Wang, Lianwen; Li, Jiangong; Fecht, Hans-Jörg
2010-11-17
The reported relaxation time for several typical glass-forming liquids was analyzed by using a kinetic model for liquids which invoked a new kind of atomic cooperativity--thermodynamic cooperativity. The broadly studied 'cooperative length' was recognized as the kinetic cooperativity. Both cooperativities were conveniently quantified from the measured relaxation data. A single-exponential activation behavior was uncovered behind the super-Arrhenius relaxations for the liquids investigated. Hence the mesostructure of these liquids and the atomic mechanism of the glass transition became clearer.
Wang, Lianwen; Li, Jiangong; Fecht, Hans-Jörg
2011-04-20
Following the report of a single-exponential activation behavior behind the super-Arrhenius structural relaxation of glass-forming liquids in our preceding paper, we find that the non-exponentiality in the structural relaxation of glass-forming liquids is straightforwardly determined by the relaxation time, and could be calculated from the measured relaxation data. Comparisons between the calculated and measured non-exponentialities for typical glass-forming liquids, from fragile to intermediate, convincingly support the present analysis. Hence the origin of the non-exponentiality and its correlation with liquid fragility become clearer.
Turton, David A; Martin, David F; Wynne, Klaas
2010-04-28
The evidence that a molecular liquid in its thermodynamically-stable state can undergo a liquid-liquid transition (LLT) is still uncertain. Therefore, trans-1,2-dichloroethene is of interest due to reports of a LLT above the melting point [S. Kawanishi, T. Sasuga and M. Takehisa, J. Phys. Soc. Jpn., 1982, 51, 1579-1583; S. Rzoska, J. Ziolo, A. Drozd-Rzoska, J. L. Tamarit and N. Veglio, J. Phys.: Condens. Matter, 2008, 20, 244124; K. Merkel, A. Kocot, R. Wrzalik and J. Ziolo, J. Chem. Phys., 2008, 129, 074503-074508]. Ultrafast optical Kerr-effect (OKE) spectroscopy enables accurate measurement of the low-frequency modes arising from interactions in liquids and therefore should be sensitive to the change in liquid structure inherent in such a transition. In the OKE data presented here, no sharp transitions are discernible, nor are there any in calorimetry data. However, the same data do reveal that neither trans- nor cis-1,2-dichloroethene is a simple liquid: in each case, a non-Arrhenius temperature dependence (with a Debye lineshape) is observed for the alpha relaxation. This dependence can be fitted by the Vogel-Fulcher-Tammann (VFT) law over the measurable temperature range suggesting that at low temperature, cooperative relaxation, due to the formation of clusters or structure, is present. Accurate analysis of the OKE spectrum in the terahertz region is generally limited by approximations inherent in the models. Here the diffusional modes are convoluted with librational modes to give a more physically meaningful approximation to the inertial response.
de Souza, Vanessa K; Wales, David J
2006-02-10
On short time scales an underlying Arrhenius temperature dependence of the diffusion constant can be extracted from the fragile, super-Arrhenius diffusion of a binary Lennard-Jones mixture. This Arrhenius diffusion is related to the true super-Arrhenius behavior by a factor that depends on the average angle between steps in successive time windows. The correction factor accounts for the fact that on average, successive displacements are negatively correlated, and this effect can therefore be linked directly with the higher apparent activation energy for diffusion at low temperature.
Using 20-million-year-old amber to test the super-Arrhenius behaviour of glass-forming systems.
Zhao, Jing; Simon, Sindee L; McKenna, Gregory B
2013-01-01
Fossil amber offers the opportunity to investigate the dynamics of glass-forming materials far below the nominal glass transition temperature. This is important in the context of classical theory, as well as some new theories that challenge the idea of an 'ideal' glass transition. Here we report results from calorimetric and stress relaxation experiments using a 20-million-year-old Dominican amber. By performing the stress relaxation experiments in a step-wise fashion, we measured the relaxation time at each temperature and, above the fictive temperature of this 20-million-year-old glass, this is an upper bound to the equilibrium relaxation time. The results deviate dramatically from the expectation of classical theory and are consistent with some modern ideas, in which the diverging timescale signature of complex fluids disappears below the glass transition temperature.
Two-temperature reaction and relaxation rates
Kolesnichenko, E.; Gorbachev, Yu.
2016-09-01
Within the method of solving the kinetic equations for gas mixtures with internal degrees of freedom developed by the authors and based on the approximate summational invariants (ASI) concept, gas-dynamic equations for a multi-temperature model for the spatially inhomogeneous case are derived. For the two-temperature case, the expressions for the non-equilibrium reaction and relaxation rates are obtained. Special attention is drawn to corresponding thermodynamic equations. Different possibilities of introducing the gas-dynamic variables related to the internal degrees of freedom are considered. One is based on the choice of quantum numbers as the ASI, while the other is based on the choice of internal (vibrational) energy as the ASI. Limits to a one-temperature situation are considered in all the cases. For the cutoff harmonic oscillator model, explicit expressions for the reaction and relaxation rates are derived.
Relaxation Mechanisms in Glassy Dynamics: the Arrhenius and Fragile Regimes
Hentschel, H. George E.; Karmakar, Smarajit; Procaccia, Itamar; Zylberg, Jacques
2012-01-01
Generic glass formers exhibit at least two characteristic changes in their relaxation behavior, first to an Arrhenius-type relaxation at some characteristic temperature, and then at a lower characteristic temperature to a super-Arrhenius (fragile) behavior. We address these transitions by studying the statistics of free energy barriers for different systems at different temperatures and space dimensions. We present a clear evidence for changes in the dynamical behavior at the transition to Ar...
Relaxation mechanisms in glassy dynamics: the Arrhenius and fragile regimes.
Hentschel, H George E; Karmakar, Smarajit; Procaccia, Itamar; Zylberg, Jacques
2012-06-01
Generic glass formers exhibit at least two characteristic changes in their relaxation behavior, first to an Arrhenius-type relaxation at some characteristic temperature and then at a lower characteristic temperature to a super-Arrhenius (fragile) behavior. We address these transitions by studying the statistics of free energy barriers for different systems at different temperatures and space dimensions. We present a clear evidence for changes in the dynamical behavior at the transition to Arrhenius and then to a super-Arrhenius behavior. A simple model is presented, based on the idea of competition between single-particle and cooperative dynamics. We argue that Arrhenius behavior can take place as long as there is enough free volume for the completion of a simple T1 relaxation process. Once free volume is absent one needs a cooperative mechanism to "collect" enough free volume. We show that this model captures all the qualitative behavior observed in simulations throughout the considered temperature range.
Local fluctuations in the relaxation rate in a glassy system
Pandit, Rajib; Flenner, Elijah; Castillo, Horacio E.
We numerically study the equilibrium dynamics of a glass-forming binary hard-sphere mixture, for different packing fractions. We extract a correlator that probes the integrated fluctuations in the local relaxation rate in the system. We find that the strength of this correlator at t =τα (the α-relaxation time) grows with packing fraction approximately as a power of τα. We also find that for a fixed packing fraction, the correlator grows as a power of time, for very long times, with an exponent that depends on the packing fraction. This exponent probes the time correlations of the relaxation rate fluctuations. We find that the exponent is around 3 for very low packing fractions, and gradually decreases to a value below 2 as the glass transition is approached. We conclude that a description of fluctuations in terms of local relaxation rates is only applicable at long times and for packing fractions close to the glass transition.
Readout of relaxation rates by nonadiabatic pumping spectroscopy
Riwar, Roman-Pascal; Roche, Benoît; Jehl, Xavier; Splettstoesser, Janine
2016-06-01
We put forward nonadiabatic charge pumping as a method for accessing the different charge relaxation rates as well as the relaxation rates of excited orbital states in double-quantum-dot setups, based on extremely size-limited quantum dots and dopant systems. The rates are obtained in a well-separated manner from plateaus, occurring when comparing the steady-state current for reversed driving cycles. This yields a reliable readout independent of any fitting parameters. Importantly, the nonadiabatic pumping spectroscopy essentially exploits the same driving scheme that the operation of these devices generally employs. We provide a detailed analysis of the working principle of the readout scheme as well as of possible errors, thereby demonstrating its broad applicability. The precise knowledge of relaxation rates is highly relevant for the implementation of time-dependently operated devices, such as electron pumps for metrology or qubits in quantum information.
NMR relaxation rate and the libron energy of solid hydrogen
Sugawara, K.; Woollam, J. A.
1978-01-01
By taking the rotational relaxation of orthohydrogen (o-H2) in solid hydrogen into account, the authors have theoretically investigated the longitudinal NMR spin lattice relaxation rate of o-H2. The rate is characterized by an anomalous maximum, as a function of temperature, at temperatures close to the mean libron energy of o-H2. Application of the theory for o-H2 concentrations between 42% and 75% reveals a nearly concentration-independent mean libron energy equivalent to about 1 K. This qualitatively and quantitatively contradicts the conclusions of other theories, but agrees with recent experiments.
Energy Technology Data Exchange (ETDEWEB)
Dasch, C.J.
1978-09-01
Single rovibrational states of HCl(v=2), HBr(v=2), DCl(v=2), and CO(v=2) were excited with a pulsed optical parametric oscillator (OPO). Total vibrational relaxation rates near - resonance quenchers were measured at 295/sup 0/K using time resolved infrared fluorescence. These rates are attributed primarily to V - V energy transfer, and they generally conform to a simple energy gap law. A small deviation was found for the CO(v) + DCl(v') relaxation rates. Upper limits for the self relaxation by V - R,T of HCl(v=2) and HBr(v=2) and for the two quantum exchange between HCl and HBr were determined. The HF dimer was detected at 295/sup 0/K and 30 torr HF pressure with an optoacoustic spectrometer using the OPO. Pulsed and chopped, resonant and non-resonant spectrophones are analyzed in detail. From experiments and first order perturbation theory, these V - V exchange rates appear to behave as a first order perturbation in the vibrational coordinates. The rotational dynamics are known to be complicated however, and the coupled rotational - vibrational dynamics were investigated theoreticaly in infinite order by the Dillon and Stephenson and the first Magnus approximations. Large ..delta..J transitions appear to be important, but these calculations differ by orders of magnitude on specific rovibrational transition rates. Integration of the time dependent semiclassical equations by a modified Gordon method and a rotationally distorted wave approximation are discussed as methods which would treat the rotational motion more accurately. 225 references.
CPMG relaxation rate dispersion in dipole fields around capillaries.
Kurz, F T; Kampf, T; Buschle, L R; Heiland, S; Schlemmer, H-P; Bendszus, M; Ziener, C H
2016-09-01
Transverse relaxation rates for Carr-Purcell-Meiboom-Gill (CPMG) sequences increase with inter-echo time in presence of microscopic magnetic field inhomogeneities due to nuclear spin diffusion. For a weak field approximation that includes diffusion effects, the CPMG relaxation rate shift for proton diffusion around capillaries in muscle tissue can be expressed in terms of a frequency correlation function and the inter-echo time. The present work provides an analytical expression for the local relaxation rate shift that is dependent on local blood volume fraction, diffusion coefficient, capillary radius, susceptibility difference and inter-echo time. Asymptotic regions of the model are in agreement with previous modeling results of Brooks et al., Luz et al. and Ziener et al. In comparison with simulation data, the model shows an equal or better accuracy than established approximations. Also, model behavior coincides with experimental data for rat heart and skeletal muscle. The present work provides analytical tools to extract sub-voxel information about uniform capillary networks that can be used to study capillary organization or micro-circulatory remodeling.
Kowalik, Sylwester; Janczarek, Iwona; Kędzierski, Witold; Stachurska, Anna; Wilk, Izabela
2017-04-01
The objective of this study was to assess the effect of relaxing massage on the heart rate (HR) and heart rate variability (HRV) in young racehorses during their first racing season. In the study, 72 Purebred Arabian racehorses were included. The study was implemented during the full race season. The horses from control and experimental groups were included in regular race training 6 days a week. The horses from the experimental group were additionally subject to the relaxing massage 3 days a week during the whole study. HR and HRV were assumed as indicators of the emotional state of the horses. The measurements were taken six times, every 4-5 weeks. The HRV parameters were measured at rest, during grooming and saddling the horse and during warm-up walking under a rider. The changes of the parameters throughout the season suggest that the relaxing massage may be effectively used to make the racehorses more relaxed and calm. Moreover, the horses from the experimental group had better race performance records. © 2016 Japanese Society of Animal Science.
Funk, Alexander M; Harvey, Peter; Finney, Katie-Louise N A; Fox, Mark A; Kenwright, Alan M; Rogers, Nicola J; Senanayake, P Kanthi; Parker, David
2015-07-07
Measurements of the proton NMR paramagnetic relaxation rates for several series of isostructural lanthanide(III) complexes have been performed in aqueous solution over the field range 1.0 to 16.5 Tesla. The field dependence has been modeled using Bloch-Redfield-Wangsness theory, allowing values for the electronic relaxation time, Tle and the magnetic susceptibility, μeff, to be estimated. Anomalous relaxation rate profiles were obtained, notably for erbium and thulium complexes of low symmetry 8-coordinate aza-phosphinate complexes. Such behaviour challenges accepted theory and can be interpreted in terms of changes in Tle values that are a function of the transient ligand field induced by solvent collision and vary considerably between Ln(3+) ions, along with magnetic susceptibilities that deviate significantly from free-ion values.
McNeil, C.J.; Bredius, M.S.; Molenaar, J.P.F.; Gandevia, S.C.
2013-01-01
Transcranial magnetic stimulation (TMS) allows an in vivo assessment of the rate of muscle relaxation during a voluntary contraction. It is unknown if this method can be applied to lower limb muscles, and the effect of stimulus intensity on relaxation rate has not been investigated in any muscle gro
The benefit of heart rate variability biofeedback and relaxation training in reducing trait anxiety†
Lee, Jieun; Kim, Jung K; Wachholtz, Amy
2015-01-01
Previous research studies have indicated that biofeedback treatment and relaxation techniques are effective in reducing psychological and physical symptoms (Hammond, 2005; Manzoni, G. M., Pagnini, F., Castelnuovo, G., & Molinari, E., 2008). However, dearth of studies has compared heart rate variability (HRV) biofeedback treatment and relaxation training to reduce trait anxiety. The objective of this study was to determine the effect of HRV biofeedback treatment and relaxation training in redu...
Heating Rate Effect on the Activation of Viscoelastic Relaxation in Silicate Glasses
Naji, Mohamed; Piazza, Francesco; Guimbretière, Guillaume; Canizarès, Aurèlien; Ory, Sandra; Vaills, Yann
Here we present a direct investigation of the heating rate effect on structural relaxation of sodium silicate glass near the glass transition by means of differential scanning calorimetry, and show the sensitivity of Brillouin light spectroscopy to the dynamic of structural relaxation in the medium range order (∼100 nm).
Rangel, David P; Baveye, Philippe C; Robinson, Bruce H
2012-06-07
We simulate spin relaxation processes, which may be measured by either continuous wave or pulsed magnetic resonance techniques, using trajectory-based simulation methodologies. The spin-lattice relaxation rates are extracted numerically from the relaxation simulations. The rates obtained from the numerical fitting of the relaxation curves are compared to those obtained by direct simulation from the relaxation Bloch-Wangsness-Abragam-Redfield theory (BWART). We have restricted our study to anisotropic rigid-body rotational processes, and to the chemical shift anisotropy (CSA) and a single spin-spin dipolar (END) coupling mechanisms. Examples using electron paramagnetic resonance (EPR) nitroxide and nuclear magnetic resonance (NMR) deuterium quadrupolar systems are provided. The objective is to compare those rates obtained by numerical simulations with the rates obtained by BWART. There is excellent agreement between the simulated and BWART rates for a Hamiltonian describing a single spin (an electron) interacting with the bath through the chemical shift anisotropy (CSA) mechanism undergoing anisotropic rotational diffusion. In contrast, when the Hamiltonian contains both the chemical shift anisotropy (CSA) and the spin-spin dipolar (END) mechanisms, the decay rate of a single exponential fit of the simulated spin-lattice relaxation rate is up to a factor of 0.2 smaller than that predicted by BWART. When the relaxation curves are fit to a double exponential, the slow and fast rates extracted from the decay curves bound the BWART prediction. An extended BWART theory, in the literature, includes the need for multiple relaxation rates and indicates that the multiexponential decay is due to the combined effects of direct and cross-relaxation mechanisms.
Relaxation rates of low-field gas-phase ^129Xe storage cells
Limes, Mark; Saam, Brian
2010-10-01
A study of longitudinal nuclear relaxation rates T1 of ^129Xe and Xe-N2 mixtures in a magnetic field of 3.8 mT is presented. In this regime, intrinsic spin relaxation is dominated by the intramolecular spin-rotation interaction due to persistent xenon dimers, a mechanism that can be quelled by introducing large amounts of N2 into the storage cell. Extrinsic spin relaxation is dominated by the wall-relaxation rate, which is the primary quantity of interest for the various low-field storage cells and coatings that we have tested. Previous group work has shown that extremely long gas-phase relaxation times T1 can be obtained, but only at large magnetic fields and low xenon densities. The current work is motivated by the practical benefits of retaining hyperpolarized ^129Xe for extended periods of time in a small magnetic field.
Uniqueness of rate-dependency, creep and stress relaxation behaviors for soft clays
Institute of Scientific and Technical Information of China (English)
朱启银; 尹振宇; 徐长节; 殷建华; 夏小和
2015-01-01
This work focuses on the uniqueness of rate-dependency, creep and stress relaxation behaviors for soft clays under one-dimensional condition. An elasto-viscoplastic model is briefly introduced based on the rate-dependency of preconsolidation pressure. By comparing the rate-dependency formulation with the creep based formulation, the relationship between rate-dependency and creep behaviors is firstly described. The rate-dependency based formulation is then extended to derive an analytical solution for the stress relaxation behavior with defining a stress relaxation coefficient. Based on this, the relationship between the rate-dependency coefficient and the stress relaxation coefficient is derived. Therefore, the uniqueness between behaviors of rate-dependency, creep and stress relaxation with their key parameters is obtained. The uniqueness is finally validated by comparing the simulated rate-dependency of preconsolidation pressure, the estimated values of secondary compression coefficient and simulations of stress relaxation tests with test results on both reconstituted Illite and Berthierville clay.
Relaxation rates of the linearized Uehling-Uhlenbeck equation for bosons.
Gust, Erich; Reichl, L E
2010-06-01
We linearize the Uehling-Uhlenbeck equation for bosonic gases close to thermal equilibrium under the assumption of a contact interaction characterized by a scattering length a. We show that the spectrum of relaxation rates is similar to that of a classical hard-sphere gas. However, the relaxation rates show a significant dependence on the fugacity z of the gas, increasing by as much as 60% of their classical value for z approaching 1. The relaxation modes are also significantly altered at higher values of z. The relaxation rates and modes are determined by the eigenvalues and eigenvectors of a Fredholm integral operator of the second kind. We derive an analytical form for the kernel of this operator and present numerical results for the first few eigenvalues and eigenvectors.
Alem, Naziha; Beezer, Anthony E; Gaisford, Simon
2010-10-31
While the use of isothermal calorimetry to quantify the rate of relaxation of one-phase amorphous pharmaceuticals, through application of models, is well documented, the resolution of the models to detect and quantify relaxation in systems containing two independent amorphous phases is not known. Addressing this knowledge gap is the focus of this work. Two fitting models were tested; the Kohlrausch-Williams-Watts model (KWW) and the modified-stretch exponential (MSE). The ability of each model to resolve relaxation processes in binary systems was determined with simulated calorimetric data. It was found that as long as the relaxation time constants of the relaxation processes were with 10(3) of each other, the models could determine that two events were occurring and could quantify the correct reaction parameters of each. With greater differences in the time constants, the faster process always dominates the data and the resolving power of the models is lost. Real calorimetric data were then obtained for two binary amorphous systems (sucrose-lactose and sucrose-indomethacin mixtures). The relaxation behaviour of all the single components was characterised as they relaxed individually to provide reference data. The ability of the KWW model to recover the expected relaxation parameters for two component data was impaired because of their inherently noisy nature. The MSE model reasonably recovered the expected parameters for each component for the sucrose-indomethacin system but not for the sucrose-lactose system, which may indicate a possible interaction in that case.
Du, G; Lewis, M M; Kanekar, S; Sterling, N W; He, L; Kong, L; Li, R; Huang, X
2017-05-01
Both diffusion tensor imaging and the apparent transverse relaxation rate have shown promise in differentiating Parkinson disease from atypical parkinsonism (particularly multiple system atrophy and progressive supranuclear palsy). The objective of the study was to assess the ability of DTI, the apparent transverse relaxation rate, and their combination for differentiating Parkinson disease, multiple system atrophy, progressive supranuclear palsy, and controls. A total of 106 subjects (36 controls, 35 patients with Parkinson disease, 16 with multiple system atrophy, and 19 with progressive supranuclear palsy) were included. DTI and the apparent transverse relaxation rate measures from the striatal, midbrain, limbic, and cerebellar regions were obtained and compared among groups. The discrimination performance of DTI and the apparent transverse relaxation rate among groups was assessed by using Elastic-Net machine learning and receiver operating characteristic curve analysis. Compared with controls, patients with Parkinson disease showed significant apparent transverse relaxation rate differences in the red nucleus. Compared to those with Parkinson disease, patients with both multiple system atrophy and progressive supranuclear palsy showed more widespread changes, extending from the midbrain to striatal and cerebellar structures. The pattern of changes, however, was different between the 2 groups. For instance, patients with multiple system atrophy showed decreased fractional anisotropy and an increased apparent transverse relaxation rate in the subthalamic nucleus, whereas patients with progressive supranuclear palsy showed an increased mean diffusivity in the hippocampus. Combined, DTI and the apparent transverse relaxation rate were significantly better than DTI or the apparent transverse relaxation rate alone in separating controls from those with Parkinson disease/multiple system atrophy/progressive supranuclear palsy; controls from those with Parkinson
Tan, Yusuf Ziya; Ozdemir, Semra; Temiz, Ahmet; Celik, Fatmanur
2015-05-01
The positive changes in human behavior caused by relaxing music demonstrate the psychological effect of music on human body. A meta-analytical study has shown that relaxing music affects blood pressure and heart rate in coronary heart patients and cancer patients. The aim of our study is to research whether there is a significant effect on heart rate and heart rate variability due to listening to relaxing music during ECG GATED MPS imaging under gamma camera. The music group (n = 50 patients) could choose from 15 different musical types including folk music (no lyric). The other 50 patients were placed in a "no music group" and did not get headphones or any music. There was a statistically significant reduction in the heart rate of patients in the music group compared to those in the control group. Relaxing music provides great benefits to both patient and clinician. There is close relationship between relaxing music and health procedure, can use every area of the health noninvasiv, safe, cheap and is a method don't have side effect. Copyright © 2015 Elsevier Ltd. All rights reserved.
Cellmer, Troy; Henry, Eric R; Kubelka, Jan; Hofrichter, James; Eaton, William A
2007-11-28
The connection between free-energy surfaces and chevron plots has been investigated in a laser temperature jump kinetic study of a small ultrafast folding protein, the 35-residue subdomain from the villin headpiece. Unlike all other proteins that have been studied so far, no measurable dependence of the unfolding/refolding relaxation rate on denaturant concentration was observed over a wide range of guanidinium chloride concentration. Analysis with a simple Ising-like theoretical model shows that this denaturant-invariant relaxation rate can be explained by a large movement of the major free energy barrier, together with a denaturant- and reaction coordinate-dependent diffusion coefficient.
Time-Dependent Behaviors of Granite: Loading-Rate Dependence, Creep, and Relaxation
Hashiba, K.; Fukui, K.
2016-07-01
To assess the long-term stability of underground structures, it is important to understand the time-dependent behaviors of rocks, such as their loading-rate dependence, creep, and relaxation. However, there have been fewer studies on crystalline rocks than on tuff, mudstone, and rock salt, because the high strength of crystalline rocks makes the detection of their time-dependent behaviors much more difficult. Moreover, studies on the relaxation, temporal change of stress and strain (TCSS) conditions, and relations between various time-dependent behaviors are scarce for not only granites, but also other rocks. In this study, previous reports on the time-dependent behaviors of granites were reviewed and various laboratory tests were conducted using Toki granite. These tests included an alternating-loading-rate test, creep test, relaxation test, and TCSS test. The results showed that the degree of time dependence of Toki granite is similar to other granites, and that the TCSS resembles the stress-relaxation curve and creep-strain curve. A viscoelastic constitutive model, proposed in a previous study, was modified to investigate the relations between the time-dependent behaviors in the pre- and post-peak regions. The modified model reproduced the stress-strain curve, creep, relaxation, and the results of the TCSS test. Based on a comparison of the results of the laboratory tests and numerical simulations, close relations between the time-dependent behaviors were revealed quantitatively.
Relaxation dynamics of glasses along a wide stability and temperature range
Rodríguez-Tinoco, C.; Ràfols-Ribé, J.; González-Silveira, M.; Rodríguez-Viejo, J.
2016-10-01
While lots of measurements describe the relaxation dynamics of the liquid state, experimental data of the glass dynamics at high temperatures are much scarcer. We use ultrafast scanning calorimetry to expand the timescales of the glass to much shorter values than previously achieved. Our data show that the relaxation time of glasses follows a super-Arrhenius behaviour in the high-temperature regime above the conventional devitrification temperature heating at 10 K/min. The liquid and glass states can be described by a common VFT-like expression that solely depends on temperature and limiting fictive temperature. We apply this common description to nearly-isotropic glasses of indomethacin, toluene and to recent data on metallic glasses. We also show that the dynamics of indomethacin glasses obey density scaling laws originally derived for the liquid. This work provides a strong connection between the dynamics of the equilibrium supercooled liquid and non-equilibrium glassy states.
Stress relaxation of entangled polystyrene solution after constant-rate, uniaxial elongation
DEFF Research Database (Denmark)
Matsumiya, Yumi; Masubuchi, Yuichi; Watanabe, Hiroshi
For an entangled solution of linear polystyrene (PS 545k; M = 545k) in dibutyl phthalate (DBP), the stress relaxation after constant-rate uniaxial elongation was examined with an extensional viscosity fixture mounted on ARES (TA Instruments). The PS concentration, c = 52 wt%, was chosen in a way...
Extended s+ scenario for the neclear spin-lattice relaxation rate in superconducting pnictides
Parker, D.; Dolgov, O.V.; Korshunov, M.M.; Golubov, Alexandre Avraamovitch; Mazin, I.I.
2008-01-01
Recently, several measurements of the nuclear spin-lattice relaxation rate T_{1}^{-1} in the superconducting Fe pnictides have been reported. These measurements generally show no coherence peak below Tc and indicate a low-temperature power-law behavior, the characteristics commonly t
NMR cross-correlated relaxation rates reveal ion coordination sites in DNA
Fiala, R.; Spackova, N.; Foldynová-Trantírková, S.; Sponer, J.; Sklenár, V.; Trantirek, L.
2011-01-01
In this work, a novel NMR method for the identification of preferential coordination sites between physiologically relevant counterions and nucleic acid bases is demonstrated. In this approach, the NMR cross-correlated relaxation rates between the aromatic carbon chemical shift anisotropy and the pr
Stress relaxation of entangled polystyrene solution after constant-rate, uniaxial elongation
DEFF Research Database (Denmark)
Matsumiya, Yumi; Masubuchi, Yuichi; Watanabe, Hiroshi;
For an entangled solution of linear polystyrene (PS 545k; M = 545k) in dibutyl phthalate (DBP), the stress relaxation after constant-rate uniaxial elongation was examined with an extensional viscosity fixture mounted on ARES (TA Instruments). The PS concentration, c = 52 wt%, was chosen in a way...
a Study of Stress Relaxation Rate in Un-Irradiated and Neutron-Irradiated Stainless Steel
Ghauri, I. M.; Afzal, Naveed; Zyrek, N. A.
Stress relaxation rate in un-irradiated and neutron-irradiated 303 stainless steel was investigated at room temperature. The specimens were exposed to 100 mC, Ra-Be neutron source of continuous energy 2-12 MeV for a period ranging from 4 to 16 days. The tensile deformation of the specimens was carried out using a Universal Testing Machine at 300 K. During the deformation, straining was frequently interrupted by arresting the cross head to observe stress relaxation at fixed load. Stress relaxation rate, s, was found to be stress dependent i.e. it increased with increasing stress levels σ0 both in un-irradiated and irradiated specimens, however the rate was lower in irradiated specimens than those of un-irradiated ones. A further decrease in s was observed with increase in exposure time. The experiential decrease in the relaxation rate in irradiated specimens is ascribed to strong interaction of glide dislocations with radiation induced defects. The activation energy for the movement of dislocations was found to be higher in irradiated specimens as compared with the un-irradiated ones.
Energy Technology Data Exchange (ETDEWEB)
Sakai, H. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)]. E-mail: sakai.hironori@jaea.go.jp; Kambe, S. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Tokunaga, Y. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Fujimoto, T. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Walstedt, R.E. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Yasuoka, H. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Aoki, D. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Homma, Y. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Yamamoto, E. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Nakamura, A. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Shiokawa, Y. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Nakajima, K. [Department of Nuclear Energy System, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Arai, Y. [Department of Nuclear Energy System, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Matsuda, T.D. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Haga, Y. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Onuki, Y. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)
2007-03-15
The spin-lattice relaxation rates (1/T{sub 1}) have been measured under zero field using nuclear quadrupole resonance (NQR) lines in superconductor PuRhGa{sub 5} and Pauli-paramagnet LuCoGa{sub 5}. In the reference LuCoGa{sub 5} with fully-occupied 4f shell, the 1/T{sub 1} shows the constant behavior of (T{sub 1}T){sup -1}=0.495+/-0.002(sK){sup -1}. On the other hand, in PuRhGa{sub 5}, 1/T{sub 1} is much larger than in LuCoGa{sub 5} and the 1/T{sub 1}{proportional_to}T behavior below {approx}30K is seen, where its (T{sub 1}T){sup -1} value is 3.27+/-0.005(sK){sup -1}. These results suggest a development of coherent Fermi liquid state incorporated with 5f electrons below {approx}30K in PuRhGa{sub 5}.
How to distinguish conformational selection and induced fit based on chemical relaxation rates
Paul, Fabian
2016-01-01
Protein binding often involves conformational changes. Important questions are whether a conformational change occurs prior to a binding event ('conformational selection') or after a binding event ('induced fit'), and how conformational transition rates can be obtained from experiments. In this article, we present general results for the chemical relaxation rates of conformational-selection and induced-fit binding processes that hold for all concentrations of proteins and ligands and, thus, go beyond the standard pseudo-first-order approximation of large ligand concentration. These results allow to distinguish conformational-selection from induced-fit processes - also in cases in which such a distinction is not possible under pseudo-first-order conditions - and to extract conformational transition rates of proteins from chemical relaxation data.
Energy Technology Data Exchange (ETDEWEB)
Ng, Ming Yen [University of Toronto, Department of Medical Imaging, Toronto General Hospital, Toronto, ON (Canada); The University of Hong Kong, Queen Mary Hospital, Department of Diagnostic Radiology, Hong Kong (China); Karimzad, Yasser; Menezes, Ravi J.; Wintersperger, Bernd J.; Li, Qin; Forero, Julian; Paul, Narinder S.; Nguyen, Elsie T. [University of Toronto, Department of Medical Imaging, Toronto General Hospital, Toronto, ON (Canada)
2016-10-15
To evaluate the heart rate lowering effect of relaxation music in patients undergoing coronary CT angiography (CCTA), pulmonary vein CT (PVCT) and coronary calcium score CT (CCS). Patients were randomised to a control group (i.e. standard of care protocol) or to a relaxation music group (ie. standard of care protocol with music). The groups were compared for heart rate, radiation dose, image quality and dose of IV metoprolol. Both groups completed State-Trait Anxiety Inventory anxiety questionnaires to assess patient experience. One hundred and ninety-seven patients were recruited (61.9 % males); mean age 56y (19-86 y); 127 CCTA, 17 PVCT, 53 CCS. No significant difference in heart rate, radiation dose, image quality, metoprolol dose and anxiety scores. 86 % of patients enjoyed the music. 90 % of patients in the music group expressed a strong preference to have music for future examinations. The patient cohort demonstrated low anxiety levels prior to CT. Relaxation music in CCTA, PVCT and CCS does not reduce heart rate or IV metoprolol use. Patients showed low levels of anxiety indicating that anxiolytics may not have a significant role in lowering heart rate. Music can be used in cardiac CT to improve patient experience. (orig.)
Potentiation increases peak twitch torque by enhancing rates of torque development and relaxation.
Froyd, Christian; Beltrami, Fernando Gabe; Jensen, Jørgen; Noakes, Timothy David
2013-01-01
The aim of this study was to measure the extent to which potentiation changes in response to an isometric maximal voluntary contraction. Eleven physically active subjects participated in two separate studies. Single stimulus of electrical stimulation of the femoral nerve was used to measure torque at rest in unpotentiated quadriceps muscles (study 1 and 2), and potentiated quadriceps muscles torque in a 10 min period after a 5 s isometric maximal voluntary contraction of the quadriceps muscles (study 1). Additionally, potentiated quadriceps muscles torque was measured every min after a further 10 maximal voluntary contractions repeated every min (study 2). Electrical stimulation repeated several times without previous maximal voluntary contraction showed similar peak twitch torque. Peak twitch torque 4 s after a 5 s maximal voluntary contraction increased by 45±13% (study 1) and by 56±10% (study 2), the rate of torque development by 53±13% and 82±29%, and the rate of relaxation by 50±17% and 59±22%, respectively, but potentiation was lost already two min after a 5 s maximal voluntary contraction. There was a tendency for peak twitch torque to increase for the first five repeated maximal voluntary contractions, suggesting increased potentiation with additional maximal voluntary contractions. Correlations for peak twitch torque vs the rate of torque development and for the rate of relaxation were r(2)= 0.94 and r(2)=0.97. The correlation between peak twitch torque, the rate of torque development and the rate of relaxation suggests that potentiation is due to instantaneous changes in skeletal muscle contractility and relaxation.
Directory of Open Access Journals (Sweden)
Tintin Sukartini
2017-07-01
Full Text Available Introduction: Limited progressive air flow in Chronic Obstructive Pulmonary Disease (COPD can caused by small airway disease (bronchiolitis obstructive and loss of elasticity of the lung (emphysema. Further it can be decreasing the quality of life in COPD patients because dyspnea and uncomfortable in activity. Progressive muscle relaxation (PMR is one of the relaxation technique that can repair pulmonary ventilation by decreasing chronic constriction of the respiratory muscles. The objective of this study was to analyze the effect of progressive muscle relaxation on raised peak expiratory flow rate (PEFR. Method: A pre-experimental one group pre-post test design was used in this study. Population was all of the COPD patients at Pulmonary Specialist Polyclinic Dr Mohamad Soewandhie Surabaya. There were 8 respondents taken by using purposive sampling. PEFR was counted by using peak flow meter every six day. Data were analyzed by using Paired t-Test with significance level p≤0.05. Result: The result showed that PMR had significance level on increasing of PEFR (p=0.012. Discussion: It can be concluded that PMR has an effect on raise PEFR. Further studies are recommended to measure the effect of PMR on respiratory rate (RR, heart rate (HR subjective dyspnoe symptoms, forced expiration volume on the first minute (FEV1 and mid maximum flow rate (MMFR in COPD patients.
Energy Technology Data Exchange (ETDEWEB)
Fries, Pascal H., E-mail: pascal-h.fries@cea.fr [Université Grenoble Alpes, INAC-SCIB, RICC, F-38000 Grenoble (France); CEA, INAC-SCIB, RICC, F-38000 Grenoble (France); Belorizky, Elie [Université Grenoble Alpes, LIPHY, F-38000 Grenoble (France); CEA, Leti-Clinatec, F-38000 Grenoble (France)
2015-07-28
For slowly tumbling entities or quasi-rigid lattices, we derive very simple analytical expressions of the quadrupole relaxation enhancement (QRE) of the longitudinal relaxation rate R{sub 1} of nuclear spins I due to their intramolecular magnetic dipolar coupling with quadrupole nuclei of arbitrary spins S ≥ 1. These expressions are obtained by using the adiabatic approximation for evaluating the time evolution operator of the quantum states of the quadrupole nuclei S. They are valid when the gyromagnetic ratio of the spin S is much smaller than that of the spin I. The theory predicts quadrupole resonant peaks in the dispersion curve of R{sub 1} vs magnetic field. The number, positions, relative intensities, Lorentzian shapes, and widths of these peaks are explained in terms of the following properties: the magnitude of the quadrupole Hamiltonian and the asymmetry parameter of the electric field gradient (EFG) acting on the spin S, the S-I inter-spin orientation with respect to the EFG principal axes, the rotational correlation time of the entity carrying the S–I pair, and/or the proper relaxation time of the spin S. The theory is first applied to protein amide protons undergoing dipolar coupling with fast-relaxing quadrupole {sup 14}N nuclei and mediating the QRE to the observed bulk water protons. The theoretical QRE agrees well with its experimental counterpart for various systems such as bovine pancreatic trypsin inhibitor and cartilages. The anomalous behaviour of the relaxation rate of protons in synthetic aluminium silicate imogolite nano-tubes due to the QRE of {sup 27}Al (S = 5/2) nuclei is also explained.
Aso, Y; Yoshioka, S; Kojima, S
2000-03-01
Isothermal crystallization of amorphous nifedipine, phenobarbital, and flopropione was studied at temperatures above and below their glass transition temperatures (T(g)). A sharp decrease in the crystallization rate with decreasing temperature was observed for phenobarbital and flopropione, such that no crystallization was observed at temperatures 20-30 degrees C lower than their T(g) within ordinary experimental time periods. In contrast, the crystallization rate of nifedipine decreased moderately with decreasing temperature, and considerable crystallization was observed at 40 degrees C below its T(g) within 4 months. The molecular mobility of these amorphous drugs was assessed by enthalpy relaxation and (1)H-NMR relaxation measurements. The enthalpy relaxation time of nifedipine was smaller than that of phenobarbital or flopropinone at the same T - T(g) values, suggesting higher molecular mobility of nifedipine. The spin-lattice relaxation time in the rotating frame (T(1rho)) decreased markedly at temperature above T(g). The slope of the Arrhenius type plot of the T(1rho) for nifedipine protons changed at about 10 degrees C below the T(g), whereas the slope for phenobarbital protons became discontinuous at about 10 degrees C above the T(g). Even at temperatures below its T(g), the spin-spin relaxation process of nifedipine could be described by the sum of its Gaussian relaxation, which is characteristic of solid protons, and its Lorentzian relaxation, which is characteristic of protons with higher mobility. In contrast, no Lorentzian relaxation was observed for phenobarbital or flopropione at temperatures below their T(g). These results also suggest that nifedipine has higher molecular mobility than phenobarbital and flopropione at temperatures below T(g). The faster crystallization of nifedipine than that of phenobarbital or flopropione observed at temperatures below its T(g) may be partly ascribed to its higher molecular mobility at these temperatures.
CONVERGENCE RATES TO TRAVELLING WAVES FOR A RELAXATION MODEL WITH LARGE INITIAL DISTURBANCE
Institute of Scientific and Technical Information of China (English)
张辉; 赵引川
2004-01-01
This paper is concerned with the convergence rates to travelling waves for a relaxation model with general flux functions. Compared with former results in this direction, the main novelty in this paper lies in the fact that the initial disturbance can be chosen large in suitable norm. Our analysis is based on the L1-stability results obtained by C. Mascia and R. Natalini in [12].
An optimized method for (15)N R(1) relaxation rate measurements in non-deuterated proteins.
Gairí, Margarida; Dyachenko, Andrey; González, M Teresa; Feliz, Miguel; Pons, Miquel; Giralt, Ernest
2015-06-01
(15)N longitudinal relaxation rates are extensively used for the characterization of protein dynamics; however, their accurate measurement is hindered by systematic errors. (15)N CSA/(1)H-(15)N dipolar cross-correlated relaxation (CC) and amide proton exchange saturation transfer from water protons are the two main sources of systematic errors in the determination of (15)N R1 rates through (1)H-(15)N HSQC-based experiments. CC is usually suppressed through a train of 180° proton pulses applied during the variable (15)N relaxation period (T), which can perturb water magnetization. Thus CC cancellation is required in such a way as to minimize water saturation effects. Here we examined the level of water saturation during the T period caused by various types of inversion proton pulses to suppress CC: (I) amide-selective IBURP-2; (II) cosine-modulated IBURP-2; (III) Watergate-like blocks; and (IV) non-selective hard. We additionally demonstrate the effect of uncontrolled saturation of aliphatic protons on (15)N R1 rates. In this paper we present an optimized pulse sequence that takes into account the crucial effect of controlling also the saturation of the aliphatic protons during (15)N R1 measurements in non-deuterated proteins. We show that using cosine-modulated IBURP-2 pulses spaced 40 ms to cancel CC in this optimized pulse program is the method of choice to minimize systematic errors coming from water and aliphatic protons saturation effects.
Kemper, Sebastian; Patel, Mitul K.; Errey, James C.; Davis, Benjamin G.; Jones, Jonathan A.; Claridge, Timothy D. W.
2010-03-01
In the application of saturation transfer difference (STD) experiments to the study of protein-ligand interactions, the relaxation of the ligand is one of the major influences on the experimentally observed STD factors, making interpretation of these difficult when attempting to define a group epitope map (GEM). In this paper, we describe a simplification of the relaxation matrix that may be applied under specified experimental conditions, which results in a simplified equation reflecting the directly transferred magnetisation rate from the protein onto the ligand, defined as the summation over the whole protein of the protein-ligand cross-relaxation multiplied by with the fractional saturation of the protein protons. In this, the relaxation of the ligand is accounted for implicitly by inclusion of the experimentally determined longitudinal relaxation rates. The conditions under which this "group epitope mapping considering relaxation of the ligand" (GEM-CRL) can be applied were tested on a theoretical model system, which demonstrated only minor deviations from that predicted by the full relaxation matrix calculations (CORCEMA-ST) [7]. Furthermore, CORCEMA-ST calculations of two protein-saccharide complexes (Jacalin and TreR) with known crystal structures were performed and compared with experimental GEM-CRL data. It could be shown that the GEM-CRL methodology is superior to the classical group epitope mapping approach currently used for defining ligand-protein proximities. GEM-CRL is also useful for the interpretation of CORCEMA-ST results, because the transferred magnetisation rate provides an additional parameter for the comparison between measured and calculated values. The independence of this parameter from the above mentioned factors can thereby enhance the value of CORCEMA-ST calculations.
Energy Technology Data Exchange (ETDEWEB)
Zhang, Guiying; Wei, Lihua; Wang, Meiling; Zhao, Kaifeng, E-mail: zhaokf@fudan.edu.cn [Institute of Modern Physics, Department of Nuclear Science and Technology, Fudan University, Shanghai 200433, China and Applied Ion Beam Physics Laboratory, Key Laboratory of the Ministry of Education, Fudan University, Shanghai 200433 (China)
2015-01-28
High quality anti-relaxation surface coatings for atomic vapor cells are essential for the preservation of atomic spin coherence and the enhancement of measurement sensitivity. In this paper, we studied the effects of water concentration in octadecyltrichlorosilane (OTS) coating solution on the relaxation rate and its reproducibility of OTS coated Rubidium vapor cells. We found that appropriate water concentration can improve the anti-relaxation performance of OTS coated cells.
Estimation of free copper ion concentrations in blood serum using T1 relaxation rates
Blicharska, Barbara; Witek, Magdalena; Fornal, Maria; MacKay, Alex L.
2008-09-01
The water proton relaxation rate constant R1 = 1/ T1 (at 60 MHz) of blood serum is substantially increased by the presence of free Cu 2+ ions at concentrations above normal physiological levels. Addition of chelating agents to serum containing paramagnetic Cu 2+ nulls this effect. This was demonstrated by looking at the effect of adding a chelating agent—D-penicillamine (D-PEN) to CuSO 4 and CuCl 2 aqueous solutions as well as to rabbit blood serum. We propose that the measurement of water proton spin-lattice relaxation rate constants before and after chelation may be used as an alternative approach for monitoring the presence of free copper ions in blood serum. This method may be used in the diagnosis of some diseases (leukaemia, liver diseases and particularly Wilson's disease) because, in contrast to conventional methods like spectrophotometry which records the total number of both bound and free ions, the proton relaxation technique is sensitive solely to free paramagnetic ions dissolved in blood serum. The change in R1 upon chelation was found to be less than 0.06 s -1 for serum from healthy subjects but greater than 0.06 s -1 for serum from untreated Wilson's patients.
Measurement of the Electron-Ion Temperature Relaxation Rate in a Dense Plasma
Taccetti, J. M.; Shurter, R. P.; Goodwin, P. M.; Benage, J. F., Jr.
2008-11-01
Current theoretical approaches to temperature relaxation, which can be categorized as binary-collision and many-body approaches, disagree. Existing experimental evidence infers a lower relaxation rate compared to the binary-collision approach, but is insufficient to determine which approach is correct. We present the most recent results from an experiment aimed at obtaining the temperature relaxation rate between ions and electrons in a dense, strongly coupled plasma by directly measuring the temperature of each component. The plasma is formed by heating a gas jet with a 10 ps laser pulse. The electrons are preferentially heated by the short pulse laser (Te 100 eV), while the ions, after undergoing very rapid (sub-ps time-scale) disorder-induced heating, should only reach a temperature of 10-15 eV. This results in a strongly coupled ion plasma with an ion-ion coupling parameter γii 3-5. We plan to measure the electron and ion temperatures of the resulting plasma independently during and after heating, using collective Thomson scattering for electrons and a high-resolution x-ray spectrometer for the ions (measuring Doppler-broadened absorption lines).
Enthalpy Relaxation of a DGEBA Epoxy as a function of Time, Temperature, and Cooling Rate
Clarkson, Caitlyn M.; McCoy, John D.; Kropka, Jamie M.
2015-03-01
Enthalpy relaxation resulting from physical aging of a DGEBA epoxy, Epon 828, cross-linked with an amine curative, Jeffamine T-403, was studied for two isothermal aging temperatures at sequential aging times up to two weeks. Results were analyzed using the peak shift method to obtain the relaxation parameters β, δ (H*), and χ. The individual effects of cooling rate from the equilibrated state, aging time, and aging temperature were isolated to understand the initial state of the glassy epoxy and its evolution during physical aging. [Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Energy Technology Data Exchange (ETDEWEB)
Spiller, M.; Brown, R.D. III; Koenig, S.H.; Wolf, G.L.
1988-11-01
The factors that determine the field-dependent increase in 1/T1 of tissue water protons were investigated for MnCl2 and Mn2+ (PDTA) (1,3-propylenediamine-N,N',N'',N'''-tetraacetic acid) introduced intravenously into rabbits. Mn2+ was used in preference to other paramagnetic ions in part because of the distinct NMRD profiles (magnetic field dependence of 1/T1) of free Mn2+ ions, their small chelate complexes, and their macromolecular conjugates, and in part because the relatively low toxicity of Mn2+ is favorable for animal studies. Tissue content of Mn2+ was determined in all samples by inductively coupled plasma analyses the state of Mn2+ in excised tissues was determined from the form of the 1/T1 NMRD profile of water protons; and distribution of contrast agent within tissue and access of water on a T1 time scale were determined by double-exponential analyses of proton relaxation behavior in intact doped tissue, as well as by the change of single-exponential relaxation rates and proton signal intensity upon gentle disruption of the tissue. MnCl2 is found in all tissues, except fat and skeletal muscle, but liver is most avid at low dose, and Mn2+ accumulates in spleen after high doses. Chelation targets Mn2+ to liver and kidney, saturating the liver chemically at relatively low dose. We suggest that pronounced increase in tissue relaxivity results from irrotationally bound Mn2+, ostensibly associated with the polar head groups of cell membranes. Compartmentalization of contrast agent and restricted diffusion of tissue water influences the maximum relaxation rates attainable, so that there is an optimal dose of these contrast agents which is rather low.
Spiller, M; Brown, R D; Koenig, S H; Wolf, G L
1988-11-01
The factors that determine the field-dependent increase in 1/T1 of tissue water protons were investigated for MnCl2 and Mn2+ (PDTA) (1,3-propylenediamine-N,N',N'',N'''-tetraacetic acid) introduced intravenously into rabbits. Mn2+ was used in preference to other paramagnetic ions in part because of the distinct NMRD profiles (magnetic field dependence of 1/T1) of free Mn2+ ions, their small chelate complexes, and their macromolecular conjugates, and in part because the relatively low toxicity of Mn2+ is favorable for animal studies. Tissue content of Mn2+ was determined in all samples by inductively coupled plasma analyses the state of Mn2+ in excised tissues was determined from the form of the 1/T1 NMRD profile of water protons; and distribution of contrast agent within tissue and access of water on a T1 time scale were determined by double-exponential analyses of proton relaxation behavior in intact doped tissue, as well as by the change of single-exponential relaxation rates and proton signal intensity upon gentle disruption of the tissue. MnCl2 is found in all tissues, except fat and skeletal muscle, but liver is most avid at low dose, and Mn2+ accumulates in spleen after high doses. Chelation targets Mn2+ to liver and kidney, saturating the liver chemically at relatively low dose. We suggest that pronounced increase in tissue relaxivity results from irrotationally bound Mn2+, ostensibly associated with the polar head groups of cell membranes. Compartmentalization of contrast agent and restricted diffusion of tissue water influences the maximum relaxation rates attainable, so that there is an optimal dose of these contrast agents which is rather low.
Strain Rate Dependence of Compressive Yield and Relaxation in DGEBA Epoxies
Arechederra, Gabriel K.; Reprogle, Riley C.; Clarkson, Caitlyn M.; McCoy, John D.; Kropka, Jamie M.; Long, Kevin N.; Chambers, Robert S.
2015-03-01
The mechanical response in uniaxial compression of two diglycidyl ether of bisphenol-A epoxies were studied. These were 828DEA (Epon 828 cured with diethanolamine (DEA)) and 828T403 (Epon 828 cured with Jeffamine T-403). Two types of uniaxial compression tests were performed: A) constant strain rate compression and B) constant strain rate compression followed by a constant strain relaxation. The peak (yield) stress was analyzed as a function of strain rate from Eyring theory for activation volume. Runs at different temperatures permitted the construction of a mastercurve, and the resulting shift factors resulted in an activation energy. Strain and hold tests were performed for a low strain rate where a peak stress was lacking and for a higher strain rate where the peak stress was apparent. Relaxation from strains at different places along the stress-strain curve was tracked and compared. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Lewis, Gregory F; Hourani, Laurel; Tueller, Stephen; Kizakevich, Paul; Bryant, Stephanie; Weimer, Belinda; Strange, Laura
2015-09-01
Decreased heart rate variability (HRV) is associated with posttraumatic stress disorder (PTSD) and depression symptoms, but PTSD's effects on the autonomic stress response and the potential influence of HRV biofeedback in stress relaxation training on improving PTSD symptoms are not well understood. The objective of this study was to examine the impact of a predeployment stress inoculation training (PRESTINT) protocol on physiologic measures of HRV in a large sample of the military population randomly assigned to experimental HRV biofeedback-assisted relaxation training versus a control condition. PRESTINT altered the parasympathetic regulation of cardiac activity, with experimental subjects exhibiting greater HRV, that is, less arousal, during a posttraining combat simulation designed to heighten arousal. Autonomic reactivity was also found to be related to PTSD and self-reported use of mental health services. Future PRESTINT training could be appropriate for efficiently teaching self-help skills to reduce the psychological harm following trauma exposure by increasing the capacity for parasympathetically modulated reactions to stress and providing a coping tool (i.e., relaxation method) for use following a stressful situation.
On the Rate of Relaxation for the Landau Kinetic Equation and Related Models
Bobylev, Alexander; Gamba, Irene M.; Zhang, Chenglong
2017-08-01
We study the rate of relaxation to equilibrium for Landau kinetic equation and some related models by considering the relatively simple case of radial solutions of the linear Landau-type equations. The well-known difficulty is that the evolution operator has no spectral gap, i.e. its spectrum is not separated from zero. Hence we do not expect purely exponential relaxation for large values of time t>0. One of the main goals of our work is to numerically identify the large time asymptotics for the relaxation to equilibrium. We recall the work of Strain and Guo (Arch Rat Mech Anal 187:287-339 2008, Commun Partial Differ Equ 31:17-429 2006), who rigorously show that the expected law of relaxation is \\exp (-ct^{2/3}) with some c > 0. In this manuscript, we find an heuristic way, performed by asymptotic methods, that finds this "law of two thirds", and then study this question numerically. More specifically, the linear Landau equation is approximated by a set of ODEs based on expansions in generalized Laguerre polynomials. We analyze the corresponding quadratic form and the solution of these ODEs in detail. It is shown that the solution has two different asymptotic stages for large values of time t and maximal order of polynomials N: the first one focus on intermediate asymptotics which agrees with the "law of two thirds" for moderately large values of time t and then the second one on absolute, purely exponential asymptotics for very large t, as expected for linear ODEs. We believe that appearance of intermediate asymptotics in finite dimensional approximations must be a generic behavior for different classes of equations in functional spaces (some PDEs, Boltzmann equations for soft potentials, etc.) and that our methods can be applied to related problems.
Spin-lattice relaxation rate studies in CeAl[sub 3] at low temperatures
Energy Technology Data Exchange (ETDEWEB)
Gavilano, J.L. (Lab. fuer Festkoerperphysik, ETH-Hoenggerberg, Zuerich (Switzerland)); Hunziker, J. (Lab. fuer Festkoerperphysik, ETH-Hoenggerberg, Zuerich (Switzerland)); Ott, H.R. (Lab. fuer Festkoerperphysik, ETH-Hoenggerberg, Zuerich (Switzerland))
1994-02-01
We have measured the spin-lattice relaxation rate (1/T[sub 1]) of the 1/2 Leftrightarrow -1/2 transition of the [sup 27]Al nuclear Zeeman-levels in CeAl[sub 3] at a frequency of 2.095 MHz and temperatures between 0.1 K and 2 K. Below 2 K the temperature dependence of 1/T[sub 1] follows a Korringa law with (T[sub 1]T)[sup -1] = 16.6 (Ksec)[sup -1]. We found no evidence of a phase transition to a magnetically ordered state in the temperature region of this experiment. (orig.)
Extracting the Electron-Ion Temperature Relaxation Rate from Ion Stopping Experiments
Grabowski, Paul E.; Frenje, Johan A.; Benedict, Lorin X.
2016-10-01
Direct measurement of i-e equilibration rates at ICF-relevant conditions is a big challenge, as it is difficult to differentiate from other sinks and sources of energy, such as heat conduction and pdV work. Another method is to use information from ion stopping experiments. Such experiments at the OMEGA laser have made precision energy loss measurements of fusion products at these conditions. Combined with the multimonochromatic x-ray imager technique, which gives temporally and spatially resolved electron temperature and density, we have a robust stopping experiment. We propose to use such stopping measurements to assess the i-e temperature relaxation rate, since both processes involve energy exchange between electrons and ions. We require that the fusion products are 1) much faster than the thermal ions so that i-i collisions are negligible compared to i-e collisions and 2) slower than the thermal electrons so that the stopping obeys a linear friction law. Then the Coulomb logarithms associated with ion stopping and i-e temperature relaxation rate are identical and a measurement of the former provides the latter. Prepared by LLNL under Contract DE-AC52-07NA27344.
Heinz, Sebastian; Mielke, Alexander
2016-04-28
We revisit the model for a two-well phase transformation in a linearly elastic body that was introduced and studied in Mielke et al. (2002 Arch. Ration. Mech. Anal. 162: , 137-177). This energetic rate-independent system is posed in terms of the elastic displacement and an internal variable that gives the phase portion of the second phase. We use a new approach based on mutual recovery sequences, which are adjusted to a suitable energy increment plus the associated dissipated energy and, thus, enable us to pass to the limit in the construction of energetic solutions. We give three distinct constructions of mutual recovery sequences which allow us (i) to generalize the existence result in Mielke et al. (2002), (ii) to establish the convergence of suitable numerical approximations via space-time discretization and (iii) to perform the evolutionary relaxation from the pure-state model to the relaxed-mixture model. All these results rely on weak converge and involve the H-measure as an essential tool.
Temperature dependence of the NMR spin-lattice relaxation rate for spin-1/2 chains
Coira, E.; Barmettler, P.; Giamarchi, T.; Kollath, C.
2016-10-01
We use recent developments in the framework of a time-dependent matrix product state method to compute the nuclear magnetic resonance relaxation rate 1 /T1 for spin-1/2 chains under magnetic field and for different Hamiltonians (XXX, XXZ, isotropically dimerized). We compute numerically the temperature dependence of the 1 /T1 . We consider both gapped and gapless phases, and also the proximity of quantum critical points. At temperatures much lower than the typical exchange energy scale, our results are in excellent agreement with analytical results, such as the ones derived from the Tomonaga-Luttinger liquid (TLL) theory and bosonization, which are valid in this regime. We also cover the regime for which the temperature T is comparable to the exchange coupling. In this case analytical theories are not appropriate, but this regime is relevant for various new compounds with exchange couplings in the range of tens of Kelvin. For the gapped phases, either the fully polarized phase for spin chains or the low-magnetic-field phase for the dimerized systems, we find an exponential decrease in Δ /(kBT ) of the relaxation time and can compute the gap Δ . Close to the quantum critical point our results are in good agreement with the scaling behavior based on the existence of free excitations.
LDA+DMFT calculations of the Knight shift and relaxation rate in VOMoO{sub 4}
Energy Technology Data Exchange (ETDEWEB)
Kiani, Amin; Pavarini, Eva [Institute for Advanced Simulation and JARA, Forschungszentrum Juelich, 52425 Juelich (Germany)
2013-07-01
By using the LDA+DMFT approach and the local vertex approximation, we calculate the magnetic linear response function of strongly correlated transition-metal oxides. From the susceptibility we obtain Knight shift and relaxation rate. We present results for the frustrated system VOMoO{sub 4}. In particular we investigate how the Knight shift and the relaxation time behave in different temperature and correlation regimes.
Nuclear relaxation rates in the herbertsmithite kagome antiferromagnets ZnCu3(OH) 6Cl2
Sherman, Nicholas E.; Imai, Takashi; Singh, Rajiv R. P.
2016-10-01
Local spectral functions and nuclear magnetic relaxation (NMR) rates, 1 /T1 , for the spin-half Heisenberg antiferromagnet on the Kagome lattice are calculated using the Moriyas Gaussian approximation, as well as through an extrapolation of multiple frequency moments. The temperature dependence of the calculated rates is compared with the oxygen 1 /T1 NMR data in Herbertsmithite. We find that the Gaussian approximation for 1 /T1 shows behavior qualitatively similar to experiments with a sharp drop in rates at low temperatures, consistent with a spin-gapped behavior. However, this approximation significantly underestimates the magnitude of 1 /T1 even at room temperature. Rates obtained from extrapolation of multiple frequency moments give very good agreement with the room temperature NMR data with J =195 ±20 K and hyperfine couplings determined independently from other measurements. The use of multiple frequency moments also leads to additional low-frequency weight in the local structure factors. The convergence of our calculations with higher-frequency moments breaks down at low temperatures, suggesting the existence of longer-range dynamic correlations in the system despite the very short range static correlations.
