mediated Shocks in Gamma-Ray Bursts: Pair Creation

NASA Astrophysics Data System (ADS)

Lundman, Christoffer; Beloborodov, Andrei M.; Vurm, Indrek

2018-05-01

Relativistic sub-photospheric shocks are a possible mechanism for producing prompt gamma-ray burst (GRB) emission. Such shocks are mediated by scattering of radiation. We introduce a time-dependent, special relativistic code which dynamically couples Monte Carlo radiative transfer to the flow hydrodynamics. The code also self-consistently follows electron–positron pair production in photon–photon collisions. We use the code to simulate shocks with properties relevant to GRBs. We focus on plane-parallel solutions, which are accurate deep below the photosphere. The shock generates a power-law photon spectrum through the first-order Fermi mechanism, extending upward from the typical upstream photon energy. Strong (high Mach number) shocks produce rising νF ν spectra. We observe that in non-relativistic shocks the spectrum extends to {E}\\max ∼ {m}e{v}2, where v is the speed difference between the upstream and downstream. In relativistic shocks the spectrum extends to energies E> 0.1 {m}e{c}2 where its slope softens due to Klein–Nishina effects. Shocks with Lorentz factors γ > 1.5 are prolific producers of electron–positron pairs, yielding hundreds of pairs per proton. The main effect of pairs is to reduce the shock width by a factor of ∼ {Z}+/- -1. Most pairs annihilate far downstream of the shock, and the radiation spectrum relaxes to a Wien distribution, reaching equilibrium with the plasma at a temperature determined by the shock jump conditions and the photon number per proton. We discuss the implications of our results for observations of radiation generated by sub-photospheric shocks.

Pair correlation function and nonlinear kinetic equation for a spatially uniform polarizable nonideal plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belyi, V.V.; Kukharenko, Y.A.; Wallenborn, J.

Taking into account the first non-Markovian correction to the Balescu-Lenard equation, we have derived an expression for the pair correlation function and a nonlinear kinetic equation valid for a nonideal polarized classical plasma. This last equation allows for the description of the correlational energy evolution and shows the global conservation of energy with dynamical polarization. {copyright} {ital 1996 The American Physical Society.}

Chloride channel blockade relaxes airway smooth muscle and potentiates relaxation by β-agonists

PubMed Central

Yim, Peter; Rinderspacher, Alison; Fu, Xiao Wen; Zhang, Yi; Landry, Donald W.; Emala, Charles W.

2014-01-01

Severe bronchospasm refractory to β-agonists continues to cause significant morbidity and mortality in asthmatic patients. We questioned whether chloride channels/transporters are novel targets for the relaxation of airway smooth muscle (ASM). We have screened a library of compounds, derivatives of anthranilic and indanyloxyacetic acid, that were originally developed to antagonize chloride channels in the kidney. We hypothesized that members of this library would be novel calcium-activated chloride channel blockers for the airway. The initial screen of this compound library identified 4 of 20 compounds that relaxed a tetraethylammonium chloride-induced contraction in guinea pig tracheal rings. The two most effective compounds, compounds 1 and 13, were further studied for their potential to either prevent the initiation of or relax the maintenance phase of an acetylcholine (ACh)-induced contraction or to potentiate β-agonist-mediated relaxation. Both relaxed an established ACh-induced contraction in human and guinea pig ex vivo ASM. In contrast, the prevention of an ACh-induced contraction required copretreatment with the sodium-potassium-chloride cotransporter blocker bumetanide. The combination of compound 13 and bumetanide also potentiated relaxation by the β-agonist isoproterenol in guinea pig tracheal rings. Compounds 1 and 13 hyperpolarized the plasma cell membrane of human ASM cells and blocked spontaneous transient inward currents, a measure of chloride currents in these cells. These functional and electrophysiological data suggest that modulating ASM chloride flux is a novel therapeutic target in asthma and other bronchoconstrictive diseases. PMID:24879056

Therapeutic plasma exchange: a paired comparison of Fresenius AS104 vs. COBE Spectra.

PubMed

Burgstaler, E A; Pineda, A A

2001-01-01

For therapeutic plasma exchange (TPE), continuous flow separators are known to be efficient as exemplified by Fresenius AS104 and COBE Spectra. The AS104 uses an interface monitoring system in the centrifuge during TPE, whereas Spectra uses computer algorithms to establish the plasma-cell interface. To determine the plasma collection efficiency (PLCE), anticoagulant (AC) volumes used, and platelets (PLT) lost of the AS104 and the Spectra, we performed a prospective paired comparison of 20 TPE (each machine). The study included 17 patients, 1.3 plasma volume exchanges (without AC), equal inlet rates, and AC ratio of 13:1. Processing times did not include reinfuse mode. Platelet loss was determined by sampling the collection bags. Inlet rates were between 60-110 ml/min. Diagnosis included peripheral neuropathies, TTP and cryoglobulinemia. The AS104 had significantly (P<0.0001) lower average whole blood processed (F:6,601 vs. S:8,584 ml), AC volume (F:532 vs. S:719 ml), and processing time (F:80 vs. S:102 minutes) than Spectra. The AS104 had significantly (P<0.0001) higher average plasma flow rates (F:53 vs. S:44 ml/minute), plasma collection efficiency (F:90 vs. S:69%), and platelet loss (F:2.0 vs. S:0.14 x 10(11) plt) than Spectra. Platelet loss correlated with inlet flow rate with the AS104 but not with the Spectra. The AS104 has a significantly higher collection efficiency than Spectra allowing it to remove the same amount of plasma in significantly less time, by processing significantly less blood, using significantly less AC, but removing significantly more platelets than Spectra. Copyright 2001 Wiley-Liss, Inc.

The Unified Radio and Plasma wave investigation

NASA Technical Reports Server (NTRS)

Stone, R. G.; Bougeret, J. L.; Caldwell, J.; Canu, P.; De Conchy, Y.; Cornilleau-Wehrlin, N.; Desch, M. D.; Fainberg, J.; Goetz, K.; Goldstein, M. L.

1992-01-01

The scientific objectives of the Ulysses Unified Radio and Plasma wave (URAP) experiment are twofold: (1) the determination of the direction, angular size, and polarization of radio sources for remote sensing of the heliosphere and the Jovian magnetosphere and (2) the detailed study of local wave phenomena, which determine the transport coefficients of the ambient plasma. A brief discussion of the scientific goals of the experiment is followed by a comprehensive description of the instrument. The URAP sensors consist of a 72.5 m electric field antenna in the spin plane, a 7.5-m electric field monopole along the spin axis of a pair of orthogonal search coil magnetic antennas. The various receivers, designed to encompass specific needs of the investigation, cover the frequency range from dc to 1 MHz. A relaxation sounder provides very accurate electron density measurements. Radio and plasma wave observations are shown to demonstrate the capabilities and limitations of the URAP instruments: radio observations include solar bursts, auroral kilometric radiation, and Jovian bursts; plasma waves include Langmuir waves, ion acousticlike noise, and whistlers.

Excited level populations and excitation kinetics of nonequilibrium ionizing argon discharge plasma of atmospheric pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akatsuka, Hiroshi

2009-04-15

Population densities of excited states of argon atoms are theoretically examined for ionizing argon plasma in a state of nonequilibrium under atmospheric pressure from the viewpoint of elementary processes with collisional radiative model. The dependence of excited state populations on the electron and gas temperatures is discussed. Two electron density regimes are found, which are distinguished by the population and depopulation mechanisms for the excited states in problem. When the electron impact excitation frequency for the population or depopulation is lower than the atomic impact one, the electron density of the plasma is considered as low to estimate the populationmore » and depopulation processes. Some remarkable characteristics of population and depopulation mechanisms are found for the low electron density atmospheric plasma, where thermal relaxation by atomic collisions becomes the predominant process within the group of close-energy states in the ionizing plasma of atmospheric pressure, and the excitation temperature is almost the same as the gas temperature. In addition to the collisional relaxation by argon atoms, electron impact excitation from the ground state is also an essential population mechanism. The ratios of population density of the levels pairs, between which exists a large energy gap, include information on the electron collisional kinetics. For high electron density, the effect of atomic collisional relaxation becomes weak. For this case, the excitation mechanism is explained as electron impact ladderlike excitation similar to low-pressure ionizing plasma, since the electron collision becomes the dominant process for the population and depopulation kinetics.« less

Nonlinear MHD simulation of magnetic relaxation during DC helicity injection in spherical torus plasmas

NASA Astrophysics Data System (ADS)

Kanki, Takashi; Nagata, Masayoshi; Kagei, Yasuhiro

2009-11-01

Recently, the intermittent plasma flow has been observed to be correlated with the fluctuations of the toroidal current It and n=1 mode in the HIST spherical torus device. During the partially driven phase mixed with a resistive decay, the toroidal ion flow velocity (˜ 40 km/s) in the opposite direction of It is driven in the central open flux region, and the oscillations in n=1 mode occur there, while during the resistive decay phase, this flow velocity reverses and results in the same as that of It, and the oscillations in n=1 mode disappear there. The purpose of the present study is to investigate the plasma flow reversal process and the relevant MHD relaxation by using the 3-D nonlinear MHD simulations. The numerical results exhibit that during the driven phase, the toroidal flow velocity (˜ 37 km/s) is in the opposite direction to It, but in the same direction as the ExB rotation induced by an applied voltage. This flow is driven by the magnetic reconnection occurring at the X-point during the repetitive process of the non-axisymmetric magnetized plasmoid ejection from the helicity injector. The oscillations of poloidal flux ψp are out of phase with those of toroidal flux ψt and magnetic energy for the dominant n=1 mode, indicating the flux conversion from ψt to ψp. The effect of the vacuum toroidal field strength on the plasma dynamics is discussed.

Thermodynamic scaling of α-relaxation time and viscosity stems from the Johari-Goldstein β-relaxation or the primitive relaxation of the coupling model.

PubMed

Ngai, K L; Habasaki, J; Prevosto, D; Capaccioli, S; Paluch, Marian

2012-07-21

By now it is well established that the structural α-relaxation time, τ(α), of non-associated small molecular and polymeric glass-formers obey thermodynamic scaling. In other words, τ(α) is a function Φ of the product variable, ρ(γ)/T, where ρ is the density and T the temperature. The constant γ as well as the function, τ(α) = Φ(ρ(γ)/T), is material dependent. Actually this dependence of τ(α) on ρ(γ)/T originates from the dependence on the same product variable of the Johari-Goldstein β-relaxation time, τ(β), or the primitive relaxation time, τ(0), of the coupling model. To support this assertion, we give evidences from various sources itemized as follows. (1) The invariance of the relation between τ(α) and τ(β) or τ(0) to widely different combinations of pressure and temperature. (2) Experimental dielectric and viscosity data of glass-forming van der Waals liquids and polymer. (3) Molecular dynamics simulations of binary Lennard-Jones (LJ) models, the Lewis-Wahnström model of ortho-terphenyl, 1,4 polybutadiene, a room temperature ionic liquid, 1-ethyl-3-methylimidazolium nitrate, and a molten salt 2Ca(NO(3))(2)·3KNO(3) (CKN). (4) Both diffusivity and structural relaxation time, as well as the breakdown of Stokes-Einstein relation in CKN obey thermodynamic scaling by ρ(γ)/T with the same γ. (5) In polymers, the chain normal mode relaxation time, τ(N), is another function of ρ(γ)/T with the same γ as segmental relaxation time τ(α). (6) While the data of τ(α) from simulations for the full LJ binary mixture obey very well the thermodynamic scaling, it is strongly violated when the LJ interaction potential is truncated beyond typical inter-particle distance, although in both cases the repulsive pair potentials coincide for some distances.

'Relaxers' damage hair: evidence from amino acid analysis.

PubMed

Khumalo, Nonhlanhla P; Stone, Janet; Gumedze, Freedom; McGrath, Emily; Ngwanya, Mzudumile R; de Berker, David

2010-03-01

'Relaxers' are used by more than two thirds of African females to straighten hair, with easy grooming and increased length often cited as reasons. A recent study reported relaxed hair lengths much shorter than expected, suggesting increased fragility; the potential for scalp inflammation and scarring alopecia remains unclear. To investigate the biochemical effects of 'relaxers' on hair. With informed consent, included participants represented 3 groups: natural hair, asymptomatic relaxed hair, and symptomatic (brittle) relaxed hair. Biochemical analysis was performed by using a Biochrom 30 amino acid analyzer. Differences in amino acid levels were assessed using either Wilcoxon rank sum test or matched-pairs signed-rank test. There was a decrease in cystine, citrulline, and arginine; however, an increase in glutamine was found in all relaxed compared to natural hair. Cystine levels (milligram per gram amino acid nitrogen) were similar in natural proximal and distal hair: 14 mg/g (range, 4-15 mg/g) versus 14 mg/g (range, 12-15 mg/g); P = .139. In asymptomatic relaxed hair, cystine levels were higher in less frequently relaxed samples proximal to scalp: 7.5 mg/g (5.6-12) versus 3.3 mg/g (1.3-9.2); P = .005. Cystine levels in distal asymptomatic relaxed and symptomatic relaxed hair were similar to each other and to those in the genetic hair fragility disease trichothiodystrophy. It was not possible to analyze lye and no-lye 'relaxers' separately. 'Relaxers' are associated with reduced cystine consistent with fragile damaged hair. A decrease in citrulline and glutamine has been associated with inflammation; prospective studies are needed to investigate whether or how 'relaxers' induce inflammation. Copyright 2009 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.

Theoretical study on the sound absorption of electrolytic solutions. II. Assignments of relaxations.

PubMed

Yamaguchi, T; Matsuoka, T; Koda, S

2007-08-14

The theory on the ultrasonic absorption spectrum of electrolytic solutions recently proposed by us is applied to the model system that resembles to the aqueous solution of MgSO4. The charges on ions are reduced to +/-1.5e in order to obtain the equilibrium structure by the integral equation theory. The theory reproduces the existence of two relaxations around 100 kHz and 1 GHz. The physical origin of the relaxation is analyzed based on the theoretical expression. The slower relaxation is shown to originate in the formation of contact ion pair, in harmony with the conventional assignment. The amplitude of this relaxation agrees with the experimental one fairly well. The absorption cross section is a weakly increasing function of the concentration of the salt in theory, whereas it depends little on the concentration in experiment, which is ascribed to the weaker association of the pair in the theory. The deviation from the Debye relaxation is found for the faster process, and the concentration dependence is small. The analysis shows that this relaxation stems from the coupling between the pressure and the long-range concentration fluctuation, and the concentration independence and the non-Debye relaxation are explained based on the theoretical analysis. In particular, the theory demonstrates that this process has the t(-3/2) tail in the time domain, which is confirmed by numerical calculation. The deviation of the theoretical relaxation amplitude from the experimental one is elucidated in terms of the theoretical expression of the coefficient.

Relaxation of a hot-electron-two-mode-phonon system in highly excited CdS1-xSex crystals

NASA Astrophysics Data System (ADS)

Žukauskas, A.; Juršėnas, S.

1995-02-01

An investigation of the electron-hole-plasma effective-temperature relaxation in highly excited CdS1-xSex mixed crystals is presented. The slow (~100-ps) relaxation stage, attributed to the depopulation of the fragments (decay products) of the initially produced nonequilibrium LO phonons, is examined with variation of the alloy composition. The relevant relaxation time dependence on x exhibiting a remarkable drop at small CdSe mole fractions is analyzed in terms of a two-route energy relaxation model considering hot-carrier plasma and two generations of nonequilibrium phonons each originating from both pure constituents of the alloy. The disorder-enhanced cross relaxation between two sublattices of the alloy is inferred to account for the experimental results.

Effect of fluctuations on the NMR relaxation beyond the Abrikosov vortex state

DOE PAGES

Glatz, A.; Galda, A.; Varlamov, A. A.

2015-08-25

Here, the effect of fluctuations on the nuclear magnetic resonance (NMR) relaxation rate W = T –1 1 is studied in a complete phase diagram of a two-dimensional superconductor above the upper critical field line H c2(T). In the region of relatively high temperatures and low magnetic fields, the relaxation rate W is determined by two competing effects. The first one is its decrease in the result of suppression of the quasiparticle density of states (DOS) due to formation of fluctuation Cooper pairs (FCPs). The second one is a specific, purely quantum relaxation process of the Maki-Thompson (MT) type, whichmore » for low field leads to an increase of the relaxation rate. The latter describes particular fluctuation processes involving self-pairing of a single electron on self-intersecting trajectories of a size up to phase-breaking length ℓ Φ which becomes possible due to an electron spin-flip scattering event at a nucleus. As a result, different scenarios with either growth or decrease of the NMR relaxation rate are possible upon approaching the normal-metal–type-II superconductor transition. The character of fluctuations changes along the line H c2(T) from the thermal long-wavelength type in weak magnetic fields to the clusters of rotating FCPs in fields comparable to Hc2(0). We find that below the well-defined temperature T* 0 ≈ 0.6T c0, the MT process becomes ineffective even in the absence of intrinsic pair breaking. The small scale of the FCP rotations ξ xy in such high fields impedes formation of long (≲ℓ Φ) self-intersecting trajectories, causing the corresponding relaxation mechanism to lose its efficiency. This reduces the effect of superconducting fluctuations in the domain of high fields and low temperatures to just the suppression of quasiparticle DOS, analogous to the Abrikosov vortex phase below the H c2(T) line.« less

EGFR mutation status of paired cerebrospinal fluid and plasma samples in EGFR mutant non-small cell lung cancer with leptomeningeal metastases.

PubMed

Zhao, Jing; Ye, Xin; Xu, Yan; Chen, Minjiang; Zhong, Wei; Sun, Yun; Yang, Zhenfan; Zhu, Guanshan; Gu, Yi; Wang, Mengzhao

2016-12-01

Central nervous system (CNS) is the prevalent site for metastases in epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI)-relapsed NSCLC patients. To understand the EGFR mutation status in paired cerebrospinal fluid (CSF) and plasma samples after EGFR-TKI treatment failure might be useful to guide the treatment of intra- and extracranial tumors in those patients. Paired CSF and plasma samples were collected from seven NSCLC patients with CNS metastases after EGFR-TKI failure. EGFR mutations were tested by amplification refractory mutation system (ARMS) and droplet digital PCR (ddPCR) methods. Gefitinib concentrations were evaluated by high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS). EGFR mutations were detected in all seven CSF samples, including three of E19-Del, three of L858R and one of E19-Del&T790M by both methods. On the other hand, majority of the matched plasma samples (5/7) were negative for EGFR mutations by both methods. The other two plasma samples were positive for E19-Del&T790M by ddPCR, and one of them had undetectable T790M by ARMS. Gefitinib concentration in CSF was much lower than that in plasma (mean CSF/plasma ratio: 1.8 %). After EGFR-TKI failure, majority of the NSCLC patients with CNS metastases remained positive detection of EGFR sensitive mutations in CSF, but much less detection in the matched plasma. Significantly low exposure of gefitinib in CSF might explain the intracranial protection of the EGFR sensitive mutation positive tumor cells.

Nuclear Magnetic Resonance Structures of GCN4p Are Largely Conserved When Ion Pairs Are Disrupted at Acidic pH but Show a Relaxation of the Coiled Coil Superhelix.

PubMed

Kaplan, Anne R; Brady, Megan R; Maciejewski, Mark W; Kammerer, Richard A; Alexandrescu, Andrei T

2017-03-21

To understand the roles ion pairs play in stabilizing coiled coils, we determined nuclear magnetic resonance structures of GCN4p at three pH values. At pH 6.6, all acidic residues are fully charged; at pH 4.4, they are half-charged, and at pH 1.5, they are protonated and uncharged. The α-helix monomer and coiled coil structures of GCN4p are largely conserved, except for a loosening of the coiled coil quaternary structure with a decrease in pH. Differences going from neutral to acidic pH include (i) an unwinding of the coiled coil superhelix caused by the loss of interchain ion pair contacts, (ii) a small increase in the separation of the monomers in the dimer, (iii) a loosening of the knobs-into-holes packing motifs, and (iv) an increased separation between oppositely charged residues that participate in ion pairs at neutral pH. Chemical shifts (HN, N, C', Cα, and Cβ) of GCN4p display a seven-residue periodicity that is consistent with α-helical structure and is invariant with pH. By contrast, periodicity in hydrogen exchange rates at neutral pH is lost at acidic pH as the exchange mechanism moves into the EX1 regime. On the basis of 1 H- 15 N nuclear Overhauser effect relaxation measurements, the α-helix monomers experience only small increases in picosecond to nanosecond backbone dynamics at acidic pH. By contrast, 13 C rotating frame T 1 relaxation (T 1ρ ) data evince an increase in picosecond to nanosecond side-chain dynamics at lower pH, particularly for residues that stabilize the coiled coil dimerization interface through ion pairs. The results on the structure and dynamics of GCNp4 over a range of pH values help rationalize why a single structure at neutral pH poorly predicts the pH dependence of the unfolding stability of the coiled coil.

Kinetic study of low-temperature CO2 plasmas under non-equilibrium conditions. I. Relaxation of vibrational energy

NASA Astrophysics Data System (ADS)

Silva, T.; Grofulović, M.; Klarenaar, B. L. M.; Morillo-Candas, A. S.; Guaitella, O.; Engeln, R.; Pintassilgo, C. D.; Guerra, V.

2018-01-01

A kinetic model describing the time evolution of ˜70 individual CO2(X1Σ+) vibrational levels during the afterglow of a pulsed DC glow discharge is developed in order to contribute to the understanding of vibrational energy transfer in CO2 plasmas. The results of the simulations are compared against in situ Fourier transform infrared spectroscopy data obtained in a pulsed DC glow discharge and its afterglow at pressures of a few Torr and discharge currents of around 50 mA. The very good agreement between the model predictions and the experimental results validates the kinetic scheme considered here and the corresponding vibration-vibration and vibration-translation rate coefficients. In this sense, it establishes a reaction mechanism for the vibrational kinetics of these CO2 energy levels and offers a firm basis to understand the vibrational relaxation in CO2 plasmas. It is shown that first-order perturbation theories, namely, the Schwartz-Slawsky-Herzfeld and Sharma-Brau methods, provide a good description of CO2 vibrations under low excitation regimes.

The Influence of Plasma Effects of Pair Beams on the Intergalactic Cascade Emission of Blazars

NASA Astrophysics Data System (ADS)

Menzler, Ulf; Schlickeiser, Reinhard

2014-03-01

The attenuation of TeV γ-rays from distant blazars by the extragalactic background light (EBL) produces relativistic electron-positron pair beams. It has been shown by Broderick et. al. (2012) and Schlickeiser et. al (2012) that a pair beam traversing the intergalactic medium is unstable to linear two-stream instabilities of both electrostatic and electromagnetic nature. While for strong blazars all free pair energy is dissipated in heating the intergalactic medium and a potential electromagnetic cascade via inverse-Compton scattering with the cosmic microwave background is suppressed, we investigate the case of weak blazars where the back reaction of generated electrostatic turbulence leads to a plateauing of the electron energy spectrum. In the ultra-relativistic Thomson limit we analytically calculate the inverse-Compton spectral energy distribution for both an unplateaued and a plateaued beam scenario, showing a peak reduction factor of Rpeak ≈ 0.345. This is consistent with the FERMI non-measurements of a GeV excess in the spectrum of EBL attenuated TeV blazars. Claims on the lower bound of the intergalactic magnetic field strengths, made by several authors neglecting plasma effects, are thus put into question.

Graph Matching: Relax at Your Own Risk.

PubMed

Lyzinski, Vince; Fishkind, Donniell E; Fiori, Marcelo; Vogelstein, Joshua T; Priebe, Carey E; Sapiro, Guillermo

2016-01-01

Graph matching-aligning a pair of graphs to minimize their edge disagreements-has received wide-spread attention from both theoretical and applied communities over the past several decades, including combinatorics, computer vision, and connectomics. Its attention can be partially attributed to its computational difficulty. Although many heuristics have previously been proposed in the literature to approximately solve graph matching, very few have any theoretical support for their performance. A common technique is to relax the discrete problem to a continuous problem, therefore enabling practitioners to bring gradient-descent-type algorithms to bear. We prove that an indefinite relaxation (when solved exactly) almost always discovers the optimal permutation, while a common convex relaxation almost always fails to discover the optimal permutation. These theoretical results suggest that initializing the indefinite algorithm with the convex optimum might yield improved practical performance. Indeed, experimental results illuminate and corroborate these theoretical findings, demonstrating that excellent results are achieved in both benchmark and real data problems by amalgamating the two approaches.

Transverse water relaxation in whole blood and erythrocytes at 3T, 7T, 9.4T, 11.7T and 16.4T; determination of intracellular hemoglobin and extracellular albumin relaxivities.

PubMed

Grgac, Ksenija; Li, Wenbo; Huang, Alan; Qin, Qin; van Zijl, Peter C M

2017-05-01

Blood is a physiological substance with multiple water compartments, which contain water-binding proteins such as hemoglobin in erythrocytes and albumin in plasma. Knowing the water transverse (R 2 ) relaxation rates from these different blood compartments is a prerequisite for quantifying the blood oxygenation level-dependent (BOLD) effect. Here, we report the Carr-Purcell-Meiboom-Gill (CPMG) based transverse (R 2CPMG ) relaxation rates of water in bovine blood samples circulated in a perfusion system at physiological temperature in order to mimic blood perfusion in humans. R 2CPMG values of blood plasma, lysed packed erythrocytes, lysed plasma/erythrocyte mixtures, and whole blood at 3 T, 7 T, 9.4 T, 11.7 T and 16.4 T were measured as a function of hematocrit or hemoglobin concentration, oxygenation, and CPMG inter-echo spacing (τ cp ). R 2CPMG in lysed cells showed a small τ cp dependence, attributed to the water exchange rate between free and hemoglobin-bound water to be much faster than τ cp . This was contrary to the tangential dependence in whole blood, where a much slower exchange between cells and blood plasma applies. Whole blood data were fitted as a function of τ cp using a general tangential correlation time model applicable for exchange as well as diffusion contributions to R 2CPMG , and the intercept R 20blood at infinitely short τ cp was determined. The R 20blood values at different hematocrit and the R 2CPMG values of lysed erythrocyte/plasma mixtures at different hemoglobin concentration were used to determine the relaxivity of hemoglobin inside the erythrocyte (r 2Hb ) and albumin (r 2Alb ) in plasma. The r 2Hb values obtained from lysed erythrocytes and whole blood were comparable at full oxygenation. However, while r 2Hb determined from lysed cells showed a linear dependence on oxygenation, this dependence became quadratic in whole blood. This possibly suggests an additional relaxation effect inside intact cells, perhaps due to hemoglobin

Injection of a coaxial-gun-produced magnetized plasma into a background helicon plasma

NASA Astrophysics Data System (ADS)

Zhang, Yue; Lynn, Alan; Gilmore, Mark; Hsu, Scott

2014-10-01

A compact coaxial plasma gun is employed for experimental investigation of plasma bubble relaxation into a lower density background plasma. Experiments are being conducted in the linear device HelCat at UNM. The gun is powered by a 120-uF ignitron-switched capacitor bank, which is operated in a range of 5 to 10 kV and 100 kA. Multiple diagnostics are employed to investigate the plasma relaxation process. Magnetized argon plasma bubbles with velocities 1.2Cs, densities 1020 m-3 and electron temperature 13eV have been achieved. The background helicon plasma has density 1013 m-3, magnetic field from 200 to 500 Gauss and electron temperature 1eV. Several distinct operational regimes with qualitatively different dynamics are identified by fast CCD camera images. Additionally a B-dot probe array has been employed to measure the spatial toroidal and poloidal magnetic flux evolution to identify plasma bubble configurations. Experimental data and analysis will be presented.

Steady state compact toroidal plasma production

DOEpatents

Turner, William C.

1986-01-01

Apparatus and method for maintaining steady state compact toroidal plasmas. A compact toroidal plasma is formed by a magnetized coaxial plasma gun and held in close proximity to the gun electrodes by applied magnetic fields or magnetic fields produced by image currents in conducting walls. Voltage supply means maintains a constant potential across the electrodes producing an increasing magnetic helicity which drives the plasma away from a minimum energy state. The plasma globally relaxes to a new minimum energy state, conserving helicity according to Taylor's relaxation hypothesis, and injecting net helicity into the core of the compact toroidal plasma. Controlling the voltage so as to inject net helicity at a predetermined rate based on dissipative processes maintains or increases the compact toroidal plasma in a time averaged steady state mode.

Investigation of Nonideal Plasma Properties

DTIC Science & Technology

1981-05-01

5-8) of nonideal cesium and noble gas plasmas available , theoretical explanations of these results are still missing. The momentum and energy...solution. In the following, the momentum relaxation time and the electrical conductivity of (i) classical and (ii) quantum plasmas is calculated for... momentum <mv > of the electrons (m is the electron mass and e > 0 is the elementary charge) a = (ne 2/m)T. () The relaxation time T is determined by

Measurements of Two-Fluid Relaxation in the Madison Symmetric Torus

NASA Astrophysics Data System (ADS)

Triana, Joseph C.

Recent measurements and extended MHD simulations expose the importance of two-fluid physics in the relaxation and self-organization of the current and momentum profiles in RFP plasmas. A hallmark of relaxation is that the inductive electric field is not balanced by resistive dissipation, prompting the study of fluctuation-induced emfs in the generalized Ohm's law, E ∥ - etaJ∥ = - ∥ + 1/ne , where the two terms on the right are known as the MHD and Hall dynamo terms, respectively. The Hall emf is measured in the outer half of the MST plasma minor radius using an armored deep-insertion Hall probe. The emf matches previously measurements in the edge ( r/a > 0.8) but in the new region examined (0.6 < r/a < 0.8) it is much larger than E - etaJ, implying the MHD dynamo must also be large and oppositely directed. Recent nonlinear simulations that include two-fluid effects using the extended-MHD NIMROD code show complex radial structure for the emf terms, but the size of the measured Hall emf is much larger than predicted by the simulations. In the two-fluid model, the Hall dynamo couples to the parallel momentum as the mean-field Maxwell stress. The simulations predict relaxation of the parallel flow profiles that is also qualitatively consistent with measurements in MST plasmas.

Two-fluid Magnetic Relaxation in the MST Reversed Field Pinch

NASA Astrophysics Data System (ADS)

Triana, Joseph; Almagri, Af; McCollam, Kj; Sarff, Js; Sovinec, Cr

2016-10-01

Recent measurements and extended MHD simulations expose the importance of two-fluid physics in the relaxation and self-organization of the current and momentum profiles in RFP plasmas. A hallmark of relaxation is that the inductive electric field is not balanced by resistive dissipation, prompting the study of fluctuation-induced emfs in the generalized Ohm's law, E- ηJ =- +/ne, the two terms on the right known as the MHD and Hall dynamo terms, respectively. The Hall emf is measured in the outer half of the MST plasma minor radius using an armored deep-insertion probe. The emf matches previous measurements in the edge (r/a>0.8) but in the new region examined (0.8>r/a>0.6) it is much larger than E- ηJ, implying the MHD dynamo must also be large and oppositely directed. Recent nonlinear simulations that include two-fluid effects using the extended-MHD NIMROD code show complex radial structure for the emf terms, but the size of the measured Hall emf is much larger than predicted by the simulations. In the two-fluid model, the Hall dynamo couples to the parallel momentum as the mean-field Maxwell stress. The simulations predict relaxation of the parallel flow profiles that is also qualitatively consistent with measurements in MST plasmas. Work supported by US DoE and NSF.

Dynamics of relaxed inflation

NASA Astrophysics Data System (ADS)

Tangarife, Walter; Tobioka, Kohsaku; Ubaldi, Lorenzo; Volansky, Tomer

2018-02-01

The cosmological relaxation of the electroweak scale has been proposed as a mechanism to address the hierarchy problem of the Standard Model. A field, the relaxion, rolls down its potential and, in doing so, scans the squared mass parameter of the Higgs, relaxing it to a parametrically small value. In this work, we promote the relaxion to an inflaton. We couple it to Abelian gauge bosons, thereby introducing the necessary dissipation mechanism which slows down the field in the last stages. We describe a novel reheating mechanism, which relies on the gauge-boson production leading to strong electro-magnetic fields, and proceeds via the vacuum production of electron-positron pairs through the Schwinger effect. We refer to this mechanism as Schwinger reheating. We discuss the cosmological dynamics of the model and the phenomenological constraints from CMB and other experiments. We find that a cutoff close to the Planck scale may be achieved. In its minimal form, the model does not generate sufficient curvature perturbations and additional ingredients, such as a curvaton field, are needed.

Formation and Sustainment of Flipped Spherical Torus Plasmas on HIST

NASA Astrophysics Data System (ADS)

Oguro, T.; Jinno, T.; Hasegawa, H.; Nagata, M.; Fukumoto, N.; Uyama, T.; Masamune, S.; Iida, M.; Katsurai, M.

2002-11-01

In order to understand comprehensively the relaxation and self-organization in the coaxial helicity injection system, we have investigated dynamics of ST plasmas produced in the HIST device by decreasing the external toroidal field (TF) and reversing its sign in time. In results, we have discovered that the ST relaxes towards flipped/reversed ST configurations. Surprisingly, it has been observed that not only toroidal flux but also poloidal flux reverses sign spontaneously during the relaxation process. This self-reversal of the poloidal field is thought to be evidence for global helicity conservation. Taylor helicity-driven relaxed theory predicts that there exists the relaxed state of the flipped ST plasma when the TF current is reversed. We found that when q_axis passes through the q_axis =1 rational barrier in the initial phase, the ST plasma becomes unstable and relaxes to flipped states through RFP states. The n=1 mode activities are essential in the formation and sustainment of the flipped ST.

Perpendicular relativistic shocks in magnetized pair plasma

NASA Astrophysics Data System (ADS)

Plotnikov, Illya; Grassi, Anna; Grech, Mickael

2018-07-01

Perpendicular relativistic (γ0= 10) shocks in magnetized pair plasmas are investigated using two-dimensional Particle-in-Cell simulations. A systematic survey, from unmagnetized to strongly magnetized shocks, is presented accurately capturing the transition from Weibel-mediated to magnetic-reflection-shaped shocks. This transition is found to occur for upstream flow magnetizations 10-3 < σ < 10-2 at which a strong perpendicular net current is observed in the precursor, driving the so-called current-filamentation instability. The global structure of the shock and shock formation time are discussed. The magnetohydrodynamics shock jump conditions are found in good agreement with the numerical results, except for 10-4 < σ < 10-2 where a deviation up to 10 per cent is observed. The particle precursor length converges towards the Larmor radius of particles injected in the upstream magnetic field at intermediate magnetizations. For σ > 10-2, it leaves place to a purely electromagnetic precursor following from the strong emission of electromagnetic waves at the shock front. Particle acceleration is found to be efficient in weakly magnetized perpendicular shocks in agreement with previous works, and is fully suppressed for σ > 10-2. Diffusive shock acceleration is observed only in weakly magnetized shocks, while a dominant contribution of shock drift acceleration is evidenced at intermediate magnetizations. The spatial diffusion coefficients are extracted from the simulations allowing for a deeper insight into the self-consistent particle kinematics and scale with the square of the particle energy in weakly magnetized shocks. These results have implications for particle acceleration in the internal shocks of active galactic nucleus jets and in the termination shocks of pulsar wind nebulae.

Perpendicular relativistic shocks in magnetized pair plasma

NASA Astrophysics Data System (ADS)

Plotnikov, Illya; Grassi, Anna; Grech, Mickael

2018-04-01

Perpendicular relativistic (γ0 = 10) shocks in magnetized pair plasmas are investigated using two dimensional Particle-in-Cell simulations. A systematic survey, from unmagnetized to strongly magnetized shocks, is presented accurately capturing the transition from Weibel-mediated to magnetic-reflection-shaped shocks. This transition is found to occur for upstream flow magnetizations 10-3 < σ < 10-2 at which a strong perpendicular net current is observed in the precursor, driving the so-called current-filamentation instability. The global structure of the shock and shock formation time are discussed. The MHD shock jump conditions are found in good agreement with the numerical results, except for 10-4 < σ < 10-2 where a deviation up to 10% is observed. The particle precursor length converges toward the Larmor radius of particles injected in the upstream magnetic field at intermediate magnetizations. For σ > 10-2, it leaves place to a purely electromagnetic precursor following from the strong emission of electromagnetic waves at the shock front. Particle acceleration is found to be efficient in weakly magnetized perpendicular shocks in agreement with previous works, and is fully suppressed for σ > 10-2. Diffusive Shock Acceleration is observed only in weakly magnetized shocks, while a dominant contribution of Shock Drift Acceleration is evidenced at intermediate magnetizations. The spatial diffusion coefficients are extracted from the simulations allowing for a deeper insight into the self-consistent particle kinematics and scale with the square of the particle energy in weakly magnetized shocks. These results have implications for particle acceleration in the internal shocks of AGN jets and in the termination shocks of Pulsar Wind Nebulae.

Relaxation and self-organization in two-dimensional plasma and neutral fluid flow systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, Amita

Extensive numerical studies in the framework of a simplified two-dimensional model for neutral and plasma fluid for a variety of initial configurations and for both decaying and driven cases are carried out to illustrate relaxation toward a self-organized state. The dynamical model equation constitutes a simple choice for this purpose, e.g., the vorticity equation of the Navier-Stokes dynamics for the incompressible neutral fluids and the Hasegawa-Mima equation for plasma fluid flow system. Scatter plots are employed to observe a development of functional relationship, if any, amidst the generalized vorticity and its Laplacian. It is seen that they do not satisfymore » a linear relationship as the well known variational approach of enstrophy minimization subject to constancy of the energy integral for the two-dimensional (2D) system suggests. The observed nonlinear functional relationship is understood by separating the contribution to the scatter plot from spatial regions with intense vorticity patches and those of the background flow region where the background vorticity is weak or absent altogether. It is shown that such a separation has close connection with the known exact analytical solutions of the system. The analytical solutions are typically obtained by assuming a finite source of vorticity for the inner core of the localized structure, which is then matched with the solution in the outer region where vorticity is chosen to be zero. The work also demonstrates that the seemingly ad hoc choice of the linear vorticity source function for the inner region is in fact consistent with the self-organization paradigm of the 2D systems.« less

Rapid determination of minoxidil in human plasma using ion-pair HPLC.

PubMed

Zarghi, A; Shafaati, A; Foroutan, S M; Khoddam, A

2004-10-29

A rapid, simple and sensitive ion-pair high-performance liquid chromatography (HPLC) method has been developed for quantification of minoxidil in plasma. The assay enables the measurement of minoxidil for therapeutic drug monitoring with a minimum detectable limit of 0.5 ng ml(-1). The method involves simple, one-step extraction procedure and analytical recovery was complete. The separation was performed on an analytical 150 x 4.6 mm i.d. microbondapak C18 column. The wavelength was set at 281 nm. The mobile phase was a mixture of 0.01 M sodium dihydrogen phosphate buffer and acetonitrile (60:40, v/v) containing 2.5 mM sodium dodecyl sulphate adjusted to pH 3.5 at a flow rate of 1 ml/min. The column temperature was set at 50 degrees C. The calibration curve was linear over the concentration range 2-100 ng ml(-1). The coefficients of variation for inter-day and intra-day assay were found to be less than 8%.

Binary rare earth element-Ni/Co metallic glasses with distinct β-relaxation behaviors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Z. G.; Wang, Z.; Wang, W. H., E-mail: whw@iphy.ac.cn

2015-10-21

We report the formation of a series of rare earth element (RE)-Ni/Co binary metallic glasses (MGs) with unusual distinct β-relaxation peak compared with that of most of the reported MGs which usually exhibit as an excess wing or a shoulder. The β-relaxation behavior of RE-Ni/Co MGs is sensitive to the composition and the atomic radii of the RE and can be tuned through changing the fraction of RE-Ni (or Co) atomic pairs. The novel RE-Ni/Co MGs with distinct β-relaxation can serve as model system to investigate the nature of the β-relaxation as well as its relations with other physical andmore » mechanical properties of MGs.« less

The Electrostatic Instability for Realistic Pair Distributions in Blazar/EBL Cascades

NASA Astrophysics Data System (ADS)

Vafin, S.; Rafighi, I.; Pohl, M.; Niemiec, J.

2018-04-01

This work revisits the electrostatic instability for blazar-induced pair beams propagating through the intergalactic medium (IGM) using linear analysis and PIC simulations. We study the impact of the realistic distribution function of pairs resulting from the interaction of high-energy gamma-rays with the extragalactic background light. We present analytical and numerical calculations of the linear growth rate of the instability for the arbitrary orientation of wave vectors. Our results explicitly demonstrate that the finite angular spread of the beam dramatically affects the growth rate of the waves, leading to the fastest growth for wave vectors quasi-parallel to the beam direction and a growth rate at oblique directions that is only a factor of 2–4 smaller compared to the maximum. To study the nonlinear beam relaxation, we performed PIC simulations that take into account a realistic wide-energy distribution of beam particles. The parameters of the simulated beam-plasma system provide an adequate physical picture that can be extrapolated to realistic blazar-induced pairs. In our simulations, the beam looses only 1% of its energy, and we analytically estimate that the beam would lose its total energy over about 100 simulation times. An analytical scaling is then used to extrapolate the parameters of realistic blazar-induced pair beams. We find that they can dissipate their energy slightly faster by the electrostatic instability than through inverse-Compton scattering. The uncertainties arising from, e.g., details of the primary gamma-ray spectrum are too large to make firm statements for individual blazars, and an analysis based on their specific properties is required.

Relaxation of a High-Energy Quasiparticle in a One-Dimensional Bose Gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Shina; Glazman, Leonid I.; Pustilnik, Michael

2010-08-27

We evaluate the relaxation rate of high-energy quasiparticles in a weakly interacting one-dimensional Bose gas. Unlike in higher dimensions, the rate is a nonmonotonic function of temperature, with a maximum at the crossover to the state of suppressed density fluctuations. At the maximum, the relaxation rate may significantly exceed its zero-temperature value. We also find the dependence of the differential inelastic scattering rate on the transferred energy. This rate yields information about temperature dependence of local pair correlations.

RELAX: detecting relaxed selection in a phylogenetic framework.

PubMed

Wertheim, Joel O; Murrell, Ben; Smith, Martin D; Kosakovsky Pond, Sergei L; Scheffler, Konrad

2015-03-01

Relaxation of selective strength, manifested as a reduction in the efficiency or intensity of natural selection, can drive evolutionary innovation and presage lineage extinction or loss of function. Mechanisms through which selection can be relaxed range from the removal of an existing selective constraint to a reduction in effective population size. Standard methods for estimating the strength and extent of purifying or positive selection from molecular sequence data are not suitable for detecting relaxed selection, because they lack power and can mistake an increase in the intensity of positive selection for relaxation of both purifying and positive selection. Here, we present a general hypothesis testing framework (RELAX) for detecting relaxed selection in a codon-based phylogenetic framework. Given two subsets of branches in a phylogeny, RELAX can determine whether selective strength was relaxed or intensified in one of these subsets relative to the other. We establish the validity of our test via simulations and show that it can distinguish between increased positive selection and a relaxation of selective strength. We also demonstrate the power of RELAX in a variety of biological scenarios where relaxation of selection has been hypothesized or demonstrated previously. We find that obligate and facultative γ-proteobacteria endosymbionts of insects are under relaxed selection compared with their free-living relatives and obligate endosymbionts are under relaxed selection compared with facultative endosymbionts. Selective strength is also relaxed in asexual Daphnia pulex lineages, compared with sexual lineages. Endogenous, nonfunctional, bornavirus-like elements are found to be under relaxed selection compared with exogenous Borna viruses. Finally, selection on the short-wavelength sensitive, SWS1, opsin genes in echolocating and nonecholocating bats is relaxed only in lineages in which this gene underwent pseudogenization; however, selection on the functional

[Evaluation of NMR relaxation method as a diagnostic tool for donor blood analysis and patients with hematologic diseases and burns].

PubMed

Gangardt, M G; Popova, O V; Shmarov, D A; Kariakina, N F; Papish, E A; Kozinets, G I

2002-08-01

Diagnostic value of the NMR-relaxation method in the blood plasma was estimated in the patients with different pathologies. The time of hydrogen nuclei longitudinal relaxation (T1) in the health donors of the blood, in the patients with oncopathology (hemoblastoses) and in the cases with anemia and burning disease were investigated. The time of the longitudinal relaxation (T1) was measured by automated NMR-relaxometer "Palma" (Russia). The working frequency was equal to 35 MHz, the temperature was 45 +/- 0.1 degrees C. For the single measurement 0.2 ml of blood obtained from heparinized venous blood 1.5 hours after its taking was used. The time of the longitudinal relaxation (T1) was shown to be 1.78 +/- 0.02 in the health donors, 1.70 +/- 0.06 s in cases with anemia, 1.97 +/- 0.48 c in patients with leucosis, 2.40 +/- 0.12 s in patients with burns. The sensitivity and the specificity of diagnostics of leucosis based upon the results of the only single T1 measurement in blood plasma were concluded to be 75%. It proves the significant T1 change both in patients with anemia and burning disease of the II-III degree. However it is evidently insufficient for selective use of NMR-relaxation blood plasma (serum) in the diagnostics of anemia and leucosis. The data obtained prove also the possibility of use of NMR-relaxation blood plasma (serum) for control of the hemostasis state during treatment or remission.

Ion-pair cloud-point extraction: a new method for the determination of water-soluble vitamins in plasma and urine.

PubMed

Heydari, Rouhollah; Elyasi, Najmeh S

2014-10-01

A novel, simple, and effective ion-pair cloud-point extraction coupled with a gradient high-performance liquid chromatography method was developed for determination of thiamine (vitamin B1 ), niacinamide (vitamin B3 ), pyridoxine (vitamin B6 ), and riboflavin (vitamin B2 ) in plasma and urine samples. The extraction and separation of vitamins were achieved based on an ion-pair formation approach between these ionizable analytes and 1-heptanesulfonic acid sodium salt as an ion-pairing agent. Influential variables on the ion-pair cloud-point extraction efficiency, such as the ion-pairing agent concentration, ionic strength, pH, volume of Triton X-100, extraction temperature, and incubation time have been fully evaluated and optimized. Water-soluble vitamins were successfully extracted by 1-heptanesulfonic acid sodium salt (0.2% w/v) as ion-pairing agent with Triton X-100 (4% w/v) as surfactant phase at 50°C for 10 min. The calibration curves showed good linearity (r(2) > 0.9916) and precision in the concentration ranges of 1-50 μg/mL for thiamine and niacinamide, 5-100 μg/mL for pyridoxine, and 0.5-20 μg/mL for riboflavin. The recoveries were in the range of 78.0-88.0% with relative standard deviations ranging from 6.2 to 8.2%. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Marcus Theory of Ion-Pairing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roy, Santanu; Baer, Marcel D.; Mundy, Christopher J.

We present a theory for ion pair dissociation and association, motivated by the concepts of the Marcus theory of electron transfer. Despite the extensive research on ion-pairing in many chemical and biological processes, much can be learned from the exploration of collective reaction coordinates. To this end, we explore two reaction coordinates, ion pair distance and coordination number. The study of the correlation between these reaction coordinates provides a new insight into the mechanism and kinetics of ion pair dissociation and association in water. The potential of mean force on these 2D-surfaces computed from molecular dynamics simulations of different monovalentmore » ion pairs reveal a Marcus-like mechanism for ion-pairing: Water molecules rearrange forming an activated coordination state prior to ion pair dissociation or association, followed by relaxation of the coordination state due to further water rearrangement. Like Marcus theory, we find the existence of an inverted region where the transition rates are slower with increasing exergonicity. This study provides a new perspective for the future investigations of ion-pairing and transport. SR, CJM, and GKS were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. MDB was supported by MS3 (Materials Synthesis and Simulation Across Scales) Initiative, a Laboratory Directed Research and Development Program at Pacific Northwest National Laboratory (PNNL). The research was performed using PNNL Institutional Computing. PNNL is a multi-program national laboratory operated by Battelle for the U.S. Department of Energy.« less

Dusty Pair Plasma—Wave Propagation and Diffusive Transition of Oscillations

NASA Astrophysics Data System (ADS)

Atamaniuk, Barbara; Turski, Andrzej J.

2011-11-01

The crucial point of the paper is the relation between equilibrium distributions of plasma species and the type of propagation or diffusive transition of plasma response to a disturbance. The paper contains a unified treatment of disturbance propagation (transport) in the linearized Vlasov electron-positron and fullerene pair plasmas containing charged dust impurities, based on the space-time convolution integral equations. Electron-positron-dust/ion (e-p-d/i) plasmas are rather widespread in nature. Space-time responses of multi-component linearized Vlasov plasmas on the basis of multiple integral equations are invoked. An initial-value problem for Vlasov-Poisson/Ampère equations is reduced to the one multiple integral equation and the solution is expressed in terms of forcing function and its space-time convolution with the resolvent kernel. The forcing function is responsible for the initial disturbance and the resolvent is responsible for the equilibrium velocity distributions of plasma species. By use of resolvent equations, time-reversibility, space-reflexivity and the other symmetries are revealed. The symmetries carry on physical properties of Vlasov pair plasmas, e.g., conservation laws. Properly choosing equilibrium distributions for dusty pair plasmas, we can reduce the resolvent equation to: (i) the undamped dispersive wave equations, (ii) and diffusive transport equations of oscillations.

Extended MHD modeling of tearing-driven magnetic relaxation

NASA Astrophysics Data System (ADS)

Sauppe, J. P.; Sovinec, C. R.

2017-05-01

Discrete relaxation events in reversed-field pinch relevant configurations are investigated numerically with nonlinear extended magnetohydrodynamic (MHD) modeling, including the Hall term in Ohm's law and first-order ion finite Larmor radius effects. Results show variability among relaxation events, where the Hall dynamo effect may help or impede the MHD dynamo effect in relaxing the parallel current density profile. The competitive behavior arises from multi-helicity conditions where the dominant magnetic fluctuation is relatively small. The resulting changes in parallel current density and parallel flow are aligned in the core, consistent with experimental observations. The analysis of simulation results also confirms that the force density from fluctuation-induced Reynolds stress arises subsequent to the drive from the fluctuation-induced Lorentz force density. Transport of the momentum density is found to be dominated by the fluctuation-induced Maxwell stress over most of the cross section with viscous and gyroviscous contributions being large in the edge region. The findings resolve a discrepancy with respect to the relative orientation of current density and flow relaxation, which had not been realized or investigated in King et al. [Phys. Plasmas 19, 055905 (2012)], where only the magnitude of flow relaxation is actually consistent with experimental results.

Radiation- and pair-loaded shocks

NASA Astrophysics Data System (ADS)

Lyutikov, Maxim

2018-06-01

We consider the structure of mildly relativistic shocks in dense media, taking into account the radiation and pair loading, and diffusive radiation energy transfer within the flow. For increasing shock velocity (increasing post-shock temperature), the first important effect is the efficient energy redistribution by radiation within the shock that leads to the appearance of an isothermal jump, whereby the flow reaches the final state through a discontinuous isothermal transition. The isothermal jump, on scales much smaller than the photon diffusion length, consists of a weak shock and a quick relaxation to the isothermal conditions. Highly radiation-dominated shocks do not form isothermal jump. Pair production can mildly increase the overall shock compression ratio to ≈10 (4 for matter-dominated shocks and 7 of the radiation-dominated shocks).

Imaging Cellular Dynamics with Spectral Relaxation Imaging Microscopy: Distinct Spectral Dynamics in Golgi Membranes of Living Cells.

PubMed

Lajevardipour, Alireza; Chon, James W M; Chattopadhyay, Amitabha; Clayton, Andrew H A

2016-11-22

Spectral relaxation from fluorescent probes is a useful technique for determining the dynamics of condensed phases. To this end, we have developed a method based on wide-field spectral fluorescence lifetime imaging microscopy to extract spectral relaxation correlation times of fluorescent probes in living cells. We show that measurement of the phase and modulation of fluorescence from two wavelengths permit the identification and determination of excited state lifetimes and spectral relaxation correlation times at a single modulation frequency. For NBD fluorescence in glycerol/water mixtures, the spectral relaxation correlation time determined by our approach exhibited good agreement with published dielectric relaxation measurements. We applied this method to determine the spectral relaxation dynamics in membranes of living cells. Measurements of the Golgi-specific C 6 -NBD-ceramide probe in living HeLa cells revealed sub-nanosecond spectral dynamics in the intracellular Golgi membrane and slower nanosecond spectral dynamics in the extracellular plasma membrane. We interpret the distinct spectral dynamics as a result of structural plasticity of the Golgi membrane relative to more rigid plasma membranes. To the best of our knowledge, these results constitute one of the first measurements of Golgi rotational dynamics.

Simple point vortex model for the relaxation of 2D superfluid turbulence in a Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Kim, Joon Hyun; Kwon, Woo Jin; Shin, Yong-Il

2016-05-01

In a recent experiment, it was found that the dissipative evolution of a corotating vortex pair in a trapped Bose-Einstein condensate is well described by a point vortex model with longitudinal friction on the vortex motion and the thermal friction coefficient was determined as a function of sample temperature. In this poster, we present a numerical study on the relaxation of 2D superfluid turbulence based on the dissipative point vortex model. We consider a homogeneous system in a cylindrical trap having randomly distributed vortices and implement the vortex-antivortex pair annihilation by removing a pair when its separation becomes smaller than a certain threshold value. We characterize the relaxation of the turbulent vortex states with the decay time required for the vortex number to be reduced to a quarter of initial number. We find the vortex decay time is inversely proportional to the thermal friction coefficient. In particular, we observe the decay times obtained from this work show good quantitative agreement with the experimental results in, indicating that in spite of its simplicity, the point vortex model reasonably captures the physics in the relaxation dynamics of the real system.