Sodium-23 NMR spin-lattice relaxation rate studies of mono- and bis-intercalation in DNA
Energy Technology Data Exchange (ETDEWEB)
Eggert, H.; Dinesen, J.; Jacobsen, J.P. (Univ. of Copenhagen (Denmark))
1989-04-18
Sodium-23 spin-lattice relaxation rate measurements have been used to study the intercalation of a series of 9-aminoacridine derivatives in DNA. The {sup 23}Na relaxation rate is strongly dependent upon the amount of intercalator added to a sodium DNA solution. The results are analyzed by a combined use of the ion condensation theory and the quadrupolar relaxation theory of polyelectrolyte solutions. This interpretation shows that the major effect in lowering the relaxation rate by intercalation is not due to the release of sodium ions but is caused by a substantial decrease in the relaxation rate R{sub b} for the remaining bound sodium ions. Likewise, titration of NaDNA solutions with MgCl{sub 2} shows that condensation of Mg{sup 2+} on the DNA double helix reduces R{sub b}. A good agreement between experiment and theory is found if the average lengthening following intercalation of a 9-aminoacridine moiety is assumed to be approximately 2.7 {angstrom}. The distinction between mono- and bis-intercalation is clearly indicated by the results. The two bis-intercalating drugs examined are found to bis-intercalate only up to r {le} 0.02. For r > 0.02 the drugs apparently mono-intercalate.
The spectral relaxation model of the scalar dissipation rate in homogeneous turbulence
Fox, R. O.
1995-05-01
A model for the effect of scalar spectral relaxation on the scalar dissipation rate of an inert, passive scalar (Sc≥1) in fully developed homogeneous turbulence is presented. In the model, wave-number space is divided into a finite number [the total number depending on the turbulence Reynolds number Reλ and the Schmidt number (Sc)] of intermediate stages whose time constants are determined from the velocity spectrum. The model accounts for the evolution of the scalar spectrum from an arbitrary initial shape to its fully developed form and its effect on the scalar dissipation rate for finite Reλ and Sc≥1. Corrsin's result [AIChE J. 10, 870 (1964)] for the scalar mixing time is attained for large Reλ in the presence of a constant mean scalar gradient and a stationary, isotropic turbulence field. Comparisons with DNS results for stationary, isotropic turbulence and experimental data for decaying, homogeneous grid turbulence demonstrate the satisfactory performance of the model.
Yacyshyn, Alexandra F; Nettleton, Jane; Power, Geoffrey A; Jakobi, Jennifer M; McNeil, Chris J
2017-09-01
Transcranial magnetic stimulation (TMS) of the motor cortex during a maximal voluntary contraction (MVC) permits functionally relevant measurements of muscle group relaxation rate (i.e., when muscles are actively contracting under voluntary control). This study's purpose was twofold: (1) to explore the impact of muscle length on TMS-induced plantar flexor relaxation rate; and (2) to incorporate ultrasonography to measure relaxation-induced lengthening of medial gastrocnemius (MG) fascicles and displacement of the muscle-tendon junction (MTJ). Eleven males (24.8 ± 7.0 years) performed 21 brief isometric plantar flexor MVCs. Trials were block-randomized every three MVCs among 20° dorsiflexion (DF), a neutral ankle position, and 30° plantar flexion (PF). During each MVC, TMS was delivered and ultrasound video recordings captured MG fascicles or MTJ length changes. Peak relaxation rate was calculated as the steepest slope of the TMS-induced drop in plantar flexor torque or the rate of length change for MG fascicles and MTJ Torque relaxation rate was slower for PF (-804 ± 162 Nm·s(-1)) than neutral and DF (-1896 ± 298 and -2008 ± 692 Nm·s(-1), respectively). Similarly, MG fascicle relaxation rate was slower for PF (-2.80 ± 1.10 cm·s(-1)) than neutral and DF (-5.35 ± 1.10 and -4.81 ± 1.87 cm·s(-1), respectively). MTJ displacement rate showed a similar trend (P = 0.06), with 3.89 ± 1.93 cm·s(-1) for PF compared to rates of 6.87 ± 1.55 and 6.36 ± 2.97 cm·s(-1) for neutral and DF, respectively. These findings indicate muscle length affects the torque relaxation rate recorded after TMS during an MVC Comparable results were obtained from muscle fascicles, indicating ultrasound imaging is suitable for measuring evoked contractile properties during voluntary contraction. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.
Structural relaxation time and cooling rate of a melt in the glass transition region
Sanditov, D. S.; Sydykov, B. S.
2015-03-01
The nature of the parameter involved in the Bartenev equation qτg = C relating the cooling rate of a glass-forming melt to its structural relaxation time in the glass transition region is discussed on the basis of the Volkenshtein-Ptitsyn theory using a number of known relationships. It is established that parameter C for amorphous substances with the same fragility is linearly temperature dependent. This parameter is shown to equal the narrow temperature range δ T g characterizing the liquid-glass transition region (by Nemilov); i.e., C = δ T g. It is concluded that δ T g for most glassy systems is only ˜0.7% of the glass transition temperature T g. The narrowness of temperature range δ T g is explained by the small fluctuation volume fraction f g "frozen" at the glass transition temperature. The concept of a close relationship between constant C and the structural order at T g (i.e., the characteristic of the inner state of a nonequilibrium "frozen" amorphous system) is developed.
Cellular Imaging Using Equivalent Cross-Relaxation Rate Technique in Rabbit VX-2 Tumor Model.
Nishiofuku, Hideyuki; Matsushima, Shigeru; Taguchi, Osamu; Inaba, Yoshitaka; Yamaura, Hidekazu; Sato, Yozo; Tanaka, Toshihiro; Kichikawa, Kimihiko
2011-01-01
Equivalent cross-relaxation rate (ECR) imaging (ECRI) is a measurement technique that can be used to quantitatively evaluate changes in structural organization and cellular density by MRI. The aim of this study was to evaluate the correlation between the ECR value and cellular density in the rabbit VX2 tumor model. Five rabbits implanted with 10 VX2 tumors in the femur muscles were included in this study. We adopted the off-resonance technique with a single saturation transfer pulse frequency of 7 ppm downfield from water resonance. The ECR value was defined as the percentage of signal loss between the unsaturated and saturated images. ECR images were constructed based on the percentage of the ECR value. Pathological specimens were divided into 34 areas and classified into two groups: the viable group and the necrotic group. ECR values were measured and compared between groups. The correlation between the ECR value and cellular density was then determined. The mean ECR value was significantly higher in the viable group than in the necrotic group (61.2% vs. 35.8%). The area under the curve that calculated by receiver operating characteristic curve was 0.991 at 7 ppm. The regression graph showed a linear relationship between the ECR value and cellular density; the correlation coefficient (r) was 0.858. There is a strong association between the ECR value and cellular density in VX2 tumors and so ECRI could be a potentially useful technique for accurately depicting viable and necrotic areas.
The influence of dimension on the relaxation process of East-like models: Rigorous results
Chleboun, P.; Faggionato, A.; Martinelli, F.
2014-08-01
We study facilitated models which extend to arbitrary dimensions the one-dimensional East process and which are supposed to catch some of the main features of the complex dynamics of fragile glasses. We focus on the low-temperature regime (small density c\\approx e^{-\\beta} of the facilitating sites). In the literature the relaxation process has been assumed to be quasi-one-dimensional and the equilibration time has been computed using the relaxation time of the East model (d=1) on the equilibrium length scale L_c=(1/c)^{1/d} in d-dimension. This led to a super-Arrhenius scaling for the relaxation time of the form T_{\\text{rel}}\\asymp \\exp(\\beta^2/dlog 2) . In a companion paper, using renormalization group ideas and electrical networks methods, we rigorously establish that instead T_{\\text{rel}}\\asymp \\exp(\\beta^2/2dlog 2) , contradicting the quasi-one-dimensional assumption. The above scaling confirms previous MCAMC simulations. Next we compute the relaxation time at finite and mesoscopic length scales, and show a dramatic dependence on the boundary conditions. Our final result is related to the out-of-equilibrium dynamics. Starting with a single facilitating site at the origin we show that, up to length scales L=O(L_c) , its influence propagates much faster (on a logarithmic scale) along the diagonal direction than along the axes directions.
Tan, Fuitze; Tengah, Asrin; Nee, Lo Yah; Fredericks, Salim
2014-05-01
Music has been employed in various clinical settings to reduce anxiety. However, meta-analysis has shown music to have little influence on haemodynamic parameters. This study aimed at investigating the effect of relaxing music on heart rate recovery after exercise. Twenty-three student volunteers underwent treadmill exercise and were assessed for heart rate recovery and saliva analysis; comparing exposure to sedative music with exposure to silence during the recovery period immediately following exercise. No differences were found between music and non-music exposure regarding: heart rate recovery, resting pulse rate, and salivary cortisol. Music was no different to silence in affecting these physiological measures, which are all associated with anxiety. Relaxing music unaccompanied by meditation techniques or other such interventions may not have a major role in reducing anxiety in certain experimental settings. Copyright © 2014 Elsevier Ltd. All rights reserved.
Benício, Kadja; Dias, Fernando A. L.; Gualdi, Lucien P.; Aliverti, Andrea; Resqueti, Vanessa R.; Fregonezi, Guilherme A. F.
2015-01-01
OBJECTIVE: To assess the influence of diaphragmatic activation control (diaphC) on Sniff Nasal-Inspiratory Pressure (SNIP) and Maximum Relaxation Rate of inspiratory muscles (MRR) in healthy subjects. METHOD: Twenty subjects (9 male; age: 23 (SD=2.9) years; BMI: 23.8 (SD=3) kg/m2; FEV1/FVC: 0.9 (SD=0.1)] performed 5 sniff maneuvers in two different moments: with or without instruction on diaphC. Before the first maneuver, a brief explanation was given to the subjects on how to perform the sniff test. For sniff test with diaphC, subjects were instructed to perform intense diaphragm activation. The best SNIP and MRR values were used for analysis. MRR was calculated as the ratio of first derivative of pressure over time (dP/dtmax) and were normalized by dividing it by peak pressure (SNIP) from the same maneuver. RESULTS: SNIP values were significantly different in maneuvers with and without diaphC [without diaphC: -100 (SD=27.1) cmH2O/ with diaphC: -72.8 (SD=22.3) cmH2O; p<0.0001], normalized MRR values were not statistically different [without diaphC: -9.7 (SD=2.6); with diaphC: -8.9 (SD=1.5); p=0.19]. Without diaphC, 40% of the sample did not reach the appropriate sniff criteria found in the literature. CONCLUSION: Diaphragmatic control performed during SNIP test influences obtained inspiratory pressure, being lower when diaphC is performed. However, there was no influence on normalized MRR. PMID:26578254
Segawa, Takuya F; Bodenhausen, Geoffrey
2013-12-01
Homogeneous line-widths that arise from transverse relaxation tend to be masked by B0 field inhomogeneity and by multiplets due to homonuclear J-couplings. Besides well-known spin-locking sequences that lead to signals that decay with a rate R1ρ without any modulations, alternative experiments allow one to determine the transverse relaxation rates R2 in systems with scalar-coupled spins. We evaluate three recent strategies by experiment and simulation: (i) moderate-amplitude SITCOM-CPMG sequences (Dittmer and Bodenhausen, 2006), (ii) multiple-quantum filtered (MQF) sequences (Barrère et al., 2011) and (iii) PROJECT sequences (Aguilar et al., 2012). Experiments where the J-evolution is suppressed by spin-locking measure the pure relaxation rate R2(Ix) of an in-phase component. Experiments based on J-refocusing yield a mixture of in-phase rates R2(Ix) and antiphase rates R2(2IySz), where the latter are usually faster than the former. Moderate-amplitude SITCOM-CPMG and PROJECT methods can be applied to systems with many coupled spins, but applications of MQF sequences are limited to two-spin systems since modulations in larger systems can only partly be suppressed.
Structural relaxation in dense liquids composed of anisotropic particles.
Shen, Tianqi; Schreck, Carl; Chakraborty, Bulbul; Freed, Denise E; O'Hern, Corey S
2012-10-01
We perform extensive molecular dynamics simulations of dense liquids composed of bidisperse dimer- and ellipse-shaped particles in two dimensions that interact via purely repulsive contact forces. We measure the structural relaxation times obtained from the long-time α decay of the self part of the intermediate scattering function for the translational and rotational degrees of freedom (DOF) as a function of packing fraction φ, temperature T, and aspect ratio α. We are able to collapse the packing-fraction and temperature-dependent structural relaxation times for disks, and dimers and ellipses over a wide range of α, onto a universal scaling function F(±)(|φ-φ(0)|,T,α), which is similar to that employed in previous studies of dense liquids composed of purely repulsive spherical particles in three dimensions. F(±) for both the translational and rotational DOF are characterized by the α-dependent scaling exponents μ and δ and packing fraction φ(0)(α) that signals the crossover in the scaling form F(±) from hard-particle dynamics to super-Arrhenius behavior for each aspect ratio. We find that the fragility of structural relaxation at φ(0), m(φ(0)), decreases monotonically with increasing aspect ratio for both ellipses and dimers. For α>α(p), where α(p) is the location of the peak in the packing fraction φ(J) at jamming onset, the rotational DOF are strongly coupled to the translational DOF, and the dynamic scaling exponents and φ(0) are similar for the rotational and translational DOF. For 1composed of dimer- and ellipse-shaped particles are qualitatively the same, despite the fact that zero-temperature static packings of dimers are isostatic, while static packings of ellipses are hypostatic. Thus, zero-temperature contact counting arguments do not apply to structural relaxation of dense liquids of anisotropic particles near the glass transition.
Institute of Scientific and Technical Information of China (English)
Guo Wei Yin; Yi Ming Li; Wei Wei; Shan Hao Jiang; Da Yuan Zhu; Wei Hong Du
2008-01-01
In order to understand whether the ameliorating effect on old ages memory disorder by the root of Salvia miltiorhiza is related to the acetylcholinesterase (AChE) inhibition, two main ingredients, salvianolic acid B (1) and rosmarinic acid (2), which were isolated from S. Miltiorhiza water extract, were investigated in vitro by NMR relaxation rate in this work. The results showed that the proton selective relaxation rates and the molecular rotational correlation time of proton pairs for compounds 1 and 2 increased significantly by adding of AChE in mixing solution. The study reveals that the two compounds might bind to the enzyme and have AChE inhibitory effect, which could contribute to the ameliorating effect at some extent on old ages memory disorder.
de Haan, Hendrick W; Paquet, Chantal
2011-12-01
The effects of including a hydrophilic coating around the particles are studied across a wide range of particle sizes by performing Monte Carlo simulations of protons diffusing through a system of magnetic particles. A physically realistic methodology of implementing the coating by cross boundary jump scaling and transition probabilities at the coating surface is developed. Using this formulation, the coating has three distinct impacts on the relaxation rate: an enhancement at small particle sizes, a degradation at intermediate particle sizes, and no effect at large particles sizes. These varied effects are reconciled with the underlying dephasing mechanisms by using the concept of a full dephasing zone to present a physical picture of the dephasing process with and without the coating for all sizes. The enhancement at small particle sizes is studied systemically to demonstrate the existence of an optimal ratio of diffusion coefficients inside/outside the coating to achieve maximal increase in the relaxation rate.
Fried, R
1987-12-01
Fifteen men and 35 women, suffering from a number of psychological and somatic disorders, were taught to relax by biofeedback-assisted deep-diaphragmatic breathing together with guided mental imagery. No instructions were given about rate. Breathing rate and pattern, PETCO2, and EEG were monitored before training and after the first three 2-minute training trials (session 1). In 27 subjects (54%), breathing patterns and rate were noted to resemble those reported by meditation practitioners (3 to 5 b/min). The PETCO2 and EEG changes support a hypothesis of metabolic hypoarousal. Four subjects spontaneously reported experiencing altered awareness. A centrally mediated hypoarousal response is tentatively implicated.
Ding, Wenxin; Žitko, Rok; Shastry, B. Sriram
2017-09-01
Using two approaches to strongly correlated systems, the extremely correlated Fermi liquid theory and the dynamical mean field theory, we compute the transverse transport coefficients, namely, the Hall constants RH and Hall angles θH, and the longitudinal and transverse optical response of the U =∞ Hubbard model in the limit of infinite dimensions. We focus on two successive low-temperature regimes, the Gutzwiller-correlated Fermi liquid (GCFL) and the Gutzwiller-correlated strange metal (GCSM). We find that the Hall angle cotθH is proportional to T2 in the GCFL regime, while upon warming into the GCSM regime it first passes through a downward bend and then continues as T2. Equivalently, RH is weakly temperature dependent in the GCFL regime, but becomes strongly temperature dependent in the GCSM regime. Drude peaks are found for both the longitudinal optical conductivity σx x(ω ) and the optical Hall angles tanθH(ω ) below certain characteristic energy scales. By comparing the relaxation rates extracted from fitting to the Drude formula, we find that in the GCFL regime there is a single relaxation rate controlling both longitudinal and transverse transport, while in the GCSM regime two different relaxation rates emerge. We trace the origin of this behavior to the dynamical particle-hole asymmetry of the Dyson self-energy, arguably a generic feature of doped Mott insulators.
Gadermaier, C; Alexandrov, A S; Kabanov, V V; Kusar, P; Mertelj, T; Yao, X; Manzoni, C; Brida, D; Cerullo, G; Mihailovic, D
2010-12-17
We determined electronic relaxation times via pump-probe optical spectroscopy using sub-15 fs pulses for the normal state of two different cuprate superconductors. We show that the primary relaxation process is the electron-phonon interaction and extract a measure of its strength, the second moment of the Eliashberg function λ[ω2] = 800 ± 200 meV2 for La(1.85)Sr(0.15)CuO4 and λ[ω2] = 400 ± 100 meV2 for YBa(2)Cu(3)O(6.5). These values suggest a possible fundamental role of the electron-phonon interaction in the superconducting pairing mechanism.
Energy Technology Data Exchange (ETDEWEB)
Ishizaka, H. [Tano General Hospital, Gunma (Japan). Dept. of Radiology]|[Gunma Univ. Hospital (Japan). Dept. of Diagnostic Radiology; Ishijima, H. [Gunma Univ. Hospital (Japan). Dept. of Diagnostic Radiology
1997-11-01
Purpose: This study was made to clarify the paramagnetic effect of iron stored in the hematopoietic tissue of bone marrow. Material and methods: The T1 and T2 relaxation times of bone-marrow water in the L1-3 vertebrae of 20 healthy individuals were measured by MR imaging with a 1.5 T magnet. The chemical shift misregistration effect was used to isolate the bone-marrow water. The results were compared with the serum ferritin concentration. Results and Conclusion: Although no correlation between the T1 relaxation rate of the water fraction and the serum ferritin concentration was evident, the T2 relaxation rate of the water fraction showed strong linear correlation with the serum ferritin concentration (r=0.87, p<0.001). Thus, T2 of bone-marrow water accurately reflects the amount of iron in normal bone marrow. This finding may be useful in the evaluation of the characteristics of hematopoietic tissue in bone marrow. (orig.).
Wicke, Susann; Schäferhoff, Bastian; dePamphilis, Claude W; Müller, Kai F
2014-03-01
Carnivorous Lentibulariaceae exhibit the most sophisticated implementation of the carnivorous syndrome in plants. Their unusual lifestyle coincides with distinct genomic peculiarities such as the smallest angiosperm nuclear genomes and extremely high nucleotide substitution rates across all genomic compartments. Here, we report the complete plastid genomes from each of the three genera Pinguicula, Utricularia, and Genlisea, and investigate plastome-wide changes in their molecular evolution as the carnivorous syndrome unfolds. We observe a size reduction by up to 9% mostly due to the independent loss of genes for the plastid NAD(P)H dehydrogenase and altered proportions of plastid repeat DNA, as well as a significant plastome-wide increase of substitution rates and microstructural changes. Protein-coding genes across all gene classes show a disproportional elevation of nonsynonymous substitutions, particularly in Utricularia and Genlisea. Significant relaxation of purifying selection relative to noncarnivores occurs in the plastid-encoded fraction of the photosynthesis ATP synthase complex, the photosystem I, and in several other photosynthesis and metabolic genes. Shifts in selective regimes also affect housekeeping genes including the plastid-encoded polymerase, for which evidence for relaxed purifying selection was found once during the transition to carnivory, and a second time during the diversification of the family. Lentibulariaceae significantly exhibit enhanced rates of nucleotide substitution in most of the 130 noncoding regions. Various factors may underlie the observed patterns of relaxation of purifying selection and substitution rate increases, such as reduced net photosynthesis rates, alternative paths of nutrient uptake (including organic carbon), and impaired DNA repair mechanisms.
Energy Technology Data Exchange (ETDEWEB)
Ootsuka, Kae; Togami, Izumi; Kitagawa, Takahiro [Okayama Univ. (Japan). School of Medicine] [and others
1996-10-01
MR imaging is a useful non-invasive technique to detect iron deposits in many organs, but it is difficult to evaluate quantitatively. This study was performed to determine the possibility whether T2 relaxation rate (1/T2) could quantify iron deposits in the reticuloendothelial system (liver, spleen and bone marrow) of 11 patients and four normal volunteers. A moderate correlation was obtained between T2-relaxation rate and the serum ferritin level. These results suggest that T2-relaxation rate may provide useful information for the repeated quantitative evaluation of patients with iron-overload-syndromes. (author)
Endo- vs. Exo-genous shocks and relaxation rates in book and music "sales"
Lambiotte, R
2005-01-01
In this paper, we analyze the response of music and book sales to an external field and to buyer herding. We distinguish endogenous and exogenous shocks. We focus on some case studies, whose data have been collected from ranking on amazon.com. We show that an ensemble of equivalent systems quantitatively respond in a similar way to a similar ''external shock'', indicating roads to universality features. In contrast to Sornette et al. [Phys. Rev. Lett. {93}, 228701 (2004)] who seemed to find power law behaviors, in particular at long times, - a law interpreted in terms of an epidemic activity, we observe that the relaxation process can be as well seen as an exponential one that saturates toward an asymptotic state, itself different from the pre-shock state. By studying an ensemble of 111 shocks, on books or records, we show that exogenous and endogenous shocks are discriminated by their short-time behaviour: the relaxation time seems to be twice shorter in endogenous shocks than in exogenous ones. We interpret...
Endo- vs. exogenous shocks and relaxation rates in book and music “sales”
Lambiotte, R.; Ausloos, M.
2006-04-01
In this paper, we analyse the response of music and book sales to an external field and a buyer herding. We distinguish endogenous and exogenous shocks. We focus on some case studies, whose data have been collected from ranking on amazon.com. We show that an ensemble of equivalent systems quantitatively respond in a same way to a similar “external shock”, indicating roads to universality features. In contrast to Sornette et al. [Phys. Rev. Lett. 93 (2004) 228701] who seemed to find power-law behaviours, in particular at long times, a law interpreted in terms of an epidemic activity, we observe that the relaxation process can be as well seen as an exponential one that saturates toward an asymptotic state, itself different from the pre-shock state. By studying an ensemble of 111 shocks, on books or records, we show that exogenous and endogenous shocks are discriminated by their short-time behaviour: the relaxation time seems to be twice shorter in endogenous shocks than in exogenous ones. We interpret the finding through a simple thermodynamic model with a dissipative force.
Graham, Matt W; Shi, Su-Fei; Wang, Zenghui; Ralph, Daniel C; Park, Jiwoong; McEuen, Paul L
2013-01-01
Using transient absorption (TA) microscopy as a hot electron thermometer, we show that disorder-assisted acoustic-phonon supercollisions (SCs) best describe the rate-limiting relaxation step in graphene over a wide range of lattice temperatures (Tl = 5-300 K), Fermi energies (E(F) = ± 0.35 eV), and optical probe energies (~0.3-1.1 eV). Comparison with simultaneously collected transient photocurrent, an independent hot electron thermometer, confirms that the rate-limiting optical and electrical response in graphene are best described by the SC-heat dissipation rate model, H = A(T(e)(3) - T(l)(3)). Our data further show that the electron cooling rate in substrate-supported graphene is twice as fast as in suspended graphene sheets, consistent with SC model prediction for disorder.
An optimized method for {sup 15}N R{sub 1} relaxation rate measurements in non-deuterated proteins
Energy Technology Data Exchange (ETDEWEB)
Gairí, Margarida, E-mail: mgairi@rmn.ub.edu [University of Barcelona (CCiTUB), NMR Facility, Scientific and Technological Centers (Spain); Dyachenko, Andrey [Institute for Research in Biomedicine (IRB) (Spain); González, M. Teresa; Feliz, Miguel [University of Barcelona (CCiTUB), NMR Facility, Scientific and Technological Centers (Spain); Pons, Miquel [University of Barcelona, Biomolecular NMR Laboratory and Organic Chemistry Department (Spain); Giralt, Ernest, E-mail: ernest.giralt@irbbarcelona.org [Institute for Research in Biomedicine (IRB) (Spain)
2015-06-15
{sup 15}N longitudinal relaxation rates are extensively used for the characterization of protein dynamics; however, their accurate measurement is hindered by systematic errors. {sup 15}N CSA/{sup 1}H–{sup 15}N dipolar cross-correlated relaxation (CC) and amide proton exchange saturation transfer from water protons are the two main sources of systematic errors in the determination of {sup 15}N R{sub 1} rates through {sup 1}H–{sup 15}N HSQC-based experiments. CC is usually suppressed through a train of 180° proton pulses applied during the variable {sup 15}N relaxation period (T), which can perturb water magnetization. Thus CC cancellation is required in such a way as to minimize water saturation effects. Here we examined the level of water saturation during the T period caused by various types of inversion proton pulses to suppress CC: (I) amide-selective IBURP-2; (II) cosine-modulated IBURP-2; (III) Watergate-like blocks; and (IV) non-selective hard. We additionally demonstrate the effect of uncontrolled saturation of aliphatic protons on {sup 15}N R{sub 1} rates. In this paper we present an optimized pulse sequence that takes into account the crucial effect of controlling also the saturation of the aliphatic protons during {sup 15}N R{sub 1} measurements in non-deuterated proteins. We show that using cosine-modulated IBURP-2 pulses spaced 40 ms to cancel CC in this optimized pulse program is the method of choice to minimize systematic errors coming from water and aliphatic protons saturation effects.
Borovkov, V I; Beregovaya, I V; Shchegoleva, L N; Potashov, P A; Bagryansky, V A; Molin, Y N
2012-09-14
Paramagnetic spin-lattice relaxation (SLR) in radical cations (RCs) of the cycloalkane series in liquid solution was studied and analyzed from the point of view of the correlation between the relaxation rate and the structure of the adiabatic potential energy surface (PES) of the RCs. SLR rates in the RCs formed in x-ray irradiated n-hexane solutions of the cycloalkanes studied were measured with the method of time-resolved magnetic field effect in the recombination fluorescence of spin-correlated radical ion pairs. Temperature and, for some cycloalkanes, magnetic field dependences of the relaxation rate were determined. It was found that the conventional Redfield theory of the paramagnetic relaxation as applied to the results on cyclohexane RC, gave a value of about 0.2 ps for the correlation time of the perturbation together with an unrealistically high value of 0.1 T in field units for the matrix element of the relaxation transition. The PES structure was obtained with the DFT quantum-chemical calculations. It was found that for all of the cycloalkanes RCs considered, including low symmetric alkyl-substituted ones, the adiabatic PESes were surfaces of pseudorotation due to avoided crossing. In the RCs studied, a correlation between the SLR rate and the calculated barrier height to the pseudorotation was revealed. For RCs with a higher relaxation rate, the apparent activation energies for the SLR were similar to the calculated heights of the barrier. To rationalize the data obtained it was assumed that the vibronic states degeneracy, which is specific for Jahn-Teller active cyclohexane RC, was approximately kept in the RCs of substituted cycloalkanes for the vibronic states with the energies above and close to the barrier height to the pseudorotation. It was proposed that the effective spin-lattice relaxation in a radical with nearly degenerate low-lying vibronic states originated from stochastic crossings of the vibronic levels that occur due to fluctuations of
Kobayashi, M; Irisawa, H
1961-10-27
The latent period of relaxation of molluscan myocardium due to anodal current is much longer than that of contraction. Although the rate and the grade of relaxation are intimately related to both the stimulus condition and the muscle tension, the latent period of relaxation remains constant, except when the temperature of the bathing fluid is changed.
Lumma, Anna-Lena; Kok, Bethany E; Singer, Tania
2015-07-01
Meditation is often associated with a relaxed state of the body. However, meditation can also be regarded as a type of mental task and training, associated with mental effort and physiological arousal. The cardiovascular effects of meditation may vary depending on the type of meditation, degree of mental effort, and amount of training. In the current study we assessed heart rate (HR), high-frequency heart rate variability (HF-HRV) and subjective ratings of effort and likeability during three types of meditation varying in their cognitive and attentional requirements, namely breathing meditation, loving-kindness meditation and observing-thoughts meditation. In the context of the ReSource project, a one-year longitudinal mental training study, participants practiced each meditation exercise on a daily basis for 3 months. As expected HR and effort were higher during loving-kindness meditation and observing-thoughts meditation compared to breathing meditation. With training over time HR and likeability increased, while HF-HRV and the subjective experience of effort decreased. The increase in HR and decrease in HF-HRV over training was higher for loving-kindness meditation and observing-thoughts meditation compared to breathing meditation. In contrast to implicit beliefs that meditation is always relaxing and associated with low arousal, the current results show that core meditations aiming at improving compassion and meta-cognitive skills require effort and are associated with physiological arousal compared to breathing meditation. Overall these findings can be useful in making more specific suggestions about which type of meditation is most adaptive for a given context and population.
Egan, Thomas F.
The NMR spin-lattice relaxation rate, T(,1)(' -1), of water is independent of the Larmor frequency, (omega)/2(pi), in the normal rf range. However, T(,1)('-1) of intracellular water in biological systems, which accounts for as much as 80% of the cell mass, is frequency-dependent. This indicates that the NMR properties of water in the cellular environment are influenced by long-correlation time processes due to the interaction of water with proteins and other macromolecular constituents of the cell. In this research, the relaxation rate T(,1)(' -1) of water in the Artemia (brine shrimp) cyst is examined as a function of: (1) the proton NMR Larmor frequency for .01 Artemia cysts between 10 and 500 MHz. At lower Larmor frequencies, below 1 MHz, the relaxation rates of water in brine shrimp cysts are influenced by additional relexation mechanisms; translational diffusion of hydration water is one possibility.
Stress states and moment rates of a two-asperity fault in the presence of viscoelastic relaxation
Directory of Open Access Journals (Sweden)
M. Dragoni
2015-02-01
Full Text Available A fault containing two asperities with different strengths is considered. The fault is embedded in a viscoelastic shear zone, subject to a constant strain rate by the motions of adjacent tectonic plates. The fault is modelled as a discrete dynamical system where the average values of stress, friction and slip on each asperity are considered. The state of the fault is described by three variables: the slip deficits of the asperities and the viscoelastic deformation. The system has four dynamic modes, for which the analytical solutions are calculated. The relationship between the state of the fault before a seismic event and the sequence of slipping modes in the event is enlightened. Since the moment rate depends on the number and sequence of slipping modes, the knowledge of the source function of an earthquake constrains the orbit of the system in the phase space. If the source functions of a larger number of consecutive earthquakes were known, the orbit could be constrained more and more and its evolution could be predicted with a smaller uncertainty. The model is applied to the 1964 Alaska earthquake, which was the effect of the failure of two asperities and for which a remarkable postseismic relaxation has been observed in the subsequent decades. The evolution of the system after the 1964 event depends on the state from which the event was originated, that is constrained by the observed moment rate. The possible durations of the interseismic interval and the possible moment rates of the next earthquake are calculated as functions of the initial state.
Malliavin, T. E.; Desvaux, H.; Aumelas, A.; Chavanieu, A.; Delsuc, M. A.
1999-09-01
We describe a quantitative processing method which gives access to the longitudinal and transverse cross-relaxation rates from off-resonance ROESY intensities. This method takes advantage of the dependence of the off-resonance ROESY experiments at any mixing time and any spin-lock angle θ on two relaxation matrices, the longitudinal and the transverse ones. This allows one to take into account multistep magnetization transfers even if the measurements are performed only at one or two mixing times. The ratio of the longitudinal to transverse cross-relaxation rates can then be used as a local indicator of the internal dynamics, without assuming a structure or a model of motion. After validation of this processing method by numerical simulations, it is applied to the analysis of the dynamics of the peptide ranalexin dissolved in pure water and in water/TFE.
Longitudinal T1 relaxation rate (R1) captures changes in short-term Mn exposure in welders.
Lewis, Mechelle M; Flynn, Michael R; Lee, Eun-Young; Van Buren, Scott; Van Buren, Eric; Du, Guangwei; Fry, Rebecca C; Herring, Amy H; Kong, Lan; Mailman, Richard B; Huang, Xuemei
2016-12-01
We demonstrated recently that the T1 relaxation rate (R1) captured short-term Mn exposure in welders with chronic, relatively low exposure levels in a cross-sectional study. In the current study, we used a longitudinal design to examine whether R1 values reflect the short-term dynamics of Mn exposure. Twenty-nine welders were evaluated at baseline and 12 months. Occupational questionnaires estimated short-term welding exposure using welding hours in the 90days prior to each study visit (HrsW90). In addition, blood Mn levels, the pallidal index (PI; globus pallidus T1-weighted intensity (T1WI)/frontal white matter T1WI), and R1 values in brain regions of interest (ROIs) were determined as Mn biomarkers at each visit. Associations between changes in estimated welding exposure and changes in purported Mn biomarkers were assessed by Spearman's correlations with adjustment for age and baseline R1, HrsW90, and blood Mn values. Changes in welding hours (HrsW90: the short-term welding exposure estimate), was associated significantly with changes in R1 values in the putamen (r=0.541, p=0.005), caudate (R=0.453, p=0.023), globus pallidus (R=0.430, p=0.032), amygdala (R=0.461, p=0.020), and hippocampus (R=0.447, p=0.025), but not with changes in blood Mn levels or the PI. Changes in R1 values correlated with changes in the short-term welding exposure estimate, but not with more traditional measures of Mn exposure (blood Mn levels or PI). These results suggest that R1 may serve as a useful marker to capture the short-term dynamics in Mn brain accumulation related to welding exposure. Copyright Â© 2016 Elsevier B.V. All rights reserved.
Measurement of the hot electron mean free path and the momentum relaxation rate in GaN
Energy Technology Data Exchange (ETDEWEB)
Suntrup, Donald J., E-mail: suntrup@physics.ucsb.edu [Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106 (United States); Gupta, Geetak; Li, Haoran; Keller, Stacia; Mishra, Umesh K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, Santa Barbara, California 93106 (United States)
2014-12-29
We present a method for measuring the mean free path and extracting the momentum relaxation time of hot electrons in GaN using the hot electron transistor (HET). In this device, electrons are injected over a high energy emitter barrier into the base where they experience quasi-ballistic transport well above the conduction band edge. After traversing the base, high energy electrons either surmount the base-collector barrier and become collector current or reflect off the barrier and become base current. We fabricate HETs with various base thicknesses and measure the common emitter transfer ratio (α) for each device. The mean free path is extracted by fitting α to a decaying exponential as a function of base width and the relaxation time is computed using a suitable injection velocity. For devices with an injection energy of ∼1 eV, we measure a hot electron mean free path of 14 nm and calculate a momentum relaxation time of 16 fs. These values are in agreement with theoretical calculations where longitudinal optical phonon scattering is the dominant momentum relaxation mechanism.
Moshchalcov, V. V.; Zhukov, A. A.; Kuznetzov, V. D.; Metlushko, V. V.; Leonyuk, L. I.
1990-01-01
At the initial time intervals, preceding the thermally activated flux creep regime, fast nonlogarithmic relaxation is found. The fully magnetic moment Pm(t) relaxation curve is shown. The magnetic measurements were made using SQUID-magnetometer. Two different relaxation regimes exist. The nonlogarithmic relaxation for the initial time intervals may be related to the viscous Abrikosov vortices flow with j is greater than j(sub c) for high enough temperature T and magnetic field induction B. This assumption correlates with Pm(t) measurements. The characteristic time t(sub O) separating two different relaxation regimes decreases as temperature and magnetic field are lowered. The logarithmic magnetization relaxation curves Pm(t) for fixed temperature and different external magnetic field inductions B are given. The relaxation rate dependence on magnetic field, R(B) = dPm(B, T sub O)/d(1nt) has a sharp maximum which is similar to that found for R(T) temperature dependences. The maximum shifts to lower fields as temperature goes up. The observed sharp maximum is related to a topological transition in shielding critical current distribution and, consequently, in Abrikosov vortices density. The nonlogarithmic magnetization relaxation for the initial time intervals is found. This fast relaxation has almost an exponentional character. The sharp relaxation rate R(B) maximum is observed. This maximum corresponds to a topological transition in Abrikosov vortices distribution.
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.
Directory of Open Access Journals (Sweden)
Michel Santos PALHETA
2014-04-01
Full Text Available Context The rectal distension in dogs increases the rate of transitory lower esophageal sphincter relaxation considered the main factor causing gastroesophageal reflux. Objectives The aim of this study was evaluate the participation of the nitrergic pathway in the increased transitory lower esophageal sphincter relaxation rate induced by rectal distension in anesthetized dogs. Methods Male mongrel dogs (n = 21, weighing 10-15 kg, were fasted for 12 hours, with water ad libitum. Thereafter, they were anesthetized (ketamine 10 mg.Kg-1 + xylazine 20 mg.Kg-1, so as to carry out the esophageal motility evaluation protocol during 120 min. After a 30-minute basal period, the animals were randomly intravenous treated whith: saline solution 0.15M (1ml.Kg-1, L-NAME (3 mg.Kg-1, L-NAME (3 mg.Kg-1 + L-Arginine (200 mg.Kg-1, glibenclamide (1 mg.Kg-1 or methylene blue (3 mg.Kg-1. Forty-five min after these pre-treatments, the rectum was distended (rectal distension, 5 mL.Kg-1 or not (control with a latex balloon, with changes in the esophageal motility recorded over 45 min. Data were analyzed using ANOVA followed by Student Newman-Keuls test. Results In comparison to the respective control group, rectal distension induces an increase in transitory lower esophageal sphincter relaxation. Pre-treatment with L-NAME or methylene blue prevents (P<0.05 this phenomenon, which is reversible by L-Arginine plus L-NAME. However, pretreating with glibenclamide failed to abolish this process. Conclusions Therefore, these experiments suggested, that rectal distension increases transitory lower esophageal sphincter relaxation in dogs via through nitrergic pathways.
Indentation load relaxation test
Energy Technology Data Exchange (ETDEWEB)
Hannula, S.P.; Stone, D.; Li, C.Y. (Cornell Univ., Ithaca, NY (USA))
Most of the models that are used to describe the nonelastic behavior of materials utilize stress-strain rate relations which can be obtained by a load relaxation test. The conventional load relaxation test, however, cannot be performed if the volume of the material to be tested is very small. For such applications the indentation type of test offers an attractive means of obtaining data necessary for materials characterization. In this work the feasibility of the indentation load relaxation test is studied. Experimental techniques are described together with results on Al, Cu and 316 SS. These results are compared to those of conventional uniaxial load relaxation tests, and the conversion of the load-indentation rate data into the stress-strain rate data is discussed.
Spin-orbit relaxation rates of Bi(6p(3)) 2D(3/2) following photolysis of Bi(CH3)3 at lambda = 193 nm
Holloway, J. S.; Koffend, J. B.; Heidner, R. F., III
1989-07-01
Rate coefficients for the collisional relaxation of the first excited spin-orbit state of Bismuth (6p3, 2D3/2) have been measured at 295 K for argon, carbon dioxide, sulfur hexaflouride, hydrogen, deuterium, hydrogen flouride. The excited Bi atoms were prepared by excimer laser photolysis of trimethyl bismuth (TMB) at 193 nm and monitored directly in emission. The rate coefficient for quenching by the precursor TMB and a lower limit for removal by CH3 photofragments have also been established. Where applicable, our results are compared with the earlier work of Bevan and Husain and of Trainor. The suitability of long-range interaction models is discussed for those cases where isotopic substitution leads to markedly different quenching rates.
Pesch, Beate; Dydak, Ulrike; Lotz, Anne; Casjens, Swaantje; Quetscher, Clara; Lehnert, Martin; Abramowski, Jessica; Stewig, Christoph; Yeh, Chien-Lin; Weiss, Tobias; van Thriel, Christoph; Herrmann, Lennard; Muhlack, Siegfried; Woitalla, Dirk; Glaubitz, Benjamin; Schmidt-Wilcke, Tobias; Brüning, Thomas
2017-08-25
Magnetic resonance imaging is a non-invasive method that allows the indirect quantification of manganese (Mn) and iron (Fe) accumulation in the brain due to their paramagnetic features. The WELDOX II study aimed to explore the influence of airborne and systemic exposure to Mn and Fe on the brain deposition using the relaxation rates R1 and R2* as biomarkers of metal accumulation in regions of interest in 161 men, including active and former welders. We obtained data on the relaxation rates R1 and R2* in regions that included structures within the globus pallidus (GP), substantia nigra (SN), and white matter of the frontal lobe (FL) of both hemispheres, as well as Mn in whole blood (MnB), and serum ferritin (SF). The study subjects, all male, included 48 active and 20 former welders, 41 patients with Parkinson's disease (PD), 13 patients with hemochromatosis (HC), and 39 controls. Respirable Mn and Fe were measured during a working shift for welders. Mixed regression models were applied to estimate the effects of MnB and SF on R1 and R2*. Furthermore, we estimated the influence of airborne Mn and Fe on the relaxation rates in active welders. MnB and SF were significant predictors of R1 but not of R2* in the GP, and were marginally associated with R1 in the SN (SF) and FL (MnB). Being a welder or suffering from PD or HC elicited no additional group effect on R1 or R2* beyond the effects of MnB and SF. In active welders, shift concentrations of respirable Mn>100μg/m(3) were associated with stronger R1 signals in the GP. In addition to the effects of MnB and SF, the welding technique had no further influence on R1. MnB and SF were significant predictors of R1 but not of R2*, indicative of metal accumulation, especially in the GP. Also, high airborne Mn concentration was associated with higher R1 signals in this brain region. The negative results obtained for being a welder or for the techniques with higher exposure to ultrafine particles when the blood
Energy Technology Data Exchange (ETDEWEB)
Yastremsky, I.A., E-mail: yastremsky@ukr.net
2015-05-15
The relaxation of non-equilibrium redistributions of the magnetization in a model Ni–Fe heterostructure is analyzed on the basis of the Landau–Lifshitz equation with the relaxation terms proposed by Bar'yakhtar. Bar'yakhtar‘s terms account for both the relativistic (local) and exchange (nonlocal) relaxations. It is demonstrated that the role of the nonlocal relaxation term (a spin current flowing between layers) increases for smaller systems. For nanometer-size systems the nonlocal relaxation term significantly enhances the relaxation of the Ni layer magnetization back to equilibrium. The reason of this size dependence is a competition of fast magnetization dynamics, induced by the nonlocal relaxation term near an interface between metals and slow, relativistic dynamics, which occurs at each point of the Ni–Fe heterostructure. This study provides insight in how to achieve an exceptionally fast remagnetization in magnetic heterostructures after laser excitation. - Highlights: • The relaxation of non-equilibrium spin states in a Ni–Fe heterostructure is analyzed. • Both the exchange (nonlocal) and relativistic (local) relaxations are accounted. • The nonlocal relaxation is concurrent with the creation of a spin current. • The role of the spin current increases for thinner metallic layers. • For nanometer-size systems the relaxation is primarily driven by the spin current.
DEFF Research Database (Denmark)
Madurga, V.; Barandiarán, J. M.; Vázquez, M.
1987-01-01
Ribbons of nominal composition Co80Nb8B12 have been prepared by the single roller quenching method using different wheel velocities ranging from 26 to 42 ms−1. X-ray diffraction patterns for ribbons prepared at low velocities show crystalline peaks but characteristic for the amorphous state...... for samples prepared at velocities above 36 ms−1. Room-temperature values of the magnetostriction constant lambdas depend on the quenching rate and changes from 4×10−7 to −1×10−6 as the wheel speed increases. Zero magnetostriction samples are obtained at about 34 ms−1. Thermal treatments change the values...... of the magnetostriction in the same way as a decrease in the quenching rate does. A dependence of the magnetostriction constant on the applied stress has been found. This dependence, fully reversible, is observed at room temperature. Journal of Applied Physics is copyrighted by The American Institute of Physics....
González, Pablo J; Barrera, Guillermo I; Rizzi, Alberto C; Moura, José J G; Passeggi, Mario C G; Brondino, Carlos D
2009-10-01
Electron transfer proteins and redox enzymes containing paramagnetic redox centers with different relaxation rates are widespread in nature. Despite both the long distances and chemical paths connecting these centers, they can present weak magnetic couplings produced by spin-spin interactions such as dipolar and isotropic exchange. We present here a theoretical model based on the Bloch-Wangsness-Redfield theory to analyze the dependence with temperature of EPR spectra of interacting pairs of spin 1/2 centers having different relaxation rates, as is the case of the molybdenum-containing enzyme aldehyde oxidoreductase from Desulfovibrio gigas. We analyze the changes of the EPR spectra of the slow relaxing center (Mo(V)) induced by the faster relaxing center (FeS center). At high temperatures, when the relaxation time T(1) of the fast relaxing center is very short, the magnetic coupling between centers is averaged to zero. Conversely, at low temperatures when T(1) is longer, no modulation of the coupling between metal centers can be detected.
Hansen, D. Flemming
2017-06-01
Many chemical and biological processes rely on the movement of monovalent cations and an understanding of such processes can therefore only be achieved by characterising the dynamics of the involved ions. It has recently been shown that 15N-ammonium can be used as a proxy for potassium to probe potassium binding in bio-molecules such as DNA quadruplexes and enzymes. Moreover, equations have been derived to describe the time-evolution of 15N-based spin density operator elements of 15NH4+ spin systems. Herein NMR pulse sequences are derived to select specific spin density matrix elements of the 15NH4+ spin system and to measure their longitudinal relaxation in order to characterise the rotational correlation time of the 15NH4+ ion as well as report on chemical exchange events of the 15NH4+ ion. Applications to 15NH4+ in acidic aqueous solutions are used to cross-validate the developed pulse sequence while measurements of spin-relaxation rates of 15NH4+ bound to a 41 kDa domain of the bacterial Hsp70 homologue DnaK are presented to show the general applicability of the derived pulse sequence. The rotational correlation time obtained for 15N-ammonium bound to DnaK is similar to the correlation time that describes the rotation about the threefold axis of a methyl group. The methodology presented here provides, together with the previous theoretical framework, an important step towards characterising the motional properties of cations in macromolecular systems.
Magnetoviscosity and relaxation in ferrofluids
Felderhof
2000-09-01
The increase in viscosity of a ferrofluid due to an applied magnetic field is discussed on the basis of a phenomenological relaxation equation for the magnetization. The relaxation equation was derived earlier from irreversible thermodynamics, and differs from that postulated by Shliomis. The two relaxation equations lead to a different dependence of viscosity on magnetic field, unless the relaxation rates are related in a specific field-dependent way. Both planar Couette flow and Poiseuille pipe flow in parallel and perpendicular magnetic field are discussed. The entropy production for these situations is calculated and related to the magnetoviscosity.
Plasmon-mediated energy relaxation in graphene
Energy Technology Data Exchange (ETDEWEB)
Ferry, D. K. [School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287-5706 (United States); Somphonsane, R. [Department of Physics, King Mongkut' s Institute of Technology, Ladkrabang, Bangkok 10520 (Thailand); Ramamoorthy, H.; Bird, J. P. [Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260-1500 (United States)
2015-12-28
Energy relaxation of hot carriers in graphene is studied at low temperatures, where the loss rate may differ significantly from that predicted for electron-phonon interactions. We show here that plasmons, important in the relaxation of energetic carriers in bulk semiconductors, can also provide a pathway for energy relaxation in transport experiments in graphene. We obtain a total loss rate to plasmons that results in energy relaxation times whose dependence on temperature and density closely matches that found experimentally.
Karampekios, Spyros; Papanikolaou, Nickolas; Papadaki, Eufrosini; Maris, Thomas; Uffman, Kai; Spilioti, Martha; Plaitakis, Andreas; Gourtsoyiannis, Nicholas
2005-03-01
The purpose of this paper is to perform quantitative measurements of the magnetization transfer rate (Kfor) and native T1 relaxation time (T1free) in the brain tissue of normal individuals and patients with multiple sclerosis (MS) by means of multiple gradient echo acquisitions, and to correlate these measurements with the magnetization transfer ratio (MTR). Quantitative magnetization transfer imaging was performed in five normal volunteers and 12 patients with relapsing-remitting MS on a 1.5 T magnetic resonance (MR) scanner. The T1 relaxation time under magnetization transfer irradiation (T1sat) was calculated by means of fitting the signal intensity over the flip angle in several 3D spoiled gradient echo acquisitions (3 degrees , 15 degrees , 30 degrees , and 60 degrees ), while a single acquisition without MT irradiation (flip angle of 3 degrees ) was utilized to calculate the MTR. The Kfor and T1free constants were quantified on a pixel-by-pixel basis and parametric maps were reconstructed. We performed 226 measurements of Kfor, T1free, and the MTR on normal white matter (NWM) of healthy volunteers (n=50), and normal-appearing white matter (NAWM) and pathological brain areas of MS patients (n=120 and 56, respectively). Correlation coefficients between Kfor-MTR, T1free-MTR, and T1free-Kfor were calculated. Lesions were classified, according to their characteristics on T1-weighted images, into isointense (compared to white matter), mildly hypointense (showing signal intensity lower than white matter and higher than gray matter), and severely hypointense (revealing signal intensity lower than gray matter). "Dirty" white matter (DWM) corresponded to areas with diffused high signal, as identified on T2-weighted images. Strong correlation coefficients were obtained between MTR and Kfor for all lesions studied (r2=0.9, pKfor and T1free measurements (r2=0.98, pKfor and T1free were found for the rest of the subgroups, except for the NAWM, in which a moderate
Energy Technology Data Exchange (ETDEWEB)
Karampekios, Spyros; Papanikolaou, Nickolas; Papadaki, Eufrosini; Gourtsoyiannis, Nicholas [University Hospital of Heraklion, Department of Radiology, Heraklion (Greece); Maris, Thomas [University Hospital of Heraklion, Department of Medical Physics, Heraklion (Greece); Uffman, Kai [University Hospital of Essen, Department of Diagnostic Radiology, Essen (Germany); Spilioti, Martha; Plaitakis, Andreas [University Hospital of Heraklion, Department of Neurology, Heraklion (Greece)
2005-03-01
The purpose of this paper is to perform quantitative measurements of the magnetization transfer rate (Kfor) and native T1 relaxation time (T1free) in the brain tissue of normal individuals and patients with multiple sclerosis (MS) by means of multiple gradient echo acquisitions, and to correlate these measurements with the magnetization transfer ratio (MTR). Quantitative magnetization transfer imaging was performed in five normal volunteers and 12 patients with relapsing-remitting MS on a 1.5 T magnetic resonance (MR) scanner. The T1 relaxation time under magnetization transfer irradiation (T1sat) was calculated by means of fitting the signal intensity over the flip angle in several 3D spoiled gradient echo acquisitions (3 , 15 , 30 , and 60 ), while a single acquisition without MT irradiation (flip angle of 3 ) was utilized to calculate the MTR. The Kfor and T1free constants were quantified on a pixel-by-pixel basis and parametric maps were reconstructed. We performed 226 measurements of Kfor, T1free, and the MTR on normal white matter (NWM) of healthy volunteers (n=50), and normal-appearing white matter (NAWM) and pathological brain areas of MS patients (n=120 and 56, respectively). Correlation coefficients between Kfor-MTR, T1free-MTR, and T1free-Kfor were calculated. Lesions were classified, according to their characteristics on T1-weighted images, into isointense (compared to white matter), mildly hypointense (showing signal intensity lower than white matter and higher than gray matter), and severely hypointense (revealing signal intensity lower than gray matter). ''Dirty'' white matter (DWM) corresponded to areas with diffused high signal, as identified on T2-weighted images. Strong correlation coefficients were obtained between MTR and Kfor for all lesions studied (r{sup 2}=0.9, p<0.0001), for mildly hypointense plaques (r{sup 2}=0.82, p<0.0001), and for DWM (r{sup 2}=0.78, p=0.0007). In contrast, comparison between MTR and T1free values
Marzola, Luca; Raidal, Martti
2016-11-01
Motivated by natural inflation, we propose a relaxation mechanism consistent with inflationary cosmology that explains the hierarchy between the electroweak scale and Planck scale. This scenario is based on a selection mechanism that identifies the low-scale dynamics as the one that is screened from UV physics. The scenario also predicts the near-criticality and metastability of the Standard Model (SM) vacuum state, explaining the Higgs boson mass observed at the Large Hadron Collider (LHC). Once Majorana right-handed neutrinos are introduced to provide a viable reheating channel, our framework yields a corresponding mass scale that allows for the seesaw mechanism as well as for standard thermal leptogenesis. We argue that considering singlet scalar dark matter extensions of the proposed scenario could solve the vacuum stability problem and discuss how the cosmological constant problem is possibly addressed.
Cross relaxation in nitroxide spin labels
Marsh, Derek
2016-11-01
Cross relaxation, and mI -dependence of the intrinsic electron spin-lattice relaxation rate We , are incorporated explicitly into the rate equations for the electron-spin population differences that govern the saturation behaviour of 14N- and 15N-nitroxide spin labels. Both prove important in spin-label EPR and ELDOR, particularly for saturation recovery studies. Neither for saturation recovery, nor for CW-saturation EPR and CW-ELDOR, can cross relaxation be described simply by increasing the value of We , the intrinsic spin-lattice relaxation rate. Independence of the saturation recovery rates from the hyperfine line pumped or observed follows directly from solution of the rate equations including cross relaxation, even when the intrinsic spin-lattice relaxation rate We is mI -dependent.
Nonlinear fractional relaxation
Indian Academy of Sciences (India)
A Tofighi
2012-04-01
We deﬁne a nonlinear model for fractional relaxation phenomena. We use -expansion method to analyse this model. By studying the fundamental solutions of this model we ﬁnd that when → 0 the model exhibits a fast decay rate and when → ∞ the model exhibits a power-law decay. By analysing the frequency response we ﬁnd a logarithmic enhancement for the relative ratio of susceptibility.
Temperature relaxation in dense plasma mixtures
Faussurier, Gérald; Blancard, Christophe
2016-09-01
We present a model to calculate temperature-relaxation rates in dense plasma mixtures. The electron-ion relaxation rates are calculated using an average-atom model and the ion-ion relaxation rates by the Landau-Spitzer approach. This method allows the study of the temperature relaxation in many-temperature electron-ion and ion-ion systems such as those encountered in inertial confinement fusion simulations. It is of interest for general nonequilibrium thermodynamics dealing with energy flows between various systems and should find broad use in present high energy density experiments.
Radovanović, J.; Mirčetić, A.; Milanović, V.; Ikonić, Z.; Indjin, D.; Harrison, P.; Kelsall, R. W.
We have explored the possibility of modulating the optical gain in the active region of mid-infrared QCLs by means of external magnetic field, which strongly influences the relaxation processes, in particular the LO phonon assisted intersubband transitions. The additional carrier confinement, induced by the field, leads to an increase in the upper laser level carrier lifetime, which results in pronounced oscillations of the optical gain. The described model was applied to two structures designed for λ˜9µm emission.
Cross relaxation in nitroxide spin labels
DEFF Research Database (Denmark)
Marsh, Derek
2016-01-01
-label EPR and ELDOR, particularly for saturation recovery studies. Neither for saturation recovery, nor for CW-saturation EPR and CW-ELDOR, can cross relaxation be described simply by increasing the value of We, the intrinsic spin-lattice relaxation rate. Independence of the saturation recovery rates from...
Sun, Phillip Zhe
2012-01-01
Chemical exchange saturation transfer (CEST) MRI is an emerging imaging technique capable of detecting dilute proteins/peptides and microenvironmental properties, with promising in vivo applications. However, CEST MRI contrast is complex, varying not only with the labile proton concentration and exchange rate, but also with experimental conditions such as field strength and RF irradiation scheme. Furthermore, the optimal RF irradiation power depends on the exchange rate, which must be estimated in order to optimize the CEST MRI experiments. Although methods including numerical fitting with modified Bloch-McConnell equations, quantification of exchange rate with RF saturation time and power (QUEST and QUESP), have been proposed to address this relationship, they require multiple-parameter non-linear fitting and accurate relaxation measurement. Our work here extended the QUEST algorithm with ratiometric analysis (QUESTRA) that normalizes the magnetization transfer ratio (MTR) at labile and reference frequencies, which effectively eliminates the confounding relaxation and RF spillover effects. Specifically, the QUESTRA contrast approaches its steady state mono-exponentially at a rate determined by the reverse exchange rate (kws), with little dependence on bulk water T1, T2, RF power and chemical shift. The proposed algorithm was confirmed numerically, and validated experimentally using a tissue-like phantom of serially titrated pH compartments. PMID:21842497
Sun, Phillip Zhe
2012-04-01
Chemical exchange saturation transfer MRI is an emerging imaging technique capable of detecting dilute proteins/peptides and microenvironmental properties, with promising in vivo applications. However, chemical exchange saturation transfer MRI contrast is complex, varying not only with the labile proton concentration and exchange rate, but also with experimental conditions such as field strength and radiofrequency (RF) irradiation scheme. Furthermore, the optimal RF irradiation power depends on the exchange rate, which must be estimated in order to optimize the chemical exchange saturation transfer MRI experiments. Although methods including numerical fitting with modified Bloch-McConnell equations, quantification of exchange rate with RF saturation time and power (QUEST and QUESP), have been proposed to address this relationship, they require multiple-parameter non-linear fitting and accurate relaxation measurement. Our work extended the QUEST algorithm with ratiometric analysis (QUESTRA) that normalizes the magnetization transfer ratio at labile and reference frequencies, which effectively eliminates the confounding relaxation and RF spillover effects. Specifically, the QUESTRA contrast approaches its steady state mono-exponentially at a rate determined by the reverse exchange rate (k(ws) ), with little dependence on bulk water T(1) , T(2) , RF power and chemical shift. The proposed algorithm was confirmed numerically, and validated experimentally using a tissue-like phantom of serially titrated pH compartments.
Relaxation Dynamics in Heme Proteins.
Scholl, Reinhard Wilhelm
highest tier, tier 0, but not on the relaxation rates. Two different viscosities in myoglobin-CO are compared. The dependence of relaxations on the thermodynamic history of a sample is shown. For substrate-free P450cam-CO, relaxations after a p-jump are observed far above the glass transition of the protein-solvent system.
Relaxation Techniques for Health
... R S T U V W X Y Z Relaxation Techniques for Health Share: On This Page What’s the ... Bottom Line? How much do we know about relaxation techniques? A substantial amount of research has been done ...
Growth rate of crystalline ice and the diffusivity of supercooled water from 126 to 262 K
Energy Technology Data Exchange (ETDEWEB)
Xu, Yuntao; Petrik, Nikolay G.; Smith, R. Scott; Kay, Bruce D.; Kimmel, Greg A.
2016-12-12
Understanding deeply supercooled water is key to unraveling many of water’s anomalous properties. However, this has proven difficult due to rapid and uncontrolled crystallization. Using a pulsed laser heating technique, we measure the growth rate of crystalline ice, G(T), for 180 K < T < 262 K, i.e. deep within water’s “no man’s land.” The self-diffusion of supercooled liquid water, D(T), is obtained from G(T) using the Wilson-Frenkel model of crystal growth. For T > 237 K, G(T) and D(T) have super-Arrhenius (“fragile”) temperature dependences, but both crossover to Arrhenius (“strong”) behavior with a large activation energy in “no man’s land.” The fact that G(T) and D(T) are smoothly varying rules out the hypothesis that liquid water’s properties have a singularity at or near 228 K. However the results are consistent with a previous prediction for D(T) that assumed no thermodynamic transitions occur in “no man’s land.