Simulation of current-filament dynamics and relaxation in the Pegasus Spherical Tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Bryan, J. B.; Sovinec, C. R.; Bird, T. M.

Nonlinear numerical computation is used to investigate the relaxation of non-axisymmetric current-channels from washer-gun plasma sources into 'tokamak-like' plasmas in the Pegasus toroidal experiment [Eidietis et al. J. Fusion Energy 26, 43 (2007)]. Resistive MHD simulations with the NIMROD code [Sovinec et al. Phys. Plasmas 10(5), 1727-1732 (2003)] utilize ohmic heating, temperature-dependent resistivity, and anisotropic, temperature-dependent thermal conduction corrected for regions of low magnetization to reproduce critical transport effects. Adjacent passes of the simulated current-channel attract and generate strong reversed current sheets that suggest magnetic reconnection. With sufficient injected current, adjacent passes merge periodically, releasing axisymmetric current rings from themore » driven channel. The current rings have not been previously observed in helicity injection for spherical tokamaks, and as such, provide a new phenomenological understanding for filament relaxation in Pegasus. After large-scale poloidal-field reversal, a hollow current profile and significant poloidal flux amplification accumulate over many reconnection cycles.« less

Average-atom treatment of relaxation time in x-ray Thomson scattering from warm dense matter.

PubMed

Johnson, W R; Nilsen, J

2016-03-01

The influence of finite relaxation times on Thomson scattering from warm dense plasmas is examined within the framework of the average-atom approximation. Presently most calculations use the collision-free Lindhard dielectric function to evaluate the free-electron contribution to the Thomson cross section. In this work, we use the Mermin dielectric function, which includes relaxation time explicitly. The relaxation time is evaluated by treating the average atom as an impurity in a uniform electron gas and depends critically on the transport cross section. The calculated relaxation rates agree well with values inferred from the Ziman formula for the static conductivity and also with rates inferred from a fit to the frequency-dependent conductivity. Transport cross sections determined by the phase-shift analysis in the average-atom potential are compared with those evaluated in the commonly used Born approximation. The Born approximation converges to the exact cross sections at high energies; however, differences that occur at low energies lead to corresponding differences in relaxation rates. The relative importance of including relaxation time when modeling x-ray Thomson scattering spectra is examined by comparing calculations of the free-electron dynamic structure function for Thomson scattering using Lindhard and Mermin dielectric functions. Applications are given to warm dense Be plasmas, with temperatures ranging from 2 to 32 eV and densities ranging from 2 to 64 g/cc.

Relaxation Assessment with Varied Structured Milieu (RELAX).

ERIC Educational Resources Information Center

Cassel, Russell N.; Cassel, Susie L.

1983-01-01

Describes Relaxation Assessment with Varied Structured Milieu (RELAX), a clinical program designed to assess the degree to which an individual is able to demonstrate self-control for overall general relaxation. The program is designed for use with the Cassel Biosensors biofeedback equipment. (JAC)

Widespread Transient Hoogsteen Base-Pairs in Canonical Duplex DNA with Variable Energetics

PubMed Central

Alvey, Heidi S.; Gottardo, Federico L.; Nikolova, Evgenia N.; Al-Hashimi, Hashim M.

2015-01-01

Hoogsteen base-pairing involves a 180 degree rotation of the purine base relative to Watson-Crick base-pairing within DNA duplexes, creating alternative DNA conformations that can play roles in recognition, damage induction, and replication. Here, using Nuclear Magnetic Resonance R1ρ relaxation dispersion, we show that transient Hoogsteen base-pairs occur across more diverse sequence and positional contexts than previously anticipated. We observe sequence-specific variations in Hoogsteen base-pair energetic stabilities that are comparable to variations in Watson-Crick base-pair stability, with Hoogsteen base-pairs being more abundant for energetically less favorable Watson-Crick base-pairs. Our results suggest that the variations in Hoogsteen stabilities and rates of formation are dominated by variations in Watson-Crick base pair stability, suggesting a late transition state for the Watson-Crick to Hoogsteen conformational switch. The occurrence of sequence and position-dependent Hoogsteen base-pairs provide a new potential mechanism for achieving sequence-dependent DNA transactions. PMID:25185517

A plasma model for reversed field pinch circuit design

NASA Astrophysics Data System (ADS)

Johnston, J. W.

1981-03-01

A plasma model has been developed for use in the design of circuits for reversed field pinch experiments. The magnetic field is assumed to evolve through a given series of relaxed states with the plasma resistivity specified as a function of time. At any instant the magnetic field configuration is determined by the field energy and the toroidal flux. If the Bessel function model is chosen as the relaxed state then the magnetic helicity can be used as an alternative to the magnetic energy without altering the results. Simulations of discharges on ZETA and ETA BETA II are presented. By suitable choices of the relaxed field configuration and plasma resistivity it is possible to obtain close agreement with the experimental waveforms. Application to the proposed RFX device is discussed.

Average-atom treatment of relaxation time in x-ray Thomson scattering from warm dense matter

DOE PAGES

Johnson, W. R.; Nilsen, J.

2016-03-14

Here, the influence of finite relaxation times on Thomson scattering from warm dense plasmas is examined within the framework of the average-atom approximation. Presently most calculations use the collision-free Lindhard dielectric function to evaluate the free-electron contribution to the Thomson cross section. In this work, we use the Mermin dielectric function, which includes relaxation time explicitly. The relaxation time is evaluated by treating the average atom as an impurity in a uniform electron gas and depends critically on the transport cross section. The calculated relaxation rates agree well with values inferred from the Ziman formula for the static conductivity andmore » also with rates inferred from a fit to the frequency-dependent conductivity. Transport cross sections determined by the phase-shift analysis in the average-atom potential are compared with those evaluated in the commonly used Born approximation. The Born approximation converges to the exact cross sections at high energies; however, differences that occur at low energies lead to corresponding differences in relaxation rates. The relative importance of including relaxation time when modeling x-ray Thomson scattering spectra is examined by comparing calculations of the free-electron dynamic structure function for Thomson scattering using Lindhard and Mermin dielectric functions. Applications are given to warm dense Be plasmas, with temperatures ranging from 2 to 32 eV and densities ranging from 2 to 64 g/cc.« less

Ion Transport via Structural Relaxations in Polymerized Ionic Liquids

NASA Astrophysics Data System (ADS)

Ganesan, Venkat; Mogurampelly, Santosh

We study the mechanisms underlying ion transport in poly(1-butyl-3-vinylimidazolium-hexafluorophosphate) polymer electrolytes. We consider polymer electrolytes of varying polymerized ionic liquid to ionic liquid (polyIL:IL) ratios and use atomistic molecular dynamics (MD) simulations to probe the dynamical and structural characteristics of the electrolyte. Our results reveal that anion diffusion along polymer backbone occurs primarily viathe formation and breaking of ion-pairs involving threepolymerized cationic monomers of twodifferent polymer chains. Moreover, we observe that the ionic diffusivities exhibit a direct correlation with the structural relaxation times of the ion-pairs and hydrogen bonds (H-bonds). These results provide new insights into the mechanisms underlying ion transport in polymerized ionic liquid electrolytes.

Strongly magnetized classical plasma models

NASA Technical Reports Server (NTRS)

Montgomery, D. C.

1972-01-01

The class of plasma processes for which the so-called Vlasov approximation is inadequate is investigated. Results from the equilibrium statistical mechanics of two-dimensional plasmas are derived. These results are independent of the presence of an external dc magnetic field. The nonequilibrium statistical mechanics of the electrostatic guiding-center plasma, a two-dimensional plasma model, is discussed. This model is then generalized to three dimensions. The guiding-center model is relaxed to include finite Larmor radius effects for a two-dimensional plasma.

After stress comes relax(ation)

NASA Astrophysics Data System (ADS)

Isa, Lucio

2015-11-01

Viscoelastic materials take a finite time to relax and dissipate stress and this time scale is directly connected to the microstructure of the material itself. In their paper, Gomez-Solano and Bechinger (2015 New J. Phys. 17 103032) perform ‘miniaturized’ mechanical tests on a range of viscoelastic materials by dragging a micron-sized bead across them using optical tweezers. Upon switching off all the external forces, they watch the bead recoil to its original position and by tracking its motion they pinpoint the relaxation time of the material. These experiments open up a new range of possibilities to characterize stress relaxation at the microscale just by watching it.

Multi-region relaxed magnetohydrodynamics in plasmas with slowly changing boundaries -- Resonant response of a plasma slab

DOE PAGES

Dewar, R. L.; Hudson, S. R.; Bhattacharjee, A.; ...

2017-04-03

The adiabatic limit of a recently proposed dynamical extension of Taylor relaxation, multi-region relaxed magnetohydrodynamics (MRxMHD), is summarized, with special attention to the appropriate definition of a relative magnetic helicity. The formalism is illustrated using a simple two-region, sheared-magnetic-field model similar to the Hahm-Kulsrud-Taylor (HKT) rippled-boundary slab model. In MRxMHD, a linear Grad-Shafranov equation applies, even at finite ripple amplitude. The adiabatic switching on of boundary ripple excites a shielding current sheet opposing reconnection at a resonant surface. The perturbed magnetic field as a function of ripple amplitude is calculated by invoking the conservation of magnetic helicity in the twomore » regions separated by the current sheet. Here, at low ripple amplitude, "half islands" appear on each side of the current sheet, locking the rotational transform at the resonant value. Beyond a critical amplitude, these islands disappear and the rotational transform develops a discontinuity across the current sheet. Published by AIP Publishing.« less

Multi-region relaxed magnetohydrodynamics in plasmas with slowly changing boundaries -- Resonant response of a plasma slab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dewar, R. L.; Hudson, S. R.; Bhattacharjee, A.

The adiabatic limit of a recently proposed dynamical extension of Taylor relaxation, multi-region relaxed magnetohydrodynamics (MRxMHD), is summarized, with special attention to the appropriate definition of a relative magnetic helicity. The formalism is illustrated using a simple two-region, sheared-magnetic-field model similar to the Hahm-Kulsrud-Taylor (HKT) rippled-boundary slab model. In MRxMHD, a linear Grad-Shafranov equation applies, even at finite ripple amplitude. The adiabatic switching on of boundary ripple excites a shielding current sheet opposing reconnection at a resonant surface. The perturbed magnetic field as a function of ripple amplitude is calculated by invoking the conservation of magnetic helicity in the twomore » regions separated by the current sheet. Here, at low ripple amplitude, "half islands" appear on each side of the current sheet, locking the rotational transform at the resonant value. Beyond a critical amplitude, these islands disappear and the rotational transform develops a discontinuity across the current sheet. Published by AIP Publishing.« less

Pinch dynamics in a low-β plasma

NASA Astrophysics Data System (ADS)

Moffatt, H. K.; Mizerski, K.

2018-02-01

The relaxation of a helical magnetic field {B}({x},t) in a high-conductivity plasma contained in the annulus between two perfectly conducting coaxial cylinders is considered. The plasma is of low density and its pressure is negligible compared with the magnetic pressure; the flow of the plasma is driven by the Lorentz force and energy is dissipated primarily by the viscosity of the medium. The axial and toroidal fluxes of magnetic field are conserved in the perfect-conductivity limit, as is the mass per unit axial length. The magnetic field relaxes during a rapid initial stage to a force-free state, and then decays slowly, due to the effect of weak resistivity η, while constrained to remain approximately force-free. Interest centres on whether the relaxed field may attain a Taylor state; but under the assumed conditions with axial and toroidal flux conserved inside every cylindrical Lagrangian surface, this is not possible. The effect of an additional α-effect associated with instabilities and turbulence in the plasma is therefore investigated in exploratory manner. An assumed pseudo-scalar form of α proportional to q η ({j}\\cdot {B}) is adopted, where {j}={{\

Density change and viscous flow during structural relaxation of plasma-enhanced chemical-vapor-deposited silicon oxide films

NASA Astrophysics Data System (ADS)

Cao, Zhiqiang; Zhang, Xin

2004-10-01

The structural relaxation of plasma-enhanced chemical-vapor-deposited (PECVD) silane-based silicon oxide films during thermal cycling and annealing has been studied using wafer curvature measurements. These measurements, which determine stress in the amorphous silicon oxide films, are sensitive to both plastic deformation and density changes. A quantitative case study of such changes has been done based upon the experimental results. A microstructure-based mechanism elucidates seams as a source of density change and voids as a source of plastic deformation, accompanied by a viscous flow. This theory was then used to explain a series of experimental results that are related to thermal cycling as well as annealing of PECVD silicon oxide films including stress hysteresis generation and reduction and coefficient of thermal-expansion changes. In particular, the thickness effect was examined; PECVD silicon oxide films with a thickness varying from 1to40μm were studied, as certain demanding applications in microelectromechanical systems require such thick films serving as heat/electrical insulation layers.

Folic acid consumption reduces resistin level and restores blunted acetylcholine-induced aortic relaxation in obese/diabetic mice.

PubMed

Seto, Sai Wang; Lam, Tsz Yan; Or, Penelope Mei Yu; Lee, Wayne Yuk Wai; Au, Alice Lai Shan; Poon, Christina Chui Wa; Li, Rachel Wai Sum; Chan, Shun Wan; Yeung, John Hok Keung; Leung, George Pak Heng; Lee, Simon Ming Yuen; Ngai, Sai Ming; Kwan, Yiu Wa

2010-09-01

Folic acid supplementation provides beneficial effects on endothelial functions in patients with hyperhomocysteinemia. However, its effects on vascular functions under diabetic conditions are largely unknown. Therefore, the effect(s) of folic acid (5.7 and 71 microg/kg/day for 4 weeks) on aortic relaxation was investigated using obese/diabetic (+db/+db) mice and lean littermate (+db/+m) mice. Acetylcholine-induced relaxation in +db/+db mice was less than that observed in +db/+m mice. The reduced relaxation in +db/+db mice was restored by consumption of 71 microg/kg folic acid. Acetylcholine-induced relaxation (with and without folic acid treatment) was sensitive to N(G)-nitro-L-arginine methyl ester, 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one, geldanamycin and triciribine. In addition, acetylcholine-induced relaxation was attenuated by resistin. The plasma level of resistin in +db/+db mice was sevenfold higher than that measured in +db/+m mice, and the elevated plasma level of resistin in +db/+db mice was reduced by 25% after treatment with 71 microg/kg folic acid. Folic acid slightly increased the ratio of reduced glutathione to oxidized glutathione in +db/+db mice. Moreover, folic acid caused a reduction in PTEN (phosphatase and tensin homolog deleted on chromosome 10) expression, an increase in the phosphorylation of endothelial nitric oxide synthase (eNOS(Ser1177)) and Akt(Ser473), and an enhanced interaction of heat shock protein 90 (HSP90) with eNOS in both strains, with greater magnitude observed in +db/+db mice. In conclusion, folic acid consumption improved blunted acetylcholine-induced relaxation in +db/+db mice. The mechanism may be, at least partly, attributed to enhancement of PI3K/HSP90/eNOS/Akt cascade, reduction in plasma resistin level, down-regulation of PTEN and slight modification of oxidative state. Copyright 2010 Elsevier Inc. All rights reserved.

Direct Visualization of Short Transverse Relaxation Time Component (ViSTa)

PubMed Central

Oh, Se-Hong; Bilello, Michel; Schindler, Matthew; Markowitz, Clyde E.; Detre, John A.; Lee, Jongho

2013-01-01

White matter of the brain has been demonstrated to have multiple relaxation components. Among them, the short transverse relaxation time component (T2 < 40 ms; T2* < 25 ms at 3T) has been suggested to originate from myelin water whereas long transverse relaxation time components have been associated with axonal and/or interstitial water. In myelin water imaging, T2 or T2* signal decay is measured to estimate myelin water fraction based on T2 or T2* differences among the water components. This method has been demonstrated to be sensitive to demyelination in the brain but suffers from low SNR and image artifacts originating from ill-conditioned multi-exponential fitting. In this study, a novel approach that selectively acquires short transverse relaxation time signal is proposed. The method utilizes a double inversion RF pair to suppress a range of long T1 signal. This suppression leaves short T2* signal, which has been suggested to have short T1, as the primary source of the image. The experimental results confirms that after suppression of long T1 signals, the image is dominated by short T2* in the range of myelin water, allowing us to directly visualize the short transverse relaxation time component in the brain. Compared to conventional myelin water imaging, this new method of direct visualization of short relaxation time component (ViSTa) provides high quality images. When applied to multiple sclerosis patients, chronic lesions show significantly reduced signal intensity in ViSTa images suggesting sensitivity to demyelination. PMID:23796545

Pair-Starved Pulsar Magnetospheres

NASA Technical Reports Server (NTRS)

Muslimov, Alex G.; Harding, Alice K.

2009-01-01

We propose a simple analytic model for the innermost (within the light cylinder of canonical radius, approx. c/Omega) structure of open-magnetic-field lines of a rotating neutron star (NS) with relativistic outflow of charged particles (electrons/positrons) and arbitrary angle between the NS spin and magnetic axes. We present the self-consistent solution of Maxwell's equations for the magnetic field and electric current in the pair-starved regime where the density of electron-positron plasma generated above the pulsar polar cap is not sufficient to completely screen the accelerating electric field and thus establish thee E . B = 0 condition above the pair-formation front up to the very high altitudes within the light cylinder. The proposed mode1 may provide a theoretical framework for developing the refined model of the global pair-starved pulsar magnetosphere.

A study of internal energy relaxation in shocks using molecular dynamics based models

NASA Astrophysics Data System (ADS)

Li, Zheng; Parsons, Neal; Levin, Deborah A.

2015-10-01

Recent potential energy surfaces (PESs) for the N2 + N and N2 + N2 systems are used in molecular dynamics (MD) to simulate rates of vibrational and rotational relaxations for conditions that occur in hypersonic flows. For both chemical systems, it is found that the rotational relaxation number increases with the translational temperature and decreases as the rotational temperature approaches the translational temperature. The vibrational relaxation number is observed to decrease with translational temperature and approaches the rotational relaxation number in the high temperature region. The rotational and vibrational relaxation numbers are generally larger in the N2 + N2 system. MD-quasi-classical trajectory (QCT) with the PESs is also used to calculate the V-T transition cross sections, the collision cross section, and the dissociation cross section for each collision pair. Direct simulation Monte Carlo (DSMC) results for hypersonic flow over a blunt body with the total collision cross section from MD/QCT simulations, Larsen-Borgnakke with new relaxation numbers, and the N2 dissociation rate from MD/QCT show a profile with a decreased translational temperature and a rotational temperature close to vibrational temperature. The results demonstrate that many of the physical models employed in DSMC should be revised as fundamental potential energy surfaces suitable for high temperature conditions become available.

Relaxation-Induced Anxiety: Paradoxical Anxiety Enhancement Due to Relaxation Training.

ERIC Educational Resources Information Center

Heide, Frederick J.; Borkovec, T. D.

1983-01-01

Documented relaxation-induced anxiety in 14 subjects suffering from tension who were given training in progressive relaxation and mantra meditation. Four of the subjects displayed clinical evidence of an anxiety reaction during a preliminary practice period. Progressive relaxation produced less evidence of relaxation-induced anxiety. (Author/JAC)

A Concept of Cross-Ferroic Plasma Turbulence

PubMed Central

Inagaki, S.; Kobayashi, T.; Kosuga, Y.; Itoh, S.-I.; Mitsuzono, T.; Nagashima, Y.; Arakawa, H.; Yamada, T.; Miwa, Y.; Kasuya, N.; Sasaki, M.; Lesur, M.; Fujisawa, A.; Itoh, K.

2016-01-01

The variety of scalar and vector fields in laboratory and nature plasmas is formed by plasma turbulence. Drift-wave fluctuations, driven by density gradients in magnetized plasmas, are known to relax the density gradient while they can generate flows. On the other hand, the sheared flow in the direction of magnetic fields causes Kelvin-Helmholtz type instabilities, which mix particle and momentum. These different types of fluctuations coexist in laboratory and nature, so that the multiple mechanisms for structural formation exist in extremely non-equilibrium plasmas. Here we report the discovery of a new order in plasma turbulence, in which chained structure formation is realized by cross-interaction between inhomogeneities of scalar and vector fields. The concept of cross-ferroic turbulence is developed, and the causal relation in the multiple mechanisms behind structural formation is identified, by measuring the relaxation rate and dissipation power caused by the complex turbulence-driven flux. PMID:26917218

Determination of antazoline hydrochloride in rat plasma and excreta by reversed-phase ion-pair chromatography and its application to pharmacokinetics.

PubMed

Wang, Rui; Chu, Yanle; Li, Xiaotian; Wan, Baoluo; Yu, Tong; Wang, Linxi; Hao, Lianqi; Guo, Maowen

2013-12-01

A reversed-phase ion pair chromatography method with liquid-liquid extraction analytical method was developed and validated for the determination of antazoline hydrochloride in plasma and excreta of rat. The aim of our study was to characterize the preclinical pharmacokinetics and excretion profiles of antazoline hydrochloride in rats after intravenous injection at the dose of 10 mg/kg. Plasma and excreta samples were extracted with ethyl acetate, and phenacetin was used as the internal standard. The result showed that the method is suitable for the quantification of antazoline hydrochloride in plasma and excreta samples. Analysis of accuracy (90.89-112.33%), imprecision (<7.1%) and recovery (>82.5%) showed adequate values. After a single intravenous administration at 10 mg/kg to rats, plasma concentration profile showed a relative fast elimination proceeding with a terminal elimination half-life of 3.53 h. Approximately 61.8 and 14.2% of the administered dose were recovered in urine and bile after 72 and 24 h post-dosing respectively; 5.9% of the administered dose was recovered in feces after 72 h post-dosing. The above results show that the major elimination route is urinary excretion. Copyright © 2013 John Wiley & Sons, Ltd.

Energy relaxation of intense laser pulse-produced plasmas

NASA Astrophysics Data System (ADS)

Shihab, M.; Abou-Koura, G. H.; El-Siragy, N. M.

2016-05-01

We describe a collisional radiative model (CRE) of homogeneously expanded nickel plasmas in vacuum. The CRE model is coupled with two separate electron and ion temperature magneto-hydrodynamic equations. On the output, the model provides the temporal variation of the electron temperature, ion temperature, and average charge state. We demonstrate the effect of three-body recombination ({∝}N_e T^{-9/2}_e) on plasma parameters, as it changes the time dependence of electron temperature from t^{-2} to t^{-1} and exhibits a pronounced effect leading to a freezing feature in the average charge state. In addition, the effect of the three-body recombination on the warm up of ions and delaying the equilibration is addressed.

Gyro-viscosity and linear dispersion relations in pair-ion magnetized plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kono, M.; Vranjes, J.; Departamento de Astrofisica, Universidad de La Laguna, Tenerife E38205

2015-11-15

A fluid theory has been developed by taking account of gyro-viscosity to study wave propagation characteristics in a homogeneous pair-ion magnetized plasma with a cylindrical symmetry. The exact dispersion relations derived by the Hankel-Fourier transformation are shown comparable with those observed in the experiment by Oohara and co-workers. The gyro-viscosity is responsible for the change in propagation characteristics of the ion cyclotron wave from forward to backward by suppressing the effect of the thermal pressure which normally causes the forward nature of dispersion. Although the experiment has been already explained by a kinetic theory by the present authors, the kineticmore » derivations are so involved because of exact particle orbits in phase space, finite Lamor radius effects, and higher order ion cyclotron resonances. The present fluid theory provides a simple and transparent structure to the dispersion relations since the gyro-viscosity is renormalized into the ion cyclotron frequency which itself indicates the backward nature of dispersion. The usual disadvantage of a fluid theory, which treats only fundamental modes of eigen-waves excited in a system and is not able to describe higher harmonics that a kinetic theory does, is compensated by simple derivations and clear picture based on the renormalization of the gyro-viscosity.« less

Magnetothermodynamics: measurements of the thermodynamic properties in a relaxed magnetohydrodynamic plasma

NASA Astrophysics Data System (ADS)

Kaur, M.; Barbano, L. J.; Suen-Lewis, E. M.; Shrock, J. E.; Light, A. D.; Schaffner, D. A.; Brown, M. B.; Woodruff, S.; Meyer, T.

2018-02-01

We have explored the thermodynamics of compressed magnetized plasmas in laboratory experiments and we call these studies `magnetothermodynamics'. The experiments are carried out in the Swarthmore Spheromak eXperiment device. In this device, a magnetized plasma source is located at one end and at the other end, a closed conducting can is installed. We generate parcels of magnetized plasma and observe their compression against the end wall of the conducting cylinder. The plasma parameters such as plasma density, temperature and magnetic field are measured during compression using HeNe laser interferometry, ion Doppler spectroscopy and a linear probe array, respectively. To identify the instances of ion heating during compression, a PV diagram is constructed using measured density, temperature and a proxy for the volume of the magnetized plasma. Different equations of state are analysed to evaluate the adiabatic nature of the compressed plasma. A three-dimensional resistive magnetohydrodynamic code (NIMROD) is employed to simulate the twisted Taylor states and shows stagnation against the end wall of the closed conducting can. The simulation results are consistent to what we observe in our experiments.

Fundamentals of Plasma Physics

NASA Astrophysics Data System (ADS)

Bellan, Paul M.

2008-07-01

Preface; 1. Basic concepts; 2. The Vlasov, two-fluid, and MHD models of plasma dynamics; 3. Motion of a single plasma particle; 4. Elementary plasma waves; 5. Streaming instabilities and the Landau problem; 6. Cold plasma waves in a magnetized plasma; 7. Waves in inhomogeneous plasmas and wave energy relations; 8. Vlasov theory of warm electrostatic waves in a magnetized plasma; 9. MHD equilibria; 10. Stability of static MHD equilibria; 11. Magnetic helicity interpreted and Woltjer-Taylor relaxation; 12. Magnetic reconnection; 13. Fokker-Planck theory of collisions; 14. Wave-particle nonlinearities; 15. Wave-wave nonlinearities; 16. Non-neutral plasmas; 17. Dusty plasmas; Appendix A. Intuitive method for vector calculus identities; Appendix B. Vector calculus in orthogonal curvilinear coordinates; Appendix C. Frequently used physical constants and formulae; Bibliography; References; Index.

Relaxation model for extended magnetohydrodynamics: Comparison to magnetohydrodynamics for dense Z-pinches

DOE PAGES

Seyler, C. E.; Martin, M. R.

2011-01-14

In this study, it is shown that the two-fluid model under a generalized Ohm’s law formulation and the resistive magnetohydrodynamics (MHD) can both be described as relaxation systems. In the relaxation model, the under-resolved stiff source terms constrain the dynamics of a set of hyperbolic equations to give the correct asymptotic solution. When applied to the collisional two-fluid model, the relaxation of fast time scales associated with displacement current and finite electron mass allows for a natural transition from a system where Ohm’s law determines the current density to a system where Ohm’s law determines the electric field. This resultmore » is used to derive novel algorithms, which allow for multiscale simulation of low and high frequency extended-MHD physics. This relaxation formulation offers an efficient way to implicitly advance the Hall term and naturally simulate a plasma-vacuum interface without invoking phenomenological models. The relaxation model is implemented as an extended-MHD code, which is used to analyze pulsed power loads such as wire arrays and ablating foils. Two-dimensional simulations of pulsed power loads are compared for extended-MHD and MHD. For these simulations, it is also shown that the relaxation model properly recovers the resistive-MHD limit.« less

The radial electric field dynamics in the neoclassical plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Novakovskii, S.V.; Liu, C.S.; Sagdeev, R.Z.

1997-12-01

A numerical simulation and analytical theory of the radial electric field dynamics in low collisional tokamak plasmas are presented. An initial value code {open_quotes}ELECTRIC{close_quotes} has been developed to solve the ion drift kinetic equation with a full collisional operator in the Hirshman{endash}Sigmar{endash}Clarke form together with the Maxwell equations. Different scenarios of relaxation of the radial electric field toward the steady-state in response to sudden and adiabatic changes of the equilibrium temperature gradient are presented. It is shown, that while the relaxation is usually accompanied by the geodesic acoustic oscillations, during the adiabatic change these oscillations are suppressed and only themore » magnetic pumping remains. Both the collisional damping and the Landau resonance interaction are shown to be important relaxation mechanisms. Scalings of the relaxation rates versus basic plasma parameters are presented. {copyright} {ital 1997 American Institute of Physics.}« less

Superexchange coupling and slow magnetic relaxation in a transuranium polymetallic complex.

PubMed

Magnani, N; Colineau, E; Eloirdi, R; Griveau, J-C; Caciuffo, R; Cornet, S M; May, I; Sharrad, C A; Collison, D; Winpenny, R E P

2010-05-14

{Np(VI)O2Cl2}{Np(V)O2Cl(thf)3}2 is the first studied example of a polymetallic transuranic complex displaying both slow relaxation of the magnetization and effective superexchange interactions between 5f centers. The coupling constant for Np(V)-Np(VI) pairs is 10.8 K, more than 1 order of magnitude larger than the common values found for rare-earth ions in similar environments. The dynamic magnetic behavior displays slow relaxation of magnetization of molecular origin with an energy barrier of 140 K, which is nearly twice the size of the highest barrier found in polymetallic clusters of the d block. Our observations also suggest that future actinide-based molecular magnets will have very different behavior to lanthanide-based clusters.

Detection of swine-origin influenza A (H1N1) viruses using a paired surface plasma waves biosensor

NASA Astrophysics Data System (ADS)

Su, Li-Chen; Chang, Ying-Feng; Li, Ying-Chang; Hsieh, Jo-Ping; Lee, Cheng-Chung; Chou, Chien

2010-08-01

In order to enhance the sensitivity of conventional rapid test technique for the detection of swine-origin influenza A (H1N1) viruses (S-OIVs), we used a paired surface plasma waves biosensor (PSPWB) based on SPR in conjunction with an optical heterodyne technique. Experimentally, PSPWB showed a 125-fold improvement at least in the S-OIV detection as compared to conventional enzyme linked immunosorbent assay. Moreover, the detection limit of the PSPWB for the S-OIV detection was enhanced 250-fold in buffer at least in comparison with that of conventional rapid influenza diagnostic test.

Breathing and Relaxation

MedlinePlus

... Programs Health Information Doctors & Departments Clinical Research & Science Education & Training Home Health Insights Stress & Relaxation Breathing and Relaxation Breathing and Relaxation Make ...

Dynamics and control of the vortex flow behind a slender conical forebody by a pair of plasma actuators

NASA Astrophysics Data System (ADS)

Meng, Xuanshi; Long, Yuexiao; Wang, Jianlei; Liu, Feng; Luo, Shijun

2018-02-01

Detailed particle-image-velocimetry (PIV) and surface pressure measurements are presented to study the vortex flow behind a slender conical forebody at high angles of attack. The results confirm the existence of two randomly appearing mirror imaged asymmetric bi-stable states of the separation vortices, giving rise to large side force and moment. A pair of carefully designed dielectric barrier discharge plasma actuators mounted near the apex and on both sides of the conical body are used to manipulate the vortex flow and thus provide control of the side forces on the body without using flaps. By making use of a duty-cycle actuation scheme that alternately actuates the port and starboard plasma actuators and optimizing the duty-cycle frequency, the present work demonstrates the feasibility of achieving a nearly perfect linear proportional control of the side force and moment in response to the duty-cycle ratio. Phase-locked PIV and surface pressure measurements are used to study the unsteady dynamic evolution of the flow within one duty-cycle actuation to reveal the flow control mechanism. It is found that under the duty-cycle actuation with the optimized frequency, the vortex flow essentially follows the plasma actuation by alternating between the two bi-stable states controlled directly by the duty-cycle ratio.

Bifunctional Rhodamine Probes of Myosin Regulatory Light Chain Orientation in Relaxed Skeletal Muscle Fibers

PubMed Central

Brack, Andrew S.; Brandmeier, Birgit D.; Ferguson, Roisean E.; Criddle, Susan; Dale, Robert E.; Irving, Malcolm

2004-01-01

The orientation of the regulatory light chain (RLC) region of the myosin heads in relaxed skinned fibers from rabbit psoas muscle was investigated by polarized fluorescence from bifunctional rhodamine (BR) probes cross-linking pairs of cysteine residues introduced into the RLC. Pure 1:1 BR-RLC complexes were exchanged into single muscle fibers in EDTA rigor solution for 30 min at 30°C; ∼60% of the native RLC was removed and stoichiometrically replaced by BR-RLC, and >85% of the BR-RLC was located in the sarcomeric A-bands. The second- and fourth-rank order parameters of the orientation distributions of BR dipoles linking RLC cysteine pairs 100-108, 100-113, 108-113, and 104-115 were calculated from polarized fluorescence intensities, and used to determine the smoothest RLC orientation distribution—the maximum entropy distribution—consistent with the polarized fluorescence data. Maximum entropy distributions in relaxed muscle were relatively broad. At the peak of the distribution, the “lever” axis, linking Cys707 and Lys843 of the myosin heavy chain, was at 70–80° to the fiber axis, and the “hook” helix (Pro830–Lys843) was almost coplanar with the fiber and lever axes. The temperature and ionic strength of the relaxing solution had small but reproducible effects on the orientation of the RLC region. PMID:15041671

Serotonin 1A Agonism Decreases Affiliative Behavior in Pair-Bonded Titi Monkeys

PubMed Central

Larke, Rebecca H.; Maninger, Nicole; Ragen, Benjamin J; Mendoza, Sally P.; Bales, Karen L.

2016-01-01

Relatively little is known about serotonergic involvement in pair-bonding despite its putative role in regulating social behavior. Here we sought to determine if pharmacological elevation of serotonin 1A (5-HT1A) receptor activity would lead to changes in social behavior in pair-bonded male titi monkeys (Callicebus cupreus). Adult males in established heterosexual pairs were injected daily with the selective 5-HT1A agonist 8-OH-DPAT or saline for 15 days using a within-subjects design. Social behavior with the female pair-mate was quantified, and plasma concentrations of oxytocin, vasopressin, and cortisol were measured. When treated with saline, subjects showed reduced plasma oxytocin concentrations, while 8-OH-DPAT treatment buffered this decrease. Treatment with 8-OH-DPAT also led to decreased plasma cortisol 15 minutes post-injection and decreased social behavior directed toward the pair-mate including approaching, initiating contact, lipsmacking, and grooming. The reduction in affiliative behavior seen with increased activity at 5-HT1A receptors indicates a substantial role of serotonin activity in the expression of social behavior. In addition, results indicate that the effects of 5-HT1A agonism on social behavior in adulthood differ between rodents and primates. PMID:27712925

Crater Relaxation and Stereo Imaging of the Icy Satellites of Jupiter and Saturn

NASA Astrophysics Data System (ADS)

Phillips, C. B.; Beyer, R. A.; Nimmo, F.; Roberts, J. H.; Robuchon, G.

2010-12-01

Crater relaxation has been used as a probe of subsurface temperature structure for over thirty years, both on terrestrial bodies and icy satellites. We are developing and testing two independent methods for processing stereo pairs to produce digital elevation models, to address how crater relaxation depends on crater diameter, geographic location, and stratigraphic position on the icy satellites of Jupiter and Saturn. Our topographic profiles will then serve as input into two numerical models, one viscous and one viscoelastic, to allow us to probe the subsurface thermal profiles and relaxation histories of these satellites. We are constructing stereo topography from Galileo and Cassini image pairs using the NASA Ames Stereo Pipeline (Moratto et al. 2010), an automated stereogrammetry tool designed for processing planetary imagery captured from orbiting and landed robotic explorers on other planets. We will also be using the commercial program SOCET SET from BAE Systems (Miller and Walker 1993; 1995). Qualitatively, it is clear that there are large spatial variations in the degree of crater relaxation among Jupiter’s and Saturn’s satellites. However, our use of stereo topography will allow quantitative measures of crater relaxation (e.g. depth:diameter ratio or equivalent) to be derived. Such measures are essential to derive quantitative estimates of the heat fluxes responsible for this relaxation. Estimating how surface heat flux has varied with time provides critical constraints on satellite thermal (and orbital) evolution. Craters undergo viscous relaxation over time at a rate that depends on the temperature gradient and crater scale. We are investigating how the near-surface satellite heat flux varied in time and space, based on our crater relaxation observations. Once we have crater profiles from our DEMs, we use them as input to two theoretical approaches: a relatively simple (viscous) numerical model in which time-varying heat fluxes can be included, and

Plasma Chemistry of Vibrationally Nonequilibrium Molecules

DTIC Science & Technology

1993-11-01

WL-TR-93-2116 PLASMA CHEMISTRY OF VIBRATIONALLY NONEQUILIBRIUM MOLECULES AD-A279 630--, J. WILLIAM RICH DEPARTMENT OF MECHANICAL ENGINEERING D THE...1AT9E L. REPORT TYPE AND DATES COVERED ONLY Man"_November 1993 Final 09 July 1990_- 08 July 1993 4 MITL AND SUBTITLE S. FUNDNG NUMERS & Plasma Chemistry of...k14. SUBIECT TERMS 15. NUMBER OF PAGES Molecular Energy Transfer; Plasma Chemistry ; Ionization; 4% Vibrational Relaxation; Nitric Oxide; Carbon

The roles of dominos and nonsimultaneous chains in kidney paired donation.

PubMed

Gentry, S E; Montgomery, R A; Swihart, B J; Segev, D L

2009-06-01

Efforts to expand kidney paired donation have included matching nondirected donors (NDDs) to incompatible pairs. In domino paired donation (DPD), an NDD gives to the recipient of an incompatible pair, beginning a string of simultaneous transplants that ends with a living donor giving to a recipient on the deceased donor waitlist. Recently, nonsimultaneous extended altruistic donor (NEAD) chains were introduced. In a NEAD chain, the last donor of the string of transplants initiated by an NDD is reserved to donate at a later time. Our aim was to project the impact of each of these strategies over 2 years of operation for paired donation programs that also allocate a given number of NDDs. Each NDD facilitated an average of 1.99 transplants using DPD versus 1.90 transplants using NEAD chains (p = 0.3), or 1.0 transplants donating directly to the waitlist (p < 0.001). NEAD chains did not yield more transplants compared with simultaneous DPD. Both DPD and NEAD chains relax reciprocality requirements and rebalance the blood-type distribution of donors. Because traditional paired donation will leave many incompatible pairs unmatched, novel approaches like DPD and NEAD chains must be explored if paired donation programs are to help a greater number of people.

Differentiable McCormick relaxations

DOE PAGES

Khan, Kamil A.; Watson, Harry A. J.; Barton, Paul I.

2016-05-27

McCormick's classical relaxation technique constructs closed-form convex and concave relaxations of compositions of simple intrinsic functions. These relaxations have several properties which make them useful for lower bounding problems in global optimization: they can be evaluated automatically, accurately, and computationally inexpensively, and they converge rapidly to the relaxed function as the underlying domain is reduced in size. They may also be adapted to yield relaxations of certain implicit functions and differential equation solutions. However, McCormick's relaxations may be nonsmooth, and this nonsmoothness can create theoretical and computational obstacles when relaxations are to be deployed. This article presents a continuously differentiablemore » variant of McCormick's original relaxations in the multivariate McCormick framework of Tsoukalas and Mitsos. Gradients of the new differentiable relaxations may be computed efficiently using the standard forward or reverse modes of automatic differentiation. Furthermore, extensions to differentiable relaxations of implicit functions and solutions of parametric ordinary differential equations are discussed. A C++ implementation based on the library MC++ is described and applied to a case study in nonsmooth nonconvex optimization.« less

Relaxation from Steady States Far from Equilibrium and the Persistence of Anomalous Shock Behavior in Weakly Ionized Gases

NASA Technical Reports Server (NTRS)

Rubinstein, Robert; Auslender, Aaron H.

1999-01-01

The decay of anomalous effects on shock waves in weakly ionized gases following plasma generator extinction has been measured in the anticipation that the decay time must correlate well with the relaxation time of the mechanism responsible for the anomalous effects. When the relaxation times cannot be measured directly, they are inferred theoretically, usually assuming that the initial state is nearly in thermal equilibrium. In this paper, it is demonstrated that relaxation from any steady state far from equilibrium, including the state of a weakly ionized gas, can proceed much more slowly than arguments based on relaxation from near equilibrium states might suggest. This result justifies a more careful analysis of the relaxation times in weakly ionized gases and suggests that although the experimental measurements of relaxation times did not lead to an unambiguous conclusion, this approach to understanding the anomalous effects may warrant further investigation.

Quark and Gluon Relaxation in Quark-Gluon Plasmas

NASA Technical Reports Server (NTRS)

Heiselberg, H.; Pethick, C. J.

1993-01-01

The quasiparticle decay rates for quarks and gluons in quark-gluon plasmas are calculated by solving the kinetic equation. Introducing an infrared cutoff to allow for nonperturbative effects, we evaluate the quasiparticle lifetime at momenta greater than the inverse Debye screening length to leading order in the coupling constant.

RELATIVISTIC CYCLOTRON INSTABILITY IN ANISOTROPIC PLASMAS

DOE Office of Scientific and Technical Information (OSTI.GOV)

López, Rodrigo A.; Moya, Pablo S.; Muñoz, Víctor

2016-11-20

A sufficiently large temperature anisotropy can sometimes drive various types of electromagnetic plasma micro-instabilities, which can play an important role in the dynamics of relativistic pair plasmas in space, astrophysics, and laboratory environments. Here, we provide a detailed description of the cyclotron instability of parallel propagating electromagnetic waves in relativistic pair plasmas on the basis of a relativistic anisotropic distribution function. Using plasma kinetic theory and particle-in-cell simulations, we study the influence of the relativistic temperature and the temperature anisotropy on the collective and noncollective modes of these plasmas. Growth rates and dispersion curves from the linear theory show amore » good agreement with simulations results.« less

Real-time observation of formation and relaxation dynamics of NH4 in (CH3OH)m(NH3)n clusters.

PubMed

Yamada, Yuji; Nishino, Yoko; Fujihara, Akimasa; Ishikawa, Haruki; Fuke, Kiyokazu

2009-03-26

The formation and relaxation dynamics of NH4(CH3OH)m(NH3)n clusters produced by photolysis of ammonia-methanol mixed clusters has been observed by a time-resolved pump-probe method with femtosecond pulse lasers. From the detailed analysis of the time evolutions of the protonated cluster ions, NH4(+)(CH3OH)m(NH3)n, the kinetic model has been constructed, which consists of sequential three-step reaction: ultrafast hydrogen-atom transfer producing the radical pair (NH4-NH2)*, the relaxation process of radical-pair clusters, and dissociation of the solvated NH4 clusters. The initial hydrogen transfer hardly occurs between ammonia and methanol, implying the unfavorable formation of radical pair, (CH3OH2-NH2)*. The remarkable dependence of the time constants in each step on the number and composition of solvents has been explained by the following factors: hydrogen delocalization within the clusters, the internal conversion of the excited-state radical pair, and the stabilization of NH4 by solvation. The dependence of the time profiles on the probe wavelength is attributed to the different ionization efficiency of the NH4(CH3OH)m(NH3)n clusters.

Numerical investigation of kinetic turbulence in relativistic pair plasmas - I. Turbulence statistics

NASA Astrophysics Data System (ADS)

Zhdankin, Vladimir; Uzdensky, Dmitri A.; Werner, Gregory R.; Begelman, Mitchell C.

2018-02-01

We describe results from particle-in-cell simulations of driven turbulence in collisionless, magnetized, relativistic pair plasma. This physical regime provides a simple setting for investigating the basic properties of kinetic turbulence and is relevant for high-energy astrophysical systems such as pulsar wind nebulae and astrophysical jets. In this paper, we investigate the statistics of turbulent fluctuations in simulations on lattices of up to 10243 cells and containing up to 2 × 1011 particles. Due to the absence of a cooling mechanism in our simulations, turbulent energy dissipation reduces the magnetization parameter to order unity within a few dynamical times, causing turbulent motions to become sub-relativistic. In the developed stage, our results agree with predictions from magnetohydrodynamic turbulence phenomenology at inertial-range scales, including a power-law magnetic energy spectrum with index near -5/3, scale-dependent anisotropy of fluctuations described by critical balance, lognormal distributions for particle density and internal energy density (related by a 4/3 adiabatic index, as predicted for an ultra-relativistic ideal gas), and the presence of intermittency. We also present possible signatures of a kinetic cascade by measuring power-law spectra for the magnetic, electric and density fluctuations at sub-Larmor scales.

Analysis of energy relaxation kinetics for control of the electron energy distributions in capacitively coupled RF discharges

NASA Astrophysics Data System (ADS)

Lee, Jung Yeol; Verboncoeur, John P.; Lee, Hae June

2018-04-01

The transition of electron energy probability functions (EEPFs) through the change of heating mode is an important issue in plasma science. A well-known example is that the increase of gas pressure, which was analyzed in terms of the ratio of the energy relaxation mean free path to the electrode gap distance, changes the EEPF from bi-Maxwellian to Maxwellian or Druyvesteyn. In this study, a new aspect of the temporal decay of kinetic energy during the energy relaxation time is theoretically analyzed and compared with a particle-in-cell Monte Carlo collision simulation of capacitively coupled plasmas. A fully kinetic description of electron transport and collisions shows drastic changes of EEPFs with the variation of the driving frequency due to the heating mode transition.

Causal hydrodynamics of gauge theory plasmas from AdS/CFT duality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Natsuume, Makoto; Okamura, Takashi; Department of Physics, Kwansei Gakuin University, Sanda, Hyogo, 669-1337

2008-03-15

We study causal hydrodynamics (Israel-Stewart theory) of gauge theory plasmas from the AdS/CFT duality. Causal hydrodynamics requires new transport coefficients (relaxation times) and we compute them for a number of supersymmetric gauge theories including the N=4 super Yang-Mills theory. However, the relaxation times obtained from the 'shear mode' do not agree with the ones from the 'sound mode', which implies that the Israel-Stewart theory is not a sufficient framework to describe the gauge theory plasmas.

Relaxation Training and Postoperative Music Therapy for Adolescents Undergoing Spinal Fusion Surgery.

PubMed

Nelson, Kirsten; Adamek, Mary; Kleiber, Charmaine

2017-02-01

Spinal fusion for idiopathic scoliosis is one of the most painful surgeries experienced by adolescents. Music therapy, utilizing music-assisted relaxation with controlled breathing and imagery, is a promising intervention for reducing pain and anxiety for these patients. It can be challenging to teach new coping strategies to post-operative patients who are already in pain. This study evaluated the effects of introducing music-assisted relaxation training to adolescents before surgery. Outcome measures were self-reported pain and anxiety, recorded on 0-10 numeric rating scale, and observed behavioral indicators of pain and relaxation. The training intervention was a 12-minute video about music-assisted relaxation with opportunities to practice before surgery. Forty-four participants between the ages of 10 and 19 were enrolled. Participants were randomly assigned to the experimental group that watched the video at the preoperative visit or to the control group that did not watch the video. All subjects received a music therapy session with a board certified music therapist on post-operative day 2 while out of bed for the first time. Pain and anxiety were significantly reduced from immediately pre-therapy to post-therapy (paired t-test; p). Copyright © 2016 American Society for Pain Management Nursing. Published by Elsevier Inc. All rights reserved.

Dielectric relaxation and localized electron hopping in colossal dielectric (Nb,In)-doped TiO2 rutile nanoceramics.

PubMed

Tsuji, Kosuke; Han, HyukSu; Guillemet-Fritsch, Sophie; Randall, Clive A

2017-03-28

Dielectric spectroscopy was performed on a Nb and In co-doped rutile TiO 2 nano-crystalline ceramic (n-NITO) synthesized by a low-temperature spark plasma sintering (SPS) technique. The dielectric properties of the n-NITO were not largely affected by the metal electrode contacts. Huge dielectric relaxation was observed at a very low temperature below 35 K. Both the activation energy and relaxation time suggested that the electronic hopping motion is the underlying mechanism responsible for the colossal dielectric permittivity (CP) and its relaxation, instead of the internal barrier layer effect or a dipolar relaxation. With Havriliak-Negami (H-N) fitting, a relaxation time with a large distribution of dielectric relaxations was revealed. The broad distributed relaxation phenomena indicated that Nb and In were involved, controlling the dielectric relaxation by modifying the polarization mechanism and localized states. The associated distribution function is calculated and presented. The frequency-dependent a.c. conductance is successfully explained by a hopping conduction model of the localized electrons with the distribution function. It is demonstrated that the dielectric relaxation is strongly correlated with the hopping electrons in the localized states. The CP in SPS n-NITO is then ascribed to a hopping polarization.

Ion-pair vortex assisted liquid-liquid microextraction with back extraction coupled with high performance liquid chromatography-UV for the determination of metformin in plasma.

PubMed

Alshishani, Anas; Makahleh, Ahmad; Yap, Hui Fang; Gubartallah, Elbaleeq Adam; Salhimi, Salizawati Muhamad; Saad, Bahruddin

2016-12-01

A new sample preparation method, ion-pair vortex assisted liquid-liquid microextraction (VALLME-BE), for the determination of a highly polar anti-diabetic drug (metformin) in plasma sample was developed. The VALLME-BE was performed by diluting the plasma in borate buffer and extracted to 150µL 1-octanol containing 0.2M di-(2-ethylhexyl)phosphoric acid as intermediate phase. The drug was next back-extracted into 20µL of 0.075M HCl solution. The effects of pH, ion-pair concentration, type of organic solvent, volume of extraction phases, ionic strength, vortexing and centrifugation times on the extraction efficiency were investigated. The optimum conditions were at pH 9.3, 60s vortexing and 2min centrifugation. The microextract, contained metformin and buformin (internal standard), was directly injected into a HPLC unit using C1 column (250mm×4.6mm×10µm) and detected at 235nm. The method was validated and calibration curve was linear with r 2 >0.99 over the range of 20-2000µgL -1 . The limits of detection and quantitation were 1.4 and 4.1µgL -1 , respectively. The accuracy was within 94.8-108% of the nominal concentration. The relative standard deviation for inter- and intra-day precision was less than 10.8%. The method was conveniently applied for the determination of metformin in plasma samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Resolving environmental microheterogeneity and dielectric relaxation in fluorescence kinetics of protein

NASA Astrophysics Data System (ADS)

Rolinski, Olaf J.; McLaughlin, Damien; Birch, David J. S.; Vyshemirsky, Vladislav

2016-09-01

The fluorescence intensity decay of protein is easily measurable and reports on the intrinsic fluorophore-local environment interactions on the sub-nm spatial and sub-ns temporal scales, which are consistent with protein activity in numerous biomedical and industrial processes. This makes time-resolved fluorescence a perfect tool for understanding, monitoring and controlling these processes at the molecular level, but the complexity of the decay, which has been traditionally fitted to multi-exponential functions, has hampered the development of this technique over the last few decades. Using the example of tryptophan in HSA we present the alternative to the conventional approach to modelling intrinsic florescence intensity decay in protein where the key factors determining fluorescence decay, i.e. the excited-state depopulation and the dielectric relaxation (Toptygin and Brand 2000 Chem. Phys. Lett. 322 496-502), are represented by the individual relaxation functions. This allows quantification of both effects separately by determining their parameters from the global analysis of a series of fluorescence intensity decays measured at different detection wavelengths. Moreover, certain pairs of the recovered parameters of tryptophan were found to be correlated, indicating the influence of the dielectric relaxation on the transient rate of the electronic transitions. In this context the potential for the dual excited state depopulation /dielectric relaxation fluorescence lifetime sensing is discussed.

Spin-lattice relaxation of optically polarized nuclei in p -type GaAs

NASA Astrophysics Data System (ADS)

Kotur, M.; Dzhioev, R. I.; Vladimirova, M.; Cherbunin, R. V.; Sokolov, P. S.; Yakovlev, D. R.; Bayer, M.; Suter, D.; Kavokin, K. V.

2018-04-01

Spin-lattice relaxation of the nuclear spin system in p -type GaAs is studied using a three-stage experimental protocol including optical pumping and measuring the difference of the nuclear spin polarization before and after a dark interval of variable length. This method allows us to measure the spin-lattice relaxation time T1 of optically pumped nuclei "in the dark," that is, in the absence of illumination. The measured T1 values fall into the subsecond time range, being three orders of magnitude shorter than in earlier studied n -type GaAs. The drastic difference is further emphasized by magnetic-field and temperature dependencies of T1 in p -GaAs, showing no similarity to those in n -GaAs. This unexpected behavior finds its explanation in the spatial selectivity of the optical pumping in p -GaAs, that is only efficient in the vicinity of shallow donors, together with the quadrupole relaxation of nuclear spins, which is induced by electric fields within closely spaced donor-acceptor pairs. The developed theoretical model explains the whole set of experimental results.

e+/- Pair Loading and the Origin of the Upstream Field in GRB Shocks

NASA Technical Reports Server (NTRS)

Ramirez-Ruiz, Enrico; Nishikawa, Ken-Ichi; Hededal, Christian B.

2006-01-01

We investigate here the effects of plasma instabilities driven by rapid e(sup plus or minus) pair cascades, which arise in the environment of GRB sources as a result of back-scattering of a seed fraction of their original spectrum. The injection of e(sup plus or minus) pairs induces strong streaming motions in the ambient medium. One therefore expects the pair-enriched medium ahead of the forward shock to be strongly sheared on length scales comparable to the radiation front thickness. Using three-dimensional particle-in-cell simulations, we show that plasma instabilities driven by these streaming e(sup plus or minus) pairs are responsible for the excitation of near-equipartition, turbulent magnetic fields. Our results reveal the importance of the electromagnetic filamentation instability in ensuring an effective coupling between e(sup plus or minus) pairs and ions, and may help explain the origin of large upstream fields in GRB shocks.

Communication: Exact analytical derivatives for the domain-based local pair natural orbital MP2 method (DLPNO-MP2)

NASA Astrophysics Data System (ADS)

Pinski, Peter; Neese, Frank

2018-01-01

Electron correlation methods based on pair natural orbitals (PNOs) have gained an increasing degree of interest in recent years, as they permit energy calculations to be performed on systems containing up to many hundred atoms, while maintaining chemical accuracy for reaction energies. We present an approach for taking exact analytical first derivatives of the energy contributions in the simplest method of the family of Domain-based Local Pair Natural Orbital (DLPNO) methods, closed-shell DLPNO-MP2. The Lagrangian function contains constraints to account for the relaxation of PNOs. RI-MP2 reference geometries are reproduced accurately, as exemplified for four systems with a substantial degree of nonbonding interactions. By the example of electric field gradients, we demonstrate that omitting PNO-specific constraints can lead to dramatic errors for orbital-relaxed properties.

Effects of progressive relaxation and classical music on measurements of attention, relaxation, and stress responses.

PubMed

Scheufele, P M

2000-04-01

The present experiment examined relaxation using different experimental conditions to test whether the effects of individual elements of relaxation could be measured, whether specific effects were revealed, or whether relaxation resulted from a generalized "relaxation response." Sixty-seven normal, male volunteers were exposed to a stress manipulation and then to one of two relaxation (Progressive Relaxation, Music) or control (Attention Control, Silence) conditions. Measurements of attention, relaxation, and stress responses were obtained during each phase of the experiment. All four groups exhibited similar performance on behavioral measures of attention that suggested a reduction in physiological arousal following their relaxation or control condition, as well as a decreased heart rate. Progressive Relaxation, however, resulted in the greatest effects on behavioral and self-report measures of relaxation, suggesting that cognitive cues provided by stress management techniques contribute to relaxation.

Interlayer electron-hole pair multiplication by hot carriers in atomic layer semiconductor heterostructures

NASA Astrophysics Data System (ADS)

Barati, Fatemeh; Grossnickle, Max; Su, Shanshan; Lake, Roger; Aji, Vivek; Gabor, Nathaniel

Two-dimensional heterostructures composed of atomically thin transition metal dichalcogenides provide the opportunity to design novel devices for the study of electron-hole pair multiplication. We report on highly efficient multiplication of interlayer electron-hole pairs at the interface of a tungsten diselenide / molybdenum diselenide heterostructure. Electronic transport measurements of the interlayer current-voltage characteristics indicate that layer-indirect electron-hole pairs are generated by hot electron impact excitation. Our findings, which demonstrate an efficient energy relaxation pathway that competes with electron thermalization losses, make 2D semiconductor heterostructures viable for a new class of hot-carrier energy harvesting devices that exploit layer-indirect electron-hole excitations. SHINES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Air Force Office of Scientific Research.

Oscillatory nonohomic current drive for maintaining a plasma current

DOEpatents

Fisch, N.J.

1984-01-01

Apparatus and methods are described for maintaining a plasma current with an oscillatory nonohmic current drive. Each cycle of operation has a generation period in which current driving energy is applied to the plasma, and a relaxation period in which current driving energy is removed. Plasma parameters, such as plasma temperature or plasma average ionic charge state, are modified during the generation period so as to oscillate plasma resistivity in synchronism with the application of current driving energy. The invention improves overall current drive efficiencies.

Oscillatory nonhmic current drive for maintaining a plasma current

DOEpatents

Fisch, Nathaniel J.

1986-01-01

Apparatus and method of the invention maintain a plasma current with an oscillatory nonohmic current drive. Each cycle of operation has a generation period in which current driving energy is applied to the plasma, and a relaxation period in which current driving energy is removed. Plasma parameters, such as plasma temperature or plasma average ionic charge state, are modified during the generation period so as to oscillate plasma resistivity in synchronism with the application of current driving energy. The invention improves overall current drive efficiencies.

Capturing molecular multimode relaxation processes in excitable gases based on decomposition of acoustic relaxation spectra

NASA Astrophysics Data System (ADS)

Zhu, Ming; Liu, Tingting; Wang, Shu; Zhang, Kesheng

2017-08-01

Existing two-frequency reconstructive methods can only capture primary (single) molecular relaxation processes in excitable gases. In this paper, we present a reconstructive method based on the novel decomposition of frequency-dependent acoustic relaxation spectra to capture the entire molecular multimode relaxation process. This decomposition of acoustic relaxation spectra is developed from the frequency-dependent effective specific heat, indicating that a multi-relaxation process is the sum of the interior single-relaxation processes. Based on this decomposition, we can reconstruct the entire multi-relaxation process by capturing the relaxation times and relaxation strengths of N interior single-relaxation processes, using the measurements of acoustic absorption and sound speed at 2N frequencies. Experimental data for the gas mixtures CO2-N2 and CO2-O2 validate our decomposition and reconstruction approach.

Diffusion of point defects in crystalline silicon using the kinetic activation-relaxation technique method

DOE PAGES

Trochet, Mickaël; Béland, Laurent Karim; Joly, Jean -François; ...

2015-06-16

We study point-defect diffusion in crystalline silicon using the kinetic activation-relaxation technique (k-ART), an off-lattice kinetic Monte Carlo method with on-the-fly catalog building capabilities based on the activation-relaxation technique (ART nouveau), coupled to the standard Stillinger-Weber potential. We focus more particularly on the evolution of crystalline cells with one to four vacancies and one to four interstitials in order to provide a detailed picture of both the atomistic diffusion mechanisms and overall kinetics. We show formation energies, activation barriers for the ground state of all eight systems, and migration barriers for those systems that diffuse. Additionally, we characterize diffusion pathsmore » and special configurations such as dumbbell complex, di-interstitial (IV-pair+2I) superdiffuser, tetrahedral vacancy complex, and more. In conclusion, this study points to an unsuspected dynamical richness even for this apparently simple system that can only be uncovered by exhaustive and systematic approaches such as the kinetic activation-relaxation technique.« less

Application of an Externally Applied Rotating Magnetic Field for Control of MHD Relaxation Phenomena in the HIST Spherical Torus Device

NASA Astrophysics Data System (ADS)

Kikuchi, Yusuke; Yoshikawa, Tatsuya; Nishioka, Tsutomu; Hashimoto, Shotaro; Fukumoto, Naoyuki; Nagata, Masayoshi

Application of an externally applied rotating magnetic field (RMF) for control of MHD relaxation phenomena driven by a coaxial helicity injection has been proposed in the HIST spherical torus device. In this letter, the plasma responses to the RMF evaluated by magnetic fields inside the plasma in HIST are shown.

Two-fluid and finite Larmor radius effects on helicity evolution in a plasma pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sauppe, J. P., E-mail: jpsauppe@gmail.com; Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706; Sovinec, C. R., E-mail: csovinec@wisc.edu

2016-03-15

The evolution of magnetic energy, helicity, and hybrid helicity during nonlinear relaxation of a driven-damped plasma pinch is compared in visco-resistive magnetohydrodynamics and two-fluid models with and without the ion gyroviscous stress tensor. Magnetic energy and helicity are supplied via a boundary electric field which initially balances the resistive dissipation, and the plasma undergoes multiple relaxation events during the nonlinear evolution. The magnetic helicity is well conserved relative to the magnetic energy over each event, which is short compared with the global resistive diffusion time. The magnetic energy decreases by roughly 1.5% of its initial value over a relaxation event,more » while the magnetic helicity changes by at most 0.2% of the initial value. The hybrid helicity is dominated by magnetic helicity in low-β pinch conditions and is also well conserved. Differences of less than 1% between magnetic helicity and hybrid helicity are observed with two-fluid modeling and result from cross helicity evolution. The cross helicity is found to change appreciably due to the first-order finite Larmor radius effects which have not been included in contemporary relaxation theories. The plasma current evolves towards the flat parallel current state predicted by Taylor relaxation theory but does not achieve it. Plasma flow develops significant structure for two-fluid models, and the flow perpendicular to the magnetic field is much more substantial than the flow along it.« less

Engineering and Scaling the Spontaneous Magnetization Reversal of Faraday Induced Magnetic Relaxation in Nano-Sized Amorphous Ni Coated on Crystalline Au.

PubMed

Li, Wen-Hsien; Lee, Chi-Hung; Kuo, Chen-Chen

2016-05-28

We report on the generation of large inverse remanent magnetizations in nano-sized core/shell structure of Au/Ni by turning off the applied magnetic field. The remanent magnetization is very sensitive to the field reduction rate as well as to the thermal and field processes before the switching off of the magnetic field. Spontaneous reversal in direction and increase in magnitude of the remanent magnetization in subsequent relaxations over time were found. All of the various types of temporal relaxation curves of the remanent magnetizations are successfully scaled by a stretched exponential decay profile, characterized by two pairs of relaxation times and dynamic exponents. The relaxation time is used to describe the reduction rate, while the dynamic exponent describes the dynamical slowing down of the relaxation through time evolution. The key to these effects is to have the induced eddy current running beneath the amorphous Ni shells through Faraday induction.

Relation between Direct Observation of Relaxation and Self-Reported Mindfulness and Relaxation States

ERIC Educational Resources Information Center

Hites, Lacey S.; Lundervold, Duane A.

2013-01-01

Forty-four individuals, 18-47 (MN 21.8, SD 5.63) years of age, took part in a study examining the magnitude and direction of the relationship between self-report and direct observation measures of relaxation and mindfulness. The Behavioral Relaxation Scale (BRS), a valid direct observation measure of relaxation, was used to assess relaxed behavior…

e(sup +/-) Pair Loading and the Origin of the Upstream Magnetic Field in GRB Shocks

NASA Technical Reports Server (NTRS)

Ramirez-Ruiz, Enrico; Nishikawa, Ken-Ichi; Hededal, Christian B.

2006-01-01

We investigate here the effects of plasma instabilities driven by rapid e(sup +/-) pair cascades, which arise in the environment of GRB sources as a result of back-scattering of a seed fraction of their original spectrum. The injection of e(sup +/-) pairs induces strong streaming motions in the ambient medium. One therefore expects the pair-enriched medium ahead of the forward shock to be strongly sheared on length scales comparable to the radiation front thickness. Using three-dimensional particle-in-cell simulations, we show that plasma instabilities driven by these streaming e(sup +/-) pairs are responsible for the excitation of near-equipartition, turbulent magnetic fields. Our results reveal the importance of the electromagnetic filamentation instability in ensuring an effective coupling between e(sup +/-) pairs and ions, and may help explain the origin of large upstream fields in GRB shocks.

Structural, electrical properties and dielectric relaxations in Na+-ion-conducting solid polymer electrolyte.

PubMed

Arya, Anil; Sharma, A L

2018-04-25

In this paper, we have studied the structural, microstructural, electrical, dielectric properties and ion dynamics of a sodium-ion-conducting solid polymer electrolyte film comprising PEO 8 -NaPF 6 +  x wt. % succinonitrile. The structural and surface morphology properties have been investigated, respectively using x-ray diffraction and field emission scanning electron microscopy. The complex formation was examined using Fourier transform infrared spectroscopy, and the fraction of free anions/ion pairs obtained via deconvolution. The complex dielectric permittivity and loss tangent has been analyzed across the whole frequency window, and enables us to estimate the DC conductivity, dielectric strength, double layer capacitance and relaxation time. The presence of relaxing dipoles was determined by the addition of succinonitrile (wt./wt.) and the peak shift towards high frequency indicates the decrease of relaxation time. Further, relations among various relaxation times ([Formula: see text]) have been elucidated. The complex conductivity has been examined across the whole frequency window; it obeys the Universal Power Law, and displays strong dependency on succinonitrile content. The sigma representation ([Formula: see text]) was introduced in order to explore the ion dynamics by highlighting the dispersion region in the Cole-Cole plot ([Formula: see text]) in the lower frequency window; increase in the semicircle radius indicates a decrease of relaxation time. This observation is accompanied by enhancement in ionic conductivity and faster ion transport. A convincing, logical scheme to justify the experimental data has been proposed.

Structural Relaxation of Vit4Amorphous Alloy by the Enthalpy Relaxation

NASA Astrophysics Data System (ADS)

O'Reilly, James; Hammond, Vincent

2002-03-01

The structural relaxation of an amorphous alloy designated Vit4 has been investigated as a function of thermal history using differential scanning calorimetry. Results indicate that the width of the glass transition region is approximately 30 °C, which is broader than molecular or polymeric glasses but similar to inorganic glasses. The broad transition implies a large distribution of relaxation times, a low activation energy, or a combination of these effects. The Tool-Narayanaswamy model for structural relaxation has been used to analyze the change in fictive temperature that occurs for a series of cooling rates. The activation energy calculated from these data the is 187 kJ/mol, a value that is low compared to other glasses. Using optimization programs, the other relaxation parameters, the characteristic relaxation time, the non-linearity parameter, x, and the fractional exponent of distribution of relaxation times, b, were determined from the experimental specific heat curves. Although the parameters were in good agreement with values typical of other glassy materials, there appears to be less correlation between them than is observed in molecular and polymeric glasses. The results obtained in this study indicate that the structural relaxation of Vit 4 is similar to other glasses except for a low activation energy with high glass transition. This could be due to a low free volume or configurational entropy. The width of the glass transition could result from a large distribution of relaxation times or a low activation energy. The exponent of the distribution of relaxation times, b, is 0.45±0.1 and the non-linearity parameter, x =0.5±0.2. The structural relaxation of Vit 4 is dominated by a low activation energy which is related to the atomic jump motion of hard spheres. The DCp at Tg should be 11.7 J/mol. deg per bead according to Wunderlich’s rule. This means that the change in Cp at Tg in Vit4 can be accounted for by one bead although there are five metal

Plasma rotation in the Peking University Plasma Test device.

PubMed

Xiao, Chijie; Chen, Yihang; Yang, Xiaoyi; Xu, Tianchao; Wang, Long; Xu, Min; Guo, Dong; Yu, Yi; Lin, Chen

2016-11-01

Some preliminary results of plasma rotations in a linear plasma experiment device, Peking University Plasma Test (PPT) device, are reported in this paper. PPT has a cylindrical vacuum chamber with 500 mm diameter and 1000 mm length, and a pair of Helmholtz coils which can generate cylindrical or cusp magnetic geometry with magnitude from 0 to 2000 G. Plasma was generated by a helicon source and the typical density is about 10 13 cm -3 for the argon plasma. Some Langmuir probes, magnetic probes, and one high-speed camera are set up to diagnose the rotational plasmas. The preliminary results show that magnetic fluctuations exist during some plasma rotation processes with both cylindrical and cusp magnetic geometries, which might be related to some electromagnetic processes and need further studies.

Formation and relaxation of quasistationary states in particle systems with power-law interactions

NASA Astrophysics Data System (ADS)

Marcos, B.; Gabrielli, A.; Joyce, M.

2017-09-01

We explore the formation and relaxation of the so-called quasistationary states (QSS) for particle distributions in three dimensions interacting via an attractive radial pair potential V (r →∞ ) ˜1 /rγ with γ >0 , and either a soft core or hard core regularization at small r . In the first part of the paper, we generalize, for any spatial dimension d ≥2 , Chandrasekhar's approach for the case of gravity to obtain analytic estimates of the rate of collisional relaxation due to two-body collisions. The resultant relaxation rates indicate an essential qualitative difference depending on the integrability of the pair force at large distances: for γ >d -1 , the rate diverges in the large particle number N (mean-field) limit, unless a sufficiently large soft core is present; for γ relaxation times and our analytic predictions. Further, as in the case of gravity, we find that the results indicate that, when large impact factors dominate, the appropriate cutoff is the size of the system (rather than, for example, the mean interparticle distance). Our results provide strong evidence that the existence of QSS is robust only for long-range interactions with a large distance behavior γ

Instability of Longitudinal Wave in Magnetized Strongly Coupled Dusty Plasma

NASA Astrophysics Data System (ADS)

Xie, Bai-Song

2003-12-01

Instability of longitudinal wave in magnetized strongly coupled dusty plasmas is investigated. The dust charging relaxation is taken into account. It is found that there exists threshold of interdust distance for the instability of wave, which is determined significantly by the dust charging relaxation, the coupling parameter of high correlation of dust as well the strength of magnetic field.

Nonthermal electron-positron pairs and the break in the hard X-ray spectrum of NGC 4151

NASA Technical Reports Server (NTRS)

Coppi, Paolo S.; Zdziarski, Andrzej A.

1992-01-01

The recent observation by the detectors on board Granat of a spectral steepening above about 50 keV imposes a constraint on possible emission models for NGC 4151. This steepening, for example, is not well fitted by an exponential rollover characteristic of a purely thermal model, or by a Compton-downscattered power law. We find that this spectral behavior is consistent with that produced by a photon-starved nonthermal pair plasma with high compactness. This is the first quantitative test of the nonthermal pair plasma model against broad-band X-ray/gamma-ray observations. Above 200 keV or so, the nonthermal pair plasma model predicts an upturn in the spectrum, and a thermal annihilation feature around 511 keV. Such spectral behavior should be looked for with GRO.

Anomalous nuclear Overhauser effects in carbon-substituted aziridines: scalar cross-relaxation of the first kind.

PubMed

Kuprov, Ilya; Hodgson, David M; Kloesges, Johannes; Pearson, Christopher I; Odell, Barbara; Claridge, Timothy D W

2015-03-16

Anomalous NOESY cross-peaks that cannot be explained by dipolar cross-relaxation or chemical exchange are described for carbon-substituted aziridines. The origin of these is identified as scalar cross-relaxation of the first kind, as demonstrated by a complete theoretical description of this relaxation process and by computational simulation of the NOESY spectra. It is shown that this process relies on the stochastic modulation of J-coupling by conformational transitions, which in the case of aziridines arise from inversion at the nitrogen center. The observation of scalar cross-relaxation between protons does not appear to have been previously reported for NOESY spectra. Conventional analysis would have assigned the cross-peaks as being indicative of a chemical exchange process occurring between correlated spins, were it not for the fact that the pairs of nuclei displaying them cannot undergo such exchange. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Mozart versus new age music: relaxation states, stress, and ABC relaxation theory.

PubMed

Smith, Jonathan C; Joyce, Carol A

2004-01-01

Smith's (2001) Attentional Behavioral Cognitive (ABC) relaxation theory proposes that all approaches to relaxation (including music) have the potential for evoking one or more of 15 factor-analytically derived relaxation states, or "R-States" (Sleepiness, Disengagement, Rested / Refreshed, Energized, Physical Relaxation, At Ease/Peace, Joy, Mental Quiet, Childlike Innocence, Thankfulness and Love, Mystery, Awe and Wonder, Prayerfulness, Timeless/Boundless/Infinite, and Aware). The present study investigated R-States and stress symptom-patterns associated with listening to Mozart versus New Age music. Students (N = 63) were divided into three relaxation groups based on previously determined preferences. Fourteen listened to a 28-minute tape recording of Mozart's Eine Kleine Nachtmusik and 14 listened to a 28-minute tape of Steven Halpern's New Age Serenity Suite. Others (n = 35) did not want music and instead chose a set of popular recreational magazines. Participants engaged in their relaxation activity at home for three consecutive days for 28 minutes a session. Before and after each session, each person completed the Smith Relaxation States Inventory (Smith, 2001), a comprehensive questionnaire tapping 15 R-States as well as the stress states of somatic stress, worry, and negative emotion. Results revealed no differences at Session 1. At Session 2, those who listened to Mozart reported higher levels of At Ease/Peace and lower levels of Negative Emotion. Pronounced differences emerged at Session 3. Mozart listeners uniquely reported substantially higher levels of Mental Quiet, Awe and Wonder, and Mystery. Mozart listeners reported higher levels, and New Age listeners slightly elevated levels, of At Ease/Peace and Rested/Refreshed. Both Mozart and New Age listeners reported higher levels of Thankfulness and Love. In summary, those who listened to Mozart's Eine Kleine Nachtmusik reported more psychological relaxation and less stress than either those who listened to

Impact of regular relaxation training on the cardiac autonomic nervous system of hospital cleaners and bank employees.

PubMed

Toivanen, H; Länsimies, E; Jokela, V; Hänninen, O

1993-10-01

The work-related strain of 50 female hospital cleaners and 48 female bank employees was recorded during a period of rationalization in the workplace, and the effect of daily relaxation to help the workers cope was tested. The subjects were arranged into age-matched pairs and randomly allocated into intervention and reference groups. The intervention period lasted six months. The relaxation method was brief and easily introduced as an alternative break in the workplace. Each training session lasted 15 min. A microcomputer-based system was used to record heart rate variability in response to quiet breathing, the Valsalva maneuver, deep breathing, and active orthostatic tests. Cardiac reflexes indicated that occupational strain (especially of a mental nature) caused the functioning of the autonomic nervous system to deteriorate. Regular deep relaxation normalized the function and improved the ability to cope.

Rogue Waves in Multi-Ion Cometary Plasmas

NASA Astrophysics Data System (ADS)

Sreekala, G.; Manesh, M.; Neethu, T. W.; Anu, V.; Sijo, S.; Venugopal, C.

2018-01-01

The effect of pair ions on the formation of rogue waves in a six-component plasma composed of two hot and one colder electron component, hot ions, and pair ions is studied. The kappa distribution, which provides an unambiguous replacement for a Maxwellian distribution in space plasmas, is connected with nonextensive statistical mechanics and provides a continuous energy spectrum. Hence, the colder and one component of the hotter electrons is modeled by kappa distributions and the other hot electron component, by a q-nonextensive distribution. It is found that the rogue wave amplitude is different for various pair-ion components. The magnitude, however, increases with increasing spectral index and nonextensive parameter q. These results may be useful in understanding the basic characteristics of rogue waves in cometary plasmas.

Equivalent Relaxations of Optimal Power Flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bose, S; Low, SH; Teeraratkul, T

2015-03-01

Several convex relaxations of the optimal power flow (OPF) problem have recently been developed using both bus injection models and branch flow models. In this paper, we prove relations among three convex relaxations: a semidefinite relaxation that computes a full matrix, a chordal relaxation based on a chordal extension of the network graph, and a second-order cone relaxation that computes the smallest partial matrix. We prove a bijection between the feasible sets of the OPF in the bus injection model and the branch flow model, establishing the equivalence of these two models and their second-order cone relaxations. Our results implymore » that, for radial networks, all these relaxations are equivalent and one should always solve the second-order cone relaxation. For mesh networks, the semidefinite relaxation and the chordal relaxation are equally tight and both are strictly tighter than the second-order cone relaxation. Therefore, for mesh networks, one should either solve the chordal relaxation or the SOCP relaxation, trading off tightness and the required computational effort. Simulations are used to illustrate these results.« less

Asymptotic solution of Fokker-Planck equation for plasma in Paul traps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shah, Kushal

2010-05-15

An exact analytic solution of the Vlasov equation for the plasma distribution in a Paul trap is known to be a Maxwellian and thus, immune to collisions under the assumption of infinitely fast relaxation [K. Shah and H. S. Ramachandran, Phys. Plasmas 15, 062303 (2008)]. In this paper, it is shown that even for a more realistic situation of finite time relaxation, solutions of the Fokker-Planck equation lead to an equilibrium solution of the form of a Maxwellian with oscillatory temperature. This shows that the rf heating observed in Paul traps cannot be caused due to collisional effects alone.

Ion acoustic shock wave in collisional equal mass plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adak, Ashish, E-mail: ashish-adak@yahoo.com; Ghosh, Samiran, E-mail: sran-g@yahoo.com; Chakrabarti, Nikhil, E-mail: nikhil.chakrabarti@saha.ac.in

The effect of ion-ion collision on the dynamics of nonlinear ion acoustic wave in an unmagnetized pair-ion plasma has been investigated. The two-fluid model has been used to describe the dynamics of both positive and negative ions with equal masses. It is well known that in the dynamics of the weakly nonlinear wave, the viscosity mediates wave dissipation in presence of weak nonlinearity and dispersion. This dissipation is responsible for the shock structures in pair-ion plasma. Here, it has been shown that the ion-ion collision in presence of collective phenomena mediated by the plasma current is the source of dissipationmore » that causes the Burgers' term which is responsible for the shock structures in equal mass pair-ion plasma. The dynamics of the weakly nonlinear wave is governed by the Korteweg-de Vries Burgers equation. The analytical and numerical investigations revealed that the ion acoustic wave exhibits both oscillatory and monotonic shock structures depending on the frequency of ion-ion collision parameter. The results have been discussed in the context of the fullerene pair-ion plasma experiments.« less

OCT-based approach to local relaxations discrimination from translational relaxation motions

NASA Astrophysics Data System (ADS)

Matveev, Lev A.; Matveyev, Alexandr L.; Gubarkova, Ekaterina V.; Gelikonov, Grigory V.; Sirotkina, Marina A.; Kiseleva, Elena B.; Gelikonov, Valentin M.; Gladkova, Natalia D.; Vitkin, Alex; Zaitsev, Vladimir Y.

2016-04-01

Multimodal optical coherence tomography (OCT) is an emerging tool for tissue state characterization. Optical coherence elastography (OCE) is an approach to mapping mechanical properties of tissue based on OCT. One of challenging problems in OCE is elimination of the influence of residual local tissue relaxation that complicates obtaining information on elastic properties of the tissue. Alternatively, parameters of local relaxation itself can be used as an additional informative characteristic for distinguishing the tissue in normal and pathological states over the OCT image area. Here we briefly present an OCT-based approach to evaluation of local relaxation processes in the tissue bulk after sudden unloading of its initial pre-compression. For extracting the local relaxation rate we evaluate temporal dependence of local strains that are mapped using our recently developed hybrid phase resolved/displacement-tracking (HPRDT) approach. This approach allows one to subtract the contribution of global displacements of scatterers in OCT scans and separate the temporal evolution of local strains. Using a sample excised from of a coronary arteria, we demonstrate that the observed relaxation of local strains can be reasonably fitted by an exponential law, which opens the possibility to characterize the tissue by a single relaxation time. The estimated local relaxation times are assumed to be related to local biologically-relevant processes inside the tissue, such as diffusion, leaking/draining of the fluids, local folding/unfolding of the fibers, etc. In general, studies of evolution of such features can provide new metrics for biologically-relevant changes in tissue, e.g., in the problems of treatment monitoring.

High e+/e– ratio dense pair creation with 10 21W.cm –2 laser irradiating solid targets

DOE PAGES

Liang, E.; Clarke, T.; Henderson, A.; ...

2015-09-14

In this study, we report results of new pair creation experiments using ~100 Joule pulses of the Texas Petawatt Laser to irradiate solid gold and platinum targets, with intensities up to ~1.9 × 10 21 W.cm –2 and pulse durations as short as ~130 fs. Positron to electron (e+/e–) ratios >15% were observed for many thick disk and rod targets, with the highest e+/e– ratio reaching ~50% for a Pt rod. The inferred pair yield was ~ few ×10 10 with emerging pair density reaching ~10 15/cm 3 so that the pair skin depth becomes < pair jet transverse size.more » These results represent major milestones towards the goal of creating a significant quantity of dense pair-dominated plasmas with e+/e– approaching 100% and pair skin depth << pair plasma size, which will have wide-ranging applications to astrophysics and fundamental physics.« less

QM/MM studies on the excited-state relaxation mechanism of a semisynthetic dTPT3 base.

PubMed

Guo, Wei-Wei; Zhang, Teng-Shuo; Fang, Wei-Hai; Cui, Ganglong

2018-02-14

Semisynthetic alphabets can potentially increase the genetic information stored in DNA through the formation of unusual base pairs. Recent experiments have shown that near-visible-light irradiation of the dTPT3 chromophore could lead to the formation of a reactive triplet state and of singlet oxygen in high quantum yields. However, the detailed excited-state relaxation paths that populate the lowest triplet state are unclear. Herein, we have for the first time employed the QM(MS-CASPT2//CASSCF)/MM method to explore the spectroscopic properties and excited-state relaxation mechanism of the aqueous dTPT3 chromophore. On the basis of the results, we have found that (1) the S 2 ( 1 ππ*) state of dTPT3 is the initially populated excited singlet state upon near-visible light irradiation; and (2) there are two efficient relaxation pathways to populate the lowest triplet state, i.e. T 1 ( 3 ππ*). In the first one, the S 2 ( 1 ππ*) system first decays to the S 1 ( 1 nπ*) state near the S 2 /S 1 conical intersection, which is followed by an efficient S 1 → T 1 intersystem crossing process at the S 1 /T 1 crossing point; in the second one, an efficient S 2 → T 2 intersystem crossing takes place first, and then, the T 2 ( 3 nπ*) system hops to the T 1 ( 3 ππ*) state through an internal conversion process at the T 2 /T 1 conical intersection. Moreover, an S 2 /S 1 /T 2 intersection region is found to play a vital role in the excited-state relaxation. These new mechanistic insights help in understanding the photophysics and photochemistry of unusual base pairs.

Structural, electrical properties and dielectric relaxations in Na+-ion-conducting solid polymer electrolyte

NASA Astrophysics Data System (ADS)

Arya, Anil; Sharma, A. L.

2018-04-01

In this paper, we have studied the structural, microstructural, electrical, dielectric properties and ion dynamics of a sodium-ion-conducting solid polymer electrolyte film comprising PEO8-NaPF6+  x wt. % succinonitrile. The structural and surface morphology properties have been investigated, respectively using x-ray diffraction and field emission scanning electron microscopy. The complex formation was examined using Fourier transform infrared spectroscopy, and the fraction of free anions/ion pairs obtained via deconvolution. The complex dielectric permittivity and loss tangent has been analyzed across the whole frequency window, and enables us to estimate the DC conductivity, dielectric strength, double layer capacitance and relaxation time. The presence of relaxing dipoles was determined by the addition of succinonitrile (wt./wt.) and the peak shift towards high frequency indicates the decrease of relaxation time. Further, relations among various relaxation times ({{τ }{{\\varepsilon \\prime}}}>~{{τ }tanδ }>{{τ }z}>{{τ }m} ) have been elucidated. The complex conductivity has been examined across the whole frequency window; it obeys the Universal Power Law, and displays strong dependency on succinonitrile content. The sigma representation ({{σ }\\prime\\prime}~versus~{{σ }\\prime} ) was introduced in order to explore the ion dynamics by highlighting the dispersion region in the Cole–Cole plot ({{\\varepsilon }\\prime\\prime}~versus~{{\\varepsilon }\\prime} ) in the lower frequency window; increase in the semicircle radius indicates a decrease of relaxation time. This observation is accompanied by enhancement in ionic conductivity and faster ion transport. A convincing, logical scheme to justify the experimental data has been proposed.

Sleep, Stress & Relaxation: Rejuvenate Body & Mind

Cancer.gov

Sleep, Stress & Relaxation: Rejuvenate Body & Mind; Relieve Stress; best ways to relieve stress; best way to relieve stress; different ways to relieve stress; does smoking relieve stress; does tobacco relieve stress; how can I relieve stress; how can you relieve stress; how do I relieve stress; reduce stress; does smoking reduce stress; how can I reduce stress; how to reduce stress; reduce stress; reduce stress levels; reducing stress; smoking reduce stress; smoking reduces stress; stress reducing techniques; techniques to reduce stress; stress relief; best stress relief; natural stress relief; need stress relief; relief for stress; relief from stress; relief of stress; smoking and stress relief; smoking for stress relief; smoking stress relief; deal with stress; dealing with stress; dealing with anger; dealing with stress; different ways of dealing with stress; help dealing with stress; how to deal with anger; how to deal with stress; how to deal with stress when quitting smoking; stress management; free stress management; how can you manage stress; how do you manage stress; how to manage stress; manage stress; management of stress; management stress; managing stress; strategies for managing stress; coping with stress; cope with stress; copeing with stress; coping and stress; coping skills for stress; coping strategies for stress; coping strategies with stress; coping strategy for stress; coping with stress; coping with stress and anxiety; emotional health; emotional health; emotional health article; emotional health articles; deep relaxation; deep breathing relaxation techniques; deep muscle relaxation; deep relaxation; deep relaxation meditation; deep relaxation technique; deep relaxation techniques; meditation exercises; mindful exercises; mindful meditation exercises; online relaxation exercises; relaxation breathing exercises; relaxation exercise; relaxation exercises; stress relaxation; methods of relaxation for stress; relax stress; relax techniques stress

Point-source helicity injection for ST plasma startup in Pegasus

NASA Astrophysics Data System (ADS)

Redd, A. J.; Battaglia, D. J.; Bongard, M. W.; Fonck, R. J.; Schlossberg, D. J.

2009-11-01

Plasma current guns are used as point-source DC helicity injectors for forming non-solenoidal tokamak plasmas in the Pegasus Toroidal Experiment. Discharges driven by this injection scheme have achieved Ip>= 100 kA using Iinj<= 4 kA. They form at the outboard midplane, transition to a tokamak-like equilibrium, and continue to grow inward as Ip increases due to helicity injection and outer- PF induction. The maximum Ip is determined by helicity balance (injection rate vs resistive dissipation) and a Taylor relaxation limit, in which Ip√ITF Iinj/w, where w is the radial thickness of the gun-driven edge. Preliminary experiments tentatively confirm these scalings with ITF, Iinj, and w, increasing confidence in this simple relaxation model. Adding solenoidal inductive drive during helicity injection can push Ip up to, but not beyond, the predicted relaxation limit, demonstrating that this is a hard performance limit. Present experiments are focused on increasing the injection voltage (i.e., helicity injection rate) and reducing w. Near-term goals are to further test scalings predicted by the simple relaxation model and to study in detail the observed bursty n=1 activity correlated with rapid increases in Ip.

ICPP: Beltrami fields in plasmas -- H-mode boundary layers and high beta equilibria

NASA Astrophysics Data System (ADS)

Yoshida, Zensho

2000-10-01

The Beltrami fields, eigenfunctions of the curl operator, represent essential characteristics of twisted, spiral, chiral or helical structures in various vector fields. Amongst diverse applications of the theory of Beltrami fields, the present paper focuses on the self-organized states of plasmas. The Taylor relaxed state is the principal example of self-organized Beltrami fields. Suppose that a plasma is produced in an external magnetic field (harmonic field). If we do not apply any drive, the plasma will disappear and the system will relax into the harmonic magnetic field. When we drive a current and sustain the total helicity, the plasma relaxes into the Taylor state and achieves the Beltrami magnetic field. When a strong flow is implemented to a plasma, self-organized states becomes qualitatively different from the conventional relaxed stats. The two-fluid effect induces a coupling among the flow, magnetic field, electric field and the pressure, resulting in a "singular perturbation" to the MHD system. To invoke this effect, one must supply a driving force to sustain a strong flow. It is equivalent to giving an internal electric field or applying a steep gradient in pressure, because these fields are tightly coupled. In the two-fluid model, the Beltrami condition demands that the vorticity parallels the flow in both electron and ion fluids. We find that a superposition of two Beltrami magnetic fields (and also two Beltrami flows) solves the simultaneous two-fluid Beltrami conditions [1]. Despite this simple mathematical structure, the set of solutions contains field configurations that are far richer than the conventional theory. The hydrodynamic pressure of a shear flow yields a diamagnetic state that is suitable for confining a high-beta plasma. The H-mode boundary layer is an example, which is spontaneously generated by the core plasma pressure [2]. Active control of shear flow will significantly extend the scope of such self-organized states [3]. [1] S. M

Rayleigh-Taylor instability in an equal mass plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adak, Ashish, E-mail: ashish-adak@yahoo.com; Ghosh, Samiran, E-mail: sran-g@yahoo.com; Chakrabarti, Nikhil, E-mail: nikhil.chakrabarti@saha.ac.in

The Rayleigh-Taylor (RT) instability in an inhomogeneous pair-ion plasma has been analyzed. Considering two fluid model for two species of ions (positive and negative), we obtain the possibility of the existence of RT instability. The growth rate of the RT instability as usual depends on gravity and density gradient scale length. The results are discussed in context of pair-ion plasma experiments.

Relaxation and collective excitations of cluster nano-plasmas

NASA Astrophysics Data System (ADS)

Reinholz, Heidi; Röpke, Gerd; Broda, Ingrid; Morozov, Igor; Bystryi, Roman; Lavrinenko, Yaroslav

2018-01-01

Nano-plasmas produced, for example, in clusters after short-pulse laser irradiation, can show collective excitations, as derived from the time evolution of fluctuations in thermodynamic equilibrium. Molecular dynamical simulations are performed for various cluster sizes. New data are obtained for the minimum value of the stationary cluster charge. The bi-local autocorrelation function gives the spatial structure of the eigenmodes, for which energy eigenvalues are obtained. By varying the cluster size, starting from a few-particle cluster, the emergence of macroscopic properties such as collective excitations is shown.

The effects of progressive muscle relaxation and autogenic relaxation on young soccer players' mood states.

PubMed

Hashim, Hairul Anuar; Hanafi Ahmad Yusof, Hazwani

2011-06-01

This study was designed to compare the effects of two different relaxation techniques, namely progressive muscle relaxation (PMR) and autogenic relaxation (AGR) on moods of young soccer players. sixteen adolescent athletes (mean age: 14.1 ± 1.3) received either PMR or AGR training. Using Profile of Mood States- Adolescents, their mood states were measured one week before relaxation training, before the first relaxation session, and after the twelfth relaxation session. Mixed ANOVA revealed no significant interaction effects and no significant main effects in any of the subscales. However, significant main effects for testing sessions were found for confusion, depression, fatigue, and tension subscales. Post hoc tests revealed post-intervention reductions in the confusion, depression, fatigue, and tension subscale scores. These two relaxation techniques induce equivalent mood responses and may be used to regulate young soccer players' mood states.

Validating predictive models for fast ion profile relaxation in burning plasmas

DOE PAGES

Gorelenkov, N. N.; Heidbrink, W. W.; Kramer, G. J.; ...

2016-07-22

The redistribution and potential loss of energetic particles due to MHD modes can limit the performance of fusion plasmas by reducing the plasma heating rate. In this work, we present validation studies of the 1.5D critical gradient model (CGM) for Alfvén eigenmode (AE) induced EP transport in NSTX and DIII-D neutral beam heated plasmas. In previous comparisons with a single DIII-D L-mode case, the CGM model was found to be responsible for 75% of measured AE induced neutron deficit [1]. A fully kinetic HINST is used to compute mode stability for the non-perturbative version of CGM (or nCGM). We have found that AEs show strong local instability drive up tomore » $$\\gamma /\\omega \\sim 20\\%$$ violating assumptions of perturbative approaches used in NOVA-K code. Lastly, we demonstrate that both models agree with each other and both underestimate the neutron deficit measured in DIII-D shot by approximately a factor of 2.« less

Classical plasma dynamics of Mie-oscillations in atomic clusters

NASA Astrophysics Data System (ADS)

Kull, H.-J.; El-Khawaldeh, A.

2018-04-01

Mie plasmons are of basic importance for the absorption of laser light by atomic clusters. In this work we first review the classical Rayleigh-theory of a dielectric sphere in an external electric field and Thomson’s plum-pudding model applied to atomic clusters. Both approaches allow for elementary discussions of Mie oscillations, however, they also indicate deficiencies in describing the damping mechanisms by electrons crossing the cluster surface. Nonlinear oscillator models have been widely studied to gain an understanding of damping and absorption by outer ionization of the cluster. In the present work, we attempt to address the issue of plasmon relaxation in atomic clusters in more detail based on classical particle simulations. In particular, we wish to study the role of thermal motion on plasmon relaxation, thereby extending nonlinear models of collective single-electron motion. Our simulations are particularly adopted to the regime of classical kinetics in weakly coupled plasmas and to cluster sizes extending the Debye-screening length. It will be illustrated how surface scattering leads to the relaxation of Mie oscillations in the presence of thermal motion and of electron spill-out at the cluster surface. This work is intended to give, from a classical perspective, further insight into recent work on plasmon relaxation in quantum plasmas [1].

Inversion in the magnetic field effect of benzilketyl:SDS radical pair at high fields

NASA Astrophysics Data System (ADS)

Misra, Ajay; Haldar, Mintu; Chowdhury, Mihir

1999-05-01

The effect of a high magnetic field (up to 13.3 T) on radical pairs generated by the hydrogen abstraction of the photoexcited benzil triplet from sodium dodecyl sulphate has been studied. It was found that both the radical pair lifetime and the free radical yield increase with an increase of field from 0 to 4 T. A further increase of field causes a decrease in both. This reversal of the magnetic field effect (MFE) above 4 T has been explained in terms of relaxation mechanism and competition between a number of rate processes. The effect of reducing the micelle size on the MFE inversion has been discussed.

The Effects of Progressive Muscle Relaxation and Autogenic Relaxation on Young Soccer Players’ Mood States

PubMed Central

Hashim, Hairul Anuar; Hanafi@Ahmad Yusof, Hazwani

2011-01-01

Purpose This study was designed to compare the effects of two different relaxation techniques, namely progressive muscle relaxation (PMR) and autogenic relaxation (AGR) on moods of young soccer players. Methods Sixteen adolescent athletes (mean age: 14.1 ± 1.3) received either PMR or AGR training. Using Profile of Mood States- Adolescents, their mood states were measured one week before relaxation training, before the first relaxation session, and after the twelfth relaxation session. Results Mixed ANOVA revealed no significant interaction effects and no significant main effects in any of the subscales. However, significant main effects for testing sessions were found for confusion, depression, fatigue, and tension subscales. Post hoc tests revealed post-intervention reductions in the confusion, depression, fatigue, and tension subscale scores. Conclusion These two relaxation techniques induce equivalent mood responses and may be used to regulate young soccer players’ mood states. PMID:22375225

Counter-facing plasma guns for efficient extreme ultra-violet plasma light source

NASA Astrophysics Data System (ADS)

Kuroda, Yusuke; Yamamoto, Akiko; Kuwabara, Hajime; Nakajima, Mitsuo; Kawamura, Tohru; Horioka, Kazuhiko

2013-11-01

A plasma focus system composed of a pair of counter-facing coaxial guns was proposed as a long-pulse and/or repetitive high energy density plasma source. We applied Li as the source of plasma for improvement of the conversion efficiency, the spectral purity, and the repetition capability. For operation of the system with ideal counter-facing plasma focus mode, we changed the system from simple coaxial geometry to a multi-channel configuration. We applied a laser trigger to make synchronous multi-channel discharges with low jitter. The results indicated that the configuration is promising to make a high energy density plasma with high spectral efficiency.

Ketamine relaxes airway smooth muscle contracted by endothelin.

PubMed

Sato, T; Matsuki, A; Zsigmond, E K; Rabito, S F

1997-04-01

Endothelins (ETs) are synthesized not only in vascular endothelial cells but also in airway epithelial cells. Increased ET-1 has been demonstrated in bronchial epithelium of asthmatic patients, and, in severe asthma attacks, ET-1 increases in plasma and bronchoalveolar lavage fluid. In this study, we investigated whether ketamine (KET) relaxes ET-induced tracheal contractions. Female guinea pigs were killed with an overdose of pentobarbital. The trachea was removed and cut spirally into two strips that were mounted in an organ bath filled with Krebs-bicarbonate buffer. The response of each strip to 10(-7) M carbachol was taken as 100% contraction to which the response to ET was referred. The contribution of the epithelium to the relaxant effect of KET was studied in denuded tracheae or in the presence of 5 x 10(-5) M indomethacin. ET-1 (3 x 10(-8) M) induced contractions that were 76 +/- 3% of those induced by carbachol. KET reversed the response to ET-1 in a dose-dependent fashion. Similarly, ET-2 (3 x 10(-8) M) induced contractions that were 74 +/- 5% of those induced by carbachol, and KET also reversed this response in a dose-dependent manner. In epithelium-denuded strips, ET-1 induced contractions that were 104 +/- 3% of those induced by carbachol, and KET still reversed this response. The tonic phase of the response to ET-1 was equal (100 +/- 6%) to the response to carbachol, and KET did not affect it significantly. In the presence of ryanodine, KET reduced the ET-1-induced contraction from 67 +/- 2% to 36 +/- 3.%, P < 0.01. In the presence of nicardipine, KET also inhibited the ET-1-induced contraction. We conclude that KET relaxes the tracheal smooth muscle contracted by ETs via a mechanism that is independent of the tracheal epithelium. The relaxant effect of KET on the ET-induced contraction of the trachealis muscle is not dependent upon blockade of 1) sarcolemma influx of Ca2+ through the dihydropyridine Ca2+ channel or 2) the release of intracellular Ca2

The spin relaxation of nitrogen donors in 6H SiC crystals as studied by the electron spin echo method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Savchenko, D., E-mail: dariyasavchenko@gmail.com; National Technical University of Ukraine “Kyiv Polytechnic Institute,” Kyiv 03056; Shanina, B.

2016-04-07

We present the detailed study of the spin kinetics of the nitrogen (N) donor electrons in 6H SiC wafers grown by the Lely method and by the sublimation “sandwich method” (SSM) with a donor concentration of about 10{sup 17 }cm{sup −3} at T = 10–40 K. The donor electrons of the N donors substituting quasi-cubic “k1” and “k2” sites (N{sub k1,k2}) in both types of the samples revealed the similar temperature dependence of the spin-lattice relaxation rate (T{sub 1}{sup −1}), which was described by the direct one-phonon and two-phonon processes induced by the acoustic phonons proportional to T and to T{sup 9}, respectively. Themore » character of the temperature dependence of the T{sub 1}{sup −1} for the donor electrons of N substituting hexagonal (“h”) site (N{sub h}) in both types of 6H SiC samples indicates that the donor electrons relax through the fast-relaxing centers by means of the cross-relaxation process. The observed enhancement of the phase memory relaxation rate (T{sub m}{sup −1}) with the temperature increase for the N{sub h} donors in both types of the samples, as well as for the N{sub k1,k2} donors in Lely grown 6H SiC, was explained by the growth of the free electron concentration with the temperature increase and their exchange scattering at the N donor centers. The observed significant shortening of the phase memory relaxation time T{sub m} for the N{sub k1,k2} donors in the SSM grown sample with the temperature lowering is caused by hopping motion of the electrons between the occupied and unoccupied states of the N donors at N{sub h} and N{sub k1,k2} sites. The impact of the N donor pairs, triads, distant donor pairs formed in n-type 6H SiC wafers on the spin relaxation times was discussed.« less

Sensitive detection of unlabeled oligonucleotides using a paired surface plasma waves biosensor.

PubMed

Li, Ying-Chang; Chiou, Chiuan-Chian; Luo, Ji-Dung; Chen, Wei-Ju; Su, Li-Chen; Chang, Ying-Feng; Chang, Yu-Sun; Lai, Chao-Sung; Lee, Cheng-Chung; Chou, Chien

2012-05-15

Detection of unlabeled oligonucleotides using surface plasmon resonance (SPR) is difficult because of the oligonucleotides' relatively lower molecular weight compared with proteins. In this paper, we describe a method for detecting unlabeled oligonucleotides at low concentration using a paired surface plasma waves biosensor (PSPWB). The biosensor uses a sensor chip with an immobilized probe to detect a target oligonucleotide via sequence-specific hybridization. PSPWB measures the demodulated amplitude of the heterodyne signal in real time. In the meantime, the ratio of the amplitudes between the detected output signal and reference can reduce the excess noise from the laser intensity fluctuation. Also, the common-path propagation of p and s waves cancels the common phase noise induced by temperature variation. Thus, a high signal-to-noise ratio (SNR) of the heterodyne signal is detected. The sequence specificity of oligonucleotide hybridization ensures that the platform is precisely discriminating between target and non-target oligonucleotides. Under optimized experimental conditions, the detected heterodyne signal increases linearly with the logarithm of the concentration of target oligonucleotide over the range 0.5-500 pM. The detection limit is 0.5 pM in this experiment. In addition, the non-target oligonucleotide at concentrations of 10 pM and 10nM generated signals only slightly higher than background, indicating the high selectivity and specificity of this method. Different length of perfectly matched oligonucleotide targets at 10-mer, 15-mer and 20-mer were identified at the concentration of 150 pM. Copyright © 2012 Elsevier B.V. All rights reserved.

Scaling of Magnetic Reconnection in Relativistic Collisionless Pair Plasmas

NASA Technical Reports Server (NTRS)

Liu, Yi-Hsin; Guo, Fan; Daughton, William; Li, Hui; Hesse, Michael

2015-01-01

Using fully kinetic simulations, we study the scaling of the inflow speed of collisionless magnetic reconnection in electron-positron plasmas from the non-relativistic to ultra-relativistic limit. In the anti-parallel configuration, the inflow speed increases with the upstream magnetization parameter sigma and approaches the speed of light when sigma is greater than O(100), leading to an enhanced reconnection rate. In all regimes, the divergence of the pressure tensor is the dominant term responsible for breaking the frozen-in condition at the x-line. The observed scaling agrees well with a simple model that accounts for the Lorentz contraction of the plasma passing through the diffusion region. The results demonstrate that the aspect ratio of the diffusion region, modified by the compression factor of proper density, remains approximately 0.1 in both the non-relativistic and relativistic limits.

An automated method for the analysis of phenolic acids in plasma based on ion-pairing micro-extraction coupled on-line to gas chromatography/mass spectrometry with in-liner derivatisation.

PubMed

Peters, Sonja; Kaal, Erwin; Horsting, Iwan; Janssen, Hans-Gerd

2012-02-24

A new method is presented for the analysis of phenolic acids in plasma based on ion-pairing 'Micro-extraction in packed sorbent' (MEPS) coupled on-line to in-liner derivatisation-gas chromatography-mass spectrometry (GC-MS). The ion-pairing reagent served a dual purpose. It was used both to improve extraction yields of the more polar analytes and as the methyl donor in the automated in-liner derivatisation method. In this way, a fully automated procedure for the extraction, derivatisation and injection of a wide range of phenolic acids in plasma samples has been obtained. An extensive optimisation of the extraction and derivatisation procedure has been performed. The entire method showed excellent repeatabilities of under 10% and linearities of 0.99 or better for all phenolic acids. The limits of detection of the optimised method for the majority of phenolic acids were 10ng/mL or lower with three phenolic acids having less-favourable detection limits of around 100 ng/mL. Finally, the newly developed method has been applied in a human intervention trial in which the bioavailability of polyphenols from wine and tea was studied. Forty plasma samples could be analysed within 24h in a fully automated method including sample extraction, derivatisation and gas chromatographic analysis. Copyright © 2011 Elsevier B.V. All rights reserved.

[Indications for relaxation in geriatrics].

PubMed

Richard, J; Picot, A; de Bus, P; Andreoli, A; Dalakaki, X

1975-11-01

On a three years base experience in the geriatiic department of Geneva's University Psychiatric Clinic the paper studies the problem of selecting aged patients to be treated by relaxation according to the method of J. De Ajuriaguerra et M. Cahen. Observations are presented in an attempt to define three main points: a) the role played by relaxation when there is an objective [corrected] impairment of the body's integrity; b) relaxation effect on aged persons neurotic states evolution; c) the reality of considering dementia as a counter-indication of relaxation therapy. These remarks complete those presented previously about the training of therapists in relaxation, the type of control to be organized for them and their patients, the technical management of the cure, the place of relaxation in the post graduate psychiatric training, the effects of the therapy on the patients human environnement behavior in and out of the hospital, the way body is perceived through relaxation by the aged patients and it's consequences on the adjustment of an aging person.

Investigation of chemical and spin dynamics in micellized radical pairs by time-resolved stimulated nuclear polarization. Theory and experiment

NASA Astrophysics Data System (ADS)

Parnachev, A. P.; Bagryanskaya, E. G.; Tarasov, V. F.; Lukzen, N. N.; Sagdeev, R. Z.

1995-10-01

A numerical solution of the stochastic Liouville equation for a microreactor model is applied to the theoretical treatment of time-resolved stimulated nuclear polarization data, obtained during the investigation of micellized radical pairs, conducted in two different modes. Escape rate constants and relaxation parameters of radical pairs formed in the photolysis of methyldeoxybenzoin and benzoin in alkyl sulfate micelles of different sizes have been obtained. The conditions of the S-T 0 quantum oscillations in SNP kinetics have been determined.