Onsager relaxation of toroidal plasmas
Energy Technology Data Exchange (ETDEWEB)
Samain, A.; Nguyen, F.
1997-01-01
The slow relaxation of isolated toroidal plasmas towards their thermodynamical equilibrium is studied in an Onsager framework based on the entropy metric. The basic tool is a variational principle, equivalent to the kinetic equation, involving the profiles of density, temperature, electric potential, electric current. New minimization procedures are proposed to obtain entropy and entropy production rate functionals. (author). 36 refs.
2016-01-01
Over recent years, several alternative relaxed clock models have been proposed in the context of Bayesian dating. These models fall in two distinct categories: uncorrelated and autocorrelated across branches. The choice between these two classes of relaxed clocks is still an open question. More fundamentally, the true process of rate variation may have both long-term trends and short-term fluctuations, suggesting that more sophisticated clock models unfolding over multiple time scales should ultimately be developed. Here, a mixed relaxed clock model is introduced, which can be mechanistically interpreted as a rate variation process undergoing short-term fluctuations on the top of Brownian long-term trends. Statistically, this mixed clock represents an alternative solution to the problem of choosing between autocorrelated and uncorrelated relaxed clocks, by proposing instead to combine their respective merits. Fitting this model on a dataset of 105 placental mammals, using both node-dating and tip-dating approaches, suggests that the two pure clocks, Brownian and white noise, are rejected in favour of a mixed model with approximately equal contributions for its uncorrelated and autocorrelated components. The tip-dating analysis is particularly sensitive to the choice of the relaxed clock model. In this context, the classical pure Brownian relaxed clock appears to be overly rigid, leading to biases in divergence time estimation. By contrast, the use of a mixed clock leads to more recent and more reasonable estimates for the crown ages of placental orders and superorders. Altogether, the mixed clock introduced here represents a first step towards empirically more adequate models of the patterns of rate variation across phylogenetic trees. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’. PMID:27325829
Relaxation of liquid bridge after droplets coalescence
Directory of Open Access Journals (Sweden)
Jiangen Zheng
2016-11-01
Full Text Available We investigate the relaxation of liquid bridge after the coalescence of two sessile droplets resting on an organic glass substrate both experimentally and theoretically. The liquid bridge is found to relax to its equilibrium shape via two distinct approaches: damped oscillation relaxation and underdamped relaxation. When the viscosity is low, damped oscillation shows up, in this approach, the liquid bridge undergoes a damped oscillation process until it reaches its stable shape. However, if the viscous effects become significant, underdamped relaxation occurs. In this case, the liquid bridge relaxes to its equilibrium state in a non-periodic decay mode. In depth analysis indicates that the damping rate and oscillation period of damped oscillation are related to an inertial-capillary time scale τc. These experimental results are also testified by our numerical simulations with COMSOL Multiphysics.
Keasberry, Natasha A.; Bañobre-López, Manuel; Wood, Christopher; Stasiuk, Graeme. J.; Gallo, Juan; Long, Nicholas. J.
2015-09-01
Magnetic resonance imaging (MRI) is an excellent imaging modality. However the low sensitivity of the technique poses a challenge to achieving an accurate image of function at the molecular level. To overcome this, contrast agents are used; typically gadolinium based agents for T1 weighted imaging, or iron oxide based agents for T2 imaging. Traditionally, only one imaging mode is used per diagnosis although several physiological situations are known to interfere with the signal induced by the contrast agents in each individual imaging mode acquisition. Recently, the combination of both T1 and T2 imaging capabilities into a single platform has emerged as a tool to reduce uncertainties in MR image analysis. To date, contradicting reports on the effect on the contrast of the coupling of a T1 and T2 agent have hampered the application of these specialised probes. Herein, we present a systematic experimental study on a range of gadolinium-labelled magnetite nanoparticles envisioned to bring some light into the mechanism of interaction between T1 and T2 components, and advance towards the design of efficient (dual) T1 and T2 MRI probes. Unexpected behaviours observed in some of the constructs will be discussed. In this study, we demonstrate that the relaxivity of such multimodal probes can be rationally tuned to obtain unmatched potentials in MR imaging, exemplified by preparation of the magnetite-based nanoparticle with the highest T2 relaxivity described to date.Magnetic resonance imaging (MRI) is an excellent imaging modality. However the low sensitivity of the technique poses a challenge to achieving an accurate image of function at the molecular level. To overcome this, contrast agents are used; typically gadolinium based agents for T1 weighted imaging, or iron oxide based agents for T2 imaging. Traditionally, only one imaging mode is used per diagnosis although several physiological situations are known to interfere with the signal induced by the contrast agents in
Active optomechanics through relaxation oscillations
Princepe, Debora; Frateschi, Newton
2014-01-01
We propose an optomechanical laser based on III-V compounds which exhibits self-pulsation in the presence of a dissipative optomechanical coupling. In such a laser cavity, radiation pressure drives the mechanical degree of freedom and its back-action is caused by the mechanical modulation of the cavity loss rate. Our numerical analysis shows that even in a wideband gain material, such dissipative coupling couples the mechanical oscillation with the laser relaxation oscillations process. Laser self-pulsation is observed for mechanical frequencies below the laser relaxation oscillation frequency under sufficiently high optomechanical coupling factor.
Allard, P; Jarvet, J; Ehrenberg, A; Gräslund, A
1995-02-01
The peptide hormone motilin was synthesised with a 13C-enriched alpha-carbon in the leucine at position 10. In aqueous solution, six different relaxation rates were measured for the 13C alpha-H alpha fragment as a function of temperature and with and without the addition of 30% (v/v) of the cosolvent d2-1,1,1,3,3,3-hexafluoro-2-propanol (HFP). The relaxation rates were analysed employing the spectral density mapping technique introduced by Peng and Wagner [(1992) J. Magn. Reson., 98, 308-332] and using the model-free approach by Lipari and Szabo [(1982) J. Am. Chem. Soc., 104, 4546-4570]. The fit to various models of dynamics was also considered. Different procedures to evaluate the overall rotational correlation time were compared. A single exponential time correlation function was found to give a good fit to the measured spectral densities only for motilin in 30% (v/v) HFP at low temperatures, whereas at high temperatures in this solvent, and in D2O at all temperatures, none of the considered models gave an acceptable fit. A new empirical spectral density function was tested and found to accurately fit the experimental spectral density mapping points. The application of spectral density mapping based on NMR relaxation data for a specific 13C-1H vector is shown to be a highly useful method to study biomolecular dynamics. Advantages are high sensitivity, high precision and uniform sampling of the spectral density function over the frequency range.
Magnetization Transfer Induced Biexponential Longitudinal Relaxation
Prantner, Andrew M.; Bretthorst, G. Larry; Neil, Jeffrey J.; Garbow, Joel R.; Ackerman, Joseph J.H.
2009-01-01
Longitudinal relaxation of brain water 1H magnetization in mammalian brain in vivo is typically analyzed on a per voxel basis using a monoexponential model, thereby assigning a single relaxation time constant to all 1H magnetization within a given voxel. This approach was tested by obtaining inversion recovery data from grey matter of rats at 64 exponentially-spaced recovery times. Using Bayesian probability for model selection, brain water data were best represented by a biexponential function characterized by fast and slow relaxation components. At 4.7 T, the amplitude fraction of the rapidly relaxing component is 3.4 ± 0.7 % with a rate constant of 44 ± 12 s-1 (mean ± SD; 174 voxels from 4 rats). The rate constant of the slow relaxing component is 0.66 ± 0.04 s-1. At 11.7 T, the corresponding values are 6.9 ± 0.9 %, 19 ± 5 s-1, and 0.48 ± 0.02 s-1 (151 voxels from 4 rats). Several putative mechanisms for biexponential relaxation behavior were evaluated, and magnetization transfer between bulk water protons and non-aqueous protons was determined to be the source of biexponential longitudinal relaxation. MR methods requiring accurate quantification of longitudinal relaxation may need to take this effect explicitly into account. PMID:18759367
Sawyer, Jean; Matteson, Colleen; Ou, Hua; Nagase, Takahisa
2017-04-14
This study investigated the effects of an intervention to reduce caregivers' articulation rates with children who stutter on (a) disfluency, (b) caregiver and child's articulation rates, and (c) caregiver and child's response time latency (RTL). Seventeen caregivers and their preschool children who stuttered participated in a group study of treatment outcomes. One speech sample was collected as a baseline, and 2 samples were collected after treatment. Posttreatment samples were of caregivers speaking as they typically would and using reduced articulation rates. Caregivers reduced articulation rates significantly in the 2 posttreatment samples, and a significant decrease of stuttering-like disfluencies (SLD) was found in the children in those 2 samples. No direct relationship was found between the caregiver's articulation rate and RTL, and there was a small correlation of RTL with the lower levels of SLD found postintervention. No significant relationships were found between the reduced levels of SLD and articulation rates for either caregivers or children. Results suggest caregivers can be trained to slow their speech, and children increased their fluency at the end of a program designed to slow caregiver articulation. The intentionally slower rate of the caregivers, however, was not significantly related to fluency.
Institute of Scientific and Technical Information of China (English)
陈霞; 姚俊岩; 邓小明
2009-01-01
目的 探讨长托宁作为术前用药,对全麻患者的心率及对维库溴铵肌松起效和恢复的影响.方法 60例全麻患者随机分为长托宁组(C组)、阿托品组(A组)和生理盐水对照组(N组),每组各20例.3组患者于诱导前20min时分别肌肉注射长托宁0.01 mg/ks、阿托品0.01 mg/ks或生理盐水1 ml,记录肌注后5、10、15、20min和诱导后1 min的心率.诱导用药咪达唑仑0.04 mg/kg、芬太尼4μg/kg、丙泊酚效应室靶浓度2 mg/L靶控输注、维库溴铵0.15 mg/kg,用Organon的TOF-WATCH SX加速度肌松监测仪监测维库溴铵的起效时间(t1)、无反应时间(t2)、临床时效(t3)和恢复指数(recoveryindex,RI).结果 与N和A组相比,C组T1缩短、RI延长,但无统计学差异(P＞0.05),t2和t3无统计学差异.A组肌注后10、15、20min、诱导后1 min的心率较C组和N组显著升高(P＜0.05),并且A组内肌注后15 min和20 min的心率显著高于基础值(P＜0.05).结论 长托宁0.01 mg//kg的术前用药剂量与肌松全麻药无明确协同作用,并且对全麻患者心率无明显影响.%Objective To investigate the effects of penehyclidine hydrochloride on heart rate (HR) and veeuronium-induced relaxation.Methods Sixty female patients were randomly assigned to three groups (n=20):0.01 mg/kg penehyclidine hydrochloride (group C),0.01 mg/kg atropine (group A) and 1ml normal saline (group N).These drugs were injected intramuscularly 20 minutes before anesthesia induction.Midazolam,fentanyl,propofol and vecuronium were given intravenously for induction.Muscle relaxation was monitored.Results HR increased in group A at 15 min and 20 min after injection(P＜0.05),and was faster than that in group C and group N at 10,15,20 min after injection,and 1 min after induction (P＜0.05).There were no differences in onset time,noresponse period,clinical relaxation duration and recovery time of vecuronium-induced relaxation among three groups.Conclusion 0.01 mg/kg penehyclidine
Spin relaxation in nanowires by hyperfine coupling
Energy Technology Data Exchange (ETDEWEB)
Echeverria-Arrondo, C. [Department of Physical Chemistry, Universidad del Pais Vasco UPV/EHU, 48080 Bilbao (Spain); Sherman, E.Ya. [Department of Physical Chemistry, Universidad del Pais Vasco UPV/EHU, 48080 Bilbao (Spain); IKERBASQUE Basque Foundation for Science, 48011 Bilbao, Bizkaia (Spain)
2012-08-15
Hyperfine interactions establish limits on spin dynamics and relaxation rates in ensembles of semiconductor quantum dots. It is the confinement of electrons which determines nonzero hyperfine coupling and leads to the spin relaxation. As a result, in nanowires one would expect the vanishing of this effect due to extended electron states. However, even for relatively clean wires, disorder plays a crucial role and makes electron localization sufficient to cause spin relaxation on the time scale of the order of 10 ns. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Precession Relaxation of Viscoelastic Oblate Rotators
Frouard, Julien
2016-01-01
Various perturbations (collisions, close encounters, YORP) destabilise the rotation of a small body, leaving it in a non-principal spin state. Then the body experiences alternating stresses generated by the inertial forces. The ensuing inelastic dissipation reduces the kinetic energy, without influencing the angular momentum. This yields nutation relaxation, i.e., evolution of the spin towards rotation about the maximal-inertia axis. Knowledge of the timescales needed to damp the nutation is crucial in studies of small bodies' dynamics. In the past, nutation relaxation has been described by an empirical quality factor introduced to parameterise the dissipation rate and to evade the discussion of the actual rheological parameters and their role in dissipation. This approach is unable to describe the dependence of the relaxation rate upon the nutation angle, because we do not know the quality factor's dependence on the frequency (which is a function of the nutation angle). This leaves open the question of relax...
Vibrational energy relaxation in liquid oxygen
Everitt, K. F.; Egorov, S. A.; Skinner, J. L.
1998-09-01
We consider theoretically the relaxation from the first excited vibrational state to the ground state of oxygen molecules in neat liquid oxygen. The relaxation rate constant is related in the usual way to the Fourier transform of a certain quantum mechanical force-force time-correlation function. A result from Egelstaff allows one instead to relate the rate constant (approximately) to the Fourier transform of a classical force-force time-correlation function. This Fourier transform is then evaluated approximately by calculating three equilibrium averages from a classical molecular dynamics simulation. Our results for the relaxation times (at two different temperatures) are within a factor of 5 of the experimental relaxation times, which are in the ms range.
Protein dynamics from nuclear magnetic relaxation.
Charlier, Cyril; Cousin, Samuel F; Ferrage, Fabien
2016-05-01
Nuclear magnetic resonance is a ubiquitous spectroscopic tool to explore molecules with atomic resolution. Nuclear magnetic relaxation is intimately connected to molecular motions. Many methods and models have been developed to measure and interpret the characteristic rates of nuclear magnetic relaxation in proteins. These approaches shed light on a rich and diverse range of motions covering timescales from picoseconds to seconds. Here, we introduce some of the basic concepts upon which these approaches are built and provide a series of illustrations.
Relaxation techniques for stress
... problems such as high blood pressure, stomachaches, headaches, anxiety, and depression. Using relaxation techniques can help you feel calm. These exercises can also help you manage stress and ease the effects of stress on your body.
Perturbations and quantum relaxation
Kandhadai, Adithya
2016-01-01
We investigate whether small perturbations can cause relaxation to quantum equilibrium over very long timescales. We consider in particular a two-dimensional harmonic oscillator, which can serve as a model of a field mode on expanding space. We assume an initial wave function with small perturbations to the ground state. We present evidence that the trajectories are highly confined so as to preclude relaxation to equilibrium even over very long timescales. Cosmological implications are briefly discussed.
Intraband Relaxation and Its Influences on Quantum Dot Lasers
Institute of Scientific and Technical Information of China (English)
DENG Sheng-Ling; HUANG Yong-Zhen; YU Li-Juan
2005-01-01
@@ A comprehensive two-level numerical model is developed to describe carrier distribution in a quantum-dot laser. Light-emission spectra with different intraband relaxation rates (2ps, 7.5ps and 20ps) are calculated and analysed to investigate the influence of relaxation rates on performance of the quantum-dot laser. The results indicate that fast intraband relaxation favours not only the ground state single mode operation but also the higher injection efficiency.
Spin relaxation in metallic ferromagnets
Berger, L.
2011-02-01
The Elliott theory of spin relaxation in metals and semiconductors is extended to metallic ferromagnets. Our treatment is based on the two-current model of Fert, Campbell, and Jaoul. The d→s electron-scattering process involved in spin relaxation is the inverse of the s→d process responsible for the anisotropic magnetoresistance (AMR). As a result, spin-relaxation rate 1/τsr and AMR Δρ are given by similar formulas, and are in a constant ratio if scattering is by solute atoms. Our treatment applies to nickel- and cobalt-based alloys which do not have spin-up 3d states at the Fermi level. This category includes many of the technologically important magnetic materials. And we show how to modify the theory to apply it to bcc iron-based alloys. We also treat the case of Permalloy Ni80Fe20 at finite temperature or in thin-film form, where several kinds of scatterers exist. Predicted values of 1/τsr and Δρ are plotted versus resistivity of the sample. These predictions are compared to values of 1/τsr and Δρ derived from ferromagnetic-resonance and AMR experiments in Permalloy.
An experiment in multispectral, multitemporal crop classification using relaxation techniques
Davis, L. S.; Wang, C.-Y.; Xie, H.-C
1983-01-01
The paper describes the result of an experimental study concerning the use of probabilistic relaxation for improving pixel classification rates. Two LACIE sites were used in the study and in both cases, relaxation resulted in a marked improvement in classification rates.
Excited-state relaxation of some aminoquinolines
Directory of Open Access Journals (Sweden)
2006-01-01
Full Text Available The absorption and fluorescence spectra, fluorescence quantum yields and lifetimes, and fluorescence rate constants ( k f of 2-amino-3-( 2 ′ -benzoxazolylquinoline (I, 2-amino-3-( 2 ′ -benzothiazolylquinoline (II, 2-amino-3-( 2 ′ -methoxybenzothiazolyl-quinoline (III, 2-amino-3-( 2 ′ -benzothiazolylbenzoquinoline (IV at different temperatures have been measured. The shortwavelength shift of fluorescence spectra of compounds studied (23–49 nm in ethanol as the temperature decreases (the solvent viscosity increases points out that the excited-state relaxation process takes place. The rate of this process depends essentially on the solvent viscosity, but not the solvent polarity. The essential increasing of fluorescence rate constant k f (up to about 7 times as the solvent viscosity increases proves the existence of excited-state structural relaxation consisting in the mutual internal rotation of molecular fragments of aminoquinolines studied, followed by the solvent orientational relaxation.
Molecular Relaxation in Liquids
Bagchi, Biman
2012-01-01
This book brings together many different relaxation phenomena in liquids under a common umbrella and provides a unified view of apparently diverse phenomena. It aligns recent experimental results obtained with modern techniques with recent theoretical developments. Such close interaction between experiment and theory in this area goes back to the works of Einstein, Smoluchowski, Kramers' and de Gennes. Development of ultrafast laser spectroscopy recently allowed study of various relaxation processes directly in the time domain, with time scales going down to picosecond (ps) and femtosecond (fs
Doppler effect induced spin relaxation boom
Zhao, Xinyu; Huang, Peihao; Hu, Xuedong
2016-03-01
We study an electron spin qubit confined in a moving quantum dot (QD), with our attention on both spin relaxation, and the product of spin relaxation, the emitted phonons. We find that Doppler effect leads to several interesting phenomena. In particular, spin relaxation rate peaks when the QD motion is in the transonic regime, which we term a spin relaxation boom in analogy to the classical sonic boom. This peak indicates that a moving spin qubit may have even lower relaxation rate than a static qubit, pointing at the possibility of coherence-preserving transport for a spin qubit. We also find that the emitted phonons become strongly directional and narrow in their frequency range as the qubit reaches the supersonic regime, similar to Cherenkov radiation. In other words, fast moving excited spin qubits can act as a source of non-classical phonons. Compared to classical Cherenkov radiation, we show that quantum dot confinement produces a small but important correction on the Cherenkov angle. Taking together, these results have important implications to both spin-based quantum information processing and coherent phonon dynamics in semiconductor nanostructures.
... 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 ...
Relaxation training after stroke: potential to reduce anxiety.
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 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.
Relaxation of polarized nuclei in superconducting rhodium
DEFF Research Database (Denmark)
Knuuttila, T.A.; Tuoriniemi, J.T.; Lefmann, K.
2000-01-01
Nuclear spin lattice relaxation rates were measured in normal and superconducting (sc) rhodium with nuclear polarizations up to p = 0.55. This was sufficient to influence the sc state of Rh, whose T, and B-c, are exceptionally low. Because B-c
Kinetic Actviation Relaxation Technique
Béland, Laurent Karim; El-Mellouhi, Fedwa; Joly, Jean-François; Mousseau, Normand
2011-01-01
We present a detailed description of the kinetic Activation-Relaxation Technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si, self-interstitial diffusion in Fe and structural relaxation in amorphous silicon.
Hyperfine relaxation of an optically pumped cesium vapor
Energy Technology Data Exchange (ETDEWEB)
Tornos, J.; Amare, J.C.
1986-07-01
The relaxation of hyperfine orientation indirectly induced by optical pumping with a sigma-polarized D/sub 1/-light in a cesium vapor in the presence of Ar is experimentally studied. The detection technique ensures the absence of quadrupole relaxation contributions in the relaxation signals. The results from the dependences of the hyperfine relaxation rate on the temperature and argon pressure are: diffusion coefficient of Cs in Ar, D/sub 0/ = 0.101 +- 0.010 cm/sup 2/s/sup -1/ at 0/sup 0/C and 760 Torr; relaxation cross section by Cs-Ar collisions, sigma/sub c/ = (104 +- 5) x 10/sup -23/ cm/sup 2/; relaxation cross section by Cs-Cs (spin exchange) collisions, sigma/sub e//sub x/ = (1.63 +- 0.13) x 10/sup -14/ cm/sup 2/.
Experimental study of 199Hg spin anti-relaxation coatings
Chowdhuri, Z; Horras, M; Kirch, K; Krempel, J; Lauss, B; Mtchedlishvili, A; Rebreyend, D; Roccia, S; Schmidt-Wellenburg, P; Zsigmond, G
2013-01-01
We report on a comparison of spin relaxation rates in a $^{199}$Hg magnetometer using different wall coatings. A compact mercury magnetometer was built for this purpose. Glass cells coated with fluorinated materials show longer spin coherence times than if coated with their hydrogenated homologues. The longest spin relaxation time of the mercury vapor was measured with a fluorinated paraffin wall coating.
Spectral Estimation of NMR Relaxation
Naugler, David G.; Cushley, Robert J.
2000-08-01
. Spectral estimation of NMR relaxation allows this information content to be extended to a set of (n + 1)-tuples (λ, ω1, … ωn), where λ is the relaxation rate.
Asymptotic representation of relaxation oscillations in lasers
Grigorieva, Elena V
2017-01-01
In this book we analyze relaxation oscillations in models of lasers with nonlinear elements controlling light dynamics. The models are based on rate equations taking into account periodic modulation of parameters, optoelectronic delayed feedback, mutual coupling between lasers, intermodal interaction and other factors. With the aim to study relaxation oscillations we present the special asymptotic method of integration for ordinary differential equations and differential-difference equations. As a result, they are reduced to discrete maps. Analyzing the maps we describe analytically such nonlinear phenomena in lasers as multistability of large-amplitude relaxation cycles, bifurcations of cycles, controlled switching of regimes, phase synchronization in an ensemble of coupled systems and others. The book can be fruitful for students and technicians in nonlinear laser dynamics and in differential equations.
Longo, David J.
A within-subjects, three condition design was employed to examine the effects of three relaxation techniques on blood pressures, pulse rates, and self-report measures of relaxation for 12 college students. Respiratory Manipulation Training incorporated instructions to exhale and not to inhale for as long as possible. When breathing could no longer…
Load Relaxation of Olivine Single Crystals
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).
Grueneisen relaxation photoacoustic microscopy
Wang, Lidai; Zhang, Chi; Wang, Lihong V.
2014-01-01
The temperature-dependent property of the Grueneisen parameter has been employed in photoacoustic imaging mainly to measure tissue temperature. Here we explore this property using a different approach and develop Grueneisen-relaxation photoacoustic microscopy (GR-PAM), a technique that images non-radiative absorption with confocal optical resolution. GR-PAM sequentially delivers two identical laser pulses with a micro-second-scale time delay. The first laser pulse generates a photoacoustic signal and thermally tags the in-focus absorbers. Owing to the temperature dependence of the Grueneisen parameter, when the second laser pulse excites the tagged absorbers within the thermal relaxation time, a photoacoustic signal stronger than the first one is produced. GR-PAM detects the amplitude difference between the two co-located photoacoustic signals, confocally imaging the non-radiative absorption. We greatly improved axial resolution from 45 µm to 2.3 µm and at the same time slightly improved lateral resolution from 0.63 µm to 0.41 µm. In addition, the optical sectioning capability facilitates the measurement of the absolute absorption coefficient without fluence calibration. PMID:25379919
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Objective To observe effects of meshed relaxing short incisions on the level of superoxide dismutase and malondialdehyde in rat tension skin flap, and to investigate the mechanism of meshed relaxing short incisions (MRSI) on wound healing process of tension skin flap. Method An experimental model was designed to investingate the changes of superoxide dismutase (SOD) and malondialdehyde (MDA) in rat skin flap tissue each period of wound healing (12h, 24h, 48h, 72h after suture). In the meantime, the biochemical reaction were employed. Results Our results showed that SOD content in rat skin flap tissue from MRSI group were significant higher than that of hypertension group (P≤ 0.05), while MDA content was significantly lower (P≤ 0.05). Conclusion The decrease of MDA contents may be one of the causes that MRSI improves microcirculation of skin flap, and reduces edema and facilitates healing of skin flap.
Rupp, Wolf; Simon, Karl-Heinz; Bohnert, Michael
2009-01-01
Complete relaxation can be achieved by floating in a darkened, sound-proof relaxation tank filled with salinated water kept at body temperature. Under these conditions, meditation exercises up to self-hypnosis may lead to deep relaxation with physical and mental revitalization. A user manipulated his tank, presumably to completely cut off all optical and acoustic stimuli and accidentally also covered the ventilation hole. The man was found dead in his relaxation tank. The findings suggested lack of oxygen as the cause of death.
Relaxing Behavioural Inheritance
Directory of Open Access Journals (Sweden)
Nuno Amálio
2013-05-01
Full Text Available Object-oriented (OO inheritance allows the definition of families of classes in a hierarchical way. In behavioural inheritance, a strong version, it should be possible to substitute an object of a subclass for an object of its superclass without any observable effect on the system. Behavioural inheritance is related to formal refinement, but, as observed in the literature, the refinement constraints are too restrictive, ruling out many useful OO subclassings. This paper studies behavioural inheritance in the context of ZOO, an object-oriented style for Z. To overcome refinement's restrictions, this paper proposes relaxations to the behavioural inheritance refinement rules. The work is presented for Z, but the results are applicable to any OO language that supports design-by-contract.
Neira, Cristina; Anzidei, Michele; Napoli, Alessandro; Kirchin, Miles A; Cavallo Marincola, Beatrice; Zaccagna, Fulvio; Catalano, Carlo; Passariello, Roberto; Tedoldi, Fabio
2011-12-01
To optimize the image acquisition parameters for improved steady-state (SS) contrast-enhanced magnetic resonance angiography (CE-MRA) of the carotid arteries with gadobenate dimeglumine. An inversion recovery fast low-angle shot (IR-FLASH) sequence for ultrafast determination of the longitudinal relaxation rate R1 was first optimized on phantoms and tested against a routine variable repetition time (TR) spin echo sequence used as reference standard. Different combinations of flip angle (FA, between 6 and 14 degrees) and inversion time (between 134 and 9000 milliseconds) were evaluated to achieve the best trade off between speed and accuracy. The optimized sequence was thereafter used in vivo in 5 subjects to determine the time evolution of blood R1 at 1.5 T after administration of gadobenate dimeglumine at 0.1 mmol/kg bodyweight. An optimal FA for angiographic measurement was thereafter derived from the Ernst equation based on experimental values of R1 previously determined in vivo. Finally, steady-state CE-MRA examinations were performed in 20 subjects to evaluate the improved contrast achieved after optimization of the FA for maximal blood signal enhancement. An ultrafast IR-FLASH sequence with a flip angle of 8 degrees and a properly defined set of inversion time values was shown to give in vitro R1 determinations that were in good agreement with those obtained using a routine, time consuming, variable-TR spin echo sequence. The use of this ultrafast IR-FLASH sequence in vivo allowed the blood signal behavior in the carotid arteries after gadobenate dimeglumine administration to be monitored. Using this sequence, the R1 decreased from 8.7±0.96 s⁻¹ at 30 seconds after injection to 3.8±0.24 s⁻¹ at 10 minutes after injection. Based on these data for R1, the optimal FA for SS CE-MRA was calculated to be 18 degrees for a gradient echo acquisition protocol with TR=7.5 milliseconds, when gadobenate dimeglumine is used. Significantly higher blood signal to noise
Relaxation matching algorithm for moving photogrammetry
Guo, Lei; Liu, Ke; Miao, Yinxiao; Zhu, Jigui
2015-02-01
Moving photogrammetry is an application of close range photogrammetry in industrial measurement to realize threedimensional coordinate measurement within large-scale volume. This paper describes an approach of relaxation matching algorithm applicable to moving photogrammetry according to the characteristics of accurate matching result of different measuring images. This method uses neighborhood matching support to improve the matching rate after coarse matching based on epipolar geometry constraint and precise matching using three images. It reflects the overall matching effect of all points, that means when a point is matched correctly, the matching results of those points round it must be correct. So for one point considered, the matching results of points round it are calculated to judge whether its result is correct. Analysis indicates that relaxation matching can eliminate the mismatching effectively and acquire 100% rate of correct matching. It will play a very important role in moving photogrammetry to ensure the following implement of ray bundle adjustment.
Magnetic relaxation in anisotropic magnets
DEFF Research Database (Denmark)
Lindgård, Per-Anker
1971-01-01
The line shape and the kinematic and thermodynamic slowing down of the critical and paramagnetic relaxation in axially anisotropic materials are discussed. Kinematic slowing down occurs only in the longitudinal relaxation function. The thermodynamic slowing down occurs in either the transverse or...
Stochastic tools hidden behind the empirical dielectric relaxation laws
Stanislavsky, Aleksander; Weron, Karina
2017-03-01
The paper is devoted to recent advances in stochastic modeling of anomalous kinetic processes observed in dielectric materials which are prominent examples of disordered (complex) systems. Theoretical studies of dynamical properties of ‘structures with variations’ (Goldenfield and Kadanoff 1999 Science 284 87–9) require application of such mathematical tools—by means of which their random nature can be analyzed and, independently of the details distinguishing various systems (dipolar materials, glasses, semiconductors, liquid crystals, polymers, etc), the empirical universal kinetic patterns can be derived. We begin with a brief survey of the historical background of the dielectric relaxation study. After a short outline of the theoretical ideas providing the random tools applicable to modeling of relaxation phenomena, we present probabilistic implications for the study of the relaxation-rate distribution models. In the framework of the probability distribution of relaxation rates we consider description of complex systems, in which relaxing entities form random clusters interacting with each other and single entities. Then we focus on stochastic mechanisms of the relaxation phenomenon. We discuss the diffusion approach and its usefulness for understanding of anomalous dynamics of relaxing systems. We also discuss extensions of the diffusive approach to systems under tempered random processes. Useful relationships among different stochastic approaches to the anomalous dynamics of complex systems allow us to get a fresh look at this subject. The paper closes with a final discussion on achievements of stochastic tools describing the anomalous time evolution of complex systems.
State resolved vibrational relaxation modeling for strongly nonequilibrium flows
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.
Transverse relaxation of scalar-coupled protons.
Segawa, Takuya F; Baishya, Bikash; Bodenhausen, Geoffrey
2010-10-25
In a preliminary communication (B. Baishya, T. F. Segawa, G. Bodenhausen, J. Am. Chem. Soc. 2009, 131, 17538-17539), we recently demonstrated that it is possible to obtain clean echo decays of protons in biomolecules despite the presence of homonuclear scalar couplings. These unmodulated decays allow one to determine apparent transverse relaxation rates R(2) (app) of individual protons. Herein, we report the observation of R(2) (app) for three methyl protons, four amide H(N) protons, and all 11 backbone H(α) protons in cyclosporin A. If the proton resonances overlap, their R(2) (app) rates can be measured by transferring their magnetization to neighboring (13)C nuclei, which are less prone to overlap. The R(2) (app) rates of protons attached to (13)C are faster than those attached to (12)C because of (13)C-(1)H dipolar interactions. The differences of these rates allow the determination of local correlation functions. Backbone H(N) and H(α) protons that have fast decay rates R(2) (app) also feature fast longitudinal relaxation rates R(1) and intense NOESY cross peaks that are typical of crowded environments. Variations of R(2) (app) rates of backbone H(α) protons in similar amino acids reflect differences in local environments.
Relaxation Dynamics of Non-Power-Law Fluids
Min, Qi; Duan, Yuan-Yuan; Wang, Xiao-Dong; Liang, Zhan-Peng; Lee, Duu-Jong
2013-12-01
The relaxation of non-Newtonian liquids with non-power-law rheology on partially wetted surfaces is rarely investigated. This study assesses the relaxation behavior of 14 partial wetting systems with non-power-law fluids by sessile drop method. These systems are two carboxymethylcellulose sodium solutions on two kinds of slides, cover glass, and silicon wafer surfaces; three polyethylene glycol (PEG400) + silica nanoparticle suspensions on polymethyl methacrylate and polystyrene surfaces. The dynamic contact angle and moving velocity of contact line relationship data for relaxation drops of the 14 tested systems demonstrate a power-law fluid-like behavior, and the equivalent power exponent for a certain fluid on different solid substrates are uniform. By analyzing the relationship between the equivalent power exponent and shear rate, it is proposed that a fluid regime with shear rates of a few tens of s controls relaxation dynamics.
Levitation force relaxation under reloading in a HTS Maglev system
He, Qingyong; Wang, Jiasu; Wang, Suyu; Wang, Jiansi; Dong, Hao; Wang, Yuxin; Shao, Senhao
2009-02-01
The loading capacity of the high-temperature superconducting (HTS) Maglev vehicle is an important parameter in the practical application. It is closely related to the levitation force of the HTS bulk. Many papers reported that the levitation force showed the relaxation characteristic. Because different loads cause different levitation gaps and different applied magnetic fields, the levitation force relaxations under the different loads are not the same. In terms of cylindrical YBCO bulk levitated over the permanent magnetic guideway, the relationship between the levitation force relaxation and the reloading is investigated experimentally in this paper. The decrement, the decrement rate and the relaxation rate of the levitation force are calculated, respectively. This work might be helpful for studying the loading capacity of the HTS Maglev vehicle.
Can Black Hole Relax Unitarily?
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.
Can Black Hole Relax Unitarily?
Solodukhin, Sergey N.
2004-01-01
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...
Can Black Hole Relax Unitarily?
Solodukhin, S N
2004-01-01
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.
Dipolar relaxation of cold sodium atoms in a magnetic field
Zygelman, B
2002-01-01
A quantum mechanical close coupling theory of spin relaxation in the stretched hyperfine level of sodium is presented. We calculate the dipolar relaxation rate of magnetically trapped cold sodium atoms in the magnetic field. The influence of shape resonances and the anisotropy of the dipolar interaction on the collision dynamics are explored. We examine the sensitivity of the calculated cross sections on the choice of asymptotic atomic state basis.
Relaxation of a qubit measured by a driven Duffing oscillator
Serban, I; Wilhelm, F K
2009-01-01
We investigate the relaxation of a superconducting qubit for the case when its detector, the Josephson bifurcation amplifier, remains latched in one of its two (meta)stable states of forced vibrations. The qubit relaxation rates are different in different states. They can display strong dependence on the qubit frequency and resonant enhancement, which is due to {\\em quasienergy resonances}. Coupling to the driven oscillator changes the effective temperature of the qubit.
Vibrational relaxation of guest and host in mixed molecular crystals
Hill, Jeffrey R.; Chronister, Eric L.; Chang, Ta-Chau; Kim, Hackjin; Postlewaite, Jay C.; Dlott, Dana D.
1988-02-01
Vibrational relaxation (VR) of dilute impurity molecules (naphthalene, anthracene) in crystalline host matrices (durene, naphthalene) is studied with the ps photon echo technique. The results obtained by echoes on vibrations in the electronically excited state are compared to previous ps time delayed coherent Raman studies of ground state vibrations of the pure host matrix. The relaxation channels for guest and host, and the effects of molecular and crystal structure on VR rates are determined.
Relaxation oscillations in a laser with a Gaussian mirror.
Mossakowska-Wyszyńska, Agnieszka; Witoński, Piotr; Szczepański, Paweł
2002-03-20
We present an analysis of the relaxation oscillations in a laser with a Gaussian mirror by taking into account the three-dimensional spatial field distribution of the laser modes and the spatial hole burning effect. In particular, we discuss the influence of the Gaussian mirror peak reflectivity and a Gaussian parameter on the damping rate and frequency of the relaxation oscillation for two different laser structures, i.e., with a classically unstable resonator and a classically stable resonator.
Microplastic relaxations of single and polycrystalline molybdenum
Energy Technology Data Exchange (ETDEWEB)
Pichl, W.; Weiss, B. [Wien Univ. (Austria). Inst. fuer Materialphysik; Chen, D.L.
1998-05-01
The microplasticity of high-purity molybdenum single crystals and of Mo polycrystals of technical purity has been investigated by relaxation step tests in uniaxial compression. A new model for the evaluation of relaxation tests in the microplastic range of b.c.c metals is presented which takes into account the decrease of the mobile dislocation density due to exhaustion of non-screw dislocations. The model allows an independent determination of the activation volume and of the microstructure parameters controlling dislocation exhaustion. The results indicate that in the high-purity single crystals the deformation rate is controlled by interactions of non-screw dislocations with the grown-in network. In the polycrystals additional interactions with impurity atoms seem to occur. In the single crystals the activity and subsequent exhaustion of two different glide systems was observed, followed by a gradual onset of screw dislocation motion. (orig.) 26 refs.
Modeling aftershocks as a stretched exponential relaxation
Mignan, A.
2015-11-01
The decay rate of aftershocks has been modeled as a power law since the pioneering work of Omori in the late nineteenth century. Although other expressions have been proposed in recent decades to describe the temporal behavior of aftershocks, the number of model comparisons remains limited. After reviewing the aftershock models published from the late nineteenth century until today, I solely compare the power law, pure exponential and stretched exponential expressions defined in their simplest forms. By applying statistical methods recommended recently in applied mathematics, I show that all aftershock sequences tested in three regional earthquake catalogs (Southern and Northern California, Taiwan) and with three declustering techniques (nearest-neighbor, second-order moment, window methods) follow a stretched exponential instead of a power law. These results infer that aftershocks are due to a simple relaxation process, in accordance with most other relaxation processes observed in Nature.
Relaxation and Diffusion for the Kicked Rotor
Khodas, M A
2000-01-01
The dynamics of the kicked-rotor, that is a paradigm for a mixed system, where the motion in some parts of phase space is chaotic and in other parts is regular is studied statistically. The evolution (Frobenius-Perron) operator of phase space densities in the chaotic component is calculated in presence of noise, and the limit of vanishing noise is taken is taken in the end of calculation. The relaxation rates (related to the Ruelle resonances) to the invariant equilibrium density are calculated analytically within an approximation that improves with increasing stochasticity. The results are tested numerically. The global picture of relaxation to the equilibrium density in the chaotic component when the system is bounded and of diffusive behavior when it is unbounded is presented.
Modeling Aftershocks as a Stretched Exponential Relaxation
Mignan, Arnaud
2015-01-01
The decay rate of aftershocks has been modeled as a power law since the pioneering work of Omori in the late nineteenth century. Considered the second most fundamental empirical law after the Gutenberg-Richter relationship, the power law paradigm has rarely been challenged by the seismological community. By taking a view of aftershock research not biased by prior conceptions of Omori power law decay and by applying statistical methods recommended in applied mathematics, I show that all aftershock sequences tested in three regional earthquake catalogs (Southern and Northern California, Taiwan) and with three declustering techniques (nearest-neighbor, second-order moment, window methods) follow a stretched exponential instead of a power law. These results infer that aftershocks are due to a simpler relaxation process than originally thought, in accordance with most other relaxation processes observed in Nature.
Institute of Scientific and Technical Information of China (English)
穆俊林; 宋景贵; 李六一; 杜好瑞; 张宁; 刘涛; 张朝辉; 张萍; 张帆
2016-01-01
目的 探讨放松治疗(RT)对卒中后抑郁(PSD)患者睡眠及心率变异性(HRV)的影响.方法 采用随机数字表法将82例PSD患者分为观察组及对照组,每组41例.2组患者均给予常规治疗(包括降颅压、稳定血压、抗血小板聚集、脑细胞保护、活血化瘀及对症支持治疗等),观察组患者在此基础上辅以RT训练.于治疗前、治疗6周后检测2组患者多导睡眠图(PSG)及HRV,同时对2组患者结果数据进行比较.结果 治疗前2组患者PSG及HRV各项指标组间差异均无统计学意义(P＞0.05);与组内治疗前比较,观察组治疗后其PSG觉醒次数[(3.52±1.43)次]减少,睡眠效率[(74.2±4.22)％]及总睡眠时间[(382.1±25.3) min]增加,睡眠潜伏期[(40.5±14.3) min]及快眼动睡眠潜伏期[(89.2±8.81) min]缩短,浅睡眠比例[(65.6±7.93)％]减少,深睡眠比例[(14.7±3.64)％]及快眼动睡眠比例[(19.7±2.88)％]增加;HRV检测指标低频成分(5.18±0.96)降低,高频成分(5.21±0.60)升高,低频/高频比值(0.99±0.31)明显降低;对照组治疗后仅见觉醒次数[(5.22±1.97)次]减少、总睡眠时间[(336.7±29.7) min]增加,HRV各项指标治疗前、后均无显著变化;治疗后观察组PSG及HRV各项指标与对照组间差异均具有统计学意义(均P＜0.05).结论 在常规干预基础上辅以RT治疗,可进一步改善PSD患者睡眠障碍及HRV,对提高康复疗效及抑制并发症发生具有积极作用,该疗法值得临床推广、应用.%Objective To explore the effect of relaxation treatment (RT) on the sleep quality and heart rate variability (HRV) of patients with post-stroke depression (PSD).Methods Eighty-two PSD patients were recruited and randomly divided into a study group (n=41) and a control group (n =41) using a random number table.Both groups were given conventional medication (reducing the intracranial pressure,stabilizing blood pressure,anti-platelet aggregation,protecting brain cells,promoting blood
Iwaoka, Nobuyuki; Hagita, Katsumi; Takano, Hiroshi
2014-03-01
On the basis of relaxation mode analysis (RMA), we present an efficient method to estimate the linear viscoelasticity of polymer melts in a molecular dynamics (MD) simulation. Slow relaxation phenomena appeared in polymer melts cause a problem that a calculation of the stress relaxation function in MD simulations, especially in the terminal time region, requires large computational efforts. Relaxation mode analysis is a method that systematically extracts slow relaxation modes and rates of the polymer chain from the time correlation of its conformations. We show the computational cost may be drastically reduced by combining a direct calculation of the stress relaxation function based on the Green-Kubo formula with the relaxation rates spectra estimated by RMA. N. I. acknowledges the Graduate School Doctoral Student Aid Program from Keio University.
Controlling spin relaxation with a cavity
Bienfait, A.; Pla, J. J.; Kubo, Y.; Zhou, X.; Stern, M.; Lo, C. C.; Weis, C. D.; Schenkel, T.; Vion, D.; Esteve, D.; Morton, J. J. L.; Bertet, P.
2016-03-01
Spontaneous emission of radiation is one of the fundamental mechanisms by which an excited quantum system returns to equilibrium. For spins, however, spontaneous emission is generally negligible compared to other non-radiative relaxation processes because of the weak coupling between the magnetic dipole and the electromagnetic field. In 1946, Purcell realized that the rate of spontaneous emission can be greatly enhanced by placing the quantum system in a resonant cavity. This effect has since been used extensively to control the lifetime of atoms and semiconducting heterostructures coupled to microwave or optical cavities, and is essential for the realization of high-efficiency single-photon sources. Here we report the application of this idea to spins in solids. By coupling donor spins in silicon to a superconducting microwave cavity with a high quality factor and a small mode volume, we reach the regime in which spontaneous emission constitutes the dominant mechanism of spin relaxation. The relaxation rate is increased by three orders of magnitude as the spins are tuned to the cavity resonance, demonstrating that energy relaxation can be controlled on demand. Our results provide a general way to initialize spin systems into their ground state and therefore have applications in magnetic resonance and quantum information processing. They also demonstrate that the coupling between the magnetic dipole of a spin and the electromagnetic field can be enhanced up to the point at which quantum fluctuations have a marked effect on the spin dynamics; as such, they represent an important step towards the coherent magnetic coupling of individual spins to microwave photons.
Institute of Scientific and Technical Information of China (English)
WANG Mao-Xiang
2009-01-01
We use dynamic Monte Carlo simulations to study the athermal relaxation of bulk extended chains and the isothermal crystallization in intermediately relaxed melts. It is found that the memory of chain orientations in the melt can significantly enhance the crystallization rates. The crystal orientation and lamellar thickness essentially depend on the orientational relaxation. Moreover, there is a transition of the nucleation mechanism during the isothermal crystallization from the intermediately relaxed melts. These results explain the mechanism of the self-nucleation by orientation and suggest that in flow-induced polymer crystallization, the orientational relaxation of chains decides the crystal orientation.
An Exact Relaxation of Clustering
DEFF Research Database (Denmark)
Mørup, Morten; Hansen, Lars Kai
2009-01-01
of clustering problems such as the K-means objective and pairwise clustering as well as graph partition problems, e.g., for community detection in complex networks. In particular we show that a relaxation to the simplex can be given for which the extreme solutions are stable hard assignment solutions and vice......Continuous relaxation of hard assignment clustering problems can lead to better solutions than greedy iterative refinement algorithms. However, the validity of existing relaxations is contingent on problem specific fuzzy parameters that quantify the level of similarity between the original...... versa. Based on the new relaxation we derive the SR-clustering algorithm that has the same complexity as traditional greedy iterative refinement algorithms but leading to significantly better partitions of the data. A Matlab implementation of the SR-clustering algorithm is available for download....
The relaxation & stress reduction workbook
National Research Council Canada - National Science Library
Davis, Martha; Eshelman, Elizabeth Robbins; McKay, Matthew
2008-01-01
"The Relaxation & Stress Reduction Workbook broke new ground when it was first published in 1980, detailing easy, step-by-step techniques for calming the body and mind in an increasingly overstimulated world...
Analysis of 2D NMR relaxation data using Chisholm approximations
Huber, S.; Haase, A.; Gleich, B.
2017-08-01
To analyze 2D NMR relaxation data based on a discrete delta-like relaxation map we extended the Padé-Laplace method to two dimensions. We approximate the forward Laplace image of the time domain signal by a Chisholm approximation, i.e. a rational polynomial in two dimensions. The poles and residues of this approximation correspond to the relaxation rates and weighting factors of the underlying relaxation map. In this work we explain the principle ideas of our algorithm and demonstrate its applicability. Therefore we compare the inversion results of the Chisholm approximation and Tikhonov regularization method as a function of SNR when the investigated signal is based on a given discrete relaxation map. Our algorithm proved to be reliable for SNRs larger than 50 and is able to compete with the Tikhonov regularization method. Furthermore we show that our method is also able to detect the simulated relaxation compartments of narrow Gaussian distributions with widths less or equal than 0.05 s-1. Finally we investigate the resolution limit with experimental data. For a SNR of 750 the Chisholm approximation method was able to resolve two relaxation compartments in 8 of 10 cases when both compartments differ by a factor of 1.7.
Negative magnetic relaxation in superconductors
Directory of Open Access Journals (Sweden)
Krasnoperov E.P.
2013-01-01
Full Text Available It was observed that the trapped magnetic moment of HTS tablets or annuli increases in time (negative relaxation if they are not completely magnetized by a pulsed magnetic field. It is shown, in the framework of the Bean critical-state model, that the radial temperature gradient appearing in tablets or annuli during a pulsed field magnetization can explain the negative magnetic relaxation in the superconductor.
Relaxing effect of rose oil on humans.
Hongratanaworakit, Tapanee
2009-02-01
One increasingly popular type of alternative therapy is aromatherapy, but scientific validation in this field is still rare. The aim of this study was to investigate the effect of rose oil (Rosa damascena Mill, Rosaceae) on human autonomic parameters and emotional responses in healthy subjects after transdermal absorption. In order to exclude any olfactory stimulation the inhalation of the fragrances was prevented by breathing masks. Forty healthy volunteers participated in the experiments. Five autonomic parameters, i.e. blood pressure, breathing rate, blood oxygen saturation, pulse rate, and skin temperature, were recorded. Emotional responses were assessed by means of rating scales. Compared to placebo, rose oil caused significant decreases of breathing rate, blood oxygen saturation and systolic blood pressure, which indicate a decrease of autonomic arousal. At the emotional level, subjects in the rose oil group rated themselves as more calm, more relaxed and less alert than subjects in the control group. These findings are likely to represent a relaxing effect of the rose oil and provide some evidence for the use of rose oil in aromatherapy, such as causing relief of depression and stress in humans.
Viscous relaxation of Ganymede's impact craters: Constraints on heat flux
Bland, Michael; 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
Dynamic isotope effects on relaxation of quadrupolar nuclei in 12 simple organic molecules
Institute of Scientific and Technical Information of China (English)
毛希安; andM.Holz
1995-01-01
Dynamic isotope effects on relaxation rate of quadrupolar nuclei are preliminarily reported. The relaxation rates of 17O and 14N in 12 simple organic molecules and their 18 corresponding deuterated species have been systematically measured. The principal components of the molecular inertia tensors have been calculated. The results show that there is an intrinsic correlation between the dynamic isotope effects of the relaxation rate and the static isotope effects of the molecular inertia. The concepts of molecular collision frequency and translation-rotation coupling have been introduced into the NMR relaxation theory. Therefore, a reasonable explanation of the experimental results has been given.
Relaxation strategies for patients during dermatologic surgery.
Shenefelt, Philip D
2010-07-01
Patient stress and anxiety are common preoperatively and during dermatologic procedures and surgeries. Stress and anxiety can occasionally interfere with performance of procedures or surgery and can induce hemodynamic instability, such as elevated blood pressure or syncope, as well as producing considerable discomfort for some patients. Detection of excess stress and anxiety in patients can allow the opportunity for corrective or palliative measures. Slower breathing, biofeedback, progressive muscular relaxation, guided imagery, hypnosis, meditation and music can help calm and rebalance the patient's autonomic nervous system and immune functioning. Handheld miniaturized heart rate variability biofeedback devices are now available. The relaxation response can easily be taught. Guided imagery can be recorded or live. Live rapid induction hypnosis followed by deepening and then self-guided imagery requires no experience on the part of the patient but does require training and experience on the part of a provider. Recorded hypnosis inductions may also be used. Meditation generally requires more prior experience and training, but is useful when the patient already is skilled in it. Live, guided meditation or meditation recordings may be used. Relaxing recorded music from speakers or headphones or live performance music may also be employed to ease discomfort and improve the patient's attitude for dermatologic procedures and surgeries.
Hypnotizability modulates the cardiovascular correlates of subjective relaxation.
Santarcangelo, Enrica L; Paoletti, Giulia; Balocchi, Rita; Carli, Giancarlo; Morizzo, Carmela; Palombo, Carlo; Varanini, Maurizio
2012-01-01
Mean values and the spectral variability of heart rate (HRV), blood pressure, and skin blood flow were studied in high and low hypnotizable subjects during simple relaxation. Similar subjective relaxation was reported by highs and lows. A parasympathetic prevalence (indicated by a higher High-Frequency component of HRV and a lower High/Low-Frequency ratio) and lower renin-angiotensin activity (indicated by a lower Very-Low-Frequency component of HRV) could be attributed to highs with respect to lows. Hypnotizability did not affect blood pressure and its variability and modulated the skin blood flow across the session only in lows. The findings confirm that relaxation cannot be defined solely on cardiovascular parameters and also indicate that hypnotizability modulates cardiovascular activity during simple relaxation and suggest it may have a protective role against cardiovascular disease.
Ferrohydrodynamic evaluation of rotational viscosity and relaxation in certain ferrofluids.
Patel, Rajesh
2012-07-01
A significant effect of aggregation dynamics for aqueous ferrofluid (AF) and kerosene based ferrofluid (KF) using magnetic field dependent capillary viscosity and magneto-optical relaxation measurements is studied. For better comparison parameters of AF and KF are kept similar. Ferrohydrodynamic equations of chain forming ferrofluids, dilute ferrofluids, and Brownian dynamic simulations are compared. It is observed that the rotational viscosity of AF is larger than that of KF due to field induced aggregates in it and strong dipolar interactions. It is also observed that at Ωτ ~ 0.04 both AF and KF viscosity becomes almost similar, suggesting similar behavior at that shear rate. The magneto-optical relaxation in AF exhibits nonexponential behavior when relaxed from higher magnetic field and follows irreversible thermodynamics, whereas for KF the relaxation is exponential and follows the effective field method. This discrepancy is explained based on aggregation dynamics of magnetic particles. Results are well described by the corresponding theoretical models.
Thermal relaxation of molecular oxygen in collisions with nitrogen atoms
Andrienko, Daniil A.; Boyd, Iain D.
2016-07-01
Investigation of O2-N collisions is performed by means of the quasi-classical trajectory method on the two lowest ab initio potential energy surfaces at temperatures relevant to hypersonic flows. A complete set of bound-bound and bound-free transition rates is obtained for each precollisional rovibrational state. Special attention is paid to the vibrational and rotational relaxations of oxygen as a result of chemically non-reactive interaction with nitrogen atoms. The vibrational relaxation of oxygen partially occurs via the formation of an intermediate NO2 complex. The efficient energy randomization results in rapid vibrational relaxation at low temperatures, compared to other molecular systems with a purely repulsive potential. The vibrational relaxation time, computed by means of master equation studies, is nearly an order of magnitude lower than the relaxation time in N2-O collisions. The rotational nonequilibrium starts to play a significant effect at translational temperatures above 8000 K. The present work provides convenient relations for the vibrational and rotational relaxation times as well as for the quasi-steady dissociation rate coefficient and thus fills a gap in data due to a lack of experimental measurements for this system.
Repeated load relaxations of type 316 austenitic stainless steel
Energy Technology Data Exchange (ETDEWEB)
Hannula, S.P.; Li, C.Y.
1984-03-01
Several experiments have shown that the shape of the load relaxation curve after reloading in a logarithmic stress vs. logarithmic strain rate plot may differ from that after the initial loading. In a recent study Korhonen and Li showed that the apparent kink in a log sigma versus log epsilon plot of the stress relaxation data, after mainly elastic and anelastic loading, is due to change of the deformation mode from an anelasticity dominated one to a plasticity dominated one. According to the state variable model by Hart, the relaxation curve in reloading should overlap with the original one after this transition in the absence of structural changes. Therefore, the crossing of stress relaxation curves after an initial plastic loading and subsequent elastic and anelastic reloadings in commercially pure aluminum at room temperature was accounted for by thermally induced effects. In the same study, consecutive stress relaxation runs were conducted on 316 SS, and no cross-over behavior was observed, which was associated with the lack of thermal effects in 316 SS at room temperature. The results demonstrate that strain aging has an effect on relaxation behavior even at room temperature, the effect being more pronounced at high strains. The phenomena can be accounted for according to a state variable model by modifying the rate constant, which is affected by the amount of mobile dislocations as well as dislocation mobility.
Relaxation to the Invariant Density for Kicked Rotor
Khodas, M A
1999-01-01
The relaxation rates to the invariant density in the chaotic phase space component of the kicked rotor (standard map) are calculated analytically for a large stochasticity parameter, K. For hyperbolic systems these are the logarithms of the poles of the matrix elements of the resolvent $ These poles are inside the unit circle. For hyperbolic systems it is a rigorous result, while very little is known about mixed systems such as the kicked rotor, that is studied in this work. Here the relaxation rates are calculated in presence of noise, in powers of $1/\\sqrt{K}$, then the limit of vanishing noise is taken and the rates are found to be non vanishing, corresponding to poles inside the unit circle. It is found that the slow relaxation rates reduce to the ones found for diffusion in the momentum direction. The fast relaxation modes are related to relaxation of inhomogeneities in the angle direction. The analytical results are compared with numerical simulations, and small deviations from the analytical formulas r...
Structural relaxation in viscous metallic liquids
Energy Technology Data Exchange (ETDEWEB)
Meyer, A. [National Inst. of Standards and Technology (BFRL), Gaithersburg, MD (United States)]|[Technische Univ. Muenchen, Muenchen (Germany); Wuttke, J.; Petry, W. [Technische Univ. Muenchen, Muenchen (Germany); Schober, H. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France); Randl, O.G. [Manufacture Michelin, Clermont-Ferrand (France)
1999-11-01
Recently, metallic alloys have been found that exhibit extremely large viscosities in the liquid state. These liquids can be quenched into bulk metallic glasses at relatively modest cooling rates. In contrast to simple metals the structural relaxation of these systems show a two step decay in the liquid state. This behaviour has long been known for molecular or ionic glass formers in their under-cooled liquid state. Applying an analysis previously used for the glass formers (mode-coupling theory) a full quantitative description of the neutron data is obtained for these metallic liquids. (authors) 3 refs., 2 figs.
Thermal Stress Relaxation of Nonhomogeneous Coatings
Institute of Scientific and Technical Information of China (English)
无
1999-01-01
Nonhomogeneous coatings (NCs) are new type of engineering structures that is not yet fully understood. One important aspect in the mechanical analysis of NCs is to determine the gradient distribution that creates the maximum thermal stress relaxation. This paper employs numerical analysis using the finite element metho d and experimental analysis using moire interference to study the stress distrib ution in NCs. Attention focused on the edge effect stresses in the coating/subst rate structures and their dependence on the different gradient distributions of this new kind of composite structure.
Effect of carrier relaxation lifetime on the performance of InAs/InP quantum-dash lasers
Khan, Mohammed Zahed Mustafa
2011-12-01
The effect of carrier relaxation process into the quantum dash (Qdash) ground state (GS) is examined theoretically by carrier-photon rate equation model incorporating the inhomogeneous broadening. Increase in the relaxation time and the inhomogeneous broadening degrades the threshold current density. Moreover, our results show that a relaxation time of less than 2 ps gives optimum laser performance. © 2011 IEEE.
Dynamical theory of spin relaxation
Field, Timothy R.; Bain, Alex D.
2013-02-01
The dynamics of a spin system is usually calculated using the density matrix. However, the usual formulation in terms of the density matrix predicts that the signal will decay to zero, and does not address the issue of individual spin dynamics. Using stochastic calculus, we develop a dynamical theory of spin relaxation, the origins of which lie in the component spin fluctuations. This entails consideration of random pure states for individual protons, and how these pure states are correctly combined when the density matrix is formulated. Both the lattice and the spins are treated quantum mechanically. Such treatment incorporates both the processes of spin-spin and (finite temperature) spin-lattice relaxation. Our results reveal the intimate connections between spin noise and conventional spin relaxation.
Petrov, Oleg V.; Stapf, Siegfried
2017-06-01
This work addresses the problem of a compact and easily comparable representation of multi-exponential relaxation data. It is often convenient to describe such data in a few parameters, all being of physical significance and easy to interpret, and in such a way that enables a model-free comparison between different groups of samples. Logarithmic moments (LMs) of the relaxation time constitute a set of parameters which are related to the characteristic relaxation time on the log-scale, the width and the asymmetry of an underlying distribution of exponentials. On the other hand, the calculation of LMs does not require knowing the actual distribution function and is reduced to a numerical integration of original data. The performance of this method has been tested on both synthetic and experimental NMR relaxation data which differ in a signal-to-noise ratio, the sampling range and the sampling rate. The calculation of two lower-order LMs, the log-mean time and the log-variance, has proved robust against deficiencies of the experiment such as scattered data point and incomplete sampling. One may consider using them as such to monitor formation of a heterogeneous structure, e.g., in phase separation, vitrification, polymerization, hydration, aging, contrast agent propagation processes. It may also assist in interpreting frequency and temperature dependences of relaxation, revealing a crossover from slow to fast exchange between populations. The third LM was found to be a less reliable quantity due to its susceptibility to the noise and must be used with caution.