Time scales of relaxation dynamics during transient conditions in two-phase flow: RELAXATION DYNAMICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlüter, Steffen; Berg, Steffen; Li, Tianyi

2017-06-01

The relaxation dynamics toward a hydrostatic equilibrium after a change in phase saturation in porous media is governed by fluid reconfiguration at the pore scale. Little is known whether a hydrostatic equilibrium in which all interfaces come to rest is ever reached and which microscopic processes govern the time scales of relaxation. Here we apply fast synchrotron-based X-ray tomography (X-ray CT) to measure the slow relaxation dynamics of fluid interfaces in a glass bead pack after fast drainage of the sample. The relaxation of interfaces triggers internal redistribution of fluids, reduces the surface energy stored in the fluid interfaces, andmore » relaxes the contact angle toward the equilibrium value while the fluid topology remains unchanged. The equilibration of capillary pressures occurs in two stages: (i) a quick relaxation within seconds in which most of the pressure drop that built up during drainage is dissipated, a process that is to fast to be captured with fast X-ray CT, and (ii) a slow relaxation with characteristic time scales of 1–4 h which manifests itself as a spontaneous imbibition process that is well described by the Washburn equation for capillary rise in porous media. The slow relaxation implies that a hydrostatic equilibrium is hardly ever attained in practice when conducting two-phase experiments in which a flux boundary condition is changed from flow to no-flow. Implications for experiments with pressure boundary conditions are discussed.« less

Nonlinear chiral plasma transport in rotating coordinates

NASA Astrophysics Data System (ADS)

Dayi, Ömer F.; Kilinçarslan, Eda

2017-08-01

The nonlinear transport features of inhomogeneous chiral plasma in the presence of electromagnetic fields, in rotating coordinates are studied within the relaxation time approach. The chiral distribution functions up to second order in the electric field in rotating coordinates and the derivatives of chemical potentials are established by solving the Boltzmann transport equation. First, the vector and axial current densities in the weakly ionized chiral plasma for vanishing magnetic field are calculated. They involve the rotational analogues of the Hall effect as well as several new terms arising from the Coriolis and fictitious centrifugal forces. Then in the short relaxation time regime the angular velocity and electromagnetic fields are treated as perturbations. The current densities are obtained by retaining the terms up to second order in perturbations. The time evolution equations of the inhomogeneous chemical potentials are derived by demanding that collisions conserve the particle number densities.

Spherical ion acoustic waves in pair ion plasmas with nonthermal electrons

NASA Astrophysics Data System (ADS)

Selim, M. M.

2016-04-01

Propagation of nonplanar ion acoustic waves in a plasma composed of negative and positive ions and nonthermally distributed electrons is investigated using reductive perturbation theory. The spherical Kadomtsev-Petviashvili (SKP) equation which describes the dynamics of the nonlinear spherical ion acoustic waves is derived. It is found that compressive and rarefactive ion-acoustic solitary wave characteristics significantly depend on the density and mass ratios of the positive to negative ions, the nonthermal electron parameter, and the geometry factor. The possible regions for the existence of spherical ion acoustic waves are defined precisely for typical parameters of (H+, O2 -) and (H+, H-) plasmas in the D and F-regions of the Earth's ionosphere, as well as for laboratory plasma (Ar+, F-).

Ion-pairing dynamics of Li{sup +} and SCN{sup -} in dimethylformamide solution: Chemical exchange two-dimensional infrared spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Kyung-Koo; Park, Kwang-Hee; Kwon, Donghyun

2011-02-14

Ultrafast two-dimensional infrared (2DIR) spectroscopy has been proven to be an exceptionally useful method to study chemical exchange processes between different vibrational chromophores under thermal equilibria. Here, we present experimental results on the thermal equilibrium ion pairing dynamics of Li{sup +} and SCN{sup -} ions in N,N-dimethylformamide. Li{sup +} and SCN{sup -} ions can form a contact ion pair (CIP). Varying the relative concentration of Li{sup +} in solution, we could control the equilibrium CIP and free SCN{sup -} concentrations. Since the CN stretch frequency of Li-SCN CIP is blue-shifted by about 16 cm{sup -1} from that of free SCN{supmore » -} ion, the CN stretch IR spectrum is a doublet. The temperature-dependent IR absorption spectra reveal that the CIP formation is an endothermic (0.57 kJ/mol) process and the CIP state has larger entropy by 3.12 J/(K mol) than the free ion states. Since the two ionic configurations are spectrally distinguishable, this salt solution is ideally suited for nonlinear IR spectroscopic investigations to study ion pair association and dissociation dynamics. Using polarization-controlled IR pump-probe methods, we first measured the lifetimes and orientational relaxation times of these two forms of ionic configurations. The vibrational population relaxation times of both the free ion and CIP are about 32 ps. However, the orientational relaxation time of the CIP, which is {approx}47 ps, is significantly longer than that of the free SCN{sup -}, which is {approx}7.7 ps. This clearly indicates that the effective moment of inertia of the CIP is much larger than that of the free SCN{sup -}. Then, using chemical exchange 2DIR spectroscopy and analyzing the diagonal peak and cross-peak amplitude changes with increasing the waiting time, we determined the contact ion pair association and dissociation time constants that are found to be 165 and 190 ps, respectively. The results presented and discussed in this paper are

Pairing from dynamically screened Coulomb repulsion in bismuth

NASA Astrophysics Data System (ADS)

Ruhman, Jonathan; Lee, Patrick A.

2017-12-01

Recently, Prakash et al. have discovered bulk superconductivity in single crystals of bismuth, which is a semimetal with extremely low carrier density. At such low density, we argue that conventional electron-phonon coupling is too weak to be responsible for the binding of electrons into Cooper pairs. We study a dynamically screened Coulomb interaction with effective attraction generated on the scale of the collective plasma modes. We model the electronic states in bismuth to include three Dirac pockets with high velocity and one hole pocket with a significantly smaller velocity. We find a weak-coupling instability, which is greatly enhanced by the presence of the hole pocket. Therefore we argue that bismuth is the first material to exhibit superconductivity driven by retardation effects of Coulomb repulsion alone. By using realistic parameters for bismuth we find that the acoustic plasma mode does not play the central role in pairing. We also discuss a matrix element effect, resulting from the Dirac nature of the conduction band, which may affect Tc in the s -wave channel without breaking time-reversal symmetry.

Comparison of relaxation with counterpressure massage techniques for reduce pain first stage of labor

NASA Astrophysics Data System (ADS)

Lisa, U. F.; Jalina, M.; Marniati

2017-09-01

Based on interviews of so me mother who entered the first stage of labor lack of care from health workers to the effort to reducing the acuteof labor. Health care workers appertain hospital in effective in implement maternity nursing interventions in reducing acute the first stage of labor. The reducing acute have two method are pharmacological and non-pharmacological. In this case, has several techniques there are: relaxation and counterpressure massage techniques that capable to reducing acute first stage of labor. The of non-pharmacological is one of authority which must be implemented by midwives especially breathing relaxation techniquesand massage. The research is Quasi Exsperimen with pretes-posttest design. The statistic test has T test paired and unpairedt test. To indicatea reducing the level of acute before and after given relaxation technique result p-value <0.001 with value mean after being given the treatment as much as 44.00 and the ranges of value 10-90, a reducing the level of acute before and after the counter pressure massage techniques p-value <0.001 with value mean after being given the treatment as much as 42.67 and the ranges of value 10-90. It is no significant difference between the relaxation and counter pressure massage techniques in reducing acute in the first stage of labor, because both techniques are highly effective use in reducing acute of labor the result p-value is 0.891. The relaxation and counter pressure massage techniques useful in provide an affection of mother care because both techniques are very effective work in reducing acute to focus on the point of pain. Therefore, the health of workers, especially for a study to apply relaxation and massage to provide of mother care, mainly to the primigravida who in experienced in process of labor.

Slow secondary relaxation in a free-energy landscape model for relaxation in glass-forming liquids

NASA Astrophysics Data System (ADS)

Diezemann, Gregor; Mohanty, Udayan; Oppenheim, Irwin

1999-02-01

Within the framework of a free-energy landscape model for the relaxation in supercooled liquids the primary (α) relaxation is modeled by transitions among different free-energy minima. The secondary (β) relaxation then corresponds to intraminima relaxation. We consider a simple model for the reorientational motions of the molecules associated with both processes and calculate the dielectric susceptibility as well as the spin-lattice relaxation times. The parameters of the model can be chosen in a way that both quantities show a behavior similar to that observed in experimental studies on supercooled liquids. In particular we find that it is not possible to obtain a crossing of the time scales associated with α and β relaxation. In our model these processes always merge at high temperatures and the α process remains above the merging temperature. The relation to other models is discussed.

Spheromak plasma flow injection into a torus chamber and the HIST plasmas

NASA Astrophysics Data System (ADS)

Hatuzaki, Akinori

2005-10-01

The importance of plasma flow or two-fluid effect is recognized in understanding the relaxed states of high-beta torus plasmas, start-up and current drive by non-coaxial helicity injection, magnetic reconnection and plasma dynamo in fusion, laboratory and space plasmas. As a new approach to create a flowing two-fluid plasma equilibrium, we have tried to inject tangentially the plasma flow with spheromak-type magnetic configurations into a torus vacuum chamber with an external toroidal magnetic field (TF) coil. In the initial experiments, the RFP-like configuration with helical magnetic structures was realized in the torus vessel. The ion flow measurement with Mach probes showed that the ion flow keeps the same direction despite the reversal of the toroidal current and the axial electric field. The ion fluid comes to flow in the opposite direction to the electron fluid by the reversal of TF. This result suggests that not only electron but also ion flow contributes significantly on the reversed toroidal current. In this case, the ratio of ui to the electron flow velocity ue is estimated as ui/ue ˜ 1/2. We also will inject the spheromak flow into the HIST spherical torus plasmas to examine the possibilities to embedding the two-fluid effect in the ST plasmas.

Anomalous relaxation in fractal structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fujiwara, S.; Yonezawa, F.

1995-03-01

For the purpose of studying some interesting properties of anomalous relaxation in fractal structures, we carry out Monte Carlo simulations of random walks on two-dimensional fractal structures (Sierpinski carpets with different cutouts and site-percolation clusters in a square lattice at the critical concentration). We find that the relaxation is of the Cole-Cole type [J. Chem. Phys. 9, 341 (1941)], which is one of the empirical laws of anomalous relaxation. Scaling properties are found in the relaxation function as well as in the particle density. We also find that, in strucures with almost the same fractal dimension, relaxation in structures withmore » dead ends is slower than that in structures without them. This paper ascertains that the essential aspects of the anomalous relaxation due to many-body effects can be explained in the framework of the one-body model.« less

Preferential solvation, ion pairing, and dynamics of concentrated aqueous solutions of divalent metal nitrate salts

NASA Astrophysics Data System (ADS)

Yadav, Sushma; Chandra, Amalendu

2017-12-01

We have investigated the characteristics of preferential solvation of ions, structure of solvation shells, ion pairing, and dynamics of aqueous solutions of divalent alkaline-earth metal nitrate salts at varying concentration by means of molecular dynamics simulations. Hydration shell structures and the extent of preferential solvation of the metal and nitrate ions in the solutions are investigated through calculations of radial distribution functions, tetrahedral ordering, and also spatial distribution functions. The Mg2+ ions are found to form solvent separated ion-pairs while the Ca2+ and Sr2+ ions form contact ion pairs with the nitrate ions. These findings are further corroborated by excess coordination numbers calculated through Kirkwood-Buff G factors for different ion-ion and ion-water pairs. The ion-pairing propensity is found to be in the order of Mg(NO3) 2 < C a (NO3) 2 < S r (NO3) 2, and it follows the trend given by experimental activity coefficients. It is found that proper modeling of these solutions requires the inclusion of electronic polarization of the ions which is achieved in the current study through electronic continuum correction force fields. A detailed analysis of the effects of ion-pairs on the structure and dynamics of water around the hydrated ions is done through classification of water into different subspecies based on their locations around the cations or anions only or bridged between them. We have looked at the diffusion coefficients, relaxation of orientational correlation functions, and also the residence times of different subspecies of water to explore the dynamics of water in different structural environments in the solutions. The current results show that the water molecules are incorporated into fairly well-structured hydration shells of the ions, thus decreasing the single-particle diffusivities and increasing the orientational relaxation times of water with an increase in salt concentration. The different structural

X-ray flares from runaway pair production in active galactic nuclei

NASA Technical Reports Server (NTRS)

Kirk, J. G.; Mastichiadis, A.

1992-01-01

The hard X-ray spectrum of AGNs is nonthermal, probably arising from an electron-positron pair cascade, with some emission reflected off relatively cold matter. There has been interest in models on which protons are accelerated and create relativistic electrons on interaction with a local radiation field. It is shown here that a sufficient column density of protons can lead to runaway pair production: photons generated by the relativistic pairs are the targets for the protons to produce more pairs. This can produce X-ray fluxes with the characteristics observed in AGN. The model predicts the maximum ratio of luminosity to source size as well as their spectrum in the early phases. The same mechanism may also be able to create the knots of synchrotron-radiating pair plasma seen in sources such as 3C273.

Particle Acceleration, Magnetic Field Generation, and Emission in Relativistic Pair Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Ramirez-Ruiz, E.; Hardee, P.; Hededal, C.; Mizuno, Y.

2005-01-01

Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created by relativistic pair jets are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet propagating through an ambient plasma with and without initial magnetic fields. The growth rates of the Weibel instability depends on the distribution of pair jets. Simulations show that the Weibel instability created in the collisionless shock accelerates particles perpendicular and parallel to the jet propagation direction. The simulation results show that this instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

TEACHING NEUROMUSCULAR RELAXATION.

ERIC Educational Resources Information Center

NORRIS, JEANNE E.; STEINHAUS, ARTHUR H.

THIS STUDY ATTEMPTED TO FIND OUT WHETHER (1) THE METHODS FOR ATTAINING NEUROMUSCULAR RELAXATION THAT HAVE PROVED FRUITFUL IN THE ONE-TO-ONE RELATIONSHIP OF THE CLINIC CAN BE SUCCESSFULLY ADAPTED TO THE TEACHER-CLASS RELATIONSHIP OF THE CLASSROOM AND GYMNASIUM, AND (2) NEUROMUSCULAR RELAXATION CAN BE TAUGHT SUCCESSFULLY BY AN APPROPRIATELY TRAINED…

A Comparison of Relaxation Strategies.

ERIC Educational Resources Information Center

Matthews, Doris B.

Some researchers argue that all relaxation techniques produce a single relaxation response while others support a specific-effects hypothesis which suggests that progressive relaxation affects the musculoskeletal system and that guided imagery affects cognitive changes. Autogenics is considered a technique which is both somatic and cognitive. This…

Turbulence, selective decay, and merging in the SSX plasma wind tunnel

NASA Astrophysics Data System (ADS)

Gray, Tim; Brown, Michael; Flanagan, Ken; Werth, Alexandra; Lukin, V.

2012-10-01

A helical, relaxed plasma state has been observed in a long cylindrical volume. The cylinder has dimensions L = 1 m and R = 0.08 m. The cylinder is long enough so that the predicted minimum energy state is a close approximation to the infinite cylinder solution. The plasma is injected at v >=50 km/s by a coaxial magnetized plasma gun located at one end of the cylindrical volume. Typical plasma parameters are Ti= 25 eV, ne>=10^15 cm-3, and B = 0.25 T. The relaxed state is rapidly attained in 1--2 axial Alfv'en times after initiation of the plasma. Magnetic data is favorably compared with an analytical model. Magnetic data exhibits broadband fluctuations of the measured axial modes during the formation period. The broadband activity rapidly decays as the energy condenses into the lowest energy mode, which is in agreement to the minimum energy eigenstate of ∇xB = λB. While the global structure roughly corresponds to the minimum energy eigenstate for the wind tunnel geometry, the plasma is high beta (β= 0.5) and does not have a flat λ profile. Merging of two plasmoids in this configuration results in noticeably more dynamic activity compared to a single plasmoid. These episodes of activity exhibit s

Relaxation Dynamics in Heme Proteins.

NASA Astrophysics Data System (ADS)

Scholl, Reinhard Wilhelm

A protein molecule possesses many conformational substates that are likely arranged in a hierarchy consisting of a number of tiers. A hierarchical organization of conformational substates is expected to give rise to a multitude of nonequilibrium relaxation phenomena. If the temperature is lowered, transitions between substates of higher tiers are frozen out, and relaxation processes characteristic of lower tiers will dominate the observational time scale. This thesis addresses the following questions: (i) What is the energy landscape of a protein? How does the landscape depend on the environment such as pH and viscosity, and how can it be connected to specific structural parts? (ii) What relaxation phenomena can be observed in a protein? Which are protein specific, and which occur in other proteins? How does the environment influence relaxations? (iii) What functional form best describes relaxation functions? (iv) Can we connect the motions to specific structural parts of the protein molecule, and are these motions important for the function of the protein?. To this purpose, relaxation processes after a pressure change are studied in carbonmonoxy (CO) heme proteins (myoglobin-CO, substrate-bound and substrate-free cytochrome P450cam-CO, chloroperoxidase-CO, horseradish peroxidase -CO) between 150 K and 250 K using FTIR spectroscopy to monitor the CO bound to the heme iron. Two types of p -relaxation experiments are performed: p-release (200 to ~eq40 MPa) and p-jump (~eq40 to 200 MPa) experiments. Most of the relaxations fall into one of three groups and are characterized by (i) nonexponential time dependence and non-Arrhenius temperature dependence (FIM1( nu), FIM1(Gamma)); (ii) exponential time dependence and non-Arrhenius temperature dependence (FIM0(A_{i}to A_{j})); exponential time dependence and Arrhenius temperature dependence (FIMX( nu)). The influence of pH is studied in myoglobin-CO and shown to have a strong influence on the substate population of the

UV-vis, IR and 1H NMR spectroscopic studies and characterization of ionic-pair crystal violet-oxytetracycline

NASA Astrophysics Data System (ADS)

Orellana, Sandra; Soto, César; Toral, M. Inés

2010-01-01

The present study shows the formation and characterization of the ionic-pair between the antibiotic oxytetracycline and the dye crystal violet in ammonia solution pH 9.0 ± 0.2 extracted into chloroform. The characterization was demonstrated using UV-vis spectrophotometry, 1H NMR, measurement of relaxation times T1 and IR spectroscopy, using a comparison between the signals of individual pure compounds with the signals with the mixture CV-OTC in different alkaline media. The formation of ionic-pair was also corroborated by new signals and chemical shifts. (2D) NMR spectroscopy experiments show that the interaction is electrostatic.

First-order finite-Larmor-radius fluid modeling of tearing and relaxation in a plasma pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

King, J. R.; Tech-X Corporation, 5621 Arapahoe Ave., Suite A Boulder, Colorado 80303; Sovinec, C. R.

Drift and Hall effects on magnetic tearing, island evolution, and relaxation in pinch configurations are investigated using a non-reduced first-order finite-Larmor-radius (FLR) fluid model with the nonideal magnetohydrodynamics (MHD) with rotation, open discussion (NIMROD) code [C.R. Sovinec and J. R. King, J. Comput. Phys. 229, 5803 (2010)]. An unexpected result with a uniform pressure profile is a drift effect that reduces the growth rate when the ion sound gyroradius ({rho}{sub s}) is smaller than the tearing-layer width. This drift is present only with warm-ion FLR modeling, and analytics show that it arises from {nabla}B and poloidal curvature represented in themore » Braginskii gyroviscous stress. Nonlinear single-helicity computations with experimentally relevant {rho}{sub s} values show that the warm-ion gyroviscous effects reduce saturated-island widths. Computations with multiple nonlinearly interacting tearing fluctuations find that m = 1 core-resonant-fluctuation amplitudes are reduced by a factor of two relative to single-fluid modeling by the warm-ion effects. These reduced core-resonant-fluctuation amplitudes compare favorably to edge coil measurements in the Madison Symmetric Torus (MST) reversed-field pinch [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)]. The computations demonstrate that fluctuations induce both MHD- and Hall-dynamo emfs during relaxation events. The presence of a Hall-dynamo emf implies a fluctuation-induced Maxwell stress, and the simulation results show net transport of parallel momentum. The computed magnitude of force densities from the Maxwell and competing Reynolds stresses, and changes in the parallel flow profile, are qualitatively and semi-quantitatively similar to measurements during relaxation in MST.« less

First-order finite-Larmor-radius fluid modeling of tearing and relaxation in a plasma pincha)

NASA Astrophysics Data System (ADS)

King, J. R.; Sovinec, C. R.; Mirnov, V. V.

2012-05-01

Drift and Hall effects on magnetic tearing, island evolution, and relaxation in pinch configurations are investigated using a non-reduced first-order finite-Larmor-radius (FLR) fluid model with the nonideal magnetohydrodynamics (MHD) with rotation, open discussion (NIMROD) code [C.R. Sovinec and J. R. King, J. Comput. Phys. 229, 5803 (2010)]. An unexpected result with a uniform pressure profile is a drift effect that reduces the growth rate when the ion sound gyroradius (ρs) is smaller than the tearing-layer width. This drift is present only with warm-ion FLR modeling, and analytics show that it arises from ∇B and poloidal curvature represented in the Braginskii gyroviscous stress. Nonlinear single-helicity computations with experimentally relevant ρs values show that the warm-ion gyroviscous effects reduce saturated-island widths. Computations with multiple nonlinearly interacting tearing fluctuations find that m = 1 core-resonant-fluctuation amplitudes are reduced by a factor of two relative to single-fluid modeling by the warm-ion effects. These reduced core-resonant-fluctuation amplitudes compare favorably to edge coil measurements in the Madison Symmetric Torus (MST) reversed-field pinch [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)]. The computations demonstrate that fluctuations induce both MHD- and Hall-dynamo emfs during relaxation events. The presence of a Hall-dynamo emf implies a fluctuation-induced Maxwell stress, and the simulation results show net transport of parallel momentum. The computed magnitude of force densities from the Maxwell and competing Reynolds stresses, and changes in the parallel flow profile, are qualitatively and semi-quantitatively similar to measurements during relaxation in MST.

Relativistic thermal plasmas - Effects of magnetic fields

NASA Technical Reports Server (NTRS)

Araki, S.; Lightman, A. P.

1983-01-01

Processes and equilibria in finite, relativistic, thermal plasmas are investigated, taking into account electron-positron creation and annihilation, photon production by internal processes, and photon production by a magnetic field. Inclusion of the latter extends previous work on such plasmas. The basic relations for thermal, Comptonized synchrotron emission are analyzed, including emission and absorption without Comptonization, Comptonized thermal synchrotron emission, and the Comptonized synchrotron and bremsstrahlung luminosities. Pair equilibria are calculated, including approximations and dimensionless parameters, the pair balance equation, maximum temperatures and field strengths, and individual models and cooling curves.

Local NMR relaxation rates T1-1 and T2-1 depending on the d -vector symmetry in the vortex state of chiral and helical p -wave superconductors

NASA Astrophysics Data System (ADS)

Tanaka, Kenta K.; Ichioka, Masanori; Onari, Seiichiro

2018-04-01

Local NMR relaxation rates in the vortex state of chiral and helical p -wave superconductors are investigated by the quasiclassical Eilenberger theory. We calculate the spatial and resonance frequency dependences of the local NMR spin-lattice relaxation rate T1-1 and spin-spin relaxation rate T2-1. Depending on the relation between the NMR relaxation direction and the d -vector symmetry, the local T1-1 and T2-1 in the vortex core region show different behaviors. When the NMR relaxation direction is parallel to the d -vector component, the local NMR relaxation rate is anomalously suppressed by the negative coherence effect due to the spin dependence of the odd-frequency s -wave spin-triplet Cooper pairs. The difference between the local T1-1 and T2-1 in the site-selective NMR measurement is expected to be a method to examine the d -vector symmetry of candidate materials for spin-triplet superconductors.

Digital PCR analysis of plasma cell-free DNA for non-invasive detection of drug resistance mechanisms in EGFR mutant NSCLC: Correlation with paired tumor samples

PubMed Central

Ishii, Hidenobu; Azuma, Koichi; Sakai, Kazuko; Kawahara, Akihiko; Yamada, Kazuhiko; Tokito, Takaaki; Okamoto, Isamu; Nishio, Kazuto; Hoshino, Tomoaki

2015-01-01

As the development of resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) has become an issue of concern, identification of the mechanisms responsible has become an urgent priority. However, for research purposes, it is not easy to obtain tumor samples from patients with EGFR mutation-positive non-small-cell lung cancer (NSCLC) that has relapsed after treatment with EGFR-TKIs. Here, using digital PCR assay as an alternative and noninvasive method, we examined plasma and tumor samples from patients with relapsed NSCLC to establish the inter-relationships existing among T790M mutation, activating EGFR mutations, HER2 amplification, and MET amplification. Paired samples of tumor and blood were obtained from a total of 18 patients with NSCLC after they had developed resistance to EGFR-TKI treatment, and the mechanisms of resistance were analyzed by digital PCR. Digital PCR analysis of T790M mutation in plasma had a sensitivity of 81.8% and specificity of 85.7%, the overall concordance between plasma and tissue samples being 83.3%. MET gene copy number gain in tumor DNA was observed by digital PCR in three patients, of whom one exhibited positivity for MET amplification by FISH, whereas no patient demonstrated MET and HER2 copy number gain in plasma DNA. Digital PCR analysis of plasma is feasible and accurate for detection of T790M mutation in NSCLC that becomes resistant to treatment with EGFR-TKIs. PMID:26334838

Taoren-Honghua herb pair and its main components promoting blood circulation through influencing on hemorheology, plasma coagulation and platelet aggregation.

PubMed

Liu, Li; Duan, Jin-ao; Tang, Yuping; Guo, Jianming; Yang, Nianyun; Ma, Hongyue; Shi, Xuqin

2012-01-31

Persicae Semen (Taoren) and Carthami Flos (Honghua) used in pair which is named as Taoren-Honghua (TH) herb pair has been used in traditional Chinese medicine (TCM) for promoting blood circulation to dissipate blood stasis for many years in China. This paper investigated the effects of TH and its main components amygdalin and hydroxysafflor yellow A (HSYA) on hemorheological disorders of blood stasis in rats. Rats were randomly divided into seven groups (control group, model group, TH group, amygdalin group, HSYA group, amygdalin+HSYA group, and aspirin group) with eight animals in each, whose gender was equally distributed throughout groups. All treatments were performed by gavage and administered seven times with an interval of 12h. After the fifth administration, the model rats except those in control group with blood stasis were established by being placed in ice-cold water during the interval between two injections of adrenaline hydrochloride (Adr); and blood samples were collected 30min after the last administration on the following day. TH could significantly decrease whole blood viscosity (WBV), plasma viscosity (PV) and packed cell volume (PCV). It also significantly prolonged thrombin time (TT) and thromboplastin time (APTT), increased prothrombin time (PT) and lowered fibrinogen content (FIB). HSYA which significantly decreased WBV and PV had no effect on plasma coagulation parameters. Amygdalin could significantly decrease PV, prolong APTT and decrease FIB, showing few effects on WBV. TH and its main components amygdalin and HSYA could significantly reduce platelet aggregation and protect vascular endothelial cells. Based on the above results, amygdalin and HSYA were responsible for the main curative effects of TH and usually had synergetic effects, such as decreasing PV and platelet aggregation percentage. The study may provide scientific information to further understanding of the mechanism(s) of TH and its main components in activating blood

Shock Wave Dynamics in Weakly Ionized Plasmas

NASA Technical Reports Server (NTRS)

Johnson, Joseph A., III

1999-01-01

An investigation of the dynamics of shock waves in weakly ionized argon plasmas has been performed using a pressure ruptured shock tube. The velocity of the shock is observed to increase when the shock traverses the plasma. The observed increases cannot be accounted for by thermal effects alone. Possible mechanisms that could explain the anomalous behavior include a vibrational/translational relaxation in the nonequilibrium plasma, electron diffusion across the shock front resulting from high electron mobility, and the propagation of ion-acoustic waves generated at the shock front. Using a turbulence model based on reduced kinetic theory, analysis of the observed results suggest a role for turbulence in anomalous shock dynamics in weakly ionized media and plasma-induced hypersonic drag reduction.

Monte Carlo studies of thermalization of electron-hole pairs in spin-polarized degenerate electron gas in monolayer graphene

NASA Astrophysics Data System (ADS)

Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek

2018-02-01

Monte Carlo method is applied to the study of relaxation of excited electron-hole (e-h) pairs in graphene. The presence of background of spin-polarized electrons, with high density imposing degeneracy conditions, is assumed. To such system, a number of e-h pairs with spin polarization parallel or antiparallel to the background is injected. Two stages of relaxation: thermalization and cooling are clearly distinguished when average particles energy < E> and its standard deviation σ _E are examined. At the very beginning of thermalization phase, holes loose energy to electrons, and after this process is substantially completed, particle distributions reorganize to take a Fermi-Dirac shape. To describe the evolution of < E > and σ _E during thermalization, we define characteristic times τ _ {th} and values at the end of thermalization E_ {th} and σ _ {th}. The dependence of these parameters on various conditions, such as temperature and background density, is presented. It is shown that among the considered parameters, only the standard deviation of electrons energy allows to distinguish between different cases of relative spin polarizations of background and excited electrons.

Effects of relaxation on depression levels in women with high-risk pregnancies: a randomised clinical trial 1

PubMed Central

de Araújo, Wanda Scherrer; Romero, Walckiria Garcia; Zandonade, Eliana; Amorim, Maria Helena Costa

2016-01-01

ABSTRACT Objective: to analyse the effects of relaxation as a nursing intervention on the depression levels of hospitalised women with high-risk pregnancies. Methods: a randomised clinical trial realised in a reference centre for high-risk pregnancies. The sample consisted of 50 women with high-risk pregnancies (25 in the control group and 25 in the intervention group). The Benson relaxation technique was applied to the intervention group for five days. Control variables were collected using a predesigned form, and the signs and symptoms of depression were evaluated using the Edinburgh Postnatal Depression Scale (EPDS). The Statistical Package for Social Sciences (SPSS), version 20.0, was used with a significance level of 5%. The Wilcoxon and paired t-tests were used to evaluate depression levels between two timepoints. Using categorical data, the McNemar test was used to analyse differences in depression severity before and after the intervention. Results: depression levels decreased in the intervention group five days after the relaxation technique was applied (4.5 ± 3, p<0.05) compared with the levels at the first timepoint (10.3±5.9). Conclusion: as a nursing intervention, relaxation was effective in decreasing the symptoms of depression in hospitalised women with high-risk pregnancies. PMID:27627126

Short communication: phylodynamics analysis of the human immunodeficiency virus type 1 envelope gene in mother and child pairs.

PubMed

Santos, Luciane Amorim; Gray, Rebecca R; Monteiro-Cunha, Joana Paixão; Strazza, Evandra; Kashima, Simone; Santos, Edson de Souza; Araújo, Thessika Hialla Almeida; Gonçalves, Marilda de Souza; Salemi, Marco; Alcantara, Luiz Carlos Junior

2015-09-01

Characterizing the impact of HIV transmission routes on viral genetic diversity can improve the understanding of the mechanisms of virus evolution and adaptation. HIV vertical transmission can occur in utero, during delivery, or while breastfeeding. The present study investigated the phylodynamics of the HIV-1 env gene in mother-to-child transmission by analyzing one chronically infected pair from Brazil and three acutely infected pairs from Zambia, with three to five time points. Sequences from 25 clones from each sample were obtained and aligned using Clustal X. ML trees were constructed in PhyML using the best evolutionary model. Bayesian analyses testing the relaxed and strict molecular clock were performed using BEAST and a Bayesian Skyline Plot (BSP) was construed. The genetic variability of previously described epitopes was investigated and compared between each individual time point and between mother and child sequences. The relaxed molecular clock was the best-fitted model for all datasets. The tree topologies did not show differentiation in the evolutionary dynamics of the virus circulating in the mother from the viral population in the child. In the BSP, the effective population size was more constant in time in the chronically infected patients while in the acute patients it was possible to detect bottlenecks. The genetic variability within viral epitopes recognized by the human immune system was considerably higher among the chronically infected pair in comparison with acutely infected pairs. These results contribute to a better understanding of HIV-1 evolutionary dynamics in mother-to-child transmission.

Leveraging extreme laser-driven magnetic fields for gamma-ray generation and pair production

NASA Astrophysics Data System (ADS)

Jansen, O.; Wang, T.; Stark, D. J.; d’Humières, E.; Toncian, T.; Arefiev, A. V.

2018-05-01

The ability of an intense laser pulse to propagate in a classically over-critical plasma through the phenomenon of relativistic transparency is shown to facilitate the generation of strong plasma magnetic fields. Particle-in-cell simulations demonstrate that these fields significantly enhance the radiation rates of the laser-irradiated electrons, and furthermore they collimate the emission so that a directed and dense beam of multi-MeV gamma-rays is achievable. This capability can be exploited for electron–positron pair production via the linear Breit–Wheeler process by colliding two such dense beams. Presented simulations show that more than 103 pairs can be produced in such a setup, and the directionality of the positrons can be controlled by the angle of incidence between the beams.

Relaxation System

NASA Technical Reports Server (NTRS)

1987-01-01

Environ Corporation's relaxation system is built around a body lounge, a kind of super easy chair that incorporates sensory devices. Computer controlled enclosure provides filtered ionized air to create a feeling of invigoration, enhanced by mood changing aromas. Occupant is also surrounded by multidimensional audio and the lighting is programmed to change colors, patterns, and intensity periodically. These and other sensory stimulators are designed to provide an environment in which the learning process is stimulated, because research has proven that while an individual is in a deep state of relaxation, the mind is more receptive to new information.

Relaxation of sound fields in rooms of diffusely reflecting boundaries and its application in acoustical radiosity simulation.

PubMed

Zhang, Honghu

2006-04-01

The acoustical radiosity method is a computationally expensive acoustical simulation algorithm that assumes an enclosure with ideal diffuse reflecting boundaries. Miles observed that for such an enclosure, the sound energy decay of every point on the boundaries will gradually converge to exponential manner with a uniform decay rate. Therefore, the ratio of radiosity between every pair of points on the boundaries will converge to a constant, and the radiosity across the boundaries will approach a fixed distribution during the sound decay process, where radiosity is defined as the acoustic power per unit area leaving (or being received by) a point on a boundary. We call this phenomenon the "relaxation" of the sound field. In this paper, we study the relaxation in rooms of different shapes with different boundary absorptions. Criteria based on the relaxation of the sound field are proposed to terminate the costly and unnecessary radiosity computation in the later phase, which can then be replaced by a fast regression step to speed up the acoustical radiosity simulation.

Pavlovian autoshaping procedures increase plasma corticosterone levels in rats.

PubMed

Tomie, Arthur; Silberman, Yuval; Williams, Kayon; Pohorecky, Larissa A

2002-06-01

Pavlovian autoshaping conditioned responses (CRs) are complex sequences of conditioned stimulus (CS)-directed skeletal-motor responses that are elicited by CS objects predictive of food unconditioned stimulus (US). Autoshaping CRs are observed under conditions known to be conducive to elevations in plasma corticosterone levels, as, for example, in response to the eating of food as well as in response to signals predictive of food. Two experiments investigated the relationships between Pavlovian autoshaping procedures, the performance of Pavlovian autoshaping CRs, and plasma corticosterone levels in male Long-Evans rats. In Experiment 1, rats in the CS-US paired group (n=30) were given 20 daily sessions of Pavlovian autoshaping training wherein the insertion of a retractable lever CS was followed by the response-independent presentation of the food US. Tail blood samples obtained after the 20th autoshaping session revealed higher plasma corticosterone levels in the CS-US paired group than in the CS-US random control group (n=10). In Experiment 2, rats (n=35) were assessed for basal plasma corticosterone levels 2 weeks prior to autoshaping training. Plasma samples obtained immediately following the first autoshaping session, and prior to the acquisition of lever-press autoshaping CR performance, revealed higher plasma corticosterone levels in the CS-US paired group (n=24) relative to basal levels. This effect was not observed in the CS-US random control group (n=11). Data suggest that corticosterone release is a physiological endocrine Pavlovian CR induced by lever CS-food US pairings during Pavlovian autoshaping procedures, rather than a by-product of autoshaping CR performance. Implications of the link between autoshaping procedures and corticosterone release are discussed.

Magnetic Field Generation During the Collision of Narrow Plasma Clouds

NASA Astrophysics Data System (ADS)

Sakai, Jun-ichi; Kazimura, Yoshihiro; Haruki, Takayuki

1999-06-01

We investigate the dynamics of the collision of narrow plasma clouds,whose transverse dimension is on the order of the electron skin depth.A 2D3V (two dimensions in space and three dimensions in velocity space)particle-in-cell (PIC) collisionless relativistic code is used toshow the generation of a quasi-staticmagnetic field during the collision of narrow plasma clouds both inelectron-ion and electron-positron (pair) plasmas. The localizedstrong magnetic fluxes result in the generation of the charge separationwith complicated structures, which may be sources of electromagneticas well as Langmuir waves. We also present one applicationof this process, which occurs during coalescence of magnetic islandsin a current sheet of pair plasmas.

Unified concept of effective one component plasma for hot dense plasmas

DOE PAGES

Clerouin, Jean; Arnault, Philippe; Ticknor, Christopher; ...

2016-03-17

Orbital-free molecular dynamics simulations are used to benchmark two popular models for hot dense plasmas: the one component plasma (OCP) and the Yukawa model. A unified concept emerges where an effective OCP (EOCP) is constructed from the short-range structure of the plasma. An unambiguous ionization and the screening length can be defined and used for a Yukawa system, which reproduces the long-range structure with finite compressibility. Similarly, the dispersion relation of longitudinal waves is consistent with the screened model at vanishing wave number but merges with the OCP at high wave number. Additionally, the EOCP reproduces the overall relaxation timemore » scales of the correlation functions associated with ionic motion. Lastly, in the hot dense regime, this unified concept of EOCP can be fruitfully applied to deduce properties such as the equation of state, ionic transport coefficients, and the ion feature in x-ray Thomson scattering experiments.« less

Plasma Effects on Fast Pair Beams. II. Reactive versus Kinetic Instability of Parallel Electrostatic Waves

NASA Astrophysics Data System (ADS)

Schlickeiser, R.; Krakau, S.; Supsar, M.

2013-11-01

The interaction of TeV gamma-rays from distant blazars with the extragalactic background light produces relativistic electron-positron pair beams by the photon-photon annihilation process. Using the linear instability analysis in the kinetic limit, which properly accounts for the longitudinal and the small but finite perpendicular momentum spread in the pair momentum distribution function, the growth rate of parallel propagating electrostatic oscillations in the intergalactic medium is calculated. Contrary to the claims of Miniati and Elyiv, we find that neither the longitudinal nor the perpendicular spread in the relativistic pair distribution function significantly affect the electrostatic growth rates. The maximum kinetic growth rate for no perpendicular spread is even about an order of magnitude greater than the corresponding reactive maximum growth rate. The reduction factors in the maximum growth rate due to the finite perpendicular spread in the pair distribution function are tiny and always less than 10-4. We confirm earlier conclusions by Broderick et al. and our group that the created pair beam distribution function is quickly unstable in the unmagnetized intergalactic medium. Therefore, there is no need to require the existence of small intergalactic magnetic fields to scatter the produced pairs, so that the explanation (made by several authors) for the Fermi non-detection of the inverse Compton scattered GeV gamma-rays by a finite deflecting intergalactic magnetic field is not necessary. In particular, the various derived lower bounds for the intergalactic magnetic fields are invalid due to the pair beam instability argument.

Light-induced racemization: artifacts in the analysis of the diastereoisomeric pairs of thioridazine 5-sulfoxide in the plasma and urine of patients treated with thioridazine.

PubMed

Eap, C B; Souche, A; Koeb, L; Baumann, P

1991-07-01

The ring sulfoxidation of thioridazine (THD), a widely used neuroleptic agent, yields two diastereoisomeric pairs, fast- and slow-eluting (FE and SE) thioridazine 5-sulfoxide (THD 5-SO). Until now, studies in which concentrations of these metabolites were measured in THD-treated patients have revealed no significant differences in their concentrations. Preliminary experiments in our laboratory had shown that sunlight and, to a lesser extent, dim daylight led to racemization and probably also to photolysis of the diastereoisomeric pairs as measured by high-performance liquid chromatography. Similar results were also obtained with direct UV light (UV lamp). In appropriate light-protected conditions, THD, northioridazine, mesoridazine, sulforidazine, and FE and SE THD 5-SO were measured in 11 patients treated with various doses of THD for at least 1 week. Significantly higher concentrations of the FE stereoisomeric pair were found. The concentration ratios THD 5-SO (FE)/THD 5-SO (SE) ranged from 0.89 to 1.75 in plasma and from 1.15 to 2.05 in urine. Because it is known that the ring sulfoxide contributes to the cardiotoxicity of the drug even more potently than the parent compound does, these results justify further studies to determine whether there is stereoselectivity in the cardiotoxicity of THD 5-SO.

To pair or not to pair: chromosome pairing and evolution.

PubMed

Moore, G

1998-04-01

Chromosome pairing in wild-type wheat closely resembles the process in both yeast and Drosophila. The recent characterisation of a mutant Ph1 wheat and the observation that chromosome pairing in the absence of Ph1 more closely resembles that of mammals and maize has shed light on the evolution of chromosome pairing in the cereals.

FDTD Simulation on Terahertz Waves Propagation Through a Dusty Plasma

NASA Astrophysics Data System (ADS)

Wang, Maoyan; Zhang, Meng; Li, Guiping; Jiang, Baojun; Zhang, Xiaochuan; Xu, Jun

2016-08-01

The frequency dependent permittivity for dusty plasmas is provided by introducing the charging response factor and charge relaxation rate of airborne particles. The field equations that describe the characteristics of Terahertz (THz) waves propagation in a dusty plasma sheath are derived and discretized on the basis of the auxiliary differential equation (ADE) in the finite difference time domain (FDTD) method. Compared with numerical solutions in reference, the accuracy for the ADE FDTD method is validated. The reflection property of the metal Aluminum interlayer of the sheath at THz frequencies is discussed. The effects of the thickness, effective collision frequency, airborne particle density, and charge relaxation rate of airborne particles on the electromagnetic properties of Terahertz waves through a dusty plasma slab are investigated. Finally, some potential applications for Terahertz waves in information and communication are analyzed. supported by National Natural Science Foundation of China (Nos. 41104097, 11504252, 61201007, 41304119), the Fundamental Research Funds for the Central Universities (Nos. ZYGX2015J039, ZYGX2015J041), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20120185120012)

Idiosyncratic reality claims, relaxation dispositions, and ABC relaxation theory: happiness, literal christianity, miraculous powers, metaphysics, and the paranormal.

PubMed

Smith, Jonathan C; Karmin, Aaron D

2002-12-01

This study examined idiosyncratic reality claims, that is, irrational or paranormal beliefs often claimed to enhance relaxation and happiness and reduce stress. The Smith Idiosyncratic Reality Claims Inventory and the Smith Relaxation Dispositions Inventory (which measures relaxation and stress dispositions, or enduring states of mind frequently associated with relaxation or stress) were given to 310 junior college student volunteers. Principal components factor analysis with varimax rotation identified five idiosyncratic reality claim factors: belief in Literal Christianity; Magic; Space Aliens: After Death experiences; and Miraculous Powers of Meditation, Prayer, and Belief. No factor correlated with increased relaxation dispositions Peace, Energy, or Joy, or reduced dispositional somatic stress, worry, or negative emotion on the Smith Relaxation Dispositions Inventory. It was concluded that idiosyncratic reality claims may not be associated with reported relaxation, happiness, or stress. In contrast, previous research strongly supported self-affirming beliefs with few paranormal assumptions display such an association.

Variable setpoint as a relaxing component in physiological control.

PubMed

Risvoll, Geir B; Thorsen, Kristian; Ruoff, Peter; Drengstig, Tormod

2017-09-01

Setpoints in physiology have been a puzzle for decades, and especially the notion of fixed or variable setpoints have received much attention. In this paper, we show how previously presented homeostatic controller motifs, extended with saturable signaling kinetics, can be described as variable setpoint controllers. The benefit of a variable setpoint controller is that an observed change in the concentration of the regulated biochemical species (the controlled variable) is fully characterized, and is not considered a deviation from a fixed setpoint. The variation in this biochemical species originate from variation in the disturbances (the perturbation), and thereby in the biochemical species representing the controller (the manipulated variable). Thus, we define an operational space which is spanned out by the combined high and low levels of the variations in (1) the controlled variable, (2) the manipulated variable, and (3) the perturbation. From this operational space, we investigate whether and how it imposes constraints on the different motif parameters, in order for the motif to represent a mathematical model of the regulatory system. Further analysis of the controller's ability to compensate for disturbances reveals that a variable setpoint represents a relaxing component for the controller, in that the necessary control action is reduced compared to that of a fixed setpoint controller. Such a relaxing component might serve as an important property from an evolutionary point of view. Finally, we illustrate the principles using the renal sodium and aldosterone regulatory system, where we model the variation in plasma sodium as a function of salt intake. We show that the experimentally observed variations in plasma sodium can be interpreted as a variable setpoint regulatory system. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

An ESR protocol based on relaxation phenomena of irradiated Japanese pepper

NASA Astrophysics Data System (ADS)

Ukai, Mitsuko; Nakamura, Hideo; Shimoyama, Yuhei

2006-03-01

We found various free radicals in a commercially available pepper in Japan before and after irradiation using electron spin resonance (ESR) spectroscopy. The typical ESR spectrum of the pepper consists of a sextet centered at g = 2.0, a singlet at the same g-value and a singlet at g = 4.0. Upon gamma ray irradiation, a new pair of signals appeared in the pepper. The progressive saturation behavior (PSB) at various microwave power levels indicated quite different relaxation behaviors of those radicals. Namely, the peak intensity of the organic free radical component decreases in a monotonic fashion, whereas the Mn 2+ and Fe 3+ ESR signals substantially keep constant. This reflects the evidence of three independent radicals in the pepper before irradiation. The PSB of the pair peaks as induced by irradiation possessed quite different PSB from that of the free radical located at g = 2.0. We proposed a new protocol for the ESR detection of irradiated foods by the PSB method at different microwave power levels. This would call for a major modification of the CEN protocol in European Union.

The relationships between suggestibility, influenceability, and relaxability.

PubMed

Polczyk, Romuald; Frey, Olga; Szpitalak, Malwina

2013-01-01

This research explores the relationships between relaxability and various aspects of suggestibility and influenceability. The Jacobson Progressive Muscle Relaxation procedure was used to induce relaxation. Tests of direct suggestibility, relating to the susceptibility of overt suggestions, and indirect suggestibility, referring to indirect hidden influence, as well as self-description questionnaires on suggestibility and the tendency to comply were used. Thayer's Activation-Deactivation Adjective Check List, measuring various kinds of activation and used as a pre- and posttest, determined the efficacy of the relaxation procedure. Indirect, direct, and self-measured suggestibility proved to be positively related to the ability to relax, measured by Thayer's subscales relating to emotions. Compliance was not related to relaxability. The results are discussed in terms of the aspects of relaxation training connected with suggestibility.

Computation of electron transport and relaxation properties in gases based on improved multi-term approximation of Boltzmann equation

NASA Astrophysics Data System (ADS)

Cai, X. J.; Wang, X. X.; Zou, X. B.; Lu, Z. W.

2018-01-01

An understanding of electron kinetics is of importance in various applications of low temperature plasmas. We employ a series of model and real gases to investigate electron transport and relaxation properties based on improved multi-term approximation of the Boltzmann equation. First, a comparison of different methods to calculate the interaction integrals has been carried out; the effects of free parameters, such as vmax, lmax, and the arbitrary temperature Tb, on the convergence of electron transport coefficients are analyzed. Then, the modified attachment model of Ness et al. and SF6 are considered to investigate the effect of attachment on the electron transport properties. The deficiency of the pulsed Townsend technique to measure the electron transport and reaction coefficients in electronegative gases is highlighted when the reduced electric field is small. In order to investigate the effect of external magnetic field on the electron transport properties, Ar plasmas in high power impulse sputtering devices are considered. In the end, the electron relaxation properties of the Reid model under the influence of electric and magnetic fields are demonstrated.

Rindler fluid with weak momentum relaxation

NASA Astrophysics Data System (ADS)

Khimphun, Sunly; Lee, Bum-Hoon; Park, Chanyong; Zhang, Yun-Long

2018-01-01

We realize the weak momentum relaxation in Rindler fluid, which lives on the time-like cutoff surface in an accelerating frame of flat spacetime. The translational invariance is broken by massless scalar fields with weak strength. Both of the Ward identity and the momentum relaxation rate of Rindler fluid are obtained, with higher order correction in terms of the strength of momentum relaxation. The Rindler fluid with momentum relaxation could also be approached through the near horizon limit of cutoff AdS fluid with momentum relaxation, which lives on a finite time-like cutoff surface in Anti-de Sitter(AdS) spacetime, and further could be connected with the holographic conformal fluid living on AdS boundary at infinity. Thus, in the holographic Wilson renormalization group flow of the fluid/gravity correspondence with momentum relaxation, the Rindler fluid can be considered as the Infrared Radiation(IR) fixed point, and the holographic conformal fluid plays the role of the ultraviolet(UV) fixed point.

The Effects of Suggestibility on Relaxation.

ERIC Educational Resources Information Center

Rickard, Henry C.; And Others

1985-01-01

Selected undergraduates (N=32) on the basis of Creative Imagination Scale scores and randomly assigned high and low suggestibility subjects to progressive relaxation (PR) and suggestions of relaxation (SR) training modes. Results revealed a significant pre-post relaxation effect, and main efffects for both suggestibility and training mode. (NRB)

Particle acceleration magnetic field generation, and emission in Relativistic pair jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Ramirez-Ruiz, E.; Hardee, P.; Hededal, C.; Kouveliotou, C.; Fishman, G. J.

2005-01-01

Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) are responsible for particle acceleration in relativistic pair jets. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic pair jet propagating through a pair plasma. Simulations show that the Weibel instability created in the collisionless shock accelerates particles perpendicular and parallel to the jet propagation direction. Simulation results show that this instability generates and amplifies highly nonuniform, small-scale magnetic fields, which contribute to the electron's transverse deflection behind the jet head. The "jitter' I radiation from deflected electrons can have different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. The growth rate of the Weibel instability and the resulting particle acceleration depend on the magnetic field strength and orientation, and on the initial particle distribution function. In this presentation we explore some of the dependencies of the Weibel instability and resulting particle acceleration on the magnetic field strength and orientation, and the particle distribution function.

Particle acceleration, magnetic field generation, and emission in relativistic pair jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Ramirez-Ruiz, E.; Hardee, P.; Hededal, C.; Kouveliotou, C.; Fishman, G. J.; Mizuno, Y.

2005-01-01

Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Recent simulations show that the Weibel instability created by relativistic pair jets is responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet propagating through an ambient plasma with and without initial magnetic fields. The growth rates of the Weibel instability depends on the distribution of pair jets. The Weibel instability created in the collisionless shock accelerates particles perpendicular and parallel to the jet propagation direction. This instability is also responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron s transverse deflection behind the jet head. The jitter radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

PAIR-DOMINATED GeV-OPTICAL FLASH IN GRB 130427A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vurm, Indrek; Hascoët, Romain; Beloborodov, Andrei M., E-mail: indrek.vurm@gmail.com

2014-07-10

We show that the light curve of the double GeV+optical flash in GRB 130427A is consistent with radiation from the blast wave in a wind-type medium with density parameter A = ρr {sup 2} ∼ 5 × 10{sup 10} g cm{sup –1}. The peak of the flash is emitted by copious e {sup ±} pairs created and heated in the blast wave; our first-principle calculation determines the pair-loading factor and temperature of the shocked plasma. Using detailed radiative transfer simulations, we reconstruct the observed double flash. The optical flash is dominated by synchrotron emission from the thermal plasma behind the forward shock, andmore » the GeV flash is produced via inverse Compton (IC) scattering by the same plasma. The seed photons for IC scattering are dominated by the prompt MeV radiation during the first tens of seconds, and by the optical to X-ray afterglow thereafter. IC cooling of the thermal plasma behind the forward shock reproduces all GeV data from a few seconds to ∼1 day. We find that the blast wave Lorentz factor at the peak of the flash is Γ ≈ 200, and the forward shock magnetization is ε{sub B} ∼ 2 × 10{sup –4}. An additional source is required by the data in the optical and X-ray bands at times >10{sup 2} s; we speculate that this additional source may be a long-lived reverse shock in the explosion ejecta.« less

Dynamics of Magnetized Plasma Jets and Bubbles Launched into a Background Magnetized Plasma

NASA Astrophysics Data System (ADS)

Wallace, B.; Zhang, Y.; Fisher, D. M.; Gilmore, M.

2016-10-01

The propagation of dense magnetized plasma, either collimated with mainly azimuthal B-field (jet) or toroidal with closed B-field (bubble), in a background plasma occurs in a number of solar and astrophysical cases. Such cases include coronal mass ejections moving in the background solar wind and extragalactic radio lobes expanding into the extragalactic medium. Understanding the detailed MHD behavior is crucial for correctly modeling these events. In order to further the understanding of such systems, we are investigating the injection of dense magnetized jets and bubbles into a lower density background magnetized plasma using a coaxial plasma gun and a background helicon or cathode plasma. In both jet and bubble cases, the MHD dynamics are found to be very different when launched into background plasma or magnetic field, as compared to vacuum. In the jet case, it is found that the inherent kink instability is stabilized by velocity shear developed due to added magnetic tension from the background field. In the bubble case, rather than directly relaxing to a minimum energy Taylor state (spheromak) as in vacuum, there is an expansion asymmetry and the bubble becomes Rayleigh-Taylor unstable on one side. Recent results will be presented. Work supported by the Army Research Office Award No. W911NF1510480.