Andersen, D.; Hull, R.
2017-02-01
The effect of asymmetric interfacial strain configurations upon the generation of misfit dislocation arrays in lattice mismatched epitaxy is considered. For example, elastic strain relaxation for Si1-xGex/Si(110) films is uniaxial, assuming glide on {111} planes as expected for the diamond cubic system, which leads to asymmetric strain relief. Here, we extend our previously developed relaxation model for generation of dislocation arrays in SiGe/Si, by accounting for how the different energetics of asymmetrically strained films affect the kinetics of the relaxation process. Similarly, non-polar III-nitride epitaxial films have asymmetric strain from the outset of growth due to the different c/a lattice parameter ratios. In both systems, the asymmetric strain is represented by an additional term in the misfit dislocation applied stress equation. In SiGe/Si(110), a simple elasticity analysis of the strain produced by the uniaxial array of dislocations predicts that the relaxation orthogonal to the dislocation line direction occurs at a faster rate than predicted by purely biaxial strain relief due to the contributions of the strain parallel to the dislocations. This difference is because the strain parallel to the dislocation line directions continues to resolve stress onto the misfit dislocations even as the orthogonal strain is minimized. As a result, the minimum strain energy is predicted to occur for a dislocation spacing, which produces tensile layer strain in the orthogonal direction. Such tensile strain may modify the (opto)electronic properties of a Si, Ge, or GeSi epilayer but is only predicted to occur for advanced stages of relaxation. These asymmetric derivations are applicable to any thin film system where strain is not strictly biaxial.
Fetal response to abbreviated relaxation techniques. A randomized controlled study.
Fink, Nadine S; Urech, Corinne; Isabel, Fornaro; Meyer, Andrea; Hoesli, Irène; Bitzer, Johannes; Alder, Judith
2011-02-01
stress during pregnancy can have adverse effects on the course of pregnancy and on fetal development. There are few studies investigating the outcome of stress reduction interventions on maternal well-being and obstetric outcome. this study aims (1) to obtain fetal behavioral states (quiet/active sleep, quiet/active wakefulness), (2) to investigate the effects of maternal relaxation on fetal behavior as well as on uterine activity, and (3) to investigate maternal physiological and endocrine parameters as potential underlying mechanisms for maternal-fetal relaxation-transferral. the behavior of 33 fetuses was analyzed during laboratory relaxation/quiet rest (control group, CG) and controlled for baseline fetal behavior. Potential associations between relaxation/quiet rest and fetal behavior (fetal heart rate (FHR), FHR variation, FHR acceleration, and body movements) and uterine activity were studied, using a computerized cardiotocogram (CTG) system. Maternal heart rate, blood pressure, cortisol, and norepinephrine were measured. intervention (progressive muscle relaxation, PMR, and guided imagery, GI) showed changes in fetal behavior. The intervention groups had higher long-term variation during and after relaxation compared to the CG (p=.039). CG fetuses had more FHR acceleration, especially during and after quiet rest (p=.027). Women in the PMR group had significantly more uterine activity than women in the GI group (p=.011) and than CG women. Maternal heart rate, blood pressure, and stress hormones were not associated with fetal behavior. this study indicates that the fetus might participate in maternal relaxation and suggests that GI is superior to PMR. This could especially be true for women who tend to direct their attention to body sensations such as abdominal activity. 2010 Elsevier Ltd. All rights reserved.
LAVENDER AROMATERAPHY AS A RELAXANT
Directory of Open Access Journals (Sweden)
IGA Prima Dewi AP
2013-02-01
Full Text Available Aromatherapy is a kind of treatment that used aroma with aromatherapy essential oil. Extraction process from essential oil generally doing in three methods, there are distilling with water (boiled, distilling with water and steam, and distilling with steam. One of the most favorite aroma is lavender. The main content from lavender is linalyl acetate and linalool (C10H18O. Linalool is main active contents in lavender which can use for anti-anxiety (relaxation. Based on some research, the conclusion indicates that essential oil from lavender can give relaxation (carminative, sedative, reduce anxiety level and increasing mood.
Statistical mechanics of violent relaxation
Spergel, David N.; Hernquist, Lars
1992-01-01
We propose a functional that is extremized through violent relaxation. It is based on the Ansatz that the wave-particle scattering during violent dynamical processes can be approximated as a sequence of discrete scattering events that occur near a particle's perigalacticon. This functional has an extremum whose structure closely resembles that of spheroidal stellar systems such as elliptical galaxies. The results described here, therefore, provide a simple framework for understanding the physical nature of violent relaxation and support the view that galaxies are structured in accord with fundamental statistical principles.
Thermal relaxation and mechanical relaxation of rice gel
Institute of Scientific and Technical Information of China (English)
丁玉琴; 赵思明; 熊善柏
2008-01-01
Rice gel was prepared by simulating the production processes of Chinese local rice noodles,and the properties of thermal relaxation and mechanical relaxation during gelatinization were studied by differential scanning calorimetry(DSC) measurement and dynamic rheometer.The results show that during gelatinization,the molecular chains of rice starch undergo the thermal relaxation and mechanical relaxation.During the first heating and high temperature holding processes,the starch crystallites in the rice slurry melt,and the polymer chains stretch and interact,then viscoelastic gel forms.The cooling and low temperatures holding processes result in reinforced networks and decrease the viscoelasticity of the gel.During the second heating,the remaining starch crystallites further melt,the network is reinforced,and the viscoelasticity increases.The viscoelasticity,the molecular conformation and texture of the gel are adjusted by changing the temperature,and finally construct the gel with the textural characteristics of Chinese local rice noodle.
Control Strategies for Accurate Force Generation and Relaxation.
Ohtaka, Chiaki; Fujiwara, Motoko
2016-10-01
Characteristics and motor strategies for force generation and force relaxation were examined using graded tasks during isometric force control. Ten female college students (M age = 20.2 yr., SD = 1.1) were instructed to accurately control the force of isometric elbow flexion using their right arm to match a target force level as quickly as possible. They performed: (1) a generation task, wherein they increased their force from 0% maximum voluntary force to 20% maximum voluntary force (0%-20%), 40% maximum voluntary force (0%-40%), or 60% maximum voluntary force (0%-60%) and (2) and a relaxation task, in which they decreased their force from 60% maximum voluntary force to 40% maximum voluntary force (60%-40%), 20% maximum voluntary force (60%-20%), or to 0% maximum voluntary force (60%-0%). Produced force parameters of point of accuracy (force level, error), quickness (reaction time, adjustment time, rate of force development), and strategy (force wave, rate of force development) were analyzed. Errors of force relaxation were all greater, and reaction times shorter, than those of force generation. Adjustment time depended on the magnitude of force and peak rates of force development and force relaxation differed. Controlled relaxation of force is more difficult with low magnitude of force control.
Intestinal, Airway, and Cardiovascular Relaxant Activities of Thymoquinone
Directory of Open Access Journals (Sweden)
Muhammad Nabeel Ghayur
2012-01-01
Full Text Available Thymoquinone (TQ is a bioactive component found in many medicinal herbs. In this study, we report the smooth and cardiac muscle relaxant activities of this compound. TQ concentration dependently suppressed spontaneously contracting rabbit jejunum while also relaxed high K+-(80 mM induced contractions in jejunum and guinea-pig ileum, indicating activity at voltage-operated Ca++ channels (VOCC. Further, TQ displaced Ca++ concentration-response curves, obtained in a Ca++-free environment, to the right, showing blockade of VOCC. Similar activity was observed with verapamil, a standard VOCC blocker. TQ also exhibited nonadrenergic relaxation of agonist-induced contractions in guinea-pig trachea. When tested in fluo-4-loaded mouse lung slices, TQ inhibited ACh-induced airway narrowing and Ca++ signalling in airway smooth muscle cells. In endothelium-intact and endothelium-denuded rat aorta, TQ inhibited high K+-induced contractions at significantly lower concentrations than phenylephrine-(PE- (1 microM induced contractions. Relaxation of PE-induced contractions was resistant to blockade by L-NAME and atropine. In guinea-pig atria, TQ showed noncholinergic relaxation of atrial force and rate of contractions. These data suggest smooth and cardiac muscle relaxant activity of TQ possibly mediated, in part, via blockade of VOCC. The results also justify the use of TQ containing plants in related health disorders like colic, diarrhoea, cough, and asthma.
Institute of Scientific and Technical Information of China (English)
王力刚; 杨洪志; 张铮; 李勃; 于维芳; 孙月吉
2015-01-01
目的：探讨菩提树放松技术合并度洛西汀对焦虑障碍心率变异性（HRV）的影响。方法将124例焦虑障碍患者随机分为研究组（度洛西汀合并菩提树放松治疗）和对照组（单用度洛西汀）各62例，采用 Zung 氏焦虑自评量表（SAS）和汉密尔顿焦虑量表（HAMA）于治疗前及治疗后第2、4、6、8周末进行评定，并分别在每次干预前后监测 HRV 值。结果（1）治疗后第2、4、6、8周末两组 SAS 和 HAMA 评分均下降（P ＜0．05），研究组评分低于对照组（P ＜0．01）；治疗后第13、14、15、16次低频功率（LF）研究组低于对照组（P ＜0．05），高频功率（HF）研究组高于对照组（P ＜0．05）。（2）研究组焦虑严重指数与 LF ／HF 值呈正相关（P ＜0．05）。结论度洛西汀合并菩提树放松技术可以有效提高焦虑障碍患者的心率变异性和疗效。%Objective To investigate the influence of duloxetine combined with Bodhi tree relaxation technique on heart rate variability (HRV)in patients with anxiety disorder.Methods 124 patients with anxiety disorder were randomized into study group (62 cases)treated with duloxetine combined with Bodhi tree relaxation technique and control group (62 cases)treated with duloxetine monotherapy.All patients were assessed with Zung′s Self-Rating Anxiety Scale (SAS)and Hamilton Anxiety Scale (HAMA)at baseline and at the end of the 2nd ,4th ,6 th ,8th week of the treatment.HRV was measured before each relaxation and was re-measured after each relaxation.Results (1 )Scores of SAS and HAMA in both groups decreased significantly at the end of the 2nd ,4th ,6 th ,8th week when compared with the baseline (P <0.05).Scores of SAS and HAMA in study group were significantly lower than those in control group at each interview-point (P <0.01).Low frequency power (LF) at the 13 th ,14th ,15 th ,16 th measurement in study group were significantly lower than those in
Dielectric relaxation of samarium aluminate
Energy Technology Data Exchange (ETDEWEB)
Sakhya, Anup Pradhan; Dutta, Alo; Sinha, T.P. [Bose Institute, Department of Physics, Kolkata (India)
2014-03-15
A ceramic SmAlO{sub 3} (SAO) sample is synthesized by the solid-state reaction technique. The Rietveld refinement of the X-ray diffraction pattern has been done to find the crystal symmetry of the sample at room temperature. An impedance spectroscopy study of the sample has been performed in the frequency range from 50 Hz to 1 MHz and in the temperature range from 313 K to 573 K. Dielectric relaxation peaks are observed in the imaginary parts of the spectra. The Cole-Cole model is used to analyze the dielectric relaxation mechanism in SAO. The temperature-dependent relaxation times are found to obey the Arrhenius law having an activation energy of 0.29 eV, which indicates that polaron hopping is responsible for conduction or dielectric relaxation in this material. The complex impedance plane plot of the sample indicates the presence of both grain and grain-boundary effects and is analyzed by an electrical equivalent circuit consisting of a resistance and a constant-phase element. The frequency-dependent conductivity spectra follow a double-power law due to the presence of two plateaus. (orig.)
Choosing a skeletal muscle relaxant.
See, Sharon; Ginzburg, Regina
2008-08-01
Skeletal muscle relaxants are widely used in treating musculoskeletal conditions. However, evidence of their effectiveness consists mainly of studies with poor methodologic design. In addition, these drugs have not been proven to be superior to acetaminophen or nonsteroidal anti-inflammatory drugs for low back pain. Systematic reviews and meta-analyses support using skeletal muscle relaxants for short-term relief of acute low back pain when nonsteroidal anti-inflammatory drugs or acetaminophen are not effective or tolerated. Comparison studies have not shown one skeletal muscle relaxant to be superior to another. Cyclobenzaprine is the most heavily studied and has been shown to be effective for various musculoskeletal conditions. The sedative properties of tizanidine and cyclobenzaprine may benefit patients with insomnia caused by severe muscle spasms. Methocarbamol and metaxalone are less sedating, although effectiveness evidence is limited. Adverse effects, particularly dizziness and drowsiness, are consistently reported with all skeletal muscle relaxants. The potential adverse effects should be communicated clearly to the patient. Because of limited comparable effectiveness data, choice of agent should be based on side-effect profile, patient preference, abuse potential, and possible drug interactions.
Relaxation properties in classical diamagnetism
Carati, A.; Benfenati, F.; Galgani, L.
2011-06-01
It is an old result of Bohr that, according to classical statistical mechanics, at equilibrium a system of electrons in a static magnetic field presents no magnetization. Thus a magnetization can occur only in an out of equilibrium state, such as that produced through the Foucault currents when a magnetic field is switched on. It was suggested by Bohr that, after the establishment of such a nonequilibrium state, the system of electrons would quickly relax back to equilibrium. In the present paper, we study numerically the relaxation to equilibrium in a modified Bohr model, which is mathematically equivalent to a billiard with obstacles, immersed in a magnetic field that is adiabatically switched on. We show that it is not guaranteed that equilibrium is attained within the typical time scales of microscopic dynamics. Depending on the values of the parameters, one has a relaxation either to equilibrium or to a diamagnetic (presumably metastable) state. The analogy with the relaxation properties in the Fermi Pasta Ulam problem is also pointed out.
Equivalent Relaxations of Optimal Power Flow
Energy Technology Data Exchange (ETDEWEB)
Bose, S; Low, SH; Teeraratkul, T; Hassibi, B
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 imply 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.
Organic semiconductors: What makes the spin relax?
Bobbert, Peter A.
2010-04-01
Spin relaxation in organic materials is expected to be slow because of weak spin-orbit coupling. The effects of deuteration and coherent spin excitation show that the spin-relaxation time is actually limited by hyperfine fields.
Relaxation Techniques to Manage IBS Symptoms
... the Day Art of IBS Gallery Contact Us Relaxation Techniques to Manage IBS Symptoms Details Content Last Updated: ... Topic Psychological Treatments Understanding Stress Cognitive Behavioral Therapy Relaxation Techniques for IBS You’ve been to the doctor ...
Beckmann, Peter A; Schneider, Evan
2012-02-07
We report (1)H spin-lattice relaxation measurements in polycrystalline 4,4'-dimethoxybiphenyl at temperatures between 80 and 300 K at NMR frequencies of ω(0)/2π = 8.50, 22.5, and 53.0 MHz. The data are interpreted in terms of the simplest possible Bloch-Wangsness-Redfield methyl group hopping model. Different solid states are observed at low temperatures. The (1)H spin-lattice relaxation is nonexponential at higher temperatures where a stretched-exponential function fits the data very well, but this approach is phenomenological and not amenable to theoretical interpretation. (We provide a brief literature review of the stretched-exponential function.) The Bloch-Wangsness-Redfield model applies only to the relaxation rate that characterizes the initial (1)H magnetization decay in a high-temperature nonexponential (1)H spin-lattice relaxation measurement. A detailed procedure for determining this initial relaxation rate is described since large systematic errors can result if this is not done carefully.
Non-uniform sampling of NMR relaxation data
DEFF Research Database (Denmark)
Schwarz-Linnet, Troels; Teilum, Kaare
2016-01-01
The use of non-uniform sampling of NMR spectra may give significant reductions in the data acquisition time. For quantitative experiments such as the measurement of spin relaxation rates, non-uniform sampling is however not widely used as inaccuracies in peak intensities may lead to errors...
Plate-wide stress relaxation explains European Palaeocene basin inversions
DEFF Research Database (Denmark)
Nielsen, S.B.; Thomsen, Erik; Hansen, D.L.
2005-01-01
of the in-plane tectonic stress. The onset of relaxation inversions was plate-wide and simultaneous, and may have been triggered by stress changes caused by elevation of the North Atlantic lithosphere by the Iceland plume or the drop in NS convergence rate between Africa and Europe....
Spin Relaxation of Electrons in Single InAs Quantum Dots
Institute of Scientific and Technical Information of China (English)
MA Shan-Shan; DOU Xiu-Ming; CHANG Xiu-Ying; SUN Bao-Quan; XIONG Yong-Hua; NIU Zhi-Chuan; NI Hai-Qiao
2009-01-01
By using polarization-resolved photoluminescence spectra, we study the electron spin relaxation in single InAs quantum dots (QDs) with the configuration of positively charged excitons X~+ (one electron, two holes). The spin relaxation rate of the hot electrons increases with the increasing energy of exciting photons. For electrons localized in QDs the spin relaxation is induced by hyperfine interaction with the nuclei. A rapid decrease of polarization degree with increasing temperature suggests that the spin relaxation mechanisms are mainly changed from the hyperfine interaction with nuclei into an electron-hole exchange interaction.
Collisionless Relaxation of Stellar Systems
Kandrup, H E
1998-01-01
The objective of the work summarised here has been to exploit and extend ideas from plasma physics and accelerator dynamics to formulate a unified description of collisionless relaxation that views violent relaxation, Landau damping, and phase mixing as (manifestations of) a single phenomenon. This approach embraces the fact that the collisionless Boltzmann equation (CBE), the basic object of the theory, is an infinite-dimensional Hamiltonian system, with the distribution function f playing the role of the fundamental dynamical variable, and that, interpreted appropriately, an evolution described by the other Hamiltonian system. Equilibrium solutions correspond to extremal points of the Hamiltonian subject to the constraints associated with Liouville's Theorem. Stable equilibria correspond to energy minima. The evolution of a system out of equilibrium involves (in general nonlinear) phase space oscillations which may -- or may not -- interfere destructively so as to damp away.
Collisionless Relaxation of Stellar Systems
Kandrup, Henry E.
1999-08-01
The objective of the work summarized here has been to exploit and extend ideas from plasma physics and accelerator dynamics to formulate a unified description of collisionless relaxation of stellar systems that views violent relaxation, Landau damping, and phase mixing as (manifestations of) a single phenomenon. This approach embraces the fact that the collisionless Boltzmann equation (CBE), the basic object of the theory, is an infinite-dimensional Hamiltonian system, with the distribution function f playing the role of the fundamental dynamical variable, and that, interpreted appropriately, an evolution described by the CBE is no different fundamentally from an evolution described by any other Hamiltonian system. Equilibrium solutions f0 correspond to extremal points of the Hamiltonian subject to the constraints associated with Liouville's Theorem. Stable equilibria correspond to energy minima. The evolution of a system out of equilibrium involves (in general nonlinear) phase space oscillations which may - or may not - interfere destructively so as to damp away.
Kinetic activation-relaxation technique
Béland, Laurent Karim; Brommer, Peter; El-Mellouhi, Fedwa; Joly, Jean-François; Mousseau, Normand
2011-10-01
We present a detailed description of the kinetic activation-relaxation technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo (KMC) algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si (crystalline silicon), self-interstitial diffusion in Fe, and structural relaxation in a-Si (amorphous silicon).
Kinetic activation-relaxation technique.
Béland, Laurent Karim; Brommer, Peter; El-Mellouhi, Fedwa; Joly, Jean-François; Mousseau, Normand
2011-10-01
We present a detailed description of the kinetic activation-relaxation technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo (KMC) algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si (crystalline silicon), self-interstitial diffusion in Fe, and structural relaxation in a-Si (amorphous silicon).
Anomalous diffusion approach to non-exponential relaxation in complex physical systems
Stanislavsky, Aleksander; Weron, Karina; Weron, Aleksander
2015-07-01
We derive the relaxation function from the simple model of two-state systems under memory effects caused by the subordination. The non-exponential relaxation is shown to result from subordination by inverse infinity divisible random processes. The wide class of such random processes includes ordinary α-stable, tempered α-stable, exponential, gamma processes and many others as particular cases. This approach generalizes the Cole-Cole, Cole-Davidson and Havriliak-Negami laws well known in experimental physics of relaxation. The presented considerations discover a direct (one-to-one) relationship between the method of random relaxation rates and the anomalous diffusion approach based on subordination of random processes that are applied for the theory of relaxation phenomena. Moreover, it is found that the space and time clusterizations are responsible on equal foots for power-law memory effects in relaxation of complex physical systems.
Probing Brownian relaxation in water-glycerol mixtures using magnetic hyperthermia
Nemala, Humeshkar; Milgie, Michael; Wadehra, Anshu; Thakur, Jagdish; Naik, Vaman; Naik, Ratna
2013-03-01
Generation of heat by magnetic nanoparticles in the presence of an external oscillating magnetic field is known as magnetic hyperthermia (MHT). This heat is generated by two mechanisms: the Neel relaxation and Brownian relaxation. While the internal spin relaxation of the nanoparticles known as Neel relaxation is largely dependent on the magnetic properties of the nanoparticles, the physical motion of the particle or the Brownian relaxation is largely dependent on the viscous properties of the carrier liquid. The MHT properties of dextran coated iron oxide nanoparticles have been investigated at a frequency of 400KHz. To understand the influence of Brownian relaxation on heating, we probe the MHT properties of these ferrofluids in water-glycerol mixtures of varying viscosities. The heat generation is quantified using the specific absorption rate (SAR) and its maximum at a particular temperature is discussed with reference to the viscosity.
Hydrogels with tunable stress relaxation regulate stem cell fate and activity
Chaudhuri, Ovijit; Gu, Luo; Klumpers, Darinka; Darnell, Max; Bencherif, Sidi A.; Weaver, James C.; Huebsch, Nathaniel; Lee, Hong-Pyo; Lippens, Evi; Duda, Georg N.; Mooney, David J.
2016-03-01
Natural extracellular matrices (ECMs) are viscoelastic and exhibit stress relaxation. However, hydrogels used as synthetic ECMs for three-dimensional (3D) culture are typically elastic. Here, we report a materials approach to tune the rate of stress relaxation of hydrogels for 3D culture, independently of the hydrogel's initial elastic modulus, degradation, and cell-adhesion-ligand density. We find that cell spreading, proliferation, and osteogenic differentiation of mesenchymal stem cells (MSCs) are all enhanced in cells cultured in gels with faster relaxation. Strikingly, MSCs form a mineralized, collagen-1-rich matrix similar to bone in rapidly relaxing hydrogels with an initial elastic modulus of 17 kPa. We also show that the effects of stress relaxation are mediated by adhesion-ligand binding, actomyosin contractility and mechanical clustering of adhesion ligands. Our findings highlight stress relaxation as a key characteristic of cell-ECM interactions and as an important design parameter of biomaterials for cell culture.
Brief relaxation training program for hospital employees.
Balk, Judith L; Chung, Sheng-Chia; Beigi, Richard; Brooks, Maria
2009-01-01
Employee stress leads to attrition, burnout, and increased medical costs. We aimed to assess if relaxation training leads to decreased stress levels based on questionnaire and thermal biofeedback. Thirty-minute relaxation training sessions were conducted for hospital employees and for cancer patients. Perceived Stress levels and skin temperature were analyzed before and after relaxation training.
POS Tagging Using Relaxation Labelling
Padro, L
1995-01-01
Relaxation labelling is an optimization technique used in many fields to solve constraint satisfaction problems. The algorithm finds a combination of values for a set of variables such that satisfies -to the maximum possible degree- a set of given constraints. This paper describes some experiments performed applying it to POS tagging, and the results obtained. It also ponders the possibility of applying it to word sense disambiguation.
Impact of luminescence quenching on relaxation-oscillation frequency in solid-state lasers
Agazzi, L.; Bernhardi, Edward; Worhoff, Kerstin; Pollnau, Markus
Measurement of the laser relaxation-oscillation frequency as a function of pump rate allows one to determine parameters of the laser medium or cavity. We show that luminescence quenching of a fraction of the rare-earth ions in a solid-state laser affects the relaxation oscillations, resulting in
Nuclear spin-lattice relaxation in nitroxide spin-label EPR
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 T1-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 Wn commonly used in the CW-EPR literature for 14N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised 14N spin-lattice relaxation rate, b = Wn/(2We), 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 14N-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 14N-relaxation: T1n = 1/Wn. Results are compared and contrasted with those for the two-level 15N-nitroxide system.
Relaxation techniques for pain management in labour.
Smith, Caroline A; Levett, Kate M; Collins, Carmel T; Crowther, Caroline A
2011-12-07
relief (risk ratio (RR) 8.00, 95% CI 1.10 to 58.19, one trial, 40 women) and lower assisted vaginal delivery (RR 0.07, 95% CI 0.01 to 0.50, two trials, 86 women). Yoga was associated with reduced pain (mean difference (MD) -6.12, 95% CI -11.77 to -0.47), one trial, 66 women), increased satisfaction with pain relief (MD 7.88, 95% CI 1.51 to 14.25, one trial, 66 women), satisfaction with the childbirth experience (MD) 6.34, 95% CI 0.26 to 12.42, one trial, 66 women), and reduced length of labour when compared to usual care (MD -139.91, 95% CI -252.50 to -27.32, one trial, 66 women) and when compared with supine position (MD -191.34, 95% CI -243.72 to -138.96, one trial, 83 women). Trials evaluating music and audio analgesia found no difference between groups in the primary outcomes pain intensity, satisfaction with pain relief, and caesarean delivery. The risk of bias was unclear for the majority of trials. Relaxation and yoga may have a role with reducing pain, increasing satisfaction with pain relief and reducing the rate of assisted vaginal delivery. There was insufficient evidence for the role of music and audio-analgesia. However, there is a need for further research.
Arresting relaxation in Pickering Emulsions
Atherton, Tim; Burke, Chris
2015-03-01
Pickering emulsions consist of droplets of one fluid dispersed in a host fluid and stabilized by colloidal particles absorbed at the fluid-fluid interface. Everyday materials such as crude oil and food products like salad dressing are examples of these materials. Particles can stabilize non spherical droplet shapes in these emulsions through the following sequence: first, an isolated droplet is deformed, e.g. by an electric field, increasing the surface area above the equilibrium value; additional particles are then adsorbed to the interface reducing the surface tension. The droplet is then allowed to relax toward a sphere. If more particles were adsorbed than can be accommodated by the surface area of the spherical ground state, relaxation of the droplet is arrested at some non-spherical shape. Because the energetic cost of removing adsorbed colloids exceeds the interfacial driving force, these configurations can remain stable over long timescales. In this presentation, we present a computational study of the ordering present in anisotropic droplets produced through the mechanism of arrested relaxation and discuss the interplay between the geometry of the droplet, the dynamical process that produced it, and the structure of the defects observed.
Relaxation response in femoral angiography.
Mandle, C L; Domar, A D; Harrington, D P; Leserman, J; Bozadjian, E M; Friedman, R; Benson, H
1990-03-01
Immediately before they underwent femoral angiography, 45 patients were given one of three types of audiotapes: a relaxation response tape recorded for this study, a tape of contemporary instrumental music, or a blank tape. All patients were instructed to listen to their audiotape during the entire angiographic procedure. Each audiotape was played through earphones. Radiologists were not told the group assignment or tape contents. The patients given the audiotape with instructions to elicit the relaxation response (n = 15) experienced significantly less anxiety (P less than .05) and pain (P less than .001) during the procedure, were observed by radiology nurses to exhibit significantly less pain (P less than .001) and anxiety (P less than .001), and requested significantly less fentanyl citrate (P less than .01) and diazepam (P less than .01) than patients given either the music (n = 14) or the blank (n = 16) control audiotapes. Elicitation of the relaxation response is a simple, inexpensive, efficacious, and practical method to reduce pain, anxiety, and medication during femoral angiography and may be useful in other invasive procedures.
Hayashi, Shigenobu; Jimura, Keiko
2017-07-08
Mechanisms of the (1)H spin-lattice relaxation in NH4H2PO4 were studied in detail by use of the effect of magic angle spinning on the relaxation. The acid and the ammonium protons have different relaxation times at the spinning rates higher than 10 kHz due to suppression of spin diffusion between the two kinds of protons. The intrinsic relaxation times not affected by the spin diffusion and the spin-diffusion assisted relaxation times were evaluated separately, taking into consideration temperature dependence. Both mechanisms contribute to the (1)H relaxation of the acid protons comparatively. The spin-diffusion assisted relaxation mechanism was suppressed to the level lower than the experimental errors at the spinning rate of 30 kHz. Copyright © 2017 Elsevier Inc. All rights reserved.
Effects of relaxation on psychobiological wellbeing during pregnancy: a randomized controlled trial.
Urech, Corinne; Fink, Nadine S; Hoesli, Irène; Wilhelm, Frank H; Bitzer, Johannes; Alder, Judith
2010-10-01
Prenatal maternal stress is associated with adverse birth outcomes and may be reduced by relaxation exercises. The aim of the present study was to compare the immediate effects of two active and one passive 10-min relaxation technique on perceived and physiological indicators of relaxation. 39 healthy pregnant women recruited at the outpatient department of the University Women's Hospital Basel participated in a randomized controlled trial with an experimental repeated measure design. Participants were assigned to one of two active relaxation techniques, progressive muscle relaxation (PMR) or guided imagery (GI), or a passive relaxation control condition. Self-reported relaxation on a visual analogue scale (VAS) and state anxiety (STAI-S), endocrine parameters indicating hypothalamic-pituitary-adrenal (HPA) axis (cortisol and ACTH) and sympathetic-adrenal-medullary (SAM) system activity (norepinephrine and epinephrine), as well as cardiovascular responses (heart rate, systolic and diastolic blood pressure) were measured at four time points before and after the relaxation exercise. Between group differences showed, that compared to the PMR and control conditions, GI was significantly more effective in enhancing levels of relaxation and together with PMR, GI was associated with a significant decrease in heart rate. Within the groups, passive as well as active relaxation procedures were associated with a decline in endocrine measures except epinephrine. Taken together, these data indicate that different types of relaxation had differential effects on various psychological and biological stress systems. GI was especially effective in inducing self-reported relaxation in pregnant women while at the same time reducing cardiovascular activity. Copyright © 2010 Elsevier Ltd. All rights reserved.
Stress retardation versus stress relaxation in linear viscoelasticity
Christov, Ivan C
2016-01-01
We present a preliminary examination of a new approach to a long-standing problem in non-Newtonian fluid mechanics. First, we summarize how a general implicit functional relation between stress and rate of strain of a continuum with memory is reduced to the well-known linear differential constitutive relations that account for "relaxation" and "retardation." Then, we show that relaxation and retardation are asymptotically equivalent for small Deborah numbers, whence causal pure relaxation models necessarily correspond to ill-posed pure retardation models. We suggest that this dichotomy could be a possible way to reconcile the discrepancy between the theory of and certain experiments on viscoelastic liquids that are conjectured to exhibit only stress retardation.
Relaxation Characteristics of 828 DGEBA Epoxy Over Long Time Periods
Hoo, Jasmine; Reprogle, Riley C.; Wisler, Brian; Arechederra, Gabriel K.; McCoy, John D.; Kropka, Jamie M.; Long, Kevin N.
The mechanical relaxation response in uniaxial compression of a diglycidyl ether of bisphenol-A epoxy was studied over long time periods. The epoxy, 828DEA, was Epon 828 cured with diethanolamine (DEA). A sample was compressed at constant strain rate and held at various strain levels for days to allow the sample to relax. The sample was then compressed further and held once more. The relaxation curves were fit with a stretched exponential function. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.
Schwarz waveform relaxation algorithm for heat equations with distributed delay
Directory of Open Access Journals (Sweden)
Wu Shu-Lin
2016-01-01
Full Text Available Heat equations with distributed delay are a class of mathematic models that has wide applications in many fields. Numerical computation plays an important role in the investigation of these equations, because the analytic solutions of partial differential equations with time delay are usually unavailable. On the other hand, duo to the delay property, numerical computation of these equations is time-consuming. To reduce the computation time, we analyze in this paper the Schwarz waveform relaxation algorithm with Robin transmission conditions. The Robin transmission conditions contain a free parameter, which has a significant effect on the convergence rate of the Schwarz waveform relaxation algorithm. Determining the Robin parameter is therefore one of the top-priority matters for the study of the Schwarz waveform relaxation algorithm. We provide new formula to fix the Robin parameter and we show numerically that the new Robin parameter is more efficient than the one proposed previously in the literature.
Proton magnetic relaxation dispersion in aqueous biopolymer systems
Conti, S.
Investigation of the magnetic field dependence of proton spin-lattice relaxation in solutions of bovine fibrinogen has been performed for Larmor frequencies between 50 Hz and 60 MHz, and complemented with measurements of spin-spin relaxation rates at 2 kHz and 25 MHz. A thorough analysis of experimental data, including the effects of protein concentration, temperature, pH and isotopic dilution, leads to an overall relaxation scheme consistent with T1 and T2 values at both low and high magnetic fields. The scheme involves water molecules slightly anisotropically bound on proteins as well as slow exchanging protein protons magnetically coupled to solute nuclei. A coherent picture, reminiscent of the traditional hydration layer, can be obtained for bound water. A major conclusion is that transfer of single protons may contribute substantially to the chemical exchange between free and bound water.
On the Relaxation Dynamics of Disordered Systems
Dobramysl, Ulrich
We investigate the properties of two distinct disordered systems: the two-species predator-prey Lotka-Volterra model with rate variability, and an elastic line model to simulate vortex lines in type-II superconductors. We study the effects of intrinsic demographic variability with inheritance in the reaction rates of the Lotka-Volterra model via zero-dimensional Monte Carlo simulations as well as two-dimensional lattice simulations. Individuals of each species are assigned inheritable predation efficiencies during their creation, leading to evolutionary dynamics and thus population-level optimization. We derive an effective subspecies mean-field theory and compare its results to our numerical data. Furthermore, we introduce environmental variability via quenched spatial reaction-rate randomness. We investigate the competing effects and relative importance of the two types of variability, and find that both lead to a remarkable enhancement of the species densities, while the aforementioned optimization effects are essentially neutral in the densities. Additionally, we collected extinction time histograms for small systems and find a marked increase in the stability of the populations against extinction due to the presence of variability. We employ an elastic line model to investigate the steady-state properties and non-equilibrium relaxation kinetics of magnetic vortex lines in disordered type-II superconductors. To this end, we developed a versatile and efficient Langevin molecular dynamics simulation code, allowing us to do a careful study of samples with or without vortex-vortex interactions or disorder allows us to disentangle the various complex relaxational features present in this system and investigate their origin. In particular, we compare disordered samples with randomly distributed point defects versus correlated columnar defects. We extract two-time quantities such as the mean-square displacement, the height and density correlations, to investigate the
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.
Relaxation phenomena in rubber/layered silicate nanocomposites
Directory of Open Access Journals (Sweden)
2007-12-01
Full Text Available Broadband Dielectric Spectroscopy (BDS is employed in order to investigate relaxation phenomena occurring in natural rubber (NR, polyurethane rubber (PUR and PUR/NR blend based nanocomposites, reinforced by 10 parts per hundred (phr Layered Silicates (LS. Nanocomposites and matrices were examined under identical conditions in a wide frequency (10–1 to 106 Hz and temperature (–100 to 50°C range. Experimental data are analyzed in terms of electric modulus formalism. The recorded relaxation phenomena include contributions from both the polymer matrices and the nanofiller. Natural rubber is a non-polar material and its performance is only slightly affected by the presence of layered silicates. Polyurethane rubber exhibits four distinct relaxation processes attributed, with ascending relaxation rate, to Interfacial Polarization (IP, glass/rubber transition (α-mode, local motions of polar side groups and small segments of the polymer chain (β, γ-mode. The same processes have been detected in all systems containing PUR. IP is present in all nanocomposites being the slowest recorded process. Finally, pronounced interfacial relaxation phenomena, occurring in the PUR+10 phr LS spectra, are attributed to nanoscale effects of intercalation and exfoliation.
Predictability of the large relaxations in a cellular automaton model
Energy Technology Data Exchange (ETDEWEB)
Tejedor, Alejandro; Ambroj, Samuel; Gomez, Javier B; Pacheco, Amalio F [Faculty of Sciences, University of Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza (Spain)
2008-09-19
A simple one-dimensional cellular automaton model with threshold dynamics is introduced. It is loaded at a uniform rate and unloaded by abrupt relaxations. The cumulative distribution of the size of the relaxations is analytically computed and behaves as a power law with an exponent equal to -1. This coincides with the phenomenological Gutenberg-Richter behavior observed in seismology for the cumulative statistics of earthquakes at the regional or global scale. The key point of the model is the zero-load state of the system after the occurrence of any relaxation, no matter what its size. This leads to an equipartition of probability between all possible load configurations in the system during the successive loading cycles. Each cycle ends with the occurrence of the greatest-or characteristic-relaxation in the system. The duration of the cycles in the model is statistically distributed with a coefficient of variation ranging from 0.5 to 1. The predictability of the characteristic relaxations is evaluated by means of error diagrams. This model illustrates the value taking into account the refractory periods to obtain a considerable gain in the quality of the predictions.
High fidelity modeling of thermal relaxation and dissociation of oxygen
Energy Technology Data Exchange (ETDEWEB)
Andrienko, Daniil A., E-mail: daniila@umich.edu; Boyd, Iain D. [Department of Aerospace Engineering, University of Michigan, 1320 Beal Ave., Ann Arbor, Michigan 48108 (United States)
2015-11-15
A master equation study of vibrational relaxation and dissociation of oxygen is conducted using state-specific O{sub 2}–O transition rates, generated by extensive trajectory simulations. Both O{sub 2}–O and O{sub 2}–O{sub 2} collisions are concurrently simulated in the evolving nonequilibrium gas system under constant heat bath conditions. The forced harmonic oscillator model is incorporated to simulate the state-to-state relaxation of oxygen in O{sub 2}–O{sub 2} collisions. The system of master equations is solved to simulate heating and cooling flows. The present study demonstrates the importance of atom-diatom collisions due to the extremely efficient energy randomization in the intermediate O{sub 3} complex. It is shown that the presence of atomic oxygen has a significant impact on vibrational relaxation time at temperatures observed in hypersonic flow. The population of highly-excited O{sub 2} vibrational states is affected by the amount of atomic oxygen when modeling the relaxation under constant heat bath conditions. A model of coupled state-to-state vibrational relaxation and dissociation of oxygen is also discussed.
Time of relaxation in dusty plasma model
Timofeev, A. V.
2015-11-01
Dust particles in plasma may have different values of average kinetic energy for vertical and horizontal motion. The partial equilibrium of the subsystems and the relaxation processes leading to this asymmetry are under consideration. A method for the relaxation time estimation in nonideal dusty plasma is suggested. The characteristic relaxation times of vertical and horizontal motion of dust particles in gas discharge are estimated by analytical approach and by analysis of simulation results. These relaxation times for vertical and horizontal subsystems appear to be different. A single hierarchy of relaxation times is proposed.
5 Things To Know About Relaxation Techniques for Stress
... X Y Z 5 Things To Know About Relaxation Techniques for Stress Share: When you’re under stress, ... creating the relaxation response through regular use of relaxation techniques could counteract the negative effects of stress. Relaxation ...
Spirooxazine Photoisomerization and Relaxation in Polymer Matrices
Directory of Open Access Journals (Sweden)
Maria Larkowska
2011-01-01
Full Text Available 9′-Hydroxy-1,3,3-trimethylspiro[indoline-2,3′[3H]naphtha[2,1-b]-1,4oxazine] (SPO-7OH was used in studies of photochromic transformations in polymer matrices. Illumination with UV lamp caused opening the spirostructure of the oxazine with formation of open merocyanine species absorbing at ca. 610 nm. The kinetic studies of thermal relaxation of the open form showed that this process can be described with a biexponential function including both photochemical reaction and rheological behaviour of the polymeric environment. Basing on Arrhenius plot of the rate constant ascribed to the photochemical reaction, the activation energy was determined, which was 66.1 and 84.7 kJ/mole for poly(methyl methacrylate-co-butyl methacrylate and poly(vinylpyrrolidone matrix, respectively.
Occupational stress, relaxation therapies, exercise and biofeedback.
Stein, Franklin
2001-01-01
Occupational stress is a widespread occurrence in the United States. It is a contributing factor to absenteeism, disease, injury and lowered productivity. In general stress management programs in the work place that include relaxation therapies, exercise, and biofeedback have been shown to reduce the physiological symptoms such as hypertension, and increase job satisfaction and job performance. Strategies to implement a successful stress management program include incorporating the coping activities into one's daily schedule, monitoring one's symptoms and stressors, and being realistic in setting up a schedule that is relevant and attainable. A short form of meditation, daily exercise program and the use of heart rate or thermal biofeedback can be helpful to a worker experiencing occupational stress.
Holographic thermal relaxation in superfluid turbulence
Energy Technology Data Exchange (ETDEWEB)
Du, Yiqiang [School of Physics, University of Chinese Academy of Sciences,Beijing 100049 (China); Niu, Chao [Institute of High Energy Physics, Chinese Academy of Sciences,Beijing 100049 (China); Tian, Yu [School of Physics, University of Chinese Academy of Sciences,Beijing 100049 (China); State Key Laboratory of Theoretical Physics,Institute of Theoretical Physics, Chinese Academy of Sciences,Beijing 100190 (China); Zhang, Hongbao [Department of Physics, Beijing Normal University,Beijing 100875 (China); Theoretische Natuurkunde, Vrije Universiteit Brussel and The International Solvay Institutes,Pleinlaan 2, B-1050 Brussels (Belgium)
2015-12-02
Holographic duality provides a first-principles approach to investigate real time processes in quantum many-body systems, in particular at finite temperature and far-from-equilibrium. We use this approach to study the dynamical evolution of vortex number in a two-dimensional (2D) turbulent superfluid through numerically solving its gravity dual. We find that the temporal evolution of the vortex number can be well fit statistically by two-body decay due to the vortex pair annihilation featured relaxation process, thus confirm the previous suspicion based on the experimental data for turbulent superfluid in highly oblate Bose-Einstein condensates. Furthermore, the decay rate near the critical temperature is in good agreement with the recently developed effective theory of 2D superfluid turbulence.
Relaxed Half-Stochastic Belief Propagation
Leduc-Primeau, François; Mannor, Shie; Gross, Warren J
2012-01-01
Low-density parity-check codes are attractive for high throughput applications because of their low decoding complexity per bit, but also because all the codeword bits can be decoded in parallel. However, achieving this in a circuit implementation is complicated by the number of wires required to exchange messages between processing nodes. Decoding algorithms that exchange binary messages are interesting for fully-parallel implementations because they can reduce the number and the length of the wires, and increase logic density. This paper introduces the Relaxed Half-Stochastic (RHS) decoding algorithm, a binary message belief propagation (BP) algorithm that achieves a coding gain comparable to the best known BP algorithms that use real-valued messages. We derive the RHS algorithm by starting from the well-known Sum-Product algorithm, and then derive a low-complexity version suitable for circuit implementation. We present extensive simulation results on two standardized codes having different rates and constr...
The Elliott-Yafet theory of spin relaxation generalized for large spin-orbit coupling
Kiss, Annamária; Szolnoki, Lénard; Simon, Ferenc
2016-03-01
We generalize the Elliott-Yafet (EY) theory of spin relaxation in metals with inversion symmetry for the case of large spin-orbit coupling (SOC). The EY theory treats the SOC to the lowest order but this approach breaks down for metals of heavy elements (such as e.g. caesium or gold), where the SOC energy is comparable to the relevant band-band separation energies. The generalized theory is presented for a four-band model system without band dispersion, where analytic formulae are attainable for arbitrary SOC for the relation between the momentum- and spin-relaxation rates. As an extended description, we also consider an empirical pseudopotential approximation where SOC is deduced from the band potential (apart from an empirical scaling constant) and the spin-relaxation rate can be obtained numerically. Both approaches recover the usual EY theory for weak SOC and give that the spin-relaxation rate approaches the momentum-relaxation rate in the limit of strong SOC. We argue that this limit is realized in gold by analyzing spin relaxation data. A calculation of the g-factor shows that the empirical Elliott-relation, which links the g-factor and spin-relaxation rate, is retained even for strong SOC.
Compaction and relaxation of biofilms
Valladares Linares, R.
2015-06-18
Operation of membrane systems for water treatment can be seriously hampered by biofouling. A better characterization of biofilms in membrane systems and their impact on membrane performance may help to develop effective biofouling control strategies. The objective of this study was to determine the occurrence, extent and timescale of biofilm compaction and relaxation (decompaction), caused by permeate flux variations. The impact of permeate flux changes on biofilm thickness, structure and stiffness was investigated in situ and non-destructively with optical coherence tomography using membrane fouling monitors operated at a constant crossflow velocity of 0.1 m s−1 with permeate production. The permeate flux was varied sequentially from 20 to 60 and back to 20 L m−2 h−1. The study showed that the average biofilm thickness on the membrane decreased after elevating the permeate flux from 20 to 60 L m−2 h−1 while the biofilm thickness increased again after restoring the original flux of 20 L m−2 h−1, indicating the occurrence of biofilm compaction and relaxation. Within a few seconds after the flux change, the biofilm thickness was changed and stabilized, biofilm compaction occurred faster than the relaxation after restoring the original permeate flux. The initial biofilm parameters were not fully reinstated: the biofilm thickness was reduced by 21%, biofilm stiffness had increased and the hydraulic biofilm resistance was elevated by 16%. Biofilm thickness was related to the hydraulic biofilm resistance. Membrane performance losses are related to the biofilm thickness, density and morphology, which are influenced by (variations in) hydraulic conditions. A (temporarily) permeate flux increase caused biofilm compaction, together with membrane performance losses. The impact of biofilms on membrane performance can be influenced (increased and reduced) by operational parameters. The article shows that a (temporary) pressure increase leads to more
Plasma Relaxation in Hall Magnetohydrodynamics
Shivamoggi, B K
2011-01-01
Parker's formulation of isotopological plasma relaxation process in magnetohydrodynamics (MHD) is extended to Hall MHD. The torsion coefficient alpha in the Hall MHD Beltrami condition turns out now to be proportional to the "potential vorticity." The Hall MHD Beltrami condition becomes equivalent to the "potential vorticity" conservation equation in two-dimensional hydrodynamics if the Hall MHD Lagrange multiplier beta is taken to be proportional to the "potential vorticity" as well. The winding pattern of the magnetic field lines in Hall MHD then appears to evolve in the same way as "potential vorticity" lines in 2D hydrodynamics.
Relaxing Chosen-Ciphertext Security
DEFF Research Database (Denmark)
Canetti, Ran; Krawczyk, Hugo; Nielsen, Jesper Buus
2003-01-01
Security against adaptive chosen ciphertext attacks (or, CCA security) has been accepted as the standard requirement from encryption schemes that need to withstand active attacks. In particular, it is regarded as the appropriate security notion for encryption schemes used as components within...... “for most practical purposes.” We propose a relaxed variant of CCA security, called Replayable CCA (RCCA) security. RCCA security accepts as secure the non-CCA (yet arguably secure) schemes mentioned above; furthermore, it suffices for most existing applications of CCA security. We provide three...
Ultrafast studies of photodissociation in solution: Dissociation, recombination and relaxation
Energy Technology Data Exchange (ETDEWEB)
King, Jason Christopher [Univ. of California, Berkeley, CA (United States)
1995-05-01
Photodissociation of M(CO)_{6} (M=Cr,Mo,W) and the formation of solvated M(CO)_{5}•S complex was studied in cyclohexane; rate-limiting step is vibrational energy relaxation from the new bond to the solvent. For both M=Cr and Mo, the primary relaxation occurs in 18 ps; for Cr, there is an additional vibrational relaxation (150 ps time scale) of a CO group poorly coupled to other modes. Relaxation of M=W occurs in 42 ps; several possible mechanisms for the longer cooling are discussed. Vibrational relaxation is also investigated for I_{2}^{-} and IBr^{-} in nonpolar and slightly polar solvents. Attempts were made to discover the mechanism for the fast energy transfer in nonpolar solvent. The longer time scale dynamics of I_{3}^{-} and IBr_{2}^{-} were also studied; both formed a metastable complex following photodissociation and 90-95% return to ground state in 100 ps, implying a barrier to recombination of 4.3 kcal/mol and a barrier to escape of ≥5.5 kcal/mol. The more complex photochemistry of M_{3}(CO)_{12} (M=Fe,Ru) is also investigated, using visible and ultraviolet radiations, dissociation, geminate recombination, vibrational relaxation, and bridging structures and their reactions were studied. Attempts were made to extend ultrafast spectroscopy into the mid-infrared, but signal-to-noise was poor.
Institute of Scientific and Technical Information of China (English)
Xifeng LI; Kaifeng ZHANG; Changli WANG; Wenbo HAN; Guofeng WANG
2007-01-01
The amorphous Fe78Si9B13 ribbons were bend stress relaxed at various temperature well below the crystallization temperature (Tx) for different time. The effect of pre-annealing on the subsequent bend stress relaxation was examined. The variation of the microstructure and microhardness during bend stress relaxation process was studied using X-ray diffraction (XRD), atomic force microscopy (AFM) and Vickers microhardness test,respectively. Curvature radius of the amorphous Fe78Si9B13 ribbons decreased with increase bend stress relaxation temperature and time. The microhardness of the stress relaxed specimens increased with time at 300℃ due to the forming of nanocrystals during bend stress relaxation. The pre-annealing reduced the decrease rate of the curvature radius of stress relaxed specimens.
Xu, Jinsheng; Ju, Yutao; Han, Bo; Zhou, Changsheng; Zheng, Jian
2013-11-01
The main goal of this work is to obtain relaxation curves of Hydroxyl-Terminated Polybutadiene (HTPB) propellant under unsteady temperature states. A series of relaxation tests of HTPB were carried out, with the strain level ɛ 0 of the tests being applied with a ramp time of strain rate . A method is proposed to compensate for stress relaxation during the period of strain rate loading. The proposed method is compared to a numerical method and a general method in terms of accuracy of determination of relaxation modulus. The results show that the relaxation moduli obtained by the proposed method and the numerical method are more accurate than those from the general method; in addition, the proposed method is more convenient in data processing. The relaxation modulus values under unsteady temperature states were obtained from a series of relaxation curves under constant temperature, and at different temperatures according to Time-Temperature Superposition Principle (TTSP). In this work, reduced time is defined as a function of time-temperature shift factor a T and a variable ψ( T) called `zero time' which depends on temperature. A comparison of test results showed that the values of relaxation modulus that take `zero time' into account are more accurate than those without `zero time'.
Nuclear spin-lattice relaxation in nitroxide spin-label EPR
DEFF Research Database (Denmark)
Marsh, Derek
2016-01-01
Nuclear relaxation is a sensitive monitor of rotational dynamics in spin-label EPR. It also contributes competing saturation transfer pathways in T1-exchange spectroscopy, and the determination of paramagnetic relaxation enhancement in site-directed spin labelling. A survey shows that the definit......Nuclear relaxation is a sensitive monitor of rotational dynamics in spin-label EPR. It also contributes competing saturation transfer pathways in T1-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 Wn commonly used in the CW-EPR literature for 14N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised 14N spin-lattice relaxation rate, b = Wn/(2We), 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 14N-nitroxyl spin labels do not accord with conventional analysis...
Nuclear magnetic relaxation by the dipolar EMOR mechanism: Multi-spin systems
Chang, Zhiwei; Halle, Bertil
2017-08-01
In aqueous systems with immobilized macromolecules, including biological tissues, the longitudinal spin relaxation of water protons is primarily induced by exchange-mediated orientational randomization (EMOR) of intra- and intermolecular magnetic dipole-dipole couplings. Starting from the stochastic Liouville equation, we have previously developed a rigorous EMOR relaxation theory for dipole-coupled two-spin and three-spin systems. Here, we extend the stochastic Liouville theory to four-spin systems and use these exact results as a guide for constructing an approximate multi-spin theory, valid for spin systems of arbitrary size. This so-called generalized stochastic Redfield equation (GSRE) theory includes the effects of longitudinal-transverse cross-mode relaxation, which gives rise to an inverted step in the relaxation dispersion profile, and coherent spin mode transfer among solid-like spins, which may be regarded as generalized spin diffusion. The GSRE theory is compared to an existing theory, based on the extended Solomon equations, which does not incorporate these phenomena. Relaxation dispersion profiles are computed from the GSRE theory for systems of up to 16 protons, taken from protein crystal structures. These profiles span the range from the motional narrowing limit, where the coherent mode transfer plays a major role, to the ultra-slow motion limit, where the zero-field rate is closely related to the strong-collision limit of the dipolar relaxation rate. Although a quantitative analysis of experimental data is beyond the scope of this work, it is clear from the magnitude of the predicted relaxation rate and the shape of the relaxation dispersion profile that the dipolar EMOR mechanism is the principal cause of water-1H low-field longitudinal relaxation in aqueous systems of immobilized macromolecules, including soft biological tissues. The relaxation theory developed here therefore provides a basis for molecular-level interpretation of endogenous soft
Utilizing RELAX NG Schemas in XML Editors
Schmied, Martin
2008-01-01
This thesis explores the possibilities of utilizing RELAX NG schemata in the process of editing XML documents. The ultimate goal of this thesis is to prototype a system supporting user while editing XML document with bound RELAX NG schema inside the Eclipse IDE. Such a system comprises two major components -- an integration of RELAX NG validator and an autocompletion engine. Design of the autocompletion engine represents the main contribution of this thesis, because similar systems are almost...
Baryogenesis via Elementary Goldstone Higgs Relaxation
Gertov, Helene; Pearce, Lauren; Yang, Louis
2016-01-01
We extend the relaxation mechanism to the Elementary Goldstone Higgs frame- work. Besides studying the allowed parameter space of the theory we add the minimal ingredients needed for the framework to be phenomenologically viable. The very nature of the extended Higgs sector allows to consider very flat scalar potential directions along which the relaxation mechanism can be implemented. This fact translates into wider regions of applicability of the relaxation mechanism when compared to the Standard Model Higgs case. Our results show that, if the electroweak scale is not fundamental but radiatively generated, it is possible to generate the observed matter-antimatter asymmetry via the relaxation mechanism.
Dielectric relaxation studies in polyvinyl butyral
Mehendru, P. C.; Kumar, Naresh; Arora, V. P.; Gupta, N. P.
1982-10-01
Dielectric measurements have been made in thick films (˜100 μm) of polyvinyl butyral (PVB) having degree of polymerization n=1600, in the frequency range 100 Hz-100 KHz and temperature range 300-373 K. The results indicated that PVB was in the amorphous phase and observed dielectric dispersion has been assigned as the β-relaxation process. The β relaxation is of Debye type with symmetrical distribution of relaxation times. The dielectric relaxation strength Δɛ and the distribution parameters β¯ increase with temperature. The results can be qualitatively explained by assuming the hindered rotation of the side groups involving hydroxyl/acetate groups.
Relaxation and Visualization Strategies for Story Telling
Institute of Scientific and Technical Information of China (English)
冯灵林
2012-01-01
The importance of training students to tell or retell story is self - evident for mastering English language. The following activity introduces relaxation and visualization strategies for story telling.
Chang, Zhiwei; Halle, Bertil
2013-10-01
In complex biological or colloidal samples, magnetic relaxation dispersion (MRD) experiments using the field-cycling technique can characterize molecular motions on time scales ranging from nanoseconds to microseconds, provided that a rigorous theory of nuclear spin relaxation is available. In gels, cross-linked proteins, and biological tissues, where an immobilized macromolecular component coexists with a mobile solvent phase, nuclear spins residing in solvent (or cosolvent) species relax predominantly via exchange-mediated orientational randomization (EMOR) of anisotropic nuclear (electric quadrupole or magnetic dipole) couplings. The physical or chemical exchange processes that dominate the MRD typically occur on a time scale of microseconds or longer, where the conventional perturbation theory of spin relaxation breaks down. There is thus a need for a more general relaxation theory. Such a theory, based on the stochastic Liouville equation (SLE) for the EMOR mechanism, is available for a single quadrupolar spin I = 1. Here, we present the corresponding theory for a dipole-coupled spin-1/2 pair. To our knowledge, this is the first treatment of dipolar MRD outside the motional-narrowing regime. Based on an analytical solution of the spatial part of the SLE, we show how the integral longitudinal relaxation rate can be computed efficiently. Both like and unlike spins, with selective or non-selective excitation, are treated. For the experimentally important dilute regime, where only a small fraction of the spin pairs are immobilized, we obtain simple analytical expressions for the auto-relaxation and cross-relaxation rates which generalize the well-known Solomon equations. These generalized results will be useful in biophysical studies, e.g., of intermittent protein dynamics. In addition, they represent a first step towards a rigorous theory of water 1H relaxation in biological tissues, which is a prerequisite for unravelling the molecular basis of soft
Nuclear relaxation via paramagnetic impurities
Dzheparov, F S; Jacquinot, J F
2002-01-01
First part of the work contains a calculation of the kinetics of nuclear relaxation via paramagnetic impurities for systems with arbitrary (including fractal) space dimension d basing on ideas, which run current for 3d objects now. A new mean-field-type theory is constructed in the second part of the work. It reproduces all results of the first part for integer d and gives a possibility to describe the process for longer time, when a crossover to Balagurov-Waks asymptotics starts to develop. Solutions of the equations of the new theory are constructed for integer d. To obtain the solutions a method of calculation of the low-energy and long-wave asymptotics for T matrix of potential scattering out of the mass shell for singular repulsive potentials is developed
Relaxing Chosen-Ciphertext Security
DEFF Research Database (Denmark)
Canetti, Ran; Krawczyk, Hugo; Nielsen, Jesper Buus
2003-01-01
Security against adaptive chosen ciphertext attacks (or, CCA security) has been accepted as the standard requirement from encryption schemes that need to withstand active attacks. In particular, it is regarded as the appropriate security notion for encryption schemes used as components within...... general protocols and applications. Indeed, CCA security was shown to suffice in a large variety of contexts. However, CCA security often appears to be somewhat too strong: there exist encryption schemes (some of which come up naturally in practice) that are not CCA secure, but seem sufficiently secure...... “for most practical purposes.” We propose a relaxed variant of CCA security, called Replayable CCA (RCCA) security. RCCA security accepts as secure the non-CCA (yet arguably secure) schemes mentioned above; furthermore, it suffices for most existing applications of CCA security. We provide three...
Resonant relaxation near a massive black hole: the dependence on eccentricity
Gürkan, M Atakan
2007-01-01
The orbits of stars close to a massive black hole are nearly Keplerian ellipses. Such orbits exert long term torques on each other, which lead to an enhanced angular momentum relaxation known as resonant relaxation. Under certain conditions, this process can modify the angular momentum distribution and affect the interaction rates of the stars with the massive black hole more efficiently than non-resonant relaxation. The torque on an orbit exerted by the cluster depends on the eccentricity of the orbit. In this paper, we calculate this dependence and determine the resonant relaxation timescale as a function of eccentricity. In particular, we show that the component of the torque that changes the magnitude of the angular momentum is linearly proportional to eccentricity, so resonant relaxation is much more efficient on eccentric orbits than on circular orbits.
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.
[Efficacy of combined relaxation exercises for children with bronchial asthma].