Strain relaxation in (0001) AlN/GaN heterostructures

NASA Astrophysics Data System (ADS)

Bourret, Alain; Adelmann, Christoph; Daudin, Bruno; Rouvière, Jean-Luc; Feuillet, Guy; Mula, Guido

2001-06-01

The strain-relaxation phenomena during the early stages of plasma-assisted molecular-beam epitaxy growth of lattice-mismatched wurtzite (0001) AlN/GaN heterostructures have been studied by real-time recording of the in situ reflection high-energy electron diffraction (RHEED), ex situ transmission electron microscopy (TEM), and atomic-force microscopy. A pseudo-two-dimensional layer-by-layer growth is observed at substrate temperatures of 640-660 °C, as evidenced by RHEED and TEM. However, the variation of the in-plane lattice parameter during growth and after growth has been found to be complex. Three steps have been seen during the deposition of lattice-mismatched AlN and GaN layers: they were interpreted as the succession of the formation of flat platelets, 3-6 monolayers high (0.8-1.5 nm) and 10-20 nm in diameter, their partial coalescence, and gradual dislocation introduction. Platelet formation leads to elastic relaxation as high as 1.8%, i.e., a considerable part of the AlN/GaN lattice mismatch of 2.4%, and can be reversible. Platelets are always observed during the initial stages of growth and are almost insensitive to the metal/N ratio. In contrast, platelet coalescence and dislocation introduction are very dependent on the metal/N ratio: no coalescence occurs and the dislocation introduction rate is higher under N-rich conditions. In all cases, the misfit dislocation density, as measured by the irreversible relaxation, is initially of the order of 7×1011 cm-2 and decreases exponentially with the layer thickness. These results are interpreted in the framework of a model that emphasizes the important role of the flat platelets for dislocation nucleation.

Nonthermal Particle Acceleration in 3D Relativistic Magnetic Reconnection in Pair Plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Werner, Gregory R.; Uzdensky, Dmitri A., E-mail: Greg.Werner@colorado.edu

As a fundamental process converting magnetic to plasma energy in high-energy astrophysical plasmas, relativistic magnetic reconnection is a leading explanation for the acceleration of particles to the ultrarelativistic energies that are necessary to power nonthermal emission (especially X-rays and gamma-rays) in pulsar magnetospheres and pulsar wind nebulae, coronae and jets of accreting black holes, and gamma-ray bursts. An important objective of plasma astrophysics is therefore the characterization of nonthermal particle acceleration (NTPA) effected by reconnection. Reconnection-powered NTPA has been demonstrated over a wide range of physical conditions using large 2D kinetic simulations. However, its robustness in realistic 3D reconnection—in particular,more » whether the 3D relativistic drift-kink instability (RDKI) disrupts NTPA—has not been systematically investigated, although pioneering 3D simulations have observed NTPA in isolated cases. Here, we present the first comprehensive study of NTPA in 3D relativistic reconnection in collisionless electron–positron plasmas, characterizing NTPA as the strength of 3D effects is varied systematically via the length in the third dimension and the strength of the guide magnetic field. We find that, while the RDKI prominently perturbs 3D reconnecting current sheets, it does not suppress particle acceleration, even for zero guide field; fully 3D reconnection robustly and efficiently produces nonthermal power-law particle spectra closely resembling those obtained in 2D. This finding provides strong support for reconnection as the key mechanism powering high-energy flares in various astrophysical systems. We also show that strong guide fields significantly inhibit NTPA, slowing reconnection and limiting the energy available for plasma energization, yielding steeper and shorter power-law spectra.« less

Electron correlation within the relativistic no-pair approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Almoukhalalati, Adel; Saue, Trond, E-mail: trond.saue@irsamc.ups-tlse.fr; Knecht, Stefan

This paper addresses the definition of correlation energy within 4-component relativistic atomic and molecular calculations. In the nonrelativistic domain the correlation energy is defined as the difference between the exact eigenvalue of the electronic Hamiltonian and the Hartree-Fock energy. In practice, what is reported is the basis set correlation energy, where the “exact” value is provided by a full Configuration Interaction (CI) calculation with some specified one-particle basis. The extension of this definition to the relativistic domain is not straightforward since the corresponding electronic Hamiltonian, the Dirac-Coulomb Hamiltonian, has no bound solutions. Present-day relativistic calculations are carried out within themore » no-pair approximation, where the Dirac-Coulomb Hamiltonian is embedded by projectors eliminating the troublesome negative-energy solutions. Hartree-Fock calculations are carried out with the implicit use of such projectors and only positive-energy orbitals are retained at the correlated level, meaning that the Hartree-Fock projectors are frozen at the correlated level. We argue that the projection operators should be optimized also at the correlated level and that this is possible by full Multiconfigurational Self-Consistent Field (MCSCF) calculations, that is, MCSCF calculations using a no-pair full CI expansion, but including orbital relaxation from the negative-energy orbitals. We show by variational perturbation theory that the MCSCF correlation energy is a pure MP2-like correlation expression, whereas the corresponding CI correlation energy contains an additional relaxation term. We explore numerically our theoretical analysis by carrying out variational and perturbative calculations on the two-electron rare gas atoms with specially tailored basis sets. In particular, we show that the correlation energy obtained by the suggested MCSCF procedure is smaller than the no-pair full CI correlation energy, in accordance with

Properties of zirconia after plasma treatment

NASA Astrophysics Data System (ADS)

Alekseenko, V. P.; Kulkov, S. N.

2017-09-01

The influence of high-frequency plasma treatment on the properties of zirconia powder is shown in the work. The powder was produced by a plasma-chemical method. The powders had a foamy form with the size of agglomerates of 5-10 μm and crystallites of 20-50 nm. The powders were treated by the pulse plasma unit with dielectric barrier discharge generator. It was shown that the plasma processing changes the acidity of water-powder suspensions from 8.1 to 4.3 pH, which signifies the powders' wettability improvement. It was revealed that more intensive mixing using ultrasound influences the acidity level, reducing it in comparison with mixing by paddle-type agitator. It was shown that these changes of surface properties have relaxation by 4% per day and extrapolation of this dependence shows that the powder will have initial properties after 400 hours storage at room conditions.

Relaxation processes in disaccharide sugar glasses

NASA Astrophysics Data System (ADS)

Hwang, Yoon-Hwae; Kwon, Hyun-Joung; Seo, Jeong-Ah; Shin, Dong-Myeong; Ha, Ji-Hye; Kim, Hyung-Kook

2013-02-01

We represented relaxation processes of disaccharide sugars (anhydrous trehalose and maltose) in supercooled and glassy states by using several spectroscopy techniques which include a broadband dielectric loss spectroscopy, photon correlation spectroscopy and X-ray diffraction (Retvield analysis) methods which are powerful tools to measure the dynamics in glass forming materials. In a dielectric loss spectroscopy study, we found that anhydrous trehalose and maltose glasses have an extra relaxation process besides α-, JG β- and γ-relaxations which could be related to a unique property of glycoside bond in disaccharides. In photon correlation spectroscopy study, we found an interesting compressed exponential relaxation at temperatures above 140°C. The q-1 dependence of its relaxation time corresponds to an ultraslow ballistic motion due to the local structure rearrangements. In the same temperature range, we found the glycosidic bond structure changes in trehalose molecule from the Raman and the Retvield X-ray diffraction measurements indicating that the observed compressed exponential relaxation in supercooled liquid trehalose could be resulted in the glycosidic bond structure change. Therefore, the overall results from this study might support the fact that the superior bioprotection ability of disaccharide sugar glasses might originate from this unique relaxation process of glycosidic bond.

Relaxation mode analysis and Markov state relaxation mode analysis for chignolin in aqueous solution near a transition temperature

NASA Astrophysics Data System (ADS)

Mitsutake, Ayori; Takano, Hiroshi

2015-09-01

It is important to extract reaction coordinates or order parameters from protein simulations in order to investigate the local minimum-energy states and the transitions between them. The most popular method to obtain such data is principal component analysis, which extracts modes of large conformational fluctuations around an average structure. We recently applied relaxation mode analysis for protein systems, which approximately estimates the slow relaxation modes and times from a simulation and enables investigations of the dynamic properties underlying the structural fluctuations of proteins. In this study, we apply this relaxation mode analysis to extract reaction coordinates for a system in which there are large conformational changes such as those commonly observed in protein folding/unfolding. We performed a 750-ns simulation of chignolin protein near its folding transition temperature and observed many transitions between the most stable, misfolded, intermediate, and unfolded states. We then applied principal component analysis and relaxation mode analysis to the system. In the relaxation mode analysis, we could automatically extract good reaction coordinates. The free-energy surfaces provide a clearer understanding of the transitions not only between local minimum-energy states but also between the folded and unfolded states, even though the simulation involved large conformational changes. Moreover, we propose a new analysis method called Markov state relaxation mode analysis. We applied the new method to states with slow relaxation, which are defined by the free-energy surface obtained in the relaxation mode analysis. Finally, the relaxation times of the states obtained with a simple Markov state model and the proposed Markov state relaxation mode analysis are compared and discussed.

Relaxation Time of High-Density Amorphous Ice

NASA Astrophysics Data System (ADS)

Handle, Philip H.; Seidl, Markus; Loerting, Thomas

2012-06-01

Amorphous water plays a fundamental role in astrophysics, cryoelectron microscopy, hydration of matter, and our understanding of anomalous liquid water properties. Yet, the characteristics of the relaxation processes taking place in high-density amorphous ice (HDA) are unknown. We here reveal that the relaxation processes in HDA at 110-135 K at 0.1-0.2 GPa are of collective and global nature, resembling the alpha relaxation in glassy material. Measured relaxation times suggest liquid-like relaxation characteristics in the vicinity of the crystallization temperature at 145 K. By carefully relaxing pressurized HDA for several hours at 135 K, we produce a state that is closer to the ideal glass state than all HDA states discussed so far in literature.

Understanding Plasmas with a High Degree of Correlation Through Modeling: From Rydberg and Fermionic Plasmas to Penning Plasmas

NASA Astrophysics Data System (ADS)

Christlieb, Andrew

2015-09-01

Ultra cold neutral plasmas have gained attention over the past 15 years as being a unique environment for studying moderately to strongly coupled neutral systems. The first ultra cold neutral plasmas were generated by ionizing a Bose Einstein condensate, generating a plasma with .1K ions and 2-4K electrons. These neutral plasmas have the unique property that the ratio of their potential energy to their kinetic energy, (Γ = PE / KE), can greatly exceed 1, leading to a strongly correlated system. The high degree of correlation means that everything from wave propagation through collision dynamics behaves quite differently from their counterpart in traditional neutral plasmas. Currently, a range of gases and different methods for cooling have been used to generate these plasmas from supersonic expansion, through penning trap configurations (reference Tom, Jake and Ed). These systems have time scales form picoseconds to milliseconds have a particle numbers from 105 to 109. These systems present a unique environment for studying the physics of correlation due to their low particle number and small size. We start by reviewing ultra cold plasmas and the current sate of the art in generating these correlated systems. Then we introduce the methods we will use for exploring these systems through direct simulation of Molecular Dynamics models; Momentum Dependent Potentials, Treecodes and Particle-Particle Particle-Mesh methods. We use these tools to look at two key areas of ultra cold plasmas; development of methods to generate a plasma with a Γ >> 1 and the impact of correlation of collisional relaxation. Our eventual goal is to use what we learn to develop models that can simulate correlation in large plasma systems that are outside of the scope of Molecular Dynamics models. In collaboration with Gautham Dharmuman, Mayur Jain, Michael Murillo and John Verboncoeur. This work it supposed by Air Force Office of Scientific Research.

Non-solenoidal Plasma Startup in the Pegasus Toroidal Experiment

NASA Astrophysics Data System (ADS)

Sontag, Aaron

2008-11-01

Non-solenoidal (NS) startup will simplify the design of future tokamaks by eliminating need for a central solenoid and is required for an ST based CTF. In Pegasus, washer-stack current sources (plasma guns) are used to initiate NS discharges via point-source DC helicity injection. Current injected parallel to the helical vacuum field can relax into a tokamak-like configuration with toroidally-averaged closed flux and tokamak-like confinement. This requires no modification of the vacuum vessel and is scalable to fusion grade systems with proper geometry. Guns in the divertor region create discharges with Ip up to 50 kA, 3 times the vacuum windup. Nonlinear 3D simulation with NIMROD shows excitation of a line-tied kink, producing poloidal flux amplification. Evidence of flux amplification includes: reversal of edge poloidal magnetic flux; Ip increase over vacuum geometric windup; plasma position subject to radial force balance; and persistence of Ip after gun shut-off. Equilibria show high edge current (li = 0.2) and elevated q (qmin> 6), allowing access to high IN (IN> 12). Guns at the outboard midplane produce Ip up to 7 times the vacuum windup with large n=1 activity when edge q passes through rational surfaces. Line averaged density up to 2x10^19 m-3 after relaxation shows an increase in particle confinement over non-relaxed cases. Maximum Ip is determined by helicity and radial force balance, tokamak stability, and Taylor relaxation. Coupling midplane gun discharges to other CD is straightforward due to Ip decay times >3 ms. Poloidal field induction has been used to create NS discharges up to 80 kA and gun plasmas with Ip of 60 kA have been ramped to over 100 kA by including OH drive. Present research is aimed at understanding the physics of this technique in order to form NS targets in excess of 200 kA and design NS startup systems for larger devices.

Surface vibrational relaxation of N2 studied by CO2 titration with time-resolved quantum cascade laser absorption spectroscopy

NASA Astrophysics Data System (ADS)

Marinov, D.; Lopatik, D.; Guaitella, O.; Hübner, M.; Ionikh, Y.; Röpcke, J.; Rousseau, A.

2012-05-01

A new method for determination of the wall de-excitation probability \\gamma _{N_2 } of vibrationally excited N2 on different surfaces exposed to low-pressure plasmas has been developed. A short dc discharge pulse of only a few milliseconds was applied to a mixture containing 0.05-1% of CO2 in N2 at a pressure of 133 Pa. Due to a nearly resonant fast vibrational transfer between N2(v) and the asymmetric ν3 mode of CO2 the vibrational excitation of these titrating molecules is an image of the degree of vibrational excitation of N2. In the afterglow, the vibrational relaxation of CO2 was monitored in situ using quantum cascade laser absorption spectroscopy. The experimental results were interpreted in terms of a numerical model of non-equilibrium vibrational kinetics in CO2-N2 mixtures. Heterogeneous relaxation was the main quenching process of N2(v) under the conditions of this study, which allowed determination of the value of \\gamma _{N_2 } from the best agreement between the experiment and the model. The new method is suitable for \\gamma _{N_2 } determination in a single plasma pulse with the discharge tube surface pretreated by a low-pressure plasma. The relaxation probability of the first vibrational level of nitrogen γ1 = (1.1 ± 0.15) × 10-3 found for Pyrex and silica is in reasonable agreement with the literature data. Using the new technique the N2(v = 1) quenching probability was measured on TiO2 surface, γ1 = (9 ± 1) × 10-3. A linear enhancement of the N2(v) wall deactivation probability with an increase in the admixture of CO2 was observed for all studied materials. In order to explain this effect, a vibrational energy transfer mechanism between N2(v) and adsorbed CO2 is proposed.

Relaxation in x-space magnetic particle imaging.

PubMed

Croft, Laura R; Goodwill, Patrick W; Conolly, Steven M

2012-12-01

Magnetic particle imaging (MPI) is a new imaging modality that noninvasively images the spatial distribution of superparamagnetic iron oxide nanoparticles (SPIOs). MPI has demonstrated high contrast and zero attenuation with depth, and MPI promises superior safety compared to current angiography methods, X-ray, computed tomography, and magnetic resonance imaging angiography. Nanoparticle relaxation can delay the SPIO magnetization, and in this work we investigate the open problem of the role relaxation plays in MPI scanning and its effect on the image. We begin by amending the x-space theory of MPI to include nanoparticle relaxation effects. We then validate the amended theory with experiments from a Berkeley x-space relaxometer and a Berkeley x-space projection MPI scanner. Our theory and experimental data indicate that relaxation reduces SNR and asymmetrically blurs the image in the scanning direction. While relaxation effects can have deleterious effects on the MPI scan, we show theoretically and experimentally that x-space reconstruction remains robust in the presence of relaxation. Furthermore, the role of relaxation in x-space theory provides guidance as we develop methods to minimize relaxation-induced blurring. This will be an important future area of research for the MPI community.

Hair Dye and Hair Relaxers

MedlinePlus

... For Consumers Consumer Information by Audience For Women Hair Dye and Hair Relaxers Share Tweet Linkedin Pin it More sharing ... products. If you have a bad reaction to hair dyes and relaxers, you should: Stop using the ...

Validating predictive models for fast ion profile relaxation in burning plasmas

NASA Astrophysics Data System (ADS)

Gorelenkov, N. N.; Heidbrink, W. W.; Kramer, G. J.; Lestz, J. B.; Podesta, M.; Van Zeeland, M. A.; White, R. B.

2016-11-01

The redistribution and potential loss of energetic particles due to MHD modes can limit the performance of fusion plasmas by reducing the plasma heating rate. In this work, we present validation studies of the 1.5D critical gradient model (CGM) for Alfvén eigenmode (AE) induced EP transport in NSTX and DIII-D neutral beam heated plasmas. In previous comparisons with a single DIII-D L-mode case, the CGM model was found to be responsible for 75% of measured AE induced neutron deficit [1]. A fully kinetic HINST is used to compute mode stability for the non-perturbative version of CGM (or nCGM). We have found that AEs show strong local instability drive up to γ /ω ∼ 20% violating assumptions of perturbative approaches used in NOVA-K code. We demonstrate that both models agree with each other and both underestimate the neutron deficit measured in DIII-D shot by approximately a factor of 2. On the other hand in NSTX the application of CGM shows good agreement for the measured flux deficit predictions. We attempt to understand these results with the help of the so-called kick model which is based on the guiding center code ORBIT. The kick model comparison gives important insight into the underlying velocity space dependence of the AE induced EP transport as well as it allows the estimate of the neutron deficit in the presence of the low frequency Alfvénic modes. Within the limitations of used models we infer that there are missing modes in the analysis which could improve the agreement with the experiments.

Rotation relaxation splitting for optimizing parallel RF excitation pulses with T1 - and T2 -relaxations in MRI

NASA Astrophysics Data System (ADS)

Majewski, Kurt

2018-03-01

Exact solutions of the Bloch equations with T1 - and T2 -relaxation terms for piecewise constant magnetic fields are numerically challenging. We therefore investigate an approximation for the achieved magnetization in which rotations and relaxations are split into separate operations. We develop an estimate for its accuracy and explicit first and second order derivatives with respect to the complex excitation radio frequency voltages. In practice, the deviation between an exact solution of the Bloch equations and this rotation relaxation splitting approximation seems negligible. Its computation times are similar to exact solutions without relaxation terms. We apply the developed theory to numerically optimize radio frequency excitation waveforms with T1 - and T2 -relaxations in several examples.

Surface vibrational relaxation of N2 studied by infrared titration with time resolved Quantum Cascade Laser diagnostics

NASA Astrophysics Data System (ADS)

Marinov, D.; Guaitella, O.; Rousseau, A.; Lopatik, D.; Hübner, M.; Röpcke, J.; Ionikh, Yu

2012-10-01

Relaxation of vibrationally excited nitrogen molecules on reactor walls is the most efficient N2(v) loss mechanism in laboratory plasmas at pressures up to few tens of mbars. In the present study a new method for determination of the de-excitation probability γN2 of vibrationally excited N2 on different surfaces has been developed. A short dc discharge pulse was applied to a mixture containing 0.05-1% of CO2, N2O or CO in N2 at 1.3 mbar. Due to a very efficient vibrational coupling between N2(v) and CO2 (N2O, CO), the vibrational excitation of these titrating molecules is an image of the vibrational excitation of N2. In the afterglow, the vibrational relaxation was monitored in-situ using quantum cascade laser absorption spectroscopy. The measurements were performed in a single discharge pulse without signal accumulation. Experimental results were interpreted in terms of a numerical model of non-equilibrium vibrational kinetics. The value of γN2 was determined from the best agreement between the measured and calculated relaxation times. Using new technique the relaxation probability of N2(v) was measured for SiO2, TiO2, Al2O3, Pyrex and anodized aluminum.

Lattice Boltzmann method for weakly ionized isothermal plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Huayu; Ki, Hyungson

2007-12-15

In this paper, a lattice Boltzmann method (LBM) for weakly ionized isothermal plasmas is presented by introducing a rescaling scheme for the Boltzmann transport equation. Without using this rescaling, we found that the nondimensional relaxation time used in the LBM is too large and the LBM does not produce physically realistic results. The developed model was applied to the electrostatic wave problem and the diffusion process of singly ionized helium plasmas with a 1-3% degree of ionization under an electric field. The obtained results agree well with theoretical values.

F-centers mechanism of long-term relaxation in lead zirconate-titanate based piezoelectric ceramics. 2. After-field relaxation

NASA Astrophysics Data System (ADS)

Ishchuk, V. M.; Kuzenko, D. V.

2016-08-01

The paper presents results of experimental study of the dielectric constant relaxation during aging process in Pb(Zr,Ti)O3 based solid solutions (PZT) after action of external DC electric field. The said process is a long-term one and is described by the logarithmic function of time. Reversible and nonreversible relaxation process takes place depending on the field intensity. The relaxation rate depends on the field strength also, and the said dependence has nonlinear and nonmonotonic form, if external field leads to domain disordering. The oxygen vacancies-based model for description of the long-term relaxation processes is suggested. The model takes into account the oxygen vacancies on the sample's surface ends, their conversion into F+- and F0-centers under external effects and subsequent relaxation of these centers into the simple oxygen vacancies after the action termination. F-centers formation leads to the violation of the original sample's electroneutrality, and generate intrinsic DC electric field into the sample. Relaxation of F-centers is accompanied by the reduction of the electric field, induced by them, and relaxation of the dielectric constant, as consequent effect.

Evolving fuzzy rules for relaxed-criteria negotiation.

PubMed

Sim, Kwang Mong

2008-12-01

In the literature on automated negotiation, very few negotiation agents are designed with the flexibility to slightly relax their negotiation criteria to reach a consensus more rapidly and with more certainty. Furthermore, these relaxed-criteria negotiation agents were not equipped with the ability to enhance their performance by learning and evolving their relaxed-criteria negotiation rules. The impetus of this work is designing market-driven negotiation agents (MDAs) that not only have the flexibility of relaxing bargaining criteria using fuzzy rules, but can also evolve their structures by learning new relaxed-criteria fuzzy rules to improve their negotiation outcomes as they participate in negotiations in more e-markets. To this end, an evolutionary algorithm for adapting and evolving relaxed-criteria fuzzy rules was developed. Implementing the idea in a testbed, two kinds of experiments for evaluating and comparing EvEMDAs (MDAs with relaxed-criteria rules that are evolved using the evolutionary algorithm) and EMDAs (MDAs with relaxed-criteria rules that are manually constructed) were carried out through stochastic simulations. Empirical results show that: 1) EvEMDAs generally outperformed EMDAs in different types of e-markets and 2) the negotiation outcomes of EvEMDAs generally improved as they negotiated in more e-markets.

The HelCat basic plasma science device

NASA Astrophysics Data System (ADS)

Gilmore, M.; Lynn, A. G.; Desjardins, T. R.; Zhang, Y.; Watts, C.; Hsu, S. C.; Betts, S.; Kelly, R.; Schamiloglu, E.

2015-01-01

The Helicon-Cathode(HelCat) device is a medium-size linear experiment suitable for a wide range of basic plasma science experiments in areas such as electrostatic turbulence and transport, magnetic relaxation, and high power microwave (HPM)-plasma interactions. The HelCat device is based on dual plasma sources located at opposite ends of the 4 m long vacuum chamber - an RF helicon source at one end and a thermionic cathode at the other. Thirteen coils provide an axial magnetic field B >= 0.220 T that can be configured individually to give various magnetic configurations (e.g. solenoid, mirror, cusp). Additional plasma sources, such as a compact coaxial plasma gun, are also utilized in some experiments, and can be located either along the chamber for perpendicular (to the background magnetic field) plasma injection, or at one of the ends for parallel injection. Using the multiple plasma sources, a wide range of plasma parameters can be obtained. Here, the HelCat device is described in detail and some examples of results from previous and ongoing experiments are given. Additionally, examples of planned experiments and device modifications are also discussed.

The in vivo relaxivity of MRI contrast agents

NASA Astrophysics Data System (ADS)

Shuter, Borys

1999-11-01

Post-contrast clinical 1H Magnetic Resonance Images have to date been interpreted with little regard for possible variations in the in-vivo properties of injected magnetic pharmaceuticals (contrast agents), particularly in their relaxivity or ability to alter tissue relaxation rates, T2-1 and T 2-1, per unit concentration. The relaxivities of contrast agents have only rarely been measured in-vivo, measurements usually being performed on excised tissues and at magnetic field strengths lower than used in clinical practice. Some researchers have simply assumed that relaxivities determined in homogeneous tissue phantoms were applicable in-vivo. In this thesis, the relaxivities of two contrast agents, Gd-DTPA and Gd-EOB-DTPA, were measured in simple tissue phantoms and in the kidney and liver of intact, but sacrificed, Wistar rats using a clinical MR scanner with a magnetic field of 1.5 Tesla. T1 and T2 were determined from sets of images acquired using a standard clinical spin-echo pulse sequence. The contrast agent concentration in tissue was assessed by radioassay of 153Gd-DTPA or 153Gd-EOB-DTPA, mixed with the normal compound prior to injection. Relaxivity was taken as the slope of a linear regression fit of relaxation rate against Gd concentration. The relaxivities of Gd-EOB-DTPA were similarly determined in normal and biliary- obstructed guinea pigs. Relaxivities in tissue differed significantly from values obtained in simple phantoms. Kidney T1 relaxivity was reduced for both compounds in normal animals. Three days or more of biliary obstruction produced further reductions in kidney T1 relaxivity of Gd-EOB-DTPA, providing strong evidence that disease affects contrast agent relaxivity. Kidney T2 relaxivity was much greater than T1 relaxivity and was also depressed by biliary obstruction. Liver T1 and T 2 relaxivites were increased above phantom values, but were not affected by the biliary obstruction. Water compartmentalisation, macromolecular binding, proton

Rate theory of ion pairing at the water liquid-vapor interface: A case of sodium iodide.

PubMed

Dang, Liem X; Schenter, Gregory K

2018-06-14

Studies on ion pairing at interfaces have been intensified recently because of their importance in many chemical reactive phenomena, such as ion-ion interactions that are affected by interfaces and their influence on kinetic processes. In this study, we performed simulations to examine the thermodynamics and kinetics of small polarizable sodium iodide ions in the bulk and near the water liquid-vapor interface. Using classical transition state theory, we calculated the dissociation rates and corrected them with transmission coefficients obtained from the reactive flux formalism and Grote-Hynes theory. Our results show that in addition to affecting the free energy of ions in solution, the interfacial environments significantly influence the kinetics of ion pairing. The results on the relaxation time obtained using the reactive flux formalism and Grote-Hynes theory present an unequivocal picture that the interface suppresses ion dissociation. The effects of the use of molecular models on the ion interactions as well as the ion-pair configurations at the interface are also quantified and discussed.

Rate theory of ion pairing at the water liquid-vapor interface: A case of sodium iodide

NASA Astrophysics Data System (ADS)

Dang, Liem X.; Schenter, Gregory K.

2018-06-01

Studies on ion pairing at interfaces have been intensified recently because of their importance in many chemical reactive phenomena, such as ion-ion interactions that are affected by interfaces and their influence on kinetic processes. In this study, we performed simulations to examine the thermodynamics and kinetics of small polarizable sodium iodide ions in the bulk and near the water liquid-vapor interface. Using classical transition state theory, we calculated the dissociation rates and corrected them with transmission coefficients obtained from the reactive flux formalism and Grote-Hynes theory. Our results show that in addition to affecting the free energy of ions in solution, the interfacial environments significantly influence the kinetics of ion pairing. The results on the relaxation time obtained using the reactive flux formalism and Grote-Hynes theory present an unequivocal picture that the interface suppresses ion dissociation. The effects of the use of molecular models on the ion interactions as well as the ion-pair configurations at the interface are also quantified and discussed.

N-acetylcysteine does not influence the activity of endothelium-derived relaxing factor in vivo.

PubMed

Creager, M A; Roddy, M A; Boles, K; Stamler, J S

1997-02-01

contributes to endothelium-derived relaxing factor bioactivity in plasma and vascular smooth muscle. Potentiation of the effects of nitroglycerin by N-acetylcysteine can be attributed to its enhanced biotransformation to an endothelium-derived relaxing factor equivalent, such as nitrosothiol. These observations support the notion of an equilibrium between nitric oxide and nitrosothiol in biological systems that may be influenced by redox state.

Chandrasekhar-Kendall modes and Taylor relaxation in an axisymmetric torus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, X.Z.; Boozer, A.H.; Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027

2005-10-01

The helicity-conserving Taylor relaxation of a plasma in a toroidal chamber to a force-free configuration, which means j=(j{sub parallel})/B)B with j{sub parallel}/B independent of position, can be generalized to include the external injection of magnetic helicity. When this is done, j{sub parallel}/B has resonant values, which can be understood using the eigenmodes of Taylor-relaxed plasmas enclosed by a perfectly conducting toroidal shell. These eigenmodes include a toroidal generalization of those found by Chandrasekhar and Kendall (CK) [Astrophys. J. 126, 457 (1957)] for a spherical chamber, which has no externally produced magnetic flux. It is shown that the CK modes inmore » an axisymmetric torus are of three types: (1) helical modes as well as axisymmetric modes that have (2) and have no (3) net toroidal flux. Yoshida and Giga (YG) [Math. Z. 204, 235 (1990)] published a fourth class of modes: axisymmetric modes that have no net toroidal flux in the chamber due to toroidal flux produced by a net poloidal current in the shell canceling the net toroidal flux from the plasma currents. Jensen and Chu [Phys. Fluids 27, 2881 (1984)], as well as Taylor [Rev. Mod. Phys. 58, 741 (1986)], considered modes in which the vector potential was zero on the axisymmetric toroidal chamber. It is shown that these Jensen-Chu-Taylor modes include only the CK helical modes and the CK axisymmetric modes without net toroidal flux. If the toroidal chamber is perfectly conducting except for a cut that prevents a net poloidal current from flowing, resonances in j{sub parallel}/B occur at the eigenvalues of the axisymmetric CK modes. Jensen and Chu studied this type of resonance. Without the cut, so a poloidal current flows to conserve the net toroidal flux, it is shown that j{sub parallel}/B resonances occur at the eigenvalues of the CK modes that have no net toroidal flux and at the eigenvalues of the YG modes, which are upshifted from the eigenvalues of the axisymmetric CK modes

Nonlinear reconnecting edge localized modes in current-carrying plasmas

DOE PAGES

Ebrahimi, F.

2017-05-22

Nonlinear edge localized modes in a tokamak are examined using global three-dimensional resistive magnetohydrodynamics simulations. Coherent current-carrying filament (ribbon-like) structures wrapped around the torus are nonlinearly formed due to nonaxisymmetric reconnecting current sheet instabilities, the so-called peeling-like edge localized modes. These fast growing modes saturate by breaking axisymmetric current layers isolated near the plasma edge and go through repetitive relaxation cycles by expelling current radially outward and relaxing it back. The local bidirectional fluctuation-induced electromotive force (emf) from the edge localized modes, the dynamo action, relaxes the axisymmetric current density and forms current holes near the edge. Furthermore, the three-dimensionalmore » coherent current-carrying filament structures (sometimes referred to as 3-D plasmoids) observed here should also have strong implications for solar and astrophysical reconnection.« less

Micro-column plasma emission liquid chromatograph

DOEpatents

Gay, Don D.

1984-01-01

In a direct current plasma emission spectrometer for use in combination with a micro-column liquid chromatograph, an improved plasma source unit. The plasma source unit includes a quartz capillary tube having an inlet means, outlet off gas means and a pair of spaced electrodes defining a plasma region in the tube. The inlet means is connected to and adapted to receive eluant of the liquid chromatograph along with a stream of plasma-forming gas. There is an opening through the wall of the capillary tube penetrating into the plasma region. A soft glass capillary light pipe is disposed at the opening, is connected to the spectrometer, and is adapted to transmit light passing from the plasma region to the spectrometer. There is also a source of electromotive force connected to the electrodes sufficient to initiate and sustain a plasma in the plasma region of the tube.

Training the max-margin sequence model with the relaxed slack variables.

PubMed

Niu, Lingfeng; Wu, Jianmin; Shi, Yong

2012-09-01

Sequence models are widely used in many applications such as natural language processing, information extraction and optical character recognition, etc. We propose a new approach to train the max-margin based sequence model by relaxing the slack variables in this paper. With the canonical feature mapping definition, the relaxed problem is solved by training a multiclass Support Vector Machine (SVM). Compared with the state-of-the-art solutions for the sequence learning, the new method has the following advantages: firstly, the sequence training problem is transformed into a multiclassification problem, which is more widely studied and already has quite a few off-the-shelf training packages; secondly, this new approach reduces the complexity of training significantly and achieves comparable prediction performance compared with the existing sequence models; thirdly, when the size of training data is limited, by assigning different slack variables to different microlabel pairs, the new method can use the discriminative information more frugally and produces more reliable model; last but not least, by employing kernels in the intermediate multiclass SVM, nonlinear feature space can be easily explored. Experimental results on the task of named entity recognition, information extraction and handwritten letter recognition with the public datasets illustrate the efficiency and effectiveness of our method. Copyright © 2012 Elsevier Ltd. All rights reserved.

Plasma motions in planetary magnetospheres

NASA Technical Reports Server (NTRS)

Hill, T. W.; Dessler, A. J.

1991-01-01

Interplanetary space is pervaded by a supersonic 'solar wind' plasma; five planets, in addition to the earth, have magnetic fields of sufficient strength to form the cometlike cavities called 'magnetospheres'. Comparative studies of these structures have indicated the specific environmental factor that can result in dramatic differences in the behavior of any pair of magnetospheres. Although planetary magnetospheres are large enough to serve as laboratories for in situ study of cosmic plasma and magnetic field behavior effects on particle acceleration and EM emission, much work remains to be done toward relating magnetospheric physics results to the study of remote astrophysical plasmas.

Non-Markovian Effects in Turbulent Diffusion in Magnetized Plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zagorodny, Anatoly; Weiland, Jan

2009-10-08

The derivation of the kinetic equations for inhomogeneous plasma in an external magnetic field is presented. The Fokker-Planck-type equations with the non-Markovian kinetic coefficients are proposed. In the time-local limit (small correlation times with respect to the distribution function relaxation time) the relations obtained recover the results known from the appropriate quasilinear theory and the Dupree-Weinstock theory of plasma turbulence. The equations proposed are used to describe zonal flow generation and to estimate the diffusion coefficient for saturated turbulence.

Can Black Hole Relax Unitarily?

NASA Astrophysics Data System (ADS)

Solodukhin, S. N.

2005-03-01

We review the way the BTZ black hole relaxes back to thermal equilibrium after a small perturbation and how it is seen in the boundary (finite volume) CFT. The unitarity requires the relaxation to be quasi-periodic. It is preserved in the CFT but is not obvious in the case of the semiclassical black hole the relaxation of which is driven by complex quasi-normal modes. We discuss two ways of modifying the semiclassical black hole geometry to maintain unitarity: the (fractal) brick wall and the worm-hole modification. In the latter case the entropy comes out correctly as well.

Adsorbate-induced lifting of substrate relaxation is a general mechanism governing titania surface chemistry.

PubMed

Silber, David; Kowalski, Piotr M; Traeger, Franziska; Buchholz, Maria; Bebensee, Fabian; Meyer, Bernd; Wöll, Christof

2016-09-30

Under ambient conditions, almost all metals are coated by an oxide. These coatings, the result of a chemical reaction, are not passive. Many of them bind, activate and modify adsorbed molecules, processes that are exploited, for example, in heterogeneous catalysis and photochemistry. Here we report an effect of general importance that governs the bonding, structure formation and dissociation of molecules on oxidic substrates. For a specific example, methanol adsorbed on the rutile TiO 2 (110) single crystal surface, we demonstrate by using a combination of experimental and theoretical techniques that strongly bonding adsorbates can lift surface relaxations beyond their adsorption site, which leads to a significant substrate-mediated interaction between adsorbates. The result is a complex superstructure consisting of pairs of methanol molecules and unoccupied adsorption sites. Infrared spectroscopy reveals that the paired methanol molecules remain intact and do not deprotonate on the defect-free terraces of the rutile TiO 2 (110) surface.

Adsorbate-induced lifting of substrate relaxation is a general mechanism governing titania surface chemistry

NASA Astrophysics Data System (ADS)

Silber, David; Kowalski, Piotr M.; Traeger, Franziska; Buchholz, Maria; Bebensee, Fabian; Meyer, Bernd; Wöll, Christof

2016-09-01

Under ambient conditions, almost all metals are coated by an oxide. These coatings, the result of a chemical reaction, are not passive. Many of them bind, activate and modify adsorbed molecules, processes that are exploited, for example, in heterogeneous catalysis and photochemistry. Here we report an effect of general importance that governs the bonding, structure formation and dissociation of molecules on oxidic substrates. For a specific example, methanol adsorbed on the rutile TiO2(110) single crystal surface, we demonstrate by using a combination of experimental and theoretical techniques that strongly bonding adsorbates can lift surface relaxations beyond their adsorption site, which leads to a significant substrate-mediated interaction between adsorbates. The result is a complex superstructure consisting of pairs of methanol molecules and unoccupied adsorption sites. Infrared spectroscopy reveals that the paired methanol molecules remain intact and do not deprotonate on the defect-free terraces of the rutile TiO2(110) surface.

Rapid wall relaxation in elongating tissues.

PubMed

Matyssek, R; Maruyama, S; Boyer, J S

1988-04-01

Reported differences in the relaxation of cell walls in enlarging stem tissues of soybean (Glycine max [L.] Merr.) and pea (Pisum sativum L.) cause measurements of the yield threshold turgor, an important growth parameter, to be in doubt. Using the pressure probe and guillotine psychrometer, we investigated wall relaxation in these species by excising the elongating tissue in air to remove the water supply. We found that the rapid kinetics usually exhibited by soybean could be delayed and made similar to the slow kinetics previously reported for pea if slowly growing or mature tissue was left attached to the rapidly growing tissue when relaxation was initiated. The greater the amount of attached tissue, the slower the relaxation, suggesting that slowly growing tissue acted as a water source. Consistent with this concept was a lower water potential in the rapidly elongating tissue than in the slowly growing tissue. Previous reports of wall relaxation in pea included slowly growing tissue. If this tissue was removed from pea, relaxation became as rapid as usually exhibited by soybean. It is concluded that the true relaxation of cell walls to the yield threshold requires only a few minutes and that the yield threshold should be constant during so short a time, thus reflecting the yield threshold in the intact plant before excision. Under these conditions, the yield threshold was close to the turgor in the intact plant regardless of the species. The presence of slowly growing or mature tissue delays wall relaxation and should be avoided during such measurements. However, this delay can be used to advantage when turgor of intact growing tissues is being measured using excised tissues because turgor does not change for a considerable time after excision.

Diabetes impairs the atrial natriuretic peptide relaxant action mediated by potassium channels and prostacyclin in the rabbit renal artery.

PubMed

Marrachelli, Vannina G; Centeno, José M; Miranda, Ignacio; Castelló-Ruiz, María; Burguete, María C; Jover-Mengual, Teresa; Salom, Juan B; Torregrosa, Germán; Miranda, Francisco J; Alborch, Enrique

2012-11-01

Diabetes is associated with increased prevalence of hypertension, cardiovascular and renal disease. Atrial natriuretic peptide (ANP) plays an important role in cardiovascular pathophysiology and is claimed to have cardioprotective and renoprotective effect in diabetic patients. The working hypothesis was that alloxan-induced diabetes might modify the vascular effects of ANP in isolated rabbit renal arteries and the mechanisms involved in such actions. Plasma ANP levels were higher in diabetic rabbits than in control rabbits. ANP (10(-12)-10(-7)M) induced a relaxation of precontracted renal arteries, which was lower in diabetic than in control rabbits. In arteries from both groups of animals, endothelium removal decreased the ANP-induced relaxation but inhibition of NO-synthesis did not modify ANP-induced relaxations. In KCl-depolarised arteries, relaxation to ANP was almost abolished both in control and diabetic rabbits. Tetraethylammonium (TEA) partly inhibited the relaxation to ANP in control rabbits but did not modify it in diabetic rabbits. Glibenclamide and 4-aminopyridine inhibited the relaxation to ANP, and these inhibitions were lower in diabetic than in control rabbits. Indomethacin potentiated the relaxation to ANP, more in control than in diabetic rabbits. In the presence of ANP the renal artery released thromboxane A(2) and prostacyclin, and the release of prostacyclin resulted decreased in diabetic rabbits. The present results suggest that diabetes produces hyporeactivity of the rabbit renal artery to ANP by mechanisms that at least include the reduced modulation by prostacyclin and a lower participation of ATP-sensitive K(+) channel (K(ATP)), voltage-sensitive K(+) channels (K(V)) and TEA-sensitive K(+) channels (K(Ca)). Copyright © 2012 Elsevier Ltd. All rights reserved.

Spatially resolved nuclear spin relaxation, electron spin relaxation and light absorption in swift heavy ion irradiated LiF crystals.

PubMed

Stork, H; Dinse, K-P; Ditter, M; Fujara, F; Masierak, W; Neumann, R; Schuster, B; Schwartz, K; Trautmann, C

2010-05-12

Spatially resolved (19)F and (7)Li spin-lattice relaxation rates are measured for LiF single crystals after irradiation with two kinds of swift heavy ions ((12)C of 133 MeV and (208)Pb of 1.78 GeV incident energy). Like in earlier studies on (130)Xe and (238)U irradiated LiF crystals, we found a strong enhancement of the nuclear spin-lattice relaxation rate within the ion penetration depth and a slight--but still significant--enhancement beyond. By evaluating the nuclear relaxation rate enhancement within the ion range after irradiation with different projectiles, a universal relationship between the spin-lattice relaxation rate and the dose is deduced. The results of accompanying X-band electron paramagnetic resonance relaxation measurements and optical absorption spectroscopy are included in a physical interpretation of this relationship. Also the reason for the enhanced relaxation rate beyond the ion range is further discussed.

Strain coupling mechanisms and elastic relaxation associated with spin state transitions in LaCoO3

NASA Astrophysics Data System (ADS)

Zhang, Zhiying; Koppensteiner, Johannes; Schranz, Wilfried; Prabhakaran, Dharmalingam; Carpenter, Michael A.

2011-04-01

Advantage is taken of the wealth of experimental data relating to the evolution with temperature of spin states of Co3 + in LaCoO3 in order to undertake a detailed investigation of the mechanisms by which changes in electronic structure can influence strain, and elastic and anelastic relaxations in perovskites. The macroscopic strain accompanying changes in the spin state in LaCoO3 is predominantly a volume strain arising simply from the change in effective ionic radius of the Co3 + ions. This acts to renormalize the octahedral tilting transition temperature in a manner that is easily understood in terms of coupling between the tilt and spin order parameters. Results from resonant ultrasound spectroscopy at high frequencies (0.1-1.5 MHz) reveal stiffening of the shear modulus which scales qualitatively with a spin order parameter defined in terms of changing Co-O bond lengths. From this finding, in combination with results from dynamic mechanical analysis at low frequencies (0.1-50 Hz) and data from the literature, four distinctive anelastic relaxation mechanisms are identified. The relaxation times of these are displayed on an anelasticity map and are tentatively related to spin-spin relaxation, spin-lattice relaxation, migration of twin walls and migration of magnetic polarons. The effective activation energy for the freezing of twin wall motion below ~ 590 K at low frequencies was found to be 182 ± 21 kJ mol - 1 (1.9 ± 0.2 eV) which is attributed to pinning by pairs of oxygen vacancies, though the local mechanisms appear to have a spread of relaxation times. It seems inevitable that twin walls due to octahedral tilting must have quite different characteristics from the matrix in terms of local spin configurations of Co3 + . A hysteresis in the elastic properties at high temperatures further emphasizes the importance of oxygen content in controlling the properties of LaCoO3.

Calculation of electronic transport coefficients of Ag and Au plasma.

PubMed

Apfelbaum, E M

2011-12-01

The thermoelectric transport coefficients of silver and gold plasma have been calculated within the relaxation-time approximation. We considered temperatures of 10-100 kK and densities of ρ plasma composition was calculated using a corresponding system of coupled mass action laws, including the atom ionization up to +4. For momentum cross sections of electron-atom scattering we used the most accurate expressions available. The results of our modeling have been compared with other researchers' data whenever possible.

Base pairing among three cis-acting sequences contributes to template switching during hepadnavirus reverse transcription

PubMed Central

Liu, Ning; Tian, Ru; Loeb, Daniel D.

2003-01-01

Synthesis of the relaxed-circular (RC) DNA genome of hepadnaviruses requires two template switches during plus-strand DNA synthesis: primer translocation and circularization. Although primer translocation and circularization use different donor and acceptor sequences, and are distinct temporally, they share the common theme of switching from one end of the minus-strand template to the other end. Studies of duck hepatitis B virus have indicated that, in addition to the donor and acceptor sequences, three other cis-acting sequences, named 3E, M, and 5E, are required for the synthesis of RC DNA by contributing to primer translocation and circularization. The mechanism by which 3E, M, and 5E act was not known. We present evidence that these sequences function by base pairing with each other within the minus-strand template. 3E base-pairs with one portion of M (M3) and 5E base-pairs with an adjacent portion of M (M5). We found that disrupting base pairing between 3E and M3 and between 5E and M5 inhibited primer translocation and circularization. More importantly, restoring base pairing with mutant sequences restored the production of RC DNA. These results are consistent with the model that, within duck hepatitis B virus capsids, the ends of the minus-strand template are juxtaposed via base pairing to facilitate the two template switches during plus-strand DNA synthesis. PMID:12578983

Base pairing among three cis-acting sequences contributes to template switching during hepadnavirus reverse transcription.

PubMed

Liu, Ning; Tian, Ru; Loeb, Daniel D

2003-02-18

Synthesis of the relaxed-circular (RC) DNA genome of hepadnaviruses requires two template switches during plus-strand DNA synthesis: primer translocation and circularization. Although primer translocation and circularization use different donor and acceptor sequences, and are distinct temporally, they share the common theme of switching from one end of the minus-strand template to the other end. Studies of duck hepatitis B virus have indicated that, in addition to the donor and acceptor sequences, three other cis-acting sequences, named 3E, M, and 5E, are required for the synthesis of RC DNA by contributing to primer translocation and circularization. The mechanism by which 3E, M, and 5E act was not known. We present evidence that these sequences function by base pairing with each other within the minus-strand template. 3E base-pairs with one portion of M (M3) and 5E base-pairs with an adjacent portion of M (M5). We found that disrupting base pairing between 3E and M3 and between 5E and M5 inhibited primer translocation and circularization. More importantly, restoring base pairing with mutant sequences restored the production of RC DNA. These results are consistent with the model that, within duck hepatitis B virus capsids, the ends of the minus-strand template are juxtaposed via base pairing to facilitate the two template switches during plus-strand DNA synthesis.

The effects of rival seminal plasma on sperm velocity in the alternative reproductive tactics of Chinook salmon.

PubMed

Lewis, Jason A; Pitcher, Trevor E

2017-04-01

Sperm competition is prevalent and intense in many animal mating systems, and is a major force driving evolution of such mating systems. The objective of this study was to determine the effect of seminal plasma on sperm velocity of male Chinook salmon (Onchorhynchus tshawytscha), which possesses a mating system with male alternative reproductive tactics and intense sperm competition. Male Chinook salmon either adopt a small, precocious sneaking tactic (jack) or a large, dominant tactic (hooknose). To test whether the seminal plasma can effect sperm velocity amongst sperm competitors, two experiments were done whereby males were paired based upon the alternative tactic each male adopted, with the first experiment consisting of jack-hooknose pairs (N = 16) and the second experiment consisting of jack-jack and hooknose-hooknose pairs (N = 12 and 14, respectively). Within each pair, milt of each male was manipulated such that seminal plasma was removed and swapped between the males in each pair and sperm velocity was measured. Jack seminal plasma caused a significant decrease (∼11.9%) in hooknose sperm velocity while causing a significant increase in jack sperm velocity (∼7%), while alternatively, hooknose seminal plasma had no affect on sperm velocity of jack or other hooknose males. This study shows that rival seminal plasma may affect the outcome of sperm competition between males; males adopting a sneaking tactic, that spawn in a disadvantageous mating position, may be able to compensate for this deficit by being more competitive through the effects of their seminal plasma on their competitor's sperm velocity. Copyright © 2016. Published by Elsevier Inc.

Runaway tails in magnetized plasmas

NASA Technical Reports Server (NTRS)

Moghaddam-Taaheri, E.; Vlahos, L.; Rowland, H. L.; Papadopoulos, K.

1985-01-01

The evolution of a runaway tail driven by a dc electric field in a magnetized plasma is analyzed. Depending on the strength of the electric field and the ratio of plasma to gyrofrequency, there are three different regimes in the evolution of the tail. The tail can be (1) stable with electrons accelerated to large parallel velocities, (2) unstable to Cerenkov resonance because of the depletion of the bulk and the formation of a positive slope, (3) unstable to the anomalous Doppler resonance instability driven by the large velocity anisotropy in the tail. Once an instability is triggered (Cerenkov or anomalous Doppler resonance) the tail relaxes into an isotropic distribution. The role of a convection type loss term is also discussed.

Investigation of effective impact parameters in electron-ion temperature relaxation via Particle-Particle Coulombic molecular dynamics

NASA Astrophysics Data System (ADS)

Zhao, Yinjian

2017-09-01

Aiming at a high simulation accuracy, a Particle-Particle (PP) Coulombic molecular dynamics model is implemented to study the electron-ion temperature relaxation. In this model, the Coulomb's law is directly applied in a bounded system with two cutoffs at both short and long length scales. By increasing the range between the two cutoffs, it is found that the relaxation rate deviates from the BPS theory and approaches the LS theory and the GMS theory. Also, the effective minimum and maximum impact parameters (bmin* and bmax*) are obtained. For the simulated plasma condition, bmin* is about 6.352 times smaller than the Landau length (bC), and bmax* is about 2 times larger than the Debye length (λD), where bC and λD are used in the LS theory. Surprisingly, the effective relaxation time obtained from the PP model is very close to the LS theory and the GMS theory, even though the effective Coulomb logarithm is two times greater than the one used in the LS theory. Besides, this work shows that the PP model (commonly known as computationally expensive) is becoming practicable via GPU parallel computing techniques.

Quasiparticle relaxation in superconducting nanostructures

NASA Astrophysics Data System (ADS)

Savich, Yahor; Glazman, Leonid; Kamenev, Alex

2017-09-01

We examine energy relaxation of nonequilibrium quasiparticles in "dirty" superconductors with the electron mean free path much shorter than the superconducting coherence length. Relaxation of low-energy nonequilibrium quasiparticles is dominated by phonon emission. We derive the corresponding collision integral and find the quasiparticle relaxation rate. The latter is sensitive to the breaking of time reversal symmetry (TRS) by a magnetic field (or magnetic impurities). As a concrete application of the developed theory, we address quasiparticle trapping by a vortex and a current-biased constriction. We show that trapping of hot quasiparticles may predominantly occur at distances from the vortex core, or the constriction, significantly exceeding the superconducting coherence length.

Plasma Experiments on an Internal Coil Device with an High Temperature Superconductor

NASA Astrophysics Data System (ADS)

Yuichi, Ogawa; Junji, Morikawa; Kotaro, Ohkuni; Dan, Hori; Shigeo, Yamakosi; Nagato, Yanagi; Toshiyuki, Mito; Masataka, Iwakuma; Toshio, Uede

2003-10-01

An internal coil device would be expected for exploring high beta plasmas based on plasma relaxation process. Prof. A. Hasegawa proposed an advanced fusion reactor with a dipole configuration, and Mahajan and Yoshida developed a new high beta state based on two-fluid relaxation theory. To study these high beta plasmas, we have constructed an internal coil device with a high temperature superconductor. The major radius of the internal coil is 15 cm, and the coil current is 50 kA. Three different types of Ag-sheathed Bi-2223 tapes are employed; i.e., a high critical current tape with a low silver ratio for the main HTS coil, a 0.3wt3atprovided by a GM refrigerator and supplied to the coil through a check valve, and the coil current is directly excited with the external power supply through removable electrodes. It took about 11 hours to cool the coil down to 21 K from the room temperature, and the nominal cable current of 118 A (overall coil current: 50 kA) has been achieved. A decay time constant of the persistent current is a few tens of hours. Plasma experiments in a dipole configuration have been initiated.

Novel Electron-Phonon Relaxation Pathway in Graphite Revealed by Time-Resolved Raman Scattering and Angle-Resolved Photoemission Spectroscopy.