Gröller, B
1991-05-01
In the framework of a pilot study, 15 children having bronchial asthma (4 female, 11 male; age 5-11;6) participated, over a period of 8 weeks, in two weekly sessions of combined relaxation, respiratory and sports exercises. The present article in particular focuses on the relaxation exercises, made up of Progressive Muscle Relaxation and Autogenic Training elements as well as of phantasy travels, mantras, and periodic music. Ongoing observation of the children during training, the findings of subsequent semi-structured interviews with them, topical instances of coping with impending asthma attacks by using the techniques learned, as well as the results of a catamnestic inquiry some three years later--all indicate a positive impact of the relaxation exercises. Statistical analysis of the data at hand revealed significant improvements in a number of pulmonary function parameters (airway resistance, forced expiratory volume for 1 s, forced vital capacity, peak expiratory flow rate). Interpretation of these findings must however take into account the entirety of the training provided.
[Effectiveness of combined relaxation exercises for children with bronchial asthma].
Gröller, B
1992-02-01
In the framework of a pilot study, 15 children having bronchial asthma (4 female, 11 male; age 5-11; 6) participated, over a period of 8 weeks, in two weekly sessions of combined relaxation, respiratory and sports exercises. The present article in particular focuses on the relaxation exercises, made up of Progressive Muscle Relaxation and Autogenic Training elements as well as of phantasy travels, mantras, and periodic music. Ongoing observation of the children during training, the findings of subsequent semi-structured interviews with them, topical instances of coping with impending asthma attacks by using the techniques learnt, as well as the result of a catamnestic inquiry some three years later--all indicate a positive impact of the relaxation exercises. Statistical analysis of the data at hand revealed significant improvements in a number of pulmonary function parameters (airway resistance, forced expiratory volume for 1 s, forced vital capacity, peak expiratory flow rate). Interpretation of these findings must however take into account the entirety of the training provided.
Spectral EEG Features of a Short Psycho-physiological Relaxation
Directory of Open Access Journals (Sweden)
Teplan Michal
2014-08-01
Full Text Available Short-lasting psycho-physiological relaxation was investigated through an analysis of its bipolar electroencephalographic (EEG characteristics. In 8 subjects, 6-channel EEG data of 3-minute duration were recorded during 88 relaxation sessions. Time course of spectral EEG features was examined. Alpha powers were decreasing during resting conditions of 3-minute sessions in lying position with eyes closed. This was followed by a decrease of total power in centro-parietal cortex regions and an increase of beta power in fronto-central areas. Represented by EEG coherences the interhemispheric communication between the parieto-occipital regions was enhanced within a frequency range of 2-10 Hz. In order to discern between higher and lower levels of relaxation distinguished according to self-rated satisfaction, EEG features were assessed and discriminating parameters were identified. Successful relaxation was determined mainly by the presence of decreased delta-1 power across the cortex. Potential applications for these findings include the clinical, pharmacological, and stress management fields.
Transverse relaxation in the rotating frame induced by chemical exchange
Michaeli, Shalom; Sorce, Dennis J.; Idiyatullin, Djaudat; Ugurbil, Kamil; Garwood, Michael
2004-08-01
In the presence of radiofrequency irradiation, relaxation of magnetization aligned with the effective magnetic field is characterized by the time constant T1 ρ. On the other hand, the time constant T2 ρ characterizes the relaxation of magnetization that is perpendicular to the effective field. Here, it is shown that T2 ρ can be measured directly with Carr-Purcell sequences composed of a train of adiabatic full-passage (AFP) pulses. During adiabatic rotation, T2 ρ characterizes the relaxation of the magnetization, which under adiabatic conditions remains approximately perpendicular to the time-dependent effective field. Theory is derived to describe the influence of chemical exchange on T2 ρ relaxation in the fast-exchange regime, with time constant defined as T2 ρ,ex . The derived theory predicts the rate constant R 2ρ, ex (=1/T 2ρ, ex) to be dependent on the choice of amplitude- and frequency-modulation functions used in the AFP pulses. Measurements of R2 ρ,ex of the water/ethanol exchanging system confirm the predicted dependence on modulation functions. The described theoretical framework and adiabatic methods represent new tools to probe exchanging systems.
Nuclear relaxation in an electric field enables the determination of isotropic magnetic shielding
Garbacz, Piotr
2016-08-01
It is shown that in contrast to the case of nuclear relaxation in a magnetic field B, simultaneous application of the magnetic field B and an additional electric field E causes transverse relaxation of a spin-1/2 nucleus with the rate proportional to the square of the isotropic part of the magnetic shielding tensor. This effect can contribute noticeably to the transverse relaxation rate of heavy nuclei in molecules that possess permanent electric dipole moments. Relativistic quantum mechanical computations indicate that for 205Tl nucleus in a Pt-Tl bonded complex, Pt(CN)5Tl, the transverse relaxation rate induced by the electric field is of the order of 1 s-1 at E = 5 kV/mm and B = 10 T.
Electron spin relaxation of copper(II) complexes in glassy solution between 10 and 120 K.
Fielding, Alistair J; Fox, Stephen; Millhauser, Glenn L; Chattopadhyay, Madhuri; Kroneck, Peter M H; Fritz, Günter; Eaton, Gareth R; Eaton, Sandra S
2006-03-01
The temperature dependence, between 10 and 120 K, of electron spin-lattice relaxation at X-band was analyzed for a series of eight pyrrolate-imine complexes and for ten other copper(II) complexes with varying ligands and geometry including copper-containing prion octarepeat domain and S100 type proteins. The geometry of the CuN4 coordination sphere for pyrrolate-imine complexes with R=H, methyl, n-butyl, diphenylmethyl, benzyl, 2-adamantyl, 1-adamantyl, and tert-butyl has been shown to range from planar to pseudo-tetrahedral. The fit to the recovery curves was better for a distribution of values of T1 than for a single time constant. Distributions of relaxation times may be characteristic of Cu(II) in glassy solution. Long-pulse saturation recovery and inversion recovery measurements were performed. The temperature dependence of spin-lattice relaxation rates was analyzed in terms of contributions from the direct process, the Raman process, and local modes. It was necessary to include more than one process to fit the experimental data. There was a small contribution from the direct process at low temperature. The Raman process was the dominant contribution to relaxation between about 20 and 60 K. Debye temperatures were between 80 and 120 K. For samples with similar Debye temperatures the coefficient of the Raman process tended to increase as gz increased, as expected if modulation of spin-orbit coupling is a major factor in relaxation rates. Above about 60 K local modes with energies in the range of 260-360 K (180-250 cm-1) dominated the relaxation. For molecules with similar geometry, relaxation rates were faster for more flexible molecules than for more rigid ones. Relaxation rates for the copper protein samples were similar to rates for small molecules with comparable coordination spheres. At each temperature studied the range of relaxation rates was less than an order of magnitude. The spread was smaller between 20 and 60 K where the Raman process dominates
Vibrational relaxation in H-H{sub 2} collisions
Energy Technology Data Exchange (ETDEWEB)
Flower, D.R. [Physics Department, The University, Durham DH1 3LE (United Kingdom); Roueff, E. [URA 173, associee au CNRS et a l' Universite Paris 7, et DAEC Observatoire de Paris, F-92195 Meudon Principal Cedex (France)
1998-12-14
We present the results of quantum mechanical calculations of the rate coefficients for vibrational relaxation {nu}=1{yields}0 of H{sub 2} in H in the temperature range 300 {<=} T {<=} 4500 K. The results were obtained using two recent and independent calculations of the H-H{sub 2} potential, for comparison purposes. Although reactive scattering is excluded from the present study, the results of quasi-classical trajectory calculations which include this process are used to estimate its contribution. The total rate coefficient which is thus obtained is found to be an order of magnitude smaller than that measured by Heidner and Kasper, but it is two orders of magnitude larger than the corresponding values for vibrational relaxation in He or H{sub 2}. The need for fresh experimental study is emphasized. (author). Letter-to-the-editor.
Liquid-state paramagnetic relaxation from first principles
Rantaharju, Jyrki; Vaara, Juha
2016-10-01
We simulate nuclear and electron spin relaxation rates in a paramagnetic system from first principles. Sampling a molecular dynamics trajectory with quantum-chemical calculations produces a time series of the instantaneous parameters of the relevant spin Hamiltonian. The Hamiltonians are, in turn, used to numerically solve the Liouville-von Neumann equation for the time evolution of the spin density matrix. We demonstrate the approach by studying the aqueous solution of the Ni2 + ion. Taking advantage of Kubo's theory, the spin-lattice (T1) and spin-spin (T2) relaxation rates are extracted from the simulations of the time dependence of the longitudinal and transverse magnetization, respectively. Good agreement with the available experimental data is obtained by the method.
Icariin on relaxation effect of corpus cavernosum smooth muscle
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
NO-cGMP pathway in penile corpus cavernosal smooth muscle plays an important role in penile erection. The level of cGMP is regulated by a balance between the rate of synthesis by guanylate cyclase and the rate of hydrolytic breakdown to guanosine 5′monophosphate (GMP) by phos- phodiesterase 5(PDE5). Icariin is isolated from natural drug Epimedii herba, it is shown to have the relaxation effect on corpus cavernosal smooth muscle of rabbit (IC50: 4×10-4 mol/L), and the mechanism of the relaxation effect of Icariin on corpus cavernosum believed to have the inhibiting effect on PDE5 and activation of NO-cGMP pathway to enhancing penile erection.
Fetal responses to induced maternal relaxation during pregnancy
DiPietro, Janet A.; Costigan, Kathleen A.; Nelson, Priscilla; Gurewitsch, Edith D.; Laudenslager, Mark L.
2008-01-01
Fetal responses to induced maternal relaxation during the 32nd week of pregnancy were recorded in 100 maternal-fetal pairs using a digitized data collection system. The 18-minute guided imagery relaxation manipulation generated significant changes in maternal heart rate, skin conductance, respiration period, and respiratory sinus arrhythmia. Significant alterations in fetal neurobehavior were observed, including decreased fetal heart rate (FHR), increased FHR variability, suppression of fetal motor activity (FM), and increased FM-FHR coupling. Attribution of the two fetal cardiac responses to the guided imagery procedure itself, as opposed to simple rest or recumbency, is tempered by the observed pattern of response. Evaluation of correspondence between changes within individual maternal-fetal pairs revealed significant associations between maternal autonomic measures and fetal cardiac patterns, lower umbilical and uterine artery resistance and increased FHR variability, and declining salivary cortisol and FM activity. Potential mechanisms that may mediate the observed results are discussed. PMID:17919804
Repeated load relaxations of Type 316 austenitic stainless steel
Energy Technology Data Exchange (ETDEWEB)
Hannula, S.P.; Li, C.Y.
1983-10-01
Results demonstrate that strain aging has a clear effect on the relaxation behavior of 316 SS even at room temperature, the effect being more pronounced at high strains. It is suggested that the phenomena can be accounted for according to a state variable model by modifying the rate constant a*, which is affected by the amount of mobile dislocations as well as the dislocation mobility.
Force Relaxation and Thin Filament Protein Phosphorylation during Acute Myocardial Ischemia
Han, Young Soo; Ogut, Ozgur
2010-01-01
Ischemia impairs myocardial function and may contribute to the progression of heart failure. In this study, rats subjected to acute ischemia demonstrated reduced Ca2+ activated force as well as a decrease in myosin binding protein-C, titin and Ser23/24 phosphorylation of troponin I (TnI). All three proteins have been demonstrated to be downstream targets of β-adrenergic receptor activation (β-AR), leading to the hypothesis that decreased β-AR during ischemia leads to reduced protein phosphorylation and reduced rate constants of force relaxation. To test this hypothesis, force relaxation transients were recorded from permeabilized perfused and ischemic rat heart fibers following photolysis of the caged chelator diazo-2. Relaxation transients were best fit by double exponential functions whereby the majority (>70%) of the force decline was described by the fast rate constant, which was ~5 times faster than the slow rate constant. However, rate constants of relaxation between perfused and ischemic fibers were not different, despite significant decreases in sarcomeric protein phosphorylation in ischemic fibers. Treatment of perfused fibers with a cAMP analog increased Ser23/24 phosphorylation of TnI, yet the rate constants of relaxation remained unchanged. Interestingly, similar treatment of ischemic fibers did not impact TnI phosphorylation or force relaxation transients. Therefore, acute ischemia does not influence the rate constants of relaxation of permeabilized fibers. These results also suggest that the physiological level of sarcomeric protein phosphorylation is unlikely to be the primary driver of relaxation kinetics in permeabilized cardiac muscle fibers. PMID:20925105
Superparamagnetic relaxation of weakly interacting particles
DEFF Research Database (Denmark)
Mørup, Steen; Tronc, Elisabeth
1994-01-01
The influence of particle interactions on the superparamagnetic relaxation time has been studied by Mossbauer spectroscopy in samples of maghemite (gamma-Fe2O3) particles with different particle sizes and particle separations. It is found that the relaxation time decreases with decreasing particl...
Postextrasystolic relaxation in the dog heart
Kuijer, P.J.P.; Heethaar, R.M.; Herbschleb, J.N.; Zimmerman, A.N.E.; Meijler, F.L.
1978-01-01
Left ventricular relaxation was studied in 8 dogs using parameters derived from the left ventricular pressure: the fastest pressure fall and the time constant of pressure decline. Effects of extrasystolic rhythm interventions were examined on the relaxation parameters of the post-relative to the pre
Superparamagnetic relaxation in alpha-Fe particles
DEFF Research Database (Denmark)
Bødker, Franz; Mørup, Steen; Pedersen, Michael Stanley;
1998-01-01
The superparamagnetic relaxation time of carbon-supported alpha-Fe particles with an average size of 3.0 Mm has been studied over a large temperature range by the use of Mossbauer spectroscopy combined with AC and DC magnetization measurements. It is found that the relaxation time varies with tem...
Windowing Waveform Relaxation of Initial Value Problems
Institute of Scientific and Technical Information of China (English)
Yao-lin Jiang
2006-01-01
We present a windowing technique of waveform relaxation for dynamic systems. An effective estimation on window length is derived by an iterative error expression provided here. Relaxation processes can be speeded up if one takes the windowing technique in advance. Numerical experiments are given to further illustrate the theoretical analysis.
Escanyé, J. M.; Canet, D.; Robert, J.
Water proton longitudinal relaxation has been investigated in frozen mouse tissues including tumors. The nonfreezable water which gives rise to a relatively sharp NMR signal at this temperature (263 K) is identified as water bound to macromolecules. Measurements have been carried out by the nonselective inversion-recovery method at 90 and 6 MHz. Partially selective inversion has been achieved at 90 MHz by the DANTE sequence. The experimental data are analyzed by means of Solomon-type equations. This analysis provides the cross-relaxation term from which the dipolar contribution to water relaxation rate, arising from interactions with macromolecular protons, is calculated. This contribution seems to be dominant. The number of water protons interacting with a given macromolecular proton is found to be of the order of 10. The data at both frequencies can be consistently interpreted in terms of water diffusion, with a characteristic time of about 10 -9 sec. These conclusions are valid for all the tissues investigated here, their relaxation parameters exhibiting only slight differences.
Rotational relaxation contributions to infrared pressure broadening in ozone
Flannery, C.; Mizugai, Y.; Steinfeld, J. I.; Spencer, M. N.
1990-01-01
The time-resolved IR double-resonance spectroscopy apparatus and procedures described by Millot et al. (1988) are used to measure the relaxation times of rotational levels in the v3 =1 state of O3. Findings reported include (1) total rotational cross sections about 20-70 percent larger than the Lennard-Jones collision cross section, consistent with an interaction dominated by dipole-dipole forces; (2) equal relaxation cross sections in the upper and lower vibrational states; (3) an estimated pressure-broadening cross section of 185 sq A, with less than 10 percent due to dephasing; (4) no strong Ka dependence of rotational relaxation rates at Ka = 4-8 in J of about 16; (5) a rate for J = 8 and Ka = 7 about 40 percent larger than the other values measured, in agreement with the pressure-broadening model of Gamache and Rothman (1985); and (6) a V-V energy-transfer rate between v3 = 1 and v1 = 1 of (2.5 + or - 0.5) x 10 to the 6th/torr sec.
Stress Relaxation in Entangled Polymer Melts
DEFF Research Database (Denmark)
Hou, Ji-Xuan; Svaneborg, Carsten; Everaers, Ralf
2010-01-01
We present an extensive set of simulation results for the stress relaxation in equilibrium and step-strained bead-spring polymer melts. The data allow us to explore the chain dynamics and the shear relaxation modulus, G(t), into the plateau regime for chains with Z=40 entanglements and into the t......We present an extensive set of simulation results for the stress relaxation in equilibrium and step-strained bead-spring polymer melts. The data allow us to explore the chain dynamics and the shear relaxation modulus, G(t), into the plateau regime for chains with Z=40 entanglements...... and into the terminal relaxation regime for Z=10. Using the known (Rouse) mobility of unentangled chains and the melt entanglement length determined via the primitive path analysis of the microscopic topological state of our systems, we have performed parameter-free tests of several different tube models. We find...
Stress and Relaxation in Relation to Personality
Directory of Open Access Journals (Sweden)
Harish Kumar Sharma
2011-09-01
Full Text Available Relaxation plays a significant role in facing stress. The aim of the present study is to see whether personality patterns determine an individual’s ability to relax. As a reaction to stress, coping is the best way to handle stress, which requires rational and conscious thinking. Does this ability to relax anyway facilitate coping reactions? A study was conducted on 100 college students. Results revealed that extraverts relax easily than introverts. In addition, if intelligence level is average or above average, relaxation does play a role in facilitating coping reactions. It suggests that in designing techniques of stress management, the personality and intelligence level must be taken into consideration to make techniques effective.
Magnetic Resonance Fingerprinting with short relaxation intervals.
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, T1 and T2 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 T1 values of a sample set deviated from their reference values by 0.3% (longest relaxation interval) and 2.4% (shortest relaxation interval). The largest T2 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 resolved
Relaxation Dynamics of Nanoparticle-Tethered Polymer Chains
Kim, Sung A
2015-09-08
© 2015 American Chemical Society. Relaxation dynamics of nanoparticle-tethered cis-1,4-polyisoprene (PI) are investigated using dielectric spectroscopy and rheometry. A model system composed of polymer chains densely grafted to spherical SiO
Resonant Relaxation near the Massive Black Hole in the Galactic Center
Hopman, C; Hopman, Clovis; Alexander, Tal
2006-01-01
The coherent torques between stars on orbits near massive black holes (MBHs) lead to resonant angular momentum relaxation. Due to the fact that orbits are Keplerian to good approximation, the torques efficiently change the magnitude of the angular momenta and rotate the orbital inclinations. As a result the stars are rapidly randomized. The galactic MBH is a good system for the observational study of resonant relaxation. The age of the young B-stars at a distance of $\\sim0.01 pc$ from the MBH is comparable to the resonant relaxation time, implying that resonant relaxation may have played an important role in their dynamical structure. In contrast, the O-stars in the stellar disks at $\\sim0.1 pc$ are younger than the resonant relaxation time, as required by their dynamical coherence. Resonant relaxation dynamics dominates the event rate of gravitational wave (GW) emission from inspiraling stars into MBHs of masses comparable to the Galactic MBH. Resonant relaxation leads to rates $\\lesssim 10$ times higher tha...
Mechanisms of relaxation and spin decoherence in nanomagnets
van Tol, Johan
Relaxation in spin systems is of great interest with respect to various possible applications like quantum information processing and storage, spintronics, and dynamic nuclear polarization (DNP). The implementation of high frequencies and fields is crucial in the study of systems with large zero-field splitting or large interactions, as for example molecular magnets and low dimensional magnetic materials. Here we will focus on the implementation of pulsed Electron Paramagnetic Resonance (ERP) at multiple frequencies of 10, 95, 120, 240, and 336 GHz, and the relaxation and decoherence processes as a function of magnetic field and temperature. Firstly, at higher frequencies the direct single-phonon spin-lattice relaxation (SLR) is considerably enhanced, and will more often than not be the dominant relaxation mechanism at low temperatures, and can be much faster than at lower fields and frequencies. In principle the measurement of the SLR rates as a function of the frequency provides a means to map the phonon density of states. Secondly, the high electron spin polarization at high fields has a strong influence on the spin fluctuations in relatively concentrated spin systems, and the contribution of the electron-electron dipolar interactions to the coherence rate can be partially quenched at low temperatures. This not only allows the study of relatively concentrated spin systems by pulsed EPR (as for example magnetic nanoparticles and molecular magnets), it enables the separation of the contribution of the fluctuations of the electron spin system from other decoherence mechanisms. Besides choice of temperature and field, several strategies in sample design, pulse sequences, or clock transitions can be employed to extend the coherence time in nanomagnets. A review will be given of the decoherence mechanisms with an attempt at a quantitative comparison of experimental rates with theory.
Effects of progressive muscle relaxation on postmenopausal stress
Directory of Open Access Journals (Sweden)
Arunima Chaudhuri
2015-01-01
Full Text Available Background: Menopause increases stress level among females and this may be a contributing factor in developing metabolic syndrome. Objectives: The objective of this study is to study the effects of progressive muscle relaxation on cardiorespiratory efficiency and autonomic functions in over weight and obese working stressed postmenopausal females. Materials and Methods: A total of 30 postmenopausal overweight or obese (body mass index [BMI]: 24.97 ± 1.28 females belonging to the age group 50-55 years were included. Stress level in the subjects was assessed according to the presumptive life event stress scale. The perceived stress scale (PSS of Sheldon Cohen was used for measuring the perception of stress. Fasting blood samples were collected to exclude diabetic subjects and analyze lipid profile. BMI and waist/hip ratio were calculated. Resting pulse rate and blood pressure, respiratory rate were measured. VO 2 max, physical fitness index, breath holding time and 40 mm endurance test time were calculated for estimation of cardiopulmonary efficiency. Autonomic function tests were carried. Subjects were given progressive muscle relaxation training for 3 months and all parameters were reevaluated. Data was analyzed using SPSS version 16 (SPSS Inc., Chicago, USA. Results: PSS in pre-training session was 26.16 ± 1.7 and in post-training session was 14.33 ± 2.01 and the difference was statistically significant. There was a significant decrease in pulse rate, blood pressure, BMI, waist/hip ratio, cholesterol, low-density lipoprotein following preventive medicine residency training. Results of autonomic function tests and cardiopulmonary efficiency test improved significantly following relaxation training. Conclusions: Increased stress levels may increase BMI and waist/hip ratio, dyslipidemia and lead to autonomic dysfunctions and increase incidence of cardiovascular disease in postmenopausal females. Lifestyle modification with relaxation exercises
Domain Relaxation in Langmuir Films
Bernoff, Andrew J.; Alexander, James C.; Mann, Elizabeth K.; Mann, J. Adin; Zou, Lu; Wintersmith, Jacob R.
2007-11-01
We report on an experimental, theoretical and computational study of a molecularly thin polymer Langmuir layer domain on the surface of a subfluid. When stretched (by a transient stagnation flow), the Langmuir layer takes the form of a bola consisting of two roughly circular reservoirs connected by a thin tether. This shape relaxes to the circular minimum energy configuration. The tether is never observed to rupture, even when it is more than a hundred times as long as it is thin. We model these experiments as a free boundary problem where motion is driven by the line tension of the domain and damped by the viscosity of the subfluid. We process the digital images of the experiment to extract the domain shape, use one of these shapes as an initial condition for the numerical solution of a boundary-integral model of the underlying hydrodynamics, and compare the subsequent images of the experiment to the numerical simulation. The numerical evolutions verify that our hydrodynamical model can reproduce the observed dynamics. They also allow us to deduce the magnitude of the line tension in the system, often to within 1%.
Supervised Discrete Hashing With Relaxation.
Gui, Jie; Liu, Tongliang; Sun, Zhenan; Tao, Dacheng; Tan, Tieniu
2016-12-29
Data-dependent hashing has recently attracted attention due to being able to support efficient retrieval and storage of high-dimensional data, such as documents, images, and videos. In this paper, we propose a novel learning-based hashing method called ''supervised discrete hashing with relaxation'' (SDHR) based on ''supervised discrete hashing'' (SDH). SDH uses ordinary least squares regression and traditional zero-one matrix encoding of class label information as the regression target (code words), thus fixing the regression target. In SDHR, the regression target is instead optimized. The optimized regression target matrix satisfies a large margin constraint for correct classification of each example. Compared with SDH, which uses the traditional zero-one matrix, SDHR utilizes the learned regression target matrix and, therefore, more accurately measures the classification error of the regression model and is more flexible. As expected, SDHR generally outperforms SDH. Experimental results on two large-scale image data sets (CIFAR-10 and MNIST) and a large-scale and challenging face data set (FRGC) demonstrate the effectiveness and efficiency of SDHR.
Spin relaxation in organic semiconductors
Bobbert, Peter
2011-03-01
Intriguing magnetic field effects in organic semiconductor devices have been reported: anomalous magnetoresistance in organic spin valves and large effects of small magnetic fields on the current and luminescence of organic light-emitting diodes. Influences of isotopic substitution on these effects points at the role of hyperfine coupling. We performed studies of spin relaxation in organic semiconductors based on (i) coherent spin precession of the electron spin in an effective magnetic field consisting of a random hyperfine field and an applied magnetic field and (ii) incoherent hopping of charges. These ingredients are incorporated in a stochastic Liouville equation for the dynamics of the spin density matrix of single charges as well as pairs of charges. For single charges we find a spin diffusion length that depends on the magnetic field, explaining anomalous magnetoresistance in organic spin valves. For pairs of charges we show that the magnetic field influences formation of singlet bipolarons, in the case of like charges, and singlet and triplet excitons, in the case of opposite charges. We can reproduce different line shapes of reported magnetic field effects, including recently found effects at ultra-small fields.
Electron Spin-Lattice Relaxation of doped Yb3+ ions in YBa2Cu3Ox
2005-01-01
The electron spin-lattice relaxation (SLR) times T1 of Yb3+ ions were measured from the temperature dependence of electron spin resonance linewidth in Y0.99Yb0.01Ba2Cu3Ox with different oxygen contents. Raman relaxation processes dominate the electron SLR. Derived from the temperature dependence of the SLR rate, the Debye temperature (Td) increases with the critical temperature Tc and oxygen content x. Keywords: EPR; ESR; Electron spin-lattice relaxation; Debye temperature; Critical tem...
Institute of Scientific and Technical Information of China (English)
周登; 张澄
2002-01-01
The principle of the minimum energy dissipation rate is applied to toroidal plasmas with a coaxial direct current helicity injection. The relaxed states are analysed based on the analytical solutions of the resulting Euler-Lagrangian equations. Three typical states are found. The relaxed states are close to the Taylor state if the ratio of current density to magnetic field on the boundary is small enough. The states will deviate from the Taylor state when the ratio increases, but when it approaches a critical value the central part of relaxed plasmas may approach a force free state, and above the critical value both current and magnetic field may reverse in the central part.
Energy Technology Data Exchange (ETDEWEB)
Yokoi, Koki [Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI (United States); Raicu, Valerică, E-mail: vraicu@uwm.edu [Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI (United States); Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI (United States)
2017-06-28
Relaxation in fractal structures was investigated theoretically starting from a simple model of a Cantorian tree and kinetic equations linking the change in the number of particles (e.g., electrical charges) populating each branch of the tree and their transfer to other branches or to the ground state. We numerically solved the system of differential equations obtained and determined the so-called cumulative distribution function of particles, which, in dielectric or mechanical relaxation parlance, is the same as the relaxation function of the system. As a physical application, we studied the relationship between the dielectric relaxation in time-domain and the dielectric dispersion in the frequency-domain. Upon choosing appropriate rate constants, our model described accurately well-known non-exponential and non-Debye time- and frequency-domain functions, such as stretched exponentials, Havrilliak–Negami, and frequency power law. Our approach opens the door to applying kinetic models to describe a wide array of relaxation processes, which traditionally have posed great challenges to theoretical modeling based on first principles. - Highlights: • Relaxation was investigated for a system of particles flowing through a Cantorian tree. • A set of kinetic equations was formulated and used to compute the relaxation function of the system. • The dispersion function of the system was computed from the relaxation function. • An analytical method was used to recover the original relaxation function from the dispersion function. • This formalism was used to study dielectric relaxation and dispersion in fractal structures.
Temperature Dependence of Electron Spin Relaxation of 2,2-diphenyl-1-picrylhydrazyl in Polystyrene
Meyer, Virginia; Eaton, Sandra S.; Eaton, Gareth R.
2012-01-01
The electron spin relaxation rates for the stable radical DPPH (2,2-diphenyl-1-picrylhydrazyl) doped into polystyrene were studied by inversion recovery and electron spin echo at X-band and Q-band between 20 and 295 K. At low concentration (340 μM, 0.01%) spin-lattice relaxation was dominated by the Raman process and a local mode. At high concentration (140 mM, 5%) relaxation is orders of magnitude faster than at the lower concentration, and 1/T1 is approximately linearly dependent on temperature. Spin lattice relaxation rates are similar at X-band and Q-band. The temperature dependence of spin echo dephasing was faster at about 140 K than at higher or lower temperatures, which is attributed to a wagging motion of the phenyl groups. PMID:23565040
Energy-resolved hot carrier relaxation dynamics in monocrystalline plasmonic nanoantennas
Méjard, Régis; Petit, Marlène; Bouhelier, Alexandre; Cluzel, Benoît; Demichel, Olivier
2016-01-01
Hot carriers are energetic photo-excited carriers driving a large range of chemico-physical mechanisms. At the nanoscale, an efficient generation of these carriers is facilitated by illuminating plasmonic antennas. However, the ultrafast relaxation rate severally impedes their deployment in future hot-carrier based devices. In this paper, we report on the picosecond relaxation dynamics of hot carriers in plasmonic monocrystalline gold nanoantennas. The temporal dynamics of the hot carriers is experimentally investigated by interrogating the nonlinear photoluminescence response of the antenna with a spectrally-resolved two-pulse correlation configuration. We measure time-dependent nonlinearity orders varying from 1 to 8, which challenge the common interpretation of multi-photon gold luminescence. We demonstrate that the relaxation of the photo-excited carriers depends of their energies relative to the Fermi level. We find a 60 % variation in the relaxation rate for electron-hole pair energies ranging from c.a....
Relaxation of a 1-D gravitational system
Valageas, P
2006-01-01
We study the relaxation towards thermodynamical equilibrium of a 1-D gravitational system. This OSC model shows a series of critical energies $E_{cn}$ where new equilibria appear and we focus on the homogeneous ($n=0$), one-peak ($n=\\pm 1$) and two-peak ($n=2$) states. Using numerical simulations we investigate the relaxation to the stable equilibrium $n=\\pm 1$ of this $N-$body system starting from initial conditions defined by equilibria $n=0$ and $n=2$. We find that in a fashion similar to other long-range systems the relaxation involves a fast violent relaxation phase followed by a slow collisional phase as the system goes through a series of quasi-stationary states. Moreover, in cases where this slow second stage leads to a dynamically unstable configuration (two peaks with a high mass ratio) it is followed by a new sequence ``violent relaxation/slow collisional relaxation''. We obtain an analytical estimate of the relaxation time $t_{2\\to \\pm 1}$ through the mean escape time of a particle from its potent...
Plasma Relaxation Dynamics Moderated by Current Sheets
Dewar, Robert; Bhattacharjee, Amitava; Yoshida, Zensho
2014-10-01
Ideal magnetohydrodynamics (IMHD) is strongly constrained by an infinite number of microscopic constraints expressing mass, entropy and magnetic flux conservation in each infinitesimal fluid element, the latter preventing magnetic reconnection. By contrast, in the Taylor-relaxed equilibrium model all these constraints are relaxed save for global magnetic flux and helicity. A Lagrangian is presented that leads to a new variational formulation of magnetized fluid dynamics, relaxed MHD (RxMHD), all static solutions of which are Taylor equilibrium states. By postulating that some long-lived macroscopic current sheets can act as barriers to relaxation, separating the plasma into multiple relaxation regions, a further generalization, multi-relaxed MHD (MRxMHD), is developed. These concepts are illustrated using a simple two-region slab model similar to that proposed by Hahm and Kulsrud--the formation of an initial shielding current sheet after perturbation by boundary rippling is calculated using MRxMHD and the final island state, after the current sheet has relaxed through a reconnection sequence, is calculated using RxMHD. Australian Research Council Grant DP110102881.
Fedorov, Dmitry V; Gradhand, Martin; Ostanin, Sergey; Maznichenko, Igor V; Ernst, Arthur; Fabian, Jaroslav; Mertig, Ingrid
2013-04-12
The effect of electron-impurity scattering on momentum and spin relaxation times in graphene is studied by means of relativistic ab initio calculations. Assuming carbon and silicon adatoms as natural impurities in graphene, we are able to simulate fast spin relaxation observed experimentally. We investigate the dependence of the relaxation times on the impurity position and demonstrate that C or Si adatoms act as real-space spin hot spots inducing spin-flip rates about 5 orders of magnitude larger than those of in-plane impurities. This fact confirms the hypothesis that the adatom-induced spin-orbit coupling leads to fast spin relaxation in graphene.
Muon spin relaxation investigation of tetranuclear iron(III) Fe_4(OCH_3)_6(dpm)_6 molecular cluster
Procissi, D.; P. Arosio; Orsini, F.; Marinone, M.; Cornia, A.; Lascialfari, A.
2009-01-01
We present a study of the spin dynamics of Fe_4(OCH_3)_6(dpm)_6 single molecule magnet by means of SQUID magnetization and muon relaxation (µ^(+)SR) measurements. In longitudinal field µ^+SR experiments performed at magnetic fields H=200, 1000 Oe, the muon asymmetry P(t) could be fitted by means of three components, the first constant, the second fast relaxing through a quasiexponential decay, and the third, the slowest relaxing, showing an exponential decay. The slowest muon relaxation rate ...
Relaxed resource advance reservation policy in grid computing
Institute of Scientific and Technical Information of China (English)
XIAO Peng; HU Zhi-gang
2009-01-01
The advance reservation technique has been widely applied in many grid systems to provide end-to-end quality of service (QoS). However, it will result in low resource utilization rate and high rejection rate when the reservation rate is high. To mitigate these negative effects brought about by advance reservation, a relaxed advance reservation policy is proposed, which allows accepting new reservation requests that overlap the existing reservations under certain conditions. Both the benefits and the risks of the proposed policy are presented theoretically. The experimental results show that the policy can achieve a higher resource utilization rate and lower rejection rate compared to the conventional reservation policy and backfilling technique. In addition, the policy shows better adaptation when the grid systems are in the presence of a high reservation rate.
Electrical control of optical emitter relaxation pathways enabled by graphene
Tielrooij, K. J.; Orona, L.; Ferrier, A.; Badioli, M.; Navickaite, G.; Coop, S.; Nanot, S.; Kalinic, B.; Cesca, T.; Gaudreau, L.; Ma, Q.; Centeno, A.; Pesquera, A.; Zurutuza, A.; de Riedmatten, H.; Goldner, P.; García de Abajo, F. J.; Jarillo-Herrero, P.; Koppens, F. H. L.
2015-03-01
Controlling the energy flow processes and the associated energy relaxation rates of a light emitter is of fundamental interest and has many applications in the fields of quantum optics, photovoltaics, photodetection, biosensing and light emission. Advanced dielectric, semiconductor and metallic systems have been developed to tailor the interaction between an emitter and its environment. However, active control of the energy flow from an emitter into optical, electronic or plasmonic excitations has remained challenging. Here, we demonstrate in situ electrical control of the relaxation pathways of excited erbium ions, which emit light at the technologically relevant telecommunication wavelength of 1.5 μm. By placing the erbium at a few nanometres distance from graphene, we modify the relaxation rate by more than a factor of three, and control whether the emitter decays into electron-hole pairs, emitted photons or graphene near-infrared plasmons, confined to control of the local density of optical states constitute a new paradigm for active (quantum) photonics and can be applied using any combination of light emitters and two-dimensional materials.
Le Chatelier's principle with multiple relaxation channels
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.
Neural control of muscle relaxation in echinoderms.
Elphick, M R; Melarange, R
2001-03-01
Smooth muscle relaxation in vertebrates is regulated by a variety of neuronal signalling molecules, including neuropeptides and nitric oxide (NO). The physiology of muscle relaxation in echinoderms is of particular interest because these animals are evolutionarily more closely related to the vertebrates than to the majority of invertebrate phyla. However, whilst in vertebrates there is a clear structural and functional distinction between visceral smooth muscle and skeletal striated muscle, this does not apply to echinoderms, in which the majority of muscles, whether associated with the body wall skeleton and its appendages or with visceral organs, are made up of non-striated fibres. The mechanisms by which the nervous system controls muscle relaxation in echinoderms were, until recently, unknown. Using the cardiac stomach of the starfish Asterias rubens as a model, it has been established that the NO-cGMP signalling pathway mediates relaxation. NO also causes relaxation of sea urchin tube feet, and NO may therefore function as a 'universal' muscle relaxant in echinoderms. The first neuropeptides to be identified in echinoderms were two related peptides isolated from Asterias rubens known as SALMFamide-1 (S1) and SALMFamide-2 (S2). Both S1 and S2 cause relaxation of the starfish cardiac stomach, but with S2 being approximately ten times more potent than S1. SALMFamide neuropeptides have also been isolated from sea cucumbers, in which they cause relaxation of both gut and body wall muscle. Therefore, like NO, SALMFamides may also function as 'universal' muscle relaxants in echinoderms. The mechanisms by which SALMFamides cause relaxation of echinoderm muscle are not known, but several candidate signal transduction pathways are discussed here. The SALMFamides do not, however, appear to act by promoting release of NO, and muscle relaxation in echinoderms is therefore probably regulated by at least two neuronal signalling systems acting in parallel. Recently, other
Stress Relaxation in Entangled Polymer Melts
DEFF Research Database (Denmark)
Hou, Ji-Xuan; Svaneborg, Carsten; Everaers, Ralf
2010-01-01
and into the terminal relaxation regime for Z=10. Using the known (Rouse) mobility of unentangled chains and the melt entanglement length determined via the primitive path analysis of the microscopic topological state of our systems, we have performed parameter-free tests of several different tube models. We find......We present an extensive set of simulation results for the stress relaxation in equilibrium and step-strained bead-spring polymer melts. The data allow us to explore the chain dynamics and the shear relaxation modulus, G(t), into the plateau regime for chains with Z=40 entanglements...
Compact vs. Exponential-Size LP Relaxations
Energy Technology Data Exchange (ETDEWEB)
Carr, R.D.; Lancia, G.
2000-09-01
In this paper we introduce by means of examples a new technique for formulating compact (i.e. polynomial-size) LP relaxations in place of exponential-size models requiring separation algorithms. In the same vein as a celebrated theorem by Groetschel, Lovasz and Schrijver, we state the equivalence of compact separation and compact optimization. Among the examples used to illustrate our technique, we introduce a new formulation for the Traveling Salesman Problem, whose relaxation we show equivalent to the subtour elimination relaxation.
Relaxation time in disordered molecular systems
Energy Technology Data Exchange (ETDEWEB)
Rocha, Rodrigo P. [Departamento de Física, Universidade Federal de Santa Catarina, 88040-900 Florianópolis-SC (Brazil); Freire, José A., E-mail: jfreire@fisica.ufpr.br [Departamento de Física, Universidade Federal do Paraná, 81531-990 Curitiba-PR (Brazil)
2015-05-28
Relaxation time is the typical time it takes for a closed physical system to attain thermal equilibrium. The equilibrium is brought about by the action of a thermal reservoir inducing changes in the system micro-states. The relaxation time is intuitively expected to increase with system disorder. We derive a simple analytical expression for this dependence in the context of electronic equilibration in an amorphous molecular system model. We find that the disorder dramatically enhances the relaxation time but does not affect its independence of the nature of the initial state.
Nuclear magnetic resonance relaxation in multiple sclerosis
DEFF Research Database (Denmark)
Larsson, H B; Barker, G J; MacKay, A
1998-01-01
OBJECTIVES: The theory of relaxation processes and their measurements are described. An overview is presented of the literature on relaxation time measurements in the normal and the developing brain, in experimental diseases in animals, and in patients with multiple sclerosis. RESULTS...... AND CONCLUSION: Relaxation time measurements provide insight into development of multiple sclerosis plaques, especially the occurrence of oedema, demyelination, and gliosis. There is also evidence that normal appearing white matter in patients with multiple sclerosis is affected. What is now needed are fast...
NMR RELAXIVITY AND IMAGING OF NEUTRAL MACROMOLECULAR POLYESTER GADOLINIUM (Ⅲ) COMPLEXES
Institute of Scientific and Technical Information of China (English)
Kai-chao Yu; Hong-bing Hu; Mai-li Liu; Han-zhen Yuan; Chao-hui Ye; Ren-xi Zhuo
1999-01-01
Five neutral macromolecular polyester gadolinium (Ⅲ) complexes with pendant hydrophobic alkyl and aromatic functional groups were prepared. The longitudinal relaxation rates of these complexes were measured. One of these Gd (Ⅲ) complexes was chosen for the acute toxicity test and T1-weighted imaging measurement. Preliminary results showed that. compared with Gd-DTPA, the neutral macromolecular gadolinium (Ⅲ) complexes provide higher T1 relaxivity enhancement and longer function duration.
High-speed laser modulation beyond the relaxation resonance frequency limit.
Sacher, Wesley D; Zhang, Eric J; Kruger, Brett A; Poon, Joyce K S
2010-03-29
We propose and show that for coupling modulated lasers (CMLs), in which the output coupler is modulated rather than the pump rate, the conventional relaxation resonance frequency limit to the laser modulation bandwidth can be circumvented. The modulation response is limited only by the coupler. Although CMLs are best suited to microcavities, as a proof-of-principle, a coupling-modulated erbium-doped fiber laser is modulated at 1 Gb/s, over 10000 times its relaxation resonance frequency.
Relaxation of 2+1 dimensional classical O(2) symmetric scalar fields
Borsanyi, S; Borsanyi, Sz.; Szep, Zs.
2001-01-01
Real time thermalization and relaxation phenomena are studied in the low energy density phase of the 2+1 dimensional classical O(2) symmetric scalar theory by solving numerically its dynamics. The near-equilibrium decay rate of on-shell waves and the power law governing the large time asymptotics of the off-shell relaxation agree with the analytic results based on linear response theory. The realisation of the Mermin-Wagner theorem is also studied in the final equilibrium ensemble.
Institute of Scientific and Technical Information of China (English)
王力刚; 孙月吉; 崔爱霞; 孙文恒
2014-01-01
目的：观察度洛西汀合并菩提树放松技术治疗广泛性焦虑障碍（ GAD）的疗效及对心率变异性的影响。方法2013年3月～2014年3月间，根据ICD⁃10中GAD诊断标准选择124例GAD患者作为研究对象，利用随机数字表分为干预组（n＝62）和对照组（n＝62）。干预组固定接受度洛西汀（20 mg／d）合并菩提树放松治疗，2次／周，连续8周；对照组仅接受度洛西汀（20 mg／d）治疗。分别于干预前和干预后第2、4、6、8周末用SAS、HAMA评定疗效，用治疗中需处理的不良反应症状量表（ TESS）评定药物的不良反应，对心率变异性（heart rate variability，HRV）的低频（low frequency，LF）与高频（high frequency，HF ）比值（LF／HF）进行观察。结果1．两组干预后SAS和HAMA评分较干预前显著降低[干预前：对照组（63．52±14．25）分，（30．26±11．25）分，干预组（64．35±14．33）分，（29．83±10．85）分，干预8周后：对照组（30．23±6．68）分，（9．28±3．20）分，干预组（25．14±5．59）分，（7．70±2．87）分]（均P＜0．05）。组间疗效差异有统计学意义（χ2＝4．09， P＜0．05），两组不良反应差异无统计学意义（P＞0．05）。2．干预组LF／HF较对照组减低，特别是第13，14，15，16次干预后，两组间差异有统计学意义（ t 13⁃16＝－2．806，－2．725，－3．572，－2．272；P 13⁃16＝0．006，0．007，0．001，0．025），焦虑严重指数值与LF／HF值呈显著正相关（ r＝0．342， P＜0．05）。结论度洛西汀合并菩提树放松技术能有效提高GAD患者的心率变异性，疗效更好。%Objective To observe the efficacy of duloxetine combined with Bodhi Tree relaxation tech⁃nique in the treatment of generalized anxiety disorder ( GAD ) and the influence of heart rate variability ( HRV ) . Methods According to the standard of ICD⁃10,124 GADs
Plate-wide stress relaxation explains European Palaeocene basin inversions
DEFF Research Database (Denmark)
Nielsen, S.B.; Thomsen, Erik; Hansen, D.L.
2005-01-01
of compression, mainly from the Alpine orogen. Here we show that the main phases differed both in structural style and cause. The Cretaceous phase was characterized by narrow uplift zones, reverse activation of faults, crustal shortening, and the formation of asymmetric marginal troughs. In contrast, the Middle...... Paleocene phase was characterized by domal uplift of a wider area with only mild fault movements, and formation of more distal and shallow marginal troughs. A simple flexural model explains how domal, secondary inversion follows inevitably from primary, convergence related inversion upon relaxation...... of the in-plane tectonic stress. The onset of relaxation inversions was plate-wide and simultaneous, and may have been triggered by stress changes caused by elevation of the North Atlantic lithosphere by the Iceland plume or the drop in NS convergence rate between Africa and Europe....
1H relaxation dispersion in solutions of nitroxide radicals: Influence of electron spin relaxation
Kruk, D.; Korpała, A.; Kubica, A.; Kowalewski, J.; Rössler, E. A.; Moscicki, J.
2013-03-01
The work presents a theory of nuclear (1H) spin-lattice relaxation dispersion for solutions of 15N and 14N radicals, including electron spin relaxation effects. The theory is a generalization of the approach presented by Kruk et al. [J. Chem. Phys. 137, 044512 (2012)], 10.1063/1.4736854. The electron spin relaxation is attributed to the anisotropic part of the electron spin-nitrogen spin hyperfine interaction modulated by rotational dynamics of the paramagnetic molecule, and described by means of Redfield relaxation theory. The 1H relaxation is caused by electron spin-proton spin dipole-dipole interactions which are modulated by relative translational motion of the solvent and solute molecules. The spectral density characterizing the translational dynamics is described by the force-free-hard-sphere model. The electronic relaxation influences the 1H relaxation by contributing to the fluctuations of the inter-molecular dipolar interactions. The developed theory is tested against 1H spin-lattice relaxation dispersion data for glycerol solutions of 4-oxo-TEMPO-d16-15N and 4-oxo-TEMPO-d16-14N covering the frequency range of 10 kHz-20 MHz. The studies are carried out as a function of temperature starting at 328 K and going down to 290 K. The theory gives a consistent overall interpretation of the experimental data for both 14N and 15N systems and explains the features of 1H relaxation dispersion resulting from the electron spin relaxation.
Microscale simulations of NMR relaxation in porous media
Mohnke, Oliver; Klitzsch, Norbert
2010-05-01
In petrophysical applications of nuclear magnetic resonance (NMR), the measured relaxation signals originate from the fluid filled pore space. Hence, in rocks or sediments the water content directly corresponds to the initial amplitude of the recorded NMR relaxation signals. The relaxation rate (longitudinal/transversal decay time T1, T2) is sensitive to pore sizes and physiochemical properties of rock-fluid interfaces (surface relaxivity), as well as the concentration of paramagnetic ions in the fluid phases (bulk relaxivity). In the subproject A2 of the TR32 we aim at improving the basic understanding of these processes at the pore scale and thereby advancing the interpretation of NMR data by reducing the application of restrictive approximated interpretation schemes, e.g. for deriving pore size distributions, connectivity or permeability. In this respect we numerically simulate NMR relaxation data at the micro sale to study the impact of physical and hydrological parameters such as internal field gradients or pore connectivities on NMR signals. Joint numerical simulations of the NMR relaxation behavior (Bloch equations) in the presence of internal gradients (Ampere's law) and fluid flow (Navier-Stokes) on a pore scale dimension have been implemented in a finite element (FE) model using Comsol Multiphysics. Processes governing the time and spatial behavior of the nuclear magnetization density in a porous medium are diffusion and surface interactions at the rock-fluid interface. Based on Fick's law of diffusive motion Brownstein and Tarr (1979) introduced differential equations that describe the relaxation behavior of the Spin magnetization in single isolated pores and derived analytical solutions for simple geometries, i.e. spherical, cylindrical and planar. However, by numerically solving these equations in a general way using a FE algorithm this approach can be applied to study and simulate coupled complex pore systems, e.g. derived from computer tomography (CT
Hydrogen sulfide and vascular relaxation
Institute of Scientific and Technical Information of China (English)
SUN Yan; TANG Chao-shu; DU Jun-bao; JIN Hong-fang
2011-01-01
Objective To review the vasorelaxant effects of hydrogen sulfide (H2S) in arterial rings in the cardiovascular system under both physiological and pathophysiological conditions and the possible mechanisms involved.Data sources The data in this review were obtained from Medline and Pubmed sources from 1997 to 2011 using the search terms "hydrogen sulfide" and ""vascular relaxation".Study selection Articles describing the role of hydrogen sulfide in the regulation of vascular activity and its vasorelaxant effects were selected.Results H2S plays an important role in the regulation of cardiovascular tone.The vasomodulatory effects of H2S depend on factors including concentration,species and tissue type.The H2S donor,sodium hydrosulfide (NarS),causes vasorelaxation of rat isolated aortic rings in a dose-dependent manner.This effect was more pronounced than that observed in pulmonary arterial rings.The expression of KATP channel proteins and mRNA in the aortic rings was increased compared with pulmonary artery rings.H2S is involved in the pathogenesis of a variety of cardiovascular diseases.Downregulation of the endogenous H2S pathway is an important factor in the pathogenesis of cardiovascular diseases.The vasorelaxant effects of H2S have been shown to be mediated by activation of KATP channels in vascular smooth muscle cells and via the induction of acidification due to activation of the CI/HCO3 exchanger.It is speculated that the mechanisms underlying the vasoconstrictive function of H2S in the aortic rings involves decreased NO production and inhibition of cAMP accumulation.Conclusion H2S is an important endogenous gasotransmitter in the cardiovascular system and acts as a modulator of vascular tone in the homeostatic regulation of blood pressure.
Krylov-subspace acceleration of time periodic waveform relaxation
Energy Technology Data Exchange (ETDEWEB)
Lumsdaine, A. [Univ. of Notre Dame, IN (United States)
1994-12-31
In this paper the author uses Krylov-subspace techniques to accelerate the convergence of waveform relaxation applied to solving systems of first order time periodic ordinary differential equations. He considers the problem in the frequency domain and presents frequency dependent waveform GMRES (FDWGMRES), a member of a new class of frequency dependent Krylov-subspace techniques. FDWGMRES exhibits many desirable properties, including finite termination independent of the number of timesteps and, for certain problems, a convergence rate which is bounded from above by the convergence rate of GMRES applied to the static matrix problem corresponding to the linear time-invariant ODE.
“I think relax, relax and it flows a lot easier”: Exploring client-generated relax strategies
Directory of Open Access Journals (Sweden)
Dianne Cirone
2014-10-01
Full Text Available Background. Some adult stroke survivors participating in Cognitive Orientation to daily Occupational Performance (CO-OP treatment programs self-generated relax strategies that have not been explored in previous CO-OP publications. The objective of this study was to describe the process by which adults with stroke used relax strategies and to explore the outcomes associated with their use. Methods. Secondary analysis of transcripts of intervention sessions from five participants was conducted. Results. All five participants applied relax strategies after initially observing a breakdown in performance that was attributed to increased fatigue or tension. The relax strategies used by the participants during their occupations included general relaxation, physical modifications to reduce tension, mental preparation, and pacing. The application of these strategies seemed to result in improved skill performance, reduced fatigue, and transfer to other activities. Conclusion. The relax strategy warrants further investigation as a potentially important therapeutic tool to improve occupational performance in individuals who have had a stroke.
Thermodynamic anomaly of the sub-Tg relaxation in hyperquenched metallic glasses
DEFF Research Database (Denmark)
Hu, L. N.; Zhou, C.; Zhang, C. Z.
2013-01-01
glass ribbons the activation energy for the onset of the sub-Tg enthalpy relaxation also varies non-monotonically with the cooling rate of fabrication. These abnormal relaxation phenomena are explained in terms of the competition between the low and the high temperature clusters during the fragile......Recently, we observed an unusual non-monotonic glass relaxation phenomenon, i.e., the three-step sub-Tg relaxation in hyperquenched CuZrAl glass ribbons [L. N. Hu and Y. Z. Yue, Appl. Phys. Lett. 98, 081904 (2011)]. In the present work, we reveal the origin of this abnormal behavior by studying...... the cooling rate dependence of the sub-Tg enthalpy relaxation in two metallic glasses. For the Cu46Zr46Al8 glass ribbons the sub-Tg enthalpy relaxation pattern exhibits a three-step trend with the annealing temperature only when the ribbons are fabricated below a critical cooling rate. For the La55Al25Ni20...
Energy Technology Data Exchange (ETDEWEB)
Pravdivtsev, Andrey N.; Yurkovskaya, Alexandra V.; Ivanov, Konstantin L., E-mail: ivanov@tomo.nsc.ru [International Tomography Center, Institutskaya 3a, Novosibirsk 630090 (Russian Federation); Department of Physics, Novosibirsk State University, Pirogova 2, Novosibirsk 630090 (Russian Federation); Vieth, Hans-Martin [Institut für Experimentalphysik, Freie Universität Berlin Arnimallee 14, 14195 Berlin (Germany)
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 times 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.
Slow spin relaxation in dipolar spin ice.
Orendac, Martin; Sedlakova, Lucia; Orendacova, Alzbeta; Vrabel, Peter; Feher, Alexander; Pajerowski, Daniel M.; Cohen, Justin D.; Meisel, Mark W.; Shirai, Masae; Bramwell, Steven T.
2009-03-01
Spin relaxation in dipolar spin ice Dy2Ti2O7 and Ho2Ti2O7 was investigated using the magnetocaloric effect and susceptibility. The magnetocaloric behavior of Dy2Ti2O7 at temperatures where the orientation of spins is governed by ``ice rules`` (T Tice) revealed thermally activated relaxation; however, the resulting temperature dependence of the relaxation time is more complicated than anticipated by a mere extrapolation of the corresponding high temperature data [1]. A susceptibility study of Ho2Ti2O7 was performed at T > Tice and in high magnetic fields, and the results suggest a slow relaxation of spins analogous to the behavior reported in a highly polarized cooperative paramagnet [2]. [1] J. Snyder et al., Phys. Rev. Lett. 91 (2003) 107201. [2] B. G. Ueland et al., Phys. Rev. Lett. 96 (2006) 027216.
Energy landscape of relaxed amorphous silicon
Valiquette, Francis; Mousseau, Normand
2003-09-01
We analyze the structure of the energy landscape of a well-relaxed 1000-atom model of amorphous silicon using the activation-relaxation technique (ART nouveau). Generating more than 40 000 events starting from a single minimum, we find that activated mechanisms are local in nature, that they are distributed uniformly throughout the model, and that the activation energy is limited by the cost of breaking one bond, independently of the complexity of the mechanism. The overall shape of the activation-energy-barrier distribution is also insensitive to the exact details of the configuration, indicating that well-relaxed configurations see essentially the same environment. These results underscore the localized nature of relaxation in this material.
Two-Body Relaxation in Cosmological Simulations
Binney, J; Binney, James; Knebe, Alexander
2002-01-01
The importance of two-body relaxation in cosmological simulations is explored with simulations in which there are two species of particles. The cases of mass ratio sqrt(2):1 and 4:1 are investigated. Simulations are run with both a fixed softening length and adaptive softening using the publicly available codes GADGET and MLAPM, respectively. The effects of two-body relaxation are detected in both the density profiles of halos and the mass function of halos. The effects are more pronounced with a fixed softening length, but even in this case they are not so large as to suggest that results obtained with one mass species are significantly affected by two-body relaxation. The simulations that use adaptive softening are slightly less affected by two-body relaxation and produce slightly higher central densities in the largest halos. They run about three times faster than the simulations that use a fixed softening length.
Structural relaxation in annealed hyperquenched basaltic glasses
DEFF Research Database (Denmark)
Guo, Xiaoju; Mauro, John C.; Potuzak, M.
2012-01-01
The enthalpy relaxation behavior of hyperquenched (HQ) and annealed hyperquenched (AHQ) basaltic glass is investigated through calorimetric measurements. The results reveal a common onset temperature of the glass transition for all the HQ and AHQ glasses under study, indicating that the primary r...... relaxation is activated at the same temperature regardless of the initial departure from equilibrium. The analysis of secondary relaxation at different annealing temperatures provides insights into the enthalpy recovery of HQ glasses.......The enthalpy relaxation behavior of hyperquenched (HQ) and annealed hyperquenched (AHQ) basaltic glass is investigated through calorimetric measurements. The results reveal a common onset temperature of the glass transition for all the HQ and AHQ glasses under study, indicating that the primary...
Directory of Open Access Journals (Sweden)
Tsen CL
2015-04-01
Full Text Available Chui-Lien Tsen,1 Yu-Harn Horng,1 Shwu-Jiuan Sheu1,2 1Department of Ophthalmology, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan; 2School of Medicine, National Yang-Ming University, Taipei, Taiwan Background: We describe the anatomical and functional outcomes of eyes that underwent a modified technique of relaxing retinotomy, dashed line relaxing retinotomy, in the management of retinal detachment with anterior proliferative vitreoretinopathy.Methods: We retrospectively reviewed 54 consecutive eyes in 52 patients who received pars plana vitrectomy with relaxing retinotomy during retinal detachment repair. Perfluorocarbon liquid (PFCL was used as a standard procedure to stabilize the retina during retinotomy to prevent slippage or inversion of the posterior flap. If PFCL was not available due to economic reasons, dashed line relaxing retinotomy was performed instead. Best-corrected visual acuity, slit-lamp biomicroscopy, intraocular pressure measurement, lens status, and fundus examination were analyzed. We excluded patients who were followed up <4 months.Results: Regarding anatomical success rates and visual outcomes, we found no significant differences between patients treated with intraoperative PFCL and those treated with dashed line relaxing retinotomy without PFCL.Conclusion: Compared to the simple and efficient PFCL-assisted relaxing retinotomy, dashed relaxing retinotomy is not the first choice when PFCL is available. Based on our results, this modified technique may offer an alternative in patients with anterior proliferative vitreoretinopathy for whom PFCL is not available. Keywords: perfluorocarbon liquid, PFCL
Effects of relaxation and stress on the capsaicin-induced local inflammatory response.
Lutgendorf, S; Logan, H; Kirchner, H L; Rothrock, N; Svengalis, S; Iverson, K; Lubaroff, D
2000-01-01
Although stress is known to modulate the inflammatory response, there has been little experimental examination of the effects of stress and stress reduction on inflammation in humans. In particular, the effects of stress and relaxation on neurogenic inflammation have been minimally studied. This study examines the effects of three experimental manipulations: mental stress, relaxation, and control on the local inflammatory response evoked by the intradermal injection of capsaicin, the active ingredient in chili peppers. Fifty subjects (28 men and 22 women) were pretrained in relaxation using an imagery-based relaxation tape and then randomized to experimental condition. Subjects participated in an evening reactivity session including 20 minutes of a stress (Stroop test), relaxation (tape), or control (video) manipulation, followed by a capsaicin injection in the forearm. Digitized flare measurements were taken for 1 hour postcapsaicin, and measurements of cardiovascular variables, cortisol, adrenocorticotrophic hormone, and norepinephrine were taken at regular intervals. The size of the maximum capsaicin-induced flare was significantly smaller in the relaxation condition than in the stress or control conditions, which did not differ from each other. Increases in norepinephrine, heart rate, and systolic blood pressure during the experimental task, but not after capsaicin, significantly predicted size of maximum flare and total area under the curve of flare measurements. These findings suggest that stress reduction may affect local inflammatory processes. Results are consistent with sympathetic modulation of the effects of relaxation on the flare response.