PubMed

Yang, Jhih-An; Parham, Stephen; Dessau, Daniel; Reznik, Dmitry

2017-01-19

Time dynamics of photoexcited electron-hole pairs is important for a number of technologies, in particular solar cells. We combined ultrafast pump-probe Raman scattering and photoemission to directly follow electron-hole excitations as well as the G-phonon in graphite after an excitation by an intense laser pulse. This phonon is known to couple relatively strongly to electrons. Cross-correlating effective electronic and phonon temperatures places new constraints on model-based fits. The accepted two-temperature model predicts that G-phonon population should start to increase as soon as excited electron-hole pairs are created and that the rate of increase should not depend strongly on the pump fluence. Instead we found that the increase of the G-phonon population occurs with a delay of ~65 fs. This time-delay is also evidenced by the absence of the so-called self-pumping for G phonons. It decreases with increased pump fluence. We show that these observations imply a new relaxation pathway: Instead of hot carriers transferring energy to G-phonons directly, the energy is first transferred to optical phonons near the zone boundary K-points, which then decay into G-phonons via phonon-phonon scattering. Our work demonstrates that phonon-phonon interactions must be included in any calculations of hot carrier relaxation in optical absorbers even when only short timescales are considered.

[Autocontrol of muscle relaxation with vecuronium].

PubMed

Sibilla, C; Zatelli, R; Marchi, M; Zago, M

1990-01-01

The optimal conditions for maintaining desired levels of muscle relaxation with vecuronium are obtained by means of the continuous infusion (I.V.) technique. A frequent correction of the infusion flow is required, since it is impossible to predict the exact amount for the muscle relaxant in single case. In order to overcome such limits the authors propose a very feasible infusion system for the self-control of muscle relaxation; furthermore they positively consider its possible daily clinical application.

Comparing nonlinear MHD simulations of low-aspect-ratio RFPs to RELAX experiments

NASA Astrophysics Data System (ADS)

McCollam, K. J.; den Hartog, D. J.; Jacobson, C. M.; Sovinec, C. R.; Masamune, S.; Sanpei, A.

2016-10-01

Standard reversed-field pinch (RFP) plasmas provide a nonlinear dynamical system as a validation domain for numerical MHD simulation codes, with applications in general toroidal confinement scenarios including tokamaks. Using the NIMROD code, we simulate the nonlinear evolution of RFP plasmas similar to those in the RELAX experiment. The experiment's modest Lundquist numbers S (as low as a few times 104) make closely matching MHD simulations tractable given present computing resources. Its low aspect ratio ( 2) motivates a comparison study using cylindrical and toroidal geometries in NIMROD. We present initial results from nonlinear single-fluid runs at S =104 for both geometries and a range of equilibrium parameters, which preliminarily show that the magnetic fluctuations are roughly similar between the two geometries and between simulation and experiment, though there appear to be some qualitative differences in their temporal evolution. Runs at higher S are planned. This work is supported by the U.S. DOE and by the Japan Society for the Promotion of Science.

Relaxation training after stroke: potential to reduce anxiety.

PubMed

Kneebone, Ian; Walker-Samuel, Natalie; Swanston, Jennifer; Otto, Elisabeth

2014-01-01

To consider the feasibility of setting up a relaxation group to treat symptoms of post stroke anxiety in an in-patient post-acute setting; and to explore the effectiveness of relaxation training in reducing self-reported tension. A relaxation group protocol was developed in consultation with a multidisciplinary team and a user group. Over a period of 24 months, 55 stroke patients attended group autogenic relaxation training on a rehabilitation ward. Attendance ranged between one and eleven sessions. Self-reported tension was assessed pre and post relaxation training using the Tension Rating Circles (TRCs). The TRCs identified a significant reduction in self-reported tension from pre to post training, irrespective of the number of sessions attended; z = -3.656, p < 0.001, r = -0.67, for those who attended multiple sessions, z = -2.758, p < 0.01, r = -0.6 for those who attended a single session. The routine use of relaxation techniques in treating anxiety in patients undergoing post-stroke rehabilitation shows potential. Self-reported tension decreased after attendance at relaxation training. The TRCs proved acceptable to group members, but should be validated against standard anxiety measures. Further exploration of the application of relaxation techniques in clinical practice is desirable. Implications for Rehabilitation Anxiety is prevalent after stroke and likely affects rehabilitation outcomes. Relaxation training is a well proven treatment for anxiety in the non-stroke population. A significant within session reduction in tension, a hallmark symptom of anxiety, was evidenced via group relaxation training delivered in a post-acute, in-patient stroke unit setting. Relaxation training a shows promise as a treatment for anxiety after stroke.

Magnetic Resonance Fingerprinting with short relaxation intervals.

PubMed

Amthor, Thomas; Doneva, Mariya; Koken, Peter; Sommer, Karsten; Meineke, Jakob; Börnert, Peter

2017-09-01

The aim of this study was to investigate a technique for improving the performance of Magnetic Resonance Fingerprinting (MRF) in repetitive sampling schemes, in particular for 3D MRF acquisition, by shortening relaxation intervals between MRF pulse train repetitions. A calculation method for MRF dictionaries adapted to short relaxation intervals and non-relaxed initial spin states is presented, based on the concept of stationary fingerprints. The method is applicable to many different k-space sampling schemes in 2D and 3D. For accuracy analysis, T 1 and T 2 values of a phantom are determined by single-slice Cartesian MRF for different relaxation intervals and are compared with quantitative reference measurements. The relevance of slice profile effects is also investigated in this case. To further illustrate the capabilities of the method, an application to in-vivo spiral 3D MRF measurements is demonstrated. The proposed computation method enables accurate parameter estimation even for the shortest relaxation intervals, as investigated for different sampling patterns in 2D and 3D. In 2D Cartesian measurements, we achieved a scan acceleration of more than a factor of two, while maintaining acceptable accuracy: The largest T 1 values of a sample set deviated from their reference values by 0.3% (longest relaxation interval) and 2.4% (shortest relaxation interval). The largest T 2 values showed systematic deviations of up to 10% for all relaxation intervals, which is discussed. The influence of slice profile effects for multislice acquisition is shown to become increasingly relevant for short relaxation intervals. In 3D spiral measurements, a scan time reduction of 36% was achieved, maintaining the quality of in-vivo T1 and T2 maps. Reducing the relaxation interval between MRF sequence repetitions using stationary fingerprint dictionaries is a feasible method to improve the scan efficiency of MRF sequences. The method enables fast implementations of 3D spatially

Interaction between vine pesticides and bovine serum albumin studied by nuclear spin relaxation data.

PubMed

Martini, Silvia; Bonechi, Claudia; Rossi, Claudio

2010-10-13

Pesticides are chemicals usually used in agriculture to prevent possible diseases to crops, such as grapes, caused by parasites. Even if most of the pesticides are degraded during the wine process, residual levels remain in the final product. The most commonly used pesticides in vine belong to several classes of chemical compounds; among them, triazoles and anilinopyrimidines have been commercially used since the 1970s and 1990s, respectively. In this work, we investigated the interaction between three of the most used fungicides belonging to the chemical classes mentioned above (myclobutanil, triadimenol, and pyrimethanil) and bovine serum albumin (BSA) by nuclear spin relaxation analysis. We found that all of the pesticides were able to form a complex with BSA; nevertheless, there were strong differences in their affinity toward the plasma protein. The nuclear magnetic resonance approach used on the basis of the analysis of selective relaxation rate enhancements of pesticide protons in the presence of BSA allowed for the calculation of the affinity indexes and the equilibrium constants of the three systems. Myclobutanil showed the highest affinity toward BSA, whereas triadimenol gave the weakest interaction with the protein. The differences in the capacity of the three pesticides to bind to albumin highlighted the existence of different binding strengths on the protein. These results indicate that myclobutanil and triadimenol, despite their structure similarity, may have very different residence times in the plasma and rates of clearance.

Contact pair dynamics during folding of two small proteins: Chicken villin head piece and the Alzheimer protein β-amyloid

NASA Astrophysics Data System (ADS)

Mukherjee, Arnab; Bagchi, Biman

2004-01-01

the slow decay is due to the attempt of the protein to form energetically more favorable pair contacts to replace the less favorable ones. This late stage contact formation is a highly cooperative process, involving participation of several pairs and thus entropically unfavorable and expected to face a large free energy barrier. This is because any new pair contact formation among hydrophobic pairs will require breaking of several contacts, before the favorable ones can be formed. This aspect of protein folding dynamics is similar to relaxation in glassy liquids, where also α relaxation requires highly cooperative process of hopping. The present analysis suggests that waiting time for the necessary pair contact formation may obey the Poissonian distribution. We also study the dynamics of Förster energy transfer during folding between two tagged amino acid pairs. This dynamics can be studied by fluorescence resonance energy transfer (FRET). It is found that suitably placed donor-acceptor pairs can capture the slow dynamics during folding. The dynamics probed by FRET is predicted to be nonexponential.

In-situ observations of flux ropes formed in association with a pair of spiral nulls in magnetotail plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Ruilong; Xie, Lun; He, Jiansen

Signatures of secondary islands are frequently observed in the magnetic reconnection regions of magnetotail plasmas. In this paper, magnetic structures with the secondary-island signatures observed by Cluster are reassembled by a fitting-reconstruction method. The results show three-dimensionally that a secondary island event can manifest the flux rope formed with an A{sub s}-type null and a B{sub s}-type null paired via their spines. We call this A{sub s}-spine-B{sub s}-like configuration the helically wrapped spine model. The reconstructed field lines wrap around the spine to form the flux rope, and an O-type topology is therefore seen on the plane perpendicular to themore » spine. Magnetized electrons are found to rotate on and cross the fan surface, suggesting that both the torsional-spine and the spine-fan reconnection take place in the configuration. Furthermore, detailed analysis implies that the spiral nulls and flux ropes were locally generated nearby the spacecraft in the reconnection outflow region, indicating that secondary reconnection may occur in the exhaust away from the primary reconnection site.« less

Relaxation and Distraction in Experimental Desensitization.

ERIC Educational Resources Information Center

Weir, R. O.; Marshall, W. L.

1980-01-01

Compared experimental desensitization with a procedure that replaced relaxation with a distraction task and with an approach that combined both relaxation and distraction. Desensitization generally was more effective than the other two procedures. (Author)

Distributed Relaxation for Conservative Discretizations

NASA Technical Reports Server (NTRS)

Diskin, Boris; Thomas, James L.

2001-01-01

A multigrid method is defined as having textbook multigrid efficiency (TME) if the solutions to the governing system of equations are attained in a computational work that is a small (less than 10) multiple of the operation count in one target-grid residual evaluation. The way to achieve this efficiency is the distributed relaxation approach. TME solvers employing distributed relaxation have already been demonstrated for nonconservative formulations of high-Reynolds-number viscous incompressible and subsonic compressible flow regimes. The purpose of this paper is to provide foundations for applications of distributed relaxation to conservative discretizations. A direct correspondence between the primitive variable interpolations for calculating fluxes in conservative finite-volume discretizations and stencils of the discretized derivatives in the nonconservative formulation has been established. Based on this correspondence, one can arrive at a conservative discretization which is very efficiently solved with a nonconservative relaxation scheme and this is demonstrated for conservative discretization of the quasi one-dimensional Euler equations. Formulations for both staggered and collocated grid arrangements are considered and extensions of the general procedure to multiple dimensions are discussed.

Recirculating wedges for metal-vapor plasma tubes

DOEpatents

Hall, Jerome P.; Sawvel, Robert M.; Draggoo, Vaughn G.

1994-01-01

A metal vapor laser is disclosed that recycles condensed metal located at the terminal ends of a plasma tube back toward the center of the tube. A pair of arcuate wedges are incorporated on the bottom of the plasma tube near the terminal ends. The wedges slope downward toward the center so that condensed metal may be transported under the force of gravity away from the terminal ends. The wedges are curved to fit the plasma tube to thereby avoid forming any gaps within the tube interior.

Continuous-time monitoring of Landau-Zener interference in a cooper-pair box.

PubMed

Sillanpää, Mika; Lehtinen, Teijo; Paila, Antti; Makhlin, Yuriy; Hakonen, Pertti

2006-05-12

Landau-Zener (LZ) tunneling can occur with a certain probability when crossing energy levels of a quantum two-level system are swept across the minimum energy separation. Here we present experimental evidence of quantum interference effects in solid-state LZ tunneling. We used a Cooper-pair box qubit where the LZ tunneling occurs at the charge degeneracy. By employing a weak nondemolition monitoring, we observe interference between consecutive LZ-tunneling events; we find that the average level occupancies depend on the dynamical phase. The system's unusually strong linear response is explained by interband relaxation. Our interferometer can be used as a high-resolution Mach-Zehnder-type detector for phase and charge.

Sustainment Study of Flipped Spherical Torus Plasmas on HIST

NASA Astrophysics Data System (ADS)

Takamiya, T.; Nagata, M.; Kawami, K.; Hasegawa, H.; Fukumoto, N.; Uyama, T.; Masamune, S.; Iida, M.; Katsurai, M.

2003-10-01

We have discovered that helicity-driven ST plasmas relax toward the flipped state by decreasing the external toroidal field and reversing its sign in time [1]. From the viewpoint of coaxial helicity injection (CHI) current drive, it is conceivable that the flipped ST (F-ST), which consists of only closed flux surfaces, compares favorably with the normal ST. We have investigated the sustainment mechanism of the F-ST plasma. The helicity-driven relaxed theory shows that there exist the mixed states of ST and F-ST in the flux conserver. Helicity is transferred to F-ST through the ST with coupling with gun electrodes. It has been found that magnetic reconnection between the toroidal magnetic field plays important role in the sustainment of the F-ST. The magnetic field in the outer edge region shows regular oscillations which have a large amplitude of the n=1 mode. The core region of the F-ST seems to be relatively stable. [1] M. Nagata, et al., Phys. Rev. Lett. 90, 225001 (2003)

Pick a Pair. Pancake Pairs

ERIC Educational Resources Information Center

Miller, Pat

2005-01-01

Cold February weather and pancakes are a traditional pairing. Pancake Day began as a way to eat up the foods that were abstained from in Lent--traditionally meat, fat, eggs and dairy products. The best-known pancake event is The Pancake Day Race in Buckinghamshire, England, which has been run since 1445. This column describes pairs of books that…

Overview of Spontaneous Frequency Chirping in Confined Plasmas

NASA Astrophysics Data System (ADS)

Berk, Herbert

2012-10-01

Spontaneous rapid frequency chirping is now a commonly observed phenomenon in plasmas with an energetic particle component. These particles typically induce so called weak instabilities, where they excite background waves that the plasma can support such as shear Alfven waves. The explanation for this phenomenon attributes the frequency chirping to the formation of phase space structures in the form of holes and clumps. Normally a saturated mode, in the presence of background dissipation, would be expected decay after saturation as the background plasma absorbs the energy of the excited wave. However the phase space structures take an alternate route, and move to a regions of phase space that are lower energy states of the energetic particle distribution. Through the wave-resonant particle interaction, this movement is locked to the frequency observed by the wave. This phenomenon implies that alternate mechanisms for plasma relaxation need to be considered for plasma states new marginal stability. It is also possible that these chirping mechanisms can be used to advantage to externally control states of plasma.

Ultra-Slow Dielectric Relaxation Process in Polyols

NASA Astrophysics Data System (ADS)

Yomogida, Yoshiki; Minoguchi, Ayumi; Nozaki, Ryusuke

2004-04-01

Dielectric relaxation processes with relaxation times larger than that for the structural α process are reported for glycerol, xylitol, sorbitol and their mixtures for the first time. Appearance of this ultra-slow process depends on cooling rate. More rapid cooling gives larger dielectric relaxation strength. However, relaxation time is not affected by cooling rate and shows non-Arrhenius temperature dependence with correlation to the α process. It can be considered that non-equilibrium dynamic structure causes the ultra-slow process. Scale of such structure would be much larger than that of the region for the cooperative molecular orientations for the α process.

The thrombin inhibitor argatroban does not influence the endothelium-dependent relaxant and contractile responses of isolated rabbit carotid arteries.

PubMed

Schrödter, Hans-Martin; Glusa, Erika

2003-06-01

Atherosclerotic endothelial dysfunctions are associated with a reduced NO production, which is probably due to impaired NO synthase (eNOS) activity or a deficiency of the substrate L-arginine. In the present studies, the influence of argatroban on isolated rabbit carotid arteries was investigated to determine whether the arginine derivative argatroban can improve the endothelium-dependent relaxation. Rings from rabbit carotid arteries were placed in 10 ml organ baths for isometric tension recording. Endothelial integrity was assessed by the acetylcholine-induced relaxation of PGF2alpha-precontracted rings; after mechanical removal of the endothelium the relaxation was abolished. Preincubation of the vessels in vitro with L-NAME, an inhibitor of the eNOS, diminished significantly the acetylcholine-induced relaxation by more than 50%. After i.v. application of L-NAME (100 mg/kg) in rabbits, relaxation in response to acetylcholine was significantly reduced compared to the control when the vessels were studied ex vivo in an organ bath. The contractile effects of phenylephrine and 5-HT were slightly enhanced. Argatroban is a selective, potent, synthetic thrombin inhibitor; after i.v. application at doses of 0.5 and 1.0 mg/kg, a significant prolongation of the plasma coagulation time (measured as thrombin time and a PTT) of up to 60 min was found in rabbits. In vitro argatroban did not affect the acetylcholine-induced relaxation or the contractile response to phenylephrine and 5-HT. After i.v. application, the ex vivo experiments in the organ bath showed that after 30 min the relaxant responses of the carotid arteries to acetylcholine and the contractile effects of phenylephrine and 5-HT were not influenced by pretreatment with argatroban. The present studies suggest that argatroban has no vascular effects in vitro and ex vivo in normal rabbits.

Experimental measurement of self-diffusion in a strongly coupled plasma

DOE PAGES

Strickler, Trevor S.; Langin, Thomas K.; McQuillen, Paul; ...

2016-05-17

Here, we present a study of the collisional relaxation of ion velocities in a strongly coupled, ultracold neutral plasma on short time scales compared to the inverse collision rate. The measured average velocity of a tagged population of ions is shown to be equivalent to the ion-velocity autocorrelation function. We thus gain access to fundamental aspects of the single-particle dynamics in strongly coupled plasmas and to the ion self-diffusion constant under conditions where experimental measurements have been lacking. Nonexponential decay towards equilibrium of the average velocity heralds non-Markovian dynamics that are not predicted by traditional descriptions of weakly coupled plasmas.more » This demonstrates the utility of ultracold neutral plasmas for studying the effects of strong coupling on collisional processes, which is of interest for dense laboratory and astrophysical plasmas.« less

Formation Process of Non-Neutral Plasmas by Multiple Electron Beams on BX-U

NASA Astrophysics Data System (ADS)

Sanpei, Akio; Himura, Haruhiko; Masamune, Sadao

An imaging diagnostic system, which is composed of a handmade phosphor screen and a high-speed camera, has been applied to identify the dynamics of multiple electron beams on BX-U. The relaxation process of those toward a non-neutral plasma is experimentally identified. Also, the radial density profile of the plasma is measured as a function of time. Assuming that the plasma is a spheroidal shape, the value of electron density ne is in the range between 2.2 × 106 and 4.4 × 108 cm-3 on BX-U.

Dynamics of Relaxation Processes of Spontaneous Otoacoustic Emissions

NASA Astrophysics Data System (ADS)

Murphy, William James

The dynamical response of spontaneous otoacoustic emissions (SOAEs) to suppression by ipsilateral pulsed external tones of different frequencies and levels is investigated in nine female subjects under normal conditions and in four female subjects during periods when aspirin is being administered. A simple Van der Pol limit-cycle oscillator driven by an external tone is used as an interpretive model. Typical results for both the onset of, and recovery from suppression yield 1/r_1 (where -r_1 is the negative linear component of the damping function) in the range of 2-25 msec. In accordance with the predictions of the model: (a) the relaxation time for the onset of suppression increases with the amount of suppression induced by the external tone, (b) the values of r _1 and the amplitudes of the unsuppressed emissions exhibit an inverse correlation, (c) the values inferred for r_1 are not significantly dependent on the frequency of the pulsed suppressor tone and (d) the inferred r_1 values are not significantly dependent upon the amount of suppression. In investigations involving subjects under aspirin administration, the changes in the relaxation time constants indicate that the main effect of aspirin administration is to reduce the negative damping parameter r_1. The salicylate is apparently not metabolized in some subjects whose emissions are negligibly affected by aspirin administration. A modification of the single-oscillator model is used to describe pulsed suppression data obtained from a primary SOAE (2545 Hz) which is suppressed by a neighboring secondary emission (2895 Hz). The response of the SOAE amplitude during pulsed suppression is modeled by a pair of Van der Pol limit-cycle oscillators with the primary oscillator linearly coupled to the displacement of the secondary higher-frequency one. The relaxation time constants for the onset of, and recovery from, suppression are 4.5 and 4.8 msec, respectively, for the primary SOAE and 7.5 and 10.5 msec for the

Observation of the hot electron interchange instability in a high beta dipolar confined plasma

NASA Astrophysics Data System (ADS)

Ortiz, Eugenio Enrique

In this thesis the first study of the high beta, hot electron interchange (HEI) instability in a laboratory, dipolar confined plasma is presented. The Levitated Dipole Experiment (LDX) is a new research facility that explores the confinement and stability of plasma created within the dipole field produced by a strong superconducting magnet. In initial experiments long-pulse, quasi-steady state microwave discharges lasting more than 10 sec have been produced with equilibria having peak beta values of 20%. Creation of high-pressure, high beta plasma is possible only when intense HEI instabilities are stabilized by sufficiently high background plasma density. LDX plasma exist within one of three regimes characterized by its response to heating and fueling. The observed HEI instability depends on the regime and can take one of three forms: as quasiperiodic bursts during the low density, low beta plasma regime, as local high beta relaxation events in the high beta plasma regime, and as global, intense energy relaxation bursts, both in the high beta and afterglow plasma regimes. Measurements of the HEI instability are made using high-impedance, floating potential probes and fast Mirnov coils. Analysis of these signals reveals the extent of the transport during high beta plasmas. During intense high beta HEI instabilities, fluctuations at the edge significantly exceed the magnitude of the equilibrium field generated by the high beta electrons and energetic electron confinement ends in under 100 musec. For heated plasmas, one of the consequences of the observed high beta transport is the presence of hysteresis in the neutral gas fueling required to stabilize and maintain the high beta plasma. Finally, a nonlinear, self-consistent numerical simulation of the growth and saturation of the HEI instability has been adapted for LDX and compared to experimental observations.

Developing a Hypnotic Relaxation Intervention to Improve Body Image: A Feasibility Study.

PubMed

Cieslak, Alison; Elkins, Gary; Banerjee, Tanima; Marsack, Jessica; Hickman, Kimberly; Johnson, Alisa; Henry, Norah; Barton, Debra

2016-11-01

To determine the content, feasibility, and best outcome of a mind-body intervention involving self-directed hypnotic relaxation to target body image.
. A five-week, uncontrolled, unblinded feasibility intervention study.
. Behavioral therapy offices in Ann Arbor, Michigan, and Waco, Texas.
. 10 female breast cancer survivors and 1 breast and gynecologic cancer survivor. 
. Adult women with a history of breast and gynecologic cancer and no major psychiatric history were eligible. The intervention included four face-to-face sessions with a research therapist lasting 40-60 minutes, logged home practice, one telephone check-in call at week 5, and one intervention feedback telephone call to complete the study. Descriptive statistics and paired t-tests were used to test feasibility and content validity.
. Stress from body changes as measured by the Impact of Treatment Scale, sexual function as measured by the Female Sexual Function Index, and sexual self-image as measured by the Sexual Self-Schema Scale for women were the variables of interest.
. The intervention content was confirmed. Changes in scores from the baseline to week 5 suggested that stress from body changes decreased and sexual self-schema and function improved during the intervention. Nine of the 11 women were satisfied with the intervention, and all 11 indicated that their body image improved. 
. Hypnotic relaxation therapy shows promise for improving body image and, in doing so, improving sexual health in this population. Additional testing of this intervention is warranted.
. Hypnotic relaxation therapy is feasible to improve body image and sexual health in women diagnosed with cancer and may be an important intervention that could be offered by nurses and other behavioral therapists.

A novel improved method for analysis of 2D diffusion relaxation data—2D PARAFAC-Laplace decomposition

NASA Astrophysics Data System (ADS)

Tønning, Erik; Polders, Daniel; Callaghan, Paul T.; Engelsen, Søren B.

2007-09-01

This paper demonstrates how the multi-linear PARAFAC model can with advantage be used to decompose 2D diffusion-relaxation correlation NMR spectra prior to 2D-Laplace inversion to the T2- D domain. The decomposition is advantageous for better interpretation of the complex correlation maps as well as for the quantification of extracted T2- D components. To demonstrate the new method seventeen mixtures of wheat flour, starch, gluten, oil and water were prepared and measured with a 300 MHz nuclear magnetic resonance (NMR) spectrometer using a pulsed gradient stimulated echo (PGSTE) pulse sequence followed by a Carr-Purcell-Meiboom-Gill (CPMG) pulse echo train. By varying the gradient strength, 2D diffusion-relaxation data were recorded for each sample. From these double exponentially decaying relaxation data the PARAFAC algorithm extracted two unique diffusion-relaxation components, explaining 99.8% of the variation in the data set. These two components were subsequently transformed to the T2- D domain using 2D-inverse Laplace transformation and quantitatively assigned to the oil and water components of the samples. The oil component was one distinct distribution with peak intensity at D = 3 × 10 -12 m 2 s -1 and T2 = 180 ms. The water component consisted of two broad populations of water molecules with diffusion coefficients and relaxation times centered around correlation pairs: D = 10 -9 m 2 s -1, T2 = 10 ms and D = 3 × 10 -13 m 2 s -1, T2 = 13 ms. Small spurious peaks observed in the inverse Laplace transformation of original complex data were effectively filtered by the PARAFAC decomposition and thus considered artefacts from the complex Laplace transformation. The oil-to-water ratio determined by PARAFAC followed by 2D-Laplace inversion was perfectly correlated with known oil-to-water ratio of the samples. The new method of using PARAFAC prior to the 2D-Laplace inversion proved to have superior potential in analysis of diffusion-relaxation spectra, as it

Defects, strain relaxation, and compositional grading in high indium content InGaN epilayers grown by molecular beam epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bazioti, C.; Kehagias, Th.; Pavlidou, E.

2015-10-21

We investigate the structural properties of a series of high alloy content InGaN epilayers grown by plasma-assisted molecular beam epitaxy, employing the deposition temperature as variable under invariant element fluxes. Using transmission electron microscopy methods, distinct strain relaxation modes were observed, depending on the indium content attained through temperature adjustment. At lower indium contents, strain relaxation by V-pit formation dominated, with concurrent formation of an indium-rich interfacial zone. With increasing indium content, this mechanism was gradually substituted by the introduction of a self-formed strained interfacial InGaN layer of lower indium content, as well as multiple intrinsic basal stacking faults andmore » threading dislocations in the rest of the film. We show that this interfacial layer is not chemically abrupt and that major plastic strain relaxation through defect introduction commences upon reaching a critical indium concentration as a result of compositional pulling. Upon further increase of the indium content, this relaxation mode was again gradually succeeded by the increase in the density of misfit dislocations at the InGaN/GaN interface, leading eventually to the suppression of the strained InGaN layer and basal stacking faults.« less

Power law X- and gamma-ray emission from relativistic thermal plasmas

NASA Technical Reports Server (NTRS)

Zdziarski, A. A.

1984-01-01

Pair equilibrium in thermal plasmas emitting power law photon spectra by repeated Compton scatterings of a soft photon source active galactic nuclei was studied. Dependence of the spectral index on optical thickness and on temperature of the plasma is discussed. The equation for pair equilibrium is solved for the maximum steady luminosity. Analytical solutions for the subrelativistic region, and for the ultrarelativistic region are found. In the transrelativistic region the solutions are expressed by single integrals over the pair production cross sections, performed numerically. The constraints on soft photon source imposed by the condition that the soft photon flux cannot exceed the black-body flux are considered. For the Comptonized synchrotron radiation model a relation between magnetic field strength and output luminosity is found.

Convex relaxations for gas expansion planning

DOE PAGES

Borraz-Sanchez, Conrado; Bent, Russell Whitford; Backhaus, Scott N.; ...

2016-01-01

Expansion of natural gas networks is a critical process involving substantial capital expenditures with complex decision-support requirements. Here, given the non-convex nature of gas transmission constraints, global optimality and infeasibility guarantees can only be offered by global optimisation approaches. Unfortunately, state-of-the-art global optimisation solvers are unable to scale up to real-world size instances. In this study, we present a convex mixed-integer second-order cone relaxation for the gas expansion planning problem under steady-state conditions. The underlying model offers tight lower bounds with high computational efficiency. In addition, the optimal solution of the relaxation can often be used to derive high-quality solutionsmore » to the original problem, leading to provably tight optimality gaps and, in some cases, global optimal solutions. The convex relaxation is based on a few key ideas, including the introduction of flux direction variables, exact McCormick relaxations, on/off constraints, and integer cuts. Numerical experiments are conducted on the traditional Belgian gas network, as well as other real larger networks. The results demonstrate both the accuracy and computational speed of the relaxation and its ability to produce high-quality solution« less

Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andreev, Pavel A., E-mail: andreevpa@physics.msu.ru

2015-06-15

We discuss the complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider the contribution of the annihilation interaction in the quantum hydrodynamic equations and in the spectrum of waves in magnetized electron-positron plasmas. We consider the propagation of waves parallel and perpendicular tomore » an external magnetic field. We also consider the oblique propagation of longitudinal waves. We derive the set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory to the linear wave behavior in absence of external fields. We calculate the contribution of the Darwin and annihilation interactions in the Landau damping of the Langmuir waves. We should mention that the annihilation interaction does not change number of particles in the system. It does not related to annihilation itself, but it exists as a result of interaction of an electron-positron pair via conversion of the pair into virtual photon. A pair of the non-linear Schrodinger equations for the electron-positron plasmas including the Darwin and annihilation interactions is derived. Existence of the conserving helicity in electron-positron quantum plasmas of spinning particles with the Darwin and annihilation interactions is demonstrated. We show that the annihilation interaction plays an important role in the quantum electron-positron plasmas giving the contribution of the same magnitude as the spin-spin interaction.« less

Centromere pairing precedes meiotic chromosome pairing in plants.

PubMed

Zhang, Jing; Han, Fangpu

2017-11-01

Meiosis is a specialized eukaryotic cell division, in which diploid cells undergo a single round of DNA replication and two rounds of nuclear division to produce haploid gametes. In most eukaryotes, the core events of meiotic prophase I are chromosomal pairing, synapsis and recombination. To ensure accurate chromosomal segregation, homologs have to identify and align along each other at the onset of meiosis. Although much progress has been made in elucidating meiotic processes, information on the mechanisms underlying chromosome pairing is limited in contrast to the meiotic recombination and synapsis events. Recent research in many organisms indicated that centromere interactions during early meiotic prophase facilitate homologous chromosome pairing, and functional centromere is a prerequisite for centromere pairing such as in maize. Here, we summarize the recent achievements of chromosome pairing research on plants and other organisms, and outline centromere interactions, nuclear chromosome orientation, and meiotic cohesin, as main determinants of chromosome pairing in early meiotic prophase.

Lavender fragrance cleansing gel effects on relaxation.

PubMed

Field, Tiffany; Diego, Miguel; Hernandez-Reif, Maria; Cisneros, Wendy; Feijo, Larissa; Vera, Yanexy; Gil, Karla; Grina, Diana; Claire He, Qing

2005-02-01

Alertness, mood, and math computations were assessed in 11 healthy adults who sniffed a cosmetic cleansing gel with lavender floral blend aroma, developed to be relaxing using Mood Mapping. EEG patterns and heart rate were also recorded before, during, and after the aroma session. The lavender fragrance blend had a significant transient effect of improving mood, making people feel more relaxed, and performing the math computation faster. The self-report and physiological data are consistent with relaxation profiles during other sensory stimuli such as massage and music, as reported in the literature. The data suggest that a specific cosmetic fragrance can have a significant role in enhancing relaxation.

Recirculating wedges for metal-vapor plasma tubes

DOEpatents

Hall, J.P.; Sawvel, R.M.; Draggoo, V.G.

1994-06-28

A metal vapor laser is disclosed that recycles condensed metal located at the terminal ends of a plasma tube back toward the center of the tube. A pair of arcuate wedges are incorporated on the bottom of the plasma tube near the terminal ends. The wedges slope downward toward the center so that condensed metal may be transported under the force of gravity away from the terminal ends. The wedges are curved to fit the plasma tube to thereby avoid forming any gaps within the tube interior. 8 figures.

Chronic ethanol feeding inhibits plasma levels of insulin-like growth factor-1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sonntag, W.E.; Boyd, R.L.

1988-01-01

The purpose of this study was to determine whether the generalized catabolic effects of chronic ethanol may be associated with a decline in plasma of insulin-like growth factor-1 (IGF-1). Male Sprague-Dawley rats were fed a liquid diet containing 5% ethanol or pair-fed a diet made isocaloric with maltose-dextrin. Animals were maintained on this diet for either 12 days or 4.5 months. Another groups of animals were fed control diet ad libitum for 2 weeks. After 12 days of feeding, plasma concentrations of IGF-1 in ad libitum fed rats were 771 +/- 41 ng/ml which was greater than concentrations in eithermore » pair-fed or ethanol-fed rats. After 4.5 months of feeding, plasma levels of IGF-1 in ad libitum and pair-fed rats were similar to the 12 day study. However, a significant decrease in plasma levels of IGF-1 was observed in ethanol-fed animals over the 4.5 month period. Results of a similar study in rats fed a high-fat diet for 4.5 months were similar to those found with the low-fat diet.« less

Direct NMR Evidence that Transient Tautomeric and Anionic States in dG·dT Form Watson-Crick-like Base Pairs.

PubMed

Szymanski, Eric S; Kimsey, Isaac J; Al-Hashimi, Hashim M

2017-03-29

The replicative and translational machinery utilizes the unique geometry of canonical G·C and A·T/U Watson-Crick base pairs to discriminate against DNA and RNA mismatches in order to ensure high fidelity replication, transcription, and translation. There is growing evidence that spontaneous errors occur when mismatches adopt a Watson-Crick-like geometry through tautomerization and/or ionization of the bases. Studies employing NMR relaxation dispersion recently showed that wobble dG·dT and rG·rU mismatches in DNA and RNA duplexes transiently form tautomeric and anionic species with probabilities (≈0.01-0.40%) that are in concordance with replicative and translational errors. Although computational studies indicate that these exceptionally short-lived and low-abundance species form Watson-Crick-like base pairs, their conformation could not be directly deduced from the experimental data, and alternative pairing geometries could not be ruled out. Here, we report direct NMR evidence that the transient tautomeric and anionic species form hydrogen-bonded Watson-Crick-like base pairs. A guanine-to-inosine substitution, which selectively knocks out a Watson-Crick-type (G)N2H 2 ···O2(T) hydrogen bond, significantly destabilized the transient tautomeric and anionic species, as assessed by lack of any detectable chemical exchange by imino nitrogen rotating frame spin relaxation (R 1ρ ) experiments. An 15 N R 1ρ NMR experiment targeting the amino nitrogen of guanine (dG-N2) provides direct evidence for Watson-Crick (G)N2H 2 ···O2(T) hydrogen bonding in the transient tautomeric state. The strategy presented in this work can be generally applied to examine hydrogen-bonding patterns in nucleic acid transient states including in other tautomeric and anionic species that are postulated to play roles in replication and translational errors.

Magnetic relaxation pathways in lanthanide single-molecule magnets.

PubMed

Blagg, Robin J; Ungur, Liviu; Tuna, Floriana; Speak, James; Comar, Priyanka; Collison, David; Wernsdorfer, Wolfgang; McInnes, Eric J L; Chibotaru, Liviu F; Winpenny, Richard E P

2013-08-01

Single-molecule magnets are compounds that exhibit magnetic bistability caused by an energy barrier for the reversal of magnetization (relaxation). Lanthanide compounds are proving promising as single-molecule magnets: recent studies show that terbium phthalocyanine complexes possess large energy barriers, and dysprosium and terbium complexes bridged by an N2(3-) radical ligand exhibit magnetic hysteresis up to 13 K. Magnetic relaxation is typically controlled by single-ion factors rather than magnetic exchange (whether one or more 4f ions are present) and proceeds through thermal relaxation of the lowest excited states. Here we report polylanthanide alkoxide cage complexes, and their doped diamagnetic yttrium analogues, in which competing relaxation pathways are observed and relaxation through the first excited state can be quenched. This leads to energy barriers for relaxation of magnetization that exceed 800 K. We investigated the factors at the lanthanide sites that govern this behaviour.

Relaxation versus adiabatic quantum steady-state preparation

NASA Astrophysics Data System (ADS)

Venuti, Lorenzo Campos; Albash, Tameem; Marvian, Milad; Lidar, Daniel; Zanardi, Paolo

2017-04-01

Adiabatic preparation of the ground states of many-body Hamiltonians in the closed-system limit is at the heart of adiabatic quantum computation, but in reality systems are always open. This motivates a natural comparison between, on the one hand, adiabatic preparation of steady states of Lindbladian generators and, on the other hand, relaxation towards the same steady states subject to the final Lindbladian of the adiabatic process. In this work we thus adopt the perspective that the goal is the most efficient possible preparation of such steady states, rather than ground states. Using known rigorous bounds for the open-system adiabatic theorem and for mixing times, we are then led to a disturbing conclusion that at first appears to doom efforts to build physical quantum annealers: relaxation seems to always converge faster than adiabatic preparation. However, by carefully estimating the adiabatic preparation time for Lindbladians describing thermalization in the low-temperature limit, we show that there is, after all, room for an adiabatic speedup over relaxation. To test the analytically derived bounds for the adiabatic preparation time and the relaxation time, we numerically study three models: a dissipative quasifree fermionic chain, a single qubit coupled to a thermal bath, and the "spike" problem of n qubits coupled to a thermal bath. Via these models we find that the answer to the "which wins" question depends for each model on the temperature and the system-bath coupling strength. In the case of the "spike" problem we find that relaxation during the adiabatic evolution plays an important role in ensuring a speedup over the final-time relaxation procedure. Thus, relaxation-assisted adiabatic preparation can be more efficient than both pure adiabatic evolution and pure relaxation.

Rapid Wall Relaxation in Elongating Tissues 1

PubMed Central

Matyssek, Rainer; Maruyama, Sachio; Boyer, John S.

1988-01-01

Reported differences in the relaxation of cell walls in enlarging stem tissues of soybean (Glycine max [L.] Merr.) and pea (Pisum sativum L.) cause measurements of the yield threshold turgor, an important growth parameter, to be in doubt. Using the pressure probe and guillotine psychrometer, we investigated wall relaxation in these species by excising the elongating tissue in air to remove the water supply. We found that the rapid kinetics usually exhibited by soybean could be delayed and made similar to the slow kinetics previously reported for pea if slowly growing or mature tissue was left attached to the rapidly growing tissue when relaxation was initiated. The greater the amount of attached tissue, the slower the relaxation, suggesting that slowly growing tissue acted as a water source. Consistent with this concept was a lower water potential in the rapidly elongating tissue than in the slowly growing tissue. Previous reports of wall relaxation in pea included slowly growing tissue. If this tissue was removed from pea, relaxation became as rapid as usually exhibited by soybean. It is concluded that the true relaxation of cell walls to the yield threshold requires only a few minutes and that the yield threshold should be constant during so short a time, thus reflecting the yield threshold in the intact plant before excision. Under these conditions, the yield threshold was close to the turgor in the intact plant regardless of the species. The presence of slowly growing or mature tissue delays wall relaxation and should be avoided during such measurements. However, this delay can be used to advantage when turgor of intact growing tissues is being measured using excised tissues because turgor does not change for a considerable time after excision. PMID:16666048

Multi-region relaxed Hall magnetohydrodynamics with flow

DOE PAGES

Lingam, Manasvi; Abdelhamid, Hamdi M.; Hudson, Stuart R.

2016-08-03

The recent formulations of multi-region relaxed magnetohydrodynamics (MRxMHD) have generalized the famous Woltjer-Taylor states by incorporating a collection of “ideal barriers” that prevent global relaxation and flow. In this paper, we generalize MRxMHD with flow to include Hall effects, and thereby obtain the partially relaxed counterparts of the famous double Beltrami states as a special subset. The physical and mathematical consequences arising from the introduction of the Hall term are also presented. We demonstrate that our results (in the ideal MHD limit) constitute an important subset of ideal MHD equilibria, and we compare our approach against other variational principles proposedmore » for deriving the partially relaxed states.« less

Measurement of He neutral temperature in detached plasmas using laser absorption spectroscopy

NASA Astrophysics Data System (ADS)

Aramaki, M.; Tsujihara, T.; Kajita, S.; Tanaka, H.; Ohno, N.

2018-01-01

The reduction of the heat load onto plasma-facing components by plasma detachment is an inevitable scheme in future nuclear fusion reactors. Since the control of the plasma and neutral temperatures is a key issue to the detached plasma generation, we have developed a laser absorption spectroscopy system for the metastable helium temperature measurements and used together with a previously developed laser Thomson scattering system for the electron temperature and density measurements. The thermal relaxation process between the neutral and the electron in the detached plasma generated in the linear plasma device, NAGDIS-II was studied. It is shown that the electron temperature gets close to the neutral temperature by increasing the electron density. On the other hand, the pressure dependence of electron and neutral temperatures shows the cooling effect by the neutrals. The possibility of the plasma fluctuation measurement using the fluctuation in the absorption signal is also shown.

Continuum kinetic modeling of the tokamak plasma edge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dorf, M. A.; Dorr, M. R.; Hittinger, J. A.

2016-05-15

The first 4D (axisymmetric) high-order continuum gyrokinetic transport simulations that span the magnetic separatrix of a tokamak are presented. The modeling is performed with the COGENT code, which is distinguished by fourth-order finite-volume discretization combined with mapped multiblock grid technology to handle the strong anisotropy of plasma transport and the complex X-point divertor geometry with high accuracy. The calculations take into account the effects of fully nonlinear Fokker-Plank collisions, electrostatic potential variations, and anomalous radial transport. Topics discussed include: (a) ion orbit loss and the associated toroidal rotation and (b) edge plasma relaxation in the presence of anomalous radial transport.

Chemical kinetics and relaxation of non-equilibrium air plasma generated by energetic photon and electron beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maulois, Melissa, E-mail: melissa.maulois@laplace.univ-tlse.fr; LAPLACE, 118 Route de Narbonne, 31 062 Toulouse Cedex; CEA/DAM, 46 500 Gramat

2016-04-15

The comprehension of electromagnetic perturbations of electronic devices, due to air plasma-induced electromagnetic field, requires a thorough study on air plasma. In the aim to understand the phenomena at the origin of the formation of non-equilibrium air plasma, we simulate, using a volume average chemical kinetics model (0D model), the time evolution of a non-equilibrium air plasma generated by an energetic X-ray flash. The simulation is undertaken in synthetic air (80% N{sub 2} and 20% O{sub 2}) at ambient temperature and atmospheric pressure. When the X-ray flash crosses the gas, non-relativistic Compton electrons (low energy) and a relativistic Compton electronmore » beam (high energy) are simultaneously generated and interact with the gas. The considered chemical kinetics scheme involves 26 influent species (electrons, positive ions, negative ions, and neutral atoms and molecules in their ground or metastable excited states) reacting following 164 selected reactions. The kinetics model describing the plasma chemistry was coupled to the conservation equation of the electron mean energy, in order to calculate at each time step of the non-equilibrium plasma evolution, the coefficients of reactions involving electrons while the energy of the heavy species (positive and negative ions and neutral atoms and molecules) is assumed remaining close to ambient temperature. It has been shown that it is the relativistic Compton electron beam directly created by the X-ray flash which is mainly responsible for the non-equilibrium plasma formation. Indeed, the low energy electrons (i.e., the non-relativistic ones) directly ejected from molecules by Compton collisions contribute to less than 1% on the creation of electrons in the plasma. In our simulation conditions, a non-equilibrium plasma with a low electron mean energy close to 1 eV and a concentration of charged species close to 10{sup 13 }cm{sup −3} is formed a few nanoseconds after the peak of X-ray flash

Ionization of pyridine: Interplay of orbital relaxation and electron correlation.

PubMed

Trofimov, A B; Holland, D M P; Powis, I; Menzies, R C; Potts, A W; Karlsson, L; Gromov, E V; Badsyuk, I L; Schirmer, J

2017-06-28

The valence shell ionization spectrum of pyridine was studied using the third-order algebraic-diagrammatic construction approximation scheme for the one-particle Green's function and the outer-valence Green's function method. The results were used to interpret angle resolved photoelectron spectra recorded with synchrotron radiation in the photon energy range of 17-120 eV. The lowest four states of the pyridine radical cation, namely, 2 A 2 (1a 2 -1 ), 2 A 1 (7a 1 -1 ), 2 B 1 (2b 1 -1 ), and 2 B 2 (5b 2 -1 ), were studied in detail using various high-level electronic structure calculation methods. The vertical ionization energies were established using the equation-of-motion coupled-cluster approach with single, double, and triple excitations (EOM-IP-CCSDT) and the complete basis set extrapolation technique. Further interpretation of the electronic structure results was accomplished using Dyson orbitals, electron density difference plots, and a second-order perturbation theory treatment for the relaxation energy. Strong orbital relaxation and electron correlation effects were shown to accompany ionization of the 7a 1 orbital, which formally represents the nonbonding σ-type nitrogen lone-pair (nσ) orbital. The theoretical work establishes the important roles of the π-system (π-π* excitations) in the screening of the nσ-hole and of the relaxation of the molecular orbitals in the formation of the 7a 1 (nσ) -1 state. Equilibrium geometric parameters were computed using the MP2 (second-order Møller-Plesset perturbation theory) and CCSD methods, and the harmonic vibrational frequencies were obtained at the MP2 level of theory for the lowest three cation states. The results were used to estimate the adiabatic 0-0 ionization energies, which were then compared to the available experimental and theoretical data. Photoelectron anisotropy parameters and photoionization partial cross sections, derived from the experimental spectra, were compared to predictions obtained

Isothermal enthalpy relaxation of glassy 1,2,6-hexanetriol

NASA Astrophysics Data System (ADS)

Fransson, Å.; Bäckström, G.

The isothermal enthalpy relaxation of glassy 1,2,6-hexanetriol has been measured at six temperatures. The relaxation time and the distribution parameters extracted from fits of the Williams-Watts relaxation function are compared with parameters obtained by other techniques and on other substances. A detailed comparison of the Williams-Watts and the Davidson-Cole relaxation functions is presented.

The Efficacy of Relaxation Training in Treating Anxiety

ERIC Educational Resources Information Center

Francesco, Pagnini; Mauro, Manzoni Gian; Gianluca, Castelnuovo; Enrico, Molinari

2009-01-01

This paper provides a review of scientific literature about relaxation training and its effects on anxiety. Research investigating progressive relaxation, meditation, applied relaxation and autogenic training were considered. All these methods proved to be effective in reducing anxiety in all kind of samples, affected or not by physical or…

Dielectric relaxations and conduction mechanisms in polyether-clay composite polymer electrolytes under high carbon dioxide pressure.

PubMed

Kitajima, Shunsuke; Bertasi, Federico; Vezzù, Keti; Negro, Enrico; Tominaga, Yoichi; Di Noto, Vito

2013-10-21

The composite material P(EO/EM)-Sa consisting of synthetic saponite (Sa) dispersed in poly[ethylene oxide-co-2-(2-methoxyethoxy)ethyl glycidyl ether] (P(EO/EM)) is studied by "in situ" measurements using broadband electrical spectroscopy (BES) under pressurized CO2 to characterize the dynamic behavior of conductivity and the dielectric relaxations of the ion host polymer matrix. It is revealed that there are three dielectric relaxation processes associated with: (I) the dipolar motions in the short oxyethylene side chains of P(EO/EM) (β); and (II) the segmental motion of the main chains comprising the polyether components (αfast, αslow). αslow is attributed to the slow α-relaxation of P(EO/EM) macromolecules, which is hindered by the strong coordination interactions with the ions. Two conduction processes are observed, σDC and σID, which are attributed, respectively, to the bulk conductivity and the interdomain conductivity. The temperature dependence of conductivity and relaxation processes reveals that αfast and αslow are strongly correlated with σDC and σID. The "in situ" BES measurements under pressurized CO2 indicate a fast decrease in σDC at the initial CO2 treatment time resulting from the decrease in the concentration of polyether-M(n+) complexes, which is driven by the CO2 permeation. The relaxation frequency (fR) of αslow at the initial CO2 treatment time increases and shows a steep rise with time with the same behavior of the αfast mode. It is demonstrated that the interactions between polyether chains of P(EO/EM) and cations in the polymer electrolyte layers embedded in Sa are probably weakened by the low permittivity of CO2 (ε = 1.08). Thus, the formation of ion pairs in the polymer electrolyte domains of P(EO/EM)-Sa occurs, with a corresponding reduction in the concentration of ion carriers.

Relaxation dynamics of a multihierarchical polymer network

NASA Astrophysics Data System (ADS)

Jurjiu, Aurel; Biter, Teodor Lucian; Turcu, Flaviu

2017-01-01

In this work, we study the relaxation dynamics of a multihierarchical polymer network built by replicating the Vicsek fractal in dendrimer shape. The relaxation dynamics is investigated in the framework of the generalized Gaussian structure model by employing both Rouse and Zimm approaches. In the Rouse-type approach, we show the iterative procedure whereby the whole eigenvalue spectrum of the connectivity matrix of the multihierarchical structure can be obtained. Remarkably, the general picture that emerges from both approaches, even though we have a mixed growth algorithm, is that the obtained multihierarchical structure preserves the individual relaxation behaviors of its components. The theoretical findings with respect to the splitting of the intermediate domain of the relaxation quantities are well supported by experimental results.

Micro-column plasma emission liquid chromatograph. [Patent application

DOEpatents

Gay, D.D.

1982-08-12

In a direct current plasma emission spectrometer for use in combination with a microcolumn liquid chromatograph, an improved plasma source unit is claimed. The plasma source unit includes a quartz capillary tube having an inlet means, outlet off gas means and a pair of spaced electrodes defining a plasma region in the tube. The inlet means is connected to and adapted to receive eluant of the liquid chromatograph along with a stream of plasma-forming gas. There is an opening through the wall of the capillary tube penetrating into the plasma region. A soft glass capillary light pipe is disposed at the opening, is connected to the spectrometer, and is adapted to transmit light passing from the plasma region to the spectrometer. There is also a source of electromotive force connected to the electrodes sufficient to initiate and sustain a plasma in the plasma region of the tube.

Continuous-Time Monitoring of Landau-Zener Interference in a Cooper-Pair Box

NASA Astrophysics Data System (ADS)

Sillanpää, Mika; Lehtinen, Teijo; Paila, Antti; Makhlin, Yuriy; Hakonen, Pertti

2006-05-01

Landau-Zener (LZ) tunneling can occur with a certain probability when crossing energy levels of a quantum two-level system are swept across the minimum energy separation. Here we present experimental evidence of quantum interference effects in solid-state LZ tunneling. We used a Cooper-pair box qubit where the LZ tunneling occurs at the charge degeneracy. By employing a weak nondemolition monitoring, we observe interference between consecutive LZ-tunneling events; we find that the average level occupancies depend on the dynamical phase. The system’s unusually strong linear response is explained by interband relaxation. Our interferometer can be used as a high-resolution Mach-Zehnder type detector for phase and charge.

Effects of water on the primary and secondary relaxation of xylitol and sorbitol: Implication on the origin of the Johari-Goldstein relaxation

NASA Astrophysics Data System (ADS)

Psurek, T.; Maslanka, S.; Paluch, M.; Nozaki, R.; Ngai, K. L.

2004-07-01

Dielectric spectroscopy was employed to study the effects of water on the primary α -relaxation and the secondary β -relaxation of xylitol. The measurements were made on anhydrous xylitol and mixtures of xylitol with water with three different water concentrations over a temperature range from 173K to 293K . The α -relaxation speeds up with increasing concentration of water in xylitol, whereas the rate of the β -relaxation is essentially unchanged. Some systematic differences in the behavior of α -relaxation for anhydrous xylitol and the mixtures were observed. Our findings confirm all the observations of Nozaki [R. Nozaki, H. Zenitani, A. Minoguchi, and K. Kitai, J. Non-Cryst. Solids 307, 349 (2002)] in sorbitol/water mixtures. Effects of water on both the α - and β -relaxation dynamics in xylitol and sorbitol are explained by using the coupling model.

46 CFR 46.10-1 - Relaxation from regulations.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Relaxation from regulations. 46.10-1 Section 46.10-1... PASSENGER VESSELS Administration § 46.10-1 Relaxation from regulations. (a) New passenger vessels making... engaged in foreign voyages by sea may be permitted relaxation from the requirements of this part if, in...

46 CFR 46.10-1 - Relaxation from regulations.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Relaxation from regulations. 46.10-1 Section 46.10-1... PASSENGER VESSELS Administration § 46.10-1 Relaxation from regulations. (a) New passenger vessels making... engaged in foreign voyages by sea may be permitted relaxation from the requirements of this part if, in...