Analytical representations for relaxation functions of glasses
Hilfer, R.
2002-01-01
Analytical representations in the time and frequency domains are derived for the most frequently used phenomenological fit functions for non-Debye relaxation processes. In the time domain the relaxation functions corresponding to the complex frequency dependent Cole-Cole, Cole-Davidson and Havriliak-Negami susceptibilities are also represented in terms of $H$-functions. In the frequency domain the complex frequency dependent susceptibility function corresponding to the time dependent stretche...
Vibrational relaxation in very high temperature nitrogen
Hansen, C. Frederick
1991-01-01
Vibrational relaxation of N2 molecules is considered at temperatures up to 40,000 K in gas mixtures that contain electrons as well as heavy collision partners. The theory of vibrational relaxation due to N2-N2 collisions is fit to experimental data to 10,000 K by choice of the shape of the intermolecular potential and size of the collision cross section. These values are then used to extrapolate the theory to 40,000 K.
Anomalous enthalpy relaxation in vitreous silica
DEFF Research Database (Denmark)
Yue, Yuanzheng
2015-01-01
scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling) has impact on enthalpy relaxation in glass. Here, we find that vitreous silica (as a strong system) exhibits striking anomalies in both glass transition and enthalpy...... the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica....
Message passing with relaxed moment matching
Qi, Yuan; Guo, Yandong
2012-01-01
Bayesian learning is often hampered by large computational expense. As a powerful generalization of popular belief propagation, expectation propagation (EP) efficiently approximates the exact Bayesian computation. Nevertheless, EP can be sensitive to outliers and suffer from divergence for difficult cases. To address this issue, we propose a new approximate inference approach, relaxed expectation propagation (REP). It relaxes the moment matching requirement of expectation propagation by addin...
Lagrange relaxation and Dantzig-Wolfe decomposition
DEFF Research Database (Denmark)
Vidal, Rene Victor Valqui
1989-01-01
The paper concerns a large-scale linear programming problem having a block-diagonal structure with coupling constraints. It is shown that there are deep connections between the Lagrange relaxation techniques and the Dantzig-Wolfe decomposition methods......The paper concerns a large-scale linear programming problem having a block-diagonal structure with coupling constraints. It is shown that there are deep connections between the Lagrange relaxation techniques and the Dantzig-Wolfe decomposition methods...
Lagrange relaxation and Dantzig-Wolfe decomposition
DEFF Research Database (Denmark)
Vidal, Rene Victor Valqui
1989-01-01
The paper concerns a large-scale linear programming problem having a block-diagonal structure with coupling constraints. It is shown that there are deep connections between the Lagrange relaxation techniques and the Dantzig-Wolfe decomposition methods......The paper concerns a large-scale linear programming problem having a block-diagonal structure with coupling constraints. It is shown that there are deep connections between the Lagrange relaxation techniques and the Dantzig-Wolfe decomposition methods...
Orientational relaxation in semiflexible dendrimers.
Kumar, Amit; Biswas, Parbati
2013-12-14
The orientational relaxation dynamics of semiflexible dendrimers are theoretically calculated within the framework of optimized Rouse-Zimm formalism. Semiflexibility is modeled through appropriate restrictions in the direction and orientation of the respective bond vectors, while the hydrodynamic interactions are included via the preaveraged Oseen tensor. The time autocorrelation function M(i)(1)(t) and the second order orientational autocorrelation function P(i)(2)(t) are analyzed as a function of the branch-point functionality and the degree of semiflexibility. Our approach of calculating M(i)(1)(t) is completely different from that of the earlier studies (A. Perico and M. Guenza J. Chem. Phys., 1985, 83, 3103; J. Chem. Phys., 1986, 84, 510), where the expression of M(i)(1)(t) obtained from earlier studies does not demarcate the flexible dendrimers from the semiflexible ones. The component of global motion of the time autocorrelation function exhibits a strong dependence on both degree of semiflexibility and branch-point functionality, while the component of pulsation motion depends only on the degree of semiflexibility. But it is difficult to distinguish the difference in the extent of pulsation motion among the compressed (0 qualitative behavior of P(i)(2)(t) obtained from our calculations closely matches with the expression for P(exact)(2)(t) in the earlier studies. Theoretically calculated spectral density, J(ω), is found to depend on the degree of semiflexibility and the branch-point functionality for the compressed and expanded conformations of semiflexible dendrimers as a function of frequency, especially in the high frequency regime, where J(ω) decays with frequency for both compressed and expanded conformations of semiflexible dendrimers. This decay of the spectral density occurs after displaying a cross-over behavior with the variation in the degree of semiflexibility in the intermediate frequency regime. The characteristic area increases with the
Dielectric relaxation spectroscopy of phlogopite mica
Energy Technology Data Exchange (ETDEWEB)
Kaur, Navjeet; Singh, Mohan; Singh, Anupinder [Department of Physics, Guru Nanak Dev University, Amritsar, Punjab 143005 (India); Awasthi, A.M. [Thermodynamics Laboratory, UGC-DAE Consortium for Scientific Research, Indore 452001 (India); Singh, Lakhwant, E-mail: lakhwant@yahoo.com [Department of Physics, Guru Nanak Dev University, Amritsar, Punjab 143005 (India)
2012-11-15
An in-depth investigation of the dielectric characteristics of annealed phlogopite mica has been conducted in the frequency range 0.1 Hz-10 MHz and over the temperature range 653-873 K through the framework of dielectric permittivity, electric modulus and conductivity formalisms. These formalisms show qualitative similarities in relaxation processes. The frequency dependence of the M Double-Prime and dc conductivity is found to obey an Arrhenius law and the activation energy of the phlogopite mica calculated both from dc conductivity and the modulus spectrum is similar, indicating that same type of charge carriers are involved in the relaxation phenomena. The electric modulus and conductivity data have been fitted with the Havriliak-Negami function. Scaling of M Prime , M Double-Prime , ac conductivity has also been performed in order to obtain insight into the relaxation mechanisms. The scaling behaviour indicates that the relaxation describes the same mechanism at different temperatures. The relaxation mechanism was also examined using the Cole-Cole approach. The study elaborates that the investigation regarding the temperature and frequency dependence of dielectric relaxation in the phlogopite mica will be helpful for various cutting edge applications of this material in electrical engineering.
Dielectric relaxation of gamma irradiated muscovite mica
Energy Technology Data Exchange (ETDEWEB)
Kaur, Navjeet [Department of Physics, Guru Nanak Dev University, Amritsar, Punjab 143005 (India); Singh, Mohan, E-mail: mohansinghphysics@gmail.com [Department of Physics, Guru Nanak Dev University, Amritsar, Punjab 143005 (India); Singh, Lakhwant [Department of Physics, Guru Nanak Dev University, Amritsar, Punjab 143005 (India); Awasthi, A.M. [Thermodynamics Laboratory, UGC-DAE Consortium for Scientific Research, Indore 452001 (India); Lochab, S.P. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)
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, using 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.
Rounded stretched exponential for time relaxation functions.
Powles, J G; Heyes, D M; Rickayzen, G; Evans, W A B
2009-12-01
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)Cole-Cole plots for dielectric and shear stress 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)).
Stress relaxation in viscous soft spheres.
Boschan, Julia; Vasudevan, Siddarth A; Boukany, Pouyan E; Somfai, Ellák; Tighe, Brian P
2017-09-27
We report the results of molecular dynamics simulations of stress relaxation tests in athermal viscous soft sphere packings close to their unjamming transition. By systematically and simultaneously varying both the amplitude of the applied strain step and the pressure of the initial condition, we access both linear and nonlinear response regimes and control the distance to jamming. Stress relaxation in viscoelastic solids is characterized by a relaxation time τ* that separates short time scales, where viscous loss is substantial, from long time scales, where elastic storage dominates and the response is essentially quasistatic. We identify two distinct plateaus in the strain dependence of the relaxation time, one each in the linear and nonlinear regimes. The height of both plateaus scales as an inverse power law with the distance to jamming. By probing the time evolution of particle velocities during relaxation, we further identify a correlation between mechanical relaxation in the bulk and the degree of non-affinity in the particle velocities on the micro scale.
On convex relaxation of graph isomorphism.
Aflalo, Yonathan; Bronstein, Alexander; Kimmel, Ron
2015-03-10
We consider the problem of exact and inexact matching of weighted undirected graphs, in which a bijective correspondence is sought to minimize a quadratic weight disagreement. This computationally challenging problem is often relaxed as a convex quadratic program, in which the space of permutations is replaced by the space of doubly stochastic matrices. However, the applicability of such a relaxation is poorly understood. We define a broad class of friendly graphs characterized by an easily verifiable spectral property. We prove that for friendly graphs, the convex relaxation is guaranteed to find the exact isomorphism or certify its inexistence. This result is further extended to approximately isomorphic graphs, for which we develop an explicit bound on the amount of weight disagreement under which the relaxation is guaranteed to find the globally optimal approximate isomorphism. We also show that in many cases, the graph matching problem can be further harmlessly relaxed to a convex quadratic program with only n separable linear equality constraints, which is substantially more efficient than the standard relaxation involving n2 equality and n2 inequality constraints. Finally, we show that our results are still valid for unfriendly graphs if additional information in the form of seeds or attributes is allowed, with the latter satisfying an easy to verify spectral characteristic.
Cross Relaxation in rare-earth-doped oxyfluoride glasses
Energy Technology Data Exchange (ETDEWEB)
Lakshminarayana, G.; Weis, Eric M. [Materials Science and Technology Division (MST-7), Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Lira, A.C. [Unidad Académica Profesional Nezahualcóyotl, Universidad Autónoma del Estado de México, Av. Bordo de Xochiaca s/n, Nezahualcóyotl, Estado de Mexico 57000, México (Mexico); Caldiño, Ulises [Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, P.O. Box 55-534, México D.F. 09340 (Mexico); Williams, Darrick J. [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Hehlen, Markus P., E-mail: hehlen@lanl.gov [Materials Science and Technology Division (MST-7), Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)
2013-07-15
{sup 5}D{sub 3} cross relaxation rate of Tb{sup 3+} can be tuned via concentration. ► The {sup 5}D{sub 3}/{sup 5}D{sub 4} emission intensity ratio was used as a probe for Tb{sup 3+} ion aggregation. ► Cross relaxation dominates the decay of the {sup 4}G{sub 5/2} excited state of Sm{sup 3+}. ► Multiple Eu{sup 3+} sites yield a non-exponential {sup 5}D{sub 0} decay via {sup 5}D{sub 0}→{sup 7}F{sub 2} hypersensitivity.
Rogers, Nicola J; Finney, Katie-Louise N A; Senanayake, P Kanthi; Parker, David
2016-02-14
Measurements of the relaxation rate behaviour of two series of dysprosium complexes have been performed in solution, over the field range 1.0 to 16.5 Tesla. The field dependence has been modelled using Bloch-Redfield-Wangsness theory, allowing estimates of the electronic relaxation time, T1e, and the size of the magnetic susceptibility, μeff, to be made. Changes in relaxation rate of the order of 50% at higher fields were measured, following variation of the para-substituent in the single pyridine donor. The magnetic susceptibilities deviated unexpectedly from the free-ion values for certain derivatives in each series examined, in a manner that was independent of the electron-releasing/withdrawing ability of the pyridine substituent, suggesting that the polarisability of just one pyridine donor in octadenate ligands can play a significant role in defining the magnetic susceptibility anisotropy.
Size-dependent MR relaxivities of magnetic nanoparticles
Joos, Alexander; Löwa, Norbert; Wiekhorst, Frank; Gleich, Bernhard; Haase, Axel
2017-04-01
Magnetic nanoparticles (MNPs) can be used as carriers for magnetic drug targeting and for stem cell tracking by magnetic resonance imaging (MRI). For these applications, it is crucial to quantitatively determine the spatial distribution of the MNP concentration, which can be approached by MRI relaxometry. Theoretical considerations and experiments have shown that R2 relaxation rates are sensitive to the aggregation state of the particles, whereas R2* is independent of aggregation state and therefore suited for MNP quantification if the condition of static dephasing is met. We present a new experimental approach to characterize an MNP system with respect to quantitative MRI based on hydrodynamic fractionation. The first results qualitatively confirm the outer sphere relaxation theory for small MNPs and show that the two commercial MRI contrast agents Resovist® and Endorem® should not be used for quantitative MRI because they do not fulfill the condition for static dephasing. Our approach could facilitate the choice of MNPs for quantitative MRI and help clarifying the relationship between size, magnetism and relaxivity of MNPs in the future.
Brownian relaxation of an inelastic sphere in air
Bird, G. A.
2016-06-01
The procedures that are used to calculate the forces and moments on an aerodynamic body in the rarefied gas of the upper atmosphere are applied to a small sphere of the size of an aerosol particle at sea level. While the gas-surface interaction model that provides accurate results for macroscopic bodies may not be appropriate for bodies that are comprised of only about a thousand atoms, it provides a limiting case that is more realistic than the elastic model. The paper concentrates on the transfer of energy from the air to an initially stationary sphere as it acquires Brownian motion. Individual particle trajectories vary wildly, but a clear relaxation process emerges from an ensemble average over tens of thousands of trajectories. The translational and rotational energies in equilibrium Brownian motion are determined. Empirical relationships are obtained for the mean translational and rotational relaxation times, the mean initial power input to the particle, the mean rates of energy transfer between the particle and air, and the diffusivity. These relationships are functions of the ratio of the particle mass to an average air molecule mass and the Knudsen number, which is the ratio of the mean free path in the air to the particle diameter. The ratio of the molecular radius to the particle radius also enters as a correction factor. The implications of Brownian relaxation for the second law of thermodynamics are discussed.
Brownian relaxation of an inelastic sphere in air
Energy Technology Data Exchange (ETDEWEB)
Bird, G. A., E-mail: gab@gab.com.au [University of Sydney, Sydney, NSW 2006 (Australia)
2016-06-15
The procedures that are used to calculate the forces and moments on an aerodynamic body in the rarefied gas of the upper atmosphere are applied to a small sphere of the size of an aerosol particle at sea level. While the gas-surface interaction model that provides accurate results for macroscopic bodies may not be appropriate for bodies that are comprised of only about a thousand atoms, it provides a limiting case that is more realistic than the elastic model. The paper concentrates on the transfer of energy from the air to an initially stationary sphere as it acquires Brownian motion. Individual particle trajectories vary wildly, but a clear relaxation process emerges from an ensemble average over tens of thousands of trajectories. The translational and rotational energies in equilibrium Brownian motion are determined. Empirical relationships are obtained for the mean translational and rotational relaxation times, the mean initial power input to the particle, the mean rates of energy transfer between the particle and air, and the diffusivity. These relationships are functions of the ratio of the particle mass to an average air molecule mass and the Knudsen number, which is the ratio of the mean free path in the air to the particle diameter. The ratio of the molecular radius to the particle radius also enters as a correction factor. The implications of Brownian relaxation for the second law of thermodynamics are discussed.
Energy Technology Data Exchange (ETDEWEB)
Carroll, Matthew R J; Woodward, Robert C; House, Michael J; St Pierre, Timothy G [Centre for Strategic Nanofabrication, School of Physics, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia); Teoh, Wey Yang; Amal, Rose [ARC Centre of Excellence for Functional Nanomaterials, School of Chemical Engineering and Industrial Chemistry, University of New South Wales, Sydney, NSW 2052 (Australia); Hanley, Tracey L, E-mail: stpierre@physics.uwa.edu.au [Bragg Institute, Australian Nuclear Science and Technology Organization, New Illawarra Road, Lucas Heights, NSW 2234 (Australia)
2010-01-22
Analytical models of proton transverse relaxation rate enhancement by magnetic nanoparticles were tested by making measurements on model experimental systems in a field of 1.4 T. Proton relaxivities were measured for five aqueous suspensions of iron oxide (maghemite) nanoparticles with nominal mean particle sizes of 6, 8, 10, 11, and 13 nm. Proton relaxivity increased with mean particle size ranging from 13 s{sup -1} mM Fe{sup -1} for the 6 nm sample, up to 254 s{sup -1} mM Fe{sup -1} for the 13 nm sample. A strong correlation between the measured and predicted values of the relaxivity was observed, with the predicted values being consistently higher than the measured values. The results indicate that the models give a reasonable agreement with experimental results and hence can be used as the basis for the design of new magnetic resonance imaging contrast and labelling agents.
Seeger, H M; Heimburg, T; Gudmundsson, Marie L.; Heimburg, Thomas; Seeger, Heiko M.
2007-01-01
In the proximity of melting transitions of artificial and biological membranes fluctuations in enthalpy, area, volume and concentration are enhanced. This results in domain formation, changes of the elastic constants, changes in permeability and slowing down of relaxation processes. In this study we used pressure perturbation calorimetry to investigate the relaxation time scale after a jump into the melting transition regime of artificial lipid membranes. This time corresponds to the characteristic rate of domain growth. The studies were performed on single-component large unilamellar and multilamellar vesicle systems with and without the addition of small molecules such as general anesthetics, neurotransmitters and antibiotics. These drugs interact with membranes and affect melting points and profiles. In all systems we found that heat capacity and relaxation times are related to each other in a simple manner. The maximum relaxation time depends on the cooperativity of the heat capacity profile and decreases...
A theoretical study of the stress relaxation in HMX on the picosecond time scale
Long, Yao; Chen, Jun
2015-12-01
The stress relaxation model of β-HMX on the picosecond time scale is studied by a theoretical approach. The relaxation of normal stress is contributed by lattice vibration, and the relaxation of shear stress is contributed by molecular rotation. Based on this model, the energy dissipation rule of the elastic wave and the profile of the shock wave are investigated. We find at low frequency the dissipation rate of the elastic wave is proportional to the power function of frequency, and under high speed shock loading the width of the stress relaxation zone is less than 0.3 μm there is a pressure peak with a height of 14 GPa near the wave front.
Kawai, Masamichi; Kazama, Takeshi; Masuko, Yoichi; Tsuda, Hiroshi; Takahashi, Jun; Kemmochi, Kiyoshi
Off-axis stress relaxation behavior of unidirectional T800H/3631 carbon/epoxy composite exposed to high temperature is examined at relatively high tensile strain levels, and a phenomenological viscoplasticity model is tested on the capability to describe the time-dependent response observed. First, stress relaxation tests are performed at 100°C on plain coupon specimens with different fiber orientations, θ=0, 10, 30, 45, and 90°. For each of the fiber orientations, in principle, stress relaxation tests are carried out at three different strain levels. The relaxation of axial stress in the unidirectional composite is clearly observed, regardless of the fiber orientation. Just after the total strain hold, the axial stress quickly relaxes with time in a short period. The stress relaxation rate of the composite tends to become zero, irrespective of the fiber orientation. The associated relaxation modulus depends on the level of strain. The entire process of the prior instantaneous tensile response and the subsequent off-axis stress relaxation behavior is simulated using a macromechanical viscoplasticity model based on an overstress concept. It is demonstrated that the model succeeds in adequately reproducing the off-axis stress relaxation behavior of the unidirectional composite laminate.
Habib, Rasikh; Asif, Muhammad Bilal; Iftekhar, Sidra; Khan, Zahiruddin; Gurung, Khum; Srivastava, Varsha; Sillanpää, Mika
2017-08-01
Relaxation and backwashing have become an integral part of membrane bioreactor (MBR) operations for fouling control. This study was carried out on real municipal wastewater to evaluate the influence of different operational strategies on membrane fouling at equivalent water yield. Four relaxation modes (MBR10+0, MBR10+1, MBR10+1.5 and MBR10+2) were tested to analyze membrane fouling behavior. For the optimization of relaxation modes, fouling rate in terms of trans-membrane pressure, hydraulic resistances and characteristics of fouling fractions were analyzed. It has been observed that cake layer resistance was minimum in MBR10+1.5 but pore blockage resistance was increased in all relaxation modes. Moreover, high instantaneous flux contributed significantly to fouling rate at the initial stage of MBR operations. Relaxation modes were also efficient in removing irreversible fouling to some extent. Under all relaxation modes, COD removal efficiency ranged from 92 to 96.5%. Ammonium and TP removal were on the lower side due to the short solids and hydraulic retention time. Copyright © 2017 Elsevier Ltd. All rights reserved.
Introductory Chemistry: A Molar Relaxivity Experiment in the High School Classroom.
Dawsey, Anna C; Hathaway, Kathryn L; Kim, Susie; Williams, Travis J
2013-07-09
Dotarem and Magnevist, two clinically available magnetic resonance imaging (MRI) contrast agents, were assessed in a high school science classroom with respect to which is the better contrast agent. Magnevist, the more efficacious contrast agent, has negative side effects because its gadolinium center can escape from its ligand. However, Dotarem, though a less efficacious contrast agent, is a safer drug choice. After the experiment, students are confronted with the FDA warning on Magnevist, which enabled a discussion of drug efficacy versus safety. We describe a laboratory experiment in which NMR spin lattice relaxation rate measurements are used to quantify the relaxivities of the active ingredients of Dotarem and Magnevist. The spin lattice relaxation rate gives the average amount of time it takes the excited nucleus to relax back to the original state. Students learn by constructing molar relaxivity curves based on inversion recovery data sets that Magnevist is more relaxive than Dotarem. This experiment is suitable for any analytical chemistry laboratory with access to NMR.
A study of internal energy relaxation in shocks using molecular dynamics based models
Energy Technology Data Exchange (ETDEWEB)
Li, Zheng, E-mail: zul107@psu.edu; Parsons, Neal, E-mail: neal.parsons@cd-adapco.com [Department of Aerospace Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Levin, Deborah A., E-mail: deblevin@illinois.edu [Department of Aerospace Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801-2935 (United States)
2015-10-14
Recent potential energy surfaces (PESs) for the N{sub 2} + N and N{sub 2} + N{sub 2} 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 N{sub 2} + N{sub 2} 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 N{sub 2} 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.
Dynamics of a molecular glass former: Energy landscapes for diffusion in ortho-terphenyl
Niblett, S. P.; de Souza, V. K.; Stevenson, J. D.; Wales, D. J.
2016-07-01
Relaxation times and transport processes of many glass-forming supercooled liquids exhibit a super-Arrhenius temperature dependence. We examine this phenomenon by computer simulation of the Lewis-Wahnström model for ortho-terphenyl. We propose a microscopic definition for a single-molecule cage-breaking transition and show that, when correlation behaviour is taken into account, these rearrangements are sufficient to reproduce the correct translational diffusion constants over an intermediate temperature range in the supercooled regime. We show that super-Arrhenius behaviour can be attributed to increasing negative correlation in particle movement at lower temperatures and relate this to the cage-breaking description. Finally, we sample the potential energy landscape of the model and show that it displays hierarchical ordering. Substructures in the landscape, which may correspond to metabasins, have boundaries defined by cage-breaking transitions. The cage-breaking formulation provides a direct link between the potential energy landscape and macroscopic diffusion behaviour.
Application of the compensated arrhenius formalism to dielectric relaxation.
Petrowsky, Matt; Frech, Roger
2009-12-17
The temperature dependence of the dielectric rate constant, defined as the reciprocal of the dielectric relaxation time, is examined for several groups of organic solvents. Early studies of linear alcohols using a simple Arrhenius equation found that the activation energy was dependent on the chain length of the alcohol. This paper re-examines the earlier data using a compensated Arrhenius formalism that assumes the presence of a temperature-dependent static dielectric constant in the exponential prefactor. Scaling temperature-dependent rate constants to isothermal rate constants so that the dielectric constant dependence is removed results in calculated energies of activation E(a) in which there is a small increase with chain length. These energies of activation are very similar to those calculated from ionic conductivity data using compensated Arrhenius formalism. This treatment is then extended to dielectic relaxation data for n-alkyl bromides, n-nitriles, and n-acetates. The exponential prefactor is determined by dividing the temperature-dependent rate constants by the Boltzmann term exp(-E(a)/RT). Plotting the prefactors versus the static dielectric constant places the data on a single master curve for each group of solvents.
A Block-Asynchronous Relaxation Method for Graphics Processing Units
Energy Technology Data Exchange (ETDEWEB)
Antz, Hartwig [Karlsruhe Inst. of Technology (KIT) (Germany); Tomov, Stanimire [Univ. of Tennessee, Knoxville, TN (United States); Dongarra, Jack [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Manchester (United Kingdom); Heuveline, Vincent [Karlsruhe Inst. of Technology (KIT) (Germany)
2011-11-30
In this paper, we analyze the potential of asynchronous relaxation methods on Graphics Processing Units (GPUs). For this purpose, we developed a set of asynchronous iteration algorithms in CUDA and compared them with a parallel implementation of synchronous relaxation methods on CPU-based systems. For a set of test matrices taken from the University of Florida Matrix Collection we monitor the convergence behavior, the average iteration time and the total time-to-solution time. Analyzing the results, we observe that even for our most basic asynchronous relaxation scheme, despite its lower convergence rate compared to the Gauss-Seidel relaxation (that we expected), the asynchronous iteration running on GPUs is still able to provide solution approximations of certain accuracy in considerably shorter time then Gauss- Seidel running on CPUs. Hence, it overcompensates for the slower convergence by exploiting the scalability and the good fit of the asynchronous schemes for the highly parallel GPU architectures. Further, enhancing the most basic asynchronous approach with hybrid schemes – using multiple iterations within the ”subdomain” handled by a GPU thread block and Jacobi-like asynchronous updates across the ”boundaries”, subject to tuning various parameters – we manage to not only recover the loss of global convergence but often accelerate convergence of up to two times (compared to the effective but difficult to parallelize Gauss-Seidel type of schemes), while keeping the execution time of a global iteration practically the same. This shows the high potential of the asynchronous methods not only as a stand alone numerical solver for linear systems of equations fulfilling certain convergence conditions but more importantly as a smoother in multigrid methods. Due to the explosion of parallelism in todays architecture designs, the significance and the need for asynchronous methods, as the ones described in this work, is expected to grow.
Nuclear Magnetic Relaxation in Polyacetylene.
1983-04-07
article by Blumberg /9/. For the sake of clarity we summarize his description for the situation in which npy ear spin diffusion is the rate limiting...13. Both inversion-recovery and saturation-recovery pulse sequences were used. The results obtained at room temperature are summarized in table 1
The use of (double) relaxation oscillation SQUIDs as a sensor
Duuren, van M.J.; Brons, G.C.S.; Kattouw, H.; Flokstra, J.; Rogalla, H.
1997-01-01
Relaxation Oscillation SQUIDs (ROSs) and Double Relaxation Oscillation SQUIDs (DROSs) are based on relaxation oscillations that are induced in hysteretic dc SQUIDs by an external L-R shunt. The relaxation frequency of a ROS varies with the applied flux Φ, whereas the output of a DROS is a dc voltage
The use of (double) relaxation oscillation SQUIDs as a sensor
van Duuren, M.J.; Brons, G.C.S.; Kattouw, H.; Flokstra, Jakob; Rogalla, Horst
1997-01-01
Relaxation Oscillation SQUIDs (ROSs) and Double Relaxation Oscillation SQUIDs (DROSs) are based on relaxation oscillations that are induced in hysteretic dc SQUIDs by an external L-R shunt. The relaxation frequency of a ROS varies with the applied flux Φ, whereas the output of a DROS is a dc
Vibrational relaxation and energy transfer of matrix isolated HCl and DCl
Energy Technology Data Exchange (ETDEWEB)
Wiesenfeld, J.M.
1977-12-01
Vibrational kinetic and spectroscopic studies have been performed on matrix-isolated HCl and DCl between 9 and 20 K. Vibrational relaxation rates for v = 2 and v = 1 were measured by a tunable infrared laser-induced, time-resolved fluorescence technique. In an Ar matrix, vibrational decay times are faster than radiative and it is found that HCl relaxes about 35 times more rapidly than CCl, in spite of the fact that HCl must transfer more energy to the lattice than DCl. This result is explained by postulating that the rate-determining step for vibrational relaxation produces a highly rotationally excited guest in a V yield R step; rotational relaxation into lattice phonons follows rapidly. HCl v = 1, but not v = 2, excitation rapidly diffuses through the sample by a resonant dipole-dipole vibrational energy transfer process. Molecular complexes, and in particular the HCl dimer, relax too rapidly for direct observation, less than or approximately 1 ..mu..s, and act as energy sinks in the energy diffusion process. The temperature dependence for all these processes is weak--less than a factor of two between 9 and 20 K. Vibrational relaxation of HCl in N/sub 2/ and O/sub 2/ matrices is unobservable, presumably due to rapid V yield V transfer to the host. A V yield R binary collision model for relaxation in solids is successful in explaining the HCl(DCl)/Ar results as well as results of other experimenters. The model considers relaxation to be the result of ''collisions'' due to molecular motion in quantized lattice normal modes--gas phase potential parameters can fit the matrix kinetic data.
The effect of iron in MRI and transverse relaxation of amyloid-beta plaques in Alzheimer's disease.
Meadowcroft, Mark D; Peters, Douglas G; Dewal, Rahul P; Connor, James R; Yang, Qing X
2015-03-01
Dysregulation of neural iron is known to occur during the progression of Alzheimer's disease. The visualization of amyloid-beta (Aβ) plaques with MRI has largely been credited to rapid proton relaxation in the vicinity of plaques as a result of focal iron deposition. The goal of this work was to determine the relationship between local relaxation and related focal iron content associated with Aβ plaques. Alzheimer's disease (n=5) and control tissue (n=3) sample slices from the entorhinal cortex were treated overnight with the iron chelator deferoxamine or saline, and microscopic gradient-echo MRI datasets were taken. Subsequent to imaging, the same slices were stained for Aβ and iron, and then compared with regard to parametric R2 * relaxation maps and gradient-echo-weighted MR images. Aβ plaques in both chelated and unchelated tissue generated MR hypo-intensities and showed relaxation rates significantly greater than the surrounding tissue. The transverse relaxation rate associated with amyloid plaques was determined not to be solely a result of iron load, as much of the relaxation associated with Aβ plaques remained following iron chelation. The data indicate a dual relaxation mechanism associated with Aβ plaques, such that iron and plaque composition synergistically produce transverse relaxation.
Energy Technology Data Exchange (ETDEWEB)
Schlüter, Steffen [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis Oregon USA; Department Soil Physics, Helmholtz-Centre for Environmental Research-UFZ, Halle Germany; Berg, Steffen [Shell Global Solutions International B.V., Rijswijk Netherlands; Li, Tianyi [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis Oregon USA; Vogel, Hans-Jörg [Department Soil Physics, Helmholtz-Centre for Environmental Research-UFZ, Halle Germany; Institut für Agrar- und Ernährungswissenschaften, Martin-Luther-Universität Halle-Wittenberg, Halle Germany; Wildenschild, Dorthe [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis Oregon USA
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, and 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.
Anomalous Enthalpy Relaxation in Vitreous Silica
Directory of Open Access Journals (Sweden)
Yuanzheng eYue
2015-08-01
Full Text Available It is a challenge to calorimetrically determine the glass transition temperature (Tg of vitreous silica. Here we demonstrate that this challenge mainly arises from the extreme sensitivity of the Tg to the hydroxyl content in vitreous silica, but also from the irreversibility of its glass transition when repeating the calorimetric scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling has impact on enthalpy relaxation in glass. Here we find that vitreous silica (as a strong system exhibits striking anomalies in both glass transition and enthalpy relaxation compared to fragile oxide systems. The anomalous enthalpy relaxation of vitreous silica is discovered by performing the hperquenching-annealing-calorimetry experiments. We argue that the strong systems like vitreous silica and vitreous Germania relax in a structurally cooperative manner, whereas the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica.
Motional Spin Relaxation in Large Electric Fields
Schmid, Riccardo; Filippone, B W
2008-01-01
We discuss the precession of spin-polarized Ultra Cold Neutrons (UCN) and $^{3}\\mathrm{He}$ atoms in uniform and static magnetic and electric fields and calculate the spin relaxation effects from motional $v\\times E$ magnetic fields. Particle motion in an electric field creates a motional $v\\times E$ magnetic field, which when combined with collisions, produces variations of the total magnetic field and results in spin relaxation of neutron and $^{3}\\mathrm{He}$ samples. The spin relaxation times $T_{1}$ (longitudinal) and $T_{2}$ (transverse) of spin-polarized UCN and $^{3}\\mathrm{He}$ atoms are important considerations in a new search for the neutron Electric Dipole Moment at the SNS \\emph{nEDM} experiment. We use a Monte Carlo approach to simulate the relaxation of spins due to the motional $v\\times E$ field for UCN and for $^{3}\\mathrm{He}$ atoms at temperatures below $600 \\mathrm{mK}$. We find the relaxation times for the neutron due to the $v\\times E$ effect to be long compared to the neutron lifetime, ...
Reduced-Complexity Semidefinite Relaxations of Optimal Power Flow Problems
DEFF Research Database (Denmark)
Andersen, Martin Skovgaard; Hansson, Anders; Vandenberghe, Lieven
2014-01-01
We propose a new method for generating semidefinite relaxations of optimal power flow problems. The method is based on chordal conversion techniques: by dropping some equality constraints in the conversion, we obtain semidefinite relaxations that are computationally cheaper, but potentially weaker......, than the standard semidefinite relaxation. Our numerical results show that the new relaxations often produce the same results as the standard semidefinite relaxation, but at a lower computational cost....
Alekseenko, Alexander; Euler, Craig
2016-05-01
We propose a Bhatnagar-Gross-Krook (BGK) kinetic model in which the collision frequency is a linear combination of polynomials in the velocity variable. The coefficients of the linear combination are determined so as to enforce proper relaxation rates for a selected group of moments. The relaxation rates are obtained by a direct numerical evaluation of the full Boltzmann collision operator. The model is conservative by construction. Simulations of the problem of spatially homogeneous relaxation of hard spheres gas show improvement in accuracy of controlled moments as compared to solutions obtained by the classical BGK, ellipsoidal-statistical BGK and the Shakhov models in cases of strong deviations from continuum.
Dielectric and specific heat relaxations in vapor deposited glycerol
Energy Technology Data Exchange (ETDEWEB)
Kasina, A., E-mail: angeline.kasina@fys.kuleuven.be, E-mail: wubbenhorst@fys.kuleuven.be; Putzeys, T.; Wübbenhorst, M., E-mail: angeline.kasina@fys.kuleuven.be, E-mail: wubbenhorst@fys.kuleuven.be [Department of Physics and Astronomy, Soft Matter and Biophysics Section, KU Leuven, Leuven (Belgium)
2015-12-28
Recently [S. Capponi, S. Napolitano, and M. Wübbenhorst, Nat. Commun. 3, 1233 (2012)], vapor deposited glasses of glycerol have been found to recover their super-cooled liquid state via a metastable, ordered liquid (MROL) state characterized by a tremendously enhanced dielectric strength along with a slow-down of the relaxation rate of the structural relaxation. To study the calorimetric signature of this phenomenon, we have implemented a chip-based, differential AC calorimeter in an organic molecular beam deposition setup, which allows the simultaneous measurement of dielectric relaxations via interdigitated comb electrodes and specific heat relaxation spectra during deposition and as function of the temperature. Heating of the as-deposited glass just above the bulk T{sub g} and subsequent cooling/reheating revealed a step-wise increase in c{sub p} by in total 9%, indicating unambiguously that glycerol, through slow vapour deposition, forms a thermodynamically stable glass, which has a specific heat as low as that of crystalline glycerol. Moreover, these glasses were found to show excellent kinetic stability as well as evidenced by both a high onset-temperature and quasi-isothermal recovery measurements at −75 °C. The second goal of the study was to elucidate the impact of the MROL state on the specific heat and its relaxation to the super-cooled state. Conversion of “MROL glycerol” to its “normal” (ordinary liquid, OL) state revealed a second, small (∼2%) increase of the glassy c{sub p}, a little gain (<10%) in the relaxed specific heat, and no signs of deviations of τ{sub cal} from that of normal “bulk” glycerol. These findings altogether suggest that the MROL state in glycerol comprises largely bulk-type glycerol that coexist with a minor volume fraction (<10%) of PVD-induced structural anomalies with a crystal-like calorimetric signature. Based on the new calorimetric findings, we have proposed a new physical picture that assumes the
Mozart versus new age music: relaxation states, stress, and ABC relaxation theory.
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
On topological relaxations of chromatic conjectures
Simonyi, Gábor
2010-01-01
There are several famous unsolved conjectures about the chromatic number that were relaxed and already proven to hold for the fractional chromatic number. We discuss similar relaxations for the topological lower bound(s) of the chromatic number. In particular, we prove that such a relaxed version is true for the Behzad-Vizing conjecture and also discuss the conjectures of Hedetniemi and of Hadwiger from this point of view. For the latter, a similar statement was already proven in an earlier paper of the first author with G. Tardos, our main concern here is that the so-called odd Hadwiger conjecture looks much more difficult in this respect. We prove that the statement of the odd Hadwiger conjecture holds for large enough Kneser graphs and Schrijver graphs of any fixed chromatic number.
Vibrational and Rotational Energy Relaxation in Liquids
DEFF Research Database (Denmark)
Petersen, Jakob
the intramolecular dynamics during photodissociation is investigated. The apparent agreement with quantum mechanical calculations is shown to be in contrast to the applicability of the individual approximations used in deriving the model from a quantum mechanical treatment. In the spirit of the Bersohn-Zewail model......, the vibrational energy relaxation of I2 subsequent to photodissociation and recombination in CCl4 is studied using classical Molecular Dynamics simulations. The vibrational relaxation times and the time-dependent I-I pair distribution function are compared to new experimental results, and a qualitative agreement...... is found in both cases. Furthermore, the rotational energy relaxation of H2O in liquid water is studied via simulations and a power-and-work analysis. The mechanism of the energy transfer from the rotationally excited H2O molecule to its water neighbors is elucidated, i.e. the energy-accepting degrees...
Relaxation and Diffusion in Complex Systems
Ngai, K L
2011-01-01
Relaxation and Diffusion in Complex Systems comprehensively presents a variety of experimental evidences of universal relaxation and diffusion properties in complex materials and systems. The materials discussed include liquids, glasses, colloids, polymers, rubbers, plastic crystals and aqueous mixtures, as well as carbohydrates, biomolecules, bioprotectants and pharmaceuticals. Due to the abundance of experimental data, emphasis is placed on glass-formers and the glass transition problem, a still unsolved problem in condensed matter physics and chemistry. The evidence for universal properties of relaxation and diffusion dynamics suggests that a fundamental physical law is at work. The origin of the universal properties is traced to the many-body effects of the interaction, rigorous theory of which does not exist at the present time. However, using solutions of simplified models as guides, key quantities have been identified and predictions of the universal properties generated. These predictions from Ngai’...
Substrate stress relaxation regulates cell spreading
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.
Nonlinear Model of non-Debye Relaxation
Zon, Boris A
2010-01-01
We present a simple nonlinear relaxation equation which contains the Debye equation as a particular case. The suggested relaxation equation results in power-law decay of fluctuations. This equation contains a parameter defining the frequency dependence of the dielectric permittivity similarly to the well-known one-parameter phenomenological equations of Cole-Cole, Davidson-Cole and Kohlrausch-Williams-Watts. Unlike these models, the obtained dielectric permittivity (i) obeys to the Kramers-Kronig relation; (ii) has proper behaviour at large frequency; (iii) its imaginary part, conductivity, shows a power-law frequency dependence \\sigma ~ \\omega^n where n1 is also observed in several experiments. The nonlinear equation proposed may be useful in various fields of relaxation theory.
Improved memristor-based relaxation oscillator
Mosad, Ahmed G.
2013-09-01
This paper presents an improved memristor-based relaxation oscillator which offers higher frequency and wider tunning range than the existing reactance-less oscillators. It also has the capability of operating on two positive supplies or alternatively a positive and negative supply. Furthermore, it has the advantage that it can be fully integrated on-chip providing an area-efficient solution. On the other hand, The oscillation concept is discussed then a complete mathematical analysis of the proposed oscillator is introduced. Furthermore, the power consumption of the new relaxation circuit is discussed and validated by the PSPICE circuit simulations showing an excellent agreement. MATLAB results are also introduced to demonstrate the resistance range and the corresponding frequency range which can be obtained from the proposed relaxation oscillator. © 2013 Elsevier Ltd.
Interactive Image Enhancement by Fuzzy Relaxation
Institute of Scientific and Technical Information of China (English)
Shang-Ming Zhou; John Q.Can; Li-Da Xu; Robert John
2007-01-01
In this paper, an interactive image enhancement (HE) technique based on fuzzy relaxation is presented, which allows the user to select different intensity levels for enhancement and intermit the enhancement process according to his/her preference in applications. First, based on an analysis of the convergence of a fuzzy relaxation algorithm for image contrast enhancement, an improved version of this algorithm, which is called FuzzIIE Method 1, is suggested by deriving a relationship between the convergence regions and the parameters in the transformations defined in the algorithm. Then a method called FuzzIIE Method 2 is introduced by using a different fuzzy relaxation function, in which there is no need to re-select the parameter values for interactive image enhancement. Experimental results are presented demonstrating the enhancement capabilities of the proposed methods under different conditions.
Spin relaxation in geometrically frustrated pyrochlores
Dunsiger, Sarah Ruth
This thesis describes muSR experiments which focus on systems where the magnetic ions occupy the vertices of edge or corner sharing triangular units, in particular the pyrochlores A2B2O7. The scientific interest in pyrochlores is based on the fact that they display novel magnetic behaviour at low temperatures due to geometrical frustration. The ground state of these systems is sensitively dependent on such factors as the range of the spin-spin interactions, disorder, anisotropy, thermal and quantum fluctuations. For example, Y2Mo2O7 shows many features reminiscent of a conventional spin glass, even though this material has nominally zero chemical disorder. It is found that the muon spin polarisation obeys a time-field scaling relation which indicates that the spin-spin autocorrelation function has a power law form in time, in stark contrast with the exponential form often assumed for conventional magnets above their transition temperature. Gd2Ti2O7 shows long range order, but only at a temperature much lower than its Curie-Weiss temperature, a signature of a frustrated system. In the paramagnetic regime, it is well described by an isotropic Heisenberg Hamiltonian with nearest neighbour couplings in the presence of a Zeeman interaction, from which the spin-spin autocorrelation function may be calculated as a power series in time. The muon spin relaxation rate decreases with magnetic field as the Zeeman energy becomes comparable with the exchange coupling between Gd spins. Thus, an independent measure of the exchange coupling or equivalently the Gd spin fluctuation rate is extracted. By contrast, Tb2Ti2O7 has been identified as a type of cooperative paramagnet. Short range correlations develop below 50 K. However, there is no long range ordering down to very low temperatures (0.075 K). The Tb3+ ion is subject to strong crystal electric field effects: point charge calculations indicate that this system is Ising like at low temperatures. Thus this system may be
Relaxation Dynamics of Semiflexible Fractal Macromolecules
Directory of Open Access Journals (Sweden)
Jonas Mielke
2016-07-01
Full Text Available We study the dynamics of semiflexible hyperbranched macromolecules having only dendritic units and no linear spacers, while the structure of these macromolecules is modeled through T-fractals. We construct a full set of eigenmodes of the dynamical matrix, which couples the set of Langevin equations. Based on the ensuing relaxation spectra, we analyze the mechanical relaxation moduli. The fractal character of the macromolecules reveals itself in the storage and loss moduli in the intermediate region of frequencies through scaling, whereas at higher frequencies, we observe the locally-dendritic structure that is more pronounced for higher stiffness.
Dynamics of cosmological relaxation after reheating
Choi, Kiwoon; Sekiguchi, Toyokazu
2016-01-01
We examine if the cosmological relaxation mechanism, which was proposed recently as a new solution to the hierarchy problem, can be compatible with high reheating temperature well above the weak scale. As the barrier potential disappears at high temperature, the relaxion rolls down further after the reheating, which may ruin the successful implementation of the relaxation mechanism. It is noted that if the relaxion is coupled to a dark gauge boson, the new frictional force arising from dark gauge boson production can efficiently slow down the relaxion motion, which allows the relaxion to be stabilized after the electroweak phase transition for a wide range of model parameters, while satisfying the known observational constraints.
Synthetic aperture radar autofocus via semidefinite relaxation.
Liu, Kuang-Hung; Wiesel, Ami; Munson, David C
2013-06-01
The autofocus problem in synthetic aperture radar imaging amounts to estimating unknown phase errors caused by unknown platform or target motion. At the heart of three state-of-the-art autofocus algorithms, namely, phase gradient autofocus, multichannel autofocus (MCA), and Fourier-domain multichannel autofocus (FMCA), is the solution of a constant modulus quadratic program (CMQP). Currently, these algorithms solve a CMQP by using an eigenvalue relaxation approach. We propose an alternative relaxation approach based on semidefinite programming, which has recently attracted considerable attention in other signal processing problems. Experimental results show that our proposed methods provide promising performance improvements for MCA and FMCA through an increase in computational complexity.
Depicting Vortex Stretching and Vortex Relaxing Mechanisms
Institute of Scientific and Technical Information of China (English)
符松; 李启兵; 王明皓
2003-01-01
Different from many existing studies on the paranetrization of vortices, we investigate the effectiveness of two new parameters for identifying the vortex stretching and vortex relaxing mechanisms. These parameters are invariants and identify three-dimensional flow structures only, i.e. they diminish in two-dimensional flows. This is also unlike the existing vortex identification approaches which deliver information in two-dimensional flows. The present proposals have been successfully applied to identify the stretching and relaxing vortices in compressible mixing layers and natural convection flows.
Institute of Scientific and Technical Information of China (English)
崔英丹; 孙月吉; 郭德纲; 宁淑娥; 陈爱年; 王智; 王浩
2013-01-01
Objective To evaluate influence of the biofeedback relaxation training on the heart rate variability of naval ser -vicemen with anxiety on surface ship .Methods 140 anxiety army men (50≤SAS standard score 0.05).In control group, lnLF(nu) values are raised than the before , there were no significant different during 10 times intervention using paired-T test or variance analysis in lnLF(nu) value (P>0.05);After the intervention, lnHF(nu) values of the intervention group were higher than before at eighth , ninth, tenth (P0.05).In control group, lnHF(nu) values were decreased than the before , there were no signifi-cant different after every intervention using paired -T test or variance analysis in lnHF (nu) value(P>0.05);Comparison of basis value before and after experimental: Comparing the foundation value of 10th and 1th of HR, lnLF(nu), lnHF (nu), there were no significant differences (P>0.05).Conclusion Biofeedback relaxation training can obviously improve the HRV frequence-domain indexes of military , reducing sympathetic nerve activity , enhanced vagus nerve activity , it is indicated that biofeedback relaxation training can improve the function state of autonomic nervous of military and alleviate anxiety.%目的：探讨生物反馈放松训练对驻舰焦虑军人心率变异性（ HRV）的影响。方法通过随机整群抽样的方法，选取海军某水面舰艇有焦虑情绪的军人140名（50≤SAS标准分＜70，不符合DSM-IV的焦虑症诊断标准）随机分为干预组和对照组各70人。干预组给予生物反馈放松训练，对照组不进行放松训练，自然安静状态下监测生理指标，即心率（HR）及心率变异性（HRV）频域指标的低频成分（LF）和高频成分（HF）的标准单位（nu），1次/d，每次持续30 min，连续10 d ，共10次。结果每次干预后干预组军人心率都低于干预前，且在第7、8、9、10次自身配对比较差异有显著性意义（P＜0．05），每次
Effects of relaxation training on cursive handwriting of fourth grade students.
Jackson, K; Hughes, H
1978-12-01
A relaxation method of handwriting improvement was examined. The experimental and no-treatment control groups were composed of 10 students receiving a poor rating on handwriting characteristics and the normal control group of 10 was composed of students receiving average ratings. All three groups received nine trials of writing. Only the experimental group received relaxation training during each trial. The handwriting of the experimental group improved significantly while that of the no-treatment control group remained the same. Although the handwriting of the normal control group also improved significantly, at posttest they were no longer significantly different from the experimental group.
Spin relaxation of a short-lived radical in zero magnetic field.
McKenzie, Iain
2011-01-21
A short-lived radical containing only one I = 1/2 nucleus, the muoniated 1,2-dicarboxyvinyl radical dianion, was produced in an aqueous solution by the reaction of muonium with the dicarboxyacetylene dianion. The identity of the radical was confirmed by measuring the muon hyperfine coupling constant (hfcc) by transverse field muon spin rotation spectroscopy and comparing this value with the hfcc obtained from DFT calculations. The muon spin relaxation rate of this radical was measured as a function of temperature in zero magnetic field by the zero field muon spin relaxation technique. The results have been interpreted using the theoretical model of Fedin et al. (J. Chem. Phys., 2003, 118, 192). The muon spin polarization decreases exponentially with time after muon implantation and the temperature dependence of the spin relaxation rate indicates that the dominant relaxation mechanism is the modulation of the anisotropic hyperfine interaction due to molecular rotation. The effective radius of the radical in solution was determined to be 1.12 ± 0.04 nm from the dependence of the muon spin relaxation rate on the temperature and viscosity of the solution, and is approximately 3.6 times larger than the value obtained from DFT calculations.
Relaxed Linearized Algorithms for Faster X-Ray CT Image Reconstruction.
Nien, Hung; Fessler, Jeffrey A
2016-04-01
Statistical image reconstruction (SIR) methods are studied extensively for X-ray computed tomography (CT) due to the potential of acquiring CT scans with reduced X-ray dose while maintaining image quality. However, the longer reconstruction time of SIR methods hinders their use in X-ray CT in practice. To accelerate statistical methods, many optimization techniques have been investigated. Over-relaxation is a common technique to speed up convergence of iterative algorithms. For instance, using a relaxation parameter that is close to two in alternating direction method of multipliers (ADMM) has been shown to speed up convergence significantly. This paper proposes a relaxed linearized augmented Lagrangian (AL) method that shows theoretical faster convergence rate with over-relaxation and applies the proposed relaxed linearized AL method to X-ray CT image reconstruction problems. Experimental results with both simulated and real CT scan data show that the proposed relaxed algorithm (with ordered-subsets [OS] acceleration) is about twice as fast as the existing unrelaxed fast algorithms, with negligible computation and memory overhead.
Energy Technology Data Exchange (ETDEWEB)
Korzhnev, Dmitry M.; Mittermaier, Anthony K.; Kay, Lewis E. [University of Toronto, Contribution from the Protein Engineering Network Centers of Excellence and the Departments of Medical Genetics, Biochemistry and Chemistry (Canada)], E-mail: kay@pound.med.utoronto.ca
2005-04-15
Artifacts associated with the measurement of methyl {sup 1}H single quantum CPMG-based relaxation dispersion profiles are described. These artifacts arise due to the combination of cross-correlated spin relaxation effects involving intra-methyl {sup 1}H-{sup 1}H dipolar interactions and imperfections in {sup 1}H refocusing pulses that are applied during CPMG intervals that quantify the effects of chemical exchange on measured transverse relaxation rates. As a result substantial errors in extracted exchange parameters can be obtained. A simple 'work-around' is presented where the {sup 1}H chemical shift difference between the exchanging states is extracted from a combination of {sup 13}C single quantum and {sup 13}C-{sup 1}H multiple quantum dispersion profiles. The approach is demonstrated with an application to a folding/unfolding reaction involving a G48M mutant Fyn SH3 domain.
Decoherence can relax cosmic acceleration
Energy Technology Data Exchange (ETDEWEB)
Markkanen, Tommi [Department of Physics, King’s College London,Strand, London WC2R 2LS (United Kingdom)
2016-11-11
In this work we investigate the semi-classical backreaction for a quantised conformal scalar field and classical vacuum energy. In contrast to the usual approximation of a closed system, our analysis includes an environmental sector such that a quantum-to-classical transition can take place. We show that when the system decoheres into a mixed state with particle number as the classical observable de Sitter space is destabilized, which is observable as a gradually decreasing Hubble rate. In particular we show that at late times this mechanism can drive the curvature of the Universe to zero and has an interpretation as the decay of the vacuum energy demonstrating that quantum effects can be relevant for the fate of the Universe.
Decoherence Can Relax Cosmic Acceleration
Markkanen, Tommi
2016-01-01
In this work we investigate the semi-classical backreaction for a quantised conformal scalar field and classical vacuum energy. In contrast to the usual approximation of a closed system, our analysis includes an environmental sector such that a quantum-to-classical transition can take place. We show that when the environment decoheres the system into a mixed state with particle number as the classical observable de Sitter space is destabilized, which is observable as a gradually decreasing Hubble rate. In particular we show that at late times this mechanism can drive the curvature of the Universe to zero and has an interpretation as the decay of the vacuum energy demonstrating that quantum effects can be relevant for the fate of the Universe.
Decoherence can relax cosmic acceleration
Markkanen, Tommi
2016-11-01
In this work we investigate the semi-classical backreaction for a quantised conformal scalar field and classical vacuum energy. In contrast to the usual approximation of a closed system, our analysis includes an environmental sector such that a quantum-to-classical transition can take place. We show that when the system decoheres into a mixed state with particle number as the classical observable de Sitter space is destabilized, which is observable as a gradually decreasing Hubble rate. In particular we show that at late times this mechanism can drive the curvature of the Universe to zero and has an interpretation as the decay of the vacuum energy demonstrating that quantum effects can be relevant for the fate of the Universe.
Electron spin relaxation in a transition-metal dichalcogenide quantum dot
Pearce, Alexander J.; Burkard, Guido
2017-06-01
We study the relaxation of a single electron spin in a circular quantum dot in a transition-metal dichalcogenide monolayer defined by electrostatic gating. Transition-metal dichalcogenides provide an interesting and promising arena for quantum dot nano-structures due to the combination of a band gap, spin-valley physics and strong spin-orbit coupling. First we will discuss which bound state solutions in different B-field regimes can be used as the basis for qubits states. We find that at low B-fields combined spin-valley Kramers qubits to be suitable, while at large magnetic fields pure spin or valley qubits can be envisioned. Then we present a discussion of the relaxation of a single electron spin mediated by electron-phonon interaction via various different relaxation channels. In the low B-field regime we consider the spin-valley Kramers qubits and include impurity mediated valley mixing which will arise in disordered quantum dots. Rashba spin-orbit admixture mechanisms allow for relaxation by in-plane phonons either via the deformation potential or by piezoelectric coupling, additionally direct spin-phonon mechanisms involving out-of-plane phonons give rise to relaxation. We find that the relaxation rates scale as \\propto B 6 for both in-plane phonons coupling via deformation potential and the piezoelectric effect, while relaxation due to the direct spin-phonon coupling scales independant to B-field to lowest order but depends strongly on device mechanical tension. We will also discuss the relaxation mechanisms for pure spin or valley qubits formed in the large B-field regime.
Yang, Haiqing; Liu, Junfeng; Zhou, Xiaoping
2017-05-01
The relaxation behavior plays an important role in evaluating the long-term safety of the surrounding rock mass. Normally, the characters of the stress relaxation behavior of a rock mass can be described as the time-dependent rheological crack propagation features. Based on the subcritical crack growth parameters obtained in the double-torsion experiment, the stress relaxation behavior of pre-cracked granite column specimens is presented. The results of the stress relaxation tests indicate that for a certain confining pressure level, the increase in the uniaxial strain contributes to the propagation of the rheological cracks. For stress relaxation tests conducted under different confining pressure conditions, the propagation of the rheological cracks depends mainly on the D value of the axial and confining pressures. Specifically, the rheological cracks tend to propagate more sufficiently with a higher D value. The experimental results are in good agreement with the analytical solution, in accordance with the Burgers model. Furthermore, the results of the stress relaxation tests conducted under different unloading rates show that the relaxation behavior of the studied material tends to be more obvious for a relatively lower unloading rate of the confining pressure. Finally, the failure patterns obtained under stress relaxation and traditional tests are compared. In detail, for the specimens in the traditional triaxial compression test, the fracture is caused by the abrupt coalescence of the wing cracks and the failure is tensile-shear mixed mode, whereas during the stress relaxation test, the failure is transformed into the smooth coalescence of the tensile rheological cracks. The present research can increase the understanding of the relaxation behavior of hard rock under different engineering environments.
Collection Development: Relaxation & Meditation, September 1, 2010
Lettus, Dodi
2010-01-01
One of the first books to document the relationship between stress and physical and emotional health was "The Relaxation Response" by Herbert Benson, M.D., with Miriam Z. Klipper. Originally published in 1975, the book grew out of Benson's observations as a cardiologist and his research as a fellow at Harvard Medical School. Benson's study of…
BRIEF REPORT: The colour relaxation equation
Xiaofei, Zhang; Jiarong, Li
1996-03-01
Colour diffusion in quark - gluon plasma (QGP) is investigated from the transport equations of QGP. The pure non-Abelian collision term describing the colour diffusion in QGP is obtained, the expression for colour relaxation time is derived and the physical picture of the colour diffusion in QGP is shown.
Control linearity and jitter of relaxation oscillators
Gierkink, Sander Laurentius Johannes
1999-01-01
The body of this thesis (chapters 3,4 and 5) deals with the analysis and improvement of a specific class of voltage- or current controlled oscillators (VCO’s respectively CCO’s) called relaxation oscillators. Before going into detail on this particular class of oscillators, first the function and ap
Relaxation for Children. (Revised and Expanded Edition.)
Rickard, Jenny
Intended as a guide to reduce negative stress in children, this book suggests relaxation and meditation techniques to help children cope with stressful events. Part 1 provides an introduction to the format of the book. Part 2 contains summaries of the 10 sessions that make up the program. Each session has six sequential stages in which students…
Relaxation Processes in Nonlinear Optical Polymer Films
Directory of Open Access Journals (Sweden)
S.N. Fedosov
2010-01-01
Full Text Available Dielectric properties of the guest-host polystyrene/DR1 system have been studied by the AC dielectric spectroscopy method at frequencies from 1 Hz to 0,5 MHz and by the thermally stimulated depolarization current (TSDC method from – 160 to 0 °C. The relaxation peaks at infra-low frequencies from 10 – 5to 10–2 Hz were also calculated using the Hamon’s approximation. Three relaxation processes, namely, α, β and δ ones were identified from the TSDC peaks, while the ε''(fdependence showed a non-Debye ρ-peak narrowing with temperature. The activation energy of the α-relaxation appeared to be 2,57 eV, while that of the γ-process was 0,52 eV. Temperature dependence of the relaxation time is agreed with the Williams-Landel-Ferry model. The ε''(fpeaks were fitted to Havriliak-Negami’s expression and the corresponding distribution parameters were obtained.
Collection Development: Relaxation & Meditation, September 1, 2010
Lettus, Dodi
2010-01-01
One of the first books to document the relationship between stress and physical and emotional health was "The Relaxation Response" by Herbert Benson, M.D., with Miriam Z. Klipper. Originally published in 1975, the book grew out of Benson's observations as a cardiologist and his research as a fellow at Harvard Medical School. Benson's study of…
Redheffer representations and relaxed commutant lifting
ter Horst, S.
2011-01-01
It is well known that the solutions of a (relaxed) commutant lifting problem can be described via a linear fractional representation of the Redheffer type. The coefficients of such Redheffer representations are analytic operator-valued functions defined on the unit disc D of the complex plane. In th
Vibrational relaxation of pure liquid water
Lindner, J; Vohringer, P; Pshenichnikov, MS; Cringus, D; Wiersma, DA; Mostovoy, M; Vöhringer, Peter; Pshenichnikov, Maxim S.
2006-01-01
Multicolor infrared ultrafast spectroscopy is applied to investigate the vibrational relaxation dynamics in liquid water at room temperature. In a sequence of experiments, both the stretching and the bending mode are photoexcited and probed. A unified model, capable of the reproduction of as much as
Relaxation Treatment for Insomnia: A Component Analysis.
Woolfolk, Robert L.; McNulty, Terrence F.
1983-01-01
Compared four relaxation treatments for sleep onset insomnia with a waiting-list control. Treatments varied in presence or absence of muscular tension-release instructions and in foci of attention. Results showed all treatment conditions reduced latency of sleep onset and fatigue; visual focusing best reduced the number of nocturnal awakenings.…
Generalized approach to non-exponential relaxation
Indian Academy of Sciences (India)
R M Pickup; R Cywinski; C Pappas; P Fouquet; B Farago; P Falus
2008-11-01
Non-exponential relaxation is a universal feature of systems as diverse as glasses, spin glasses, earthquakes, financial markets and the universe. Complex relaxation results from hierarchically constrained dynamics with the strength of the constraints being directly related to the form of the relaxation, which changes from a simple exponential to a stretched exponential and a power law by increasing the constraints in the system. A global and unified approach to non-exponentiality was first achieved by Weron and was further generalized by Brouers and Sotolongo-Costa, who applied the concept of non-extensive entropy introduced by Tsallis to the relaxation of disordered systems. These concepts are now confronted with experimental results on the classical metallic spin glasses CuMn, AuFe and the insulating system EuSrS. The revisited data have also be complemented by new results on several compositions of the classical CuMn spin glass and on systems, like CoGa and CuCo, the magnetic behaviour of which is believed to arise from magnetic clusters and should be characteristic for superparamagnetism.
Relaxation dynamics of multilayer triangular Husimi cacti
Galiceanu, Mircea; Jurjiu, Aurel
2016-09-01
We focus on the relaxation dynamics of multilayer polymer structures having, as underlying topology, the Husimi cactus. The relaxation dynamics of the multilayer structures is investigated in the framework of generalized Gaussian structures model using both Rouse and Zimm approaches. In the Rouse type-approach, we determine analytically the complete eigenvalues spectrum and based on it we calculate the mechanical relaxation moduli (storage and loss modulus) and the average monomer displacement. First, we monitor these physical quantities for structures with a fixed generation number and we increase the number of layers, such that the linear topology will smoothly come into play. Second, we keep constant the size of the structures, varying simultaneously two parameters: the generation number of the main layer, G, and the number of layers, c. This fact allows us to study in detail the crossover from a pure Husimi cactus behavior to a predominately linear chain behavior. The most interesting situation is found when the two limiting topologies cancel each other. For this case, we encounter in the intermediate frequency/time domain regions of constant slope for different values of the parameter set (G, c) and we show that the number of layers follows an exponential-law of G. In the Zimm-type approach, which includes the hydrodynamic interactions, the quantities that describe the mechanical relaxation dynamics do not show scaling behavior as in the Rouse model, except the limiting case, namely, a very high number of layers and low generation number.
Noise in (double) relaxation oscillation SQUIDs
Adelerhof, Derk Jan; Adelerhof, Derk Jan; Flokstra, Jakob; Rogalla, Horst
1994-01-01
We have modelled the effect of two intrinsic noise sources on the flux noise spectral density of (Double) Relaxation Oscillation SQUIDs ((D)ROSs) based on hysteretic Josephson tunnel junctions. An important noise source is the spread in the critical current of the SQUID due to thermal fluctuations.
Reactor flush time correction in relaxation experiments
den Otter, M.W.; Bouwmeester, Henricus J.M.; Boukamp, Bernard A.; Verweij, H.
2001-01-01
The present paper deals with the analysis of experimental data from conductivity relaxation experiments. It is shown that evaluation of the chemical diffusion and surface transfer coefficients for oxygen by use of this technique is possible only if accurate data for the conductivity transient can be
Collisionless relaxation in beam-plasma systems
Energy Technology Data Exchange (ETDEWEB)
Backhaus, Ekaterina Yu. [Univ. of California, Berkeley, CA (United States)
2001-01-01
This thesis reports the results from the theoretical investigations, both numerical and analytical, of collisionless relaxation phenomena in beam-plasma systems. Many results of this work can also be applied to other lossless systems of plasma physics, beam physics and astrophysics. Different aspects of the physics of collisionless relaxation and its modeling are addressed. A new theoretical framework, named Coupled Moment Equations (CME), is derived and used in numerical and analytical studies of the relaxation of second order moments such as beam size and emittance oscillations. This technique extends the well-known envelope equation formalism, and it can be applied to general systems with nonlinear forces. It is based on a systematic moment expansion of the Vlasov equation. In contrast to the envelope equation, which is derived assuming constant rms beam emittance, the CME model allows the emittance to vary through coupling to higher order moments. The CME model is implemented in slab geometry in the absence of return currents. The CME simulation yields rms beam sizes, velocity spreads and emittances that are in good agreement with particle-in-cell (PIC) simulations for a wide range of system parameters. The mechanism of relaxation is also considered within the framework of the CME system. It is discovered that the rapid relaxation or beam size oscillations can be attributed to a resonant coupling between different modes of the system. A simple analytical estimate of the relaxation time is developed. The final state of the system reached after the relaxation is complete is investigated. New and accurate analytical results for the second order moments in the phase-mixed state are obtained. Unlike previous results, these connect the final values of the second order moments with the initial beam mismatch. These analytical estimates are in good agreement with the CME model and PIC simulations. Predictions for the final density and temperature are developed that show
The short-time intramolecular dynamics of solutes in liquids. II. Vibrational population relaxation
Goodyear, Grant; Stratt, Richard M.
1997-08-01
Events such as the vibrational relaxation of a solute are often well described by writing an effective equation of motion—a generalized Langevin equation—which expresses the surrounding medium's influence on the intramolecular dynamics in terms of a friction and a fluctuating force acting on the solute. These quantities, though, can be obtained from the instantaneous normal modes (INMs) of the system when the relaxation takes place in a fluid, suggesting that we should be able to analyze in some detail the solvent motions driving the relaxation, at least for short times. In this paper we show that this promise can indeed be realized for the specific case of a vibrating diatomic molecule dissolved in an atomic solvent. Despite the relatively long times typical of vibrational population relaxation, it turns out that understanding the behavior of the vibrational friction at the short times appropriate to INMs (a few hundred femtoseconds) often suffices to predict T1 times. We use this observation to probe the dependence of these relaxation rates on thermodynamic conditions and to look at the molecular mechanisms underlying the process. We find that raising the temperature at any given density or raising the density at any given temperature will invariably increase the rate of energy relaxation. However, since these two trends may be in conflict in a typical constant-pressure laboratory experiment, we also find that it is possible to make sense of the "anomalous" inverted temperature dependence recently seen experimentally. We find, as well, that the INM theory—which has no explicit collisions built into it—predicts exactly the same density dependence as the venerable independent-binary-collision (IBC) theory (an intriguing result in view of recent claims that experimental observations of this kind of dependence provide support for the IBC theory). The actual mechanisms behind vibrational population relaxation are revealed by looking in detail at the
O:H-O Bond Anomalous Relaxation Resolving Mpemba Paradox
Huang, Xi Zhang Yongli; Sun, Chang Q
2013-01-01
We demonstrate that the Mpemba paradox arises intrinsically from the release rate of energy initially stored in the covalent H-O part of the O:H-O bond in water albeit experimental conditions. Generally, heating raises the energy of a substance by lengthening and softening all bonds involved. However, the O:H nonbond in water follows actively the general rule of thermal expansion and drives the H-O covalent bond to relax oppositely in length and energy because of the inter-electron-electron pair coupling [J Phys Chem Lett 4, 2565 (2013); ibid 4, 3238 (2013)]. Heating stores energy into the H-O bond by shortening and stiffening it. Cooling the water as the source in a refrigerator as a drain, the H-O bond releases its energy at a rate that depends exponentially on the initially storage of energy, and therefore, Mpemba effect happens. This effect is formulated in terms of the relaxation time tau to represent all possible processes of energy loss. Consistency between predictions and measurements revealed that th...
Directory of Open Access Journals (Sweden)
M khani
2005-01-01
Full Text Available Introduction: Invasive diagnostic procedures such as coronary angiography, in most cases, are accompanied by stress and anxiety for patients,which may effect on hemodynamic signs. Materials and Methods:This research, as a quasi experimental study, has the objective to determine the influence of applying methods of relaxation on hemodynamic signs in hospitalized 40 patients, experienciny coronary angiography (CA,, has been studied, in regard to existing conditions and methods of sampling and random allocation to two groups of control and relaxation at 2003 . Data collection tool included demographic and disease related information sheet, as well as record sheets for hemodynamic parameters at intervals of 8-12 and ½ hrs before, during and after the angiography. For relaxation group, the researcher would speak individually about the influence of relaxation, the day before angiography; Then with the aid of client himself/herself, performed relaxation instances in a single bout, and eventually asked client to perform relaxation technique 2-3 times before going for angiography. In control group was attended in the usual manner preangiographically. Homodynamic parameters were measured in both groups 8-12 and ½ hrs, before during and after CA. Afterward, resulted data were analyzed statistically by T-Test Chi-squre. Results: With T-Test, respiratory rates½ hrs, beforeAngiography, diastolic blood pressure and Respiratory Rate after Angiography showed statisticaly significant difference between two groups (P0.05.but most of parameters showed clinically significant difference between two groups. Conclusion: Therfore it is offered that relaxation method is applied after invasive procedures.
Nuclear magnetic relaxation by the dipolar EMOR mechanism: Three-spin systems
Chang, Zhiwei; Halle, Bertil
2016-07-01
In aqueous systems with immobilized macromolecules, including biological tissue, the longitudinal spin relaxation of water protons is primarily induced by exchange-mediated orientational randomization (EMOR) of intra- and intermolecular magnetic dipole-dipole couplings. Starting from the stochastic Liouville equation, we have developed a non-perturbative theory that can describe relaxation by the dipolar EMOR mechanism over the full range of exchange rates, dipole couplings, and Larmor frequencies. Here, we implement the general dipolar EMOR theory for a macromolecule-bound three-spin system, where one, two, or all three spins exchange with the bulk solution phase. In contrast to the previously studied two-spin system with a single dipole coupling, there are now three dipole couplings, so relaxation is affected by distinct correlations as well as by self-correlations. Moreover, relaxation can now couple the magnetizations with three-spin modes and, in the presence of a static dipole coupling, with two-spin modes. As a result of this complexity, three secondary dispersion steps with different physical origins can appear in the longitudinal relaxation dispersion profile, in addition to the primary dispersion step at the Larmor frequency matching the exchange rate. Furthermore, and in contrast to the two-spin system, longitudinal relaxation can be significantly affected by chemical shifts and by the odd-valued ("imaginary") part of the spectral density function. We anticipate that the detailed studies of two-spin and three-spin systems that have now been completed will provide the foundation for developing an approximate multi-spin dipolar EMOR theory sufficiently accurate and computationally efficient to allow quantitative molecular-level interpretation of frequency-dependent water-proton longitudinal relaxation data from biophysical model systems and soft biological tissue.
Multi-scales nuclear spin relaxation of liquids in porous media
Korb, Jean-Pierre
2010-03-01
The magnetic field dependence of the nuclear spin-lattice relaxation rate 1/T(ω) is a rich source of dynamical information for characterizing the molecular dynamics of liquids in confined environments. Varying the magnetic field changes the Larmor frequency ω, and thus the fluctuations to which the nuclear spin relaxation is sensitive. Moreover, this method permits a more complete characterization of the dynamics than the usual measurements as a function of temperature at fixed magnetic field strength, because many common solvent liquids have phase transitions that may alter significantly the character of the dynamics over the temperature range usually studied. Further, the magnetic field dependence of the spin-lattice relaxation rate, 1/T(ω), provides a good test of the theories that relate the measurement to the microdynamical behavior of the liquid. This is especially true in spatially confined systems where the effects of reduced dimensionality may force more frequent reencounters of the studied proton spin-bearing molecules with paramagnetic impurities at the pore surfaces that may alter the correlation functions that enter the relaxation equations in a fundamental way. We show by low field NMR relaxation that changing the amount of surface paramagnetic impurities leads to striking different pore-size dependences of the relaxation times T and T of liquids in pores. Here, we focus mainly on high surface area porous materials including calibrated porous silica glasses, granular packings, heterogeneous catalytic materials, cement-based materials and natural porous materials such as clay minerals and rocks. Recent highlights NMR relaxation works are reviewed for these porous materials, like continuous characterization of the evolving microstructure of various cementitious materials and measurement of wettability in reservoir carbonate rocks. Although, the recent applications of 2-dimensional T-T and T-z-store-T correlation experiments for characterization of
Ziv, Naomi; Rotem, Tomer; Arnon, Zahi; Haimov, Iris
2008-01-01
A large percentage of older people suffer from chronic insomnia, affecting many aspects of life quality and well-being. Although insomnia is most often treated with medication, a growing number of studies demonstrate the efficiency of various relaxation techniques. The present study had three aims: first, to compare two relaxation techniques--music relaxation and progressive muscular relaxation--on various objective and subjective measures of sleep quality; second, to examine the effect of these techniques on anxiety and depression; and finally, to explore possible relationships between the efficiency of both techniques and personality variables. Fifteen older adults took part in the study. Following one week of base-line measurements of sleep quality, participants followed one week of music relaxation and one week of progressive muscular relaxation before going to sleep. Order of relaxation techniques was controlled. Results show music relaxation was more efficient in improving sleep. Sleep efficiency was higher after music relaxation than after progressive muscular relaxation. Moreover, anxiety was lower after music relaxation. Progressive muscular relaxation was related to deterioration of sleep quality on subjective measures. Beyond differences between the relaxation techniques, extraverts seemed to benefit more from both music and progressive muscular relaxation. The advantage of non-pharmacological means to treat insomnia, and the importance of taking individual differences into account are discussed.
Traaseth, Nathaniel J; Chao, Fa-An; Masterson, Larry R; Mangia, Silvia; Garwood, Michael; Michaeli, Shalom; Seelig, Burckhard; Veglia, Gianluigi
2012-06-01
NMR relaxation methods probe biomolecular motions over a wide range of timescales. In particular, the rotating frame spin-lock R(1ρ) and Carr-Purcell-Meiboom-Gill (CPMG) R(2) experiments are commonly used to characterize μs to ms dynamics, which play a critical role in enzyme folding and catalysis. In an effort to complement these approaches, we introduced the Heteronuclear Adiabatic Relaxation Dispersion (HARD) method, where dispersion in rotating frame relaxation rate constants (longitudinal R(1ρ) and transverse R(2ρ)) is created by modulating the shape and duration of adiabatic full passage (AFP) pulses. Previously, we showed the ability of the HARD method to detect chemical exchange dynamics in the fast exchange regime (k(ex)∼10(4)-10(5) s(-1)). In this article, we show the sensitivity of the HARD method to slower exchange processes by measuring R(1ρ) and R(2ρ) relaxation rates for two soluble proteins (ubiquitin and 10C RNA ligase). One advantage of the HARD method is its nominal dependence on the applied radio frequency field, which can be leveraged to modulate the dispersion in the relaxation rate constants. In addition, we also include product operator simulations to define the dynamic range of adiabatic R(1ρ) and R(2ρ) that is valid under all exchange regimes. We conclude from both experimental observations and simulations that this method is complementary to CPMG-based and rotating frame spin-lock R(1ρ) experiments to probe conformational exchange dynamics for biomolecules. Finally, this approach is germane to several NMR-active nuclei, where relaxation rates are frequency-offset independent. Copyright © 2012 Elsevier Inc. All rights reserved.
Single-Molecule Imaging Reveals Topology Dependent Mutual Relaxation of Polymer Chains
Abadi, Maram
2015-08-24
The motion and relaxation of linear and cyclic polymers under entangled conditions are investigated by means of a newly developed single-molecule tracking technique, cumulative-area (CA) tracking. CA tracking enables simultaneous quantitative characterization of the diffusion mode, diffusion rate, and relaxation time that have been impossible with a widely used conventional single-molecule localization and tracking method, by analyzing cumulative areas occupied by the moving molecule. Using the novel approach, we investigate the motion and relaxation of entangled cyclic polymers, which have been an important but poorly understood question. Fluorescently labeled 42 kbp linear or cyclic tracer dsDNAs in concentrated solutions of unlabeled linear or cyclic DNAs are used as model systems. We show that CA tracking can explicitly distinguish topology-dependent diffusion mode, rate, and relaxation time, demonstrating that the method provides an invaluable tool for characterizing topological interaction between the entangled chains. We further demonstrate that the current models proposed for the entanglement between cyclic polymers which are based on cyclic chains moving through an array of fixed obstacles cannot correctly describe the motion of the cyclic chain under the entangled conditions. Our results rather suggest the mutual relaxation of the cyclic chains, which underscore the necessity of developing a new model to describe the motion of cyclic polymer under the entangled conditions based on the mutual interaction of the chains.
Relaxation with Immersive Natural Scenes Presented Using Virtual Reality.
Anderson, Allison P; Mayer, Michael D; Fellows, Abigail M; Cowan, Devin R; Hegel, Mark T; Buckey, Jay C
2017-06-01
Virtual reality (VR) can provide exposure to nature for those living in isolated confined environments. We evaluated VR-presented natural settings for reducing stress and improving mood. There were 18 participants (9 men, 9 women), ages 32 ± 12 yr, who viewed three 15-min 360° scenes (an indoor control, rural Ireland, and remote beaches). Subjects were mentally stressed with arithmetic before scenes. Electrodermal activity (EDA) and heart rate variability measured psycho-physiological arousal. The Positive and Negative Affect Schedule and the 15-question Modified Reality Judgment and Presence Questionnaire (MRJPQ) measured mood and scene quality. Reductions in EDA from baseline were greater at the end of the natural scenes compared to the control scene (-0.59, -0.52, and 0.32 μS, respectively). The natural scenes reduced negative affect from baseline ( 1.2 and 1.1 points), but the control scene did not ( 0.4 points). MRJPQ scores for the control scene were lower than both natural scenes (4.9, 6.7, and 6.5 points, respectively). Within the two natural scenes, the preferred scene reduced negative affect ( 2.4 points) more than the second choice scene ( 1.8 points) and scored higher on the MRJPQ (6.8 vs. 6.4 points). Natural scene VR provided relaxation both objectively and subjectively, and scene preference had a significant effect on mood and perception of scene quality. VR may enable relaxation for people living in isolated confined environments, particularly when matched to personal preferences.Anderson AP, Mayer MD, Fellows AM, Cowan DR, Hegel MT, Buckey JC. Relaxation with immersive natural scenes presented using virtual reality. Aerosp Med Hum Perform. 2017; 88(6):520526.
The effects of cyclic tensile and stress-relaxation tests on porcine skin.
Remache, D; Caliez, M; Gratton, M; Dos Santos, S
2017-09-11
When a living tissue is subjected to cyclic stretching, the stress-strain curves show a shift down with the increase in the number of cycles until stabilization. This phenomenon is referred to in the literature as a preconditioning and is performed to obtain repeatable and predictable measurements. Preconditioning has been routinely performed in skin tissue tests; however, its effects on the mechanical properties of the material such as viscoelastic response, tangent modulus, sensitivity to strain rate, the stress relaxation rate, etc….remain unclear. In addition, various physical interpretations of this phenomenon have been proposed and there is no general agreement on its origin at the microscopic or mesoscopic scales. The purpose of this study was to investigate the effect of the cyclical stretching and the stress-relaxation tests on the mechanical properties of the porcine skin. Cyclic uniaxial tensile tests at large and constant strain were performed on different skin samples. The change in the reaction force, and skin's tangent modulus as a function of the number of cycles, as well as the strain rate effect on the mechanical behavior of skin samples after cycling were investigated. Stress-relaxation tests were also performed on skin samples. The change in the reaction force as a function of relaxation time and the strain rate effect on the mechanical behavior of skin samples after the stress-relaxation were investigated. The mechanical behavior of a skin sample under stress-relaxation test was modeled using a combination of hyperelasticity and viscoelasticity. Overall, the results showed that the mechanical behavior of the skin was strongly influenced by cycling and stress relaxation tests. Indeed, it was observed that the skin's resistance decreased by about half for two hours of cycling; the tangent modulus degraded by nearly 30% and skin samples became insensitive to the strain rates and accumulated progressively an inelastic deformation over time during
Turton, David A; Sonnleitner, Thomas; Ortner, Alex; Walther, Markus; Hefter, Glenn; Seddon, Kenneth R; Stana, Simona; Plechkova, Natalia V; Buchner, Richard; Wynne, Klaas
2012-01-01
The structure and dynamics of ionic liquids (ILs) are unusual due to the strong interactions between the ions and counter ions. These microscopic properties determine the bulk transport properties critical to applications of ILs such as advanced fuel cells. The terahertz dynamics and slower relaxations of simple alkylammonium nitrate protic ionic liquids (PILs) are here studied using femtosecond optical Kerr-effect spectroscopy, dielectric relaxation spectroscopy, and terahertz time-domain spectroscopy. The observed dynamics give insight into more general liquid behaviour while comparison with glass-forming liquids reveals an underlying power-law decay and relaxation rates suggest supramolecular structure and nanoscale segregation.
[Brain activity during different stages of the relaxation process].
gorev, A S; Kovaleva, A V; Panova, E N; Gorbacheva, A K
2012-01-01
A group of adults participated in experiment in which they were asked to reach relaxed state by using relaxation techniques (active relaxation) and to maintain this state without any technique (passive relaxation). Some changes of EEG-characteristics during relaxation were analyzed. This experiment includes four situations (different functional states): baselinel, active relaxation, passive relaxation, baseline2. EEG was recorded from 10 cortical leads: O1, O2, TPO (left and right), P3, P4, C3, C4, F3 and F4. A comparative EEG analysis was done for 10 frequency bands from 5 to 40 Hz. In each experimental situation we revealed general trends for EEG parameters and also some specific changes in EEG, which characterized brain organization during passive and active relaxed states.
Masenda, H.; Geburt, S.; Bharuth-Ram, K.; Naidoo, D.; Gunnlaugsson, H. P.; Johnston, K.; Mantovan, R.; Mølholt, T. E.; Ncube, M.; Shayestehaminzadeh, S.; Gislason, H. P.; Langouche, G.; Ólafsson, S.; Ronning, C.
2016-12-01
Emission Mössbauer Spectroscopy following the implantation of radioactive precursor isotope 57Mn+ ( T 1/2= 1.5 min) into ZnO single crystals at ISOLDE/CERN shows that a large fraction of 57Fe atoms produced in the 57Mn beta decay is created as paramagnetic Fe3+ with relatively long spin-lattice relaxation times. Here we report on ZnO pre-implanted with 56Fe to fluences of 2×1013, 5×10 13 and 8 × 1013 ions/cm2 in order to investigate the dependence of the paramagnetic relaxation rate of Fe3+ on fluence. The spectra are dominated by magnetic features displaying paramagnetic relaxation effects. The extracted spin-lattice relaxation rates show a slight increase with increasing ion fluence at corresponding temperatures and the area fraction of Fe3+ at room temperature reaches a maximum contribution of 80(3)% in the studied fluence range.
Bertisch, Suzanne M; Wells, Rebecca Erwin; Smith, Michael T; McCarthy, Ellen P
2012-12-15
Though relaxation training is recommended for insomnia, national patterns of use remain unknown. Similarly, rates of complementary and alternative medicine (CAM) use by adults with insomnia are not well established. We sought to elucidate the patterns and reasons for use of relaxation techniques and CAM use by adults with insomnia symptoms. We used the 2007 National Health Interview Survey (n = 23,358) to estimate prevalence of use among adults by self-reported insomnia symptom status. Among adults reporting insomnia symptoms (n = 4,415), we examined reasons for use and disclosure to medical professionals. We employed logistic regression to determine the adjusted associations between relaxation techniques use, CAM use, and insomnia symptoms. Among adults with insomnia symptoms, 23% used relaxation techniques and 45% used CAM annually. After adjustment, adults with insomnia symptoms had higher likelihood of using relaxation techniques (aOR 1.48, 95% CI 1.32, 1.66) and CAM (aOR 1.29, 95% CI 1.15, 1.44) compared with adults without insomnia. Deep breathing exercise was the most commonly used relaxation technique. Fewer than 2% of adults with insomnia used CAM specifically for insomnia. Only 26% of adults with insomnia symptoms disclosed their relaxation techniques use to medical professionals. Being male, lower educational and physical activity levels, income relaxation techniques use among adults with insomnia symptoms. While adults with insomnia symptoms commonly use relaxation techniques and CAM, few are using for their insomnia. Facilitating discussions about relaxation techniques may foster targeted use for insomnia.
The Application of Stress-Relaxation Test to Life Assessment of T911/T22 Weld Metal
Cao, Tieshan; Zhao, Jie; Cheng, Congqian; Li, Huifang
2016-03-01
A dissimilar weld metal was obtained through submerged arc welding of a T911 steel to a T22 steel, and its creep property was explored by stress-relaxation test assisted by some conventional creep tests. The creep rate information of the stress-relaxation test was compared to the minimum and the average creep rates of the conventional creep test. Log-log graph showed that the creep rate of the stress-relaxation test was in a linear relationship with the minimum creep rate of the conventional creep test. Thus, the creep rate of stress-relaxation test could be used in the Monkman-Grant relation to calculate the rupture life. The creep rate of the stress-relaxation test was similar to the average creep rate, and thereby the rupture life could be evaluated by a method of "time to rupture strain." The results also showed that rupture life which was assessed by the Monkman-Grant relation was more accurate than that obtained through the method of "time to rupture strain."
Characteristics of the secondary relaxation process in soft colloidal suspensions
Saha, Debasish; Joshi, Yogesh M.; Bandyopadhyay, Ranjini
2015-11-01
A universal secondary relaxation process, known as the Johari-Goldstein (J-G) β-relaxation process, appears in glass formers. It involves all parts of the molecule and is particularly important in glassy systems because of its very close relationship with the α-relaxation process. However, the absence of a J-G β-relaxation mode in colloidal glasses raises questions regarding its universality. In the present work, we study the microscopic relaxation processes in Laponite suspensions, a model soft glassy material, by dynamic light scattering (DLS) experiments. α- and β-relaxation timescales are estimated from the autocorrelation functions obtained by DLS measurements for Laponite suspensions with different concentrations, salt concentrations and temperatures. Our experimental results suggest that the β-relaxation process in Laponite suspensions involves all parts of the constituent Laponite particle. The ergodicity breaking time is also seen to be correlated with the characteristic time of the β-relaxation process for all Laponite concentrations, salt concentrations and temperatures. The width of the primary relaxation process is observed to be correlated with the secondary relaxation time. The secondary relaxation time is also very sensitive to the concentration of Laponite. We measure primitive relaxation timescales from the α-relaxation time and the stretching exponent (β) by applying the coupling model for highly correlated systems. The order of magnitude of the primitive relaxation time is very close to the secondary relaxation time. These observations indicate the presence of a J-G β-relaxation mode for soft colloidal suspensions of Laponite.
Relaxation of Magnetic Nanoparticle Chain without Applied Field*
Institute of Scientific and Technical Information of China (English)
HE Liang-Ming
2011-01-01
The relaxation ofa one-dimensional magnetic nanoparticle linear chain with lattice constant a is investigated in absence of applied field. There is an equilibrium state (or steady state) where all magnetic moments of particles lie along the chain (x-axis), back to which the magnetic nanoparticle chain at other state will relax. It is found that the relaxation time Tx is determined by Tx = 10β × a3. This relaxation is compared with that of single magnetic nanoparticle system.
Stress relaxation of narrow molar mass distribution polystyrene following uniaxial extension
DEFF Research Database (Denmark)
Nielsen, Jens Kromann; Rasmussen, Henrik K.; Hassager, Ole
2008-01-01
The stress in the startup of uniaxial elongational flow until steady state, followed by stress relaxation, has been measured for a narrow molar mass distribution polystyrene inelt with a molecular weight of 145 kg/mol. The experiments are conducted on a filament stretching rheometer, where a clos...... rates. (C) 2008 The Society of Rheology....
Can Children with AD/HD Learn Relaxation and Breathing Techniques through Biofeedback Video Games?
Amon, Krestina L.; Campbell, Andrew
2008-01-01
This study investigated "The Journey to Wild Divine" as a biofeedback management tool teaching breathing and relaxation skills to children with Attention-Deficit/Hyperactivity Disorder (AD/HD). The children played the game by manipulating their heart rate using breathing techniques taught in the game, measured through three finger sensors. Parents…
Relaxation of the electron spin in quantum dots via one- and two-phonon processes
Energy Technology Data Exchange (ETDEWEB)
Calero, C. [Department of Physics and Astronomy, Lehman College, City University of New York, 250 Bedford Park Boulevard West, Bronx, NY 10468-1589 (United States)]. E-mail: carlos.calero-borrallo@lehman.cuny.edu; Chudnovsky, E.M. [Department of Physics and Astronomy, Lehman College, City University of New York, 250 Bedford Park Boulevard West, Bronx, NY 10468-1589 (United States); Garanin, D.A. [Department of Physics and Astronomy, Lehman College, City University of New York, 250 Bedford Park Boulevard West, Bronx, NY 10468-1589 (United States)
2007-09-15
We have studied direct and Raman processes of the decay of electron spin states in a quantum dot via radiation of phonons corresponding to elastic twists. Universal dependence of the spin relaxation rate on the strength and direction of the magnetic field has been obtained in terms of the electron gyromagnetic tensor and macroscopic elastic constants of the solid.
颗粒介质弹性的弛豫∗%Relaxation of granular elasticity
Institute of Scientific and Technical Information of China (English)
孙其诚; 刘传奇; 周公旦
2015-01-01
In granular materials, particles constitute a complex force chains network through contact with each other, and elastic energies are stored due to deformation of particles. This elastic behavior is macroscopic manifestation of inter-particle contacts. Elastic constants or elastic moduli are of fundamental importance for granular material. Due to the hyper-static property of inter-particle forces, the bulk elastic energy stored in the contacts is metastable in the viewpoint of energy landscape, i.e. a high energy state may approaches a more stable state (i.e. relatively lower state) under the action of external perturbations or internal stress, resulting in the elastic modulus reduction. This process is the so-called elasticity relaxation. It may be more obvious in granular materials. The time-dependent behavior of granular materials, especially the creep, has been studied in experiments and numerical simulations, while the stress relaxation has few reported investigations. Stress relaxation is defined as the process in vohich the initial strain is maintained and the stress decays with the time. From energetic viewpoint, elastic energy is stored in the deformation of particles. The granular system is in a metastable state when confined in a state easy to break the balance. Generally speaking, the shape and grading of particles, volume fraction, surface friction properties, initial structure features, ageing time, loading strain rate will all play important roles in stress relaxation. In this work, it is believed that the elastic relaxation is the only mechanism to describe the stress relaxation, and the mechanism of it is analyzed from the viewpoint of the potential energy surface. Stress relaxation is calculated by means of the so-called two-granular temperature theory (TGT) we developed previously (Sun Q et al. 2015 Sci. Rep. 5 9652). The stress decays fast at the beginning, then decreases gradually slowly to a stable value. The logarithmic fit is first proposed
Electron-vibration relaxation in oxygen plasmas
Laporta, V.; Heritier, K. L.; Panesi, M.
2016-06-01
An ideal chemical reactor model is used to study the vibrational relaxation of oxygen molecules in their ground electronic state, X3Σg-, in presence of free electrons. The model accounts for vibrational non-equilibrium between the translational energy mode of the gas and the vibrational energy mode of individual molecules. The vibrational levels of the molecules are treated as separate species, allowing for non-Boltzmann distributions of their population. The electron and vibrational temperatures are varied in the range [0-20,000] K. Numerical results show a fast energy transfer between oxygen molecules and free electron, which causes strong deviation of the vibrational distribution function from Boltzmann distribution, both in heating and cooling conditions. Comparison with Landau-Teller model is considered showing a good agreement for electron temperature range [2000-12,000] K. Finally analytical fit of the vibrational relaxation time is given.
Relaxation time estimation in surface NMR
Grunewald, Elliot D.; Walsh, David O.
2017-03-21
NMR relaxation time estimation methods and corresponding apparatus generate two or more alternating current transmit pulses with arbitrary amplitudes, time delays, and relative phases; apply a surface NMR acquisition scheme in which initial preparatory pulses, the properties of which may be fixed across a set of multiple acquisition sequence, are transmitted at the start of each acquisition sequence and are followed by one or more depth sensitive pulses, the pulse moments of which are varied across the set of multiple acquisition sequences; and apply processing techniques in which recorded NMR response data are used to estimate NMR properties and the relaxation times T.sub.1 and T.sub.2* as a function of position as well as one-dimensional and two-dimension distributions of T.sub.1 versus T.sub.2* as a function of subsurface position.
Relaxation Based Electrical Simulation for VLSI Circuits
Directory of Open Access Journals (Sweden)
S. Rajkumar
2012-06-01
Full Text Available Electrical circuit simulation was one of the first CAD tools developed for IC design. The conventional circuit simulators like SPICE and ASTAP were designed initially for the cost effective analysis of circuits containing a few hundred transistors or less. A number of approaches have been used to improve the performances of congenital circuit simulators for the analysis of large circuits. Thereafter relaxation methods was proposed to provide more accurate waveforms than standard circuit simulators with up to two orders of magnitude speed improvement for large circuits. In this paper we have tried to highlights recently used waveform and point relaxation techniques for simulation of VLSI circuits. We also propose a simple parallelization technique and experimentally demonstrate that we can solve digital circuits with tens of million transistors in a few hours.
Electrochemical relaxation at electrically conducting polymers
Nateghi, M. R.; zarandi, M. B.
2008-08-01
In this study, slow relaxation (SR) associated with the electroreduction of polyaniline (PAn) films during polarization to high cathodic potentials was investigated by cyclic voltammetry technique. Anodic voltammetric currents were used as experimental variable to indicate the relaxation occurring in PAn films deposited electrochemically on the Pt electrode surface. The dependence of SR on polymer film thickness, waiting potential, and mobility of the doped anion was investigated. Percolation threshold potential for heteropolyanion doped PAn was estimated to be between 150 and 200 mV depending on polymer thickness on the electrode surface. A new model of the conducting to insulating conversion is described by the percolation theory and mobility gap changes during the process.
Electrochemical relaxation at electrically conducting polymers
Energy Technology Data Exchange (ETDEWEB)
Nateghi, M R [Department of Chemistry, Islamic Azad University, Yazd-Branch, Yazd (Iran, Islamic Republic of); Zarandi, M B [Department of physics, Yazd University, Yazd (Iran, Islamic Republic of)
2008-08-15
In this study, slow relaxation (SR) associated with the electroreduction of polyaniline (PAn) films during polarization to high cathodic potentials was investigated by cyclic voltammetry technique. Anodic voltammetric currents were used as experimental variable to indicate the relaxation occurring in PAn films deposited electrochemically on the Pt electrode surface. The dependence of SR on polymer film thickness, waiting potential, and mobility of the doped anion was investigated. Percolation threshold potential for heteropolyanion doped PAn was estimated to be between 150 and 200 mV depending on polymer thickness on the electrode surface. A new model of the conducting to insulating conversion is described by the percolation theory and mobility gap changes during the process.
Relaxation time estimation in surface NMR
Energy Technology Data Exchange (ETDEWEB)
Grunewald, Elliot D.; Walsh, David O.
2017-03-21
NMR relaxation time estimation methods and corresponding apparatus generate two or more alternating current transmit pulses with arbitrary amplitudes, time delays, and relative phases; apply a surface NMR acquisition scheme in which initial preparatory pulses, the properties of which may be fixed across a set of multiple acquisition sequence, are transmitted at the start of each acquisition sequence and are followed by one or more depth sensitive pulses, the pulse moments of which are varied across the set of multiple acquisition sequences; and apply processing techniques in which recorded NMR response data are used to estimate NMR properties and the relaxation times T.sub.1 and T.sub.2* as a function of position as well as one-dimensional and two-dimension distributions of T.sub.1 versus T.sub.2* as a function of subsurface position.
Multi-region relaxed magnetohydrodynamics with flow
Dennis, G R; Dewar, R L; Hole, M J
2014-01-01
We present an extension of the multi-region relaxed magnetohydrodynamics (MRxMHD) equilibrium model that includes plasma flow. This new model is a generalization of Woltjer's model of relaxed magnetohydrodynamics equilibria with flow. We prove that as the number of plasma regions becomes infinite our extension of MRxMHD reduces to ideal MHD with flow. We also prove that some solutions to MRxMHD with flow are not time-independent in the laboratory frame, and instead have 3D structure which rotates in the toroidal direction with fixed angular velocity. This capability gives MRxMHD potential application to describing rotating 3D MHD structures such as 'snakes' and long-lived modes.
Multi-region relaxed magnetohydrodynamics with flow
Energy Technology Data Exchange (ETDEWEB)
Dennis, G. R., E-mail: graham.dennis@anu.edu.au; Dewar, R. L.; Hole, M. J. [Research School of Physics and Engineering, Australian National University, ACT 0200 (Australia); Hudson, S. R. [Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543 (United States)
2014-04-15
We present an extension of the multi-region relaxed magnetohydrodynamics (MRxMHD) equilibrium model that includes plasma flow. This new model is a generalization of Woltjer's model of relaxed magnetohydrodynamics equilibria with flow. We prove that as the number of plasma regions becomes infinite, our extension of MRxMHD reduces to ideal MHD with flow. We also prove that some solutions to MRxMHD with flow are not time-independent in the laboratory frame, and instead have 3D structure which rotates in the toroidal direction with fixed angular velocity. This capability gives MRxMHD potential application to describing rotating 3D MHD structures such as 'snakes' and long-lived modes.
Braided magnetic fields: equilibria, relaxation and heating
Pontin, D I; Russell, A J B; Hornig, G
2015-01-01
We examine the dynamics of magnetic flux tubes containing non-trivial field line braiding (or linkage), using mathematical and computational modelling. The key results obtained from recent modelling efforts are summarised, in the context of testable predictions for the laboratory. We discuss the existence of braided force-free equilibria, and demonstrate that for a field anchored at perfectly-conducting plates, these equilibria exist and contain current sheets whose thickness scales inversely with the braid complexity - as measured for example by the topological entropy. By contrast, for a periodic domain braided exact equilibria typically do not exist, while approximate equilibria contain thin current sheets. In the presence of resistivity, reconnection is triggered at the current sheets and a turbulent relaxation ensues. We discuss the properties of this relaxation, and in particular the existence of constraints that may mean that the final state is not the linear force-free field predicted by Taylor's hypo...
Relaxation in Technique Leading to New Beginnings().
Koritar, Endre
2016-12-01
This paper explores how standard analytic technique may result in a repetition of past traumatic experiences in the transference and countertransference analytic situation. Relaxation and elasticity of technique can lead to re-integration of previously fragmented ego functions, and in remembering and re-experiencing of previously repressed symbolic representations of fragmenting past traumatic experiences, resulting in neocatharsis and working through, thus healing wounds and scars sustained in self development. This healing process will be described through a detailed depiction of an analytic process introducing relaxation of technique, in a response by the analyst, to the patient's Orpha (self-protective) function. Responsiveness to the patient's implicitly or explicitly expressed needs, in the analytic space, may require a departure from standard technique for a deeper level of dynamic work where symbolization of unrepresented emotional experiences becomes possible.
Institute of Scientific and Technical Information of China (English)
李树志; 熊利泽; 侯立朝; 陈绍洋; 计根林
2001-01-01
目的：研究不同肌肉松弛药用于先心病患者麻醉诱导时对血压和心率的影响。方法：48例择期先天性心脏病矫形手术患者，心功能Ⅱ～Ⅲ级，随机分为6组，每组8例。泮库溴铵、阿曲库铵和维库溴铵（剂量均为0.1 mg/kg）分别合用安定（0.2 mg/kg）和小剂量芬太尼（5 μg/kg）或大剂量芬太尼（10 μg/kg）。记录插管前、后的血压、心率变化。结果：与小剂量芬太尼合用进行麻醉诱导时，泮库溴铵有增快心率作用(P<0.01)，对血压影响不明显，阿曲库铵有明显减慢心率作用和降压作用(P<0.05或P<0.01)，维库溴铵有轻度减慢心率作用(P<0.01)，对血压影响不大；与大剂量芬太尼合用时，泮库溴铵对心率的影响不显著，并引起血压轻度下降(P<0.05)，阿曲库铵仍表现明显有减慢心率作用(P<0.05)，其降压作用的时间有所延长(P<0.05或P<0.01)，维库溴铵减慢心率作用时间有所延长(P<0.01)，并使血压显著下降(P<0.05或P<0.01)。结论：先心病矫治术麻醉诱导时宜选择泮库溴铵和较小剂量芬太尼(5 μg/kg)合用，可减少诱导时心动过缓的发生率。%AIM: To study the effects of different muscle relaxants on blood pressure and heart rate of the patients with congenital heart disease during anesthetic induction. METHODS: Forty-eight patients with Grade Ⅱ～Ⅲ of ASA physical status, scheduled forelective correction surgery for the heart defects, were randomly divided into six groups with 8 cases in each group. 0.1 mg/kg of pancuronium, atracurium or vecuronium was used combined with diazepam 0.2 mg/kg and fentanyl 5 μg/kg or 10 μg/kg respectively. Blood pressure(BP) and heart rate (HR) before and after intubation were recorded in this study. RESULTS: When co-administered with fentanyl 5 μg/kg for anesthetic induction, pancuronium induced an increase in HR (P<0.01) with no significant change in BP, atracurium resulted in slight
RELAXATION TIME LIMITS PROBLEM FOR HYDRODYNAMIC MODELS IN SEMICONDUCTOR SCIENCE
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
In this article, two relaxation time limits, namely, the momentum relaxation time limit and the energy relaxation time limit are considered. By the compactness argument, it is obtained that the smooth solutions of the multidimensional nonisentropic Euler-Poisson problem converge to the solutions of an energy transport model or a drift diffusion model, respectively, with respect to different time scales.
Relaxation Techniques for Handicapped Children: A Review of Literature.
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…
Institute of Scientific and Technical Information of China (English)
年申生; 吴岳嵩; 苏佳灿; 侯铁胜; 张春才
2002-01-01
Objective To observe effects of meshed relaxing short incisions (MRSI) on the content of endothelin (ET) in rat tension skin flap,and to investigate the mechanism of meshed relaxing short incisions(MRSI) on wound healing process of tension skin flap.Method We designed an experimental model to investigate the change of ET content caused by MRSI and observe the distribution of ET in rat skin flap tissue each period of wound healing.In the meantime,the immunohistochemistry and auto image analysis were employed.Results Our results showed:(1) ET positive immunologic reaction granules involved in small vascular endothelial cell in rat skin flap tissue increased with prolonging of time within 3 days;(2) the content of ET in MRSI group were significant lower than that of hypertension group (P< 0.05) .Conclusion The decrease of ET contents may be one of the causes that MRSI improves microcirculation of skin flap, and reduces edema and facilitates healing of skin flap.
Relaxation Criteria for Iterated Traffic Simulations
Kelly, Terence; Nagel, Kai
Iterative transportation microsimulations adjust traveler route plans by iterating between a microsimulation and a route planner. At each iteration, the route planner adjusts individuals' route choices based on the preceding microsimulations. Empirically, this process yields good results, but it is usually unclear when to stop the iterative process when modeling real-world traffic. This paper investigates several criteria to judge relaxation of the iterative process, emphasizing criteria related to traveler decision-making.
Dimension reduction for systems with slow relaxation
Venkataramani, Shankar C; Restrepo, Juan M
2016-01-01
We develop reduced, stochastic models for high dimensional, dissipative dynamical systems that relax very slowly to equilibrium and can encode long term memory. We present a variety of empirical and first principles approaches for model reduction, and build a mathematical framework for analyzing the reduced models. We introduce the notions of universal and asymptotic filters to characterize `optimal' model reductions. We discuss how our methods apply to the practically important problem of modeling oil spills.
p-q growth via relaxation methods
Directory of Open Access Journals (Sweden)
Irene Benedetti
2004-01-01
Full Text Available Local Lipschitz continuity of local minimizers of vectorial integrals ∫Ω f(x,Dudx is proved when f satisfies p-q growth condition and ξ↦f(x,ξ is not convex. The uniform convexity and the radial structure condition with respect to the last variable are assumed only at infinity. In the proof, we use semicontinuity and relaxation results for functionals with nonstandard growth.
Models of Flux Tubes from Constrained Relaxation
Indian Academy of Sciences (India)
Α. Mangalam; V. Krishan
2000-09-01
We study the relaxation of a compressible plasma to an equilibrium with flow. The constraints of conservation of mass, energy, angular momentum, cross-helicity and relative magnetic helicity are imposed. Equilibria corresponding to the energy extrema while conserving these invariants for parallel flows yield three classes of solutions and one of them with an increasing radial density profile, relevant to solar flux tubes is presented.
Active nematic gels as active relaxing solids
Turzi, Stefano S
2017-01-01
I put forward a continuum theory for active nematic gels, defined as fluids or suspensions of orientable rodlike objects endowed with active dynamics, that is based on symmetry arguments and compatibility with thermodynamics. The starting point is our recent theory that models (passive) nematic liquid crystals as relaxing nematic elastomers. The interplay between viscoelastic response and active dynamics of the microscopic constituents is naturally taken into account. By contrast with standar...
Relaxation time measurements by an electronic method.
Brousseau, R.; Vanier, J.
1973-01-01
Description of a simple electronic system that permits the direct measurement of time constants of decaying signals. The system was used in connection with relaxation experiments on hydrogen and rubidium masers and was found to operate well. The use of a computing counter in the systems gives the possibility of making averages on several experiments and obtaining the standard deviation of the results from the mean. The program for the computing counter is given.
Energy Technology Data Exchange (ETDEWEB)
Yanagawa, Yasuhiro; Kimura, Atsuomi; Fujiwara, Hideaki [Osaka Univ., Suita (Japan). Medical School; Kinoshita, Yoshimasa; Hattori, Mineyuki; Hiraga, Takashi; Iida, Hidehiro
2001-04-01
Using laser optical pumping, the nuclear spin polarization of noble gases can be strongly enhanced. The purpose of this study was to make a simple apparatus that can provide hyperpolarized {sup 129}Xe gas, which can then be used in an attempt to obtain magnetic resonance imaging (MRI). We would also like to study the relaxation behavior of hyperpolarized {sup 129}Xe gas through the measurement of the relaxation time. First, we demonstrated that hyperpolarized {sup 129}Xe gas can be applied to magnetic resonance imaging of the stomach, by using a rat as a model. This was performed under a 4.7 T magnet field using the following imaging parameters for the hyperpolarized {sup 129}Xe gas: TR=50 ms, TE=15 ms, FOV=10 x 10 cm{sup 2}, matrix size 64 x 64, THK=2.54 cm. By using these parameters, we were able to obtain a hyperpolarized image of the stomach in rats for the first time. Next, we measured the relaxation times of the hyperpolarized {sup 129}Xe gas enclosed in cavities such as the stomach of rats as well as in phantoms created by glass and gelatin bulbs. The cavity size dependency of the relaxation time was analyzed on the basis of the kinetic theory of gases. This analysis showed a linear relationship between the relaxation rate (1/T{sub 1}) and a square inverse of the cavity diameter (1/d{sup 2}). From this relationship, the wall effect on the {sup 129}Xe relaxation can be estimated in the novel parameter t{sub 1}, {sub wall}. This shows drastic dependency on the material of the wall, suggesting a potential use of the relaxation experiment as a diagnostic tool for organ surfaces in the future. (author)
Electron spin relaxation due to reorientation of a permanent zero field splitting tensor.
Schaefle, Nathaniel; Sharp, Robert
2004-09-15
Electron spin relaxation of transition metal ions with spin S> or =1 results primarily from thermal modulation of the zero field splitting (zfs) tensor. This occurs both by distortion of the zfs tensor due to intermolecular collisions and, for complexes with less than cubic symmetry, by reorientational modulation of the permanent zfs tensor. The reorientational mechanism is much less well characterized in previous work than the distortional mechanism although it is an important determinant of nuclear magnetic resonance (NMR) paramagnetic relaxation enhancement phenomena (i.e., the enhancement of NMR relaxation rates produced by paramagnetic ions in solution or NMR-PRE). The classical density matrix theory of spin relaxation does not provide an appropriate description of the reorientational mechanism at low Zeeman field strengths because the zero-order spin wave functions are stochastic functions of time. Using spin dynamics simulation techniques, the time correlation functions of the spin operators have been computed and used to determine decay times for the reorientational relaxation mechanism for S=1. In the zfs limit of laboratory field strengths (H(Zeem)spin decay is exponential, the spin relaxation time, tau(S) (composite function) approximately 0.53tau(R)((1)), where tau(R)((1)) is the reorientational correlation time of a molecule-fixed vector. The value of tau(S) (composite function) is independent of the magnitude of the cylindrical zfs parameter (D), but it depends strongly on low symmetry zfs terms (the E/D ratio). Other spin dynamics (SD) simulations examined spin decay in the intermediate regime of field strengths where H(Zeem) approximately H(zfs) (composite function), and in the vicinity of the Zeeman limit. The results demonstrate that the reorientational electron spin relaxation mechanism is often significant when H(zfs) (composite function)> or =H(Zeem), and that its neglect can lead to serious errors in the interpretation of NMR-PRE data.
Funk, Alexander M; Fries, Pascal H; Harvey, Peter; Kenwright, Alan M; Parker, David
2013-02-07
The rates of longitudinal relaxation for ligand nuclei in four isostructural series of lanthanide(III) complexes have been measured by solution state NMR at 295 K at five magnetic fields in the range 4.7-16.5 T. The electronic relaxation time T(le) is a function of both the lanthanide ion and the local ligand field. It needs to be considered when relaxation probes for magnetic resonance applications are devised because it affects the nuclear relaxation, especially over the field range 0.5 to 4.7 T. Analysis of the data, based on Bloch-Redfield-Wangsness theory describing the paramagnetic enhancement of the nuclear relaxation rate has allowed reliable estimates of electronic relaxation times, T(1e), to be obtained using global minimization methods. Values were found in the range 0.10-0.63 ps, consistent with fluctuations in the transient ligand field induced by solvent collision. A refined theoretical model for lanthanide electronic relaxation beyond the Redfield approximation is introduced, which accounts for the magnitude of the ligand field coefficients of order 2, 4, and 6 and their relative contributions to the rate 1/T(le). Despite the considerable variation of these contributions with the nature of the lanthanide ion and its fluctuating ligand field, the theory explains the modest change of measured T(le) values and their remarkable statistical ordering across the lanthanide series. Both experiment and theory indicate that complexes of terbium and dysprosium should most efficiently promote paramagnetic enhancement of the rate of nuclear relaxation.
Stress-relaxation tests in the work-hardening regime of tungsten single crystals below 300 K
Energy Technology Data Exchange (ETDEWEB)
Brunner, D. [Max-Planck-Institut fuer Metallforschung, Heisenbergstrasse 3, 70569 Stuttgart (Germany)], E-mail: d.brunner@mf.mpg.de
2008-06-15
The influence of work hardening on the results of stress-relaxation tests was studied for highly pure tungsten single crystals isothermally deformed at four temperatures of 274, 241, 131, and 78 K. A method accounting for strong work hardening on the determination of the strain-rate sensitivity from stress-relaxation tests is introduced by establishing special diagrams of SR tests denoted as YX diagrams.
Anisotropy dependent magnetization relaxation in (Cd,Mn)Te quantum wells
Energy Technology Data Exchange (ETDEWEB)
Goryca, M.; Nawrocki, M. [Institute of Experimental Physics, Warsaw University, Hoza 69, 00-681 Warsaw (Poland); Kossacki, P.; Pacuski, W.; Maslana, W. [Institute of Experimental Physics, Warsaw University, Hoza 69, 00-681 Warsaw (Poland); Joined Group Nanophysique et Semiconducteurs, CNRS/CEA/ Universite Joseph Fourier Grenoble, BP 87, 38402 Saint Martin d' Heres cedex (France); Ferrand, D.; Tatarenko, S. [Joined Group Nanophysique et Semiconducteurs, CNRS/CEA/ Universite Joseph Fourier Grenoble, BP 87, 38402 Saint Martin d' Heres cedex (France); Cibert, J. [Laboratoire Louis Neel, CNRS, BP166, 38042 Grenoble cedex 9 (France)
2006-07-01
An optical study of magnetization relaxation is presented for p-doped quantum wells with magnetic ions. The magnetic anisotropy of the system is controlled by the heavy-light hole splitting, tuned by uniaxial strain. We show that a suppression of the magnetic anisotropy results in an enhancement of the observed relaxation rate by a factor of at least 20. This is explained by the fact that the decrease of the anisotropy results in the lowering of the energy barrier for the domain magnetization flip process. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Measurement of Magnetization Curve and Magnetic Relaxation for 2H-NbSe2 Crystals
Institute of Scientific and Technical Information of China (English)
Zhang Ning; Liu Hai-lin; Yu Zhu-xing; Xiong Rui; Shi Jing
2004-01-01
The characteristics of electronic transport properties: behaviors of magnetization curve and magnetic relaxation of a typical normal superconductor 2H-NbSe2 are investigated. The results show that TCand ΔTC of the samples are 7.2,0.18 K, indicating that superconducting energy gap at zero temperature is 1.1 meV. No fish tail shape is found in the magnetization curves at several temperatures. The relationship between remnant magnetic moment and time reveals that the magnetic flux creep of the sample agrees with the Kim-Anderson thermal activation model with the relaxation rate S=0.000 36 at T=6 K.
Vibrational relaxation and decoherence of Rb_2 attached to helium nanodroplets
Grüner, Barbara; Heister, Philipp; Strunz, Walter T; Stienkemeier, Frank; Mudrich, Marcel
2010-01-01
The vibrational wave-packet dynamics of diatomic rubidium molecules (Rb_2) in triplet states formed on the surface of superfluid helium nanodroplets is investigated both experimentally and theoretically. Detailed comparison of experimental femtosecond pump-probe spectra with dissipative quantum dynamics simulations reveals that vibrational relaxation is the main source of decoherence. The rate constant for vibrational relaxation in the first excited triplet state is found to be constant ~0.5ns^-1 for the lowest vibrational levels v< 15 and to increase sharply when exciting to higher energies.
A preliminary investigation of the dynamic viscoelastic relaxation of bovine cortical bone
Directory of Open Access Journals (Sweden)
Loete T.J.C.
2015-01-01
Full Text Available A new experimental approach is proposed to characterize the dynamic viscoelastic relaxation behaviour of cortical bone. Theoretical models are presented to show that a linear viscoelastic material, when allowed to relax between two long elastic bars, will produce stress, strain and strain rate histories that contain characteristic features. Furthermore, typical experimental results are presented to show that these characteristic features are observed during split Hopkinson bar tests on bovine cortical bone using a Cone-in-Tube striker. The interpretation of this behaviour in the context of a standard linear viscoelastic model is discussed.
Carroll, Matthew R J; Huffstetler, Phillip P; Miles, William C; Goff, Jonathon D; Davis, Richey M; Riffle, Judy S; House, Michael J; Woodward, Robert C; St Pierre, Timothy G
2011-08-12
Iron oxide magnetic nanoparticles are good candidates for magnetic resonance imaging (MRI) contrast agents due to their high magnetic susceptibilities. Here we investigate 19 polyether-coated magnetite nanoparticle systems comprising three series. All systems were synthesized from the same batch of magnetite nanoparticles. A different polyether was used for each series. Each series comprised systems with systematically varied polyether loadings per particle. A highly significant (p coatings used in this study, any changes in relaxivity from differences in water exclusion or diffusion rates caused by the polymer are minor in comparison with the changes in relaxivity resulting from variations in the degree of aggregation.
Effect of relaxation on adiabatic following
Energy Technology Data Exchange (ETDEWEB)
Nayfeh, M.H.
1976-09-01
A solution is presented for the damped optical Bloch equations under the excitation of a smooth pulse by first deriving three independent third-order equations of the Bloch vector components. Each equation is reduced to quadratures by assuming that the logarithmic time derivative of the field amplitude is small compared to the Rabi frequency. This results in an approximate summation of the infinite-order time-dependent perturbation in the field amplitude. The relaxation-dependent induced damping of the population inversion is calculated. Also calculated are additional relaxation-dependent contributions to the intensity-dependent refractive index. The time-integrated intensity contribution tends to cause line asymmetry, which becomes, at later times, linear in ..gamma../sub 2/ when ..gamma../sub 2/ very-much-greater-than ..gamma../sub 1/ and zero when 2..gamma../sub 2/ = ..gamma../sub 1/, where ..gamma../sub 1/ and ..gamma../sub 2/ are the atomic energy and phase-changing relaxations, respectively. The dependence of the spectral broadening on pulse length, pressure, and length of the sample is discussed. (AIP)
Fingerprinting Molecular Relaxation in Deformed Polymers
Wang, Zhe; Lam, Christopher N.; Chen, Wei-Ren; Wang, Weiyu; Liu, Jianning; Liu, Yun; Porcar, Lionel; Stanley, Christopher B.; Zhao, Zhichen; Hong, Kunlun; Wang, Yangyang
2017-07-01
The flow and deformation of macromolecules is ubiquitous in nature and industry, and an understanding of this phenomenon at both macroscopic and microscopic length scales is of fundamental and practical importance. Here, we present the formulation of a general mathematical framework, which could be used to extract, from scattering experiments, the molecular relaxation of deformed polymers. By combining and modestly extending several key conceptual ingredients in the literature, we show how the anisotropic single-chain structure factor can be decomposed by spherical harmonics and experimentally reconstructed from its cross sections on the scattering planes. The resulting wave-number-dependent expansion coefficients constitute a characteristic fingerprint of the macromolecular deformation, permitting detailed examinations of polymer dynamics at the microscopic level. We apply this approach to survey a long-standing problem in polymer physics regarding the molecular relaxation in entangled polymers after a large step deformation. The classical tube theory of Doi and Edwards predicts a fast chain retraction process immediately after the deformation, followed by a slow orientation relaxation through the reptation mechanism. This chain retraction hypothesis, which is the keystone of the tube theory for macromolecular flow and deformation, is critically examined by analyzing the fine features of the two-dimensional anisotropic spectra from small-angle neutron scattering by entangled polystyrenes. We show that the unique scattering patterns associated with the chain retraction mechanism are not experimentally observed. This result calls for a fundamental revision of the current theoretical picture for nonlinear rheological behavior of entangled polymeric liquids.
Graph Matching: Relax at Your Own Risk.
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.
Cortex phellodendri Extract Relaxes Airway Smooth Muscle
Directory of Open Access Journals (Sweden)
Qiu-Ju Jiang
2016-01-01
Full Text Available Cortex phellodendri is used to reduce fever and remove dampness and toxin. Berberine is an active ingredient of C. phellodendri. Berberine from Argemone ochroleuca can relax airway smooth muscle (ASM; however, whether the nonberberine component of C. phellodendri has similar relaxant action was unclear. An n-butyl alcohol extract of C. phellodendri (NBAECP, nonberberine component was prepared, which completely inhibits high K+- and acetylcholine- (ACH- induced precontraction of airway smooth muscle in tracheal rings and lung slices from control and asthmatic mice, respectively. The contraction induced by high K+ was also blocked by nifedipine, a selective blocker of L-type Ca2+ channels. The ACH-induced contraction was partially inhibited by nifedipine and pyrazole 3, an inhibitor of TRPC3 and STIM/Orai channels. Taken together, our data demonstrate that NBAECP can relax ASM by inhibiting L-type Ca2+ channels and TRPC3 and/or STIM/Orai channels, suggesting that NBAECP could be developed to a new drug for relieving bronchospasm.