Rate theory of solvent exchange and kinetics of Li(+) - BF4 (-)/PF6 (-) ion pairs in acetonitrile.

PubMed

Dang, Liem X; Chang, Tsun-Mei

2016-09-07

In this paper, we describe our efforts to apply rate theories in studies of solvent exchange around Li(+) and the kinetics of ion pairings in lithium-ion batteries (LIBs). We report one of the first computer simulations of the exchange dynamics around solvated Li(+) in acetonitrile (ACN), which is a common solvent used in LIBs. We also provide details of the ion-pairing kinetics of Li(+)-[BF4] and Li(+)-[PF6] in ACN. Using our polarizable force-field models and employing classical rate theories of chemical reactions, we examine the ACN exchange process between the first and second solvation shells around Li(+). We calculate exchange rates using transition state theory and weighted them with the transmission coefficients determined by the reactive flux, Impey, Madden, and McDonald approaches, and Grote-Hynes theory. We found the relaxation times changed from 180 ps to 4600 ps and from 30 ps to 280 ps for Li(+)-[BF4] and Li(+)-[PF6] ion pairs, respectively. These results confirm that the solvent response to the kinetics of ion pairing is significant. Our results also show that, in addition to affecting the free energy of solvation into ACN, the anion type also should significantly influence the kinetics of ion pairing. These results will increase our understanding of the thermodynamic and kinetic properties of LIB systems.

Rate theory of solvent exchange and kinetics of Li+ - BF4-/PF6- ion pairs in acetonitrile

NASA Astrophysics Data System (ADS)

Dang, Liem X.; Chang, Tsun-Mei

2016-09-01

In this paper, we describe our efforts to apply rate theories in studies of solvent exchange around Li+ and the kinetics of ion pairings in lithium-ion batteries (LIBs). We report one of the first computer simulations of the exchange dynamics around solvated Li+ in acetonitrile (ACN), which is a common solvent used in LIBs. We also provide details of the ion-pairing kinetics of Li+-[BF4] and Li+-[PF6] in ACN. Using our polarizable force-field models and employing classical rate theories of chemical reactions, we examine the ACN exchange process between the first and second solvation shells around Li+. We calculate exchange rates using transition state theory and weighted them with the transmission coefficients determined by the reactive flux, Impey, Madden, and McDonald approaches, and Grote-Hynes theory. We found the relaxation times changed from 180 ps to 4600 ps and from 30 ps to 280 ps for Li+-[BF4] and Li+-[PF6] ion pairs, respectively. These results confirm that the solvent response to the kinetics of ion pairing is significant. Our results also show that, in addition to affecting the free energy of solvation into ACN, the anion type also should significantly influence the kinetics of ion pairing. These results will increase our understanding of the thermodynamic and kinetic properties of LIB systems.

Enhanced laser beam coupling to a plasma

DOEpatents

Steiger, Arno D.; Woods, Cornelius H.

1976-01-01

Density perturbations are induced in a heated plasma by means of a pair of oppositely directed, polarized laser beams of the same frequency. The wavelength of the density perturbations is equal to one half the wavelength of the laser beams. A third laser beam is linearly polarized and directed at the perturbed plasma along a line that is perpendicular to the direction of the two opposed beams. The electric field of the third beam is oriented to lie in the plane containing the three beams. The frequency of the third beam is chosen to cause it to interact resonantly with the plasma density perturbations, thereby efficiently coupling the energy of the third beam to the plasma.

Magnetic resonance imaging relaxation time in Alzheimer's disease.

PubMed

Tang, Xiang; Cai, Feng; Ding, Dong-Xue; Zhang, Lu-Lu; Cai, Xiu-Ying; Fang, Qi

2018-05-05

The magnetic resonance imaging (MRI) relaxation time constants, T1 and T2, are sensitive to changes in brain tissue microstructure integrity. Quantitative T1 and T2 relaxation times have been proposed to serve as non-invasive biomarkers of Alzheimer's disease (AD), in which alterations are believed to not only reflect AD-related neuropathology but also cognitive impairment. In this review, we summarize the applications and key findings of MRI techniques in the context of both AD subjects and AD transgenic mouse models. Furthermore, the possible mechanisms of relaxation time alterations in AD will be discussed. Future studies could focus on relaxation time alterations in the early stage of AD, and longitudinal studies are needed to further explore relaxation time alterations during disease progression. Copyright © 2018 Elsevier Inc. All rights reserved.

Interface roughness mediated phonon relaxation rates in Si quantum dots.

NASA Astrophysics Data System (ADS)

Ferdous, Rifat; Hsueh, Yuling; Klimeck, Gerhard; Rahman, Rajib

2015-03-01

Si QDs are promising candidates for solid-state quantum computing due to long spin coherence times. However, the valley degeneracy in Si adds an additional degree of freedom to the electronic structure. Although the valley and orbital indices can be uniquely identified in an ideal Si QD, interface roughness mixes valley and orbital states in realistic dots. Such valley-orbit coupling can strongly influence T1 times in Si QDs. Recent experimental measurements of various relaxation rates differ from previous predictions of phonon relaxation in ideal Si QDs. To understand how roughness affects different relaxation rates, for example spin relaxation due to spin-valley coupling, which is a byproduct of spin-orbit and valley-orbit coupling, we need to understand the effect of valley-orbit coupling on valley relaxation first. Using a full-band atomistic tight-binding description for both the system's electron and electron-phonon hamiltonian, we analyze the effect of atomic-scale interface disorder on phonon induced valley relaxation and spin relaxation in a Si QD. We find that, the valley splitting dependence of valley relaxation rate governs the magnetic field dependence of spin relaxation rate. Our results help understand experimentally measured relaxation times.

Dielectric relaxation of gamma irradiated muscovite mica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaur, Navjeet; Singh, Mohan, E-mail: mohansinghphysics@gmail.com; Singh, Lakhwant

2015-03-15

Highlights: • The present article reports the effect of gamma irradiation on the dielectric relaxation characteristics of muscovite mica. • Dielectric and electrical relaxations have been analyzed in the framework of dielectric permittivity, electric modulus and Cole–Cole formalisms. • The frequency dependent electrical conductivity has been rationalized using Johnsher’s universal power law. • The experimentally measured electric modulus and conductivity data have been fitted using Havriliak–Negami dielectric relaxation function. - Abstract: In the present research, the dielectric relaxation of gamma irradiated muscovite mica was studied in the frequency range of 0.1 Hz–10 MHz and temperature range of 653–853 K, usingmore » the dielectric permittivity, electric modulus and conductivity formalisms. The dielectric constants (ϵ′ and ϵ′′) are found to be high for gamma irradiated muscovite mica as compared to the pristine sample. The frequency dependence of the imaginary part of complex electric modulus (M′′) and dc conductivity data conforms Arrhenius law with single value of activation energy for pristine sample and two values of activation energy for gamma irradiated mica sample. The experimentally assessed electric modulus and conductivity information have been interpreted by the Havriliak–Negami dielectric relaxation explanation. Using the Cole–Cole framework, an analysis of real and imaginary characters of the electric modulus for pristine and gamma irradiated sample was executed which reflects the non-Debye relaxation mechanism.« less

Ion-pair chromatography coupled to inductively coupled plasma-mass spectrometry (IPC-ICP-MS) as a method for thiomolybdate speciation in natural waters.

PubMed

Lohmayer, Regina; Reithmaier, Gloria Maria Susanne; Bura-Nakić, Elvira; Planer-Friedrich, Britta

2015-03-17

Molybdenum precipitates preferentially under reducing conditions; therefore, its occurrence in sediment records is used as an indicator of paleoredox conditions. Although thiomolybdates (MoO4-xSx(2-) with x = 1-4) supposedly are necessary intermediates in the process of molybdenum precipitation under anoxic conditions, there is no information about their abundance in natural environments, because of a lack of element-specific methods with sufficiently low detection limits. Here, we optimized ion-pair chromatographic separation for coupling to an inductively coupled plasma-mass spectrometry detector (IPC-ICP-MS). 2-Propanol (10%-25% gradient) replaced the previously used acetonitrile (25%-75%) as the solvent, to reduce the carbon load into the plasma. In synthetic solutions, formation of thiomolybdates was found to occur spontaneously in the presence of excess sulfide and the degree of thiolation was highest at pH 7. Excess hydroxyl led to a transformation of thiomolybdates to molybdate. Under acidic to neutral conditions, precipitation of molybdenum and hydrolysis of tetrathiomolybdate were observed. Flash-freezing was found to be suitable to stabilize tetrathiomolybdate, with <4% transformation over more than two months. High ionic strengths matrices (>2 mM) negatively affected the detection of molybdate, which eluted mainly in the dead volume, but had no negative effect on higher thiolated molybdates. Detection limits were ∼10 nM. With the newly developed IPC-ICP-MS method, thiomolybdates were found to form spontaneously in euxinic marine waters after adding a molybdate spike and occur naturally in sulfidic geothermal waters.

Gd-DTPA T1 relaxivity in brain tissue obtained by convection-enhanced delivery, magnetic resonance imaging and emission spectroscopy

NASA Astrophysics Data System (ADS)

Haar, Peter J.; Broaddus, William C.; Chen, Zhi-jian; Fatouros, Panos P.; Gillies, George T.; Corwin, Frank D.

2010-06-01

A common approach to quantify gadolinium (Gd) contrast agents involves measuring the post-contrast change in T1 rate and then using the constant T1 relaxivity R to determine the contrast agent concentration. Because this method is fast and non-invasive, it could be potentially valuable in many areas of brain research. However, to accurately measure contrast agent concentrations in the brain, the T1 relaxivity R of the specific agent must be accurately known. Furthermore, the macromolecular content and compartmentalization of the brain extracellular space (ECS) are expected to significantly alter R from values measured in aqueous solutions. In this study, the T1 relaxivity R of gadolinium-diethylene-triamine penta-acetic acid (Gd-DTPA) was measured following direct interstitial infusions of three different contrast agent concentrations to the parenchyma of rat brains. Changes in magnetic resonance (MR) T1 values were compared to brain slice concentrations determined with inductively coupled plasma atomic emission spectroscopy (ICP-AES) to determine R in 15 rats. Additionally, samples of cerebrospinal fluid, blood and urine were analyzed to evaluate possible Gd-DTPA clearance from the brain. The T1 relaxivity R of Gd-DTPA in the brain ECS was measured to be 5.35 (mM s)-1 in a 2.4 T field. This value is considerably higher than estimations used in studies by other groups. Measurements of brain Gd-DTPA tissue concentrations using MRI and ICP-AES demonstrated a high degree of coincidence. Clearance of Gd-DTPA was minimal at the time point immediately after infusion. These results suggest that the environment of the brain does in fact significantly affect Gd T1 relaxivity, and that MRI can accurately measure contrast agent concentrations when this relaxivity is well characterized.

Plasma lipids, lipoproteins, and triglyceride turnover in eu- and hypo-thyroid rats and rats on a hypocaloric diet.

PubMed

Dory, L; Krause, B R; Roheim, P S

1981-08-01

Lipid and lipoprotein concentration, and triglyceride turnover were studied in control, thyroidectomized, and pair-fed control rats (pair-fed to match the food intake of the thyroidectomized rats). Thyroidectomy induced a significant increase in plasma cholesterol (and low density lipoprotein) concentrations and a decrease in plasma triglyceride (and very low density lipoprotein) concentrations. Changes in similar direction but of smaller magnitude were observed in the plasma of the pair-fed control rats. To further investigate triglyceride metabolism in these three groups of animals, triglyceride turnover was studied in fasted, unrestrained, and unanesthetized rats, following injection of [2-3H]glycerol. Peak incorporation of [2-3H]glycerol into plasma triglyceride occurred in all three groups of animals at 25 min after precursor administration, although the maximal incorporation was substantially lower in the thyroidectomized group than in either of the control groups. Thereafter, plasma triglyceride radioactivity decayed monoexponentially with a half-life of 24 +/- 1 min for both normal and pair-fed control rats, compared with the half-life of 41 +/- 3 min observed in the thyroidectomized rats. The calculated apparent fractional catabolic rates were thus 0.029 min-1 for both control groups and only 0.017 min-1 for the thyroidectomized animals. The apparent total catabolic rates of plasma triglyceride were 299 +/- 11, 138 +/- 11, and 48 +/- 4 micrograms triglyceride . min-1 for the normal controls, pair-fed controls, and thyroidectomized rats, respectively. These data further emphasize the importance of thyroid hormones in regulating plasma lipid and lipoprotein metabolism and, specifically, indicate that hypothyroidism results in a reduction of triglyceride secretion into, and the removal from, circulation. Furthermore, evidence was presented that the decreased caloric intake of the hypothyroid animals cannot, in itself, account for this observation.

Enhancing elastic stress relaxation in SiGe/Si heterostructures by Si pillar necking

NASA Astrophysics Data System (ADS)

Isa, F.; Salvalaglio, M.; Arroyo Rojas Dasilva, Y.; Jung, A.; Isella, G.; Erni, R.; Timotijevic, B.; Niedermann, P.; Gröning, P.; Montalenti, F.; von Känel, H.

2016-10-01

We demonstrate that the elastic stress relaxation mechanism in micrometre-sized, highly mismatched heterostructures may be enhanced by employing patterned substrates in the form of necked pillars, resulting in a significant reduction of the dislocation density. Compositionally graded Si1-xGex crystals were grown by low energy plasma enhanced chemical vapour deposition, resulting in tens of micrometres tall, three-dimensional heterostructures. The patterned Si(001) substrates consist of micrometre-sized Si pillars either with the vertical {110} or isotropically under-etched sidewalls resulting in narrow necks. The structural properties of these heterostructures were investigated by defect etching and transmission electron microscopy. We show that the dislocation density, and hence the competition between elastic and plastic stress relaxation, is highly influenced by the shape of the substrate necks and their proximity to the mismatched epitaxial material. The SiGe dislocation density increases monotonically with the crystal width but is significantly reduced by the substrate under-etching. The drop in dislocation density is interpreted as a direct effect of the enhanced compliance of the under-etched Si pillars, as confirmed by the three-dimensional finite element method simulations of the elastic energy distribution.

Chloride channel blockers promote relaxation of TEA-induced contraction in airway smooth muscle

PubMed Central

Yim, Peter D.; Gallos, George; Perez-zoghbi, Jose F.; Trice, Jacquelyn; Zhang, Yi; Siviski, Matthew; Sonett, Joshua; Emala, Charles W.

2014-01-01

Enhanced airway smooth muscle (ASM) contraction is an important component in the pathophysiology of asthma. We have shown that ligand gated chloride channels modulate ASM contractile tone during the maintenance phase of an induced contraction, however the role of chloride flux in depolarization-induced contraction remains incompletely understood. To better understand the role of chloride flux under these conditions, muscle force (human ASM, guinea pig ASM), peripheral small airway luminal area (rat ASM) and airway smooth muscle plasma membrane electrical potentials (human cultured ASM) were measured. We found ex vivo guinea pig airway rings, human ASM strips and small peripheral airways in rat lungs slices relaxed in response to niflumic acid following depolarization-induced contraction induced by K+ channel blockade with tetraethylammonium chloride (TEA). In isolated human airway smooth muscle cells TEA induce depolarization as measured by a fluorescent indicator or whole cell patch clamp and this depolarization was reversed by niflumic acid. These findings demonstrate that ASM depolarization induced contraction is dependent on chloride channel activity. Targeting of chloride channels may be a novel approach to relax hypercontractile airway smooth muscle in bronchoconstrictive disorders. PMID:24662476

Chloride channel blockers promote relaxation of TEA-induced contraction in airway smooth muscle.

PubMed

Yim, Peter D; Gallos, George; Perez-Zoghbi, Jose F; Trice, Jacquelyn; Zhang, Yi; Siviski, Matthew; Sonett, Joshua; Emala, Charles W

2013-01-01

Enhanced airway smooth muscle (ASM) contraction is an important component in the pathophysiology of asthma. We have shown that ligand gated chloride channels modulate ASM contractile tone during the maintenance phase of an induced contraction, however the role of chloride flux in depolarization-induced contraction remains incompletely understood. To better understand the role of chloride flux under these conditions, muscle force (human ASM, guinea pig ASM), peripheral small airway luminal area (rat ASM) and airway smooth muscle plasma membrane electrical potentials (human cultured ASM) were measured. We found ex vivo guinea pig airway rings, human ASM strips and small peripheral airways in rat lungs slices relaxed in response to niflumic acid following depolarization-induced contraction induced by K(+) channel blockade with tetraethylammonium chloride (TEA). In isolated human airway smooth muscle cells TEA induce depolarization as measured by a fluorescent indicator or whole cell patch clamp and this depolarization was reversed by niflumic acid. These findings demonstrate that ASM depolarization induced contraction is dependent on chloride channel activity. Targeting of chloride channels may be a novel approach to relax hypercontractile airway smooth muscle in bronchoconstrictive disorders.

A saw-tooth plasma actuator for film cooling efficiency enhancement of a shaped hole

NASA Astrophysics Data System (ADS)

Li, Guozhan; Yu, Jianyang; Liu, Huaping; Chen, Fu; Song, Yanping

2017-08-01

This paper reports the large eddy simulations of the effects of a saw-tooth plasma actuator and the laidback fan-shaped hole on the film cooling flow characteristics, and the numerical results are compared with a corresponding standard configuration (cylindrical hole without the saw-tooth plasma actuator). For this numerical research, the saw-tooth plasma actuator is installed just downstream of the cooling hole and a phenomenological plasma model is employed to provide the 3D plasma force vectors. The results show that thanks to the downward force and the momentum injection effect of the saw-tooth plasma actuator, the cold jet comes closer to the wall surface and extends further downstream. The saw-tooth plasma actuator also induces a new pair of vortex which weakens the strength of the counter-rotating vortex pair (CRVP) and entrains the coolant towards the wall, and thus the diffusion of the cold jet in the crossflow is suppressed. Furthermore, the laidback fan-shaped hole reduces the vertical jet velocity causing the disappearance of downstream spiral separation node vortices, this compensates for the deficiency of the saw-tooth plasma actuator. Both effects of the laidback fan-shaped hole and the saw-tooth plasma actuator effectively control the development of the CRVP whose size and strength are smaller than those of the anti-counter rotating vortex pair in the far field, thus the centerline and the spanwise-averaged film cooling efficiency are enhanced. The average film cooling efficiency is the biggest in the Fan-Dc = 1 case, which is 80% bigger than that in the Fan-Dc = 0 case and 288% bigger than that in the Cyl-Dc = 0 case.

A comparison of equivolume, equiosmolar solutions of hypertonic saline and mannitol for brain relaxation during elective supratentorial craniotomy.

PubMed

Hernández-Palazón, Joaquín; Fuentes-García, Diego; Doménech-Asensi, Paloma; Piqueras-Pérez, Claudio; Falcón-Araña, Luis; Burguillos-López, Sebastián

2016-01-01

Hyperosmolar solutions have been used in neurosurgery to reduce brain volume and facilitate surgical exposure. The purpose of this study was to compare the effects of equivolume, equiosmolar solutions of mannitol and hypertonic saline (HS) on brain relaxation, intensive care unit (ICU) and hospital stay, postoperative outcomes and incidence of side-effects in patients undergoing elective supratentorial craniotomy. In a randomised, prospective, double-blind study, 60 patients undergoing elective supratentorial craniotomy were randomised 1:1 to receive 3 ml/kg of either 20% mannitol or 3% HS. The primary outcome was the surgical condition of the brain assessed by the neurosurgeon using a 4-point scale after opening the dura (1 = relaxed, 2 = satisfactory, 3 = firm and 4 = bulging). Secondary outcomes were electrolytes, blood gases, plasma osmolality and haemodynamic variables measured at 0 min, 30 min, 2 h and 6 h after infusion. Also, predefined postoperative complications, length of ICU and hospital stay were recorded. Appropriate statistical tests were used for comparison; p < 0.05 was considered significant. There was no difference in brain relaxation [mannitol, 1(1-3) versus HS, 1(1.4) points; p = 0.55]. Patients with brain midline shift showed a worse response to hyperosmolar solutions than those without midline shift: 37% versus 8%, respectively; OR = 6.6 (95% CI, 1.54-28.83); p = 0.006. Plasma osmolality increased during the study period (6 h) in both the groups (p < 0.05 compared with baseline). No significant differences in postoperative complications or length of ICU and hospital stay were observed between the groups. Single doses of 3 ml/kg of 20% mannitol and 3% HS are safe and effective for intraoperative brain debulking during elective supratentorial craniotomy, but less effective in patients with pre-existing mass effect and midline shift.

Bayesian Modeling of NMR Data: Quantifying Longitudinal Relaxation in Vivo, and in Vitro with a Tissue-Water-Relaxation Mimic (Crosslinked Bovine Serum Albumin).

PubMed

Meinerz, Kelsey; Beeman, Scott C; Duan, Chong; Bretthorst, G Larry; Garbow, Joel R; Ackerman, Joseph J H

2018-01-01

Recently, a number of MRI protocols have been reported that seek to exploit the effect of dissolved oxygen (O 2 , paramagnetic) on the longitudinal 1 H relaxation of tissue water, thus providing image contrast related to tissue oxygen content. However, tissue water relaxation is dependent on a number of mechanisms, and this raises the issue of how best to model the relaxation data. This problem, the model selection problem, occurs in many branches of science and is optimally addressed by Bayesian probability theory. High signal-to-noise, densely sampled, longitudinal 1 H relaxation data were acquired from rat brain in vivo and from a cross-linked bovine serum albumin (xBSA) phantom, a sample that recapitulates the relaxation characteristics of tissue water in vivo . Bayesian-based model selection was applied to a cohort of five competing relaxation models: (i) monoexponential, (ii) stretched-exponential, (iii) biexponential, (iv) Gaussian (normal) R 1 -distribution, and (v) gamma R 1 -distribution. Bayesian joint analysis of multiple replicate datasets revealed that water relaxation of both the xBSA phantom and in vivo rat brain was best described by a biexponential model, while xBSA relaxation datasets truncated to remove evidence of the fast relaxation component were best modeled as a stretched exponential. In all cases, estimated model parameters were compared to the commonly used monoexponential model. Reducing the sampling density of the relaxation data and adding Gaussian-distributed noise served to simulate cases in which the data are acquisition-time or signal-to-noise restricted, respectively. As expected, reducing either the number of data points or the signal-to-noise increases the uncertainty in estimated parameters and, ultimately, reduces support for more complex relaxation models.

129 Xe NMR Relaxation-Based Macromolecular Sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gomes, Muller D.; Dao, Phuong; Jeong, Keunhong

2016-07-29

A 129Xe NMR relaxation-based sensing approach is reported on that exploits changes in the bulk xenon relaxation rate induced by slowed tumbling of a cryptophane-based sensor upon target binding. The amplification afforded by detection of the bulk dissolved xenon allows sensitive detection of targets. The sensor comprises a xenon-binding cryptophane cage, a target interaction element, and a metal chelating agent. Xenon associated with the target-bound cryptophane cage is rapidly relaxed and then detected after exchange with the bulk. Here we show that large macromolecular targets increase the rotational correlation time of xenon, increasing its relaxation rate. Upon binding of amore » biotin-containing sensor to avidin at 1.5 μM concentration, the free xenon T 2 is reduced by a factor of 4.« less

Picosecond absorption relaxation measured with nanosecond laser photoacoustics.

PubMed

Danielli, Amos; Favazza, Christopher P; Maslov, Konstantin; Wang, Lihong V

2010-10-18

Picosecond absorption relaxation-central to many disciplines-is typically measured by ultrafast (femtosecond or picosecond) pump-probe techniques, which however are restricted to optically thin and weakly scattering materials or require artificial sample preparation. Here, we developed a reflection-mode relaxation photoacoustic microscope based on a nanosecond laser and measured picosecond absorption relaxation times. The relaxation times of oxygenated and deoxygenated hemoglobin molecules, both possessing extremely low fluorescence quantum yields, were measured at 576 nm. The added advantages in dispersion susceptibility, laser-wavelength availability, reflection sensing, and expense foster the study of natural-including strongly scattering and nonfluorescent-materials.

Calorimetric and relaxation properties of xylitol-water mixtures

NASA Astrophysics Data System (ADS)

Elamin, Khalid; Sjöström, Johan; Jansson, Helén; Swenson, Jan

2012-03-01

We present the first broadband dielectric spectroscopy (BDS) and differential scanning calorimetry study of supercooled xylitol-water mixtures in the whole concentration range and in wide frequency (10-2-106 Hz) and temperature (120-365 K) ranges. The calorimetric glass transition, Tg, decreases from 247 K for pure xylitol to about 181 K at a water concentration of approximately 37 wt. %. At water concentrations in the range 29-35 wt. % a plentiful calorimetric behaviour is observed. In addition to the glass transition, almost simultaneous crystallization and melting events occurring around 230-240 K. At higher water concentrations ice is formed during cooling and the glass transition temperature increases to a steady value of about 200 K for all higher water concentrations. This Tg corresponds to an unfrozen xylitol-water solution containing 20 wt. % water. In addition to the true glass transition we also observed a glass transition-like feature at 220 K for all the ice containing samples. However, this feature is more likely due to ice dissolution [A. Inaba and O. Andersson, Thermochim. Acta, 461, 44 (2007)]. In the case of the BDS measurements the presence of water clearly has an effect on both the cooperative α-relaxation and the secondary β-relaxation. The α-relaxation shows a non-Arrhenius temperature dependence and becomes faster with increasing concentration of water. The fragility of the solutions, determined by the temperature dependence of the α-relaxation close to the dynamic glass transition, decreases with increasing water content up to about 26 wt. % water, where ice starts to form. This decrease in fragility with increasing water content is most likely caused by the increasing density of hydrogen bonds, forming a network-like structure in the deeply supercooled regime. The intensity of the secondary β-relaxation of xylitol decreases noticeably already at a water content of 2 wt. %, and at a water content above 5 wt. % it has been replaced by a

The focusing effect in backward Raman amplification in plasma

NASA Astrophysics Data System (ADS)

Li, Zhaoli; Peng, Hao; Zuo, Yanlei; Su, Jingxin; Yang, Suhui

2018-04-01

In this paper, the focusing effect on backward Raman amplification in plasma is investigated. A fluid model, used to simulate the backward Raman amplification and including the relativistic, ponderomotive, and thermal self-focusing and the mutual-focusing effect simultaneously, is proposed and investigated. The focusing effect is shown to severely distort the profile of the seed when the seed intensity was as high as 10 17 W/cm2. Reducing the plasma density can relax the focusing effect, but at the cost of decreasing the amplification efficiency. Changing the profile of the seed has a limited effect on mitigating the focusing effect. A Gaussian profile of the pump and a defocusing shape of the plasma density seem to be an effective way to mitigate the focusing effect without decreasing the amplification efficiency.

The Unquiet State of Violent Relaxation

NASA Astrophysics Data System (ADS)

Henriksen, Richard

2005-08-01

In 1967 Lynden-Bell presented a statistical mechanical theory for the relaxation of collisionless systems. Since then this theory has been studied numerically and theoretically by many authors. Nakamura in 2000 gave an alternate theory that differed from that of Lynden- Bell by predicting a Gaussian equilibrium distribution function rather than Fermi-Dirac. More recently Henriksen in 2004 has used a coarsegraining technique on cosmological infall systems that also predicts a Gaussian equilibrium distribution function. These relaxed states are thought to occur from the centre of the system outwards. Simulations of cosmological cold dark-matter halos however persist in finding central density cusps (the NFWprofile), which are inconsistent with the predicted distribution functions and perhaps with the observations of some galaxies. Some numerical studies (e.g.Merrall & Henriksen 2003) that attempt to measure the distribution function of dark matter do find Gaussian functions, provided that the initial asymmetry is not too great. Moreover recent work at Queen's reported here by MacMillan, suggests that it is the growth of asymmetry during the infall that produces the cusped behaviour. So put briefly, the essential physics of dark-matter relaxation remains "obscure" as does the validity of the theoretical predictions. "Violent virialization" occurs rapidly, well before subscale relaxation, but the scale at which the relaxation stops (and why) remains unclear. I will present some results that argue for wave-particle relaxation (Landau damping as frequently suggested by Kandrup) and in addition I will suggest that the evolution of isolated systems is very different from that of systems constantly disturbed by infall. Isolated systems may become trapped in an unrelaxed state by the development or existence of multipolar internal structure. Nevertheless a suitable coarse graining of the system may restore the predicted distribution functions.

Base pairing and base mis-pairing in nucleic acids

NASA Technical Reports Server (NTRS)

Wang, A. H. J.; Rich, A.

1986-01-01

In recent years we have learned that DNA is conformationally active. It can exist in a number of different stable conformations including both right-handed and left-handed forms. Using single crystal X-ray diffraction analysis we are able to discover not only additional conformations of the nucleic acids but also different types of hydrogen bonded base-base interactions. Although Watson-Crick base pairings are the predominant type of interaction in double helical DNA, they are not the only types. Recently, we have been able to examine mismatching of guanine-thymine base pairs in left-handed Z-DNA at atomic resolution (1A). A minimum amount of distortion of the sugar phosphate backbone is found in the G x T pairing in which the bases are held together by two hydrogen bonds in the wobble pairing interaction. Because of the high resolution of the analysis we can visualize water molecules which fill in to accommodate the other hydrogen bonding positions in the bases which are not used in the base-base interactions. Studies on other DNA oligomers have revealed that other types of non-Watson-Crick hydrogen bonding interactions can occur. In the structure of a DNA octamer with the sequence d(GCGTACGC) complexed to an antibiotic triostin A, it was found that the two central AT base pairs are held together by Hoogsteen rather than Watson-Crick base pairs. Similarly, the G x C base pairs at the ends are also Hoogsteen rather than Watson-Crick pairing. Hoogsteen base pairs make a modified helix which is distinct from the Watson-Crick double helix.

Relaxing music counters heightened consolidation of emotional memory.

PubMed

Rickard, Nikki S; Wong, Wendy Wing; Velik, Lauren

2012-02-01

Emotional events tend to be retained more strongly than other everyday occurrences, a phenomenon partially regulated by the neuromodulatory effects of arousal. Two experiments demonstrated the use of relaxing music as a means of reducing arousal levels, thereby challenging heightened long-term recall of an emotional story. In Experiment 1, participants (N=84) viewed a slideshow, during which they listened to either an emotional or neutral narration, and were exposed to relaxing or no music. Retention was tested 1 week later via a forced choice recognition test. Retention for both the emotional content (Phase 2 of the story) and material presented immediately after the emotional content (Phase 3) was enhanced, when compared with retention for the neutral story. Relaxing music prevented the enhancement for material presented after the emotional content (Phase 3). Experiment 2 (N=159) provided further support to the neuromodulatory effect of music by post-event presentation of both relaxing music and non-relaxing auditory stimuli (arousing music/background sound). Free recall of the story was assessed immediately afterwards and 1 week later. Relaxing music significantly reduced recall of the emotional story (Phase 2). The findings provide further insight into the capacity of relaxing music to attenuate the strength of emotional memory, offering support for the therapeutic use of music for such purposes. Copyright © 2011 Elsevier Inc. All rights reserved.

Ultrafast energy relaxation in single light-harvesting complexes.

PubMed

Malý, Pavel; Gruber, J Michael; Cogdell, Richard J; Mančal, Tomáš; van Grondelle, Rienk

2016-03-15

Energy relaxation in light-harvesting complexes has been extensively studied by various ultrafast spectroscopic techniques, the fastest processes being in the sub-100-fs range. At the same time, much slower dynamics have been observed in individual complexes by single-molecule fluorescence spectroscopy (SMS). In this work, we use a pump-probe-type SMS technique to observe the ultrafast energy relaxation in single light-harvesting complexes LH2 of purple bacteria. After excitation at 800 nm, the measured relaxation time distribution of multiple complexes has a peak at 95 fs and is asymmetric, with a tail at slower relaxation times. When tuning the excitation wavelength, the distribution changes in both its shape and position. The observed behavior agrees with what is to be expected from the LH2 excited states structure. As we show by a Redfield theory calculation of the relaxation times, the distribution shape corresponds to the expected effect of Gaussian disorder of the pigment transition energies. By repeatedly measuring few individual complexes for minutes, we find that complexes sample the relaxation time distribution on a timescale of seconds. Furthermore, by comparing the distribution from a single long-lived complex with the whole ensemble, we demonstrate that, regarding the relaxation times, the ensemble can be considered ergodic. Our findings thus agree with the commonly used notion of an ensemble of identical LH2 complexes experiencing slow random fluctuations.

Mode of coreceptor use by R5 HIV type 1 correlates with disease stage: a study of paired plasma and cerebrospinal fluid isolates.

PubMed

Karlsson, Ulf; Antonsson, Liselotte; Repits, Johanna; Medstrand, Patrik; Owman, Christer; Kidd-Ljunggren, Karin; Hagberg, Lars; Svennerholm, Bo; Jansson, Marianne; Gisslén, Magnus; Ljungberg, Bengt

2009-12-01

Through the use of chimeric CXCR4/CCR5 receptors we have previously shown that CCR5-tropic (R5) HIV-1 isolates acquire a more flexible receptor use over time, and that this links to a reduced viral susceptibility to inhibition by the CCR5 ligand RANTES. These findings may have relevance with regards to the efficacy of antiretroviral compounds that target CCR5/virus interactions. Compartmentalized discrepancies in coreceptor use may occur, which could also affect the efficacy of these compounds at specific anatomical sites, such as within the CNS. In this cross-sectional study we have used wild-type CCR5 and CXCR4 as well as chimeric CXCR4/CCR5 receptors to characterize coreceptor use by paired plasma and cerebrospinal fluid (CSF) isolates from 28 HIV-1-infected individuals. Furthermore, selected R5 isolates, with varying chimeric receptor use, were tested for sensitivity to inhibition by the CCR5 antagonist TAK-779. Discordant CSF/plasma virus coreceptor use was found in 10/28 patients. Low CD4+ T cell counts correlated strongly with a more flexible mode of R5 virus CCR5 usage, as disclosed by an increased ability to utilize chimeric CXCR4/CCR5 receptors, specifically receptor FC-2. Importantly, an elevated ability to utilize chimeric receptors correlated with a reduced susceptibility to inhibition by TAK-779. Our findings show that a discordant CSF and plasma virus coreceptor use is not uncommon. Furthermore, we provide support for an emerging paradigm, where the acquisition of a more flexible mode of CCR5 usage is a key event in R5 virus pathogenesis. This may, in turn, negatively impact the efficacy of CCR5 antagonist treatment in late stage HIV-1 disease.

Relaxation as a Factor in Semantic Desensitization

ERIC Educational Resources Information Center

Bechtel, James E.; McNamara, J. Regis

1975-01-01

Relaxation and semantic desensitization were used to alleviate the fear of phobic females. Results showed that semantic desensitization, alone or in combination with relaxation, failed to modify the evaluative meanings evoked by the feared object. (SE)

Nuclear spin-lattice relaxation in nitroxide spin-label EPR.

PubMed

Marsh, Derek

2016-11-01

Nuclear relaxation is a sensitive monitor of rotational dynamics in spin-label EPR. It also contributes competing saturation transfer pathways in T 1 -exchange spectroscopy, and the determination of paramagnetic relaxation enhancement in site-directed spin labelling. A survey shows that the definition of nitrogen nuclear relaxation rate W n commonly used in the CW-EPR literature for 14 N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised 14 N spin-lattice relaxation rate, b=W n /(2W e ), preserves the expressions used for CW-EPR, whilst rendering them consistent with expressions for saturation recovery rates in pulsed EPR. Furthermore, values routinely quoted for nuclear relaxation times that are deduced from EPR spectral diffusion rates in 14 N-nitroxyl spin labels do not accord with conventional analysis of spin-lattice relaxation in this three-level system. Expressions for CW-saturation EPR with the revised definitions are summarised. Data on nitrogen nuclear spin-lattice relaxation times are compiled according to the three-level scheme for 14 N-relaxation: T 1 n =1/W n . Results are compared and contrasted with those for the two-level 15 N-nitroxide system. Copyright © 2016 Elsevier Inc. All rights reserved.

Definition, evaluation, and management of brain relaxation during craniotomy.

PubMed

Li, J; Gelb, A W; Flexman, A M; Ji, F; Meng, L

2016-06-01

The term 'brain relaxation' is routinely used to describe the size and firmness of the brain tissue during craniotomy. The status of brain relaxation is an important aspect of neuroanaesthesia practice and is relevant to the operating conditions, retraction injury, and likely patient outcomes. Brain relaxation is determined by the relationship between the volume of the intracranial contents and the capacity of the intracranial space (i.e. a content-space relationship). It is a concept related to, but distinct from, intracranial pressure. The evaluation of brain relaxation should be standardized to facilitate clinical communication and research collaboration. Both advantageous and disadvantageous effects of the various interventions for brain relaxation should be taken into account in patient care. The outcomes that matter the most to patients should be emphasized in defining, evaluating, and managing brain relaxation. To date, brain relaxation has not been reviewed specifically, and the aim of this manuscript is to discuss the current approaches to the definition, evaluation, and management of brain relaxation, knowledge gaps, and targets for future research. © The Author 2016. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Body mass index, metabolic factors, and striatal activation during stressful and neutral-relaxing states: an FMRI study.

PubMed

Jastreboff, Ania M; Potenza, Marc N; Lacadie, Cheryl; Hong, Kwangik A; Sherwin, Robert S; Sinha, Rajita

2011-02-01

Stress is associated with alterations in neural motivational-reward pathways in the ventral striatum (VS), hormonal/metabolic changes, and weight increases. The relationship between these different factors is not well understood. We hypothesized that body mass index (BMI) status and hormonal/metabolic factors would be associated with VS activation. We used functional magnetic resonance imaging (fMRI) to compare brain responses of overweight and obese (OW/OB: BMI ≥ 25 kg/m(2): N=27) individuals with normal weight (NW: BMI<18.5-24.9 kg/m(2): N=21) individuals during exposure to personalized stress, alcohol cue, and neutral-relaxing situations using a validated, autobiographical, script-driven, guided-imagery paradigm. Metabolic factors, including fasting plasma glucose (FPG), insulin, and leptin, were examined for their association with VS activation. Consistent with previous studies, stress and alcohol cue exposure each increased activity in cortico-limbic regions. Compared with NW individuals, OW/OB individuals showed greater VS activation in the neutral-relaxing and stress conditions. FPG was correlated with VS activation. Significant associations between VS activation and metabolic factors during stress and relaxation suggest the involvement of metabolic factors in striatal dysfunction in OW/OB individuals. This relationship may contribute to non-homeostatic feeding in obesity.

Collisional damping rates for plasma waves

NASA Astrophysics Data System (ADS)

Tigik, S. F.; Ziebell, L. F.; Yoon, P. H.

2016-06-01

The distinction between the plasma dynamics dominated by collisional transport versus collective processes has never been rigorously addressed until recently. A recent paper [P. H. Yoon et al., Phys. Rev. E 93, 033203 (2016)] formulates for the first time, a unified kinetic theory in which collective processes and collisional dynamics are systematically incorporated from first principles. One of the outcomes of such a formalism is the rigorous derivation of collisional damping rates for Langmuir and ion-acoustic waves, which can be contrasted to the heuristic customary approach. However, the results are given only in formal mathematical expressions. The present brief communication numerically evaluates the rigorous collisional damping rates by considering the case of plasma particles with Maxwellian velocity distribution function so as to assess the consequence of the rigorous formalism in a quantitative manner. Comparison with the heuristic ("Spitzer") formula shows that the accurate damping rates are much lower in magnitude than the conventional expression, which implies that the traditional approach over-estimates the importance of attenuation of plasma waves by collisional relaxation process. Such a finding may have a wide applicability ranging from laboratory to space and astrophysical plasmas.

Repeatability and reliability of muscle relaxation properties induced by motor cortical stimulation.

PubMed

Molenaar, Joery P; Voermans, Nicol C; de Jong, Lysanne A; Stegeman, Dick F; Doorduin, Jonne; van Engelen, Baziel G

2018-03-15

Impaired muscle relaxation is a feature of many neuromuscular disorders. However, there are few tests available to quantify muscle relaxation. Transcranial magnetic stimulation (TMS) of the motor cortex can induce muscle relaxation by abruptly inhibiting corticospinal drive. The aim of our study is to investigate if repeatability and reliability of TMS-induced relaxation is greater than voluntary relaxation. Furthermore, effects of sex, cooling and fatigue on muscle relaxation properties were studied. Muscle relaxation of deep finger flexors was assessed in twenty-five healthy subjects (14 M and 11 F, aged 39.1{plus minus}12.7 and 45.3{plus minus}8.7 years old, respectively) using handgrip dynamometry. All outcome measures showed greater repeatability and reliability in TMS-induced relaxation compared to voluntary relaxation. The within-subject coefficient of variability of normalized peak relaxation rate was lower in TMS-induced relaxation than in voluntary relaxation (3.0 vs 19.7% in men, and 6.1 vs 14.3% in women). The repeatability coefficient was lower (1.3 vs 6.1 s -1 in men and 2.3 vs 3.1 s -1 in women), and the intraclass correlation coefficient was higher (0.95 vs 0.53 in men and 0.78 vs 0.69 in women), for TMS-induced relaxation compared to voluntary relaxation. TMS enabled to demonstrate slowing effects of sex, muscle cooling, and muscle fatigue on relaxation properties that voluntary relaxation could not. In conclusion, repeatability and reliability of TMS-induced muscle relaxation was greater compared to voluntary muscle relaxation. TMS-induced muscle relaxation has the potential to be used in clinical practice for diagnostic purposes and therapy effect monitoring in patients with impaired muscle relaxation.

Relaxation-optimized transfer of spin order in Ising spin chains

NASA Astrophysics Data System (ADS)

Stefanatos, Dionisis; Glaser, Steffen J.; Khaneja, Navin

2005-12-01

In this paper, we present relaxation optimized methods for the transfer of bilinear spin correlations along Ising spin chains. These relaxation optimized methods can be used as a building block for the transfer of polarization between distant spins on a spin chain, a problem that is ubiquitous in multidimensional nuclear magnetic resonance spectroscopy of proteins. Compared to standard techniques, significant reduction in relaxation losses is achieved by these optimized methods when transverse relaxation rates are much larger than the longitudinal relaxation rates and comparable to couplings between spins. We derive an upper bound on the efficiency of the transfer of the spin order along a chain of spins in the presence of relaxation and show that this bound can be approached by the relaxation optimized pulse sequences presented in the paper.

Rounded stretched exponential for time relaxation functions.

PubMed

Powles, J G; Heyes, D M; Rickayzen, G; Evans, W A B

2009-12-07

A rounded stretched exponential function is introduced, C(t)=exp{(tau(0)/tau(E))(beta)[1-(1+(t/tau(0))(2))(beta/2)]}, where t is time, and tau(0) and tau(E) are two relaxation times. This expression can be used to represent the relaxation function of many real dynamical processes, as at long times, t>tau(0), the function converges to a stretched exponential with normalizing relaxation time, tau(E), yet its expansion is even or symmetric in time, which is a statistical mechanical requirement. This expression fits well the shear stress relaxation function for model soft soft-sphere fluids near coexistence, with tau(E)relaxation (both the modulus and viscosity forms). It is shown that both the dielectric spectra and dynamic shear modulus imaginary parts approach the real axis with a slope equal to 0 at high frequency, whereas the dynamic viscosity has an infinite slope in the same limit. This indicates that inertial effects at high frequency are best discerned in the modulus rather than the viscosity Cole-Cole plot. As a consequence of the even expansion in time of the shear stress relaxation function, the value of the storage modulus derived from it at very high frequency exceeds that in the infinite frequency limit (i.e., G(infinity)).

Relaxation therapies for asthma: a systematic review

PubMed Central

Huntley, A; White, A; Ernst, E

2002-01-01

Background: Emotional stress can either precipitate or exacerbate both acute and chronic asthma. There is a large body of literature available on the use of relaxation techniques for the treatment of asthma symptoms. The aim of this systematic review was to determine if there is any evidence for or against the clinical efficacy of such interventions. Methods: Four independent literature searches were performed on Medline, Cochrane Library, CISCOM, and Embase. Only randomised clinical trials (RCTs) were included. There were no restrictions on the language of publication. The data from trials that statistically compared the treatment group with that of the control were extracted in a standardised predefined manner and assessed critically by two independent reviewers. Results: Fifteen trials were identified, of which nine compared the treatment group with the control group appropriately. Five RCTs tested progressive muscle relaxation or mental and muscular relaxation, two of which showed significant effects of therapy. One RCT investigating hypnotherapy, one of autogenic training, and two of biofeedback techniques revealed no therapeutic effects. Overall, the methodological quality of the studies was poor. Conclusions: There is a lack of evidence for the efficacy of relaxation therapies in the management of asthma. This deficiency is due to the poor methodology of the studies as well as the inherent problems of conducting such trials. There is some evidence that muscular relaxation improves lung function of patients with asthma but no evidence for any other relaxation technique. PMID:11828041

Relaxation therapies for asthma: a systematic review.

PubMed

Huntley, A; White, A R; Ernst, E

2002-02-01

Emotional stress can either precipitate or exacerbate both acute and chronic asthma. There is a large body of literature available on the use of relaxation techniques for the treatment of asthma symptoms. The aim of this systematic review was to determine if there is any evidence for or against the clinical efficacy of such interventions. Four independent literature searches were performed on Medline, Cochrane Library, CISCOM, and Embase. Only randomised clinical trials (RCTs) were included. There were no restrictions on the language of publication. The data from trials that statistically compared the treatment group with that of the control were extracted in a standardised predefined manner and assessed critically by two independent reviewers. Fifteen trials were identified, of which nine compared the treatment group with the control group appropriately. Five RCTs tested progressive muscle relaxation or mental and muscular relaxation, two of which showed significant effects of therapy. One RCT investigating hypnotherapy, one of autogenic training, and two of biofeedback techniques revealed no therapeutic effects. Overall, the methodological quality of the studies was poor. There is a lack of evidence for the efficacy of relaxation therapies in the management of asthma. This deficiency is due to the poor methodology of the studies as well as the inherent problems of conducting such trials. There is some evidence that muscular relaxation improves lung function of patients with asthma but no evidence for any other relaxation technique.

Load relaxation of olivine single crystals

NASA Astrophysics Data System (ADS)

Cooper, Reid F.; Stone, Donald S.; Plookphol, Thawatchai

2016-10-01

Single crystals of ferromagnesian olivine (San Carlos, AZ, peridot; Fo88-90) have been deformed in both uniaxial creep and load relaxation under conditions of ambient pressure, T = 1500°C and pO2 = 10-10 atm; creep stresses were in the range 40 ≤ σ1 (MPa) ≤ 220. The crystals were oriented such that the applied stress was parallel to [011]c, which promotes single slip on the slowest slip system in olivine, (010)[001]. The creep rates at steady state match well the results of earlier investigators, as does the stress sensitivity (a power law exponent of n = 3.6). Dislocation microstructures, including spatial distribution of low-angle (subgrain) boundaries, additionally confirm previous investigations. Inverted primary creep (an accelerating strain rate with an increase in stress) was observed. Load relaxation, however, produced a singular response—a single hardness curve—regardless of the magnitude of creep stress or total accumulated strain preceding relaxation. The log stress versus log strain rate data from load-relaxation and creep experiments overlap to within experimental error. The load-relaxation behavior is distinctly different than that described for other crystalline solids, where the flow stress is affected strongly by work hardening such that a family of distinct hardness curves is generated, which are related by a scaling function. The response of olivine for the conditions studied, we argue, indicates flow that is rate limited by dislocation glide, reflecting specifically a high intrinsic lattice resistance (Peierls stress).

Load Relaxation of Olivine Single Crystals

NASA Astrophysics Data System (ADS)

Cooper, R. F.; Stone, D. S.; Plookphol, T.

2016-12-01

Single crystals of ferromagnesian olivine (San Carlos, AZ, peridot; Fo90-92) have been deformed in both uniaxial creep and load relaxation under conditions of ambient pressure, T = 1500ºC and pO2 = 10-10 atm; creep stresses were in the range 40 ≤ σ1 (MPa) ≤ 220. The crystals were oriented such that the applied stress was parallel to [011]c, which promotes single slip on the slowest slip system in olivine, (010)[001]. The creep rates at steady state match well the results of earlier investigators, as does the stress sensitivity (a power-law exponent of n = 3.6). Dislocation microstructures, including spatial distribution of low-angle (subgrain) boundaries, additionally confirm previous investigations. Inverted primary creep (an accelerating strain rate with an increase in stress) was observed. Load-relaxation, however, produced a singular response—a single hardness curve—regardless of the magnitude of creep stress or total accumulated strain preceding relaxation. The log-stress v. log-strain rate data from load-relaxation and creep experiments overlap to within experimental error. The load-relaxation behavior is distinctly different that that described for other crystalline solids, where the flow stress is affected strongly by work hardening such that a family of distinct hardness curves is generated, which are related by a scaling function. The response of olivine for the conditions studied, thus, indicates flow that is rate-limited by dislocation glide, reflecting specifically a high intrinsic lattice resistance (Peierls stress).

The calculation of thermophysical properties of nickel plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Apfelbaum, E. M.

2015-09-15

The thermophysical properties of Nickel plasma have been calculated for the temperatures 10–60 kK and densities less than 1 g/cm{sup 3}. These properties are the pressure, internal energy, heat capacity, and the electronic transport coefficients (electrical conductivity, thermal conductivity, and thermal power). The thermodynamic values have been calculated by means of the chemical model, which also allows one to obtain the ionic composition of considered plasma. The composition has been used to calculate the electronic transport coefficients within the relaxation time approximation. The results of the present investigation have been compared with the calculations of other researchers and available data ofmore » measurements.« less

Ultraslow dielectric relaxation process in supercooled polyhydric alcohols

NASA Astrophysics Data System (ADS)

Yomogida, Yoshiki; Minoguchi, Ayumi; Nozaki, Ryusuke

2006-04-01

Complex permittivity was obtained on glycerol, xylitol, sorbitol and sorbitol-xylitol mixtures in the supercooled liquid state in the frequency range between 10μHz and 500MHz at temperatures near and above the glass transition temperature. For all the materials, a dielectric relaxation process was observed in addition to the well-known structural α and Johari-Goldstein β relaxation process [G. P. Johari and M. Goldstein, J. Chem. Phys. 53, 2372 (1970)]. The relaxation time for the new process is always larger than that for the α process. The relaxation time shows non-Arrhenius temperature dependence with correlation to the behavior of the α process and it depends on the molecular size systematically. The dielectric relaxation strength for the new process shows the effect of thermal history and decreases exponentially with time at a constant temperature. It can be considered that a nonequilibrium dynamics causes the new process.

Relaxation-phenomena in LiAl/FeS-cells

NASA Astrophysics Data System (ADS)

Borger, W.; Kappus, W.; Panesar, H. S.

A theoretical model of the capacity of strongly relaxing electrochemical systems is applied to the LiAl/FeS system. Relaxation phenomena in LiAl and FeS electrodes can be described by this model. Experimental relaxation data indicate that lithium transport through the alpha-LiAl layer to the particle surface is the capacity limiting process at high discharge current density in the LiAl electrode in LiCl-KCl and LiF-LiCl-LiBr mixtures. Strong relaxation is observed in the FeS electrode with LiCl-KCl electrolyte caused by lithium concentration gradients and precipitation of KCl in the pores.

Left-handed transmission in a simple cut-wire pair structure

NASA Astrophysics Data System (ADS)

Tung, Nguyen Thanh; Thuy, Vu Tran Thanh; Park, Jin Woo; Rhee, Joo Yull; Lee, YoungPak

2010-01-01

It is well known that, together with the plasma behavior of continuous wires, the use of cut-wire pair as a metamagnetic component is to drive the negative permeability in the left-handed combined structure. In this study, we have investigated a strange left-handed transmission in a metamaterial consisting of only conventional cut-wire pair structure without additional adjustment. It is shown that the observed left-handed behavior, which occurs at a frequency three times higher than that for the combined structure, originates from the fundamental negative permittivity provided by the symmetric resonant mode and a negative permeability by the third-order asymmetric resonance. Our results would simplify extremely the fabricating procedure, especially, for terahertz regime as well as reveal many possibilities to design optical devices based on the electromagnetic responses of cut-wire structure.

Developing a Learning Algorithm-Generated Empirical Relaxer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitchell, Wayne; Kallman, Josh; Toreja, Allen

2016-03-30

One of the main difficulties when running Arbitrary Lagrangian-Eulerian (ALE) simulations is determining how much to relax the mesh during the Eulerian step. This determination is currently made by the user on a simulation-by-simulation basis. We present a Learning Algorithm-Generated Empirical Relaxer (LAGER) which uses a regressive random forest algorithm to automate this decision process. We also demonstrate that LAGER successfully relaxes a variety of test problems, maintains simulation accuracy, and has the potential to significantly decrease both the person-hours and computational hours needed to run a successful ALE simulation.