Probing relaxation times in graphene quantum dots
Volk, Christian; Neumann, Christoph; Kazarski, Sebastian; Fringes, Stefan; Engels, Stephan; Haupt, Federica; Müller, André; Stampfer, Christoph
2013-01-01
Graphene quantum dots are attractive candidates for solid-state quantum bits. In fact, the predicted weak spin-orbit and hyperfine interaction promise spin qubits with long coherence times. Graphene quantum dots have been extensively investigated with respect to their excitation spectrum, spin-filling sequence and electron-hole crossover. However, their relaxation dynamics remain largely unexplored. This is mainly due to challenges in device fabrication, in particular concerning the control of carrier confinement and the tunability of the tunnelling barriers, both crucial to experimentally investigate decoherence times. Here we report pulsed-gate transient current spectroscopy and relaxation time measurements of excited states in graphene quantum dots. This is achieved by an advanced device design that allows to individually tune the tunnelling barriers down to the low megahertz regime, while monitoring their asymmetry. Measuring transient currents through electronic excited states, we estimate a lower bound for charge relaxation times on the order of 60–100 ns. PMID:23612294
Tension and relaxation in the individual.
Newbury, C R
1979-06-01
Increasing materialism in society is resulting in more wide spread nervous tension in all age groups. While some degree of nervous tension is necessary in everyday living, its adverse effects require that we must learn to bring it under control. Total tension is shown to have two components: a controllable element arising from factors in the environment and the inbuilt uncontrollable residue which is basic in the individual temperament. The effects of excessive or uncontrolled stress can be classified as 1) emotional reactions such as neurotic behaviour (anxiety hypochondria, hysteria, phobia, depression obsessions and compulsions) or psychotic behaviour and 2) psychosomatic reactions (nervous asthma, headache, insomnia, heart attack). Nervous energy can be wastefully expended by such factors as loss of temper, wrong attitudes to work, job frustration and marital strains. Relaxation is the only positive way to control undesirable nervous tension and its techniques require to be learned. A number of techniques (progressive relaxation, differential relaxation, hypnosis, the use of biofeedback, Yoga and Transcendental Meditation) are described and their application to dental practice is discussed.
Ideal relaxation of the Hopf fibration
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.
Yan, Wan; Fang, Liang; Heuchel, Matthias; Kratz, Karl; Lendlein, Andreas
2015-01-01
Stress relaxation can strongly influence the shape-memory capability of polymers. Recently a modified Maxwell-Wiechert model comprising two Maxwell units and a single spring unit in parallel has been introduced to successfully describe the shape recovery characteristics of amorphous polyether urethanes. In this work we explored whether such a modified Maxwell-Wiechert model is capable to describe the stress relaxation behavior of a semi-crystalline multiblock copolymer named PCL-PIBMD, which consists of crystallizable poly(ɛ-caprolactone) (PCL) segments and crystallizable poly(3S-isobutylmorpholine-2,5-dione) (PIBMD) segments. The stress relaxation behavior of PCL-PIBMD was explored after uniaxial deformation to different strains ranging from 50 to 900% with various strain rates of 1 or 10 or 50 mm·min -1. The modeling results indicated that under the assumption that in PCL-PIBMD both PCL and PIBMD blocks have narrow molecular weight distributions and are arranged in sequence, the two relaxation processes can be related to the amorphous PCL and PIBMD domains and the spring element can be associated to the PIBMD crystalline domains. The first Maxwell unit representing the faster relaxation process characterized by the modulus E1 and the relaxation time τ1 is related to the amorphous PCL domains (which are in the rubbery state), while the second Maxwell unit (E2 ; τ2) represents the behavior of the amorphous PIBMD domains, which are in the glassy state at 50 °C. Increasing strain rates resulted in an increase of E1 and a significant reduction in τ1, whereas the elastic modulus as well as the relaxation time related to the amorphous PIBMD domains remained almost constant. When a higher deformation was applied (ɛ ≥ 200% ) lower values for the elastic moduli of the three model elements were obtained. In general the applied model was also capable to describe the relaxation behavior of PCL-PIBMD at a deformation temperature of 20 °C, where additional crystalline
Plasma relaxation mechanics of pulsed high power microwave surface flashover
Energy Technology Data Exchange (ETDEWEB)
Beeson, S.; Dickens, J.; Neuber, A. [Center for Pulsed Power and Power Electronics, Department of Electrical and Computer Engineering and Department of Physics, Texas Tech University, Lubbock, Texas 79409 (United States)
2013-09-15
Microwave transmission and reflection characteristics of pulsed radio frequency field generated plasmas are elucidated for air, N{sub 2}, and He environments under pressure conditions ranging from 10 to 600 torr. The pulsed, low temperature plasma is generated along the atmospheric side of the dielectric boundary between the source (under vacuum) and the radiating environment with a thickness on the order of 5 mm and a cross sectional area just smaller than that of the waveguide. Utilizing custom multi-standard waveguide couplers and a continuous low power probing source, the scattering parameters were measured before, during, and after the high power microwave pulse with emphasis on the latter. From these scattering parameters, temporal electron density estimations (specifically the longitudinal integral of the density) were calculated using a 1D plane wave-excited model for analysis of the relaxation processes associated. These relaxation characteristics ultimately determine the maximum repetition rate for many pulsed electric field applications and thus are applicable to a much larger scope in the plasma community than just those related to high power microwaves. This manuscript discusses the diagnostic setup for acquiring the power measurements along with a detailed description of the kinematic and chemical behavior of the plasma as it decays down to its undisturbed state under various gas type and pressure conditions.
Gamma dosimetric parameters in some skeletal muscle relaxants
Manjunatha, H. C.
2017-09-01
We have studied the attenuation of gamma radiation of energy ranging from 84 keV to 1330 keV (^{170}Tm, ^{22} Na,^{137} Cs, and ^{60}Co) in some commonly used skeletal muscle relaxants such as tubocurarine chloride, gallamine triethiodide, pancuronium bromide, suxamethonium bromide and mephenesin. The mass attenuation coefficient is measured from the attenuation experiment. In the present work, we have also proposed the direct relation between mass attenuation coefficient (μ /ρ ) and mass energy absorption coefficient (μ _{en}/ρ ) based on the nonlinear fitting procedure. The gamma dosimetric parameters such as mass energy absorption coefficient (μ _{en}/ρ ), effective atomic number (Z_{eff}), effective electron density (N_{el}), specific {\\upgamma }-ray constant, air kerma strength and dose rate are evaluated from the measured mass attentuation coefficient. These measured gamma dosimetric parameters are compared with the theoretical values. The measured values agree with the theoretical values. The studied gamma dosimetric values for the relaxants are useful in medical physics and radiation medicine.
Ion beam induced stress formation and relaxation in germanium
Energy Technology Data Exchange (ETDEWEB)
Steinbach, T., E-mail: Tobias.Steinbach@uni-jena.de [Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, D-07743 Jena (Germany); Reupert, A.; Schmidt, E.; Wesch, W. [Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, D-07743 Jena (Germany)
2013-07-15
Ion irradiation of crystalline solids leads not only to defect formation and amorphization but also to mechanical stress. In the past, many investigations in various materials were performed focusing on the ion beam induced damage formation but only several experiments were done to investigate the ion beam induced stress evolution. Especially in microelectronic devices, mechanical stress leads to several unwanted effects like cracking and peeling of surface layers as well as changing physical properties and anomalous diffusion of dopants. To study the stress formation and relaxation process in semiconductors, crystalline and amorphous germanium samples were irradiated with 3 MeV iodine ions at different ion fluence rates. The irradiation induced stress evolution was measured in situ with a laser reflection technique as a function of ion fluence, whereas the damage formation was investigated by means of Rutherford backscattering spectrometry. The investigations show that mechanical stress builds up at low ion fluences as a direct consequence of ion beam induced point defect formation. However, further ion irradiation causes a stress relaxation which is attributed to the accumulation of point defects and therefore the creation of amorphous regions. A constant stress state is reached at high ion fluences if a homogeneous amorphous surface layer was formed and no further ion beam induced phase transition took place. Based on the results, we can conclude that the ion beam induced stress evolution seems to be mainly dominated by the creation and accumulation of irradiation induced structural modification.
Dose Impaired Relaxation of Left Ventricle Affect Early Outcomes
Directory of Open Access Journals (Sweden)
Jamshid Bagheri
2010-05-01
Full Text Available "nAlthough systolic dysfunction is revealed as a prognostic factor in cardiac surgery , the role of diastolic dysfunction as a predictive factor is less evaluated. In this retrospective study from 872 patients that underwent isolated coronary artery bypass graft(Jan 2008-Feb 2009,388 patients had normal left ventricular ejection fraction (>50%. These are divided in two groups, Group 1: 361 patients without diastolic dysfunction (impaired relaxation and Group 2: 27 patients with diastolic dysfunction ( impaired relaxation . Mean age in group 1 was 57.72 year and in group 2 was 61.16 year (P =0.07. Risk factors such as diabetes mellitus, hypertention and dyslipidemia were similar. Although overall complication rate was higher in group 2( 11.1% vs 2.8% P value 0.05,but when each complication was studied individually no significant statistical difference was found. Also no significant statistical difference was found in mortality (2.2% in group 1 vs 7.4% in group 2 P =0.1. In conclusion, from clinical standpoint diastolic dysfunction can be an important factor in assessing surgical outcome in patients whom underwent coronary artery bypass grafting.
Effective rotational correlation times of proteins from NMR relaxation interference
Lee, Donghan; Hilty, Christian; Wider, Gerhard; Wüthrich, Kurt
2006-01-01
Knowledge of the effective rotational correlation times, τc, for the modulation of anisotropic spin-spin interactions in macromolecules subject to Brownian motion in solution is of key interest for the practice of NMR spectroscopy in structural biology. The value of τc enables an estimate of the NMR spin relaxation rates, and indicates possible aggregation of the macromolecular species. This paper reports a novel NMR pulse scheme, [ 15N, 1H]-TRACT, which is based on transverse relaxation-optimized spectroscopy and permits to determine τc for 15N- 1H bonds without interference from dipole-dipole coupling of the amide proton with remote protons. [ 15N, 1H]-TRACT is highly efficient since only a series of one-dimensional NMR spectra need to be recorded. Its use is suggested for a quick estimate of the rotational correlation time, to monitor sample quality and to determine optimal parameters for complex multidimensional NMR experiments. Practical applications are illustrated with the 110 kDa 7,8-dihydroneopterin aldolase from Staphylococcus aureus, the uniformly 15N-labeled Escherichia coli outer membrane protein X (OmpX) in 60 kDa mixed OmpX/DHPC micelles with approximately 90 molecules of unlabeled 1,2-dihexanoyl- sn-glycero-3-phosphocholine (DHPC), and the 16 kDa pheromone-binding protein from Bombyx mori, which cover a wide range of correlation times.
Gd-HOPO Based High Relaxivity MRI Contrast Agents
Energy Technology Data Exchange (ETDEWEB)
Datta, Ankona; Raymond, Kenneth
2008-11-06
Tris-bidentate HOPO-based ligands developed in our laboratory were designed to complement the coordination preferences of Gd{sup 3+}, especially its oxophilicity. The HOPO ligands provide a hexadentate coordination environment for Gd{sup 3+} in which all he donor atoms are oxygen. Because Gd{sup 3+} favors eight or nine coordination, this design provides two to three open sites for inner-sphere water molecules. These water molecules rapidly exchange with bulk solution, hence affecting the relaxation rates of bulk water olecules. The parameters affecting the efficiency of these contrast agents have been tuned to improve contrast while still maintaining a high thermodynamic stability for Gd{sup 3+} binding. The Gd- HOPO-based contrast agents surpass current commercially available agents ecause of a higher number of inner-sphere water molecules, rapid exchange of inner-sphere water molecules via an associative mechanism, and a long electronic relaxation time. The contrast enhancement provided by these agents is at least twice that of commercial contrast gents, which are based on polyaminocarboxylate ligands.
Gamma dosimetric parameters in some skeletal muscle relaxants
Indian Academy of Sciences (India)
H C MANJUNATHA
2017-09-01
We have studied the attenuation of gamma radiation of energy ranging from 84 keV to 1330 keV $(^{170}Tm, ^{22}Na, ^{137}Cs, and ^{60}Co)$ in some commonly used skeletal muscle relaxants such as tubocurarine chloride, gallamine triethiodide, pancuronium bromide, suxamethonium bromide and mephenesin. The mass attenuation coefficient is measured from the attenuation experiment. In the present work, we have also proposed the direct relation between mass attenuation coefficient $(\\mu/\\rho)$ and mass energy absorption coefficient $(\\mu_{en}/\\rho)$ based on the nonlinear fitting procedure. The gamma dosimetric parameters such as mass energy absorption coefficient $(\\mu_{en}/\\rho)$, effective atomic number $\\rm{(Z_eff )}$, effective electron density $(N_\\rm{el})$, specific $\\gamma$-ray constant, air kerma strength and dose rate are evaluated from the measured mass attentuation coefficient. These measured gamma dosimetric parameters are compared with the theoretical values. The measured values agree with the theoretical values. The studied gamma dosimetric values for the relaxants are useful in medical physics and radiation medicine.
Non-uniform sampling of NMR relaxation data
Energy Technology Data Exchange (ETDEWEB)
Linnet, Troels E.; Teilum, Kaare, E-mail: kaare.teilum@bio.ku.dk [University of Copenhagen, SBiNLab and the Linderstrøm-Lang Centre for Protein Science, Department of Biology (Denmark)
2016-02-15
The use of non-uniform sampling of NMR spectra may give significant reductions in the data acquisition time. For quantitative experiments such as the measurement of spin relaxation rates, non-uniform sampling is however not widely used as inaccuracies in peak intensities may lead to errors in the extracted dynamic parameters. By systematic reducing the coverage of the Nyquist grid of {sup 15}N Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion datasets for four different proteins and performing a full data analysis of the resulting non-uniform sampled datasets, we have compared the performance of the multi-dimensional decomposition and iterative re-weighted least-squares algorithms in reconstructing spectra with accurate peak intensities. As long as a single fully sampled spectrum is included in a series of otherwise non-uniform sampled two-dimensional spectra, multi-dimensional decomposition reconstructs the non-uniform sampled spectra with high accuracy. For two of the four analyzed datasets, a coverage of only 20 % results in essentially the same results as the fully sampled data. As exemplified by other data, such a low coverage is in general not enough to produce reliable results. We find that a coverage level not compromising the final results can be estimated by recording a single full two-dimensional spectrum and reducing the spectrum quality in silico.
The efficiency of resonant relaxation around a massive black hole
Eilon, Ehud; Alexander, Tal
2008-01-01
Resonant relaxation (RR) is a rapid relaxation process that operates in the nearly-Keplerian potential near a massive black hole (MBH). RR dominates the dynamics of compact remnants that inspiral into a MBH and emit gravitational waves (extreme mass ratio inspiral events, EMRIs). RR can either increase the EMRI rate, or strongly suppress it, depending on its still poorly-determined efficiency. We use small-scale Newtonian N-body simulations to measure the RR efficiency and to explore its possible dependence on the stellar number density profile around the MBH, and the mass-ratio between the MBH and a star (a single-mass stellar population is assumed). We develop an efficient and robust procedure for detecting and measuring RR in N-body simulations. We present a suite of simulations with a range of stellar density profiles and mass-ratios, and measure the mean RR efficiency in the near-Keplerian limit. We do not find a statistically significant dependence on the density profile or the mass-ratio. Our numerical...
Anomalous hyperfine coupling and nuclear magnetic relaxation in Weyl semimetals
Okvátovity, Zoltán; Simon, Ferenc; Dóra, Balázs
2016-12-01
The electron-nuclear hyperfine interaction shows up in a variety of phenomena including, e.g., NMR studies of correlated states and spin decoherence effects in quantum dots. Here we focus on the hyperfine coupling and the NMR spin relaxation time T1 in Weyl semimetals. Since the density of states in Weyl semimetals varies with the square of the energy around the Weyl point, a naive power counting predicts a 1 /T1T ˜E4 scaling, with E the maximum of temperature (T ) and chemical potential. By carefully investigating the hyperfine interaction between nuclear spins and Weyl fermions, we find that while its spin part behaves conventionally, its orbital part diverges unusually, with the inverse of the energy around the Weyl point. Consequently, the nuclear spin relaxation rate scales in a graphenelike manner as 1 /T1T ˜E2ln(E /ω0) , with ω0 the nuclear Larmor frequency. This allows us to identify an effective hyperfine coupling constant, which is tunable by gating or doping. This is relevant for the decoherence effect in spintronics devices and double quantum dots, where hyperfine coupling is the dominant source of spin-blockade lifting.
Sandler, Hubertus; Fendel, Uta; Buße, Petra; Rose, Matthias; Bösel, Rainer; Klapp, Burghard F
2017-01-01
Vibroacoustic stimulation by a Body Monochord can induce relaxation states of various emotional valence. The skin conductance level (SCL) of the tonic electrodermal activity is an indicator of sympathetic arousal of the autonomic nervous system and thus an indicator of the relaxation response. Salivary cortisol is considered to be a stress indicator of the HPA-axis. The effects of the treatment with a Body Monochord and listening to relaxation music (randomized chronological presentation) on SCL and salivary cortisol in relation to the emotional valence of the experience were examined in patients with psychosomatic disorders (N = 42). Salivary cortisol samples were collected immediately before and after the expositions. Subjective experience was measured via self-rating scales. Overall, both the exposure to the Body Monochord as well as the exposure to the relaxation music induced an improvement of patients' mood and caused a highly significant reduction of SCL. A more emotionally positive experience of relaxation correlated with a slightly stronger reduction of the SCL. Both treatment conditions caused a slight increase in salivary cortisol, which was significant after exposure to the first treatment. The increase of salivary cortisol during a relaxation state is contrary to previous findings. It is possible that the relaxation state was experienced as an emotional challenge, due to inner images and uncommon sensations that might have occurred.
Sandler, Hubertus; Fendel, Uta; Buße, Petra; Rose, Matthias; Bösel, Rainer; Klapp, Burghard F.
2017-01-01
Vibroacoustic stimulation by a Body Monochord can induce relaxation states of various emotional valence. The skin conductance level (SCL) of the tonic electrodermal activity is an indicator of sympathetic arousal of the autonomic nervous system and thus an indicator of the relaxation response. Salivary cortisol is considered to be a stress indicator of the HPA-axis. The effects of the treatment with a Body Monochord and listening to relaxation music (randomized chronological presentation) on SCL and salivary cortisol in relation to the emotional valence of the experience were examined in patients with psychosomatic disorders (N = 42). Salivary cortisol samples were collected immediately before and after the expositions. Subjective experience was measured via self-rating scales. Overall, both the exposure to the Body Monochord as well as the exposure to the relaxation music induced an improvement of patients’ mood and caused a highly significant reduction of SCL. A more emotionally positive experience of relaxation correlated with a slightly stronger reduction of the SCL. Both treatment conditions caused a slight increase in salivary cortisol, which was significant after exposure to the first treatment. The increase of salivary cortisol during a relaxation state is contrary to previous findings. It is possible that the relaxation state was experienced as an emotional challenge, due to inner images and uncommon sensations that might have occurred. PMID:28114399
Dielectric relaxation and the conformer equilibrium in the liquid and glassy states of β- D-fructose
Tombari, E.; Cardelli, C.; Salvetti, G.; Johari, G. P.
2001-01-01
To investigate the ionic and molecular dynamics in the liquid and glassy states of β- D-fructose, its dielectric relaxation spectra (12 Hz-500 kHz) and dynamic heat capacity (3.33 mHz) have been measured from 5 K above its melting point through the vitrification range, by allowing sufficient time for attainment of the conformer (or chemical) equilibria. Effects of the change in the conformer population on thermal cycling has been further studied. The dielectric behavior of liquid β- D-fructose is characteristically different from that of other molecular liquids in three ways: (i) the contribution to orientation polarization associated with the fast relaxation process, which persists in the glassy state, is relatively high in the liquid state of β- D-fructose; (ii) this contribution decreases with temperature exceptionally rapidly on cooling; and (iii) the difference in the rates of the two process is exceptionally large. The dynamic heat capacity change through the vitrification region is ˜160 J/(mol K), and is spread over ˜20 K range, and the enthalpy relaxation time is ˜50 s at 383 K. Transformation of β-pyranose to other conformers and other conformer transformation equilibria change on thermal cycling with the result that the overall relaxation rate increases at T>315 K and decreases at T<315 K. The relaxation spectrum becomes broader, the dc conductivity increases and the rate of the Johari-Goldstein relaxation whose Arrhenius energy is 42.1 kJ/mol increases.
Average-atom treatment of relaxation time in x-ray Thomson scattering from warm dense matter.
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.
Woźniak-Braszak, Aneta
2017-02-01
Molecular dynamics of the solid 3-(trifluoromethyl) benzoic acid containing proton (1)H and fluorine (19)F nuclei was explored by the solid-state NMR off - resonance technique. Contrary to the previous experiments the proton nuclei system I relaxed in the off - resonance effective field B→e while fluorine nuclei system S was saturated for short time in comparison to the relaxation time T1I. New cross - relaxation solid - state NMR off - resonance experiments were conducted on a homebuilt pulse spectrometer operating at the on-resonance frequency of 30.2MHz, at the off - resonance frequency varied between 30.2 and 30.6MHz for protons and at the frequency of 28.411MHz for fluorines, respectively. Based on the experimental data the dispersions of the proton off - resonance spin - lattice relaxation rate ρρ(I), the fluorine off - resonance spin - lattice relaxation rate ρρ(S) and the cross - relaxation rate σρ in the rotating frame were determined. Copyright © 2016 Elsevier Inc. All rights reserved.
Lehrer, Paul M.
1978-01-01
Compared physiological effects of progressive relaxation, alpha feedback, and a no-treatment condition. Nonpatients showed more psychophysiological habituation than patients in response to hearing very loud tones and to reaction time tasks. Patients showed greater physiological response to relaxation than nonpatients. After relaxation, autonomic…
Stress relaxation following uniaxial extension of polystyrene melt and oligomer dilutions
DEFF Research Database (Denmark)
Huang, Qian; Rasmussen, Henrik K.
2016-01-01
The filament stretching rheometer has been used to measure the stress relaxation following the startup of uniaxial extensional flow, on anarrow molar mass distribution (NMMD) polystyrene melt and styrene oligomer dilutions thereof. All samples used here were characterizedin molecular weight......, mechanical spectroscopy, and constant strain rate uniaxial extension in the work of Huang et al. [Macromolecules 46,5026–5035 (2013); ACS Macro Lett. 2, 741–744 (2013)]. The stress relaxation following the steady extensional stress was measured on a285 kg/mole NMMD polystyrene and two 1.92 kg/mole styrene...... oligomer dilutions thereof {PS-285k, PS-285k/2k-72, and PS-285k/2k-44 inthe work of Huang et al. [Macromolecules 46, 5026–5035 (2013)]}. The two dilutions contained 28 and 56 wt. % oligomer, respectively.Further, the stress relaxation on a 545 kg/mole NMMD polystyrene diluted with 48 wt. % 0.972 kg...
Thermal and relaxational properties of glass-forming material, 3,3-dimethyl-1-butanol
Energy Technology Data Exchange (ETDEWEB)
Massalska-Arodz, Maria [H. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Cracow (Poland) and Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043 (Japan)]. E-mail: Maria.Massalska-Arodz@ifj.edu.pl; Nakamoto, Tadahiro [Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043 (Japan); Wasiutynski, Tadeusz [H. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Cracow (Poland); Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043 (Japan); Mayer, Jacek [H. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Cracow (Poland); Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043 (Japan); Krawczyk, Jan [H. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Cracow (Poland); Sorai, Michio [Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043 (Japan)]. E-mail: sorai@chem.sci.osaka-u.ac.jp
2004-10-01
As a part of a project for glass-formers having various values of fragility, molecular dynamics of a glass-forming material 3,3-dimethyl-1-butanol has been presented on the basis of the dielectric relaxation studies. Three characteristic relaxations were observed. To provide thermodynamic aspects of this material, adiabatic heat-capacity calorimetry has also been performed in the (13 to 302) K temperature range. The stable crystal of this material melts at T{sub m} = 235.7 K. When the material is rapidly cooled at a rate greater than 5 K min{sup -1}, the liquid is easily super-cooled and eventually transformed to a glassy state. Standard thermodynamic quantities are evaluated for both the stable crystalline and the glassy states. Structural relaxation processes are discussed in relation to the phase behaviour revealed by the calorimetry.
Relaxation dynamics of aftershocks after large volatility shocks in the SSEC index
Mu, Guo-Hua; Zhou, Wei-Xing
2008-09-01
The relaxation dynamics of aftershocks after large volatility shocks are investigated based on two high-frequency data sets of the Shanghai Stock Exchange Composite (SSEC) index. Compared with previous relevant work, we have defined main financial shocks based on large volatilities rather than large crashes. We find that the occurrence rate of aftershocks with the magnitude exceeding a given threshold for both daily volatility (constructed using 1-minute data) and minutely volatility (using intra-minute data) decays as a power law. The power-law relaxation exponent increases with the volatility threshold and is significantly greater than 1. Taking financial volatility as the counterpart of seismic activity, the power-law relaxation in financial volatility deviates remarkably from the Omori law in Geophysics.
A Tropical Atmosphere Model with Moisture: Global Well-posedness and Relaxation Limit
Li, Jinkai
2015-01-01
In this paper, we consider a nonlinear interaction system between the barotropic mode and the first baroclinic mode of the tropical atmosphere with moisture; that was derived in [Frierson, D.M.W.; Majda, A.J.; Pauluis, O.M.: Dynamics of precipitation fronts in the tropical atmosphere: a novel relaxation limit, Commum. Math. Sci., 2 (2004), 591-626.] We establish the global existence and uniqueness of strong solutions to this system, with initial data in $H^1$, for each fixed convective adjustment relaxation time parameter $\\varepsilon>0$. Moreover, if the initial data enjoy slightly more regularity than $H^1$, then the unique strong solution depends continuously on the initial data. Furthermore, by establishing several appropriate $\\varepsilon$-independent estimates, we prove that the system converges to a limiting system, as the relaxation time parameter $\\varepsilon$ tends to zero, with convergence rate of the order $O(\\sqrt\\varepsilon)$. Moreover, the limiting system has a unique global strong solution, fo...
Collective relaxation dynamics and crystallization kinetics of the amorphous Biclotymol antiseptic.
Tripathi, Pragya; Romanini, Michela; Tamarit, Josep Lluis; Macovez, Roberto
2015-11-10
We employ dielectric spectroscopy to monitor the relaxation dynamics and crystallization kinetics of the Biclotymol antiseptic in its amorphous phase. The glass transition temperature of the material as determined by dielectric spectroscopy is Tg = 290 ± 1K. The primary (α) relaxation dynamics is observed to follow a Vogel-Fulcher-Tammann temperature dependence, with a kinetic fragility index m = 86 ± 13, which classifies Biclotymol as a relatively fragile glass former. A secondary relaxation is also observed, corresponding to an intramolecular dynamic process of the non-rigid Biclotymol molecule. The crystallization kinetics, measured at four different temperatures above the glass transition temperature, follows an Avrami behavior with exponent virtually equal to n = 2, indicating one-dimensional crystallization into needle-like crystallites, as experimentally observed, with a time-constant nucleation rate. The activation barrier for crystallization is found to be Ea = 115 ± 22 kJ mol(-1).
Approximate method for solving relaxation problems in terms of material`s damagability under creep
Energy Technology Data Exchange (ETDEWEB)
Nikitenko, A.F.; Sukhorukov, I.V.
1995-03-01
The technology of thermoforming under creep and superplasticity conditions is finding increasing application in machine building for producing articles of a preset shape. After a part is made there are residual stresses in it, which lead to its warping. To remove residual stresses, moulded articles are usually exposed to thermal fixation, i.e., the part is held in compressed state at a certain temperature. Thermal fixation is simply the process of residual stress relaxation, following by accumulation of total creep in the material. Therefore the necessity to develop engineering methods for calculating the time of thermal fixation and relaxation of residual stresses to a safe level, not resulting in warping, becomes evident. The authors present an approximate method of calculation of stress-strain rate of a body during relaxation. They use a system of equations which describes a material`s creep, simultaneously taking into account accumulation of damages in it.
[Spin-lattice relaxation of water protons in plant and animal cells].
Samuilov, F D; Nikiforov, E A; Nikiforova, V I
2012-01-01
NMR-spin echo method has been used to study spin-lattice relaxation time of protons T1 in plant and animal cells - muscle tissue of fish, the cells of which unlike plant cells have no developed system of vacuoles, plastids and a solid cell wall. According to the values of T1 time a new NMR parameter K, a coefficient of relaxation effectiveness of a cell structure, has been calculated. This parameter can be used for quantitative characterization of the influence of different cell structures, the tissue water interact with, for a time of spin-lattice relaxation of water protons. It has been ascertained that the values of K coefficient in animal tissue and in storing tissues of some plants differ little; it may be stipulated by permanent transmembrane water exchange which occurs at high rate in the living cell. It has been concluded that there exists a certain similarity between water state in protoplast of plant and animal cells.
Preference for different relaxation techniques by COPD patients: comparison between six techniques.
Hyland, Michael E; Halpin, David Mg; Blake, Sue; Seamark, Clare; Pinnuck, Margaret; Ward, David; Whalley, Ben; Greaves, Colin J; Hawkins, Adam L; Seamark, Dave
2016-01-01
A review of the effectiveness of relaxation techniques for chronic obstructive pulmonary disease patients has shown inconsistent results, but studies have varied in terms of technique and outcome measures. To determine patient preference for different relaxation techniques. Chronic obstructive pulmonary disease patients were presented with six techniques via a DVD and asked to rate the techniques in terms of effectiveness, rank in order of likely use, and comment. Patients differed in the technique preferred and reason for that preference, but the most commonly preferred technique both for effectiveness and ease of use was "thinking of a nice place" followed by progressive relaxation and counting. Familiarity and ease of activity were commonly given reasons for preference. Rather than providing patients with a single technique that they might find difficult to implement, these results suggest that it would be better to give a choice. "Thinking of a nice place" is a popular but under-investigated technique.
CUSTOM RELAXATION INDUCED IMPURITY PHOTOCONDUCTIVITY IN THE UNITED AII BVI and AIII BV
Directory of Open Access Journals (Sweden)
L. B. Atlukhanova
2016-01-01
Full Text Available Two types of non-standard relaxation induced impurity photoconductivity (IIP observed in photoconductors CdS, ZnSe, GaAs and others, depending on the kinetic characteristics of the traps are described. In one case, at the stage of post flashing monotonic decay which is typical for relaxation associated with slow traps (the ratio of the speed of the electron capture to the recombination rate (R << 1, the photo response is experiencing vibrations of low frequency (f =0.03-0.3Hz. Relaxation of the second type characterized by rapid photoelectric traps (R >> 1: measurement alternating signal (f > 20 Hz relaxation curves take the form of curves usual impurity photoconductivity. Electronic processes responsible for relaxation of non-standard IIP are analyzed. For example, fast-centers, which include the characteristic AIIBVI donor Agi0, for the first time in semiconductors experimentally, investigated the dependence of the cross section of electron capture by traps energy released during localization.
Evaluation of a new disposable silicon limbal relaxing incision knife by experienced users
Directory of Open Access Journals (Sweden)
Parvu Valentin
2009-12-01
Full Text Available Abstract Background Previous research has suggested that the silicon BD Atomic Edge™ knife has superior performance characteristics when compared to a metal knife and performance similar to diamond knife when making various incisions. This study was designed to determine whether a silicon accurate depth knife has equivalent performance characteristics when compared to a diamond limbal relaxing incision (LRI knife and superior performance characteristics when compared to a steel accurate depth knife when creating limbal relaxing incision. Methods Sixty-five ophthalmic surgeons with limbal relaxing incision experience created limbal relaxing incisions in ex-vivo porcine eyes with silicon and steel accurate depth knives and diamond LRI knives. The ophthalmic surgeons rated multiple performance characteristics of the knives on Visual Analog Scales. Results The observed differences between the silicon knife and diamond knife were found to be insignificant. The mean ratio between the performance of the silicon knife and the diamond knife was shown to be greater than 90% (with 95% confidence. The silicon knife's mean performance was significantly higher than the performance of the steel knife for all characteristics. (p-value Conclusions For experienced users, the silicon accurate depth knife was found to be equivalent in performance to the diamond LRI knife and superior to the steel accurate depth knife when making limbal relaxing incisions in ex vivo porcine eyes. Disposable silicon LRI knives may be an alternative to diamond LRI knives.
Origin of the magnetic-field dependence of the nuclear spin-lattice relaxation in iron
Seewald, G; Körner, H J; Borgmann, D; Dietrich, M
2008-01-01
The magnetic-field dependence of the nuclear spin-lattice relaxation at Ir impurities in Fe was measured for fields between 0 and 2 T parallel to the [100] direction. The reliability of the applied technique of nuclear magnetic resonance on oriented nuclei was demonstrated by measurements at different radio-frequency (rf) field strengths. The interpretation of the relaxation curves, which used transition rates to describe the excitation of the nuclear spins by a frequency-modulated rf field, was confirmed by model calculations. The magnetic-field dependence of the so-called enhancement factor for rf fields, which is closely related to the magnetic-field dependence of the spin-lattice relaxation, was also measured. For several magnetic-field-dependent relaxation mechanisms, the form and the magnitude of the field dependence were derived. Only the relaxation via eddy-current damping and Gilbert damping could explain the observed field dependence. Using reasonable values of the damping parameters, the field depe...
LOW-FREQUENCY DIELECTRIC RELAXATION IN SILVER STEARATE LAYERS
Directory of Open Access Journals (Sweden)
Smirnov, A.P.
2016-05-01
Full Text Available The low-frequency dielectric relaxation process in silver stearate layers was studied. The increasing of dielectric permittivity with frequency decreasing and temperature increasing in studied sample are associated with the dipole-relaxation polarization mechanisms. The dispersion of loss factor could be connected with the contribution of relaxation mechanism and conductivity. The shape of the Cole-Cole diagram shows that silver stearate is a non-Debye dielectric material characterized by a wide distribution of relaxators, according to the Cole-Cole relaxation model.
ON THE CENTRAL RELAXING SCHEMES I:SINGLE CONSERVATION LAWS
Institute of Scientific and Technical Information of China (English)
Hua-zhong Tang
2000-01-01
In this first paper we present a central relaxing scheme for scalar conservation laws, based on using the local relaxation approximation. Our scheme is obtained without using linear or nonlinear Riemann solvers. A cell entropy inequality is studied for the semidiscrete central relaxing scheme, and a second order MUSCL scheme is shown to be TVD in the zero relaxation limit. The next paper will extend the central relaxing scheme to multi-dimensional systems of conservation laws in curvilinear coordinates, including numerical experiments for 1D and 2D problems.
Kurauskas, Vilius; Weber, Emmanuelle; Hessel, Audrey; Ayala, Isabel; Marion, Dominique; Schanda, Paul
2016-09-01
Transverse relaxation rate measurements in magic-angle spinning solid-state nuclear magnetic resonance provide information about molecular motions occurring on nanosecond-to-millisecond (ns-ms) time scales. The measurement of heteronuclear ((13)C, (15)N) relaxation rate constants in the presence of a spin-lock radiofrequency field (R1ρ relaxation) provides access to such motions, and an increasing number of studies involving R1ρ relaxation in proteins have been reported. However, two factors that influence the observed relaxation rate constants have so far been neglected, namely, (1) the role of CSA/dipolar cross-correlated relaxation (CCR) and (2) the impact of fast proton spin flips (i.e., proton spin diffusion and relaxation). We show that CSA/D CCR in R1ρ experiments is measurable and that the CCR rate constant depends on ns-ms motions; it can thus provide insight into dynamics. We find that proton spin diffusion attenuates this CCR due to its decoupling effect on the doublet components. For measurements of dynamics, the use of R1ρ rate constants has practical advantages over the use of CCR rates, and this article reveals factors that have so far been disregarded and which are important for accurate measurements and interpretation.
Kirtil, Emrah; Dag, Damla; Guner, Selen; Unal, Kubra; Oztop, Mecit H
2017-09-01
Liposomes are lipid bilayer vesicles that can be used as encapsulation systems for bioactive agents to provide increased protection against environmental stresses (such as pH or temperature extremes). Time Domain Nuclear Magnetic Resonance (TD-NMR) that is based on differentiation of specimen contents with respect to magnetic relaxation rates provides detailed information on amount, state and distribution of water and oil and provide reproducible results on the samples. These make TD-NMR particularly suitable for time-dependent monitoring of emulsion system dynamics. In this study, spin-spin (T2) relaxation times and relaxation spectra were used for characterizing green tea extract loaded and unloaded liposomes prepared with soy (S75) and egg lecithins (E80) by different preparation methods (such as homogenization type, pressure and solvent type). Mean particle sizes of liposomes were found to be the most influential factor in shaping mono-exponential T2 relaxation times. The differences in particle sizes of E80 and S75 samples along with samples with different homogenization pressures could be monitored with T2 relaxation times. Additionally, T2 relaxation times were found to be correlated with particle shape irregularity, and chemical instability of samples due to lipid oxidation. With relaxation spectrum analysis, particular components in the sample could be distinguished (internal/external water and lipid bilayers), which gave more elaborate results on mechanisms of instability. Copyright © 2017 Elsevier Ltd. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Prantner, Viktoria; Isaksson, Hanna; Nissi, Mikko J; Jurvelin, Jukka S [Department of Physics and Mathematics, University of Eastern Finland, PO Box 1627, 70211 Kuopio (Finland); Naervaeinen, Johanna; Groehn, Olli H J [Department of Neurobiology, A I Virtanen Institute for Molecular Sciences, University of Eastern Finland, PO Box 1627, 70211 Kuopio (Finland); Lammentausta, Eveliina [Department of Diagnostic Radiology, Oulu University Hospital, PO Box 50, 90029 OYS, Oulu (Finland); Avela, Janne, E-mail: hanna.isaksson@uef.f [Department of Biology of Physical Activity, University of Jyvaeskylae, PO Box 35, 40014 Jyvaeskylae (Finland)
2010-12-07
Nuclear magnetic resonance (NMR) spectroscopy provides a potential tool for non-invasive evaluation of the trabecular bone structure. The objective of this study was to determine the reproducibility of the NMR relaxation parameters (T{sub 2}, Carr-Purcel-T{sub 2}, T{sub 1}{rho}) for fat and water and relate those to the structural parameters obtained by micro-computed tomography ({mu}CT). Especially, we aimed to evaluate the effect of freezing on the relaxation parameters. For storing bone samples, freezing is the standard procedure during which the biochemical and cellular organization of the bone marrow may be affected. Bovine trabecular bone samples were stored at -20 {sup 0}C for 7 days and measured by NMR spectroscopy before and after freezing. The reproducibility of NMR relaxation parameters, as expressed by the coefficient of variation, ranged from 3.1% to 27.9%. In fresh samples, some correlations between NMR and structural parameters (Tb.N, Tb.Sp) were significant (e.g. the relaxation rate for T{sub 2} of fat versus Tb.Sp: r = -0.716, p < 0.01). Freezing did not significantly change the NMR relaxation times but the correlations between relaxation parameters and the {mu}CT structural parameters were not statistically significant after freezing, suggesting some nonsystematic alterations of the marrow structure. Therefore, the use of frozen bone samples for NMR relaxation studies may provide inferior information about the trabecular bone structure.
Chang, Zhiwei; Halle, Bertil
2015-12-01
A system of three dipole-coupled spins exhibits a surprisingly intricate relaxation behavior. Following Hubbard's pioneering 1958 study, many authors have investigated different aspects of this problem. Nevertheless, on revisiting this classic relaxation problem, we obtain several new results, some of which are at variance with conventional wisdom. Most notably from a fundamental point of view, we find that the odd-valued spectral density function influences longitudinal relaxation. We also show that the effective longitudinal relaxation rate for a non-isochronous three-spin system can exhibit an unusual inverted dispersion step. To clarify these and other issues, we present a comprehensive theoretical treatment of longitudinal relaxation in a three-spin system of arbitrary geometry and with arbitrary rotational dynamics. By using the Liouville-space formulation of Bloch-Wangsness-Redfield theory and a basis of irreducible spherical tensor operators, we show that the number of relaxation components in the different cases can be deduced from symmetry arguments. For the isochronous case, we present the relaxation matrix in analytical form, whereas, for the non-isochronous case, we employ a computationally efficient approach based on the stochastic Liouville equation.
Energy Technology Data Exchange (ETDEWEB)
Chang, Zhiwei; Halle, Bertil, E-mail: bertil.halle@bpc.lu.se [Department of Chemistry, Division of Biophysical Chemistry, Lund University, P.O. Box 124, SE-22100 Lund (Sweden)
2015-12-21
A system of three dipole-coupled spins exhibits a surprisingly intricate relaxation behavior. Following Hubbard’s pioneering 1958 study, many authors have investigated different aspects of this problem. Nevertheless, on revisiting this classic relaxation problem, we obtain several new results, some of which are at variance with conventional wisdom. Most notably from a fundamental point of view, we find that the odd-valued spectral density function influences longitudinal relaxation. We also show that the effective longitudinal relaxation rate for a non-isochronous three-spin system can exhibit an unusual inverted dispersion step. To clarify these and other issues, we present a comprehensive theoretical treatment of longitudinal relaxation in a three-spin system of arbitrary geometry and with arbitrary rotational dynamics. By using the Liouville-space formulation of Bloch-Wangsness-Redfield theory and a basis of irreducible spherical tensor operators, we show that the number of relaxation components in the different cases can be deduced from symmetry arguments. For the isochronous case, we present the relaxation matrix in analytical form, whereas, for the non-isochronous case, we employ a computationally efficient approach based on the stochastic Liouville equation.
Rotational relaxation in molecular hydrogen and deuterium: Theory versus acoustic experiments
Energy Technology Data Exchange (ETDEWEB)
Montero, S., E-mail: emsalvador@iem.cfmac.csic.es [Laboratory of Molecular Fluid Dynamics @ Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid (Spain); Pérez-Ríos, J. [Physics Department, Purdue University, West Lafayette, Indiana 47907 (United States)
2014-09-21
An explicit formulation of the rotational relaxation time in terms of state-to-state rate coefficients associated to inelastic collisions is reported. The state-to-state rates needed for the detailed interpretation of relaxation in H{sub 2} and D{sub 2}, including isotopic variant mixtures, have been calculated by solving the close-coupling Schrödinger equations using the H{sub 2}–H{sub 2} potential energy surface by Diep and Johnson [J. Chem. Phys. 112, 4465 (2000)]. Relaxation related quantities (rotational effective cross section, bulk viscosity, relaxation time, and collision number) calculated from first principles agree reasonably well with acoustic absorption experimental data on H{sub 2} and D{sub 2} between 30 and 293 K. This result confirms at once the proposed formulation, and the validation of the H{sub 2}–H{sub 2} potential energy surface employed, since no approximations have been introduced in the dynamics. Accordingly, the state-to-state rates derived from Diep and Johnson potential energy surface appear to be overestimated by up to 10% for H{sub 2}, and up to 30% for D{sub 2} at T = 300 K, showing a better agreement at lower temperatures.
Cruzeiro, E. Zambrini; Tiranov, A.; Usmani, I.; Laplane, C.; Lavoie, J.; Ferrier, A.; Goldner, P.; Gisin, N.; Afzelius, M.
2017-05-01
We present a detailed study of the lifetime of optical spectral holes due to population storage in Zeeman sublevels of Nd3 +:Y2SiO5 . The lifetime is measured as a function of magnetic field strength and orientation, temperature, and Nd3 + doping concentration. At the lowest temperature of 3 K we find a general trend where the lifetime is short at low field strengths, then increases to a maximum lifetime at a few hundred mT, and then finally decays rapidly for high field strengths. This behavior can be modeled with a relaxation rate dominated by Nd3 +-Nd3 + cross relaxation at low fields and spin lattice relaxation at high magnetic fields. The maximum lifetime depends strongly on both the field strength and orientation, due to the competition between these processes and their different angular dependencies. The cross relaxation limits the maximum lifetime for concentrations as low as 30 ppm of Nd3 + ions. By decreasing the concentration to less than 1 ppm we could completely eliminate the cross relaxation, reaching a lifetime of 3.8 s at 3 K. At higher temperatures the spectral hole lifetime is limited by the magnetic-field-independent Raman and Orbach processes. In addition we show that the cross relaxation rate can be strongly reduced by creating spectrally large holes of the order of the optical inhomogeneous broadening. Our results are important for the development and design of new rare-earth-ion doped crystals for quantum information processing and narrow-band spectral filtering for biological tissue imaging.
Ferreira, Miguel F; Gonçalves, Janaina; Mousavi, Bibimaryam; Prata, Maria I M; Rodrigues, Sérgio P J; Calle, Daniel; López-Larrubia, Pilar; Cerdan, Sebastian; Rodrigues, Tiago B; Ferreira, Paula M; Helm, Lothar; Martins, José A; Geraldes, Carlos F G C
2015-03-07
The relaxivity displayed by Gd(3+) chelates immobilized onto gold nanoparticles is the result of the complex interplay between the nanoparticle size, the water exchange rate and the chelate structure. In this work we study the effect of the length of ω-thioalkyl linkers, anchoring fast water exchanging Gd(3+) chelates onto gold nanoparticles, on the relaxivity of the immobilized chelates. Gold nanoparticles functionalized with Gd(3+) chelates of mercaptoundecanoyl and lipoyl amide conjugates of the DO3A-N-(α-amino)propionate chelator were prepared and studied as potential CA for MRI. High relaxivities per chelate, of the order of magnitude 28-38 mM(-1) s(-1) (30 MHz, 25 °C), were attained thanks to simultaneous optimization of the rotational correlation time and of the water exchange rate. Fast local rotational motions of the immobilized chelates around connecting linkers (internal flexibility) still limit the attainable relaxivity. The degree of internal flexibility of the immobilized chelates seems not to be correlated with the length of the connecting linkers. Biodistribution and MRI studies in mice suggest that the in vivo behavior of the gold nanoparticles was determined mainly by size. Small nanoparticles (HD = 3.9 nm) undergo fast renal clearance and avoidance of the RES organs while larger nanoparticles (HD = 4.8 nm) undergo predominantly hepatobiliary excretion. High relaxivities, allied to chelate and nanoparticle stability and fast renal clearance in vivo suggest that functionalized gold nanoparticles hold great potential for further investigation as MRI contrast agents. This study contributes to a better understanding of the effect of linker length on the relaxivity of gold nanoparticles functionalized with Gd(3+) complexes. It is a relevant contribution towards "design rules" for nanostructures functionalized with Gd(3+) chelates as Contrast Agents for MRI and multimodal imaging.
Magneto-dependent stress relaxation of magnetorheological gels
Xu, Yangguang
2017-09-01
The stress relaxation behaviors of magnetorheological (MR) gels under stepwise shear loading are systematically investigated. The particle-enhanced effect, the magneto-induced effect, and the temperature-enhanced effect on the stress relaxation of MR gels are discussed. For further analysis of the magneto-induced stress relaxation mechanism in MR gels, a phenomenological model is established to describe the stress relaxation behavior of the matrix and the magnetic particle chains. All characteristic parameters introduced in the model, i.e. relaxation time, instantaneous modulus, and stable modulus, have well-defined physical meanings and are fitted based on the experimental results. The influence of each parameter on the macroscopic response is discussed and it is found that the relaxation stress induced by the magneto-mechanical coupling effect plays an important role in the stress relaxation process of MR gels.
Lamley, Jonathan M; Lougher, Matthew J; Sass, Hans Juergen; Rogowski, Marco; Grzesiek, Stephan; Lewandowski, Józef R
2015-09-14
Typically, protein dynamics involve a complex hierarchy of motions occurring on different time scales between conformations separated by a range of different energy barriers. NMR relaxation can in principle provide a site-specific picture of both the time scales and amplitudes of these motions, but independent relaxation rates sensitive to fluctuations in different time scale ranges are required to obtain a faithful representation of the underlying dynamic complexity. This is especially pertinent for relaxation measurements in the solid state, which report on dynamics in a broader window of time scales by more than 3 orders of magnitudes compared to solution NMR relaxation. To aid in unraveling the intricacies of biomolecular dynamics we introduce (13)C spin-lattice relaxation in the rotating frame (R1ρ) as a probe of backbone nanosecond-microsecond motions in proteins in the solid state. We present measurements of (13)C'R1ρ rates in fully protonated crystalline protein GB1 at 600 and 850 MHz (1)H Larmor frequencies and compare them to (13)C'R1, (15)N R1 and R1ρ measured under the same conditions. The addition of carbon relaxation data to the model free analysis of nitrogen relaxation data leads to greatly improved characterization of time scales of protein backbone motions, minimizing the occurrence of fitting artifacts that may be present when (15)N data is used alone. We also discuss how internal motions characterized by different time scales contribute to (15)N and (13)C relaxation rates in the solid state and solution state, leading to fundamental differences between them, as well as phenomena such as underestimation of picosecond-range motions in the solid state and nanosecond-range motions in solution.
High Relaxivity Gd(III)–DNA Gold Nanostars: Investigation of Shape Effects on Proton Relaxation
Rotz, Matthew W.; Culver, Kayla S. B.; Parigi, Giacomo; MacRenaris, Keith W.; Luchinat, Claudio; Odom, Teri W.; Meade, Thomas J.
2015-01-01
Gadolinium(III) nanoconjugate contrast agents (CAs) have distinct advantages over their small-molecule counterparts in magnetic resonance imaging. In addition to increased Gd(III) payload, a significant improvement in proton relaxation efficiency, or relaxivity (r1), is often observed. In this work, we describe the synthesis and characterization of a nanoconjugate CA created by covalent attachment of Gd(III) to thiolated DNA (Gd(III)–DNA), followed by surface conjugation onto gold nanostars (DNA–Gd@stars). These conjugates exhibit remarkable r1 with values up to 98 mM−1 s−1. Additionally, DNA–Gd@stars show efficient Gd(III) delivery and biocompatibility in vitro and generate significant contrast enhancement when imaged at 7 T. Using nuclear magnetic relaxation dispersion analysis, we attribute the high performance of the DNA–Gd@stars to an increased contribution of second-sphere relaxivity compared to that of spherical CA equivalents (DNA–Gd@spheres). Importantly, the surface of the gold nanostar contains Gd(III)–DNA in regions of positive, negative, and neutral curvature. We hypothesize that the proton relaxation enhancement observed results from the presence of a unique hydrophilic environment produced by Gd(III)–DNA in these regions, which allows second-sphere water molecules to remain adjacent to Gd(III) ions for up to 10 times longer than diffusion. These results establish that particle shape and second-sphere relaxivity are important considerations in the design of Gd(III) nanoconjugate CAs. PMID:25723190
Lu, Zijie; Manias, Evangelos; MacDonald, Digby D.; Lanagan, Michael
2009-10-01
Dielectric spectra of dimethyl sulfoxide (DMSO)/water mixtures, over the entire concentration range, have been measured using the transmission line method at frequencies from 45 MHz to 26 GHz and at temperatures of 298-318 K. The relaxation times of the mixtures show a maximum at an intermediate molar fraction of DMSO. The specific structure of mixtures in different concentration regions was determined by the dielectric relaxation dynamics, obtained from the effect of temperature on the relaxation time. A water structure "breaking effect" is observed in dilute aqueous solutions. The average number of hydrogen bonds per water molecule in these mixtures is found to be reduced compared to pure water. The increase in the dielectric relaxation time in DMSO/water mixtures is attributed to the spatial (steric) constraints of DMSO molecules on the hydrogen-bond network, rather than being due to hydrophobic hydration of the methyl groups. The interaction between water and DMSO by hydrogen bonding reaches a maximum at a DMSO molar fraction of 0.33, reflected by the maximum activation enthalpy for dielectric relaxation in this concentration, suggesting the formation of a stoichiometric compound, H2O-DMSO-H2O. In highly concentrated solutions, negative activation entropies are observed, indicating the presence of aggregates of DMSO molecules. A distinct antiparallel arrangement of dipoles is obtained for neat DMSO in the liquid state according to the Kirkwood correlation factor (gK = 0.5), calculated from the static permittivity. The similarity of the dielectric behavior of pure DMSO and DMSO-rich mixtures suggests that dipole-dipole interactions contribute significantly to the rotational relaxation process in these solutions.
DO FOOT REFLEXOLOGY AND RELAXATION TRAINING DECREASE PREMENSTRUAL SYMPTOMS IN ADOLESCENT FEMALES
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Marwa A. Mohamed
2016-10-01
Full Text Available Background: Premenstrual syndrome is a current condition characterized by troublesome symptoms as tension, irritability, depression, headache, anxiety and loss of self-control, so the aim of this study was to investigate the effect of foot reflexology augmented with relaxation training on premenstrual syndrome in adolescent females. Methods: A sample of 50 volunteers, virgin females diagnosed as premenstrual syndrome was selected from the students of Faculty of Physical Therapy, Cairo University. Their age was ranged between 19 to 23 years with mean value of (21.53±2.27 yrs and BMI was ≤28 Kg/m² with mean value of (24.04±2.41 Kg/m².A detailed medical history was obtained to screen other pathological conditions that may affect the results. Females were randomly assigned into two equal groups. Group (A consisted of 25 subjects who received foot reflexology in addition to relaxation training techniques twice a week for 8 weeks. Group (B consisted of 25 patients, who received relaxation training techniques only twice a week for 8 weeks. Assessment of all subjects in both groups was carried out before and after the treatment program through heart rate, respiratory rate in addition to plasma cortisol level and daily symptoms report chart. Results: Showed a statistical highly significant decrease (p<0.001 in heart rate, respiratory rate, plasma cortisol level as well as daily symptoms report score in group (A while there was a statistical significant decrease (p<0.05 in all variables in group (B. Conclusions: Adding foot reflexology to relaxation training had a great positive effect on premenstrual syndrome in adolescent females than relaxation training only.
Van Noten, P; Van Leemputte, M
2013-03-15
After active shortening, isometric force production capacity of muscle is reduced (force depression, FD). The mechanism is incompletely understood but increasing cross-bridge detachment and/or decreasing attachment rate might be involved. Therefore we aimed to investigate the relation between work delivered during shortening (W), and change in half-relaxation time (Δ0.5RT) and change in the slow phase of muscle relaxation (Δkslow), considered as a marker for cross-bridge detachment rate, after shortening and after a short (0.7s) interruption of activation (deactivation). We hypothesized that shortening induces an accelerated relaxation related to W which is, similar to FD, largely abolished by a short deactivation. In 10 incubated supra-maximally stimulated mouse soleus muscles, we varied the amount of FD at L0 by varying shortening amplitude (0.6, 1.2 and 2.4mm). We found that W not only induces FD (R(2)=0.92) but also a dose dependent accelerated relaxation (R(2)=0.88 and R(2)=0.77 for respectively Δkslow and Δ0.5RT). In cyclic movements this is of functional significance, because the loss in force generating capacity might be (partially) compensated by faster relaxation. After a short deactivation, both FD and Δkslow were largely abolished but Δ0.5RT remained largely present. Under the assumption that Δkslow reflects a change in cross-bridge detachment rate, these results support the idea that FD is an intrinsic sarcomeric property originating from a work induced reduction of the number of force generating cross-bridges, however not via decreased attachment but via increased detachment rate. Copyright © 2013. Published by Elsevier Ltd.
Relaxing the cosmological constant: a proof of concept
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Alberte, Lasma [SISSA,Via Bonomea 265, 34136 Trieste (Italy); INFN - Sezione di Trieste,Via Valerio 2, 34127 Trieste (Italy); Creminelli, Paolo; Khmelnitsky, Andrei [Abdus Salam International Centre for Theoretical Physics (ICTP),Strada Costiera 11, 34151, Trieste (Italy); Pirtskhalava, David [Institute of Physics, École Polytechnique Fédérale de Lausanne,CH-1015, Lausanne (Switzerland); Trincherini, Enrico [Scuola Normale Superiore,Piazza dei Cavalieri 7, 56126, Pisa (Italy); INFN - Sezione di Pisa,56200, Pisa (Italy)
2016-12-06
We propose a technically natural scenario whereby an initially large cosmological constant (c.c.) is relaxed down to the observed value due to the dynamics of a scalar evolving on a very shallow potential. The model crucially relies on a sector that violates the null energy condition (NEC) and gets activated only when the Hubble rate becomes sufficiently small — of the order of the present one. As a result of NEC violation, this low-energy universe evolves into inflation, followed by reheating and the standard Big Bang cosmology. The symmetries of the theory force the c.c. to be the same before and after the NEC-violating phase, so that a late-time observer sees an effective c.c. of the correct magnitude. Importantly, our model allows neither for eternal inflation nor for a set of possible values of dark energy, the latter fixed by the parameters of the theory.
On relaxation nature of glass transition in amorphous materials
Sanditov, Damba S.; Ojovan, Michael I.
2017-10-01
A short review on relaxation theories of glass transition is presented. The main attention is paid to modern aspects of the glass transition equation qτg = C, suggested by Bartenev in 1951 (q - cooling rate of the melt, τg - structural relaxation time at the glass transition temperature Tg). This equation represents a criterion of structural relaxation at transition from liquid to glass at T = Tg (analogous to the condition of mechanical relaxation ωτ = 1, where the maximum of mechanical loss is observed). The empirical parameter С = δTg has the meaning of temperature range δTg that characterizes the liquid-glass transition. Different approaches of δTg calculation are reviewed. In the framework of the model of delocalized atoms a modified kinetic criterion of glass transition is proposed (q/Tg)τg = Cg, where Cg ≅ 7·10-3 is a practically universal dimensionless constant. It depends on fraction of fluctuation volume fg, which is frozen at the glass transition temperature Cg = fg/ln(1/fg). The value of fg is approximately constant fg ≅ 0.025. At Tg the process of atom delocalization, i.e. its displacement from the equilibrium position, is frozen. In silicate glasses atom delocalization is reduced to critical displacement of bridge oxygen atom in Si-O-Si bridge necessary to switch a valence bond according to Muller and Nemilov. An equation is derived for the temperature dependence of viscosity of glass-forming liquids in the wide temperature range, including the liquid-glass transition and the region of higher temperatures. Notion of (bridge) atom delocalization is developed, which is related to necessity of local low activation deformation of structural network for realization of elementary act of viscous flow - activated switch of a valence (bridge) bond. Without atom delocalization (;trigger mechanism;) a switch of the valence bond is impossible and, consequently, the viscous flow. Thus the freezing of atom delocalization process at low temperatures
Relaxing the Cosmological Constant: a Proof of Concept
Alberte, Lasma; Khmelnitsky, Andrei; Pirtskhalava, David; Trincherini, Enrico
2016-01-01
We propose a technically natural scenario whereby an initially large cosmological constant (c.c.) is relaxed down to the observed value due to the dynamics of a scalar evolving on a very shallow potential. The model crucially relies on a sector that violates the null energy condition (NEC) and gets activated only when the Hubble rate becomes sufficiently small --- of the order of the present one. As a result of NEC violation, this low-energy universe evolves into inflation, followed by reheating and the standard Big Bang cosmology. The symmetries of the theory force the c.c. to be the same before and after the NEC-violating phase, so that a late-time observer sees an effective c.c. of the correct magnitude. Importantly, our model allows neither for eternal inflation nor for a set of possible values of dark energy, the latter fixed by the parameters of the theory.
Length and sequence relaxation of copolymers under recombination reactions
Blokhuis, Alex; Lacoste, David
2017-09-01
We describe the kinetics and thermodynamics of copolymers undergoing recombination reactions, which are important for prebiotic chemistry. We use two approaches: the first one, based on chemical rate equations and the mass-action law describes the infinite size limit, while the second one, based on the chemical master equation, describes systems of finite size. We compare the predictions of both approaches for the relaxation of thermodynamic quantities towards equilibrium. We find that for some choice of initial conditions, the entropy of the sequence distribution can be lowered at the expense of increasing the entropy of the length distribution. We consider mainly energetically neutral reactions, except for one simple case of non-neutral reactions.
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Wen-Hsien Li
2016-05-01
Full Text Available 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.