The development and stability of non-thermal plasma in space

NASA Astrophysics Data System (ADS)

Kasper, Justin

2017-10-01

This talk will review our understanding of non-thermal ion and electron velocity distribution functions (VDFs) in space plasma, with a focus on pressure anisotropy and unequal temperatures in the solar wind and corona. Under typical solar wind plasma conditions, which are common for a range of astrophysical plasmas, relaxation processes such as Coulomb collisions are sufficiently slow compared to interactions between particles and electromagnetic fluctuations that ion and electron VDFs can depart significantly from the classical Maxwell-Boltzmann distribution and maintain these non-thermal features for times greater than the dynamical scales of the system. These non-thermal properties of the plasma are very important as they can significantly modify aspects of the plasma such as heat flux, susceptibility to kinetic instabilities, and interaction with waves and turbulence. Major open questions in the field will be reviewed, along with current and planned observational capabilities of instruments on spacecraft such as Wind and the upcoming Parker Solar Probe, with an eye to potential crossover with laboratory plasma experiments.

Escape time, relaxation, and sticky states of a softened Henon-Heiles model: Low-frequency vibrational mode effects and glass relaxation

NASA Astrophysics Data System (ADS)

Toledo-Marín, J. Quetzalcóatl; Naumis, Gerardo G.

2018-04-01

Here we study the relaxation of a chain consisting of three masses joined by nonlinear springs and periodic conditions when the stiffness is weakened. This system, when expressed in their normal coordinates, yields a softened Henon-Heiles system. By reducing the stiffness of one low-frequency vibrational mode, a faster relaxation is enabled. This is due to a reduction of the energy barrier heights along the softened normal mode as well as for a widening of the opening channels of the energy landscape in configurational space. The relaxation is for the most part exponential, and can be explained by a simple flux equation. Yet, for some initial conditions the relaxation follows as a power law, and in many cases there is a regime change from exponential to power-law decay. We pinpoint the initial conditions for the power-law decay, finding two regions of sticky states. For such states, quasiperiodic orbits are found since almost for all components of the initial momentum orientation, the system is trapped inside two pockets of configurational space. The softened Henon-Heiles model presented here is intended as the simplest model in order to understand the interplay of rigidity, nonlinear interactions and relaxation for nonequilibrium systems such as glass-forming melts or soft matter. Our softened system can be applied to model β relaxation in glasses and suggest that local reorientational jumps can have an exponential and a nonexponential contribution for relaxation, the latter due to asymmetric molecules sticking in cages for certain orientations.

Gaussian signal relaxation around spin echoes: Implications for precise reversible transverse relaxation quantification of pulmonary tissue at 1.5 and 3 Tesla.

PubMed

Zapp, Jascha; Domsch, Sebastian; Weingärtner, Sebastian; Schad, Lothar R

2017-05-01

To characterize the reversible transverse relaxation in pulmonary tissue and to study the benefit of a quadratic exponential (Gaussian) model over the commonly used linear exponential model for increased quantification precision. A point-resolved spectroscopy sequence was used for comprehensive sampling of the relaxation around spin echoes. Measurements were performed in an ex vivo tissue sample and in healthy volunteers at 1.5 Tesla (T) and 3 T. The goodness of fit using χred2 and the precision of the fitted relaxation time by means of its confidence interval were compared between the two relaxation models. The Gaussian model provides enhanced descriptions of pulmonary relaxation with lower χred2 by average factors of 4 ex vivo and 3 in volunteers. The Gaussian model indicates higher sensitivity to tissue structure alteration with increased precision of reversible transverse relaxation time measurements also by average factors of 4 ex vivo and 3 in volunteers. The mean relaxation times of the Gaussian model in volunteers are T2,G' = (1.97 ± 0.27) msec at 1.5 T and T2,G' = (0.83 ± 0.21) msec at 3 T. Pulmonary signal relaxation was found to be accurately modeled as Gaussian, providing a potential biomarker T2,G' with high sensitivity. Magn Reson Med 77:1938-1945, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Milrinone Relaxes Pulmonary Veins in Guinea Pigs and Humans

PubMed Central

Rieg, Annette D.; Suleiman, Said; Perez-Bouza, Alberto; Braunschweig, Till; Spillner, Jan W.; Schröder, Thomas; Verjans, Eva; Schälte, Gereon; Rossaint, Rolf; Uhlig, Stefan; Martin, Christian

2014-01-01

Introduction The phosphodiesterase-III inhibitor milrinone improves ventricular contractility, relaxes pulmonary arteries and reduces right ventricular afterload. Thus, it is used to treat heart failure and pulmonary hypertension (PH). However, its action on pulmonary veins (PVs) is not defined, although particularly PH due to left heart disease primarily affects the pulmonary venous bed. We examined milrinone-induced relaxation in PVs from guinea pigs (GPs) and humans. Material and Methods Precision-cut lung slices (PCLS) were prepared from GPs or from patients undergoing lobectomy. Milrinone-induced relaxation was studied by videomicroscopy in naïve PVs and in PVs pre-constricted with the ETA-receptor agonist BP0104. Baseline luminal area was defined as 100%. Intracellular cAMP was measured by ELISA and milrinone-induced changes of segmental vascular resistances were studied in the GP isolated perfused lung (IPL). Results In the IPL (GP), milrinone (10 µM) lowered the postcapillary resistance of pre-constricted vessels. In PCLS (GP), milrinone relaxed naïve and pre-constricted PVs (120%) and this relaxation was attenuated by inhibition of protein kinase G (KT 5823), adenyl cyclase (SQ 22536) and protein kinase A (KT 5720), but not by inhibition of NO-synthesis (L-NAME). In addition, milrinone-induced relaxation was dependent on the activation of KATP-, BKCa 2+- and Kv-channels. Human PVs also relaxed to milrinone (121%), however only if pre-constricted. Discussion Milrinone relaxes PVs from GPs and humans. In GPs, milrinone-induced relaxation is based on KATP-, BKCa 2+- and Kv-channel-activation and on cAMP/PKA/PKG. The relaxant properties of milrinone on PVs lead to reduced postcapillary resistance and hydrostatic pressures. Hence they alleviate pulmonary edema and suggest beneficial effects of milrinone in PH due to left heart disease. PMID:24498166

Milrinone relaxes pulmonary veins in guinea pigs and humans.

PubMed

Rieg, Annette D; Suleiman, Said; Perez-Bouza, Alberto; Braunschweig, Till; Spillner, Jan W; Schröder, Thomas; Verjans, Eva; Schälte, Gereon; Rossaint, Rolf; Uhlig, Stefan; Martin, Christian

2014-01-01

The phosphodiesterase-III inhibitor milrinone improves ventricular contractility, relaxes pulmonary arteries and reduces right ventricular afterload. Thus, it is used to treat heart failure and pulmonary hypertension (PH). However, its action on pulmonary veins (PVs) is not defined, although particularly PH due to left heart disease primarily affects the pulmonary venous bed. We examined milrinone-induced relaxation in PVs from guinea pigs (GPs) and humans. Precision-cut lung slices (PCLS) were prepared from GPs or from patients undergoing lobectomy. Milrinone-induced relaxation was studied by videomicroscopy in naïve PVs and in PVs pre-constricted with the ETA-receptor agonist BP0104. Baseline luminal area was defined as 100%. Intracellular cAMP was measured by ELISA and milrinone-induced changes of segmental vascular resistances were studied in the GP isolated perfused lung (IPL). In the IPL (GP), milrinone (10 µM) lowered the postcapillary resistance of pre-constricted vessels. In PCLS (GP), milrinone relaxed naïve and pre-constricted PVs (120%) and this relaxation was attenuated by inhibition of protein kinase G (KT 5823), adenyl cyclase (SQ 22536) and protein kinase A (KT 5720), but not by inhibition of NO-synthesis (L-NAME). In addition, milrinone-induced relaxation was dependent on the activation of K ATP-, BK Ca (2+)- and Kv-channels. Human PVs also relaxed to milrinone (121%), however only if pre-constricted. Milrinone relaxes PVs from GPs and humans. In GPs, milrinone-induced relaxation is based on K ATP-, BK Ca (2+)- and Kv-channel-activation and on cAMP/PKA/PKG. The relaxant properties of milrinone on PVs lead to reduced postcapillary resistance and hydrostatic pressures. Hence they alleviate pulmonary edema and suggest beneficial effects of milrinone in PH due to left heart disease.

The WHISPER Relaxation Sounder and the CLUSTER Active Archive

NASA Astrophysics Data System (ADS)

Trotignon, J. G.; Décréau, P. M. E.; Rauch, J. L.; Vallières, X.; Rochel, A.; Kougblénou, S.; Lointier, G.; Facskó, G.; Canu, P.; Darrouzet, F.; Masson, A.

The Waves of HIgh frequency and Sounder for Probing of Electron density by Relaxation (WHISPER) instrument is part of the Wave Experiment Consortium (WEC) of the CLUSTER mission. With the help of the long double sphere antennae of the Electric Field and Wave (EFW) instrument and the Digital Wave Processor (DWP), it delivers active (sounding) and natural (transmitter off) electric field spectra, respectively from 4 to 82 kHz, and from 2 to 80 kHz. These frequency ranges have been chosen to include the electron plasma frequency, which is closely related to the total electron density, in most of the regions encountered by the CLUSTER spacecraft. Presented here is an overview of the WHISPER data products available in the CLUSTER Active Archive (CAA). The instrument and its performance are first recalled. The way the WHISPER products are obtained is then described, with particular attention being paid to the density determination. Both sounding and natural measurements are commonly used in this process, which depends on the ambient plasma regime. This is illustrated using drawings similar to the Bryant plots commonly used in the CLUSTER master science plan. These give a clear overview of typical density values and the parts of the orbits where they are obtained. More information on the applied software or on the quality/reliability of the density determination can also be highlighted.

Multiscale Relaxation Dynamics in Ultrathin Metallic Glass-Forming Films

NASA Astrophysics Data System (ADS)

Bi, Q. L.; Lü, Y. J.; Wang, W. H.

2018-04-01

The density layering phenomenon originating from a free surface gives rise to the layerlike dynamics and stress heterogeneity in ultrathin Cu-Zr glassy films, which facilitates the occurrence of multistep relaxations in the timescale of computer simulations. Taking advantage of this condition, we trace the relaxation decoupling and evolution with temperature simply via the intermediate scattering function. We show that the β relaxation hierarchically follows fast and slow modes in films, and there is a β -relaxation transition as the film is cooled close to the glass transition. We provide the direct observation of particle motions responsible for the β relaxation and reveal the dominant mechanism varying from the thermal activated to the cooperative jumps across the transition.

Stress Relaxation in Tensile Deformation of 304 Stainless Steel

NASA Astrophysics Data System (ADS)

Li, Xifeng; Li, Jiaojiao; Ding, Wei; Zhao, Shuangjun; Chen, Jun

2017-02-01

Improved ductility by stress relaxation has been reported in different kinds of steels. The influence of stress relaxation and its parameters on the ductility of 304 stainless steel has not been established so far. Stress relaxation behavior during tensile tests at different strain rates is studied in 304 stainless steel. It is observed that stress relaxation can obviously increase the elongation of 304 stainless steel in all cases. The elongation improvement of interrupted tension reaches to 14.9% compared with monotonic tension at 0.05 s-1. Contradicting with the published results, stress drop during stress relaxation increases with strain at all strain rates. It is related with dislocation motion velocity variation and martensitic transformation.

Relaxed Poisson cure rate models.

PubMed

Rodrigues, Josemar; Cordeiro, Gauss M; Cancho, Vicente G; Balakrishnan, N

2016-03-01

The purpose of this article is to make the standard promotion cure rate model (Yakovlev and Tsodikov, ) more flexible by assuming that the number of lesions or altered cells after a treatment follows a fractional Poisson distribution (Laskin, ). It is proved that the well-known Mittag-Leffler relaxation function (Berberan-Santos, ) is a simple way to obtain a new cure rate model that is a compromise between the promotion and geometric cure rate models allowing for superdispersion. So, the relaxed cure rate model developed here can be considered as a natural and less restrictive extension of the popular Poisson cure rate model at the cost of an additional parameter, but a competitor to negative-binomial cure rate models (Rodrigues et al., ). Some mathematical properties of a proper relaxed Poisson density are explored. A simulation study and an illustration of the proposed cure rate model from the Bayesian point of view are finally presented. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultrafast energy relaxation in single light-harvesting complexes

DOE PAGES

Maly, Pavel; Gruber, J. Michael; Cogdell, Richard J.; ...

2016-02-22

Energy relaxation in light-harvesting complexes has been extensively studied by various ultrafast spectroscopic techniques, the fastest processes being in the sub–100-fs range. At the same time, much slower dynamics have been observed in individual complexes by single-molecule fluorescence spectroscopy (SMS). In this work, we use a pump–probe-type SMS technique to observe the ultrafast energy relaxation in single light-harvesting complexes LH2 of purple bacteria. After excitation at 800 nm, the measured relaxation time distribution of multiple complexes has a peak at 95 fs and is asymmetric, with a tail at slower relaxation times. When tuning the excitation wavelength, the distribution changesmore » in both its shape and position. The observed behavior agrees with what is to be expected from the LH2 excited states structure. As we show by a Redfield theory calculation of the relaxation times, the distribution shape corresponds to the expected effect of Gaussian disorder of the pigment transition energies. By repeatedly measuring few individual complexes for minutes, we find that complexes sample the relaxation time distribution on a timescale of seconds. Furthermore, by comparing the distribution from a single long-lived complex with the whole ensemble, we demonstrate that, regarding the relaxation times, the ensemble can be considered ergodic. Lastly, our findings thus agree with the commonly used notion of an ensemble of identical LH2 complexes experiencing slow random fluctuations.« less

Ultrafast energy relaxation in single light-harvesting complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maly, Pavel; Gruber, J. Michael; Cogdell, Richard J.

Energy relaxation in light-harvesting complexes has been extensively studied by various ultrafast spectroscopic techniques, the fastest processes being in the sub–100-fs range. At the same time, much slower dynamics have been observed in individual complexes by single-molecule fluorescence spectroscopy (SMS). In this work, we use a pump–probe-type SMS technique to observe the ultrafast energy relaxation in single light-harvesting complexes LH2 of purple bacteria. After excitation at 800 nm, the measured relaxation time distribution of multiple complexes has a peak at 95 fs and is asymmetric, with a tail at slower relaxation times. When tuning the excitation wavelength, the distribution changesmore » in both its shape and position. The observed behavior agrees with what is to be expected from the LH2 excited states structure. As we show by a Redfield theory calculation of the relaxation times, the distribution shape corresponds to the expected effect of Gaussian disorder of the pigment transition energies. By repeatedly measuring few individual complexes for minutes, we find that complexes sample the relaxation time distribution on a timescale of seconds. Furthermore, by comparing the distribution from a single long-lived complex with the whole ensemble, we demonstrate that, regarding the relaxation times, the ensemble can be considered ergodic. Lastly, our findings thus agree with the commonly used notion of an ensemble of identical LH2 complexes experiencing slow random fluctuations.« less

Nonlinear dynamics of two-dimensional electron plasma

NASA Astrophysics Data System (ADS)

Matthaeus, W. H.; Servidio, S.; Rodgers, D.; Montgomery, D. C.; Mitchell, T.; Aziz, T.

2008-12-01

The turbulent relaxation of a magnetized two dimensional (2D) electron plasma experiment has been investigated. The nonlinear dynamics of this kind of plasma can be approximated in leading order as a 2D guiding center fluid, which behaves in complete analogy to the 2D Euler equations. Departures form this analogy include dissipative and three dimensional effects. Here we examine the characteristics of the experimental data and compare these to solutions of 2D dissipative Navier Stokes equations. We find, perhaps remarkably, that the two systems show similar time histories, including increase of entropy and decrease of the ratio of enstrophy-to-energy. Attempts to re-examine the theories of selective decay and maximum entropy are reviewed, including difficulties that are peculiar to the one species case. Distinguishing between these possibilities has potentially important implications for self organizing systems in space and astrophysical plasmas, including the ionosphere and solar corona. Research supported by DOE grant DE- FG02-06ER54853.

Comparison of different cardiac relaxation indices.

PubMed

Alipov, N N; Izrail'tyan, I M; Sokolov, A V; Trubetskaya, L V; Kuznetsova, T E

2001-05-01

Sensitivity (response to epinephrine infusion) and specificity (response to changes in pre- and afterload) of some cardiac relaxation indices were compared in acute experiments on cats treated with ganglionic blocker arfonad. Some new indices proposed by us provide better characteristics than widely used relaxation time constant (t) and maximum first derivative of the left ventricular pressure (-dP/dt)max.

Plasma anisotropy and the radial particle flux in a rippled tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hazeltine, R. D.

We show that an often used relation between the radial particle flux and the divergence of the gyrotropic stress is an algebraic identity, unrelated to momentum conservation. Our calculation is completely general with regard to toroidal geometry and plasma collisionality. The result bears on the role of anisotropy in momentum relaxation and also clarifies certain methodological issues.

Dielectric relaxation of high-k oxides

PubMed Central

2013-01-01

Frequency dispersion of high-k dielectrics was observed and classified into two parts: extrinsic cause and intrinsic cause. Frequency dependence of dielectric constant (dielectric relaxation), that is the intrinsic frequency dispersion, could not be characterized before considering the effects of extrinsic frequency dispersion. Several mathematical models were discussed to describe the dielectric relaxation of high-k dielectrics. For the physical mechanism, dielectric relaxation was found to be related to the degree of polarization, which depended on the structure of the high-k material. It was attributed to the enhancement of the correlations among polar nanodomain. The effect of grain size for the high-k materials' structure mainly originated from higher surface stress in smaller grain due to its higher concentration of grain boundary. PMID:24180696

Momentum dependence in pair production by an external field

NASA Astrophysics Data System (ADS)

Asakawa, M.

1992-08-01

The transverse and the longitudinal momentum dependences of the pair production under an adiabatically exerted uniform abelian external field are calculated with their importance in models for the production of quark-gluon plasma in ultrarelativistic heavy ion collisions in mind. The importance of the initial condition is revealed. We show that superposition of acceleration by the external field and barrier penetration is reflected in the longitudinal momentum dependence. The peculiar nature of the boost invariant system which is expected to be approximately realized in ultrarelativistic nuclear collisions is pointed out.

The effects of music relaxation and muscle relaxation techniques on sleep quality and emotional measures among individuals with posttraumatic stress disorder

PubMed Central

Blanaru, Monica; Bloch, Boaz; Vadas, Limor; Arnon, Zahi; Ziv, Naomi; Kremer, Ilana; Haimov, Iris

2012-01-01

Posttraumatic stress disorder (PTSD), an anxiety disorder with lifetime prevalence of 7.8%, is characterized by symptoms that develop following exposure to traumatic life events and that cause an immediate experience of intense fear, helplessness or horror. PTSD is marked by recurrent nightmares typified by the recall of intrusive experiences and by extended disturbance throughout sleep. Individuals with PTSD respond poorly to drug treatments for insomnia. The disadvantages of drug treatment for insomnia underline the importance of non-pharmacological alternatives. Thus, the present study had three aims: first, to compare the efficiency of two relaxation techniques (muscular relaxation and progressive music relaxation) in alleviating insomnia among individuals with PTSD using both objective and subjective measures of sleep quality; second, to examine whether these two techniques have different effects on psychological indicators of PTSD, such as depression and anxiety; and finally, to examine how initial PTSD symptom severity and baseline emotional measures are related to the efficiency of these two relaxation methods. Thirteen PTSD patients with no other major psychiatric or neurological disorders participated in the study. The study comprised one seven-day running-in, no-treatment period, followed by two seven-day experimental periods. The treatments constituted either music relaxation or muscle relaxation techniques at desired bedtime. These treatments were randomly assigned. During each of these three experimental periods, subjects' sleep was continuously monitored with a wrist actigraph (Ambulatory Monitoring, Inc.), and subjects were asked to fill out several questionnaires concerned with a wide spectrum of issues, such as sleep, depression, and anxiety. Analyses revealed a significant increase in objective and subjective sleep efficiency and a significant reduction in depression level following music relaxation. Moreover, following music relaxation, a highly

Electron-impact vibrational relaxation in high-temperature nitrogen

NASA Technical Reports Server (NTRS)

Lee, Jong-Hun

1992-01-01

Vibrational relaxation process of N2 molecules by electron-impact is examined for the future planetary entry environments. Multiple-quantum transitions from excited states to higher/lower states are considered for the electronic ground state of the nitrogen molecule N2 (X 1Sigma-g(+)). Vibrational excitation and deexcitation rate coefficients obtained by computational quantum chemistry are incorporated into the 'diffusion model' to evaluate the time variations of vibrational number densities of each energy state and total vibrational energy. Results show a non-Boltzmann distribution of number densities at the earlier stage of relaxation, which in turn suppresses the equilibrium process but affects little the time variation of total vibrational energy. An approximate rate equation and a corresponding relaxation time from the excited states, compatible with the system of flow conservation equations, are derived. The relaxation time from the excited states indicates the weak dependency of the initial vibrational temperature. The empirical curve-fit formula for the improved e-V relaxation time is obtained.

Bolt clampup relaxation in a graphite/epoxy laminate

NASA Technical Reports Server (NTRS)

Shivakumar, K. N.; Crews, J. H., Jr.

1982-01-01

A simple bolted joint was analyzed to calculate bolt clampup relaxation for a graphite/epoxy (T300/5208) laminate. A viscoelastic finite element analysis of a double-lap joint with a steel bolt was conducted. Clampup forces were calculated for various steady-state temperature-moisture conditions using a 20-year exposure duration. The finite element analysis predicted that clampup forces relax even for the room-temperature-dry condition. The relaxations were 8, 13, 20, and 30 percent for exposure durations of 1 day, 1 month, 1 year, and 20 years, respectively. As expected, higher temperatures and moisture levels each increased the relaxation rate. The combined viscoelastic effects of steady-state temperature and moisture appeared to be additive. From the finite-element analysis, a simple equation was developed for clampup force relaxation. This generalized equation was used to calculate clampup forces for the same temperature-moisture conditions as used in the finite-element analysis. The two sets of calculated results agreed well.

Aging of Johari-Goldstein Relaxation in Structural Glasses

NASA Astrophysics Data System (ADS)

Yardimci, Hasan; Leheny, Robert L.

2006-03-01

Using frequency-dependent dielectric susceptibility measurements we characterize the aging in two supercooled liquids, sorbitol and xylitol, below their calorimetric glass transition temperatures, Tg. In addition to the alpha relaxation that tracks the structural dynamics, the susceptibilities of both liquids possess a secondary Johari-Goldstein relaxation at higher frequencies. Following a quench below Tg, the susceptibility slowly approaches equilibrium behavior. For both liquids, features of the Johari-Goldstein relaxation display a dependence on the time since the quench, or aging time, that is very similar to the age dependence of the alpha peak. However, one can not assign a single fictive temperature to both the alpha and Johari-Goldstein relaxations. For example, the peak frequency of the Johari-Goldstein relaxation remains constant during aging for sorbitol while it increases with age for xylitol, inconsistent with a decreasing fictive temperature. This behavior contrasts with that of the high frequency tail of the alpha peak whose shape and position track the aging of the main part of the peak.

Slow relaxation of cascade-induced defects in Fe

DOE PAGES

Béland, Laurent Karim; Osetsky, Yuri N.; Stoller, Roger E.; ...

2015-02-17

On-the-fly kinetic Monte Carlo (KMC) simulations are performed to investigate slow relaxation of non-equilibrium systems. Point defects induced by 25 keV cascades in α -Fe are shown to lead to a characteristic time-evolution, described by the replenish and relax mechanism. Then, we produce an atomistically-based assessment of models proposed to explain the slow structural relaxation by focusing on the aggregation of 50 vacancies and 25 self-interstital atoms (SIA) in 10-lattice-parameter α-Fe boxes, two processes that are closely related to cascade annealing and exhibit similar time signature. Four atomistic effects explain the timescales involved in the evolution: defect concentration heterogeneities, concentration-enhancedmore » mobility, cluster-size dependent bond energies and defect-induced pressure. In conclusion, these findings suggest that the two main classes of models to explain slow structural relaxation, the Eyring model and the Gibbs model, both play a role to limit the rate of relaxation of these simple point-defect systems.« less

Relaxation Techniques for Handicapped Children: A Review of Literature.

ERIC Educational Resources Information Center

Zipkin, Dvora

1985-01-01

The paper discusses four major relaxation training approaches used with handicapped children: progressive muscle relaxation, biofeedback, yoga, and mental relaxation, which includes guided fantasy, imagery, and meditation. Descriptions of these techniques, the effects of their use with various populations, and reviews of recent studies of their…

Relaxation Training: Its Usefulness in the Middle School Curriculum.

ERIC Educational Resources Information Center

Matthews, Doris B.

A study examined multiple outcomes of relaxation training simultaneously in seventh grade classrooms. "Project Relaxation" measured cognitive (achievement) and affective (discipline, attendance, tardiness, and self-concept) changes with a program of relaxation training for 532 seventh grade students in 10 private and public middle schools in South…

Relaxation effect of abacavir on rat basilar arteries.

PubMed

Li, Rachel Wai Sum; Yang, Cui; Chan, Shun Wan; Hoi, Maggie Pui Man; Lee, Simon Ming Yuen; Kwan, Yiu Wa; Leung, George Pak Heng

2015-01-01

The use of abacavir has been linked with increased cardiovascular risk in patients with human immunodeficiency virus infection; however, the mechanism involved remains unclear. We hypothesize that abacavir may impair endothelial function. In addition, based on the structural similarity between abacavir and adenosine, we propose that abacavir may affect vascular contractility through endogenous adenosine release or adenosine receptors in blood vessels. The relaxation effect of abacavir on rat basilar arteries was studied using the myograph technique. Cyclic GMP and AMP levels were measured by immunoassay. The effects of abacavir on nucleoside transporters were studied using radiolabeled nucleoside uptake experiments. Ecto-5' nucleotidase activity was determined by measuring the generation of inorganic phosphate using adenosine monophosphate as the substrate. Abacavir induced the relaxation of rat basilar arteries in a concentration-dependent manner. This relaxation was abolished when endothelium was removed. In addition, the relaxation was diminished by the nitric oxide synthase inhibitor, L-NAME, the guanylyl cyclase inhibitor, ODQ, and the protein kinase G inhibitor, KT5820. Abacavir also increased the cGMP level in rat basilar arteries. Abacavir-induced relaxation was also abolished by adenosine A2 receptor blockers. However, abacavir had no effect on ecto-5' nucleotidase and nucleoside transporters. Short-term and long-term treatment of abacavir did not affect acetylcholine-induced relaxation in rat basilar arteries. Abacavir induces acute endothelium-dependent relaxation of rat basilar arteries, probably through the activation of adenosine A2 receptors in endothelial cells, which subsequently leads to the release of nitric oxide, resulting in activation of the cyclic guanosine monophosphate/protein kinase G-dependent pathway in vascular smooth muscle cells. It is speculated that abacavir-induced cardiovascular risk may not be related to endothelial dysfunction

Ultra-intense Pair Creation using the Texas Petawatt Laser and Applications

NASA Astrophysics Data System (ADS)

Liang, Edison; Henderson, Alexander; Clarke, Taylor; Lo, Willie; Chaguine, Petr; Dyer, Gilliss; Riley, Nathan; Serratto, Kristina; Donovan, Michael; Ditmire, Todd

2014-10-01

Pair plasmas and intense gamma-ray sources are ubiquitous in the high-energy universe, from pulser winds to gamma-ray bursts (GRB). Their study can be greatly enhanced if such sources can be recreated in the laboratory under controlled conditions. In 2012 and 2013, a joint Rice-University of Texas team performed over 130 laser shots on thick gold and platinum targets using the 100 Joule Texas Petawatt Laser in Austin. The laser intensity of many shots exceeded 1021 W.cm-2 with pulses as short as 130 fs. These experiments probe a new extreme regime of ultra-intense laser - high-Z solid target interactions never achieved before. In addition to creating copious pairs with the highest density (>1015/cc) and emergent e +/e- ratio exceeding 20% in many shots, these experiments also created the highest density multi-MeV gamma-rays, comparable in absolute numbers to those found inside a gamma-ray burst (GRB). Potential applications of such intense pair and gamma-ray sources to laboratory astrophysics and innovative technologies will be discussed. Work supported by DOE HEDLP program.

Determination of HF artificial ionospheric turbulence characteristics using comparison of calculated plasma wave decay rates with the measured see decay rates

NASA Astrophysics Data System (ADS)

Grach, Savely; Bareev, Denis; Gavrilenko, Vladimir; Sergeev, Evgeny

Damping rates of plasma waves with ω ˜ ωuh (ω is the plasma wave frequency, ωuh is the upper hybrid frequency) were calculated for frequencies close to and distant from the double resonance where ωuh ˜ nωce (ωce is the electron cyclotron frequency, n=4,5 are the gyroharmonic num-bers). The calculations were performed numerically on the base of full plasma wave dispersion relation not restricted by both the 'long wave limit' and 'short wave limit', i.e. a fulfillment of the inequalities |∆| |k |vTe and |∆| |k |vTe was not required. Here ∆ = ω - nωce , vTe = (Te /me )1/2 is the electron thermal velocity and k is the projection of the wave vector onto the magnetic field direction. It is shown that the plasma wave damping rates do not differ noticeably from ones calculated under the long wave and short wave limits. The results obtained are compared with the data of the relaxation of the stimulated electromagnetic emission (SEE) after the pump wave turn off, which demonstrate an essential decrease of the relaxation time near 4th electron gyroharmonic, so far as the SEE relaxation is attributed to the damping of plasma waves responsible for the SEE generation. The comparison allows to determine characteristics of plasma waves mostly contributing to the SEE generation, such as wave numbers and the angles between the wave vectors and geomagnetic field, and the altitude region of the SEE source. The dependence of the decay rate on ∆ can be applied also to interpretation of the SEE spectral shape at different pump frequencies near gyroharmonics. The work is supported by RFBR grants 10-02-00642, 09-02-01150 and Federal Special-purpose Program "Scientific and pedagogical personnel of innovative Russia".

Le Chatelier's principle with multiple relaxation channels

NASA Astrophysics Data System (ADS)

Gilmore, R.; Levine, R. D.

1986-05-01

Le Chatelier's principle is discussed within the constrained variational approach to thermodynamics. The formulation is general enough to encompass systems not in thermal (or chemical) equilibrium. Particular attention is given to systems with multiple constraints which can be relaxed. The moderation of the initial perturbation increases as additional constraints are removed. This result is studied in particular when the (coupled) relaxation channels have widely different time scales. A series of inequalities is derived which describes the successive moderation as each successive relaxation channel opens up. These inequalities are interpreted within the metric-geometry representation of thermodynamics.

Slow relaxation in weakly open rational polygons.

PubMed

Kokshenev, Valery B; Vicentini, Eduardo

2003-07-01

The interplay between the regular (piecewise-linear) and irregular (vertex-angle) boundary effects in nonintegrable rational polygonal billiards (of m equal sides) is discussed. Decay dynamics in polygons (of perimeter P(m) and small opening Delta) is analyzed through the late-time survival probability S(m) approximately equal t(-delta). Two distinct slow relaxation channels are established. The primary universal channel exhibits relaxation of regular sliding orbits, with delta=1. The secondary channel is given by delta>1 and becomes open when m>P(m)/Delta. It originates from vertex order-disorder dual effects and is due to relaxation of chaoticlike excitations.

Communication: Relaxation-limited electronic currents in extended reservoir simulations

NASA Astrophysics Data System (ADS)

Gruss, Daniel; Smolyanitsky, Alex; Zwolak, Michael

2017-10-01

Open-system approaches are gaining traction in the simulation of charge transport in nanoscale and molecular electronic devices. In particular, "extended reservoir" simulations, where explicit reservoir degrees of freedom are present, allow for the computation of both real-time and steady-state properties but require relaxation of the extended reservoirs. The strength of this relaxation, γ, influences the conductance, giving rise to a "turnover" behavior analogous to Kramers turnover in chemical reaction rates. We derive explicit, general expressions for the weak and strong relaxation limits. For weak relaxation, the conductance increases linearly with γ and every electronic state of the total explicit system contributes to the electronic current according to its "reduced" weight in the two extended reservoir regions. Essentially, this represents two conductors in series—one at each interface with the implicit reservoirs that provide the relaxation. For strong relaxation, a "dual" expression-one with the same functional form-results, except now proportional to 1/γ and dependent on the system of interest's electronic states, reflecting that the strong relaxation is localizing electrons in the extended reservoirs. Higher order behavior (e.g., γ2 or 1/γ2) can occur when there is a gap in the frequency spectrum. Moreover, inhomogeneity in the frequency spacing can give rise to a pseudo-plateau regime. These findings yield a physically motivated approach to diagnosing numerical simulations and understanding the influence of relaxation, and we examine their occurrence in both simple models and a realistic, fluctuating graphene nanoribbon.

Body Mass Index, Metabolic Factors, and Striatal Activation During Stressful and Neutral-Relaxing States: An fMRI Study

PubMed Central

Jastreboff, Ania M; Potenza, Marc N; Lacadie, Cheryl; Hong, Kwangik A; Sherwin, Robert S; Sinha, Rajita

2011-01-01

Stress is associated with alterations in neural motivational-reward pathways in the ventral striatum (VS), hormonal/metabolic changes, and weight increases. The relationship between these different factors is not well understood. We hypothesized that body mass index (BMI) status and hormonal/metabolic factors would be associated with VS activation. We used functional magnetic resonance imaging (fMRI) to compare brain responses of overweight and obese (OW/OB: BMI ⩾25 kg/m2: N=27) individuals with normal weight (NW: BMI<18.5–24.9 kg/m2: N=21) individuals during exposure to personalized stress, alcohol cue, and neutral-relaxing situations using a validated, autobiographical, script-driven, guided-imagery paradigm. Metabolic factors, including fasting plasma glucose (FPG), insulin, and leptin, were examined for their association with VS activation. Consistent with previous studies, stress and alcohol cue exposure each increased activity in cortico-limbic regions. Compared with NW individuals, OW/OB individuals showed greater VS activation in the neutral-relaxing and stress conditions. FPG was correlated with VS activation. Significant associations between VS activation and metabolic factors during stress and relaxation suggest the involvement of metabolic factors in striatal dysfunction in OW/OB individuals. This relationship may contribute to non-homeostatic feeding in obesity. PMID:21048702

Broadband spectral analysis of non-Debye dielectric relaxation in percolating heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tuncer, Enis; Bellatar, J; Achour, M E

2011-01-01

In this study, the main features of dielectric relaxation in carbon black epoxy composites are discussed using several types of complementary modelling (i.e., the Cole-Cole phenomenological equation, Jonscher s universal dielectric response, and an approach that relies on a continuous distribution of relaxation times). These methods of characterizing the relaxation were conducted below Tg. Through the numerical model we can obtain the characteristic effective relaxation time and exponents straightforwardly. However, the true relaxation spectrum can be obtained from the distribution of relaxation times calculated from the complex dielectric permittivity. Over the compositional range explored, relaxation occurs by a Vogel-Tammam-Fulcher-like temperaturemore » dependence within the limits of experimental accuracy.« less

Substrate stress relaxation regulates cell spreading

NASA Astrophysics Data System (ADS)

Chaudhuri, Ovijit; Gu, Luo; Darnell, Max; Klumpers, Darinka; Bencherif, Sidi A.; Weaver, James C.; Huebsch, Nathaniel; Mooney, David J.

2015-02-01

Studies of cellular mechanotransduction have converged upon the idea that cells sense extracellular matrix (ECM) elasticity by gauging resistance to the traction forces they exert on the ECM. However, these studies typically utilize purely elastic materials as substrates, whereas physiological ECMs are viscoelastic, and exhibit stress relaxation, so that cellular traction forces exerted by cells remodel the ECM. Here we investigate the influence of ECM stress relaxation on cell behaviour through computational modelling and cellular experiments. Surprisingly, both our computational model and experiments find that spreading for cells cultured on soft substrates that exhibit stress relaxation is greater than cells spreading on elastic substrates of the same modulus, but similar to that of cells spreading on stiffer elastic substrates. These findings challenge the current view of how cells sense and respond to the ECM.

High resolution NMR study of T{sub 1} magnetic relaxation dispersion. IV. Proton relaxation in amino acids and Met-enkephalin pentapeptide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pravdivtsev, Andrey N.; Yurkovskaya, Alexandra V.; Ivanov, Konstantin L., E-mail: ivanov@tomo.nsc.ru

2014-10-21

Nuclear Magnetic Relaxation Dispersion (NMRD) of protons was studied in the pentapeptide Met-enkephalin and the amino acids, which constitute it. Experiments were run by using high-resolution Nuclear Magnetic Resonance (NMR) in combination with fast field-cycling, thus enabling measuring NMRD curves for all individual protons. As in earlier works, Papers I–III, pronounced effects of intramolecular scalar spin-spin interactions, J-couplings, on spin relaxation were found. Notably, at low fields J-couplings tend to equalize the apparent relaxation rates within networks of coupled protons. In Met-enkephalin, in contrast to the free amino acids, there is a sharp increase in the proton T{sub 1}-relaxation timesmore » at high fields due to the changes in the regime of molecular motion. The experimental data are in good agreement with theory. From modelling the relaxation experiments we were able to determine motional correlation times of different residues in Met-enkephalin with atomic resolution. This allows us to draw conclusions about preferential conformation of the pentapeptide in solution, which is also in agreement with data from two-dimensional NMR experiments (rotating frame Overhauser effect spectroscopy). Altogether, our study demonstrates that high-resolution NMR studies of magnetic field-dependent relaxation allow one to probe molecular mobility in biomolecules with atomic resolution.« less

A quantum relaxation-time approximation for finite fermion systems

NASA Astrophysics Data System (ADS)

Reinhard, P.-G.; Suraud, E.

2015-03-01

We propose a relaxation time approximation for the description of the dynamics of strongly excited fermion systems. Our approach is based on time-dependent density functional theory at the level of the local density approximation. This mean-field picture is augmented by collisional correlations handled in relaxation time approximation which is inspired from the corresponding semi-classical picture. The method involves the estimate of microscopic relaxation rates/times which is presently taken from the well established semi-classical experience. The relaxation time approximation implies evaluation of the instantaneous equilibrium state towards which the dynamical state is progressively driven at the pace of the microscopic relaxation time. As test case, we consider Na clusters of various sizes excited either by a swift ion projectile or by a short and intense laser pulse, driven in various dynamical regimes ranging from linear to strongly non-linear reactions. We observe a strong effect of dissipation on sensitive observables such as net ionization and angular distributions of emitted electrons. The effect is especially large for moderate excitations where typical relaxation/dissipation time scales efficiently compete with ionization for dissipating the available excitation energy. Technical details on the actual procedure to implement a working recipe of such a quantum relaxation approximation are given in appendices for completeness.

State resolved vibrational relaxation modeling for strongly nonequilibrium flows

NASA Astrophysics Data System (ADS)

Boyd, Iain D.; Josyula, Eswar

2011-05-01

Vibrational relaxation is an important physical process in hypersonic flows. Activation of the vibrational mode affects the fundamental thermodynamic properties and finite rate relaxation can reduce the degree of dissociation of a gas. Low fidelity models of vibrational activation employ a relaxation time to capture the process at a macroscopic level. High fidelity, state-resolved models have been developed for use in continuum gas dynamics simulations based on computational fluid dynamics (CFD). By comparison, such models are not as common for use with the direct simulation Monte Carlo (DSMC) method. In this study, a high fidelity, state-resolved vibrational relaxation model is developed for the DSMC technique. The model is based on the forced harmonic oscillator approach in which multi-quantum transitions may become dominant at high temperature. Results obtained for integrated rate coefficients from the DSMC model are consistent with the corresponding CFD model. Comparison of relaxation results obtained with the high-fidelity DSMC model shows significantly less excitation of upper vibrational levels in comparison to the standard, lower fidelity DSMC vibrational relaxation model. Application of the new DSMC model to a Mach 7 normal shock wave in carbon monoxide provides better agreement with experimental measurements than the standard DSMC relaxation model.

Non-thermal plasma jet without electrical shock for biomedical applications

NASA Astrophysics Data System (ADS)

Baik, Ku Youn; Kang, Han Lim; Kim, Junseong; Park, Shin Young; Bang, Ji Yun; Uhm, Han S.; Choi, Eun Ha; Cho, Guangsup

2013-10-01

A plasma jet without an electrical shock was generated through a Y-shaped tube in which voltages with opposite phases were applied to a pair of tubes. The plasma plume generated at the intersection had a plasma potential of a 60-90 V and high concentrations of reactive species sufficient to induce a high level of lethality on gram-negative bacteria on a tissue mimic. The selective lethality of bacteria on an epithelial-cell-containing tissue mimic could be modulated using oxidant and antioxidant chemicals, thereby leading to the possibility of a shock-reduced plasma jet for biomedical applications.

Electromagnetically Driven Plasma-Field Dynamics in Modified Ionosphere

NASA Astrophysics Data System (ADS)

Kochetov, Andrey; Terina, Galina

Under sounding of an artificial ionospheric turbulence by short probing radio pulses of ordinary polarization the two types of scattered signals were observed: a "caviton" signal (CS) and a "plasma" signal (PS), which appeared with the heating transmitter switching on and disap-peared after its switching off (G.I. Terina J. Atm. Terr. Phys, 57, 1995, 273, Izv. VUZov, Radiofizika, 39, 1998, 203). The scattered signal of PS type was revealed also after the heating switching off. It was called an "aftereffect plasma signal" (AEPS) (G.I. Terina Izv .VUZov, Radiofizika, 43, 2000, 958). This signal had large time and spatial delays and appeared mostly when corresponding PS had envelope fluctuations. The aftereffect phenomenon was expressed at time on CS by amplitude increasing at once after the heating transmitter turning off. The theoretical model of this phenomenon is proposed in and some peculiarities of the aftereffect phenomena of the scattered signals in modified ionospheric plasma are considered and discussed. For theoretical interpretation of the characteristics of CS and AEPS the numerical solution of nonlinear Shrüdinger equation (NSE) with driven extension were carried out in inhomogeneous plasma layer with linear electron density profile (A.V. Kochetov, V.A. Mironov, G.I. Terina, Adv. Space Reseacrh, 29, 2002, 1369) and for the one with prescribed density depletion (and A.V. Kochetov, G.I. Terina, Adv. Space Reseacrh, 38, 2006, 2490). The simulation results obtained for linear inhomogeneous plasma layer and for plasma one with density depletion al-low us to interpret the aftereffect of CS and PS qualitatively. The field amplitude increase at relaxation stage displayed at calculations allows us to interpret of CS aftereffect. The large time delays of AEPS can be explained as a result of powerful radio waves trapping in the forming at the plasma resonance regions density depletions (E. Mjøhus, J. Geophys. Res. 103, 1998, 14711; B. Eliasson and L. Stenflo, J

Rate constants of quenching and vibrational relaxation in the OH({{A}^{2}}{{ \\Sigma }^{+}},v=0,1 ), manifold with various colliders

NASA Astrophysics Data System (ADS)

Martini, L. M.; Gatti, N.; Dilecce, G.; Scotoni, M.; Tosi, P.

2017-03-01

Laser induced fluorescence is intensively used for the detection of OH in many atmospheric pressure discharge devices. At this pressure, a quantitative knowledge of the collision phenomena in the upper excited state is critical. Here we report the measurement at T  =  300 K of a set of rate constants of electronic quenching and vibrational relaxation of the OH≤ft({{A}2}{{ Σ }+},{{v}\\prime}=0,1\\right) electronic state, by collision with N2, O2, H2O, CO2, CO, H2, D2, CH4, C2H2, C2H4, C2H6. These are the main gases in applications like plasma medicine, hydrocarbons reforming and CO2 conversion. Available literature data are revisited, and new data are added, mostly relevant to {{v}\\prime}=1 quenching and vibrational relaxation.

Dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with ethylene carbonate

NASA Astrophysics Data System (ADS)

Pal, P.; Ghosh, A.

2016-07-01

In this paper, we have studied the dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with ethylene carbonate. Structural and thermal properties have been examined using X-ray diffraction and differential scanning calorimetry, respectively. We have analyzed the complex conductivity spectra by using power law model coupled with the contribution of electrode polarization at low frequencies and high temperatures. The temperature dependence of the ionic conductivity and crossover frequency exhibits Vogel-Tammann-Fulcher type behavior indicating a strong coupling between the ionic and the polymer chain segmental motions. The scaling of the ac conductivity indicates that relaxation dynamics of charge carriers follows a common mechanism for all temperatures and ethylene carbonate concentrations. The analysis of the ac conductivity also shows the existence of a nearly constant loss in these polymer electrolytes at low temperatures and high frequencies. The fraction of free anions and ion pairs in polymer electrolyte have been obtained from the analysis of Fourier transform infrared spectra. It is observed that these quantities influence the behavior of the composition dependence of the ionic conductivity.

Electronic and optical properties of Cu2XSnS4 (X = Be, Mg, Ca, Mn, Fe, and Ni) and the impact of native defect pairs

NASA Astrophysics Data System (ADS)

Chen, Rongzhen; Persson, Clas

2017-05-01

Reducing or controlling cation disorder in Cu2ZnSnS4 is a major challenge, mainly due to low formation energies of the anti-site pair ( CuZn - + ZnCu +) and the compensated Cu vacancy ( VCu - + ZnCu +). We study the electronic and optical properties of Cu2XSnS4 (CXTS, with X = Be, Mg, Ca, Mn, Fe, and Ni) and the impact of defect pairs, by employing the first-principles method within the density functional theory. The calculations indicate that these compounds can be grown in either the kesterite or stannite tetragonal phase, except Cu2CaSnS4 which seems to be unstable also in its trigonal phase. In the tetragonal phase, all six compounds have rather similar electronic band structures, suitable band-gap energies Eg for photovoltaic applications, as well as good absorption coefficients α(ω). However, the formation of the defect pairs ( C u X + X Cu) and ( V Cu + X Cu) is an issue for these compounds, especially considering the anti-site pair which has formation energy in the order of ˜0.3 eV. The ( C u X + X Cu) pair narrows the energy gap by typically ΔEg ≈ 0.1-0.3 eV, but for Cu2NiSnS4, the complex yields localized in-gap states. Due to the low formation energy of ( C u X + X Cu), we conclude that it is difficult to avoid disordering from the high concentration of anti-site pairs. The defect concentration in Cu2BeSnS4 is however expected to be significantly lower (as much as ˜104 times at typical device operating temperature) compared to the other compounds, which is partly explained by larger relaxation effects in Cu2BeSnS4 as the two anti-site atoms have different sizes. The disadvantage is that the stronger relaxation has a stronger impact on the band-gap narrowing. Therefore, instead of trying to reduce the anti-site pairs, we suggest that one shall try to compensate ( C u X + X Cu) with ( V Cu + X Cu) or other defects in order to stabilize the gap energy.

A bioinspired redox relay that mimics radical interactions of the Tyr-His pairs of photosystem II

NASA Astrophysics Data System (ADS)

Megiatto, Jackson D., Jr.; Méndez-Hernández, Dalvin D.; Tejeda-Ferrari, Marely E.; Teillout, Anne-Lucie; Llansola-Portolés, Manuel J.; Kodis, Gerdenis; Poluektov, Oleg G.; Rajh, Tijana; Mujica, Vladimiro; Groy, Thomas L.; Gust, Devens; Moore, Thomas A.; Moore, Ana L.

2014-05-01

In water-oxidizing photosynthetic organisms, light absorption generates a powerfully oxidizing chlorophyll complex (P680•+) in the photosystem II reaction centre. This is reduced via an electron transfer pathway from the manganese-containing water-oxidizing catalyst, which includes an electron transfer relay comprising a tyrosine (Tyr)-histidine (His) pair that features a hydrogen bond between a phenol group and an imidazole group. By rapidly reducing P680•+, the relay is thought to mitigate recombination reactions, thereby ensuring a high quantum yield of water oxidation. Here, we show that an artificial reaction centre that features a benzimidazole-phenol model of the Tyr-His pair mimics both the short-internal hydrogen bond in photosystem II and, using electron paramagnetic resonance spectroscopy, the thermal relaxation that accompanies proton-coupled electron transfer. Although this artificial system is much less complex than the natural one, theory suggests that it captures the essential features that are important in the function of the relay.

Determinants of relaxation rate in rabbit skinned skeletal muscle fibres

PubMed Central

Luo, Ye; Davis, Jonathan P; Smillie, Lawrence B; Rall, Jack A

2002-01-01

The influence of Ca2+-activated force, the rate of dissociation of Ca2+ from troponin C (TnC) and decreased crossbridge detachment rate on the time course of relaxation induced by flash photolysis of diazo-2 in rabbit skinned psoas fibres was investigated at 15 °C. The rate of relaxation increased as the diazo-2 chelating capacity (i.e. free [diazo-2]/free [Ca2+]) increased. At a constant diazo-2 chelating capacity, the rate of relaxation was independent of the pre-photolysis Ca2+-activated force in the range 0.3-0.8 of maximum isometric force. A TnC mutant that exhibited increased Ca2+ sensitivity caused by a decreased Ca2+ dissociation rate in solution (M82Q TnC) also increased the Ca2+ sensitivity of steady-state force and decreased the rate of relaxation in fibres by approximately twofold. In contrast, a TnC mutant with decreased Ca2+ sensitivity caused by an increased Ca2+ dissociation rate in solution (NHdel TnC) decreased the Ca2+ sensitivity of steady-state force but did not accelerate relaxation. Decreasing the rate of crossbridge kinetics by reducing intracellular inorganic phosphate concentration ([Pi]) slowed relaxation by approximately twofold and led to two phases of relaxation, a slow linear phase followed by a fast exponential phase. In fibres, M82Q TnC further slowed relaxation in low [Pi] conditions by approximately twofold, whereas NHdel TnC had no significant effect on relaxation. These results are consistent with the interpretation that the Ca2+-dissociation rate and crossbridge detachment rate are similar in fast-twitch skeletal muscle, such that decreasing either rate slows relaxation, but accelerating Ca2+ dissociation has little effect on relaxation. PMID:12482894

Dynamics of human serum albumin studied by acoustic relaxation spectroscopy.

PubMed

Hushcha, T; Kaatze, U; Peytcheva, A

Sonic absorption spectra of solutions of human serum albumin (SA) in water and in aqueous phosphate buffer systems have been measured between 0.2 and 2000 MHz at different temperatures (15-35 degrees C), pH values (1.8-12.3), and protein concentrations (1-40 g/L). Several spectra, indicating relaxation processes in the whole frequency range, have been found. The spectra at neutral pH could be fitted well with an analytical function consisting of the asymptotic high frequency absorption and two relaxation contributions, a Debye-type relaxation term with discrete relaxation time and a term with asymmetric continuous distribution of relaxation times. Both relaxation contributions were observed in water and in buffer solutions and increased with protein concentration. The contribution represented by a Debye-type term is practically independent of temperature and was attributed to cooperative conformational changes of the polypeptide chain featuring a relaxation time of about 400 ns. The distribution of the relaxation times corresponding to the second relaxation contribution was characterized by a short time cutoff, between about 0.02 and 0.4 ns depending on temperature, and a long time tail extending to microseconds. Such relaxation behavior was interpreted in terms of solute-solvent interactions reflecting various hydration layers of HSA molecules. At acid and alkaline pH, an additional Debye-type contribution with relaxation time in the range of 30-100 ns exists. It seems to be due to proton transfer reactions of protein side-chain groups. The kinetic and thermodynamic parameters of these processes have been estimated from these first measurements to indicate the potential of acoustic spectra for the investigation of the elementary kinetics of albumin processes. Copyright 2004 Wiley Periodicals, Inc. Biopolymers, 2004

Viscous relaxation of Ganymede's impact craters: Constraints on heat flux

USGS Publications Warehouse

Bland, Michael T.; Singer, Kelsi N.; McKinnon, William B.; Schenk, Paul M.

2017-01-01

Measurement of crater depths in Ganymede’s dark terrain have revealed substantial numbers of unusually shallow craters indicative of viscous relaxation [see companion paper: Singer, K.N., Schenk, P. M., Bland, M.T., McKinnon, W.B., (2017). Relaxed impact craters on Ganymede: Regional variations and high heat flow. Icarus, submitted]. These viscously relaxed craters provide insight into the thermal history of the dark terrain: the rate of relaxation depends on the size of the crater and the thermal structure of the lithosphere. Here we use finite element simulations of crater relaxation to constrain the heat flux within the dark terrain when relaxation occurred. We show that the degree of viscous relaxation observed cannot be achieved through radiogenic heating alone, even if all of the relaxed craters are ancient and experienced the high radiogenic fluxes present early in the satellite’s history. For craters with diameter ≥ 10 km, heat fluxes of 40–50 mW m-2−2"> can reproduce the observed crater depths, but only if the fluxes are sustained for ∼1 Gyr. These craters can also be explained by shorter-lived “heat pulses” with magnitudes of ∼100 mW m-2−2"> and timescales of 10–100 Myr. At small crater diameters (4 km) the observed shallow depths are difficult to achieve even when heat fluxes as high as 150 mW m-2−2"> are sustained for 1 Gyr. The extreme thermal conditions required to viscously relax small craters may indicate that mechanisms other than viscous relaxation, such as topographic degradation, are also in play at small crater diameters. The timing of the relaxation event(s) is poorly constrained due to the sparsity of adequate topographic information, though it likely occurred in Ganymede’s middle history (neither recently, nor shortly after satellite formation). The consistency between the timing and magnitude of the heat fluxes derived here and those inferred from other tectonic features suggests that a single event